Electric brake device

Abstract

An actuator 23 d for pushing a plurality of friction plates 44, 44 to a plurality of plates 37, 37 to be braked is composed of members including electroactive polymer, the shape of the elastomer of which is changed by electric energy.

What is claimed is:  
     
         1 . An electric brake device comprising: 
 a rotating member for rotating together with a wheel;    a friction member opposed to the rotating member; and    an electric actuator for pressing the friction member to a braking surface of the rotating member, wherein the electric actuator includes an electroactive polymer in which a shape of an elastomer is changed by electric energy.    
     
     
         2 . The electric brake device according to  claim 1 , wherein the rotating member includes a disc-shaped rotor, further comprising: 
 a pair of pads, wherein the friction member is attached to one side of a backing plate;    a support member provided crossing over an outer circumferential edge portion of the disc-shaped rotor, wherein the pair of pads are supported by the support member and opposed to the rotor;    a cylinder arranged in a caliper supported by the support member; and    a piston, disposed in the cylinder, freely movable in an axial direction of the rotor, and    wherein the electroactive polymer is arranged between the piston and a bottom portion of the cylinder.    
     
     
         3 . The electric brake device according to  claim 1 , wherein the rotating body includes a cylindrical drum having a bottom, further comprising: 
 a backing plate arranged on an opening portion side of the drum; and    a pair of brake shoes arranged on a backing plate and respectively having a friction member, wherein each friction member is opposed to an inner circumferential face of the drum, and the brake shoes can be freely displaced in the radial direction of the drum,    wherein the electroactive polymer is arranged between end portions of the pair of brake shoes in the circumferential direction.    
     
     
         4 . The electric brake device according to  claim 1 , wherein the rotating body includes a cylindrical drum having a bottom, further comprising: 
 a backing plate arranged on an opening portion side of the drum;    a pair of brake shoes arranged on a backing plate and respectively having a friction member, wherein each friction member is opposed to an inner circumferential face of the drum, and the brake shoes can be freely displaced in the radial direction of the drum; and    a portion for fixing the electroactive polymer to the backing plate arranged in a portion closer to the center than the inner circumferential edge of the pair of brake shoes,    wherein the electroactive polymer is arranged between an outer circumferential face of the portion for fixing the electroactive polymer and an inner circumferential edge of the pair of brake shoes.    
     
     
         5 . The electric brake device according to  claim 1 , wherein the rotating body includes a cylindrical drum having a bottom, further comprising: 
 a cylinder extending from the central side of the drum to the inner circumferential side, and having a bottom; and    a piston slidably engaged in the cylinder,    wherein the friction member, has an arcuate shape, is supported by an outer end portion of the piston, and is opposed to an inner circumferential face of the drum, and    the electroactive polymer is arranged between the bottom portion of the cylinder and an inner end face of the piston.    
     
     
         6 . The electric brake device according to  claim 1 , wherein the rotating body includes a plurality of ring-shaped plates supported on an outer circumferential face of a member to be braked in such a manner that the plurality of ring-shaped plates can not be rotated in the circumferential direction of the member to be braked and can be freely displaced in the axial direction, further comprising: 
 a housing provided in the periphery of the ring-shaped plates, wherein both sides of the ring-shaped plates are surrounded by the housing in an axial direction, and the housing is not rotatable; and    a plurality of ring-shaped friction plates, which are composed of friction members supported in such a manner that the plurality of ring-shaped friction plates can not be rotated in the circumferential direction and can be freely displaced in the axial direction, wherein each ring-shaped friction plate is arranged between the ring-shaped plates,    wherein the electroactive polymer is arranged at least one of between the inside portion on one side of the housing in the axial direction and the friction plate opposed to the inside portion and between the friction plates.