JP7070013B2 - Friction fastening device - Google Patents

Description

The present invention relates to a friction fastening device applied to a clutch and a brake in an automatic transmission of an automobile.

Conventionally, a friction fastening device such as a clutch or a brake of an automatic transmission of an automobile is driven by hydraulic pressure by a hydraulic pump, so that the driving resistance is large and the weight of the automatic transmission is increased, resulting in an increase in size. In order to reduce the drive resistance of the friction fastening device and to reduce the weight and compactness of the automatic transmission, it is effective to use an electric actuator to eliminate hydraulic pressure.

Conventionally, Patent Document 1 describes a clutch using a polymer actuator in which an actuator element in which a conductive polymer tube is bundled and wound in a spiral shape is housed in a space partitioned by a cylindrical cylinder and a cylindrical piston. A device has been proposed. However, it is difficult to effectively convert the stretching force of the conductive polymer tube into the operating force of the actuator, the number of parts is increased, and the structure is complicated.

Patent Documents 2 and 3 propose a clutch device using a polymer actuator in which an elastic container containing a gel-like electric field-responsive volume phase transition polymer and an electrolyte is housed between a cylinder and a piston. .. However, since this product contains a gel-like polymer and an electrolyte in an elastic container, it has a problem of lacking durability.

Due to such conventional problems, the use of electric actuators for friction fastening devices has not been put into practical use. There are two types of electrical actuators: piezoelectric type (piezoelectric ceramic) and dielectric type (polymer actuator). The piezoelectric type has a drawback that the pushing force is large but the displacement is small, and the dielectric type has a drawback that the displacement amount is large but the pushing force is small. Therefore, in order to apply it to a friction fastening device such as a clutch or a brake, a mechanism for expanding the displacement is required for the piezoelectric actuator, and a boosting mechanism is required for the dielectric actuator.

Japanese Unexamined Patent Publication No. 2005-83466 Japanese Unexamined Patent Publication No. 2005-155871 Japanese Unexamined Patent Publication No. 2011-106564

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to secure an increase in the pressing force of a polymer actuator having a large displacement but a small pressing force, and to reduce the driving resistance, reduce the weight and make it compact. An object of the present invention is to provide a friction fastening device that can be used.

In order to solve the above problems, the present invention takes the following measures.

The invention of claim 1 is provided between a drum and a hub, and includes a plurality of friction plates that alternately engage the drum and the hub, and a piston that presses the plurality of friction plates and fastens them to each other. In the friction fastening device, the piston is provided with a plurality of pressing portions in the axial direction, and a plurality of polymer actuators are provided in the axial direction between the drum and the piston, and each of the plurality of polymer actuators is provided. One side is coupled to one of the plurality of coupling portions of the drum, and the other side is coupled to one of the plurality of pressing portions.

According to the second aspect of the present invention, each of the plurality of polymer actuators is composed of two annular electrode plates and a polymer member interposed between the two electrode plates, and the outer peripheral edge of the electrode plate on one side is formed. It is coupled to one of the plurality of coupling portions of the drum, and the inner peripheral edge of the electrode plate on the other side is coupled to one of the plurality of pressing portions.

According to the third aspect of the present invention, at least one of the plurality of connecting portions of the drum and the plurality of pressing portions of the piston is formed in a stepped shape extending toward the anti-friction plate side.

The invention of claim 4 is configured to operate the piston by pressing a plurality of pressing portions of the piston by a contraction operation by applying a voltage to the polymer actuator.

According to the invention of claim 1, since a plurality of pressing portions of the piston are pressed by a plurality of polymer actuators arranged in the axial direction, an increase in the pressing force of the polymer actuator having a large displacement but a small pressing force is ensured. can do. As a result, the friction fastening device can be made hydraulic-less, and the drive resistance can be reduced, the weight can be reduced, and the size can be reduced.

According to the second aspect of the present invention, a plurality of polymer actuators can be arranged side by side in the axial direction between the drum and the piston, the structure is simple, and the assembly is easy.

According to the third aspect of the present invention, since the plurality of coupling portions of the drum and the plurality of pressing portions of the piston spread toward the anti-friction plate side, a plurality of polymer actuators can be sequentially assembled and assembled. It will be easier. Further, the polymer members of the plurality of polymer actuators can be increased as the distance from the anti-friction plate direction increases, and the pressing force of the piston can be further increased.

According to the fourth aspect of the present invention, a large pressing force can be applied to the piston by the contraction operation in which the force generated by the polymer actuator is large, and the pressing force of the piston can be further increased.

It is the schematic of the automatic transmission to which the friction fastening device of this invention is applied. FIG. 3 is a cross-sectional view showing a state of the friction fastening device of the first embodiment applied to a clutch when the friction fastening device is not fastened (a) and when the friction fastening device is fastened (b). An exploded perspective view of a piston of a friction fastening device and a polymer actuator. An enlarged cross-sectional view showing (a) before applying a voltage and (b) after applying a voltage of a polymer actuator. The perspective view which shows the modification of the polymer actuator. FIG. 2 is a cross-sectional view showing a state of the friction fastening device of the second embodiment applied to a brake when not fastened (a) and fastened (b). An enlarged cross-sectional view showing before voltage application (a) and after voltage application (b) of another modification of the polymer actuator.

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

<Automatic transmission configuration>
First, the configuration of an example automatic transmission in which the friction fastening device of the present invention is used will be described with reference to FIG. This automatic transmission 1 is applied to a horizontally-mounted vehicle such as a front engine front drive vehicle, and has a torque converter 3 attached to an engine output shaft 2 and an output of the torque converter 3 as main components. It has a speed change mechanism 5 in which rotation is input via an input shaft 4, and the speed change mechanism 5 is housed in a transmission case 6 in a state of being arranged on the axis of the input shaft 4.

Then, the output rotation of the speed change mechanism 5 is transmitted from the output gear 7 arranged in the middle portion of the input shaft 4 on the axis of the input shaft 4 to the differential device 9 via the counter drive mechanism 8. The left and right axles 9a and 9b are driven.

The torque converter 3 is arranged facing the case 3a connected to the engine output shaft 2, the pump 3b fixed in the case 3a, and the pump 3b, and is driven by the pump 3b via hydraulic oil. The stator 3e is interposed between the turbine 3c, the pump 3b and the turbine 3c, and is supported by the transmission case 6 via the one-way clutch 3d to increase torque, and the case 3a and the turbine. It is provided between the 3c and the lockup clutch 3f that directly connects the engine output shaft 2 and the turbine 3c via the case 3a. Then, the rotation of the turbine 3c is transmitted to the speed change mechanism 5 via the input shaft 4.

On the other hand, the transmission mechanism 5 has first, second, and third planetary gear sets (hereinafter, simply referred to as "first, second, and third gear sets") 10, 20, and 30, which are inside the transmission case 6. On the anti-torque converter side of the output gear 7 in the above, the output gears 7 are arranged in order from the torque converter side.

Further, as friction elements constituting the speed change mechanism 5, a first clutch 40 and a second clutch 50 are arranged on the torque converter side of the output gear 7, and a second clutch 40 is arranged on the anti-torque converter side of the output gear 7. The 1-brake 60, the 2nd brake 70, and the 3rd brake 80 are arranged in order from the torque converter side, and further, the one-way clutch 90 is arranged in parallel with the 1st brake 60.

The first, second, and third gear sets 10, 20, and 30 are all single pinion type planetary gear sets, and are meshed with the sun gears 11, 21, and 31, respectively. It is composed of a plurality of pinions 12, 22, 32, carriers 13, 23, 33 supporting these pinions 12, 22, 32, respectively, and ring gears 14, 24, 34 meshed with the pinions 12, 22, 32, respectively. ing.

The input shaft 4 is connected to the sun gear 31 of the third gear set 30, and the sun gear 11 of the first gear set 10 and the sun gear 21 of the second gear set 20, the ring gear 14 of the first gear set 10 and the second gear set 20. The carrier 23, the ring gear 24 of the second gear set 20, and the carrier 33 of the third gear set 30 are connected to each other. The output gear 7 is connected to the carrier 13 of the first gear set 10.

Further, the sun gear 11 of the first gear set 10 and the sun gear 21 of the second gear set 20 are connected to the input shaft 4 via the first clutch 40 so as to be connectable to and from the input shaft 4, and the carrier 23 of the second gear set 20 is described above. It is connected to the input shaft 4 via the second clutch 50 so as to be connectable and detachable.

Further, the ring gear 14 of the first gear set 10 and the carrier 23 of the second gear set 20 are connected to and from the transmission case 6 via the first brake 60 and the one-way clutch 90 arranged in parallel. The ring gear 24 of the second gear set 20 and the carrier 33 of the third gear set 30 are connected to the transmission case 6 via the second brake 70 so as to be connectable and detachable, and the ring gear 34 of the third gear set 30 is further connected. It is detachably connected to the transmission case 6 via the third brake 80.

With the above configuration, according to the speed change mechanism 5, the first and second clutches 40 and 50 and the first, second and third brakes 60, 70 and 80 are combined in the engaged state to advance 6th speed and reverse speed. And can be obtained. The first brake 60 is fastened only in the first speed in which the engine brake is operated, and in the first speed in which the engine brake is not operated, the one-way clutch 90 locks to form the first speed.

<First Embodiment of Friction Fastening Device>
Subsequently, an embodiment of the friction fastening device 100A applied to the first clutch 40 and the second clutch 50 of the automatic transmission 1 will be described. Since the friction engaging device 100A applied to the first clutch 40 and the second clutch 50 has basically the same structure, the friction engaging device 100A applied to the first clutch 40 will be described with reference to FIG.

The first clutch 40 has a drum 41 and a hub 42. The drum 41 has a shaft portion 41a connected to the input shaft 4, and rotates integrally with the input shaft 4. The hub 42 has a smaller diameter than the drum 41 and is arranged concentrically with the drum 41 inside the drum 41. The hub 42 has a shaft portion 42a connected to the sun gears 11 and 21 of the first gear set 10 and the second gear set 20, and rotates integrally with the sun gears 11 and 21.

A friction fastening device 100A is provided between the drum 41 and the hub 42. The friction fastening device 100A includes a plurality of friction plates 101a, 101b, a piston 102 that presses the friction plates 101a, 101b, and first, second, and third polymer actuators 103a, 103b, 103c that drive the piston 102. It is composed of and.

Of the plurality of friction plates 101a and 101b, the plurality of friction plates 101a arranged inside the drum 41 are spline-coupled to the drum 41 so as to be movable in the axial direction and are rotatably arranged integrally with the drum 41. Has been done. The plurality of friction plates 101b arranged on the outside of the hub 42 are spline-coupled to the hub 42 so as to be movable in the axial direction and are rotatably arranged integrally with the hub 42. The friction plates 101a of the drum 41 and the friction plates 101b of the hub 42 are alternately arranged and face each other via the facing materials 101c provided on both sides of the friction plates 101b of the hub 42.

As shown in FIG. 3, the piston 102 has a cylindrical shape and is arranged inside the drum 41. At the end of the piston 102 on the friction plate side, a ring-shaped pressing plate 102a that presses the friction plates 101a and 101b is provided. A shaft portion 102b is provided at the end of the piston 102 on the anti-friction plate side, and the shaft portion 102b can be moved axially by spline coupling to the shaft portion 41a of the drum 41 and can rotate integrally with the drum 41. Have been placed. A plurality of pressing portions 102c are formed at predetermined intervals in the axial direction by being provided on the outer peripheral surface of the piston 102 in a stepped shape extending toward the anti-friction plate side. On the other hand, the inner peripheral surface of the drum 41 facing the outer peripheral surface of the piston 102 is also provided in a stepped shape extending toward the anti-friction plate side, so that a plurality of connecting portions 41b are formed at predetermined intervals in the axial direction. There is.

Explaining the first polymer actuator 103a, as shown in FIG. 3, the first polymer actuator 103a is composed of a support plate 104, a movable plate 105, and a polymer member 106.

The support plate 104 has an annular shape, and as shown in FIG. 4, the first electrode plate 104a is integrally provided on the surface facing the polymer member 106. The support plate 104 and the first electrode plate 104a are electrically insulated from each other. The outer peripheral edge of the support plate 104 is appropriately coupled to the coupling portion 41a of the drum 41 by appropriate means. The inner peripheral edge of the support plate 104 has an inner diameter larger than the outer peripheral surface between the pressing plate 102a of the piston 102 and the first pressing portion 102c. The first electrode plate 104a is electrically connected to the first terminal 104b provided on the outer peripheral surface of the support plate 104 via the conductive portion 104c. The first terminal 104b is connected to the first contact 107 provided on the inner surface of the drum 41.

The movable plate 105 has an annular shape, and a second electrode plate 105a is integrally provided on the surface facing the polymer member 106. The movable plate 105 and the second electrode plate 105a are electrically insulated from each other. The outer peripheral edge of the movable plate 105 has an outer diameter smaller than the inner surface between the first coupling portion 41b and the second coupling portion 41b of the drum 41. The inner peripheral edge of the movable plate 105 has an inner diameter smaller than the inner diameter of the support plate 104 so that the first pressing portion 102c of the piston 102 can be pressed. Further, the inner peripheral edge of the movable plate 105 is appropriately coupled to the first pressing portion 102c so as not to move in the axial direction. The second electrode plate 105b is electrically connected to the second terminal 105b provided on the outer peripheral surface of the movable plate 105 via the conductive portion 105c. The second terminal 105b is connected to the second contact 110 provided on the inner surface of the piston 102.

The polymer member 106 has an annular shape, one end surface thereof is joined to the first electrode plate 104a of the support plate 104, and the other end surface is connected to the second electrode plate 105a of the movable plate 105. The polymer member 106 is formed by laminating an elastomer 106a such as acrylic or silicon having a high dielectric constant and elasticity and an intermediate electrode 106b in the axial direction. One of the opposing intermediate electrodes 106b is connected to the first electrode plate 104a of the support plate 104, and the other is connected to the second electrode plate 105a of the movable plate 105. When a voltage is applied between the first electrode plate 104a and the second electrode plate 105a, the voltage contracts from the state of FIG. 4A in the thickness direction and expands in the plane direction as shown in FIG. 4B. When released, it returns to the state shown in FIG. 4 (a) due to its inherent elasticity.

The required displacement amount of the polymer member 106 is calculated by (clutch clearance + clutch wear amount) × number of friction plates. Assuming that the clutch clearance is 0.3 mm, the amount of clutch wear is 0.1 mm, and the number of friction plates is 4, the required displacement amount of the polymer member is 1.2 mm.
The force generated when a voltage is applied to the polymer member 106 is obtained by the relative permittivity of the material × the permittivity of the vacuum × (voltage / film thickness) ² , and the amount of displacement is the relative permittivity of the material × the permittivity of the vacuum ×. (Voltage / film thickness) ² / Since it is calculated by the elastic coefficient, the smaller the film thickness, the larger the generated force and the amount of displacement can be obtained. Therefore, as the polymer material, it is preferable to laminate as many thin elastomers as possible so that the required displacement amount can be obtained. Further, by providing a plurality of polymer actuators, the generated force obtained by one polymer actuator can be doubled by the number of polymer actuators.

The second polymer actuator 103b and the third polymer actuator 103c have the same configuration as the first polymer actuator 103a, but as shown in FIG. 2, the support plate 104 having a larger area than the first actuator 103a is movable. The plate 105 and the polymer member 106 are used.

The first electrode plate 104a of the support plate 104 of the first, second, and third polymer actuators 103a, 103b, 103c is provided on the bearing 6a of the transmission case 6 that supports the input shaft 4 via the inside of the drum 41. It is connected to one electrode of the power supply 109 provided outside the transmission case 6 via a connecting component 108 such as a brush. Similarly, the second electrode plate 105a of the movable plate 105 of the first, second, and third polymer actuators 103a, 103b, 103c includes the inside of the piston 102, the shaft portion 102b of the piston 102, and the shaft portion 41a of the drum 41. Then, it passes through a connecting component 111 such as a brush provided on the bearing 6a of the transmission case 6 and is connected to the other electrode of the power supply 109 via a switch 112 which is turned on and off by a control device (not shown).

As shown in FIG. 5, at least three protrusions 105d are provided on the inner peripheral edge of the movable plate 105 at equal intervals, and the first pressing portion 102c of the piston 102 is pressed by the plurality of protrusions 105d. good. Further, as shown in FIG. 5, the polymer member 106 may have a segment shape divided into a plurality of parts in the circumferential direction.

Next, the operation of the first clutch 40 using the friction fastening device 100A will be described.

Referring to FIG. 2A, when the first clutch 40 is not engaged, the drum 41 and its friction plate 101a, the piston 102, and the polymer actuators 103a, 103b, 103c rotate together with the input shaft 4, and the hub 42 and The friction plate 101b is stopped. When the switch 112 is turned on by the engagement command of the first clutch 40, the voltage of the power supply 109 is applied to the first, second and third polymer actuators 103a, 103b and 103c. As a result, as shown in FIG. 2B, the polymer members 106 of the first, second, and third polymer actuators 103a, 103b, and 103c contract in the axial direction, and the movable member 105 is the first piston 102. , The second and third pressing portions 102c are pressed. As a result, the piston 102 moves toward the friction plate side, and the pressing plate 102a of the piston 102 presses the friction plate 101a of the drum 41 and the friction plate 101b of the hub 42, so that the first clutch 40 is engaged and the hub 42 is engaged. And its friction plate 101b rotate together with the drum 41 and its friction plate 101a, and the rotational force of the drum 41 is transmitted to the sun gears 11 and 21 of the first and second gear sets 10 and 20 via the hub 42.

When the switch 112 is turned off by the release command of the first clutch 40, the application of the voltage to the first, second and third polymer actuators 103a, 103b and 103c is canceled, and the first, second and third polymer actuators are eliminated. The polymer members 106 of 103a, 103b, and 103c are restored by the inherent elasticity, and the movable member 105 pulls back the first, second, and third pressing portions 102c of the piston 102. As a result, the piston 102 moves toward the anti-friction plate side and returns to the state shown in FIG. 2 (a). As a result, the friction plate 101a of the drum 41 and the friction plate 101b of the hub 42 are not pressed, so that the first clutch 40 is released, the hub 42 and its friction plate 101b stop their rotation, and the drum 41 to the hub 42 The rotational force to is cut off.

In the friction fastening device 100A of the embodiment, since the plurality of pressing portions 102c of the piston 102 are pressed by the plurality of polymer actuators 103a, 103b, 103c arranged in the axial direction, the polymer having a large displacement but a small pressing force. It is possible to secure an increase in the pressing force of the actuator. As a result, the friction fastening device 100A can be made hydraulic-less, and the drive resistance can be reduced, the weight of the automatic transmission 1 can be reduced, and the size of the automatic transmission 1 can be reduced.

Further, in each of the plurality of polymer actuators 103a, 103b, 103c, the outer peripheral edge of the support plate 104 is coupled to one of the plurality of coupling portions 41b of the drum 41, and the inner peripheral edge of the movable plate 105 is the plurality of pressing portions 102c. Since it is coupled to one of the above, a plurality of polymer actuators 103a, 103b, 103c can be arranged side by side in the axial direction between the drum 41 and the piston 102, and the structure is simple and the assembly is easy.

Since the plurality of coupling portions 41b of the drum 41 and the plurality of pressing portions 102c of the piston 102 extend toward the anti-friction plate side, the plurality of polymer actuators 103a, 103b, 103c can be sequentially assembled and assembled. Will be easier. Further, the polymer members 106 of the plurality of polymer actuators 103a, 103b, 103c can be increased as the distance from the anti-friction plate direction increases, and the pressing force of the piston 102 can be further increased.

Since the polymer actuators 103a, 103b, 103c are configured to press the plurality of pressing portions 102c of the piston 102 by the contraction operation by applying a voltage to operate the piston 102, a large pressing force is applied to the piston. It can be made to act, and the pressing force of the piston can be further increased.

<Second Embodiment of Friction Fastening Device>
Next, an embodiment of the friction fastening device 100B applied to the first brake 60, the second brake 70, and the third brake 80 will be described. Since the friction fastening device 100B of the first brake 60, the second brake 70, and the third brake 80 has basically the same structure, the friction fastening device 100B of the first brake 60 will be described with reference to FIG.

In the first brake 60, the drum 61 does not rotate integrally with the transmission case 6, the hub 62 is the ring gear 14 of the first gear set 10, and the piston 102 is axially on the support portion 6b of the transmission case 6. It has the same configuration as the first clutch 40 described above, except that it is movably supported. Further, the first terminal 104b of the support plate 104 of the first, second, and third polymer actuators 103a, 103b, and 103c is a power supply 109 provided outside the transmission case 6 through the inside of the transmission case 6. It is connected to one of the electrodes. The second terminal 105b of the movable plate 105 of the first, second, and third polymer actuators 103a, 103b, 103c passes through the inside of the piston 102, the support portion 6b of the transmission case 6, and the other electrode of the power supply 109. , Connected via a switch 112 that is turned on and off by a control device (not shown).

Since the other configurations of the friction fastening device 100B are the same as those of the friction fastening device 100A of the first clutch 40, the same reference numerals are given and the description of the configuration is omitted, and the operation thereof will be described below.

Referring to FIG. 6A, when the first brake 60 is not fastened, the drum 61 and its friction plate 101a, the piston 102, and the polymer actuators 103a, 103b, 103c are stationary, and the hub 62 and its friction plate 101b are stationary. It's spinning. When the switch 112 is turned on by the engagement command of the first brake 60, the voltage of the power supply 109 is applied to the first, second and third polymer actuators 103a, 103b and 103c. As a result, as shown in FIG. 6B, the polymer members 106 of the first, second, and third polymer actuators 103a, 103b, and 103c contract in the axial direction, and the movable member 105 is the first piston 102. , The second and third pressing portions 102c are pressed. As a result, the piston 102 moves toward the friction plate side, and the pressing plate 102a of the piston 102 presses the friction plate 101a of the drum 61 and the friction plate 101b of the hub 62, so that the first brake 60 is fastened and the hub 62 is engaged. And its friction plate 101b stop its rotation.

When the switch 112 is turned off by the release command of the first brake 60, the application of the voltage to the first, second and third polymer actuators 103a, 103b and 103c is canceled, and the first, second and third polymer actuators are eliminated. The polymer members 106 of 103a, 103b, and 103c are restored by their elasticity, and the movable member 105 pulls back the first, second, and third pressing portions 102c of the piston 102. As a result, the piston 102 moves toward the anti-friction plate side and returns to the state shown in FIG. 6A. As a result, the pressure on the friction plate 101a of the drum 61 and the friction plate 101b of the hub 61 is eliminated, so that the first brake 60 is released, and the hub 62 and its friction plate 101b resume their rotation.

FIG. 7 is a modification of the polymer actuators 103a, 103b, 103c. The support plate 104 and the movable plate 105 of the polymer actuator 103a of FIG. 7 are arranged in the opposite direction to the polymer actuator 103a of FIG. 4, that is, the support plate 105 is arranged on the friction plate and the support plate 104 is arranged on the anti-friction plate side. ing. Further, the polymer member 106 does not have the elastomer 106a and the intermediate electrode 106b laminated in the axial direction as in the polymer actuator 106 in FIG. 4, but the elastomer 106a and the intermediate electrode 106b are laminated in the radial direction. .. When a voltage is applied to the first electrode plate 104a and the second electrode plate 105a, the polymer member 106 contracts in the radial direction and expands in the axial direction. The pressing portion 102c of the piston 102 is pressed.

The present invention is not limited to the above embodiment, and various modifications can be made. For example, when applied to a brake, the ring gear of the gear set is used as a hub in the above embodiment, but the carrier of the pinion may be used as a hub. Further, the shape of the polymer member of the polymer actuator is formed in an annular shape or a segment shape thereof in the above embodiment, but a small circular polymer member is arranged in the circumferential direction between the annular support plate and the movable plate. May be good.

As described above, the friction fastening device according to the present invention may be suitably used for clutches and brakes of transmissions of automobiles.

1 Automatic transmission 41 Drum 41b Coupling
42 Hub 61 Drum 61b Coupling 62 Hub 100A, 100B Friction Fastener
101a, 101b Friction plate 102 Piston 102c Pressing part 103a, 103b, 103c Polymer actuator 104 Support plate 105 Movable plate 106 Polymer member

Claims (4)

A friction fastening device provided between a drum and a hub, comprising a plurality of friction plates that alternately engage the drum and the hub, and a piston that presses the plurality of friction plates and fastens them to each other. A plurality of axially pressing portions are provided on the piston, and a plurality of axially polymer actuators are provided between the drum and the piston, and one side of each of the plurality of polymer actuators is a plurality of the drums. A friction fastening device that is coupled to one of the coupling portions of the above and the other side is coupled to one of the plurality of pressing portions. Each of the plurality of polymer actuators is composed of two annular electrode plates and a polymer member interposed between the two electrode plates, and the outer peripheral edge of the electrode plate on one side is a plurality of coupling portions of the drum. The friction fastening device according to claim 1, wherein the inner peripheral edge of the electrode plate on the other side is coupled to one of the plurality of pressing portions. The friction fastening device according to claim 1 or 2, wherein at least one of the plurality of connecting portions of the drum and the plurality of pressing portions of the piston is formed in a stepped shape extending toward the anti-friction plate side. The friction fastening device according to any one of claims 1 to 3, wherein the piston is operated by pressing a plurality of pressing portions of the piston by a contraction operation by applying a voltage to the polymer actuator. ..

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