LAN cable manufacturing method

Abstract

To provide a LAN cable including a plurality of insulation wires formed using an extruder, and having excellent transmission characteristics, while suppressing variation in thickness of an insulator layer, and a manufacturing method of the LAN cable.SOLUTION: A manufacturing method of a LAN cable includes: a step of coating an outer periphery of a conductor 2 running inside a head of an extruder, with an insulator fused through a mouthpiece 18 attached to the head 17 to produce an insulation wire 20; and a twisting step of twisting a plurality of insulation wires together. A bore diameter of the mouthpiece is 3.4 to 4.5 mm.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a LAN cable. [Background technology]

[0002] It is known that flexible cables (crossover cables, jumper cables, jumper wires) are used to transmit high voltages between railway vehicles. Patent Document 1 (JP 2017-33737 A) describes the use of a material that has a tension member arranged in the center and multiple conductors that are twisted around the tension member without being compressed, as a conductor that constitutes a bending-resistant LAN cable. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-33737 Summary of the Invention [Problem to be solved by the invention]

[0004] The insulated wire that makes up a LAN cable is composed of a conductor and an insulating layer covering the conductor. To reduce the variation in the thickness of the insulating layer and stabilize transmission characteristics, the opening diameter of the base of the extruder that forms the insulated wire is sometimes reduced. However, reducing the size of the base can result in a problem of reduced far-end crosstalk attenuation, a characteristic of LAN cables. The object of the present invention is to provide a LAN cable that reduces the variation in the thickness of the insulating layer and has good transmission characteristics.

[0005] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0006] A brief summary of a representative embodiment of the present invention will be given below.

[0007] One embodiment of the method for manufacturing a LAN cable includes a step of producing an insulated wire by coating the outer circumference of a conductor running inside an extruder head with molten insulation through a nozzle attached to the head, and a twisting step of twisting together multiple insulated wires, wherein the opening diameter of the nozzle is 3.4 to 4.5 mm. [Effects of the Invention]

[0008] According to one embodiment disclosed in the present application, it is possible to provide a LAN cable that has reduced variations in the thickness of the insulating layer and has good transmission characteristics. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a conductor constituting a LAN cable according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing an extruder for producing a LAN cable according to an embodiment of the present invention. [Figure 3] 1 is a cross-sectional view of a LAN cable according to an embodiment of the present invention; [Figure 4] 1 is a graph showing the relationship between far-end crosstalk attenuation and frequency. [Figure 5] 1 is a graph showing the relationship between far-end crosstalk attenuation and frequency. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings. In all drawings for explaining the embodiments, components having the same functions are designated by the same reference numerals, and repeated explanations thereof will be omitted. In the following embodiments, explanations of the same or similar parts will not be repeated unless particularly necessary.

[0011] (Embodiment) When manufacturing an insulated wire composed of a conductor with a diameter of 1.2 to 1.3 mm and an insulating layer covering the outer periphery thereof using an extruder, the opening diameter of the die is set to 3.4 to 4.5 mm.

[0012] <Manufacturing Method of LAN Cable> Hereinafter, with reference to FIGS. 1 to 3, a cross-over cable for railway vehicles as the LAN cable of the present embodiment will be described. FIG. 1 is a cross-sectional view of a conductor constituting the LAN cable of the present embodiment. FIG. 2 is a schematic view showing an extruder for manufacturing the LAN cable of the present embodiment. FIG. 3 is a cross-sectional view showing the LAN cable of the present embodiment. The LAN cable of the present embodiment is a LAN (Local Area Network) cable used as a cross-over cable for railway vehicles provided for transmitting, for example, a high voltage between two mutually connected railway vehicles, and is called a LAN jumper cable or a LAN jumper wire.

[0013] First, a conductor 2 formed by twisting a plurality of copper wires is manufactured. For example, the conductor 2 has a plurality of conducting wires 2a arranged at the center and a plurality of conducting wires 2b twisted and arranged around the conducting wires 2a. For example, one conductor 2 has a bundle of three conducting wires 2a twisted together, and 12 conducting wires 2b are arranged around the bundle of conducting wires, and 18 conducting wires 2b are further arranged around them. The diameter of one conducting wire 2a is, for example, about 0.26 mm, and the diameter of one conducting wire 2b is, for example, about 0.18 mm. The diameter of the conductor 2 manufactured in this way is 1.2 to 1.3 mm. For the conducting wires 2a and 2b, for example, tinned soft copper wires can be used. The conducting wire 2a is not limited to a conductor, and may be, for example, a high-tensile steel wire (for example, a piano wire), a steel wire, or a fiber-reinforced plastic (FRP) wire.

[0014] Next, a plurality of materials for manufacturing an insulating layer covering the conductor 2 are prepared. Examples of these materials include a chlorine-based polymer, a silane solution, and a silane crosslinking catalyst solution.

[0015] Next, an insulated wire 20 is produced using an extruder 10 shown in FIG. 2. As shown in FIG. 2, the extruder 10 includes a cylinder 15, a screw 13 rotatably provided within the cylinder 15, a hopper 12 that supplies material into the cylinder 15, and a head 17. The extruder 10 also includes a neck 16 between the head 17 and the screw 13, and a breaker plate 14 between the neck 16 and the screw 13. The head 17 has a die 18, and the conductor 2 passing through the head 17 is coated with an insulating layer 3 (see FIG. 3) within the head 17, passes through the die 18, and is drawn out from the head 17 as an insulated wire 20. That is, a step of producing the insulated wire 20 is performed in which the outer periphery of the conductor 2 traveling within the head 17 of the extruder 10 is coated with molten insulation through the die 18 attached to the head 17.

[0016] In this process, some or all of the above-mentioned materials are introduced into the cylinder 15 from the hopper 12. Subsequently, the screw 13 is rotated about its axis to knead the materials, while feeding the kneaded material, an insulator, into the head 17 via the breaker plate 14. At the same time, the conductor 2 is fed into the head 17 in a direction intersecting the rotation axis of the screw 13. The kneaded insulator is, for example, an ethylene-propylene rubber copolymer blend. The temperature of the insulator in the cylinder 15 is maintained at, for example, 150 to 200°C. Specifically, the insulator temperature is set to, for example, 180°C. In this manner, while the conductor 2 is inserted through the head 17 of the extruder 10, the insulator (resin) is extruded into the head 17 from the screw 13 side to coat the outer periphery of the conductor 2. This completes the extrusion coating process, forming an insulated wire 20 in which the outer periphery of the conductor 2 is coated with an insulating layer 3 (coating layer) made of the insulator.

[0017] In this extrusion coating process, the insulating layer 3 becomes viscous due to high temperatures, so the thickness of the insulating layer 3 constituting the insulated wire 20 drawn out from the head 17 is determined by the opening diameter of the mouthpiece opening.

[0018] One of the main features of this embodiment is that the diameter of the opening of the base 18 through which the insulated wire 20 passes is 3.4 to 4.5 mm. Here, the diameter of the opening of the base 18 is, for example, 3.45 mm. If the diameter of the opening of the base 18 is, for example, 3.3 mm, undulations will occur in the insulated wire 20 due to the resin pressure during extrusion. This undulation will cause a decrease in the far-end crosstalk attenuation of a LAN cable manufactured using the insulated wire 20, so here the diameter of the opening of the base 18 is set to 3.4 mm or more. Furthermore, if the diameter of the opening of the base 18 is too large, variations will occur in the thickness of the insulating layer 3, so the diameter of the opening is set to 4.5 mm or less.

[0019] Next, the insulated wire 20 drawn out from the extruder 10 is immersed in a water bath for a certain period of time while being moved to cool. That is, after the above process of producing the insulated wire 20 and before the twisting process described below, a process of immersing the insulated wire 20 in water to cool it is performed. Here, to prevent the insulated wire 20 from being compressed due to the contraction stress of the insulating layer 3, the insulated wire 20 is rapidly cooled in water at 25°C or lower rather than slowly cooled in water at about 50°C. However, excessive rapid cooling can reduce the wall thickness deviation of the insulating layer 3. Therefore, to prevent wall thickness deviation of the insulated wire 20, the insulated wire 20 is cooled in water at 15°C or higher. That is, the insulated wire 20 is cooled by immersing it in water at 15 to 25°C. Here, the cooling temperature of the insulated wire 20 is set to 19°C, for example. The finished outer diameter of the cooled insulated wire 20 is approximately 3.2 mm.

[0020] The method for measuring the thickness deviation is as follows: first, a cross-sectional photograph of the insulating layer 3 is taken, and the thickness is measured at five arbitrary locations at an angle of approximately 60°. Of these thicknesses, the minimum and maximum values ​​are identified, and the value calculated by dividing the minimum value by the maximum value multiplied by 100 is the thickness deviation. Since there are four insulated wires 20, all four are measured. If all of the measured thickness deviation values ​​are 85% or higher, the wire passes. If even one of the values ​​is less than 85%, the wire fails.

[0021] Next, as shown in Fig. 3, a LAN cable 1 including a plurality of insulated wires 20 is manufactured. The LAN cable 1 is manufactured by the following process.

[0022] That is, first, a plurality of insulated wires 20 are prepared, each having a conductor 2 coated with an insulating layer 3, which has been manufactured through the extrusion process and cooling process. Here, four insulated wires 20 are prepared. Next, the plurality of insulated wires 20 and a plurality of inclusions 4 are twisted together to form the core of the LAN cable 1. That is, the core of the LAN cable 1 is formed by performing a twisting process in which a plurality of insulated wires 20 are twisted together. Here, for example, four insulated wires 20 and four inclusions 4 are twisted together around one inclusion 4 to form a twisted wire (core).

[0023] Next, tape (aluminum foil-coated tape) 5 is wound around the outer periphery of the core. That is, tape 5 is wound transversely around the extending core.

[0024] Next, the braid 6 is placed on the outer periphery of the tape 5 .

[0025] Next, tape (aluminum foil-coated tape) 7 is wound around the outer periphery of the braid 6. That is, the tape 7 is wound transversely around the extending braid 6.

[0026] Next, the outer periphery of the tape 7 is covered with the inner sheath 8. In this covering step, for example, an extruder is used.

[0027] Next, the pressing tape 9 is wound around the outer periphery of the inner sheath 8. That is, the pressing tape 9 is wound horizontally around the extending inner sheath 8.

[0028] Next, the outer periphery of the pressing tape 9 is covered with the outer sheath 10. In this covering step, for example, an extruder is used.

[0029] The LAN cable 1 of this embodiment is manufactured through the above steps. That is, here, a core is formed by twisting together a plurality of insulated wires, and the core is covered with tape, braid, sheath, etc. to produce the LAN cable.

[0030] The insulated wire 20 transmits a signal of, for example, 1 MHz to 100 MHz. One or more twisted pair wires that transmit differential signals may be used as the insulated wire 20. In this embodiment, two twisted pair wires are used. The inclusion 4 may be made of, for example, glass fiber.

[0031] The tapes 5 and 7 may be made of a resin tape made of a resin such as polyethylene terephthalate (PET) or polypropylene resin with aluminum foil attached. The braid (braided tube) 6 is formed by braiding conductors and is connected to the ground. The braid 6 is, for example, an interwoven braid. The pressing tape 9 may be made of a resin tape made of a resin such as polyethylene terephthalate (PET) or polypropylene resin.

[0032] Materials that can be used for the inner sheath 8 and the outer sheath 10 include, for example, polyvinyl chloride (PVC), polyethylene (PE), ethylene propylene rubber (EP rubber), and non-halogen flame-retardant materials made by blending polyolefin with a non-halogen flame retardant (such as a metal hydroxide).

[0033] (Effects of the embodiment) When producing the insulated wire that forms the core of a LAN cable, it is possible to reduce the opening diameter of the nozzle that forms the extruder that forms the insulated wire, for example to about 3.3 mm, as a comparative example. However, if the opening diameter of the nozzle is small, undulations will occur in the insulated wire 20, which may result in the far-end crosstalk attenuation, one of the transmission characteristics of the LAN cable, being lower than desired. FEC is the amount of crosstalk attenuation between the two insulated wires that make up the LAN cable at the output end of the LAN cable, and if this is small, crosstalk in the LAN cable will become a problem.

[0034] The results of an experiment conducted by the inventors are shown in Figure 4. Figure 4 is a graph showing the relationship between FEXT attenuation and frequency in a LAN cable of a comparative example. The vertical axis of the graph shown in Figure 4 represents FEXT attenuation, and the horizontal axis represents frequency.

[0035] The conditions for the experiment were as follows: piano wire was used for the central inclusion; the conductor diameter was 1.28 mm and was constructed of twisted copper wires; the insulation layer thickness was 0.95 mm; the inclusion (string inclusion) located on the outside of the insulation layer had a diameter of 1.3 mm; the twist pitch of the insulated wire and string inclusion was 18 mm; the braid thickness was 0.45 mm; the inner sheath thickness was 0.8 mm, and the outer sheath thickness was 1.2 mm. The far-end crosstalk attenuation was determined to pass or fail in accordance with the contents of IC61156-1 (Cat5E standard).

[0036] In this experiment, the inventors measured the far-end crosstalk attenuation (see Figure 4) and wall thickness deviation of a comparative LAN cable formed using an extruder with a 3.3 mm nozzle opening diameter. In this experiment, if the far-end crosstalk attenuation graph shown by the solid line in Figure 4 contains any point below the standard value shown by the triangular plot, the cable is judged as failing. As a result of the experiment, as shown in Figure 4, the comparative LAN cable was judged as failing the far-end crosstalk attenuation. The comparative LAN cable also failed the wall thickness deviation.

[0037] In contrast, in the present embodiment, when an insulated wire 20 having a conductor 2 with a diameter of 1.2 to 1.3 mm is produced by the extruder 10 shown in Fig. 2, the opening diameter of the mouthpiece 18 is set to 3.4 to 4.5 mm to prevent undulations from occurring in the insulated wire 20. By setting the opening diameter of the mouthpiece 18 to a relatively large value in this manner, the resin pressure in the extrusion coating process is reduced. This increases the wall thickness deviation of the insulated wire 20, making it possible to produce an insulated wire 20 having a continuous cross section that is close to a perfect circle.

[0038] The results of an experiment conducted by the inventors are shown in Fig. 5. Fig. 5 is a graph showing the relationship between FEXT attenuation and frequency in the LAN cable of this embodiment. The vertical axis of the graph shown in Fig. 5 represents FEXT attenuation, and the horizontal axis represents frequency.

[0039] The conditions for this experiment were the same as those for the experiment (see FIG. 4) for measuring the amount of far-end crosstalk attenuation carried out on the LAN cable of the comparative example described above.

[0040] In the experiment, the inventors measured the far-end crosstalk attenuation (see FIG. 4) and wall thickness deviation of a LAN cable according to this embodiment formed using an extruder with a base opening diameter of 3.45 mm. As shown in FIG. 5, the far-end crosstalk attenuation of the LAN cable according to this embodiment, shown by the solid line, is not below the standard value shown by the triangular plot. In other words, as a result of the experiment, the far-end crosstalk attenuation of the LAN cable according to this embodiment was judged to be acceptable. The wall thickness deviation of the LAN cable according to this embodiment was also acceptable.

[0041] As described above, according to this embodiment, crosstalk in the LAN cable can be reduced, thereby stabilizing the transmission characteristics of the LAN cable. In other words, it is possible to provide a LAN cable with good transmission characteristics by suppressing variations in the thickness of the insulating layer.

[0042] 2, the insulated wire 20 drawn out from the extruder 10 is cooled at a temperature of 15 to 25°C. This prevents the insulated wire 20 from being compressed by the contraction stress of the insulating layer 3, and also prevents variations in the thickness of the insulating layer 3 due to excessive rapid cooling. Preventing uneven thickness of the insulated wire 20 in this way reduces crosstalk in the LAN cable 1, thereby improving the performance of the LAN cable.

[0043] The invention made by the present inventors has been specifically described above based on the embodiments, but it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0044] 1 LAN cable 2 conductors 2a, 2b conductor 3 braids 4 Inclusions 6 braid 5, 7 Tape (aluminum foil tape) 9. Holding tape 8 Inner sheath 10 outer sheath 11 Extruder 12 Hopper 13 Screw 14 Breaker plate 15 cylinders 16 neck 17 heads 18 nozzle 20 Insulated wire

Claims

[Claim 1] a step of producing an insulated wire by coating the outer periphery of a conductor running through a head of an extruder with a molten insulator through a die attached to the head; a twisting step of twisting a plurality of the insulated wires together; a step of immersing the insulated wires in water to cool them after the step of preparing the insulated wires and before the step of stranding the wires; A method for manufacturing a LAN cable, comprising: The opening diameter of the nozzle is 3.4 to 4.5 mm, The cooling temperature in the cooling step is 15 to 25°C, The diameter of the conductor is 1.2 to 1.3 mm; A method for manufacturing a LAN cable, wherein the insulator is an ethylene-propylene rubber copolymer blend.

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