EXHAUST EMISSION CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To prevent the increase of fuel consumption with enrichment due to a main fuel only and the degradation of exhausting characteristics with enrichment due to an addition fuel when controlling the regeneration of catalyzers with the enrichement of an exhaust air/fuel ratio in an internal combustion engine with an upstream catalyzer 12 and a downstream catalyzer 13 in an exhaust passage. SOLUTION: Oxygen is released from the upstream catalyzer 12 quickly while enriching an exhaust air/fuel ratio by the supply of the additional fuel in the beginning of starting the regeneration control of the downstream catalyzer 13, and when reductant components are easy to pass through the upstream catalyzer after the oxygen has been released from the upstream catalyzer 12, the exhaust air/fuel ratio is enriched by enriching of the air/fuel ratio of a main fuel. Thus, NOx held in the downstream catalyzer 13 is effectively reduced without increasing the amount of the reductant components exhausted from the upstream catalyzer 12 to the air.