Note: Descriptions are shown in the official language in which they were submitted.
CA 02399314 2002-09-19
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This application is a divisional of Canadian Patent Application
No. 2,152,122 filed June 19, 1995.
AUTOMATICALLY ADJUSTING FRICTION TORQUE DEVICE
FIELD OF THE INVENTION
This invention relates generally to a friction torque device,
and more particularly to a friction torque device that
automatically adjusts to compensate for wear on a friction surface
within the device.
BACKGROUND OF THE INVENTION
A friction clutch or brake includes an engaging member
having a friction surface that wears over the life of the
device. In order for the friction torque device to continue
operating effectively, the relative position -of the engaging
members must be adjusted or realigned to comgensate for wear
that occurs on the friction surface.
More specifically, in a friction clutch, torque is
transmitted from a driving member to a driven member, each
member rotating about an axis. The driven member is interposed
between the driving member and a pressure plate. In aormal
operation, a release assembly cooperates with the pressure plate
to selectively move the pressure plate axially towards' the
driven member in order to engage and disengage the clutch. As
wear occurs on a friction surface of the driven member, the
pressure plate must be moved an additional axial increment to
engage the driven member with the driving member. The relative
position of the pressure plate must therefore be compensated
internally for this additional increment of movement.
With most heavy duty friction clutches, the adjustment of
a release bearing and spring assembly is manually achieved in
order to compensate for wear on the friction surface of the
driven member. Manual adjustment, however, requires continuous
CA 02399314 2002-09-19
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monitoring to determine if adjustment is necessary, as well as
manpower to perform the adjustment. If the adjustment is not
timely completed, the clutch will operate leas effectively.
It is also laiown in the art to provide a clutch with an
automatic adjustment mechanism. While a number of such
mechanisms do compensate for wear, numerous parts are typically
required for the desired result. Further, the operative parts
are frequently disposed outside the cover of the clutch, thereby
subjecting the parts to possible damage and an increased
likelihood of breakdown. More significantly,. prior art
automatic adjustment mechanisms often do not fully, or timely
compensate for wear on the friction surface. This is due, in
part, to incomplete adjustment, or delayed adjustment after the
friction surface has worn.
It is therefore a goal of this invention to provide a
friction torque device with an automatic adjustment mechanism
which has a simple structure with a minimum of interconnected
parts, wherein the parts are disposed within a housing or cover
for the device. It is a further goal of the invention to
provide an automatic adjustment mechanism that directly and
effectively adjusts the friction torque device during normal
operation.
~lllltY OF T~ I~TI01~
A friction torque device includes an adjustment mechanism
for adjusting the relative position of a release bearing and
spring assembly in response to wear on a friction surface of a
driven member. The friction torque device transmits torque from
a driving member to the driven member, which is coupled to an
axially extending driven shaft. A cover is secured to the
driving member for rotation therewith. The pressure plate and
CA 02399314 2002-09-19
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driven member are sandwiched between the driving member and the
cover. A release assembly extends circumferentially about the
driven shaft.
The adjustment mechanism includes a first annular cam
ring, and a second annular cam ring adjacent the first annular
cam ring. Opposed axial faces of the cam rings include
corresponding annular tamped surfaces for caroming. The cam
rings rotate with respect to each other for axial displacement
of the cam rings. The adjustment of the clutch is automatically
set each time the clutch is fully disengaged. The adjustment is
a direct function of increased movement of the pressure plate
due to wear on friction surfaces, which is triggered by a pin or
pin assembly that cooperates with the pressure plate. The
increment of wear on the friction surface of driven member is
directly translated into a gap between the annular cam rings.
The cam rings cam against each other to displace this gap when
the clutch is fully disengaged.
In a first embodiment, the adjustment mechanism is coupled
to the cover. A radially extending lever is interposed between
the release assembly and the adjustment mechanism, wherein the
lever pivots about an axial end of the adjustment mechanism.
The lever cooperates with the axial end of the adjusuaent
mechanism and the release assembly to move the pressure plate to
engage and disengage the friction device. The axial end of the
adjustment mechanism is at a first position relative to cover
prior to wear on said friction surface. The lever provides a
pulling force on the axial end of the adjustment mechanism to
move the axial end of the adjustment mechanism to a second
position relative to cover after wear has occurred on the
friction surface. Such movement occurs when the clutch is fully
disengaged. The first embodiment includes a pin assembly for
securing the pressure plate to the cover, which allows for free
axial movement of the pressure plate with respect to the cover
CA 02399314 2002-09-19
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within a limited range. The pin assembly forms an interference
fit with the cover, such that a force greater than the
interference fit is able to move the pin assembly with respect
to the cover. Further, in order to provide a biasing force on
the adjustment mechanism, a first set of straps secure the
pressure plate to the cover and a second set of straps secure
the adjust~t mechanism to the pressure plate. The straps allow
for slight axial movement, but otherwise prevent relative
rotation of the members to which the straps are secured. The
straps further serve to bias the lever against the pressure
plate.
In a second embodiment, the adjustment mechanism is
coupled to the pressure plate. An annular diaphragm spring
extends radially between the release assembly sad the cover, and
pivots about a fulcrum on the pressure plate. The fulcrum of
the pressure plate is formed on the adjustment mechanism. The
first cam ring rotates with respect to the second cam ring to
move the fulcrum from a first axial position with respect to the
pressure plate, to a second axial position. The second axial
position is spaced away from the first a:ial position. The
first cam ring is rotated in response to wear on a friction
surface of the device. The second embodiment includes a, pin
which allows for free axial movement of the pressure plate
between the driving member and the cover within a limited
range. The pin forms an interference fit with the pressure
plate, such that a force greater than the interference fit is
able to move the pin relative the pressure plate.
These and other features of the present invention can be
best understood from the following specification and drawings,
of which the following is a brief description.
CA 02399314 2002-09-19
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BgIBF ,~BSC~IPTIOIf OF 1'~ DBAilII~6S
Figure 1 is an environmental view illustrating an
automatically adjusting clutch mounted in a heavy duty vehicle.
Figure 2 is a perspective view of the automatically
adjusting clutch.
Figure 3 is a cross-sectional view of the automatically
adjusting clutch.
Figure 4 is as exploded perspective view of an adjustment
mechanism within the clutch.
Figure 5 is a fragmentary plan view of the adjustment
mechanism.
Figure 6 is a fragmentary perspective view of the
automatically adjusting clutch.
Figure 7 is a partial radial cross-sectional view of the
automatically adjusting clutch, including a connection pin
assembly.
Figure 8 is an enlarged partial cross-sectional view of a
portion of the automatically adjusting clutch.
Figure 9A is a partial radial cross-sectional view of the
clutch shown in an engaged position.
Figure 9B is a partial radial cross-sectional view of the
clutch shown in an intermediate disengaged position prior to
adjustment.
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Figure 9C is a partial radial cross-sectional view of the
clutch shown in a fully disengaged position after ad3ustment,
Figure 10 is an alternate embodiment of an automatically
adjusting clutch.
DBTAIhBD DBSCgIPTI011 OF 1'8B PBBFBItBBD BI~ODII~IT
referring now to Figure 1, a friction torque device is
shown as a heavy duty clutch 20 which selectively transmits
torque from an engine flywheel 22 to a -driven shaft 24 of a
vehicle transmission 26. Flywheel 22 is the driving member
providing torque.. which is selectively transmitted to the
transmission. A standard clutch release assembly 28 is employed
for affecting clutch disengagement from flywheel 22. Such
movement of release assembly 28 is achieved by depression of a
clutch pedal 30 in a vehicle cab. Clutch pedal 30 is
mechanically linked to release assembly 28. A full stroke of
pedal 30 will fully disengage clutch 20, moving release assembly
28 to an extreme right position.
referring to Figures 2 and 3, flywheel 22 is fixed to a
cover 32 for rotation therewith. Cover 32 is in a fixed
position relative to flywheel 22, and includes a radially
extending wall 33 which is spaced from flywheel 22 a fixed
distance. A pressure plate 34 and a driven member 36 are
sandwiched between flywheel 22 and cover 32, which rotate about
drive axis A-A. Driven member 36 is rotationally fixed to the
axially extending driven shaft 24. As will be apparent to those
skilled in the art, pressure plate 34 is selectively moved the
left to frictionally engage pressure plate 34, driven member 36
and flywheel 22 to transmit torque from flywheel 22 to driven
shaft 24. Driven member 36 includes a friction pad 38 on each
axial side of the driven member. In Figure 2, the relative
thiclaiess of friction pad 38 is enlarged to emphasis the effect
CA 02399314 2002-09-19
of wear which occurs on a friction surface 40 of friction pad 38
over the life of clutch 20.
Due to the wear on friction surface 40, driven member 36
must be moved to the left an additional axial distance to engage
flywheel 22. During operation of the clutch, and more
specifically, when the clutch is fully disengaged, an adjustment
mechanism 42 automatically adjusts the clutch to compensate for
this wear.
Adjustment mechanism 42 is annular and . includes an
adjusting ring 44, a left cam ring 46 rigidly secured to
adjusting ring 44, and a right cam ring 48 adjacent left cam
ring. Adjustment ring 44, left cam ring 46 and right cam ring
48 eztend, about axis A-A. Adjustment mechanism.42 is mounted to
cover 32 for rotational movement therewith, but is otherwise
axially movable within a limited range. As will be described,
right cam ring 48 is mounted for limited rotational movement
with respect to adjusting ring 44, left cam ring 46, and cover
32.
Release assembly 28 includes a sleeve 50 positioned
circumferentially about driven shaft 24. A pull assembly 52 is
carried by sleeve 50, and secured at one end thereof. A
retainer 54 is secured to the opposite end of sleeve 50, and
positioned circumferentially about sleeve 50. As shown in
Figure 3, release assembly 28 contacts a transmission housing 55
when moved to an extreme right position. The transmission
housing is a stop for release assembly 28, and defines the fully
disengaged position of clutch 20. Transmission housing 55 is in
a fazed axially spaced location with respect to flywheel 22, and
permits release assembly 28 to be returned to a control location
for adjustment of clutch 20. Another form of a stop could
extend from cover 32 to provide a control location for axial
CA 02399314 2002-09-19
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movement of release assembly 28, the atop providing an extreme
right position for the release assembly.
Coil springs 5G are interposed between cover 32 and
retainer 54 forming a spring assembly. As is well lmown in the
art, coil springs 5b urge retainer 54 to the left, or engaged
position. To engage and disengage the clutch, a plurality of
levers 58 are radially_ interposed between retainer 54 and
ad3ustment mechanism 42. As more clearly seen in Figure 8, a
radially inner portion 60 of each lever 58 is received in a
peripheral groove 62 formed in retainer 54. A radially outer
portion 64 of each lever 58 has an opening 66 which receives a
leftwardly projecting pivot extension 68 formed on a left face
of adjusting ring 44. Pivot extension 68 is the extreme left
axial end of adjustment mechanism 42. Pivot eztension 68
further includes a radial lip 70 extending radially inwardly.
Lip 70 assists in securing lever 58 to adjusting ring 44.
A leftwardly extending projection 72 of lever 58 is
intermediate the radially inner portion 60 and radially outer
portion 64 of each lever. Projection 72 pivotally and
pressingly engages an annular shoulder 74 formed on the right
side of pressure plate 34. Thus, leftward movement of retainer
assembly 28 causes lever 58 to apply a leftward force on
pressure plate to engage the clutch members.
Referring now to Figures 4 and 5, an axial face 75 of Left
cam ring 46 includes a plurality of studs 76 each extending into
a corresponding aperture 78 formed in adjusting ring 44 to
fixedly secure left cam ring 46 to adjusting ring. Adjusting
ring 44 and left cam ring 48 are rotationally fixed to cover 32,
but are otherwise permitted limited axial movement. In
contrast, right cam ring 48 is permitted limited rotational
movement with respect to cover 32.
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An axial face 79 of left cam ring 46, which is opposite
adjusting ring 44, includes a plurality of annular ramps 80.
Ramps 80 extend the full circumferential extent of left cam ring
46. Each of the ramps 80 extends from a first axial position 82
to a second axial position 84, defining an axially e,~ctend~ng ledge
86 in between the ramps.
An axial face 87 of right cam ring 48 includes a plurality
of annular ramps 88. The opposite axial face 83 of right cam
ring 48 contacts cover 32. Ramps~88 of right cam ring 48
contact ramps 80 of left cam ring 46 and are dimensioned and
shaped to conform to ramps 80 for caroming. "Further, the
contacting surfaces of ramps 80 and 88 include serrations 90.
Serrations 90 assist in locking the contacting surfaces
together, increasing the frictional resistance between left cam
ring 46 and right cam ring 48. Therefore, a greater force is
required for right cam ring 48 to rotate with respect to left
cam ring 46 w2th serations than without sexations. Serations 90
may not be desired i,rith all clutches.
Right cam ring 48 is biased to rotate with respect to
cover 32 by a spring assembly 91. Spring assembly 91 includes
bracket 92 and spring 94. Bracket 92 is secured to cover 32 by
rivets 95. Bracket 92 includes a spring seat 96 at one
circumferencial end and an arm 98 at the other circumferentisl
end. Spring 94 is received radially inward of right cam ring
48, and extends between seat 96 of bracket 92 and a notch 100
formed in right cam ring 48. Bracket 92 secures one end of
spring 94, and assists in maintaining spring 94 in a curved
orientation, which provides an inner radial clearance. In so
doing, spring 94 may be placed in tension without interfering
with other members of the clutch. Preferably, spring 94 is
formed from a continuous coil, wherein each end of spring 94 are
wound to flair outwardly to define a catch plate at each end of
the spring. One end of spring 94 forms a first catch plate 102
which is received within seat 96 of bracket 92, and the other
CA 02399314 2002-09-19
_ _ -10-
end of spring 94 forms a second catch plate 104, which is
received within notch 100.
An indicator tab 106 extends from right cam ring 48
through a circumferentially extending slot 108 in cover 32.
Indicator tab 106 indicates the amount that right cam ring 48
has rotated with respect to cover 32, thus indicating the amount
of adjustment which has occurred within clutch 20. Further,
indicator tab 106 may be used to re-set the adjustment mechanism
42 when friction pads 38 are replaced.
As shown in phantom in Figure 5, counterclockwise,rotation
of right cam ring 48 applies a tension to spring 94. ~ihen under
tension, spring 94 applies a biasing force on right cam ring 48
so that right cam ring rotates with respect to left cam ring
under conditions required for ad3ustment. As right cam ring 48
rotates clockwise, ramps 80 and 88 cam against each other,
moving adjusting ring 44 from a first axial position to a second
axial position,. the second axial position being spaced a greater
axial distance frown wall 33 of cover 32 than the first axial position:
~e ca~mti:ng thereby increases an axial displacement of left cam ring
and right cam ring. 'I~e mechanism 42 is designed to stop adjusting
when the clutch is fully worn. ~~en the friction surfaces 40 are
fulllr worn, tab 106 contacts an end of slot 108 to prevent further
rotation of right coin ring 48.
As illustrated in Figures 3 and 6, pressure plate 34 is
attached to cover 32 by a strap 110 and a pin connection
assembly i12. For convenience, although a plurality of straps
110 and pin connection assemblies 112 are circumferentially
spaced about cover 32, only one set will be described. Each
strap 110 extends in a generally circumferential orientation
with respect to cover 32. An end 114 of strap 110 is attached
to cover 32, while the other end 116 is attached to pressure
plate 34 at a location spaced from end 114. Strap 110 is
CA 02399314 2002-09-19
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sufficiently flexible to allow pressure plate to be moved
axially with respect to cover 32, but is otherwise sufficiently
rigid to prevent rotation of pressure plate with respect to
cover 32.
As more clearly seen in Figures 3 and 7, pin connection
assembly 112 includes a pin 118 and pin housing 120. Pin 118 is
threadably received in a radially outer portion of pressure
plate 34. An apposite end of pin 118 includes an enlarged head
122. Pin housing 120 extends circumferentially about pin 118
between pressure plate 34 and head 122.
A alight clearance 124 is provided between pin housing 120
and~head 122 of pin 118 permitting pressure plate 34 a small
amount of relative movement. Pressure plate 34 is thereby
7
freely movable an axial distance defined by clearance 124.
During normal operation, clearance 124 permits sufficient axial
movement of pressure plate with respect to cover 32 to engage
and disengage the clutch. Pin housing 120 is received in an
aperture 126 of cover 32, forming an interference fit between
the outer dimension of pin housing 120 and aperture 126.
Pressure plate 34 is movable an additional axial distance
defined by the axial dimension of pin housing 120, assuming the
force is sufficient to overcome the interference fit between~pin
housing 120 and cover 32.
Figure 7 illustrates a radial cross-section of pin
connection assembly 120 and strap 110. Clutch 20 is shown in
the disengaged position, so clearance 124 is between head 122 of
pin I18 and pin housing 120.
referring again to Figures 3 and 6, adjustment mechanism
42 is seated in an annular cavity 128 formed in cover 32 and
secured to cover 32 by a strap 130. For convenience, although a
plurality of straps 130 are circumferentially spaced about cover
CA 02399314 2002-09-19
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32, only one will be described. Each strap 130 extends in a
generally circumferential orientation with respect to cover 32.
An end 132 of strap 130 is attached to pressure plate 34 by pin
118, while the other end 134 is attached to axial face 136 of
adjusting ring 44 at a location spaced from end I32. Further,
end 134 of strap 130 is located radially in~atdly of ernd
132. Strap 130 is sufficiently flexible to allow adjusting ring
44 to be moved axially with respect to cover 32 and pressure
plate 34, but is otherwise sufficiently rigid to prevent
rotation of adjusting ring 44 with respect to cover 32. right
cam ring 48, which is not directly secured to adjusting ring 44
or left cam ring 46, is sandwiched between cover 32 and-left cam
ring 44.
Strap 130 serves an additional purpose which is to bias
adjusting ring 44 towards lever 58, or to the left as shown in
Figure 3. Thus, axial face 136 of adjusting ring 44 applies a
leftward force on lever 58. Such force maintains lever 58 in
contact with pressure plate 34. Therefore, if release assembly
28 is moved to as eztreme right position, a gap will be created
between left cam ring 46 and right cam ring 48, as opposed to
lever 58 and pressure plate 34. The significance of this will
become apparent once the interaction of lever and adjustment
mechanism 42 ring is understood.
Clutch 20 is disengaged by rightward movement of release
assembly 28, and more specifically, rightward movement of
retainer 54. A fully disengaged position of clutch 20 is
defined as the position when release assembly 28 contacts a
stop, namely transmission housing 55. In an initial condition
of clutch 20, prior to wear on friction surface 40 of driven
member 36, retainer 54 moves a constant distance from the
engaged position to the fully disengaged position of clutch 20.
Similarly, pressure plate 34 moves a constant distance from an
engaged position to a disengaged position. This distance of
CA 02399314 2002-09-19
" -13-
travel for pressure plate is approximately .040 inch (1.02 mm),
assuming no wear .on friction surface 40. Pin assembly 112
permits pressure plate to move freely this distance, due to
clearance 124.
After wear has occurred on friction surface 40, pressure
plate must move an additional axial distance to engage the
clutch. This additional increment of travel is shown as "d" and
indicated as reference numeral 138. In this intermediate
condition of clutch 20, the axial movement of pressure plate
exceeds the clearance 124 provided by pin assembly 112.
Therefore, in order for pressure plate 34 to move the additional
distance "d", pin housing 120 is moved an axial distance "d"
relative to cover. Head 122 of pin 118 applies a force on a
right end 138 of pin housing 120, as seen in Figure 3. Pin
housing 120 will then move axially to the left relative to cover
32 because the force of coil springs 56 exceeds the force of the
interference fit between pin housing 120 and cover 32. The
clutch 20 will continue to operate at this position, and will
remain unadjusted until release assembly is moved to a fully
disengaged position.
Due to pin assembly 112, pressure plate 34 is now spaced
from an end of cover 32 by an additional distance "d", as~seen
in Figure 7. The pre-adjusted position of cover 32 relative to
pressure plate 34 is shown in phantom. The force the
interference fit between pin housing 120 and cover 32 is
sufficient to prevent pin housing 120 from moving axially to the
right with respect to cover 32. This is due to the relatively
weak force which is applied for rightward movement of pressure
plate. In contrast, the leftward force applied by coil springs
56 is much greater.
During adjustment, pressure plate 34 contacts a left end
140 of pin housing 120 when release assembly 28 is moved to the
CA 02399314 2002-09-19
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fully disengaged position. Pin housing 120 prevents further
rightward movement of pressure plate. Strap 130 applies a
leftward biasing force on adjusting ring 44 towards pressure
plate 34. This biasing force moves adjusting ring 44 and left
cam ring 46 to the left, creating gap "d". Gap "d" is created
between left cam ring 46 and right cam ring 48.
In response to the gap "d," right cam ring 48 rotates with
respect to left cam ring 46 causing caroming between ramps 80 and
88. This caroming action locks adjusting ring 44 into the
position provided by lever 58. In so doing, an extreme left
axial end of adjustment mechanism is moved from a first position
to a second position, the second position being spaced a greater
axial distance from cover 32 than the first position.
Referring now to Figures 9A-9C, the caroming action of
adjustment mechanism 42 is illustrated from another
cross-sectional view. Radial cross-sections of the relative
position of the clutch members are shown before and after
adjustment. The clutch is shown in an engaged position in
Figure 9A, after wear has occurred on friction surface 40 of
driven member 36. Because of wear on friction surface 40,
pressure plate has moved an additional axial distance in order
to engage driven member 36 with flywheel 22.
The clutch is shown in an intermediate disengaged position
in Figure 9B. In this intermediate position, adjustment
mechanism 42 has not yet been activated to adjust clutch 20 in
response to the wear on friction surface 40. The clutch will
operate unadjusted until it is fully disengaged.
Clutch 20 is shown in the fully disengaged position in
Figure 9C after adjustment. When clutch 20 is fully disengaged,
pull assembly 52 of release assembly 28 contacts transmission
housing 55, which is the extreme right position for release
CA 02399314 2002-09-19
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assembly 28, as shown in Figure 3. The radially outer portion
64 of lever 58 leverages adjusting ring away from cover 32, and
creates a gap between left cam ring 46 and right cam ring 48.
The biasing forces on right cam ring 48 caused by spring 94
urges the rotation of right cam ring 48. This, in turn, results
in caroming along ramps 80 and 88 to increase the axial
displacement of adjustment mechanism 42 to fill the gap.
This action repeats each time wear has occurred on
friction surface 40, and when clutch 20 is fully disengaged.
Further, this adjustment action occurs . automatically during
normal operation of the clutch.
A second embodiment of the invention is illustrated in
Figure 10. An adjustment mechanism 142 is incorporated in a
clutch 144 having a diaphragm spring 146. Clutch 144 transmits
torque from a flywheel 148 to an axially extending driven shaft
150. A cover 152 is secured to flywheel 148 for rotation
therewith. A pressure plate 154 and a driven member 156 are
sandwiched between flywheel 148 and cover 152. Driven member
156 is secured to driven shaft 150 for rotation therewith.
Driven member 156 includes friction surfaces 157. A retainer
assembly 158 extends circumferentially about driven shaft 150.
Diaphragm spring 146 is interposed between cover 152 sad
retainer assembly 158 to apply a leftward force on pressure
plate 154. Diaphragm spring 146 acts against a fulcrum 160 to
maintain clutch 144 in the engaged position. To disengage
clutch 144, retainer assembly 158 is moved to the right. Clutch
144 automatically adjusts to wear on friction surfaces 152 of
driven member 156 in a manner similar to that of clutch 20.
A pin 164 is received within an aperture 166 of pressure
plate 154, forming an interference fit. Pin 164 includes a left
end 167 and a right end 168. Left end 167 of pin 164 extends
through an opening 170 in cover 152 to contact flywheel 148.
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Right end 168 contacts a radially extending flange 172 of cover
152. A clearance 174 is provided for pin 164 between flywheel
148 and flange 172 for axial movement of pressure plate.
Clearance 174 is the axial movement required to engage and
disengage clutch 144 assuming no wear on friction surfaces 157.
Adjustment mechanism 142 includes a cam ring 176 and a caom
ring 178, each being received in an annular pocket 180 formed in
pressure plate 154. Cam ring 176 is biased to rotate with
respect to pressure plate 154 by a spring 182 received in an
annular cavity 184 adjacent cam ring 178. Cam ring 178 includes
fulcrum I60. Cam ring 178 is axially movable with respect to .
pressure plate 154, but is otherwise rotationally fixed to
pressure plate 154. The ramped contacting surfaces of cam ring
176 and cam ring 178 are similar in dimension and shape as that
described for cam rings 46 and 48. rotation of cam ring 176
results in caroming that moves cam ring 178 to the right.
A locking member 186 extends through an aperture 188 in
diaphragm spring 146, to maintain fulcrum 160 in contact with
diaphragm spring 146. Clutch 144 adjusts in a manner similar to
that described for the first embodiment. Prior to wear on
friction surface 162, the relative position of pin 164 with
respect to pressure plate 154 remains unchanged due to clearance
174. If wear has occurred on friction surface 162, pin 164 will
contact flywheel 148, and pressure plate will move an additional
distance to the left. The leftward force on pressure plate
provided by diaphragm spring 146 exceeds the force of the
interference fit of pin 164 and pressure plate 154, thereby
forcing pin 164 to slide within aperture 166 of pressure plate
154.
When retainer assembly 158 is moved to a fully disengaged
position, which is at a fixed axial location with respect to
flywheel 148, adjustment mechanism 142 is activated. Right end
CA 02399314 2002-09-19
__ _17-
168 of pin 164 contacts flange 172 of cover 152 preventing
rightward movement of pressure plate 154. Again, the rightward
force is not sufficient to overcome the interference fit of pin
164 and pressure plate 154. Locking member 186 is then able to
pull cam ring 178 to the right because further rightward
movement of pressure plate 154 is prohibited by pin 164. This
action creates a gap between cam ring 176 and cam ring 178. As
in the first embodiment, the romped surfaces of the cam rings
rotate with respect to each other to displace this gap. The
caroming action locks cam ring 178 in position, which maintains
fulcrum 160 at a position which is axially spaced from the
pressure plate an additional increment.
Rumerous advantages are achieved by the use of a clutch
having the inventive automatic adjustment. mechanism as
described. The adjustment of the clutch is automatically set
each time the clutch is fully disengaged. The adjustment is a
direct function of increased movement of the pressure plate due
to wear on friction surfaces, which is triggered by a pin or pin
assembly that cooperates with the pressure plate. The increment
of wear on the friction surface of driven member is directly
translated into a gap between the annular cam rings, each having
contacting caroming surfaces. The annular cam rings cam against
each other when the clutch is fully disengaged to displace this
gap. Therefore, the clutch automatically adjusts over the life
of the clutch and operates at peak efficiency. The adjustment
mechanism is internal to the clutch, and therefore not subject
to the external environment which could cause damage to the
components.
The inventive clutch automatically compensates for wear on
the mechanical linkage between clutch pedal 30 and release
assembly 28. In addition, the clutch will automatically set
clutch brake squeeze and compensate for wear on the clutch brake
throughout the life of the clutch.
CA 02399314 2002-09-19
-18-
The embodiment of Figures 1-9 includes the wear indicator
tab so that an operator is aware of how much ad3ustment has
taken place, and can estimate the remaining life of the clutch.
This visual indicator is outside the clutch, and provides this
information without disassembly of the clutch. Further, the
ad3ustment mechanism compensates for-manufacturing variations in
the cover assembly, allowing the clutch to be initialized upon
the first full disengagement.
Further, in the first embodiment, the set of straps which
secure the pressure plate to the ad~us.tment mechanism also
maintains the lever against the pressure plate. Therefore,
noise is reduced or eliminated due to vibration that may
otherwise occur between the pressure plate and the lever.
Further, wear on the pressure plate shoulder 74 is reduced due
to the decreased vibration of lever 58.
The embodiments disclosed herein have been discussed for
the purpose of familiarizing the reader with the novel aspects
of the invention. Although preferred embodiments of the
invention have been shown and described, many changes,
modifications and substitutioas may be made by one having
ordinary skill in the art without necessarily departing from the
spirit and scope of the invention as described in the following
claims.
