| 摘要 |
PURPOSE:To reduce the power loss of a variable pump, by connecting a main flow line with a divided flow line through a switching means and decreasing a delivery quantity of the variable pump to almost zero by a delivery quantity control part, in the standby condition of a return end or the like where almost no power is required for a reciprocating actuator. CONSTITUTION:A variable pump 1 additionally provides the first delivery quantity control part 8, controlling a delivery quantity in a range reaching an intermediate flow from a large flow, and the second delivery quantity control part 9 controlling a delivery quantity to its range decreasing to almost zero. When an actuator 7 is in forward operation, a rise of the pressure in a main flow line 2 first connects the first control part 8 with the main flow line 2 through the first pressure control valve 10 and the following rise of the pressure connects the second control part 9 with the main flow line 2 through the second pressure control valve 20, respectively. On the contrary, when the actuator is in return operation, a control circuit, switching a switching means 38 to connect the main flow line 2 with a divided flow line 35 and enabling the main flow line 2 to be connected with the second control part 9 through the third pressure control valve 30, decreases a delivery quantity of the variable pump 1 to almost zero.
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