WO2007008819A2 - Spark plug having 360 degree ground electrode - Google Patents

Abstract

A spark plug (100, Figures 1-5) is provided having a center electrode (107), having an axis and a base (110) having threads on it and end The spark plug also includes a generally circular ground electrode (113) generally concentric with an extension of the axis of the center electrode and having a substantially centrally located opening The ground electrode is supported in relation to the center electrode by a plurality of curved supporting arms (112) extending between the circular ground electrode and the end of the base Th end of the base is arcuately notched between the arms.

Description

SPARK PLUG HAVING 360 DEGREE GROUND ELECTRODE

Related Applications

This application claims the benefit of the filing date of co-pending U.S. Provisional Patent Application Serial No. 60/698,035 entitled SPARK PLUG CONSISTING OF A YTTRIUM CENTER ELECTRODE, ZERO MAINTENANCE GAP SETTINGS, AND 360° GROUND ELECTRODE, filed 11 July 2005, and of U.S. Patent Application of Grahame Ranee, et al, entitled SPARK PLUG HAVING 306 DEGREE GROUND ELECTRODE, Docket No. LSG 3240002 filed 10 July 2006, the entire contents of which are hereby incorporated by reference for all purposes. Technical Field

The invention relates to ignition of engine fuel and, more particularly, to a spark plug providing enhanced longevity, reliability and combustion efficiency. Background

Approximately 80% of the spark plugs manufactured today consist of a copper center electrode and a rectangular "L" shaped ground electrode spaced from the center electrode by a distance often referred to as a "gap". The spark gap has to be set prior to fitting into the combustion engine, to produce heat and spark timing suitable for the particular combustion characteristics of the engine. Due to erosion of the electrode by the spark during operation, the gap between the center and ground electrodes tends to increase. Thus, this type of plug tends to require regular adjustment to maintain the gap, has a short useful life, operates inefficiently and requires frequent replacement over the engine life. Other types of spark plugs have multiple ground electrodes. For example, a spark plug may have two, three, or four L-shaped, rectangular ground electrodes, or multiple V-shaped ground electrodes, or a circular ground electrode with a gap formed therein. A layer of Platinum or Iridium is added at the points where the spark is present to minimize erosion and extend the life of the plug. This layer can also be used in single-ground electrode plugs. These plugs typically have a relatively longer life. Nevertheless, the spark created by the plug tends to travel the shortest distance between the center and ground electrodes. The result is the spark tends to jump the majority of the time to only one of the multi-ground electrodes. Both single and multiple ground electrodes have a tendency to misfire.

Misfiring is the failure of the fuel-air mixture on one or more cylinders to undergo combustion while the car is running. This engine condition can be caused by worn, dirty or incorrectly gapped sparked plugs. If a misfire occurs, the unburned fuel/air mixture is passed through the exhaust system into the environment. This increases fuel consumption and emissions.

The purpose of the spark is to produce a flame at the end of the compression stroke to ignite the fuel-air mixture and generate the power for the combustion engine. A strong flame causes a faster and more complete burn of the fuel-air mixture. A weak to moderate flame instead causes a slower and less complete burn of the fuel-air mixture.

Rectangular, L-shaped ground electrode spark plugs are hampered by frequent misfires and a weak flame. A characteristic of such plugs is that the spark tends to jump across the gap on the side of the ground electrode facing away from the engine cylinder charged with a fuel-air mixture ready to be ignited. Because the point of flame ignition is similarly on the same side of the ground electrode as the spark, the flame ignited must propagate or burn around the ground electrode to begin burning the remainder of the fuel-air mixture in the cylinder. This causes a quenching effect on the flame ignition and overall combustion of the fuel-air mixture in the cylinder.

The weak and slow-burning flame produced leads to incomplete combustion of the fuel-air mixture, the need for more fuel to power the engine than would otherwise be required and resulting higher emissions. Unburned fuel is expelled through a catalytic converter and out of the tail pipe in the form of Oxides of Nitrogen, Hydrocarbons and Carbon Monoxide. These chemicals are big contributors to smog, hi addition, the relatively dirty exhaust contributes to clogging the catalytic converter, reducing its cleansing effect and life.

The use of multiple ground electrodes, including L-shaped, partially circular, and other such configurations, tends to reduce the number of misfires. However, the flame produced is only slightly stronger than use of a single rectangular "L" shaped ground electrode. Many of the various types of multiple ground electrode spark plugs produce a sideways spark, which results in a flame traveling in an arc back to the center. A sideways spark travels horizontally between the electrodes, rather than traveling vertically or at an angle, so that when a flame occurs, the flame travels in an arc back to the center above the point where the spark originated. The burn rate is nevertheless only slightly faster than the "L" shaped ground electrode. Accordingly, there is a need for a more durable, efficient and reliable spark plug that addresses the foregoing short-comings of pre-existing spark plugs.

A spark plug and method of manufacturing the spark plug addressing some or all of the foregoing short-comings are provided that reduce concentrations of heat and to enhance the flow of air and fuel to and around the electrodes, propagation of the flame produced and cooling of the electrodes and support structure. Summary of the Invention

In accordance with an embodiment of the invention, a spark plug has a center electrode having an axis and a base having threads on it and an end. The spark plug also includes a generally circular ground electrode generally concentric with an extension of the axis of the center electrode and has a substantially centrally located opening. The ground electrode is supported in relation to the center electrode by a plurality of curved supporting arms extending between the circular ground electrode and the end of the base. The end of the base is arcuately notched between the arms. Brief Description of the Drawings For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

FIGURES IA and IB depict orthogonal views of a spark plug constructed in accordance with an embodiment of the present invention. FIGURE 2 depicts a cross-sectional view of a typical spark plug in accordance with the prior art.

FIGURE 3 A depicts a cross-section through a part of a spark plug including a circular electrode for use in the present invention, prior to welding of the part onto an end of a base. FIGURE 3B depicts an end view of a part of a spark plug including a circular electrode for use in the present invention, prior to welding of the part onto an end of a base.

FIGURE 3 C depicts a side view of a part of a spark plug including a circular electrode for use in the present invention, prior to welding of the part onto an end of a base. FIGURE 3D depicts an orthogonal view of a part of a spark plug including a circular electrode for use in the present invention, prior to welding of the part onto an end of a base.

FIGURE 4A depicts a cross-section through a part of a spark plug including a circular electrode and arms having through-holes, for use in the present invention, prior to welding of the part onto an end of a base.

FIGURE 4B depicts an end view of a part of a spark plug including a circular electrode and arms having through-holes, for use in the present invention, prior to welding of the part onto an end of a base. FIGURE 4C depicts a side view of a part of a spark plug including a circular electrode and arms having through-holes, for use in the present invention, prior to welding of the part onto an end of a base.

FIGURE 4D depicts an orthogonal view of a part of a spark plug including a circular electrode and arms having through-holes, for use in the present invention, prior to welding of the part onto an end of a base.

FIGURE 5 A depicts an orthogonal view of a part of a spark plug including a circular electrode and a bottom support ring having areas of reduced thickness, for use in the present invention, prior to welding of the part onto an end of a base.

FIGURE 5B depicts a cross-section through a ring of the spark plug of Figure 5 A, for use in the present invention, prior to welding of the part onto an end of a base. Detailed Description

Referring now to the drawings in detail, and initially to FIGURE 2 thereof, a cross sectional view of a typical multiple-ground electrode spark plug 200 in accordance with the prior art is depicted. The spark plug includes a cable nut 201 for terminating the high voltage cable from the ignition system. The cable nut 201 is screwed onto the threaded part of the pin 202, connected to the center electrode 207 through resistor 205. Surrounding the cable nut 201, pin 202, resistor 205 and center electrode 207 is a ceramic insulator 203. The ceramic insulator 203 is inserted into the metal shell 204. The metal shell 204 includes a threaded base 210 having an end 211. An internal gasket 206 is used to prevent any leakage when the fuel-air mixture is ignited. Multiple arms 212 of a ground electrode 208 are welded to the end 211 of the threaded base 210 of the shell 204. Special rib shaping (A) is provided on the ceramic insulator 203.

Referring now to FIGURES IA and IB, a spark plug 100 constructed in accordance with an embodiment of the present invention is depicted. The spark plug includes a center electrode 107. Center electrode 107 can be made of any conductive material having suitable electrical and heat conductivity characteristics. In one embodiment, center electrode 107 is made of a metal including Yttrium metal, a common metal found in earth. This low cost metal has the same long life characteristics of Platinum and Iridium and it is resistant to chemical erosion and corrosion.

Surrounding center electrode 107 is a ceramic insulator 103. The ceramic insulator 103 is inserted into a metal shell 104. The metal shell 104 includes a threaded base 110 having an end 111. The spark plug 100 can include a generally circular, or 360° ground electrode 113 having a central generally circular hole 114 and being generally concentric with an extension of the axis of the center electrode 107. Circular ground electrode 113 can be attached to the end 111 of base 110 by means of multiple curved arms 112 extending from end 111 of the threaded base 110 of the shell 104. Each of the arms 112 can be L-shaped with an arcuate elbow, or smoothly curved throughout. Special rib shaping (A) can be provided on the ceramic insulator 103. In one embodiment, the circular ground electrode 103 is constructed of a metal including Titanium.

As depicted in FIGURES IA and IB, the end 111 can be generally arcuately notched between said arms 112. This improves thermal dynamics, helping to eliminate hot spots that may cause pre-ignition and improves spark performance.

In one embodiment, the spark plug 100 has three arms. Of course, two, four or any number of arms can also be used. In one embodiment, each of the arms is approximately 30 degrees of arc wide, although the arc can be substantially greater or lesser. In one embodiment, the spark plug 100 has upper radiused connections 119 between arms 112 and circular ground electrode 113. This improves thermal dynamics, helping to eliminate hot spots that may cause pre-ignition and improves spark performance, as well as minimizing notch weakness at the connection.

In one embodiment, the spark plug 100 has lower radiused connections 120 between arms 112 and the end 111 of the base 110. This also improves thermal dynamics, helping to eliminate hot spots that may cause pre-ignition and improves spark performance as well as minimizing notch weakness at the connection.

In one embodiment, each of the arms 112 has a generally rectangular cross- section with rounded corners 115. The rounded corners 115 help to eliminate hot spots that may cause pre-ignition and improve spark performance.

In one embodiment, the arms 112 can have through-holes 116 in them. These holes 116 are believed to improve cooling of the electrodes and improve performance. However, such holes 116 are optional.

Production of the spark plug 100 with the 360° ground electrode 113 can be achieved as follows. With reference to FIGURES 3A-D, a part 300 can be made by any convenient means, including through metal injection molding or machining. Part 300 includes a 360° top ring or circular ground electrode 113 connected by two or more arched arms 112 connected to a temporary bottom support ring 117 for welding purposes only. Rounded edges or corners 115 are provided on the arched arms 112 and the top ring or circular electrode 113, and at the juncture between the base of each arched arm 112 and the bottom support ring 117 to reduce localized heating and sparking.

In one embodiment, the configuration of the arched arms 112 provides no substantially horizontal support segment connecting the radius of the arched arm 112 and the top ring 113. This is believed to improve cooling of the electrodes and improve performance.

As depicted in FIGURES 4A-D, holes 116 can be provided in the top of each arched arm 112 of part 300' for extra cooling if required in high performance vehicles. Because the design of the part 300' is otherwise the same as for part 300, it need not be further described.

Referring now to FIGURES IA and IB, the bottom support ring 117 is welded to the end 111 of base 110. Once the 360° weld is complete, the bottom ring 117 can be milled or otherwise machined to a depth of up to 2.5 mm between each of the arched connectors, sufficient to expose at least a portion of the end 111 of the base 110. A portion of the end 111 of the base 110 can also be milled or otherwise machined. In either case, the milling produces a generally arcuate notch between the arms 112 and also leaves a lower generally radiused connection 120 between the arms 112 and the end 111 of the base 110. The spark plug 100 allows the fuel-air mixture to cool the hottest part of the spark plug, which is the ceramic insulator 103, center electrode 107 and the end 111 of the metal shell or base 104. After the 360° circular ground electrode 113 is attached to the end 111 of the base 110 by means of the welding of the bottom ring 117 as described above, and the portions of the ring 117 and/or end 111 are removed through the milling process, as described above, the ceramic insulator 103 and internal gasket (not shown) are fitted. Then the center electrode 107 is precision fitted to one of four gap settings. The gap will not be required to be reset at any time during the life of the spark plug. The resistor (not shown), pin (not shown) and cable nut 101 are finally fitted.

In the alternative to milling the ring 117 as described above, and as depicted in Figure 5 A, the ring 117 may be formed with arcuate notches 121 between the connectors 112. These arcuate notches 121 may extend completely between the arched connectors 112. The arcuate notches 121 may also form circular arcs that extend between adjacent connectors 112. Thus, the amount of milling performed on the ring 117, after it is welded to the end 111, may be reduced or eliminated entirely along with the associated process cost. Preferably, the ring 117 is formed having enough material to permit a continuous weld between the ring 117 and the end 111.

Optionally, the depth of the ring 117 may also vary across its width as depicted in Figure 5B. More particularly, Figure 5B shows that the depth of the ring 117 may decrease from a thickness "A" at its outermost, or front, edge to a depth "B" at its innermost or back edge. It is believed that a decreasing ring depth will allow the fuel to concentrate on the center electrode thereby improving cooling. Figure 5B also shows that the ring 117 may have a maximum depth "C" in the vicinity of the connectors 112. In one embodiment, the depths "A," "B," and "C" are 1.0 mm, 0.5 mm, and 2.8 mm respectively. Of note, the crescent shaped surface appearing in Figure 5B is the three dimensional surface of the ring 117 that is formed by the arcuate notch 121 and the varying depth of the ring 117. Otherwise, the design of the part 300 is the same as previously described and need not be described further.

In operation, a spark produced by a spark plug 100 having a 360° circular ground electrode 113 as shown and described herein originates centrally between the center electrode 107 and the circular ground electrode 113 and consequently a stronger flame produced thereby travels from the center electrode 107 vertically through the hole 114 in the ground electrode 113. Operation of this spark plug results in a stronger flame, more complete fuel combustion, fewer emissions, and reduced chance of misfire. The invention depicted and described herein has a number of significant advantages over the prior art. For example, as enumerated below:

1. The removal of the portions of the bottom ring between the arms once the welding process is complete eliminates heat build up in the ceramic insulator and extended metal shell, thus preventing pre-ignition. 2. Factory precision gap settings eliminates the need for regular maintenance to reset the spark plug gaps. The correct spark plug for the vehicle can be easily fitted. 3. The spark continuously occurs around the 360° ground electrode. This significantly reduces the chances of misfiring. 4. The flame is directed from the center electrode through the center hole in the top ring, producing a much faster and more complete burn of the fuel-air mixture. Magnetic fields around the 360° ground electrode contribute to a high intensity flame. 5. The burn rate for this design is 30% faster than other plugs. 6. The burn rate for this design yields a fuel consumption improvement of up to 10% in 8 cylinder combustion engines.

7. The burn rate for this design yields an average emissions reduction of up to 20% for Oxides of Nitrogen, Carbon Monoxide and Hydrocarbons. 8. The Yttrium center electrode provides long life for the spark plug, equivalent to those of Platinum and Iridium. The 360° ground electrode metal alloy can include small percentages (e.g., a fraction of a percent) of Titanium, Yttrium, or combinations thereof.

9. The extended metal shell contributes to the faster and more complete burn of the fuel-air mixture.

10. Arched connectors and rings eliminate any hot spots.

11. Holes in the arched connectors provide enhanced cooling to the inside of the arched connectors for high performance combustion engines.

12. This design eliminates any point erosion, which is commonly found in "L" shaped and multiple ground electrodes.

13. This design significantly reduces spark plug fouling.

14. This design significantly improves engine cleanliness through reduction of carbon deposits on engine piston and cylinder chamber.

Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.

Claims

Claims:

1. A spark plug comprising: a center electrode having an axis; a base having threads thereon and an end; and a generally circular ground electrode generally concentric with an extension of the axis of said center electrode and having a substantially centrally located opening, said ground electrode being supported in relation to said center electrode by a plurality of curved supporting arms extending between said circular ground electrode and said end of said base, said end of said base being arcuately notched between said arms.

2. The spark plug defined in Claim 1, wherein said arms are generally L-shaped with an arcuate elbow.

3. The spark plug defined in Claim 1, wherein there are three arms.

4. The spark plug defined in Claim 1, wherein each of said arms is approximately 30 degrees of arc wide.

5. The spark plug defined in Claim I₃ further comprising radiused connections between said arms and said circular ground electrode.

6. The spark plug defined in Claim 1, further comprising radiused connections between said arms and said end of said base.

7. The spark plug defined in Claim 1, wherein each of said arms has a generally rectangular cross-section with rounded corners.

8. The spark plug defined in Claim 1 , wherein at least one of said arms has a through-hole therein.

9. The spark plug defined in Claim 1 , wherein each of said arms has a through- hole therein.

10. The spark plug defined in Claim 1, wherein said center electrode includes Yttrium.

11. The spark plug defined in Claim 1 , wherein said curved supporting arms have no substantially horizontal support segment connecting the curved supporting arms to the circular ground electrode.

12. A method of making a spark plug having a circular ground electrode comprising the steps of: providing a base having threads thereon and an end; providing a generally circular ground electrode having a substantially centrally located opening and a generally circular support ring, said ground electrode being supported in relation to said support ring by a plurality of curved supporting arms, said supporting arms extending between said circular ground electrode and said support ring; welding said support ring to said end of said base; and machining away at least a sufficient portion of said lower circular ring between each of said arms to expose at least a portion of said end of said base between each of said arms.

13. The method defined in Claim 12, further comprising the step of machining away a portion of said end of said base between each of said arms.

14. The method defined in Claim 13, wherein said machining away of at least a sufficient portion of said lower circular ring between each of said arms creates an arcuate notch in said end of said base between each of said arms.

15. The method defined in Claim 14, wherein said machining away of at least a sufficient portion of said lower circular ring between each of said arms and a portion of said end of said based between each of said arms creates an arcuate notch in said end of said base between each of said arms.

16. The method defined in Claim 12, wherein said arms are generally L-shaped with an arcuate elbow.

17. The method defined in Claim 12, wherein there are three arms.

18. The method defined in Claim 12, wherein each of said arms is approximately 30 degrees of arc wide.

19. The method defined in Claim 12, further comprising radiused connections between said arms and said upper circular ground electrode.

20. The method defined in Claim 12, further comprising radiused connections between said arms and said end of said base.

21. The method defined in Claim 12, wherein each of said arms has a generally rectangular cross-section with rounded corners.

22. The method defined in Claim 12, wherein at least one of said arms has a through-hole therein.

23. The method defined in Claim 12, wherein each of said arms has a through- hole therein.

24. The method defined in Claim 12, wherein said arms have no substantially horizontal support segment connecting the curved supporting arms to the circular ground electrode.

25. A ground electrode for a spark plug, the spark plug including a center electrode having an axis, a base having threads thereon, and an end, the ground electrode comprising: a generally circular electrode having a substantially centrally located opening; a ring adapted to be attached to said base; and a plurality of curved supporting arms extending between said circular electrode and said ring, said circular electrode to be generally concentric with an extension of said axis of said center electrode when said ring is attached to said base.

26. The ground electrode defined in Claim 25, wherein said ring being arcuately notched between said arms.

27. The ground electrode defined in Claim 26, wherein the thickness of said ring varies across the width of said ring.