| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce the volume of sulfate emitted into the atmosphere. <P>SOLUTION: A particulate filter is arranged in the exhaust passage of an internal combustion engine where the air-fuel ratio of air fuel mixture burnt in a combustion chamber is kept lean, and an NOx catalyst is supported on a particulate filter. If engine back pressure P representing the volume of fine particles accumulated on the particulate filter becomes higher than a first threshold P1, the temperature of the particulate filter is increased to a targeted temperature TPM, and the oxidation of the fine particles is performed to hold them at the targeted temperature TPM for a targeted time tPM, while keeping lean the air-fuel ratio of exhaust gas flowing into the particulate filter. The volume of SOx that has been accumulated in the NOx catalyst without forming sulfate is determined. When the volume of SOx that has been accumulated in the NOx catalyst without forming sulfate is large, the targeted temperature TPM is made to be lower, whereas the targeted time tPM is made to be longer compared to that when it is small. <P>COPYRIGHT: (C)2004,JPO |
