| 摘要 |
PURPOSE:To ensure a smooth stopping operation of a variable volume member by increasing the set pressure of a pressure-reducing valve to increase pressure to the pressure receiving section of a control valve when the pump discharge pressure exceeds a certain value so that the control valve is changed over to the side for operating the variable volume member in the direction to reduce the volume. CONSTITUTION:While an operating valve 6 is opened, differential pressure DELTAP is produced between the front and rear of the operating valve 6 by the discharge amount Q of a variable volume pump 1. If the differential pressure DELTAP is large for example, a first control valve 2 affords communication between ports 16, 18, introduces discharge pressure into a circuit 20 leading to a control cylinder 5 and operates a variable volume member 4 in the direction to reduce its volume. When the pump discharge pressure exceeds a certain value, a second control valve 3 is moved toward a second position against a spring 10 to introduce the discharge pressure into the circuit 20 in preference to the first control valve 2 so that a variable volume member 4 is operated in the direction to reduce its volume. Then, the spring pressure of a pressure-reducing valve 14 is increased to increase the set pressure so that the second control valve 3 is moved toward a first position to stop the operation of a cylinder 5. |
