| 摘要 |
A technique is provided that can complete reduction and release of SOx from a storage-reduction type NOx catalyst in a shorter period of time in a SOx regeneration treatment of bringing an air-fuel ratio and temperature in the storage-reduction type NOx catalyst to a state where the reduction and release of the SOx is possible by alternately executing rich burn in which burning in a cylinder of an internal combustion engine is performed at a rich air-fuel ratio and lean burn in which the burning is performed at a lean air-fuel ratio. By supplying fuel to exhaust gas from a fuel addition valve provided to an exhaust pipe during a lean period in which the lean burn is executed, the temperature of the storage-reduction type NOx catalyst is maintained at a temperature that enables the reduction and release of the SOx. During a rich period in which the rich burn is executed, a rich atmosphere of the storage-reduction type NOx catalyst is achieved to cause the reduction and release of the SOx. Further, the SOx is reduced and released from the storage-reduction type NOx catalyst also during the lean period by achieving a rich air-fuel ratio of the exhaust gas by the fuel addition from the fuel addition valve.
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