STUDY CONTROL METHOD OF AIR-FUEL RATIO IN INTERNAL-COMBUSTION ENGINE

摘要

PURPOSE:To improve control of air-fuel ratio in a wide operational range, by changing a study item or the like in accordance with an operational condition of an engine when a correction item of air-fuel ratio used at calculation of a fuel injection quantity is correctively studied in accordance with a deviation between the detected air-fuel ratio and the target air fuel ratio. CONSTITUTION:In a digital control circuit 54, a basic injection quantity calculated from an intake pipe pressure sensor 23 and crank angle sensor 44 is corrected in accordance with a deviation between the air-fuel ratio by an O2 sensor 34 and the target air-fuel ratio. While an air-fuel ratio correction item, used when a fuel injection quantity is calculated, is correctively studied in accordance with said deviation. In this case, when speed of an engine obtained from an output of said sensor 44 is at least a prescribed value, a loaded condition of the engine is decided by intake pipe pressure. Then a multiplication item for the basic injection quantity at decision of a normal operational condition while an addition item at decision of an idle operational condition are studied. While here a permissible limit is set to a study result of the multiplication item and/or addition item.