Pump system

A pump system comprising:

• a hydraulic pump of a variable capacity type having a discharge capacity that is changeable;
• a regulator that changes the discharge capacity of the hydraulic pump according to a command signal that is input to the regulator;
• an opening degree control valve connected to the hydraulic pump and having an opening degree that is changeable;
• a first pressure sensor that measures upstream pressure that is hydraulic pressure of a working fluid flowing from the hydraulic pump to the opening degree control valve;
• a second pressure sensor that measures downstream pressure that is hydraulic pressure of the working fluid flowing from the opening degree control valve;
• and
• a control device that controls the discharge capacity of the hydraulic pump according to pump characteristics indicating a relationship between a command discharge flow rate and the command signal, wherein:
• by changing the command signal to be output to the regulator, under a measurement condition in which the opening degree of the opening degree control valve is fixed at a predetermined opening degree, the control device causes the first pressure sensor and the second pressure sensor to detect the upstream pressure and the downstream pressure, respectively, with a plurality of command signals different from each other, calculates, for each command signal, an actual discharge flow rate of the working fluid discharged from the hydraulic pump, on the basis of the opening degree of the opening degree control valve and a pressure difference between pressure on an upstream side of the opening degree control valve and pressure on a downstream side of the opening degree control valve that is calculated on the basis of the upstream pressure and the downstream pressure detected, and calibrates the command signal on the basis of the actual discharge flow rate calculated.

A pump system comprising:

• a hydraulic pump of a variable capacity type having a discharge capacity that is changeable;
• 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 changeable;
• a first pressure sensor that measures hydraulic pressure of a working fluid flowing from the hydraulic pump to the unloader valve;
• and
• a control device that controls the discharge capacity of the hydraulic pump according to pump characteristics indicating a relationship between a command discharge flow rate and the command signal, wherein:
• by changing the command signal to be output to the regulator, under a measurement condition in which the opening degree of the unloader valve is fixed at a predetermined opening degree, the control device causes the first pressure sensor to detect the hydraulic pressure with a plurality of command signals different from each other, calculates, for each command signal, an actual discharge flow rate of the working fluid discharged from the hydraulic pump, on the basis of the opening degree of the unloader valve and a pressure difference between pressure on an upstream side of the unloader valve and predetermined pressure on a downstream side of the unloader valve that is calculated on the basis of the hydraulic pressure detected, and creates the pump characteristics so that the command discharge flow rate with respect to each command signal matches the actual discharge flow rate.