Power steering apparatus

A power steering device comprising:

• a steering mechanism having an input shaft that rotates according to a steering operation of a steering wheel, an output shaft that is connected to the input shaft through a torsion bar and a transmission mechanism that transmits rotation of the output shaft to steered wheels;
• a power cylinder having a pair of hydraulic chambers that are divided by a piston and providing a steering force to the steering mechanism;
• a torque sensor detecting a steering torque of the steering mechanism;
• a rotary valve selectively supplying working fluid that is supplied from a pump provided outside the steering mechanism to the pair of hydraulic chambers of the power cylinder according to relative rotation between the input shaft and the output shaft;
• an electric motor providing a steering force to the input shaft;
• a control unit in which a microcomputer is mounted;
• and
• a torque command signal operating section provided in the control unit, the torque command signal operating section configured to calculate a torque command signal for driving and controlling the electric motor on the basis of the steering torque and a vehicle speed and when the vehicle speed is a predetermined vehicle speed or greater, set the torque command signal to 0.