JP7295817B2 - Conductor stranded wire for wire harness - Google Patents

Description

TECHNICAL FIELD The present invention relates to a conductor stranded wire for wire harnesses that can be used for wire harnesses used for electrical wiring in automobiles and the like. The present invention relates to excellent conductor strands for wire harnesses.

2. Description of the Related Art Conventionally, a member called a wire harness, in which a terminal is attached to an electric wire including a conductor, has been used for electrical wiring of vehicles such as automobiles, trains, and aircraft. Twisted wires made of copper or copper alloys are usually used for the conductors of such wire harnesses for automobiles. On the other hand, in recent years, with the weight reduction of automobiles, the expansion of vehicle interior space, and the increase in the number of signal wires, there is a strong demand for weight reduction and size reduction of current wire harnesses, and wire diameter reduction is required.

One of the ways to reduce the diameter of electric wires is to reduce the diameter of conductors. However, strength generally decreases as conductors are made thinner. The use of lightweight, high-strength fibers to aid the strength of the conductor may not provide the desired conductivity. In view of such thinning of conductors, twisted wires in which strands of different types are combined are being studied in order to obtain a balance between high strength and conductivity.

Patent Literature 1 discloses a stranded wire in which a group of fine conductor wires are arranged on the outer periphery of a reinforcing cord made of aramid fiber, carbon fiber, polyamide fiber, or the like. Patent Literature 2 discloses a high-tension electric wire in which a plurality of annealed copper wires are arranged around carbon fibers. Patent Literature 3 discloses a coated electric wire in which a plurality of conductor strands and a fibrous reinforcing material arranged therebetween are combined.

However, since the cross-sectional area of the conductor becomes smaller as the electric wire becomes thinner, the conductor resistance decreases and the conductor resistance increases. In contrast to the drag force of 70N or more and the electrical resistance of 760mΩ/m or less required for stranded wires, if copper alloy wires are used for signal wires with a diameter of ^0.13mm2 , which is currently the thinnest, both strength and conductivity are insufficient. It has been confirmed that In particular, ultra-thin wires may break due to the impact of handling due to their fineness.

Although Patent Document 1 discloses improvements in press-contact connectability and bending resistance by controlling the shape of conductors, there is no mention of the characteristics of ultra-fine wires, and the wire diameter and material characteristics disclosed in Examples are disclosed. However, it does not meet the requirements of the current ultra-fine wire described above. The target wire diameter (cross-sectional area) of the electric wire described in Patent Document 2 is within the range of the prior art, and is thicker than the extra-thin wire. The example of Patent Document 3 shows that when the conductor is tough pitch annealed copper showing the same electrical resistance, the tensile strength is increased by about 4.5 times, but the drag force is less than 70 N for thinner conductors. is inferred. Therefore, it is desired to develop an ultrafine wire that satisfies the above requirements in terms of both strength and conductivity even if the cross-sectional area is smaller than the diameter of the current wire.

Japanese Utility Model Publication No. 7-40258 JP-A-2002-150841 JP 2012-3853 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductor stranded wire for a wire harness, which has good electrical conductivity and excellent impact resistance even if it is an ultrafine wire.

An aspect of the present invention is a conductor stranded wire for a wire harness in which a plurality of conductors adjacent to the outer periphery of one or more core wires are stranded, and the cross-sectional area of the stranded wire is 0.04 mm ² or more and 0.06 mm ² or less. wherein the ratio of the tensile test force of the core wire to the tensile test force of all the conductors included in the plurality of conductors is 9 or more and 23 or less, and the ratio of the elongation of the core wire to the elongation of each conductor included in the plurality of conductors is A conductor stranded wire for a wire harness, characterized by having a conductivity of 0.10 or more and 0.25 or less and a conductivity of 40% IACS or more.

An aspect of the present invention is the conductor stranded wire for wire harness, wherein the core wire has a filling rate of 85% or more and 100% or less in the cross-sectional area.

An aspect of the present invention is the conductor stranded wire for wire harness, wherein the core wire has a diameter of 0.12 mm or more and 0.20 mm or less and a tensile strength of 3000 MPa or more.

In an embodiment of the present invention, among the plurality of conductors, the total number of conductors is 9 or more and 14 or less, the diameter of each conductor is 0.050 mm or more and 0.060 mm or less, and the tensile strength of each conductor is 230 MPa or more. 280 MPa or less, each conductor has an elongation of 8% or more and 40% or less, and each conductor has a conductivity of 98% IACS or more.

An aspect of the present invention is a conductor stranded wire for wire harnesses that does not break after 100,000 times in a 180° repeated bending test under conditions of a temperature of 80° C. or less and a radius of curvature of 18 mm.

An aspect of the present invention is an impact resistance test in which a weight of 400 g is placed on one end of a 300 mm long wire made of a bundle of five stranded wires, and the weight is free-dropped from the same height as the position where the other end is fixed. WHEREIN: It is the conductor twisted wire for wire harnesses which does not cause disconnection.

An aspect of the present invention is a conductor stranded wire for wire harnesses, which has a tensile test force of 70 N or more.

According to the aspect of the present invention, the conductor stranded wire for wire harness has a plurality of conductors twisted around one or more core wires. Also, the cross-sectional area of the stranded wire is 0.04 mm ² or more and 0.06 mm ² or less. Furthermore, the ratio of the tensile test force of the core wire to the tensile test force of all the conductors provided by the plurality of conductors is 9 or more and 23 or less, and the ratio of the elongation of the core wire to the elongation of each conductor provided by the plurality of conductors is 0.10 or more. .25 or less and a conductivity of 40% IACS or more. As a result, it is possible to provide a conductor stranded wire for a wire harness that has good conductive properties and excellent impact resistance even if it is an ultra-thin wire.

In addition, even if such a conductor stranded wire for wire harness is used as an ultrafine wire, disconnection due to impact is suppressed, and furthermore, weight reduction of about 30 to 60% and weight reduction of 10 to 30% compared to conventional wire harness size reduction (diameter comparison) is also expected. As a result, it is possible to contribute to the reduction in weight, the expansion of the space inside the vehicle due to size reduction, and the increase in the number of signal lines while maintaining the arrangement space of the wire harness, which are required for automobiles in recent years.

FIG. 1 is a schematic cross-sectional view explaining an outline of a conductor stranded wire for wire harnesses, which is an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining a repeated bending test for evaluating the bending resistance of the wire harness conductor stranded wire according to the present embodiment.

A wire harness conductor twisted wire (hereinafter, sometimes simply referred to as “twisted wire”), which is an embodiment of the present invention, will be described below. It should be noted that the embodiments shown below are merely examples of typical embodiments used to specifically describe the present invention, and various embodiments can be made within the scope of the present invention.

[Twisted wire]
<Structure of stranded wire>
The stranded wire according to the present embodiment is formed by twisting together a plurality of conductors adjacent to the outer periphery of one or more core wires. FIG. 1 is an example of a schematic cross-sectional view illustrating the outline of a stranded wire according to an embodiment of the present invention. As shown in FIG. 1, the twisted wire 3 according to the embodiment of the present invention includes (one) core wire 1 arranged at the center of the twisted wire 3 and a plurality of core wires arranged so as to surround the outer periphery of the core wire 1. (12) conductors 2; In order to impart appropriate strength to the stranded wire 3, the stranded wire 3 is formed by twisting a core wire 1 and a plurality of conductors 2 together. By arranging a plurality of conductors 2 in a twisted manner around the outer periphery of the core wire 1, the conductors 2 tighten the core wire 1 and the porosity of the stranded wire 3 is reduced. Thereby, the strength of the twisted wire 3 can be maintained high, and the cross-sectional area of the twisted wire 3 can be reduced. The degree of twisting of the stranded wire 3 can be appropriately designed according to the number, diameter, etc. of the core wire 1 and the conductor 2 so that the cross-sectional area of the stranded wire 3 is within a desired range. Such a twisted wire 3 plays a role of signal communication in wire harnesses used in vehicles such as automobiles, trains, and aircraft, especially wire harnesses for automobiles. Also, a coated wire can be formed by coating the twisted wire 3 in the circumferential direction with a coating resin that is an insulator (not shown). The material of the coating resin may be any insulating resin used for general coated electric wires, and can be appropriately designed according to the application.

<Extra-thin wire>
An ultra-thin wire is an electric wire whose current-carrying part has a cross-sectional area of 0.13 mm ² or less, and is composed of a stranded wire of the smallest cross-sectional area class currently used in vehicles such as automobiles. The cross-sectional area of the stranded wire according to the present embodiment is 0.04 mm ² or more and 0.06 mm ² or less, which is smaller than the cross-sectional area of the stranded wire used for conventional automotive electric wires. Therefore, the stranded wire according to this embodiment, which includes a core wire and a plurality of conductors, can be used as an extra-fine wire. Moreover, it is preferable that the diameter of the core wire is 0.12 mm or more and 0.20 mm or less, and the diameter of each of the plurality of conductors is 0.050 mm or more and 0.060 mm or less. As a result, when a stranded wire of one or more core wires and a plurality of conductors is produced, it becomes easier to maintain the cross-sectional area of the conductors within the range required for an extra-fine wire, and furthermore, the durability of the resulting stranded wire is increased. Flexibility (repeated bending properties) can be improved. If multiple cores are used, the diameter of each core may be the same or different. Also, the diameter of each conductor may be the same or different for each of the plurality of conductors. The diameters of the core wires and conductors can be appropriately selected within the above range depending on the number of core wires and conductors, changes in the cross-sectional area of the stranded wire before and after the compression step, and the like. However, it is preferable that 40% or more of the total cross-sectional area of the stranded wire is a conductor, since the conductor bears the electrical conductivity of the entire stranded wire.

<Core wire>
The core wire used for the stranded wire according to this embodiment preferably has a tensile strength of 3000 MPa or more, and more preferably has a tensile strength of 4000 MPa or more. When the tensile strength of the core wire is 3000 MPa or more, high strength can be imparted to the stranded wire, and when the stranded wire is used as an ultrafine wire, breakage due to impact can be easily suppressed. In addition, since the core wire has a higher tensile strength, it is possible to improve the flex resistance while imparting to the stranded wire a strength that can more reliably ensure impact resistance. Although the upper limit of the tensile strength of the core wire is not particularly limited, it is preferably 8000 MPa or less from the viewpoint of handling in manufacturing. Thus, the core wire having a high tensile strength makes it easier to impart excellent impact resistance to the stranded wire, and the increase in tensile strength can also improve the bending resistance. Regarding the conductivity of the core wire, if the desired conductivity can be imparted to the entire conductor by using a conductor having a conductivity of a certain level or higher, the core wire does not have to have conductivity (0% IACS can be). On the other hand, if the core wire has even a slight conductivity, it can contribute to weight reduction and size reduction due to the reduction in the number of conductors.

The material of the core wire is not particularly limited as long as it can be used as a tension member, but examples of materials having high tensile strength as described above include polyparaphenylene benzoxazole (PBO) fiber wire and carbon steel wire. (piano wire), stainless steel wire, etc., and PBO fiber having a tensile strength of 4000 MPa or more is more preferable. If multiple cores are used, the material of such cores may be the same or different. Furthermore, in order to improve the conductivity of the core wire and improve the production as a stranded wire, the surface of the core wire is plated with a metal that exhibits conductivity, such as Cu, Ni, Sn, Ag, Au, etc. good too.

When the core wire is formed by twisting strands like a PBO fiber wire, the cross section of the core wire may have some voids. In such a case, in order to impart a drag force of 70 N or more to the twisted wire, the filling area ratio of the strands used for the core wire, that is, the filling ratio in the cross-sectional area of the core wire, is 85% or more and 100% or less. preferable. When the filling rate in the cross-sectional area of the core wire is 85% or more, it is possible to suppress insufficient strength due to a decrease in drag force of the stranded wire, and to impart excellent impact resistance to the stranded wire. The upper limit of the filling rate in the cross-sectional area of the core wire is not particularly limited. is 100%.

Although the number of core wires is not particularly limited, it is preferably one. As a result, a plurality of conductors can be easily twisted around the core wire while imparting appropriate strength and conductivity to the stranded wire in a well-balanced manner.

<Conductor>
In the plurality of conductors used for the stranded wire according to this embodiment, each conductor preferably has a tensile strength of 230 MPa or more and 280 MPa or less. When the tensile strength of each conductor is 230 MPa or more, sufficient strength can be imparted to the stranded wire, and breakage can be suppressed when the stranded wire is used as an extra-fine wire. Regarding the upper limit of the tensile strength of each conductor, the upper limit of the tensile strength of each conductor is 280 MPa or less in order to clarify that the conductor and the core wire are made of different materials.

In the plurality of conductors, each conductor preferably has an elongation of 8% or more and 40% or less. Since the elongation of each conductor is 8% or more, it is possible to impart sufficient strength to the stranded wire in the same manner as the tensile strength, and to suppress breakage when the stranded wire is used as an ultra-thin wire. . Although the upper limit of elongation of each conductor is not particularly limited in terms of performance, it is 40% or less as a practical upper limit. Thus, each conductor satisfies the desired tensile strength and elongation, so that the stranded wire can be imparted with excellent bending resistance and impact resistance, and disconnection can be suppressed.

Among the plurality of conductors, the conductivity of each conductor is preferably 98% IACS or higher, more preferably 100% IACS or higher. Since each conductor has a conductivity of 98% IACS or more, it is possible to impart good conductivity to the stranded wire. can be improved. The higher conductivity of each conductor allows the strands to have a smaller cross-sectional area while still imparting good electrical conductivity to the strands.

In the plurality of conductors, the material of each conductor is not particularly limited as long as the stranded wire satisfies a predetermined conductivity and can form a stranded wire together with the core wire. For example, pure copper such as C1100 series tough pitch copper , or a copper alloy that satisfies the above properties (tensile strength, elongation and electrical conductivity). The material of each conductor may be the same or different. Moreover, when using the same kind of copper alloy, the content of the metal component contained in each copper alloy may mutually be the same or different.

Among the plurality of conductors, the total number of conductors is not particularly limited, but is preferably 9 or more and 14 or less. As a result, a plurality of conductors can be easily twisted around the core wire while imparting appropriate strength and conductivity to the stranded wire in a well-balanced manner. In particular, when the total number of conductors is 9 or more, it is possible to improve the bending resistance of the resulting stranded wire.

<Relationship between core wire tensile test force and conductor tensile test force>
In the stranded wire according to the present embodiment, the ratio of the tensile test force of the core wire to the tensile test force of all the conductors provided by the plurality of conductors (hereinafter also referred to as "tensile test force ratio") is 9 or more and 23 or less. When the tensile test force ratio is 9 or more, a desired resistance can be imparted to the stranded wire, and excellent impact resistance can be achieved. On the other hand, if the tensile test force ratio exceeds 23, there is a risk that the electrical conductivity will be insufficient due to insufficient cross-sectional area of the conductor. Therefore, by setting the upper limit of the tensile test force ratio to 23 or less, insufficient conductivity of the stranded wire can be prevented. Here, the tensile test force of the core wire and the whole conductor is calculated based on the product of the tensile strength and the cross-sectional area, and can be obtained by considering factors such as the filling rate and the number of wires, if necessary. For example, the tensile test force of one core wire can be obtained by multiplying the product of the cross-sectional area of the core wire (radius ² × π) and the tensile strength by the filling factor (filling factor/100). If each conductor is the same, the tensile test force for all conductors can be obtained by multiplying the product of the cross-sectional area (radius ² x π) and the tensile strength of each conductor by the number of conductors (the number of conductors). can ask. When two or more types of core wires and conductors are used, the tensile test force ratio can be calculated by the same calculation formula for each type of conductor, and the sum can be obtained. Thus, by satisfying the desired tensile test force ratio, the stranded wire can be imparted with excellent impact resistance, and disconnection can be suppressed.

<Relationship between core wire elongation and conductor elongation>
In the stranded wire according to this embodiment, the ratio of elongation of the core wire to the elongation of each conductor included in the plurality of conductors (elongation ratio) is 0.10 or more and 0.25 or less. Here, each elongation of the core wire and the conductor was measured according to the breaking elongation standard of JIS Z2241 (2011). If the elongation ratio exceeds 0.25, there are many cases where the conductor breaks before the core wire, and sufficient strength cannot be obtained. Therefore, when the elongation ratio is 0.25 or less, the ductility of the conductor with respect to the core wire can be increased, and breakage of the stranded wire can be suppressed. Also, the lower limit of the elongation ratio is not particularly limited in terms of performance, but is 0.10 or more as a practical lower limit. Thus, by satisfying the desired elongation ratio of the stranded wire, it is possible to impart excellent bending resistance and impact resistance to the stranded wire, and it is possible to suppress wire breakage.

<Tensile test force of stranded wire>
In the stranded wire according to this embodiment, it is preferable that the tensile test force of the stranded wire, that is, the drag force, is 70 N or more. Here, the tensile test force of the stranded wire can be obtained from the sum of the tensile test force of all the conductors included in the plurality of conductors and the tensile test force of the core wire calculated as described above. Since the tensile test force (resistance) of the stranded wire is 70 N or more, bending deformation (buckling deformation) of the tip portion can be suppressed when the stranded wire is inserted into a connector or the like. In addition, since drag is highly correlated with flex resistance and impact resistance, elements with high drag are essential for electric wires. A conventional electric wire can meet the required predetermined strength (prevention of disconnection) by combining strands having an average tensile strength of at least 700 MPa at the minimum diameter (0.13 mm ² ). On the other hand, in the case of ultrafine wires with a cross-sectional area of 0.04 mm ² or more and 0.06 mm ² or less, such as the stranded wire according to the present embodiment, the thinner the diameter, the higher the strength required. A tensile strength of 1167-1750 MPa is required. Such tensile strength is not achievable using copper and copper alloys, which are common wire materials. In the case of an extra-fine wire with a cross-sectional area of 0.04 mm ² or more and 0.06 mm ² or less, the tensile test force of the stranded wire is 70 N or more, so that the prescribed strength required for the extra-fine wire is achieved. It becomes possible to apply it to various uses as. In particular, when a stranded wire is used as a single wire in design, the tensile test force of the stranded wire is preferably 80 N or more.

<Conductivity of stranded wire>
In the stranded wire according to this embodiment, the electrical conductivity of the stranded wire is 40%IACS or higher. Although there is not always a clear threshold value for conductivity, the twisted wire is required to have a conductivity of 40% IACS or more in view of the effects of current loss, heat generation, and the risk of fire. Moreover, if the conductivity of the twisted wire is 40% IACS or more, it means that the twisted wire having the conductivity that can play a role as a signal line is obtained.

When the stranded wire according to the present embodiment is used as a signal wire, the conductivity that can be equivalent to the conductivity that can serve as a signal wire is, for example, the conductivity of a conductor measured in accordance with the JIS H0505 (1975) standard. It can be determined based on the electrical resistance calculated from the ratio. Specifically, the electric resistance per unit length of the stranded wire measured according to JIS H0505 (1975) is preferably 760 mΩ/m or less. As a result, the stranded wire is imparted with electrical conductivity that can serve as a signal wire, and a stranded wire having good electrical conductivity can be obtained even if the wire is very thin.

<Flexibility of stranded wire>
The stranded wire according to the present embodiment can be evaluated for bending resistance by subjecting the stranded wire to a predetermined repeated bending test. As a predetermined repetition test, for example, a stranded wire is bent 180 degrees under conditions of a predetermined temperature and a predetermined radius of curvature, and a bending test is performed repeatedly. Specifically, a repeated bending test of 180 degrees is performed a certain number of times under conditions of a temperature of 80° C. or less and a radius of curvature of 18 mm to evaluate the presence or absence of breakage of the stranded wire. In such a repeated bending test, it is preferable that no disconnection occurs after the test of 100,000 times, and it is more preferable that no disconnection occurs after the test of 200,000 times. Twisted wire means excellent bending resistance. Such a repeated bending test is called a mandrel test, and is performed using a mandrel tester as shown in FIG. 2, for example. As shown in FIG. 2, one end of the stranded wire 10 is fixed to the movable arm 20, and the minimum weight 30 that does not cause slack in the stranded wire 10 is hung from the other end. The outer circumference of a circular or partial circular mandrel 40 having a desired bending radius is arranged to face the stranded wire 10 . A gap G of 1.1 times the wire diameter of the stranded wire is formed between the mandrels 40 facing each other, and the bending resistance of the stranded wire 10 can be evaluated by repeatedly bending the movable arm 20 by 180°. Since the stranded wire 10 has bending resistance under predetermined conditions, it can be applied as an ultra-thin wire to applications that require bending.

<Impact resistance of stranded wire>
Impact resistance can be evaluated by performing a predetermined impact resistance test on the stranded wire according to the present embodiment. Here, as a predetermined impact resistance test, for example, there is an impact resistance test in which a predetermined weight is placed on one end of a fixed length electric wire and the weight is freely dropped from the same height as the position where the other end is fixed. done. Specifically, in an impact resistance test, a 400 g weight was placed on one end of a 300 mm long wire bundled with five twisted wires, and the weight was free-dropped from the same height as the position where the other end was fixed. Evaluate whether or not the stranded wires are broken. If the stranded wire does not break, it means that the stranded wire has excellent impact resistance. Incidentally, such an impact resistance test is a test performed assuming a case in which an assembler mistakenly pulls a conductor when incorporating the covered electric wire as a wire harness into an automobile, causing disconnection of the conductor. If the stranded wire does not break in the impact resistance test, it can be guaranteed that the wire will not break even with the load that can be applied in the case assumed as described above.

Next, an example of a method for manufacturing a stranded wire according to this embodiment will be described.

[Manufacturing method of stranded wire]
The stranded wire according to the present embodiment is manufactured through a stranded wire process of preparing core wires and conductors (strands) of various wire diameters, twisting a plurality of conductors around the outer circumference of the core wire, and optionally a compression process. When the conductor is plated, the plating may peel off, so the compression process can be omitted, and the plating can be applied after the compression process. The manufacturing conditions of the compression process can be appropriately designed according to the number of core wires and conductors, the desired cross-sectional area of the stranded wire after the compression process, etc., but usually the die hole is smaller than the outer diameter of the stranded wire. Compressed by passing a conductor through In addition, heat treatment for straightening can be arbitrarily performed before the twisting process. When the heat treatment is performed, the conditions are appropriately set so that the material strength does not decrease by 10% or more. In the twisting process, the twist pitch between the core wire and the conductor can be set to, for example, 20 to 25, but is not limited to this. In addition, by coating the obtained stranded wire with an insulating coating resin as necessary, a coated electric wire provided with a conductor stranded wire for a wire harness can be produced.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these.

<Examples 1 to 15, Comparative Examples 1 to 12>
For each core wire having a diameter of 0.100 to 0.210 mm shown in Table 1, a plurality of conductors having a diameter of 0.045 to 0.065 mm were twisted together to form a stranded wire. The number of conductors is 7 to 14, and the core wire is made of PBO fiber (manufactured by Toyobo, "Zylon"), carbon steel wire (general-purpose SWP-B), polyarylate resin (manufactured by Teijin, "Technora"), and liquid crystal. Polyester fiber (made by KB SEIREN, XXION) is used, and annealed copper of tough pitch copper, hard copper or specified copper alloy (Cu-0.02 mass% Sn and Cu-0.3 mass% Sn) is used for the conductor. bottom. For the tough-pitch annealed copper, the heat treatment conditions in the final process of making the wire were changed in order to make a difference in strength and elongation performance. The conditions with high strength and elongation are those with final heat treatment at low temperature or short time and with finer grain control, while the conditions with low strength and elongation are those with final heat treatment at high temperature or long time. , which is obtained by growing crystal grains. Tough-pitch hard copper and copper alloys (Cu-0.02% by mass Sn, Cu-0.3% by mass Sn) were produced by selecting a wire drawing process as the final process of producing a wire and then work-hardening it. When the core wire was PBO fiber, the filling rate was controlled by compression conditions. The following measurements and evaluations were performed on each of the obtained twisted wires. Each measurement and test evaluation are shown in Tables 1 and 2.

[Measuring method]
<Measurement of cross-sectional area of stranded wire and filling rate of core wire>
The gap between the core wire and each conductor was filled with resin so that the cross section of the stranded wire could be observed, and then the stranded wire was polished. After that, the magnification of the optical microscope was set to 200 to 500 times, and the cross-sectional area of the stranded wire was measured using industrial size measurement software ("Hybrid Measure ver. 3.0.8" manufactured by Innotek). For the core wire, the boundary between the conductor and the entire conductor was considered to be the outer circumference of the wire. The filling rate (%) of the core wire is obtained by dividing the value obtained by multiplying the average cross-sectional area of each material used for the core wire and the number of core wires by the cross-sectional area of the stranded wire, and multiplying the value by 100. values were used.

<Measurement of tensile strength>
Metal and carbon fibers were measured according to JIS Z2241 (2011) standards. For the resin fiber, the tensile strength of the core wire and each conductor was measured twice according to the JIS K7161 standard, and the average value was calculated as the tensile strength.

<Measurement of elongation>
The elongation of all samples was measured according to the breaking elongation standard of JIS Z2241 (2011).

<Conductivity of conductor>
The electrical conductivity of each conductor was measured twice according to the standard of JIS H0505 (1975), and the average value was calculated as the electrical conductivity.

[Evaluation method]
<Tensile test force ratio of stranded wire>
The tensile test force ratio of the stranded wire was calculated from the ratio of the tensile test force of the core wire to the tensile test force of the entire conductor. The tensile test force of the core wire was obtained by multiplying the product of the cross-sectional area of the core wire (radius ² ×π) and the tensile strength by an element of the filling rate (filling rate/100). In addition, since the tensile test force for all conductors is the same for each conductor, a value obtained by multiplying the product of the cross-sectional area (radius ² ×π) of each conductor and the tensile strength by the number of conductors was used.

<Tensile test force of stranded wire>
The tensile test force (drag) of the stranded wire was calculated from the sum of the tensile test force of the whole conductor and the tensile test force of the core wire. If the tensile test force of the stranded wire was 70 N or more, it was evaluated that the tensile test force was at an acceptable level.

<Conductivity of stranded wire>
The conductivity of the obtained conductor was measured twice according to the standard of JIS H0505 (1975), and the average value was calculated as the conductivity. Also, the obtained electrical conductivity was converted into electrical resistance per unit length, and if the value was 760 mΩ/m or less, it was evaluated as having good electrical conductivity. The electrical resistance per unit length is {1.7241×10 ⁻⁵ (mΩ/m)×100 (%IACS)/conductivity of stranded wire (%IACS)}/cross-sectional area of stranded wire (m ² ) ({(electric resistance value of pure copper×conductivity of pure copper)/conductivity of stranded wire}/cross-sectional area of stranded wire).

<Flexibility of stranded wire>
A repeated bending test (mandrel test) was performed at room temperature (20° C.) under conditions of a bending radius of 180 degrees and a bending radius (curvature radius) of 18 mm. Even if the number of tests exceeds 100,000 times, if all the strands of the stranded wire are unbroken, the result is a pass "○", and if even one strand is broken, the failure is "×". If all the strands were unbroken even after 200,000 cycles, the characteristics were considered to be better and evaluated as "⊚." If the evaluation in the repeated bending test was "O" or higher, it was evaluated that the stranded wire was imparted with excellent bending resistance.

<Impact resistance of stranded wire>
A weight (400 g) is attached to one end of a 300 mm long wire bundled with five stranded wires obtained, and the other end is fixed and the weight is allowed to fall freely from the same position. If there was no disconnection, it was evaluated as "O", and if even one element wire was disconnected, it was evaluated as "X".

As shown in Table 2, none of the stranded wires obtained in Examples 1 to 15 caused disconnection in the repeated bending test and impact resistance test, and the obtained conductivity was 760 mΩ/m or less was also achieved in terms of electrical resistance. Therefore, even with ultra-thin wires with a cross-sectional area of 0.04 mm ² or more and 0.06 mm ² or less, which are thinner than conventional wires, stranded wires with good conductive properties and excellent impact resistance can be obtained. I was able to get In addition, the stranded wires obtained in Examples 1 to 15 are also excellent in bending resistance and have a tensile test force of 70 N or more, so they can be evaluated as being applicable to various applications as ultrafine wires.

On the other hand, in Comparative Examples 1, 4, 5, 9, and 11, the cross-sectional area of the stranded wire was less than 0.04 mm ² , and the stranded wire was too thin, resulting in high conductor resistance and poor conductivity. In Comparative Examples 1 to 3 and 9 to 12, since the stranded wires did not have a predetermined tensile test force ratio, the strength was insufficient, and breakage of the stranded wires occurred in the impact resistance test. In addition, due to insufficient strength, it was not possible to impart the desired resistance to the stranded wire.

In Comparative Examples 6 and 7, the stranded wire did not have a predetermined elongation ratio, so the strength was insufficient, and breakage of the stranded wire occurred not only in the impact resistance test but also in the repeated bending test. In Comparative Example 8, although the stranded wire did not have a predetermined elongation ratio, the strength of the stranded wire was improved because a copper alloy containing 0.3% by mass of Sn was used as the conductor. On the other hand, since the conductivity of the conductor is insufficient, the conductivity of the stranded wire as a whole is low, and the desired conductivity and electrical resistance cannot be imparted to the stranded wire.

1 Core Wire 2 Conductor 3 Conductor Twisted Wire for Wire Harness (Twisted Wire)
10 Conductor stranded wire for wire harness (stranded wire)
20 movable arm 30 weight 40 mandrel

Claims (7)

A conductor stranded wire for a wire harness in which a plurality of conductors adjacent to the outer periphery of one or more core wires are twisted together,
The twisted wire has a cross-sectional area of 0.04 mm ² or more and 0.06 mm ² or less,
The ratio of the tensile test force of the core wire to the tensile test force of all the conductors included in the plurality of conductors is 9 or more and 23 or less,
A ratio of elongation of the core wire to elongation of each conductor included in the plurality of conductors is 0.10 or more and 0.25 or less, and
A conductor stranded wire for a wire harness, characterized by having an electrical conductivity of 40% IACS or more. The conductor stranded wire for wire harness according to claim 1, wherein the core wire has a filling rate of 85% or more and 100% or less in a cross-sectional area. The conductor stranded wire for a wire harness according to claim 1 or 2, wherein the core wire has a diameter of 0.12 mm or more and 0.20 mm or less and a tensile strength of 3000 MPa or more. In the plurality of conductors, the total number of conductors is 9 or more and 14 or less, the diameter of each conductor is 0.050 mm or more and 0.060 mm or less, the tensile strength of each conductor is 230 MPa or more and 280 MPa or less, and each The conductor stranded wire for a wire harness according to any one of claims 1 to 3, wherein elongation of the conductor is 8% or more and 40% or less, and conductivity of each conductor is 98%IACS or more. The wire harness conductor according to any one of claims 1 to 4, wherein no disconnection occurs after 100,000 times in a 180-degree repeated bending test under conditions of a temperature of 80 ° C. or less and a curvature radius of 18 mm. stranded wire. A 400g weight is placed on one end of a 300mm long wire bundled with five stranded wires, and the weight is dropped from the same height at which the other end is fixed. The conductor stranded wire for wire harnesses according to any one of claims 1 to 5. The conductor stranded wire for wire harness according to any one of claims 1 to 6, having a tensile test force of 70 N or more.

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