HYDRAULIC DRIVE DEVICE OF WORKING MACHINE

摘要

A hydraulic drive device of working machine, comprising a merge valve (2) connected to a directional control valve (1) of a first directional control valve group through a center bypass passage (3), a merge circuit (5) communicating the merge valve (2) with the supply port of a directional control valve for merge (4), an actuator for merge (20) controlled by the directional control valve for merge (4), and a release valve (10) releasing the merge by the merge valve (2) when the load pressure of the actuator for merge (20) exceeds a specified value, wherein a total horse power is controlled so that the total value of the input torques of two hydraulic pumps (15) and (18) does not exceed the output torque of an engine (30), whereby a merge is stopped forcibly when the load pressure of the actuator for merge where the pressure oils from two hydraulic pumps are merged with each other becomes higher than a specified pressure and the actuator for merge is driven only by the pressure oil from one hydraulic pump.