| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent fluctuation in operation due to load pressure change of a hydraulic actuator by providing a pressure compensating mechanism in one of plural hydraulic pumps for driving a boom, an arm and a bucket and revolving a main body part. SOLUTION: Pump circuits C1-3 of hydraulic pumps P1-3 are respectively provided with a pressure compensating mechanism 11, and in the case of the pressure compensating mechanism 11 of the pump P3, for example, a pressure compensating flow control valve 21 is provided with a pressure compensating spool 22 for opening and closing a bypass circuit 12 for letting pressure oil from the pump P3 escape to an oil tank. When the load pressure of a hydraulic actuator is increased from the condition where the upstream pressure of a flow control part is balanced with the downstream pressure, the spool 22 is pushed in the closing direction and much pressure oil flows to the pump circuit C3, so that the pump pressure rises to be again balanced, and the spool 22 is stopped. The same can be said with the case where the load pressure is decreased. Accordingly, each hydraulic actuator can be stably operated regardless of increase and decrease in load pressure.</p> |
