| 摘要 |
<p>PURPOSE: To raise a use temperature limit and to maintain high purifying performance for a bypass catalyst by actively restoring the bypass catalyst from deterioration. CONSTITUTION: A main catalyst 32 is arranged on the downstream side of an exhaust pipe 31, while a platinum group catalyst 34 is arranged in a bypass passage 33 which diverges on the upstream side of the exhaust pipe 31 and converges again on the upstream side of the main catalyst 32, and a valve 35, which is positioned in a divergent part or a convergent part in the bypass passage 33 and can switch the passage, is arranged. In this case, a determining means 36 determines if the platinum group catalyst 34 deteriorates or not, and in determination of deterioration in the platinum catalyst 34, the valve 35 is switched to the side, on which the bypass passage 33 is fully opened, in the deterioration restoring area consisting of an exhaust high temperature area and an area, in which an air-fuel ratio is richened, by means of a deterioration restoring means 37.</p> |
