Composite line and robot

Abstract

The composite wire is formed by bundling a plurality of wire rods including a first metal wire (10) and a second metal wire (20). The first metal wire (10) has a tungsten wire containing tungsten as a main component, and an oxide film covering the surface of the tungsten wire. The second metal wire (20) contains copper as a main component. The oxide film has an average thickness of 2 nm or more and 50 nm or less. The ratio of the surface roughness Ra of the first metal wire (10) to the wire diameter of the first metal wire (10) is 0.0049 or less.

Description

Technical Field

[0001] The present invention relates to a composite line and a robot. Background Art

[0002] Patent Document 1 discloses a stranded wire formed by twisting a plurality of metal wires, wherein a metal having a lower standard electrode potential than that of the metal wires is interposed between gaps between the metal wires.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 3152714 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] In composite wires such as stranded wires, when wires made of different metals are bundled, corrosion is likely to occur due to contact between the dissimilar metals.

[0008] Therefore, an object of the present invention is to provide a composite wire capable of suppressing corrosion even when wires made of different metals are bundled.

[0009] Means for solving problems

[0010] A composite wire according to one embodiment of the present invention is a composite wire formed by bundling a plurality of wires including a first metal wire and a second metal wire. The first metal wire includes a tungsten wire containing tungsten as a main component and an oxide film covering a surface of the tungsten wire. The second metal wire includes copper as a main component. The average thickness of the oxide film is from 2 nm to 50 nm. The ratio of the surface roughness Ra of the first metal wire to the wire diameter of the first metal wire is 0.0049 or less.

[0011] A robot according to one embodiment of the present invention includes the above-mentioned composite wire as an electric wire connected to a driving unit.

[0012] Effects of the Invention

[0013] According to the present invention, even when wires made of different metals are bundled, corrosion can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram showing the appearance of a tungsten wire according to the embodiment.

[0015] Figure 2 It is a schematic diagram showing a cross section of a stranded wire according to the embodiment.

[0016] Figure 3Schematic diagram showing a cross section of a first metal wire according to an embodiment.

[0017] Figure 4A 1 is an SEM image of a cross section of a sample of the first metal wire according to the embodiment.

[0018] Figure 4B is Figure 4A Images of the oxide film were extracted from the SEM images.

[0019] Figure 5 This is a flowchart showing a method for producing a tungsten wire according to an embodiment.

[0020] Figure 6 This is a flow chart showing the corrosion test method.

[0021] Figure 7 This is a graph showing the relationship between the ratio of the surface roughness Ra of the first metal wire to the wire diameter of the first metal wire and the corrosion loss in the corrosion test of each sample.

[0022] Figure 8 This is a diagram showing a robot as an example of a product using the stranded wire according to the embodiment. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present invention will be described in detail using the accompanying drawings. In addition, the embodiments described below each represent a specific example of the present invention. Therefore, the numerical values, shapes, materials, constituent elements, configurations of constituent elements, connection methods, steps, and the order of steps shown in the following embodiments are examples and are not intended to limit the present invention. Therefore, constituent elements in the following embodiments that are not described in the independent claims are described as arbitrary constituent elements.

[0024] In addition, each figure is a schematic diagram and may not be strictly illustrated. Therefore, for example, the scales in each figure may not be consistent. In addition, in each figure, the same reference numerals are used for substantially the same structure, and repeated descriptions are omitted or simplified.

[0025] In addition, in this specification, terms indicating the relationship between elements, terms indicating the shape of elements such as circles, and numerical ranges do not express only strict meanings, but also include substantially equivalent ranges, such as expressions with differences of several percent.

[0026] (Implementation Method)

[0027] [Twisted wire]

[0028] First, use Figures 1 to 3 The twisted wire according to the embodiment will be described. Figure 1It is a schematic diagram showing the appearance of the stranded wire 1 according to the present embodiment. Figure 2 It is a schematic diagram showing a cross section of the stranded wire 1 according to the present embodiment. Figure 3 Schematic diagram showing a cross section of the first metal wire 10 of the stranded wire 1 of this embodiment. Figure 1 and Figure 2 In FIG, the internal structure of the oxide film 12 of the first metal wire 10 is omitted. Figure 2 , a cross section of the strand 1 is shown when it is cut in a direction perpendicular to the axial direction of the strand 1 (the direction in which the strand 1 extends). Figure 3 , a cross section of the first metal wire 10 is shown when it is cut in a direction perpendicular to the wire axis direction of the first metal wire 10 (the direction in which the first metal wire 10 extends). Figure 3 In FIG. 1 , the thickness of the oxide film 12 is exaggerated.

[0029] Figure 1 and Figure 2 The stranded wire 1 shown is an example of a composite wire formed by bundling a plurality of wires. Figure 1 As shown, the stranded wire 1 is a metal strand formed by twisting together multiple wires. The stranded wire 1 is stored, for example, by being wound around a bobbin, also known as a bobbin, reel, drum, or drum. The storage method for the stranded wire 1 is not particularly limited; however, the stranded wire 1 is stored in a manner that prevents excessive bending. The total length of the stranded wire 1 can range from approximately cm to m, or even km.

[0030] The stranded wire 1 is used, for example, as an electrical wire. As described later, the stranded wire 1 uses a first metal wire 10 comprising a tungsten wire 11 as a wire material, thereby achieving a thinner diameter and / or higher strength compared to a stranded wire using only copper wire as a wire material. The application of the stranded wire 1 as an electrical wire is not particularly limited. For example, the stranded wire 1 is used as an electrical wire connected to a robot's drive unit, utilizing its thin diameter and / or high strength.

[0031] like Figure 2 As shown, the plurality of wires constituting the stranded wire 1 include a first metal wire 10 and a second metal wire 20. Figure 2 In the example shown, the plurality of wires consists of one first metal wire 10 and six second metal wires 20, and the strand 1 is a mixed strand formed by twisting these wires. In the strand 1, the first metal wire 10 and the second metal wire 20 are in contact. The first metal wire 10 is a metal wire primarily composed of tungsten and has a higher tensile strength than the second metal wire 20, as will be described in detail later. The second metal wire 20 is a metal wire primarily composed of copper and has a higher electrical conductivity than the first metal wire 10.

[0032] exist Figure 2In the example shown, the stranded wire 1 is composed of seven stranded wires twisted together from seven single wires. It should be noted that the number of wires comprising the stranded wire 1 is not particularly limited, and the stranded wire 1 may be composed of various numbers of wires, depending on the target strength and wire diameter. For example, the stranded wire 1 may be three stranded wires twisted together from three wires, 19 stranded wires twisted together from 19 wires, or 37 stranded wires twisted together from 37 wires. Furthermore, the stranded wire 1 is not limited to a stranded wire twisted together from single wires; it may also be a stranded wire formed by further twisting single wires, such as a 7x7 stranded wire twisted together from seven strands of seven. Examples of such a stranded wire 1 include, but are not limited to, 7 x 19 stranded wires (19 stranded wires twisted together into 7 strands), 6 x 7 stranded wires (7 stranded wires twisted together into 6 strands), or 3 x 7 stranded wires (7 stranded wires twisted together into 3 strands). Furthermore, the number of wires in the stranded wires in this case may not all be the same, and strands made by twisting different numbers of wires may also be used. Furthermore, in the illustrated example, all wires (the first metal wire 10 and the plurality of second metal wires 20) have the same diameter, but a combination of wires of different diameters may also be used in the stranded wire 1.

[0033] exist Figure 2 In the example shown, a single first metal wire 10 serves as the core wire located at the radial center of the stranded wire 1. In the stranded wire 1, a plurality of second metal wires 20 radially surround the first metal wire 10, serving as the core wire. Specifically, the stranded wire 1 is formed by winding six second metal wires 20 around the first metal wire 10. By winding the second metal wires 20 around the relatively strong first metal wire 10, the stranded wire 1 is more resistant to bending.

[0034] It should be noted that the stranded wire 1 only needs to include at least one first metal wire 10 and at least one second metal wire 20 as a plurality of wires, and there is no particular limitation on the number of each of the first metal wire 10 and the second metal wire 20 included in the stranded wire 1. For example, the stranded wire 1 may be composed of at least one first metal wire 10 and at least one second metal wire 20. To improve conductivity and resistance to bending, the number of second metal wires 20 may be greater than the number of first metal wires 10. Furthermore, there are no particular limitations on the positions of the first metal wire 10 and the second metal wire 20 in the stranded wire 1. In other words, there are no restrictions on the arrangement in which the plurality of wires including the first metal wire 10 and the second metal wire 20 are twisted. For example, the axial core wire may be the second metal wire 20, and the wires surrounding the axial core wire may include the first metal wire 10.

[0035] Wire diameter of strand 1 For example, it is 500 μm or less, but it is not limited thereto. The diameter of the stranded wire 1 may be 400 μm or less, 300 μm or less, 200 μm or less, 150 μm or less, or 100 μm or less. It is the diameter of the circumscribed circle of the plurality of wires constituting the strand 1 in the cross section of the strand 1. Figure 2 In the case of 7 strands shown, the wire diameter The length of the strand 1 in the radial direction at the position where the three wires are arranged in the radial direction is calculated. For example, the length of the strand 1 in the radial direction at the position where the three wires are arranged in the radial direction (i.e., the diameter of the circumscribed circle of the strand 1) is measured with a vernier caliper or the like at a predetermined number of arbitrary positions (e.g., two or more) and the measured values ​​are averaged to calculate the wire diameter.

[0036] like Figure 3 As shown, the first metal wire 10 includes a tungsten wire 11 containing tungsten as a main component and an oxide film 12 provided on the surface of the tungsten wire 11 .

[0037] The tensile strength of the first metal wire 10 is, for example, 3500 MPa or greater, but is not limited thereto. The tensile strength of the first metal wire 10 may be 4000 MPa or greater, 4500 MPa or greater, or 5000 MPa or greater. For example, a first metal wire 10 having a tensile strength of 5500 MPa or greater is also achievable.

[0038] The tensile strength of a wire such as the first metal wire 10 is obtained by dividing the breaking strength (stress at break) of the wire by the cross-sectional area of ​​the wire. The tensile strength is measured, for example, in accordance with Japanese Industrial Standard JIS H4460-8.

[0039] The higher the tensile strength of the first metal wire 10, the higher the tensile strength of the strand 1, which contributes to increasing the strength of the strand 1. As a result, the strand 1 can be reduced in diameter while maintaining strength, thereby achieving a reduced diameter and / or increased strength.

[0040] The wire diameter of the first metal wire 10 For example, it is 100 μm or less, but it is not limited thereto. It can be less than 80 μm, less than 60 μm, less than 35 μm, less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm, less than 13 μm, less than 11 μm, less than 10 μm, less than 9 μm, less than 8 μm, less than 7 μm. For example, it is also possible to achieve a wire diameter of The first metal wire 10 is an extremely thin wire of about 5 μm.

[0041] like Figure 3 As shown, wire diameter It is the sum of the diameter of the tungsten wire 11 and twice the average thickness t of the oxide film 12. It should be noted that the average thickness t of the oxide film 12 is sufficiently smaller than the diameter of the tungsten wire 11, so the wire diameter It can be considered to be substantially equal to the diameter of the tungsten wire 11 .

[0042] The surface roughness Ra of the first metal wire 10 is relative to the wire diameter of the first metal wire 10. The ratio is 0.049 or less. This effectively suppresses corrosion of the stranded wire 1. Surface roughness Ra is also known as "arithmetic mean roughness." Surface roughness Ra is measured, for example, in accordance with Japanese Industrial Standard JIS B 0601. For example, the surface of the first metal wire 10 is scanned using a laser microscope or the like, and the surface roughness Ra of the first metal wire 10 along the circumferential direction is calculated based on the scanned data using surface roughness Ra measurement software.

[0043] The tungsten wire 11 contains tungsten (W) as its main component. "Main component" means an element whose content is greater than 50 mass%. For example, the tungsten content in the tungsten wire 11 is 90 mass% or greater. The tungsten content in the tungsten wire 11 can be 95 mass% or greater, 99 mass% or greater, 99.9 mass% or greater, or 99.99 mass% or greater. While the tungsten wire 11 is pure tungsten wire, it may contain unavoidable impurities that are inevitably introduced during the manufacturing process.

[0044] Furthermore, the tungsten wire 11 may be composed of an alloy of tungsten and one or more metals other than tungsten. That is, the tungsten wire 11 may be a tungsten alloy wire, which is a tungsten alloy wire. The metal other than tungsten is, for example, rhenium (Re). The rhenium content in the tungsten wire 11 composed of rhenium-tungsten alloy (ReW) is, for example, 0.1 mass% or more and 10 mass% or less, but is not limited to this. For example, the rhenium content may be 1 mass% or more, 3 mass% or more, or even 5 mass% or more.

[0045] A high rhenium content can improve the tensile strength of the tungsten wire 11. On the other hand, if the rhenium content is too high, it becomes difficult to thin the tungsten wire 11 while maintaining a high tensile strength. Specifically, wire breakage is more likely to occur, making long-wire drawing difficult. Reducing the rhenium content to a tungsten content of 90 mass% or higher can improve the workability of the tungsten wire 11. Furthermore, by reducing the content of rare and expensive rhenium, inexpensive mass production of long-wire tungsten wire 11 is possible.

[0046] Alternatively, the metal used for the alloy with tungsten may be osmium (Os), ruthenium (Ru), or iridium (Ir). The content of osmium, ruthenium, or iridium is, for example, the same as the content of rhenium. These conditions also produce the same effects as the rhenium-tungsten alloy. Furthermore, the tungsten wire 11 may be composed of an alloy of tungsten and two or more metals other than tungsten.

[0047] Alternatively, tungsten wire 11 may be doped with potassium (K). The doped potassium exists at the tungsten grain boundaries. The potassium (K) content is, for example, 0.010 mass% or less. Even potassium-doped tungsten wire can achieve a metal wire with a tensile strength higher than that of typical piano wire. This effect is not limited to potassium oxide; oxides of other substances, such as cerium and lanthanum, can also be used. Tungsten wire 11 may also contain rare earth elements.

[0048] Oxide film 12 is an oxide film containing tungsten oxide as its main component. For example, the tungsten oxide contained in oxide film 12 mainly contains WO3. Oxide film 12 may also contain tungsten oxide with a composition other than WO3, such as WO2 or W3O8. Furthermore, as the average thickness t of oxide film 12 increases, the amount of WO2 contained in oxide film 12 tends to increase. The stranded wire 1 is formed by twisting together a first metal wire 10 and a second metal wire 20 composed of different metals. However, the presence of oxide film 12 on first metal wire 10 suppresses corrosion.

[0049] In this embodiment, the oxide film 12 is provided along the circumferential and axial directions of the outer side surface of the tungsten wire 11. For example, the oxide film 12 is provided over the entire outer side surface of the tungsten wire 11. For example, the oxide film 12 is provided with a uniform thickness regardless of the location. It should be noted that "uniform thickness" has a strict meaning, that is, it not only means that the thickness is constant at all locations, but also that the deviation is within a specified range. For example, when the thickness of the oxide film 12 is measured at any 10 points on the first metal wire 10, the deviation of the measured thickness values ​​(the ratio of the deviation to the average value) is less than 30%.

[0050] The average thickness t of the oxide film 12 is measured as follows.

[0051] First, the first metal wire 10 is formed into a cross section perpendicular to the wire axis. The cross section is polished by BIB (Broad Ion Beam) processing. Specifically, the first metal wire 10 is irradiated with an argon ion beam, and the irradiated portion is ion-etched to form a smooth cross section.

[0052] Figure 4A This is a SEM (Scanning Electron Microscope) image of a cross section of the first metal wire 10 according to the present embodiment. Figure 4B is Figure 4AAn image of the oxide film 12 was extracted from the SEM image.

[0053] like Figure 4A As shown in FIG. 1 , in the SEM image, the tungsten crystals constituting the tungsten wire 11 can be observed by the difference in color. Furthermore, it can be seen that an oxide film 12 is formed along the surface of the tungsten wire 11. The oxide film 12 can be observed in a color different from the tungsten crystals constituting the tungsten wire 11, so as shown in FIG. Figure 4B As shown, only the oxide film 12 can be emphasized and extracted.

[0054] The area S of the oxide film 12 appearing in the cross section is measured through image processing. The average thickness t of the oxide film 12 can be calculated by dividing the measured area S by the length L of the outer circumference of the tungsten wire 11. The length L can be calculated from the wire diameter of the tungsten wire 11 by treating the cross section of the tungsten wire 11 as a circle. The average thickness t of the oxide film 12 can also be calculated by averaging the values ​​obtained by measuring the thickness of the oxide film 12 at any plurality of locations (e.g., 10 or more locations) on the first metal wire 10 using an SEM image or the like.

[0055] In this embodiment, the average thickness t of the oxide film 12 is greater than or equal to 2 nm and less than or equal to 50 nm. By ensuring that the average thickness t of the oxide film 12 falls within this range, corrosion of the stranded wire 1 can be effectively suppressed. The average thickness t of the oxide film 12 can be greater than or equal to 50 nm, or can be greater than or equal to 10 nm and less than or equal to 50 nm.

[0056] The second metal wire 20 is a copper wire containing copper (Cu) as a main component. For example, the copper content of the second metal wire 20 is 90 mass% or more. The copper content of the second metal wire 20 can be 95 mass% or more, or 99 mass% or more.

[0057] Alternatively, the second metal wire 20 may be made of an alloy of copper and one or more metals other than copper. Furthermore, the second metal wire 20 may also contain non-metallic elements. Examples of metals and non-metallic elements other than copper include tin (Sn), silver (Ag), silicon (Si), beryllium (Be), iron (Fe), magnesium (Mg), zirconium (Zr), zinc (Zn), chromium (Cr), phosphorus (P), titanium (Ti), aluminum (Al), arsenic (As), and nickel (Ni). The second metal wire 20 can be strengthened by including tin or silver, for example. Alternatively, the second metal wire 20 may be plated with tin, palladium (Pd), or the like.

[0058] Generally, the tensile strength of a copper wire containing copper as a main component is 2000 MPa or less. The stranded wire 1 can achieve higher strength by including the first metal wire 10 as a wire material in addition to the second metal wire 20 .

[0059] [Manufacturing method]

[0060] Next, use Figure 5 A method for manufacturing the stranded wire 1 according to the present embodiment will be described. Figure 5 This is a flowchart showing a method for manufacturing the stranded wire 1 according to the present embodiment.

[0061] First, a tungsten wire 11 having a predetermined wire diameter, tensile strength, and surface roughness Ra and containing tungsten as a main component is prepared ( S10 ).

[0062] For example, first, a tungsten ingot is prepared. Specifically, the tungsten ingot is produced by pressing and sintering tungsten powder. To produce tungsten alloy wire, a mixture of tungsten powder and alloying metal powder is pressed and sintered. To produce doped tungsten wire, doped tungsten powder doped with potassium or other substances is pressed and sintered.

[0063] Next, the prepared ingot is repeatedly subjected to die forging and heating to form a wire of a predetermined diameter (e.g., approximately 3 mm). Heating forms an oxide layer on the wire surface, and lubricants such as carbon are allowed to penetrate the oxide layer, thereby suppressing wire breakage during wire drawing (wire drawing).

[0064] The wire is then drawn (thinned) using a drawing die, such as a single-crystal diamond die or a polycrystalline diamond die. Drawing is performed while heating. This process is repeated. During repeated drawing, the die aperture and heating temperature are adjusted to gradually decrease. This produces a tungsten wire 11 with high tensile strength.

[0065] The surface roughness Ra of the tungsten wire 11 is also adjusted based on the type of wire drawing die used. For example, using a single-crystal diamond die reduces the surface roughness Ra of the tungsten wire 11, while using a polycrystalline diamond die increases the surface roughness Ra of the tungsten wire 11. It should be noted that even if an oxide film 12 is formed on the tungsten wire 11 as described later, the surface roughness Ra remains largely unchanged. Therefore, the surface roughness Ra of the first metal wire 10 can be adjusted by adjusting the surface roughness Ra of the tungsten wire 11.

[0066] Finally, electrolytic polishing is performed to adjust the wire diameter to the desired value. For example, electrolytic polishing can be performed by immersing the tungsten wire 11 and the counter electrode in an electrolyte such as sodium hydroxide solution, generating a potential difference between the tungsten wire 11 and the counter electrode. Alternatively, electrolytic polishing can be omitted.

[0067] Next, in order to remove impurities, moisture and other substances attached during electrolytic polishing at one time, heating is performed in a reducing atmosphere. The heating temperature is, for example, above 600°C and below 1400°C. Thereafter, an oxide film 12 is formed on the surface of the prepared tungsten wire 11 (S20). Thus, the first metal wire 10 is obtained. The oxide film 12 is formed by heating the tungsten wire 11 after wire drawing in an oxidizing atmosphere. By adjusting the inert gas partial pressure in the oxidizing atmosphere, the average thickness t of the oxide film 12 can be controlled. The inert gas is, for example, nitrogen or argon. In addition, by adjusting the heating temperature and heating time, the average thickness t of the oxide film 12 can also be controlled. Specifically, the lower the inert gas partial pressure, the higher the heating temperature, or the longer the heating time, the greater the average thickness t of the oxide film 12. In addition, the heating temperature is, for example, above 200°C and below 1200°C, but is not limited thereto.

[0068] For example, the tungsten wire 11 before heating is electrolytically polished to remove the oxide layer attached to the surface during wire drawing. This can suppress variations in the thickness of the oxide film 12 formed on the surface and form an oxide film 12 with excellent film quality.

[0069] Next, a second metal wire 20 containing copper as its main component, having a predetermined wire diameter and tensile strength, is prepared (S30). For example, industrial copper wire can be used as the second metal wire 20. For example, industrial copper wire having the desired wire diameter and tensile strength is obtained. Step S30 can be performed at any time, as long as it precedes step S40 described below.

[0070] Next, the first metal wire 10 obtained in step S20 and the second metal wire 20 prepared in step S30 are twisted together to form a stranded wire 1 (S40). The stranded wire 1 is formed by twisting together a plurality of wires including at least one first metal wire 10 and at least one second metal wire 20. For example, when the stranded wire 1 is Figure 2 In the case of the seven strands shown, one first metal wire 10 is used as the axial core wire located at the center of the strand 1, and six second metal wires 20 are wound around the axial core wire. The winding direction is not particularly limited and can be either an S twist or a Z twist.

[0071] [Corrosion test]

[0072] Next, a corrosion test conducted to confirm the corrosion suppression effect of the stranded wire 1 will be described.

[0073] Figure 6 Flowchart 1 is a flowchart showing a corrosion test method. In the corrosion test, first, a sample for the corrosion test is prepared, and the prepared sample is immersed in salt water at 35° C. for 2 hours, thereby allowing the salt water to adhere to the sample ( S110 ).

[0074] The corrosion test samples used were made by tightly wrapping a single first metal wire 10 around an industrially available copper stranded wire, made by twisting 10 flexible copper wires. The copper stranded wire used had a wire diameter of 50 μm for the flexible copper wire, a wire diameter of 230 μm for the stranded copper wire, and a tensile strength of 245 MPa. The tensile strength of the stranded copper wire was calculated by dividing the breaking strength by the cross-sectional area of ​​the 10 flexible copper wires. The first metal wire 10 used will be described later.

[0075] Next, the sample with salt water attached is placed in a test tank and dried at 60°C and humidity 20% RH to 30% RH for 4 hours (S120). Then, the dried sample is moistened at 50°C and humidity above 95% RH for 30 minutes (S130). Finally, the moistened sample is rinsed with pure water and ultrasonically cleaned for 30 minutes to obtain a sample after the corrosion test (S140). In this way, in the corrosion test, corrosion is promoted by salt, water and temperature. In addition, since the corroded part is removed by cleaning, the more corroded the sample is, the less weight it has after the corrosion test.

[0076] To evaluate corrosion, the weight of the sample before and after the corrosion test was measured, and the ratio of the sample weight loss due to the corrosion test was calculated as the corrosion loss. Specifically, the corrosion loss = (weight before test - weight after test) / weight before test.

[0077] Next, use Tables 1 to 3 and Figure 7 The results of corrosion tests using samples of the actually produced first metal wire 10 will be described.

[0078] The inventor of this application made a wire diameter Fourteen samples of the first metal wire 10 having different combinations of surface roughness Ra and average thickness t of the oxide film 12 were subjected to the above-mentioned corrosion test. The wire diameter of the first metal wire 10 of each sample was The surface roughness Ra, the average thickness t of the oxide film 12, and the corrosion loss are shown in Table 1. The wire diameter of the first metal wire 10 is measured by adjusting the hole diameter of the wire drawing die and the electrolytic polishing conditions according to the first metal wire 10 used in each sample. The value obtained. In addition, the surface roughness Ra is a value obtained by measuring the surface roughness Ra of the first metal wire 10 obtained by changing the type of wire drawing die in the formation of the tungsten wire 11 according to the first metal wire 10 used in each sample. In addition, the average thickness t of the oxide film 12 is a value obtained by measuring the average thickness t of the oxide film 12 obtained by adjusting the inert gas partial pressure, heating temperature and heating time in the formation of the oxide film 12 according to the first metal wire 10 used in each sample. In addition, the record of "2 to 10 nm" in the average thickness t in Table 1 means that when the oxide film 12 is formed with an average thickness t of about 5 nm as a target, the oxide film 12 is formed with an average thickness t of a value in the range of 2 to 10 nm. In addition, the wire diameter The tensile strength of the first metal wire 10 with a diameter of 20 μm is 3750 MPa. The tensile strength of the first metal wires 10 with a thickness of 30, 33, and 50 μm was 3550 MPa. The samples used in the test were adjusted so that the length of the copper strands used and the length of the first metal wires 10 used were the same.

[0079] In Table 1 shown below, except for the wire diameter of the first metal wire 10 In addition to the surface roughness Ra of the first metal wire 10, the average thickness t of the oxide film 12, and the etching loss, the surface roughness Ra of the first metal wire 10 relative to the wire diameter of the first metal wire 10 is also shown. The ratio (hereinafter sometimes referred to as "Ra / wire diameter ”). In addition, in Table 1, Ra / wire diameter The results of the corrosion loss of each sample are shown in a manner that decreases from the upper side to the lower side.

[0080] [Table 1]

[0081]

[0082] In addition, in Table 2 shown below, according to Ra / wire diameter The results of the corrosion loss of each sample shown in Table 1 are shown for each combination of the average thickness t of the oxide film 12 (row) and the average thickness t of the oxide film 12 (column).

[0083] [Table 2]

[0084]

[0085]

[0086] Figure 7 It shows the Ra / wire diameter of each sample in the corrosion test The relationship between the corrosion loss and the Figure 7In the figure, the horizontal axis represents Ra / wire diameter of the first metal wire 10 of each sample. The vertical axis represents the corrosion loss of each sample. Figure 7 This is a graph that shows Table 1 and Table 2. Figure 7 In the figure, the results of the sample using the first metal wire 10 with an average thickness t of 2 to 10 nm are represented by circular marks, the results of the sample using the first metal wire 10 with an average thickness t of 50 nm are represented by quadrilateral marks, and the results of the sample using the first metal wire 10 with an average thickness t of 90 nm are represented by triangular marks.

[0087] The inventors also conducted the above-mentioned corrosion tests on samples consisting of a copper stranded wire, a tungsten wire 11 that had not been treated to form an oxide film 12, and a sample consisting of a copper stranded wire wound around a tungsten wire 11 that had not been treated to form an oxide film 12. The results are shown in Table 3.

[0088] [Table 3]

[0089] sample Corrosion reduction Copper stranded wire only 0.1％ Tungsten wire only 11 0.0％ Copper stranded wire + tungsten wire 11 1.7％

[0090] As shown in Table 3, corrosion tests showed little corrosion in the copper stranded wire alone and in the tungsten wire 11 alone. However, in the sample wound with the tungsten wire 11 that had not been treated to form the oxide film 12, corrosion was significant, resulting in a significant weight loss. This is because contact between dissimilar metals easily causes corrosion.

[0091] On the other hand, as shown in Tables 1, 2 and Figure 7 As shown, in each sample in which the first metal wire 10 with the oxide film 12 formed on the tungsten wire 11 was wound around the copper strand, corrosion was suppressed in the corrosion test. This is presumably because the oxide film 12 formed on the first metal wire 10 suppressed contact between the tungsten wire 11 and the copper wire.

[0092] In addition, in each sample, Ra / wire diameter was confirmed The smaller the thickness, the smaller the corrosion loss. In addition, among the samples, there is no difference in corrosion loss between the samples with an average thickness t of the oxide film 12 of 2 to 10 nm and 50 nm, and the corrosion loss is smaller than that of the sample with an average thickness t of the oxide film 12 of 90 nm. In particular, when the average thickness t of the oxide film 12 is 2 to 10 nm or 50 nm, and Ra / wire diameter is is 0.0049( Figure 7 For the samples below the single dot chain line extending in the longitudinal direction, the corrosion loss was 1.0% ( Figure 7Significant corrosion suppression was confirmed below the horizontally extending single-dot chain line in FIG. This is presumably because, in addition to the fact that the oxide film 12 prevents contact between the tungsten wire 11 and the copper wire, the surface roughness Ra of the first metal wire 10 and the average thickness t of the oxide film 12 cause changes in the standard electrode potential of the first metal wire 10, reducing the standard electrode potential difference between the first metal wire 10 and the copper stranded wire.

[0093] In addition, in the sample where the average thickness t of the oxide film 12 is 90 nm, even if Ra / wire diameter Even if the Ra / wire diameter is adjusted, no significant corrosion inhibition effect can be confirmed. This is presumably because, if the average thickness t of the oxide film 12 is greater than 90 nm, the standard electrode potential of the first metal wire 10 is unlikely to change even if the surface roughness Ra of the first metal wire 10 changes.

[0094] As can be seen from the above, by setting the average thickness t of the oxide film 12 to be within the range of 2 nm to 50 nm, and by setting Ra / wire diameter When the ratio is set to 0.0049 or less, the corrosion loss of the sample is significantly reduced, and the corrosion of the sample is suppressed.

[0095] It should be noted that the above corrosion test was performed using a sample in which the first metal wire 10 was wound around a copper strand, but it is considered that the same effect as in the above test can be obtained as long as a stranded wire such as the stranded wire 1 includes the first metal wire 10 and the second metal wire 20 as a plurality of wires.

[0096] [Effects, etc.]

[0097] As described above, the stranded wire 1 of this embodiment is a stranded wire formed by bundling a plurality of wires including a first metal wire 10 and a second metal wire 20. The first metal wire 10 includes a tungsten wire 11 containing tungsten as a main component and an oxide film 12 covering the surface of the tungsten wire 11. The second metal wire 20 contains copper as a main component. The average thickness t of the oxide film 12 is greater than or equal to 2 nm and less than or equal to 50 nm. The surface roughness Ra of the first metal wire 10 is greater than or equal to the wire diameter of the first metal wire 10. The ratio is less than 0.0049.

[0098] This can suppress corrosion even when wires made of different metals are twisted and bundled as in the stranded wire 1. Furthermore, by including the first metal wire 10 as a wire in the stranded wire 1, a smaller diameter and / or higher strength can be achieved.

[0099] In addition, for example, the wire diameter of the first metal wire 10 It may be 100 μm or less.

[0100] Therefore, the line diameter When the thickness is small, the specific surface area of ​​the first metal wire 10 increases, so the corrosion suppression effect of the oxide film 12 is more effective. In addition, the strength of the first metal wire 10 can be easily improved.

[0101] In addition, for example, the first metal wire 10 may be located at the radial center of the stranded wire 1 .

[0102] This can improve the strength of the stranded wire 1 in a balanced manner. In addition, since the relatively soft second metal wire 20 is located outside the first metal wire 10, the stranded wire 1 can be made resistant to bending.

[0103] In addition, for example, the stranded wire 1 can also be used as an electric wire.

[0104] Thus, the stranded wire 1 includes the first metal wire 10 as a wire material, thereby enabling reduction in diameter and / or increase in strength of the electric wire, and suppressing corrosion of the electric wire.

[0105] [Example of use]

[0106] Next, an example of a product using the stranded wire 1 according to the above-described present embodiment will be described.

[0107] Figure 8 This is a diagram showing a robot 200 as an example of a product using the stranded wire 1 according to the present embodiment.

[0108] like Figure 8 As shown, the robot 200 includes a drive unit 210, a control unit 220, and a stranded wire 1 as an electric wire connected to the drive unit 210. The robot 200 is, for example, a factory automation robot. Alternatively, the robot 200 may be an autonomous mobile robot or other robot for use other than factory automation.

[0109] In robot 200, strand 1 serves as an electrical wire connected to drive unit 210. Drive unit 210 includes a drive mechanism such as a motor or actuator, and operates based on a control signal from control unit 220. Control signals are transmitted from control unit 220 to drive unit 210 via strand 1, an electrical wire connecting drive unit 210 and control unit 220. In other words, strand 1 is a signal wire for transmitting signals and is connected to drive unit 210.

[0110] The control unit 220 controls the operation of the driving unit 210. The control unit 220 is a control device including a processor or a microcomputer, for example.

[0111] As described above, the stranded wire 1 can achieve a reduced diameter and / or increased strength, while also suppressing corrosion. Therefore, in the robot 200, by using the stranded wire 1 as the electrical wire connected to the drive unit 210, the robot 200 can be made smaller and / or have a higher load tolerance. Furthermore, the stranded wire 1 is less susceptible to corrosion, thereby improving the durability and reliability of the robot 200.

[0112] It should be noted that the stranded wire 1 connected to the driving unit 210 can also be used as an electric wire for supplying power to the driving unit 210. In this way, the robot 200 can be miniaturized and / or subjected to high loads as described above, and durability and reliability can be improved. In the case where the stranded wire 1 is used as an electric wire for supplying power, as in the case of Figure 8 As shown, the stranded wire 1 can be connected to the control unit 220 to supply power to the drive unit 210 via the control unit 220 . The robot 200 can also include the stranded wire 1 as an electric wire connecting another power supply circuit (not shown) or an external power supply to the drive unit 210 .

[0113] Furthermore, the stranded wire 1 can also be used as an electric wire in products other than robots, such as home appliances, analysis devices, and production equipment. This allows products using the stranded wire 1 to be miniaturized and / or have higher load resistance, thereby improving durability and reliability.

[0114] (other)

[0115] As mentioned above, although the composite wire of the present invention has been described based on the above-mentioned embodiment, the present invention is not limited to the above-mentioned embodiment.

[0116] For example, in the above embodiment, a stranded wire 1 is described as an example of a composite wire. However, the composite wire of the present invention is not limited to a stranded wire. The composite wire of the present invention is not particularly limited as long as it is a composite wire composed of a plurality of wires including a first metal wire 10 and a second metal wire 20, which are assembled and bundled. For example, the composite wire of the present invention can be bundled by coating, by using a binding material, or by using an insulating coating. By including the first metal wire 10 and the second metal wire 20 among the plurality of wires constituting the composite wire, corrosion can be suppressed even when wires composed of different metals are bundled.

[0117] In addition, the present invention also includes methods obtained by implementing various modifications thought of by those skilled in the art to each embodiment and its modifications, and methods achieved by arbitrarily combining the constituent elements and functions in each embodiment and its modifications without departing from the main purpose of the present invention.

[0118] Hereinafter, examples of the composite wire and the robot according to the present invention described based on the above-mentioned embodiment will be described. The stranded wire and the robot according to the present invention are not limited to the following examples.

[0119] For example, a composite wire according to a first embodiment of the present invention is a composite wire formed by bundling a plurality of wires including a first metal wire and a second metal wire, wherein the first metal wire includes a tungsten wire containing tungsten as a main component and an oxide film covering a surface of the tungsten wire, and the second metal wire includes copper as a main component, wherein the average thickness of the oxide film is greater than or equal to 2 nm and less than or equal to 50 nm, and the ratio of the surface roughness Ra of the first metal wire to the wire diameter of the first metal wire is less than or equal to 0.0049.

[0120] Furthermore, for example, a composite wire according to a second aspect of the present invention is the composite wire according to the first aspect, wherein the wire diameter of the first metal wire is 100 μm or less.

[0121] Furthermore, for example, a composite wire according to a third aspect of the present invention is the composite wire according to the first aspect or the second aspect, wherein the first metal wire is located at the radial center of the composite wire.

[0122] Furthermore, for example, a composite wire according to a fourth aspect of the present invention is the composite wire according to any one of the first to third aspects, and is used as an electric wire.

[0123] Furthermore, for example, a robot according to a fifth aspect of the present invention includes the composite wire according to any one of the first to fourth aspects as an electric wire connected to a driving unit.

[0124] Furthermore, for example, a robot according to a sixth aspect of the present invention is the robot according to the fifth aspect, wherein the electric wire is a signal wire connected to the driving unit.

[0125] Explanation of symbols

[0126] 1 stranded wire (composite wire)

[0127] 10First metal wire

[0128] 11 tungsten wire

[0129] 12 oxide film

[0130] 20 Second metal wire

[0131] 200 robots

[0132] 210 drive unit

Claims

1. A composite wire, A composite wire is formed by bundling a plurality of wires including a first metal wire and a second metal wire. The first metal wire includes a tungsten wire containing tungsten as a main component and an oxide film covering a surface of the tungsten wire. The second metal wire contains copper as a main component, The average thickness of the oxide film is greater than or equal to 2 nm and less than or equal to 50 nm. A ratio of the surface roughness Ra of the first metal wire to the wire diameter of the first metal wire is 0.0049 or less.

2. The composite wire according to claim 1, The first metal wire has a diameter of 100 μm or less.

3. The composite wire according to claim 1, The first metal wire is located at the radial center of the composite wire.

4. The composite wire according to any one of claims 1 to 3, Used as electrical wire.

5. A robot, The composite wire according to claim 4 is provided as an electric wire connected to the driving unit.

6. The robot according to claim 5, The electric wire is a signal line connected to the driving unit.

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