Air-to-fuel ratio adjusting system for an internal combustion engine

A method for adjusting an air-to-fuel ratio of an air-fuel mixture to be supplied to an internal combustion engine comprising the steps of:

• applying an air-fuel mixture to an internal combustion engine through a main passage;
• measuring the concentration of an oxygen component in the exhaust gases of said engine;
• applying additional air to the air-fuel mixture through a bypass in accordance with the oxygen concentration in the exhaust gases;
• detecting idling conditions of said engine;
• detecting percolation phenomenon of a fuel to be supplied to said engine;
• and
• stopping the control of the amount of the additional air both when said engine is at the idling operation and when the percolation of the fuel is not taking place.

An air-to-fuel ratio adjusting system for an internal combustion engine comprising:

• a carburetor coupled to an intake manifold of an internal combustion engine and including a main passage and a bypass passage for supplying air-fuel mixture to said engine, said carburetor also including a float chamber for storing fuel therein and a fuel nozzle opening to said main passage at one end and communicated with said float chamber at the other end;
• a throttle valve pivotally disposed in said main passage for controlling the amount of air-fuel mixture through said main passage;
• a control valve disposed in said bypass passage for varying the opening area of said bypass passage;
• said bypass passage communicating with said main passage downstream of said throttle valve, whereby said control valve controls the amounts of additional air supplied to said main passage through said bypass passage;
• driving means coupled to said control valve for driving the same;
• air-to-fuel ratio sensing means disposed in an exhaust system of said engine for detecting the composition of exhaust gases emitted from said engine and generating an air-to-fuel ratio signal;
• an actuating circuit, connected to said air-to-fuel ratio sensing means and said driving means, for actuating said driving means in accordance with said air-to-fuel ratio signal,
• engine speed detecting means for detecting the rotational speed of said engine;
• percolation detecting means for detecting the percolation of the fuel in said float chamber;
• and
• an idling control circuit, connected to said actuating circuit, said engine speed detecting means and said percolation detecting means, for stopping the actuation of said driving means by said actuating circuit during a time:
• 1. when the rotational speed of said engine is below a predetermined value, and
• 2. when percolation of the fuel is not taking place.