| 摘要 |
In S poisoning recovery control of a NSR catalyst, a target exhaust air-fuel ratio is set to strong rich until a peak position of SOx accumulation amount in the NSR catalyst is moved to a center portion of the NSR catalyst (ST5). After the peak position of the SOx accumulation amount is moved to the center portion of the NSR catalyst, the target exhaust air-fuel ratio is set to weak rich when a floor temperature of the NSR catalyst exceeds a predetermined value (ST8). Thus, a release speed of H 2 S and SO 2 is decreased to improve exhaust emission and reduce malodor of an exhaust gas. After the peak position of the SOx accumulation amount is moved to the center portion of the NSR catalyst, the target exhaust air-fuel ratio is set to the strong rich when the floor temperature of the NSR catalyst is less than or equal to the predetermined value (ST9). Thus, a time period required for the S poisoning recovery control is shortened and a fuel consumption rate is improved. |
