Actuator

Abstract

An actuator capable of realizing a high output with a compact size is proposed. An actuator provided with a motor including a cylindrical rotor, and a reducer including an input shaft coaxial with a rotational shaft of the motor and involved in the rotor. The reducer has a cylindrical shape, the reducer further includes an output shaft coaxial with the rotational shaft of the motor, the motor further includes a stator, and the actuator is further provided with a casing which supports the reducer and the stator.

What is claimed is: 
     
         1 . An actuator, comprising:
 a motor that includes a cylindrical rotor;   a reducer that includes:
 an input shaft coaxial with a rotational shaft of the motor; 
 an output shaft coaxial with the rotational shaft of the motor; and 
 a web generator coaxial with the rotational shaft of the motor; and 
   a torque sensor fixed to the output shaft, wherein the torque sensor is configured to measure torque based on rotation of the output shaft.   
     
     
         2 . The actuator according to  claim 1 , wherein
 the reducer further includes a circular spline,   the reducer is a wave gear reducer,   the output shaft includes a flex spline, and   the circular spline, the flex spline, and the web generator are arranged in this order from an outside of the wave gear reducer to an inside of the wave gear reducer.   
     
     
         3 . The actuator according to  claim 2 , wherein
 the web generator comprises an oval portion and a bearing,   the oval portion is fixed to the rotational shaft of the motor,   the web generator is configured to rotate in synchronization with the cylindrical rotor, and   the web generator serves as the input shaft of the reducer.   
     
     
         4 . The actuator according to  claim 2 , wherein the circular spline includes:
 a cylindrical first outer peripheral surface nested in the cylindrical rotor, and   a cylindrical second outer peripheral surface, wherein a diameter of the cylindrical second outer peripheral surface is larger than a diameter of the cylindrical first outer peripheral surface.   
     
     
         5 . The actuator according to  claim 4 , further comprises a first bearing supported by an inner peripheral surface of the reducer, wherein
 the inner peripheral surface faces the cylindrical second outer peripheral surface, and   the first bearing is configured to rotatably support the output shaft.   
     
     
         6 . The actuator according to  claim 5 , further comprises a second bearing supported inside the flex spline, wherein the second bearing is configured to rotatably support the rotational shaft of the motor. 
     
     
         7 . The actuator according to  claim 1 , wherein the reducer has a cylindrical shape. 
     
     
         8 . The actuator according to  claim 1 , further comprises a casing, wherein
 the motor further includes a stator, and   the casing is configured to support the reducer and the stator.   
     
     
         9 . The actuator according to  claim 1 , further comprises a brake on a side opposite to the reducer with respect to the motor, wherein
 the brake includes a main body and a rotating portion, and   the rotating portion is coaxial with the rotational shaft of the motor.   
     
     
         10 . The actuator according to  claim 9 , further comprises a third bearing supported by the main body, wherein the third bearing is configured to rotatably support the rotational shaft of the motor. 
     
     
         11 . The actuator according to  claim 9 , wherein the brake further includes:
 a mover between the main body and the rotating portion,   an elastic member configured to apply elastic force toward the rotating portion to the mover, wherein the elastic member is fixed to the main body, and   an electromagnet configured to attract the mover toward the main body at a time of energization.   
     
     
         12 . The actuator according to  claim 9 , wherein a part of the main body is nested in the cylindrical rotor. 
     
     
         13 . The actuator according to  claim 12 , wherein
 the cylindrical rotor includes a support,   the support includes a plane orthogonal to a direction of extension of the cylindrical rotor,   the plane supports the rotational shaft of the motor,   the reducer is nested in the cylindrical rotor on a first side of the cylindrical rotor with the support as a boundary, and   the part of the main body is nested in the cylindrical rotor on a second side opposite to the first side with the support as the boundary.   
     
     
         14 . The actuator according to  claim 9 , further comprising:
 a first encoder configured to measure a rotational angle of the output shaft; and   a second encoder configured to measure a rotational angle of the cylindrical rotor.   
     
     
         15 . The actuator according to  claim 14 , wherein the second encoder is on a side on which the brake is located with respect to the motor. 
     
     
         16 . The actuator according to  claim 14  wherein
 the rotational shaft of the motor is a hollow tube, 
 the rotational shaft of the motor includes a cable configured to connect the first encoder to the second encoder, and 
 the cable is inside the rotational shaft of the motor. 
 
     
     
         17 . The actuator according to  claim 1 , wherein the torque sensor includes:
 a first rotating body fixed to the output shaft,   a second rotating body,   a distortion part fixed to the first rotating body and the second rotating body, wherein the distortion part is configured to transmit rotational torque from the first rotating body to the second rotating body based on a strain of the distortion part, and   a measuring unit configured to measure the rotational torque based on the strain of the distortion part.   
     
     
         18 . The actuator according to  claim 1 , wherein
 the rotational shaft of the motor is a hollow tube,   the rotational shaft of the motor includes a cable configured to connect the torque sensor to an external device, and   the cable is inside the rotational shaft of the motor.