| 摘要 |
For an engine provided with an LPL-EGR mechanism which recirculates a low-pressure EGR gas from downstream of an NSR catalyst in an exhaust system into an intake system via an EGR cooler, the NOx storage amount of each of a low-temperature NOx storage material and a high-temperature NOx storage material supported on the NSR catalyst is calculated (step ST6). If the temperature of the NSR catalyst rapidly increases, most of the NOx emitted from the low-temperature NOx storage material will not be stored in the high-temperature NOx storage material, so it is assumed that there will be discharge from the NSR catalyst, so NOx reduction treatment is performed (Step ST9). By this means, the amount of NOx flowing into the LPL-EGR mechanism can be reduced, and corrosion of the EGR cooler is prevented by suppressing generation of an acidic aqueous solvent caused by NOx. |
