Wire conductor and insulation wire

Abstract

To provide a wire conductor capable of minimizing buckling effect when inserted into a connector terminal even with a conductor cross-sectional area smaller than 0.13 mm2; and to provide an insulation wire comprising such a wire conductor.SOLUTION: A wire conductor 10 includes a single core wire 11 formed from stainless steel, and a copper coating layer 12 formed from copper or copper alloy, which coats an outer periphery of the core wire. The wire conductor has a conductor cross-section area of less than 0.13 mm2 and a Young's modulus of less than 1.1×105 Mpa, and is used in a single wire state. An insulation wire 1 includes the wire conductor 10, and an insulation coating 20 that coats the outer periphery of the wire conductor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to electrical conductors and insulated wires. [Background technology]

[0002] In automobiles, communication wires are connected to various communication devices via connectors, but as devices become smaller, connectors are also becoming smaller and lighter. As connectors become smaller, the communication wires connected to them are also required to have smaller diameters. For example, Patent Document 1 describes a stranded conductor using wires of a Cu alloy containing Fe, with a conductor cross-sectional area of ​​0.13 mm 2 In general, smaller sizes are used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-085344 A [Patent Document 2] JP 2018-37324 A Summary of the Invention [Problem to be solved by the invention]

[0004] The conductor used in the above Patent Document 1 has a conductor cross-sectional area of ​​0.13 mm 2 Even if the conventional copper alloy stranded wire is thinned to a certain extent, the wire strength and the connection strength when connecting to a connector can be sufficiently ensured. However, with the recent miniaturization of connectors, 2 There is also a demand for communication cables that are even smaller than the conductor cross-sectional area of ​​0.13 mm. 2In the region smaller than 100 mm, it is difficult to reduce the diameter of the stranded conductor, and it is possible to consider making the conductor into a solid wire. However, if a conventional copper alloy wire is used as a solid wire as is, it is difficult to ensure sufficient wire strength. When the wire strength is reduced, the wire conductor is more likely to buckle. When the wire conductor is inserted into a connector terminal for connection, if the wire conductor comes into contact with the wall surface of the connector terminal, the wire conductor may buckle. If the wire conductor buckles, it becomes difficult to successfully complete the insertion of the wire conductor into the connector terminal.

[0005] Therefore, the conductor cross-sectional area is set to 0.13 mm 2 The present invention aims to provide an electric wire conductor capable of minimizing the effect of buckling when inserted into a connector terminal even when the electric wire conductor is smaller than the diameter of the connector. Also, the present invention aims to provide an insulated electric wire including such an electric wire conductor. [Means for solving the problem]

[0006] The electric wire conductor of the present disclosure has a solid core wire made of stainless steel and a copper coating layer made of copper or a copper alloy and coating the outer periphery of the core wire, and has a conductor cross-sectional area of ​​0.13 mm 2 and Young's modulus is less than 1.1 × 10 5 MPa and is used in a single wire state.

[0007] The insulated wire of the present disclosure includes the conductor and an insulating coating that covers the outer periphery of the conductor. Effect of the Invention

[0008] The electric wire conductor and the electric wire for communication according to the present disclosure have a conductor cross-sectional area of ​​0.13 mm 2 The present invention provides an electric wire conductor capable of minimizing the effect of buckling when inserted into a connector terminal even if the electric wire conductor is smaller than the above-mentioned dimension, and an insulated electric wire including such an electric wire conductor. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing a solid insulated wire according to one embodiment of the present disclosure. [Diagram 2] 2A and 2B are cross-sectional views showing a flat electric wire, each showing a different form. [Diagram 3] 3A and 3B are side views for explaining buckling of a wire, with FIG. 3A showing the state before buckling occurs and FIG. 3B showing the state after buckling occurs. [Figure 4] FIG. 4 is a diagram showing the measurement results of the buckling force for insulated wires having three types of electric conductors. [Diagram 5] Figures 5A to 5C are photographs of the state after buckling for insulated electric wires having three types of electric conductors. Figure 5A shows a copper-clad SUS wire after softening, Figure 5B shows a copper-clad SUS wire without softening, and Figure 5C shows a Cu-Sn alloy wire. All of them show the case where the test distance was 2.0 mm. [Figure 6] FIG. 6 is a diagram showing the measurement results of the amount of buckling for insulated wires having three types of electric conductors. [Figure 7] FIG. 7 is a diagram showing the evaluation results regarding the relationship between the tensile strength and the amount of buckling of the electric wire conductor. [Figure 8] 8A and 8B are diagrams showing the evaluation results of the relationship between the tensile strength and crimp strength of the electric wire conductor, where Fig. 8A shows the case of low compression and Fig. 8B shows the case of high compression. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. The electric wire conductor according to the present disclosure has a solid core wire made of stainless steel and a copper coating layer made of copper or a copper alloy and coating the outer periphery of the core wire, and has a conductor cross-sectional area of ​​0.13 mm 2 and Young's modulus is less than 1.1 × 10 5 MPa and is used in a single wire state.

[0011] The above-mentioned electric wire conductor has a structure in which a copper coating layer is provided on the outer periphery of a core wire made of stainless steel, and the conductor cross-sectional area is 0.13 mm2 Even though the wire conductor has a small diameter of less than 1.1×10, it has high material strength and is unlikely to buckle when the wire conductor is inserted into a connector terminal, etc. In other words, because the copper coating layer made of a low-rigidity material is disposed around the core wire made of stainless steel with high rigidity, even if the wire conductor is deformed when inserted into a connector terminal, the deformation is easily eliminated and is unlikely to lead to irreversible buckling. Due to the presence of the low-rigidity copper coating layer, the Young's modulus of the entire wire conductor is 1.1×10 5 The Young's modulus is a small value of less than MPa, and the buckling force is smaller than that of materials with a higher Young's modulus. Therefore, even a small force can easily cause buckling when inserted into a connector terminal, but the copper coating layer contributes to promoting the elimination of deformation at the time of buckling, so the amount of deformation of the wire conductor due to buckling is kept small. As a result, the impact of buckling when inserted into a connector terminal is reduced.

[0012] Here, the Young's modulus of the core wire is 1.2×10 5 MPa or more. In this case, when the core wire has a high Young's modulus, the electric conductor as a whole exhibits a high effect of reducing the buckling force and the amount of deformation of the electric conductor due to buckling, and thus the effect of reducing the influence of buckling is enhanced.

[0013] The conductor preferably has a tensile strength of 950 MPa or more. This increases the strength of the conductor, making it less likely to buckle when inserted into a connector terminal, and also provides high strength at the crimped portion when the connector terminal is inserted into the conductor and crimped. The conductor having such a tensile strength can be suitably manufactured by heat treatment.

[0014] The stainless steel constituting the core wire is preferably SUS 304H, which is a material that exhibits high Young's modulus, tensile strength, and breaking elongation, and can be suitably used as a constituent material of the core wire.

[0015] The insulated wire according to the present disclosure includes the conductor and an insulating coating that covers the outer circumference of the conductor. 2 The wire conductor has a small conductor cross-sectional area of ​​less than 1 mm and has excellent small diameter, but by using a wire conductor having the above-mentioned specified structure and physical properties, the wire conductor is less susceptible to buckling when inserted into a connector terminal. Therefore, the wire conductor can be suitably used in automobiles, etc., as a communication wire connected to a small connector.

[0016] Here, it is preferable that a plurality of the electric wire conductors are arranged in parallel, the outer circumference of each of the electric wire conductors is covered with the insulating coating to form a coating portion, and the coating portions are connected by a connecting portion that is integrated with the insulating coating of the coating portion. By arranging a plurality of electric wire conductors in parallel, the strength of the insulated electric wire as a whole is improved. In addition, by arranging a plurality of electric wire conductors in parallel and stably maintaining the distance between the electric wire conductors by the connecting portion, the insulated electric wire can be used as a communication electric wire with stable communication characteristics. Since the electric wire conductor is less susceptible to buckling when inserted into a connector terminal, it is also possible to insert the electric wire conductor into the multiple terminals in a connector having multiple terminals at the same time.

[0017] In this case, it is preferable that the distance between at least one pair of adjacent conductors is 0.2 mm or more and 1.2 mm or less, so that the two conductors can be suitably used as a pair of wires for transmitting differential signals while maintaining sufficient insulation between the conductors.

[0018] [Details of the embodiment of the present disclosure] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. In this specification, the terms "parallel" and "perpendicular" that indicate the shape and arrangement of the components include not only a strict geometrical concept but also an error range that is generally acceptable for a communication cable. In addition, in this specification, various physical properties are values ​​measured in the atmosphere at room temperature (approximately 15 to 25°C).

[0019] <Outline of Electric Wire Conductors and Communication Wires> FIG. 1 shows a cross section of an insulated wire 1 according to one embodiment of the present disclosure, including a conductor wire 10 according to one embodiment of the present disclosure.

[0020] The electric wire conductor 10 according to the embodiment of the present disclosure is used in a solid wire state. In other words, the electric wire conductor 10 is used in a state in which each electric wire conductor 10 is individually insulated, and a plurality of uninsulated electric wire conductors 10 are not used in a state of being gathered together by twisting or forming a bundle. In the insulated electric wire 1 shown in FIG. 1, an insulating coating 20 is formed by covering the outer periphery of one electric wire conductor 10.

[0021] The electric wire conductor 10 has a core wire 11 and a copper coating layer 12 that coats the outer circumference of the core wire 11. The core wire 11 and the copper coating layer 12 are integrally bonded. The core wire 11 is made of stainless steel (SUS). The type of SUS is not particularly limited, but austenitic SUS, particularly SUS 304H and SUS 304L, can be preferably used. The copper coating layer 12 is made of copper or a copper alloy. From the viewpoint of keeping the rigidity of the copper coating layer 12 low, it is preferable that the copper coating layer 12 is made of pure copper that does not contain any additive elements except for unavoidable impurities. Other types of layers may be arranged between the core wire 11 and the copper coating layer 12 for the purpose of increasing the bonding between the core wire 11 and the copper coating layer 12, but it is preferable that the copper coating layer 12 is formed in direct contact with the surface of the core wire 11.

[0022] The chemical compositions of SUS 304H and SUS 304L are summarized in Table 1 below. They differ from each other in the C and Ni contents. [Table 1]

[0023] The electric wire conductor 10 has an overall conductor cross-sectional area of ​​0.13 mm 2The electric wire conductor 10 has such a small conductor cross-sectional area, so that the insulated electric wire 1 can be made thin, and can be suitably used for connection to small connectors in automobiles. 2 A thin electric wire conductor having a cross-sectional area of ​​less than 0.10 mm can be used more suitably for communication purposes than for electrical current carrying purposes. 2 There is no particular lower limit to the conductor cross-sectional area, but from the viewpoint of suppressing a decrease in strength due to excessive thinning, it is preferable that the conductor cross-sectional area is, for example, 0.02 mm 2 It is recommended to set it at 0.05mm or more. 2 A conductor cross-sectional area of ​​10 mm or less can be particularly preferably adopted.

[0024] The electric wire conductor 10 according to the present embodiment includes a core wire 11 made of SUS, and the high material strength of SUS gives the electric wire conductor 10 a high tensile strength as a whole. Therefore, even in a solid wire state or when the diameter is reduced, the electric wire conductor 10 has a higher conductor strength than a conventional electric wire conductor entirely made of a copper alloy. In addition, the electric wire conductor 10 is less likely to buckle than a conventional electric wire conductor entirely made of a copper alloy because of the structure in which the copper coating layer 12 having low rigidity is disposed on the outer periphery of the core wire 11 made of SUS having high rigidity. The specific characteristics of the core wire 11 will be described in detail later, but in order to exert sufficient strength in the electric wire conductor 10, the outer diameter of the core wire 11 is preferably 0.11 mm or more, more preferably 0.12 mm or more. On the other hand, in order to ensure a sufficient thickness of the copper coating layer 12 while maintaining the thinness of the electric wire conductor 10, the outer diameter of the core wire 11 is preferably 0.17 mm or less.

[0025] In the electric wire conductor 10, the copper coating layer 12 is disposed around the highly rigid core wire 11 made of SUS as described above, thereby reducing the buckling of the electric wire conductor 10, and at the same time, is responsible for electrical conduction. Although the SUS constituting the core wire 11 is not a metal having a very high electrical conductivity, the presence of the copper coating layer 12 made of copper or a copper alloy, which is a metal having a high electrical conductivity, can ensure sufficient electrical conductivity in the electric wire conductor 10 as a whole. The thickness of the copper coating layer 12 is determined, for example, so that the electric resistance of the electric wire conductor 10 as a whole is 660 mΩ / m or less. If the electric resistance of the electric wire conductor 10 is 660 mΩ / m or less, the electric wire conductor 10 has sufficient electrical conductivity as a communication electric wire. More preferably, the electric resistance of the electric wire conductor 10 is 600 mΩ / m or less. There is no particular lower limit on the electric resistance of the electric wire conductor 10, but it is preferable to set it to, for example, 500 mΩ / m or more from the viewpoint of preventing the copper coating layer 12 from becoming too thick. Generally, the thickness of the copper coating layer 12 may be set to be not less than 40 μm and not more than 70 μm.

[0026] The insulating coating 20 is made of an organic polymer as a base material. The type of organic polymer is not particularly limited, and olefin-based polymers such as polyolefins and olefin-based copolymers, halogen-based polymers such as polyvinyl chloride, various elastomers, rubbers, etc. can be used. Various additives may be added to the organic polymer as appropriate. The thickness of the insulating coating 20 is not particularly limited, but from the viewpoint of providing sufficient insulation, it is preferable to set it to, for example, 0.1 mm or more. On the other hand, from the viewpoint of increasing the small diameter of the insulated wire 1, it is preferable to keep it to 0.25 mm or less.

[0027] <Characteristics of Electric Wire Conductors> Next, the characteristics of the electric conductor 10 will be described in detail.

[0028] As described above, the electric wire conductor 10 according to this embodiment has a two-layer structure with the copper coating layer 12 on the outer periphery of the core wire 11 made of SUS (hereinafter, may be referred to as a copper-clad SUS wire). The SUS constituting the core wire 11 is a metal with high rigidity and a high Young's modulus. On the other hand, the copper or copper alloy, particularly pure copper constituting the copper coating layer 12, is a metal with low rigidity and a Young's modulus lower than that of SUS. In the copper-clad SU wire 10, the SUS core wire 11 and the copper coating layer 12 are combined, so that the overall Young's modulus is 1.1×10 5 As will be shown in the examples below, the Young's modulus of Cu-Sn alloy wire, which is a copper alloy having relatively high strength among the copper alloys generally used as the constituent material of electric wire conductors, is 1.1 × 10 5 The Young's modulus of the copper-clad SUS wire 10 according to the present embodiment is about 1.0×10 MPa, which is lower than that of the Cu—Sn alloy wire. The Young's modulus of the copper-clad SUS wire 10 is further softened by heat treatment to reduce the copper coating layer to 1.0×10 5 MPa or even 9.0×10 4 MPa, 8.0×10 4 Although there is no particular lower limit for the Young's modulus of the copper-clad SUS wire 10, from the viewpoint of effectively suppressing buckling, it is set to 4.0×10 4 The Young's modulus of the metal wire is evaluated by a tensile test in accordance with JIS Z 2241.

[0029] The copper-clad SUS wire 10 according to the present embodiment has a lower Young's modulus than the Cu-Sn alloy wire, and therefore has a smaller buckling force than the Cu-Sn alloy wire. The buckling force is the magnitude of the force required to cause the wire to buckle, and the larger the value, the greater the force required to cause the wire to buckle. In particular, as shown in Euler's formula below, the higher the Young's modulus of the material constituting the outer periphery of the wire, the greater the buckling force of the wire. This is because the material of the outer periphery of the wire has a large cross-sectional two-dimensional moment I and contributes to the buckling force P. P = (π 2 xE x I) / (4 x L 2 ) (1) Here, P is the buckling force (N), E is Young's modulus (MPa), and I is the two-dimensional moment of area (mm 4 ), L is the sample length (mm).

[0030] Therefore, the buckling force P is more likely to be smaller when the copper coating layer 12 with a low Young's modulus E is present on the outer periphery of the electric wire conductor than when the Cu-Sn alloy with a high Young's modulus E is present. In other words, the copper-clad SUS wire 10 according to the present embodiment is more likely to have a smaller buckling force than a conventional Cu-Sn alloy wire. This means that the copper-clad SUS wire 10 is more likely to buckle even when inserted into a connector terminal with a small force. In fact, it has been confirmed in the following examples that the copper-clad SUS wire 10 exhibits a smaller buckling force than the Cu-Sn alloy wire. Thus, from the viewpoint of the magnitude of the buckling force, it can be said that the copper-clad SUS wire 10 is more likely to buckle than the Cu-Sn alloy wire.

[0031] However, the copper-clad SUS wire 10 according to the present embodiment has a structure in which the copper coating layer 12, which has low rigidity, i.e. high flexibility, is disposed around the SUS core wire 11, which has high rigidity. This is because the SUS core wire 11, which has a high Young's modulus, exhibits a large restoring force, and the copper coating layer 12, which has a low Young's modulus, can flexibly eliminate the deformation. In other words, even if a force that causes buckling is applied to the copper-clad SUS wire 10, a force that restores the wire to a state without buckling or a state with small buckling is likely to act. Therefore, even if a force that causes buckling is applied to the copper-clad SUS wire 10, the application of the force is unlikely to lead to irreversible and large buckling deformation. In particular, when the copper-clad SUS wire 10 is subjected to a heat treatment as described later and the copper coating layer 12 is softened, the copper-clad SUS wire 10 is excellent in the effect of suppressing irreversible buckling deformation.

[0032] Here, as shown in FIG. 4A, one end of the wire 10' is fixed as the fixed end 10a, and the other end is the moving end 10b. A force F is applied in the direction toward the fixed end 10a to buckle the wire 10' as shown in FIG. 4B. The amount of deformation of the wire 10' in the vertical direction due to buckling, that is, the amount of buckling Δy, is more likely to be suppressed to be smaller when the wire 10' is a copper-clad SUS wire 10 than when the wire 10' is a Cu-Sn alloy wire. Here, the amount of buckling Δy is defined as the distance between the straight line connecting both ends 10a, 10b of the wire 10' and the top of the buckling portion 10c. When the wire 10' is a copper-clad SUS wire 10, the angle θ of the buckling portion 10c is kept larger than when the wire 10' is a Cu-Sn alloy wire, and the buckling portion 10c is less likely to bend sharply. In addition, even if deformation that temporarily increases the buckling amount Δy occurs during application of force F, such as during insertion into a connector terminal, the deformation is likely to be reversibly eliminated when application of force F is stopped. In other words, from the viewpoint of the magnitude of the buckling amount Δy when buckling occurs, it can be said that the copper-clad SUS wire 10 is less likely to buckle than the Cu-Sn alloy wire. In fact, as confirmed in the later examples, the Cu-Sn alloy wire has a large buckling amount Δy and the buckling portion 10c is likely to form a sharply bent shape (see FIG. 5C), whereas the copper-clad SUS wire 10 has a small buckling amount Δy and the buckling portion 10c is likely to have a gentle, curved shape rather than a sharply bent shape (see FIG. 5A).

[0033] Thus, the copper-clad SUS wire 10 is more likely to buckle than the Cu-Sn alloy wire in that the buckling force is smaller, but the impact of buckling is smaller in that the amount of buckling when buckling occurs is kept small. In other words, the copper-clad SUS wire 10 is more likely to buckle even with a small force during insertion into a connector terminal, but the amount of buckling when buckling occurs is kept small. In addition, deformation due to buckling is less likely to be irreversibly maintained.

[0034] As in the case of a Cu-Sn alloy wire, even if the buckling force is large and the wire conductor does not buckle unless a large force is applied, if the buckling amount becomes large once buckling occurs and the buckled state is irreversibly maintained, the influence of buckling will become large. For example, the influence of buckling may cause a situation in which the wire conductor cannot be inserted into the connector terminal to the end, or the wire conductor inserted into the connector terminal continues to maintain a buckled state. On the other hand, even if buckling occurs without applying a large force when inserting the wire conductor 10 into the connector terminal, as in the case of the copper-clad SUS wire according to the present embodiment, if the amount of buckling that occurs at that time is small, the insertion of the wire conductor 10 into the connector terminal can be completed in a state close to normal even if buckling occurs. In addition, even if buckling occurs due to the angle or positional deviation when inserting the wire conductor 10 into the connector terminal, at least a part of the buckling is reversibly eliminated by removing the wire conductor 10 from the connector terminal and stopping the application of force. Therefore, by correcting the angle or position and then reinserting the electric wire conductor 10, it becomes possible to normally insert the electric wire conductor 10 into the connector terminal. As described above, in the electric wire conductor 10 made of the copper-clad SUS wire according to the present embodiment, the effect of the structure in which the low-rigidity copper coating layer 12 is disposed on the outer periphery of the high-rigidity SUS core wire 11 is that the amount of buckling is kept small and the buckling is easily eliminated, thereby making it possible to keep the effects of buckling small.

[0035] In this embodiment, the SUS core wire 11 and the copper coating layer 12 may have any physical properties as long as the copper-clad SUS wire 10 as a whole exhibits the above-mentioned predetermined Young's modulus. Since SUS has a higher Young's modulus than copper and copper alloys, the SUS core wire 11 alone exhibits a higher Young's modulus than the copper-clad SUS wire 10. However, the Young's modulus of the SUS core wire 11 is 1.1×10, which is the value of the Cu-Sn alloy wire. 5 It is preferable that the Young's modulus of the SUS core wire 11 is more than 1.2×10 5 MPa or more, or 1.5×10 5The higher the Young's modulus of the SUS core wire 11, the higher the buckling strength of the copper-clad SUS wire 10 as a whole will be, and the higher the restoring strength will be, which is excellent in the effect of suppressing the amount of buckling to a small value, and the higher the Young's modulus of the SUS core wire 11, the greater the effect of suppressing the amount of buckling to a small value, and the higher the Young's modulus of the copper-clad SUS wire 10 as a whole will be.

[0036] The copper-clad SUS wire 10 has a high tensile strength compared to conventional general Cu-Sn alloy wires because it has a core wire 11 made of SUS. The tensile strength of the copper-clad SUS wire 10 can be adjusted by heat treatment conditions, but as shown in the following examples, the tensile strength does not have a significant effect on the amount of buckling. However, if the copper-clad SUS wire 10 has a high tensile strength, when the copper-clad SUS wire 10 inserted into a connector terminal is crimped, a high crimp strength can be obtained at the crimped portion. In other words, the copper-clad SUS wire 10 compressed at the crimped portion is less likely to break. By utilizing the small amount of buckling of the copper-clad SUS wire 10, the copper-clad SUS wire 10 can be inserted into a connector terminal while minimizing the effect of buckling, and then the high tensile strength of the copper-clad SUS wire 10 can be used to form a crimped portion having a high connection strength through crimping. From the viewpoint of effectively increasing the crimp strength at the crimped portion, the tensile strength of the copper-clad SUS wire 10 is preferably 950 MPa or more, and more preferably 970 MPa or more. The tensile strength of the metal wire can be evaluated as the tensile strength at break by a tensile test in accordance with JIS Z 2241.

[0037] The upper limit of the tensile strength of the copper-clad SUS wire 10 is not particularly set, but if the tensile strength is too high, the connection strength at the connection part with the connector terminal may be lowered. If the copper-clad SUS wire 10 has high strength and becomes too hard, when crimping to the connector terminal, the material on the connector terminal side may lose strength, or the copper-clad SUS wire 10 may not be deformed sufficiently, so that the connector terminal may not be able to hold the copper-clad SUS wire 10 firmly, and the connection strength may be lowered. In order to avoid such situations and to ensure high connection strength, it is preferable to keep the tensile strength of the copper-clad SUS wire 10 at 1200 MPa or less, and further at 1080 MPa or less. The copper-clad SUS wire 10 having a tensile strength in the range of 950 MPa or more and 1200 MPa or less can be suitably manufactured through a heat treatment described later.

[0038] When the copper-clad SUS wire 10 is connected to a crimp terminal, the crimp strength at the crimped portion is greatly affected by the tensile strength of the copper-clad SUS wire 10 as described above. However, the breaking elongation of the copper-clad SUS wire 10 also affects the crimp strength. For example, if the breaking elongation of the copper-clad SUS wire 10 as a whole is 1.5% or more, further 1.8% or more, 2.0% or more, or 2.2% or more, a high crimp strength is easily obtained. Furthermore, if the copper-clad SUS wire 10 has such a breaking elongation, even if the tensile strength of the copper-clad SUS wire 10 fluctuates due to fluctuations in heat treatment conditions, a high crimp strength can be stably obtained. SUS 304H can be suitably used as a SUS material that achieves both high tensile strength and breaking elongation after heat treatment. The breaking elongation of the metal wire can be evaluated by a tensile test in accordance with JIS Z 2241.

[0039] <Manufacturing method of electric wire conductor> A method for manufacturing the electric wire conductor 10 according to this embodiment configured as a copper-clad SUS wire may be, for example, to manufacture a SUS core wire 11 having a predetermined diameter by wire drawing, and then form a copper coating layer 12 by plating or vapor deposition on the surface of the core wire 11. Alternatively, the copper-clad SUS wire 10 can also be manufactured by fitting a ring-shaped copper material that will become the copper coating layer 12 around the SUS material that will become the core wire 11, and drawing them together to a predetermined diameter.

[0040] The copper-clad SUS wire 10 obtained as described above may be used as it is to form an insulated electric wire 1 and to connect it to a connector terminal, but it is preferable to perform a heat treatment (annealing) on ​​the obtained copper-clad SUS wire 10. By performing the heat treatment, the copper coating layer 12 is softened. Then, the flexibility of the copper coating layer 12 is improved, and the effect of reducing the amount of buckling in the copper-clad SUS wire 10 by providing the highly flexible copper coating layer 12 on the outer periphery of the highly rigid SUS core wire 11 is enhanced. The heat treatment temperature can be, for example, in the range of 100°C or more and 400°C or less. More preferably, the heat treatment is performed at 250°C or more and 400°C or less. The heat treatment may be performed by a continuous softening method in which the copper-clad SUS wire 10 is heated by passing electricity through it, or by a batch-type softening method in which the copper-clad SUS wire 10 is heated in a batch furnace at a predetermined temperature.

[0041] After the heat treatment, the Young's modulus of the copper-clad SUS wire 10 as a whole is typically 9.0×10 4 MPa or higher, 9.0×10 4 The hardness of the copper coating layer 12 in the cross section of the copper-clad SUS wire 10 is typically 130 Hv or more, or even 150 Hv or more before the heat treatment, but becomes 120 Hv or less, or even 100 Hv or less after softening due to the heat treatment.

[0042] <Another form of insulated wire – flat wire> The electric wire conductor 10 configured as the copper-clad SUS wire according to the above embodiment may be used in any form, and is not limited to a form constituting a simple insulated electric wire 1 in which the entire circumference of a single electric wire conductor 10 is covered with an insulating coating 20 as shown in Fig. 1. As an example of a case in which an insulated electric wire of another form is formed using the electric wire conductor 10 according to the above embodiment, a flat electric wire will be briefly described.

[0043] Cross sections of the flat electric wire 2 are shown in Fig. 2A and Fig. 2B. Fig. 2A and Fig. 2B show different forms. The flat electric wire 2 includes a plurality of electric wire conductors 10 according to the embodiment of the present disclosure described above. The number of electric wire conductors 10 is not particularly specified, but a number of 2 or more and 8 or less can be preferably adopted. In particular, it is sufficient that the number is an even number so that a pair wire can be formed.

[0044] In the flat electric wire 2, a plurality of electric wire conductors 10 are arranged in parallel in one direction with their axial directions aligned in parallel. The outer periphery of each arranged electric wire conductor 10 is individually covered with an insulating coating 20, and a plurality of covering parts 30 each consisting of the electric wire conductor 10 and the insulating coating 20 are formed. The covering parts 30 are connected to each other by a connecting part 25. The insulating coating 20 and the connecting part 25 constituting the covering part 30 are integrally formed using the same material. In the embodiment shown in FIG. 2A, the connecting part 25 is formed by connecting the covering parts 30 having a substantially circular cross section. On the other hand, in the embodiment shown in FIG. 2B, adjacent covering parts 30 are directly joined so that the substantially circular cross-sectional shapes are overlapped with each other, and a part of the insulating coating 20 constituting the covering parts 30 functions as the connecting part 25. In either form, from the viewpoints of ensuring the flexibility of the flat electric wire 2 and ease of tearing during terminal processing, it is preferable that the thickness of the connecting portion 25 (the dimension perpendicular to the parallel direction of the electric wire conductor 10) is smaller than the diameter of the covering portion 30.

[0045] The interval between the electric wire conductors 10 arranged in parallel is not particularly limited, but it is preferable that the distance d between adjacent electric wire conductors 10 (the distance between the centers of the electric wire conductors 10) is 0.2 mm or more, further 0.4 mm or more, or 0.8 mm or more. In this way, the insulation between the electric wire conductors 10 can be sufficiently ensured. In particular, in the embodiment of FIG. 2A, the distance d between adjacent electric wire conductors 10 is preferably 0.4 mm or more. On the other hand, it is preferable that the distance d between at least one pair of adjacent electric wire conductors 10 is 1.2 mm or less, further 1.0 mm or less. In this way, the two electric wire conductors 10 can be suitably used as a pair wire for transmitting a differential signal while ensuring a required characteristic impedance. Note that, when the flat electric wire 2 includes three or more electric wire conductors 10, the distance d between the electric wire conductors 10 may be longer than 1.2 mm at a location other than between the two electric wire conductors 10 constituting the pair, or all the electric wire conductors 10 may be arranged at equal intervals of 1.2 mm or less.

[0046] By using the flat electric wire 2, it is possible to connect a plurality of electric wire conductors 10 at once to a connector having a plurality of terminals arranged side by side. As described above, the electric wire conductor 10 according to the embodiment of the present disclosure can suppress the buckling amount to be small, thereby suppressing the influence of buckling when inserted into a connector terminal, and the operation of inserting a plurality of electric wire conductors 10 into a plurality of connector terminals at once and simultaneously can be easily performed. The electric wire conductor 10 according to the embodiment of the present disclosure has high strength, but by arranging a plurality of electric wire conductors 10 in parallel, the strength of the flat electric wire 2 as a whole can be further increased. In addition, since the electric wire conductor 10 has high strength, if independent insulated electric wires 1 as shown in FIG. 1 are twisted together to form a twisted pair wire, it is difficult to stably maintain the twisted structure due to the high rigidity of the electric wire conductor 10. However, by forming the flat electric wire 2 in which a plurality of electric wire conductors 10 are arranged side by side, and further by maintaining a constant distance d between the electric wire conductors 10 by the connecting portion 25, it becomes possible to stably transmit a differential signal. EXAMPLES

[0047] Examples are shown below. Note that the present invention is not limited to these examples. Unless otherwise specified, the preparation and evaluation of samples were carried out in air at room temperature.

[0048] [1] Conductor material and buckling force First, the relationship between the material of the electric wire conductor and the buckling force was examined.

[0049] <Sample preparation> Three types of electric wire conductors were prepared as samples. First, a copper-clad SUS wire was prepared, which had a core wire made of SUS 304H material and a copper coating layer made of pure copper. The outer diameter of the core wire was φ0.16 mm, and the thickness of the copper coating layer was 45 μm. The copper-clad SUS wire as a whole had an outer diameter of φ0.25 mm and a conductor cross-sectional area of ​​0.05 mm. 2 The obtained copper-clad SUS wire was used as a "non-softened" sample. On the other hand, the obtained copper-clad SUS wire was subjected to continuous softening to use as a "softened" sample. Separately, a Cu-Sn alloy wire with a diameter of 0.25 mm (Sn content: 0.3 mass%) was prepared.

[0050] The physical properties of each of the electric wire conductors prepared above are shown in Table 2 below. The table also shows the physical properties of the SUS core wire alone (φ0.16 mm, not softened) used as the raw material for the copper-clad SUS wire.

[0051] [Table 2]

[0052] The copper-clad SUS wires, both softened and unsoftened, and the Cu-Sn alloy wires were coated with insulating coating to produce insulated electric wires. The insulating coating was formed by extrusion molding of PVC to a thickness of 0.20 mm.

[0053] <Evaluation method> The buckling force was measured for the insulated electric wires having each of the electric conductors prepared above. Each insulated electric wire was cut to a length of 30 mm, and a buckling test was performed. In the buckling test, as shown in FIG. 3A, one end of the insulated electric wire was fixed end 10a, and the other end was movable end 10b, and a force F was applied to the movable end 10b to push it toward the fixed end 10a. At this time, the movement distance of the movable end 10b was taken as the test distance, and the relationship with the applied force F was recorded. The maximum value of the applied force F was the buckling force. The movement speed of the movable end 10b was 25 mm / min. In the test machine used, the jigs holding both ends of the sample insulated electric wire each had a hole 10 mm deep for fixing the sample.

[0054] <Evaluation Results> Figure 4 shows the relationship between the test distance and the force applied to the insulated wire obtained in the buckling test. The buckling force, which is read as the maximum value of the applied force, is shown in Table 3 below.

[0055] [Table 3]

[0056] According to Figure 4 and Table 3, the copper-clad SUS wire shows a smaller buckling force than the Cu-Sn alloy wire, both when softened and when not softened. In other words, the copper-clad SUS wire buckles even with a smaller force than the Cu-Sn alloy wire. In particular, the copper-clad SUS wire that has been softened shows a smaller buckling force.

[0057] According to Euler's formula shown above as formula (1), the buckling force is larger for materials with a higher Young's modulus. According to Table 2, the Cu-Sn alloy wire has a higher Young's modulus than the copper-clad SUS wire, and the measurement results of the buckling force are consistent with the relationship shown in Euler's formula. According to Euler's formula, the material located on the outer periphery of the electric wire conductor contributes greatly to the buckling force due to the effect of the cross-sectional two-dimensional moment. The copper-clad SUS wire has a copper coating layer made of a material with a low Young's modulus on the surface, and correspondingly, it can be interpreted that the difference in buckling force is larger than the difference in Young's modulus as a whole in comparison with the Cu-Sn alloy wire. In addition, it is considered that the buckling force of the copper-clad SUS wire after softening is even smaller than the buckling force of the copper-clad SUS wire without softening, corresponding to the further reduction in the Young's modulus of the copper-clad SUS wire, especially the Young's modulus of the outer periphery, by the heat treatment.

[0058] Here, theoretical calculations based on Euler's formula were used to separate the contribution of the insulation coating from the contribution of the wire conductor to the buckling force, and it was confirmed that in the case of a softened copper-clad SUS wire, the contribution of the wire conductor accounted for more than half of the buckling force of the entire insulated wire measured in the test. In other words, it can be said that the difference in the buckling force of each insulated wire obtained in the test is due to the difference in the buckling force of the wire conductor itself.

[0059] [2] Conductor material and buckling amount Next, the relationship between the material of the electric wire conductor and the amount of buckling was examined.

[0060] <Sample preparation> The samples used were insulated electric wires with three types of conductors, the same as those used in the above test [1]: softened copper-clad SUS wire, unsoftened copper-clad SUS wire, and Cu-Sn alloy wire.

[0061] <Evaluation method> The buckling tests were conducted in the same manner as in the above test [1]. The buckling tests were stopped when the wire reached a predetermined test distance, set at 0.5 mm intervals between 0.5 mm and 2.5 mm. The wire was then removed from the test machine and the amount of buckling, Δy, i.e., the change in the longitudinal dimension, was measured. For each test distance, measurements were conducted three times, with the sample replaced, and the average amount of buckling was recorded.

[0062] <Evaluation Results> 5A to 5C show the state of the insulated electric wire having a softened copper-clad SUS wire, a non-softened copper-clad SUS wire, and a Cu-Sn alloy wire, respectively, when buckled at a test distance of 2.0 mm. In the case of the Cu-Sn alloy wire in FIG. 5C, the central buckling part is bent sharply, and the angle θ of the buckling part is small. The amount of buckling is also large. On the other hand, in the case of the softened copper-clad SUS wire in FIG. 5A, the insulated electric wire has a gentle arch shape, and the angle θ of the buckling part is large. The amount of buckling is also clearly smaller than in the case of FIG. 5C. In the case of the non-softened copper-clad SUS wire in FIG. 5B, the state is intermediate between FIG. 5A and FIG. 5C.

[0063] The tendency seen in the comparison of Figures 5A to 5C is clearly shown in the results of measuring the amount of buckling in Figure 6. Over the entire test distance, the two types of copper-clad SUS wires show smaller amounts of buckling than the Cu-Sn alloy wire. This result is interpreted as meaning that in the copper-clad SUS wire, the low-rigidity copper coating layer is arranged around the high-rigidity SUS core wire, making it easier for deformation due to buckling to be flexibly eliminated.

[0064] Furthermore, when comparing the results of the copper-clad SUS wire without and after softening, the amount of buckling was slightly smaller in the softened state in the area up to a test distance of 2.0 mm. This result is interpreted as meaning that the flexibility of the copper coating layer is improved by heat treatment, further enhancing the effect of eliminating deformation due to buckling. Furthermore, when the hardness of the copper coating layer was measured on the cross section of the copper-clad SUS wire, it was 152Hv without softening and 93Hv after softening.

[0065] [3] Tensile strength and buckling amount of copper-clad SUS wire Next, the relationship between the tensile strength and the amount of buckling of the copper-clad SUS wire was examined.

[0066] <Sample preparation> We prepared samples similar to the insulated wire with the heat-treated copper-clad SUS wire produced in the above test [1]. However, in this case, we produced several copper-clad SUS wires with different tensile strengths by varying the heat treatment conditions for softening. Regardless of the heat treatment conditions, the electrical resistance of the wire conductor was 660 mΩ / m or less.

[0067] <Evaluation method> The tensile strength at break of each of the copper-clad SUS wires prepared above was evaluated by a tensile test conforming to JIS Z 2241. In addition, a buckling test was performed on the insulated wires having each copper-clad SUS wire in the same manner as in the above test [2], and the buckling amount Δy was measured at a test distance of 5.0 mm. The length of the insulated wire used in the test was 30 mm. Here, too, the same measurement was performed three times by replacing the sample, and the average value of the buckling amount was recorded.

[0068] <Evaluation Results> Figure 7 shows the relationship between the tensile strength and the amount of buckling of copper-clad SUS wire in a bar graph. According to Figure 7, even if the tensile strength changes, the amount of buckling does not show a systematic change, and the amount of buckling is similar across the entire range of tensile strength. This result shows that the tensile strength of copper-clad SUS wire does not have a significant effect on the amount of buckling.

[0069] Buckling of electric wire conductors and the elimination of buckling deformation are due to behavior in the elastic region of the electric wire conductor, and are thought to have almost no relation to the tensile strength, which corresponds to behavior in the plastic region, and especially at the time of breakage. Even in Euler's equation shown as formula (1), the buckling strength is a quantity that depends on Young's modulus, which is a physical property in the elastic region. This is consistent with the evaluation results in Figure 7. In general, the tensile strength of SUS wires can change significantly depending on the heat treatment conditions, but Young's modulus is not affected much by the heat treatment conditions.

[0070] [4] Tensile strength and crimp strength of copper-clad SUS wire Next, we examined the relationship between the tensile strength of the copper-clad SUS wire and the crimp strength at the terminal connection.

[0071] <Sample preparation> As in the above test [3], several copper-clad SUS wires with different tensile strengths were prepared by varying the heat treatment conditions for softening. 2 A copper alloy conductor (tensile strength: 740 MPa, breaking elongation: 2.1%) was also prepared.

[0072] <Evaluation method> The tensile strength at break of each of the prepared electric wire conductors was evaluated by a tensile test conforming to JIS Z 2241. The prepared electric wire conductors were cut to a length of 104 mm and crimped to obtain a conductor with a terminal. The crimp terminals used were made of a copper alloy, and in the crimping connection, the electric wire conductor was sandwiched and compressed from opposite directions in a region having a length of 1.6 to 3.0 mm along the axial direction of the electric wire conductor. The degree of compression of the conductor was changed to form two types of crimped parts, low compression and high compression. The low compression state is adopted in a connection between a normal connector terminal and an electric wire conductor, and the high compression state corresponds to a state in which the electric wire conductor is compressed under harsher conditions than normal.

[0073] A crimp terminal was fixed to the obtained conductor with terminal, and the end of the electric wire conductor was pulled. The maximum force applied until the electric wire conductor broke at the crimped portion was recorded as the crimp strength. The pulling speed was 100 mm / min. Note that in all samples, the breakage of the crimped portion occurred due to the breakage of the electric wire conductor itself inside the crimp terminal, rather than the separation and removal of the electric wire conductor from the crimp terminal.

[0074] <Test Results> Figures 8A and 8B show the relationship between the tensile strength and crimp strength of copper-clad SUS wire. Figure 8A shows the case of low compression, and Figure 8B shows the case of high compression. In each figure, the crimp strength level of 30N is shown by a solid line.

[0075] In the case of low compression in FIG. 8A, a crimp strength of 30N or more is obtained in the entire range of tensile strengths of 950MPa or more. On the other hand, in the case of high compression, a crimp strength of 30N or more is obtained in the range of tensile strengths of the electric wire conductor from 950MPa to 1080MPa. In the range of tensile strengths higher than 1080MPa, the crimp strength decreases. This is thought to be because the material strength of the crimp terminal decreases due to the hardness of the electric wire conductor, and the electric wire conductor cannot be firmly held by the crimp terminal. The crimp strength of the copper alloy conductor of the reference sample was 23.6N in the case of low compression and 25.4N in the case of high compression.

[0076] As shown in the above test [3], the tensile strength of the copper-clad SUS wire does not affect the amount of buckling, but the results of Figures 8A and 8B show that it does affect the crimp strength of the terminal connection. In other words, if the copper-clad SUS wire is inserted into the terminal connection of a connector terminal while suppressing the effect of buckling, in order to ensure high crimp strength after crimping, it is sufficient to set the tensile strength appropriately. As described above, the low compression state is adopted in the connection of a normal connector terminal, and in such a normal terminal connection, in order to ensure a high crimp strength of 30N or more, it is sufficient to select the heat treatment conditions of the copper-clad SUS wire so that a tensile strength of 950MPa or more is obtained. In addition, when terminal connection is expected to be performed under conditions of higher compression than usual, it is preferable not to increase the tensile strength too much. The breaking elongation of the copper-clad SUS wire tested here was in the range of 1.9% to 2.2%.

[0077] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0078] The configuration of the flat electric wire described above can also be applied to the case where any electric wire conductor other than the electric wire conductor according to the embodiment of the present disclosure is used. For example, even when a copper alloy wire such as a Cu-Sn alloy is used, the conductor cross-sectional area is 0.32 mm 2 By arranging thin electric conductors having a diameter of less than 1 mm in parallel, it is possible to obtain the effect of reducing the diameter of the electric conductors and improving the strength. That is, in an insulated electric wire including a plurality of electric conductors, the insulated electric wire can be configured as follows, with the objective of ensuring the strength of the electric wire when the diameter of the electric conductors is reduced.

[0079] Conductor cross-sectional area is 0.32 mm 2 A single wire conductor of less than 100 mm is arranged in parallel. The outer periphery of each of the electric wire conductors is covered with an insulating covering to form a covering portion, An insulated wire, wherein the covering portions are connected to each other by connecting portions that are integral with the insulating covering of the covering portions.

[0080] In the insulated electric wire, it is preferable that the distance between at least one pair of adjacent two of the electric conductors is 0.2 mm or more and 1.2 mm or less. It is particularly preferable that the distance is 1.0 mm or less. In addition, the above-described configurations can be suitably applied to the configuration of the flat electric wire. [Explanation of symbols]

[0081] 1. Insulated wire 2 Flat Wire 10 Electric wire conductor (copper-clad stainless steel wire) 10' wire rod 10a fixed end 10b Moving end 10c Buckling part 11 Core Wire 12 Copper coating layer 20 Insulation coating 25 Connecting part 30 Covering section d Distance between conductors F is the force applied to the wire Δy Buckling amount θ Angle of buckling part

Claims

1. A solid core wire made of stainless steel; A copper coating layer is made of copper or a copper alloy and coats the outer periphery of the core wire. Conductor cross-sectional area is 0.13 mm ２ is less than Young's modulus is 1.1 x 10 ５ is less than MPa, The tensile strength is 1080 MPa or less, An electric wire conductor used in a solid wire state.

2. The Young's modulus of the core wire is 1.2×10 ５ The conductor according to claim 1, wherein the tensile strength is MPa or more.

3. The conductor according to claim 1 or 2, having a tensile strength of 950 MPa or more.

4. The conductor according to claim 1 , wherein the stainless steel constituting the core wire is SUS 304H.

5. The electric wire conductor according to claim 1 , wherein the core wire is subjected to a heat treatment at 100° C. or more and 400° C. or less in a state where the copper coating layer is formed on a surface of the core wire.

6. The conductor according to any one of claims 1 to 5, and an insulating coating covering an outer periphery of the electric conductor.

7. A plurality of the electric wire conductors are arranged in parallel, The outer periphery of each of the electric wire conductors is covered with the insulating covering to form a covering portion, The insulated wire according to claim 6 , wherein the covering portions are connected to each other by connecting portions that are integral with the insulating covering of the covering portions.

8. 8. The insulated wire according to claim 7, wherein a distance between at least one pair of adjacent conductors is 0.2 mm or more and 1.2 mm or less.

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