| 摘要 |
An exhaust emission control device for an internal combustion engine is provided that can suppress the adherence of HC to an EGR path and the like accompanying enrichment of the exhaust air/fuel ratio. The exhaust emission control device includes: a high-pressure EGR path 6 that recirculates a portion of the exhaust gas upstream of a turbine 81 into an intake manifold 3; a high-pressure EGR control portion 43; a low-pressure EGR path 10 that recirculates a portion of the exhaust gas downstream of the turbine 81 into intake plumbing 2; a low-pressure EGR control portion 44; a NOx purification catalyst 31 that is provided inside exhaust plumbing 4 downstream of an exhaust inlet of the low-pressure EGR path 10, traps NOx under an oxidizing atmosphere, and purifies the trapped NOx under a reducing atmosphere; a NOx purification catalyst reduction control unit 41 that performs reduction control of the exhaust air/fuel ratio; and an EGR switching portion 45 that selects recirculation control of exhaust gas by the low-pressure EGR control portion 44 in a case of the exhaust air/fuel ratio being at least a predetermined threshold value, and selects recirculation control of exhaust gas by the high-pressure EGR control portion 43 in a case of being lower than the threshold value. |
