Method for manufacturing multi-pair transmission cable

Abstract

To provide a multi-pair transmission cable configured to prevent or reduce deterioration of transmission characteristics.SOLUTION: A method for manufacturing a multi-pair transmission cables includes: a first twisting step of forming a pair of twisted line by twisting a pair of electric wires together in a first direction; and a second twisting step of forming a cable aggregate by twisting a plurality of the pair of twisted lines together in a second direction opposite to the first direction. In the second twisting step, the plurality of the pairs of twisted lines are twisted together in the second direction while adding retwisting.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a multi-pair transmission cable. [Background technology]

[0002] A multi-pair transmission cable is known that includes multiple twisted pairs and a sheath that covers the twisted pairs (Patent Document 1). Each twisted pair includes a pair of twisted electric wires, and is generally called a "twisted pair cable." In this specification, multiple twisted pairs may be collectively referred to as a "cable assembly." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-25765 Summary of the Invention [Problem to be solved by the invention]

[0004] When multiple twisted pairs are twisted together to form a cable assembly, each of the twisted pairs may be twisted and rotated in the opposite direction to the twisting direction while twisting the multiple twisted pairs together, that is, so-called "twist-back" may be added. By twisting the multiple twisted pairs together while twisting them back, distortion of each twisted pair is prevented. As a result, the attenuation of the multi-pair transmission cable can be stabilized.

[0005] On the other hand, if the twisting is performed as described above when forming the cable assembly, there is a risk that the twist of each twisted pair wire will open up. More specifically, there is a risk that the twist pitch of each twisted pair wire (the twist pitch of a pair of electric wires) will be stretched from the initial twist. Furthermore, if the twist pitch of the twisted pairs constituting the cable assembly is stretched, there is a risk that the transmission characteristics of the multi-pair transmission cable will deteriorate. For example, there is a risk that crosstalk will increase.

[0006] The inventors of the present invention inspected a multi-pair transmission cable whose transmission characteristics did not satisfy the standard values, and obtained the results shown in Table 1. In this inspection, the open twist (stretch of twist pitch) of each twisted pair was inspected for a cable assembly of 4-pair LAN (Local Area Network) cables whose transmission characteristics did not satisfy the Category 5e (Cat.5e) standard values.

[0007] Specifically, the twist pitch of each of the four twisted pairs (No. 1 to No. 4) constituting the cable assembly was measured at three different points (points a, b, and c) and the average value (mm) was calculated. Furthermore, the ratio of the calculated average value to the design value (mm) (average value / design value) was calculated as the elongation rate (%).

[0008] The design values ​​of the twist pitch of each twisted pair (No. 1 to No. 4) are intentionally shifted to prevent crosstalk.

[0009] [Table 1]

[0010] This inspection confirmed that the twist pitch of all the twisted pairs had elongated, and the average elongation rate of the twist pitch of the four twisted pairs exceeded 110%.

[0011] As a result of the above-mentioned tests, the inventors of the present invention have found that in order to prevent or suppress the deterioration of the transmission characteristics of the multi-pair transmission cable, it is important to prevent the twist of the twisted pairs constituting the cable assembly from opening. In other words, it is important to prevent the twist pitch of the twisted pairs constituting the cable assembly from elongating. [Means for solving the problem]

[0012] A method for manufacturing a multi-pair transmission cable according to one embodiment includes a first twisting step of twisting a pair of electric wires in a first direction to form a twisted pair, and a second twisting step of twisting a plurality of the twisted pairs in a second direction opposite to the first direction to form a cable assembly. In the second twisting step, the plurality of the twisted pairs are twisted in the second direction while being twisted back. Effect of the Invention

[0013] According to the present invention, a multi-pair transmission cable in which degradation of transmission characteristics is prevented or suppressed is realized. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of a multi-pair transmission cable according to an embodiment. [Diagram 2] 1A to 1C are process diagrams illustrating a method for manufacturing a multi-pair transmission cable according to an embodiment. [Diagram 3] 1 is a diagram showing measurement results of transmission characteristics of a multi-pair transmission cable according to an embodiment. [Figure 4] FIG. 11 is a cross-sectional view of a multi-pair transmission cable according to another embodiment. [Diagram 5] FIG. 13 is a diagram showing measurement results of transmission characteristics of a multi-pair transmission cable according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all drawings for describing the embodiment, the same or substantially the same configurations and elements are designated by the same reference numerals. In addition, as a rule, once a configuration or element has been described, it will not be described repeatedly.

[0016] <Embodiment 1> <Overview of multi-pair transmission cables> 1 is a cross-sectional view of a multi-pair transmission cable 1A according to the present embodiment. The multi-pair transmission cable 1A has a cable assembly 20 made up of a plurality of twisted pairs 10 that are twisted together. More specifically, the multi-pair transmission cable 1A has a cable assembly 20 made up of four twisted pairs 11, 12, 13, and 14 that are twisted together. In other words, the multi-pair transmission cable 1A is a four-pair transmission cable (four-pair LAN cable).

[0017] Around the cable assembly 20, a separator 30, a shielding tape 41, a shielding braid 42, and a sheath 50 are provided in this order from the radially inner side to the radially outer side.

[0018] <Twisted pair wire> Each twisted pair 10 is a twisted pair cable having a pair of twisted electric wires 15. Each electric wire 15 is an insulated wire having a central conductor 16 and an insulator 17 that covers the central conductor 16.

[0019] In each twisted pair 10, a pair of electric wires 15 are twisted together in a first direction. From another perspective, each twisted pair 10 is composed of a pair of electric wires 15 twisted together in the first direction.

[0020] Each pair of electric wires 15 shown in Fig. 1 is twisted counterclockwise in the cross section shown in Fig. 1. In the following description, the twisting direction (first direction / left direction) of a pair of electric wires 15 in each twisted pair wire 10 may be referred to as the "pair twisting direction."

[0021] Although simplified in Fig. 1, the central conductor 16 is formed of a plurality of copper wires, and the insulator 17 is formed of polyethylene.

[0022] <Cable assembly> The cable assembly 20 is a bundle of four twisted pairs 11, 12, 13, and 14. The four twisted pairs 11, 12, 13, and 14 constituting the cable assembly 20 are twisted together in a second direction that is opposite to the pair twisting direction.

[0023] That is, the four twisted wire pairs 11, 12, 13, and 14 shown in Fig. 1 are twisted clockwise in the cross section shown in Fig. 1. In the following description, the twist direction (second direction / rightward) of the four twisted wire pairs 11, 12, 13, and 14 in the cable assembly 20 may be referred to as the "collective twist direction."

[0024] In this way, in the multi-pair transmission cable 1A according to the present embodiment, the pair twisting direction and the group twisting direction are opposite to each other. More specifically, the four twisted pairs 11, 12, 13, and 14 constituting the cable assembly 20 are right-twisted, while the pair of electric wires 15 constituting each of the twisted pairs 11, 12, 13, and 14 are left-twisted.

[0025] <separator> The separator 30 is made of polyethylene and covers the cable assembly 20. In other words, the separator 30 is a covering layer that holds together the four twisted wire pairs 11, 12, 13, and 14.

[0026] <Shield layer> As described above, the shielding tape 41 and the shielding braid 42 are provided around the cable assembly 20. The shielding tape 41 is a PET (Poly Ethylene Terephthalate) tape with a metal such as aluminum vapor-deposited on its surface. From another perspective, the shielding tape 41 is a laminate tape in which a metal film is laminated on one surface of a PET film.

[0027] The shielding tape 41 is wound around the separator 30 to cover the separator 30. More specifically, the shielding tape 41 is wound longitudinally around the outer periphery of the separator 30. However, the shielding tape 41 may be wound in an overlapping manner with a predetermined lap width.

[0028] The shielding braid 42 is formed in a cylindrical (sleeve-like, tubular) shape using a conductive wire such as a copper wire or an aluminum wire, or a resin thread covered with a metal film. The shielding braid 42 is placed over the shielding tape 41 to cover the shielding tape 41.

[0029] As a result, a double-layered shielding layer 40 is formed by the shielding tape 41 and the shielding braid 42. However, the shielding layer 40 may be formed by either the shielding tape 41 or the shielding braid 42. In other words, the shielding layer 40 may be a single layer or multiple layers.

[0030] <Sheath> The sheath 50 is made of polyethylene and forms the outermost layer of the multi-pair transmission cable 1 A. From another perspective, the cable assembly 20 is covered by the sheath 50, and the separator 30 and the shield layer 40 are interposed between the cable assembly 20 and the sheath 50.

[0031] <Manufacturing method> Next, an example of a method for manufacturing the multi-pair transmission cable 1A having the above configuration will be described. Fig. 2 is a process chart showing a method for manufacturing the multi-pair transmission cable 1A.

[0032] The first twisting step (STEP 1) shown in Fig. 2 is a step of forming the twisted pair wire 10 shown in Fig. 1. In the first twisting step, a pair of electric wires 15 is twisted together in a first direction at a predetermined pitch. In other words, the pair of electric wires 15 is left-twisted at a predetermined pitch.

[0033] The second twisting step (STEP 2) shown in Fig. 2 is a step for forming the cable assembly 20 shown in Fig. 1. In the second twisting step, four twisted pairs 10 formed in the first twisting step are prepared. That is, twisted pairs 11, 12, 13, and 14 shown in Fig. 1 are prepared.

[0034] Next, the twisted pairs 11, 12, 13, and 14 are twisted together in a second direction at a predetermined pitch using a twisting machine. In other words, the twisted pairs 11, 12, 13, and 14 are right-twisted at a predetermined pitch.

[0035] However, in the second twisting step, twisted pairs 11, 12, 13, and 14 are twisted together with a twist rate of 100%. Specifically, while a twisting machine that twists four twisted pairs 11, 12, 13, and 14 makes one rotation, the bobbins that pay out each of twisted pairs 11, 12, 13, and 14 are rotated one rotation in the direction opposite to the rotation direction of the twisting machine.

[0036] If the twisting direction (collective twisting direction) in the second twisting step is the same as the twisting direction (pair twisting direction) in the first twisting step, a force (twist) in the opposite direction to the pair twisting direction will be applied to twisted pairs 11, 12, 13, and 14, which may cause the twist to open.

[0037] However, the twisting direction (collective twisting direction) in the second twisting step in this embodiment is opposite to the twisting direction (pair twisting direction) in the first twisting step. Therefore, even if the twist is turned back in the second twisting step, no force (twist) in the opposite direction to the pair twisting direction is applied to the twisted pairs 11, 12, 13, and 14. Therefore, there is no risk of the twist of the twisted pairs 11, 12, 13, and 14 opening in the second twisting step. In other words, there is no risk of the twist pitch of the twisted pairs 11, 12, 13, and 14 extending in the second twisting step.

[0038] The separator covering step (STEP 3) shown in Fig. 2 is a step of forming the separator 30 shown in Fig. 1 around the cable assembly 20 shown in Fig. 1. In the separator covering step, a molten resin material is extruded around the cable assembly 20 to form a resin layer that covers the cable assembly 20.

[0039] The shielding layer forming step (STEP 4) shown in Fig. 2 is a step of forming the shielding layer 40 shown in Fig. 1. In the shielding layer forming step, a shielding tape 41 is longitudinally wrapped around the separator 30 covering the cable assembly 20. Then, a shielding braid 42 is placed over the shielding tape 41.

[0040] The covering step (STEP 5) shown in Fig. 2 is a step of forming the sheath 50 shown in Fig. 1. In the covering step, a molten resin material is extruded around the shielding layer 40 to form a resin layer that covers the shielding layer 40. In other words, the cable assembly 20 is extrusion covered via the separator 30 and the shielding layer 40. As described above, the resin material used in this embodiment is polyethylene.

[0041] The present inventors measured the transmission characteristics of the multi-pair transmission cable 1A according to this embodiment, and obtained the measurement results shown in Fig. 3. In this measurement, the multi-pair transmission cable 1A according to this embodiment and another multi-pair transmission cable as a comparative example were prepared, and the near-end crosstalk attenuation of both was measured.

[0042] The multi-pair transmission cable prepared as a comparative example is a multi-pair transmission cable having the same or substantially the same configuration as the multi-pair transmission cable 1A according to the present embodiment, except that the group twist direction and the pair twist direction are the same.

[0043] From another perspective, the multi-pair transmission cable prepared as a comparative example is a multi-pair transmission cable manufactured by changing the twisting direction (collective twisting direction) of the twisted pairs in the second twisting process (STEP 2) shown in Figure 2 to the first direction.

[0044] The measurement device used was the "Vega 2004 DT" manufactured by AESA Cortaillod, Inc. The measurement method used was in accordance with the IEC 61935-1 standard.

[0045] As a result of the measurements, the near-end crosstalk attenuation of the multi-pair transmission cable 1A in this embodiment did not fall below the standard value of Category 5e (Cat.5e), but the near-end crosstalk attenuation of the multi-pair transmission cable prepared as a comparison example fell below the standard value of Category 5e (Cat.5e) in some bands.

[0046] Furthermore, the inventors conducted the following tests to confirm that the manufacturing method according to the present embodiment can prevent elongation of the twist pitch of the twisted pair wire, and obtained the results shown in Table 2.

[0047] The test subject for this test was a cable assembly manufactured as follows: First, the first twisting process (STEP 1) shown in Figure 2 was carried out to form four twisted pairs (No. 1 to No. 4). Note that the twisting direction of each twisted pair was the same (first direction), but the design values ​​of the twist pitch of each twisted pair were intentionally shifted to prevent crosstalk.

[0048] Next, the second twisting process (STEP 2) shown in Figure 2 was carried out, and the four twisted pairs (No. 1 to No. 4) were twisted together in the second direction with a twist rate of 100% to form a cable assembly.

[0049] Then, for each of the four twisted pairs (No.1 to No.4) that make up the cable assembly, the twist pitch was measured at two different points (points a and b) and the average value (mm) was calculated. Furthermore, the ratio of the calculated average value to the design value (mm) (average value / design value) was calculated as the elongation rate (%).

[0050] [Table 2]

[0051] In this inspection, the average elongation of the twist pitch of the four twisted pairs (No. 1 to No. 4) was below 105%.

[0052] <Embodiment 2> 4 is a cross-sectional view of a multi-pair transmission cable 1B according to the present embodiment. The multi-pair transmission cable 1B has the same or substantially the same structure as the multi-pair transmission cable 1A according to the first embodiment.

[0053] More specifically, the multi-pair transmission cable 1B according to the present embodiment has a cable assembly 20 made up of four twisted pairs 11, 12, 13, and 14. Furthermore, a separator 30, a shielding tape 41, a shielding braid 42, and a sheath 50 are provided around the cable assembly 20 in this order from the radially inner side to the radially outer side.

[0054] Moreover, the multi-pair transmission cable 1B according to the present embodiment is manufactured by the same or substantially the same manufacturing method as the multi-pair transmission cable 1A according to embodiment 1. More specifically, the multi-pair transmission cable 1B according to the present embodiment is manufactured by a manufacturing method including the steps shown in Fig. 2. The details of each step shown in Fig. 2 have already been described.

[0055] On the other hand, the multi-pair transmission cable 1B according to the present embodiment differs from the multi-pair transmission cable 1A according to the first embodiment in the following points.

[0056] In the multi-pair transmission cable 1B according to the present embodiment, the thickness of the insulator 17 is different in each twisted pair wire 10. As described above, each twisted pair wire 10 has a pair of electric wires 15, and each electric wire 15 has a central conductor 16 and an insulator 17.

[0057] In the multi-pair transmission cable 1B, the thicknesses of the insulators 17 of the electric wires 15 constituting each twisted pair 10 are different. Specifically, the thickness (t1) of the insulator 17 of the electric wires 15 constituting the twisted pair 11 is 0.259 mm, and the thickness (t2) of the insulator 17 of the electric wires 15 constituting the twisted pair 12 is 0.229 mm. In addition, the thickness (t4) of the insulator 17 of the electric wires 15 constituting the twisted pair 14 is 0.229 mm, and the thickness (t3) of the insulator 17 of the electric wires 15 constituting the twisted pair 13 is 0.235 mm.

[0058] From another perspective, the thicknesses (t2, t4) of the insulators 17 of the electric wires 15 that make up the twisted pair 12 and the insulators 17 of the electric wires 15 that make up the twisted pair 14 are approximately 88.5% of the thickness (t1) of the insulators 17 of the electric wires 15 that make up the twisted pair 11.

[0059] Moreover, the thickness (t3) of the insulator 17 of the electric wire 15 constituting the twisted pair 13 is about 90.8% of the thickness (t1) of the insulator 17 of the electric wire 15 constituting the twisted pair 11. In the multi-pair transmission cable 1A, the insulators 17 of the electric wires 15 in all the twisted pairs 10 have the same thickness (0.238 mm).

[0060] The present inventors measured the transmission characteristics of the multi-pair transmission cable 1B according to this embodiment under the same conditions and method as in embodiment 1, and obtained the measurement results shown in Fig. 5. As a result of the measurement, the near-end crosstalk attenuation of the multi-pair transmission cable 1B according to this embodiment did not fall below the standard value of Category 5 (Cat. 5). For comparison, the measurement results of the multi-pair transmission cable 1A are also shown in Fig. 5.

[0061] The use of the multi-pair transmission cables 1A, 1B is not particularly limited. The multi-pair transmission cables 1A, 1B are arranged, for example, in railroad cars and automobiles. The multi-pair transmission cables arranged in railroad cars and automobiles vibrate as the railroad cars and automobiles move. For this reason, when manufacturing a multi-pair transmission cable to be arranged in railroad cars and automobiles, it is desirable to prevent distortion from remaining in the twisted pairs. In other words, it is desirable to twist the twisted pairs together by adding twisting.

[0062] Therefore, the multi-pair transmission cables 1A and 1B in which the elongation of the twist pitch caused by twisting is prevented or suppressed are particularly suitable for use in railway cars and automobiles.

[0063] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the first direction (twist direction) is not limited to the left direction, and the second direction (group twist direction) is not limited to the right direction. In other words, the pair twist direction in the above-described embodiment can be changed to the right direction, and the group twist direction can be changed to the left direction.

[0064] The twist-back ratio in the second twisting step shown in Fig. 2 is not limited to 100% and may be less than 100%. However, the higher the twist-back ratio, the easier it is for the twisted wire pair 10 to open, but the less likely distortion of the twisted wire pair 10 occurs.

[0065] Therefore, it is preferable that the twist back ratio in the second twisting step is 50% or more and 100% or less. From another perspective, by setting the twist back ratio to 50% or more and 100% or less and making the collective twist direction opposite to the pair twist direction, it is possible to prevent distortion of twisted wire pair 10 while preventing the twist of twisted wire pair 10 from opening.

[0066] 1 and 4 may include an insert (e.g., a cross insert). From another perspective, in the second twisting step (STEP 2) shown in FIG. 2, the twisted pairs 11, 12, 13, and 14 may be twisted together with the insert.

[0067] A shielding layer may be provided around each twisted pair 10 shown in Figures 1 and 4. In this case, the shielding layer 40 shown in Figures 1 and 4 may be omitted or may be left in place.

[0068] The number of twisted pairs 10 included in the cable assembly 20 can be increased or decreased as appropriate. The materials of the central conductor 16 and the insulator 17 of the electric wire 15 can be changed as appropriate. The material of the sheath 50 can also be changed as appropriate. [Explanation of symbols]

[0069] Reference Signs List 1A, 1B...multi-pair transmission cable, 10, 11, 12, 13, 14...twisted pair wire, 15...electric wire, 16...center conductor, 17...insulator, 20...cable assembly, 30...separator, 40...shield layer, 41...shield tape, 42...shield braid, 50...sheath

Claims

1. A method for manufacturing a multi-pair transmission cable having a cable assembly including a plurality of twisted pairs, comprising: a first twisting step of twisting a pair of electric wires in a first direction to form the twisted pair; a second twisting step of twisting a plurality of the twisted pairs in a second direction opposite to the first direction to form the cable assembly; In the second twisting step, a plurality of the twisted pairs are twisted together in the second direction while being twisted back.

2. The method for manufacturing a multi-pair transmission cable according to claim 1 , wherein a twist back rate in the second twisting step is 50% or more and 100% or less.

3. The method for manufacturing a multi-pair transmission cable according to claim 1 , further comprising a shield layer forming step of covering the cable assembly with at least one of a shield tape and a shield braid.

4. The method for manufacturing a multi-pair transmission cable according to claim 1 , wherein in the second twisting step, four of the twisted pairs are twisted together in the second direction to form the cable assembly.

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