| 摘要 |
<P>PROBLEM TO BE SOLVED: To securely control an air/fuel ratio of exhaust gas flowing into a NOx catalyst to a predetermined air/fuel ratio during the execution of sulfur poisoning recovery control. <P>SOLUTION: In this exhaust emission control device for an internal combustion engine, a plurality of cylinders #1 to #4 are provided, and these cylinders #1 to #4 are divided into at least two cylinder groups. Exhaust branch pipes 5, 6 are connected with the respective cylinder groups, and these exhaust branch pipes 5, 6 are jointed in the downstream side and connected with one common exhaust pipe 7. The NOx catalyst 10 is arranged in the one common exhaust pipe 7, and as the sulfur poisoning recovery control of the NOx catalyst 10, exhaust gas at a rich air fuel ratio is exhausted from one cylinder group and exhaust gas at a lean air fuel ratio is exhausted from the other cylinder group. An air fuel ratio sensor 14 is arranged at the downstream side of the NOx catalyst 10. At the time of the sulfur poisoning recovery control, sulfur poisoning recovery air fuel ratio control to control an air fuel ratio in each of the cylinders #1 to #4 by using an output value from the air fuel ratio sensor 14 is performed so that an air fuel ratio of exhaust gas flowing into the NOx catalyst 10 reaches a predetermined air fuel ratio. <P>COPYRIGHT: (C)2007,JPO&INPIT |
