SPARK PLUG

Abstract

A spark plug having a center electrode and/or a ground electrode with an attached spark portion. The spark portion has a base material and a protective material wherein the base material is highly resistant to spark erosion and the protective material is highly resistant to corrosion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given here below, the appended claims, and the accompanying drawings in which:

FIG. 1 is an exemplary diagram of an Iridium spark portion that has been severely corroded;

FIG. 2 is a partial sectional view of a spark plug;

FIG. 3 is an enlarged sectional view of the center electrode including spark portion of the spark plug;

FIG. 4 is an enlarged sectional view of the center electrode including spark portion of the spark plug;

FIG. 5 is an enlarged sectional view of the center electrode including spark portion of the spark plug;

FIG. 6 is an enlarged sectional view of the center electrode including spark portion of the spark plug;

FIG. 7 is an enlarged sectional view of the center electrode including spark portion of the spark plug;

FIG. 8 is an enlarged sectional view of the center electrode including spark portion of the spark plug;

FIG. 9 is an enlarged sectional view of the ground electrode including a spark portion;

FIG. 10 is an enlarged sectional view of the spark portion illustrating the diffused boundary;

FIG. 11 is an enlarged sectional view of the center electrode including spark portion of the spark plug having multiple layers of protective material before diffusion of the protective material with the base material; and

FIG. 12 is an enlarged sectional view of the ground electrode including a spark portion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention as illustrated in the figures is directed to a spark plug 10 (FIG. 2) having a ground electrode 12 and a center electrode 20. The center electrode 20 and/or the ground electrode 12 include a spark portion 30. The spark portion 30 may be bonded, welded 38, or otherwise attached to the center electrode 20 (FIG. 2) and/or the ground electrode 12 (FIG. 9).

The spark portion 30 includes a base material 36 and a protective material 34 that generally forms an outer or protective layer (FIGS. 3-9). As illustrated in FIG. 10, the protective material 34 may become diffused with the base material, forming a spark portion 30 without a distinct layer between the protective material 34 and base material 36. More particularly, the base material 36 is primarily formed from a material resistant to spark erosion, such as Iridium (Ir), Platinum (Pt), Palladium (Pd), Rhodium (Rh), Ruthenium (Ru), Rhenium (Re), or alloys thereof. The most commonly used elements of the above group include Platinum and Iridium. Exemplary additions to form alloys of the above base material include one or more elements selected from the group consisting of Iridium, Platinum, Palladium, Rhodium, Ruthenium, Rhenium, Zirconium (Zr), Nickel (Ni), and Tungsten (W). Another exemplary base material 36 formed from an alloy is described in more detail in U.S. patent application Ser. No. 11/691,288, filed on Mar. 26, 2007 and entitled “Spark Plug”. While the present invention contemplates Iridium or Platinum as the base material or an Iridium alloy or Platinum alloy, the present invention is not constrained only to the use of Iridium or Platinum, or Iridium or Platinum alloys, as the base material. Yet another exemplary Iridium alloy suited for use as the base material includes 94% to 99% Iridium, 1% to 3% Rhodium, 0.1% to 1.5% Tungsten, and 0.01% to 0.1% Zirconium by weight. For large industrial spark plugs, the base material typically has a diameter of approximately 1.8 mm to 4 mm, for vehicle spark plugs 0.4 mm to 2.1 mm, and hobby spark plugs 0.25 mm to 2.1 mm.

The protective material 34, when combined with the base material, prevents the corrosion or oxidation of the base material in the presence of Calcium and Phosphorus. The protective material 34 is formed from a corrosion and oxidation resistant element. In the prevent invention, the protective material 34 is formed from Nickel or a Nickel alloy. Exemplary Nickel alloys include 85% Nickel and 15% Chrome by weight.

While the protective material 34 may be formed out of a single alloy as described above, each of the elements may also be placed in separate layers on the base material. It has been found that placing separate successive layers of each individual element instead of alloys thereof provides sufficient protection as desired and lowers the material cost. For example, if a base material is Iridium or an Iridium alloy, Copper may be applied as a first layer through plating and then Nickel may be applied as an outer layer through a successive plating option. Of course, Chromium could be substituted for the Copper to achieve similar corrosion resistant results. Of course, various orders of arrangement may also be used with the Nickel being on the inner layer and in direct contact with the base material. The inventors have also found that any arrangement of layers for protective materials including Copper, Nickel, and Chromium may be used, however one particularly useful protective layered material is formed by plating a Copper first layer 34a to the base material 36, a second layer 34b of Chromium adhered to the Copper through a plating operation and then a third layer 34c of Nickel adhered to the Chromium through a plating operation, as illustrated in an exaggerated sectional view in FIG. 11. However, it should be noted that as the individual layers may later become diffused together along with the base material.

Sparks typically originate on the edge 44 of the spark portion 30 and, as Nickel is subject to spark erosion, the protective material must be formed thin enough so that the spark across the spark gap 14 primarily originates on the base material 36 and not the protective material 34 during continued operation of the spark plug. In some embodiments, for manufacturing ease, the discharge surface 40 may also be coated with a sacrificial protective material 36 that erodes away from the discharge surface 40 during operation, but remains on the sides of the spark portion 30 to protect against corrosion in the presence of Calcium and Phosphorus. Therefore, the protective material 34 is generally formed having a thickness of less than 0.09 mm. Adding a layer with a thickness of 0.002 mm to 0.018 provides sufficient corrosion protection to the base material while yet avoiding spark erosion. As the protective material 34 is formed with a very thin layer of material, any gap changes due to spark erosion are not substantial to effect performance of the spark plug. Also, areas susceptible to corrosion, such as the side surfaces, are generally not susceptible to spark erosion, yet the protective material protects the side surface from corrosion. The edge 44 and discharge surface 40 of the spark portion 30 are typically not susceptible to corrosion in the presence of Phosphorus and Calcium as the spark activity prevents this corrosion mechanism in the presence of Phosphorus and Calcium.

The spark portion 30 in the illustrated embodiment is shaped in a cylindrical or polygon shape having an outer circumference 42 and a first end or discharge surface 40. The end opposing the discharge surface 40 is attached to the center electrode 20. The center electrode 20 is generally made out of a corrosion resistance element or alloy such as Nickel or a Nickel alloy, however other elements and alloys may be used, such as an Iron based center electrode. As illustrated in the figures, the protective material 34 does not extend over the first end or discharge surface 40. As the discharge surface 40 constantly has sparks emanating therefrom during operation, corrosion to the discharge surface 40 is minimal or non-existent as the sparking predominately keeps the discharge surface 40 free of corrosive elements.

As stated above, to prevent spark erosion, the spark portion 30 has a protective material that is plated, sputter, flame sprayed, or plasma coated with a thickness that is less than 0.09 mm. Therefore, the amount of protective material 34 added or deposited to the base material 36 is minimal. Therefore, enough protective material is deposited to the outer circumference of the base material to form a spark portion 30 that is highly resistant to corrosion while yet minimizing the amount of material deposited on the spark surface to prevent excessive gap growth through spark erosion.

By using a thin layer as described above, during the firing of the spark plug or component of the spark plug in a furnace during the manufacturing process and potentially the later operation of the spark plug in an engine, the protective material 34 becomes diffused into the base material 36, so that the protective material and base material are diffused together so that a definite boundary between the protective material 34 and base material 36 may be hard to determine, as illustrated in FIG. 10. More specifically, because the base material 36 is diffused with the protective material 34 around the outer circumference, in a cross-sectional view the spark portion 30 moves from being predominately Nickel near the outer circumference 42 through a diffused area 90 where the amount of protective material continually decreases away from the outer circumference (FIG. 10). FIGS. 3-10 illustrate a protective material 34 in an exaggerated fashion as to the thickness before diffusion. As illustrated in FIG. 10, the illustrated layer being between approximately 100% protective material at the outer circumference and decrease to at least 10% where the inner boundary 91 is illustrated, even though no distinct boundary exists once diffusion occurs. More specifically, the diffused area of protective material extends from the outer circumference 42 where the protective material 34 forms almost 100% of the material toward the center 32 of the spark portion 30 until the base material 36 is substantially predominate such as being more than 90% by weight at that given area forming the inner boundary 91. As illustrated in FIG. 10, an area 64 where equal amounts of base material and protective material may be found. One skilled in the art would recognize that FIGS. 3-9 for visual clarity illustrate the layer of protective material or diffused area as being much thicker relative to the base material than is described in the specification or claimed in the claims.

As the spark plug in operation has the base material 36 diffused into the protective material and the protective material 34 diffused into the base material 36, it is very difficult during operation for the protective material 34 to become separated from the base material 36 as may happen with thicker cladded materials. For example, a clad base with an outer layer having a thickness greater than 0.09 mm, may have dissimilar thermal profiles due to the dissimilar materials, which may have become separated over time as the spark plug continually fluctuates between hot and cold thermal cycles. Therefore, providing a thin layer that becomes diffused into the base material instead of having distinct individual layers allows the spark plug to increase the longevity of operation through increased spark erosion resistance, increased corrosion resistance, as well as increased durability.

The spark plug 10 including the spark portion 30 may be made through any known method. The manufacture of spark plugs is well known, including the addition of a spark portion 30 on the center electrode 20 and/or the ground electrode 12. In the present invention, the spark portion 30 may be bonded, resistance welded, laser welded, or attached through any known method to the center electrode 20 and/or ground electrode 12. The spark plug 10 generally includes a metallic shell, an insulator, and the center electrode 20 disposed in the insulator such that the spark portion 30 on the center electrode 20 projects toward the ground electrode 12 with the discharge surface 40 (FIG. 2).

The insulator is typically formed out of Alumina and has a passage through which the center electrode 20 extends. The metallic shell is formed out of a cylindrically shaped metal sleeve including threaded portions which thread into an engine block. The metallic shell is typically formed out of plain carbon steel or stainless steel or other materials.

The spark portion 30 is generally first formed by forming the base material 36 from Platinum, Palladium, Rhodium, Iridium, Ruthenium, Rhenium, or alloys thereof. The base material 36 of the spark portion 30 may be formed through any known method. The base material 36 may be formed in metal sheets, discs, wires, or rods through hot forming, hot rolling, or hot wire drawing. Another method of forming the base material 36 is to take a metal powder and melt the powder to form the base material 36. The melting process may be done through arc melting, beam melting, laser melting, high frequency induction melting, plasma melting, or any other known method.

With the base material 36 formed in approximately the desired shape, typically in the form of an elongated rod or wire, the protective material 34 is then added to the base material 36 forming the rod or wire. The protective material 34 may be added through processes such as electrolytic on non-electrolytic plating, electrodeposition, sputtering, flame spraying, or even co-extrusion. It is important that the thickness of the protective material when added to the base layer is not more than 0.09 mm. Of course, any other means of providing a thin layer of less than 0.09 mm on the outside surface of a base material may be used to apply the protective material 34 to the base material 36. Once the spark portion 30 is formed with a protective material 34 on the outside of the base material 36, the elongated portion is cut, stamped, or pressed to the appropriate length and the individual pieces are prepared to be attached to either the center electrode 20 or the ground electrode 12.

Methods of attaching the spark portion to the ground electrode 12 and/or center electrode 20 include welding such as by resistance, laser, or other means to the center or ground electrode 12/20. Another method is to form impressions or depressions on the outer surface of the spark portion 30 to create mechanical locking mechanisms (not illustrated). The center electrode 20 is drilled out to the same diameter as the spark portion 30 and the spark portion 30 is inserted into the hole (FIG. 7). The center electrode 20 is then heated such as with a laser so that the metal melts around the inserted spark portion 30 and forms into the depressions on the outer surface. Of course other forming operations to the spark portion 30 such as making a headed rivet may be performed and then the spark portion may be attached to the center electrode 20 as is known in the art. Furthermore, the spark portion 30 may be attached to another wire or disc and welded thereto and then in turn welded to the center electrode 20 to enhance the bond between the center electrode 20 and the spark portion 30.

The center electrode 20 is illustrated in FIG. 3 welded directly to the center electrode 20, the center electrode 20 may be processed to reduce the diameter of the nickel tip 21 of the center electrode and provide a cavity 22 for receiving a spark portion 30. The spark portion 30 may include a variety configurations, such as an assembled spark portion 30 formed from more than one material and then having the protective material applied. More specifically, as an example, the spark portion may be formed from a nickel portion and iridium portion, which is assembled onto the center electrode (FIG. 6). The protective material 36 may cover both portions and be applied before or after assembly to the center electrode. As illustrated in FIGS. 3 and 4, the spark portion 30 may be first processed to be coat the base portion 36 with the protective material 34. The spark portion 30 when coated with the protective material 34 is then welded to the center electrode 20. The weld pools 38 occur from the welding of the spark portion 30 to the center electrode 20. The spark portion 30 in FIGS. 5 and 6 is applied after the base material 36 is attached to the center electrode 20. More specifically, the base material 36 is attached to the center electrode 20, and then the protective material 34 is applied to the center electrode 20 and the base material 36. This allows for easy application of the protective material during the manufacturing process. In FIG. 6, a multi-layer rivet is formed as the spark portion having the base material attached to another material 33, typically Nickel alloy. An example of an assembled spark portion 30 may be found in U.S. patent application Ser. No. 11/602,028, filed Nov. 20, 2006, entitled “Method Of Forming A Spark Plug With Multi-Layer Firing Tip, U.S. patent application Ser. No. 11/602,146, filed Nov. 20, 2006, entitled “Spark Plug With Multi-Layer Firing Tip, and U.S. patent application Ser. No. 11/602,169, filed Nov. 20, 2006, entitled “Spark Plug With Multi-Layer Firing Tip”, which are incorporated here by reference. As described above, just the spark portion 30 may include a layer of protective material, or the center electrode and base portion may include the layer of protective material. The protective material 34 is applied to the multi-layer rivet to form the spark portion 30. The multi-layer rivet spark portion 30 is then attached to the center electrode, such as by welding. The multilayer rivet in FIG. 6 is illustrated as being attached to the center electrode and then coated with the protective material however, it could first be coated with the protective material and then attached. FIG. 9 illustrates the spark portion 30 being applied to the ground electrode 12.

The protective material may be further enhanced through chemical or heat treatment. The heat or chemical treatment may occur before or after the spark portion 30 is attached to the center electrode 20. For example, heat treatment of the spark portion 30 may occur during manufacture of the spark plug, such as the final firing of the spark plug 10 so that the connection between the base material 36 and the protective material 34 is enhanced by the protective material 34 becoming diffused into the base material 36. The diffusing of the materials may happen so that the interface between the two layers creates a diffuse boundary layer instead of a distinct boundary. Furthermore, diffusing the interface between the two layers allows a more intimate connection at the molecular level as the two materials become similar, each having a portion of the other diffused within while providing the desired spark erosion resistance on the discharge surface as well as the desired corrosion resistance on the outer circumference. Therefore, enough protective material is deposited to the outer circumference of the base material to form a spark portion 30 that is highly resistant to corrosion while minimizing the amount of material deposited to prevent excessive spark erosion near the edge 44.

During the manufacturing process, the protective material is at least partially diffused into the base material, which provides enhanced protection from corrosion. More specifically, during the firing of the glass seal, such as at temperatures above 530° C., the protective material starts to diffuse into the base material. For example, when a Nickel protective material 34 becomes diffused into a base material 36 of Iridium, the Iridium Nickel alloy provides enhanced protection that surpasses the performance of either Nickel or Iridium by itself. Therefore, the protective material forms a diffused area 39, as illustrated in FIG. 13. The diffused area 39 provides protection, even if the protective material that is not diffused 34 erodes away. Furthermore, it has been found that the combination of the base material with the protective material provides enhanced protection. More specifically, as the spark plug is fired to form the glass seal, typically at temperatures of about 750° C. to 1000° C., the protective material becomes diffused into the base material to form the diffused are 39. The diffused area, moving from the center of the spark portion, is primarily the base material, until a section 79 is reached that the base material and protective material are present in approximately equal amounts, to primarily the protective material proximate to the outer edge of the spark portion 30. The diffused area 39 is also proximate to the outer portion of the spark portion 30. Depending on the applied thickness of the protective material, the diffused area may not be exposed during the manufacturing process and the outer surface is only the protective material. However, during operation of the engine, the protective material may form the outer surface of the spark portion. The diffused area generally is of less thickness than the layer of applied protective material, and typically has a thickness of less than 0.007 mm, and more particularly 0.005 mm.

The foregoing discussion discloses and describes an exemplary embodiment of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.

Claims

1. A spark plug having a center electrode and a ground electrode, and wherein at least one of said center electrode and said ground electrode comprise a spark portion, said spark portion including a base material and a protective material comprising Nickel, said protective layer having a thickness of less than 0.09 mm.

2. The spark plug of claim 1 wherein said base material is includes at least one element selected from the group consisting of Platinum, Palladium, Rhodium, Iridium, Ruthenium, and Rhenium.

3. The spark plug of claim 1 wherein said base material is selected from an alloy of one of the elements selected from the group consisting of Platinum, Palladium, Rhodium, Iridium, Ruthenium, and Rhenium.

4. The spark plug of claim 1 wherein said protective material further includes at least one element selected from the group consisting of Copper, Chromium, Vanadium, Zirconium, Tungsten, Osmium, Gold, Iron, and Aluminum, said at least one element forming less than 15% of said protective material.

5. The spark plug of claim 1 wherein said protective material comprises approximately 85% Nickel and approximately 15% Chromium.

6. The spark plug of claim 1 wherein the protective material consists essentially of Nickel.

7. The spark plug of claim 1 wherein said spark portion is an elongated shape having a first end and an outer circumference and wherein said base material and said protective material define said first end and said protective material defines substantially all of said outer circumference.

8. The spark plug of claim 1 wherein said protective material is plated on said base material.

9. The spark plug of claim 1 wherein said protective material is sputtered, electro-deposition, extruded, or flame sprayed.

10. The spark plug of claim 1 wherein said base material includes an outer base circumferential surface and wherein protective material is at least partially diffused into said base material.

11. The spark plug of claim 1 wherein said base material includes an outer base circumferential surface and wherein when said spark portion is heated above 530° C., the boundary between said base material and said protective material becomes a diffused alloy.

12. The spark plug of claim 1 wherein said base material includes an outer base circumferential surface and wherein when said spark portion is heated between approximately 760° C.-820° C. to diffuse the boundary between said base material and said protective material to form a diffused alloy of the base material and protective material.

13. The spark plug of claim 1 further including a diffused area proximate to an outer surface of the spark portion.

14. The spark plug of claim 1 further including an area forming an alloy of the base material and the protective material.

15. The spark plug of claim 1 wherein said protective material is applied with a thickness of 0.005 mm to 0.09 mm.

16. The spark plug of claim 15 wherein said protective material is applied with a thickness of 0.005 to 0.025 mm.

17. The spark plug of claim 15 wherein said protective material is applied with a thickness of 0.007 mm to 0.02 mm.

18. The spark plug of claim 15 wherein said spark portion includes a diffused area having a thickness of less than said applied protective material.

19. The spark plug of claim 15 wherein said spark portion includes a diffused area having a thickness of 0.005 mm to 0.09 mm.

20. The spark plug of claim 1 wherein said spark portion includes a diffused area extending from an outer circumference of the spark portion toward the center, said diffused are having a thickness of less than 0.025 mm.

21. The spark plug of claim 1 wherein said spark portion includes a diffused area extending from an outer circumference of the spark portion toward the center, said diffused are having a thickness of less than 0.012 mm.

22. A spark plug having a center electrode and a ground electrode, and wherein at least one of said center electrode and said ground electrode comprise a spark portion, said spark portion including a base material and a protective material comprising Nickel, wherein the protective material is at least partially diffused into the base material.

23. The spark plug of claim 22 wherein said base material includes an element selected from the group consisting of Platinum, Palladium, Rhodium, Iridium, Ruthenium, and Rhenium.

24. The spark plug of claim 22 wherein said base material is selected from an alloy including at least one element of the group consisting of Platinum, Palladium, Rhodium, Iridium, Ruthenium, and Rhenium.

25. The spark plug of claim 22 wherein said protective material further includes at least one element selected from the group consisting of Copper, Chromium, Vanadium, Zirconium, Tungsten, Osmium, Gold, Iron, and Aluminum, said at least one element forming less than 15% of said protective material.

26. The spark plug of claim 22 wherein said protective material comprises approximately 85% Nickel and approximately 15% Chromium.

27. The spark plug of claim 22 wherein said spark portion is an elongated shape having a first end and an outer surface and wherein said base material and said protective material define said first end and said protective material defines substantially all of said outer surface.

28. The spark plug of claim 22 wherein said protective material has a thickness of less than 0.09 mm.

29. The spark plug of claim 22 wherein said protective material is plated on said base material.

30. The spark plug of claim 22 wherein the protective material is at least partially diffused into said base material.

31. The spark plug of claim 30 wherein the boundary between said base material and said protective material becomes a diffused alloy when said spark portion is heated above 530°.

32. The spark plug of claim 19 wherein said protective layer and said base material meet at a diffuse area.

33. The spark plug of claim 32 wherein said diffuse area is generally formed from an alloy of Nickel and a material selected from the group consisting of Platinum, Palladium, Rhodium, Iridium, Ruthenium, and Rhenium.

34. The spark plug of claim 32 wherein said diffuse area includes a first side and a second side with a section therebetween and wherein said first side is formed primarily from the base material and said second side is formed primarily from the protective material.

35. The spark plug of claim 34 wherein said section of said diffuse area is formed from an approximately equal percentage of said base material and the protective material.

36. The spark plug of claim 32 wherein after said protective material is diffused with said base material, and a small amount of base material may be found on the outer circumference of the spark portion.