HYDRAULIC WORKING MACHINE

摘要

PROBLEM TO BE SOLVED: To provide a hydraulic working machine in which a jack-up selector valve can be switched insensitively to a change of the working attitude of the working machine, a change of the bottom pressure of a hydraulic cylinder with a temperature change of the pressure oil to be supplied to the hydraulic cylinder, and a change of the bottom pressure when starting the jack-up operation.

SOLUTION: This hydraulic working machine includes a valve control means which switches the jack-up selector valve 25 to a first switching position 25a so as to hold a flow rate control valve 26 on a passage closing side and controls a center bypass selector valve 27 so as to be held at an opening position 27a when the rod pressure detected by a rod pressure sensor 101 is less than a preset threshold value Pr, and which switches the jack-up selector valve 25 to a second switching position 25b so as to hold the flow rate control valve 26 on a passage opening side and controls the center bypass selector valve 27 so as to be held at a closing position 27b when the rod pressure detected by the rod pressure sensor 101 is not less than the rod pressure threshold value Pr.

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