Electronically-controlled plasma ignition device for internal combustion engines

An electronically-controlled plasma ignition system for an internal combustion engine, including

• at least one spark-plug for each cylinder of the engine,
• sensor means for monitoring the rotation of the drive shaft of the engine,
• a plurality of coils having each a primary winding and a secondary winding;
• the secondary winding of each coil being coupled to a respective spark-plug;
• a plurality of high frequency electrical-current generators each connected to the primary winding of a respective coil;
• and
• electronic control means coupled to said sensor means, for activating each of the high frequency electrical-current generators in correspondence with the combustion phase in the corresponding cylinder to generate an electronic plasma between the electrodes of the associated spark-plug;
• each of the said coils including a respective auxiliary winding magnetically coupled to the secondary winding for providing a signal which is indicative of the impedance between the electrodes of the associated spark-plug;
• each of said high frequency electrical current generators including an oscillator coupled to the primary winding and the auxiliary winding of the associated coil;
• each of said oscillators being adapted to apply to the primary winding of the corresponding coil a signal having an intensity which is variable as a function of the signal provided by the associated auxiliary winding, so as to maintain in each combustion phase a substantially constant plasma-flow between the electrodes of the associated spark-plug.