Power assistance steering systems for vehicles.

摘要

A power assistance steering system (10) for a vehicle comprises steering gear (12) having an internal hydraulic ram supplied with hydraulic fluid by a pump (14) from a reservoir (16) via a solenoid valve (18) controlled by a micro-processor (20) which also controls an electric motor (22) for driving pump (14). Steering input torque is sensed by a torque sensor (36) and steering direction is sensed by a direction switch (34). Output signals from these devices are fed to micro-processor (20) which controls solenoid valve (18) and pump motor (22) accordingly, varying the motor speed in accordance with the pressure requirements of the steering ram as sensed by the torque sensor. In a further embodiment the pump is driven at a constant speed and proportional control valve (74) is controlled by a micro-processor (78) to vary the fluid pressure supply.