DEVICE FOR CONTROLLING AIR-FUEL RATIO OF INTERNAL COMBUSTION ENGINE

PURPOSE:To prevent the generation of the odor of catalyst exhaust by correcting an air-fuel ratio feedback control constant to be an over-rich side at the time of the nonactive condition of a lower course side air-fuel ratio detecting means, while preventing the effect of the over-rich side correction to the control constant after the time corresponding to the executing condition of the air-fuel ratio feedback control after the correction. CONSTITUTION:When a lower course side air-fuel ratio detecting means M4 is judged to be in a nonactive condition by a judging means M5, a control constant setting means M9 corrects an air-fuel ratio feedback control constant used by an air-fuel ratio feedback control means M7 to be an over-rich side based on a control constant which is calculated by a control constant calculating means M6 at the time corresponding to an air-fuel ratio feedback control executing condition. When a defined time elapsed after the start of calculation of the air-fuel ratio feedback control constant by the means M6 in accordance with the judgment of corresponding to the defined air-fuel ratio feedback control executing condition by the judging means M5, a renewing means M10 makes the means M9 start to renew the air-fuel ratio feedback control constant to suppress the over-rich of air-fuel ratio.