Electric wire conductors and insulated wires

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] This disclosure relates to electric wire conductors and insulated electric wires. [Background technology]

[0002] In automobiles, communication wires are connected to various communication devices via connectors. As devices become smaller, connectors are also being made smaller and lighter. When connectors become smaller, the communication wires connected to them also need to be thinner. For example, Patent Document 1 describes a stranded conductor using strands of a Cu alloy containing Fe, with a conductor cross-sectional area of ​​0.13 mm². 2 They are using versions that have been reduced to this size. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-085344 [Patent Document 2] Japanese Patent Publication No. 2018-37324 [Overview of the project] [Problems that the invention aims to solve]

[0004] As with the conductor used in the above-mentioned Patent Document 1, the conductor cross-sectional area is 0.13 mm². 2 Up to a certain extent, even if the diameter of conventional copper alloy stranded wire is reduced, sufficient wire strength and connection strength during connector connection can be ensured. However, with the miniaturization of connectors in recent years, the conductor cross-sectional area has decreased to 0.13 mm². 2 Even smaller communication wires are needed, with a conductor cross-sectional area of ​​0.13 mm². 2In regions smaller than a certain size, it is difficult to reduce the diameter of stranded conductors, and it is possible to use single-strand conductors. However, if conventional copper alloy wires are used as single strands, it becomes difficult to ensure sufficient wire strength. When wire strength is low, the wire conductor is more prone to buckling. When inserting a wire conductor into a connector terminal for connection, if the wire conductor comes into contact with the wall of the connector terminal, buckling may occur in the wire conductor. If buckling occurs in the wire conductor, it becomes difficult to properly insert the wire conductor into the connector terminal.

[0005] Therefore, the conductor cross-sectional area is 0.13 mm². 2 The objective is to provide a wire conductor that can be made smaller than the standard size while minimizing the effects of buckling when inserted into a connector terminal, and an insulated wire equipped with such a wire conductor. [Means for solving the problem]

[0006] The electric wire conductor of this disclosure comprises a single core wire made of stainless steel and a copper coating layer made of copper or a copper alloy that covers the outer circumference of the core wire, and has a conductor cross-sectional area of ​​0.13 mm². 2 It is less than 1.1 × 10⁻⁶, and the Young's modulus is 1.1 × 10⁻⁶. 5 It is less than MPa and is used in a single-wire configuration.

[0007] The insulated wire of this disclosure comprises a wire conductor and an insulating coating that covers the outer circumference of one of the wire conductors. [Effects of the Invention]

[0008] The electric wire conductors and communication wires relating to this disclosure have a conductor cross-sectional area of ​​0.13 mm². 2 The present invention relates to a wire conductor that can be made smaller while minimizing the effects of buckling when inserted into a connector terminal, and an insulated wire equipped with such a wire conductor. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a cross-sectional view showing a single-wire insulated electric wire according to one embodiment of the present disclosure. [Figure 2] Figures 2A and 2B are cross-sectional views showing a flat wire. Figures 2A and 2B show different forms respectively. [Figure 3] Figures 3A and 3B are side views explaining the buckling of a wire rod. Figure 3A shows the state before buckling, and Figure 3B shows the state after buckling. [Figure 4] Figure 4 is a diagram showing the measurement results of the buckling force for an insulated wire having three types of wire conductors. [Figure 5] Figures 5A to 5C are photographs taken of the state after buckling for an insulated wire having three types of wire 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 show the case where the test distance is 2.0 mm. [Figure 6] Figure 6 is a diagram showing the measurement results of the amount of buckling for an insulated wire having three types of wire conductors. [Figure 7] Figure 7 is a diagram showing the evaluation results regarding the relationship between the tensile strength and the amount of buckling of a wire conductor. [Figure 8] Figures 8A and 8B are diagrams showing the evaluation results regarding the relationship between the tensile strength and the crimping strength of a wire conductor. Figure 8A shows the case of low compression, and Figure 8B shows the case of high compression.

Embodiments for Carrying Out the Invention

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

[0011] The above 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, so that the conductor cross-sectional area is 0.13 mm2 Despite being small, it possesses high material strength, and the wire conductor is less likely to buckle when inserted into a connector terminal. In other words, because a copper coating layer made of a low-rigidity material is placed on the outer circumference of the core wire made of high-rigidity stainless steel, even if the wire conductor is deformed when inserted into a connector terminal, the deformation is easily reversed, making it less likely 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 × 10⁻⁶. 5 The value becomes small, below MPa, and the buckling force is smaller than that of materials with an even higher Young's modulus. Therefore, although buckling is more likely to occur even with a small force when inserting into the connector terminal, the copper coating layer helps to resolve the deformation during buckling, thus keeping the amount of deformation of the wire conductor due to buckling to a minimum. As a result, the impact of buckling when inserting into the connector terminal is reduced.

[0012] Here, the Young's modulus of the core wire is 1.2 × 10⁻⁶. 5 It is desirable that the pressure be MPa or higher. This results in a higher Young's modulus for the core wire, which in turn significantly reduces the buckling force and the amount of deformation of the wire conductor due to buckling, thereby mitigating the effects of buckling.

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

[0014] The stainless steel constituting the core wire is preferably SUS 304H. SUS 304H is a material that exhibits high Young's modulus, tensile strength, and elongation at break, making it suitable for use as a core wire component.

[0015] The insulated wire according to this disclosure comprises a wire conductor and an insulating coating that covers the outer circumference of one of the wire conductors. This insulated wire is 0.13 mm 2 Having a small conductor cross-sectional area of ​​less than 100 mm and excellent small diameter, while possessing the above-mentioned predetermined structure and physical properties as a wire conductor, the wire conductor becomes less susceptible to buckling when inserted into the connector terminal. Therefore, it can be suitably used as a communication wire connected to a small connector, such as in automobiles.

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

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

[0018] [Details of the embodiments of this disclosure] Embodiments of this disclosure will be described in detail below with reference to the drawings. In this specification, terms indicating the shape and arrangement of members, such as "parallel" and "perpendicular," include not only geometrically precise concepts but also errors within the range generally acceptable for communication wires. Furthermore, in this specification, various physical properties are values ​​measured in air at room temperature (generally 15-25°C).

[0019] <Overview of electric wire conductors and communication wires> Figure 1 shows a cross-section of an insulated wire 1 according to one embodiment of the present disclosure, including a wire conductor 10 according to one embodiment of the present disclosure.

[0020] The electric wire conductor 10 according to the embodiments of this disclosure is used in a single-wire state. That is, the electric wire conductor 10 is used in a state in which each wire conductor is individually insulated, and multiple uninsulated electric wire conductors 10 are not used together by twisting or forming bundles. In the insulated electric wire 1 shown in Figure 1, an insulating coating 20 is formed by covering the outer circumference of a single electric wire conductor 10.

[0021] The electric wire conductor 10 has a core wire 11 and a copper coating layer 12 that covers the outer circumference of the core wire 11. The core wire 11 and the copper coating layer 12 are integrally joined. The core wire 11 is made of stainless steel (SUS). The type of SUS is not particularly limited, but austenitic SUS, especially SUS 304H and SUS 304L, can be suitably used. The copper coating layer 12 is made of copper or a copper alloy. Preferably, from the viewpoint of keeping the rigidity of the copper coating layer 12 low, it is best to make it from pure copper that does not contain additive elements except for unavoidable impurities. Other types of layers may be placed between the core wire 11 and the copper coating layer 12 for purposes such as improving 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] Here, the component compositions of SUS 304H and SUS 304L are summarized in Table 1 below. The two differ from each other in their C and Ni content. [Table 1]

[0023] The wire conductor 10 has an overall conductor cross-sectional area of ​​0.13 mm². 2The conductor cross-sectional area is less than 0.13 mm². Because the wire conductor 10 has such a small conductor cross-sectional area, the insulated wire 1 can be made thinner, making it suitable for use in applications such as connecting to small connectors inside automobiles. 2 Small diameter wire conductors, less than 0.10 mm², are more suitable for communication applications than for current carrying. From the viewpoint of increasing the small diameter, the conductor cross-sectional area is 0.10 mm². 2 The following is even more preferable. There is no particular lower limit for the conductor cross-sectional area, but from the viewpoint of suppressing a decrease in strength due to excessive thinning, for example, 0.02 mm 2 This should be left as is. 0.05mm 2 The conductor cross-sectional area can be particularly favorably adopted.

[0024] The electric wire conductor 10 according to this embodiment includes a core wire 11 made of SUS, and due to the high material strength of SUS, the electric wire conductor 10 as a whole has high tensile strength. Therefore, even in a single-wire state or when the diameter is reduced, it has higher conductor strength than conventional electric wire conductors that are made entirely of copper alloy. Furthermore, because it has a structure in which a low-rigidity copper coating layer 12 is arranged on the outer circumference of the core wire 11 made of high-rigidity SUS, it is less prone to large buckling compared to conventional electric wire conductors that are made entirely of copper alloy. The specific characteristics of the core wire 11 will be explained in detail later, but from the viewpoint of exhibiting sufficient strength in the electric wire conductor 10, the outer diameter of the core wire 11 should be 0.11 mm or more, more preferably 0.12 mm or more. On the other hand, from the viewpoint of ensuring sufficient thickness of the copper coating layer 12 while maintaining the small diameter of the electric wire conductor 10, the outer diameter of the core wire 11 should be kept to 0.17 mm or less.

[0025] In the electric wire conductor 10, the copper coating layer 12, as described above, is arranged on the outer circumference of the highly rigid core wire 11 made of SUS, thereby reducing buckling of the electric wire conductor 10, while simultaneously contributing to electrical conductivity. Although the SUS that constitutes the core wire 11 is not a metal with particularly high conductivity, the presence of the copper coating layer 12, which is made of copper or a copper alloy, a metal with high conductivity, ensures sufficient conductivity for the electric wire conductor 10 as a whole. The thickness of the copper coating layer 12 is determined, for example, so that the electrical resistance of the electric wire conductor 10 as a whole is 660 mΩ / m or less. If the electrical resistance of the electric wire conductor 10 is 660 mΩ / m or less, it will have sufficient conductivity as a communication wire. More preferably, the electrical resistance of the electric wire conductor 10 should be 600 mΩ / m or less. There is no particular lower limit set for the electrical resistance of the electric wire conductor 10, but from the viewpoint of preventing the copper coating layer 12 from becoming too thick, it is preferable to set it to, for example, 500 mΩ / m or more. Generally, the thickness of the copper coating layer 12 should be set to 40 μm or more and 70 μm or less.

[0026] The insulating coating 20 is constructed using an organic polymer as the base material. The type of organic polymer is not particularly limited, and olefin-based polymers such as polyolefins and olefin copolymers, halogen-based polymers such as polyvinyl chloride, various elastomers and rubbers 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 improving 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 wire conductor 10 will be explained in detail.

[0028] The electric wire conductor 10 according to this embodiment has a two-layer structure, as described above, with a copper coating layer 12 on the outer circumference of a core wire 11 made of SUS (hereinafter sometimes referred to as copper-covered SUS wire). The SUS that constitutes the core wire 11 is a highly rigid metal with a high Young's modulus. On the other hand, the copper or copper alloy, especially pure copper, that constitutes the copper coating layer 12 is a less rigid metal with a lower Young's modulus than SUS. In the copper-covered SU wire 10, the Young's modulus of the whole is 1.1 × 10⁻¹⁰ due to the combination of the SUS core wire 11 and the copper coating layer 12. 5 The pressure is kept below MPa. As will be shown in later examples, among the copper alloys that have been conventionally used as constituent materials for electric wire conductors, the Young's modulus of Cu-Sn alloy wire, which is a copper alloy with relatively high strength, is 1.1 × 10⁻⁶. 5 The pressure is approximately MPa, and the Young's modulus of the copper-clad SUS wire 10 according to this embodiment is lower than that of the Cu-Sn alloy wire. The Young's modulus of the copper-clad SUS wire 10 is further reduced to 1.0 × 10⁻¹⁰ by the softening of the copper coating layer through heat treatment. 5 Less than MPa, and even 9.0 × 10 4 Less than MPa, 8.0 × 10 4 It may be less than MPa. There is no particular lower limit set for the Young's modulus of copper-clad SUS wire 10, but from the viewpoint of effectively suppressing buckling, etc., 4.0 × 10 4 It is preferable that the Young's modulus is MPa or higher. 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 this embodiment has a lower Young's modulus than the Cu-Sn alloy wire, resulting in a lower buckling force than the Cu-Sn alloy wire. Buckling force is the magnitude of the force required to cause buckling in a wire; a larger value indicates that a larger force is required to cause buckling in the wire. In particular, as shown in Euler's equation below, the higher the Young's modulus of the material constituting the outer circumference of the wire, the greater the buckling force of the wire. This is because the material on the outer circumference of the wire contributes to the buckling force P with a large two-dimensional moment I in cross-section. P=(π 2 ×E×I) / (4×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 (mm²). 4 ), where L is the sample length (mm).

[0030] Therefore, the buckling force P tends to be smaller when a copper coating layer 12 with a low Young's modulus E is present on the outer circumference of the wire conductor than when a Cu-Sn alloy with a high Young's modulus E is present. In other words, the copper-coated SUS wire 10 according to this embodiment tends to have a lower buckling force than conventional Cu-Sn alloy wires. This means that the copper-coated SUS wire 10 is more prone to buckling even when inserted into a connector terminal with little force. In fact, in later embodiments, it has been confirmed that the copper-coated SUS wire 10 exhibits a smaller buckling force than the Cu-Sn alloy wire. Thus, from the viewpoint of the magnitude of buckling force, the copper-coated SUS wire 10 is more prone to buckling than the Cu-Sn alloy wire.

[0031] However, the copper-covered SUS wire 10 according to this embodiment has a structure in which a low-rigidity, i.e., highly flexible copper coating layer 12 is attached to the outer circumference of a high-rigidity SUS core wire 11. As a result, even if deformation is applied due to buckling, the deformation is easily resolved. 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 resolve the deformation due to this restoring force. In other words, even if a force that causes buckling is applied to the copper-covered SUS wire 10, a force that restores it to a state without buckling or with minimal buckling is easily exerted. Therefore, even if a force that causes buckling is applied to the copper-covered SUS wire 10, the application of that force is unlikely to lead to irreversible and large buckling deformation. In particular, as will be shown later, when the copper-covered SUS wire 10 has undergone heat treatment and the copper coating layer 12 has softened, it is excellent in suppressing irreversible buckling deformation of the copper-covered SUS wire 10.

[0032] Here, as shown in Figure 4A, consider the case where one end of the wire 10' is fixed to become the fixed end 10a, and the other end is made the movable end 10b, and a force F is applied in the direction toward the fixed end 10a, causing the wire 10' to buckle as shown in Figure 4B. The amount of deformation of the wire 10' in the longitudinal direction due to buckling, i.e., the buckling amount Δy, is more easily kept small when the wire 10' is a copper-clad SUS wire 10 than when it is a Cu-Sn alloy wire. Here, the buckling amount Δy is defined as the distance between the straight line connecting both ends 10a and 10b of the wire 10' and the top of the buckled portion 10c. When the wire 10' is a copper-clad SUS wire 10, the angle θ of the buckled portion 10c is also kept larger than when it is a Cu-Sn alloy wire, and the buckled portion 10c is less likely to bend sharply. Furthermore, even if deformation occurs that temporarily increases the buckling amount Δy while applying force F, such as when inserting into a connector terminal, the deformation is easily reversed when the application of force F is stopped. In other words, in terms of the magnitude of the buckling amount Δy when buckling occurs, the copper-clad SUS wire 10 is less prone to buckling than the Cu-Sn alloy wire. In fact, as can be seen in later embodiments, with the Cu-Sn alloy wire, the buckling amount Δy is large and the buckled portion 10c tends to form a sharp bend (see Figure 5C), whereas with the copper-clad SUS wire 10, the buckling amount Δy is kept small and the buckled portion 10c tends to take on a gentle, curved shape rather than a sharp bend (see Figure 5A).

[0033] Thus, while the copper-clad SUS wire 10 is more prone to buckling than the Cu-Sn alloy wire in that it has a lower buckling force, the amount of buckling when it does occur is kept small, resulting in a smaller impact from buckling. In other words, the copper-clad SUS wire 10 is prone to buckling even with small forces during insertion into connector terminals, but the amount of buckling when it does occur is kept small. Furthermore, deformation due to buckling is less likely to be irreversibly maintained.

[0034] Even if the buckling force is large and the wire conductor does not buckle unless a large force is applied, as in the case of Cu-Sn alloy wire, if the amount of buckling is large once buckling occurs and the buckled state is irreversibly maintained, the impact of buckling will be significant. For example, it may become impossible to fully insert the wire conductor into the connector terminal due to the effects of buckling, or the wire conductor inserted into the connector terminal may remain in a buckled state. On the other hand, as in the copper-clad SUS wire of this embodiment, even if buckling occurs without applying a large force when inserting the wire conductor 10 into the connector terminal, if the amount of buckling that occurs is small, the insertion of the wire conductor 10 into the connector terminal can be completed in a near-normal state even if buckling has occurred. Furthermore, even if buckling occurs due to deviations in angle or position when inserting the wire conductor 10 into the connector terminal, at least a portion of the buckling can be reversibly resolved by removing the wire conductor 10 from the connector terminal and stopping the application of force. Therefore, by correcting the angle and position and then reinserting the wire conductor 10, it becomes possible to properly insert the wire conductor 10 into the connector terminal. In this way, in the wire conductor 10 made of copper-covered SUS wire according to this embodiment, the effect of the structure in which a low-rigidity copper coating layer 12 is arranged on the outer circumference of a high-rigidity SUS core wire 11 is that the amount of buckling is kept small and buckling is easily resolved, thereby minimizing the effects of buckling.

[0035] In this embodiment, as long as the copper-clad SUS wire 10 as a whole exhibits the predetermined Young's modulus, the physical properties of the SUS core wire 11 and the copper coating layer 12 do not matter. Because 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 × 10⁻¹⁰, which is the value for Cu-Sn alloy wire. 5 It is preferable that it exceeds MPa. Furthermore, the Young's modulus of the SUS core wire 11 is 1.2 × 10⁻⁶. 5 MPa or higher, and 1.5 × 10 5It is preferable that the Young's modulus is MPa or higher. A higher Young's modulus of the SUS core wire 11 increases the buckling force of the copper-covered SUS wire 10 as a whole, and also exhibits a high restoring force, which is excellent in suppressing the amount of buckling. Thus, the effects of buckling can be reduced from the standpoint of both improving buckling force and reducing the amount of buckling.

[0036] The copper-clad SUS wire 10 has a core wire 11 made of SUS, which gives it higher tensile strength compared to conventional Cu-Sn alloy wires. The tensile strength of the copper-clad SUS wire 10 can be adjusted by heat treatment conditions, but as shown in later embodiments, the tensile strength does not have a significant effect on the amount of buckling. However, if the copper-clad SUS wire 10 has high tensile strength, high crimping strength can be obtained at the crimped portion when the copper-clad SUS wire 10 inserted into the connector terminal is crimped. 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 the connector terminal while minimizing the effect of buckling, and then, by utilizing the high tensile strength of the copper-clad SUS wire 10, a crimped portion with high connection strength can be formed after crimping. From the viewpoint of effectively increasing the crimping strength at the crimped portion, the tensile strength of the copper-clad SUS wire 10 is preferably 950 MPa or higher, and more preferably 970 MPa or higher. The tensile strength of a metal wire can be evaluated as the tensile strength at fracture by a tensile test in accordance with JIS Z 2241.

[0037] There is no specific upper limit to the tensile strength of the copper-clad SUS wire 10, however, if the tensile strength is too high, it may actually reduce the connection strength at the connection point with the connector terminal. This is because if the copper-clad SUS wire 10 has high strength and becomes too hard, when crimping it to the connector terminal, a decrease in strength may occur in the material on the connector terminal side, or the copper-clad SUS wire 10 may not be able to be sufficiently deformed, resulting in the connector terminal not being able to firmly hold the copper-clad SUS wire 10, and thus reducing the connection strength. To avoid these situations and ensure high connection strength, it is preferable to keep the tensile strength of the copper-clad SUS wire 10 below 1200 MPa, and even below 1080 MPa. Copper-clad SUS wire 10 having a tensile strength in the range of 950 MPa to 1200 MPa can be suitably manufactured after undergoing the heat treatment described later.

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

[0039] <Manufacturing method for electric wire conductors> As a method for manufacturing the electric wire conductor 10 according to this embodiment, which is configured as a copper-clad SUS wire, for example, a SUS core wire 11 having a predetermined diameter can be manufactured by drawing the wire, and then a copper coating layer 12 can be formed on the surface of the core wire 11 by plating or vapor deposition. Alternatively, the copper-clad SUS wire 10 can also be manufactured by fitting an annular copper material that will become the copper coating layer 12 around the SUS material that will become the core wire 11, and drawing the wire integrally to a predetermined diameter.

[0040] The copper-coated SUS wire 10 obtained as described above may be used as is to construct an insulated wire 1 and connect to a connector terminal, but it is preferable to heat-treat (anneal) the obtained copper-coated SUS wire 10. Heat treatment softens the copper coating layer 12. This improves the flexibility of the copper coating layer 12, and in the copper-coated SUS wire 10, the effect of reducing buckling is enhanced by providing a highly flexible copper coating layer 12 on the outer circumference of the highly rigid SUS core wire 11. Examples of heat treatment temperatures include a range of 100°C or higher and 400°C or lower. More preferably, the heat treatment should be performed at 250°C or higher and 400°C or lower. The heat treatment may be performed by a continuous softening method in which the copper-coated SUS wire 10 is heated by electric current, or by a batch softening method in which the copper-coated SUS wire 10 is heated in a batch furnace at a predetermined temperature.

[0041] After heat treatment, the Young's modulus of the copper-clad SUS wire 10 as a whole is typically 9.0 × 10⁻⁶. 4 From high levels above MPa, 9.0 × 10 4 The hardness drops to below MPa. The change in the state of the copper coating layer 12 due to heat treatment can also be confirmed using the hardness of the copper coating layer 12 as an indicator. Typically, the hardness of the copper coating layer 12 in the cross-section of the copper-clad SUS wire 10 is 130 Hv or higher, and even 150 Hv or higher, before heat treatment, whereas after softening due to heat treatment, it drops to 120 Hv or lower, and even to 100 Hv or lower.

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

[0043] Cross-sections of the flat wire 2 are shown in Figures 2A and 2B. Figures 2A and 2B show different configurations. The flat wire 2 includes a plurality of wire conductors 10 according to the embodiments of the present disclosure described above. The number of wire conductors 10 is not particularly specified, but a number of 2 to 8 is preferably used. In particular, an even number is preferable so that pairs of wires can be formed.

[0044] In the flat wire 2, multiple wire conductors 10 are aligned parallel to each other in one direction, with their axial directions parallel. The outer circumference of each wire conductor 10 is individually covered with an insulating coating 20, forming multiple covered portions 30 consisting of a wire conductor 10 and an insulating coating 20. The covered portions 30 are connected by connecting portions 25. The insulating coating 20 that constitutes the covered portion 30 and the connecting portion 25 are integrally molded using the same material. In the configuration shown in Figure 2A, the connecting portion 25 is formed by connecting the covered portions 30, which have a substantially circular cross-section. On the other hand, in the configuration shown in Figure 2B, adjacent covered portions 30 are directly joined by overlapping their substantially circular cross-sectional shapes, and a part of the insulating coating 20 that constitutes these covered portions 30 functions as a connecting portion 25. In either configuration, from the viewpoint of ensuring the flexibility of the flat 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 wire conductors 10) is smaller than the diameter of the covering portion 30.

[0045] The spacing between the parallel-arranged wire conductors 10 is not particularly limited, but it is preferable that the distance d between adjacent wire conductors 10 (distance between the centers of the wire conductors 10) be 0.2 mm or more, more preferably 0.4 mm or more, or 0.8 mm or more. This ensures sufficient insulation between the wire conductors 10. In particular, in the configuration shown in Figure 2A, it is preferable that the distance d between adjacent wire conductors 10 be 0.4 mm or more. On the other hand, it is preferable that the distance d between at least one pair of adjacent wire conductors 10 is 1.2 mm or less, more preferably 1.0 mm or less. This allows those two wire conductors 10 to be suitably used as a pair of wires for transmitting differential signals while ensuring the necessary characteristic impedance. When the flat wire 2 contains three or more wire conductors 10, the distance d between wire conductors 10 in locations other than between the two wire conductors 10 constituting a pair may be longer than 1.2 mm, or all wire conductors 10 may be arranged at equal intervals of 1.2 mm or less.

[0046] Using the flat wire 2, it becomes possible to connect multiple wire conductors 10 to a connector having multiple terminals arranged side by side at once. As described above, the wire conductor 10 according to the embodiment of the disclosure has a small amount of buckling, so the effect of buckling when inserting it into the connector terminal can be kept small, and the operation of inserting multiple wire conductors 10 into multiple connector terminals at once and simultaneously can be performed. The wire conductor 10 according to the embodiment of the disclosure has high strength, but by arranging multiple of them in parallel, the strength of the flat wire 2 as a whole can be further increased. In addition, because the wire conductor 10 has high strength, if a twisted pair wire is constructed by twisting together independent insulated wires 1 as shown in Figure 1, it is difficult to stably maintain the twisted structure due to the high rigidity of the wire conductor 10. However, by using a flat wire 2 in which multiple wire conductors 10 are arranged side by side, and further maintaining a constant distance d between the wire conductors 10 with a connecting part 25, it becomes possible to stably transmit differential signals. [Examples]

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

[0048] [1] Material and buckling force of electric wire conductors First, we investigated the relationship between the material of the electric wire conductor and the buckling force.

[0049] <Sample preparation> Three types of electric wire conductors were prepared as samples. First, a copper-clad SUS wire was fabricated, consisting of 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 overall outer diameter of the copper-clad SUS wire was φ0.25 mm, and the conductor cross-sectional area was 0.05 mm². 2 The obtained copper-clad SUS wire was used as the "unsoftened" sample. On the other hand, the obtained copper-clad SUS wire was subjected to continuous softening and used as the "softened" sample. Separately, a φ0.25 mm Cu-Sn alloy wire (Sn content: 0.3 mass%) was prepared.

[0050] The physical properties of each wire conductor prepared as described above are shown in Table 2 below. The table also shows the physical properties of the SUS core wire alone (φ0.16 mm, unsoftened) used as the raw material for the copper-clad SUS wire.

[0051] [Table 2]

[0052] Insulated wires were fabricated by forming an insulating coating on the outer circumference of the copper-clad SUS wires (both softened and unsoftened) and Cu-Sn alloy wires prepared as described above. The insulating coating was formed to a thickness of 0.20 mm by extrusion molding of PVC.

[0053] <Evaluation Method> Buckling force was measured for each insulated wire containing the wire conductors prepared as described above. Each insulated wire was cut to 30 mm and subjected to a buckling test. In the buckling test, as shown in Figure 3A, one end of the insulated wire was fixed 10a and the other end was movable 10b, and a force F was applied to the movable end 10b, pushing it toward the fixed end 10a. The distance traveled by the movable end 10b was defined as the test distance, and its relationship to the applied force F was recorded. The maximum value of the applied force F was the buckling force. The travel speed of the movable end 10b was set to 25 mm / min. The testing machine used had 10 mm deep holes in the jigs that held both ends of the insulated wire sample 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, copper-clad SUS wire exhibits a smaller buckling force than Cu-Sn alloy wire, both when softened and when not softened. In other words, copper-clad SUS wire buckles with less force than Cu-Sn alloy wire. In particular, copper-clad SUS wire that has undergone softening exhibits a smaller buckling force.

[0057] According to Euler's equation (1) shown above, materials with a higher Young's modulus have a greater buckling force. Table 2 shows that Cu-Sn alloy wire has a higher Young's modulus than copper-clad SUS wire, and the measured buckling force results are consistent with the relationship shown in Euler's equation. Furthermore, according to Euler's equation, the material located on the outer circumference of the wire conductor contributes significantly to the buckling force due to the effect of the two-dimensional moment of cross-section. Copper-clad SUS wire has a copper coating layer made of a material with a low Young's modulus on its surface, and correspondingly, it can be interpreted that the difference in buckling force is larger than the difference in the overall Young's modulus when compared to Cu-Sn alloy wire. In addition, it is thought that the buckling force of the copper-clad SUS wire after softening is even smaller than that of the unsoftened copper-clad SUS wire, corresponding to the further reduction in Young's modulus of the copper-clad SUS wire, especially on the outer circumference, due to heat treatment.

[0058] Here, theoretical calculations based on Euler's equation separated the contribution of the insulating coating to the buckling force from the contribution of the wire conductor. It was confirmed that, in the case of the softened copper-coated SUS wire, the contribution of the wire conductor accounted for more than half of the total buckling force of the insulated wire measured in the test. In other words, the difference in buckling force of each insulated wire obtained in the test can be attributed to the difference in the buckling force of the wire conductor itself.

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

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

[0061] <Evaluation Method> A buckling test was performed in the same manner as in the above test [1]. In this test, the buckling test was stopped when the wire reached a predetermined test distance set at 0.5 mm intervals between 0.5 mm and 2.5 mm. The insulated wire was then removed from the testing machine, and the buckling amount Δy, i.e., the change in the vertical dimension, was measured. For each test distance, the sample was changed and the measurement was performed three times, and the average value of the buckling amount was recorded.

[0062] <Evaluation Results> Figures 5A to 5C show the state of insulated wires after buckling at a test distance of 2.0 mm, specifically a softened copper-clad SUS wire, an unsoftened copper-clad SUS wire, and a Cu-Sn alloy wire. In the case of the Cu-Sn alloy wire in Figure 5C, the central buckled section is sharply bent, and the angle θ of the buckled section is small. The amount of buckling is also large. On the other hand, in the case of the softened copper-clad SUS wire in Figure 5A, the insulated wire takes on a gently curved shape, and the angle θ of the buckled section is large. The amount of buckling is also clearly smaller than in the case of Figure 5C. In the case of the unsoftened copper-clad SUS wire in Figure 5B, the state is intermediate between Figures 5A and 5C.

[0063] The trends observed in the comparison of Figures 5A to 5C are clearly reflected in the buckling measurement results in Figure 6. Across the entire test distance, the two types of copper-coated SUS wires showed smaller buckling amounts than the Cu-Sn alloy wire. This result can be interpreted as the fact that in the copper-coated SUS wire, the low-rigidity copper coating layer is placed around the outer circumference of the high-rigidity SUS core wire, making it easier for deformation due to buckling to be flexibly resolved.

[0064] Furthermore, comparing the results of the copper-coated SUS wire in its unsoftened and softened states, the buckling amount was slightly smaller in the softened state up to a test distance of 2.0 mm. This result is interpreted as the heat treatment improving the flexibility of the copper coating layer and further enhancing its effect in eliminating deformation due to buckling. Incidentally, when the hardness of the copper coating layer was measured in the cross-section of the copper-coated SUS wire, it was 152 Hv in the unsoftened state and 93 Hv in the softened state.

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

[0066] <Sample preparation> Samples similar to those of the insulated wires with heat-treated copper-clad SUS wires prepared in the above test [1] were prepared. However, in this case, multiple copper-clad SUS wires with different tensile strengths were prepared by varying the heat treatment conditions for softening. In all cases, the electrical resistance of the wire conductor was 660 mΩ / m or less.

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

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

[0069] Buckling of electric wire conductors and the resolution of buckling deformation are due to the behavior of the electric wire conductor in the elastic region, and are considered to be largely unrelated to the tensile strength, which corresponds to the behavior in the plastic region, specifically at fracture. Even in Euler's equation shown as equation (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 wire can change significantly depending on the heat treatment conditions, but Young's modulus is not very affected by the heat treatment conditions.

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

[0071] <Sample preparation> Similar to the above test [3], multiple copper-clad SUS wires with different tensile strengths were prepared by varying the heat treatment conditions for softening. In addition, a conductor cross-sectional area of ​​0.05 mm² was used as a reference sample. 2 We also prepared copper alloy conductors (tensile strength: 740 MPa, elongation at break: 2.1%).

[0072] <Evaluation Method> Each fabricated wire conductor was evaluated for its tensile strength at break by a tensile test in accordance with JIS Z 2241. The fabricated wire conductors were then cut to a length of 104 mm and crimped together using crimp terminals to obtain conductors with terminals. Copper alloy crimp terminals were used. During the crimping process, the conductor was compressed by clamping it from opposing directions in a region of 1.6 to 3.0 mm along the axial direction of the wire conductor. By varying the degree of compression on the conductor, two types of crimped sections were formed: low compression and high compression. The low compression state is typically used in connections between connector terminals and wire conductors, while the high compression state corresponds to a condition where the wire conductor is compressed under more severe conditions than usual.

[0073] The crimp terminals were fixed to the obtained terminal-equipped conductors, and the ends of the wire conductors were pulled. The maximum force applied until the wire conductor broke at the crimped portion was recorded as the crimping strength. The tensile speed was set to 100 mm / min. In all samples, the breakage at the crimped portion occurred not because the wire conductor separated and came out of the crimp terminal, but because the wire conductor itself broke inside the crimp terminal.

[0074] <Test Results> Figures 8A and 8B show the relationship between the tensile strength and crimping 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 level of crimping strength of 30N is shown by a solid line.

[0075] In the low-compression case shown in Figure 8A, a crimping strength of 30 N or more was obtained across the entire range of tensile strengths above 950 MPa. On the other hand, in the high-compression case, a crimping strength of 30 N or more was obtained in the region where the tensile strength of the wire conductor was between 950 MPa and 1080 MPa. In the region where the tensile strength was higher than 1080 MPa, the crimping strength decreased. This is thought to be because the hardness of the wire conductor reduced the material strength of the crimp terminal, making it impossible to firmly hold the wire conductor with the crimp terminal. The crimping strength of the copper alloy conductor of the reference sample was 23.6 N in the low-compression case and 25.4 N in the high-compression case.

[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 in Figures 8A and 8B show that it does affect the crimping strength of the terminal connection. In other words, if the copper-clad SUS wire is inserted into the terminal connection of the connector terminal while suppressing the effect of buckling, in order to ensure high crimping strength after crimping, it is necessary 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 crimping strength of 30 N or more, it is sufficient to select the heat treatment conditions of the copper-clad SUS wire so that a tensile strength of 950 MPa or more can be obtained, and if terminal connection under conditions of higher compression than usual is expected, it is preferable not to increase the tensile strength too much. The elongation at break 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 in any way to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0078] Furthermore, the flat wire configuration described above can also be applied when using any wire conductor other than the wire conductor according to the embodiment of this disclosure. For example, even when using copper alloy wire such as Cu-Sn alloy, the conductor cross-sectional area is 0.32 mm². 2 By arranging multiple small-diameter wire conductors in parallel, it is possible to reduce the diameter of the wire conductors while simultaneously improving their strength. In other words, in an insulated wire containing multiple wire conductors, the challenge is to ensure wire strength when reducing the diameter of the wire conductors, and the insulated wire can be constructed as follows.

[0079] Conductor cross-sectional area is 0.32 mm² 2 Multiple single-strand wire conductors less than 100m in length are arranged in parallel. Each of the aforementioned wire conductors is covered with an insulating coating to form a coated portion. An insulated electric wire in which the covered portions are connected by connecting portions that are integrated with the insulating coating of the covered portions.

[0080] In the insulated wire, 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. In particular, it is preferable that the distance is 1.0 mm or less. Furthermore, the configurations described above can be suitably applied to the flat wire. [Explanation of symbols]

[0081] 1. Insulated wire 2 Flat wires 10. Electrical wire conductor (copper-clad SUS wire) 10' wire rod 10a fixed end 10b Moving end 10c Buckling part 11 core wires 12 Copper coating layer 20 Insulating coating 25 Connecting part 30 Covered part d Distance between wire conductors Force applied to the F wire Δy Buckling amount θ Angle of the buckling section

Claims

1. A single-strand core wire made of stainless steel, It has a copper coating layer made of copper or a copper alloy that covers the outer circumference of the core wire, Conductor cross-sectional area is 0.13 mm² ２ It is less than, Young's modulus is 1.1 × 10⁻⁶ ５ It is less than MPa, The tensile strength is 1080 MPa or less. A wire conductor used in a single-strand configuration.

2. The Young's modulus of the aforementioned core wire is 1.2 × 10⁻⁶ ５ The electric wire conductor according to claim 1, wherein the pressure is MPa or higher.

3. A wire conductor according to claim 1 or claim 2, wherein the tensile strength is 950 MPa or more.

4. The electric wire conductor according to any one of claims 1 to 3, wherein the stainless steel constituting the core wire is SUS 304H.

5. The electric wire conductor according to any one of claims 1 to 4, wherein the copper coating layer is formed on the surface of the core wire and then subjected to heat treatment at a temperature of 100°C to 400°C.

6. A wire conductor according to any one of claims 1 to 5, An insulated wire having an insulating coating that covers the outer circumference of one of the aforementioned wire conductors.

7. The aforementioned electric wire conductors are arranged in parallel in multiples, Each outer circumference of the aforementioned wire conductor is covered with the insulating coating, thereby forming a covered portion. The insulated wire according to claim 6, wherein the spaces between the covering portions are connected by connecting portions that are integrated with the insulating covering of the covering portions.

8. The insulated wire according to claim 7, wherein the 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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