JP7634515B2 - 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, communication cables 1 are known that have a cable core 10 made of multiple twisted pair wires 8, each of which is made of two insulated wires 6 with conductors 2 insulated by an insulator 4, and are covered with a winding 20, a shielding layer 30, and an outer sheath layer 40 (see, for example, Patent Document 1, etc.).

JP 2011-49052 A

In recent years, LAN cables have come to be used in a wider range of fields, and there is a demand for high-quality communication cables with more stable electrical characteristics. In particular, there is an increasing demand for Cat. 6 and Cat. 6A products compatible with frequencies of 250 MHz or 500 MHz, and there is a demand for such communication cables with good electrical characteristics.
SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, a primary object of the present invention is to provide a high-quality communication cable having good electrical characteristics, and a method for manufacturing the same.

In order to solve the above problems, according to one aspect of the present invention,
The cable comprises a cable core having a plurality of twisted pairs, each of which is made by twisting two insulated electric wires together at a predetermined pair pitch length (mm) , and the twisted pairs are twisted together at a predetermined collective pitch length (mm) ;
one of the insulated electric wires constituting each of the twisted pair wires is a monochrome insulated electric wire in which a conductor is covered with an insulator of a monochrome color, and the other is a color-banded insulated electric wire in which a conductor is covered with an insulator having n color bands (n is an integer of 1 or more) extending in a length direction,
The twist ratio of each of the twisted pairs is expressed by the following formula (1) and is 7 times or more and 8 times or less than the pair pitch length (mm) of each of the twisted pairs,
The collective pitch length (mm) is 1.3 times or more and 1.5 times or less (but less than 100 mm) the minimum value of the plurality of twist back rates.
A communications cable is provided.
Twist back rate [%] = 100 - x / n ... (1)
(x represents the number of color bands that cross the color banded insulated electric wire in the width direction and are identified within a length range 100 times the pair pitch length (mm) when the color banded insulated electric wire of each twisted pair is viewed from the front.)

According to another aspect of the present invention,
A step of preparing a plurality of insulated wires each having a conductor covered with an insulator;
a step of twisting the two insulated electric wires in a predetermined direction while twisting the two insulated electric wires in a direction opposite to the twisting direction of the insulated electric wires to twist the two insulated electric wires with a predetermined pair pitch length (mm) to form a twisted pair wire;
and a step of preparing a plurality of the twisted wires by repeating the step of preparing the insulated electric wire and the step of forming the twisted wire, and twisting the plurality of the twisted wires together at a predetermined collective pitch length (mm) to form a cable core,
In the twisted wire forming step, a twist rotation rate represented by the following formula (2) is set to 7 times or more and 8 times or less the pair pitch length (mm) of each of the twisted wires,
The present invention provides a method for manufacturing a communication cable, wherein in the forming step of the cable core, the collective pitch length (mm) is set to be 1.3 to 1.5 times (but less than 100 mm) the minimum value of the plurality of twist rotation rates.
Twist-back rotation rate (%) = (number of rotations when twisting back) / (number of rotations when twisting pairs) × 100 (2)

The present invention provides a high-quality communication cable with good electrical characteristics and a method for manufacturing the same.

FIG. 2 is a schematic cross-sectional view of a communication cable. FIG. 2 is a schematic cross-sectional view of an insulated wire. 3A to 3C are schematic diagrams for explaining the single-color insulated electric wires and the color-banded insulated electric wires that constitute the twisted pair wire, and the twist back ratio. 4A to 4C are schematic diagrams showing the state of wires in an insulated wire when twisted in pairs.

Hereinafter, a communication cable according to a preferred embodiment of the present invention will be described.
The communication cable is a communication cable made up of a so-called LAN (Local Area Network) twisted pair cable.

The communication cable of this embodiment may include a cable core in which a plurality of twisted pairs, each of which is made by twisting two insulated electric wires together, are twisted together at a predetermined assembly pitch length. Below, as shown in FIG. 1, a communication cable 1 having a cable core 10, a winding 20, a shielding layer 30, and an outer sheath layer 40 will be described as an example. However, the communication cable according to this embodiment is not limited to this structure.

The cable core 10 is composed of a plurality of (here, four pairs) twisted pairs 8 formed by twisting two insulated electric wires 6 together at a predetermined pair pitch length, and a cross insert 9 for isolating the plurality of twisted pairs 8. The cross insert 9 and the twisted pairs 8 are twisted together at a collective pitch length described below (in this specification, such twisting is also referred to as "collective twist").
Each twisted pair wire 8 is composed of two insulated wires 6, which are twisted together in a certain direction with a pair pitch length described below (in this specification, this twisting is also referred to as "twisted pair").
As shown in FIG. 1 , each insulated wire 6 in the twisted pair wire 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 made of a solid wire as shown in Fig. 2. The conductor 2 (solid wire) is, for example, a soft copper wire made of a copper alloy or the like.
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.

In this embodiment, a winding 20 is formed around the cable core 10. The winding 20 is made of a nonwoven tape having a thickness of 0.3 mm to 0.4 mm. The winding 20 makes it easier to keep the distance between the cable core 10 and the shielding layer 30 (described below) constant, which tends to improve the high-frequency electrical characteristics of the communication cable 1.

A shielding layer 30 is disposed around the winding 20. The shielding layer 30 may be composed of one layer or two or more layers. In this embodiment, the shielding layer 30 is composed of a shielding tape. The shielding tape is composed of, for example, an Al/PET tape in which an aluminum foil (Al) is attached to a polyethylene terephthalate (PET) substrate. The shielding tape is wound transversely along the length of the cable core 10 and covers the outer periphery of the winding 20.
In this specification, "horizontal winding" means winding a long tape in a spiral shape along the longitudinal direction of the cable core 10 or the winding 20, and means winding the side edge of the tape while overlapping it on the previously wound 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 according to the application and usage environment of the communication cable 1, and the desired hardness, and is selected from, for example, polyvinyl chloride, polyethylene, etc.

Here, in this embodiment, in accordance with the ANSI/TIA-568.2 standard, one of the two insulated wires 6 constituting the twisted pair wire 8 described above is a monochrome insulated wire 6a in which the conductor 2 is covered with a monochrome (e.g., blue, orange, green, brown) insulator 4a as shown in FIG. 3A. The other is a color-banded insulated wire 6b in which the conductor is covered with an insulator 4b having n (n is 1 or more) color bands 4s arranged on a white background 4w. In the insulator 4b, the color bands 4s are arranged so as to extend in the length direction of the color-banded insulated wire 6b. The number (n) of color bands 4s in each color-banded insulated wire 6b may be 1 or more, but is usually 1 or 2. For example, two color bands 4s (n=2) may be arranged, one on each side of the color-banded insulated electric wire 6b, or only one color band 4s (n=1) may be arranged on either the front or back side of the color-banded insulated electric wire 6b.

Each of the twisted pairs 8 has a structure in which the insulated wires 6 (single-color insulated wires 6a and color-banded insulated wires 6b) are individually twisted in a predetermined direction and then collectively twisted into pairs, and the cable core 10 has a structure in which the twisted pairs 8 are further collective twisted. The states of the insulated wires 6 and the twisted pairs 8 when twisted into pairs and collective twisted will be described with reference to Figs. 4A to 4C.
In this embodiment, as shown in Fig. 4A, when preparing the twisted pair wire 8, each of the insulated electric wires 6 (solid-color insulated electric wires 6a and color-banded insulated electric wires 6b) is rotated and twisted in the direction opposite to the normal twisting direction (direction C in Fig. 4A). Then, two insulated electric wires 6 in this state are twisted in the direction opposite to the twisting direction C (direction D in Fig. 4B). Then, the four pairs of twisted wires 8 are collective twisted along the interposers 9 in the same direction as the twisting direction D (direction E in Fig. 4C).

Here, the degree to which the twisted pair of the twisted wire 8 is twisted back can be determined by the twist back ratio represented by the following formula (1).
Twist back rate [%] = 100 - x / n ... (1)
In the above formula (1), n represents the number of color bands in each color-banded insulated electric wire 6b. x represents the number of color bands that cross the color-banded insulated electric wire 6b in the width direction and are observed within a length range 100 times the pair pitch length of the twisted pairs 8 when each color-banded insulated electric wire 6b is viewed from the front. In this specification, the "pair pitch length" refers to the length of one pitch of the twisted pairs. The front view of the color-banded insulated electric wire 6b also includes the state when the color-banded insulated electric wire 6b on the back side of the single-color insulated electric wire 6a is viewed from the front side.
3B and 3C are schematic diagrams showing the color-striped insulated electric wire 6b of the twisted pair wire 8 when viewed from the front. FIG. 3B is a schematic diagram when the twist-back rate is less than 100%. FIG. 3C is a schematic diagram when the twist-back rate is 100%. When calculating the repetition rate, the number of color stripes 4s crossing the color-striped insulated electric wire 6b in the width direction is counted. For example, in FIG. 3B, color stripes 4s crossing the color-striped insulated electric wire 6b in the width direction are confirmed at the locations indicated by arrows, and the number of these stripes is counted. On the other hand, in FIG. 3C, although the color stripes 4s are visible, the color stripes 4s crossing the color-striped insulated electric wire 6b in the width direction are not confirmed. Therefore, the number of color stripes 4s in this case is 0.

The inventors' investigations revealed that there is a close relationship between the twist ratio, the pair pitch length and aggregate pitch length of the twisted pairs 8, and the stability of the electrical characteristics of the communication cable. In general communication cables, the pair pitch length of the twisted pairs 8 is set to a different value for each twisted pair 8, but the twist ratio is generally constant for each twisted pair 8.
In contrast, in this embodiment, the twist back ratio of each twisted pair wire 8 is set to 7 to 8 times, preferably 7.6 to 7.9 times, more preferably 7.63 to 7.90 times, the pair pitch length of each twisted pair wire 8. Furthermore, the collective pitch length when collective twisting the twisted pairs 8 is set to 1.3 to 1.5 times the minimum value of the multiple twist back ratios. However, the collective pitch length is set in a range of less than 100 mm. In addition, in this specification, the "collective pitch length" refers to the length of one pitch of collective twist.
The reason why the electrical characteristics of the communication cable 1 are improved by setting the twisting ratio and the collective pitch length as described above is unclear, but it is thought to be as follows. For example, a twisted pair 8 with a long pair pitch length is more likely to untwist and is less likely to become stable than a twisted pair 8 with a short pair pitch length. If the twisting ratio of such a twisted pair 8 with a long pair pitch length is set to be the same as that of other twisted pairs 8 with a short pair pitch length, the twisted pair 8 with the long pair pitch length is more likely to be loaded, which may lead to a deterioration in electrical characteristics. In contrast, by setting the twisting ratio in accordance with the pair pitch length, it is possible to prevent excessive load from being applied to a specific twisted pair 8, such as a twisted pair with a long pair pitch length, and it is thought that the electrical characteristics are stabilized.

Next, we will explain the manufacturing method of the communication cable 1.

In the method for manufacturing the communication cable 1, a soft copper wire (solid wire) is prepared as the conductor 2.
Thereafter, while conveying the conductor 2 in the lengthwise direction, the polyethylene resin is extruded from the die of the extruder, and the conductor 2 is covered with the insulator 4 to form the insulated wire 6. At this time, the insulator 6 is colored, so that one of the pair of insulated wires 6 becomes the above-mentioned single-color insulated wire 6a, and the other becomes the color-banded insulated wire 6b.
Thereafter, each insulated electric wire 6 (the solid color insulated electric wire 6a and the color-banded insulated electric wire 6b) is individually twisted a predetermined number of times in a predetermined direction, while two insulated electric wires 6 are bundled together and twisted a predetermined number of times in a predetermined direction to form a twisted pair wire 8.
In this process, a general-purpose twisting machine is used, and on the supply side, each insulated electric wire 6 is twisted a predetermined number of times in the direction opposite to the normal twisting direction, and on the winding side, two insulated electric wires 6 are twisted a predetermined number of times in the normal twisting direction.
The above-mentioned preparation of the insulated wires and the formation of the twisted wires are repeated to prepare a plurality of twisted wires (four pairs in this example). The plurality of twisted wires 8 are then arranged along the cross inserts 9 and twisted together at a predetermined collective pitch length to form the cable core 10.

Next, while the cable core 10 is being transported in the length direction, a nonwoven fabric tape is wound transversely around the cable core 10 to form a press winding 20 around the cable core 10.
Thereafter, an Al/PET tape is wound transversely around the roll 20 to form a shielding layer 30 .
Furthermore, while transporting the cable core 10 with the winding 20 and shielding layer 30 formed therearound in the longitudinal direction, polyethylene, polyvinyl chloride, etc. is extruded around it to form an outer sheath layer 40, thereby producing the above-mentioned communication cable 1.

In this embodiment, the twist back rotation rate is calculated based on the twist back rotation number and the pair twist rotation number in the above-mentioned twisted pair production process, as shown in the following formula (2). The twist back rotation rate has the same technical meaning as the twist back rate shown in the above-mentioned formula (1).
Twist-back rotation rate [%] = (number of twist-back rotations of each insulated electric wire 6) / (number of twist-back rotations of two insulated electric wires 6) × 100 (2)
In the above-mentioned process for producing the twisted pairs, the number of twisting rotations and the number of twisting rotations when producing each twisted pair 8 are adjusted so that the twisting rotation ratio is 7 to 8 times, preferably 7.6 to 7.9 times, and more preferably 7.63 to 7.90 times the desired pair pitch length (finished pair pitch length). The absolute values of the number of twisting rotations for twisting each insulated electric wire 6 and the number of twisting rotations are appropriately selected depending on the type of communication cable 1 and the type of twisted pair 8.
Furthermore, in this embodiment, the collective pitch length when multiple pairs of twisted wires are collective twisted is adjusted to be 1.3 to 1.5 times (but less than 100 mm) the minimum value among multiple twist back rotation rates.
By setting the twist rotation rate and the collection pitch length in this manner, it becomes easier to obtain a communication cable 1 with good electrical characteristics.

(1) Preparation of Samples (1.1) Sample 1 (Comparative Example)
A soft copper wire (single wire) having an outer diameter of 0.565 mm was prepared as a conductor.
Thereafter, high density polyethylene (blue) was prepared as an insulating resin, which was extruded through the die of an extruder to cover the conductor with the insulating resin, thereby forming a blue insulated wire having an outer diameter of 1.020 to 1.080 mm. Similarly, a conductor was prepared, and high density polyethylene (white and blue) was prepared as an insulating resin, which was extruded through the die of an extruder to cover the conductor, thereby forming an insulated wire with a color band having an outer diameter of 1.020 to 1.080 mm, in which a single blue band was arranged on a white background and extended in the longitudinal direction.
Next, the two insulated wires were twisted clockwise at a constant number of rotations while twisting the two insulated wires counterclockwise at a predetermined pair pitch length to form a twisted pair. The same process was repeated to form a total of four twisted pairs (blue pair, green pair, orange pair, and brown pair). The twisting ratio was 75% for each twisted pair.
Thereafter, the four twisted pairs were group-twisted to the right with a predetermined group pitch length.
The twist ratio, pair pitch length, and aggregate pitch length of each twisted pair are shown in Table 1.

A nonwoven tape having a thickness of 0.35 mm was prepared as a winding material and wound transversely around the cable core. Subsequently, a shielding tape was prepared and wound transversely around the winding material.
Thereafter, a mixture of flame-retardant polyethylene and polyvinyl chloride (PVC) was prepared as a material for the outer jacket layer, and this was extruded through a die of an extruder to form an outer jacket layer having a thickness of 0.4 mm around the shielding layer.

(1.2) Samples 2 to 4
A communication cable was produced in the same manner as in Sample 1, except that the pitch length, twist ratio, collective twist direction and collective pitch length were changed as shown in Table 1.

(2) Electrical Property Test of Samples Each sample was cut into 200 m pieces, and the return loss (RL) and near-end crosstalk attenuation (NEXT) of each twisted pair of each cut piece were measured. The measurement results are shown in Table 1.

(3) Summary As shown in Table 1, when the twist ratio of the twisted pair was between 7 and 8 times the pair pitch length of each twisted pair and the collective pitch length was between 1.3 and 1.5 times the minimum twist ratio of the twisted pair, the return loss (RL) and near-end crosstalk attenuation (NEXT) showed good values (Samples 2 and 3) compared to the case where the twist ratio was constant (75%) (Sample 1).
On the other hand, even if the twist ratio of the twisted pair was between 7 and 8 times the pitch length of each twisted pair and the collective pitch length was between 1.3 and 1.5 times the minimum twist ratio of the twisted pair, the return loss was low when the collective pitch length was 100 mm or longer (Sample 4).

REFERENCE SIGNS LIST 1 Communication cable 2 Conductor 4 Insulator 6 Insulated wire 8 Twisted pair wire 9 Cross insert 10 Cable core 20 Winding 30 Shielding layer 40 Outer sheath layer

Claims (2)

The cable comprises a cable core having a plurality of twisted pairs, each of which is made by twisting two insulated electric wires together at a predetermined pair pitch length (mm) , and the twisted pairs are twisted together at a predetermined collective pitch length (mm) ;
one of the insulated electric wires constituting each of the twisted pair wires is a monochrome insulated electric wire in which a conductor is covered with an insulator of a monochrome color, and the other is a color-banded insulated electric wire in which a conductor is covered with an insulator having n color bands (n is an integer of 1 or more) extending in a length direction,
The twist ratio of each of the twisted pairs is expressed by the following formula (1) and is 7 times or more and 8 times or less than the pair pitch length (mm) of each of the twisted pairs,
A communication cable, wherein the collective pitch length (mm) is 1.3 times or more and 1.5 times or less (but less than 100 mm) the minimum value of the plurality of twist ratios.
Twist back rate [%] = 100 - x / n ... (1)
(x represents the number of color bands that cross the color banded insulated electric wire in the width direction and are identified within a length range 100 times the pair pitch length (mm) when the color banded insulated electric wire of each twisted pair is viewed from the front.) A step of preparing a plurality of insulated wires each having a conductor covered with an insulator;
a step of twisting the two insulated electric wires in a predetermined direction while twisting the two insulated electric wires in a direction opposite to the twisting direction of the insulated electric wires to twist the two insulated electric wires with a predetermined pair pitch length (mm) to form a twisted pair wire;
and a step of preparing a plurality of the twisted wires by repeating the step of preparing the insulated electric wire and the step of forming the twisted wire, and twisting the plurality of the twisted wires together at a predetermined collective pitch length (mm) to form a cable core,
In the twisted wire forming step, a twist rotation rate represented by the following formula (2) is set to 7 times or more and 8 times or less the pair pitch length (mm) of each of the twisted wires,
A manufacturing method for a communication cable, wherein in the forming process of the cable core, the collective pitch length (mm) is set to be 1.3 to 1.5 times (but less than 100 mm) the minimum value of the multiple twist rotation rates.
Twist-back rotation rate (%) = (number of rotations when twisting back) / (number of rotations when twisting pairs) × 100 (2)

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