JPH1125766A - Communication cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve differential signal transmission of high rate and high density and reduce the difference in propagation delay time by simultaneously applying insulative coating to two or four conductors by a single coating equipment, in which a paired strand or a cad strand is twisted together in such a manner that coating timings of insulative coating wires applied at the same time as with the insulative coating does not shift in a longitudinal direction. SOLUTION: Two tin-plated soft copper wires 1 are coated with foamable polyethylene, thereby forming insulative coating layers so as to manufacture insulating coating wires 7. The two insulating coating wires 7 are twisted in such a manner that manufacturing timings become identical according to marks 9 indicated during the manufacture, to be covered with a shielding layer of an aluminum-polyester laminate tape, and then with a vinyl sheath, thereby providing a two-core shield communication cable. Consequently, it is possible to provide a communication cable having an extremely small difference in propagation delay times, thus achieving a cable which is optimum for a differential signal transmitting communication cable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal wiring of an electric / electronic device and a communication cable mainly for transmitting a differential signal for connecting the device to the outside.

[0002]

2. Description of the Related Art In parallel signal transmission, since one signal is transmitted to two pairs of insulated wires that form a pair or a pair of quad type communication cables, the propagation delay time difference between the pair of insulated wires is not so large. No problem. However, in the case of differential signal transmission, signals of opposite potentials are simultaneously input to two pairs of insulation-covered wires and treated as one signal, so that the propagation delay time difference between the pair of insulation-covered wires is large. It becomes a problem. FIG. 6 shows two pairs of twisted insulated wires 27, 27 simultaneously having positive and negative signals 21, 21.
Is input, this signal is applied to each of the insulated wires 27,
27, it is taken out from the output terminal. If the lengths of the insulated wires are different from each other or if the dielectric constant of the insulator covering the conductor is different, the output time is shifted, and the output waveform 21
^{,, 21,} but it may become impossible to transmit accurate data deviated as shown in FIG. Here, the propagation delay time is the time required for a signal to be input from one end of a cable and for the signal to pass through a conductor and be output from the other end. It is represented by the required transmission time (ns / m). Also, the difference in signal transmission time per unit length of cable between two insulated wires in the case of a pair of cables is called a propagation delay time difference.

[0003] As described above, since the propagation delay time difference is a major problem in the differential signal transmission cable, in order to eliminate the propagation delay time difference, the pitch of the twisted pair or the quad twist is adjusted at the time of manufacturing the cable so that each insulation coating is not formed. A solution is being attempted by adjusting the line length (physical length). In addition, since the propagation delay time is also affected by the dielectric constant of the insulator covering the conductor serving as the transmission line, a solution has been made by adjusting the dielectric constant of the insulator of each insulation-coated wire. .

[0004] However, in the case of a conventional multi-pair or multi-quad type communication cable used for differential signal transmission, a pair of insulating coating wires is coated with another coating device or the same coating device. However, since the coating time was different, the conditions for coating the conductor (resin composition, molding temperature, pressure, etc.) changed slightly, and the subtle differences caused the dielectric constant of the insulation of each insulating coated wire. The rates are not equal in the longitudinal direction, and even if the physical lengths are adjusted and twisted, the propagation delay time difference due to the difference in the dielectric constant cannot be corrected.

[0005]

In recent years, with the demand for high-speed and high-density transmission in differential signal transmission, the frequency for transmitting a signal has become extremely high, so that the wavelength (pulse length) has become very short. However, the allowable range for the propagation delay time difference required for the communication cable has become extremely small. An object of the present invention is to provide a communication cable for differential signal transmission that has a small propagation delay time difference that satisfies the demand for high-speed and high-density transmission in differential signal transmission.

[0006]

As described above, the most important problem in differential signal transmission is the difference in propagation delay time. One of the causes of this propagation delay time difference is the length of the insulated wire when twisted in pairs or quads, but this is a physically solvable problem. The other cause, that is, variation in the dielectric constant of the insulator constituting the insulated wire cannot be physically solved. When covering an insulator with a conductor, it is impossible to completely cover the length of the long conductor with the thickness of the insulation, the mixing ratio of the insulating composition, etc., and the dielectric constant of the insulated wire is long. It fluctuates to some extent in the direction. Therefore, even if a plurality of insulated wires with an insulated coating are prepared and twisted and quad-twisted cables are manufactured, the dielectric constant of each insulated wire is different, so the propagation delay time of each wire is different. Will be different. The present invention provides a twisted pair of two insulated wires, or 4
In a communication cable in which four insulated wires are quad-twisted, each of the two or four insulated wires is simultaneously subjected to insulated coating with one coating facility, and the pair twist, or The quad twist is a communication cable characterized in that the insulated wires that have been simultaneously insulated are twisted so that their covering time does not shift in the longitudinal direction. The communication cable constructed in this way is a pair (2
) Or one quad (four) insulated wire has a dielectric constant of 2
Almost the same communication cable is formed at the positions corresponding to the four or four longitudinal directions. In addition, the communication cable of the present invention configured as described above has a propagation delay time difference of 0.5% or less of the propagation delay time of the cable.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a manufacturing process diagram of two insulated wires constituting a communication cable of the present invention.
Reference numeral 2 denotes a coating device, which comprises an extruder 3, a crosshead 4, a cooling tank 5, and a take-up device 6. Reference numeral 7 denotes an insulated wire. First, the two conductors 1, 1 are introduced into the crosshead 4. As shown in FIG. 2, the crosshead 4 has conductor insertion holes 43, 43 for passing the conductors 1, 1 separately.
And a die 42 having a nipple. The resin composition (insulating resin) melted by the extruder 3 enters between the nipple 41 and the die 42, and covers the conductors 1 and 1 with the insulating resin. The wires 7, 7 that have passed through the crosshead 2 and are insulated are cooled in a cooling bath 5, taken up by a take-up machine 6, and taken up by a take-up drum 8. It should be noted that a dielectric constant measuring device and an outer diameter measuring device are provided between the cooling water tank 5 and the take-off machine 6, and the fluctuation information is returned to the extruder 3 or the cooling water tank 5 to push out the extruder 3 and the cooling water tank. By adjusting the cooling conditions of No. 5 and making the dielectric constant and outer diameter of the insulated wire uniform in the longitudinal direction, a communication cable more excellent for differential signal transmission can be constructed.
In the figure, reference numeral 9 denotes a mark written on the insulated wire 7. The mark 9 is simultaneously written on the same position of the two insulated wires 7 at the time of manufacturing.
Can be made to have the same manufacturing time in the longitudinal direction. This marking may be applied immediately before the end of the production, or may be applied at regular intervals. The two insulation-coated wires 7, 7 manufactured in this manner are twisted at the same time (marked locations) at the same coating time so that the composition of the resin composition constituting the insulation coating layer is one. However, since the extrusion temperature, the pressure, and the like are the same, the thickness of the insulating layer varies the same, and therefore, a cable having the same dielectric constant distribution in the longitudinal direction can be configured. Therefore, there is no difference in propagation delay time between the two insulated wires 7 due to the dielectric constant, and the communication cable is excellent for differential signal transmission.

[0008]

EXAMPLE A communication cable shown in FIG. 3 was manufactured using the apparatus shown in FIG. The outer periphery of the tin-plated annealed copper wires 1 and 1 having an outer diameter of 0.3 mm (seven strands of 0.1 mm) is coated with foamed polyethylene (foaming rate of 60% or more) to provide an insulating coating layer 11. 0.8 mm insulated wires 7 were produced.
The two insulated wires 7, 7 are twisted in pairs according to the marks marked during manufacture so that the manufacturing time is the same, a shielding layer 12 is provided on the outer periphery with an aluminum-polyester laminate tape, and a vinyl outer skin 13 is applied. A two-core shielded communication cable 10 was used. The propagation delay time and the propagation delay time difference of the obtained communication cable 10 were measured. FIG. 4 shows the results. As is clear from FIG. 4, the average of the propagation delay time of the shielded communication cable of the second embodiment is 3.9 n.
s / m, and the maximum difference in propagation delay time is 0.016 ns.
/ M, the propagation delay time difference is within 0.5% of the propagation delay time.

[0009]

[Comparative Example] Two insulated wires were manufactured in separate steps under the same conditions as in the example, and twisted in a pair with the same physical length, and a two-core shielded communication cable was manufactured in the same manner as in the example. The propagation delay time and propagation delay time difference were measured for the communication cable. The result is shown in FIG.

As is apparent from a comparison between FIG. 4 and FIG. 5, it is understood that each of the insulated wires 7 has a different propagation delay time in the longitudinal direction. By adjusting the variation of the propagation delay time in the longitudinal direction as in the present invention, the insulated wires having different propagation delay times in the longitudinal direction are adjusted in the longitudinal direction.
The propagation delay time difference between the insulated wires is canceled out, and the cable can be made such that the difference is substantially uniform in the longitudinal direction (in the embodiment, at most 0.5%). As described above, the communication cable of the present invention has a small propagation delay time difference, and is therefore most suitable as a communication cable for differential signal transmission, and can be applied to a very high frequency. On the other hand, in the cable manufactured by the conventional method, the propagation delay time cannot be canceled between the two insulated wires, and therefore, the difference in the propagation delay time greatly varies in the longitudinal direction, and the difference is 0.09 ns / m at the maximum. (2.3% of the average delay time).
If a communication cable having such a difference in propagation delay time in the longitudinal direction is used as a communication cable for differential signal transmission, the transmission signal may not be able to be transmitted accurately. This makes the cable unsuitable as a differential signal transmission cable having an increased height.

In the above embodiment, an example was described in which two insulated wires were twisted in pairs. However, four conductors were simultaneously insulated and twisted in quads to produce a quad-type communication cable. Of course you can. Also, the insulating coating composition is not limited to foamed polyethylene, and it goes without saying that a resin suitable for differential signal transmission can be employed. In the above-described embodiment, a device for coating the conductor 1 with the insulator 2 is as follows.
Although the apparatus for extruding and covering using a pair of nipples 41 and dies 42 has been described, the present invention is only required to extrude a plurality of insulated wires that are extruded simultaneously so as to have the same dielectric constant. It is also possible to extrude 1 with a crosshead 4 incorporating two dies in a nipple or with a crosshead 4 incorporating two sets of nipples and dies.

[0012]

According to the present invention, it is possible to provide a communication cable having a very small propagation delay time difference, and it is possible to provide a cable most suitable as a communication cable for differential signal transmission, which has been particularly high in frequency in recent years.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a manufacturing process of an insulated wire constituting a communication cable of the present invention.

FIG. 2 is an exploded explanatory view showing a part of the apparatus shown in FIG. 1;

FIG. 3 is a front view showing an embodiment of the communication cable of the present invention.

FIG. 4 is a graph showing a propagation delay time and a propagation delay time difference of the communication cable of the present invention.

FIG. 5 is a graph showing a propagation delay time and a propagation delay time difference of a conventional communication cable.

FIG. 6 is an explanatory diagram showing a propagation state of positive and negative signals of a conventional communication cable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductor 2 Insulation coating device 7 Insulation coating wire 10 Communication cable

Continued on the front page (72) Inventor Takeshi Okamoto 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (1)

[Claims] (1) twisting two insulated wires, or
In a communication cable in which four insulated wires are quad-twisted, each of the two or four insulated wires is simultaneously subjected to insulated coating with one coating facility, and the pair twist, or A communication cable characterized in that quad-twisting is performed by twisting together an insulated wire coated with an insulative coating so that the covering time does not shift in the longitudinal direction.