EXHAUST EMISSION CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of quickly and accurately judging existence of abnormality of sulfur discharge control discharging sulfur from an exhaust emission control catalyst.

SOLUTION: Rich periods and lean periods are repeated alternately during S discharge control and air fuel ratio of exhaust emission is controlled to a target air fuel ratio (14.3) by fuel addition from an addition valve 68 during the rich period. It is determined whether actual exhaust gas air fuel ratio detected from the air fuel ratio sensor 48 reaches theoretical air fuel ratio at every completion time of the rich period when fuel addition from the addition valve 68 completes. Times of judgment that the actual exhaust gas air fuel ratio reaches the theoretical air fuel ratio are counted by a counter C. When the counter C gets to an allowable value or greater, it is judged that abnormality in S discharge control occurs.

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