Air fuel ratio control apparatus for internal combustion engine

Abstract

An apparatus capable of performing correct determination of a misfire limit without involving influence by differences between individual internal combustion engines, and thus capable of realizing highly precise lean control. During lean control, a mean deviation MD.sub..lambda.=1 of angular-velocity differences, which has been learned during the adoption of the stoichiometric air-fuel ratio (i.e., during .lambda.=1) in the relevant internal combustion engine, is subtracted from the current mean deviation MD.sub.L of angular-velocity differences occurring in the engine, so that the fuel injection amount is corrected in accordance with the resultant difference .DELTA.MD, which is attributable to an increase in the risk of misfire. Thus, the mean deviation component MD.sub..lambda.=1 which corresponds to the stoichiometric air-fuel ratio and which may differ between individual internal combustion engines, is eliminated, and only the component .DELTA.MD attributable to an increase in the risk of misfire is used to control the air-fuel ratio, thereby eliminating influence of differences between internal combustion engines to enable correct determination of a misfire limit.

Dependencies are inferred from the claim text.