Linear solenoid-operated valve for use in power steering system

Abstract

A solenoid-operated valve particularly for use in a speed-responsive power steering system on a motor vehicle comprises a valve housing having two ports opening into a bore in the housing, a spool axially slidable in the bore and slot defining a bypass passageway extending between the two ports and variable in cross section upon axial movement of the spool. The spool is spring-biased in a direction to close the bypass passageway, but attractable by an energized solenoid to open the bypass passageway when the solenoid is supplied with an electric current dependent on the speed of travel of the vehicle. The spool has therein a restrictor disposed in the bypass passageway adjacent to the slot to restrict the flow of a fluid through the bypass passageway into and out of the bore in the housing. The restrictor develops a pressure drop while the fluid flows through the bypass passageway to maintain the spool substantially in equilibrium while the fluid under pressure flows through the bypass passageway in either direction upon axial shifting of the spool. The solenoid-operated valve enables dirigible wheels to be assisted in getting turned to the right or left by equal or balanced steering forces generated by the power steering system.