JPH044516A - Shielded cable with drain wire - Google Patents

Abstract

PURPOSE:To indicate an equal shield effect in the direction of electromagnetic wave, to reduce weight, and to reduce size by providing a drain wire in a spiral form in such a way that it is buried in or is connected with a conductive resinous layer. CONSTITUTION:A conductor 11 is provided in the center, and an insulated layer 14, a coated insulated layer 15 are provided on the outer periphery of the conductor, while a drain wire 13 is provided along the conductive resinous layer 14. The drain wire 13 is provided in a spiral form in such a way that it is buried in or connected to the conductive resinous layer 14. Since the drain wire 13 is wound in a spiral in such a way that it is connected to the conductive resinous layer 14, anisotropy of a shield effect can be eliminated. The excellent shield effect ranging over high frequency region can be obtained, while the features of light weight and small size are achieved by thinning the cable diameter through the flattening of the drain wire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shielded electric wire with a drain wire used for electrical connection of electronic equipment and the like.

[Conventional technology]

Conventionally, as shown in FIG. 5, this type of shielded wire has a conductor 1 at its center, an insulating layer 2 and a shielding layer 4 on its outer periphery.
There is known a device in which an outer insulating layer 5 is provided and a drain wire 3 is provided along the shield layer 4 for the purpose of improving the workability of grounding connection (Japanese Utility Model Publication No. 53-48998). As the shield layer 4, a metal conductor such as metal braid or metal foil is used.

[Problem to be solved by the invention]

In the conventional shielded electric wire with a drain wire, since an electric wire (conductor) with a circular cross section is used as the drain wire 3, the diameter of the shielded electric wire becomes thick, which becomes an obstacle to miniaturization and space reduction.

Further, when a conductive resin is used as the shield layer 4, if the drain wire 3 is provided parallel to the conductor 1 as in the conventional case, anisotropy occurs and a uniform shielding effect cannot be obtained.

Furthermore, a shielded wire that does not have a drain wire and uses conductive resin has been disclosed, but it is difficult to put it into practical use because high conductivity cannot be obtained, so metal braid or metal foil has been put into practical use. . However, metal braids require a high braid density and tend to be heavy and expensive, and metal foils lack flexibility and are not durable due to deterioration due to corrosion.

The present invention has been made in view of the above problems, and exhibits an average shielding effect in the direction of electromagnetic waves,
To provide a shielded electric wire with a drain wire having a structure that is lightweight, compact and can be manufactured at low cost.

[Means to solve the problem]

In order to achieve the above-mentioned object, in the present invention, as described in claim A shielded wire including a drain wire provided along with a conductive resin layer is characterized in that the drain wire is embedded in or in contact with the conductive resin layer and is provided in a spiral shape.

As described in claim (2), it is preferable to use a highly conductive conductive resin having a volume resistivity of 10<-3> to 10<4>[Omega].

The spiral winding of the drain wire is 200 times/m or less, and one or more wires are wound in parallel or crossing each other (claim (3)
)).

In addition, in order to reduce the diameter of the shielded wire, claim (4)
1, as described in (5), the cross-sectional area S1 of the conductive resin layer
and the cross-sectional area S2 of the drain wire, S1/sz<t5
00, and the drain wire is preferably in the shape of a flat ribbon.

[For production]

In the shielded electric wire with drain wire of the present invention, since the drain wire is spirally wound around the inner or outer surface of the conductive resin layer while being in contact with the conductive resin layer, the anisotropy of the shielding effect is eliminated.

As a conductive resin layer, the volume resistivity is 104 to 10-2Ω
・Despite using the conductive material shown in the mark, excellent shielding properties are obtained, and compared to conventional metal braids and metal foils, it is lighter and cheaper to manufacture, does not deteriorate due to corrosion, and is durable. and confidence improves.

Furthermore, by using a flat drain wire, the diameter of the shield wire can be made smaller and smaller, and by attaching it in a spiral shape, an excellent shielding effect up to high frequency overload can be obtained.

Hereinafter, the above configuration and operation will be specifically explained with reference to drawings showing examples.

〔Example〕

In FIG. 1, A is a shielded electric wire with a drain wire, in which a conductor 11 made of copper wire is covered with an insulating layer 12, and a drain wire 13 is spirally wound thereon at a rate of 10 times/m, and further conductive. resin layer 14 and outer insulation layer 15
It is coated and insulated with.

Preferably, the drain wire 13 is wound at least twice per meter. In the illustrated example, the drain wire 13 is wound around the outer periphery of the insulating layer 12, that is, inside the conductive resin layer 14, but it can also be wound around the outside of the conductive resin layer 14 as long as it is in contact with it. . Alternatively, it may be embedded inside the conductive resin layer 14.

As shown in the drawing, this drain wire 13 is preferably a ribbon-shaped metal conductor (hereinafter referred to as a rectangular conductor) with a flat cross section. This rectangular conductor can also be plated. It is desirable that the rectangular conductor has a width to thickness ratio of 1 or more, preferably 10 or more. Alternatively, a flat braid made of thin conductors arranged in a ribbon shape may be used.

In addition, in relation to the cross-sectional area (Sz) of the drain wire 13 and the cross-sectional area (S, ) of the conductive resin layer 14, Sl /
It is desirable that sz <1soo, and within this range, either a single wire or a double wire may be used. In the case of a double wire, the wires can be wound parallel to each other or crossing each other.

For the conductive resin layer 14, a conductive resin having a volume resistivity of 104Ω or less is used.

The compositions of the matrix (base material) of the conductive resin, the conductivity imparting material, and other additives are not particularly limited. For example, the matrix may be a thermoplastic resin such as PE, PP, EVA, or PVC, a thermosetting resin such as an epoxy resin or a phenolic resin, a rubber such as silicone rubber, EPDM, CR, or fluorine rubber, or a styrene-based or olefin-based resin. thermoplastic elastomers and UV curing resins are used. One or two of metal powder, metal fiber, carbon blank, PAN carbon fiber, pinch carbon fiber, vapor-grown carbon fiber, or metal-plated or graphitized carbon fibers are added to this matrix as a conductivity imparting material. By combining more than one species, a conductive resin with a desired volume resistivity can be obtained. Additionally, additives such as processing aids, fillers, reinforcing materials, etc. can also be added.

For example, as a conductive resin, 20 to 160 parts by weight of graphitized vapor-grown carbon fiber pulverized to 0.1 to 50 μm are added to 100 parts by weight of ethylene vinyl acetate resin as the base material, and then pressurized. By kneading using a compounding machine such as a kneader, a Henschel mixer, or a twin-screw extrusion mixer, and extrusion molding according to a conventional method, the volume resistivity is 10-3 to 103Ω.
A highly conductive material can be obtained.

[Test example]

Test Example 1 A copper conductor with a cross-sectional area of 0.3 m'' and an outer diameter of 1.1 mm using PVC.
φ coated electric wire, l, 5 tm x 0.1 t
A rectangular conductor plated (tin plating: 1 μm) is spirally wound around a copper conductor of 10° Ω at a rate of 10 turns/m, and this is wrapped around a 10° Ω copper conductor using vapor-grown carbon fiber as a conductivity imparting material. A shielded electric wire with a drain wire was produced by covering the wire with a conductive resin having a volume resistivity to a thickness of 0.5 m, and providing an insulating jacket layer thereon.

This shielded wire was eccentrically placed in a copper pipe 16 (inner diameter 10 nφ, length 100 cm) of measuring device B shown in FIG. 2, and the anisotropy of the shielding effect was confirmed. In the figure, 17
indicates a FET probe, and 18 indicates a spectrum analyzer.

The measurement method is to apply an electric field to the copper pipe and measure the induced voltage (■.) to the electric wire placed inside the pipe, and then measure the induced voltage (■.) to the inner electric wire when the drain wire is connected to the ground. , ) were measured, and the initial attenuation at each frequency was determined using the following formula.

In the formula, S: shielding effect, vo: initial induced voltage, ■,
,: The induced voltage measurement results after shielding are shown in curve a in FIG.

Comparative Test Examples 1 to 3 A copper conductor with a cross-sectional area of 0.3 m'' and an outer diameter of 1.1 nφ made of PVC.
A 0.3 m" copper conductor is attached in parallel to the wire coated with a drain wire (see Figure 5), and a volume resistivity of 100 Ω is applied using vapor-grown carbon fiber as a conductivity imparting agent. coated with a conductive resin having a thickness of 0.5 m,
A shielded wire with a drain wire (A') was produced by providing an outer insulating layer thereon.

This shield vAA' is eccentrically placed so that the drain wire 3 is on the lower side (Comparative Test Example 1) and the upper side (Comparative Test Example 2) at the bottom of the copper pipe 16 as shown in FIG. Similar to 1, the anisotropy of the shielding effect was confirmed.

The results are shown in curves 1 and 2 in FIG. 4, respectively.

In addition, as Comparative Test Example 3, in place of the conductive resin with a volume resistivity of 10°Ω·1 in Test Example 1,
'Make an electric wire with a drain wire using one of Ω・1,
The measurement results are shown in curve d in FIG.

As is clear from Fig. 4, anisotropy is seen in curves (a) and (c) in which the drain wires are parallel, whereas curve (a) in which the drain wire in test example 1 is made in a spiral shape shows anisotropy. In addition, the shielding effect at high frequencies is far superior to curve d.

〔Effect of the invention〕

As explained above, the shielded electric wire with a drain wire of the present invention has no anisotropy, has an excellent shielding effect in a high frequency range, and can reduce the diameter of the electric wire by flattening the drain wire.

Also, as a shield layer, a volume resistivity of 10-3 to 10
Excellent workability due to the adoption of 4Ω conductive resin,
It is lighter and more compact, and has a shielding effect comparable to that of metal braid.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the shielded electric wire with a drain wire of the present invention, Fig. 2 is an explanatory diagram of an apparatus for measuring the shielding effect of the shielded electric wire according to the above, and Figs. FIG. 4 is a graph showing the shielding characteristics obtained in Test Example 1 and Comparative Tests 1 and 2. FIG. 5 is a perspective view of a conventional example. A... Shielded electric wire with drain wire, 11... Conductor, 12... Insulating layer, 13... Drain wire, 14...
...Conductive resin layer, 15... Outer insulation layer. Patent applicant Yazaki Sogyo Co., Ltd. Figure 1 Figure 2 (a) (b) Figure 4

Claims (5)

[Claims] (1) In a shielded wire in which an insulating layer, a conductive resin layer, and an insulating jacket layer are sequentially provided on the outer periphery of a conductor, and a drain wire is provided along with the conductive resin layer,
A shielded electric wire with a drain wire, characterized in that the drain wire is embedded in or in contact with a conductive resin layer and provided in a spiral shape. (2) Volume resistivity of conductive resin is 10^-^3~10^
The shielded electric wire with drain wire according to claim (1), which has a resistance of 4 Ω·cm. (3) Claim (1) in which one or more drain wires are attached spirally in parallel or intersectingly at a pitch of 200 times/m or less.
) or (2) shielded wire with drain wire. (4) The ratio of the cross-sectional area (S_1) of the conductive wire resin layer to the cross-sectional area (S_2) of the drain wire is S_1/S_2<150.
The shielded electric wire with a drain wire according to any one of claims (1) to (3), wherein the shielded electric wire is formed to have a drain wire. (5) The shielded electric wire with a drain wire according to any one of claims (1) to (4), wherein the drain wire is formed in a flat ribbon shape.