Abstract: The invention relates to a steering force controller for power steering apparatus which controls a steering force by controlling an oil pressure supplied to an oil pressure reaction chamber of a reaction mechanism. A pressure controlling mechanism which controls the oil pressure supplied to the oil pressure reaction chamber operates to increase a channel area between a reaction passage which communicates with the oil pressure reaction chamber and a feed passage which communicates with the discharge port of a pump and at the same time reduce a channel area between the reaction passage and a discharge passage which communicates with a tank associated with the pump in accordance with a displacement of the spool in one direction which is caused by a solenoid. In this manner, the flexibility in controlling the pressure within the reaction chamber is enhanced. Chambers formed at the opposite ends of the spool valve communicate with the tank and are maintained under a low pressure.

Abstract: A hydraulic reaction force apparatus for a power steering system has a pump, a power cylinder, a control valve, a first variable orifice, a hydraulic reaction force chamber, and a spool valve. The spool valve has a supply port connected to the pump, a reaction port connected to the hydraulic reaction force chamber, a tank port connected to a tank and a second variable orifice controlled by a spool in the spool valve. The opening of the second variable orifice is changed by a displacement of the spool caused by the pressure difference between upstream and downstream pressures of the first variable orifice, thereby connecting the reaction port to the supply port and the tank port and controlling the magnitude of the hydraulic reaction force.

Abstract: A control apparatus for a power steering system has a travel condition data memory, a plurality of vehicle velocity response data memories, a correction data memory, and a driver. Traveling condition data is read out in response to average vehicle velocity data and average steering angle data. Vehicle velocity response data is read out from one of the vehicle velocity response data memories in response to the traveling condition data and instantaneous vehicle velocity data. The vehicle velocity response data is added by the driver to the correction data from the correction data memory. The corrected vehicle velocity response data is used to drive a control valve, thereby obtaining an optimal steering force.