Patent ID: 6918385

Claim:
An air-fuel ratio detecting apparatus of an engine for detecting an air-fuel ratio of a combustion mixture in the engine, said apparatus comprising: an oxygen concentration detector generating a detection signal according to oxygen concentration in an engine exhaust gas, said detection signal being abruptly changed upon said air-fuel ratio reaching a stoichiometric air-fuel ratio; a temperature detector generating a detection signal according to a temperature of said oxygen concentration detector; and an air-fuel ratio calculator receiving the detection signal from said oxygen concentration detector and the detection signal from said temperature detector, to calculate the air-fuel ratio based on these detection signals, wherein said air-fuel ratio calculator converts the detection signal from said oxygen concentration detector to a value having a characteristic linear to the air-fuel ratio in an air-fuel ratio area containing therein the stoichiometric air-fuel ratio, to calculate the air-fuel ratio based on the value after conversion, and modifies said conversion characteristic of the detection signal in the air-fuel ratio area containing therein said stoichiometric air-fuel ratio according to the temperature of said oxygen concentration detector.