Construction machine

A construction machine comprising:

• a prime mover;
• a tank that stores a hydraulic operating fluid;
• a hydraulic pump that is driven by the prime mover and delivers, as a hydraulic fluid, the hydraulic operating fluid sucked in from the tank;
• a hydraulic actuator that is driven by the hydraulic fluid delivered from the hydraulic pump;
• a meter-in valve that adjusts a flow rate of the hydraulic fluid supplied from the hydraulic pump to the hydraulic actuator;
• a meter-in spool position adjusting device that adjusts a spool position of the meter-in valve;
• and
• a controller that outputs a command signal to the meter-in spool position adjusting device, wherein
• the construction machine includes:
• a velocity sensor for sensing an operation velocity of the hydraulic actuator;
• a meter-in spool position sensor that senses the spool position of the meter-in valve;
• a pressure sensor that senses a differential pressure across the meter-in valve;
• and
• a pressure adjusting device that adjusts the differential pressure across the meter-in valve, and
• the controller has a calibration mode in which the controller derives operation characteristics that represent a relation among the spool position of the meter-in valve, the operation velocity of the hydraulic actuator, and the differential pressure across the meter-in valve, and
• is configured to, in a case where the spool position of the meter-in valve has changed in a direction to increase an opening area of the meter-in valve in the calibration mode, output a command signal to reduce the differential pressure across the meter-in valve to the pressure adjusting device such that increase in the flow rate of the hydraulic fluid to be flown into the meter-in valve is suppressed.