| 摘要 |
PROBLEM TO BE SOLVED: To restrain deterioration of purifying performance to the minimum by sufficiently supplying HC and Co to a NOx stored and reduced type three-way catalyst, and providing a means for feedback controlling the air fuel ratio of combustion mixture to a target air fuel ratio. SOLUTION: A first air fuel ratio detecting means 4, a NOx stored and reduced type three-way catalyst 2, a three-way catalyst 3, and a second air fuel ratio detecting means 5 are sequentially arranged, a first air duel ratio feedback means 6a and a second air fuel feedback means 6b are connected to the first air fuel ratio detecting means 4 and the second air fuel ratio detecting means 5 in such a manner as to perform data communication, the first air fuel ratio feedback means 6a feedback controls the air fuel ratio of exhaust mixture to a target air fuel ratio according to the exhaust air fuel ratio detected by the first air fuel ratio detecting means 4, and the second air fuel ratio feedback means 6b feedback controls the air fuel ratio of the combustion mixture to a target air fuel ratio according to the exhaust air fuel ratio detected by the second air fuel ratio detecting means 5 immediately after the target air duel ratio of combustion mixture is swtiched from lean to storichiometry or rich. |
