JP7390913B2 - LAN cable - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act 1. Tatsuta Electric Cable Co., Ltd. sold to Daitron Co., Ltd. on February 6, 2019 2. Tatsuta Electric Cable Co., Ltd. sold to Mitsubishi Heavy Industries Engineering Co., Ltd. on February 7, 2019 3. On March 5, 2019, Tatsuta Electric Cable Co., Ltd. sold to Nippon Sharyo Manufacturing Co., Ltd.

The present invention relates to a LAN cable.

A LAN cable includes twisted wires made of paired wires, and a collection of a plurality of the twisted wires is housed in a cylindrical covering material. In some conventional LAN cables, the covering material has a single layer structure. Further, in another LAN cable, the covering material has a plurality of resin layers formed of a resin composition.

Conventionally, an extruder equipped with a crosshead is used to form the resin layer into a cylindrical shape that covers the aggregate. For example, the resin layer may be formed by melt-kneading a resin composition in an extruder, moving it toward the tip of the extruder, and supplying the kneaded material obtained by the melt-kneading to a crosshead attached to the tip of the extruder. , by moving the linear core containing the aggregate in the extrusion direction through the nipple of the crosshead while extruding the kneaded material into a cylindrical shape from a circular discharge port formed between the die and the nipple of the crosshead. Covered in aggregate.

By the way, LAN cables are required to have crosstalk characteristics of a certain level or higher. In order to improve the crosstalk characteristics, it is important that the strands and twisted wires constituting the aggregate are appropriately arranged. For example, in Patent Document 1, in a LAN cable whose coating material has an inner sheath and an outer sheath as a resin layer, in order to prevent misalignment of a plurality of twisted pairs, It is disclosed that the surrounding area was covered with an interposition.

JP2006-172788A

In order to prevent the deterioration of crosstalk characteristics due to the above-mentioned strands and strands not being properly arranged, it is recommended to insert polypropylene yarn or the like in the space between the strands of the strands and the covering material. One possible method is to fill the coating material with a large amount of material so that the strands do not come into direct contact with each other, but after careful consideration, the present inventor found that it is better to have a state in which there is insufficient intervening material, which has better crosstalk characteristics. We learned that it is easy to manufacture LAN cables.

That is, an object of the present invention is to provide a LAN cable with excellent crosstalk characteristics.

The LAN cable according to the present invention includes:
A LAN cable comprising a twisted wire made of paired wires, and an aggregate of the plurality of twisted wires is covered with a covering material having a single-layer structure or a multi-layer structure formed in a cylindrical shape,
A space is formed between the aggregate and the covering material, and the space is filled with an interposer made of polypropylene resin,
In the cross-sectional view, the area between the circumscribed circle of the stranded wire and the inner circumferential circle of the covering material is determined, the product of the area and the unit length is defined as the accommodation space for the intervening material, and the polypropylene is filled in all of the accommodation space. When the mass of the polypropylene resin when filled with resin is taken as 100%, the mass ratio of the filled intervening material per unit length is 25% or more and 55% or less.

According to such a configuration, when the mass ratio of the filled intervening material is 55% or less, the space formed between the aggregate and the covering material can be filled with more than a certain amount of air. Excellent crosstalk characteristics are obtained. In addition, when the mass ratio is 25% or more, the arrangement of the twisted wires is stabilized, resulting in excellent crosstalk characteristics.

The LAN cable preferably includes:
The covering material has the multilayer structure having a plurality of resin layers,
The resin layer includes a first resin layer arranged on the inside and a second resin layer arranged on the outside,
The hardness of the first resin layer is higher than the hardness of the second resin layer.

Here, the LAN cable is also required to have a certain level of flexibility or more in order to improve workability. However, upon study by the present inventor, it was found that when a resin with relatively low hardness is used for the resin layer of the covering material in order to improve flexibility, the crosstalk characteristics deteriorate. This is because when the hardness of the resin layer decreases, when the resin layer is formed using an extruder, the melted and kneaded resin comes into close contact with the core that forms the aggregate, which causes pressure to be applied to the core. Accordingly, it is thought that the arrangement of each twisted wire changes and the crosstalk characteristics deteriorate.
Therefore, according to the above configuration, since the hardness of the first resin layer arranged on the inner side is relatively high, the arrangement state of the aggregate is stabilized, so that crosstalk characteristics are excellent. Since the hardness of the second resin layer disposed on the second resin layer is relatively low, the LAN cable becomes easier to bend, thereby improving workability.

The LAN cable preferably includes:
The first resin layer contains polyethylene resin, and the second resin layer contains polyethylene resin and ethylene vinyl acetate copolymer resin.

According to this configuration, since the second resin layer contains the ethylene-vinyl acetate copolymer resin, the hardness is relatively lower than that of the first resin layer, so that crosstalk characteristics and workability are further improved.

As described above, according to the present invention, a LAN cable with excellent crosstalk characteristics can be provided.

FIG. 1 is a cross-sectional view of a LAN cable according to one embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A LAN cable according to an embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the LAN cable 1 of this embodiment includes a center line 10 and a stranded wire 30 consisting of paired twisted wires 20, and a plurality of strands 30 are gathered around the center line 10. One aggregate 40 is formed, and the aggregate 40 is covered with a covering material 50 having a cylindrical multilayer structure. Although the LAN cable 1 of this embodiment has four stranded wires 30, it is not limited to this, and may have two stranded wires 30, for example. Furthermore, although the LAN cable 1 of this embodiment has the covering material 50 having a multilayer structure, it may have the covering material 50 having a single layer structure.

The center line 10 is made of fibers having a high modulus of elasticity, thereby imparting tensile strength to the LAN cable 1. Examples of such fibers include aramid fibers and polyarylate fibers.

The stranded wire 30 is constructed by twisting a pair of wires 20 together. The twisting pitch of the strands 20 is preferably short in order to improve crosstalk characteristics, and is usually 9 to 18 mm. Further, it is preferable that the four twisted wires 30 have different twisting pitches, thereby improving crosstalk characteristics.

The wire 20 is an insulated wire in which a conductor 21 is covered with an insulator 22 . The conductor 21 is composed of a single copper wire or a stranded wire in which a plurality of copper wires are twisted together. The outer diameter of the conductor 21 is usually 0.5 to 0.6 mm. Note that the conductor 21 may be formed of another conductive material, for example, an aluminum wire.

The insulator 22 is made of an electrically insulating resin composition. Examples of such resin compositions include polyethylene resin (PE). The thickness of the insulator 22 is usually 0.1 to 0.25 mm.

In this embodiment, four twisted wires 30 are gathered around the center line 10 to form an assembly 40.

A space is formed between the aggregate 40 and the covering material 50, and the space is filled with an interposer 60 made of polypropylene resin (PP). The polypropylene resin may be a homopolymer, a random copolymer, or a block copolymer. The polypropylene resin used usually has a specific gravity ρ of 0.90 to 0.91.

In this embodiment, the filling amount of the interposer 60 is adjusted to improve the crosstalk characteristics of the LAN cable, as will be described later. Therefore, from the viewpoint of easy adjustment of the filling amount, it is preferable that the interposer 60 is made of PP yarn.

With the above configuration, in the cross-sectional view of the LAN cable 1 of this embodiment, four circumscribed circles C1 circumscribing the stranded wires 30 and an inner circumferential circle C2 of the covering material 50 are drawn. In this embodiment, it is assumed that the inner circumferential circle C2 coincides with the circumscribed circle of the aggregate 40. In this case, in the cross-sectional view, four intervening regions A are formed between the circumscribed circle C1 and the inner circumferential circle C2. Then, if the area of one intervening region A is S, then the LAN cable 1 has a storage space with a volume V calculated as the product of the total area 4S of the four intervening regions A and the unit length per unit length. It has R. The LAN cable 1 has a specific filling amount of the interposer 60 accommodated in the accommodation space R.

In the present embodiment, the filling amount of the interposers 60 filled in the accommodation space R is calculated based on the mass M 0 of the polypropylene resin when the entire accommodation space R is filled with the polypropylene resin, and the mass M ₀ of the polypropylene resin is taken as 100%. It is expressed as the ratio of the mass M ₁ of the intervention 60 actually filled in R, that is, the mass ratio P (%) of the mass M ₁ to the mass M ₀ . The mass proportion P is preferably 55% or less, more preferably 50% or less, and even more preferably 45% or less. This improves the crosstalk characteristics of the LAN cable 1. Considering this from the perspective of relative permittivity, the relative permittivity of polypropylene resin is approximately 2.0, and the relative permittivity of air is 1.0. By setting the upper limit, an appropriate amount of air is present in the accommodation space R, and it is considered that the relative dielectric constant in the accommodation space R is accordingly reduced and the crosstalk characteristics are improved.

Moreover, the mass proportion P is preferably 25% or more, more preferably 30% or more, even more preferably 35% or more, and even more preferably 40% or more. This stabilizes the arrangement of the assembly 40, thereby improving the crosstalk characteristics of the LAN cable 1.

The area S of the intervening region A is calculated, for example, from the diameter r ₁ of the circumscribed circle C1 and the diameter r ₂ of the inner circumferential circle C2. The diameter r ₁ of the circumscribed circle C1 is determined by measuring the diameter of the stranded wire in the test piece according to the test method specified in JIS C 3005, and multiplying the measured value by 1.71. Further, the diameter _r2 of the inner circumferential circle C2 is a value measured by a method conforming to the test method specified in the above-mentioned JIS.

In this embodiment, M ₀ and M ₁ are assumed to be values converted to the fineness (denier) of the PP yarn, as shown below. Furthermore, M ₀ and M ₁ will be explained as the masses of the polypropylene resin or PP yarn filled in the accommodation space R (corresponding to the volume of V/4) corresponding to one intervening region A.

As M ₀ , the mass w ₀ (g/m) of the polypropylene resin in the accommodation space R calculated by the product of the specific gravity ρ of the polypropylene resin and the area S (mm ² ) of the intervening region A is expressed as the mass w of 1 denier. (g/m, ie, w=1/9000), the value converted to fineness (denier) shall be adopted. That is, a value calculated by M ₀ =w ₀ /w is adopted as M ₀ .

For _M1 , for example, cut out three test pieces of unit length from the LAN cable 1, measure the mass (g/m) of the PP yarn included in each test piece, and calculate the average value of each mass as a unit. The value converted to fineness (denier) by assuming the mass w ₁ (g/m) of the PP yarn included in the LAN cable 1 per length and dividing the mass w ₁ by the mass w (g/m) of 1 denier. shall be adopted. That is, it is assumed that M ₁ adopts a value calculated by M ₁ =w ₁ /w.

As the mass ratio P (%), a value calculated by M ₁ /M ₀ ×100 is adopted.

Next, the covering material 50 will be explained in detail.

The covering material 50 of this embodiment has a multilayer structure and includes a resin layer 52 for protecting the aggregate 40. The resin layer 52 is composed of an extruded tube formed into a tube shape by an extruder. Preferably, the resin layer 52 includes a first resin layer 521 disposed on the inside and a second resin layer 522 disposed on the outside. In the present embodiment, the first resin layer 521 covers the assembly 40 with a pressure tape 51 that forms part of the covering material 50 interposed therebetween. Further, the second resin layer 522 is disposed on the outermost side.

The hardness of the first resin layer 521 is preferably higher than the hardness of the second resin layer 522. This will be explained in detail next. In a LAN cable, the second resin layer 522 is usually formed to be thicker than the first resin layer 521. Therefore, in order to make the LAN cable 1 easier to bend, it is preferable that the second resin layer 522, which is relatively thick, is formed to have low hardness. However, when the hardness of the resin layer is lowered, when the resin layer is formed using an extruder, the melted and kneaded resin comes into close contact with the core that forms the aggregate, and pressure is applied to the core. The arrangement of each twisted wire may change, which may be a factor in deteriorating crosstalk characteristics. Therefore, in order to make the LAN cable 1 bendable by setting the hardness of the second resin layer 522, which has a relatively large thickness, to be relatively low, the hardness of the first resin layer 521, which has a relatively small thickness, must be set to a relatively low value. It is preferable to set it relatively high to stabilize the arrangement of each stranded wire.

More specifically, the thickness of the first resin layer 521 is preferably 0.2 to 0.4 mm, and the thickness of the second resin layer 522 is preferably 1.0 to 1.8 mm. Further, it is preferable that the first resin layer 521 has a Shore D hardness of 40 to 45, and the second resin layer 522 has a Shore D hardness of 33 to 38. Note that the Shore D hardness is a value measured by a test method specified in JIS K 7215.

In order to achieve the above hardness, it is preferable that the first resin layer 521 contains a polyethylene resin, and the second resin layer 522 contains a polyethylene resin and an ethylene-vinyl acetate copolymer resin. The proportion of the ethylene vinyl acetate copolymer resin contained in the second resin layer 522 is preferably 10 to 30% by mass based on the mass of the second resin layer 522. Further, the content of vinyl acetate contained in the ethylene vinyl acetate copolymer resin is preferably 10 to 40%.

Examples of the presser tape 51 include plastic tapes such as polyethylene, polystyrene, or polyester, or paper tapes.

In addition to the above, the covering material 50 of this embodiment includes a plurality of shielding layers 53 arranged between the first resin layer 521 and the second resin layer 522. The shielding layer 53 includes a first shielding layer 531 disposed on the inside and a second shielding layer 532 disposed on the outside. Note that the shielding layer 53 may be only one of the first shielding layer 531 and the second shielding layer 532.

The first shielding layer 531 is formed of a resin tape to which metal foil is attached. As the metal foil, aluminum foil is preferable. As the resin tape, a polyester resin tape such as polyethylene terephthalate (PET) is preferable. The thickness of the first shielding layer 531 is typically 0.03 to 0.07 mm.

The second shielding layer 532 is composed of a braid made of tin-plated annealed copper wire. The thickness of the second shielding layer 532 is typically 0.2 to 0.4 mm.

As mentioned above, although the embodiment has been shown as an example, the LAN cable according to the present invention is not limited to the configuration of the above embodiment. Further, the LAN cable according to the present invention is not limited to the above-mentioned effects. The LAN cable according to the present invention can be modified in various ways without departing from the gist of the present invention.

For example, in the above embodiment, in the cross-sectional view, the inner circumferential circle C2 of the covering material 50 matches the circumferential circle of the aggregate 40, so that the circumferential circle C1 of the stranded wire 30 and the inner circumferential circle C2 of the covering material 50 Although four intervening regions A are formed between the It may be connected to In this case, the area S is, for example, one-fourth of the total area of the intervening regions.

The present invention will be further explained below with reference to Examples.

[Manufacture example 1]
Seven electrical annealed copper wires specified in JIS C 3102 were twisted together to form a conductor (outer diameter 0.6 mm) and covered with a polyethylene insulator to form a wire (outer diameter 1.0 mm). . The strands were twisted in pairs to form four strands.
Four strands were twisted together with PP yarns around a centerline formed by aramid fibers to form an assembly.
Next, it was covered with a pressing tape. At this time, the PP yarn contained per unit length corresponding to one intervening region of the LAN cable was adjusted to be 4000 denier. Note that the fineness of the PP yarn used varies by ±500 deniers, so M ₁ =3500 to 4500 deniers.Next, by covering with heat-resistant polyethylene using an extruder, the first resin layer (thickness 0.3 mm, outer diameter 5.1 mm, and Shore D hardness 41). Next, a resin tape with aluminum foil was coated to form a first shielding layer. Further, a braid was formed using a tin-plated annealed copper wire specified in JIS C 3152 to form a second shielding layer (outer diameter 5.7 mm). Finally, a second resin layer (thickness: 1.4 mm, Shore D hardness: 37) was formed by coating with heat-resistant polyethylene, resulting in a LAN cable with a length of 100 m (mass: 90 kg/km).
In this LAN cable, the diameter _r1 of the circumscribed circle C1 of the stranded wires was 1.71 mm, and the diameter _r2 of the inner circumferential circle C2 of the covering material was 4.4 mm. Further, the area S of one intervening region A calculated from the diameter r ₁ and the diameter r ₂ was 1.36 mm ² . Table 1 shows the numerical values and mass ratio P for determining the mass ratio P of the intervening material for this LAN cable.

In addition to the above, according to Production Example 1, adjustments were made so that M ₁ = 5000 (4500 to 5500) denier and M ₁ = 3000 (2500 to 3500) denier, and the mass proportion P of the intervention was 45.0%. (40.5-49.5%) and 27.0% (22.5-31.5%) LAN cables were manufactured.

[Evaluation method of crosstalk characteristics]
ANSI/TIA-568-B. Evaluation was made by measuring the near-end crosstalk attenuation of each LAN cable in the frequency range of 1 to 100 MHz in accordance with the Category 5 standard of No. 2, and determining the minimum margin from the standard value. The results are shown in Table 2. Note that the larger the value of the minimum margin, the better the crosstalk characteristics of the LAN cable.

As shown in Table 2, the crosstalk characteristics were improved by reducing the mass ratio P of the intervention to less than 100%. In particular, it was observed that the crosstalk characteristics of the LAN cable with a mass ratio P of 36.0% were significantly improved.

1: LAN cable,
10: center line,
20: Element wire, 21: Conductor, 22: Insulator,
30: twisted wire,
40: aggregate,
50: Covering material, 51: Pressure wrapping tape,
52: resin layer, 521: first resin layer, 522: second resin layer,
53: shielding layer, 531: first shielding layer, 532: second shielding layer,
60: intervention,
C1: Circumscribed circle, C2: Inner circumferential circle, A: Intervening area

Claims (3)

A LAN cable comprising a twisted wire made of paired wires, and an aggregate of the plurality of twisted wires is covered with a covering material having a single-layer structure or a multi-layer structure formed in a cylindrical shape,
A space is formed between the aggregate and the covering material, and the space is filled with polypropylene yarn, which is an intervening material made of polypropylene resin ,
In the cross-sectional view, the area between the circumscribed circle of the stranded wire and the inner circumferential circle of the covering material is determined, the product of the area and the unit length is defined as the accommodation space for the intervening material, and the polypropylene is filled in all of the accommodation space. A LAN cable, wherein, when the mass of the polypropylene resin filled with resin is taken as 100%, the mass ratio of the filled intervening material per unit length is 25% or more and 55% or less. The covering material has the multilayer structure having a plurality of resin layers,
The resin layer includes a first resin layer arranged on the inside and a second resin layer arranged on the outside,
The LAN cable according to claim 1, wherein the first resin layer has a higher hardness than the second resin layer. 3. The LAN cable according to claim 2, wherein the first resin layer contains a polyethylene resin, and the second resin layer contains a polyethylene resin and an ethylene-vinyl acetate copolymer resin.

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