EP1413029B1 - Method for placing a precious metal tip on an electrode, electrode and spark plug - Google Patents

Method for placing a precious metal tip on an electrode, electrode and spark plug Download PDF

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Publication number
EP1413029B1
EP1413029B1 EP02753022A EP02753022A EP1413029B1 EP 1413029 B1 EP1413029 B1 EP 1413029B1 EP 02753022 A EP02753022 A EP 02753022A EP 02753022 A EP02753022 A EP 02753022A EP 1413029 B1 EP1413029 B1 EP 1413029B1
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EP
European Patent Office
Prior art keywords
electrode
metal tip
region
precious metal
noble metal
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EP02753022A
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German (de)
French (fr)
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EP1413029A1 (en
Inventor
Oliver Tenschert
Heinz Ulm
Jochen Fischer
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Robert Bosch GmbH
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Robert Bosch GmbH
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01TSPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00Sparking plugs
    • H01T13/20Sparking plugs characterised by features of the electrodes or insulation
    • H01T13/39Selection of materials for electrodes
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01TSPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T21/00Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs
    • H01T21/02Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs of sparking plugs

Definitions

  • the invention is based on a method for mounting a noble metal tip on an electrode, an electrode and a spark plug according to the preamble of the independent claims.
  • the electrode may be a ground or center electrode of a spark plug.
  • the inventive method for attaching a noble metal tip on an electrode, the electrode according to the invention and the spark plug according to the invention with the features of the independent claims have the advantage that the noble metal tip in a first region and the electrode in a second region adjacent to the first region , Is melted to form a mixed alloy in these areas, wherein the first region is chosen so that it is completely encased in a ring around the material of the noble metal tip. Due to the mixed alloy, the connection between the Precious metal tip and the electrode durable. Due to the approximately annular complete sheathing of the first region of the material of the noble metal tip, the noble metal tip and the connection between the noble metal tip and the electrode remain wear-resistant and resistant to corrosion and erosion.
  • the two areas are melted by means of laser energy.
  • the two areas for the formation of the mixed alloy defined and melt with high local precision, so that melting of the noble metal tip or the electrode outside the two areas can be prevented.
  • the melting process in the two areas for forming the mixed alloy by using the laser energy with appropriate laser power can be realized very quickly.
  • Another advantage is that the laser energy is applied by a laser element by means of a laser pulse. In this way, the energy required to melt the two areas can be provided precisely and in a defined and predetermined manner by selecting the power and time of the laser pulse.
  • FIG. 1 shows a first step
  • FIG. 2 shows a second step
  • FIG. 3 shows a third step
  • FIG. 4 shows a fourth step of the method according to the invention for forming an electrode according to the invention, for example for a spark plug.
  • Such lifetime can be achieved at least for spark plugs with a ground electrode designed as a roof electrode only by the use of noble metal alloys on the center electrode and the opposite ground electrode.
  • These precious metal alloys may be attached to the respective electrodes of the spark plug by, for example, extrusion, plating, resistance welding and laser welding or laser alloying.
  • These electrodes are made of nickel alloys, for example.
  • the process technology for the preparation of the connection between the noble metal alloy and such an electrode high demands are made, because the Properties of the noble metal alloys in comparison to nickel alloys in terms of melting and boiling point and thermal expansion coefficient differ greatly.
  • An inexpensive joining method is resistance welding.
  • the noble metal alloy When the noble metal alloy is bonded to the nickel alloy by resistance welding, it may be heated in the region of its juxtaposition when this compound is heated due to the different coefficients of thermal expansion and diffusion zone thicknesses in the boundary region between the noble metal alloy and the nickel alloy Tearing open the connection.
  • the resulting gap corrosion occurs, especially when the electrode is inserted as a ground or center electrode in the combustion chamber of an internal combustion engine and is surrounded by the local gas mixtures. Thus, the life of such compounds is limited.
  • One method that results in a more stable bond between the noble metal alloy and the nickel alloy is to attach a weld between the noble metal alloy and the nickel alloy using a laser welding process.
  • the attachment of such welds is relatively expensive and requires a relatively high cost of materials for the noble metal alloy.
  • 5 denotes an electrode which may be, for example, the center electrode of a spark plug.
  • the electrode 5 comprises a tip 20 which can form a depression according to FIG. 1, but need not.
  • the electrode 5 is metallic and may for example be formed at least partially from nickel. In the following, it will be assumed by way of example that the electrode 5 is formed from a nickel alloy.
  • FIG. 1 furthermore shows a noble metal tip 1, which may be formed from a pure noble metal or from a noble metal alloy.
  • pure precious metals can be used, for example, gold, platinum or iridium. When using precious metal alloys, this can also be done using gold, platinum or iridium.
  • the noble metal tip 1 should be formed as a noble metal alloy and contain a proportion of platinum.
  • the noble metal tip 1 is shaped on its underside 35 such that it can be received as accurately as possible from the tip 20 of the electrode 5.
  • the noble metal tip 1 on its underside 35 a highlighting, which corresponds to the recess 20 at the top of the electrode 5.
  • the diameter of the precious metal tip is 1 It is about the same size as the diameter of the electrode 5 in the region of its tip 20. However, it could also be chosen larger or smaller.
  • the noble metal tip 1 is now set accurately on the tip 20 of the electrode 5, as indicated by the arrow in FIG.
  • the noble metal tip 1 is welded to the electrode 5 in the region in which the noble metal tip 1 adjoins the electrode 5, for example by a resistance welding method.
  • This area is identified by the reference numeral 40 in FIG. He is referred to below as the welding area.
  • the thickness of the resulting diffusion zone in the welding region 40 is usually a few microns and is thus prone to thermal stress cracks due to the different thermal expansion coefficients of the noble metal tip 1 and the nickel-containing electrode fifth
  • the noble metal tip 1 is melted in a first region 10 and the electrode 5 in a second region 15, which is adjacent to the first region 10, in order in these regions 10, 15 a mixed alloy of the material of the noble metal tip 1 and the Material of the electrode 5 to form, so a mixed alloy of the noble metal alloy of the noble metal tip 1 and the nickel alloy of the electrode 5 according to the example chosen here.
  • the first region 10 is determined in such a way that it is completely surrounded by the material of the noble metal tip 1 approximately annularly, as can be seen in FIG.
  • like reference numerals designate like elements.
  • the welding region 40 is in the region of a boundary region 25 of the first area 10 to the second area 15 in Figure 3 for clarity by hatching highlighted and indicated by the reference numeral 45. He is referred to below as the border welding area.
  • the boundary welding region 45 is also melted, which after the second process step according to FIG. 2 as part of the welding region 40 resulted in the described diffusion zone between the noble metal tip 1 and the electrode 5.
  • the complete mixing of the material of the noble metal tip 1 and of the material of the electrode 5 results in the third process step according to FIG. 3.
  • an approximately homogeneous noble metal-nickel alloy in the second area 15 and in the boundary welding area 45, an approximately homogeneous noble metal-nickel alloy, the ring according to Figure 3 in the region of the noble metal tip 1 approximately annularly completely from the material of the noble metal tip 1, in the region of the electrode 5 completely from the material of the electrode 5 and is completely surrounded by the diffusion zone in the region of the welding region 40. It is crucial, above all, that the first region 10 is completely surrounded by the material of the noble metal tip 1 in a ring-shaped manner.
  • the mixed alloy is completely separated in the region of the noble metal tip 1 to its combustion chamber side face of the atmosphere surrounding the noble metal tip 1 and thus protected from environmental influences and not exposed to erosion and corrosion, especially in the combustion chamber of an internal combustion engine.
  • the mixed alloy forming in the first region 10, in the second region 15 and in the boundary welding region 45 is completely separated from the surrounding atmosphere in the region of the electrode 5, since the second region 15, with the exception of its boundary region 50, also reaches the boundary welding region 45 first Area 10 is completely surrounded by the material of the electrode 5.
  • the connection between the noble metal tip 1 and the electrode 5 is made particularly stable and durable and is no longer subject to the risk of cracking in the region of the diffusion zone between precious metal tip 1 and electrode 5.
  • approximately annular shield of resulting mixed alloy of noble metal fractions and nickel contents in front of the surrounding atmosphere is prevented, especially in the region of the connection between the noble metal tip 1 and the electrode 5 that the erosion and corrosion-prone mixed alloy is exposed to harmful environmental influences, so that the connection between the noble metal tip 1 and the electrode 5 particularly is durable.
  • the melting of the first region 10, the boundary welding region 45 and the second region 15 can be realized for example by means of laser energy.
  • the laser energy can be applied.
  • reference numeral 55 denotes a laser beam.
  • the laser beam is focused on the first region 10, the boundary welding region 45 and the second region 15 and ensures a locally precise melting of these regions and thus the formation of a homogeneous homogeneous mixed alloy which is as constant as possible in these regions.
  • the laser energy can be applied, for example, by means of a laser pulse to a, in the case of a spark plug combustion chamber side, end face of the noble metal tip 1.
  • the laser energy is not applied to the entire end face of the noble metal tip 1, but to an approximately circular area which is surrounded by an approximately annular region of the end face.
  • the precious metal tip 1 Only in the circular region of the end face and underneath is the precious metal tip 1 thus melted to give the first region 10, which is completely encased in an annular manner by the material of the noble metal tip 1.
  • the use of a laser pulse enables a specific and defined provision of the energy required for the melting of the first region 10, the second region 15 and the boundary welding region 45.
  • the laser pulse may have a power of about 1 kW for a time of about 10 ms.
  • the mixed alloy identified by the reference numeral 60 has a coefficient of thermal expansion between that of the noble metal alloy of the noble metal tip 1 and that of the nickel alloy of the electrode 5. Cracks due to thermal stresses are thereby avoided, especially in the area of the mixed alloy 60.
  • the connection between the noble metal tip 1 and the electrode 5 is thus durable. This is all the more the greater the cross section of the mixed alloy 60 in the region of the weld region 40, ie the diffusion zone. Only a combustion chamber-side end face 100 of the mixed alloy 60 is not surrounded by the non-melted material of the noble metal tip 1 and thus exposed directly to the combustion chamber. Since, according to FIG.
  • the first region 10 is completely surrounded by non-molten material of the noble metal tip 1 approximately annularly, the mixed alloy 60 according to FIG. 4 is largely shielded from environmental influences in the region of the noble metal tip 1.
  • the mixed alloy 60 according to FIG. 4 is largely shielded from environmental influences in the region of the noble metal tip 1.
  • the very good erosion and corrosion properties of the noble metal alloy used continue before.
  • corrosion and erosion are prevented and the durability of the connection between the noble metal tip 1 and the electrode 5 is increased.
  • the formed electrode 5 with the noble metal tip 1 is thus durable with minimal use of precious metals under combustion chamber conditions as well as erosion and corrosion resistant.
  • the second process step of the welded joint and the third process step of the laser alloy can be carried out in a short cycle time and simultaneously. Thus, the manufacturing time is not increased compared to a pure welded joint or laser alloy.
  • the electrode 5 is exemplified here as the center electrode of a spark plug.
  • a noble metal tip may also be attached to a ground electrode, such as a roof electrode or a side electrode.
  • a spark plug can be provided in which both the center electrode and one or more ground electrodes each comprise a noble metal tip, the noble metal tip of the center electrode of the noble metal tip facing a ground electrode to form the spark gap to minimize electrode wear and extend the life of the spark plug ,
  • the spark plug is referenced in all figures by the reference numeral 65 and is for clarity only on the basis of a section of the electrode 5, which acts in this example as the center electrode of the spark plug 65, shown.
  • like reference numerals designate like elements, and the electrode 5 and the noble metal tip 1 are shown in a longitudinal section.

Description

Stand der TechnikState of the art

Die Erfindung geht von einem Verfahren zur Anbringung einer Edelmetallspitze auf einer Elektrode, von einer Elektrode und von einer Zündkerze nach der Gattung der unabhängigen Ansprüche aus.The invention is based on a method for mounting a noble metal tip on an electrode, an electrode and a spark plug according to the preamble of the independent claims.

Aus der WO91/02393 ist es bereits bekannt, eine Edelmetallspitze auf eine Elektrode zu schweißen. Bei der Elektrode kann es sich dabei um eine Masse- oder Mittelelektrode einer Zündkerze handeln.From WO91 / 02393 it is already known to weld a noble metal tip to an electrode. The electrode may be a ground or center electrode of a spark plug.

Vorteile der ErfindungAdvantages of the invention

Das erfindungsgemäße Verfahren zur Anbringung einer Edelmetallspitze auf einer Elektrode, die erfindungsgemäße Elektrode und die erfindungsgemäße Zündkerze mit den Merkmalen der unabhängigen Ansprüche haben demgegenüber den Vorteil, dass die Edelmetallspitze in einem ersten Bereich und die Elektrode in einem zweiten Bereich, der dem ersten Bereich benachbart ist, aufgeschmolzen wird, um in diesen Bereichen eine Mischlegierung zu bilden, wobei der erste Bereich so gewählt wird, das er etwa ringförmig vollständig vom Material der Edelmetallspitze ummantelt ist. Durch die Mischlegierung wird die Verbindung zwischen der Edelmetallspitze und der Elektrode dauerhaltbar. Aufgrund der etwa ringförmigen vollständigen Ummantelung des ersten Bereichs vom Material der Edelmetallspitze bleibt die Edelmetallspitze und die Verbindung zwischen der Edelmetallspitze und der Elektrode verschleißfest und unanfällig gegenüber Korrosion und Erosion.The inventive method for attaching a noble metal tip on an electrode, the electrode according to the invention and the spark plug according to the invention with the features of the independent claims have the advantage that the noble metal tip in a first region and the electrode in a second region adjacent to the first region , Is melted to form a mixed alloy in these areas, wherein the first region is chosen so that it is completely encased in a ring around the material of the noble metal tip. Due to the mixed alloy, the connection between the Precious metal tip and the electrode durable. Due to the approximately annular complete sheathing of the first region of the material of the noble metal tip, the noble metal tip and the connection between the noble metal tip and the electrode remain wear-resistant and resistant to corrosion and erosion.

Durch die in den Unteransprüchen aufgeführten Maßnahmen sind vorteilhafte Weiterbildungen und Verbesserungen des Verfahrens und der Elektrode gemäß den unabhängigen Ansprüchen möglich.The measures listed in the dependent claims advantageous refinements and improvements of the method and the electrode according to the independent claims are possible.

Besonders vorteilhaft ist es, dass die beiden Bereiche mittels Laserenergie aufgeschmolzen werden. Auf diese Weise lassen sich die beiden Bereiche für die Bildung der Mischlegierung definiert vorgeben und mit hoher örtlicher Präzision aufschmelzen, sodass ein Aufschmelzen der Edelmetallspitze oder der Elektrode außerhalb der beiden Bereiche verhindert werden kann. Außerdem läßt sich der Aufschmelzvorgang in den beiden Bereichen zur Bildung der Mischlegierung durch Verwendung der Laserenergie bei entsprechender Laserleistung besonders schnell realisieren.It is particularly advantageous that the two areas are melted by means of laser energy. In this way, the two areas for the formation of the mixed alloy defined and melt with high local precision, so that melting of the noble metal tip or the electrode outside the two areas can be prevented. In addition, the melting process in the two areas for forming the mixed alloy by using the laser energy with appropriate laser power can be realized very quickly.

Ein weiterer Vorteil besteht darin, dass die Laserenergie von einem Laserelement mittels eines Laserpulses aufgebracht wird. Auf diese Weise läßt sich die zum Aufschmelzen der beiden Bereiche erforderliche Energie durch Wahl von Leistung und Zeit des Laserpulses präzise und in definierter und vorgegebener Weise zur Verfügung stellen.Another advantage is that the laser energy is applied by a laser element by means of a laser pulse. In this way, the energy required to melt the two areas can be provided precisely and in a defined and predetermined manner by selecting the power and time of the laser pulse.

Zeichnungdrawing

Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung dargestellt und in der nachfolgenden Beschreibung näher erläutert. Es zeigen Figur 1 einen ersten Schritt, Figur 2 einen zweiten Schritt, Figur 3 einen dritten Schritt und Figur 4 einen vierten Schritt des erfindungsgemäßen Verfahrens zur Bildung einer erfindungsgemäßen Elektrode, beispielsweise für eine Zündkerze.An embodiment of the invention is illustrated in the drawing and explained in more detail in the following description. FIG. 1 shows a first step, FIG. 2 shows a second step, FIG. 3 shows a third step, and FIG. 4 shows a fourth step of the method according to the invention for forming an electrode according to the invention, for example for a spark plug.

Beschreibung des AusführungsbeispielsDescription of the embodiment

Die Anforderungen an Zündkerzen hinsichtlich ihrer Dauerhaltbarkeit sind in den vergangenen Jahren stetig gestiegen. Derzeit werden bereits Wechselintervalle für die Zündkerzen von 60.000,00 km bis 100.000,00 km von verschiedenen Automobilherstellern vorgegeben. Der Trend geht somit zu sogenannten Lifetime-Zündkerzen, deren Haltbarkeitsdauer möglichst nahe an die Haltbarkeitsdauer des Fahrzeugs herankommen soll.The requirements for spark plugs with regard to their durability have steadily increased in recent years. Currently, replacement intervals for the spark plugs from 60,000.00 km to 100,000.00 km are specified by various car manufacturers. The trend is therefore to so-called Lifetime spark plugs whose durability should come as close as possible to the durability of the vehicle.

Derartige Lebensdauer sind zumindest für Zündkerzen mit einer als Dachelektrode ausgebildeten Masseelektrode nur durch den Einsatz von Edelmetalllegierungen an der Mittelelektrode und der gegenüberliegenden Masseelektrode erreichbar. Diese Edelemetalllegierungen können beispielsweise durch Fliesspressen, Plattieren, Widerstandsschweissen und Laserschweissen oder Laserlegieren auf den jeweiligen Elektroden der Zündkerze befestigt werden. Diese Elektroden bestehen beispielsweise aus NickelLegierungen.Such lifetime can be achieved at least for spark plugs with a ground electrode designed as a roof electrode only by the use of noble metal alloys on the center electrode and the opposite ground electrode. These precious metal alloys may be attached to the respective electrodes of the spark plug by, for example, extrusion, plating, resistance welding and laser welding or laser alloying. These electrodes are made of nickel alloys, for example.

An die Verfahrenstechnik zur Herstellung der Verbindung zwischen der Edelmetalllegierung und einer solchen Elektrode werden hohe Anforderungen gestellt, weil sich die Eigenschaften der Edelmetalllegierungen im Vergleich zu Nickellegierungen hinsichtlich Schmelz- und Siedepunkt sowie Wärmeausdehnungskoeffizient stark unterscheiden. Ein kostengünstiges Verbindungsverfahren ist das Widerstandsschweissen. Wird die Edelmetalllegierung mit der Nickellegierung durch Wiederstandsschweissen verbunden, so kann es bei Erwärmung dieser Verbindung aufgrund der unterschiedlichen Wärmeausdehnungskoeffizienten und der geringen Diffusionszonendicken im Grenzbereich zwischen der Edelmetalllegierung und der Nickellegierung, also der geringen gegenseitigen Durchmischung der Edelmetalllegierung und der Nickellegierung in dem Bereich ihres Aneinandergrenzens zum Aufreissen der Verbindung kommen. In dem so entstandenen Spalt tritt Korrosion auf, vor allem dann, wenn die Elektrode als Masse- oder Mittelelektrode in den Brennraum einer Brennkraftmaschine eingeführt ist und von den dortigen Gasgemischen umgeben ist. Somit wird die Lebensdauer derartiger Verbindungen begrenzt.The process technology for the preparation of the connection between the noble metal alloy and such an electrode high demands are made, because the Properties of the noble metal alloys in comparison to nickel alloys in terms of melting and boiling point and thermal expansion coefficient differ greatly. An inexpensive joining method is resistance welding. When the noble metal alloy is bonded to the nickel alloy by resistance welding, it may be heated in the region of its juxtaposition when this compound is heated due to the different coefficients of thermal expansion and diffusion zone thicknesses in the boundary region between the noble metal alloy and the nickel alloy Tearing open the connection. In the resulting gap corrosion occurs, especially when the electrode is inserted as a ground or center electrode in the combustion chamber of an internal combustion engine and is surrounded by the local gas mixtures. Thus, the life of such compounds is limited.

Eine Methode, die zu einer stabileren Verbindung zwischen der Edelmetalllegierung und der Nickellegierung führt, besteht im Anbringen einer Schweißnaht zwischen der Edelmetalllegierung und der Nickellegierung unter Verwendung eines Laserschweissverfahrens. Das Anbringen solcher Schweißnähte ist jedoch vergleichsweise aufwendig und bedingt einen vergleichsweise hohen Materialaufwand für die Edelmetalllegierung.One method that results in a more stable bond between the noble metal alloy and the nickel alloy is to attach a weld between the noble metal alloy and the nickel alloy using a laser welding process. However, the attachment of such welds is relatively expensive and requires a relatively high cost of materials for the noble metal alloy.

Eine demgegenüber einfachere Methode stellt das sogenannte Laserlegieren dar, bei dem die Edelmetalllegierung und die Nickellegierung in einander benachbarten Bereichen vollständig aufgeschmolzen und dabei vermischt, das heißt legiert werden. Die dabei entstehende Edelmetall-NickelLegierung ist jedoch hinsichtlich Erosion und Korrosion weniger resistent als reine Edelmetalllegierungen.By contrast, a simpler method is the so-called laser alloying, in which the noble metal alloy and the nickel alloy in adjacent areas completely melted and thereby mixed, that is alloyed. However, the resulting noble metal-nickel alloy is less resistant to erosion and corrosion than pure precious metal alloys.

Mit dem erfindungsgemäßen Verfahren sollen nun die genannten Nachteile, die sich bei der Verbindung der Edelmetalllegierung mit der Nickellegierung durch Widerstandsschweissen, Laserschweissen oder Laserlegieren ergeben, weitgehend vermieden werden. Dabei sollen dauerhaltbare, verschleißfeste Elektroden hergestellt werden, wobei die Verbindung zwischen einem Edelmetall oder einer Edelmetalllegierung mit der Elektrode mit geringem Aufwand realisierbar sein soll.With the method according to the invention, the disadvantages mentioned, which result in the connection of the noble metal alloy with the nickel alloy by resistance welding, laser welding or laser alloying, should now be largely avoided. In this case, durable, wear-resistant electrodes are to be produced, wherein the connection between a noble metal or a noble metal alloy with the electrode should be feasible with little effort.

In Figur 1 kennzeichnet 5 eine Elektrode, die beispielsweise die Mittelelektrode einer Zündkerze sein kann. Die Elektrode 5 umfaßt eine Spitze 20 die gemäß Figur 1 eine Vertiefung bilden kann, aber nicht muß. Die Elektrode 5 ist metallisch ausgebildet und kann beispielsweise zumindest teilweise aus Nickel gebildet sein. Im folgenden soll beispielhaft angenommen werden, dass die Elektrode 5 aus einer Nickellegierung gebildet ist.In Fig. 1, 5 denotes an electrode which may be, for example, the center electrode of a spark plug. The electrode 5 comprises a tip 20 which can form a depression according to FIG. 1, but need not. The electrode 5 is metallic and may for example be formed at least partially from nickel. In the following, it will be assumed by way of example that the electrode 5 is formed from a nickel alloy.

In Figur 1 ist weiterhin eine Edelmetallspitze 1 dargestellt, die aus einem reinen Edelmetall oder aus einer Edelmetalllegierung gebildet sein kann. Als reine Edelmetalle können dabei beispielsweise Gold, Platin oder Iridium Verwendung finden. Bei Verwendung von Edelmetalllegierungen kann dies ebenfalls unter Verwendung von Gold, Platin oder Iridium erfolgen. Unter Edelmetalllegierungen sind dabei Legierungen zu verstehen, die lediglich Edelmetalle enthalten. In diesem Beispiel soll die Edelmetallspitze 1 als Edelmetalllegierung ausgebildet sein und einen Anteil Platin enthalten. Gemäß Figur 1 ist die Edelmetallspitze 1 an ihrer Unterseite 35 derart geformt, dass sie möglichst passgenau von der Spitze 20 der Elektrode 5 aufgenommen werden kann. Gemäß Figur 1 weist die Edelmetallspitze 1 an ihrer Unterseite 35 eine Hervorhebung auf, die mit der Vertiefung an der Spitze 20 der Elektrode 5 korrespondiert. Der Durchmesser der Edelmetallspitze 1 ist dabei etwa genauso groß gewählt wie der Durchmesser der Elektrode 5 im Bereich ihrer Spitze 20. Er könnte aber auch größer oder kleiner gewählt werden.FIG. 1 furthermore shows a noble metal tip 1, which may be formed from a pure noble metal or from a noble metal alloy. As pure precious metals can be used, for example, gold, platinum or iridium. When using precious metal alloys, this can also be done using gold, platinum or iridium. Under noble metal alloys are understood to mean alloys containing only precious metals. In this example, the noble metal tip 1 should be formed as a noble metal alloy and contain a proportion of platinum. According to FIG. 1, the noble metal tip 1 is shaped on its underside 35 such that it can be received as accurately as possible from the tip 20 of the electrode 5. According to Figure 1, the noble metal tip 1 on its underside 35 a highlighting, which corresponds to the recess 20 at the top of the electrode 5. The diameter of the precious metal tip is 1 It is about the same size as the diameter of the electrode 5 in the region of its tip 20. However, it could also be chosen larger or smaller.

Gemäß Figur 1 wird nun in einem ersten Verfahrensschritt die Edelmetallspitze 1 passgenau auf die Spitze 20 der Elektrode 5 gesetzt, wie durch den Pfeil in Figur 1 angedeutet ist.According to FIG. 1, in a first method step, the noble metal tip 1 is now set accurately on the tip 20 of the electrode 5, as indicated by the arrow in FIG.

Anschließend wird in einem zweiten Verfahrensschritt gemäß Figur 2 die Edelmetallspitze 1 mit der Elektrode 5 in dem Bereich, in dem die Edelmetallspitze 1 an die Elektrode 5 grenzt, miteinander verschweißt, beispielsweise durch ein Widerstandsschweißverfahren. Dieser Bereich ist in Figur 2 mit dem Bezugszeichen 40 gekennzeichnet. Er wird im folgenden auch als Schweißbereich bezeichnet.Subsequently, in a second method step according to FIG. 2, the noble metal tip 1 is welded to the electrode 5 in the region in which the noble metal tip 1 adjoins the electrode 5, for example by a resistance welding method. This area is identified by the reference numeral 40 in FIG. He is referred to below as the welding area.

Die Dicke der sich dabei ergebenden Diffusionszone im Schweißbereich 40 beträgt in der Regel wenige µm und ist damit anfällig hinsichtlich von Wärmespannungsrissen aufgrund der unterschiedlichen Wärmeausdehnungskoeffizienten der Edelmetallspitze 1 und der nickelhaltigen Elektrode 5.The thickness of the resulting diffusion zone in the welding region 40 is usually a few microns and is thus prone to thermal stress cracks due to the different thermal expansion coefficients of the noble metal tip 1 and the nickel-containing electrode fifth

In einem dritten Verfahrensschritt wird die Edelmetallspitze 1 in einem ersten Bereich 10 und die Elektrode 5 in einem zweiten Bereich 15, der dem ersten Bereich 10 benachbart ist, aufgeschmolzen, um in diesen Bereichen 10, 15 eine Mischlegierung aus dem Material der Edelmetallspitze 1 und dem Material der Elektrode 5 zu bilden, also eine Mischlegierung aus der Edelmetalllegierung der Edelmetallspitze 1 und der Nickellegierung der Elektrode 5 gemäß dem hier gewählten Beispiel. Dabei wird der erste Bereich 10 so bestimmt, dass er etwa ringförmig vollständig vom Material der Edelmetallspitze 1 ummantelt ist, wie in Figur 3 erkennbar ist. In sämtlichen Figuren kennzeichnen dabei gleiche Bezugszeichen gleiche Elemente. Der Schweißbereich 40 ist im Bereich eines Grenzbereichs 25 des ersten Bereichs 10 zum zweiten Bereich 15 in Figur 3 zur Veranschaulichung durch Schraffur hervorgehoben und durch das Bezugszeichen 45 gekennzeichnet. Er wird im folgenden auch als Grenzschweißbereich bezeichnet. Beim Aufschmelzen des ersten Bereichs 10 und des zweiten Bereichs 15 wird auch der Grenzschweißbereich 45 aufgeschmolzen, der nach dem zweiten Verfahrensschritt gemäß Figur 2 als Teil des Schweißbereichs 40 die beschriebene Diffusionszone zwischen der Edelmetallspitze 1 und der Elektrode 5 ergab. Im ersten Bereich 10, im zweiten Bereich 15 und im Grenzschweißbereich 45 ergibt sich beim dritten Verfahrensschritt gemäß Figur 3 eine möglichst vollständige Durchmischung des Materials der Edelmetallspitze 1 und des Materials der Elektrode 5. Es ergibt sich somit nach dem dritten Verfahrensschritt gemäß Figur 3 im ersten Bereich 10, im zweiten Bereich 15 und im Grenzschweißbereich 45 eine annähernd homogene Edelmetall-Nickel-Legierung, die gemäß Figur 3 im Bereich der Edelmetallspitze 1 etwa ringförmig vollständig vom Material der Edelmetallspitze 1, im Bereich der Elektrode 5 vollständig vom Material der Elektrode 5 und im Bereich des Schweißbereichs 40 vollständig von der Diffusionszone umgeben ist. Entscheidend ist dabei vor allem, dass der erste Bereich 10 etwa ringförmig vollständig vom Material der Edelmetallspitze 1 ummantelt ist.In a third method step, the noble metal tip 1 is melted in a first region 10 and the electrode 5 in a second region 15, which is adjacent to the first region 10, in order in these regions 10, 15 a mixed alloy of the material of the noble metal tip 1 and the Material of the electrode 5 to form, so a mixed alloy of the noble metal alloy of the noble metal tip 1 and the nickel alloy of the electrode 5 according to the example chosen here. In this case, the first region 10 is determined in such a way that it is completely surrounded by the material of the noble metal tip 1 approximately annularly, as can be seen in FIG. In all figures, like reference numerals designate like elements. The welding region 40 is in the region of a boundary region 25 of the first area 10 to the second area 15 in Figure 3 for clarity by hatching highlighted and indicated by the reference numeral 45. He is referred to below as the border welding area. When melting the first region 10 and the second region 15, the boundary welding region 45 is also melted, which after the second process step according to FIG. 2 as part of the welding region 40 resulted in the described diffusion zone between the noble metal tip 1 and the electrode 5. In the first region 10, in the second region 15 and in the boundary welding region 45, the complete mixing of the material of the noble metal tip 1 and of the material of the electrode 5 results in the third process step according to FIG. 3. Thus, according to the third method step according to FIG Area 10, in the second area 15 and in the boundary welding area 45, an approximately homogeneous noble metal-nickel alloy, the ring according to Figure 3 in the region of the noble metal tip 1 approximately annularly completely from the material of the noble metal tip 1, in the region of the electrode 5 completely from the material of the electrode 5 and is completely surrounded by the diffusion zone in the region of the welding region 40. It is crucial, above all, that the first region 10 is completely surrounded by the material of the noble metal tip 1 in a ring-shaped manner.

Auf diese Weise ist die Mischlegierung im Bereich der Edelmetallspitze 1 bis auf ihre brennraumseitige Stirnfläche vollständig von der die Edelmetallspitze 1 umgebenden Atmosphäre getrennt und somit vor Umwelteinflüssen geschützt und nicht der Erosion und Korrosion besonders im Brennraum einer Brennkraftmaschine ausgesetzt. Gemäß Figur 3 ist die sich im ersten Bereich 10, im zweiten Bereich 15 und im Grenzschweißbereich 45 bildende Mischlegierung vollständig im Bereich der Elektrode 5 von der umgebenden Atmosphäre getrennt, da auch der zweite Bereich 15 mit Ausnahme seines Grenzbereichs 50 zum Grenzschweißbereich 45 bzw. zum ersten Bereich 10 vollständig vom Material der Elektrode 5 umgeben ist.In this way, the mixed alloy is completely separated in the region of the noble metal tip 1 to its combustion chamber side face of the atmosphere surrounding the noble metal tip 1 and thus protected from environmental influences and not exposed to erosion and corrosion, especially in the combustion chamber of an internal combustion engine. According to FIG. 3, the mixed alloy forming in the first region 10, in the second region 15 and in the boundary welding region 45 is completely separated from the surrounding atmosphere in the region of the electrode 5, since the second region 15, with the exception of its boundary region 50, also reaches the boundary welding region 45 first Area 10 is completely surrounded by the material of the electrode 5.

Durch die Mischlegierung wird die Verbindung zwischen der Edelmetallspitze 1 und der Elektrode 5 besonders stabil und dauerhaft gemacht und unterliegt nicht mehr der Gefahr einer Rissbildung im Bereich der Diffusionszone zwischen Edelmetallspitze 1 und Elektrode 5. Durch die im Bereich der Edelmetallspitze 1 etwa ringförmige Abschirmung der sich ergebenden Mischlegierung aus Edelmetallanteilen und Nickelanteilen vor der umgebenden Atmosphäre wird besonders im Bereich der Verbindung zwischen der Edelmetallspitze 1 und der Elektrode 5 verhindert, dass die erosions- und korrosionsanfällige Mischlegierung schädlichen Umwelteinflüssen ausgesetzt wird, sodass die Verbindung zwischen der Edelmetallspitze 1 und der Elektrode 5 besonders dauerhaltbar wird.By the mixed alloy, the connection between the noble metal tip 1 and the electrode 5 is made particularly stable and durable and is no longer subject to the risk of cracking in the region of the diffusion zone between precious metal tip 1 and electrode 5. By in the precious metal tip 1 approximately annular shield of resulting mixed alloy of noble metal fractions and nickel contents in front of the surrounding atmosphere is prevented, especially in the region of the connection between the noble metal tip 1 and the electrode 5 that the erosion and corrosion-prone mixed alloy is exposed to harmful environmental influences, so that the connection between the noble metal tip 1 and the electrode 5 particularly is durable.

Das Aufschmelzen des ersten Bereichs 10, des Grenzschweißbereichs 45 und des zweiten Bereichs 15 kann beispielsweise mittels Laserenergie realisiert werden. Dazu kann beispielsweise von einem Laserelement 30 wie in Figur 3 dargestellt die Laserenergie aufgebracht werden. In Figur 3 kennzeichnet das Bezugszeichen 55 einen Laserstrahl. Der Laserstrahl ist dabei auf den ersten Bereich 10, den Grenzschweißbereich 45 und den zweiten Bereich 15 fokussiert und sorgt für eine örtlich präzise Aufschmelzung dieser Bereiche und damit zur Bildung einer möglichst konstanten homogenen Mischlegierung in diesen Bereichen. Die Laserenergie kann dabei beispielsweise mittels eines Laserpulses auf eine, im Falle einer Zündkerze brennraumseitige, Stirnfläche der Edelmetallspitze 1 aufgebracht werden. Dabei wird die Laserenergie nicht auf die gesamte Stirnfläche der Edelmetallspitze 1 aufgebracht, sondern auf einen etwa kreisförmigen Bereich, der von einem etwa kreisringförmigen Bereich der Stirnfläche umgeben ist.The melting of the first region 10, the boundary welding region 45 and the second region 15 can be realized for example by means of laser energy. For this purpose, for example, by a laser element 30 as shown in Figure 3, the laser energy can be applied. In Fig. 3, reference numeral 55 denotes a laser beam. The laser beam is focused on the first region 10, the boundary welding region 45 and the second region 15 and ensures a locally precise melting of these regions and thus the formation of a homogeneous homogeneous mixed alloy which is as constant as possible in these regions. The laser energy can be applied, for example, by means of a laser pulse to a, in the case of a spark plug combustion chamber side, end face of the noble metal tip 1. The laser energy is not applied to the entire end face of the noble metal tip 1, but to an approximately circular area which is surrounded by an approximately annular region of the end face.

Nur im kreisförmigen Bereich der Stirnfläche und darunter wird die Edelmetallspitze 1 somit aufgeschmolzen, um den ersten Bereich 10 zu ergeben, der etwa ringförmig vollständig vom Material der Edelmetallspitze 1 ummantelt ist. Die Verwendung eines Laserpulses ermöglicht eine gezielte und definierte Zurverfügungstellung der für das Aufschmelzen des ersten Bereiches 10, des zweiten Bereichs 15 und des Grenzschweißbereichs 45 erforderlichen Energie. Der Laserpuls kann beispielsweise eine Leistung von etwa 1 kW für eine Zeit von etwa 10 ms aufweisen.Only in the circular region of the end face and underneath is the precious metal tip 1 thus melted to give the first region 10, which is completely encased in an annular manner by the material of the noble metal tip 1. The use of a laser pulse enables a specific and defined provision of the energy required for the melting of the first region 10, the second region 15 and the boundary welding region 45. For example, the laser pulse may have a power of about 1 kW for a time of about 10 ms.

Somit ergibt sich gemäß Figur 4 nach dem dritten Verfahrensschritt zwischen der Edelmetallspitze 1 und der Elektrode 5 die mit dem Bezugszeichen 60 gekennzeichnete Mischlegierung mit einem Wärmeausdehnungskoeffizienten, der zwischen dem der Edelmetalllegierung der Edelmetallspitze 1 und dem der Nickellegierung der Elektrode 5 liegt. Risse aufgrund von Wärmespannungen werden dadurch vor allem im Bereich der Mischlegierung 60 vermieden. Die Verbindung zwischen der Edelmetallspitze 1 und der Elektrode 5 ist somit dauerhaltbar. Dies um so mehr, je größer der Querschnitt der Mischlegierung 60 im Bereich des Schweißbereichs 40, also der Diffusionszone, ist. Lediglich eine brennraumseitige Stirnfläche 100 der Mischlegierung 60 ist nicht vom nicht aufgeschmolzenenen Material der Edelmetallspitze 1 umgeben und somit direkt dem Brennraum ausgesetzt. Da gemäß Figur 3 der erste Bereich 10 etwa ringförmig vollständig von nicht aufgeschmolzenem Material der Edelmetallspitze 1 ummantelt ist, ist die Mischlegierung 60 gemäß Figur 4 im Bereich der Edelmetallspitze 1 weitgehend von Umwelteinflüssen abgeschirmt. Somit liegen mit Ausnahme der brennraumseitigen Stirnfläche 100 der Mischlegierung 60 an der Oberfläche der Edelmetallspitze 1 vor allem in dem dem Brennraum zugewandten Teil des Schweißbereichs 40 die sehr guten Erosions- und Korrosionseigenschaften der verwendeten Edelmetalllegierung weiterhin vor. Somit wird vor allem im Schweißbereich 40 eine Korrosion und Erosion verhindert und die Dauerhaltbarkeit der Verbindung zwischen der Edelmetallspitze 1 und der Elektrode 5 erhöht.Thus, according to FIG. 4, after the third method step between the noble metal tip 1 and the electrode 5, the mixed alloy identified by the reference numeral 60 has a coefficient of thermal expansion between that of the noble metal alloy of the noble metal tip 1 and that of the nickel alloy of the electrode 5. Cracks due to thermal stresses are thereby avoided, especially in the area of the mixed alloy 60. The connection between the noble metal tip 1 and the electrode 5 is thus durable. This is all the more the greater the cross section of the mixed alloy 60 in the region of the weld region 40, ie the diffusion zone. Only a combustion chamber-side end face 100 of the mixed alloy 60 is not surrounded by the non-melted material of the noble metal tip 1 and thus exposed directly to the combustion chamber. Since, according to FIG. 3, the first region 10 is completely surrounded by non-molten material of the noble metal tip 1 approximately annularly, the mixed alloy 60 according to FIG. 4 is largely shielded from environmental influences in the region of the noble metal tip 1. Thus, with the exception of the combustion chamber end face 100 of the mixed alloy 60 on the surface of the noble metal tip 1, especially in the combustion chamber facing part of the weld region 40, the very good erosion and corrosion properties of the noble metal alloy used continue before. Thus, especially in the welding area 40, corrosion and erosion are prevented and the durability of the connection between the noble metal tip 1 and the electrode 5 is increased.

Die gebildete Elektrode 5 mit der Edelmetallspitze 1 ist somit bei minimalem Edelmetalleinsatz unter Brennraumbedingungen dauerhaltbar sowie erosions- und korrosionsfest. Der zweite Verfahrensschritt der Schweißverbindung und der dritte Verfahrensschritt der Laserlegierung lassen sich in kurzer Taktzeit und gleichzeitig durchführen. Somit wird die Herstellungszeit im Vergleich zu einer reinen Schweißverbindung oder Laserlegierung nicht erhöht.The formed electrode 5 with the noble metal tip 1 is thus durable with minimal use of precious metals under combustion chamber conditions as well as erosion and corrosion resistant. The second process step of the welded joint and the third process step of the laser alloy can be carried out in a short cycle time and simultaneously. Thus, the manufacturing time is not increased compared to a pure welded joint or laser alloy.

Die Elektrode 5 ist hier beispielhaft als Mittelelektrode einer Zündkerze ausgebildet. In entsprechender Weise kann eine Edelmetallspitze auch an einer Masseelektrode, beispielsweise einer Dachelektrode oder einer Seitenelektrode angebracht werden. Somit kann eine Zündkerze geschaffen werden, bei der sowohl die Mittelelektrode als auch eine oder mehrere Masseelektroden jeweils eine Edelmetallspitze aufweisen, wobei die Edelmetallspitze der Mittelelektrode der Edelmetallspitze einer Masseelektrode zur Ausbildung der Funkenstrecke gegenüberliegt, um den Elektrodenverschleiß zu minimieren und die Lebensdauer der Zündkerze zu verlängern. Die Zündkerze wird in sämtlichen Figuren durch das Bezugszeichen 65 referenziert und ist übersichtlichkeitshalber nur anhand eines Ausschnitts der Elektrode 5, die in diesem Beispiel als Mittelelektrode der Zündkerze 65 fungiert, dargestellt.The electrode 5 is exemplified here as the center electrode of a spark plug. Similarly, a noble metal tip may also be attached to a ground electrode, such as a roof electrode or a side electrode. Thus, a spark plug can be provided in which both the center electrode and one or more ground electrodes each comprise a noble metal tip, the noble metal tip of the center electrode of the noble metal tip facing a ground electrode to form the spark gap to minimize electrode wear and extend the life of the spark plug , The spark plug is referenced in all figures by the reference numeral 65 and is for clarity only on the basis of a section of the electrode 5, which acts in this example as the center electrode of the spark plug 65, shown.

In sämtlichen Figuren kennzeichnen gleiche Bezugszeichen gleiche Elemente und ist die Elektrode 5 und die Edelmetallspitze 1 in einem Längsschnitt dargestellt.In all figures, like reference numerals designate like elements, and the electrode 5 and the noble metal tip 1 are shown in a longitudinal section.

Claims (13)

  1. Method for placing a precious metal tip (1) on an electrode (5), in particular a spark plug electrode, wherein in one step the precious metal tip (1) is welded onto the electrode (5), characterized in that in a further step the precious metal tip (1), in a first region (10), and the electrode (5), in a second region (15) which is adjacent to the first region (10), are melted, in order to form a mixed alloy (60) in these regions (10, 15), wherein the first region (10) is selected in such a way that it is completely surrounded, approximately in the form of a ring, by the material of the precious metal tip (1).
  2. Method according to Claim 1, characterized in that the welding method selected for the first step is a resistance welding method.
  3. Method according to Claim 1 or 2, characterized in that the two regions are melted by means of laser energy.
  4. Method according to Claim 3, characterized in that the laser energy is applied to an end face of the precious metal tip (1) by means of a laser pulse from a laser element (30).
  5. Method according to Claim 4, characterized in that the laser pulse applies a power of approximately 1kW for a period of approximately 10ms.
  6. Method according to one of the preceding claims, characterized in that the material selected for the electrode (5) is a non-precious metal, preferably nickel or a nickel alloy.
  7. Method according to one of the preceding claims, characterized in that the material selected for the precious metal tip (1) is a precious metal alloy, in particular with a gold, iridium or platinum content.
  8. Method according to one of Claims 1 to 6, characterized in that the material selected for the precious metal tip (1) is a pure precious metal, in particular gold, iridium or platinum.
  9. Electrode (5), in particular for a spark plug (65), having a precious metal tip (1), wherein the precious metal tip (1) is welded to the electrode (5), characterized in that the precious metal tip (1), in a first region (10), and the electrode (5), in a second region (15) which is adjacent to the first region (10), form a mixed alloy (60), wherein the first region (10) is completely surrounded, approximately in the form of a ring, by the material of the precious metal tip (1).
  10. Electrode (5) according to Claim 9, characterized in that the electrode (5) is formed from a non-precious metal, preferably nickel or a nickel alloy.
  11. Electrode (5) according to Claim 9 or 10, characterized in that the precious metal tip (1) is formed from a precious metal alloy, in particular with a gold, iridium or platinum content.
EP02753022A 2001-07-20 2002-07-17 Method for placing a precious metal tip on an electrode, electrode and spark plug Expired - Lifetime EP1413029B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10134671 2001-07-20
DE2001134671 DE10134671A1 (en) 2001-07-20 2001-07-20 Applying precious metal tip to electrode used in production of a spark plug comprises welding tip to electrode, and fusing tip in first region and electrode in second region to form mixed alloy
PCT/DE2002/002614 WO2003017443A1 (en) 2001-07-20 2002-07-17 Method for placing a precious metal tip on an electrode, electrode and spark plug

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EP1413029A1 EP1413029A1 (en) 2004-04-28
EP1413029B1 true EP1413029B1 (en) 2007-04-25

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JP (1) JP2004538617A (en)
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CN101859984A (en) * 2009-04-09 2010-10-13 日本特殊陶业株式会社 Ignition plug for I. C. engine and manufacture method thereof

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US7049733B2 (en) * 2003-11-05 2006-05-23 Federal-Mogul Worldwide, Inc. Spark plug center electrode assembly
US9673593B2 (en) 2012-08-09 2017-06-06 Federal-Mogul Ignition Company Spark plug having firing pad
US9318879B2 (en) 2012-10-19 2016-04-19 Federal-Mogul Ignition Company Spark plug having firing pad
EP2933887B1 (en) * 2012-12-17 2019-03-27 NGK Spark Plug Co., Ltd. Spark plug
US9041274B2 (en) 2013-01-31 2015-05-26 Federal-Mogul Ignition Company Spark plug having firing pad
JP5995912B2 (en) 2014-06-04 2016-09-21 日本特殊陶業株式会社 Spark plug and method of manufacturing spark plug

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GB2234920A (en) * 1989-08-11 1991-02-20 Ford Motor Co Forming an erosion resistant tip on an electrode
EP0549368B1 (en) * 1991-12-27 1998-05-27 Ngk Spark Plug Co., Ltd An electrode for a spark plug and a method of manufacturing the same
JP3121309B2 (en) * 1998-02-16 2000-12-25 株式会社デンソー Spark plugs for internal combustion engines
US6337533B1 (en) * 1998-06-05 2002-01-08 Denso Corporation Spark plug for internal combustion engine and method for manufacturing same
DE19961769A1 (en) * 1998-12-21 2000-06-29 Denso Corp Spark plug for an internal combustion engine with a straight column ground electrode
JP3361479B2 (en) * 1999-04-30 2003-01-07 日本特殊陶業株式会社 Manufacturing method of spark plug

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CN101859984A (en) * 2009-04-09 2010-10-13 日本特殊陶业株式会社 Ignition plug for I. C. engine and manufacture method thereof
CN101859984B (en) * 2009-04-09 2013-03-27 日本特殊陶业株式会社 Spark plug for internal-combustion engine and manufacturing method thereof

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WO2003017443A1 (en) 2003-02-27
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EP1413029A1 (en) 2004-04-28
JP2004538617A (en) 2004-12-24

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