| 摘要 |
PROBLEM TO BE SOLVED: To effectively maintain temperature of cooling water while an engine is stopped without providing a heat accumulator of large capacity. SOLUTION: A cooling water system leading to a heater core 6 of an air conditioning unit is provided with a branch passage having a piping 26 and equipped with a heat recovery device 20 and a heat accumulator 30. A casing 21 of the heat recover device is located in a first branch pipe 14 of an exhaust pipe. The first branch pipe 14 opens and closes by means of a first open-close valve 17. With this configuration, even if the cooling water temperature is low, the water temperature is raised by the heat recovery device up to the temperature at which the heat can be accumulated. Therefore, heating function can easily be maintained while the vehicle is stopped idling. Furthermore, when the temperature of the cooling water exceeds a predetermined value, the branch passage is closed by a control valve 25 to stabilize the water temperature. On the other hand, when the temperature of the heat recovery device exceeds a predetermined value, the first branch pipe is closed by the first open-close valve. Also, when exhaust gas temperature is low, the first open-close valve is closed to prevent release of heat from the cooling water at the heat recovery device.
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