| 摘要 |
<p>PROBLEM TO BE SOLVED: To control the excessive heat generation of a front catalyst caused by the misfire without providing a sensor to detect the internal temperature of the front catalyst. SOLUTION: A main passage 51a is branched from a bypass passage 51b on the upstream side of an exhaust pipe, a catalyst 52 is installed in the main passage 51a, and a valve 53 to switch the flow of the exhaust gas to the main passage and to the bypass passage 51b is provided. A judging means 54 judges whether or not the exhaust temperature is in the range of the flame-out capable of permitting the temperature rise of the catalyst 52 in the region where the exhaust temperature is below the prescribed value T1, and a valve switching means 55 switches a switching valve 53 so that the exhaust gas flows on the catalyst 52 side when the exhaust temperature is in the range of the misfire capable of permitting the temperature rise of the catalyst 52 in the region where the exhaust temperature is below the prescribed value based on the judged result, or to the bypass passage 51b side when the exhaust temperature is not in the range of the misfire capable of permitting the temperature rise of the catalyst 52 in the region where the exhaust temperature is below the prescribed value T1.</p> |
