Method of producing a spark plug via flared tip attachment

A side electrode for a spark plug is provided. The side electrode includes a side wire having a first end and a second end; an opening proximate to the first end, the opening extending from a first surface of the side wire to a second surface of the side wire, wherein the first surface has a flared portion proximate to the opening; and an electrode tip secured to the first end of the side wire, the electrode tip having a tip portion and a shaft portion, wherein the tip portion is located on the second surface and the shaft portion is secured to the side wire by engaging the flared portion.

BACKGROUND

A known failure mechanism for spark plugs in combustion engines is the failure of the ground or side electrode due to service in oxidizing conditions and at elevated temperatures. Currently, a sphere of precious metal alloy is resistance welded to the Ni-based super alloy ground electrode. This tip and weld is often the nucleation point for failure. Spark plug failure can result from poorer spark erosion resistance due to oxidation of the electrode, scale formation resulting in increased spark resistance, and oxidation of the electrode-tip interface leading to increased spark resistance or the tip falling off. Cost savings is also a driving force. By improving the weld interface and/or using a more erosion resistant tip material, one can increase the spark plug life. However, better tip materials have been shown to cause resistance welding difficulties.

Standard spark plugs are manufactured by welding a precious metal or precious metal alloy tip to a ground electrode of some base material (typically nickel-based alloy). The precious metal tip composition is such that it can be welded to the base side electrode material. However, this weld can fail due to several causes, some of which were previously mentioned. Also, some tip materials (such as iridium and iridium based alloys), which have been shown to perform better in spark plug applications than the current practice of platinum-based alloys, are extremely difficult to weld resistively.

Accordingly, it is desirable to provide a side electrode for spark plugs designed to have a side wire/electrode tip attachment that is less susceptible to failure and has an electrode tip formed from erosion resistant tip materials.

SUMMARY

In one exemplary embodiment, a side electrode for a spark plug is provided. The side electrode includes a side wire having a first end and a second end; an opening proximate to the first end, the opening extending from a first surface of the side wire to a second surface of the side wire, wherein the first surface has a flared portion proximate to the opening; and an electrode tip secured to the first end of the side wire, the electrode tip having a tip portion and a shaft portion, wherein the tip portion is located on the second surface and the shaft portion is secured to the side wire by engaging the flared portion.

In another exemplary embodiment, a side electrode for a spark plug is provided. The side electrode includes a side wire having a first end and a second end; an opening proximate to the first end, the opening extending from a first surface of the side wire to a second surface of the side wire, wherein the first surface has a flared portion proximate to the opening; and an electrode tip secured to the first end of the side wire, the electrode tip having a first member and a second member, the first member and the second member each having a tip portion and a shaft portion, wherein the tip portion of second member is located on the second surface and the tip portion of the first member is secured to the side wire by engaging the flared portion.

In yet another exemplary embodiment, a side electrode for a spark plug is provided. The side electrode includes a side wire having a first end and a second end; an opening proximate to the first end, the opening extending from a first surface of the side wire to a second surface of the side wire, wherein the first surface has a flange portion proximate to the opening, a flared portion formed adjacent to the flange portion, the flared portion is located proximate to the opening; an electrode tip secured to the first end of the side wire, the electrode tip having a tip portion and a shaft portion, wherein the tip portion is located on the second surface and the shaft portion is secured to the side wire by engaging the flared portion; and a side wire element inserted into the flange portion and secured to the electrode tip.

In another exemplary embodiment, a spark plug is provided. The spark plug includes an insulator shell; a center electrode disposed in the insulator shell such that one end of the center electrode protrudes from the insulator shell; a metal shell exterior to the insulator shell; a side electrode having a side wire with a first end coupled to the metal shell and a second end facing the protruding end of the center electrode forming a spark discharge gap therebetween, an opening proximate to the first end of the side wire, the opening extending from a first surface of the side wire to a second surface of the side wire, wherein the first surface has a flared portion proximate to the opening; and an electrode tip secured to the first end of the side wire, the electrode tip having a tip portion and a shaft portion, wherein the tip portion is located on the second surface and the shaft portion is secured to the side wire by engaging the flared portion.

In another exemplary embodiment of the present invention, a method for fabricating a side electrode for spark plugs is provided. The method includes forming an opening in a side wire having a first end and a second end, the opening formed proximate to the first end and extending from a first surface of the side wire to a second surface of the side wire; forming a flared portion on the first surface proximate to the opening; and securing an electrode tip to the first end of the side wire, the electrode tip having a tip portion and a shaft portion, wherein the tip portion is located on the second surface and the shaft portion is secured to the side wire by engaging the flared portion.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention are directed to a side electrode designed to have a side wire/electrode tip attachment that is less susceptible to failure. This side electrode design for spark plugs allows an electrode tip to be secured to a side wire with or without the aid of welding. Exemplary embodiments of the present invention are also directed to a side electrode having an electrode tip (e.g., rivet, cylinder, sphere of a metal, etc.) being formed from one or a combination of erosion resistant tip materials. More specifically, the electrode tip in accordance with exemplary embodiments of the present invention is formed from at least one or more precious metals, precious metal alloys, base metals or a combination thereof. Exemplary embodiments of the present invention are also directed to a spark plug incorporating the side electrode and a method of fabricating or assembling the same.

In accordance with an exemplary embodiment of the present invention, flaring a side wire would allow an electrode tip (rivet/cylinder/etc.) to be inserted into an opening (with the flared portion on a side opposite the center electrode of a spark plug) that can be made by cutting, stamping, or drilling into the side wire, in which the shaft portion of the electrode tip would be inserted. The end of the electrode tip opposite the center electrode (shaft portion) is impacted with an impacting device having a point (or other shape) in order to expand the shaft portion of the electrode tip to wedge it into place or engage it to the flared portion at a surface of the side wire. Optionally, the other side of the electrode tip (tip portion) near the center electrode is coined or impacted to ensure the electrode tip is locked in placed.

Referring now toFIGS. 1-18, a side electrode10is shown according to exemplary embodiments of the present invention. As shown inFIG. 1, the side electrode10generally comprises a side wire12and an electrode tip14being secured to the side wire12through one or more means as described herein. In exemplary embodiments, the electrode tip14comprises a rivet, a two-part rivet, dual rivet, a cylinder, or a sphere of metal.

In accordance with one exemplary embodiment, the side wire12has an opening20for receiving the electrode tip14. In accordance with one non-limiting exemplary embodiment, the opening20has a diameter close to that of the diameter of the narrow end/shaft of the electrode tip14. The side wire12has a first end22and a second end24. The opening20is proximate to the second end24of the side wire12and extends from a first surface26of the side wire12to a second surface28of the side wire12. The first surface26of the side wire12has a flared portion30proximate to the opening20as shown. In accordance with one exemplary embodiment, cutting, stamping, and/or drilling into the side wire12can form the opening20and the flared portion30of the side wire12.

The side wire12is formed from one or more various types of super alloys, such as nickel-based alloys. Of course, other materials or a combination of materials can be used to form the side wire12and should not be limited to the example set forth herein.

In accordance with one exemplary embodiment, the electrode tip14has a tip portion40and a shaft portion42. The tip portion40has a head portion43. The shaft portion42is inserted into the opening20from the second surface28such that the shaft portion ends up at the flared portion30of the side wire12and the head of the tip portion40is facing the center electrode of a spark plug, in which the side electrode10is incorporated into. In other words, the tip portion40of the electrode tip14is located on the second surface28of the side wire12and the shaft portion42is located at the flared portion30of the side wire12when the shaft portion42is inserted in the opening. The shaft portion42of the electrode tip14is secured to the side wire12by engaging the flared portion30as shown. In accordance with one embodiment, the shaft portion42of the electrode tip14is secured to the side wire12and engaged to flared portion30by impacting the shaft portion42in the flared portion utilizing an impact device44that is impacted by a force, which is indicated by arrow46.

The impact device44is an impact head of variable cross-section geometry. The impact device44impacts the shaft portion42in the flared portion expanding an end of the shaft portion42in the flared portion30and wedging the shaft portion42into place. In accordance with one exemplary embodiment, the impact device44is configured to create a wedge shaped cross-section the end of the side electrode (the shaft portion) facing away from the center electrode during impact. Of course the shape formed at the shaft portion42can vary depending on the cross-section geometry of the impact head.

In accordance with one exemplary embodiment, the electrode tip14comprises a rivet50as shown inFIGS. 1-3. In accordance with one exemplary embodiment, the rivet50is formed from at least one precious metal, precious metal alloy, base metal or a combination thereof. For example, rivet50may comprise of nickel, platinum, tungsten, iridium and/or rhodium. Of course, other combinations of metals and/or metal alloys can be used to form rivet50. In accordance with one exemplary embodiment, the rivet50includes a hollow core52as shown inFIG. 2. This would decrease the amount of precious metal required to form rivet50. The size of the hollow core52can vary depending on the application and should not be limited to the size as shown.

In accordance with one exemplary embodiment, the rivet50may also comprises an additional material, such as clad. In other words, at least a portion of the rivet50is formed from a clad material. For example, rivet50may have clad portions (indicated by reference numeral54) integrally formed or co-extruded with the other portion(s) of the rivet50, which can be formed from one or a combination of metals (precious metals, precious metal alloys, base metals), in accordance with one exemplary embodiment. The use of clad will decrease the amount of precious metal required to form rivet50. Clad can be formed on the outside or inside of the precious metal rivet50depending on the application as shown inFIG. 3. In accordance with one exemplary embodiment, the head43of the tip portion40is coined to ensure the rivet50is locked in place.

In accordance with an alternative exemplary embodiment of the present invention, the electrode tip14comprises a two-part rivet56as shown inFIGS. 4-6. In this embodiment, the two-part rivet56comprises a first member58and a second member60making up the shaft portion of rivet56and the tip portion of rivet56respectively. The two-part rivet56is generally rivet50cut through the shaft perpendicular to the shaft wall. In this embodiment, the first member58is inserted into opening20at the flared portion30of the side wire12and the end of the second member60opposite its head portion is inserted into the opening20proximate the second surface28of the side wire12. Moreover, the first member58is secured to the second member60by a resistance-welding device62in accordance with one exemplary embodiment. Of course, other means for securing the first member to the second member can be used in other exemplary embodiments of the present invention. In accordance with one exemplary embodiment, the head portion of the second member56is coined to ensure the two-part rivet is locked in place.

The first member58and/or the second member60of the rivet can be formed from at least one precious metal, precious metal alloy, base metal or a combination thereof. For example, the first member58and the second member60can each comprise of nickel, platinum, tungsten, iridium and/or rhodium. Of course, other combinations of metals and/or metal alloys can be used to form the first member58and/or the second member60of the two-part rivet. In accordance with one exemplary embodiment, the first member58and the second member60each includes a hollow core64as shown inFIG. 5. This would decrease the amount of precious metal required to form the two-part rivet. The size of the hollow core64can vary depending on the application and should not be limited to the size as shown.

In accordance with one exemplary embodiment, the first member58and/or the second member60may also comprise an additional material, such as clad. In other words, at least a portion of the first member58and/or the second member60is formed from a clad material. For example, the first member58and/or the second member60may have clad portions (indicated by reference numeral66) integrally formed or co-extruded with the other portion(s) of the first member58and/or the second member60, which can be formed from one or a combination of metals (precious metals, precious metal alloys, base metals), in accordance with one exemplary embodiment. The use of clad will decrease the amount of precious metal required to form the two-part rivet56. Clad can be formed on the outside or inside of the first member58and/or the second member depending on the application as shown inFIG. 6.

In accordance with another alternative exemplary embodiment of the present invention, the electrode tip14comprises a cylinder70. The cylinder70as the electrode tip can be easier and cheaper to produce than a rivet. Various embodiments of the electrode tip14as a cylinder70are shown inFIGS. 7-9. In accordance with one exemplary embodiment, the cylinder70is formed from at least one precious metal, precious metal alloy, base metal or a combination thereof. For example, cylinder70can comprise of nickel, platinum, tungsten, iridium and/or rhodium. Of course, other combinations of metals and/or metal alloys can be used to form cylinder70. In accordance with one exemplary embodiment, the cylinder70includes a hollow core72as shown inFIG. 8. This would decrease the amount of precious metal required to form cylinder70. The size of the hollow core72can vary depending on the application and is not limited to the size as shown.

In accordance with one exemplary embodiment of the present invention, cylinder70may also comprise an additional material, such as clad. In other words, at least a portion of the cylinder70is formed from a clad material. For example, cylinder70may have clad portions (indicated by reference numeral74) integrally formed or co-extruded with the other portion(s) of the cylinder70, which can be formed from one or a combination of metals (precious metals, metal alloys, base metals), in accordance with one exemplary embodiment. The use of clad will decrease the amount of precious metal required to form cylinder70. Clad can be formed on the outside or inside of the cylinder70depending on the application as shown inFIG. 9.

In accordance with one exemplary embodiment, the tip portion40of the cylinder70is also impacted to lock the cylinder70in place. The tip portion40of the cylinder70can be impacted at the same or different time as the shaft portion42of the cylinder70. In accordance with one exemplary embodiment, the tip portion40of the cylinder70is impacted by the same impact head for the shaft portion42or by another impact head76of variable cross-section geometry driven by another force, which is indicated by arrow78in accordance with another exemplary embodiment. Another wedge-shape cross-section is formed at the tip portion40of cylinder70during impact, thus locking the cylinder in place. Of course the shape formed at the tip portion40can vary depending on the cross-section geometry of impact head76. Once the tip portion40of the cylinder70is impacted, the tip portion40of cylinder70can further be coined as shown.

In accordance with yet another alternative exemplary embodiment of the present invention, the electrode tip14comprises a dual-rivet assembly80having a first rivet82and a second rivet84. The first rivet82and the second rivet84each include a tip portion and a shaft portion. Specifically, the first rivet82has a tip portion86and a shaft portion88while the second rivet84has a tip portion90and a shaft portion92. The shaft portions88,92of both rivets are each inserted into opening20. In this embodiment, shaft portion88of first rivet82is inserted into the opening from the first surface of the side wire12such that the tip portion86of the first rivet82is located on the first surface26and is secured to the side wire by engaging the flared portion30. The tip portion86of the first rivet82is secured to the side wire by mechanical impact as described above. The shaft portion92of the second rivet84is inserted into the opening from the second surface of the side wire12so that the tip portion90of the second rivet84is facing the center electrode.

The first rivet82and the second rivet84are secured together through a resistance-welding process as described above in accordance with one exemplary embodiment. Of course, other means for securing the first rivet82to the second rivet84can be used in other exemplary embodiments of the present invention. In accordance with one exemplary embodiment, the head of tip portion90is coined to ensure the dual rivet assembly is locked in place.

In accordance with one exemplary embodiment, the first rivet82and/or the second rivet84is formed from at least one precious metal, precious metal alloy, base metal or a combination thereof. For example, first rivet82and/or the second rivet84comprise of nickel, platinum, tungsten, iridium and/or rhodium. Of course, other combinations of metals (precious metals, precious metal alloys, base metals) can be used to form the first rivet82and/or the second rivet84. In accordance with one exemplary embodiment, the first rivet82and/or the second rivet84includes a hollow core94as shown inFIG. 11. This would decrease the amount of precious metal required to form the dual-rivet assembly80. The size of the hollow core94can vary depending on the application and is not limited to the size as shown.

In accordance with one exemplary embodiment of the present invention, the first rivet82and/or the second rivet84may also comprise an additional material, such as clad. In other words, at least a portion of the first rivet82and/or the second rivet84is formed from a clad material. For example, the first rivet82and/or the second rivet84may have clad portions (indicated by reference numeral96) integrally formed or co-extruded with the other portion(s) of the first rivet82and/or the second rivet84, which can each be formed from one or a combination of metals (precious metals, metal alloys, base metals), in accordance with one exemplary embodiment. The use of clad will decrease the amount of precious metal required to form dual-rivet assembly80. Clad can be formed on the outside or inside of the dual-rivet assembly80depending on the application as shown inFIG. 12.

Referring now toFIGS. 13-18, a side electrode100is shown according to alternative exemplary embodiments of the present invention. As shown inFIG. 13, the side electrode100generally comprises a side wire102and an electrode tip104being secured to the side wire102through one or more means as described herein. In exemplary embodiments, the electrode tip104comprises a rivet, a hollow rivet, a cylinder, or a hollow cylinder.

In accordance with an exemplary embodiment of the present invention, the side wire100has an opening106for receiving an electrode tip104. In accordance with one non-limiting exemplary embodiment, the opening106has a diameter close to that of the diameter of the narrow end/shaft of the electrode tip104. The side wire102has a first end108and a second end110. The opening106is proximate to the second end110of the side wire102and extends from a first surface112of the side wire102to a second surface114of the side wire102. The first surface112of the side wire102has a flange portion116proximate to the opening106as shown. In one exemplary embodiment, the side wire102further includes a flared portion118located adjacent to the flange portion116and proximate to opening106. The flange portion116has an inner diameter larger than the inner diameter of the flared portion118in accordance with one exemplary embodiment. In accordance with one exemplary embodiment, cutting, stamping, and/or drilling into the side wire102can form the opening106, the flange portion116, and the flared portion118of the side wire102.

The side wire102is formed from one or more various types of super alloys, such as nickel-based alloys. Of course, other materials or a combination of materials can be used to form the side wire102and should not be limited to the example set forth herein.

In accordance with one exemplary embodiment, the electrode tip104has a tip portion120and a shaft portion122. The tip portion120has a head portion124. The shaft portion122is inserted into the opening106from the second surface114such that the shaft portion ends up at the flange portion116of the side wire102and the head of the tip portion120is facing the center electrode of a spark plug, in which the side electrode100can be incorporated into. In other words, the tip portion120of the electrode tip104is located on the second surface114of the side wire102and the shaft portion122is located at the flange portion116of the side wire102when the shaft portion122is inserted in the opening. The shaft portion122of the electrode tip104is secured to the side wire102by engaging the flared portion118as shown. In accordance with one embodiment, the shaft portion122of the electrode tip104is secured to the side wire102and engaged to flared portion118by impacting the shaft portion122as described above. Once the shaft portion122is engaged to the flared portion118a piece of side wire element or cylinder130is inserted into the flange portion100as shown inFIG. 13. In this embodiment, the side wire element130is secured to the side wire and/or the shaft portion122of the electrode tip. The side wire element130can be secured to the shaft portion of the electrode tip through a resistance welding process as described above. Of course, other means for securing the side wire element130to the side wire and/or the electrode tip can be used in other exemplary embodiments of the represent invention. The head of the tip portion can then be coined to ensure the electrode tip is locked in place. Coining as described herein can also provide a larger surface area uniformly distanced from the center wire and to accurately set the distance between the center and side electrodes.

In accordance with one exemplary embodiment, the side wire element130can be formed from the same or different material as the side wire102. For example, the side wire element130and the side wire102can be formed from one or more various types of super alloys, such as nickel-based alloys. Of course, other materials or a combination of materials can be used to form the side wire element130and the side wire102.

Any one of the electrode tip configurations as described above can be incorporated into side wire102. In accordance with one exemplary embodiment, the electrode tip104comprises a rivet with varying configurations, such as the ones illustrated inFIGS. 13-15. Details of these varying rivet configurations are similar to the details for the rivet inFIGS. 1-3. In accordance with another exemplary embodiment, the electrode tip104comprises a cylinder with varying configurations, such as the ones illustrated inFIG. 16-18. Details of these varying cylinder configurations are similar to the details for the cylinder inFIGS. 7-9.

Referring now toFIG. 19, a spark plug generally indicated by numeral200includes an annular metal housing202, which is threaded at204for installation into an internal combustion engine (not shown). A side electrode206extends from the housing202to define a firing gap with a center electrode208. In one embodiment, the center electrode includes an electrode tip comprising a rivet210or sphere (not shown) of metal, which in one exemplary embodiment is formed from one of various platinum alloys and is secured to the end face212of an outer sheath214which projects from an insulator216, which is mounted within the housing202. In addition, the side electrode206includes an electrode tip218secured to a side wire220in accordance with one exemplary embodiment. It will be appreciated that electrode tip218can be configured to be any one of the electrode tips described above in accordance with exemplary embodiments of the present invention. It will further be appreciated that side wire220can be configured to be any one of the side wires described above in accordance with exemplary embodiments of the present invention.

In accordance with an exemplary embodiment, the electrode tip formed from rivet(s), cylinder(s), pads(s), and/or spheres can be formed from at least one precious metal, precious metal alloy, base metal or a combination thereof. Further, in exemplary embodiments of the present invention, the electrode tip can additionally comprise of a clad structure in which the precious metal is either inside or outside. In accordance with an exemplary embodiment, the second surface of the side wire can also be flared. Thus, either one or both surfaces of the side wire proximate the opening can be flared. It should be understood that the spark plug configuration in which the side electrode is incorporated into can vary depending on the application and should not be limited to the configuration described herein.