| 摘要 |
<P>PROBLEM TO BE SOLVED: To make a three-way catalyst effectively function as early as possible after completion of a sulfur poisoning recovery control of a NOx catalyst. <P>SOLUTION: An exhaust emission control device for an internal combustion engine has a plurality of cylinders #1 to #4. The cylinders are divided into at least two cylinder groups. The cylinder groups are respectively connected with exhaust branch pipes 5, 6, and the exhaust branch pipes are merged downstream to be connected with a common exhaust pipe 7. The three-way catalysts 8, 9 are respectively disposed in the exhaust pipes, and the NOx catalyst 10 is disposed in the common exhaust pipe. The exhaust emission control device performs a sulfur poisoning recovery control of the NOx catalyst, by discharging exhaust gas of a rich air-fuel ratio from one cylinder group and discharging exhaust gas of a lean air-fuel radio from the other cylinder group. When the sulfur poisoning recovery control is completed, an exhaust air-fuel ratio reverse control is performed to discharge the exhaust gas of the lean air-fuel ratio from the cylinder group which has discharged the exhaust gas of the rich air-fuel ratio during the sulfur poisoning recovery control. <P>COPYRIGHT: (C)2007,JPO&INPIT |
