DEVICE AND METHOD FOR CONTROLLING AIR-FUEL RATIO IN INTERNAL COMBUSTION ENGINE

摘要

A device and a method for controlling an air-fuel ratio in an internal combustion engine capable of maximally maintaining the exhaust gas purification capacity of a catalyst device by rapidly changing the air-fuel ratio from a rich state to a lean state or vice versa when the same state of air-fuel ratio is continued. The device comprises an oxygen sensor outputting a binary signal indicating whether the concentration of oxygen contained in exhaust gases exceeds a specified threshold or not and controls so that the air-fuel ratio reciprocates between the rich state and the lean state by integrally controlling to cumulatively increase or decrease the air-fuel ratio by a specified correction value based on the binary signal outputted from the oxygen sensor. When the binary signal from the oxygen sensor exceeds a specified engine cycle number and the rich state or the lean state is continued in the air-fuel ratio control, the correction amount is increased.