Electronic device to control an ignition coil of an internal combustion engine and electronic ignition system thereof for detecting a preignition in the internal combustion engine

An electronic ignition system to detect a pre-ignition in an internal combustion engine, the system comprising:

• a coil having a primary winding with a first terminal connected to a battery voltage and having a secondary winding with a first terminal connected to a spark plug;
• an electronic control device comprising:
• a high-voltage switch connected in series to the primary winding of the coil and configured to switch between a closed position and an open position;
• a driving unit configured to:
• control a closure of the high-voltage switch during a phase of charging energy into the primary winding;
• control an opening of the high-voltage switch during a phase of transfer of energy from the primary winding to a secondary winding of the coil and during a phase of measurement of an ionization current subsequent to the phase of transfer of energy, wherein said ionization current is generated by ions produced during a process of combustion of a comburent-combustible mixture in a combustion chamber of a cylinder of the internal combustion engine by means of a spark generated by the spark plug in the phase of transfer of energy;
• a bias circuit configured to generate said ionization current during the phase of measurement of the ionization current, wherein said bias circuit is connected in series to a second terminal of the secondary winding;
• an integrating circuit interposed between the bias circuit and a reference voltage;
• wherein said integrating circuit is configured to:
• in a case wherein a pre-ignition of the comburent-combustible mixture in the combustion chamber during the phase of charging occurs, pre-charge during the phase of charging energy into the primary winding by means of a further ionization current flowing through the secondary winding during the phase of charging, so as to measure a value of the integral of the ionization current which flows through the secondary winding during the phase of charging due to said pre-ignition;
• in a case wherein the pre-ignition of the comburent-combustible mixture does not occur, maintain a charge state substantially constant during the phase of charging energy;
• completely discharge by means of the current flowing through the secondary winding during the phase of transfer of energy from the primary winding to the secondary winding;
• wherein the primary winding has a second terminal connected to the high-voltage switch;
• an electronic control unit connected to the driving unit of the electronic control device and comprising an output terminal adapted to generate an ignition signal having a first value indicating a start of the phase of charging the primary winding and having a second value indicating a start of the phase of transfer of energy from the primary winding to the secondary winding,
• and wherein the driving unit is further configured to receive the ignition signal and generate, as a function thereof, a control signal for opening and closing the high-voltage switch,
• wherein the electronic control device further comprises a local control unit connected to the integrating circuit and to the electronic control unit,
• the local control unit comprising:
• a first input terminal adapted to receive the ignition signal;
• a second input terminal adapted to receive an integrating voltage signal representative of the voltage across the integrating circuit;
• an output terminal adapted to generate a combustion monitoring signal carrying, during the phase of transfer of energy, a voltage pulse having a length increasing with the increase of the value of the integrating voltage signal in the phase of charging energy of a previous cycle;
• wherein the electronic control unit further comprises an input terminal adapted to receive the combustion monitoring signal,
• and wherein the electronic control unit is configured to detect a presence of a pre-ignition as a function of a comparison between the length of said voltage pulse and a pre-ignition threshold.

An electronic ignition system to detect a pre-ignition in an internal combustion engine, the system comprising:

• a coil having a primary winding with a first terminal connected to a battery voltage and having a secondary winding with a first terminal connected to a spark plug;
• an electronic control device comprising:
• a high-voltage switch connected in series to the primary winding of the coil and configured to switch between a closed position and an open position;
• a driving unit configured to:
• control a closure of the high-voltage switch during a phase of charging energy into the primary winding;
• control an opening of the high-voltage switch during a phase of transfer of energy from the primary winding to a secondary winding of the coil and during a phase of measurement of an ionization current subsequent to the phase of transfer of energy, wherein said ionization current is generated by ions produced during a process of combustion of a comburent-combustible mixture in a combustion chamber of a cylinder of the internal combustion engine by means of a spark generated by the spark plug in the phase of transfer of energy;
• a bias circuit configured to generate said ionization current during the phase of measurement of the ionization current, wherein said bias circuit is connected in series to a second terminal of the secondary winding;
• an integrating circuit interposed between the bias circuit and a reference voltage;
• wherein said integrating circuit is configured to:
• in a case wherein a pre-ignition of the comburent-combustible mixture in the combustion chamber during the phase of charging occurs, pre-charge during the phase of charging energy into the primary winding by means of a further ionization current flowing through the secondary winding during the phase of charging, so as to measure a value of the integral of the ionization current which flows through the secondary winding during the phase of charging due to said pre-ignition;
• in a case wherein the pre-ignition of the comburent-combustible mixture does not occur, maintain a charge state substantially constant during the phase of charging energy;
• completely discharge by means of the current flowing through the secondary winding during the phase of transfer of energy from the primary winding to the secondary winding;
• wherein the primary winding has a second terminal connected to the high-voltage switch;
• an electronic control unit connected to the driving unit of the electronic control device and comprising an output terminal adapted to generate an ignition signal having a first value indicating a start of the phase of charging the primary winding and having a second value indicating a start of the phase of transfer of energy from the primary winding to the secondary winding,
• wherein the driving unit is further configured to receive the ignition signal and generate, as a function thereof, a control signal for opening and closing the high-voltage switch,
• wherein the electronic control device further comprises:
• a local control unit connected to the integrating circuit and to the electronic control unit;
• a current generator adapted to generate a trigger current controlled by the local control unit;
• wherein the local control unit comprises:
• a first input terminal adapted to receive the ignition signal;
• a second input terminal adapted to receive an integrating voltage signal representative of the voltage across the integrating circuit;
• an output terminal adapted to generate a control signal of the current of said current generator;
• wherein the current generator is configured to generate, during the phase of transfer of energy, a current pulse having two variation edges that define a distance increasing with the increase of the value of the integrating voltage signal in the phase of charging energy of a previous cycle, and wherein the electronic control unit is configured to detect a presence or an absence of a pre-ignition as a function of a comparison between the distance of said current pulse and a pre-ignition threshold.