HYDRAULIC DRIVE SYSTEM USED IN CONSTRUCTION MACHINE AND PROVIDED WITH EXHAUST GAS PURIFICATION DEVICE

摘要

A construction machine hydraulic drive system that performs load sensing control is arranged to be capable of efficiently burning and removing deposits on a filter in an exhaust gas purifying device through pump output increasing control and to be free from faults in the pump output increasing control even when an actuator is operated during the pump output increasing control. A solenoid switching valve (70) is switched so that output pressure of an engine speed detecting valve (13) is guided to a pressure receiving portion (17d) of an LS control valve (17b) and a pressure receiving portion (15d) of an unloading valve (15) when a start of regeneration is not directed, and delivery pressure of a pilot pump (30) is guided to the pressure receiving portion (17d) and the pressure receiving portion (15d) when the start of the regeneration is directed, to thereby disable load sensing control to increase capacity of a main pump (2) and increase set pressure of the unloading valve (15).