The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 14, 1990
Filed:
Aug. 01, 1988
Laurence L Miller, West Lafayette, IN (US);
TRW Inc., Lyndhurst, OH (US);
Abstract
A power steering system includes a bypass valve for bypassing fluid from a main fluid conduit connected between an engine-driven, power steering pump and an actuatable, open-center, steering control valve which is actuated upon turning of a vehicle steering wheel. When the steering control valve is actuated, the demand for fluid through the steering control valve to a power steering motor increases. The fluid pressure in the main conduit varies as a function of the demand for fluid to the steering control valve. The bypass valve is urged toward an open condition by a fluid pressure signal. The bypass valve is urged toward a closed condition by a spring and by a fluid pressure which varies as a function of the demand for fluid to the steering control valve and as a function of an electrical signal which varies as a function of at least one vehicle operating parameter, such as vehicle speed. The fluid pressure which urges the bypass valve toward a closed condition is controlled by (i) a pressure responsive pilot valve assembly which is responsive to the fluid pressure in the main conduit and (ii) a solenoid operated pilot valve assembly which is responsive to the electrical signal which varies as a function of vehicle speed.