Exhaust gas purification device for internal combustion engine

An exhaust gas purification device of an internal combustion engine, comprising in an exhaust passage, a catalyst for purifying a component in an exhaust gas and having an active element for activating an oxidation reaction or a reduction reaction of the component in the exhaust gas and a carrier for caning the active element, in which catalyst, the active element transforming as a solid solution in the carrier when a temperature of the catalyst is higher than or equal to a predetermined solid solution temperature which is a predetermined temperature and an atmosphere in the catalyst is an oxidation atmosphere and the active element precipitating from the carrier when the temperature of the catalyst is higher than or equal to a predetermined precipitation temperature which is a predetermined temperature and the atmosphere in the catalyst is a reduction atmosphere,

• wherein an air-fuel ratio of an exhaust gas flowing into the catalyst is controlled to an air-fuel ratio leaner than the stoichiometric air-fuel ratio when an active element solid solution degree, which indicates a proportion of the active element having transformed as a solid solution in the carrier relative to the total active element is smaller than a target solid solution which is a target active element solid solution degree or smaller than a lower limit of a target solid solution degree range which is a range of the target active element solid solution degree and the temperature of the catalyst is higher than or equal to the predetermined solid solution temperature during the operation of the engine, and
• wherein the air-fuel ratio of the exhaust gas flowing into the catalyst is controlled to an air-fuel ratio richer than the stoichiometric air-fuel ratio when the active element solid solution degree is larger than the target solid solution degree or larger than an upper limit of the target solid solution degree range and the temperature of the catalyst is higher than or equal to the predetermined precipitation temperature.