Communication cable and laying method thereof

Abstract

A communication cable includes: a twisted wire obtained by twisting two insulated wires having a conductor cross-sectional area of 0.13 sq to 0.35 sq; and a sheath configured to cover an outer periphery of the stranded wire, in which a twist pitch of the stranded wire is in a range of 25 mm to 37.5 mm. The characteristic impedance of the communication cable is preferably 100 + / -10 Omega.

Description

TECHNICAL FIELD

[0001] The present application relates to a communication cable and a laying method of a communication cable. BACKGROUND

[0002] For a two-core differential transmission cable for an automotive communication cable, such as a cable for Ethernet communication, it is necessary to strictly control the characteristic impedance. Meanwhile, conventional communication cables prevent loosening of a twisted structure by keeping a twist pitch below a certain range, and minimize changes and secular changes in transmission characteristics of the characteristic impedance (see Patent Literature JP 2020-181821 A). SUMMARY

[0003] While the communication cable described in JP 2020-181821 A contributes to manufacturing properties and stability of communication performance, no consideration is given to superiority in EMC performance. Furthermore, it is known that electromagnetic induction occurs in a non-shielded type communication cable when there is a transmission path in which an AC signal is flowing nearby, which affects communication performance. In particular, when the twist pitches are the same as each other, the amount of induction increases, and it can be impossible to establish communication. Furthermore, when the twist pitch is too small, there is a problem that each wire has a strong twist remaining during end processing and end processing efficiency is reduced.

[0004] The present application has been made in view of these problems in the conventional technology. An object of the present application is to provide a communication cable excellent in noise resistance, manufacturing properties, and end processing properties, and a laying method of a communication cable.

[0005] The communication cable according to a first embodiment of the present application includes a twisted wire obtained by twisting two insulated wires each having a conductor cross-sectional area of 0.13 sq to 0.35 sq, and a sheath configured to cover an outer periphery of the twisted wire, wherein a twist pitch of the twisted wire is in a range of 25 mm to 37.5 mm.

[0006] The laying method of a communication cable according to a second embodiment of the present application is a laying method of at least two communication cables: a communication cable A including a twisted wire obtained by twisting two insulated wires each having a conductor cross-sectional area of 0.13 sq to 0.35 sq, and a sheath covering an outer periphery of the twisted wire, and a communication cable B including a twisted wire obtained by twisting two insulated wires each having a conductor cross-sectional area of 0.13 sq to 0.35 sq, and a sheath covering an outer periphery of the twisted wire, the method including laying the communication cable A and the communication cable B in parallel at a distance of less than 30 mm, wherein a difference between a twist pitch of the twisted wire of the communication cable A and a twist pitch of the twisted wire of the communication cable B is set to 2 mm or more.

[0007] According to the present application, it is possible to provide a communication cable excellent in noise resistance, workability, and end processing, and a laying method of the communication cable. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a cross-sectional view of a communication cable according to the present embodiment.

[0009] Figure 2 is a side view showing a part of a stranded wire in a communication cable according to the present embodiment.

[0010] Figure 3 is a graph showing an inductance with respect to a transmission frequency in accordance with a twist pitch.

[0011] Figure 4 is a graph showing a twist processing cost with respect to a twist pitch.

[0012] Figure 5 is a graph showing a settable range of a twist pitch based on a twist processing cost with respect to a twist pitch and an inductance with respect to a twist pitch.

[0013] Figure 6 is a graph showing a degree of ground balance (LCTL; longitudinal conversion transfer loss) with respect to a transmission frequency.

[0014] Figure 7 is a graph showing a near-end crosstalk with respect to a transmission frequency in accordance with a twist pitch difference. DETAILED DESCRIPTION

[0015] Hereinafter, a communication cable and a laying method of the communication cable according to the present embodiment will be described in detail with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for the purpose of description, and are sometimes different from actual ratios.

[0016] [COMMUNICATION CABLE]

[0017] The communication cable of the present embodiment has a stranded wire formed by twisting two insulated electric wires each having a conductor cross-sectional area of 0.13 sq to 0.35 sq, and a sheath covering an outer periphery of the stranded wire, and a twist pitch of the stranded wire is in a range of 25 mm to 37.5 mm. Note that the conductor cross-sectional area of 0.13 sq to 0.35 sq is specified in ISO 21111-8.

[0018] By setting the twist pitch of the twisted wire to 25 mm to 37.5 mm, the communication cable of the present embodiment is excellent in noise resistance, and is excellent in manufacturability and end processing. More specifically, by setting the twist pitch of the twisted wire to 25 mm to 37.5 mm, an appropriate inductance can be ensured, and thus the noise resistance is excellent. Furthermore, since the twist pitch has an appropriate length, the processing efficiency can be improved. The communication cable of the present embodiment will be described in detail below.

[0019] Figure 1 is a cross-sectional view showing an example of the communication cable of the present embodiment. Figure 1 The communication cable 10 shown includes a twisted wire formed by twisting a pair of insulated electric wires 12, 12 as a communication line. Each insulated electric wire 12 has a conductor 14 and an insulating coating 16 that covers the outer periphery of the conductor 14. The communication cable 10 includes a sheath 18 made of an insulating material and covering the outer periphery of the entire twisted wire. The sheath 18 continuously surrounds the outer periphery of the twisted wire on the entire circumference around the longitudinal axis thereof. In Figure 1 In the present embodiment, a gap is provided between the insulated electric wire 12 and the sheath 18, but the sheath 18 can also be configured to have a structure that fills the gap. That is, the outer surface of the insulated electric wire 12 can be configured to be directly covered by the sheath 18.

[0020] The insulated electric wire has a conductor cross-sectional area of 0.13 sq to 0.35 sq. When the area is less than 0.13 sq, the strength of the electric wire is weakened, and when the area is greater than 0.35 sq, the electric wire cannot be twisted at a specified pitch.

[0021] Here, the twist pitch will be described. As Figure 2 indicated, the twist pitch P of the twisted wire is one turn of the twist of the insulated electric wire 12, and is defined as the length of one turn of the twist of the insulated electric wire 12 in the length direction.

[0022] In the communication cable of the present embodiment, as described above, by setting the twist pitch of the twisted wire to a range of 25 mm to 37.5 mm, the communication cable is excellent in noise resistance, manufacturability, and end processing. The reason for this will be explained below.

[0023] To reduce the induced voltage generated on the communication line side by the magnetic flux emitted from the insulated electric wire, it is effective to twist two insulated electric wires in pairs to form a twisted pair structure. The twisted pair structure eliminates the generated induced voltage and reduces noise. Table 1 below lists the noise reduction rate of twisted wires having different twist pitches (source: THE NIKKAN KOGYO SHIMBUN, LTD., "Noise Countermeasures Handbook"). More specifically, the noise reduction rate (ratio and dB) is shown for twisted wires having twist pitches of 4 inches (≈100 mm), 3 inches (≈75 mm), 2 inches (≈50 mm), and 1 inch (≈25 mm), respectively, and parallel wires. As listed in Table 1, the noise reduction effect increases as the twist pitch decreases. However, when the twist pitch is too small, the production rate of the communication cable decreases, resulting in an increase in cost, and the twist ratio of the core increases. As a result, there are other side effects, such as an increase in conductor resistance. Therefore, it is important to consider the cost-benefit balance when setting the twist pitch.

[0024] [Table 1]

[0025]

[0026] Meanwhile, Figure 3 A graph showing the simulation results of the induced amount of twisted wires having twist pitches of 15 mm, 25 mm, 37.5 mm, and 75 mm with respect to the transmission frequency is shown. In this simulation, using electromagnetic field analysis software, a signal was input to twisted pairs having different twist pitches, the dielectric amount corresponding to the signal was measured, and a graph was created. Then, based on the created graph, a signal was input to each twisted pair, and the dielectric amount generated by the induction of the twisted pair was obtained by simulation. Figure 3 The simulation results shown indicate that, in the case of a twist pitch of 15 mm to 37.5 mm, the induced amount does not change significantly. When the twist pitch exceeds 37.5 mm, the induced amount increases, which adversely affects the peripheral transmission line through which the AC signal flows.

[0027] Furthermore, the twist processing cost with respect to the twist pitch was studied. Figure 4 is a graph showing the twist processing cost with respect to the twist pitch. As Figure 4 shown, the longer the twist pitch, the higher the manufacturing efficiency and the smaller the number of parts required, and thus the cable cost can be reduced. On the other hand, the shorter the twist pitch, the higher the material weight per unit length, and thus the cost increases.

[0028] Considering the above, by studying Figure 3 and Figure 4 the range of the twist pitch of the twisted wire in which the twist processing cost can be reduced and the increase in the induced amount can be controlled can be obtained. Thus, Figure 5A plot shown in FIG. 6 is a plot of the twist pitch, and at the same time, a plot of the inductance is plotted. Figure 3 A plot shown in FIG. 6 is a plot of the twist pitch, and at the same time, a plot of the inductance is plotted. Figure 4 A plot shown in FIG. 6 is a plot of the twist pitch, and at the same time, a plot of the inductance is plotted. Figure 5 A plot shown in FIG. 6 is a plot of the twist pitch, and at the same time, a plot of the inductance is plotted. Figure 4 A plot shown in FIG. 6 is a plot of the twist pitch, and at the same time, a plot of the inductance is plotted. Figure 3 A plot shown in FIG. 6 is a plot of the twist pitch, and at the same time, a plot of the inductance is plotted. Figure 5 As is apparent from the above, the twist pitch of the twisted wire ranges from 25 mm to 37.5 mm, in which range the inductance does not increase, and the twist processing cost decreases. The twist pitch ranges from 25 mm to 37.5 mm are shown as "settable ranges" in Figure 5

[0029] For the above reasons, in the communication cable of the present embodiment, the twist pitch of the twisted wire is set to a range from 25 mm to 37.5 mm. When the twist pitch of the twisted wire is less than 25 mm, there is strong twisting when the twisted wire is unwound during the end processing, and the processing efficiency decreases. When the twist pitch is greater than 37.5 mm, the inductance increases, and there is a possibility of adversely affecting the peripheral communication circuit. In addition, after the pair twist processing, the drum winding is performed by extrusion molding to form a sheath, and at this time, the twist is resolved. When the twist is resolved, the distance between the two electric wires becomes unstable, and the communication performance decreases.

[0030] Furthermore, as described below, in consideration of the case where the communication cable of the present embodiment is installed in a car, it is preferable that the twist pitch of the twisted wire be 27 mm or more. Generally, when a transmission path through which an AC signal flows is laid out in a range of less than 30 mm in the periphery of a non-shielded cable, a phenomenon called crosstalk is observed, which affects communication with each other and decreases the communication quality. For crosstalk, the closer the twist pitches to each other, the more likely resonance occurs, thereby tending to increase the influence. Figure 6 A plot shown in FIG. 6 is a plot of the twist pitch, and at the same time, a plot of the inductance is plotted. Figure 6 As is apparent from the above, when in contact with the measurement target, the communication quality of A is low.

[0031] ​When laid in a car, communication cables are bundled, and in most cases the distance between them is 30 mm or less. In addition, many unshielded twisted wires for CAN (Controller Area Network) as an in-vehicle network are already in use in cars. Since such cables are designed for higher speed communication, the influence of the twisted wires is fatal to communication quality. In order to eliminate this danger, it is preferable to use a twist pitch different from that of the above-mentioned twisted wires. More specifically, since the twist pitch of the unshielded twisted wire for CAN is 20 to 30 mm according to the official standard (SAE standard J2284), it is preferable to set a twist pitch deviating from the median value of this range, i.e., 25 mm. Here, a graph showing near-end crosstalk with respect to transmission frequency is shown in FIG. 8. Figure 7 A graph showing near-end crosstalk with respect to transmission frequency by the difference in twist pitch of the twisted wires is shown in FIG. 8. Figure 7 The graph in FIG. 8 shows the case where the difference in twist pitch of the twisted wires is 0 mm, 2 mm, 5 mm, and 10 mm, respectively. As is apparent from FIG. 8, Figure 7 It is apparent that the longer the difference in twist pitch between the twisted wires, the lower the near-end crosstalk. In summary, it is preferable to deviate by 2 mm or more from the median twist pitch of 25 mm of the unshielded twisted wire for CAN. When the difference in twist pitch between the communication lines is less than 2 mm, the mutual resonance is strong, and the crosstalk reference is not satisfied. Therefore, in the present embodiment, it is preferable that the twist pitch be 27 mm or more.

[0032] In the communication cable of the present embodiment, it is preferable that the twist pitch of the twisted wires be 34 mm or less. As is apparent from FIG. 9, Figure 7 It is confirmed that the longer the difference in twist pitch between the twisted wires, the smaller the amount of crosstalk. However, when the twist pitch is greater than 34 mm, the concave-convex when viewed in the length direction decreases, and the adhesion to the sheath is quickly impaired, and thus peeling from the sheath can occur during stripping of the twisted wires. Therefore, it is preferable that the twist pitch of the twisted wires be 34 mm or less.

[0033] The communication cable of the present embodiment preferably has a characteristic impedance in the range of 100 ± 10 Ω. An insulated wire for Ethernet communication generally requires a characteristic impedance of 100 ± 10 Ω. With this characteristic impedance, the communication cable can be appropriately used for high-speed communication in a car or the like.

[0034] Next, the components of the communication cable of the present embodiment will be described in detail respectively.

[0035] The insulated electric wire includes a conductor and an insulating covering that covers the conductor and is made of an insulator. The conductor can be composed of only one strand, or can be a combined stranded wire composed of a plurality of strands. In addition, the conductor can be composed of only one stranded wire, or can be a combined stranded wire composed of a plurality of stranded wires. Furthermore, the conductor can be a round compact conductor or a round conductor. The material that forms the conductor is not particularly limited, but is preferably at least one electrically conductive metal material selected from the group consisting of copper, copper alloy, aluminum, and aluminum alloy.

[0036] The outer diameter of the conductor is not particularly limited, but is preferably 0.435 mm or more, and more preferably 0.440 mm or more. By setting the diameter of the conductor as described above, the electrical resistance of the conductor can be reduced. The diameter of the conductor is not particularly limited, but is preferably 0.465 mm or less, and more preferably 0.460 mm or less. By setting the outer diameter of the conductor as described above, the insulated electric wire can be easily laid even in a narrow path and a short path.

[0037] The material of the insulating covering is not particularly limited, as long as the electrical insulation of the conductor can be ensured. As a base resin that forms the insulating covering, an olefin resin such as cross-linked polyethylene and polypropylene, or an electrically insulating resin such as a vinyl chloride resin can be optionally used. Specifically, examples of the base resin that forms the insulating covering used include polyvinyl chloride, heat-resistant polyvinyl chloride, cross-linked polyvinyl chloride, polyethylene, cross-linked polyethylene, foamed polyethylene, cross-linked foamed polyethylene, chlorinated polyethylene, polypropylene, polyamide (nylon), polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, ethylene-tetrafluoroethylene-hexafluoropropylene copolymer, ethylene tetrafluoroethylene, perfluoroalkoxy alkane, natural rubber, chlorobutadiene rubber, butyl rubber, ethylene propylene rubber, chlorosulfonated polyethylene rubber, and silicone rubber. One of these materials can be used alone, or two or more can be used in combination.

[0038] Examples of the polypropylene resin that is the base resin that forms the insulating covering include homopolypropylene (homo-PP), random polypropylene (random-PP), block polypropylene (block-PP), and copolymers with components copolymerizable with propylene such as other olefins. Examples of the other olefins copolymerizable with propylene include α-olefins such as ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, and 3-methyl-1-hexene.

[0039] The thickness of the insulating covering is not particularly limited, but is preferably 0.15 mm or more, and more preferably 0.18 mm or more. By setting the thickness of the insulating covering as described above, the conductor can be effectively protected. The thickness of the insulating covering is not particularly limited, but is preferably 0.32 mm or less. By making the thickness of the insulating covering as described above, the insulated electric wire can be easily laid even in a narrow path.

[0040] As described above, the twisted wire is obtained by twisting two insulated electric wires to have a twist pitch in a predetermined range.

[0041] The sheath is an insulating member that covers the periphery of the twisted wire, and is composed of, for example, polyolefin or the like.

[0042] The communication cable of the present embodiment can be produced using a known method, for example, a general extrusion method. Specifically, after twisting two insulated electric wires, the sheath can be formed by extruding a sheath material to cover the outer surface of the insulated electric wires.

[0043] <Method of laying communication cables>

[0044] The method of laying the communication cables of the present embodiment is a method of laying at least two communication cables A and B.

[0045] The communication cable A includes a twisted wire obtained by twisting two insulated electric wires having a conductor cross-sectional area of 0.13 sq to 0.35 sq, and a sheath that covers the periphery of the twisted wire.

[0046] The communication cable B includes a twisted wire obtained by twisting two insulated electric wires having a conductor cross-sectional area of 0.13 sq to 0.35 sq, and a sheath that covers the periphery of the twisted wire.

[0047] The difference between the twist pitch of the twisted wire of the communication cable A and the twist pitch of the twisted wire of the communication cable B is set to 2 mm or more. Further, the communication cable A and the communication cable B are laid in parallel at a distance of less than 30 mm.

[0048] As described above, when a transmission path through which an AC signal flows is laid in the periphery of a non-shielded cable and laid in a range of less than 30 mm, a phenomenon called crosstalk is observed, which affects the communication of each other and reduces the communication quality. From this point of view, when laying two communication cables, it is preferable to keep a distance of 30 mm or more from each other. However, as described above, when the communication cables are laid in a car, the communication cables are bundled, and the distance between them is usually 30 mm or less. Thus, in the present embodiment, assuming a case where it is difficult to lay the communication cables at a distance of 30 mm or more, such as in a car, the occurrence of crosstalk is controlled by separating the adjacent communication cables by 2 mm or more.

[0049] In the method of laying the communication cables of the present embodiment, both the communication cables A and B are the above-described communication cables of the present embodiment. Thus, the description will be omitted here.

[0050] In the communication cable laying method of the present embodiment, when the communication cable A and the communication cable B are laid in parallel at a distance of less than 30 mm, the difference between the lay length of the twisted wire of the communication cable A and the lay length of the twisted wire of the communication cable B is set to 2 mm or more. When the difference between the lay lengths is less than 2 mm, the mutual resonance is strong, and the crosstalk standard is not satisfied. The difference between the lay lengths is preferably 2 mm or more, and more preferably 5 mm or more. Note that the upper limit of the difference between the lay lengths is 12.5 mm.

[0051] As described above, the communication cable laying method of the present embodiment can control the occurrence of crosstalk when laying at least two communication cables.

[0052] Although the present application has been described above with reference to the embodiments, the present application is not limited to this, and the configuration of the components can be replaced with any configuration having the same function as long as it is within the scope of the claims.

Claims

1. A communication cable, comprising: Stranded wire, which is obtained by twisting two insulated wires with a conductor cross-sectional area of ​​0.13sq to 0.35sq; as well as A sheath, configured to cover the outer periphery of the stranded wires, wherein, The twist pitch of the stranded wire is in the range of 25 mm to 37.5 mm.

2. The communication cable according to claim 1, wherein, The characteristic impedance of the communication cable is 100±10Ω.

3. A method for laying at least two communication cables, wherein the at least two communication cables comprise: Communication cable A, comprising stranded wires obtained by twisting two insulated wires with a cross-sectional area of ​​0.13 sq to 0.35 sq and a sheath covering the outer periphery of the stranded wires; And a communication cable B, which comprises stranded wires obtained by twisting two insulated wires with a conductor cross-sectional area of ​​0.13 sq to 0.35 sq and a sheath covering the outer periphery of the stranded wires, the method comprising: The communication cable A and the communication cable B are laid parallel to each other at a distance of less than 30mm, wherein, The difference between the twist pitch of the stranded wires of communication cable A and the twist pitch of the stranded wires of communication cable B is set to be 2 mm or more.

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