Exhaust gas purification apparatus for internal combustion engine

摘要

An internal combustion engine wherein three-way catalysts are arranged in an exhaust passage of a first cylinder group and an exhaust passage of a second cylinder group and a common NOx storage catalyst is arranged downstream of the three-way catalysts. When the NOx storage catalyst should be raised in temperature, the air-fuel ratio of a part of the cylinders in each cylinder group is made rich and the air-fuel ratio of a part of the cylinders in each cylinder group is made lean to raise the NOx storage catalyst in temperature by the heat of oxidation reaction at the three-way catalysts.