Communication cable and routing method thereof

Abstract

To provide a communication cable excellent in noise resistance, manufacturability, and terminal workability.SOLUTION: A communication cable comprising: a twisted wire obtained by twisting two insulated electric wires having a cross-sectional area of 0.13 to 0. 35sq; and a sheath covering an outer periphery of the twisted wire, wherein a twist pitch of the twisted wire is 25 to 37. 5mm. Preferably, the characteristic impedance is 100 ± 10 Ω.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a communication cable and a method for routing the same. [Background technology]

[0002] Two-core differential transmission cables used in automotive communication cables, such as those used for Ethernet communication, require strict control of their characteristic impedance. In contrast, conventional communication cables prevent loosening of the twisted structure by keeping the twist pitch within a certain range, minimizing variations in various transmission characteristics and changes over time in the characteristic impedance (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-181821 Summary of the Invention [Problem to be solved by the invention]

[0004] The communication cable described in Patent Document 1 contributes to manufacturability and stable communication performance, but does not take into consideration superior EMC performance. It is also known that unshielded communication cables can generate electromagnetic induction when a transmission line carrying AC signals is present nearby, affecting communication performance. In particular, if the twist pitches of the wires are the same, the amount of induction increases, potentially preventing communication. Furthermore, if the twist pitch is too small, a strong twist tendency remains in each wire during terminal processing, which can lead to problems such as reduced terminal processing efficiency.

[0005] The present invention has been made in view of the problems inherent in the prior art, and an object of the present invention is to provide a communication cable and a routing method thereof that are excellent in noise resistance, manufacturability, and terminal workability. [Means for solving the problem]

[0006] The communication cable according to the first aspect of the present invention comprises a stranded wire formed by twisting together two insulated wires having a conductor cross-sectional area of ​​0.13 to 0.35 sq, and a sheath that covers the outer periphery of the stranded wire, and the twist pitch of the stranded wire is 25 to 37.5 mm.

[0007] A second aspect of the present invention relates to a method for routing a communication cable, which is a method for routing at least two communication cables: a communication cable A comprising a twisted wire formed by twisting together two insulated wires having a conductor cross-sectional area of ​​0.13 to 0.35 sq and a sheath covering the outer periphery of the twisted wire; and a communication cable B comprising a twisted wire formed by twisting together two insulated wires having a conductor cross-sectional area of ​​0.13 to 0.35 sq and a sheath covering the outer periphery of the twisted wire, wherein the difference in twist pitch between the twisted wires of communication cable A and communication cable B is 2 mm or more, and communication cable A and communication cable B are routed in parallel at a distance of less than 30 mm. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a communication cable that is excellent in noise resistance, manufacturability, and terminal processability, and a method for routing the same. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a communication cable according to an embodiment of the present invention. [Figure 2] 2 is a side view showing a part of the stranded wire in the communication cable of the present embodiment. FIG. [Figure 3] 10 is a graph showing the amount of induction with respect to the transmission frequency for each twist pitch; [Figure 4] 10 is a graph showing twisting costs relative to twist pitch. [Figure 5] 10 is a graph showing the possible range of twist pitch settings based on the twist processing cost relative to the twist pitch and the induction amount relative to the twist pitch. [Figure 6]1 is a graph showing longitudinal conversion transfer loss (LCTL) versus transmission frequency. [Figure 7] 10 is a graph showing near-end crosstalk versus transmission frequency as a function of twist pitch. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a communication cable and a method for routing the same according to the present embodiment will be described in detail with reference to the drawings. Note that the dimensional proportions in the drawings are exaggerated for the sake of convenience and may differ from the actual proportions.

[0011] <Communication cable> The communication cable of this embodiment includes a twisted wire formed by twisting together two insulated wires having a conductor cross-sectional area of ​​0.13 to 0.35 sq, and a sheath that covers the outer periphery of the twisted wire, and the twist pitch of the twisted wire is 25 to 37.5 mm. The conductor cross-sectional area of ​​0.13 to 0.35 sq is specified in ISO21111-8.

[0012] In the communication cable of this embodiment, by setting the twist pitch of the twisted wire to 25 to 37.5 mm, the cable has excellent noise resistance, manufacturability, and terminal processability. More specifically, by setting the twist pitch of the twisted wire to 25 to 37.5 mm, an appropriate induction amount can be secured, resulting in excellent noise resistance. Furthermore, the twist pitch is an appropriate length, which improves processing efficiency. The communication cable of this embodiment will be described in detail below.

[0013] FIG. 1 is a cross-sectional view showing an example of a communication cable according to the present embodiment. The communication cable 10 shown in FIG. 1 includes a twisted wire formed by twisting together a pair of insulated wires 12, 12 as a communication line. Each insulated wire 12 includes a conductor 14 and an insulating coating 16 that covers the outer periphery of the conductor 14. The communication cable 10 also includes a sheath 18 made of an insulating material that covers the outer periphery of the entire twisted wire. The sheath 18 continuously surrounds the outer periphery of one twisted wire over the entire circumference centered on the longitudinal axis. In FIG. 1, a gap is provided between the insulated wire 12 and the sheath 18, but the sheath 18 may have a solid structure. In other words, the outer surface of the insulated wire 12 may be directly covered by the sheath 18.

[0014] The insulated wire has a conductor cross-sectional area of ​​0.13 to 0.35 sq. If it is less than 0.13 sq., the wire strength is weakened, and if it exceeds 0.35 sq., it cannot be twisted at the specified pitch.

[0015] The twist pitch will now be described. As shown in Fig. 2, the twist pitch P of the twisted wire is one turn of the insulated wire 12, and means the length of the insulated wire 12 in the longitudinal direction.

[0016] In the communication cable of this embodiment, as described above, the twist pitch of the twisted wires is set to 25 to 37.5 mm, which provides excellent noise resistance, manufacturability, and terminal processability. The reasons for this will be explained below.

[0017] Twisting two insulated wires together to form a twisted pair is an effective way to reduce the induced voltage generated in communication lines by magnetic flux emitted from an insulated wire. This twisted pair structure cancels out the induced voltage, reducing noise. Table 1 below shows the noise reduction rates of twisted wires with different twist pitches (Source: Nikkan Kogyo Shimbun, "Noise Countermeasures Handbook"). More specifically, the table shows the noise reduction rates (ratio and dB) for twisted wire and parallel wire with twist pitches of 4 inches (≒100 mm), 3 inches (≒75 mm), 2 inches (≒50 mm), and 1 inch (≒25 mm). As shown in Table 1, the smaller the twist pitch, the greater the noise reduction effect. However, an excessively small twist pitch can increase costs due to reduced productivity of communication cables and increase the twist ratio of the cores. This can result in other side effects, such as increased conductor resistance. Therefore, when setting the twist pitch, it is important to also consider the balance between cost and effectiveness.

[0018] [Table 1]

[0019] Meanwhile, Figure 3 shows a graph of the simulation results of induction versus transmission frequency for twisted wires with twist pitches of 15 mm, 25 mm, 37.5 mm, and 75 mm. In this simulation, electromagnetic field analysis software was used to input signals to twisted pair wires with different twist pitches, and the dielectric values ​​corresponding to the signals were measured and a graph was created. Next, based on the created graph, a signal was input to each twisted pair wire, and the dielectric values ​​induced from the twisted pair wire at that time were calculated by simulation. The simulation results shown in Figure 3 show that there is no significant change in induction between twist pitches of 15 and 37.5 mm. However, when the twist pitch exceeds 37.5 mm, the induction increases, adversely affecting the transmission path through which nearby AC signals flow.

[0020] Next, we will consider the twisting cost versus twist pitch. Figure 4 is a graph showing the twisting cost versus twist pitch. As shown in Figure 4, the longer the twist pitch, the more efficient the manufacturing process and the fewer components are required, making it possible to reduce cable costs. On the other hand, the shorter the twist pitch, the higher the material weight per unit length, resulting in higher costs.

[0021] By examining the contents of both Figures 3 and 4, it is believed possible to determine the twist pitch range of the twisted wire that can suppress an increase in induction while keeping twisting costs down. Therefore, Figure 5 shows a graph in which the horizontal axis of the graph in Figure 3 represents twist pitch, and the graph in Figure 4 is simultaneously plotted. In Figure 5, A corresponds to the graph in Figure 4, and B corresponds to the graph in Figure 3 with twist pitch on the horizontal axis. From Figure 5, it can be seen that the twist pitch range of the twisted wire that can suppress twisting costs and does not increase induction is 25 to 37.5 mm. This twist pitch range is shown in Figure 5 as the "settable range."

[0022] For the above reasons, the twist pitch of the twisted wires in the communication cable of this embodiment is set to 25 to 37.5 mm. If the twist pitch of the twisted wires is less than 25 mm, the twisted wires will have a strong tendency to twist when untwisted during terminal processing, reducing processing efficiency. If the twist pitch is more than 37.5 mm, the amount of induction will increase, which may adversely affect surrounding communication circuits. Furthermore, after twisting, the wires are wound on a drum to form a sheath by extrusion molding, and the twist will break down during this process. If the twist breaks down, the distance between the two wires will become unstable, resulting in reduced communication performance.

[0023] Furthermore, when considering the case where the communication cable of this embodiment is installed in an automobile, it is preferable that the twist pitch of the twisted wires is 27 mm or more, as will be described below. Generally, when unshielded cables are routed within a range of less than 30 mm of transmission lines through which AC signals flow, they affect each other's communications, resulting in a phenomenon known as crosstalk, which reduces communication quality. The closer the twist pitches of the cables, the more likely the crosstalk is to resonate, and the greater the impact. Figure 6 is a graph showing the earth balance load (LCTL) versus transmission frequency, where A is when the cable is in contact with the object being measured, and B is when the cable is 30 mm or more away from the object being measured. Figure 6 also shows that communication quality is lower in case A, where the cable is in contact with the object being measured.

[0024] When routing communication cables inside an automobile, the cables are usually bundled together, with the distance between them being 30 mm or less. Furthermore, unshielded twisted wires for the in-vehicle network CAN (Controller Area Network) are already widely used in automobiles. Because such cables are designed for higher-speed communications, the effects of the twisted wires can be fatal to communication quality. To eliminate this risk, it is preferable to use a twist pitch different from that of the twisted wires. More specifically, since the official standard for the twist pitch of unshielded twisted wires for CAN is 20 to 30 mm (SAE Standard J2284), it is preferable to set the twist pitch outside of the 25 mm median value of that range. Here, a graph showing near-end crosstalk versus transmission frequency as a function of twist pitch difference in the twisted wire is shown in Figure 7. The graph in Figure 7 shows the cases where the twist pitch difference in the twisted wire is 0 mm, 2 mm, 5 mm, and 10 mm. Figure 7 shows that the near-end crosstalk decreases as the twist pitch difference in the twisted wire increases. For these reasons, it is preferable to separate the twist pitch of the unshielded twisted wires for the CAN by at least 2 mm from the median twist pitch of 25 mm. If the twist pitch difference between the communication lines is less than 2 mm, the mutual resonance will be strong and the crosstalk standard will not be satisfied. Therefore, in this embodiment, the twist pitch is preferably 27 mm or more.

[0025] In addition, in the communication cable of this embodiment, the twist pitch of the twisted wires is preferably 34 mm or less. Figure 7 shows that the amount of crosstalk tends to decrease as the difference in twist pitch between the twisted wires increases. However, if the twist pitch exceeds 34 mm, the unevenness when viewed in the longitudinal direction decreases, and the adhesion to the sheath is rapidly reduced, which may cause the twisted wire to peel off from the sheath when stripped. Therefore, the twist pitch of the twisted wire is preferably 34 mm or less.

[0026] The communication cable of this embodiment preferably has a characteristic impedance in the range of 100±10 Ω. A characteristic impedance of 100±10 Ω is a value typically required for insulated wires for Ethernet communication. By having such a characteristic impedance, the communication cable can be suitably used for high-speed communication in automobiles, etc.

[0027] Next, each element of the communication cable of this embodiment will be described in detail below.

[0028] An insulated wire includes a conductor and an insulating covering that covers the conductor and is made of an insulator. The conductor may be made of only one strand, or may be a bunched stranded wire made by bundling multiple strands. The conductor may also be made of only one twisted wire, or may be a concentric stranded wire made by bundling multiple bunched twisted wires. Furthermore, the conductor may be a circular compacted conductor or a circular conductor. The material that makes up the conductor is not particularly limited, but is preferably at least one conductive metal material selected from the group consisting of copper, copper alloys, aluminum, aluminum alloys, etc.

[0029] 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 resistance of the conductor can be reduced. Furthermore, 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, it is possible to easily route the insulated wire even in a narrow and short path.

[0030] The insulating coating may be made of any material, provided that it is capable of providing electrical insulation against the conductor. The base resin constituting the insulating coating may be any electrically insulating resin, such as an olefin resin, such as cross-linked polyethylene or polypropylene, or a vinyl chloride resin. Specifically, examples of the base resin constituting the insulating coating 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, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene, perfluoroalkoxyalkane, natural rubber, chloroprene rubber, butyl rubber, ethylene-propylene rubber, chlorosulfonated polyethylene rubber, and silicone rubber. These materials may be used alone or in combination.

[0031] Examples of polypropylene resins used as the base resin constituting the insulating coating include homopolypropylene (homoPP), random polypropylene (randomPP), block polypropylene (blockPP), and copolymers with other olefins copolymerizable with propylene. Examples of 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.

[0032] The thickness of the insulating coating is not particularly limited, but is preferably 0.15 mm or more, and more preferably 0.18 mm or more. By making the insulating coating thicker as described above, the conductor can be effectively protected. Furthermore, the thickness of the insulating coating is not particularly limited, but is preferably 0.32 mm or less. By making the insulating coating thicker as described above, the insulated wire can be easily routed even in narrow passages.

[0033] As described above, a stranded wire is obtained by twisting two insulated wires together within a predetermined twist pitch range.

[0034] The sheath is an insulating member that covers the periphery of the stranded wire, and is made of, for example, polyolefin.

[0035] The communication cable of this embodiment can be produced by a known method, for example, a general extrusion molding method. Specifically, the sheath can be formed by twisting two insulated wires together and then extruding a sheath material onto the outer surface of the insulated wires to cover them.

[0036] <Communication cable routing method> The communication cable routing method of this embodiment is a method for routing at least two communication cables, a communication cable A and a communication cable B, as follows. Communication cable A is a cable that includes a twisted wire made by twisting together two insulated wires with a conductor cross-sectional area of ​​0.13 to 0.35 sq. and a sheath that covers the outer periphery of the twisted wire. Communication cable B is provided with a twisted wire made by twisting together two insulated wires having a conductor cross-sectional area of ​​0.13 to 0.35 sq, and a sheath that covers the outer periphery of the twisted wire. The difference in twist pitch between the twisted wires of communication cable A and communication cable B is set to 2 mm or more. Additionally, communication cable A and communication cable B are routed in parallel with each other at a distance of less than 30 mm.

[0037] As described above, when unshielded cables are routed within a range of less than 30 mm of transmission lines through which AC signals flow, the cables affect each other's communications, resulting in a degradation in communication quality, a phenomenon known as crosstalk. From this perspective, when two communication cables are routed, it is preferable to separate them by 30 mm or more. However, as described above, when routing communication cables inside an automobile, the cables are often bundled together, resulting in a distance of 30 mm or less between them. Therefore, in this embodiment, assuming a case where space constraints, such as inside an automobile, make it difficult to route communication cables at a distance of 30 mm or more, the occurrence of crosstalk is suppressed by separating adjacent communication cables by 2 mm or more.

[0038] In the communication cable routing method of this embodiment, both the communication cable A and the communication cable B are the communication cables of this embodiment described above, and therefore, a description thereof will be omitted here.

[0039] In the communication cable routing method of this embodiment, when communication cable A and communication cable B are routed in parallel at a distance of less than 30 mm, the difference in twist pitch between the twisted wires of communication cable A and communication cable B is set to 2 mm or more. If the twist pitch difference is less than 2 mm, the mutual resonance will be strong and the crosstalk standard will not be satisfied. The twist pitch difference is preferably 2 mm or more, and more preferably 5 mm or more. The upper limit of the twist pitch difference is 12.5 mm.

[0040] As described above, the communication cable routing method of this embodiment can suppress the occurrence of crosstalk when routing at least two communication cables.

[0041] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment. [Explanation of symbols]

[0042] 10 Communication Cable 12 Insulated wire 14 Conductors 16 Insulation coating 18 Sheath

Claims

1. The cable includes a stranded wire formed by twisting together two insulated wires having a conductor cross-sectional area of ​​0.13 to 0.35 sq., and a sheath that covers the outer periphery of the stranded wire, A communication cable, wherein the twist pitch of the twisted wire is 25 to 37.5 mm.

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

3. A method for installing at least two communication cables, namely, a communication cable A including a stranded wire formed by twisting together two insulated wires having a conductor cross-sectional area of ​​0.13 to 0.35 sq and a sheath covering the outer periphery of the stranded wire, and a communication cable B including a stranded wire formed by twisting together two insulated wires having a conductor cross-sectional area of ​​0.13 to 0.35 sq and a sheath covering the outer periphery of the stranded wire, 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 2 mm or more, A communication cable routing method in which the communication cable A and the communication cable B are routed in parallel at a distance of less than 30 mm.

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