Servolenkung

A power steering apparatus is provided, which is adapted to generate a steering assist force by a hydraulic pressure of a pump (26) driven by an electric motor (27). The apparatus includes: a vehicle speed sensor (16) for sensing a vehicle speed; and a control circuit (30, S10) for switching a control mode between an assist mode in which a first voltage (V1) is applied to the electric motor (27) and a standby/off mode in which no voltage or a second voltage (V2) lower than the first voltage (V1) is applied to the electric motor (27). The control circuit (30, S10) includes a threshold computation circuit (30, 33) for determining a threshold of a predetermined physical quantity (motor current and/or steering angle) as a function of the vehicle speed V sensed by the vehicle sensor (16), and comparison means (S7, S8) for comparing a level of the physical quantity with the threshold determined by the threshold computation circuit (33). The control mode is switched from the assist mode to the standby mode on the basis of a comparison result obtained by the comparison means (S7, S8).