APPARATUS FOR CONTROLLING THE AIR-FUEL RATIO IN AN INTERNAL COMBUSTION ENGINE

摘要

APPARATUS FOR CONTROLLING THE AIR-FUEL RATIO IN AN INTERNAL COMBUSTION ENGINE Apparatus for controlling the air fuel ratio in an internal combustion engine to substantially maintain the ratio at a predetermined value while the engine is operating under various load conditions. The engine has a carburetor with an air passageway through which air is drawn into the engine. Fuel is supplied to the carburetor through a fuel system and mixed with air passing through the carburetor. The carburetor has a conduit through which air is introduced into the fuel system and the engine further has a chamber for combustion of the resulting air-fuel mixture and combustion products are exhausted. The apparatus comprises an air metering unit fox metering the quantity of air introduced into the fuel system through the conduit to control the air-fuel ratio of the mixture. The presence of oxygen in the combustion products, which is a function of the air-fuel ratio of the mixture, is sensed and a first electrical signal representative of the oxygen content is supplied. The first electrical signal is compared with a predetermined reference level which is a function of the predetermined value to produce a second electrical signal having first and second signal elements, a first signal element being produced when the air-fuel ratio of the mixture is greater than the predetermined level and a second signal element being produced when the ratio is less than the level. A control responsive to the second electrical signal supplies to the air metering unit a control signal by which the quantity of air introduced into the conduit is controlled. A change in the control signal is produced whenever the second electrical signal has a transition from one signal element to the other thereby for the air metering unit to change the quantity of air introduced into the conduit by an amount necessary to substantially maintain the air-fuel ratio at the predetermined value,