EP3221937B1 - Spark plug electrode, method for the production thereof, and spark plug - Google Patents

Spark plug electrode, method for the production thereof, and spark plug Download PDF

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Publication number
EP3221937B1
EP3221937B1 EP15774604.1A EP15774604A EP3221937B1 EP 3221937 B1 EP3221937 B1 EP 3221937B1 EP 15774604 A EP15774604 A EP 15774604A EP 3221937 B1 EP3221937 B1 EP 3221937B1
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EP
European Patent Office
Prior art keywords
weld seam
noble metal
spark plug
plug electrode
metal pin
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EP15774604.1A
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German (de)
French (fr)
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EP3221937A1 (en
Inventor
Detlef Hartmann
Dennis QUEST
Guido HANNICH
Stefan Nufer
Dominic LANG
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Robert Bosch GmbH
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Robert Bosch GmbH
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Publication of EP3221937A1 publication Critical patent/EP3221937A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
    • H01T13/39—Selection of materials for electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T21/00—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs
    • H01T21/02—Apparatus or processes specially adapted for the manufacture or maintenance of spark gaps or sparking plugs of sparking plugs

Definitions

  • the present invention relates to a spark plug electrode with increased mechanical robustness, a permanently high-performance spark plug and a method for producing the spark plug electrode that can be easily implemented.
  • Spark plug electrodes with good corrosion and erosion resistance are conventionally produced by welding a noble metal pin, usually made of platinum or iridium-based alloys, onto an electrode base body.
  • the basic electrode body is made of a non-precious metal. Due to the different coefficients of thermal expansion of the noble metal and the non-noble metal, mechanical stresses occur at the weld seam, which reduce the mechanical stability and thus the durability and resilience of the spark plug electrode.
  • DE10137523A1 discloses a spark plug electrode according to the preamble of claim 1 and a method according to the preamble of claim 10.
  • the spark plug electrode according to the invention according to main claim 1, on the other hand, is characterized by a high mechanical load capacity and a very good maximum durability.
  • This is achieved according to the invention in that an electrode base body and a noble metal pin are connected to one another by a connecting zone which has at least one first weld seam and one second weld seam.
  • the connection zone preferably comprises exactly one first weld seam and one second weld seam, the first weld seam and the second weld seam further preferably running completely through the spark plug electrode.
  • a further advantage of the spark plug electrode according to the invention is therefore that mechanical stresses occurring during engine operation in the connection zone are spread across several Areas, namely the interfaces or connection surfaces precious metal pin / connection zone and connection zone / base body, as well as the interface or connection surface between the first weld seam and the second weld seam, are distributed.
  • the stability of the spark plug electrode, and in particular its mechanical stability, is thus increased with a very high efficiency.
  • the first weld seam is arranged between the noble metal pin and the base body and the second weld seam is arranged either between the first weld seam and the noble metal pin or between the first weld seam and the base body.
  • a noble metal concentration in the first weld seam is smaller than a noble metal concentration in the second weld seam.
  • a noble metal concentration in the first weld seam is greater than a noble metal concentration in the second weld seam.
  • the precious metal concentration runs downhill from the precious metal pin to the base body. A sudden decrease in the precious metal concentration from the precious metal pin to the base body is prevented by forming the connection zone with at least two weld seams with different precious metal contents.
  • the correspondingly different precious metal contents result in a further advantage: since the coefficient of thermal expansion of a material is formed in a first approximation by a linear superposition of the coefficients of thermal expansion of all elements and connections present in the area to be examined, the coefficient of thermal expansion also changes from the precious metal pin via the connection zone to Basic body step by step, i.e. essentially running uniformly and not erratically. In this way, mechanical stresses in the connection zone, and in particular at the interfaces or connection surfaces of the noble metal pin / connection zone and connection zone / base body, are further reduced in the spark plasma. The stability of the spark plug electrode is significantly increased with very high performance.
  • Thermal expansion coefficients that change abruptly along the spark plug electrode can also advantageously be avoided in that a proportion of noble metal is present in the first weld seam and in the second Weld seam is at least 40 mass%.
  • the proportion of noble metal in the first weld seam and in the second weld seam is particularly advantageously at least 50% by mass, the proportions each being based on the total weight of the first weld seam and the second weld seam.
  • the noble metal concentration in the connection zone in the longitudinal direction XX of the spark plug electrode per interval of 100 ⁇ m length of the connection zone is a maximum of 40 Mass%, preferably by a maximum of 25 mass%, changes.
  • a length L1 of the noble metal pin in the longitudinal direction X-X of the spark plug electrode is a maximum of 900 ⁇ m.
  • the ignition spark can thus be very well formed centrally on the precious metal pin.
  • the length L1 of the noble metal pin is 80 ⁇ m to 200 ⁇ m.
  • the stability of the spark plug electrode can furthermore advantageously be improved in that a length L2 of the connection zone in the longitudinal direction X-X of the spark plug electrode is 50 ⁇ m to 700 ⁇ m and in particular 100 ⁇ m to 600 ⁇ m.
  • the noble metal is selected from iridium (Ir), rhodium (Rh), platinum (Pt), palladium (Pd), rhenium (Re) and alloys of these elements.
  • nickel can be added to the precious metal or the alloy of the aforementioned precious metals.
  • the base body is formed from a nickel-containing alloy, with a proportion of nickel in the alloy in particular at least 50% by mass, based on the total weight of the alloy.
  • a spark plug which comprises a spark plug electrode as disclosed above.
  • the spark plug electrode can be designed as a center electrode or a ground electrode. Furthermore, both the center electrode and the ground electrode, and possibly also a plurality of provided ground electrodes, can also be formed by the spark plug electrode according to the invention.
  • the spark plug is characterized by high mechanical resistance with very good spark generation. Change intervals of up to about 100,000 km can be achieved.
  • a method for producing a spark plug electrode with a base body and a noble metal pin is described in claim 10. It should be noted here that this method is particularly suitable for producing the spark plug electrode described above. The method is simple, can be implemented without high technical effort using standard processes and allows the production of a high-performance, mechanically permanently stable spark plug electrode at low cost. While a conventional spark plug electrode is produced by simply welding a noble metal pin onto an electrode base body, the invention provides for the formation of at least two weld seams. A first weld seam is formed by performing a first welding process by which the noble metal pin and the base body of the spark plug electrode are connected. A second welding process is then carried out, as a result of which a second weld seam is formed.
  • the second welding process can be carried out either in an area between the first weld seam and the noble metal pin or in an area between the first weld seam and the base body. If the second welding process is carried out between the first weld seam and the noble metal pin, as explained in the first case, then a noble metal concentration in the first weld seam is lower than in the second weld. If the second welding process is carried out between the first weld seam and the base body, a noble metal concentration in the first weld seam is greater than in the second weld seam. The first weld seam and the second weld seam form a connection zone between the noble metal pin and the base body, through which the noble metal pin is firmly connected to the base body.
  • the respective materials are melted at an interface between the noble metal pin and the base body and combine to form a mixed material in which a portion of the noble metal of the noble metal pin and a portion of the material of the base body, i.e. in particular the base metal of the base body, are approximately equal are.
  • the precious metal concentration from the precious metal pin via the connection zone to the base body suddenly decreases from 100% by mass to about 50% by mass to 0% by mass. Consequently, the coefficient of thermal expansion also has an abrupt course, since, as already described above, it is composed approximately linearly of the coefficients of thermal expansion of the elements and connections forming the examined area.
  • the gradient of the gradient traversed by the coefficient of thermal expansion is reduced by the formation of the second weld seam and possibly further weld seams.
  • the gradual change in the coefficient of thermal expansion is moderated.
  • a particularly uniform weld seam can be formed locally in the desired area.
  • using a continuous wave laser (CW laser) promotes the formation of a homogeneous weld seam.
  • the second welding process is carried out in an area which is 5 ⁇ m to 50 ⁇ m, in particular 10 ⁇ m to 30 ⁇ m, away from a connection surface or interface of the first weld seam and the precious metal pin in the direction of the precious metal pin lies. This promotes a second weld seam with a large layer thickness and good stability, which is beneficial to the overall mechanical stability of the spark plug electrode.
  • a particularly uniform change in the concentration gradient of the elements and thus also in the coefficient of thermal expansion is advantageously achieved in that a laser beam completely penetrates the materials to be welded during the first welding process and the second welding process.
  • the laser beam acts per time interval on a section of the same size of the materials to be welded.
  • the spark plug 1 comprises a ground electrode 2 and a center electrode 3.
  • An insulator 4 is provided in such a way that the center electrode 3 projects somewhat from the insulator 4 in a known manner.
  • the center electrode 3 has a noble metal pin 11.
  • the insulator 4 itself is partially surrounded by a housing 5.
  • the reference numeral 6 denotes an electrical connection nut.
  • An electrically conductive connection is provided from the electrical connection nut 6 via a connection bolt 7 and an electrically conductive connection element 8 to the center electrode 3.
  • FIG. 2 shows in detail a structure of a spark plug electrode 10 according to a preferred embodiment of the invention.
  • the spark plug electrode 10 can be designed as a ground electrode or a center electrode.
  • the spark plug electrode 10 comprises a base body 12 which, if it is designed as a center electrode, is connected to an electrically conductive connecting element.
  • the foot of the base body 12 is included Compared to the rest of the area of the base body 12, it is thickened so that it can be stably attached to the spark plug 1.
  • the base body 12 is advantageously formed from a nickel-containing alloy, a proportion of nickel in the alloy in particular being at least 50% by mass, based on the total weight of the alloy.
  • the spark plug electrode also has a noble metal pin 11 which is used to generate the spark plasma.
  • the noble metal pin 11 can consist of a pure noble metal, in particular of Ir, Rh, Pt, Pd or Re or of alloys of these elements. Furthermore, it is also possible for the noble metal pin 11 to be formed from alloys of the aforementioned elements and nickel as a further component.
  • the noble metal pin 11 has a length L1 of preferably a maximum of 900 ⁇ m and in particular of 80 ⁇ m to 200 ⁇ m in the longitudinal direction X-X of the spark plug electrode 10. This is particularly advantageous for the stable generation of ignition sparks.
  • connection zone 13 consists of two weld seams, a first weld seam 14 which faces the base body 12 and a second weld seam 15 which faces the noble metal pin 11.
  • the noble metal pin 11 is arranged in a stable manner on the base body 12 through the connection zone 13.
  • connection zone 13 has a length L2 of 10 ⁇ m to 700 ⁇ m and in particular 100 ⁇ m to 600 ⁇ m in the longitudinal direction X-X of the spark plug electrode 10. A mechanically stable connection between the noble metal pin 11 and the base body 12 is thus obtained.
  • a noble metal concentration in the first weld seam 14 is smaller than a noble metal concentration in the second weld seam 15.
  • a noble metal concentration in both the first weld seam 14 and in the second weld seam 15 is smaller than in the noble metal pin 11 and 11 but also larger than in the base body 12.
  • a length L3 of the first weld seam 14 and a length L4 of the second weld seam 15 in the longitudinal direction X-X of the spark plug electrode 10 are approximately the same.
  • the course of the noble metal concentration from noble metal pin 11 to base body 12 shows that a coefficient of thermal expansion from noble metal pin 11 to base body 12 also changes essentially continuously, without increasing or decreasing sharply. If high temperatures act on the spark plug electrode 10 during engine operation, they can be better tolerated. There are lower mechanical stresses at the interfaces 16-18, namely the interface 16 precious metal pin 11 / second weld seam 15, the interface 17 second weld seam 15 / first weld seam 14 and the interface 18 first weld seam 14 / base body 12. The service life of the spark plug electrode 10 is thus significantly increased.
  • FIG. 12 shows an element distribution in a section of the spark plug electrode 10 from FIG Figure 2 .
  • the areas of different chemical elements are shown with different hatching.
  • the vertical dashed lines divide the spark plug electrode 10 into its different areas along the longitudinal direction XX of the spark plug 10.
  • the mass distribution of the elements in percent by mass (% by mass) is plotted against the length of the spark plug electrode 10 in ⁇ m.
  • the left-hand section represents that of the noble metal pin 11. It can be seen here that the noble metal pin 11 consists of 100% by mass of noble metal, namely an alloy of Ir and Rh.
  • the section of the second weld seam 15 adjoins the left section.
  • the proportion of noble metal which is to be understood as a total proportion of the noble metals Ir and Rh, is lower here than in the noble metal pin 11.
  • the proportion of noble metal has decreased from 100% by mass to about 75% by mass.
  • the remaining 25 mass% is allotted to nickel, which was added in the formation of the connection zone 13.
  • the section of the first weld seam 14 adjoins the section of the second weld seam 15. Here the precious metal concentration has decreased further.
  • a noble metal proportion in the first weld seam 14 is now approximately 60% by mass.
  • the remaining 40% by mass are allotted to nickel.
  • the right-hand section shows the distribution of elements in the base body 12.
  • the base body 12 consists of almost 100% by mass of nickel (or a nickel-containing alloy).
  • the noble metal concentration decreases further from the second weld seam 15 towards the base body 12.
  • the noble metal concentration in the connection zone 13 changes in the longitudinal direction X-X of the spark plug electrode 10 per interval of 100 ⁇ m length of the connection zone 13 by a maximum of 40% by mass and mostly by a maximum of 25% by mass. There are no sudden changes in the element concentration with a change of in particular more than 50% by mass. By providing further weld seams, in areas of greater change in the noble metal concentration, a further mitigation of the gradient in the noble metal concentration can be achieved.
  • the length L3 of the first weld seam 14 and the length L4 of the second weld seam 15 in the longitudinal direction X-X of the spark plug electrode 10 are approximately the same size.
  • the change in concentration of the noble metal is therefore particularly uniform.
  • FIG. 13 shows a schematic sectional view during the manufacturing process of the spark plug electrode 10 from FIG Figure 2 .
  • a noble metal pin 11 is arranged on a base body 12.
  • a laser beam symbolized by (h * v)
  • the laser beam melts the adjoining materials of the noble metal pin 11 and the base body 12 in the connection surface 20, so that a first weld seam 14 is formed which contains the elements of the noble metal pin 1 and the base body 12 in a relatively balanced mixed concentration.
  • the spark plug electrode 10 is rotated in the direction of arrow C during the welding process A, so that the laser beam hits the joint surface 20 of all Sides irradiated uniformly.
  • the laser beam is preferably formed by a CW laser and completely penetrates the materials to be welded. After the first weld 14 has been formed by the first welding process A, the laser beam is realigned, advantageously to an area 19 between the first weld 14 and the noble metal pin 11.
  • the laser beam can, however, also target an area between the first weld 14 and the base body 12, but this leads to a somewhat more pronounced change in the precious metal concentration from the precious metal pin 11 to the first weld 14 and is therefore less preferred.
  • the laser beam is preferably directed onto an area 19 which is located away from the connecting surface 20 of the first weld seam 14 and the noble metal pin 11 by a height h in the direction of the noble metal pin 11.
  • the height h is in particular 5 ⁇ m to 50 ⁇ m and in particular 10 ⁇ m to 30 ⁇ m.
  • a second weld 15 is formed with a further mixed concentration of the elements, the noble metal concentration in the second weld 15 being greater than the noble metal concentration in the first weld 14 due to the melting of further noble metal from the noble metal pin 11.
  • the length L1 of the noble metal pin 11 and the length of the base body 12 have decreased in favor of the connection zone 13. Due to the decreasing noble metal concentration starting from noble metal pin 11 via connection zone 13 to base body 12 without sudden decrease in noble metal concentration, a curve of the coefficient of thermal expansion along these areas is also obtained without abrupt change. Stresses at the interfaces 16, 17, 18 of the areas adjacent to one another are reduced. This increases the mechanical stability of the spark plug electrode 10.

Description

Stand der TechnikState of the art

Die vorliegende Erfindung betrifft eine Zündkerzenelektrode mit erhöhter mechanischer Robustheit, eine dauerhaft hoch leistungsfähige Zündkerze sowie ein einfach umsetzbares Verfahren zur Herstellung der Zündkerzenelektrode.The present invention relates to a spark plug electrode with increased mechanical robustness, a permanently high-performance spark plug and a method for producing the spark plug electrode that can be easily implemented.

Zündkerzenelektroden mit guter Korrosions- und Erosionsbeständigkeit werden herkömmlicherweise durch Aufschweißen eines Edelmetallstifts, meist aus Platin- oder Iridium-Basislegierungen, auf einen Elektrodengrundkörper hergestellt. Der Elektrodengrundkörper ist aus einem Nichtedelmetall gebildet. Aufgrund der unterschiedlichen Wärmeausdehnungskoeffizienten des Edelmetalls und des Nichtedelmetalls treten an der Schweißnaht mechanische Spannungen auf, die die mechanische Stabilität und damit die Haltbarkeit und Belastbarkeit der Zündkerzenelektrode reduzieren.Spark plug electrodes with good corrosion and erosion resistance are conventionally produced by welding a noble metal pin, usually made of platinum or iridium-based alloys, onto an electrode base body. The basic electrode body is made of a non-precious metal. Due to the different coefficients of thermal expansion of the noble metal and the non-noble metal, mechanical stresses occur at the weld seam, which reduce the mechanical stability and thus the durability and resilience of the spark plug electrode.

DE10137523A1 offenbart eine Zündkerzenelektrode gemäß dem Oberbegriff des Anspruchs 1 und ein Verfahren gemäß dem Oberbegriff des Anspruchs 10. DE10137523A1 discloses a spark plug electrode according to the preamble of claim 1 and a method according to the preamble of claim 10.

Offenbarung der ErfindungDisclosure of the invention

Die erfindungsgemäße Zündkerzenelektrode gemäß dem Hauptanspruch 1 zeichnet sich dagegen durch eine hohe mechanische Belastbarkeit und eine sehr gute maximale Dauerhaltbarkeit aus. Dies wird erfindungsgemäß dadurch erzielt, dass ein Elektrodengrundkörper und ein Edelmetallstift durch eine Verbindungszone miteinander verbunden sind, die mindestens eine erste Schweißnaht und eine zweite Schweißnaht aufweist. Bevorzugt umfasst die Verbindungszone genau eine erste Schweißnaht und eine zweite Schweißnaht, wobei weiter vorzugsweise die erste Schweißnaht und die zweite Schweißnaht vollständig durch die Zündkerzenelektrode verlaufen. Vorteilhaft an der erfindungsgemäßen Zündkerzenelektrode ist somit ferner, dass im Motorbetrieb auftretende mechanische Spannungen in der Verbindungszone auf mehrere Bereiche, nämlich die Grenzflächen bzw. Verbindungsflächen Edelmetallstift/Verbindungszone und Verbindungszone/Grundkörper, sowie die Grenzfläche bzw. Verbindungsfläche zwischen der ersten Schweißnaht und der zweiten Schweißnaht, verteilt werden. Die Stabilität der Zündkerzenelektrode, und insbesondere ihre mechanische Stabilität, ist somit bei sehr hoher Leistungsfähigkeit erhöht.The spark plug electrode according to the invention according to main claim 1, on the other hand, is characterized by a high mechanical load capacity and a very good maximum durability. This is achieved according to the invention in that an electrode base body and a noble metal pin are connected to one another by a connecting zone which has at least one first weld seam and one second weld seam. The connection zone preferably comprises exactly one first weld seam and one second weld seam, the first weld seam and the second weld seam further preferably running completely through the spark plug electrode. A further advantage of the spark plug electrode according to the invention is therefore that mechanical stresses occurring during engine operation in the connection zone are spread across several Areas, namely the interfaces or connection surfaces precious metal pin / connection zone and connection zone / base body, as well as the interface or connection surface between the first weld seam and the second weld seam, are distributed. The stability of the spark plug electrode, and in particular its mechanical stability, is thus increased with a very high efficiency.

Die Unteransprüche zeigen bevorzugte Weiterbildungen der Erfindung.The subclaims show preferred developments of the invention.

Gemäß einer vorteilhaften Weiterbildung ist die erste Schweißnaht zwischen dem Edelmetallstift und dem Grundkörper angeordnet und die zweite Schweißnaht ist entweder zwischen der ersten Schweißnaht und dem Edelmetallstift oder zwischen der ersten Schweißnaht und dem Grundkörper angeordnet. Im ersten Fall ist eine Edelmetallkonzentration in der ersten Schweißnaht kleiner als eine Edelmetallkonzentration in der zweiten Schweißnaht. Im zweiten Fall ist eine Edelmetallkonzentration in der ersten Schweißnaht größer als eine Edelmetallkonzentration in der zweiten Schweißnaht. In beiden Fällen durchläuft die Edelmetallkonzentration vom Edelmetallstift zum Grundkörper ein absteigendes Gefälle. Eine sprunghafte Abnahme der Edelmetallkonzentration vom Edelmetallstift zum Grundkörper wird durch das Ausbilden der Verbindungszone mit mindestens zwei Schweißnähten mit unterschiedlichen Edelmetallgehalten verhindert. Durch die entsprechend ausgebildeten unterschiedlichen Edelmetallgehalte ergibt sich ein weiterer Vorteil: da der Wärmeausdehnungskoeffizient eines Materials in erster Näherung durch eine lineare Überlagerung der Wärmeausdehnungskoeffizienten aller im zu untersuchenden Bereich vorliegenden Elemente und Verbindungen gebildet wird, ändert sich auch der Wärmeausdehnungskoeffizient vom Edelmetallstift über die Verbindungszone bis zum Grundkörper schrittweise, also im Wesentlichen gleichförmig verlaufend und nicht sprunghaft. Damit werden im Funkenplasma mechanische Spannungen in der Verbindungszone, und insbesondere an den Grenzflächen bzw. Verbindungsflächen Edelmetallstift/Verbindungszone und Verbindungszone/Grundkörper weiter reduziert. Die Stabilität der Zündkerzenelektrode ist bei sehr hoher Leistungsfähigkeit deutlich erhöht.According to an advantageous development, the first weld seam is arranged between the noble metal pin and the base body and the second weld seam is arranged either between the first weld seam and the noble metal pin or between the first weld seam and the base body. In the first case, a noble metal concentration in the first weld seam is smaller than a noble metal concentration in the second weld seam. In the second case, a noble metal concentration in the first weld seam is greater than a noble metal concentration in the second weld seam. In both cases, the precious metal concentration runs downhill from the precious metal pin to the base body. A sudden decrease in the precious metal concentration from the precious metal pin to the base body is prevented by forming the connection zone with at least two weld seams with different precious metal contents. The correspondingly different precious metal contents result in a further advantage: since the coefficient of thermal expansion of a material is formed in a first approximation by a linear superposition of the coefficients of thermal expansion of all elements and connections present in the area to be examined, the coefficient of thermal expansion also changes from the precious metal pin via the connection zone to Basic body step by step, i.e. essentially running uniformly and not erratically. In this way, mechanical stresses in the connection zone, and in particular at the interfaces or connection surfaces of the noble metal pin / connection zone and connection zone / base body, are further reduced in the spark plasma. The stability of the spark plug electrode is significantly increased with very high performance.

Sich sprunghaft ändernde Wärmeausdehnungskoeffizienten entlang der Zündkerzenelektrode können ferner vorteilhaft dadurch vermieden werden, dass ein Anteil an Edelmetall in der ersten Schweißnaht und in der zweiten Schweißnaht mindestens 40 Masse-% beträgt. Besonders vorteilhaft liegt der Anteil an Edelmetall in der ersten Schweißnaht und in der zweiten Schweißnaht bei mindestens 50 Masse-%, wobei die Anteile jeweils auf das Gesamtgewicht der ersten Schweißnaht und der zweiten Schweißnaht bezogen sind.Thermal expansion coefficients that change abruptly along the spark plug electrode can also advantageously be avoided in that a proportion of noble metal is present in the first weld seam and in the second Weld seam is at least 40 mass%. The proportion of noble metal in the first weld seam and in the second weld seam is particularly advantageously at least 50% by mass, the proportions each being based on the total weight of the first weld seam and the second weld seam.

Im Lichte eines sich stetig, also idealisiert kontinuierlich, ändernden Wärmeausdehnungskoeffizienten, und damit einer besonders guten mechanischen Beständigkeit der Zündkerzenelektrode ist es erfindungsgemäß erforderlich, dass sich die Edelmetallkonzentration in der Verbindungszone in Längsrichtung X-X der Zündkerzenelektrode je Intervall von 100 µm Länge der Verbindungszone maximal um 40 Masse-%, vorzugsweise um maximal 25 Masse-%, ändert.In the light of a steadily, idealized continuously, changing coefficient of thermal expansion, and thus a particularly good mechanical resistance of the spark plug electrode, it is necessary according to the invention that the noble metal concentration in the connection zone in the longitudinal direction XX of the spark plug electrode per interval of 100 μm length of the connection zone is a maximum of 40 Mass%, preferably by a maximum of 25 mass%, changes.

Zur stabilen Erzeugung eines Funkenplasmas ist weiter vorteilhaft vorgesehen, dass eine Länge L1 des Edelmetallstifts in Längsrichtung X-X der Zündkerzenelektrode maximal 900 µm, beträgt. Der Zündfunke lässt sich somit sehr gut zentral am Edelmetallstift ausbilden. Im Hinblick auf eine Kostenreduzierung der Zündkerzenelektrode ist es ferner von Vorteil, wenn die Länge L1 des Edelmetallstifts 80 µm bis 200 µm beträgt.For stable generation of a spark plasma, it is further advantageously provided that a length L1 of the noble metal pin in the longitudinal direction X-X of the spark plug electrode is a maximum of 900 μm. The ignition spark can thus be very well formed centrally on the precious metal pin. With a view to reducing the cost of the spark plug electrode, it is also advantageous if the length L1 of the noble metal pin is 80 μm to 200 μm.

Die Stabilität der Zündkerzenelektrode kann ferner vorteilhat dadurch verbessert werden, dass eine Länge L2 der Verbindungszone in Längsrichtung X-X der Zündkerzenelektrode 50 µm bis 700 µm und insbesondere 100 µm bis 600 µm, beträgt.The stability of the spark plug electrode can furthermore advantageously be improved in that a length L2 of the connection zone in the longitudinal direction X-X of the spark plug electrode is 50 μm to 700 μm and in particular 100 μm to 600 μm.

Ein sich in der Verbindungszone stetig ändernder Wärmeausdehnungskoeffizient, und damit eine besonders hohe mechanische Dauerbeständigkeit der Zündkerzenelektrode wird vorteilhaft dadurch erhalten, dass eine Länge L3 der ersten Schweißnaht und eine Länge L4 der zweiten Schweißnaht in Längsrichtung X-X der Zündkerzenelektrode in etwa gleich groß ist.A steadily changing coefficient of thermal expansion in the connection zone, and thus a particularly high mechanical durability of the spark plug electrode, is advantageously obtained in that a length L3 of the first weld seam and a length L4 of the second weld seam in the longitudinal direction X-X of the spark plug electrode are approximately the same.

Zur Verbesserung der Korrosions- und Erosionsbeständigkeit der Zündkerzenelektrode bei sehr guter Erzeugung eines Zündfunkenplasmas ist das Edelmetall ausgewählt aus Iridium (Ir), Rhodium (Rh), Platin (Pt), Palladium (Pd), Rhenium (Re) und Legierungen dieser Elemente. Zur Kostenreduzierung kann dem Edelmetall bzw. der Legierung der vorbenannten Edelmetalle Nickel zulegiert werden.To improve the corrosion and erosion resistance of the spark plug electrode with very good spark plasma generation, the noble metal is selected from iridium (Ir), rhodium (Rh), platinum (Pt), palladium (Pd), rhenium (Re) and alloys of these elements. To reduce costs, nickel can be added to the precious metal or the alloy of the aforementioned precious metals.

Ein ausgewogenes Eigenschaftsspektrum im Hinblick auf die mechanischen und physikalischen Eigenschaften der Zündkerzenelektrode bei optimierter Kostenstruktur wird vorteilhaft dadurch erhalten, dass der Grundkörper aus einer nickelhaltigen Legierung gebildet ist, wobei ein Anteil an Nickel in der Legierung insbesondere mindestens 50 Masse-%, bezogen auf das Gesamtgewicht der Legierung, beträgt.A balanced range of properties with regard to the mechanical and physical properties of the spark plug electrode with an optimized cost structure is advantageously obtained in that the base body is formed from a nickel-containing alloy, with a proportion of nickel in the alloy in particular at least 50% by mass, based on the total weight of the alloy.

Ebenfalls erfindungsgemäß wird auch eine Zündkerze beschrieben, die eine wie vorstehend offenbarte Zündkerzenelektrode umfasst. Die Zündkerzenelektrode kann dabei als Mittelelektrode oder Masseelektrode ausgebildet sein. Ferner können auch sowohl die Mittelelektrode als auch die Masseelektrode, ggf. auch mehrere vorgesehene Masseelektroden, durch die erfindungsgemäße Zündkerzenelektrode gebildet sein. Die Zündkerze zeichnet sich durch eine hohe mechanische Beständigkeit bei sehr guter Funkenerzeugung aus. Es können Wechselintervalle von bis zu etwa 100.000 km erzielt werden.According to the invention, a spark plug is also described which comprises a spark plug electrode as disclosed above. The spark plug electrode can be designed as a center electrode or a ground electrode. Furthermore, both the center electrode and the ground electrode, and possibly also a plurality of provided ground electrodes, can also be formed by the spark plug electrode according to the invention. The spark plug is characterized by high mechanical resistance with very good spark generation. Change intervals of up to about 100,000 km can be achieved.

Ferner erfindungsgemäß wird in Anspruch 10 ein Verfahren zur Herstellung einer Zündkerzenelektrode mit einem Grundkörper und einem Edelmetallstift beschrieben. Hierbei sei angemerkt, dass sich dieses Verfahren insbesondere zur Herstellung der vorstehend beschriebenen Zündkerzenelektrode eignet. Das Verfahren ist einfach, ohne hohen technischen Aufwand unter Anwendung von Standardprozessen umsetzbar und erlaubt die Herstellung einer hoch leistungsfähigen, mechanisch dauerhaft stabilen Zündkerzenelektrode bei geringem Kostenaufwand. Während eine herkömmliche Zündkerzenelektrode durch einfaches Schweißen eines Edelmetallstifts auf einen Elektrodengrundkörper hergestellt wird, ist erfindungsgemäß die Bildung von mindestens zwei Schweißnähten vorgesehen. Eine erste Schweißnaht wird dabei durch Ausführen eines ersten Schweißvorganges gebildet, durch den der Edelmetallstift und der Grundkörpers der Zündkerzenelektrode verbunden werden. Anschließend wird ein zweiter Schweißvorgang ausgeführt, wodurch eine zweite Schweißnaht gebildet wird. Der zweite Schweißvorgang kann entweder in einem Bereich zwischen der ersten Schweißnaht und dem Edelmetallstift oder in einem Bereich zwischen der ersten Schweißnaht und dem Grundkörper ausgeführt werden. Wird der zweite Schweißvorgang wie im ersten Fall dargelegt, zwischen der ersten Schweißnaht und dem Edelmetallstift ausgeführt, so ist eine Edelmetallkonzentration in der ersten Schweißnaht kleiner als in der zweiten Schweißnaht. Wird der zweite Schweißvorgang zwischen der ersten Schweißnaht und dem Grundkörper ausgeführt, so ist eine Edelmetallkonzentration in der ersten Schweißnaht größer als in der zweiten Schweißnaht. Die erste Schweißnaht und die zweite Schweißnaht bilden eine Verbindungszone zwischen dem Edelmetallstift und dem Grundkörper, durch die der Edelmetallstift fest mit dem Grundkörper verbunden wird. Durch den ersten Schweißvorgang werden an einer Grenzfläche des Edelmetallstifts und des Grundkörpers die jeweiligen Materialien aufgeschmolzen und verbinden sich zu einem Mischmaterial, in dem ein Anteil an Edelmetall des Edelmetallstifts und ein Anteil an Material des Grundkörpers, also insbesondere an Nichtedelmetall des Grundkörpers in etwa gleich groß sind. Somit nimmt die Edelmetallkonzentration vom Edelmetallstift über die Verbindungszone zum Grundkörper sprunghaft von 100 Masse-% über etwa 50 Masse-% zu 0 Masse-% ab. Folglich hat auch der Wärmeausdehnungskoeffizient einen sprunghaften Verlauf, da er sich, wie vorstehend bereits beschrieben, annähernd linear aus den Wärmeausdehnungskoeffizienten der den untersuchten Bereich bildenden Elemente und Verbindungen zusammensetzt. Die Steigung des vom Wärmeausdehnungskoeffizienten durchlaufenen Gefälles wird durch das Ausbilden der zweiten Schweißnaht, und ggf. weiterer Schweißnähte, verkleinert. Mit anderen Worten wird die stufenweise Änderung des Wärmeausdehnungskoeffizienten abgemildert. Es ergibt sich eine verlaufende und damit eine in etwa annähernd kontinuierliche Änderung des Wärmeausdehnungskoeffizienten. Dies ist darin begründet, dass durch den zweiten Schweißvorgang das Material der ersten Schweißnaht erneut aufgeschmolzen und entweder mit weiterem Edelmetall aus dem Edelmetallstift durch Ausführen des Schweißvorganges zwischen der ersten Schweißnaht und dem Edelmetallstift, oder mit weiterem Material aus dem Grundkörper durch Ausführen des Schweißvorganges zwischen der ersten Schweißnaht und dem Grundkörper, legiert wird. Somit ergibt sich in der zweiten Schweißnaht eine weiter abgestufte Mischkonzentration der aufgeschmolzenen Ausgangselemente, die zwischen derjenigen des reinen Edelmetalls und der ersten Schweißnaht oder zwischen derjenigen des Grundkörpermaterials und der ersten Schweißnaht liegt. Hierbei kann derselbe Verfahrensaufbau wie für das Ausführen des ersten Schweißvorganges verwendet werden, mit dem Unterschied, dass die Ausrichtung des Laserstrahls örtlich leicht verändert wird. Der technische Aufwand ist somit identisch. Daher kann das Verfahren bei geringfügig erhöhtem Zeitaufwand kostengünstig ausgeführt werden.Furthermore, according to the invention, a method for producing a spark plug electrode with a base body and a noble metal pin is described in claim 10. It should be noted here that this method is particularly suitable for producing the spark plug electrode described above. The method is simple, can be implemented without high technical effort using standard processes and allows the production of a high-performance, mechanically permanently stable spark plug electrode at low cost. While a conventional spark plug electrode is produced by simply welding a noble metal pin onto an electrode base body, the invention provides for the formation of at least two weld seams. A first weld seam is formed by performing a first welding process by which the noble metal pin and the base body of the spark plug electrode are connected. A second welding process is then carried out, as a result of which a second weld seam is formed. The second welding process can be carried out either in an area between the first weld seam and the noble metal pin or in an area between the first weld seam and the base body. If the second welding process is carried out between the first weld seam and the noble metal pin, as explained in the first case, then a noble metal concentration in the first weld seam is lower than in the second weld. If the second welding process is carried out between the first weld seam and the base body, a noble metal concentration in the first weld seam is greater than in the second weld seam. The first weld seam and the second weld seam form a connection zone between the noble metal pin and the base body, through which the noble metal pin is firmly connected to the base body. As a result of the first welding process, the respective materials are melted at an interface between the noble metal pin and the base body and combine to form a mixed material in which a portion of the noble metal of the noble metal pin and a portion of the material of the base body, i.e. in particular the base metal of the base body, are approximately equal are. Thus, the precious metal concentration from the precious metal pin via the connection zone to the base body suddenly decreases from 100% by mass to about 50% by mass to 0% by mass. Consequently, the coefficient of thermal expansion also has an abrupt course, since, as already described above, it is composed approximately linearly of the coefficients of thermal expansion of the elements and connections forming the examined area. The gradient of the gradient traversed by the coefficient of thermal expansion is reduced by the formation of the second weld seam and possibly further weld seams. In other words, the gradual change in the coefficient of thermal expansion is moderated. This results in a gradual and thus approximately continuous change in the coefficient of thermal expansion. This is due to the fact that the material of the first weld seam is melted again through the second welding process and either with further precious metal from the precious metal pin by performing the welding process between the first weld seam and the precious metal pin, or with further material from the base body by performing the welding process between the first weld seam and the base body, is alloyed. This results in a further graded mixed concentration of the melted starting elements in the second weld seam, which lies between that of the pure noble metal and the first weld seam or between that of the base body material and the first weld seam. The same method structure can be used here as for carrying out the first welding process, with the difference that the alignment of the laser beam is slightly changed locally. The technical effort is therefore identical. The method can therefore be carried out inexpensively with a slightly increased expenditure of time.

Die für die erfindungsgemäße Zündkerzenelektrode beschriebenen Vorteile, vorteilhaften Effekte und Weiterbildungen finden auch Anwendung auf die erfindungsgemäße Zündkerze sowie das erfindungsgemäße Verfahren zur Herstellung einer Zündkerzenelektrode.The advantages, advantageous effects and developments described for the spark plug electrode according to the invention are also applied to the spark plug according to the invention and to the method according to the invention for producing a spark plug electrode.

Durch die vorteilhafte Weiterbildung, dass das Schweißen durch Laserschweißen ausgeführt wird, kann lokal im gewünschten Bereich eine besonders gleichförmige Schweißnaht ausgebildet werden. Insbesondere durch Verwendung eines Continuous-Wave Lasers (CW-Laser), wird das Ausbilden einer homogenen Schweißnaht gefördert.Due to the advantageous development that the welding is carried out by laser welding, a particularly uniform weld seam can be formed locally in the desired area. In particular, using a continuous wave laser (CW laser) promotes the formation of a homogeneous weld seam.

Eine weitere vorteilhafte Weiterbildung des Verfahrens sieht vor, dass der zweite Schweißvorgang in einem Bereich ausgeführt wird, der von einer Verbindungsfläche bzw. Grenzfläche der ersten Schweißnaht und des Edelmetallstifts 5 µm bis 50 µm, insbesondere 10 µm bis 30 µm, in Richtung des Edelmetallstifts entfernt liegt. Hierdurch wird eine zweite Schweißnaht mit großer Schichtdicke und guter Stabilität gefördert, was der mechanischen Gesamtstabilität der Zündkerzenelektrode zuträglich ist.Another advantageous development of the method provides that the second welding process is carried out in an area which is 5 μm to 50 μm, in particular 10 μm to 30 μm, away from a connection surface or interface of the first weld seam and the precious metal pin in the direction of the precious metal pin lies. This promotes a second weld seam with a large layer thickness and good stability, which is beneficial to the overall mechanical stability of the spark plug electrode.

Eine besonders gleichförmige Änderung des Konzentrationsgefälles der Elemente und damit auch des Wärmeausdehnungskoeffizienten wird vorteilhaft dadurch erzielt, dass ein Laserstrahl während des ersten Schweißvorganges und des zweiten Schweißvorganges die zu schweißenden Materialien vollständig durchdringt.A particularly uniform change in the concentration gradient of the elements and thus also in the coefficient of thermal expansion is advantageously achieved in that a laser beam completely penetrates the materials to be welded during the first welding process and the second welding process.

Dieser Effekt kann noch dadurch verstärkt werden, dass die Zündkerzenelektrode während der Schweißvorgänge rotiert wird. Der Laserstrahl wirkt so pro Zeitintervall auf einen gleichgroßen Abschnitt der zu schweißenden Materialien ein.This effect can be increased by rotating the spark plug electrode during the welding process. The laser beam acts per time interval on a section of the same size of the materials to be welded.

Kurze Beschreibung der ZeichnungenBrief description of the drawings

Nachfolgend werden Ausführungsbeispiele der Erfindung unter Bezugnahme auf die begleitende Zeichnung im Detail beschrieben. Dabei sind gleiche bzw. funktional gleiche Bauteile mit den gleichen Bezugszeichen bezeichnet.Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings. The same or functionally identical components are denoted by the same reference symbols.

In der Zeichnung ist:

Figur 1
eine Teilschnittansicht einer Zündkerze gemäß einer Ausführungsform der Erfindung,
Figur 2
eine Schnittansicht einer Zündkerzenelektrode gemäß einer Ausführungsform der Erfindung,
Figur 3
eine Elementverteilung in einem Ausschnitt der Zündkerzenelektrode aus Figur 2 und
Figur 4
eine schematische Schnittansicht während des Herstellprozesses der Zündkerzenelektrode aus Figur 2.
In the drawing is:
Figure 1
a partial sectional view of a spark plug according to an embodiment of the invention,
Figure 2
a sectional view of a spark plug electrode according to an embodiment of the invention,
Figure 3
an element distribution in a section of the spark plug electrode Figure 2 and
Figure 4
a schematic sectional view during the manufacturing process of the spark plug electrode Figure 2 .

Ausführungsformen der ErfindungEmbodiments of the invention

Nachfolgend wird unter Bezugnahme auf die Figuren 1 bis 4 eine Zündkerze 1 gemäß einem bevorzugten Ausführungsbeispiel der Erfindung sowie eine Zündkerzenelektrode 10 gemäß einem bevorzugten Ausführungsbeispiel der Erfindung im Detail beschrieben.In the following, with reference to the Figures 1 to 4 a spark plug 1 according to a preferred embodiment of the invention and a spark plug electrode 10 according to a preferred embodiment of the invention are described in detail.

Wie aus Figur 1 ersichtlich ist, umfasst die Zündkerze 1 eine Masseelektrode 2 und eine Mittelelektrode 3. Ein Isolator 4 ist derart vorgesehen, dass die Mittelelektrode 3 in bekannter Weise etwas vom Isolator 4 vorsteht. Die Mittelelektrode 3 weist einen Edelmetallstift 11 auf. Der Isolator 4 selbst ist teilweise von einem Gehäuse 5 umgeben. Das Bezugszeichen 6 bezeichnet eine elektrische Anschlussmutter. Von der elektrischen Anschlussmutter 6 ist eine elektrisch leitfähige Verbindung über einen Anschlussbolzen 7 und ein elektrisch leitfähiges Verbindungselement 8 zur Mittelelektrode 3 vorgesehen.How out Figure 1 As can be seen, the spark plug 1 comprises a ground electrode 2 and a center electrode 3. An insulator 4 is provided in such a way that the center electrode 3 projects somewhat from the insulator 4 in a known manner. The center electrode 3 has a noble metal pin 11. The insulator 4 itself is partially surrounded by a housing 5. The reference numeral 6 denotes an electrical connection nut. An electrically conductive connection is provided from the electrical connection nut 6 via a connection bolt 7 and an electrically conductive connection element 8 to the center electrode 3.

Figur 2 zeigt im Detail einen Aufbau einer Zündkerzenelektrode 10 gemäß einer bevorzugten Ausführungsform der Erfindung. Die Zündkerzenelektrode 10 kann dabei als Masseelektrode oder Mittelelektrode ausgebildet sein. Die Zündkerzenelektrode 10 umfasst einen Grundkörper 12, der im Falle der Ausbildung als Mittelelektrode mit einem elektrisch leitfähigen Verbindungselement verbunden ist. Der Fuß des Grundkörpers 12 ist dabei gegenüber dem übrigen Bereich des Grundkörpers 12 verdickt ausgebildet, so dass er stabil an der Zündkerze 1 befestigt werden kann. Figure 2 shows in detail a structure of a spark plug electrode 10 according to a preferred embodiment of the invention. The spark plug electrode 10 can be designed as a ground electrode or a center electrode. The spark plug electrode 10 comprises a base body 12 which, if it is designed as a center electrode, is connected to an electrically conductive connecting element. The foot of the base body 12 is included Compared to the rest of the area of the base body 12, it is thickened so that it can be stably attached to the spark plug 1.

Der Grundkörper 12 ist vorteilhafterweise aus einer nickelhaltigen Legierung gebildet, wobei ein Anteil an Nickel in der Legierung insbesondere mindestens 50 Masse-%, bezogen auf das Gesamtgewicht der Legierung, beträgt.The base body 12 is advantageously formed from a nickel-containing alloy, a proportion of nickel in the alloy in particular being at least 50% by mass, based on the total weight of the alloy.

Die Zündkerzenelektrode weist ferner einen Edelmetallstift 11 auf, der zur Erzeugung des Funkenplasmas dient. Der Edelmetallstift 11 kann aus einem reinen Edelmetall bestehen, insbesondere aus Ir, Rh, Pt, Pd oder Re oder aus Legierungen dieser Elemente. Ferner ist es auch möglich, dass der Edelmetallstift 11 aus Legierungen der vorstehend genannten Elemente und Nickel als weiterem Bestandteil gebildet wird. Der Edelmetallstift 11 hat in Längsrichtung X-X der Zündkerzenelektrode 10 eine Länge L1 von vorzugsweise maximal 900 µm und insbesondere von 80 µm bis 200 µm. Dies ist zur stabilen Erzeugung von Zündfunken besonders vorteilhaft.The spark plug electrode also has a noble metal pin 11 which is used to generate the spark plasma. The noble metal pin 11 can consist of a pure noble metal, in particular of Ir, Rh, Pt, Pd or Re or of alloys of these elements. Furthermore, it is also possible for the noble metal pin 11 to be formed from alloys of the aforementioned elements and nickel as a further component. The noble metal pin 11 has a length L1 of preferably a maximum of 900 μm and in particular of 80 μm to 200 μm in the longitudinal direction X-X of the spark plug electrode 10. This is particularly advantageous for the stable generation of ignition sparks.

Der Edelmetallstift 11 und der Grundkörper 12 sind durch eine Verbindungszone 13 miteinander verbunden. Die Verbindungszone 13 besteht in diesem Ausführungsbeispiel aus zwei Schweißnähten, einer ersten Schweißnaht 14, die dem Grundkörper 12 zugewandt ist, und einer zweiten Schweißnaht 15, die dem Edelmetallstift 11 zugewandt ist. Durch die Verbindungszone 13 wird der Edelmetallstift 11 stabil an dem Grundkörper 12 angeordnet.The noble metal pin 11 and the base body 12 are connected to one another by a connecting zone 13. In this exemplary embodiment, the connection zone 13 consists of two weld seams, a first weld seam 14 which faces the base body 12 and a second weld seam 15 which faces the noble metal pin 11. The noble metal pin 11 is arranged in a stable manner on the base body 12 through the connection zone 13.

Die Verbindungszone 13 weist in Längsrichtung X-X der Zündkerzenelektrode 10 eine Länge L2 von 10 µm bis 700 µm und insbesondere von 100 µm bis 600 µm, auf. So wird eine mechanisch stabile Verbindung zwischen dem Edelmetallstift 11 und dem Grundkörper 12 erhalten.The connection zone 13 has a length L2 of 10 μm to 700 μm and in particular 100 μm to 600 μm in the longitudinal direction X-X of the spark plug electrode 10. A mechanically stable connection between the noble metal pin 11 and the base body 12 is thus obtained.

Untersucht man die Verbindungszone 13, so ist eine Edelmetallkonzentration in der ersten Schweißnaht 14 kleiner als eine Edelmetallkonzentration in der zweiten Schweißnaht 15. Insgesamt gesehen ist aber eine Edelmetallkonzentration sowohl in der ersten Schweißnaht 14 als auch in der zweiten Schweißnaht 15 kleiner als im Edelmetallstift 11 und aber ferner größer als im Grundkörper 12. Es gibt demnach in der Zündkerzenelektrode 10 vier Bereiche mit jeweils unterschiedlichen Konzentrationen an Edelmetall. Dabei nimmt die Edelmetallkonzentration vom Edelmetallstift 11, in dem die Edelmetallkonzentration je nach verwendetem Ausgangsmaterial bei 100% oder darunter liegt, über die zweite Schweißnaht 15 und die erste Schweißnaht 14, im Wesentlichen stetig, also verlaufend, ohne sprunghafte Änderung, zum Grundkörper 12, in dem die Edelmetallkonzentration 0% beträgt (oder je nach verwendetem Material des Grundkörpers 12, gering ist), ab.If the connection zone 13 is examined, a noble metal concentration in the first weld seam 14 is smaller than a noble metal concentration in the second weld seam 15. Overall, however, a noble metal concentration in both the first weld seam 14 and in the second weld seam 15 is smaller than in the noble metal pin 11 and 11 but also larger than in the base body 12. There are accordingly four areas in the spark plug electrode 10, each with different concentrations of noble metal. The precious metal concentration of the precious metal pin 11, in which the Depending on the starting material used, the precious metal concentration is 100% or below, via the second weld seam 15 and the first weld seam 14, essentially steadily, i.e. continuously, without sudden changes, to the base body 12, in which the precious metal concentration is 0% (or depending on the type of material used Material of the base body 12, is low), from.

Für eine stetig abnehmende Edelmetallkonzentration ist es dabei von Vorteil, wenn eine Länge L3 der ersten Schweißnaht 14 und eine Länge L4 der zweiten Schweißnaht 15 in Längsrichtung X-X der Zündkerzenelektrode 10 in etwa gleich groß sind.For a steadily decreasing precious metal concentration, it is advantageous if a length L3 of the first weld seam 14 and a length L4 of the second weld seam 15 in the longitudinal direction X-X of the spark plug electrode 10 are approximately the same.

Aus dem Konzentrationsverlauf der Edelmetallkonzentration vom Edelmetallstift 11 zum Grundkörper 12 ergibt sich, dass sich auch ein Wärmeausdehnungskoeffizient vom Edelmetallstift 11 zum Grundkörper 12 im Wesentlichen kontinuierlich ändert, ohne stark sprunghaft anzusteigen oder abzunehmen. Wirken im Motorbetrieb hohe Temperauren auf die Zündkerzenelektrode 10, so können diese besser toleriert werden. Es kommt zu geringeren mechanischen Spannungen an den Grenzflächen 16-18, nämlich der Grenzfläche 16 Edelmetallstift 11/zweite Schweißnaht 15, der Grenzfläche 17 zweite Schweißnaht 15/erste Schweißnaht 14 und der Grenzfläche 18 erste Schweißnaht 14/Grundkörper 12. Die Lebensdauert der Zündkerzenelektrode 10 wird damit signifikant erhöht.The course of the noble metal concentration from noble metal pin 11 to base body 12 shows that a coefficient of thermal expansion from noble metal pin 11 to base body 12 also changes essentially continuously, without increasing or decreasing sharply. If high temperatures act on the spark plug electrode 10 during engine operation, they can be better tolerated. There are lower mechanical stresses at the interfaces 16-18, namely the interface 16 precious metal pin 11 / second weld seam 15, the interface 17 second weld seam 15 / first weld seam 14 and the interface 18 first weld seam 14 / base body 12. The service life of the spark plug electrode 10 is thus significantly increased.

Figur 3 zeigt eine Elementverteilung in einem Ausschnitt der Zündkerzenelektrode 10 aus Figur 2. Die Bereiche unterschiedlicher chemischer Elemente sind mit unterschiedlicher Schraffur dargestellt. Die senkrechen Strichlinien unterteilen die Zündkerzenelektrode 10 in ihre unterschiedliche Bereiche entlang der Längsrichtung X-X der Zündkerze 10. Es ist die Massenverteilung der Elemente in Masseprozent (Masse-%) gegen die Länge der Zündkerzenelektrode 10 in µm aufgetragen. Der linke Abschnitt stellt denjenigen des Edelmetallstifts 11 dar. Hier ist zu sehen, dass der Edelmetallstift 11 zu 100 Masse-% aus Edelmetall, nämlich aus einer Legierung aus Ir und Rh, besteht. An den linken Abschnitt schließt sich der Abschnitt der zweiten Schweißnaht 15 an. Der Anteil an Edelmetall, worunter ein Gesamtanteil der Edelmetalle Ir und Rh verstanden werden soll, ist hier geringer als im Edelmetallstift 11. Der Anteil an Edelmetall hat von 100 Masse-% auf etwa 75 Masse-% abgenommen. Die restlichen 25 Masse-% entfallen dabei auf Nickel, das bei der Bildung der Verbindungszone 13 zulegiert wurde. An den Abschnitt der zweiten Schweißnaht 15 schließt sich der Abschnitt der ersten Schweißnaht 14 an. Hier hat die Edelmetallkonzentration weiter abgenommen. Ein Edelmetallanteil in der ersten Schweißnaht 14 liegt nun bei etwa 60 Masse-%. Die restlichen 40 Masse% entfallen auf Nickel. Der rechte Abschnitt zeigt die Elementverteilung im Grundkörper 12. Der Grundkörper 12 besteht nahezu zu 100 Masse-% aus Nickel (oder einer nickelhaltigen Legierung). Die Edelmetallkonzentration nimmt von der zweiten Schweißnaht 15 zum Grundkörper 12 hin weiter ab. Figure 3 FIG. 12 shows an element distribution in a section of the spark plug electrode 10 from FIG Figure 2 . The areas of different chemical elements are shown with different hatching. The vertical dashed lines divide the spark plug electrode 10 into its different areas along the longitudinal direction XX of the spark plug 10. The mass distribution of the elements in percent by mass (% by mass) is plotted against the length of the spark plug electrode 10 in μm. The left-hand section represents that of the noble metal pin 11. It can be seen here that the noble metal pin 11 consists of 100% by mass of noble metal, namely an alloy of Ir and Rh. The section of the second weld seam 15 adjoins the left section. The proportion of noble metal, which is to be understood as a total proportion of the noble metals Ir and Rh, is lower here than in the noble metal pin 11. The proportion of noble metal has decreased from 100% by mass to about 75% by mass. The remaining 25 mass% is allotted to nickel, which was added in the formation of the connection zone 13. The section of the first weld seam 14 adjoins the section of the second weld seam 15. Here the precious metal concentration has decreased further. A noble metal proportion in the first weld seam 14 is now approximately 60% by mass. The remaining 40% by mass are allotted to nickel. The right-hand section shows the distribution of elements in the base body 12. The base body 12 consists of almost 100% by mass of nickel (or a nickel-containing alloy). The noble metal concentration decreases further from the second weld seam 15 towards the base body 12.

Gut zu erkennen ist, dass sich die Edelmetallkonzentration in der Verbindungszone 13 in Längsrichtung X-X der Zündkerzenelektrode 10 je Intervall von 100 µm Länge der Verbindungszone 13 maximal um 40 Masse-% und zumeist um maximal 25 Masse-%, ändert. Sprunghafte Änderungen der Elementkonzentration mit einer Änderung von insbesondere mehr als 50 Masse-%, liegen nicht vor. Durch das vorsehen weiterer Schweißnähte kann in Bereichen stärkerer Änderung der Edelmetallkonzentration eine weitere Abmilderung der Steigung der Edelmetallkonzentration erzielt werden.It can be clearly seen that the noble metal concentration in the connection zone 13 changes in the longitudinal direction X-X of the spark plug electrode 10 per interval of 100 μm length of the connection zone 13 by a maximum of 40% by mass and mostly by a maximum of 25% by mass. There are no sudden changes in the element concentration with a change of in particular more than 50% by mass. By providing further weld seams, in areas of greater change in the noble metal concentration, a further mitigation of the gradient in the noble metal concentration can be achieved.

Ferner zu erkennen ist, dass die Länge L3 der ersten Schweißnaht 14 und die Länge L4 der zweiten Schweißnaht 15 in Längsrichtung X-X der Zündkerzenelektrode 10 in etwa gleich groß sind. Die Konzentrationsänderung des Edelmetalls ist damit besonders gleichförmig.It can also be seen that the length L3 of the first weld seam 14 and the length L4 of the second weld seam 15 in the longitudinal direction X-X of the spark plug electrode 10 are approximately the same size. The change in concentration of the noble metal is therefore particularly uniform.

Figur 4 zeigt eine schematische Schnittansicht während des Herstellprozesses der Zündkerzenelektrode 10 aus Figur 2. Zuerst wird ein Edelmetallstift 11 auf einem Grundkörper 12 angeordnet. Auf eine Verbindungsfläche 20 zwischen dem Edelmetallstift 11 und dem Grundkörper 12 wird ein Laserstrahl, symbolisiert durch (h*v), gerichtet. So wird ein erster Schweißvorgang A ausgeführt. Der Laserstrahlt schmilzt die in der Verbindungsfläche 20 aneinander angrenzenden Materialien des Edelmetallstifts 11 und des Grundkörpers 12 auf, so dass eine erste Schweißnaht 14 gebildet wird, die die Elemente des Edelmetallstifts 1 und des Grundkörpers 12 in einer relativ ausgewogenen Mischkonzentration enthält. Figure 4 FIG. 13 shows a schematic sectional view during the manufacturing process of the spark plug electrode 10 from FIG Figure 2 . First, a noble metal pin 11 is arranged on a base body 12. A laser beam, symbolized by (h * v), is directed onto a connecting surface 20 between the noble metal pin 11 and the base body 12. A first welding process A is thus carried out. The laser beam melts the adjoining materials of the noble metal pin 11 and the base body 12 in the connection surface 20, so that a first weld seam 14 is formed which contains the elements of the noble metal pin 1 and the base body 12 in a relatively balanced mixed concentration.

Die Zündkerzenelektrode 10 wird während des Schweißvorganges A in Richtung des Pfeils C rotiert, so dass der Laserstrahl die Verbindungsfläche 20 von allen Seiten gleichförmig bestrahlt. Der Laserstrahl wird dabei vorzugsweise durch einen CW-Laser ausgebildet und durchdringt die zu schweißenden Materialien vollständig. Nach dem Ausbilden der ersten Schweißnaht 14 durch den ersten Schweißvorgang A, wird der Laserstrahl neu ausgerichtet, und zwar vorteilhafterweise auf einen Bereich 19 zwischen der ersten Schweißnaht 14 und dem Edelmetallstift 11. Der Laserstrahl kann aber auch auf einen Bereich zwischen der ersten Schweißnaht 14 und dem Grundkörper 12 gelenkt werden, was aber zu einer sich etwas stärker ändernden Edelmetallkonzentration vom Edelmetallstift 11 zur ersten Schweißnaht 14 führt und daher weniger bevorzugt ist.The spark plug electrode 10 is rotated in the direction of arrow C during the welding process A, so that the laser beam hits the joint surface 20 of all Sides irradiated uniformly. The laser beam is preferably formed by a CW laser and completely penetrates the materials to be welded. After the first weld 14 has been formed by the first welding process A, the laser beam is realigned, advantageously to an area 19 between the first weld 14 and the noble metal pin 11. The laser beam can, however, also target an area between the first weld 14 and the base body 12, but this leads to a somewhat more pronounced change in the precious metal concentration from the precious metal pin 11 to the first weld 14 and is therefore less preferred.

Der Laserstrahl wird im zweiten Schweißvorgang B vorzugsweise auf einen Bereich 19 gelenkt, der von der Verbindungsfläche 20 der ersten Schweißnaht 14 und des Edelmetallstifts 11 um eine Höhe h in Richtung des Edelmetallstifts11 entfernt liegt. Die Höhe h beträgt dabei insbesondere 5 µm bis 50 µm und insbesondere 10 µm bis 30 µm.In the second welding process B, the laser beam is preferably directed onto an area 19 which is located away from the connecting surface 20 of the first weld seam 14 and the noble metal pin 11 by a height h in the direction of the noble metal pin 11. The height h is in particular 5 μm to 50 μm and in particular 10 μm to 30 μm.

Durch den zweiten Schweißvorgang B werden die erste Schweißnaht 14 und der Edelmetallstift 11 aufgeschmolzen. Es bildet sich eine zweite Schweißnaht 15 mit einer weiteren Mischkonzentration der Elemente, wobei die Edelmetallkonzentration in der zweiten Schweißnaht 15 durch das Einschmelzen von weiterem Edelmetall aus dem Edelmetallstift 11 größer ist als die Edelmetallkonzentration in der ersten Schweißnaht 14.As a result of the second welding process B, the first weld seam 14 and the noble metal pin 11 are melted. A second weld 15 is formed with a further mixed concentration of the elements, the noble metal concentration in the second weld 15 being greater than the noble metal concentration in the first weld 14 due to the melting of further noble metal from the noble metal pin 11.

Die Länge L1 des Edelmetallstifts 11 und die Länge des Grundkörpers 12 haben zu Gunsten der Verbindungszone 13 abgenommen. Durch die, ausgehend vom Edelmetallstift 11 über die Verbindungszone 13 hin zum Grundkörper 12, abnehmende Edelmetallkonzentration ohne sprunghafte Abnahme der Edelmetallkonzentration, wird ein Verlauf des Wärmeausdehnungskoeffizienten entlang dieser Bereiche ebenfalls ohne sprunghafte Änderung erhalten. Spannungen an den Grenzflächen 16, 17, 18 der aneinander angrenzenden Bereiche sind reduziert. Dies erhöht die mechanische Stabilität der Zündkerzenelektrode 10.The length L1 of the noble metal pin 11 and the length of the base body 12 have decreased in favor of the connection zone 13. Due to the decreasing noble metal concentration starting from noble metal pin 11 via connection zone 13 to base body 12 without sudden decrease in noble metal concentration, a curve of the coefficient of thermal expansion along these areas is also obtained without abrupt change. Stresses at the interfaces 16, 17, 18 of the areas adjacent to one another are reduced. This increases the mechanical stability of the spark plug electrode 10.

Claims (14)

  1. Spark plug electrode, comprising a main body (12) and a noble metal pin (11) which is arranged on the main body (12),
    - wherein the main body (12) and the noble metal pin (11) are connected to one another by a connecting zone (13), and
    - wherein the connecting zone (13) has at least one first weld seam (14) and one second weld seam (15),
    - wherein the first weld seam (14) is arranged between the noble metal pin (11) and the main body (12), wherein the second weld seam (15) is arranged between the first weld seam (14) and the noble metal pin (11), and a noble metal concentration in the first weld seam (14) is lower than a noble metal concentration in the second weld seam (15), or
    - wherein the second weld seam (15) is arranged between the first weld seam (14) and the main body (12) and a noble metal concentration in the first weld seam (14) is higher than a noble metal concentration in the second weld seam (15),
    characterized in that the noble metal concentration in the connecting zone (13) changes at most by 40% by mass in the longitudinal direction (X-X) of the spark plug electrode (10) for each interval of 100 µm of length of the connecting zone (13).
  2. Spark plug electrode according to Claim 1, characterized in that a proportion of noble metal in the first weld seam (14) and in the second weld seam (15) is at least 40% by mass, in particular at least 50% by mass, based on the total weight of the first weld seam (14) and the second weld seam (15).
  3. Spark plug electrode according to either of the preceding claims, characterized in that the noble metal concentration in the connecting zone (13) changes by at most 25% by mass in the longitudinal direction (X-X) of the spark plug electrode (10) for each interval of 100 µm of length of the connecting zone (13).
  4. Spark plug electrode according to one of the preceding claims, characterized in that a length (L1) of the noble metal pin (11) in the longitudinal direction (X-X) of the spark plug electrode (10) is at most 900 µm, in particular 80 µm to 200 µm.
  5. Spark plug electrode according to one of the preceding claims, characterized in that a length (L2) of the connecting zone (13) in the longitudinal direction (X-X) of the spark plug electrode (10) is 50 µm to 700 µm, in particular 100 µm to 600 µm.
  6. Spark plug electrode according to one of the preceding claims, characterized in that a length (L3) of the first weld seam (14) and a length (L4) of the second weld seam (15) in the longitudinal direction (X-X) of the spark plug electrode (10) are of approximately the same size.
  7. Spark plug electrode according to one of the preceding claims, characterized in that the noble metal is selected from iridium, rhodium, platinum, palladium, rhenium, alloys of these elements and alloys of these elements with nickel.
  8. Spark plug electrode according to one of the preceding claims, characterized in that the main body (12) is formed from a nickel-containing alloy, wherein a proportion of nickel in the alloy is, in particular, at least 50% by mass, based on the total weight of the alloy.
  9. Spark plug comprising a spark plug electrode (10) according to one of the preceding claims.
  10. Method for producing a spark plug electrode (10) comprising a main body (12) and a noble metal pin (11), comprising the steps of:
    - executing a first welding process (A) for connecting the noble metal pin (11) and the main body (12) of the spark plug electrode (10) so as to form a first weld seam (14) and
    - executing a second welding process (B) in a region (19) between the first weld seam (14) and the noble metal pin (11) so as to form a second weld seam (15), wherein a noble metal concentration in the first weld seam (14) is lower than a noble metal concentration in the second weld seam (15), or executing a second welding process (B) in a region between the first weld seam (14) and the main body (12) so as to form a second weld seam (15), wherein a noble metal concentration in the first weld seam (14) is higher than a noble metal concentration in the second weld seam (15),
    wherein the first weld seam (14) and the second weld seam (15) form a connecting zone (13) of the noble metal pin (11) and the main body (12),
    characterized in that the noble metal concentration in the connecting zone (13) changes by at most 40% by mass, preferably by at most 25% by mass, in the longitudinal direction (X-X) of the spark plug electrode (10) for each interval of 100 µm of length of the connecting zone (13).
  11. Method according to Claim 10, characterized in that the welding is performed by laser welding, in particular using a continuous-wave laser.
  12. Method according to either of Claims 10 and 11, characterized in that the second welding process (B) is executed in a region (19) which is at a distance of 5 µm to 50 µm, in particular 10 µm to 30 µm, in the direction of the noble metal pin (11) from a connecting surface (16) of the first weld seam (14) and the noble metal pin (11) .
  13. Method according to one of Claims 10 to 12, characterized in that a laser beam passes completely through the materials to be welded during the first welding process (A) and the second welding process (B).
  14. Method according to one of Claims 10 to 13, characterized in that the spark plug electrode (10) is rotated during the welding processes (A, B).
EP15774604.1A 2014-11-21 2015-10-01 Spark plug electrode, method for the production thereof, and spark plug Active EP3221937B1 (en)

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PCT/EP2015/072719 WO2016078816A1 (en) 2014-11-21 2015-10-01 Spark plug electrode, method for the production thereof, and spark plug

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DE102017214311A1 (en) 2017-08-17 2019-02-21 Robert Bosch Gmbh Spark plug electrode and method for making this spark plug electrode and spark plug with spark plug electrode
JP2021082539A (en) 2019-11-21 2021-05-27 株式会社デンソー Spark plug, and center electrode manufacturing method
US20220059999A1 (en) * 2020-08-21 2022-02-24 Federal-Mogul Ignition Llc Spark plug electrode and method of manufacturing the same
US11870222B2 (en) 2021-05-04 2024-01-09 Federal-Mogul Ignition Gmbh Spark plug electrode and method of manufacturing the same
DE102023107904A1 (en) 2022-03-29 2023-10-05 Federal-Mogul Ignition Gmbh SPARK PLUG, SPARK PLUG ELECTRODE AND METHOD FOR PRODUCING THE SAME

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US10008832B2 (en) 2018-06-26
CN107078471A (en) 2017-08-18
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ES2857073T3 (en) 2021-09-28
US20170331260A1 (en) 2017-11-16

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