AIR-FUEL RATIO JUDGING METHOD OF INTERNAL COMBUSTION ENGINE BASED ON ION CURRENT

摘要

An air-fuel ratio judging method of an internal combustion engine based on an ion current in which a generation period during which an ion current generated in the combustion chamber of the internal combustion engine exceeds a preset value is measured, and an air-fuel ratio under operating state of the internal combustion engine is judged based on the measured generation period. A decision is made that an air-fuel ratio is other than a theoretical air-fuel ratio when the measured generation period is below a reference value. The reference value is set based on a generation period corresponding to ignition timing when an actual air-fuel ratio is a theoretical air-fuel ratio, and a larger reference value is set as the delay angle of ignition timing increases.