Communication cable

Abstract

The invention provides a communication cable which suppresses the diameter increase of the cable itself and reduces the transmission impedance. A LAN cable (communication cable) (10) is provided with a plurality of conductors (1), a plurality of insulators (2) respectively covering the plurality of conductors (1), a shield layer (5) covering the plurality of insulators (2), and a sheath (6) covering the shield layer (5). The shield layer (5) includes an inner layer (3) comprising a metal tape (3a) and an outer layer (4) having a braid layer (4a) comprising a bare wire (4b). The metal tape (3a) is wound in a longitudinal additional winding manner and covers the plurality of insulators (2). The braided layer (4a) is a layer in which bare wires (4b) are braided at a braiding pitch that is at least five times the lower braiding diameter (4c) and has a braiding density of at least 96%.

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 having a reduced transfer impedance in a frequency range of 0.1 MHz to 100 MHz. Background Art

[0002] As an example of a communication cable such as a LAN cable, Patent Document 1 describes a communication cable (shielded cable) having a plurality of conductive wires, a shielding layer provided outside the plurality of conductive wires, and a protective layer provided around the shielding layer.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Utility Model Publication No. 59-104424 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In order to reduce the transmission impedance in the communication cable described in Patent Document 1, for example, it is effective to increase the cross-sectional area of ​​the shield layer included in the communication cable.

[0008] Specifically, if the shield layer can be made thicker by increasing the diameter of the braided bare wire or increasing the thickness of the shield tape, the transfer impedance can be easily reduced.

[0009] However, if the shield layer is thickened, it becomes difficult to reduce the diameter and weight of the communication cable, and there is a concern that the operability of the communication cable may be reduced.

[0010] An object of the present invention is to provide a communication cable capable of suppressing the increase in diameter of the cable itself and reducing the transmission impedance.

[0011] Methods for solving problems

[0012] 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 comprises an inner layer composed of a metallic tape material and an outer layer provided on the inner layer and having a braided layer composed of metal fine wires; the tape material covers the plurality of insulating layers by additional longitudinal winding along the length direction of the plurality of conductors, and the braided layer is a layer formed by braiding the metal fine wires with a braiding density of 96% or more and a braiding pitch of 5 times or more of the braided lower diameter.

[0013] In one embodiment of the present invention, the braided layer is a layer formed by braiding the metal thin wires at a braiding pitch that is 10 times or more of a braided lower diameter.

[0014] In another aspect of the present invention, a braided lower diameter of the braided layer is greater than or equal to 3.0 mm and less than or equal to 4.0 mm.

[0015] Effects of the Invention

[0016] According to the present invention, in the communication cable, it is possible to suppress the increase in diameter of the cable itself and reduce the transmission impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional view showing an example of the cross-sectional structure of the communication cable of the present invention.

[0018] Figure 2 Yes means Figure 1 A perspective view of the longitudinal additional winding of the metal tape in the communication cable.

[0019] Figure 3 Yes means Figure 1 Data diagram of the shielding condition of the shielding layer in the preliminary evaluation of the communication cable.

[0020] Figure 4 Is based on Figure 3 The evaluation result diagram shows the preliminary evaluation results of the communication cable implemented under the shielding conditions shown.

[0021] Figure 5 Is based on Figure 4 The evaluation result diagram of the preliminary evaluation of the communication cable is a data diagram of the shielding conditions of the shielding layer in the confirmation evaluation of the communication cable implemented.

[0022] Figure 6 Is based on Figure 5 The evaluation result diagram shows the confirmation evaluation results of the communication cable implemented under the shielding conditions shown.

[0023] Description of Reference Numerals

[0024] 1: conductor (wire), 2: insulator (insulating layer), 2a: assembly, 3: inner layer, 3a: metal tape (tape material), 4: outer layer, 4a: braided layer, 4b: bare wire (metal thin wire), 4c: braided lower diameter, 5: shielding layer, 6: sheath, 10: LAN cable (communication cable), A1, B1, C1, D1, E1, F1: samples, L: length direction. DETAILED DESCRIPTION

[0025] 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 for railway vehicles. It should be noted that in the following description, the same or substantially the same components, elements, etc. are, in principle, denoted by the same reference numerals.

[0026] <Configuration of LAN Cable>

[0027] Figure 1 and Figure 2 As shown in Figure 2 , the LAN cable 10 has a plurality of conductors (wires) 1, a plurality of insulators (insulation layers) 2 that respectively cover the plurality of conductors 1, a shielding layer 5 that covers the aggregate 2a of the plurality of insulators 2, and a sheath 6 that covers the shielding layer 5. Specifically, the plurality of conductors 1 are respectively covered by the insulators 2, and further, the plurality of conductors 1 covered by the insulators 2 are covered by the shielding layer 5. And the shielding layer 5 is covered by the sheath 6 as a protective layer.

[0028] In this embodiment, the case where the LAN cable 10 has 4 conductors 1 will be described. Therefore, the aggregate 2a is an aggregate of 4 insulators 2 that respectively cover 4 conductors 1, and the shielding layer 5 is a layer that covers this aggregate (aggregate 2a) of 4 insulators 2.

[0029] As Figure 2 shown, in this embodiment, as an example, 4 insulators 2 (conductors 1) are stranded, and the aggregate 2a of these 4 insulators 2 is wrapped by a metal tape 3a described later.

[0030] As Figure 1 shown, 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 bare wires (metal fine wires) 4b. That is, the shielding layer 5 includes an inner layer 3 formed by winding the metal tape 3a and an outer layer 4 formed on the outside of the inner layer 3 and formed by braiding the bare wires 4b to form the braided layer 4a.

[0031] In addition, as Figure 2 shown, the metal tape 3a in the shielding layer 5 covers the aggregate 2a by longitudinal additional winding along the length direction L of the 4 conductors 1. That is, the metal tape 3a covers the aggregate of 4 insulators 2 by longitudinal additional winding.

[0032] Furthermore, the braided layer 4a in the shielding layer 5 is a layer formed by braiding the bare wires 4b with a braiding density of 96% or more and a braiding pitch that is 5 times or more the braiding lower diameter 4c shown in Figure 1 Figure 1 .

[0033] <Regarding Transfer Impedance>

[0034] The LAN cable 10 is required to reduce the transfer impedance mainly in the frequency range of 0.1 MHz to 100 MHz.

[0035] In order to reduce the transfer impedance, the shield layer 5 needs to be optimized (optimization of the tape winding method, braiding density / braiding pitch, etc.), and in the low frequency region, it is considered to be particularly effective to reduce the conductor resistance of the shield layer 5.

[0036] It should be noted that if the shielding layer 5 can be made thicker by increasing the diameter of the bare wire 4b in the braided layer 4a or by increasing the thickness of the metal tape 3a, the transmission impedance can be easily reduced. However, in this case, it becomes difficult to reduce the diameter and weight of the LAN cable 10, and the operability of the LAN cable 10 is also reduced.

[0037] In the present embodiment, preliminary evaluation and confirmation evaluation were performed in order to find shielding conditions that can reduce the transfer impedance while suppressing the increase in the diameter of the LAN cable 10 itself.

[0038] <Preliminary evaluation>

[0039] like Figure 3 As shown, the braiding conditions of the shield layer 5 were used as parameters, and a preliminary evaluation was carried out to confirm the influence of the braiding conditions and the winding conditions of the metal tape 3a on a plurality of evaluation samples. Figure 3 The evaluation results of the preliminary evaluation shown are shown in Figure 4 .

[0040] In the preliminary evaluation, the bare wire diameter, the number of strands, the number of spindles, the weaving pitch, the weaving density and the winding method of the metal tape 3a are used as parameters as the weaving conditions of the shielding layer 5, and samples A1, B1, C1, D1, E1 and F1 for evaluation are prepared respectively, and preliminary evaluation is carried out on these samples A1, B1, C1, D1, E1 and F1.

[0041] It should be noted that, as an example, the braided lower diameter 4c of the samples A1, B1, C1, D1, E1, and F1 used for the preliminary evaluation is 3.95 mm.

[0042] The following summary Figure 4 The evaluation results of the preliminary evaluation shown in the figure. As a method of reducing the conductor resistance of the shield layer 5, in order to increase the volume of the shield layer 5, it is also possible to increase the volume of the metal tape 3a. Therefore, in sample D1, the width of the overlapping winding of the metal tape 3a is widened, and the layer of the metal tape 3a is thickened. However, since the tape length of the metal tape 3a is increased, the resistance becomes higher due to the skin effect in the high-frequency region, resulting in an increase in the transfer impedance (it is believed that the influence of the increase in resistance due to the skin effect is greater than the effect caused by the increase in the volume of the metal part).

[0043] In addition, since the thickness of the metal strip 3a itself is very thin, it is considered that the effect of reducing the transmission impedance due to the thickness of the metal strip 3a is also extremely small on the low-frequency side (samples A1, B1, C1, and D1).

[0044] Because the overlapping 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 overlapping winding to longitudinal attachment (samples E1 and F1).

[0045] As a result, the effect of reducing the transfer impedance can be confirmed especially above 30 MHz. It should be noted that even when comparing the evaluation results of sample A1 and sample E1, in sample E1, by setting the winding method of the metal strip 3a to be longitudinally attached, it can be confirmed that the margin in the frequency region above 30 MHz is increased.

[0046] From the above, it was confirmed that the longitudinal winding of the metal tape 3 a (samples E1 and F1 ) is effective in reducing the transmission impedance at 30 MHz or higher.

[0047] Furthermore, if the winding method of the metal tape 3 a is longitudinally added, it is considered that increasing the diameter of the bare wire 4 b is also effective as a method of reducing the conductor resistance of the shield layer 5 .

[0048] It should be noted that in the low frequency region of 0.1 MHz, as a method for reducing conductor resistance based on braiding conditions, the bare wire 4b was made thicker and the braiding density was increased to 96% or more, thereby obtaining a result that met the target value of transfer impedance (sample F1).

[0049] It should be noted that according to the braiding conditions of sample F1, the braided lower diameter 4c is 3.95mm, the braiding pitch is 20mm, and the winding method of the metal tape 3a is longitudinal addition. In addition, 20mm / 3.95mm=5.06. In addition, as a method of reducing the conductor resistance of the shielding layer 5, a method of increasing the braiding pitch can also be considered.

[0050] If the braiding pitch is increased, it is considered possible to suppress the increase in diameter of the LAN cable 10 and reduce the transmission impedance without increasing the thickness of the shield layer 5 .

[0051] <Confirmation of evaluation>

[0052] According to the evaluation results of the above-mentioned preliminary evaluation, if Figure 5 As shown, the braiding conditions of the shield layer 5 were used as parameters, and a confirmation evaluation was carried out to confirm the influence of the braiding conditions and the winding conditions of the metal tape 3a on the two samples. Figure 5 The evaluation results of the confirmation evaluation shown are shown in Figure 6 .

[0053] In the confirmation evaluation, as in the preliminary evaluation, the bare wire diameter, the number of strands, the number of spindles, the weaving pitch, the weaving density and the winding method of the metal tape 3a are used as parameters as the weaving conditions of the shielding layer 5, and samples before improvement and samples after improvement (countermeasures) are prepared, and confirmation evaluation is carried out on these two samples.

[0054] In addition, as an example, it was confirmed that the braided lower diameter 4c of the sample before improvement and the sample after improvement (countermeasure proposal) used in the evaluation was 3.71 mm.

[0055] Figure 5 The evaluation results of the confirmation evaluation shown are summarized as follows. In order to avoid the thickening of the bare wire 4b of the shield layer 5, the confirmation evaluation was attempted by increasing the braiding pitch. As shown in the sample data after improvement (countermeasures), it is effective to set the braiding pitch to more than 10 times the braiding lower diameter 4c on the basis of setting the winding method of the metal tape 3a to longitudinal addition.

[0056] Specifically, according to the improved (countermeasure) braiding conditions of the sample, the braiding lower diameter 4c is 3.71 mm, the braiding pitch is 40 mm, the braiding density is 96% or more, and the winding method of the metal belt 3a is longitudinal addition. In addition, 40 mm / 3.71 mm=10.78.

[0057] Therefore, it is effective to combine the winding method of the metal tape 3a to be longitudinally added, the braiding density to be 96% or more, and the braiding pitch to be 10 times or more of the braiding lower diameter 4c.

[0058] 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.

[0059] That is, in the LAN cable 10 , it is possible to reduce the transmission impedance while suppressing the increase in the diameter of the cable itself.

[0060] Furthermore, since the diameter of the cable itself can be suppressed from being increased, a decrease in the operability of the LAN cable 10 can be suppressed.

[0061] It should be noted that, as in the case of sample F1 evaluated in advance, if the braided lower diameter 4c is 3.95 mm, by setting the winding method of the metal tape 3a to be longitudinally added, and setting the braiding density to be greater than 96%, and then setting the braiding pitch to be greater than 5 times the braided lower diameter 4c, the transmission impedance of the shielding layer 5 can be suppressed to less than 10 mΩ / m in the entire region between frequencies of 0.10 MHz and 100 MHz.

[0062] In addition, as described above, when the winding method of the metal belt 3a is set to be longitudinally added and the weaving density is set to be greater than 96%, and the weaving pitch is further set to be greater than 5 times the weaving lower diameter 4c, it is effective to set the weaving lower diameter 4c to be greater than 3.0 mm and less than 4.0 mm.

[0063] The present invention is not limited to the above-mentioned embodiments, and various changes can be made without departing from the scope of the present invention. For example, in the above-mentioned embodiments, the communication cable is a LAN cable 10 used for railway vehicles, but the above-mentioned communication cable can also be a LAN cable used for other than railway vehicles, or a communication cable other than a LAN cable.

Claims

1. A communication cable, comprising: Multiple conductors; A plurality of insulating layers respectively covering the plurality of conductive wires; a shielding layer covering the plurality of insulating layers; as well as a sheath covering the shielding layer, The shielding layer comprises: an inner layer composed of a metallic strip material; as well as an outer layer, which is provided on the inner layer and has a braided layer composed of metal fine wires, The tape material is wrapped around the plurality of insulating layers by additionally winding along the longitudinal direction of the plurality of conductors. The braided layer is a layer formed by braiding the metal thin wires at a braiding density of 96% or more and a braiding pitch of 5 times or more of a braided lower diameter.

2. The communication cable according to claim 1, wherein: The braided layer is a layer formed by braiding the metal fine wires at a braiding pitch that is more than 10 times the braided lower diameter.

3. The communication cable according to claim 1 or 2, wherein: The braided lower diameter of the braided layer is greater than or equal to 3.0 mm and less than or equal to 4.0 mm.

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