Power Rack & Pinion: Operation
The steering gear box consists of two sections: one including a cylinder and the other a valve. See Fig 1 . Main components of the cylinder section are a gear box, a rack and a tube, and main components of the valve section are a valve case, a sleeve and a stub shaft. See Fig 2 . The sleeve is linked with the pinion through a pin and the valve and stub shaft are integrated into one unit. Then the pinion and the stub shaft are linked to each other by means of the torsion bar. Thus, when the stub shaft moves, the valve changes its position, thereby switching the hydraulic passage from the pump to the cylinder to help steering operation. When turning the steering wheel feels heavy due to P/S fluid leakage or for some other reason (i.e., when in the manual steering mode), the stub shaft and pinion are in direct linkage and the force is output directly through the pinion and rack.
Belt-driven P/S oil pump is a constant delivery vane type. An idle up system increases idle speed when power steering pump pressure exceeds 284-383 psi (1958-2641 kPa).