| 摘要 |
PROBLEM TO BE SOLVED: To increase opportunity of desorbing sulfur components occluded in an exhaust emission control catalyst.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 flowing into the exhaust emission control catalyst and a combustion air-fuel ratio when combustion is carried out in each cylinder. 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 also executes inter-cylinder air-fuel ratio control to control the combustion air-fuel ratio among the cylinders so that 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 is smaller than a rich shift quantity when the temperature of the exhaust emission control catalyst is low, and the average air-fuel ratio is also controlled so that the lean shift quantity is greater than the rich shift quantity when the temperature is high.SELECTED DRAWING: Figure 10 |
