Hydraulic control system and setting method and calibration method of target engine torque during relief in hydraulic control system

A hydraulic control system for a work machine configured to comprise a hydraulic pump of variable displacement type driven by an engine to supply oil to a plurality of hydraulic actuators via a pump oil passage;

• a relief valve disposed in a relief oil passage in communication with the pump oil passage, the relief valve for controlling a pressure in the pump oil passage during a relief when the relief valve opens;
• the hydraulic control system comprising:
• a pump pressure sensor for detecting the pressure in the pump oil passage;
• a controller operably connected to the hydraulic pump, the pump pressure sensor, and the engine, the controller configured to:
• calculate an engine torque in a state where the pump flow rate is regulated so that a detected pressure value of the pump oil passage during the relief reaches a preset target relief pressure, the engine torque being calculated based on the pump flow rate and the detected pressure value;
• set the calculated engine torque as a target engine torque of the engine driving the hydraulic pump during relief;
• and
• output a control command to the hydraulic pump during relief to control the flow rate of the hydraulic pump to the pump oil passage so that the engine torque of the engine driving the hydraulic pump during the relief becomes the target engine torque during relief.