JPH1092230A - Shielding wire and shielding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shielding wire and a shielding method capable of restricting electromagnetic noise to be radiated. SOLUTION: A shielding wire 13 in which a terminator is connected to a signal related earth between first and second shielding layers 5 and 8 covering an outside of a core wire 2 is provided, and a common mode current to be excited from the core wire 2 is grounded by the shielding wire 13. A third shield layer 11 is provided by covering an outside of the second shield layer 8 so as to restrict electromagnetic noise to be excited in the first shield layer 5 by a drift capacity generated between the second shield layer 8 and the third shield layer 11 by connecting this third shield layer 8 to a frame ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shield structure of an interface cable in an electronic device, particularly, an exchange.

[0002]

2. Description of the Related Art Conventionally, as a structure of this type of shielded wire, for example, in addition to the shielded wires shown in FIGS.
10 and the shielded wires shown in FIGS. 11 and 12.

More specifically, the shielded wires shown in FIGS. 7 and 8 are a single braided shielded wire, FIG. 7 is a side view showing a part of the shielded wire, and FIG. 8 is a DD line of FIG. FIG. 7 and 8, the shield wire 51 is composed of a core wire 52 and a core wire 5.
The shield layer 55 is formed by covering the outside of the core wire 52 with a soft copper braided wire 54 with an insulating material 53 interposed therebetween, and an insulating material such as polyvinyl chloride (PVC) covering the outside of the shield layer 55. And an outer cover 56.

9 and 10 are double-braided shielded wires, FIG. 9 is a side view showing a part of the shielded wire, and FIG. 10 is a direction along line EE in FIG. It is the front view which looked more. 9 and 10, the shield wire 61 is composed of a core wire 62 and a first shield layer 65 in which the outside of the core wire 62 is covered with a soft copper braided wire 64 with an insulating material 63 interposed therebetween. A second shield layer 68 in which the outside of the first shield layer 65 is covered with a soft copper braided wire 67 with an insulating material 66 interposed between the first shield layer 65 and the second shield layer 68 And an outer cover 69 made of an insulating material such as polyvinyl chloride (PVC) covering the outside of the cover.

The shield wires shown in FIGS. 11 and 12 are shield wires having an aluminum foil shield structure. FIG. 11 is a side view showing a part of the shield wire, and FIG. 12 is a view along the line FF in FIG. It is the front view seen from the direction. 11 and 1
2, the shield wire 71 includes a core wire 72, a shield layer 75 formed by providing an aluminum foil 74 outside the insulating material 73 and covering the outside of the core wire 72, and a polyvinyl chloride covering the outside of the shield layer 75. (PVC) or the like.

[0006]

However, in the conventional shielded wire structure described above, when used as an interface cable between frames in an exchange or the like, the steep rise and fall of the signal waveform causes the soft copper braided wire 54 and the like. Shield layers 55 (see FIGS. 7 and 8), shield layers 65 and 68 (see FIGS. 9 and 10) made of soft copper braided wires 64 and 67, and a shield layer 75 made of aluminum foil 74 and the like.
Electromagnetic noise is induced in each of the shielded wires 51, 6
There is a problem that the 1, 71 shield layers 55, 65, 68, and 75 function as antennas and emit electromagnetic noise.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a shielded wire and a shielded method capable of suppressing radiated electromagnetic noise.

[0008]

Means for Solving the Problems The present invention is characterized by taking the following technical means in order to achieve the above object.
In other words, a shield wire whose terminal is connected to a signal system ground is provided between the first shield layer and the second shield layer covering the outside of the core wire, and the common mode current induced from the core wire is shielded. A ground line is provided, and a third shield layer is provided so as to cover the outside of the second shield layer, and the third shield layer is connected to a frame ground to cause electromagnetic noise induced in the first shield layer. Is suppressed by the stray capacitance generated between the second shield layer and the third shield layer.

According to this, the electromagnetic noise induced in the first shield layer due to the sharp rise and fall of the signal waveform is reduced by providing the third shield layer.
It is reduced by the stray capacitance generated between the second shield layer and the third shield layer. In addition, by providing a shield wire whose terminal is connected to the signal system ground between the first shield layer and the second shield layer, the common mode current induced from the core wire is short-circuited to the signal system ground, A noise reduction effect is obtained.

Further, the present invention is characterized by taking the following technical means in order to achieve the above object. That is, a shield layer covering the outside of the core wire is provided, and a part of the core wire is not covered with the shield layer, but a part thereof is covered with a resistance band having a resistivity twice or more that of the shield layer. In addition, the rising component of the electromagnetic noise on the shield layer is smoothed.

According to this, by providing the resistance band in the shield layer, the rising component of the electromagnetic noise riding on the shield layer can be smoothed, and the radiation noise reduction effect can be obtained.

[0012]

1 and 2 show a shielded wire as a first embodiment of the present invention. FIG. 1 is a side view showing a part of the shielded wire, and FIG. FIG. 2 is a front view thereof as viewed from a direction along the line A-A. In FIG. 1 and FIG. 2, this shielded wire 1 is obtained by providing a core wire 2 formed by bundling tinned soft copper wires and an aluminum foil 4 provided outside a tubular insulating material 3 made of polyester resin. And a first shielding layer 5 covering the outside of the outer casing 2 and a tubular insulating material 6 also made of polyester resin.
A second shield layer 8 provided outside the first shield layer 5 by providing an aluminum foil 7 on the outside of the first shield layer 5, and a second shield layer 8 interposed between the second shield layer 8 and an insulating material 9. Third shield layer 1 having layer 8 covered with soft copper braided wire 10
1 and a jacket 12 made of an insulating material such as polyvinyl chloride (PVC) that covers the outside of the third shield layer 11. Further, a shield line 13 is provided between the first shield layer 5 and the second shield layer 8.

The shield wire 1 thus configured is used by connecting the shield wire 13 to the signal system ground and connecting the third shield layer 11 to FG (frame ground) of the housing or the like. . Here, FIG. 3 shows an example of a noise waveform generated in each part when the shield wire 1 is used. In FIG. 3, (a) shows a signal waveform on the core wire 2 and (b) shows a second waveform. And (c) shows a noise waveform riding on the third shield layer 11, respectively.

Therefore, in the shield wire 1 thus configured, the terminal is connected to the signal ground between the first shield layer 5 and the second shield layer 8 covering the outside of the core wire 2. By providing the shield wire 13,
The common mode current induced from the core wire 2 is
3 allows grounding. In addition, since the third shield layer 11 is provided so as to cover the outside of the second shield layer 8 and the third shield layer 11 is connected to the frame ground, electromagnetic waves induced in the first shield layer 11 are formed. Noise can be suppressed by stray capacitance generated between the second shield layer 8 and the third shield layer 11, and electromagnetic noise radiated from the shield wire can be reduced.

In the above embodiment, the structure in which the outside of the third shield layer 11 is covered with the jacket 12 made of an insulating material such as polyvinyl chloride (PVC) is disclosed. If you do not need to consider the protection of
The outer cover 12 may be omitted.

FIGS. 4 to 6 show a shielded wire according to a second embodiment of the present invention. FIG. 4 is a perspective view showing a part of the shielded wire, and FIG. FIG. 6 is a schematic sectional view taken along line CC of FIG. 4. In FIG. 4 to FIG. 6, the shield wire 21 is a tube-shaped polyester resin formed by leaving a part of the core wire 22 formed by bundling tinned soft copper wires in a ring shape. And a shielding layer 25 provided with an aluminum foil 24 on the outside of the insulating material 23.
The portion left in a ring shape without being covered with the shield layer 25 has a resistance component having a specific resistance (resistivity) twice or more that of the shield layer 25, for example, carbon (C)
Over the resistance band 26 formed by the above. In addition, shield layer 2
5 is covered with a jacket 27 made of an insulating material such as polyvinyl chloride (PVC). The outer cover 27 may be omitted if it is not necessary to consider the safety of the human body and the protection of the shield layer 25 or the resistance band 26.

Therefore, in the shield wire 21 configured as described above, a part of the core wire 22 is not covered with the shield layer 25, and a part of the core wire 22 has a resistivity twice or more that of the shield layer 25. 26, the rising component of the electromagnetic noise on the shield layer 25 can be smoothed. Thereby, a radiation noise reduction effect can be obtained. In addition to the above-described embodiment, the first shield layer may be formed of a conductive braided wire, and the second and third shield layers may be formed of a polyester material to which an aluminum foil is attached. The shield layer may be formed of a conductive braided wire. In any case, each shield layer can be formed of a polyester material to which an aluminum foil is attached or a conductive braided wire.

[0018]

As described above, according to the present invention,
The effect of reducing the radiated noise can be expected by suppressing the radiated electromagnetic noise.

[Brief description of the drawings]

FIG. 1 is a side view of a shield wire shown as a first embodiment of the present invention.

FIG. 2 is a front view of the shielded wire as viewed from a direction along the line AA in FIG. 1;

FIG. 3 is a diagram illustrating an example of each waveform generated in each section of the shield line illustrated in FIG. 1;

FIG. 4 is a perspective view of a shield wire shown as a second embodiment of the present invention.

FIG. 5 is a schematic sectional view taken along the line BB of FIG. 4;

FIG. 6 is a schematic sectional view taken along line CC of FIG. 4;

FIG. 7 is a side view showing an example of a conventional shielded wire.

FIG. 8 is a front view of the shielded wire as viewed from a direction along the line DD in FIG. 7;

FIG. 9 is a side view showing another example of the conventional shielded wire.

FIG. 10 is a front view of the shielded wire as seen from a direction along the line EE in FIG. 9;

FIG. 11 is a side view showing still another example of the conventional shielded wire.

FIG. 12 is a front view of the shielded wire as seen from a direction along the line FF in FIG. 11;

[Explanation of symbols]

 1, 13, 21 Shielded wire 2, 22 Core wire 3, 6, 23 Insulation material 4, 7 Aluminum foil 5 First shield layer 8 Second shield layer 9 Insulation material 10 Soft copper braided wire 11 Third shield layer 12 Outside 25 shield layer 26 resistance band

Claims (6)

[Claims] A first shield layer insulated between the core wire and the core wire and covering the outside of the core wire with a conductor; and a first shield layer insulated between the first shield layer and the first shield layer. A second shield layer formed by covering the outside of the layer with a conductor; and a shield provided between the first shield layer and the second shield layer, the terminal of which is connected to a signal ground. And a third shield layer insulated between the wire and the second shield layer and covered with a conductor on the outside of the second shield layer, and having a termination connected to a frame ground. Characteristic shield wire. 2. The first shield layer and the second shield layer are each formed of a polyester material having an aluminum foil attached to one surface thereof, and the third shield layer is formed outside an insulator. 2. The shielded wire according to claim 1, wherein the shielded wire is formed of a conductive braided wire. 3. A semiconductor device comprising: a core wire; and a shield layer insulated from the core wire and covering the outside of the core wire with a conductor, and a part of the core wire is not covered by the shield layer, but a part thereof. A shielded band having a resistivity twice or more that of the shield layer. 4. The shielded wire according to claim 3, wherein an outside of said shield layer and said resistance band is covered with an insulating jacket. 5. A common mode current induced from said core wire, wherein a shield wire whose end is connected to a signal system ground is provided between a first shield layer and a second shield layer covering the outside of the core wire. Is grounded by the shield wire, and a third shield layer is provided so as to cover the outside of the second shield layer, and the third shield layer is connected to a frame ground to be induced in the first shield layer. Wherein said electromagnetic noise is suppressed by stray capacitance generated between said second shield layer and said third shield layer. 6. A resistor having a shield layer covering the outside of a core wire, and having a part of the core wire not covered with the shield layer, but having a part of the resistivity twice or more that of the shield layer. A method of shielding a shielded wire, wherein a rising component of electromagnetic noise riding on the shield layer is covered by a band.