| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic system which can save energy in a pressure holding operation, and further can improve the responsibility of a hydraulic cylinder, etc., in a cold period. SOLUTION: A controller 20 closes the portion between a pump port P and a first load port A by positioning an electromagnetic selector valve 2 to a neutral position S0, and also controls a hydraulic pump 1 via a motor 15 so as to open a relief valve 11 when the temperature detected by a temperature sensor 13 is lower than a preset temperature in the pressure holding operation of the hydraulic cylinder 5. Thus, in the pressure holding operation in the cold period, high pressure working fluid is discharged from the relief valve 11 into a tank 12. As a result, the energy of the pressure of the working fluid is converted into thermal energy, and the temperature of the working fluid can be quickly raised. Therefore, the viscosity of the working fluid can be lowered even in the cold period, and the sufficient responsibility can be achieved. COPYRIGHT: (C)2008,JPO&INPIT
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