JP7707741B2 - Automatic transmission - Google Patents

Description

The present invention relates to an automatic transmission equipped with multiple clutches and multiple planetary gear sets.

One example of the above automatic transmission is disclosed in Patent Document 1 below. The automatic transmission described in Patent Document 1 has three clutches and three planetary gear sets arranged in the axial direction. Specifically, in the automatic transmission of Patent Document 1, a first clutch (rear clutch), a second clutch (intermediate clutch), and a third clutch (front clutch) are arranged in this order from one axial side (rear side), and the first planetary gear set, the second planetary gear set, and the third planetary gear set are arranged in this order on one axial side of the first clutch. The first clutch, the second clutch, and the third clutch are all connected to the sun gear (third sun gear) of the third planetary gear set.

JP 2020-169681 A

In the automatic transmission of Patent Document 1, the three planetary gear sets and three clutches are arranged separately on one side and the other side of the axial direction, so there is a problem that the power transmission path between the three clutches and the third sun gear (i.e., the sun gear of the planetary gear set farthest from the clutch) is likely to become long. The lengthening of the power transmission path leads to an increase in the mass of the parts that make up the power transmission path, that is, the rotating parts that rotate together with the third sun gear. If the mass of the rotating parts increases, the inertia of the rotating parts may slow down the rotation change of the third sun gear during a gear shift that causes a sudden change in the rotation speed of the third sun gear, and the gear shift response may deteriorate. Of course, the increase in the mass of the rotating parts can be suppressed by replacing at least a part of the rotating parts with lightweight parts such as aluminum die-cast products. However, doing so inevitably increases the unit price of the parts, which is undesirable in terms of manufacturing costs.

The present invention was made in consideration of the above circumstances, and aims to provide an automatic transmission that can achieve both reduced manufacturing costs and improved shift response.

In order to solve the above problem, an automatic transmission according to one aspect of the present invention includes a first clutch and a second clutch arranged in an axial direction, a third clutch arranged on one axial side of the first and second clutches, an intermediate planetary gear set arranged between the first and second clutches and the third clutch, an outer planetary gear set arranged on one axial side of the third clutch, and a connecting member connecting the first clutch, the second clutch, and the third clutch to a common rotating element provided in the outer planetary gear set , wherein the first clutch and the second clutch each include a plurality of friction plates arranged in the axial direction and a cylindrical hub member engaging with inner peripheral edges of the friction plates, and the third clutch includes a plurality of friction plates arranged in the axial direction and a cylindrical drum member engaging with an outer peripheral edge of the friction plates, and the connecting member includes a first connecting member connecting the hub members of the first and second clutches to the drum member of the third clutch, and a second connecting member connecting the drum member of the third clutch to the common rotating element (claim 1).

According to the present invention, the first and second clutches and the third clutch are distributed in the axial direction with the intermediate planetary gear set in between, so that the power transmission path between the first to third clutches and the common rotating element connected thereto can be simplified compared to a case where the planetary gear set group and the clutch group are arranged together on one side and the other side of the axial direction, respectively (a structure similar to that of Patent Document 1 mentioned above). As a result, the mass of the rotating parts that rotate integrally with the common rotating element can be reduced without taking special measures such as replacing the rotating parts with expensive lightweight parts, and the shift response of the automatic transmission can be improved while suppressing manufacturing costs.

In addition, as connecting members connecting the first to third clutches and a common rotating element, a first connecting member connecting the hub members of the first and second clutches and the drum member of the third clutch, and a second connecting member connecting the drum member of the third clutch to the common rotating element are provided, so that the first to third clutches and the common rotating element can be connected to each other with a simple and rational structure.

The third clutch may include a plurality of friction plates arranged in the axial direction, a cylindrical drum member that engages with the outer circumferential edges of the friction plates, and a piston that presses the friction plates in the axial direction. In this case, it is preferable that the piston includes a sub-piston that is supported by a transmission case and defines an engagement hydraulic chamber between the transmission case and the sub-piston, a rotatable main piston that is arranged axially opposite the sub-piston and presses the friction plates, and a bearing that connects the sub-piston and the main piston so as to be rotatable relative to each other (claim 2 ).

According to this configuration, the engagement hydraulic chamber for the third clutch is formed not by a rotatable main piston that presses against the friction plate, but between a sub-piston supported by the transmission case and the transmission case. In this case, centrifugal force does not act on the engagement hydraulic chamber, so there is no need to provide a centrifugal balance chamber to cancel the effect of the centrifugal force. Therefore, the structure of the hydraulic supply system can be simplified while ensuring controllability of the piston by the hydraulic pressure supplied to the engagement hydraulic chamber.

According to another aspect of the present invention, there is provided an automatic transmission comprising: a first clutch and a second clutch arranged in an axial direction; a third clutch arranged on one axial side of the first and second clutches; an intermediate planetary gear set arranged between the first and second clutches and the third clutch; an outer planetary gear set arranged on one axial side of the third clutch; and a connecting member connecting the first clutch, the second clutch, and the third clutch to a common rotating element provided in the outer planetary gear set, the third clutch comprising a plurality of friction plates arranged in the axial direction, a cylindrical drum member engaging with outer circumferential edges of the friction plates, and a piston pressing the friction plates in the axial direction, the drum member comprising a peripheral wall portion extending in the axial direction at a radially outer side of the friction plates and engaging with the outer circumferential edge of the friction plates. a vertical wall portion extending radially inward from one axial end of the peripheral wall portion, and a plurality of inner protrusions extending from the radially inner end of the vertical wall portion to the other axial side, the piston including a sub-piston supported by a transmission case to define a fastening hydraulic chamber between the transmission case and the sub-piston, a rotatable main piston arranged axially opposite the sub-piston and pressing the friction plate, and a bearing connecting the sub-piston and the main piston so as to be rotatable relative to each other , the main piston having a pressing portion pressing the friction plate, and a plurality of openings formed radially inward from the pressing portion and through which the inner protrusions are inserted, and the connecting member including a downstream connecting member connecting the other axial end of the inner protrusion and the common rotating element (Claim 3 ).

According to the present invention , the pressing portion of the main piston can be disposed inside the drum member to enable the pressing portion to press the friction plate, while the drum member can be connected to the common rotating element via the downstream connecting member.

Preferably, the third clutch is provided with a return spring on the other axial side of the main piston for urging the main piston in a release direction to release the pressure on the friction plate, and the return spring is arranged radially inward of the friction plate so as to overlap with the friction plate when viewed in the radial direction (Claim 4 ).

This configuration allows the axial dimension of the third clutch to be shortened, making the automatic transmission more compact in the axial direction.

Preferably, the return spring is disposed at a position facing the bearing across the main piston (claim 5 ).

This configuration allows for a rational arrangement in which the bearing that pushes the main piston in the tightening direction and the return spring that pushes the main piston back in the release direction face each other in the axial direction.

As described above, the automatic transmission of the present invention can achieve both reduced manufacturing costs and improved shift response.

1 is a schematic diagram showing a configuration of an automatic transmission according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the automatic transmission. 4 is an engagement table showing the relationship between engagement/disengagement of each frictional engagement element and the gear position. FIG. 3 is an enlarged cross-sectional view of a portion of FIG. 2 . FIG. 5 is a view equivalent to FIG. 4 , in which a group of rotating parts that rotate integrally with the third sun gear are shown in color. FIG. 11 is a cross-sectional view showing the structure of a comparative example in which the arrangement of a clutch and the like is different from that of the above embodiment.

The following describes an embodiment of the present invention with reference to the drawings.

[Overall configuration of automatic transmission]
1 and 2 are a schematic diagram and a cross-sectional view showing the configuration of an automatic transmission 1 according to an embodiment of the present invention. The automatic transmission 1 shown in the drawings is a longitudinally mounted automatic transmission mounted on a front-engine, rear-drive (FR) vehicle. In other words, the automatic transmission 1 is a transmission that transmits the power of a drive source including an internal combustion engine disposed at the front of the vehicle to a propeller shaft while changing the speed. The power transmitted to the propeller shaft is transmitted to rear wheels via a differential mechanism.

The automatic transmission 1 includes a transmission mechanism 10, a transmission case 11, an input shaft 12, an output shaft 13, and a valve body 14 (Fig. 2). The transmission mechanism 10 is a multi-stage transmission mechanism capable of achieving multiple gear stages with different gear ratios, and includes frictional fastening elements such as clutches and brakes (CL1-CL3, BR1, BR2) in addition to planetary gear sets (PG1-PG4) described below. The transmission case 11 is a case that houses the transmission mechanism 10. The input shaft 12 is a shaft member that inputs power to the transmission mechanism 10 and is coaxially connected to the output shaft of the drive source. The output shaft 13 is a shaft member that outputs power from the transmission mechanism 10 and is coaxially connected to the propeller shaft. The input shaft 12 is disposed inside the transmission case 11, and the output shaft 13 is disposed so as to protrude from the inside of the transmission case 11 to the outside.

The input shaft 12 and the output shaft 13 are arranged coaxially along the vehicle longitudinal direction. That is, the input shaft 12 and the output shaft 13 are arranged to extend along the same axis X (FIG. 2) that extends in the vehicle longitudinal direction. The axis X is the substantial central axis of the transmission mechanism 10 of the automatic transmission 1. The automatic transmission 1 is mounted on the vehicle with the input shaft 12 located at the front of the vehicle and the output shaft 13 located at the rear of the vehicle along the axis X. For this reason, in the following, one side of the direction parallel to the axis X (the central axis of the input shaft 12 and the output shaft 13) of the automatic transmission 1 and away from the drive source (right side of the figure) is sometimes referred to as the "rear", and the other side of the direction parallel to the axis X and closer to the drive source (left side of the figure) is sometimes referred to as the "front". In addition, with respect to the automatic transmission 1, the direction along the axis X is sometimes referred to as the "axial direction", and the direction perpendicular to the axis X is sometimes referred to as the "radial direction". Furthermore, the direction along the circumference of a circle centered on axis X is sometimes called the "circumferential direction."

The transmission mechanism 10 comprises a first planetary gear set PG1, a second planetary gear set PG2, a third planetary gear set PG3, and a fourth planetary gear set PG4 aligned in the axial direction. The first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4 are arranged in the axial direction aligned in this order from the front. Hereinafter, the planetary gear sets will be abbreviated as "gear sets" as appropriate. For example, the first planetary gear set PG1 will be abbreviated as the first gear set PG1.

The first gear set PG1 has a first sun gear S1, a first ring gear R1, and a first carrier C1 as rotating elements. The first carrier C1 supports a plurality of first pinions P1 that are spaced apart from one another in the circumferential direction. Each first pinion P1 meshes with both the first sun gear S1 and the first ring gear R1.

The second gear set PG2 has a second sun gear S2, a second ring gear R2, and a second carrier C2 as rotating elements. The second carrier C2 supports a plurality of second pinions P2 that are spaced apart from one another in the circumferential direction. Each second pinion P2 meshes with both the second sun gear S2 and the second ring gear R2.

The third gear set PG3 has a third sun gear S3, a third ring gear R3, and a third carrier C3 as rotating elements. The third carrier C3 supports a plurality of third pinions P3 that are spaced apart from one another in the circumferential direction. Each third pinion P3 is meshed with both the third sun gear S3 and the third ring gear R3.

The fourth gear set PG4 has a fourth sun gear S4, a fourth ring gear R4, and a fourth carrier C4 as rotating elements. The fourth carrier C4 supports a number of fourth pinions P4 that are spaced apart from one another in the circumferential direction. Each fourth pinion P4 is meshed with both the fourth sun gear S4 and the fourth ring gear R4.

In this embodiment, a double sun gear type gear set in which the sun gear S1 is divided into two in the axial direction is used as the first gear set PG1. On the other hand, normal type gear sets in which the sun gear is not divided in the axial direction are used as the other second to fourth gear sets PG2 to PG4.

Specifically, the first sun gear S1 of the first gear set PG1 includes a front sun gear S1a and a rear sun gear S1b. The rear sun gear S1b is separately arranged on the rear side of the front sun gear S1a. The front sun gear S1a and the rear sun gear S1b have the same number of teeth and are meshed with a common first pinion P1. Therefore, the rotation speeds of the front sun gear S1a and the rear sun gear S1b are always equal. In other words, the front sun gear S1a and the rear sun gear S1b always rotate at the same speed, and when the rotation of one stops, the rotation of the other also stops.

The input shaft 12 is connected to the first carrier C1 via a power transmission member 18 that passes between each of the divided gears of the first sun gear S1 (i.e., the front sun gear S1a and the rear sun gear S1b). The first sun gear S1 (specifically, the rear sun gear S1b) is connected to the fourth sun gear S4 via a power transmission member 15. The second carrier C2 is connected to the fourth carrier C4 via a power transmission member 16. The output shaft 13 is connected to the fourth carrier C4.

The transmission mechanism 10 includes a first clutch CL1, a second clutch CL2, a third clutch CL3, a first brake BR1, and a second brake BR2 as frictional engagement elements for switching the power transmission paths through the first to fourth gear sets PG1 to PG4 described above.

The first clutch CL1 is disposed near the front of the first gear set PG1, the second clutch CL2 is disposed further forward of the first clutch CL1, and the third clutch CL3 is disposed rearward of the second gear set PG2. That is, the first to third clutches CL1 to CL3 are disposed so that they are lined up from the front in the order of the second clutch CL2, the first clutch CL1, and the third clutch CL3. The combination of the first clutch CL1 and the second clutch CL2 and the third clutch CL3 face each other in the axial direction (front-rear direction) with the first gear set PG1 and the second gear set PG2 in between. In other words, the first to third clutches CL1 to CL3 are arranged in two groups, with the third clutch CL3 located on one axial side (rear side) of the first and second gear sets PG1 and PG2, and the remaining two clutches (the first and second gear sets CL1 and CL2) located on the other axial side (front side) of the same gear sets PG1 and PG2.

The first brake BR1 and the second brake BR2 are arranged separately in front of and behind the first to third clutches CL1 to CL3. Specifically, the first brake BR1 is arranged further forward of the second clutch CL2, which is the frontmost clutch. The second brake BR2 is arranged further rearward of the third clutch CL3, which is the rearmost clutch (and in front of the third gear set PG3).

The first clutch CL1 is a frictional fastening element that connects and disconnects the input shaft 12 and the first carrier C1 to and from the third sun gear S3. Specifically, the first clutch CL1 includes a rotatable cylindrical drum member 31 connected to the first carrier C1, a rotatable cylindrical hub member 32 connected to the third sun gear S3 via the power transmission members 21, 22, etc., a plurality of friction plates 33 arranged between the drum member 31 and the hub member 32, and a piston 34 that can press the friction plates 33 in the axial direction. The first clutch CL1 connects and disconnects the input shaft 12 and the first carrier C1 to and from the third sun gear S3 in response to the pressing of the piston 34 against the friction plates 33 or the release of the pressing. Here, the hub member 32 of the first clutch CL1 also serves as a hub member for the second clutch CL2 described later. For this reason, hereinafter, the hub member 32 is referred to as the common hub member 32.

The second clutch CL2 is a frictional fastening element that connects and disconnects the first ring gear R1 and the second sun gear S2 to and from the third sun gear S3. Specifically, the second clutch CL2 includes a rotatable cylindrical drum member 41 connected to the first ring gear R1 and the second sun gear S2 via the power transmission member 23, the above-mentioned common hub member 32 connected to the third sun gear S3 via the power transmission members 21, 22, etc., a plurality of friction plates 43 arranged between the drum member 41 and the hub member 32, and a piston 44 that can press the friction plates 43 in the axial direction. The second clutch CL2 connects and disconnects the first ring gear R1 and the second sun gear S2 to and from the third sun gear S3 in response to the pressing of the piston 44 against the friction plates 43 or the release of the pressing.

The third clutch CL3 is a frictional fastening element that connects and disconnects the second ring gear R2 and the third sun gear S3. Specifically, the third clutch CL3 includes a rotatable cylindrical drum member 51 connected to the third sun gear S3 via the power transmission member 22, a rotatable cylindrical hub member 52 connected to the second ring gear R2, a plurality of friction plates 53 arranged between the drum member 51 and the hub member 52, and a piston 54 that can press the friction plates 53 in the axial direction. The third clutch CL3 connects and disconnects the second ring gear R2 and the third sun gear S3 in response to the pressing of the piston 54 against the friction plates 53 or the release of the pressing.

The first brake BR1 is a frictional fastening element that connects and disconnects the transmission case 11 and the first sun gear S1 (more specifically, the front sun gear S1a). Specifically, the first brake BR1 includes a cylindrical drum member 61 fixed to the transmission case 11, a rotatable cylindrical hub member 62 connected to the front sun gear S1a via a power transmission member 17, a plurality of friction plates 63 arranged between the drum member 61 and the hub member 62, and a piston 64 that can press the friction plates 63 in the axial direction. The first brake BR1 connects and disconnects the transmission case 11 and the first sun gear S1 in response to the piston 64 pressing against the friction plates 63 or the release of the pressing force.

The second brake BR2 is a frictional fastening element that connects and disconnects the transmission case 11 and the third ring gear R3. Specifically, the second brake BR2 includes a cylindrical drum member 71 fixed to the transmission case 11, a rotatable cylindrical hub member 72 connected to the third ring gear R3, a plurality of friction plates 73 arranged between the drum member 71 and the hub member 72, and a piston 74 that can press the friction plates 73 in the axial direction. The second brake BR2 connects and disconnects the transmission case 11 and the third ring gear R3 in response to the piston 74 pressing against the friction plates 73 or the release of the pressing force.

The valve body 14 is a hydraulic circuit device that controls the engagement and release of each of the frictional engagement elements (clutches CL1 to CL3 and brakes BR1, BR2) described above. Although detailed illustration is omitted, for example, the valve body 14 includes multiple oil passages through which the oil supplied to each of the frictional engagement elements flows, and multiple solenoid valves that switch the flow of each oil passage.

In the automatic transmission 1 having the above-described structure, the first gear set PG1 and the second gear set PG2 correspond to the "intermediate planetary gear set" in the present invention, and the third gear set PG3 corresponds to the "outer planetary gear set" in the present invention. The power transmission member 21 corresponds to the "first connecting member" in the present invention, and the power transmission member 22 corresponds to the "second connecting member" or "downstream connecting member" in the present invention.

Figure 3 is an engagement table showing the relationship between the engagement/disengagement of each frictional engagement element and the gear position. As shown in this figure, in the automatic transmission 1 of this embodiment, nine gear positions, 1st to 8th forward gears and reverse gear, are achieved according to the selective engagement or disengagement of each frictional engagement element by the valve body 14 described above. In the engagement table of Figure 3, a circle indicates that the corresponding frictional engagement element is engaged, and a blank space indicates that the corresponding frictional engagement element is released (disengaged).

Specifically, each gear is achieved as follows. That is, first gear is achieved by engaging the first clutch CL1, the first brake BR1, and the second brake BR2. Second gear is achieved by engaging the second clutch CL2, the first brake BR1, and the second brake BR2. Third gear is achieved by engaging the first clutch CL1, the second clutch CL2, and the second brake BR2. Fourth gear is achieved by engaging the second clutch CL2, the third clutch CL3, and the second brake BR2. Fifth gear is achieved by engaging the first clutch CL1, the third clutch CL3, and the second brake BR2. Sixth gear is achieved by engaging the first clutch CL1, the second clutch CL2, and the third clutch CL3. Seventh gear is achieved by engaging the first clutch CL1, the third clutch CL3, and the first brake BR1. Eighth gear is achieved by engaging the second clutch CL2, the third clutch CL3, and the first brake BR1. Reverse gear is achieved by engaging the third clutch CL3, the first brake BR1, and the second brake BR2.

[Detailed structure of each clutch]
Next, the structure of each of the above-mentioned clutches CL1 to CL3 will be described in more detail. FIG. 4 is an enlarged cross-sectional view of a part of FIG. 2. As shown in FIGS. 2 and 4, the first clutch CL1 includes a piston support member 35, a partition member 36, and a return spring 37 in addition to the above-mentioned drum member 31, common hub member 32, friction plate 33, and piston 34. The piston support member 35 is a member that supports the piston 34 so that it can move in the axial direction. The return spring 37 is a spring that urges the piston 34 in a release direction (a direction away from the friction plate 33; rearward in this case). The partition member 36 is a member that serves to make the space in which the return spring 37 is disposed a hydraulic chamber (a centrifugal balance chamber 39 described later).

The drum member 31 includes a peripheral wall portion 31a extending in the axial direction (front-rear direction) on the radial outside of the friction plate 33, and a vertical wall portion 31b extending radially inward from the rear end of the peripheral wall portion 31a. The vertical wall portion 31b is joined to the first carrier C1 by, for example, welding its radially inner end portion to the axial middle portion of the first carrier C1.

The common hub member 32 includes a peripheral wall portion 32a extending in the axial direction (front-rear direction), a vertical wall portion 32b extending radially inward from the front of the peripheral wall portion 32a, and a shaft portion 32c extending forward from the radially inner end of the vertical wall portion 32b. The peripheral wall portion 32a has a rear peripheral wall 32a1 and a front peripheral wall 32a2 that are continuous in the axial direction. The rear peripheral wall 32a1 is disposed so as to face the peripheral wall portion 31a of the drum member 31 from the radially inner side, and the front peripheral wall 32a2 is disposed so as to face the peripheral wall portion 41a of the drum member 41 from the radially inner side. The rear peripheral wall 32a1 functions as a hub that holds the friction plates 33 (hub-side friction plates 33b, described in more detail below) of the first clutch CL1, and the front peripheral wall 32a2 functions as a hub that holds the friction plates 43 (hub-side friction plates 43b, described in more detail below) of the second clutch CL2.

The peripheral wall portion 32a (rear peripheral wall 32a1) extends rearward to a position surrounding the outer periphery of the front portion of the first pinion P1. In other words, the first gear set PG1 is disposed close to the first clutch CL1 so that the front portion of the first pinion P1 fits inside the common hub member 32. In this way, the first clutch CL1 and the first gear set PG1 are disposed side by side in the fore-and-aft direction with a partial overlap when viewed in the radial direction.

The friction plates 33 include a plurality of drum-side friction plates 33a that engage with the inner peripheral surface of the peripheral wall portion 31a of the drum member 31, and a plurality of hub-side friction plates 33b that engage with the outer peripheral surface of the peripheral wall portion 32a of the common hub member 32. Each drum-side friction plate 33a is attached to the drum member 31 in a state in which it can rotate integrally with the drum member 31 and can move axially by having its outer peripheral edge spline-fitted to the peripheral wall portion 31a of the drum member 31. Each hub-side friction plate 33b is attached to the common hub member 32 in a state in which it can rotate integrally with the common hub member 32 and can move axially by having its inner peripheral edge spline-fitted to the rear peripheral wall 32a1 of the peripheral wall portion 32a of the common hub member 32. The drum-side friction plates 33a and the hub-side friction plates 33b are attached to the drum member 31 and the common hub member 32, respectively, in a state in which they are alternately arranged in the axial direction.

The piston 34 includes a pressing portion 34a that faces the friction plate 33 from the rear, an extension portion 34b that extends forward from the radially inner end of the pressing portion 34a, and a pressure-receiving portion 34c that extends radially inward from the front end of the extension portion 34b. The piston 34 is held by the drum member 31 in a state in which it can rotate integrally with the drum member 31 and can move axially by having the pressing portion 34a spline-fitted into the peripheral wall portion 31a of the drum member 31.

The piston support member 35 includes a support portion 35a that is formed in a hook shape in cross section to follow the shape of the pressure receiving portion 34c of the piston 34, and a shaft portion 35b that extends forward from the radially inner end of the support portion 35a. The piston 34 is supported by the piston support member 35 in a state in which it can move axially by fitting the pressure receiving portion 34c into the piston support member 35 from the front.

The piston support member 35 is connected to the first carrier C1 by, for example, welding the rear surface of its support portion 35a to the front end portion of the first carrier C1. Here, the first carrier C1 is connected not only to the piston support member 35, but also to the drum member 31 as described above. In addition, the piston 34 is engaged with the drum member 31 so that it cannot rotate relative to the drum member 31. As a result, the first carrier C1, drum member 31, piston 34, and piston support member 35 all rotate at the same rotational speed.

Openings h1 are formed in the extension portion 34b of the piston 34. The openings h1 are provided to avoid interference with the first pinion P1, and are provided at multiple locations in the circumferential direction corresponding to the first pinion P1.

A fastening hydraulic chamber 38 is formed between the pressure receiving portion 34c of the piston 34 and the piston support member 35. The hydraulic pressure supplied to the fastening hydraulic chamber 38 acts as a force pushing the pressure receiving portion 34c forward. As a result, the pressing portion 34a of the piston 34 presses the friction plate 33, and the first clutch CL1 is engaged.

The partition member 36 is disposed adjacent to the front side of the pressure receiving portion 34c of the piston 34. A centrifugal balance chamber 39 is formed between the partition member 36 and the pressure receiving portion 34c. The centrifugal balance chamber 39 is a hydraulic chamber for canceling hydraulic fluctuations caused by centrifugal forces acting on the fastening hydraulic chamber 38. The centrifugal balance chamber 39 is formed to face the fastening hydraulic chamber 38 across the pressure receiving portion 34c.

The return spring 37 is disposed in the centrifugal balance chamber 39. The return spring 37 is sandwiched between the pressure-receiving portion 34c of the piston 34 and the partition member 36, and exerts a resilient force that separates the piston 34 and the partition member 36 from each other. This resilient force constantly urges the piston 34 in the release direction, i.e., backward, away from the friction plate 33. When the first clutch CL1 is engaged, the required hydraulic pressure is supplied to the engagement hydraulic chamber 38 so that the piston 34 is pressed forward (in the engagement direction) against the urging force of the return spring 37.

The common hub member 32 and the piston support member 35 are rotatably supported on the outer periphery of a common boss member 80 in a state where they are aligned in the axial direction so that the vertical wall portion 32b of the common hub member 32 is in front of the piston support member 35. The boss member 80 is a cylindrical member concentric with the input shaft 12 and is fixed to the transmission case 11. The common hub member 32 is supported rotatably about the axis X of the automatic transmission 1 by having its shaft portion 32c inserted into the boss member 80. Similarly, the piston support member 35 is supported rotatably about the axis X by having its shaft portion 35b inserted into the boss member 80. The shaft portion 32c of the common hub member 32 and the shaft portion 35b of the piston support member 35 are adjacent to each other in the axial direction, and a thrust bearing 81 is disposed between them. The common hub member 32 and the piston support member 35 are supported so as to be rotatable relative to each other across the thrust bearing 81.

The power transmission member 17 is coaxially inserted into the boss member 80, and the input shaft 12 is coaxially inserted into the power transmission member 17. The input shaft 12 and the power transmission member 17 are supported so as to be capable of relative rotation about a common axis X. The rear end of the power transmission member 17 is connected to the inner circumferential surface of the first sun gear S1 (more specifically, the front sun gear S1a) by spline fitting. The rear end of the input shaft 12 is connected to the inner circumferential surface of the power transmission member 18 by spline fitting.

An oil passage e1 extending in the axial direction is formed inside the boss member 80. An oil passage e2 communicating with the oil passage e1 is formed in the piston support member 35. The oil passage e2 communicates with the fastening hydraulic chamber 38. The piston 34 is pressed against the friction plate 33 or the pressure is released by supplying and discharging hydraulic pressure to the fastening hydraulic chamber 38 through the oil passage e2. When the piston 34 is pressed against the friction plate 33, the drum side friction plate 33a and the hub side friction plate 33b are in close contact with each other so that they cannot rotate relative to each other, and the first clutch CL1 is in a fastened state. When the pressure on the friction plate 33 by the piston 34 is released, the drum side friction plate 33a and the hub side friction plate 33b are allowed to rotate relative to each other, and the first clutch CL1 is in a released state.

Although not shown, the piston support member 35 also has an oil passage that connects the centrifugal balance chamber 39 to the internal oil passage e1 of the boss member 80. Through this oil passage, oil pressure is supplied to the centrifugal balance chamber 39 to cancel hydraulic pressure fluctuations in the fastening hydraulic chamber 38 caused by centrifugal force. Here, the oil passage e1 of the boss member 80 includes multiple independent unit oil passages that are spaced apart in the circumferential direction. The oil passage that connects to the centrifugal balance chamber 39 and the oil passage e2 that connects to the fastening hydraulic chamber 38 described above are formed to connect to different unit oil passages. This is also true for the oil passage e3 for the fastening hydraulic chamber 48 and the oil passage for the centrifugal balance chamber 49, which will be described later.

The second clutch CL2 includes the drum member 41, common hub member 32, friction plate 43, and piston 44 described above, as well as a piston support member 45, a partition member 46, and a return spring 47. The piston support member 45 is a member that supports the piston 44 so that it can move axially. The return spring 47 is a spring that urges the piston 44 in the release direction (the direction away from the friction plate 43; forward in this case). The partition member 46 is a member that turns the space in which the return spring 47 is located into a hydraulic chamber (a centrifugal balance chamber 49 described later).

The drum member 41 includes a peripheral wall portion 41a extending in the axial direction (front-rear direction) on the radial outside of the friction plate 43, and a vertical wall portion 41b extending radially inward from the rear end of the peripheral wall portion 41a. The vertical wall portion 41b is connected to the radially outer end of the power transmission member 23. The power transmission member 23 is connected to the first ring gear R1 by welding or the like, and is connected to the second sun gear S2 by spline fitting. In other words, the power transmission member 23 connects the first ring gear R1, the second sun gear S2, and the drum member 41 to each other.

The friction plates 43 include a plurality of drum-side friction plates 43a that engage with the inner circumferential surface of the peripheral wall portion 41a of the drum member 41, and a plurality of hub-side friction plates 43b that engage with the outer circumferential surface of the peripheral wall portion 32a of the common hub member 32. Each drum-side friction plate 43a is attached to the drum member 41 in a state in which it can rotate integrally with the drum member 41 and can move axially by having its outer circumferential edge spline-fitted to the peripheral wall portion 41a of the drum member 41. Each hub-side friction plate 43b is attached to the common hub member 32 in a state in which it can rotate integrally with the common hub member 32 and can move axially by having its inner circumferential edge spline-fitted to the front peripheral wall 32a2 of the peripheral wall portion 32a of the common hub member 32. The drum-side friction plates 43a and the hub-side friction plates 43b are attached to the drum member 41 and the common hub member 32, respectively, in a state in which they are alternately arranged in the axial direction.

The piston 44 includes a pressing portion 44a and a pressure-receiving portion 44b located radially inside the pressing portion 44a. The pressing portion 44a is disposed so as to face the friction plate 43 from the front. The pressure-receiving portion 44b is disposed so as to face the vertical wall portion 32b of the common hub member 32 from the front.

The piston support member 45 is rotatably supported on the outer periphery of the shaft portion 32c of the common hub member 32. The piston 44 is supported by the piston support member 45 in a state in which it can move axially by fitting its pressure-receiving portion 44b into the piston support member 45 from the rear.

A fastening hydraulic chamber 48 is formed between the pressure-receiving portion 44b of the piston 44 and the piston support member 45. The hydraulic pressure supplied to the fastening hydraulic chamber 48 acts as a force pushing the pressure-receiving portion 44b rearward. As a result, the pressing portion 44a of the piston 44 presses the friction plate 43, and the second clutch CL2 is engaged.

The partition member 46 is provided to seal between the pressure receiving portion 44b of the piston 44 and the vertical wall portion 32b of the common hub member 32. This forms a centrifugal balance chamber 49 between the pressure receiving portion 44b and the vertical wall portion 32b. The centrifugal balance chamber 49 is a hydraulic chamber for canceling hydraulic fluctuations caused by centrifugal forces acting on the fastening hydraulic chamber 48. The centrifugal balance chamber 49 is formed to face the fastening hydraulic chamber 48 across the pressure receiving portion 44b.

The return spring 47 is disposed in the centrifugal balance chamber 49. The return spring 47 is sandwiched between the pressure-receiving portion 44b of the piston 44 and the vertical wall portion 32b of the common hub member 32, and constantly biases the piston 44 forward (in the disengagement direction). When the second clutch CL2 is engaged, the required hydraulic pressure is supplied to the engagement hydraulic chamber 48 so that the piston 44 is pressed backward (in the engagement direction) against the biasing force of the return spring 47.

An oil passage e3 is formed in the shaft portion 32c of the common hub member 32, which communicates with the internal oil passage e1 of the boss member 80. The oil passage e3 communicates with the fastening hydraulic chamber 48. The piston 44 is pressed against the friction plate 43 or the pressure is released by supplying and discharging hydraulic pressure to the fastening hydraulic chamber 48 through the oil passage e3. When the piston 44 is pressed against the friction plate 43, the drum side friction plate 43a and the hub side friction plate 43b are in close contact with each other and cannot rotate relative to each other, and the second clutch CL2 is in a fastened state. When the pressure on the friction plate 43 by the piston 44 is released, the drum side friction plate 43a and the hub side friction plate 43b are allowed to rotate relative to each other, and the second clutch CL2 is in a released state.

Although not shown, an oil passage is also formed in the shaft portion 32c of the common hub member 32, connecting the centrifugal balance chamber 49 to the internal oil passage e1 of the boss member 80. Through this oil passage, oil pressure is supplied to the centrifugal balance chamber 49 to cancel oil pressure fluctuations in the fastening oil pressure chamber 48 caused by centrifugal force.

Figure 5 is an exploded perspective view of the third clutch CL3. As shown in this Figure 5 and the previous Figures 2 and 4, the third clutch CL3 includes a return spring 57 in addition to the drum member 51, hub member 52, friction plate 53, and piston 54 described above. The return spring 47 is a spring that biases the piston 54 in the release direction (the direction away from the friction plate 43; rearward in this case).

The drum member 51 includes a peripheral wall portion 51a extending in the axial direction (front-rear direction) on the radial outside of the friction plate 53, a vertical wall portion 51b extending radially inward from the rear end of the peripheral wall portion 51a, and an inner protrusion 51c extending forward from the radially inner end of the vertical wall portion 51b. As shown in FIG. 5, the inner protrusions 51c are a number of protrusions arranged at regular intervals in the circumferential direction along the inner edge of the vertical wall portion 51b, and are formed in a comb-like shape. Each inner protrusion 51c is positioned so as to penetrate the piston 54 through an opening h2, which will be described later.

The front end of the peripheral wall portion 51a of the drum member 51 is connected to the rear end of the power transmission member 21. Specifically, the power transmission member 21 includes a peripheral wall portion 21a extending in the axial direction (front-rear direction) and a vertical wall portion 21b extending radially inward from the front end of the peripheral wall portion 21a. The vertical wall portion 21b is formed to extend radially in front of the first and second clutches CL1, CL2. The peripheral wall portion 21a extends in the axial direction radially outside the first and second clutches CL1, CL2 and is disposed so as to face the peripheral wall portion 51a of the drum member 51. The radially inner end of the vertical wall portion 21b is spline-fitted to the outer circumferential surface of the shaft portion 32c of the common hub member 32 (the hub member 32 shared by the first and second clutches CL1 and CL2), and the rear end of the peripheral wall portion 21a is spline-fitted to the front end of the peripheral wall portion 51a of the drum member 51. In other words, the drum member 51 is connected to the common hub member 32 via the power transmission member 21.

The inner protrusion 51c of the drum member 51 is connected to the radially inner end of the power transmission member 22. Specifically, the power transmission member 22 includes a vertical wall portion 22a facing the piston 54 from the front, a flange portion 22b extending rearward from the radially outer end of the vertical wall portion 22a, and a shaft portion 22c extending rearward from the radially inner end of the vertical wall portion 22a. The shaft portion 22c is formed to extend in the axial direction (front-rear direction) on the radially inner side of the piston 54. The rear end of the shaft portion 22c is connected to the inner peripheral surface of the third sun gear S3 by spline fitting, and the flange portion 22b is connected to the inner protrusion 51c of the drum member 51 by welding or the like. In other words, the drum member 51 is connected to the third sun gear S3 via the power transmission member 22.

As described above, the drum member 51 is connected to the common hub member 32 and the third sun gear S3 via the power transmission members 21 and 22, respectively. This means that the first clutch CL1, the second clutch CL2, and the third clutch CL3 are connected to the rotating elements of the same planetary gear set. In other words, the common hub member 32 of the first and second clutches CL1 and CL2 is connected to the drum member 51 of the third clutch CL3 via the power transmission member 21, and the drum member 51 of the third clutch CL3 is connected to the third sun gear S3 via the power transmission member 22, so that the first to third clutches CL1 to CL3 are connected to the common third sun gear S3.

The power transmission member 22 is rotatably supported by the bearing 92 inside the partition wall portion 112 of the transmission case 11. That is, the transmission case 11 includes a drum-shaped case body 111 and the partition wall portion 112 that protrudes radially inward from the case body 111. The partition wall portion 112 is provided between the third clutch CL3 and the second brake BR2 in the axial direction. The partition wall portion 112 has a boss portion 113 that extends in the axial direction at its radially inner end. The boss portion 113 includes a front boss 113a that protrudes forward and a rear boss 113b that protrudes rearward. The rear boss 113b is located slightly radially outward from the front boss 113a, and the bearing 92 is disposed between the rear boss 113b and the shaft portion 22c of the power transmission member 22.

The power transmission member 16 is coaxially inserted into the power transmission member 22, and the power transmission member 15 is coaxially inserted into the power transmission member 16. The front end of the power transmission member 15 is connected to the inner peripheral surface of the first sun gear S1 (specifically, the rear sun gear S1b) by spline fitting. The front end of the power transmission member 16 is connected to the second carrier C2 via the auxiliary connecting member 90.

The hub member 52 includes a peripheral wall portion 52a extending in the axial direction (front-rear direction) and a support body 52b supporting the peripheral wall portion 52a. The support body 52b is fitted onto the power transmission member 16 so as to be rotatable relative to the power transmission member 16. The support body 52b has a vertical wall extending radially outward from the outer periphery of the power transmission member 16. The peripheral wall portion 52a is joined to the rear surface of the vertical wall of the support body 52b by welding or the like so as to protrude rearward from the vertical wall. The peripheral wall portion 52a faces the peripheral wall portion 51a of the drum member 51 from the radially inner side. The hub member 52 is joined to the second ring gear R2 by, for example, welding the radially outer end of the support body 52b to the rear end of the second ring gear R2.

The friction plates 53 include a plurality of drum-side friction plates 53a that engage with the inner peripheral surface of the peripheral wall portion 51a of the drum member 51, and a plurality of hub-side friction plates 53b that engage with the outer peripheral surface of the peripheral wall portion 52a of the hub member 52. Each drum-side friction plate 53a is attached to the drum member 51 in a state in which it can rotate integrally with the drum member 51 and can move axially by having its outer peripheral edge spline-fitted to the peripheral wall portion 51a of the drum member 51. Each hub-side friction plate 53b is attached to the hub member 52 in a state in which it can rotate integrally with the hub member 52 and can move axially by having its inner peripheral edge spline-fitted to the peripheral wall portion 52a of the hub member 52. The drum-side friction plates 53a and the hub-side friction plates 53b are attached to the drum member 51 and the hub member 52, respectively, in a state in which they are alternately arranged in the axial direction.

The piston 54 includes a main piston 54a arranged behind the friction plate 53, a sub-piston 54b arranged further behind the main piston 54a, and a bearing 54c arranged between the main piston 54a and the sub-piston 54b. The main piston 54a is a piston part that directly presses the friction plate 53. The sub-piston 54b is a piston part that moves in the axial direction when hydraulic pressure is supplied to a fastening hydraulic chamber 58 (described later). The bearing 54c is a bearing that connects the main piston 54a and the sub-piston 54b while allowing the main piston 54a to rotate relative to the sub-piston 54b. In other words, the piston 54 is a composite piston that combines two piston parts (the main piston 54a and the sub-piston 54b) that can move together in the axial direction and rotate relative to each other.

The sub-piston 54b is supported by the partition wall 112 of the transmission case 11. Specifically, the sub-piston 54b is supported by the partition wall 112 in a state in which it can move in the axial direction along the outer circumferential surface of the front boss 113a of the partition wall 112. However, the sub-piston 54b cannot rotate relative to the partition wall 112 (transmission case 11). In other words, the sub-piston 54b is supported by the transmission case 11 in a state in which it can move in the axial direction but cannot rotate around its axis.

The main piston 54a is supported forward of the sub-piston 54b along the outer circumferential surface of the front boss 113a of the partition wall 112 so as to be movable in the axial direction. The main piston 54a has a pressing portion 54a1 that faces the friction plate 53 from the rear. The pressing portion 54a1 is spline-fitted to the peripheral wall portion 51a of the drum member 51, so that the main piston 54a is held by the drum member 51 in a state in which it can rotate integrally with the drum member 51 and can move in the axial direction.

Openings h2 are formed at multiple locations in the circumferential direction of the main piston 54a. The multiple openings h2 are provided at positions radially inward of the pressing portion 54a1 of the main piston 54a (at the radial middle portion of the main piston 54a), and are arranged at regular intervals in the circumferential direction (see FIG. 5 in particular). The multiple openings h2 are also provided at positions corresponding to the multiple inner protrusions 51c of the drum member 51, and are formed to be able to receive the multiple inner protrusions 51c, respectively. That is, the inner protrusions 51c of the drum member 51 penetrate the main piston 54a in the axial direction through the openings h2 of the main piston 54a. Then, with the inner protrusions 51c penetrating the main piston 54a (inserted through the openings h2), the flange portion 22b of the power transmission member 22 is joined to the front end of the inner protrusions 51c by welding or the like. In other words, the drum member 51 is connected to the power transmission member 22 while intersecting the main piston 54a in a three-dimensional manner.

An engagement hydraulic chamber 58 is formed between the sub-piston 54b and the partition wall 112 of the transmission case 11. The hydraulic pressure supplied to the engagement hydraulic chamber 58 acts as a force pushing the sub-piston 54b forward. In response to this force, the sub-piston 54b moves forward, and the main piston 54a moves forward together with the sub-piston 54b. As a result, the pressing portion 54a1 of the main piston 54a presses the friction plate 53, and the third clutch CL3 is engaged.

An oil passage e4 that communicates with the engagement hydraulic chamber 58 is formed in the partition wall portion 112 of the transmission case 11. By supplying and discharging hydraulic pressure to the engagement hydraulic chamber 58 through the oil passage e4, the piston 54 (more specifically, the main piston 54a) is pressed against the friction plate 53 or the pressure is released. When the piston 54 is pressed against the friction plate 53, the drum side friction plate 53a and the hub side friction plate 53b are tightly attached so that they cannot rotate relative to each other, and the third clutch CL3 is in an engaged state. When the pressure on the friction plate 53 by the piston 54 is released, the drum side friction plate 53a and the hub side friction plate 53b are allowed to rotate relative to each other, and the third clutch CL3 is in a released state.

The return spring 57 is arranged so as to be sandwiched between the vertical wall portion 22a of the power transmission member 22 and the main piston 54a. Such a return spring 57 exerts a resilient force that separates the main piston 54a and the vertical wall portion 22a from each other. Due to this resilient force, the piston 54 is constantly urged in the release direction, i.e., backward, away from the friction plate 53. When the third clutch CL3 is engaged, the required hydraulic pressure is supplied to the engagement hydraulic chamber 58 so that the piston 54 is pressed forward (in the engagement direction) against the urging force of this return spring 57.

The axial position of the return spring 57 is set at a position where at least a part of the return spring 57 is hidden inside the friction plate 53, in other words, at a position where the return spring 57 and the friction plate 53 overlap each other when viewed in the radial direction. In this embodiment, the axial position of the return spring 57 is set so that most of the rear side of the friction plate 53 and most of the front side of the return spring 57 overlap each other when viewed in the radial direction. In addition, the radial position of the return spring 57 is set at a position where the return spring 57 faces the bearing 54c with the main piston 54a in between.

Here, the engagement hydraulic chamber 58 for the third clutch CL3 is a non-rotating hydraulic chamber formed between a part of the transmission case 11 (partition wall portion 112) and the sub-clutch 48b, so the internal hydraulic pressure is not affected by centrifugal force. Therefore, unlike the first and second clutches CL1 and CL2 described above, the third clutch CL3 does not have a centrifugal balance chamber.

[Action and Effect]
As described above, the automatic transmission 1 of this embodiment includes the first to third clutches CL1 to CL3 arranged in the front-rear direction along the axis X, the first and second gear sets PG1 and PG2 arranged between the third clutch CL3 located at the rearmost position among them and the other two clutches (i.e., the first and second clutches CL1 and CL2), and the third gear set PG3 arranged further rearward of the third clutch CL3. In addition, all of the first to third clutches CL1 to CL3 are connected to the third sun gear S3 of the third gear set PG3. This configuration has the advantage that the mass of the rotating parts connected to the third sun gear S3 can be reduced, and the shift response of the automatic transmission 1 can be improved.

Figure 6 is a diagram equivalent to Figure 4, in which the rotating parts connected to the third sun gear S3 and rotating together with the third sun gear S3 are shown in color. As shown in Figure 6, in the above embodiment, the rotating parts rotating together with the third sun gear S3 are mainly the common hub member 32 of the first and second clutches CL1 and CL2, the piston 44 and piston support member 45 of the second clutch CL2, the drum member 51 and main piston 54a of the third clutch CL3, the power transmission member 21 connecting the common hub member 32 and the drum member 51, and the power transmission member 22 connecting the drum member 51 and the third sun gear S3. In the above embodiment, the third clutch CL3 is disposed between the first and second gear sets PG1 and PG2 and the third gear set PG3, so that the power transmission path can be simplified and the mass of the rotating parts constituting the power transmission path can be reduced, for example, compared to the comparative example shown below.

Figure 7 is a cross-sectional view showing the structure of a comparative example in which the arrangement of clutches, etc. is different from that of the above embodiment. The automatic transmission 1' of this comparative example is equipped with a first clutch CL1', a second clutch CL2', and a third clutch CL3' as clutches corresponding to the first clutch CL1, the second clutch CL2, and the third clutch CL3, respectively, of the above embodiment. The automatic transmission 1' of the comparative example is also equipped with a first gear set PG1', a second gear set PG2', and a third gear set PG3' as clutches corresponding to the first gear set PG1, the second gear set PG2, and the third gear set PG3, respectively, of the above embodiment. Unlike the above embodiment, the comparative example does not adopt a layout in which the clutches and gear sets are alternately arranged in the axial direction. That is, in the comparative example, the second clutch CL2', the first clutch CL1', and the third clutch CL3' are arranged in that order from the front, and the first to third gear sets PG1' to PG3' are arranged in that order behind the rearmost third clutch CL3'. Note that the third clutch CL3' and the first gear set PG1' are arranged so as to partially overlap, but unlike the above embodiment, no gear set is arranged between the two clutches.

In the automatic transmission 1' of the comparative example, the rotating parts that rotate integrally with the third sun gear S3' of the third gear set PG3' are mainly the drum member 51' and piston 54' of the third clutch CL3', the hub member 31', piston 34' and piston support member 35' of the first clutch CL1', the hub member 42', piston 44' and piston support member 45' of the second clutch CL2', and the two power transmission members 21', 22' that connect the hub member 42' and the third sun gear S3'. In FIG. 7, these rotating parts are shown in color in the same manner as in FIG. 6 described above. As shown in FIG. 7, in the comparative example, the drum member 51' of the third clutch CL3' is disposed radially inward of the power transmission member 21'. Also, the drum member 51' is the rotating part that is farthest from the third sun gear S3' on the power transmission path. In order to transmit the rotation of the drum member 51' to the third sun gear S3', in the comparative example, the drum member 51' of the third clutch CL3' is connected to the hub member 42' of the second clutch CL2'. Specifically, the shaft portion 51a' of the drum member 51' is significantly extended forward, and the front end of the shaft portion 51a', which is enlarged (lengthened) due to the extension, is inserted into the hollow shaft portion 42a' of the hub member 42' and coupled. In this way, in the comparative example, the enlargement of the drum member 51' or the lengthening of the power transmission path is unavoidable, so the mass of the colored rotating parts that rotate integrally with the third sun gear S3' tends to be large as a whole. In the comparative example, the hub member 31' of the first clutch CL1' is integrated with the drum member 51' of the third clutch CL3', which reduces the weight to some extent, but the influence of the above-mentioned circumstances is large, and the mass of the rotating parts is still likely to increase.

In contrast, in the embodiment shown in FIG. 6, as is clear from a comparison with FIG. 7 (comparative example), the power transmission path to the third sun gear S3 is simple, and the axial dimension of the drum member 51 of the third clutch CL3 is relatively small. This makes it possible to reduce the mass of the colored rotating parts including the drum member 51, thereby improving the shift response of the automatic transmission 1. If the mass of the rotating parts rotating together with the third sun gear S3 is large, the inertia of the rotating parts may slow down the rotation change of the third sun gear S3 during a shift in which the rotation speed of the third sun gear S3 changes suddenly, and the shift response may deteriorate. In contrast, according to the above embodiment in which the mass of the rotating parts rotating together with the third sun gear S3 can be reduced, the rotation speed of the third sun gear S3 can be changed quickly during a shift, improving the shift response.

Even in the comparative example of FIG. 7, for example, if at least some of the colored rotating parts are replaced with lightweight parts such as aluminum die-cast parts, it is possible to reduce the mass of the rotating parts and improve the gear shift response. However, in this case, an increase in the unit price of the parts is unavoidable, which is not desirable in terms of manufacturing costs. In contrast, in the above embodiment, the size (volume) of the rotating parts is itself sufficiently smaller than in the comparative example, so the mass of the rotating parts can be kept low without making modifications that increase costs as described above, and good gear shift response can be achieved while suppressing manufacturing costs.

In addition, in the above embodiment, the drum member 31 and piston support member 35 of the first clutch CL1 are connected to the first carrier C1, so that the piston 34 and piston support member 35 can be mechanically separated from the third sun gear S3. That is, the piston 34 and piston support member 35 rotate integrally with the first carrier C1, but do not rotate integrally with the third sun gear S3. In this way, in the above embodiment, the piston 34 and piston support member 35 are excluded from the group of rotating parts that rotate integrally with the third sun gear S3, so that the mass of the group of rotating parts can be further reduced compared to the comparative example of FIG. 7 in which the corresponding piston 34' and piston support member 35' rotate integrally with the third sun gear S3', and the shift response can be effectively improved.

In the above embodiment, the piston 54 of the third clutch CL3 is a composite piston that combines two piston parts (main piston 54a and sub-piston 54b) that can rotate relative to each other, so that the centrifugal balance chamber can be omitted, unlike the other first and second clutches CL1 and CL2. That is, the piston 54 of the third clutch CL3 includes a sub-piston 54b that is supported by the partition wall portion 112 of the transmission case 11 and defines an engagement hydraulic chamber 58 between the partition wall portion 112 and the sub-piston 54b, a rotatable main piston 54a that is arranged in a position axially opposite to the sub-piston 54b and presses the friction plate 53, and a bearing 54c that connects the main piston 54a and the sub-piston 54b so that they can rotate relative to each other. In this case, the members that form the engagement hydraulic chamber 58 (the partition wall portion 112 and the sub-piston 54b) do not rotate, and centrifugal force does not act on the engagement hydraulic chamber 58. This means that the centrifugal balance chamber, which is a hydraulic chamber for canceling the effect of the centrifugal force, can be omitted. In other words, there is no need to provide a chamber equivalent to the centrifugal balance chambers 39, 49 for the other clutches CL1, CL2 at a position opposite the engagement hydraulic chamber 58 across the piston 54 (main piston 54a). Therefore, the structure of the hydraulic supply system can be simplified while ensuring the controllability of the piston 54 by the hydraulic pressure supplied to the engagement hydraulic chamber 58.

In the above embodiment, the drum member 51 of the third clutch CL3 is provided with a comb-tooth shaped inner protrusion 51c, and an opening h2 through which the inner protrusion 51c is inserted is formed in the main piston 54a of the piston 54. The inner protrusion 51c is coupled to the power transmission member 22 in a state where it penetrates the main piston 54a. With this configuration, the pressing portion 54a1 of the main piston 54a is disposed inside the drum member 51 to enable the pressing portion 54a1 to press the friction plate 53, while the drum member 51 can be connected to the third sun gear S3 via the power transmission member 22.

In addition, in the above embodiment, the return spring 57 of the third clutch CL3 is arranged so as to overlap the friction plate 53 on the radial inner side of the friction plate 53 when viewed in the radial direction. With this configuration, the axial dimension of the third clutch CL3 can be shortened, and the automatic transmission 1 can be made more compact in the axial direction.

In addition, in the above embodiment, the return spring 57 is disposed at a position facing the bearing 54c across the main piston 54a. With this configuration, it is possible to realize a rational arrangement in which the bearing 54c, which pushes the main piston 54a forward (fastening direction), and the return spring 57, which pushes the main piston 54a back (releasing direction), face each other in the axial direction.

[Modification]
Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention.

For example, in the above embodiment, the hub members of the first clutch CL1 and the second clutch CL2 are shared by a common hub member 32, but dedicated hub members may be prepared for each of the first clutch CL1 and the second clutch CL2.

In the above embodiment, two gear sets consisting of the first gear set PG1 and the second gear set PG2 are arranged between the first and second clutches CL1, CL2 and the third clutch CL3, but the number of gear sets arranged between the first and second clutches CL1, CL2 and the third clutch CL3 is not limited to two, and may be one or three or more.

In the above embodiment, a double sun gear type planetary gear set in which the sun gear S1 is divided into two in the axial direction is used as the first gear set PG1, but the first gear set PG1 may be a gear set similar to the other second to fourth gear sets PG2 to PG4 (i.e., a normal type gear set in which the sun gear is not divided in the axial direction).

In the above embodiment, an example was described in which the present invention was applied to a longitudinally mounted automatic transmission mounted on a FR (front engine, rear drive) vehicle, but the automatic transmissions to which the present invention can be applied are not limited to longitudinally mounted automatic transmissions, and the present invention can also be applied to a transversely mounted automatic transmission mounted on a FF (front engine, front drive) vehicle.

1 Automatic transmission CL1 First clutch CL2 Second clutch CL3 Third clutch PG1 First planetary gear set (intermediate planetary gear set)
PG2 2nd planetary gear set (intermediate planetary gear set)
PG3 3rd planetary gear set (outer planetary gear set)
S3 Third sun gear (common rotating element)
21 Power transmission member (first connecting member)
22 Power transmission member (second connecting member; downstream connecting member)
32 Common hub member (hub member of first clutch and second clutch)
33 Friction plate (of first clutch) 43 Friction plate (of second clutch) 51 Drum member (of third clutch) 51a Circumferential wall portion 51b Vertical wall portion 51c Inner protrusion 53 Friction plate (of third clutch) 54 Piston (of third clutch) 54a Main piston 54a1 Pressing portion 54b Sub-piston 54c Bearing 57 Return spring 58 Fastening hydraulic chamber h2 Opening (of piston)

Claims (5)

A first clutch and a second clutch arranged in an axial direction;
a third clutch disposed on one axial side of the first and second clutches;
an intermediate planetary gear set disposed between the first and second clutches and the third clutch;
an outer planetary gear set disposed on one axial side of the third clutch;
a connecting member connecting the first clutch, the second clutch, and the third clutch to a common rotating element included in the outer planetary gear set ,
Each of the first clutch and the second clutch includes a plurality of friction plates arranged in an axial direction and a cylindrical hub member that engages with inner peripheral edges of the friction plates,
The third clutch includes a plurality of friction plates arranged in an axial direction and a cylindrical drum member that engages with an outer circumferential edge of the friction plates,
the connecting member includes a first connecting member that connects the hub members of the first and second clutches and the drum member of the third clutch, and a second connecting member that connects the drum member of the third clutch to the common rotating element . 2. The automatic transmission according to claim 1,
The third clutch includes a plurality of friction plates arranged in an axial direction, a cylindrical drum member that engages with outer peripheral edges of the friction plates, and a piston that presses the friction plates in the axial direction,
the piston includes a sub-piston supported by a transmission case to define an engagement hydraulic chamber between the piston and the transmission case, a rotatable main piston disposed axially opposite the sub-piston and pressing the friction plates, and a bearing connecting the sub-piston and the main piston so as to be rotatable relative to one another. A first clutch and a second clutch arranged in an axial direction;
a third clutch disposed on one axial side of the first and second clutches;
an intermediate planetary gear set disposed between the first and second clutches and the third clutch;
an outer planetary gear set disposed on one axial side of the third clutch;
a connecting member connecting the first clutch, the second clutch, and the third clutch to a common rotating element included in the outer planetary gear set,
The third clutch includes a plurality of friction plates arranged in an axial direction, a cylindrical drum member that engages with outer peripheral edges of the friction plates, and a piston that presses the friction plates in the axial direction,
the drum member includes a peripheral wall portion extending in the axial direction on the radially outer side of the friction plate and engaging with an outer circumferential edge of the friction plate, a vertical wall portion extending radially inward from one axial end of the peripheral wall portion, and a plurality of inner protrusions extending from a radially inner end of the vertical wall portion to the other axial side,
the piston includes a sub-piston supported by a transmission case to define an engagement hydraulic chamber between the transmission case and the sub-piston, a rotatable main piston disposed axially opposite the sub-piston and pressing the friction plate, and a bearing connecting the sub-piston and the main piston so as to be rotatable relative to each other;
the main piston has a pressing portion that presses the friction plate, and a plurality of openings that are formed radially inward from the pressing portion and through which the inner protrusions are inserted,
the connecting member includes a downstream connecting member that connects the other axial end of the inner projection to the common rotating element. 4. The automatic transmission according to claim 3 ,
the third clutch includes a return spring, provided on the other axial side of the main piston, for urging the main piston in a release direction in which the friction plate is released from the pressure applied thereto,
The automatic transmission, wherein the return spring is disposed radially inside the friction plate so as to overlap with the friction plate as viewed in the radial direction. 5. The automatic transmission according to claim 4 ,
The return spring is disposed at a position facing the bearing across the main piston.