US2180358A

US2180358A - Ignition system

Info

Publication number: US2180358A
Application number: US194784A
Authority: US
Inventors: Frederick J Hooven
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-03-09
Filing date: 1938-03-09
Publication date: 1939-11-21
Anticipated expiration: 1956-11-21

Description

F- J. HoovEN IGNITION SYSTEM Filed March 9, 1938 QOOQ L ft/40, 1%

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f INVENTOR Jawa/./p/vm ATTORNEY.

, Y Patented-Nat. 21,1939

UNITED-f STATES PATENT OFFICE IGNITION SYSTEM Frederick J. Hooven, Dayton, Ohio Application March 9, 1938, Serial No. 194,784

12 Claims.

This invention relates to ignition systems such as are used on internal combustion engines.

One object of the invention is the provision of ignition means which enables the use of a coil small enough to be built integral with the spark plug of an engine or the like, allowing the elimination of radio interference without the use of extended shielded high voltage leads, and especially adapted for high speed engine operation.

Another object of the invention is the provision of ignition means in which the energy of the spark is substantially the same regardless of the speed of engine operation, making it possible to regulate the spark energy to a value which will 15 give eillcient operation at all speeds without requiring the provision of an excessive energy at any particular speed, and reducing the deterioration of spark plug electrodes and contact points.

Another object of the invention is the provision of an ignition system for producing successive sparks and including a condenser or condensers which are charged from a source of charging current periodically connected thereto and which are discharged periodically through a transformer Winding or windings which are also effective in providing part of the charging circuit for the condenser.

Another object of the invention is the provision of an ignition system in which a pair of condensers are alternately charged from a common source of charging current and periodically discharged alternately through diierent primary windings of spark coils to thereby energizel said primary windings.

Another object of the invention is the provision of an ignition system having a continuous source of charging current connected uninterruptedly to a storage condenser and connected to a coil energizing condenser or condensers by means of a single series of distributor contacts which establish circuits for the charge or discharge of the coil energizing condenser or condensers through the coil windings, the construction being such that the distributor contacts open at a time when no current is flowing through them. Another object of the invention` is the provision of an ignition system having a distributor in a. low voltage circuit which periodically establishes connections between condensers and the primary windings of spark coils which are arranged at the spark plug locations where they are effectively shielded against electrical radiation, the distributor also controlling the charging of the condensers.

(Cl. 12S- 148) Another object resides in the method oi opera-` tion of an ignition system of the character referredvto. 1

Other objects and advantages of the invention will be apparent from the following description, the appended claims, and the accompanying drawing in which:

Fig. 1 is a diagrammatic showing of the various electrical connections of an ignition system embodying the present invention;

Fig. 2 is a diagrammatic showing of a modled construction in which rectifying space discharge tubes are provided in the circuits connected to the distributor; and

Fig. 3 is a vertical sectional view of a spark plug and coil unit.

Referring more particularly to the drawing by reference numerals, Fig. 1 shows an electrical ignition system for producing electric sparks at a number of spark gaps, the system being especially adapted for energizing the spark plugs of an internal combustion engine and particularly engines adapted for aeronautical use. 4In Fig. l the several spark plugs of the engine are designated l0, Il, l2 and i3, it being understood that these plugs may be of any suitable number in accordance with the number engine.

In the usual ignition system of airplane engines, the distributor is provided in the high voltage part of the system and the high voltage Wires leading from the distributor to theseveral spark plugs of the engines are shielded to prevent radio interference by metal casings which increase the capacity effect of the high voltage part of the system to such an extent as to require the supply of comparatively large amounts o1 power in the production of the sparks at the spark plugs. In accordance with the preferred arrangement of the present invention, however, the distributor is provided in the lower voltage part of the system and the primary windings of the spark coils are arranged closely adjacent the spark plugs themselves so that the wires leading to the primary windings at the spark plugs are comparatively low voltage wires and their shielding may be effected where they extend from the distributor to the spark plug locations without substantially increasing the capacity effect of the high tension part of the system. Thus the central electrode I5 of the spark plug Il! is connected to one end of the secondary winding l 6 associated with that spark plug, the other end of the secondary I6 being connected to the metal body portion I8 of the spark plug as shown diaof cylinders in the l coils. The four transformer coils are designated 23, 24, 26 and 23 and include the

primary windings

21, 28, 29 and 30 respectively.

'I'he several primary windings of the transformer coils 23 to 28 inclusive are electrically connected' to a common-lead 32 which is preferably grounded and to the several leads 23,', 24', 25', and 26 which extend respectively to contact members 23a, 24a, 25a, and 26a of a distributor. Cooperating with these contact members are additional contact members 23h, 24h, 25h and 26h respectively, the contact members to which the same numbers are applied cooperating with one another and being normally open or disconnected, but being periodically connected together to establish an electric circuit by means of a cam 34 provided on the rotatable distributor member 3E. It will be understood that the distributor member 35 is carried by a rotatable shaft 36 which is operated in timed relation with respect to the several engine cylinders so as to close the several circuits periodically and successively to produce sparks at the spark plugs at the required time.

'I'he engine with which the spark plugs vare associated is provided with an electrical generator 31 which may be driven from a separate battery-operated motor 39 or which may be connected mechanically to the engine shaft as desired. This generator, which is preferably adapted to supply direct current of a voltage preferably of the order of 250 volts, is connected across a condenser 38 which may have a capacity of about 4 microfarads and which acts as an electrical storage or reservoir member. Connected across the storage condenser 38 there are two coil energizing condensers 40 and 4|, one side of each of these condensers being connected to opposite sides of the storage condenser 38 to which an uninterrupted supply of direct current is furnished from the generator 31. The two condensers 40 and 4|, each of which may have a capacity of about .3 microfarad, are connected to the common wire 32 which leads to the several primary windings of the transformers. The wires 42 and 43 which extend from those sides of the condensers 40 and 4| that are connected to the source of charging current extend to alternate contact members of the distributor as shown, the Wire 4 2 being connected to the contact members 24b and 2Gb while the wire 43 is connected to the contact members 23h and 25h. These wires 42 and 43 are preferably enclosed in metal shielding tubes 44 and 46, and shielding tubes 41 are provided to enclose the wires 23', 24', 25' and 26' and 32 throughout their extent to the transformer windings at the spark plug locations.

The operation of the described arrangement is v such that the condensers Ml and 4| are periodically and successively connected to the uninterrupted source of charging current furnished from a suitable D. C. supply source such as generator 31 and storage condenser 38, and are charged thereby; and are periodically connected to the transformer coils 'and discharged or charged through the transformer coils which are thus energized to produce a suiiiciently high voltage across the ends of the secondary windings to cause sparking at the spark plugs. With the two condensers 40 and 4| connected as shown through the distributor contacts, one of these condensers will be discharged through a primary winding of through Wire 32 to the point 48. This places the primary winding 21 across the condenser 4| so that the'charge on that condenser is dissipated through the winding 21 and a spark is thus produced between the electrodes I5 and Il of the spark plug I0. And since the primary winding 21 is placed across the condenser 4| that winding 21 will form a conductive path through which the condenser 40 will be charged from the storage condenser 33. The charging current of condenser 43 and the discharging current from condenser 4| act together, one adding to the effect of the gther to produce a current ow through the wind- As the distributor cam 34 continues to rotate in a clockwise direction it will open the circuit to the winding 21, and since the two condensers 4i and 4| are connected in series across the charging condenser 38, the charge of the condenser 4l will be maintained and the condenser 4I will remain in a discharged state until the contacts 24a and 24h are connected together by cam 34. 'I'he closing of these contacts connects the primary winding 28 of transformer coil 24 to Athe wire 42 and the return wire 32, thus placing the winding 23 across the condenser 40, and therefore placing it in series with the condenser 4| across the charging source 31, 33 so that the condenser 4B will now be discharged through the winding 23, and the condenser 4| will be charged from the charging source through the winding 28. The distributor then opens the circuit to the winding 23 and closes the circuit to the winding 29 as the distributor cam continues its rotational movements, thewlnding 23 thus being connected across the condenser 4|, which discharges again, and connected in series with the condenser 40 which charges again. These operations are repeated in timed succession so that each condenser is periodically charged and discharged at successive sparking times, iirst one of the condensers and then one of the others being connected through a primary winding to the storage generator 31 and condenser 33 which are suiciently large in capacity, as compared with the size of the condensers 40 and 4I, to supply a charge to those condensers between the time elapsing from the opening of a pair of contacts of the distributor to the closure of the next succeedlng pair. The storage or reservoir condenser 33 is itself maintained substantially charged as it is connected continuously to the generator 31. The generator itself may be of comparatively small size.

Even though the two condensers 40 and .4| are not the same in capacity eifect, the charging current of one added to the discharging current o f the other is substantially constant, so that the several primary windings associated with the several spark plugs are supplied with the same amounts of current, and sparks of substantially uniform intensity are successively produced at the several s park plugs. Even if one of the condensers 40 and 4| is entirely omitted, if the capacity of the remaining condenser is sumcient, it will supply sumcient current irst by charging through and then lay-discharging across the successive' primary windings.

To provide a hotter spark under starting conditions or for emergency, a pair of auxiliary condensers 49 and 50 are connected in series across tions, however, the switch 5i is open, and the condensers 49 and 50 remain connected across the reservoir condenser 38 and thus they themselves act as reservoir condensers and serve to increase the capacity of the storage or reservoir part of the system. Under normal conditions of operation, after the engine has been started, a hot spark is not required, and a spark that is hotter than necessary is even a disadvantage as it increases the wear or deterioration of the spark plug electrodes.

It will be understood that the time required for the discharge of a condenser 40 or 4I and the .charging of the other one of these condensers through a primary winding is exceedingly small, so that a ow of current takes place across the contacts 23a and 23h for example as those contacts approach one another and even a little before they close, it having been found that the time during which current ilows across contacts 23a and 23h is so exceedingly small that the ow probably ceases before the contacts actually touch one another. When these contacts 23a and 23h open, the iiow of current through the winding which they connect in circuit has stopped so that no ow of current is interrupted as these contacts separate. This entirely eliminates sparking across the contacts of the distributor at the time of opening ofthe contacts, and any spark produced as the contacts close does not adversely affect the operation because the Voltage is suiliciently high when the contact is made to insure instantaneous ow of current even if the contacts are pitted. The

contacts may therefore remain in service for very extended periods of time even though they are made of ordinary cheap material, for example tungsten.

It will also be apparent that in the form of construction described, a single series of distributor contacts are provided in the low voltage part of the system which requires no supplemental circuit breaking or interrupting devices, since the opposite sides of the condensers.

\ 40 and 4l, arranged in series,v are connected continuously across an uninterrupted supply of charging current. The arrangement is such that no interval of time is required, as is customarily necessary between sparking impulses, for the recharge of an energy reservoir, such as building up a current in a coil or the' recharging of a condenser preparatory to the production of a succeeding spark. This greatly reduces the minimum time between successive sparks and allows the sparks to loe-created as often as desired, thus removing the limitations on the speed of operation even in an engine having many cylinders.

In accordance with the present invention the natural frequency of oscillation of the ignition system is extremely high. The higher the natural eiect of oscillation of the system, the less it is affected by leakage resistance across the fected by a leakage resistance of 25,000 ohms Yacross the gap, whereas a high grade magneto .of conventional construction is unable to perform satisfactorily with a leakage resistance less than about 200,000 ohms. This factor is very important because, in addition to serving as an increased safety factor, it allows the use of a much colder running spark plug. With a cold running spark plug, an important obstacle to the development of high output engines is removed, for as is well known, the limitation in the increased cooling of spark plugs is thetendency for them to foul up with deposits of carbon or other material while idling or running at part load, and with vconventional ignition systemsit is necessary to operate the plug so that it becomes hot enough to burn oi such carbon deposits in order to prevent electrical leakage such as would cause misring.

In accordance with the modiiied arrangement shown in Fig. 2, there is a similar arrangement of a motor 39 operating a generator 31 which is connected to a storage 'condenser 38. to auxiliary starting condensers 49 and 50' and to the coil energizing condensers 40 and 4l'. The spark coils including the primary windings 21, 28', 29'nand 30' are similarly associated with the secondary windings and with the spark plug electrodes and are similarly connected to the contact members of the distributor 35. However in this construction rectifying space discharge tubes 53 and 54 are connected to the wires 42 and 43 between the condensers 40' and 4|'v and the

contact members

51, 59 and 58, 60 ofthe distributor. The space discharge tube 54 comprises spaced elements 6l and 62 and an energizing or grid element 63, the latter being connected to impedances 64 and' 55 and a small condenser 66 as shown so that when the contact 51 closes current ows through the winding 21', `through the impedance 64 to the l grid 63 and then through the gas contained within the tube to the element 6l, this flow of current between the elements 63 and 5l rendering the gas which separates elements 6l and 62 conductive so that the flow of 'current then takes place 'across those elements. The impedance of part 64 may be suflcient to slightly delay the time at which the main current iiow starts across elements 5I and 62 .so that the contact 54 will be closed before this current llow starts. The, sparking effect across the contacts at the time the contacts close is thus eliminated. And as the glow tube provides for flow of current in one Adirection only between the electrodes 6l and 62, any surging or oscillation tendency that might otherwise be produced is completely damped out instantaneously. The glow tubel 53 is similarly connected to the wire 42'. The glow tubes are also effective in enabling a greater charge to be appliedto the condensers than would otherwise be obtained. This may take place because the inductance of the primary winding of the spark coil and the capacity of the condenser 40 or 4l when connected to that winding and charging can produce a voltage across the condenser in excess of the voltage across the storage condenser due to the oscillatory currents that arise in the circuit and the inductive action which builds up the voltage through the unidirectional path pro- Fig. 3 shows the mechanical arrangement of the primary and secondary windingsV of a spark voltage coil or transformer on the spark plug itself. The

central electrode I5 is separated from the metal body I8 by suitable insulation 10, the lower ends of the body I8 having fingers 1| providing a plu-f' rality of spark,gaps 12 to the central electrode. Detachably secured to the body I8 of the spark plug is a metal casing shield 13, of cylindrical form; having its lower end 14 threaded so it may be readily engaged in a detachable manner with threads provided on the body member I8. With.- in the casing 13A is a metal contact member 15 which may form a magnetic core for the secondary winding I6 which is preferably arranged in honeycomb formation and which is electrically connected directly to the contact member 15 at oneend of the secondary Winding. The other end of the secondary winding is electrically connected by wire 16 to the metal casing and therefore to thebody member of the plug. The wire 16 is also connected to one end of the primary winding 12, the other end of the primary winding being connected as indicatedat 11 to a metal contact member 18 which is provided above the insulation washer 19. The wire 23', having a shielding conduit 41, extends through the coupling member 80 and into the space 8l at the top of the casing where it may rest on the contact member 18, being held down against that contact member by a spring 82 engaged by an adjustable holding screw 83 which is threaded ln 'the top of the casing. An insulating disk 80a is provided on the lug 84 at the end of wire '23' and between that lug and the spring. When the screw 83 is loosened and removed, the lug 811 may be liftd from the contact member 18 and pulled out through the opening which the coupling member provides.

The windings 21 and I6 are preferably surrounded and enclosed in a homogenous body 86 of heat-resistant insulating material such as a suitable ceramic or plastic. The electrical connection between the secondary winding of the coil and the central electrode of the spark plug is effected by a spring blade 81 connected to the top of the plug electrode and bearingyieldingly against the contact member 15, against which it is held by means ofthe spring 82 which holds the entire coil structure downwardly in a yielding manner'in the casing 13. The primary and' secondary windings together with their enclosing shield which prevents radio disturbance may thus be readily removed from the spark plug itself and may be readily attached to the lead wire. The plug may be connected to the engine by using a wrench on the usual hexagonal nut portion 89,

and the coil and casing then added, after which the wire 23 is connected.

The primary winding 21 of the coil may consist cf about 25 turns applied to a honeycomb secondary winding having about 800 turns, the latter being capable of generating current at sufciently high voltage of the order of several thousand volts to break down the gap across the plug terminals. There are no long shielding wires to Vgreatly increase the capacity of the high voltage part of the system, and the shielding of -the comparatively low voltage wires of the system is a simple matter and can` be accomplished without materially increasing the power required by the high voltage system. Condensers may therefore be used to energize the primary windings of the transformers and. to produce a suiiiciently hot spark for effective operation. And since the time 'required for charging and discharging the condensers is almost infinitesimal, the system' is especially useful for high speed aeronautical engines and especially enginesin which the eliminationof radio interference is 'a very desirable factor. y

While the methodand forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to this precise method and these forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. The method of successively energizing the primary windings of spark coils to create sparks at successive spark plugs comprising periodically charging a condenser through a primary winding from a source of charging current while discharging a secondcondenser through the same primary winding to thereby energize said primary windmg, and then discharging the first condenser through a second Winding while charging the second condenser through the second winding to thereby energize the second winding.

2. An ignition system of the character de- .scribed comprising a direct current generator, a

storage condenser connected across said generator, a coil energizing condenser connected electrically at one side to one side of said storage 4 condenser, a series of primary windings, a sec ondary winding for each primary winding, a series of spark gaps connected to\s`aid secondary windings, and a series of contact means for alternately placing the coil energizing condenser across a primary winding and subsequently connecting the coil energizing condenser to the storage condenser through another primary winding, and means for operating said contact means in timed succession.

3. An ignition system of the character desaid storage means, a series of primary windings, a secondary winding and a spark plug associated with each primary winding, and a distributor for successively connecting the primary Windings one'at a time across one of said Condensers and at the same time in series with the other condenser across said storage means.

5. An ignition system of the character described comprising a power source of uninterrupted charging current, a pair of condensers, a

' series of transformer coils, a spark plug associated with each transformer coil, the transformer coils for the respective spark plugs being located at the spark plug locations, a distributor having circuit closing means for each translformer coil, and connections between said source,

condensers, coils and distributor for placing one of said condensers across a transformer coil whiler connecting the other condenser to the power source through the same transformer coil.

6. An ignition system of the character described comprising a power source of continuous charging current, storage means connected across said source, a pair of condensers connected across said storage means, a series of primary windings, a secondary winding and a spark plug associated with each primary winding, a distributor for successively connecting the primary windings one at a time across one of said condensers and at the same time in series with the other condenser across said storage means, a supplemental condenser, and means operable to connect said supplemental condenser across one of said pair of condensers.

'7. An ignition system of the character described comprising a power source of continuous charging current; a pair of condensers connected in series across said storage means, a series of primary windings, a secondary winding and a spark plug associated with each primary winding, a distributor for successively connecting the primary windings one at a time across a condenser and in series with the other condenser across said power source, and a rectifying space discharge tube connected between each of said condensers and said distributor.

8. The method of energizing a transformer means to create sparks at the spark plugs of an ignition system comprising periodically charging a pair of condensers alternately from a common source of charging current, and periodically discharging the condensers alternately through the transformer means so that the charging current of one condenser and the discharging current of the other condenser ow simultaneously through the transformer means to energize the same.

9. The method of energizing the primary part of a spark coil system to create sparks at the spark plugs comprising periodically charging a winding energizing condenser mainly from a storage condenser and to a comparatively small extent from a direct current generator and passing the charging current through a primary winding of the system to energize the same, and

then discharging the energizing condenser 10. The method of energizing the primary partV of a spark plug system to create sparks at the spark plugs comprising periodically charging a condenser through a primary winding'of the system from a source of charging current while simultaneously discharging a second condenser through the same winding to thereby energize the winding, and then discharging the first condenser through a primary winding of the system while simultaneously charging the second condenser from the same source.

11. An ignition system of the character described comprising a direct current generator, a storage condenser connected across said generator continuously, a coil-energizing condenser connected electrically to one side of said storage condenser, transformer means, a series of spark plugs energized by said transformer means, and contact means for alternately connecting said coil-energizing condenser across the transformer means and connecting said condenser to said storage condenser through said transformer means to discharge and charge the energizing condenser alternately at successive spark intervals.

12. An ignition system of the character described comprising a direct current generator, a storage condenser connected across said generator continuously, a pair of energizing condensers connected in series across said storage condenser, transformer means, spark plugs associated with said transformer means, and contact means for placing one of said energizing condensers across the transformer means while simultaneously connecting the other energizing condenser to the storage condenser through the transformer means.

FREDERICK J. HOOVEN.