Arrangement for controlling the air-fuel ratio of an internal combustion engine of a motor vehicle

摘要

An arrangement for controlling the air-fuel ratio of a motor vehicle driven by an internal combustion engine contains an emission control system with a three-way catalytic converter for controlling the air-fuel ratio according to the operation of the engine. A vacuum sensor for detecting the heavy load operation of the engine (an engine speed detection circuit and a circuit for supplying a predetermined voltage) are provided. The engine speed detection circuit is so designed that it generates an output signal when the engine speed is lower than a predetermined value. A feedback control circuit controls the air-fuel ratio to be at the stoichiometric air-fuel ratio in the normal operating state. A first switch device is activated by the output signal of the vacuum sensor, in order to connect the output of the circuit for supplying a predetermined voltage to the input of the feedback control circuit when heavy load operation is detected, and to deactivate the feedback control circuit. A second switch is activated by the output signal of the engine speed detection circuit in order to cease control of the air-fuel ratio in order to supply the engine with a rich air-fuel mixture by way of the carburettor. <IMAGE>