| 摘要 |
<p>A control valve (10) controls fluid flow between a pump (34) and a motor (20) in a hydraulic power assist steering system (12) for a vehicle having steerable wheels. The control valve (10) includes a valve core (40) and a valve sleeve (50) supported for relative rotation. The control valve (10) has an inlet port (80) for receiving fluid from the pump (34) and a return passage (100) for directing fluid from the control valve to the pump (34). The control valve (10) has a first motor port (84) for enabling fluid flow between the control valve and the motor (20). First and second closing orifices (1A-L, 2A-L) are in series between the first motor port (84) and the return passage (100). A third closing orifice (2-L) is located between a second motor port (86) and the return passage (100). The orifice (1A-L) is a relatively high pressure orifice and the orifice (2A-L) is a relatively low pressure orifice. Two high pressure orifices (1-L, 1A-L) spaced on opposite sides of the inlet port (80) remain at least partially open except when the valve is fully turned.</p> |
