US2840623A - Ignition system for internal combustion engines - Google Patents

Description

June 24, 1958 P. B. MIDDLETON v 2,840,

IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed Feb. 25, 1956 v s Sheets-Sheet 1 INVENTOR.

24M 464M 1 M June 24, 1958 MlDDLETON 2,840,623

IGNITION SYSTEM FOR. INTERNAL COMBUSTION ENGINES Filed Feb. 23, 1956 3 Sheets-Sheet 2 3e I3 57 ll INVENTOR. F/ 1.4 1 M 739 1am zda-w gmow 9 M J m 1 5 I P. B. MIDDLETON 2,840,623

IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed Feb. 23, 1956 3 Sheets-Sheet 3 VOLTAGE' |--o-E FIRING CYCLE -I fig 6 7 75 INVENTOR.

168? IFMW VIM United States Patent IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES Philip B. Middleton, Culver, Ind., assignor to Studebaker- Packard Corporation, Detroit, Mich., a corporation of Michigan Application February 23, 1956, Serial No. 567,274

11 Claims. (Cl. 123- 148) a This invention relates to ignition systems for internal combustion engines and particularly to a low tension, high frequenc electronic ignition system.

A main object of the invention is to provide a new and improved low tension, high frequency ignition system.

Another object of the invention is to provide a new and improved distributor for ignition systems.

Other objects of the invention will become apparent from the following specification, the drawing relating thereto, and the appended claims.

In the drawing:

Fig. 1 is a vertical elevational view of a distributor for ignition systems embodying the inventionhaving a portion broken away to show a section;

Fig. 2 is similar to Fig. 1 except that the distributor cap is not shown and the distributor rotor is omitted to permit a clear illustration of electrical components in the distributor;

Fig. 3 is a cross sectional view taken on line I II-II*I of Fig. 1;

Fig. 4 is a cross sectional view taken on line IV--'IV of Fig. l;

Fig; 5 is a schematic circuit diagram of an ignition system embodying the invention; and

Fig. 6 is a graph showing the voltage changes of an oscillating circuit in which the main condenser in the ignition system is disposed during each firing cycle.

Referring to the drawings, there is shown in Figs. 1 to 4: a distributor 10 constructed in accordance with the invention. The distributor comprises, in general, a cylindrical housing member 11, a cap member 12 which fits on housing 11, and a rotor member 13.

A shaft 14, which is adapted to be engine driven in accordance with standard practice, is rotatably mounted in housing 11 in bearings which are not shown. Shaft '14 has an upper portion which drives rotor 13 and upon which the rotor is seated. In accordance with standard practice, centrifugal means may be provided in the distributor, in the portion thereof which is not broken away, foradvancing rotor 13 and the upper portion 15 of the shaft relative to the lower portion of the shaft in plate relative to plate 23 and housing 11 in response to engine throttle conditions to advance or retard elec-, trode 21 relative to rotor 13. A mechanism of this type, which is vacuum operated, is commonly used for distributor breaker plates and need not be referred to fur ther herein. 1 r l Circuit means are mounted or provided in housing 11 Patented June 24, 1958 which are adapted to receive current from a source externally of the distributor and such current is transmitted through electrode 21. scribed in detail further on in the specification.

Rotor 13 comprises, in general, a body made of several portions of nonconducting material to which is added certain conducting elements which 'form parts of primary and secondary circuits. The body of rotor 13 includes a can shaped portion 25 for supporting a primary winding, a tubular portion 26 which extends through and is press fitted in a hole in the bottom of can shaped portion 25, a base portion 27 having a hole into which tubular portion 26 is press fitted and a downwardly facing counterbored recess provided with a key for receiving shaft portion 15 in driving engagement, a cap portion 28 having ahole to receive the upper portion of tubular portion 26 in press fitting engagement and a downwardly facing recess to receive the upper portion of can portion '25 in press fitting engagement, and an arm 29 which e'xtends radially from cap portion 28.

' Tubular portion 26 should be of a material comparable to good porcelain or insolate because it must function to insulate separated coils or pics of the secondary cir- 'cuit from each other, there being a potential difference of several thousand volts between the pics? The pies will be referred to more in detail further on in the specification. Can portion 25 must likewise be of high quality insulating material since it serves to insulate the primary winding from the secondary, the potential difference therebetween being several thousand volts. Base portion 27 must have ruggedness since it receives the torqueyof the drive mechanism through shaft portion 15 to which it is keyed.

An annularly shaped multiple electrode having a plurality of electrodes 35 to 42 is fixedly mounted in press with electrode 21 mounted on plate 20 so that electrodes 35 to 42 sequentially form gaps with electrode 21 during rotation of rotor 13. .The number of electrodes 35 to 42 provided corresponds to the number of cylinders an en-' gine has for which the distributor is to be used. Electrodes 35 to 42 are in the form of blades so that upon rotation of rotor 13 a fan action is obtained which circulates air and produces a cooling effect on other elements in the distributor.

Rotor 13 is provided with a primary winding 45 and a secondary winding 46 to form an ignition coil having the characteristics of a high frequency oscillation transformer, Secondary winding 46 is wound in pies on tubular portion 26 and primary winding 45 is wound on the outside of can --s-haped portion 25. The pie type construction is a standard well-known type of coil winding. One end of'primary :winding 45 is connected by a wire .47 to the multiple electrode upon which electrodes 35 to 42are formed and the other end is grounded through the housing ll of the distributor'by being connected by a wire 48 and a conducting element 49 to a conducting rod 50. The circuit for this ground includes a nonmagnetic conducting r0d 50 which has the form of an elongatedrscrew andis disposedfiin the tubular portion 26 of the rotor, a slip ring '5l which is press fitted on the base portion 27 of the rotor, a conducting element 52 between rod 50 and slip ring Sl, and contacts 53 whichare mounted on the bottomside'of plate 23 and rubbingly engage slip ring 51. Contacts 53 are grounded to housing 11 of the distributor by. virtue of plate 23 being connected to the housing. Conducting. rod 50 is provided with threads at the top thereof and has a-nut54 applied thereto, Thetopof rod 50,turnsin a bearing 55 mounted in the distributor cap 12 andservesto center the rotation of rotor 13; I

The circuit means will be de-' surfaces which lie 'in and. define a circular locus 65. A

conducting tip 67 is provided on the arm '29 of rotor cap portion 28 to which one end .of the secondary wind in; 46 is attached; :Tip 67 has an en d surface in closely spaced relation to or on locus 65 in accor'dance with standard practice. Secondary .winding 46, which is woundfonthe. tubular portion 26 of rotor 13, has one end thereof connected to conducting rod 50 through wire 52, which is also a part of the primary circuit, for grounding-the secondary winding 1 46. The distributor is designed to. be timed in a known manner so that at the instant it is designed tofire a spark plug, one vof the electrodes 35 to 42 passes the electrode 21 on plate 20; and at that instant conducting element 67 is in general alignmentwith one of the contacts 56 to 63 with which the plug to be fired is connected. The circumferential width of the tip 67 should of course be wide enough so as to be generally aligned with one of the contacts 56 to 63 at the'time of firing regardless of the position of rotor 13 relative to the engine driven shaft14 due to action of spark modifier or vacuum advance mechanism. r

The foregoing description refers primarily to the physical construction of the distributor. Reference is now made to the ignitioncircuit shown in Fig. 5.

In the'schematic circuit diagram of Fig. a high voltage source is provided (not shown) which supplies a D. C. voltage potential on the order of 2000 volts. The voltage source supplies a storage condenser 70, grounded at. 71'. which in turn supplies a main condenser 72 which is grounded at 73. i A safety gap 74, grounded tohousing 1 1,I is provided for main condenser 72 which limits the voltagelo which the storage condenser 72 can be charged by thesource. Main condenser 72 is in an oscillatory circuitwhich includes a stationary gap device 75, 'the electrode 21 which is mounted on plate of the distrihutor, and primary winding 45 which is wound on can portion 25 of rotor 13. 1

It will be observed,yas illustrated in Figs. .1 to 4, particularly Fig. 2, that the storage condenser 70, the main condenser 72 and the "stationary gap device 75 may be mounted in the housing 11 of the distributor. An opening surrounded by a. bushing 77 is provided in distributor housing 11 to provide entrance for a wire 78 to connect the voltage source to the storage condenser 70 mounted Referring again to the schematic diagram shown in Fig. 5, the operation is as follows. Storage condenser 70 is of relatively large capacity and, during the charging and. discharging of main. condenser 72, the voltage of storage condenser. 70 varies roughly between 1000 and.

2000 volts. The rotation of rotor 13 causes the electrodes to 42 mounted thereonto sequentially form gaps with electrode 21 mounted on plate 20 and, upon the forming of each gap and during the time interval one of the electrodes 35 to 42 in the gap forming proximity to stationary electrode 21, main condenser 72 chargesand discharges thousands of times arid the discharge is. through theprimary winding 45. This is a high frequency oscillatory discharge by virtue of there being provided. a tuned or oscillatory-circuitin which main condenser 72and.

primary winding 45 are disposed. The voltage changes in the tuned circuit during the formation of a gap by of secondary winding46, the mutual inductance of the primary and secondary windings 45 and 46, the addi-' tional inductanceof the secondary circuit, and the series one of the electrodes 35 to 42 with the stationary electrode 21 is illustrated in Fig. 6. Referring to Fig. 5, the oscillatory circuit is traced from main condenser 72 through the stationary gap device 75, stationary electrode 21, one of the rotating electrodes 35 to 42, primary winding 45, conducting rod 50, conducting element 52, slip ring 51, contacts 53 and the housing 11 to which contacts 53 and main condenser 72 are grounded. In Fig. 6 the abscissa of the graph is broken to indicate that there are many more voltage changes in theoscillatory circuit during one firing cycle than can be illustrated. The firing cycle is the time interval that one of the electrodes 35 to 42 is in gap forming proximity to stationary electrode 21.

The voltage to which main condenser 72 is periodically charged is greater than the break-down voltage of the gaps sequentially formed between electrodes 35 to 42 and stationary electrode 21, and the break-down voltage of the gap in the stationary gap device 75, to permit an electronic oscillatory discharge of main condenser 72. As each of the electrodes 35 to 42 recedes from the stationary electrode 21 during rotation of rotor 13 the oscillatory circuit is broken. Stationary gap device 75 rapidly quenches the oscillating current, this being its function. A high frequency choke coil 76 is disposed between the oscillatory circuit and storage condenser 70 and the resistance and inductance characteristics of the choke coil 76 prevents feed back of the oscillating current from the oscillatory circuit to the storage condenser 70. Coil 76 should bewound in a manner so that it withstands high voltage without flashover. The resistance characteristics of coil 76 must be suitable to dissipate a substantial part of the primary circuit energy during intervals of firing the secondary circuit.

The ignition coil formed by the primary and secondary windings 45 and 46' is preferably a high frequency oscillation transformer. In a particular embodiment of the invention a turn ratio of the secondary winding 46 to the primary winding 45 on the order of twenty to one was found satisfactory although it will be understood that such ratio will vary widely for various applications of the invention. The windings 45 and 46, which are inductively and electronically coupled, should be low loss,

high frequency coils wound on or supported by a low loss mounting. The secondary winding 46 should preferably have an inductance of at least one millihcnry, should be constructed to provide for maximum inductance and should have a high voltage rating. 7 7

Secondary winding 46 should furthermore be supported by and be near insulators such as tubular portion 26 that have low loss and high insulating characteristics. Secondary winding 46 should be wound'in a manner so as to resist the tendency to lose high frequency energy or encounter breakdown of the insulation under high frequency, high voltage conditions.

The circuit in which the secondary winding 46 is disposed includes the conducting tip 67 mounted on the arm 29 of rotor 13 to which one end of the secondary winding 46 is connected, the contacts 56 to 63 in the distributor cap with which conducting tip 67 is sequentially aligned during rotation of rotor 13, high frequency ignition cables (cable 80 in Fig. 5) and spark plugs (spark plug 81 in Fig. 5) connected to contacts 56 to 63, the ground return from the spark plugs, and the grounded conducting rod 50 to which the opposite end of the secondary winding 46 is conducted.

The oscillatory discharges of the main condenser 72 in the primary circuit, which is an oscillatory circuit, induces stepped up oscillatory voltages in the secondary circuit having a frequency determined by the inductance and shunt capacitance'in the secondary circuit. Al-

ternate conducting paths provided by introducing more or fewer distributor cap contacts, cables and spark plugs the distributor is through the grounded distributor hous-.

ing 11. The wire entering the distributor through bushing 77 serves as an entry point for electrons to the ungrounded, insulated portions of the circuits in the distributor and the insulation surrounding this wire should be of'high" dielectric strength and value because of the high voltage of the supply source.

The following voltage figures are to be considered as being illustrative and not limiting with regard to the scope of the invention. In an actual embodiment of the invention the main condenser was charged tokbetween 1600 and 2000 volts and the firing voltage in the secondary circuit was on the order of 20,000 volts. The frequency of the voltage in the secondary circuit was onthe order of 500 kilocycles per second.

The ability of a low tension, high frequency ignition.

system to fire fouled spark plugs may be explained by the fact that the sparking voltage is applied to the spark plug electrodes for such a short period of time that appreciable current leakage through parallel conducting paths formed by deposits on the spark plug insulator surface cannot occur.

The ignition system of the present invention provides a sustained ignition by virtue of their being provided a series of sparks across the electrodes of a spark plug during each firing interval or cycle. These separate oscillatory electronic discharges during each firing interval or cycle, as illustrated by the graph in Fig. 6 showing the voltage changes of the main condenser 72 during each firing interval or cycle, are impulses of approximately the same magnitude and each impulse represents a separate spark which causes regeneration and/ or reignition of the ignition flame. This is to be distinguished from a conventional high tension system in which there is only one principal spark during a firing interval or cycle,

The invention may be embodied in other specific forms Without departing from the spirit or essential characteristics thereof. The present embodiment of the invention is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

It is claimed and desired to secure by Letters Patent:

1. An ignition system comprising a direct current volt age source, a storage condenser supplied by said source, a main condenser charged by said storage condenser during each firing cycle, a high frequency ignition coil having primary and secondary windings, an oscillatory circuit including said primary winding and said main condenser, means for periodically rendering said oscillatory circuit conductive to effect the discharge of said main condenser to said primary winding after said main condenser is charged to a predetermined potential during each firing cycle, and spark plug distributor means connected with said secondary winding.

2. An ignition system comprising a direct current voltage source, a storage condenser electrically connected to and supplied by said voltage source, a main condenser charged by said storage condenser during each firing cycle, a high frequency oscillation transformer having primary and secondary windings, an oscillatory circuit including said primary winding and said condenser, ro-

tatable means for periodically rendering said oscillatory1 circuit conductive to effect the discharge of said main,

condenser to saidprimary winding, means between said oscillatory circuit and said storage'condenser to prevent feed back from said oscillatory circuit to said storage condenser, and spark plug distributor means connected with said secondary winding.

3. An ignition system comprising a direct current voltage source, a storagecondenser electrically connected to and supplied by said voltage source, a main condenser charged by said storage condenser during each firing cycle, a high frequency oscillation transformer havingprimary and secondary windings, an oscillatory circuit including said primary winding and said main condenser, rotatable means for periodically rendering said oscillatory circuit conductive to efiect the discharge of said 7 main condenser to said primary winding after said main condenser is charged to a predetermined potential during each firing cycle, radio frequency choke coil and resistance means between said oscillatory circuit and said storage condenser to prevent feed back from said oscillatory circuit to said storagecondenser, stationary gap means in said oscillatory circuit to efiect rapid quenching denser for rendering, said oscillatory circuit conductive.

to effect the discharge of said main condenser to said primary winding after said'main condenser is charged to a predetermined potential during each firing cycle,'and spark plug distributor means connected with said secondary winding.

5. An ignition system comprising a direct current vol age source, a storage condenser electrically connected to and supplied by said voltage source, a main condenser charged by said storage condenser during each firing cycle, a rotatably mounted high frequency oscillation transformer having primary and secondary windings, an oscillatory circuit including said primary winding and said main condenser, rotatable multiple electrodes connected to and rotatable with said primary winding for periodically rendering said oscillatory circuit conductive to elfect the discharge of said main condenser to said primary Winding after said main condenser is charged to a predetermined potential during each firing cycle, a radio frequency choke coil and resistance means between said oscillatory circuit and said storage condenser to prevent feed back from said oscillatory circuit to said storage condenser, stationary gapmeans in said oscillatory circuit to eifect rapid quenching of the oscillating current, and spark plug distributor means connected with said secondary winding.

6. A distributor for an ignition system comprising a housing member, a rotor rotatably mounted in said housing member, a drive shaft rotatably mounted in said housing member connected to said rotor in driving relation and adapted to be driven by an engine, primary and secondary windings mounted on said rotor and connected in series, an electrode mounted in said housing, a plurality of electrodes on said rotor connected to said primary winding and sequentially forming gaps with said electrode mounted in said housing upon rotation of said rotor, and

ingrnember connected to said rotorin driving relation and adapted to be driven by an'engine, primary and secondary windings mounted on said rotor and connected in series, an electrode mounted insaid housing a plurality of electrodes on said rotorconnected to said primary winding and sequentially forming gaps with, said electrode mounted in said housing upon rotationofsaid rotor, a distributing electrode mounted on the body of said rotor and connected :to said secondary winding, and circuit means in hou'singadapted to receive current from an external source and s'up'plycurre'nt to said primary winding through said electrode mounted in said housing.

8. A distributor for an ignition system comprising a housing member, a cap member, a rotor having a body formed of insulating material rotatably mountedin said housing member, a drive shaft rotatably'mountcd-in said housing memberhaving a first portion adapted to be driven by an engine and a second portionconnected to said rotor indrivirig relation, said second portion-and said rotor being adapted to being advanced relative to said first portion in'responseto increased zengine speed, primary and secondary windings mounted on said rotor,- an annularly shaped, plate memb r pivotallymounted in said housing member adapted to'be" pivoted in -response to j engine throttleconditions, an electrode mountedon said plate and electrically insulated -therefrom,[a plurality; of

on the body of said rotor, conductor Jrneans connecting said primaryand secondary windings to said' slip' ring, grounded contacts on said-housing for engaging said slip ring, ardistributing electrode mounted on-the of said rotor and connected to said secondary winding, a

plurality of electrodes mounted in said'cap housing with which gaps are sequentially formed by said distributing electrodeupon rotationxof said rotor, and circuit means 8 in said housing adapted to receive current from an external source and supply current to said primary winding through said electrode on said plate.

9. A distributor in accordance with claim 7 in which said circuit means comprise a main condenser charged eluding said primary winding and said main condenser.

i 10. A distributor in accordance With claim 7 in which said circuit means comprise storage condenser, a main condenser grounded to saidhousing and charged by said storage condenser during each firing cycle, gap means in.

parallel with said'main condenser, an oscillatory circuit including said primary winding and said main condenser, means between said oscillatory circuit and said storage condenser to prevent feed back from saidoscillatory circuit to said storage condenser, and stationary-gap means in said oscillatory circuit to effect rapid quenching of the oscillating current.

11. A distributorin accordance with claim 7 in which said circuit means comprise a storage condenser connected to andtsupplied by said external voltage source and grounded to'said housing, a main ondenser grounded to-said h'ousing and charged by said storage condenser during each'firing cycle, gap means in parallel with said main condenser, an oscillatory circuit including said primarywinding and said main condenser, choke coil and resistance means between said oscillatory circuit and said .storage condenser to prevent feed back from said os- UNITED STATES PATENTS 2,276,966 Hansell Mar. 17, 1942 'Peroutky May 8, 1951

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