Power steering apparatus

Claim 1

A power steering apparatus for an automotive vehicle including means for actuating a steering mechanism, a primary source of fluid under pressure, a secondary source of fluid under pressure responsive to the vehicle speed for supply of fluid under pressure in proportion to the vehicle speed, and a hydraulic power cylinder for providing a hydraulic power assist to the driver's steering effort applied to the steering mechanism of the vehicle, the power steering apparatus comprising: a housing; an input member rotatably mounted in said housing; an output member, directly connected to said means for actuating said steering mechanism, rotatably mounted in said housing and arranged coaxially with said input member for relative rotation; a valve rotor integral with said input member; a valve sleeve rotatably mounted in said housing and arranged in surrounding relationship with said valve rotor, said valve sleeve being connected integrally with said output member to cooperate with said valve rotor for selectively directing fluid under pressure from said primary source to opposite ends of said power cylinder in response to relative rotation between said input and output members; a cam mechansim including a cam follower element axially movable in an internal axial bore in said output member and being engaged at the inner end thereof with the inner end of said input member in such a manner as to permit relative rotation of said input and output members and to effect axial movement of said cam follower element upon the application of a predetermined manual torque to said input member, said cam follower element including a cam piece axially movable in the inner end portion of said internal axial bore in said output member and directly engaged with the inner end portion of said output member for rotation therewith, and a rod portion extending outwardly from said cam piece and arranged axially movably in said internal axial bore, said cam piece being formed with a pair of solid cam surfaces and said input member being formed in its inner end with a pair of recessed cam surfaces which directly engage with said solid cam surfaces; and a pressure mechanism arranged to apply a hydraulic pressure from said secondary source to the outer end of said rod portion of said cam follower element for increasing a resistance to relative rotation between said input and output members in accordance with increase of the vehicle speed.