摘要:
A three way catalyst (20) and an NO x storage catalyst (22) are arranged in an engine exhaust passage. In an engine low load operating region, a combustion is performed under a lean air-fuel ratio, and when NO x should be released from the NO x storage catalyst (22), the air-fuel ratio in a combustion chamber (5) is made rich. In an engine medium load operating region, the base air-fuel ratio is made lower as compared with the engine low load operating region, and the air-fuel ratio in the combustion chamber (5) is made rich at a shorter period as compared with the engine low load operating region. When the operating state of the engine is switched from the engine low load operating region to the engine medium load operating region, the air-fuel ratio in the combustion chamber (5) is temporarily made rich, and the degree of richness of the air-fuel ratio at this time is stepwise lowered.
摘要:
In an internal combustion engine, inside of an engine exhaust passage, a hydrocarbon feed valve (15) and an exhaust purification catalyst (13) are arranged. At the time of engine operation, the amplitude of change of the concentration of hydrocarbons which flow into the exhaust purification catalyst (13) is made to become within a predetermined range of amplitude by control of the injection amount of hydrocarbons from the hydrocarbon feed valve (15), the concentration of hydrocarbons flowing into the exhaust purification catalyst (13) is made to vibrate by a predetermined range of period by control of the injection period of hydrocarbons from the hydrocarbon feed valve (15), and thereby the NO x contained in the exhaust gas and the NO x stored in the exhaust purification catalyst (13) are reduced.
摘要:
In an internal combustion engine, inside of an engine exhaust passage, a hydrocarbon feed valve (15) and an exhaust treatment catalyst (13) are arranged. On a substrate (45) of the exhaust treatment catalyst (13), a coat layer comprised of at least two layers of a top coat layer (46) and a bottom coat layer (47) is formed. The top coat layer (46) is comprised of an exhaust purification catalyst for reacting NO x contained in exhaust gas and reformed hydrocarbons, while the bottom coat layer (47) is comprised of an NO x absorption catalyst. The concentration of hydrocarbons which flows into the exhaust treatment catalyst (13) is made to vibrate within a predetermined range of amplitude and within a predetermined range of period. Due to this, NO x contained in exhaust gas and NO x desorbed from the NO x absorption catalyst (47) are reduced in the exhaust purification catalyst (46).
摘要:
In an internal combustion engine, inside an engine exhaust passage, a hydrocarbon feed valve (15) an exhaust purification catalyst (13), and a particulate filter (14) are arranged. If the hydrocarbon feed valve (15) feeds hydrocarbons by a period of within 5 seconds, a reducing intermediate is produced inside the exhaust purification catalyst (13). This reducing intermediate is used for NO x purification processing. When the stored SO x should be released from the exhaust purification catalyst (13), the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst (13) is made rich, the reducing intermediate built up on the exhaust purification catalyst (13) is made to be desorbed in the form of ammonia, and the desorbed ammonia is used to make the exhaust purification catalyst (13) release the stored SO x .