| 摘要 |
This boom drive device is provided with a boom switching valve for extending and retracting a boom hydraulic cylinder. When the boom switching valve is in a lowering position in which lowering operations are performed, work fluid discharged from the working chamber of the boom hydraulic cylinder is recirculated to a tank. A portion of the discharged work fluid is separated upstream of the boom switching valve, supplied through a regenerative passage to a generator, and used in power generation in the generator. A regeneration control spool valve is provided in the regenerative passage. When the boom switching valve is switched to the lowering position, after the flow cross-sectional area of the work fluid flowing from the work chamber to the tank has reached a prescribed level, the shock accompanying power generation start in the generator is lessened by opening the regeneration control spool valve. |
