INTERNAL COMBUSTION ENGINE EXHAUST GAS PURIFICATION DEVICE

摘要

In an internal combustion engine, inside of an engine exhaust passage, a hydrocarbon feed valve (16), an exhaust purification catalyst (13), a particulate filter (14), and an NO 2 reduction catalyst (15) 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 (16). When the NO 2 which is produced at the particulate filter (14) should be reduced to NO, the injection amount of hydrocarbons is increased whereby the pass through amount of hydrocarbons which pass straight through the exhaust purification catalyst (13) is increased.