US 3780343 A
An ignition control system for a vehicle in which a high voltage capacitor is charged from the vehicle battery through a D.C. to D.C. converter and discharged through the ignition coil upon the firing of a silicon controlled rectifier by a pulse generator controlled by the contact breaker of the vehicle distributor.
Claims available in
Description (OCR text may contain errors)
United States Patent Stonham Dec. 18, 1973 [5 IGNITION SUPPORT SYSTEM 3.596,!74 7/1971 Hovenga 315/209 sc  Inventor: Frederick Ryan Stonham, 45 Clarke 3333 33; 51323 -1 Hove, England 3,596,133 7/1971 Warren et al. 315 209 c1) x  Filed: May 12, 1971 Primary ExaminerAlfred L. Brody  Appl 142601 Att0rneyLyon and Lyon  US. Cl 315/211, 123/148 E, 123/148 5, 57 AB TRA 315/209 CR, 315/209 CD D S CT [51 Int. Cl. F02p 1/00, F02p 11/04 An ignition control System for a vehicle in which a 158 Field of Search 315/209, 211, 209 CR, high voltage Capacitor is charged from the vehicle 315/209 23 4 E, 4 s tery through a DC. to DC. converter and discharged 1 through the ignition coil upon the firing of a silicon 5 References Cited controlled rectifier by a pulse generator controlled by UNITED STATES PATENTS the contact breaker of the vehicle distributor.
3,504,658 4/1970 Chavis 315/209 SC 6 Claims, 1 Drawing Figure flaw/I67 flZFA/(EQ //1/ Fwy/ ame,
r --mm5/5 I 112 I l 1 Z cll e l 72/6662 @1, 5 i h g l I PZz/J-M/ l l i @5502 l 7/Z/l7!//fifl1/ 24 79 6 //5 "4744/7272 (wag flair aurfiz/r 5a l 'L. a z par/ w HZ fl/WAC/ZQZ I I FflfflfW/fl/L /a/1//7/04/ l m: EA l i /225 2 572% l I M005 WM M7 6 I 12/ um I t 9 91/ 50% (am/2017 7/ imam/Mm 4 l l 11 11 1 1 1 me meme I mama/v I l l TYLT l 11 2 2 71 J 511/ m jz/pflly f 169/ y AIOEM/IL 544725417 70 IGNITION SUPPORT SYSTEM This invention relates to electronic ignition systems for internal combustion engines and in particular coil ignition systems of the so-called Kettering type.
The Kettering system fails to meet the requirements for high compression high-speed large horsepower engines insofar as the amount of energy delivered to the spark plugs is dependent on the contact breaker points dwell time which naturally decreases as engine speed increases. The situation is further greatly aggravated by the effects of contact bounce" or float and is most marked in six or eight cylinder engines of the competition type. Points maintenance and frequent replacement has to be carried out at quite short intervals with such engines.
By comparison an electronic system offers considerable advantages over the electro-mechanically derived spark.
Several forms of capacitative discharge ignition systems employing silicon controlled rectifiers (S.C.R.s) have been proposed but all have, in general, been too expensive to appeal to a wider market than the competition field. I
The present invention has as its first object the provision of an inexpensive high-performance electronic system compatible with existing coil ignition systems and capable of being converted back to a conventional Kettering system if desired.
The invention also lends itself to association with an all-electronic ignition system wherein the contact breaker is substituted by brush/commutator or pulse generator driven by a magnetic or photo-electric pickoff or other contactless switch.
A further object resides in easily immobilizing the vehicle and rendering it more thief-proof.
A still further object of the invention permits application to vehicles with either positive or negative grounding systems.
According to the invention there is provided an ignition control system comprising an electrical pulse generator arranged to be triggered from an internal combustion engine distributor contact breaker, a unidirectional source of potential comparable with the back E.M.F. generated across the primary of an ignition coil, a means for switching said potential under the control of said pulse generator and a capacitor connected between said unidirectional source and the primary tap of the ignition coil.
An embodiment of the invention will now be described with reference to the accompanying drawing in which the block diagram comprising the single figure shows a pair of contacts 1 which are the contacts of a conventional distributor. A two-position multiple link which can conveniently take the form of an octal plug and socket 2 is situated on the unit, the dashboard or other location accessible to the driver. It will be readily understood that the octal socket is modified by having a second keyway displaced the pin pitch from that provided by the manufacturer. The plug will normally have a cover on which an index mark is engraved to be associated with either of two suitably indicated positions (normal and electronic) on a panel supporting the socket.
Removal of the plug performs the same service as removing the distributor rotor arm from the distributor and enables the vehicle to be immobilized. An even greater immunity to vehicle theft is obtained by removing the capacitor from the distributor and incorporating it as capacitor 4 in the ignition control unit. With the octal ignition selector plug removed it becomes no longer possible to link the battery 6 direct to the lowvoltage terminal of the ignition coil 3 and push-start the vehicle.
In the normal position the ignition coil 3 has its primary circuit extended to one pole of the battery 6 through the ignition switch in the usual way, and likewise the other end of theignition coil primary winding is connected to contact (g) which is joined to contact (c) and extended by a link joining pins 0, and b, in the octal plug to contact (b). The contact (b), which is joined to the contact (e), is connected, to the contact breaker 1. At the same time capacitor 4 is placed across the contact breaker points by the insertion of pin e into contact (f), the plug having a connection linking pins 6 d and pin d in the normal position of the plug in the octal socket being inserted into, contact (e).
In the electronic position of the octal plug in its socket, the contact (a) will connect the input of a pulse generator 5 through the a, b, plug link to contact (11) which is linked to contact (2) and to one point of the contact breaker l. The pulse generator, which is tran sistorized, takes its supply direct from the vehicle battery 6.
The battery 6 also feeds, for the purpose of the electronic ignition mode, a solid-state converter unit 10 of conventional form supplying an output of some 500 volts positive irrespective of whether the negative or positive pole of the battery is grounded. The 500 volt converter output is stabilized by a plurality of neon stabilizers 9 of which one 9a can be employed as an indi cator on the unit panel. A zener diode is another method employed as an alternative to the neons.
Across the output of the converter is a silicon controlled rectifier (SCR) 7 which when triggered puts a low impedance on the 500 volt line and stops the converter. The capacitor 8 which has been charged to 500 volt is simultaneously caused to discharge through the following path to the coil 3 contact (h), a link joining pin it, and g of the plug, and contact (g). Each time the contact breaker 1 opens the pulse generator triggers the SCR 7 causing the capacitor 8 to deliver its charge through the coil 3 from which the usual high tension lead conveys the ignition voltage to the distributor. During the intervals when the pulse generator 5 is not energizing the SCR 7, the capacitor 8 recharges from the converter supply 10 which recommences as soon as the trigger is lifted. Random spikes surplus to the re quired output pulses from the pulse generator 5 are arranged to be suppressed using the 500 volt supply.
There is further taken as an input to pulse generator 5 a portion of the 500 volt supply from the converter 10 as determined by an R.P.M. limiting control 11 to limit the amplitude of the pulses produced by generator 5 in dependence upon the repetition frequency of the pulses. The control 11 may include a potentiometer 1 la which may be set to a speed associated with its control knob to determine a limiting value of R.P.M. by means of which over-reving of the engine is prevented. Typically, the potentiometer setting could determine the magnitude of the voltage applied to a capacitor 5a in the pulse generator 5. By decreasing the maximum value to which such a capacitor 5a could be charged, the time required to develop a voltage thereacross of sufficient amplitude to trigger the SCR 7 would be increased. If the R.P.M. exceeded a certain level, insufficient charging time would be provided between se' quential discharges of the capacitor 5a, with the result that the SCR 7 would not be fired at all and the engine would immediately decrease in speed.
It made presettable and not normally accessible, the potentiometer lla can be set to a value in accordance with the engine manufacturers specified maximum R.P.M. or it can be used to govern down the engine to prevent the vehicle from being driven above a predetermined speed. When fitted to a marine engine a maximum throttle setting can be maintained even though, in a rough sea, the propeller is periodically breaking the surface.
What is claimed is: l. A control system for an ignition system including an ignition coil and a distributor having a steel breaker comprising:
a battery for producing an output voltage; converter means coupled to said battery for producing a voltage substantially higher than that produced by said battery;
capacitor means coupled to said converter means for providing a capacitance and adapted to be charged by said converter means;
controllable means coupled to said converter means and said capacitor means and being controllable for removing said higher voltage from said capacitor means and for causing said capacitor means to discharge through said ignition coil;
pulse generator means for generating trigger pulses and for controlling said controllable means in response to the opening of said contact breaker in said distributor; and
means for controlling the amplitude of the trigger pulses generated by said pulse generator means so as to reduce the amplitude of the trigger pulses with an increase in the repetition frequency of the trigger pulses.
2. The control system of claim 1 wherein said controllable means comprise a silicon controlled rectifier and wherein said pulse generator means applies a trigger pulse to the gate electrode of said silicon controlled rectifier.
3. A control system as in claim 2 wherein said means for controlling the amplitude of the trigger pulses includes a second capacitor, means for regulating the rate of charging of said second capacitor and means for applying the trigger pulses to the gate of said silicon controlled rectifier with the amplitude of the trigger pulses dependent on the voltage attained across said second capacitor.
4. A control system as in claim 3 wherein the means for regulating the rate of charging of the second capacitor is adjustable.
5. A control system as in claim 1, including a removable plug unit through which connections are made from said pulse generator means to said contact breaker and said ignition coil.
6. A control system as in claim 5 including a further capacitor, wherein said removable plug unit is insertable in a second position to form a conventional ignition circuit with said ignition coil, said contact breaker and said further capacitor.