Patent ID: 8589038

Claim:
A hydraulic drive system for a working machine, said hydraulic drive system being provided with plural work hydraulic actuators for driving a work element constituting the working machine, a hydraulic pressure source for producing, by a hydraulic pump, pressure oil to be fed to the plural work hydraulic actuators, an engine as a drive source for the hydraulic pump, an exhaust gas purification device for capturing, by a filter, particulate matter in exhaust gas produced by the engine, a forced regeneration means for burning particulate matter deposited on the filter, and a control means for controlling the forced regeneration means, wherein: the hydraulic drive system is further provided with: a forced regeneration command means for commanding conduct of forced regeneration when operated, an attitude detection means for detecting a proper attitude specified beforehand as a safe attitude of the work element during forced regeneration, and a non-operated state detection means for detecting that all the hydraulic actuators for driving the working machine, said hydraulic actuators including the plural work hydraulic actuators, are in non-operated states; and taking as conditions for the conduct of forced regeneration that the non-operated states have been detected by the non-operated state detection means and the proper attitude has been detected by the attitude detection means, the control means makes the forced regeneration means conduct forced regeneration when the conduct of forced regeneration is commanded by the forced regeneration command means.