Power steering gear with improved responsiveness

Abstract

An integral power steering gear includes a valve within the piston exhibiting improved responsiveness and overall operation. The piston incorporates a rack along the side in engagement with an output pinion. Dual washer springs are provided at the ends of the valve mounted in face-to-face, sliding contact. The spring rate that is thus doubled provides an improved response pattern for the power steering gear. The neutral flow of hydraulic fluid is reduced by narrowing the opening between the adjacent grooves in the valve and the piston. These features together give an improved performance envelope in both of the critical parameters; i.e., steering wheel movement versus net output and steering wheel torque input versus net output. Essentially, the envelope is substantially closed with these improvements giving the desirable improved responsiveness and better feel to the steering. With the spring rate doubled, better mechanical action of the valve including centering of the valve is obtained even under heavy loading and deflection of the piston due to engagement between the rack and pinion. Reduced travel of the springs results from the increased spring rate giving longer lived springs and assuring against permanent set in the springs. Because of quicker response, there is reduced incidence of bottoming out of the valve in the piston. The dual springs are also provided with a pre-load feature that can further increase the spring rate and insures the improved responsiveness and obviates any tendency for sponginess.