JP2553942Y2 - Flat cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improvement of an ultra-thin flat floor cable that can be wired under an office carpet.

[Prior art] Flat cables were originally developed by NASA for wiring under carpets in artificial satellites with extremely limited space in order to save cable wiring space. As carpeting on the floor of a newly-built building has become more common, undercarpet wiring systems that lay wiring under such carpets and do not expose cables indoors have become remarkably popular.

The mission of flat cables used for this purpose is to be ultra-thin and capable of wiring a large number of core wires at once. At the same time, the spread of cables has been rapidly spreading.

FIG. 2 is a cross-sectional view showing an example of a communication flat cable which is widely used today.
A pair of core wires coated with an insulator (usually polyethylene) 2 are arranged in parallel, and a PVC (polyvinyl chloride, the same applies hereinafter) protective layer 7 is provided around the outer periphery thereof for the purpose of mechanical protection of the core wires and imparting flame retardancy.
, And a plurality of them are arranged in parallel, and the outer cover is commonly and collectively covered with an aluminum laminate tape 8 as shown in the figure to form an ultra-thin shape of about 1.2 mm.

[Problem to be Solved by the Invention] Even with the above configuration, it can be used without any problem in the voice band, but there is a problem in using it in a high frequency region for digital transmission expected in the future.

That is, a self-extinguishing PVC protective layer 7 is provided for the purpose of protecting external pressure constantly received by the wiring under the carpet and imparting flame retardancy for indoor use.
As is well known, has a large dielectric constant, and has a frequency characteristic and a temperature characteristic because of its polarity, so the attenuation in a high frequency region is large, and a mismatch in a high frequency region due to a characteristic variation in a temperature and a frequency is preferable. Absent.

In order to avoid such an inconsistency, it is most preferable to remove the PVC protective layer 7 and use only the core wire. However, without the protective layer, the metal tape of the laminate layer is made of two insulating cores due to the external pressure constantly applied. Since the eddy current loss occurs due to the drop between the wires and the proximity to the conductor, which results in a large transmission loss in a high frequency region, the protective layer cannot be removed.

Further, as in the conventional example, the metal laminate tape 8
However, in a structure in which a plurality of the core wires are entirely covered with a common metal tape in a state of a common covering, the induction current flows through the entire cable, so that the coupling between the pair and the shield is reduced,
The crosstalk attenuation is not sufficient, and it is necessary to increase the distance between pairs as shown in FIG. 2 in order to improve this. However, it is not desirable from the viewpoint of the request.

An object of the present invention is to solve the above-mentioned problems of the prior art, to provide a new flat cable that has an electrically stable structure, improves crosstalk attenuation, and is sufficiently applicable to high-speed digital transmission. It is intended to provide.

[Means for Solving the Problems] In the present invention, insulated core wires are paired in parallel, a tubular polyethylene protective layer is provided thereon, and a metal laminated tape having a metal tape surface inside is further provided thereon. The coated wire is a unit pair wire, and a plurality of the unit wire pairs are contacted and arranged in parallel to form a flat polyvinyl chloride jacket.

[Operation] If the protective layer is formed by forming a polyolefin, particularly a typical polyethylene, into a tube, there is no possibility that the metal tape is deformed and falls between the core wires even when there is an external pressure. Also,
The protective layer itself is made of polyethylene with a low dielectric constant, and since it is formed into a tube, an air layer with a lower dielectric constant is formed between the core wires. Signals can be stably transmitted and received with extremely low loss.

Further, since the metal laminate tape on the outer periphery of the protective layer is covered so that the metal tape is on the inside, the shields are electrically in non-contact with each other, the coupling between the shields is increased, and the shields are shielded. , A sufficiently excellent crosstalk characteristic can be obtained.

[Embodiments] The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing an embodiment of a flat cable according to the present invention in which a pair of core wires are adjacent to each other and a jacket 5 is provided.

A pair of conductors 1 coated with a polyethylene insulating material 2 is coated on the outer circumference with a tubular protective layer 3 made of polyethylene, and the outer circumference is coated with a metal laminated tape 4 having a metal tape surface inside. And one of the pair
The pairs are arranged in parallel in an adjacent state, and cover the trapezoidal outer cover 5 made of PVC.

FIG. 3 is a partially enlarged cross-sectional view enlarging a portion indicated by a dashed-dotted circle A in FIG. 1 in order to clarify the configuration of the metal laminate tape 4. As shown in FIG. 3, the metal tape layer 4a of the metal laminate tape 4 is coated on the inside, that is, on the polyethylene protective layer 3 side.

The flat cable according to the present invention configured as described above is formed by first forming a protective layer made of polyethylene having a small dielectric constant into a tube shape, so that the flat cable is compared with the PVC protective layer 7 of FIG. The dielectric constant is greatly reduced.
In addition, since the polyethylene protective layer 3 is formed in a tubular shape, a space 6 is formed between the pair of core wires arranged in parallel, and air having a lower dielectric constant exists in the space 6. And the dielectric constant around the core wire is much smaller than that of the conventional example.

The achievement of such a large reduction in the dielectric constant is a major factor in improving and stabilizing high-frequency transmission characteristics, and as a result, high-frequency digital signals can be transmitted without any trouble.

In addition, the fact that the metal tape 4a of the metal laminate tape 4 is arranged on the inside means that even when the core pairs are brought into contact with each other as shown in FIG. As a result, each core pair can be independently arranged in a non-contact state. As a result, the coupling between the pair and the shield is increased, which means that a structure having a large attenuation result and sufficiently excellent crosstalk characteristics can be obtained, and even if the number of core pairs is increased as in the conventional example. It is not necessary to increase the distance between pairs, and each core pair can be arranged adjacently in parallel, so that a great advantage that the width of the entire cable can be reduced can be expected.

As described above, the protective layer 3 is made of polyethylene, but the outer cover which does not greatly affect the transmission characteristics is made of PVC which has a self-extinguishing effect and is excellent in flame retardancy. Can exhibit the same characteristics as those of the conventional example, and there is no problem.

In addition, when the core pair according to the present invention using the polyethylene tube as the protective layer is applied to the conventional flat cable shown in FIG. 2, the crosstalk attenuation is not improved, but the loss can be reduced.

In addition, the shape of the outer cover 5 is not limited to the trapezoidal shape of the embodiment, and it is a matter of course that an appropriate shape such as a wavy shape can be selected.

[Effects of the Invention] As described above, according to the flat cable according to the present invention, the width of the cable can be reduced and made compact at almost the same thickness, but the crosstalk characteristics are excellent even when high-speed digital signals are transmitted. It is capable of performing stable transmission with loss, and is extremely significant as a device that can respond to an undercarpet wiring system for high-speed digital transmission, which is expected to have a great demand in the future.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a cable according to the present invention,
FIG. 2 is a sectional view of a conventional example, and FIG. 3 is an enlarged sectional view of a portion A in FIG. 1: conductor, 2: insulator, 3: polyethylene protective layer, 4: metal laminate tape, 4a: metal layer, 5: jacket (PVC), 6: space.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Isamu Omoto 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Hitachi Cable Co., Ltd. (56) References JP-A-63-102112 (JP, A) JP-A-Hei 1-298605 (JP, A) Fully open Showa 61-54627 (JP, U) Fully open Showa 60-140309 (JP, U) Fully open Showa 63-198116 (JP, U) Fully open flat 2-76422 (JP, U U)

Claims (1)

(57) [Scope of request for utility model registration] An insulated core wire is arranged in parallel to form a pair, a tube-shaped polyethylene protective layer is provided thereon, and a metal laminate tape having a metal tape surface inside is coated thereon. A flat cable having a plurality of unit pair wires in contact with each other and arranged in parallel to form a flat polyvinyl chloride jacket.