Patent ID: 7363134

Claim:
A power steering apparatus comprising: an oil pump for supplying a steering assist power cylinder with hydraulic fluid; an electric motor for driving the oil pump; a vehicle speed detecting unit for detecting vehicle speed; a steering angle detecting unit for detecting a steering angle; a rotational speed detecting unit for detecting rotational speed of the electric motor; and a controller capable of performing operations of: calculating steering speed based on the steering angle detected by the steering angle detecting unit; calculating a rate of change of the calculated steering speed; judging whether the calculated rate of change is smaller than or equal to 0 or not; and reducing a gain of feedback control based on a deviation between a target rotational speed of the electric motor based on the vehicle speed detected by the vehicle speed detecting unit and on the calculated steering speed and the rotational speed detected by the rotational speed detecting unit, in comparison with a gain at time of judgment, when it is judged that the rate of change remains smaller than or equal to 0 for a predetermined time period, wherein rotation of the electric motor is controlled by the feedback control to assist steering with oil pressure generated by the oil pump, and the reduced gain is kept until the deviation becomes larger than 0.