| 摘要 |
PROBLEM TO BE SOLVED: To reconcile NOx emission volume reduction and CO<SB>2</SB>emission volume reduction by directly managing a NOx emission volume released into the atmosphere and thus reliably maintaining a desirable NOx emission volume in every operating condition without degrading fuel economy, in an exhaust emission control device for an internal combustion engine. SOLUTION: A NOx sensor 27 detects a NOx concentration released into the atmosphere from a storage type NOx catalyst 25. From the output of the NOx sensor 27, a total NOx emission volume A is computed. If the total NOx emission volume A reaches a NOx emission criterion volume A<SB>0</SB>corresponding to a NOx emission criterion volume defined by NOx emission regulation before a travel distance C reaches a given travel distance C<SB>0</SB>, an exhaust air-fuel ratio is varied to a rich air-fuel ratio to cause the storage type NOx catalyst 25 to release NOx efficiently, and then varied to a stoichiometric air-fuel ratio to cause a three-way catalytic function to purify or reduce NOx. COPYRIGHT: (C)2003,JPO |
