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Plasma ignition system for an internal combustion engine

  • US 4,510,915 A
  • Filed: 09/29/1982
  • Issued: 04/16/1985
  • Est. Priority Date: 10/05/1981
  • Status: Expired due to Fees
First Claim
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1. A plasma ignition system for an internal combustion engine, comprising:

  • (a) a plurality of plasma spark plugs each having a discharge gap between a central electrode and a grounded side electrode, said discharge gap being located in a corresponding engine cylinder;

    (b) a DC-DC converter for boosting a low DC voltage into a high DC voltage;

    (c) a plurality of ignition energy charging means, each having a first diode connected to said DC-DC converter, a first capacitor having a first terminal connected to said first diode and a second terminal connected to ground via a second diode, the first capacitor being charged by the high DC voltage from said DC-DC converter via a series path including said first and second diodes;

    (d) a plurality of reverse blocked triode thyristors, each having an anode connected to the first terminal of said first capacitor and a grounded cathode, each thryistor being selectively turned on so as to discharge the energy stored in the said first capacitor therethrough;

    (e) a plurality of voltage boosting transformers, each having a primary winding and secondary winding and a magnetic core that couples the primary and secondary windings to each other, the magnetic core having a tendency to saturate in response to current resulting from discharges of the first capacitor, first and second ends of said primary winding of each transformer being respctively connected in series with the second terminal of said first capacitor and to ground via a second capacitor having a capacitance value smaller than said first capacitor whereby a damped oscillation is generated in the second capacitor when the capacitive energy is discharged from said first capacitor through said thyristor, first and second ends of said secondary winding being respectively connected in series with the second terminal of said first capacitor and to the central electrode of the corresponding plasma spark plug, whereby the voltage applied to said corresponding primary winding is boosted and the boosted voltage is applied to the corresponding spark plug;

    (f) an ignition trigger signal generator for (1) circularly generating and coupling a trigger signal to a gate of said corresponding thyristor according to a predetermined ignition order of the engine cylinders in response to the engine revolving through a predetermined angle and (2) generating and coupling another pulse signal having a predetermined pulsewidth to said DC-DC converter in synchronization with the ignition trigger signal for halting derivation of the high DC voltage for a period of time determined by said pulsewidth of the pulse signal; and

    (g) a plurality of core-less inductors each connected in series with the secondary winding of said corresponding voltage boosting transformer and the electrodes for restricting an abrupt large discharge current flow through the corresponding plasma spark plug discharge gap so as to extend the ignition energy flow through said gap by the corresponding plasma ignition plug.

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