Patent Document ID: 4552115
Application ID: 06599973
Patent Flag: 1

Claim One:
1. An air-fuel ratio control system for an internal combustion engine comprising: air-fuel ratio detecting means for detecting the air-fuel ratio of a mixture supplied to the engine to produce an air-fuel ratio signal, engine operating condition detecting means for detecting an operating condition of the engine to produce an engine operating condition signal, basic fuel quantity setting means responsive to said engine operating condition signal for determining a basic quantity of fuel supply under a specific engine operating condition and producing a basic fuel quantity signal, control gain memorizing means having memories of at least one control gain, feedback control means responsive to said air-fuel ratio signal and the control gain for producing a feedback control signal for modifying the basic fuel quantity signal so that the air-fuel ratio of the mixture is changed toward a desired value, supplementary signal producing means for producing based on said feedback control signal a supplementary signal for supplementing said basic fuel quantity signal, supplementary signal memorizing means for memorizing the supplementary signal, substituting means for substituting for the supplementary signal memorized in the supplementary signal memorizing means of a supplementary signal newly produced by the supplementary signal producing means, fuel supply control means for controlling the quantity of fuel supplied to the engine in accordance with the basic fuel quantity signal, with the feedback control signal and with the supplementary signal which is memorized in the supplementary signal memorizing means, control gain modifying means for decreasing the control gain from said control gain memorizing means in response to an increase in the number of times wherein supplementary signals are substituted for each other.