Oven-rotation prevention method and circuit in the non-contact type ignition circuit for the internal combustion engine

Claim 2

An overrotation prevention circuit in a non-contact ignition circuit for an internal combustion engine, comprising: an ignition coil, the secondary winding of said ignition coil being connected to a spark gap, the primary winding of said ignition coil when having a forward voltage induced therein, carrying a current which flows when a first gated thyristor is non-conducting, said current flowing through a transistor connected by its emitter and collector across said primary winding, and said current and said transistor are cut off to cause a spark at said gap when said first gated thyristor is caused to conduct; a capacitor being connected in a undirectional charging circuit across said primary winding, said capacitor being charged when said primary winding has an inverse voltage induced therein; a discharge circuit for discharging said capacitor after said charging, said discharging current causing said first thyristor to continue in a non-conducting state, whereby sparking at said gap is delayed; a switching circuit, said switching circuit causing said capacitor to discharge when the rotation rate of said engine exceeds a selected limit.

Claim 3

The overrotation prevention circuit of claim 1 wherein said discharging current directly causes the gate-to-cathode voltage of said first thyristor to decrease thereby preventing conduction of said first thyristor during discharge.

Claim 4

The overrotation circuit of claim 1, and further comprising: a first resistor connected between said collector and the transistor base, and said first thyristor is inserted between said transistor base and said emitter with the first thyristor anode connected to said transistor base; a first thyristor gate circuit comprised of resistive elements and a diode, said gate circuit connected in parallel across said primary winding and one of said resistive elements being connected between said gate and said cathode of said first thyristor, said diode poled to flow current toward said cathode of said first thyristor; and a second resistor is inserted between said capacitor and the gate of said first thyristor, whereby an RC discharge circuit is provided to determine the duration of said delay in sparking; and a second gated thyristor in said switching circuit, and said capacitor discharges through the load terminals of said second thyristor and said discharge circuit when said second thyristor conducts; and a zener diode between the anode and gate of said second gated thyristor, the cathode of said zener diode and one terminal of said capacitor connected to the anode of said second thyristor; and a second resistor connected between the gate and cathode of said second gated thyristor; the cathodes of said first and second thyristors being connected together; and a second diode connected across said second thyristor, the cathode of said second diode being connected to the anode of said second thyristor and to said one terminal of said capacitor, and a third diode connected by its anode to the other terminal of said capacitor, said second and third diodes in series with said capacitor being connected across said primary winding to form said unidirectional charging circuit; and a third diode connected between the gate and cathode of said first thyristor, said gate connecting to the cathode of said third diode.

Claim 5

The overrotation circuit of claim 1, and further comprising: a first resistor connected between said collector and the transistor base, and said first thyristor is inserted between said transistor base and said emitter with the first thyristor anode connected to said transistor base; a first thyristor gate circuit comprised of resistive elements and a diode, said gate circuit connected in parallel across said primary winding and one of said resistive elements being connected between said gate and said cathode of said first thyristor, and one of said resistive elements being variable, said diode poled to flow current toward said cathode of said first thyristor; whereby the trigger time of said first thyristor is selected by the setting of said variable resistive element.

Claim 6

The overrotation prevention circuit of claim 4 wherein a second resistor is inserted between said capacitor and the gate of said first thyristor, whereby said discharge circuit is an RC circuit to determine the duration of said delay in sparking.

Claim 7

The overrotation prevention circuit of claim 5 wherein: said switching circuit includes a second gated thyristor having a gate circuit comprising a coil with a variable resistor across its terminals, the anode of said second thyristor being connected to one terminal of said capacitor, the cathodes of said first and second thyristors being connected together to one end of said coil, and the gate of said second thyristor being connected to the sliding terminal of said variable resistor; and wherein a second diode is connected across said second thyristor, the cathode of said second diode being connected to the anode of said second thyristor and to said one terminal of said capacitor, and a third diode connected by its anode to the other terminal of said capacitor, said second and third diodes in series with said capacitor being connected across said primary winding to form said unidirectional charging circuit; and wherein a third diode is connected between the gate and cathode of said first thyristor, said gate connecting to the cathode of said third diode.

Claim 8

The overrotation prevention circuit of claim 1 wherein said switching circuit includes a second gated thyristor and said capacitor discharges through the load terminals of said second thyristor and said discharge circuit when said second thyristor conducts.

Claim 9

The overrotation prevention circuit of claim 7 and further comprising: a zener diode between the anode and gate of said second gated thyristor, the cathode of said zener diode and said capacitor connected to the anode of said second thyristor; and a first resistor connected between the gate and cathode of said second gated thyristor, whereby at a condition of overrotation of said engine, the charge stored in said capacitor causes said zener diode to breakdown and conduct current through said resistor, triggering said second thyrister to discharge said capacitor and delay the spark at said gap.

Claim 10

The overrotation prevention circuit of claim 1 wherein the charge stored in said capacitor during said inverse voltage increases as said rotation rate of said engine increases, and the time for discharging said capacitor remains constant, whereby said spark is delayed over a greater angle of engine rotation as said engine overrotation rate increases.