| 摘要 |
PROBLEM TO BE SOLVED: To effectively prevent the heat deterioration of a catalyst and the deterioration of fuel efficiency from being caused by continuously performing SOx purge or a temperature retaining mode.SOLUTION: An exhaust emission control system includes a NOx reduction type catalyst 32 provided in an exhaust passage 13 of an internal combustion engine 10, a SOx purge control part 60 for performing SOx purge control such that injection system control to increase a fuel injection amount raises an exhaust temperature up to a first target temperature where SOx desorbs to recover the NOx reduction type catalyst 32 from sulfur poisoning, a prohibition processing part 70 for prohibiting the performance of the SOx purge control depending on the operating condition of the internal combustion engine 10, a temperature retaining mode control part 71 for performing temperature retaining mode control such that a fuel injection amount is controlled during a period for prohibiting the SOx purge control to keep the exhaust temperature as a second target temperature lower than the first target temperature, and a termination processing part 72 for terminating the SOx purge control when the sulfur occlusion amount of the NOx reduction type catalyst 32 is lowered down to a first occlusion amount threshold value by performing the SOx purge control.SELECTED DRAWING: Figure 1 |
