| 摘要 |
PROBLEM TO BE SOLVED: To provide a verification method, for the function of a catalyst, in which whether the function of the catalyst used to remove NOX (nitrogen oxides) is sufficient or not is verified by using a gas sensor which can measure the concentration of the NOX. SOLUTION: First, in order to restore the function of a catalyst, an air-fuel ratio is controlled so as to be shifted to the rich (R) side. After that, the air-fuel ratio is controlled to the lean side. Then, the air-fuel ratio is controlled to the lean side, and the concentration of NOX is measured. When the concentration of NOX is sufficiently low in the same manner as a concentration in the operation of an ordinary engine 2, it is regared that the function of the catalyst is restored. The concentration of NOX is higher than the concentration in the operation of the ordinary engine 2 even when a rich spike is hit so as to execute a treatment to restore the function of the catalyst. Then, it is regarded that the function of the catalyst is not restored. |
