JP7629949B2 - Communication cable and its manufacturing method - Google Patents

Description

The present invention relates to a communication cable and a method for manufacturing the same.

Communication cables such as LAN (Local Area Network) cables are used to connect various devices, such as between servers, between a server and a switch, and between a server and a personal computer. As shown in FIG. 1, a communication cable 1 is known as such a communication cable, which includes a cable core 10 in which four pairs of twisted wires 8, each of which includes two insulated wires 6, are twisted together. In this communication cable 1, an inner sheath layer 20, a shielding layer 30, and an outer sheath 40 are arranged around the outer periphery of the cable core 10 (for example, Patent Document 1, etc.).

JP 2018-041568 A

In recent years, LAN cables have come to be used in a wider range of fields. For example, LAN cables are often used in driving parts of industrial devices and parts associated therewith, and in such places, the LAN cables are repeatedly bent. For this reason, LAN cables are required to have performance that does not change electrical characteristics even when repeatedly bent (also referred to as "flex resistance" in this specification).
Furthermore, according to careful investigations by the inventors, it has become clear that when a cable is repeatedly bent at only one point, the electrical characteristics are more likely to deteriorate over time than when the cable is repeatedly bent at multiple points.
An object of the present invention is to provide a communication cable that exhibits good electrical characteristics even when repeatedly bent at multiple locations on a single cable, and a method for manufacturing the same.

In order to solve the above problem, according to one aspect of the present invention,
The cable includes a plurality of twisted pairs formed by twisting a pair of insulated electric wires together, and the plurality of twisted pairs are twisted together to form a cable core.
the twist pitch of each of the plurality of twisted pairs is 15 times or less than the outer diameter of the twisted pairs, and the maximum twist pitch of the plurality of twisted pairs is in the range of 9 times or more and 15 times or less than the outer diameter of the twisted pairs;
The twist pitch of the cable core is 14 times or more and 17 times or less than the outer diameter of the cable core.
A communications cable is provided.

According to another aspect of the present invention for solving the above problem,
Providing a plurality of insulated wires;
a step of twisting a predetermined number of the insulated electric wires into pairs to obtain a plurality of twisted pairs; and a step of twisting the plurality of twisted pairs together to obtain a cable core.
having
In the step of obtaining the plurality of twisted pairs, the twist pitch of each of the twisted pairs is 15 times or less the outer diameter of the twisted pair , and the maximum twist pitch of the plurality of twisted pairs is in the range of 9 times or more and 15 times or less the outer diameter of the twisted pair,
In the step of obtaining the cable core, a twist pitch of the cable core is 14 times or more and 17 times or less than an outer diameter of the cable core.
A method for manufacturing a communications cable is provided.

The communication cable of the present invention has excellent bending resistance, and its electrical characteristics are unlikely to change even if it is repeatedly bent or folded in multiple places. Furthermore, the manufacturing method of the communication cable of the present invention makes it easy to manufacture a communication cable with excellent bending resistance.

1 is a schematic cross-sectional view showing a structure of a communication cable. FIG. 2 is a schematic diagram showing a schematic enlarged cross-sectional view of an insulated wire. FIG. 1 is a diagram illustrating a method for a bending test.

The following describes a communication cable according to a preferred embodiment of the present invention. The communication cable of this embodiment is a communication cable made up of a twisted pair cable for a so-called LAN (Local Area Network).

The communication cable of this embodiment may include other configurations as long as it has a cable core and an outer sheath layer disposed around the cable core. Below, the communication cable 1 shown in FIG. 1, that is, the communication cable 1 having the cable core 10, the inner sheath layer 20, the shielding layer 30, and the outer sheath layer 40, is used as an example for explanation. However, the communication cable according to this embodiment is not limited to this structure.

The cable core 10 is composed of a plurality of (four pairs in this example) twisted wire pairs 8 and a cross insert 9 for isolating the plurality of twisted wire pairs 8 from one another. The cross insert 9 and the twisted wire pairs 8 are twisted in a constant direction along the length of the communication cable 1 with a twist pitch described below.
Each twisted pair 8 is composed of a pair (two in this case) of insulated wires 6, which are twisted together in a fixed direction with a twist pitch described below. The twist direction of the twisted pair 8 and the twist direction of the cable core 10 may be the same or different. As shown in Fig. 1, each insulated wire 6 in the twisted pair 8 is composed of a conductor 2 and an insulator 4, and the conductor 2 is covered with the insulator 4.
The conductor 2 is composed of a plurality of (30 in this example) strands 2a as shown in Fig. 2, and each strand 2a is a soft copper wire made of a copper alloy or the like. The conductor 2 may be, for example, a non-compressed conductor in which a plurality of strands 2a are simply twisted together as shown in Fig. 2, or may be a compressed conductor in which a plurality of strands 2a are twisted together and then compressed into a desired shape. The outer diameter of the conductor 2 is usually 0.2 mm or more and 0.7 mm or less.
On the other hand, the insulator 4 is made of a resin such as polyethylene.
The cross insert 9 is made of a resin such as polyethylene. The cross insert 9 extends in the longitudinal direction of the communication cable 1 and is a member for separating the twisted pairs 8 from each other in a non-contact state.

An inner sheath layer 20 is formed around the cable core 10. The inner sheath layer 20 may be a layer formed by extrusion coating with polyethylene, and the thickness of the inner sheath layer 20 is preferably 0.2 mm or more and 0.4 mm or less. The inner sheath layer 20 tends to keep the distance between the cable core 10 and the shielding tape described below constant, and tends to improve the high-frequency electrical characteristics of the communication cable 1. The Shore hardness (Shore D hardness) of the inner sheath layer 20, measured using an indenter type D in accordance with JIS K7215 (Durometer hardness test method for plastics), is preferably 32 or more and 38 or less. When the inner sheath layer 20 has the Shore D hardness, the electrical characteristics of the communication cable 1 are improved.

A shielding layer 30 is disposed around the inner sheath layer 20. The shielding layer 30 may be composed of one layer or two or more layers. In this embodiment, it is composed of two layers, a shielding tape and a braided wire. The shielding tape is composed of, for example, an Al/PET tape in which aluminum foil (Al) is attached to a polyethylene terephthalate (PET) substrate, and the shielding tape is wound horizontally along the length of the cable core 10 to cover the outer periphery of the inner sheath layer 20. In this specification, "horizontal winding" means that a long tape is wound in a spiral shape along the length of the cable core 10 or the inner sheath layer 20, and the side edge of the tape is wound while overlapping the tape that was previously wound. On the other hand, the braided wire is composed of a tin-plated soft copper wire with an outer diameter of 0.1 mm, which covers the outer periphery of the shielding tape.

An outer jacket layer 40 is disposed around the shielding layer 30. The outer jacket layer 40 is disposed so as to cover the above-mentioned shielding layer 30, and is the outermost layer of the communication cable 1. The material of the outer jacket layer 40 is appropriately selected depending on the application and usage environment of the communication cable 1, and the desired hardness, and is selected from, for example, polyvinyl chloride, polyethylene, etc.
The communication cable 1 of this embodiment typically has an outer diameter of 3.0 mm or more and 20.0 mm or less.

The twist pitch of the twisted wire pairs 8 and the twist pitch of the cable core 10 in the above-mentioned communication cable 1 will be described below.
In conventional communication cables, when the cable is repeatedly bent at multiple locations, its electrical properties may deteriorate over time. According to the study by the present inventors, it has become clear that, among the multiple twisted pairs of a communication cable, those with a relatively large twist pitch are more likely to suffer from deterioration in electrical properties. It has also become clear that in twisted pairs with deteriorated electrical properties, the twisted state of the twisted pairs is disturbed at the bent locations. The reason for this is that, when the communication cable is repeatedly bent at multiple locations, forces are applied to each twisted pair from various directions. It is considered that the twisted pairs with a large twist pitch are more susceptible to such influence than other twisted pairs, and are more likely to suffer from disturbance in the twisted state.
Therefore, in this embodiment, the twist pitch of all the twisted pairs 8 is set to 15 times or less the outer diameter of the twisted pairs 8 (also referred to as "core diameter" in this specification). The lower limit of this ratio is not particularly limited, but is usually preferably 7 times or more. The core diameter is the maximum diameter of each twisted pair 8 in the cross section of the communication cable 1, and is the length represented by a1 or a2 in FIG. 1. The absolute value of the core diameter in this embodiment is not particularly limited, but the core diameter of a general communication cable 1 is usually 0.4 mm or more and 1.2 mm or less, and the same can be done in this embodiment. Meanwhile, in this specification, the twist pitch refers to the length of the twisted pairs 8 required for the insulated wire 6 to make one revolution around the central axis of the twisted pairs 8.
The twist pitches of the multiple twisted pairs 8 in the communication cable 1 are usually set to different values to prevent interference between signals flowing through each conductor 2. Therefore, in this embodiment, the value of the twist pitch for each core diameter (twist pitch/core diameter) is different for each twisted pair 8, and there are four numerical values. In this embodiment, the maximum value among these is set to 15 or less. If the value of the twist pitch for the core diameter in all the twisted pairs 8 is 15 or less, the twist state is unlikely to be disturbed in all the twisted pairs 8, and the twist state is unlikely to change even if the communication cable 1 is bent at multiple points.

On the other hand, in this embodiment, the twist pitch of the cable core 10 is set to be 14 times or more and 17 times or less than the outer diameter of the cable core (also referred to as the "twist outer diameter" in this specification). The twist outer diameter is the outer diameter of the cable core 10, and is the length indicated by b in FIG. 1. In addition, in this specification, the "twist pitch" is a so-called collective twist pitch, and refers to the length of the cable core 10 required for the twisted pair wires 8 to make one revolution around the central axis of the cable core 10. In this embodiment, the outer diameter (twist outer diameter) of the cable core is not particularly limited, but the twist outer diameter of a general communication cable 1 is usually 2.0 mm or more and 8.0 mm or less, and the same can be done in this embodiment.
As described above, if the twist pitches of all the twisted pairs 8 are set to 15 times or less the core diameter, the twisted state of the twisted pairs 8 is unlikely to change. However, simply adjusting the twist pitch may not result in good electrical characteristics, depending on the twist pitch of the cable core 10. Therefore, in this embodiment, the twist pitch of the cable core 10 is set to 14 to 17 times the twisted outer diameter, thereby improving the electrical characteristics.

Next, a method for manufacturing the above-mentioned communication cable 1 will be described. However, the method for manufacturing the communication cable is not limited to this method.
First, a plurality of soft copper wires (strands 2a) (30 in this embodiment) are bundled and twisted in a certain direction to form the conductor 2. At this time, the conductor 2 may be compressed as necessary. Thereafter, polyethylene is extruded around the conductor 2 while conveying it in the length direction, thereby obtaining the insulated wire 6 in which the conductor 2 is covered with the insulator 4.
Next, a predetermined number of insulated wires 6 (here, two at a time) are bundled together and twisted in a certain direction to form a twisted pair wire 8. This process is repeated to prepare a plurality of (here, four sets) twisted pairs 8. At this time, the twist pitch of each pair is adjusted so that it is 15 times or less the outer diameter of the twisted pair wire 8 to be produced.
Then, a plurality of (four pairs in this case) twisted pairs 8 are respectively arranged along the cross inserts 9 and twisted together to obtain the cable core 10. At this time, the twist pitch is adjusted to be 14 to 17 times the outer diameter of the cable core 10 to be produced.

Next, while the cable core 10 is being conveyed in the length direction, polyethylene is extruded around the cable core 10 to form an inner sheath layer 20 around the cable core 10 .
Thereafter, an Al/PET tape is wound transversely around the inner coating layer 20 , and a braided wire is further placed around the tape to form the shielding layer 30 .
Furthermore, while conveying the cable core 10 around which the inner sheath layer 20 and the shielding layer 30 have been formed in the lengthwise direction, polyvinyl chloride is extruded around it to form the outer sheath layer 40, thereby producing the above-mentioned communication cable 1.

(1) Preparation of Samples (1.1) Sample 1 (Comparative Example)
Preparation of insulated wire Thirty soft copper wires (element wires) with an outer diameter of 0.08 mm were twisted together in a predetermined direction to prepare a stranded conductor with an outer diameter of 0.5 mm. High-density polyethylene was prepared and extruded from a die of an extruder to cover the stranded conductor with an insulator to obtain an insulated wire. The same process was repeated to obtain multiple insulated wires.

- Preparation of twisted pair Two insulated wires were twisted together to prepare a first twisted pair with a twist pitch of about 9 times the outer diameter (core diameter) of the desired first twisted pair of 0.9 mm. Similarly, two insulated wires were combined to prepare a second twisted pair (twist pitch = 13 times the core diameter), a third twisted pair (twist pitch = 10 times the core diameter), and a fourth twisted pair (twist pitch = 16 times the core diameter).

- Preparation of cable core A cross insert was prepared, and four pairs of twisted wires were arranged along the cross insert and twisted together so that the twist pitch was 18 times the desired outer diameter (twist pitch) of the cable core of 4.5 mm, to obtain a cable core.

Preparation of the inner jacket layer, shielding layer, and outer jacket layer Polyethylene was prepared as the inner jacket layer, and this was extruded from the die of the extruder to form an inner jacket layer with a thickness of 0.3 mm around the cable core. Next, a shielding tape was prepared and wrapped transversely around the inner jacket layer. Furthermore, a tin-plated soft copper wire with an outer diameter of 0.1 mm was braided to form a shielding layer consisting of the shielding tape and the braided wire. Furthermore, polyvinyl chloride (PVC) was prepared as the material for the outer jacket layer, and this was extruded from the die of the extruder to form an outer jacket layer with a thickness of 0.4 mm around the shielding layer.
Through the above steps, a communication cable with an outer diameter of 7 mm was manufactured.

(1.2) Sample 2 (Comparative Example)
An insulated wire was produced in the same manner as in Sample 1, except that the twist pitch of the fourth twisted wire was changed so that the twist pitch was 15 times the desired core diameter of 0.9 mm.

(1.3) Sample 3 (Comparative Example)
An insulated wire was produced in the same manner as in Sample 2, except that the twist pitch of the cable core was changed so that it was 13 times the desired twisted outer diameter of 4.5 mm.

(1.4) Sample 4 (Example)
An insulated wire was produced in the same manner as in Sample 2, except that the twist pitch of the cable core was changed so that it was 16 times the desired twisted outer diameter of 4.5 mm.

(1.5) Sample 5 (Example)
An insulated wire was produced in the same manner as in Sample 2, except that the twist pitch of the cable core was changed so that it was 14 times the desired twisted outer diameter of 4.5 mm.

(1.6) Sample 6 (Example)
An insulated wire was produced in the same manner as in Sample 2, except that the twist pitch of the cable core was changed so that it was 17 times the desired twisted outer diameter of 4.5 mm.

(2) Evaluation (2.1) Measurement of Electrical Characteristics For each sample of communication cable 1, return loss (RL), near-end crosstalk (NEXT), and delay time difference (Delay), etc. were measured using a general-purpose LAN cable automatic measuring device. The results are shown in Table 1.

(2.2) Bending test An RJ45 connector was installed on both ends of each of the above samples (communication cables 1) with a length of 5 m, and the both ends were fixed to the lower fixing part 211 of the tester, as shown in FIG. 3. Meanwhile, the center part of the length direction of the communication cable 1 was held by the upper gripping part 212 of the tester, and two U-shaped bent parts 1a with a bending radius of 50 mm were provided in the communication cable 1. Then, the above gripping part 212 was reciprocated in parallel with the length direction of the sample with a stroke of 500 mm. The speed was 60 reciprocations/min. After the bending test, the return loss (RL) of each sample of the communication cable 1 was measured using a general-purpose LAN cable automatic measuring device. The results are shown in Table 2.

(3) Summary As shown in Tables 1 and 2 above, in Sample 1 (Comparative Example 1) including a twisted pair wire in which the twist pitch was more than 15 times the core diameter, the basic electrical properties before the U-shaped folding test satisfied the ANSI/TIA-568.2 standard, but the return loss (RL) after the U-shaped folding test was low.
On the other hand, even when the twist pitch was changed to 15 times or less the core diameter, the basic electrical properties before the U-shaped folding test did not satisfy the ANSI/TIA-568.2 standard in Samples 2 and 3 (Comparative Examples 2 and 3). In other words, even when the twist pitch was changed to 15 times or less the core diameter, when the (collective) twist pitch was not changed from Sample 1 (18 times the twist outer diameter) or when the (collective) twist pitch was made too small (13 times the twist outer diameter), the electrical properties were degraded.
In contrast, in Samples 4 to 6 (Examples 4 to 6), the basic electrical properties before the U-shaped folding test met the ANSI/TIA-568.2 standard, and the return loss (RL) after the U-shaped folding test was also unlikely to decrease. In other words, when all the pair twist pitches were set to 15 times or less the respective core diameters, and further, when the (collective) twist pitch was set to 14 to 17 times the twist outer diameter, each electrical property became significantly better.
From the above, it can be seen that an excellent communication cable can be obtained by making the twist pitch of all twisted pairs no more than 15 times the outer diameter (core diameter) of the twisted pairs and further making the twist pitch of the cable core between 14 and 17 times the outer diameter (twisted outer diameter) of the cable core.

The communication cable of the present invention has excellent bending resistance, and its electrical characteristics are unlikely to change even if it is repeatedly bent at multiple points. Therefore, the communication cable can be used in a variety of fields.

REFERENCE SIGNS LIST 1 communication cable 1a bent portion 2 conductor 2a strand 4 insulator 6 insulated electric wire 8 twisted pair 9 cross insert 10 cable core 20 inner sheath layer 30 shielding layer 40 outer sheath layer 211 fixed portion 212 gripping portion

Claims (2)

The cable includes a plurality of twisted pairs formed by twisting a pair of insulated electric wires together, and the plurality of twisted pairs are twisted together to form a cable core.
the twist pitch of each of the plurality of twisted pairs is 15 times or less than the outer diameter of the twisted pairs, and the maximum twist pitch of the plurality of twisted pairs is in the range of 9 times or more and 15 times or less than the outer diameter of the twisted pairs;
The twist pitch of the cable core is 14 times or more and 17 times or less than the outer diameter of the cable core.
Communication cable. Providing a plurality of insulated wires;
a step of twisting a predetermined number of the insulated wires into pairs to obtain a plurality of twisted pairs ;
twisting the plurality of twisted wire pairs to obtain a cable core;
having
In the step of obtaining the plurality of twisted pairs, the twist pitch of each of the twisted pairs is 15 times or less the outer diameter of the twisted pair , and the maximum value of the twist pitch of the plurality of twisted pairs is in the range of 9 times or more and 15 times or less the outer diameter of the twisted pair,
In the step of obtaining the cable core, a twist pitch of the cable core is 14 times or more and 17 times or less than an outer diameter of the cable core.
A method for manufacturing communication cables.

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