| 摘要 |
<p>A hydraulic power-steering system has a reversing spool-type valve whose spool may be displaced by the steering wheel and which is connected between a hydraulic pump and a power cylinder in turn connected to the vehicle wheels. This power cylinder has a piston whose effective surface areas exposed in respective chambers are of different size. The spool valve has a pair of input branches connected to the high-pressure side of the pump and a pair of output branches connected to the low-pressure side of the pump, and may assume an intermediate position in which each of the input branches is connected to a respective one of the output branches for hydrodynamic flow through the valve. In addition this valve has a pair of control ports connected to the respective chambers of the power cylinder, and connectable via respective compartments of the valve to respective input and output branches. A restriction is provided in that output branch connectable to the chamber of the piston face of smaller area so that in an intermediate position of the valve pressure builds up in the respective compartment and maintains the piston in balance. Displacement of the spool to one side or the other blocks and unblocks the input and output branches to displace the piston of the power cylinder.</p> |
