WO1993021674A1

WO1993021674A1 - High performance spark plug

Info

Publication number: WO1993021674A1
Application number: PCT/US1993/002547
Authority: WO
Inventors: Augustus J. Hipp; James E. Johnson
Original assignee: Hipp Augustus J; Johnson James E
Priority date: 1992-04-09
Filing date: 1993-03-17
Publication date: 1993-10-28
Also published as: AU3925993A; MX9302031A

Abstract

A spark plug (10) that maximizes the spark pattern, minimizes interference with movement of gases and flame front propagation and provides substantial improvement in performance in comparison to commercially utilized spark plugs is disclosed which comprises a center electrode (12) having an electrical cable connection end (14) and a spark-emitting end, an insulator member (16) encapsulating the center electrode, a metal housing member (20) surrounding the insulator member, and a ground electrode member (13) having spark-receiving sites, the spark-emitting sites of the center electrode (12) being disposed in a first plane and having a peripheral spark pattern, and the spark-receiving sites of the ground electrode (13) being disposed in a second plane parallel to the first plane and the spark-receiving sites being disposed at a uniform, pre-set gap in relation to the spark-emitting sites.

Description

HIGH PERFORMANCE SPARK PLUG FIELD OF THE INVENTION

This invention relates to spark plugs used in internal combustion engines and, more particularly, to a spark plug characterized by substantially improved performance.

DESCRIPTION OF THE PRIOR ART

Internal combustion engine spark plugs in current commercial use characteristically include a center electrode having an exposed end in the base of the spark plug. Typically, in an automotive spark plug, the center electrode is about 0.100 to 0.110 inch in diameter, provides a surface area of about 0.01 square inches, a circumference of about 0.35 inch, and is spaced from a ground electrode. The usual ground electrode configuration comprises a L-shaped single arm welded or otherwise affixed to an edge of the plug and bent over toward the center electrode at substantially a right angle.

In general, this type of spark plug provides satisfactory performance. However, it has been appreciated for many years by those working in this field that it would be highly desirable to provide spark plugs having improved performance. More specifically, use of the previously described commercial spark plugs may thus provide a less than desired burn cycle and/or burn efficiency. What can result is the overheating of parts of the spark plug, incomplete combustion and the production of undesirable, unburned hydrocarbons, carbon monoxide and oxides of nitrogen, in the combustion ^~" chamber exhaust gases.

Over the years, substantial efforts have been undertaken in an attempt to provide spark plugs having desired performance characteristics. Thus, U.S.

2,684,060 to Schechter discloses a spark plug having an insulating element 11 providing support for a centrally disposed electrode 12. The center electrode 12 includes a rod-shaped element 13 embedded in, and projecting from, the end of the insulator 11. The lower end of the element 13 is provided with a disc-shaped electrode 14. The disc-shaped electrode performs the function of covering the opening in the end of the ground electrode, offering obstructive resistance to the products of combustion and also serves to dissipate heat which would normally be absorbed by the insulator. It is further stated that another advantage is that an external spark is provided, rather than one that takes place in close proximity to the insulator and the interior of the spark plug. Because of the disc shape of the electrode and the configuration of the adjacent surface of the shell electrode, the products of combustion, it is stated, are directed away from the insulator and the interior.

Further, U.S. 4,161,937 to Gerry discloses a variety of igniter or spark plug configurations. At least a portion of the air-fuel mixture is ionized in proximity of the electrodes of the igniters thereby creating a plasma at least in proximity of such electrodes. The plasma may then be subjected to a magnetic field created by virtue of the igniter base material being permanently or electromagnetically magnetized. Still other prior work includes U.S. 3,009,075 to

Hensley. Hensley discloses a spark plug that has a self- contained protective shield for preventing the accumulation of foreign matter upon the spark plug, so as to enhance the efficiency. U.S. 3,394,285 to Lindsay discloses a two-gap spark plug with a series resistor for each gap.

Additionally, U.S. 2,269,682 to Paulson discloses various spark plug configurations that are said to operate using electrodes of small mass and of considerable total surface area in relation to their mass. U.S. 4,419,601 to Ha ai et al. discloses a spark plug including a resistive semiconductor body connecting a center electrode and an earth electrode to perform a creeping discharge at low discharge voltages while keeping adequate ignition performances.

The aforementioned patents represent only part of the considerable work undertaken over the years. Yet, despite all of this substantial work, there remains a need for a spark plug configuration providing performance improvements in relation to commercially utilized spark plugs.

SUMMARY OF THE INVENTION In accordance with the present invention, a spark plug has been developed that maximizes the spark pattern, minimizes interference with movement of gasses and flame front propagation and provides substantial improvement in performance in comparison to commercially utilized spark plugs. Thus, employing spark plugs according to the present invention can greatly reduce ignition delay time even under conditions of high compression. In addition, utilizing the spark plugs of the present invention allows increased burning efficiency in the combustion chamber, resulting in a cooler running engine, increased engine horsepower and mileage per gallon or liter of fuel consumed as well as reduced oxides of nitrogen, carbon monoxide and hydrocarbon emissions. ^"

Pursuant to the present invention, the spark plug includes a center electrode having ah enlarged diameter and a circumference or perimeter significantly larger than that of the center electrode of commercial spark plugs, as discussed above, and having spark-emitting sites concentrically (or complementary) disposed about the periphery of the center electrode in a first plane. A ground electrode, disposed at a fixed, pre-set gap in relation to the spark-emitting sites of the center electrode, comprising spark-receiving sites disposed in a second plane and concentric to the spark-emitting sites of the center electrode. In order to achieve the enhanced performance in accordance with the present invention, the first and second planes must be parallel. Also, the center electrode spark-emitting sites must be concentric to the spark-receiving sites of the ground electrode and uniformly spaced therefrom by the desired fixed spark gap.

BRIEF DESCRIPTION OF THE DRAWINGS The invention may be best understood by those having ordinary skill in the art by reference to the following detailed description, when considered in conjunction with the accompanying drawings in which:

FIGURE 1 is an isometric view of one embodiment of the spark plug of the present invention;

FIG. 2 is a cross-sectional view taken generally along the line 2-2 of FIGURE 1 and illustrating the positioning of the center electrode in relation to the end of the spark plug housing; FIG. 3 is a partial cross-sectional and schematic view of a spark plug configuration according to the present invention, schematically showing the relative positioning of the center electrode in relation to that of the ground electrode; FIG. 4 is a partial cross-sectional view of a spark plug wherein the metal skirt is reduced in thickness; FIG. 5 is a plan view of the most preferred configuration for a center electrode for the spark plug of the present invention; FIG. 6 is a plan view of yet another embodiment that may be used for the center electrode;

FIG. 7 is a partial cross-sectional view of an alternative embodiment for a center electrode and showing a configuration utilizing a skirt member; FIG. 8 is a partial isometric view of a further, and preferred, embodiment of a spark plug of the present invention in which the center electrode is positioned beneath the ground electrode;

FIG. 9 is a partial cross-sectional view taken generally along the line 9-9 of FIG. 8 and further illustrating the positioning of the center electrode and the ground electrode;

FIG. 9a is a partial detail view of the embodiment shown in FIGS. 8 and 9, and further illustrating the relative positioning between the center and ground electrodes and the ground electrode support legs;

FIG. 10 is a partial isometric view of yet another embodiment of the spark plug of the present invention and showing an embodiment in which the insulator projects above the end of the spark plug housing; FIG. 11 is a partial isometric view of yet another embodiment for a ground electrode for use in the spark plug of this invention;

FIG. 12 is a partial isometric view of a further embodiment of a spark plug according to the present invention and showing a double ring configuration; and

FIGS. 13, 13a and 13b are isometric and side views of a partially assembled ground electrode having a mounting ring.

DETAILED DESCRIPTION OF THE INVENTION

Throughout the following detailed description, the same reference numerals refer to the same elements in all Figures. The spark plug has been shown in a base-up position in the drawings for ease of illustration. However, the base is considered in its usual position in service for purposes of the description which follows.

As shown in FIGURE 1, the spark plug 10 of the present invention can suitably assume the configuration of a conventional automotive internal combustion engine spark plug, except having the unique center and ground electrodes of the present invention. Thus, the spark plug 10 includes a terminal element 14 for-connecting to a coil wire (not shown) . A high quality insulator 16 encapsulates the center electrode which terminates at the bottom of the spark plug 10 as exposed center electrode 12. Many suitable ceramic materials are known in the art and may be employed to make the insulator. Also, a high temperature resistant polymer or other appropriate heat resistant insulative material could, of course, be employed for the insulator.

The bottom of the spark plug 10 comprises a metal shell or housing member 20 and a nut portion 22. Shell or housing member 20 thus terminates in a shank 24 having a threaded shank skirt 26 and ground electrode 13. As will be discussed hereinafter, the interior^" portion of shank 24 terminates in one ground electrode configuration of this invention in this embodiment.

Pursuant to one aspect of the present invention, a center electrode having spark-emitting sites about its periphery is provided. To this end, as shown in FIGS. 1 and 2, planar center electrode 12 is affixed to a center electrode member 11. Planar center electrode 12, as shown in FIGS. 1 and 2, is in the form of a plain solid disc. Center electrode 12 may be formed of any corrosion-resistant metal capable of providing spark- emitting sites. As is known in this field, many suitable materials may be used in spark plug manufacture. Illustrative examples include alloys such as nickel/chromium, platinum and the like.

The center electrode 12 may be affixed to center electrode member 11 by any suitable means. For example, center electrode 12 may be welded, brazed or otherwise fused with the center electrode member. Indeed, if desired, the center electrode and center electrode member may be of a unitary configuration.

In accordance with another aspect of the present invention, a ground electrode is provided which is disposed at a fixed, pre-set gap in relation to the spark-emitting sites of the center electrode, providing spark-receiving sites disposed in a second plane. To this end, and as shown in FIGS. 1 and 2 , a ground electrode 13 is formed by the skirt portion of the spark plug housing. Thus, the metal end of the spark plug housing defines a skirt portion 26 terminating in an annular ground electrode surface 13. As can be seen, annular ground electrode surface 13 is concentric to the center electrode and generally to the longitudinal axis of the spark plug. In general, the distance between the spark-emitting sites of the center electrode and the spark-receiving sites of the ground electrode will typically be about 0.030 to 0.060 inch (viz. - 0.76-1.152 mm). However, a greater or lesser spacing may be desired, or even required, for special application spark plugs, where combustion chambers of unusual design are employed, or when fuels such as propane, methanol, ethanol, or other fuels are substituted for gasoline. The distance or gap appropriate for a particular application may be readily determined by straightforward testing, as is known.

Upon firing, multiple electrical sparks move from the peripheral surface 12A of the center electrode 12 to the peripheral surface 13A of ground electrode 13. While no preferred angle has been experimentally determined, it is believed suitable and desirable to provide an angle of the spark from the center electrode 12 to the surface of the ground electrode 13 of from about 15° to about 75° from the longitudinal axis of the spark plug. This angle may be easily controlled merely by selecting the desired vertical spacing between the center electrode and ground electrode and selecting the diameter of the center electrode 12 for forming the pre-set gap during the manufacturing process.

Pursuant to the present invention, in order to achieve a uniform, consistent spark pattern and the enhanced performance characteristic of the spark plugs of the present invention, it is critical that the planes of the spark-emitting sites of the center electrode and that of the spark-receiving sites of the ground electrode be parallel. Additionally, it is further critical that the spark-emitting sites in any annular configuration of the center electrode be concentric to the spark-receiving sites of the ground electrode with uniform spacing between such emitting and receiving sites being maintained by the desired fixed spark gap.

In accordance with the present invention, an enhanced and uniform circular spark pattern is provided, thereby enlarging the combustion area and improving the combustion flame spread around the periphery of the center electrode. Such a uniform flame spread results in more complete combustion of the fuel mixture, increased horsepower for a given amount of fuel consumed and increased fuel economy, as well as other advantages as herein described. Thus, and of great significance, the ignition delay, dwell time, or combustion chamber smolder time is greatly reduced and the anticipated spark plug life is greatly increased in comparison to that of a conventional spark plug since the distribution of the sparks along the ground electrode surface prevents the single point-type burn which occurs when using a conventional ground electrode. In addition, the present configuration continues to fire in substantially the same firing pattern under very high compressions where other spark plugs tend to cease all but sporadic firing.

In general, the positioning of the planar spacing of the center electrode from that of the ground electrode may be varied within wide limits. To this end, as is diagrammatically show in FIG. 3, the planar location of the center electrode may vary from A, to B, to c and, as is known, even to D. The dotted lines, designated GA, GB, GC and GD, define the uniform annular spark gap between the respective center electrode spark-emitting surface and the spark-receiving surface of the ground electrode configurations shown. As seen in configuration D of FIG. 3, the center electrode 12 must be of a smaller diameter than in the other configurations A, B and C of FIG. 3. Reducing the diameter of center electrode 12 to achieve configuration D is undesirable; and, in order to maximize the diameter of center electrode 12, the thickness of the bottom end of the spark plug skirt 26 must be reduced to about 0.035 inch or even less to accommodate such larger diameter center electrode 12 as shown in FIG. 4, so as to provide the desired enlarged spark pattern of the present invention. The minimum thickness will, in general, be determined by the desired service life for particular applications. Thus, referring to FIG. 4, center electrode 12, having spark-emitting sites 12A about tne periphery of electrode 12, fires to the spark-receiving sites 13A around the inner periphery of ground electrode 13 in an enlarged spark-emitting and receiving pattern to increase the ignition front size and improve propagation of the combustion flame front. In the configuration —shown in FIG. 4, the spark-emitting sites and spark- receiving sites lie in the same or substantially the same plane and the spark-emitting sites are concentric toy—and uniformly spaced from, the spark-receiving sites to achieve the desired improved spark pattern. In addition to the center electrode shown in the embodiment of FIGS. 1 and 2, the center electrode may assume other configurations so long as the appropriate annular spark pattern is provided in accordance with this invention. Of course, it is critical to the present invention to maintain a parallel relationship between the plane of the center electrode spark-emitting sites and the plane of the spark-receiving sites of the ground electrode, while maintaining the concentricity of the spark-emitting sites of the center electrode and the spark-receiving^ites of the ground electrode with the uniform annular spacing of the spark-emitting and spark receiving surfaces being maintained, regardless of the geometric configurations used.

More particularly, to allow the maximum enhancement in spark pattern and performance to be achieved, the annular spark-emitting surface is continuous. Such a surface, regardless of how the rest of the center electrode may be configured, is attained by using a center electrode having a uniform, continuous peripheral surface. In this fashion, the entire periphery of the center electrode constitutes the spark-emitting surface. The performance is thus enhanced because of the size of the spark pattern. Also, the multiple spark-emitting sites involved can significantly increase the expected service life in comparison to that of a conventional spark plug. Thus, the use of the present invention eliminates the spark concentration generally believed to be responsible for the erosion of the center electrode in spark plugs of conventional design.

However, while not providing maximum enhancement to the spark pattern, substantial improvement in the pattern and in the performance in comparison to that of a , conventional spark plug may be achieved by configurations where the peripheral surface of the center electrode is not continuous, but an annular spark pattern in accordance with this invention is provided when multiple spark-emitting sites are disposed in a single plane about a circle formed by concentric multiple spark-emitting sites. In accordance with this invention, an annular spark pattern is provided where the spark-emitting surface is a continuous or discontinuous ring, or a series of equal length radial arms extending in the same ^~~ plane from a central hub, to provide spark-emitting sites about a ring uniformly spaced from the spark-receiving sites and concentrically disposed thereto. Indeed, many other configurations for the ground electrode can be envisioned, including a variety of complex shapes. However, the use of a continuous, circular ring provides significant advantages in manufacture and assembly. Thus, as to the latter point, the use of a circular ring simplifies assembly insofar as insuring and achieving the essential concentricity and uniform gap between the spark-emitting and spark- receiving sites.

Further, other center electrode configurations may be used for increasing the periphery of the spark- emitting surface, provided that the spark-emitting and receiving sites of such electrodes lie in parallel planes, opposing electrode configurations provide a uniform spark gap between such sites and such configurations do not interfere significantly with gas movement and flame front propagation. However, spark- emitting and receiving sites which provide concentric configurations are the more desirable configurations and simplify manufacturing techniques.

FIGS. 5 and 6 show alternative configurations that may be used as a.center electrode in the present invention. Center electrode 12 may be a continuous ring as shown or a discontinuous ring, symmetrical or asymmetrical, or in the form of radial arms, symmetrical or asymmetrical, in a single plane as depicted in FIG. 6. So long as the spark-emitting sites are concentric to the spark-receiving sites and are uniformly spaced therefrom, any of the foregoing configurations of FIGS. 5 and 6 may be used to provide improved spark patterns in accordance with the present invention.

Thus, a most preferred configuration for the center electrode for a spark plug of this invention is shown in FIG. 5. The center electrode 12 thus has a central portion 12• , a plurality of arms 12", each of equal length and radiating from the center portion 12 ' to the periphery 12A of the electrode. This configuration is advantageous because it provides maximum spark-emitting sites, and minimum restriction to flame front propagation and movement of combustion gasses. Indeed, regardless of the particular configuration employed for the center electrode, it is preferred in accordance with the present invention to minimize the restriction to flame front propagation and movement of combustion gasses. This objective can be accomplished by using a center electrode configuration having as much open area as possible, consistent with providing the desired surface for the spark-emitting sites. Thus, upon firing, the speed of ignition is enhanced, as is the propagation of the flame front, so as to achieve complete fuel combustion. This will result in reductions in the emissions of undesired hydrocarbons and oxides. As used herein, the terminology open center electrode thus refers to an electrode configuration that minimizes the restriction to flame front propagation and movement of combustion gasses.

FIG. 7 shows an alternative configuration that may be used for a center electrode in the spark plug of this invention. In this illustrative alternative embodiment, center electrode 12 is shaped to provide a ridge-like ring 12A as the spark-emitting surface and the spark- receiving surface of the ground electrode 13 likewise may have a similar ridge-like ring 13A, as shown.

FIGS. 8, 9 and 9a show a preferred embodiment of a spark plug according to the present invention^ In this embodiment, the center electrode 12 is positioned beneath the ground electrode 13. Thus, ground electrode 13 is raised above skirt 26 by utilizing legs 15. This embodiment is preferred .because it projects the spark pattern toward the combustion chamber while presenting minimum restriction to flame propagation and combustion gas movement. In this configuration, the gap distance Y between the center electrode 12 and the ground electrode 13 must be less than the distance X from the center electrode 12 to ground electrode mounting leg 15 in order to prevent the center electrode from firing to the leg, as shown in FIG 9a. In some spark plug configurations, the insulator portion projects beyond the end of the skirt or threaded portion of the plug housing. For this type of configuration, FIG. 10 shows a suitable spark plug pursuant to the present invention. To this end, legs 15 position ground electrode 13 above the threaded end of the housing skirt 26. Center electrode 12 is positioned at the end of center electrode member 11.

Yet another configuration that may be employed for the ground electrode is shown in FIG. 11. In this embodiment, the ground electrode 13 comprises a series of uniform annular saw teeth 13A which provide spark- receiving sites and which are uniformly spaced from and concentric with the spark-emitting sites. As may be appreciated, the ground electrode must have a configuration and be positioned such that the — critical relationships hereinbefore discussed are maintained, but the shape of the ground electrode need not be complementary to that of the center electrode. For example, if the saw tooth configuration as shown in FIG. 11 is utilized for the ground electrode, the accompanying center electrode need not have a matching or similar saw tooth configuration, provided that the distance between the multiple spark-emitting and spark- receiving sites is uniform and such sites are^" concentrically disposed in parallel planes. It may, of course, facilitate assembly in providing the desired uniform gap to utilize center and ground electrodes of complementary shapes. The center electrode may be fabricated by stamping, molding, or indeed by any other process as is known in the art. Similarly, the ground electrode may be made by molding, machining, grinding or any other processes, as are also known in the art. Pursuant to a further aspect of the present invention, it is believed that a double ring ground electrode configuration provides particular advantages when made of material different from that of the metal housing 20 of the remainder of the spark plug. In this embodiment, it is believed that a magnetic field is induced because of a coil effect, in part due to the dissimilar materials and the high current surge of the arc-strike, and that the magnetic field causes the randomly oriented fuel molecules to polarize and realign. This thereby exposes a greater surface area of the fuel molecule to the spark. This phenomenon also eliminates the quenching effect as seen in other spark plug configurations, thus enhancing the flame kernel growth. FIG. 12 shows such a double ring ground electrode configuration. Ground electrode ring 13 is thus connected to the housing mounting ring 17 by leg 15. The double ring configuration is mounted onto the spark plug skirt to obtain desired spark gap.

Further, in this embodiment, the ground electrode end of the skirt portion 26 is machined or ground to provide an interior or an exterior shoulder 18 as shown in FIGS. 13, 13a and 13b. The double ring ground electrode comprises the ground electrode 13, leg 15 and the mounting ring 17. The ground electrode and mounting ring are interconnected by at least one leg 15, but more may be used as desired. In assembling this configuration, the leg 15 length is chosen in combination with the depth of shoulder 18 along the longitudinal axis of the spark plug to achieve the desired spark gap between center electrode 12 and ground electrode 13. The mounting ring is placed upon shoulder 18 and is welded or otherwise fused to the threaded shank skirt portion 26 to complete the assembly.

Alternatively, the mounting ring may be attached to the end surface 13 of FIG. 1 in those instances where the ground electrode 13 is raised above the skirt portion as shown in FIGS. 8-10, with or without the use of a machined shoulder. In this latter configuration, the gap between the center electrode and ground electrode is determined by the length of the leg or legs 15.

Claims

WHAT IS CLAIMED IS:

1. A spark plug for an internal combustion engine, said spark plug having a longitudinal axis and comprising a center electrode having an electrical cable connection end and a spark-emitting end configuration providing spark-emitting sites, an insulator member encapsulating said center electrode, a bottom portion of the insulator member enclosed by a metal housing member, a bottom portion of the metal housing member having a cylindrical hollow shirt and a ground electrode member having spark- receiving sites in electrical contact with the skirt, the spark-emitting sites of said center electrode configuration being disposed in a first plane and providing a peripheral spark pattern, the spark-receiving sites of said ground electrode being disposed in an opposed complementary configuration to that of said center electrode in a second plane parallel to said first plane and said spark-receiving sites being disposed at a uniform, pre-set gap in relation to said spark-emitting sites, said center electrode having a peripheral surface length greater than 0.35 inch.

2. The spark plug of claim 1 wherein said first and second planes are vertically spaced along said longitudinal axis.

3. The spark plug of claim 1 wherein said metal housing member terminates in a skirt member adjacent said spark-emitting end of said center electrode and said skirt member is said ground electrode member.

4. The spark plug of claim 3 wherein said center and ground electrodes are concentric.

5. The spark plug of claim 1 wherein said spark- emitting and spark-receiving sites are concentric.

6. The spark plug of claim 1 wherein said center electrode has a uniform, continuous peripheral surface and said peripheral surface comprises the spark-emitting sites.

7. The spark plug of claim 1 wherein said center electrode comprises a central portion, a uniform, continuous peripheral surface spatially disposed from said central portion to provide an open area and said peripheral surface comprising the spark-emitting sites, and a plurality of spaced radial arms connecting said central portion and said peripheral surface.

8. The spark plug of claim l wherein said center electrode comprises a solid, annular disc.

9. The spark plug of claim 1 wherein said center electrode has a peripheral surface and a ring depending from said peripheral surface toward said metal housing member, said ring comprising the spark-emitting sites.

10. The spark plug of claim 1 wherein said ground electrode is disposed further along said longitudinal axis than said metal housing member and said center electrode at said spark-emitting end, at least one leg supporting said ground electrode in relation to said metal housing member.

11. The spark plug of claim 1 including a double ring member, said metal housing member having a skirt member adjacent to said spark-emitting end of said center electrode and said skirt member having a shoulder, said double ring member comprising a first ring seated in said shoulder, a second ring disposed along said longitudinal axis at said spark-emitting end further than said first ring and said second ring comprising said ground electrode, and at least one leg connecting said first and second rings.

12. The spark plug of claim 11 wherein said double ring member is of a metal different than that of said metal housing member.

13. The spark plug of claim 1 wherein said insulator member projects along said longitudinal axis at said spark-emitting end beyond said metal housing member, said ground electrode is disposed along said longitudinal axis at said spark-emitting end beyond said metal housing member, and a plurality of legs supporting said ground electrode in relation to said metal housing member.

14. The spark plug of claim 1 wherein said spark- emitting sites of said center electrode are emitted to a ground electrode comprising the metal housing member.

__ 15. The spark plug of claim 14 wherein said spark- emitting and spark-receiving sites lie in opposed, complementary configurations and said spark-receiving__ sites are uniformly spaced from the periphery of the center electrode spark-emitting sites.

16. The spark plug of claim 1 wherein said center electrode has spark-emitting sites which define an annular spark pattern.

17. The spark plug of claim 16 wherein said center electrode spark-emitting sites are spaced from said metal housing to define the spark gap and said spark-receiving sites are in. an annular configuration defined by said metal housing.

18. The spark plug of claim 1 wherein said center electrode has a periphery greater than 0.5 inch in length.

19. The spark plug of claim 1 wherein said center electrode lying in said first plane has a diameter greater than about 0.115 inch.

20. The spark plug of claim 19 wherein said center electrode has a circumference greater than 0.35 inch and provides annular spark-emitting sites about said circumference.

21. The spark plug of claim 1 wherein the sparks emitted by said spark-emitting sites to said spark- receiving sites are emitted at an angle of from 15 degrees to 75 degrees, measured from the longitudinal axis of said spark plug.