| 摘要 |
In an internal combustion engine, a hydrocarbon feed valve (15) and an exhaust purification catalyst (13) are arranged in an engine exhaust passage. A first NO X removal method which reduces NO X contained in an exhaust gas by a reducing intermediate which is generated by injecting hydrocarbons from the hydrocarbon feed valve (15) within a predetermined range of period and a second NO x removal method in which an air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst (13) is made rich by a period which is longer than this predetermined range are used. If the first NO X removal method is started when a rich control for making the air-fuel ratio of the exhaust gas which flows into the exhaust purification catalyst (13) rich is ended, the amount of injection of hydrocarbons from the hydrocarbon feed valve (15) is made to gradually increase. |
