US2621312A - Ignition control - Google Patents

Description

Dec. 9, 1952 J. J. MAscUcH ETAL IGNITION CONTROL Filed Sept. 19, 1950 INVENToRs. {EFP/f J.' Mnscucf/ l I 1 i Y l x l x l X X X X i x 1+ Patentecl Dec. 9, i952 IGNITION CONTROL Joseph J. Mascuch, Maplewood, and Melville F. Peters, East Orange, N. 3.

Application September 19, 1950, Serial No. 185,617 20 Claims.I (Cl. B15- 46) This invention relates to internal combustion engines and particularly to the control of the delivery of fuel igniting sparks across the electrodes of a spark plug constituting a part of the combustion chamber assembly in an internal combustion engine.

In United States patent applications, Nos. 126,771 and 126,772, led on November 12, 1949 by Melville F. Peters, one of the joint applicants making this present application, it is explained that in the conventional high-tension series gap types of ignition systems there is a substantial amount of electrical energy remaining in the central conductive path of the spark plug after the initial spark discharge across the firing points of the spark plug. In said applications it is also explained that this residual energy frequently creates a reverse potential gradient condition that opposes further flow of current to the spark plug in suicient strength to produce a second spark -discharge across the plug electrodes. It is this impediment to follow-up flow that frequently interferes with successful starting of an internal combustion engine. The patent applications above-identified disclose methods and means for removing from the hightension cable the objectionable residual energy above described.

The present invention provides a novel cable terminal construction adapted to serve automatically as a residual energy removing instrumentality, and also as a voltage build-up accelerator for converting the relatively slow build-up rate of the generating unit (spark coil or magneto) into a more rapid build-up rate, effective to reduce substantially the likelihood of mislring of the spark plug; the novel terminal construction including a, tubular grounded conductor of high resistance material and a conductive coupling incorporating a series gap and a series resistance unit intermediate the cable conductor and said series gap. Since the grounded tubular element functions to maintain the central plug conductor at ground potential between rings, it follows that each successive series gap breakdown occurs at a potential that is correspondingly lower than normally would be necessary for such break-down. Because of this ability to lire at lower potential, a spark plug equipped with such a grounded resistor, interposed directly between the series gap coupling and ground, lends itself to high frequency operation, whether it be a conventional plug or a radio-shielded plug; the herein-disclosed terminal being applicable to either type,

In the drawings: e f

Fig. l is a longitudinal sectional view of a portion of a radio-shielded spark plug to Vwhich is applied a cable terminal embodying the invention;

Fig. 2 is a longitudinal sectional view of a comparable cable terminal'applied to a conventional, un-shielded plug; and

Fig. 3 is a circuit diagram explaining the electrical action, in both embodiments.

In the embodiment shown in Fig. l, the radioshielding `barrel I3 extends upwardly from the base i l, with its wrench-receiving portion l2, and is lined with the usual non-conducting sleeve 9, serving as a socket for reception of the novel cable terminal, attached to the cable in the following manner: The insulationsurrounding the lower half-inch (more or less) of the hollow, spirally-wound central conductor E@ of the cable is removed, and a bolt 34 having a longitudinally disposed slot along its shank, to receive the exposed conductor end, is then pressed into the cable center; being preceded by a metal washer 32. A lock washer 33 and nut 3l] are then placed on the shank of the bolt B and serve to pinch the exposed end of the conductor 2li therebetween by deflecting it side-wise, as illustrated, as the bolt is pushed firmly into place. -A bushing 3l of insulating material, with a transversely disposed, centrally apertured shelf, is now slipped over the cable end, until the transverse shelf abuts the nut portion of the bolt. In this position the lower end of the bolt extends downwardly below said shelf to receive the central coupling assembly, consisting of the nut 35, the resistance plug I4, the upper gap element 23, the non-conducting spacer 25, and the lower gap element 24.

The inner diameter of the sleeve 9 lining the plug barrel i3 is somewhat greater than the outer diameter of the bushing 3l containing the central conductive assembly just described. This difference in diameters is taken up by employing, as the high resistance grounding shunt, a

tubular element 2l, to whose lower end is attached a thimble 4| having a central opening over which the depending knob 42 of the gap element 24 is upset to unite the tube 2l and thimble 4l to the remainder of the cable terminal assembly. The thimble includes a second cylindrical section 43 serving to position the coiled compression spring 44 constituting the conductive coupling between thimble 4l and thehead portionll of the central conducting spindley I0 whose lower tip constitutes the sparking electrode, or ring point of the plug, as indicated schematically at I6 in Fig. 3. At its upper end. the high-resistance shunt tube 2I is anged to over-lie the upper end of the barrel I3, being pressed thereagainst by the action of screwing the cap 46 on the threads of the barrel. Cap l5y presses down on the tube flange by way of the intervening bulge 6B formed in the cable shielding sleeve 48; the cap 4S thus servingV as the, anchoring means for the cable and its shielding, as well as a conductive coupling between the shielding circuit elements 48 and I3.

The high-resistance shunt tube 2| may be fashioned out of conductive porcelain or other ceramic, conductive rubber or conductive plastic materials other than rubber. The only restrictions are that it be composed of materials whose electrical resistance is less than infinite, and that said materials be such that their resistance de. creases as temperature increases.

In the embodiment of Fig. 2 the high-resistance shunt tube 2I, like the tube 2I of Fig. 1,is in direct circuit relationship between v the grounded spark-plugbase I and the seriesl gap element 25 of the cable terminal assembly I3I4-23-2, which assembly conductively couples the ventilated cable conductor 2 0 to the spark plug central electrodespindle Ill by way of conductive coating Ill, seriesgap elements 2.3-24,

and metallic, elbow-shaped, thimble d4' whose i lower end embracesH the head portion l5r of the electrode spindle Il); the parts 4Q' and 5f of Fig. 2 vthus corresponding in function to the parts M and 4 5 of Fig. 1-. Conductive coating I4, applied to the inner surfaces of dielectric sleeve 3 I, serves as series resistor between the cable conductor 20 and the series gap elements 23, 2d. Its resistance value will correspond tothat of resistor I4 of Fig. l.

The high-resistance shunttube 2| of Fig. 2 will have the same electrical properties, and mode of operation, as the correspondingly numbered tube 2l of Fig.I l; but it will also have sufcient elasticity to permit its being ntted over the cable assembly ZIJ-SI-ZS-Z-Ii after the relatively rigid metallic tting 44' has been secured in rivet fashion to the series gap element 24 of the assembly, as indicated at 42. The lower portion of tube 2I is thereafter pushed downwardly over the dielectric body IS of the plug,

until its lower lip 5I snaps under the wrenchreceiving bulge I2 of the base II, to complete the grounding circuit- As this operation is being performed the metallic elbow 4' is simultaneously positioned in embracing relationship to the spark-plug spindle head 45', thus completing the central conductive circuit leading to the spark gap IB-I9, by way of spindle I6.

In both embodiments, each sparking cycle is initiated by a build-up of high-frequency energy to the voltage value determined by the dimension of the series gap 23-24; the series resistor I4 also being a factor in this building-up process. When the gap sparking voltage value is reached, energy discharge occurs-first across series gap 23-24, and in predetermined time sequence thereafter across the spark-plug points IB, I9. Since the wave front is steep, due to the continuous metallic path from gap element 24 to point I8 (in both embodiments), little energy is lost through grounded high-resistance shunt tube 2I during the brief duration 0f each spark discharge across ISB-I9.. On the other hand, immediately following cessation of energy flow across sapK Iii-H, alliesidual enfasi remaining. ,inthe central conductive circuit is shunted through the said tube 2| to ground, thus dropping the said central conductive circuit (including the series gap elements 23-24) to ground potential and thereby clearing the central conductive line against any possibility of impeding the voltage build-up for the next succeeding spark discharge cycle.

The use of ,the high resistance shunt 2I (as in either embodiment) produces high frequency operation because its action in reducing the central conductive circuit to ground potential after everyiiring cycle makes it possible for the plug to re-re at a radically lower voltage peak, and hence .in a radically vshorter time interval. This can be expressed in the form of equations, as follows: Without thisshunt 2 I (l) V=either or C2 C1 butv by introducing the shunt 2I (2) V=ethcr V1 or V2 In these equations v representsthe break-down voltage of the plug (ring point) while V1 is the break-down voltage of the series gap 23-24; V2 the break-down voltage of the spark gap; C1 the capacitance of the series gap; and Cathe capace itance of the spark gap. If Ci and C2 are approximately equal, it follows thatthe value V obtained from Equation2 will be only about onethe plug and cable assemblies are so interfittedI as to permit free passage of all developed gases out of the plug cavities by way of said conductor,

, or into the plug cavities in reverse fashion, for

pressurizing. However, the invention is equally eiective whenapplied to a structure wherein the series gap is sealed against entry or emergence of gases, and it isaccordingly to be understood that the expression series gap in the claims ernbraces all known types of series gap installations.

What we claim is:

1. In an ignition circuit, a spark plug having a central Spindle terminating in a spark discharge electrode, a cable terminal assembly electrically and mechanically coupled to said centralspindle,

said cable terminal assembly including a combi-l nation gap and resistor to ground operating to convert a conventional ignition system into a high-frequency system by draining oli' to ground,

by way of said resistor, all residual energy remaining in said ignition system at the conclusion y of a spark discharge at said electrode.

2. In an ignition circuit, a spark plug having a central spindle terminating in a spark discharge electrode, a dielectric body surrounding said spindle, a metallic shell supporting said body, a cable terminal assembly including a metallic thimble forming part of the central conductive path between the cable conductor and said spindle, and means constituting a current path for draining oil to ground, by way of said metallic thimble and said Shell, any residual energy re-` maining in said central conductive path at the conclusion of a spark discharge at said electrode.

3. An ignition circuit as defined in claim 2, wherein said draining-off means includes a tubular element forming a direct electrical couple of high resistance between said metallic thimble and said shell.

4. An ignition circuit as defined in claim 2, wherein said cable terminal assembly includes a pair of spaced elements consituting a series gap in said central conductive path, one of said gap elements being integrated with said thimble.

5. An ignition circuit as dened in claim 2, wherein said draining-off means includes a tubular element interposed in telescopic relationship to the shielding extension of the spark-plug shell, and constituting part of the cable terminal assembly.

6. An ignition circuit as dened in claim 2, wherein said draining-off means includes a tubular element whose one end surrounds the cable terminal assembly and whose other end surrounds and attaches to the spark-plug shell.

7. An ignition circuit as dened in claim 2, wherein said draining-ofi means includes an element having a lower degree of conductivity than said central conductive path.

8. In an ignition circuit, a spark plug having a central spindle terminating in a spark discharge electrode, a cable terminal assembly electrically and mechanically coupled to said central spindle, said cable terminal assembly including a resistor and series gap in the central conductive path leading to said central spindle, and a shunt path to ground of substantially higher resistance than said central conductive path.

9- An ignition circuit as defined in claim 8, wherein said shunt path includes a tubular element forming part of said cable terminal assembly.

10. In an ignition circuit, a spark plug having a central spindle terminating in a spark discharge electrode, and a cable terminal assembly electrically and mechanically coupled to said central spindle, said cable terminal assembly including a pair of resistance elements, one in series with said spindle and the other in shunt.

11. An ignition circuit as denned in claim 10, wherein said series resistance element is a factor in controlling the rapidity of voltage build-up prior to spark discharge, and wherein said shunt resistance element operates to remove residual energy following spark discharge.

12. In an ignition circuit, a spark plug having a central conductive path of pre-determined resistance, and means detachably mounted on the spark plug to establish a shunt path to ground of substantially higher resistance than said central conductive path.

13. An ignition circuit as defined in claim 12, wherein said central conductive path includes a series gap. and wherein said shunt path originates at said series gap.

14. A terminal assembly attachable to an ignition cable and including a residual energy grounding resistor opreating to transform a conventional spark generating and discharging system into a high frequency system by increasing the rate of secondary voltage build-up in the central conductive path of the plug.

15. A `spark plug cable terminal assembly including a tubular element forming a high resistance couple between the central conductive path of the plug and the grounded outer shell of the plug, and operating to remove from said central conductive path all residual energy remaining therein following spark discharge.

16. A cable terminal assembly as dened in claim 15, and further including a pair of spaced elements forming a series gap, said tubular element `being in direct electrical association with said gap elements.

17. A cable terminal assembly as defined in claim 15, wherein said tubular element ts concentrically around the cable, and has detachable connection with the spark plug outer shell.

18. A cable terminal assembly as defined in claim 15, wherein said tubular element extends into the annular space between the end portion of the cable and the surrounding cylindrical eX- tension of the spark plug.

19. A cable terminal assembly as defined in claim 15, wherein said tubular element has a snapgn connection with the spark plug, adjacent its ase. Y

20. In an ignition circuit, a spark plug having a central conductive path, and a cable terminal assembly attachable to said spark plug, said cable terminal assembly including a second conductive path of higher resistance than said central conductive path, but connecting directly therewith.

JOSEPH J. MASCUCH. MELVLLE F. PETERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,938,308 Weigand Dec, 5, 1933 2,322,773 Peters June 29, 1943 2,323,399 Jacobi July 6, 1943 2,323,931 Peters July 13, 1943l 2,379,942 Webber July 10, 1945 2,399,314 Barker Apr. 30, 1946*

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