| 摘要 |
PURPOSE:To smooth oil circulation in an oiltight chamber by interposing No.1 pressure control valve, which opens under the oil pressure in the oiltight chamber, between the oiltight chamber and a lubricating chamber, moreover interposing No.2 pressure control valve between the secondary side of the No.1 pressure control valve and a tank. CONSTITUTION:On the way of a supply passage 51 connecting an oiltight chamber 31 to a lubricating chamber 75, there is interposed No.1 pressure control valve 50 which opens under the oil pressure in the oiltight chamber 31. Between a tank T and the supply passage 51, which connects the No.1 pressure control valve 50 to the lubricating chamber 75, there is interposed No.2 pressure control valve 50' which opens under oil pressure lower than the set value of the No.1 pressure control valve 50. Thereby, even if a hydraulic motor M or a hydraulic pump P operates at high speed or high load so that the oil pressure in the lubricating chamber 75 increases, the operation of the No.1 pressure control valve 50 can be kept normal, accordingly, oil circulation in the oiltight chamber 31 becomes smooth so as to avoid increase of oil temperature, thereby rendering it possible to prevent durability of the hydraulic pump P and the hydraulic motor M from lowering.
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