| 摘要 |
PROBLEM TO BE SOLVED: To prevent overheat of an engine by opening a flow control valve of a bypass oil passage which passes a delivery oil passage of a hydraulic pump and a hydraulic oil tank when an operation state is detected and a temperature of a cooling water is higher than a predetermined temperature. SOLUTION: When a temperature of engine cooling water is lower than a set temperature, an operation of a remote control valve 13 is detected by a pressure sensor 14. Only when a pedal 13a is operated, a signal for fully closing a bypass flow control valve 15 is outputted from a controller 17 to an electromagnetic proportional valve 18 to make a pilot port 27 operate, whereby all flow from a hydraulic pump 9 is supplied to a hydraulic cylinder 11. Next, when an operation state of the cylinder 11 is detected by the sensor 14 and a temperature detected by a cooling water temperature sensor 19 rises to a predetermined temperature, the valve 15 divides the flow from the pump 9 between a flow to the cylinder 11 and a flow for returning from the valve 15 to the hydraulic oil tank, in response to the cooling water temperature. Accordingly, hydraulic oil to the hydraulic cylinder 11 is reduced, and load of the pump 9 is reduced, whereby overheat of an engine 8 can be prevented.
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