Spark plug electrode and spark plug

Abstract

A spark plug with a spark point attached to a ceramic-conductive interface can help improve thermal conductivity at the spark gap. The spark plug electrode comprises a conductive core with a conductive weld zone and a ceramic sheath that extends at least partially around the conductive core and includes a spark-forming section. The ceramic sheath and the conductive core form a ceramic-conductive interface at the spark-forming section, with the ceramic-conductive interface at least partially surrounding the conductive weld zone of the conductive core. The spark point is bonded to the spark-forming section within the conductive weld zone or bonded in such a way that it at least partially overlaps the ceramic-conductive interface.

Description

AREA

[0001] This disclosure relates generally to spark plugs and other ignition devices for internal combustion engines, and in particular to ceramic spark plug electrodes. BACKGROUND

[0002] In internal combustion engines, there is a clear trend towards combustion occurring at higher temperatures and pressures, due at least in part to efficiency and emissions requirements. Spark plugs used in these engine environments exhibit increased wear, resulting from spark erosion and a tendency towards pre-ignition due to excessively hot electrode surfaces. Therefore, minimizing electrode erosion through efficient cooling is desirable.

[0003] Modern spark plug electrodes used in these high-temperature environments are designed as multi-component parts, typically a nickel-based housing with a copper core, to ensure both optimized heat dissipation from the spark gap to the cylinder head and good resistance to spark erosion. However, with frequent load changes, such as those occurring in start-stop applications, the nickel alloys used today (e.g., Inconel) exhibit the problem of carbide precipitation at the grain boundaries in the temperature range of 450–850 °C.

[0004] Fig. 1 and Fig. Figure 2 shows typical state-of-the-art spark plug electrodes that have undergone temperature cycling analysis. The illustrated spark plug electrodes are bridge ground electrodes exhibiting undesirable cracks at the iridium ignition tip and the Inconel bridge ground electrode. The arrows in Fig. 1 indicate cracking in both the tip and the ground electrode body, while Fig. Figure 2 shows a micrograph of the crack formation in the mass electrode body. It was found that the indicated cracks all corresponded to the same type of origin and each exhibited an oxygen seam that followed the grain boundaries and simultaneously affected the underlying base material.

[0005] As stated, cracks were observed on the top of the bridge ground electrode body, where there is no heat-affected zone.

[0006] The tests revealed that this cracking can be attributed, at least in part, to the oxidation of Inconel at low temperatures in start-stop applications. Specifically, low-temperature oxidation of chromium occurs in the range of 450–850 °C. This oxidation is caused, at least in part, by chromium carbide precipitation at the grain boundaries. EDX mapping was used to visualize chromium migration to the grain boundaries and chromium carbide oxidation at these boundaries. At the spark plug's operating temperature and with the engine running in start-stop mode, the chromium carbides at the grain boundaries are oxidized. Since chromium oxide has a larger volume than chromium carbides, the structure expands, and this cycle repeats with each engine heat cycle. Therefore, an electrode that withstands thermal stresses better would be desirable.In the past, materials such as ceramics were used, but it can be difficult to attach the ceramic to the metal housing or to attach a metallic ignition tip to a ceramic electrode body. SUMMARY

[0007] According to one embodiment, a spark plug electrode and a spark plug with the electrode are provided, the electrode having a conductive core with a conductive weld zone and a ceramic sheath that extends at least partially around the conductive core. The ceramic sheath and the conductive core form a ceramic-conductive interface at the spark-generating section, the ceramic-conductive interface at least partially surrounding the conductive weld zone of the conductive core. The ignition tip is bonded to the spark-generating section within the conductive weld zone or bonded in such a way that it at least partially overlaps the ceramic-conductive interface.

[0008] In some embodiments, the conductive core and the ceramic cladding form a bridge ground electrode body. The bridge ground electrode body can extend from a first end to a second end, with a central section between the first and second ends, the ignition tip being bonded to the central section. The conductive core can also extend from the first end to the second end.

[0009] In some embodiments, the conductive core and the ceramic sheath form a disc-shaped ground electrode body with an annular tip that is bonded to the conductive weld zone and at least partially overlaps the ceramic-conductive interface. The ignition tip can also be bonded to a second conductive weld zone and a second ceramic-conductive interface of the disc-shaped ground electrode body.

[0010] In some embodiments, the ceramic cladding consists of a ceramic material configured to minimize the oxidation of chromium carbides in the conductive core, preferably a ceramic material with a thermal conductivity of more than 50 W / m / K and / or an electrical conductivity of more than 4 Siemens per meter. To name a particularly advantageous material combination: the ceramic material can be based on aluminum nitride, and the conductive core can consist of a tungsten-based metal material.

[0011] In some embodiments, the ceramic casing features a mechanical locking section configured for connection to a spark plug housing. The mechanical locking section may be a retention notch extending from a terminal end to a distal end, possibly with a second retention notch also extending from the terminal end to the distal end.

[0012] In some embodiments, the ignition tip has a plurality of locking projections, wherein one or more locking projections of the plurality of locking projections extend into the conductive core and one or more locking projections of the plurality of locking projections extend into the ceramic casing.

[0013] Methods for manufacturing the spark plug electrode may include multi-material jetting of the conductive core and the ceramic sheath, or inserting the conductive core into the ceramic sheath to create the ceramic-conductive interface that at least partially surrounds the conductive weld zone. The method may include fixing the ignition tip within the conductive weld zone or in such a way that it at least partially overlaps the ceramic-conductive interface.

[0014] According to a further embodiment, a spark plug is provided comprising a housing with an axial bore, an insulator located at least partially within the axial bore of the housing, a center electrode located at least partially within the axial bore of the insulator, and a ground electrode configured to form a spark gap with the center electrode. The center electrode and the ground electrode overlap at least partially in an overlap zone, and the spark gap has a ceramic-conductive interface located at least partially within the overlap zone, with a ceramic section situated directly adjacent to the spark gap to partially cover at least a conductive portion of the conductive core.

[0015] Various aspects, embodiments, examples, features, and alternatives set forth in the preceding sections, in the claims, and / or in the following description and drawings may be included independently or in any combination thereof. For example, features disclosed in connection with one embodiment are applicable to all embodiments in the absence of any incompatibility of features. DRAWINGS

[0016] Preferred exemplary embodiments are described below in conjunction with the accompanying drawings, wherein the same reference numerals denote the same elements and wherein the following applies: Fig. Figure 1 shows a bridge ground electrode according to the state of the art; Fig. Figure 2 is a micrograph of one of the cracks in the bridge ground electrode of Fig. 1; Fig. Figure 3 shows a cross-sectional view of a spark plug according to one embodiment; Fig. 4 is a view of the spark plug of Fig. 3 from the bottom; Fig. Figure 5 is a perspective view of the ignition end of the spark plug. Fig. 3 and Fig. 4; Fig. Figure 6 is a perspective view of the ground electrode of Fig. 3 to 5; Fig. Figure 7 is a cross-sectional view of the ground electrode of Fig. 3 to 6; Fig. Figure 8 is a flowchart and a schematic illustration of an exemplary manufacturing process; Fig. Figure 9 shows a partial cross-sectional view of a spark plug ignition end according to another embodiment; Fig. 10 is a view of the ground electrode of the spark plug from Fig. 9 from the bottom; Fig. Figure 11 is a cross-sectional view of the ground electrode of the spark plug. Fig. 9 and Fig. 10; Fig. Figure 12 is a cross-sectional view of a spark plug ignition end according to another embodiment; Fig. Figure 13 shows a spark plug igniter according to another embodiment; and Fig. Figure 14 shows a spark plug ignition device according to yet another embodiment. DESCRIPTION

[0017] The spark plug and spark plug electrodes of this disclosure can improve the service life of the spark plug by effectively minimizing cracking caused by thermal cycling. The ground electrode, the center electrode, or both the ground and center electrodes contain ceramic, in contrast to a standard nickel-based electrode body or a sheath with a copper core. No carbide precipitation at the grain boundaries has been observed with ceramic electrodes in the temperature range of approximately 450–850 °C. Furthermore, it is possible for the entire electrode to exhibit high thermal conductivity (e.g., greater than or equal to 160 W / m / K), including the surfaces that are in contact with the spark plug housing.In current electrodes, even those containing a certain amount of ceramic, the contact surfaces between the electrode and the housing are usually made entirely of a nickel alloy. This can at least partially prevent heat transfer, as the more thermally conductive core has no connection to the housing. In the present embodiments, increased thermal conductivity of the electrode leads to better cooling of the spark gap and thus to a longer service life of the spark plug. Furthermore, a ceramic electrode is significantly more resistant to chemical influences (e.g., sulfur compounds, sulfuric acids, etc.) compared to the commonly used nickel and copper electrodes. These chemicals are increasingly generated during the combustion of landfill gas.

[0018] However, the use of ceramic for the electrode can be problematic, as ceramic cannot generally be reliably welded to metal. Accordingly, the present disclosure attempts to overcome some of these challenges by implementing various mechanical locking mechanisms, such as crimping to the spark plug housing. Furthermore, the present electrodes can include a ceramic sheath and a conductive core, with the conductive core selectively exposed in certain areas to facilitate attachment to the housing, with a spark plug tip, or both.

[0019] The electrodes described herein can be used in spark plugs and other ignition devices, including industrial plugs, aircraft igniters, or any other device used to ignite an air / fuel mixture in an engine. This includes spark plugs used in automotive internal combustion engines, particularly in stop-start applications, gasoline direct injection (GDI) engines, lean-burn engines, fuel-efficiency engines, low-emission engines, or combinations thereof. The various electrodes can provide improved ignition capability, effective pad and electrode retention, and minimized thermal cracking.

[0020] With reference to Fig. Figure 3 includes a spark plug 10, a center electrode 12, an insulator 14, a metal housing 16, and a ground electrode 18. Other components may include a terminal pin, an internal resistor, various gaskets, and internal seals, all of which are known to those skilled in the art. The insulator 14 is generally arranged within an axial bore 20 of the housing 16 on an internal step 22 and may have an end section exposed outside the housing at a firing end 24 of the spark plug 10. The center electrode 12 may also include an exposed section outside an internal bore 26 of the insulator 14 at the firing end 24 of the spark plug 10. The center electrode 12 and / or the ground electrode 18 could have a different configuration than specifically illustrated in the figures, and the materials used for them could differ from those expressly described herein.The insulator 14 consists of a material, for example a ceramic material, that electrically insulates the center electrode 12 from the metal housing 16 (preferably a ceramic material that is less conductive than that used for the electrodes 12, 18). The metal housing 16 provides an outer structure for the spark plug 10 and may have threads for installation in an engine.

[0021] The center electrode 12 and the ground electrode 18 form a spark gap G in an overlap zone 28, where the center electrode and the ground electrode are aligned along an axial axis (e.g. longitudinal axis A) or a radial axis (see e.g. Fig. 9) overlap at least partially. In an advantageous embodiment, the center electrode 12 has an ignition tip 30 and the ground electrode 18 has an ignition tip 32. The ignition tips 30, 32 are generally oriented such that they promote spark formation at the spark gap G. While in this embodiment both the center electrode 12 and the ground electrode 18 have a similarly constructed ignition tip 30, 32, it is possible that one of the center electrodes or the ground electrode has an alternatively constructed ignition tip, or that one or both electrodes have no ignition tip at all, to name just a few possibilities. In this embodiment, the ignition tips 30, 32 define a spark-forming section 34, which generally defines the spark gap G. In embodiments in which there is no ignition tip or only one, the spark-forming section 34 is generally located in the overlap zone 28.

[0022] Each firing tip 30, 32 advantageously consists of a precious metal-based material. Generally, a precious metal-based material contains 50 wt.% or more precious metals such as platinum (Pt), iridium (Ir), rhodium (Rh), palladium (Pd), ruthenium (Ru), gold (Au), and / or alloys thereof. Other additives are possible, such as one or more alloying elements, rare earth elements, etc. In some embodiments, the firing pad 30, 32 is a multilayered structure, such as a plated strip or a multilayered rivet, to name just a few possibilities. In such an embodiment, only a section of the firing tip 30, 32 may be precious metal-based. In still other embodiments, the firing tip 30, 32 consists of a non-precious metal-based material such as nickel (Ni) and / or tungsten (W), or an alloy thereof.Furthermore, the ignition tips 30, 32 are also possible in other shapes and configurations, such as a column-shaped rod, a rivet, a circular ring, etc.

[0023] With particular reference to the in Fig. 3 to 8 illustrated and in Fig. In a particularly characterized embodiment as described in Figures 4 to 6, the ground electrode 18 has a bridge ground electrode body 36. The bridge ground electrode body 36 extends fully radially from a first end 38 to a second end 40, with both ends being attached to the housing 16. Given the difficulties of joining ceramic to the metal housing 16, it can be advantageous for a ceramic bridge electrode body 36 to have two attachment points at each end 38, 40. In this embodiment, the housing 16 has a plurality of attachment projections 41 configured to assist in mechanically locking the ground electrode 18 in place. With the bridge ground electrode body 36, the housing 16 has four attachment projections 41 that extend predominantly axially and then engage radially with the body on both sides of each end 38, 40.

[0024] The ground electrode 18 encloses a conductive core 42 and a ceramic sheath 44, which extends at least partially around the conductive core and covers a large portion of its outer surface. The conductive core 42 and the ceramic sheath 44 together form a ceramic-conductive interface 46, which is either exposed at the overlap zone 28 / spark-forming section 34 or covered by the ignition tip 32. Unlike previous ceramic electrodes, where the ceramic is located almost entirely or completely at the overlap zone 28 / spark-forming section 34, the conductive core 42 is at least partially exposed at a conductive welding zone 48. This can be used to facilitate improved spark formation (e.g., when no ignition tip is used) and / or to simplify the attachment of the ignition tip 32.Furthermore, since in this embodiment the conductive core 42 extends over the entire length from the spark-forming section 34 to the housing 16 (at both ends 38, 40), the conductivity can be improved.

[0025] The conductive core 42 consists of a non-ceramic-based material (e.g., a predominantly or entirely metal-based material, less than 50 wt.% ceramic, or preferably no ceramic) and, in a particularly advantageous embodiment, is a nickel (e.g., Inconel), steel, or tungsten alloy. Preferably, the conductive core 42 is sufficiently electrically conductive (e.g., greater than or equal to 4 Siemens per meter (S / m)). In the illustrated embodiments, the conductive core 42 has a stranded or wire configuration with a rounded cross-sectional shape. This can be advantageous in the fabrication and containment of the conductive core 42, as described in more detail herein. At least one portion of the conductive core 42 is exposed and forms an exposed ceramic-conductive interface 46 and a conductive weld zone 48 located at the spark gap G in the overlap zone 28.In this embodiment, the conductive core 42 is completely embedded in the ceramic casing 44, so that the ceramic-conductive interface 46 at the spark-generating section 34 is a planar surface. This can help to improve the attachment of the ignition tip 32.

[0026] The ceramic cladding 44 is a ceramic-based material (e.g., a material that is predominantly or entirely ceramic-based with 50 wt.% or more ceramic). The ceramic material is configured to minimize the oxidation of chromium carbides in the conductive core 42, which can occur in the exposed conductive weld zone 48, particularly if the core is made of a nickel-based material such as Inconel. Advantageously, the ceramic material for the ceramic cladding 44 is more conductive than the ceramic material for the insulator 14, which is a separate component from the ceramic cladding. Unlike the insulator 14, in this embodiment the ceramic cladding 44 is connected to a distal end of the housing 16, closer to the spark gap G.Furthermore, in the illustrated embodiments, the material for the ceramic cladding 44 is an aluminum nitride ceramic (AlN ceramic), while the material for the insulator 14 is an aluminum oxide ceramic. The use of an aluminum nitride-based ceramic, particularly with a conductive tungsten-based core 42, is advantageous due to their similar material properties. A particular similarity exists with respect to their coefficients of thermal expansion ([10^6 / K] AlN = 4.5, W = 4.4; compared to Cu = 16.8, Ni = 12.8), as well as their thermal conductivity ([W / m / K] AlN = 170, W = 164; compared to Cu = 400, Ni = 90). These similarities can help to control thermal fluctuations in the materials, which is particularly advantageous in applications with more intensive temperature changes, such as in stop-start motors.

[0027] Another example of a ceramic material is silicon nitride-molybdenum disilicide (Si3N4-MoSi2). This material can be used, for example, to produce electrically conductive and electrically insulating layers, particularly with a multi-material jetting manufacturing process. This involves modifying the solids content in the injection-molded suspension and adjusting the sintering process. This means that both the cladding 44 and the core 42 of the electrode can be produced with Si3N4-MoSi2, resulting in a solid component made of Si3N4-MoSi2. However, it is printed once for electrical conductivity and once for electrical insulation. This material possesses sufficient electrical properties because it is both insulating and electrically conductive and can be sintered together with other materials. A combination of a cladding 44 made of aluminum nitride (thermally conductive) and Si3N4-MoSi2 for the core 42 is also conceivable.

[0028] The ceramic coating 44 forms the main body section of the electrode 18 and helps to thermally shield a large part of the surface of the conductive core 42 from the spark gap G at the spark-generating section 34. This can help to minimize cracking. In the illustrated embodiment, the ceramic coating 44 forms three outer surfaces of the ground electrode 18 and approximately half of the fourth outer surface, which faces the spark gap G. This arrangement enables better shielding of the core 42 and helps to orient the ceramic-conductive interface 46 and the conductive weld zone 48 at the spark-generating section 34 in the overlap zone 28.

[0029] In the illustrated embodiment, the ceramic casing 44 has a mechanical locking section 50 in the form of two retaining notches 52, 54, which help to hold the ground electrode 18 in relation to the housing 16. Each retaining notch 52, 54 extends from the first end 38 to the second end 40 on opposite sides of the electrode 18. The retaining notches 52, 54 help to structurally receive and lock the crimped mounting projections 41 into the housing 16. Given the difficulties of welding the components, the mechanical locking 50, which provides a structural, mechanical connection between the subcomponents, can help to improve the retention of the electrode 18 in relation to the housing 16.

[0030] The ceramic conductive interface 46 is configured to at least partially surround the conductive weld zone 48. In this embodiment, the ceramic conductive interface 46 forms a continuous, planar surface, which helps to provide a larger attachment zone for the ignition pad or ignition tip 32. Unlike other spark plugs with ceramic electrodes, the ceramic conductive interface 46 provides a conductive weld zone 48 located directly adjacent to the spark-generating section of the ceramic sheath 44, thereby enabling the tip 32 to be more securely attached to the spark gap G at the overlap zone 28. In the illustrated implementations, the ceramic sheath 44 and the conductive core 42 are in direct contact at the ceramic conductive interface 46, without any gap between them. This can be achieved mechanically (e.g., by means of a clamping device), as described in more detail below.This can be achieved by means of an interference fit or by the use of processes such as multi-material jetting. This arrangement between the ceramic cladding 44 and the conductive core 42 at the ceramic-conductive interface 46 can improve the structure of the ground electrode 18 to promote the connection between the two components and also enable an improved connection with the tip 32. In embodiments where the differences in the coefficient of thermal expansion between the two components are less than approximately 0.6 W / M / K, a gap of up to approximately 0.2 mm is permissible due to the alloy composition. Furthermore, the encasing of the conductive core 42 with the ceramic cladding 44 can help to minimize the oxidation of carbides from the conductive core.

[0031] Accordingly, the arrangement provides a ceramic section 56 of the ceramic sheath 44, which is located directly at the spark gap G, wherein the ceramic section covers at least a conductive section 58 of the conductive core 42 adjacent to the spark gap G and shields the core from oxidation. While the core 42 is largely shielded from oxidation, at least part of the core is exposed in the conductive weld zone 48 at the spark gap G to facilitate conductive spark formation and / or attachment of a firing tip 32.

[0032] In the embodiment of Fig. From 3 to 8, the ceramic-conductive interface 46 extends completely from the first end 38 to the second end 40 along the longest extent of the ground electrode 18. A central section 60 (approximately 25% of the length on either side of the midpoint between the first and second ends) is located midway between the first end 38 and the second end 40. With the bridge ground electrode body 36, the ignition tip 32 is advantageously located completely within this central section 60. However, it is possible to attach the tip 32 at other locations along the electrode 18, although it is desirable for it to be located completely within the conductive welding zone 48 or such that it at least partially overlaps the ceramic-conductive interface 46.

[0033] Fig. Figure 8 schematically illustrates a manufacturing process 100. Process 100 is just one option for creating a spark plug electrode 12, 18 for the spark plug 10; however, other processes could also be used. In an alternative embodiment, for example, an additive manufacturing or 3D printing process such as multi-material jetting is employed. In multi-material jetting, the materials are essentially sintered together to create a ceramic-metal material combination. Furthermore, in multi-material jetting, for example, additional locking projections 62 (see, for example, Figure 8) can be incorporated. Fig. 7) are integrated into the ignition pad 32, wherein at least some locking projections extend into the ceramic casing 44 and at least some locking projections extend into the conductive core 42. The locking projections 62 have a barbed or protruding edge to facilitate bonding between dissimilar materials (ceramic / metal). In other embodiments, such as the method of Fig. 8, the ceramic casing 44 and the conductive core 42 are separate components which are then mechanically coupled.

[0034] In step 102 of process 100, a conductive core 42 in the form of a wire 64 is provided together with the ceramic sheath 44. The ceramic sheath 44 advantageously consists of a ceramic material with high thermal conductivity, for example, aluminum nitride. The sheath 44 includes a rounded inner wall 66 and two retaining notches 52, 54 on opposite sides. The ceramic sheath 44 can be produced by pressing and subsequent sintering or by machining, either in the green state or after sintering, to name just a few examples. Additionally, machinable aluminum nitride blanks can be used for the sheath 44. The rounded inner wall 66 corresponds to the contour of the wire 64 of the conductive core 42. The conductive core 42 has a geometric shape that allows it to bond with the ceramic sheath 44.The conductive core 42 consists of an electrically conductive material (e.g., nickel, steel, or tungsten alloy) and facilitates heat and current transfer to the spark plug housing 16. Furthermore, the conductive core 42 provides an area that is better suited for welding a spark plug tip 30, 32.

[0035] Step 104 of the process involves joining the conductive core 42 and the ceramic sheath 44. Possible joining methods include insertion for a transition fit; pressing for an oversize fit; or thermal joining for a shrink fit. This step aligns the rounded inner wall 66 of the sheath 44 with the outer contour of the wire 64 to form a continuous ceramic conductive interface 46 that follows the shape of the rounded inner wall 66 and exposes a conductive weld zone 48 at the spark-generating section 34.

[0036] Step 106 involves flattening the conductive core 42 to facilitate the creation of a conductive weld zone 48 that is more suitable for attaching the tip 32. This also creates a generally planar ceramic-conductive interface 46 (e.g., "generally planar" means completely planar or a dimension 68 that is in the range of about -1.0 mm to +1.0 mm, or preferably -0.5 mm to +0.5 mm). This step 106 can be performed by machining, or the conductive core 42 may already have the flattened area prior to assembly with the sheath 44. In the illustrated embodiment, the conductive weld zone 48 has a width 70 which can range from about 0.01 mm to 6.00 mm inclusive, which is generally smaller than a width 72 of the ignition tip 32 (e.g. about 0.3 mm to 6 mm).This arrangement allows more ceramic to be provided in the direction of the spark-generating section 34 to promote heat transfer.

[0037] Step 108 involves attaching the ignition tip 32. In this implementation, the ignition tip 32 is attached such that it overlaps the ceramic-conductive interface 46 and is attached to the conductive weld zone 48 of the conductive core 42. Attachment between a metallic ignition tip 32 (e.g., a tungsten alloy, a nickel alloy, or a precious metal alloy such as iridium, platinum, ruthenium, or palladium) and the metallic conductive core 42 (e.g., a nickel alloy, a steel alloy, or a tungsten alloy) is preferred and allows electrical conductivity from the spark gap G. The tip 32 can be welded to the conductive weld zone 48 (e.g., by laser or resistance welding) or joined in some other way (e.g., by shrink-fitting or crimping). Furthermore, the tip 32 can be manufactured using an additive manufacturing process (e.g.,Multimaterial jetting, powder bed or powder nozzle) can be additively produced directly on the ceramic conductive interface 46 or the conductive weld zone 48.

[0038] As described in detail here, in addition to the one in Fig. In addition to the manufacturing process 100 illustrated in Figure 8, other manufacturing processes are certainly possible. Furthermore, it is possible to include other or alternative steps. For example, in the illustrated spark plug 10, the electrode 18, after being formed using the process 100, can be crimped in place such that the mounting projections 41 of the housing 16 are crimped into the retaining notches 42, 54 of the ceramic coating 44. In some embodiments, for example, in multi-material jetting, an additional conductive weld zone 48 may be present, arranged to facilitate the welding of the electrode 18 to the housing 16. Other potential manufacturing steps and processes are also quite conceivable.

[0039] Fig. Figures 9 to 11 illustrate a second embodiment of a spark plug 210 (where the same reference numerals denote the same components). In this embodiment, the ground electrode 218 has a disc-shaped body 274. This embodiment has a different shape compared to the bridge ground electrode body 36, although other body shapes (e.g., rod-shaped, wire-shaped, column-shaped, etc.) are also conceivable. The ground electrode 218 is an annular ground electrode ignition tip 232, which is attached to an inner annular region 276 of the disc-shaped body 274. This inner annular region 276 encloses two ceramic-conductive interfaces 246 (one of which is, for example, in Fig. 11 (shown as dashed lines), each surrounding a separate conductive weld zone 248. As shown in particular in Fig. As shown in Figure 10, the conductive core 242 includes two radially extending prongs 278, 280, which extend from the inner ring region 276.

[0040] In this implementation, the electrode 218 has various mechanical locking features, such as a retaining edge 282 that helps to hold the annular ignition tip 232 in place. The retaining edge 282 is a mechanical locking section in the ceramic casing 244 that helps to secure the ignition tip 232. Furthermore, in this implementation, the housing 216 may include a fastening projection 241 that helps to crimp the ground electrode 218 into place. Depending on the arrangement and / or shape of the ground electrode 218, other mechanical locking sections 250 may be included.

[0041] Fig. Figure 12 illustrates a third embodiment of a spark plug 310. In this implementation, the center electrode 312 has the arrangement of a conductive core 342 and a ceramic coating 344. Furthermore, in this embodiment, the ignition tip 330 is located entirely within the conductive weld zone 348, so that it is completely surrounded by the ceramic-conductive interface 346 at the spark-forming section 334. In this embodiment, due to the more traditional structure of each electrode 312, 318, a production process such as multi-material jetting can be preferred to facilitate the co-sintering of the components 342, 344. Other shapes and configurations of the center electrode 312 and the ground electrode 318 are certainly possible.

[0042] Fig. 13 and Fig. Figure 14 illustrates a fourth and a fifth embodiment of a spark plug 410, 510 (where the same reference numerals denote the same components). These embodiments are related, wherein the spark plug 410 includes a bridge ground electrode 418 and the spark plug 510 includes two bridge ground electrodes 518, 518'. Compared to the other embodiments, the electrode bodies 418, 518, 518' are cantilevered towards the center electrode to create an overlap at the spark gap (where the center electrode is configured similarly to the other illustrated embodiments, in Fig. 13 and Fig. 14 (however, this is not particularly visible). In these embodiments, the longest extension of each ground electrode body 418, 518, 518' does not directly intersect the central axis of the spark plug, but rather has a tendon-like configuration. In other embodiments, such as the one in Fig. As illustrated in Figure 13, it is possible that only a single ground electrode body 418 is present, the longest extension of which is oriented orthogonally to what is shown in particular. In such an example, the longest extension could be cantilevered over the center electrode and crimped or snapped at one end on both sides (resulting in a J-gap-like configuration). The embodiment of Fig.14 can be advantageous because it includes two ignition points 530, 532', each of which can generate a spark with the center electrode. In both arrangements, the housing mounting projections 441, 541 can include those that engage directly with the mechanical locking feature 450, 550, as well as housing mounting projections that serve to passively support the ground electrode 418, 518 (see, for example, the opposing projections 441, 541, which in this implementation have a through-hole). Other configurations are technically possible.

[0043] It is to be understood that the foregoing is a description of one or more preferred exemplary embodiments. The invention is not limited to the specific embodiment(s) disclosed herein, but is defined exclusively by the claims below. Furthermore, the statements contained in the foregoing description refer to specific embodiments and are not to be understood as limitations on the scope of protection of the invention or on the definition of the terms used in the claims, unless a term or expression is expressly defined above. Various other embodiments and various changes and modifications of the disclosed embodiment(s) will be obvious to the person skilled in the art. All such other embodiments, changes, and modifications are to fall within the scope of protection of the accompanying claims.

[0044] As used in this patent specification and the claims, the terms "for example," "e.g.," "as," and "the like," and the verbs "comprising," "comprising," "including," and their other verb forms, when used in conjunction with a list of one or more components or other items, are each to be interpreted as open-ended, meaning that the list is not to be considered as excluding other, additional components or items. Other terms are to be interpreted in their broadest reasonable sense unless used in a context that requires a different interpretation. Furthermore, the term "and / or" is to be interpreted as an inclusive OR. Therefore, for example, the expression "A, B, and / or C" is to be interpreted as covering all of the following: "A"; "B"; "C"; "A and B"; "A and C"; "B and C"; and "A, B, and C."

Claims

[1] Spark plug electrode, comprising: a conductive core with a conductive weld zone; a ceramic coating that extends at least partially around the conductive core and has a spark-generating section, wherein the ceramic coating and the conductive core form a ceramic-conductive interface at the spark-forming section, wherein the ceramic-conductive interface at least partially surrounds the conductive weld zone of the conductive core; and a sparking tip that is bonded to the spark-forming section within the conductive welding zone or is bonded in such a way that it at least partially overlaps the ceramic-conductive interface. [2] Spark plug electrode according to claim 1, wherein the conductive core and the ceramic coating form a bridge ground electrode body. [3] Spark plug electrode according to claim 2, wherein the bridge ground electrode body extends from a first end to a second end and a central section is located between the first and the second end, wherein the ignition tip is bonded in the central section. [4] Spark plug according to claim 3, wherein the conductive core extends from the first end to the second end. [5] Spark plug electrode according to claim 1, wherein the conductive core and the ceramic coating form a disk-shaped ground electrode body. [6] Spark plug electrode according to claim 5, wherein the ignition tip is an annular tip which is bonded to the conductive weld zone and at least partially overlaps the ceramic conductive interface, wherein the ignition tip is also bonded to a second conductive weld zone and a second ceramic conductive interface of the disc-shaped ground electrode body. [7] Spark plug electrode according to claim 1, wherein the ceramic coating consists of a ceramic material configured to minimize the oxidation of chromium carbides in the conductive core. [8] Spark plug electrode according to claim 7, wherein the ceramic material is based on aluminium nitride. [9] Spark plug electrode according to claim 8, wherein the conductive core consists of a metal material based on tungsten or nickel and the ceramic sheath consists of a ceramic material having an electrical conductivity of greater than or equal to 4 Siemens per meter. [10] Spark plug electrode according to claim 1, wherein the ceramic coating has a mechanical locking section configured to be connected to the ignition tip or a housing of a spark plug. [11] Spark plug electrode according to claim 10, wherein the mechanical locking section is a retaining notch, wherein the retaining notch extends from a first end to a second end and a second retaining notch also extends from the first end to the second end. [12] Spark plug electrode according to claim 1, wherein the ignition tip comprises a plurality of locking projections, wherein one or more locking projections of the plurality of locking projections extend into the conductive core and one or more locking projections of the plurality of locking projections extend into the ceramic sheath. [13] Method for manufacturing the spark plug electrode according to claim 1, comprising the step of multi-material jetting of the conductive core and the ceramic coating. [14] Method for manufacturing the spark plug electrode according to claim 1, comprising the steps: Inserting the conductive core into the ceramic cladding to create the ceramic-conductive interface that at least partially surrounds the conductive weld zone; and The ignition tip should be positioned within the conductive welding zone or in such a way that the ceramic-conductive interface is at least partially overlapped. [15] Spark plug comprising the spark plug electrode according to claim 1.

Images