EXHAUST EMISSION CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To determine deterioration of a catalyst having oxidizing capabilities more accurately.SOLUTION: An exhaust emission control device for an internal combustion engine comprises a catalyst provided in an exhaust passage of the internal combustion engine and having oxidizing capabilities and a NOx sensor provided downstream of the catalyst and detecting a NOx concentration in exhaust, wherein the exhaust emission control device comprises a determination means for determining that the catalyst is deteriorated when a length of a locus of a detection value of the NOx sensor in a predetermined period is equal to or more than a threshold.