Pump calibration system and method for a hydraulic pump of a variable capacity

A pump calibration system comprising:

• a hydraulic pump of a variable capacity type having a discharge capacity that is variable;
• a regulator that changes the discharge capacity of the hydraulic pump according to a command signal that is input to the regulator;
• an unloader valve disposed between the hydraulic pump and a tank and having an opening degree that is variable;
• a pressure sensor that measures a discharge pressure of the hydraulic pump;
• and
• a control device that controls the discharge capacity of the hydraulic pump by outputting the command signal to the regulator and calibrates a pump characteristic indicating a relationship between the command signal and the discharge capacity or a discharge flow rate of the hydraulic pump, wherein:
• the control device includes an initial state storage mode and a calibration mode,
• in the initial state storage mode, the control device stores, as a first reference pressure in advance, a pressure detected by the pressure sensor when a first reference signal that is predetermined is output to the regulator under a measurement condition in which the opening degree of the unloader valve is fixed to a predetermined value and the hydraulic pump is driven to rotate at a predetermined number of revolutions, and
• stores, as a second reference pressure in advance, a pressure detected by the pressure sensor when a second reference signal that is predetermined is output to the regulator under the measurement condition, and
• in the calibration mode, the control device changes the command signal that is output to the regulator under the measurement condition, sets the first reference pressure to the discharge pressure detected by the pressure sensor, sets a first actual signal to the command signal with which the discharge pressure detected is the first reference pressure, changes the command signal that is output to the regulator under the measurement condition, sets the second reference pressure to the discharge pressure detected by the pressure sensor, sets a second actual signal to the command signal with which the discharge pressure detected is the second reference pressure, and calibrates the pump characteristic on the basis of the first actual signal and the second actual signal.

A pump calibration method for calibrating a pump characteristic indicating a relationship between a discharge capacity or a discharge flow rate of a hydraulic pump of a variable capacity type and a command signal that is input to a regulator in changing of the discharge capacity by the regulator, the pump calibration method comprising:

• storing a first reference pressure detected by a pressure sensor when the regulator changes the discharge capacity of the hydraulic pump according to a first reference signal that is input to the regulator under a measurement condition in which an opening degree of an unloader valve disposed between the hydraulic pump and a tank is fixed to a predetermined value, the measurement condition being predetermined;
• deriving a first actual signal by changing the command signal that is output to the regulator under the measurement condition, the first actual signal being the command signal with which a discharge pressure of the hydraulic pump detected is the first reference pressure;
• and
• calibrating the pump characteristic according to a difference between the first actual signal and the first reference signal, wherein:
• in the storing, the first reference pressure is detected before a calibration condition that is predetermined is satisfied;
• and
• in the deriving, after the calibration condition is satisfied, the command signal that is output to the regulator is changed to derive the first actual signal.