| 摘要 |
Provided is a construction machine in which a rod-side pressure in a boom cylinder can be relieved without difficulty. The construction machine includes: a hydraulic pump 14; a working attachment including a boom, a boom cylinder 6, and another fluid-supplied cylinder; first and second operation devices 10, 11 for the boom cylinder 6 and the fluid-supplied cylinder; first and second control valves 12, 13; a flow-rate-limiting section 16; and an anti-cavitation circuit 17. The fluid-supplied cylinder is, for instance, an arm cylinder 7 closer to a leading end than the boom cylinder 6, receiving supply of hydraulic fluid from the hydraulic pump 14, together with the boom cylinder 6. A reaction force upon work accompanying extension of the fluid-supplied cylinder increases the rod-side pressure of the boom cylinder 6 and reduces a head-side pressure. The flow-rate-limiting section 16 limits a supply flow rate to a head-side fluid chamber 6a of the boom cylinder 6 from the hydraulic pump 14 only during a boom raising operation in a situation where the rod-side pressure of the boom cylinder 6 is higher than the head-side pressure thereof. The anti-cavitation circuit 17 replenishes hydraulic fluid from a tank T to the head-side fluid chamber 6a. |
