Method and apparatus for detecting ion current in an internal combustion engine ignition system

摘要

The invention relates to a method for detecting ion current in an ignition circuit included in the ignition system of an internal combustion engine, where a measuring voltage is applied to the ignition circuit and a measuring device is utilized for detecting ion current possibly present in the ignition circuit. In known solutions of this kind, it has been necessary to use comparatively expensive electronic components, usually not manufactured as standard, to protect the outside voltage source from high voltages occurring in the ignition circuit. The problems are aggravated when the prior art is applied to capacitive ignition systems. The present invention solves the problems involved in an advantageous manner and is essentially distinguished in that a constant measuring voltage is applied to the grounded connection of the ignition circuit between a secondary winding of the ignition circuit and a capacitor in the ground connection, and in that a possible ion current in the ignition circuit is detected in means, by a signal representing the ion current being taken off from the ground connection of the secondary winding.