Abstract: A power steering unit capable of finely controlling the steering assistance power generated by a hydraulic actuator in accordance with the steering direction and driving condition without requiring a complex structure is provided at low cost. The right steering assistance power generating state or the left steering assistance power generating state can be alternatively selected by switching the flow path of hydraulic fluid to the hydraulic actuator 10 for generating the steering assistance power with a motor-operated switching valve 23. The switching valve 23 is controlled so that the steering assistance power acts in accordance with the determined steering direction, and an electric motor 22 for driving a pump 21 is controlled so that the pressure of the hydraulic fluid discharged from the pump 21 is varied in accordance with the determined driving condition.

Abstract: An electric power steering system is provided, which comprises a steering assist electric motor, and a reduction gear mechanism for reducing a rotation speed of a rotatable shaft of the electric motor. The reduction gear mechanism comprises a worm shaft driven by the rotatable shaft, and a worm wheel driven by the warm shaft. The electric power steering system further comprises a joint for coupling the rotatable shaft to the worm shaft for transmission of a driving force. Longitudinally biasing means is provided in association with the joint for longitudinally biasing the worm shaft.

Abstract: In a power transmission ring, a plastic ring is provided with first and second tapered raceway surfaces on one and the other of lateral surfaces thereof, the first and second tapered raceway surfaces conforming to first and second power transmission surfaces of first and second sheaves, respectively. A metallic ring is provided with first and second tapered surfaces on one and the other of lateral surfaces thereof in parallel relation with the first and second raceway surfaces, respectively, and unified with the plastic ring.

Abstract: An electric power steering system is provided, which comprises a steering assist electric motor, and a reduction gear mechanism for reducing a rotation speed of a rotatable shaft of the electric motor. The reduction gear mechanism comprises a worm shaft driven by the rotatable shaft, and a worm wheel driven by the warm shaft. The electric power steering system further comprises a joint for coupling the rotatable shaft to the worm shaft for transmission of a driving force. Longitudinally biasing means is provided in association with the joint for longitudinally biasing the worm shaft.

Abstract: In a power transmission ring, a plastic ring is provided with first and second tapered raceway surfaces on one and the other of lateral surfaces thereof, the first and second tapered raceway surfaces conforming to first and second power transmission surfaces of first and second sheaves, respectively. A metallic ring is provided with first and second tapered surfaces on one and the other of lateral surfaces thereof in parallel relation with the first and second raceway surfaces, respectively, and unified with the plastic ring.