System for controlling air-fuel ratio

A system for controlling an air-fuel ratio for a carburetor of an internal combustion engine having an intake passage, an exhaust passage, a throttle valve, detecting means for detecting the concentration of a constituent of gases passing through said exhaust passage, air-fuel mixture supply means, and electromagnetic valve means for correcting the air-fuel ratio of the air-fuel mixture supplied by said air-fuel mixture supply means, the improvement comprising:

• comparator means for comparing the output signal of said detecting means with a reference value,
• an integration circuit means for integrating the output of said comparator means,
• a middle value detecting circuit means for detecting a middle value between peak values of the output of said integration circuit means,
• throttle sensor means for producing an output signal dependent upon the operation of said throttle valve,
• acceleration and deceleration detecting means for differentiating the output of said throttle sensor means,
• summing circuit means for summing said outputs of said middle value detecting circuit means and said acceleration and deceleration detecting circuit means,
• driving circuit means for generating an output in dependency on the output signal of said summing circuit means for driving said electromagnetic valve means, whereby the air-fuel ratio is controlled to a value substantially equal to the stoichiometric air-fuel ratio.

A system for controlling an air-fuel ratio for a carburetor of an internal combustion engine having an intake passage, an exhaust passage, a throttle valve, detecting means for detecting the concentration of a constituent of gases passing through said exhaust passage, air-fuel mixture supply means, and an on-off electromagnetic valve means for correcting the air-fuel ratio of the air-fuel mixture supplied by said air-fuel mixture supply means, the improvement comprising:

• comparator means for comparing the output signal of said detecting means with a reference value,
• integration circuit means for integrating the output of said comparator means,
• a middle value detecting circuit means for detecting a plurality of middle values between two adjacent maximum and minimum values of the output of said integration circuit means, and
• throttle sensor means for producing an output signal dependent upon the operation of said throttle valve,
• acceleration and deceleration detecting circuit means for differentiating the output of said throttle sensor means,
• pulse generator means for generating a pulse train having pulse-repetition frequency varying in dependency on the output signal of said throttle sensor means,
• summing circuit means for summing the output of said middle value detecting circuit means and the output of said acceleration and deceleration detecting circuit means and the output of said pulse generator means,
• a triangular wave pulse generator, and
• comparing circuit means for comparing the output of said summing circuit means with triangular pulses from said triangular wave pulse generator for producing pulses driving said on-off electromagnetic valve.