Hydraulic drive system for construction machine

A hydraulic, drive system for a construction machine comprising:

• a first pump and a second pump that are driven by a prime mover;
• a plurality of first actuators driven by a hydraulic fluid delivered from the first pump;
• a plurality of second actuators driven by a hydraulic fluid delivered from the second pump;
• a plurality of first flow control valves that control the hydraulic fluid supplied to the plurality of first actuators;
• a plurality of second flow control valves that control the hydraulic fluid supplied to the plurality of second actuators;
• a plurality of operation lever devices that operate the plurality of first flow control valves and the plurality of second flow control valves, and drive the plurality of first actuators and the plurality of second actuators;
• a first regulator that adjusts a delivery flow rate of the first pump;
• and
• a second regulator that adjusts a delivery flow rate of the second pump,
• the first regulator adjusting the delivery flow rate of the first pump such that a consumed torque of the first pump does not become larger than a first allowable torque, and adjusting the delivery flow rate of the first pump such that a total of the consumed torque of the first pump and a consumed torque of the second pump does not become larger than a predetermined allowable torque,
• the second regulator adjusting the delivery flow rate of the second pump such that the consumed torque of the second pump does not become larger than a second allowable torque, and adjusting the delivery flow rate of the second pump such that the total of the consumed torque of the first pump and the consumed torque of the second pump does not become larger than the predetermined allowable torque, wherein
• the construction machine hydraulic drive system further comprises:
• a plurality of operation amount sensors that sense operation amounts of the plurality of operation lever devices;
• a first pressure sensor that senses a delivery pressure of the first pump;
• a second pressure sensor that senses a delivery pressure of the second pump;
• a controller configured to calculate a ratio between a sum of estimated demanded powers of the plurality of first actuators and a sum of estimated demanded powers of the plurality of second actuators on a basis of sensed values of the plurality of operation amount sensors and sensed values of the first pressure sensor and the second pressure sensor, and output, on a basis of the ratio, a first command value and a second command value for adjusting allocation between the first allowable torque of the first pump and the second allowable torque of the second pump;
• and
• a first torque control valve and a second torque control valve that generate a first output pressure and a second output pressure on a basis of the output first command value and second command value, and
• the first regulator and the second regulator being configured to adjust the first allowable torque and the second allowable torque, on a basis of the first output pressure and the second output pressure, such that the first allowable torque and the second allowable torque become values to which the predetermined allowable torque is allocated according to the ratio.