Exhaust purification system of internal combustion engine

摘要

In an internal combustion engine, inside of an engine exhaust passage, an upstream side air-fuel ratio sensor (23), a hydrocarbon feed valve (15), an exhaust purification catalyst (13), and a downstream side air-fuel ratio sensor (24) are arranged in this order from the upstream. At the time of engine operation, the injection amount of hydrocarbons from the hydrocarbon feed valve (15) is controlled based on the air-fuel ratio detected by the upstream side air-fuel ratio sensor (23) and the downstream side air-fuel ratio sensor (24) so that the amplitude of change of the concentration of hydrocarbons which flow into the exhaust purification catalyst (13) becomes within a predetermined range of amplitude.

主权项

1. An exhaust purification system of an internal combustion engine comprising:
a hydrocarbon feed valve for feeding hydrocarbons arranged in an engine exhaust passage, an exhaust purification catalyst for reacting NOX contained in exhaust gas and reformed hydrocarbons arranged in the engine exhaust passage downstream of the hydrocarbon feed valve, a downstream side air-fuel ratio sensor for detecting an air-fuel ratio of the exhaust gas arranged in the engine exhaust passage downstream of the exhaust purification catalyst, precious metal catalysts carried on an exhaust gas flow surface of the exhaust purification catalyst, a basic exhaust gas flow surface part formed around the precious metal catalysts, 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 catalysts and held on the basic exhaust gas flow surface part, the NOX contained in the exhaust gas is chemically reduced by the reducing intermediate held on the basic exhaust gas flow surface part, and the exhaust purification catalyst has a property of chemically reducing the NOX that is contained in the exhaust gas without storing, or with storing a fine amount of, nitrates in the basic exhaust gas flow surface part,when the electronic control unit controls the vibration period of the hydrocarbon concentration longer than the predetermined range, the exhaust purification catalyst has a property of being increased in a storage amount of NOX that is contained in the exhaust gas andthe concentration of hydrocarbons that flow into the exhaust purification catalyst is made to vibrate within the predetermined range of period by control of an injection period of hydrocarbons from the hydrocarbon feed valve, and the amplitude of a change of concentration of hydrocarbons that flow into the exhaust purification catalyst is made to become within the predetermined range of amplitude by control of an injection amount of hydrocarbons from the hydrocarbon feed valve based on an output signal of the downstream side air-fuel ratio sensor.