Air-fuel ratio feedback control method for a multi-fuel internal combustion engine

摘要

An air-fuel ratio feedback control method for a multi-fuel internal combustion engine using a dual O2 sensor system is provided, in which the concentration of oxygen in exhaust gas on the upstream side of an exhaust gas purifier is detected, a value corresponding to the detected oxygen concentration is compared with a first target value, and the air-fuel ratio is feedback-controlled in accordance with the result of the comparison. The mixture ratio of at least two fuels is detected, and a second target value is set in accordance with the detected fuel mixture ratio. On the other hand, the concentration of oxygen in the exhaust gas on the downstream side of the exhaust gas purifier is detected, and a value corresponding to the detected downstream-side oxygen concentration is obtained. The first target value is corrected in accordance with the difference between the obtained value and the second target value.