Communication cable and method for manufacturing the same

Abstract

The present invention provides a communication cable compatible with high-frequency data transmission that can suppress the suck-out phenomenon in the high-frequency band while maintaining a characteristic impedance Z0 of approximately 100Ω. [Solution] A communication cable 1 is disclosed, in which a plurality of insulated wires 12, each having a conductor 14 covered with an insulator 16, are twisted together, and a press winding 20 is superimposed on the twisted body and covered with shielding layers 40 and 50. The communication cable 1 has a conductor 14 that is made of a single wire or compressed stranded wire with a circular cross-section, a diameter of 0.45 mm, a thickness of 0.290 to 0.315 mm, a plurality of insulated wires 12 that are 7.0 mm or more in diameter and twisted together at a pitch less than or equal to the value derived by (speed of light × NVP / frequency) × (1 / dielectric constant of insulator 16), a thickness of 0.050 to 0.100 mm and a superimposed thickness of 0.100 to 0.200 mm.

Description

[Technical Field]

[0001] The present invention relates to a communication cable compatible with high-frequency data transmission. [Background Art]

[0002] In recent years, the performance of information and communication devices and the multi-functionalization of in-vehicle multimedia have been advancing in automobiles. Going forward, with keywords such as Advanced Driver-Assistance Systems (ADAS) and autonomous driving, further performance improvement and increase in the number of mounted devices are expected to progress. These advancements have led to an increase in the capacity of information communication, and high-frequency data transmission is required. However, there are several issues in high-frequency data transmission, for example, suppressing intra-pair skew (difference in intra-pair propagation delay time), and suppressing the suck-out phenomenon (abrupt drop in the frequency characteristic of signal attenuation) in the high-frequency band.

[0003] Patent Document 1 discloses a multi-core cable that attempts to solve these problems of high-frequency data transmission. In the technology of Patent Document 1, eight pairs of coaxial electric wires (11 to 18) are accommodated in a multi-core cable (1). Each coaxial electric wire 10 has a center conductor (21) covered with an insulator (22), and the outer periphery thereof is covered with an outer conductor (23) and a jacket (24). In the outer conductor, fine metal wires (M) are horizontally wound (spirally wound) around the insulator as an inner layer (23A), and a metal resin tape (T) is horizontally wound around the inner layer as an outer layer (23B). In this technology, in particular, by setting the winding directions of the fine metal wires and the metal resin tape to be opposite to each other and setting the difference in winding angles (angle θ3) within a certain range, the suck-out phenomenon is suppressed (see paragraphs 0017 to 0027, Figures 1 to 2, Examples, Figure 4, etc.). [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6269718 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0005] On the other hand, for communication cables that support high-frequency data transmission, the characteristic impedance Z0 is standardized to be around 100Ω, and there is a requirement to suppress the suck-out phenomenon in the high-frequency band while maintaining a constant characteristic impedance Z0. Therefore, the main objective of the present invention is to provide a communication cable that is compatible with high-frequency data transmission and can suppress the suck-out phenomenon in the high-frequency band while maintaining a characteristic impedance Z0 of approximately 100 Ω. [Means for solving the problem]

[0006] The inventors of the present invention conducted extensive technical studies to solve the above problems and found that by controlling the twist pitch of the insulated wire to be constant, and by simultaneously controlling the distance between conductors and the distance between conductors and the shielding layer to be constant, it is possible to support high-frequency data transmission, thus completing the present invention. In other words, according to the present invention, a communication cable is provided in which a plurality of insulated wires, each having a conductor covered with an insulator, are twisted together, and the twisted body is covered with a shielding layer by repeatedly winding a pressure winding, The conductor is composed of a single wire or compressed stranded wire with a circular cross-section, The diameter of the aforementioned conductor is 0.45 mm. The thickness of the insulator is 0.290 to 0.315 mm. Multiple insulated wires are twisted together with a length of 7.0 mm or more and a pitch less than or equal to the value derived by (speed of light × NVP / frequency) × (1 / dielectric constant of the insulator), A communication cable is provided, characterized in that the thickness of the press winding is 0.050 to 0.100 mm and the thickness of the overlapping winding of the press winding is 0.100 to 0.200 mm. [Effects of the Invention]

[0007] According to the present invention, by controlling the twisting pitch of insulated wires to be constant, the in-pair skew is 10 ps / m or less, the transmission state is stable, and the insertion loss (IL) does not drop (decrease) to high frequencies such as 10 GHz, thereby suppressing signal attenuation. Furthermore, by controlling the distance between conductors and the distance between conductors and the shielding layer to be constant, the characteristic impedance Z0 can be maintained at approximately 100 Ω while suppressing the suck-out phenomenon in the high-frequency band. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view showing the general configuration of a communication cable. [Modes for carrying out the invention]

[0009] A preferred embodiment of the present invention, specifically a communication cable, will be described below. In this specification, the "~" symbol indicating a numerical range means that the lower and upper limits are included within that numerical range.

[0010] Figure 1 is a cross-sectional view showing the schematic configuration of communication cable 1. As shown in Figure 1, the communication cable 1 has a twisted body 10, a winding 20, a first shielding layer 40, a second shielding layer 50, and an outer sheath 60, with the outer circumference of the twisted body 10 being wound and covered in this order by the winding 20, the first shielding layer 40, the second shielding layer 50, and the outer sheath 60.

[0011] The twisted wire pair 10 is composed of two 2-core (two wires) insulated wires 12, with a first-class core 10A and a second-class core 10B used as a pair. A second twisted wire pair may be added with a third-class core and a fourth-class core, which may be used as a pair (it may consist of four cores), or additional pairs of cores may be added and used. When adding pairs of cores, the insulated wires 12 are quad-twisted.

[0012] The insulated wire 12 is composed of a conductor 14 and an insulator 16, and has a structure in which the outer circumference of the conductor 14 is covered with the insulator 16. The conductor 14 has a circular cross-section and is a compressed stranded wire formed by twisting and compressing multiple strands together. The conductor 14 may also be a single wire as long as it has a circular cross-section. The conductor 14 (including the strands) is preferably a soft copper wire, and its outer circumference may be coated with a plating layer (not shown) of tin, nickel, or silver. The outer diameter of the conductor 14 is preferably 0.4 to 0.6 mm, and more preferably 0.45 mm. The insulator 16 is formed by extruding an insulating resin from the die of an extruder. The insulating resin is preferably composed of cross-linked polyethylene (XLPE) or polypropylene (PP). The thickness of the insulator 16 is preferably 0.2 to 0.4 mm.

[0013] The press-wrap 20 is constructed by overlapping and winding tape-shaped polyethylene terephthalate (PET) or polypropylene (PP). The press-wrap 20 may also be made of tape-shaped nonwoven fabric. "Overlapping winding" includes both horizontal winding and vertical winding. "Horizontal winding" means winding a long piece of tape spirally along the length of the object to be wound, overlapping the side edges of the tape with the previously wound tape. "Vertical winding" means winding a long piece of tape in a cylindrical shape, arranging it along the length of the object to be wound and wrapping both side edges inward.

[0014] The first shielding layer 40 is constructed by winding multiple layers of metal tape. The metal tape is constructed by laminating a metal foil and a resin tape, preferably by laminating aluminum foil and polyethylene terephthalate tape (Al / PET tape). In the first shielding layer 40, the metal foil is wound in an overlapping manner so that it is exposed on the outer circumference. On the other hand, the second shielding layer 50 is configured by braiding a plurality of metal wires. The second shielding layer 50 may alternatively be configured by laterally winding a plurality of metal wires at a pitch equal to or less than a predetermined pitch. Each of said metal wires is preferably a so-called tinned annealed copper wire (TA; Tinned Annealed copper), which is obtained by coating an annealed copper wire with a tin plating layer.

[0015] The jacket 60 is a so-called sheath, and is formed by extruding a jacket resin from a die of an extruder. Said jacket resin is preferably composed of polyvinyl chloride (PVC; PolyVinyl Chloride), polyolefin (PO; PolyOlefin) or thermoplastic elastomer (TPE; Thermoplastic Elastomers).

[0016] In the present embodiment, the twisted pair body 10 is composed of two-core (two) insulated wires 12 as described above, and has a configuration in which the two insulated wires 12 are twisted together at a constant pitch.

[0017] The upper limit and lower limit of the pair twisting pitch of the insulated wires 12 are set from the viewpoints of intra-pair skew and insertion loss (IL).

[0018] The lower limit of the pair twisting pitch is assumed from the viewpoint of whether stable production, which can suppress intra-pair skew, is possible. Practically, the lower limit is 7.0 mm, and preferably 7.9 mm. As the pair twisting pitch of the insulated wires 12 becomes shorter, the twisting of the pair becomes excessively dense, and the twisting balance between the insulated wires 12 becomes unstable. As a result, a difference occurs in the physical lengths of the insulated wires 12 (variation in length), making it difficult to suppress intra-pair skew.

[0019] The upper limit of the twisted-pair pitch is derived from the viewpoint of suppressing the suck-out phenomenon at high frequencies (for example, up to over 10 GHz). Through repeated prototyping of communication cable 1 and measurement of insertion loss, the inventors found that the upper limit of the twisted-pair pitch correlates with the material (dielectric constant) of the insulator 16 and can be derived from the following relational expression due to the dielectric constant of the insulator 16. In detail, while wavelength is generally expressed as wave speed / frequency, the inventors found that the upper limit of the twisted-pair pitch approximates the value obtained by dividing the wavelength by the dielectric constant of the insulator 16 (see Example). According to this, if the speed of light is 100, the speed of the signal propagating within the cable pair is approximately 70% as a matter of common technical knowledge (NVP: Nominal Velocity of Propagation). If the frequency is set to 10 GHz, the upper limit of the twisted-pair pitch can theoretically be derived as shown in the following equation. Upper limit of the twist pitch [mm] = (wavelength) × (dielectric constant of insulator 16) = (Speed ​​of light × NVP / frequency) × (Dielectric constant of insulator 16) = 300,000,000 [m / s] × 0.7 / 10 × 10 9 [Hz] × (dielectric constant of insulator 16) × 1,000 [mm]

[0020] When the wavelength of the signal transmitted within the cable pair and the twisted pair pitch of the insulated wire 12 resonate in sync, a suck-out phenomenon occurs. As shown in Table 1, (i) when the insulator 16 is made of cross-linked polyethylene, if the upper limit of the twisted pair pitch of the insulated wire 12 exceeds approximately 9.55 mm, a resonance point is formed at a low frequency of 10 GHz or less, and (ii) when the insulator 16 is made of polypropylene, if the upper limit of the twisted pair pitch of the insulated wire 12 exceeds approximately 10.00 mm, a resonance point is formed at a low frequency of 10 GHz or less, and in both cases, a suck-out phenomenon is likely to occur.

[0021] [Table 1]

[0022] In this embodiment, the distance between the conductors 14 and the distance between the conductors 14 and the first shielding layer 40 are further controlled to be constant. In other words, assuming the diameter of the conductor 14 is 0.45 mm (26 AWG), (i) the thickness of the insulator 16 is 0.290 to 0.315 mm, and the distance between the conductors 14 is controlled to be constant, and (ii) the thickness of the press winding 20 is 0.050 to 0.100 mm, and the overlapping thickness of the press winding 20 is 0.100 to 0.200 mm, and the distance between the conductor 14 and the first shielding layer 40 is also controlled to be constant. The twisted pair pitch of the insulated wire 12 is preferably 8.11 to 8.51 mm.

[0023] Next, we will explain how to manufacture the communication cable 1.

[0024] First, a single wire or compressed stranded wire with a circular cross-section is prepared as the conductor 14. An insulating resin is extruded and coated onto the conductor 14, and an electron beam is irradiated onto it to crosslink it and form an insulator 16, thereby manufacturing an insulated electric wire 12. Then, the two insulated wires 12 are twisted together at a constant pitch (paired twist).

[0025] Subsequently, polyethylene terephthalate tape (PET tape) is wrapped around the twisted body 10 in a layered manner to form a pressed winding 20. Subsequently, a metal tape is wrapped over the pressed winding 20 to form a first shielding layer 40, and multiple metal wires are braided together to form a second shielding layer 50.

[0026] Finally, the outer sheath 60 is formed by extruding and coating the second shielding layer 50 with an outer sheath resin, thereby manufacturing the communication cable 1.

[0027] With the above-described communication cable 1, if the twisting pitch of the insulated wires 12 is controlled to be constant, the in-pair skew is 10 ps / m or less, the transmission state is stable, and the insertion loss (IL) does not drop below 10 GHz, thus suppressing signal attenuation. Furthermore, if the distance between the conductors 14 and the distance between the conductors 14 and the first shielding layer 40 are controlled to be constant, the characteristic impedance Z0 can be maintained at approximately 100 Ω while suppressing the suck-out phenomenon in the high-frequency band (see the example below). This communication cable 1 provides a communication cable that supports high-frequency data transmission with a simple configuration that involves controlling the twisting pitch of the insulated wires 12, the distance between the conductors 14, and the distance between the conductors 14 and the first shielding layer 40.

[0028] Furthermore, the communication cable 1 can be used for any communication purpose, preferably for automotive applications, and more preferably for transmitting images or video signals from an in-vehicle camera. In other words, the communication cable 1 is preferably a cable that conforms to the ISO-6722 standard or the ISO-19642 standard. [Examples]

[0029] (1) Sample preparation (1.1) Sample 1 First, a soft copper wire (26AWG compressed stranded wire) with a diameter of 0.45 mm was prepared as the conductor. Subsequently, polypropylene (PP) was extruded and coated onto the conductor to form an insulator with a thickness of 0.290 mm, and an insulated wire with an outer diameter of 1.03 mm was formed. Subsequently, two insulated wires were twisted together at a pitch of 8.11 mm to form a twisted wire body.

[0030] Subsequently, a 0.100 mm thick polyethylene terephthalate tape (PET tape) was wrapped around the twisted body as a pressing winding, overlapping by half (overlapping by half the width of the PET tape), resulting in an overlapping winding thickness of 0.200 mm.

[0031] Subsequently, an Al / PET tape was prepared as the first shielding layer, and the Al / PET tape was wrapped around the pressed winding with a 1 / 2 overlap to form a first shielding layer with an outer diameter of 2.64 mm. Subsequently, 85 tin-plated soft copper wires (TA) with a diameter of 0.1 mm were prepared as a second shielding layer, and these tin-plated soft copper wires were braided with the first shielding layer to form a second shielding layer with an outer diameter of 3.10 mm. Finally, polyolefin (PO) was extruded and coated onto the second shielding layer to produce a communication cable with an outer diameter of 4.00 mm.

[0032] (1.2) Samples 2-6 In Sample 1, the thickness of the insulator, the pitch of the twisted strands, the thickness of the push winding, and the thickness of the overlapping push windings were changed as shown in Table 2. In Sample 6, the first and second shielding layers were formed directly on the twisted strands without using a pressing winding method.

[0033] (2) Evaluation of the sample Each sample was cut to a length of 5m, and its characteristic impedance Z0, intrinsic skew, and insertion loss in the high-frequency band were measured. The measurement results are shown in Table 2. In Table 2, the insertion loss values ​​represent the frequencies at which the suck-out phenomenon was observed.

[0034] [Table 2]

[0035] (3) Summary As shown in Table 2, the characteristic impedance Z0 was maintained at approximately 100Ω in all samples, and the in-body skew was good at less than 10 ps / m. On the other hand, in samples 1-2, the suck-out phenomenon was not observed until the frequency reached 10 GHz, whereas in samples 3-6, the suck-out phenomenon was observed before the frequency reached 10 GHz. From the above, it was found that in providing communication cables compatible with high-frequency data transmission, it is useful to control the thickness of the insulator, the thickness of the sluice winding, and the thickness of the overlapping sluice windings to be constant, in addition to the twisted pair pitch, that is, to control the distance between conductors and the distance between conductors and shielding layers to be constant. [Industrial applicability]

[0036] The present invention relates to a communication cable and a method for manufacturing the same, and is particularly useful in providing a communication cable that is compatible with high-frequency data transmission and can suppress the suck-out phenomenon in the high-frequency band while maintaining a characteristic impedance Z0 of approximately 100Ω. [Explanation of Symbols]

[0037] 1. Communication cable 10 pairs of twisted bodies 10A~10B 1st~2nd type wire core 12 Insulated wires 14 Conductors 16 Insulator 20 Pressed Roll 40 First shielding layer 50 Second shielding layer 60 Outer cover

Claims

1. A communication cable comprising multiple insulated wires, each having a conductor covered with an insulator, twisted together, and then covered with a shielding layer by repeatedly winding a pressure winding around the twisted wire, The conductor is composed of a single wire or compressed stranded wire with a circular cross-section, The diameter of the conductor is 0.45 mm. The thickness of the insulator is 0.290 to 0.315 mm. Multiple insulated wires are twisted together at a pitch of 7.0 mm or more and less than or equal to the value derived by (speed of light × NVP / frequency) × (1 / dielectric constant of the insulator), A communication cable characterized in that the thickness of the press winding is 0.050 to 0.100 mm and the thickness of the overlapping winding of the press winding is 0.100 to 0.200 mm.

2. In the communication cable described in claim 1, The aforementioned insulator is polypropylene, A communication cable characterized in that multiple insulated wires are twisted together at a pitch of 7.0 mm or more and 10.00 mm or less.

3. In the communication cable described in claim 1, The aforementioned insulator is polypropylene, A communication cable characterized in that multiple insulated wires are twisted together at a pitch of 8.11 to 8.51 mm.

4. In a communication cable according to any one of claims 1 to 3, A communication cable characterized by its use in automotive applications.

5. The process involves preparing a conductor with a circular cross-section, either a single wire or a compressed stranded wire, and a diameter of 0.45 mm. The process involves covering the aforementioned conductor with an insulator having a thickness of 0.290 to 0.315 mm to form an insulated wire, A step of twisting together multiple insulated wires at a pitch of 7.0 mm or more and at a pitch less than or equal to the value derived by (speed of light × NVP / frequency) × (1 / dielectric constant of the insulator), The process involves overlapping the twisted body with a press winding of 0.050 to 0.100 mm in thickness to make the overlapping winding thickness 0.100 to 0.200 mm, and then covering it with a shielding layer. A method for manufacturing a communication cable, characterized by comprising the following features.

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