| 摘要 |
PURPOSE: An apparatus and method for controlling coolant temperature is provided to prevent damage of cylinder block and cylinder head caused due to thermal overshoot, and breakdown of thermostat and radiator caused due to surge pressure, while significantly improving fuel efficiency. CONSTITUTION: A thermostat is arranged in the passage of inlet side of a water jacket(20), and a first cooling liquid passage(24) is arranged between an upper outlet(21) of the water jacket and an upper inlet(23) of a radiator(22). A thermostat cap(26), a thermostat housing(27) and a water pump(28) are disposed in a second cooling liquid passage(30) connected to a lower inlet(29) of the thermostat. A bypass path(31) is arranged between the thermostat housing and the junction portion(J) of the first cooling liquid passage so as to interconnect the first cooling liquid passage and the second cooling liquid passage without passing through the radiator. The thermostat includes a main valve(12) for shutting the second cooling liquid passage, and a bypass valve(15) for shutting a bypass port(32) of the bypass path. A first coolant bypass solenoid(41) is arranged to the thermostat housing, and connected to the second cooling liquid passage through a bypass pipe(42). The first coolant bypass solenoid controls the first coolant to be bypassed before the coolant temperature compared in the electronic control unit reaches the temperature for opening the main valve of the thermostat, thus controlling coolant temperature to be maintained near the completely heated state of engine.
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