EXHAUST EMISSION PURIFICATION SYSTEM OF INTERNAL COMBUSTION ENGINE

In an internal combustion engine including an NSR catalyst and an SCR, to provide an exhaust purifying system that can limit aggravation of emissions by allowing the SCR to recover effectively from degraded performance caused by poisoning. An exhaust purifying system for an internal combustion engine 10 capable of a lean burn operation includes an NSR catalyst 16 disposed in an exhaust passage 12 of the internal combustion engine 10; an SCR 18 disposed downstream of the NSR catalyst 16; means for detecting sulfur poisoning of the SCR 18; and means for increasing a bed temperature of the SCR 18 when the poisoning detecting means detects sulfur poisoning of the SCR 18. The temperature increasing means includes bank control, stoichiometric control, and rich spike control, any one of which is selected for performance according to an operating condition of the internal combustion engine 10.