Importance

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Abstract

An air-fuel ratio control apparatus for an internal combustion engine is provided which includes an air-fuel ratio determining circuit which determines an air-fuel ratio of exhaust gases flowing upstream of a catalytic converter for controlling the air-fuel ratio of the exhaust gases so as to agree with a target air-fuel ratio under feedback control, a sorbed substance amount determining circuit for determining the amount of substances sorbed in the catalytic converter, and a target air-fuel ratio determining circuit for determining said target air-fuel ratio so that the amount of substances determined by said sorbed substance amount determining means falls within a given range. The sorbed substance amount determining circuit determines the amount of substances sorbed in the catalytic converter based on the air-fuel ratio determined by said air-fuel ratio determining circuit using a catalytic converter model established using parameters indicating adsorption reaction of exhaust gas components entering the catalytic converter, oxidation-reducing reaction of the substances sorbed in the catalytic converter with the exhaust gas components, desorption reaction of the substances sorbed in the catalytic converter, and a non-reacted portion of the exhaust gas components.

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First Claim