| 摘要 |
<p>The purpose of the present invention is to determine the deterioration of a catalyst accurately and improve reliability even in a turbo-charged internal combustion engine. An engine (10) comprises an exhaust gas purification catalyst (26), a turbo supercharger (36), a bypass passage (38), a waste gate valve (40), and others. An ECU (60) switches a desired air-fuel ratio (At) between a rich side and a lean side alternately by means of active air-fuel ratio control, whereby the real air-fuel ratio (Ar) is altered. The amount of absorbed oxygen (OSC) of the exhaust gas purification catalyst (26) is measured on the basis of the vibration period of the desired air-fuel ratio (At) and the desired air-fuel ratio (At) while performing the active air-fuel control, and the determination whether or not the exhaust gas purification catalyst (26) is deteriorated is performed on the basis of the measured value. The ECU (60) also closes the waste gate valve (40) when the determination on the deterioration is performed, so that different two kinds of exhaust gases having different flow passages reach around an air-fuel ration sensor (56), whereby it becomes possible to prevent the deterioration in accuracy of the determination on the deterioration.</p> |
