Steering: Description and Operation

Vane pump (1) is belt-driven from the engine to discharge oil under pressure. Oil under pressure is controlled by the flow control valve (2) located inside the oil pump assembly in response to engine speed and is delivered to control valve (4) via hose A (3). When the steering wheel is turned, control valve (4) connected to the pinion shaft activates to form an oil flow circuit corresponding to the rotation direction of the steering wheel. Oil will then be delivered to chamber A or B via pipe A (5) or B (6). Oil in chamber A or B acts on rack pinion (8) to produce the force required to move rack shaft (9) to the left or the right. This helps reduce the effort required to operate the steering wheel. Movement of rack piston (8) in turn causes oil in the other chamber to return to oil reservoir (11) via pipe A (5) or B (6), control valve (4) and hose B (10). If the hydraulic system becomes inoperative, the steering shaft will then be connected to the pinion shaft mechanically via control valve 63. Thus, the steering shaft can act as one similar to a manual steering system to move the rack and pinion. To control the maximum oil pressure setting, relief valve (12) is built into flow control valve (2) of the oil pump assembly to release excess oil pressure.