| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To execute earlier the determination of catalyst deterioration in an internal combustion engine (for example, a lean-burn engine or a cylinder injection engine), in which stoichiometric operation for controlling an air-fuel ratio to be close to a stoichiometric condition and lean operation for controlling it to be lean are changed over depending on an operated condition, even under the conditions that the determination of the catalyst deterioration cannot be executed by a conventional system when determining the presence or not of the catalyst deterioration in accordance with the output of an exhaust gas sensor on the downstream side of a catalyst. <P>SOLUTION: Whether the determination of the catalyst deterioration is finished or not is determined (Step 101), and if the determination of the catalyst deterioration is not finished, a stoichiometric operation region is enlarged (Step 102). Thus, the operation region adequate for the determination of the catalyst deterioration is enlarged and the determination of the catalyst deterioration is executed earlier. After the determination of the catalyst deterioration is finished, the enlargement of the stoichiometric operation region is cancelled and a lean operation region is enlarged (Step 103). Thus, the frequency of executing the lean operation is increased to improve the fuel consumption saving effect of the lean operation. <P>COPYRIGHT: (C)2003,JPO</p> |
