| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic circuit for a construction machine that can appropriately reduce, according to a working condition, a passing pressure loss until return oil from the bottom side of a hydraulic cylinder is discharged to a tank. SOLUTION: The hydraulic circuit for the construction machine includes a discharge selector valve 22 connected to a hydraulic pump 12 in tandem with a selector valve 16, and having a discharge passage 22c for discharging the return oil from the bottom side of the hydraulic cylinder 80 to the tank T and switching the flow rate of the return oil returned to the tank T through the discharge passage 22c, and a working state determining means 30 determining whether a working state is a specific working state or not to accelerate the discharge of the return oil from the bottom side of the hydraulic cylinder 80. When determining the specific working state by the working state determining means 30, the discharge selector valve 22 is switched so that the discharge passage 22c communicates with the bottom side of the hydraulic cylinder 80, and at least part of the return oil from the bottom side of the hydraulic cylinder 80 is returned to the tank T through the discharge passage 22c of the discharge selector valve 22. COPYRIGHT: (C)2011,JPO&INPIT |
