| 摘要 |
In an exhaust path (4) of an internal combustion engine (2), a catalyst (6) including an oxygen storage capacity, a first air-fuel ratio sensor (10) installed upstream of the catalyst (6), and a second air-fuel ratio sensor (12) installed downward of the catalyst are disposed. An air-fuel ratio of the internal combustion engine (2) is controlled to a rich air-fuel ratio richer than a theoretical air-fuel ratio, or a lean air-fuel ratio leaner than the theoretical air-fuel ratio. In a state that is determined as a state where the catalyst (6) stores oxygen to an upper limit of an oxygen storage amount after the air-fuel ratio is switched to the lean air-fuel ratio from the rich air-fuel ratio, or a state where the catalyst (6) releases oxygen to a lower limit of the oxygen storage amount after the air-fuel ratio is switched to the rich air-fuel ratio from the lean air-fuel ratio, a first output that is the output of the first air-fuel ratio sensor (10), and a second output that is the output of the second air-fuel ratio sensor (12) are detected. Based on a difference between the first output and the second output, the output of the first air-fuel ratio sensor (10) is corrected. |
