JP2012243502A - Cable for differential signal transmission and harness using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cable for differential signal transmission in which the distance between a pair of conductors is uniform and variation of the characteristic impedance is reduced, by preventing the pair of conductors from being displaced or inverted, and to provide a harness using the cable.SOLUTION: The cable for differential signal transmission includes: a dual-core 14 where two cores 13, 13, consisting of a conductor 11 coated with an insulation layer 12, are arranged in parallel; a fixing layer 15 provided on the periphery of the dual-core 14 by filling, and fixing the arrangement of the two cores 13, 13 while covering the dual-core 14 collectively; a shield 16 provided on the outside of the fixing layer 15; and a jacket 17 covering the outside of the shield 16.

Description

  The present invention relates to a differential signal transmission cable wired in an electronic device such as an electronic book, a notebook computer, a mobile phone, a liquid crystal television, and a printer, and a harness using the same.

  In electronic devices such as electronic books, notebook computers, mobile phones, liquid crystal televisions, and printers, differential signal transmission is used for signal transmission between electronic devices or between substrates (circuit boards) in the electronic devices.

  The differential signal is a signal in which the phase is inverted by 180 ° is transmitted through two conductors that make a pair, and the difference between the signals received on the receiving side is synthesized and output. Since the currents flowing through the pair of conductors flow in opposite directions, there is an advantage that the electromagnetic waves radiated from the transmission line are small. Moreover, since the noise received from the outside is equally superimposed on a pair of conductors, the influence of the noise can be canceled by combining and outputting the difference on the receiving side.

  As shown in FIG. 6, as a differential signal transmission cable 60 used for transmission by differential signals, two cores 63, 63 in which a conductor 61 is covered with an insulating layer 62 are arranged in parallel, A shield 64 made of a double transverse shield is provided. Further, a shield tape 65 having a metal layer is wound around the inner surface of a polyethylene terephthalate (PET) tape so that the metal layer is in contact with the shield 64, and the periphery is covered with a jacket 66. (For example, Patent Document 1).

  Further, in Patent Document 2, a pair of inner conductors extending in parallel are covered with a foamed insulator, and an outer conductor is provided around the foamed insulator, and the outer conductor is separated by a gap with an insulating jacket together with the foamed insulator. There has been proposed a cable for differential signal transmission that is completely covered.

  Further, in Patent Document 3, a tape-like polyethylene foam is wound around a wire core in which conductors arranged in parallel with a space between each other are covered with a foamed polyethylene insulating layer, and a shield layer and an external part are wound around this. A differential signal transmission cable in which a covering layer is sequentially formed has been proposed.

JP 2003-36740 A JP 2001-35270 A JP 2000-40423 A

  However, in the differential signal transmission cable 60 described in Patent Document 1, the cores 63 and 63 that are independent from each other are collectively collected by the shield 64 and the arrangement of the cores 63 and 63 is fixed. A force is applied in the winding direction of the shield 64, and the two cores 63, 63 may be twisted in this direction. As a result, the paired conductors 61 and 61 may be displaced in the cable circumferential direction, or in the worst case, the positions of the paired conductors 61 and 61 may be reversed, leading to variations in characteristic impedance.

  Further, at the end of the differential signal transmission cable 60, when the jacket 66 is stripped, the ground bar is soldered to the shield 64 and grounded, the solder enters the gap 67 between the shield 64 and the core 63, There is a possibility that the insulating layer 62 may be damaged by coming into contact with the insulating layer 62 of the core 63 to cause insulation failure.

  Further, when the jacket 66, the shield tape 65, and the shield 64 are stripped at the end of the differential signal transmission cable 60, the cores 63, 63 are independent from each other. There is also a problem that the position is shifted in the cable longitudinal direction, the line lengths of the conductors 61 and 61 are different, and a skew is generated between the conductors.

  On the other hand, in the differential signal transmission cables described in Patent Document 2 and Patent Document 3, it is said that the occurrence of skew can be prevented. Further, the differential signal transmission cable described in Patent Document 3 In this case, no gap is formed between the shield and the core, and it is said that it is possible to prevent insulation failure due to solder entering the gap.

  However, when the insulating layer is extrusion-coated around the conductor, the material of the insulating layer is extruded around the conductor while passing the conductor, and this is passed through the die to form an insulating layer of a predetermined shape. In some cases, the conductors are displaced and the distance between the conductors of the pair of conductors becomes non-uniform along the longitudinal direction of the cable, resulting in variations in characteristic impedance.

  Therefore, an object of the present invention is to prevent the paired conductors from being displaced or reversed, and to perform differential signal transmission with a uniform distance between the conductors of the paired conductors and small variations in characteristic impedance. It is to provide a cable for use and a harness using the same.

  The present invention devised to achieve this object is a two-core core formed by arranging two cores, each of which is a conductor covered with an insulating layer, in parallel, and is provided around the two-core core. A difference comprising: a fixed layer that collectively covers the two-core cores and fixes the arrangement of the two cores; a shield provided outside the fixed layer; and a jacket that covers the outside of the shield. This is a dynamic signal transmission cable.

  The insulating layer and the fixed layer are preferably made of a fluororesin, and the melting point of the fluororesin that constitutes the fixed layer is preferably equal to or lower than the melting point of the fluororesin that constitutes the insulating layer.

  The fluororesin constituting the insulating layer is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and the fluororesin constituting the fixed layer is a tetrafluoroethylene-hexafluoropropylene copolymer (FEP). And good.

  The shield may be formed of a metal strip provided along the longitudinal direction of the two-core core on one flat surface of the fixed layer.

  The two cores may be arranged in contact with each other.

  The distance between the conductors of the two-core core is preferably equal to the distance between the terminals of the connector.

  Moreover, this invention is a harness provided with the said cable for differential signal transmission, and the connector connected to the edge part of the said cable for differential signal transmission.

  According to the present invention, a cable for differential signal transmission that prevents a pair of conductors from being displaced or reversed and has a uniform distance between conductors of a pair of conductors and a small variation in characteristic impedance. And a harness using the same can be provided.

It is sectional drawing which shows the cable for differential signal transmission which concerns on embodiment of this invention. It is sectional drawing which shows the cable for differential signal transmission which concerns on the modification of embodiment of this invention. It is sectional drawing which shows the cable for differential signal transmission which concerns on the modification of embodiment of this invention. It is sectional drawing which shows the cable for differential signal transmission which concerns on the modification of embodiment of this invention. It is sectional drawing which shows the cable for differential signal transmission which concerns on the modification of embodiment of this invention. It is sectional drawing which shows the conventional cable for differential signal transmission.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing a differential signal transmission cable according to a preferred embodiment of the present invention.

  As shown in FIG. 1, a differential signal transmission cable 10 according to the present embodiment includes a two-core core 14 in which two cores 13 and 13 each having a conductor 11 covered with an insulating layer 12 are arranged in parallel. The periphery of the two-core core 14 is collectively covered, the fixing layer 15 that fixes the arrangement of the two cores 13, 13, the shield 16 provided outside the fixing layer 15, and the outer side of the shield 16 is covered And a jacket 17 to be provided.

  The conductor 11 is composed of AWG (American Wire Gauge) 38 to 42 strands obtained by twisting a plurality of (for example, seven) strands 18. Each strand 18 is made of a metal having excellent conductivity, such as copper or a copper alloy. The conductor 11 may be made of a single wire, but is preferably made of a stranded wire from the viewpoint of flexibility.

  The insulating layer 12 is made of a low dielectric constant fluororesin, for example, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) having a dielectric constant of 2.1. Thus, the signal speed can be increased by forming the insulating layer 12 of a low dielectric constant material.

  The core 13 is formed by extrusion coating the insulating layer 12 on the outer periphery of the conductor 11. Specifically, the material of the insulating layer 12 is extruded around the conductor 11 while the conductor 11 is fed out, and this is passed through a die to form the insulating layer 12 having a predetermined diameter.

  The two cores 13 and 13 are arranged in contact with each other to form a two-core core 14. At this time, the inter-conductor width of the two-core core 14 (distance to the conductors 11 and 11) is the distance between the terminals of the connector connected to the end of the differential signal transmission cable 10 (for example, 0.3 to 0). 0.5 mm), the outer diameter of the insulating layer 12 is preferably adjusted during the manufacture of the core 13.

  The fixed layer 15 is made of a low dielectric constant fluororesin, for example, a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) having a dielectric constant of 2.1. Similarly to the insulating layer 12 described above, the fixed layer 15 is made of a low dielectric constant material, so that the signal speed can be increased.

  Further, the melting point of the fluororesin constituting the fixed layer 15 is preferably equal to or lower than the melting point of the fluororesin constituting the insulating layer 12. Thereby, when the fixing layer 15 is collectively covered around the two-core 14, the insulating layer 12 is melted due to the heat of the fluororesin constituting the fixing layer 15, and the dimension of the fixing layer 15 varies. It can be prevented from falling out of the specified range. In addition, although melting | fusing point of PFA and FEP changes with product grades, PFA is 300-310 degreeC and FEP is 280-290 degreeC.

  In the conventional differential signal transmission cable 60, the fixed layer 15 is covered so as to fill a gap 67 formed between the core 63 and the shield 64 and to have a flat surface 15a. Specifically, while feeding the two cores 13 and 13 in contact with each other, the material of the fixed layer 15 is fully extruded around the core, and this is passed through a die to form the fixed layer 15 having a predetermined shape.

  The shield 16 is constituted by a double horizontal winding shield in which a wire is double-wound and wound around the outer periphery of the fixed layer 15. A shield tape 19 having a metal layer with a thickness of about 0.1 to 10 μm is wound around the outer periphery of the shield 16 on the inner surface of a polyethylene terephthalate (PET) tape. The shield tape 19 is spirally wound around the outer periphery of the shield 16 so that the metal layer contacts the shield 16.

  The jacket 17 is formed by winding a PET tape on the shield tape 19 or extruding and coating a fluorine resin such as PFA, FEP, ethylene-tetrafluoroethylene copolymer (ETFE) on the shield tape 19. .

  According to the differential signal transmission cable 10 having such a structure, a two-core core 14 formed by arranging two cores 13 and 13 in which a conductor 11 is covered with an insulating layer 12 in parallel, A fixed layer 15 that is provided around the periphery and covers the two-core core 14 at a time and fixes the arrangement of the two cores 13, a shield 16 provided outside the fixed layer 15, and a shield 16 Since the two cores 13 and 13 are integrally fixed by the fixing layer 15 by providing the jacket 17 that covers the outside of the conductor, the positional deviation and inversion of the paired conductors 11 and 11 and the line length It is possible to prevent the occurrence of skew due to the difference. In addition, since the gap between the shield 16 and the core 13 is filled with the fixed layer 15, it is possible to prevent the occurrence of insulation failure due to the solder entering the gap.

  Further, when the periphery of the two cores 13 and 13 in which the conductor 11 is covered with the insulating layer 12 is collectively covered with the fixing layer 15, the periphery of the paired conductors 11 is directly covered with the fixing layer 15. As compared with the above, the outer diameter of the coating target with respect to the die diameter is increased, and the positional deviation of the coating target within the die can be reduced. As a result, the positional deviation of the conductor 11 can be reduced, and the distance between the conductors 11 and 11 forming a pair can be made even more uniform in the cable longitudinal direction. Therefore, according to the differential signal transmission cable 10, it is possible to reduce variations in characteristic impedance over the longitudinal direction of the cable.

  Further, conventionally, when the object to be coated in the die, that is, when the conductors are displaced, the distance between the conductors may become extremely narrow in some cases, and when the current is passed through the paired conductors, the insulation between the conductors is sufficient. There was a risk of dielectric breakdown. On the other hand, in the differential signal transmission cable 10, the periphery of the two cores 13, 13 where the conductor 11 is insulated by the insulating layer 12 is covered with the fixed layer 15 in a comprehensive manner. Even if the core 13 is displaced at the time of covering 15, the distance between the conductors does not become smaller than the outer diameter of the insulating layer 12, and the insulation between the conductors can be sufficiently maintained.

  Further, in the conventional differential signal transmission cable, when the conductor of the differential signal transmission cable is connected to the connector terminal, the paired conductors are extended to the distance between the connector terminals, so that the shield and the conductor are connected. The distance between the terminals increases, the impedance increases between them, and impedance mismatch occurs at the terminal. On the other hand, in the differential signal transmission cable 10, the outer diameter of the insulating layer 12 of the core 13 is adjusted so that the distance between the conductors of the two-core core 14 is equal to the distance between the terminals of the connector. There is no need to expand the conductor in accordance with the terminal of the connector, and an increase in impedance and mismatch at the terminal can be prevented.

  The present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention.

  For example, in the differential signal transmission cable 10, the shield 16 is configured with a double horizontal shield, but in addition to the double horizontal shield, a single horizontal shield is also used depending on the shield characteristics required for the product. 16a (see differential signal transmission cable 20 in FIG. 2), braid 16b (see differential signal transmission cable 30 in FIG. 3), or metal strip 16c (see differential signal transmission cable 40 in FIG. 4). You may comprise. In particular, when the metal strip 16c is used, as shown in FIG. 4, a metal strip 16c having a flat cross section obtained by rolling a wire having a round cross section on one flat surface 15a of the fixed layer 15 is formed. (For example, a thickness of 0.03 to 0.08 mm, a width of 0.4 to 1.0 mm) is vertically added, and the shield tape 19 is wound around the outer periphery thereof, and the metal strip 16c is attached to one flat surface 15a of the fixed layer 15. It should be fixed. In this differential signal transmission cable 40, since the jacket 17 covered with the metal strip 16c is raised, the front and the back of the differential signal transmission cable 40 can be visually discriminated, and consequently the differential signal transmission cable. The arrangement positions of the cores 13 and 13 at both ends of the cable 40 can be distinguished.

  Further, in the differential signal transmission cable 10, the outer diameter of the insulating layer 12 of the core 13 is adjusted so that the distance between the conductors of the two-core 14 is equal to the distance between the terminals of the connector. As in the differential signal transmission cable 50, the separation distance between the cores 13 and 13 may be adjusted so that the distance L between the conductors of the two-core core 14 is equal to the distance between the terminals of the connector. In the differential signal transmission cable 10, when the distance between the terminals of the connector is large, it is necessary to increase the outer diameter of the insulating layer 12, and accordingly, the thickness of the differential signal transmission cable (flat surface 15 a, In the differential signal transmission cable 50, the distance between the cores 13 and 13 can be adjusted without increasing the thickness of the differential signal transmission cable. It becomes possible to adjust the distance between them.

  In the differential signal transmission cables 10, 20, 30, and 50, the configuration in which the shield tape 19 is provided on the outer periphery of the shield 16 has been described, but a configuration in which the shield tape 19 is not provided may be employed.

  Furthermore, by connecting connectors to the ends of these differential signal transmission cables 10, 20, 30, 40, and 50 to form a harness, a harness that reduces variations in characteristic impedance can be obtained.

  Therefore, according to the present invention, it is possible to prevent the paired conductors 11 and 11 from being displaced or inverted, the distance between the conductors of the paired conductors 11 and 11 is uniform, and the characteristic impedance varies. A small differential signal transmission cable 10, 20, 30, 40, 50 and a harness using the same can be provided.

DESCRIPTION OF SYMBOLS 10 Differential signal transmission cable 11 Conductor 12 Insulating layer 13 Core 14 Two-core core 15 Fixed layer 16 Shield 17 Jacket 18 Strand 19 Shield tape

Claims (7)

A two-core core in which two cores whose conductors are covered with an insulating layer are arranged in parallel;
A fixed layer provided around the two-core core to cover the two-core core collectively and fix the arrangement of the two cores;
A shield provided outside the fixed layer;
A jacket covering the outside of the shield;
A differential signal transmission cable comprising:   The differential signal transmission cable according to claim 1, wherein the insulating layer and the fixed layer are made of a fluororesin, and a melting point of the fluororesin constituting the fixed layer is equal to or lower than a melting point of the fluororesin constituting the insulating layer.   The fluororesin constituting the insulating layer is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and the fluororesin constituting the fixed layer is a tetrafluoroethylene-hexafluoropropylene copolymer (FEP). The differential signal transmission cable according to claim 2.   The cable for differential signal transmission according to any one of claims 1 to 3, wherein the shield is configured by a metal strip provided along one longitudinal surface of the fixed layer along a longitudinal direction of the two-core core. .   The differential signal transmission cable according to claim 1, wherein the two cores are arranged in contact with each other.   The differential signal transmission cable according to claim 1, wherein a distance between conductors of the two-core core is equal to a distance between terminals of the connector. A differential signal transmission cable according to any one of claims 1 to 6,
A connector connected to an end of the differential signal transmission cable;
A harness comprising: