JP2019175853A - Insulated wire and multi-core cable - Google Patents

Abstract

To provide an insulated wire having excellent flex resistance and flexibility while maintaining wear resistance, and a multi-core cable having it in a cable core.SOLUTION: An insulated wire has an inner layer that is in close contact with a conductor and coats the periphery of the conductor, and an outer layer that coats the periphery of the inner layer. The inner layer is formed of polyvinyl chloride (PVC); the outer layer is formed of ethylene tetrafluoroethylene copolymer resin (ETFE); the thickness of the inner layer is greater than the thickness of the outer layer; and between the inner layer and the outer layer, there is an air layer having a smaller thickness than the thickness of the inner layer and the thickness of the outer layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an insulated wire and a multicore cable.

  A multi-core cable (hereinafter sometimes referred to as a robot cable) used for electrical wiring of an industrial robot or the like follows a movement of the robot and is repeatedly bent over a predetermined number of times (hereinafter referred to as “ Also referred to as “repetitive bending”. Therefore, the insulated wire accommodated in the multicore cable is required to have excellent bending resistance that can withstand repeated bending. Further, when the multi-core cable is repeatedly bent, there is a possibility that a plurality of insulated wires housed in the cable are rubbed together and the insulating coating surface of the insulated wires is worn. The wear on the surface of the insulation coating is remarkable because when the cable includes a twisted pair of two insulated wires twisted together, the pairs of twisted wires are locally contacted and rubbed intensely. As described above, since the insulated wire used for the wiring of the industrial robot is required to have bending resistance and wear resistance of the insulating coating, a fluororesin is often used for the insulating coating.

  On the other hand, a fluororesin is hard because it has high tensile strength, and an insulated wire coated with the fluororesin is inferior in flexibility. Therefore, in order to improve the flexibility of the insulated wire, an insulated wire having a two-layer coating of soft resin on the inside and a fluororesin on the outside has been proposed (Patent Document 1, Patent Document 2, Patent Document 3). reference).

  In the insulated wire described in Patent Document 1, a first layer made of a composition mainly composed of an ethylene-polar monomer copolymer is coated on the periphery of a conductor, and the outer periphery of the first layer is made of a radiation crosslinkable fluororesin. The second layer is coated, and the first layer and the second layer are bonded without being subjected to an adhesion treatment, and the first layer and the second layer are both crosslinked. It has.

  The insulated wire described in Patent Document 2 is an insulated wire in which the periphery of a conductor is covered with at least two insulating layers of an inner insulating layer and an outer insulating layer outside the conductor, and the inner insulating layer is EVA, EEA. And an olefin resin such as EBA, and the outer insulating layer includes a fluororesin.

  In the insulated wire described in Patent Document 3, a first layer made of a composition containing acrylic rubber is coated on the circumference of the conductor, and a second layer made of a fluororesin is coated on the outer circumference of the first layer. The first layer and the second layer are in close contact with each other.

JP 2010-284895 A JP 2013-225405 A JP 2009-272100 A

  However, the insulated wires described in Patent Documents 1 to 3 are all assumed to be used in automobiles, electric machines, electronic devices, and the like, and are assumed to be used in robot cables that undergo severe bending repeatedly. It has not been. In particular, it is desirable to withstand repeated bending even when a multicore cable including a plurality of insulated wires in a cable core is bent and arranged with a small bending radius.

  An object of the present invention is to provide an insulated wire excellent in bending resistance and flexibility while maintaining wear resistance, and a multi-core cable including the same in a cable core.

  The present invention provides the following insulated wires [1] to [4] and multicore cables [5] and [6] for the purpose of solving the above problems.

[1] An inner layer that is in close contact with the conductor and covers the outer periphery of the conductor; and an outer layer that covers the outer periphery of the inner layer, and the inner layer is made of polyvinyl chloride (PVC), It is formed of ethylene tetrafluoroethylene copolymer resin (ETFE), and the thickness of the inner layer is larger than the thickness of the outer layer, and between the inner layer and the outer layer, the thickness of the inner layer and the An insulated wire having an air layer with a thickness smaller than that of an outer layer.
[2] The insulated wire according to [1], wherein the outer layer is provided non-adhered to the inner layer.
[3] The insulated wire according to [1] or [2], wherein the ethylene tetrafluoroethylene copolymer resin forming the outer layer has a fluidity (MFR) of 20 g / 10 min or more.
[4] The insulated wire according to any one of [1] to [3], wherein the outer layer has a thickness of ¼ or more and ½ or less of the thickness of the inner layer.
[5] A multi-core cable comprising a cable core including a plurality of insulated wires according to any one of [1] to [4], and a sheath provided on an outer periphery of the cable core.
[6] The multi-core cable according to [5], wherein the cable core includes a twisted pair of twisted two insulated wires.

  ADVANTAGE OF THE INVENTION According to this invention, the insulated wire excellent in bending resistance and a softness | flexibility, maintaining abrasion resistance, and the multicore cable which contains it in a cable core can be provided.

It is a cross-sectional view which shows an example of the structure of the multicore cable which concerns on the 1st Embodiment of this invention. It is a cross-sectional view which expands and shows the insulated wire of the multicore cable shown in FIG. It is a cross-sectional view which shows an example of the structure of the multicore cable which concerns on the 2nd Embodiment of this invention.

[Embodiment]
Embodiments of the present invention will be described with reference to the drawings. In addition, although embodiment described below is shown as a suitable specific example in implementing this invention, although there are some parts which have illustrated various technical matters that are technically preferable. The technical scope of the present invention is not limited to this specific embodiment. Moreover, the dimensional ratio of each component in each drawing does not necessarily match the dimensional ratio of an actual insulated wire and a multicore cable.

<First Embodiment>
A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the multicore cable 1 is provided on a cable core 4 including a plurality of insulated wires 2, a presser winding 6 wound around the cable core 4, and an outer periphery of the presser winding 6. A shield layer 7 and a sheath 8 provided on the outer periphery of the shield layer 7. In addition, in order to fill the gap around the insulated wire 2, for example, an inclusion containing an aramid fiber, a suf yarn, or the like may be provided.

  FIG. 1 shows an example in which the number of insulated wires 2 is four. The number of insulated wires 2 is not limited to four, and may be one, two, three, or five or more. Preferably, the number of insulated wires 2 is 50 or less. The cable core 4 may include other electric wires and cables such as a coaxial cable in addition to the insulated electric wires 2.

(Insulated wire 2)
FIG. 2 is an enlarged cross-sectional view showing the insulated wire 2 of the multicore cable 1 shown in FIG. As shown in FIGS. 1 and 2, the insulated wire 2 covers a conductor layer 21 including a plurality of strands 211 (see the broken lines in FIGS. 1 and 2) and the outer periphery of the conductor layer 21. And an insulating coating layer 22 including an insulator. The broken lines in FIGS. 1 and 2 are provided for convenience of description of the conductor layer 21 and do not indicate a boundary surface that exists as an entity on the actual multicore cable 1. The conductor layer 21 is an example of a conductor.

The thickness of the insulating coating layer 22 (see “L ₃ ” in FIG. 2) is preferably 0.50 mm or less, and can be, for example, about 0.25 mm. In the following description, the multi-core cable 1 in which the insulating coating layer 22 has a thickness (L ₃ ) of 0.25 mm will be described as an example.

[Conductor layer 21]
The conductor layer 21 includes a stranded wire in which a plurality of strands 211 are twisted together. The number of the strands 211 is not particularly limited to the number shown in FIG. 1, but is preferably 30 or 60, for example.

  Each strand 211 is preferably thin. The diameter of each strand 211 (see “d” in FIG. 2) can be, for example, about 0.08 mm. Moreover, as the strand 211, a soft copper wire can be used, for example. The annealed copper wire may be subjected to plating such as silver plating.

When the diameter d of the strand 211 is 0.08 mm and the number is 60 (that is, 23AWG (American Wire Gauge)), the diameter of the conductor layer 21 (“φ” in FIG. 2) is about 0.72 mm. In this case, the longitudinal sectional area of the conductor layer 21 (that is, a circular area surrounded by a broken line) is about 0.30 mm ² .

[Insulating coating layer 22]
The insulating coating layer 22 includes an inner layer 221 that covers the outer periphery of the conductor layer 21 and an outer layer 223 that covers the outer periphery of the inner layer 221. In the insulating coating layer 22, the thickness of the inner layer 221 is larger than the thickness of the outer layer 223. In addition, the thickness between the inner layer 221 and the outer layer 223 is smaller than the thickness of the inner layer 221 (see “L ₁ ” in FIG. 2) and the thickness of the outer layer 223 (see “L ₂ ” in FIG. 2). An air layer 222 may be provided. Details will be described later.

(1) Inner layer 221
The inner layer 221 is a layer that plays a role of improving the flexibility of the insulated wire 2. As the flexibility of the insulated wire 2 is improved, the flexibility of the multi-core cable 1 is also improved as a result. Therefore, it is preferable to use a soft material having resistance to repeated bending (that is, difficult to break) as a material for forming the inner layer 221. Specifically, it is preferable to use a material having a tensile strength equal to or less than a predetermined value as a material for forming the inner layer 221.

  Further, as the material for forming the inner layer 221, for example, it is preferable to use a material that is thin (for example, a thickness of about 0.4 mm or less) and that can be easily processed by covering molding such as an extrusion method. Furthermore, in order for the multi-core cable 1 to have a heat resistance that can withstand a predetermined temperature (for example, a rated temperature), it is preferable to use a material having a heat resistance equal to or higher than a predetermined temperature as a material for forming the inner layer 221. . Preferably, the rated temperature is 80 ° C. or higher. In the present embodiment, the rated temperature is 105 ° C.

  As a result of examination in view of the above, the inventors have obtained knowledge that PVC (polyvinyl chloride) (melting point: about 170 ° C., tensile strength: 35 MPa or less) is optimal as a material for forming the inner layer 221. . In addition, although PVC can use a general thing as a coating | covering material of an electric wire or a cable, it is more preferable to use what has an elongation rate of 200% or more. Moreover, it is preferable that the tensile strength of PVC is 1/2 or less of the tensile strength of the material which forms the outer layer 223 mentioned later. Such PVC is suitable for the inner layer 221 because it has resistance to repeated bending.

The inner layer 221 preferably has a thickness that is 2/3 or more of the thickness of the insulating coating layer 22. Specifically, the thickness L ₁ of the inner layer 221 can be preferably within 0.4 mm, more preferably about 0.18 mm.

  The inner layer 221 covers the outer periphery of the conductor layer 21 so as to be in close contact with the conductor layer 21 by, for example, a solid extrusion method. Specifically, the inner layer 221 covers the outer periphery of the conductor layer 21 so as to be in close contact with the outer peripheral surface 211Aa of the plurality of strands 211A arranged on the outermost side among the strands 211 constituting the conductor layer 21. To do. Of the plurality of strands 211A arranged on the outermost side, a gap (see “S” in FIG. 2) between adjacent strands 211A is preferably filled with PVC forming the inner layer 221. .

(2) Outer layer 223
The outer layer 223 is provided with the bending resistance and wear resistance of the insulated wire 2 in order to prevent malfunction even if the multi-core cable 1 is repeatedly bent a predetermined number of times (for example, 10 million times) or more. It is a layer that plays the role of satisfying sex. Therefore, it is preferable to use a material having high bending resistance and high wear resistance as a material for forming the outer layer 223.

  The outer layer 223 covers the outer side of the inner layer 221 by an extrusion method, as will be described later. Therefore, it is preferable to use a material having a melting point that is not too larger than the melting point of the inner layer 221 as a material for forming the outer layer 223.

  As a result of studying in view of the above, the inventors have proposed that the material for forming the outer layer 223 is ETFE (ethylene tetrafluoroethylene copolymer resin) (melting point: about 270 ° C., tensile strength), which is one of fluororesins. 50 MPa or more) was found to be optimal. If it is ETFE, the bending resistance and abrasion resistance required for the insulated wire 2 can be satisfied. ETFE preferably has an elongation of 150% or more. Moreover, ETFE preferably has a heat resistance of 150 ° C. or higher.

  Furthermore, it is preferable to use ETFE having an MFR (Melt Flow Rate; fluidity) of 20 g / 10 min or more. Here, MFR is an index indicating the ease of flow of the target material, and indicates the amount of resin extruded per 10 minutes. By using ETFE having an MFR greater than or equal to a predetermined value, the outer layer 223 can be processed thinly (for example, within 0.1 mm).

Specifically, the following materials can be used for ETFE.
・ "EP506" manufactured by Daikin Industries, Ltd.
・ "Fullon C-88AXM" manufactured by Asahi Glass Co., Ltd. (AGC Glass (common name))

The outer layer 223 preferably has a thickness of ¼ or more and ½ or less of the thickness L ₁ of the inner layer 221. The outer layer 223 preferably has a thickness L ₂ that is 1/3 or less of the thickness (L ₃ ) of the insulating coating layer 22. Specifically, the thickness L ₂ of the outer layer 223 can be more preferably within 0.1 mm, and even more preferably about 0.07 mm. Thus, by making the outer layer 223 thinner, it is possible to reduce the diameter of the multi-core cable 1 and to suppress the temperature rise of the outer layer 223 during processing to suppress deterioration of the inner layer 221 during processing. .

  The outer layer 223 covers the outer periphery of the inner layer 221 by, for example, a tube extrusion method. Note that the outer peripheral surface of the inner layer 221 and the inner peripheral surface of the outer layer 223 are preferably not in close contact. That is, it is preferable that the outer layer 223 is provided non-adhering to the inner layer 221. In other words, it is preferable that an air layer 222 having a minute thickness compared to the thickness of each layer is included between the inner layer 221 and the outer layer 223.

(Other configurations)
The presser winding 6 uses, for example, a resin tape containing polyester or the like. The presser roll 6 may be Japanese paper. The shield layer 7 is formed by braiding a conducting wire, for example. The shield layer 7 may be one in which a tape with a conductor is wound.

  The sheath 8 is not particularly limited, but is formed using a material such as PVC, PE (polyethylene), FEP (tetrafluoroethylene / hexafluoropropylene copolymer resin), or the like. In addition, the sheath 8 may be composed of a single layer or may be composed of multiple layers.

(Operation and effect of the first embodiment)
According to the embodiment of the present invention, an inner layer 221 formed of polyvinyl chloride (PVC) covering the outer periphery of the conductor layer 21 so as to be in close contact with the conductor layer 21, and an ethylene tetrafluoroethylene copolymer resin (ETFE). And the outer layer 223 covering the outer periphery of the inner layer 221 formed by the above-described method, and the thickness of the inner layer 221 made of polyvinyl chloride (PVC) is larger than the thickness of the outer layer 223 made of ethylene tetrafluoroethylene copolymer resin (ETFE). Therefore, it is possible to provide an insulated wire excellent in bending resistance and flexibility while maintaining wear resistance, and a multicore cable including the same in a cable core.

  Specifically, the inner layer 221 is made of a soft material such as polyvinyl chloride (PVC) so as to be larger than the thickness of the outer layer 223, thereby improving the flexibility of the multi-core cable 1 and making the outer layer 223 flexible and resistant. By forming ethylene tetrafluoroethylene copolymer resin (ETFE), which is a highly wearable material, smaller than the thickness of the inner layer 221, the wear resistance of the insulated wire 2 can be satisfied. Further, by providing the outer layer 223 in a non-contact manner with the inner layer 221, the inner layer 221 is easily bent due to a minute gap generated between the inner layer 221 and the outer layer 223, so that the bending resistance can be further satisfied. In addition, the multi-core cable 1 including such an insulated wire 2 in the cable core has improved flexibility. As an example of improved flexibility, the inventors have confirmed that the bending radius can be reduced from about 6D to about 3D by the multicore cable 1 according to the embodiment of the present invention. D represents the self-diameter of the multicore cable 1.

  Thus, the flexibility of the multi-core cable 1 is improved (that is, the bending radius can be reduced). For example, when the multi-core cable 1 is arranged in a movable cable bear (registered trademark) (not shown), Collision and rubbing between the sheath 8 and the inner wall of the traveling cable bear (registered trademark) can be reduced (that is, damage to the sheath 8 and generation of dust can be suppressed). That is, even when the multi-core cable 1 including a plurality of insulated wires 2 in the cable core is bent and arranged with a small bending radius, it can withstand repeated bending.

  In the above embodiment, the number of the insulated wires 2 is four, but is not limited to this. In addition, this invention has an advantage, so that there are many insulated wires 2. As shown in FIG.

<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view showing an example of the structure of the multi-core cable 1 according to the second embodiment of the present invention. The multi-core cable 1 according to the second embodiment is different from the multi-core cable 1 according to the first embodiment in that the multi-core cable 1 includes a twisted pair wire 20 obtained by twisting a pair (two) of insulated wires 2. To do. Hereinafter, the same constituent elements as those in the first embodiment will be denoted by the same reference numerals and redundant description will be omitted, and differences from the first embodiment will be mainly described.

  As shown in FIG. 3, the cable core 4 includes three pairs of twisted wires 20 formed by twisting two insulated wires 2 as a pair. In addition, the number of the twisted pair wires 20 is not limited to three, and may be one, two, four or more, and can be appropriately adjusted according to the purpose. Preferably, the number of twisted wires 20 is 25 or less.

  Moreover, the structure of the insulated wire 2 has the same structure as the insulated wire 2 which concerns on 1st Embodiment mentioned above. Detailed description is omitted. In addition, in FIG. 3, although the structure which twisted together the seven strands 211 as the conductor layer 21 was mentioned as an example, the number of the strands 211 as a strand is not limited to seven, For example, 19, 19 or 37 may be used.

  When a plurality of twisted wires 20 are included, if the multi-core cable 1 is bent, there is a greater possibility that the adjacent twisted wires 20 rub against each other and wear compared to a case where the twisted wires 20 are not twisted. The same applies to the case where the twisted pair wire 20 and the other insulated wires 2 rub against each other and wear. Therefore, the surface of the insulated wire 2 is covered with ETFE that is not easily worn.

(Operation and effect of the second embodiment)
As described above, also in the second embodiment, as in the first embodiment, an insulated wire excellent in bending resistance and flexibility while maintaining wear resistance, and a multi-core cable including the same in a cable core are provided. Can be provided. Further, by covering the surface of the insulated wire 2 with ETFE that is not easily worn, when the multi-core cable 1 is bent, friction between the twisted wires 20 and friction between the twisted wire 20 and the insulated wires 2 occur. Even if it is a case, it can suppress that the insulated wire 2 is worn out by repeated bending.

  While the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. In addition, it should be noted that not all the combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

1: multi-core cable, 2: insulated wire, 4: cable core, 6: presser winding, 7: shield layer, 8: sheath, 20: twisted wire, 21: conductor layer, 22: insulation coating layer, 211, 211A : Strand, 211Aa: outer peripheral surface of strand, 221: inner layer, 222: air layer, 223: outer layer

Claims (6)

An inner layer that closely contacts the conductor and covers the outer periphery of the conductor; and an outer layer that covers the outer periphery of the inner layer,
The inner layer is made of polyvinyl chloride (PVC),
The outer layer is made of ethylene tetrafluoride ethylene copolymer resin (ETFE),
The thickness of the inner layer is greater than the thickness of the outer layer,
Between the inner layer and the outer layer, there is an air layer having a thickness smaller than the thickness of the inner layer and the thickness of the outer layer,
Insulated wire. The outer layer is provided non-adhering to the inner layer,
The insulated wire according to claim 1. The ethylene tetrafluoroethylene copolymer resin forming the outer layer has a fluidity (MFR) of 20 g / 10 min or more.
The insulated wire according to claim 1 or 2. The outer layer has a thickness of ¼ or more and ½ or less of the thickness of the inner layer.
The insulated wire according to any one of claims 1 to 3. A cable core including a plurality of insulated wires according to any one of claims 1 to 4,
A sheath provided on the outer periphery of the cable core;
Multicore cable with The cable core includes a twisted pair of twisted two insulated wires;
The multi-core cable according to claim 5.