JP2006351414A - Coaxial cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the diameter of a coaxial cable, and enable improvement of handling property and downsizing of an equipment. <P>SOLUTION: The coaxial cable 1 is constituted of the center conductor 3, an insulator 5 arranged and installed at the outer periphery of this center conductor 3, a first outside conductor 9 consisting of the longitudinally attached metal/plastic composite tape so as to have an overlapping part 9A at the outer periphery of this insulator 5, a second outside conductor 11 consisting of laterally wound metal/plastic composite tape so as to have an overlapping part 11A at the outer periphery of this first insulator 9, and the outer jacket 13 covering the outer periphery of this second outside conductor 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coaxial cable, and more particularly, to a coaxial cable that is used for information communication and is capable of reducing the diameter, improving handleability, and reducing the size of equipment.

  Currently, with the advancement of computerization of automobiles and home appliances and high-frequency transmission being required, coaxial cables are used instead of conventional ribbon electric wires and twisted pair wires. In addition, information electronic devices are also increasing in speed and size. For coaxial cables used in these environments, not only transmission characteristics, but also reduction in diameter and improvement in handling are essential.

  Referring to FIGS. 7A and 7B, as a conventional coaxial cable 101, a central conductor 103 of a single wire or a stranded wire provided at the center of the cable, and the outer side of the central conductor 103 are covered substantially concentrically. An insulator 105 made of a fluorine-based resin such as polyethylene (PE) or PTFE, a first outer conductor 107 vertically attached (or laterally wound) outside the insulator 105, and an outer periphery of the first outer conductor 107 A structure in which an outer conductor composed of a second outer conductor 109 formed of a braid is provided, and an outer sheath 111 made of a resin such as PVC or polyethylene (PE) is applied to the outer periphery of the outer conductor. is there.

  The first outer conductor 107 may be a metal / plastic composite tape in which a metal layer is provided on one surface of a plastic tape or a simple metal tape. In the case of metal / plastic composite tape, the metal surface faces outward. In Patent Document 1, the first outer conductor 107 is a horizontal winding or vertical attachment of a single aluminum foil, and the second outer conductor 109 is a copper braid.

  In addition, the external conductor includes those composed of the first external conductor 107 and the second external conductor 109 as described above, and those that are simply in a metal pipe state.

  The coaxial cable 101 is classified into two types according to the characteristic impedance. The 50Ω system is D-type and the 75Ω system is C-type. In addition, as a product name, the outer diameter numerical value of the insulator 105 (insulating layer) is added in front of the above alphabets such as C and D. For example, in the case of the 2.5C type, a 75Ω type coaxial cable having an outer diameter of the insulator 105 of 2.5 mm is obtained.

  As another conventional coaxial cable, as in Patent Document 2, a plastic tape with a conductive layer is laterally wound or vertically attached to the outer periphery of a central conductor so that the conductive layer faces outward, and the conductive layer Some of the attached plastic tapes have outer coatings. In this case, the plastic tape is an insulator.

Further, as another conventional coaxial cable, as in Patent Document 3, a shielding layer is provided on the outer periphery of the core formed by providing an insulating layer on the outer periphery of the inner conductor (corresponding to the central conductor in FIG. 7). The outer periphery of this shielding layer is covered with a jacket. In addition, there is a structure in which the shielding layer has a large overlapping portion by vertically attaching a metal tape having a tensile elongation of 1.3% of the outer periphery of the insulator and having a tensile elongation of 2% or more.
Japanese Patent Laid-Open No. 9-293418 JP-A-8-287743 JP 2002-352637 A

  By the way, in the conventional coaxial cable 101 as in Patent Document 1, for example, as shown in FIGS. 7A and 7B, the outer conductor is the first outer conductor 107 and the second metal tape. In the structure using the braid as the external conductor 109, it is possible to secure a certain degree of bending ease, but there is a problem that the outer diameter becomes thick. For example, the outer diameter of the cable is about 4 mm in the case of the 2.5C type coaxial cable 101 and about 3 mm in the case of the 1.5D type coaxial cable 101. The minimum bending radius of these coaxial cables 101 is as large as about 60 mm, and there is a problem that wiring in a narrow place becomes difficult.

  On the other hand, when a metal pipe is used as the outer conductor, the electrical characteristics are good, but there is a problem that the coaxial cable 101 is difficult to bend because of the pipe shape. In order to solve this problem, some metal pipes have a spiral or ring-like groove to make it easy to bend, but there is a problem that they are vulnerable to repeated bending.

  In addition, in the coaxial cable as in Patent Document 2, when a plastic tape with a conductive layer is vertically attached, it becomes a pipe state, so that when the bend is given, the joint of the tape is opened or inside the bend. There was a problem that the electric characteristics deteriorated due to a wandering. On the other hand, when a plastic tape with a conductive layer is wound sideways, it is effective for bending, but the conductive layer is connected in a spiral shape, resulting in a long electrical path. There was a problem of adversely affecting the characteristics.

  Further, in the coaxial cable as in Patent Document 3, the shielding layer is made of metal even when it is bent by being vertically attached with a metal tape having a tensile elongation of 1.3 times the outer circumference of the insulator and having a tensile elongation of 2% or more. The tape joints are kept from opening and the bendability is improved, but the overlapping part of the metal tape must be widened, and it is necessary to select a material that considers bendability. In order to improve the thickness of the metal tape, a certain amount of metal tape is required. Therefore, there is a problem in that there is a limit in reducing the diameter and improving the bendability.

  The present invention has been made to solve the above-described problems.

  A coaxial cable according to the present invention includes a first external conductor comprising a center conductor, an insulator disposed on the outer periphery of the center conductor, and a metal / plastic composite tape vertically attached so as to have an overlapping portion on the outer periphery of the insulator. Consists of a conductor, a second outer conductor made of a metal / plastic composite tape that is wound in a lateral manner so as to have an overlapping portion on the outer periphery of the first outer conductor, and a jacket covering the outer periphery of the second outer conductor It is characterized by being.

  In the coaxial cable according to the present invention, it is preferable that the metal surface of the first outer conductor is directed outward and the metal surface of the second outer conductor is directed inward in the coaxial cable.

  As will be understood from the means for solving the problems as described above, according to the present invention, the outer conductor does not use a braid as in the prior art, that is, originally a thin and light metal / plastic composite tape. By using two sheets, it is possible to reduce the diameter and weight of the conventional coaxial cable that employs a metal tape or a metal braid as an outer conductor.

  Further, the outer conductor is composed of two metal / plastic composite tapes, the first outer conductor is constituted as a vertical attachment in the first layer, and the second outer conductor is constituted as a horizontal winding in the second layer, The flexibility of the coaxial cable can be improved and it can be bent more easily than the case where only the vertical attachment is used. That is, the laterally wound second outer conductor is effective against bending, and also has an effect of suppressing an attempt to open the overlapping portion of the metal / plastic composite tape of the first outer conductor attached vertically.

  In addition, two metal / plastic composite tapes form the first outer conductor as a vertical attachment on the first layer, and the second outer conductor as a horizontal winding on the second layer. It can be improved more than just the case.

  Embodiments of the present invention will be described below with reference to the drawings.

  Referring to FIGS. 1A and 1B, a coaxial cable 1 according to this embodiment includes a central conductor 3 of a single wire or a stranded wire provided in the center and a substantially concentric shape outside the central conductor 3. An insulator 5 made of a fluorine-based resin such as polyethylene (PE) or PTFE, and a metal / plastic composite tape 7 vertically attached so as to have an overlapping portion 9A on the outer periphery of the insulator 5 (see FIG. 2) A first outer conductor 9 made of metal, a second outer conductor 11 made of a metal / plastic composite tape 7 that is laterally wound so as to have an overlapping portion 11A on the outer periphery of the first outer conductor 9, and the second outer conductor 11 And an outer cover 13 as an outermost layer made of a resin such as PVC or polyethylene (PE) coated on the outer periphery of the cover.

  The coaxial cable 1 is classified into two types according to the characteristic impedance. The 50Ω system is D-type and the 75Ω system is C-type. In addition, as a product name, the outer diameter numerical value of the insulator 5 (insulating layer) is added in front of the alphabets such as C and D described above. For example, in the case of the 2.5C type, a 75Ω type coaxial cable having an outer diameter of the insulator 5 of 2.5 mm is obtained.

  The first outer conductor 9 and the second outer conductor 11 will be described in detail. The metal / plastic composite tape 7 constituting the first and second outer conductors 9 and 11 is as shown in FIG. In this structure, for example, a metal foil 15 as a metal layer is attached to one side of the plastic tape 17 and fixed. In the metal / plastic composite tape 7, the metal foil 15 may be an aluminum foil or a copper foil, or other metal foil.

  In this embodiment, for example, in the structure of the metal / plastic composite tape 7, an aluminum foil as the metal foil 15 is attached to one surface of the plastic tape 17 via an adhesive layer (not shown), for example. Alternatively, as another embodiment, the plastic tape 17 may be vapor-deposited and fixed on one side, or may be fixed by another method.

  The first outer conductor 9 configured as described above is vertically attached to the outer periphery of the insulator 5 as shown in FIGS. 3 and 5. More specifically, the plastic tape 17 is vertically attached to the outer periphery of the insulator 5 so that the metal foil 15 of the first outer conductor 9 faces the outside so as to have an overlapping portion 9A. Further, the second outer conductor 11 configured as described above is wound around the outer periphery of the first outer conductor 9 as shown in FIGS. 4 and 5. More specifically, the plastic tape 17 is horizontally wound around the outer periphery of the metal foil 15 of the first outer conductor 9 so that the metal foil 15 of the second outer conductor 11 faces the inner side and has an overlapping portion 11A.

  With the above configuration, as shown in FIG. 5, the surfaces of the metal foils 15 of the first and second outer conductors 9 and 11 are in close contact with each other, and apparently form one metal layer. Furthermore, since the second outer conductor 11 is wound sideways, it is effective against bending and also has an effect of suppressing changes in the metal / plastic composite tape 7 attached to the first outer conductor 9 in the vertical direction. In addition, the outer diameter of the coaxial cable 1 of this embodiment is a small diameter because there is no braided layer as in the prior art. As a result, the flexibility of the coaxial cable 1 can be maintained and the electrical characteristics can be prevented from being deteriorated.

  Next, as shown in Table 1, 1.5D type and 2.5C type of the coaxial cable 1 according to the embodiment of the present invention, and 1.5D type and 2.5C type of the coaxial cable 19 of the comparative example. The structure and properties of the molds were compared. The coaxial cable 19 of the comparative example has substantially the same structure as the conventional coaxial cable 101, but has a structure in which the outer conductor has a single metal / plastic composite tape 7 and a braid.

  Further, as comparative characteristics, the attenuation amount (dB / 100 mm at 0.5 GHz), the minimum bending radius (mm) and the weight (kg / 100 m) of each of the coaxial cables 1 and 19.

  As shown in Table 1, the structure of the outer conductor is different in each coaxial cable 1, 19. The material and outer diameter of each coaxial cable 1, 19 are as shown in Table 1. is there.

  That is, in the coaxial cable 1 of this embodiment, the structure of each metal / plastic composite tape 7 of the first and second outer conductors 9 and 11 is a copper foil when the metal foil 15 is 1.5D type. The 5C type is an aluminum foil, and its thickness is 9 microns (μm). The plastic tape 17 is PET (polyethylene terephthalate), and its thickness is 25 microns (μm).

  In the coaxial cable 19 of the comparative example, the structure of the outer conductor is a metal / plastic composite tape 7 and a braided structure provided on the outer periphery thereof. The structure of the metal / plastic composite tape 7 corresponds to the coaxial cable 1 described above. The metal foil is a copper foil in the case of 1.5D type, and is an aluminum foil in the case of 2.5C type. Micron (μm). The plastic tape is PET (polyethylene terephthalate), and the thickness thereof is 25 microns (μm).

  As shown in Table 1, the coaxial cable 1 of this embodiment has an attenuation of 46.1 (dB / 100 mm) of the comparative example in the 1.5D type compared to the coaxial cable 19 of the comparative example. On the other hand, it is almost the same as 46.9 (dB / 100 mm), and the minimum bending radius is 38.0 (mm) smaller than 45.0 (mm) of the comparative example, and the cable weight is that of the comparative example. It is about 0.7 (kg / 100m) and 1/2 with respect to 1.4 (kg / 100m), and the difference of 0.7 (kg / 100m) is also lighter.

  In the 2.5C type, the attenuation is approximately the same as 29.1 (dB / 100 mm) with respect to 28.4 (dB / 100 mm) in the comparative example, and the minimum bending radius is 60.0 (in comparison example). mm) is 54.0 (mm), and the cable weight is 1.7 (kg / 100 m), which is approximately 2/3 of 2.4 (kg / 100 m) of the comparative example. The difference of 0.7 (kg / 100m) is also lighter.

  As described above, the coaxial cable 1 of this embodiment achieves improved bendability and weight reduction without changing the attenuation, as compared with the conventional comparative example.

  Next, in order to investigate the difference in attenuation due to the winding method of the metal / plastic composite tape 7 on the outer conductor, (1) the case where the two metal / plastic composite tapes 7 are crossed by horizontal winding, and (2) As in this embodiment, two metal / plastic composite tapes 7 are vertically attached to the first layer and horizontally wound to the second layer, and (3) one metal / plastic composite tape 7 is vertically attached. Comparison was made between the amount of attenuation and frequency characteristics using a 1.5D type coaxial cable for the three cases. The result is shown in FIG.

  As can be seen from FIG. 6, the structure in which the first layer (2) is vertically attached and the second layer is horizontally wound has the best result.

From the above, the coaxial cable 1 of this embodiment has the following effects.
(1) Since the outer conductor does not use a braid as in the past, that is, by using a metal / plastic composite tape 7 that is originally thin and light, a normal tape that employs a metal tape or metal braid as an outer conductor is used. It is possible to reduce the diameter and weight of the coaxial cable.

(2) The surface of the metal foil 15 of the metal / plastic composite tape 7 constituting the first and second outer conductors 9 and 11 is made to face each other so that the first and second outer conductors 9 and 11 appear. In the above, since it is in a pipe state, that is, one metal layer, the electrical characteristics can be improved (in the embodiment, the amount of attenuation is reduced) as compared with the case of only horizontal winding.

(3) The outer conductor is composed of two metal / plastic composite tapes 7 with the first layer vertically attached and the second layer horizontally wound. Flexibility can be improved and bending can be facilitated.

  That is, the second outer conductor 11 that is laterally wound is effective for bending, and prevents the overlapping portion 9A of the metal / plastic composite tape 7 of the first outer conductor 9 attached vertically to be opened. There is also an effect.

  In the above-described embodiment, the surfaces of the metal foils 15 of the metal / plastic composite tape 7 constituting the first and second outer conductors 9 and 11 are opposed to each other. In order to achieve this, the metal foil 15 of the metal / plastic composite tape 7 does not necessarily face each other. Even in this case, the electrical characteristics are improved by the metal foil 15 of the two metal / plastic composite tapes 7 than when only one metal / plastic composite tape 7 is used.

(A) is sectional drawing of the coaxial cable of embodiment of this invention, (B) is the perspective view. It is a fragmentary sectional view of a metal plastic composite tape. It is state explanatory drawing when attaching the metal and plastic composite tape of a 1st outer conductor vertically to the outer periphery of an insulator. It is state explanatory drawing when a metal and plastic composite tape of a 2nd outer conductor is wound horizontally on the outer periphery of a 1st outer conductor. It is a fragmentary sectional view of the metal / plastic composite tape of the 1st, 2nd outer conductor arrange | positioned at the outer periphery of an insulator. It is a graph of the amount of attenuation and frequency characteristics in three ways of winding a metal / plastic composite tape on an outer conductor. (A) is sectional drawing of the conventional coaxial cable, (B) is the perspective view.

Explanation of symbols

1 Coaxial cable (in this embodiment)
3 Central conductor 5 Insulator 7 Metal / plastic composite tape 9 First outer conductor 9A Overlap portion 11 Second outer conductor 11A Overlap portion 13 Cover 15 Metal foil 17 Plastic tape 19 Coaxial cable (for comparative example)

Claims (2)

  A first outer conductor comprising a central conductor, an insulator disposed on an outer periphery of the central conductor, a metal / plastic composite tape vertically attached so as to have an overlapping portion on the outer periphery of the insulator, and the first outer conductor It is characterized by comprising a second outer conductor made of a metal / plastic composite tape that is laterally wound so as to have an overlapping portion on the outer periphery of the conductor, and a jacket covering the outer periphery of the second outer conductor. Coaxial cable.   The coaxial cable according to claim 1, wherein the metal surface of the first outer conductor is directed outward and the metal surface of the second outer conductor is directed inward.

Images