| 摘要 |
PURPOSE:To provide an abnormal air-fuel ratio detector in which abnormality in an air-fuel ratio sensor on the downstream side is decided with no effect of the reduction of O2 storage effect due to deterioration of the catalyst. CONSTITUTION:The abnormal air-fuel ratio detector comprises air-fuel ratio sensors on the upstream side and the downstream side, i.e., linear air-fuel ratio sensors for detecting the air-fuel ratio linearly, means for calculating a gas response delay time between both air-fuel ratio sensors basing on the detection results from the air-fuel ratio sensors at the time of air-fuel ratio feedback control under lean state, and means for detecting abnormality in the downstream side air-fuel ratio sensor basing on a delay time thus calculated. Since the detection results from the air-fuel ratio sensors in an air-fuel ratio lean region not susceptive to O2 storage effect is employed, deteriorated state of catalyst has no effect on the delay time being calculated and thereby abnormality can be detected accurately in the downstream side air-fuel ratio sensor. Furthermore, a stabilized lean state can be realized using linear air-fuel ratio sensors. |
