JPH1089380A - Multiple friction engagement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple friction engagement device which can improve durability, reduce size and weight, and reduce a manufacturing cost. SOLUTION: In a multiple friction engagement device, a ring groove 58 is formed on an inner periphery near an end face 50a of a piston 50 for fitting and locking a snap ring 59. A recession 64 is formed between the piston end face 50a and a drive plate 46 along an end face inner peripheral edge of the piston 50 so as to form a non-abutting range 65, for avoiding abutting between an inner peripheral edge of the piston end face 50a and the drive plate 46. Stress generated on a bottom 58a of the ring groove 58 due to reaction force from the drive plate 46 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-plate friction engagement device.

[0002]

2. Description of the Related Art A commonly used automatic transmission is constructed by combining a torque converter and a multi-stage transmission mechanism such as a planetary gear unit. To control the shift of such an automatic transmission, a plurality of frictional engagement devices, for example, brakes and clutches, which are arranged in a multi-stage transmission mechanism, are selectively operated to switch a power transmission system path from an engine, and to perform a required shift. You are going to get a step.

As a multi-plate friction engagement device used in an automatic transmission, there is a prior art disclosed in Japanese Patent Application Laid-Open No. 4-262125, for example.

The multiple disc type frictional engagement device disclosed in this prior art has a first clutch 11 as shown in FIG.
0 and the second clutch 120, and the first clutch 11
0 denotes a spline groove 111a formed on the inner periphery of the clutch drum 111 when the clutch drum 111 is coupled to the input shaft.
, Retaining plate 112, drive plate 11
Driven plates 114 are fitted alternately with the drive plate 113 so that the outer circumference of the third clutch 3 is fitted and the inner circumference is fitted into a spline groove 115 a formed on the outer circumference of the first clutch hub 115. The retaining plate 112 and the driven plate 11 are attached to a snap ring 118 ′ fixed to the clutch drum 111 via the distal end of the first piston 117 divided into teeth.
4. The power from the input shaft is transmitted to the first clutch hub 115 by pressing the friction plates of the drive plate 113 to frictionally engage each other.

On the other hand, the second clutch 120 has a spline groove 125 a formed on the outer periphery of the second clutch hub 125 while the outer periphery of the retaining plate 122 and the drive plate 123 is fitted into the spline groove 117 a on the inner periphery of the first piston 117. Driven plate 1 whose inner circumference fits
24 are alternately arranged with the drive plate 123,
A snap ring 128 fitted and locked in a ring groove 118 formed in the first piston 117 via a second piston 127 fitted to the first piston 117 by the hydraulic pressure of the hydraulic chamber 126.
Retaining plate 122, driven plate 12
4 and a friction plate, such as the drive plate 123, is pressed so as to frictionally engage with each other, so that power from the input shaft is transmitted to the second clutch hub 125, and a return spring is attached to the second piston 127. 1
29 pressing forces are urged.

[0006]

According to the above prior art, the snap ring 1 is provided near the tip of the first piston 117.
When the first clutch 110 is fastened, the first piston 117
When the drive plate 113, the driven plate 114, and the retaining plate 112 are pressed against the snap ring 128 by the tips divided in a comb shape, the reaction force is applied to the end face 1 of the first piston 117 as shown in FIG.
17a, the tip of the first piston 117, particularly the inner peripheral side where the ring groove 118 is formed due to the reaction force, has the ring groove 1 as shown by a dashed line 117 'in FIG.
Deformed slightly to 18 side. With this deformation, the ring groove 11
Compressive stress is concentrated on the bottom edge 118a of the base member 8.

On the other hand, the second clutch 120
When the drive plate 123, the driven plate 124, and the retaining plate 122 are pressed against the snap ring 128 by the piston 127, the load is applied to the two ends of the first piston 117 via the side surface 118b of the ring groove 118 as shown in FIG. As shown by a chain line 117 ″, it is received by being slightly deformed. With this deformation, tensile stress concentrates on the bottom edge 118 a of the ring groove 118 and is generated.

Therefore, the bottom edge 118 of the ring groove 118
a, the durability of the periphery of the ring groove 118 of the first piston 117 is reduced due to the concentration of the compressive and tensile stresses repeatedly generated, and the tip of the first piston 117 is deformed to induce the first and second clutches 110. , 120 may be malfunctioned.

As a countermeasure, it is supposed that increasing the reference wall thickness of the first piston 117 to improve the strength would increase the size and weight of the first piston 117 and increase the manufacturing cost.

Accordingly, it is an object of the present invention to provide a multi-plate type frictional engagement device capable of improving durability, reducing size and weight, and reducing manufacturing costs.

[0011]

According to a first aspect of the present invention, there is provided a multi-disc friction engagement device comprising: a drum; a plurality of friction plates movably provided in the drum in an axial direction;
A hub, a plurality of friction plates arranged coaxially and alternately on the friction plate and movably provided in the hub in the axial direction, and a ring groove on an inner periphery near an end portion; A multi-plate friction engagement device having a piston that frictionally engages each friction plate by pressing an arranged friction plate by an end portion, wherein the piston has an end face and a friction plate pressed by the piston end face. In addition, the friction plate has a non-contact range along the inner peripheral edge of the piston end surface to avoid contact between the inner peripheral edge of the piston end surface and the friction plate.

Further, another multi-plate friction engagement device according to the present invention includes a plurality of friction plates provided on the inner periphery of the drum so as to be movable in the axial direction and a plurality of friction plates provided on the first hub so as to be movable in the axial direction. Frictional plates are alternately arranged coaxially with each other, and the alternately arranged friction plates are pressed by the end face of the first piston to frictionally engage each friction plate; and A plurality of friction plates provided on the inner periphery so as to be movable in the axial direction independently of the friction plates and a plurality of friction plates provided on the second hub so as to be movable in the axial direction are coaxially and alternately arranged. The friction plates arranged alternately are pressed by the end faces of the second piston against snap rings which are fitted and locked in a ring groove formed on the inner periphery near the end of the first piston. Second A multi-plate friction engagement device having a friction engagement device, wherein the first piston end surface extends along an inner peripheral edge of the end surface of the first piston between an end surface of the first piston and a friction plate pressed by the first piston end surface. A non-contact range for avoiding contact between the inner peripheral edge of the end face and the friction plate, and a reaction force from the friction plate exerted on the non-contact range of the piston end face is avoided; The influence on the inner peripheral side of the tip is reduced, and the minute deformation that occurs on the inner peripheral side of the piston tip is suppressed, the stress generated at the bottom of the ring groove is reduced, and the strength of the piston tip is improved and durability is secured. Is done.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view schematically showing a drive system of an automatic transmission having a multiple disc type frictional engagement device according to the present invention.

In FIG. 1, reference numeral 1 denotes a crankshaft of the engine. A torque converter 3 and a multi-stage transmission mechanism 20 are arranged coaxially with the crankshaft 1 and are accommodated in a transmission case 2 in order from the engine side.

The torque converter 3 has an input shaft 4 which is rotatably supported on the transmission case 2 coaxially with the crankshaft 1. The outer periphery of the input shaft 4 is rotatably surrounded by a stator shaft 5 connected to the transmission case 2, and an oil pump drive shaft 6 a integrally connected to the impeller 6 is rotatably fitted to the stator shaft 5. I have.

The impeller 6 is driven to rotate integrally with the crankshaft 1 by connecting its outer periphery to the crankshaft 1 via a drive plate 7.

A turbine 8 is spline-fitted to the input shaft 4 so as to face the impeller 6, and a one-way clutch 9 is attached to the stator shaft 5 between the impeller 6 and the turbine 8.
The stator 9 is interposed and supported via a.

Further, a lock-up clutch 10 is interposed between the drive plate 7 and the input shaft 4 so that the stator shaft 5
An oil pump 11 driven by an oil pump drive shaft 6a is provided at a base end of the oil pump.

When the crankshaft 1 of the engine rotates, the impeller 6 is integrally rotated via a drive plate 7 coupled to the crankshaft 1, and the rotation of the impeller 6 causes the turbine 8 to rotate in the same direction as the impeller 6. By transmitting the torque, the input shaft 4 that is spline-fitted with the turbine 8 is rotationally driven. Further, the torque of the turbine 8 is increased by reversing the outflow direction of the oil flowing out of the turbine 8 by the stator 9 in a direction that promotes the rotational force of the impeller 6.

On the other hand, the so-called torque converter, which causes the drive plate 7 and the input shaft 4 to be directly connected to each other by the lock-up clutch 10 when the vehicle speed or the rotation speed reaches a predetermined speed, is eliminated, and the rotation speed of the engine is reduced accordingly. The aim is to save fuel and improve quietness.

A multi-stage transmission mechanism 20 having a front planetary gear unit 21 and a rear planetary gear unit 31 is arranged coaxially with the input shaft 4.

The front planetary gear unit 21 of the multi-stage transmission mechanism 20 includes a front sun gear 22 rotatably fitted to the input shaft 4, a front ring gear 23, a front carrier 24, and a front sun gear 22 rotatably supported by the front carrier 24. And a plurality of front pinion gears 25 meshing with the front ring gear 23, respectively. The front sun gear 22 is self-centered by the plurality of front pinion gears 25.

The rear planetary gear unit 31 includes a rear sun gear 32 spline-fitted to the input shaft 4, a rear ring gear 33, a rear carrier 34 integrally connected to the front ring gear 23, and the rear sun gear 32 A plurality of rear pinion gears 35 mesh with the ring gear 33, respectively, and the output from the rear carrier 34 is transmitted to the output shaft 14 disposed coaxially with the input shaft 4.

A reverse clutch 41 is interposed between the input shaft 4 and the front planetary gear unit 21 and serves as a first frictional engagement device for selectively transmitting the power of the input shaft 4 to the front sun gear 22. A high clutch 51 serving as a second friction engagement device for selectively transmitting the power of the input shaft 4 to the front carrier 24 is interposed, and the reverse clutch 41 and the high clutch 51 allow the multi-plate friction engagement device 40 to be engaged. Make up. Between the transmission case 2 and the front sun gear 22, there is provided a 2 & 4 brake 70 for selectively rotating and locking the front sun gear 22 for fastening.

Further, the front carrier 24 is provided with a low clutch drum 26 which rotates integrally with the front carrier 24.
And the low clutch drum 26 and the rear ring gear 33
Between the front carrier 24 and the rear ring gear 33
And a low one-way clutch 81 between the low clutch drum 26 and the transmission case 2 and a low-and-low clutch for preventing the low one-way clutch 81 from idling. Reverse brakes 82 are provided in parallel.

Next, the operation of the automatic transmission configured as described above will be described with reference to the operation explanatory view of the engagement device shown in FIG. In this operation explanatory diagram, marks indicate the engaged states of the corresponding clutches or brakes, and * indicates that the output from the drive side by the low one-way clutch is in a power transmission state.

First, the power of the engine is transmitted from the crankshaft 1 to the input shaft 4 via the torque converter 3. Here, in the parking (P) range and the neutral (N) range, the clutch and the brake are released and the rear sun gear 32 rotates, but idles and the power transmission is cut off, and the power transmission thereafter is stopped.

Next, the case where the drive (D) range which is the forward gear is set will be described.

At the first speed, the low clutch 80 is engaged, and the low one-way clutch 81 is in a power transmission state.
Other clutches and brakes are controlled to the released state.

Therefore, the low clutch drum 26 is prevented from rotating backward by the engagement of the low clutch 80 and the action of the low one-way clutch 81, and the rear ring gear 33 is fixed. Therefore, the power from the input shaft 4 is input to the rear sun gear 32 while the rear carrier 34 and the front ring gear 2
3, the front planetary gear unit 21 is also driven to rotate via the front ring gear 23, but the front sun gear 22, the front pinion gear 2
5, the entire front planetary gear unit 21 remains stationary, and the rotation of the rear carrier 34 on the output side becomes the first-speed gear ratio at which the rotation is most reduced, and the power is transmitted to the output shaft 14.

At the second speed, the low clutch 80 is engaged, the 2 & 4 brake 70 is engaged, and the other clutches and brakes are controlled to the released state, as at the first speed.

Therefore, by engaging the low clutch 80, the front carrier 24 and the rear ring gear 33 are integrally engaged via the low clutch drum 26, and the front sun gear 22 is fixed to the transmission case 2 by the 2 & 4 brake 70, as in the case of the first speed. Power from the input shaft 4 is input to the rear sun gear 32.

The rotation of the rear sun gear 32 causes the front ring gear 23 that has received the rotation of the rear carrier 34 to decelerate the front carrier 24, and inputs this reduced rotation to the rear ring gear 33 via the low clutch drum 26 and the low clutch 80. Since the rotation of the rear ring gear 33 is slower than the rotation of the rear carrier 34, the rotation of the rear ring gear 33 is added to the rotation of the rear carrier 34 to speed up the rotation of the rear carrier 34. Therefore, the rotation of the rear carrier 34 is faster than the rotation at the first speed. Rear ring gear 33
And the deceleration becomes smaller.

The shift from the first gear to the second gear is performed by the low clutch drum 26 fitted to the front carrier 24 with the engagement of the front sun gear 22 by the 2 & 4 brake 70.
Rotates to automatically disengage the low one-way clutch 81 and shift from the first speed to the second speed. When the engagement of the front sun gear 22 is released by releasing the 2 & 4 brake 70, the low clutch drum 26 is prevented from rotating by the operation of the low one-way clutch 81, and the rear ring gear 3
3 is the fixed first speed. Therefore, the shift between the first speed and the second speed is automatically performed by the action of the 2 & 4 brake 70.

At the third speed, the high clutch 51 and the low clutch 80 are engaged, and the other clutches and brakes are controlled to be released.

Therefore, when the high clutch 51 and the low clutch 80 are engaged, the power from the input shaft 4 is input to the rear sun gear 32 of the rear planetary gear unit 31, and the high clutch 51, the front carrier 24 of the front planetary gear unit 21, and the low clutch drum. 26 and the rear ring gear 3 via the low clutch 80
3 and simultaneously, the rear carrier 34 also rotates integrally and rotates directly one-to-one with respect to the input shaft 4 to rotate the rear carrier 3.
4 to the output shaft 14.

Therefore, at the second speed, the front sun gear 22 is fixed, and the rear ring gear 33 and the front carrier 24
The low clutch drum 26 that rotates integrally with the front carrier 2 is coupled via a low clutch 80. On the other hand, at the third speed, the front sun gear 22 is disengaged by the 2 & 4 brake 70 and the high clutch 51 is engaged to engage the front carrier 2
Since the input shaft 4 and the input shaft 4 are connected, the speed change between the second speed and the third speed is performed by changing the 2 & 4 brake 70 and the high clutch 51.

Next, in the case of the fourth speed, the high clutch 51 and the 2 & 4 brake 70 are engaged, and the other clutches and brakes are controlled to be released.

Therefore, the front sun gear 22 is fixed by the engagement of the 2 & 4 brake 70, and the output from the input shaft 4 is input to the front carrier 24 by the engagement of the high clutch 51, and the speed of the front ring gear 23 is increased to cause the front ring gear 23 to move from the rear carrier to the rear carrier. The overdrive rotation speed increased via 34 is output to the output shaft 14.

Here, at the 3rd speed, the front carrier 24 and the input shaft 4 are connected by the high clutch 51 and the front carrier 24 and the rear ring gear 33 are connected by the low clutch 80 to rotate integrally. Is released from the front carrier 24 by releasing the low clutch 80.
Since the front sun gear 22 is fixed by releasing the engagement of the rear ring gear 33 and the 2 & 4 brake 70, the shift between the third speed and the fourth speed is changed by switching the low clutch 80 and the 2 & 4 brake 70. You.

In the first to third speeds when the 3rd range is set, the first to third speeds in the drive (D) range are used.
In the case of the first speed and the second speed when the 2nd range is set, the drive (D) range 1
The description is omitted because it is the same as in the case of the first or second speed.

When the first range is set, the low clutch 80 and the low & reverse brake 82 are engaged to prevent idling of the low one-way clutch 81, and the other clutches and brakes are controlled to be released.

That is, the engagement of the low clutch 80 and the low & reverse brake 82 prevents rotation of the low clutch drum 26 and fixes the rear ring gear 33. The power from the input shaft 4 is input to the rear sun gear 32,
The rotation of the rear carrier 34 on the output side becomes the first-speed gear ratio at which the speed is most reduced, and the rotation of the rear ring gear 33 is prevented even when power is input from the output shaft 14 side, thereby ensuring the engine braking function. .

In the reverse (R) range of the reverse stage, the reverse clutch 41 and the low & reverse brake 82 are engaged, and the other clutches and brakes are controlled to be released.

Accordingly, by engaging the low & reverse brake 82, the front carrier 24 is fixed via the low clutch drum 26, and the power from the input shaft 4 drives the front sun gear 22 via the reverse clutch 41 to rotate. The rotation of the front sun gear 22 is controlled by the front carrier 2
The so-called reverse rotation of the front ring gear 23, which is decelerated with respect to the rotation of the front sun gear 22 and rotated in the opposite direction by the front pinion gear 25 rotatably supported by the front ring gear 4, via a rear carrier 34 connected to the front ring gear 23. Output to the output shaft 14. Next, the multi-plate type frictional engagement device 40, 2 & 4 brake 70 indicated by A in FIG.
The portion of the front planetary gear unit 21 will be described in detail with reference to FIGS.

FIG. 3 is a sectional view of a main part. The input shaft 4 is coaxial with the crankshaft 1 of the engine via a bush 4b by a hollow oil pump cover 16 supported by the transmission case 2 via an oil pump housing. A spline 4a is rotatably supported on the upper side and spline-fits a clutch drum base 42 described later.

The oil pump cover 16 extends along the input shaft 4.
From the side, the clutch drum base 42 and the high clutch 51
Of the second clutch hub 52 and the first of the reverse clutch 41
Clutch hub 44, front planetary gear unit 2
1. The rear planetary gear units 31 are arranged side by side with thrust bearings interposed therebetween, and the rear planetary gear units 31 are supported on the transmission case 2 via thrust bearings, whereby the axial movement of each of the above members is restricted.

The front planetary gear unit 21 is rotatably supported by the input shaft 4 via a bush 52c. Front carrier 24 fitted to spline 52a formed in second clutch hub 52 of high clutch 51
, Meshed with the front sun gear 22 and the front ring gear 23, and
The front sun gear 22 and the front ring gear 23 are self-centered by a plurality of front pinion gears 25 rotatably supported via a needle bearing 25a.

A multi-plate frictional engagement device comprising a reverse clutch 41 as a first frictional engagement device and a high clutch 51 as a second frictional engagement device between the front planetary gear unit 21 and the input shaft 4. A 2 & 4 brake 70 is interposed between the front planetary gear unit 21 and the transmission case 2.

Next, the multi-plate friction engagement device 40 will be described. In the reverse clutch 41, one end of a clutch drum 43 is rotatably supported by the oil pump cover 16 and spline-fitted to a spline 4a of the input shaft 4. It is attached to the clutch drum base 42. On the other hand, the first clutch hub 44 is connected to and attached to the front sun gear 22 of the front planetary gear unit 21. In this way, the reverse clutch 41 is interposed between the input shaft 4 and the front sun gear 22 so as to be able to transmit power by bypass.

The outer periphery of the retaining plate 45 and the outer periphery of the drive plate 46 of the reverse clutch 41 are fitted into spline grooves 43a formed on the inner periphery of the clutch drum 43, and the driven plate 47 is connected to the drive plate 46.
And the inner circumference is fitted into a spline groove 44a formed on the outer circumference of the first clutch hub 44.

The friction plates, that is, the retaining plate 45 and the driven plate 47 are attached to the snap ring 48 fixed to the clutch drum 43 via the end face 50a of the first piston 50 by the hydraulic pressure supplied to the first hydraulic chamber 49. By pressing the drive plate 46 to cause the retaining plate 45, the driven plate 47, and the drive plate 46 to frictionally engage with each other, the power from the input shaft 4 is transmitted to the front sun gear 22 of the front planetary gear unit 21.

The first piston 50 is divided into a plurality of comb-like tips at its distal end in order to avoid contact with the retaining plate 53 and the drive plate 55 of the high clutch 51 described later.

The high clutch 51 shares the clutch drum 43 with the reverse clutch 41 and the second clutch hub 52
Is a spline 52a whose base is rotatably supported by the input shaft 4 via a bush 52c and is formed on the base.
As described above, the front carrier 24 of the front planetary gear unit 21 is spline-fitted. In this way, the high clutch 51 is interposed between the input shaft 4 and the front carrier 24 so as to be able to transmit power by bypassing.

The outer circumferences of the retaining plate 53 and the drive plate 54 of the high clutch 51 are fitted into the spline grooves 43a formed on the inner circumference of the clutch drum 43, and the spline grooves 52b formed on the outer circumference of the second clutch hub 52. Drive plates 55 whose inner circumferences are fitted with the drive plates 54 are alternately arranged.

Then, the second piston 56 is fitted into the cylinder portion 50b formed on the first piston 50, and the first piston 56
The retaining plate 53 is pressed by pressing friction plates such as the retaining plate 53, the driven plate 55, and the drive plate 54 against a snap ring 59 fitted and locked in a ring groove 58 formed on the inner periphery of the piston 50. , Driven plate 55 and drive plate 54
And other friction plates are frictionally engaged with each other so that the power from the input shaft 4 can be transmitted to the front planetary gear unit 2.
The power is transmitted to the first front carrier 24.

On the opposite side of the second piston 56 from the second hydraulic chamber 57, a balance hydraulic chamber 61 for canceling the centrifugal hydraulic pressure generated in the first hydraulic chamber 49 and the second hydraulic chamber 57 by the retainer 60 is provided. The pressing force of the return spring 62 acts on the first piston 50 and the second piston 56.

As for the 2 & 4 brake 70, a spline groove 71 is formed in the transmission case 2 so that the brake hub 72 extends along the outer circumference of the first clutch hub 44 of the reverse clutch 41.
By being integrally formed with the transmission case 4, the transmission case 2 and the front sun gear 22 of the front planetary gear unit 21 are interposed so as to be engageable by bypass.

A retaining plate 75 is inserted into a spline groove 71 formed on the inner periphery of the transmission case 2.
Drive plates 77 are fitted alternately with the driven plates 76 such that the outer periphery of the driven plate 76 is fitted and the inner periphery of the driven plate 76 is fitted in a spline groove 72 a formed on the outer periphery of the brake hub 72.

Then, the retaining plates 75, the drive plates 77, the driven plates 76, etc. are pressed against the snap rings 74 fixed to the transmission case 2 via the pistons 78 to press the retaining plates 75, the drive plates 77, and the like. The front sun gear 22 is formed to be engaged with the transmission case 2 by frictionally engaging the friction plates such as the driven plate 76 with each other.

Next, when the reverse clutch 41 is engaged, the retaining plate 45, the driven plate 47, the drive plate 46 and the like are pressed against the snap ring 48 fixed to the clutch drum 43, and the high clutch 5
The tip of the first piston 50 having a ring groove 58 for fitting and locking a snap ring 59 for receiving the load of the retaining plate 53, the driven plate 55 and the drive plate 54 pressed by the second piston 56 when fastening 1. Is described.

The distal end of the first piston 50 is provided with a ring groove 58 for fitting and locking a snap ring 59 as shown in FIG.
The concave surface 64 is formed in the end face 50a opposite to the end face 50a with a predetermined width dimension a stepwise from the inner peripheral edge where the ring groove 58 is formed along the end face 50a toward the outer periphery.
Are formed in a non-contact area 65 that avoids contact with the drive plate 46 and a contact area 66 that contacts the drive plate 46.

Accordingly, since the end face 50a of the first piston 50 is formed into the non-contact range 65 and the contact range 66 by the concave portion 64, the retaining plate 45, the driven plate 47, and the drive plate 46 for fastening the reverse clutch 41. Is pressed against the snap ring 48 provided on the clutch drum 43, the reaction force from the drive plate 46 directly acts only on the contact area 66 of the end face 50 a of the first piston 50, and the non-contact The influence on the contact area 65 is reduced and the ring groove 58 is formed on the inner peripheral side of the distal end portion of the first piston 50 in which the ring groove 58 is formed.
Slight deformation to the side 8 is suppressed.

As the minute deformation is suppressed and reduced, the stress generated at the bottom 58a of the ring groove 58, particularly at the end thereof, is reduced, and the strength of the tip of the first piston 50 is improved, and the durability is improved. Can be secured.

FIG. 5 shows the intensity ratio of the bottom portion 58a of the ring groove 58 with the change of the ratio a / h of the width dimension a of the non-contact area 65 to the depth h of the ring groove 58, that is, the ring groove bottom intensity ratio. FIG. 4 is an explanatory diagram of piston strength.

As is apparent from the piston strength explanatory diagram, the bottom strength of the ring groove 58 increases as the width dimension a of the non-contact area 65 formed on the end face 50a of the first piston 50 increases, and the piston strength improves. Based on the conventional piston strength of a / h = 0, which does not have the non-contact range width dimension a, the strength is improved by about 20% at a / h = 0.6, and a / h = 1 At 0.8, the strength improvement can be achieved up to about 200%.

As the width a of the non-contact area 65 increases, the strength at the bottom of the ring groove 58 increases and the piston strength is improved. However, since the thickness b of the piston is finite, the non-contact is increased. The contact area 6 increases as the width a of the area 65 increases.
6 decreases, and the contact pressure in the contact area 66 where the reaction force from the drive plate 46 acts increases. Therefore, when the strength of the bottom 58a of the ring groove 58 is sufficiently ensured and the increase in the surface pressure acting on the contact area 66 is taken into consideration, the ring groove 5
The ratio a / h of the width dimension a of the non-contact range 65 to the depth h dimension of 8 is preferably about 0.6 to 1.5.

In the above description, the end face 50 of the first piston 50
The non-contact area 65 is formed by removing a in the form of a step, but is not limited to the step, but may be formed in an arbitrary shape such as forming a non-contact area 65 by removing a chamfer as shown in FIG. It is also possible.

Next, another embodiment of the present invention will be described with reference to FIG.
And FIG.

In FIG. 7, the same reference numerals are given to the parts corresponding to those in FIG. 3, and the detailed description is omitted. However, the multi-plate frictional engagement device 40 is similar to the above-described embodiment in that the input shaft 4 and the front sun gear 22 are connected. A reverse clutch 41 interposed between the input shaft 4 and the front carrier 24 for transmitting power, and a high clutch 51 interposed between the input shaft 4 and the front carrier 24 for transmitting power;
The reverse clutch 41 is mounted on the snap ring 48 fixed to the clutch drum 43 via the first piston 50 by the hydraulic pressure supplied to the first hydraulic chamber 49.
5. The power from the input shaft 4 is transmitted to the front sun gear 22 by pressing the driven plate 47 and the drive plate 46.

On the other hand, the high clutch 51 is
The second piston 56 is fitted in the cylinder portion 50b formed in the first piston 50, and the ring groove 5 formed in the first piston 50 via the second piston 56 by the hydraulic pressure supplied to the second hydraulic chamber 57.
The retaining ring 53, the driven plate 55, and the drive plate 54 are pressed against the snap ring 59 that is fitted and locked with the engagement member 8 to transmit the power from the input shaft 4 to the front carrier 24.

Next, when the reverse clutch 41 is engaged, the tip of the first piston 50 for pressing the retaining plate 45, the driven plate 47, the drive plate 46 and the like against the snap ring 48 fixed to the clutch drum 43 and the first piston 50 The drive plate 46 in contact with the piston 50 will be described with reference to FIG.

The distal end of the first piston 50 has a ring groove 58 for fitting and locking a snap ring 59, and the end face 50a facing the drive rate 46 is formed flat.

On the other hand, when the drive rate 46 is pressed by the end face 50a of the first piston 50, the drive plate 46 extends from the inner peripheral edge of the end of the first piston 50 toward the outer periphery over a predetermined width dimension a. It has a recess 67 which is removed in a step-like manner to avoid contact with the piston 50.

Therefore, a non-contact area 65 having a predetermined width a and a contact area 66 contacting the drive plate 46 are formed at the end 50a of the first piston 50 from the inner peripheral edge toward the outer periphery.

Therefore, the end face 50 a of the first piston 50 is formed into a non-contact range 65 and a contact range 66 by the concave portion 67 formed in the drive rate 46, and the retaining plate 45 and the driven plate 45 for fastening the reverse brake 41. 47 and the drive plate 46 pressed against the snap ring 48 provided on the clutch drum 43,
The reaction force from the drive plate 46 mainly acts only on the contact area 66 of the end face 50a of the first piston 50, and the influence on the non-contact area 65 is reduced to form the first piston 50 in which the ring groove 58 is formed. Slight deformation to the side of the ring groove 58 generated on the inner peripheral side of the distal end portion of 50 is suppressed.

With the reduction of the minute deformation, the ring groove 58
Generated in the bottom 58a of the first piston 5
In addition, the strength of the leading end of No. 0 is improved, and the durability is improved.

Also in this embodiment, the ratio a of the width dimension a of the non-contact area 65 to the depth dimension h of the ring groove 58
With the increase in / h, the strength at the bottom of the ring groove 58 is increased, and the strength of the piston is improved. In consideration of the surface pressure of the contact area 66 where the reaction force from the drive plate 46 acts and the securing of the bottom strength of the ring groove 58, the width a of the non-contact area 65 with respect to the depth dimension h of the ring groove 58 is considered.
It is preferable to set the concave portion 67 formed in the drive plate 46 so that the ratio a / h = about 0.6 to 1.5.

In each of the above embodiments, a case has been described in which the strength of the first piston 50 of the multiple disc friction engagement device 40 used in the automatic transmission is improved to ensure durability, but a drive plate or a driven plate is used. The present invention can be widely applied to other multi-plate type frictional engagement devices such as clutches or brakes that operate by pressing a friction plate such as the above.

[0081]

According to the multi-disc friction engagement device of the present invention described above, a multi-disc friction engagement device having a ring groove on the inner periphery near the end of the piston and pressing the friction plate by the end surface of the piston. A non-contact area is provided between the piston end face and the friction plate pressed by the piston end face to avoid contact between the piston end face inner circumference and the friction plate along the piston end face inner circumference along the piston end face. The effect of the reaction force from the friction plate on the inner peripheral side of the portion is suppressed, the stress generated at the bottom of the ring groove is reduced, the strength and durability of the piston tip are improved, and the non-contact range is reduced. Since the piston is easily formed, for example, by forming a concave portion on the end or the friction plate, it is not necessary to increase the reference thickness of the piston, so that the size and weight can be reduced, and the manufacturing cost can be reduced. Etc. having the present invention unique advantages.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a drive system of an automatic transmission having a multi-plate friction engagement device according to the present invention.

FIG. 2 is an operation explanatory view of an engagement device used in the drive system.

FIG. 3 is a cross-sectional view of a principal part explaining an embodiment of a multiple disc type frictional engagement device.

FIG. 4 is an enlarged view of a portion B in FIG. 3;

FIG. 5 is an explanatory diagram of piston strength.

FIG. 6 is an explanatory view illustrating another embodiment of the multiple disc type frictional engagement device.

FIG. 7 is a sectional view of an essential part for explaining still another embodiment of the multi-plate friction engagement device.

FIG. 8 is an enlarged view of a portion C in FIG. 7;

FIG. 9 is a cross-sectional view of a main part illustrating a conventional multi-plate friction engagement device.

[Explanation of symbols]

 Reference Signs List 40 multi-plate friction engagement device 41 reverse clutch 43 clutch drum 44 first clutch hub 45 retaining plate 46 drive plate 47 driven plate 50 first piston 50a end face 51 high clutch 52 second clutch hub 53 retaining plate 54 drive plate 55 Driven plate 56 Second piston 58 Ring groove 58a Bottom part 59 Snap ring 64 Depression 65 Non-contact area 67 Depression a Width dimension of non-contact area h Depth dimension of ring groove

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 29, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a drive system of an automatic transmission having a multi-plate friction engagement device according to the present invention.

FIG. 2 is an operation explanatory view of an engagement device used in the drive system.

FIG. 3 is a cross-sectional view of a principal part explaining an embodiment of a multiple disc type frictional engagement device.

FIG. 4 is an enlarged view of a portion B in FIG. 3;

FIG. 5 is an explanatory diagram of piston strength.

FIG. 6 is an explanatory view illustrating another embodiment of the multiple disc type frictional engagement device.

FIG. 7 is a sectional view of an essential part for explaining still another embodiment of the multi-plate friction engagement device.

FIG. 8 is an enlarged view of a portion C in FIG. 7;

FIG. 9 is a cross-sectional view of a main part illustrating a conventional multi-plate friction engagement device.

FIG. 10 shows a piston in a conventional multi-plate friction engagement device.
It is explanatory drawing which shows the front-end | tip part.

DESCRIPTION OF SYMBOLS 40 Multi-plate friction engagement device 41 Reverse clutch 43 Clutch drum 44 First clutch hub 45 Retaining plate 46 Drive plate 47 Driven plate 50 First piston 50a End face 51 High clutch 52 Second clutch hub 53 Retaining Plate 54 Drive plate 55 Driven plate 56 Second piston 58 Ring groove 58a Bottom part 59 Snap ring 64 Depression 65 Non-contact area 67 Depression a Width dimension of non-contact area h Depth dimension of ring groove

Claims (7)

[Claims] 1. A drum, a plurality of friction plates provided on the drum so as to be movable in an axial direction, a hub, and a hub arranged alternately and coaxially with the friction plate so as to be movable in the hub in the axial direction. A plurality of friction plates provided, and a piston having a ring groove on the inner periphery near the end, and frictionally engaging each friction plate by pressing the alternately arranged friction plates with an end face. In the multi-plate friction engagement device, between the piston end surface and the friction plate pressed by the piston end surface, the contact between the piston end surface inner periphery and the friction plate along the piston end surface inner periphery is avoided. A multi-plate friction engagement device having an abutment range. 2. The multiple disc friction engagement device according to claim 1, wherein the non-contact area is formed by a concave portion provided on at least one of a piston end face and a friction plate pressed by the piston end face. 3. A plurality of friction plates provided movably in the axial direction on the inner periphery of the drum and a plurality of friction plates provided movably in the axial direction on the first hub are coaxially and alternately arranged. A first frictional engagement device that presses these alternately arranged friction plates by an end face of a first piston to frictionally engage the friction plates, and a shaft on the inner periphery of the drum independently of the friction plates. A plurality of friction plates movably provided in the second hub and a plurality of friction plates movably provided in the second hub in the axial direction are alternately arranged coaxially, and these alternately arranged friction plates are A second frictional engagement device that presses against a snap ring fitted and locked in a ring groove formed in the inner periphery near the end of the first piston by an end surface of the two pistons to frictionally engage each friction plate. Plate type friction engagement device Between the end surface of the first piston and the friction plate pressed by the end surface of the first piston, along the inner peripheral edge of the end surface of the first piston, and the contact between the inner peripheral edge of the end surface of the first piston end surface and the friction plate A multi-plate type frictional engagement device characterized by having a non-contact range for avoiding the problem. 4. The multi-plate friction engagement device according to claim 3, wherein the first piston and the second piston reciprocate coaxially. 5. The multiple disc type frictional engagement device according to claim 3, wherein the non-contact area is formed by a concave portion provided along an inner peripheral edge of the first piston end face. 6. The multiple disc type frictional engagement device according to claim 3, wherein the non-contact area is formed by a concave portion provided in a friction plate abutting on an end face of the first piston. 7. The ring groove according to claim 1, wherein the depth dimension of the ring groove is h and the width dimension of the non-contact area is a, wherein a / h ≒ 0.6-1.5. Multi-plate friction engagement device.