DEVICE AND METHOD FOR EXHAUST-EMISSION CONTROL OF INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To provide a device and a method for exhaust-emission control of an internal combustion engine provided with a NOx catalyst in an exhaust path in which the NOx catalyst can be regenerated favorably from SOx poisoning irrespective of the operation condition of the internal combustion engine.

SOLUTION: An air-fuel ratio of exhaust gas is controlled firstly to a 1st predetermined air-fuel ratio at which the volume of discharged smoke is set at an allowable upper limit. Then, the exhaust ratio is intermittently controlled to a 2nd predetermined air-fuel ratio which is overrich richer than the 1st air- fuel ratio enabling the NOx catalyst to recover from SOx poisoning, and the temperature of the NOx catalyst is controlled in the range of predetermined temperatures in which the catalyst can be recovered from SOx poisoning and the degradation of the NOx catalyst is not accelerated.

COPYRIGHT: (C)2004,JPO