| 摘要 |
PURPOSE: To surely remove a purifying capacity degrading material other than nitrogen oxide (NOx) deposited to exhaust purifying catalyst for maintaining satisfactorily a function of the exhaust purifying catalyst in an internal combustion engine provided with the exhaust purifying catalyst (NOx catalyst) for adsorbing nitrogen oxide in the exhaust gas in lean combustion running to reduce the adsorbed nitrogen oxide in rich combustion running for maintaining the adsorbing capacity of the nitrogen oxide. CONSTITUTION: An exhaust path is composed of first exhaust paths 14a, 14b, second exhaust paths 30a, 30b shorter than the first exhaust path and valve means 31a, 31b for opening and closing the second exhaust paths. The engine is provided with a deposit amount estimating means for estimating an amount of purifying capacity degrading material deposited to exhaust purifying catalysts 13a, 13b and a catalyst temperature raising means for opening the second exhaust path by a valve means when the deposition amount reaches a predetermined value and supplying exhaust gas through the second exhaust path to the exhaust purifying catalyst with a temperature higher than that through the first exhaust path. |
