JP7486300B2 - Bend-resistant insulated wire - Google Patents

Description

The present invention relates to a bend-resistant insulated electric wire. More specifically, the present invention relates to a bend-resistant insulated electric wire that is excellent in bendability and lightweight, and is particularly suitable for use as wiring in automobiles.

In recent years, the number of wiring locations has increased in automobiles, industrial robots, electrical equipment, thermal equipment, etc., as their performance has improved. The demands for reliability of the electric wires used in these wiring have also increased. Furthermore, there is a demand for lighter electric wires themselves due to the demands for energy saving and compactness.

In response to such demands, for example, Patent Document 1 proposes a harness electric wire conductor in which a stranded wire with copper wires arranged around an aramid fiber bundle or string is compressed and heat-treated. Patent Document 2, which relates to an overhead transmission line, proposes an insulated electric wire in which a tension member such as aramid fiber or glass fiber is arranged in the center, a stranded conductor consisting of multiple stranded soft copper wires is provided on the outside, and an insulating coating is applied to the outside. Patent Document 3 proposes a thin-diameter electric wire for a wire harness having a structure in which multiple organic fibers with a maximum elongation of 10% or more are twisted around a central wire made of copper or copper alloy formed with a maximum elongation of 10% or more, and the weight ratio of the organic fibers to the copper or copper alloy and the cross-sectional area of the thickness are specified.

JP 2008-91214 A Japanese Patent Application Laid-Open No. 4-138616 JP 2003-123542 A

Each of the electric wires of the above-mentioned conventional technologies has a fiber in the center, a metal wire around the fiber, and an insulator around the metal wire. However, with these electric wires, some of the fiber tends to protrude from between the metal wires, which can lead to a poor appearance of the electric wire. In addition, moisture and oil can adhere to the fiber, and moisture and other substances adhering to the fiber can cause foaming and roughness of the insulation when the insulation is provided around the metal wire. The deterioration of the wire's appearance and foaming and roughness of the insulation cause localized non-uniformity, which reduces the flex life.

In addition, in Patent Document 1, the fiber core comes into contact with the extruded resin when covering the insulator, and is therefore thermally affected, which can prevent the fiber core from functioning as a fiber core. This phenomenon is more likely to occur when the extrusion temperature is high, and can cause the flex life to decrease.

The present invention was made to solve the above problems. The purpose is to provide a bend-resistant insulated electric wire that is lightweight and has excellent flexibility, and is particularly suitable for use in automotive wiring.

The bend-resistant insulated electric wire of the present invention is characterized by having a fiber core made of two or more types of fiber yarn, a stranded conductor made by twisting multiple metal wires arranged around the outer periphery of the fiber core, and an insulator arranged around the outer periphery of the stranded conductor.

According to this invention, the fiber core is made of two or more types of fiber yarn, so that the stress applied during bending is dispersed and stress concentration is unlikely to occur, and bending characteristics can be improved. Such a fiber core meanders following the twist of the stranded conductor made of multiple metal wires, so the center position of the fiber core and the center position of the stranded conductor do not match, and it is not located at the center of the bend-resistant insulated electric wire. As a result, it can flexibly deform with the stress applied during bending, and the bend-resistant insulated electric wire has good flexibility. Note that the center position refers to the center position calculated from the outline of the cross section of the fiber core and the center position calculated from the outline of the cross section of the stranded conductor. Since the two do not match, the insulated electric wire is likely to become flat when a load is applied to it, and the flat shape prevents stress concentration in a specific area, and the stress escapes, improving bending characteristics.

In the bend-resistant insulated electric wire according to the present invention, it is preferable that the center position of the fiber core does not coincide with the center position of the stranded conductor, and the fiber core meanders in accordance with the twist of the stranded conductor.

In the bend-resistant insulated electric wire according to the present invention, it is preferable that the deviation between the center position of the fiber core and the center position of the stranded conductor is 0.10 to 0.30 mm.

In the bend-resistant insulated electric wire of the present invention, the outer diameter of the stranded conductor is 1.6 mm or less.

In the bend-resistant insulated electric wire according to the present invention, the fiber core is composed of at least a first fiber thread and a second fiber thread having a dtex 1.5 to 4 times that of the first fiber thread. In the case of three or more types, at least two types of fiber threads should have this relationship.

According to the present invention, it is possible to provide a bend-resistant insulated electric wire that is excellent in flexibility and lightweight, and is particularly suitable for automotive wiring. In particular, since the fiber core is composed of two or more types of fiber yarns with different thicknesses, the stress applied when bending is dispersed and stress concentration is unlikely to occur, resulting in good bending characteristics. Since the fiber core meanders following the twist of the stranded conductor made of multiple metal wires, the center position of the fiber core does not coincide with the center position of the stranded conductor, and it is not located at the center of the bend-resistant insulated electric wire. As a result, it can flexibly deform with the stress applied when bending, resulting in a bend-resistant insulated electric wire with good flexibility.

FIG. 1 is a schematic explanatory diagram illustrating an example of a bend-resistant insulated electric wire according to the present invention. FIG. 2 is an explanatory diagram of each dimension constituting the bend-resistant insulated electric wire. FIG. 4 is an explanatory diagram of a twisted state of a stranded conductor. FIG. 1 is an explanatory diagram showing an embodiment of a bending test. FIG. 1 is an explanatory diagram showing an embodiment of a flexibility test.

The following describes the bend-resistant insulated electric wire of the present invention with reference to the drawings. Note that the present invention is not limited to the illustrated embodiment.

[Flex-resistant insulated wire]
1 and 2, a bend-resistant insulated electric wire 10 according to the present invention (hereinafter, also referred to as "insulated electric wire 10") has a fiber core 1 made of two or more types of fiber yarns 1a and 1b, a stranded conductor 2 formed by twisting a plurality of metal wires 3 provided on the outer periphery of the fiber core 1, and an insulator 4 provided on the outer periphery of the stranded conductor 2. Note that "having" means that other configurations may be included as long as they do not impair the effects of the present invention, and for example, means that a pressure winding film may be provided between the stranded conductor 2 and the insulator 4, a plating or insulating coating layer may be provided on the surface of the metal wires 3, and a fusion layer may be provided on the outer periphery of the insulator 4.

The components of the bend-resistant insulated wire are explained in detail below.

(fiber core)
The fiber core 1 is an essential component located approximately at the center of the bend-resistant insulated electric wire 10, and is preferably a high-tension body that functions as a winding core. As an example of the fiber core 1, a fiber thread formed by bundling a plurality of fibers is preferably used. The fibers constituting the fiber thread are preferably strong and heat-resistant. For example, the fibers may be polyester fibers such as Tetoron (registered trademark), wholly aromatic polyamide fibers such as Kevlar (registered trademark), polyarylate fibers such as Vectran (registered trademark), glass fibers, etc. The materials of the fibers may be the same or different materials.

The fiber core 1 is made of fiber yarns that are bundled, twisted, or braided to have a concentric (perfect circle) or nearly concentric cross section. In this case, it is more preferable to use twisted fiber yarns to make the fiber core 1 have a more concentric or nearly concentric cross section. The outer diameter of the fiber core 1 is not particularly limited, but may be in the range of 0.1 to 1.0 mm, for example. Since the fiber core 1 made of fiber yarns is flexible and easily deformed, the outer diameter of the fiber core 1 is evaluated as the outer diameter when the fiber core 1 is a perfect circle, and as the outer diameter converted from the cross-sectional area of the fiber core 1 to the cross-sectional area of a perfect circle when the fiber core 1 is flat.

The fiber core 1 is composed of two or more types of fiber threads 1a and 1b with different thicknesses. This configuration disperses the stress applied during bending, making it difficult for stress concentration to occur, and allows for good bending characteristics. The fiber core 1 is composed of at least a first fiber thread 1a and a second fiber thread 1b with a dtex that is 1.5 to 4 times, preferably 1.5 to 2 times, that of the first fiber thread 1a. The third fiber thread other than these may have a dtex smaller than that of the first fiber thread 1a, a dtex larger than that of the second fiber thread 1b, or a dtex between that of the first fiber thread 1a and the second fiber thread 1b. The thickness of the fiber thread is usually expressed as a fineness (dtex) that indicates the fiber thread in weight conversion, and 1 dtex is 1 g for a length of 10,000 m. The dtex range of two or more types of fiber threads with different thicknesses is preferably 110 to 2,000 dtex. If it is less than 110 dtex, it is likely to lack durability. On the other hand, if it exceeds 2000 dtex, the outer diameter becomes large, which is likely to affect workability and processability.

The fiber core 1 meanders in accordance with the twisting of the stranded conductor 2, which is made up of multiple metal wires 3, and the center position C1 of the fiber core 1 and the center position C2 of the stranded conductor 2 do not coincide, and the fiber core 1 is not located at the center of the bend-resistant insulated wire 10. As a result, the bend-resistant insulated wire 10 can flexibly deform due to the stress applied when bent, and has good flexibility. Note that the center position refers to the center position C1 calculated from the outline of the cross section of the fiber core 1 and the center position C2 calculated from the outline of the cross section of the stranded conductor 2. Since the two do not coincide, the insulated wire 10 is likely to become flat when a load is applied to it, and the flat shape prevents stress concentration in a specific area, allowing stress to escape and improving bending characteristics.

The deviation between the center position C1 of the fiber core 1 and the center position C2 calculated from the outline of the cross section of the stranded conductor 2 described below is preferably 0.10 to 0.30 mm. Such deviation makes the insulated wire 10 prone to become flat when a load is applied to the insulated wire 10, and this flat shape prevents stress concentration in specific areas, allowing the load stress applied to the insulated wire 10 to escape, improving the bending characteristics. If the deviation is less than 0.10 mm, the effect of relieving stress concentration may not be obtained. If the deviation exceeds 0.30 mm, the wire may become excessively flat.

The fiber core 1 is provided approximately at the center of the cross section of the bend-resistant insulated wire 10. "Approximately at the center" means that the center position C1 of the fiber core 1 is not provided at the center position of the cross section of the bend-resistant insulated wire 10 (specifically, the center position C2 of the cross section of the twisted conductor 2), and the center position C1 of the fiber core 1 and the center position C2 of the twisted conductor 2 are shifted and do not coincide. The center position C1 of the fiber core 1 is a position calculated from the outline of the cross section of the fiber core 1, and means the so-called center of gravity of the outline. Note that after the twisted conductor 2 described below is provided around the fiber core 1, it is often difficult to maintain the circular or approximately circular cross section due to the pressure applied by the twisted conductor 2, and it is likely to become deformed into an approximately triangular or approximately rectangular shape as shown in FIG. 1.

(Stranded conductor)
The stranded conductor 2 is an essential component provided on the outer periphery of the fiber core 1, and is a stranded wire formed by stranding a large number of metal wires 3 as shown in FIG. 3. By stranding a large number of metal wires 3 to form the stranded conductor 2, the center position C1 of the fiber core 1 and the center position C2 of the stranded conductor 2 can be shifted from each other without being coincident with each other, and weight reduction can also be achieved. The number of wires is preferably 50 to 150. If the number of metal wires 3 is less than 50, durability is insufficient. On the other hand, if the number of metal wires 3 exceeds 150, the outer diameter becomes large, which tends to affect workability and processability. Furthermore, by configuring the number of metal wires 3 having a small outer diameter within the following range, the overall outer diameter after the stranded conductor 2 is provided can be reduced, and the overall diameter and weight of the bend-resistant insulated electric wire can be reduced.

The relationship between the twist pitch P of the metal wire 3 and the outer diameter of the stranded conductor 2 is preferably in the range of 5 to 25 times the "twist pitch P (mm)" ÷ "outer diameter (mm) of the stranded conductor". By keeping it within this range, it is possible to suppress unraveling, reduce the variation in bending characteristics, and furthermore, the cross section is more likely to be rounded, resulting in good appearance and durability. If this value is less than 5 times, the metal wire 3 will be tightly wound, so the stranded conductor 2 is more likely to overlap, and the metal wire 3 may float. As a result, the cross section may not be rounded, or it may become hard and not satisfy the bending characteristics or may cause variation. On the other hand, if this value exceeds 25 times, the twist may become loose and the thread may pop out, and the wire may behave as if it is unraveling during work. As a result, the cross section may not be rounded, and the bending characteristics may also vary.

The outer diameter of the metal strands 3 is preferably in the range of 0.02 mm or more and 0.2 mm or less. In this way, a large number of thin metal strands 3 are twisted together to form the stranded conductor 2, which allows the stranded conductor 2 to be made thinner, and the entire insulated electric wire can be made thinner, lighter, and more flexible. As a result, the large number of metal strands 3 reduces stress concentration and improves tensile strength and bending characteristics. If the outer diameter of the metal strands 3 is less than 0.02 mm, the metal strands themselves will be thinner, requiring a larger number of strands, and the absolute value of the single wire strength will be smaller. On the other hand, if the outer diameter of the metal strands 3 exceeds 0.2 mm, the surface unevenness will be large.

The metal wire 3 is not particularly limited in type as long as it is a metal with good electrical conductivity, but is preferably a metal conductor with good electrical conductivity such as copper wire, copper alloy wire, aluminum wire, aluminum alloy wire, copper-aluminum composite wire, or a metal conductor with a plating layer applied to the surface thereof. Copper wire and copper alloy wire are particularly preferred. As the plating layer, a solder plating layer, a tin plating layer, a gold plating layer, a silver plating layer, a nickel plating layer, or the like is preferred. An insulating film (not shown) may be provided on the surface of the metal wire 3 as necessary. The type of the insulating film is not particularly limited, but examples thereof include a general enamel film, such as urethane, polyester, polyesterimide (PEI), polyimide (PI), polyamideimide (PAI), etc. The thickness is not particularly limited, but examples of the thickness are generally in the range of 1, 2, or 3 according to the Japanese Industrial Standards (JIS C 3202:2014).

The outer diameter D2 of the stranded conductor 2 is preferably 1.6 mm or less. In this way, the stranded conductor 2 with the above outer diameter D2 can realize a thinner insulated electric wire 10 with excellent bending resistance, and can be made lighter. There is no particular lower limit to the outer diameter of the stranded conductor 2, but it can be 0.12 mm depending on the outer diameter of the fiber core 1 and the outer diameter and number of the metal wires 3 described above.

(Insulator)
The insulator 4 is provided so as to cover the stranded conductor 2. For example, after the stranded conductor 2 is provided, the insulator 4 can be formed by resin extrusion or the like so as to cover the outer periphery of the conductor. The constituent material of the insulator 4 may be any resin material that has insulating properties and is heat resistant, such as polyimide resin, acrylic resin, polyvinyl chloride (PVC), polyamide resin, polyester resin, fluorine-based resin, etc. The thickness of the insulator 4 may be about 0.05 mm or more and 1.0 mm or less, but a thicker thickness is better in order to improve bending characteristics, and for example, about 0.1 mm to 0.3 mm is preferable.

The relationship between the thickness of the insulator 4 and the outer diameter of the stranded conductor 2 is preferably such that "thickness of the insulator 4 (mm)" ÷ "outer diameter of the stranded conductor (mm)" is in the range of 0.15 to 0.30. By keeping this within this range, durability and flexibility can be achieved at the same time. If this value is less than 0.15, durability may be insufficient. On the other hand, if this value exceeds 0.30, flexibility may be insufficient.

The thickness of the insulator 4 is preferably uniform. However, since the insulator 4 is mainly formed by resin extrusion, it is preferable that the surface after the stranded conductor 2 is provided, which is the stage before the resin extrusion, has small surface irregularities due to the metal wires 3. In the present invention, the stranded conductor 2, which is made by twisting together a large number of metal wires 3, is provided to cover the fiber core 1, so that the surface irregularities of the stranded conductor 2 are small. Therefore, the outer diameter after the insulator 4 is formed around the outer periphery by resin extrusion also has small surface irregularities, and the thickness of the insulator 4 is uniform in each part. As a result, local stress concentration can be reduced, and the flex life is extended.

(Cross-sectional area)
The cross-sectional area of the fiber core 1 is preferably within a range of 5 to 20% of the cross-sectional area of the stranded conductor 2. By setting it within this range, it is possible to achieve both good appearance and durability. If the cross-sectional area is less than 5%, durability may be insufficient. On the other hand, if the cross-sectional area exceeds 20%, the appearance may be poor. Each cross-sectional area can be easily calculated by image analysis of the captured cross-sectional image.

The cross-sectional area of the metal wire 3 is preferably within the range of 4-20% of the cross-sectional area of the fiber core 1. By setting it within this range, productivity and durability can be achieved at the same time. If the cross-sectional area is less than 4%, the wire may break during production. On the other hand, if the cross-sectional area exceeds 20%, durability may decrease. Each cross-sectional area can be easily calculated by image analysis of the captured cross-sectional image.

The present invention will be described in more detail below with reference to examples. Note that the present invention is not limited to these examples.

[Example 1]
A fiber core 1 having an outer diameter of about 0.245 mm was used, which was composed of a first fiber thread 1a (220 dtex) made of aramid (polyamide) fiber and a second fiber thread 1b (440 dtex) made of aramid (polyamide) fiber. 100 soft copper wires having an outer diameter of 0.08 mm were used on the fiber core 1 and twisted together at a twist pitch of 15 mm to form a stranded conductor 2 having an outer diameter of 0.97 mm. Next, FEP resin (insulator 4) was formed to a thickness of 0.2 mm by melt extrusion to produce an insulated wire 10 having an outer diameter of 1.4 mm.

[Example 2]
The same procedure as in Example 1 was repeated except that a stranded conductor 2 having an outer diameter of 0.72 mm was prepared by stranding 50 metal wires having an outer diameter of 0.08 mm at a stranding pitch of 11 mm, and an insulated wire 10 having an outer diameter of 1.1 mm was prepared.

[Example 3]
The same procedure as in Example 1 was repeated except that a stranded conductor 2 having an outer diameter of 0.94 mm was prepared by stranding 50 metal wires having an outer diameter of 0.11 mm at a stranding pitch of 14 mm to prepare an insulated wire 10 having an outer diameter of 1.3 mm.

[Example 4]
The same procedure as in Example 1 was repeated except that a stranded conductor 2 having an outer diameter of 1.17 mm was prepared by stranding 150 metal wires having an outer diameter of 0.09 mm at a stranding pitch of 18 mm to prepare an insulated wire 10 having an outer diameter of 1.6 mm.

[Example 5]
The same procedure as in Example 1 was repeated except that a stranded conductor 2 having an outer diameter of 0.76 mm was prepared by stranding 150 metal wires having an outer diameter of 0.05 mm at a stranding pitch of 11 mm, and an insulated wire 10 having an outer diameter of 1.2 mm was prepared.

[Example 6]
A fiber core 1 having an outer diameter of about 0.220 mm was used, which was composed of a first fiber thread 1a (110 dtex) made of aramid (polyamide) fiber and a second fiber thread 1b (440 dtex) made of aramid (polyamide) fiber. 100 soft copper wires having an outer diameter of 0.08 mm were used on the fiber core 1 and twisted together at a twist pitch of 14 mm to form a stranded conductor 2 having an outer diameter of 0.96 mm. Next, FEP resin (insulator 4) was formed to a thickness of 0.2 mm by melt extrusion to produce an insulated wire 10 having an outer diameter of 1.4 mm.

[Flexibility test and flexibility]
A bending test was performed for each Example by the method shown in Fig. 4. In the bending test, as shown in Fig. 4, an insulated electric wire 10 having a length of 1000 mm produced in each Example was sandwiched between mandrels 42, 42 having a radius of 5 mm, a load 41 was attached to the lower end of the insulated electric wire 10, and the number of bendings was measured in a direction perpendicular to the mandrel 42 at a speed of 30 times per minute, with each bending being counted as one bending at 90 degrees on both sides. The number of bendings was evaluated as the number of bendings until the resistance value of the insulated electric wire 10 increased by 10%. Since the number of bendings of all of the insulated electric wires of Examples 1 to 5 exceeded 20,000 times, the evaluation was made "○", and the measurement was terminated when the number of bendings exceeded 20,000 times.

Flexibility was evaluated using the method shown in Figure 5. In the flexibility test, both ends of an insulated electric wire 10 with a length of 700 mm were fixed with a fixture 31, and the maximum width W was measured when no weight 32 was attached, and when a 2 g weight 32 was attached to the lowest point of the insulated electric wire 10. The smaller the maximum width W, the more flexible the wire. When the insulated electric wires of Examples 1 to 6 were tested, all of the maximum widths were 150 mm or less, so it can be said that all of the insulated electric wires of Examples 1 to 6 are flexible.

[Center position deviation]
The obtained bend-resistant insulated electric wire 10 was cured in resin, and a cross section was cut out, polished, and observed under a microscope. The distance L between the center position C1 of the fiber core 1 and the center position C2 of the stranded conductor 2 was measured.

REFERENCE SIGNS LIST 1 fiber core 1a first fiber thread 1b second fiber thread 2 stranded conductor 3 metal strand 4 insulator 10 bend-resistant insulated wire A1 cross-sectional area of fiber core A2 cross-sectional area of stranded conductor A3 cross-sectional area of one metal strand D1 outer diameter of fiber core D2 outer diameter of stranded conductor D3 outer diameter of bend-resistant insulated wire d outer diameter of metal strand C1 center position of fiber core C2 center position of stranded conductor L distance between C1 and C2 P twist pitch of stranded conductor T thickness of insulator

Claims (3)

A bend-resistant insulated electric wire comprising: a fiber core having an outer diameter of 0.1 to 1.0 mm and made of two or more kinds of fiber yarns having different thicknesses, the fiber core being composed of at least a first fiber yarn and a second fiber yarn having a dtex 1.5 to 2 times that of the first fiber yarn; a stranded conductor formed by twisting 50 to 150 metal wires having an outer diameter of 0.02 mm or more and 0.2 mm or less and provided on the outer periphery of the fiber core; and an insulator provided on the outer periphery of the stranded conductor, wherein no insulating coating is provided on the surface of the metal wires, the deviation between the center position of the fiber core and the center position of the stranded conductor is 0.10 to 0.30 mm, and the cross-sectional area of the fiber core is within the range of 5 to 20% of the cross-sectional area of the stranded conductor . The bend-resistant insulated electric wire according to claim 1, wherein the center position of the fiber core does not coincide with the center position of the stranded conductor, and the fiber core meanders in accordance with the twist of the stranded conductor. 3. The bend-resistant insulated electric wire according to claim 1, wherein the stranded conductor has an outer diameter of 1.6 mm or less.

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