JP4687638B2 - Connecting the cable unit and ground wire - Google Patents

Description

  The present invention relates to a cable unit in which a signal cable is covered with a cylindrical protective tube having a conductive layer inside and an insulating layer formed outside, and a method of connecting a ground wire to the cable unit.

  Many electronic devices use a signal cable, such as a flat cable, to realize transmission and reception of signals between electronic components. Among such electronic devices, in an electronic device that requires high signal quality, such as an audio device, electromagnetic noise superimposed on the signal is a serious problem.

  For this reason, many techniques for shielding a signal cable from electromagnetic noise have been proposed. For example, Patent Document 1 discloses a technique for shielding an electric wire from electromagnetic noise by covering the electric wire with a shield body configured by laminating a metal foil layer and an insulating layer and grounding the shield body. ing. In this patent document 1, in order to connect the electric wire coat | covered with the shield body to an electronic component, the said electric wire is pulled out from the middle of the shield body. Further, in order to ground the shield body, an end portion of the shield body is folded outward to form a ground terminal, and the ground terminal is fastened to the body or the shield case with a screw or the like.

  As another shielding technique, a flat cable as a signal cable is inserted into a cylindrical shield tube having a conductive layer on the inner side and an insulating layer on the outer side, and at the inner side of the shield tube, that is, on the conductive layer. A technique for connecting a ground terminal of a ground wire is also known.

Japanese Patent Laid-Open No. 9-308042

  According to these conventional techniques, the electromagnetic noise can be shielded to some extent. However, in the technique described in Patent Document 1, the conductive layer is exposed to the outside in the ground terminal formed by folding the end of the shield body. In this case, the conductive layer may contact or short-circuit with other electronic components or connectors, which may cause some trouble. In addition, it is difficult to cover the shield body up to the vicinity of the end of the wire because the wire is drawn out from the middle of the shield body. As a result, there is a problem in that the area of the portion of the electric wire that is not covered with the shield body becomes large and is affected by electromagnetic noise.

  In the case of the technique of covering the flat cable with the shield tube, the conductive layer is hardly exposed to the outside, so that the problem of short circuit with other electronic components is solved to some extent. However, the conductive layer is exposed at the end of the shield tube, that is, at the cut-off section of the shield tube. In order to prevent a short circuit between the conductive layer exposed at the end of the shield tube and the connector connected to the end of the flat cable, also in the technology, the shield tube is shortened and the shield tube end It was necessary to separate the flat cable end. As a result, the area of the flat cable that is electromagnetically shielded is also reduced, which may lead to a decrease in signal quality. Furthermore, in the case of a configuration in which a ground terminal is connected to the inside of the shield tube, it is necessary to make the shield tube wider than a flat cable in order to secure a space for connecting the ground terminal. When a wide shield tube is used, there are problems such as an increase in space for cable wiring and an increase in cost. Furthermore, the ground terminal connected to the inside of the shield tube has also contributed to the difficulty of inserting the flat cable into the shield tube.

  Therefore, an object of the present invention is to provide a cable unit and a ground wire connection method that can more easily prevent noise.

  The cable unit of the present invention is a cable unit in which a conductive layer is formed inside and a cylindrical protective tube having an insulating layer formed outside and a signal cable is covered, and one end of the protective tube covered with the signal cable is After being folded once outward, the conductive layer of the folded portion is folded at least once so as to face each other, and the ground wire and the conductive layer are connected with one end of the ground wire sandwiched between the facing conductive layers. It is characterized by that.

  In a preferred aspect, one end of the protective tube is cut off in the circumferential direction so as to be non-cylindrical. In another preferred embodiment, the end of the protective tube is covered with an insulator.

Another ground wire connection method according to the present invention is a connection method in which a ground wire is connected to a cable unit in which a signal cable is covered with a cylindrical protective tube, and a conductive layer is formed on the inner side and an insulating layer is formed on the outer side. is one end of the protective tube wrapping conductive layer of the folded-back portion after folding outwardly one or more times to face each other and, the ground wire and the conductive layer in a state of sandwiched one end of the ground wire between the opposing conductive layer And is connected.

  According to the present invention, after one end of the shield tube is folded outward, the shield tube is folded one or more times so that the conductive layers face each other, and connected with the ground wire sandwiched between the facing conductive layers. . In this case, although the ground wire is connected to the outside of the shield tube, the conductive layer is not exposed to the outside. As a result, it is possible to prevent problems such as a short circuit with other electronic components without affecting the flat cable insertion operation, and to more easily prevent electromagnetic noise.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a cable unit 10 according to an embodiment of the present invention. The cable unit 10 is configured by covering a flat cable 12 with a shield tube 14.

  As is well known, the flat cable 12 is a signal line in which a number of core members 16 are bundled in a band shape with a covering material 18 made of an insulator. At both ends of the flat cable 12, the core material 16 is exposed to the outside, and a connector (not shown) is press-contacted to the both ends. Both ends of the flat cable 12 are connected to different electronic components through the pressure contacted connectors, and signals are transmitted and received between the different electronic components. At this time, the signal transmitted and received by the flat cable 12 may be affected by electromagnetic noise emitted from electronic components or the like present in the surrounding area, and the signal quality may deteriorate. Conversely, electromagnetic noise may be emitted from the flat cable 12 to reduce the quality of other signals. The deterioration of signal quality due to such electromagnetic noise becomes a serious problem in devices that require high signal quality, such as audio devices.

  Therefore, in this embodiment, the flat cable 12 is covered with the shield tube 14, and the flat cable 12 is shielded from electromagnetic noise. The shield tube 14 is a cylindrical member in which a conductive layer 22 is formed on the inner side and an insulating layer 20 is formed on the outer side. By connecting a ground terminal of a ground wire to the conductive layer 22 of the shield tube 14 and grounding, the electromagnetic noise of the flat cable 12 is shielded.

  Here, FIG. 2 is a schematic configuration diagram of a conventional cable unit 50. As apparent from FIG. 2, conventionally, in order to connect the ground terminal of the ground wire to the conductive layer, the shield tube 54 is wider than the flat cable 52, and a margin is provided on the side of the shield tube 54. Then, a conductive member (hereinafter referred to as “earth terminal”) 56 a provided at one end of the ground wire 56 is inserted into a portion of the shield tube 54 that is wider than the flat cable 52, and the inside of the ground terminal 56 a and the shield tube 54. It was crimped in the state which contacted the conductive layer. In such a conventional method, the shield tube 54 is wide, and thus the entire cable unit 50 is wide, and a space for wiring the cable unit 50 is required. In addition, since a wide shield tube is used, the cost is increased. Further, normally, after connecting the ground wire 56 to the shield tube 54, the flat cable 52 is inserted into the shield tube 54. At this time, the ground terminal 56a connected to the inner side of the shield tube 54 is obstructed and flat. The insertion work of the cable 52 may be difficult. Further, in the conventional configuration, the conductive layer is exposed at the end face 54 a of the shield tube 54. The exposed conductive layer of the shield tube end face 54a may come into contact with a connector or the like provided at the end of the flat cable 52 to cause a short circuit. Therefore, conventionally, the shield tube 54 is shorter than the flat cable 52 in order to prevent a short circuit with a connector or the like. In this case, the area of the portion of the flat cable 52 that is not covered with the shield tube 54 becomes large, and thus it is easily affected by electromagnetic noise.

  As described above, the conventional cable unit has various problems such as a complicated manufacturing process, an increase in cost, and a reduction in electromagnetic noise shielding performance. Therefore, in the present embodiment, the ground wire is connected to the shield tube in a special manner to solve the above various problems. Hereinafter, this point will be described in detail.

  3 to 5 are views in the vicinity of one end of the shield tube 14 and showing a process of connecting the ground wire 24. The shield tube 14 used in the cable unit 10 is adjusted in advance to have substantially the same length as the flat cable 12 to be covered. When connecting the ground wire 24 to the shield tube 14, first, one end of the shield tube 14 is partially cut off to form a substantially rectangular, in other words, a non-cylindrical fin-shaped portion 30 (folded portion). (See FIG. 3). Subsequently, the fin-shaped portion 30 is folded outward. At this time, the conductive layer 22 comes to the outside. Further, the folded fin-shaped portion 30 is further folded at approximately the center so that the conductive layers 22 exposed to the outside face each other. In other words, the fin-shaped part 30 is once folded in the outside and then folded in the vicinity of the center thereof. FIG. 4 is a view showing the state of the shield tube 14 at this time. As is clear from FIG. 4, after the mountain fold and the valley fold, the insulating layer 20 is exposed to the outside in the fin-shaped portion 30. Subsequently, the ground terminal 24a of the ground wire 24 is sandwiched between the conductive layers 22 that are opposed to each other by the folding. In this state, the folded fin portion 30 is swaged with the ground wire 24 and fixed. At this time, the ground terminal 24a of the ground wire 24 comes into contact with the conductive layer 22 of the shield tube 14 from both sides. As a result, the continuity between the ground wire 24 and the conductive layer 22 can be reliably ensured, and as a result, the shield tube 14 can be reliably grounded. Further, since the ground terminal 24a is crimped after being sandwiched between the folded fin portions 30, the ground terminal 24a is not easily dropped, and the ground state can be stably maintained.

  Further, according to the present embodiment, the ground terminal 24a is connected to the outside of the shield tube 14 that is tubular as a whole. As a result, when the flat cable 12 is inserted through the shield tube 14, contact between the flat cable 12 and the ground terminal 24a is prevented. As a result, the insertion work of the flat cable 12 can be facilitated. Further, since the ground terminal 24 a is connected to the outside of the cylindrical portion of the shield tube 14, the entire width of the shield tube 14 can be made substantially the same as that of the flat cable 12. As a result, the cost can be reduced and the space required for the wiring of the cable unit 10 can also be reduced.

  By the way, in the state where this ground terminal 24a is connected, the end surface of the cylindrical portion of the shield tube 14 remains exposed to the outside. The conductive layer 22 is also exposed at this end face. When the conductive layer 22 on the end surface comes into contact with another electronic component or a connector connected to a flat cable and short-circuits, the device may malfunction or break down.

  Therefore, in this embodiment, after connecting the ground terminal 24 a, the end surface of the shield tube 14 is covered with the insulating tape 26. FIG. 5 is a view showing a state in which the insulating tape 26 is wound around the edge of the shield tube 14. The insulating tape 26 is a sheet-like member made of an insulating material and having an adhesive material applied on one side thereof. The insulating tape 26 is wound around the edge of the shield tube 14 to cover the conductive layer 22 exposed at the end face. Thereby, even if the edge part of the shield tube 14 and a connector contact, it does not short-circuit. Therefore, the shield tube 14 can be disposed up to the vicinity of the end of the flat cable 12. As a result, as is apparent from the comparison between FIGS. 1 and 2, the area of the flat cable 12 that is not covered with the shield tube 14 can be greatly reduced. As a result, electromagnetic noise can be shielded more reliably than in the prior art.

  Here, even in the conventional configuration as illustrated in FIG. 2, the conductive layer exposed at the end can be covered to some extent by winding the insulating tape around the end periphery of the shield tube 54. However, in the conventional configuration in which the ground terminal 56a is connected to the inside of the cylindrical shield tube 54, since the ground wire 56 extending from the end portion interferes, an insulating tape is applied over the entire circumference of the shield tube end portion. I couldn't wind it. On the other hand, in the present embodiment, as described above, since the ground terminal 24a is connected to the outer side of the cylindrical shape, the ground wire 24 does not interfere with the insulating tape 26 at the end of the shield tube. An insulating tape 26 can be wound around the entire periphery of the tube end. As a result, as described above, a short circuit between the connector and the shield tube end can be reliably prevented.

  In order to prevent interference between the insulating tape 26 wound around the peripheral edge and the ground wire 24 connected to the folded fin-shaped portion 30 as much as possible, the ground terminal 24a is provided near the valley fold line of the folded portion, in other words, In this case, it is desirable that the crimping is performed at a position as far as possible from the end face of the cylindrical portion of the shield tube 14 around which the insulating tape 26 is wound. The ground wire 24 may be connected only to one end of the shield tube, but the insulating tape 26 is wound around both ends of the shield tube 14.

  When the ground wire 24 is connected to the shield tube 14 and the insulating tape 26 is wound around the end surface of the shield tube by the method as described above, the flat cable 12 is inserted into the shield tube 14 and the cable unit 10. It becomes.

  According to the cable unit 10 of this embodiment, since the almost entire surface of the flat cable 12 can be covered with the shield tube 14, it is difficult to be affected by electromagnetic noise, and high-quality signal transmission is possible. . Moreover, since the width of the shield tube 14 can be reduced, the space required for the wiring of the cable unit 10 can be reduced, and the shield tube 14 having a size close to the width of the flat cable 12 can be used, thereby reducing the cost.

  The configuration described above is an example, and other configurations may be appropriately changed as long as the end portion of the shield tube is folded and the ground wire is connected to the folded portion. For example, in the present embodiment, a flat cable is exemplified as the signal line to be covered, but naturally, other signal lines, for example, signal lines having a circular cross section may be covered. In this embodiment, the end of the shield tube is folded twice, but may be folded once or three or more times. When the insulating tape 26 is wound around the end of the shield tube 14, the fin-shaped portion 30 is folded in a mountain to expose the conductive layer 22 to the outside, and the grounding terminal 24 a is caulked on the exposed conductive layer 22. Even if the conductive layer 22 is folded back (valley-folded) so as to face each other, the sandwiched state of the ground terminal 24 a by the conductive layer 22 can be maintained by the subsequent winding of the insulating tape 26.

It is a schematic block diagram of the cable unit which is embodiment of this invention. It is a schematic block diagram of the conventional cable unit. It is a figure which shows the connection process of a ground wire. It is a figure which shows the other connection process of a ground wire. It is a figure which shows the other connection process of a ground wire.

Explanation of symbols

  10 Cable unit, 12 Flat cable, 14 Shield tube, 20 Insulating layer, 22 Conductive layer, 24 Ground wire, 24a Ground terminal, 26 Insulating tape, 30 Fin-shaped part.

Claims (4)

A cable unit in which a signal cable is covered with a cylindrical protective tube having a conductive layer inside and an insulating layer formed outside,
One end of the protective tube covering the signal cable is folded once outward and then folded back at least once so that the conductive layers of the folded portion face each other, with one end of the ground wire sandwiched between the conductive layers facing each other A cable unit characterized in that a ground wire and a conductive layer are connected. The cable unit according to claim 1,
One end of the protective tube is partly cut off in the circumferential direction so as to be non-cylindrical. The cable unit according to claim 1 or 2,
An end portion of the protective tube is covered with an insulator. A connection method for connecting a ground wire to a cable unit in which a signal cable is covered with a cylindrical protective tube,
Conductive layer on the inside, outside the folding the conductive layer of the folded-back portion is at least once to face each other after the end of the protective tube in which an insulating layer is formed folded outward end of the ground wire between the opposing conductive layer A method for connecting a ground wire, wherein the ground wire and the conductive layer are connected in a state of sandwiching the wire.

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