| 摘要 |
The present invention provides a hydraulic control system with preferred operating performance, response in operation and stability, and with system efficiency enhanced greatly. In case that each of the directional control valves 3, 4 and 5 is in the neutral position, the pressure oil supply to each of the valves from the discharge line 11 of the variable displacement hydraulic pump 1 is stopped. The pressure on the signal line 18 is connected through the solenoid operated on-off valve 56 to the tank 32. Therefore, the pressure on the signal line 18 is low. On the other hand, the pressure oil in the discharge line 11 is discharged to the tank through the pressure generating means 31 against the spring 55 mounted on the flow control valve 29 with pressure compensation. In the case, the discharge rate of the pump is held to be at minimum level when the pressure signal Po applied to the pump discharge rate control mechanism B is low. Then, oil quantity passing through the flow control valve with pressure compensation becomes also to minimum. When the pressure on the pressure signal line C rises, the discharge rate of the pump is held to be at minimum level. The minimum discharge rate can be set at very small level, depending on the constitution of the variable displacement hydraulic pump provided with the pressure generating means and the pump discharge rate control mechanism.
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