| 摘要 |
PROBLEM TO BE SOLVED: To suppress a reduction in the oxygen occlusion capacity by suppressing a reduction in the activity of a catalytic noble metal due to sulfur components.SOLUTION: An exhaust emission control device for an internal combustion engine having a plurality of cylinders includes an exhaust emission control catalyst 20, a downstream side air-fuel ratio sensor 41, and a control device for controlling the average air-fuel ratio of exhaust gas and a combustion air-fuel ratio among the cylinders. The control device executes average air-fuel ratio control to control the average air-fuel ratio to be a rich air-fuel ratio and a lean air-fuel ratio alternately, and inter-cylinder air-fuel ratio control to control the combustion air-fuel ratio among the cylinders so that, even when the average air-fuel ratio is controlled to be the lean air-fuel ratio by the average air-fuel ratio control, the combustion air-fuel ratio is the rich air-fuel ratio in at least one of the plurality of cylinders. In the average air-fuel ratio control, the average air-fuel ratio is controlled so that a lean shift quantity with the average air-fuel ratio controlled to be the lean air-fuel ratio is smaller than a rich shift quantity with the average air-fuel ratio controlled to be the rich air-fuel ratio.SELECTED DRAWING: Figure 4 |
