Hydraulic reaction variable assist power steering control hydraulic "detent"

A fluid pressure operated power steering gear mechanism for a vehicle comprising:

• a fluid pressure source, a steering pressure movable part adapted to be connected to a steering linkage for a vehicle, a drive member connected to said pressure movable part, a driving shaft, a torsion rod connecting said driving shaft to said drive member;
• a rotary steering valve means situated in and partly defining pressure distribution and flow return passages extending between said pressure source and said pressure movable part to establish steering pressure and steering pressure differential forces on said pressure movable part;
• said steering valve means comprising an internal valve member and a surrounding sleeve valve member, said internal valve member and said sleeve valve member having registering valve lands, one of said valve members being connected to said driving shaft and the other being drivably connected to said drive member whereby deflection of said torsion rod effects changes in the flow area through said steering valve means and a corresponding pressure differential change acting on said pressure movable part;
• at least two pressure reaction pistons in said sleeve, passage structure in said steering valve means for distributing steering pressure from said steering valve means to said pressure movable part and to said reaction pistons thereby establishing opposed steering reaction forces;
• means for applying said reaction forces to one of said valve members whereby relative angular displacement of said valve members is resisted;
• at least one modulator valve means communicating with said passage structure for modulating said steering pressure to produce a modified pressure on said reaction pistons thereby providing an increased rate of increase in steering pressure for a given steering torque change, and detent means for establishing a detent torque that resists relative angular displacement of said valve members as said steering torque is applied to said driving shaft.

A fluid pressure operated power steering gear mechanism for a vehicle comprising:

• a fluid pressure source, a steering pressure movable part adapted to be connected to a steering linkage for a vehicle, a drive member connected to said pressure movable part, a driving shaft subjected to steering torque connected to said drive member;
• a valve housing, a rotary steering valve means situated in said housing and partly defining pressure distribution and flow return passages extending between said pressure source and said pressure movable part for establishing steering pressure and steering pressure differential forces on said pressure movable part;
• said steering valve means comprising an internal valve member and a surrounding sleeve valve member, said internal valve member and said sleeve valve member having registering valve lands, one of said valve members being connected to said driving shaft and the other being drivably connected to said drive member whereby relative rotary displacement of said valve members effects a change in the flow area through said steering valve means and a corresponding pressure differential change acting on said pressure movable part;
• at least two pressure reaction pistons in said sleeve valve member, passage structure in said valve means for distributing steering pressure from said steering valve means to said pressure movable part and to said reaction pistons thereby establishing opposed steering torque reaction forces;
• means for applying said reaction forces to one of said valve members whereby relative angular displacement of said valve members is resisted;
• modulator valve means communicating with said passage structure for modifying said steering pressure to provide a change in reaction pressure and an increased rate of increase in steering pressure for a given steering torque change, detect means for establishing a detent torque that resists relative angular displacement of said valve members as steering torque is applied to said driving shaft;
• and
• vehicle speed sensitive proportional valve means in fluid communication with said modulator valve means for increasing the rate of increase in steering pressure for a given increase in steering torque applied to said driving shaft as vehicle speed increases.