JP3299064B2 - Communication cable core and communication cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication cable and a communication cable, which greatly reduce the attenuation of an information signal transmitted in a high frequency band and are excellent in workability.

[0002]

2. Description of the Related Art As a cable core of a communication cable, a single-core conductor made of a single wire or a round-shaped stranded wire made of a stranded wire formed by twisting a plurality of metal wires having a circular cross section is used. Used. A plurality of cable cores are bundled to form a communication line cable.

On the other hand, the transmission speed on a communication line has been increased by multiplex transmission of telephones and digital data transmission of a computer, and information signals in a high frequency band of up to about 100 MHz have been transmitted over communication cables. I have.

[0004]

With an increase in transmission speed in a communication line, a skin effect and a proximity effect appear remarkably, and signal attenuation may increase rapidly. In particular, in the case of a communication cable composed of a stranded conductor, the skin effect becomes more remarkable, the S / N ratio is greatly reduced, and the signal waveform is distorted. As a result, there is a disadvantage that information to be transmitted is lost. ing.

On the other hand, when a communication cable is installed in an intelligent building or the like, excellent workability is also required.
For example, it is also an important issue to exhibit good characteristics with respect to connectivity and bending characteristics with a connector.

In view of the above facts, the present invention provides a communication cable core and a communication cable which can reduce the amount of signal attenuation even when transmitting an information signal in a high frequency band of 100 MHz and have excellent workability during installation. The purpose is to provide a cable.

[0007]

Further, the communication cable of the present invention has two or four core pairs twisted with two communication cable cores as a pair, and these core pairs are insulated. A communication cable covered with a coating, wherein each communication cable core comprises a conductor in which a plurality of metal strands are twisted, and an insulating coating covering an outer peripheral portion of the conductor, and a metal constituting the conductor. The wires are in surface contact with adjacent metal wires, and the outer periphery of the conductor has a substantially smooth circular cross section.

[0008]

[0009]

In the case of a round stranded conductor widely used in a communication cable, since the strands are merely twisted, a semicircular projection is formed on the outer periphery of the conductor when viewed from the cross-sectional direction of the cable. It has a formed shape. On the other hand, when the transmission rate of the information signal to be transmitted is increased, the skin effect becomes remarkable, and the skin depth forming the transmission path becomes shallower as the transmission rate increases. For this reason, in the case of the conventional round stranded conductor, the area where the effective transmission path is formed decreases rapidly as the skin depth decreases, and the signal attenuation increases sharply.

In view of the above, in the present invention, a round-shaped stranded conductor is extruded, and the conductor is compressed toward the center thereof. By this compression molding, the density of the conductor itself is further increased, and the outer periphery of the cross section becomes circular. As a result, even if the transmission rate is increased and the skin effect occurs and the skin depth becomes shallow, the effect of the skin effect is further reduced because the conductor itself has a dense structure, and compared to the conventional round stranded conductor. Thus, the signal attenuation can be greatly reduced. In addition, since the stranded wire is compression molded, the flexibility and bending resistance are only slightly lower than those of the round stranded wire, and the flexibility and bending resistance are much larger than those of the single-core conductor. This makes it possible to realize a communication cable having excellent workability and a communication cable which is extremely useful when arranging along an intricate route in an intelligent building.

In addition, since the outer circumference of the conductor has a substantially circular shape, the outer diameter of the current path has a stable shape, so that a change in capacitance between the current path and the ground can be reduced, and the signal transmission characteristic can be reduced. Stable characteristics can be obtained also from the surface.

Further, the communication cable of the present invention is less susceptible to the skin effect and proximity effect than the conventional twisted or quad-twisted communication cable having the same outer diameter of the insulator. Stable capacitance, inductance, and characteristic impedance can be obtained over a wide transmission band, and the signal transmission characteristics can be further improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing an embodiment of a cable core of the present invention. FIG. 1 (a) shows a case of a double structure, and FIG. 1 (b) shows a case of a compression stranded wire of a triple structure. Reference numeral 1 denotes a conductor through which an information signal flows, and is a stranded wire obtained by twisting a plurality of metal wires 2 using a single-core soft copper wire as a central wire and further extruding. Since the extruding process is performed, each element wire comes into surface contact with an adjacent element wire, and a dense conductor is formed. In addition, since the extrusion process is performed with a circular cross section, the outer periphery of the conductor is smoothly continuous and compression molded into a substantially circular cross section. An outer peripheral portion of the conductor 1 is covered with an insulator 3 (PE material or PVC material) to form a cable core 4.

FIG. 2 shows two or four cable cores 4.
Is a diagram showing a communication cable 7 which is protected by an outer sheath 6 of an insulator (PE material). FIG.
(B) is an eight-core cable having a quad twist.

The change in the current path due to the skin effect when an information signal in a high-frequency band is transmitted using the cable 4 will be described with reference to FIG. (A) shows a compression stranded conductor according to the present invention, (b) shows a single core conductor, (c) shows a round stranded conductor, and the hatched portion shows a current path region at high frequency.

Here, the skin depth (the width of a region where current can flow) T due to the skin effect is

(Equation 1) When the conductor material is soft copper wire,

(Equation 2) Becomes

In equation (2), since the information signals transmitted by the three conductors are the same, the skin depth T due to the skin effect
In the same way, the current path area that affects the attenuation largely depends on the density of the metal strands 2 constituting the conductor and the shape of the conductor outer circumference. It can be seen that it becomes large and the attenuation is small.

Next, the attenuation characteristics of the communication cable will be described. FIG. 4 is a graph showing the relationship between the amount of attenuation and the frequency when a cable of three conductors having the same outer diameter is prototyped. In FIG. 4, the vertical axis indicates the attenuation, and the horizontal axis indicates the frequency. The solid line indicates the attenuation characteristics of the compression stranded conductor according to the present invention, the dashed line indicates the characteristics of the single-core conductor, and the dashed line indicates the characteristics of the round stranded conductor.

As is apparent from FIG. 4, in the band where the transmission frequency is low, the communication cables using the three types of conductors exhibit almost the same attenuation characteristics. However, as the transmission frequency increases, the cable using the conventional round stranded conductor has a remarkable skin effect, and the attenuation increases rapidly. In contrast, in the case of the cable according to the present invention, the attenuation increases as the transmission rate increases.
The amount of attenuation is considerably smaller than that of the cable using the round stranded conductor. On the other hand, the attenuation of the cable using the single-core conductor is smaller than that of the cable of the present invention. Therefore, as in the present invention, by forming the stranded conductor by compression so that the outer periphery of the cross section is substantially circular, it is possible to approximate the attenuation characteristics of the single-core conductor.

On the other hand, as described above, in the case of a single-core conductor,
Poor bending resistance and difficulty in workability. On the other hand, the cable of the present invention has sufficient bending resistance and flexibility of the stranded conductor. Therefore, the communication cable according to the present invention has both the good characteristics of the round stranded conductor and the excellent transmission characteristics of the single-core conductor.

Further, since the shape of the outer peripheral portion of the compressed stranded conductor according to the present invention is substantially smooth and circular, as shown in FIG. 5 (a), compared to FIG. 5 (b) of the conventional round stranded conductor. The press-connecting connector 5 and the like are connected with a wide contact area, and the resistance generated at the connection portion can be reduced.

[0022]

As described above, according to the present invention, each of the wires constituting the conductor is compression-molded so as to make surface contact with the wires adjacent to each other and to have a circular cross section at the outer periphery. The communication cable itself has a dense structure, and as a result, it is less affected by the skin effect even if the transmission rate is increased, and at the same time, it has flexibility and pliability as a twisted wire and excellent communication efficiency. can do. That is, it is possible to realize a communication cable having good workability of the round stranded conductor and good transmission characteristics of the single-core conductor.

Further, since it has a more dense and stable outer shape, stable capacitance, inductance and characteristic impedance can be obtained, and as a result, signal transmission characteristics as a communication line cable are further improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a cable core according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a 4-core or 8-core communication cable.

FIG. 3 is an explanatory diagram for explaining a skin effect in three types of conductors.

FIG. 4 is a diagram showing the relationship between the frequency of an information signal and the amount of attenuation in the same example.

FIG. 5 is a view when a press-connecting connector is connected to a compression stranded conductor and a round stranded conductor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductor 2 Metal wire 3 Insulator 4 Cable core 5 Press-connecting connector 6 Insulator outer coating 7 Communication cable

Claims (1)

(57) [Claims] 1. A communication cable comprising two or four core pairs twisted as a pair with two communication cable cores, and these core pairs are covered with an insulating coating. The core wire includes a conductor in which a plurality of metal wires are twisted, and an insulating coating that covers an outer peripheral portion of the conductor, and the metal wires constituting the conductor are arranged between adjacent metal wires. A communication cable, which is in surface contact and has a substantially smooth circular cross section at the outer periphery of a conductor.