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

A method as claimed in any one of the preceding claims, characterized in that for manually initiated voltage supply in starting an engine, ignition pulses are generated in the ignition circuit when a piston in the cylinder pertaining to the ignition circuit is at its T.D.C.,

• a signal representing a time interval during which ignition generated combustion can be obtained is applied to the detecting means for the ignition circuit, and in that
• a signal representing ion current is processed in the detection means for detecting possible combustion during said time interval, and for delivering a corresponding output signal which is to serve as a basis for further ignition pulses generated in a predetermined order in all ignition circuits.

A method of detecting ion current in a capacitive ignition system of a multi-cylinder internal combustion engine having a plurality of ignition circuits and ignition coils, comprising the steps of

• applying a substantially constant measuring voltage to at least one ignition circuit in a ground connection between one end of a secondary winding of an ignition coil and a measuring capacitor disposed in the connection, the other end of the secondary winding being connected to a central electrode of an ignition means for igniting a fuel-air mixture in one of the engine cylinders, detecting ion current in the ignition circuit in detecting means connected to the ground connection of said secondary winding and processing a signal representing ion current in the detecting means at least during one predetermined time interval corresponding to the rotation of the crankshaft through a certain angle range.

An arrangement for detecting ion current in the ignition system of a multi-cylinder internal combustion engine having a plurality of ignition circuits, the ignition in the cylinders following a certain order controlled by an electronic unit, there being included in said ignition circuits a secondary winding of an ignition coil and ignition means for igniting a fuel-air mixture in the engine cylinders, at least one of the ignition circuits being connected to an outside voltage source which causes ion current in the ignition circuit when there is combustion in the combustion chamber, characterized in that

• the outside voltage source is connected to the ignition circuit between a measuring capacitor and one end of the secondary winding, the other end of which is connected to a central electrode of the ignition means, and in that the capacitor is included in a line connected to ground and departing from said one end of the secondary winding, the means for detecting ion current flowing in the ignition circuit being connected to said line.