HYDRAULIC DRIVE SYSTEM FOR CONSTRUCTION MACHINE

摘要

A hydraulic motor (52) is arranged in a control hydraulic line (51) connecting a second hydraulic fluid supply line (4a) (for supplying the hydraulic fluid delivered from the main pump (2) to flow control valves (26a to 26h)) to a tank (T). A generator (53) connected with the rotating shaft (52a) of the hydraulic motor (52). Maximum load pressure (PLmax) is detected by a pressure sensor (54). Power generation control of the generator (53) is performed by a second control device (55) so that the hydraulic motor (52) rotates when the delivery pressure of the main pump (2) exceeds target control pressure (Pun) determined by adding a preset value (Pb) to the maximum load pressure (PLmax). AC power generated by the generator (53) is stored in a battery (41).

主权项

1. A hydraulic drive system for a construction machine including a prime mover, a main pump of the variable displacement type driven by the prime mover, a plurality of actuators driven by hydraulic fluid delivered from the main pump, a plurality of flow control valves that respectively control the flow of the hydraulic fluid supplied from the main pump to the actuators, and a pump control device that performs load sensing control for the delivery flow rate of the main pump so that delivery pressure of the main pump becomes higher than maximum load pressure of the actuators by target differential pressure, comprising:
a hydraulic motor arranged in a control hydraulic line connecting a hydraulic fluid supply line for supplying the hydraulic fluid from the main pump to the flow control valves, to a tank, the hydraulic motor being drivable by the hydraulic fluid delivered from the main pump; a generator connected with the rotating shaft of the hydraulic motor; a control device that performs power generation control of the generator so that the delivery pressure of the main pump becomes higher than a target control pressure determined by adding a preset value to the maximum load pressure with the rotation of the hydraulic motor; and an electricity storage device that stores electric power generated by the generator.