Patent ID: 8684127
Filing Date: 2014-04-01
Classification: B62D,F16D,F16H

Abstract:
1. An electric power steering system that includes a motor that applies assist force for assisting steering operation to a steering system; a speed reducing mechanism that is formed such that a worm gear to be rotated by the motor is meshed with a wheel gear coupled to the steering shaft; and a shaft coupling that drivably couples the worm gear to an output shaft of the motor such that the worm gear is tiltable with respect to the output shaft, wherein a proximal end part of the worm gear, adjacent to the motor, is supported by a first rolling bearing, a distal end part of the worm gear is supported by a second rolling bearing that is provided so as to be movable in a direction to approach to or distance from the wheel gear, and the second rolling bearing is urged by urging means so as to get close to the wheel gear, wherein: the shaft coupling includes a fixing part coupled to the output shaft so as to be integrally rotatable and a cylindrical part having an inner periphery in non-circular cross section and fixed to the fixing part, a coupling part having an outer periphery in non-circular cross section, the outer periphery being inserted in the cylindrical part and being engageable with the inner periphery in a circumferential direction, is formed in the proximal end part, any one of the inner periphery and the outer periphery is ridged such that a gap that allows the coupling part to tilt is provided inside the cylindrical part, and the cylindrical part presses an inner ring of the first rolling bearing toward an axially distal end side of the worm gear.