JP7476782B2 - Automatic transmission - Google Patents

Description

The present invention relates to an automatic transmission mounted on a vehicle.

In automatic transmissions installed in vehicles such as automobiles, the power transmission path of the transmission mechanism using multiple planetary gear sets is generally switched by selectively engaging multiple frictional engagement elements such as clutches and brakes, forming gears according to the driving conditions of the vehicle.

In recent years, automatic transmissions have been made more multi-speed in order to improve fuel efficiency, etc., and as a result, there is a trend toward increasing the number of planetary gear sets that make up the transmission mechanism. However, as the number of planetary gear sets increases, the axial dimension of the entire transmission increases, causing problems with vehicle mountability.

In the automatic transmission disclosed in Patent Document 1, three hydraulic clutches for switching the power transmission path of the transmission mechanism are arranged on the same axis and overlapping in the axial direction. This allows the axial dimension of the entire transmission to be reduced compared to when these clutches are arranged side by side in the axial direction.

However, in the automatic transmission described in Patent Document 1, multiple clutches are arranged to overlap in the axial direction, so the radial dimension of the entire transmission is larger than when the clutches are arranged side by side in the axial direction. As a result, for example, in a so-called transversely mounted automatic transmission in which the rotating shaft of the automatic transmission is arranged in the vehicle body width direction, the automatic transmission may interfere with vehicle body parts such as the drive shaft that are arranged on the outer diameter side of the automatic transmission.

In response to this, in an automatic transmission with an axial one-side clutch and an axial other-side clutch arranged side by side, it is conceivable to suppress an increase in the radial dimension of the clutch by arranging the friction plates of the one-side clutch and the other-side clutch side by side in the axial direction, and to suppress an increase in the axial dimension compared to when the piston is arranged side by side with the one-side and other-side clutches by arranging the piston of the one-side clutch and the piston of the other-side clutch so as to overlap in the axial direction and providing a comb-like comb tooth portion arranged in the circumferential direction on the tip side of the one-side clutch on the piston of the other-side clutch and penetrating the friction plate of the one-side clutch in the axial direction.

JP 2015-172378 A

However, if a comb tooth portion is provided on the piston, the centrifugal force generated when the clutch rotates may cause the tip of the comb tooth portion to deform and expand radially outward, which may cause stress concentration at the base end of the comb tooth portion.

The present invention aims to provide an automatic transmission with multiple clutches that can suppress stress concentration at the base end of a comb tooth portion of a piston that has a comb tooth portion that axially penetrates a friction plate.

In order to solve the above problems, the automatic transmission according to the present invention is characterized by the following configuration.

The present invention provides an automatic transmission having an axial one-side clutch and an axial other-side clutch arranged side by side in the axial direction on the axis of a power transmission shaft, the one-side clutch and the other-side clutch each having a cylindrical drum member, a cylindrical hub member facing the drum member, friction plates engaged between the drum member and the hub member so as to be slidable in the axial direction, and a piston that presses the friction plates, the friction plates of the one-side clutch and the other-side clutch are arranged in parallel in the axial direction, the pistons of the one-side clutch and the other-side clutch are arranged on one side of the friction plates of the one-side clutch in the axial direction and are arranged so as to overlap in the axial direction, the piston of the other-side clutch has a cylindrical pressing part that presses the friction plates of the other-side clutch, a comb tooth part that penetrates the friction plates of the one-side clutch in the axial direction is provided at the tip side of the pressing part located on the friction plate side of the other-side clutch, and an annular ring member is arranged on the outer periphery of the comb tooth part.

According to the present invention, an annular ring member is disposed on the outer periphery of the other piston having the comb teeth portion, so that deformation of the tip of the comb teeth portion that would otherwise expand radially outward due to centrifugal force when the clutch rotates is suppressed, and stress concentration at the base end of the comb teeth portion can be suppressed.

The friction plates of the one clutch and the other clutch are aligned in the axial direction, and the piston on the other side is provided with a comb tooth portion that axially penetrates the friction plates of the one clutch. This makes it possible to suppress the increase in the radial dimension of the automatic transmission compared to when the friction plates of the one and other clutches are overlapped in the axial direction, and also suppresses the increase in the axial dimension compared to when the pistons are aligned in the axial direction.

The comb tooth portion may be provided with a step portion for regulating the axial position of the ring member.

This configuration allows the axial position of the ring member to be determined with a simple structure that simply requires providing a step in the comb tooth portion. For example, the ring member can be fixed to the piston even when the piston and ring member are made of different materials, such as aluminum and iron, which are difficult to fix by welding or the like.

The base end of the comb tooth portion of the other clutch may be set to have a radial thickness greater than the tip end of the comb tooth portion and an intermediate portion connecting the tip end and the base end.

According to this configuration, the radial thickness of the base end of the comb tooth portion is set larger than the radial thickness of the comb tooth portion other than the base end, so the bending rigidity of the base end can be improved compared to when the radial thickness of the base end is set small like the radial thickness of the comb tooth portion other than the base end. This makes it possible to suppress stress concentration at the base end caused by the tip side deforming radially outward. On the other hand, by setting only the radial thickness of the base end to be large, the increase in the weight of the comb tooth portion other than the base end is suppressed, so the increase in the radially outward deformation due to centrifugal force is easily reduced, and the stress at the base end can be reduced. As a result, there is no need to set the radial thickness of the base end larger than necessary, and the weight of the entire piston can be reduced.

A hollow portion may be provided between the base end of the comb tooth portion and the ring member.

This configuration reduces the weight of the comb teeth, which helps reduce radial outward deformation caused by centrifugal force and suppresses stress at the base end.

The ring member may be disposed at the tip of the comb tooth portion.

With this configuration, by placing a ring member at the tip of the comb tooth portion, which is subject to a large amount of radially outward deformation due to centrifugal force when the clutch rotates, and restraining the deformation of the comb tooth portion, it becomes easier to suppress the amount of radially outward deformation of the comb tooth portion, and stress concentration at the base end of the comb tooth portion is more effectively suppressed.

The other-side clutch may have a first other-side clutch arranged on the one-side clutch side and a second other-side clutch arranged on the other side of the first other-side clutch in the axial direction, and the piston of the first other-side clutch may axially penetrate the friction plates of the one-side clutch, and the piston of the second other-side clutch may axially penetrate the friction plates of the one-side clutch and the friction plates of the first other-side clutch.

With this configuration, the piston of the second other-side clutch penetrates the friction plates of the one-side clutch and the first other-side clutch in the axial direction, so even when the friction plates of the three clutches are arranged side by side in the axial direction, the increase in radial dimension can be suppressed compared to when the one-side clutch and the first and second other-side clutches are overlapped in the axial direction, and the increase in axial dimension can be suppressed compared to when the pistons are arranged side by side in the axial direction.

The ring member may include a first ring member arranged at the tip of the comb tooth portion of the second other-side clutch, and a second ring member arranged at an intermediate portion between the friction plate of the one-side clutch and the friction plate of the first other-side clutch in the comb tooth portion of the second other-side clutch.

The piston of the second other-side clutch, which passes through the friction plates of the one-side clutch and the first other-side clutch, has the radially outward deformation of the tip of the comb tooth portion suppressed by the first ring member, and the radially outward deformation of the middle portion of the piston suppressed by the second ring member. This more effectively suppresses deformation of the comb tooth portion, and more effectively suppresses stress concentration at the base end.

According to the present invention, in an automatic transmission equipped with multiple clutches, it is possible to suppress stress concentration at the base end of the comb teeth of a piston having a comb teeth portion that axially penetrates a friction plate.

1 is a cross-sectional view of a rear portion of an automatic transmission according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part of FIG. FIG. 4 is an exploded perspective view of the drums, pistons and friction plates of the first to third clutches. FIG. 4 is a perspective view of the piston of the second clutch; FIG. 4 is a perspective view of the piston of the third clutch; 6 is a cross-sectional view of a piston of the second clutch taken along line VI-VI in FIG. 4. FIG. 7 is a cross-sectional view of the piston of the third clutch taken along line VII-VII in FIG. 5 .

The following describes an embodiment of the present invention.

Figure 1 shows the configuration of the opposite drive source side of an automatic transmission (hereinafter, the opposite drive source side is referred to as the rear or one axial side, and the drive source side is referred to as the front or other axial side). In the rear part of the transmission case 1, which has a main body case 1a and an end cover 1b that closes the opening at the rear end, a first clutch 10 as a one-side clutch, each of which has a plurality of friction plates 13, 23, 33 arranged axially from the rear on an input shaft 2 extending from the drive source side, a second clutch 20 as a first other-side clutch, and a third clutch 30 as a second other-side clutch are arranged.

The first and second planetary gear sets 40, 50 are arranged axially on the input shaft 2, and each of the first and second planetary gear sets 40, 50 has a sun gear 41, 51, a ring gear 42, 52, and a pinion carrier 43, 53 as rotating elements.

The first, second and third clutches 10, 20 and 30 each have a drum member 11, 21 and 31 that are coupled together and rotate together when engaged, and a hub member 12, 22 and 32. The drum member 31 of the third clutch 30, which is located furthest on the other axial side (the driving source side), is connected to the sun gear 51 of the second planetary gear set 50. The hub member 32 of the third clutch 30 is connected to the ring gear 42 of the first planetary gear set 40.

The drum member 21 of the second clutch 20 is disposed on one axial side of the drum member 31 of the third clutch 30. The drum member 21 is connected to the drum members 11, 31 of the first and third clutches 10, 30 so as to rotate together. The drum member 21 is spline-fitted to the inner periphery of the drum member 11 of the first clutch 10. The drum member 11 of the first clutch 10 is fitted to the inner periphery of the drum member 31 of the third clutch 30. The drum member 21 is connected to the sun gear 51 of the second planetary gear set 50 via the drum members 11, 31 of the first and third clutches 10, 30. The hub member 22 of the second clutch 20 is connected to a ring gear of another planetary gear set (not shown).

On one axial side of the drum member 21 of the second clutch 20, the drum member 11 of the first clutch 10 is integrally formed with the other-side extension portion 11e (described later) to which the drum member 21 of the second clutch 20 is spline-fitted. The drum member 11 of the first clutch 10 is connected to the sun gear 51 of the second planetary gear set 50 via the drum member 31 of the third clutch 30. The hub member 12 of the first clutch 10 is connected to the input shaft 2 of the automatic transmission.

Next, the configuration of the first, second, and third clutches 10, 20, and 30 will be explained with reference to Figures 2 and 3. Note that Figure 3 is an exploded perspective view of the pistons, friction plates, and drum members that make up the first to third clutches 10, 20, and 30.

The first, second and third clutches 10, 20 and 30 each have a drum member 11, 21, 31, a hub member 12, 22, 32, a number of friction plates 13, 23, 33 arranged in the axial direction between them and splined alternately to the drum members 11, 21, 31 and the hub members 12, 22, 32, pistons 14, 24, 34 arranged on one axial side of these friction plates 13, 23, 33, and hydraulic chambers 15, 25, 35 provided on one axial side of the pistons 14, 24, 34. When fastening pressure is supplied to any of these hydraulic chambers 15, 25, 35, the pistons 14, 24, 34 of the clutches 10, 20, 30 to which the fastening pressure is supplied press the friction plates 13, 23, 33 to connect the drum members 11, 21, 31 and the hub members 12, 22, 32, thereby fastening the clutches 10, 20, 30.

The first, second and third clutches 10, 20 and 30 are provided with cancel chambers 16, 26 and 36 on the opposite side of the hydraulic chambers 15, 25 and 35 across the pistons 14, 24 and 34. The cancel chambers 16, 26 and 36 are provided to prevent dragging of the friction plates 13, 23 and 33 caused by the friction plates 13, 23 and 33 being pressed by the centrifugal force acting on the hydraulic oil in the hydraulic chambers 15, 25 and 35 in the released state. As a result, the centrifugal force acting on the hydraulic oil supplied to the cancel chambers 16, 26 and 36 presses the pistons 14, 24 and 34, thereby canceling the pressing force due to the centrifugal force acting on the hydraulic oil in the hydraulic chambers 15, 25 and 35.

Return springs 17, 27 that urge the pistons 14, 24 in the clutch release direction are disposed in the cancellation chambers 16, 26 of the first clutch 10 and the second clutch 20, respectively. In the third clutch 30, a urging member 37 (described later) is disposed between multiple friction plates 33.

The multiple friction plates 13, 23, 33 of the first, second, and third clutches 10, 20, 30 each include multiple outer friction plates 13a, 23a, 33a splined to the drum members 11, 21, 31, and multiple inner friction plates 13b, 23b, 33b splined to the hub member 12 and arranged alternately in the axial direction with the multiple outer friction plates 13a, 23a, 33a.

The drum member 11 of the first clutch 10 comprises an outer cylindrical portion 11a with which the outer friction plate 13a engages, an extension portion 11b extending further axially to one side from one axial end of the outer cylindrical portion 11a, a vertical wall portion 11c extending radially inward from one axial end of the extension portion 11b, and a tubular portion 11d extending axially to one side and the other side from the radially inner inner end of the vertical wall portion 11c.

The hub member 12 of the first clutch 10 comprises an inner cylindrical portion 12a with which the inner friction plate 13b engages, a disk portion 12b extending radially inward from one axial end of the inner cylindrical portion 12a, and a spline portion 12c extending from the inner end of the disk portion 12b to one and the other axial sides and spline-fitted to the input shaft 2.

As shown in FIG. 3, the outer circumferential surface of the outer friction plate 13a is provided with a spline portion 13a1 that is spline-engaged with the outer cylindrical portion 11a, and the inner circumferential surface of the inner friction plate 13b is provided with a spline portion 13b1 that is spline-engaged with the inner cylindrical portion 12a.

The outer friction plate 13a has a radially outer portion provided with a plurality of first through holes 13c for passing the piston 24 of the second clutch 20 axially therethrough, and a plurality of second through holes 13d for passing the piston 34 of the third clutch 30 axially therethrough.

The first through holes 13c and the second through holes 13d are arranged at equal intervals in the circumferential direction, and the first through holes 13c and the second through holes 13d are arranged at different positions in the circumferential direction. More specifically, the circumferential center of each first through hole 13c and the circumferential center of each second through hole 13d adjacent to the first through hole 13c are arranged in a state where their circumferential positions are shifted. As a result, compared to the case where the circumferential length of the thin-walled portion formed between these through holes 13c and 13d is increased by overlapping the circumferential positions of these through holes 13c and 13d, the circumferential length of the thin-walled portion is suppressed, and the decrease in rigidity of the thin-walled portion can be suppressed. In this embodiment, the circumferential positions of one end of each first through hole 13c and the other end of the second through hole 13d adjacent to the first through hole 13c overlap, but the one end and the other end do not have to overlap.

As shown in FIG. 2, the radial position of each first through hole 13c is located outside the outer periphery of each inner friction plate 13b. The radial position of each second through hole 13d is located outside the radial position of each first through hole 13c and inside the spline portion 13a1.

The piston 14 has a pressing portion 14a that is disposed on one axial side of the friction plates 13a, 13b and extends radially, pressing the friction plates 13a, 13b when fastened, a cylindrical portion 14b that extends axially from the inner end of the pressing portion 14a to one axial side, and a pressure receiving portion 14c that has a pressure receiving surface that receives hydraulic pressure supplied to the hydraulic chamber 15. In this embodiment, the pressing portion 14a and the cylindrical portion 14b are configured as separate bodies from the pressure receiving portion 14c. The cylindrical portion 14b is connected to the upper end of the pressure receiving portion 14c, which is formed in a disk shape.

As mentioned above, the radial inner side of the spline portion 13a1 of the outer friction plate 13a requires a radial dimension to provide the first and second through holes 13c, 13d. Therefore, the radial position of the spline portion 13a1 is offset from the pressing point P1 where the pressing portion 14a of the piston 14 presses the friction plate 13a.

A retaining member 13e is disposed on the other axial side of the multiple friction plates 13. In this embodiment, the flange portion 21b extending radially from one axial end of the drum member 21 of the second clutch 20 (described later) is used as the retaining member 13e.

When the clutch is engaged, the axial load input from the piston 14 to the friction plate 13 is received by the flange portion 21b. Therefore, if the flange portion 21b and the pressure point P1 are offset, for example, as in the case where the radial position of the inner end of the flange portion 21b is located near the spline portion 13a1, the radially inner portion of the friction plate 13 is more likely to move axially than the radially outer portion, and the radially inner portion of the friction plate 13 may deform so as to be positioned on the other axial side than the outer portion.

In contrast, in this embodiment, the radial inner end of the flange portion 21b extends to approximately the same position as the radial inner ends of the multiple friction plates 13, and the axial thickness (plate thickness) of the flange portion 21b is set to be thicker overall than the plate thickness of the outer friction plate 13a. The plate thickness of the flange portion 21b is set to be thicker at the radial inner portion, particularly at the portion corresponding to the pressing point P1 where the piston 14 abuts against the outer friction plate 13a, than at the radial outer portion. In this way, the radial position of the inner end of the flange portion 21b is located near the spline portion 13a1, and the bending rigidity is increased compared to when the plate thickness of the flange portion 21b is set to be equal to that of the outer friction plate 13a, so that deformation of the friction plate 23 due to the axial load input to the friction plate 13 is suppressed.

In the flange portion 21b, similar to the outer friction plate 13a, a plurality of first flange through holes 21c for passing the piston 24 of the second clutch 20 through in the axial direction and a plurality of second flange through holes 21d for passing the piston 34 of the third clutch 30 through in the axial direction are provided. The first flange through holes 21c are provided at positions corresponding to the first through holes 13c of the outer friction plate 13a, and the second flange through holes 21d are provided at positions corresponding to the second through holes 21d. The first flange through holes 21c and the second flange through holes 21d are each arranged at equal intervals in the circumferential direction, and each first flange through hole 21c and each second flange through hole 21d are arranged at different positions in the circumferential direction.

The circumferential center of each first flange through hole 21c and the circumferential center of each second flange through hole 21d adjacent to the first flange through hole 21c are provided in a state of being shifted in circumferential position. As a result, compared to the case where the circumferential length of the thin-walled portion formed between these through holes 21c and 21d is increased by overlapping the circumferential positions of these through holes 21c and 21d, the circumferential length of the thin-walled portion is suppressed, and the decrease in rigidity of the thin-walled portion can be suppressed. In this embodiment, the circumferential positions of one end of each first flange through hole 21c and the circumferential other end of the second flange through hole 21d adjacent to the first flange through hole 21c overlap in the circumferential position, but the one end and the other end do not have to overlap.

As shown in FIG. 2, the drum member 21 of the second clutch 20 has an outer cylindrical portion 21a with which the outer friction plate 23a engages, and a flange portion 21b that extends radially inward from one axial end of the outer cylindrical portion 21a.

Since the flange portion 21b is formed integrally with the retaining member 13e as described above, the rigidity of the flange portion 21b is increased compared to a case where the axial thickness is thin due to, for example, the flange portion 21b being formed separately from the retaining member 13e. When the clutch 20 rotates, a centrifugal force acts on the outer cylindrical portion 21a, which tends to deform (expand) the outer cylindrical portion 21a radially outward as a whole. When a centrifugal load acts on the outer cylindrical portion 21a, stress concentration occurs at the corner formed by the outer cylindrical portion 21a and the flange portion 21b, which may cause cracks or the like to occur at the corner. In contrast, since the flange portion 21b is formed integrally with the retaining member 13e as described above, the rigidity of the flange portion 21b is increased, and the expansion of the diameter due to the centrifugal load acting on the outer cylindrical portion 21a can be suppressed.

The outer peripheral surface of the outer cylindrical portion 21a is spline-fitted to the other-side extension portion 11e that extends from the outer cylindrical portion 11a of the first clutch 10 to the other axial direction. The other-side extension portion 11e extends further axially than the outer cylindrical portion 21a, and a retaining member 23e (described below) is spline-fitted to the other axial side of the outer cylindrical portion 21a. The axial position of the drum member 21 is determined by the surface on the other axial direction of the outer cylindrical portion 21a abutting the surface on one axial direction of the retaining member 23e.

The other side extension 11e is located radially outward from the outer cylindrical portion 11a, and a vertical wall portion 11f is formed between the outer cylindrical portion 11a and the other side extension 11e, so that the surface of one axial side of the flange portion 21b abuts against the vertical wall portion 11f.

The hub member 22 includes an inner cylindrical portion 22a with which the inner friction plate 23b engages, a disk portion 22b extending radially inward from one axial end of the inner cylindrical portion 22a, and a power transmission portion 22c extending axially from the inner end of the disk portion 22b to one axial end and connected to another rotating element.

As shown in FIG. 3, the outer circumferential surface of the outer friction plate 23a is provided with a spline portion 23a1 that is spline-engaged with the outer cylindrical portion 21a, and the inner circumferential surface of the inner friction plate 23b is provided with a spline portion 23b1 that is spline-engaged with the inner cylindrical portion 22a.

The outer friction plate 23a has a number of third through holes 23c at its radially outer side for axially passing the pistons 34 of the third clutch 30 described below.

The third through holes 23c are arranged evenly in the circumferential direction, and the circumferential position of each third through hole 23c is arranged to correspond to the circumferential position of each second through hole 13d. The circumferential position of each third through hole 23c is arranged to coincide with the circumferential position of each second through hole 13d.

The radial position of each third through hole 23c is located outside the outer periphery of the inner friction plate 23b and radially inside the spline portion 23a1. The radial position of the outer periphery of the inner friction plate 23b is located radially outside the first through hole 13c (see FIG. 2).

The piston 24 has a cylindrical pressing portion 24a that is disposed on one axial side of the multiple friction plates 13 of the first clutch 10 and extends in the axial direction, a radial portion 24b that extends radially inward from the end of the pressing portion 24a on one axial side, a cylindrical portion 24c that extends further axially to one side from the inner end of the radial portion 24b, and a pressure-receiving portion 24d that has a pressure-receiving surface that receives the hydraulic pressure supplied to the hydraulic chamber 25.

The pressing portion 24a has an end portion on the other axial side adjacent to one axial side of the friction plate 23, and presses the friction plate 23 when fastened. As shown in FIG. 4, the pressing portion 24a has a plurality of comb teeth 28 that are provided at the tip side portion located on the friction plate 23 side of the pressing portion 24a, extend in the axial direction, and are arranged in the circumferential direction to form a comb tooth shape, and a connecting portion 28f that connects the base end portion 28a of the comb teeth 28 in the circumferential direction. The circumferential position of each comb tooth 28 is arranged to correspond to each first through hole 13c of the plurality of friction plates 13 and each first flange through hole 21c of the flange portion 21b. Each comb tooth 28 penetrates each first through hole 13c and each first flange through hole 21c, so that the piston 24 and the plurality of friction plates 13 intersect in a comb tooth shape. The axial position of the radial portion 24b is arranged at a position that does not interfere with the piston 14 of the first clutch 10 when fastened.

Since the hydraulic chamber 25 is positioned with a radial offset relative to the friction plate 23, the radial positions of the pressing portion 24a and the pressure receiving portion 24d of the piston 24 are also offset in the same way.

As mentioned above, a radial dimension is required to provide the third through hole 23c on the radially inner side of the spline portion 23a1 of the outer friction plate 23a. Therefore, the radial position of the spline portion 23a1 and the pressing point P2 where the pressing portion 24a of the piston 24 presses the friction plate 23 are also offset.

A retaining member 23e is disposed on the other axial side of the multiple friction plates 23. The retaining member 23e has a larger outer diameter than the outer friction plates 23a, and as described above, is spline-fitted to the other-side extension 11e. The axial dimension (plate thickness) of the retaining member 23e is set to be thicker overall than the plate thickness of the other outer friction plates 23a. The plate thickness of the radially inner portion of the retaining member 23e is set to be even thicker than the radially outer portion. A restricting member 23f (in this embodiment, the drum member 31 of the third clutch 30) that restricts the axial movement of each friction plate 23 is disposed on the other axial side of the retaining member 23e.

As shown in FIG. 2, the drum member 31 of the third clutch 30 has an outer cylindrical portion 31a with which the outer friction plate 33a engages, and an engagement portion 31b that extends from one axial end of the outer cylindrical portion 31a to one axial side and engages with the outer peripheral surface of the other-side extension portion 11e of the first clutch 10.

The drum member 31 has a radial protrusion 31c that extends radially inward from the other axial end of the outer cylindrical portion 31a (a position adjacent to the retaining member 23e of the second clutch 20).

The other axial end of the other-side extension 11e is provided with a protrusion 11e1 that protrudes radially outward and functions as a stopper against which the end face on one axial side of the mating portion 31b of the third clutch 30 abuts. The radial protrusion 31c is provided on the drum member 31 and therefore does not move in the axial direction, but is used as a restricting member 23f that restricts the axial movement of the friction plate 23 of the second clutch 20.

As shown in FIG. 2, as described above, the drum member 31 of the third clutch 30 has an outer cylindrical portion 31a with which the outer friction plate 33a engages, a cylindrical fitting portion 31b extending further axially to one side from the outer cylindrical portion 31a, and a radial protrusion 31c provided between the outer cylindrical portion 31a and the fitting portion 31b. The drum member 31 is formed with a T-shaped cross section by the outer cylindrical portion 31a, the fitting portion 31b, and the radial protrusion 31c.

When the clutch 20 is engaged, the axial load input from the piston 24 to the friction plate 23 is received by the restricting member 23f via the retaining member 23e. If the radial position of the inner end of the restricting member 23f is offset from the pressure point P2, the radially inner portion of the friction plate 23 is more likely to move axially than the radially outer portion, and the radially inner portion of the friction plate 23 may deform so as to be positioned on the other axial side than the outer portion.

As described above, the axial dimension (thickness) of the retaining member 23e is set to be thicker overall than the thickness of the outer friction plate 23a, and the thickness of the radially inner portion, particularly the portion corresponding to the pressure point P2 where the piston 24 abuts against the outer friction plate 23a, is set to be thicker than the radially outer portion, thereby suppressing deformation of the friction plate 23.

The hub member 32 has an inner cylindrical portion 32a with which the inner friction plate 33b engages, and a disk portion 32b that extends radially inward from one axial end of the inner cylindrical portion 32a.

The outer circumferential surface of the outer friction plate 33a is provided with a spline portion 33a1 that is spline-engaged with the outer cylindrical portion 31a, as in the first and second clutches 10 and 20, and the inner circumferential surface of the inner friction plate 33b is provided with a spline portion 33b1 that is spline-engaged with the inner cylindrical portion 32a.

In the third clutch 30, biasing members 37, each composed of a wave spring or the like, are disposed between adjacent outer friction plates 33a, and the biasing members 37 are arranged to elastically bias the adjacent outer friction plates 33a in the direction of separation. These biasing members 37 are disposed on the outer periphery of the inner friction plates 33b.

The biasing members 37 are provided so that the clutch clearance is distributed between each of the adjacent outer friction plates. These biasing members 37 also function as return springs that move the piston 34 toward the opposite side of the friction plate.

The piston 34 has a cylindrical pressing portion 34a that is arranged on one axial side of the multiple friction plates 13 of the first clutch 10 and extends in the axial direction, and a pressure-receiving portion 34b that is arranged radially inward of the pressing portion 34a and has a pressure-receiving surface that receives the hydraulic pressure supplied to the hydraulic chamber 35.

The pressing portion 34a has an end portion on the other axial side adjacent to one axial side of the friction plate 33, and presses the friction plate 33 when fastened. As shown in FIG. 5, the pressing portion 34a has a plurality of comb teeth 38 that are provided at the tip side portion located on the friction plate 33 side of the pressing portion 34a, extend in the axial direction, and are arranged in the circumferential direction to form a comb tooth shape, and a connecting portion 38h that connects the base end portion 38a of the comb teeth 38 in the circumferential direction. The circumferential position of each comb tooth 38 is arranged so as to correspond to each second through hole 13d and each third through hole 23c of the plurality of friction plates 13, 23 and each second flange through hole 21d of the flange portion 21b. Each comb tooth 38 penetrates each second through hole 13d, each third through hole 23c, and each second flange through hole 21d, so that the piston 34, the plurality of friction plates 13, 23, and the flange portion 21b intersect in a comb tooth shape.

The outer friction plate 33a located furthest to the other side in the axial direction among the multiple friction plates 33 constitutes a retaining member 33e, similar to the first clutch 10. The axial dimension (plate thickness) of the retaining member 33e is set to be thicker overall than the plate thicknesses of the other outer friction plates 33a. A restricting member 33f that restricts the axial movement of each friction plate 13 is arranged on the other axial side of the retaining member 33e.

The hydraulic chambers 15, 25, 35 and the cancellation chambers 16, 26, 36 of the first, second, and third clutches 10, 20, 30 are formed using the drum member 11 of the first clutch 10. Next, the configuration of these hydraulic chambers 15, 25, 35 and the cancellation chambers 16, 26, 36 will be explained.

The end cover 1b constituting the transmission case 1 is provided with a boss portion 1c extending forward along the rotation centerline, and the sleeve member 3 is fitted and fixed to the outer periphery of the boss portion 1c. The drum member 11 is provided with an extension portion 11b extending from the outer cylindrical portion 11a to one side in the axial direction, a vertical wall portion 11c extending radially inward from the end portion on one axial side of the extension portion 11b and arranged so that the surface on one axial side faces the surface on the other axial side of the end cover 1b, and a tube portion 11d extending in the axial direction at the radially inner end of the vertical wall portion 11c. The drum member 11 is rotatably supported by the boss portion 1c of the end cover 1b via the sleeve member 3 by the tube portion 11d being rotatably fitted to the outer periphery of the sleeve member 3.

The drum member 11 has a cylindrical first cylinder portion 73 and a cylindrical second cylinder portion 74 that extend forward from the radial middle portion and the outer periphery of the front surface of the vertical wall portion 11c, respectively. The piston 14 of the first clutch 10 is fitted between the outer periphery of the cylindrical portion 11d and the inner periphery of the first cylinder portion 73, the piston 24 of the second clutch 20 is fitted between the outer periphery of the first cylinder portion 73 and the inner periphery of the second cylinder portion 74, and further, the piston 34 of the third clutch 30 is fitted between the outer periphery of the second cylinder portion 74 and the inner periphery of the extension portion 11b of the vertical wall portion 11c.

The hydraulic chamber 15 of the first clutch 10 is oil-tightly formed by the outer peripheral surface of the tube portion 11d, the front surface of the vertical wall portion 11c, the inner peripheral surface of the first cylinder portion 73, and the back surface of the pressure receiving portion 14c. The hydraulic chamber 25 of the second clutch 20 is oil-tightly formed by the front surface of the vertical wall portion 11c, the outer peripheral surface of the first cylinder portion 73, the inner peripheral surface of the second cylinder portion 74, and the back surface of the pressure receiving portion 24d. The hydraulic chamber 35 of the third clutch 30 is oil-tightly formed by the front surface of the vertical wall portion 11c, the inner peripheral surface of the extension portion 11b, the outer peripheral surface of the second cylinder portion 74, and the back surface of the pressure receiving portion 34b.

The cancel chamber 16 of the first clutch 10 is oil-tightly formed by the rear surface of the seal plate 75 attached to the front of the outer circumferential surface of the tube portion 11d, the outer circumferential surface of the tube portion 11d, the front surface of the pressure receiving portion 14c, and the inner circumferential surface of the cylindrical portion 14b. The cancel chamber 26 of the second clutch 20 is oil-tightly formed by the rear surface of the seal plate 76 attached to the front of the outer circumferential surface of the first cylinder portion 73, the outer circumferential surface of the first cylinder portion 73, the front surface of the pressure receiving portion 24d, and the inner circumferential surface of the cylindrical portion 24c. The cancel chamber 36 of the third clutch 30 is oil-tightly formed by the rear surface of the seal plate 77 attached to the front of the outer circumferential surface of the second cylinder portion 74, the outer circumferential surface of the second cylinder portion 74, the front surface of the pressure receiving portion 34b, and the inner circumferential surface of the connection portion 34c.

In each of the cancellation chambers 16, 26 of the first clutch 10 and the second clutch 20, return springs 17, 27 are disposed between the seal plate 75 and the pistons 14, 24, respectively, and the pistons 14, 24 are biased in the clutch release direction. As described above, the return spring 37 of the third clutch 30 is disposed between the multiple friction plates 33a.

Here, the vertical wall portion 11c is provided perpendicular to the axis, and the rear surface of the hydraulic chambers 15, 25, 35 of each clutch is formed by the inner peripheral portion, intermediate portion, and outer peripheral portion of this vertical wall portion 11c. Therefore, each hydraulic chamber 15, 25, 35 overlaps in the axial direction, with the hydraulic chamber 25 of the second clutch 20 overlapping on the outer peripheral side of the hydraulic chamber 15 of the first clutch 10, and the hydraulic chamber 35 of the third clutch 30 overlapping on the outer peripheral side of the hydraulic chamber 25.

The cancel chambers 16, 26, 36 of the clutches 10, 20, 30, which are provided in front of the hydraulic chambers 15, 25, 35 across the pistons 14, 24, 34, also overlap in the axial direction, with the cancel chamber 26 of the second clutch 20 overlapping on the outer periphery of the cancel chamber 16 of the first clutch 10, and the cancel chamber 36 of the third clutch 30 overlapping on the outer periphery of the cancel chamber 26.

The vertical wall portion 11c of the drum member 11 is provided with fastening hydraulic oil supply passages 80a, 80b, 80c that supply fastening hydraulic oil to the hydraulic chambers 15, 25, 35 of the first, second, and third clutches 10, 20, 30, respectively, and cancellation hydraulic oil supply passages 90a, 90b, 90c that supply centrifugal cancellation hydraulic oil to the cancellation chambers 16, 26, 36 (see Figure 1).

When the comb teeth 28, 38 of the pistons 24, 34 of the second and third clutches 20, 30 have an axial length greater than or equal to a predetermined value, the centrifugal force generated when each clutch rotates tends to deform the tip ends 28b, 38b of the comb teeth 28, 38 so as to expand radially outward, as shown by the phantom lines in Figs. 6 and 7, and stress concentration may occur at the base ends 28a, 38a of the comb teeth 28, 38. Stress concentration at the base ends 28a, 38a may cause damage to the pistons. In this embodiment, the axial length greater than or equal to a predetermined value means the axial length of the comb teeth 28, 38 when the centrifugal force generated when the pistons 24, 34 of the aluminum die-cast product rotate at 11,200 rpm causes the maximum stress σmax at the base end 28a to be equal to or greater than the stress standard (e.g., 170 MPa). In addition, the maximum stress σmax is proportional to the bending moment of the base end 28a, 38a and inversely proportional to the section modulus of the comb teeth 28, 38, so the axial length of the comb teeth 28, 38 beyond a certain value varies depending on the piston density, piston diameter, piston radial thickness, rotation speed, stress standard, etc.

The piston 24 of the second clutch 20 and the piston 34 of the third clutch 30 are provided with ring members 24f, 34d, and 34e for suppressing the expansion of the comb tooth portions 28, 38. The pistons 24, 34 of the second clutch 20 and the piston 34 of the third clutch 30 will be described with reference to Figures 2 to 7. The piston 24 of the second clutch 20 and the piston 34 of the third clutch 30 are formed, for example, from an aluminum material, and the ring members 24f, 34d, and 34e are formed from an iron material or the like.

As shown in Figures 4 and 6, the comb tooth portion 28 of the second clutch 20 has a base end portion 28a on one axial side, a tip end portion 28b on the other axial side, and an intermediate portion 28c connecting the base end portion 28a and the tip end portion 28b.

The comb tooth portion 28 of the piston 24 has an axial length L1 that penetrates the friction plate 13 of the first clutch 10 and presses against the friction plate 23 of the second clutch 20. In this embodiment, the axial length L1 from the base end 28a of the comb tooth portion 28 to the tip surface is set to 27.5 mm.

The tip 28b of the comb tooth portion 28 is provided with a step 28e for regulating the axial position of the ring member 24f. The step 28e is formed by positioning the outer circumferential surface 28d of the tip 28b radially inward relative to the outer circumferential surface of the intermediate portion 28c. The step 28e is formed by a vertical wall portion that connects the outer circumferential surface 28d of the tip 28b and the outer circumferential surface of the intermediate portion 28c.

A ring-shaped ring member 24f is fitted onto the tip 28b of the comb tooth portion 28. As described above, the ring member 24f is made of a material different from the piston 24, such as iron. The ring member 24f is formed into a circular shape with a rectangular cross section. The inner diameter of the ring member 24f is set to be approximately the same as or slightly smaller than the outer diameter of the tip 28b. The ring member 24f is pressed into the tip 28b, and its axial position is determined by inserting it to a position where the side of the axial end side (opposite the driving source side) of the ring member 24f abuts against the step 28e.

The axial dimension of the ring member 24f is set to be slightly smaller than the axial dimension of the tip 28b. The side surface of the other axial end of the ring member 24f (the driving source side) is located on one axial side of the tip surface of the piston 24. The tip surface of the piston 24 protrudes toward the friction plate 23 side beyond the ring member 24f.

The radial thickness of the base end 28a of the comb tooth portion 28 is set to be larger than the tip end 28b and the intermediate portion 28c. The base end 28a is inclined so that the radial thickness increases from the intermediate portion 28c toward one axial side. The outer peripheral surface of the base end 28a is inclined radially outward from the intermediate portion 28c toward one axial side, and the inner peripheral surface of the base end 28a is inclined radially inward from the intermediate portion 28c toward one axial side, so that the radial thickness of the base end 28a is set to be larger than that of the intermediate portion 28c. The base end 28a is connected to the radial portion 24b via a connecting portion 28f that connects the base end 28a in the circumferential direction.

The piston 24 is provided with the radial positions of the pressure receiving portion 24d and the pressing portion 24a offset. Therefore, when hydraulic pressure acts on the pressure receiving portion 24d, the axial load acting on the pressure receiving portion 24d is input to the inner end of the radial portion 24b via the cylindrical portion 24c. As a result, the inner end of the radial portion 24b tries to deform in a Z-shape so that it is located on the other axial side than the outer end. In contrast, the axial thickness of the radial portion 24b is set to be larger than the radial thickness of the connection portion 38h of the piston 34 of the third clutch 30 described below, for example. In this way, the bending rigidity of the radial portion 24b of the piston 24 is increased compared to when the radial thickness is small, so that bending deformation of the radial portion 24b at the time of fastening is suppressed.

The pressure-receiving portion 24d of the piston 24 has a number of recesses 24e arranged in the circumferential direction, recessed from the other axial side to the one axial side. One axial end of the return spring 27 described above is housed in this recess 24e.

As shown in Figures 5 and 7, the comb tooth portion 38 of the third clutch 30 has a base end portion 38a on one axial side, a tip end portion 38b on the other axial side, and an intermediate portion 38c that connects the base end portion 38a and the tip end portion 28b.

The comb tooth portion 38 of the piston 34 has an axial length L2 that penetrates the friction plate 13 of the first clutch 10, the flange portion 21b of the second clutch, and the friction plate 23 of the second clutch 20, and presses against the friction plate 33 of the third clutch 30. In this embodiment, the axial length L2 from the base end 38a of the comb tooth portion 38 to the tip surface is set to 49.4 mm.

The tip 38b of the comb tooth portion 38 is provided with a first step 38e for regulating the axial position of the first ring member 34d. The first step 38e is formed by positioning the outer peripheral surface 38d of the tip 38b radially inward relative to the outer peripheral surface of the intermediate portion 28c. The first step 38e is formed by a vertical wall portion that connects between the outer peripheral surface 38d of the tip 38b and the outer peripheral surface of the intermediate portion 38c.

A ring-shaped first ring member 34d is fitted around the tip 38b of the comb tooth portion 38. As described above, the first ring member 34d is made of a material different from the piston 34, such as iron. The first ring member 34d has a rectangular cross section and is formed in a circular shape. The inner diameter of the first ring member 34d is set to be approximately the same as or slightly smaller than the outer diameter of the tip 38b. The first ring member 34d is pressed into the tip 38b, and the axial position is determined by inserting the first ring member 34d until the side of the axial end side (opposite the driving source side) abuts against the first step 38e.

The axial dimension of the first ring member 34d is set to be slightly smaller than the axial dimension of the tip 38b. The side surface of the other axial end (driving source side) of the first ring member 34d is located on one axial side of the tip surface of the piston 34. The tip surface of the piston 34 protrudes toward the friction plate 33 side more than the first ring member 34d.

A second step 38g is provided in the intermediate portion 38c between the tip end 38b and the base end 38a of the comb tooth portion 38 to regulate the axial alignment of the second ring member 34e. A protruding portion 38f that protrudes radially outward is provided in the intermediate portion 38c. The second step 38g is formed by positioning the outer circumferential surface of the protruding portion 38f radially outward relative to the outer circumferential surface of the intermediate portion 38c. The second step 38g is formed by a vertical wall portion that connects the outer circumferential surface of the intermediate portion 38c located between the tip end 38b and the protruding portion 38f and the outer circumferential surface of the protruding portion 38f.

A ring-shaped second ring member 34e is fitted onto the middle portion 38c of the comb tooth portion 38. As described above, the second ring member 34e is made of a material different from the piston 34, such as iron. The second ring member 34e has a rectangular cross section and is formed into a circular shape. The inner diameter of the second ring member 34e is set to be larger than the outer diameter of the tip portion 38b and approximately the same as or slightly smaller than the outer diameter of the middle portion 38c. The second ring member 34e is pressed into the outer periphery of the middle portion 38c, and the axial position is determined by inserting the second ring member 34e to a position where the side of the axial end side (opposite the driving source side) abuts against the second step portion 38g.

2, the axial position of the second ring member 34e is set to be located between the retaining member 13e (in this embodiment, the flange portion 21b of the drum member 21 of the second clutch 20) located at the most axial other side among the plurality of friction plates 13 of the first clutch 10 and the friction plate 23 located at the most axial one side among the plurality of friction plates 23 of the second clutch 20. The friction plate 23 of the second clutch 20 penetrates between the first ring member 34d and the second ring member 34e of the comb tooth portion 38, and the friction plate 13 of the first clutch 10 penetrates between the second ring member 34e and the base end portion 38a of the comb tooth portion 38. The axial dimension of the protruding portion 38f is set to be approximately the same as or slightly larger than the axial dimension of the radially outer portion of the flange portion 21b.

The intermediate portion 38c between the base end 38a and the second ring member 34e is provided with a hollow portion 38i that is recessed radially inward relative to the base end 38a and the protruding portion 38f. The hollow portion 38i is formed by a circumferential groove that is provided so as to hollow the outer circumferential surface of the intermediate portion 38c between the base end 38a and the second ring member 34e radially inward.

As shown in FIG. 7, the radial thickness of the base end 38a of the comb tooth portion 38 is set to be greater than the tip end 38b and the intermediate portion 38c. The base end 38a is inclined so that the radial thickness increases from the removed portion 38i toward one axial side. The outer peripheral surface of the base end 38a is formed to be inclined radially outward from the removed portion 38i toward one axial side, so that the radial thickness of the base end 38a is set to be greater than that of the removed portion 38i. The base end 38a is connected to the pressure receiving portion 34b via a connecting portion 38h that connects the base end 38a in the circumferential direction.

The radial thickness of the connection portion 38h is set to be even greater than that of the base end portion 38a. The inner peripheral surface of the base end portion 38a is formed to be inclined radially inward toward one axial side, and the radial thickness of the connection portion 38h is set to be greater than that of the base end portion 38a.

Next, the operation of the automatic transmission according to this embodiment will be described. First, the first clutch 10 is engaged by supplying engagement pressure (engagement hydraulic oil) to the hydraulic chamber 15 of the first clutch 10 via the engagement hydraulic oil supply passage 80a, and the input shaft 2 and the sun gear 51 of the second planetary gear set 50 are connected.

The second clutch 20 is engaged by supplying engagement pressure to the hydraulic chamber 25 of the second clutch 20 via the engagement hydraulic oil supply passage 80b, and the ring gear of another planetary gear (not shown) and the sun gear 51 of the second planetary gear set 50 are connected.

The third clutch 30 is engaged by supplying engagement pressure to the hydraulic chamber 35 of the third clutch 30 via the engagement hydraulic oil supply passage 80c, and the ring gear 42 of the first planetary gear set 40 and the sun gear 51 of the second planetary gear set 50 are connected.

In the automatic transmission of this embodiment, the pressing portion 24a of the piston 24 of the second clutch 20 passes through the first through hole 13c provided in the outer friction plate 13a of the first clutch 10, and is therefore able to press against the multiple friction plates 23 of the second clutch 20 that are arranged on the other axial side of the multiple friction plates 13 of the first clutch 10.

The pressing portion 34a of the piston 34 of the third clutch 30 passes through the second through hole 13d of the outer friction plate 13a of the first clutch 10 and the third through hole 23c of the outer friction plate 23a of the second clutch 20, so that it can press the multiple friction plates 33 of the third clutch 30 arranged on the other axial side of the multiple friction plates 23 of the second clutch 20.

This allows the friction plates 13, 23, 33 of the first, second, and third clutches 10, 20, 30 to be arranged in parallel in the axial direction, while the pistons 14, 24, 34 of the first, second, and third clutches 10, 20, 30 can be arranged to overlap in the axial direction.

As a result, the radial dimension can be reduced compared to when the friction plates 13, 23, 33 of the first, second, and third clutches 10, 20, 30 are overlapped in the axial direction, and the axial dimension can be shortened compared to when the pistons 14, 24, 34, hydraulic chambers 15, 25, 35, and cancellation chambers 16, 26, 36 are arranged in parallel in the axial direction in addition to the friction plates 13, 23, 33.

As described above, when the comb teeth 28, 38 of the pistons 24, 34 of the second and third clutches 20, 30 have an axial length greater than a predetermined value, the centrifugal force generated when each clutch rotates tends to deform the tip ends 28b, 38b of the comb teeth 28, 38 so that their diameters expand radially outward, as shown by phantom lines in Figures 6 and 7. This can cause stress concentration at the base ends 28a, 38a of the comb teeth 28, 38.

According to the present invention, annular ring members 24f, 34e, 34d are arranged on the outer circumference of the second and third pistons 24, 34, so that deformation of the tip ends 28b, 38b of the comb teeth 28, 38 that would otherwise expand radially outward due to centrifugal force when the second and third clutches 20, 30 rotate is suppressed, and stress concentration at the base ends 28a, 38a of the comb teeth 28, 38 can be suppressed.

The comb tooth portion 28, 38 is provided with a step portion 28e, 38e, 38g for regulating the axial position of the ring member 24f, 34e, 34d, so that the axial position of the ring member 24f, 34d, 34e can be determined with a simple structure that only requires the step portion 28e, 38e, 38g to be provided on the comb tooth portion 28, 38. For example, when the ring member 24f, 34e, 34d is press-fitted into the comb tooth portion 28, 38 and abuts against the step portion 28e, 38e, 38g, the ring member 24f, 34d, 34e can be fixed to the piston 24, 34 even when the piston 24, 34 and the ring member 24f, 34d, 34e are made of different materials such as aluminum and iron, which are difficult to fix by welding or the like.

The radial thickness of the base end 28a, 38a of the comb tooth portion 28, 38 of the second and third clutches is set to be larger than the radial thickness of the comb tooth portion 28, 38 other than the base end 28a, 38a (the tip end 28b, 38b and the intermediate portion 28c, 38c of the comb tooth portion 28, 38), so that the bending rigidity of the piston 24, 34 can be improved. This makes it possible to suppress stress concentration at the base end 28a, 38a caused by the tip end 28b, 38b side deforming radially outward. On the other hand, by setting the radial thickness of the comb tooth portion 28, 38 other than the base end 28a, 38a to be smaller than the base end 28a, 38a, the increase in the weight of the comb tooth portion 28, 38 is suppressed, so that the radially outward deformation due to centrifugal force is easily suppressed, and the stress at the base end 28a, 38a can be suppressed. As a result, there is no need to set the radial thickness of the base ends 28a, 38a larger than necessary, and the overall weight of the pistons 24, 34 is reduced.

The comb tooth portion 38 is provided with a hollow portion 38i between the base end portion 38a and the second step portion 38g, thereby reducing the weight of the comb tooth portion 38. This makes it easier to reduce radially outward deformation of the comb tooth portion 38 due to centrifugal force, and suppresses stress concentration at the base end portion 38a.

By placing ring members 24f, 34d on the tip ends 28b, 38b of the comb tooth portions 28, 38, which are subject to a large amount of radially outward deformation due to centrifugal force when the second and third clutches 20, 30 rotate, and restraining the deformation, the amount of radially outward deformation of the comb tooth portions 28, 38 is more easily suppressed, and stress concentration at the base ends 28a, 38a of the comb tooth portions 28, 38 is more effectively suppressed.

The piston 34 of the third clutch 30, which penetrates the friction plates 13 of the first clutch 10 and the friction plates 23 of the second clutch 20, can suppress radially outward deformation of the tip end 38b of the piston 34 by the first ring member 34d, while suppressing radially outward deformation of the middle part 38c of the piston 34 by the second ring member 34e, so that deformation of the comb tooth part 38 is more effectively suppressed and stress concentration at the base end 38a is more effectively suppressed.

In the above embodiment, the friction plates 13, 23, 33 of the three clutches, the first, second, and third clutches 10, 20, and 30, are arranged in the axial direction. However, even if the friction plates of two clutches, such as the first and second clutches 10 and 20, are arranged in the axial direction, the same effect can be obtained by providing the piston 24 of the second clutch 20 with a comb-tooth portion 28 that passes through the friction plates 13 of the first clutch 10, and by arranging a ring member 24f at the tip 28b of the comb-tooth portion 28.

In addition, in this embodiment, the drum members 11, 21, and 31 of the first, second, and third clutches 10, 20, and 30 are separately provided, but these drum members may be integrally formed.

The present invention is not limited to the illustrated embodiments, and various improvements and design changes are possible without departing from the spirit of the present invention.

As described above, according to the present invention, in an automatic transmission equipped with multiple clutches, a piston equipped with a comb-tooth portion is inserted through friction plates arranged in the axial direction, thereby reducing stress concentration at the base end of the comb-tooth portion while suppressing increases in the radial and axial dimensions of the clutch. This may be advantageously used in the manufacturing industry for this type of automatic transmission or the vehicle on which it is mounted.

2 Power transmission shaft 10 First clutch (one-side clutch)
11, 21, 31 Drum member 12, 22, 32 Hub member 13, 23, 33 Friction plate 14, 24, 34 Piston 20 Second clutch (first other-side clutch, other-side clutch)
28, 38 Comb tooth portions 28a, 38a Base end portions 28b, 38b Tip portions 28c, 38c Intermediate portion 28e Step portion 24f Ring member 30 Third clutch (second other-side clutch, other-side clutch)
34d First ring member (ring member)
34e Second ring member (ring member)
38e First step (step)
38g Second step (step)
38i Removal part

Claims (7)

an automatic transmission having an axial one-side clutch and an axial other-side clutch arranged side by side in the axial direction on an axis of a power transmission shaft, the one-side clutch and the other-side clutch each including a cylindrical drum member, a cylindrical hub member facing the drum member, friction plates engaged between the drum member and the hub member so as to be slidable in the axial direction, and a piston pressing the friction plates,
The friction plates of the one-side clutch and the other-side clutch are arranged side by side in the axial direction,
the pistons of the one-side clutch and the other-side clutch are disposed on one side of the friction plate of the one-side clutch in the axial direction and are disposed so as to overlap each other in the axial direction,
The piston of the other clutch includes a cylindrical pressing portion that presses the friction plate of the other clutch,
a comb-tooth portion penetrating the friction plate of the one-side clutch in the axial direction is provided at a tip end portion of the pressing portion located on the friction plate side of the other-side clutch,
An automatic transmission in which an annular ring member is disposed on an outer periphery of the comb tooth portion. The automatic transmission according to claim 1, wherein the comb tooth portion is provided with a step portion for regulating the axial position of the ring member. An automatic transmission according to claim 1 or 2, in which the base end of the comb tooth portion of the other clutch is set to have a radial thickness greater than the tip end of the comb tooth portion and the intermediate portion connecting the tip end and the base end. The automatic transmission according to any one of claims 1 to 3, wherein a hollow portion is provided between the base end of the comb tooth portion and the ring member. An automatic transmission according to any one of claims 1 to 4, wherein the ring member is disposed at the tip of the comb tooth portion. the other-side clutch includes a first other-side clutch disposed on a side of the one-side clutch, and a second other-side clutch disposed on the other side of the first other-side clutch in the axial direction,
The piston of the first other-side clutch penetrates the friction plate of the one-side clutch in the axial direction,
6. The automatic transmission according to claim 1, wherein the piston of the second other-side clutch axially passes through the friction plates of the one-side clutch and the friction plates of the first other-side clutch. The ring member is
a first ring member disposed at a tip end of the comb tooth portion of the second other-side clutch;
7. The automatic transmission according to claim 6, further comprising: a second ring member disposed in an intermediate portion between the friction plates of the one-side clutch and the friction plates of the first other-side clutch in the comb tooth portion of the second other-side clutch.

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