Inventors:
Frederick D. Venable - Lafayette IN
Bernard C. Hudgens - West Lafayette IN
Lowell D. Stingley - Clarks Hill IN
Gary L. Vandermolen - Fort Wayne IN
International Classification:
F15B 1304
Abstract:
A switching valve (50) for a hydraulic power steering system (10) includes a longitudinally movable valve spool (80). A spring (86) biases the spool (80) to a neutral position. The switching valve (50) is configured to direct hydraulic fluid from a primary pump (34) to a steering control valve (14) when the spool (80) is in a primary position, and to direct hydraulic fluid from an auxiliary pump (38) to the control valve (14) when the spool (80) is in an auxiliary position. The spool (80) is movable against a bias of the spring (86) from the neutral position to the primary position under the influence of a hydraulic fluid pressure differential between the opposite ends of the spool (80). The switching valve (50) defines a flow path for directing hydraulic fluid from the primary pump (34) to an end of the spool (80) when the spool (80) is in the neutral position. The flow path extends axially over a flat portion (124) of an outer surface of the spool (80).