HYDRAULIC DRIVE SYSTEM ADAPTED FOR USE IN CONSTRUCTION MACHINE AND PROVIDED WITH EXHAUST GAS PURIFICATION DEVICE

摘要

A hydraulic drive system executing the load sensing control is designed to be capable of efficiently combusting and removing filter deposits inside an exhaust gas purification device (42) by pump output power increasing control when there is no actuator operation, eliminating interference between the actuator operation and the pump output power increasing control even when they are performed at the same time, and achieving these effects with ease and at a low cost. The hydraulic drive system comprises: a solenoid selector valve (46) which selects between tank pressure and delivery pressure of a pilot pump (30) upstream of an engine revolution speed detecting valve (13) and outputs the selected pressure to a shuttle valve (45) ; and a solenoid selector valve (48) which is arranged in a line (12b) leading the output pressure of a differential pressure reducing valve (11) to an LS control valve (17b) and selects between enabling and disabling of the load sensing control. When the exhaust gas purification device (42) needs regeneration, a controller (49) executes switching to make the solenoid selector valve (46) output the delivery pressure of the pilot pump (30) as dummy load pressure and to make the solenoid selector valve (48) disable the load sensing control.