Note: Descriptions are shown in the official language in which they were submitted.
1071897
B~CKGROUND OF TI~E INVENTION
This invention relates to gear transmissions, and in
particular it relates to an improved two-speed planetary gear
transmission.
Many types of two-speed gear transmissions are known,
such as for use with a hydrodynamic transmission, i.e. a torque
converter, and these include planetary gear transmissions providing
direct drive by using a clutch to operatively connect the input
and output shafts for rotation together, and providing overdrive
or underdrive by using a brake to hold one of the sun or ring
gears stationary relative to a casing. However, such known two~
speed gear transmissions include power shift friction couplings
: . .
and are normally very heavy due to the hlgh capacity of the clutch
and the brake. If the transmission is simplified by the use of
a free wheel instead of a power shift coupling, then of course the
gear transmission cannot transmit torque in both directions, i.e.
driving torque and braking torque. Moreover, the forces of the
clutch or brake which are exerted upon rotary bearings of the
two-speed gear transmission which are in motion have either resulted
` in short bearing life and/or have resulted in requiring a rather
large design of the transmission so as to provide an overall
structure and bearings which can withstand such clutch and brake
forces.
Hence, there exists a need for providing a two-speed
planetary gear transmission having improved clutch and brake force
characteristics which will permit the design of a two-speed planetary
gear transmission of the type described which is more compact and/or
wherein the wear upon the bearings is reduced, and which can transmit
. . .
torque in both directions, i.e. drive torque and braking torque,
in both direct drive and overdrive or underdrive.
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~071897
SUMM~Y OF TI~E INVENT~N
Hence, it is a purpose of the present invention to
provide a new and improved two-speed planetary gear transmission
which will overcome the disadvantages of the prior art. The pre-
sent i~vention includes a number of features which achleve this
purpose.
In accordance with a first feature of the present in-
vention, there is provided a two-speed planetary gear mounted in
a stationary casing wherein direct drive between the
gears is brought about by engagement of a first friction coupling,
referred to hereinafter as a clutch, under the action of a spring
arrangement, and the other drive such as overdrive or underdrive
is brought about by engagement of a second friction coupling,
referred to hereinafter as the brake, under the action of a further
actuating means such as a servo-motor which overcomes the spring
force to disconnect the clutch and to thereafter connect the
brake. The spring arrangement has the characteristic of exerting
its greatest force at its position corresponding to clutch engage-
ment or close thereto, and a significantly lower spring force at
its position corresponding to brake engagement. With such
characteristics, it is possible to use the strong spring force
both for strong clutch engagement and also for retarding the action
of the servo-motor to significantly reduce the level of torque
transfer in the interval between clutch disengagement and brake
engagement, thus providing a soft transition from clutch to brake,
and yet essentially eliminating the spring resistellce to the servo-
motor since, as the servo-motor approaches and reaches its brake
engaging position, because of the weaker spring force existing at
that time, the servo-motor can be of a relatively smaller construction
since it does not have to overcome a strong spring force near and
` 1071897
, at brake engagement.
In accordance with a second feature of the present in-
vention, there is provided a two-speed planetary gear transmission
` mounted in a stationary casing wherein direct drive between the
input and output shafts is brought about by a clutch engaged under -,
. . .
the action of a spring arrangement and the other drive such as
overdrive or underdrive is brought about by a brake engaged under
the action of a further actuating device which first overcomes
the spring force and then causes engagement of the brake, and
wherein the usual rotary bearings are provided for relative
rotation as required between the respective parts of the planetary
gear, the input and output shafts and the stationary casing,
and wherein the spring arrangement and further actuating device
are arranged such that when each exerts its`maximum force
to cause engagement of the clutch or brake, respectively, the closed
path'of the forceloop created by each bypasses any rotary bearings
across which there is relative rotary motion at that time.
Accordingly,-significant bearing wear usually resulting from
: ~ .
strong axial forces thereon while in motion is eliminated in the
arrangement of the present invention, thereby significantly
extendlng bearing life and/or permitting a smaller overall con-
struction.
A planetary gear transmission includi~ng-both of the
first and second above described features has the significant
advantage of providing an arrangement in which the spring and other
actuating device such as a servo-motor can both be quite strong
since they cooperate with each other rather than fight each other,
and since-such strong forces are not transmitted through the moving
rotar,y bearings, such rotary bearings have less wear and a longer
life and as a result thereof the overall design of the bearings and
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,
,
1071897
the transmission can be more compact.
The above described feature concerning bypassing of
the moving rotary bearings by the spring and servo-motor forces
can be stated a different way, namely all of the elements-in the
force loop associated with the spring during clutch engagement or
, . . .
associated with the servo-motor during brake engagement do not
rotate relative to each other, i.e. they all rotate together or
they all remain statlonary. Viewed in this manner it of course
necessarily follows that the path oE the force loop in each case
does not cross over any moving rotary bearings.
Another feature of the present invention is that with
the construction provided therein, it is possible to provide
torque transfer in both directions, i.e. driving torque and
braking torque, for both speeds of the gear transmission. However,
if desired it is also possible to use a free wheel connection
between the input shaft and the output shaft in parallel with the
clutch in the event that it is necessary to hold the clutch engaged
only for lower torque at,coasting.
- The two-speed planetary gear transmission according to
the present invention is particularly suitable for use with a
hydrodynamic torque converter having one of the torque transmitting
bladed components, i.e. the pump blades or the turbine blades
released from the input driving source or the output shaft,
respectlvely, since the reduction in torque provided by such a
releasable torque converter component is so significant that
it will permit a reduction in the friction surfaces of the clutch
and brake of the planetary gear transmission to a minimum size
allowing synchronization when no torque is being transmitted
therethrough, after which the forces causing engagement of the
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1071897
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Clutch can be raised to enable transmission of high torque. More-
ovèr, this arrangement provides a so~t transition from one gear to
the other. Torque converters of the type having a releasable
bladed component are shown and described in my U.S. Patent No.
.~
3,893,551 which relates to a torque converter having a releasable
pump component and my U.S. Patent No. 3,893,864, which relates to
a torque converter having a releasable turbine component.
The above described spring arrangement characteristics
may conveniently be provided by using a selleville spring. If such
a spring is dished for example to the right, then the forces exerted
by that spring to the right are essentially nil when the spring
lies in a plane and essentially nil when the spring is in its
fully dished position. Midway between those two positions, however,
it is at a maximum. Stated differently, the force characteristics
of the Belleville spring are similar to a sin~e curve. HRnce, when
using such a spring in the present inventlon the spring would be
arranged suçh that in the clutch engaged position the selleville
spring would be half-way between its plane condition and its fully
dished condition, and upon brake engagement the spring would reach
substantially its plane low force condition. The spring arrangement
may include a plurality of Belleville springs or even a combination
of different types of springs, the characteristics of which are as
described above. ~ -
Braking is preferably achieved by a servo-motor station-
arily mounted in the casing. As the servo-motor is initially
actuated/ it meets the resistence of the high spring force,-thus
retarding the servo-motor, thereby assuring a momentary siqni-flcant
drop in torque transfer through the planetary gear transmission,
further assuring a soft transition between gear speeds. Then, as
the servo-motor continues, it eventually moves the spring to the
lO~i~397
position whereat its force opposing the servo-motor is minimal,
whereby the servo-motor forces can be concentrated on engaging
the brake.
Several embodiments are provided, in each of which the
above described features of the present invention are achieve.
In accordance with a first embodiment, either the input
shaft is operatively engaged with the planetary gear carrier, the
sun gear is adapted to be braked and the ring gear connected to
the output shaft for overdrive or the input shaft is operatively
~
engaged with the ring gear, the sun gear is adapted to be braked,
and the planetary gear carrier is connected to the output shaft
for underdrive. In accordance with this first embodiment, an
element extending from the sun gear is slidable between a first
position at which the sun and ring gears are engaged for rotation
together and a second position wherein the sun gear is connected
to the stationary casing. In accordance with this first embodi-
ment, said slidable part includes conical frictional surfaces for
engagement at each of the two positions. In the specific arrange-
.,
ment of overdrive, a first embodiment may include springs actingbetween a first part movable with the sun gear and a second part
which via a rotary bearing acts against the ring gear. In direct
drive, the sun and ring gears move together so that said rotary
bearing is not in motion.
In accordance with another embodiment of the invention,
the sun gear which is adapted for engagement with the casing
during overdrive and underdrive may include means for connection
to the casing or for connection of the sun and ring gear together,
by means of friction engaging discs rather than conical frictional
surfaces. In accordance with one specific embodiment, the sun
i(~ql89'~
gear may include a slidable part slidable in one direction under
the influence of the spring arrangement to cause engagement of
disc frictional surfaces for connection of the sun and ring gears
together for rotation as a unit and for movement in the opposite
direction under the influence of the servo-motor for a disc type
frictional engagement between said slidable part and the stationary
casing. In this embodiment the spring means may act between two
parts associated with the sun gear.
In accordance with still another embodiment of the pre-
: sent invention, the sun gear may include, in addition to fric-
tional clutch and brake surfaces, a spring arrangement including
a combination of springs, namely a coil spring for continuously
urging the clutch into engagment coupled with a Belleville spring,
wherein the parts are so arranged that during the very initial
portion of the servo-motor actuation, it moves quite easily,
opposing only the coil spring, thereby relatively easily dis-
engaging the clutch, after which initial moment it opposes the
full force of a Belleville spring, whereupon it is significantly
retarded, thereby assuring the interval of minimal torque trans-
fer through the planetary gear transmission, after which the servo-
. motor overcomes the spring force as said spring force is signifi- -
: cantly reduced in accordance with the above described spring
characteristics.
The ob~ects and advantages of the present invention will
become apparent from the detailed description to follow, together
with the accompany1ng drewings.
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1071897
BRIEF DESCRIPTION OF TIIE DR~WINGS
There follows a detailed description of preferred
embodiments of the present invention to be read together with the
: accompanying drawings in which:
,, Figure 1 is a partial side elevational and partial
cross-sectional view of a transmission including a torque converter
in combination with a two-speed planetary gear transmission of the
present type.
- Figure lA is an enlarged view of that portion of
Figure 1 showing the two-speed planetary gear transmission.
Figure 2 is a side elevational and cross-sectional
view similar to Figure 1 but showing a modified version of the
` present invention.
Figure 3 is a graph illustrating the general character-
istics of a BelleviL~type spring.
- Figure 4 is a longitudinal cross-sectional view
through a two-speed planetary gear transmission showing another
embodiment of the present invention.
Figure 5 is a graph illustrating the force character- -
istics of the Belle~illespring shown in Figure 4.
Figure 6 is a longitudinal cross-sectional view
through a two-speed planetary gear transmission showing another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, like elements are repre-
sented by like numerals throughout the several views.
Referring to Figure 1, there is shown at the left
hand side thereof a torque converter T, of a type which is
similar to that shown in my U.S. Patent No. 3,893,551 in that it
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~: 1071897
. includes a releasable pump member. One could also use a releasable
turbine member torque converter of the type shown in my U.S. Patent
No. 3,839,864. Referring to Figure 1, there is shown a rotary
casing 5 which is the main drive input to the transmission. For
hydraullc drive the pump member 8 including a ring of pump blades
: is moved to the left whereby via coupling 7 it engages intermediate
; member 6 which is fixed to the casing 5. For direct drive between
the rotary casing 5 and the output shaft of the torque converter,
a servo-piston 9 within rotary casing 5 is moved to the right,
frictionally engaging friction surfaces of a flange member 9a
between element 9 and element 6, whereby torque is transferred
from rotary casing 5 to the flange 9a which is in turn connected
to the turbine output shaft, thereby providing direct drive.
Referring now to the right hand side of Figur-e 1 and
also Figure lA, the gear transmission G includes a planetary gear
system P concentrically mounted relative to an input shaft 10 and
an output shaft 12, the latter being connected to an output f~ange
12'.- The planetary gear P includes a planetary gear carrier 14
drivingly connected to the input shaft 10 by means of spline
connection I6. One or more planet gears 18 is supported by the
carrler 14. Sun gear 20 of the planetary gear is carried on a
member 22, which will be described in greater detail below, and
which forms a common part with the first coupling which is a
clutch and the second coupling which is a brake.
.
An outer ring gear 24 of the planetary gear has a
conical outer surface 2~, which together with a correspondingly
- - shaped conical surface 30 on the member 22 constitutes the first
coupling which is a clutch. As is evident from Figure 1, the
member 24 is rigidly connected to the output shaft 12 at 32 for
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1071897
rotation therewith. The second coupling or brake comprises a
conical surface 34, also formed on the member 22, and a correspondingly
shaped conical surface 36 formed on a stationary abutment 38
rigid with the stationary casing 40 of the transmission, said
surface 36 including a band of friction material 42 thereon.
Connection of the clutch 28, 30 and disconnection of
the brake 34, 36 is accomplished by a spring arrangement S which
in this embodiment comprises one or more overcentered springs 43.
In a preferred arrangement, these springs are of the Belleville
type. On their radial inner surfaces, the springs are supported
on an intermediate flanged sleeve 46 which is in turn mounted on
shaft 12 by means of conical roller bearing 44. On the other
side the springs 43 are urged against an intermediate member 23
which is fixçd to member 22 for rotation therewith.
Also illustrated in Figures 1 and lA is a servo-motor
V including an annular non-rotating piston 48 movable axially
within cylinder 50 which is rigid with the stationary casing 40.
The interface between elements 23 and 48 is a plane bearing sur-
face 52 and is lubricated by oil delivered through channels 53
formed ln the piston 48.
The output shaft elements 12 and 12' are supported in
the casing 40 in the area of cylinder 50 by means of roller bearing
54.
In the position as shown in Figures 1 and lA, the first
coupling or clutch 28, 30 is shown in the engaged position under
the action of springs 43 and in the absence of sufficient pressure
within cylinder 50 to overcome such spring force. In the position
as shown, the springs 43 exert their maximum force to the right,
and their minimum force is exerted when the springs 43 have been
moved to the left to a plane position. To further understand these
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; ` 1071897
spring characteristics, references made to Figurc 3 which shows
; the general characteristics of a Belleville spring arranged in
~ a vertical plane and naturally dished to the right. When the
'r~ spring lies in a vertical plane, i.e. at point O along the
horizontal axial of Figure 3, it exerts no biasing force to the
right. As the spring deflects to the right the force which it
-~ exerts in that direction increases to a peak and then falls off,
obviously becoming zero when the spring has reached its natural
~; relaxed dished position. Thus, in the present invention a spring
is selected and arranged such that in the position as shown in
Figures 1 and lA the spring is dished to the right only a portion
of its total deflection. If one desires that the absolute maximum
- force of the spring be felt in the clutch engaged position, one
`; `
would select deflection to point A at the clutch engaged position.
Alternatively, it may be desirable to select a point other than A,
for example A' which is past the peak so that the maximum spring
the
resistence to travel of t~he servo-motor 48 is not at~instant it
initiates travel, but rather slightly beyond that point. Alter-
natively, if one wishes to have a spring characteristic which is
less than its maximum in the position illustrated in Figures 1 and
lA, and decreases thereafter, then one would select a point such
as A".
Whichever specific spring characteristics are selected,
it is a feature of the invention that when the clutch is dis-
connected by movement of piston 48 to the left, such movement is
initially retarded by the then existing strong biasing force of
spring 43. This will assure momentary disengagement, concurrently,
of both the clutch and the brake, thereby providing an interval
of significantly reduced torque through the planetary gear system
G. As a result thereof, there will a smooth transition from clutch
engagement to clutch disengagement and to brake engagement. It is
.
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iO7189q
another feature of the invention that after this momentary
interval, as the piston 48 continues its movemnt to the left,
the resistence offered by springs 43 greatly diminishes, whereby
the piston 48 is capable of effecting a firm engagement of brake
34, 36.
The embodiment of Figures 1 and lA operates as an
overdrive since upon engagement of the brake 34, 36, the output
shaft rotates faster than the input shaft. However, it will be
evident that such a planetary gear system can be varied in several
ways. The planetary gear holder can be connected to the output
shaft rather than the input shaft with the ring gear connectable
to the input shaft. In any of these combinations, it is of course
understood in the art that whenever, upon brake engagement, the -
output shaft rotates faster than the input shaft then the arrange-
ment is an overdrive while conversely if the output shaft rotates
slower than the input shaft, It constitutes and underdrive.
As described above, an important feature of the present
invention is that the spring and servo-motor forces, when at a
maximum, are not transmitted through rotary bearings in motion.
Any time a force is exerted, such as by springs 43, it is of course
understood by basic physics principles that the force path is
transmitted through a closed loop. When the spring 43 exerts lts
maximum force, the path of the "closed loop" is through elements 46,
44, 12, 24, 28, 30, 22, 23 and back to springs 43. This path of
corse crosses rotary bearing 44. However, upon clutch engagement
there is not relative rotary movement across bearing 44 since all
of the elements described above as constituting the loop rotate
together as a unit to effect direct drive upon engagement of said
clutch. O course there is relative rotary movement across bearing
44 when the clutch is disengages and the brake engaged. However,
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1071897
:;
-- at this time the residual axial force of spring 43 is csscntially
negligible so that any detrimental effect thereof on the bearings 44
is nil. As.in the case of clutch engagement, so too in the case of
brake engagement the force loop does not pass through rotary bearings
; in motion, and in fact in this case the force loop remains in
,~ .
stationàry parts of the system. Specifically, the force loop
would pass from element 48 to elements 23, 22, 34, 36, 38, 40 and
50 and back to element 48.
.
Referring now to Figure 2, the embodiment shown therein
is identical to the embodiment of Figures 1 and lA with the sole
exception that it includes in addition to the structure shown in
Figures 1 and lA a roller-type free wheel F disposed in parallel
with the first coupling or clutch 28, 30. The free wheel F is
actually mounted within an extension of the member 24 as shown
in the inner part 56 directly connected with the planet gear
carrier 14.This arrangement may be used for example where the
first coupling or clutch has to hold only for lower levels of
torque at coasting.
; As a modification of the embodiment described in
Figures 1 and lA, such arrangement can also of course be constructed
with two intermeshing planet gears between the sun and the ring
gear rather than a single planet gear, thereby functioning as a
reserve gear. This of course cannot be done in the embodiment of
Figure 2 which includes a free wheel.
Another embodiment of the invention is shown in Figure 4.
In Figure 4, co-axial primary input shaft 102 and
secondary output tubular shaft 102, the latter connected to output
flange 102', are mounted in a casing C by bearings 100 and 104
respectively and, in addition, a third bearing 102 is disposed
between the axially overlapping ends of the two shafts. An outer
ring gear 106 i5 carried on the primary shaft 101 by a spline
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` 1071897
conneetion 108 and inner teeth 110 of the ring gear mcsl- with
teeth 112 of the planet gears of which one is designated 114.
The planet gears 114 are mounted on shafts 116 supported in a
planet carrier 118. The teeth 112 of the planet gears 114 also
mesh with teeth 120 of a sun gear 122 which is in turn carried by
the secondary shaft 102. The outer gear ring 106 also has an
external ring of teeth 111 which mesh with an internally toothed
or splined disc brake plate 130 of a disc brake generally
designated B.
An annular disc member 124 is carried on the sun gear
122 by a spline connection 126 and, by means of a further spline
connection 132, the disc member 124 supports an annular and axially
slidable member 134. The member 134 has an inwardly projecting
flange`l36 and also carries by means of the spline connection 132
an annular member 138 having surface 138A which together with
the disc brake plate 130-and a surface 124A on member 124,
constitute essential components of the disc brake B. The member
138 is axially locked to the member 134 by circlips or other
locking means 139 and axia-l movement ~to the left as seen in
Figures 1 and 2) of the member 124 and consequently member 138 is
limited by spring loaded stops 141, which may be hydraulically
damped.
A clutch pad 136A is attached to the flange 136 and,
together with clutch part 140 which is supported on the casing C
via a spline connection 142, constitutes clutch CL. The clutch
CL is normally urged toward its engaged position by a Belleville
spring assembly 128. Disengagement of the clutch CL is effected
by displacement (to the left in Figures 1 and 2) of-an annular
servo-piston 144 which is movable in an annular cylinder 146 and
vla a lever system 148.
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The axial thrust applied to the sun gear 122 during
operation of the clutch CL is absorbed by an axial thrust bearing
150 disposed between the sun gear 122 and the planet carrier 118.
This construction, when compared with the customary construction
of placlng a thrust bearing externally relatlve to the planetary
gear system, possesses the advantages of reduced dimensions and
lower overall weight of the gear transmission.
Another feature of the invention is a spring arrange- -
ment incorporating a plurality of Belleville springs wherein one
of the springs is loaded in the conventional manner while the
other two counterbalance each other resulting in 2 flattening out
of the force curve of the spring arrangement, thereby providing
. , .
a low axial force over, a wide range, at least in the clutch
disengaged position, thereby rendering the spring arrangement
somewhat less sensitive. This is illustrated in the graph of
Figure 5 wherein plotting force on the vertical axis'and deflec- -
tion distance on the horizontal axis, the three springs may have
the characteristics of the three curves A, B and C, all having
the same characteristics on the right hand side but differing on
the left hand side. The net result thereof will be a strong
clutch engaging force at the right hand end of the deflection
range and a low but more level force at the lower end of the
deflection range.
- In the position as illustrated in Figure 4, the clutch
is engaged for locking the sun and ring gears for rotation together
for direct,drive between the input and output shafts. The spring
arrangement 128 is urging elemeht 136 to the right along with
elements 134 and 138, thereby causing frictional engagement be-
tween elements 138, 130 and 132, whereby the element 130 by means
of its engagement with teeth 11 cause the sun gear and hence also
the planet gears and the planet gear carrier 118 and the output
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1071897
shaft 102 to be rotated together with input shaft 101 and ring
gear 106. To shift gears, piston 144 is urged to the left. Its
initial movements are smoothed out somewhat by the fact that it
acts through a lever 148, the latter engaging the intermediate
member 140 which in turns urges inwardly projecting flange 136
, . . .
and hence also axially slidable member 134 to the left. At first,
movement of these elements is retarded by springs 128 thereby
assuring a momentary drop in the level of torque transfer
through the planetary gear system while the clutch is becoming
disengaged and before the brake is engaged, and also assuring
a smooth transition from clutch engagement to brake engagement.
As described above, the particular type of spring arrangement
provided herein will further assure such smooth transition. After
a predetermined travel of the piston 144, the axial force exerted
by the springs 128 will be reduced, whereby the piston will
continue to urge element 134 and hence also annular member 138
to the left until the latter engages frictional surface 141 which
may incidently include a hydraulic damping system 143, whereupon
the sun gear will be fixed to the stationary casing C, i.e. the
brake will be engaged.
- This particular embodiment, while assuring a reduction
in the level of torque transfer between clutch and brake engage-
ment, nonetheless avoidsa complete elimination of torque transfer
so that there is not a complete break in the drive line during the
transition between gear speeds. When the piston 144 starts to
move forward and contacts the lever system 148 which in turn
engages the member 140, then for the first one tenth of a second
a oil film results in a low coefficient of friction. This is
sufficient to lnitiate disengagement of the clutch. When the
axial force of the spring arrangement 128 is then reduced, the
torque transfer falls off more and a higher coefficient of friction
is now obtained. The characteristics of the springs 128 will then
107~897
determine the lower limit of torque transfer before the brake B
engages. Obviously, if desired, one could retain a torque
transfer as high as desired, for example more than 50~ higher
then that which would otherwise be obtained simply by selectina
a lining on the left hand side of element 138 with a higher
coefficient of friction then on the right hand side thereof.
As illustrated in Figure 4, this embodiment acts as
an underdrive since, upon engagement of the brake, the input
shaft including the ring gear 106 rotates faster than the planet
carrier 118 and the output shaft 102 connected thereto.
As with the embodiment of Figures l, lA and 2, in this
embodiment the high axial forces exerted by the springs in the
clutch engaged position and by the servo-motor in the brake engaged
position do not pass through rotary bearings, across which there
is relative motion. Specifically, in the clutch engaged position
the spring force passes through elements 124, 122, across bearing
150 which is not in motion at this time, and via elements 118,
116, 106, 130, 138, 134, and 136 back to springs 128. All of
these parts rotate together so that there is not force transfer
across such moving rotary bearings. Similarly, the force of
servo-motor 144 passes through stationary elements to member 134
and through elements 138 and 141 back to casing C, cylinder 146
and servo-motor 144.
Figure 6 illustrates another embodiment of the present
invention. The stationary casing is represented by the numeral 200.
An input shaft 201 is engaged with a ring gear 203 of the planetary
gear system through internal teeth 202 of the ring gear. Said
ring gear includes external teeth 204 which engage with disc
plates 205 which, in a manner to be described in greater detail
below, constitute the friction elements for the direct drive clutch.
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1071897
The planetary gear system further includes one or morc
planet gears 210 mounted on a planet carrier 211 which is connected
at spline connection 212, at which it is held by a circlip 213 to
an output shaft 214 which is connected to the output flange 215.
The output shaft 214 is supported on a stationary portion of the
transmission through rotary bearings 216 and 217.A further bearing
218 supports the shaft 214 in the stationary casing 200.
The sun gear 225 engages the planets 216 at teeth 226,
and also mounted on teeth 226 are a pair of circlips 227, between
which are mounted a annular member 228 and a spring such as a
Belleville spring 229 urging the member 228 to the right. At its
outer end the annular member 228 includes a cup shaped portion 230
which, in a manner-to be described below, receives a coil spring
242, and radially outwardly therefrom there is provided an outer
flange portion 231 with a bearing block 232 thereon.
This embodiment includes an intermediate member 235
which includes a cylindrical portion 236 with internal teeth 237
thereon. A reactlon member 238 is mounted on teeth 237 and fixed
against axial movement by circlips while a pair of discs 239 are
slidably mounted on teeth 237. These pass between the previously
described discs 205. In a manner to be described below, frictional
engagement of plates 205 and 239 constitute the direct drive clutch.
The member 235 further includes a cup portion 240, and
a spring 242 extends between and exerts an axial force between~the
two cup shaped portions 230 and 240.
A friction disc 250 is mounted on member 236 and extends
outwardly therefrom between a pair of friction discs 253 which are
on
slidableAspline 252 which is rigid with the casing 200. These
discs 250 and 253, when engaged, constitute the brake engagement
for the second driving speed, i.e. overdrive or underdrive.
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1071897
.:
The arrangement further includes an annular piston 260
mounted in a cylinder 259 formed in the casing 200. Friction
material 261 provides a bearing surface against the riyht hand
side of member 235, and the interface 262 between 235 and 261
is lubricated by oil through channels 263, one of which is shown
in the ~rawings.
It will of course be apparent that the embodiment of
Figure 6 acts as an underdrive in the same manner as the embodi-
ment of Figure 4.
The embodiment of Figure 6 operates as follows. The
spring arrangement in this case constitutes a combination of springs,
namely 229 and 242. Belleville spring 229 is shown in its maximum
axial force position whereat it urges member 228 as far as it will
go, limited by the right hand circlip 227. However, for final
movement of the elements toward the clutch engaged position, the
coil spring 242 urges member 235 to the right, carrying member
238 with it and thereby urging the discs 205 and 239 into engagement
with each other. This of course locks the ring gear 203 and the
sun gear 225 together, the latter via elements 235 and 228.
Although it is apparent that member 235 moves axially relative to
the member 228, it will also be apparent that these parts are
mounted to move angularly together. In the clutch engaged positlon,
the discs 250 and 253 of the brake are of course disengaged.
To shift from clutch to brake, i.e. from direct drive
to second drive, the piston 260 is moved to the left. This initial
movement does not meet great resistence since it does not off set
Belleville spring 229, but rather it off se-ts only the coil spring
242, moving the member 235 to the left until shoulder 235a abuts
shoulder 228a.During this slight movement, the discs 239 and 205
are of course separated from each other such that torque transfer
thereacross is substantially reduced. A main feature of this
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embodiment is that at said point in time when the shoulder 23~a abuts
shoulder 228a, further movement thereof is significantly retarded
by the maximum axial force of spring 229. This assures a momentary
interval of low torque transfer before the discs 250 and 253 of the
brake become engaged. Then, as the piston 260 continues to move,
the spring force of 229 is in fact overcome as the member 235
urges the member 228 such that the portion 231 of the latter,
and in particular the bearing block 232 thereof, forces the plates
250 and 253 into frictional engagement, whereby the brake is
engaged, stalling the sun gear so that the ring can turn the
planets and planet carrier in second gear, i.e. in this case under-
drive. During the latter portion of the leftward movement of
elements 235 and 228, the axial force exerted by spring 229 is
of course at a minimum so that the elements are effective to assure
positive engagement of the brake.
As with the previous embodiments, the high forces
effecting clutch and brake engagement do not pass through rotary
bearings in motion. It is evident that the servo-motor force,
upon brake actuation, passes through elements 263, 235, 231, 253,
252 and 200 back to the cylinder 259 and the piston 260. During
-clutch engagement the force of spring 242 passes simply through
the`element 228, the discs 205 and 239, and the member 236 back
to the right side of spring 242 so that in this case the force
: follows a rather small loop. Similarly, the path of the forces
created by spring 229 also follows a path which excludes a~ rotary
bearings in motion, namely a path from spring 229 through sun gear
225, carrier 211 and-planets 216 to the ring gear 203 and through
the discs 205 and 239 back to element 228 and the spring 229.
Although the invention has been described in considerable
detailed with respect to preferred embodiments thereof, it will be
apparent that the invention is capable of numerous modifications
and variations apparent to those skilled in the art without departing
from the spirit and scope of the invention as defined in the claims.
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