| 摘要 |
In a method of controlling an exhaust gas system of an internal combustion engine including a nitrogen oxide reducing catalyst capable of adsorbing nitrogen oxide under a lean atmosphere and a nitrogen oxide sensor disposed downstream of the nitrogen oxide reducing catalyst, the nitrogen oxide reducing catalyst and the nitrogen oxide sensor are disposed in the exhaust gas system operated mainly under a lean condition, respectively. An output value of the nitrogen oxide sensor is compared with a predetermined value, and an operation condition of the internal combustion engine is temporarily changed into a stoichiometric condition or a rich condition, or a fuel is injected upstream of the nitrogen oxide reducing catalyst, so that the nitrogen oxide adsorbed to the nitrogen oxide reducing catalyst is detached or decomposed, and again the internal combustion engine is operated under the lean condition. Deterioration of the catalyst is determined based on Nox amount which is calculated from the sensor output, exhaust has flow amount and vehicle running distance.
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