Patent ID: 8733493

Claim:
A hydraulic power steering system that includes: an oil pump; a steering assist device that is operated by hydraulic fluid supplied from the oil pump; a flow rate control valve that controls a flow of the hydraulic fluid that is supplied from the oil pump to the steering assist device; an electric motor that drives the flow rate control valve; a first oil passage that connects the oil pump and the flow rate control valve with each other; a second oil passage that connects the steering assist device and the flow rate control valve with each other; and a control unit that controls the electric motor, comprising: a rotation angle sensor that detects a rotation angle of an output shaft of the electric motor, wherein the flow rate control valve includes a rotary valve that rotates together with the output shaft of the electric motor and a housing that has an internal space connected to the first oil passage and the second oil passage, and the control unit reflects an output from the rotation angle sensor on control of the electric motor.