Patent ID: 6281682
Filing Date: 2001-08-28
Classification: F02P

Abstract:
A sensor for detecting ignition current flowing through a spark plug of an internal combustion engine at the time of spark discharge of the spark plug and ion current flowing though the spark plug at the time of combustion of fuel in a cylinder of the engine, the engine having an ignition system with a high voltage path between an ignition coil and the spark plug, the sensor comprising:an ignition path connected in series with said high voltage path and having at least two reverse current preventing diodes for permitting current to flow through said high voltage path only in one direction; anda detection path having a first current detecting diode connected at an electrode to that same polarity electrode of one of said reverse current preventing diodes closer to said spark plug, for detecting said ignition current and said ion current by way of said first current detecting diode;wherein a path portion of said detection path on the side of said first current detecting diode opposite to said ignition path and a path portion of said ignition path connecting between said reverse current preventing diodes are capacitively coupled.