US3809044A - Capacitor triggered ignition system - Google Patents

Abstract

Disclosed herein is an ignition circuit ignition for an internal combustion engine, which circuit comprises a charge capacitor connected to the positive and negative terminals of a source of direct current generated in response to engine rotation, and an SCR connected to the charge capacitor in series with each other and in parallel with respect to the source and including an anode connected to the positive terminal, and a cathode connected to the negative terminal, and a gate, together with means for triggering the gate to discharge the charge capacitor including connection of the positive terminal to ground, a mechanical switch having a first grounded contact and a second contact electrically connectable to said first contact in response to engine rotation, and a trigger capacitor connected to the second switch and to the gate, whereby upon closing of the switch contacts, the charge capacitor is partially discharged through the contacts and through the trigger capacitor to trigger the gate, whereby to fully discharge the charge capacitor through the primary winding of an ignition coil connected in series with the SCR and the charge capacitor.

Description

United States Patent [191 Jereb et a1.

3,809,044 May 7, 1974 CAPACITOR TRIGGERED IGNITION SYSTEM Outboard Marine Corporation, Waukegan, Ill.

[22] Filed: Jan. 22, 1971 [21] Appl. No.: 108,887

[73] Assignee:

[52] US. Cl. 123/148 E, 123/148 MCD [51] Int. Cl. F02a l/00 [58] Field of Search 123/148 E [56] References Cited UNITED STATES PATENTS 3,045,148 7/1962 McNulty 123/148 E 3,461,851 8/1969 Stephens 123/148 E 3,563,221 2/1971 Tada 123/148 E 3,516,396 6/1970 Lawson r 123/148 E 3,529,587 9/1970 Sasayama... 123/148 E 3,418,988 12/1968 Lewis 123/148 E 3,312,860 4/1967 Strum..... 123/148 E 3,357,415 3/1968 Huntzinger 123/148 3,461,345 8/1969 Gilbert 123/148 3,213,840 10/1965 Corfield 123/148 OTHER PUBLICATIONS SAE Journal, pp. 74-78, McClelland and Z011, July 1963. Popular Electronics, 11/66, pp. 53-57, 100, Gellman.

Primary Examiner-Laurence M. Goodridge Assistant ExaminerRonald B. Cox Attorney, Agent, or Firm- Michael, Best & Friedrich [57] ABSTRACT Disclosed herein is an ignition circuit ignition for an internal combustion engine, which circuit comprises a charge capacitor connected to the positive and h5 5 tive terminals of a source of direct current generated in response to engine rotation, and an SCR connected to the charge capacitor in series with each other and in parallel with respect to the source and including an anode connected to the positive terminal, and a cathode connected to the negative terminal, and a gate, together with means for triggering the gate to discharge the charge capacitor including connection of the positive terminal to ground, a mechanical switch having a first grounded contact and a second contact electrically connectable to said first contact in response tolengine rotation, and a trigger capacitor connected to the second switch and to the gate, whereby upon closing of theswitch contacts, the charge capacitor is partially discharged through the contacts and vthrough the trigger capacitor to trigger the gate,

whereby to fully discharge the charge capacitor through the primary winding of an ignition coil con- 12 Claims, 2 Drawing Figures BACKGROUND OF INVENTION pacitor discharge ignition systems which are triggered by mechanical switches or breakers in response to engine rotation.

SUMMARY OF INVENTION The invention provides a capacitor discharge ignition circuit including solid-state switch means for discharging a charge capacitor to fire a spark plug or other ignition device, which switch means is triggered to discharge the charge capacitor by means including a mechanical switch operable in response to engine rotation and by employing a portion of the charge on the charge capacitor to turn on the solid-state switch means upon closure of the mechanical switch.

While the invention can be employed in connection with a single cylinder engine, the inventionis also applicable to multi-cylinder engines when using a single solid-state switch means and a distributor. In addition, the invention has particular utility in connection with multi-cylinder engines wherein the capacitor discharge ignition circuit includes separate switch controlledsparking sub-circuits for each cylinder and a separate mechanically operated trigger sub-circuit for each switch controlled-sparking sub-circuit.

One of the features of the invention resides in the use of a charge capacitor to perform the dual functions of providing the primary voltage to cause spark ignition, as well as of providing the potential, in response to mechanical switch closure, to trigger the solid-state switch.

Another feature of the invention resides in the provision of a relatively low current flow through the mechanical switch contacts to effect triggering of the solid-state switch means.

One of the principal objects of the invention is the provision of a capacitor discharge ignition circuit controlled by a mechanical switch, which circuit can be employed in a single or multi-cylinder engine.

Another of the principal objects of the invention is .the provision of a capacitor discharge ignition system in which spark producing discharge of the charge capacitor is triggered by a portion of the charge on the charge capacitor in response to closure of a mechanical switch operative in response to engine rotation.

Another object of the invention is the provision of a new and improved mechanical switch controlled capacitor discharge ignition system which is modest in cost and which will provide a long and useful life.

Other objects and advantages of the invention will become known by reference to the following description and accompanying drawings.

DRAWINGS P16. 1 is a schematic diagram of one ignition circuit embodying various of the features of the invention.

FIG. 2 is a schematic diagram of a second ignition circuit embodying various of the features of the invention.

GENERAL DESCRIPTION Shown in H0. 1 of the drawings is a capacitor discharge ignition circuit 11 which includes various of the features of the invention. The circuit 11 includes means for charging a charge capacitor 31 and for maintaining the charge on the charge capacitor in the absence of a completed discharge path. More specifically, such charging and charge maintenance means preferably includes asource 13 of direct current including positive and negative terminals 17 and 19, respectively and means for preventing current flow counter to the current flow. While various arrangements are possible, in the construction disclosed in FIG. 1, thesource 13 includes a permanent magnet alternator 21 (shown schematically as including a coil 22) which is connected to a full-wave rectifyingbridge 23 including the positive and negative terminals 17 and 19, respectively, and a plurality ofdiodes 27 which serve to rectify the current produced by the alternator, as well as to maintain the charge on the capacitor 31 by preventing reverse current flow.

The charge capacitor 31 is connected to the positive and negative terminals 17 and 19 of the directcurrent source 13. Also connected to the positive and negative terminals of the directcurrent voltage source 13, in parallel relation to the charge capacitor 31, is afirst ignition sub-circuit 33 including a primary ignition coil winding 37 connected in series with an electronic solidstate, semi-conductor switch means 41 which preferably has a predetermined switch over voltage to change the operative state. The primary ignition coil winding 37 is also connected to a secondary ignition coil winding 43 which, in turn, is connected to asparking device 47, such as a spark plug.

While other solid-state switches could possibly be employed, in the disclosed construction, the switch means 41 comprises a silicon control rectifier including an anode 51 connected through the primary ignition coil winding 37 to the positive terminal 17 of thefullwave rectifying bridge 23, or other direct current source, together with a cathode 53 which is connected to the negative terminal 19 of the full-wave rectifyingbridge 23 or other direct current source. Thesilicon control rectifier 41 further includes agate 57 which is connected to a first triggeringsub-circuit 61 which forms a part of thefirst ignition sub-circuit 33.

The first triggeringsub-circuit 61 includes atriggering capacitor 63 having afirst plate 67 connected to thegate 57 and asecond plate 69 connected to onecontact 71 of a cam driven mechanical switch orbreaker 73 which includes asecond contact 77 connected to a common potential orground 79 and which is operated to open and close thecontacts 71 and 77 in response to rotation of a shaft (not shown) driven in synchronism with engine operation. The first triggeringsubcircuit 61 further includes adiode 81 having ananode 83 connected to thesecond plate 69 of thetriggering capacitor 63 and having acathode 87 connected toground 79. 7

in order to charge the triggeringcapacitor 63 when the switch contacts 71 and 77. are closed and in order to afford reverse flow from the triggeringcapacitor 63 after triggering of the SCR 4], the positive terminal 17 of the directcurrent voltage source 13 is also connected toground 79.

In order to eliminate possible triggering of theSCR 41, in response to possible generation of radio frequency signals by the collapsing fields of the ignition coil, acapacitor 89 is provided between thegate 57 and the cathode 53 of theSCR 41.

When the disclosed arrangement is employed in connection with a multi-cylinder engine, additional ignition sub-circuits can be connected to the positive and negative terminals 17 and 19 of the directcurrent voltage source 13 in lieu of the use of a distributor. Thus, the circuit 1 1 shown in FIG. 1 is especially designed for use in connection with a two-cylinder engine, and asecond ignition sub-circuit 91 is connected to the positive and negative terminals 17 and 19, respectively, of the directcurrent voltage source 13. Thesecond ignition sub-circuit 91 is identical to thefirst ignition subcircuit 33 and, as can be seen in the drawings, is connected in parallel therewith.

In order to eliminate cross firing of the cylinders, each of theignition sub-circuits 31 and 91 further includes afiltering capacitor 93 and a resistor 97 which are connected in series and which, as a unit, are connected in parallel with the anode 51 and cathode 53 of thesemi-conductor switch 41.

In order to permit grounding of the circuit 11 and thereby prevent engine ignition operation, the negative terminal 19 of the direct current voltage source is connected through aresistor 99 to a manually or otherwise operatedignition control switch 101 connected toground 79. When theswitch 101 is closed, the circuit is inoperable to effect ignition. However, upon opening of theswitch 101, the circuit 11 is effective to effect operative engine ignition.

In operation, rotation of the engine causes charging of the charge capacitor 31 when themechanical switches 73 are open. When it is desired to produce a spark at the ignition device, theassociated switch 73 is closed. As a consequence, a portion of the charge on the charge capacitor 31 causes the triggeringcapacitor 63 to be charged due to the closed condition of theswitch 73 and due to an effective electrical connection caused by the common grounded condition of theswitch contact 77 and the positive terminal 17 of the directcurrent voltage source 13. Suchcharging of the triggeringcapacitor 63 produces a very fast pulse of proper potential at thegate 57 of theSCR 41, thereby switching the SCR to the on condition. The remaining charge on thecharge capacitor 41 is now conducted through theprimary winding 37 of the ignition coil and back through the full-wave rectifier 23, thereby also ringing out or damping reverse current flow. Discharge of the charge capacitor 31 through the primary ignition coil winding 37 sets up a high voltage potential in thesecondary winding 43 to cause the generation of a spark at thespark plug 47.

After the-charge on the charge coil 31 has been depleted and thespark plug 47 consequently discharged, theswitch 73 then opens and the charge previously applied to theplate 69 of the triggeringcapacitor 63 is discharged through thediode 81. In this regard, the discharge path for the triggeringcathode 63 is through thediode 81 and through the connection effected by thecommon ground 79 back to the charge capacitor 31. Reverse current pulsations associated with the triggeringcapacitor 63 are damped by thediode 81. At the appropriate time, the switch contacts for thesecond ignition sub-circuit 91 are closed and then opened to produce similar sparking by thesecond ignition sub-circuit 91.

Shown in FIG. 2 is another capacitordischarge ignition circuit 105 which embodies various of the features of the invention. Except as will be described, thecircuit 105 is generally the same as the circuit 11 shown in FIG. 1 and common reference numerals have been applied to common components.

In regard tothe differences between theignition circuits 105 and 11, instead of using the full-wave rectifyingbridge 23 shown in FIG. 1 to provide unidirectional or direct current to the charge capacitor 31, in the construction shown in FIG. 2, the source of direct current including a winding orcoil 22 which is connected, at

one end orterminal 106, through alead 107 toground 79 and to the grounded or positive plate of the charge capacitor 31. The source of direct current also includes means for restricting current to unidirectional flow including connection of the other end orterminal 108 of thecoil 22 through adiode 109 to the other plate of the charge capacitor 31 and the connection of a diode 1 11 in parallel with the charge capacitor 31 across the ends or terminals of thecoil 22..Thus, as a result of the use oftheme diodes 109 and 111, as shown in FIG. 2, the charge capacitor 31 is subject to unidirectional current.

Thecircuit 105 also differs from the circuit 11 in that thediodes 81 are replaced byresistors 113 which are connected in parallel with thetrigger capacitors 63 and which serve to bleed off excess charge and to damp oscillation.

Still further, thecircuit 105 shown in FIG. 2 differs from the circuit 11, shown in FIG. 1, by the elimination of thefiltering capacitors 93 and the resistors 97.

Because of the above enumerated differences, thecircuit 105 is considerably more economical than the circuit 11, which economy is achieved without decrease in operational effectiveness.

Typical values of various of the components employed in the FIG. 2 embodiment are as follows:

Coil 22 5,000 Turns No. 37 Wire Charge Capacitor 31 1 micro farads'Capacitors 63 and 89 0.002micro farads Diode 109 2,000 Peak inverse voltage Diode 111 600 Peakinverse voltage Resistors 99 ohms, Awatt Resistors 113 10 meg ohms, )4 watt I Operation of the circuit shown in FIG. 2 is substantially the same as that described with respect to the circuit 1 1 of FIG. 1 in that triggering of the SCR occurs in response to closure of theswitches 73.

The disclosed arrangements including use of the triggering capacitor eliminates multiple triggering of the solid-state switch due to possible bouncing engagement of the mechanical switch contacts. In addition, use of a portion of the charge on the charge capacitor to trigger the gate of the SCR and particularly the relatively low current flow produced thereby allows the mechanical switch contacts to be closed for a substantial period of time so that an anti-reverse cam can be used to prevent the engine from running backwards. In addition, the current pulse at the gate rises quickly as the mechanical switch contacts are closed and provides a trigger signal which is precise and of short duration.

It is to be especially noted that in the disclosed constructions, the charge coil serves the dual function of providing the primary ignition voltage which serves to produce engine sparking and consequent engine operation, as well as the voltage which charges the triggering capacitor which, in turn, turns on the solid-state switch.

Various of the features of the invention are set forth in the following claims.

What is claimed is: t

1. An ignition circuit for an internal combustion engine, said circuit comprising a charge capacitorincluding opposed plates, means for charging said charge capacitor and for maintaining the charge on said charge capacitor in the absence of the completion of a discharge path, saidcharging and charge maintenance means comprising a source of direct current including a negative terminal connected to one of said charge capacitor plates and a grounded positive terminal connected to the other of said charge capacitor plates, an ignition sub-circuit including an ignition coil and solidstate switch means connected in series with each other and in parallel with said charge capacitor, said solidstate switch means including an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, and a triggering sub-circuit including means for triggering said switch means to complete said ignition sub-circuit so as to discharge said charge capacitor through said ignition coil and comprising a switch having a first contact connected to ground and a second contact electrically connectable with said first contact in response to engine rotation, and a triggering capacitor having a first plate connected to said second contact and a second plate connected to said gate, whereby upon closing of said switch contacts to complete said triggering sub-circuit, said charge capacitor is partially discharged through said switch contacts and through said triggering capacitor to trigger said solid-state switch means, whereby to fully discharge said charge capacitor.

2. An ignition circuit in accordance with claim 1 wherein said source of direct current includes a permanent magnet alternator including a coil and a full-wave rectifying bridge connected to said coil and including said first and second terminals.

3. An ignition circuit in accordance with claim 1 wherein said source of direct current includes a coil which generates voltage in response to rotation of a magnet, and means connected to said coil and to said charge capacitor for restricting current to unidirectional flow.

4. An ignition circuit in accordance with claim 1 and further including a diode having an anode connected to said first plate of said triggering capacitor and a cathode connected to ground.

5. An ignition circuit in accordance with claim 1 and further including a resistor connected in parallel with said triggering capacitor.

6. An ignition circuit in accordance with claim 1 including a capacitor connected across said gate and said cathode.

7. An ignition circuit in accordance with claim 1 and further including a grounding switch connected to said negative terminal.

8. An ignition circuit comprising a charge capacitor including opposed plates, means for charging said charge capacitor and for maintaining the charge on said charge capacitor in the absence of the completion of a discharge path, said charging and charge maintenance means comprising a source of direct current including a negative terminal connected to one of said charge capacitor plates and a grounded positive terminal connected to the other of said charge capacitor plates, first and second ignition sub-circuits connected across said terminals and in parallel with said charge capacitor, each of said ignition sub-circuits including an SCR having an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, and an ignition coil primary winding connected in series with one, of said anode and said cathode, and a gate triggering sub-circuit for completing at least one of said ignition sub-circuits and comprising a switch having a first contact connected to ground and a second contact, and a triggering capacitor having a first plate connected to said second contact and a second plate connected to said gate, whereby upon closing of said switch contacts to complete said triggering subcircuit, said charge capacitor is partially discharged through said switch contacts and through said triggering capacitor to trigger said gate, whereby to fully discharge said charge capacitor through said primary winding.

9. An ignition circuit for an internal combustion engine, said circuit comprising a spark device, a permanent magnet alternator, a full-wave rectifying bridge connected to said alternator and having a positive terminal connected to ground and a negative terminal, a charge capacitor having plates respectively connected to said terminals, a series connected ignition primary coil and SCR connected to said terminals in parallel relation to said charge capacitor, said SCR having an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, a secondary ignition coil connected to said primary coil and to said spark device, a second capacitor having a first plate connected to said gate and a second plate, a switch including a first contact connected to ground and a second contact connected to said second plate of said second capacitor, said switch being operable to open and close said contacts in response to engine rotation, and a diode having an anode connected to said second plate of said second capacitor and a cathode connected to ground.

10. An ignition circuit for an internal combustion engine, said circuit comprising a sparkdevice, a permanent magnet alternator, a full-waveirectifying bridge connected to said alternator andhaving a positive terminal connected to ground and a negative terminal, a charge capacitor having plates respectively connected to said terminals, an ignition sub-circuit including an SCR having an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, an ignition primary coil connected in series with one of said anode and said cathode, and a secondary ignition coil connected to said primary coil and to said spark device, and a triggering sub-circuit including a second capacitor having a first plate connected to said gate and a second plate, and a switch including a first contact connected to ground and a second contact con nected to said second plate of said second capacitor, said switch being operable to open and close said contacts in response to engine rotation.

11. An ignition circuit for an internal combustion engine, said circuit comprising a source of direct current including a negative terminal and a grounded positive terminal, a charge capacitor connected across said terminals, solid-state switch means connected across said terminals and in parallel with said charge capacitor, and including an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, and means for triggering said switch means to discharge said charge capacitor comprising a switch having a first contact connected to ground and a second contact electrically connectable with said first contact in response to engine rotation, and a triggering capacitor having a first plate connected to said second contact and a second plate connected to said gate, whereby upon closing of said switch contacts, said charge capacitor is partially discharged through said switch contacts and through said triggering capacitor to trigger said solid-state switch means, whereby to fully discharge said charge capacitor.

12. An ignition circuit comprising a source of direct current including a negative terminal and a grounded positive terminai, a charge capacitor connected to said terminals, and first and second ignition sub-circuits connected across said terminals and in parallel with said charge capacitor, each of said ignition sub-circuits including an SCR having an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, an ignition coil primary winding connected across said terminals in series with one of said anode and said cathode, and a gate triggering subcircuit comprising a switch having a first contact connected to ground and a second contact, and a triggering capacitor having a first plate connected to said second contact and a second plate connected to said gate, whereby upon closing of said switch contacts, said charge capacitor is partially discharged through said switch contacts and through said triggering capacitor to trigger said gate, whereby to fully discharge said charge primary winding.

capacitor through said Patent No. 3,809 a 044 I I Dated y 7 a 1974 Inventor(s Richard F. Jereb, Philip A. Anderson It is certifiedvthat error anpears in the shove-identified patent and that said Letters Patent -are' hereby corrected as shown: below:

In the Abstract:

line 1: I I l delete "ignition" second occurrencej I line l6 I l I delete "switch", insert contact Column 2, lines 11-13 delete "and means for preventing 7 current flow counter to the current flow" Y Column 4 line l4 I I delete "including", insert Column 4, line 15 before "ground", insert a positive terminal 110 which is connected to Column A, line 18 r I before '"means", insert rectifying Column 4, line 20 after, "to", insert a negative terminal 112 which is connected to Column 5, line 42 delete "first and second" and I insert negative and positive--- Signed and sealed this 22nd day of October 1974.

L (SEAL) I i I I .J

Attest M COY M. GIBSON 3R. I c. MARSHALL DANN Attesting' Officer v Commissioner of Patents

Claims (12)

1. An ignition circuit for an internal combustion engine, said circuit comprising a charge capacitor including opposed plates, means for charging said charge capacitor and for maintaining the charge on said charge capacitor in the absence of the complEtion of a discharge path, said charging and charge maintenance means comprising a source of direct current including a negative terminal connected to one of said charge capacitor plates and a grounded positive terminal connected to the other of said charge capacitor plates, an ignition sub-circuit including an ignition coil and solid-state switch means connected in series with each other and in parallel with said charge capacitor, said solidstate switch means including an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, and a triggering sub-circuit including means for triggering said switch means to complete said ignition sub-circuit so as to discharge said charge capacitor through said ignition coil and comprising a switch having a first contact connected to ground and a second contact electrically connectable with said first contact in response to engine rotation, and a triggering capacitor having a first plate connected to said second contact and a second plate connected to said gate, whereby upon closing of said switch contacts to complete said triggering sub-circuit, said charge capacitor is partially discharged through said switch contacts and through said triggering capacitor to trigger said solid-state switch means, whereby to fully discharge said charge capacitor.

2. An ignition circuit in accordance with claim 1 wherein said source of direct current includes a permanent magnet alternator including a coil and a full-wave rectifying bridge connected to said coil and including said first and second terminals.

3. An ignition circuit in accordance with claim 1 wherein said source of direct current includes a coil which generates voltage in response to rotation of a magnet, and means connected to said coil and to said charge capacitor for restricting current to unidirectional flow.

4. An ignition circuit in accordance with claim 1 and further including a diode having an anode connected to said first plate of said triggering capacitor and a cathode connected to ground.

5. An ignition circuit in accordance with claim 1 and further including a resistor connected in parallel with said triggering capacitor.

6. An ignition circuit in accordance with claim 1 including a capacitor connected across said gate and said cathode.

7. An ignition circuit in accordance with claim 1 and further including a grounding switch connected to said negative terminal.

8. An ignition circuit comprising a charge capacitor including opposed plates, means for charging said charge capacitor and for maintaining the charge on said charge capacitor in the absence of the completion of a discharge path, said charging and charge maintenance means comprising a source of direct current including a negative terminal connected to one of said charge capacitor plates and a grounded positive terminal connected to the other of said charge capacitor plates, first and second ignition sub-circuits connected across said terminals and in parallel with said charge capacitor, each of said ignition sub-circuits including an SCR having an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, and an ignition coil primary winding connected in series with one of said anode and said cathode, and a gate triggering sub-circuit for completing at least one of said ignition sub-circuits and comprising a switch having a first contact connected to ground and a second contact, and a triggering capacitor having a first plate connected to said second contact and a second plate connected to said gate, whereby upon closing of said switch contacts to complete said triggering sub-circuit, said charge capacitor is partially discharged through said switch contacts and through said triggering capacitor to trigger said gate, whereby to fully discharge said charge capacitor through said primary winding.

9. An ignition circuit for an internal combustion engine, said circuit comprising a spark device, a permanent magnet aLternator, a full-wave rectifying bridge connected to said alternator and having a positive terminal connected to ground and a negative terminal, a charge capacitor having plates respectively connected to said terminals, a series connected ignition primary coil and SCR connected to said terminals in parallel relation to said charge capacitor, said SCR having an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, a secondary ignition coil connected to said primary coil and to said spark device, a second capacitor having a first plate connected to said gate and a second plate, a switch including a first contact connected to ground and a second contact connected to said second plate of said second capacitor, said switch being operable to open and close said contacts in response to engine rotation, and a diode having an anode connected to said second plate of said second capacitor and a cathode connected to ground.

10. An ignition circuit for an internal combustion engine, said circuit comprising a spark device, a permanent magnet alternator, a full-wave rectifying bridge connected to said alternator and having a positive terminal connected to ground and a negative terminal, a charge capacitor having plates respectively connected to said terminals, an ignition sub-circuit including an SCR having an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, an ignition primary coil connected in series with one of said anode and said cathode, and a secondary ignition coil connected to said primary coil and to said spark device, and a triggering sub-circuit including a second capacitor having a first plate connected to said gate and a second plate, and a switch including a first contact connected to ground and a second contact connected to said second plate of said second capacitor, said switch being operable to open and close said contacts in response to engine rotation.

11. An ignition circuit for an internal combustion engine, said circuit comprising a source of direct current including a negative terminal and a grounded positive terminal, a charge capacitor connected across said terminals, solid-state switch means connected across said terminals and in parallel with said charge capacitor, and including an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, and means for triggering said switch means to discharge said charge capacitor comprising a switch having a first contact connected to ground and a second contact electrically connectable with said first contact in response to engine rotation, and a triggering capacitor having a first plate connected to said second contact and a second plate connected to said gate, whereby upon closing of said switch contacts, said charge capacitor is partially discharged through said switch contacts and through said triggering capacitor to trigger said solid-state switch means, whereby to fully discharge said charge capacitor.

12. An ignition circuit comprising a source of direct current including a negative terminal and a grounded positive terminal, a charge capacitor connected to said terminals, and first and second ignition sub-circuits connected across said terminals and in parallel with said charge capacitor, each of said ignition sub-circuits including an SCR having an anode connected to said positive terminal, a cathode connected to said negative terminal, and a gate, an ignition coil primary winding connected across said terminals in series with one of said anode and said cathode, and a gate triggering sub-circuit comprising a switch having a first contact connected to ground and a second contact, and a triggering capacitor having a first plate connected to said second contact and a second plate connected to said gate, whereby upon closing of said switch contacts, said charge capacitor is partially discharged through said switch contacts and through said triggering capacitor to triggeR said gate, whereby to fully discharge said charge capacitor through said primary winding.

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