Communication cable and method for manufacturing the same

Abstract

The present invention provides a communication cable with good electrical characteristics and a method for manufacturing the same. [Solution] The communication cable 1 comprises a paired stranded wire 8 formed by twisting together two insulated wires 6, each having a conductor 2 made of multiple strands twisted together and an insulator 4 covering it. In the communication cable 1, the twisting rate of the insulated wires 6 is less than 100%. The twisting rate of the insulated wires 6 corresponds to the value obtained by counting the number of twisted pair pitches for 100 pitches when viewing the paired stranded wire 8 from the front, and subtracting the value X obtained by dividing the number of color bands in the length range of said 100 pitches by the number of color bands (2 or 1), and is expressed by the following formula (1). Twist rate (%) = 100 - value x ... (1)

Description

Technical Field

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

Background Art

[0002] Communication cables such as LAN (Local Area Network) cables are used for connecting various devices, such as between servers, between a server and a switch, and between a server and a personal computer. As such a communication cable, as shown in FIG. 1, a cable core 10 includes a plurality of twisted pairs 8 in which a plurality of insulated electric wires 6 obtained by insulating a conductor 2 with an insulator 4 are twisted together, and the cable core 10 has a structure covered with a wrapping 20, a shielding tape 30, and an outer jacket 40. A communication cable 1 having such a structure is known (for example, Patent Document 1 and the like).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] Here, the conductor 2 of the insulated wire 6 of the communication cable 1 may be composed of multiple strands 2a, as shown in the enlarged cross-sectional view in Figure 2A. In this case, for example, as shown in the schematic diagram in Figure 2B, the multiple strands 2a are twisted together in a certain direction (direction A in Figure 2B). On the other hand, the stranded wire 8 is also made by twisting the insulated wire 6 together in a certain direction (direction B in Figure 3), as shown in the schematic diagram in Figure 3. Therefore, if the twisting direction A of the strands 2a and the twisting direction B of the stranded wire 8 are the same, the strands 2a may be excessively twisted when the stranded wire 8 is made, which may affect the electrical characteristics of the communication cable 1. On the other hand, if the twisting direction A of the strands 2a and the twisting direction B of the stranded wire 8 are opposite, the twist of the strands 2a may be unraveled when the stranded wire 8 is made, which may also affect the electrical characteristics of the communication cable 1. Therefore, when manufacturing a paired stranded wire 8, it is known that individual insulated wires 6 are rotated in the opposite direction to the twisting direction of the individual wires 2a (also referred to as "re-twisting" in this specification), and then multiple insulated wires 6 are bundled together and twisted together (also referred to as "paired twisting" in this specification).

[0005] Generally, it is believed that the twist of the individual wires 2a can be brought to an appropriate state if the number of rotations during twisting back and the number of rotations during pair twisting are the same. Specifically, if the twist direction of the individual wires 2a in each insulated wire 6 is to the right, it is believed that if the insulated wire 6 is rotated to the left to the extent that the twist of the individual wires 2a is unraveled, and then rotated in the desired direction the same number of times as the twisting back (pair twisting), the state of the twist of the individual wires 2a will be approximately the same as before twisting, and the characteristics of the communication cable 1 will be improved.

[0006] However, after diligent research by the inventors, it became clear that when the communication cable 1 is manufactured using this method, a spike occurs in the return loss (RL), one of the electrical characteristics of the communication cable 1, on the high-frequency side of 200 MHz or higher.

[0007] The main objective of the present invention is to provide a communication cable with good electrical characteristics and a method for manufacturing the same. [Means for solving the problem]

[0008] To solve the above problems, according to one aspect of the present invention, It comprises a pair of stranded wires, each having a conductor made of multiple strands twisted together and an insulator covering it, One of the stranded wires is covered with an insulator of a single color. The other insulated wire of the aforementioned stranded wire is covered with an insulator having a line-shaped color band of the same color as the aforementioned single color. When the number of twisted wires for 100 pitches is counted with the aforementioned twisted wires viewed from the front, and the number of color bands in that length range of 100 pitches is divided by the number of color bands, the value obtained by X is such that the twisting rate of the insulated wires, as calculated by the following formula (1), is provided. Twist rate (%) = 100 - value x ... (1)

[0009] Furthermore, according to another aspect of the present invention, The process involves preparing two insulated wires, each having a conductor made of multiple strands twisted together and an insulator covering it. The process includes the steps of twisting each of the insulated wires in the opposite direction to the twisting direction of the individual wires, and twisting the two insulated wires together in the same direction as the twisting direction of the individual wires, A communication cable is provided in which the twisting rotation ratio, calculated by the following formula (2), is less than 100%. Twist rotation rate (%) = (Number of twist rotations of each insulated wire) / (Twist rotation of the pair of insulated wires) × 100 ... (2) [Effects of the Invention]

[0010] According to the present invention, a communication cable with good electrical characteristics such as return loss (RL) and a method for manufacturing the same are provided. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view of a communication cable. [Figure 2A] This is a schematic cross-sectional view of an insulated electric wire. [Figure 2B] This is a schematic diagram showing the state of individual wires within an insulated wire. [Figure 3] This is a schematic diagram showing the state of insulated wires in stranded pairs. [Figure 4] This is a schematic diagram showing the state of individual wires within an insulated wire. [Figure 5] This is a conceptual diagram to explain the twist rate. [Modes for carrying out the invention]

[0012] A preferred embodiment of the present invention, specifically a communication cable, will be described below. The communication cable in question is a communication cable composed of twisted-pair cables used for so-called LANs (Local Area Networks).

[0013] As shown in Figure 1, the communication cable 1 mainly consists of a cable core 10, a winding 20, a shielding tape 30, and an outer sheath 40.

[0014] The cable core 10 is composed of multiple pairs (four pairs in this case) of twisted wires 8 and a cross-shaped separator 9 for separating the multiple pairs of twisted wires 8 from each other. Each pair of stranded wires 8 has a structure in which multiple (in this case, two) insulated wires 6 are twisted together, as shown in Figure 3. The insulated wires 6 have a structure in which a conductor 2 is covered with an insulator 4. As shown in Figure 2A, the conductor 2 is composed of multiple (in this case, seven) soft copper wires (strands 2a), and the insulator 4 is made of polyethylene resin. The arrangement of the strands 2a in the conductor 2 is not particularly limited, and in this embodiment it is composed of a central strand and six concentric strands arranged concentrically around the central strand, but is not limited to this configuration. Also, the conductor 2 may be an uncompressible conductor made by simply twisting together multiple strands 2a, as shown in Figure 2A, or it may be a compressed conductor made by twisting together multiple strands 2a and then compressing them into a desired shape. The cross spacer 9 is made of polyethylene resin. The cross spacer 9 extends in the longitudinal direction of the communication cable 1 and separates the twisted pairs 8 from each other in a non-contact state. The cross spacer 9 is twisted along the longitudinal direction of the communication cable 1, and accordingly, the twisted pairs 8 are also twisted while being separated from each other by the cross spacer 9.

[0015] Around the cable core 10, a wrapping 20 is installed. The wrapping 20 is a member for keeping the distance between the conductor 2 and the shielding tape 30 in the cable core 10 constant. The type of the wrapping 20 is not particularly limited. In this embodiment, the wrapping 20 is made of, for example, a high-density polyethylene tape. Also, the winding method of the wrapping 20 is not particularly limited. In this embodiment, it is wound horizontally along the longitudinal direction of the cable core 10. In this specification, "horizontal winding" means winding a long tape in a spiral shape along the longitudinal direction of the cable core 10, and winding it while overlapping the side edge portion of the tape on the tape wound first. The thickness and number of layers of the wrapping 20 are not particularly limited as long as the object and effect of this embodiment are not impaired.

[0016] Around the wrapping 20, a shielding tape 30 is installed. The shielding tape 30 is composed of, for example, an Al / PET tape in which an aluminum foil (Al) is attached to a polyethylene terephthalate resin substrate (PET). The shielding tape 30 is wound horizontally along the longitudinal direction of the cable core 10 and covers the outer periphery of the wrapping 20. The outer sheath 40 is made of polyvinyl chloride resin. The outer sheath 40 is a so-called sheath that covers the outer periphery of the wrapping and forms the outermost layer of the communication cable 1. [[ID=X]]

[0017] In this embodiment, the twisted pair 8 has a structure in which each insulated wire 6 is twisted back in the direction opposite to the twisting direction of the individual wires 2a and then a plurality of insulated wires 6 are collectively twisted. The state of the individual wires 2a in the insulated wire 6 will be described using FIG. 4. Figure 4(a) shows the state of the insulated wire 6 before twisting, where the individual wires 2a are twisted together in the direction indicated by A (to the right in this case). At this time, the individual wires 2a are moderately close to each other within the insulator 4. When the insulated wire 6 is twisted back in the opposite direction C (to the left in this case) to the twisting direction A of the individual wires 2a, the twist of the individual wires 2a is undone, and gaps are created between the individual wires 2a (Figure 4(b)). Then, multiple twisted insulated wires 6 are prepared (two in this embodiment, however, for convenience, only one insulated wire 6 is shown in Figure 4(c)), and these are rotated together in a predetermined direction D (to the right in this case) (pair twisting). As a result, the individual wires 2a in the insulated wire 6 are also twisted in a predetermined direction E (to the right in this case), and the spacing between the multiple individual wires 2a narrows again, causing them to be in close contact (Figure 4(c)). Note that the twisting direction A of the individual wires 2a may be to the left, in which case the twisting direction C of the insulated wire 6 will be to the right and the pair twisting direction D will be to the left.

[0018] In this embodiment, the twisting and pairing of the stranded wires 8 is performed such that the twisting ratio of the insulated wires 6 is less than 100%. According to the ANSI / TIA-568.2 standard, as shown in Figure 5(a), one insulated wire 6a of the twisted pair 8 is covered with a single-color insulator 4 (for example, blue, green, orange, or brown), and the other insulated wire 6b is covered with an insulator 4 with a white background and a line-shaped color band 6c of the same single color. The number of color bands 6c is basically either two, one on the front and one on the back of the insulated wire 6b, or one on either the front or back. The twist ratio of the insulated wire 6 can be defined based on this. The twisting ratio of the insulated wire 6 basically corresponds to the value obtained by counting the number of twisted pair pitches for 100 pitches when viewing the paired wires 8 from the front, and subtracting the value X obtained by dividing the number of color bands in the length range of those 100 pitches (Figure 5(b)) by the number of color bands 6c (2 or 1), and is expressed by the following formula (1). Twist rate (%) = 100 - value x ... (1) However, as shown in Figure 5(c), if the insulated wire 6 is not substantially twisted, the number of color bands will be one, and the twisting rate in this case will be 100%. Figures 5(b) and 5(c) are schematic diagrams to make it easier to understand the front view of the color band 6c.

[0019] As described above, it has been conventionally believed that when the twisting ratio is 100%, the state of the twisted strands 2a becomes close to the state before twisting, resulting in good electrical characteristics of the communication cable. However, our own investigation has revealed that when the twisting ratio is 100%, the electrical characteristics of the communication cable are not sufficient. One possible reason for this is that the strands 2a that are untwisted are not sufficiently tightened by the pair twisting, resulting in gaps between multiple strands 2a. In contrast, when the twisting ratio is less than 100%, the strands 2a that are untwisted are sufficiently twisted by the pair twisting, so no gaps are created between multiple strands 2a after pair twisting, resulting in good electrical characteristics. Furthermore, the twisting ratio mentioned above is preferably 70% to 90%, as this tends to result in better electrical characteristics for the communication cable.

[0020] In conventional communication cables, when the number of twisted pair pitches per meter of stranded wire is 100 or more, spikes tend to occur in the return loss (RL), and the electrical characteristics tend to deteriorate. Therefore, in stranded wires where the number of twisted pair pitches per meter of stranded wire is 100 or more, it is particularly effective to set the twist-reversal ratio to less than 100%. In this embodiment, the communication cable 1 includes four pairs of twisted wires 8, and it is sufficient that at least one pair of twisted wires 8 satisfies the above twist ratio. Preferably, two or more pairs, more preferably three or more pairs, and most preferably all four pairs satisfy the above twist ratio.

[0021] Next, we will explain how to manufacture the communication cable 1.

[0022] As conductor 2, a stranded conductor is prepared by twisting together multiple soft copper wires (strands 2a) at a predetermined pitch. Subsequently, polyethylene resin is extruded from the extruder die while the conductor 2 is conveyed in the longitudinal direction, covering the conductor 2 with an insulator 4 to form an insulated wire 6. Subsequently, each insulated wire 6 is twisted back a predetermined number of times in the opposite direction to the twisting direction of the individual wires 2a, and multiple (in this case, two) insulated wires 6 are bundled together and twisted in a predetermined direction a predetermined number of times to form a paired wire 8. In this process, a general-purpose twisting machine is used, and on the supply side, each insulated wire 6 is twisted back a predetermined number of times along the opposite direction C to the twisting direction A of the individual wires 2a, and on the winding side, the two insulated wires 6 are twisted back a predetermined number of times along the twisting direction D. Considering the processing content of this process, the twisting rate in equation (1) is derived from the twisting turn rate in equation (2) below, and has the same technical significance as the twisting turn rate in equation (2). Twist rotation rate (%) = (Number of twist rotations along direction C of each insulated wire 6) / (Number of pair twist rotations along direction D of the two insulated wires 6) × 100 ... (2) Subsequently, multiple pairs (four pairs in this case) of twisted wires 8 are arranged along the cross-shaped separator 9 to form the cable core 10.

[0023] Next, a high-density polyethylene tape is prepared as the winding 20, and this is wound horizontally around the cable core 10. After that, Al / PET tape is wrapped horizontally around the pressing wrap 20 as shielding tape 30. Subsequently, while the cable core 10 with the winding 20 and shielding tape 30 wrapped around it is conveyed in the longitudinal direction, polyvinyl chloride resin is extruded from the extruder die, the shielding tape 30 is covered with the outer sheath 40, and the communication cable 1 is manufactured.

[0024] In this embodiment, in the process of twisting each of the insulated wires 6 described above and the process of twisting two insulated wires 6 together, the number of rotations during twisting and the number of rotations during pair twisting are adjusted so that the twisting rotation rate in equation (2) is less than 100%. Setting the twisting rotation rate to 70% or more and 90% or less makes it easier to obtain a communication cable 1 with particularly good electrical characteristics. The twisting rotation rate is usually the same value as the twisting rate in equation (1). As described above, by setting the twisting rotation rate to less than 100%, multiple strands 2a can be sufficiently tightly bound together by pair twisting, resulting in good electrical characteristics for the resulting communication cable. The number of rotations in the twisting process of each insulated wire 6, and the number of rotations in the twisting process of multiple insulated wires 6 are appropriately selected according to the type of communication cable and the type of twisted wire 8. However, as mentioned above, if the twisting pitch per meter of twisted wire is 100 or more, setting the twisting rotation rate to less than 100% makes it easier to obtain particularly good electrical characteristics in the resulting communication cable. When manufacturing the communication cable 1 in this embodiment, it is sufficient to set the twisting rotation rate to less than 100% when making at least one pair of twisted wires 8, preferably two or more pairs, more preferably three or more pairs, and most preferably all four pairs of twisted wires 8. [Examples]

[0025] (1) Sample preparation (1.1) Sample 1 (Example) A single wire with an outer diameter of 0.565 mm was used as the conductor, and high-density polyethylene was prepared as the resin for the insulator. This was extruded from the die of an extruder to cover the conductor with the insulator, forming an insulated wire with an outer diameter of 1.025 to 1.075 mm. Subsequently, the two insulated wires were each rotated to the right at 1000 rpm while being twisted together to the left at 1330 rpm to form a twisted wire. The twisting rotation rate in equation (2) is 1000 / 1330 × 100 = 75%. The same process was repeated to form a total of four pairs of twisted wires (blue pair, green pair, orange pair, and brown pair). The number of twisted wires per meter of each pair was approximately 130 for the blue pair, 120 for the green pair, 90 for the orange pair, and 80 for the brown pair. The twist-back ratio in equation (1) for each pair of stranded wires obtained was also 75%.

[0026] Next, a cross-shaped separator was prepared, and four pairs of twisted wires were placed along the separator and twisted to the right to form the cable core. Next, a nonwoven fabric was prepared as a press winding and wound horizontally around the cable core. Furthermore, shielding tape was prepared and wound horizontally around the press winding. Then, polyvinyl chloride was prepared as the resin for the outer sheath, and this was extruded from the die of an extruder to cover the shielding tape with the outer sheath, thereby manufacturing a communication cable with an outer diameter of approximately 7.5 mm.

[0027] (1.2) Sample 2 (Example) A conductor was prepared by twisting seven strands of soft copper wire (strands) with an outer diameter of 0.2 mm to the right. Then, high-density polyethylene was prepared as the insulating resin, and this was extruded from the die of an extruder to coat the conductor with the insulating material, forming an insulated wire with an outer diameter of 1.020 to 1.080 mm. Next, the two insulated wires were each rotated to the left at 1000 rpm, twisting them back together, while simultaneously twisting them to the right to form a paired wire. The twisting rotation rate in equation (2) is 1000 / 1330 × 100 = 75%. The same process was repeated to form a total of four pairs of twisted wires (blue pair, green pair, orange pair, and brown pair). At this time, the twist pitch per meter of each pair of twisted wires was approximately 130 for the blue pair, 120 for the green pair, 90 for the orange pair, and 80 for the brown pair. The twist-back ratio in equation (1) for each pair of stranded wires obtained was also 75%.

[0028] Next, a cross-shaped separator was prepared, and four pairs of twisted wires were placed along the separator and twisted to the left to form the cable core. Next, high-density polyethylene tape (HDPE tape) was prepared as a backing and wound horizontally around the cable core. Furthermore, shielding tape was prepared and wound horizontally around the backing. Then, polyvinyl chloride (PVC) was prepared as the resin for the outer sheath, and this was extruded from the die of an extruder to cover the shielding tape with the outer sheath, thereby manufacturing a communication cable with an outer diameter of approximately 6.6 mm.

[0029] (1.3) Samples 3-5 (Comparative Example) In Sample 2, the stranding direction of the individual wires, the twisting direction of the insulated wires, and the paired twisting direction were as shown in Table 1, and the twisting turn rate (twisting rate) was set to 100%. Otherwise, the communication cables were manufactured in the same way as in Sample 2.

[0030] (2) Electrical characteristics test of the sample Each sample was cut to 200m length, and the return loss (RL) was measured for each stranded wire in each cut section. The measurement results are shown in Table 1.

[0031] [Table 1]

[0032] (3) Summary As shown in Table 1, when the twist-return ratio (twist-return rate) was 75%, as in Sample 2, no spikes occurred in the high-frequency return loss (RL) for all stranded wires, regardless of whether the number of twisted pair pitches was 100 or more or less than 100. Other electrical characteristics were also comparable to those of a single-wire conductor. In contrast, as in Samples 3-5, when the twist-return ratio (twist-return rate) was 100% for stranded wires with a number of twisted pair pitches of 100 or more, spikes occurred on the high-frequency side of the return loss (RL). Furthermore, samples with twist-turn ratios of 70% and 90% were also prepared, similar to Sample 2, and the return loss (RL) was measured for each sample, yielding the same results as Sample 2. [Explanation of symbols]

[0033] 1. Communication cable 2 conductors 4. Insulator 6. Insulated wires 8 stranded wires 9 Cruciform intervention 10 cable cores 20 Pressed Roll 30 Shielding Tape 40 Outer cover

Claims

1. It comprises a pair of stranded wires, each having a conductor made of multiple strands twisted together and an insulator covering it, One of the stranded wires is covered with an insulator of a single color. The other insulated wire of the aforementioned stranded wire is covered with an insulator having a line-shaped color band of the same color as the aforementioned single color. A communication cable in which, when the number of twisted wires for 100 pitches is counted with the aforementioned twisted wires viewed from the front, and the number of color bands in a length range of 100 pitches is divided by the number of color bands, the twist-return rate of the insulated wire, as calculated by the following formula (1), is less than 100%. Twist rate (%) = 100 - value X ... (1)

2. In the communication cable described in claim 1, A communication cable in which the twisting ratio of the insulated wire is 70% or more and 90% or less.

3. In the communication cable according to claim 1 or 2, A communication cable having a twist pitch of 100 or more strands per meter of the aforementioned twisted wire.

4. The process involves preparing two insulated wires, each having a conductor made of multiple strands twisted together and an insulator covering it. The process includes the steps of twisting each of the insulated wires in the opposite direction to the twisting direction of the individual wires, and twisting the two insulated wires together in the same direction as the twisting direction of the individual wires, A communication cable having a twist-return ratio of less than 100%, as calculated by the following formula (2). Twist rotation rate (%) = (Number of twist rotations of each insulated wire) / (Number of twist rotations of the pair of insulated wires) × 100 ... (2)

5. In the method for manufacturing a communication cable according to claim 4, A method for manufacturing a communication cable in which the twisting rotation rate is 70% or more and 90% or less.

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