Spark plug with cooling feature and method of making same

Abstract

The invention relates to a spark plug with cooling features and a method of manufacturing the same. A spark plug has one or more cooling features that reduce the temperature of the ground electrode, and may be manufactured using an additive manufacturing process. The cooling features include internal cooling channels that may be filled with a thermally conductive solid (passive cooling example) or a thermally conductive fluid (active cooling example). In a passive cooling example, the internal cooling channel is filled with a thermally conductive solid that is inserted into the channel, melted and solidified such that it forms a metallic bond with the walls of the channel. In an active cooling example, the internal cooling channel is filled with a thermally conductive fluid that flows through the channel and removes heat from the ground electrode. In both examples, the internal cooling channel of the ground electrode is aligned with a corresponding cooling channel formed in the case.

Description

Technical Field

[0001] The present invention relates generally to spark plugs and other ignition devices, and more particularly to spark plug components having cooling features. Background Technology

[0002] Spark plugs are used to ignite combustion in internal combustion engines. Typically, a spark plug ignites the air / fuel mixture in the combustion chamber, creating a spark in the spark gap between two or more electrodes. This spark ignites the air / fuel mixture, triggering the combustion reaction in the combustion chamber, which is the reason for the engine's power stroke. High temperatures, pressures and voltages, the rapid repetition of the combustion reaction, and the presence of corrosive materials in the combustion gases create the harsh environment in which spark plugs must operate. This harsh environment leads to electrode erosion and / or corrosion, which negatively impacts spark plug performance over time.

[0003] To meet increasingly stringent emission requirements, internal combustion engines are designed to perform combustion processes at increasingly higher temperatures. The high-temperature environment within the engine can further exacerbate electrode corrosion and increase the likelihood of pre-ignition due to overheated electrode surfaces, particularly at the ground electrode. Furthermore, the high temperatures within the engine impose significant thermal loads on various spark plug components, including the precious metal ignition tips welded to the center and / or ground electrodes. These thermal loads generate stress on welds or joints due to differences in coefficients of thermal expansion, melting temperatures, and / or other material properties. Therefore, there is a growing trend in industry to develop spark plugs with various types of cooling features, such as a heat-conducting core extending within the electrode and transferring heat away from the spark gap. Conventional manufacturing techniques for forming electrodes with heat-conducting cores typically involve inserting a block of heat-conducting material into a recess in the electrode material and then co-stretching the materials together into an elongated electrode.

[0004] Another trend in industry involves using additive manufacturing technologies, such as 3D printing, to produce various types of spark plug components, including electrodes. However, due to limitations in manufacturing processes and the materials involved, it is difficult to efficiently produce additively manufactured spark plug electrodes with built-in cooling features, such as thermally conductive cores.

[0005] The spark plugs described in this article are designed to address one or more of the aforementioned drawbacks and challenges. Summary of the Invention

[0006] According to one embodiment, a spark plug is provided, comprising: a shell having an axial bore; an insulator at least partially disposed within the axial bore of the shell and having an axial bore; a center electrode at least partially disposed within the axial bore of the insulator; a ground electrode attached to the shell and having an electrode base; and a cooling feature having a first internal cooling channel formed within the electrode base of the ground electrode, a first thermally conductive material located within the first internal cooling channel, a second internal cooling channel formed within the shell, and a second thermally conductive material located within the second internal cooling channel, wherein the first internal cooling channel is aligned with the second internal cooling channel, and the first thermally conductive material is thermally coupled to the second thermally conductive material, such that during operation, the cooling feature can remove heat from the area near the spark surface.

[0007] According to various implementation schemes, spark plugs may have any one or more of the following characteristics, either individually or in any technically feasible combination: - The electrode base of the ground electrode includes multiple laser-deposited layers, one of which is arranged on top of the other and defines a first internal cooling channel; - Multiple laser-deposited layers of the electrode substrate are made from nickel-based materials using powder bed fusion technology; - The ground electrode includes an electrode tip made of a noble metal-based material, the electrode tip having a spark surface and being attached to an electrode base, such that a first thermally conductive material is directly thermally coupled to the electrode tip at the heat input portion; - The cooling feature is a passive cooling feature, the first thermally conductive material is a solid material bonded to the first internal cooling channel by means of a first metal bond, and the second thermally conductive material is a solid material bonded to the second internal cooling channel by means of a second metal bond; - Each of the first thermally conductive material and the second thermally conductive material is made of at least one of copper-based material, silver-based material or tin-based material; -The first and second thermally conductive materials are the same material; -The first thermally conductive material and the second thermally conductive material are different materials; - The cooling feature is an active cooling feature, and the first thermally conductive material and the second thermally conductive material are fluid materials flowing within the first internal cooling channel and the second internal cooling channel; - The first and second thermally conductive materials are the same material and include at least one of water, ethylene glycol, liquid sodium, or mixtures thereof; - The first internal cooling channel includes a heat output portion having a flared opening or an enlarged opening for improving alignment with the second internal cooling channel; - The grounding electrode is a bridge-type grounding electrode that extends across the entire axial bore of the shell and is attached to the shell at a first position and a second position. The first internal cooling channel includes a heat input portion, a first heat output portion, a second heat output portion, and a main channel portion. The first heat output portion branches off from the main channel portion at a first end of the main channel portion and extends to a region near the first attachment surface of the shell where the grounding electrode is attached. The second heat output portion branches off from the main channel portion at a second end of the main channel portion and extends to a region near the second attachment surface of the shell where the grounding electrode is attached. The heat input portion branches off from the main channel portion in an intermediate section between the first and second ends. - The grounding electrode is an arc-shaped grounding electrode that extends through a portion of the axial hole in the housing and is attached to the housing at a first location.

[0008] According to another embodiment, a grounding electrode for a spark plug is provided, the grounding electrode comprising: an electrode base having a plurality of laser-deposited layers disposed on top of another; and a cooling feature having an internal cooling channel and a thermally conductive material, the internal cooling channel being filled with the thermally conductive material and including a heat input portion, a heat output portion, and a main channel portion; the heat input portion being connected to the main channel portion and extending into a region near the spark surface; and the heat output portion being connected to the main channel portion and extending into a region near the attachment surface of the grounding electrode to the spark plug housing; wherein the plurality of laser-deposited layers form walls within the electrode base defining the internal cooling channel.

[0009] According to various implementation schemes, the grounding electrode may have any one or more of the following characteristics, either individually or in any technically feasible combination: -The heat output portion of the internal cooling channel located in the ground electrode is configured to align with and thermally couple to the heat input portion of the internal cooling channel located in the spark plug housing when the ground electrode is attached to the housing at the attachment surface. - The cooling characteristic is a passive cooling characteristic, and the thermally conductive material is a solid material that is bonded to the wall defining the internal cooling channel by means of metal bonding; - The cooling characteristic is an active cooling characteristic, and the thermally conductive material is a fluid material that flows within the internal cooling channels; - The ground electrode is a bridge-type ground electrode, configured to extend across the entire axial bore of the spark plug housing and attach to the spark plug housing at a first position and a second position. The internal cooling channel includes a heat input portion, a first heat output portion, a second heat output portion, and a main channel portion. The first heat output portion branches off from the main channel portion at a first end and extends to a region near the first attachment surface of the ground electrode where it is attached to the spark plug housing. The second heat output portion branches off from the main channel portion at a second end and extends to a region near the second attachment surface of the ground electrode where it is attached to the spark plug housing. The heat input portion branches off from the main channel portion in an intermediate section between the first and second ends. - The ground electrode is an arc-shaped ground electrode that is configured to extend through a portion of the axial bore of the spark plug housing and be attached to the spark plug housing at a first location; According to another embodiment, a method for manufacturing a ground electrode for a spark plug is provided, the method comprising the steps of: forming an electrode base using an additive manufacturing process, the electrode base being formed layer by layer such that a plurality of laser-deposited layers are disposed one on top of another and defining an internal cooling channel; adding a thermally conductive material to the internal cooling channel; heating the thermally conductive material such that the thermally conductive material at least partially melts and fills the internal cooling channel; and allowing the at least partially melted thermally conductive material to solidify and form a metallic bond with the wall of the internal cooling channel, wherein the internal cooling channel and the thermally conductive material are part of a cooling feature for removing heat from an area near the spark surface. Attached Figure Description

[0010] Preferred embodiments will now be described with reference to the accompanying drawings, wherein the same reference numerals denote the same elements, and wherein: Figure 1 This is a partial cross-sectional view of a first example of a spark plug with cooling features, wherein the spark plug includes a bridge-type ground electrode and the cooling features are an example of passive cooling. Figure 2 yes Figure 1 An enlarged cross-sectional view of the ignition end of a spark plug; Figure 3 yes Figure 1 An enlarged bottom view of the spark plug; Figure 4 This is a partial cross-sectional view of a second example of a spark plug with cooling features, wherein the spark plug includes an arc-shaped ground electrode and the cooling features are an example of passive cooling. Figure 5 This is a partial cross-sectional view of a third example of a spark plug with cooling features, wherein the spark plug includes a bridge-type ground electrode and the cooling features are an example of active cooling. Figure 6 yes Figure 5 An enlarged cross-sectional view of the ignition end of a spark plug; Figure 7 This is a partial cross-sectional view of a fourth example of a spark plug with cooling features, wherein the spark plug includes an arc-shaped ground electrode and the cooling features are an example of active cooling. Figure 8 yes Figure 7 An enlarged cross-sectional view of the mating surfaces of the spark plug components; and Figures 9A to 9D Several cross-sectional views of a grounding electrode manufactured using an additive manufacturing process are shown. Detailed Implementation

[0011] The spark plugs described herein have one or more cooling features that reduce the temperature of the electrodes and can be manufactured using additive manufacturing processes. According to one example, the spark plug includes an additively manufactured ground electrode having a cooling feature in the form of an internal cooling channel, which may be filled with a thermally conductive solid (passive cooling example) or a thermally conductive fluid (active cooling example). In the passive cooling example, the internal cooling channel may be filled with a thermally conductive solid, such as a copper-based material (e.g., brazing alloy, copper-molybdenum alloy), a silver-based material (e.g., silver-titanium alloy), or a tin-based material (e.g., solder), which is inserted into the channel, melts, and solidifies, forming a metallic bond with the surrounding ground electrode. In the active cooling example, the internal cooling channel may be filled with a thermally conductive fluid (e.g., water, ethylene glycol, liquid sodium, and / or mixtures thereof), which flows through the channel and removes heat from the ground electrode. In both the passive and active cooling examples, preferably, the internal cooling channel of the ground electrode is aligned with a corresponding cooling channel formed in the housing. This allows heat or thermal energy from the ground electrode to be transferred through the ground electrode and internal cooling channels in the housing and into the engine, where the heat or thermal energy can be better dissipated.

[0012] The spark plugs described herein can be used in a variety of applications, including industrial spark plugs, automotive spark plugs, aviation igniters, glow plugs, or any other device for igniting air / fuel mixtures in engines or other machines. This includes, but is by no means limited to, the exemplary industrial spark plugs shown in the accompanying drawings and described below. Other embodiments and applications are also possible, such as various types of plugs with different axial, radial, and / or semi-surface spark gaps; pre-combustion chambers, non-pre-combustion chambers, shielded and / or unshielded configurations; multiple center electrode and / or ground electrode configurations; and plugs for burning or igniting gasoline, diesel, natural gas, hydrogen, propane, butane, etc. The spark plugs and methods of this application are by no means limited to the exemplary examples shown and described herein. Unless otherwise stated, all percentages provided herein are weight percentages (wt%), and all references to axial, radial, and circumferential directions are based on the central axis A of the spark plug.

[0013] refer to Figures 1 to 3 An example of an industrial spark plug with cooling features for improving thermal management is shown. Spark plug 10 includes a center electrode 12, an insulator 14, a metal shell 16, a ground electrode 18, and one or more cooling features 20.

[0014] The center electrode 12 is disposed within an axial bore of the insulator 14 and includes an ignition end extending from the free end 22 of the insulator 14 and an optional electrode tip 24 made of a noble metal-based material (such as iridium-based, platinum-based, ruthenium-based, palladium-based, and / or rhodium-based materials). The insulator 14 is disposed within an axial bore of the metal housing 16 and is made of a material sufficient to electrically insulate the center electrode 12 from the metal housing 16 (e.g., a ceramic material). The housing 16 is preferably made of steel. As shown, the free end 22 of the insulator 14 may retract into the free end 30 of the metal housing 16, or it may extend out of the metal housing 16. The metal housing 16 includes threads 32 for an opening that allows the housing to be screwed into a cylinder head, an axial bore 34 extending parallel to the central axis A, and several other features known in the art.

[0015] The ground electrode 18 may be a bridge electrode extending across the entire axial bore 34 of the housing 16 and attached to the free end 30 of the housing at multiple locations (e.g., the ground electrode may be welded to the housing on the left and right sides of the plug, as shown). The ground electrode 18 may be in the shape of a rod, bar, plate, strip, or some other construction and includes an electrode base 40 preferably made of a nickel-based material and an electrode tip 42 made of a noble metal-based material (such as iridium-based, platinum-based, ruthenium-based, palladium-based, and / or rhodium-based materials). The electrode tip 42 may be in the form of a flat pad or disc opposite the corresponding electrode tip 24 of the center electrode, such that the electrode tip provides a spark surface for the emission, reception, and exchange of electrons through the spark gap G. Electrode tips 24 and 42 may be formed from the same noble metal base material, or they may be formed from different noble metal base materials; the shapes of the electrode tips may be rivets, cylinders, rods, pillars, wires, spheres, bulges, cones, flat pads, discs, plates, rings, sleeves, etc.; they may be formed individually and then welded to the corresponding electrodes by laser, electron beam, and / or resistance welding; or they may be formed directly on the corresponding electrodes using additive manufacturing processes, to name just a few possibilities. In one example, ground electrode 18 is formed using an additive manufacturing process (such as powder bed fusion) and includes multiple thin laser-deposited layers disposed on top of another, as will be explained.

[0016] The center electrode 12 and / or ground electrode 18 may include an electrode base made of a nickel-based material. As used herein, the term "nickel-based material" refers to a material in which nickel is the single largest component by weight of the material, and may or may not contain other components (e.g., the nickel-based material may be pure nickel, nickel with some impurities, or a nickel-based alloy). According to one example, the electrode base of the center electrode and / or ground electrode is made of a nickel-based material having a relatively high weight percentage of nickel, such as a nickel-based material containing 98 wt% or more of nickel. In different examples, the electrode base of the center electrode and / or ground electrode is made of a nickel-based material having a lower weight percentage of nickel, such as a nickel-based material containing 50 wt% to 90 wt% of nickel (e.g., INCONEL™ 600, 601, 738). A particularly suitable nickel-based material has about 60 wt% to 75 wt% nickel, 10 wt% to 20 wt% chromium, and small amounts of other elements. Other materials, including non-nickel-based materials such as tungsten-based materials, may also be used alternatively for the electrode base.

[0017] Cooling feature 20 is designed to reduce the operating temperature of spark plug 10 by removing heat from the area near spark gap G, and may be part of center electrode 12, ground electrode 18, and / or housing 16. According to Figures 1 to 3The illustrated embodiment shows that cooling feature 20 is an example of passive cooling and includes an internal cooling channel 50 located within the ground electrode 18, internal cooling channels 52 and 54 located within the housing 16, and a solid thermally conductive material 56 that fills the internal cooling channels and transfers heat from the area near the spark gap to the cylinder head or other parts of the engine, where heat can dissipate more easily. The exact size, shape, and location of cooling feature 20 may vary depending on the application.

[0018] The internal cooling channel 50 is a channel or space within the grounding electrode 18, which is designed to receive the heat-conducting material 56. The internal cooling channel 50 extends for most of the length of the grounding electrode 18 and has a heat input section 70, heat output sections 72, 74 and a main channel section 76.

[0019] The heat input portion 70 can be positioned directly below the electrode tip 42, one of the hottest parts of the spark plug, so that heat generated at the spark gap G can be drawn away from the electrode tip 42 and transferred through the thermally conductive material 56. In one example, the heat input portion 70 extends upwards to the outer surface 80 of the ground electrode 18, exposing the thermally conductive material 56 to and directly contacting the underside of the electrode tip 42 for direct thermal coupling. According to an indirect thermal coupling example, the heat input portion 70 is similarly positioned below the electrode tip 42, but does not extend all the way to the outer surface 80, leaving a thin layer of electrode base material between the thermally conductive material 56 and the underside of the electrode tip 42. In both direct and indirect thermal coupling examples, the heat input portion 70 extends into an area near the spark surface, which, in the absence of a separate electrode tip, can be part of a separate electrode tip 42 or part of the outer surface 80. At opposite ends, the heat input portion 70 engages or connects to the main channel portion 76.

[0020] Heat output portions 72 and 74 can be positioned below corresponding cooling features 52 and 54 within the housing 16, aligning and thermally coupling the cooling features of these different components. Much like the heat input portion 70, heat output portions 72 and 74 connect to and branch off from the main channel portion 76, and may or may not extend all the way to the outer surface 80 to be directly or indirectly thermally coupled to the corresponding cooling features within the housing. In examples of direct and indirect coupling, heat output portions 72 and 74 extend into the region near an attachment surface, which may be only part of the outer surface 80 or some other attachment surface.

[0021] The main channel portion 76 is the primary heat conduit of the internal cooling channel 50 and may have a larger cross-sectional area than the heat input and / or output portions 70, 72, 74, but this is not necessary. One or more of the heat input and / or output portions 70, 72, 74 may also have flared or enlarged openings at the outer surface 80 to improve thermal coupling and / or alignment with the cooling features of the electrode tip 42 or the housing 16. The internal cooling channel is surrounded or enclosed by the electrode base 40, such that the individual laser-deposited layers of the electrode base define the internal cooling channel 50. Because the internal cooling channel 50 is an intricate internal space, it is difficult to manufacture efficiently using conventional techniques such as drilling or machining. This is why additive manufacturing processes such as powder bed fusion are preferably used to form the internal cooling channel, as will be explained later.

[0022] Internal cooling channels 52 and 54 are located within the housing 16 and are also designed to receive thermally conductive material 56. Each of the internal cooling channels 52 and 54 has a heat input portion 90 and 92, which are aligned with the corresponding heat output portions 72 and 74 of the internal cooling channel 50, respectively, and has a main channel portion 94 and 96.

[0023] The heat input portions 90, 92 extend to the outer surface 98, causing the corresponding channels 52, 54 to open and be exposed at the lower end of the housing 16. This allows the thermally conductive material in channels 52, 54 to directly contact and engage with the thermally conductive material in channel 50, thereby improving the thermal coupling of the entire cooling feature 20. The heat input portions 90, 92 may have the same shape and / or dimensions as the heat output portions 72, 74, or one set of input / output portions may be significantly larger than the other. Figure 2 As best shown, internal cooling channels 52, 54 are oriented at an angle θ relative to internal cooling channel 50 (e.g., the channels may be perpendicular to each other or slightly angled) and extend upward into the housing 16 in the vicinity or region of thread 32. In one example, internal cooling channels 52, 54 are generally perpendicular to internal cooling channel 50 (i.e., angle θ is 85° to 95°) and extend in a generally axial direction within the housing 16. In different examples, internal cooling channels 52, 54 are slightly angled to internal cooling channel 50 (i.e., angle θ is 95° to 125°), such that they diverge slightly radially outward to extend closer to thread 32 to enhance thermal coupling.

[0024] The main channel portions 94, 96 can be straight or linear channels extending only a portion upward along the thread 32 (e.g., drilled), however, this is not necessary, as the channels can be curved or bent, and can be longer or shorter than shown. The main channel portions 94, 96 can even be helical, extending upward through the housing 16 in a spiral or coiled manner and in close thermal communication with the thread 32. Most of the thermal coupling from the spark plug to the engine occurs at or near the thread 32; therefore, it is desirable that the internal cooling channels 52, 54 be as close to the thread as possible to increase heat transfer to the engine. If the internal cooling channels 52, 54 are straight, they can preferably be manufactured using conventional techniques such as drilling, machining, milling, and / or etching. On the other hand, if the internal cooling channels 52, 54 are curved, helical, and / or complex in shape, it is desirable to manufacture the housing and channels using additive manufacturing processes, etc.

[0025] Solid thermally conductive material 56 is inserted into different internal cooling channels 50, 52, 54 and is designed to efficiently transfer heat or thermal energy within the channel. The same thermally conductive material 56 can be used in each of the internal cooling channels 50, 52, 54, or a different material can be used in one channel relative to the other. Each of the internal cooling channels 50, 52, 54 may comprise a single homogeneous thermally conductive material running through the channel (i.e., a single-material core), or they may comprise multiple materials (i.e., a multi-material core). Preferably, the solid thermally conductive material 56 completely fills the internal cooling channel 50 of the ground electrode 18, such that there are no gaps and the material is flush with the outer surface 80 at the heat input and output portions 70, 72, 74. A similar flush alignment is preferred for the solid thermally conductive material 56 located at the bottom and outer surface 98 of the internal cooling channels 52, 54. When the flush-aligned thermally conductive material in channel 50 comes into contact with the flush-aligned thermally conductive material in channels 52 and 54, the cooling feature in the grounding electrode is directly thermally coupled to the cooling feature in the shell.

[0026] The solid thermally conductive material 56 is made of one or more thermally conductive materials, such as copper-based, silver-based, tin-based, and / or aluminum-based materials, and has a greater thermal conductivity than the surrounding ground electrode 18 and / or shell 16. This solid thermally conductive material may have a thermal conductivity greater than 70 W / m•K (measured at 100°C), and even more preferably greater than 140 W / m•K (measured at 100°C). Preferably, the solid thermally conductive material has a melting temperature greater than 900°C, such that the material can withstand different steps in the spark plug manufacturing process at temperatures exceeding 750°C without undergoing a change in its aggregate state. As used herein, the term "copper-based material" refers to a material in which copper is the single largest component by weight, and may or may not contain other components (e.g., copper-based material may be pure copper, copper with some impurities, or a copper-based alloy). According to one example, the solid thermally conductive material 56 is a copper-based material, such as a copper-molybdenum alloy or a brazing alloy (e.g., brass); a silver-based material, such as a silver-titanium alloy; or a tin-based material, such as solder. However, other materials may also be used.

[0027] exist Figure 4 In, among which Figures 1 to 3 Similar reference numerals denote similar features, illustrating another example of passive cooling, except in this example, cooling feature 120 is part of a center electrode 112, several ground electrodes 118, 118', and an optional housing 116. Each of the center electrode 112 and the ground electrodes 118, 118' has an arcuate configuration and is designed to face the corresponding electrode across spark gaps G, G'. Cooling feature 120 may include an internal cooling channel 148 located in the center electrode 112, internal cooling channels 150, 150' located in the ground electrodes 118, 118', and optional internal cooling channels 152, 154 located in the housing 116. Each of the internal cooling channels may further include one or more heat input portions, heat output portions, and / or main channel portions, as described above. The internal cooling channels 150 and 150' of the grounding electrodes 118 and 118' can be directly thermally coupled to the internal cooling channels 152 and 154 of the shell 116 (i.e., the solid thermally conductive material 156 in one channel directly contacts the solid thermally conductive material in the opposite channel), or the internal cooling channels 150 and 150' and their corresponding thermally conductive materials can be indirectly thermally coupled to the internal cooling channels of the shell (as shown in the figure). In different embodiments, the internal cooling channels 152 and 154 of the shell are omitted, so that the cooling characteristics of the grounding electrodes 118 and 118' are thermally coupled to the shell itself.

[0028] The aforementioned implementation schemes are all examples of passive cooling, in which the thermally conductive material is a solid material. Now let's turn to... Figures 5 to 8An example of active cooling is shown, where the heat-conducting material is a fluid circulating within internal cooling channels, thus transferring heat from the area around the spark gap to the cooler parts of the engine. Figure 5 and Figure 6 In this embodiment, spark plug 210 includes a center electrode 212, an insulator 214, a metal shell 216, a ground electrode 218, and one or more cooling features 220. Unless otherwise indicated, reference numerals in the following embodiments similar to those in the foregoing embodiments denote similar features, and various constructions and / or features of the foregoing passive cooling examples can also be applied to the following active cooling examples. Repeated descriptions have been omitted.

[0029] Cooling feature 220 is designed to reduce the operating temperature of spark plug 210 by removing heat from the area near spark gap G, and may be part of housing 216 and ground electrode 218. In this active cooling example, cooling feature 220 includes an internal cooling channel 250 passing through ground electrode 218, internal cooling channels 252, 254 extending within housing 216, and a fluid thermally conductive material 256 that flows through the internal cooling channels and carries heat from the area near spark gap to the cylinder head or other parts of the engine, where the heat can be dissipated. Cooling feature 220 may also include other items such as a fluid pump, heat exchanger, and return channels in the cylinder head and / or engine (not shown) to facilitate the circulation of fluid thermally conductive material 256. The exact type, size, shape, and / or location of cooling feature 220 may vary depending on the application and the specific fluid thermally conductive material used.

[0030] The internal cooling channel 250 is a channel or conduit within the grounding electrode 218 and is designed to allow the flow of fluid thermally conductive material 256. In one example, the internal cooling channel 250 extends for most of the length of the grounding electrode 18, is typically radially aligned with the longitudinal axis A, and has a heat input portion 270, a heat output portion 272, a fluid return portion 274, and a main channel portion 276. Because the internal cooling channel 250 conveys the fluid thermally conductive material 256, the channel can be designed to improve fluid dynamics (e.g., to reduce fluid friction, etc.).

[0031] If the ground electrode 218 has a noble metal-based electrode tip 242, the heat input portion 270 can be positioned directly below and close enough to allow heat generated at the spark gap G to be absorbed and transferred through the circulating thermally conductive material 256. If the ground electrode 218 does not include a separate electrode tip 242, the heat input portion 270 can pass only below the portion of the outer surface 280 that forms the spark gap G with the opposing electrode tip 224 of the center electrode 212. Figure 6In this diagram, the heat input portion 270 is shown only as a straight channel segment extending into the region near the spark surface. Alternatively, the heat input portion 270' (dashed line) may branch off from the straight channel segment and diverge, allowing it to pass more closely over the spark surface and increase thermal coupling therebetween. The exact construction of the heat input portion and its spacing or distance from the spark surface can vary depending on the specific application. If the ground electrode 218 includes a separate electrode tip 242, the heat input portion 270 can even extend upwards all the way to the outer surface 280, exposing the thermally conductive material 256 to the underside of the electrode tip and directly contacting the underside of the electrode tip for direct thermal coupling. In this example, the underside of the electrode tip 242 helps to enclose the internal cooling channel 250.

[0032] The heat output portion 272 is positioned below the corresponding cooling feature in the housing 216, such that the ground electrode and the internal cooling channels 250, 254 of the housing can be aligned and fluidly communicated with each other. The heat output portion 272 connects to and branches off from the main channel portion 276, extending to the outer surface 280, thus opening to the opposing internal cooling channel 254. Although not strictly necessary, it is preferred that one or more of the heat output portion 272 and / or the fluid return portion 274 have a flared or enlarged opening at the outer surface 280 to improve thermal coupling with the cooling features of the housing 16. Figure 6 As shown, the flared openings of the heat output portion 272 and the fluid return portion 274 are preferably wider than the corresponding portions of the internal cooling channels 254 and 254, respectively. Besides potentially improving the flow of the thermally conductive fluid 256 between the channels, the flared and oversized construction of the openings 272 and 274 helps ensure the positional accuracy and alignment of the channels. For example, if there is a small misalignment when the ground electrode 218 is attached to the housing 216, the flared and oversized openings at 272 and 274 can still allow sufficient fluid coupling at the interface of the channels. Depending on the possibilities, the fluid return portion 274 and the heat input portion 292 in the ground electrode 218 can be flared or enlarged, while the fluid output portion 290 in the housing and the heat output portion 272 in the ground electrode remain small in size. This arrangement will still enjoy the aforementioned advantages of improved alignment and fluid coupling, but will also potentially enjoy improved hydrodynamics by having component indirect interface (where the smaller opening enters the larger opening, thus reducing fluid bottlenecks). The internal cooling channel 250 is surrounded or enclosed by the electrode base 240, which is preferably formed using an additive manufacturing process and includes multiple thin laser-deposited layers defining the internal cooling channel.

[0033] The main channel portion 276 is the primary heat conduit of the internal cooling channel 250 and can have any number of different configurations, including straight, curved, wavy, and / or other simple or complex configurations. Because the ground electrode 218, which includes the laser-deposited layer defining the internal cooling channel 250, is formed using an additive manufacturing process, there is a significant degree of design freedom available regarding the channel's construction, including complex configurations and designs that would otherwise be unavailable for such an internal space. For example, the main channel portion 276 may include an enlarged recessed or convex bulbous section near the heat input portion 270 to help collect additional heat from the area near the spark surface. Other configurations and features are also possible.

[0034] Internal cooling channels 252 and 254 are located within the housing 216 and are also designed to transport fluid-conducting thermal material 256. Internal cooling channel 252 has a main channel portion 294 connected to a fluid output portion 290, which is fluidly coupled to a fluid return portion 274, so that once heat has been removed from the fluid 256, the thermal material 256 can return in direction B to the ground electrode 218. Heat exchange devices, such as cooling fins or some type of cooler, may be located outside the spark plug or in the cylinder head and can be used to extract heat from the fluid 256, cooling the fluid before it returns to the ground electrode 218. Internal cooling channel 254 includes a heat input portion 292 aligned with and fluidly coupled to the heat output portion 272. Once the heated fluid 256 has collected heat from the area near the spark gap and leaves the ground electrode 218, the heated fluid enters the heat input portion 292 and travels through the main channel portion 296 on its way to the engine. The reverse process occurs when the cooled fluid returns through the main channel portion 294 and the fluid output portion 290 before returning to the ground electrode 218. The internal cooling channels 252 and 254 include fluid ports at opposite ends of the channels as portions 290 and 292, allowing the channels to be fluidly coupled to corresponding channels in the cylinder head.

[0035] The main channel portions 294, 296 can be straight or linear channels extending through the thread 32 (e.g., drilled holes). However, this is not necessary, as the channels can be curved or bent, and can also exit the spark plug at other locations.

[0036] refer to Figure 7 and Figure 8Another embodiment of an active cooling example using circulating fluid to cool spark plug electrodes is shown, wherein similar reference numerals denote similar features. Each of the center electrode 312 and ground electrodes 318, 318' has an arcuate configuration and is designed to face the corresponding electrode across the spark gap G, G'. Cooling feature 320 may include internal cooling channels 350, 350' located in the ground electrodes 318, 318', internal cooling channels 352, 354 located in the housing 316, and liquid or fluid thermally conductive material 356, 356' flowing through them respectively. Each of the internal cooling channels may further include one or more heat input portions, heat output portions, and / or main channel portions, as described above. This embodiment is similar to... Figures 5 to 6 One difference between the previously shown active cooling embodiments is that internal cooling channels 350 and 352 can form a first closed fluid loop, and internal channels 350' and 354 can form a second closed fluid loop that is separate from and fluid-isolated from the first closed fluid loop. In such an embodiment, internal cooling channel 350 includes an input section 360 that delivers cooler fluid to the spark gap region and an output section 362 that carries hotter fluid away from the spark gap region in the circulation direction B. Internal cooling channel 354 may include similar input and output sections for circulating fluid in direction B'. In this embodiment, there is no fluid circulation channel in the center electrode 312. Figure 8 An enlarged view is shown of an example of the component indirect mating surface 366 between the housing 316 and the ground electrode 318, wherein the openings of the input section 360 and the output section 362 are flared or enlarged to facilitate improved thermal coupling and alignment between the cooling features. Alternatively, the opening on the housing side of section 362 can be enlarged compared to the ground electrode side to enhance hydrodynamics. It should also be noted that the fluid circulation direction B in various active cooling examples can be reversed.

[0037] Now go to Figures 9A-9D This illustrates several stages of an exemplary process for manufacturing a grounding electrode (such as the previously described grounding electrode 18) having one or more cooling features. Figure 9AInitially, the ground electrode 18 can be formed layer-by-layer using additive manufacturing processes such as powder bed fusion. Some non-limiting examples of potential powder bed fusion techniques include selective laser melting (SLM), selective laser sintering (SLS), direct metal laser sintering (DMLS), electron beam melting (EBM), and / or any other suitable 3D printing technique. The ground electrode 18 can be made from a nickel-based powder bed irradiated by a laser or electron beam, causing the powder to melt and solidify into thin laser-deposited layers 400 to 410. This process begins with an initial laser-deposited layer 400 and is repeated to produce multiple laser-deposited layers 400 to 410, which are sequentially built or stacked on top of each other such that the layers are parallel to each other (in this context, "parallel" does not require perfect parallelism). Each laser-deposited layer 400 to 410 has an average layer thickness T, which can be, for example, between 5 µm and 60 µm. It should be understood that although the figures only show a few dozen laser-deposited layers, an actual additively manufactured ground electrode can have dozens or even hundreds of individual laser-deposited layers, which may be visible or invisible once the ground electrode is fabricated. As described herein, ground electrodes fabricated using additive manufacturing processes are still considered to have multiple laser-deposited layers, even if these layers cannot be seen or observed individually, because these layers sometimes melt or mix with each other. This mixing makes it difficult to observe individual or discrete layers even under magnification, but does not change the fact that the ground electrode consists of multiple laser-deposited layers stacked one on top of another.

[0038] One reason additive manufacturing is suitable for forming the ground electrode 18 is the complex shape of the internal cooling channel 50 or the thermally conductive volume, which would otherwise be difficult (if not impossible) to manufacture cost-effectively. For example, the shape of the internal cooling channel 50, and its heat input portion 70, heat output portions 72, 74, and its main channel portion 76, would likely prevent its manufacture using conventional drilling, boring, and milling techniques. During the additive manufacturing process, a laser or electron beam follows a predefined pattern for each laser-deposited layer, such that it melts only the powder in those regions where a new laser-deposited layer is to be formed, but not the powder in those regions corresponding to the internal cooling channel 50. For each successive layer, the predetermined pattern can be slightly modified, allowing for complex and irregular cross-sectional shapes of the internal cooling channel 50. In this way, the various laser-deposited layers form the walls defining the internal cooling channel 50 within the electrode base 40, as they are built around the channel layer by layer. Furthermore, the additive manufacturing process is capable of producing internal geometries that facilitate degassing of the solid thermally conductive material. When a solid thermally conductive material (e.g., solder) is introduced into the internal cooling channel 50 by melting, the internal geometry of the channel, for example, with an angle of 3° to 18°, promotes the freedom of movement of bubbles or defects, allowing the material to be degassed quickly and successfully.

[0039] Once the ground electrode 18, with its stacked laser-deposited layers 400 to 410 defining internal cooling channels 50, is formed, a thermally conductive material 56 is added, such as... Figure 9B As shown. In this passive cooling example, the thermally conductive material 56 of the finished spark plug is a solid material, such as a copper-based, silver-based, or tin-based material. For the thermally conductive material 56 to properly fill the internal cooling channel 50, the material must be in a powder, paste, and / or other type of state, allowing it to adequately fill the various input and output sections, as well as any other cracks, corners, or spaces within the channel. In one example, the thermally conductive material 56 is a copper-based material and is initially in a paste state when inserted into the internal cooling channel 50. Preferably, as... Figure 9B As shown, thermally conductive material 56 is filled into the top or near the top of the internal cooling channel 50.

[0040] After the internal cooling channel 50 is fully filled with the thermally conductive material 56, the assembled component is heated so that the material 56 at least partially melts and settles within the channel 50. Induction heating can be used for this step, but other heating techniques are certainly possible. Those skilled in the art will understand that due to curing shrinkage, the top of the thermally conductive material 56 retracts slightly downwards or backwards into the channel, thereby forming several grooves 420 to 424. Therefore, as... Figure 9C As shown, the top of the thermally conductive material 56 is not flush with the top of the electrode base 40. Once cured, the thermally conductive material 56 can form a metallic bond with the surrounding wall of the internal cooling channel 50.

[0041] The manufacturing process can then use grinding, milling, and / or other machining processes to remove the electrode base material, thereby forming an outer surface 80 at the top of the portion where the electrode base 40 and the heat-conducting material 56 are flush with each other, see [reference needed] Figure 9D Once the grounding electrode is attached and in place, the flush outer surface 80 can improve the direct thermal coupling between the cooling characteristics of the grounding electrode 18 and the housing 16.

[0042] Several different potential techniques exist for forming the cooling features of shell 16. For embodiments in which shell 16 has internal cooling channels (such as channels 52, 54, 252, 254, 352, 354) composed of straight or linear segments, the channels can be formed using conventional techniques (such as drilling, boring, etching, and / or other machining techniques). For example, Figure 5 Channels 252 and 254 can be formed by drilling a first linear channel segment from the bottom of the shell 16 and then drilling a second linear channel segment from the side of the shell, such that they meet and connect with each other. For embodiments where the shell 16 has internal cooling channels with curved, spiral, complex, and / or other non-linear sections, the entire shell or only portions of the shell including these sections can be formed using additive manufacturing processes, as explained above. An example of this embodiment is when the internal cooling channels of the shell follow a spiral and / or coiled path (not shown) that allows them to be in close thermal communication with the thread 32. Other examples also exist. Then, as described above, a thermally conductive material can be added to the internal cooling channels, heated, cured, and machined to a flush outer surface 98.

[0043] With the cooling features now formed on both the ground electrode and the housing, the ground electrode can be attached to the housing so that the cooling features are aligned and thermally coupled to each other. In one example, the flush outer surface 80 of the ground electrode 18 presses against the flush outer surface 98 of the housing 16, so that the thermally conductive materials 56 in the two components are directly thermally coupled together. Depending on the application, the thermally conductive materials 56 in the ground electrode and the housing can be the same material, or they can be different materials. Once properly aligned—as described above, the process can be aided or simplified by flared or enlarged openings in the channel—the ground electrode 18 can be laser welded or resistance welded to the bottom of the housing 16.

[0044] The above manufacturing process relates to a passive cooling example. For an active cooling example, a similar process can be used to additively manufacture grounding electrodes 218, 318 with complex internal cooling channels 350, 350, 250'. However, instead of inserting, melting, and solidifying the thermally conductive material, the active cooling implementation may simply add the thermally conductive material 256, 356, 356' in fluid or liquid form to the channels. When forming the electrode base in the previous steps, casting risers acting as small funnels can be added to the openings of the internal cooling channels to better fill the fluid thermally conductive material, but this is only optional. After completing the foregoing steps, the grounding electrodes 218, 318 can be attached to the housings 216, 316, as previously described.

[0045] It should be understood that the foregoing is a description of one or more preferred exemplary embodiments of the present invention. The invention is not limited to the specific embodiments disclosed herein, but is defined only by the appended claims. Furthermore, the statements contained in the foregoing description relate to specific embodiments and should not be construed as limiting the scope of the invention or the definition of terms used in the claims, unless the terms or phrases are expressly defined above. Various other embodiments, as well as various changes and modifications to the disclosed embodiments, will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to fall within the scope of the appended claims.

[0046] As used in this specification and claims, the terms “e.g.,” “such as,” and “etc.”, as well as the verbs “comprising,” “having,” “containing,” and other verb forms thereof, when used in conjunction with a list of one or more parts or other items, shall each be interpreted as open-ended, meaning that the list shall not be considered to exclude other, additional parts or items. Other terms shall be interpreted using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.

Claims

1. A spark plug (10), the spark plug comprising: Shell (16), the shell having an axial hole (34); An insulator (14) is at least partially disposed within the axial hole of the housing and has the axial hole; A central electrode (12) is at least partially disposed within the axial hole of the insulator; Grounding electrode (18), the grounding electrode being attached to the housing and having an electrode base (40); and Cooling feature (20) having a first internal cooling channel (50) formed in the electrode base of the ground electrode, a first thermally conductive material (56) located in the first internal cooling channel, a second internal cooling channel (52, 54) formed in the shell, and a second thermally conductive material (56) located in the second internal cooling channel. The first internal cooling channel is aligned with the second internal cooling channel, and the first thermally conductive material is thermally coupled to the second thermally conductive material, such that during operation, the cooling feature is able to remove heat from the area near the spark surface.

2. The spark plug (10) according to claim 1, wherein the electrode base (40) of the ground electrode (18) comprises a plurality of laser-deposited layers (400-410), one of the plurality of laser-deposited layers being disposed on top of the other and defining the first internal cooling channel (50).

3. The spark plug (10) according to claim 2, wherein the plurality of laser-deposited layers (400-410) of the electrode base (40) are made of nickel-based materials using powder bed fusion technology.

4. The spark plug (10) according to claim 1, wherein the ground electrode (18) comprises an electrode tip (42) made of a noble metal base material, the electrode tip comprising the spark surface and attached to the electrode base (40), such that the first thermally conductive material (56) is directly thermally coupled to the electrode tip at the heat input portion (70).

5. The spark plug (10) according to any one of claims 1 to 4, wherein the cooling feature (20) is a passive cooling feature, the first thermally conductive material (56) is a solid material bonded to the first internal cooling channel (50) by means of a first metal bond, and the second thermally conductive material (56) is a solid material bonded to the second internal cooling channel (52, 54) by means of a second metal bond.

6. The spark plug (10) according to claim 5, wherein each of the first thermally conductive material and the second thermally conductive material (56) is made of at least one of a copper-based material, a silver-based material or a tin-based material.

7. The spark plug (210) according to any one of claims 1 to 4, wherein the cooling feature (220) is an active cooling feature, and the first thermally conductive material and the second thermally conductive material (256) are fluid materials flowing within the first internal cooling channel and the second internal cooling channel (250, 252, 254).

8. The spark plug (210) according to claim 7, wherein the first thermally conductive material and the second thermally conductive material (256) are the same material and include at least one of water, ethylene glycol, sodium or mixtures thereof.

9. The spark plug (210) according to any one of claims 1 to 4, wherein the first internal cooling channel (250) includes a heat output portion (272) having a flared opening or an enlarged opening for improving alignment with the second internal cooling channel (254).

10. The spark plug (10) according to claim 1, wherein the ground electrode (18) is a bridge-type ground electrode extending through the entire axial bore (34) of the housing (16) and attached to the housing at a first position and a second position, the first internal cooling channel (50) comprising a heat input portion (70), a first heat output portion (72) and a second heat output portion (74) and a main channel portion (76). The first heat output portion (72) branches off from the main channel portion at the first end of the main channel portion and extends to the area near the first attachment surface of the ground electrode attached to the housing; The second heat output section (74) branches off from the main channel section at the second end of the main channel section and extends into the area near the second attachment surface of the ground electrode where it is attached to the housing; and The heat input portion branches off from the main channel portion at the intermediate section between the first end and the second end of the main channel portion.

11. The spark plug of claim 1, wherein the ground electrode (118, 118') is an arc-shaped ground electrode that extends through a portion of the axial bore of the housing (116) and is attached to the housing at a first location.

12. A grounding electrode (18) for a spark plug (10), the grounding electrode comprising: Electrode base (40), the electrode base having a plurality of laser-deposited layers (400-410) arranged on top of one another. and Cooling feature (20) having an internal cooling channel (50) and a thermally conductive material (56), the internal cooling channel being filled with the thermally conductive material and including a heat input portion (70), a heat output portion (72, 74) and a main channel portion (76). The heat input portion is connected to the main channel portion and extends into the area near the spark surface; and The heat output section is connected to the main channel section and extends into the area near the attachment surface of the ground electrode attached to the spark plug housing (16); The plurality of laser-deposited layers form walls within the electrode base that define the internal cooling channels.

13. The grounding electrode (18) according to claim 12, wherein the cooling feature (20) is a passive cooling feature, and the thermally conductive material (56) is a solid material bonded to the wall defining the internal cooling channel (50) by means of a metal bond.

14. The grounding electrode (218) according to claim 12, wherein the cooling feature (220) is an active cooling feature, and the thermally conductive material (256) is a fluid material flowing within the internal cooling channel.

15. A method for manufacturing a ground electrode (18) for a spark plug (10), the method comprising the steps of: The electrode base (40) is formed using an additive manufacturing process, the electrode base being formed layer by layer, such that multiple laser-deposited layers (400-410) are arranged one on top of the other and define an internal cooling channel (50). Add thermally conductive material (56) to the internal cooling channel; The thermally conductive material is heated such that it at least partially melts and fills the internal cooling channel; as well as The thermally conductive material, which is allowed to be at least partially melted, is solidified and forms a metallic bond with the wall of the internal cooling channel, wherein the internal cooling channel and the thermally conductive material are part of a cooling feature (20) for removing heat from the area near the spark surface.

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