Electric wire conductor and insulated wire

Abstract

Provided are: an electric wire conductor which is formed of aluminum or an aluminum alloy, has a flattened shape, and exhibits excellent bendability and conductivity while having high rigidity; and an insulated wire which includes such an electric wire conductor.　Disclosed is an electric wire conductor 2 composed of integrally continuous aluminum or an aluminum alloy, wherein a cross-section orthogonal to the longitudinal direction thereof has a flattened shape which is long in the width direction x and is short in the height direction y, and with respect to the hardness in the cross-section, the difference between the maximum value and the minimum value of Vickers hardness is 40% or more of the minimum value. Also disclosed is an insulated wire 1 including the electric wire conductor 2 and an insulation coating 3 which covers the outer periphery of the electric wire conductor 2.

Description

Electric wire conductor and insulated electric wire

[0001] The present disclosure relates to an electric wire conductor and an insulated electric wire.

[0002] In automobiles, in recent years, due to the higher functionality of in-vehicle units and the downsizing of vehicles, the space available for routing electric wires has become smaller. Therefore, in automotive electric wires, the shape of the conductor may be flattened to save space in the height direction. As an electric wire having such a flat conductor, busbar electric wires as disclosed in Patent Documents 1 and 2 are known. A busbar electric wire includes a conductor made of a single metal wire formed into a flat shape. In addition to busbar electric wires, flat electric wires provided with stranded conductors have also been developed as disclosed in Patent Document 3. In this case, a stranded wire formed by twisting a plurality of metal strands into a flat shape is used as the conductor. Busbar electric wires have high rigidity in addition to space-saving properties. On the other hand, flat electric wires using stranded conductors have high flexibility.

[0003] Japanese Patent Application Laid-Open No. 2020-177878, Japanese Patent Application Laid-Open No. 2020-113511, Japanese Patent Application Laid-Open No. 2017-224565

[0004] As described above, flat electric wires provided with stranded conductors are excellent in flexibility, but in cases where the deformation of the electric wire becomes a problem in the processing and routing of the electric wire, such as when performing automatic assembly, there is a high demand for busbar electric wires in terms of having high rigidity. When bending the electric wire, assembling a wire harness from the electric wire, transporting the electric wire or the wire harness, or assembling the electric wire or the wire harness into a vehicle by automatic assembly or the like, when a large force such as a force that swings the electric wire is applied to the electric wire by an operator or mechanical equipment, the electric wire may be deformed. However, if the electric wire has high rigidity, the deformation caused by the application of those forces can be suppressed.

[0005] In busbar cables, increasing the rigidity of the conductor is effective by using an alloy with a high-strength composition as the conductor material, or by increasing the strength of the conductor material through processing such as tempering. However, when the rigidity of the conductor increases, it becomes difficult to bend the cable in the width direction (edgewise direction) of the flattened shape of the conductor, and damage such as cracking is more likely to occur at the bending point. Thus, it is difficult to achieve both rigidity and flexibility in the conductor. In addition, conductor materials whose rigidity has been increased by the selection of alloy composition or processing tend to have low conductivity. High conductivity is important for cable conductors, and in order to ensure sufficient conductivity while using a conductor material with low conductivity, it becomes necessary to increase the conductor cross-sectional area. Aluminum is sometimes used as a constituent material for cable conductors for purposes such as weight reduction, but when aluminum is used, the difficulty of bending due to increased rigidity, and the decrease in conductivity and the resulting increase in conductor cross-sectional area become particularly noticeable.

[0006] In view of the above, the objective is to provide an aluminum or aluminum alloy wire conductor having a flattened shape, high rigidity, and excellent flexibility and conductivity, and an insulated wire equipped with such a wire conductor.

[0007] The electric wire conductor of this disclosure is made of a single continuous piece of aluminum or aluminum alloy, and has a flattened cross-section perpendicular to the longitudinal direction, which is long in the width direction and short in the height direction, and the difference between the highest and lowest values ​​of the Vickers hardness in the cross-section is 40% or more of the lowest value.

[0008] The insulated wire of this disclosure comprises a wire conductor and an insulating coating that covers the outer circumference of the wire conductor.

[0009] The wire conductors and insulated wires of this disclosure are wire conductors made of aluminum or aluminum alloy having a flattened shape, high rigidity, and excellent flexibility and conductivity, and insulated wires equipped with such wire conductors.

[0010] Figure 1 is a perspective view showing a wire conductor and an insulated wire according to one embodiment of the present disclosure. Figure 2 is a schematic diagram showing the hardness distribution in the wire conductor. Figures 3A to 3C show the measured cross-sectional shape and hardness distribution in the cross-section for wire conductors A1 to A3, respectively. In each figure, the left column shows the measurement points on the cross-sectional photograph. The middle column shows the measured hardness at each height position, and the right column shows the two-dimensional distribution of hardness. Figures 4A to 4C show the measured cross-sectional shape and hardness distribution in the cross-section for wire conductors B1 to B3, respectively. The contents of each column are the same as in Figures 3A to 3C. Figure 5 shows the strain distribution obtained by simulation for a wire conductor assuming sample A3.

[0011] [Description of Embodiments of the Disclosure] First, embodiments of the Disclosure will be listed and described. The wire conductor and insulated wire according to the embodiments of the Disclosure have the following configuration.

[0012] [1] The electric wire conductor according to the embodiment of the present disclosure is made of a single continuous piece of aluminum or aluminum alloy, and has a flattened shape in which the dimensions of the cross section perpendicular to the longitudinal direction are longer in the width direction and shorter in the height direction, and the difference between the highest and lowest values ​​of the Vickers hardness in the cross section is 40% or more of the lowest value.

[0013] The above-mentioned electric wire conductor has a flattened cross-section with a hardness distribution such that the difference between the highest and lowest Vickers hardness values ​​is 40% or more of the lowest value. Due to the contribution of the high-hardness regions, the electric wire conductor has high rigidity. Therefore, even if force is applied to the electric wire conductor during processing or wiring, it is less likely to deform. On the other hand, the low-hardness regions remain soft and highly conductive, so the electric wire conductor as a whole is easy to bend and has high conductivity. In this way, the electric wire conductor, with its hardness distribution, has high rigidity while also being easy to bend and highly conductive. A flattened electric wire conductor with a hardness distribution in its cross-section can be easily manufactured by rolling a single-core wire along the height direction in a single process.

[0014] [2] In the embodiment of [1] above, the electric wire conductor has a high-hardness region and a low-hardness region with lower hardness than the high-hardness region in its cross-section, and the high-hardness region preferably occupies a region in the cross-section that extends in a band shape inclined toward the center from a position on the outside in the width direction and on the outside in the height direction. In this case, the high-hardness region will be distributed in the cross-section of the conductor in the shape of the letter "X". An X-shaped hardness distribution is easily formed in an electric wire conductor when a manufacturing method is adopted in which a single-core wire is rolled in a single process. Because the high-hardness region is distributed in an X shape, even if the area of ​​the high-hardness region is small, it can effectively contribute to improving the rigidity of the electric wire conductor, making it easier to achieve a high level of both rigidity, flexibility and high conductivity in the electric wire conductor.

[0015] [3] In the embodiment of [2] above, the high hardness region is preferably a region with a hardness of 45 HV or higher, and the low hardness region is preferably a region with a hardness of less than 45 HV. Then, by having a sufficiently high hardness in the high hardness region and a sufficiently low hardness in the low hardness region, improvements in rigidity due to the high hardness region and improvements in flexibility and conductivity due to the low hardness region can be effectively achieved.

[0016] [4] In the embodiment of [2] or [3] above, the high hardness region may have a hardness of 88% or more of the maximum value in Vickers hardness, and the low hardness region may have a hardness of less than 88% of the maximum value. Then, the difference between the high hardness region and the low hardness region makes it possible to effectively achieve both improved rigidity due to the contribution of each region, and improved flexibility and conductivity.

[0017] [5] In any of the embodiments described in [2] to [4] above, it is preferable that the area occupied by the high-hardness region in the cross-section is smaller than the area occupied by the low-hardness region. In this case, the effect of improving the flexibility and conductivity of the electric wire conductor can be particularly enhanced by the contribution of the low-hardness region.

[0018] [6] An insulated wire according to an embodiment of the present disclosure comprises a wire conductor as described in [1] to [5] above, and an insulating coating covering the outer circumference of the wire conductor. The wire conductor provided in this insulated wire has a flat cross-sectional shape, and its cross-section has a hardness distribution such that the difference between the highest and lowest values ​​on the Vickers hardness scale is 40% or more of the lowest value. Therefore, due to the contributions of the high-hardness region and the low-hardness region within the wire conductor, the insulated wire has high rigidity while also being flexible and highly conductive.

[0019] [Details of Embodiments of the Disclosure] Below, the wire conductor and insulated wire according to embodiments of the Disclosure will be described in detail with reference to the drawings. The insulated wire according to embodiments of the Disclosure is composed of a wire conductor according to embodiments of the Disclosure.

[0020] <Outline of Electric Wire Conductor and Insulated Wire> Figure 1 shows an insulated wire 1 and an electric wire conductor 2 according to one embodiment of the present disclosure in a perspective view. In this specification, terms indicating the shape and arrangement of members, such as vertical and rectangular, include not only geometrically precise concepts but also errors within the generally acceptable range for insulated wires and electric wire conductors, such as ±15% in length and ±15° in angle. Furthermore, unless otherwise specified in this specification, a cross-section refers to a cross-section perpendicular to the longitudinal direction (axial direction) of the insulated wire 1 and the electric wire conductor 2.

[0021] The insulated wire 1 is configured as a busbar wire and has a wire conductor 2 and an insulating sheath 3. In Figure 1, the insulating sheath 3 at the end is partially removed for display. The wire conductor 2 is configured as a busbar wire, that is, as a single continuous conductor. The wire conductor 2 has a flattened shape. That is, the cross-section of the wire conductor 2 is longer in the width direction (x direction) and shorter in the height direction (y direction) than in the width direction. The insulated wire 1 as a whole also has a flattened cross-section, reflecting the shape of the wire conductor 2. Here, the width direction (x direction) is the direction along the longest side or diameter that makes up the cross-section of the wire conductor 2. The height direction (y direction) is the direction perpendicular to the width direction in the cross-section.

[0022] The wire conductor 2 is made of aluminum or an aluminum alloy. Aluminum and aluminum alloys are excellent in terms of lightness. Preferably, the wire conductor 2 is made of a wrought aluminum alloy such as the 1000 series, 5000 series, or 6000 series, which contains pure aluminum. The wire conductor 2 has a hardness distribution in its cross-section, which will be explained in detail later, and due to the effect of this hardness distribution, it has high rigidity, as well as excellent flexibility and conductivity.

[0023] The conductor cross-sectional area of ​​the wire conductor 2 is not particularly limited, but is 0.5 mm. ２ That's all, and 100mm ２ The following are examples. In particular, 10 mm ２ As shown below, a smaller conductor cross-sectional area makes it easier to obtain a wire conductor 2 with a clearly defined hardness distribution, as described later, and also enhances the effect of improving rigidity. On the other hand, 30 mm ２ As described above, a larger conductor cross-sectional area enhances the space-saving effect of the flattened shape and improves the ease of bending. The flattening ratio of the wire conductor 2, that is, the ratio of the height dimension to the width dimension, is not particularly limited, but a range of approximately 1:2 to 1:9 can be suitably exemplified. The specific cross-sectional shape of the wire conductor 2 is also not particularly limited as long as it is a flattened shape with a long width, and examples include rectangles, ellipses, oblongs, and oval shapes (a shape in which arcs are joined to both ends of the long side of a rectangle; a small oval shape). As will be described later, when manufacturing the wire conductor 2 by single-pass rolling of a single-core wire, an oval cross-section is easily formed.

[0024] The insulating coating 3 is made of an insulating material and covers the outer circumference of the wire conductor 2. Preferably, the insulating coating 3 continuously covers the entire circumference of one wire conductor 2. The material constituting the insulating coating 3 is not particularly limited, and various polymer materials can be used. Additives may be added to the polymer material as appropriate.

[0025] The applications of the insulated wire 1 according to this embodiment are not particularly limited, but it is particularly suitable for use as an automotive wire. In automotive wires, space saving is required, and the flattened insulated wire 1 is advantageous in that it is excellent in saving space in the height direction. Furthermore, as will be described later regarding the wire conductor 2, the insulated wire 1 is highly rigid yet easy to bend, making it suitable for processing and wiring while applying force, and in particular suitable for automated assembly. The insulated wire 1 may be used individually or multiple wires may be combined to form a wire harness.

[0026] <Hardness Distribution in Electric Wire Conductors> The electric wire conductor 2 according to this embodiment has a non-uniform hardness distribution in its cross-section. Specifically, the hardness difference ratio in the cross-section of the electric wire conductor 2 is 40% or more. The hardness difference ratio is defined as the ratio of the difference between the highest value (H1) and the lowest value (H2) of the Vickers hardness in the cross-section of the electric wire conductor 2 to the lowest value (H2). In other words, the hardness difference ratio is calculated as (H1 - H2) / H2 × 100%.

[0027] In the electric wire conductor 2, regions with high hardness contribute to improving the overall strength of the electric wire conductor 2. Thus, the rigidity of the electric wire conductor 2 is increased by including these high-strength regions. On the other hand, regions with low hardness increase the flexibility of the electric wire conductor 2, contributing to the overall ease of bending the electric wire conductor 2. Furthermore, in aluminum and aluminum alloys, the conductivity tends to decrease as hardness increases through the selection of component composition and treatments such as tempering and work hardening. However, the presence of regions with low hardness in the electric wire conductor 2 maintains high conductivity in those regions, resulting in high conductivity for the electric wire conductor 2 as a whole.

[0028] In this embodiment, the wire conductor 2 has both high-hardness and low-hardness regions in its cross-section, thereby achieving both improved rigidity due to the contribution of the high-hardness region and improved flexibility and conductivity due to the contribution of the low-hardness region. In particular, the hardness difference ratio is 40% or more, and a sufficiently large hardness difference exists between the high-hardness and low-hardness regions, so both the effect of improved rigidity due to the high-hardness region and the effect of improved flexibility and conductivity due to the low-hardness region can be obtained at a high level. Because the wire conductor 2 has high rigidity, even if a large force is applied to the insulated wire 1 during processing or routing, the wire conductor 2 is less likely to deform. On the other hand, if the wire conductor 2 has excellent flexibility, not only can bending processing associated with routing be easily performed, but damage such as cracking is less likely to occur in the wire conductor 2 when bent. Furthermore, if the wire conductor 2 has high conductivity, it becomes unnecessary to increase the conductor cross-sectional area to ensure conductivity, and the effect of space saving through flattening can be easily utilized.

[0029] From the viewpoint of further enhancing the rigidity improvement effect in the high-hardness region and the flexibility and conductivity improvement effect in the low-hardness region, it is preferable that the hardness difference ratio be 45% or more, and more preferably 50% or more. There is no particular upper limit set for the hardness difference ratio, but it is generally 70% or less. In addition, there are no particular limitations on the specific values ​​of the maximum (H1) and minimum (H2) hardness values, but from the viewpoint of enhancing the above effects, for example, the maximum value (H1) is preferably 47 HV or more, and more preferably 50 HV or more. There is no particular upper limit set for the maximum value (H1), but for example, it is 60 HV or less. In addition, it is preferable that the minimum value (H2) be 40 HV or less, and more preferably 35 HV or less. There is no particular lower limit set for the minimum value (H2), but for example, it is preferably 30 HV or more.

[0030] In the cross-section of the electric wire conductor 2, the specific pattern in which regions with different hardness are distributed is not particularly limited, but the distribution pattern illustrated in Figure 2 can be cited as a preferred example. In the configuration shown in Figure 2, a high-hardness region 21 with relatively high hardness and a low-hardness region 22 with lower hardness than the high-hardness region 21 exist in the cross-section, and the high-hardness region 21 has an X-shaped distribution. That is, the high-hardness region 21 extends in a sloping, band-like manner from the four corners of the flattened shape, outward in the width direction (x direction) and outward in the height direction (y direction), toward the center. This sloping band-like region extends toward the center from four directions, and as a whole, the high-hardness region 21 is distributed in an "X" shape. The low-hardness region 22 is distributed in a position outside the X-shaped high-hardness region 21.

[0031] An X-shaped hardness distribution is easily formed when the electric wire conductor 2 is manufactured using a method in which a single-core wire is rolled in a single process, as will be described later. In an X-shaped hardness distribution, the high-hardness region 21, which has high strength, crosses the cross-section diagonally. Therefore, even if the area of ​​the high-hardness region 21 is small, the high-hardness region 21 effectively contributes to improving the overall strength of the electric wire conductor 2 and the resulting improvement in rigidity. By reducing the area of ​​the high-hardness region 21, the area of ​​the low-hardness region 22 becomes larger, so the effect of improving flexibility and conductivity due to the contribution of the low-hardness region 22 can be greatly enhanced. In this way, by adopting an X-shaped hardness distribution, it becomes easier to achieve a high level of balance between the contributions of both the high-hardness region 21 and the low-hardness region 22.

[0032] When an X-shaped hardness distribution is adopted, the specific hardness of the high-hardness region 21 and the low-hardness region 22 is not particularly limited, but it is preferable that the high-hardness region 21 has a hardness of 45 HV or more, and the low-hardness region 22 has a hardness of less than 45 HV. It is also preferable that the hardness of the high-hardness region 21 be 88% or more of the maximum value of the cross-sectional hardness (H1 above), and the hardness of the low-hardness region 22 be less than 88% of the maximum value (H1). It is also preferable that the hardness of the high-hardness region 21 be 95% or more of the maximum value (H1), and the hardness of the low-hardness region 22 be less than 95% of the maximum value (H1). By having these hardness levels in the high-hardness region 21 and the low-hardness region 22, it becomes easier to obtain high levels of both the rigidity improvement effect from the high-hardness region 21 and the flexibility and conductivity improvement effects from the low-hardness region 22.

[0033] In a cross-section with an X-shaped hardness distribution, the area ratio of the high-hardness region 21 to the low-hardness region 22 is not particularly limited, but it is preferable that the area occupied by the high-hardness region 21 is smaller than the area occupied by the low-hardness region 22. In other words, it is preferable that the area ratio of the low-hardness region 22 in the cross-section is greater than 50%. When this is done, the effect of improving flexibility and conductivity in the electric wire conductor 2 is particularly high. More preferably, the area ratio of the low-hardness region 22 is 60% or more, and even more preferably 65% ​​or more. When the electric wire conductor 2 is processed into a flat shape by rolling, the high-hardness region 21 is easily formed by work hardening, so there is little need to intentionally ensure a large area ratio of the high-hardness region 21. However, from the viewpoint of sufficiently obtaining the effect of improving rigidity by the high-hardness region 21, it is preferable to keep the area ratio of the low-hardness region 22 in the cross-section to 80% or less, and even more preferably 70% or less.

[0034] The hardness distribution in the cross-section of the electric wire conductor 2 can be evaluated, for example, by actual measurement using a micro-Vickers hardness tester. Furthermore, since the hardness of metallic materials has a high positive correlation with material strain, the hardness distribution can also be estimated using the strain magnitude distribution as an indicator. For example, the distribution of equivalent plastic strain in the cross-section of the electric wire conductor 2 can be estimated by simulation using CAE (Computer-Aided Engineering), and it can be assumed that hardness is higher in areas with greater strain.

[0035] <Method for Manufacturing Electric Wire Conductors and Insulated Wires> Next, an example of a method for manufacturing electric wire conductors 2 and insulated wires 1 according to this embodiment will be described. Electric wire conductors 2 can be suitably manufactured by rolling a round single-core wire (a single-core wire with a substantially circular cross-section). In the rolling process, the single-core wire is sandwiched between a pair of rolling rolls from opposing directions, and a load is applied to form the single-core wire into a flat shape having a desired flatness ratio. Preferably, the rolling process is carried out by a single rolling pass. In the single-rolling process, the round single-core wire is rolled into a flat shape by only one rolling pass, rolling from above and below in the height direction, to form the final electric wire conductor 2. In this way, by limiting the rolling process to only one pass in the height direction and not performing multiple rolls or rolling from the width direction, an electric wire conductor 2 with a flat shape having a large hardness difference in the cross-section can be suitably manufactured. In particular, an electric wire conductor 2 having an X-shaped hardness distribution in the cross-section is easily manufactured. The hardness distribution in the cross-section of the resulting electric wire conductor 2 can also be adjusted by specific rolling conditions, such as the linear speed during rolling. Furthermore, the hardness distribution can also be adjusted by whether or not heat treatment is performed after rolling and by the conditions under which it is performed. However, heat treatment tends to soften the electric wire conductor 2, so omitting heat treatment makes it easier to maintain the non-uniform hardness distribution formed during rolling.

[0036] After manufacturing the wire conductor 2 by rolling, the insulated wire 1 according to this embodiment can be manufactured by forming an insulating coating 3 on the outer circumference of the obtained wire conductor 2 by extrusion molding or the like. Both the rolling process of the wire conductor 2 and the extrusion molding process of the insulating coating 3 can be carried out continuously on a long wire, and both processes can also be carried out directly and consecutively (without winding the wire in between). Therefore, by continuously manufacturing a long insulated wire 1 including the rolling process and the extrusion molding process, a flat insulated wire 1 can be manufactured with high productivity.

[0037] Examples are shown below. However, the present invention is not limited to these examples. Here, we actually fabricated electric wire conductors and verified the relationship between the hardness distribution in the cross-section and various properties. Unless otherwise specified, the preparation and evaluation of samples were carried out at room temperature in air.

[0038] <Preparation of Samples> Three types of wire conductors were prepared as Samples A1 to A3. All of the wire conductors were made of pure aluminum and manufactured by single rolling of round single-core wires (φ1.8 mm) into busbar wires with a conductor cross-sectional area of 2 mm ２ ², a height of 0.9 mm, and a flatness ratio of 1:3. However, in the three types of wire conductors, the hardness was changed by varying the rolling conditions. Specifically, as will be actually confirmed for the hardness distribution later, Sample A1 was a soft material with a low hardness throughout, Sample A2 was a hard material with a high hardness throughout, and Sample A3 was a hardness-distributed material with a non-uniform hardness distribution. For Sample A1, the whole was softened by performing a heat treatment (350 °C × 3 hours) after rolling.

[0039] Similarly, as Samples B1 to B3, wire conductors with a conductor cross-sectional area of 60 mm ２ ², a height of 3.2 mm, and a flatness ratio of 1:7 were manufactured by single rolling of round single-core wires (φ9 mm). B1 was a soft material, B2 was a hard material, and B3 was a hardness-distributed material.

[0040] <Test Method> (1) Confirmation of Cross-Sectional Shape and Evaluation of Hardness Distribution For each sample, a cross-sectional photograph was taken to confirm the cross-sectional shape. Also, the hardness distribution of the cross-section was evaluated. Specifically, at each of a plurality of measurement points arranged in a matrix, indicated by dots on the left-column cross-sectional photographs of FIGS. 3A to 3C and 4A to 4C, the hardness of the wire conductor was measured using a micro-Vickers hardness tester. In FIGS. 3A to 3C, as the height-direction position is indicated by numbers, three stages of measurement points are set. In FIGS. 4A to 4C, although the dots may be difficult to see, five stages of measurement points are set by almost equally dividing the upper side of the height direction by more than half. (2) Measurement of Strength As an index of rigidity, the strength of the wire conductor of each sample was measured. As the strength, the tensile strength of the wire conductor was measured by a metal material tensile test method conforming to JIS Z 2241.

[0041] (3) Measurement of Conductivity The conductivity of the wire conductor of each sample was measured by the four-terminal method.

[0042] (4) In order to evaluate the ease of bending of the bending test wire conductors, a bending test was carried out. In the bending test, the wire conductors of Samples A1 to A3 were bent in the width direction (edgewise bending) respectively. The bending angle was 45°. After the bending was carried out, the bent portion was visually observed to determine whether cracks had occurred in the conductor.

[0043] (5) The strain distribution in the cross section of the wire conductor was estimated by strain evaluation simulation. In the simulation, for the wire conductor of Sample A3, elastoplastic analysis using the finite element method with CAE was performed to estimate the distribution of equivalent plastic strain in the cross section.

[0044] <Test Results> Figures 3A to 3C show the results of confirmation of the cross-sectional shape and evaluation of the hardness distribution for Samples A1 to A3, and Figures 4A to 4C show the same for Samples B1 to B3. First, cross-sectional photographs are shown in the left column of each figure. It is confirmed that an oval-shaped flat cross section is formed in all samples.

[0045] Furthermore, the hardness distributions measured at each measurement point shown in the cross-sectional photographs are shown in the middle and right columns of each figure. The middle column shows the hardness values measured at each measurement point in a graph. In the graph, as shown by the circled numbers in Figures 3A to 3C, for each height position in ascending order from above, the hardness values measured at the measurement points in each width direction position (with the distance from the center of the width direction represented as negative on the left side with the center as the reference) are shown. The right column shows the hardness values obtained at each position two-dimensionally in a gray scale. In view of the symmetry of the wire conductor, the hardness measurement was carried out only in the upper left region of the cross-sectional photograph, but in the two-dimensional display of Figures 4A to 4C, the measurement results are replicated symmetrically up and down and shown. Also, the two-dimensional display of Figures 4A to 4C shows the scales in the vertical and horizontal directions changed. At the bottom of Figures 3C and 4C, a common legend for the two-dimensional displays of Figures 3A to 3C and Figures 4A to 4C is shown respectively. The lower limit value of each hardness range represents "above", and the upper limit value represents "less than".

[0046] Observing the obtained hardness distribution, samples A1 and B1 in Figures 3A and 34A show low hardness throughout the entire cross-section, confirming that they are soft materials. On the other hand, samples A2 and B2 in Figures 3B and 34B show high hardness throughout the entire cross-section, confirming that they are hard materials. In contrast to these, samples A3 and B3 in Figures 3C and 34C show greater non-uniformity in the hardness distribution within the cross-section than the other samples, confirming that they are materials with distributed hardness. More specifically, as shown in the two-dimensional distribution in the right column, the high-hardness region is distributed in an X-shape, and the low-hardness region surrounds this X-shaped region. Furthermore, according to the strain distribution corresponding to sample A3 in Figure 5, there is a non-uniform distribution of strain magnitude within the cross-section, and the region with large strain is distributed in an X-shape. These simulation results also support the finding that in hardness-distributed materials, hardness, a physical property that has a high correlation with strain, exhibits a non-uniform distribution in the cross-section of the electric wire conductor, and moreover, an X-shaped distribution.

[0047] Tables 1 and 2 below show the maximum (H1) and minimum (H2) hardness values, the hardness difference ratio ((H1 - H2) / H2 × 100%), and the area ratio of the low hardness region (below 45 HV) obtained from the hardness distribution in Figures 3 and 4, respectively. The area ratio was calculated as the percentage of measurement points where a measurement value of less than 45 HV was obtained out of all measurement points in the hardness distribution in Figures 3A-3C and 4A-4C. Tables 1 and 2 also show the measurement results for conductivity and strength. Table 1 also shows the results of the bending test.

[0048]

[0049]

[0050] According to Tables 1 and 2, samples A1 and B1 (soft materials) and A2 and B2 (hard materials) show small hardness difference ratios of 30% or less, while samples A3 and B3 (hardness-distributed materials) show hardness difference ratios of 40% or more. Furthermore, in these hardness-distributed materials, the area ratio of the low-hardness region exceeds 50%. Regarding strength, the soft materials show low values, less than half that of the hard materials, while the hardness-distributed materials show significantly higher values ​​than the soft materials. On the other hand, the conductivity of the hard materials is significantly lower compared to the soft materials, while the hardness-distributed materials show high conductivity close to that of the soft materials. In addition, in bending tests, cracks occurred in the wire conductors of the hard materials, while no cracks occurred in the soft materials or hardness-distributed materials.

[0051] Thus, hard materials excel in rigidity, as indicated by the strength of the wire conductor, while soft materials excel in conductivity and flexibility. Although hardness-distributed materials do not match hard materials or soft materials when considered individually, they exhibit high properties in both rigidity, as indicated by the strength of the wire conductor, and conductivity. Flexibility is also high. In short, hardness-distributed materials achieve a good balance between rigidity, conductivity, and flexibility.

[0052] The present invention is not limited in any way to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0053] 1. Insulated wire 2. Wire conductor 21. High hardness region 22. Low hardness region 3. Insulation coating x: width direction y: height direction

Claims

1. A wire conductor made of a single continuous piece of aluminum or aluminum alloy, having a flattened cross-section perpendicular to the longitudinal direction, which is longer in the width direction and shorter in the height direction, and having a Vickers hardness of 40% or more between the highest and lowest values ​​in the cross-section.

2. The electric wire conductor according to claim 1, wherein the cross-section of the electric wire conductor has a high-hardness region and a low-hardness region with a hardness lower than that of the high-hardness region, and the high-hardness region occupies a region in the cross-section that extends in an inclined, band-like shape from a position on the outer side in the width direction and the outer side in the height direction toward the center.

3. The electric wire conductor according to claim 2, wherein the high hardness region is a region with a hardness of 45 HV or more, and the low hardness region is a region with a hardness of less than 45 HV.

4. The electric wire conductor according to claim 2, wherein, in terms of Vickers hardness, the high hardness region has a hardness of 88% or more of the maximum value, and the low hardness region has a hardness of less than 88% of the maximum value.

5. The electric wire conductor according to any one of claims 2 to 4, wherein in the cross-section, the area occupied by the high-hardness region is smaller than the area occupied by the low-hardness region.

6. An insulated wire comprising a wire conductor according to any one of claims 1 to 4, and an insulating coating covering the outer circumference of the wire conductor.

Images