| 摘要 |
This invention is to reduce NOx occluded in a NOx catalyst in a more appropriate manner. In this invention, in case where an amount of NOx occluded when an execution condition for NOx reduction control holds is more than a predetermined amount of occlusion, NOx reduction control is performed by lowering the O 2 concentration of the exhaust gas by means of said O 2 concentration lowering means and at the same time supplying a reducing agent to the NOx catalyst by a reducing agent supplying means (S105, S106). In addition, in case where the amount of NOx occluded when the execution condition for NOx reduction control holds is equal to or less than the predetermined amount of occlusion, NOx reduction control is executed by supplying the reducing agent to the NOx catalyst by the reducing agent supplying means without lowering the O 2 concentration of the exhaust gas by the O 2 concentration lowering means (S106).
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