US2066959A - Mgh tension ignition system - Google Patents

Description

Jan. 5, 1937. c 2,066,959

HIGH TENSION IGNITION SYSTEM Filed April 25, 1936 Irwverwtor: Bernard M. Cain,

is Attor eg.

Patented. Jan. 5, 1937 NITED STATES PATENT OFFICE 2,066,959 mon TENSION rem'non' srsrmu.

mam M. Gain, Ballston Lake, N. Ynassignor to General Electric Company, a corporation of New York Application April 25,1936, Serial-No. 76,425

' r (or. 123-148) My invention relates to ignition systems for internal combustionengines, particularly to elecfuel injection type in which the compression pressure is of the same order as in engines in which the fuel is supplied in vaporized form from a carburetor, it has been found that in i order to obtain a satisfactory ignition of the fuel sprayed into the cylinders by the injection pumps it is necessary to provide a substantially continuous are at spark plug electrodes during the period of fuel injection, the are beginning slightly before fuel injection is begun and continuing until after fuel injection has ceased.

From tests of electric ignition means for the firing" of fuel injection engines the conclusion has been reached that the best method for providing the required ignition arc, persisting for the entire ignition period, would be to produce a rapid succession of ignition'sparks, during the ignition period. It has been proposed in the past to provide the required rapid succession of ignition sparks by'mean's of electric apparatus including ignition transformers of the so-called vibrating spark coil type, but this method has proved to be unsatisfactory.

To avoid the use of vibrating coils with their attendant difficulties of adjustment and operation I have developed and successfully tested a system in which the required high frequency ignition is provided by means of high'frequency alternating current apparatus. In this system the alternating current was produced by means of a D. C. to A. C. inductor-alternator type of dynamotor which operated from a 12-volt storage battery. The output of the dynamotor was applied to two ignition transformers which supplied high alternating voltage to the spark plugs by means of high voltage distributors. This latter system proved to be very satisfactory from the standpoint of successful operation, but was open to the objections of relatively high cost of construction and of relatively low efficiency, resulting in a large drain on the storage battery, which in turn required a greater generating capacity in the charging and lighting generator thereby further adding to the cost of the system.

In accordance with my present invention the disadvantages inherent in the vibrating coil system and other like systems for producing the required rapid succession of ignition sparks are avoided, and the. advantages of the dynamotor system of ignition above described are retained without the disadvantages of low efficiency and high cost of the latter system, by the provision of an electric inverter system which includes a motor driven mechanical commutator. In my new and improved ignition systemthe motor driven commutator controls the flow, from. thestorage battery, of rapidly recurring impulses through the opposite halves of a reactor, the end terminals of which are connected through rectifier devices to-alternate segments of the commutator. The breaking of heavy currents at the commutator is prevented by the provision of commutating capacitive means 'co-acting with the rectifiers. Suitable interrupter means is provided to connect the ignition transformer periodically-to the reactor, the ignition transformer output being conducted to the spark plugs through a distributor means.

It is a further feature of my invention that, in practical installations, as in motor vehicles, where the storage battery voltage is limited, for example to 12-vol ts, in order to obtain an A. C. output which has the high voltage required for the ignition transformers I arrange the above mentioned reactor as an autotransformer having taps at points either side of center, to which the leads to the commutator apparatus are connected. I

My invention will be better understood iron the following description when considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. l is a diagrammatic representation of an internal combustion engine ignition system in which my invention has been embodied;' and Fig. 2 illustrates diagrammatically a modification of the system shown in Fig. 1, in which the reactor is arranged tem for a six-cylinder internal combustion engine (not shown), a source of low voltage direct current which comprises a storage battery ill is arranged to drive a direct current motor ii on the shaft 62 of which is mounted a commutator apparatus indicated generally by the numeral it, the purpose of which is to cause current from battery it to flow alternately through the two halves, it, lb of a reactor iii. The commutator apparatus It comprises two slip, rings ll, 58 and a commutator l9 having an even number of segments 20 to M, alternate segments being connected respectively to the slip rings 011-, it. Thus segments 20, 22, 24, 26, 28, at are connected to slip ring ll and segments-Zll, 23, 25, 27, 29,30 to slip ring it.

One terminal.of battery Ill, as the positive terminal 32, is connected to the midpoint 33 of reactor it the end terminals 34, 35 of which The end terminals 34, 33 of reactor ii are connected through leads 4!, 43 to the series-connected primaries 41, 43 of high tension ignition transformers 43, 30, the parallel-connected secondaries ll, 32 of which are connected through distributors I3, 34 to two sets of spark plug means indicated by the numeral 55. To determine the sparking periods of the ignition system, one of the connections, as the lead 43, be-

tween reactor l3 and transformers 49, in-

cludes an ignition interrupter 33 having fixed contact 31, and movable contact 53 actuated by engine driven cam 53.

In operation of the system shown in Fig. 1, as the commutator I3 is rotated by motor II the segments 20 to 3| are alternately connected to one or the other of slip' rings [1, i3, connection being made from battery It first to slip ring l1 for example, whereupon current from the positive terminal 32 of the battery flows through the upper half ll of reactor l3, rectifier 33, slipring I1, one of the corresponding segments, as

segment 23, of the commutator, and reactor or choke coil 43, back to the negative terminal 40 of the battery, choke 43 operating to maintain the battery current substantially constant. Di-

rection of rotation of commutator I! being assumed to be counterclockwise, connectionis next made from battery I. to slip ring i3 through segment 2|, the battery current then flowing through the lower half II of reactor l6 and through rectifier 31. Assuming that the ignition apparatus has been operating for a time suillcient to insure steady speed conditions at the motor driven commutator apparatus l3, the

voltage between end points 34, 35 of reactor ii are then symmetrical alternating voltages having an average value of zero. 4

When the commutator is in its illustrated position with brush 42 on segment 20 so that connection is made only to the slip ring i1, current from battery II will flow through rectifier 33. But at midpoint 33 of reactor I! the current divides, part flowing in the direction of end point 34 and part in the direction of end point 33. A portion of that current which flows in the direction of end point 35 will flow to'the load constituted by primaries 41, 43, assuming interrupter 53 to be closed, and anotherportion will fiow to condenser 44. Condenser 44 will then becharged as a result of this current so that the potential of end point 33 of reactor I. will become positive with respect to end point 34. As soon as the succeeding segment, in the present case segment 2i, makes contact with brush 42 and before segment 23 leaves the brush, the condenser 44 will tend to discharge during this period when slip ring I1 is connected to slip ring N by reason of brush 42 being in contact with both segments 24 and 2|. However, the discharge or short-circuit of condenser 44 through the slip rings and contiguous segments bridged by brush 42 cannot take place, since the current from condenser 44 would be obliged to flow in a reverse direction through the rectifier 38 in order to return to end point 34 from slip ring l1.

At the moment that the brush 42 is thus bridging across two contiguous slip rings, battery l0 tends to continue-sending current through slip ring l1 connected to segment 20 which is on the point of. passing from under brush 42. But condenser 44, which has been charged so that its negative side is connected to end point 34 connected to the positive side of the battery, and so that its positive side is connected through rectifier31- and slip ring I 8 to the negative side of the battery, opposes the flow of current in the circuit including rectifier 36 and slip ring l1. At the same time the polarity of condenser 34 is such that the condenser discharge, through rectifier 31, is in the same direction as that of the battery current just commencing to flow through slip ring l3 connected to segment 2| which is now beginning to make contact with the brush 42. Therefore as the commutator continues to rotate thereby disconnecting slip ring I1 from the circuit, the battery current is transferred without necessitating sudden breaking of a large current flow at brush 42, so that it now flows through rectifier 31 and slip ring I8 instead of through rectifier 36 and slip ring H.

The capacity of condenser 44 must be such that end point 34 will have impressed thereon by the condenser a potential negative with respect to that of brush 42 until after the commutator segment connecting brush 42 to slip ring i1 has passed from underneath the brush. When end point 34 finally does become positive with respect to brush 42 there will be no flow of current through the rectifier 33 since then slip ring I1 is not connected with brush 42.

The alternating voltage produced across reactor i6 is impressed, during periods determined by the interrupter 53, on the primaries 41, 48 and thence from the secondaries Si, 52 and through distributors I3, 34 on the spark plug means 55. Two ignition transformers, as illustrated, are preferably provided since tests show that for the proper firing of fuel injection engines of the type herein described two spark plugs per cylinder are desirable.

In the embodiment of the invention illustrated in Fig. 1 the commutator I9 is shown for convenience as having 12 segments only. In practice the number of commutator segments and the speed of motor I I, which drives the commutator apparatus, are so chosen that,the voltage impulses induced in reactor l3 and supplied to the spark plugs are of relatively very high frequency. It has been found, for example, that for efficient ignition of the fuel charges supplied to internal combustion engines which are of the fuel injection type and require electrical ignition means, ignition sparks should be supplied at a rate of the order of 5,000 per second, and that for proper overlapping of the fuel injection periods by the spark supply periods, the ignition spark should persist at the above noted rapidly recurring intervals during at least 15 degrees of engine rotation at each fuel injection period. The ignition apparatus hereinabove described, in accordance with my invention, is readily constructed and operated to fulfil the foregoing ignition requirements with minimum current drain on'the direct current source comprising the storage battery and the charging equipment therefor.

In Fig. 2 the apparatus is essentially similar to that shown in Fig. 1 except that in Fig. 2 the reactor, i6, is connected to the commutator apparatus through the rectifiers at points 60, 6| intermediate the midpoint and the extremities of. the reactor, the commutating condenser 44 and the leads 45 and 46 being connected to the end points of the reactor as in the embodiment of Fig. 1.

. With the battery and commutator circuits connected to the end points of the reactor as shown in Fig. 1, the battery being of the voltage rating usual in motor vehicle practice, the relatively low voltage, approximately twice that of the battery, impressed between the end points of reactor, 16,

necessitates the breaking of a relatively large cur-,

rent by the interrupter contacts in order to obtain the required output voltage in the system.

In operation of the modification illustrated in Fig. 2, however, the voltage fromthe battery is stepped up bythe autotransformer connection comprising the intermediate taps 60, GI, and the required output voltage for the system is maintained without excessive current flow across the contacts of the-interrupter.

In the embodiments of my invention hereinabove described, among other elements of the invention a D. C to A. C. inverter apparatus is provided constituted by'a source of. direct current (it), an inductance (It), a pair of rectifiers preferably of the copper oxide type (36, 31),

a commutating condenser (ll) and a mechanical switch means (l3) to cause current from the source to flow alternately through the respective rectiflers and through opposite halves of the inductance. This D. C. to A. C. inverter apparatus is claimed broadly in an application of Marvin M. Morack filedconcurrentlywith and assigned to the same assignee as my present application.

My invention has been described herein in particular embodiments for purposes of illustration. It is to be understood however, that the invention is susceptible of various changes and modifi cations and that by theappended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.

' What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an ignition system for an internal combustion engine, a low .voltage direct current source, a reactor connected at its midpoint to the positive terminal of said source, means for conducting current from said source at high frequency alternately through opposite sections of said reactor, said means 1 including a rotating commutator, a motor supplied with current from said source to drivesaid commutator, two rectifiers connected respectively between terminals of said sections of said reactor and alternate segments of said commutator, and a brushsufllciently wide to make contactsimultaneously with two contiguous segments 0. said commutator, a ccmmutating condenser in parallel with said reactor of sufflcient capacity to prevent the breaking of a large current flow at said commutator as saidbrush breaks contact with a given segment; a high tension ignition transformer, and an ignition interrupter to connect said transformer to said reactorv for a predetermined period during each firing period of said engine, whereby a plurality of sparks are supplied to said engine during each of said predetermine periods.

2. In an ignition system for an internal com-v bustion engine, a low voltage source of direct current, a reactor connected at its midpoint to one terminal of said source, a commutator having two sets of segments, the segments of one set being spaced alternately from those of the other set, a brush connected to the other terminal of the current source coacting with said commutator and sufliciently wide to bridge the gap between adjacent segments, two slip rings connected respectively to one and the other of said sets of segments, a motor actuated by current from said source to drive said slip rings and said commutator, two rectiflers connected respectively between one of the slip rings and one section of said reactor and between the other of the slip rings and anot er section of the reactor, the number ofsaid seknents and the speed of said motor being such at voltage impulses of the order of 5,000 per second are produced in said reactor, a commutating condenser connected in parallel with said reactor, a high tension ignition transformer having a primary, and an ignition interrupter to connect said primary to said reactor for approximately of engine rotation at each firing period of the-engine.

3. In an ignition system for an internal combustion engine, a low voltage direct current source, a reactor connected at its midpoint to one terminal of said source. each half of said reactor having a terminal intermediate said mid- 1 point and an end terminal, means to cause curconnected across said end terminals, a high tension ignition transformer, and an ignition interrupter to connect said transformer across said end terminals for a predetermined period during each firing period of said engine.

4. In an ignition system for an internal combustion engine; a low voltage direct .current source, a" reactor connected at its midpoint to one terminal of saidsource, a commutator, a motor supplied with current from said source to I drive said commutator, two rectifiers connected respectively between alternate segments of said commutator and points of said reactor intermediate of the end points thereof and said midpoint. a brush connected to another terminal of said source bridging the gap between contiguous segments of said commutator, the number of the segments and the speed of the motor being such that voltage impulses of the order of 5,000 per second are produced 'in said reactor, a commutating condenser connected in parallel with said reactor, a high tension ignition transformer, and an ignition interrupter to connect said transformer across said end points of the reactor for approximately 15 of engine rotation at each firing

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