EXHAUST EMISSION CONTROL DEVICE

摘要

PROBLEM TO BE SOLVED: To efficiently perform an absorption/discharge reduction cycle of NOx and realize a NOx removal of high level without deteriorating fuel consumption under oxygen excessive environment in such as diesel engine or lean burn engine. SOLUTION: It is determined that an NOx absorbing catalyst absorbs NOx of fifty percent of absorbing capacity based on revolution integrated valueΣENe (Step 3), an operation in which reducing component concentration in exhaust is reduced (step 7) is carried out for a first predetermined period (C0) by advance or the like of a fuel injection timing in diesel engine. Next, an operation in which reducing component concentration in exhaust is increased (step 9) is carried out for a second predetermined period (C1) by retard or the like of the fuel injection timing. The NOx discharging rate is increased by once decreasing the reducing component concentration. Discharged NOx is reduced with high efficiency by increasing the reducing component concentration under specific oxygen concentration.