| 摘要 |
PURPOSE:To prevent generation of cavitation at the time of speed reduction of a hydraulic motor by providing a relief valve in the vicinity of the end portion of a return oil path leading from a changeover valve to a tank. CONSTITUTION:A relief valve 13 is provided on a return oil path 8 leading from a changeover valve 3 through a tank 7 and the pilot oil path 15 of the relief valve 13 is connected to the discharge side oil path 4 of a hydraulic pump 2. And the return oil path 8 is connected to a hydraulic motor 1 through check valves 11, 12. Then, oil can directly be supplied from the return oil path 8 even when oil supply to the hydraulic motor 1 is decreased at the time of speed reduction of the hydraulic motor 1, and generation of cavitation in the hydraulic motor 1 can be prevented.
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