Electric power steering device

An electric power steering device including an electric motor for generating an auxiliary torque according to a steering torque, and a plurality of sets of friction clutch mechanisms for transmitting the auxiliary torque to a steering system including an output shaft connected to a steering wheel, said plurality of sets of friction clutch mechanisms comprising:

• an input member connected to said electric motor;
• an output member disposed concentrically with said input member with a space defined therebetween and connected to said output shaft;
• a plurality of tapering spaces defined between an inside surface of one of said input member and said output member and an outside surface of the other of said input member and said output member;
• a plurality of locking members movably disposed in said tapering spaces, respectively, for selectively engaging and disengaging said input and output members;
• a plurality of urging members for urging said locking members toward a tapering direction of said tapering spaces;
• a plurality of rotatable position control members connected to said steering handle for positioning said locking members;
• rotation of said position control members causing said locking members of said friction clutch mechanisms to move into and out of wedging engagement between said inside surface and said outside surface to thereby selectively engage and disengage said input member and said output member for transmitting the auxiliary torque from said electric motor to said output shaft;
• said input member and said output member being mounted such that they are relatively movable in a radial direction;
• when a selected one of said plurality of sets of friction clutch mechanisms is disengaged in response to rotation of said position control members, said input member and said output member being relatively displaced in said radial direction by a force exerted from said locking members of the remaining set of friction clutch mechanisms so as to reduce a frictional engagement force acting between said locking members of said remaining set of friction clutch mechanisms and said inside and outside surfaces of said input and output members.