EXHAUST PURIFYING SYSTEM FOR INTERNAL COMBUSTION ENGINE

摘要

There is provided an exhaust gas purification system for an internal combustion engine in which exhaust gas that is in a state in which an even concentration distribution of reducing agent is achieved is caused to flow into an exhaust gas purification apparatus. The system includes a small-diameter catalyst 7 that is provided in an exhaust pipe 3 upstream of an NOx catalyst 4 and adapted in such a way that not the entire amount but a portion of the exhaust gas flowing in the exhaust pipe 3 passes through it, a fuel addition valve 5 that is provided upstream of the small-diameter catalyst 7 and adds fuel to the exhaust gas flowing into the small-diameter catalyst 7, and an isolation pipe 8 that separates the cross section of the exhaust pipe 3 into a catalyst side passage 8a through which catalyst outflowing exhaust gas is caused to pass and a detour side passage 3c through which catalyst detouring exhaust gas is caused to pass, over a region from the downstream end of the small-diameter catalyst 7 to a predetermined position between the small-diameter catalyst 7 and the NOx catalyst 4.