HYDRAULIC DRIVE SYSTEM FOR CONSTRUCTION MACHINERY

摘要

This hydraulic drive system for construction machinery is provided with: a bidirectional pump connected to a revolving motor through a pair of supply/discharge lines; a regulator for changing the tilt angle of the bidirectional pump; and a control device for controlling the regulator on the basis of a revolving signal outputted from a revolving control valve, wherein the control device calculates a motor flow rate which passes through the revolving motor during revolving acceleration in which the revolving signal increases, and an indicated flow rate determined from the revolving signal. When the indicated flow rate is greater than a reference flow rate which is obtained by adding a predetermined value to the motor flow rate, the control device controls the regulator such that the tilt angle of the bidirectional pump becomes a tilt angle that achieves the reference flow rate; and when the indicated flow rate is equal to or less than the reference flow rate, the control device controls the regulator such that the tilt angle of the bidirectional pump becomes a tilt angle that achieves the indicated flow rate.