| 摘要 |
In an exhaust gas purification system provided with two or more exhaust gas purification devices each having an oxygen occlusion ability arranged in series in an exhaust passage, a technique is provided in which the degradation of each of the exhaust gas purification devices can be detected in a distinguished manner with a simple structure. In an exhaust gas purification system having an NSR and a filter with an oxygen occlusion ability arranged in series from an upstream side, an NSR outflow gas air fuel ratio is estimated based on an NSR inflow gas air fuel ratio and an oxygen occlusion ability in the NSR, and a filter outflow gas air fuel ratio is estimated based on the NSR outflow gas air fuel ratio (filter inflow gas air fuel ratio) and an oxygen occlusion ability in the filter. Further, a filter outflow gas air fuel ratio is detected, and the degradation of the NSR and the degradation of the filter are determined in a distinguished manner based on the estimated NSR outflow gas air fuel ratio, the estimated filter outflow gas air fuel ratio, and the actually detected filter outflow gas air fuel ratio. |
