Sensor for detecting ignition current and ion current in ignition secondary circuit

摘要

An ignition secondary sensor is provided which is disposed in a high voltage path between an ignition coil and a spark plug for use with a detecting circuit for detecting ignition current and ion current flowing through a spark plug. The sensor comprises an ignition path connected in series with the high voltage path and having a pair of reverse current preventing diodes and a detection path connected to a spark plug side end portion of the ignition path and having a pair of current detecting diodes. A path portion of the detection path on the side of the current detecting diodes opposite to the ignition path and a path portion of the ignition path connecting between the reverse current preventing diodes are capacitively coupled. The detecting circuit is connected to the sensor for detecting the ignition current (ignition timing) on the basis of current flowing into the sensor therefrom and the ion current (combustion timing) on the basis of current flowing from the sensor thereinto.