HYDRAULIC DRIVE DEVICE FOR CONSTRUCTION MACHINERY

摘要

The purpose of the present invention is to control overall torque with good precision, by detecting the absorbed torque of a second hydraulic pump with good precision using a purely hydraulic configuration and feeding back same to a first hydraulic pump, and to enable effective utilization of the rated output torque of the motor. For said purpose, a hydraulic drive device is provided with: a torque feedback circuit (112v), to which the discharge pressure and the load sensing drive pressure of a main pump (202) are led and which corrects the main pump (202) discharge pressure so that the main pump (202) discharge pressure achieves characteristics that simulate the absorbed torque of the main pump (202) and outputs same; and a torque feedback piston (112f), to which the output pressure of said torque feedback circuit is led and which controls the capacity of a main pump (102) so as to decrease the capacity of the main pump (102) and reduce maximum torque (T12max) as said output pressure increases. The torque feedback circuit (112v) comprises a first and second variable pressure reducing valves (112g, 112q).