AIR-FUEL RATIO CONTROLLER OF INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To provide both an improvement in exhaust emission purifying capability and reduction in fuel consumption in an internal combustion engine which performs enriching control at the time of recovery from fuel cutting. SOLUTION: When an output of an O2sensor on a catalyst downstream side indicates a lean state in recovery from fuel cutting, enriching control is started and then when oxygen inside a catalyst has been judged to be consumed during implementing the enriching control, the enriching control is terminated. However, even if the judgment has been made in the course of consuming oxygen, when the output of the O2sensor at the catalyst downstream side changes to a rich side, the enriching control is terminated, thus permitting the enriching control at the time of the recovery from the fuel cutting to be timely terminated at all times. By performing such control, even if the fuel cutting for the purpose of improving fuel economy is frequently iterated, exhaust emission can be prevented from becoming more noxious. Regardless of catalyst deterioration due to repeated use over the years, consistently stable enriching control (increase in fuel volume) at the time of the recovery from the fuel cutting is realized. COPYRIGHT: (C)2009,JPO&INPIT