Method for manufacturing an assembly for a spark plug and spark plug

Abstract

A method for manufacturing a center pin (20) and center electrode carrier (13) or center electrode (6) assembly for a spark plug (1), the spark plug (1) usable to ignite a combustible air-fuel mixture in an internal combustion engine, comprising providing a wire or rod (19) having a core (21) of a first material, preferably over its length, surrounded by an outer layer (22) of a second material, the second material being different from the first material, the core being exposed at one end of the wire or rod, and a center electrode carrier (13) or center electrode (6) assembly for a spark plug (1), the spark plug (1) usable to ignite a combustible air-fuel mixture in an internal combustion engine, the method comprising providing a wire or rod (19) having a core (21) of a first material, preferably over its length, surrounded by an outer layer (22) of a second material, the second material being different from the first material, the core being exposed at one end of the wire or rod, and A core electrode (6) is provided at said one end of the wire or rod (19), and a high-energy beam, preferably a laser beam, is directed at the exposed core (21), and the powder is melted onto the exposed core (21) by the high-energy beam, so that in the contact area (18) of the powder and the exposed core (21), a microstructure consisting of the core (21) material and the powder is formed after re-solidification of the core (21) material and the powder, and the core (21) is covered by the re-solidified powder (25) at one end of the wire or rod.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an assembly of a center pin and a center electrode carrier or a center electrode for a spark plug, each having the features of the preamble of claim 1, a method for manufacturing a spark plug, an assembly of a center pin and a center electrode carrier for a spark plug having the features of the preamble of claim 15, and a spark plug having such an assembly.

Background Art

[0002] Spark plugs are known in various embodiments from the prior art. Since efforts have been made to improve the service life, requirements regarding airtightness and temperature management, that is, to ensure proper heat transfer between one spark plug and the other cylinder head or spark plug sleeve, have become more important.

[0003] Known spark plugs have a center electrode pointing along the longitudinal axis of the spark plug and at least one ground electrode arranged radially spaced from the center electrode. An ignition gap is formed between the contact area (ignition area) of the center electrode and the at least one ground electrode.

[0004] It is known to form the center electrode in at least two parts, and the ignition area is formed by a noble metal body arranged on a center electrode carrier. Each noble metal body is connected to a ground electrode carrier and a center electrode carrier respectively by a welding joint. Such spark plugs are disclosed, for example, in European Patent Application Publication No. 0859436 or European Patent Application Publication No. 3068001.

[0005] Spark plugs are manufactured, for example, by a laser welding process.

[0006] Spark plugs are exposed to high temperatures and high pressures during the operation of combustion engines because at least a part of the spark plug is in direct contact with the combustion chamber and thus the combustion process. As time passes, the electrode material wears out, leading to a reduction in lifespan. Another drawback of spark plugs known from the prior art is the respective change in the surface side and surface area of the electrodes, in particular the spark plug pins and the noble metal body facing the combustion chamber (in the ignition direction), caused by high-temperature corrosion or oxidation.

[0007] The spark plug is mounted on the cylinder head of an internal combustion engine or on a spark plug sleeve. In this case, by screwing the male thread part (or male thread) of the spark plug body, which at least partially surrounds the ignition means, into the female thread part of the cylinder head or the spark plug sleeve, the ignition means is arranged at the end of the spark plug facing the combustion chamber.

[0008] Heat is transferred to the spark plug by combustion in the combustion chamber, and this heat is dissipated beyond the male thread to the cylinder head or the spark plug sleeve. Therefore, since it is well known that insufficient heat dissipation shortens the lifespan of the spark plug, it is important to have a certain thermal conductivity between the male thread and the cylinder head or the spark plug sleeve.

[0009] In the prior art, attempts were made to place the spark plug as far outside the combustion chamber as possible, but this has the drawback that the ignition position of the spark plug is not arranged inside the combustion chamber as required for proper ignition of the air-fuel mixture.

[0010] A further strategy of the prior art is to dissipate as quickly and completely as possible (often using a spark plug sleeve) the heat introduced into the components of the spark plug into the cylinder head. For this purpose, the central electrode carrier often has a core made of a material with good thermal conductivity, such as copper. To shield and protect the core from the combustion gases, the core is embedded in a material with good resistance to high-temperature corrosion (see U.S. Patent No. 4,575,343). The assembly of the core and the shielding material is called the central pin.

[0011] Manufacturing the central pin by press-fitting copper into a nickel pin by cold forming, as described, for example, in U.S. Patent No. 4,575,343, is expensive, and the life of a spark plug having such a central pin is often insufficient. Different manufacturing methods for the central pin are shown in U.S. Patent No. 3,356,882, where a plurality of electrode rods consisting of a copper core and an Inconel mantle are welded to an Inconel strip. Using a punch, the capped electrodes are sheared from the Inconel strip.

[0012] In both prior art manufacturing techniques, the exact position of the copper core cannot be controlled, resulting in unknown heat behavior and thus accidental variations in spark plug life. SUMMARY OF THE INVENTION

[0013] It is an object of the present invention to provide a method for manufacturing an assembly of a central pin and a central electrode carrier or central electrode for a spark plug, a method for manufacturing a spark plug, an assembly of a central pin and a central electrode carrier or central electrode for a spark plug, and a spark plug having such an assembly, wherein the resulting assembly and spark plug are each easier to manufacture and preferably have a longer life.

[0014] This is achieved by a method having the features of claim 1, a method for manufacturing a spark plug including such a method, an assembly having the features of claim 15, and a spark plug having such an assembly. Some advantageous embodiments of the invention are defined in the dependent claims.

[0015] The present invention provides a method for manufacturing an assembly of a center pin and a center electrode carrier or a center electrode for a spark plug, the spark plug being usable for igniting a combustible mixture in an internal combustion engine, a wire or rod is provided having a core of a first material surrounded by an outer layer of a second material, preferably over its length, the second material being different from the first material, and the core being exposed at one end of the wire or rod, a center electrode carrier or a center electrode is provided at said one end of the wire or rod, a high-energy beam, preferably a laser beam, is directed at the exposed core, and powder is melted onto the exposed core by the high-energy beam, whereby, in the contact region of the powder and the exposed core, a microstructure composed of the material of the core and the powder is formed after re-solidification of the material of the core and the powder, and the core is covered by the re-solidified powder at one end of the wire or rod characterized in that.

[0016] It should be noted that the second and third steps of the above steps do not need to be performed in a given order. As will be explained below, in providing the center electrode carrier or the center electrode, it is even possible to provide the molten powder such that the presence of the second or third step is not obvious.

[0017] Techniques for melting powder on a given surface with a high-energy beam (usually a laser beam) are well known in the art (usually referred to as laser metal deposition). In the present invention, it is preferred to inject the powder into the laser beam by means of a powder nozzle. However, it is also possible to first apply the powder to the surface and then apply a laser beam to the powder on the surface to melt it. The application and melting of the powder can be carried out such that the new powder melts on top of the re-solidified powder layer to form a layer.

[0018] Preferably, over its length, using a wire or rod having a core of a first material surrounded by an outer layer of a second material, where the second material is different from the first material and at one end of the wire or rod where the core is exposed, in a plane perpendicular to the extension of the wire or rod, there is an advantage that the core material and the outer layer material form a plane. It is possible to attach the central electrode carrier or the central electrode itself on the said plane or on the outer layer of the wire or rod (it is not necessary to remove material from the said plane). This is advantageous because by selecting the central electrode carrier or the extension of the central electrode perpendicular to the said plane, the distance between the said plane (and thus the core material) and the central electrode carrier sheet for the central electrode or the central electrode itself can be selected in a reproducible manner. The re-solidified powder serves to prevent wear of the core depending on the conditions in the combustion chamber by sealing the exposed surface of the core. Due to the contact area with close contact between the re-solidified powder and the core material, heat from the combustion chamber can be efficiently transferred from the re-solidified powder to the core of the central pin through the contact area.

[0019] In a first variant of the present invention, the central electrode carrier or the central electrode can each be attached (preferably welded) to the central pin independently of the application of the powder. As a result, the powder serves to seal the core material and, in some cases, the weld seam between the central electrode carrier or the central electrode and the central pin, but does not itself form the central electrode carrier or the central electrode (part thereof).

[0020] In the second modification of the present invention, the re-solidified powder can be used to at least partially construct the center electrode carrier or the center electrode (naturally, sealing the exposed core) by applying the powder so that the re-solidified powder forms the center electrode carrier or at least a part of the center electrode, respectively.

[0021] Preferably, the center electrode is made of a noble metal. In particular, the center electrode is a pellet made of a noble metal.

[0022] The present invention also provides an assembly of a center pin for a spark plug and a center electrode carrier or a center electrode, and the spark plug can be used to ignite a combustible mixture in an internal combustion engine. The center pin includes a wire or rod preferably having a core of a first material surrounded by an outer layer of a second material over at least a portion of its length, and the second material is different from the first material. The center electrode carrier or the center electrode is attached to one end of the wire or rod. The core of the center pin is provided in the form of a molten powder and then covered with a re-solidified material, and in the contact region between the re-solidified powder and the core, a microstructure composed of the core material and the powder exists.

[0023] Protection is also sought for a spark plug including such an assembly.

[0024] By using a wire or rod, the assembly of the center pin for a spark plug and the center electrode carrier or the center electrode, and the manufacture of a spark plug having such an assembly are simplified, without shortening the life, or even extending the life.

[0025] The types of wires or rods that can be used in the present invention are commercially available, for example, in the form of so-called clad wires or clad rods (for example, wires or rods of nickel-clad copper), which are combinations of two materials in the form of wires or rods.

[0026] Alternatively, they can be readily manufactured by using a wire or rod having a hollow core made of a second material into which a wire or rod made of a first material is drawn. To ensure a tight fit, the assembly is stretched to produce the wire or rod having a core of the first material surrounded by an outer layer of the second material.

[0027] The wire or rod can be obtained in a desired length, for example, by cutting a longer wire or rod, or can be provided in a length such that several of the desired lengths are obtained. If necessary, one end of the wire or rod to which the body is to be attached or formed can be adjusted, for example, by grinding, turning, milling, grinding and / or polishing the end face of the wire or rod, before attaching or forming the body.

[0028] The core should be completely covered by the re-solidified powder in order to seal it against the combustion chamber so as to protect the core from the combustion gas. It is advantageous if the core is completely covered by the re-solidified powder.

[0029] According to a preferred embodiment of the present invention, the step of providing a central electrode carrier at the one end of the wire or rod includes the step of attaching or forming a body (preferably, the body is made of at least one metal such as nickel) to the one end of the wire or rod, and the body forms a central electrode carrier, or functions as an intermediate product for the central electrode carrier, and the central electrode carrier is obtained from the intermediate product by at least one further manufacturing step.

[0030] In this preferred embodiment, in a first alternative form, it is assumed that the body attached to or formed at the one end of the wire or rod directly forms a central electrode carrier with the central electrode attached thereto. In this case, the body can be manufactured with desired dimensions regardless of the wire or rod. The body can have a shoulder that is part of or forms all of the attachment surface for the central electrode attached to the central electrode carrier.

[0031] In a second alternative form, in this preferred embodiment, it is assumed that the body attached to or formed at the one end of the wire or rod functions as an intermediate product of the central electrode carrier, and the central electrode carrier is obtained from the intermediate product by at least one further manufacturing step. In this case, the body indirectly forms the central electrode carrier in the sense that at least one further manufacturing step, and possibly several manufacturing steps, are required to obtain the central electrode carrier with the central electrode attached thereto.

[0032] In this second alternative form, the body can be attached in the form of a component to the one end of the wire or rod (for example, by welding, preferably by laser beam welding), and at least one further step can be carried out after attaching the body. However, it is preferred to use powder deposition technology to form the body at the end of the wire or rod.

[0033] In a first embodiment of such powder deposition technology, powder is deposited layer by layer on the one end of the wire or rod, preferably melted by a high-energy beam (for example, a laser beam or an electron beam), and re-solidified to form at least one layer, so that at least one layer of the body is manufactured.

[0034] In a second embodiment of such a powder deposition technique, a laser beam is directed at the one end of the wire or rod to melt its surface, and powder is introduced into a weld joint whose surface is melted by the laser beam, so that the powder melts and is connected to the melted surface. The powder is deposited until the body is manufactured.

[0035] As the powder, preferably, corrosion-resistant nickel powder (for example, those available under the trade names of Inconel 600® or Inconel 625®) or other powder materials suitable for the laser material deposition process are used.

[0036] Regarding both the first alternative (where the body directly forms the central electrode carrier) and the second alternative (where the body functions as an intermediate product) of the preferred embodiment, the body has a dimension greater in at least one direction, preferably in the direction of the longitudinal axis of the wire or rod, and in the further manufacturing step for obtaining the central electrode carrier from the intermediate product, at least one step of removing material from the body and reducing the dimension, preferably to obtain a body having a dimension corresponding to that of the central electrode carrier can be included.

[0037] Regarding both the first and second alternatives of the preferred embodiment, the further manufacturing step for obtaining the central electrode carrier from the intermediate product can include at least one step of forming a shoulder on the body. This shoulder can be part of or form the entire mounting surface for the central electrode to be mounted on the central electrode carrier.

[0038] In a preferred embodiment that can be combined with each of the foregoing embodiments, the mounting surface of the central electrode carrier for the central electrode has a predetermined distance to the core in the longitudinal axis direction of the wire or rod. By selecting a specific predetermined distance, for example, at least 0.05 mm, preferably greater than 0.1 mm, and most preferably greater than 0.2 mm, it is possible to obtain a spark plug with a lower temperature of the central electrode during operation than in the prior art in a reproducible manner. To ensure good heat dissipation, the distance between the central electrode and the core of the wire or rod should be as small as possible. However, to protect the core from the conditions in the combustion chamber, the distance should not be too small. In this embodiment of the present invention, an optimal predetermined distance can be found (for example, by a series of experimental tests in which different distances are tried and the resulting temperatures are observed, or by calculation or computer simulation), and a spark plug having this distance can be reproducibly manufactured.

[0039] Regarding this embodiment, the distance between the core of the first material and the material covering the core can be controlled (in other words, the distance from the mounting surface of the central electrode carrier to the core can be controlled). Compared with the prior art, it is possible to have a smaller distance that improves heat transfer while ensuring a sufficient distance to protect the core material.

[0040] For example, before attaching the body from one end to the other end, the length of the wire or rod can be measured. Using this information, after attaching the body, it is possible to remove as much material from the body as necessary to obtain the desired predetermined distance. Alternatively or additionally, markings can be made on one end of the rod.

[0041] According to the assembly and spark plug manufactured according to this embodiment of the present invention, it is shown that the heat transfer from the central electrode to the cylinder head during the operation of the combustion engine is improved, the temperature of the central electrode is reduced, and the lifespan is extended. As a result, it becomes possible to increase the output density in the combustion chamber.

[0042] For example, it was found that the temperature of the center electrode was reduced by 80 to 100°C compared to the conventional technology.

[0043] As an example, such spark plugs allow power densities of more than 22 bar BMEP.

[0044] By way of example, the predetermined distance from the mounting surface of the central electrode carrier to the core can be obtained by using a body (e.g., as provided by one of the previous embodiments) that has a larger dimension at least in the direction of the longitudinal axis of the wire or rod, and forming the predetermined distance by removing material of the body (e.g., by cutting, turning or grinding) along a direction parallel to the longitudinal axis of the wire or rod. Alternatively, it is of course possible to form a body that already has the desired distance when combined with the wire or rod.

[0045] In one embodiment of the invention, the wire or rod (preferably clad wire) used has a core made of a material with a higher thermal conductivity than that of the outer layer, the core preferably comprising or made of copper or a copper alloy, although other materials with high thermal conductivity such as silver or gold can also be used.

[0046] In one embodiment of the invention the wire or rod (preferably clad wire) is used with an outer layer made of a material more resistant to high temperature corrosion than the core, and the outer layer preferably comprises or consists of nickel or a nickel alloy.

[0047] In one embodiment of the present invention, the center electrode carrier comprises or consists of a metal, preferably nickel.

[0048] To ensure the good functionality of the central pin, i.e., the wire or rod having a body (functioning as a central electrode carrier), in one embodiment, it is assumed that there is a layer with a minimum thickness at the tip of the core. The layer thickness can be at least 0.05 mm, preferably at least 0.1 mm. In some embodiments, the layer can have a thickness of at least 0.2 mm.

[0049] One embodiment of a spark plug is ignition means arranged at the end of the spark plug facing the combustion chamber when the spark plug is attached to an internal combustion engine, the ignition means including a central electrode and a ground electrode, preferably a wall at least partially surrounding the ignition means, a sealing region used to seal the combustion chamber against the environment, and further includes The wall includes a sealing region located at the end of the wall facing the combustion chamber when the spark plug is attached to an internal combustion engine. The sealing region is the end portion of the wall facing the combustion chamber when the spark plug is attached to an internal combustion engine. In particular, it is preferred that the sealing region is designed as a chamfer. However, it should be noted that the present invention can be used with all types of spark plugs regardless of the type of sealing.

[0050] It should be understood that the structural features of the spark plug or any of its components described with respect to the method of the present invention are also intended to refer to the assembly or spark plug of the present invention.

[0051] Further details and advantages of the present invention will be apparent from the accompanying drawings and the following description of the drawings.

Brief Description of the Drawings

[0052]

Figure 1

Figure 2

Figure 3a

Figure 3b

Figure 3c

Figure 3d

Figure 4

Figure 5a

Figure 5b

Figure 6

Figure 7a

Figure 7b

Figure 7c

Figure 8

Embodiments for Carrying Out the Invention

[0053] Figure 1 shows a cross-sectional view of an embodiment of an assembly according to the present invention, manufactured by an embodiment of the method of the present invention, and includes a central pin 20 consisting of a wire or rod 19 having a core 21 of a first material surrounded by an outer layer 22 of a second material over its length (see Figure 2 showing a cross-sectional view of such a wire or rod 19), the second material being different from the first material. In this embodiment, the central electrode 6 is welded to the end of the wire or rod, preferably to a shoulder cut into the outer layer 22. A high-energy beam, preferably a laser beam, is directed at the exposed core 21, and powder is melted onto the exposed core 21 by the high-energy beam, whereby a microstructure composed of the material of the core 21 and the powder is formed in the contact region 18 between the powder and the exposed core 21 after re-solidification of the material of the core 21 and the powder, and the core 21 is covered by the re-solidified powder 25 at one end of the wire or rod 19. In this embodiment, the re-solidified powder 25 also covers the weld seam 10 existing between the central electrode 6 and the outer layer 22.

[0054] Figures 3a and 3b show an embodiment of a spark plug 1 according to the present invention, with the end of the spark plug 1 facing the combustion chamber being shown in more detail when the spark plug 1 is attached to an internal combustion engine.

[0055] This spark plug includes ignition means 2 implemented by a central electrode 6 and a ground electrode 7, with a spark gap 8 between the central electrode 6 and the ground electrode 7. The ground electrode 7 is arranged on a ground electrode carrier 9. In this particular embodiment, the wall 3 surrounding the ignition means 2 is formed as part of the spark plug body. This spark plug body surrounds the ground electrode carrier 9, and at least one ground electrode 7 is connected to the ground electrode carrier 9, for example by laser beam welding.

[0056] The weld seam 10 is preferably of a type that is part of the chamfer. Thus, in such an embodiment, it may be necessary for the weld seam 10 to be deep enough so that the ground electrode carrier 9 is properly fixed by the weld seam 10.

[0057] The manufacturing method can include a step of manufacturing a groove for the welding seam 10 at a depth such that at least a part of the welding seam 10 functions as a connection part between the ground electrode carrier 9 and the spark plug body even after the chamfered part 5 is manufactured.

[0058] The center electrode 6 is connected to the center electrode carrier 13 by laser beam welding. The center electrode carrier 13 (made of or containing metal, preferably nickel) is arranged at the end of a center pin 20 made of a wire or rod 19 having a core 21 and an outer layer 22 in contact with the core 21. The center electrode carrier 13 and the center pin 20 form an assembly according to the present invention.

[0059] The center pin 20 is arranged inside an opening of an insulator 14 made of, for example, ceramic. As shown in FIG. 3d, an anti-rotation lock 16 is provided on the center pin 20, which is one end of the center pin 20.

[0060] In order to seal the combustion chamber from the environment, in this embodiment, the spark plug 1 includes a sealing region 4 designed as a chamfered part 5. This chamfered part 5 is provided on the wall 3 (formed by the spark plug body in this embodiment). It should be noted that the center pin 20 according to the present invention can be used for any type of spark plug 1, and in particular, can also be used for a spark plug 1 sealed from the environment as taught in the art.

[0061] The spark plug body (wall 3) further includes an attachment part 11 for attaching the spark plug 1 to an internal combustion engine and / or a cylinder head and / or a spark plug sleeve. This attachment part 11 is provided as a (male) thread 12 in this embodiment.

[0062] Figure 3c is an isometric view of a second embodiment similar to the embodiment of Figure 3a The only difference is that the welding seam 10 does not exist in Figure 3c ​

[0063] Figure 3c In [Figure], the ground electrode 7 is designed as a ring electrode, and it can be seen that the ring electrode surrounds the central electrode 6 formed in a circular shape, and an annular spark gap 8 is formed between the ground electrode 7 and the central electrode 6.

[0064] Furthermore, in this embodiment, it can be seen that by the chamfered portion 5 extending to the ground electrode carrier 9, the advantage of improved heat transfer between the spark plug body 3 and the spark plug sleeve and between the ground electrode carrier 9 and the spark plug sleeve is obtained.

[0065] The sealing region 4 in the form of the chamfered portion 5 is designed to form an angle α with respect to the perpendicular y to the central axis x of the spark plug 1. This can be seen in more detail from [Figure 3b]. The angle α of the chamfered portion 5 with respect to the perpendicular y to the central axis x of the spark plug 1 can be, for example, in a wide range of angles between 20° and 45°. When the spark plug 1 is attached to the spark plug sleeve or directly to the cylinder head, the male thread 12 is configured to cooperate with the female thread of the spark plug sleeve or the cylinder head to press the chamfered portion 5 of the spark plug 1 and abut it against the surface of the spark plug sleeve or the cylinder head, respectively.

[0066] The spark plug 1 can be substantially symmetric with respect to the central axis x.

[0067] Figure 4 shows a cross-sectional view of a wire or rod suitable for the assembly according to the present invention, and it can be seen that the wire or rod is formed as a clad wire or clad rod made of a material (preferably including or consisting of copper or a copper alloy) in which the core 21 has a higher thermal conductivity than the outer layer 22. The core 21 can be composed of any material having a high thermal conductivity, such as silver or gold. The outer layer 22 is made of a material (preferably including or consisting of nickel) that is more resistant to high-temperature corrosion than the core 21.

[0068] Figure 5a and Figure 5b show a side view and a cross-sectional view of an assembly according to the invention, in which a body is formed on a wire or rod as an intermediate product. Such a wire or rod can be obtained, for example, from coil 27, preferably in a desired length by cutting (see Figure 7a ). By machining the first end of the wire or rod, for example by turning, milling, grinding or polishing, it can be made suitable for the following steps.

[0069] It can be made possible to manufacture a central pin 20 made of a wire or rod by a drawing process. In this case, for example, a core 21 having an exemplary diameter of 2 - 3 mm is introduced into an outer layer 22 (for example, a tube having an initial outer diameter of 5 mm and an inner diameter of 3.8 mm) in a first step. In the next step, the assembly is processed by a stretching method to obtain a wire or rod having a core 21 and an outer layer 22 according to the invention. Such a drawing process is well known from the prior art. The obtained wire or rod can have, for example, a diameter of 3.8 mm, but of course, all diameters can be produced by this stretching technique. In the next step, the wire or rod can be processed as described above and also described below.

[0070] A powder deposition technique is used to form a body at one end of the wire or rod, i.e., an unsolidified powder 26 (see Figure 7b ) is deposited on said one end of the wire, preferably melted by a high-energy beam (for example, a laser beam 24 - see Figure 7b ) or an electron beam) and (re) solidified to form a re-solidified powder 25 to form at least one layer, so that at least one layer of the body is manufactured.

[0071] As described above, the body functions as an intermediate product of the central electrode carrier 13 and has dimensions that are larger in at least one direction, preferably in the longitudinal axis direction of the wire or rod.

[0072] In a further manufacturing step (following the figure 7c ) for obtaining the central electrode carrier 13 from the intermediate product, the dimensions are reduced by removing material from the body shown in this figure, preferably corresponding to the dimensions of the central electrode carrier 13, and a body is obtained that has a desired predetermined distance d between the core 21 of the wire or rod and the attachment surface of the central electrode carrier 13. The desired dimensions are indicated by the dashed lines in the figure 7c .

[0073] In the embodiment according to the figure 8 , a wire or rod is fed into the manufacturing process, and in the manufacturing process, at least the outer layer 22 is removed in the region of one end of the wire or rod, preferably by rotation or milling (it is also possible to slightly reduce the diameter of the core diameter, for example, by rotation or milling). In the next step, a layer having the above-mentioned thickness is applied to the uncoated portion of the core 21 in the region of one end by the powder deposition technique as described above. This process also results in a shoulder in the region of one end of the wire or rod, after which the central electrode can be attached, for example, by a welding process.

[0074] Regardless of the embodiment, by being able to appropriately define the distance between the central electrode carrier 13 (and thus up to the central electrode 6) and the core 21, a beneficial result is obtained that has a favorable effect on the thermal conductivity.

Explanation of Reference Numerals

[0075] 1 Spark plug 2 Ignition means 3 Wall 4 Sealing region 5 Chamfered portion 6 Central electrode 7 Ground electrode 8 Spark gap 9 Ground electrode carrier 10 Weld seam 11 Attachment part 12 Male thread 13 Central electrode carrier 14 Insulator 15 Powder nozzle 16 Anti-rotation lock 17 Depression 18 Contact area of powder and exposed core 19 Wire or rod 20 Central pin 21 Core 22 Outer layer 23 Shoulder 24 Laser beam 25 (Re) solidified powder 26 (Uncured) powder 27 Coil of wire or rod 28 Powder nozzle d Distance x Central axis of spark plug y Perpendicular to the central axis of the spark plug α Angle with respect to the perpendicular to the central axis of the spark plug

Claims

1. An assembly of a center pin (20) for a spark plug (1) and a center electrode carrier (13) or a center electrode (6), wherein the spark plug (1) can be used to ignite a combustible mixture in an internal combustion engine, the center pin (20) includes a wire or rod (19) having a core (21) of a first material surrounded by an outer layer (22) of a second material over its length, and the second material is different from the first material, the center electrode carrier (13) or the center electrode (6) is attached to one end of the wire or rod, the core (21) of the center pin (20) is covered with a re-solidified material after being provided in the form of molten powder, and a microstructure composed of the material of the core (21) and the powder exists in the contact region (18) between the re-solidified powder (25) and the core (21), An assembly, wherein an anti-rotation lock (16) is provided on the center pin (20) which is one end of the center pin (20).

2. A spark plug (1) that can be used to ignite a combustible fuel in an internal combustion engine, characterized in that the spark plug (1) includes the assembly according to Claim 1.

3. Ignition means (2) arranged at the end of the spark plug (1) facing the combustion chamber when the spark plug (1) is attached to the internal combustion engine, the ignition means (2) including the center electrode (6) and the ground electrode (7), a wall (3) at least partially surrounding the ignition means (2), a sealing region (4) used to seal the combustion chamber against the environment, and further includes, The wall (3) includes a sealing region (4) located at an end of the wall (3) facing the combustion chamber when the spark plug (1) is attached to the internal combustion engine. The sealing region (4) is a terminal portion of the wall (3) facing the combustion chamber when the spark plug (1) is attached to the internal combustion engine. In particular, the sealing region (4) is designed as a chamfer (5). The spark plug according to claim 2.

4. A method for manufacturing the assembly according to claim 1, providing a wire or rod (19) having a core (21) of the first material surrounded by an outer layer (22) of the second material, the second material being different from the first material, and the core being exposed at one end of the wire or rod, providing the central electrode carrier (13) or the central electrode (6) at the one end of the wire or rod (19), and the central electrode carrier (13) or the central electrode (6) being bonded to the outer layer (22) at an interface, respectively, directing a high-energy beam, which is a laser beam, at the exposed core (21), melting a powder onto the exposed core (21) by the high-energy beam, so that in a contact region (18) between the powder and the exposed core (21), a microstructure composed of the material of the core (21) and the powder is formed after re-solidification of the material of the core (21) and the powder, and the core (21) is covered by re-solidified powder (25) at the one end of the wire or rod, and the powder is provided to cover an interface between each of the central electrode carrier (13) or the central electrode (6) and the re-solidified outer layer (22). A method characterized by the above.

5. The central electrode carrier (13) or the central electrode (6) is welded to the outer layer (22) by forming a welded joint before the powder is melted onto the exposed core (21). The method according to claim 4. **Claim 6**: The method according to claim 5, wherein after re-solidification, powder is supplied so as to cover the weld joint between the central electrode carrier (13) and the outer layer (22) or between the central electrode (6) and the outer layer (22). **Claim 7**: The method according to claim 5 or 6, wherein before the powder melts on the exposed core (21), material is removed from the exposed core (21) to form a depression (17), and the depression (17) is filled with the melted powder. **Claim 8**: The step of providing the central electrode carrier (13) or the central electrode (6) at one end of the wire or rod (19) includes the step of attaching or forming a body to the one end of the wire or rod (19), and the body forms the central electrode carrier (13) or the central electrode (6), or functions as an intermediate product for the central electrode carrier (13) or the central electrode (6), and the central electrode carrier (13) or the central electrode (6) is obtained from the intermediate product by at least one further manufacturing step. The method according to claim 4. **Claim 9**: The body functions as the intermediate product for the central electrode carrier (13) or the central electrode (6), and has a dimension greater than that in at least one direction, the longitudinal axis direction of the wire or rod. The further manufacturing step for obtaining the central electrode carrier (13) or the central electrode (6) from the intermediate product includes at least one step of removing the material from the body to obtain a body having dimensions corresponding to those of the central electrode carrier (13) or the central electrode (6) respectively. The method according to claim 8. **Claim 10**: The further manufacturing step for obtaining the central electrode carrier (13) from the intermediate product includes at least one step of forming a shoulder (23) on the body. The method according to claim 8 or 9. **Claim 11**: The method according to at least one of claims 8 to 10, wherein the body forms the central electrode carrier (13) or the central electrode (6) and is welded to the one end of the wire or rod (19) by laser welding, and the body has the shoulder (23) or is placed on the shoulder (23) formed at the one end of the wire or rod (19). **Claim 12**: The method according to at least one of claims 8 to 11, wherein the mounting surface of the central electrode carrier (13) or the central electrode (6) for the central electrode has a predetermined distance (d) to the core (21) in the longitudinal axis direction of the wire or rod. **Claim 13**: The method according to claim 12, wherein the predetermined distance (d) from the mounting surface of the central electrode carrier (13) to the core (21) is obtained by using a body having at least a dimension larger than that in the longitudinal axis direction of the wire or rod, and the material of the body is removed along a direction parallel to the longitudinal axis of the wire or rod so that the predetermined distance (d) is formed. **Claim 14**: The method according to at least one of claims 4 to 13, wherein the wire or rod (19) is made of a material in which the core (21) has a higher thermal conductivity than the thermal conductivity of the outer layer (22), and the core (21) contains copper or is made of copper. **Claim 15**: The method according to at least one of claims 4 to 14, wherein the wire or rod (19) is made of a material in which the outer layer (22) has a higher resistance to high-temperature corrosion than the core (21), and the outer layer (22) contains nickel or is made of nickel. **Claim 16**: The method according to at least one of claims 4 to 15, wherein the central electrode carrier (13) contains a metal or is made of a metal, contains nickel or is made of nickel, and / or the central electrode (6) contains a noble metal or is made of a noble metal. A method for manufacturing a spark plug (1) that can be used to ignite a combustible mixture in an internal combustion engine, characterized in that the method according to at least one of claims 4 to 16 is used to manufacture the assembly of the central pin (20) and the central electrode carrier (13) of the spark plug (1).

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