EXHAUST PURIFICATION DEVICE OF INTERNAL COMBUSTION ENGINE

摘要

According to the present invention a ternary catalyst (20) and an NO storage catalyst (22) are disposed in an engine exhaust passage. In a pre established low load operation area of the engine combustion is performed with a lean base air fuel ratio in a combustion chamber (5) and a rich air fuel ratio is used in the combustion chamber (5) when NO is to be emitted from the NO storage catalyst (22). In a pre established high load operation area of the engine feedback control is performed to bring the air fuel ratio in the combustion chamber (5) to a theoretical air fuel ratio. In a pre established medium load operation area of the engine combustion is performed in the combustion chamber (5) with a lower base air fuel ratio than the base air fuel ratio in the low load operation area of the engine and a richer air fuel ratio is used in the combustion chamber (5) with a shorter cycle than the rich air fuel ratio cycle for NO emission in the low load operation area of the engine.