Spark plug with cathode and anode compositions for extended use life

Abstract

A spark plug (38) includes: a spark plug housing (40); a cathode (62) including at least one electrode fork (64) and formed primarily of iridium; and an anode (72) formed at least predominantly of iron or steel. The material composition of the cathode and anode provides extended spark plug service life, especially in high power density applications employing pre-chamber spark plugs. Related methods are also disclosed.

Description

Technical Field

[0001] This disclosure generally relates to a spark plug, and more specifically to a spark plug having an iridium cathode and an iron or steel anode configured to extend service life. Background Technology

[0002] Spark plugs have been used in internal combustion engines for over a century. They are used to generate an electric spark that ignites the fuel-air mixture in the engine cylinders, causing a controlled combustion reaction that drives the piston to rotate the crankshaft. Many different spark plug designs are known, including so-called J-gap or other open-cell spark plugs commonly used in automotive engines, as well as pre-combustion chamber spark plugs for a variety of applications, including heavy-duty engine applications that typically operate with a stoichiometric lean-air-fuel ratio.

[0003] Spark plugs are generally considered consumable parts whose lifespan can be significantly shorter than the lifespan of the entire engine platform. When a spark is generated, the physical phenomena involved in spark formation often cause the ejection of ions from the spark electrode material, leading to electrode erosion over time. In most systems, as electrode erosion continues, the spark gap between the cathode and anode electrodes eventually widens, making the voltage potential required to generate a spark that can bridge the spark gap impractically high. Spark plugs are typically replaced when the so-called breakdown voltage becomes too high.

[0004] Spark plugs used in many modern engines typically consist of electrodes made of precious metals, which have proven to extend spark plug life compared to conventional materials. For example, iridium cathodes paired with nickel anodes are generally known to offer a longer lifespan compared to certain other combinations of materials. Engineers have also experimented with various other combinations of metallic materials, gradually improving spark plug lifespan, but these typically increase material costs.

[0005] In recent years, numerous engine platforms have been developed or modified to achieve increased power density, where relatively smaller or lighter engines produce increased power output compared to conventional arrangements. Increased power density (where relatively more fuel and air are burned per engine cycle for a given cylinder size) presents new challenges relative to spark plug life, in some cases requiring more frequent spark plug replacements. One known spark plug strategy for extending life is described in U.S. Patent No. 11,035,334B1 to Cress. Summary of the Invention

[0006] In one aspect, a spark plug includes: a spark plug housing defining a longitudinal axis; a first electrode including at least one electrode fork; and a second electrode including an electrode surface extending circumferentially around the longitudinal axis and spaced apart from the at least one electrode fork by a spark gap distance. The first electrode is primarily formed of iridium, and the second electrode is at least primarily formed of iron or steel.

[0007] In another aspect, a pre-combustion chamber spark plug includes a spark plug housing forming a pre-combustion chamber, a center electrode, and a ground electrode. The ground electrode includes a ground electrode surface, and a spark gap within the pre-combustion chamber is defined between the center electrode and the ground electrode surface. The center electrode is primarily formed of iridium, and the ground electrode surface is at least primarily formed of iron or steel.

[0008] In another aspect, a method of operating an ignition system for an internal combustion engine includes: energizing an iridium electrode fork positioned in a pre-combustion chamber spark plug at a distance from the spark gap of an iron or steel anode, generating a spark at the spark gap defined between the iridium electrode fork and the iron or steel anode, and igniting a mixture of gaseous fuel and air in an engine cylinder via the spark. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of an internal combustion engine system according to one embodiment; Figure 2 This is a schematic diagram of a spark plug according to one embodiment; Figure 3 Is it like this? Figure 2 A cross-sectional side view of a portion of the spark plug; Figure 4 Is it like this? Figure 2 and Figure 3 A cross-sectional axial view of a portion of the spark plug; Figure 5 This is a cross-sectional side view of a portion of a spark plug according to another embodiment; Figure 6 This is a perspective view of a known spark plug design that has been removed after use; Figure 7 Spark plugs that are removed after use according to this disclosure; and Figure 8 This is a graph showing a comparison of engine ignition time and breakdown voltage between spark plugs of known design and spark plugs according to this disclosure. Detailed Implementation

[0010] refer to Figure 1The image illustrates an internal combustion engine system 10 according to one embodiment. The engine system 10 includes an engine 12 having an engine housing 14 with a combustion cylinder 16 formed therein. A piston 18 is movable in the cylinder 16 in a generally conventional manner (typically in a four-stroke engine cycle) between a bottom dead center (BDC) and a top dead center (TDC) position. The piston 18 is coupled to a crankshaft 20, which is operable to rotate a load, such as a generator, a drivetrain in a land or marine vehicle, a pump, a compressor, or something else. The cylinder 16 can be one of any number of cylinders arranged in any suitable configuration (such as inline, V-type, or another arrangement).

[0011] Engine system 10 also includes air inlet 22 and fuel supply source 24, which together are configured to provide fuel and airflow to cylinder 16. Engine system 10 may be turbocharged and may include a compressor in the turbocharger to compress intake air or a mixture of intake air and fuel for delivery to cylinder 16. For example, in other embodiments, fuel may enter via fumigation, but may also be port-injected or directly injected. Exhaust from cylinder 16 may be delivered to exhaust outlet 30 via an aftertreatment device (not shown). Intake valve 26, movable in engine housing 14, controls the intake air and fuel flow into cylinder 16. Exhaust valve 28 conventionally operates to control the exhaust flow to exhaust outlet 30. In one practical embodiment, engine 12 operates using gaseous fuels such as methane, ethane, natural gas, or various blends of hydrocarbon fuels with non-hydrocarbon fuels including hydrogen.

[0012] Engine system 10 also includes an ignition system 32. Ignition system 32 includes an electronic control unit 34 having or connected to an ignition circuit system or coil 36. Ignition system 32 also includes a spark plug 38 positioned to generate an electric spark that ignites a fuel mixture, such as gaseous fuel and air, in cylinder 16 for combustion. Spark plug 38 may include a pre-combustion chamber spark plug.

[0013] Still referencing Figure 2-4 Spark plug 38 includes a spark plug housing 40 defining a longitudinal axis 42. Spark plug 38 also includes an electrical terminal 44 electrically connected to an ignition coil 36, an insulator 46, a hexagonal portion 48, and a mounting section 50. The mounting section 50 may have external threads.

[0014] The spark plug housing 40 may also include a pre-combustion chamber tip 52 forming a pre-combustion chamber 60 and including at least one outlet 54 of the pre-combustion chamber 60. As will be appreciated by those skilled in the art, the piston 18 in the moving cylinder 16 can push a fuel and air mixture into the pre-combustion chamber 60 through the outlet 54 for ignition via a spark. The ignition of the fuel and air in the ignition charge in the pre-combustion chamber 60 generates a hot jet of combustion gases that exits the spark plug 38 through the outlet 54 and ignites the larger main charge of fuel and air in the cylinder 16. The spark plug housing 40 may also include an outer surface 56 on the pre-combustion chamber tip 52 and an inner surface 58 formed at least partially on the pre-combustion chamber tip 52 defining the pre-combustion chamber 60. One or more outlets 54 extend from the inner surface 58 to the outer surface 56. As further discussed herein, the inner surface 58 may form an electrode surface including an anode or a ground electrode surface.

[0015] Spark plug 38 also includes a first electrode 62, which includes at least one electrode fork 64. The first electrode 62 may be electrically connected to terminal 44 and thus electrically connected to ignition coil 36 in ignition system 32. Ignition coil 36 may be configured to energize the first electrode 62, which serves as a cathode. In the illustrated embodiment, the first electrode 62 includes a plurality of electrode forks 64, 65, 66, and 67. Each corresponding electrode fork may include a leg portion 68 curved toward electrode tip 70. Spark plug 38 also includes a second electrode 72. The second electrode 72 may serve as a ground electrode or anode and includes an electrode surface extending circumferentially around longitudinal axis 42 and spaced apart from at least one electrode fork 64, 65, 66, 67 by a spark gap distance. As described above, inner surface 58 may form the ground electrode surface of the second electrode or anode 72.

[0016] As from Figure 4 As can be seen, the four electrode forks are part of the first electrode 62. It is conceivable that in some embodiments, a single electrode fork may be used, or more than four electrode forks, such as six, seven, or eight, may be arranged circumferentially around the longitudinal axis 42. When the spark plug 38 is engaged and an electric spark is generated at the spark gap 74, the emission of ions from the first electrode 62 and the second electrode 72 can occur, leading to erosion of the electrode materials over time. It has been found that the combination of an iridium cathode and an iron or steel anode can result in a longer service life than conventionally achievable, including up to 30% or even longer service life compared to conventional pre-combustion chamber spark plugs comprising an iridium cathode and a nickel anode or other combinations of materials.

[0017] For this purpose, the first electrode 62 may be formed primarily of iridium. The second electrode 72 may be formed at least primarily of iron or steel. In an embodiment, the second electrode 72 is substantially composed of iron or steel. In a further refinement, the second electrode 72 may be substantially composed of low-carbon steel (such as ST523 mild steel) without any alloying elements. The second electrode or anode may be substantially nickel-free, meaning that the second electrode 72 may contain no more than trace amounts of nickel. In one refinement, the first electrode 62 may contain at least 90% iridium, and in a further refinement, it may contain at least 95% iridium. In an even further refinement, the first electrode 62 may contain approximately 97% iridium, with the remainder composed of other elements. The first electrode 62 may be partially formed of at least one of rhodium, hafnium, or niobium. A practical embodiment includes a first electrode primarily containing iridium, wherein the remainder of the first electrode 62 comprises all or part of rhodium.

[0018] As from Figure 4 As can be seen, multiple electrode forks 64, 65, 66, and 67 are circumferentially spaced around the longitudinal axis 42. It can also be noted that electrode surface 58 extends circumferentially around the multiple electrode forks and is radially spaced from them. Figure 4 In the middle, electrode surface 58 is radially spaced outward from multiple electrode forks. Now turn to Figure 5 Another embodiment with a different construction is shown. Figure 5 In this configuration, the pre-combustion chamber spark plug 138 includes a spark plug housing 140 defining a longitudinal axis 142. A first electrode or cathode is shown at 162 and will be understood to include a plurality of electrode forks circumferentially spaced around the longitudinal axis 142. A second electrode or anode 172 is positioned radially inside the first electrode 162. Therefore, it should be understood that in Figure 2-4 In the embodiment, the first electrode 162 includes a center electrode, and the second electrode 172 includes an outer electrode, while Figure 5 In this case, the first electrode or cathode 162 includes an outer electrode, and the second electrode or anode 172 includes a central electrode. The material composition of electrode 162 may be similar to that of electrode 62, and the material composition of electrode 172 may be similar to that of electrode 72.

[0019] Industrial applicability Still largely refer to the attached diagram, but also refer to... Figure 6 and Figure 7 , Figure 6 A spark plug 238 is shown removed from use after ignition in an environment where it is ignited in an actual engine or a simulated engine. The spark plug 238 includes a cathode 262 formed primarily of iridium and an anode 272 formed primarily of nickel. Figure 7A spark plug ignited in an engine or simulated engine environment is shown, and includes a cathode 362 primarily made of iridium and an anode 372 made of steel. (Comparison) Figure 6 and Figure 7 It can be readily recognized that the material from the cathode 262 in the known design is significantly more severely corroded than the cathode 362 in the design according to this disclosure. Figure 6 and Figure 7 This indicates that the spark plugs underwent actual testing under similar usage conditions.

[0020] Still referencing Figure 8 Figure 400 shows actual test data, which compares the breakdown voltage on the Y-axis with the engine's equivalent ignition time on the X-axis, including spark plugs of known design (similar to...). Figure 6 A comparison is made between the trace 410 of spark plug 238 (as described above) and the traces 420 and 430 of spark plugs according to this disclosure. As discussed above, spark plug life is typically limited by the breakdown voltage becoming too high, making continued ignition impractical. It can be seen that the breakdown voltage of the known spark plug 410 increases relatively faster than that of spark plugs 420 and 430. The ends of traces 420 and 430 show the maximum breakdown voltage after a longer period of use than the ends of trace 410, clearly demonstrating an extended life beyond known designs. This extended life reflects the surprising finding that the pairing of an iridium-based cathode with an iron-based anode results in less material erosion compared to the use of conventionally employed iridium cathodes and nickel anodes.

[0021] As mentioned above, the increased power density in some engines has exacerbated the challenge of extending spark plug life. Operating an ignition system according to this disclosure may include energizing an iridium electrode fork positioned in the pre-combustion chamber spark plug at a distance from the spark gap of the iron or steel anode. As discussed herein, fuel and air are propelled into the pre-combustion chamber based on piston movement, such that the generation of a spark triggers combustion of the fuel and air in the pre-combustion chamber to ignite the main charge in the associated cylinder. While this disclosure is not limited to any particular ignition density, in some applications, the gaseous fuel and air mixture in the engine cylinder may have a density of at least 20 kg / m³, at least 25 kg / m³, or possibly even higher.

[0022] This specification is for illustrative purposes only and should not be construed as limiting the scope of this disclosure in any way. Therefore, those skilled in the art will understand that various modifications can be made to the embodiments currently disclosed without departing from the full and reasonable scope and spirit of this disclosure. Other aspects, features, and advantages will become apparent from the accompanying drawings and appended claims. As used herein, the articles “a” and “an” are intended to include one or more items and may be used interchangeably with “one or more”. The term “one” or similar language is used when intended to refer to only one item. Furthermore, as used herein, the terms “has,” “have,” “having,” etc., are intended to be open-ended terms. Additionally, the phrase “based on” is intended to mean “at least partially based on” unless otherwise expressly stated.

Claims

1. A spark plug (38, 138), comprising: Spark plug housing (40, 140) that defines the longitudinal axis. First electrode (62, 162), the first electrode includes at least one electrode fork (64, 65, 66, 67); The second electrode (72, 172) includes an electrode surface (58) that extends circumferentially around the longitudinal axis and is spaced apart from the at least one electrode fork by a spark gap distance. The first electrode is primarily formed of iridium; and The second electrode is formed primarily of iron or steel.

2. The spark plug according to claim 1, wherein the second electrode is substantially composed of iron or steel.

3. The spark plug (38) according to claim 1 or 2, wherein: The first electrode includes a plurality of electrode forks spaced circumferentially around the longitudinal axis; and The electrode surface extends circumferentially around the plurality of electrode forks and is radially spaced outward from the plurality of electrode forks.

4. The spark plug according to claim 1 or 2, wherein: The spark plug housing includes a pre-combustion chamber tip (52), the pre-combustion chamber tip forming a pre-combustion chamber (60, 160) and including at least one outlet (54) of the pre-combustion chamber, and the spark gap within the pre-combustion chamber is defined between the at least one electrode fork and the electrode surface; and The tip of the pre-combustion chamber includes an outer surface (56), and the spark plug housing includes an inner surface forming the electrode surface.

5. The spark plug according to any one of the preceding claims, wherein the first electrode is partially formed of at least one of rhodium, hafnium, or niobium, and the second electrode is substantially nickel-free.

6. The spark plug according to any one of the preceding claims, wherein the first electrode contains at least 90% iridium.

7. The spark plug of claim 6, wherein the first electrode contains at least 95% iridium.

8. An ignition system (32) comprising a spark plug according to any of the preceding claims, and further comprising an electrical terminal (44) electrically connected to the first electrode, and an ignition coil (36) connected to the electrical terminal and configured to energize the first electrode, which is a cathode.

9. A pre-combustion chamber spark plug (38), comprising: Spark plug housing (40) forming the pre-combustion chamber (60); Central electrode (62); Grounding electrode (72); The grounding electrode includes a grounding electrode surface (58), and the spark gap in the pre-combustion chamber is defined between the center electrode and the grounding electrode surface; The central electrode is primarily formed of iridium; and The surface of the grounding electrode is formed primarily of iron or steel.

10. The pre-combustion chamber spark plug of claim 9, wherein the grounding electrode is substantially nickel-free.

11. The pre-combustion chamber spark plug according to claim 9 or 10, wherein the center electrode contains at least 90% iridium, and the remainder of the center electrode contains rhodium, and the ground electrode is formed of low carbon steel.

12. The pre-combustion chamber spark plug according to claim 11, wherein: The central electrode includes multiple electrode forks (64, 65, 66, 67). The spark plug housing includes a pre-combustion chamber tip (52) and forms the ground electrode; and The surface of the grounding electrode extends circumferentially around the plurality of electrode forks and is radially spaced from the plurality of electrode forks.

13. A method of operating an ignition system (32) for an internal combustion engine (12), comprising: Energize the iridium electrode fork (64, 65, 66, 67) positioned in the pre-combustion chamber spark plug (38, 138) at a distance from the spark gap of the iron or steel anode (72, 172); A spark is generated at the spark gap defined between the iridium electrode fork and the iron or steel anode; and The mixture of gaseous fuel and air in the engine cylinder (18) is ignited by the spark.

14. The method of claim 13, wherein the iridium electrode is formed of iridium plus at least one of rhodium, hafnium or niobium, and the iron or steel anode is substantially nickel-free.

15. The method according to claim 13 or 14, wherein the mixture of gaseous fuel and air in the engine cylinder has a density of at least 20 kg / m³.

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