Vehicle power steering control device

Claim 2

A hydraulic power steering device for use on vehicle, comprising a fluid pressure and flow control valve, a valve body having a bore therein, a hollow valve spool slidably disposed in said valve body bore, said valve spool being operatively associated with a steering wheel, two spring seats slidably disposed within said hollow valve spool and forming a reaction chamber between said seats, each of said spring seats having a flange peripherally formed thereon acting as a stopper, spring means mounted in said reaction chamber between said spring seats, said spring means being so preloaded as to urge said spring seats away from each other, said valve body having a first passage adapted to be connected to a fluid pump and communicating at its outlet end with a first annular groove formed in said valve body bore having formed a second annular groove and a third annular groove spaced on both sides of said first groove, said second annular groove and said third annular groove being adapted to be connected to a fluid reservoir through a second passage and a third passage, respectively, a power cylinder having a piston and a rod and connected at one end to a fourth passage and at the other end to a fifth passage, said valve spool having a fourth annular groove and a fifth annular groove therein adapted to selectively connect said first passage with said fourth passage and said fifth passage, respectively, to control fluid flow through said control valve to said power cylinder in response to movement of said valve spool relative to said valve body in either direction, a modulator valve for controlling a pressure from said fluid pump in proportion to vehicle speed and passage means connecting said modulator valve to said reaction chamber in said control valve wherein the reaction applied to the steering wheel by said control valve corresponds to the sum of the hydraulic pressure in said reaction chamber and the force of said spring means and therefore depends upon steering effort on said power cylinder and also upon vehicle speed.

Claim 3

A hydraulic power steering device according to claim 1, in which the reaction applied to the steering wheel increase with vehicle speed.

Claim 4

A hydraulic power steering device according to claim 1, in which one of said spring seats has a small diameter portion which is slidably received in a bore formed in a closure member mounted on one end of said valve body.

Claim 5

A hydraulic power steering device according to claim 3, in which said one spring seat has an axial passageway through which the hydraulic pressure from said modulator valve is introduced into said reaction chamber.

Claim 6

A hydraulic power steering device according to claim 1, in which said modulator valve is of the conventional nozzle-flapper type comprising a nozzle having an inlet port connected through a conduit having an orifice to said fluid pump and an outlet port to said reaction chamber, a torque motor electrically connected to a vehicle speed sensor to receive a d.c. current proportional to vehicle speed, and a spring for normally urging a flapper away from the nozzle tip so as to open it.

Claim 7

A hydraulic power steering device according to claim 1, in which said modulator valve is of the conventional poppet type having a pressure control chamber into which the hydraulic pressure from said fluid pump is introduced through a constriction, said chamber having an outlet port connected to said reaction chamber and a pressure-modulating port connected to said fluid reservoir, a plunger having its tip portion facing said pressure-modulating port so as to close it, a spring around said plunger, and a solenoid operaTively associated with said plunger so as to move it in response to a d.c. current proportional to vehicle speed and supplied to the coil of said solenoid.

Claim 8

A hydraulic power steering device according to claim 1, in which said modulator valve comprises a first valve operatively associated with the transmission output shaft so as to provide a signal pressure corresponding to vehicle speed, said first valve comprising a valve body fixedly mounted on, and rotatable with a driven shaft of said vehicle, said valve body having an inlet port connected to said fluid pump, an outlet port through which said signal pressure is provided, and drain ports connected to said fluid reservoir, a valve member slidably mounted in said valve body, a U-shaped member carrying said valve member and suspended by spring means from the transmission output shaft, said valve member having a land adapted to control fluid communication between said inlet port and said outlet port in response to centrifugal force exerted thereon by rotation of the transmission output shaft, a second valve for controlling a fluid pressure delivered from said fluid pump in response to said signal pressure from said first valve, said second valve comprising a valve body having a bore therein, a valve spool slidably disposed in said valve body bore and having spaced lands provided thereon, a small bore concentric with said valve body bore and adapted to slidably receive an extension of said valve spool, said valve body having a first passage adapted to be connected to the outlet port of said first valve and communicating with said small bore of said valve body, a second passage adapted to be connected to said fluid pump and communicating with the space between said spaced lands, a third passage adapted to be connected to said fluid pump and communicating with one end space of said valve body bore, a fourth passage adapted to be connected to said reaction chamber and communicating with the other end space of said valve body bore, a fifth passage adapted to be connected to said reaction chamber and positioned such that fluid communication between said reaction chamber and the space between said spaced lands increases as said valve spool moves in one direction, a sixth passage adapted to be connected to said fluid reservoir and positioned such that fluid communication between said reservoir and the space between said spaced lands decreases as said valve spool moves in said one direction, said valve spool being biased in said one direction by said signal pressure exerted on said end thereof transmitted through said first passage and by a pressure transmitted through said third passage to said one end space of said valve body bore, said valve spool being also biased in the opposite direction by a pressure transmitted through said fourth passage to the other end space of said valve body bore, wherein a pressure transmitted through said fifth passage to said reaction chamber depends upon steering effort as well as upon vehicle speed.