| 摘要 |
Even under satisfaction of an EGR condition during operation of an engine (step S110), when it is determined that the cooling power of a cooling system is less than a preset reference power, based on a cooling water temperature Tw and an outside air temperature Tout (step S130), an EGR valve is controlled to prohibit circulation of exhaust into a gas inlet line (steps S120 and S160). The reference power is set as a criterion of assuring a minimum required power for cooling down the engine even when the EGR is performed during the operation of the engine. This arrangement effectively prevents a decrease in cooling power of the cooling system. When it is determined that the cooling power of the cooling system is not less than the preset reference power (step S130), the EGR valve is controlled to allow circulation of the exhaust into the gas inlet line with a target EGR amount R* calculated from an intake air amount Qa (steps S140 to S160). This arrangement ensures the appropriate operation of the engine.
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