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Abstract

An exhaust gas purifying apparatus including an HC absorbent located in an upstream region of a selective reduction type NOx catalyst for improving a NOx purification efficiency. In the exhaust gas purifying apparatus, an HC absorbing device is disposed upstream of a NOx catalyst converter arranged in an exhaust gas passageway. The selective reduction type NOx catalyst accommodated in the HC absorbing device uses a carrier, which is easy to absorb the HC when a temperature of the exhaust gas is lowered, and easy to desorb the HC when the temperature of the exhaust gas is raised, and a selective reduction type NOx catalyst accommodated in the NOx catalyst converter uses a carrier which has a strong absorption of HC for retention. In order to prevent a catalyst temperature of the NOx catalyst converter from being lowered to a temperature lower than a purification temperature window in an operating state of deceleration, an ECU corrects an opening degree of an EGR valve to be increased, and thereby a flow rate of the exhaust gas which flows into the NOx catalyst converter is decreased when an inlet gas temperature detected by an inlet gas temperature sensor is lowered to a temperature lower than a set temperature. Thus, lowering of the catalyst temperature is suppressed.

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First Claim