WO2015118942A1

WO2015118942A1 - Shielded wire

Info

Publication number: WO2015118942A1
Application number: PCT/JP2015/051381
Authority: WO
Inventors: 亮真上柿
Original assignee: 株式会社オートネットワーク技術研究所; 住友電装株式会社; 住友電気工業株式会社
Priority date: 2014-02-06
Filing date: 2015-01-20
Publication date: 2015-08-13
Also published as: JP2015149175A

Abstract

A shielded wire (1) has a core portion (2), and a braided shield layer (3) which covers the outer periphery of the core portion (2). The core portion (2) is provided with a coated wire (21) which has a conductor (211) and insulating material (212) that covers the perimeter of the conductor (211). The braided shield layer (3) is configured so that a plurality of strands (31) are woven thereinto. The strands (31) each comprise Al wire or Al alloy wire as base material (311), and each have, on the surface thereof, a plating coating (312) comprising a metal that is less susceptible to oxidation than Al.

Description

Shielded wire

The present invention relates to a shielded electric wire.

For example, shielded wires are used in places where countermeasures against electromagnetic noise are required in automobiles and electrical equipment. The shielded electric wire has a core part that transmits electrical signals and the like, and a shield layer that covers the outer periphery of the core part. Intrusion of electromagnetic noise from the outside to the core part, and electromagnetic noise from the core part to the outside The radiation can be suppressed by the shield layer. As the shield layer, for example, a braided shield layer formed by braiding metal strands is known.

Conventionally, a wire made of Cu or a Cu alloy has been used as a metal wire used for a shield layer from the viewpoint of conductivity and workability. In recent years, in order to reduce the weight of the entire shielded electric wire, a shield layer made of a lighter strand is desired. For example, Patent Document 1 describes a shielded electric wire having a shield layer configured by braiding a metal-coated fiber formed by forming a metal film on the outer periphery of a heat-resistant fiber.

JP 2013-110053 A

However, the shield layer using the metal-coated fiber as in Patent Document 1 has a problem that it is liable to cause a connection failure when connected to the ground wire.

On the other hand, it has been studied to employ a strand made of Al (aluminum) or an Al alloy, which is lighter and cheaper than Cu (copper), for the shield layer. Since the element wire made of Al or Al alloy is easily electrically connected to the ground wire, the above-described problem of poor connection can be avoided. However, since Al has the property of being relatively easily oxidized, a film of Al ₂ O ₃ which is a nonconductor is inevitably formed on the surface. Due to the presence of the Al ₂ O ₃ film, the wire composed of Al or Al alloy has a high AC resistance in a high frequency region where the influence of the skin effect becomes significant. Therefore, there is a problem that the shielding performance against electromagnetic noise in the high frequency region is lowered.

The present invention has been made in view of such a background, and intends to provide a shielded electric wire that is inexpensive and lightweight and has excellent shielding performance.

One aspect of the present invention is a core portion including a covered electric wire having a conductor and an insulating material coated around the conductor;
A braided shield layer covering the outer periphery of the core part, comprising a plurality of strands knitted,
The element wire is a shielded electric wire characterized in that an Al wire or an Al alloy wire is used as a base material, and a plating film made of a metal that is harder to be oxidized than Al is provided on the surface.

The shielded electric wire has a braided shield layer formed by braiding a plurality of strands and covering the outer periphery of the core portion. Moreover, the said strand is comprised by using Al wire or Al alloy wire as a base material, and has the plating film which consists of a metal which is hard to oxidize than Al on the surface. Therefore, it is possible to prevent the Al ₂ O ₃ film from being formed on the surface of the base material. Moreover, since the said plating film is comprised from the metal which is harder to oxidize than Al, it can suppress that the oxide film which is a nonconductor is formed on the surface of the said strand. As a result, the element wire can reduce the AC resistance in the high frequency region as compared with the conventional element wire not having a plating film. And the said braided shield layer improves the shielding performance with respect to the electromagnetic noise of a high frequency area | region by using the said strand, and has the outstanding shielding performance.

Moreover, since the said strand uses the Al wire or Al alloy wire for the said base material, it is cheap and lightweight compared with the strand which consists of Cu or Cu alloy.

As described above, the shielded electric wire is inexpensive and lightweight and has excellent shielding performance.

The side view of the shielded electric wire in Example 1. FIG. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. Sectional drawing of the strand in Example 1. FIG. FIG. 3 is an explanatory diagram of measurement of an induced noise amount in the first embodiment. Sectional drawing equivalent to FIG. 2 of the 2-core shielded electric wire which has a core part provided with two covered electric wires. Sectional drawing equivalent to FIG. 2 of the 3 core shielded electric wire which has a core part provided with the three covered electric wires. Sectional drawing equivalent to FIG. 2 of the 4-core shielded electric wire which has a core part provided with four covered electric wires.

The shielded wire may be configured as a power line that transmits a relatively large current such as operating power, or may be configured as a signal line that transmits a relatively small current such as a control signal. Moreover, the said shielded electric wire may be comprised as a single core shielded electric wire which has one said covered electric wire, and may be comprised as a multi-core shielded electric wire which has two or more said covered electric wires.

As a conductor used for the said covered electric wire, it is using the metal wire which has the outstanding electrical conductivity, such as Cu wire, Cu alloy wire, Sn (tin) plating Cu alloy wire, Al wire, and Al alloy wire, for example. it can. The conductor may be composed of a single metal wire, or may be composed of a stranded wire in which a large number of the metal wires are twisted together.

In addition, as the insulating material used for the covered electric wire, a conventionally known material can be used as the insulating material for the electric wire. From the viewpoints of insulation and manufacturability, a crosslinked polyethylene resin or a crosslinked polyvinyl chloride resin is often used as the insulating material.

The element wire constituting the braided shield layer is composed of an Al wire or an Al alloy wire as a base material, and has a plating film made of a metal that is harder to be oxidized than Al on the surface. Examples of the metal used for the plating film include metals having a higher standard oxidation-reduction potential than Al, such as Au (gold), Ag (silver), Cu (copper), Ni (nickel), and Sn (tin). Can be used. From the viewpoint of cost and conductivity, the plating film is preferably made of Sn.

Moreover, it is preferable that the thickness of the said plating film is 1 micrometer or more. In this case, the shielding performance in the high frequency region can be sufficiently improved. When the thickness of the plating film is less than 1 μm, the durability of the plating film may be insufficient depending on the application. That is, for example, when used as an automobile wire harness, the plating film may be worn away by vibration or bending, and the plating film may be easily peeled off. When the plating film is peeled off from the base material, an Al ₂ O ₃ film is formed on the surface of the base material, resulting in a decrease in shielding performance. From the viewpoint of enhancing the durability of the plating film and suppressing the above-described problems, the thickness of the plating film is preferably 1 μm or more.

Further, an intermediate film may be provided between the plating film and the base material as necessary. As an intermediate film, what has the effect | action which improves the adhesiveness of the said plating film and the said base material can be used, for example. For example, a Zn plating film, a Ni plating film, or the like can be used as the intermediate film.

The shielded electric wire having the above-described configuration can improve the shielding characteristics in a frequency region of 1 MHz or more as compared with a shielded electric wire using a bare wire having no plating film on the surface. Therefore, the shielded electric wire is suitable for applications that need to reduce electromagnetic noise in a frequency region of 1 MHz or higher. Such applications include, for example, automobile wire harnesses.

Example 1
An example of the shielded wire will be described with reference to FIGS. As shown in FIGS. 1 and 2, the shielded electric wire 1 includes a core portion 2 and a braided shield layer 3 that covers the outer periphery 22 of the core portion 2. The core part 2 is composed of a single covered electric wire 21 having a conductor 211 and an insulating material 212 covered around the conductor 211. The braided shield layer 3 is configured by braiding a plurality of strands 31. As shown in FIGS. 2 and 3, the element wire 31 has an Al wire as a base material 311, and has a plating film 312 made of Sn that is less oxidized than Al on the surface. Hereinafter, the configuration of the shielded electric wire 1 will be described in detail.

The covered electric wire 21 is made by forming a Cu wire having a cross-sectional area of 3 mm ² as a conductor 211 and extruding an insulating material 212 around the conductor 211.

As shown in FIG. 2, the braided shield layer 3 is formed in a unit of a bundle of strands 32 in which three strands 31 are arranged side by side. The braided shield layer 3 of this example has 24 pairs of strands 32. Although not shown in the drawing, each strand bundle 32 is knitted while being wound around the outer periphery 22 of the core portion 2 in a spiral shape. In this example, the twisting pitch of the strand bundle 32, that is, the distance that the strand bundle 32 travels in the longitudinal direction of the core portion 2 when the strand bundle 32 makes a spiral turn around the outer periphery 22 of the core portion 2 is 20 mm.

As shown in FIG. 3, the strand 31 has an Al wire with a diameter of 0.18 mm as a base material 311 and has a plating film 312 made of Sn on the surface. In addition, an intermediate film 313 made of Ni formed by plating is provided between the base material 311 and the plating film 312. The thickness of the plating film 312 in the shielded electric wire 1 of this example is 1 μm. The plating film 312 and the intermediate film 313 are formed by a conventionally known method.

In this example, the shielding performance was evaluated using the shielded electric wire 1 configured as described above. The evaluation method will be described below.

<Shield performance evaluation>
As shown in FIG. 4, the shielded electric wire 1 was placed in a straight line, one end 11 thereof was connected to the output terminal 41 of the network analyzer 4, and the other end 12 was connected to the 50 Ω termination resistor 5. Further, the noise induction wire 6 was arranged in parallel with the shielded electric wire 1, and one end 61 thereof was connected to the input terminal 42 of the network analyzer 4. The other end 62 of the noise induction wire 6 was opened.

Next, the AC signal generated from the network analyzer 4 was input to the noise induction wire 6 and the frequency of the AC signal was swept between 300 kHz and 3 GHz. Thereby, inductive noise derived from the AC signal was generated in the shielded electric wire 1, and the intensity of the reflected signal reflected from the shielded electric wire 1 toward the output terminal 41 was measured by the network analyzer 4. The intensity ratio of the reflected signal with respect to the AC signal was calculated using the intensity of the obtained reflected signal and the intensity of the AC signal input to the noise induction line 6, and the value was used as the amount of induced noise.

Further, a comparative electric wire consisting only of the core portion 2 without the braided shield layer 3 was prepared separately, and the amount of induction noise of the comparative electric wire was calculated by the same method as described above. And the difference of the induction noise amount of the shielded electric wire 1 and the induction noise amount of the comparison electric wire obtained when the frequency of the AC signal was 10 MHz was obtained. As a result, the shielded electric wire 1 was able to reduce the amount of induced noise for a 10 MHz AC signal by 50 dB compared to the comparative electric wire.

(Example 2)
This example is an example of the shielded electric wire 1 using the wire 31 in which the thickness of the plating film 312 is changed from 1 μm to 2 μm. In this example, the shielded electric wire 1 was produced in the same manner as in Example 1 except that the film thickness of the plating film 312 was changed.

Further, similarly to Example 1, the amount of induction noise was measured using the shielded electric wire 1 and the comparative electric wire, and the difference between the two was determined. As a result, the shielded electric wire 1 of this example was able to reduce the amount of induced noise with respect to an AC signal of 10 MHz by 51 dB compared to the comparative electric wire.

(Comparative Example 1)
This example is an example of the shielded electric wire 1 using an annealed copper wire having a diameter of 0.18 mm. In this example, a shielded electric wire 1 was produced in the same manner as in Example 1 except that the annealed copper wire was used as the element wire 31.

Further, similarly to Example 1, the amount of induction noise was measured using the shielded electric wire 1 and the comparative electric wire, and the difference between the two was determined. As a result, the shielded electric wire 1 of this example was able to reduce the amount of induction noise for an AC signal of 10 MHz by 55 dB compared to the comparative electric wire.

(Comparative Example 2)
This example is an example of the shielded electric wire 1 using an Al wire having a diameter of 0.18 mm. That is, the shielded electric wire 1 of the present example includes the braided shield layer 3 having the base wire 311 itself in a state before the plating film 312 is formed on the surface as the element wire 31. Others are the same as in the first embodiment.

Further, similarly to Example 1, the amount of induction noise was measured using the shielded electric wire 1 and the comparative electric wire, and the difference between the two was determined. As a result, the shielded electric wire 1 of this example was able to reduce the amount of induced noise for an AC signal of 10 MHz by 38 dB compared to the comparative electric wire.

As is known from Examples 1 and 2 and Comparative Examples 1 and 2, the shielded wire 1 using the wire 31 having the plated film 312 made of Sn on the surface is a comparative wire that does not have the braided shield layer 3. In comparison, the amount of induced noise for an AC signal of 10 MHz could be reduced by 50 to 51 dB. This value is equivalent to the shielded electric wire 1 (Comparative Example 1) using a conventional annealed copper wire, and it can be seen that the shielded electric wires 1 of Example 1 and Example 2 have excellent shielding performance in a high frequency region. .

On the other hand, as in Comparative Example 2, when an Al wire that does not form the plating film 312 on the surface is used as the element wire 31, compared to a comparative electric wire that does not have the braided shield layer 3, The amount of induced noise is reduced by 38 dB. From the above results, the shielded electric wire 1 of Comparative Example 2 using the Al wire without forming the plating film 312 on the surface as the element wire 31 is inferior in shielding performance in the high frequency region as compared with the shielded electric wires 1 of Examples 1 and 2. I understand that.

In addition, although Example 1 and Example 2 showed the example of the single core shielded electric wire 1 which has the one covered electric wire 21 in the core part 2, the covered electric wire 21 of the core part 2 is suitably used according to a use. You may increase the number. For example, FIG. 5 shows an example of a two-core shielded electric wire 102 having two covered electric wires 21. FIG. 6 shows an example of a three-core shielded electric wire 103 having three covered electric wires 21. FIG. 7 shows an example of a four-core shielded electric wire 104 having four covered electric wires 21. Of the reference numerals used in FIGS. 5 to 7, the same reference numerals as those used in FIGS. 1 and 2 represent the same components as in the first embodiment.

Moreover, although Example 1 and Example 2 showed the example of the shielded electric wire 1 with the braided shield layer 3 exposed on the surface, the sheath covering the outer periphery 33 (see FIG. 2) of the braided shield layer 3 as necessary. A part may be provided. A sheath part can be comprised from the material which has insulation, such as a crosslinked polyethylene resin and a crosslinked vinyl chloride resin, for example.

Claims

A core portion including a covered electric wire having a conductor and an insulating material coated around the conductor;
A braided shield layer covering the outer periphery of the core part, comprising a plurality of strands knitted,
The above-mentioned elemental wire is constituted by using an Al wire or an Al alloy wire as a base material, and has a plating film made of a metal that is harder to be oxidized than Al on the surface.
The shielded wire according to claim 1, wherein the plated film is made of Sn.
The shielded wire according to claim 1 or 2, wherein the plating film has a thickness of 1 µm or more.
The shielded electric wire according to any one of claims 1 to 3, wherein the shielded electric wire is used for reducing electromagnetic noise in a frequency region of 1 MHz or more.