Insulated wire, method for manufacturing insulated wire, and cable

Abstract

The present invention provides an insulated wire with a coating layer that is resistant to tearing, a method for manufacturing an insulated wire, and a cable. [Solution] An insulated electric wire 1 comprising a conductor 2 and a covering layer 5 formed on the outermost surface so as to cover the conductor 2, wherein the thickness of the covering layer 5 is 0.08 mm or less, the covering layer 5 is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), and the shrinkage rate of the covering layer 5 when an insulated electric wire 1 with a length of 15 mm is held at 310°C for 5 minutes is 27% or less.

Description

[Technical Field]

[0001] This invention relates to insulated wires, methods for manufacturing insulated wires, and cables. [Background technology]

[0002] In recent years, the miniaturization and minimal invasiveness of insulated wires have been progressing in order to enhance the functionality of electronic devices such as VR equipment and wearable devices, as well as in the miniaturization and minimal invasiveness of medical devices. For example, extremely thin coaxial wires with an outer diameter of 0.6 mm or less are used as insulated wires for signal transmission. In order to realize such extremely thin coaxial wires, the thickness of the coating layer is being considered.

[0003] Prior art documents related to the invention of this application include Patent Documents 1 and 2. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-192567 [Patent Document 2] Japanese Patent Publication No. 2009-224284 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, although the coating layer is formed by extrusion molding, the strain during extrusion molding can cause the orientation of the resin molecules constituting the coating layer to become aligned, which can make the coating layer prone to tearing.

[0006] Therefore, the present invention aims to provide an insulated wire with a coating layer that is less prone to tearing, a method for manufacturing an insulated wire, and a cable. [Means for solving the problem]

[0007] The present invention aims to solve the above problems and provides an insulated electric wire comprising a conductor and a covering layer formed on the outermost surface so as to cover the conductor, wherein the thickness of the covering layer is 0.08 mm or less, the covering layer is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), and the covering layer has a shrinkage rate of 27% or less when the insulated electric wire with a length of 15 mm is held at 310°C for 5 minutes.

[0008] Furthermore, the present invention aims to solve the above problems and provides a method for manufacturing an insulated electric wire comprising a conductor and a coating layer formed on the outermost surface so as to cover the periphery of the conductor, wherein the coating layer is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), and the method comprises a coating layer forming step in which the coating layer is formed by extrusion molding, the molding temperature during extrusion molding in the coating layer forming step is 340°C or more and 360°C or less, and the drawdown ratio (DDR) is 400 or more.

[0009] Furthermore, the present invention aims to solve the above problems by providing a cable comprising an assembly composed of a plurality of insulated wires and a sheath that covers the periphery of the assembly, wherein at least one of the insulated wires constituting the assembly is an insulated wire of the present invention. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an insulated wire with a coating layer that is less prone to tearing, a method for manufacturing an insulated wire, and a cable. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing a cross-section perpendicular to the longitudinal direction of an insulated electric wire according to one embodiment of the present invention. [Figure 2] This is a diagram illustrating the rate of contraction. [Figure 3] This is a diagram illustrating the drawdown ratio. [Figure 4](a) to (e) are diagrams illustrating a cracking test. [Figure 5] It is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a cable according to an embodiment of the present invention. [Figure 6] It is a diagram illustrating a bending test. MODE FOR CARRYING OUT THE INVENTION

[0012] Embodiment Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0013] FIG. 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of an insulated wire 1 according to the present embodiment. The insulated wire 1 includes a conductor 2 and a coating layer 5 formed so as to cover the periphery of the conductor 2 and serving as the outermost layer. In the present embodiment, the insulated wire 1 is constituted by a coaxial cable 10 further comprising, between the conductor 2 and the coating layer 5, an insulator 3 covering the periphery of the conductor 2 and a shield layer 4 covering the periphery of the insulator 3.

[0014] The coaxial cable 10 is used as a medical insulated wire 1 that is inserted into a human body, such as for an endoscope or a catheter, for example. The coaxial cable 10 has an extremely small diameter to reduce the burden on the human body, and has a very small outer diameter of 0.6 mm or less, more preferably 0.4 mm or less, and still more preferably 0.27 mm or less.

[0015] Note that the coaxial cable 10 may be used for applications other than medical applications. For example, it may be used as wiring for electronic devices such as VR devices and wearable devices.

[0016] (Conductor 2) The conductor 2 consists of a stranded conductor formed by twisting together multiple metal strands 2a. The metal strands 2a can be made of copper or a copper alloy, and their surface may be plated. The outer diameter of the conductor 2 is 0.15 mm or less, more preferably 0.06 mm or less. In this embodiment, seven metal strands 2a made of silver-plated copper alloy wire with an outer diameter of 0.013 mm were concentrically twisted to form a conductor 2 with an outer diameter of 0.039 mm. The twist pitch of the conductor 2 was 0.7 mm. The twist pitch of the conductor 2 is the interval along the longitudinal direction of the insulated wire 1 at which the positions of the metal strands 2a are the same in the circumferential direction of the insulated wire 1.

[0017] (Insulator 3) The insulator 3 is preferably made of a fluororesin that can be molded into a thin wall. Here, an insulator 3 made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer) with a thickness of 0.023 mm was used. The outer diameter of the insulator 3 was set to 0.085 mm.

[0018] (Shield layer 4) The shield layer 4 consists of a horizontally wound shield in which multiple metal wires 4a are spirally wound around the insulator 3. The metal wires 4a can be made of copper or a copper alloy, and their surface may be plated. In this embodiment, the shield layer 4 is constructed using 16 metal wires 4a made of silver-plated copper alloy wire with an outer diameter of 0.020 mm. The twisting direction of the shield layer 4 should be the same as the twisting direction of the conductor 2. This allows the twist to loosen appropriately in response to bending or twisting when the coaxial cable 10 is bent or twisted, thereby releasing stress and improving resistance to bending and twisting. The twisting direction of the conductor 2 and the shield layer 4 is the direction in which the metal wires 2a and 4a rotate from one end to the other end of the coaxial cable 10, as viewed from one end.

[0019] (Coating layer 5) The coating layer 5 constitutes the outermost layer of the coaxial cable 10. The coating layer 5, like the insulator 3, is preferably made of a fluororesin that can be molded into a thin wall. In this embodiment, the coating layer 5 was made of a resin composition mainly composed of PFA. To reduce the diameter of the coaxial cable 10, the thickness of the coating layer 5 is preferably at least 0.08 mm, more preferably 0.04 mm, and even more preferably 0.025 mm. The outer diameter of the coating layer 5, i.e., the outer diameter of the coaxial cable 10, is at least 0.6 mm, more preferably 0.4 mm, and even more preferably 0.2 mm. In this embodiment, the thickness of the coating layer 5 was set to 0.02 mm, and the overall outer diameter of the coaxial cable 10 was set to 0.165 mm.

[0020] The coating layer 5 exhibits a shrinkage rate (shrinkback) of 27% or less when a 15 mm long coaxial wire 10 sample is held at 310°C for 5 minutes. To measure the shrinkage rate, as shown in Figure 2, a 15 mm long coaxial wire 10 is prepared as a sample and held at 310°C for 5 minutes. If the initial length of the coating layer 5 is L1 and the length of the coating layer 5 after shrinkage is L2, then the following equation (1) Contraction rate = {(L1-L2) / L1} × 100 ... (1) The shrinkage rate can be determined by this method.

[0021] When the coating layer 5 is extruded, if the molding temperature is low and the resin is stretched during extrusion, the orientation of the resin molecules constituting the coating layer 5 will align along the axial direction of the coaxial line 10. When the orientation of the resin molecules constituting the coating layer 5 is aligned, the coating layer 5 becomes prone to tearing in the axial direction. Furthermore, when the orientation of the resin molecules constituting the coating layer 5 is aligned, the shrinkage rate increases in high-temperature environments as the resin molecules try to return to a state of random orientation. As in this embodiment, by reducing the shrinkage rate of the coating layer 5 to 27% or less, the orientation of the resin molecules constituting the coating layer 5 becomes not aligned along the axial direction (i.e., the molecular orientation is relatively random), making the coating layer 5 less prone to tearing in the axial direction.

[0022] In order to reduce the shrinkage rate of the coating layer 5, it is necessary to relatively increase the molding temperature during extrusion molding of the coating layer 5. More specifically, the molding temperature (crosshead and die temperature) during extrusion molding of the coating layer 5 is preferably 340°C or higher and 360°C or lower, more preferably 350°C or higher and 360°C or lower. By setting the molding temperature during extrusion molding of the coating layer 5 to 350°C or higher, it is possible to suppress the alignment of molecules of the resin constituting the coating layer 5 along the axial direction, making the coating layer 5 less prone to cracking in the axial direction. By setting the molding temperature during extrusion molding of the coating layer 5 to 360°C or lower, it is possible to suppress foaming of the resin constituting the coating layer 5 during extrusion molding, and suppress a decrease in insulation of the coating layer 5 caused by pinholes or the like generated in the coating layer 5.

[0023] Furthermore, in order to reduce the shrinkage rate of the coating layer 5, it is preferable to increase the drawdown ratio (DDR) during extrusion molding of the coating layer 5. In the present embodiment, the drawdown ratio during extrusion molding is set to 400 or more. As shown in FIG. 3, when extrusion-molding the coating layer 5, the resin 303 is extruded from between the inner wall of the hole 301a provided in the die 301 of the extruder 300 and the outer wall of the core metal 302 to mold the coating layer 5. At this time, the inner diameter of the hole 301a of the die 301 is D die , the outer diameter of the core metal 302 is D tip , the outer diameter of the entire coaxial cable 10 after forming the coating layer 5 is D wire , the outer diameter of the shield layer 4 is D core , then the drawdown ratio is represented by the following formula (2). DDR=(D die 2 -D tip 2 ) / (D wire 2 -D core 2 ) ···(2)

[0024] As mentioned above, in this embodiment, the molding temperature during the extrusion molding of the coating layer 5 is set to a relatively high temperature. However, if the coating layer 5 contains titanium dioxide as a coloring agent, the titanium dioxide acts as a catalyst, accelerating the decomposition of the resin during extrusion molding. Therefore, if the coating layer 5 contains titanium dioxide as a coloring agent, the resin is prone to decomposition and foaming in the extruder, and the insulating properties of the coating layer 5 tend to decrease, such as the formation of pinholes in the molded coating layer 5. For this reason, in this embodiment, the coating layer 5 does not contain titanium dioxide. Titanium dioxide is a white coloring agent and is commonly used, for example, when coloring the coating layer 5 white or gray. In this embodiment, zinc oxide is used instead of titanium dioxide as a white coloring agent.

[0025] When using zinc oxide as a white coloring agent, the amount of zinc oxide added to the coating layer 5 should be set so that the zinc element in the coating layer 5 is between 0.4 mass% and 5.0 mass%. If the oxide element in the coating layer 5 is less than 0.4 mass%, sufficient coloring cannot be expected, and if it exceeds 5.0 mass%, the mechanical strength and insulating properties of the coating layer 5 may decrease.

[0026] (Method of manufacturing insulated electric wire 1) When manufacturing an insulated electric wire 1, the following steps are performed sequentially: a conductor forming step in which multiple metal strands 2a are twisted together to form a conductor 2; an insulator forming step in which an insulator 3 is formed around the conductor 2 by extrusion molding; a shield layer forming step in which multiple metal strands 4a are wound horizontally around the insulator 3 to form a shield layer 4; and a coating layer forming step in which a coating layer 5 is formed around the shield layer 4 by extrusion molding.

[0027] In this embodiment, the molding temperature during extrusion molding in the coating layer formation process is set to 350°C or higher and 360°C or lower, and the drawdown ratio (DDR) is set to 400 or higher. This makes it possible to obtain a coating layer 5 with a shrinkage ratio of 27% or less and that is resistant to axial tearing.

[0028] (Examples) The coaxial wires 10 of Examples 1 to 4 were prototyped using a 15 mm extruder 300 with a full-flight screw with an L / D ratio of 20, a bore 301a with an inner diameter of 4.0 mm, and a mandrel 302 with an outer diameter of 2.5 mm. The coating layer 5 had a melt viscosity of approximately 1.5 (1.0~2.0) × 10 at 335°C and a shear rate of 121.6 (1 / s). 3 A resin composition mainly composed of PFA with a Pa / s rating was used. The molding temperature (crosshead and die temperature) during extrusion molding of the coating layer 5 was set to 355°C, and the DDR was set to 840. The screw rotation speed was 0.8 rpm in Example 1 and 1.0 rpm in Examples 2-4. The coloring agent used was zinc oxide in Example 1, carbon in Example 2, no coloring agent in Example 3, and cobalt blue in Example 4.

[0029] The shrinkage rate of the coating layer 5 was measured for the coaxial wires 10 of the prototyped Examples 1 to 4. As explained in Figure 2, the shrinkage rate was measured by cutting the coaxial wire 10 to a length of 15 mm to make a sample, placing the sample in a constant temperature bath maintained at 310°C for 5 minutes to shrink the coating layer 5, and then measuring the length of the coating layer 5 after shrinkage. Here, the shrinkage rate of the coaxial wires 10 of Examples 1 to 4 was measured nine times, and the average value and standard deviation σ were calculated. Furthermore, the minimum variation value obtained by subtracting 3σ from the average value and the maximum variation value obtained by adding 3σ to the average value were calculated.

[0030] Furthermore, cracking tests were conducted on the coating layer 5 of the coaxial wires 10 of Examples 1 to 4. In the cracking test, as shown in Figure 4(a), a razor blade 100 was used to make a 20mm to 30mm cut 101 along the longitudinal direction of the coating layer 5 at the tip of the coaxial wire 10, and then, as shown in Figure 4(b), the coating layer 5 was pulled towards the base end to peel it off. As a result, as shown in Figure 4(c), if the cut 101 easily progressed in the longitudinal direction of the coaxial wire 10, the coating layer 5 was considered prone to cracking and was deemed unsuccessful. On the other hand, as shown in Figure 4(d), if the coating layer 5 fractured without the cut 101 progressing, or as shown in Figure 4(e), if the crack progressed from the cut 101 but under load caused the coating layer 5 to undergo plastic deformation (necking) as the crack progressed, the coating layer 5 was considered unprone to cracking and was deemed successful. Here, the cracking test was performed 20 times for each of the coaxial wires 10 of Examples 1 to 4.

[0031] Furthermore, the coaxial cables 10 of Examples 1 to 4 were inspected for the presence or absence of foaming. The inspection for the presence or absence of foaming was performed in-line using a spark tester to conduct a spark test (inspection for the presence or absence of pinholes).

[0032] Similarly, a comparative example using titanium dioxide as a coloring agent was subjected to the same tests as in Examples 1-4. In the comparative example, the molding temperature during extrusion molding of coating layer 5 was set to 340°C, the screw rotation speed to 0.8 rpm, and the DDR to 840. For shrinkage rate, nine measurements were taken as in Examples 1-4, and the mean value, standard deviation σ, minimum variation (mean value - 3σ), and maximum variation (mean value + 3σ) were determined. In addition, 20 crack tests were performed as in Examples 1-4. The results are summarized in Table 1.

[0033] [Table 1]

[0034] As shown in Table 1, in Examples 1 to 4, the average shrinkage rate of the coating layer 5 was 13.0% or less. Furthermore, in Examples 1 to 4, the coating layer 5 passed the cracking test (20 out of 20 times), and there was no foaming of the coating layer 5. In contrast, in the comparative example, the average shrinkage rate of the coating layer 5 was a large 35.9%. Furthermore, in the comparative example, the coating layer 5 failed the cracking test (3 out of 20 times), and foaming occurred in the coating layer 5.

[0035] Furthermore, in the comparative example, the crack test failed only 3 times out of 20 trials, indicating that it sometimes passed the crack test. From these results, it can be concluded that the comparative example is on the borderline where the pass or fail of the crack test depends on the variability. Therefore, it is considered that by setting the shrinkage rate of the coating layer 5 to 27.0% or less, which is lower than the minimum value of shrinkage rate variability in the comparative example, an insulated wire 1 with a coating layer 5 that is less prone to cracking can be realized. Note that the maximum value of shrinkage rate variability in Examples 1 to 4 was 22.6% or less, which is smaller than the minimum value of shrinkage rate variability in the comparative example (27.2%).

[0036] (cable) Next, a cable 110 using the insulated wire 1 according to this embodiment will be described. Figure 5 is a cross-sectional view showing a section perpendicular to the longitudinal direction of the cable 110 according to this embodiment.

[0037] The cable 110 comprises an assembly 111 composed of multiple insulated wires 1, and a sheath 113 that covers the assembly 111 collectively. In this embodiment, a binding tape 112 is wrapped around the assembly 111, and the sheath 113 is provided around the binding tape 112.

[0038] In cable 110, at least one of the insulated wires 1 constituting the bundle 111 may be an insulated wire 1 according to this embodiment, and other insulated wires may be included. In the illustrated example, four insulated wires 1 according to this embodiment are twisted together to form the bundle 111.

[0039] Nonwoven fabric tape, paper tape, resin tape, etc., can be used as the binding tape 112. In this embodiment, a polyester tape with copper vapor-deposited on one side was used as the binding tape 112. The copper layer formed by vapor deposition acts as a shielding layer. This makes it possible to reduce the outer diameter of the cable 110 compared to the case where a shielding layer is provided separately from the binding tape 112. The thickness of the binding tape 112 was set to 0.01 mm and the width to 2.0 mm. The binding tape 112 is wound in a spiral shape so that a portion of it overlaps in the width direction.

[0040] The twisting direction of the bundle 111 and the winding direction of the binding tape 112 are set to be in opposite directions. This prevents the twisted cores from unraveling and improves durability against repeated bending. The twisting direction of the bundle 111 is the direction in which the insulated wire 1 rotates from one end to the other when viewed from one end of the cable 110. The winding direction of the binding tape 112 is the direction in which the binding tape 112 rotates from one end to the other when viewed from one end of the cable 110.

[0041] The sheath 113 is preferably made of a fluororesin that can be molded into a thin wall. Here, a sheath 113 made of PFA with a thickness of 0.025 mm was used. The overall outer diameter of the cable 110 is approximately 0.47 mm.

[0042] (Bending test) A prototype cable 110, as shown in Figure 5, was fabricated and subjected to a bending test. In the bending test, as shown in Figure 6, a weight with a load W = 25 gf was suspended from the lower end of the cable 110 under test, and pulleys 200 with a diameter of 15 mm were placed on both sides of the cable 110. The cable 110 was then moved along the pulleys 200 to apply a 150° bend in the left-right direction. The bending speed was set to 30 times / minute, and the number of bends was defined as one round trip in the left-right direction (arrows a to d in the figure), and the bending of the cable 110 was repeated. During the test, a voltage was continuously applied to the conductor 2 and shield layer 4 of the insulated wire 1 (coaxial cable 10) contained in the cable 110, and the end of the lifespan was determined when the value of the current flowing through the conductor 2 and shield layer 4 decreased by 20% from the start of the test.

[0043] The bending test results confirmed that the cable did not reach the end of its lifespan even after more than 60,000 bending cycles. In other words, this embodiment confirmed that a cable 110 with sufficiently high resistance to bending can be realized.

[0044] (Operation and Effects of the Embodiment) As described above, the insulated wire 1 according to this embodiment is equipped with a coating layer 5 with a thickness of 0.08 mm or less, which is made of a resin composition mainly composed of PFA, and the coating layer 5 has a shrinkage rate of 27% or less when an insulated wire 1 with a length of 15 mm is held at 310°C for 5 minutes.

[0045] This configuration suppresses the alignment of the resin molecules constituting the coating layer 5 along the axial direction, thereby enabling the creation of an insulated wire 1 in which the coating layer 5 is less prone to tearing. This is particularly effective when the outer diameter is small and the coating layer 5 is thin. More specifically, it is particularly effective in small-diameter coaxial cables 10 in which the outer diameter of the conductor 2 is 0.06 mm or less, the thickness of the coating layer 5 is 0.025 mm or less, and the outer diameter of the coating layer 5 is 0.27 mm or less.

[0046] (Summary of the embodiments) Next, the technical concept understood from the embodiments described above will be described using the reference numerals and other symbols from the embodiments. However, the reference numerals and other symbols in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[0047] [1] An insulated electric wire (1) comprising a conductor (2) and a covering layer (5) formed on the outermost surface so as to cover the periphery of the conductor (2), wherein the thickness of the covering layer (5) is 0.08 mm or less, the covering layer (5) is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), and the covering layer (5) has a shrinkage rate of 27% or less when the insulated electric wire (1) with a length of 15 mm is held at 310°C for 5 minutes.

[0048] [2] The insulated wire (1) according to [1], further comprising an insulator (3) covering the conductor (2) and a shielding layer (4) covering the insulator (3) between the conductor (2) and the covering layer (5), wherein the outer diameter of the covering layer (5) is 0.6 mm or less.

[0049] [3] The insulated wire (1) described in [2], wherein the outer diameter of the coating layer (5) is 0.27 mm or less, and the thickness of the coating layer is 0.025 mm or less.

[0050] [4] The insulated wire (1) according to [1], wherein the coating layer (5) does not contain titanium oxide.

[0051] [5] A method for manufacturing an insulated electric wire (1), comprising a conductor (2) and a coating layer (5) formed on the outermost surface so as to cover the conductor (2), wherein the coating layer (5) is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), and the method comprises a coating layer forming step of forming the coating layer (5) by extrusion molding, wherein the molding temperature during extrusion molding in the coating layer forming step is 340°C or more and 360°C or less, and the drawdown ratio (DDR) is 400 or more.

[0052] [6] A cable (110) comprising an assembly (111) composed of multiple insulated wires, and a sheath (113) that covers the assembly (111) collectively, wherein at least one of the insulated wires constituting the assembly (111) is an insulated wire (1) as described in any one of items [1] to [4].

[0053] (Note) Although embodiments of the present invention have been described above, the embodiments described above do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. Moreover, the present invention can be implemented with appropriate modifications without departing from its spirit. [Explanation of symbols]

[0054] 1...Insulated wire 10…Coaxial line 2... Conductor 3…Insulator 4…Shield layer 5…Covering layer

Claims

1. A conductor and An insulated wire comprising a covering layer formed on the outermost surface so as to cover the periphery of the conductor, The thickness of the coating layer is 0.08 mm or less. The coating layer is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), The coating layer has a shrinkage rate of 27% or less when the insulated wire, which is 15 mm long, is held at 310°C for 5 minutes. Insulated wire.

2. The conductor and the covering layer further comprise an insulator covering the conductor and a shielding layer covering the insulator. The outer diameter of the coating layer is 0.6 mm or less. The insulated wire according to claim 1.

3. The outer diameter of the coating layer is 0.27 mm or less. The thickness of the coating layer is 0.025 mm or less. The insulated wire according to claim 2.

4. The coating layer does not contain titanium dioxide. The insulated wire according to claim 1.

5. A conductor and A method for manufacturing an insulated wire, comprising a covering layer formed on the outermost surface so as to cover the periphery of the conductor, The coating layer is made of a resin composition mainly composed of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), The process includes a coating layer forming step in which the coating layer is formed by extrusion molding, The molding temperature during extrusion molding in the aforementioned coating layer formation process is 340°C to 360°C, and the drawdown ratio (DDR) is 400 or higher. A method for manufacturing insulated electric wires.

6. A collection of multiple insulated wires, The assembly comprises a sheath that covers the entire surroundings of the assembly, At least one of the insulated wires constituting the assembly is an insulated wire according to any one of claims 1 to 3. cable.

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