JP2006164754A - Shield cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shield cable superior in bending lifetime. <P>SOLUTION: The shield cable has an insulating layer, a shield layer, and an insulating sheath coated on the outer circumference of a lead wire successively. The shield layer is composed of a braided wire having the number of braiding of 36 and density of braiding of 85-100%. In particular, in the shield cable, the insulating layer has outer diameter of 5.9 to 6.4 mm, and the braided wire has the number of braiding of 6 to 12, and the element wire diameter of 0.055 to 0.125 mm, and the braid pitch of 18 to 55 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a shielded cable, and more particularly to a shielded cable having a shield layer formed by braiding.

  Conventionally, wiring for electrical connection of sensors and electrical components in factories and vehicles has been provided with a shield layer on the outer periphery of the conductor (core wire) in order to cut noise from the outside and noise emitted to the outside. Electric wires (hereinafter referred to as “shielded cables”) are often used. For example, in the case of an automobile, it is wiring for in-vehicle multimedia such as an in-vehicle camera and a car navigation system.

First, the structure of a conventional shielded cable will be described with reference to FIG.
FIG. 1 is a conceptual diagram showing a hierarchical structure of each part of a shielded cable for an example of a conventional shielded cable. In FIG. 1, reference numeral 10 denotes a power or signal conducting wire (core wire), which is formed by twisting many copper alloy thin wires 11 and bundling them into one circular wire. Reference numeral 20 denotes an insulating layer (insulating coating) that covers the outer periphery of the core wire 10. Reference numeral 30 denotes an insulating sheath that also serves as an outer skin of the shielded cable. Reference numeral 40 denotes a shield layer which covers the outer periphery of the insulating layer 20 and covers the outer periphery of the insulating sheath 30 in order to shield electromagnetic waves.

Next, the shield layer 40 of this shielded cable will be described with reference to FIG.
FIG. 2 is a diagram conceptually showing the structure of the shield layer 40. (1) of FIG. 2 is a side view of the shielded cable shown in FIG. 1 with the insulating sheath 30 as its outer skin removed and the left side with the shield layer 40 removed. In the drawing, 41 is a bundle of fine metal wires (wire bundle) constituting the shield layer, and this wire bundle is woven to form a shield layer 40 having a net-like structure (hereinafter referred to as “braid”). As is apparent from the figure, the shield layer 40 has a structure in which two pairs of wire bundles 41 are spirally wound around the outer periphery of the insulating layer 20 from opposite directions. Further, these two sets of wire bundles 41 are woven so as to alternately enter under the other set bundle.

  FIG. 2 (2) shows a cross section of the wire bundle 41 constituting this braid. In the figure, reference numeral 42 denotes a strand. As is apparent from the figure, the strand 41 has a plurality of thin metal wires 42 arranged in parallel in the horizontal direction. The number of strands constituting one strand of bundle is called the number. The strand diameter (diameter) is about 0.08 mm. The material of the strand is copper alloy or the like.

Since the strand bundle 41 is spirally wound around the outer periphery of the insulating layer 20, the same strand bundle 41 comes at a certain pitch in the line direction of the insulating layer 20. When this pitch (braided pitch) is p and the sum of the diameter of the insulating layer 20 and the thickness of the wire bundle 41 is x, the relationship p = x × π / tan α is established. Here, α is an angle formed by the wire bundle 41 with the linear direction of the insulating layer 20 and is also referred to as a braiding angle.
Generally, the braiding pitch is about 50 mm when x is about 6 mm.
The number of strands 41 constituting this braid is called the number of hits. The number of hits is generally an even number, especially a multiple of 4.

  In addition, since the strand 41 has a thickness, a gap that is not covered by the strand 41 is formed in the apex portion of the quadrangle formed by overlapping the strands 41 in two directions. This is indicated by 49 in FIG. The ratio of the area of the portion covered by the wire bundle 41 to the total surface area of the insulating layer 20 is referred to as the braid density. The braid density is ideally as close to 100% as possible in terms of shielding performance, but is 85 to 90% in terms of ensuring flexibility (flexibility) and manufacturing cost.

Some shielded cables have a structure in which, in addition to the core wire covered with insulation, the drain wire is covered with a shield layer and further covered with an insulating sheath.
In addition, the shield layer is not braided but may be a copper foil or a PET tape with an aluminum foil.
JP-A-1-232923 JP-A-9-51870 JP-A-9-75298 JP-A-9-84749 JP-A-9-117409

In recent years, demands for ensuring the safety and reliability of equipment have become stricter.
Shielded cables are no exception. That is, for example, for use in automobiles, electric cars, hybrid cars, off-road cars, off-road bikes, and the like are being developed and maintained in addition to use in in-vehicle multimedia. In order to be adopted for these, it is necessary to be a shielded cable that ensures safety and reliability.
In other words, these automobiles can be used for various harsh applications for a long period of time, and not only the vehicle body but also the shielded cable needs to have a mechanical strength higher than that of the conventional one, particularly a long bending life. It is said.

In particular, when the structure of the shield layer of the shield cable is composed of a braid, since the structure is complicated, it has been desired to develop a shield cable having a longer bending life than the conventional one.
In addition, when the braided wire breaks due to bending fatigue or the like, the sharp fracture surface damages the insulation coating and the insulation sheath, not only shortening the bending life but also deteriorating the shielding performance. For this reason, it has been desired to develop a braid that does not break the strand even when repeated bending load is applied.
In addition, it is desired to develop other excellent performances such as good compatibility with the insulation coating on the inside and the insulation sheath on the outside, low cost, and good shielding performance. It was.

As a result of intensive studies, the present inventor has found that the above problems can be solved by setting the braid to a specific number of striking, braid density, number of possessions, and braiding pitch, and has completed the present invention.
The invention according to claim 1 is a shielded cable in which an outer periphery of a conducting wire is sequentially covered with an insulating layer, a shield layer, and an insulating sheath, and the shield layer has a number of strikes of 36 and a braid density of 85 to 100%. A shielded cable characterized by comprising a braid.
Here, the conducting wire includes a single wire and a stranded wire. Further, a drain line or the like may be included.

  By configuring the shield layer with a braid and setting the number of hits and the braid density within the above ranges, a shielded cable having high bending performance and shielding performance can be obtained.

  When the number of strikes is 36 and the braid density is less than the above range, a part of the strands of the braid falls into the gap indicated by 49 in FIG. 2, and the bundle of strands is disturbed and the strands are broken. It becomes easy and the bending performance and the shielding performance are lowered.

The invention according to claim 2 is the shielded cable, wherein the insulating layer has an outer diameter of 5.9 to 6.4 mm.
The outer diameter is more preferably 6.0 to 6.2 mm.
Further, the cross section of the wire is not completely circular and may be somewhat distorted.

The invention according to claim 3 is the shielded cable, wherein the braid has six to twelve braids.
In the case where the outer diameter is 5.9 to 6.4 mm, it is particularly preferable that the number of holdings is eight.

The invention according to claim 4 is the shielded cable, wherein the braid has a strand diameter of 0.055 to 0.125 mm.
The strand diameter is particularly preferably 0.08 ± 0.005 mm.

The invention described in claim 5 is the shielded cable, wherein the braid has a braid pitch of 18 to 55 mm.
The braiding pitch is preferably 27 to 33 mm, and more preferably 29 to 31 mm.

The invention according to claim 6 is the shielded cable, wherein the braid has six pieces,
The strand diameter is 0.075 to 0.085 mm and the braiding pitch is 18 to 22 mm.
The wire diameter is 0.115 to 0.125 mm and the braiding pitch is 18 to 44 mm,
This is a shielded cable characterized by being any of the above.

The invention according to claim 7 is the shielded cable, wherein the braid has seven pieces.
The shielded cable is characterized in that the strand diameter is 0.075 to 0.085 mm and the braiding pitch is 18 to 22 mm.

The invention according to claim 8 is the shielded cable, wherein the braid has eight pieces,
The strand diameter is 0.055 to 0.075 mm and the braiding pitch is 18 to 22 mm.
The wire diameter is 0.075 to 0.085 mm and the braiding pitch is 18 to 33 mm,
The wire diameter is 0.085 to 0.095 mm and the braiding pitch is 18 to 44 mm.
The strand diameter is 0.095 to 0.115 mm and the braiding pitch is 27 to 55 mm.
The strand diameter is 0.115 to 0.125 mm and the braiding pitch is 36 to 55 mm,
This is a shielded cable characterized by being any of the above.

The invention according to claim 9 is the shielded cable, wherein the braid has nine pieces.
The shielded cable is characterized in that the strand diameter is 0.075 to 0.085 mm and the braiding pitch is 18 to 44 mm.

The invention according to claim 10 is the shielded cable, wherein the braid has ten pieces.
The shielded cable is characterized in that the strand diameter is 0.075 to 0.085 mm and the braiding pitch is 27 to 55 mm.

The invention according to claim 11 is the shielded cable, wherein the braid has 11 pieces.
The shielded cable is characterized in that the strand diameter is 0.075 to 0.085 mm and the braiding pitch is 27 to 55 mm.

The invention according to claim 12 is the shielded cable, wherein the braid has 12 pieces,
The strand diameter is 0.075 to 0.085 mm and the braiding pitch is 36 to 55 mm.
The strand diameter is 0.055 to 0.065 mm and the braiding pitch is 18 to 44 mm.
This is a shielded cable characterized by being any of the above.

  The invention according to claim 13 is the shielded cable, wherein the braid is made of copper or an alloy containing copper as a main component.

  The invention according to claim 14 is the shielded cable, wherein the braid is a copper wire in which the element wire is tin-plated.

  In the present invention, since the configuration of the braid of the shield layer is a specific configuration, a shielded cable having high bending performance and shielding performance can be provided.

Examples of the present invention and comparative examples are shown below. The present invention is not limited to the following examples. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.
(Example)
This example is a braided shield layer of a shielded cable having an insulation coating outer shape of 6.1 mm and a sheath outer shape of 8.1 mm. The main points are shown below.
Number of strokes 36 strokes Number of handles 8 Strand diameter 0.08mm
Braid pitch 30mm
Braided cross section 1.45mm ²
Braid density 91%
Wire material Copper alloy (copper containing 0.2 wt% tin)

The shielded cable itself is the same as the conventional one shown in FIG. 1 except for the braided structure of the shield layer. The main points are shown below.
Conductor (core wire) Nominal size 8.0mm ²
Conductor material Copper alloy
Conductor twist diameter 4.5mm
Insulation layer Material Polyethylene (Conducting wire) Insulation thickness 0.8mm
Finished outline 6.1mm
Insulating sheath Sheath material Polyurethane (Shield wire sheath) Sheath thickness 0.8mm
Finished outline 8.1mm

(Comparative example)
In order to evaluate the performance of the above example, the same shielded cable as in the above example was manufactured except for the braiding material and braiding pitch of the shield layer. Only the parts different from the embodiment will be described below.
Braid pitch 50mm
Braid density 86%
Wire material Tinned annealed copper

(Test equipment and test method)
The above-described shielded cable was subjected to a bending life test using the apparatus shown in FIG.
In FIG. 3, reference numeral 50 denotes a shielded cable, and reference numeral 40 denotes a portion where the insulating sheath is removed and the shield layer is exposed. Reference numeral 60 denotes a bending life test apparatus. The test device 60 includes a weight 61, two rollers 62 and 63, a chuck 64, a disconnection detection device 65, and a bending mechanism (not shown).

As shown in FIG. 3, the shield cable 50 is attached to the test apparatus 60 by sandwiching the upper part of the shield cable 50 with a chuck 64 and suspending a weight 61 at the lower part. As a result, a pulling force of 4.9 N is applied to the shielded cable 50. The shield cable 50 is lightly sandwiched between two rollers 62 and 63 near the upper center of the shield cable 50 to restrain movement.
Further, the upper and lower ends of the shield cable 50 electrically connect the exposed shield layers 40 to the plus side and minus side wires of the disconnection detection device 65, respectively.

Under the above, by a bending mechanism (not shown), the upper part of the shield cable 50 together with the chuck 64 is bent 90 degrees leftward with the roller 62, 63 as a shaft, and then returned to the original position. Therefore, the shield wire turns to the left again after turning to the left. This bending is repeated at a constant speed. The radii of the rollers 62 and 63 are 30 mm.
The disconnection detection device 65 measures the electrical resistance of the shield layer 40. If the strands constituting the shield layer 40 break due to bending fatigue due to bending, the electrical resistance increases accordingly. For this reason, it is possible to detect the degree of breakage of the strands by detecting an increase in the electrical resistance of the shield layer.

(Test results)
Using the test apparatus, 600,000 bending tests were performed at a rate of 60 times / minute at a room temperature of 23 ° C.
The test results of Examples and Comparative Examples are shown in FIG.
4A is an example, and FIG. 4B is a comparative example. The shielded cable of the example does not show any increase in electrical resistance in the 600,000 bending tests.
On the other hand, although the comparative example is slight, an increase in electric resistance starts to be observed around 100,000 times, increases remarkably at 250,000 times, and increases remarkably at around 420,000 times. That is, the breakage of the wire is remarkable.

(Shield effect)
About the shielded cable of the said Example and a comparative example, the comparative test of the shielding effect of the electromagnetic wave which is the objective of a shield was done. As the test method, an absorption clamp method was used, and leakage of current from the test wire was moved along the wire for each frequency band, and a peak was measured. And the difference of the measured value of an unshielded electric wire and a shielded electric wire was made into the shielding effect. The result is shown in FIG. As shown in FIG. 5, the shielding effect of the shield of the shielded cable using the braid of the example is comparable to the comparative example in the frequency range of 0.01 to 1 MHz.

(Compatibility with insulating materials)
After the bending test, damage to the contact portion between the core wire of the shielded cable and the insulating layer, the insulating layer and the braid, and the braid and the insulating sheath was observed with the naked eye. As a result, no damage such as peeling or generation of cracks was observed.
(Other examples)
In addition to the above, under the number of strikes of 36, shield cables having various braided structures were manufactured by varying the number of pieces to be held, the strand diameter and the braid pitch, and their bending tests were performed.
Table 1 shows particularly preferable results obtained when the number of hits is 36 and the number of handles is 6 to 12, the wire diameter is 0.055 to 0.125 mm, and the braiding pitch is 18 to 55 mm.

It is a conceptual diagram which shows the structure of the conventional shielded cable. It is a conceptual diagram which shows the structure of the braiding of a shield layer. It is a figure which shows the test apparatus and test method of the bending life of a shield layer. It is a figure which shows the result of the bending performance test of a shielded cable. It is a figure which shows the result of the shield performance test of a shielded cable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Conductive wire 11 Fine wire 20 Insulating layer 30 Insulating sheath 40 Shield layer 41 Wire bundle 42 Wire 50 Shield cable 60 Bending life test device 61 Weight 62, 63 Roller 64 Chuck 65 Disconnection detection device

Claims (14)

  A shielded cable in which an outer periphery of a conducting wire is sequentially covered with an insulating layer, a shield layer, and an insulating sheath, wherein the shield layer is formed of a braid having a number of strikes of 36 and a braid density of 85 to 100%. cable.   The shield cable according to claim 1, wherein the insulating layer has an outer diameter of 5.9 to 6.4 mm.   The shielded cable according to claim 1 or 2, wherein the braid has 6 to 12 braids.   The shielded cable according to any one of claims 1 to 3, wherein the braid has a strand diameter of 0.055 to 0.125 mm.   The shield cable according to any one of claims 1 to 4, wherein the braid has a braid pitch of 18 to 55 mm. The braid has 6 pieces,
The strand diameter is 0.075 to 0.085 mm and the braiding pitch is 18 to 22 mm.
The wire diameter is 0.115 to 0.125 mm and the braiding pitch is 18 to 44 mm,
The shielded cable according to claim 1, wherein the shielded cable is any one of the above. The braid has 7 pieces,
The shielded cable according to any one of claims 1 to 5, wherein the strand diameter is 0.075 to 0.085 mm and the braid pitch is 18 to 22 mm. The braid has 8 pieces,
The strand diameter is 0.055 to 0.075 mm and the braiding pitch is 18 to 22 mm.
The wire diameter is 0.075 to 0.085 mm and the braiding pitch is 18 to 33 mm,
The wire diameter is 0.085 to 0.095 mm and the braiding pitch is 18 to 44 mm.
The strand diameter is 0.095 to 0.115 mm and the braiding pitch is 27 to 55 mm.
The strand diameter is 0.115 to 0.125 mm and the braiding pitch is 36 to 55 mm,
The shielded cable according to claim 1, wherein the shielded cable is any one of the above. The braid has nine pieces,
The shielded cable according to any one of claims 1 to 5, wherein the strand diameter is 0.075 to 0.085 mm and the braid pitch is 18 to 44 mm. The braid has 10 pieces,
The shielded cable according to any one of claims 1 to 5, wherein the strand diameter is 0.075 to 0.085 mm and the braid pitch is 27 to 55 mm. The braid has 11 pieces,
The shielded cable according to any one of claims 1 to 5, wherein the strand diameter is 0.075 to 0.085 mm and the braid pitch is 27 to 55 mm. The braid has 12 pieces,
The strand diameter is 0.075 to 0.085 mm and the braiding pitch is 36 to 55 mm.
The strand diameter is 0.055 to 0.065 mm and the braiding pitch is 18 to 44 mm.
The shielded cable according to claim 1, wherein the shielded cable is any one of the above.   The shielded cable according to any one of claims 1 to 12, wherein the braid is made of copper or an alloy containing copper as a main component. The shielded cable according to claim 13, wherein the braid is a copper wire in which an element wire is tin-plated.

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