| 摘要 |
The device according to the present invention controls air-fuel ratio of the exhaust gas flowing into the catalytic converter in such a manner that the exhaust gas flowing into the catalytic converter fluctuates around a center value on the lean air-fuel ratio side compared to the stoichiometric air-fuel ratio when it performs the determination of deterioration of the catalytic converter. In this condition, the device calculates the rich gas inflow amount which is the amount of HC and CO in the exhaust gas flowing into the catalytic converter and the rich gas outflow amount which is the amount of HC and CO in the exhaust gas flowing out from the catalytic converter. The device, then, determines the degree of deterioration of the catalytic converter based on the calculated values of the rich gas inflow amount and the rich gas outflow amount. Since the difference between the rich gas inflow amount and the rich gas outflow amount represents the amount of HC and CO oxidized by the catalytic converter, the deterioration of the catalytic converter can be determined accurately by comparing the rich gas inflow amount and the rich gas outflow amount. <IMAGE> |
