US2940014A

US2940014A - Electronic ignition system

Info

Publication number: US2940014A
Authority: US
Publication date: 1960-06-07
Anticipated expiration: 1977-06-07

Description

June 7, 1960 A. c. LEGEAY ETAL 2,940,014

ELECTRONIC IGNITION SYSTEM Filed June 28, 1955 TJC'J.

Z/ 20 07 6a k we ATTORNEY United States Patent ELECTRONIC IGNITION SYSTEM Andre Camille Legeay, Paris, and .Jean Emilien Chauvineau, 'Lozere, France, assignors toF. Alexander, New York, N.Y.

Filed June 28, 1955, Ser. No.518,434

6 Claims. (Cl. 315-209) The present invention relates to electronic ignition systems for use in internal combustion engines and the like, including reciprocating engines, gas turbines, jet and turbo-'jet engines, and the like prime movers or motors utilizing an explosive or inflammable fluid or gaseous mixture as operating filel.

Among the more general objects of the invention is the provision-of an improved ignition system which will enable a more exact timing and more .eflicient ignition andcombustion and which furthermore provides a new and more eflicient methodof firing the explosive mixture in the cylinder or combustion chamber of an internal combustion engine.

Among the more specific objects of the invention -is the provision of a new and improved ignition system which will reduce or 'eliminatesparking orarcingbetween the ignition control contacts, frequently occurring in conventional ignition systems as a result of fouling or disabling of one or more spark gaps, and other defects.

Another object is to reduce the wear on the igition control or distributor contacts by the elimination of any interrupting currents between the contacts.

Still a further object is the provision of an ignition device of light weight and reduced bulk which can be readily substituted for the conventional igintion coil and condenser as used in standard engines,'such as for motorcars, etc., substantially without requiring any essential change in .the circuit connections of'the electrical system.

A "further object is the provision of an ignition system capable of operating equally well at different altitudes and independently of atmospheric pressure changes.

Other objects are to avoid 'misfiring, eliminate the usual troublesome contact points and to generally increase the efliciency or reduce the fuel consumption of internal combustion engines, in particular of motorcar engines.

Still another object of the invention is the provision of a novel electronic ignition system *for .internal combustion engines utilizing the effects of high frequency ionizing the combustible fuel mixture, to readily initiate the ignition and to improve the over-all efficiency of the combustion, substantially without the drawbacks and defects of the conventional high frequency discharge ignition systems knownin the prior art.

The foregoing and ancillary objects, as well as novel aspects of the invention, 'will be better understood from the following detailed description taken in conjunction with the accompanying drawing, forming part of this specification and wherein:

Fig. l is an electrical circuit diagram'of an improved e'lectronicignition system for internal combustion engines embodying the principles of the invention; 7

Fig. 1A illustrates a series of ignition pulse "volt-age trains utilized by the invention;

Fig. 2 and Figs. 3A and 3B are partial views of'the interrupter or ignition control contact mechanism of Fig. 1, illustrating a preferred designthereof according to the invention;

Figs. 4 and 5 are further partial views of the ignition control mechanism and distributor, illustrating in greater detail the design and "operation according'to the invention;

'Fig. 6 is a graph illustrating a series of high voltage ignition sparks; and

Fig. 7 is a cross-section through a preferred-construction of a peakingitrans'former used in the peak voltage generator of Fig. 1 formingpart of the invention.

.Like reference characters identify likepartsin the different viewsof the'drawing.

With the foregoing "objects in view, the invention involves generallythep'rovision of means for and a method of producing a series of loW-fr'quehcy'high voltageimpulses or ignition sparks during 'a single ignition period having a predetermined recurrence frequency, in such a manner that during high engine speeds a sulficient number of discrete sparks'is availabletoi'insureignition and e'fiicient combustion of the explosive mixture, 'while during idling or low engine speeds, the period of the peak voltage trains or number of discrete sparks increases in proportion to 'thefreduced engine speed, providingtherebmin addition to improvedall-over 'efficiency, the advantage of easy and ready starting and more feflicient operation of the engine at idling and low speed operation.

In order to carry the invention into efiect there is utilized an electronic system .gener'atii'lg a peaked voltage wavebeing constituted bya series efttgh vdlt'age pulses at relatively low frequency and having a steep-fronted shape, "such as square or triangular, to insure asuln'cient number of harmonics and to provide the equivalent of a high frequency wave without "the use of any high frequency generator or circuits. As a result, the pulses or voltage peaks behave from the ,point of view of ionization of the combustible gas or .miXture in the manner similar to a continuous high frequency wave or voltage applied to a spark gap, such as the spark 'plug of the type as'used in conventional'internal combustion engines.

"In other Words, the invention utilizes a series of discrete 'high'voltag'e sparks in place of a single ignition spark during a single ignition period, resulting in improved :efiiciency of the combustion of the explosive mixture and, in turn, in iincrea'sed'thermal efficiency of the engine. As a result, replacement of a conventional ignition system by the improved system according to the present invention will result in a substantial increase of outputpower for a given fuel consumption, or vice 'versa, in'reduced fuel consumption for a given output power. The train or series of sparks during a single ignition period consists of elementaryjsparksahaving substantially the same power, independently of the operating condition of the engine, such as starting, idling or operation, thus insuring reliability of operation and optimum efficiency at all times. Furthermore, by-the use of multiple spark ignition according to the invention, interference with or interruption of the'ig'nition as fa result of fouling of the spark plugs, moisture and other causes is greatlyreduced or minimized.

Referring to Fig. '1, there is shown a pulse voltage generator connected to the distributor of areciprocating internal combustion engine as used in motorcars or the like and assumed to be of the four cylinder type in the example illustrated. The'pulse voltage generator, in the example shown, consists of a square wave oscillator or multivibrator comprised of a twin-triode amplifier tube 10 having 'two triode sections mounted in a common envelope and each comprising a cathode, grid and .plate electrode of conventional design. The cathodes of both triode sections, which may be in the form of separate tubes,ja=re connected directly to ground or other potential reference point, such as the metal chassis or frame at the engineIwhile electrodes are grounded through grid leak resistors 11a and 11b and the plates are connected to the positive terminal of a suitable high voltage supply source indicated by the plus sign through load resistors 12 andf12b, respectively. Each of the plates of one section is furthermore connected to the grid of the other section through a coupling capacitor 13a and 13b, respectively whereby to cause the circuit tooperate'as a self-running bi stable relaxation oscillator by alternately passing current through the triode sections at a frequency determined by the circuit constants, that is, the grid leak resistances 11a and 11b and feedback capacitors 13a and.1 3b.

' The square wave output voltage producedby'the multivibrator is-applied to the grid of a pentode power ampli fier; and peak voltage generator 14 by way of a grid cou: pling capacitor 15 and grid leak resistance 16, to produce high voltage peaks or pulses in the outputfor plate cirin ineificient by-passing or excess voltage suppression and too low value causing a reduction of the amplitude of tor or battery by'the aid of any suitable direct current voltage transformer, such as a vibrator power supply of the type commonly used in connection with automobile radio sets. In the example illustrated, there is shown for this, purpose a vibrator type direct current transformer connected to the standard electric supply system, comprising the generator 32, storage battery 33 and autocuitlof the amplifier by the action of a special'plate peaking'inductance 17. More specifically, during the posi' tive half 'cycles of the impressed square wave voltage or conducting periods of the tube 14, magnetic energy will be stored inithe coil or inductance'17 which energyrat the starting of the negative half-cycles of the impressed volt: ageor interruption of the current through the tube, collapses: suddenly in such a manner as to generate aseries of steep-fronted peak voltages 01' pulses at the anode of tube 14,.as shown at V, Fig. lAL These pulse trains or peak voltages are applied to the

contacts

25a, 25b, 25c and 25d of a distributor 24byway of a movable or rotary contact arm or finger 23, to ignite or fire the

spark plugs

26a, 26b, 26c, 26d connected to said contacts, respectively, in the manner shown andfrea'dily understood.

In order to produce and apply ignition pulses only during the time of connection of a spark plug to its respective distributor contact, or iniother words to pro vide a series of discrete pulse trains during successive time periods ,m separated by suitable time intervals n, Fig. 1A, there is further provided a make and break deviceperiodic interrupter inserted, in the example shown, in the ground circuit of one of the cathodes of the multi-vibrator '10 and comprised of V a spring-biased pivoted contact arm having a projection 21 cooperating with a rotating cam 22' synchronized with the movable distributor contact 23, as indicated bythe curved arrows a and dot-dash line 22a in the drawing. Contact arm 20 being grounded carries a first contact 18a which cooperates with a secondstationary contact 18b, said contacts being inserted in the ground lead of one of the cathodes of the multivibrator, to effect a control of the multi-vibrator'to produce a train or series of discrete peak voltages or pulses in synchronism with the connecting periods of the spark plugs 26:: to 26d to the output of the amplifier 14. The number ofvoltage'pulses or sparks during each ignition period may be suitably chosen to insure a sufiicient num-' ber of discrete ignitions or sparks at maximum operating speed of the engine and to cause the number of sparks to increase as the speed is reduced for the purpose [further understood from the following.

In the case of conventional engines'ior motorcars, a pulse or spark repetition frequency of from 1000 to 5000 pulses per second has been found to provide satisfactory results, although the optimum number of sparks for each ignition period varies according todifferent engines and can be determined by experiment, 7

In order to prevent arcing or'sp'arking between the distributor contacts as a result of excess voltages due to unsatisfactory operation or fouling of one or more of the spark plugs, there is advantageously provided an excess voltage arrester connected between the plate of the amplifier'14 and ground and comprising, in the example shown, a resistor 28 and gaseous discharge tube 30. Any equivalent means or device may be provided for this pur-v pose, "-as will be understood. The value of resistor 28 shouldbe suitably selected, toohigh a value. resulting maticcut-out 32, by way of a switch 34 and interference filter 35 of known construction. The vibrator shown is of the synchronous interrupter and mechanical rectifier typ'eand comprises a grounded vibrating element or reed 40 carrying a contact 41 which cooperates with a magnet core having a winding 42 connected to the circuit to causeicontinuous vibration. of the element by automatic interrupter action, in a manner well known and understood by those skilled in the art. I

,iCooperating ,withthe' element 40 are a first pair of interrupting contacts 37a and 37b: connected to the opposite endsfof the primary winding 36a of a voltage step up transformer 36, the center point of said winding being connected tothe low, voltage source, that is,.the gene erator 32 or battery 33. The element 40 is furthermore arranged to cooperate witha pair of synchronousrectitying contacts 38a and 38b connected to the opposite ends of the "transformer secondary 36b, whereby to provide a stepped-up direct current output voltage between the center point'of winding 36b and ground. This output voltage serves to supply the pulse generator through a further switch or circuit breaker 45. Resistors 43a and 43b and capacitors 44a and 46 connected to the winding 36b act 'as a filter to smoothen or steady the direct current output voltage, in a manner well known in connection with vibrator type power supply devices of this type. The output voltage of the vibrator may have a sufficient value for energizing the multi-vibrator or other pulse voltage generator, depending upon the type of tubes orv circuits used. I

According to a'preferred embodiment, the switch 45 may be of the mercury type, to interrupt or disconnect the pulse voltage generator in case of extreme shock to which the motor or vehicle may be subjected and to avoid interference with or undesirable operation of the ignition system, 1

j'There is thus provided by the invention a new and improved ignition system which while using peaked or pulsed voltage of relatively low frequency provides all the benefits. of a high frequency ignition system, sub stantially without .the drawbacks and defects of the latter. By choosing a suitable pulse recurrence frequency of the voltage peaks V, that is, such as to provide a suflicient number of discrete peaks or pulses during maximum engine speed, there will be insured a suflicient contentIof-high'ha'rmonics of adequate amplitudes to cause high frequency ionization of the gaseous mixture,-resultmg both in reliable starting of the ignition and in increased combustion efliciency. v I Assuming, .by way. of example, a maximum engine speed of 3000 revolutions per minute, that is, 50 revolutrons per secondyand a contact angle a=18 (see Fig. 4), the period of one revolution will be equal to 3'3 sec. while a single contact closing period will be equal to Assuming further a peak voltage recurring frequency of 5000 pulses per second, the number of pulses per single ignition at maximum engine speed will be 5 pulses and 50 pulses at an engine speed of 300 revolutions per minute. Provided the instantaneous or peak value of the pulses is of a sufficient magnitude, say from 3000 to 5000 volts, there is insured in this manner an adequate amount of high harmonic frequencies of sufiicient intensity to cause ionization of the gaseous mixture and, in turn, insure ready starting of the ignition and other desirable effects.

In order, according to an improved feature of the invention, to avoid arcing or sparking between, the distributor contacts, the interrupter and the distributor are designed in such a manner as to cause the movable or rotary contact 23 of the distributor to engage a stationary contact 25a-25d prior to the starting of a train or series of voltage peaks and to interrupt the train of voltage pulses before the rotary contact 23 leaves or becomes disengaged from the stationary contacts of the distributor. This design and operation will be further understood by reference to Figs. 2, 3A and 3B.

Referring to Fig. 3A, there is shown the instant when the contacts 18a and 19b become closed or engaged as indicated by the arrow 1) showing the movement of the contact arm 29, thus starting the operation of the multi vibrator or other pulse generator to produce a series of trains of pulses or peak voltages V, as shown in Fig. 1A. This instant corresponds to a position of the rotary contact of the distributor having already engaged one of the stationary contacts such as 25b as shown at 23 in Fig. 2. Fig. 3B shows the position of the cam 22 at the instant when the contacts 18a and 18b become again separated or disengaged, as indicated by the arrow 0 in the drawing. The corresponding position of the contact arm 23a, shown in dotted lines in Fig. 2, is such as to still engage the stationary contact 25b. As a result the contact arm 23 engages and disengages the stationary contacts 25a25d of the distributor in a substantially currentless condition, thus avoiding arcing or sparking and deterioration or wear of the contacts of the distributor. Furthermore, since the periodic interrupter or contactor 20 actuated by the cam 22 carries only the relatively weak space discharge current of the multi-vibrator, arcing of the interrupter contacts is practically negligible, whereby to result in high operating stability and long life of both the interrupter and distributor. It will be understood that the control of the multi-vibrator or pulse generator by interrupting the ground return of one of the tubes or sections is by way of example only, many other ways to start and stop the pulses V, such as by interruption of the grid circuit of either of the multi-vibrator sections or tubes or of the power amplifier, being possible and suggesting themselves to those skilled in the art.

If the ignition system according to the invention is used in connection with engines of the type provided with the automatic ignition advance with increasing engine speeds by means of centrifugal advance weights or equivalent means, further provision should be made according to the invention in the design and/or adjustment of the distributor and pulse train interrupter, to take care of any manual or automatic advance adjusting range by the proper dimensioning of the distributor contacts in relation to the angular operating range of the interrupter, in the manner shown and more clearly understood by reference to Figs. 4 and 5.

Fig. 4 shows the position of the cam 22 in the center of the closing period of contacts 18a and 18b assumed to have an angular operating range equal to 20. In this case the contacts of the distributor, as shown in Fig. 5, may have an angular Width of 35 this including a range of 2.5 at each end to avoid arcing or sparking as explained in reference to Figs. 2, 3A and 3B, and an additional to take care of the manual and/or 6 automatic advance adjustment of the ignition, depending on the type or design of the engine, as will be readily understood.

Fig. 6v shows the shape of a pair of elementary sparks S produced by the high voltage pulses V which behave in the manner of a high frequency wave as a result of its high harmonic content, in the manner pointed out hereinabove.

In order to obtain sharp-pointed or peaked voltage pulses V at the output of the pulse voltage generator, it is advantageous to' use a special low-leakage type of peaking trans-former 17, as shown in Fig. 7. In the latter, the inductance comprises a hollow cylindrical housing 50 consisting of a suitable insulating material capable of withstanding high voltage such as Plexiglas or an equivalent synthetic insulating material and having mounted therein a number of pancake-shaped induction coils 51 spaced from each other and supported by a center mag netic core 52 of high permeability.

For practical purposes, it is possible to use a standard distributor for the purpose of the invention, with slight modification to. comply with the requirements of the invention, as pointed out, and using a high grade insulating material, such as nylon or Teflon as a base member in which are mounted by directly molding or otherwise securing the fixed contacts ZSa-ZSd for cooperation with the rotary contact 23.

In the foregoing the invention has been described with specific reference to an illustrative device. It will be evident, however, that numerous variations and modifications, as well as the substitution of equivalent parts and elements for those shown and described for illustration, may be made without departing from the broader scope and spirit of the invention as set forth in the appended claims. The specification and drawing are accordingly to be regarded in an illustrative rather than in a limiting sense.

We claim:

1. In an internal combustion engine having a plurality of spark plugs and a spark plug distributor; an ignition system comprising a source producing a peaked voltage wave constituted by a series of spaced discrete and unidirectional high voltage pulses having a substantially constant pulse recurrence frequency independent of the engine speed, said distributor periodically connecting the spark plugs to said source, a periodic make and break device synchronized with said distributor and connected to said source, to control the spark plug firing periods, said recurrence frequency having a value to provide a multiplicity of high voltage pulses during each spark plug fin'ng period having a predetermined minimum at maximum engine speed and increasing in number in proportion as the engine speed decreases, said pulses being separated from each other by spacing intervals to effect a corresponding number of discrete ignition sparks during each spark plug firing period.

2. An ignition system as claimed in claim 1, said source being comprised of a square voltage generator and an amplifier having an input circuit controlled thereby and including a peaking inductance in its output circuit, to convert the square wave generated into a series of discrete unidirectional high voltage pulses.

3. In an ignition system as claimed in claim 2, said generator consisting of a pair of amplifier devices connected to form a multi-vibrator and said make and break device being connected in the input circuit of one of said amplifier devices.

4. In an ignition system as claimed in claim 1, including excess voltage arresting means connected in parallel with said source and distributor.

5. In an internal combustion engine comprising a plurality of spark plugs and a spark plug distributor having stationary contacts connected to said spark plugs and a cooperating rotating contact synchronized with said engine; an ignition system comprising a source connected to said rotating contact'and producing a peaked voltage wave'being constituted by a'series' of spaced unidirectional high voltage pulses having a substantially constant pulse. recurrence frequency independent of the 1 engine speed, "a make andrbreak device connectedto said source and synchronized with said distributor, said make and break device having a ratio of closing to opening periods related to the ratio of spark plug firing closing to opening periods of said distributor, to cause a substantially currentless connection and disconnection of the distributor contacts by said rotating contact, said pulse recurrence frequency having a value to provide a multiplicity of high voltage pulses during each spark plugfiring period being apredetermined minimum at maximum engine speed andtincrea'sing in number in proportion as the engine speed decreases, said pulses being separated from each other by spacng'intervals to efiect a corresponding number of discrete ignition sparks during each spark plug firing period. 7 I

6. An ignition system for internal combustion engines as claimed in claim 4, including ignition advance and retarding means associated with said distributor, the relative closing and opening periods of said make and break device and of said distributor, respectively, designedto maintain a currentless :connection and disconnection of the distributor contacts throughout the full ignition advance andretard operating range of said engine.

7 7 References Cited in the file of this patent UNITED STATES PATENTS 1,207,193 Mason Dec. 5, 1916 1,334,095 Hill Mar. 16, 1920 1,589,489 Snook June 22, 1926 1,605,724 Heaton Nov. 2, 1926 1,968,930 Cotter et a1. Aug. 7, 1934 2,353,527 Touceda 'et a1. July 11, 1944 2,389,637 Ruben Nov, 27, 1945 2,392,192 1 Robinson Jan.- 1, 1946 2,447,377 Tognola et a1; Aug. 17, 1948 2,632,133 McNulty Mar. 17, 1953 2,833,963 Tognola' May 6, 1958 FOREIGN PATENTS Belgium; Mar. 31, 1952 .n a r,