JP2017174552A - Communication cable for railway - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication cable for a railway, capable of combining prevention of bite damage by rat with reduction of attenuation amount of a transmission signal.SOLUTION: A communication cable for a railway (10) has a cable core (13) including a wire core bundle (11) formed by bundling a plurality of insulation wire cores, a first sheath layer (15) covering an outer periphery of the cable core, a metal made rat repellent layer (16) covering an outer periphery of the firs sheath layer and a second sheath layer (17) covering an outer periphery of the rat repellent layer. The rat repellent layer (16) is a conductive layer which is proximate to the cable core (13). The first sheath layer (15) has thickness determined so that attenuation amount of transmitted signal through the cable core (13) is predetermined targeted attenuation amount or less.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a railway communication cable.

  Conventionally, there has been proposed a communication cable including a cable core including a wire core bundle in which a plurality of insulated wire cores are bundled (for example, a twisted pair or quad-twisted wire core bundle). This type of communication cable is generally configured to cover the cable core with a protective sheath formed of a soft synthetic resin from the viewpoint of protecting the cable core and ensuring the flexibility of the communication cable.

  On the other hand, a railway communication cable is usually arranged outdoors (for example, in a cable trough provided along a railway track). By the way, as is well known, acupuncture has a habit of scuffing the incisors by biting the surroundings (not necessarily edible) in order to prevent the mouth from being clogged by the incisors that are constantly growing. . Due to this behavior, the kite may bite the railway cable. In this case, since the protective sheath of the railway communication cable is also formed from the same synthetic resin as described above, damage (biting due to wrinkles) that part or all of the cable core is bitten occurs. It should be noted that biting by a heel can occur not only in a railway communication cable but also in a normal communication cable (for example, a telephone cable and a LAN cable).

  Therefore, one of the conventional communication cables (hereinafter referred to as “conventional cable”) wraps a stainless steel tape around the cable core in order to prevent biting by the heel, and the outer periphery of the stainless steel tape is covered with a sheath containing a moth repellent. It is configured to cover. As a result, the conventional cable protects the cable core with the stainless steel tape when the heel bites the conventional cable (prevents the heel teeth from reaching the cable core), and again by the moth repellent contained in the sheath. (See, for example, Patent Document 1).

JP 2005-44652 A

  The conventional cable described above forms a protective layer for preventing the teeth of the eyelids from reaching the cable core with a stainless steel tape that is superior in strength to the protective sheath. However, when a conductive layer such as stainless steel tape is provided in the vicinity of the cable core, the cable is caused by the electrostatic capacitance generated between the conductive layer and the cable core and the eddy current generated in this layer. In some cases, the amount of attenuation of a signal (transmission signal) transmitted through the core increases.

  The attenuation of the transmission signal can be ignored in practice when the length of the communication cable (that is, the transmission distance of the signal) is short. However, when it is necessary to transmit a signal over a long distance, such as a communication cable for railways, a countermeasure considering this attenuation (for example, providing a repeater that amplifies the transmission signal for each length considering the attenuation) Is required. Therefore, as the attenuation amount of the transmission signal increases, the number of repeaters to be provided per unit length of the transmission distance increases. Therefore, from the viewpoint of the installation cost of the repeater and the like, it is preferable that the attenuation amount of the transmission signal is as small as possible particularly in the railway communication cable.

  This invention is made in view of the situation mentioned above, The objective is to provide the communication cable for railroads which can make the prevention of the bite by a gutter and the reduction of the attenuation amount of a transmission signal compatible. is there.

In order to achieve the above-described object, a railway communication cable according to the present invention is characterized by the following (1) to (4).
(1)
A cable core including a wire core bundle in which a plurality of insulated wire cores are bundled, a first sheath layer covering the outer periphery of the cable core, a metal fender layer covering the outer periphery of the first sheath layer, and the protection A railway communication cable comprising a second sheath layer covering the outer periphery of the heel layer,
The fender layer is a conductive layer closest to the cable core,
The first sheath layer has a thickness determined so that an attenuation amount of a signal transmitted through the cable core is equal to or less than a predetermined target attenuation amount,
It must be a railway communication cable.
(2)
In the railway communication cable described in (1) above,
The thickness of the first sheath layer is
Attenuation amount smaller by a predetermined amount than the attenuation amount assuming that the fender layer is disposed adjacent to the cable core is determined as the target attenuation amount,
It must be a railway communication cable.
(3)
In the railway communication cable according to (1) or (2) above,
The thickness of the first sheath layer is 1.0 to 5.0 mm.
It must be a railway communication cable.
(4)
In the railway communication cable according to any one of (1) to (3) above,
The thickness of the first sheath layer is
In the case where the frequency of the signal is 10 kHz or more, the attenuation of the signal is reduced by at least 10% compared to the attenuation when it is assumed that the protective layer is disposed adjacent to the cable core. The thickness is the quantity,
It must be a railway communication cable.

  According to the railway communication cable having the configuration (1), the cable core and the metal fender layer are separated by the first sheath layer, and the cable core and the fender layer of the metal layer are separated from each other. There will be no conductive layer between them. In other words, the fender layer mainly affects the attenuation of the transmission signal of the cable core. Furthermore, the thickness of the first sheath layer is set to a thickness at which the attenuation amount of the transmission signal of the cable core is equal to or less than a predetermined target attenuation amount. Therefore, compared to the case where a metal fender layer is wound so as to be adjacent to the cable core as in the conventional cable, the attenuation amount of the transmission signal can be reduced by the thickness of the first sheath layer, and the attenuation amount can be reduced. It can be made below a predetermined target attenuation. In addition, in the railway communication cable of this configuration, the metal fender layer also functions as a shield layer (electrostatic shield layer) for shielding external noise in addition to the function of preventing biting by a flaw. become.

  Therefore, according to the railway communication cable having the above-described configuration, it is possible to achieve both prevention of biting by a heel and reduction of the attenuation amount of the transmission signal. Furthermore, in addition to solving the above-described problems, the railway cable having the above-described configuration also has a shielding function for shielding external noise by including a metal fender layer.

  By the way, as a method for setting the thickness of the first sheath layer so that the attenuation amount of the transmission signal is equal to or less than the target attenuation amount, for example, the attenuation amount (loop resistance, self-inductance, capacitance, leakage of a known communication cable) Using a theoretical formula regarding conductance and angular frequency (details will be described later), the attenuation is defined as the diameter of the cable core, the frequency of the transmission signal, the material of the first sheath layer, the thickness of the first sheath layer, etc. A method of calculating (estimating) based on the above may be used. Normally, the thickness of the first sheath layer is set so that the first sheath layer becomes thicker as the target attenuation amount is smaller.

  According to the railway communication cable having the configuration (2), the target attenuation is based on the attenuation amount (attenuation amount to be compared) when the fender layer is arranged adjacent to the cable core as in the conventional cable. The amount will be determined. Specifically, as an example, an attenuation amount that is smaller than the attenuation amount of the comparison target by a predetermined ratio (for example, an attenuation amount that is reduced by at least 10% from the attenuation amount of the comparison object in a predetermined frequency range (10 kHz or more)). Can be used as the target attenuation. In general, the thicker the first sheath layer, the smaller the attenuation of the transmission signal. However, when the first sheath layer is excessively thick, handling of the communication cable becomes difficult (for example, it is difficult to bend). Therefore, a target attenuation amount that also considers such ease of handling may be used.

  According to the railway communication cable having the configuration (3), the thickness of the first sheath layer is set to 1.0 to 5.0 mm, so that a generally assumed structure (for example, the diameter of the cable core, the insulated wire) With respect to a railway communication cable having the number of cores and bundles of cores, the frequency of transmission signals, the material of the first sheath layer, etc., the attenuation amount of the transmission signals can be sufficiently reduced. Specifically, according to the test conducted by the inventor and the like (details will be described later), if the thickness of the first sheath layer is 1.0 mm or more, compared to the attenuation amount of the comparison target described above, If the attenuation of the transmission signal can be reduced by at least 10% in a predetermined frequency range (for example, 10 kHz or more) and the thickness of the first sheath layer is 5.0 mm or less, handling of the communication cable for railway becomes excessively difficult. It will never be. In addition, it is thought that the influence which the thermal contraction and thermal expansion of a 1st sheath layer exerts on the twist pitch (namely, noise reduction effect) of a wire core bundle becomes large as a 1st sheath layer becomes thick. However, since a railway communication cable generally does not need to strictly manage the twisting pitch of the wire core bundle as compared with a LAN cable or the like (a variation in the twisting pitch can be allowed), the first sheath layer is 1.0 to 5. There is no substantial disadvantage even if the thickness is 0 mm.

  According to the railway communication cable having the configuration (4), the attenuation of the transmission signal can be sufficiently reduced as in the case (3).

  ADVANTAGE OF THE INVENTION According to this invention, the communication cable for railroads which can be compatible with prevention of the bite by a collar and reduction of the attenuation amount of a transmission signal can be provided. Furthermore, according to the present invention, it is possible to provide a railway communication cable having a shield function for shielding external noise.

  The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading through a mode for carrying out the invention described below (hereinafter referred to as “embodiment”) with reference to the accompanying drawings. .

FIG. 1 is a schematic diagram showing a use state of a railway communication cable according to the present embodiment. FIG. 2 is a diagram illustrating an internal configuration of the railway communication cable according to the present embodiment. 3 is a cross-sectional view of the railway communication cable shown in FIG. FIG. 4 is a graph for comparing the attenuation of the transmission signal in the railway communication cable shown in FIG. 2 with other communication cables.

  Hereinafter, embodiments of a railway communication cable (hereinafter referred to as “communication cable 10”) according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the communication cable 10 is accommodated inside a cable trough 92 arranged along a railroad track 91. As shown in FIGS. 2 and 3, the communication cable 10 includes a cable core 13 including a plurality of wire core bundles (quad stranded wires in this example) 11 and interposition members 12. Further, the communication cable 10 includes a press-wound tape 14 for bundling the cable core 13, a first sheath layer 15 that covers the outer periphery of the cable core 13, a metal fender layer 16 that covers the outer periphery of the first sheath layer 15, A second sheath layer 17 that covers the outer periphery of the fender layer 16 and a drain wire 18 that contacts the fender layer 16 are provided. In this example, the communication cable 10 includes three wire core bundles 11. However, the number of the wire core bundles 11 included in the communication cable 10 is not necessarily limited to three, and is determined according to the use of the communication cable 10 or the like. Any number of core bundles 11 may be provided.

  The wire core bundle 11 includes a conductor core wire 11a obtained by reducing the diameter of a conductive metal such as copper, a copper alloy, and an aluminum alloy, an insulator 11b that covers the conductor core wire 11a, and a press winding tape 11c. (See FIG. 3). The insulator 11b is a thermoplastic resin such as polyvinyl chloride and polyethylene, and is provided so as to cover the entire length of the conductor core wire 11a by extrusion molding or the like.

  The presser winding tape 14 is a nonwoven fabric tape made of polyester or the like, for example. The presser winding tape 14 is spirally wound around the outer peripheral surface of the bundled three wire core bundles 11, and these wire core bundles 11 are fixed in a bundled state.

  The interposition member 12 is defibrated paper made of, for example, polypropylene (PP). As the interposition member 12, a material having flexibility (flexibility) is preferably used so that the communication cable 10 can be freely bent when the communication cable 10 is installed. The interposition member 12 is provided over the entire length of the communication cable 10 so as to fill the gaps between the plurality of wire core bundles 11. The interposition member 12 is not always necessary.

  The first sheath layer 15 is an insulating flexible tube formed from, for example, a thermoplastic resin such as polyethylene. The first sheath layer 15 has the same length as the wire core bundle 11, and accommodates a plurality of wire core bundles 11, interposition members 12, and presser winding tapes 14 inside thereof. Further, the first sheath layer 15 is disposed so that the inner peripheral surface thereof is in close contact with the presser winding tape 14.

  The thickness of the first sheath layer 15 is set such that the transmission signal attenuation of the cable core 13 is equal to or less than a predetermined target attenuation. Specifically, in this example, a predetermined frequency range (10 kHz) with reference to the attenuation amount (attenuation amount for comparison) when the fender layer 16 is disposed adjacent to the cable core 13 as the target attenuation amount. In the above, an attenuation amount that is smaller than the attenuation amount of the comparison target by a predetermined amount (an amount reduced by 10% from the attenuation amount of the comparison object) is used. The thickness of the first sheath layer 15 for setting the attenuation amount of the transmission signal to be equal to or less than the target attenuation amount can be calculated based on, for example, a well-known theoretical formula for the attenuation amount of the communication cable shown in the following equation. In the following equation, R is loop resistance (Ω / loopkm), L is self-inductance (H / km), C is capacitance (F / km), G is leakage conductance (S / km), and ω is angular frequency ( = 2πf, where f is the frequency (Hz).

  From another viewpoint, if the thickness of the first sheath layer 15 is set to 1.0 to 5.0 mm, a generally assumed structure (for example, the diameter of the cable core, the frequency of the transmission signal, and the first For a railway communication cable having a sheath layer material or the like, the attenuation of the transmission signal can be sufficiently reduced (at least about 10%).

  The fender layer 16 is formed by winding a metal tape made of a metal such as stainless steel and iron on the outer circumference of the first sheath layer 15 one by one or two. The thickness of the fender layer 16 is preferably 0.03 to 0.1 mm, and more preferably 0.03 to 0.07 mm, taking into account the fender effect and the flexibility of the communication cable 10. .

  The second sheath layer 17 is an insulating flexible tube formed from a thermoplastic resin. The second sheath layer 17 can be made of, for example, linear low density polyethylene (L-LDPE) and ethylene / ethyl acrylate copolymer resin (EEA). Considering the influence of the thermal contraction / thermal expansion of the second sheath layer 17 on the twist pitch (that is, the noise reduction effect) of the wire core bundle 11, a linear low density with a relatively small degree of thermal contraction / thermal expansion. Although it is preferable to use polyethylene (L-LDPE), railway communication cables generally do not need to strictly manage the twist pitch of the wire core bundle 11 as compared to LAN cables or the like (a variation in the twist pitch can be allowed). Even if ethylene / ethyl acrylate copolymer resin (EEA) is used, there is no substantial disadvantage.

  The drain wire 18 connects the fender layer 16 and an external earth member so as to ground the fender layer 16.

  Here, the inventor conducted a test comparing the attenuation amount of the transmission signal of the communication cable 10 having the above-described configuration with communication cables having other configurations. Specifically, the communication cable 10 (Example) having the above configuration (the thickness of the first sheath layer 15 is 1.0 mm and the thickness of the fender layer 16 is 0.05 mm), and the cable core 13 as in the conventional cable. About the sample (comparative example) different from the communication cable 10 in that the fender layer 16 is disposed adjacent to the sample, and the sample (reference example) different from the communication cable 10 in that the fender layer 16 is not provided. The attenuation of the transmission signal was measured while changing the frequency of the transmission signal. Regarding the configuration other than the arrangement or presence / absence of the first sheath layer 15, the communication cables of the example, the comparative example, and the reference example have the same configuration. Therefore, description of these other configurations is omitted. The results of this test are shown in the graph of FIG.

  As shown in FIG. 4, it was confirmed that the communication cable 10 (Example) having the above configuration has a small attenuation in all frequency regions as compared with the communication cable of the comparative example. In particular, it has been confirmed that the attenuation amount of the communication cable 10 is 10% or more smaller than the attenuation amount of the communication cable of the comparative example in the frequency range (10 kHz or more). Further, it was confirmed that the attenuation effect by the communication cable 10 becomes more remarkable as the frequency of the transmission signal becomes higher. Considering the above-described theoretical formula for the attenuation amount, it is considered that the attenuation amount becomes smaller as the thickness of the first sheath layer 15 is made larger than 1.0 mm.

  In addition, it was confirmed that the communication cable 10 (Example) has a slightly larger attenuation of the transmission signal than the communication cable of the reference example. However, it was confirmed that the communication cable 10 was able to realize an attenuation amount closer to that of the communication cable of the reference example than the communication cable of the comparative example.

  From the above test results, the transmission signal attenuation of the communication cable 10 having the above-described configuration is superior to the sample (comparative example) in which the conductive layer is provided so as to be adjacent to the cable core 13 as in the conventional cable. It became clear that. In other words, according to the communication cable 10, it has been clarified that both prevention of bite caused by wrinkles and reduction in attenuation of the transmission signal can be achieved. In addition, the communication cable 10 also has a shielding function for shielding external noise by providing the metal fender layer 16.

  In addition, this invention is not limited to said each embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like can be made as appropriate. In addition, the material, shape, dimensions, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

Here, the features of the embodiment of the above-described railway communication cable according to the present invention are summarized and listed in the following (1) to (4), respectively.
(1)
A cable core (13) including a wire core bundle (11) in which a plurality of insulated wire cores are bundled, a first sheath layer (15) covering the outer periphery of the cable core, and a metal covering the outer periphery of the first sheath layer A railway communication cable (10) comprising a protective fender layer (16) and a second sheath layer (17) covering the outer periphery of the fender layer,
The fender layer (16) is a conductive layer closest to the cable core (13),
The first sheath layer (15) has a thickness determined so that an attenuation amount of a signal transmitted through the cable core (13) is equal to or less than a predetermined target attenuation amount,
Railway communication cable.
(2)
In the railway communication cable described in (1) above,
The thickness of the first sheath layer (15) is
Attenuation amount smaller by a predetermined amount than the attenuation amount when it is assumed that the fender layer (16) is disposed adjacent to the cable core (13) is determined as the target attenuation amount.
Railway communication cable.
(3)
In the railway communication cable according to (1) or (2) above,
The thickness of the first sheath layer (15) is 1.0 to 5.0 mm.
Railway communication cable.
(4)
In the railway communication cable according to any one of (1) to (3) above,
The thickness of the first sheath layer (15) is
In the case where the frequency of the signal is 10 kHz or more, the attenuation of the signal is reduced by at least 10% compared to the attenuation when it is assumed that the protective layer is disposed adjacent to the cable core. The thickness is the quantity,
Railway communication cable.

10 Communication cable (Railway communication cable)
DESCRIPTION OF SYMBOLS 11 Wire core bundle 12 Interposition member 13 Cable core 14 Pressing winding tape 15 1st sheath layer 16 Fender layer 17 2nd sheath layer 18 Drain wire 92 Cable trough

Claims (3)

A cable core including a wire core bundle in which a plurality of insulated wire cores are bundled, a first sheath layer covering the outer periphery of the cable core, a metal fender layer covering the outer periphery of the first sheath layer, and the protection A railway communication cable comprising a second sheath layer covering the outer periphery of the heel layer,
The fender layer is a conductive layer closest to the cable core,
The first sheath layer has a thickness determined so that an attenuation amount of a signal transmitted through the cable core is equal to or less than a predetermined target attenuation amount,
Railway communication cable. The railway communication cable according to claim 1,
The thickness of the first sheath layer is
Attenuation amount smaller by a predetermined amount than the attenuation amount assuming that the fender layer is disposed adjacent to the cable core is determined as the target attenuation amount,
Railway communication cable. In the railway communication cable according to claim 1 or 2,
The thickness of the first sheath layer is 1.0 to 5.0 mm.
Railway communication cable.

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