Exhaust purification system of internal combustion engine

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. The concentration of hydrocarbons which flows into the exhaust purification catalyst (13) is made to vibrate by within a predetermined range of amplitude of a 200 ppm or more and within a predetermined range of period of 5 second or less, whereby the NOx which is contained in exhaust gas is reduced at the exhaust purification catalyst (13). At this time, the nitrogen-containing intermediate which is produced in the NOx reduction process is exhausted from the exhaust purification catalyst (13). An intermediate purification catalyst (14) for removal of the exhausted nitrogen-containing intermediate is arranged downstream of the exhaust purification catalyst (13).

主权项

1. An exhaust purification system of an internal combustion engine comprising:
an engine exhaust passage; an exhaust purification catalyst for reacting NOx contained in exhaust gas and reformed hydrocarbons arranged inside of the engine exhaust passage; a precious metal catalyst carried on an exhaust gas flow surface of the exhaust purification catalyst; a basic exhaust gas flow surface part formed around the precious metal catalyst; an intermediate purification catalyst arranged inside of the engine exhaust passage and downstream of the exhaust purification catalyst; and an electronic control unit, wherein the electronic control unit is configured to control a vibration of a concentration of hydrocarbons flowing into the exhaust purification catalyst within a predetermined range of amplitude and within a predetermined range of period, and is configured to control the vibration period of the hydrocarbon concentration longer than the predetermined range of period, wherein
when the electronic control unit controls the vibration of the concentration of hydrocarbons flowing into the exhaust purification catalyst within the predetermined range of amplitude and within the predetermined range of period, a reducing intermediate containing nitrogen and hydrocarbons is produced on the precious metal catalyst and held on the basic exhaust gas flow surface part, the NOx contained in the exhaust gas catalyst is chemically reduced by a reducing action of the reducing intermediate held on the basic exhaust gas flow surface part in the exhaust purification catalyst, the exhaust purification catalyst has a property of chemically reducing the NOx that is contained in the exhaust gas without storing, or storing a fine amount of nitrates in the basic exhaust gas flow surface part, and a nitrogen-containing intermediate is exhausted from the exhaust purification catalyst, wherein
the intermediate purification catalyst chemically removes the exhausted nitrogen-containing intermediate, andwhen the electronic control unit controls the vibration period of the hydrocarbon concentration longer than the predetermined range of period, the exhaust purification catalyst has a property of being increased in a storage amount of NOx that is contained in the exhaust gas.