| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for controlling air-fuel ratio with which control of a theoretical air-fuel ratio can be performed highly accurately and reliably. SOLUTION: The method involves controlling the ratio of air to fuel supplied to an internal combustion engine (air-fuel ratio A/F) to theoretical air-fuel ratio (λ-1) using an air-fuel ratio sensor. In this case, a solid electrolyte body 20 with oxygen ion conductivity, a first electrode 21 provided on the solid electrolyte body 20 and in contact with an atmosphere and a second electrode 22 in contact with exhausted gas from the internal combustion engine are provided, wherein predetermined voltage has been applied between the first electrode 21 and the second electrode 22 for detecting a limiting current value generated between both electrodes 21, 22. A single-cell-type limiting current air-fuel ratio sensor 2 is used to detect the limiting current value Ip according to oxygen concentration and not combusted gas concentration in the exhausted gas, and the air-fuel ratio A/F is controlled to obtain Ip=0, thereby controlling it to the theoretical air-fuel ratio (λ=1). |
