JPH0410307A - Noise preventing shielded wire - Google Patents

Abstract

PURPOSE:To form a noise filter with the simple structure and with only installation of an inductor by forming an insulating material in the periphery of a signal wire made of the conductive material with a dielectric layer obtained by mixing dielectric and ceramic powder material in high polymeric material. CONSTITUTION:A signal wire 1 is made of a copper wire as excellent conductive material, and a cylindrical dielectric layer 3 is formed concentrically with the signal wire 1, and the periphery thereof is covered with an electromagnetic shielded material 2 to form a pair of conductors which consist of the electromagnetic shielded conductor 2 and the signal wire 1 of the center. The periphery of the dielectric layer 3 is covered with the electromagnetic shielded conductor 2 made of knitted narrow copper wires as excellent conductive material, and furthermore, the periphery thereof is covered with an insulating covering layer 4 made of the insulating resin. This dielectric layer 3 is made of the high polymeric material obtained by mixing the high dielectric and ceramic powder with the organic material. An inverted L type or a T type noise filter is formed by only connecting an inductor to an input side signal wire and an output side signal wire in series.

Description

Detailed Description of the Invention A. Object of the Invention [Field of Industrial Application] The present invention is intended to prevent electromagnetic noise generated in electronic equipment from being electromagnetic interference to other equipment due to conduction or radiation. It relates to noise prevention shielded wires that connect within devices or between electronic devices.

[Conventional technology]

Conventionally, in order to prevent electromagnetic interference caused by conduction or radiation of electromagnetic noise generated in electronic equipment to other equipment, it has been necessary to prevent electromagnetic noise that propagates on signal lines from occurring in each equipment. In a simple configuration, a feed-through capacitor is used at the exit or inlet of the signal line, as shown in Fig. 4, in which the equipment casing 7 is grounded by a grounding wire 5, and a capacitor 6 is inserted between it and the signal MA1. Either wrap the signal line and attach a closed magnetic circuit inductor to the outer periphery of the cable, or combine a capacitor and inductor to form a filter circuit.
They were inserted into signal lines to reduce electromagnetic noise, and to prevent electromagnetic radiation from outside, shielded wires were used to cover the signal lines with a metal mesh with good electrical conductivity. . On the other hand, when using conventional shielded wires for connections between devices, it is necessary to mount noise filters on the input and output sides of the devices, which requires extra inlet filters and outlet filters. It is necessary to incorporate a noise filter on the board, so a feed-through capacitor is used in the part that connects the signal line on the output side of the device, a bead inductor is inserted in series with the signal line on the board, and a reverse type or Countermeasures have been taken, such as constructing a π-shaped noise filter or constructing a T-shaped noise filter by passing the signal line cable through the center hole of the toroidal magnetic core. Furthermore, in order to suppress electromagnetic noise in a frequency band of 100 MHz or higher, a capacitor was inserted between the signal line and the ground to suppress electromagnetic noise.

[Problem to be solved by the invention]

The present invention allows the signal line itself that connects within electronic equipment or between electronic equipment to retain the characteristic of suppressing electromagnetic noise, and is capable of suppressing electromagnetic noise by conduction or radiation. In order to suppress electromagnetic noise,
We provide a noise prevention shielded wire that eliminates the noise filters conventionally mounted on the input and output sides of signal lines between electronic devices, or that has a simple configuration and can be configured by simply mounting an inductor. The purpose is to

Structure of the Invention [Means for Solving the Problems] The noise prevention shield wire according to the present invention uses a polymer material kneaded with dielectric ceramic powder around the signal line in order to suppress electromagnetic noise in a high frequency band. The shielded wire of the present invention is constructed by covering the surface of the polymer material with dielectric properties, which covers the signal line, with an electromagnetic shielding conductor made of a copper net made of a good electrical conductor. A noise prevention shield that can easily create a noise filter by simply inserting a bead inductor etc. in series with the signal line on the board by creating a capacitance between the signal line and the electromagnetic shielding conductor. It is a line. That is, a signal line through which signals are conducted is coated with a polymer material having a high dielectric constant, in which dielectric ceramic powder is dispersed in a polymer material, and an electromagnetic shielding conductor is formed using a Wi wire or metal foil. Noise-preventing shielded wire that is manufactured by covering the outer periphery with an electrically insulating polymer material, and has a large distributed capacitance between the signal line and the electromagnetic shielding conductor, which suppresses electromagnetic noise. shall be.

That is, the present invention has the following features: 1. A signal line made of a good electrical conductor that conducts an electric signal is wrapped with an electrical insulating material, the outer periphery of the electrical insulating material is covered with an electromagnetic shielding conductor, and the outermost periphery is covered with an electrical insulating material. The noise prevention shielded wire is characterized in that the electrical insulating material around the signal wire made of a conductive material is formed by a dielectric layer made by kneading dielectric ceramic powder into a polymeric material. .

2. The surrounding area around which multiple signal lines are formed in parallel is formed by a dielectric layer made by kneading dielectric ceramic powder into a polymer material, the outer periphery is covered with an electromagnetic shielding conductor, and the outermost periphery is covered with an electrically insulating material. This is a noise prevention shield wire characterized by the following:

[Effect]

In conventional shielded wires that connect electronic devices, the electrical insulation material that surrounds the signal wire through which the central signal is transmitted usually has a low dielectric constant to prevent signal attenuation during signal transmission. Polyethylene etc. are used. Unlike conventional shielded wires, the present invention creates a high-permittivity polymer material by kneading ceramic powder with a high dielectric constant into a polymer material, instead of the polyethylene used in conventional shield wires. The shielded wire is replaced with a high-permittivity polymer material.

In the shielded wire of the present invention, the center conductor through which the signal wire passes is wrapped with a vinyl chloride polymer material kneaded with ceramic powder and has a dielectric constant of about 60, and the outer periphery is covered with copper mesh or copper foil. It has a structure in which it is wrapped in an electromagnetic shielding conductor, and the outer periphery is further covered with an organic electrical insulating material made of a polymeric material. The signal line through which the signal is transmitted is wrapped in a polymer material with a high dielectric constant, and the outer periphery is further covered with an electromagnetic shielding conductor that is a good electrical conductor made of copper mesh, so the signal line and the electromagnetic shielding conductor are This has the same effect as connecting a large capacitance in parallel to the signal line, and has the effect of suppressing electromagnetic noise only by the capacitance of the shield line.

For example, when connecting a bead inductor to the output side of a device to which a shielded wire using the shielded wire of the present invention is connected, an inverted noise filter is configured, and the shielded wire is inserted between the
When a bead inductor is connected to the input and output side signal lines, a T-shaped noise filter is formed. In addition, the noise prevention shield wire of the present invention has a capacitance value that can be changed in any way depending on the amount of high dielectric ceramic powder added to the polymer material, which is dispersed in the polymer material forming the dielectric integrated layer. The value of the capacitance of the shield wire can be selected depending on the frequency band used.

〔Example〕

The noise prevention shield wire of the present invention will be explained.

FIG. 1 shows the structure of a noise prevention shield wire according to an embodiment of the present invention. In FIG. 1, a signal line 1 made of copper wire, which is a good electrical conductor, and a cylindrical dielectric layer 3 are formed concentrically around the signal line, and the outer periphery of the dielectric layer 3 is covered with an electromagnetic shielding conductor.
The electromagnetic shielding conductor and the central signal line form a pair of conductors. The outer periphery of the dielectric layer is wrapped with an electromagnetic shielding conductor 2 made by knitting thin copper wires that are good electric conductors of metal, and the outer periphery is further covered with an insulating coating layer 4 made of an electrically insulating resin. The signal line 1 may be a copper wire of 0.3φ■■, and the electromagnetic shielding conductor 2 may be a cylindrical mesh made of copper wire or a copper foil having a thickness of about 6 μm, for example. The electromagnetic shielding conductor that covers the outer periphery of the dielectric layer is conductive, and the mesh conductor has strength against bending of the shield wire, but when using the shield wire of the present invention in a fixed manner, copper foil, aluminum foil, etc. It may also be used by wrapping a ribbon around it.

The dielectric layer 3 is made by selecting and combining a high dielectric material such as ceramic powder with high dielectric properties, a polymer binder, rubber, a composite polymer, a solvent, a plasticizer, etc. It is made of a polymeric material made by kneading high dielectric ceramic powder into an organic material.

Dielectric materials include copper, nickel, magnesium, tungsten, and titanium oxides [Pb ((NiNb) (M
gW)) TiO+), barium titanium calcium oxide (BaTi03, CaTi0:+), and lead (Pb
) Perovskite-based dielectric materials, tantalum oxide (Ta20s), etc. may be used.

The polymer material into which the dielectric powder is kneaded is vinyl chloride resin, and examples of rubber include silicone rubber, butyl rubber, propylene rubber, etc. Devices for this dispersion include ball mills, attritors, sand mills, homogenizers, three-roll mills, and raikai machines, but any of these may be used to mix the ceramic powder and the polymer material.

Next, a noise prevention shield wire according to an embodiment of the present invention will be explained. After coarsely pulverizing a sintered block of lead/perovskite dielectric material with a dielectric constant ε of about 8000, it is milled in a toluene solvent using a sand mill to form a block of 0.5 μm to 1.5 μm. After making ceramic powder with a particle size and scattering the solvent, add ceramic powder made of polyvinyl butyral and dielectric material to a weight ratio of approximately 75% ceramic powder to polyvinyl butyral, and add ethyl cellosolve as a solvent. Then, it was made into a slurry using a ball mill. A 0.3 mmφ copper wire was passed through this slurry to form a dielectric layer of 200 μm to 300 μm around the outer periphery of the copper wire. This dielectric layer was covered with a copper mesh, and the whole was covered with vinyl, which has electrical insulation properties, to produce a noise-preventing shielded wire. The value of the dielectric constant ε of the dielectric layer used in the obtained shielded wire was approximately 60, and the capacitance of the noise prevention shielded wire having an outer diameter of φ1.7 mm and a length of 1 m was 1700 PF. A 1 m long noise prevention shielded wire according to the example is connected to an oscillator with an internal impedance of 50Ω, and the terminating resistor at both ends is when the noise prevention shielded wire is inserted with 50Ω termination and when the noise prevention shielded wire is not inserted. The results of measuring the attenuation characteristics are shown in Figure 2.

It was confirmed that the attenuation rate was approximately 40 dB at 500 MHz.

FIG. 3 shows another embodiment of the noise prevention shield wire according to the present invention, in which a plurality of conductors are wrapped in parallel layers at approximately equal intervals, and the outer periphery is further covered with a mesh-like electromagnetic shielding conductor of a good electrical conductor.
Furthermore, the outer periphery is coated with an organic electrical insulating material. The dielectric layer that surrounds the conductors arranged in parallel at the center is made by adding dielectric ceramic powder to polyvinyl butyral, and then adding and kneading ethyl cellosolve.The dielectric layer has a dielectric constant ε of 6.
A flat cable type noise prevention shielded wire is formed by forming a dielectric layer having a characteristic of about 0, and further covering the outer periphery with an electromagnetic shielding conductor.

C0 Effect of the invention [Effect of the invention] This noise prevention shield wire has the advantage of being able to easily form a filter circuit because it has a capacitance structure, and an inductor is connected in series to the input and output signal lines. It is possible to construct an inverted or T-shaped noise filter using only a single circuit, the number of noise components on the equipment board is reduced, and the suppression effect is superior to that of conventional electromagnetic noise prevention circuits of this type.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of the noise prevention shield wire according to the present invention. FIG. 2 is a characteristic diagram showing the attenuation characteristics at high frequencies of one embodiment of the noise prevention shielded wire according to the present invention. FIG. 3 is a perspective view showing a flat cable type noise prevention shield wire according to the present invention. FIG. 4 is a side sectional view showing a conventional noise prevention filter. 1... Signal line, 2-- Electromagnetic shielding conductor, 3... Dielectric layer. 4... Insulating coating layer, 5... Grounding wire, 6... Capacitor, 7... Equipment housing, 8... Solder. Figure 1 Figure 3 Figure 2 m Back plate (MHz)

Claims (1)

[Claims] 1. A signal line made of a good electrical conductor that conducts electrical signals is wrapped with an electrically insulating material, the outer periphery of the electrically insulating material is covered with an electromagnetic shielding conductor, and the outermost periphery is covered with an electrically insulating material. 1. A noise prevention shielded wire, characterized in that the electrical insulating material around the signal wire made of a conductive material is formed of a dielectric layer made by kneading dielectric ceramic powder into a polymeric material. 2. The surrounding area around which multiple signal lines are formed in parallel is formed by a dielectric layer made by kneading dielectric ceramic powder into a polymer material, the outer periphery is covered with an electromagnetic shielding conductor, and the outermost periphery is covered with an electrically insulating material. Noise prevention shield wire characterized by the