JP6003516B2 - Automatic transmission - Google Patents

Description

  The present invention belongs to a technical field of an automatic transmission mounted on a vehicle.

  An automatic transmission mounted on a vehicle includes a plurality of friction engagement elements such as a multi-plate clutch and a multi-plate brake, and a gear including a planetary gear set, etc., is selectively engaged according to the operating state of the engine. The power transmission path of the mechanism is changed to automatically shift to a predetermined gear stage.

  In the friction engagement element described in Patent Document 1, a first piston that presses the friction plate and a second piston that presses the first piston toward the side close to the friction plate are serially arranged in this order from the friction plate side to the stroke direction. It is the structure arranged in.

  According to this, when the possibility of fastening the frictional engagement element occurs, the first piston is caused to stroke toward the side close to the friction plate by causing the second piston to stroke toward the side close to the friction plate. Thus, the clearance of the friction plate (the clutch clearance of the frictional engagement element) can be narrowed.

  When the first piston is further stroked to the side closer to the friction plate at the stage where it is necessary to fasten the frictional engagement element, the clutch clearance is narrowed in advance, so that the friction plate is pressed by the first piston. Complete in a short time.

  As a result, by having a plurality of pistons, it is possible to fasten the friction fastening elements with high responsiveness, and to fasten the friction fastening elements accurately and at the proper timing, resulting in a shift in the fastening timing of the friction fastening elements. It is possible to suppress shift shocks and the like.

  In Patent Document 1, an oil passage for supplying hydraulic pressure for stroke of the first piston toward the side close to the friction plate opens to the side wall of the first piston housing portion facing the outer peripheral end of the first piston. It is described that.

JP 2005-265063 A (paragraph 0015, FIG. 2, FIG. 7, FIG. 8, FIG. 9, FIG. 10)

  By the way, the automatic transmission is required to be compact in order to improve mountability on a vehicle. In this regard, in the technique described in Patent Document 1, since the oil passage for supplying hydraulic pressure for causing the first piston to stroke is opened in the side wall of the first piston housing portion, the transmission case is elongated in the axial direction. Therefore, there is a problem that downsizing of the automatic transmission is hindered.

  Therefore, the present invention provides an automatic transmission that can fasten the frictional engagement element with high responsiveness by having a plurality of pistons, and that can fasten the frictional engagement element with high accuracy at an appropriate timing. It aims to provide while ensuring compactness.

That is, the present invention is a friction in which a first piston that presses the friction plate and a second piston that moves the first piston to the side close to the friction plate are arranged in series in this order from the friction plate side in the stroke direction. An automatic transmission including a fastening element, wherein the first piston is fitted into the second piston so as to be movable together with the second piston and movable relative to the second piston. A first hydraulic chamber that is provided in the transmission case and is movably fitted in a recess that opens to the side close to the friction plate, and is supplied with hydraulic pressure to stroke the first piston to the side close to the friction plate. And a second hydraulic chamber to which a hydraulic pressure is supplied to stroke the second piston toward the side close to the friction plate, and the first hydraulic chamber includes the first piston and the second piston. And a non-operating hydraulic pressure chamber defined between the second piston and the recess, and communicated with the hydraulic pressure chamber via a communication hole provided in the second piston. A hydraulic chamber, and the second hydraulic chamber is defined between the second piston and the recess, and is used for a first hydraulic chamber that supplies hydraulic pressure to the non-actuated hydraulic chamber. An automatic transmission characterized in that an oil passage and a second hydraulic chamber oil passage for supplying hydraulic pressure to the second hydraulic chamber are respectively opened in a bottom wall provided on a side of the recess that is separated from the friction plate. (Claim 1).

  According to the present invention, the first piston that presses the friction plate and the second piston that moves the first piston to the side close to the friction plate are arranged in series in this order in the stroke direction from the friction plate side. Thus, by providing a plurality of pistons, it is possible to fasten the frictional engagement element with high responsiveness, and to provide an automatic transmission capable of fastening the frictional engagement element accurately and at appropriate timing.

  In addition, according to the present invention, the first hydraulic chamber to which hydraulic pressure for causing the first piston fitted into the second piston to stroke toward the side close to the friction plate is supplied is the first piston and the second piston. And a non-operating hydraulic chamber defined between the second piston and a recess provided in the transmission case. A communication hole that communicates the working hydraulic chamber and the non-actuating hydraulic chamber is provided in the second piston, and an oil passage for the first hydraulic chamber that supplies hydraulic pressure to the non-actuating hydraulic chamber is formed in the bottom wall of the recess. It is open.

  The communication hole includes an operating hydraulic chamber defined between the first piston and the second piston arranged in series in the stroke direction, and a non-operating hydraulic chamber defined between the second piston and the recess. Therefore, it is not necessary to provide the communication hole, for example, at the outer peripheral end of the second piston. That is, the communication hole can be provided in the central portion of the second piston. Therefore, for example, there is no inconvenience that the outer peripheral end of the second piston becomes longer in the stroke direction because the communication hole is provided. Further, for example, there is no problem that the opening of the oil passage has to be elongated in the stroke direction so that the communication hole and the oil passage always communicate with each other even when the second piston strokes. Therefore, the hydraulic pressure can be supplied to the first hydraulic chamber without lengthening the transmission case in the axial direction, so that the automatic transmission can be made compact and can be mounted on the vehicle.

  In the present invention, it is preferable that the second hydraulic chamber is defined on an inner peripheral side with respect to the non-actuating hydraulic chamber (Claim 2).

  According to this configuration, the second hydraulic chamber for causing the second piston to stroke is defined on the inner peripheral side of the non-operating hydraulic chamber between the second piston and the recess of the transmission case. The volume of the second hydraulic chamber is reduced, and the amount of hydraulic oil required to stroke the second piston can be reduced.

  In the present invention, a seal member that defines an outer peripheral end of the non-actuating hydraulic chamber and a seal member that defines an inner peripheral end are attached to the second piston, and the seal members overlap each other in the stroke direction. It is preferable that they are arranged (claim 3).

  According to this configuration, the seal member that defines the outer peripheral end of the non-operating hydraulic chamber and the seal member that defines the inner peripheral end are disposed so as to overlap each other in the stroke direction. Compared to the case where the second pistons are not overlapped with each other in the direction, the second piston is prevented from being elongated in the stroke direction. In this respect, the axial direction of the transmission case is shortened.

  In addition, since the seal member that defines the inner peripheral end of the non-actuating hydraulic chamber has a shorter peripheral length than the seal member that defines the outer peripheral end, the sliding resistance when the second piston is stroked is reduced. This is advantageous in that the piston is stroked quickly.

  According to the present invention, by providing a plurality of pistons, the frictional engagement element can be fastened with high responsiveness, and the automatic transmission that can fasten the frictional engagement element accurately and at an appropriate timing is provided by the automatic transmission. Provided while ensuring compactness.

1 is a skeleton diagram of an automatic transmission according to an embodiment of the present invention. It is a fastening table | surface of the said automatic transmission. It is a block diagram which shows the hydraulic path from the oil pump of the said automatic transmission to a friction fastening element. It is sectional drawing which shows the structure of the LR brake (low reverse brake) of the said automatic transmission. FIG. 5 is a schematic view showing a positional relationship among a first piston, a second piston, a driven plate, and a return spring of the LR brake when viewed in the axial direction A of FIG. 4. It is sectional drawing similar to FIG. 4 which shows the operation | movement of the said LR brake. It is sectional drawing similar to FIG. 4 which shows another operation | movement of the said LR brake. It is a control system figure of the automatic transmission. It is a flowchart of ND control which the control controller of the said automatic transmission performs. It is a time chart of the ND control. FIG. 5 is a cross-sectional view showing the structure of the LR brake when a communication hole for supplying hydraulic pressure to the first hydraulic chamber is provided at the outer peripheral end of the second piston, as compared with FIG. 4.

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

(1) Overall Configuration In the present embodiment, the present invention is applied to the automatic transmission 1 shown in FIG. The automatic transmission 1 is mounted on a horizontally mounted automobile such as a front engine front drive vehicle, for example, and includes a transmission mechanism 2 and a transmission case 3 that houses the transmission mechanism 2. The engine output rotation is input to the input shaft 4 of the speed change mechanism 2 via a torque converter (not shown). The output rotation of the speed change mechanism 2 is taken out from the output gear 5 and transmitted to the drive wheels via a differential device (not shown).

  The speed change mechanism 2 includes a first planetary gear set 10, a second planetary gear set 20, and a third planetary gear set 30. These constitute a power transmission path of the speed change mechanism 2 and are arranged coaxially on the axis of the input shaft 4 in the order described above from the engine side.

  The transmission mechanism 2 further includes a low clutch 40 and a high clutch 50, an LR brake (low reverse brake) 60, a 2-6 brake 70, and an R-3-5 brake 80. These are frictional engagement elements, and are arranged coaxially on the axis of the input shaft 4 in the order described above from the engine side.

  The first planetary gear set 10 and the second planetary gear set 20 are a single pinion type, and the third planetary gear set 30 is a double pinion type. Each planetary gear set 10, 20, 30 has sun gears 11, 21, 31, and pinions 12, 22, 32 (inner pinion in the case of the third planetary gear set 30) that mesh with the sun gears 11, 21, 31. The internal gears 14, 24, 34 that mesh with the carriers 13, 23, 33 that support the pinions 12, 22, 32 and the pinions 12, 22, 32 (the outer pinion in the third planetary gear set 30). And.

  The sun gear 11 of the first planetary gear set 10 and the sun gear 21 of the second planetary gear set 20 are connected, and further connected to the input shaft 4 via the low clutch 40 so as to be freely connected and disconnected.

  The internal gear 14 of the first planetary gear set 10 and the carrier 23 of the second planetary gear set 20 are connected to each other, and are connected to the input shaft 4 via the high clutch 50 so as to be freely connectable and disconnectable. Via the transmission case 3.

  The internal gear 24 of the second planetary gear set 20 and the internal gear 34 of the third planetary gear set 30 are connected, and are further connected to the transmission case 3 via a 2-6 brake 70 so as to be freely connected and disconnected.

  The carrier 33 of the third planetary gear set 30 is connected to the transmission case 3 via the R-3-5 brake 80 so as to be freely connected and disconnected, and the sun gear 31 of the third planetary gear set 30 is connected to the input shaft 4 to thereby connect the first planetary gear. The carrier 13 of the set 10 is connected to the output gear 5.

  In the automatic transmission 1 according to the present embodiment, the frictional engagement elements 40, 50, 60, 70, and 80 are selectively engaged as shown in the engagement table (◯ indicates engagement) in FIG. The power transmission paths of the planetary gear sets 10, 20, and 30 are switched to achieve the forward 1st to 6th speeds and the reverse speed.

  At the first forward speed, which is one of the start gears, the low clutch 40 and the LR brake 60 are engaged. The rotation of the input shaft 4 is input to the sun gear 11 of the first planetary gear set 10. The input rotation is decelerated by the first planetary gear set 10 with a large reduction ratio, and then extracted from the carrier 13 of the first planetary gear set 10 to the output gear 5.

  In the second forward speed, the low clutch 40 and the 2-6 brake 70 are engaged. The rotation of the input shaft 4 is input to the sun gear 11 of the first planetary gear set 10 and the internal gear 14 of the first planetary gear set 10 via the carrier 23 of the second planetary gear set 20. The input rotation is decelerated at a reduction ratio smaller than the first speed, and then extracted from the carrier 13 of the first planetary gear set 10 to the output gear 5.

  At the third forward speed, the low clutch 40 and the R-3-5 brake 80 are engaged. The rotation of the input shaft 4 is performed by the sun gear 11 of the first planetary gear set 10, the internal gear 34 of the third planetary gear set 30 and the internal gear 14 of the first planetary gear set 10 via the carrier 23 of the second planetary gear set 20. Is input. The input rotation is decelerated at a reduction ratio smaller than the second speed, and then taken out from the carrier 13 of the first planetary gear set 10 to the output gear 5.

  At the fourth forward speed, the low clutch 40 and the high clutch 50 are engaged. The rotation of the input shaft 4 is input to the sun gear 11 of the first planetary gear set 10 and the internal gear 14 of the first planetary gear set 10 via the carrier 23 of the second planetary gear set 20 (no deceleration). The input rotation causes the entire first planetary gear set 10 to rotate integrally with the input shaft 4, so that rotation with a reduction ratio of 1 is extracted from the carrier 13 of the first planetary gear set 10 to the output gear 5.

  At the fifth forward speed, the high clutch 50 and the R-3-5 brake 80 are engaged. The input shaft 4 is rotated through the internal gear 34 of the third planetary gear set 30 and the sun gear 11 of the first planetary gear set 10 via the sun gear 21 of the second planetary gear set 20 and the carrier 23 of the second planetary gear set 20. Input to the internal gear 14 of the first planetary gear set 10 (no deceleration). The input rotation is accelerated and then taken out from the carrier 13 of the first planetary gear set 10 to the output gear 5.

  At the sixth forward speed, the high clutch 50 and the 2-6 brake 70 are engaged. The rotation of the input shaft 4 is caused by the sun gear 11 of the first planetary gear set 10 via the sun gear 21 of the second planetary gear set 20 and the internal gear 14 of the first planetary gear set 10 via the carrier 23 of the second planetary gear set 20. (No deceleration). The input rotation is increased at a speed increase ratio larger than the fifth speed, and then extracted from the carrier 13 of the first planetary gear set 10 to the output gear 5.

  The LR brake 60 and the R-3-5 brake 80 are engaged at a reverse speed, which is one of the start gears. The rotation of the input shaft 4 is input to the sun gear 11 of the first planetary gear set 10 via the internal gear 34 of the third planetary gear set 30 and the sun gear 21 of the second planetary gear set 20. The rotation of the input rotation is reversed by the second planetary gear set 20, and after being reduced by the first planetary gear set 10 with a large reduction ratio, the rotation direction of the input shaft 4 from the carrier 13 of the first planetary gear set 10. Is taken out by the output gear 5 as rotation in the opposite direction.

  As shown in FIG. 3, in this embodiment, the hydraulic pressure discharged from the oil pump is adjusted to a predetermined line pressure (indicated by “PL” in the figure) by a regulator valve (not shown), It is always supplied to the hydraulic circuit 200 through a dedicated oil passage, and is supplied to the hydraulic circuit 200 via the manual valve 140 when the D range or R range is selected.

  The hydraulic circuit 200 includes a first linear solenoid valve (hereinafter, the solenoid valve is referred to as “SV”) 121, a second linear SV 122, an on / off SV 123, and a shift valve 130. The first linear SV 121 is for supplying hydraulic pressure to the hydraulic chamber of the low clutch 40. The second linear SV 122 is for supplying hydraulic pressure to an A chamber 61 (first hydraulic chamber) of the LR brake 60 described later. The on / off SV 123 is for switching the position of the spool of the shift valve 130. The shift valve 130 communicates or blocks the second linear SV 122 and the A chamber 61, and a predetermined line pressure supply oil passage 124 and a B chamber 62 (second hydraulic chamber) of the LR brake 60 described later. For communicating or blocking. The spool of the shift valve 130 is always urged to the left with respect to FIG. 3 by a return spring (not shown). A chamber oil passage 63 (first oil chamber oil passage) is provided between the shift valve 130 and the A chamber 61, and a B chamber oil passage 64 (between the shift valve 130 and the B chamber 62). A second hydraulic chamber oil passage) is provided.

  The on / off SV 123 is a normally open type. Therefore, the on / off SV 123 outputs hydraulic pressure in the non-energized state (off), and the spool of the shift valve 130 is positioned on the right side in FIG. The first and second linear SVs 121 and 122 are normally closed types. Therefore, the first and second linear SVs 121 and 122 do not supply hydraulic pressure to the corresponding frictional engagement elements, that is, the low clutch 40 and the LR brake 60 in the non-energized state (off).

(2) Structure of LR brake Next, the structure of the LR brake 60, which is a characteristic part of the present embodiment, will be described with reference to FIGS. 4, 6, and 7, the right side is the engine side and the left side is the anti-engine side.

  As shown in FIG. 4, in this embodiment, the LR brake 60 includes two hydraulic chambers (A chamber 61 and B chamber 62) and two pistons (first piston 65 and first piston 65) as main components. 2 pistons 66) and a plurality of friction plates (drive plate 69a and driven plate 69c). The first piston 65 and the second piston 66 are arranged coaxially on the axis of the input shaft 4 and are arranged in series in the above order in the stroke direction from the friction plates 69a and 69c.

  The first piston 65 has an annular shape when viewed in the axial direction A (see FIG. 5). As shown in FIG. 4, the outer peripheral portion swells toward the opposite engine side, the intermediate portion extends in the radial direction, and the inner peripheral portion. Is inclined to the engine side. The second piston 66 also has an annular shape when viewed in the axial direction A (see FIG. 5). As shown in FIG. 4, the outer peripheral end projects to the anti-engine side, the outer peripheral portion bulges to the engine side, Bulges to the anti-engine side, the inner peripheral portion is inclined to the engine side, and the inner peripheral end portion protrudes to the anti-engine side.

  The first piston 65 has a smaller outer diameter and a larger inner diameter than the second piston 66. The first piston 65 is fitted on the surface of the second piston 66 on the side opposite to the engine.

  A first outer peripheral seal member 67a and a first inner peripheral seal member 67b are mounted on the outer peripheral end portion and the inner peripheral end portion of the first piston 65, respectively. The first outer peripheral seal member 67 a is in contact with the outer peripheral portion of the second piston 66 and is slidable with respect to the second piston 66. The first inner peripheral seal member 67 b is in contact with the inner peripheral end of the second piston 66 and is slidable with respect to the second piston 66. The first outer peripheral seal member 67a and the first inner peripheral seal member 67b are oil-tightly attached to the first piston 65, respectively. Therefore, the first outer peripheral seal member 67a and the first inner peripheral seal member 67b are provided between the first piston 65 and the second piston 66 in the A chamber 61 (more specifically, the A chamber working chamber 61a of the A chamber 61). (See FIG. 7). The A chamber working chamber 61a corresponds to the working hydraulic chamber of the present invention. The first piston 65 is fitted into the second piston 66 so as to be movable together with the second piston 66 and relatively movable with respect to the second piston 66 by the first seal members 67a and 67b.

  The transmission case 3 is provided with a recess 3a that is open on the non-engine side. The concave portion 3a has an annular shape when viewed in the axial direction A, and a protruding portion (hereinafter referred to as “intermediate protruding portion”) 3b is formed at an intermediate portion in the radial direction. The second piston 66 is fitted in the recess 3a.

  A second outer peripheral seal member 68a, a second intermediate seal member 68b, and a second inner peripheral seal member 68c are mounted on the outer peripheral portion, the intermediate portion, and the inner peripheral portion of the second piston 66, respectively. The second outer peripheral seal member 68a is in contact with the outer peripheral wall of the recess 3a and is slidable with respect to the recess 3a. The second intermediate seal member 68b is in contact with the peripheral wall of the intermediate protrusion 3b (in this embodiment, the radially inner peripheral wall) and is slidable with respect to the recess 3a. The second inner peripheral seal member 68c is in contact with the inner peripheral wall of the recess 3a and is slidable with respect to the recess 3a. The second outer peripheral seal member 68a, the second intermediate seal member 68b, and the second inner peripheral seal member 68c are oil-tightly attached to the second piston 66, respectively. For this reason, the second outer peripheral seal member 68a and the second intermediate seal member 68b are provided between the outer peripheral portion of the second piston 66 and the outer peripheral portion of the concave portion 3a. A working chamber 61b) is defined (see FIG. 6). The A chamber non-operating chamber 61b corresponds to the non-operating hydraulic chamber of the present invention. Further, the second intermediate seal member 68b and the second inner peripheral seal member 68c define a B chamber 62 between the inner peripheral portion of the second piston 66 and the inner peripheral portion of the recess 3a (see FIG. 4). That is, the B chamber 62 is disposed on the inner peripheral side in the radial direction with respect to the A chamber non-working chamber 61b. The second piston 66 is movably fitted into the recess 3a by the second seal members 68a, 68b, 68c.

  As shown in FIG. 4, the A chamber oil passage 63 led from the shift valve 130 opens through the wall of the transmission case 3 to the bottom wall on the engine side of the outer peripheral portion of the recess 3 a. Similarly, the B chamber oil passage 64 led from the shift valve 130 passes through the wall of the transmission case 3 and opens to the bottom wall on the engine side of the inner peripheral portion of the recess 3a. The A chamber oil passage 63 opens in the radial direction between the second outer peripheral seal member 68a and the second intermediate seal member 68b, that is, into the A chamber non-operating chamber 61b, and the B chamber oil passage 64 extends in the radial direction. , The second intermediate seal member 68b and the second inner peripheral seal member 68c are open to the B chamber 62.

  The second outer peripheral seal member 68a corresponds to a seal member that defines the outer peripheral end of the non-operating hydraulic chamber (A chamber non-operating chamber 61b) of the present invention, and the second intermediate seal member 68b is the non-operating hydraulic chamber of the present invention. This corresponds to a seal member that defines the inner peripheral end of the (A chamber non-operating chamber 61b). The second outer peripheral seal member 68a and the second intermediate seal member 68b are disposed so as to overlap each other in the stroke direction.

  A communication hole 66 a that communicates between the A chamber working chamber 61 a and the A chamber non-working chamber 61 b is provided in the outer peripheral portion of the second piston 66. The hydraulic pressure supplied to the A chamber non-operating chamber 61b through the A chamber oil passage 63 is supplied to the A chamber operating chamber 61a through the communication hole 66a. The first piston 65 receives the hydraulic pressure supplied to the A-chamber working chamber 61a and strokes on the side opposite to the engine, that is, the side close to the friction plates 69a and 69c (see FIG. 7). In other words, the A chamber 61 is a hydraulic chamber to which hydraulic pressure is supplied to stroke the first piston 65 toward the side close to the friction plates 69a and 69c, and the first piston 65 presses the friction plates 69a and 69c. It is a piston for.

  Here, the A chamber working chamber 61a defined between the first piston 65 and the second piston 66 and the A chamber non-working chamber 61b defined between the second piston 66 and the recess 3a are defined as follows. , Located in series in the stroke direction. Therefore, the communication hole 66 a that communicates these with each other is provided not in the outer peripheral end portion of the second piston 66 but in the central portion, that is, the outer peripheral portion of the second piston 66.

  The second piston 66 receives the hydraulic pressure supplied to the B chamber 62 via the B chamber oil passage 64 and strokes to the opposite engine side, that is, the side close to the friction plates 69a and 69c (see FIG. 6). That is, the B chamber 62 is a hydraulic chamber to which a hydraulic pressure is supplied to stroke the second piston 66 toward the side close to the friction plates 69a and 69c. The second piston 66 causes the first piston 65 to move to the friction plate 69a. , 69c is a piston for moving it to the side close to it.

  As shown in FIG. 4, the A chamber air vent passage 3 c facing the top of the A chamber 61 and the B chamber air vent passage 3 d facing the top of the B chamber 62 are formed in the transmission case 3.

  A rubber ball 162 and an A chamber air vent plug 163 are inserted into the A chamber air vent passage 3c. When a negative pressure is generated in the A chamber 61, the rubber ball 162 abuts the tapered surface of the A chamber air vent passage 3c to close the A chamber 61. On the other hand, when the hydraulic pressure is supplied to the A chamber 61, the rubber ball 162 allows the air mixed in the A chamber 61 to pass away from the tapered surface. The passed air is discharged to the outside of the transmission case 3 through a gap between the A chamber air vent plug 163 and the A chamber air vent passage 3c.

  The B chamber air vent plug 164 is inserted into the B chamber air vent passage 3d. When hydraulic pressure is supplied to the B chamber 62, the air mixed into the B chamber 62 is discharged to the outside of the transmission case 3 through the gap between the B chamber air vent plug 164 and the B chamber air vent passage 3d. Is done.

  The drive plate 69a is spline-engaged with the outer peripheral surface of the internal gear 14 (see FIG. 1) of the first planetary gear set 10. Facing 69b is stuck on both sides of drive plate 69a. The driven plate 69 c is spline-engaged with the inner surface spline portion 3 e of the transmission case 3. A retaining plate 69d is further spline-engaged with the inner surface spline portion 3e. The retaining plate 69d is restricted from moving toward the non-engine side by a snap ring 69e.

  The LR brake 60 is a multi-plate brake, and a plurality of drive plates 69a and a plurality of driven plates 69c are alternately arranged. The friction plates 69a and 69c are disposed between the retaining plate 69d and an outer peripheral portion (hereinafter, sometimes referred to as a “pressing portion”) of the first piston 65 that swells on the opposite side of the engine. It is placed between them. The friction plates 69a and 69c are restricted from moving toward the non-engine side by a retaining plate 69d.

  A return spring 161 is interposed between the retaining plate 69d and the outer peripheral end of the second piston 66. As shown in FIG. 5, a plurality of return springs 161 are provided, and are arranged at equal intervals in the circumferential direction of the second piston 66. The return spring 161 does not act on the first piston 65, but acts only on the second piston 66, thereby connecting the second piston 66 and the first piston 65 fitted in the second piston 66 to the friction plates 69a, 69c. It urges to the side away from.

  The inner surface spline portion 3e is provided with a stopper member 160 formed of a snap ring in the vicinity of the outer peripheral end portion of the second piston 66. The second piston 66 has a portion extending in the radial direction between an outer peripheral end projecting on the anti-engine side and an outer peripheral portion bulging on the engine side abuts on the stopper member 160, so that Movement to the side close to the plates 69a and 69c is restricted (see FIG. 6).

(3) Operation of LR brake Next, the operation of the LR brake 60 will be described.

(I) Release State When the LR brake 60 is in the release state, hydraulic pressure is not supplied to the A chamber 61 and the B chamber 62. As a result, as shown in FIG. 4, the first piston 65 and the second piston 66 are both moved away from the friction plates 69a and 69c by the urging force of the return spring 161.

  In the second piston 66, the intermediate portion that bulges away from the engine comes into contact with the intermediate protrusion 3b of the recess 3a and stops. The first piston 65 is stopped by the intermediate portion extending in the radial direction coming into contact with the intermediate portion of the second piston 66. That is, the position of the first piston 65 and the position of the second piston 66 in this released state are the initial position of the first piston 65 and the initial position of the second piston 66, respectively.

  Since the relative position of the first piston 65 with respect to the second piston 66 changes variously according to the zero clearance position described later, the initial position of the second piston 66 is structurally constant, but the first piston 65 The initial position of is not constant. However, here, when the initial position of the first piston 65 is structurally farthest from the friction plates 69a and 69c (the intermediate portion of the first piston 65 is in contact with the intermediate portion of the second piston 66). Case).

  In this released state, the distance that the second piston 66 can move before the stopper member 160 moves to the side close to the friction plates 69a and 69c, that is, the stroke amount of the second piston 66 is W, and the friction plate If the clearances 69a and 69c (the clutch clearance of the LR brake 60) are V, the dimensions of each part of the LR brake 60 are set so that W ≦ V, preferably W = V.

  In FIG. 4, for the sake of convenience, all the friction plates 69 a and 69 c are adjacent to each other in a non-pressed state (the facing 69 b is not deformed), and the friction plate 69 c that is closest to the engine is on the side opposite to the engine of the first piston. Of the facing 69b adhered to the engine-side surface of the retaining plate 69d and the anti-engine-side surface of the friction plate 69a closest to the engine when contacting the bulging outer peripheral portion (ie, the pressing portion). A distance between the surface opposite to the engine side is indicated as a clutch clearance V.

(Ii) When engaged-to the standby position When the released LR brake 60 is engaged, first, the hydraulic pressure is applied to the B chamber 62 with the first piston 65 and the second piston 66 positioned at the initial positions, respectively. Is supplied. As a result, as shown in FIG. 6, due to the hydraulic pressure supplied to the B chamber 62, the second piston 66 and the first piston 65 fitted into the two piston 66 are both close to the friction plates 69a and 69c. Is stroked.

  At this time, the second piston 66 strokes while the return spring 161 is contracted, that is, against the urging force of the return spring 161.

  In the second piston 66, a portion extending in the radial direction between the outer peripheral end protruding toward the non-engine side and the outer peripheral portion protruding toward the engine contacts the stopper member 160 and stops. The first piston 65 stops while maintaining the state in which the intermediate portion extending in the radial direction is in contact with the intermediate portion of the second piston 66. That is, the position of the first piston 65 and the position of the second piston 66 when the stroke of the second piston 66 ends are the standby position of the first piston 65 and the standby position of the second piston 66, respectively.

  As described above, since the relative position of the first piston 65 with respect to the second piston 66 varies in accordance with the zero clearance position, the standby position of the second piston 66 is structurally constant. The standby position of the piston 65 is not constant. However, here, the case where the intermediate portion of the first piston 65 is in contact with the intermediate portion of the second piston 66 will be described.

  In this standby state, (stroke amount W of second piston 66) ≦ (clutch clearance V), preferably (stroke amount W of second piston 66) = (clutch clearance V). Even when the amount W becomes zero, the first piston 65 does not press the friction plates 69a and 69c (that is, the engagement of the LR brake 60 has not yet started). Specifically, when W <V, the clutch clearance is narrowed (that is, the engagement response is improved), and when W = V, the clutch clearance is zero (that is, the engagement response is improved).

(Iii) At the time of fastening-to the pressing completion position Next, the hydraulic pressure is supplied to the A chamber 61 with the first piston 65 and the second piston 66 positioned at the standby positions. Accordingly, as shown in FIG. 7, only the first piston 65 is stroked to the side close to the friction plates 69a, 69c by the hydraulic pressure supplied to the A chamber 61.

  At this time, the first piston 65 strokes without being affected by the return spring 161.

  The first piston 65 presses the friction plates 69a and 69c at the pressing portion, completes the pressing of the friction plates 69a and 69c, that is, stops the rotation of the drive plate 69a and stops moving. That is, the position of the first piston 65 when the stroke of the first piston 65 is the pressing completion position of the first piston 65. At this time, the drive plate 69a, the facing 69b, the driven plate 69c, the retaining plate 69d, the snap ring 69e and the like are elastically deformed by the pressing force of the first piston 65 (particularly the thickness of the facing 69b is reduced). Thereby, the LR brake 60 will be in a fastening state.

(Iv) When released-to the zero clearance position When the LR brake 60 in the engaged state is released, first, the first piston 65 is positioned at the pressing completion position and the second piston 66 is positioned at the standby position Thus, the hydraulic pressure in the A chamber 61 is discharged. As a result, the pressing force of the first piston 65 is removed. Therefore, as shown in FIG. 6, the friction plates (drive plate 69a, facing 69b, driven plate 69c, retaining plate 69d, and snap ring that have been pressed until then are used. Only the first piston 65 is moved away from the friction plates 69a and 69c.

  The first piston 65 is pushed back by the elastic restoring force to release the pressing of the friction plates 69a and 69c and stops. The position of the first piston 65 at this time is the position where the clutch clearance is the smallest among the clutch clearances where power is not transmitted (that is, the position where the clutch clearance is zero). That is, the position of the first piston 65 at this time is the zero clearance position of the first piston 65.

  This zero clearance position is a position determined by the structural state (for example, thickness and other dimensions) of the friction plate (including drive plate 69a, facing 69b, driven plate 69c, retaining plate 69d, snap ring 69e, etc.) Moreover, it reflects the current structural situation (thickness reduction due to wear, etc.). For example, if the friction plates 69a and 69c are new, the thickness decrease due to wear is small, so the distance that the first piston 65 is pushed back becomes long, the zero clearance position is displaced to the engine side, and the friction plates 69a and 69c If it is old, the thickness is reduced due to wear, etc., so that the distance to which the first piston 65 is pushed back is shortened, and the zero clearance position is displaced to the non-engine side.

  The standby position of the first piston 65 before the L-R brake 60 is engaged and the zero clearance position after the engagement are not always the same. That is, each time the LR brake 60 is engaged, the zero clearance position is updated according to the current structural state of the friction plate, and the relative position of the first piston 65 with respect to the second piston 66 varies depending on the zero clearance position. . Therefore, in many cases, the standby position of the first piston 65 before the LR brake 60 is engaged and the zero clearance position after the engagement do not match.

(V) When released—Up to the initial position Next, the hydraulic pressure in the B chamber 62 is discharged with the first piston 65 positioned at the zero clearance position and the second piston 66 positioned at the standby position. As a result, as shown in FIG. 4, the first piston 65 and the second piston 66 are both moved away from the friction plates 69a and 69c by the urging force of the return spring 161, and are positioned at their initial positions. As a result, the LR brake 60 is released.

  At this time, since the return spring 161 acts only on the second piston 66 and does not act on the first piston 65, the relative position of the first piston 65 with respect to the second piston 66 is maintained without being disturbed. That is, the first piston 65 and the second piston 66 return to the initial positions while the zero clearance position is recorded.

  The initial position of the first piston 65 before engagement of the LR brake 60 and the initial position of the first piston 65 after engagement are not always the same. That is, each time the LR brake 60 is engaged, the zero clearance position is updated according to the current structural state of the friction plate, and the relative position of the first piston 65 with respect to the second piston 66 varies depending on the zero clearance position. . Therefore, in many cases, the initial position of the first piston 65 before the LR brake 60 is engaged and the initial position of the first piston 65 after the engagement are not the same.

(4) Control Operation of Control Controller In the automatic transmission 1 according to the present embodiment, a control controller 100 is provided as shown in FIG. The controller 100 controls the supply and discharge of hydraulic pressure to the hydraulic chamber of the low clutch 40 and the supply and discharge of hydraulic pressure to the A chamber 61 and the B chamber 62 of the LR brake 60. As is well known, the control controller 100 is a microprocessor including a CPU, a ROM, a RAM, and the like. Specifically, the controller 100 detects a signal from the range sensor 101 that detects the selected range, a signal from the brake fluid pressure sensor 102 that detects a brake fluid pressure that reflects the amount of depression of the brake pedal, and an input shaft. And a signal from the turbine rotational speed sensor 103 that detects the rotational speed of 4, and based on these signals, control signals are supplied to the first linear SV 121, the second linear SV 122, and the on / off SV 123 provided in the hydraulic circuit 200. Is output, and ND control is performed. In the ND control, the low clutch 40 and the LR brake 60 are engaged and the low clutch 40 and the LR brake 60 are engaged, and then the vehicle starts. This is control for shifting to a state in which the first forward speed, which is the shift speed, is achieved.

  Next, the ND control performed by the controller 100 will be described based on the flowchart shown in FIG. 9 and the time chart shown in FIG.

  First, the N range is selected until the ND control is started (until time t1). In the N range, the energization amount of the first linear SV 121 is zero, the low clutch pressure (the hydraulic pressure in the hydraulic chamber of the low clutch 40) is drained, and the low clutch 40 is released. Further, the on / off SV 123 is turned off, and the spool of the shift valve 130 is located on the right side with respect to FIG. Therefore, the A chamber hydraulic pressure (the hydraulic pressure of the A chamber 61) and the B chamber hydraulic pressure (the hydraulic pressure of the B chamber 62) of the LR brake 60 are drained, and the LR brake 60 is released. As a result, the first piston 65 and the second piston 66 are in the initial position, and the clutch clearance is large. The brake fluid pressure is high and the driver has not yet requested a start. The energization amount of the second linear SV 122 is set to zero.

  If the controller 100 determines from the signal from the range sensor 101 that there has been a switch from the N range to the D range, it starts ND control (time t1).

  That is, the controller 100 increases the energization amount of the first linear SV 121 from zero to the maximum value (Max) in step S1. As a result, the low clutch pressure increases to the line pressure (PL), and the low clutch 40 is engaged.

  In step S1, the controller 100 switches the on / off SV 123 from off to on. As a result, the spool of the shift valve 130 is positioned on the left side with respect to FIG. 3, the B chamber 62 of the LR brake 60 communicates with the line pressure supply oil passage 124, and the B chamber hydraulic pressure increases to the line pressure (PL). To do. As a result, the first piston 65 and the second piston 66 stroke to the standby position, and the clutch clearance becomes zero (time t2). At this time, the turbine rotational speed slightly decreases to N1.

  Next, when the controller 100 determines in step S2 that the brake fluid pressure has become less than a predetermined pressure (a driver has requested a start) based on a signal from the brake fluid pressure sensor 102, the second linear SV 122 is energized. The amount is gradually increased from zero (time t3). As a result, the hydraulic pressure is supplied to the A chamber 61 of the LR brake 60, and the A chamber hydraulic pressure gradually increases. As a result, the first piston 65 strokes to the pressing completion position, and the turbine rotational speed further decreases.

  In step S3, the controller 100 determines that the turbine rotational speed has reached the target value N2 based on the signal from the turbine rotational speed sensor 103 (the pressing of the friction plates 69a and 69c has been completed, that is, the rotation of the drive plate 69a has been completed). If it is determined that it has stopped, the energization amount of the second linear SV 122 is increased to the maximum value (Max) (time t4). As a result, the A chamber oil pressure increases to the line pressure (PL), and the LR brake 60 is engaged. Thus, the first forward speed in which the low clutch 40 and the LR brake 60 are engaged is achieved.

  Conventionally, instead of the LR brake 60, a one-way clutch is used to achieve the first forward speed. When the one-way clutch is used, there is an advantage that the one-way clutch is naturally locked only by engaging the low clutch, and a first-speed power transmission path is formed. For this reason, it is possible to satisfactorily suppress a shift shock or the like caused by a shift in the engagement timing of the friction engagement element.

  However, the one-way clutch not only increases the cost, weight, and size of the automatic transmission, but also has a problem that drag resistance occurs and the fuel consumption decreases because most of the running time is idle.

  Therefore, in this embodiment, the one-way clutch is abolished and the low clutch 40 and the LR brake 60 are engaged at the first forward speed.

  However, an unpleasant shift shock occurs when the engagement timing of the friction engagement element to be engaged later shifts between the low clutch 40 and the LR brake 60. In particular, since the start gear stage such as the first forward speed has a large reduction ratio and a large torque, the generated shift shock becomes larger.

  Therefore, in this embodiment, paying attention to the fact that the clutch element generates centrifugal hydraulic pressure in the hydraulic chamber and the brake element does not generate centrifugal hydraulic pressure in the hydraulic chamber, the low clutch 40 affected by the centrifugal hydraulic pressure is fastened first. The LR brake 60 that is not affected by the centrifugal hydraulic pressure is fastened later. In this way, since the LR brake 60 is not affected by the centrifugal hydraulic pressure, the LR brake 60 that is to be fastened later can be fastened with high accuracy at an appropriate timing.

  Further, in the present embodiment, the LR brake 60 has a two-stage piston structure and a two-stage stroke structure, and the first piston 65 is put on standby at a stage (time t1) when the LR brake 60 may be engaged. Since the first piston 65 is stroked from the standby position to the pressing completion position at a stage (time t3) when the clutch clearance is narrowed by the stroke to the position and the LR brake 60 needs to be engaged (time t3), The LR brake 60 can be fastened with good responsiveness, the LR brake 60 can be fastened with high accuracy and at appropriate timing, and the shift shock caused by the shift of the fastening timing of the LR brake 60 Can be suppressed even better.

(5) Operation, etc. As described above, the automatic transmission 1 according to this embodiment has the first piston 65 that presses the friction plates 69a and 69c, and the first piston 65 on the side close to the friction plates 69a and 69c. The second piston 66 to be moved is provided with the LR brake 60 arranged in series in this order in the stroke direction from the friction plates 69a and 69c side. The automatic transmission 1 can be fastened with high responsiveness, and the L-R brake 60 can be fastened with accuracy and at appropriate timing. In addition, the automatic transmission 1 according to the present embodiment has the following characteristic configuration.

  The first piston 65 is fitted in the second piston 66 so as to be movable together with the second piston 66 and relatively movable with respect to the second piston 66. The second piston 66 is movably fitted in a recess 3 a provided in the transmission case 3. The A chamber 61 is supplied with hydraulic pressure for moving the first piston 65 toward the side close to the friction plates 69a and 69c, and the hydraulic pressure for moving the second piston 66 toward the side close to the friction plates 69a and 69c. A B chamber 62 to be supplied is provided.

  The A chamber 61 to which hydraulic pressure is applied to stroke the first piston 65 fitted into the second piston 66 to the side close to the friction plates 69 a and 69 c is provided between the first piston 65 and the second piston 66. The A chamber working chamber 61a defined between the second piston 66 and the recess 3a, and the A chamber communicating with the A chamber working chamber 61a through a communication hole 66a provided in the second piston 66. A non-operating chamber 61b is provided, and an A chamber oil passage 63 for supplying hydraulic pressure to the A chamber non-operating chamber 61b opens in the bottom wall of the recess 3a.

  In addition, the B chamber 62 to which hydraulic pressure is applied to stroke the second piston 66 to the side close to the friction plates 69a and 69c is defined between the second piston 66 and the recess 3a. A B chamber oil passage 64 for supplying hydraulic pressure to the B chamber 62 opens in the bottom wall of the recess 3a.

  The A chamber working chamber 61a defined between the first piston 65 and the second piston 66 and the A chamber non-working chamber 61b defined between the second piston 66 and the recess 3a are in the stroke direction. Is located in series. Therefore, the communication hole 66a that communicates them with each other is not provided in the outer peripheral end of the second piston 66, for example, but is provided in the center (the outer peripheral portion of the second piston 66) rather than the outer peripheral end. . Therefore, for example, there is no inconvenience that the outer peripheral end of the second piston 66 becomes longer in the stroke direction as much as the communication hole 66a is provided. Further, for example, the communication hole 66a and the A chamber oil passage 63 always communicate with each other even when the second piston 66 strokes, so that the opening of the A chamber oil passage 63 must be elongated in the stroke direction. There is no such trouble. Therefore, the hydraulic pressure can be supplied to the A chamber 61 without making the transmission case 3 axially long, and the automatic transmission 1 can be made compact and can be mounted on the vehicle.

  FIG. 11 is a cross-sectional view showing the structure of the LR brake when a communication hole j for supplying hydraulic pressure to the A chamber d is provided at the outer peripheral end of the second piston c, in contrast to FIG. . In order to stroke the first piston b fitted into the second piston c toward the side close to the friction plate a, first, the first hydraulic chamber d for the first piston b is moved to the first piston b and the second piston c. It is conceivable to define between

  For example, in FIG. 11, symbol a is a friction plate, symbol b is a first piston, symbol c is a second piston, symbol d is a chamber A for the first piston b, symbol e is B for the second piston c. The chamber, symbol f is a return spring. The outer peripheral end of the second piston c is bent toward the side close to the friction plate a, and the seal member g attached to the first piston b can contact the outer peripheral end of the second piston c and slide in the stroke direction. Like that. An oil passage i for supplying hydraulic pressure to the A chamber d is opened in the wall portion of the transmission case h facing the outer peripheral end of the second piston c, and a communication hole j for communicating the oil passage i with the A chamber d. Is provided at the outer peripheral end of the second piston c. The hydraulic pressure supplied from the oil passage i is supplied to the A chamber d through the communication hole j.

  However, since the communication hole j is provided, the outer peripheral end of the second piston c becomes longer in the stroke direction. Further, it is necessary to lengthen the opening k of the oil passage i in the stroke direction so that the communication hole j and the oil passage i always communicate with each other even when the second piston c strokes. For this reason, the transmission case h becomes longer in the axial direction, and the downsizing of the automatic transmission is hindered, and the mountability on the vehicle is lowered. The LR brake shown in FIG. 11 has such a problem, whereas the LR brake 60 according to the present embodiment has solved the problem.

  In FIG. 11, symbol m is an oil passage for supplying hydraulic pressure to the B chamber e, and symbols n and p are attached to the second piston c to seal the oil passage i, the opening k, and the communication hole j. It is a sealing member.

  In the present embodiment, there is provided a return spring 161 that acts only on the second piston 66 and biases the first piston 65 and the second piston 66 away from the friction plates 69a and 69c.

  According to this configuration, as described in detail above, the friction plate (drive plate 69a, facing 69b, driven plate 69c, retaining plate) may be caused by the individual difference of the LR brake 60 or the secular change. Since the zero clearance position is renewed even when the clutch clearance becomes large due to wear of the plate 69d and snap ring 69e), the standby position of the first piston 65 with respect to the second piston 66 changes, As a result, the length of the first piston 65 from the standby position to the pressing completion position does not increase. As a result, the time required for the first piston 65 to complete the pressing of the friction plates 69a and 69c is not lengthened, the engagement responsiveness of the LR brake 60 is not lowered, and the engagement timing of the LR brake 60 is reduced. An automatic transmission 1 in which accuracy is not lowered is provided.

  In the present embodiment, the B chamber 62 is defined on the inner peripheral side with respect to the A chamber non-working chamber 61b.

  According to this configuration, the B chamber 62 for causing the second piston 66 to stroke between the second piston 66 and the recess 3a is defined on the inner peripheral side of the A chamber non-operating chamber 61b. The volume of the B chamber 62 is reduced, and the amount of hydraulic oil required to stroke the second piston 66 can be reduced.

  In the present embodiment, a second outer peripheral seal member 68a that defines the outer peripheral end of the A chamber non-working chamber 61b and a second intermediate seal member 68b that defines the inner peripheral end are mounted on the second piston 66, and both the seal members 68a and 68b are arranged so as to overlap each other in the stroke direction.

  According to this configuration, since both the sealing members 68a and 68b are arranged so as to overlap each other in the stroke direction, when both the sealing members 68a and 68b are arranged without overlapping each other in the stroke direction, In comparison, the second piston 66 is suppressed from being elongated in the stroke direction, and in this respect, the axial direction of the transmission case 3 is shortened.

  Further, since the second intermediate seal member 68b that defines the inner peripheral end of the A chamber non-operating chamber 61b has a shorter peripheral length than the second outer peripheral seal member 68a that defines the outer peripheral end, the second piston 66 is caused to stroke. The sliding resistance is reduced, and the second piston 66 can be stroked quickly.

  On the other hand, in FIG. 11, the seal members n and p mounted on the second piston c are both arranged on the outer peripheral surface of the second piston c and have a long peripheral length. Is disadvantageous in that the second piston c is rapidly stroked.

  In the above embodiment, the low clutch 40 is not provided with a balance chamber for canceling the centrifugal hydraulic pressure in addition to the normal hydraulic chamber, but may be provided depending on the situation.

  Further, between the second piston 66 and the recess 3a, the A chamber non-working chamber 61b can be disposed on the inner peripheral side, and the B chamber 62 can be disposed on the outer peripheral side. In this case, the communication hole 66a is provided in the inner peripheral portion of the second piston 66, the A chamber oil passage 63 is opened in the bottom wall of the inner peripheral portion of the concave portion 3a, and the B chamber oil passage 64 is provided in the outer peripheral portion of the concave portion 3a. Open in the bottom wall.

  In the above embodiment, the second intermediate seal member 68b is brought into contact with the peripheral wall on the radially inner side of the intermediate projecting portion 3b so as to be slidable with respect to the concave portion 3a. The member 68b may be brought into contact with the peripheral wall on the radially outer side of the intermediate protrusion 3b so as to be slidable with respect to the recess 3a.

  The control operations in FIGS. 9 and 10 are examples, and the present invention is not limited to this. For example, the time change of the low clutch pressure, the time change of the A chamber oil pressure, and the time change of the B chamber oil pressure may be different from those shown in FIG. The second linear SV 122 may increase the energization amount from zero to the maximum value (Max) from the beginning.

  In the ND control, the LR brake 60 may be fastened first, and the low clutch 40 may be fastened later.

  Further, the present invention is not limited to the ND control in which the first forward speed, which is one of the start gears, is achieved from the state where the vehicle is stopped, but at the other one of the start gears from the state where the vehicle is stopped. From the NR control in which a certain reverse speed is achieved, that is, from the state in which the LR brake 60 and the R-3-5 brake 80 are released and the power transmission path of the transmission mechanism 30 is interrupted, the LR brake 60 And the R-3-5 brake 80 may be engaged, and control may be performed to shift to a state in which the reverse speed, which is the starting speed, is achieved.

  Further, for example, from the state where the 2-1 shift control while the vehicle is running, that is, the low clutch 40 and the 2-6 brake 70 are engaged and the second forward speed is achieved, the low clutch 40 and the LR brake 60 are May be controlled to shift to a state in which the first forward speed is achieved.

  Further, the frictional engagement element according to the present invention can be applied to other frictional engagement elements other than the LR brake 60, such as the 2-6 brake 70 and the R-3-5 brake 80.

DESCRIPTION OF SYMBOLS 1 Automatic transmission 3 Transmission case 3a Recess 3b Intermediate protrusion 3c A chamber air vent passage 3d B chamber air vent passage 10 First planetary gear set 20 Second planetary gear set 30 Third planetary gear set 40 Low clutch 60 LR Brake (low reverse brake)
61 Room A (First hydraulic chamber)
61a Chamber A working chamber (working hydraulic chamber)
61b A non-operating chamber (non-operating hydraulic chamber)
62 Room B (2nd hydraulic chamber)
63 Oil passage for room A (oil passage for first hydraulic chamber)
64 Oil passage for room B (oil passage for second hydraulic chamber)
65 1st piston 66 2nd piston 66a Communication hole 67a 1st outer periphery seal member 67b 1st inner periphery seal member 68a 2nd outer periphery seal member (seal member which prescribes | regulates an outer periphery end)
68b Second intermediate seal member (seal member defining inner peripheral end)
68c Second inner peripheral seal member 69a Drive plate (friction plate)
69b facing 69c driven plate (friction plate)
69d Retaining plate 69e Snap ring 100 Control controller 121 First linear solenoid valve 122 Second linear solenoid valve 123 On-off solenoid valve 124 Line pressure supply oil passage 160 Stopper member 161 Return spring 162 Rubber ball 163 A chamber air vent plug 164 B Air vent plug for room V Clutch clearance W Stroke amount of second piston

Claims (3)

A first piston that presses the friction plate, and a second piston that moves the first piston to the side close to the friction plate are provided with a friction fastening element arranged in series in this order in the stroke direction from the friction plate side. A transmission,
The first piston is fitted into the second piston so as to be movable together with the second piston and movable relative to the second piston,
The second piston is movably fitted in a recess provided in the transmission case and opening on the side close to the friction plate ,
A first hydraulic chamber to which hydraulic pressure is supplied to stroke the first piston toward the side close to the friction plate; and second hydraulic pressure to supply stroke to the side close to the friction plate. A hydraulic chamber,
The first hydraulic chamber is defined between a working hydraulic chamber defined between the first piston and the second piston, and between the second piston and the recess, and is provided in the second piston. A non-actuating hydraulic chamber that communicates with the operating hydraulic chamber via the communication hole formed,
The second hydraulic chamber is defined between the second piston and the recess,
A first hydraulic chamber oil passage for supplying hydraulic pressure to the non-actuating hydraulic chamber and a second hydraulic chamber oil passage for supplying hydraulic pressure to the second hydraulic chamber are provided on the side of the concave portion away from the friction plate. An automatic transmission characterized by opening in the bottom wall. The automatic transmission according to claim 1, wherein
2. The automatic transmission according to claim 1, wherein the second hydraulic chamber is defined on an inner peripheral side with respect to the non-actuating hydraulic chamber. The automatic transmission according to claim 2, wherein
A seal member that defines an outer peripheral end of the non-operating hydraulic chamber and a seal member that defines an inner peripheral end are attached to the second piston,
An automatic transmission characterized in that both seal members are arranged so as to overlap each other in the stroke direction.

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