Composite wire and robot

Abstract

A composite wire is obtained by bundling several individual wires, each containing a first metal wire (10) and a second metal wire (20). The first metal wire (10) contains a tungsten wire, with tungsten as its main component, and an oxide film covering a surface of the tungsten wire. The second metal wire (20) contains copper as its main component. The oxide film has an average thickness of at least 2 nm and at most 50 nm. 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 composite wires and robots. background

[0002] Patent Publication (PTL) 1 discloses a stranded wire comprising several twisted metal strands. Metal is inserted between the metal strands in the stranded wire and has a standard electrode potential that is lower than that of the individual metal strands. List of citation points for patent publications

[0003] PTL 1: Japanese patent no. 3152714 Summary of the invention: Technical problem

[0004] If individual wires made of different types of metals are bundled together in a composite wire, such as a stranded wire, corrosion tends to occur easily as a result of contact between the different types of metals.

[0005] One object of the present invention is to provide a composite wire that can counteract corrosion even when individual wires composed of different types of metals are bundled together. Solution to the problem

[0006] A composite wire according to one aspect of the present invention is obtained by bundling several individual wires comprising a first metal wire and a second metal wire, wherein the first metal wire comprises a tungsten wire containing tungsten as the main component and an oxide film covering a surface of the tungsten wire, the second metal wire contains copper as the main component, the oxide film has an average thickness of at least 2 nm and at most 50 nm, and the ratio of a surface roughness Ra of the first metal wire to a wire diameter of the first metal wire is 0.0049 or less.

[0007] A robot according to one aspect of the present invention includes the aforementioned composite wire, which is used as an electrical wire, wherein the electrical wire is connected to a drive. Advantageous effects of the invention

[0008] According to the present invention, corrosion can also be counteracted when individual wires composed of different types of metals are bundled together. Brief description of the drawing Fig. Figure 1 is a schematic external view illustrating a tungsten wire according to one embodiment. Fig. Figure 2 is a schematic cross-sectional view illustrating a stranded wire according to the embodiment. Fig. Figure 3 is a schematic cross-sectional view illustrating a first metal wire according to the embodiment. Fig.4A is a SEM (Scanning Electron Microscope SEM) image of a cross-section of a test product of the first metal wire according to the embodiment. Fig. 4B is an image obtained by extracting an oxide film from the SEM image in Fig. 4A receives. Fig. Figure 5 is a flowchart illustrating a manufacturing process for the tungsten wire according to the embodiment. Fig. Figure 6 is a flowchart illustrating a corrosion test procedure. Fig. Figure 7 is a graph illustrating 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 weight loss in a corrosion test of each test product. Fig. Figure 8 shows a robot as an example of a product that uses the stranded wire according to the embodiment. Brief description of embodiments

[0009] Embodiments of the present invention are described in detail below with reference to the drawing. All embodiments described below are specific examples of the present invention. Therefore, numerical values, shapes, materials, components, positions and joining methods of the components, steps, the sequence of steps, and the like, as specified in the following embodiments, are examples and are not intended to limit the present invention. Accordingly, of the components of the following embodiments, those not listed in the independent claims are described as arbitrary components.

[0010] Each figure is a schematic view and not necessarily an exact representation. Therefore, for example, the scales and similar details in the figures are not necessarily accurate. Furthermore, essentially identical components in the figures are assigned the same reference symbols, and redundant explanations have been omitted or simplified.

[0011] In the present description, terms that specify the relationships between components, terms that specify the shapes of components, such as circular, and numerical ranges are not expressions that have exclusively strict meanings, but rather expressions that include essentially equivalent ranges, such as differences of a few percent. Type of stranded wire

[0012] First, a stranded wire is selected according to one embodiment based on Fig. 1 to 3 described. Fig.Figure 1 is a schematic external view illustrating a stranded wire 1 according to the present embodiment. Fig. Figure 2 is a schematic cross-sectional view illustrating the stranded wire 1 according to the present embodiment. Fig. Figure 3 is a schematic cross-sectional view illustrating a first metal wire 10 of the stranded wire 1 according to the present embodiment. Fig. 1 and Fig. 2 are internal components, such as an oxide film 12, of the first metal wire 10, omitted. The cross-section of the stranded wire 1 is, as in Fig. Figure 2 shows the cross-section of the first metal wire 10 in a direction perpendicular to the axial direction (direction in which the stranded wire 1 extends). The cross-section of the first metal wire 10 is as shown in Figure 2. Fig.Figure 3 is shown, taken in a direction perpendicular to an axial direction (direction in which the first metal wire 10 extends) of the first metal wire 10. Fig. 3 is an exaggerated representation of the thickness of the oxide film 12.

[0013] The stranded wire 1, which is in Fig. 1 and Fig. Figure 2 is an example of a composite wire that contains several bundled individual wires. In detail, this means that, as shown in Fig.As shown in Figure 1, the stranded wire 1 is a metallic stranded wire comprising several individual wires twisted together. The stranded wire 1 is stored, for example, by being wound around a spool frame, which may also be called a bobbin, reel, reel, drum, or the like. There are no specific limitations to the method of storing the stranded wire 1; the wire 1 is stored in such a way as to avoid excessive bending. The total length of the stranded wire 1 can range from the order of centimeters to the order of meters, or may be on the order of kilometers.

[0014] The stranded wire 1 is used, for example, as an electrical wire. Since the first metal wire 10, which contains the tungsten wire 11, is used as a single wire in the stranded wire 1, as described below, the stranded wire 1 can achieve a reduced diameter and / or increased strength relative to a stranded wire that uses only copper wires as single wires. Although there is no specific limitation regarding applications where the stranded wire 1 is used as an electrical wire, it is used, for example, as an electrical wire connected to a robot drive, taking advantage of the fact that the stranded wire 1 has a small diameter and / or high strength.

[0015] As in Fig. As shown in Figure 2, the several individual wires that form the stranded wire 1 include the first metal wire 10 and the second metal wire 20. In the case of the Fig.In the example shown, the multiple individual wires comprise a first metal wire 10 and six second metal wires 20, and the stranded wire 1 is a mixed stranded wire obtained by twisting the aforementioned wires together. In the stranded wire 1, the first metal wire 10 is in contact with every second metal wire 20. As will be described in detail below, the first metal wire 10 is a metal wire containing tungsten as its main component and has a higher tensile strength than the second metal wires 20. Every second metal wire 20 is a metal wire containing copper as its main component and has a higher conductivity than the first metal wire 10.

[0016] At the in Fig.In the example shown, stranded wire 1 is a 7-core stranded wire comprising seven solid wire strands twisted together. The number of strands forming stranded wire 1 is not subject to any specific limitation; stranded wire 1 can be composed of any number of strands of different types, depending on the desired strength and wire diameter. For example, stranded wire 1 can be a 3-core stranded wire comprising three twisted strands, a 19-core stranded wire comprising 19 twisted strands, or a 37-core stranded wire comprising 37 twisted strands.Furthermore, the stranded wire 1 is not limited to a stranded wire comprising twisted solid single wires; it can also be a stranded wire formed by further intertwining it with a stranded wire comprising twisted solid wires, as is the case with a 7-by-7-core stranded wire comprising seven twisted 7-core stranded wires. Another example of a stranded wire 1 includes, but is not specifically limited to, a 7-by-19-core stranded wire (comprising seven twisted 19-core stranded wires), a 6-by-7-core stranded wire (comprising six twisted 7-core stranded wires), or a 3-by-7-core stranded wire (comprising three twisted 7-core stranded wires).The number of individual wires twisted together in the stranded wire need not always be the same; the stranded wire can contain stranded wires with varying numbers of twisted individual wires. Although all the individual wires (the first metal wire 10 and the several second metal wires 20) have the same wire diameter in the example shown, a combination of individual wires with different wire diameters can be used in the stranded wire 1.

[0017] At the in Fig.In the example shown, a first metal wire 10 is a central single wire located radially in the center of the stranded wire 1. Within the stranded wire 1, the first metal wire 10, serving as the central single wire, is surrounded radially by several second metal wires 20. Specifically, this means that the stranded wire 1 is formed by wrapping six second metal wires 20 around the first metal wire 10. Accordingly, the second metal wires 20 are wrapped around the first metal wire 10 with comparatively high tensile strength, resulting in the stranded wire 1 exhibiting increased bending strength.

[0018] The number of first metal wires 10 and second metal wires 20 contained in the stranded wire 1 is not subject to any special limitation, provided that the stranded wire 1 contains at least one first metal wire 10 and at least one second metal wire 20 as multiple individual wires. For example, the stranded wire 1 contains at least one first metal wire 10 and at least one second metal wire 20. From the standpoint of improving conductivity and bending strength, the number of second metal wires 20 may be greater than the number of first metal wires 10. The positions of the first metal wire 10 and the second metal wire 20 in the stranded wire 1 are also not subject to any special limitation. In particular, there is no limitation on those positions in which the multiple individual wires containing the first metal wire 10 and the second metal wire 20 are twisted together.The middle single wire can be, for example, the second metal wire 20, and the single wires surrounding the middle single wire can be the first metal wire 10.

[0019] The wire diameter φ1 of the stranded wire 1 is, for example, 500 µm or less; however, it is not limited to this. The wire diameter φ1 of the stranded wire 1 can be 400 µm or less, 300 µm or less, 200 µm or less, 150 µm or less, and 100 µm or less. The wire diameter φ1 of the stranded wire 1 is the diameter of a circumscribed circle formed by the several individual wires that make up the stranded wire 1, in the cross-section of the stranded wire 1. In the case of the Fig.In the 7-core stranded wire shown in Figure 2, the wire diameter φ1 is the length of the stranded wire 1 in the radial direction at a position where three individual wires are arranged radially. The length of the stranded wire 1 in the radial direction at the position where the three individual wires are arranged radially (that is, the diameter of the circumscribed circle of the stranded wire 1) is measured, for example, by using a caliper or similar instrument at a predetermined number of arbitrary points (for example, two or more) and calculating the wire diameter φ1 by averaging the measured values.

[0020] As in Fig. As shown in Figure 3, the first metal wire 10 includes the tungsten wire 11, which contains tungsten as its main component, and also the oxide film 12, which is provided over the surface of the tungsten wire 11.

[0021] The tensile strength of the first metal wire 10 is, for example, 3500 MPa or more; however, it is not limited to this. The tensile strength of the first metal wire 10 can be 4000 MPa or more, 4500 MPa or more, or 5000 MPa or more. The first metal wire 10 can, for example, also be realized with a high tensile strength of 5500 MPa or more.

[0022] The tensile strength of a single wire, for example the first metal wire 10, is obtained by dividing the breaking or tensile strength (stress during breaking or tearing) of the single wire by the cross-sectional area of ​​the single wire. The tensile strength is measured, for example, based on the Japanese industrial standard JIS H 4460 8.

[0023] Since the tensile strength of the stranded wire 1 increases with the increase in the tensile strength of the first metal wire 10, there is an advantage with regard to the increase in the strength of the stranded wire 1. As a result, a reduction in diameter can be achieved while maintaining the strength, so that a reduced diameter and / or an increased strength of the stranded wire 1 can be realized.

[0024] The wire diameter φ2 of the first metal wire 10 is, for example, 100 µm or less; however, it is not limited to this. The wire diameter φ2 can be 80 µm or less, 60 µm or less, 35 µm or less, 30 µm or less, 25 µm or less, 20 µm or less, 15 µm or less, 13 µm or less, 11 µm or less, 10 µm or less, 9 µm or less, 8 µm or less, or 7 µm or less. For example, an ultrathin first metal wire 10 with a wire diameter φ2 of approximately 5 µm can be realized.

[0025] As in Fig. As shown in Figure 3, the wire diameter φ2 is the sum of the diameter of the tungsten wire 11 and twice the average thickness t of the oxide film 12. Since the average thickness t of the oxide film 12 is sufficiently smaller than the diameter of the tungsten wire 11, the wire diameter φ2 can be considered to be essentially equal to the diameter of the tungsten wire 11.

[0026] A ratio of the surface roughness Ra of the first metal wire 10 to the wire gauge φ2 of the first metal wire 10 is 0.049 or less. Corrosion in the stranded wire 1 can thus be effectively prevented. The surface roughness Ra is also referred to as the "arithmetic mean roughness". The surface roughness Ra is calculated, for example, based on the Japanese industrial standard JIS B 0601. The surface of the first metal wire 10 is scanned using a laser microscope or similar instrument, and the surface roughness Ra in the circumferential direction of the first metal wire 10 is calculated from the scanned data using surface roughness Ra measurement software.

[0027] The tungsten wire 11 contains tungsten (W) as its main component. The term "main component" implies that the percentage content of an element is greater than 50 wt%. For example, the percentage of tungsten contained in the tungsten wire 11 is 90 wt% or more. The percentage of tungsten contained in the tungsten wire 11 can be 95 wt% or more, 99 wt% or more, 99.9 wt% or more, or 99.99 wt% or more. Although the tungsten wire 11 is a so-called pure tungsten wire, it may contain an unavoidable impurity, the introduction of which during the manufacturing process cannot be prevented.

[0028] The tungsten wire 11 can be composed of an alloy of tungsten and at least one type of non-tungsten metal. In other words, the tungsten wire 11 can be a tungsten alloy wire that serves as a tungsten wire composed of a tungsten alloy. The non-tungsten metal is, for example, rhenium (Re). The percentage of rhenium contained in the tungsten wire 11 composed of a rhenium-tungsten alloy (ReW) is, for example, at least 0.1 wt% and at most 10 wt%; however, it is not limited to this. The percentage of rhenium can, for example, be 1 wt% or more, 3 wt% or more, or 5 wt% or more.

[0029] If the percentage of rhenium is high, the tensile strength of the tungsten wire 11 can be increased. However, if the percentage of rhenium is too high, it is difficult to reduce the diameter while maintaining high tensile strength. In detail, this means that wire breakage tends to occur easily, making wire drawing over longer lengths difficult. By reducing the percentage of rhenium and selecting a rhenium content of 90 wt% or more, the processability of the tungsten wire 11 can be improved. Furthermore, reducing the percentage of rhenium, which is rare and expensive, enables the mass production of cost-effective, long tungsten wires 11.

[0030] The metal used in the alloy with tungsten can be osmium (Os), ruthenium (Ru), or iridium (Ir). The percentage of osmium, ruthenium, or iridium is, for example, similar to the percentage of rhenium. In these cases, an advantage similar to that of the rhenium-tungsten alloy can be achieved. The tungsten wire 11 can be composed of an alloy of tungsten and at least two types of non-tungsten metals.

[0031] The tungsten wire 11 can be a doped tungsten wire, specifically one doped with potassium (K). The potassium used for doping is present at the grain boundaries of tungsten crystals. The percentage of potassium (K) is, for example, 0.010 wt% or less. Even with a potassium-doped tungsten wire, a metal wire can be produced that exhibits a tensile strength higher than that of a piano wire or string. In addition to potassium oxide, a similar effect can be achieved with an oxide of another material, such as cerium or lanthanum. The tungsten wire 11 can also contain a rare-earth element.

[0032] The oxide film 12 contains tungsten oxide as its main component. The tungsten oxide contained in the oxide film 12 contains, for example, WO3 as its main component. However, the oxide film 12 can also contain tungsten oxide with a composition other than WO3, such as WO2 or W3O8. The WO2 content of the oxide film 12 tends to increase with increasing average thickness t of the oxide film 12. Although the stranded wire 1 contains the first metal wire 10 and the second metal wire 20, which are composed of different types of metals and twisted together, the oxide film 12 contained in the first metal wire 10 helps to counteract corrosion.

[0033] In the present embodiment, the oxide film 12 is provided in the circumferential direction of the outer surface of the tungsten wire 11 as well as in the axial direction thereof. The oxide film 12 is provided, for example, over the entire outer surface of the tungsten wire 11. The provided oxide film 12 has a uniform thickness, regardless of its location. The term "uniform thickness" is not only strictly defined; it does not mean that the thickness is the same at all points, but also that a thickness variation exists within a predetermined range. If, for example, the thickness of the oxide film 12 is measured at ten arbitrary locations on the first metal wire 10, the variation in the measured thickness values ​​(percentage deviation from an average value) is 30% or less.

[0034] The average thickness t of the oxide film 12 is measured in the following manner.

[0035] A cross-section perpendicular to the axial direction of the first metal wire 10 is formed. This cross-section is polished by a BIB (Broad Ion Beam BIB) process. In detail, this means that the first metal wire 10 is irradiated with an argon ion beam such that the irradiated surface is ion-etched, resulting in a smooth or continuous cross-section.

[0036] Fig. 4A is a SEM (Scanning Electron Microscope SEM) image of the cross-section of the first metal wire 10 according to the present embodiment. Fig. 4B is an image obtained by extracting oxide film 12 from the SEM image of Fig. 4A receives.

[0037] As in Fig.As shown in Figure 4A, the SEM image allows the observation of tungsten crystals forming the tungsten wire 11, corresponding to color differences. It is also evident that the oxide film 12 is formed along the surface of the tungsten wire 11. Since the oxide film 12 is observable in a color different from that of the tungsten crystals forming the tungsten wire 11, only the oxide film 12 can be labeled and extracted, as shown in Figure 4A. Fig. 4B is shown.

[0038] The area S of the oxide film 12 present in the cross-section is measured using image processing. By dividing the measured area S by the length L of the outer circumference of the tungsten wire 11, the average thickness t of the oxide film 12 can be calculated. The length L can be calculated from the wire diameter of the tungsten wire 11, taking into account that the cross-section of the tungsten wire 11 is circular. The average thickness t of the oxide film 12 can be calculated by averaging thickness values ​​of the oxide film 12 measured at several arbitrary locations (for example, at ten or more locations) of the first metal wire 10, for example, using the SEM image.

[0039] In the present embodiment, the average thickness t of the oxide film 12 is at least 2 nm and at most 50 nm. If the average thickness t of the oxide film 12 meets this range, corrosion in the stranded wire 1 can be effectively prevented. The average thickness t of the oxide film 12 can be at least 5 nm and at most 50 nm, or it can be at least 10 nm and at most 50 nm.

[0040] The second metal wire 20 is a copper wire containing copper (Cu) as its main component. The percentage of copper contained in the second metal wire 20 is, for example, 90% by mass or more. The percentage of copper contained in the second metal wire 20 can be 95% by mass or more, or 99% by mass or more.

[0041] The second metal wire 20 can be composed of an alloy of copper and at least one type of non-copper metal. The second metal wire 20 can also contain a non-metallic element. Examples of metals that are neither copper nor non-metallic 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). For example, the presence of tin or silver can increase the strength of the second metal wire 20. Furthermore, the second metal wire 20 can be plated with tin, palladium (Pd), or the like.

[0042] Typically, the tensile strength of a copper wire containing copper as its main component is 2000 MPa or less. By including the first metal wire 10 as individual strands in addition to the second metal wire 20, the strength of the stranded wire 1 can be increased. Manufacturing process

[0043] Next, a manufacturing process for the stranded wire 1 according to the present embodiment will be described using the following examples. Fig. 5 described. Fig. Figure 5 is a flowchart illustrating the manufacturing process of the stranded wire 1 according to the present embodiment.

[0044] First, a tungsten wire 11, which has a predetermined wire diameter, a predetermined tensile strength and a predetermined surface roughness Ra and contains tungsten as its main component, is prepared (S10).

[0045] First, a tungsten blank is prepared. Specifically, this means that the tungsten blank is formed by pressing and sintering tungsten powder. In this case, if a tungsten alloy wire is to be produced, a mixture of tungsten powder and metal powder for the alloy is pressed and sintered. For a doped tungsten wire, doped tungsten powder, doped with potassium or a similar element, is pressed and sintered.

[0046] The prepared blank is then repeatedly drawn (swaged) and heated to form a wire with a predetermined diameter (for example, approximately 3 mm). An oxide layer forms on the wire's surface through heating, and this layer is impregnated with a lubricant, such as one composed of carbon, to counteract cracks or breaks that may occur during the wire drawing process.

[0047] Wire drawing (thinning) is then carried out using a wire drawing die, such as a monocrystalline diamond die or a polycrystalline diamond die. The wire drawing is performed while the die is heated. The wire drawing process is repeated. With each repetition, adjustments are made by gradually reducing the die hole diameter and the heating temperature. In this way, a tungsten wire 11 with high tensile strength is produced.

[0048] The surface roughness Ra of the tungsten wire 11 is adjusted according to the type of wire drawing tool used. The surface roughness Ra of the tungsten wire 11 decreases when using a monocrystal diamond tool, whereas the surface roughness Ra of the tungsten wire 11 increases when using a polycrystal diamond tool. Since the surface roughness Ra hardly changes even with an oxide film 12 formed on a tungsten wire 11, which will be described below, the surface roughness Ra of the first metal wire 10 can be adjusted by adjusting the surface roughness Ra of the tungsten wire 11.

[0049] Finally, the wire diameter is adjusted to a desired size by electrolytic polishing. In a state where the tungsten wire 11 and a counter electrode are immersed in an electrolyte solution, such as a sodium hydroxide solution, the electrolytic polishing is carried out, for example, by applying a voltage between the tungsten wire 11 and the counter electrode. The electrolytic polishing step can also be omitted.

[0050] To remove impurities, moisture, and other substances that adhere during electrolytic polishing, heating is then carried out in a reducing atmosphere. The heating temperature is, for example, at least 600 °C and at most 1400 °C. Subsequently, the oxide film 12 is formed on the surface of the prepared tungsten wire 11 (S20). The first metal wire 10 is thus obtained. The oxide film 12 is formed by heating the tungsten wire 11 in an oxidizing atmosphere after the wire drawing process. The average thickness t of the oxide film 12 can be controlled by adjusting the partial pressure of an inert gas in the oxidizing atmosphere. The inert gas is, for example, nitrogen gas or argon gas. The average thickness t of the oxide film 12 can also be controlled by adjusting the heating temperature and the heating time.In detail, this means that the average thickness t of the oxide film 12 increases with decreasing partial pressure of the inert gas, increasing heating temperature, or increasing heating time. The heating temperature is, for example, at least 200 °C and at most 1200 °C; however, it is not limited to this range.

[0051] The tungsten wire 11 is subjected to electrolytic polishing before heating, for example, to remove the oxide layer that adheres to its surface during wire drawing. This counteracts any thickness variation in the oxide film 12 to be formed on the surface, and allows for the formation of an oxide film 12 with excellent film quality.

[0052] Subsequently, the second metal wire 20, which has a predetermined wire diameter and tensile strength and contains copper as its main component, is prepared (S30). For example, an industrial copper wire can be used as the second metal wire 20. This results, for example, in an industrial copper wire with a desired wire diameter and tensile strength. Step S30 can be performed at any time, as long as it is before step S40, which is described below.

[0053] The stranded wire 1 is then formed by twisting together the first metal wire 10 obtained in step S20 and the second metal wire 20 prepared in step S30 (S40). The stranded wire 1 is formed by twisting together several individual wires, each containing at least one first metal wire 10 and at least one second metal wire 20. In the case where the stranded wire 1 is, for example, a 7-core stranded wire, we will proceed as follows: Fig. As shown in Figure 2, the first metal wire 10 serves as the central single wire located in the middle of the stranded wire 1, and the stranded wire 1 is formed by winding six second metal wires 20 around the central single wire. The winding direction is not subject to any special restriction in this case, and either an S-twist or a Z-twist can be used. Corrosion test

[0054] The following description deals with a corrosion test that is carried out to demonstrate an effect that counteracts corrosion in the stranded wire 1.

[0055] Fig. Figure 6 is a flowchart illustrating a corrosion test procedure. The corrosion test involves first preparing a test item for the corrosion test and immersing the prepared test item in salt water for two hours at 35 °C to cause the salt water to adhere to the test item (S110).

[0056] With regard to the test product for the corrosion test, the test product used is obtained by tightly winding the first metal wire 10 around an industrially available copper stranded wire, which contains ten twisted flexible copper wires. Regarding the copper stranded wire used, the wire diameter of each flexible copper wire is 50 µm, while the wire diameter of the copper stranded wire is 230 µm and the tensile strength of the copper stranded wire is 245 MPa. The tensile strength of the copper stranded wire is calculated by dividing the tensile strength by the cross-sectional area of ​​the ten flexible copper wires. The first metal wire 10 is described below.

[0057] The test specimen, along with the adhering salt water, is then placed in a test tank and dried for four hours at 60 °C and a relative humidity of 20% to 30% (S120). The dried specimen is then moistened for 30 minutes at 50 °C and a relative humidity of 95% or higher (S130). Finally, the moistened specimen is rinsed in pure water and ultrasonically cleaned for 30 minutes, resulting in a corrosion-tested specimen (S140). Accordingly, the corrosion test causes an acceleration of corrosion corresponding to the salt, water, and temperature. Since a corroded section is removed by cleaning, the weight of the corroded specimen is lower after the corrosion test.

[0058] To assess corrosion, the weight of the test product before and after the corrosion test are measured, and the ratio of weight loss of the test product due to the corrosion test is calculated as corrosion weight loss. In other words: (Corrosion weight loss) = (Weight before test - Weight after test) / Weight before test.

[0059] Next, the results of the corrosion test, which was carried out on test products using first metal wires produced in practice 10, are presented in Tables 1 to 3 and Fig. 7 described.

[0060] In connection with the present invention, test specimens were produced using fourteen first metal wires 10 with different combinations of wire diameter φ2, surface roughness Ra, and average thickness t of the oxide film 12, and the corrosion test described above was performed on each test specimen. For each test specimen, the wire diameter φ2 of the first metal wire 10, its surface roughness Ra, the average thickness t of the oxide film 12, and the corrosion weight loss are given in Table 1. The wire diameter φ2 is a value obtained by adjusting the hole diameter of the wire drawing die and the conditions of electrolytic polishing according to the first metal wire 10 used in each test specimen, and by measuring the wire diameter φ2 of the resulting first metal wire 10.The surface roughness Ra is a value obtained by changing the type of wire drawing tool used to form the tungsten wire 11, according to the first metal wire 10 used in each test specimen, and measuring the surface roughness Ra of the first metal wire 10 obtained. The average thickness t of the oxide film 12 is a value obtained by adjusting the partial pressure of the inert gas, the heating temperature, and the heating time for forming the oxide film 12, according to the first metal wire 10 used in each test specimen, and measuring the average thickness t of the oxide film 12 obtained. In Table 1, an average thickness t of "2 to 10 [nm]" indicates that if the oxide film 12 is to be formed with a target average thickness t of approximately 5 nm, the oxide film 12 will have an average thickness t in the range between 2 nm and 10 nm. 10 nm is formed.The tensile strength of the first metal wire 10 with a wire diameter φ2 of 20 µm is 3750 MPa. The tensile strength of the first metal wires 10 with wire diameters φ2 of 30, 33, and 50 µm is 3550 MPa. The test specimens used in the test are adapted such that they have the same length for the copper stranded wires used and the same length for the first metal wires 10 used.

[0061] In addition to the wire diameter φ2 of the first metal wire 10, the surface roughness Ra of the first metal wire 10, the average thickness t of the oxide film 12, and the corrosion weight loss, Table 1 below also shows the ratio of the surface roughness Ra of the first metal wire 10 to the wire diameter φ2 of the first metal wire 10 (hereinafter sometimes referred to as "Ra / wire diameter φ2"). Furthermore, Table 1 presents the corrosion weight loss results for the respective test products such that "Ra / wire diameter φ2" decreases from top to bottom. [Table 1] Wire diameter φ2[µm] Ra[µm] Average thickness t [nm] Ra / wire diameter φ2 Corrosion weight loss 33 0,17 90 0,0052 1,4% 30 0,15 90 0,0050 1,4% 20 0,10 2-10 0,0050 1,5% 33 0,16 50 0,0048 1,0% 30 0,14 50 0,0047 0,9% 33 0,15 2-10 0,0045 0,7% 30 0,13 2-10 0,0043 0,6% 33 0,14 2-10 0,0042 0,9% 30 0,12 50 0,0040 0,7% 50 0,19 2-10 0,0038 0,4% 30 0,11 2-10 0,0037 0,2% 33 0,08 90 0,0024 1,2% 33 0,07 50 0,0021 0,5% 33 0,06 2-10 0,0018 0,5%

[0062] Table 2 below shows the result of the corrosion weight loss of each test product shown in Table 1 for each combination of “Ra / wire diameter φ2” (column) and average thickness t of the oxide film 12 (row). [Table 2] Ra / wire diameter φ2 average thickness t 2 nm -10 nm 50 nm 90 nm 0,0052 1,4% 0,0050 1,5% 1,4% 0,0048 1,0% 0,0047 0,9% 0,0045 0,7% 0,0043 0,6% 0,0042 0,9% 0,0040 0,7% 0,0038 0,4% 0,0037 0,2% 0,0024 1,2% 0,0021 0,5% 0,0018 0,5%

[0063] Fig. Figure 7 is a graph illustrating the relationship between "Ra / wire diameter φ2" and the corrosion weight loss during the corrosion test of each test product. Fig. 7 denotes the abscissa axis “Ra / wire diameter φ2” of the first metal wire 10 of each test product, whereas the ordinate axis shows the corrosion weight loss of each test product. Fig. Figure 7 is a graphical representation of Tables 1 and 2. Fig.7 is the result of each test product in which the first metal wire 10 with an average thickness t in a range between 2 nm and 10 nm is used, indicated by a circular marking, the result of each test product in which the first metal wire 10 with an average thickness t of 50 nm is used is indicated by a rectangular marking, and the result of each test product in which the first metal wire 10 with an average thickness t of 90 nm is used is indicated by a triangular marking.

[0064] In connection with the present invention, the corrosion test described above was also carried out on test products comprising: a copper-only stranded wire, a tungsten-only wire 11 that had not been subjected to any process for the formation of the oxide film 12, and a tungsten wire 11 that had not been subjected to any process for the formation of the oxide film 12 and that was wound around a copper-only stranded wire. The results are shown in Table 3. [Table 3] Test product Corrosion weight loss Copper stranded wire only 0,1% Tungsten wire only 11 0,0% Copper stranded wire + tungsten wire 11 1,7%

[0065] In the case of the copper-only and tungsten-only stranded wire, as shown in Table 3, corrosion test-induced corrosion is hardly noticeable. In contrast, in the test product containing the wound tungsten wire 11, which has not been subjected to any process to form the oxide film 12, the corrosion caused by the corrosion test is noticeable, and the weight is significantly reduced. This is because corrosion tends to occur easily as a result of contact between different types of metals.

[0066] In contrast, as shown in Tables 1 and 2 and in Fig.As shown in Figure 7, in every test specimen obtained by winding the first metal wire 10, which contains the tungsten wire 11 and the oxide film 12 formed on it, around a copper stranded wire, corrosion caused by the corrosion test is counteracted. This is probably due to the fact that the oxide film 12 formed on the first metal wire 10 counteracts contact between the tungsten wire 11 and the copper wire.

[0067] It is also confirmed for each test product that the corrosion weight loss tends to decrease with decreasing "Ra / wire diameter φ2". Regarding the test products, those with an average thickness t of the oxide film 12 in the range between 2 nm and 10 nm and at 50 nm show no differences in corrosion weight loss and exhibit a lower corrosion weight loss than the test product with an average thickness t of the oxide film 12 at 90 nm. In particular, for a test product with an average thickness t of the oxide film 12 in the range between 2 nm and 10 nm or at 50 nm and with an "Ra / wire diameter φ2" of 0.0049 or less (single-point dashed line extending into Fig. 7 in the vertical direction) the corrosion weight loss (single-point dashed line extending in Fig.7 in the horizontal direction) is equal to 1.0% or less, thus confirming a noticeable corrosion counteraction. This is probably due to the fact that, in addition to the oxide film 12, which counteracts the 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 have caused a change in the standard electrode potential of the first metal wire 10, which reduces the difference in standard electrode potential between the first metal wire 10 and the copper stranded wire.

[0068] In the test specimen with an average oxide film thickness t of 90 nm, a noticeable corrosion counter-effect is not confirmed even with a reduced "Ra / wire diameter φ2". In other words, the corrosion weight loss cannot be controlled or regulated by adjusting "Ra / wire diameter φ2". This is probably because when the average oxide film thickness t exceeds 90 nm, the standard electrode potential of the first metal wire 10 is less likely to change, even with a change in the surface roughness Ra of the first metal wire 10.

[0069] By selecting the average thickness t of the oxide film 12 accordingly in a range between at least 2 nm and at most 50 nm and by selecting “Ra / wire diameter φ2” at 0.0049 or less, the corrosion weight loss of a test product decreases noticeably, so that the corrosion of the test product is visibly counteracted.

[0070] Although the aforementioned corrosion test was carried out using test products obtained by wrapping the first metal wire 10 around a copper stranded wire, it can also be considered that effects similar to those of the previously described test can be achieved if the stranded wire, for example the stranded wire 1, contains the first metal wire 10 and the second metal wire 20 as the several individual wires. Effects and the like

[0071] As described above, the stranded wire 1 according to the present embodiment is obtained by bundling several individual wires, which include the first metal wire 10 and the second metal wire 20. The first metal wire 10 includes the tungsten wire 11, which contains tungsten as its main component, and also includes the oxide film 12, which covers the surface of the tungsten wire 11. The second metal wire 20 contains copper as its main component. The oxide film 12 has an average thickness t of at least 2 nm and at most 50 nm. The ratio of the surface roughness Ra of the first metal wire 10 to the wire diameter φ2 of the first metal wire 10 is 0.0049 or less.

[0072] Accordingly, corrosion can even be counteracted in the case of a bundle of individual wires designed as stranded wire 1, which are composed of different types of metals and twisted together. Furthermore, a reduced diameter and / or increased tensile strength can be achieved in the stranded wire 1, which contains the first metal wire 10 as a single wire.

[0073] Furthermore, the wire diameter φ2 of the first metal wire 10 can be, for example, 100 µm or less.

[0074] Since the specific surface area of ​​the first metal wire 10 increases when the wire diameter φ2 is small, the corrosion countermeasure effect of the oxide film 12 is more effective. Additionally, the strength of the first metal wire 10 can be readily increased.

[0075] Furthermore, the first metal wire 10 can be located, for example, in the middle of the stranded wire 1 in the radial direction.

[0076] Accordingly, the strength of the stranded wire 1 can be increased in a balanced way. Since the second metal wire 20, which is comparatively soft, is located outside the first metal wire 10, the stranded wire 1 can exhibit improved bending strength.

[0077] Furthermore, the stranded wire 1 can, for example, be used as an electrical wire.

[0078] Accordingly, in the case of the stranded wire 1, which includes the first metal wire 10 as a single wire, the diameter of the electrical wire 10 can be reduced and / or its strength increased, while corrosion of the electrical wire can be counteracted. Example of use

[0079] Next, an example of a product is described in which the stranded wire 1 is used according to the embodiment described above.

[0080] Fig. Figure 8 shows a robot 200 as an example of a product in which the stranded wire 1 is used according to the present embodiment.

[0081] As in Fig. As shown in Figure 8, robot 200 comprises a drive 210, a controller 220, and the stranded wire 1 as an electrical wire connected to the drive 210. Robot 200 is, for example, a factory automation robot. However, robot 200 can also be a robot not used for factory automation, such as an autonomous mobile robot.

[0082] In robot 200, the stranded wire 1 is used as an electrical wire connected to the drive 210. The drive 210 contains a drive mechanism, which includes a motor, actuator, or the like, and operates based on a control signal from the controller 220. The control signal is transmitted from the controller 220 to the drive 210 via the stranded wire 1, which serves as the electrical wire connecting the drive 210 and the controller 220. In other words, the stranded wire 1 is a signal wire connected to the drive 210 and serves to transmit a signal.

[0083] The control unit 220 controls the operation of the drive 210. The control unit 220 is, for example, a control device that includes a processor or a microcomputer.

[0084] As mentioned above, the diameter of the stranded wire 1 can be reduced and / or its tensile strength increased, while counteracting corrosion. Therefore, using the stranded wire 1 as an electrical wire connected to the drive 210 in the robot 200 allows for a reduction in size and / or a higher load tolerance of the robot 200, and also enables improved durability and reliability of the robot 200, since the stranded wire 1 is corrosion-resistant.

[0085] The stranded wire 1, which is connected to the drive 210, can be used as an electrical wire to supply electrical drive power to the drive 210. Similar to what was previously stated, this also allows for a reduction in size and / or a high load tolerance of the robot 200 and also enables improved durability and reliability. If the stranded wire 1 is used as an electrical wire to supply electrical power, the stranded wire 1 can be connected to the controller 220, as shown in Fig. 8 shown, to supply the electrical power to the drive 210 via the control or regulation 220, or the stranded wire 1, which serves as an electrical wire connecting another power supply circuit or an external power source (not shown) to the drive 210, can be contained in the robot 200.

[0086] The stranded wire 1 can be used as an electrical wire incorporated in a non-robot product, such as a household appliance, an analytical device, or a manufacturing machine. Accordingly, the size of a product utilizing the stranded wire 1 can be reduced, and / or the product can be made more tolerant of high loads and may also exhibit improved durability and reliability. Miscellaneous

[0087] Although the composite wire according to the present invention has been described above with reference to the aforementioned embodiment, the present invention is not limited to the aforementioned embodiment.

[0088] Although the stranded wire 1 in the aforementioned embodiment has been described as an example of a composite wire, the composite wire according to the present invention is not limited to a stranded wire as an example. The composite wire according to the present invention is not subject to any specific limitation as long as it is a composite wire in which several individual wires, comprising the first metal wire 10 and the second metal wire 20, are bundled together. In the composite wire according to the present invention, the several individual wires can be bundled, for example, by a coating process, they can be bundled using a binding agent, or they can be bundled using an insulating coating.Since the multiple individual wires forming the composite wire include the first metal wire 10 and the second metal wire 20, corrosion can be counteracted even in the case of a bundle of individual wires composed of different types of metals.

[0089] The present invention comprises embodiments that can be conceived by a person skilled in the art and that can be obtained by modifying a respective embodiment and the respective modifications of the embodiment in various ways, as well as embodiments that can be obtained by combining the components and functions of a respective embodiment and the respective modifications of the embodiment in any way, as long as the embodiments do not deviate from the scope of the present invention.

[0090] Examples of the composite wire and the robot according to the present invention, which have been described on the basis of the aforementioned embodiment, are given below. The stranded wire and the robot according to the present invention are not limited to the following examples.

[0091] For example, a composite wire according to a first aspect of the present invention is obtained by bundling several individual wires comprising a first metal wire and a second metal wire. The first metal wire comprises a tungsten wire containing tungsten as the main component and an oxide film covering a surface of the tungsten wire; the second metal wire contains copper as the main component, the oxide film has an average thickness of at least 2 nm and at most 50 nm, and the ratio of a surface roughness Ra of the first metal wire to a wire diameter of the first metal wire is 0.0049 or less.

[0092] Furthermore, a composite wire according to a second aspect of the present invention is, for example, the composite wire according to the first aspect, wherein the first metal wire has a wire diameter of 100 µm or less.

[0093] Furthermore, a composite wire according to a third aspect of the present invention is, for example, the composite wire according to the first or second aspect, wherein the first metal wire is located in a radial direction in a center of the composite wire.

[0094] Furthermore, a composite wire according to a fourth aspect of the present invention is, for example, the composite wire according to one of the first to third aspects, wherein the composite wire is used as an electrical wire.

[0095] Furthermore, a robot according to a fifth aspect of the present invention includes, for example, the composite wire according to one of the first to fourth aspects, wherein the composite wire is used as an electrical wire and the electrical wire is connected to a drive.

[0096] Furthermore, according to a sixth aspect of the present invention, the robot is, for example, the robot according to the fifth aspect, in which the electrical wire is a signal wire connected to the drive. Reference symbol list 1 stranded wire (composite wire) 10 first metal wire 11 Tungsten wire 12 Oxide film 20 second metal wire 200 robots 210 drive QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 3152714

[0003]

Claims

[1] Composite wire obtained by bundling several individual wires, each containing a first metal wire and a second metal wire, wherein the first metal wire includes a tungsten wire containing tungsten as its main component and an oxide film covering a surface of the tungsten wire, the second metal wire contains copper as its main component the oxide film has an average thickness of at least 2 nm and at most 50 nm, and a ratio of surface roughness Ra of the first metal wire to wire diameter of the first metal wire of 0.0049 or less. [2] Composite wire according to claim 1, wherein the first metal wire has a wire diameter of 100 µm or less. [3] Composite wire according to claim 1, wherein the first metal wire is located in a radial direction in a center of the composite wire. [4] Composite wire according to any one of claims 1 to 3, wherein the composite wire is used as an electrical wire. [5] Robots, in general: the composite wire according to claim 4, which is used as an electrical wire, wherein the electrical wire is connected to a drive. [6] Robot according to claim 5, wherein the electrical wire is a signal wire connected to the drive.

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