| 摘要 |
PROBLEM TO BE SOLVED: To prevent the overheating of a hydraulic system and an engine by rapidly decreasing the temperature of a working fluid, even if the temperature of the working fluid is increased because of the continuity of a relief state wherein a relief valve for setting a circuit pressure is kept open. SOLUTION: A working fluid temperature sensor 29 for detecting the temperature of the working fluid is provided; the relief valve for setting the circuit pressure serves as a variable relief valve 27 which can variably control the set pressure. The set pressure of the variable relief valve 27 is controlled so as to be lowered up to a low set pressure lower a standard set pressure PS, which is set when the temperature T of the working fluid is as low as/lower than a set pressure TS, in the case wherein the temperature T of the working fluid, measured by the sensor 29, exceeds the preset temperature TS. COPYRIGHT: (C)2006,JPO&NCIPI
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