JPH094684A - Automatic transmission for transverse engine-mounted vehicle - Google Patents

Abstract

PURPOSE: To facilitate size reduction while attaining multistage in an automatic transmission for transverse engine-mounted vehicle. CONSTITUTION: This automatic transmission is provided with a driving gear 21 disposed, in connection with an output element R2 of a main shifting mechanism 1, on a main shifting shaft 10 formed with the main shifting mechanism 1, a driven gear 22 fitted on a differential gear shaft 40, a reduction mechanism 2 of chain transmission by a chain 23 wound around the driving gear 21 and the driven gear 22, and a sub shifting mechanism 3 connected to the differential gear 4 in the diametrical inner circumference side of the driven gear 22 enlarged by the reduction mechanism. It is possible to decrease axial dimension by overlapping the driven gear 22 and the sub shifting mechanism 3 in the diametrical direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic transmission for a horizontal engine type vehicle, and more particularly to an automatic transmission for a horizontal engine type vehicle having a two-shaft multistage structure.

[0002]

2. Description of the Related Art Conventionally, a general automatic transmission for an engine horizontal type vehicle having a main transmission mechanism and an auxiliary transmission mechanism in multiple stages has a main transmission that is connected to a crankshaft of an engine and has a main transmission mechanism. The shaft is the first shaft, the sub-transmission shaft provided with a sub-transmission mechanism for increasing the number of stages of the transmission is the second shaft, and the differential gear shaft connected to the wheels of the vehicle is the third shaft.
It has a shaft configuration. In the case of such a shaft arrangement, in order to avoid interference of the mechanisms arranged on the respective shafts, there is a limit to the reduction of the distance between the shafts, and it is inevitable that the automatic transmission becomes large. Further, if the multi-axis configuration is used as described above, the weight and the number of parts also increase as the number of axes increases.

Therefore, in the technique disclosed in Japanese Patent Publication No. 3-58929, a structure in which the auxiliary transmission mechanism is arranged on the differential gear shaft is adopted. However, like this technique,
If the sub-transmission mechanism is simply arranged coaxially with the differential device, a remarkable reduction in the axial dimension of the mechanism on the differential device shaft cannot be expected. Further, it is necessary to provide a counter gear between the main transmission shaft and the differential gear shaft for transmitting output rotation on the main transmission shaft as rotation in the same direction to the sub transmission mechanism on the differential gear shaft,
It is difficult to reduce the distance between the main transmission shaft and the differential shaft.

On the other hand, although a sub-transmission mechanism is not provided, sprockets are respectively provided on the main transmission shaft and the differential gear shaft in order to eliminate the need for the counter gear.
As one that is designed to transmit power by chain transmission,
There is a technique disclosed in Japanese Patent Laid-Open No. 63-207722.
However, in this technique, since the chain transmission mechanism is simply used as a mechanism for transmitting the rotational power in the same rotation direction, in order to obtain the final reduction ratio suitable for driving the axle shaft on the differential gear shaft, Separately, a planetary gear as a reduction mechanism is arranged between the differential device and the driven sprocket. Therefore, even with this technique, it is not possible to expect a significant reduction in the axial dimension of the mechanism on the differential gear shaft.

[0005]

SUMMARY OF THE INVENTION The present invention has been devised in view of these circumstances, and achieves both multi-stage and downsizing by efficiently combining a chain transmission mechanism and an auxiliary transmission mechanism. It is a general first object of the present invention to provide an automatic transmission for a vehicle having an engine laterally mounted therein.

Further, in an automatic transmission, a parking gear for a parking brake must be provided integrally with the output shaft, but since the parking gear is for locking the output member, the gear meshes with each other. The axial width must be large in order to secure a sufficient surface pressure of the part. If such a gear is arranged separately,
The effect of efficiently combining the chain transmission mechanism and the auxiliary transmission mechanism is diminished. Therefore, a second object of the present invention is to incorporate the parking gear into the auxiliary transmission mechanism.

By the way, when the chain transmission mechanism and the sub-transmission mechanism are combined as described above, the support of the driven gear of the chain transmission mechanism may become complicated. May increase directional dimension. Therefore, a third object of the present invention is to support the driven gears of the chain transmission mechanism in a well-balanced manner without increasing the size in the axial direction.

Further, as described above, when the chain transmission mechanism and the auxiliary transmission mechanism are combined, the arrangement position of the servo mechanism related to the transmission element of the auxiliary transmission mechanism is restricted. Therefore, a fourth object of the present invention is to dispose the above servo mechanism so as not to hinder the miniaturization of the device.

Further, when the chain transmission mechanism and the auxiliary transmission mechanism are combined, it becomes difficult to secure the capacity of the servo mechanism for operating the speed change element of the auxiliary transmission mechanism. Therefore, a fifth object of the present invention is to obtain a configuration capable of securing the capacity of the servo mechanism.

[0010]

In order to solve the above-mentioned problems, an automatic transmission for an engine horizontal vehicle according to the present invention comprises a main transmission mechanism arranged on a main transmission shaft connected to a crankshaft of an engine. A drive gear connected to an output element of the main transmission mechanism and arranged between the engine on the main transmission shaft and the main transmission mechanism, and a driven gear arranged on the differential gear shaft; A reduction gear mechanism including a chain connecting a drive gear and a driven gear, and an auxiliary transmission mechanism arranged on the radially inner side of the driven gear on the differential gear shaft are configured.

In the above structure, the subtransmission mechanism has a ring gear, a carrier, and a sun gear,
The driven gear may be connected to the ring gear, the carrier may be connected to a differential device, the ring gear and the carrier may be connected by a clutch, and the sun gear may be connected to a transmission case by a brake.

In the above structure, the carrier may have a carrier cover, and the carrier cover may be formed integrally with the parking gear.

On the other hand, the automatic transmission for an engine horizontal type vehicle of the present invention is connected to a main transmission mechanism arranged on a main transmission shaft connected to a crankshaft of an engine and an output element of the main transmission mechanism. A drive gear arranged between the engine on the main transmission shaft and the main transmission mechanism, a driven gear arranged on the differential gear shaft, and a chain connecting the drive gear and the driven gear. A reduction gear mechanism, a ring gear connected to the driven gear on the inner peripheral side of the driven gear, a pinion gear that meshes with the ring gear, and a carrier that is coupled to the differential gear, and a sun gear that meshes with the pinion gear. And a sub-transmission mechanism having a clutch that connects the ring gear and the carrier and a brake that fixes the sun gear, and the driven gear is formed integrally with a backing plate of the clutch. Having a flange, said flange,
It is also possible to adopt a configuration in which it is sandwiched between a step portion of the driven gear and a snap ring, fixed to the driven gear, and rotatably axially supported by a differential gear.

On the other hand, the automatic transmission for a vehicle with horizontal engine according to the present invention is connected to the main transmission mechanism arranged on the main transmission shaft connected to the crankshaft of the engine and the output element of the main transmission mechanism. A drive gear arranged between the engine on the main transmission shaft and the main transmission mechanism, a driven gear arranged on the differential gear shaft, and a chain connecting the drive gear and the driven gear. And a sub-transmission mechanism arranged on the radially inner side of the driven gear, wherein the driven gear is supported by a flange portion extending along the differential gear case, The sub-transmission mechanism may be configured to have a clutch servo mechanism in which a piston is arranged with the inner peripheral side of the flange portion as a cylinder.

In the above structure, the sub transmission mechanism has a ring gear, a carrier, and a sun gear, the driven gear is connected to the ring gear, the carrier is connected to a differential device, and the ring gear and the carrier are connected. May be connected by a clutch, and the sun gear may be connected by a brake to the transmission case.

Further, in the above structure, the flange portion has an inner peripheral wall extending back from the end opposite to the side supporting the driven gear, and the inner peripheral surface side of the inner peripheral wall is The piston may be supported on the differential gear shaft, and the outer peripheral surface side may be a sliding support portion of the piston.

[0017]

According to the structure of the first aspect of the present invention, since the drive gear on the main transmission shaft and the driven gear on the differential gear shaft are connected by the chain, the main transmission shaft The distance between the shaft and the differential gear shaft can be shortened, and the transmission mechanism by the chain is used as the speed reduction mechanism, and as a result, the auxiliary transmission mechanism is provided on the radially inner side of the driven gear whose diameter is increased. , The auxiliary transmission mechanism can be provided on the differential gear shaft with a compact structure without increasing the axial dimension of the mechanism on the differential gear shaft, and the bearing of the differential gear can be downsized. As a result, it is possible to increase the number of stages of the horizontal engine automatic transmission with an overall compact structure.

According to the third aspect of the invention, the carrier cover of the carrier of the auxiliary speed change mechanism is integrated with the parking gear. Therefore, in addition to the above effects, the number of parts of the related mechanism is reduced. The effect that can be obtained is obtained.

In addition, according to the configuration of claim 4,
The effect that the driven gear can be supported and the movement of the driven gear in the axial direction can be regulated without separately providing a special member without increasing the axial dimension is obtained.

Further, according to the structure of claim 5,
Since the driven gear is supported by the flange portion extending along the differential gear case of the driven gear, and the piston is disposed as the cylinder of the clutch servo mechanism on the inner peripheral side of the flange portion, In addition to the effect that it can be made compact, not only does the servo mechanism of the clutch of the auxiliary transmission mechanism have a compact structure that does not require a special axial space, but also the external shape of the differential device is not hindered. Since the pressure receiving area of the piston of the clutch servo mechanism can be increased, a sufficient torque capacity of the clutch can be secured.

In particular, according to the structure of claim 7, the space required for supporting the flange portion and the space for supporting the piston are overlapped in the radial direction, so that the axial dimension for supporting them is increased. Can be reduced.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. To explain from a schematic structure, this automatic transmission for a vehicle with horizontal engine is arranged on a main transmission shaft 10 connected to a crankshaft of an engine (not shown). A main transmission mechanism 1 and a drive gear 21 connected to an output element (a ring gear in this example) R2 of the main transmission mechanism 1 and arranged between the engine on the main transmission shaft 10 and the main transmission mechanism 1; A reduction gear mechanism 2 including a driven gear 22 arranged on the differential gear shaft 40, a chain 23 connecting the driving gear 21 and the driven gear 22, and a driven gear 22 on the differential gear shaft 40. And an auxiliary transmission mechanism 3 disposed on the radially inner side.

In this example, the subtransmission mechanism 3 has a ring gear R3, a carrier C3, and a sun gear S3. The driven gear 22 is connected to the ring gear R3, the carrier C3 is integrally formed with the differential device 4, the ring gear R3 and the carrier C3 can be engaged by the clutch C-3, and the sun gear S3 is the brake B-4. By this, the transmission case 9 can be locked. The carrier C3 has a carrier cover 31, and the carrier cover 31 is formed integrally with the parking gear 5.

The ring gear R3 is connected to the driven gear 22 on the inner peripheral side of the driven gear 22, and has a carrier C3.
Supports a pinion gear P3 that meshes with the ring gear R3, and is connected to the differential device 4. The sun gear S3 meshes with the pinion gear P3. The flange 24 of the driven gear 22 is integrally formed with the backing plate 33, and the driven gear 22 is fixed to the flange 24 by the step portion 35A of the driven gear 22 and the snap ring 36.

Further, the configuration of each part will be described in detail. The main transmission shaft 10 is connected to the engine through the torque converter 8, and the main transmission mechanism 1 arranged on the main transmission shaft 10 is It is composed of two planetary gear units, their sun gears S1 and S2 are connected to each other, and the carrier C1 at the front stage is connected to the ring gear R at the rear stage.
2, the front stage ring gear R1 is connected to the main transmission shaft 10 by a clutch C-1 as a first input element. The sun gears S1 and S2 are connected to the main transmission shaft 10 by a clutch C-2 so as to serve as a second input element, and
It can be fixed to the transmission case 9 by a band brake B-1 to serve as a reaction force element. The carrier C2 at the rear stage is to be a reaction force element by the brake B-2 by the transmission case 9
It can be fixed to. The rear stage ring gear R2 is connected to a drive gear 21 integrated with the flange 12 via a ring gear flange 12 integrally formed with the speed change shaft 11 rotatably supported on the outer periphery of the main speed change shaft 10.
It is an output element of the main transmission mechanism 1.

The drive gear 21 of the reduction mechanism 2 is a small-diameter sprocket, and the driven gear 22 is a large-diameter sprocket. Power is transmitted by a chain 23 wound around both sprockets 21 and 22. , Exhibits a deceleration function according to the tooth ratio of both sprockets 21 and 22. The drive sprocket 21 is supported by the transmission case 9 via a pair of needle bearings over a width substantially corresponding to its width, while the driven sprocket 22 is widened on its inner diameter side. Helical teeth are formed on one inner peripheral surface divided into two by the circular groove formed on the inner peripheral side to form a ring gear R3 of the auxiliary transmission mechanism 3. The other inner peripheral surface is supported by a differential gear case (hereinafter referred to as a differential case) 41 via roller bearings.

The carrier C3 of the auxiliary transmission mechanism 3 is integrated with the differential case 41, and teeth are formed on the outer periphery of the carrier cover 31, which constitutes the parking gear 5 as described above. The pinion gear P3 rotatably supported by the carrier C3 includes a ring gear R3 and a sun gear S3.
And the inner periphery of the sun gear S3 is supported by the transmission case 9 via a bush. A drum 34 of the band brake B-4 is provided continuously with the sun gear S3. An end portion of the driven sprocket 22 is extended to form a drum 35 of the multi-plate clutch C-3, and an outer periphery of a differential case 41 facing the inner diameter side serves as a clutch hub. The backing plate 33 of the clutch C-3 is
While fitting into the spline of the clutch drum 35,
In a state where one end surface is brought into contact with a step portion 35A forming a step on the larger diameter side than the spline teeth provided on the spline,
The other end surface is locked by a snap ring 36 that is fitted and inserted in a circumferential groove that traverses the spline, and is fixedly connected to the clutch drum 35 so as not to move in the axial direction. The inner diameter side of the backing plate 33 has an outer end moved to the differential case 41 via a thrust washer, an inner end moved to the differential case 41 via a thrust roller bearing, and more specifically, an axial movement via a return spring seat. Is regulated and supported.

Servo mechanism 30 for the multi-plate clutch C-3
Is provided on a carrier C3 integrated with the differential case 41, and the carrier C3 is used as a cylinder, and a piston 37 slidably fitted therein is provided. The friction element of the clutch C-3 is arranged by fitting the separator plate to the inner peripheral spline of the clutch drum 35 and the friction material to the outer peripheral spline of the differential case 41.

In the automatic transmission constructed as described above, the input rotation entering the main transmission shaft 10 is transmitted to the drive sprocket 21 from the ring gear R2 after being shifted by the main transmission mechanism 1 to three forward gears and one reverse gear. However, to briefly explain the shift mode in the main transmission 1, when only the clutch C-1 is engaged, the differential rotation becomes the output of the ring gear R2 by the input of the ring gear R1, and the low speed and the addition of the brake B-2 are added. The carrier C2 is fixed by the engagement and the output of the ring gear R2 is medium speed, and the additional engagement of the clutch C2 directly connects the planetary gear unit of the preceding stage, and the ring gear R2 is directly connected.
2 becomes high speed, and when the clutch C-2 is engaged, differential reverse rotation is generated by the sun gear S1 input and the ring gear R2.
Becomes the output and becomes a slow reverse. These outputs are combined with the speed change by the auxiliary speed change mechanism 3 to be described later, as a whole, as shown in the operation chart of FIG.
It becomes the first reverse speed.

The torque transmitted to the drive sprocket 21 passes through the chain 23 and the driven sprocket 22.
However, at that time, the auxiliary transmission mechanism 3 having the underdrive configuration is decelerated by the diameter ratio of both sprockets 21 and 22 and the torque is amplified, and the clutch C is attached to the differential gear 41 integrated with the ring gear R3 or the carrier C3. −
3 is input. When releasing the clutch C-3,
By the engagement of the brake B-4, the rotation of the carrier C3 due to the revolution of the pinion gear P3 is output to the differential case 41 with the sun gear S3 as a reaction force element. At the time of power transmission through this path, a thrust force is applied to the ring gear R3 of the auxiliary transmission mechanism 3 formed of a helical gear, and this force is generated by the thrust bearing and the thrust washer supporting the flange 24 also serving as the backing plate 33.
1 is supported by the transmission case 9. When the clutch is disengaged, the output of the main transmission mechanism 1 is decelerated for each shift stage including reverse by the deceleration action of the sub transmission mechanism 3, and the first to third speeds (1st to 3rd) and the reverse (R) stage are achieved. To be achieved.

On the other hand, when the clutch C-3 is engaged and the brake B-4 is released to make the sun gear S3 idle, the driven sprocket 22 is rotated by the clutch C-3.
It is transmitted to the differential case 41 via -3 as it is, and is transmitted to the differential device 4 to achieve the fourth speed (4th) speed in a state where the maximum speed output of the main transmission mechanism 1 is not decelerated.

In summary, in the automatic transmission of the first embodiment described above, the speed reduction mechanism 2 is used as the chain transmission mechanism for shortening the shaft distance, so that the inner peripheral side of the driven sprocket 22 having a large diameter can be secured. By arranging the auxiliary transmission mechanism 3 by utilizing it, the axial length of the mechanism on the differential gear shaft 40 is made compact, and by arranging it on the inner peripheral side of the driven sprocket 22 having a large diameter, the auxiliary transmission mechanism The mechanism 3 can also have a gear structure with a sufficiently large diameter, and as a result, the parking gear 5 can be utilized by using the carrier cover 31 made of a press plate.
Can be formed because the surface pressure of the gear can be small because of the large diameter. Further, by disposing the auxiliary transmission mechanism 3 on the inner peripheral side of the driven sprocket 22,
The outer periphery of the carrier C3 integrated with the differential case 41,
The driven sprocket 22 can be supported in a well-balanced manner at two positions of the meshing portion with the pinion gear P3 without requiring a special space.

Next, FIG. 3 shows a second embodiment in which the present invention is applied to an automatic transmission having a larger torque capacity. In this example, with respect to the main transmission mechanism 1 and some of the other mechanisms,
Although there are differences in size and detailed shape,
Since the structure is substantially the same as that of the embodiment, the same reference numerals are given to the corresponding members and the description thereof will be omitted, and only different points will be described below.

In this example, what is essentially different from the previous example is that the clutch servo mechanism 30A is arranged radially outside the differential case 41. In this example, the driven sprocket 22 is supported by the differential case 41 via a bell-shaped flange portion 24A which is a separate body from the driven sprocket 22.
The flange portion 24A extends so as to cover the differential case 41, and the large diameter side inner periphery that supports the driven sprocket 22 is a drum of the multi-plate clutch C-3.
The servo mechanism 30A of the multi-plate clutch C-3 is provided on the flange portion 24A, and the flange portion 24A is used as a cylinder so as to conform to the bell shape thereof and is slidably fitted to the cylinder. A piston 37A is provided. The friction element of the clutch C-3 fits the separator plate to the inner peripheral spline of the flange portion 24A,
The friction material is arranged so as to be fitted to the spline on the outer periphery of the differential case 41. An inner peripheral wall 241 is formed on the small diameter side of the flange 24A, that is, on the side opposite to the side supporting the driven sprocket 22. The inner peripheral wall 241 extends from the end of the flange 24A and extends. 41
It is supported on the shaft via a needle bearing, and the outer peripheral surface side is a sliding support portion of the piston 37A.

In this example, during power transmission, the thrust force applied to the ring gear R3 of the auxiliary transmission mechanism 3 composed of a helical gear is changed by the thrust bearings supporting the flange portion 24A, one directly and the other through the differential case 41. It is supported by the machine case 9. In this example, unlike the previous example, the wineway clutch F-1 is provided between the brake drum 34 and the transmission case 9.

Also in the automatic transmission constructed as described above, power transmission is performed as in the case of the first embodiment,
Each shift stage as shown in the operation chart of FIG. 4 is achieved.

In summary, in the automatic transmission of the second embodiment, the servo mechanism diameter of the servo mechanism 30A of the clutch C-3 substantially extends from the inner diameter of the driven sprocket 22 to the outer diameter of the differential shaft 40. Since it is possible to secure a large diameter equivalent to the inner diameter of the driven sprocket 22 for the friction element of the clutch C-3, it is possible to secure a large clutch capacity.

The present invention has been described above in detail based on two embodiments. However, the present invention can be carried out by changing various concrete configurations of details within the scope of the matters described in the claims. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an automatic transmission for an engine horizontal vehicle according to a first embodiment of the present invention.

FIG. 2 is an operation chart showing a shift operation of the automatic transmission according to the above embodiment.

FIG. 3 is a cross-sectional view showing an automatic transmission for an engine horizontal vehicle according to a second embodiment of the present invention.

FIG. 4 is an operation chart showing a shift operation of the automatic transmission according to the above embodiment.

[Explanation of symbols]

 1 Main Transmission Mechanism 2 Reduction Mechanism 3 Sub Transmission Mechanism 4 Differential Gear 5 Parking Gear 9 Transmission Case 10 Main Transmission Shaft 21 Drive Sprocket (Drive Gear) 22 Driven Sprocket (Driven Gear) 23 Chain 24, 24A Flange 30, 30A Clutch servo mechanism 31 Carrier cover 33 Backing plate 35A Step portion 36 Snap ring 37, 37A Piston 40 Differential gear shaft C3 Carrier P3 Pinion gear R2 Ring gear (output element) R3 Ring gear S3 Sun gear B-4 Brake C-3 Clutch

Claims (7)

[Claims] 1. A main speed change mechanism disposed on a main speed change shaft connected to a crankshaft of an engine, and an output element of the main speed change mechanism connected between the engine and the main speed change mechanism on the main speed change shaft. A drive gear arranged on the differential gear shaft, a driven gear arranged on the differential gear shaft, and a reduction mechanism including a chain connecting the drive gear and the driven gear; An automatic transmission for an engine horizontal type vehicle, comprising: an auxiliary transmission mechanism arranged on the radially inner side of a driven gear. 2. The sub-transmission mechanism includes a ring gear, a carrier, and a sun gear, the driven gear is connected to the ring gear, the carrier is connected to a differential device, and the ring gear and the carrier are clutches. The automatic transmission for a horizontal engine type vehicle according to claim 1, wherein the sun gear is connected to the transmission case by a brake. 3. The carrier has a carrier cover,
3. The automatic transmission for an engine horizontal type vehicle according to claim 2, wherein the carrier cover is formed integrally with a parking gear. 4. A main speed change mechanism arranged on a main speed change shaft connected to a crankshaft of the engine, and an output element of the main speed change mechanism connected between the engine and the main speed change mechanism on the main speed change shaft. A drive gear disposed on the differential gear shaft, a driven gear disposed on the differential gear shaft, and a reduction mechanism including a chain connecting the drive gear and the driven gear, and an inner peripheral side of the driven gear. A ring gear connected to the driven gear, a pinion gear that meshes with the ring gear is supported, a carrier that is connected to a differential gear, a sun gear that meshes with the pinion gear, and a clutch that connects the ring gear and the carrier, An auxiliary transmission mechanism having a brake for fixing a sun gear, the driven gear has a flange integrally formed with a backing plate of the clutch, and the flange has the Is fixed to the driven gear is interposed between the Ya stepped portion and the snap ring, rotatably axially supported transverse engine standing automatic transmission for a vehicle differential. 5. A main speed change mechanism disposed on a main speed change shaft connected to a crankshaft of the engine, and an output element of the main speed change mechanism connected between the engine and the main speed change mechanism on the main speed change shaft. A drive gear disposed on the differential gear shaft, a driven gear disposed on the differential gear shaft, and a reduction mechanism including a chain connecting the drive gear and the driven gear, and a radial direction of the driven gear. An auxiliary transmission mechanism disposed on an inner peripheral side, the driven gear is supported by a flange portion extending along a differential gear case, and the auxiliary transmission mechanism has an inner peripheral side of the flange portion. An automatic transmission for a vehicle with horizontal engine having a clutch servo mechanism in which a piston is arranged with the cylinder as a cylinder. 6. The sub-transmission mechanism includes a ring gear, a carrier, and a sun gear, the driven gear is connected to the ring gear, the carrier is connected to a differential device, and the ring gear and the carrier are clutches. 6. The automatic transmission for a horizontal engine-mounted vehicle according to claim 5, wherein the sun gear is connected to the transmission case by a brake. 7. The flange portion has an inner peripheral wall extending back from an end opposite to the side supporting the driven gear, and the inner peripheral surface side of the inner peripheral wall has a differential device. The automatic transmission for an engine transverse type vehicle according to claim 5, wherein the automatic transmission is supported on a shaft, and the outer peripheral surface side is a sliding support portion of the piston.