Exhaust gas purification device for internal combustion engine

An exhaust purification device for an internal combustion engine, comprising:

• an engine exhaust passage;
• an exhaust purification catalyst arranged inside the engine exhaust passage and having an exhaust gas flow surface, a precious metal catalyst being carried on the exhaust gas flow surface, a basic exhaust gas flow surface part being formed around the precious metal catalyst, the exhaust purification catalyst having a property of reducing NO x which is contained in the exhaust gas when making a concentration of hydrocarbons which flow into the exhaust purification catalyst vibrate with a vibration amplitude within a predetermined range of amplitude and with a vibration period within a predetermined range of period and having a property of being increased in amount of storage of NOx which is contained in the exhaust gas when making the vibration period of the hydrocarbon concentration longer than the predetermined range of period;
• a hydrocarbon feed valve arranged upstream of the exhaust purification catalyst in the engine exhaust passage;
• and
• an electronic control unit,
• wherein the electronic control unit is configured to selectively perform one of
• a first NOx removal method, and
• a second NOx removal method,
• wherein the electronic control unit is configured to control the hydrocarbon feed valve to inject hydrocarbon with a period within the predetermined range of period to thereby reduce NOx contained in the exhaust gas when the first NOx removal method is to be performed,
• wherein the electronic control unit is configured to control an air-fuel ratio of the exhaust gas which flows into the exhaust purification catalyst rich with a period longer than the predetermined range of period to thereby release stored NOx from the exhaust purification catalyst and reduce the NOx when the second NOx removal method is to be performed,
• wherein the electronic control unit is configured to judge whether the exhaust purification catalyst is clogged due to buildup of particulates in the exhaust gas, and
• wherein the electronic control unit is configured to perform the second NOx removal method when it is judged that the exhaust purification catalyst is clogged due to buildup of particulates in the exhaust gas.