Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02446426 2003-11-12
23091-91D
CLUTCH COVER
The invention relates to improvements in
friction clutches, especially for use in motor vehicles.
More particularly, the invention relates to improvements
in friction clutches of the type wherein a pressure plate.
is non-rotatably but axially movably connected to a
housing or cover and is biased by one or more prestressed
resilient devices (e.g., in the form of diaphragm ,'
springs) to urge a clutch plate or clutch disc against a
rotary counterpressure plate (e.g., a flywheel) which is
driven by the output element of an internal combustion
engine in a motor vehicle. The clutch disc can serve to
transmit torque to the input element of a variable-speed
transmission in the power train between the engine and
the wheels of a motor vehicle.
Friction clutches of the above outlined
character are disclosed, for example~ in published German
patent application Serial No. 24 60 963, In German Pat.
No. 24 41 141, in German Pat. No. 898 531 and in German
Auslegeschrift No. 1 267 916.
One feature of the present invention resides in
the provision of an engageable and disengageable torque
transmitting friction clutch which can be utilized with
advantage in vehicles, particularly motor vehicles. The
improved friction clutch comprises a housing or cover
which is rotatable about a predetermined maxis~ a pressure
plate, means (e. g., a group of leaf springs) for non-
rotatably connecting the pressure plate to the housing
with limited freedom of movement in the direction of the
predetermined axise a rotary counterpressure plate (e. g.~
a flywheel which is driven by the output element of an
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engine in a motor vehicle) adjacent the pressure plate, a
torque transmitting clutch disc between the two plates,
and at least one resilient device reacting against the
housing to bias the pressure plate toward the
counterpressure plate in order to clamp the clutch disc.
against the counterpressure plate and to thus rotate the
clutch disc about the predetermined axiso The clutch
disc has friction linings which are engageable by and
disengageable from at least one of the two plates and are
subject to wear as a result of repeated engagement with
and disengagement from the at least one plate, and the
friction clutch further comprises an adjusting unit
including means for compensating for wear upon the
friction linings to thereby maintain the bias of the at
least one resilient device upon the pressure plate at a
substantially constant value, means for engaging and
disengaging the friction clutch including actuating means
movable along a predetermined path to engage and
disengage the friction clutch, and means for varying the
torque transmitted by the friction clutch andJor by the
clutch disc including means for gradually reducing the
transmitted torque at least during a portion of movement
of the actuating means along the predetermined path to
disengage the friction clutch.
The pressure plate comprises a portion which is
engaged and biased by the at least one resilient device,
and the disengagement of the friction clutch can involve
axial movement of the pressure plate away from the
counterpressure plate against the bias of the at least
one resilient device. The friction clutch can further
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comprise means for gradually reducing the torque which is
transmittable by the friction clutch at least during a
portion of axial movement of the pressure plate~
The friction clutch can also comprise means for
securing the housing to -the counterpressure plate to
thus establish a power train between the actuating means
and the securing means. The torque varying means can be
disposed in the power train.
The pressure plate has a friction surface which
LO is engageable with the friction linings to establish a
power train between the actuating means and the clutch
disc, and the torque varying means can be disposed in
such power train.
The friction linings can include a first and. a
second set of friction linings, and the torque varying
means can be disposed axially between the two sets of
friction linings.
The torque varying means can include means for
axially yieldably locating at least one of the two p later
20 and the friction linings relative to the others of the
two plates and the friction linings, and the torque
varying means can be acted upon by a variable force which
decreases to a minimal value in response to disengagement
of the friction clutch and gradually increases to a
maximum value at least during a portion of movement of
the actuating means along the predetermined path to
engage the friction clutch.
The means for varying the torque which is
transmittable by the friction clutch can include means
30 for reducing the transmitted torque during approximately
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40-70 percent of movement of the actuai:.ing means alone
the predetermined path in a direction to disengage the
friction clutch and for gradually increasing the torque
which is transmittable by the friction clutch during
approximately 40-70 ;percent of movement of the actuating
means along the predetermined path in ~i direction to
engage the friction clutch.
The at least one resilient device (such a s a
diaphragm spring) can have a depressive force-to
displacement ratio at least during a portion of movement
of the actuating means along the predetermined path in a
direction to disengage the friction clutch.
As mentioned above, the at least one resilient
device can comprise G, diaphragm spring which bears
against the pressure plate. The friction clutc h
preferably further cc~nprises a seat which tiltably mounts
the diaphragm spring in the housing. The diaphragm
spring c an comprise an annular portion and the actuating
means can comprise prongs or tongues which extend from
the annular portion of the diaphragm spring. Such prongs
can be of one piece with the annular portion of the
diaphragm spring. The seat can comprise two portions
(e a g o , in the norm of wire rings) which are disposed at
opposite sides of the diaphragm spring. The latter can
have a substantially sinusoidal force-to-dis placement
characteristic curve :including a maximum, a minimum, a
depressive portion between the minimum and -the maximum,
an operating point at the depressive portion in engaged
condition of .the friction clutch, and a rat l o of forces
from approximately 3~0.4 to 1:0.7 between -the maximum and
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the minimum.
If the friction clutch is used in a motor
vehicle, the means for engaging and disengaging the
friction clutch can further comprise means for moving the
actuating means and such moving means can include or
constitute a pedal which is similar or analogous to the
gas pedal of the motor vehicle.
Another feature of the invention resides in the
provision of a motor vehicle having a gas pedal, an
engageable and disengageable friction clutch, means fom
engaging and disengaging the friction clutch including
actuating means movable along a predetermined path to
disengage the clutch, and means for moving the actuating
means including a second pedal which is similar or
analogous to the gas pedal of the motor vehicle..
An additional feature of the invention resides
in the provision of a preassembled engageable and
disengageable clutch assembly or aggregate which
comprises a housing, a pressure plate, a counterpressure
plate which is rotat~able about a predetermined axis,
means for non-rotatably connecting the pressure plate to
the counterpressure plate with limited freedom of
movement in the direction of the predeterm~.ned axis, a
torque transmitting clutch disc between the two plates,
at least one resilient device which reacts against the
housing to bias the pressure plate toward the
counterpressure plate and to thereby clamp the clutch
disc between the two plates, friction linings which form
part of the clutch disc and are engageable by and
disengageable from at least one of the two plates so that
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they are subject to wear as a result of repeated
engagement with and disengagement from the at least one
plate, an adjusting unit including means for compensating
at least for wear upon the friction linings to thereby
maintaira the bias of the at least one resilient device
upon the pressure plate at a substantially constant
value, means for engaging and disengaging tl°ie clutch
aggregate or assembly including actuating means movable
along a predetermined path to disengage the clutch
aggregate or assembly, and means for gradually reducing
the torque which is transmitted by the clutch disc during
a porti~n of movement of the actuating means to disengage
the clutch assembly or aggregate. The torque reducing
means can include at least one resilient element which. is
in series With the at least one resilient device.
Still another feature of the invention resides
in the provision of a clutch aggregate or assembly which
comprises a twin-mass flywheel including a first rotary
mass connectable to an output shaft of a combustion
engine and a second mass rotatable relative to the first
mass, an oscillation damper having means for opposing
rotation of the two masses relative to each other, and a
torque transmitting friction clutch including a
counterpressure plate forming part of the second mass, a
pressure plate, means for non-rotatably connect ing the
pressure plate to the counterpressure plate with limited
freedom of axial movement, a torque transmitting clutch
disc between the two plates, at least one resilient
device acting upon the pressure plate to bia s the clutch
disc against the counterpressure plate, frict ion linings
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forming part of the clutch disc and being engageable with
and disengageable from at least one of the two plates and
being subject to wear as a result of repeated engagement
with and disengagement from the at least one p1 ate, an
adjusting unit including means for compensating at least
for wear upon the friction linings to thereby maintain
the bias of the at least one resilient device upon the
pressure plate at a substantially constant value, means
for engaging and disengaging the friction clutch
l0 including actuating means movable along a predetermined
path to disengage the friction clutch, and means for
gradually reducing the torque which can be transmitted by
the friction clutch and/or by its clutch disc during a
portion of movement of the actuating means in a direction
to disengage the friction clutch.
The friction clutch of the just outlined clutch
aggregate or assembly can further comprise a housing and
means f or securing the housing to the second mass so that
the housing is separable from the second mass only in
20 response to at least partial destruction or deformation
of one of the two parts including the housing and the
second mass.
The clutch disc of the aforementioned clutch
aggregate or assembly can be provided with at least one
substantially annular friction surface and the damper can
be located radially outwardly of the.friction surface.
A further feature of the invention resides in
the provision of a clutch aggregate or assembly fox use
with a combustion engine, particularly in a motor
30 vehicle. Such clutch aggregate or assembly comprises a
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torque transmitting friction clutch including a pressure
plate, ~a counterpressure plate (such as a flywheel) which
is rotatable about a predetermined axis ~ means for non-
rotatab 1y connecting the pressure plate to the
counterpressure plate with limited freedom of axial
movement, a torque transmitting clutch disc between the
two plates, at least one resilient device acting upon the
pressure plate to bias the clutch disc against the
counterpressure plate, friction linings forming part of
the clutch disc and being engageable with and
disengageable from at: least one of the two plates and
being subject to wear. as a result of repeated engagement
with and disengagement from the at least one p late, an.
adjusting unit including means for compensating at lea st
for wear upon the friction linings to thereby maintain
the bias of the at least one resilient device upon the
pressure plate at a substantially constant value duriIlg
the useful life of the friction clutch, means for
engaging and disengaging the friction clutch including
2~ actuating means movable along a predetermined path to
disengage the friction clutch, means for gradually
reducing the torque which can be transmitted by the
friction clutch and/or by the clutch disc during a
portion of movement of the actuating means i n a direction
to disengage the fr~.ction clutch, and axial 1y elastic
means for coupling t:he friction clutch with an output
shaft of the combustion engine. The coupling means has a
stiffness or rigidity which is selected in such a way
that any axial, turning, wobbling (tilting) and/or
30 flexing vibrations which are induced by the output shaft
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of the engine and would normally be transmitted to the
friction clutch are damped and/or otherwise suppressed ?oy
the coupling means to an extent which ensures proper
operation of the friction clutch, and espec~.ally proper
operation of the adjusting unit.
The stiffness of the coupling' means can be
selected in such a wc~y that the force to be applied, to
the actuating means f or disengagement of the friction
clutch is taken up by the coupling means without
appreciable axial shifting of the clutch aggregate or
assembly.
The adjusting unit of the just discus sed
aggregate or assembly can comprise resilient means in
series with the at least one resilient device. Such
aggregate or assembly can further comprise means for
damping rotational and/or axial and/or radial v ibraticans
of the counterpressure plate and such damping means is
connectable between the output shaft of the engine and
the counterpressure plate.
An additional feature of the invention resides
in the provision of a driving unit, particular 1y for a se
in motor vehicles, ~rhich comprises an at least partia 1 1y
automatic (i.e., fully automatic or semiautomatic)
transmission, an engine, and a torque transmitting
friction clutch disposed between the engine and the
transmission and being controlled at least in dependency
on the operation of the transmission. The friction
clutch of such driving unit camprises a pressure plate:, a
counterpressure plate (such as a flywheel) rotatable
about a predetermined axis and connectable to the output
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shaft of the engine, means for non-rotatably connectixig
the pre ssure plate to the counterpressure plate with
limited freedom of movement in the direction of the
predetermined axis, a torque transmitting clutch disc
between the two plates, at least one resilient device
acting upon the pressure plate to bias the clutch disc
against the counterpressure plate, friction 1i n ings
forming part of the clutch disc and being engageable with.
and disengageable from at least one of the two plates and
being subject to wear as a result of repeated engagement
with and disengagement from the at least one plate, an
adjusting unit including means for compensating at least
for wear upon the friction linings to thereby maintain
the bias of the at least one resilient device upon the
pressure plate at a substantially constant value, means
for engaging and disengaging the friction clutch
including actuating means movable along a predetermined
path to engage and disengage the friction clutch, and
torque varying means including means for gradually
reducing the torque which can be transmitted by the
friction clutch and/or by the clutch disc during a
portion of movement of the actuating means a long the
predetermined path in a direction to disengage the
friction clutch.
The at least one resilient device (e.g., a
diaphragm spring) can have a degressive force-to-
displacement ratio, at least during a portion of movement
of the actuating means. along the predetermined path in a
direction to disengage the friction clutch.
The means for varying the torque which can be
1 ~.
CA 02446426 2003-11-12
23091-91D
transmitted by the friction clutch can include means for
reducing the transmittable torque during approximately
40-70 percent of movement of the actuating means along the
predetermined path in a direction to disengage the friction
clutch and for gradually increasing the torque which can be
transmitted by the friction clutch during approximately
40-70 percent of movement of the actuating means along the
path in a direction to engage the friction clutch.
According to a broad aspect, the invention
provides a clutch cover assembly, comprising: a friction
member connected to an output member, said friction member
engaging with an input rotation member when pressed toward
said input rotation member; a clutch cover fixed to said
input rotation member; a pressure plate located within said
clutch cover for pressing said friction member; an urging
member for urging said pressure plate toward said friction
member, said urging member being a diaphragm spring,
radially outward end of which urges said pressure plate; a
support mechanism movable toward said friction member and
for supporting said urging member, said support mechanism
supporting radially middle portion of said diaphragm spring;
and a movement regulation mechanism for moving said support
mechanism toward said friction member according to wear
displacement of said friction member.
The novel features which are considered as
characteristic of the invention are set forth in particular
in the appended claims. The improved friction clutch
itself, however, both as to its construction and its mode of
operation, together with additional features and advantages
thereof, will be best understood upon perusal of the
following detailed description of certain presently
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23091-91D
preferred specific embodiments with reference to the
accompanying drawings.
FIG. 1 is a fragmentary elevational view as seen
from the right-hand side of FIG. 2 and shows a friction
clutch which embodies one form of the present invention;
FIG. 2 is a sectional view substantially as seen
in the direction of arrows from the line II-II in FIG. l;
FIG. 3 is a plan view of a first annular
adjusting or wear compensating member which is utilized in
an adjusting unit of the friction clutch shown in FIGS. Z
and 2;
FIG. 4 is a fragmentary sectional view
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substantially as seen in the direction of arrows from the
line IV-IV in FIG. 3;
FIG. 5 is a plan view of a second annular
adjusting or wear compensating member which is utilized
in the adjusting unit of the friction clutch shown an
FIGS. 1 W '1d 2;
FIG. 6 is a fragmentary sectional view , '
substantially as seen in the direction of arrows from the
line VI-VI in FIG. 5;
FIG. 7 is a plan view of a torsion spring which
is utilized in the adjusting unit of the friction clutch
shown in FIGS: 1 and 2;
FIG. 7a is an end elevational view of the
torsion spring;
FIG. 8 is a diagram wherein the curves denote
variations of the force generated by a diaphragm spring
which is used to bias a pressure plate against a c2utch
disc in the friction clutch of FIGS. 1 and 2;
FIG. 9 is a diagram wherein the curves denote
variations of certain characteristics of a resilient
sensor in the friction clutch ~f FIGS,. 1 and 2;
FIG. 10 is a diagram with curves denoting the
forces to be applied in order to disengage the friction
clutch of FIGS. 1 and 2;
FIG. 11 is a diagram with curves denoting the
reduction of forces acting upon the housing and upon the
sensor of the friction clutch of FIGS. 1 and 2 during
disengagement of the friction clutch;
FIG. 12 is a fragmentary elevational view as
seen from the right-hand side of FIG. ~.3 and shows a
3. 3
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second friction clutch;
FIG. 13 is a sectional view substant i ally as
seen in the direction of arrows from the line XI II-XIII
in FIG. 12;
FIG. 14 is a plan view of an annular adjusting
or wear compensating member which is utilized i.n an
adjusting unit forming part of the second friction
clutch;
FIG. 15 is a fragmentary axial sectional view
of a third friction clutchp
FIG. 16 is a plan view of an annular adjusting
or wear compensating member which is utilized in the
third friction clutch;
FIG. 17 is a sectional view substantially as
seen in the direction of arrows from the line XVI3-XVI =
in FIG. 16;
FIG. 18 is a diagraan with curves denoting the:
characteristics of a diaphragm spring corresponding to
that used in the friction clutch of FIGS. 1 and 2;
FIG. 19 is a diagram wherein the cur~res
indicate variations of disengaging force whets a friction
clutch employs diaphragm springs exhibiting
characteristics corresponding to those denoted by the
curves in the diagram of FIG. 18~
FIG. 20 is a fragmentary elevations 1 view as
seen from the upper side of FIG. 21 and illustrates a
fourth friction clutch;
FIG. 20a illustrates, in a partial sections 1
view, a detail as seen in the direction of arrow XXA in
FIG. 20;
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FIG. 21 is a sectional view substantially as
seen in the direction of arrows from the line XXI-XXI in
FIG. 20;
FIG. 22 is a fragmentary plan view of an
annular adjusting or wear compensating member which can
be utilized in the adjusting unit of the fourth friction
clutch; ,'
FIG. 23 is a fragmentary axial sectional view
of a fifth friction clutch;
FIG. 24 is a fragmentary axial sect~.onal view
of a sixth friction clutch;
FIG. 25 is a plan view of an annular adjusting
member which can be utilized in the adjusting unit ~f the
second or fourth friction clutch;
FIG. 26 is a fragmentary axial sectional view
of a seventh friction clutch;
FIG. 2'7 is a fragmentary axial sectional view
of an eighth friction clutch;
FIG. 28 is a fragmentary elevational viera of a
ninth friction clutch as seen from the right-hand side of
FIG. 29, with certain parts broken away;
FIG. 29 is a sectional view as seen in the
direction of arrows from the line XXIX-XXIX in FIG. 28 ;
FIG. 30 is an enlarged fragmentary s actions 1
view as seen in the direction of arrows from the line
XXX-XXX in FIG. 28;
FIG. 31 is an enlarged sectional view
substantially as seen in the direction of arrows from the
line XXXI-XXXI in FIG. 28;
FIG. 32 is a fragmentary plan view of a ring-
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shaped adjusting member in the adjusting unit of the
:ninth friction clutch shown in FIGS. 28 and 29;
FIG. 33 is a fragmentary axial sectional view
of a tenth friction clutch;
FIG. 34 is a fragmentary axial sectional view
of an a leventh friction clutch;
FIG. 35 is an axial sectional view of an
aggregate embodying a friction clutch of the class shown
in FIGS. 1 to 27 and a twin-mass flywheel which transmits
l0 torque from the output element of an engine in a motor
vehicle t~ the housing of the friction clutch;
FIG. 36 is a fragmentary axial sect Tonal view
of a preassembled aggregate employing a friction clutch
of the class shown in FIGS. 1 and 2 and the manner of
insulating the friction clutch from stray movements of
the output element of the engine in a motor vehicle; and
FIG. 37 is a fragmentary axial sectional view
of a preassembled aggregate which constitutes a
modification of the aggregate shown in FIG. 3 6.
20 Referring first to FzGS. 1 and 2, there is
shown a torque transmitting friction clutch 3 whicrr
comprises a housing or cover 2 and a pressure plate 3
which is non-rotatably but axially movably (within
limits) connected to the cover 2. A resilient device in
the form of a diaphragm spring 4 is insta11ee1, in
stressed condition, between the bottom wall or end wal 1
2a of the cover 2 and the pressure plate 3 so as to bias
the pressure plate in a direction to the lef t, as viewed
in FIG. 2, namely against the adjacent set o f friction
30 linings 7 forming part of a torque transmitting clutch
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plate or clutch disc 8. The diaphragm spring 4 is
tiltable relative to the cover 2 at a location which is
determined by an annular seat assembly 5 (hereinafter
called seat for short) carried by the bottom wa 11 2a.
The normal stressed condition of the diaphragm spring 4
is such that it urges the pressure plate 3 against the
adjacent set of friction linings 7 of the clutch disc 8
whereby a second set of friction linings forming part of
the clutch disc bears against the adjacent friction
surface of a rotary counterpressure plate 6 her a shown as
a flywheel and hereinafter called flywheel for short.
The illustrated clutch disc 8 comprises a centrally
located hub 8a which can be installed on the input shaft
(not shown) of a variable-speed transmission in a motor
vehicle and carries two sets of friction linings 7 with
resilient segments 10 between the two sets of linings.
The clutch 1 is engaged and the flywheel 6 transmits
torque to the input shaft of the transmission when the
two sets of friction linings 7 of the clutch disc 8 are
clamped between the neighboring friction surfaces of the
pressure plate 3 and flywheel E~.
The means for connecting the pressure plate 3
with the cover 2 comprises several circumferentially
extending leaf springs 9 (see particularly F'IG. 1) which
hold the pressure plate 3 against rotation but permit it
to move, within limits~ axially of the cover 2. The
purpose of the resilient segments 10 between the two sets
of friction linings 7 forming part of the clutch disc 8
is to establish a progressive buildup (verist ion) of
torque during engagement of the friction clutch 1. Such
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resilient segments permit limited axial shifting of the
two sets of friction linings 7 toward each other to thus
establish a progressive increase of axial forces which
act upon the friction linings. However, it is equally
within the purview of the invention to employ a clutch
disc which replaces the illustrated clutch disc 8 and
comprises one or two sets of friction linings 7 having no
freedom of axial movement relative to each other. Such
friction linings can be glued or otherwise of f axed to
opposite sides of a suitable plate-like carrier
surrounding the hub of the modified clutch disc.
The illustrated diaphragm spring 4 comprises a
circumferentially complete annular main or primary or
basic portion 4a which is adjacent one or more axially
extending protuberances or portions 3a of the pressure
plate 3 and serves to generate the major part of force s
which are necessary to bias the pressure plate 3 against
the adjacent friction linings 7 so as to urge the other
set of friction linings against the friction surface o f
2 0 the flywheel 6 . The ma in or pr imary port ion 4 a of the
diaphragm spring .4 carries radially inwardly extending
yieldable prongs 4b having radially innermost portions or
tips 4c engageable by a bearing, a pedal or other
component which forms part of means for disengaging the
friction clutch 1. The main or primary port ion 4a of the
diaphragm spring 4 includes a radially outer part wh i ch
engages the portion or portions 3a of the pressure plate
3, and a radially inner part which is disposed between
two portions 11 and 1~ of the seat 5. Such radially
30 inner portion of the main or primary portion 4 a is
~. 8
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tiltable between the portions 11 and 12 in order to move
the radially outer portion of the diaphragm spring 4
toward or away from the flywheel 6, i.e., to engage or
disengage the clutch 1.
The illustrated portions 11 and 12 of the seat
are wire rings which flank the radially inner part of
the main or primary portion 4a of the diaphragm spring 4
at a locat ion radially inwardly of the portion or
portions 3 a of the pressure plate 3. A resilient
IO distance or displacement monitoring sensor 33, here shown
as a diaphragm spring, is provided to bias the inner ring
or portion 11 of the seat 5 toward the bottom wall 2a of
the cover 2. The illustrated resilient sensor 13 in the
form of a diaphragm spring can be replaced by other
biasing means without departing from the spirit of the
invention . The annular radially outer portion 13b of the
sensor 13 is circumferentially complete and comp rises an
outermost part or portion 13a which reacts against an
abutment 14 at the inner side of the cover 2. The sensor
20 13 further comprises radially inwardly extending elastic
tongues 13c which bear upon the adjacent side of the ring
11.
The abutment 14 for the radially outermost part
13b of the annular portion 13a of the sensor 1 3 can
comprise~a circumferentially complete annulus which is
welded or otherwise secured to the inner side of the
cover 2. alternatively, the abutment 14 can comprise two
or more arcuate sections which are affixed to the inner
side of the cover 2 to be engaged by the adj acent part
30 13b of the sensor 13. The individual segments or
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portions of the abutment 14 can be bo:t~ded, riveted or
otherwise affixed to the cover 2. It is also possible to
provide an abutment 14 consisting of one or more
projections which are of one piece with the cover 2 and
are configurated to extend into the path of leftward
movement (reference being had to FIG. 2) of the radially
outermost part 13a of the sensor 13. Such. abutment can
consist of radially inwardly deformed portions of the.
cover 2 or it can include one or more lugs or prongs
which are bent from. the adjacent portion of the cover to
thus establish holes in the cover adjacent the radial l~r
outermost part 13a of the sensor 13. The making of such
inwardly extending portions, lugs or prongs can take
place subsequent tcs installation of the sensor 13 in the
interior of the cover 2. The sensor 13 can b~ stressed
as a result of the making of abutment 14 , or the seneor
is already maintained in stressed condition at the tame
the abutment 14~ is either installed or formed as an
integral part of the cover 2.
It is also possible to provide a more
pronounced connection between the sensor 13 and the
abutment 14. For example, it is possible to provide a
bayonet mount which can establish a positive but
separable connection between the sensor 13 anc'i the
abutment 14 . The c:onf iguration of the bayonets mount can
be such that the sensor 13 can be installed in the coyer
2 to have its radially outermost part 13a located to the
left of the abutment 14, as viewed in FIG. 2. The
radially outermost part 13a is then shifted axially
toward the bottom wall 2a of the cover 2 to stress the
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sensor 1 3 and to cause such radially outermost part 13 a
to advance over 'the adj scent portion or portions of the
abutment 14. The next step involves turning of the
sensor 13 relative to the abutment 1.4 and/or vine versa
so as to releasably lock the radially outermost part 13 a
of the sensor in the position which is shown ia°a FIG. 2 ,
namely at the right°hand side of the alt~utment 14. In
such friction clutches, the radially outermost part 13a
of the sensor 13 can comprise a plurality of prongs or
arms extending radially outwardly beyo:~d the
circumf erentially complete annular portion 13b of the
sensor. The abutment 14 then comprises a plurality of
recesses or tooth spaces ~ which permit the prorags of the
sensor 13 to pass therethrough before the sensor is
turned so that its prongs are moved out of alignment with
the tooth spaces of the abutment 14.
The means for centering the diaphragm spring 4
and/or the sensor 13 in the cover 2 and for
simultaneously preventing rotation of such springs
relative to the pressure plate 3 comprises ax l ally
parallel rivets 15. Such rivets can further serve as a
means for centering the rings 11 and 12 of the seat 5 in
the cover 2. Each rivet 15 comprises an e=longated shank
15a which extends in parallelism with the axis (?~-X) of
rotation of the clutch plate 8 and is anchored in the
bottom wall 2a of the cover 2. The sr~anks 15a extend
through slots 4d between the neighboring prongs 4b of the
diaphragm spring 4. The tongues 13c of the s~nsar 13
comprise portions 13d which straddle the adj s cent
portions of the shanks 15a so that then rivets 15 hold the
~1
CA 02446426 2003-11-12
sensor 13 against rotation in the cover 2.
The resilient sensor 13 is designed to furnish
a substantially constant force during a predetermined
stage of its axial deformation. The purpose of the
sensor 13 is to bias the ring 11 toward the bottom wal:L
2a of the cover 2 as well as to take up the clutch
disengaging force when such force is being applied to ~t~e
tips 4c of prongs 4b forming part of the diaphragm spring
4. Depression of the tips 4c in a direction to the left,
as viewed in FIG. 2 , results in tilting of the diaphragm
spring 4 between the rings 11 and 12 oi= the seat 5
whereby the main or primary portion 4a of the spring 4 is
moved away from the flywheel 6 so that the pressure plate
3 can be retracted bvy the leaf springs 9 and releases the
adjacent set of friction linings 7. In other words, trace
clutch disc 8 ceases to rotate with the flywheel 6. Tlm
arrangement is such that a state of equilifrium, ssr a
state at least closely approximating equilibrium, exists
between (a) that force which is generated upon the ring
11 during the application of disengaging force to the
tips 4c of the prongs 4b and (b) the counterforce whic-~
is furnished by the sensor 13 and acts upon the ring :L ~. .
The term "disengagin.g force" is intended to c'ienote that
maximum force which must be applied to the tips 4c of the
prongs 4b in order t.o disengage the friction clutch 1
Such disengaging force can also be applied t~ the prongs
4b by disengaging levers or by a pedal, not shown.
In accordance with a feature of the invention,
the ring 12 between the diaphragm spring 4 and the bottom
wall 2a of the cover 2 is biased by an adjusting or
22
CA 02446426 2003-11-12
regulating unit 16 which is installed in t:he cover. The
adjusting unit 16 ensures that, when the rings 11 and 12
of the seat 5 are shifted axially in a direction toward
the pressure plate 3 and flywheel 6, no undesirable
clearance will develop between the ring Z2 and the cover
2. Otherwise stated, there will be no clearance between
the ring 12 and the diaphragm spring 4. Such posi t Toning
of the ring 12 relative to the diaphragm spring 4 T s
desirable and advantageous because this ensures that
there is no undesirable lost motian during actuation of~
the friction clutch 1 which, in turn, ensures optimum
efficiency and superior operation of the friction c latch.
Axial shifting of the rings 11 and 12 of the seat 5
toward the pressure plate 3 and flywheel 6 will take
place as a result of wear upon the friction surfaoes of
the pressure plate 3 and flywheel 6 as well as (and
particularly) due to wear upon the friction lining s 7.
The exact mode of automatic operation of the adju sting
unit 16 will be described in full detail with reference
to the diagrams which are shown in FIGS. 8, 9, 10 and 11.
The adjusting tanit 16 comprises a spring-biased
ring-shaped adjusting or wear compensating member 17
which is shown in FIGS. 3 and 4. The adjusting member 17 is
installed between the diaphragm spring 4 and the bottom
wall 2a of the cover 2 and comprises a set of inc lines or
ramps 18. X111 of the ramps I8 are inclined in the same
direction circumferentially of the member 17. When the
member 17 is installed in the Cover 2, its ramps 18 face
the bottom wall 2a. That side of the member 17 which
faces away from the bottom wall 2a is flat or
23
CA 02446426 2003-11-12
substantially flat and is provided with a
circumf erentially extending groove 19 (FIG. 2) which
receives a portion of the ring 12. Ire this manner, tine
ring 12 (which is centered by the shanks 15a o~ the
rivets 15 ) centers the member 17 in the cower 2 . I°he
configuration of the groove 19 and/or of the adjacent
portion of the member 17 can be such that the ring 12 is
not only held against uncontrolled radial movements but
is also held against, axial movement relative to the
member 17. For example, the configuration of the surface
bounding the groove 19 can be such that the r i ng 12 can
be received therein by snap action. ~~lternatively, the
plane surface of the member 17 which faces away from the
bottom wall 2a can be provided with spaced-apart
projections or other configurations which enable the
member 17 to clampingly or otherwise engage (ea.g., by
snap action) the adjacent portions of the ring 12 and to
thus ensure that thz.s ring is held against any
uncontrolled radial and/or axial movements relative i~o
the member 17.
If the temperature of the friction clutch :L in
the region of the adjusting unit 16 fluctuates within a
wide range, it is advisable to provide for some
compensatory movement between the ring 12 and the member
17 of the adjusting unit 16. For example,. th is can be
achieved by making the ring 12 a split ring s~ that it
can expand or contract in the circumferential directiora
of the member 17. It is also possible to assemble the
ring 12 of two, three or more discrete arcuate sections,
i.e., to provide two or more interruptions ~n such ring
2~
CA 02446426 2003-11-12
in order to even more fully compensate for eventual
pronounced f luctuat.ions of the temperature of the
adjusting unit 16. This enables them-ing Z2 to conform
its diameter to the varying diameter of the groove 19"
The member l7 which is shown in FIGS. 3 and 4
is made of a plastic material, for example, of a heat.-
resistant thermoplastic substance which can be reinf~~rced
by glass fibers or 'the like. This renders it possible to
mass-produce the member 17 in an inje<~tion molding or
other suitable machine. However, it is equally within
the purview of the invention to make ithe an,ember 17 of a
metallic sheet material or of a sintered metal. Still
further, it is within the scope of the invention to make
the ring 12 of one piece with the member 1.7. This is
possible regardless of whether the me:~ber 17 is made of a
metallic or plastic mater~.al. Analogously, the ring 11
can be made of one piece with the sensor ~.3; all that is
necessary is to provide the tongues 13c of the sensor 13
with suitable projections in the form of beads or the
2~ like which together constitute a composite or one~piece
ring 11.
The rivets 15, and more particularly the shanks
15a of such rivets, preferably further constitute ~ means
for centering the member 17 of the adjusting unit 16 in
the cover 2 of the friction clutch 1. The rivets 15 are
preferably equidistant from each other in the
circumferential direction of the cover 2. The shanks 15a
extend through suitable openings 21 which are provided in
the member 17 and are bounded by surfaces 20 which are
30 engaged by the shanks 15a to thus cer.~ter the member 17 in
CA 02446426 2003-11-12
the cover 2. The illustrated openings 21 are elongated
slots having a substantially constant width (as measured
in the radial direction) and extend circumferentially of
the member 17. These openings 21 are closely adjacent
the radially inner portion of the member 17. As can be
seen in FIG. 3, the member 17 further comprises lobesc 22
which are disposed radially inwardly of the respect,i'~e
openings 21.
The member 17 which is shown in FIG~ 3
l0 comprises three openings 21 and a total of five ramps 18
between each pair of neighboring openings. The slopes
(note the angle 23 in FYG. 4) of the ramps 18 are
selected in such a way that the ramps enable the member
17 to compensate for wear upon the pressure plate 3,
flywheel 6 and friction linings 7 during the entire
useful life of the friction clutch 1. The same applies
for the length of the openings 21 in the circumferen~tial
direction of the member 17. Such length is selected with
a view to permit are angular adjustment of the member 1?
20 relative to the botaom wall 2a of the cover 2 which is
necessary for compensate for the aforediscussed wear upon
the pressure plate 3, flywheel 6 and friction linings 7.
The length of the openings 21 can be selected in such a
way that the member 17 is free to perform an angular
movement in the range of between 8 and 60°, preferably
within a range of between 10 and 30°.. In the embodiment
which is illustrated in FIG. 3, the angular adjustabil ity
of the member 17 relative to the cover 2 is approximately
12°. Furthermore, the angle 23 (which is shown in FIG. 4
30 and denotes the slope of the ramps 18) is also in the
26
CA 02446426 2003-11-12
range of 12°. This angle 23 is selected in such a way
that, wY~en the ramps 18 of the member 17 and the
complementary inclines or ramps 24 of a second annular
displacing member 25 (shown in FIGS. 5 and 6 and
hereinafter called annulus) are in frictional engagement
with each other, the member 17 and the annulus 25 cannot
slip because the friction between the abutting surfaces
of the ramps 18 and 24 is too pronounced. lD~pending oaz
the nature of the material of the member 17 and annulus
25 and on the finish of the abutting surfaces of the
ramps 18 and 24, the angle 23 can be in the range of
between 5 arid 20°.
The member 17 is stressed in the
circumf erential diresaion by a ring-shaped torsion spring
26 which is shOWn iri FIGS. 1, 2, 7 arid 7a. The bias of
the spring 26 is selected in s~a~h a way that the member
17 is stressed in a direction which is neces nary for
adjustment in order to compensate for 'wear upon the
pressure plate 3, flywheel 6 and friction 3~i.nings 7. In
other words, the spr~.ng 26 tends to bias the member 17 in
a direction such that, as the ramps 18 slide along the
complementary ramps 24 of the annulus 25, t1 is results in
axial displacement of the member 17 in a direction toward
the pressure plate 3, i.e., axially of and away frown the
bottom wall 2a of the cover 2. It is clear that the
illustrated torsion spring 26 constitmtes but one form of
means for biasing the member 17 in a direction to slide
along the annulus 25 and to thereby advance axially
toward the pressure plate 3. This torsion spring
comprises a relatively small number of cony~lutions 35
27
CA 02446426 2003-11-12
(:for example, not more than two convolutions) and two
legs 27 and 28: The leg 27 extends radially outwardly
(see particularly FIGS. 7 and 7a), and the leg 28 extends
in part radially and in part axially (see FIG. 7a). The
leg 27 is non-rotatably anchored in or is otherwise
connected with the member 17, and the leg 28 is non-
rotatably anchored in or is otherwise secured to the
cover 2. The spring 26 is installed in stressed
condition.
1~ A presently preferred form of the displacing
annulus 25 is shown in FIGS. 5 and 6. This annulus
comprises the aforediscussed ramps 24 which are
complementary to the ramps 18 of the member 17. The
surfaces along which the ramps 18 abut the ramps 24 can
be congruent surfaces. The angle 29 which is shown in
FIG. 6 preferably matches the angle 23 which is shown in
FIG. 4. As can be readily seen by comparing FIGS. 3 and
5, the distribution of ramps 24 on the annulus 25 is the
same as, or at least similar to, that of the ramps 18 on
20 the member 17. The annulus 25 is non-rotatably secured
to the housing 2. To this end, the annulus 25 is
provided with a plurality of holes 30 which can receive
portions of the rivets 15 so that such. rivets also serve
as a means for non-rotatably coupling the annulus 25 to
the bottom wall 2a of the cover 2. This can be seen :in
the upper portion of FIG. 2.
FIG. 2 further shows, by broken lines, that the
means for biasing the member 17 in the circumferential
direction of the cover 2 can comprise an additional
30 torsion spring 26a which can be configurated in the same
28
CA 02446426 2003-11-12
way as the torsion spring 26. Thus, one leg of the
torsion spring 26a can be anchored in the member 1'7 and
its other leg can be anchored in the cover 2. The
torsion spring 26a is also installed in sires sed
condition so that it always tends to turn the zcaember 17
relative to the c~ver 2.
An advantage of the utilization of two t~r~ion
springs 26, 26a is that their bias can increa se under the
action of centrifugal force when the fz~iction clutch 1 is
in use and its cover 2 rotates with the pressure plate: 3
and flywheel 6. The flywheel 6 can receive torque from
the output element of an engine in a motor vehicle. F'or
example, the increased bias of the spring 26 in respordse
to the action of centrifugal force can be compensated f or
by the torsion spring 26a. To this end, the springs 2E
and 26a are convoluted in such a way that, at least when
acted upon by centrifugal force, they generate and apply
to the member 17 forces which act in opposite directions
as seen in the circumferential direction of the member
17. The diameters of convolutions of the t or°sion spring
26a are larger than the diameters of convo~_tations 35 of
the torsion spring 26. Reference may be had to FIG. 2.
This enables the designer of the clutch to select the
centrifugal forces acting upon the torsion springs 26 and
26a in such a way that the forces acting up~a~ the member
1'7 in the circumferential direction are at least
substantially balanced. Adequate balancing can be
achieved by appropriate selection of the diameters of
convolutions of the springs 26, 26a, by appr ~priate
selection of the diameters of wires of which these
29
CA 02446426 2003-11-12
springs are made andjor by appropriate select ion of the
number of their convolutions. FIG. 2 shows that the
torsion spring 26 is located radially inwardly and the
torsion spring 26a .is located radially outwardly of the
member 17. However, it is equally possible to install
each of these springs radially inwardly or radially
outwardly of the member 17.
FIG. 7 shows the torsion spring 26 in a plain
view. When this spring is not under stress, its legs 27,
28 make an angle 3I which can be in the range of 40-120.
The leg 27 will be moved (relative to the leg 28) to the
position 32 when the friction linings 7 are new (i.e.,
prior to being subjected to any wear). The leg 27
assumes the position 33 of FIG. 7 when the linings 7 have
undergone a maximum permissible amount of wear. The
angle 34 of adjustment (between the positions 32 and 33
shown in FIG. 7) is approximately 12°. The spring 26 of
FIG. 7 is designed in such a way that, when in unstressed
condition, only a single convolution 35 extends between
the legs 27 and 28. The remaining portion of the spg~ing
26 (namely outside of the angle 31) has two convolutions
35 (FIG. 7a) which overlie each other as seen in the
axial direction of the spring 26.
The spring 26a is similar to the spring 26 b~zt,
in the embodiment of FIGS. 1 and 2, has a larger diameter
and is stressed in a different direction as concerns its
bias upon the member 17. The force which the spring 2 6
applies to the member 17 is greater than the force oi= the
spring 26a.
3 0 When the wear upon the component parts of tshe
CA 02446426 2003-11-12
fricti on clutch 1 is minimal, i.e., when the clutch is
yet to be put to use, the angular positions of the member
17 and annulus 25 relative to each other are such that
the axially extending peaks 18a of the ramps 18 forming
part of the member 17 extend close to or actually abut
the axially extending peaks 24a of the ramps 24 on the
annulus 25. In other words, the combined thickness of
the member 17 and annulus 25 then assumes a n'inimum
value, i.e., these parts occupy a minimum amount of space
1O in the axial direction of the cover 2 :between the bottom
wall 2a and the diaphragm spring 4.
In the friction clutch 1 Of FIGS. 1 arid 2, the
annulus 25 constitutes a separately produced part which
is installed at the inner side of the bottom wall 2a of
the cover 2. However, it is also possible to make the
annulus 25 an integral part of the cover 2~ for example,
the lobes 24 can be stamped out of the bottoBn wall 2a to
extend toward the member Z7 of the adjusting unit 16.
Such mode of making the annulus 25 (namely its lobes 2 4)
2~ is particularly advantageous i.f the cover 2 is madde of a
single piece of metallic sheet material.
The shoulders 38 on the pallets 3 6 of lobes 22
of the member 17 can be utilized to ensure proper angular
positioning of the member 17 in the cover 2 during
assembly of the friction clutch 1. The sho~,alders 38 can
be engaged by a suitable turning or retainirag tool which
reacts against the cover 2. The tool is put to use
during assembly of the-friction clutch 1 and is removed
when the attachment of the cover 2 to the flywheel 6 (by
30 threaded fasteners 6a one of which is shorn in FIG. 2) is
3i
CA 02446426 2003-11-12
completed. The adjusting unit 16 becomes operative as
soon as the aforementioned tool is removed, l . a . , as soon
as the member 17 is free to turn relative to the cover 2
( if and when necessary) to compensate for wear upon the
parts 3, 6 and/or 7. As shown in FIG. 1, the bottom wa 11
2a of the cover 2 has circumferentially extending
elongated slot-shaped windows 37 which enable the prongs
or analogous extensions of the tool to engage the
shoulders 38 an the pallets 36 of the lobes 22 of the
member 17 during assembly of the friction clutch 1. The
shoulders 38 can be replaced with other configurations
(e. g., holes) in-or on the member 17, as long as the tool
can properly engage and hold the member 1°7 in requisite
position during assembly of the friction clutch 1. The
length of the windows 37 should at least Buff ice t~
ensure that the member 17 can be turned bacl~ through the
maximum angle which is required to compensate for wear
upon the pressure plate 3, f ly~wheel 6 and/or friction
linings 7. It is also possible to assemble the frict ion
clutch 1 in a first step and to thereupon employ a too 1
which is to be used to turn the member 17 relative to the
cover 2. The prongs of the tool are inserted through the
windows 37 of the bottom wall 2a and engage the shoulders
38 on the pallets 3~ of the lobes 22. The member 17 is
then turned back in a direction to ensure that its ramps
18 cooperate with the ramps 24 of the annulus 25 in a
sense to move the member 17 closer to the bottom wa 1 1 2a
to a position from which the member 17 must turn in order
to compensate for wear upon the parts 3, C and/or 7 in
actual use of the friction clutch 1. The member 17 l s
32
CA 02446426 2003-11-12
then located at a minimum distance from the b~ttom wall
2a and is secured in such position, for example; with a
clamp or a pin extending into registering openings of the
cover 2 and member 17 to prevent angular displacement of
the thus coupled parts 2, 17 relative to each other. The
clamp or pin is removed when the attachment of the cover
2 to the flywheel 6 is completed, i.e., the unit 16 is
then ready to perform its adjusting action if and when
necessary, depending on the extent of wear upon the
pressure plate 3, flywheel 6 and/or friction linings 7.
The dimensions of the windows 37 in the cover 2
are selected in such a way that the member 17 can be
returned to its "retracted" position (at a min imal
distance from the bottom wall 2a) if and when the cover 2
is to be detached from the flywheel 6. This involves
disengagement of the clutch 1 (i.e., the application of
axial force against the tips 4c of the prongs 4b in a
direction toward the clutch disc 8) so that the diaphragm
spring 4 no longer exerts an axially oriented force
against the ring 11 of the seat 5 and the member 17 care
be readily turned relative to the cover 2.
Referring to the diagram of FIG. 8, the
sinusoidal curve 40 denotes the axial7.y oriented force
which develops in response to changes of conicity of the
diaphragm spring 4 as a result of deformation between two
abutments spaced apart from each other a distance
corresponding to that of the seat 5 from the projecting
portion or portions 3a of the pressure plate 3. The
distance between such abutments is measured a long the
3~ abscissa, and the force which is generated by the
3~
CA 02446426 2003-11-12
diaphragm spring 4 is measured along the ordinate of the
coordinate system of FIG. 8. The (operating) point 41 of
the curve 40 denotes the force which is generated by the
diaphragm spring 4 upon installation of the friction
clutch 1 and while the clutch is engaged~ at such time,
the spring 4 exerts a maximum force upon the portion or
portions 3a of the pressure plate 3 and the latter ei~erts
a maximum force which is used to clamp the friction
linings 7 of the clutch disc 8 between the friction
l0 surfaces of the pressure plate 3 and flywheel 6. The
point 41 can be shifted along the curve 40 toward or away
from the abscissa by changing the conicity of the
diaphragm spring 4 in assembled condition of the frict ion
clutch 1.
The curve 42 denotes in FIG. 8 the axial
spreading force which is applied by the resilient
segments 10 between the two sets of fraction linings 7.
Such spreading force of the segments 10 opposes the force
which the diaphragm spring 4 applies to the pressure
20 plate 3. It is desirable and advantageous that the force
which develops as a result of resilient deformation of
the segments 10 at least match the bias of the diaphragm
spring 4~ it is also possible to select the mounting of
the diaphragm spring 4 and the resiliency and bias of the
segments 10 in such a way that the force which is denoted
by the curve 42 exceeds the force which is denoted by the
curve 40. The stressing of the resilient segments 10
decreases in response to disengagement of the friction
clutch 1, and the extent to which the stressing decreases
30 is denoted by the distance 43. This results in a
34
CA 02446426 2003-11-12
corresponding axial shifting or deformation of the
diaphragm spring 4 whexeby the segments l0 assist the
disengagement of the friction clutch. In other words,
the required maximum disengaging force is less than that
which would be necessary at the point 4l of the curve 40
in FIG. 8 if the resilient segments 8 were omitted. The
point 44 on the curve 40 denotes the magnitude of the
force of diaphragm spring 4 at the instant of
disengagement of the friction clutch 1, i.e., the
friction linings 7 are no longer engaged by the friction
surfaces of the pressure plate 3 and flywheel 6 when the
point 44 is exceeded. Due to the degressive
characteristic curve of the diaphragm spring 4, the
disengaging force which is to be applied at such time is
much less than that corresponding to the force denoted by
the point 41 of the curve 40. The disengaging force
which must be applied in the friction clutch 1 decreases
all the way to the minimum or lowest point 45 of the
sinusoidal curve 40. From there an, the required
disengaging force rises again and the extent o~ axial
movement of the tips 4c of prongs 4b along their
predetermined path can be selected in such a way that the
magnitude of this force does not exceed that at the point
44 (i.e., the maximum disengaging force] and preferably
remains therebelow. In other words, the force should not
rise above that denoted by the point 4~.
The magnitude of the force which is generated by
the sensor 13 is denoted by the curve 47 which is shown
in FIG. 9. This curve actually denotes the force which
is generated when the conicity of the sensor 13 is
CA 02446426 2003-11-12
changed as a result of stressing. Such change in
stressing of the sensor 13 takes place as a result of
variations of the distance between two abutments whose
radial spacing corresponds to that of the abutment 14 at
the inner side of the cover 2 from the ring 11 of the
seat 5. The distance 48 covered by the sensor 13 is that
during which the axial force generated by the sensor
remains substantially constant. The magnitude of this
force is selected in such a way that it at least
approximates the magnitude of the clutch disengaging
force as denoted by the point 44 on the curve 40 of FIG.
8. The supporting force to be furnished by the sensor 13
is less than that at the point 44 of the curve 40 by a
value corresponding to the lever arm of the diaphragm
spring 4. In most instances, such transmission ratio is
between 1:3 and 1:5 but can also be less than 1:3 or
greater than 1:5 for certain applications of the improved
friction clutch.
The just mentioned transmission ratio of the
diaphragm spring 4 denotes the ratio of radial distance
of the seat 5 from the portion or portions 3a of the
pressure plate 3 to the radial distance of the seat 5
from the tips 4c of the prongs 4b forming part of the
diaphragm spring 4 and being depressible, for example, by
a disengaging bearing of the friction clutch.
The mounting of the sensor 13 in the friction
clutch 1 is selected in such a way that the sensor can
perform an axial movement in the region of the seat 5~
namely in a direction toward the friction linings 7, to
an extent corresponding at least to the axial. adjustment
CA 02446426 2003-11-12
of the pressure plate 3 toward the flywheel 6 as a result
of wear upon the friction surfaces of the parts 3, 6 and
as a result of wear upon the friction linings 7. This
ensures that the axially oriented supporting force for
the seat 5 remains constant regardless of the wear upon
the parts 3, 6 and 7. In other words, the substantial 1y
linear portion 48 of the curve 47 in FrG. 9 should hive a
length not less than that corresponding to the
aforediscussed extent of wear and preferably exceeding
the latter. This ensures that the adjusting unit 16 can
also compensate, at least in part, for eventual
tolerances during assembly of the friction clutch 1.
In order to ensure the establish~eent of a
practically unchanged (i.e., predetermined release point
44 for the friction linings 7 when the friction clutch
is disengaged, it is possible to employ torque varying
means 10 known as a so-called twin-segment biasing means
which is to operate between the two sets of friction
linings 7. Such biasing means can comprise pairs of
discrete parallel resilient segments which are disposed
back-to-back. The segments which are disposed back-to-
back can be subjected to a certain initial stress ~.n the
axial direction of the clutch disc 8 so that the axis 1
force which is generated by all such pairs of segments
relative to each other at least matches the disengaging
force denoted by the point 44 of the sinusoidal curve 40
when the clutch disc 8 is not clamped between the
pressure plate 3 and the flywheel 6. It is preferred to
ensure that the combined force of the pairs of resilient
segments slightly exceed that force of the diaphragm
37
CA 02446426 2003-11-12
spring 4 which is denoted by the point 44 on the curve 4 O
of FI G. 8. Prestressing of resilient segments between
the friction linings 7 of the clutch disc 8 renders it
possible to at least substantially compensate for so-
called penetration or embedding losses which develop
during the useful life of the friction clutch 1 as a
result of penetration of the segments 10 into the
adjacent friction linings '7. Such penetration of
segments 10 into the adjacent linings ~ is to be expected
in actual use of the friction clutch 1" It has been
found that an axial stressing or give of the segments 1 O
in the range of 0.3 mm to 0.8 mm (preferably
approximately 0.5 mm) is quite satisfactory. By proper 1y
limiting the extent of axial movability of the two sets
of friction linings 7 relative to each other and by
properly selecting the bias of the segments 10 between
the two sets of friction linings, one can ensure that, at
least during disengagement of the friction clutch I, the
pressure plate 3 covers a predetermined distance 43 in a
direction away from the friction linings under the act i on
of the resilient segments 10. In order to achieve such
predetermined distance 43, it is possible to limit the
extent of axial movement of the two sets of friction
linings 7 in directions toward as well as away from each
other, e.g., by the provision of suitable stops, i.e., in
directions to stress the segments 10 as well as to enable
these segments to dissipate energy. Suitable resilient
means for use between the two sets of friction linings 7
are disclosed, for example,.ira commonly owned copending
German patent application Serial No. :P 42 06 880.0 the
38
CA 02446426 2003-11-12
teaching of which can be referred to, if necessary.
Tn order to guarantee an optimal operation of
the friction clutch 1, i.e., to ensure that the adjusting
unit 16 will be capable of automatically compensating for
wear upon the parts 3, 5 and/or 7 of the friction clutch,
it is desirable t.o ensure that the sum of forces which
are applied by the diaphragm spring 9, sensor 13 and
resilient segments 10, as well as the.force which is
applied to the diaphragm spring 4 solely by the sensor 13
when the pressure plate 3 is already disengaged from the
adjacent friction linings 7, at least equals but
preferably exceeds the variable disengaging force which
is being applied to the tips 4c of prongs 4b during
disengagement oz the friction clutch 1. The variable
disengaging force is denoted by the cwrve ~9 in the
diagram of FIG. 10.
The heretofore discussed mode of operat ion of
the friction clutch 1 pertains primarily or exclusively
to a predetermined mode of installing the diaphragm
~0 spring 4 and without taking into consideration the wear
upon the friction linings 7. When a certain amount of
wear has taken place (such wear is particularly
pronounced upon the friction linings 7), the position of
the pressure plate 3 changes in that the pressure plate
migrates toward the flywheel 6 whereby the conicity of
the diaphragm spring 4 (and hence the bias of this spring
upon the portion or portions 3a of the pressur a plate)
changes accordingly while the friction clutch 1 remains
in engaged condition. Such change of bias of the
30 diaphragm spring 4 upon the pressure plate 3 entails that
39
CA 02446426 2003-11-12
the point 41 of the curve 40 in the diagram of FIG. 8
migrates toward the point 41° and that the point 44
migrates toward the point 44'. This terminates the state
of equilibrium between the diaphragm spring 4 and the
sensor 13 at the ring 11 during disengagement of the
friction clutch 1. Wear upon the friction linings °7
entails an increase in the magnitude of force which is
applied by the diaphragm spring 4 to the sensor 13 and
also causes a shifting of the progress of the disengaging
force in a sense toward an increase of such force. The
thus obtained progress of the disengaging force is
denoted in FIG. 10 by the broken-line curve 50. Since
the magnitude of the disengaging force increases, the
axially oriented force of the sensor 13 upon the
diaphragm spring 4 during disengagement of the friction
clutch 1 is overcome so that the sensor 13 yields in the
region of the seat 5 through an axial distance
corresponding essentially to the extent of wear upon the
friction linings 7. During such deformation stage of
2~ the sensor 13 (which can be said to constitute a means
for monitoring the extent of wear upon the parts 3, 6
and/or 7), the diaphragm spring 4 bears against the
portion or portions 3a of the pressure plate 3 whereby
the conicity of the spring 4 changes together with the
amount of energy which is stored therein. Thus, the
energy which is stored by the diaphragm spring 4 a:Lso
changes together with the force which the spring 4 exerts
upon the ring 11, i.e., upon the sensor 13 and upon the
pressure plate 3. As can be seen in FIG. 8, such change
30 takes place in a sense to reduce the magnitude of the
4 Ce
CA 02446426 2003-11-12
force which is applied by the diaphragm spring 4 and
continues to take place until the magnitude of the axia 1
force applied by the spring 4 to the sensor 13 at the
ring 11 is at least substantially neutralized or balanc;~d
by the oppositely directed force which is exerted by the
sensor 13. In other words, and referring aga in to the
diagram of FIG. 8, tlxe points 41' and 44' of the curve ~! 0
then migrate toward the points 41 and 44, r~espectively~
When the reestablishment ~f the state of equilibrium is
completed, the pressure plate 3 is again ready to be
disengaged from the adjacent friction linings 7. During
the aforediscussed stage of adjustment in order to
compensate for wear upon the friction linings 7, while
the friction clutch 1 is being disengaged, the member 1'7
of the adjusting unit 16 is caused to turn about the ax is
X-x of the clutch disc 8 under the bias of the stressed
torsion spring 26 which causes a displacement of the ring
12 to an extent corresponding to the extent ~f wear upon
the friction linings 7~ this, in turn, eliminates any
play at the seat 5. When the adjusting step is
completed, the magnitude of the disengaging force again
corresponds to that denoted by the curve 49 in the
diagram of FIG. 10. The curves 50A and 51 in the diagram
of FIG. 10 denote the axial displacement of the- pressure
plate 3 when the magnitude of the disengaging force
varies in accordance with the curves 4~ and 50,
respectively.
The curves which are shown in the diagram of
FIG. 11 denote the variations of forces act ing upon the
cover 2 and upon the sensor 13 during disengagement of
41
CA 02446426 2003-11-12
the friction clutch 1. The extreme values are omitted.
Starting with the engaged condition of FIG. 2, the cover
2 and the pressure plate 3 are first acted upon by a
force whose magnitude corresponds to th.e operating or
installation point 4I of the diaphragm spring 4 as
denoted by the curve 40 of FIG. 8. As the disengagement
of the friction clutch 1 progresses, the magnitude p~ the
axial f once exerted by the diaphragm spring 4 upon the
cover 2 and the ring 12 decreases in accordance with the
1~ curve 52 of FIG. 11., namely to the point 53. When the
point 53 is exceeded in the direction of disengagement of
the friction clutch 3, a conventional frictional clutch
(wherein the diaphragm spring is tiltable at a fixed
location relative to the clutch cover, i.e., wherein t:he
ring 11 is fixedly installed in the cover) would operevte
in such a way that the force exerted by the diaphragm
spring 4 upon the cover 2 at the level. of the seat 5
would change (reverse) its direction. However, the novel
friction clutch 1 operates in such a way that the change
20 in the axial direction of the force applied by the
diaphragm spring 4 in the region of the seat 5 is taken
up by the sensor 13. tnihen the magnitude of the force
which is being applied by the diaphragm spring 4 reaches
the vaiua denoted by the point 54 on the curve 52 of FIG.
11, the diaphragm spring 4 becomes disengaged fro~a the
portion or portions 3a of the pressure plate 3. The
resilient segments 10 between the two sets of friction
linings 7 generate an axially oriented force which
assists the disengagement of the friction clutch 1 at
30 least to the point 54 on the curve 52 of FIG. 11. The
~2
CA 02446426 2003-11-12
force wh l ch is generated by the resilient segments 1~
decreases as the extent of displacement of tips 4c of
prongs 41~ t,oward the clutch disc 8 increases during
disengagement of the friction clutch 1, i.e., in response
to progressing axial displacement of the pressure plate. 3
in a direction away from the flywheel 6. Thus, the curve
52 of FIG ~ 11 denotes a resultant of a disengaging force
which is being applied to the tips 4c during
disengagement of the friction clutch l on the one hand
and of the axial force which is being applied by the
resilient segments 1~ of the clutch disc 8 upon the
diaphragm spring 4 in the region of portion or portions
3a of the pressure plate 3. When the point 54 is
exceeded in the direction of disengagement of the
friction clutch 1, the axially oriented force which is,
being applied by the diaphragm spring 4 to the ring 13, l s
compensated for by the oppositely directed force whicra l s
being applied by the sensor 13. These two forces are
balanced by the pressure plate 3 not later than when the
axial pressure upon the friction linings 7 is
terminated. As the disengaging operation progresses, the
axially oriented force which is being applied by the
sensor 13 at the seat 5 preferably exceeds, at least
slightly. the prevailing disengaging force. The portion
55 of the curve 5~ in the diaphragm of F1~. 11 indicates
that, as the extent of movement to disengage the frica l on
clutch 1 increases ~ the disengaging force ( and the force
applied by diaphragm spring 4 to the ring 11, decreases
when compared with the disengaging force denoted by the
point 54 of the curve 52. The brokers°line curve 56 in
43
CA 02446426 2003-11-12
the diagram of FIV. 11 denotes that condition of the
friction clutch 1 when the friction linings 7 have
undergone a certain amount of wear but prior to any
compensation for such wear in the region of the. seat 5.
It will be noted that the change of orientat ion
Iconicity) of the diaphragm spring 4 due to wear upon the
friction linings 7 results in an increase of the
magnitude of forces which are being applied to the cover
2, to the ring 11 and/or to the sensor 13. This causes,
the point 54 to migrate in a direction towarel 54P which ,
in turn, entails that in the course of the next-following
disengaging operation the axial force which is being
applied by the diaphragm spring 4 to the sensor 13 at the
ring 11 exceeds the appositely directed force of the
sensor 13; this causes an adjustment in the
aforedescribed manner as a result of axial relaxation of
the sensor 13. Such adjustment entails that the point
54' migrates toward the point 54 which, in turn,
reestablishes the desired state of equilibrium at the
seat 5, namely between the diaphragm spring 4 and the
sensor 13.
In actual practice (i.e., when the friction
clutch 1 is in use), adjustments by the unit 16 are
effected continuously or nearly continuously (i.e., by
minute steps). The distances between the carious points
on the curves of FIGS. 8 t~ 11 are greatly exaggerated
for the sake of clarity.
It is very likely that certain changes of
various functional parameters and/or operating points
will take place during the useful life of the friction
44
CA 02446426 2003-11-12
clutch s.. For example, improper actuation of the
friction clutch J. can result in overheating of the
resilient segments l0 in the clutch disc 8 which can
cause a reduction of the resiliency of these segments,
i . a . , a reduction of the extent of axial movabi 1 ity of
the parts l0. Nevertheless, it is possible to ensure
reliable operation of the friction clutch 1 by , '
appropriate selection of the characteristic curve 40 of
the diaphragm spring 4 and a corresponding conformance of
the curve 47 denoting the displacement~to-force
relationship of the sensor 13 ~ A redu~caion of axial
movability of the segments 10 would merely ergtail that
the conicity of the diaphragm spring 4 in the? friction
clutch 1 of FIGS. Z and 2 would change in a sense to
reduce the magnitude of the force which the spring 4
exerts upon the portion or portions 3a of the pressure
plate 3. This can be seen in the diagram of FIG.
Furthermore, this we>uld bring about a corresponding
change of axial deformation of the sensor 13 and a
corresponding axial displacement of the ring 11.
In accordance with a further. feature of the
invention, it is possible to construct the improved
friction clutch in such a way that the resultant of
forces acting upon the diaphragm spring 4 increases in
response to increasing wear upon the friction linings 7.
Such increase can be limited to a certain stage or
portion of the maximum permissible displacement due t:o
wear upon the friction linings 7. As mentioned above,
the wear upon the friction linings is norma 1 1y more
pronounced than the wear upon the flywheel 6 and upon the
CA 02446426 2003-11-12
pressure plate 3d therefore, the preceding and the nexa~-
following passages of this description refer primarily or
exclusively to wear upon the friction =Linings. The
increase of the magnitude of forces acting upon the
diaphragm spring 4 can take place as a result of
appropriate design of the sensor 13. FIG. ~ shows by
broken lines, as at 47a, the characteristic curve
denoting a thus modified sensor 1.3 within the range 48.
If the magnitude of forces acting upon the diaphragm
spring 4 increases a.n response to progressing wear upon
the friction linings 7, one can at least partially
compensate for a reduction of the force which the spring
4 applies to the pr~assure plate 3 due to a reduction of
resiliency of the segments 10, e.g., as a resu It ref
penetration or embedding of these segments into the
adjacent friction linings 7. It is particular 1y
advantageous if the force for the diaphragm spring 4
increases proportionally with (i.e., at the same rate or
nearly at the same rate asy the setting or reduction of
bias of the segments 10, for example, due to the
aforediscussed embedding into the adjacent friction
linings 7. In other words, as the thickness of the
clutch disc 8 in the region of the friction linings ;~
decreases (i.e., as the distance between the two sets of
friction linings decreases due to the reduced bias of the
segments 10 as a result of penetration into the friction
linings and/or due to wear upon the friction linings),
the magnitude of forces acting upon the diaphragm spr.i.ng
4 increases accordingly. It is of particular advantage
if the magnitude of such forces increases in such a way
46
CA 02446426 2003-11-12
that the increase is :more pronounced dux°ing a f first stacge
and less pronounced during a next-following second stagy .
These two stages are 'within the distance 48 as measured
along the abscissa of the coordinate system which is
shown in FIG. 9. The just outlined design is desirable
and advantageous because- the major part of penetration of
segments 10 into the adjacent friction linings 7 takes
place mainly during a relatively short period of the full
useful life of the friction clutch; thereafter, the
positions of the segncents 10 relative to the adjacent
friction linings 7 care more or less stabilized. Thus,
once a certain penetg°ation has taken place, thus variable
parameter or factor c:an be disregarded because it no
longer affects the operation of the adjusting unit 16.
The change of magnitude of the force acting upon the
diaphragm spring 4 can also take place at least during a
certain stage of wea~~ upon the friction linings 7.
The preceding description of operation of the
adjusting unit 15 to compensate for wear upon the
friction linings.? did not take into consideration the
axially oriented forces which are or which can be
generated by the leaf springs 9 serving to axially
movably but non-rotatably couple the pressure plate 3 t~
the flywheel 6 and cover 2. If the leaf springs g are
installed in stressed condition so that they tend to move
the pressure plate 3 axially and away from the adjacent
friction linings 7, i.e., in a sense to bias the portion
or portions 3a of the pressure plate 3~ against the
diaphragm spring 4, the leaf springs ~ are in a condi~ti.on
to assist the disengagement of the friction clutch 1.
47
CA 02446426 2003-11-12
Thus, the axially oriented force which is applied by the
leaf springs 9 is superimposed 'upon the forces which are
being applied by the sensor 13 and by the diaphragm
spring 4 as well as upon the disengaging force which is
being applied (e. g., by a suitable disengaging bearing
against the tips 4c of the prongs 4b. Such function of
the leaf springs 9 is not considered in the d iagrams'of
FIGS. 8 to I1. fhe overall force which is being applied
to the diaphragm sprang 4 in disengaged condit ion of the
friction clutch 1 to cause the spring 4 to bear upon the
ring 12 of the seat ~ is the sum of forces which are
generated primarily by the leaf springs 9, sensor 13 and
the applied disengaging force acting upon the tips 4c of
prongs 4b forming part of the spring 4.
The leaf springs 9 can be installed between the
cover 2 and the pressure plate 3 in such a way that the it
axially oriented force acting upon the diaphragm spring 4
increases in response to progressing wear upon the
friction linings 7. For example, the magnitude of axial
force exerted by the leaf springs 9 upon the diaphragm
spring 4 in response: to increasing wear upon the frict i on
linings 7 can increase in accordance with a curve 47b
which is shown in the diagram of FIG. ~ and denotes the
variations of such force upon the spring 4 within the
distance 48. FIG. g further shows that, as the
deformation of the sensor 13 increases, the restoring
force of the leaf springs 9 upon the pressure plate 3
(this force is also applied to the di,aphrag~ spring 4)
also increases. ~y totalizing the forces denoted by the
curve 47b and the characteristic curve of t~-ae diaphragm
48
CA 02446426 2003-11-12
spring, one arrives at a resultant force which acts upon
the spring 4 in the axial direction in a sense to bias
this spring against tie ring 12 of the seat 5. In order_y
to obtain a variation of forces as denoted by the curve
47b of FIG. 9, it is desirable to design the sensor Z3 i.n
such a way that its characteristic curve corresponds to
that shown at 47c in FIG. 9. By summarizing the forces
denoted by the curves 47b and 47c in the diagram of FIG.
9, one arrives at a ~.um of forces denoted by the curve
47a. Thus, the magn~.tude of the force to be applied by
the sensor 13 can be reduced by the.simple expedient of
stressing the leaf springs 9. Furthermore, by properly
designing and mounting the leaf springs 9, it is possik~le
to reduce (at least in part) the bias of the resilient
segments ZO and/or (at least in part) the extent of
penetration of segments ZO into the adjacent friction
linings 7. Thus, one can ensure that the diaphragm
spring 4 maintains a substantially unchanged operating
point or the same operating range, i.e., the bias of t9Ze
spring 4 upon the pressure plate 3 remains at least
substantially unchanged during the entire useful life of
the friction clutch 1. It is further necessary or
desirable to take ir.~~to consideration (during designing of
the improved friction clutch and particularly in
connection with the design of the sensor 13 and leaf
springs 9) the resultant axial forces which are generated
by the torsion springs 26, 26a and act upon the member 17
of the adjusting unit 16 in a sense to oppose the bias of
the sensor 13 and/or the bias ~f the leaf springs 9.
If the friction clutch of tl:~e present invewtion
4~
CA 02446426 2003-11-12
is des i fined to employ prestressed leaf springs 9, it is
further necessary or advisable to take into consideration
that the prestressin.g of the springs 9 influences the
axial f once which the pressure plate 3 applies to the
adjacent friction linings '7. 'thus, if the leaf springs 9
are pre stressed in a sense to urge the pressure plate 3
toward the diaphrag~a spring 4, the force which is applied
by the diaphragm spring ~ is reduced by the extent of
prestre ssing of the leaf springs 9. Consequent 1y, the:
friction clutch then operates in such a way that the
resultant axial force acting upon the pressure plate ?.
and hence upon the adjacent friction linings °~ includes
the force of the spring 4 and the force resulting from
prestressing of the leaf springs 9. If one assumes that
the curve 40 in the diagram of FIG. 8 denotes the
resultant of the forces due to bias of: the spring 4 plus
the force attributable to prestressing of the leaf
springs 9 in unused condition of the friction clutch, a
reduction of the distance of the pressure plate 3 froxa
the flywheel 6 due to wear upon the friction linings 7
would result in a shifting of the resulting forces in a
sense toward a reduction of forces. :EIG. 8 shows a
broken-line curve 4~7a which corresponds, for example, to
a wear in the range of 1.5 mm. Such wear can develop
during the useful life of the friction clutch Z, and a
shifting from the curve 4 0 toward the curare 4 Oa resul.ts
in a reduction of axial force which is being applied by
the diaphragm spring 4 to the sensor 1.3 during
disengagement of the friction clutch; such reduction of
the axial force is ,attributable to th.e fact that, as tree
CA 02446426 2003-11-12
wear upon the friction linings 7 progresses, the moment
which i s being applied by the leaf springs 9 to the
spring 4 and acts in the opposite direction also
increases. Such moment develops due to the existence of
a radial clearance between the seat 5 and the diameter of
the annulus defined by the portion or portions 3a of the
pressure plate 3, i.e., at the locus of engagement ,'
between the pressure plate and the spring ~. In
designing the friction clutch 1, it is of particular
importance to ensure that the increasing bias of the leaf
springs 9 (as a result of wear upon the friction linings
7) is less than the increase of disengaging force which
is also attributable to wear upon the friction linings
and causes a tilting of the sensor 13 which is necessary
to cause the unit 16 to carry out the necessary
adjustment. Otherwise, the biasing force of the pressure
plate 3 upon the friction linings 7 would decrease in
engaged condition of the friction clutch and this would
prevent any adjustments of the seat 5.
An important advantage of the torque varying
resilient segments 10 is that the torque which is being
transmitted by the hub 8a of the clutch disc 8 to the
input element of a transmission decreases gradually, at
least during a portion of movement of the prongs 4b of
the diaphragm spring 4 in the direction to disengage the
friction clutch 1. Furthermore, the resilient segments
10 ensure a gradual (progressive) increase of torque
which is being transmitted by the clutch disc 8, at least
during a portion of movement of the prongs 4b in a
direction to engage the friction clutch l, particularly
~1
CA 02446426 2003-11-12
during the initial stage of clamping of the two sets of
friction linings 7 at opposite sides of the resilient
segments 10 between the friction surfaces of the pressure
plate 3 and flywheel or counterpressure plate E~.
Another important advantage of the iztaproved
friction clutch 1 is that the stressing of the diaphrac~a
spring 4 in engaged condition of the friction c latch 1
remains at least substantially unchanged during each and
every stage of useful life of the friction clutch.
Otherwise stated, the bias of the diaphragm spring 4 upon
the adjacent portion or portions 3a of the pressure plate
3 remains at least substantially unchanged irrespective
of the extent of wear upon the friction linings 7.
A further important advantage of the friction
clutch 1 is that, due to gradual reduction of torque
which can be transmitted by the clutch disc 8 during
disengagement of the friction clutch, it is now possible
to greatly reduce (minimize] the magnitude of the force
which must be appl~.ed to disengage the clutch, i.e., it
is possible to optimize the progress of variation of
disengaging force when the pressure plate 3 is being
moved away from the flywheel ~. This is due to the fact
that the resilient segments ~.0 assist the actuation of
the friction clutch, particularly the disengagement of
the clutch when the tips 4c of the prongs 4b forming part
of the diaphragm spring 4 move in a direction to permit
the resilient segments 2b to dissipate energy while the
pressure plate 3 is in the process of moving axially and
away from the flywheel 6. Though FIGS. ~ and 2 show a
friction clutch wherein the resilient segments 10 are
~2
CA 02446426 2003-11-12
disposed between the two sets of friction linings ?a it
is equally possible to employ resilient means which are
or is analogous to the segments 10 but are or is designed
and mounted to apply a reaction force to the prongs 4b of
the diaphragm spring 4 (i.e., to the actuating means of
the means for engaging and disengaging the friction
clutch 1) and/or to another part of the diaphragm spring
4 and/or to the pressure plate 3 and/or to the flywheel
6, Such reaction force acts counter to the action of the
diaphragm spring 4 in a direction to urge the pressure
plate 3 against the adjacent set of friction linings ?.
Furthermore, the resilient segments 10 and/or their
equivalents) is or are disposed in series with the
diaphragm spring 4.
A particularly desirable and advantageous
feature of the resilient segments 10 and/or of their
equivalent (s) is that they can ensure a gradual reduction
of torque which is being transmitted by the clutch disc 8
during a portion of movement of the prongs 4 b in a
direction to effect a disengagement of the friction
clutch 1, i.e., that such reduction of transmittable
torque takes place during a certain stage of movement of
the pressure plate 3 away from the flywheel 6.
An equivalent of the resilient segments 10 can
be installed in the power train between the seat ~ for
the diaphragm spring 4 and the fasteners 6a which secure
the cover 2 to the flywheel 6, or between the diaphragm
spring 4 and the fasteners 6a. Alternatively, or in
addition to the provision of torque varying means between
the two sets of friction linings ? and/or between the
53
CA 02446426 2003-11-12
seat 5 -and the fasteners 6a, it is also possible (and
often desirable and advantageous) to install torque
varying means between the seat ~ or the diaphragm spring
4 on the one hand, and the friction surface of the
pressure plate 3 on the other hand. Reference may be
had, for example, to published German patent application
Serial No. 37 42 354 and/or to published German patent
applicat ion Serial No. 1 450 201.
Still further, it is possible to install an
equivalent of the resilient segments 10 in another
portion of the friction clutch in addition to the
segments ~.0 between the two sets of friction linings 7.
As concerns the installation of resilient segments
between two sets of friction linings, reference may be
had, for example, to published German patent application
Serial No. 36 31 863.
Still further, it is within the purview of the
invention to gradually increase and/or reduce the
magnitude of transmitted torque during engagement or
disengagement of the friction clutch by instal ling an
equivalent of resilient segments 1~ in a manner as
disclosed in published German patent application Serial
No. 21 64 297. Thus, it is possible to employ a
composite (twin-mass) flywheel including a first mass
which is connected to and receives torque from the output
element of an internal combustion engine, and a second
mass which constitutes or includes a counterpressure
plate and is axially movably coupled with the f first mass
by resilient means so that the resilient means opposes a
movement of the second mass at least toward or at least
54
CA 02446426 2003-11-12
away from the first mass .
The operation of the improved friction clutch
is part icularly satisfactory if the resilient torque
varying means is installed to permit movements of certain
parts of the friction clutch toward and away from each
other against the opposition of a spring bias. The
arrangement is preferably such that the magnitude of the
force opposing axial movements of certain parts relative
to each other is smallest when the friction clutch is
disengaged but that the magnitude of the force opposing
axial movements of certain parts relative to each other
gradually rises to a maximum value during clamping of the
friction linings 7, i.e., during engagement of the
fraction clutch. Such rise of the opposing force need
not take place during the entire engagement stage. It
has been found that the improved friction clutch operates
highly satisfactorily if the magnitude of the
aforediscussed force which opposes axial movements of
certain parts of the friction clutch relative to each
other gradually increases during between 40 and 70
percent of movement of the prongs 4b in a direction to
engage the friction clutch and gradually decree ses during
between about 40 and 70 percent of movement of the prongs
4b in a direction to disengage the friction clutch. The
remaining portions of movement of the prongs 4 b during
engagement and disengagement of the friction c latch are
needed to ensure reliable interruption of power flow, to
establish full transmission of torque and/or to
compensate for possible deformation of certain parts of
the friction clutch (especially the clutch disc, the
CA 02446426 2003-11-12
pressure plate and/or the counterpressure plate).
The feature that the diaphragm spring 4 has a
depressive force-to-displacement ratio is desirable and
advantageous because this renders it possible to minimize
the forces which are required to engage or disengage the
friction clutch, especially to minimize the forces which
are required to disengage the clutch. Such depressive
character need not be effective during the ent ire stage
of disengagement of the friction clutch. ~ther~,rise
stated, it is desirable to ensure that the magnitude of
the force which is being applied by the diaphragm spring
4 will decrease at least during a certain stage of its
compression or deforming movement while the friction
clutch is being disengaged so that, during such stage,
the stressing and/or deformation of the diaphragm spring
4 is assisted by the resilient torque varying segments 10
and/or their equivalents.
At the same time, and due to the depressive
force-to-distance ratio of the spring 4 during a certa in
stage of disengagement of the friction clutch, the
magnitude of the force which the spring 4 exerts upon the
friction linings 7 through the pressure plate 3 is on the
decrease. In the absence of any other superimposed
spring-generated forces, the effective force which is
required to disengage the improved friction clutch equals
the difference between the force which is being applied
by the torque varying means 10 (and/or their equivalent
or equivalents) and the force of the diaphragm spring 4.
When the pressure plate 3 is being lifted off the
adjacent friction linings 7, i.e., when the pressure
56
CA 02446426 2003-11-12
plate releases the clutch disc 8, the remainder of
movement of the prongs ~b in a direction to complete the
disengagement oz the friction clutch 1 will be effected
primarily by the diaphragm spring 4. The force-to-
displacement ratios of the diaphragm spring 4 and torque
varying means 10 can be related to each other in such a
way that, when the clutch disc 8 is released by the
pressure plate 3, a relatively small force is needed to
actuate the diaphragm spring. In other words, by
properly relating the aforediscussed ratios or
characteristics of the spring 4 arid torque varying means
10 (e.g., by causing these characteristics to be
identical or to only negligibly deviate Pram each other),
it is possible to ensure that only a very small force
(and in an extreme case zero forced is necessary to move
the diaphragm spring 4 up to the instant of disengagement
of the clutch disc 8 by the pressure plate 3.
Though it is possible to bias the pressure
plate 3 by a resilient device other than a diaphragm
spring 4 , it is presently preferred to employ a diaphragm
spring and to mount the diaphragm spring in the seat 5 so
that it is tiltable relative to the cover 2 and can bear
against one or more selected portions 3a of the pre ssure
plate 3. This also simplifies the means for engaging and
disengaging the friction clutch I because the radially
inwardly extending prongs 4b of such diaphragm spring can
constitute the actuating means of such clutch
engaging/disengaging means. However, it is equally
possible to employ modified engaging/disengaging means,
e.g., including levers which are pivotably mounted on the
57
CA 02446426 2003-11-12
cover 2 or on another part of the friction clutch.
The diaphragm spring 4 can be replaced, for
example, with coil springs which are then installed in
the friction clutch in such a way that their force acting
axially upon the pressure plate 3 reaches a maximum value
when the clutch is engaged but decreases during
disengagement of the clutch. These characteristics can
be achieved, for example, by mounting the coil springs in
such a way that they are inclined with reference to the
to rotational axis x-X of the clutch.
The utilization of a diaphragm spring 4 which
is tiltable relative to a seat 5 on the housing 2 of the
improved friction clutch is desirable and advantageous on
the additional ground that this renders it pos Bible to
design the clutch as a so~-called push-type or depressioa-i--
type clutch. In such friction clutches, the means for
disengaging the clutch is normally moved in a direction
toward the pressure plate, i.e., in a direct iota to the
Left as seen in FIG. 2. However, the present invention
20 can be embodied with equal advantage in so-cal led pull-
type friction clutches wherein (again referring to FIG.
2) the prongs 4b or the equi~9alents of such actuating
means must be moved in a direction to the rfight in order
to disengage the friction clutch.
As already described with reference to FIG.
it is often preferred to employ a diaphragm spring ~
having a substantially sinusoidal characterfist is curve
and being installed in the housing 2 in such a way that,
when the friction clutch is engaged ~ the operating point
30 of the diaphragm spring is located within a degressive
58
CA 02446426 2003-11-12
portion of the curve following the first maximum of such
curve. The so-called force ratio of the diaphragm spring
4 whose characteristic curve coincides with or is similar
to the sinusoidal curve in the diaphragm of FIG. 8 can be
within a range of approximately 1:0.~ and 1:0.7 between
the first maximum and the next-following lowest point or
minimum of the curve.
If the improved friction clutch is installed in
a motor vehicle, the means for engaging and disengaging
can further comprise a pedal which resembles or is
analogous to a standard gas pedal and is installed in the
vehicle to serve as a means for moving the tips 4c of the
prongs 4b along their predetermined path in a direction
to disengage andjor engage the friction clutch. The
utilization of a pedal which is similar or analogous to a
gas pedal is of particular advantage in view of the
aforediscussed characteristics of the improved friction
clutch. Thus, and since the force which is required to
disengage the friction clutch is relatively sans 11 or
extremely small, such relatively small force can be
selected (metered) with a high degree of accuracy and
reproducibility if the means for moving the prongs 4b
along their path is a pedal, i.e., a device whose
manipulation is familiar to all drivers.
A further important advantage of the improved
friction clutch is that, due to the aforediscussed
possibility of greatly reducing the maximum forces which
must be applied during the entire useful life of the
clutch (i.e., that the forces to be applied need not be
increased as the wear upon the friction linings 7
CA 02446426 2003-11-12
progresses), it is now possible to reduce the dimensions
of various component parts of the friction clutch and to
greatly reduce the strength or stability of such parts.
This, in turn, contributes to a significant reduction: of
the cost of the friction clutch. Furthermore, the
afo rediscussed reduction of disengaging force renders it
pos Bible to greatly reduce losses due to friction and/or
losses due to decreasing resiliency of many parts of the
friction clutch, particularly in the disengaging means.
This greatly enhances the efficiency of the friction
clutch disengaging system. Moreover, this renders it
possible to achieve an optimal design of the friction
clutch and to render the manipulation of the friction
clutch more comfortable to the operator.
The aforediscussed improvements which were
described in connection with and are shown in the x
embodiment of rIGS. 1 to 11 can be utilized in a number
of presently known friction clutches. Examples of
friction clutches whose operation and/or other
characteristics can be improved by incorporating therein
the features of the present invention axe those described
and shown, for example, in German Pats. Nos. 29 16 755
and 29 20 932, in published German patent applications
Serial Nos. 35 18 781 and 40 92 382, in published French
patent applications Serial Nos. 2 605 692, 2 605 477, 2
599 444 and 2 599 446~ in British Pat. No. 1 567 018, in
U.S. Pats. Nos. 4,924,991, 4,191,285 and 4,05?,131, in
published Japanese patent application Serial No.
51-126452, and in Japanese Utility Models idos. 3-25026,
3-123, 2-124326, 1-163218~ 3-19131 arid 3'53628.
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CA 02446426 2003-11-12
Reference may also be had to commonly awned
copending. German patent applications T~Tos . P ~ 2 07
528.9 and F 42 06 904. Z. The entire disclosures of these
copending applications are believed to be of interest in
connection with this specification.
The provision of the adjusting unit 16~ which
compensates for wear upon at least one component
(particularly the friction linings 7) of the improved
friction clutch l, brings about the additional advantage
that it is now possible to optimize the design and the
operation o~ tiie friction clutch, especially of the
diaphragm spring 4 which is called upon to bia s the
pressure plate 3 against the adjacent set of friction
linings 7 in engaged condition of the clutch. The
diaphragm spring 4 can be designed in such a way that it
is merely called upon to furnish only that force which is
required for transmission of the desired torque, i.e., to
clamp the pressure plate 3 against the clutch disc 8 only
with a force which ensures that the clutch dis c 8 can
transmit requisite torque to the input element of a
variable-speed transmission or the like. As mentioned
above, it is not absolutely necessary to employ a
resilient device in the norm of a diaphragm spring, such
as the diaphragm spring 4; it is also possible to employ
two or more resilient devices such as a set of coil
springs which cari be distributed and oriented in a manner
as already described hereinbefore.
FIGS. 12 and 13 illustrate certain de tails of a
modified torque transmitting friction clutch 101. One of
the differences between the friction clutches 1 and 7.01
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is that the latter employs three coil spr ings 126 (itwo
shown in FIG. 12) which replace the torsion springs 26~
26a in the friction clutch 1 and serve to bias the
annular member 117 of the adjusting unit 116 for the bias
c~f the diaphragm spring 4. As concerns its function, the
member 117 is an equivalent of the member 17, i.e~, it
can cooperate with an annulus corresponding to the
annulus 25 of FIGS. 5 and 6 to move the portion 111 of
the seat 105 in a direction to the right (as viewed in
FIG. 13) to an extent which is necessary to compensate
for wear upon the friction linings :107 of the clutch
plate or disc 108.
The friction clutch 101 employs three coil
springs 126 which are equidistant from each other p_n the
circumferential direction of the housing or cover 2 and
are installed in stressed condition to bias the member
117 relative to the bottom wall 2a of the cover. As can
be seen in FIG. 14, the inner marginal portion of i:.he
member 117 is prcwided with axially, radially and
circumferentially~ extending projections 127 which serve
a~ stops for the adjacent ends of the respective coil
springs 126. The stops 127 are acted upon by the
respective springs 126 in a sense to tend to turn the
member 117 about the axis of the ccsver 2 in a direction
to move the port~_on 111 of the seat: 105 for the diaphragm
spring 4 toward tahe pressure plate 103. The springs 126
have an arcuate shape because they are adjacent the
convex outer sides of arcuate guides 129 forming part of
or affixed to thf: member 117~ The other end of each coil
spring 126 is in engagement with a discrete post 128
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which is anchored in the bottom wall 2a of the coven 2.
,:.
The illustrated posts 128 have external threads which
mate with the threads of tapped bores provided therefor
in the bottom wall 2a. However, it is equally possible
to replace the externally threaded posts 128 with
integral projections in the form of lugs or the like
which are obtained by displacing selected portions of the
bottom wall 2a in a direction toward the pressure plate
103. Such making of posts or like parts which are of one
piece with the bottom wall 2a is particularly
advantageous and simple if the cover 2 ~_s made of a
metallic sheet material.
The length of the arcuate guides 129 is
preferably selected in such a way that they can
adequately guide the respective coil springs 126 during
each stage of angular displacement of the member 117
relative to the bottom wall 2a~ i.e., during each stage
of compensation for wear upon the friction linings 107,
pressure plate 103 and/or counterpa-essure plate 105. The
configuration of the guides 129 is such that they can
properly prop the respective coil springs 126 from within
(i.e., at the concave sides of the arcuate springs) as
well as in the axial direction of the bottom wall 2a.
Each of the guides 129 can define an arcuate groove or
channel which receives a portion of the respective coil
spring 126 between the respective post 128 and the:
respective projection 127. This ensures highly
predictable positioning of the coil springs 126 relative
to the member 117 and guarantees that these coil springs
can turn the member 117 in the proper direction (to move
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the seat portion 111 toward the pressure p late 103)
whenever necessary in order to compensate for wear 'upon
the linings 107, pressure plate 103 and/or
counterpressure plate 106. The configurat ion of the
surfaces bounding the channels of tl~.e guides 129 on the
member 117 can conform to the configuration of the
adjacent portions of the respective coil springs 126.
Such configuration of the surfaces bounding the channels
or grooves in the guides 129 ensures that the coil
springs 126 are adequately guided when the cover 2 is
idle as well as when the cover is rotated by the
counterpressure plate 106 (this counterpressure plate can
constitute or form part of a flywheel which receives
torque from the output shaft of a combust ion engine in a
motor vehicle).
In order to even more reliably ensure optimal
retention of coif. springs 126 in requisite positions
relative to the bottom wall 2a and the member 117, the
radially inner portion of the bottom wall 2a can be
provided with axially extending arms 130 which are
disposed radially inwardly of the coil springs (se.e FIG.
Z3) . The individual arms 130 can be replaced with a
circumferentially complete cylindrical collar of t:he
bottom wall 2a. The arms 130 or the aforementioned
circumferentiall~r complete collar of the bottom wall 2a
can perform the ~~dditional function of serving as an
abutment for the adjacent portions of the diaphragm
spring 4, i.e., such collar or the army 130 can limit the
extent of dissipation of energy by the diaphragm spring
4.
64
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The provision of means for guiding the coil
springs 126 exhibits the advantage that, when the
friction clutch 101 is rotated by a combustion engine or
the like, the convolutions of the springs 126 cannot
leave the illustrated positions under the action of
centrifugal force, ioe~, they cannot move into frictional
engagement with the adjacent portions (such as ramps) oz
the member 117; this would result in the development of
undesirable friction which would prevent the springs 126
ZO from changing the angular position of the member 117 in a
manner to accurately compensate for wear upon
the friction linings 10'7, pressure plate 103 and/or
counterpressure plate 106. When the friction clutch 101
is driven, the coil springs 126 preferably behave not
unlike solid bodies, i.e.,~ they are in frictional
engagement with the adjacent guides 129 and such
frictional engagement suffices to prevent any angular
displacement of the member 117. The arrangement can be
such that, when the rotational speed of the friction
20 clutch 101 exceeds the idling speed of the eragine,
frictional engagement between the coil springs 126 and
the guides 129 under the action of centrifugal force
suffices to prevent any angular displacement of the
member 117 relative to the bottom wall 2a of the cover 2,
i.e., the springs 126 cannot change the angular position
of the member 117. Thus, the angular position of the
member 217 with reference to the cover 2 (in order to
move the seat portion 111 toward the pressure plate 103)
can take place only when the rotational speed of the
30 friction clutch 101 does not exceed the idling speed of
CA 02446426 2003-11-12
the engine. In ~ther words, it is necessary to operate
the friction clutch 101 in such a way that its rotational
speed is relatively low in order to enable the springs
126 to change the angular position of the member 117
relative to the bottom wall 2a {3f necessary).
It is equally possible to block any turning of
the member 117 relative to the bottom wall 2a in any one
of a number of other ways, i.e., not necessarily as a
result of pronounced frictional engagement with the:
surfaces bounding the grooves or channels of the
respective guides 129. For example, the arrangemerat may
be such that the coil springs 126 can change the angular
position of the member 117 relative to the bottom wall 2a
only when the friction clutch 101 is not driven.
The just discussed feature of the friction
clutch 101 can be incorporated with equal advantage in
the friction clutch 1 of FIGS. 1 and 2. The arrangement
may be such that the angular position of the member 17
relative to the annulus 25 can be changed only when the
clutch 1 is riot driven at all or when the clutch 1
rotates within a relatively low range of speeds. For
example, the housing or cover 2 of the friction clutch 1
of FIGS. 1 and 2 can be provided with means which prevent
the torsion spring 26 and/or 26a from changing the
angular position of the member 17 relative to the annulus
when the member 17 is acted upon by centrifugal. force,
i.e., when the friction clutch 1 is driven by the engine
in a motor vehicle or the like. For example, the bottom
wall 2a of the cover 2 in the friction clutch 1 can carry
one or more flyweights which move radially outwardly
66
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under the action of centrifugal force to thereby
interfere with any chant;es in the angular position of the
member 17 relative to the annulus 25, either by directly
engaging the member 17 and/or by preventing the spring 26
and/or 26a from changing the~angular position oz the
member 17 in the cover 2. The flyweight or flyweights
can be aesigned and mounted to bear against the radiaily
innermost portion of thca member 17 when the Eric tion
clutch 1 of FIGS. 1 and 2 is driven. The flywefight or
flyweights must be capable of engaging and hold i ng the
member i7 with a force which exceeds the bias of the
springs 26, 26a, at least when the rotational speed of
the friction clutch 1 reaches a certain value.
Referring again to FIGS. 12-14, the friction
clutch i01 can be modified by providing radial supports
for portions of or for the entire coil springs 126. Such
radial supports can be installed on or they can form part
of the bottom wall 2a of the cover 2 in the fri etion
clutch 101: for example, the radial supports c an be made
of. one piece with the posts 128. Thus, each post 128 can
be replaced with a substantially L-shaped. element which
includes a portion extending in the circumferen tial
direction of the cover 2 and into the adjacent end
convolutions of the respective coil spring 12~: Such
portions of the L-shaped elements act not unlike
retainers and hold the surrounding end canvolut ions of
the respective coil springs 126 against radial movement
relative to the bottom wall 2a.
FIG. 13 illustxvates that the wire ring 11 of
the seat 5 which is shown in FIG. 2 can be omitted. Mor°e
67
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specifically, the wire ring 11 is replaced by a radia lly
inner portion 111 of the sensor 113. The portion 111 can
be assembled of several sections each forming part of one
of the tongues 113c of the sensor 11.3. Those sides of
the tongues 113c which engage the diaphragm spring 4 in
lieu of a wire rirxg 11 or the like c:an have a convex: or
substantially convex shape. Thus, the sensor 113 of FIG.
13 can perform the combined functions of the sensor 13
and wire ring 11 in the friction clutch 1 of FIGS. ~. and
2.
FIGS. 15 to 17 illustrate certain details of a
further torque transmitting friction clutch 201 wherein
the circumferentially complete annular adjusting member
17 or 117 is replaced with a set of discrete buttow- or
washer-like adjusting and wear compensating members 217.
The discrete members 217 are equidistant from each other
in the circumferential direction of the cover or housing
202 and each of these members has a ramp 218 which
extends at one of its sides in the circumferential
direction to cooperate with an adjacent ramp 224 of the
annulus 225 forming part of the bottom wall 202a of the
cover 202. Each of the illustrated members 217 hav; a
central opening 219 (e. g., a circular bore or hole) which
receives a portion of an axially parallel pin-shaped
extension 215a of a rivet in such a way tYaat each nnember
217 can turn about the axis of the respective extension
215a. The annulus 225 is an integral part of the bottom
wall 202a and is provided with the oforementioned ramps
224 cooperating with the ramps 218 of the neighbor:i.ng
members 217 to automatically shift (when necessary) the
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ring 212 of the seat 205 toward the pressure plate 203 in
order to compensate for wear upon the frict ion linings
207, the pressure plate 203 and/or the counterpressure
plate: (not shown in FIG. 15j. The members 2 17 are
turnable about the axes of the respective extensions 215a
by springs 226 in a sense to move the ramp s 218 along the
neighboring ramps 224 and to thus shift the ring 212
toward the pressure plate 203. Eacri spring 226 resembles
a helix which surrounds the respective extension 215a,
which reacts against the bottom wall 202a and which bears
against the corresponding member 217. The end portions
of the helical springs 226 are suitably bent so that they
can more reliably engage the bottom wall 2 02a and the
respective members 217, respectively. For example, the
end portions of the springs 226 can be provided with
lugs, legs or like projections. When the diaphragm
spring 204 is moved axially of the friction clutch 201 of
FIG. 15 due to wear upon the friction linings 207,,
pressure plate 203 and/or the non-illustrated
counterpressure plate, the springs 226 are free to change
the angular positions of the respective members 21'7
relative to the corresponding extensions 2 15a and to thus
move the ring 212 toward the pressure plate 203; this
compensates for the aforediscussed wear, primarily upon
the friction linings 207.
The sensor 213 of the friction clutch 201 of
FIG. 15 bears against lugs 214 which are shown in the
form of integral portions of the axially extending part
of the cover 202. The lugs 214 preferably constitute
inwardly bent parts of the cover which are deformed to
69
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the extent necessary to engage the radially outer port ion
of the sensor 213.
An advantage of the discrete annular members
217 is that they are less likely to change their
positions under the action of centrifugal force, i.e.~
they are not like:Ly to turn about the respe=ctive
extens ions 215a a s a result of rotat=ion of the coven 2 02
about its own axis. In other words,. the adjusting action
of such discrete members 217 is not affected by the
magnitude of the centrifugal force.
The discrete annular adjusting members 217 fn
the friction clutch which is shown in FIG. 15 can be
replaced with discrete wedge-like or analogous adjust ing
members which are mounted for movement in the radial
and/or circumferential direction of the c~ver 202 i,n
order to cooperate with complementary parts on the bottom
wall 202a in a sense to displace the ring 212 toward the
pressure plate 203 when the need arises, i.e., in order
to compensate for wear upon the counterpre ssure plate,
the pressure plate 203 and/or the friction linings 207.
Each wedge-like adjusting member can be provided with a
longitudinally extending recess to receive a portion of
an extension 215a or a like part of or on the bottom wall
202x. This ensures that each wedge-like member can carry
out a movement only in a direction which i.s necessary to
adjust the axial position of the ring 212~ The
arrangement may be such that the wedge-like members which
are to be used in lieu of the discrete washer-like
members 217 of F1G. I5 are acted upon by centrifugal
force in order to move radially and/or circumferentially
CA 02446426 2003-11-12
" of tha wall 202a in order to compensate for iaear,
particularly for wear upon the friction linings 207.
However, it is equally possible to employ springs which .
cooperate with wef~ge-like adjusting members to shift such
adjusting members along suitable configurations (such as
ramps 224) of the bottom wall 202a an order to move the
ring 212 axially toward the pressure plate 203. The
extensions 21,5a can be replaced with other suitable guide
means for the wedge-like adjusting members which cam be
used in lieu of the washer-like members 217; for
example, the bottom wall 202a can be grooved to est;.ablish
predetermined paths for movement of the wedge-like
members relative to the cover 202.
The ramps 224 can be provided on the bottom
wall 202a to project toward the adjacent annular members
217 from a plane which is normal to the axis of the cover
202. Alternatively, such ramps can be prcwided on the
adjacent portions of the diaphragm spring 204. This also
applies for the embodiments of FIGS. 1-2 and 12-13. It
is also possible to provide the annular members 17, 117
and/or 217 with two sets of ramps 218, one at each side,
and to provide complementary ramps 24, 12 4 or 224 on the
bottom wall 2a, 102a or 202a and on the corresponding
diaphragm spring 4, 104 or 204. If the adjusting members
are wedges or if they resemble wedges, it is advisable to
make them from a lightweight material in order to
minimize the influence of centrifugal force.
The selection of materials for the cooperating
ramps (such as 18 and 24) also plays an important role in
connection with the reliability of adjustment of the
71
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diaphragm spring toward the clutch disc of the improved
friction clutch. An important prerequisite is to select
the material of the member 17 or 117 or of the members
217 and the material of the adjacent annulus 25, 125 or
225 in such a way that the ramps of such parts will. not
exhibit a tendency to adhere to each other irrespective
of the momentary stage of the useful life of the
respective friction clutch. For example, adherence of
one set of ramps tc the neighboring ramps can be
prevented or avoided by coating at least one of these
sets of ramps with a suitable friction-reducing ma-cerial.
If the one and/or the other set oz ramps consists of a
metallic material, the coating substance will or can be
selected with a view to prevent corrosion.
Another mode of preventing the ramps of one set
from adhering to the ramps of the other set or sets (and
from thus preventing, or interfering with accuracy of,
adjustment of the aiaphragm spring toward the pressure
plate in order to compensate for wear) is to make the
materials of the two or more sets of ramps (such as the
materials of the annular member 1°7 and the annulus 25 in
the embodiment of FIGS. 1 ana 2) of materials having
different thermal expansion coefficients. As a rule, the
temperature of the friction clutch 1 will fluctuate in
actual use as well as prior to and between actual uses) or
during and subsequent to actual use. This will entail
certain minimal movements of the neighboring ramps 18, 24
relative to each other whenever the temperature of the
member 17 and annulus 25 changes. The aforementioned
mode of selecting the materials of the member I7 and
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annulus 25 (so that they have different thermal expansion
coefficients) ensures that the ramps 18 cannot adhere to
the ramps 24, i.e., that the adjusting unit 16 is always
in condition to carry out all necessary adjustments ira
exact dependency on the extent of wear upon the friction
linings 7 and/or pressure plate 3 and/or counterpressure
plate or flywheel 6.
Still another mode of preventing adherence of
neighboring sets of ramps to each other is to selects the
30 configuration and/or the deformability (stability) of the
corresponding parts (such as the member 17 and the
annulus 25 in the friction clutch 1 of FIGS. 1 and 2)
with a view to ensure that the actian of centrifugal
force upon the parts 17 and 25 is not the same, i.e.,
that such parts will perform certain movements relative
to each other in response to rotation' of the friction
clutch 1 with the result that the extent of movement of
the ramps 18 will depart from that of the ramps 24 and
the two sets of ramps will be incapable of adhering' to
20 one another.
~ further mode of preventing the ramps of' one
set from adhering to the ramps of the neighboring set or
sets is to ensure that the ramps of at lea st one set
(e.g., the ramps 18 in the friction clutch 1 of FIGS. 1-
2) are caused to perform at least some ax i al movements
relative to the neighboring ramps (such as 24) during
each disengagement of the friction clutch ( ~.. e. ~ dtaring
movement of the tips 4c of prongs 4b of the diaphragm
spring 4 along a predetermined path extend ing toward the
30 pressure plate 3 in order to deform the diaphragm spring
. . . 73
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4 and to permit the leaf springs 9 to shift the pressure
plate 3 axially and away from the flywheel 6) . The
adjusting member 17 of the unit 16 i;n the embodiment of
FIGS. 1-2 can be coupled with a suitable part or it can
be provided with suitable parts which move axially ~n
resporxse to development of wear at 7, 3 and/or 6. e'ouch
part or parts can be installed adjacent the seat 5, e.g.,
on the diaphragm spring 4 and/or on the sensor 13.
The diagram of FIG. 18 shows the character istic
curve 340 of a diaphragm spring corresponding to the
diaphragm spring 4 of FIGS. 1 and 2. The curve 340 has a
minimum or lowest point 345 denotinc; a re3.~atively s~~nall
force which is generated by the diaphragm spring and is
in the range of approximately 450 nm (as measured along
the ordinate) . The highest point or maximum of the curve
340 is located in the range of 7680 nm. The transmission
of force as a result of deformation of the diaphragm
spring, and as indicated by the curve 340 of FIG. 18~
takes place while the diaphragm spring bears against one
and reacts against another of two stops which are spaced
apart from each other in the radial direct ion of the
respective friction clutch. The situation is analogous
to that described with reference to the characteristic
curve 40 of the diaphragm spring 4 in the diagram of FIG.
8.
The characteristic curve 340 of the diaphragm
spring (such as 4) can be combined with the
characteristic curve 342 of a resilient a lament
corresponding to the segments 10 in the clutch disc 8 of
the friction clutch 1. As can be seen in FIG. 18, the
74
CA 02446426 2003-11-12
distance-to-force progress of the curve 342 is similar to
' that of the curve 340, i.e., these curves are rather
close to each other which denotes that a friction clutch
embodying the corresponding diaphragm spring~and
resilient segments 10 can be actuated in response t~o
exertion of a very small force. within the operating
range of the resilient segments 10, the theoretical
disengaging force corresponds to the difference between
two vertically aligned points, one on the curve 340 and
the other on the curve 342. One such difference is shown
in FIG. 18, as at 360. The actually required disengaging
force is further reduced by the corresponding lever° arms
of the actuating means, such as the prongs 4b of tie
diaphragm spring 4 in the friction clutch 3 of FIG:. 1
and 2. All this is analogous to the construction and
mode of operation of the friction clutch 1 as already
described with reference to FIGS. 1-2 and 8 -11.
The diagram of FIG. 18 further contains a curve
440 which is indicated by broken lines and has a minimum
or lowest point 445 denoting a negative f~rce which is
generated by a diaphragm spring. In other words, a
certain part of the force which is denoted by the curve
440 does not assist in engagement of the friction clutch
but rather tends to disengage the friction clutch" Thus,
if the deformation of diaphragm spring which is denoted
by the curve 440 progresses beyond the point 461, the
friction clutch does not exhibit a tendency to become
engaged but automatically remains disengaged. The
broken-line curve 442 denotes in FIG. 18 the
characteristic curve of resilient segments (such as 10 in
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the friction clutch of~ '~''IGS . 1-2 ) which can be used in
COIl~unction with the diaphragm spring having a
characters s tic curve corresponding to that shown at 440.
The curve 349 in the diagram of FIG. 19 denotes
the progress of a disengaging force which is to be
applied to the tips of the prongs of a diaphragm spring
(i.e., to the actuating means of the means for engaging
and diseng aging the friction clutch) when the friction
clutch ernp logs a diaphragm spring and resilient segments
of the character denoted by the curves 340 and 3 42 of
FIG. 18. As can be seen in FIG. 19, the curve 3 49
remains in the positive force range (above the abscissa
of the coordinate system of FIG. 19) which means that a
certain force in a direction to disengage the friction
clutch must be applied as long as the friction c hitch is
to remain in disengaged condition (the pressure plate 3
of FIGS. 1-2 is then disengaged from the adjacent set of
friction linings 7).
The broken--line curve 349 in the diagram of
FIG. 19 denotes the progress of a clutch diseng aging
force which develops when the diaphragm spring and the
resilient segments of the friction clutch sahib it
characteristic curves of the type shown at 440 and 442 in
the diagram of rFIG. 18. The curve 449 includes a portion
tat 449a) which denotes an initial decrease of the
disengaging force toward the abscissa and thereupon
transits from the positive side to the negative side of
the abscissa. This denotes that a friction clutch
employing a diaphragm spring represented by the curve 440
and resilient segments represented by the curve 442 can
76
CA 02446426 2003-11-12
remain in disengaged condition without the need for the
application of any disengaging force to the tips of the
prongs (actuating means) of the diaphragm spring.
FTGS. 20, 20a, 21 and 22 a.llustrate a portion
of a torque transmitting friction clutch 501, wherein the
diaphragm spring 513 which performs the function of a
sensor is coupled to the housing or cover 502 by a
bayonet mount 514 so that the sensor 513 is maintained in
a predetermined axial position relative to the bottom
wall 502a of the cover 502. The main portion 513b of the
sensor 513 is provided with radially outwardly extending
coupling portions or arms 5134 which are off set relative
to the general plane of the main portion 513b in a
direction toward the bottom wall 502a and into female
coupling portions 502ao provided in the substantially
axially extending marginal portion 502b of the cover 502;
the marginal portion 502b surrounds the bottom walk. 5~2a
and extends toward the pressure plate 503 of the fzW coon
clutch 501. The female coupling portions 5~2a~ which are
shown in the drawing constitute lugs of one piece with
the cover 502 and obtained as a result of appropriate
deformation of corresponding parts of the marginal
portion 502b. Each female coupling portion 502a° (these
coupling portions form part of the bayonet mount 514 and
are of one piece with the cover 502 is preferably
flanked by at least one slit or slot (such as the slits
502c, 502d) in the adjacent portion of the cover 502. By
actually separating certain parts of the coupling
portions 502a~ from the adjacent portions of the cover
502, the portions 502a~ can be moxw readily shaped t~
.,. . . . ??
CA 02446426 2003-11-12
assume an optimum configuration for cooperation with the
male coupling portions 513d of the bayonet mount 514.
As can be readily seen in F"IG. 21, the
positions and shapes of the coupling portions 502a' and
513d (which together constitute the bayonet mount 57.4)
are selected in s~.ach a way that they can further per. form
the function of means for centering the sensor 5x3
relative to the cover 5a2° To this end, the female
coupling portions 502a' are provided with rather shal low
centering recesses 502e for parts of the respective male
coupling portions 513d.
In order to ensure predictable and optimal
positioning of the sensor 513 relative to the cover 5 02
during establishment of engagement between the coupling
portions 502a' and 513d of the bayonet mount 514, the
substantially axially extending marginal portion 502b of
the cover 502 is preferably provided with at least three
equidistant female coupling portions 502a'. The
arrangement is such that the portions 502a' and 513d of
the bayonet mount 514 permit a predetermined angular
displacement of the cover 502 and the sensor 513 relative
to each other before the bayonet mount is effective to
maintain the sensor in an optimum position at a certain
distance from the outer side of the bottom wall 502a as
well as in properly centered position relative to the
cover 502. At such time, the male coupling portions 513d
abut stops 502f which form part of the cower 502 and
serve to prevent further rotation of the cover 502 and
sensor 513 relative to each other in order to activate
the bayonet mount 514. As can be seen in FIG. 20a, each
7g
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stop 502f can constitute an axially extending projection
of the cover 502 ~ FTGm 20a further shows that at least
one of the female coupling portions 502a' (but preferably
at least two or a:!1 three coupling portions 502x' ) :~s
provided with an additional stop 502g which also prevents
rotation of the sensor 5013 relative to the cover 502.
Each stop 502g is engaged by the adjacent male coupling
portion 513d of the sensor 513 when the bayonet mount 514
is fully assembled.
In the embodiment which is shown in FIGS. 2 0 to
22, each of the female coupling portions 5 02a' is
provided with a first stop 502f and with a second stop
502g for the respective male coupling port ion 513dd ~ne
of the stops 502f, 502g holds the respective coupling
portion 513d against rotation in one direction and the
other of the stops 502f., 502g holds the respective
coupling portion 513d against rotation in the opposite
direction. fhe stops 502g serve to pre~rent accidental or
unintentional separation of the bayonet mount 514, i.e.,
24 they prevent accidental separation of the sensor 513 from
the cover 502. C)nce the bayonet mount 514 is active, the
sensor 513 is held in a predetermined angular position
relative to the bottom wall 502a of .the cover 502.
In order to render the bayonet anount 514
effective, the sensor 513 is first subjected to an
initial stress by deforming it axially toward the bottom
wall 502a of the cover 502 so that the male coupling
portions 5134 can enter the adjacent slots or slits 502c
and 5024 of the cover 502 by moving in the
30 circumferential direction of the frictiora clutch '501. In
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CA 02446426 2003-11-12
this manner, the male coupling portions 513 4 can be moved
behind the adjacent female coupling portions 502x'. The
next step of rendering the bayonet mount 5 14 operative
invo lees turning of the cover 502 and the sensor 513
relative to each other until at least some of the
coupling portions 513d reach and are arrested by the
corresponding stops 502f. The sensor 513 then dissipates
some energy so that at least some of the n~a le coupling
port ions 513d move axially and away from the bottom wall
502a and enter the spaces between the respective stops
502f and 5028. This ensures that the sensor 513 care no
longer become accidentally separated from the (female]
coupling portions 502a' of the cover 502. Once the
bayonet mount 514 is effective to reliably hold the
sensor 513 in the interior of the cover 502 , the assembly
of the friction clutch 501 can proceed without risking
accidental changes in the (centered) posit ion of the
sensor 513 relative to the cover 502 and,for unintentional
separation of the sensor from the corer~ At such tines,
each of the female coupling portions 502a~ is overlapped
by one of the male coupling portions 513d.
In the heretofore described embodiments of the
improved friction clutch, that circumferentially complete
portion of the sensor (such as the main portion 513b of
the sensor 513) which actually generates the force (e. g.,
the force to urge the diaphragm spring 50 4 of FIG. 2 1
against the ring 512) extends radially outwardly beyond
the points or lines of contact between the diaphragm
spring and the pressure plate (such as the diaphragm
spring 504 and the portion 503a of the pressure plate 503
CA 02446426 2003-11-12
shown in FIG. 21) . However, it is often desirable and
advantageous to position the main portion of the sensor
radially inwardly of the locations oi° engagement bet~;aeen
the diaphragm spring and the pressure plate, i.e~,
radially inwardly of the circle including the points or
lines of contact between the diaphragm spring and the
pressure plate. with reference to the friction clutch. 1
of FIGS. 1 and 2, this would mean that the
circumferentially complete portion 13b of the sensor 13
would be located radially inwardly of the points of
contact between the diaphragm spring 4 and the projecting
portions 3a of the pressure plate 3.
Referring again to the friction clutch 50~L of
FIGS. 20 to 22, the ramps 524 of the adjusting unit 516
are provided directly at the inner side of the bottom
wall 502a of the :over 502. The lataer is made of :sheet
metal and the ramps 524 are obtained by appropriate
deformation of an annular portion of the bottom wall
502a. The means for biasing the annular member 517 of
the adjusting unit 516 includes coil springs 526 which
are guided by suutably curved guide elements or mandrels
528 forming part of the member 517 (see particularly FIG.
22). The coil springs 526 react against the cover X02
and bear against the respective projections 527 of the
member 517 so that the latter tends to turn in a
direction to move (under the action of the ramps 524)
toward the pressure plate 503 and to thus compensate for
wear upon the pressure plate 503, the counterpressure
plate (not shown in FIGS. 20-22) an.d/or friction linings
507 between the counterpressure plate and the pressure
. , 81
CA 02446426 2003-11-12
plate 503 . As can be seen in F IG. 21_, each anandrel 528 can
have an elongated rectanc$ular cross-sectional outline to
extend substantially diametrically across the entire
space within the surrounding convolutions of the
respective coil spring 526~ The length of the arcuate
mandrels 528 can approximate but can be less than the
length of the respective coil springs 526. The
utilization of relatively long mandrels 528 ensures
predictable and satisfactory guidance of the respective
coil springs 526 at least in the radial direction of the
member 517. In addition, the mandrels 528 can be
designed and dimensioned to effectively prevent any; or
any appreciable, axial movements (buckling) of
intermediate portions of the respective coil springs 526.
Another important advantage of the mandrels 528 is that
they simplify the assembly of the friction clutch 501.
FIG. 22 shows one of several radially inwardly
extending projections 527 which are or can be of one
piece with the major portion of the member 517 and carry
t:cze respective mandrels 528. If the member 517 is made
of a plastic material (e.g., a material which -can be
shaped in an injection molding or extruding machine), the
projections 527 can be made of one piece with the
respective mandrels 528 as well as with the
circumferentially complete main portion of the member
517, namely that portion which is provided with ramps 518
serving to cooperate with the ramps 524 on the bottom
wall 502a of the cover 502. , However, it is equally
within the purview of the invention to mass produce the
mandrels 528 (or the mandrels 528 and the corresponding
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CA 02446426 2003-11-12
projections 527) i.r~dependently of the main portion of the
member 517 and to thereupon assemble the parts 527 or the
parts 527, 528 with the main portion of the member 51.7,
e.g., by resorting to connections which operate with snap
action. It is also possible to make the mandrels 528
from a one-piece ring which is severed at a required
number of locations to permit entry of the thus obtained
arcuate portions of the ring into the corresponding coil
springs 526 and to affix each arcuate portion of the
subdivided ring to one of the projections 527. The
connections between the arcuate portions of the
aforementioned ring (i.e>, of a blank .for the making of
the mandrels 528 o:r their equivalents) and the
projections 52'7 can be designed to operate by snap
action. It is preferred to provide 'the member 517 with
at least three preferably equidistawt projections 527.
If desired or necessary, t:he friction clutch
501 can be constructed in such a way that it comprises
one or more additional systems for prevent ing undesirable
20. movements of the coil springs 526 relative to the cover
502 and/or member 517. For example, and as already
explained with reference to the friction c latch 101 of
FIGS. 12-13, the cover 502 and/or the member 517 can be
provided with suitable means for preventing any
undesirable movem~:nts of the coil springs 526 under the
action of centrifugal force.
The means for coupling one end of each coil
spring 526 to the cover 502 of the friction clutch 501
comprises retainers or stops 526x~ gone shown in each of
30 FIGS. 20 and 21) which can constitute suitably deformed
83
CA 02446426 2003-11-12
portions of the cover 502 and extend in the axial
direction of the friction clutch. The configuration of
the retainers 526ao is preferably such that they not only
abut the adjacent outermost convolutions of the
respective coil springs 526 but that they are also
capable of otherwise guiding or locating the respective
coil springs (e. g., in the radial and/or axial direction
of the friction clutch 501).
In the friction clutch 601 of FIG. 23, the
sensor 613 is located at the outer side of the bottom
wall 602a of the housing or cover 602~ i.e.~ at i~hat side
of the bottom wall 602a which faces away from the
pressure plate 603. An advantage of such mounting of the
sensor 613 is that it is subjected to less pronounced
thermal stresses; this reduces the likelihood of
undesirable redaction or decrease of resiliency of the
sensor 613 as a result of excessive thermal stressing.
Moreover, the sensor 613 at the outer side of the bottom
wall 602a is subjected to much more pronounced cooling
action when the friction clutch 601 is in use.
The operative connection between the sensor 613
and the diaphragm spring 604 in the clutch 601 of FIG. 23
is established by way of distancing elements in the form
of rivets 615 (only one shown). The shanks of these
rivets extend through slots between the neighboring
prongs of the diaphragm spring 604 and through openings
in the bottom wall 602a of the cover 602. The axes of
the rivets 615 are parallel to the axis of the friction
clutch 601, and each of these rivets has a head which
overlies the outer side of the sensor 613. The rivets
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CA 02446426 2003-11-12
615 constitute but one form of means which can be used to
operatively connect the sensor 613 with the cdiaphragm
spring 604. For example, the sensor 613 can be provided
with axially extending projections in the form of lugs or
the like having suitable tips overlying the ring.611 of
the seat 605 to ~aainta~.n the ring 611 in uninterrupted
contact with the main portion of the diaphragm spring
604. In fact, it is possible to design the sensor 613 in
such a way that it is made of one piece with parts which
replace the rivets 615 as well as the ring.6 11 of the
seat 605.
Referring to FIG. 24, there is shown a port ion
of a friction clutch 707. with a sensor 713 which is
located radially inwardly of the locations of contact
between the diaphragm spring 704 and the portion or
portions 703a of the pressure plate 703. Thus, the
sensor 713 is located radially inwardly of the seat 7 05.
The radially inner portions (tongues] of the sensor 713
react against the adjacent portions of the cover 702. To
this end, the cover 702 is provided with arms 715 which
extend through the slots between the prongs of the
diaphragm spring 704 and are engaged by the adjacent
portions of the sensor 713. 'It is equally possible to
provide the radially inner portion of the sensor 713 with
arms which extend through slots between the prongs of the
diaphragm spring 704 and engage the cover 7 02. Instead
of extending through the slots between the prongs of the
diaphragm spring 704, the aforementioned arms of the
sensor 713 can extend through specially provided openings
in the diaphragm spring 7 04.
. .... . . ,. 85
CA 02446426 2003-11-12
The annular adjusting member 817 which is shown
in FIG. 25 can be utilized with advantage in the frict ion
clutch of FIGS. 20, 2~a and 21 in lieu of the annular
member 517 of FIG. 22. The radially inner portion of the
member 817 is provided with projections 827 c~rhich extend
radia 1 1y inwardly and have radially inward 1y projecting
extensions 827x. The extensions 827a serve as abutments
for the adjacent end convolutions of arcuate coil springs
826 extending in the circumferential direction of the
to member 817. The other end convolution of each coil
spring 826 bears against a retainer 826a forming part of
a housing or cover (not shown but csirresponding to the
cover 5o2 of FIGS. 20 and 21.) and extending in
parallelism with the axis of the friction clutch
employing the member 817.
In order to facilitate assembly of the member
817 with the coil springs 826, there is provided a sp lit
ring 828 which is concentric or nearly concentric with
the member 817 and extends through the extensions 827 a,
20 through the coil springs 826 and through the retainers
826x. The ring 828 is affixed to the extensions 827x;
for example, the extensions 827a can be provided with
grooves or sockets extending in the circumferential
direction of the member 817 and being dimensioned and
configurated to receive the respective portions of the
split ring 828 by snap action. Each ratafiner 82,6a can be
provided with a groove 826b which extends in substantial
parallelism with the axis of the member 8 17 and is
configurated and dimensioned to receive the adjacent
3~ portion of the split ring 828 with freedom of movement of
86
CA 02446426 2003-11-12
the ring r a lative to the retainer 826a in the
circumferential direction of the member 817. At the very
least, the ring 828 can move circumferentially of the
member 817 'to the extent which is necessary to compensate
for wear upon the friction linings, the pressure p late
and/ or the coon terpressure plate in the friction c latch
which employs the structure of FIG. 25.
It is presently preferred to configurate the
projections 827 and the retainers 826a in such a way that
the sockets of the extensions 827a (for reception of the
adjacent portions of the split ring 828 by snap action)
face in one axial direction and the grooves 826b ( for
reception of adjacent portions of the ring 828 with
freedom of movement in the circumferential direr tion of
the member 81~) face in the opposite axial direction. In
other words, the sockets of the extensions 827x. can be
open in a direction toward or away from the bottom wall
of the housing or cover- of the friction clutch employing
the structure of FIG. 25 ~ and the grooves 826b of the
retainers 826a can be open in a direction away from the
bottom wall of such housing or cover.
FIG. 26 illustrates a friction clutch 9 01 with
a diaphragm spring 904 having' a main portion 90 4 a. The
median part of the main portion 9a4a is in con tar t with
the parts of the seat 905 and the radially outermost part
of the main portion 904a is positioned to bear against
the projecting portion or portions 903a of the pres sure
plate 903 when the friction clutch 901 is engaged. The
prongs 904b of the diaphragm spring 904 (i.e., the
actuating means of the means for engaging and disengaging
87
CA 02446426 2003-11-12
the friction clutch 901) extend radially inwardly beyond
the main portion 904a, i.e., radially inwardly beyond the
seat 905. The distance of the seat 905 from the radially
innermost part of main portion 904a of the diaphragm
spring 904 is greater than in heretofore known friction
clutches wherein the means for biasing the pressure plate
toward the friction linings of the clutch disc includes a
diaphragm spring reacting against the housing or cover of
the friction clutch. In the embodiment of FIG..26,.the
ratio of the width of that part of the main portion 904a
which extends radially inwardly beyond the seat 905 to
the width of that part of the main portion 904a which
extends radially outwardly beyond the seat 905 is
approximately 1:2. It is often desirable that such ratio
be between 1s6 and 1:2. By select~_ng the position of the
seat 905 relative to the main portion 904a of the
diaphragm spring 904 in the just outlined manner, the
maker of the friction clutch 901 reduces the likelihood
of damage to and/or overstressing of the main portion
904a in the region of engagement with the seat 905. In
other respects, the friction clutch 901 of FIG. 26 can be
constructed and assembled in a manner as described with
reference to the friction clutch 101 of FIGS. 12 and 13.
FIG. 26 further shows, by broken lines, an
axially extending centering projection 903b on the
illustrated axially projecting portion 903a of the
pressure plate 903. The pressure plate 903 can be
provided with a circumferentially complete projecting
portion 903a or with a discontinuous projecting portion,
e.g., with at least three equidistant discrete projecting
88
CA 02446426 2003-11-12
port ions 903a. The single projecting port ion or mach
discrete projecting portion 903a of 'the pressure plate
903 can be provided with a centering projection 903b for
the diaphragm sprang 904. The centering projections 903b
render it possible to dispense with all other means for
centering the diaphragm spring 904 relative to the bottom
wall 902a of the housing or cover 902. Though FIG. 26
shows a rivet 9~.~ which is to center the diaphragm spring
904, such rivet is optional if the project ing portion or
portions 903a of the pressure plate 903 are provided with
centering projections 903b.
It is further possible to replace the rivets
915 and/or the centering projection or projections 903b
of the pressure plate 903 in the friction clutch 901 of
FIG. 26 with a set of centering projections which are of
one piece with or are affixed (e.g., welded) to the
bottom wall 902a of the cover 902. For example, the
centering projections of the cover 902 can constitute
lugs which are bent out of the bottom wall. 902a and
extend in parallelism with the axis of the friction
clutch 901 toward the pressure plate 903. Alternatively,
the centering projections of the cover 9172 can constitute
inwardly bulging portions (rather than lugs) of the
bottom wail 902a.
The diaphragm spring which constitutes the
sensor 913 in the friction clutch 901 of FIG. 2'7 is
designed in such a way that its cireumferentially
complete main or basic portion 913a is disposed radially
inwardly of the projecting portion or portions 903a of
the pressure plate 903. In order to prop the diaphragm
89
CA 02446426 2003-11-12
spring 904 on the one hand, and to be adequately propped
agains t the cover 902 on the other hand, the sensor 913
is further provided with radial arms in the form of
tongues including a set extending from the main portion
913a radially inwardly to form part of the seat~905 such
as a substitute for the wire ring I1 in the seat 5 of
FIGS. 1-2) and a set extending from the main portion 9I3a
radialiy outvaardly to react against lugs forming part of
the substantially axially extending portion of the cover
902.
Referring to FIG. 27, there is shown a friction
clutch 1001 including a diaphragm spring 1013
cons tituting a sensor anti serving to transmit a force
which opposes the force to be applied in order to
disengage the friction clutch and which also opposes the
force of the diaphragm spring resilient device) 1004.
The sensor 1013 reacts against the housing or cover 1002
and bears against the projecting portion or portions
1003 a of the pressure plate 1003. In other words, the
l sensor 1013 is installed in axially stressed condition
between the cover 1002 and the pressure plate 1003. In
this embodiment of the present invention, the seat 1005
does not provide for the diaphragm spring 1004 a bearing
for tilting of the diaphragm spring in a direction to
dis engage the friction clutch 1001. The diaphragm spring
1004 engages a wire ring 1012 which forms part of the
seat 1005 and contacts that side of the main portion of
the diaphragm spring 1004 which faces toward the annular
adjusting member 1017 and the bottom wall I002a of the
30 cover 1002. The sensor 1013 constitutes the means for
CA 02446426 2003-11-12
biasing the main portion of the diaphragm spring 1004
against the wire ring 1012 of the seat 1005. The sensor
1013 is dimensioned, configurated and installed in such a
way that, during disengagement of the friction clutch
1001, the axial force generated by the sensor 1013 and
acting upon the diaphragm spring 1004 is or becomes
larger than the force which is to be applied to disengage
the friction clutch 1001a The arrangement should be such
as to ensure that, when the wear upon the friction
linings (not shown in FIG. 27) is nil or minimal, the
diaphragm spring 1004 continuously engages the wire ring
1012 of the seat 1005. To this end, and as already
described in connection with the previously discussed
embodiments of the improved friction clutch, it is
necessary to properly relate the superimposed forces
acting in the axial direction of the friction clutch
1001. Such forces are generated by the sensor 1013, by
the resilient segments (not shown) of the clutch disc in
the friction clutch 1001, by leaf springs (if any) which
connect the pressure plate 1003 with the cover 1002 in
such a way that the parts 1002, 1003 have a certain
freedom of axial movement but cannot turn relative to
each other, by the diaphragm spring 100, by the means
for disengaging the friction clutch 1001, and by
resilient means (e.g~, coil springs or torsion springs)
acting upon the member 10I~ of the adjusting unit in
order to compensate for wear upon the pressure plate
1003, the counterpressure plate (not shown) and~or the
friction linings of the clutch disc between the pressure
plate 1003 and the counterpressure plate.
91
CA 02446426 2003-11-12
FIGS. 28 to 32 illustrate a further torque
transmitting friction clutch 1101 having a housing or
cover 1102 and a pressure plate 1103. The ,latter is
connected with the cover 1102 in the aforedescribed
manner, i.e., with some freedom of axial movement but
without any freedom.of angular movement. A diaphragm
spring 1104 is installed in the cover 1102 between the
bottom wall 1302a and the pressure plate 1103 to bias the
pressure plate 1103 against the adjacent set of friction
linings 1107 forming part of a clutch plate or clutch
disc 1108. When the diaphragm spring ll04 is free to
bias the pressure plate 1103 in a direction away from the
bottom wall 1102a of the cover 1102, the other set of
friction linings 1107 of the clutch disc 1108 is caused
to bear against the friction surface of a counterpressure
plate 1106, e.g., a flywheel or a portion of a flywheel
which receives torque from a suitable prime mover,
particularly from the output element (e. g., a crankshaft)
of an internal combustion engine in a motor vehicle. The
clutch disc 1108 then transmits torque to the input
element of a variable-speed transmission in the power
train between the flywheel 1106 and the wheels of the
motor vehicle.
The means for non-rotatably but axially movably
connecting the.pressure plate 1103 to the cover 1102
comprises a set of substantially tangentially extending
leaf springs 1109 (rIG. 28).
The clutch disc 1108 comprises resilient
segments 1110 which~are designed and mounted to a stablish
a progressive buildup of torque during engagement of the
92
CA 02446426 2003-11-12
friction clutch 1101. This is achieved in that the
segments 1110 permit the two sets of friction linings
1107 (namely the set engageable by the friction surface
of the pressure plate 1103 and the set engageable by the
friction surface of the flywheel 1106) to perform limited
axial movements toward each other and to thus permit a
progressive buildup of forces acting upon the friction
linings 110? in the axial direction of the clutch 1101.
However, it is equally within the purview of the
invention to employ a modified clutch disc wherein the
two sets of friction linings are installed at a fixed
axial distance from each other, e.g., by being bonded or
otherwise affixed to opposite sides of at least one rigid
washer-like carrier extending radially outwardly from the
hub 1108a of the clutch disc. In the thus modified
friction clutch 1101, a functional equivalent of the
resilient segments 1110 can be installed at another
point, e.g., between the diaphragm spring 1104 and the
pressure plate 1103 andJor between the cover 1102 on the
one hand and the pressure plate 1103 ar the flywheel 1100
on the other hand.
In the embodiment of FIGS. 28 to 32, the
diaphragm spring 1104 comprises a circumferentially
complete main pcrtion 1104a and prongs 1104b (actuating
means of the means for engaging and disengaging the
friction clutch 1101) which are of one piece with and
extend radially inwardly from the main portion 1104a.
The radially outer part of the main portion 1104 a biases
the pressure plate 1103 against the adjacent friction
linings 1107 when the friction clutch 1101 is engaged,
93
CA 02446426 2003-11-12
and a radially inner part of the vain portion 1104a
cooperates with the seat 1105 in order to ensure that the
diaphragm spring can be tilted relative to the bottom
wall 1102a of the cover 1102. The seat 1105 includes two
annular portions 1111 and 1112 which are disposed at
opposite sides of the main portion 1104a of the diaphragm
spring 1104 and each of which can constitute a wire ring.
These wire rings provide a bearing which enables the
corresponding part of the main portion 1104a of the
diaphragm spring 1104 to be tilted in order to urge the
pressure plate 1103 toward the fiywheel_1106 or to permit
the pressure plate to move away from the flywheel, e.g.,
under the bias of the leaf springs 1109.
The means for preventing rotation of the
diaphragm spring 1104 relative to the bottom wall 1102a
and for centering the diaphragm spring in the cover 1102
comprises a set of distancing elements in the form of
rivets 1115 which are anchored in the bottom wall 1102a
and extend in parallelism with the axis of the friction
J clutch 1101. The shanks 1115a of the rivets 1115 extend
through slots between the neighboring prongs 1104b of the
diaphragm spring 1104.
The friction clutch 1101 further comprises
means for compensating for wear upon the pressure plate
1103, upon the flywheel 1106 and particularly upon the
friction linings 1107 of the clutch disc 1108. Such
compensating means comprises an adjusting unit 1116 which
operates between the pressure plate 1103 and the
diaphragm spring 7.104, as well as a device 1117 which
0 limits the extent of movability of the pressure plate
94
CA 02446426 2003-11-12
1103 in a direction away from the flywheel 1106, ~. . a ~ , in
a direction to release the clutch disc 1108 and to thus
disengage the friction clutch 1101~ The dev ice 1117 can
be said to constitute a means for monitoring the extent
of axial movements of the pressure plate 110 3 relative to
the flywheel 1106 and/or the bottom wall 110 2a of the
cover 1102.
The monitoring device 1117 ascerta ins the
extent of wear upon the pressure plate 1103~ the flywheel
1106 and/or the friction linings 1107 and comprises a set
of sleeves 1118 each of which is non-rotatab 1y installed
in a bore or hole 1120 of the pressure plate 1103» Each
sleeve 1118 has an axially parallel slot or passage 1121
to permit entry of a pair of resilient elements 1122 in
the form of leaf springs in the axial direction of the
friction clutch 1101. The leaf springs 1122 of each pair
bear against each other and at least one leaf spring 1122
of each pair can have an arcu~te shape. It is presently
preferred to utilize pairs of leaf springs 1 122 wherein
each leaf spring has an arcuate shape, and the leaf
springs of each pair are bent in opposite directions, for
example, in such a way that a convex side of one leaf
spring 1122 of each pair bears against a convex side of
the other leaf spring 1122 of the respective pair.
The leaf springs 1122 of each pair are
installed in the respective sleeves 1118 with a
predetermined amount of initial stress so that a certain
predetermined frictional resistance must be. overcome
before the leaf springs of a pair of such springs can
move relative to the respective sleeve 1118 in the axial
~5
CA 02446426 2003-11-12
direction of the friction clutch 1101. The length of the
leaf springs 1122 in the axial direction of the friction
clutch 1101 is selected in such a way that, when the
friction clutch is engaged so that the frict i_on linings
1107 are clamped between the neighboring friction
surfaces of the pressure plate 1103 and flywheel 1106; a
certain clearance or gap 1124 is maintained between the
leaf springs and an axially f fixed part of then friction
clutch, e.g., the marginal portion 1123 of the cover
1.102. The width of the clearance 1124 corresponds to the
predetermined axial movability of the pressure plate 1103
relative to the cover 1102. Then the fricti on clutch
1101 is engaged, those ends 1122a of the lea f springs
1122 which are remote from the cover 1102 come into
abutment with the flywheel 1106; this ensures that the
pressure plate 1103 is moved axially of the friction
clutch 1101 with reference to the leaf springs 1.22 to an
extent which exactly corresponds to the extent of wear
upon the pressure plate 1103, upon the flywheel 1106 but
mainly or exclusively upon the friction linings 1107.
The displacement of the pressure plate 1103 relative to
the leaf springs 1122 takes place against the oppositi ~n
of the friction existing between the leaf springs 1122
and the respective sleeves 1118~ These sle wes can be
made of a plastic material or from another material which
preferably has a high coefficient of frict i on.
In the illustrated embodiment, the bores or
holes 1120 receive the sleeves 2118 in such a way that
each sleeve is a press fit therein and is held against
movement in the axial as well as in the cir cumferentia 1
96
CA 02446426 2003-11-12
direction. The bores or holes 1120 are provided in lobes
1125 of the pressure plate 1103. Each lobe 1125 (only
one shown in FIG. 28) extends radially outwardly and
further serves to carry one end portion of one of the
leaf springs 1109. The connections between the leaf
springs 1109 and the respective lobes 1125 of the
pressure plate 1103 include rivets 1109a. A shift~.rig of
sleeves 1118 in a direction toward the flywheel 1106 can
also be avoided or prevented in that each sleeve 1118 i s
provided with a collar 1118a at that end which is
adjacent the cover 1102. Such collar engages the
pressure plate 1103. Any movement of a sleeve 1118 in
the respective bore or hole 1120 in a direct ion toward
the cover 1102 can be prevented by such configuration of
the leaf springs 1109 (as shown in FIG. 28 by broken
lines at 1119) that each leaf spring 1109 partially
overlies the respective sleeve 1118 and, if necessary,
fixedly secures the sleeve 1118 in its bore or hole 1120.
Turning of a sleeve 1118 in its bore or hole 1120 can
also be prevented by imparting to each sleeve a profile
(e: g., by providing it with an extension) which receives
the portion 1119 of the respective leaf spring 1109.
The adjusting unit 1116 comprises a
compensating element in the form of a ring 1120 having a
U-shaped cross-sectional outline and being acted upon by
the diaphragm spring 1104. A substantial portion of the
ring 1126 is shown in FIG. 32 and a portion of tk~is ring
(as seen from its open side) is also shown in FIG 30.
The ring 1126 comprises a circumferentially complete
bottom wall or end wall 112'x, a circumferentially
9~
CA 02446426 2003-11-12
,complete radially inner cylindrical sidewal l 1130 and a
circumferentially complete radially outer cylindrical
sidewall 1131. That side of the end wall or bottom wall.
1127 which faces the diaphragm spring 1104 c s provided
with at least one rang-shaped axial projection 112. If
the wall 1127 carries several projections 1 128, they ar-e
preferably equidistant from each other in the
circumf erential direction of the ring 1126. Furthermore,
if the ring 1126 is made of a metallic sheet ~ater~.al,
the projections 112 can constitute deformed portions of
the end wall 1127. If the projections 1128 are segment
shaped, the neighboring projections 1:128 define radial
passages between the main portion 1104a of the diaphragm
spring 1104 and the ring 1126~ such passages permit
circulation of air to achieve desirable coo ling of the
corresponding portion of the friction clutch 110 1
Referring t~ fIG. 29, the ring 1126 is centered
relative to the pressure pla~.e 1103 by at least one
shoulder 1129 which is provided on the pres scare plate
1103 adjacent the inner sidewall 1133 of the ring 1126.
The shoulder 1129 can constitute a circumf erentially
complete surface of the pressure plate 1103 or a
composite surface consisting of a plurality of discrete
arcuate sections adjacent the outer side of the sidewall
1130 of the ring 1126.
The walls 1127, 1130, 1131 of the ring 1126
define a ring-shaped space 1126a and the outer wall 1131
is provided with a set of equidistant projections or
lobes 1132 which extend radially outwardly and cooperate
with complementary projections 1133 of the axially
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CA 02446426 2003-11-12
movable leaf springs 1122 forming part of the monitoring
device 1117. The complementary projections 1133 can
constitute suitably shaped integral parts of the leaf
springs 1122 and extend radially inwardly to overlie and
to be thus located in the path of movement of projections
1132 on the radially outer sidewall 1131 of the ring
1126. This ensures that the ring 1126 cannot move. away
from the pressure plate 1103 in a direction toward the
cover 1102.
A displacing device 1134 between the ring 1126
and the pressure plate 1103 serves to automatically reset
the ring 1126 during disengagement of the friction clutch
1101 in order to compensate for wear upon the pressure
plate 1103 and/or flywheel 1106 but mainly for wear upon
the friction linings 1107. The displacing device 1134
performs a self-locking blocking) action during
engagement of the friction clutch 1101 to thus ensure
that the ring 1126 will assume a predetermined axial
position relative to the pressure plate 1103 while the
friction clutch is in the process of being engagede The
position of the ring 1126 relative to the pressure plate
1103 can change only during disengagement of the friction
clutch 1101 and only to the extent determined by the
amount of wear upon the aforementioned parts 1103, 1$06
and/or 1107.
The displacing device 1134 comprises a
plurality of pairs of wedges 1135, 1136, and such pairs
are preferably equidistant from each other in the
circumferential direction of the ring 1126. The pairs of
wedges 1135, 1136 are installed in the circular internal
99
CA 02446426 2003-11-12
space 1126a of the ring 1126~ The wedges 1136 contact a
ring-shaped surface 1137 of the pressure plate 1103 and
are non-rotatably secured to the ring 1126 but are
axially movably installed in the internal space 11.26a.
To this end, the sidewalls 1130, 1131 of the ring 1126
are provided with guide means in the form of ribs 1138,
1139 constituting projections extending into the space
1126a and confining the wedges 1136 to movement in the
axial direction of the friction clutch 1101. To this
end, the wedges 1136 are provided with recesses or
grooves 1140, 1141 to receive the ribs 1138, 1139,
respectively. The grooves 1140, 1141, as well as the
ribs 1138, 1139, extend in parallelism with the axis X-X
of the friction clutch 1101.
As can be seen in SIG. 30, the wedges 1135 are
installed axially in the space 1126a of the ring 1126,
namely between the bottom wall or end wall 1127 and the
adjacent wedges 1136. The wedges 1135, 1136 respectively
include or define ramps 1143~ 1142 which extend in the
circumferential direction of the ring 1126 and slope
axially of the friction clutch 1101 in a direction from
the inner side of the end wall 1127 toward the open side
of the ring 1126. The ramps 1143 of the wedges 1135 abut
the ramps 1142 of the adjacent wedges 1136~ Those sides
of the wedges 1135 which face away from the respective
ramps 1143 are adjacent the inner side of the end wall
1127, and each wedge 1135 can be shifted in the
circumferential direction of the ring 1126 in order to
compensate for wear upon the pressure plate 1103,
flywheel 1106 and/or friction linings 1107~ The ramps
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CA 02446426 2003-11-12
1142 of the wedges 1136 bear against the ramps 1143 of
the adjacent wedges 1135. Such engagement between the
ramps 1142 and the adjacent ramps 1143 is achieved by the
provision of coil springs 1144 which are received in the
space 1126a of the ring 1126. Each spring 1 144 reacts
against one of the wedges 1136 (which are held against
movement in the circumferential direction of the ring
1126) and bears against one of the wedges 1135 (i.e.,
against one of those wedges which are movable in the
circumferential direction of the ring 1126). The wedges
1135, 1136 are respectively provided with projections
1145, 1146 which extend into the adjacent end
convolutions of the respective springs 1144. These
springs are further confined and guided by the internal
surfaces of the walls 1127, 1130 and 1131 of the ring
1126.
The friction clutch 1101 is constructed in such
a way that the ring 1126 cannot rotate relative to the
pressure plate 1103. As can be seen in FIG. 31, the
pressure plate 1103 is provided with axially extending
projections in the form of pins or studs 1147 extending
through holes or bores 1148 provided in the
aforementioned projections 1132 extending redially
outwardly from the sidewall 1131 of the ring 1126. Such
non-rotatable mounting of the ring 1126 relative to the
pressure plate 1103 ensures that, when the friction
clutch 1101 is in use, the projections 1132 are always
overlapped by the projections 1133 of the leaf. springs
1122.
The wedges 1135, 1136 in the space 1126a of the
I01
CA 02446426 2003-11-12
ring 1126 are assumed to be made of a heat-resistant
plastic material, such as a thermoplastic or a pressure
setting substance. The material of these wedges can be
reinforced by filaments of glass fibers or the like. Such
construction of the wedges 1135, 1136 is preferred at
this tine because it renders it possible to mass produce
the wedges in an injection molding or other readily
available plastic processing machine. However, it is
also possible, and often preferred, to make at least one
set of the wedges 1135, 1136 of a material ~gaving a high
coefficient of friction, e.g., from the material of which
the friction linings 1107 are made. Still further, it is
possible to make the wedges 1135 and/or 1136 of metallic
sheet material or from a suitable sintered metal.
The inclination and the length of the ramps
1142, 1143 are selected in such a way that one ensures
reliable adjustment of the wedges 1135, 1136 relative to
each other in order to compensate for wear upon the
pressure plate 1103, flywheel 1106 andlor friction
linings 1107 during the entire useful life of the
friction clutch 1101. The inclination (angle 1149 in
FIG. 30) of the ramps 1142, 1143 with reference to a
plane which is normal to the axis X-X of the friction
clutch 1101 is selected with a view to ensure that
friction which develops when the ramps 1142, 1143 are
biased against each other suffices to prevent any
slippage of the wedges 1135 and the associated wedges
1136 relative to each other. The magnitude of the angles
1149 (slope oz the ramps 1142, 1143) will depend upon the
0 selection of materials of the wedges 1135, 1136 and is
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CA 02446426 2003-11-12
normally between approximately 5 and 20 degrees,
preferably close to or exactly 10 degrees. The wedges
1135 which can mope in the circumferential direction of
the ring 1126 are oriented in such a way that their tips
face in the direction harrow 1150) of rotation of the
friction clutch 1101. Furthermore, the magnitude of the
angles 1149 and the bias of the springs 1144 are such
that the resultant axial force acting upon the ring 1126
is smaller than the force which is required to move the
leaf springs 1122 of the. monitoring device 1117.
It is further important or desirable to select
the characteristics of the diaphragm spring 1104 in such
a way that the force to be applied by this spring against
the pressure plate 1103 can be increased by a value
corresponding to the force which is needed to displace
the leaf springs 1122 plus the stressing of leaf springs
1109 between the cover 1102 and the pressure plate 1103.
Furthermore, the component parts of the friction clutch
1101 should be designed in such a way that; in comparison
with the wear upon the friction linings 1107, the wear at
the locus or loci of engagement of the ring 1126 with the
diaphragm spring 3104 as well as the wear between the
leaf springs 1122 and the flywheel 1106 and between the
leaf springs 1122 and the cover 1302 be sma 11 or
negligible.
Referring again to FIO. 30, and in order to
avoid unintentional shifting of the ramps 1 142, 1143 of
the wedges 1136, 1135 relative to each other, at least
one of each pair of cooperating ramps 1142, 1143 can be
provided with relatively small projections or
103
CA 02446426 2003-11-12
protuberances which tend to be caught by the adjacent
ramps. These protuberances can be designed and
dimensioned with a view to permit necessary movements of
the pairs of wedges 1135~ 1136 relative to each other in
order to compensate for wear upon the parts 1103~ 1106
and/or 1107 but to prevent any undesirable slippage of
the ramps 21428 1243 relative to one another. It is
normally preferred to provide the just discussed minute
protuberances on each of the ramps 1142 as well as on
1~ each of the ramps 1143 and to orient the protuberances in
such a way that those on the ramps 1142 mate or mesh or
become interlaced with the protuberances of the ramps
1143. For example, the protuberances can constitute
relatively small (e. g., minute) sawtooth-shaped profiles
on the ramps 1142 and/or 1143. Such protuberances should
be capable of preventing accidental or unintentional
shifting of the pairs of wedges 1135, 1136 relative to
each other but they should not interfere with those
adjustments of the ramps 1142, 1143 relative to each
20 other which are needed to compensate for the
aforediscussed wear, mainly upon the friction linings
1107 but preferably also (if any) upon their friction
surfaces of the pressure plate 1103 and flywheel 1106.
FIG. 30 shows (enlarged for better illustration)
protuberances 1143a in the form of sawteeth which are
applied to one of the two abutting ramps 1142, 1143. If
only one of the ramps 1142, 1143 is provided with
protuberances 1143a and/or analogous pratuberances, they
can be designed in such a way that their hardness exceeds
30 the hardness of the material of the adjacent (non-
104
CA 02446426 2003-11-12
profiled or non-serrated) ramps; this ensures that the
relatively hard protuberances will be capable of
penetrating (to a small or minute extent) into the
adjacent ramps 1142 or 1143 to thus further reduce the
likelihood of accidental displacement of the wedges 1136
relative to the adjacent wedges 1135 in the
circumferential direction of the ring 1126.
In the absence of any undertakings to the
contrary, the temperature of the arcuate leaf springs
1122 would be likely to rise to a rather high value in
response to engagement of the pressure plate 1103 with
the adjacent set of friction linings 1107. This cohld
result in a reduction of resiliency of the leaf springs
1122. Therefore, the sleeves 1118 for the leaf springs
1122 are preferably made of a material exhibiting a low
heat conductivity and a high friction coefficient to
prevent excessive transfer of heat from the pressure
plate 1103 during engagement of the friction clutch 1101.
The material of the wedges 1135, 1136 can be the same as
that of the sleeves 1118.
In order to ensure satisfactory cooling of the
friction clutch 1101, especially of the pressure plate
1103, the latter can be provided with substantially
radially extending grooves, channels and/or other
passages which are preferably equidistant from each other
in the circumferential direction of the cover 1102 and
one of which is shown in FIG. 29 by broken lines, as at
1151. The arrangement may be such that the passages 1151
alternate with pairs of wedges 1135, 3136 in the
circumferential direction of the ring 1126. Each passage
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CA 02446426 2003-11-12
1151 is provided in the pressure plate 1103 between the
adjacent set of friction linings 1107 and the ring 1126.
The cooling action can be enhanced still further by
providing the ring 1126 with axially extending slots
starting at the bottom wall or end wall 1127 adjacent the
coil springs 1144. This establishes ~radiallextending
passages between the diaphragm spring 1104 aid the ring
1126.
The resistance of various selected parts of the
friction clutch 1101 to wear can be enhanced by providing
such parts with coats consisting of suitable wear-
resistant material. For example, certain pa its can be
provided with layers of hard chrome or molyhdenum.
Alternatively, selected parts of the fricti~n clutch can
be provided with inserts, shells or envelope s of highly
wear-resistant material. For example, the leaf springs
1122 can be provided with shoes of plastic material, at
least in the regions where these leaf springs contact or
are likely to contact the flywheel 1106 and ~ or the cover
1102.
The leaf springs 1109 which transynit torque
between the pressure plate 1103 and the cover 1102 ire
installed in stressed condition in such a way that they
shift the pressure plate in a direction tow erd the bottom
wall 1102a of the cover 1102 in response t~ disengagement
of the friction clutch 1101~ This ensures that the ring
1126 continues to abut the diaphragm spring 1104 during
the entire stage of disengagement of the friction clutch
1101, i.e., until the monitoring device 1117 becomes
effective.
106
CA 02446426 2003-11-12
The path of movement of the tips 1104c of
prongs 1104b of the diaphragm spring 1104 (i_e., of the
actuating means in the means for engaging and disengaging
the friction clutch 1101) is preferably selected in such
a way that the radially outermost portion of the
diaphragm spring 1104 is slightly spaced apa3rt from the
ring 1126 when the movement of the tips 1104 c in a~~
direction to disengage the friction clutch i ~ completed.
Thus, when the friction clutch is being dise3ngaged, the
distance covered by the diaphragm spring 1l0 4 in the
region of the seat 1105 (where the diaphragm spring bears
(directly or indirectly) against the pressur a plate 1103)
exceeds the extent of movement (clearance 11 24) of the
pressure plate 1103 away from the flywheel 1 106 (as
determined by the leaf springs 1122).
Those relative positions of variou s parts of
the friction clutch 1101 which are shown in FIG. 29 are
assumed by these parts when the extent of wear upon the
pressure plate 1103, flywheel 1106 and friction linings
1107 is minimum or nil. Once the friction linings 1107
have undergone a certain amount of wear, the pressure
plate 1103 changes its position in a direction toward the
flywheel 1106 (when the friction clutch 110 1 is engaged).
This results in a change of conicity of the diaphragm
spring 1104 as well as in a change of bias ~f the
diaphragm spring upon the pressure plate 11f73, preferably
in a sense to increase the bias. This, in turns causes
the pressure plate 1103 to change its axial position
relative to the leaf springs 1122 which abut the flywheel
1106 in the axial direction of the friction clutch.
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CA 02446426 2003-11-12
Since the ring 1126 is biased by the diaphragm spring
1104, this ring shares the axial movement of the pressure
plate 1103 toward the flywheel 1106 to an extent which is
determined by wear (primarily upon the friction linings
3107. This, in turn, causes the projections 1132 of the
ring 1126 to move axially and away from the corresponding
projections 1133 of the leaf springs 1122 through a
distance which also corresponds to or at lea st
approximates the reduction in the thickness of friction
linings 1107 due to wear as a result of repeated
frictional engagement with and disengagement from the
friction surfaces of the pressure plate 1103 and flywheel
1106. The axial position of the ring 1126 relative to
the pressure plate 1103 remains unchanged during
engagement of the friction clutch 1101 because the ring
is acted upon by the diaphragm spring 1104 in a direction
toward the pressure plate and the displacing device 1134
is self-locking in the course of the clutch engaging
operation, i.e., the device 1134 acts as a means for
"locking'° the ring 1126 to the pressure plate 1103 during
engagement of the friction clutch. When the clutch is
being disengaged, i.e., when the tips 1104c of the prongs
1104b move along their path in the opposite direction,
the pressure plate 1103 is biased by the leaf springs
1109 which urge the pressure plate toward the bottom wall
1102a of the cover 1102. The pressure plate 1103 ceases
to move axially toward the bottom wall 1102 a until the
leaf springs 1122 engage the cover 1102 and more
specifically the marginal portion 1123 of thus cover.
The extent of movement of the prongs 1104b in a direction
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CA 02446426 2003-11-12
to disengage the friction clutch 1101 corresponds to the
extent of movement of the pressure plate 1103 away from
the flywheel 1106, and the axial position of the ring
1126 relative to the pressure plate remains unchanged.
If the movement of the prongs 1104b in a direction to
disengage the friction clutch 1101 continues, the
pressure plate 1103 comes to a halt (i.e., its axial
position remains unchanged) but the ring 1126 continues
to share the axial movement of the adjacent portion of
the diaphragm spring 1104 (namely of the portion which
bears upon the end wall 1127 of the ring 1126). The ring
1126 is arrested and no longer moves toward the bottom
wall 1102a of the cover 1102 when the projections 1132 at
the end wall 1127 of the ring reengage the projections
1133 of the leaf springs 1122. axial shifting of the
ring 1126 is effected by the wedges 1135 which are biased
by the coil springs 1144 to move relative to the adjacent
wedges 1136 in the circumferential direction of the ring
1126 until the projections 1132 again engage and bear
against the respective projections 1133 on the Leaf
springs 1122.
In the friction clutch 1101 of FIGS. 29 to 32,
the pressure plate 1103 can be disengaged from the
adjacent set of friction linings 1107 (i.e., moved
axially and away from the flywheel 1106) by the stressed
Leaf springs 1109. Thus, the leaf springs 1109 always
tend to disengage the pressure plate 1103 from the clutch
disc 1108, i.e~, to move the pressure plate toward the
bottom wall 1102a of the cover 1102. If the diaphragm
spring 1104 continues to perform a movement in a sense to
109
CA 02446426 2003-11-12
disengage the friction clutch, the radially outer portion
of the diaphragm spring moves axially and away from the
ring 1126 because the ring 1126 is arrested and no longer
moves toward the bottom wall 1102a when its projections
1132 reengage the projections 1133 of the leaf springs
1122. Such, even very slight disengagement of the
diaphragm spring 1104 from the ring 1126 during
disengagement of the friction clutch 1101 is of
particular advantage for the system including the devices
1117 and 1134.
The devices 1117 and 1134 ensure that
adjustment of the ring 1126 as a result of shifting of
the wedges 1135 and their ramps 1143 relative to the
ramps 1142 of the wedges 1136 invariably compensates for
wear upon the pressure plate 1103, flywheel 1106 and
friction linings 1107. This is attributable to the fact
that the ring 1126 is clamped between the adjusting
elements (wedges) 1135, 1136 on the one hand, and the
leaf springs 1122 on the other hand (as seen in the axial
direction of the friction clutch 1101)~' this prevents
the ring 1126 from performing an axial movement greater
than that corresponding to wear (primarily) upon the
friction linings 1107. Tn addition, the devices 1117 and
1134 ensure that, even if the prongs 1104b of the
diaphragm spring 1104 cover a distance greater than
necessary to disengage the friction clutch 1101, or if
the pressure plate 1103 is caused to perform axial
vibratory movements relative to the flywheel 1106, the
wedges 1135, 1136 do not effect any adjustment of the
type required to take place in order to compensate for
110
CA 02446426 2003-11-12
wear upon the friction linings 1107. The reason is that
the leaf springs 1122 do not move relative to the
pressure plate 1103 and/or vice versa, even in the event
of a pronounced impact of their stops or projections 1133
against the marginal portion 1123 of the cover 1102. The
reason is that the displacing device 1134 is self-locking
by way of the projections 13.32. Thus, even if the
friction clutch 1101 is disengaged, the leaf springs 1122
can be acted upon by forces acting in the axial direction
.0 of the friction clutch toward the flywheel 1106 and ''
having a magnitude exceeding that between the leaf
springs 1122 and the pressure plate 1103 without risking
any axial displacement of the pressure plate and leaf
springs 1122 relative to each other.
The improved adjusting unit 1116 ensures that,
for all practical purposes, only a certain part of the
characteristic curve of the. diaphragm spring 1104
requires consideration during the entire useful life of
the friction clutc~i (i.e., while the wear upon the
20 friction linings 110? progresses from zero to a maximum
permissible value). i~ioreover, the bias of the pressure
plate 1103 upon the friction linings 1107 in engaged
condition of the zriction clutch is the same irrespective
of the extent of wear upon the friction linings because
the bias of the diaphragm spring 1104 upon the pressure
plate remains unchanged. Shis, ira turn, renders it
possible to employ a diaphragm spring 1104 having a
degressive characteristic curve during actuation of the
means for disengaging the friction clutch, preferably in
30 combination with a clutch piste or clutch disc 1108
111
CA 02446426 2003-11-12
wherein the two sets of friction linings 1107 are biased
apart by resilient segments 11,10 or the like. Thi s
renders it possible to reduce the magnitude of the effective
clutch disengaging force to a relatively lod,~ leve 1 and to
maintain the disengaging force at such low level during
the entire useful life of the friction clutch 1101, as
long as the characteristic curve of the resilient
segments 1110 remains at least substantially unchanged
during the useful life of the friction clutch. When the
0 friction clutch is being disengaged, the diaphragm spring
1104 is tilted at the seat 1105 whereby the stres sing of
the resilient segments 1110 decreases during a certain
portion of axial movement of the prongs 1104b along their
path, i.e., during a certain stage of axial movement of
the pressure plate 1103 away from the flywheel 1105. The
resilient segments 1110 dissipate energy during the just
mentioned stage of movement of the pressure plate 1103
away from the flywheel 1106 to thus Assisi in
disengagement of the friction clutch. This mean s that
20 the maximum force which is required to disengage the
friction clutch 1101 is smaller than the theoretical
force generated by and attributable to the mode of
installation of the diaphragm spring 1104 in eng aged
condition of the friction clutch. When the rang a of
resiliency of the segments 111'0 is exceeded, the friction
linings 1107 are released (disengaged from the pressure
plate 1103 and flywheel 1106) and, due to the depressive
characteristic curve of the diaphragm spring 1104 during
disengagement of the friction clutch, the remaining
30 disengaging force which is. to be applied is muc h less
112
CA 02446426 2003-11-12
than that disengaging force which would correspond to the
installation point or position of FIG. 29. As the
disengagement of the friction clutch 1101 continues, the
magnitude of the disengaging force continues to decrease
at least until the lowest point of the preferably
sinusoidal characteristic curve of the diaphragm spring
1104 is reached. .
It is advantageous to design the devices 1117
and 1134 in the friction clutch 1101 of FIGS. 28 and 29
in such a way that, when the friction clutch is driven,
the individual convolutions of the coil springs 1144 in
the space 1126a of the ring 1126 abut the radially outer
sidewall 1131 of the ring 1126. Friction between the
springs 1144 and the sidewall 1131 then opposes or
completely neutralizes the forces which the springs 1144
tend to apply in the circumferential direction of the
ring 1126, i.e., those forces which would tend to shift
the wedges 1135 relative to the wedges 1136 and to thus
compensate for wear upon the friction linings 1107 at a
time when such compensation is not necessary. In other
words, the springs 1144 act not unlike rigid bodies when
the friction clutch 1101 is driven by the internal
combustion engine of a motor vehicle or by any other
prime mover, and such behavior of the springs 1144 is
attributable to friction between their convolutions and
the adjacent internal surf ace of the radially outer
sidewall 1131 of the ring 1126. In addition, the wedges
1135 are also acted upon by centrifugal force which urges
them against the internal surface of the radially outer
sidewall 1131 of the ring 1126 so that the wedges 1135
113
CA 02446426 2003-11-12
are in frictional engagement with the sidewall 1131 and
are not likely to move in the circumferential direction
of the ring 1126 while the friction clutch 1101 rotates
and the springs 1144 are acted upon by centrifugal force.
The arrangement may be such that the magnitude of
centrifugal force acting upon the springs 1144 and wedges
1135 suffices to prevent any undesirable shifting of
these wedges in the circumferential direction of the ring
1126 unless the rotational speed of the friction clutch
1101 is within the idling RPM range of the internal
combustion engine provided that the friction clutch is
put to use between the engine and the variable-speed
transmission of a motor vehicle. At such time, the
springs 1144 are incapable of effecting any shifting of
the wedges 1135 relative to the adjacent wedges 1136.
Thus, the friction clutch 1101 can be designed in such a
way that any compensation for wear upon the friction
linings 1107 can take place only when the RPM of the
engine is within or at least close to the idling RPM.
Blocking of adjustment to compensate far wear upon the
friction linings 1107 during certain stages of operation
of the motor vehicle which employs the improved friction
clutch 1101 can also be accomplished only when the
internal combustion engine or any other prime mover which
is used to rotate the friction clutch is idle or its RPM
is negligible, i.e., when the flywheel 1106 does riot
rotate and does not transmit torc~eie to the pressure plate
1103 and cover 1102 or the RPM of the flywheel 1106 is
minimal. All that is necessary is to carry out
corresponding adjustments in the design of the displacing
114
CA 02446426 2003-11-12
device 1134.
The materials of the wedges 1135, 1136 and of
the parts which cooperate with these wedges are
preferably selected in such a way that the wedges of the
pairs of wedges 1135, 1136 do not tend to adhere to each
other during any stage of useful life of the friction
clutch 1101, i.e., that adherence between the ramps~1142,
1143 of pairs of cooperating wedges 1135, 1136 cannot
rise to a value at which the device 1134 would be
incapable of compensating for wear upon the friction
linings 1107. Undesirable adherence of the ramps 1142 to
the adjacent ramps 1143 can be prevented by coating at
least one of the ramps of each pair of wedges 1135, 1136
with a suitable friction reducing or preventing
(lubricating) material.
It is further possible to prevent adherence of
the ramps 1142 and the neighboring ramps 1143 to each
other by providing the friction clutch 1101 with one or
mare systems or devices which apply to the ramps 1135 an
axially oriented force in a direction axially of the
friction clutch and away from the neighboring wedges 1136
in order to break the bonds (if any) between the
neighboring ramps 1142 and 1143 in response to each
disengagement of the friction clutch. This ensures that
the device 1134 is ready to accurately compensate for any
and all wear upon the friction linings 1107 and, if
necessary, also upon the friction surfaces of the
flywheel 1106 and pressure plate 1103.
Referring to FIG. 3~, the position of the
mobile wedge 1135 which is illustrated therein relative
115
CA 02446426 2003-11-12
to the adjacent wedge 1136 departs from the initial
position, namely from that position which the wedge 1135
assumes (as seen in the circumferential direction of the
ring 1126) when the wear upon the friction linings 1107
'is negligible, minimal or nil, for example, prior to
mounting of the pressure plate 1103 and the cover 1102 on
the flywheel 1106. At such time, the ring 1126 assumes a
position at a minimal axial distance from the pressure
plate 1103. Expressed otherwise, the combined thickness
of the pressure plate 1103 and ring 1126 then assumes a
minimum value. In order to ensure that the wedges 1136
will remain in their fully retracted positions (nearest
to the end wall 1127 of the ring 1126) while the cover
1102 and/or the pressure plate 1103 is being connected to
the flywheel 1106, the wedges 1135 are prefer ably
provided with portions (e.g., in the form of recesses or
notches 1152 shown in FIB. 30) which can receive the
working ends of suitable retaining or retracting tools.
Such tools are put to use during assembly of the
structure including the ring 1126, coil springs 1144 and
wedges 1135, 1136 and/or during attachment of the cover
1102 and pressure plate 1103 to the flywheel 1106 in
order to ensure that the mobile wedges 1135 will be fully
retracted when the friction clutch 1101 is assembled and
the wear upon its parts 1103, 1106, 1107 is still zer~ or
negligible. It is clear that the just discussed tools
are removed (disengaged from the wedges 1135 and/or 1136)
when the assembly of the friction clutch 11~ 1 is
completed; this ensures that the device 113 4 is then
ready to ensure necessary adjustments to compensate for
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wear upon the parts 1103, 1106 and/or 11.07. As can be
seen in FIGS. 30 and 32, the ring 1126 is provided with
elongated slots 1153 which enable the working ends of one
or more retaining tools to enter the notches 1152 ~f the
wedges 1135, 1136. For example, the means for retract ing
the wedges 1135 or for maintaining the wedges 1135 in
retracted positions prior to completed assembly of the
friction clutch 1101 can comprise one or more turning or
rotating tools. The length of the slots 1153 (which
extend in the circumferential direction of the ring 1.12 6)
should suffice to ensure that the wedges 1135D can be
shifted relative to the associated wedges 1136 through a
distance not less than the maximum range of adjustment of
wedges 1135 relative to the wedges 1136 for the purpose
to compensate for maximum wear upon the friction linings
1107. When the wedges 1135 are moved to the it fully
retracted starting positians (corresponding to those when
the wear upon the linings 1107 is zero), the thus
retracted wedges 1135 can be maintained in such positions
by the leaf springs 1122 which secure the ring 1126 in
the retracted angular position. The self-adjusting
connections between the leaf springs 1122 and the
pressure plate 1103 must be designed in such a way that
the shifting or displacing force which is required to
move the leaf springs 1122 relative to the pressure p late
1103 exceeds the resultant of forces acting upon the ring
1126 and furnished by the coil springs 1144, i.e., by the
springs which tend to shift the wedges 1135 relative to
the adjacent wedges 1136.
FIG. 30 shows that the wedges 1135 and their°
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ramps 1143 are separately produced parts which are
introduced into the space 1126a of and are secured 'to the
ring 1126. It is possible to avoid the making of
discrete wedges 1135 by the simple expedient of properly
shaping (deforming, such as stamping) the end wall 1127
of the ring 1126, i.e.,-the wedges 1135 can constitute
integral parts of (they can be of one piece with) the
ring 1126. The springs 1144 are then designed to turn
the ring 1126 (with its integral wedges 1135 and/or ramps
1143) relative to the pressure plate 1103. The other
wedges 1136 (or at least the ramps 1142) can be of one
piece with the pressure plate 1103. Alternatively, the
wedges 1136 can be produced in a separate step to be
thereupon affixed (e. g., welded, glued and/or otherwise
bonded) to the pressure plate 1103. The thus modified
friction clutch must employ a ring 1126 with projections
corresponding to but being much longer than the
projections 1132 (as seen in the circumferential
direction of the ring 1126) in order to ensure that the
length of the modified projections corresponding to the
projections 1132 will at least match that angular
displacement of the ring 1126 which is necessary to
ensure a full range of automatic adjustments of the axial
position of the pressure plate 1103 relative to the
flywheel 1106 in order to compensate for wear upon the
parts 1103, 1106 and/or 1107. This ensures that an axial
limit or stop between the leaf springs 1122 and the ring
1126 is established and maintained during the entire
useful life of the thus modified friction clutch. In the
just described embodiment of the friction clutch (i.e.,
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in that modification of the friction clutch wherein the
wedges 1135 are of one piece with the ring 112 6 and the
wedges 1136 are of ore piece with the pressure plate
1103), the angular position of the ring' 112 relative to
the pressure plate 1103 can be changed from w 3thaut upon
completed assembly of the friction clutch. For example,
it is possible to change the angular position of the ring
1126 in response to engagement of its projectfans 1132
which are made accessible through windows or ~ther
suitable radially extending openings in the radially
outer portion of the cover 1102. Such openings or
windows can further serve to receive the torque
transmitting lobes 1125 of the pressure plate 1103 and/or
the leaf springs 1109.
The adjusting unit 1116 which is shown in FIGS.
28-32 and its aforedescribed modifications exhibit the
advantage that the novel features thereof can be embodied
with equal advantage in so-called pul:L-type friction
clutches wherein the diaphragm spring has a radially
outer portion tiltably mounted on the cover or housing
and radially inner portions bearing upon the pressure
plate. A portion of such pull type friction clutch 1201
is shown in FIG. 33. A unit 1234 which compensates .for
wear at least upon the friction linings knot shown in
FIG. 33) is installed between the diaphragm spring 1204
and the pressure plate 1203 and can be constructed and
assembled in a manner as described with reference to the
embodiment of FIGS. 28-32. The ring 1226 of the
compensating unit 1234 cooperates with wear detecting or
sensing means 1222 by way of sensor elements 1217. The
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positions of the wear detecting means 3.222 relative to
the pressure plate 1203 are adjusted in that their end
portions 1222a engage the housing or cover 1202. The
wear detecting means 1222 are provided with projections
or abutments 1233 which Limit the extent of axial
movability of the pressure plate 1203 during
disengagement of the. friction clutch 1201. In order to
ensure satisfactory functioning of the unit 1234, the
ring 1226 is mounted in such a way that it has freedom of
at least some axial movability relative to the detecting
means 1222. This can be achieved by establishing a
connection 1233a between the detecting means 1222a and
radially extending abortions or arms 1226a of the ring
1226, whereby the tips of the arms 2226a have a certain
minimal freedom of movability relative to the respective
detecting means 1222 and/or vice versa. The arms 1226a
can be received in the notches of the adjacent detecting
means 1222 without any clearance if such arms are
sufficiently resilient to permit the required axial
movements of the ring 1226 and the detecting means 1222
relative to each other.
FIG. 34 shows a portion of a friction clutch
1301 wherein the sensor elements 131 extend directly
into the main portion of the pressure plate 1303. The
wear detecting means 1322 are provided with stops or
heads 1322a which cooperate with complementary stops 1323
forming part of the housing or cover 1302. The stops
1323 are of one piece with securing means 1302a°' forming
part of a seat 1305 for the diaphragm spring 1304. The
illustrated securing means 1302a°' include prongs or lugs
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which are of one piece with the cover 2302 and extend
axially of the friction clutch 1301 through the diaphragm
spring 1304. The wear compensating device 1334 is
disposed radially outwardly of the sensor elements 131'7
which, in turn, are adjacent the circumferentially
complete main portion 1304a of the diaphragm spring 1304.
An advantage of the improved friction clutch is
that its useful life can be prolonged by the simple
expedient of employing thicker friction linings, i.e., by
establishing a longer path for adjustment of the pressure
plate relative to the counterpressure plate in order to
compensate for wear upon the friction linings~ In
addition, the improved friction clutch renders it
possible to reduce the magnitude of the disengaging force
by employing an energy storing resilient device (e. g.,
the diaphragm spring 4 or 1104) with a depressive force-
to-displacement ratio or characteristic in combination
with at least one resilient element (such as the segments
3.~ or 1110) which opposes the bias of the resilient
device that acts upon the pressure plate. The at least
one resilient device ensures a gradual increase or
decrease of the torque which can be transmitted by trre
friction clutch and its clutch disc during a portion at
least of engagement or disengagement of the friction
clutch, i.e., during at least a portion of movement of
the actuating means (such as the prongs 4b and their tips
4c) of the clutch engaging and disengaging means along
its predetermined path. The resilient element is
preferably installed in series with the diaphragm spring.
The design of the improved friction clutch is such that
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the magnitude of the disengaging force can be reduced to
a surprisingly large extent; moreover, such reduction of
the required disengaging force exists and remains at
least substantially unchanged during the entire useful
life o~ the improved fzrictaon clutch. In other words, if
it fluctuates at a:11, the disengaging force fluctuates
within a very narrow range.
A further important advantage of the improved
friction clutch is that it can employ a diaphragm spring
whose distance-to-force ratio is relatively steep within.
the entire operating range. The utilization of such
diaphragm springs in heretofore known friction clutches
would result in highly pronounced rise of the disengaging
force in response to wear upon the friction linings.
In a fraction Clutch whaCh is not provided with
the improved wear compensating or adjusting unit, the
point 41 (FiG. 8) on the curve 40 migrates along the
sinusoidal path in a direction toward the maximum 41a.
As already discussed hereinabove, the point 41 denotes an
axial force which is generated by the diaphragm spring 4
in the fraction clutch 1 of FIGS. I-2 when the friction
clutch is engaged, i?uring disengagement of the friction
clutch, the magnitude of the disengaging force decreases
in a direction toward and up to the point 41b. In
general, the level of progress of the disengaging force
increases in comparison to the level.of the progress of
disengaging force when the friction liraings are devoid of
wear. Thus, the distance 43 shown in FIG. 8 is shifted
in a direction to the left toward the position 43a until
the point ~1 coincities with the maximum 41a. The poiazt
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CA 02446426 2003-11-12
44 is then transferred accordingly along the path which
is denoted by the curve 40. As the wear upon the
friction linings prc'gresses, the installation point of
the curve denoting t:he magnitude of the force of the
diaphragm spring in engaged condition of the friction
clutch migrates from the maximum 41a gvradually toward the
point 41b, i.e.,, them bias of the diaphragm spring upon
the pressure plate :Ln a conventional friction clutch
decreases at a gradual rate. That force of the diaphragm
spring which is applied to the pressure plate at the
point 41b in the diagram of FIG. 8 corresponds to the
force which is applied when the wear upon the friction
linings is nil (rots the point 41). l3s soon as the
maximum 41a is exceeded, disengagement; of the friction
clutch first entails an increase of the disengaging
force, at least during a portion of movement of the
actuating means (such as the prongs and the tips of
prongs forming part of the diaphragm spring). When the
maximum permissible wear upon the friction linings is:
reached (note the point 41b in the diagram of FIG. 8),
the magnitude of the disengaging force must increase
during each and every stage of disengagement of a
conventional friction clutch which is not equipped W_th
the novel adjusting unit. Such rise of the magnitude of
disengaging force ~_s observable even if the friction
linings of the conventional friction clutch cooperate
with the resilient segments 10 or with a substitute for
such resilient segments (as indicated in FIG. 8 by the
broken line 42a).
In desigaling the improved friction clutch, aald
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particularly its adjusting unit, it is necessary to take
into consideration that, if the friction clutch is
utilized in a power train receiving torque from the
output element (such as a crankshaft) of an internal
combustion engine in a motor vehicle, the output shaft is
likely to transmit to the flywheel, such as the flywheel
6 in the friction clutch 1 of FTGS. 1 and 2, at least
some axial and/or other (such as wobbling) vibratory or
stray movements. The flywheel transmits such undesirable
stray movements to other component parts of the friction
clutch. This could induce the adjusting unit l6 in the
friction clutch 1 of FIGS. 1 and 2 (.or the adjusting unit
of any other of the various heretofore described friction
clutches) to carry out certain adjustments for non-
existent wear upon the flywheel, the pressure plate
and/or the friction linings of the friction clutch. Tn
other words, it is necessary to undertake certain steps
in order to prevent undesirable axial, wobbling and/or
other stray movements of the flywheel from influencing
the adjusting unit. In the friction clutches which are
shown in FIGS. 1 to 27, i.e., in those which are equipped
with a sensor corresponding to the sense>r 13 in the
friction clutch 1 of FIGS. 1 and 2, the adjusting force
of this sensor must exceed the forces of inertia which
can influence the sensor. Such inertial forces are the
sums of forces due to inertia of the main diaphragm
spring (the spring 4 in the friction clutch Z), of the
adjusting member (such as 17) and/or the adjusting
elements (such as 18 and 24), a certain portion of the
3U mass of the sensor (such as 13) and, at least in certain
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CA 02446426 2003-11-12
instances, the masses of some additional components
multiplied by the maximum possible axial acceleration of
these parts and/or components, all due to axial and/oz~
other vibratory or other stray movements of the flywheel
in response to stray movements of the output element of
the prime mover.
By way of example, and referring to the .
friction clutch 100. of FIG. 27 wherein the sensor 10:13
engages the pressure plate 2003, it is also necessary to
take into consideration the inertia of the pressure plate
1003. Thus, it is necessary to ensure that the force
which is generated by the sensor will exceed the sum of
forces which act upon the sensor and are obtained by
multiplying the maximum axial acceleration with the
combined mass of al:L parts which act upon the sensor due
to their inertia. Such inertial forces can exert an
undesirable influence, particularly during actuation of
the friction clutch and also in disengaged condition of
the friction clutch.
In the embodiments of the improved friction
clutch which are shown in FIGS. 2S to 34, the wear
detecting means and the wear compensating means must also
be designed with a view to take into consideration those
forces which develop as a result of inertia of all parts
which are set in motion in response to axis l and/or other
vibratory movements which are transmitted from the output
element of the prime mover to the flywheel of the
friction clutch.
All in all, the designer of a friction clutch
with built-in wear compensating or ad~ustzng means must
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CA 02446426 2003-11-12
take into consideration the masses of 'those a laments
which can be acted upon and can be set in mot ion in
response to transmission of axial, rotary, wobbling
and/or other stray movements from the output element of
the prime mover to the flywheel of the fricti on clutch.
In the embodiments of FIGS. 28~-34, it is part icularly
important to take into consideration the inertia of a7L1
such parts which influence the operation of the ramps"
such as the ramps 11.42, 1143 in the ring 1126 of the
friction clutch 1101. shown in FIGS. 28 and 29.
FIG. 35 snows a friction clutch which embodies
ar is mounted ora one (secondary) mass or flywheel 140;3 of
a composite (twin) ~:lywheel 1401 further including a
flywheel or primary mass 1402 and a damper 1409 between
the masses 1402, 1403~ The primary mass 140 2 of the
composite flywheel 1401 can be connected to the output
element (e. g., a crankshaft, not shown) of ara internal
combustion engine and transmits torque to the' secondary
mass or flywheel 14c~3 corresponding, f or example, to the
flywheel 6 in the friction clutch l of FIGS. 1 and 2.
The friction clutch which embodies or is combined with
the secondary flywheel 1403 is denoted by the reference
character 1404. Tl'~~e friction clutch 1404 further
comprises a pressure plate 1428 and a torque transmitting
clutch disc or clutch plate 1405 between the pressure
plate 1428 and the secondary mass 1403. The hub 1405a of
the clutch disc 1405 can transmit torque to the inpujt
element of a variable-speed transmission in the power
train of a motor vehicle. The shaft ~f the input element
of the transmission is indicated at X~X.
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An antifriction bearing 1406 is installed
between the masses 1402 and 1403 of the composite
flywheel 1401; this bearing is disposed radially
inwardly of bolts 1408 or other suitable fasteners which
are used to secure the primary mass 1402 to the output
element of the engine. The primary mass 1402 has bores
or holes 1407 for the shanks 1440a of the fasteners~1408.
The damper 1409 between the masses 1402, 1403 of the
flywheel 1401 includes energy storing elements in the
form of coil springs 1410 acting in the circumferential
direction of the flywheel 1401 and being confined in an
annular compartment 1412 constituting the radially outer
part of a chamber 1411 between the masses 1402 and 1403.
The chamber 1411 is at least partially filled with a
viscous fluid, such as oil, grease or another lubricant.
At least the major part of the primary mass
1402 is constituted by a member 1413 which is made of a
metallic sheet material and includes a substantially
radially extending flange-like portion 1414 having an
axial protuberance a415 which is of one piece therewii:.h
and is located radially inwardly of the holes or bores
3407 for the fasteners 1408. The antifriction bearing
1406 which is shown in FIG. 3~ comprises a single row o f
spherical rolling elements 1406a and an inner race 1416
surrounding the free end of the axially extending
protuberance 1415 of the flange 1414. The outer race
1417 of the bearing 1406 is received in a central opening
provided in the radially innermost portion of the
secondary mass 1403; the latter resembles a
substantially flat disc or washer.
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The radially outermost part of the flange 14A4
forming part of the primary mass 1402 is of one piece
with a first wall 1418 which surrounds at least one-half
of the compartment 1412 and is welded or otherwise
sealingly secured to a second wall 1419 surrounding
another part of the compartment 1412. The wa 11 1418
and/or 1419 can directly or indirectly guide the radially
outermost portions of convolutions forming part of the
energy storing elements 1410 in the coaapartment 1412.
The reference character 1420 denotes a welded seam which
connects the walls 1418, 1419 to each other radially
outwardly of the compartment 1412 and ensures that the
confined viscous fluid cannot escape from the chamber
1411 under the action of centrifugal force wren the
composite flywheel 1401 receives torque from the output
element of the engine.
The compartment 1412 is divided into a series
of arcuate sections, one for each energy storing element
1410, and such sections are separated by partitions which
constitute abutments for the adjacent end convolutions of
the respective energy storing elements 1410. The
partitions can be made of one piece with the wall 1418
and/or 1419 of the primary mass 1402; they may
constitute inwardly bent pockets of the wal 1s 1418 and
1419. Such mode of making partitions between the energy
storing elements 1410 is particularly desirable when the
parts of the primary mass 1402 are made of a ductile
metallic sheet material.
The energy storing elements 1410 are further
acted upon by radially outwardly extending arms 1421
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CA 02446426 2003-11-12
adjacent the secondary mass 1403. The arms 1421 also
alternate with the energy storing elements 1410, as seen
in the circumferential direction of the composite
flywheel 1401, and cooperate with the aforediscussed
pockets of the primary mass 1402 to ensure that the
elements 1410 store energy (or additional energy)
whenever the mass 1402 turns relative to the mass 1403
and/or vice versa. These arms are provided on or can
constitute integral parts of the housing or cover 1422 of
.0 the friction clutch 1404. ~s shown, the arms 1421 are of
one piece with the axially extending portion 1423 of the
cover 1422. Each arm 1421 extends radially outwardly
into the compartment 1412 between the ends of the two
neighboring energy storing elements 1410. The axially
extending portion 1423 of tree cover 1422 has a portion
1423a which extends beyond the arms 1421 in a direction
toward the mass 1402 and surrounds the mass 1403. The
means for connecting the cover 1422 to the mass 1403 can
comprise inwardly extending portions (not specifically
20 shown) of the portion 1423 and complementary sockets in
the periphery of the ~~ass 1403. Other connecting means
(e.g., in the form of radially a>tending pins or the
like) can be used with similar advantage.
The cover L422 includes a bottom wall 1426 which
extends substantial 1y at right angles to the axis X-X constitutin<
the common axis of the clutch 1404 and the input element of the
transmission. and is remote from the arms 1421. This bottom wall
is outwardly adjacent a diaphragm spring 1427 which acts not
unlike a two-armed lever and serves to urge the pressure
30 plate 1428 axially toward the friction linings 1429 of the
129
CA 02446426 2003-11-12
clutch disc 1405. The projecting portion or portions
1428a of the pressure plate 1428 are engaged by the
circumferentiahly complete radially outer main portion of
the diaphragm spring 1427, and the latter includes
radially inwardly extending prongs 1427a forming part of
actuating means for the friction clutch 1404, i.e., of
means for engaging and disengaging the clutch.
FIG. 35 further shows resilient segments 1465
which are disposed between the two groups or sets of
friction linings 1429 and perform the same function as
the segments 10 in the friction clutch 1 of FIGS. 1 and
2.
The chamber 1411 and its compartment 1412 are
disposed, at least to a large extent, radially outwardly
of the secondary mass 1403 of the composite flywheel
1401. This renders it possible to position the member
1413 of the primary mass 1402 (i.e., of that mass which
is to be directly connected with the output element of an
engine) into immediate or close proximity to the
secondary mass 1403 in a region radially inwardly of the
chamber 1411. FIG. 35 shows a relatively narrow
clearance 1430 which is established hetween the member
1413 of the primary mass 1402 and the secondary mass
1403. Such design contributes significantly to
compactness of the friction clutch 1404, as seen in the
direction of the axis X-X, and more particularly of the
aggregate including the friction clutch 1404 proper, the
composite flywheel 1401 and the clutch disc 1405.
The chamber 2411 is sealed by an annular
sealing element 1431 which is installed between the
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CA 02446426 2003-11-12
radially inner portion of the wall 1419 (i.e., of the
primary mass 1402) and the axially extending portion 1423
of the cover 1422.
The aforementioned clearance 1430 between the
member 141.3 of the primary mass 1402 and the secondary
mass 1403 can be utilized to ensure desirable cooling of
the composite flywheel 1401. This is achieved by
inducing one or more currents of cool atmospheric air to
flow through the clearance when the aforementioned
aggregate or assembly is in actual use, i.e., when the
output element of the engine drives the primary mass 1402
and the latter drives the secondary mass 1403 through the
damper 1409 including the energy storing elements 1410 in
the compartment 1412 of the chamber 1411. The means for
cooling the flywheel 1401 further comprises passages or
channels 1433 which extend through the secondary mass
1403 radially inwardly of a friction surface 1432 which
is engageable by the adaacent set of friction linings
1429 when the friction clutch 1404 is engaged. The
channels 1433 communicate with the clearance 1430. The
cooling action is further enhanced by the provision of
additional channels 1435 which extend axially through the
secondary mass 1403 and are disposed radially outwardly
of the friction surface 1432. The channels 1435
communicate with the clearance 1430, the same as the
channels 1433. The channels 1433 supply cool atmospheric
air into the radially inner portion of the clearance
1430, and such air then flows radially outwardly to cool
the composite flywheel 1401 and to leave the clearance
1430 through the channels 1435. These chanriels can admit
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CA 02446426 2003-11-12
the atmospheric air into the cover 1422 which is provided
with outlets to permit escape of heated air into the
surrounding atmosphere.
The secondary mass 1403 j.s provided with holes
or bores 1434 which are disposed radially inwardly of the
channels 1433 and are aligned with the holes or bores
1407 to permit introduction of the fasteners 1408 which
serve to affix the primary mass 1402 to the output
element (e. g., a crankshaft) of an engine. In addition,
l0 the holes or bores 1434 can also promote circulation of
air in the clearance 1430, i.e., they can contria~ute to
more satisfactory cooling of the composite flywh eel 1401.
A further sealing element 1436 is disposed :in
the clearance 1430 to seal the latter from the r adially
innermost portion of the annular chamber 1413 for the
supply of viscous fluid and for the energy storing
elements 1410 of the damper 1409. The sealing element
1436 can include or constitute a membrane or a diaphragm
spring.
c0 The wall 1.418 of the primary mass 140 2 is
provided with a starter gear 1439 which is preferably
welded thereto.
The composite flywheel. 1401 inciucling the
masses 1402, 1403 and the group including the friction
clutch 1404 and the clutch disc 1405 together constitute
a preassembled module A which is or can be ass emblec~ at
the manufacturing plant and can be put to star age or
shipped to a maker of motor vehicles to be affixed to the
output element of an engine by the fasteners 1408 or in
30 any other suitable way. The assembly of the rnodulo A at
132
CA 02446426 2003-11-12
the plant contributes significantly to lower cost of the
improved aggregate, to lower cost of its storage and
shipment, and to lower cost of its attachment to the
output element of an engine. In order to assemble the
module A, the friction clutch 1404 is assembled with the
secondary mass 1403 and with the clutch disc 1405 in~ a
first step. The thus obtained subassembly including the
components 1403, 1404 and 1405 is thereupon assembled
with the primary mass 1402 by placing the member 1413 of
the primary mass next to the secondary mass 1403 so that
the masses 1402, 1403 are coaxial with one another. This
takes place before the wall 1419 is affixed (welded) to
the wall 1418 of the primary mass 1402~ The wall 7.419
surrounds the axially extending portion 1423 of the cover
1422 and is welded (at 1420) to the wall 1418 in a next
following step. ~f course, the energy storing elements
1410 are inserted into the compartment 1412 of the
chamber 1411 prior to welding of the walls 1418, 1419 to
each other.
The antifriction bearing 1406 is installed
between the masses 1402, 1403 in automatic response to
proper positioning of the member 1413 of the mass 1402
relative to the mass 1403; such bearing is installed
first on the axially extending protuberance 1415 of
flange 1414 of the member 1413. The fasteners 1408 are
inserted into the holes 1407 of the portion 1414a of the
flange 1414 before the masses 1402, 1403 are angularly
movably coupled to each other by the damper 1409~ Each
fastener 1408 can constitute a hexagon socket screw,
i.e., a screw with a polygonal socket 1440 in its head.
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The initial positions of the fasteners correspond to that
of the fastener 1408 shown in the lower half of FIG. 35.
It is preferred to provide means for yieldably holding
the shanks 1440a of the fasteners 1408 in the axial
positions corresponding to that of the shank forming part
of the fastener 1408 shown in the lower half of FIG. 35.
The holding means prevent accidental displacement or loss
of the fasteners 1408 and ensure that the shanks 1440a of
these fasteners are maintained in optimum positions for
introduction into complementary tapped bores or holes of
the output element of the engine.
The clutch disc 1405 is centered between the
pressure plate 1428 of the friction clutch 1404 and the
friction surface 1432 of the secondary mass 1403 of the
composite flywheel 1401 and is maintained in such
position while the module A is in storage or in transport
to the automobile assembly plant. The angular position
of the clutch disc 1405 in the module A is such that its
holes or bores 1443 are aligned with the holes o~ bores
1434 in the secondary mass 1403; this renders it
possible to introduce the working end of a tool (e.g., a
device analogous to a screwdriver) into the sockets 1440
in the heads of fasteners 1408 in order to drive the
shanks 1440a of such fasteners into the complementary
tapped bores or holes in the output element of the
engine. The tool can further extend through aligned
holes or bores 1444 which are provided in the prongs
1427a of the diaphragm spring 1427 and communicate with
the slots between neighboring prongs. The diameters of
the holes or bores 1443 are smaller than the diameters of
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CA 02446426 2003-11-12
the heads of the fasteners 1408 so that, once
installed in a manner as shown in the lower part of FIG.
35, the fasteners 1408 of a module A cannot become lost
or misplaced because they are confined in optimum
positions for attachment to the output element of an
engine in a motor vehicle. The openings 1444 in the
prongs 1427a of the diaphragm spring 1427 can constitute
simple recesses or notches; such recesses or notches
communicate with the slots between the respective prone
2427a to provide room for introduction of the
aforediscussed tool which must also pass through the
holes 1443 ana into the holes 1434 in order to enter the
sockets 1440 in the heads of the respective fasteners
1408.
It is often preferred to distribute the tapped
holes or bores in the output element of the engine and
the holes or bores 1407 in the member 1414 of the primary
mass 1402 in such a way that the mass 1402 can be affixed
to the output element in a single angular position, i.e.,
the holes 1407 need not be equidistant from each. other.
The dimensions of the openings I434, 1443 and 1444 are
selected in such a way that they permit~the working end
of a tool to engage the heads of the fasteners 1408, one
after the other, even if the holes 1434 are uniformly
distributed in the secondary mass 1403, the holes 1443
are uniformly distributed in the clutch disc 1405 and
the holes 1444 are uniformly distributed in the pronged
portion of the diaphragm spring 1427. The working end of
the tool has a shape such that it can be non-rotatably
received in the preferably hexagonal socket 1440 in the
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head of a fastener 1408.
The assembly of a module A at the manufacturing
plant contributes significantly to convenience,
simplicity and lower cost of installation of the
aggregate (including the composite flywheel 1401, the
friction clutch 1404 and the clutch disc 1405) in a motor
vehicle. This will be readily appreciated since the
making of the module A renders it possible to dispense
with a number of time-consuming operations which are
necessary to install heretofore known friction clutches
in automotive vehicles. For example, the clutch disc 1405
is properly centered in the module A so that no centering
of the clutch disc is needed immediately prior to or during
attachment of the composite flywheel 1401 to th a output
element of the engine. Furthermore, the clutch disc 1405
is already installed between the secondary mass 1403 and
the pressure plate 1428 at the time the secondary mass
1403 is to be coupled to the primary mass 1402 by the
bearing 1406 and the damper 1409, and trre friction clutch
1404 is properly attached to the output element as soon
as the latter is connected with the primary mass 1402 by
fasteners 1408. Still further, it is no longer necessary
to employ a centering mandrel, to center the clutch disc
1405 relative to the pressure plate 1428 at the motor
vehicle assembly plant, to select and insert the
fasteners 1408, to connect the friction clutch 1404 with
the composite flywheel 1401 and/or to extract a centering
mandrel during or subsequent to attachment of the
friction clutch to the engine.
The friction clutch 1404 is provided with an
- 136
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,adjusting unit 1445 which is or can be identical with or
analogous to any one of the adjusting units shown in and
described with reference to FIGS. 1 through 27. The
adjusting unit 1445 includes a sensor 2446 (e.g., in the
form of a diaphragm spring corresponding, for example, to
the spring 13~ and an annular member 1447 corresponding,
for example, to the member 17 in the friction clutch 1 of
FIGS. 1 and 2.
It is normally preferred, primarily for the
purpose of reducing the cost, to establish a permanent
connection between the cover 1422 and the secondary mass
1403. Such permanent connection can be established by
bonding (such as welding] or by deformation of selected
portions of the mass 1403 and/or cover 1422 so that the
separation of these parts would involve at least partial
destruction (such as extensive deformation) of the cover
and/or of the secondary mass. The establishment of such
permanent connection renders it possible to avoid the use
of screws, bolts and/or other threaded or other
fasteners. Since the aggregate including the twin~mass
flywheel 1401, the clutch disc 1405 and the friction
clutch 1404 is designed to remain fully assembled during
its entire useful life, i.e~, until the wear upon the
friction linings 1429 becomes excessive, there is no
urgent need to establish a readily separable connection
between these parts or to establish a connection which
would permit repeated assembly and dismantling of the
aggregate. In spite of the absence of means for
permitting repeated dismantling and assembly of the
aggregate which is shown in FIG. 35, such aggregate
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functions satisfactorily during its entire useful life
because the adjusting unit 1445 compensates for wear upon
the friction linings 1429 but preferably also for wear
upon one or more additional parts such as the secondary
mass 1403 andlor the pressure plate 1428. The dimensions
of the freshly installed friction linings 1429 c an be
selected with a view to ensure that they do nat become useless
due to excessive wear prior to expiration of the
anticipated useful life of the aggregate. As a rule, the
useful life of the aggregate will be selected to at least
match the anticipated life span of the motor vehicle in
which the aggregate is being put to use.
Twin-mass flywheels which can be used with
advantage in the improved aggregate, e.g., in a manner
as shown in FTG. 35, are disclosed, by way of example, .
in published German patent applications Serial Nos.
37 21 712~ 37 21 711, 41 17 571, 41 17 582 and
41 17 571.
The features which are disclosed in
the just enumerated published patent applications
can be readily combined with the features of the
improved friction clutch andlor with the features of the
improved aggregate in a number of different ways. By way
of example only, the aforementioned published German
patent application Serial No. 41 17 579 discloses several
manners of establishing a connection between the housing
or cover and a flywheel in such a way that the connection
cannot be terminated without at least partial destruction
of the flywheel and,/or housing.
The utilization of an adjusting device 1445 in
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an aggregate which employs a composite flywheel for
transmission of torque from a prime mover to the cover
and/or pressure plate of a friction clutch is advisable
and advantageous on the additional ground that the damper
1409 between the masses 1402, 1403 can prevent the
transmission to the mass 1403 (i.e., to the
counterpressure plate of the friction clutch 1404) .of a
number of stray movements which would be likely to
adversely influence the operation of the adjusting unit
1445. The damper 1409 is preferably installed radially
outwardly of the friction linings 1429 and radially
outwardly of the friction surface 1432 on the secondary'
mass 1403 andjor pressure plate 1403. In a composite
flywheel of the type shown in FIG. 35, the friction
diameter of the clutch disc 1405 should be smaller than
in conventional friction clutches which renders it
necessary to increase the biasing force in dependency on
the ratio of average friction radii in order to be in a
position to transmit a predetermined engine torque. If a
conventional friction clutch (without the adjusting un it
1445) were used, this would necessitate an increase of
the disengaging force. ~y employing in the aggregate of
FIG. 35 a friction clutch with an adjusting unit 1445
(e. g., an adjusting unit of the type described with
reference to FIGS. 1 to 7a~, it is now possible t~ reduce
the disengaging force and to thus avoid an increase of
disengaging force above that which is required in a
conventional friction clutch. In fact, it is now
possible to reduce the disengaging force below that which
must be applied in a conventional friction clutch in
139
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spite of the fact that the adjusting unit 1445 renders it
possible to compensate for wear during the entire useful
life of the friction clutch and/or of the structure (such
as a motor vehicle) in which the improved friction clutch
is put to use.
Referring to FIGS. 36 and 3~, there is shown a
torque transmitting arrangement or assembly 1501
comprising a counterpressure plate 1503 which is non-
rotatably connectable to the output element K (e.g., a
crankshaft) of an internal combustion engine, and a
friction clutch 1504 connected to the plate 1503 in such
a way that a clutch plate or clutch disc 1505 is disposed
between the plate 1503 and a pressure plate 1528 of the
friction clutch 1504. The hub of the clutch disc 1505
transmits torque to the input element (e.g., an
externally splined shaft) of a variable-speed
transmission in the power train between the friction
clutch 1504 and the wheels of a motor vehicle. The ax i.s
of the input element of the transmission is shown at X-X.
The friction clutch 1504 comprises a housing or
cover 1522 having an axially extending marginal portion
1523 which surrounds the pressure plate 1528 and the
friction linings 1529 of the clutch disc 1505. The free
end 1523a of the marginal portion 1523 (the latter can be
said to resemble a relatively short sleeve or tube)
surrounds the counterpressure plate 1503 and is non-
rotatably connected thereto. For example, the free end
1523a can be provided With radially inwardly extending
protuberances, lugs or like parts 1524 which extend into
complementary sackets or recesses of the counterpressure
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plate 1503 to ensure that this plate and the cover 1522
rotate as a unit. However, it is also possible to
connect the cover 1522 with the counterpressure plate
1503 in any one of a number of other ways; for example,
these parts can be welded to each other or the
connections between these parts can include threaded
fasteners, pins, studs, posts or like parts preferably
extending in the radial direction of the counterpressure
plate 1503 and of the marginal portion 1523 of the cover
1522. The just discussed connecting means preferably
also serve to accurately center the counterpressure plate
1503 and the cover 1522 relative to each other.
The cover 1522 comprises an annular section or
bottom wall 1526 which extends radially inwardly of the
marginal portion 1523 and is outwardly adjacent a
diaphragm spring 1527 which acts not unlike a two-armed
lever and serves to bias the pressure plate 1528 toward
the adjacent set of friction linings 1529 f orm.ing part
of the clutch disc 1505. The radially outermost part of
the circumferentially complete main portion of the
diaphragm spring 1527 can bear against the projecting
portion or portions of the pressure plate 1528, and a
radially inner part of such main portion is tiltably
mounted at the inner side of the bottom wall 1526 by a
seat. The radially inwardly extending prongs 1527a of
the diaphragm spring 1527 constitute the actuating means
of the means for engaging and disengaging the friction
clutch 1504. When the clutch 1504 is engaged, the
radially outermost part of the main portion of diaphragm
spring 1527 causes the pressure plate 1528 to bear
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against the adjacent set of friction linings 1529 and
also causes the other set of friction linings 1529 to
bear against the friction surface of the counterpressure
plate 1503. The means for engaging and disengaging the
friction clutch 150'4 further comprises a conventional
bearing or a pedal (similar or analogous to a gas pedal
in a motor vehicle) which must be actuated by the driver
in order to move the prongs 1527a along their
predetermined path and to thus effect the engagement o:r
disengagement of the friction clutch 1504.
The means for transmitting torque between the
pressure plate 1528 and the cover 1522 of the friction
clutch 1504 which is shown in FIG. 36 comprises leaf
springs 1521 each having a first end portion affixed to
the cover 1552 and a second end portion affixed to the
pressure plate 1528. It is presently preferred to employ
rivets 1521a or analogous fasteners as a means for
connecting the leaf springs 1521 to the pressure plate
1528 and/or to the cover 1522. As can be seen in the
upper part of FIG. 36, the rivets 1521a are preferably of
the type known as blind rivets; in FIG. 35P one such
blind rivet is denoted by the character 1490.
The friction clutch 1504,..i.e., the torque
transmitting arrangement or assembly 1501, comprises an
adjusting unit 1545 which is analogous to the adjusting
units of friction clutches shown in FIGS. 1 to 27 and
includes a diaphragm spring or sensor 1546 and an annular
adjusting member 1547. The adjusting unit 1545 serves to
compensate for wear upon the pressure plate 1528 and upon
the counterpressure plate 1503 but particularly or
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primarily for wear upon the friction linings 1529.
The adjusting unit 1545 includes ramps which
are provided directly in the annular member 1547 and are
designed in such a way that they establish air
transmitting passages 1547x. The member 1547 is located
at the inner side of the bottom wall 1526 of the cover
1522, and the passages 1547a extend in the direction~of
rotation of the friction clutch 1504. Such passages
promote desirable Gaoling of the friction clutch 1504
when the counterpressure plate 1503 is rotated by the
output element K of the engine because the passages
induce the flow of currents of cool air. This reduces
the thermal stresses upon the annular member 1547 which
can be made of a suitable plastic material. The annular
member 1447 of the adjusting unit 1445 of the friction
clutch 1404 shown in FIG. 35 can be constructed and
conf igurated in the same way as the annular member 154 7.
The means for affixing the counterpressure
plate 1503 to the output element K of the engine
comprises an axially elastic coupling element 1550 which
enables the plate 1503 to perform limited axial movements
relative to the output element and/or vice versa. The
illustrated coupling element 1550 is a disc having a
stiffness or rigidity such that it can effectively damp
axial, wobbling, angular and/or other stray movements
which the output element K wauld transmit to the frict i on
clutch 1504 and which could interfere with accuracy of
adjustments carried out by the unit 1545. The coupling
element 1550 need not damp any and all stray movements~
however, its damping action should be sufficient to
143
CA 02446426 2003-11-12
ensure that the unit 1545 can properly adjust the
position of the pressure plate 1528 in dependency upon
the extent of wear on certain parts of the friction
clutch 1504 and the aggregate 1501, especially in
dependency on the wear upon the friction linings 1529.
Furthermore, the elastic coupling element 1550 ensures
proper operation of the friction clutch 1504 by ensuring
proper operation of the adjusting unit 1545. Otherwise
stated, the coupling element 2550 should constitute a
barrier which is capable of transmitting torque from the
output element K of the engine to the counterpressure
plate 1503 but is also capable of shielding the
counterpressure plate 2503 and the friction clutch 1504
from any such axial, angular and/or other stray movements
or the output element K which could adversely affect the
operation of the friction clutch 1504 and particularly
the operation of the adjusting unit 1545. In the absence
of the coupling element 1550, or of a functional
equivalent of this coupling element, the unit 1545 would
be likely to carry out unnecessary axial adjustments of the
position of the pressure plate 1528 relative to the
counterpressure plate 1503 or not to carry out such
adjustments when they are warranted in view of the extent
of wear upon the friction linings 1529. Unnecessary
adjustments by the unit 1545 would be attributable
primarily to the mass of various parts of the aggregate
1501 and to acceleration of such mass due to vibration of
the output element K and (in the absence of the elastic
coupling element 1550) of various parts of the friction
clutch 1504. Alternatively, the relatively simple
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adjusting unit 1545 would have to be replaced with a much
more complex adjusting unit, namely a unit designed with
a view to take into consideration a host of additional
variables including the inertia-induced forces acting
upon the component parts of the adjusting unit.
Moreover, all such inertia-induced forces would have to
be properly related to each other in order to ensure~that
the thus modified adjusting unit would respond only and
alone to signals pertaining to the extent of wear upon
l0 the pressure plate 1528, the counterpressure plate 1503
and/or the friction linings 1529. As a rule, a thus
modified adjusting unit (to be used in lieu of the unit
1545 in the absence of the coupling element 1550) would
require a number of additional parts and its space
requirements would greatly exceed those of the unit 154 5:
The adjusting unit 1545 of FIG. 36 operates
between the cover 1522 and the pressure plate 1528 of the
friction clutch 1504. However, it is equally possible to
equip the aggregate 1501 with a friction clutch of the
20 type shown in FIGS. 28 to 34, i.e., with a friction
clutch wherein the adjusting means serving to compensate
for wear upon the friction linings is disposed between
the diaphragm spring and the pressure plate which is
biased by the diaphragm spring.
The radially outer portion of the
counterpressure plate 2503 in the aggregate 1501 of FIG.
36 is fixedly connected to the elastic caupling element
1550 by bolts 1551 or analogous threaded fasteners. For
example, the bolts 1551 can be replaced with blind rivets
30 of the type shown in FIG. 35, as at 1490, to connect leaf
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springs with the pressure plate 1428 of the friction
clutch 1404.. A narrow radially extending gap 1552 is
established between the neighboring surfaces of the
counterpressure plate 1503 and the coupling a lament 155
radially inwardly of the fasteners 1551; the width of
this gap (as measured in the direction of the axis %~%)
determines the maximum amplitude of axial stray movements
which can be damped by the element 1550 when the
aggregate 1501 of FIG. 36 is in use. fore specifically~
the width of the gap 1552 determines the maximum
amplitude of those. axial movements which are directed
from the output element K toward the counterpressure
plate 1503. The width of the gap 1552 further determines
the extent of maximum movability of the friction clutch
1504 and counterpressure plate 1503 toward the output
element K. As a rule, the central portion of the
counterpressure plate 1503 does not contact the coupling
element 1550 if the engine functions properly.
The counterpressure plate 1503 is a ring which
surrounds an axial protuberance 1553 of a washer-like
member 1554; the latter is fixedly secured to the
central portion of the elastic coupling element 1550 and
can serve as a means for centering the element 1550 on a
coaxial stub-like tubular projection 1555 of the output
element K. The radially inner portion of the element
1550 is clamped between a front end face 155 of the
output element K and the centering member 15 54.
The axial protuberance 1553 of the centering
member 1554 has radially outwardly extending portions
1558 which constitute stops in that they limit the extent
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CA 02446426 2003-11-12
of movability of the counterpressure plate 15 O3 axially
and away from the central portion of the elastic coupling
element 1550 and output element K. To this end, the
projecting portions or stops 1558 extend behind the
central portion of the plate 1503, i.e., such central
portion of the plate 1503 is located between the central
portion of the element 1550 and the stops 155 8. A narrow
slot or clearance 1559 is normally established between
the stops 1558 and the central portion of the plate 1503,
and the width of this clearance 1559 can aqua 1 or
approximate the width of the gap 1552.
The surface surrounding the central opening of
the counterpressure plate 1503 can be slipped onto the
centering member 1554 without any or with a minimum of
play, i.e., the plate 1503 can be mounted on the member
1554 without any or with a minimum of radial play but i s
movable axially thereon to the extent which is determined
by the gap 1552 and the clearance 1559~ In other words,
the centering member 1554 can be said to constitute a
guide which confines the counterpressure plate 1503 to
movements in the direction of the axis X-X. However, it
is equally within the purview of the invention, and often
preferable, to mount the radially inner port ion of the
ring-shaped counterpressure plate 1503 on the portion
1553 of the centering member 1554 with at least some
radial play to thus ensure that, in normal operation of
the aggregate 1501 (and assuming that the op~rat3on of
the engine including the output element X is
satisfactory), the counterpressure plate 150 3 need not be
in any contact with the centering member 155 4 and/or its
147
CA 02446426 2003-11-12
portion 1553 and/or the projections 1558 and/or the
central portion of the elastic coupling element 155~.
It is further within the purview of the
invention to provide the aggregate 1501 with additional
means for preventing the transfer of stray movements
between the output element K and the counterpressure
plate 1503 or to use such additional means in lieu of the
element 1550 . For example, the additional preventing
means can be designed to damp any such stray movements
which cannot be damped and/or otherwise counteracted by
the caupling element 1550 to thus even further ensure
reliable operation of the adjusting unit 1545. Such
additional preventing means can be designed to destroy
energy which is attributable to vibratory and/or other
stray movements of the output element K, e.g., in a
manner as shown in FIG. 37, namely by relying on
friction.
FIG. 37 shows that the radially innermost
portion of the counterpressure plate 1503 and the
external surface of the annular portion 1553 of the
centering member 1554 are separated from each other by a
further damper 1560. For example, the damper 1560 can
consist of or can utilize a ring which is undulated in
the circumferential direction so that its undulations
extend radially. the ring of the damper 1560 can be
installed in radially stressed candition to establish
friction between its external surface and the surface
surrounding the central opening of the counterpressure
plate 1503 whenever the output element K causes the
member 1554 and its portion 1553 to perform stray
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movements in the direction of the axis X-K. In other
words, the ring 1560 can prevent the transfer of stray
movements from the output element K to the
counterpressure plate 1503 or reduces the amplitude of
such movements to an acceptable minimum. It is possible
to utilize a friction generating ring 1560 in the form of
a split ring.
The radially outermost portion of the elastic
coupling element 1550 carries a starter gear 1561 which
can be welded or otherwise affixed thereto.
The coupling element 1550, the counterpressure
plate 1503, the clutch disc 1505 and the friction clutch
1504 can be assembled into a module (corresponding to the
module A shown in FIG. 35) which can be assembled at the
manufacturing plant for convenient storage, shipment to
an automobile assembling plant, arid mounted on the output
element K of an engine with substantial savings in space,
initial cost and assembly cost. The fasteners 1556 which
are shown in FIG 36 and serve to secure the centering
member 1554 and the coupling element 1550 to the output
element K can constitute hexagon socket screws or bolts.
As already described with reference to FIG. 35, such
fasteners can be installed in the aforediscussed module
in such a way that they cannot be lost and are maintained
in optimum positions for attachment to the output element
K of the engine.
The clutch disc 1505 of the aggregate 1501
which is shown in FIG. 3.6 is installed between and is
centered relative to the pressure plate 1528 of the
friction clutch 1504 and the counterpressure plate 1503
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CA 02446426 2003-11-12
o.f the aggregate 1501. Moreover, the openings or holes
1562 which are provided in the clutch disc 1505 are in at
least partial alignment with openings :564 in the pronged
radially inner portion 1527a of the diaphragm spring 1527
in order to permit the penetration of the working end of
a tool 1563 into the polygonal sockets in the heads of
the fasteners 1556 when it becomes necessary to drive the
shanks of such fasteners into complementary tapped bores
or holes in the output element K. The illustrated clutch
disc 1505 comprises an input portion including the
friction linings 1529, an output portion including the
aforementioned hub which can be non-rotatably slipped
onto the input element of a transmission, and a suitable
damper employing coil springs or otherwise configurated
energy storing elements disposed between the input and
output portions~ the holes 1562 are disposed radially
inwardly of the damper between the input and output
portions of the clutch disc 1505 which is shown in FIG.
36. The holes 1564 in the pronged portion 1527a of the
diaphragm spring 3527 are optional, i..e., such holes or
bores are necessary only if the tool 1.563 cannot pass
through the slots between the neighboring prongs of the
diaphragm spring 1527. The extent of alignment between
the holes or bores 1564, the holes or bores 1562 and the
heads of the fasteners 1556 should suffice t~ ensure that
the working end of the tool 1563 will be capable of
entering the sockets in the heads of the fasteners 1556
even if the holes which are provided in the central
portion of the elastic coupling element 1550 to permit
the shanks of the fasteners to pass therethrough are not
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CA 02446426 2003-11-12
exact 1y equidistant from each other. As already
described with reference to FIG. 35,,such unequal
distribution of holes in the coupling element 1550 and in
the output element K is often desirable in order to
ensure that the counterpressure plate 1503 can be mounted
on the output element K in a single predetermined angular
i
position of these parts relative to each other.
As already described with reference to the
previously discussed embodiments of the present
l0 invention, the adjusting unit 1545 enables the friction
clutch 1504 to operate satisfactorily during its entire
useful life. This is due to the fact that the unit 154 5
can compensate at least for wear upon the friction
linings 1529 of the clutch disc 1505. Moreover, the
adjusting unit 1545 renders it possible to permit the
utilization of a diaphragm spring 1527 which is best
suited to ensure that the magnitude of the force acting
upon the pressure plate 1528 to clamp the friction
linings 1529 between the friction surfaces of the plates
20 1503, 1528 remains within an optimal range f or a long
interval of time, particularly uhtil the wear upon the
linings 1529 has progressed to an extent which warrants
discarding of the aggregate 1501. The diaphragm spring
1527 is preferably designed and mounted in such a way
that it must merely furnish a. force which is necessary to
ensure adequate biasing of the pressure plate 1528 for
the purpose of transmitting the designed torque from the
clutch disc 1505 to the input element of the variable-
speed transmission in the power train of a motor vehicle.
30 The adjusting unit X545 ensures proper positioning of the
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diaphragm spring 1527 during the entire life span of the
aggregate 1501, i.e., it ensures that the bias of the
diaphragm spring 1527 upon the pressure plate 1528 is
satisfactory and practically unchanged whenever the
friction clutch 1504 is engaged during the entire life
span of the friction clutch.
The clutch disc 1505 further comprises
resilient segments 1565 which constitute a means fox
gradually reducing the torque which is transmitted by the
clutch disc 1505 during a portion of movement of the
prongs I527a along their path to disengage the friction
clutch 1504. Furthermore, the segments 1565 ensure a
gradual increase of torque which can be transmitted from
the clutch disc 1505 to the variable-speed transmission
during engagement of the friction clutch 1504, i.e.,
while the prongs 1527a of the diaphragm spring 1527 axe
caused to move in the opposite direction. This, in turn,
renders it possible to reduce the magnitude of the force
which is necessary to disengage the friction clutch 1504
and to ensure a more satisfactory variation of such
force in the course of the actual disengaging operation.
Thus, a desired variation of clutch disengaging forces
can be achieved by the simple expedient of properly
relating the forces which are generated by the resilient
segments 1565 (or equivalents of such segments) and the
diaphragm spring 15.27, i.e., by properly relating the
force-to-displacement ratios of such resilient means.
This renders it possible to optimally design the elastic
coupling element 1550, i.e., to ensure that the element
1550 will damp any and all stray movements which would be
I52
CA 02446426 2003-11-12
likely to adversely influence the operation of the
adjusting unit 1545. As mentioned above, such stray
movements can include axial wobbling, bending, angular,
tilting and/or other movements which are carried out by
the output element K and should not be transmitted to the
counterpressure plate 1503. T1-ie magnitude of disengaging
forces acting upon the coupling element 1550 is minimal.
Thus, the forces which are required. to disengage the
friction clutch 1504 can be taken up by the element 1550
without any appreciable axial displacement of the '
aggregate 1501.
The elastic coupling element 1550 can be
readily designed and mounted in such a way that it can
shield the counterpressure plate 1503 dens. hence
also the adjusting unit 1545, from a substantial
number of stresses which could result in unintentional
or unnecessary adjustment or adjustments of the distance
between the'pressure plate 1528 and the counterpressure
plate 1503. It is particularly important to ensure
that the coupling element be capable of reliably
counteracting the transmission of axial and wobbling
movements of the output element K of a prime mover
to the friction clutch 1504. As concerns the construction
and mounting of the elastic coupling element 1550,
reference may also be had, for example, to to the
published European patent applications Serial I~3os.
0 385 752 and 0464 997 as well as to the SAE Technical
Paper No. 9 003 91.
The coupling element 1550 is p~_r-ticularly
effective in preventing undesirable adjustments by the
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CA 02446426 2003-11-12
unit 1545 due to axial stray movements of the pressure
plate 1525 relative to the cover 1522 when the friction
clutch 1504 is disengaged. Such undesirable adjustments
would be attributable to vibratory movements of the
counterpressure plate 1503 and/or diaphragm spring 1527.
Any unintentional adjustments of the diaphragm spring
1527, i.e., any adjustments which are not necessary to
compensate for wear upon the friction linings 1529 but
are attributable to axial, wobbling and/or other stray
movements of the output element K, could result in an
undesirable reduction of the bias of the diaphragm spring
upon the pressure plate 1528 below an acceptable minimum
and would prevent the friction clutch 1504 (and its
clutch disc 1505) from transmitting torques of desired
magnitude.
The aforediscussed design of the improved
friction clutch renders it possible to maintain the
disengaging force at a low value in spite of a reduction
of the outer diameter of the friction linings and the
resulting need to increase the bias of the diaphragm
spring or its equivalents) upon the pressure plate.
Since the disengaging force is reduced, the stressing of
the bearing (such as the bearing 1405 in FIB. 35) is less
pronounced. Thus, it is possible to employ a less
expensive antifriction bearing and/or a bearing whose
space requirements are low.
Still another advantage of the improved
friction clutch and/or of an aggregate which employs such
friction clutch and/or of a driving unit which employs
the improved friction clutch and/or the improved
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CA 02446426 2003-11-12
aggegate is that compensation for wear entails a
pronounced lengthening of the useful life of the friction
clutch. This renders it possible to avoid frequent (or
any) replacement of parts which are subject to wear,
particularly the clutch disc 1405. This, in turn, brings
about the aforediscussed advantage that it is now
possible to establish a permanent connection between the
counterpressure plate and the cover of the friction
clutch, i.e., a connection whose termination necessitates
at least partial destruction of «t least one of the
interconnected parts. Such connection can include that
which is shown in FIG. 36 and/or a connection which
employs rivets, welded seams or the like. The
establishment of a permanent or practically permanent
connection is particularly desirable and advantageous
when the dimensions of the space which is available for
the improved friction clutch and/or the improved
aggregate and/or the improved driving unit are small or
extremely small, e.g., in a compact motor vehicle. Thus,
even relatively small reductions of space requirements
(such as avoiding the use of screws or bolts whose heads
would project radially outwardly beyond the cover 1422
and/or beyond the composite flywheel 1401) are important
to ensure that the friction clutch can be used in a
particular series of motor vehicles. The construction
which is shown in FIG. 35, as well as the construction
wriich is shown.in FIG. 36, ensures that, with the
exception of the starter gear 1561, the radially
outermost part of the composite flywheel 1401 or the
radially outermost part of the cover 1522 determines the
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maximum space requirements of the improved aggregate or
driving unit because the means for connecting the cover
to the counterpressure plate 1403 or 1503 does not extend
radially beyond the flywheel 1401 or the housing 1522.
The improved friction clutch with automatic
compensation for wear upon one or more parts (e. g., with
the adjusting unit 1545 of FIG. 36) can be utilized with
particular advantage in driving units which are used in
motor vehicles, especially in vehicles employing at least
l0 partially automatic (including automatic and
semiautomatic) transmissions. The friction clutch is
then installed between a prime mover (such as the engine
of a vehicle) and the transmission and is operated or
controlled at least in dependency upon the operation of
the at least partly automatic transmission. It is
presently preferred to establish a fully automatic
control for the friction clutch. Automated and fully
automatic controls for a friction clutch are disclosed,
for example, in published German patent application
20 Serial No. 40 11 650.9 to which reference may be had, if
necessary.
In heretofore known driving units which employ
an automatic or semiautomatic transmission and a
conventional friction clutch, actuation of the friction
clutch and the design of actuating means (such as
electric motors and/or cylinder and piston assemblies)
present numerous problems. Actuation of a conventional
friction clutch necessitates the applicatiori of a
relatively large disengaging force which, in turn,
30 necessitates the use of rather bulky and powerful
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actuating means therefor. This contributes to the
weight, space requirements and cost of such driving
units, i.e., of units which employ at least partly
automated transmissions in conjunction with conventional
friction clutches. Moreover, the inertia of relatively
large, bulky and heavy actuators which are employed in
conventional driving units prolongs their reaction time.
If the actuators are cylinder and piston unit s, the
application of relatively large forces to actuate the
friction clutch necessitates the flow of large quantities
of a hydraulic or pneumatic fluid which also contributes
to longer reaction times of such actuators. Moreover, it
is necessary to employ one or more relatively large pumps
which are required to supply the cylinder and piston
units with requisite quantities of a pressurized fluid.
Attempts to eliminate some drawbacks of the
just discussed conventional driving units include the
utilization of compensating springs which ar ~ intended to
reduce the actuating force necessary to disengage the
friction clutch and to thus permit the utili nation of
smaller (more compact) actuators. Reference may be had,
for example, to published German patent application
Serial No. 33 09 427. However, since the disengaging
force varies during the useful life of a conventional
friction clutch (the required force is relatively small
when the friction clutch is new but increases with
increasing wear upon the friction linings during the life
span of the friction clutch), a compensating spring can
reduce only a relatively small fraction of the normally
required disengaging force. If one takes iazto
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consideration all tolerances, it is still necessary to
provide actuators which must furnish a disengaging force
exceeding that which is necessary for an unused
conventional friction clutch, and this in spite of the
utilization of compensating springs. ~n the ~ther hand,
a driving unit which employs the improved friction clutch
with an adjusting unit capable of compensating for wear
at least upon the friction linings, and with a prime
mover as well as an automatic or semiautomat is
transmission, renders it possible to greatly reduce the
disengaging force well below that which is required for
proper operation of conventional driving units. Such
reduction can take place directly in the friction clutch,
and the magnitude of the disengaging force remains
practically unchanged during the entire useful life of
the friction clutch. This renders it possib 1e to
simplify and thus reduce the cost, bulk and reaction time
of the actuators with attendant savings in space
requirements and weight of the entire driving unit.
Thus, the driving unit can be designed to st and
relatively small pressures and/or forces. Furthermore,
this results in a substantial reduction or even complete
elimination of losses due to friction and/or decreasing
resiliency of parts in the disengaging means for the
improved friction clutch.
The improved friction clutch and/~r the
aggregate or assembly employing the improved friction
clutch is susceptible of numerous additional
modifications without departing from the spirit of the
present invention. For example, the features of various
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described and shown clutches and/or aggregates can be
used interchangeably or in combination with each other.
Furthermore, the improved friction clutch and/or the
improved aggregate and/or a motor vehicle which embodies
the improved friction clutch or aggregate can also embody
numerous additional features which are known per se but
could further enhance the useful life and/or other
desirable characteristics of the improved friction clutch
and/or aggregate. Still further, at least some
1~ individual features of the aforedescribed friction
clutches and/or aggregates embody features which are or
could be considered to be novel and patentable per se.
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