Method of controlling air-fuel ratio of internal combustion engine so as to effectively maintain the air fuel ratio at a desired air-fuel ratio of lambda =1

摘要

A method of controlling the air-fuel ratio so as to be effectively maintained at a desired air-fuel ratio of lambda =1 is composed of a combination of an electronic map control for effecting the air-fuel ratio control on the basis of map data read out from a data map stored in ROM as air-fuel ratio control data in correspondence to various operation parameters of an engine and an O2-feedback control for controlling the air-fuel ratio on the basis of oxygen quantity detected from the exhaust gas. Upon the occurrence of changes in the control quantity for a predetermined number of times in the course of the O2-control, the latter is changed over to the map control. At that time point, a control quantity for the map control is corrected on the basis of a mean control quantity during the O2-feedback control. Unless a significant variation takes place in the engine operating conditions, the map control is continued for a predetermined time and then changed over to the O2-control. Upon the occurrence of a significant variation in the engine operating conditions, the map feedback control is immediately changed over to the O2-control.