EXHAUST GAS PURIFICATION APPARATUS FOR INTERNAL COMBUSTION ENGINE

摘要

In an internal combustion engine, an Nox selective reduction catalyst (14) is disposed within an engine exhaust gas passage, and an Nox occlusion catalyst (12) is disposed within an engine exhaust gas passage on the upstream of the Nox selective reduction catalyst (14). When the occluded Noxamount of the Nox occlusion catalyst (12) has exceeded a predetermined permissible value, the temperature of the Nox occlusion catalyst (12) is raised to release Nox from the Nox occlusion catalyst (12). The amount of urea supplied is reduced by an amount of the reduced occluded Nox computed based on the amount of supplied urea determined from the operation conditions of the engine, and the amount of urea supplied is increased by an amount of the reduced released Nox computed based on the amount of supplied urea determined from the operation conditions of the engine.