Hydraulic-power steering system with magnetic torque overlay

摘要

A hydraulic-power steering system (10) is provided. A power-steering valve (12) controls and varies a level of steering assist. A magnetic actuator (14) varies torsional stiffness of the valve (12) to change torque and produce a sufficient amount of the torque to generate full assist. A first valve (24) is operatively connected to a steering pump (22) and allows the full assist at a relatively low steering torque and through which flow from the steering pump (22) is directed. A second valve (32) is operatively connected to the steering pump (22). Current is applied to a solenoid valve (32) that allows an increasing amount of the flow to be directed through the second valve (32) in response to an input signal of increasing vehicle speed above a threshold value and closes in response to a signal identifying any of a plurality of advanced steering functions.