JP3280772B2 - Electromagnetic shielding cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shielding cable, and more particularly to an electromagnetic wave shielding cable used for connection between electronic devices.

[0002]

2. Description of the Related Art Conventionally, a shield layer is formed on a cable as a measure for shielding electromagnetic waves from the cable, but common mode noise is generated due to the antenna effect of the shield layer. Therefore, as a means for reducing the antenna effect of the shield layer, a method of inserting a ferrite core into a cable has been adopted.

[0003] However, regardless of the method of holding the ferrite core (resin molding, cover case, etc.), the appearance is not preferable, and there are many problems in handling such as cracking of the ferrite core in the cable assembly. .

An object of the present invention is to provide an electromagnetic wave shielding cable which does not require a ferrite core, is therefore aesthetically pleasing, and has no handling problems such as cracking of the ferrite core.

[0005]

According to the present invention, there is provided an electromagnetic wave shielding cable in which a shield layer and a sheath are sequentially coated on a conductor coated with an insulator. It is characterized by being composed of resin.

Preferably, based on 100 parts by weight of the resin,
It is characterized in that powder ferrite is mixed in an amount of 100 to 700 parts by weight.

[0007] More preferably, a protective layer for covering the sheath is provided.

[0008]

According to the electromagnetic wave shielding cable of the present invention, since the resin constituting the sheath is mixed with the powdered ferrite, the electromagnetic wave radiation preventing effect is at least as high as that obtained when the ferrite core is inserted through the cable. Further, since it is not necessary to insert a ferrite core into the cable and the cable can be used in a normal form as a cable, the appearance is excellent.

In particular, when a protective layer covering the sheath is formed, the mechanical strength of the electromagnetic wave shielding cable (hereinafter also referred to as "cable sheath") is improved.

[0010]

The present invention will now be described in more detail with reference to Examples and Experimental Examples, which by no means limit the present invention.

FIG. 1 is a partially cutaway side view showing an embodiment of the electromagnetic wave shielding cable of the present invention. The electromagnetic shielding cable 1 includes a central conductor 2, an insulator 3 covering the conductor 2, a braided conductive shield 4 covering the insulator 3,
And a sheath 5 for covering the conductive shield 4.

The conductor 2 is a stranded wire , for example, a tinned soft copper stranded wire.

The insulator 3 that covers the conductor 2 is not particularly limited as long as it has electrical insulation properties. Specific examples include thermoplastic resins such as vinyl chloride resin, crosslinked vinyl chloride resin, polyethylene resin, crosslinked polyethylene resin, polypropylene resin, polyester resin, silicone resin, and fluorine resin.

The braided conductive shield 4 covering the insulator 3 prevents radio waves from causing electromagnetic interference on the cable, and is made of, for example, a 0.10 mm tinned soft copper wire.

The sheath 5 covering the conductive shield 4 is
It is made of a resin mixed with powdered ferrite, and examples of the base resin include a vinyl chloride resin, an ethylene-vinyl acetate copolymer, and a fluororesin. The mixing amount of the powdered ferrite is not particularly limited, but is preferably 100 to 700 parts by weight, more preferably 200 to 600 parts by weight, and still more preferably 400 to 500 parts by weight, based on 100 parts by weight of the base resin. A commonly used compounding agent such as an antioxidant, an antioxidant, a stabilizer, and a flame retardant may be added to the sheath 5.

FIG. 2 is a sectional view showing another embodiment of the electromagnetic wave shielding cable of the present invention. In FIG. 2, portions denoted by the same reference numerals as those in FIG. 1 indicate the same or corresponding portions. The cable sheath 10 shown in FIG. 2 is a multi-core cable, and a plurality (eight in FIG.
Are coated on the insulator 3 and twisted together.

The plurality of stranded conductors 2 are covered with a laminate tape 6 made of aluminum foil and polyester tape, and further covered with a braided conductive shield 4. Further, the conductive shield 4 includes a sheath 5
And further covered with a protective layer 7 for protecting the sheath 5.

Examples of the constituent material of the protective layer 7 include vinyl chloride resin, fluorine resin, polyethylene resin, polyester resin, urethane resin, and silicone resin.

The ratio of the thickness (D) of the sheath 5 to the thickness (d) of the protective layer 7 is preferably D: d = 5: 95-9.
5: 5, more preferably D: d = 50: 50 to 80: 2
0. If the ratio of the thickness of the sheath 5 is less than 5, the electromagnetic wave shielding effect may be weak, while if the ratio of the thickness of the sheath 5 exceeds 95, appropriate mechanical strength may not be provided. However, the ratio varies depending on the mixing amount of the powdered ferrite mixed into the sheath 5, and the ratio between the thickness (D) of the sheath 5 and the thickness (d) of the protective layer 7 is as follows.
It is not necessarily limited to the above range.

Since the sheath of the electromagnetic wave shielding cable made of a resin mixed with powdered ferrite is used as an exterior, the electromagnetic wave shielding cable is blackish and has a rough surface state, and has a matte (rough) shape, which is not aesthetically preferable. If the amount of powdered ferrite mixed into the sheath 5 is large, the mechanical strength of the sheath 5 may be reduced. However, the sheath 5 is covered with the protective layer 7 to form a two-layer sheath. Thereby, the mechanical strength of the sheath is reinforced, coloring is possible, the surface condition is smooth, and the appearance is good.

As a method of coating the protective layer 7 on the sheath 5, a method of simultaneously extruding the layers 5 and 7 is known.
Although advantageous from the viewpoint of the adhesive property of the interface, it is also possible to cover the sheath 5 with the protective layer 7 in a separate step. If necessary, the adhesive strength at the interface between the layers 5 and 7 may be imparted via a hot melt adhesive such as an ethylene-vinyl acetate copolymer.

As in the case of the sheath 5, the protective layer 7 may contain additives such as antioxidants, antioxidants, stabilizers, and flame retardants which are generally used.

A connector portion including a plug or a receptacle is connected to an end portion of an interface bus cable for connecting electronic devices such as a personal computer and a printer. Normally, the connector portion is provided with a conductive cover such as a metal cover or a metal tape, but when the electromagnetic wave shielding cable of the present invention is used as an interface bus cable, the connector portion is also provided with electromagnetic wave shielding measures. Desirably, for example, it is preferable to take measures such as mixing powder ferrite with the resin constituting the connector cover, or forming a ferrite layer on the inner surface of the connector cover.

Experimental Example [Preparation of Cable] Two insulated cores of a tin-plated soft copper stranded wire having an outer diameter of 0.39 mm and covered with a heat-resistant PVC having a thickness of 0.13 mm were twisted to prepare a twisted pair wire. After twisting together the eight pairs of the twisted pair wires, an aluminum / polyester laminate tape having a thickness of 0.05 mm was wound thereon, and a braid of a 0.1 mm tin-plated soft copper wire was applied. Further, a 0.9 mm thick heat-resistant PVC (LG-055 manufactured by Riken Vinyl Industry Co., Ltd.) is placed on the braid.
1) Cable with outer diameter 6.0 covered with sheath (Sample 1)
Was prepared.

Separately, a cable (sample 2) in which a ferrite core (model number RI-16-28-9 of Kitagawa Kogyo Co., Ltd.) having an inner diameter of 0.9 mm, an outer diameter of 16 mm, and a length of 28 mm was inserted through the cable of sample 1 and a sample In the cable of No. 1, the sheath was changed to the sheath described in Table 1 below (Sample 3,
4) was produced.

[0026]

[Table 1]

An interface bus for connecting a personal computer (PC9801 NV of NEC Corporation) and a printer (PR1012 of NEC Corporation) by connecting connectors to both ends of the cables of the above-mentioned samples 1-4. A cable device was manufactured. Further, a connector in which powder ferrite was mixed with a resin constituting the connector cover on the printer side was connected to the cable of Sample 3, and a cable device (Sample 5) was manufactured.

[Test method] In a shield room,
Using a spectrum analyzer, the antenna was separated by 1.5 m, and the noise spectrum was measured when the personal computer and the printer were operated independently at the same time without being connected by a cable. Next, the above personal computer and printer were connected using the cable devices of Samples 1 to 5, and the noise spectrum was measured. Using the level of the noise spectrum in Sample 1 as a reference value, the change in level in Samples 2 to 5 was examined.

[Test Results] FIG. 3 shows the noise spectrum when the personal computer and the printer were operated independently, and FIGS. 4 to 8 show the noise spectra of the samples 1 to 5, respectively. In FIG. 4, the noise spectrum whose level has risen from the level of FIG. 3 by connecting the cable is indicated by a circle.

The electromagnetic wave shielding effect of the ferrite core is as follows.
The maximum was about 7 dB (see FIG. 5). In Sample 3 using the cable of the present invention, the thickness was about the same as that of the ferrite core (see FIG. 6), and in Sample 4 whose sheath thickness was twice as large as that of Sample 3, the maximum was about 9 dB (see FIG. 7). . Also,
Sample 5 using a connector in which powdered ferrite was mixed with the resin constituting the connector cover had almost the same effect as Sample 3 (see FIG. 8).

Samples 3 and 4, which are the electromagnetic wave shielding cables of the present invention, have a mechanical strength of 1.06 kg / mm ² or more, which is almost the same as the cable of sample 1.

[0032]

According to the electromagnetic shielding cable of the present invention,
The effect of preventing electromagnetic wave radiation is at least as high as that obtained when a ferrite core is inserted through a cable. Further, since it is not necessary to insert a ferrite core into the cable and the cable can be used in a normal form as a cable, the appearance is excellent.

In particular, when a protective layer covering the sheath is formed, the mechanical strength of the cable sheath is improved, and the appearance is also improved.

[Brief description of the drawings]

FIG. 1 is a cutaway partial side view showing an embodiment of an electromagnetic wave shielding cable according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the electromagnetic wave shielding cable of the present invention.

FIG. 3 is a diagram showing a noise spectrum when a personal computer and a printer are operated independently.

FIG. 4 shows a personal computer and a printer as sample 1
FIG. 4 is a diagram showing a noise spectrum when the connection is made with the cable device of FIG.

FIG. 5 shows a personal computer and a printer as sample 2
FIG. 4 is a diagram showing a noise spectrum when the connection is made with the cable device of FIG.

FIG. 6 shows a personal computer and a printer as sample 3.
FIG. 4 is a diagram showing a noise spectrum when the connection is made with the cable device of FIG.

FIG. 7 shows a personal computer and a printer as sample 4.
FIG. 4 is a diagram showing a noise spectrum when the connection is made with the cable device of FIG.

FIG. 8 shows a personal computer and a printer as sample 5.
FIG. 4 is a diagram showing a noise spectrum when the connection is made with the cable device of FIG.

[Explanation of symbols]

 1,10 Electromagnetic wave shielding cable 2 Conductor 3 Insulator 4 Conductive shield (shield layer) 5 Sheath 7 Protective layer

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shoji Nakaoka 663 Mishima, Arita-shi, Wakayama Mitsubishi Cable Industry Co., Ltd. Mishima Works (56) References JP-A-4-215213 (JP, A) JP-A-4- 104407 (JP, A) Japanese Utility Model Application Hei 5-61921 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01B 11/00 H01B 11/06 H01B 7/18

Claims (2)

(57) [Claims] 1. A laminated tape, a shield layer, a sheath, and a protective layer are sequentially coated on a stranded conductor covered with an insulator, and the sheath comprises 100 parts by weight of resin and 100 parts by weight of powdered ferrite. An electromagnetic wave shielding cable comprising a resin mixed with about 700 parts by weight, wherein the sheath and the protective layer are formed by simultaneously extruding the sheath and the protective layer. 2. The electromagnetic wave shielding cable according to claim 1, wherein the ratio of the thickness (D) of the sheath and the thickness (d) of the protective layer is D: d = 50: 50 to 80:20.