Ignition device for an internal combustion engine

Claim 1

An ignition system for an internal combustion engine comprising a voltage generator, a capacitor, a charging circuit for said capacitor connecting said voltage generator to said capacitor and including a diode through which said capacitor is charged in use, an ignition coil having first and second primary windings on which the second primary winding has a greater impedance than the first primary winding, and a secondary winding, a spark plug having its electrodes connected across the secondary winding, a thyristor connecting said capacitor to the first primary winding so that the secondary winding has induced therein a high voltage signal each time said thyristor is triggered, said high voltage signal being of short duration and having a rapid rise front and creating an electric spark between the electrodes of the spark plug, a timing circuit operating in synchronism with rotation of the internal combustion engine to trigger said thyristor, and an auxiliary circuit connected across said second primary winding and including a further capacitor, a charging circuit for said further capacitor and means controlling discharge of saiD further capacitor through the second primary winding for prolonging the arc created between the electrodes of said spark plug on triggering of the thyristor, and wherein said means for controlling the discharge of the capacitor through the second primary winding comprises a further thyristor connected for triggering by said timing circuit simultaneously with the triggering of the first mentioned thyristor.