Air-fuel mixture ratio correcting system for carburetor

Claim 1

An air-to-fuel ratio controlling system for an internal combustion engine comprising: a carburetor connected to an intake manifold of an internal combustion engine and including an intake passage, a fuel supply means for supplying fuel through a fuel passage into said intake passage to form, in said intake passage, an air-fuel mixture to be supplied to said engine, and a main valve positioned in said intake passage for controlling the amount of the air-fuel mixture; means connected with said fuel supply means for controlling the amount of the fuel to be supplied into said intake passage to compensate the air-to-fuel ratio of said air-fuel mixture; a pulse motor coupled to said fuel control means for driving the same in order to control the degree of the fuel supply; a pulse generator for generating a train of pulses having a frequency which varies in proportion to the rotational speed of said engine; a frequency divider connected to said pulse generator for converting the train of pulses from said pulse generator into plural trains of pulses having different and lower frequencies; detecting means for detecting a rapid change of the operational speed of said internal combustion engine; selecting means connected to said detecting means for selecting one of said plural trains of pulses from said frequency divider in accordance with the detected change in the operational speed of said engine; air-to-fuel ratio sensing means disposed in an exhaust manifold of said internal combustion engine for detecting the air-to-fuel ratio of the air-fuel mixture supplied to said engine; and a control circuit connected to said selecting means, said air-to-fuel ratio sensing means and said pulse motor for driving said pulse motor at a speed determined by the selected train of pulses from said selecting means, the rotational direction of said pulse motor depending on the output from said air-to-fuel ratio sensing means.