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|1. (WO2018043401) HYDRAULIC DRIVE SYSTEM FOR CONSTRUCTION MACHINE|
|Applicants:||KAWASAKI JUKOGYO KABUSHIKI KAISHA
|Title:||HYDRAULIC DRIVE SYSTEM FOR CONSTRUCTION MACHINE|
This hydraulic drive system is provided with: a hydraulic actuator; a control valve for controlling the supply and discharge of hydraulic oil to and from the hydraulic actuator; a pilot operation valve connected to an operation valve by a pair of pilot lines; an electromagnetic proportional pressure reducing valve provided to at least one of the pair of pilot lines; an operation detector for outputting an operation amount signal corresponding to the tilt angle of the operation lever of the pilot operation valve; and a control device which, immediately after the amount of variation per unit time in the operation amount signal outputted from the operation detector decreases by a value exceeding or equal to a threshold value, starts to control the electromagnetic proportional pressure reducing valve so that pressure at a pilot port of the control valve will be gradually reduced to zero by the communication between the secondary pressure port of the electromagnetic proportional pressure reducing valve and the tank port thereof.