JP2019190598A - Automatic transmission - Google Patents

Abstract

To reduce a drive loss and weight by fastening and releasing a clutch by using a piezoelectric actuator, and to constitute an automatic transmission compact in a size in a radial direction, in the automatic transmission in which the two clutches are overlappingly arranged in an axial direction.SOLUTION: A first clutch 40 comprises a first rotating member 41, a second rotating member 42 arranged at an external peripheral side, and a piezoelectric actuator 45 connected to an external peripheral face of the first rotating member 41, and pressing the second rotating member 42. A second clutch 50 comprises the first rotating member 41, a third rotating member 52 arranged at an internal peripheral side, and a piezoelectric actuator connected to an internal peripheral face of the first rotating member 41, and pressing the third rotating member 52. The first clutch piezoelectric actuator 45 and the second clutch piezoelectric actuator are overlapped radially on each other, and arranged in different positions in a peripheral direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an automatic transmission mounted on a vehicle, and belongs to the technical field of an automatic transmission for a vehicle.

  An automatic transmission mounted on a vehicle generally includes a transmission mechanism that is connected to a drive source such as an engine and includes a plurality of planetary gear sets (planetary gear mechanisms) and a plurality of frictional engagement elements such as clutches and brakes. By selectively engaging a plurality of frictional engagement elements, a power transmission path passing through each planetary gear set is switched to achieve a plurality of forward shift speeds and typically one reverse speed.

  The friction engagement element includes a plurality of friction plates and a piston that presses the plurality of friction plates and fastens the friction engagement element when hydraulic pressure is supplied to the hydraulic chamber, and uses a hydraulically operated piston to perform friction engagement. Multi-plate frictional engagement elements that engage and disengage elements are known.

  However, in a multi-plate friction engagement element using hydraulic pressure, a hydraulic pump is used to supply the hydraulic pressure. Therefore, driving loss increases as the hydraulic pump is driven, and the weight increases due to the hydraulic pump. Can cause a drop.

  On the other hand, instead of using a hydraulically-actuated piston as a frictional engagement element of an automatic transmission, it is conceivable to use a piezoelectric actuator that is an electric actuator to engage and release the frictional engagement element. For example, Patent Document 1 relates to a clutch device disposed between an internal combustion engine, an electric machine, and a transmission, but discloses that a piezoelectric actuator is used as an electric actuator.

Special table 2015-500965 gazette

  In an automatic transmission having a speed change mechanism including a plurality of frictional engagement elements, there are cases where two clutches are arranged to overlap in the axial direction. For each of the two clutches arranged to overlap in the axial direction, instead of using a hydraulically operated piston, the clutch is engaged and disengaged using a piezoelectric actuator that is an electric actuator. It is considered that driving loss and weight can be reduced. However, it is a problem how to achieve engagement and disengagement of the clutch using the piezoelectric actuator.

  Further, when the two clutches are arranged so as to overlap in the axial direction, it is considered that the two clutches are arranged on the inner side and the outer side in the radial direction, but the radial dimension may be increased. .

  Accordingly, the present invention is an automatic transmission in which two clutches are arranged so as to overlap in the axial direction, and realizes engagement and disengagement of the clutch using a piezoelectric actuator to reduce drive loss and weight and radial direction. It is an object to make it compact.

  In order to solve the above problems, the present invention is configured as follows.

  First, the invention according to claim 1 of the present application is an automatic transmission having a transmission mechanism including a plurality of frictional engagement elements including a first clutch and a second clutch that are arranged in an axially overlapping manner in a transmission case. In the transmission, the first clutch is coupled to and applied to a first rotating member, a second rotating member disposed on the outer peripheral side of the first rotating member, and an outer peripheral surface of the first rotating member. And a plurality of first clutch piezoelectric actuators that are displaced radially outward in response to a voltage to press the second rotating member and fasten the first clutch, and the second clutch includes the first rotating member. A third rotating member disposed on the inner peripheral side of the first rotating member; and a third rotating member coupled to an inner peripheral surface of the first rotating member and displaced radially inward according to an applied voltage. Press the rotating member to tighten the second clutch A plurality of second clutch piezoelectric actuators, and the plurality of first clutch piezoelectric actuators and the plurality of second clutch piezoelectric actuators are arranged at different positions in the circumferential direction so as to overlap in the radial direction. It is characterized by.

  The invention according to claim 2 is the invention according to claim 1, wherein the plurality of frictional engagement elements include a plurality of brakes arranged side by side in the axial direction, A brake drum, and a plurality of brake piezoelectric actuators that are coupled to the transmission case and press the brake drum to fasten the brake, wherein each of the plurality of brake piezoelectric actuators corresponds to an applied voltage The brake drums of the plurality of brakes are formed on the outer peripheral side of the brake drums of the plurality of brakes and are configured to press in the radial direction by being displaced in the radial direction based on the expansion / contraction displacement of the piezoelectric element that expands and contracts in the axial direction. And the brakes corresponding to the plurality of brakes. Rk in the piezoelectric actuator is characterized by being disposed at different positions in the circumferential direction.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the speed change mechanism has a predetermined speed change when a non-voltage is applied to the piezoelectric actuators of the plurality of frictional engagement elements. The piezoelectric actuator of the frictional engagement element that is configured to achieve a stage and is fastened at the predetermined shift stage is formed to fasten the frictional engagement element when a non-voltage is applied, and is released at the predetermined shift stage. The frictional engagement element piezoelectric actuator is formed to release the frictional engagement element when no voltage is applied.

  According to the first aspect of the present invention, the first clutch is coupled to the first rotating member, the second rotating member disposed on the outer peripheral side, and the outer peripheral surface of the first rotating member to perform the second rotation. A piezoelectric actuator that presses the member, and the second clutch is coupled to the first rotating member, the third rotating member disposed on the inner peripheral side, and the inner peripheral surface of the first rotating member, and is connected to the third rotating member. And a piezoelectric actuator for pressing.

  As a result, the first clutch and the second clutch are each engaged using a piezoelectric actuator, so that the drive loss and weight of the hydraulic pump are reduced as compared with the case where the brake is engaged using a hydraulically operated piston. Can be achieved.

  In addition, the first clutch piezoelectric actuator and the second clutch piezoelectric actuator overlap in the radial direction and are arranged at different positions in the circumferential direction, thereby overriding the first clutch and the second clutch in the radial direction. Since it can wrap and arrange | position, it can comprise compactly in radial direction.

  Therefore, in an automatic transmission in which two clutches are overlapped in the axial direction, the clutch is engaged and disengaged using a piezoelectric actuator to reduce drive loss and weight and to be compact in the radial direction. can do.

  According to the second aspect of the present invention, each of the plurality of brakes arranged side by side in the axial direction includes a brake drum and a plurality of piezoelectric actuators that are coupled to the transmission case and press the brake drum. Each of the plurality of piezoelectric actuators is formed so as to be displaced in the radial direction based on the expansion / contraction displacement of the piezoelectric element that expands / contracts in the axial direction and presses the brake drum, and in the circumferential direction on the outer peripheral side of the plurality of brake drums. Distributed.

  As a result, the plurality of brakes are fastened by using a plurality of piezoelectric actuators arranged in the circumferential direction, so that the hydraulic pump can be compared with the case where the brakes are fastened by using hydraulically operated pistons. It is possible to reduce the driving loss and weight.

  Even when a piezoelectric actuator with a small displacement is used, the piezoelectric actuator is arranged on the outer peripheral side of the brake drum of a plurality of brakes arranged side by side in the axial direction so as to overlap the plurality of brake drums in the axial direction. The piezoelectric actuators corresponding to the respective brakes are arranged at different positions in the circumferential direction, so that the piezoelectric actuators of the respective brakes are arranged on the outer peripheral side of the respective brake drums. The actuator can be formed long in the axial direction, and the displacement amount of the piezoelectric actuator can be increased, and the engagement and release of the brake can be realized using the piezoelectric actuator.

  In addition, each brake is pressed and released by a plurality of piezoelectric actuators distributed in the circumferential direction to engage and release the brake. Therefore, a multi-plate type is used as a band type brake including a plurality of piezoelectric actuators. The amount of displacement for fastening can be reduced as compared with the case of using this brake, and the fastening and releasing of the brake can be effectively realized.

  Therefore, when a plurality of brakes are arranged side by side in the axial direction, the driving loss and weight can be reduced by realizing the fastening and releasing of the plurality of brakes using the piezoelectric actuator.

  According to a third aspect of the present invention, the speed change mechanism is configured to achieve a predetermined speed when a non-voltage is applied to each piezoelectric actuator of the plurality of frictional engagement elements, and at the predetermined speed. The piezoelectric actuator of the frictional engagement element to be fastened is formed so as to fasten the frictional engagement element when a non-voltage is applied, and the piezoelectric actuator of the frictional engagement element released at a predetermined speed is applied to the frictional engagement element when a non-voltage is applied. Formed to release elements.

  Thus, even when a failure occurs in which a voltage cannot be applied to each of the piezoelectric actuators of the plurality of frictional engagement elements while the vehicle equipped with the automatic transmission is running, the speed change mechanism is, for example, the fourth speed A predetermined shift speed such as a shift speed can be achieved and fail-safe traveling at the predetermined shift speed can be performed.

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 friction engaging element of an automatic transmission. It is sectional drawing of the friction engaging element of an automatic transmission, and its periphery. It is a figure which shows the frictional engagement element of the automatic transmission seen from the Y4-Y4 direction of FIG. It is a figure which shows the frictional engagement element of the automatic transmission seen from the Y5-Y5 direction of FIG. It is explanatory drawing for demonstrating the piezoelectric actuator of a 1st brake. FIG. 3 is a cross-sectional view of a brake of the automatic transmission and its surroundings. It is sectional drawing of the clutch of an automatic transmission, and its periphery. It is a perspective view which shows the 1st rotation member and the piezoelectric actuator couple | bonded with the 1st rotation member. It is a perspective view which shows the piezoelectric actuator couple | bonded with the 1st rotation member. It is explanatory drawing for demonstrating the piezoelectric actuator of a 1st clutch.

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

  FIG. 1 is a skeleton diagram of an automatic transmission according to an embodiment of the present invention. The automatic transmission 1 is mounted on a horizontal engine type vehicle such as a front engine or a front drive vehicle, and is connected to a drive source such as an engine in a transmission case 2 and includes a plurality of planetary gear sets, clutches and brakes. A speed change mechanism 4 including a plurality of frictional engagement elements such as the above is provided.

  The transmission mechanism 4 includes first, second, and third planetary gear sets (as a plurality of planetary gear sets) arranged side by side in the axial direction from the drive source side (right side in the drawing) on the input shaft 3 connected to the drive source. (Hereinafter referred to as “first, second, and third gear sets”) 10, 20, and 30.

  The speed change mechanism 4 also transmits power from the input shaft 3 to the gear sets 10, 20, 20 as a plurality of frictional engagement elements for switching the power transmission path constituted by the gear sets 10, 20, 30 on the input shaft 3. A first clutch 40 and a second clutch 50 that selectively transmit to the 30 side, and a first brake 60, a second brake 70, and a third brake 80 that fix predetermined rotating elements of the gear sets 10, 20, 30. I have.

  The first clutch 40 and the second clutch 50 are disposed so as to overlap in the axial direction. The first brake 60, the second brake 70, and the third brake 80 are arranged on the opposite drive source side of the first clutch 40 and the second clutch 50 along the axial direction from the drive source side.

  Of the first, second, and third gear sets 10, 20, 30, the first gear set 10 and the second gear set 20 are single pinion type, and are engaged with the sun gears 11, 21 and these sun gears 11, 21. Each of the plurality of pinions 12 and 22 includes carriers 13 and 23 that respectively support the pinions 12 and 22, and ring gears 14 and 24 that mesh with the pinions 12 and 22.

  The third gear set 30 is a double sun gear type, and supports a sun gear 31, a plurality of first pinions 32a meshed with the sun gear 31, a second pinion 32b meshed with the first pinion 32a, and these pinions 32a and 32b. Carrier 33, and a ring gear 34 meshed with the second pinion 32b.

  The input shaft 3 is connected to the sun gear 31 of the third gear set 30 and the input member 41 of the first clutch 40 and the second clutch 50, and the sun gear 11 of the first gear set 10 and the sun gear 21 of the second gear set 20. Are coupled to the output member 42 of the first clutch 40, and the output member 52 of the second clutch 50 is coupled to the carrier 23 of the second gear set 20.

  Further, the ring gear 14 of the first gear set 10 and the carrier 23 of the second gear set 20 are coupled, and a first brake 60 is disposed between these and the transmission case 2, and the ring gear 24 of the second gear set 20 The ring gear 34 of the third gear set 30 is coupled, a second brake 70 is disposed between them and the transmission case 2, and further, between the carrier 33 of the third gear set 30 and the transmission case 2. A third brake 80 is provided.

  The output gear 5 that outputs the output of the automatic transmission 1 to the drive wheel side is connected to the carrier 13 of the first gear set 10. The output gear 5 is disposed between the first clutch 40 and the second clutch 50 and the first gear set 10 in the axial direction.

  With the above-described configuration, the automatic transmission 1 has a combination of engagement states of the first clutch 40, the second clutch 50, the first brake 60, the second brake 70, and the third brake 80, as shown in FIG. The first to sixth gears in the range and the reverse gear in the R range are formed.

  The first brake 60, the second brake 70, and the third brake 80 in the present embodiment correspond to a plurality of brakes arranged side by side in the axial direction according to the present invention, and the first clutch 40 and the second clutch in the present embodiment. 50 corresponds to the two clutches arranged to overlap in the axial direction according to the present invention.

  3 is a cross-sectional view of the frictional engagement element of the automatic transmission and its surroundings, FIG. 4 is a view showing the frictional engagement element of the automatic transmission as viewed from the Y4-Y4 direction of FIG. 3, and FIG. It is a figure which shows the frictional engagement element of the automatic transmission seen from Y5-Y5 direction.

  As shown in FIGS. 3 to 5, the automatic transmission 1 includes a transmission mechanism 4 on an input shaft 3 that is rotatably supported in a transmission case 2. The transmission case 2 is provided with a vertical wall portion 2b extending radially inward on the axially central side of the outer peripheral portion 2a formed in a cylindrical shape, and the first clutch 40 and the first clutch 40 on the drive source side of the vertical wall portion 2b. The two clutches 50 are disposed so as to overlap in the axial direction, and the first brake 60, the second brake 70, and the third brake 80 are disposed side by side in the axial direction on the counter drive source side of the vertical wall portion 2b.

  First, the first brake 60, the second brake 70, and the third brake 80 of the automatic transmission 1 will be described.

  As shown in FIG. 3, the first brake 60 is coupled to the brake drum 61 as a rotating member formed in a cylindrical shape and the transmission case 2 and presses the brake drum 61 to fasten the first brake 60. And a plurality of piezoelectric actuators 62. The brake drum 61 is formed integrally with the ring gear 14 on the outer peripheral side of the ring gear 14 of the first gear set 10, and is coupled to the ring gear 14 of the first gear set 10 and the carrier 23 of the second gear set 20.

  The piezoelectric actuator 62 includes a piezoelectric element 63 that expands and contracts in the axial direction according to an applied voltage, and a displacement conversion mechanism 64 that expands and converts the expansion and contraction displacement of the piezoelectric element 63 into a radial displacement orthogonal to the axial direction. The piezoelectric element 63 is expanded and contracted in the axial direction according to the applied voltage. The piezoelectric element 63 is displaced in the radial direction to press the brake drum 61.

  The piezoelectric element 63 is formed in a quadrangular prism shape so as to extend in the axial direction. As a material of the piezoelectric element 63, for example, a ceramic material such as lead zirconate titanate (PZT) is used. The displacement conversion mechanism 64 includes a displacement conversion member 65 to which end faces on both sides in the axial direction of the piezoelectric element 63 are respectively attached and which expands and converts the axial expansion / contraction displacement of the piezoelectric element 63 into a radial displacement.

  The displacement converting member 65 is formed using a metal material, and is connected to the side surface portions 65a on both sides to which the piezoelectric element 63 is attached and the radially outer ends of the side surface portions 65a on both sides and extends in the axial direction. 65b and an inner surface portion 65c extending in the axial direction by connecting the radially inner ends of the side surface portions 65a on both sides, and formed in a substantially quadrangular cross section when viewed in the circumferential direction.

  The outer surface portion 65b of the displacement converting member 65 is provided to be inclined so as to be recessed inward in the radial direction from both axial sides toward the axial center side (see FIG. 6), and both axial sides on the radial center side of the outer surface portion 65b. A fixing portion 65d is provided that protrudes radially outward from the end portion. The inner surface portion 65c of the displacement converting member 65 is provided to be inclined so as to be recessed radially outward from both axial sides toward the axial center side (see FIG. 6), and both axial sides on the radial center side of the inner surface portion 65c. An output portion 65e that protrudes inward in the radial direction from the end portion is provided.

  The displacement converting member 65 has a distance from the corner portion between the side surface portion 65a and the inner surface portion 65c on both sides to the output portion 65e on the inner surface portion 65c, respectively, between the side surface portion 65a and the inner surface portion 65c on both sides. Is formed to be longer than the distance from the side portion 65a to the portion to which the piezoelectric element 63 is attached, and to expand and convert the axial expansion / contraction displacement of the piezoelectric element 63 into a radial displacement. As the displacement conversion member 65, it is possible to use a displacement conversion member having another shape that converts the expansion / contraction displacement in the axial direction of the piezoelectric element 63 into the displacement in the radial direction.

  The output portion 65e of the displacement converting member 65 is connected to a pressing portion 65f disposed on the outer peripheral side of the brake drum 61 so as to face the brake drum 61. The pressing portion 65f causes the brake drum 61 to be connected via the friction material 66. It comes to press. The friction material 66 is formed using, for example, paper.

  As shown in FIG. 4, each of the plurality of piezoelectric actuators 62 is fitted to a first brake spline 2 c formed on the outer peripheral portion 2 a of the transmission case 2, and the fixed portion 65 d of the displacement converting member 65 is the first. It is fixedly attached to the brake spline 2 c and is coupled to the transmission case 2.

  The piezoelectric actuator 62 is adapted to apply a predetermined voltage to the piezoelectric element 63 by a voltage applying device (not shown). The operation of the voltage application device is controlled by a control device (not shown).

  The plurality of piezoelectric actuators 62 are arranged at substantially the same position in the axial direction, and the brake drums 61, 71 are arranged on the outer peripheral sides of the brake drums 61, 71, 81 of the first brake 60, the second brake 70, and the third brake 80, respectively. , 81 overlap with each other in the axial direction and are distributed in the circumferential direction. In the automatic transmission 1, the seven piezoelectric actuators 62 are arranged at substantially equal intervals in the circumferential direction.

  FIG. 6 is an explanatory diagram for explaining the piezoelectric actuator of the first brake. In FIG. 6, the cross-sectional shape of the piezoelectric actuator is exaggerated for easy understanding. When no voltage is applied to the piezoelectric element 63, the piezoelectric actuator 62 includes a pressing portion 65 f connected to the output portion 65 e of the displacement converting member 65 and the brake drum 61 as shown in FIG. The brakes 60 are disengaged from each other in the radial direction.

  On the other hand, when a predetermined voltage is applied to the piezoelectric element 63, the piezoelectric actuator 62 expands and displaces the piezoelectric element 63 in the axial direction according to the applied voltage as shown in FIG. The displacement of the element 63 in the axial direction is enlarged and converted in the radial direction by the displacement conversion member 65, the output portion 65e is displaced inward in the radial direction, and the pressing portion 65f is displaced inward in the radial direction to press the brake drum 61. The brake 60 is in the engaged state.

  Thus, the first brake piezoelectric actuator 62 is formed to be displaced in the radial direction and press the brake drum 61 based on the expansion / contraction displacement of the piezoelectric element 63 that expands / contracts in the axial direction according to the applied voltage. Yes. The plurality of first brake piezoelectric actuators 62 are configured in the same manner, and the application of voltage is similarly controlled, so that the first brake 60 is engaged and released.

  FIG. 7 is a cross-sectional view of the brake and its surroundings of the automatic transmission. FIG. 7A is a sectional view of the second brake of the automatic transmission and its surroundings, and FIG. 7B is a sectional view of the third brake of the automatic transmission and its surroundings. The second brake and the third brake are formed in substantially the same manner as the first brake, and the same components as those in the first brake are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 7A, the second brake 70 is coupled to the brake drum 71 as a rotating member formed in a cylindrical shape and the transmission case 2, and presses the brake drum 71 to press the second brake 70. And a plurality of piezoelectric actuators 72 for fastening 70. The brake drum 71 is disposed on the side opposite to the drive source of the ring gear 24 of the second gear set 20 and is coupled to the ring gear 24 of the second gear set 20 and the ring gear 34 of the third gear set 30. The brake drum 71 of the second brake 70 has an outer diameter substantially equal to that of the brake drum 61 of the first brake 60 and is disposed on the side opposite to the drive source of the brake drum 61.

  The piezoelectric actuator 72 is formed in substantially the same manner as the piezoelectric actuator 62, has a piezoelectric element 63 and a displacement conversion mechanism 64, and is radial based on the expansion / contraction displacement of the piezoelectric element 63 that expands / contracts in the axial direction according to the applied voltage. And the brake drum 71 is pressed.

  In the piezoelectric actuator 72, the output portion 65 e of the displacement converting member 65 is connected to a pressing portion 75 f disposed on the outer peripheral side of the brake drum 71 so as to face the brake drum 71, and the pressing portion 75 f is interposed via the friction material 66. Thus, the brake drum 71 is pressed.

  As shown in FIG. 4, each of the plurality of piezoelectric actuators 72 is fitted into a second brake spline 2d formed on the outer peripheral portion 2a of the transmission case 2, and the fixed portion 65d of the displacement converting member 65 is a second one. It is fixedly attached to the brake spline 2 d and is coupled to the transmission case 2.

  The plurality of piezoelectric actuators 72 are arranged at substantially the same position in the axial direction, and the brake drums 61, 71 are arranged on the outer peripheral sides of the brake drums 61, 71, 81 of the first brake 60, the second brake 70, and the third brake 80. , 81 overlap with each other in the axial direction and are distributed in the circumferential direction. In the automatic transmission 1, seven piezoelectric actuators 72 are arranged at substantially equal intervals in the circumferential direction. The plurality of second brake piezoelectric actuators 72 are respectively disposed adjacent to one side in the circumferential direction of the first brake piezoelectric actuator 62.

  Also for the piezoelectric actuator 72, a predetermined voltage is applied to the piezoelectric element 63 by the voltage application device controlled by the control device. When a non-voltage is applied to the piezoelectric actuator 72, the pressing portion 75f connected to the output portion 65e of the displacement converting member 65 is disposed away from the brake drum 71 in the radial direction, and the brake 70 is released, while the voltage is At the time of application, the piezoelectric element 63 expands and displaces in the axial direction according to the applied voltage, and the axial displacement of the piezoelectric element 63 expands and is converted in the radial direction so that the output portion 65e is displaced radially inward. The pressing portion 75f is displaced inward in the radial direction to press the brake drum 71, and the brake 70 is brought into an engaged state.

  Thus, the second brake piezoelectric actuator 72 is formed to be displaced in the radial direction and press the brake drum 71 based on the expansion / contraction displacement of the piezoelectric element 63 that expands / contracts in the axial direction according to the applied voltage. Yes. The plurality of second brake piezoelectric actuators 72 are configured in the same manner, and the voltage application is similarly controlled, so that the second brake 70 is engaged and released.

  As shown in FIG. 7B, the third brake 80 is coupled to the brake drum 81 as a rotating member formed in a cylindrical shape and the transmission case 2 and presses the brake drum 81 to press the third brake 80. And a plurality of piezoelectric actuators 82 for fastening 80. The brake drum 81 is disposed on the outer peripheral side of the ring gear 34 of the third gear set 30 and is coupled to the carrier 33 of the third gear set 30. The brake drum 81 of the third brake 80 has an outer diameter substantially the same as that of the brake drum 71 of the second brake 70 and is disposed on the counter drive source side of the brake drum 71.

  The piezoelectric actuator 82 is formed in substantially the same manner as the piezoelectric actuator 62, has a piezoelectric element 63 and a displacement conversion mechanism 64, and is radial based on the expansion / contraction displacement of the piezoelectric element 63 that expands / contracts in the axial direction according to the applied voltage. And the brake drum 81 is pressed.

  In the piezoelectric actuator 82, the output portion 65 e of the displacement converting member 65 is connected to a pressing portion 85 f disposed on the outer peripheral side of the brake drum 81 so as to face the brake drum 81, and the pressing portion 85 f is interposed via the friction material 66. Thus, the brake drum 81 is pressed.

  As shown in FIG. 4, each of the plurality of piezoelectric actuators 82 is fitted to a third brake spline 2e formed on the outer peripheral portion 2a of the transmission case 2, and a fixed portion 65d of the displacement converting member 65 is a third one. It is fixedly attached to the brake spline 2e and is coupled to the transmission case 2.

  The plurality of piezoelectric actuators 82 are arranged at substantially the same position in the axial direction, and the brake drums 61, 71 are arranged on the outer peripheral sides of the respective brake drums 61, 71, 81 of the first brake 60, the second brake 70, and the third brake 80. , 81 overlap with each other in the axial direction and are distributed in the circumferential direction. In the automatic transmission 1, seven piezoelectric actuators 82 are disposed at substantially equal intervals in the circumferential direction. Each of the plurality of third brake piezoelectric actuators 82 is disposed adjacent to the other circumferential side of the first brake piezoelectric actuator 62.

  Also for the piezoelectric actuator 82, a predetermined voltage is applied to the piezoelectric element 63 by the voltage application device controlled by the control device. When a non-voltage is applied to the piezoelectric actuator 82, the pressing portion 85f connected to the output portion 65e of the displacement converting member 65 is disposed to be spaced apart from the brake drum 81 in the radial direction, and the brake 80 is released, while the voltage is At the time of application, the piezoelectric element 63 expands and displaces in the axial direction according to the applied voltage, and the axial displacement of the piezoelectric element 63 expands and is converted in the radial direction so that the output portion 65e is displaced radially inward. The pressing portion 85f is displaced radially inward to press the brake drum 81, and the brake 80 is brought into an engaged state.

  Thus, the third brake piezoelectric actuator 82 is formed to be displaced in the radial direction and press the brake drum 81 based on the expansion / contraction displacement of the piezoelectric element 63 that expands / contracts in the axial direction according to the applied voltage. Yes. The plurality of third brake piezoelectric actuators 82 are configured in the same manner, and voltage application is similarly controlled, and the third brake 80 is engaged and released.

  The first brake 60, the second brake 70, and the third brake 80 are engaged and disengaged according to the engagement table shown in FIG. 2, and the brakes 60, 70, The voltage applied to the 80 piezoelectric actuators 62, 72, 82 is controlled.

  Next, the first clutch 40 and the second clutch 50 of the automatic transmission 1 will be described.

  FIG. 8 is a cross-sectional view of the clutch of the automatic transmission and its periphery, and shows a cross-sectional view of the clutch different from the clutch shown in FIG. 3 and its periphery. FIG. 9 is a perspective view showing the first rotating member and the piezoelectric actuator coupled to the first rotating member, and FIG. 10 is a perspective view showing the piezoelectric actuator coupled to the first rotating member.

  As shown in FIG. 3, the first clutch 40 includes a first rotating member 41 as a clutch hub formed in a bottomed cylindrical shape, and is disposed on the outer peripheral side of the first rotating member 41 formed in a bottomed cylindrical shape. And a plurality of piezoelectric actuators 45 that are coupled to the outer peripheral surface of the first rotating member 41 and press the second rotating member 42 to fasten the first clutch 40. ing.

  The first rotating member 41 is an input member of the first clutch 40, and is formed in a substantially disc shape extending inward in the radial direction from the drive source side of the cylindrical portion 41a and the cylindrical portion 41a extending in the axial direction in a substantially cylindrical shape. A vertical wall portion 41 b and coupled to the input shaft 3.

  The second rotating member 42 is an output member of the first clutch 40, and is formed in a substantially disc shape extending inward in the radial direction from the side opposite to the driving source of the cylindrical portion 42a and the cylindrical portion 42a in the axial direction. And is connected to the sun gear 11 of the first gear set 10 and the sun gear 21 of the second gear set 20 by being coupled to a power transmission member X1 extending in the axial direction.

  As shown in FIG. 8, the second clutch 50 includes a first rotating member 41 as a clutch drum formed in a bottomed cylindrical shape, and a bottomed cylindrical shape formed on the inner peripheral side of the first rotating member 41. A third rotating member 52 serving as a clutch hub, and a plurality of piezoelectric actuators 55 coupled to the inner peripheral surface of the first rotating member 41 and pressing the third rotating member 52 to fasten the second clutch 50; It has.

  The first rotating member 41 is an input member of the first clutch 40 and an input member of the second clutch 50, and includes a cylindrical portion 41 a and a vertical wall portion 41 b and is coupled to the input shaft 3.

  The third rotating member 52 is an output member of the second clutch 50, and is formed in a substantially disc shape extending inward in the radial direction from the side opposite to the driving source of the cylindrical portion 52a and the cylindrical portion 52a. A vertical wall portion 52b that is coupled to the power transmission member X2 extending in the axial direction and coupled to the carrier 23 of the second gear set 20.

  As shown in FIGS. 5 and 9, the first rotating member 41 includes a plurality of inner recesses 43 that are recessed in a substantially rectangular cross section from the radially inner side to the radially outer side in the cylindrical portion 41 a in the circumferential direction. Is formed. In the automatic transmission 1, seven inner recesses 43 are formed in the cylindrical portion 41a so as to be spaced apart at substantially equal intervals in the circumferential direction.

  Each of the plurality of inner recesses 43 of the first rotating member 41 includes a bottom surface portion 43a and side surface portions 43b on both sides extending radially inward from both circumferential sides of the bottom surface portion 43a. The outer peripheral surface of the bottom surface portion 43a is formed in an arc shape, and hollow portions 43c extending in the axial direction are formed inside the side surface portions 43b on both sides.

  The first rotating member 41 also has a substantially rectangular cross section from the radially outer side to the radially inner side of the cylindrical portion 41a by the side surface portion 43b of the adjacent inner concave portion 43 and the portion of the cylindrical portion 41a where the inner concave portion 43 is not formed. A plurality of outer recesses 44 that are recessed in a concave shape are formed dispersed in the circumferential direction. In the automatic transmission 1, seven outer recessed portions 44 are formed in the cylindrical portion 41a so as to be spaced apart at substantially equal intervals in the circumferential direction.

  A piezoelectric actuator 45 is disposed in each of the outer concave portions 44 of the first rotating member 41. The piezoelectric actuator 45 is coupled to the outer peripheral surface of the portion of the cylindrical portion 41 a where the inner concave portion 43 is not formed, and is coupled to the outer peripheral surface of the first rotating member 41.

  Piezoelectric actuators 55 are disposed in the inner recesses 43 of the first rotating member 41, respectively. The piezoelectric actuator 55 is coupled to the inner peripheral surface of the portion of the cylindrical portion 41 a where the inner concave portion 43 is formed, and is coupled to the inner peripheral surface of the first rotating member 41.

  The plurality of first clutch piezoelectric actuators 45 and the plurality of second clutch piezoelectric actuators 55 are arranged at substantially the same position in the axial direction, overlap in the axial direction, overlap in the radial direction, and differ in the circumferential direction. Placed in position.

  As shown in FIG. 3, the first clutch piezoelectric actuator 45 expands the expansion / contraction displacement of the piezoelectric element 46 in a radial direction orthogonal to the axial direction. And a displacement conversion mechanism 47 that converts the displacement, and is formed so as to be displaced in the radial direction and press the second rotating member 42 based on the expansion / contraction displacement of the piezoelectric element 46 that expands / contracts in the axial direction according to the applied voltage. Has been.

  The piezoelectric element 46 is formed to extend in the axial direction in a quadrangular prism shape. As a material of the piezoelectric element 46, for example, lead zirconate titanate (PZT) is used. The displacement conversion mechanism 47 is provided with a displacement conversion member 48 to which end faces on both sides in the axial direction of the piezoelectric element 46 are respectively attached and which expands and converts the axial expansion / contraction displacement of the piezoelectric element 46 into a radial displacement.

  The displacement conversion member 48 is formed using a metal material, and an outer surface portion that extends in the axial direction by connecting side surfaces 48a on both sides to which the piezoelectric elements 46 are attached and radially outer ends of the side surfaces 48a on both sides. 48b and an inner surface portion 48c extending in the axial direction by connecting the radially inner ends of the side surface portions 48a on both sides, and formed in a substantially quadrangular cross section when viewed in the circumferential direction.

  The inner surface portion 48c of the displacement converting member 48 is provided to be inclined so as to protrude radially inward from both axial sides toward the axial center (see FIG. 11). Fixed portions 48d that protrude radially inward from the ends on both sides in the direction are provided. The outer surface portion 48b of the displacement converting member 48 is provided to be inclined so as to protrude radially outward from both axial sides toward the axial center side (see FIG. 11), and the outer surface portion 48b has a shaft on the radially central side. Output portions 48e are provided that protrude radially outward from the ends on both sides in the direction.

  The displacement converting member 48 has a corner portion between the side surface portion 48a and the outer surface portion 48b on both sides, and the distance from the corner portion between the side surface portion 48a and the outer surface portion 48b on both sides to the output portion 48e on the outer surface portion 48b. Is formed to be longer than the distance from the side portion 48a to the portion to which the piezoelectric element 46 is attached, and is configured to expand and convert the axial expansion / contraction displacement of the piezoelectric element 46 into radial displacement. As the displacement conversion member 48, a displacement conversion member having another shape that converts the expansion / contraction displacement in the axial direction of the piezoelectric element 46 into the displacement in the radial direction can be used.

  The output part 48 e of the displacement conversion member 48 functions as a pressing part 48 e that is arranged to face the cylindrical part 42 a of the second rotating member 42, and the pressing part 48 e causes the second rotating member 42 to pass through the friction material 49. It comes to press. The friction material 49 is formed using, for example, paper.

  Each of the plurality of piezoelectric actuators 45 is disposed in the outer recessed portion 44 of the cylindrical portion 41a of the first rotating member 41, and the fixing portion 48d of the displacement converting member 48 is fixedly attached to the outer peripheral surface of the cylindrical portion 41a. The rotary member 41 is coupled to the outer peripheral surface.

  The piezoelectric actuator 45 is adapted to apply a predetermined voltage to the piezoelectric element 46 by a voltage application device (not shown). The operation of the voltage application device is controlled by a control device (not shown).

  The plurality of piezoelectric actuators 45 are axially overlapped with the outer peripheral surface of the cylindrical portion 41 a of the first rotating member 41 and are distributed in the circumferential direction. In the automatic transmission 1, seven piezoelectric actuators 45 are arranged at substantially equal intervals in the circumferential direction.

  FIG. 11 is an explanatory diagram for explaining the piezoelectric actuator of the first clutch. In FIG. 11, the cross-sectional shape of the piezoelectric actuator is exaggerated for easy understanding. The piezoelectric actuator 45 is arranged such that the pressing portion 48e of the displacement converting member 48 presses the second rotating member 42 when no voltage is applied to the piezoelectric element 46, as shown in FIG. The first clutch 40 is engaged.

  On the other hand, when a predetermined voltage is applied to the piezoelectric element 46, the piezoelectric actuator 45 expands and displaces the piezoelectric element 46 in the axial direction according to the applied voltage as shown in FIG. The displacement in the axial direction of the element 46 is expanded and converted in the radial direction by the displacement conversion member 48, the pressing portion 48e is displaced inward in the radial direction, and is separated from the cylindrical portion 42a of the second rotating member 42 in the radial direction. One clutch 40 is released.

  Thus, the first clutch piezoelectric actuator 45 is formed to be displaced in the radial direction and press the second rotating member 42 based on the expansion / contraction displacement of the piezoelectric element 46 that expands / contracts in the axial direction according to the applied voltage. Has been. The plurality of first clutch piezoelectric actuators 45 are configured in the same manner, and the voltage application is similarly controlled, so that the first clutch 40 is engaged and disengaged.

  The second clutch piezoelectric actuator 55 is formed in substantially the same manner as the first clutch piezoelectric actuator 45, and the same components as those in the first clutch piezoelectric actuator 45 are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 8, the piezoelectric actuator 55 has a piezoelectric element 46 and a displacement conversion mechanism 47, and is displaced in the radial direction based on the expansion / contraction displacement of the piezoelectric element 46 that expands / contracts in the axial direction according to the applied voltage. The third rotating member 52 is pressed.

  Also for the piezoelectric actuator 55, the displacement conversion mechanism 47 includes a displacement conversion member 48 that converts the expansion / contraction displacement in the axial direction of the piezoelectric element 46 into a radial displacement, and the displacement conversion member 48 includes side surface portions 48a on both sides. And an outer surface portion 48b and an inner surface portion 48c, which are formed so as to expand and convert the axial expansion / contraction displacement of the piezoelectric element 46 into a radial displacement.

  In the piezoelectric actuator 55, a fixing portion 58 d is provided on the radially central side of the outer surface portion 48 b of the displacement converting member 48 so as to protrude radially outward from the ends on both sides in the axial direction. An output portion 58e that protrudes radially inward from the ends on both axial sides is provided at the center in the direction.

  The output part 58 e of the displacement conversion member 48 functions as a pressing part 58 e that is disposed to face the cylindrical part 52 a of the third rotating member 52, and the pressing part 58 e causes the third rotating member 52 to pass through the friction material 49. It comes to press.

  Each of the plurality of piezoelectric actuators 55 is disposed in the inner concave portion 43 of the cylindrical portion 41a of the first rotating member 41, and the fixing portion 58d of the displacement converting member 48 is fixedly attached to the inner peripheral surface of the cylindrical portion 41a. The rotary member 41 is coupled to the inner peripheral surface.

  The plurality of piezoelectric actuators 55 are axially overlapped with the outer peripheral surface of the cylindrical portion 41 a of the first rotating member 41 and are distributed in the circumferential direction. In the automatic transmission 1, the seven piezoelectric actuators 55 are arranged at substantially equal intervals in the circumferential direction.

  Also for the piezoelectric actuator 55, a predetermined voltage is applied to the piezoelectric element 46 by the voltage application device controlled by the control device. The piezoelectric actuator 55 is arranged so that the pressing portion 48e of the displacement converting member 48 presses the third rotating member 53 when the non-voltage is applied, and the second clutch 50 is engaged, while the applied voltage is applied when the voltage is applied. Accordingly, the piezoelectric element 46 expands and displaces in the axial direction, and the axial displacement of the piezoelectric element 46 is enlarged and converted in the radial direction by the displacement converting member 48, and the pressing portion 48e is displaced radially outward. The second clutch 50 is disengaged from the cylindrical portion 52a of the three-rotating member 52 in the radial direction.

  Thus, the second clutch piezoelectric actuator 55 is formed to be displaced in the radial direction and press the third rotating member 52 based on the expansion / contraction displacement of the piezoelectric element 46 that expands / contracts in the axial direction according to the applied voltage. Has been. The plurality of second clutch piezoelectric actuators 55 are configured in the same manner, and the voltage application is similarly controlled, so that the second clutch 50 is engaged and released.

  The first clutch 40 and the second clutch 50 are engaged and disengaged according to the engagement table shown in FIG. 2, and the piezoelectric actuators 45 and 55 of the clutches 40 and 50 are achieved so that the transmission mechanism 4 achieves a predetermined gear position. The voltage applied to is controlled.

  In the automatic transmission 1, the application of voltage to the piezoelectric actuator of each frictional engagement element is controlled to engage and release each frictional engagement element, and the speed change mechanism 4 has 1 to 6 speeds in the D range shown in FIG. The stage and the reverse speed stage in the R range are each achieved.

  In the present embodiment, the speed change mechanism 4 is configured to achieve the fourth speed stage when no voltage is applied to the piezoelectric actuator of each friction engagement element, and the piezoelectric actuators of the friction engagement elements 40 and 50 that are engaged at the fourth speed stage. 45, 55 are formed to fasten the frictional engagement elements 40, 50 when a non-voltage is applied, and the piezoelectric actuators 62, 72, 82 of the frictional engagement elements 60, 70, 80 released at the fourth speed are The frictional engagement elements 60, 70, 80 are formed to be released when a voltage is applied.

  The speed change mechanism 4 is configured to achieve the fourth speed when no voltage is applied to the piezoelectric actuator of each friction engagement element, but is configured to achieve another speed such as the third speed, for example. Is also possible. In this case, the piezoelectric actuator of the frictional engagement element that is fastened at the other speed stage is formed to fasten the frictional fastening element when a non-voltage is applied, and the piezoelectric actuator of the frictional fastening element that is released at the other speed stage. The actuator is configured to release the frictional engagement element when no voltage is applied. Further, each frictional engagement element is engaged and released according to the engagement table shown in FIG. 2, and the voltage applied to the piezoelectric actuator of each frictional engagement element is controlled so that the transmission mechanism 4 achieves a predetermined shift stage.

  Thus, in the automatic transmission 1 according to the present embodiment, the first clutch 40 is provided on the outer peripheral surface of the first rotating member 41, the second rotating member 42 disposed on the outer peripheral side, and the first rotating member 41. The piezoelectric actuator 45 which couple | bonds and presses the 2nd rotation member 42 is provided, and the 2nd clutch 50 is the 1st rotation member 41, the 3rd rotation member 52 arrange | positioned at an inner peripheral side, and the 1st rotation member 41. And a piezoelectric actuator 55 that presses against the third rotating member 52.

  As a result, the first clutch 40 and the second clutch 50 are engaged using the piezoelectric actuators 45 and 55, respectively, so that the brake is driven by the hydraulic pump as compared with the case where the brake is engaged using the hydraulically operated piston. Loss and weight can be reduced.

  Further, the first clutch piezoelectric actuator 45 and the second clutch piezoelectric actuator 55 overlap each other in the radial direction and are arranged at different positions in the circumferential direction, so that the first clutch 40 and the second clutch 50 are connected. Since it can arrange | position so that it may overlap in radial direction, it can comprise compactly in radial direction.

  Therefore, in an automatic transmission in which two clutches are overlapped in the axial direction, the clutch is engaged and disengaged using a piezoelectric actuator to reduce drive loss and weight and to be compact in the radial direction. can do.

  A plurality of brakes 60, 70, 80 arranged side by side in the axial direction are respectively coupled to the brake drums 61, 71, 81 and the transmission case 2 to press the brake drums 61, 71, 81. The piezoelectric actuators 62, 72, 82 are provided, and the plurality of piezoelectric actuators 62, 72, 82 are respectively displaced in the radial direction based on the expansion / contraction displacement of the piezoelectric element 63 that expands / contracts in the axial direction, and the brake drums 61, 71, It is formed so as to press 81, and is arranged in the circumferential direction on the outer peripheral side of the plurality of brake drums 61, 71, 81.

  As a result, the plurality of brakes 60, 70, 80 are fastened by using the plurality of piezoelectric actuators 62, 72, 82 arranged in the circumferential direction, and the brakes are fastened by using hydraulically operated pistons. Compared with the case where it is done, the drive loss and weight by a hydraulic pump can be reduced.

  Even when the piezoelectric actuators 62, 72, 82 having a small displacement amount are used, the piezoelectric actuators 62, 72, 82 are brake drums 61, 71, 81 of the plurality of brakes 60, 70, 80 arranged in the axial direction. The piezoelectric actuators 62, 72, and 82 that are disposed on the outer peripheral side of the plurality of brake drums 61, 71, and 81 in the axial direction and correspond to the plurality of brakes 60, 70, and 80 respectively are located at different positions in the circumferential direction As a result, the piezoelectric actuator can be formed longer in the axial direction than the case where the piezoelectric actuators of the respective brakes are arranged on the outer peripheral side of each brake drum of the plurality of brakes. Increase the amount of displacement and use a piezoelectric actuator to engage and release the brake It is possible.

  The brakes 60, 70, 80 are respectively engaged with the brakes 60, 70, 80 by pressing the brake drums 61, 71, 81 by a plurality of piezoelectric actuators 62, 72, 82 arranged dispersed in the circumferential direction. Since release is performed, the amount of displacement for fastening can be reduced as compared to the case of using a multi-plate brake as a band type brake composed of a plurality of piezoelectric actuators, and effective engagement and release of the brake can be achieved. Can be realized.

  Therefore, when a plurality of brakes are arranged side by side in the axial direction, the driving loss and weight can be reduced by realizing the fastening and releasing of the plurality of brakes using the piezoelectric actuator.

  Further, the speed change mechanism 4 achieves a predetermined speed when a non-voltage is applied to the piezoelectric actuators 45, 55, 62, 72, 82 of the plurality of frictional engagement elements 40, 50, 60, 70, 80, respectively. The piezoelectric actuators 45 and 55 of the frictional engagement elements 40 and 50 configured and fastened at a predetermined speed are formed to fasten the frictional fastening elements 40 and 50 when a non-voltage is applied, and are released at a predetermined speed. The piezoelectric actuators 62, 72, 82 of the frictional engagement elements 60, 70, 80 are formed to release the frictional engagement elements 60, 70, 80 when no voltage is applied.

  Thus, even when a failure occurs in which a voltage cannot be applied to each of the piezoelectric actuators of the plurality of frictional engagement elements while the vehicle equipped with the automatic transmission is running, the speed change mechanism is, for example, the fourth speed A predetermined shift speed such as a shift speed can be achieved and fail-safe traveling at the predetermined shift speed can be performed.

  In the present embodiment, the speed change mechanism 4 is configured to achieve the fourth speed stage when a non-voltage is applied to the piezoelectric actuator of each frictional engagement element. Piezoelectric actuator configured to fasten the frictional engagement element and release the frictional engagement element when a voltage is applied, or to release the frictional engagement element when no voltage is applied and to tighten the frictional engagement element when a voltage is applied Using the piezoelectric actuator, the friction engagement elements are engaged and released according to the engagement table shown in FIG. 2, and the applied voltage to the piezoelectric actuator of each friction engagement element is controlled so that the speed change mechanism 4 achieves a predetermined gear stage. It is also possible.

  In the present embodiment, the automatic transmission 1 is a horizontal automatic transmission for a front engine / front drive vehicle or the like, but a vertical automatic transmission for a front engine / rear drive vehicle or the like is also applicable. It is possible to apply similarly.

  The present invention is not limited to the illustrated embodiments, and various improvements and design changes can be made without departing from the scope of the present invention.

  As described above, according to the present invention, in an automatic transmission in which two clutches are overlapped in the axial direction, the clutch is engaged and released using a piezoelectric actuator to reduce drive loss and weight. Therefore, it is possible to use the automatic transmission of this type or a vehicle equipped with this type of automatic transmission suitably.

DESCRIPTION OF SYMBOLS 1 Automatic transmission 2 Transmission case 4 Transmission mechanism 10, 20, 30 Gear set 40 First clutch 41 First rotation member 42 Second rotation members 45, 55, 62, 72, 82 Piezoelectric actuators 46, 63 Piezoelectric elements 48, 65 Displacement converting member 50 Second clutch 52 Third rotating member 60, 70, 80 Brake 61, 71, 81 Brake drum

Claims (3)

An automatic transmission having a speed change mechanism including a plurality of frictional engagement elements including a first clutch and a second clutch arranged in an axially overlapping manner in a transmission case,
The first clutch is coupled to the first rotating member, the second rotating member disposed on the outer peripheral side of the first rotating member, and the outer peripheral surface of the first rotating member, and in the radial direction according to the applied voltage. A plurality of first clutch piezoelectric actuators that are displaced outward and press the second rotating member to fasten the first clutch;
The second clutch is coupled to the first rotating member, a third rotating member disposed on the inner peripheral side of the first rotating member, and an inner peripheral surface of the first rotating member and according to an applied voltage. A plurality of second clutch piezoelectric actuators that are displaced radially inward and press the third rotating member to fasten the second clutch,
The plurality of first clutch piezoelectric actuators and the plurality of second clutch piezoelectric actuators are arranged at different positions in the circumferential direction so as to overlap in the radial direction.
An automatic transmission characterized by that. The plurality of frictional engagement elements include a plurality of brakes arranged side by side in the axial direction,
Each of the plurality of brakes includes a brake drum, and a plurality of brake piezoelectric actuators coupled to the transmission case and pressing the brake drum to fasten the brake.
Each of the plurality of brake piezoelectric actuators is formed so as to be displaced in the radial direction based on expansion / contraction displacement of a piezoelectric element that expands / contracts in an axial direction according to an applied voltage, and presses the brake drum. The brake drums are arranged on the outer peripheral side of the brake drum in the circumferential direction so as to overlap the brake drums of the plurality of brakes in the axial direction,
The brake piezoelectric actuators respectively corresponding to the plurality of brakes are arranged at different positions in the circumferential direction.
The automatic transmission according to claim 1. The speed change mechanism is configured to achieve a predetermined speed when a non-voltage is applied to the piezoelectric actuators of the plurality of frictional engagement elements,
The piezoelectric actuator of the frictional engagement element that is engaged at the predetermined shift stage is formed to engage the frictional engagement element when a non-voltage is applied,
The piezoelectric actuator of the frictional engagement element that is released at the predetermined shift stage is formed to release the frictional engagement element when a non-voltage is applied.
The automatic transmission according to claim 1 or 2, wherein the automatic transmission is provided.

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