METHOD FOR MANUFACTURING A SPARK PLUG AND SPARK PLUG FOR AN INTERNAL COMBUSTION ENGINE

Description

[0001] The present invention relates to a method of producing a spark plug for an internal combustion engine according to the preamble of claim 1 and a spark plug for an internal combustion engine according to the preamble of claim 12.

[0002] Spark plugs known by the state of the art are used to ignite flammable air-fuel mixtures inside combustion chambers, wherein by the spark plugs sparks are initiated at a spark gap between at least two electrodes (in most cases between a middle electrode and a ground electrode). In detail the spark is build between two sides of the at lest two electrodes facing each other.

[0003] Therefore, the electrodes are challenged by special operation conditions regarding temperature, electrical conductivity, wear resistance and so on.

[0004] For this reason, it is known by the state of the art to provide electrodes by special materials (e.g. precious metals) . As these materials are rare and therefore relatively expensive, it is known to provide only the region of the spark building surfaces by such materials.

[0005] Spark plugs for internal combustion engines known by the state of the art comprising at least one electrode having an electrode plate welded onto an electrode carrier, can be seen for example by WO 2021 / 072 458 A1 or US 7,615,914 B2.

[0006] Further embodiments known by the state of the art are disclosed for example by DE 10 2022 118404 A1, US 2022 / 149598 A1 or US 2022 / 059999 A1.

[0007] By use of such electrode plates the expensive and rare material can be reduced to the area in which they are used.

[0008] However, the electrode plates must be of a certain size in order to make it possible to weld the electrode plates onto the electrode carrier without affecting the sides of the electrode plate facing the spark gap. Therefore, the electrode plates are limited in downsizing and reduction of material.

[0009] The object of the present invention is therefore to provide a method for production of spark plugs for an internal combustion engine, wherein the at least partially previously named disadvantages of the state of the art can be improved and / or rare or expensive materials can be saved and / or materials can be used much more efficient.

[0010] This objective is achieved according to the present invention by a method for producing a spark plug according to claim 1 and a spark plug for an internal combustion engine according to claim 12.

[0011] According to the invention regarding a method to produce a spark plug for an internal combustion engine it is provided that at least one electrode is generated by welding an electrode plate onto an electrode carrier, preferably by laser beam welding, wherein before welding the electrode plate onto the electrode carrier, the electrode plate is manufactured by providing a precious metal plate and building up a deposition layer on the precious metal plate by a build-up welding process.

[0012] By use of the invention the dimension of the precious metal plate used as electrode can be reduced to a minimum. By use of build-up welding the precious metal plate can be enlarged by a material not as precious as the precious metal plate to enable the electrode plate to be welded onto the electrode carrier.

[0013] Therefore, it is possible to reduce the use of rare precious metal materials for the electrode plate to a minimum, wherein the efficient use of such materials can be increased.

[0014] Precious metals are expensive, time consuming and energy consuming in production. Such metals are also related to rare occurrences. Therefore, by reduction of use of such materials for producing spark plugs the economic and ecological aspects can be improved.

[0015] Already present internal combustion engines can be upgraded with at least one spark plug according to invention.

[0016] All measures and features described in connection with the prior art can also be taken in connection with the invention.

[0017] Advantageous embodiments are defined in the dependent claims.

[0018] It can be provided that the build-up welding process is done by an additive manufacturing process, wherein the deposition layer is additive manufactured onto the precious metal plate.

[0019] Additive manufacturing processes can be provided by a build-up welding process and / or an 3D-print process.

[0020] It can be provided that the build-up welding process is done by a laser metal deposition (LMD) process, wherein a powder is melded at the surface of the precious metal plate to build up the deposition layer.

[0021] It can be provided that the build-up welding process is executed underwater. By processing the build-up process underwater, the components, especially the precious metal plate, can be cooled especially well, wherein less distortion and thermal effects can be realized.

[0022] It can be provided that the precious metal plate and the deposition layer are provided by different metal materials.

[0023] It can be provided that the precious metal plate is provided by a precious metal alloy, preferably comprising rhodium and / or iridium.

[0024] It can be provided that the deposition layer is provided by a metal alloy comprising nickel.

[0025] It can be provided that the deposition layer of the electrode plate is at least partially welded onto the electrode carrier.

[0026] It can be provided that a side of the precious metal plate facing away from the deposition layer is placed in such a way that this side faces a spark gap of the spark plug.

[0027] It can be provided that the electrode plate, preferably the deposition layer, is manufactured by a machining process, preferably grinding, polishing and / or lapping, after build-up welding and before welding onto the electrode carrier.

[0028] It can be provided that the electrode plate is trimmed after build-up welding and before welding onto electrode carrier to a predefined size, preferably by laser cutting.

[0029] It can be provided that in a first step a precious metal plate is processed by the build up process to generate the electrode plate, wherein the electrode plate is much bigger as used for only one electrode plate at the electrode carrier. In a second step the electrode plate is trimmed and cut into parts, preferably by laser cutting, wherein a plurality of electrode plates for joining to electrode carriers are provided.

[0030] It can be provided that the precious metal plate is provided with a thickness less than 0.5 mm and more than 0.05 mm, preferably less than 0.3 mm and more than 0.1 mm, particularly preferred with a thickness of 0.15 mm, before build-up welding.

[0031] It can be provided that the precious metal plate is provided by a flat rolled sheet metal, particularly preferred proved in coils.

[0032] Furthermore, protection is sought for a spark plug for an internal combustion engine, comprising at least one electrode having an electrode plate welded onto an electrode carrier, preferably by laser beam welding, wherein the electrode plate comprises a precious metal plate having a deposition layer produced by a build-up welding process before being welded to the electrode carrier.

[0033] It can be provided that the deposition layer is placed between the precious metal plate and the electrode carrier.

[0034] It can be provided that the at least one electrode is formed as ground electrode and / or a middle electrode of the spark plug.

[0035] Further details and advantages of the invention are apparent from the accompanying figures and the following description of the drawings. The figures show: Fig. 1a first embodiment of a spark plug, Fig. 2the ground electrode carrier in isolation, Fig. 3a detail view of Fig. 2, and Fig. 4 to 6a method of producing a spark plug.

[0036] Fig. 1 shows a first embodiment of a spark plug 1 according to the invention.

[0037] The insulator body 11 (usually made from ceramic) is pushed into an upper spark plug housing portion 12, with the incorporation of a seal 13 at both sides.

[0038] The lower portion 14 of the spark plug housing is also pushed onto the insulator body 11.

[0039] In a further production step, the upper portion 12 and the lower portion 14 are preferably pressed together in the region of the insulator bead 15.

[0040] In the pre-stressed condition, the housing portions are welded together by means of laser at the region 16. Due to the welding process in the region 16 on the upper housing portion 11 the housing components are permanently pre-stressed and sealing integrity is thus afforded between the housing 11, 14 - seal 13 and insulator body 1.

[0041] An electrode carrier 2 of the ground electrode 8 can be mounted at the engine side on the lower housing portion 14.

[0042] The electrode carrier 2 of the ground electrode 8 could possibly also be produced in one piece, that is to say as an integral component of the lower housing portion 14.

[0043] The design configuration of the electrode carrier 2 of the ground electrode 8 with four electrode fingers provides good mixture accessibility.

[0044] The electrode carriers 2 of the ground electrode 8 are provided with electrode plates 3, they are welded to the electrode carriers 2 at one side or both sides by means of laser (In Fig. 3 and 4 the ground electrode will be explained in more detail).

[0045] The welding is such that the gap is closed at the electrode sides. In other words, between the precious metal plate 5 and the electrode carrier (fingers) 2 there is no open gap (or opening) through which gas can enter.

[0046] The welding processes used can be pulsed laser, continuously operating lasers (CW-lasers), electron beam welding processes or vacuum or high-vacuum brazing processes as well as plasma welding or resistance welding.

[0047] The middle electrode base 17 of the insulator body 11 is welded to a middle electrode carrier 18 in the region 19. The middle electrode carrier 18 is pushed onto the middle electrode base 17 until it bears flush against the insulator base 20. In that position it is welded to the middle electrode base 17 in the region 19.

[0048] The weld in the region 19 can be produced along the entire length of the middle electrode base 17, in which case therefore welding is affected from the outside through the middle electrode carrier 18 onto the middle electrode base 17. It is possible to use one or more spot welds and one or more seam welds which on the longitudinal axis can be arranged if required at a plurality of locations at the periphery or radially if required at a plurality of locations at the periphery.

[0049] The middle electrode carrier 18 is designed with four separate electrode fingers, onto which electrode plates 3 are welded as middle electrodes 9.

[0050] The electrode plates 3 welded onto the middle electrode carrier 18 can be provided in the same way as the electrode plates 3 welded onto the ground electrode carrier 2, as will be explained in more detail by the following figures.

[0051] Fig. 2 shows the ground electrode carrier 8 known from Fig. 1 in isolation in a perspective view. Fig. 3 shows de detail A indicated in Fig. 2.

[0052] The ground electrode carrier 8 shown by Fig. 2 comprises four electrode fingers, each being designed to receive an electrode plate 3 and build a spark gap 7 regarding a corresponding middle electrode 9.

[0053] The electrode carrier 8 or each of the electrode fingers of the electrode carrier 8 carry an electrode plate 3.

[0054] The electrode plates 3 are welded onto an electrode carrier 4 and comprise a precious metal plate 5 having a deposition layer 6.

[0055] The welding process to join the electrode plates 3 onto the electrode carriers 2 is done by laser beam welding, wherein between the electrode plates 3 and the electrode carriers 2 a weld seam 10 is indicated.

[0056] As can be seen the weld seam 10 takes a part of the components which are welded, wherein at least in the region of the weld seam 10 the material properties of the components which are welded are affected massively.

[0057] Therefore, at least the surface forming a part of the spark gap 7 of the electrode plate 3 has to be prevented from the material affect by the welding process.

[0058] In fact of this, according to the embodiment of Fig. 2 and 3 the electrode plate 3 comprises a precious metal plate 5 having a deposition layer 6 produced by a build-up welding before being welded to the electrode carrier 4.

[0059] By use of the deposition layer 6 the thickness of the electrode plate 3 can be increased, wherein the welding process to join the electrode plate 3 onto the electrode carrier 2 does only mainly affect the deposition layer 6.

[0060] The precious metal plate 5 can be reduced with a thickness to a minimum, wherein the use of precious metal (e.g. precious metal alloy, preferably comprising rhodium and / or iridium) can be reduced.

[0061] The deposition layer 6 provided by build-up welding at the precious metal plate 5 can be provided by a material differing from the precious metal plate 5, as the deposition layer 6 is not used in direct contact with the spark gap 7 and the sparks acting there.

[0062] The deposition layer 6 can therefore be provided by a material being less precious than the material for the precious metal plate 5, as the deposition layer 6 is affected by fewer demands.

[0063] The deposition layer 6 can for example be provided by a metal alloy comprising nickel.

[0064] Therefore, the electrode plate 3 is placed at the electrode carrier 4 in such a way that the deposition layer 6 is welded onto the electrode carrier 4, while a side of the precious metal plate 5 facing away from the deposition layer 6 (and from the weld seam 10) is placed in such a way that this side faces a spark gap 7 of the spark plug 1.

[0065] In other words, the deposition layer 6 is placed between the precious metal plate 5 and the electrode carrier 4.

[0066] Fig. 4 to 6 show a method of producing a spark plug 1 for an internal combustion engine, wherein it is disclosed in detail how to manufacture an electrode 2 as shown by the preceding figures.

[0067] It can be seen in Fig. 4 that in a first step a precious metal plate 5 is provided, wherein at the precious metal plate 5 by a build-up welding process the deposition layer 6 is build up.

[0068] The build-up welding process is done by a laser metal deposition (LMD) process, wherein a powder is melded at the surface of the precious metal plate 5 to build up the deposition layer 6.

[0069] The powder is provided by a material building the deposition layer 6, preferably a metal alloy comprising nickel.

[0070] The precious metal plate 5 is provided with a thickness less than 0.5 mm and more than 0.05 mm, preferably less than 0.3 mm and more than 0.1 mm, particularly preferred with a thickness of 0.15 mm, before build-up welding.

[0071] As the precious metal plate 5 is provided by a very thin plate, the risk of a delay caused by the build-up welding process is relatively high, wherefore it can be provided that the build-up welding process is executed underwater.

[0072] After building up the deposition layer 6 the electrode plate 3, preferably the deposition layer 6, is manufactured by a machining process, preferably grinding, polishing and / or lapping, as can be seen in Fig. 5.

[0073] Fig. 5 illustrates that electrode plate 3 is trimmed and cut into parts by laser cutting, wherein a plurality of electrode plates 3 for joining to electrode carriers 4 is provided out of the electrode plate 3 manufactured in Fig 4.

[0074] In a next step, as shown by Fig. 6, the electrode plate 3 is welded onto the electrode carrier 4 by laser beam welding.Used Reference Signs:

[0075] 1spark plug 2electrode 3electrode plate 4electrode carrier 5precious metal plate 6deposition layer 7spark gap 8ground electrode 9middle electrode 10weld seam 11insulator body 12upper housing portion 13seal 14lower housing portion 15insulator bead 16region 17middle electrode base 18middle electrode carrier 19region 20insulator base

Claims

1. A method of producing a spark plug (1) for an internal combustion engine, wherein at least one electrode (2) is generated by welding an electrode plate (3) onto an electrode carrier (4), preferably by laser beam welding, characterised in that before welding the electrode plate (3) onto the electrode carrier, the electrode plate (3) is manufactured by providing a precious metal plate (5) and building up a deposition layer (6) on the precious metal plate (5) by a build-up welding process.

2. Method according to claim 1, wherein the build-up welding process is done by an additive manufacturing process, wherein the deposition layer (6) is additive manufactured onto the precious metal plate (5).

3. Method according to one of the preceding claims, wherein the build-up welding process is done by a laser metal deposition (LMD) process, wherein a powder is melded at the surface of the precious metal plate (5) to build up the deposition layer (6).

4. Method according to at least one of the preceding claims, wherein the build-up welding process is executed underwater.

5. Method according to at least one of the preceding claims, wherein the precious metal plate (5) and the deposition layer (6) are provided by different metal materials.

6. Method according to at least one of the preceding claims, wherein the precious metal plate (5) is provided by a precious metal alloy, preferably comprising rhodium and / or iridium.

7. Method according to at least one of the preceding claims, wherein the deposition layer (6) is provided by a metal alloy comprising nickel.

8. Method according to at least one of the preceding claims, wherein the deposition layer (6) of the electrode plate (3) is at least partially welded onto the electrode carrier (4).

9. Method according to at least one of the preceding claims, wherein a side of the precious metal plate (5) facing away from the deposition layer (6) is placed in such a way that this side faces a spark gap (7) of the spark plug (1).

10. Method according to at least one of the preceding claims, wherein the electrode plate (3), preferably the deposition layer (6), is manufactured by a machining process, preferably grinding, polishing and / or lapping, after build-up welding and before welding onto the electrode carrier (4).

11. Method according to at least one of the preceding claims, wherein the precious metal plate (5) is provided with a thickness less than 0.5 mm and more than 0.05 mm, preferably less than 0.3 mm and more than 0.1 mm, particularly preferred with a thickness of 0.15 mm, before build-up welding.

12. A spark plug (1) for an internal combustion engine, comprises at least one electrode (2) having an electrode plate (3) welded onto an electrode carrier (4), preferably by laser beam welding, characterised in that the electrode plate (3) comprises a precious metal plate (5) having a deposition layer (6) produced by a build-up welding process before being welded to the electrode carrier (4).

13. Spark plug (1) according to claim 12, wherein the deposition layer (6) is placed between the precious metal plate (5) and the electrode carrier (4).

14. Spark plug (1) according to claim 12 or 13, wherein the at least one electrode (2) is formed as ground electrode (8) of the spark plug (1).