CN115023772A

CN115023772A - Communication cable and method for manufacturing the same

Info

Publication number: CN115023772A
Application number: CN202180010702.6A
Authority: CN
Inventors: 光地伸明; 河田正义; 坂本乔
Original assignee: SWCC Showa Cable Systems Co Ltd
Current assignee: SWCC Corp
Priority date: 2020-01-24
Filing date: 2021-01-22
Publication date: 2022-09-06
Also published as: JPWO2021149787A1; JP7111915B2; WO2021149787A1

Abstract

Provided is a communication cable which is a communication cable for high-frequency data transmission and which can simplify the internal structure of the cable. Disclosed is a communication cable (1) wherein a plurality of insulated wires (12) each having a conductor (14) covered with an insulator (16) are twisted. In a communication cable (1), an intervening cord (20) is interposed between insulated wires (12), and the insulated wires (12) are twisted at a pitch of 17.5mm or less.

Description

Communication cable and method for manufacturing the same

Technical Field

The present invention relates to a communication cable corresponding to high frequency data transmission.

Background

In recent years, in view of the increasing performance of information communication devices and the increasing versatility of on-vehicle multimedia in automobiles, the development of higher performance and more equipped devices will be Advanced in future using Advanced Driver-Assistance Systems (ADAS) and automatic driving as key items. Such progress increases the capacity of information traffic, and requires high-frequency data transmission.

However, there are some problems in high-frequency data transmission, for example, suppression of skew in pairs (difference in propagation delay time in pairs) and suppression of a bell-out phenomenon in a high-frequency band (rapid decrease in frequency characteristics of a signal attenuation amount).

Patent document 1 discloses a multi-core cable for solving the above-described problem of high-frequency data transmission.

In the technique of patent document 1, 8 pairs of coaxial wire pairs (11 to 18) are housed in a multi-core cable (1). The center conductor (21) of each coaxial cable (10) is covered with an insulator (22), and the outer periphery thereof is covered with an outer conductor (23) and a sheath (24). In the external conductor, a thin metal wire (M) is laterally wound (spirally wound) around the insulator as an inner layer (23A), and a metal resin tape (T) is laterally wound around the inner layer as an outer layer (23B).

In this technique, in particular, the winding directions of the thin metal wire and the metal resin tape are set to be opposite directions, and the difference (angle θ 3) between the winding angles is set within a certain range, thereby suppressing the slipping-in phenomenon (refer to paragraphs 0017-0027, fig. 1-2, example, fig. 4, and the like).

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 6269718

Disclosure of Invention

Technical problem to be solved by the invention

However, in the wire pair of patent document 1, as described above, the outer conductor is disposed in the coaxial wire and is configured by the thin metal wire and the metal resin tape, and the winding direction and the winding angle of the thin metal wire and the metal resin tape need to be set. The technique of patent document 1, that is, the internal structure of the cable is very complicated, and there is room for improvement in the internal structure of the cable.

It is therefore a primary object of the present invention to provide a communication cable corresponding to high-frequency data transmission, and capable of achieving simplification of the internal structure of the cable.

Means for solving the problems

In order to solve the above-mentioned problems, according to the present invention, there is provided a communication cable,

a communication cable obtained by twisting a plurality of insulated wires each having a conductor covered with an insulator,

an intervening cord is interposed between the insulated wires,

the insulated wires are twisted at a pitch of 17.5mm or less.

Effects of the invention

According to the present invention, (i) since the intervenient cord is provided, the inner deflection is 10ps/m or less, and the transmission state is stable. (ii) Since the insulated wires are twisted at a pitch of 17.5mm or less, the Insertion Loss (IL) does not decrease (decrease) to 6GHz, and the attenuation of the signal is suppressed.

Drawings

Fig. 1 is a cross-sectional view showing a schematic configuration of a communication cable according to embodiment 1.

Fig. 2A is a flowchart schematically illustrating a method for manufacturing a communication cable according to embodiment 1.

Fig. 2B is a schematic diagram for explaining a piping manner.

Fig. 2C is a schematic diagram for explaining the pressure manner.

Fig. 3A is a cross-sectional view showing a schematic configuration of a communication cable according to embodiment 2.

Fig. 3B is a flowchart schematically illustrating a method for manufacturing a communication cable according to embodiment 2.

Fig. 4 is a graph showing the relationship between the frequency and the insertion loss of sample 1.

Fig. 5 is a graph showing the relationship between the frequency and the insertion loss of sample 2.

Fig. 6 is a graph showing the relationship between the frequency and the insertion loss of sample 11.

Fig. 7 is a graph showing the relationship between the frequency and the insertion loss of the sample 12.

Fig. 8 is a graph showing the relationship between the frequency and the insertion loss of sample 13.

Fig. 9 is a graph showing the relationship between the frequency and the insertion loss of the sample 14.

Fig. 10 is a graph showing the relationship between the frequency and the insertion loss of the sample 15.

Fig. 11A is a graph showing the relationship between the frequency and the insertion loss of the sample 21.

Fig. 11B is a graph comparatively showing the relationship between the frequency and the insertion loss of the samples 11 and 21.

Detailed Description

Hereinafter, a communication cable according to a preferred embodiment of the present invention will be described.

In the present specification, "to" indicating a numerical range has a meaning including a lower limit value and an upper limit value in the numerical range.

[ embodiment 1]

Fig. 1 is a sectional view showing a schematic structure of a communication cable 1.

As shown in fig. 1, the communication cable 1 has a four-core stranded wire 10, an intervening cord 20, a 1 st shield layer 30, a 2 nd shield layer 40, and a sheath 50, and the 1 st shield layer 30, the 2 nd shield layer 40, and the sheath 50 are sequentially wound around and cover the outer circumference of the four-core stranded wire 10.

The four-core stranded wire 10 is composed of four-core (4) insulated wires 12, and each insulated wire 12 has a structure in which it is stranded at a pitch of 7.0mm or more and 17.5mm or less, preferably 7.0mm or more and 16mm or less, more preferably 7.0mm or more and 14mm or less, and still more preferably 10.0mm or more and 14mm or less.

The lower limit value and the upper limit value of the twist pitch of the insulated electric wire 12 are set from the following viewpoints.

The lower limit value is actually 7.0mm, preferably 10.0mm, from the viewpoint of whether or not the inward shift can be suppressed and stable manufacturing can be achieved. The shorter the twist pitch of the insulated wires 12, the denser the twisted pair becomes, and the balance of the twisting of the insulated wires 12 with each other becomes unstable. As a result, the insulated wires 12 have a difference in physical length (variation in length), and it is difficult to suppress the inward deviation. If the twist pitch of the insulated wire 12 is set to be narrow, the amount of use (length) of the insulated wire 12 increases, which is disadvantageous in terms of manufacturing and cost, and the lower limit value is also assumed from the viewpoint of manufacturing availability.

The upper limit value is derived from the viewpoint of suppressing the cup joint phenomenon at a high frequency (up to 6 GHz), and is 17.5 mm. Generally, the twist pitch is 1/2 in terms of wavelength, expressed in terms of wave velocity/frequency. If the speed of light is set to 100, the speed of the signal transmitted within the cable pair is about 70% as a technical common sense (NVP: Nominal Velocity of Propagation). If the frequency is set to 6GHz, the upper limit of the twist pitch is theoretically derived as follows. If the wavelength of the signal transmitted in the cable pair is synchronized with the twist pitch of the insulated wire 12 and resonates, a sleeving phenomenon occurs. If the upper limit of the twist pitch of the insulated wire 12 exceeds 17.5mm, a resonance point is formed at a low frequency (6GHz or less), and a cup joint phenomenon is likely to occur.

Upper limit of twisting pitch

Two (wavelength) × (1/2)

(light velocity × NVP/frequency) × (1/2)

＝300，000，000[m/s]×0.7/6[GHz]×1/2

About 17.5[ mm ]

In the four-core stranded wire 10, the 1 st wire core 10A and the 2 nd wire core 10B are used in pairs, and the 3 rd wire core 10C and the 4 th wire core 10D are used in pairs. The four-core twisted wire 10 may be formed by a pair (2 cores) of the 1 st core 10A and the 2 nd core 10B, or by adding a pair of the 5 th core to the core after the 6 th core.

The insulated wire 12 is composed of a conductor 14 and an insulator 16, and has a structure in which the outer periphery of the conductor 14 is covered with the insulator 16.

The conductor 14 has a structure in which a plurality of element wires are twisted, and each element wire is made of a conductive metal material. Each element wire is preferably a soft copper wire, and the outer periphery thereof is covered with a plating layer (not shown) of any one of tin, nickel, and silver.

The outer diameter of the conductor 14 is preferably 0.45 to 0.50 mm.

The insulator 16 is formed by extruding an insulating resin from a die of an extruder. The insulating resin is preferably crosslinked polyethylene (XLPE: Cross-linked polyethylene) or polypropylene.

The thickness of the insulator 16 is preferably 0.15 to 0.35 mm.

The intervening cord 20 is disposed in the center of the four-core stranded wire 10(4 insulated wires 12). The intervening cord 20 is a linear member having a circular cross-sectional shape, and is provided so that the arrangement relationship of the insulated wires 12 is constant.

The interventional rope 20 is preferably High Density Polyethylene (HDPE). The intervening tether 20 may be constructed of nylon, polypropylene, polyethylene terephthalate, or the like.

The diameter of the intervention rope 20 is preferably 0.3-0.5 mm.

The 1 st shield layer 30 is formed by overlapping and winding a metal tape.

The metal tape is formed by bonding a metal foil and a resin tape, and is preferably formed by bonding an aluminum foil and a polyethylene terephthalate tape (PET tape). In the 1 st shield layer 30, the metal foil is wound so as to be exposed on the outer periphery.

The thickness of the metal adhesive tape is preferably 0.03-0.06 mm.

On the other hand, the 2 nd shield layer 40 is formed by transversely winding a plurality of wires at a constant pitch or less. The 2 nd shield layer 40 may be braided with a plurality of wires. The wires are preferably so-called tin-plated Annealed copper wires (TA) in which the Annealed copper wires are covered with a tin plating.

The outer diameter of the metal wire is preferably 2.9 to 3.1 mm.

The sheath 50 is a so-called skin layer, and is formed by extruding a sheath resin from a die of an extruder. The resin for the sheath is preferably made of PolyVinyl Chloride (PVC) or Thermoplastic elastomer (TPE).

The thickness of the sheath 50 is preferably 0.2 to 0.6 mm.

Next, a method for manufacturing the communication cable 1 will be described with reference to fig. 2A.

First, a plurality of wires are twisted to form a conductor 14, an insulating resin is extruded to cover the conductor 14, and an electron beam is irradiated thereto to crosslink the conductor 14, thereby forming an insulator 16, thereby manufacturing the insulated wire 12 (S1).

Thereafter, 4 insulating wires 12 are twisted at a pitch of 17.5mm or less with the high-density polyethylene intervening cord 20 disposed at the center (four-core twisting, S2).

Thereafter, the metal tape is lap-wound around the four-core stranded wires 10 to form the 1 st shield layer 30, and a plurality of metal wires are transversely wound to form the 2 nd shield layer 40 (S3).

Finally, the 2 nd shield layer 40 is extruded and covered with a sheath resin to form the sheath 50(S4), whereby the communication cable 1 can be manufactured.

The extrusion of the resin for the sheath can be in a pipeline mode or a pressure mode.

The pipe system is a system in which a joint is inserted from an opening of a die to an extrusion port and the molten resin is extruded in a pipe shape (cylindrical shape) so as to always pass through the center of the joint when the extruded body passes through the die (see fig. 2B). According to the pipe system, even if the shape of the extruded body is irregular, the thickness of the sheath is constant, and the extruded body is not crushed.

The pressure method is a method in which a tab is inserted from an opening of a die to a middle portion, passes through a center of the tab when an extruded body passes through the die, and then passes through the inside of the die, and a molten resin is extruded while being pressed against the extruded body (see fig. 2C). According to the pressure method, the resin for the sheath is easily brought into close contact with the surface of the extruded body.

According to the above communication cable 1, (i) since the intervening cord 20 is provided, the skew is 10ps/m or less, and the transmission state is stable. (ii) Since the insulated wires 12 are twisted at a pitch of 17.5mm or less, the Insertion Loss (IL) is not reduced (lowered) to 6GHz, and the attenuation of the signal in a high frequency band is suppressed (see examples 1 and 2 below).

According to the communication cable 1, the communication cable which is compatible with high-frequency data transmission and in which the internal structure of the cable can be simplified can be provided by a simple configuration in which the intervening cord 20 is provided and the twist pitch of each insulated wire 12 is set to a constant value or less.

[ embodiment 2]

Embodiment 2 is the same as embodiment 1 except for the following points.

As shown in fig. 3A, in the communication cable 2, the four-core stranded wires 10 are covered with the wrapping 25, the wrapping 25 is covered with the 1 st shielding layer 30, and the wrapping 25 is formed between the four-core stranded wires 10 and the 1 st shielding layer 30.

The wrapping 25 is formed by winding a tape-shaped polyethylene terephthalate (PET) in an overlapping manner. The wrapping 25 may be formed of a tape-like nonwoven fabric.

The thickness of the wrapping 25 is preferably 0.02-0.5 mm.

When the conductor-to-conductor distance between a pair of the 1 st type core 10A and the 2 nd type core 10B (or a pair of the 3 rd type core 10C and the 4 th type core 10D) is dc and the shortest distance between the conductor 14 of the pair and the 1 st shield layer 30 is ds, the dc/ds value is 2 or less.

The relationship of the dc/ds value of 2 or less may be satisfied in at least one of the pair of the 1 st type core 10A and the 2 nd type core 10B and the pair of the 3 rd type core 10C and the 4 th type core 10D, and preferably both of the pair.

A method of manufacturing the communication cable 2 is explained with reference to fig. 3B.

After the step S2 of twisting the insulated electric wires 12, a polyethylene terephthalate tape (PET tape) is lap-wound around the four-core twisted wire 10 to form the lap 25(S5), and then a metal tape is lap-wound around the lap 25 to form the 1 st shield layer 30.

In the method for manufacturing the communication cable 2, care is taken to set (design) the dc/ds value to 2 or less from the step S1 of manufacturing the insulated wire 12 to the step S3 of covering with the 1 st shield layer 30.

According to the above communication cable 2, the taped package 25 is intentionally formed between the four-core stranded wires 10 and the 1 st shielding layer 30, a physical distance is secured between the 1 st type wire core 10A and the 1 st type wire core 10B, and the conductor 14 of the pair wire and the 1 st shielding layer 30, and the dc/ds value is set to 2 or less.

According to this structure, the electromagnetic coupling between the pair of lines and the 1 st shield layer 30 can be weakened, and the attenuation of the signal in the high frequency band can be suppressed (refer to example 3 below).

In addition, as long as the communication cable 1 or the communication cable 2 is for communication use, it can be used for any use, preferably for vehicle-mounted use, and more preferably for transmission of an image or video signal of a vehicle-mounted camera.

In the case where the communication cable 1 or 2 is used for an in-vehicle use and it is desired to maintain the characteristics for a long period of time, it is better to form the sheath 50 by using a pressure method than a piping method. This is because the relationship between the members within the sheath 50 is fixed (maintained).

[ example 1]

Here, the presence or absence of the influence of the intervening cords in the high-frequency data transmission is verified.

(1) Preparation of samples

(1.1) sample 1

First, 7 tin-plated annealed copper wires having a diameter of 0.16mm were stranded to form a conductor having an outer diameter of 0.48 mm.

Thereafter, the conductor was extruded and covered with polyethylene, and was irradiated with an electron beam to be crosslinked, to form an insulated wire having an outer diameter of 1.12mm composed of crosslinked polyethylene (XLPE).

Thereafter, 4 insulated wires were stranded (four-core stranded) at a pitch of 30mm in a state where an intervening cord made of high density polyethylene having a diameter of 0.45mm was disposed at the center, to form a four-core stranded wire having an outer diameter of 2.70 mm.

Then, a metal tape obtained by bonding an aluminum foil and a polyethylene terephthalate tape (PET tape) was prepared as a 1 st shield layer, and this metal tape 1/4 was wound in a state of being overlapped on four-core stranded wires to form a 1 st shield layer having an outer diameter of 2.82 mm.

Thereafter, 84 tin-plated annealed copper wires (TA) having a diameter of 0.1mm were prepared as a 2 nd shield layer, and the tin-plated annealed copper wires were transversely wound around the 1 st shield layer at a pitch of 32mm or less to form a 2 nd shield layer having an outer diameter of 3.02 mm.

Finally, polyvinyl chloride (PVC) was extruded in a pipe manner and covered on the 2 nd shield layer to manufacture a communication cable having an outer diameter of 3.82 mm.

(1.2) sample 2

The intervening cord was removed in sample 1 and set as sample 2.

(2) Evaluation of samples

Each sample was cut by 5m and the insertion loss in the intra-pair skew and high band was measured for it.

The measurement results are shown in table 1 and fig. 4 to 5. In the measurement results, results for each pair of the 1 st type core to the 2 nd type core and the 3 rd type core to the 4 th type core are shown.

[ Table 1]

(3) Summary of the invention

As shown in Table 1, the intra-pair skew for sample 1 was well below 10ps/m, as opposed to over 10ps/m for sample 2.

It is known that the provision of an intervening cord helps to stabilize the transport state.

However, both samples 1 and 2 observed a sleeving phenomenon before IL dropped to 6GHz, and high frequency data transmission could not be achieved with or without an intervening cord.

[ example 2]

Here, the influence of the stranding pitch of the four-core stranded wire in high-frequency data transmission was verified.

(1) Preparation of samples

(1.1) sample 11

4 insulated electric wires were stranded (four-core stranded) at a pitch of 14mm in sample 1 according to example 1, and this was set as sample 11.

Specifically, 7 tin-plated annealed copper wires having a diameter of 0.16mm were stranded to form a conductor having an outer diameter of 0.48 mm.

Thereafter, 4 insulated wires were stranded (four-core stranded) at a pitch of 14mm with an intervening cord of high density polyethylene having a diameter of 0.45mm disposed at the center, to form a four-core stranded wire having an outer diameter of 2.70 mm.

(1.2) sample 12

In sample 11, the extrusion of the sheath resin was changed to "pressure type", and this was designated as sample 12.

(1.3) samples 13 to 15

The twist pitch of the insulated electric wire was changed to "18 mm" in sample 11, and this was set as sample 13.

In sample 11, the strand pitch of the insulated wire was changed to "18 mm", and the extrusion of the resin for a sheath was changed to "pressure type", which was set as sample 14.

In sample 11, the strand pitch of the insulated wire was changed to "60 mm", and the extrusion of the resin for a sheath was changed to "pressure type", which was set as sample 15.

(2) Evaluation of samples

The measurement results are shown in table 2 and fig. 6 to 10. In the measurement results, results for each pair of the 1 st type core to the 2 nd type core and the 3 rd type core to the 4 th type core are shown.

[ Table 2]

(3) Summary of the invention

As shown in Table 2, samples 11-15 all had intervening cords with an internal deflection below 10ps/m and a stable transmission.

Samples 11-12 all observed no nesting until the IL passed 6GHz, whereas samples 13-15 all observed nesting until the IL dropped to 6 GHz.

It is found that twisting the insulated wires at a pitch of 17.5mm or less after providing the intervening cord not only suppresses the internal skew but also contributes to suppression of attenuation of signals in a high frequency band.

[ example 3]

(1) Preparation of samples

In sample 1 according to example 1, 4 insulated wires were twisted (four-core twisted) at a pitch of 14mm, and the four-core twisted wires were covered with a wrapping and set as sample 21.

Specifically, 7 tinned annealed copper wires having a diameter of 0.16mm were stranded to form a conductor having an outer diameter of 0.48 mm.

Thereafter, the conductor was extruded and covered with polyethylene, and was irradiated with an electron beam to be crosslinked, to form an insulated wire having an outer diameter of 0.88mm composed of crosslinked polyethylene (XLPE).

Thereafter, 4 insulated wires were stranded (four-core stranded) at a pitch of 14mm with an intervening cord of high density polyethylene having a diameter of 0.35mm disposed at the center, thereby forming a four-core stranded wire having an outer diameter of 2.13 mm.

Thereafter, a polyethylene terephthalate tape (PET tape) having a thickness of 0.1mm was prepared as a wrapping, and the PET tape was lap-wound around the four-core stranded wires 1/2 to form a wrapping having an outer diameter of 2.69 mm.

Then, a metal tape obtained by bonding an aluminum foil and a polyethylene terephthalate tape (PET tape) was prepared as a 1 st shield layer, and the metal tape 1/4 was wound in a lap-wound manner so as to form a 1 st shield layer having an outer diameter of 2.81 mm.

Thereafter, 84 tin-plated annealed copper wires (TA) having a diameter of 0.1mm were prepared as a 2 nd shield layer, and the tin-plated annealed copper wires were transversely wound around the 1 st shield layer at a pitch of 32mm or less to form a 2 nd shield layer having an outer diameter of 3.01 mm.

Finally, polyvinyl chloride (PVC) is extruded in a pipeline mode and covers the No. 2 shielding layer to manufacture the communication cable with the outer diameter of 3.81 mm.

(2) Evaluation of samples

(2.1) calculation of inter-conductor distance dc and conductor-shield interlayer shortest distance ds

The inter-conductor distance dc between the pair lines of the 1 st type core and the 2 nd type core and the shortest distance ds between the conductor of the pair line and the 1 st shielding layer in the samples 11, 21 are calculated, respectively.

In sample 11, the values of dc, ds and dc/ds are as follows.

dc (outer diameter of insulated wire 1.12 mm-outer diameter of conductor 0.48mm) + diameter of intervening cord 0.45mm 1.09mm

ds (outer diameter of insulated wire 1.12 mm-outer diameter of conductor 0.48 mm). times. 1/2 (0.32 mm)

dc/ds value 1.09/0.32 3.41

In sample 21, the values of dc, ds and dc/ds are as follows.

dc (0.88 mm outside diameter of insulated wire-0.48 mm outside diameter of conductor) + 0.35mm diameter of intervening cord-0.75 mm

ds (outer diameter of insulated wire 0.88 mm-conductor outer diameter 0.48mm) x 1/2+ wrapping 1/2, 0.28 mm-0.48 mm

dc/ds value of 0.75/0.48 of 1.56

(2.2) measurement of internal skew and insertion loss

The sample 21 was cut by 5m, and the insertion loss in the intra-pair skew and the high frequency band was measured.

The internal skew was 2.10ps/m and 0.26 ps/m.

Fig. 11A shows the measurement result of the insertion loss. The measurement results show the results of each pair of the 1 st core to the 2 nd core and the 3 rd core to the 4 th core.

(3) Summary of the invention

In sample 21, the internal skew was also 10ps/m or less and the transmission state was stable, and as shown in FIG. 11A, no telescoping was observed until IL passed 6 GHz.

As shown in fig. 11B, when sample 11 is compared with sample 21, sample 21 has less insertion loss with respect to sample 11.

It is found that covering the four-core twisted wire with a wrapping and setting the dc/ds value to 2 or less is particularly useful for suppressing the attenuation of signals in a high frequency band.

Industrial applicability of the invention

The present invention relates to a communication cable and a method for manufacturing the same, and is particularly useful for providing a communication cable that is compatible with high-frequency data transmission and that can simplify the internal structure of the cable.

Description of the reference symbols

1 communication cable

2 communication cable

10 four-core stranded wire

10A to 10D No. 1 to 4 cores

12 insulated wire

14 conductor

16 insulator

20 intervention rope

25 wrapping

30 st shield layer

40 nd 2 shielding layer

50 sheath.

Claims

1. A communication cable obtained by twisting a plurality of insulated wires each having a conductor covered with an insulator,

an intervening cord is interposed between the insulated wires,

the insulated wires are twisted at a pitch of 17.5mm or less.

2. The communication cable of claim 1,

the insulated wires are twisted at a pitch of 14mm or less.

3. The communication cable of claim 1 or 2, comprising:

a wrapping covering a plurality of the insulated wires; and

a shielding layer covering the wrapping,

a plurality of the insulated electric wires are constituted by one or more pairs,

when the distance between the conductors of a pair of lines is dc and the shortest distance between the conductors of the pair of lines and the shield layer is ds, the dc/ds value is 2 or less.

4. The communication cable of any one of claims 1 to 3,

for vehicle use.

5. A method of manufacturing a communication cable, comprising:

a step of forming an insulated wire by covering a conductor with an insulator; and

and a step of twisting the insulated wires at a pitch of 17.5mm or less with the intervening cord disposed at the center.

6. The method of manufacturing a communication cable according to claim 5, comprising:

covering a plurality of the insulated wires with a wrapping; and

covering the lapping with a shielding layer,

forming a plurality of the insulated wires by one or more pairs in a process of twisting the plurality of the insulated wires,

in the steps from the step of forming the insulated wire to the step of covering the insulated wire with the shield layer, a distance between conductors of a pair of paired wires is dc, and a shortest distance between a conductor of the paired wires and the shield layer is ds, and in this case, a value of dc/ds is set to 2 or less.