CYLINDER CONTROL DEVICE OF CONSTRUCTION MACHINE

摘要

PROBLEM TO BE SOLVED: To attain both assurance of a holding pressure in a hydraulic pressure cylinder and loosening of shock occurred when a piston reaches its stroke end.SOLUTION: A control valve 13 has an opening characteristic in which it is held at a neutral position P1 under a state having no operating command from operating means 14, an opening area of a supply passage becomes large and an opening area of a breed passage becomes small as the control valve 13 moves from the neutral position P1 toward an operating position P3. A controller 18 stores in advance a map where a subtraction value of a driving force for use in changing-over the control valve 13 to the operating position P3 is set in association with a position of a piston 8b in such a way that the subtraction value is increased as the piston 8b is nearer to its stroke end, and identifies the subtraction value on the basis of the map and a result of detection by an angular sensor 17. Further, the controller 18 corrects the map in such a way that the maximum value of the subtraction value in the map may become smaller as a holding pressure in a boom cylinder 8 detected by a pressure sensor 16 is higher.SELECTED DRAWING: Figure 2