| 摘要 |
PURPOSE:To enhance the durability of a slide-contact member by providing a control valve means for communicating a supply oil passage with the low pressure side of a hydraulic closed circuit when the hydraulic pressure of the supply oil passage exceeds a first set value, and for communicating the supply oil passage with an oil chamber when the hydraulic pressure exceeds a second set value. CONSTITUTION:During deenergization of a hydraulic actuator (hydraulic cylinder) 63 a control valve 175 is operated in response to the hydraulic oil of a supply oil passage 170 which is high. When the hydraulic pressure of the supply oil passage 170 exceeds a first set value, oil is fed into a hydraulic closed circuit C. Further, when the hydraulic pressure exceeds a second set value greater than the first set valve, oil is fed into an oil chamber (lubrication chamber) 75. Accordingly, when the amount of leaking oil from a slide contact part is large, the amount of oil fed into the oil chamber 75 becomes small in association with the supply of oil in a sufficient amount into the hydraulic closed circuit C while when it is small, the hydraulic pressure in the supply oil passage 170 increases in association with the supply of oil which is fed into the hydraulic closed circuit C and which becomes small, so that the amount of oil fed into the oil chamber 75 increases, thereby it is possible to always maintain a sufficient amount of oil in the oil chamber 75.
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