| 摘要 |
In a power assistance system for a vehicle steering mechanism fluid pressure providing the assistance is supplied from a pump (4) driven intermittently by an infinitely-variable electric motor means (5). For a rack and pinion mechanism (1) fluid pressure chambers (6, 7) are formed by sealing boots (8,9) at each end of the rack (3), and are connected through the pump (4), which is operative to create a pressure differential between the chambers, and thus across the rack (3) to provide power assistance. The electric motor (5) is energised as required to drive the pump (4) in the appropriate direction, and when the motor and pump are inoperative fluid is allowed to flow freely between the chambers (6, 7) to accommodate fluid displacement as a result of unassisted operation of the steering. The pump (4) is preferably a turbine pump, which allows fluid flow when inoperative. The system provides power assistance efficiently, and relatively cheaply. |
