The Application of Ionic Current Detection System for the Combustion Limit Control

An in-vehicle detecting system, which directly monitors the combustion condition in each cylinder by detecting the ionic current generated in the vicinity of combustion flame surface in the internal combustion engine, has been developed for engine control. This system comprises the existing ignition plug employed as an ion probe, an additional ignition coil added with electronic components for the detection, and a detection module to process the ionic current and to provide the engine management system with various information indicating the combustion condition. This system allows the judgment of misfire or normal combustion in the overall engine driving conditions and the detection of knocking level in each cylinder. Furthermore, the development is now under way for practically driving the engine drive with leaner mixture, namely, the control of air fuel ratio in each cylinder through the information based on this ionic current indicating the combustion condition.

This paper describes the constitution and basic operation of the detection system, the results regarding the ability to detect misfire and the ability to detect and control knocking level in an actual engine, the study of these result, and the data applied to lean limit control of air fuel ratio.