Method and apparatus for generating an ion current between electrodes of a spark plug

An apparatus for generating an ion current between a central electrode and one or more side electrodes of a spark plug of a spark ignition engine which is supplied repeatedly with an ignition voltage from an ignition voltage source, the apparatus comprising:

• an engine control unit (ECU) configured to determine during an engine cycle for each spark plug a target ignition point and/or an activation point for the ignition voltage source lying before the target ignition point;
• and
• a second voltage source configured to provide a second voltage which generates the ion current , the second voltage source including an electrical energy storage device structured for being charged only outside the first time interval Δt1;
• wherein the second voltage source is configured to be connected to the electrodes of the spark plug in every engine cycle for a first time interval Δt1, which is shorter than the duration of the engine cycle;
• and
• wherein the ion current flowing as a result of the application of the second voltage to the electrodes of the spark plug follows a path which avoids the ignition voltage source.

A method for generating an ion current between a central electrode and one or more side electrodes of a spark plug of a spark ignition engine that is repeatedly supplied with an ignition voltage from an ignition voltage source, the method comprising:

• assigning an engine control unit (ECU) to the spark ignition engine;
• determining with the ECU in an engine cycle for the spark plug a target ignition point and/or an activation point for the ignition voltage source before the target ignition point;
• providing a second voltage source that outputs a second voltage;
• and
• connecting the second voltage to the electrodes of the spark plug for a first time interval Δt1, which is shorter than the duration of the engine cycle, thereby generating the ion current;
• and
• charging the second voltage source at times outside the first time interval Δt1 and storing electrical energy produced by the charging;
• wherein the ion current flowing as a result of the application of the second voltage to the electrodes of the spark plug follows a path which avoids the ignition voltage source.