Patent ID: 8656706

Claim:
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, the exhaust gas purification catalyst including a precious metal catalyst on an exhaust gas flow surface of the exhaust purification catalyst and a basic exhaust gas flow surface part is formed around the precious metal catalyst, the exhaust purification catalyst has a property of reducing the NOx which is contained in exhaust gas if a concentration of hydrocarbons flowing into the exhaust purification catalyst is made to change within a predetermined range of amplitude and within a predetermined range of period and has a property of being increased in storage amount of NOx which is contained in exhaust gas if a vibration period of the hydrocarbon concentration is made longer than the predetermined range, and an electronic control unit configured to perform, at the time of engine operation, a main concentration changing action in which the concentration of hydrocarbons flowing into the exhaust purification catalyst is made to change within said predetermined range of amplitude and within said predetermined range of period, and the electronic control unit is configured to perform, before each main concentration changing action, an auxiliary concentration changing action in which the concentration of hydrocarbons is made to change by an amplitude smaller than the amplitude at the time of each main concentration changing action.