HYDRAULIC CONTROL DEVICE OF CONSTRUCTION MACHINE

摘要

PROBLEM TO BE SOLVED: To achieve an efficient use of a pumping rate during operation to lift a boom.SOLUTION: A hydraulic control device of a hydraulic shovel comprises: a boom cylinder 5 to drive a boom 4; a hydraulic pump 6 to supply pressure oil to activate the boom cylinder 5; a boom direction control valve 9; and a boom operation device 11 to switch the boom direction control valve 9. The hydraulic control device is provided with control means which has: an operation section which calculates thrust force of the boom cylinder 5 during operation to lift the boom 4; and a determination section to determine whether or not the thrust force calculated by the operation section is equal to or larger than a prescribed value F0 to be preliminarily set. The control means also includes a controller 12 which controls in a manner that: does not limit a rate of the pressure oil to be supplied from the hydraulic pump 6 to the boom direction control valve 9 when the thrust force is determined to be equal to or larger than the prescribed value F0 by the determination section; and limits the rate of the pressure oil to be supplied from the hydraulic pump 6 to the boom direction control valve 9 when the thrust force is determined to be less than the prescribed value F0 by the determination section.