| 摘要 |
PROBLEM TO BE SOLVED: To prevent any drive pressure reduction or speed reduction of a working machine by switching a series circuit and a parallel circuit according to the load condition. SOLUTION: When the load pressure of a hydraulic cylinder 3 for a bucket exceeds a predetermined value, a regeneration cancel valve 54 is positioned on the opening side. All the pressure oil discharged from a hydraulic cylinder 2 for a boom is discharged to a tank 14 via return oil passages 35 and 35b, a fixed regeneration ratio valve 43, and a pressure control valve 55. The pressure oil delivered from a hydraulic pump 1 is fed to the hydraulic cylinder 3 for the bucket via oil passages 24 and 24b, a pressure compensation valve 9, and an operation valve 7 for the bucket. This means, when the load of the hydraulic cylinder 3 for the bucket is large, the line is switched to the parallel circuit, and the pressure oil delivered from the hydraulic pump 1 is fed to the hydraulic cylinder 3 for the bucket. |
