Hydraulically power assisted steering gear with pressure relief stop
AssigneeGeneral Motors Corporation
InventorsPaul O. Wendler, John F. Yonker
Life of this patent
Estimating the term…
Abstract
Rack and pinion steering gear with hydraulic power assist that is reduced as the vehicle wheels approach their positive wheel stops so that hydraulic loads on the steering gear and linkage are reduced and the power steering pump is not forced to excessive operation in relief.
Claims6
A rack and pinion power assist steering gear for steering the dirigible wheels of a vehicle through a steering linkage comprising a steering gear housing, a pinion gear operatively mounted in said housing, a rack meshing with said pinion gear and operatively connected to said dirigible wheels, a hydraulic power unit for providing power assist steering, said power unit comprising a hydraulic cylinder and a piston operatively mounted therein drivingly connected to said rack, said piston having first and second contact faces on opposite ends thereof and having annular seal means between said faces to hydraulically separate first and second fluid chamber, a source of fluid pressure, power steering valve means operatively connected to said source of fluid pressure for hydraulically charging and exhausting said first and second chambers to effect axial movement of said piston and power assist steering, first and second displaceable valves disposed internally of said cylinder and respectively operatively mounted in said first and second chambers at a predetermined axial position with respect to one another and respectively contacted and displaced by said first and second contact faces, a fluid flow path external of said hydraulic cylinder operatively connected to said first and second valve for hydraulically interconnecting said first and second chambers only when said piston strokes to predetermined positions whereby one of said valves is contacted and displaced by one of said contact faces to open said fluid flow path to provide an exhaust passage back to said source through said chambers and said valve to eliminate the hydraulic assist of the steering and thereby to eliminate the hydraulic loads on the steering linkage.
A rack and pinion power assist steering gear for steering the dirigible wheels of a vehicle through a steering linkage toward positive wheel stops comprising a steering gear housing, a pinion gear operatively mounted in said housing, a rack meshing with said pinion gear and operatively connected to said dirigible wheels, a hydraulic power unit for providing power assist steering, said power unit comprising a hdyraulic cylinder having one end thereof secured to said housing, and a piston operatively mounted therein having annular seal means between opposite end faces thereof to form first and second fluid chambers, said piston being drivingly connected to said rack, power steering valve means for hydraulically charging and exhausting said first and second chambers to effect axial travel of said piston and power assist steering, first and second displaceable valves respectively operatively mounted in said first and second fluid chambers for displacement by an end face of said piston associated therewith, and a fluid flow conduit external of said cylinder operatively connected to said first and second valves for hydraulically interconnecting said first and second chambers when said piston strokes to predetermined positions adjacent to the ends of said cylinder whereby one of said valves is displaced by an associated end face of said piston and the other of said valves is displaced by pressure fluid in an associated one of said chambers to provide an exhaust passage from one of said chambers to the other of said chambers and then to said valve means to thereby reduce the hydraulic assist of the steering and the hydraulic loads on the steering linkage.
Dependencies are inferred from the claim text.