| 摘要 |
PURPOSE:To attain an accidental fire detection with high reliability by distinguishing a lean spike caused by an accidental fire from a lean period caused by an air-fuel ratio feedback control through the length of succeeding period of a condition of an output of an air-fuel ratio sensor which is inclined to a high oxygen density side compared to a specified slice level. CONSTITUTION:An accidental fire detecting device which is arranged on an exhaust passage of an internal combustion engine has a comparing means 2 which compares a specified slice level to an output of an air-fuel ratio sensor 1 for outputting relatively to residual oxygen density in the exhaust gas. A measuring means 3 measures a period during which an output condition inclined to a high-oxygen density side compared to the slice level scceeds. The measured succeeding period is compared to a judgement reference value. When it is shorter than the reference value, an accidental fire is judged by an accidental fire judging means 4. When the succeeding period is longer than the judgment reference value, a lean condition accompanied with the air-fuel ratio feedback control is judged. |
