| 摘要 |
<p>PURPOSE:To exactly detect the degree of deterioration of a catalyst by calculating the absolute quantity of oxygen adsorbed to the catalyst after switching of the air-fuel ratio based on the quantity of exhaust gas circulated through the catalyst by the time a detected air-fuel ratio has reached a desired air-fuel ratio, and the deviation of the desired air-fuel ratio from a theoretical air-fuel ratio. CONSTITUTION:A catalyst 11 is arranged in the exhaust system 10 of an internal combustion engine. Further, an air-fuel ratio sensor 18 is arranged at least downstream of the catalyst 11 in order to detect the air-fuel ratio of an air-fuel mixture supplied from a fuel injection valve 12, etc. In this case, the detected air-fuel ratio is switched to each scheduled air-fuel ratio on the rich side or on the lean side with respect to a theoretical air-fuel ratio by a means A. Besides, after the switching of the air-fuel ratio, the quantity of gas circulated through the catalyst by the time when each scheduled air-fuel ratio is reached, is detected by a means B. Then, the absolute quantity of oxygen adsorbed by the catalyst is calculated by a means C based on the deviation of each scheduled air-fuel ratio from the theoretical air-fuel ratio after the switching of the air-fuel ratio, and the quantity of gas circulated through the catalyst. Thus, the degree of deterioration of the catalyst is detected by a means D based on the absolute quantity of oxygen.</p> |
