WO2025041450A1 - Flat cable - Google Patents

Abstract

A flat cable (10) is provided with at least three layers of flat cable conductors spaced apart from each other. The at least three layers of flat cable conductors include an inner cable conductor (11), one outer cable conductor (13B), and the other outer cable conductor (13A). The other outer cable conductor (13A) is on the opposite side to the one outer cable conductor (13B) in the thickness direction. The inner cable conductor (11) is disposed so as to be sandwiched between the one outer cable conductor (13B) and the other outer cable conductor (13A) in the thickness direction. At least one of the one outer cable conductor (13B), the other outer cable conductor (13A), and the inner cable conductor (11) has a lower DC conductor resistance in a cable end portion than in the regions other than the cable end portion.

Description

Flat Cable

The present invention relates to a flat cable.

A flat cable having a configuration in which multiple flat ribbon cable conductors are laminated with an insulator between them is known as a cable suitable for carrying high-frequency currents of 10 KHz or more. Such a flat cable is proposed, for example, in JP 2015-146296 A (Patent Document 1). JP 2015-146296 A discloses a flat cable having a flat ribbon inner conductor and a pair of flat ribbon outer conductors arranged in parallel on both sides of the inner conductor with an inner insulator between them. The inner conductor carries a forward current, and the outer conductor carries a return current.

The flat cable in Patent Document 1 has a total of three layers of flat ribbon conductors (flat ribbon cable conductors). This makes it possible to suppress the skin effect and proximity effect, resulting in low heat generation. Hereinafter, the skin effect and proximity effect will be collectively referred to as the skin effect, etc. However, it is desirable for the user to have two connection terminals to the target device. This is because electrical devices normally have two terminals, for example a positive terminal and a negative terminal. For this reason, in Patent Document 1, a pair of flat ribbon outer conductors are bundled together so that one and the other ends of the cable have two terminals.

JP 2015-146296 A

The two-layered portion where a pair of flat-strip outer conductors are bundled together is more susceptible to skin effect than the three-layered portion. For this reason, the two-layered portion is more likely to heat up to high temperatures.

The present invention has been made in consideration of the above problems. The object of the present invention is to provide a flat cable that has three layers of flat ribbon cable conductors and can suppress heat generation.

The flat cable according to the present disclosure comprises at least three layers of flat ribbon cable conductors spaced apart from one another. The at least three layers of flat ribbon cable conductors include an inner cable conductor, one outer cable conductor, and the other outer cable conductor. The other outer cable conductor is opposite the one outer cable conductor in the thickness direction. The inner cable conductor is arranged so as to be sandwiched between the one outer cable conductor and the other outer cable conductor in the thickness direction. At least one of the one outer cable conductor, the other outer cable conductor, and the inner cable conductor has a smaller DC conductor resistance at the cable end than in areas other than the cable end.

According to the present disclosure, the direct current conductor resistance of the flat ribbon cable conductor is small, so even if it is affected by the skin effect, the high frequency conductor resistance is still small. This makes it possible to suppress heat generation.

FIG. 2 is a top view of the flat cable according to the embodiment. 2 is a first example of a side view of the flat cable of FIG. 1 as viewed from the lateral direction indicated by the arrow II in FIG. 1 . 2 is a schematic cross-sectional view of a portion taken along line III-III in FIG. 1. 1 is a schematic perspective view of a flat cable according to an embodiment of the present invention with an outer insulation partly removed to expose a flat ribbon-shaped cable conductor present therein. FIG. 2 is a second example of a side view of the flat cable of FIG. 1 as viewed from the lateral direction indicated by the arrow II in FIG. 1 . 11 is a photograph showing an aspect in which the cross-sectional area of the cable conductor at the second end is made larger than that of other regions. 2 is a photograph showing an enlarged view of the second end of the flat cable of the present embodiment as viewed from above; FIG. 8 is a photograph showing a side view of the part shown in FIG. 7 as viewed from the lateral direction indicated by the arrow VIII. 1 is a photograph showing a first example of a bundling mode of two outer cable conductors. 13 is a photograph showing a second example of a bundling mode of two outer cable conductors. 4 is a flow chart that generally illustrates a method for manufacturing a flat cable. 1 is a table illustrating the impedance of a cable end of a flat cable.

Hereinafter, the present embodiment will be described with reference to the drawings.
<Configuration of flat cable 10>
FIG. 1 is a top view of a flat cable according to the present embodiment. FIG. 2 is a first example of a side view of the flat cable of FIG. 1 as viewed from the lateral direction indicated by the arrow II in FIG. 1. Referring to FIG. 1 and FIG. 2, a flat cable 10 of the present embodiment is a linear member extending in the left-right direction of the figure. The left-right direction in FIG. 1 and FIG. 2 in which the flat cable 10 extends is hereinafter referred to as the cable length direction. The region of the flat cable 10 other than both ends in the cable length direction (for example, the region where the external insulator 14C is disposed) is a cable main body 10A. One end (cable end) of the flat cable 10 in the cable length direction (left side in FIG. 1 and FIG. 2) is a first end 10E1. The other end (cable end) of the flat cable 10 in the cable length direction (right side in FIG. 1 and FIG. 2) is a second end 10E2.

The cable ends are the ends of the flat cable 10 in the cable length direction (extension direction) (areas within a certain length in the cable length direction from the end face that is the endmost). In the following, the cable ends are considered to be the first end 10E1 and the second end 10E2, excluding the cable body 10A.

The vertical direction of the flat cable 10 in FIG. 1, which intersects (is perpendicular to) the cable length direction, is hereinafter referred to as the width direction. In other words, the direction on the main surface of each flat ribbon cable conductor constituting the flat cable 10, which intersects (is perpendicular to) the cable length direction, is hereinafter referred to as the width direction. The vertical direction in FIG. 2, which intersects (is perpendicular to) the cable length direction, is hereinafter referred to as the thickness direction. Furthermore, for example, the direction extending radially from the central axis of the entire flat cable 10 extending along the cable length direction is hereinafter referred to as the radial direction.

The first end 10E1 is the input side, i.e., the side where an electrical signal is input to the flat cable 10. The second end 10E2 is the output side. The output side is the side where a user connects an electrical device or the like to which a signal or the like that passes through the flat cable 10 should be supplied. For example, the flat cable 10 is used in a non-contact power supply system for an electric vehicle or the like. Specifically, for example, the output terminal of a high-frequency power supply device may be connected to the first end 10E1, and a coil (mechanical device: load device) that generates an electromagnetic field may be connected to the second end 10E2. However, the uses of the flat cable 10 are not limited to the above uses. For example, an induction heating device may be connected to the second end 10E2 of the flat cable 10.

3 is a schematic cross-sectional view of a portion along line III-III in FIG. 1. FIG. 4 is a schematic perspective view of the flat cable according to the present embodiment with the external insulation partly removed to expose the flat ribbon cable conductor present therein. FIG. 4 shows an embodiment of region IV in FIG. 1. With reference to FIGS. 3 and 4, the flat cable 10 has three flat ribbon cable conductor layers in the thickness direction. The flat ribbon cable conductor includes one internal cable conductor 11 and two external cable conductors 13. The two external cable conductors 13 are external cable conductor 13A (the other external cable conductor) and external cable conductor 13B (one external cable conductor). In the following description, the external cable conductors 13A and 13B may be referred to as "one" or "the other" or may be omitted. The internal cable conductor 11 is arranged to be sandwiched between the upper external cable conductor 13A and the lower external cable conductor 13B in the thickness direction. The other external cable conductor 13A is positioned on the opposite side of the thickness direction from the one external cable conductor 13B.

As shown in FIG. 4, the external cable conductor 13A has an external main surface 13Aa (second main surface) and an internal main surface 13Ab (fourth main surface). The external cable conductor 13B has an external main surface 13Ba (third main surface) and an internal main surface 13Bb (first main surface). The internal main surface 13Ab and the internal main surface 13Bb face the internal cable conductor 11. The internal cable conductor 11 has an upper main surface 11A and a lower main surface 11B. The upper main surface 11A faces the external cable conductor 13A, and the lower main surface 11B faces the external cable conductor 13B.

The inner cable conductor 11 is a flat ribbon-shaped cable conductor other than the outer cable conductor 13. Most of the surface of the inner cable conductor 11 is covered by the inner insulator 12. However, not all parts of the surface of the inner cable conductor 11 are necessarily covered by the inner insulator 12. The inner insulator 12 may be a single layer in the cable body 10A. At least either the first end 10E1 or the second end 10E2, the portion of the inner insulator 12 exposed in FIG. 2 may be a single layer, but may also be two layers.

In at least some regions of the cable body 10A, as shown in FIG. 3, the inner cable conductor 11, the outer cable conductor 13A, and the outer cable conductor 13B are arranged to be spaced apart by the inner insulator 12. In addition, the three layers of flat ribbon cable conductors stacked in the thickness direction are covered by the outer insulator 14C at least in the cable body 10A.

As shown in FIG. 2, the three-layer flat ribbon cable conductor of the flat cable 10 has the bundling insulator 14X and the internal insulator 12 exposed at the second end 10E2, which is the cable end. The second end 10E2 includes a two-layered portion having two layers of flat ribbon cable conductors: the bundled cable conductors (bundled cable conductors) in the bundling insulator 14X and the internal cable conductor 11 in the internal insulator 12.

The bundled cable conductor is formed by bundling the external cable conductors 13 out of the three layers of flat ribbon cable conductors. Specifically, one external cable conductor 13B is bundled with the other external cable conductor 13A on the opposite side in the thickness direction and is electrically connected to each other. At the second end 10E2, the bundled external cable conductors 13A and 13B are covered with a bundling insulator 14X.

In FIG. 2, at the second end 10E2 on the output side, a two-layered portion is formed by the bundled cable conductor composed of the external cable conductors 13A and 13B and the internal cable conductor 11. Hereinafter, the state in which the external cable conductors 13A and 13B are bundled may be referred to as the bundled cable conductors 13A and 13B. A terminal TB10 is provided at the second end 10E2 between the bundled cable conductors 13A and 13B and the internal cable conductor 11. The terminal TB10 is included in the second end 10E2. Specifically, a terminal TB10-X is connected to the end of the bundled cable conductors 13A and 13B, and a terminal TB10-2 is connected to the end of the internal cable conductor 11. As a result, the second end 10E2 has a two-terminal configuration.

In FIG. 2, the first end 10E1 on the input side also has a two-layered portion formed by the bundled cable conductors 13A, 13B and the internal cable conductor 11, just like the second end 10E2. A terminal TA10 is provided at the input side end of the bundled cable conductors 13A, 13B and the internal cable conductor 11. The terminal TA10 is included in the first end 10E1. Specifically, a terminal TA10-X is connected to the end of the bundled cable conductors 13A, 13B, and a terminal TA10-2 is connected to the end of the internal cable conductor 11. This makes the first end 10E1 a two-terminal unit.

However, the flat cable 10 of this embodiment is not limited to the embodiment shown in FIG. 2. FIG. 5 is a second example of a side view of the flat cable of FIG. 1 as viewed from the lateral direction indicated by the arrow II in FIG. 1. Referring to FIG. 5, the flat cable 10 of the second example has a two-terminal embodiment at the second end 10E2, similar to the first example shown in FIG. 2. However, at the first end 10E1, the three layers of flat ribbon cable conductors are not bundled and exist individually. In other words, the inner cable conductor 11, the outer cable conductor 13A, and the outer cable conductor 13B exist separately. At the first end 10E1, the inner cable conductor 11 is also covered with the inner insulator 12. At least at the first end 10E1, the outer cable conductor 13A is covered with the outer insulator 14A, and the outer cable conductor 13B is covered with the outer insulator 14B. As for the terminal TA10, terminal TA10-1 is connected to the end of the external cable conductor 13A, and terminal TA10-3 is connected to the end of the external cable conductor 13B. Terminal TA10-2 is connected to the end of the internal cable conductor 11, as with the others. As a result, the first end 10E1 has three terminals. The flat cable 10 may have such a configuration.

Although not shown, depending on the usage, the flat cable 10 may have the following configuration different from either FIG. 2 or FIG. 5. That is, the first end 10E1 may be two-layered to have two terminals like the second end 10E2 in FIG. 5, and the second end 10E2 may be three terminals instead of two-layered like the first end 10E1 in FIG. 5.

In such a case, this embodiment may be applied to the second end 10E2, which is not two-layered but has three terminals. Alternatively, this embodiment may be applied to the first end 10E1, which has three terminals as shown in FIG. 5. The first end 10E1 may be used as the output side, and the second end 10E2 may be used as the input side. In this case, a mechanical device for output by a user may be connected to the first end 10E1, and an input power source may be connected to the second end 10E2.

Alternatively, the flat cable 10 may have three terminals at both the first end 10E1 and the second end 10E2, as in the first end 10E1 of FIG. 5. The first end 10E1 may be the output side and the second end 10E2 may be the input side, or vice versa. In other words, this embodiment is not limited to a configuration in which at least either the first end 10E1 or the second end 10E2 is bound to have two terminals.

At least one of the external cable conductor 13B, the other external cable conductor 13A, and the internal cable conductor 11 has a smaller DC conductor resistance at the cable end, i.e., the second end 10E2 (first end 10E1), than in the area other than the cable end, i.e., the area other than the second end 10E2 (and the first end 10E1).

To achieve this, at least one of the external cable conductor 13B, the external cable conductor 13A, and the internal cable conductor 11 may have a larger cross-sectional area at the cable end, i.e., the second end 10E2, than the area other than the cable end, i.e., the area other than the second end 10E2. The cross-sectional area here refers to the area at a cross section that intersects (is perpendicular to) the cable length direction, for example, as shown in FIG. 3. The cross-sectional area of the cable end, i.e., the second end 10E2, is preferably 1.2 to 2.5 times the cross-sectional area of the area other than the cable end, i.e., the area other than the second end 10E2.

However, it is not necessary for the entire cable end to have a small series conductor resistance or a large cross-sectional area. Only a portion of the cable end, or only another portion of the cable end, may have a smaller DC conductor resistance or a larger cross-sectional area than the cable body.

FIG. 6 is a photograph showing an embodiment in which the cross-sectional area of the cable conductor at the second end is made larger than that of other regions. Referring to FIG. 6, in order to achieve the above, in this embodiment, another flat band cable conductor 13C is electrically joined to each of one external cable conductor 13B and the other external cable conductor 13A. Also in this embodiment, another flat band cable conductor 11C is electrically joined to the internal cable conductor 11. The other flat band cable conductors 11C, 13C are formed from the same material and in the same manner as the internal cable conductor 11 and the external cable conductor 13.

The other flat ribbon cable conductors 11C, 13C may be installed so as to overlap (almost) the entire main surface of the portion of the inner cable conductor 11, one outer cable conductor 13B, and the other outer cable conductor 13A that is exposed outside the outer insulator 14C (so as to have (almost) the same area as the exposed portion), or may be installed so as to overlap a portion of the main surface. Also, the other flat ribbon cable conductors 11C, 13C and the flat ribbon cable conductors 11, 13 of the flat cable 10 may be arranged in a direction along the main surface, and the side portions may be joined together.

In FIG. 6, the other flat ribbon cable conductors 11C, 13C are electrically joined by solder SD. In FIG. 6, the other flat ribbon cable conductors are joined to only a small area of each cable conductor (an area of 10% or less of the surface area). This is also acceptable. However, for example, the other flat ribbon cable conductors may be joined to more than half of the surface area of each cable conductor.

The method of joining the other flat ribbon cable conductors 11C, 13C to the cable conductor is not limited to using solder SD. For example, the two may be joined by welding, cold pressure welding, sleeve pressure welding, or other methods. This forms a joint.

The means for making the resistance of the cable end, such as the second end 10E2, smaller than that of other regions is not limited to joining the other flat ribbon cable conductors 11C, 13C. For example, the flat ribbon cable conductors (the inner cable conductor 11 and the outer cable conductor 13) may be formed from the beginning with a cross-sectional area larger at the second end 10E2 and the first end 10E1 than that of the cable body 10A, without joining other conductor members.

Furthermore, the means for making the resistance of the cable end such as the second end 10E2 smaller than that of the other regions is not limited to the above, and may be as follows. Specifically, as a first example, either silver or gold, which is a material having a lower electrical resistance than the other regions, may be used in the area where the cable ends are bundled to form a two-layered structure. Alternatively, as a second example, a silver conductor may be connected to the end of a flat ribbon cable conductor made of copper. Alternatively, as a third example, a copper conductor may be connected to the end of a flat ribbon cable conductor made of aluminum. Furthermore, as a fourth example, terminals TA10, TB10 (see FIG. 1) made of either silver or gold may be used. The two-layered area is more likely to generate heat than the other areas, but by applying such a treatment, the flat cable will generate less heat over its entire length. Note that the same treatment may be applied not only to the two-layered area, but also to the other areas. Even in this case, the effect of suppressing heat generation can be obtained.

Alternatively, referring again to Figures 2 and 5, for example, terminal TB10-X (rectangular terminal), which is part of second end 10E2, or another terminal (for example, terminal TA10-1 in Figure 5) can be processed to be thicker than the other terminals, as shown by the dotted line in the figure. This also makes it possible to make the cross-sectional area of the terminal larger than the others, thereby reducing the DC conductor resistance.

Here, the size, material, etc. of each member constituting the flat cable 10 will be described. Referring again to the cross-sectional view of FIG. 3, the internal cable conductor 11 is a bundle of many copper wires (particularly soft copper wires) 3 extending in the cable length direction. The wires 3 may be braided by plain weaving, flat knitting, circular knitting, or other methods. Alternatively, the wires 3 may be gathered together in large numbers by various methods such as child twisting, bunched twisting, longitudinal laying, and transverse winding. In this way, many strands of wires 3 may be twisted together and wound in a track shape on the cross section of FIG. 3.

The external cable conductor 13 (external cable conductors 13A, 13B) is also formed of the same material and in the same manner as the internal cable conductor 11. However, the external cable conductors 13A, 13B are thinner than the internal cable conductor 11. Specifically, the cross-sectional area of each of the external cable conductors 13A, 13B shown in FIG. 3 is preferably 1/2 the cross-sectional area of the internal cable conductor 11 shown in FIG. 3. In other words, the sum of the cross-sectional areas of the external cable conductor 13A and the external cable conductor 13B is preferably equal to the cross-sectional area of the internal cable conductor 11.

The material forming the strand 3 may be any conductive material. For example, the material forming the strand 3 may be copper, aluminum, an aluminum alloy, a copper alloy, gold, silver, or a non-metal such as carbon fiber or a conductive polymer.

The internal insulator 12 and the external insulators 14A, 14B, 14C, 14X are all made of cross-linked polyolefin colored black and are formed to surround the outside of the conductor. However, the materials of the internal insulator 12 and the external insulators 14A, 14B, 14C, 14X are not limited to the above and may be any of the following: That is, the above insulators may be any selected from the group consisting of flame-retardant polyolefin, polyolefin, vinyl chloride, polytetrafluoroethylene (Teflon (registered trademark), etc.), nylon, natural rubber, chloroprene rubber, ethylene propylene rubber (PE rubber), chlorosulfonated polyethylene rubber, silicon rubber, urethane, flame-retardant cross-linked polyethylene, and cross-linked polyethylene. In terms of distinction, some of the above insulators may be colored other than black (for example, white).

The terminal TB10 at the second end 10E2 is a flat-angle terminal. That is, the terminal TB10-X installed on the bundled cable conductors 13A and 13B, and the terminal TB10-2 installed on the internal cable conductor 11 are flat-angle terminals. The terminal TA10 at the first end 10E1 is a flat-angle terminal. That is, the terminal TA10-X installed on the bundled cable conductors 13A and 13B, and the terminal TA10-2 installed on the internal cable conductor 11 are flat-angle terminals. The material forming the flat-angle terminal may be any conductive material. The material forming the flat-angle terminal may be any one selected from the group consisting of, for example, copper, brass, phosphor bronze, silver, and gold. The flat cable 10 does not need to have a flat-angle terminal attached.

Rectangular terminals (terminals TA10, TB10) are installed at each cable end of the two-layer or three-layer flat ribbon cable conductor. The portion where the rectangular terminals (terminals TA10, TB10) are arranged is included in the first end 10E1 or the second end 10E2. In other words, the rectangular terminals (terminals TA10, TB10) are part of the first end 10E1 or the second end 10E2 (cable end).

It surrounds a part (end) of the cable conductor from the outside and has a shape with a through hole in the center when viewed from above. By passing a bolt or the like through this through hole, the flat cable 10 can be connected to the terminal of another electrical device, etc. However, the flat cable 10 may not have terminals installed, and the user may attach terminals to the first end and second end of the flat cable 10.

By forming each of the above components thin in the thickness direction, the flat cable 10 is formed as a flat electric wire having a flat shape.

FIG. 7 is a photograph showing the flat cable of this embodiment as viewed from above, with the second end of FIG. 1 enlarged. FIG. 8 is a photograph showing the part shown in FIG. 7 as viewed from the side as indicated by arrow VIII. With reference to FIGS. 7 and 8, the flat cable 10 shown in FIGS. 1 and 2 actually has the configuration shown in the photograph. Note that the first end 10E1, which is not shown, is also processed in the same manner as the second end 10E2. Next, an embodiment in which one external cable conductor 13B and the other external cable conductor 13A are bundled together to form a bundled cable conductor will be described.

Figure 9 is a photograph showing a first example of a bundling mode for two external cable conductors. Referring to Figure 9, in the bundled cable conductors 13A, 13B, the first inner main surface 13Bb of one external cable conductor 13B is joined to the second outer main surface 13Aa of the other external cable conductor 13A. To achieve this, as shown in Figure 9, a partial area of one external cable conductor 13B may be twisted inside out. In this case, one external cable conductor 13B is usually turned over once, but may be turned over more than once.

As another example of a mode of bundling two external cable conductors, a portion of one external cable conductor 13B may be twisted and turned inside out so that the outer third main surface 13Ba of one external cable conductor 13B is joined to the outer second main surface 13Aa of the other external cable conductor 13A. In this case, one external cable conductor 13B is usually turned inside out twice, but may be turned inside out more than that.

Figure 10 is a photograph showing a second example of a bundling mode for two external cable conductors. Referring to Figure 10, in the second example of bundled cable conductors, one external cable conductor 13B and the other external cable conductor 13A are bent so as to extend in a direction intersecting the internal cable conductor 11. In this state, the outer third main surface 13Ba of one external cable conductor 13B is joined to the outer second main surface 13Aa of the other external cable conductor 13A.

<Production Method>
Fig. 11 is a flow chart showing a schematic diagram of a method for manufacturing a flat cable. Referring to Fig. 11, first, an inner cable conductor 11, one outer cable conductor 13B, and the other outer cable conductor 13A constituting a three-layer flat ribbon cable conductor are prepared (S10). Specifically, a large number of strands 3 shown in Fig. 3 are flat-braided to form the inner cable conductor 11, one outer cable conductor 13B, and the other outer cable conductor 13A. Each of these cable conductors is processed to become a flat-shaped electric wire whose thickness dimension is sufficiently smaller than its width dimension as shown in Fig. 3. In order to make each cable conductor flat, the strands are flat-braided. The flat-braided conductor may be rolled in its thickness direction to further reduce its thickness.

In addition, the inner cable conductor 11 and the outer cable conductors 13A and 13B may be formed from conductor foil.

Next, the internal insulator 12 extruded by the extruder is installed so as to cover the outer circumference of the cable body 10A, the first end 10E1, and the second end 10E2 of the internal cable conductor 11. The cable body 10A, the first end 10E1, and the second end 10E2 may be covered with the same internal insulator 12, or different internal insulators 12 may be covered.

Furthermore, the outer periphery of one of the external cable conductors 13B and the other external cable conductor 13A may be covered with an insulator, similar to the inner cable conductor 11.

As shown in Figure 3, each of the three flat ribbon cable conductors is stacked (S20). At this time, for example, a pair of outer cable conductors 13 are stacked so as to follow the inner cable conductor 11 (so as to almost overlap in a plan view). The outer periphery of each cable conductor is processed so that the parts that need to be insulated from other conductors are appropriately covered with insulation extruded by an extruder.

Next, at least one of the first end 10E1 and the second end 10E2 of the formed flat ribbon cable conductors 11, 13, one external cable conductor 13B and the other external cable conductor 13A are bundled (S30). One external cable conductor 13B and the other external cable conductor 13A are bundled, for example, at one or both of the first end 10E1 and the second end 10E2 to form a bundled cable conductor. As shown in FIG. 9, one external cable conductor 13B is twisted and turned inside out (S31) and placed so as to be close to the other cable conductor 13A (S32). Next, the main surface of one external cable conductor 13B is adjusted to face the main surface of the other external cable conductor 13A (S33), and both cable conductors are joined by solder or the like (S34).

For this reason, as necessary, the insulation covering the radial outside of the portion that is to be the joint between one external cable conductor 13B and the other external cable conductor 13A is cut away. In particular, when one external cable conductor 13B and the other external cable conductor 13A are individually covered with insulation, the insulation at the end is cut away.

A bundling insulator 14X is provided so as to cover the outer circumference of the bundled cable conductor (the bundled portions of the first end 10E1 and the second end 10E2). Furthermore, an external insulator 14C is provided on the outermost part of the cable main body 10A. A heat shrink tube made of the same material as the internal insulator 12, the external insulator 14C, etc. may be further provided to cover the bundling insulator. Specifically, the material forming the internal insulator 12, the external insulator 14C, etc., and the heat shrink tube may be any one selected from the group consisting of ethylene propylene rubber, polyethylene, polypropylene, polyvinyl chloride, fluoropolymer, silicone, and polyurethane. Instead of a heat shrink tube, an insulating tape or extruded resin may be provided. In this way, a finishing process in which the insulator is applied is performed (S40).

The terminals (rectangular terminals TA10, TB10) are formed by placing a copper pipe over the end of the cable conductor, compressing it into a rectangular shape (press compression joining), and attaching it to the cable conductor.

<Action and effect>
Below, although there will be some overlap with the above, a summary of the configuration of this embodiment and its functions and effects will be described.

The flat cable 10 according to the present embodiment includes at least three layers of flat ribbon cable conductors 11, 13A, 13B spaced apart from each other. The at least three layers of flat ribbon cable conductors 11, 13A, 13B include an inner cable conductor 11, one outer cable conductor 13B, and the other outer cable conductor 13A. The other outer cable conductor 13A is on the opposite side of the one outer cable conductor 13B in the thickness direction. The inner cable conductor 11 is arranged to be sandwiched between the one outer cable conductor 13B and the other outer cable conductor 13A in the thickness direction. At least one of the one outer cable conductor 13B, the other outer cable conductor 13A, and the inner cable conductor 11 has a smaller DC conductor resistance at the cable end 10E2 (one end of the cable: here, the second end 10E2, but it may also be the first end 10E1. It may also be the output side end or the input side end) than the area other than the cable end 10E2 (cable main body 10A).

By making the DC conductor resistance at the cable end smaller than that in other areas, it is possible to prevent the cable end from becoming too hot, regardless of the number of layers at the cable end of the flat ribbon cable conductor. In other words, the amount of heat generated at the cable end is reduced. Even if the cable end has three terminals, or if it becomes two terminals due to two layers, the amount of heat generated is reduced. Even when the skin effect, etc. are taken into account, the high frequency conductor resistance is reduced, and it is possible to prevent the cable from becoming too hot.

In the flat cable 10, the flat ribbon cable conductors have at least three layers: the flat ribbon cable conductors 11, 13A, and 13B. The three layers can suppress the skin effect, etc.

In the above-mentioned flat cable 10, at least one of the external cable conductor 13B, the external cable conductor 13A, and the internal cable conductor 11 has a larger cross-sectional area at the cable end (e.g., second end 10E2) than the area (e.g., cable main body 10A) other than the cable end (e.g., second end 10E2). Increasing the size of the cross section of the conductor at the cable end that intersects with the cable length direction reduces the DC conductor resistance, and therefore reduces the high frequency conductor resistance even when the skin effect, etc. is taken into consideration, making it possible to suppress high temperatures. The area with a larger cross-sectional area is not limited to the flat ribbon cable conductor portion, but may also be the terminal portion.

In the flat cable 10, other flat ribbon cable conductors 11C, 13C are electrically connected to at least one of the external cable conductor 13B at one end of the cable (second end 10E2), the external cable conductor 13A at the other end, and the internal cable conductor 11.

By attaching flat ribbon cable conductors 11C, 13C to the main surfaces of flat ribbon cable conductors 11, 13, the size of the cross section of the conductor at the cable end intersecting the cable length direction can be increased. This reduces the DC conductor resistance, so that even when the skin effect is taken into account, the high frequency conductor resistance is also reduced, and high temperatures can be suppressed.

In the flat cable 10, at least one cable end (one end of the cable: for example, the second end 10E2, but it may also be the input side) of the at least three layers (for example, three layers) of flat ribbon cable conductors 11, 13 includes a two-layered portion (the conductor layer in the bundling insulator 14X and the internal cable conductor 11 in the internal insulator 12) having two layers of flat ribbon cable conductors 11, 13, that is, the bundled cable conductors (the two external cable conductors 13A, 13B in the bundling insulator 14X) and the internal cable conductor 11. The bundled cable conductors 13A, 13B are formed by bundling one external cable conductor 13B and the other external cable conductor 13A of the at least three layers (for example, three layers) of flat ribbon cable conductors 11, 13.

Cable ends with two-layered conductors are more susceptible to skin effect and high temperatures than cable ends with three layers. If the DC conductor resistance of the two-layered cable end is made smaller than that of other areas, the high-frequency conductor resistance is reduced and high temperatures can be prevented, even when the skin effect and other factors are taken into account. Therefore, it is possible to achieve both the skin effect and other effects caused by the flat cable 10 having three layers of flat ribbon cable conductors 11, 13A, 13B, and the effect of suppressing temperature rise due to the reduced electrical resistance (high-frequency conductor resistance) at the end where the conductor is two layers according to user specifications.

In the flat cable 10, the bundled cable conductors 13A and 13B are twisted and turned inside out so that the first inner main surface 13Bb of one of the external cable conductors 13B is joined to the second outer main surface 13Aa of the other external cable conductor 13A.

This allows the cable end to have two terminals. For example, one outer cable conductor 13B and the other outer cable conductor 13A can be more firmly connected than when the first inner main surface 13Bb of one outer cable conductor 13B is connected to the fourth inner main surface 13Ab of the other outer cable conductor 13A (not turned over).

For example, when one external cable conductor 13B and the other external cable conductor 13A are stretched so as to cross the internal cable conductor 11 and then joined and bundled together so as not to short-circuit with the internal cable conductor 11, the joint between one external cable conductor 13B and the other external cable conductor 13A is likely to come apart. This is due to the repulsive force, i.e., restoring force, of the external cable conductor 13. However, according to the present invention, the two external cable conductors 13 are bundled together in a state in which they are both extended along the cable length direction. This makes it possible to prevent repulsive forces from occurring between them, and to firmly connect them.

In the flat cable 10, the bundled cable conductors 13A and 13B are twisted and turned over in one of the external cable conductors 13B so that the third outer main surface 13Ba of the one external cable conductor 13B is joined to the second outer main surface 13Aa of the other external cable conductor 13A.

This allows the cable end to have two terminals. For example, one outer cable conductor 13B and the other outer cable conductor 13A can be more firmly connected than when the first inner main surface 13Bb of one outer cable conductor 13B is connected to the fourth inner main surface 13Ab of the other outer cable conductor 13A (not turned over).

In the flat cable 10, the bundled cable conductors 13A and 13B are bent so that one external cable conductor 13B and the other external cable conductor 13A extend in a direction intersecting the internal cable conductor 11, and the outer third main surface 13Ba of one external cable conductor 13B is joined to the outer second main surface 13Aa of the other external cable conductor 13A. This makes it possible to suppress short circuits between the external cable conductor 13 and the internal cable conductor 11, compared to when, for example, the external cable conductor 13 extends in the cable length direction in the same manner as the internal cable conductor 11.

In the above-mentioned flat cable 10, flat terminals TB10, TA10 are provided on each of at least three layers of flat ribbon cable conductors (inner cable conductor 11 and outer cable conductors 13A, 13B) at the cable ends (second end 10E2, first end 10E1). When flat terminals TB10, TA10 are used as terminals, the cross section of the contact area between the flat ribbon cable conductor to which it is attached becomes larger than when round terminals are used, resulting in less heat generation.

Furthermore, when rectangular terminals TB10 and TA10 are used, the contact area when the opposing surfaces of the terminals come into contact is larger than when round terminals are used. The opposing surfaces of the terminals refer to the respective surfaces where the terminal of one external cable conductor and the terminal of the other external cable conductor face each other and the terminal of the internal cable conductor. For this reason, the use of rectangular terminals reduces heat generation at the terminals.

In the above-mentioned flat cable 10, the main surfaces of the bundled cable conductors 13A, 13B at the cable ends (second end 10E2, first end 10E1) face the main surface of the internal cable conductor 11. This makes it possible to suppress an increase in impedance in the conductors at the cable ends. In addition, the skin effect in the conductors at the cable ends is suppressed, making it possible to reduce heat generation. Next, the effect of suppressing an increase in impedance due to such a configuration will be explained using FIG. 12.

FIG. 12 is a table for explaining the impedance of the cable end of a flat cable. Referring to FIG. 12, the upper part of the table shows an example of the cable main body 10A of the flat cable 10 having the cross section of FIG. 3 of this embodiment. The cross-sectional area of the central inner cable conductor 11 is 10 mm ² , and the cross-sectional area of the pair of outer cable conductors 13A, 13B is 5 mm ^2. The conductors are covered with the outer insulator 14C from the outside in the radial direction. The middle part of the table shows an example of a cable end when two configurations consisting of only the inner cable conductor 11 and the inner insulator 12 of FIG. 3 of this embodiment are arranged so as to be overlapped with each other in the thickness direction h with a gap of 2 mm. The lower part of the table shows an example of a cable end when two configurations consisting of only the inner cable conductor 11 and the inner insulator 12 of FIG. 3 of this embodiment are arranged side by side in the width direction w with a gap of 2 mm. In both the middle and lower parts, the cross-sectional area of the central inner cable conductor 11 is 10 mm ² .

The dimensions shown in Fig. 12 are exemplified values when flat braided copper wires are used for all conductors. In the table, "inner 11" indicates the inner cable conductor 11, and "outer 13" indicates the outer cable conductor 13 (two outer cable conductors 13A and 13B are bundled at the end). In performing the electromagnetic field simulation shown in the next section, the conductivity of the conductor was set to 6.0 x ¹⁰⁷ S/m. This is based on the assumption that the conductor is copper. The relative dielectric constant of the insulator was set to 2.3. This is based on the assumption that the insulator is polyethylene.

In Fig. 12, the cross-sectional area of the conductors forming the forward and return paths is 10 ^mm2 , so the DC conductor resistance R0 is a uniform value. DC conductor resistance R0 is the round-trip resistance with the inner conductor as the forward path and the outer conductor as the return path. In Fig. 12, the value of DC conductor resistance R0 is α. For example, a high-frequency signal of 30 kHz increases the conductor resistance due to the skin effect, etc. If the rate of increase for DC conductor resistance R0 is k, the high-frequency conductor resistance at 30 kHz can be expressed as R = R0 x k.

This k was determined using electromagnetic field simulation software ("Femtet" manufactured by Murata Software Co., Ltd.). As a result, k was 1.54 for the three-layer flat cable main body 10A (see FIG. 3) in the upper part of FIG. 12. In contrast, k was 2.37 for the overlapped cable end in the middle part of FIG. 12, and k was 3.28 for the parallel cable end in the lower part.

From this, it can be seen that the high-frequency conductor resistance of the two-layered terminal portion (first end portion 10E1 and second end portion 10E2) is greater than that of the cable main body 10A consisting of three layers of flat ribbon cable conductors. However, the degree of increase in conductor resistance k differs depending on the conductor arrangement at the terminal portion (cable end portion). It is preferable to arrange the main surfaces of the bundled cable conductors 13A and 13B so that they face the main surface of the internal cable conductor 11, as this reduces k. Therefore, as described above, it is more preferable that in the flat cable 10, the main surfaces of the bundled cable conductors 13A and 13B at the cable ends (second end portion 10E2, first end portion 10E1) face the main surface of the internal cable conductor 11.

In the above, an example has been described in which the flat cable 10 has an inner cable conductor 11, an outer cable conductor 13A, and an outer cable conductor 13B as three layers of flat ribbon cable conductors. However, it is sufficient that the flat cable 10 has at least three layers of flat ribbon cable conductors. In other words, the flat cable 10 may have a configuration in which four or more layers of flat ribbon cable conductors are stacked in the thickness direction. For example, when the flat cable 10 has four layers of flat ribbon cable conductors, two of them may be bundled at least one of the first end and the second end of the flat cable 10 to form a two-layer structure, which can be used as a two-terminal. Alternatively, only two of the four layers may be bundled, and the other two layers may not be bundled, which can be used as a three-terminal, which can be used as a three-terminal. For example, if the flat cable 10 has five layers of flat ribbon cable conductors, they may be divided into three and two, and each may be bundled at least at either the first end or the second end of the flat cable 10 to form a two-layer structure that can be used as a two-terminal. Alternatively, two of the five layers may be bundled together to form a three-layer structure that can be used as a three-terminal.

The content of the above description such as "three layers of flat ribbon cable conductors" can basically be read as "at least three layers of flat ribbon cable conductors." In other words, cases in which the flat cable 10 has four or more layers of flat ribbon cable conductors are also included within the scope of this disclosure.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. Unless there is a contradiction, at least two of the embodiments disclosed herein may be combined. The basic scope of the present disclosure is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Various aspects of the present disclosure are summarized below as appendices.
(Appendix 1)
The cable has at least three layers of flat ribbon conductors spaced apart from one another;
the at least three-layer flat ribbon cable conductor includes an inner cable conductor, one outer cable conductor, and another outer cable conductor on the opposite side of the one outer cable conductor in a thickness direction;
the inner cable conductor is disposed so as to be sandwiched between the one outer cable conductor and the other outer cable conductor in a thickness direction,
A flat cable, wherein at least one of the one outer cable conductor, the other outer cable conductor, and the inner cable conductor has a DC conductor resistance smaller at a cable end than at a region other than the cable end.

(Appendix 2)
2. The flat cable according to claim 1, wherein the at least three layers of flat ribbon cable conductor are three layers of flat ribbon cable conductor.

(Appendix 3)
3. The flat cable according to claim 1, wherein at least one of the one outer cable conductor, the other outer cable conductor, and the inner cable conductor has a larger cross-sectional area at the cable end than at a region other than the cable end.

(Appendix 4)
4. The flat cable according to claim 3, wherein another flat ribbon cable conductor is electrically joined to at least one of the one outer cable conductor, the other outer cable conductor, and the inner cable conductor at the cable end.

(Appendix 5)
At least one of the cable ends of the at least three layers of flat ribbon cable conductors includes a two-layered portion having two flat ribbon cable conductors, a bundled cable conductor and the inner cable conductor,
The flat cable according to any one of appendix 1 to 4, wherein the bundled cable conductor is formed by bundling the one outer cable conductor and the other outer cable conductor of the at least three layers of flat ribbon cable conductors.

(Appendix 6)
6. The flat cable of claim 5, wherein in the bundled cable conductor, a portion of one of the outer cable conductors is twisted inside out so that an inner first main surface of the one of the outer cable conductors is joined to an outer second main surface of the other of the outer cable conductors.

(Appendix 7)
6. The flat cable of claim 5, wherein in the bundled cable conductor, a portion of one of the outer cable conductors is twisted inside out so that an outer third main surface of the one of the outer cable conductors is joined to an outer second main surface of the other of the outer cable conductors.

(Appendix 8)
6. The flat cable according to claim 5, wherein, in the bundled cable conductor, the one outer cable conductor and the other outer cable conductor are bent so as to extend in a direction intersecting with the inner cable conductor, and an outer third main surface of the one outer cable conductor is joined to an outer second main surface of the other outer cable conductor.

(Appendix 9)
9. The flat cable according to claim 5, wherein at the cable end, a main surface of the bundled cable conductor faces a main surface of the inner cable conductor.

(Appendix 10)
The flat cable according to any one of appendixes 1 to 9, wherein a flat terminal is provided on each of the at least three layers of flat ribbon cable conductors at the cable end portion.

3 wire, 10 flat cable, 10A cable body, 10E1 first end, 10E2 second end, 11 inner cable conductor, 11A upper main surface, 11B lower main surface, 11C, 13C other flat ribbon cable conductors, 12 inner insulator, 13, 13A, 13B outer cable conductor, 13Aa, 13Ba outer main surface, 13Ab, 13Bb inner main surface, 14A, 14B, 14C outer insulator, 14X bundling insulator, SD solder, TA10, TA10-1, TA10-2, TA10-3, TA10-X, TB10, TB10-2, TB10-X terminal.

Claims (10)

The cable has at least three layers of flat ribbon conductors spaced apart from one another;
the at least three-layer flat ribbon cable conductor includes an inner cable conductor, one outer cable conductor, and another outer cable conductor on the opposite side of the one outer cable conductor in a thickness direction;
the inner cable conductor is disposed so as to be sandwiched between the one outer cable conductor and the other outer cable conductor in a thickness direction,
A flat cable, wherein at least one of the one outer cable conductor, the other outer cable conductor, and the inner cable conductor has a DC conductor resistance smaller at a cable end than at a region other than the cable end. The flat cable according to claim 1, wherein the at least three layers of flat ribbon cable conductor are three layers of flat ribbon cable conductor. The flat cable according to claim 1 or 2, wherein at least one of the one outer cable conductor, the other outer cable conductor, and the inner cable conductor has a larger cross-sectional area at the cable end than in a region other than the cable end. The flat cable according to claim 3, wherein another flat ribbon cable conductor is electrically connected to at least one of the one outer cable conductor, the other outer cable conductor, and the inner cable conductor at the cable end. At least one of the cable ends of the at least three layers of flat ribbon cable conductors includes a two-layered portion having two flat ribbon cable conductors, a bundled cable conductor and the inner cable conductor,
3. The flat cable according to claim 1, wherein the bundled cable conductor is formed by bundling the one outer cable conductor and the other outer cable conductor of the at least three layers of flat ribbon cable conductors. The flat cable according to claim 5, wherein a portion of one of the outer cable conductors is twisted and turned inside out so that the first inner main surface of the one of the outer cable conductors is joined to the second outer main surface of the other of the outer cable conductors. The flat cable according to claim 5, wherein a portion of one of the outer cable conductors is twisted and turned inside out so that the third outer main surface of the one of the outer cable conductors is joined to the second outer main surface of the other of the outer cable conductors. The flat cable according to claim 5, wherein the one outer cable conductor and the other outer cable conductor are bent so as to extend in a direction intersecting the inner cable conductor, and the third main surface on the outside of the one outer cable conductor is joined to the second main surface on the outside of the other outer cable conductor. The flat cable of claim 5, wherein at the cable end, the main surface of the bundled cable conductor faces the main surface of the inner cable conductor. The flat cable according to claim 1 or 2, wherein a flat terminal is provided on each of the at least three layers of flat ribbon cable conductors at the cable end.

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