Fluid controlled having variable ancillary control functions

Reference Number: N 02-03

Inventors: Stephenson, Dwight B.; Carlson, Keith R.; Rasmussen, Kenneth G.

USPTO Link: 5186211

Invention Summary

Accordingly, it is an object of the present invention to provide a hydrostatic power steering device in which one or more of the steering functions is variable, or controllable, in response to an input other than merely steering wheel rotation.

The above and other objects of the present invention are accomplished by the provision of a hydrostatic power steering device operable to control the flow of fluid from a source of pressurized fluid, the device being of the type including housing means defining an inlet port for connection to the source of fluid, and a return port. Valve means is disposed in the housing means and comprises a primary, rotatable valve member and a cooperating, relatively rotatable follow-up valve member. The primary and follow-up valve members define a neutral rotary position and a rotary operating position in which the primary valve member is rotatably displaced, or deflected, from the neutral rotary position, relative to the follow-up valve member. The housing means and the valve means cooperate to define a main fluid path communicating between the inlet port and the return port when the valve members are in the rotary operating position. Fluid actuated means imparts follow-up movement to the follow-up valve member in response to the flow of fluid therethrough, the fluid actuated means being disposed in series flow relationship in the main fluid path. The follow-up valve member defines a first axial position. The primary valve member defines fluid passage means, and the follow-up valve member defines fluid port means, the fluid passage means and the fluid port means being disposed to define a variable flow control orifice having a first orifice area versus valve deflection relationship as the primary and follow-up valve members are displaced between the neutral rotary position and the rotary operating position, when the follow-up valve member is in the first axial position.

The device is characterized by means operable to bias the follow-up valve member toward the first axial Position, and means operable to displace the follow-up valve member from the first axial position toward a second axial position. One of the fluid passage means and the fluid port means are configured such that the variable flow control orifice has a second orifice area versus deflection relationship as the primary and follow-up valve members are displaced between the neutral rotary position and the rotary operating position, when the follow-up valve member is in the second axial position.