| 摘要 |
PURPOSE:To prevent noise made by a fixed throttle, by connecting a flow control valve with the fixed throttle serving as a bypass to a communication passage for communicating a passage on the side of a servo valve with a passage on the side of a reaction mechanism through the fixed throttle and discharging a rate of flow in front of the fixed throttle to a low pressure side. CONSTITUTION:A feed passage 45 is communicated with a relief passage 47 by a communication passage 90 through a fixed throttle 91 and the communication passage 90 is connected to a flow control valve 92 with the fixed throttle 91 serving as a bypass. The flow control valve 92 is actuated by a differential pressure b, c across the fixed throttle 91. When the differential pressure is greater than a pressure PG produced by a gear when a vehicle travels at a high speed, an excessive rate of flow is fed to a low pressure side. With this arrangement, a rate of flow q1 in back of the fixed throttle 91 can be controlled to constant when the pressure PG produced by the gear exceeds a prescribed value. Therefore, noise made by the fixed throttle 91 in the communication passage 90 in steering at a low speed can be prevented.
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