Method of controlling air-fuel ratio and ignition timing in internal combustion engine and apparatus therefor

Claim 1

Apparatus for controlling an air-fuel ratio and an ignition timing in an internal combustion engine, comprising: fuel injection control means for controlling an on-off timing of a fuel injection valve in accordance with fuel injection time duration corresponding to the engine rotational speed and engine load; ignition timing control means for controlling an on-off timing of an igniter in accordance with a spark advance angle corresponding to the engine rotational speed and engine load; memory means for storing a target air-fuel ratio which is leaner than a stoichiometric air-fuel ratio, a stoichiometeric air-fuel ratio and an air-fuel ratio which is richer than the stoichiometric air-fuel ratio; determining means for determining whether or not the engine load is within a predetermined range and the variation in the engine load is also within a predetermined range; fuel injection correcting means for correcting the on-off timing of the fuel injection valve so that the air-fuel ratio approaches the target air-fuel ratio when said determining means determines that the engine load is within a predetermined range; and ignition timing correcting means for correcting the on-off timing of the igniter so that the ignition timing approaches the required ignition timing corresponding to said target air-fuel ratio when said determining means determines that the engine load is within a predetermined range and the variation in the engine load is within a predetermined range.