Load sensing control circuit

A load sensing control circuit comprising:

• a plurality of actuators;
• a variable displacement pump that supplies a pressure fluid to the plurality of actuators;
• switch valves provided respectively in connecting passages that connect the variable displacement pump to the respective actuators;
• compensator valves provided respectively in the connecting passages between the switch valves and the actuators, the compensator valves each including a first pressure chamber and a second pressure chamber;
• and
• a selection unit that selects a maximum load pressure of the plurality of actuators,
• wherein the variable displacement pump is configured to discharge pressure fluid at a discharge amount corresponding to the load pressure selected by the selection unit;
• and
• a pump discharge amount is divided in accordance with respective switch amounts of the switch valves by leading pressure between the compensator valves and the switch valves to the respective first pressure chambers of the compensator valves, leading the maximum load pressure selected by the selection unit to the respective second pressure chambers of the compensator valves, and controlling respective openings of the compensator valves in accordance with respective pressure actions between the first pressure chambers and the second pressure chambers,
• the load sensing control circuit further comprising:
• a drain passage that connects the first pressure chamber of at least one of the compensator valves to a tank;
• and
• a pressure control unit provided in the drain passage and that controls a pressure in the first pressure chamber of the at least one of the compensator valves connected to the tank,
• the pressure control unit is configured to open/close the drain passage, and when opening the drain passage, to increase a differential pressure between the first pressure chamber and the second pressure chamber of the at least one of the compensator valves and to decrease an opening degree of the at least one of the compensator valves compared with when closing the drain passage.