| 摘要 |
<p>Differential pressures across flow control valves (6a, 6b, 6c) are controlled by pressure compensating valves (7a, 7b, 7c) to a differential pressure DELTA PLS having the same value, and the differential pressure DELTA PLS is maintained at a target differential pressure DELTA PLSref by a pump capacity control device (5). To modify the target differential pressure DELTA PLSref depending upon a change in revolution speed of an engine (1), a flow rate detecting valve (31) is provided on discharge passages (30a, 30b) in a fixed capacity hydraulic pump (30) so that a differential pressure DELTA Pp across a variable restriction (31a) in the flow rate detecting valve (31) is conducted to a setting modifying device (32) to modify the target differential pressure DELTA PLSref. The flow rate detecting valve (31) acts to change an opening area of the variable restriction (31a) depending upon the differential pressure DELTA Pp across the variable restriction (31a) itself, and to change the differential pressure DELTA Pp in accordance with the revolution speed of the engine (1). Accordingly, saturation phenomenon is improved in accordance with the engine revolution speed, and a favorable minute operability is obtained in the case where the engine revolution speed is set low. <IMAGE></p> |
