Communication cable

Abstract

To reduce a transmission impedance, while suppressing an increase of a diameter of a cable itself in the communication cable.SOLUTION: It is a LAN cable (communication cable) 10 that includes multiple conductors 1, multiple insulators 2 that cover each of the multiple conductors 1, a shield layer 5 that covers the multiple insulators 2, and a sheath 6 that covers the shield layer 5. The shield layer 5 includes an inner layer 3 made of a metal tape 3a and an outer layer 4 having a braided layer 4a made of bare wires 4b. The metal tape 3a is wound in a vertical overlay manner to cover the multiple insulators 2. The braided layer 4a is a layer where the braid density is 96% or more, and the bare wires 4b are woven with a braid pitch that is five times or more the braided minimum diameter 4c.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a communication cable such as a LAN cable for railway vehicles, and more particularly to a communication cable with reduced transfer impedance in the frequency range of 0.1 MHz to 100 MHz. [Background technology]

[0002] As an example of a communication cable such as a LAN cable, Patent Document 1 describes a communication cable (shielded cable) having multiple conductors, a shielding layer provided on the outside of the multiple conductors, and a protective layer provided on the outer periphery of the shielding layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 59-104424 Summary of the Invention [Problem to be solved by the invention]

[0004] In the communication cable described in the above Patent Document 1, in order to reduce the transfer impedance, for example, it is effective to increase the cross-sectional area of ​​the shield layer of the communication cable.

[0005] Specifically, if the shielding layer can be made thicker by increasing the diameter of the braided wire or the thickness of the shielding tape, it is easy to reduce the transfer impedance.

[0006] However, if the shielding layer is made thicker, it becomes difficult to reduce the diameter and weight of the communication cable, and there is a concern that this may cause a decrease in the ease of handling of the communication cable.

[0007] An object of the present invention is to provide a communication cable that can reduce the transfer impedance while suppressing an increase in the diameter of the cable itself. [Means for solving the problem]

[0008] The communication cable of the present invention comprises a plurality of conductors, a plurality of insulating layers respectively covering the plurality of conductors, a shielding layer covering the plurality of insulating layers, and a sheath covering the shielding layer. The shielding layer includes an inner layer made of a metallic tape material, and an outer layer provided on the inner layer and having a braided layer made of fine metal wires, the tape material being wrapped around the plurality of conductors in the length direction to cover the plurality of insulating layers, the braided layer being a layer in which the fine metal wires have a braid density of 96% or more and are braided at a braid pitch of 5 times or more the lower braid diameter.

[0009] In one embodiment of the present invention, the braided layer is a layer in which the thin metal wires are braided at a braid pitch that is 10 times or more the diameter of the braid.

[0010] In another aspect of the present invention, the braided layer has a lower braid diameter of 3.0 mm or more and 4.0 mm or less. Effect of the Invention

[0011] According to the present invention, in a communication cable, it is possible to reduce the transfer impedance while suppressing an increase in the diameter of the cable itself. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing an example of a cross-sectional structure of a communication cable according to the present invention. [Diagram 2] 2 is a perspective view showing a metal tape longitudinally wrapped around the communication cable of FIG. 1. FIG. [Diagram 3] FIG. 2 is a data diagram showing shielding conditions of a shielding layer in a pre-evaluation of the communication cable of FIG. 1. [Figure 4] FIG. 4 is an evaluation result diagram showing the results of a pre-evaluation of the communication cable carried out based on the shielding conditions shown in FIG. [Diagram 5]This is a data diagram showing the shield condition of the shield layer in the verification evaluation of the communication cable, which is carried out based on the evaluation result diagram of the preliminary evaluation of the communication cable in FIG. 4. [Figure 6] This is an evaluation result diagram showing the result of the verification evaluation of the communication cable carried out based on the shield condition shown in FIG. 5.

Embodiment for Carrying out the Invention

[0013] Hereinafter, an example of an embodiment of the communication cable of the present invention will be described. The communication cable of this embodiment is, for example, a LAN cable 10 used in a railway vehicle. In the following description, the same or substantially the same components and elements are generally denoted by the same reference numerals.

[0014] <Configuration of LAN Cable> The LAN cable 10 shown in FIGS. 1 and 2 includes a plurality of conductors (wires) 1, a plurality of insulators (insulation layers) 2 that respectively cover the plurality of conductors 1, a shield layer 5 that covers an aggregate 2a of the plurality of insulators 2, and a sheath 6 that covers the shield layer 5. Specifically, each of the plurality of conductors 1 is covered by an insulator 2, and further, the plurality of conductors 1 each covered by an insulator 2 are covered by a shield layer 5. And the shield layer 5 is covered by a sheath 6 which is a protective layer.

[0015] In this embodiment, the case where the LAN cable 10 has four conductors 1 will be described. Therefore, the aggregate 2a is a collection of four insulators 2 each covering one of the four conductors 1, and the shield layer 5 is a layer that covers this collection (aggregate 2a) of the four insulators 2.

[0016] As shown in FIG. 2, in this embodiment, as an example, four insulators 2 (conductors 1) are twisted together, and the aggregate 2a of these four insulators 2 is wrapped by a metal tape 3a described later.

[0017] 1, the shielding layer 5 includes an inner layer 3 made of a metallic tape material (metal tape 3a) and an outer layer 4 provided on the inner layer 3 and having a braided layer 4a made of wires (thin metal wires) 4b. In other words, the shielding layer 5 includes the inner layer 3 formed by winding the metal tape 3a and the outer layer 4 formed outside the inner layer 3 and in which the braided layer 4a is formed of the wires 4b.

[0018] 2, the metal tape 3a in the shielding layer 5 covers the assembly 2a by being wrapped around the four conductors 1 in the length direction L. That is, the metal tape 3a covers the assembly of four insulators 2 by being wrapped around the four conductors 1 in the length direction L.

[0019] Furthermore, the braided layer 4a in the shield layer 5 is a layer in which the braid density of the wires 4b is 96% or more and the wires 4b are braided at a braid pitch 5 times or more the braid diameter 4c shown in FIG.

[0020] <Transfer impedance> In the LAN cable 10, it is required to reduce the transfer impedance mainly in the frequency range of 0.1 MHz or more and 100 MHz or less.

[0021] Reducing this transfer impedance requires optimization of the shielding layer 5 (optimization of the tape winding method, braid density, braid pitch, etc.), but in the low-frequency range, it is considered particularly effective to reduce the conductor resistance of the shielding layer 5.

[0022] It is easy to reduce the transfer impedance if the shield layer 5 can be made thicker by increasing the diameter of the wires 4b in the braided layer 4a or by increasing the thickness of the metal tape 3a, etc. In this case, however, it becomes difficult to reduce the diameter and weight of the LAN cable 10, and it also leads to a decrease in the handleability of the LAN cable 10.

[0023] In this embodiment, a preliminary evaluation and a confirmation evaluation were carried out in order to find shielding conditions that can reduce the transfer impedance while suppressing an increase in the diameter of the LAN cable 10 itself.

[0024] <Preliminary evaluation> As shown in Fig. 3, a pre-evaluation was carried out to confirm the influence of the braiding conditions and the winding conditions of the metal tape 3a on a number of evaluation samples, using the braiding conditions of the shielding layer 5 as parameters. The evaluation results of the pre-evaluation shown in Fig. 3 are shown in Fig. 4.

[0025] In the pre-evaluation, samples A1, B1, C1, D1, E1 and F1 were prepared for evaluation using the braiding conditions for the shielding layer 5 as parameters, namely, wire diameter, number of strands, braid pitch, braid density and winding method of the metal tape 3a, and pre-evaluation was performed on these samples A1, B1, C1, D1, E1 and F1.

[0026] The braid diameter 4c of each of the samples A1, B1, C1, D1, E1 and F1 used in the pre-evaluation is, for example, 3.95 mm.

[0027] The results of the pre-evaluation shown in Fig. 4 are summarized below. One possible way to reduce the conductor resistance of the shielding layer 5 is to increase the volume of the shielding layer 5 by increasing the volume of the metal tape 3a. Therefore, in sample D1, the lap width of the metal tape 3a was increased to make the layer of the metal tape 3a thicker. However, because the length of the metal tape 3a is increased, the resistance increases due to the skin effect in the high frequency range, resulting in an increase in transfer impedance (it is believed that the impact of the increase in resistance due to the skin effect is greater than the effect of the increase in the volume of the metal part).

[0028] Furthermore, since the metal tape 3a itself is very thin, the effect of reducing the transfer impedance due to the thickness of the metal tape 3a is considered to be extremely small even on the low frequency side (samples A1, B1, C1, D1).

[0029] Because the wrap width of the metal tape 3a affects the transfer impedance due to the skin effect, the winding method of the metal tape 3a was changed from wrap winding to vertical winding (samples E1 and F1).

[0030] As a result, a reduction in the transfer impedance was confirmed, especially at frequencies above 30 MHz. In addition, when the evaluation results of Sample A1 and Sample E1 were compared, it was confirmed that Sample E1 had a larger tolerance in the frequency range above 30 MHz by winding the metal tape 3a vertically.

[0031] From the above, it was confirmed that winding the metal tape 3a vertically (samples E1 and F1) was effective in reducing the transfer impedance at 30 MHz or higher.

[0032] Furthermore, if the metal tape 3a is wound vertically, it is considered that increasing the diameter of the wires 4b is also an effective means for reducing the conductor resistance of the shield layer 5.

[0033] In addition, in the low frequency range of 0.1 MHz, by increasing the diameter of the wires 4b as a means of reducing the conductor resistance based on the braiding conditions and setting the braid density to 96% or more, results were obtained that satisfied the target value of the transfer impedance (sample F1).

[0034] According to the braiding conditions of sample F1, the braid diameter 4c is 3.95 mm, the braid pitch is 20 mm, and the metal tape 3a is wound vertically. Also, 20 mm / 3.95 mm=5.06. In addition, a possible prescription for reducing the conductor resistance of the shield layer 5 is to increase the braid pitch.

[0035] It is believed that by increasing the braid pitch, it is possible to prevent the diameter of the LAN cable 10 from increasing without increasing the thickness of the shield layer 5, and to reduce the transfer impedance.

[0036] <Confirmation evaluation> Based on the results of the preliminary evaluation described above, a confirmation evaluation was carried out to confirm the influence of the braiding conditions and the winding conditions of the metal tape 3a on two types of samples, using the braiding conditions of the shielding layer 5 as parameters, as shown in Fig. 5. The results of the confirmation evaluation shown in Fig. 5 are shown in Fig. 6.

[0037] In the confirmation evaluation, similar to the preliminary evaluation, the braiding conditions in the shielding layer 5 were set as parameters, namely, wire diameter, number of strands, braid pitch, braid density, and winding method of the metal tape 3a. A sample before improvement and a sample after improvement (countermeasure proposal) were prepared, and a confirmation evaluation was performed on these two types of samples.

[0038] The braid diameter 4c of the unimproved sample and the improved (measures proposed) sample used in the confirmation evaluation is, for example, 3.71 mm.

[0039] The results of the confirmation evaluation shown in Figure 5 are summarized below. In order to avoid thickening of the wires 4b of the shield layer 5, confirmation evaluation was attempted by enlarging the braid pitch. As a result, as shown in the data of the sample after improvement (measure proposal), it was found that it was effective to wind the metal tape 3a vertically and set the braid pitch to 10 times or more the lower braid diameter 4c.

[0040] Specifically, according to the braiding conditions of the improved sample (measures proposal), the braided diameter 4c is 3.71 mm, the braid pitch is 40 mm, the braid density is 96% or more, and the metal tape 3a is wound vertically. Also, 40 mm / 3.71 mm=10.78.

[0041] For this reason, it is effective to combine winding the metal tape 3a vertically, setting the braid density at 96% or more, and setting the braid pitch at 10 times or more the lower braid diameter 4c.

[0042] As a result, in the frequency range of 0.10 MHz to 100 MHz, the transfer impedance of the shield layer 5 of the LAN cable 10 can be suppressed to a target value of 10 mΩ / m or less.

[0043] That is, in the LAN cable 10, the transfer impedance can be reduced while preventing the cable itself from becoming thicker.

[0044] Furthermore, since the cable itself can be prevented from becoming thicker, the ease of handling of the LAN cable 10 can be prevented from decreasing.

[0045] In addition, if the lower braid diameter 4c is 3.95 mm, as in the case of the pre-evaluation sample F1, by winding the metal tape 3a vertically, setting the braid density to 96% or more, and setting the braid pitch to 5 times or more the lower braid diameter 4c, the transfer impedance of the shielding layer 5 can be kept to 10 mΩ / m or less over the entire frequency range from 0.10 MHz to 100 MHz.

[0046] In addition, from the above, when the metal tape 3a is wound vertically, the braid density is 96% or more, and the braid pitch is 5 times or more the lower braid diameter 4c, it is effective to set the lower braid diameter 4c to 3.0 mm or more and 4.0 mm or less.

[0047] 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, in the above-described embodiment, the communication cable is a LAN cable 10 used in a railway vehicle, but the communication cable may be a LAN cable used for something other than a railway vehicle, or may be a communication cable other than a LAN cable. [Explanation of symbols]

[0048] 1 Conductor (wire) 2. Insulator (insulating layer) 2a Aggregate 3 Inner layer 3a Metal tape (tape material) 4 Outer layer 4a braided layer 4b Element wire (metal thin wire) 4c Braid lower diameter 5 Shielding Layer 6 Sheath 10 LAN cable (communication cable) A1, B1, C1, D1, E1, F1 Sample L Length direction

Claims

1. A plurality of conductors; A plurality of insulating layers respectively covering the plurality of conductive wires; a shield layer covering the insulating layers; A sheath that covers the shielding layer; A communication cable having The shield layer includes an inner layer made of a metallic tape material, and an outer layer provided on the inner layer and having a braided layer made of thin metallic wires, The tape material is wrapped around the plurality of conductors in a longitudinal direction to cover the plurality of insulating layers, The braided layer is a layer in which the thin metal wires have a braid density of 96% or more and are braided at a braid pitch of 5 times or more the lower braid diameter.

2. 2. The communication cable according to claim 1, The braided layer is a layer in which the thin metal wires are braided at a braid pitch that is 10 times or more the diameter of the braid.

3. 3. The communication cable according to claim 1, A communication cable, wherein the braided layer has a bottom braid diameter of 3.0 mm or more and 4.0 mm or less.

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