Abstract: In an air-fuel ratio control apparatus for detecting the air-fuel ratio from the oxygen content of the exhaust gas from an engine and feedback controlling the air-fuel ratio at the desired ratio through an integrating circuit, the circuit constant of the integrating circuit is increased with increase in the altitude to improve the control response characteristic.

Abstract: An air-fuel ratio compensating apparatus for the carburetor of an internal combustion engine has first and second valves having equal control (input) current-opening characteristics and provided in main and slow system air bleed paths respectively to control sectional area of flow in the main and slow system air bleed paths in relation to the output of an air-fuel ratio sensor, electronic control circuit which sends the control current to the first and second valves in such a way that the opening of the second valve is always larger than that of the first valve. Thus, flow of the main system air bleed is restrained during the initial part of the acceleration period so as to reduce the amount of noxious component in the exhaust gas.

Abstract: A control circuit comprises a switching element connected in series with the coil of an actuator for generating a drive current when rendered conductive. A drive current sensing resistor is coupled in a circuit with the switching element and the coil to develop a first voltage in response to the switching element being rendered conductive. A surge current sensing resistor is coupled in a circuit with the coil through a unidirectionally conducting element to develop a second voltage in response to the switching element being rendered nonconductive. The first and second voltage are amplified and fed to a differential integrator to which an actuator control signal is also applied. The output of the differential integrator is compared with the instantaneous value of a ramp voltage to generate gating pulses applied to the switching element.

Abstract: A device for controlling air-fuel ratio for an internal combustion engine with a use of the signal from an oxygen sensor adjacent to a three-way catalytic converter, the device comprising throttle sensor for detecting the transient running state of the engine and supplying the detected signal to a controller, integration by an integration circuit in the controller being commenced at a predetermined value produced in an initial voltage setting circuit in the controller, regardless of the preceding value of the output of the integration circuit, in such a transient state as a sudden deceleration.

Abstract: The output of an exhaust gas sensor disposed in the exhaust system of an engine is amplified by a variable gain amplifier circuit. The gain of the amplifier circuit is controlled so that the peak output voltage thereof is kept constant irrespective of changes in the output of the exhaust gas sensor due to, for example, its deterioration. The output of the exhaust gas sensor is integrated and compared with a reference value by a comparator circuit which generates a reference voltage variable with the output waveform of the exhaust gas sensor whereby a stable feedback control is realized even though the air-fuel ratio of the mixture produced from a carburetor is greatly changed.