Electrode

Abstract

To provide a technique for reducing variation in discharge voltage in an electrode.SOLUTION: The electrode is made of an alloy containing 3 to 7 types of metal elements. Among the metal elements contained in the alloy, when the top three metal elements with the largest number of moles, in descending order, are designated as the first metal element, the second metal element and the third metal element, the number of moles of the second metal element is 0.8 times or more and 1.0 time or less the number of moles of the first metal element, and the number of moles of the third metal element is 0.5 times or more and 1.0 time or less the number of moles of the first metal element.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electrode. [Background technology]

[0002] Discharge electrodes have been known for some time (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-069826 [Patent Document 2] Japanese Patent Application Publication No. 9-291327 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even with prior art such as that disclosed in Patent Document 1, there is still room for improvement in the technology for reducing the variation in discharge voltage in the electrodes.

[0005] An object of the present invention is to provide a technique for reducing the variation in discharge voltage in an electrode. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided an electrode comprising an alloy containing three to seven metal elements, wherein the metal elements contained in the alloy have the top three metal elements in terms of mole number, in descending order, as a first metal element, a second metal element, and a third metal element, and the number of moles of the second metal element is 0.8 to 1.0 times the number of moles of the first metal element, and the number of moles of the third metal element is 0.5 to 1.0 times the number of moles of the first metal element.

[0008] According to this configuration, of the three to seven metal elements contained in the alloy forming the electrode, if the top three metal elements by mole number are, in descending order, a first metal element, a second metal element, and a third metal element, the number of moles of the second metal element is 0.8 to 1.0 times the number of moles of the first metal element, and the number of moles of the third metal element is 0.5 to 1.0 times the number of moles of the first metal element. This makes it possible to reduce variations in discharge voltage when the electrode is used as a discharge electrode.

[0009] (2) In the electrode of the above embodiment, the alloy may contain four to six metal elements. With this configuration, the alloy forming the electrode contains four to six metal elements, so that the top three metal elements with the largest molar ratios are each contained in an appropriate molar ratio. This can further reduce the variation in discharge voltage.

[0010] (3) In the electrode of the above embodiment, the first metal element, the second metal element, and the third metal element may each be any one of titanium, zirconium, niobium, hafnium, tantalum, vanadium, chromium, and iron. According to this configuration, among the metal elements contained in the alloy forming the electrode, the top three metal elements with the largest molar numbers are transition metal elements with thermal conductivities of 100 W / (m·K) or less and melting points of 1500°C or higher. This results in a relatively low thermal conductivity of the alloy, which makes it easier for the tip of the electrode to reach a high temperature during discharge, thereby stabilizing discharge and reducing variations in discharge voltage. Furthermore, because the melting point of the alloy is relatively high, even if the tip of the electrode reaches a high temperature during discharge, local melting and scattering of the alloy can be suppressed. This reduces variations in discharge voltage.

[0011] (4) In the electrode of the above embodiment, any one of the first metal element, the second metal element, and the third metal element may be titanium, niobium, or hafnium. According to this configuration, among the metal elements contained in the alloy forming the electrode, any one of the top three metal elements with the largest number of moles is titanium, niobium, or hafnium, which has excellent corrosion resistance. This makes it difficult for the discharge surface to become rough, thereby further reducing the variation in discharge voltage.

[0012] (5) In the electrode of the above embodiment, the metal element may be any one of titanium, zirconium, niobium, hafnium, tantalum, vanadium, and chromium. According to this configuration, the metal element contained in the alloy forming the electrode is a transition metal element with a thermal conductivity of 100 W / (m·K) or less and a melting point of 1600°C or higher. This relatively low thermal conductivity of the alloy makes it easier for the tip of the electrode to reach a high temperature during discharge, stabilizing discharge and reducing the variation in discharge voltage. Furthermore, because the melting point of the alloy is relatively high, even if the tip of the electrode reaches a high temperature during discharge, localized melting and scattering can be suppressed. This reduces the variation in discharge voltage.

[0013] (6) In the electrode of the above embodiment, the alloy may have a single-phase crystalline phase. According to this configuration, the alloy has a single-phase crystalline phase. This makes it easier for the discharge surface to wear evenly when the electrode is used for discharge. Therefore, it is possible to further reduce the variation in discharge voltage.

[0014] (7) In the electrode of the above embodiment, the alloy may have multiple crystalline phases with different compositions, and the multiple crystalline phases may have the same crystalline structure. According to this configuration, the alloy has multiple crystalline phases with different compositions but the same crystalline structure. This makes it easier for the discharge surface to wear evenly. Therefore, it is possible to further reduce the variation in discharge voltage.

[0015] The present invention can be realized in various forms, for example, in the form of an apparatus including an electrode, a method for manufacturing an electrode and an apparatus including an electrode, a method for controlling an apparatus including an electrode, an apparatus for manufacturing an electrode, a computer program for causing an apparatus for manufacturing an electrode to manufacture an electrode, or the like. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is an external view of a spark plug equipped with an electrode according to a first embodiment. [Figure 2] FIG. 10 is a diagram illustrating the results of a first evaluation test on electrodes. [Figure 3] FIG. 10 is a diagram illustrating a test method for a first evaluation test. [Figure 4] FIG. 10 is a diagram illustrating a first result of a second evaluation test on an electrode. [Figure 5] FIG. 10 is a diagram illustrating a second result of a second evaluation test on electrodes. DETAILED DESCRIPTION OF THE INVENTION

[0017] First Embodiment 1 is an external view of a spark plug equipped with an electrode according to a first embodiment. The spark plug 10 of this embodiment is attached to, for example, an internal combustion engine (not shown) and generates a discharge to combust fuel supplied into a cylinder. The spark plug 10 of this embodiment includes an insulator 11, an electrode 1, a metallic shell 12, and a ground electrode 13.

[0018] The insulator 11 is a substantially cylindrical member formed to extend along the central axis C10 of the spark plug 10. The insulator 11 is made of a material having excellent insulating properties, heat resistance, and thermal conductivity, such as alumina (Al2O3). A terminal 14 is provided at one end 11a of the insulator 11. An electrode 1 electrically connected to the terminal 14 is provided at the other end 11b of the insulator 11.

[0019] The electrode 1 is an alloy containing multiple metal elements. The electrode 1 is held by the insulator 11 by being partially inserted into a hole (not shown) formed in the other end 11b of the insulator 11. The tip 1a of the electrode 1 is formed so that the outer diameter becomes smaller as it gets further away from the insulator 11.

[0020] The electrode 1 is made of an alloy containing three to seven metal elements. Regarding the alloy of the electrode 1, the top three metal elements in terms of mole count are designated, in descending order, as the first metal element, the second metal element, and the third metal element. The mole count of the second metal element is 0.8 to 1.0 times the mole count of the first metal element, and the mole count of the third metal element is 0.5 to 1.0 times the mole count of the first metal element. Thus, the alloy of the electrode 1 has relatively large mole percentages for the top three metal elements in terms of mole count, and the mole counts are relatively close to each other. This reduces the variation in the discharge voltage of the electrode 1. The electrode 1 is preferably made of an alloy containing four to six metal elements. In this embodiment, the electrode 1 is made of an alloy containing five metal elements.

[0021] In the alloy of the electrode 1, the first metal element, the second metal element, and the third metal element are each preferably a transition metal element selected from the group consisting of titanium (Ti), zirconium (Zr), niobium (Nb), hafnium (Hf), tantalum (Ta), vanadium (V), chromium (Cr), and iron (Fe). These metals are all transition metal elements with thermal conductivities of 100 W / (m·K) or less and melting points of 1500°C or higher. Furthermore, it is more preferable that any one of the first metal element, the second metal element, and the third metal element is titanium, niobium, or hafnium. Furthermore, it is more preferable that the metal element contained in the alloy is one of titanium, zirconium, niobium, hafnium, tantalum, vanadium, and chromium. The alloy of the electrode 1 of this embodiment contains 20 mol% each of titanium, niobium, hafnium, zirconium, and tantalum. The metal elements contained in the alloy of electrode 1 are identified using an electron probe microanalyzer (EPMA) or a scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The alloy of electrode 1 may contain a small amount of yttrium. In addition to the five metal elements, the alloy of electrode 1 may also contain impurities.

[0022] The alloy of electrode 1 of this embodiment has a single crystalline phase. The crystalline phase possessed by the alloy of electrode 1 of this embodiment has a body-centered cubic (BCC) structure of the same composition. The crystalline structure of the crystalline phase possessed by the alloy of electrode 1 is identified by a combination of visual observation of the cross section in an SEM image and X-ray diffraction (XRD) using an X-ray diffractometer. Note that in this embodiment, "the alloy has a single crystalline phase" also includes cases where, in addition to a single crystalline phase, trace components such as the above-mentioned yttrium and impurities are contained.

[0023] The metallic shell 12 is a generally cylindrical metal member formed to extend along the central axis C10 of the spark plug 10. The metallic shell 12 is formed of a conductive metal such as low-carbon steel or a metallic material primarily composed of iron. The metallic shell 12 is provided so as to partially cover the insulator 11. The metallic shell 12 has a seat portion 12a that protrudes radially outward from the metallic shell 12, and a body portion 12c having a thread groove 12b formed on its outer periphery. When the spark plug 10 is mounted in an internal combustion engine, the thread groove 12b of the body portion 12c is fitted into a threaded hole formed in the internal combustion engine, whereby an annular gasket (not shown) is sandwiched between the seat portion 12a and the body portion 12c, ensuring airtightness of the threaded hole of the internal combustion engine.

[0024] The ground electrode 13 is a metal member joined to the body portion 12c of the metallic shell 12 on the side opposite to the seat portion 12a. The ground electrode 13 is formed of a metal material such as a Ni-based alloy containing nickel as a main component. Examples of alloying elements added to the Ni-based alloy of the ground electrode 13 include manganese, chromium, and aluminum. The ground electrode 13 has a shape that is bent into a substantially L-shape, and a tip portion 13a is positioned to face the electrode 1.

[0025] Next, a method for manufacturing the electrode 1 will be described. In manufacturing the electrode 1, first, elemental metals of titanium, niobium, hafnium, zirconium, and tantalum are placed in a copper container so that the number of moles is the same. The five types of elemental metals placed in the copper container are arc-melted in an argon atmosphere to produce an ingot of a metal represented by the composition formula ZrNbTaTiHf. The produced metal ingot is processed into the shape of the electrode 1 to produce the electrode 1 of the spark plug 10. Note that the method for manufacturing the alloy of the electrode 1 is not limited to this. It may also be high-frequency melting, the Bridgman method, metal additive manufacturing, powder sintering, mechanical alloying, or the like.

[0026] Next, we will explain the evaluation test of the electrodes. In this evaluation test, we produced multiple electrode samples that differed in at least one of the number and type of metal elements contained in alloys that can be used for the electrodes, and performed two types of evaluations regarding the variation in discharge voltage.

[0027] Figure 2 is a diagram illustrating the results of the first evaluation test for electrodes. In the first evaluation test, the discharge voltage was measured multiple times for each of the 13 types of samples shown in Figure 2, which differ in the number and type of metal elements, when used as a discharge electrode, and the calculated variations in discharge voltage were compared.

[0028] Each of the 13 types of samples shown in FIG. 2 was manufactured by a method similar to the manufacturing method of the electrode 1 of the first embodiment. Specifically, for each of the 13 types of samples, the elemental metals of the multiple metal elements shown in FIG. 2 were first placed in a copper container so as to have the mole percentages shown in FIG. 2. The multiple elemental metals placed in the copper container were arc-melted in an argon atmosphere to produce metal ingots that would become each of the 13 types of samples. The manufactured metal ingots were then machined into shapes to be used in the discharge tests described below.

[0029] Figure 2 shows "Rm," which is the ratio of the number of moles of other metal elements to the number of moles of the first metal element, for each of the 13 samples used in the first evaluation test, where the top three metal elements by mole number are, in descending order, the first metal element, the second metal element, and the third metal element. That is, "Rm" shown in Figure 2 is the value obtained by dividing the mole percentage of each metal element shown in the "Molar percentage of metal elements contained in samples" in Figure 2 by the mole percentage of the first metal element for each sample. For example, in Sample 2, the first metal element is vanadium (43.0 mol%), the second metal element is cobalt (30.0 mol%), and the third metal element is aluminum (27.0 mol%). 2, the molar percentage of cobalt is 30.0 mol% divided by the molar percentage of vanadium, 43.0 mol%, which is 0.70, and the molar percentage of aluminum is 27.0 mol% divided by the molar percentage of vanadium, 43.0 mol%, which is 0.63. Note that when the molar percentages of multiple metal elements contained in a sample are the same, as in Sample 1, any one of the first metal element, second metal element, and third metal element may be selected.

[0030] FIG. 3 is a diagram illustrating the test method of the first evaluation test. In the first evaluation test, a discharge test was performed using the evaluation device Ex1 shown in FIG. 3 to calculate the variation in discharge voltage for each sample. The evaluation device Ex1 includes a chamber Ch and a power supply unit Ps. The chamber Ch can accommodate a sample Sp and a counter electrode Ce therein. The sample Sp and the counter electrode Ce in the chamber Ch are arranged so that a gap Gp is ​​1.05 mm. The sample Sp and the counter electrode Ce in the chamber Ch are each connected to a power supply unit Ps, and discharge occurs using electricity supplied by the power supply unit Ps. In the discharge test, the chamber Ch to which the sample Sp was attached was set under predetermined conditions (nitrogen atmosphere, room temperature), and discharge was performed at a frequency of 100 Hz for one hour, after which the discharge voltage was measured after 1000 discharges. From the measured values ​​of the discharge voltage for 1000 discharges, the variation in discharge voltage "σ" shown in FIG. 2 was calculated. V (unit: V) was calculated.

[0031] Figure 2 shows the calculated σ V The result of the discharge voltage variation judged based on the value of "" is shown as "Judgment". "Judgment" is the result of the calculated discharge voltage variation ("σ V ") are classified into the following symbols S, A, B, C, and D. It is desirable that the variation in discharge voltage of the samples be 1500V or less (i.e., S, A, B, and C are within the acceptable range for "judgment"). S:σ V ≦700V A:700V<σ V ≦900V B:900V<σ V ≦1100V C:1100V<σ V ≦1500V D:1500V<σ V

[0032] As shown in Figure 2, among Samples 1 to 13, Samples 5 to 13 are VBased on this, the "judgment" was S, A, B, or C, and it was confirmed that the variation in discharge voltage was smaller than that of Samples 1 to 4, which were "judgment" D. Each of Samples 5 to 13 is made of an alloy containing 3 to 7 metal elements. If the top three metal elements in terms of mole count are, in descending order, the first metal element, the second metal element, and the third metal element, the mole count of the second metal element is 0.8 to 1.0 times the mole count of the first metal element, and the mole count of the third metal element is 0.5 to 1.0 times the mole count of the first metal element. In this way, the alloys forming each of Samples 5 to 13 have relatively large mole percentages for the top three metal elements in terms of mole count, and the mole counts are relatively close to each other, which is thought to be why the variation in discharge voltage is smaller.

[0033] On the other hand, unlike the alloy of electrode 1 of this embodiment, Sample 1 contains eight metal elements, with the molar percentage of each metal element being relatively small. Although Samples 2 to 4 each contain three metal elements, as shown by "Rm" in FIG. 2 , at least one of the ratio of the number of moles of the second metal element to the number of moles of the first metal element and the ratio of the number of moles of the third metal element to the number of moles of the first metal element does not satisfy the above-mentioned condition. Specifically, in Sample 2, the number of moles of the second metal element (cobalt) is 0.7 times the number of moles of the first metal element (vanadium), and in Sample 3, the number of moles of the third metal element (aluminum) is 0.38 times the number of moles of the first metal element (vanadium). Furthermore, in Sample 4, the number of moles of each of the second metal element (cobalt) and the third metal element (aluminum) is 0.125 times the number of moles of the first metal element (vanadium). Thus, if the ratio of the number of moles of the second and third metal elements to the number of moles of the first metal element is small, it is difficult to form a uniform discharge surface, and the discharge surface is likely to become rough, which results in a large variation in discharge voltage after use as a discharge electrode for a certain period of time.

[0034] Among Samples 5 to 13, Samples 7 to 13 were "judged" as S, A, or B, and it was confirmed that the variation in discharge voltage was even smaller than that of Samples 5 and 6, which were "judged" as C. Each of Samples 7 to 13 is an alloy containing four or five metal elements, and therefore the top three metal elements with the largest mole counts are each contained in appropriate mole numbers. This is thought to have resulted in the smaller variation in discharge voltage for each of Samples 7 to 13. On the other hand, Sample 5 contains seven metal elements, and therefore the mole numbers of the top three metal elements with the largest mole counts (e.g., titanium, chromium, and molybdenum) are smaller than those of Samples 7 to 13. Furthermore, Sample 6 contains only three metal elements, and therefore the mole numbers of the metal elements are larger than those of Samples 7 to 13. This is thought to have resulted in Samples 5 and 6 having larger variation in discharge voltage than Samples 7 to 13.

[0035] Among Samples 7 to 13, Samples 8 to 13 were rated S or A, confirming that the variation in discharge voltage was even smaller than that of Sample 7, which was rated B. In each of Samples 8 to 13, the first metal element, the second metal element, and the third metal element were titanium, zirconium, niobium, hafnium, tantalum, vanadium, chromium, and iron (for example, in Sample 8, the first metal element was titanium, the second metal element was zirconium, and the third metal element was vanadium). Titanium, zirconium, niobium, hafnium, tantalum, vanadium, chromium, and iron are transition metal elements each with a thermal conductivity of 100 W / (m·K) or less and a melting point of 1500°C or more. The alloys of Samples 8 to 13 are mainly formed by a combination of metal elements with such relatively low thermal conductivities and relatively high melting points. This results in a relatively low thermal conductivity of the alloy, which makes it easier for the tip of the electrode to reach a high temperature during discharge, stabilizing the discharge and reducing the variation in discharge voltage. Furthermore, because the melting point of the alloy is relatively high, even if the tip of the electrode reaches a high temperature during discharge, the alloy is prevented from melting locally and scattering. This reduces the variation in discharge voltage. Note that Sample 7 contains aluminum, which has a relatively low melting point (melting point: 660°C), so when the tip of the electrode reaches a high temperature during discharge, the sample melts locally and scatters. This is thought to be why the variation in discharge voltage was greater than that of Samples 8 to 13.

[0036] Among Samples 8 to 13, Samples 12 and 13 received an S rating, demonstrating even smaller variations in discharge voltage compared to Samples 8 to 11, which received an A rating. In Samples 12 and 13, the first, second, and third metal elements are titanium, niobium, or hafnium, each of which has excellent corrosion resistance. Furthermore, in Samples 12 and 13, the metal elements contained in the alloy are titanium, zirconium, niobium, hafnium, tantalum, vanadium, or chromium. This further reduces the likelihood of the discharge surface becoming rough, thereby reducing variations in discharge voltage compared to Samples 8 to 11. Samples 8 to 10 contain copper (thermal conductivity: 400 W / (m·K)), which has relatively high thermal conductivity, making the tip of the electrode less likely to heat up during discharge, resulting in unstable discharge. Sample 11 contains aluminum, which has a relatively low melting point, which, as mentioned above, makes the sample prone to localized melting and scattering. It is believed that these factors caused the variations in discharge voltage of Samples 8 to 11 to be greater than those of Samples 12 and 13.

[0037] Figure 4 is a diagram illustrating the first results of the second evaluation test on the electrodes. Figure 5 is a diagram illustrating the second results of the second evaluation test on the electrodes. In the second evaluation test, the changes in crystal structure and the magnitude of the variation in discharge voltage due to the presence or absence of heat treatment were evaluated for Samples 11 and 13, out of the 13 types of samples tested in the first evaluation test. In the second evaluation test, samples with heat treatment were prepared by arc-melting multiple types of metal elements and then lowering the temperature by holding the melt at 200°C for 2 hours. On the other hand, samples without heat treatment were prepared by lowering the temperature without holding it at a specific temperature. The crystal structure of the samples was confirmed by a combination of visual observation of the cross section in an SEM image and XRD using an X-ray diffractometer, as with the alloy of Electrode 1. The "σ" which indicates the variation in discharge voltage shown in Figures 4 and 5 is V" was calculated by the same method as in the first evaluation test. "Judgment" showing the judgment results shown in Figures 4 and 5 was judged by the same method as in the first evaluation test.

[0038] Figure 4 shows the results of evaluating the effect of heat treatment on Sample 13. As shown in Figure 4, multiple types of crystal structures (BCC structure, HCP structure) were confirmed in Sample 13 with heat treatment. On the other hand, since only the BCC structure was confirmed in Sample 13 without heat treatment, it is considered that Sample 13 without heat treatment has a single crystal phase. The degree of variation in discharge voltage, σ V In the "with heat treatment" test, Sample 13 had a larger discharge voltage than Sample 13 without heat treatment, which revealed that the variation in discharge voltage increases when the alloy is subjected to heat treatment, in which the temperature is maintained above a certain level, when it is produced.

[0039] Figure 5 shows the results of evaluating the effect of heat treatment on Sample 11. As shown in Figure 5, multiple types of crystal structures (BCC structure, HCP structure) were confirmed in Sample 11 with heat treatment. On the other hand, only one type of crystal structure (BCC#1 structure, BCC#2 structure) was confirmed in Sample 11 without heat treatment, although the composition was different. The degree of variation in discharge voltage was greater in Sample 11 with heat treatment than in Sample 11 without heat treatment, which revealed that the variation in discharge voltage increases when the alloy is produced through heat treatment, in which the temperature is maintained above a certain level.

[0040] According to the electrode 1 of the present embodiment described above, among the three to seven metal elements contained in the alloy forming the electrode 1, the top three metal elements by mole number are, in descending order, the first metal element, the second metal element, and the third metal element. The number of moles of the second metal element is 0.8 to 1.0 times the number of moles of the first metal element, and the number of moles of the third metal element is 0.5 to 1.0 times the number of moles of the first metal element. This reduces the variation in discharge voltage in the electrode 1.

[0041] Furthermore, the electrode 1 of this embodiment can reduce variations in discharge voltage, thereby increasing the degree of freedom in designing the gap size and the like in the design of the spark plug 10 including the electrode 1. This improves the productivity of the spark plug 10 including the electrode 1.

[0042] Furthermore, according to the electrode 1 of this embodiment, the alloy forming the electrode 1 contains four to six metal elements, which means that the top three metal elements with the largest molar ratios are each contained in an appropriate molar ratio, thereby further reducing the variation in discharge voltage.

[0043] Furthermore, according to the electrode 1 of this embodiment, among the metal elements contained in the alloy forming the electrode 1, the top three metal elements with the largest number of moles are either titanium, zirconium, niobium, hafnium, tantalum, vanadium, chromium, or iron. Titanium, zirconium, niobium, hafnium, tantalum, vanadium, chromium, and iron are transition metal elements with thermal conductivities of 100 W / (m·K) or less and melting points of 1500°C or higher. This relatively low thermal conductivity of the alloy makes it easier for the tip of the electrode 1 to reach high temperatures during discharge, stabilizing discharge and reducing variations in discharge voltage. Furthermore, because the melting point of the alloy is relatively high, even if the tip of the electrode 1 reaches high temperatures during discharge, localized melting and scattering of the alloy can be suppressed. This reduces variations in discharge voltage.

[0044] Furthermore, according to the electrode 1 of this embodiment, one of the top three metal elements with the largest number of moles among the metal elements contained in the alloy forming the electrode 1 is titanium, niobium, or hafnium, which has excellent corrosion resistance. This makes it difficult for the discharge surface to become rough, thereby further reducing the variation in discharge voltage.

[0045] Furthermore, according to the electrode 1 of this embodiment, the metal element contained in the alloy forming the electrode 1 is any one of titanium, zirconium, niobium, hafnium, tantalum, vanadium, and chromium. As a result, the tip of the electrode 1 is likely to reach a high temperature during discharge, stabilizing the discharge and reducing the variation in discharge voltage. Furthermore, even if the tip of the electrode 1 reaches a high temperature during discharge, it is possible to prevent local melting and scattering. This reduces the variation in discharge voltage.

[0046] Furthermore, according to the electrode 1 of this embodiment, the alloy has a single crystal phase, which makes it easier for the discharge surface to wear evenly, thereby reducing variations in discharge voltage.

[0047] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0048] [Variation 1] In the above embodiment, the electrode 1 is made of an alloy containing five types of metal elements. The number of types of metal elements contained in the alloy of the electrode 1 is not limited to this. It is sufficient that the alloy contains three or more and seven or less types of metal elements.

[0049] [Variation 2] In the above-described embodiment, the metal elements contained in the alloy are titanium, niobium, hafnium, zirconium, and tantalum, and the top three metal elements by mole are titanium, niobium, and hafnium. The top three metal elements by mole, the first metal element, the second metal element, and the third metal element, are preferably, but not limited to, titanium, zirconium, niobium, hafnium, tantalum, vanadium, chromium, and iron. The number of moles of the second metal element may be 0.8 to 1.0 times the number of moles of the first metal element, and the number of moles of the third metal element may be 0.5 to 1.0 times the number of moles of the first metal element.

[0050] [Variation 3] In the above-described embodiment, the alloy of electrode 1 has a single crystalline phase. However, as explained in FIG. 5 , the alloy of electrode 1 may have multiple crystalline phases, and these multiple crystalline phases may have different compositions but the same crystalline structure. Furthermore, the multiple crystalline phases of the electrode alloy may have different crystalline structures. However, if the electrode alloy has multiple crystalline phases with different compositions and the multiple crystalline phases have the same crystalline structure, the discharge surface wears evenly, suppressing localized wear and reducing the variation in discharge voltage.

[0051] [Variation 4] In the above-described embodiment, the electrodes are provided in a spark plug. However, the application of the electrodes is not limited to this. For example, the electrodes may be applied to a plasma generating device, a discharge device, or the like.

[0052] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0053] <Application example 1> An electrode, It is made of an alloy containing 3 to 7 metal elements, Among the metal elements contained in the alloy, the top three metal elements in terms of mole number are designated as a first metal element, a second metal element, and a third metal element in descending order. the number of moles of the second metal element is 0.8 times or more and 1.0 times or less the number of moles of the first metal element, The number of moles of the third metal element is 0.5 times or more and 1.0 times or less the number of moles of the first metal element. electrode. <Application example 2> The electrode according to Application Example 1, The alloy is characterized by containing four or more and six or less metal elements. electrode. <Application example 3> The electrode according to Application Example 1 or Application Example 2, Each of the first metal element, the second metal element, and the third metal element is any one of titanium, zirconium, niobium, hafnium, tantalum, vanadium, chromium, and iron. electrode. <Application Example 4> The electrode according to any one of Application Examples 1 to 3, Any one of the first metal element, the second metal element, and the third metal element is titanium, niobium, or hafnium. electrode. <Application example 5> The electrode according to any one of Application Examples 1 to 4, The metal element is any one of titanium, zirconium, niobium, hafnium, tantalum, vanadium, and chromium. electrode. <Application Example 6> The electrode according to any one of Application Examples 1 to 5, The alloy is characterized in that the crystalline phase is a single phase. electrode. <Application Example 7> The electrode according to any one of Application Examples 1 to 6, The alloy has a plurality of crystalline phases with different compositions, The plurality of crystalline phases have the same crystalline structure. electrode. [Explanation of symbols]

[0054] 1...Electrode

Claims

1. An electrode, It is made of an alloy containing 3 to 7 metal elements, Among the metal elements contained in the alloy, the top three metal elements in terms of mole number are designated as a first metal element, a second metal element, and a third metal element in descending order. the number of moles of the second metal element is 0.8 times or more and 1.0 times or less the number of moles of the first metal element, The number of moles of the third metal element is 0.5 times or more and 1.0 times or less the number of moles of the first metal element. electrode.

2. 10. The electrode of claim 1, The alloy is characterized by containing four or more and six or less metal elements. electrode.

3. 3. The electrode of claim 2, Each of the first metal element, the second metal element, and the third metal element is any one of titanium, zirconium, niobium, hafnium, tantalum, vanadium, chromium, and iron. electrode.

4. 4. The electrode according to claim 2 or claim 3, Any one of the first metal element, the second metal element, and the third metal element is titanium, niobium, or hafnium. electrode.

5. 3. The electrode according to claim 1 or claim 2, The metal element is any one of titanium, zirconium, niobium, hafnium, tantalum, vanadium, and chromium. electrode.

6. 3. The electrode according to claim 1 or claim 2, The alloy is characterized in that the crystalline phase is a single phase. electrode.

7. 3. The electrode according to claim 1 or claim 2, The alloy has a plurality of crystalline phases with different compositions, The plurality of crystalline phases have the same crystalline structure. electrode.

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