Automatic transmission

Abstract

To achieve both curbing of a manufacturing cost and improvement in shift responsiveness.SOLUTION: An automatic transmission 1 comprises: a first clutch CL1 and a second clutch CL2 aligned in a shaft direction; a third clutch CL3 arranged on one side of the first and second clutches CL1 and CL2 in the shaft direction; an intermediary planetary gear set (PG1 and PG2) arranged between a set of the first and second clutches CL1 and CL2 and third clutches CL3; an outer planetary gear set (PG3) arranged on the one side of the third clutch CL3 in the shaft direction; and a connection member (21 and 22) which connects each of the first clutch CL1, the second clutch CL2 and the third clutch CL3 to a common rotary element (S3) provided on the outer planetary gear set (PG3).SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an automatic transmission having a plurality of clutches and a plurality of planetary gear sets.

Background Art

[0002] As an example of the above automatic transmission, the one disclosed in Patent Document 1 below is known. The automatic transmission described in Patent Document 1 includes three clutches arranged axially and three planetary gear sets. 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 side (rear side) in the axial direction, and a first planetary gear set, a second planetary gear set, and a third planetary gear set are arranged in this order on one side in the axial direction 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.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the automatic transmission of the above-mentioned Patent Document 1, since three planetary gear sets and three clutches are arranged separately on one side and the other side in the axial direction, there is a problem that the power transmission path between the three clutches and the third sun gear (that is, the sun gear of the planetary gear set farthest from the clutch) is likely to be lengthened. The lengthening of the power transmission path leads to an increase in the mass of the component group constituting the power transmission path, that is, the rotating component group that rotates integrally with the third sun gear. When the mass of the rotating component group increases, at the time of gear shift when the rotational speed of the third sun gear changes rapidly, the rotational change of the third sun gear is dulled by the influence of the inertia of the rotating component group, and there is a possibility that the gear shift responsiveness deteriorates. Of course, if at least a part of the rotating component group is replaced with a lightweight component such as an aluminum die-cast product, the increase in the mass of the rotating component group can be suppressed. However, if this is done, an increase in the unit price of the components cannot be avoided, which is not preferable in terms of manufacturing cost.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide an automatic transmission capable of achieving both suppression of manufacturing cost and improvement of gear shift responsiveness.

Means for Solving the Problems

[0006] As a means for solving the above problems, the relating to one aspect automatic transmission includes a first clutch and a second clutch arranged in the axial direction, a third clutch arranged on one side in the axial direction 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 side in the axial direction of the third clutch, and a connecting member that connects the first clutch, the second clutch, and the third clutch to a common rotating element provided in the outer planetary gear set The first clutch and the second clutch each include a plurality of friction plates arranged axially and a cylindrical hub member engaged with the inner peripheral edge of the friction plate. The third clutch includes a plurality of friction plates arranged axially and a cylindrical drum member engaged with the outer peripheral edge of the friction plate. 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. , and is characterized by this (Claim 1).

[0007] According to the present invention, since the first and second clutches and the third clutch are axially distributively arranged with the intermediate planetary gear set interposed therebetween, compared with the case where the planetary gear set group and the clutch group are respectively grouped and arranged on one axial side and the other axial side (the same structure as Patent Document 1 described above), the power transmission path between the first to third clutches and the common rotating element connected thereto can be simplified. As a result, without taking special measures such as replacing the rotating parts group that rotates integrally with the common rotating element with expensive lightweight parts, the mass of the rotating parts group can be reduced, the manufacturing cost can be suppressed, and the shift response of the automatic transmission can be improved.

[0009] In addition, as a connecting member that connects the first to third clutches and the common rotating element, 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 are provided. , with a simple and reasonable structure, the first to third clutches and the common rotating element can be connected to each other.

[0010] The third clutch may include a plurality of friction plates arranged axially, a cylindrical drum member that engages with the outer peripheral edge of the friction plate, and a piston that presses the friction plates axially. In this case, the piston preferably includes a sub-piston supported by the transmission case and defining a fastening hydraulic chamber between the sub-piston and the transmission case, a rotatable main piston axially opposed to the sub-piston and pressing the friction plates, and a bearing that rotatably connects the sub-piston and the main piston (claim 2 ).

[0011] According to this configuration, the fastening hydraulic chamber for the third clutch is formed between the sub-piston supported by the transmission case and the transmission case, rather than the rotatable main piston that presses the friction plates. In this case, since centrifugal force does not act on the fastening hydraulic chamber, it is not necessary to provide a centrifugal balance chamber for canceling the influence of the centrifugal force. Therefore, the structure of the hydraulic supply system can be simplified while ensuring the controllability of the piston by the supply oil pressure to the fastening hydraulic chamber.

[0012] An automatic transmission according to another aspect of the present invention includes a first clutch and a second clutch arranged axially, 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 that connects 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 includes a plurality of friction plates arranged axially, a cylindrical drum member engaged with the outer peripheral edge of the friction plate, and a piston that presses the friction plates axially.The drum member includes a peripheral wall portion that extends axially on the radially outer side of the friction plate and engages with the outer peripheral edge of the friction plate, a vertical wall portion that extends radially inward from one axial end of the peripheral wall portion, and a plurality of inner protrusions that extend axially from the radially inner end of the vertical wall portion. The piston includes a sub-piston supported by the transmission case and defining a fastening hydraulic chamber between the sub-piston and the transmission case, a rotatable main piston arranged axially opposite to the sub-piston and pressing the friction plates, and a bearing that connects the sub-piston and the main piston so as to be relatively rotatable. The main piston has a pressing portion that presses the friction plate and a plurality of openings that are formed radially inside the pressing portion and through which the respective inner protrusions are inserted. The connecting member includes a downstream connecting member that connects the other axial end of the inner protrusion to the common rotating element. which is characterized by (Claim 3 ).

[0013] The present invention According to this, while arranging the pressing portion of the main piston inside the drum member to enable pressing of the friction plate by the pressing portion, the drum member can be connected to the common rotating element via the downstream connecting member.

[0014] Preferably, the third clutch includes a return spring that biases the main piston in the release direction for releasing the pressing of the friction plate on the other axial side of the main piston. The return spring is arranged radially inside the friction plate so as to overlap the friction plate in a radial view (Claim 4 ).

[0015] According to this configuration, the axial dimension of the third clutch can be shortened, and the automatic transmission can be made more compact in the axial direction.

[0016] Preferably, the return spring is arranged at a position facing the bearing with the main piston interposed therebetween (Claim 5 ).

[0017] According to this configuration, a reasonable arrangement can be realized in which the bearing that presses the main piston in the fastening direction and the return spring that presses the main piston back in the release direction face each other axially.

Advantages of the Invention

[0018] As described above, according to the automatic transmission of the present invention, it is possible to achieve both cost reduction in manufacturing and improvement in shift responsiveness.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0021] [Overall Configuration of the Automatic Transmission] FIGS. 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 this figure is a longitudinally-mounted automatic transmission mounted on a vehicle of the FR type (front engine - rear drive type). That is, the automatic transmission 1 is a transmission that transmits the power of a drive source including an internal combustion engine arranged at the front of the vehicle to the propeller shaft while changing the speed. The power transmitted to the propeller shaft is transmitted to the rear wheels via a differential mechanism.

[0022] 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 (Figure 2). The transmission mechanism 10 is a multi-stage transmission mechanism capable of achieving a plurality of gear stages with different gear ratios, and includes, in addition to the planetary gear sets (PG1 to PG4) described later, friction engagement elements such as clutches and brakes (CL1 to CL3, BR1, BR2). The transmission case 11 is a case that houses the transmission mechanism 10 inside. 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 inside the transmission case 11 to the outside.

[0023] The input shaft 12 and the output shaft 13 are coaxially arranged along the longitudinal direction of the vehicle. That is, the input shaft 12 and the output shaft 13 are arranged so as to extend along the same axis X (Figure 2) extending in the longitudinal direction of the vehicle. 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 in a state where the input shaft 12 is located on the front side of the vehicle and the output shaft 13 is located on the rear side of the vehicle along the axis X. For this reason, hereinafter, one side in the direction parallel to the axis X (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 in the figure) is referred to as "rear", and the other side in the direction parallel to the axis X and approaching the drive source (left side in the figure) may be referred to as "front". Further, with respect to the automatic transmission 1, the direction along the axis X may be referred to as the "axial direction", and the direction orthogonal to the axis X may be referred to as the "radial direction". Furthermore, the direction along the circumference of a circle centered on the axis X may be referred to as the "circumferential direction".

[0024] The transmission mechanism 10 includes 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 arranged in the axial direction. These first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4 are arranged in this order from the front side along the axial direction. Hereinafter, the planetary gear set will be appropriately abbreviated as "gear set". For example, the first planetary gear set PG1 is abbreviated as the first gear set PG1.

[0025] The first gear set PG1 includes, as rotating elements, a first sun gear S1, a first ring gear R1, and a first carrier C1. The first carrier C1 supports a plurality of first pinions P1 arranged at intervals in the circumferential direction. Each first pinion P1 meshes with both the first sun gear S1 and the first ring gear R1.

[0026] The second gear set PG2 includes, as rotating elements, a second sun gear S2, a second ring gear R2, and a second carrier C2. The second carrier C2 supports a plurality of second pinions P2 arranged at intervals in the circumferential direction. Each second pinion P2 meshes with both the second sun gear S2 and the second ring gear R2.

[0027] The third gear set PG3 includes, as rotating elements, a third sun gear S3, a third ring gear R3, and a third carrier C3. The third carrier C3 supports a plurality of third pinions P3 arranged at intervals in the circumferential direction. Each third pinion P3 meshes with both the third sun gear S3 and the third ring gear R3.

[0028] The fourth gear set PG4 includes, as rotating elements, a fourth sun gear S4, a fourth ring gear R4, and a fourth carrier C4. The fourth carrier C4 supports a plurality of fourth pinions P4 arranged at intervals in the circumferential direction. Each fourth pinion P4 meshes with both the fourth sun gear S4 and the fourth ring gear R4.

[0029] Here, in the present embodiment, as the first gear set PG1, a double sun gear type gear set in which the sun gear S1 is axially divided into two is used. On the other hand, as the other second to fourth gear sets PG2 to PG4, normal type gear sets in which the sun gear is not axially divided are used.

[0030] 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 arranged separately behind the front sun gear S1a. The front sun gear S1a and the rear sun gear S1b have the same number of teeth and mesh with a common first pinion P1. For this reason, the rotational speeds of the front sun gear S1a and the rear sun gear S1b are always equal. That is, the front sun gear S1a and the rear sun gear S1b always rotate at the same speed, and when one rotation stops, the other rotation also stops.

[0031] The input shaft 12 is connected to the first carrier C1 via a power transmission member 18 that passes between the divided gears of the first sun gear S1 (that is, 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.

[0032] 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 friction engagement elements for switching the power transmission path by the first to fourth gear sets PG1 to PG4 described above.

[0033] The first clutch CL1 is disposed near the front side 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 at the rear side of the second gear set PG2. That is, the first to third clutches CL1 to CL3 are arranged in the order of the second clutch CL2, the first clutch CL1, and the third clutch CL3 from the front side. Also, the combination of the first clutch CL1 and the second clutch CL2 and the third clutch CL3 are axially opposed (front-rear direction) with the first gear set PG1 and the second gear set PG2 interposed therebetween. In other words, the first to third clutches CL1 to CL3 are divided into two sets such that the third clutch CL3 is located on one side (rear side) in the axial direction of the first and second gear sets PG1 and PG2, and the remaining two clutches (the first and second clutches CL1 and CL2) are located on the other side (front side) in the axial direction of the gear sets PG1 and PG2.

[0034] The first brake BR1 and the second brake BR2 are arranged separately before and after the first to third clutches CL1 to CL3. Specifically, the first brake BR1 is disposed further forward of the second clutch CL2 which is the most forward clutch. The second brake BR2 is disposed further rearward of the third clutch CL3 which is the most rearward clutch (and in front of the third gear set PG3).

[0035] The first clutch CL1 is a friction engagement element that connects and disconnects the input shaft 12 and the first carrier C1, and 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 power transmission members 21, 22, etc., a plurality of friction plates 33 disposed between the drum member 31 and the hub member 32, and a piston 34 capable of axially pressing the friction plates 33. The first clutch CL1 connects and disconnects the input shaft 12 and the first carrier C1, and the third sun gear S3 according to the pressing or release of the piston 34 against the friction plates 33. Here, the hub member 32 of the first clutch CL1 also serves as the hub member for the second clutch CL2 described later. Therefore, hereinafter, the hub member 32 will be referred to as the common hub member 32.

[0036] The second clutch CL2 is a friction engagement element that connects and disconnects the first ring gear R1 and the second sun gear S2, and 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 a power transmission member 23, the above-mentioned common hub member 32 connected to the third sun gear S3 via power transmission members 21, 22, etc., a plurality of friction plates 43 disposed between the drum member 41 and the hub member 32, and a piston 44 capable of axially pressing the friction plates 43. The second clutch CL2 connects and disconnects the first ring gear R1 and the second sun gear S2, and the third sun gear S3 according to the pressing or release of the piston 44 against the friction plates 43.

[0037] The third clutch CL3 is a friction engagement 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 a power transmission member 22, a rotatable cylindrical hub member 52 connected to the second ring gear R2, a plurality of friction plates 53 disposed between the drum member 51 and the hub member 52, and a piston 54 capable of axially pressing the friction plates 53. The third clutch CL3 connects and disconnects the second ring gear R2 and the third sun gear S3 in response to the pressing or release of the piston 54 against the friction plates 53.

[0038] The first brake BR1 is a friction engagement element that connects and disconnects the transmission case 11 and the first sun gear S1 (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 disposed between the drum member 61 and the hub member 62, and a piston 64 capable of axially pressing the friction plates 63. The first brake BR1 connects and disconnects the transmission case 11 and the first sun gear S1 in response to the pressing or release of the piston 64 against the friction plates 63.

[0039] The second brake BR2 is a friction engagement 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 disposed between the drum member 71 and the hub member 72, and a piston 74 capable of axially pressing the friction plates 73. The second brake BR2 connects and disconnects the transmission case 11 and the third ring gear R3 in response to the pressing or release of the piston 74 against the friction plates 73.

[0040] The valve body 14 is a hydraulic circuit device for controlling the engagement and release of each of the above-described friction engagement elements (clutches CL1 to CL3 and brakes BR1, BR2). Although detailed illustration is omitted, for example, the valve body 14 includes a number of oil passages through which the oil supplied to each friction engagement element flows, and a number of solenoid valves for switching the flow of each oil passage.

[0041] In the automatic transmission 1 having the above 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. Further, 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 the "downstream connecting member" in the present invention.

[0042] Figure 3 is an engagement table showing the relationship between the engagement / release of each friction engagement element and the gear position. As shown in this figure, in the automatic transmission 1 of the present embodiment, nine types of gear positions, namely, forward speeds 1 to 8 and reverse speed, are achieved according to the selective engagement or release of each friction engagement element by the above-described valve body 14. In the engagement table of Figure 3, a solid circle indicates that the corresponding friction engagement element is engaged, and a blank space indicates that the corresponding friction engagement element is released (disengaged).

[0043] Specifically, each gear stage is achieved as follows. That is, the first gear is achieved by engaging the first clutch CL1, the first brake BR1, and the second brake BR2. The second gear is achieved by engaging the second clutch CL2, the first brake BR1, and the second brake BR2. The third gear is achieved by engaging the first clutch CL1, the second clutch CL2, and the second brake BR2. The fourth gear is achieved by engaging the second clutch CL2, the third clutch CL3, and the second brake BR2. The fifth gear is achieved by engaging the first clutch CL1, the third clutch CL3, and the second brake BR2. The sixth gear is achieved by engaging the first clutch CL1, the second clutch CL2, and the third clutch CL3. The seventh gear is achieved by engaging the first clutch CL1, the third clutch CL3, and the first brake BR1. The eighth gear is achieved by engaging the second clutch CL2, the third clutch CL3, and the first brake BR1. The reverse gear is achieved by engaging the third clutch CL3, the first brake BR1, and the second brake BR2.

[0044] [Detailed Structure of Each Clutch] Next, the more detailed structure of each of the above-described clutches CL1 to CL3 will be described. 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, in addition to the above-described drum member 31, common hub member 32, friction plate 33, and piston 34, a piston support member 35, a partition member 36, and a return spring 37. The piston support member 35 is a member that supports the piston 34 so as to be movable in the axial direction. The return spring 37 is a spring that biases the piston 34 in the release direction (the direction away from the friction plate 33; here, backward). The partition member 36 is a member for making the space in which the return spring 37 is disposed into a hydraulic chamber (a centrifugal balance chamber 39 described later).

[0045] The drum member 31 includes a peripheral wall portion 31a extending in the axial direction (front-rear direction) on the radially outer side 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 coupled to the first carrier C1 by, for example, welding the radially inner end thereof to the axial intermediate portion of the first carrier C1.

[0046] 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 portion 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 plate 33 (specifically, the hub-side friction plate 33b described later) of the first clutch CL1, and the front peripheral wall 32a2 functions as a hub that holds the friction plate 43 (specifically, the hub-side friction plate 43b described later) of the second clutch CL2.

[0047] 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 closer to the first clutch CL1 so that the front portion of the first pinion P1 enters the inside of the common hub member 32. Thus, the first clutch CL1 and the first gear set PG1 are arranged so as to be aligned in the front-rear direction in a relation of partially overlapping when viewed in the radial direction.

[0048] The friction plate 33 includes 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 where it can rotate integrally with the drum member 31 and can move axially by spline fitting its outer peripheral edge 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 where it can rotate integrally with the common hub member 32 and can move axially by spline fitting its inner peripheral edge 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 of being alternately arranged axially.

[0049] The piston 34 includes a pressing portion 34a that faces the friction plate 33 from the rear, an extending portion 34b that extends forward from the end portion on the radially inner side of the pressing portion 34a, and a pressure receiving portion 34c that extends radially inward from the front end portion of the extending portion 34b. The piston 34 is held by the drum member 31 in a state where it can rotate integrally with the drum member 31 and can move axially by spline fitting its pressing portion 34a to the peripheral wall portion 31a of the drum member 31.

[0050] The piston support member 35 includes a support portion 35a formed in a hook shape in a cross-sectional view so as to follow the shape of the pressure receiving portion 34c of the piston 34, and a shaft portion 35b that extends forward from the end portion on the radially inner side of the support portion 35a. The piston 34 is supported by the piston support member 35 in a state where it can move axially by fitting its pressure receiving portion 34c to the piston support member 35 from the front.

[0051] The piston support member 35 is coupled to the first carrier C1 such that the rear surface of its support portion 35a is welded to the front end portion of the first carrier C1 or the like. Here, the first carrier C1 is coupled not only to the piston support member 35 but also to the drum member 31 as described above. Further, the piston 34 is engaged with the drum member 31 so as not to be relatively rotatable. From this, the first carrier C1, the drum member 31, the piston 34, and the piston support member 35 all rotate at the same rotational speed.

[0052] An opening h1 is formed in the extended portion 34b of the piston 34. The opening h1 is an opening for avoiding interference with the first pinion P1 and is provided at a plurality of circumferential locations corresponding to the first pinion P1.

[0053] 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 to push the pressure receiving portion 34c forward. Thereby, the pressing portion 34a of the piston 34 presses the friction plate 33, and the first clutch CL1 is fastened.

[0054] 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 the hydraulic pressure fluctuation caused by the centrifugal force acting on the fastening hydraulic chamber 38. The centrifugal balance chamber 39 is formed so as to face the fastening hydraulic chamber 38 with the pressure receiving portion 34c interposed therebetween.

[0055] 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 exhibits an elastic force that separates the piston 34 and the partition member 36 from each other. Due to this elastic force, the piston 34 is constantly biased in the release direction, that is, backward, away from the friction plate 33. When the first clutch CL1 is fastened, a required hydraulic pressure is supplied to the fastening hydraulic chamber 38 so that the piston 34 is pressed forward (fastening direction) against the biasing force of the return spring 37.

[0056] 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 an axially aligned state such that the vertical wall portion 32b of the common hub member 32 is positioned 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 rotatably supported about the axis X of the automatic transmission 1 by inserting its shaft portion 32c into the boss member 80. Similarly, the piston support member 35 is rotatably supported about the axis X by inserting its shaft portion 35b 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 therebetween. The common hub member 32 and the piston support member 35 are supported so as to be relatively rotatable with the thrust bearing 81 interposed therebetween.

[0057] A power transmission member 17 is coaxially inserted into the boss member 80, and further, an 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 relatively rotatable about a common axis X. The rear end portion of the power transmission member 17 is coupled to the inner peripheral surface of the first sun gear S1 (specifically, the front sun gear S1a) by spline fitting. The rear end portion of the input shaft 12 is coupled to the inner peripheral surface of the power transmission member 18 by spline fitting.

[0058] Inside the boss member 80, an oil passage e1 extending in the axial direction is formed. Further, in the piston support member 35, an oil passage e2 communicating with the oil passage e1 is formed. The oil passage e2 communicates with the fastening hydraulic chamber 38. By supplying and discharging hydraulic pressure to the fastening hydraulic chamber 38 through the oil passage e2, the piston 34 is pressed against the friction plate 33 or the pressing is released. 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 as not to be relatively rotatable, and the first clutch CL1 is in a fastened state. When the pressing of the friction plate 33 by the piston 34 is released, relative rotation between the drum-side friction plate 33a and the hub-side friction plate 33b is allowed, and the first clutch CL1 is in a released state.

[0059] Although not shown, the piston support member 35 is also formed with an oil passage that communicates the centrifugal balance chamber 39 with the internal oil passage e1 of the boss member 80. Through this oil passage, hydraulic pressure for canceling the hydraulic pressure fluctuation in the fastening hydraulic chamber 38 due to centrifugal force is supplied to the centrifugal balance chamber 39. Here, the oil passage e1 of the boss member 80 includes a plurality of independent unit oil passages arranged at intervals in the circumferential direction. The oil passage leading to the centrifugal balance chamber 39 and the oil passage e2 leading to the above-described fastening hydraulic chamber 38 are formed so as to communicate with different unit oil passages. This also applies to 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.

[0060] The second clutch CL2 includes, in addition to the drum member 41, the common hub member 32, the friction plate 43, and the piston 44 described above, 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 as to be axially movable. The return spring 47 is a spring that biases the piston 44 in the release direction (the direction away from the friction plate 43; here, forward). The partition member 46 is a member for making the space in which the return spring 47 is disposed into a hydraulic chamber (the centrifugal balance chamber 49 to be described later).

[0061] The drum member 41 includes a peripheral wall portion 41a that extends in the axial direction (front-rear direction) on the radially outer side of the friction plate 43, and a vertical wall portion 41b that extends radially inward from the rear end of the peripheral wall portion 41a. The vertical wall portion 41b is coupled to the radially outer end portion of the power transmission member 23. The power transmission member 23 is coupled to the first ring gear R1 by welding or the like and is spline-fitted to the second sun gear S2. 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.

[0062] The friction plate 43 includes a plurality of drum-side friction plates 43a that engage with the inner peripheral 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 peripheral surface of the peripheral wall portion 32a of the common hub member 32. The outer peripheral edge of each drum-side friction plate 43a is spline-fitted to the peripheral wall portion 41a of the drum member 41, so that it is attached to the drum member 41 in a state where it can rotate integrally with the drum member 41 and can move in the axial direction. The inner peripheral edge of each hub-side friction plate 43b is spline-fitted to the front peripheral wall 32a2 of the peripheral wall portion 32a of the common hub member 32, so that it is attached to the common hub member 32 in a state where it can rotate integrally with the common hub member 32 and can move in the axial direction. 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 of being alternately arranged in the axial direction.

[0063] The piston 44 includes a pressing portion 44a and a pressure-receiving portion 44b on the radially inner side thereof. The pressing portion 44a is arranged to face the friction plate 43 from the front. The pressure-receiving portion 44b is arranged to face the vertical wall portion 32b of the common hub member 32 from the front.

[0064] 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 where it can move in the axial direction by fitting the pressure-receiving portion 44b thereof to the piston support member 45 from the rear.

[0065] A fastening hydraulic chamber 48 is formed between a pressure receiving portion 44b of the piston 44 and a piston support member 45. The hydraulic pressure supplied to the fastening hydraulic chamber 48 acts as a force to push the pressure receiving portion 44b rearward. Thereby, a pressing portion 44a of the piston 44 presses a friction plate 43, and the second clutch CL2 is fastened.

[0066] A partition member 46 is provided so as to seal between the pressure receiving portion 44b of the piston 44 and a vertical wall portion 32b of a common hub member 32. Thereby, a centrifugal balance chamber 49 is formed between the pressure receiving portion 44b and the vertical wall portion 32b. The centrifugal balance chamber 49 is a hydraulic chamber for canceling hydraulic pressure fluctuations caused by centrifugal force acting on the fastening hydraulic chamber 48. The centrifugal balance chamber 49 is formed so as to face the fastening hydraulic chamber 48 with the pressure receiving portion 44b interposed therebetween.

[0067] A 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 release direction). When the second clutch CL2 is fastened, a required hydraulic pressure is supplied to the fastening hydraulic chamber 48 so that the piston 44 is pressed rearward (in the fastening direction) against the biasing force of the return spring 47.

[0068] An oil passage e3 communicating with an internal oil passage e1 of a boss member 80 is formed in a shaft portion 32c of the common hub member 32. The oil passage e3 communicates with the fastening hydraulic chamber 48. By supplying and discharging hydraulic pressure to the fastening hydraulic chamber 48 through the oil passage e3, the piston 44 is pressed against the friction plate 43 or the pressing is released. 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 so as not to be relatively rotatable, and the second clutch CL2 is in a fastened state. When the pressing of the friction plate 43 by the piston 44 is released, relative rotation between the drum-side friction plate 43a and the hub-side friction plate 43b is allowed, and the second clutch CL2 is in a released state.

[0069] Although not shown, an oil passage that communicates the centrifugal balance chamber 49 with the internal oil passage e1 of the boss member 80 is also formed in the shaft portion 32c of the common hub member 32. Through this oil passage, oil pressure for canceling the hydraulic pressure fluctuations in the fastening hydraulic chamber 48 due to centrifugal force is supplied to the centrifugal balance chamber 49.

[0070] FIG. 5 is an exploded perspective view of the third clutch CL3. As shown in this FIG. 5 and the previous FIGS. 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; here, rearward).

[0071] The drum member 51 includes a peripheral wall portion 51a that extends in the axial direction (front-rear direction) on the radially outer side of the friction plate 53, a vertical wall portion 51b that extends radially inward from the rear end of the peripheral wall portion 51a, and an inner projection 51c that extends forward from the radially inner end of the vertical wall portion 51b. The inner projection 51c is a plurality of projections arranged at regular intervals in the circumferential direction along the inner edge of the vertical wall portion 51b, and is formed in a comb-like shape, so to speak. Each inner projection 51c is arranged to penetrate the piston 54 through an opening h2 described later.

[0072] The front end portion of the peripheral wall portion 51a of the drum member 51 is coupled to the rear end portion 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 axially 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 portion of the vertical wall portion 21b is coupled to the outer peripheral surface of the shaft portion 32c of the common hub member 32 (the hub member 32 shared by the first and second clutches CL1, CL2) by spline fitting, and the rear end portion of the peripheral wall portion 21a is coupled to the front end portion of the peripheral wall portion 51a of the drum member 51 by spline fitting. In other words, the drum member 51 is connected to the common hub member 32 via the power transmission member 21.

[0073] The inner projection 51c of the drum member 51 is coupled to the radially inner end portion 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 short from the radially outer end portion of the vertical wall portion 22a, and a shaft portion 22c extending rearward from the radially inner end portion of the vertical wall portion 22a. The shaft portion 22c is formed to extend in the axial direction (front-rear direction) inside the piston 54 in the radial direction. The rear end portion of the shaft portion 22c is coupled to the inner peripheral surface of the third sun gear S3 by spline fitting, and the flange portion 22b is coupled to the inner projection 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.

[0074] 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. That is, 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, whereby the first to third clutches CL1 to CL3 are connected to the common third sun gear S3.

[0075] The power transmission member 22 is rotatably supported by a 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 projects 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 projects forward and a rear boss 113b that projects rearward. The rear boss 113b is located slightly radially outside 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.

[0076] The power transmission member 16 is coaxially inserted into the power transmission member 22, and further, the power transmission member 15 is coaxially inserted into the power transmission member 16. The front end portion of the power transmission member 15 is coupled to the inner peripheral surface of the first sun gear S1 (specifically, the rear sun gear S1b) by spline fitting. The front end portion of the power transmission member 16 is coupled to the second carrier C2 via the auxiliary connecting member 90.

[0077] The hub member 52 includes a peripheral wall portion 52a extending in the axial direction (front-rear direction) and a support body 52b that supports the peripheral wall portion 52a. The support body 52b is externally inserted in a relatively rotatable manner into 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 by welding or the like so as to project rearward from the vertical wall of the support body 52b. 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 such that the radially outer end portion of its support body 52b is welded to the rear end portion of the second ring gear R2 or the like.

[0078] The friction plate 53 includes 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 where it can rotate integrally with the drum member 51 and can move in the axial direction by spline fitting its outer peripheral edge 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 where it can rotate integrally with the hub member 52 and can move in the axial direction by spline fitting its inner peripheral edge 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 of being alternately arranged in the axial direction.

[0079] The piston 54 includes a main piston 54a disposed on the rear side of the friction plate 53, a sub-piston 54b disposed further rearward of the main piston 54a, and a bearing 54c disposed between the main piston 54a and the sub-piston 54b. The main piston 54a is a piston component that directly presses the friction plate 53. The sub-piston 54b is a piston component that moves axially under the hydraulic pressure 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 formed by combining two piston components (the main piston 54a and the sub-piston 54b) that can move integrally in the axial direction and are relatively rotatable.

[0080] The sub-piston 54b is supported by a partition wall portion 112 of the transmission case 11. Specifically, the sub-piston 54b is supported by the partition wall portion 112 in a state where it can move axially along the outer peripheral surface of the front boss 113a of the partition wall portion 112. However, the sub-piston 54b cannot rotate with respect to the partition wall portion 112 (transmission case 11). That is, the sub-piston 54b is supported by the transmission case 11 in a state where it can move axially and cannot rotate about its axis.

[0081] The main piston 54a is supported on the outer peripheral surface of the front boss 113a of the partition wall portion 112 so as to be axially movable on the front side of the sub-piston 54b. The main piston 54a has a pressing portion 54a1 that faces the friction plate 53 from the rear. The main piston 54a is held by the drum member 51 in a state where it can rotate integrally with the drum member 51 and move axially when its pressing portion 54a1 is spline-fitted to the peripheral wall portion 51a of the drum member 51.

[0082] At a plurality of circumferential positions of the main piston 54a, openings h2 are formed. These plurality of openings h2 are provided at positions radially inner than the pressing portion 54a1 in the main piston 54a (radial middle portion of the main piston 54a), and are arranged to be spaced at regular intervals in the circumferential direction (see particularly FIG. 5). Further, the plurality of openings h2 are provided at positions corresponding to the plurality of inner protrusions 51c of the drum member 51, and are formed to be able to receive the plurality of inner protrusions 51c respectively. That is, the inner protrusion 51c of the drum member 51 penetrates the main piston 54a in the axial direction through the opening h2 of the main piston 54a. And in a state where the inner protrusion 51c penetrates the main piston 54a (state of being inserted into the opening h2), the flange portion 22b of the power transmission member 22 is coupled to the front end portion of the inner protrusion 51c by welding or the like. In other words, the drum member 51 is connected to the power transmission member 22 while three-dimensionally intersecting the main piston 54a.

[0083] A fastening hydraulic chamber 58 is formed between the sub-piston 54b and the partition wall portion 112 of the transmission case 11. The hydraulic pressure supplied to the fastening hydraulic chamber 58 acts as a force to push the sub-piston 54b forward. Receiving this force, the sub-piston 54b moves forward, and together with the sub-piston 54b, the main piston 54a moves forward. Thereby, the pressing portion 54a1 of the main piston 54a presses the friction plate 53, and the third clutch CL3 is engaged.

[0084] An oil passage e4 communicating with the fastening hydraulic chamber 58 is formed in the partition wall portion 112 of the transmission case 11. By supplying and discharging the hydraulic pressure to the fastening hydraulic chamber 58 through the oil passage e4, the piston 54 (specifically, the main piston 54a) is pressed against the friction plate 53 or the pressing 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 in close contact with each other so as not to be relatively rotatable, and the third clutch CL3 is in an engaged state. When the pressing of the friction plate 53 by the piston 54 is released, the relative rotation between the drum-side friction plate 53a and the hub-side friction plate 53b is allowed, and the third clutch CL3 is in a released state.

[0085] 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 an elastic force that separates the main piston 54a and the vertical wall portion 22a from each other. Due to this elastic force, the piston 54 is constantly biased in the release direction, that is, rearward, away from the friction plate 53. When the third clutch CL3 is engaged, a required hydraulic pressure is supplied to the engagement hydraulic pressure chamber 58 so that the piston 54 is pressed forward (engagement direction) against the biasing force of the return spring 57.

[0086] 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 in a radial view. In the present 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 in a radial view. Further, 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 interposed therebetween.

[0087] Here, since the engagement hydraulic pressure chamber 58 for the third clutch CL3 is a non-rotating hydraulic pressure chamber formed between a part of the transmission case 11 (partition wall portion 112) and the sub-clutch 48b, the internal hydraulic pressure is not affected by centrifugal force. Therefore, in the third clutch CL3, unlike the cases of the first and second clutches CL1 and CL2 described above, a centrifugal balance chamber is not provided.

[0088] [Function and Effect] As described above, the automatic transmission 1 of the present embodiment includes first to third clutches CL1 to CL3 arranged in the front-rear direction along its axis X, and first and second gear sets PG1 and PG2 arranged between the third clutch CL3 located on the rearmost side among them and the other two clutches (i.e., the first and second clutches CL1 and CL2), and a third gear set PG3 arranged further rearward of the third clutch CL3. Further, the first to third clutches CL1 to CL3 are all connected to the third sun gear S3 of the third gear set PG3. According to such a configuration, there is an advantage that the mass of the rotating component group connected to the third sun gear S3 can be reduced, and the shift responsiveness of the automatic transmission 1 can be improved.

[0089] FIG. 6 is a view corresponding to FIG. 4 showing a rotating component group connected to the third sun gear S3 and rotating integrally with the third sun gear S3, with the rotating component group colored. As shown in this FIG. 6, in the above embodiment, the rotating component group rotating integrally with the third sun gear S3 mainly includes a common hub member 32 of the first and second clutches CL1 and CL2, a piston 44 and a piston support member 45 of the second clutch CL2, a drum member 51 and a main piston 54a of the third clutch CL3, a power transmission member 21 connecting the common hub member 32 and the drum member 51, and a power transmission member 22 connecting the drum member 51 and the third sun gear S3. In the above embodiment, by arranging the third clutch CL3 between the first and second gear sets PG1 and PG2 and the third gear set PG3, for example, compared with the comparative example shown below, the power transmission path can be simplified, and the mass of the rotating component group constituting the power transmission path can be reduced.

[0090] FIG. 7 is a cross-sectional view showing the structure of a comparative example in which the arrangement of a clutch or the like is different from that of the above-described embodiment. The automatic transmission 1' of this comparative example includes 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 of the above-described embodiment, respectively. Further, the automatic transmission 1' of the comparative example includes a first gear set PG1', a second gear set PG2', and a third gear set PG3' as gear sets corresponding to the first gear set PG1, the second gear set PG2, and the third gear set PG3 of the above-described embodiment, respectively. In the comparative example, unlike the above-described embodiment, a layout in which the clutches and the gear sets are alternately arranged in the axial direction is not adopted. That is, in the comparative example, the second clutch CL2', the first clutch CL1', and the third clutch CL3' are arranged in this order from the front side, and the first to third gear sets PG1' to PG3' are arranged in this order on the rear side of the third clutch CL3' on the rearmost side. Although the third clutch CL3' and the first gear set PG1' are arranged so as to partially overlap, unlike the above-described embodiment, no gear set is arranged between the two clutches.

[0091] In the automatic transmission 1' of the comparative example, the rotating component group that rotates integrally with the third sun gear S3' of the third gear set PG3' mainly includes 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 component groups are shown colored 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 inside the power transmission member 21'. Further, the drum member 51' is the rotating component farthest from the third sun gear S3' on the power transmission path. In order to transmit the rotation of such a 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' extends greatly forward, and the front end portion of the shaft portion 51a' enlarged (elongated) by the extension is inserted into and coupled to the hollow shaft portion 42a' of the hub member 42'. Thus, in the comparative example, since the enlargement of the drum member 51' or the elongation of the power transmission path cannot be avoided, the mass of the colored rotating component group that rotates integrally with the third sun gear S3' tends to increase as a whole. In the comparative example, although the hub member 31' of the first clutch CL1' is integrated with the drum member 51' of the third clutch CL3' to achieve some weight reduction, due to the above-described circumstances, the influence is significant, and an increase in the mass of the rotating component group is still likely to occur.

[0092] In contrast, in the embodiment shown in FIG. 6, as is clear from 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. As a result, it becomes possible to reduce the mass of the colored rotating component group including the drum member 51, and the shift responsiveness of the automatic transmission 1 can be improved. If the mass of the rotating component group that rotates integrally with the third sun gear S3 is large, when shifting such that the rotational speed of the third sun gear S3 changes rapidly, the change in rotation of the third sun gear S3 is dulled by the influence of the inertia of the rotating component group, and the shift responsiveness may deteriorate. On the other hand, according to the above-described embodiment in which the mass of the rotating component group that rotates integrally with the third sun gear S3 can be reduced, the rotational speed of the third sun gear S3 can be rapidly changed during shifting, and the shift responsiveness can be improved.

[0093] Even in the comparative example of FIG. 7, for example, if at least a part of the colored rotating component group is replaced with a lightweight component such as an aluminum die-cast product, it is possible to reduce the mass of the rotating component group and improve the shift responsiveness. However, in this case, an increase in the unit price of the parts is inevitable, which is not preferable in terms of manufacturing cost. In contrast, in the above-described embodiment, since the size (volume) of the rotating component group itself is sufficiently smaller than that of the comparative example, the mass of the rotating component group can be kept low without making the modification accompanied by the above cost increase, and good shift responsiveness can be realized while suppressing the manufacturing cost.

[0094] Further, in the above embodiment, since the drum member 31 and the piston support member 35 of the first clutch CL1 are connected to the first carrier C1, the piston 34 and the piston support member 35 can be mechanically separated from the third sun gear S3. That is, the piston 34 and the piston support member 35 rotate integrally with the first carrier C1 and do not rotate integrally with the third sun gear S3. Thus, in the above embodiment, since the piston 34 and the piston support member 35 are excluded from the group of rotating parts that rotate integrally with the third sun gear S3, compared with 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', the mass of the group of rotating parts can be further reduced, and the shift responsiveness can be effectively improved.

[0095] Further, in the above embodiment, since the piston 54 of the third clutch CL3 is a composite piston in which two relatively rotatable piston parts (main piston 54a and sub-piston 54b) are combined, different from the other first and second clutches CL1, CL2, the centrifugal balance chamber can be omitted. That is, the piston 54 of the third clutch CL3 includes a sub-piston 54b supported by the partition wall portion 112 of the transmission case 11 and defining a fastening hydraulic chamber 58 therebetween, a rotatable main piston 54a disposed at a position axially opposed to the sub-piston 54b and pressing the friction plate 53, and a bearing 54c connecting the main piston 54a and the sub-piston 54b so as to be relatively rotatable. In this case, the members (partition wall portion 112 and sub-piston 54b) forming the fastening hydraulic chamber 58 do not rotate, and no centrifugal force acts on the fastening hydraulic chamber 58. This means that the centrifugal balance chamber, which is a hydraulic chamber for canceling the influence of the centrifugal force, can be omitted. That is, there is no need to provide a room corresponding to the centrifugal balance chambers 39, 49 for the other clutches CL1, CL2 at a position facing the fastening hydraulic chamber 58 with the piston 54 (main piston 54a) interposed therebetween. Therefore, while ensuring the controllability of the piston 54 by the supply hydraulic pressure to the fastening hydraulic chamber 58, the structure of the hydraulic supply system can be simplified.

[0096] Further, in the above-described embodiment, the drum member 51 of the third clutch CL3 is provided with comb-shaped inner projections 51c, and an opening h2 through which the inner projections 51c are inserted is formed in the main piston 54a of the piston 54. The inner projections 51c are coupled to the power transmission member 22 in a state of penetrating the main piston 54a. According to such a configuration, while arranging the pressing portion 54a1 of the main piston 54a inside the drum member 51 to enable pressing of the friction plate 53 by the pressing portion 54a1, the drum member 51 can be connected to the third sun gear S3 via the power transmission member 22.

[0097] Further, in the above-described embodiment, the return spring 57 of the third clutch CL3 is arranged so as to overlap with the friction plate 53 in the radial direction inside the friction plate 53. According to such a configuration, the axial dimension of the third clutch CL3 can be shortened, and the automatic transmission 1 can be made compact in the axial direction.

[0098] Further, in the above-described embodiment, the return spring 57 is arranged at a position facing the bearing 54c with the main piston 54a interposed therebetween. According to such a configuration, a reasonable arrangement can be realized in which the bearing 54c that pushes the main piston 54a forward (fastening direction) and the return spring 57 that pushes the main piston 54a backward (release direction) face each other in the axial direction.

[0099] [Modification Example] As described above, the preferred embodiments of the present invention have been described, but 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.

[0100] For example, in the above-described embodiment, the hub members of the first clutch CL1 and the second clutch CL2 are shared by the common hub member 32, but dedicated hub members may be prepared for the first clutch CL1 and the second clutch CL2, respectively.

[0101] In the above embodiment, two gear sets, namely a first gear set PG1 and a second gear set PG2, are arranged between the first and second clutches CL1 and CL2 and the third clutch CL3. However, the number of gear sets arranged between the first and second clutches CL1 and CL2 and the third clutch CL3 is not limited to two, and may be one or three or more.

[0102] In the above embodiment, as the first gear set PG1, a double sun gear type planetary gear set in which the sun gear S1 is axially divided into two parts is used. However, as the first gear set PG1, a gear set similar to the other second to fourth gear sets PG2 to PG4 (that is, a normal type gear set in which the sun gear is not axially divided) may be used.

[0103] In the above embodiment, an example in which the present invention is applied to a longitudinally-mounted automatic transmission mounted on a FR type (front engine - rear drive type) vehicle has been described. However, the automatic transmission to which the present invention can be applied is not limited to a longitudinally-mounted one, and the present invention can also be applied to a horizontally-mounted automatic transmission mounted on an FF type (front engine - front drive type) vehicle.

Explanation of Reference Numerals

[0104] 1 Automatic transmission CL1 First clutch CL2 Second clutch CL3 Third clutch PG1 First planetary gear set (intermediate planetary gear set) PG2 Second planetary gear set (intermediate planetary gear set) PG3 Third 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 the first and second clutches) 33 Friction plate (of the first clutch) Friction plate (of the second clutch) Drum member (of the third clutch) Peripheral wall portion Vertical wall portion Inner projection Friction plate (of the third clutch) Piston (of the third clutch) Main piston Pressing portion Sub-piston Bearing Return spring Fastening hydraulic chamber Opening (of the piston)

Claims

1. A first clutch and a second clutch arranged in the 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, A connecting member for connecting the first clutch, the second clutch, and the third clutch to a common rotating element provided in the outer planetary gear set, The first clutch and the second clutch each include a plurality of friction plates arranged in the axial direction and a cylindrical hub member engaged with the inner peripheral edge of the friction plate, The third clutch includes a plurality of friction plates arranged in the axial direction and a cylindrical drum member engaged with the outer peripheral edge of the friction plate, 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. An automatic transmission characterized by this.

2. In the automatic transmission according to Claim 1, The third clutch includes a plurality of friction plates arranged in the axial direction, a cylindrical drum member engaged with the outer peripheral edge of the friction plate, and a piston that presses the friction plate in the axial direction, The piston includes a sub-piston supported by the transmission case and defining a fastening hydraulic chamber between the sub-piston and the transmission case, a rotatable main piston axially opposed to the sub-piston and pressing the friction plate, and a bearing that rotatably connects the sub-piston and the main piston. An automatic transmission characterized by this.

3. A first clutch and a second clutch arranged in the 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, A connecting member for 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 includes a plurality of friction plates arranged in the axial direction, a cylindrical drum member engaged with the outer peripheral edge of the friction plate, and a piston that presses the friction plate in the axial direction, The drum member includes a peripheral wall portion that extends in the axial direction on the radially outer side of the friction plate and engages with the outer peripheral edge of the friction plate, a vertical wall portion that extends radially inward from one axial end of the peripheral wall portion, and a plurality of inner protrusions that extend from the radially inner end of the vertical wall portion to the other axial side. The piston includes a sub-piston that is supported by the transmission case and defines a fastening hydraulic chamber between the sub-piston and the transmission case, a rotatable main piston that is axially opposed to the sub-piston and presses the friction plate, and a bearing that rotatably connects the sub-piston and the main piston. The main piston has a pressing portion that presses the friction plate, and a plurality of openings that are formed radially inward of the pressing portion and through which the respective inner protrusions are inserted. The connecting member includes a downstream connecting member that connects the other axial end of the inner protrusion and the common rotating element. The automatic transmission is characterized by this.

4. In the automatic transmission according to claim 3, The third clutch includes a return spring that biases the main piston in the release direction to release the pressing of the friction plate on the other axial side of the main piston. The return spring is arranged radially inside the friction plate so as to overlap the friction plate in a radial view. The automatic transmission is characterized by this.

5. In the automatic transmission according to claim 4, The return spring is arranged at a position facing the bearing with the main piston interposed therebetween. The automatic transmission is characterized by this.

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