| 摘要 |
PURPOSE:To efficiently utilize pressurized oil from a pump by improving connection and the like between a discharge port of a pump and a three-port type pressure control valve. CONSTITUTION:Actuators 6-8 can make operations independently through supply of pressurized oil from three variable pumps 18-20, for example, when a main arm selector valve 13 is switched into neutral to stop driving of an arm cylinder 5 belonging to the third actuator group and a selector valve 15 for turning is switched, pressurized oil is supplied to a turning motor 9 not only from the first variable pump 18 but also from the third variable pump 20. Since the third variable pump 20 discharges a predetermined quantity of pressurized oil through control of a load sensing valve 39 to supply it to the motor 9 even during a driving stoppage of the third actuator group, the pressurized oil of the third pump can be effectively utilized. |
