Air-to-fuel ratio control systems for internal combustion engines

Abstract

An air-to-fuel ratio control system for an internal combustion engine comprises means for performing a feedback control for keeping a fuel mixture to have the theoretical air-to-fuel ratio or approximations thereof in response to the output of an air-to-fuel ratio sensor, means for conducting the learning to compute a supplemental feedback quantity of fuel used for revising the quantity of fuel by which the fuel actually supplied is determined in at least one of partitions of the operating condition of the engine under the feedback control, means for memorizing the supplemental feedback quantity of fuel in at least one of memorizing areas partitioned in accordance with the partitions of the operating condition of the engine as a resultant of the learning, means for renewing the resultant of the learning in each of the remaining memorizing areas on the strength of the resultant of the learning newly memorized in at least one of memorizing areas, and means for supplying the fuel of the quantity computed with the renewed resultant of the learning in each memorizing area so as to produce the fuel mixture having a desired air-to-fuel ratio different from the theoretical air-to-fuel ratio and approximations thereof through an open-loop control under the situations where the operation of the engine meets predetermined conditions.