Air-fuel ratio control apparatus

Claim 1

An air-fuel ratio control apparatus for an internal combustion engine comprising: oxygen concentration detecting means for detecting a concentration of oxygen in an exhaust gas from the engine and comparing a detection signal with a reference value corresponding to a stoichiometric air-fuel ratio to generate a difference signal; integrating means for integrating the difference signal to generate an integration signal; driver means responsive to the integration signal to control a driving current of air-fuel ratio control means; intake pressure detecting means for detecting an intake pressure in said engine and generating an intake pressure detection signal in accordance with said intake pressure; speed detecting means for detecting a rotational speed of said engine and comparing the same with a reference value corresponding to a predetermined engine speed to generate a speed detection signal; idle detecting means responsive to said intake pressure detection signal and said speed detection signal to detect an idling condition of said engine and generate an idle detection signal; air-fuel ratio control halting means responsive to said idle detection signal to apply an air-fuel ratio control stop signal to said driver means; average value means responsive to said idle detection signal to average said integration signal and generate an average value signal; and average value hold means for decreasing said average value signal by a predetermined value and using said decreased value as an integration initial signal when said engine comes into an acceleration operation from said idling condition.