POWER STEERING GEAR WITH PISTON NUT AND SCREW

摘要

POWER STEERING GEAR WITH PISTON NUT AND SCREW This power steering gear comprises a piston nut movably mounted in a housing for turning a gear sector and the steerable wheels of a vehicle operatively connected thereto. The piston nut is mechanically moved by a rotatable screw, threadedly engaged with the piston nut and operatively connected to an input stub shaft. Hydraulic power assist is provided with the piston nut forming separate expansible and contractible chambers filled with hydraulic fluid and controlled by integral valve means in the gear. The threads of the piston nut and screw are profiled to contact at their minor diameters to increase thread efficiency by reducing the friction radius. The threads of the piston nut are made with optimized thickness to reduce flank clearance to further restrict the hydraulic flow path through the thread to effectively seal the chambers from each other.