| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic circuit of a construction machine or its control method in which a swing motion priority valve is controlled on the basis of a boom lifting-up pilot pressure and a bottom pressure of a boom cylinder when a boom lifting-up operation and an arm closing operation are simultaneously carried out and the boom lifting-up operation is preferentially performed.SOLUTION: There is provided control means operated such that a swing pilot pressure inputted to a control port of a swing direction control valve is detected, a boom lifting-up pilot pressure inputted to the control port corresponding to a boom-lifting up direction of a boom direction control valve is detected, a bottom pressure of a boom cylinder is detected and an operation of a swing priority valve arranged in an upstream side oil passage of an arm direction control valve supplying operation oil to an arm cylinder. The control means controls a degree of opening of the swing priority valve on the basis of the detected swing pilot pressure and controls a degree of opening of the swing priority valve under further application of the boom-up pilot pressure and the bottom pressure of the boom cylinder when the boom lifting-up and the arm closing are simultaneously carried out. |
