Abstract: An air-fuel ratio control apparatus includes a specific integration means for integrating the rich or lean signal determined depending upon the detected concentration of the predetermined exhaust gas component, to produce an integration signal which is increased when the rich signal is applied and decreased only when the lean signal, having a duration longer than a predetermined period, is applied. If the short lean signal, having a duration shorter than or equal to the predetermined period, is produced, the above integration signal is utilized for adjusting the air-fuel ratio condition.

Abstract: An air-fuel ratio control device of an internal combustion engine having a carburetor. An air bleed passage is connected to a fuel outflow passage of the carburetor, and an electromagnetic control valve is arranged in the air bleed passage. The control valve is controlled by the detecting signal of an oxygen concentration detector arranged in the exhaust passage so that the air-fuel ratio of a mixture fed into the cylinder of an engine becomes equal to the stoichiometric air-fuel ratio. When the vehicle is decelerated, the mean value of the potential level, which has been applied to the electromagnetic control valve before deceleration, is stored. When the throttle valve is opened during the deceleration and, then, the oxygen concentration detector detects that a rich air-fuel mixture is fed into the cylinder of the engine, the above-mentioned mean value is instantaneously applied to the electromagnetic control valve.

Abstract: An air-fuel ratio control device of an internal combustion engine having a carburetor. An air bleed passage is connected to a fuel outflow passage of the carburetor, and an electromagnetic control valve is arranged in the air bleed passage. The control valve is controlled by the detecting signal of an oxygen concentration detector arranged in the exhaust passage so that the air-fuel ratio of a mixture fed into the cylinder of an engine becomes equal to the stoichiometric air-fuel ratio. After the completion of the warm-up of an engine, the opening area of the control valve is maintained within a fixed range. Before the completion of the warm-up of an engine, the opening degree of the control valve becomes larger than the above-mentioned fixed range.