Importance

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Abstract

An exhaust gas after-treatment device, including an oxidation catalyst and a diesel particulate filter in order from an upstream side, is provided in an exhaust passage of an internal combustion engine. A target value of an exhaust gas recirculation rate in exhaust gas recirculation control is set to be a second exhaust gas recirculation rate higher than a first exhaust gas recirculation rate at a time of a normal operation of the engine and the control is performed, when a catalyst index temperature that indexes a temperature of the oxidation catalyst falls within a set temperature region between a lower limit set temperature and an upper limit set temperature which are preliminarily set, and where an estimated particulate matter deposition amount of the diesel particulate filter is less than a preliminarily set regeneration start threshold value, after an operation state of the engine transitions from a traveling operation state to idling. During idling after travel of a vehicle, generation of NO₂ by the oxidation catalyst and emission of NO₂ to the atmosphere are decreased.

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First Claim