Internal combustion engine misfire circuit using ion current sensing

摘要

An internal combustion engine misfire sensing circuit comprises an ion current sensing circuit for sensing an ion current in the combustion chamber of an internal combustion engine, a current/voltage conversion circuit for converting the sensed ion current into a voltage and a waveform shaping circuit for shaping the waveform of an output of the current/voltage conversion circuit. The waveform shaping circuit includes a second comparator for comparing a voltage of a third capacitor with first and second reference voltages for outputting a misfire sensing signal and a capacitor charging/discharging circuit for charging the third capacitor in response to the rising up of an output of the current/voltage conversion circuit and discharging the third capacitor based on the input of the misfire sensing signal. With this arrangement a misfire can be sensed even in an internal combustion engine having multiple cylinders, the number of parts can be reduced as well as the area of circuits can be reduced.