| 摘要 |
There is disclosed a control valve arrangement for power steering systems having a servomotor piston which carries a piston valve constructed with a pair of reaction chambers having relief valves and communicating with each other in such a manner as to provide variable resistance against the manual force being applied to a steering wheel which actuates the piston valve. The purpose of thus effecting an automatically varying force is to impart to the vehicle driver a simulated sense of mechanical steering, i.e., simulated road resistance feel, but with a decreasing requirement of force expenditure during vehicle parking operations, or during low speed driving. The construction permits the use of simple parts in a very compact arrangement in which either reaction chamber imparts road resistance feel by being subjected only to servopump inlet pressure while the other is subjected to exhaust pressure. The unbalance of force acts on the piston valve in a direction opposite the manually impressed force. However, both reaction chambers have relief valves, biased closed, but exposed upstream to inlet pressure. Should that pressure exceed a certain limit, the reaction chamber under exhaust pressure will have an inlet pressure feed mixing with exhaust pressure to effect a force opposing the road resistance force of the other reaction chamber. Thus, manual steering effort during parking or driving at slow speeds is decreased even though servomotor pressure may increase.
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