JP2004259599A - Shielded cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent shielded cable with communication characteristics and productivity improved without deteriorating shielding performance. <P>SOLUTION: The shielded cable 11 is provided with the center conductor 12, an inner insulating body 13 fitted at the periphery of the center conductor 12, a tape wrapping body 15 with a layered structure with plastic layer 14b laminated on an aluminum foil layer 14a and structured by attaching and winding in a longitudinal direction a tape with a width longer than an outer-periphery length of the inner insulating body 13 around the inner insulating body 13 with the aluminum foil layer inside so that one end edge part 14B is overlapped on the other end edge part 14B, and an outer insulation coating 16 fitted at the periphery of the tape wrapping 15. By structuring the plastic layer 14b of the tape 14 with conductive resin, discontinuity of conductivity at overlapped parts is eliminated. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a shielded cable, and more specifically, has an inner insulator provided around a center conductor, a layered structure in which a plastic layer is laminated on a metal foil layer, and has a lateral width longer than the circumference of the outer periphery of the inner insulator. A shield comprising: a tape envelope formed by vertically wrapping a tape having the tape around the inner insulator with the metal foil layer inside; and an outer insulating coating provided around the tape envelope. Regarding cable improvement.
[0002]
[Prior art]
A shielded cable (also referred to as a metal cable having a shield) requires good communication characteristics and shielding to avoid signal leakage and noise contamination in a communication line, and the cable is extremely high in a multiplex digital network. Grade communication characteristics and shielding properties are required. In particular, the quality of communication characteristics and shielding properties of the coaxial drop-in cable are extremely important. Further, in the case of a coaxial cable used for leading-in to a terminal, a structure that can be freely bent is required, and the outer conductor needs to be highly flexible and to maintain a shielding property.
[0003]
In order to ensure high shielding properties and communication characteristics, it is preferable to use an aluminum pipe as a shielding body or an outer conductor, but there is a disadvantage that the flexibility is lacking.
Therefore, in a shielded cable used in a conventional information communication field, a tape-shaped shield in which a plastic layer is laminated on an aluminum foil layer is used to provide electrostatic shielding (see, for example, Patent Document 1).
[0004]
For example, the conventional shielded cable 1 shown in FIG. 2 has a layer structure in which a central conductor 2, an internal insulator 3 provided around the central conductor 2, and a plastic layer 4b laminated on an aluminum foil layer 4a. A tape formed by wrapping a tape 4 having a lateral width longer than the peripheral length of the outer periphery of the inner insulator 3 around the inner insulator 3 with the aluminum foil layer (metal foil layer) 4a inside. It has an enclosure 5 and an outer insulating coating 6 provided around the tape enclosure 5.
[0005]
In the shielded cable 1, first, as shown in FIG. 2A, the aluminum foil layer 4a in the surplus edge portions 7A and 7B on both sides of the tape 4 which are tightly surrounded and surrounded on the entire circumference of the inner insulator 3 are mutually connected. Are attached to each other to form a fin-shaped surplus portion 8.
Next, as shown in FIG. 2B, the fin-shaped surplus portion 8 is folded in two, and then the plastic layer 4b of the fin-shaped surplus portion 8 is applied to the plastic portion of the surrounding portion already in close contact with the internal insulator 3. The overlap portion 9 is formed by folding over the layer 4b, and the end faces 7a, 7b of the surplus edge portions 7A, 7B on both sides in the longitudinal direction of the tape enclosure 5 are sealed in the plastic layer 4b.
[0006]
An outer insulating coating 6 is provided around the tape surrounding body 5 by extrusion. The plastic layer 4b is melted by the heat at the time of the extrusion and fused to the outer insulating coating 6.
Therefore, the fin-shaped surplus portion 8 can maintain the continuity of the aluminum foil layer 4a and prevent a reduction in the shielding effect. In addition, even when the shielded cable 1 is bent or twisted, peeling can be reliably prevented, and loss of the shielding effect can be reliably avoided.
[0007]
[Patent Document 1]
Japanese Patent No. 3088998 [0008]
[Problems to be solved by the invention]
However, in the conventional shielded cable 1 shown in FIG. 2, since the thickness of the overlapped portion of the overlap portion 9 is increased, the internal insulator 3 and the external insulating coating 6 may be greatly deformed. However, there is a possibility that communication characteristics such as return loss are adversely affected.
Further, in the manufacturing process of the shielded cable 1, a folding step of folding the fin-shaped surplus portion 8 is added, so that there is a problem that productivity is reduced.
[0009]
Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide a good shielded cable capable of improving communication characteristics and productivity without lowering shielding performance.
[0010]
[Means for Solving the Problems]
An object of the present invention is to provide a center conductor, an inner insulator provided around the center conductor, and a layered structure in which a plastic layer is laminated on a metal foil layer, and a lateral width longer than a circumferential length of an outer periphery of the inner insulator. A tape envelope constituted by vertically wrapping a tape having a peripheral edge around the inner insulator so that one edge portion overlaps the other edge portion with the metal foil layer inside. A shielded cable having an outer insulating coating provided around the tape enclosure,
This is achieved by a shielded cable, wherein the plastic layer is made of a conductive resin.
[0011]
According to the shielded cable having the above configuration, since the plastic layer of the tape constituting the tape enclosure is made of a resin having conductivity, the conductivity is not interrupted at the overlapping portion of the tape, and continuity is maintained and shielding is performed. The effect is prevented from lowering, and high frequency noise is prevented from being mixed in from the overlapped portion.
Further, in the overlapping portion, since one edge portion of the tape is merely wrapped in the vertical direction so as to overlap the other edge portion, the thickness of the overlapping portion may be increased. In addition, there is no possibility that the inner insulator or the outer insulating coating is greatly deformed. Further, since a troublesome folding step such as folding a fin-like surplus portion as in the related art is not required, the productivity does not decrease.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
As shown in FIG. 1, the shielded cable 11 of the present embodiment includes a center conductor 12, an inner insulator 13 provided around the center conductor 12, an aluminum foil layer (metal foil layer) 14a, and a plastic layer 14b. A tape 14 having a layer structure obtained by laminating a tape and having a lateral width longer than the circumference of the outer periphery of the inner insulator 13 is provided at one edge portion of the inner insulator 13 with the aluminum foil layer 14a inside. This is a coaxial cable having a tape envelope 15 formed by wrapping in a longitudinal direction so that 14B overlaps the other edge portion 14A, and an outer insulating coating 16 provided around the tape envelope 15. .
[0013]
The tape 14 is a tape-shaped shield formed by laminating a plastic layer 14b made of a conductive resin on an aluminum foil layer 14a. One end of the tape 14 is longer than the peripheral length of the outer periphery of the internal insulator 13. An edge portion 14B is wrapped in the longitudinal direction so as to overlap with the other edge portion 14A that directly contacts the internal insulator 13.
[0014]
In addition, as the material of the plastic layer 14b having conductivity, a resin having conductivity itself or a resin obtained by adding a conductive material such as carbon black at 30 to 40% by weight to a resin such as polyethylene can be used. . As the resin material at that time, any resin material may be used as long as it is fused together when forming the outer insulating coating 16 made of polyethylene, flame-retardant polyethylene, or the like, and other resin materials may be used.
[0015]
In the shielded cable 11, the tape 14 is attached to the inner insulator 13 in the longitudinal direction such that the one edge portion 14B overlaps the other edge portion 14A with the aluminum foil layer 14a inside. After winding, an outer insulating coating 16 is provided around the tape enclosure 15 by extrusion, and the plastic layer 14b is melted by heat during the extrusion, and is fused to the outer insulating coating 16. .
[0016]
In the shielded cable 11, since the plastic layer 14b of the tape 14 constituting the tape enclosure 15 is made of a conductive resin, the overlapping portion of one edge portion 14B and the other edge portion 14A of the tape 14 is formed. In this case, the conductivity is not interrupted.
That is, the plastic layer 14b (portion indicated by reference numeral 17) sandwiched between the aluminum foil layers 14a of the both end portions 14B and 14A of the tape 14 itself has conductivity. The conduction continuity is maintained at the joining portion.
Therefore, it is possible to prevent a reduction in the shielding effect at the overlapping portion of the tape 14, and it is possible to reliably prevent high frequency noise from being mixed from the overlapping portion.
[0017]
Further, in the overlapping portion, one edge portion 14B of the tape 14 is merely wrapped in the vertical direction so as to overlap the other edge portion 14A, so that the thickness of the overlapping portion is reduced. Without increasing, there is no possibility that the inner insulator 13 or the outer insulating coating 16 is greatly deformed.
[0018]
Therefore, the shielded cable 11 has improved communication characteristics such as return loss, and does not require a troublesome turn-back step as in the manufacturing process of the conventional shielded cable 1 shown in FIG. improves.
[0019]
Incidentally, the configuration of the center conductor, the inner insulator, the metal foil layer, the plastic layer, the tape, the tape envelope, the outer insulating coating, and the like in the shielded cable of the present invention are not limited to the configuration of the above-described embodiment, It goes without saying that various forms can be adopted based on the spirit of the present invention.
For example, although an aluminum foil layer is used in the above embodiment, another metal foil layer such as a copper foil layer may be used. Further, in the above-described embodiment, an example in which the shielded cable of the present invention is applied to a coaxial cable has been described, but application to a cable having a similar shielding structure, such as a CCP cable, is also possible.
[0020]
【The invention's effect】
As described above, according to the shielded cable of the present invention, since the plastic layer of the tape is formed of a resin having a conductive property, the conductivity is not interrupted at the overlapping portion of the tape forming the tape enclosure, High frequency noise from the overlapping portion can be reliably prevented from being mixed. Further, in the overlapping portion, since one edge portion of the tape is merely wrapped in the longitudinal direction so as to overlap the other edge portion, the thickness of the overlapping portion does not increase. In addition, there is no possibility that the inner insulator or the outer insulating coating is significantly deformed. Therefore, it is possible to provide a good shielded cable that can improve communication characteristics and productivity without lowering the shielding performance.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a configuration of a shielded cable according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing a configuration of a conventional shielded cable, in which (a) shows a state in which a fin-shaped surplus portion is formed at a surplus end edge portion and a tape is wrapped in the longitudinal direction, and (b) Indicates an external conductor in the form of a tape in which a fin-shaped surplus portion is folded in two and an overlap portion is formed.
[Explanation of symbols]
11 shielded cable 12 center conductor 13 inner insulator 14 tape 14a aluminum foil layer (metal foil layer)
14b Plastic layer 14A Other edge portion 14B One edge portion 15 Tape enclosure 16 External insulating coating

Claims (1)

A tape having a center conductor, an inner insulator provided around the center conductor, and a layer structure in which a plastic layer is laminated on a metal foil layer and having a width greater than the circumference of the outer periphery of the inner insulator. A tape envelope formed by wrapping around the inner insulator in the longitudinal direction so that one edge portion is overlapped with the other edge portion with the metal foil layer being inside; A shielded cable having an outer insulating coating provided around,
A shielded cable wherein the plastic layer is made of a conductive resin.

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