Power steering device and zero-point setting device for torque sensor in power steering device

A power steering device (100) is provided which is capable of detecting an initial torque of torque detection means (10) precisely in a short period of time in the initial setting therefor. In detecting the initial torque of the torque detection means (10), assist power generating means such as an electric motor (20) for applying assist power to a handle shaft (2) is used to rotate a steering handle (1) within a minute rotational range in positive and negative-going directions from a neutral position in the steering direction. The rotation of the steering handle (1) in this initial setting is performed so that the amplitude of the repetitive rotations in the positive and negative-going directions are decremented as time passes. Then, an output of the torque detection means (10) is detected as the initial torque with the steering handle (1) being held stationarily at the neutral position. In another aspect of the present invention, a zero-point detection device for a torque sensor (10) in a power steering device is provided having steerable wheel (6) oscillating means which comprises turntables rotatable within a minute rotational range in positive and negative going directions and a turntable oscillating device for oscillating the turntables within the minute angular range in its steering direction by applying a drive power of a decremental pattern so that the amplitude of the oscillation is decreased gradually. Upon termination of the oscillation, an output of the torque detection means (10) is detected as the initial torque with the steering handle (1) being held stationarily at the neutral position.