阅读说明：本技术 电绝缘线缆 (Electrically insulated cable ) 是由 松村友多佳 田中成幸 藤田太郎 小堀孝哉 石川雅之 于 2019-07-19 设计创作，主要内容包括：一种电绝缘线缆,具备芯电线和覆盖集合电线的包覆层,所述芯电线由包括导体和覆盖所述导体的绝缘层的至少一根绝缘线构成,在所述芯电线与所述包覆层之间具备以将所述芯电线覆盖的方式配置的包覆件；所述包覆件与所述绝缘层之间的-30℃下的摩擦系数为0.20以下。(An electrically insulated cable comprising a core wire and a covering layer covering a collective wire, wherein the core wire comprises at least one insulated wire including a conductor and an insulating layer covering the conductor, and a covering material disposed so as to cover the core wire is provided between the core wire and the covering layer; the coefficient of friction between the covering and the insulating layer at-30 ℃ is 0.20 or less.)

1. An electrically insulated cable comprising:

a core wire composed of at least one insulated wire including a conductor and an insulating layer covering the conductor; and

a covering layer covering the core wire,

a covering member disposed so as to cover the core wire is provided between the core wire and the covering layer,

the coefficient of dynamic friction between the covering member and the insulating layer at-30 ℃ is 0.20 or less.

2. The electrically insulated cable of claim 1,

the thickness of the covering member is 3 μm or more and 200 μm or less.

3. The electrically insulated cable according to claim 1 or 2,

the wrapping is a strap member.

4. The electrically insulated cable of claim 3,

the belt member is a polyester paper or a polyethylene terephthalate film.

5. The electrically insulated cable according to claim 3 or 4,

the belt member is formed of a thermoplastic resin having a melting point higher than that of a material forming the covering layer.

6. The electrically insulated cable according to any one of claims 1 to 5,

the clad includes a first clad covering the clad and a second clad covering the first clad.

7. The electrically insulated cable according to any one of claims 1 to 6,

the core wire includes two or more insulated wires each having substantially the same diameter as each other and having a cross-sectional area of 1.5mm²～3.0mm²The conductor of (1).

8. The electrically insulated cable according to any one of claims 1 to 7,

the electrically insulated cable is an electrically insulated cable for vehicle use.

9. The electrically insulated cable of claim 8,

the electrically insulated cable is an electrically insulated cable for an electric parking brake.

Technical Field

The present disclosure relates to electrically insulated cables. The present application claims japanese patent application No. 2018-158425 filed on 2018, 8, 27 as a priority. The entire contents of the disclosure in this japanese patent application are incorporated herein by reference.

Background

In an Electronic Parking Brake (EPB) system mounted on a vehicle, an electrically insulated cable (EPB cable) that electrically connects a brake caliper inside a wheel house and an electronic control unit on a vehicle body side is used. Patent document 1 (japanese patent application laid-open No. 2015-156386) discloses an electrically insulated cable including: an insulated wire comprising a conductor and an insulating layer covering the conductor, a core wire (stranded wire) obtained by stranding a plurality of the insulated wires, a first coating layer covering the core wire, and a second coating layer covering the first coating layer, and also disclosed is use as a cable for EPB (paragraph 0020). The cable disclosed in patent document 1 is characterized in that a tape member that covers the core wire is disposed between the core wire and the first coating layer, and the core wire is easily separated from the first coating layer and exposed by removing the tape member.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2015-156386

Disclosure of Invention

The present inventors have studied and found that bending resistance is improved when a core wire inside an electrically insulated cable is easily moved without being constrained in the cable when the cable is bent. Further, it has been found that when the outer periphery of the core wire is covered with a covering member having a small frictional resistance with the insulating layer of the insulated wire constituting the core wire, the core wire is easily moved in the cable when the cable is bent, and the bending resistance of the cable is improved, and the present disclosure including the following configurations has been completed.

An electrically insulated cable according to an aspect of the present disclosure includes:

a core wire composed of at least one insulated wire including a conductor and an insulating layer covering the conductor; and

a covering layer covering the core wire,

a covering material is provided between the core wire and the covering layer so as to cover the core wire.

The coefficient of dynamic friction between the covering member and the insulating layer at-30 ℃ is 0.20 or less.

Drawings

Fig. 1 is a sectional view showing a configuration of an example of an embodiment of an electrically insulated cable of the present disclosure.

Fig. 2 is a sectional view showing another example of the configuration of the embodiment of the electrically insulated cable of the present disclosure.

Fig. 3 is a diagram schematically illustrating a method of measuring a dynamic friction coefficient in the embodiment.

Fig. 4 is a diagram schematically illustrating a method of a bending test in the embodiment.

Detailed Description

[ problem to be solved by the present disclosure ]

In an in-vehicle cable such as an EPB cable, it is required to have a core wire exposed easily and to have resistance to flying stones during traveling of an automobile (impact resistance: resistance to damage). Further, the cable is also required to have a property (excellent bending resistance) that the cable is not easily deteriorated (e.g., broken) by repeated bending during traveling. The EPB cable is supposed to be used in an environment from a low temperature of about-40 ℃ to a high temperature of about 120 ℃, and is likely to be broken by repeated bending particularly at a low temperature. Therefore, improvement of the bending resistance at low temperatures is particularly required.

A technical problem of the present disclosure is to provide an electrically insulated cable including a core wire and a coating layer covering the core wire, the core wire being composed of at least one insulated wire including a conductor and an insulating layer covering the conductor, the electrically insulated cable being capable of being used as a cable for EPB, a cable for Wheel Speed Sensor (WSS), or the like, and having superior bending resistance, particularly superior bending resistance at low temperatures, than the related art.

[ Effect of the present disclosure ]

According to the present disclosure, an electrically insulated cable excellent in bending resistance, particularly excellent in bending resistance at low temperatures, can be provided.

[ description of embodiments of the present disclosure ]

Hereinafter, a mode for carrying out the present disclosure will be specifically described. The present invention is not limited to the following embodiments, and includes all modifications within the meaning and scope equivalent to the claims.

An electrically insulated cable according to an aspect of the present disclosure includes:

a core wire composed of at least one insulated wire including a conductor and an insulating layer covering the conductor; and

a covering layer covering the core wire,

a covering material is provided between the core wire and the covering layer so as to cover the core wire.

The coefficient of dynamic friction between the covering member and the insulating layer at-30 ℃ is 0.20 or less.

In the electrically insulated cable of the present disclosure, the outer periphery of the core wire is covered with a covering member, and the coefficient of dynamic friction between the covering member and the insulating layer constituting the insulated wire at-30 ℃ is 0.20 or less. By disposing a covering member having a small friction with the core wire between the core wire and the covering layer, the core wire can easily move without restriction in the movement of the core wire within the cable when the cable is bent. This improves the bending resistance even at low temperatures, and suppresses cable deterioration (disconnection or the like) caused by repeated bending of the cable during traveling.

First, each element constituting the electrically insulated cable of the present disclosure will be explained.

(1) Core wire

The core wire is composed of at least one insulated wire. In the case where the core wire is constituted by one insulated wire, the insulated wire itself is the core wire. In addition, in the case where the core wire is composed of two or more (plural) insulated wires,the aggregate of the plurality of insulated wires is a core wire. When the core wire is an aggregate of a plurality of insulated wires, the core wire may be, for example, a stranded wire obtained by stranding a plurality of insulated wires. For example, in the case where the electrically insulated cable is a cable for EPB, it may have a cross-sectional area of about 1.5mm²～3.0mm²The range of conductors is formed by twisting two or more insulated wires each having substantially the same diameter as each other to form a core wire. In the case of a signal such as a cable for a Wheel Speed Sensor (WSS) or a cable for grounding, one insulated wire having a conductor with a smaller cross-sectional area than that of the cable for an EPB may be used as a core wire, or two or more insulated wires each having substantially the same diameter (insulated wires having a conductor with a smaller cross-sectional area than that of the cable for an EPB) may be twisted to form a core wire.

One core wire may also include insulated wires for more than two purposes. For example, the cross-sectional area of each of the grooves may be about 1.5mm²～3.0mm²The conductor of the range and more than two insulated wires used as EPB with the same diameter, and more than one insulated wires used as signal or grounding cables with the cross section area smaller than the conductor of the range and the same diameter are twisted to form a core wire.

(2) Insulated wire

At least one insulated wire constituting the core wire has a conductor and an insulating layer covering the conductor.

The conductor is a wire made of a conductive and flexible material such as copper, aluminum, a copper alloy, or an aluminum alloy, and a stranded wire obtained by stranding tens to hundreds of thin wires having an outer diameter of about 0.1mm is often used. The cross-sectional area of the conductor (the cross-sectional area of the plurality of wires) is preferably 1.5mm in the case of a power supply line (e.g., an EPB cable) for power supply²～3.0mm²More preferably 1.6mm, in the above range²～2.5mm²The range of (1). In the case of a cable for use as a signal line having a smaller cross-sectional area than a power line (for example, a cable for WSS), it is often preferable to use 0.13mm²～0.5mm²A stranded wire of the range of (1), more preferablySelecting 0.18mm²～0.35mm²A strand of the range (1).

The insulated wire can be formed by the same method as a normal insulated wire, and for example, can be formed by melt-extruding a resin forming an insulating layer onto the outer periphery of the conductor as described above and coating the resin. After coating, the resin may be crosslinked by ionizing radiation irradiation or the like.

The resin forming the insulating layer may be a polyolefin resin, and preferably a flame-retardant polyolefin resin. For example, the insulating layer may be formed of flame-retardant polyethylene to which flame retardancy is imparted by blending a flame retardant. By forming the insulating layer with the flame-retardant polyolefin resin, the flame retardancy and the insulation property of the core electric wire (insulated wire) can be ensured even in a state where the covering material such as the covering layer and the tape member is removed and a part of the core electric wire (insulated wire) is exposed.

Examples of the polyolefin-based resin include, but are not limited to, High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), Very Low Density Polyethylene (VLDPE), ethylene-vinyl acetate copolymer resin (EVA), ethylene-methyl acrylate copolymer resin (EMA), and ethylene-ethyl acrylate copolymer resin (EEA). As a material for forming the insulating layer, other materials such as fluorine-based resin can be given.

In the case of an EPB-use insulated wire used for an EPB-use cable, the thickness of the insulating layer is preferably in the range of 0.2mm to 0.8mm, more preferably in the range of 0.25mm to 0.7 mm. The outer diameter of the insulating layer is preferably in the range of 2.5mm to 4.0mm, and more preferably in the range of 2.5mm to 3.8 mm.

(3) Cladding piece

The covering member is a covering member (for example, a film-like covering member) having a coefficient of kinetic friction at-30 ℃ with respect to the insulating layer constituting the insulated wire of 0.20 or less, and is disposed between the core wire and the covering layer so as to cover the entire outer circumference of the core wire. In the electrically insulated cable described in patent document 1, the outer periphery of the core wire is also covered with a covering material (tape member), but the tape member is formed of artificial fiber or the like formed of a resin material such as thin paper or polyester made of pulp, and has a coefficient of friction with the insulating layer at-30 ℃ of greater than 0.20. Therefore, the movement of the core wire in the cable is restricted during bending and becomes difficult to move, and as a result, excellent bending resistance cannot be obtained.

In this embodiment, the covering member is made of a material having a coefficient of kinetic friction at-30 ℃ with the insulating layer of 0.20 or less, thereby achieving excellent bending resistance of the cable. Further, it is clear from the result that the bending resistance at-30 ℃ is excellent, the bending resistance is also excellent in the range of-40 ℃ to 0 ℃.

As the covering material, a band-shaped tape member is preferably used from the viewpoint of ease of covering, and a method of winding the tape member around the outer periphery of the core wire to cover the entire outer periphery is preferably employed.

The belt member is required to have strength that is less likely to be broken by repeated bending. Since the tape member is usually wound around the outer periphery of the core electric wire, easy winding is required in this case. The thickness and shape (width, etc.) of the belt member, the forming material are preferably selected in consideration of the strength and the ease of winding.

From the above points of view, examples of the material for forming the belt member include paper, nonwoven fabric, polyester paper, polyester film, nylon film, polyolefin film, polyimide film, liquid crystal polymer film, fluorine-based resin film, and the like. Among these, polyester paper and films are preferable, and polyester paper and PET films, which are nonwoven fabrics made of polyester such as polyethylene terephthalate (PET), are particularly preferable. For the purpose of reducing the friction coefficient and improving the film strength, the surface may be coated with a release agent, a high-hardness resin, or the like, plated or evaporated with metal, or bonded with a metal foil.

The thickness of the covering material such as the belt member is preferably in the range of 3 μm to 200 μm. When the thickness is less than 3 μm, the tape may be stretched in the winding step of winding the core wire around the outer periphery, which makes handling difficult. When the thickness is more than 200 μm, the tape has high rigidity and is easily unwound even when wound, and the outer diameter of the coated layer coated after winding may become unstable.

Further, in the case where the coating layer is formed by melt extrusion of a resin as a material for forming the coating layer after the coating layer is coated with the coating material, the coating material such as the belt member is required not to be melted or deformed by heating in the melt extrusion. Therefore, the covering material such as the belt member is preferably formed of a material having a melting point higher than that of the material forming the covering layer. Specifically, it is preferably made of a material having a melting point of 160 ℃ or higher, for example, a thermoplastic resin. When the melting point is less than 160 ℃, the coating material may melt or deform during the process of forming the coating layer on the outer periphery.

(4) Coating layer

The electric insulated cable of the present disclosure includes a coating layer (sheath) covering an outer periphery of a tape member (core wire) to protect the core wire. The coating layer is required to have resistance (impact resistance) to flying stones and the like during driving of an automobile, flexibility for ensuring flexibility of the cable, and excellent bending resistance in which deterioration such as disconnection of a conductor and increase in resistance does not occur even when the coating layer is repeatedly bent during driving.

The clad layer may be composed of two or more layers. Generally, an electrically insulated cable mounted on a vehicle, such as an EPB cable or a WSS cable, has a double-layer structure in which a coating layer is composed of a first coating layer (inner sheath layer) that covers a core wire covered with the band member and a second coating layer (outer sheath layer) that covers the first coating layer.

In order to improve the flexibility of the cable, a material having excellent flexibility is preferable as a material constituting the first coating layer (inner sheath layer). In particular, when the first coating layer (inner sheath layer) has a large elastic modulus at low temperatures, the cable has low bending resistance at low temperatures, and therefore, in order to improve the bending resistance at low temperatures, it is preferable to use a material that is soft at low temperatures. Cables mounted on vehicles are also required to have excellent abrasion resistance, excellent heat resistance, and the like, and are often required to have flame retardancy.

(A) First coating (inner sheath)

Examples of the material forming the first coating layer include polyolefin resin such as polyethylene and ethylene-vinyl acetate copolymer (EVA), polyurethane elastomer, polyester elastomer, and a resin obtained by mixing these. By forming the first coating layer from the polyolefin-based resin, flexibility of the cable at low temperature can be improved, and bending resistance can be improved. By forming the first coating layer from a polyurethane elastomer, the abrasion resistance of the cable can be improved. In addition, by forming the first coating layer from a polyester elastomer, the heat resistance of the cable can be improved. Among the above exemplified resins, polyethylene is particularly preferable from the viewpoint of price and the like.

As a material for forming the first coating layer, a resin containing VLDPE as a main component and having a small ratio of elastic modulus at low temperature to elastic modulus at high temperature may be used. By using such a resin, a cable having excellent bending resistance in a wide temperature range from room temperature to low temperature can be manufactured. Other resins such as EVA, EEA, and acid-modified VLDPE may be added to the resin containing VLDPE as a main component within a range not to impair the gist of the present disclosure.

The material forming the first coating layer may contain various additives such as an antioxidant, a colorant, and a flame retardant as long as the gist of the present disclosure is not impaired.

In the case of a power supply line for power supply use (e.g., a cable for EPB), the thickness of the first coating layer is preferably in the range of 0.3mm to 1.5mm, and more preferably in the range of 0.45mm to 1.2 mm.

(B) Second coating layer (outer sheath layer)

The second coating layer is the outer jacket layer of the cable. In the case of a cable mounted on a vehicle such as an EPB cable, the cable is likely to be damaged by flying stones during traveling, and therefore, the material forming the second coating layer is required to be a resin having excellent resistance to external damage and abrasion in order to suppress the damage. In addition, a material excellent in flexibility is desired so that the cable becomes flexible. Further, when the cable is required to have flame retardancy, the second coating layer is required to have high flame retardancy.

Therefore, as a material for forming the second coating layer, a polyurethane resin, for example, a flame-retardant polyurethane resin is preferably used from the viewpoint of resistance to external damage, flexibility, and the like. In the case of a power supply line for power supply use (e.g., a cable for EPB), the thickness of the second coating layer is preferably in the range of 0.3mm to 0.7mm in general.

(5) Examples of embodiments of the electrically insulated cable of the present disclosure

(A) Example 1 of embodiment

Fig. 1 is a cross-sectional view of an example of an embodiment of an electrically insulated cable according to the present disclosure. The electrically insulated cable shown in fig. 1 is a cable used as an EPB cable, and has a core wire in which two insulated wires are twisted, and a coating layer composed of two layers.

In fig. 1, 1 is a conductor. The conductor 1 is a stranded wire made of a copper alloy and formed by stranding about 400 wires having an outer diameter of about 0.1mm, and has an outer diameter of about 2mm to 3 mm. An insulating layer 2 made of flame-retardant polyethylene and having a thickness of about 0.5mm covers the outer periphery of the conductor 1 to form an insulating wire 3. The two insulated wires 3 thus formed are twisted to form a core wire 4.

The tape member 5 is spirally wound around the outer periphery of the core wire 4, covering the entire outer periphery of the core wire 4. The belt member 5 is formed of polyester paper having a dynamic friction coefficient of 0.19 with the insulating layer 2, and is a belt having a width of about 5mm and a thickness of about 0.033 mm. Instead of the tape made of polyester paper, a tape made of another material having a coefficient of kinetic friction with the insulating layer 2 of 0.20 or less may be used as the tape member 5. Examples of the other material include a polyester resin film such as PET and PBT, and a polyethylene film, but the other material is not particularly limited as long as the coefficient of dynamic friction with the insulating layer 2 is 0.20 or less. However, it is preferable to use a material which has flexibility that enables easy winding, strength that is not easily broken by bending or the like of the cable, and does not melt or deform by heat when forming the coating layer (melt extrusion of resin).

In the electrically insulated cable according to the embodiment shown in fig. 1, the coating layer covering the outer periphery of the tape member 5 (core wire 4) has a two-layer structure including a first coating layer (inner sheath layer) and a second coating layer (outer sheath layer). In fig. 1, 6 is a first clad layer and 7 is a second clad layer.

The first coating layer 6 is formed of polyethylene and has a thickness of about 0.6 mm. The second coating layer 7 is formed of polyurethane and has a thickness of about 0.5 mm. The material forming the first coating layer 6 is not limited to polyethylene, and a resin that improves flame retardancy, abrasion resistance, and bending resistance (flexibility) of the cable is preferably used. The material for forming the second coating layer 7 is not limited to polyurethane, and a resin excellent in flame retardancy, scratch resistance, and bending resistance (flexibility) is preferably used.

(B) Example 2 of embodiment

Fig. 2 is a cross-sectional view of another example of an embodiment of an electrically insulated cable of the present disclosure. The electrically insulated cable shown in fig. 2 is a cable used for EPB and WSS, and has a core wire formed by twisting four insulated wires, and a coating layer formed of two layers.

Referring to fig. 2, the conductor 11 is a stranded wire formed by stranding about 400 wires having an outer diameter of about 0.1mm, and has an outer diameter of about 2mm to 4 mm. The outer circumference of the conductor 11 is covered with an insulating layer 21 made of flame-retardant polyethylene and having a thickness of about 0.4mm to form an insulated wire 31. Power transmission for EPB is performed through the insulated wire 31. The conductor 12 is a stranded wire made of a copper alloy and formed by stranding 48 wires having an outer diameter of about 0.1mm, and has an outer diameter of about 1.5mm to 2.5 mm. The outer circumference of the conductor 12 is covered with an insulating layer 22 made of flame-retardant polyethylene and having a thickness of about 0.4mm to 0.8mm to form an insulated wire 32. Power transmission for WSS is performed through the insulated wire 32. The two insulated wires 31 and the two insulated wires 32 thus formed are twisted to form a core wire 41.

A tape member 51 is spirally wound around the outer periphery of the core wire 41 so as to cover the entire outer periphery of the core wire 41, and the tape member 51 is made of polyester paper having a kinetic friction coefficient of 0.19 with the flame-retardant polyethylene forming the insulating layers 21 and 22. The belt member 51 may be formed of a belt having the same width and thickness as those of the belt member 5 of example 1 of the embodiment, or may be formed of the same material as that of the belt member 5.

In the electrically insulated cable according to the embodiment shown in fig. 2, the coating layer on the outer periphery of the covering tape member 51 (core wire 41) has a two-layer structure including a first coating layer (inner sheath layer) and a second coating layer (outer sheath layer), where 61 in fig. 2 is the first coating layer and 71 is the second coating layer.

The thickness of the first clad layer 61 may be the same as that of the first clad layer 6 of example 1 of the embodiment, and in addition, the same material as that of the first clad layer 6 may be used for its formation material. The thickness of the second clad layer 71 may be the same as that of the second clad layer 7 in example 1 of the embodiment, and the same material as that of the second clad layer 7 may be used for its formation material.

(6) Method of manufacturing an electrically insulated cable of the present disclosure

Next, a method of manufacturing the electrically insulated cable of the present disclosure will be explained.

The insulated wire can be manufactured by coating the outer periphery of the conductor as described above with an insulating resin which is a material constituting the insulating layer. The insulating resin can be coated by the same method as in the production of a known insulated wire, for example, by melt extrusion of the insulating resin. After the insulating layer is formed, the resin forming the insulating layer may be crosslinked by ionizing radiation irradiation or the like to improve heat resistance of the insulating layer.

The core wire may be formed of one insulated wire, but when formed of two or more insulated wires, the core wire is formed by twisting two or more insulated wires manufactured as described above. The insulated wires may be twisted by supplying the insulated wires from two or more supply reels around which the insulated wires are wound to a twisting unit (a device for twisting a plurality of insulated wires).

The core electric wire thus formed is covered with a covering member. For example, a tape member supplied from a tape supply reel (reel on which the tape member is wound) is wound to form a tape-covered core electric wire (core electric wire whose outer periphery is covered with the tape member). The belt member is, for example, spirally wound around the outer periphery of the core electric wire.

The coated core electric wire is fed to the first resin coating portion, and a resin material such as polyethylene is coated on the outer periphery thereof to form a first coating layer (inner sheath layer). The coating of the resin material can be performed, for example, by melt-extruding the resin material to the outer periphery of the core-coated electric wire. After the first coating layer is formed, the electric wire is sent to the second resin coating portion, and the second coating layer (outer sheath layer) is formed by coating the outer periphery of the first coating layer with a resin material for forming the outer sheath layer, thereby producing the electrically insulated cable of the present disclosure in which the coating layer is composed of two layers of the inner sheath layer and the outer sheath layer. After the second coating layer is formed, electron beam irradiation or the like may be performed on the cable in order to crosslink the resin of the coating layer to improve scratch resistance or the like.

Examples

The present disclosure will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

(1) Material for forming electrically insulated cable for bending test

The following materials were used to fabricate an electrically insulated cable for a bending test.

1) Formation material of insulating layer: flame-retardant polyethylene resin

2) Formation material of the first coating layer (inner sheath layer): non-flame-retardant polyethylene resin

3) Formation material of the second coating layer (outer sheath layer): non-flame-retardant polyurethane

4) Material for forming belt member

■ PET tape: thickness 6 μm (Lumiror manufactured by Dongli Co., Ltd.)

■ polyester paper: thickness 33 μm (manufactured by Tianzhong Special paper-making Co., Ltd.)

■ tissue paper: thickness 30 μm (manufactured by Dawang paper-making Co., Ltd.)

■ Teflon (registered trade Mark) tape: thickness 50 μm (NAFLON PTFE tape manufactured by NICIAS Co., Ltd.)

■ demolding of PET tapes: thickness 100 μm (manufactured by Tohcello chemical Co., Ltd.)

■ aluminum foil PET composite film: thickness 62 μm (Al/PET, product of PANAC Co., Ltd.)

■ PET tape: thickness 25 μm (DIAFOIL, Mitsubishi chemical corporation)

■ polyester paper: thickness 25 μm (manufactured by Toyo textile Co., Ltd.)

(2) Measurement of coefficient of dynamic friction of belt member

For the above-mentioned belt member, the coefficient of dynamic friction at-30 ℃ with the material forming the insulating layer (flame-retardant polyethylene) was measured by the method shown below.

A sheet having a width of 15mm X a length of 30mm was produced as a friction material from the above belt member-forming material.

A sheet having a width of 20mm, a length of 120mm and a thickness of 1mm was prepared from the material for forming the insulating layer, and used as a material to be rubbed.

As schematically shown in fig. 3, a friction material was placed on the material to be rubbed, a 100g weight was placed on the friction material, and a load of 0.98N was applied to the friction material. After the rubbing material and the material to be rubbed were set at-30 ℃ in this state, the rubbing material was pulled and moved at a test speed of 100 mm/min as shown in FIG. 3. The force required for traction (test force) was measured, and the average value of the test forces at a moving distance of 10mm to 20mm was taken as the friction force. The friction force thus obtained was divided by the load (0.98N) to calculate the coefficient of kinetic friction. The coefficient of dynamic friction of each belt member thus measured is shown in table 1.

(3) Manufacturing method of electric insulation cable for bending test

As the conductor, a composite strand having an outer diameter of 2.0mm, which was obtained by further stranding seven strands each formed by stranding 52 wires having an outer diameter of 0.08m and made of a copper alloy, was used. Flame-retardant polyethylene was melt-extruded to the outer periphery of the conductor to form an insulating layer having a thickness of 0.4mm, thereby producing an insulated wire.

The manufactured insulated wires were twisted two by two to manufacture core wires. The tape members shown in table 1 were each wound around the outer periphery of the core wire in a spiral manner at a winding width of 3mm to cover the outer periphery of the core wire. A non-flame-retardant polyethylene resin was melt-extruded around the outer periphery of the core wire around which the tape member was wound, to form a first coating layer having a thickness of 0.5 mm. Then, a non-flame-retardant polyurethane was melt-extruded and coated to form a second coating layer having a thickness of 0.5mm, thereby preparing a sample of the electrical insulated cable for bending test.

(4) Bending test

For the thus obtained bending test electrical insulated cable, a bending test electrical insulated cable was produced using a cable according to JISC 6851: 2006 (optical fiber characteristic test method) a bending test was performed.

Specifically, as shown in fig. 4, the bending test insulated cable was sandwiched between two mandrels A, B having a diameter of 60mm, which were horizontally arranged in parallel to each other, and the following operations were repeated in a thermostatic bath at-30 ℃. The upper end is bent by 90 ° to the horizontal direction so as to abut against the upper side of one mandrel a, and then bent by 90 ° to the horizontal direction so as to abut against the upper side of the other mandrel B. This repetition is performed while measuring the resistance value by connecting two conductors in the cable, and the number of times when the resistance rises to ten times or more of the initial resistance value (one bending is counted as bending to the right side, to the left side, and then back to the right side) is used as the index value of the bending resistance. The results are shown in the column "number of bends" in table 1.

[ Table 1]

As shown in Table 1, when the belt member having a coefficient of dynamic friction at-30 ℃ of 0.20 or less was used (samples 1 to 5), the number of times of bending was large, and excellent bending resistance was obtained. On the other hand, when a belt member having a coefficient of dynamic friction at-30 ℃ exceeding 0.20 was used (samples 6 to 8), the number of times of bending was small and the bending resistance was low. From the results, it was found that excellent bending resistance can be obtained in the electrically insulated cable by using a tape member having a coefficient of dynamic friction at-30 ℃ of 0.20 or less as the tape member.

Description of the reference numerals

1. 11, 12: a conductor; 2. 21, 22: an insulating layer; 3. 31, 32: an insulated wire; 4. 41: a core wire; 5. 51: a belt member; 6. 61: a first coating layer (inner sheath layer); 7. 71: a second coating layer (outer jacket layer).