Capacitor discharge ignition system

In a capacitor discharge ignition system comprising an ignition transformer having a low voltage primary winding and a high voltage secondary winding adapted to be coupled in sequence at predetermined times to a plurality of spark devices, means for generating a pulse at said predetermined times, a source of direct current potential, an AC power capacitor coupled in series with said primary winding across said source and being charged thereby, gate means for short-circuiting said source in response to a control signal whereby said power capacitor discharges through said primary winding, and control means for providing a said control signal in response to each said pulse;

• the improvement comprising an AC ringing capacitor directly connected across said primary winding and proportioned to provide a damped oscillatory current therein when said gate means removes said short circuit thereby clamping the peak induced voltage in said secondary winding to a low predetermined value to inhibit misfiring;
• a clamp diode coupling the midpoint between said power capacitor and primary winding to a source of reference potential lower than said first-named source, said diode being polarized for current flow toward said reference and cooperating with said ringing capacitor to provide a DC high voltage spark at said device;
• and switch means for selectively disconnecting said diode from said reference source.

In a capacitor discharge ignition system comprising an ignition transformer having a low voltage primary winding and a high voltage secondary winding adapted to be coupled in sequence at predetermined times to a plurality of spark devices, means for generating a pulse at said predetermined times, a source of direct current potential, an AC power capacitor coupled in series with said primary winding across said source and being charged thereby, gate means for short-circuiting said source in response to a control signal whereby said power capacitor discharges through said primary winding, and control means for providing a said control signal in response to each said pulse;

• the improvement comprising an AC ringing capacitor directly connected across said primary winding and proportioned to provide a damped oscillatory current therein when said gate means removes said short circuit thereby clamping the peak induced voltage in said secondary winding to a low predetermined value to inhibit misfiring;
• said direct current source including a DC to AC inverter having an output circuit, and a rectifier coupled to said output circuit, and further comprising another AC capacitor smaller than said power capacitor series-connected in said output circuit for inhibiting stopping of the oscillation of said inverter by said gate means being turned ON;
• switch means for selectively short-circuiting said other capacitor;
• a diode coupled to the midpoint between said power capacitor and primary winding, second switch means for selectively coupling said diode to first and second sources of reference potential both lower than said first-named source and one lower than the other, said diode being polarized for current flow toward said reference sources thereby to provide a DC high voltage spark at said device, said second switch means being adapted selectively to disconnect said diode from said reference sources, and third switch means for selectively disconnecting said power capacitor from said primary winding and for coupling the same and said contacts in series across another source of direct current potential thereby alternatively to provide a Kettering ignition system.

In a capacitor discharge ignition system comprising an ignition transformer having a low voltage primary winding and a high voltage secondary winding adapted to be coupled in sequence at predetermined times to a plurality of spark devices, means for generating a pulse at said predetermined times, a source of direct current potential, an AC power capacitor coupled in series with said primary winding across said source and being charged thereby, gate means for short-circuiting said source in response to a control signal whereby said power capacitor discharge through said primary winding, and control means for providing a said control signal in response to each said pulse;

• the improvement comprising an AC ringing capacitor directly connected across said primary winding and proportioned to provide a damped oscillatory current therein when said gate means removes said short circuit thereby clamping the peak induced voltage in said secondary winding to a low predetermined value to inhibit misfiring;
• said pulse generating means including breaker contacts adapted to be opened at said predetermined times, said control means comprising a clamping circuit for providing a turn-on pulse for said gate means at only one predetermined instant in response to opening said breaker contacts, said clamping circuit including an inductor having a winding coupled in series with said breaker contacts across another source of direct current potential, and a bi-directional clamp comprising two oppositely polarized diodes connected in parallel across said inductor winding and said breaker contacts, and means coupling said clamping circuit to said gate means for applying said pulses thereto.