| 摘要 |
An internal combustion engine has a reduction occlusion type NOx catalyst located in an exhaust passage for adsorbing NOx. A controller of the engine temporarily discontinues a lean combustion mode when a predetermined condition is satisfied during the lean combustion mode. When the amount of NOx adsorbed in the catalyst is greater than an acceptable value, the controller executes a rich-spike control procedure to reduce NOx adsorbed in the catalyst by temporarily switching the combustion mode of the engine to a rich combustion mode. The controller determines whether the amount of NOx adsorbed in the catalyst is greater than a predetermined determination value, which is smaller than the acceptable value, when lean combustion is discontinued. When the amount of NOx adsorbed in the catalyst is determined to be greater than the determination value, the controller executes rich-spike control procedure. <IMAGE> |
