Device for purifying exhaust gas of engine

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

• an exhaust gas purifying catalyst arranged in the exhaust passage;
• a start catalyst arranged in the exhaust passage upstream of the exhaust gas purifying catalyst;
• means for forming a gas including oxygen;
• means for forming a gas including a reducing agent;
• means for forming at least one of the gas including oxygen and the gas including the reducing agent from the exhaust gas of the engine;
• and
• means for mixing the gas including oxygen and the gas including the reducing agent disposed upstream of the start catalyst and feeding the gas mixture to the exhaust gas purifying catalyst without the gas mixture flowing into the start catalyst.

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

• an exhaust gas purifying catalyst arranged in the exhaust passage;
• a start catalyst arranged in the exhaust passage upstream of the exhaust gas purifying catalyst;
• means for forming a gas including oxygen;
• means for forming a gas including a reducing agent;
• means for forming at least one of the gas including oxygen and the gas including the reducing agent from the exhaust gas of the engine;
• and
• means for mixing the gas including oxygen and the gas including the reducing agent and feeding the gas mixture to the exhaust gas purifying catalyst without the gas mixture flowing into the start catalyst;
• wherein the engine has a plurality of cylinders, the cylinders being divided into a plurality of cylinder groups, wherein the air-fuel ratio of the exhaust gas of a part of the cylinder groups is made lean to form the gas including oxygen, and the air-fuel ratio of the exhaust gas of at least one of the remaining cylinder groups is made rich to form the gas including the reducing agent, and each cylinder has a fuel injector directly injecting fuel into the cylinder, and wherein the fuel injector of the at least one of the remaining cylinder groups injects fuel secondarily at the combustion stroke or the exhaust stroke of the engine to form the gas including the reducing agent.