US 1469582 A
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Description (OCR text may contain errors)
Get. 2 1923.
E. G. BURESCH IGNITION SYSTEM Filed Dec. 50 1921 2 Sheets-Sheet 1 v f, Eduard Q Zersch/ Oct. 2 1923.
E. G. BURESCH IGNITION SYSTEM Filed Dec. 50 1921 2 Sheets-Sheet 2 @NMS .LA/savana wsu 7A/ovh:
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UII@ STATES Le StZ rait-ir EDWARD G. BURESCH, 0F CHICAGO, ILLINOIS, ASSIGNOR 'IO RESISTOLITE `HH?Ill'lll'i'tIE CO., 0F CHICAGO, ILLINOIS, A CORPORATION 0F ILLINOIS.
Application filed. December 30, 1921.
To all 'whom t may concern:
Be it known that I, EDWARD G. Bumsen, a citizen of the United States, residingl at Chicago, in the county of @ook and state of Illinois, have invented a certain new and useful Improvement in Ignition Systems, of which the following is a full, clear,'concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.
My invention relates to ignition systems for internal combustion engines and the like, and to a method of and means for securing i improved operation of systems of this character.
It is well known that in ignition systems of the battery type there is a tendency for the breaker points in the primary circuit to be burned or pitted at low speeds if the current strength through the induction coil is to be great enough at high speeds to provide satisfactory discharges at the plugs.
rIhe thing that is desired at the plugs is a disruptive discharge. There must be a certain minimum amount ofv energy but this need not be great. This disruptive discharge is secured by the breaking down of a magnetic field in linkage with the secondary of the coil. In order to secure the voltage for the desired disruptive discharge above nientioned the magnetic field must be broken down at a certain rate (magnetic lines per second) and, in order to have the proper amount of energy in the discharge, a certain size or quantum of magnetic field must be broken down at the above rate. Vliatever there is in excess in the way of rate, or in the way of energy of discharge, is not essential.
It is well known that the real electrical problem is the setting up and breaking down of the magnetic field at high speeds. If the coil is designed to accomplish this function satisfactorily at high frequency, that is, at high engine speeds, then the mechanical problem of maintaining the breaker points in operative condition at low speeds becomes a limiting factor. Also, the mechanical problem of keeping the coil cool at all speeds, must be taken into account. i
If only a given frequency of interruption of current (constant engine speed) were encountered it would be possible to proportion the constants of the coil, and of the circuit,
Serial No. 525,851.
so that the natural period of the circuit would be the same as the frequency of interruption. But in a circuit such as the ignition circuit of an automobile, the frequency varies over a wide range. If the ratio of resistance of the circuit to the inductance of the circuit could be varied in inverse proportion with the frequency, it would be possible to secure greatly amplified eects at the plugs.
I have provided a novel electrical ignition circuit which I believe accomplishes the desired result of varying, to a certain extent, the ratio of the electrical constants of the circuit in accordance with the frequency.
Not only do I provide for a change of the average value of the constants of the circuit over athe range of speed or frequency, but also I provide for a change in the constants of the circuit during the time of each individual Contact,A particularly so at the lower engine speeds or frequencies.
My invention also secures certain advantages of operation, namely, ability to give powerful disruptive discharges at the plugs over a wide range of frequencies, with freedom from heating of the coil and freedom from injury to the contact points.
In order to acquaint those skilled in the art with the manner4 of constructing and operating my invention I shall now describe, in connection with the accompanying drawings, an embodiment of the invention.
In the drawings:
Figure 1 is a diagram of an ignition circuit embodying my invention;
Fig. 2 is a perspective view of one form of controlling resistance;
Fig. 3 is an elevational view of another form of controlling resistance;
Fig. 4 is a diagram illustrating the operation of a circuit embodying my invention as compared with the operation of circuits heretofore known; and
Fig. 5 is a curve of the resistance of a controlling element at various speeds of interruption (or frequency) which I have tested and ascertained with the aid of the oscillograph./
I have shown in Fig. l an elementary diagram an automobile ignition circuit having tii/e induction coil l for supplying disruptive discharges at the spark plugs 2, only one ofwhich is shown, for the sake of clearness. The induction coil has a primary winding 3 and a secondary winding 4 which is connectedon one side to ground at 5, and on the other side is connected through a distributor shown at 6 tothe spark plugs in their proper sequence. The primary coll 3 is connected on one side to battery 7, which battery is grounded, and on the other side the primary is connected to ground at 3 through a suitable itnerrupter 3, which has preferably a condenser 10, ot suitable capacity, bridged across the circuit breaker. lln the conductor 11, which connects the primary coil with the interrupter 9, l have indicated a controlling element 12 for governing the electrical constants oit' the llne, depending upon the frequency of interruptions at the interrupter 9. The controlling device 12 may be connected on either side of the primary winding 3, in tact anywhere in series in the primary circuit. This control element 12 comprises a resistance having a positive tempera-ture co-eliicient and having a minute cross-section or other suitable configuration to permit the resistance to heat up substantially instantaneously, and likewise to cool with equal rapidity.
lf have found suitable for this purpose, a small wire or filament of drawn tungsten of such cross section as to permit the normal How of current through the primary of the coil 1 to raise the temperature to incandescence. Other metals having suitable character such as tantalum, osmium, etc. may be used. l consider that any material whether metal or otherwise so long as it has the capability' of operation herein described may be employed and comes within the scope of my invention. To protect the incandescent filament from oxidation, and from excessive heating, T preferably enclose the same in an evacuated glass bulb 13, having suitable terminals such as 15 and 16, mounted thereupon in electrical connection with the filament 14. As shown in Fig. 2 ll provide the terinianls 14 and 15 in the shape of ferrules which are cemented upon the ends of the glass bulb 13, these errules having extending portions 17 and 18 which may be clamped under suitable clamping screws for making a firm contact and a secure mounting for the control element. T'he portions 17 and 18 may be looped, o-r otherwise bent out of astraight line, so as to provide a resilient suspension tor the body of the controller 12. This is desirable to preserve the device against mechanical jarring as much as ossible.
he glass bulb 13 is preferably filled with nitrogen or argon gas for the dual purpose ofA preventing uneven heating of the filament 14, and also for dissipating the heat of the filament as rapidly as possible upon decrease of the current flow.
In Fig. 3 T have shown the controlling and 3 it is desirable that contacts 19 and 20, arranged at one end of the tube or bulb 21, the metallic lament 22 beinw arranged substantially centrally of the bulb 21, and being surrounded by arelatively large body ot' gas, such as nitrogen or argon, to secure the results previously mentioned. Thisl form of controller may be employed not only to secure the desirable results inherent in this form of resistance, but also to be mounted in such position as to give a visual indication of the operation of the circuit. Obviously the device of F ig. 2 may also be so employed, but the striking advantage that is secured by the overshooting eHect of the resistance wire, may be secured whether or not the resulting incandescence is visible.
This controlling resistance may be mounted upon the dash, or in suitable view of the driver of the vehicle, in the case of an automobile ignition circuit, to indicate the operation of the circuit.
This it does in a twofold manner-first it indicates by a steady glow when the circuit is closed and the engine is not in operation,'second it indicates by flashes at low engine speeds the operation of' the plugs on the engine. lt also indicates by lack of brilliancy when the battery is low.
Tn the forms illustrated in bothligs. 2 the bulb 13 or 21, as the case may be, provide a relatively large bod of gas about the resistance element so t at it may operate with great rapid'ity, and be suitab-ly protected.
The operation of the system will now be described in connection with a statement of the relation between the devices included in the circuit.
The character of the resistance 14 is such that it will permit an initial rush of current therethrough of relatively great value to establish the magnetic field in the iron core,ll which forms a part ot' the induction coil 1. After the magnetic field is set up, the flo-w of current may be reduced without a material effect upon said magnetic field, and this is accomplished by the rapid rise in temperature ot the resistance 14. It is known that a tungsten lamp of this character will have, when heated up by normal current flow, a resistance about ten to twelve times the resistance when cold, that is, at room temperature. This metallic resistance is adapted toy heat up in a period of time materially less than the period of contact between interruptions at low speeds, that is starting speed or idling of the gas engine. rlhe time required for heating up may, however, be greater than the period of closed circuit upon higher engine speeds withoutl in anywise adversely effecting the operation of the system.
lill() When the system shown in Fig. 1 is in operation on low speed, that is on starting, idling or low speed, the contacts 9 will be closed and opened to establish and break down the magnetic field in the core of the induction coil 1. The distributor 6 moving in synchronism with the interrupter 9 connects in circuit the proper plug 2 for firing the corresponding cylinder. At such idling or starting speeds and even at lou7 running speeds the number of interruptions per minute is relatively 10W and the time during which current flows through the coil 3 for each interruption is relatively great. The controlling resistance 14 rises to incandescence for each closing of the Contact 9 and cools off during each period of interruption. The coil may be so proportioned with respect to the resistance that a rapid rise in magnetism may occur in this coil upon closing of the contact, occasioned by a very rapid influx of current, which current would tend to rise to a high value, but Which upon attaining a value suiiicient to magnetize the core to the desired degree, will heat up the controlling resistance and cause an immediate decrease of current flow. In other words, the coil and the resistance are so related to each other that the over-shooting of the resistance 14 will cause the setting up of a magnetic iield in the coil of the desired value, with the immediate reduction in current flow through the primary of the coil thereafter. This reduction in current fiow by the heating of the resistance 14 greatly reduces the. amount of heat which is developed in the primary of the coil 1, and it reduces the amount of current How which must be broken by the contact 9. It is well known that the heat developed due to current flow is in proportion to the square of the current fioW. The rapid rise in magnetization of the coil occasioned by the initialr rush of current occupies only a very small portion of the time, and the cutting down of current as soon as resistance 14 heats up, greatly reduces the amount of energy which is liberated as heat in the coil 3.
As the speed increases the impulses of current through the primary circuit and through the controlling resistance 14 become shorter, with the result that the resistance is called upon to a less and less degree to hold back the flow of current. Upon high engine speeds the resistance 14 does not come to incandescence, with the result that the average temperature during the time that the contacts are closed is materially different from what it is during low speeds. That is to say, during high speeds the effective resistance of the controlling resistance 14 is low to permit as rapid a building up of. magnetic field as possible, and the break occurs so quickly after the make of the circuit that thecurrent fio-W will have time to reach its peak where it establishes a fiow of current, and will not be effective to. cause a noticeable development of heat in the coil. Upon low speeds the time between make and break is so great that the controlling resistance will have time to heat vup and become incandescent after the magnetic field has been established by the initial rush of current. In this Way, the rapid rise of current at first and its subsequent lessening in value permits the iron of the core to be brought to a peculiarly sensitive condition where its flux has begun to diminish, and the amount of current which is holding the magnetismV is less than that which was required to set it up. The magnetic field seems to be in a condition where it is ready to break down uponthe opening of the circuit more rapidly than it would otherwise break down.
Thus the resistance of the primary of the inductance coil may be made 10W and the coil designed to magnetize very rapidly. The important relation is, as above indicated, namely, that the magnetization of the coil rise to the desired value within the time of minimum contact, that is, during the maximum engine speed. Then upon longer contact such as occurs at lower engine speed, the controlling resistance acts to limit the current flow and thereby prevents corrosion and pitting of the contact at the breaker 9.
I have made numerous experiments with controlling resistances of this character and find that the ignition of an automobile is very y greatly improved by the useI of the same.
In the diagram of Fig. 4 I have indicated in the upper set of curves the general character of the operation of a coil as practiced in the prior art, and in the lower set of curves the operation of a system built according to my invention.
In the curve C of Fig. 4 the building up of current in the 'primary Winding 3 is shown as it occurs in systems of the prior art. The curve F shows the manner in which the fiux of magnetism builds up in the iron core. Assuming .that on the line O-X which represents time, the period from O to B represents the longest time during which contact is closed in the normal operation ot the system, that is upon idling. The current will build up to its maximum value and will substantially saturate the core Within thev given period. The interruption occurs at the instant of time designated by the line B, and the falling ofil of current is accompanied by a decrease in the flux according to the latter part of the curve F. Due to the necessity for designing the vcoil so as not to be overheated upon low speed, the rate of dying out of the current 4, Lacasse I and the rate of decrease of the magnetic flux, will not be as rapid as would be possible in the same coil at higher speeds. Interruption of the current flow at higher speeds will give a more desirable characteristic, as will be obvious if the interruption of current flow occurs at the point of time marked by the line A.
As shown in thelower set of curves of Fig. 4 the curve C shows the current flow, and the curve F shows the magnetic fiux which .is set up thereby. It will be observed that the current flow rises to a sharp peak and then drops down immediately thereafter. This is due to the limiting action of the controlling resistance 14. Since the current has already started downwardly from its maximum value, the interruption of the primary circuit will tend to give a sharper breakdown of the magnetic flux and a more powerful disruptive discharge. At the same time it is possible to proportion the coil so as to permit a quick initial magnetization and a quick breakdown of the magnetic field. Even if high frequency be reached, as in the neighborhood of the line A, the setting up of the magnetic field being very rapid, satisfactory ignition will at all times be produced. Since the amount of current which is permitted to flow through the coil 3 is greatly reduced, the heating of the same will be materially lower, since heating is proportional to the square of the current flow.
The freedom from trouble at the contacts 9 is very marked. The contacts 9 are generally damaged by excessive current flow at low speeds in systems of the prior art, but according to my invention, 'these contact points will stay clean and give satisfactory service over a long period of time.
The curves shown in Fig. 4: are not intended to be accurate representations of the values involved, but are intended to illustrate the nature of the phenomena which occur.
The diagram of Figure d has purposely been exaggerated to bring out the important function of the controlling resistance. Whether the overshooting of the current is as noticeable as shown in Figure t or not, is not essential. rl`he interrelation of the coil and the controlling resistance which permits the magnetism of the coil to be set up in a period of time comparable to that of the minimum period of contact and which secures a limitation of current flow thereafter by introducing the incandescent resistance Aof the' filament, is the rimportant thing. As previously explained, the maximum inductive effect of the coil is secured when the interrupter opens the circuit at that stage .of the current flow Where the incandescent resistance has begun its actioi of reducingthe current flow. .The maximum efl'ect may be secured at any desired engine speed by proper proportioning of the coil and the controlling resistance.
In Fig. 5 I have plotted a curve of the varying effective or mean resistance of the controller 12 through a range of interruptions which indicates the decrease of effectiveJ resistance of the controller as the speed of interruption increases. These values are actual values of a test made with the aid of the oscillograph on a system employing a present standard Remy battery ignition coil and a controller of the type shown in Fig. 3 using a tungsten filament and filled with Argon. The decrease in effective resistance is very noticeable.
The rate of temperature change in the filament 141 is great due to the small thermal capacity thereof. After the filament is once incandescent it tends to cool very quickly becausev of the conductivity of hcat from the filament.
The invention is applicable not only to battery systems of either the open or the closed circuit but also to magneto ignition systems.
l. In an ignition system for gas engines, a spark coil having a core, a primary winding and a secondary winding adapted to provide a disruptive discharge at the engine plugs, af primary circuit including said primary winding, an interrupter and a controlling resistance, said resistance having a high positive temperature co-eicient and comprising a filament enclosed in a protective glass bullo," said coil,'core and resistance being proportioned to permit the core to become saturated to the required degree for each contact of the interrupter-at high engine speed and to cause the protective resistance to rise to a high temperature `and thereby limit the current flow during the time of contact. of the interrupter at lower speed.
2. lin an ignition system for as engines and the like, a primary circuit including a source of current, a primary winding, an interrupter adapted to make and break said circuit, and a resistance, said resistance having a positive temperature co-efticient and being of a cross-section small enough to be raised substantially to incandescence during the individual makes of said interrupter.
3. In combination, a primary winding. a circuit therefor, a'variable speed interrupter for opening and closingthecircuit through said prianarv, and an enclosed instantaneously heated metallic filament resistor of positive temperature co-eficient in series in said circuit, said primary winding and said resistor beingso related as to permit an initial rush of current for setting up a magnetic field and to increase the resistance in the circuit by thermal action of the reing a primary circuit having a source of current, a pr1mary Winding and an interrupter, which comprises ermitting an initial surge of current ofp a predetermined value, and thereafter cutting down the flow of current prior to the breaking of the circuit by said interrupter While the engine is running.
In witness whereof, I hereunto subscribe by name this 12 day of December, 1921.
EDWARD G. BURESCH.