Device for purifying exhaust gas of an engine

A device for purifying an exhaust gas of an engine having an exhaust passage, comprising:

• an exhaust gas purifying catalyst arranged in the exhaust passage, of which an endurance temperature when an exhaust gas air-fuel ratio of the inflowing exhaust gas is lean or stoichiometric is higher than a rich endurance temperature which is an endurance temperature when an exhaust gas air-fuel ratio of the inflowing exhaust gas is rich;
• exhaust gas air-fuel ratio control means for controlling the exhaust gas air-fuel ratio of the exhaust gas flowing into the exhaust gas purifying catalyst;
• making-rich means adapted for controlling the exhaust gas air-fuel ratio control means to make the exhaust gas air-fuel ratio of the exhaust gas flowing into the exhaust gas purifying catalyst rich;
• and
• avoiding-rich means for controlling the exhaust gas air-fuel ratio control means to make the exhaust gas air-fuel ratio of the exhaust gas flowing into the exhaust gas purifying catalyst lean or stoichiometric when the making-rich operation of the making-rich means is to be performed and when a temperature representing a temperature of the exhaust gas purifying catalyst is equal to or higher than the rich endurance temperature.