Air-fuel ratio adjusting device in an internal combustion engine having a carburetor

Claim 1

An air-fuel ratio adjusting device for use in an internal combustion engine having a carburetor including a main fuel supply system, comprising: an oxygen sensor provided in the exhaust system of said internal combustion engine for detecting oxygen concentration in the exhaust gas; a control unit connected to said oxygen sensor including means for comparing the air-fuel ratio in the air-fuel mixture in the engine with the theoretical air-fuel ratio through the detected oxygen concentration and generating a control signal corresponding to the difference between the engine air-fuel ratio and the theoretical air-fuel ratio, and means for continuously generating a pulse signal with a time interval initiated in response to the engine rotation, the pulse width of said pulse signal being varied in response to said control signal; an electromagnetic fuel injection system provided separately from said main fuel supply system in the carburetor, and having a solenoid valve means energized by said varied pulse signal of said control unit; a first passage connected to said fuel injection system at its one end and connected to a fuel tank at its other end; a second passage connected to said main fuel supply system at its one end and divided at its other end into two passages, one of which is connected to the fuel tank and the other of which is connected to said first passage; a pump provided in said first passage at a position between the fuel tank and the point of connection of said first and second passages; and regulator means including a first regulator provided in said divided passage of said second passage which is connected to said first passage, and a second regulator provided in said divided passage of said second passage which is connected to the fuel tank, whereby said regulators cause said pump to deliver fuel at different pressure to said main fuel supply system and said fuel injection system.