Power steering apparatus

A power steering apparatus for turning a steerable wheel of a vehicle in response to steering operation by a driver. The apparatus comprises a hydraulic pump for pumping a fluid from a reservoir so as to supply pressurized fluid to a power cylinder formed in a gear housing through a direction control valve which is operable in response to rotation of the steering wheel for selectively delivering the pressurized fluid to pair of pressure chambers of the power cylinder. The apparatus further comprises an electric motor for rotating the hydraulic pump, an accumulator for accumulating the pressurized fluid discharged from the hydraulic pump, a detector for detecting the pressure of the pressurized fluid and for outputting a signal corresponding to the detected pressure, and a controller responsible to the signal from the detector for activating the electric motor only when the detected pressure is below a predetermined level. The hydraulic pump and the electric motor are mounted on the gear housing.