| 摘要 |
PROBLEM TO BE SOLVED: To highly accurately control the air-fuel ratio, by properly making exhaust gas flow to the downstream side of an exhaust passage, regardless of a pressure difference in the exhaust gas exhausted from a cylinder group of right and left banks, in an internal combustion engine. SOLUTION: A cylinder group is arranged by separately arranging a plurality of cylinders as the right and left, or first and second, banks 12 and 13. An exhaust gathering pipe 61 is arranged for connecting first and second exhaust pipes 57 and 58 to the cylinder group of the respective banks 12 and 13 and merging a downstream end part of the respective exhaust pipes 57 and 58. First and second front stage three-way catalysts 59 and 60 are arranged in the respective exhaust pipes 57 and 58, and first and second control valves 65 and 66 are arranged. The upstream sides of the front-stage three-way catalysts 59 and 60 and the control valves 65 and 66 in the respective exhaust pipes 57 and 58 are communicated by a communicating tube 64, and an NOx storage-reduction type catalyst 62 is arranged in the exhaust gathering pipe 61. An air-fuel ratio sensor 86 is arranged for detecting the air-fuel ratio of the exhaust gas flowing in the communicating tube 64. An ECU 79 controls the respective control valves 65 and 66 for opening and closing, based on a detecting result of the air-fuel ratio sensor 86. COPYRIGHT: (C)2008,JPO&INPIT
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