U.S. patent application number 11/136604 was filed with the patent office on 2005-12-01 for cushion plate.
This patent application is currently assigned to AISIN AW CO., LTD.. Invention is credited to Ishikawa, Takayuki, Kita, Akihiko, Nozaki, Hiroyuki, Ogawa, Yukitoshi, Tsuzuki, Shigeo.
Application Number | 20050263367 11/136604 |
Document ID | / |
Family ID | 35423981 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050263367 |
Kind Code |
A1 |
Kita, Akihiko ; et
al. |
December 1, 2005 |
Cushion plate
Abstract
A cushion plate is provided, for example, between a piston of a
hydraulic servo and an adjacent friction plate in a frictional
engagement element of an automatic transmission. The cushion plate
is deflected by a pressing force of the piston to absorb an
engagement shock. The cushion plate includes a main body portion
formed into a belleville-spring shape, and a plurality of pawls
that extend from the outer periphery of the main body for spline
engagement with a member that is splined to, for example, the
friction plate. A side wall of each pawl is formed with a curved
recess extending circumferentially of the cushion plate and located
adjacent the juncture (base) of the pawl at the outer periphery of
the main body.
Inventors: |
Kita, Akihiko; (Anjo-shi,
JP) ; Tsuzuki, Shigeo; (Anjo-shi, JP) ;
Nozaki, Hiroyuki; (Anjo-shi, JP) ; Ogawa,
Yukitoshi; (Toyota-shi, JP) ; Ishikawa, Takayuki;
(Toyota-shi, JP) |
Correspondence
Address: |
GEORGE A. LOUD
625 SLATERS LANE
FOURTH FLOOR
ALEXANDRIA
VA
22314
US
|
Assignee: |
AISIN AW CO., LTD.
Anjo-shi
JP
TOYOTA JIDOSHA KABUSHIKI KAISHA
Toyota-shi
JP
|
Family ID: |
35423981 |
Appl. No.: |
11/136604 |
Filed: |
May 25, 2005 |
Current U.S.
Class: |
192/85.34 ;
192/109A; 192/48.611; 192/85.41 |
Current CPC
Class: |
F16D 13/683 20130101;
F16D 13/70 20130101; F16D 25/0638 20130101; F16D 25/12
20130101 |
Class at
Publication: |
192/085.00A ;
192/109.00A |
International
Class: |
F16D 025/0638 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 1, 2004 |
JP |
2004-163896 |
Claims
What is claimed is:
1. A cushion plate in the form of a belleville-spring for absorbing
shock in a frictional engagement device, comprising: a main annular
plate body portion defining an outer periphery; a pawl extending
radially outward from the outer periphery of the main body for
spline engagement, said pawl having opposing side walls extending
radially outward from a base joined to the periphery of the main
body and a curved recess in at least one side wall, said curved
recess located adjacent the base and extending circumferentially of
the main body.
2. The cushion plate according to claim 1, wherein the curved
recess is located radially outward of the periphery of the main
body.
3. A multi-plate frictional engagement element for an automatic
transmission comprising: a piston controlled by oil pressure for
axial movement; an outer friction plate in splined engagement with
a member on an outer peripheral side of the element; an inner
friction plate in splined engagement with a member on an inner
peripheral side of the element, the outer friction plate and the
inner friction plate being axially arranged and pressed into
frictional contact by the piston, so that the member on the outer
peripheral side and the member on the inner peripheral side becomes
mutually engaged; a cushion plate according to claim 1 provided
axially between the piston and the outer friction plate, the pawl
being splined to the member on the outer peripheral side.
4. The multi-plate frictional engagement element according to claim
3 wherein the pawl is inclined in the direction from which the main
body is pressed.
5. The multi-plate frictional engagement element according to claim
3, wherein the member on the outer peripheral side is a case of the
automatic transmission, and the multi-plate frictional engagement
element is a multi-plate brake that fixes the member on the inner
peripheral side against rotation relative to the case when
engaged.
6. A multi-plate frictional engagement element for an automatic
transmission comprising: a piston controlled by oil pressure for
axial movement; an outer friction plate in splined engagement with
a member on an outer peripheral side of the element; an inner
friction plate in splined engagement with a member on an inner
peripheral side of the element, the outer friction plate and the
inner friction plate being axially arranged and pressed into
frictional contact by the piston, so that the member on the outer
peripheral side and the member on the inner peripheral side becomes
mutually engaged; a cushion plate according to claim 2 provided
axially between the piston and the outer friction plate, the pawl
being splined to the member on the outer peripheral side.
7. The multi-plate frictional engagement element according to claim
6 wherein the pawl is inclined in the direction from which the main
body is pressed.
8. The multi-plate frictional engagement element according to claim
6, wherein the member on the outer peripheral side is a case of the
automatic transmission, and the multi-plate frictional engagement
element is a multi-plate brake that fixes the member on the inner
peripheral side against rotation relative to the case when engaged.
Description
[0001] This application claims priority of Japanese Patent
Application No. 2004-163896 filed Jun. 1, 2004. The disclosure of
Japanese Patent Application No. 2004-163896 filed on Jun. 1, 2004
including the specification, drawings and abstract is incorporated
herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a cushion plate used as a
buffer in a multi-plate frictional engagement element provided in,
for example, an automatic transmission of a vehicle. Specifically,
the present invention relates to a cushion plate in which stress
concentration is reduced when it is deflected.
[0004] 2. Description of the Related Art
[0005] Vehicular automatic transmissions utilize a multi-plate
clutch or a multi-plate brake for changing a power transmission
path within the transmission mechanism. In the multi-plate clutch
or brake, movement of a piston of a hydraulic servo (actuator) is
controlled based on the pressure of oil supplied from, for example,
a hydraulic (oil pressure) controller, thereby pressing or
releasing a friction plate unit and engageing or disengaging the
clutch or brake. The clutch or brake has a cushion plate shaped
like a belleville-spring between the piston and the friction plate
unit. When the clutch or the brake is engaged, the cushion plate is
deflected to absorb engagement shock (see, for example, Japanese
Patent Application Laid Open No. 10-246249).
[0006] However, the cushion plate may be dragged with the friction
plate of the clutch, the brake or the like, by flow of the
lubrication oil in the direction of rotation. Furthermore, for
example when the cushion plate is used in a clutch, it may rotate
relative to the clutch drum. That is, the cushion plate may be
abraded undesirably by friction with an adjacent member rotating
relative to the cushion plate.
[0007] Therefore, it is preferable that, for example, pawls 101b be
integral with and extend from the body 101a of the cushion plate
101 as shown in FIG. 4(a) and FIG. 4(b), and that the friction
plate 41a adjacent the cushion plate 101 be in spline engagement
with the cushion plate 101 via a spline 4s, as shown in FIG.
5(a).
[0008] However, as shown in FIG. 5(b), when piston 43 of a
hydraulic servo moves in the direction indicated by arrow A, the
belleville-spring shaped cushion plate 101 is pushed toward the
adjacent friction plate 41a, and is deflected. As the cushion plate
101 is compressed in this manner, it is extended radially outward
as indicated by arrow B, and the plate body 101a receives a turning
force as indicated by arrow .omega.1-.omega.2 shown on FIG. 4(b).
In other words, a circumferential direction tensile stress is
generated in the outer peripheral portion of the cushion plate 101.
Thus, a maximum stress .sigma.ymax, greater than the average stress
.sigma.yn, is generated as a concentrated stress shown as stress
distribution of a cross section y-y in FIG. 4(b). In other words, a
relatively large stress concentration occurs at base portions 101g
of the pawls 101b, adversely affecting durability.
[0009] Furthermore, as shown in FIG. 6, for example, if an arc at a
base portion 101g' of a cushion plate 101' is enlarged in order to
reduce stress concentration, the base portion 101g' may undesirably
contact a corner 4sa of the spline 4s, thereby reducing the contact
area between side surface 101f' of a pawl 101b' and a side surface
4sb of the spline 4s. Such a small contact area is undesirable
when, for example, the cushion plate 101' receives a large
rotational force.
[0010] Moreover, as shown in FIG. 7(a) and FIG. 7(b) for example,
if a plate body 201a of a cushion plate 201 has recesses 201c
extending radially inward at a base portion 201g of pawls 201b, it
is possible to increase the size of an arc at the base portion
201g. However, since tensile stress is generated in the
circumferential direction as indicated by the arrow
.omega.1-.omega.2, a maximum stress .sigma.zmax (which is larger
than the maximum stress .sigma.ymax) and average stress .sigma.zn,
are created in an area of stress concentration shown as a cross
section z-z. In other words, a relatively large concentration of
stress occurs at the recess portions 201c.
SUMMARY OF THE INVENTION
[0011] Accordingly, It is an object of the present invention to
provide a cushion plate having pawls and designed to prevent
abrasion, in which stress concentration at a base portion of the
pawls is reduced.
[0012] According to a first aspect of the present invention, a
curved recess is formed at a base portion of a pawl so as to create
a circumferentially extending indentation, thereby reducing
concentration of stress at the base portions of the pawls and
improving durability of the cushion plate.
[0013] According to a second aspect of the present invention, the
recesses are formed radially outward of the outer periphery of the
plate main body, thereby avoiding a reduction in the radial
dimension of the plate body. Thus, it is possible to prevent
generation of a relatively large concentration of stress at the
base portions of the pawls and, accordingly, the durability of the
cushion plate is improved.
[0014] According to a third aspect of the present invention, the
pawl is inclined in the direction from which the plate body is
pressed. Therefore, when the plate body is pressed, it is possible
to prevent the pawl from bending relative to the plate body. Thus,
the circumferentially extending recesses prevent generation of
stress at the base portion where the width of the pawl is smallest.
Accordingly, the durability of the cushion plate is improved.
[0015] According to a fourth aspect of the present invention, the
cushion plate is incorporation into a multi-plate frictional
engagement element of an automatic transmission. Therefore, it is
possible to absorb shock of engagement in the automatic
transmission. Furthermore, since the pawl is splined to a member on
the outer peripheral side, rotation relative to an outer friction
plate is prevented. Thus, it is possible to prevent abrasion of the
cushion plate.
[0016] According to a fifth aspect of the present invention, the
cushion plate is incorporated into a multi-plate brake.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a cross-sectional view, with partial omissions, of
an example of an automatic transmission to which a cushion plate
according to the present invention is applied;
[0018] FIG. 2(a) is a front view of the cushion plate according to
the present invention, and FIG. 2(b) is an enlarged view of a
portion X in FIG. 2(a);
[0019] FIGS. 3(a) and 3(b) illustrate operation of the cushion
plate according to the present invention, wherein FIG. 3(a) is a
view showing the state where a hydraulic servo is released, and
FIG. 3(b) is a view showing the state where the hydraulic servo is
engaged;
[0020] FIG. 4(a) is a front view of a cushion plate provided with
pawls and FIG. 4(b) is an enlarged view of a portion Y in FIG.
4(a);
[0021] FIGS. 5(a) and 5(b) illustrate operation of the hydraulic
servo and the cushion plate, wherein FIG. 5(a) is a view showing
the released state, and FIG. 5(b) is a view showing the engaged
state;
[0022] FIG. 6 is an enlarged view of an arc at a base portion of a
pawl; and
[0023] FIG. 7(a) is a front view of a cushion plate provided with
recesses extending radially inward and FIG. 7(b) is an enlarged
view of a portion Z in FIG. 7(a).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Hereinafter, an embodiment according to the present
invention will be described with reference to the drawings.
Firstly, an example of an automatic transmission to which the
present invention is applied will be described briefly with
reference to FIG. 1. As shown in FIG. 1, a belt-type continuously
variable transmission (CVT) 50 is provided with, for example, an
input shaft 3 and a pulley mechanism. Drive rotation is input from
an engine to the input shaft 3 through a torque converter (not
shown) or the like. The pulley mechanism includes a metal belt (not
shown) held between a primary pulley 5 and a secondary pulley (not
shown). The primary pulley 5 is supported by a transmission case 4
(a member on the outer periphery) through a ball bearing 7. The
rotational speed of the primary pulley 5 is changed continuously by
altering the pulley width, and the rotation as changed is output to
the drive wheels through the secondary pulley. The belt-type CVT 50
has a forward/reverse switching device 60 interposed in the power
transmission path between the primary pulley 5 and the input shaft
3. The forward/reverse switching device 60 switches the rotation of
the input shaft 3 between forward rotation and reverse rotation,
and outputs the switched rotation.
[0025] The forward/reverse switching device 60 is disposed in the
transmission case 4, and includes a planetary gear unit SP, a
multi-plate forward movement clutch C-1 and a multi-plate reverse
movement brake (i.e. a multi-plate frictional engagement element)
B-1 respectively provided around the input shaft 3. The planetary
gear unit SP includes a sun gear S, a ring gear R, and a carrier
CR. The sun gear S is rotatably supported on the input shaft 3 and
is coupled to the primary pulley 5. The ring gear R is coupled to a
clutch drum 32 as described below. The carrier CR has a pinion P1
meshing with the ring gear R and the sun gear S.
[0026] The forward movement clutch C1 has a friction plate unit 31
and a hydraulic servo 30. The friction plate unit 31 includes a
plurality of outer friction plates 31a and inner friction plates
31b. The hydraulic servo 30 controls the state of engagement of the
friction plate unit 31. The hydraulic servo 30 includes the clutch
drum 32, a piston 33, a cancellation plate 34, and a return spring
35, which form an oil chamber 36 and a cancellation oil chamber 37.
The clutch drum 32 is rotatably supported by a lid member 4a fixed
to the transmission case 4, and an inner peripheral annular end
portion of the clutch drum 32 is coupled to the input shaft 3.
Splines 32s are formed on the inner surface of the outer peripheral
side annulus of the clutch drum 32 and the outer friction plates
31a and the ring gear R are in spline engagement therewith. The
axial position of the ring gear R is fixed by a snap ring 38 and
the rotation of the input shaft 3 is constantly input to the ring
gear R.
[0027] The piston 33 is axially movable relative to the clutch drum
32. A portion 33a of the piston 33 is in spline engagement with the
spline 32s. A pressing portion 33a is provided facing the friction
plate unit 31 to apply a pressing (engaging) force thereto. Seal
rings a1 and a2 form the oil tight oil chamber 36 between the
piston 33 and the clutch drum 32. The return plate 34 is prevented
from axial movement by a snap ring 39 fitted in the outer surface
of the inner cylindrical portion of clutch drum 32. The return
spring 35 is compressed between the return plate 34 and the piston
33, and seal rings a1 and a3 form the cancellation oil chamber 37.
Furthermore, the inner friction plates 31b, provided between
adjacent outer friction plates 31a, (and the ring gear R) are
splined to a hub member 62. The hub member 62 is coupled to the sun
gear S.
[0028] Thus, when working oil is supplied from the hydraulic
controller (not shown) to the oil chamber 36, the piston 33 presses
against the friction plate unit 31, and the forward movement clutch
C-1 is engaged. Thus, the rotation of the input shaft 3 is
transmitted to the primary pulley 5 through the clutch drum 32, the
friction plate unit 31, the hub member 62, and the sun gear S. The
rotational speed of the input shaft 3 is changed in a stepless
manner by the pulley mechanism, and rotation at that changed speed
is transmitted to the drive wheels as forward speed rotation
[0029] Likewise, the reverse movement brake B-1 has a friction
plate unit 41 and a hydraulic servo 40. The friction plate unit 41
includes a plurality of outer friction plates 41a and inner
friction plates 41b. The hydraulic servo 40 controls the engagement
state of the frictional plate unit 41. The hydraulic servo 40
includes a cylinder 42, a piston 43, a cancellation plate 44, and a
return spring 45, which form an oil chamber 46. The cylinder 42 is
formed in an inner surface of the transmission case 4. The piston
43 is slidably mounted within the cylinder 42 for axial movement
therein. The piston 43 has an extended portion 43a extending toward
and facing the friction plate unit 41 for applying a pressing force
thereto. Seal rings a4 and a5 form an oil tight oil chamber 46
between the piston 43 and the cylinder 42. The return plate 44 is
prevented from axial movement by a snap ring 49 fitted in the inner
peripheral surface of the transmission case 4. The return spring 45
is compressed between the return plate 44 and the piston 43.
[0030] The outer friction plates 41a are in spline engagement with
a spline 4s formed on the inner peripheral surface of the
transmission case 4. Furthermore, one of outer friction plates 41a,
that friction plate furthest opposite the piston 43, is prevented
from axial movement by a snap ring 49 fitted in the inner
peripheral surface of the transmission case 4. Moreover, the inner
friction plates 41b provided between adjacent outer friction plates
41a (alternating therewith) are splined to a hub member 61 (a
member on the radially inner side). The hub member 61 is integrally
coupled to the carrier CR.
[0031] Thus, when working oil is supplied from the hydraulic
control unit to the oil chamber 46, the piston 43 presses the
friction plate unit 41, and the reverse movement brake B-1 is
engaged. The carrier CR, through the hub member 61, is held against
rotation relative to the transmission case 4. Thus, while the
rotation of the input shaft 3 is constantly inputted to the ring
gear R through the clutch drum 32, the rotation of the ring gear R
is reversed through the pinion P1 of the fixed carrier CR, output
to the sun gear S, and transmitted to the primary pulley 5. The
rotational speed of the input shaft 3 is changed in a stepless
maner by the pulley mechanism, and rotation at the changed speed is
transmitted to the drive wheels as reverse speed, speed-changed
rotation.
[0032] A cushion plate 1 according to the present invention is
positioned axially between the edge (pressing) portion 43a of the
piston 43 and the one of the outer friction plates 41a nearest the
piston 43. Note that in the embodiment of the present invention
(described here), the cushion plate 1 is described as being used in
the reverse movement brake B-1. Of course, the cushion plate 1 may
also be used in the forward movement clutch C-1, and in any other
frictional engagement mechanism, without limitation.
[0033] The cushion plate 1 according to the present invention is
shown in FIG. 2(a) as including a plate body 1a defining a central
axis CT, and a plurality of pawls 1b for spline engagement with the
spline 4s formed on the inner peripheral surface of the
transmission case 4. For example, six pawls 1b may be provided at
equal circumferential spacings. The plate body 1a is formed as an
annular disk. When no load (pressing force) is applied to the plate
body 1a, the plate body 1a is inclined so that its outer peripheral
portion 1d is extended toward the outer friction plates 41a, and
its inner peripheral portion 1e is extended toward the piston 43
(see FIG. 1). That is, the plate body 1a is shaped as a so-called
belleville-spring.
[0034] As shown in FIG. 2(b), each of the pawls 1b is formed
integrally on the plate body 1a, and extends radially outwardly
from the outer peripheral portion 1d of the plate body 1a. When
viewed from the front, each of the pawls 1b has a rectangular shape
with side surfaces 1f. Curved recesses 1c are formed at the
radially innermost ends of side surfaces 1f, i.e., on both sides 1g
of each of the pawls 1b. The recesses 1c create circumferential
indentations as indicated by an arrow .omega.1-.omega.2. The curved
shape of the circumferential indentations indicated by the arrow
.omega.1-.omega.2, i.e., the recess portions 1c may have a
generally semicircular shape, a generally oval shape, or any other,
more complicated shape. It is preferred that the recess portions 1c
do not extend radially inward from the outer peripheral portion 1d
of the plate body 1a.
[0035] As shown in FIG. 3(a), each of the pawls 1b is formed so as
to incline at a predetermined angle .theta. from the plate body 1a
toward the piston 43 (i.e., in the direction from which the plate
body 1a is pressed). The predetermined angle .theta. is determined
such that the pawl 1b does not contact the adjacent friction plate
41a when the reverse movement brake B-1 is released as shown in
FIG. 3(a), and such that the pawl 1b will remain engaged with the
spline 4s on the inner peripheral surface of the transmission case
4 when the reverse movement brake B-1 is engaged as shown in FIG.
3(b).
[0036] Next, operation of the cushion plate 1 will be described
with reference to engagement and release of the reverse movement
brake B-1. As shown in FIG. 3(a), when the reverse movement brake
B-1 is released, the piston 43 does not press against the cushion
plate 1 (the piston 43 is spaced from the cushion plate 1).
Furthermore, the pawl 1b of the cushion plate 1 is engaged with the
spline 4s on the inner peripheral surface of the transmission case
4, and the outer friction plate 41a nearest the piston 43 is also
engaged with the spline 4s. Therefore, even with a flow of
lubrication oil in the direction of rotation, the cushion plate 1
will not rotate relative to the outer friction plate 41a or to the
spline 4s (i.e., the transmission case 4), and thus, no abrasion
occurs.
[0037] Moreover, even if a large turning force (torque) is applied
to the cushion plate 1 in the direction of rotation, the recesses
1c in the side surfaces 1f of the pawls 1b provide the pawls 1b
with a sufficient length to establish a large contact area with the
spline 4s and to sufficiently resist rotational force.
[0038] Note the lack of relative rotation between the cushion plate
1 and the piston 43, even with the piston 43 in contact with the
cushion plate 1 since the piston 43 does not normally rotate.
Therefore, no abrasion occurs in this case either. Further, when
the cushion plate 1 is used in the clutch, since the cushion plate
1 and the outer friction plates are normally in spline engagement
with the clutch drum, the cushion plate 1, the outer friction
plates, and the piston rotate integrally with the clutch drum, and
no relative rotation and no abrasion occur in this case either.
[0039] As shown in FIG. 3(b), when the reverse movement brake B-1
is engaged, drive of the piston 43 is controlled by the pressure of
the oil supplied to the oil chamber 46, and the piston moves
axially as indicated by arrow A, thereby pressing the cushion plate
1 in the direction indicated by the arrow A. Thus, the cushion
plate 1 is deflected by a pressing force (a clamping force) between
the piston 43 and the adjacent friction plate 41a. The pressing
force of the piston 43 is received by a snap ring 48, the outer
friction plate 41a, and the inner friction plate 41b (see FIG.
1).
[0040] When the cushion plate 1 is deflected by the pressing force
of the piston 43, the inner peripheral portion 1e of the plate body
1a is pushed inwardly in the direction indicated by the arrow A.
Thus, the plate body 1a is pushed in the direction indicated by
arrow B, i.e., radially outward from the central axis CT, and the
outer periphery 1d is turned as indicated by the arrow
.omega.1-.omega.2. Consequently, tensile stress is generated in the
circumferential direction as indicated by the arrow
.omega.1-.omega.2 at the base portions 1g of each of the pawls 1b.
A maximum stress .sigma.xmax, with an average stress .sigma.xn, is
generated as shown in the stress distribution of cross section x-x
in FIG. 2(b). However, since the recesses 1c extend in the
circumferential direction, as indicated by the arrow
.omega.1-.omega.2, the stress concentration at the base portions 1
g of each of the pawls 1b is reduced (that is, the maximum stress
.sigma.xmax becomes smaller than a maximum stress .sigma.ymax and
smaller than a maximum stress .sigma.zmax).
[0041] Furthermore, because each of the pawls 1b is inclined at the
predetermined angle .theta., from the plate body 1a toward the
piston 43, the pawls 1b are not bent by the pressing force of the
piston 43. In other words, although the circumferentially extending
recesses 1c at the base portions 1g of the pawls 1b reduce the
circumferential width of the base portions 1g, because the pawls 1b
do not bend it is possible to prevent concentration of stress at
the base portions 1g.
[0042] As described above, in the cushion plate 1 according to the
present invention, the curved recesses 1c formed at the base
portions 1g of the pawls 1b, are in the form of circumferentially
extending indentations. Thus, the splined engagement of the pawls
1b prevents rotation relative to the friction plates 41, the spline
4s on the inner peripheral surface of the transmission case 4, and
the piston 42. This lack of relative rotation prevents abrasion of
the cushion plate while reducing stress concentration at the base
portions 2g of the pawls 1b, thereby improving the durability of
the cushion plate 1. Moreover, a larger contact area is provided
between the pawls 1b and the spline 4s. Thus, even if, for example,
a large rotational force is applied to the cushion plate 1, the
force can be sufficiently withstood.
[0043] Furthermore, since the recesses 1c are positioned outwardly
from the outer periphery 1d of the plate body 1a, it is possible to
eliminate a narrowing of the width of the plate body 1a, i.e., the
radial dimension indicated by the arrow B. Thus, it is possible to
prevent generation of a relatively large stress concentration at
the base portions 1g of the pawls 1b. Accordingly the durability of
the cushion plate 1 is improved.
[0044] Moreover, since the pawls 1b are inclined from the plate
body 1a toward the piston 43 in the direction from which the plate
body 1a is pressed, the pawls 1b are prevented from bending with
respect to the plate body 1a when the plate body 1a is pressed.
Thus, circumferentially extending recesses 1c prevent stress
concentration at the base portions 1g. Accordingly, the durability
of the cushion plate 1 is improved.
[0045] Furthermore, since the cushion plate 1 is used in the brake
B-1 of the automatic transmission 50, it is possible to absorb
shock of engagement in the automatic transmission 50.
[0046] In the embodiment described above, the cushion plate 1
according to the present invention is used in the reverse movement
brake B-1 of the belt-type CVT 50. As a matter of course, the
cushion plate 1 is also applicable in the same way to any
multi-plate frictional engagement element of any automatic
transmission.
[0047] Furthermore, although the above-described cushion plate 1 is
shown as having pawls 1b at six locations, any number of pawls may
be provided, if adapted to engage splines on the interior of the
transmission case.
[0048] In the above-described embodiment, a configuration where the
recesses 1c create circumferentially extending indentations at the
basees 1g on both sides of the pawls 1b has been described as
preferred. However, the scope of the resent invention also includes
a structure wherein recesses are formed only in one location at the
base of the pawl.
[0049] The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The present embodiments are therefore to be considered in
all respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are therefore
intended to be embraced therein.
* * * * *