CONTROLLING DEVICE FOR AIR-FUEL RATIO OF INTERNAL-COMBUSTION ENGINE

PURPOSE:To secure optimum air-fuel ratio at the starting time, and to improve the performance of an engine at that time, by a method wherein a penumatic control valve is controlled in response to the temperature of a carburettor at the starting time, in a device to which a fresh-air introducing path, provided with a pneumatic control valve and going around a carburettor, is provided. CONSTITUTION:The air-fuel ratio controlling device is provided with the primary fresh-air introducing path 17 to which a pneumatic control valve 16 of bimetal type is provided, and the secondary fresh-air introducing path 14, going around a carburettor 12, which is provided with a pneumatic control valve 26, and the pneumatic control valve 26 is controlled by a control circuit 18. In this case, the control circuit 18 receives the respective output from an oxygen density sensor 6, provided to an exhaust system, and a temperature sensor 25, provided in a float chamber 22, and controls the pneumatic control valve 26 by the output of a temperature sensor 25, at the starting time of an engine. With such an arrangement, the specific fuel ratio, especially at the starting time in high temperature, is controlled best, as a result, the performance of an engine is maintained in good condition.