Patent ID: 7975471

Claim:
An exhaust purification apparatus of an internal combustion engine comprising: six or more cylinders divided into a first cylinder group made up of at least three cylinders, and a second cylinder group made up of at least three cylinders; a common first exhaust passageway connected to the first cylinder group; a common second exhaust passageway connected to the second cylinder group; first and second catalysts respectively provided in the common first exhaust passageway and the common second exhaust passageway; and a common NOx storage reduction catalyst connected to the common first exhaust passageway and the common second exhaust passageway on a downstream side from each of the first and second catalysts; and a controller that controls an air-fuel ratio of each of the six or more cylinders; wherein, when a temperature of the common NOx storage reduction catalyst is to be raised, an average air-fuel ratio of one cylinder group of the first cylinder group and the second cylinder group is made rich, and an average air-fuel ratio of an other cylinder group of the first cylinder group and the second cylinder group is made lean, for the one cylinder group whose average air-fuel ratio is made rich when the temperature of the common NOx storage reduction catalyst is to be raised, the controller effects control such that an air-fuel ratio in at least two cylinders of the one cylinder group is made rich and an air-fuel ratio in an other cylinder or other cylinders of the one cylinder group is made stoichiometric or lean, or the air-fuel ratio in at least one cylinder of the one cylinder group is made rich and the air-fuel ratio in an other cylinder or other cylinders of the one cylinder group is made stoichiometric, and for the other cylinder group whose average air-fuel ratio is made lean when the temperature of the common NOx storage reduction catalyst is to be raised, the controller effects control such that an air-fuel ratio in at least two cylinders of the other cylinder group is made lean and an air-fuel ratio in an other cylinder or other cylinders of the other cylinder group is made stoichiometric or rich, or the air-fuel ratio in at least one cylinder of the other cylinder group is made lean and the air-fuel ratio in an other cylinder or other cylinders of the other cylinder group is made stoichiometric.