CATALYST DETERIORATION MONITORING SYSTEM AND CATALYST DETERIORATION MONITORING METHOD

摘要

A storage reduction NOx catalyst is disposed in an exhaust passage for an internal combustion engine. A NOx sensor is disposed upstream of the NOx catalyst. An inflow NOx amount, which is the amount of NOx that has flown into the NOx catalyst, is calculated by accumulating the output of the NOx sensor. A total storage amount, which is the sum of the amounts of oxygen and NOx stored in the NOx catalyst, is calculated based on an output generated by an exhaust gas sensor disposed downstream of the NOx catalyst when a rich spike is being executed. The deterioration of the NOx catalyst is determined based on the inflow NOx amount and the total storage amount.