Communication wire and wire harness

Abstract

To provide a communication wire in which an outer periphery of a pair of conductors is coated collectively with insulation coating, and which can be fixed firmly to an external base material, and a wire harness equipped with such a communication wire.SOLUTION: A communication wire 1 has: a signal line 10 having a pair of conductors 11, 11, and an insulation coating 12 which integrally coats an outer periphery of the pair of conductors 11, 11; and a sheath 20 which coats an outer periphery of the signal line 10. In the signal line 10, the entire aggregate including the pair of conductors 11, 11 and the insulation coating 20 is stranded, and the pair of conductors 11, 11 is in a spirally mutually crossed state with the insulation coating 20 laid between the conductors, and smoothness of a surface along a parallel direction in which the pair of conductors 11, 11 is arrayed in parallel is higher than that of an outer peripheral surface of the signal line 10 on an outer peripheral surface of the sheath 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to communication wires and wire harnesses. [Background technology]

[0002] In order to assemble a plurality of electric wires while maintaining a space-saving effect in the height direction, a wire harness may be constructed by fixing electric wires to the surface of a sheet material made of a resin sheet or a nonwoven fabric. For example, Patent Document 1 discloses a wire harness in which electric wires are fixed to a sheet material by sewing or welding, and the wire harness is arranged along a plate-like member included in an interior member of a vehicle. Of various electric wires, it is also conceivable to fix communication electric wires to a sheet material and incorporate them into the wire harness.

[0003] As a type of communication wire including a pair of conductors and used for transmitting differential signals, a wire in which a pair of conductors are arranged in parallel and an insulating coating is collectively provided on the outer circumference of the conductors may be used (two-core integrated wire). For example, Patent Documents 2 and 3 disclose such a type of two-core integrated wire. As disclosed in these documents and Patent Document 4, there is also a form in which a helical twist is added to a two-core integrated wire in which an insulating coating is collectively provided on the outer circumference of a pair of conductors. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-196174 A [Patent Document 2] Japanese Utility Model Application Publication No. 60-123920 [Patent Document 3] JP 2003-36739 A [Patent Document 4] JP 2015-191877 A Summary of the Invention [Problem to be solved by the invention]

[0005] It is conceivable to form a wire harness by fixing a communication electric wire made of a two-core integrated electric wire as disclosed in Patent Documents 2 to 4 to a substrate made of nonwoven fabric or the like as in the embodiment disclosed in Patent Document 1. However, in that case, due to the shape of the pair of conductors, an uneven structure is generated on the surface of the communication electric wire, so that the communication electric wire may not be fixed firmly enough to the substrate. In particular, when the two-core integrated electric wire is twisted in a spiral shape, the fixing to the substrate is likely to be incomplete, and the influence due to this is likely to occur. For example, FIG. 6 shows a schematic cross section of a two-core integrated electric wire 10 fixed to a substrate 30, and the insulating coating 12 that covers the pair of conductors 11, 11 collectively may be fixed firmly to the substrate 30 in the vicinity of one conductor 11 (below the conductor 11 on the left side of the figure), but may not be fixed firmly to the substrate 30 in the vicinity of the other conductor 11. In this way, if the communication electric wire cannot be firmly fixed to the substrate near both of the pair of conductors, not only will the communication electric wire not be stably held by the substrate in the wire harness, but the inter-wire distance between the pair of conductors may vary along the axial direction of the communication electric wire, and the symmetry between the pair of conductors may be reduced, which may cause the communication electric wire to have unstable communication-related characteristics such as characteristic impedance and low noise resistance.

[0006] Therefore, an object of the present invention is to provide a communication electric wire in which the outer periphery of a pair of conductors is collectively covered with an insulating coating and which can be firmly fixed to an external base material, and to provide a wire harness including such a communication electric wire. [Means for solving the problem]

[0007] The communication wire of the present disclosure comprises a signal wire having a pair of conductors and an insulating coating that integrally covers the outer periphery of the pair of conductors, and a sheath that covers the outer periphery of the signal wire, wherein the signal wire is formed by twisting the entire assembly including the pair of conductors and the insulating coating, so that the pair of conductors are spirally crossed with each other with the insulating coating sandwiched therebetween, and the smoothness of the surface along the parallel direction in which the pair of conductors are arranged in parallel with each other is higher at the outer surface of the sheath than at the outer surface of the signal wire.

[0008] The wire harness of the present disclosure includes the communication electric wires and a base material, and the communication electric wires are fixed to the base material on a surface along the parallel direction. Effect of the Invention

[0009] The communication electric wire and wire harness according to the present disclosure are a communication electric wire in which the outer periphery of a pair of conductors is collectively covered with an insulating coating, and are a communication electric wire that can be firmly fixed to an external substrate, and a wire harness including such a communication electric wire. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view showing a communication wire according to one embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view showing a cross section of the communication electric wire taken perpendicular to the axial direction. [Diagram 3] FIG. 3 is a plan view showing a two-core integrated parallel electric wire that is a raw material for manufacturing the communication electric wire. [Figure 4] FIG. 4 is a plan view showing the wire harness according to the embodiment of the present disclosure. [Diagram 5] FIG. 5 is a cross-sectional view showing a portion where the communication wires are fixed to the substrate in the wire harness. [Figure 6] FIG. 6 is a cross-sectional view showing a state in which a communication electric wire without a sheath is fixed to a substrate. [Figure 7]7A and 7B show models for estimating the fixing strength of a communication electric cable to a substrate. Fig. 7A shows the case where no sheath is provided, and Fig. 7B shows the case where a sheath is provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be described. A communication wire and a wire harness according to the embodiments of the present disclosure have the following configuration.

[0012] [1] A communication electric wire according to the present disclosure comprises a signal wire having a pair of conductors and an insulating coating integrally covering the outer periphery of the pair of conductors, and a sheath covering the outer periphery of the signal wire, wherein the signal wire is formed by twisting the entire assembly including the pair of conductors and the insulating coating, and the pair of conductors are in a state where they are spirally crossed with each other with the insulating coating sandwiched therebetween, and the smoothness of the surface along the parallel direction in which the pair of conductors are arranged in parallel with each other is higher at the outer surface of the sheath than at the outer surface of the signal wire.

[0013] In the above-mentioned communication electric wire, the signal wire is made of a two-core integrated electric wire in which the outer circumference of a pair of conductors is collectively covered with an insulating coating, and the two-core integrated electric wire is twisted, so that the communication electric wire has high stability of communication characteristics and high noise resistance. A sheath is provided on the outer circumference of the signal wire, and the smoothness of the outer circumference surface of the sheath along the parallel direction of the conductors is higher than that of the outer circumference surface of the signal wire. In this way, by providing a sheath with a high smoothness on the outer circumference surface, when fixing the communication electric wire to the surface of the substrate, the communication electric wire can be easily fixed by contacting the surface of the substrate with a large area compared to a case where the sheath is not provided. Then, the communication electric wire can be firmly fixed to the substrate compared to a case where the sheath is not provided. In addition, the communication electric wire can be easily fixed by contacting the surface of the substrate with high symmetry with respect to the pair of conductors. As a result, when the communication electric wire is fixed to the substrate, the communication electric wire is less likely to separate from the substrate, the twisted structure of the signal wire is stably maintained, and the distance between the conductors and the symmetry between them are kept high, so that the communication characteristics of the communication electric wire, including the characteristic impedance, are stably maintained. The noise resistance of the communication electric wire is also kept high.

[0014] [2] In the above aspect [1], in a cross section of the communication electric wire cut perpendicularly to the axial direction, the outer edge of the sheath may have a side along the parallel direction. This allows the outer peripheral surface of the sheath to contact the substrate over a large area, making it easier to fix the communication electric wire particularly firmly to the substrate. In addition, since the communication electric wire can be fixed to the substrate with high symmetry at locations near each of the pair of conductors, the effect of maintaining high symmetry of the pair of conductors even when fixed to the substrate is excellent.

[0015] [3] In the above aspect [2], in a cross section of the communication electric wire cut perpendicularly to the axial direction, the sheath may have an outer shape of a rectangle or a rectangle with chamfered corners. In this case, when a plurality of electric wires are arranged and fixed to the surface of a substrate, the distance between the parallel electric wires and the communication electric wire can be easily determined by the length of the side of the rectangle in the cross section.

[0016] [4] A wire harness according to the present disclosure includes a communication wire according to any one of [1] to [3] above and a substrate, and the communication wire is fixed to the substrate on a surface along the parallel direction.

[0017] In the above wire harness, the communication electric wire constituting the wire harness has a sheath with a smooth outer peripheral surface around the signal wire formed by twisting the two-core integrated electric wire, and is fixed to the substrate at the outer peripheral surface of the sheath, resulting in a wire harness in which the communication electric wire is fixed more firmly to the substrate than in a wire harness without a sheath. In addition, since the communication electric wire is fixed to the substrate with high symmetry with respect to a pair of conductors, a change in the inter-wire distance between the conductors due to loosening of the twisted structure of the signal wire and a decrease in symmetry between the pair of conductors are unlikely to occur. As a result, the communication characteristics of the communication electric wire can be stably maintained for a long period of time, and the communication electric wire is highly resistant to noise in the wire harness.

[0018] [5] In the above aspect [4], the substrate may be made of a nonwoven fabric, and the communication wire may be fixed to the substrate by fusion. In this case, even if the communication wire is firmly fixed to the substrate, the wire harness can maintain high flexibility, and the wire harness can be easily handled. In addition, the communication wire can be easily and firmly fixed to the substrate.

[0019] [6] In the above embodiment [4] or [5], the substrate and the sheath may contain the same type of organic polymer and be fused to each other. By containing the same type of organic polymer in the substrate and the sheath, high fixing strength can be obtained at the fusion point between the substrate and the communication electric wire. In addition, in many cases, additives added to the same type of polymer material are the same or similar, so that migration of additives such as plasticizers is unlikely to occur through the fusion point between the sheath and the substrate.

[0020] [Details of the embodiment of the present disclosure] The communication wire and wire harness according to the embodiment of the present disclosure will be described in detail below with reference to the drawings. The wire harness according to the embodiment of the present disclosure is configured to include the communication wire according to the embodiment of the present disclosure. In this specification, terms indicating the shape or arrangement of components, such as "parallel," "straight," and "rectangle," include not only strict geometrical concepts, but also errors within a generally acceptable range for communication wires and wire harnesses, such as approximately ±15% in length and approximately ±15° in angle.

[0021] <Communication cable configuration> First, a communication wire according to an embodiment of the present disclosure will be described. Fig. 1 shows a plan view of a communication wire 1 according to an embodiment of the present disclosure. Fig. 2 shows a cross section of the communication wire 1 cut perpendicularly to the axial direction (longitudinal direction).

[0022] The communication electric wire 1 has a signal wire 10 and a sheath 20. The outer circumference of the signal wire 10 is covered with the sheath 20. In FIG. 1, the sheath 20 is removed at one end so that the signal wire 10 can be seen. The communication electric wire 1 may include components other than the signal wire 10 and the sheath 20, but from the viewpoint of enhancing the effect of providing the sheath 20 described later, it is preferable that no other components are provided between the signal wire 10 and the sheath 20 and on the outer circumference of the sheath 20. Hereinafter, when simply referring to a cross section in this specification, this refers to a cross section perpendicular to the axial direction of the communication electric wire 1. In addition, relative directions such as the horizontal direction and the up-down direction follow the directions shown in the cross-sectional view of FIG. 2. In other words, the horizontal direction refers to the parallel direction in which a pair of conductors 11, 11 described below are arranged in parallel with each other, and the up-down direction refers to the direction perpendicular to the horizontal direction in the cross section.

[0023] The signal line 10 is an electric wire that transmits differential signals, and includes a pair of conductors 11, 11 and an insulating coating 12. The insulating coating 12 integrally covers the outer peripheries of the pair of conductors 11, 11, and the signal line 10 is configured as a two-core integrated electric wire. In other words, the insulating coating 12 covers the outer peripheries of each of the pair of conductors 11, 11, and the portions that cover the outer peripheries of the conductors 11, 11 are structured to be integral and continuous with each other. The insulating coating 12 serves to insulate the pair of conductors 11, 11 from each other and from the outside.

[0024] In the signal wire 10, the entire assembly including the pair of conductors 11, 11 and the insulating coating 12 that collectively covers the conductors 11, 11 is twisted, and the pair of conductors 11, 11 cross each other in a spiral shape with a layer of the insulating coating 12 sandwiched between them. In other words, the signal wire 10 is configured as a two-core integrated parallel electric wire in which the insulating coating 12 is formed around the periphery of the conductors 11, 11 arranged in parallel, and an assembly of the conductors 11, 11 and the insulating coating 12 is formed (shown in a plan view in FIG. 3), and the entire assembly is twisted. As described above, the parallel direction (horizontal direction) refers to the direction in which the pair of conductors 11, 11 are arranged in parallel with each other, but strictly speaking, due to the twisted structure of the two-core integrated electric wire, the direction connecting the centers of gravity of the two conductors 11, 11 changes along the axial direction. In a parallel electric wire state where the conductors 11 and 11 are not twisted (twisted), the direction connecting the centers of gravity of the two conductors 11 and 11 corresponds to the parallel direction. In a twisted state, the direction connecting the centers of gravity of the two conductors 11 and 11 at two adjacent midpoints among the intersections where the two conductors 11 and 11 intersect corresponds to the parallel direction.

[0025] In the signal line 10, by adopting a two-core integrated structure in which a pair of conductors 11, 11 are collectively covered with a common insulating cover 12, the structure of the signal line 10 can be simplified, the distance between the pair of conductors 11, 11 can be kept stable, and the stability of communication-related characteristics such as characteristic impedance can be improved. Furthermore, by adding twisting to the two-core integrated electric wire, the symmetry of the pair of conductors 11, 11 is improved and common mode noise is suppressed, thereby improving the noise resistance of the signal line 10. In addition, the bending resistance of the signal line 10 is improved, and communication-related characteristics such as characteristic impedance are less likely to change when bent.

[0026] The conductor 11 included in the signal line 10 may be made of any conductive material, and suitable examples include metal materials such as copper, copper alloy, aluminum, and aluminum alloy. The conductor 11 may be made of a single wire, but is preferably made of a twisted wire in which a plurality of elemental wires 11a are twisted together, from the viewpoint of workability when twisting the two-core integrated electric wire and bending flexibility of the signal line 10. In this case, after twisting the plurality of elemental wires 11a, compression molding may be performed to form a compressed twisted wire as shown in FIG. 2. The plurality of elemental wires 11a constituting the conductor 11 may all be the same elemental wire, or may be made of two or more types of elemental wires. The size of the conductor 11 is not particularly limited, but from the viewpoint of suitability as a communication electric wire, it is preferable that the size of the conductor 11 is 0.01 mm or less. 2 More than that, 0.22mm 2 The following ranges can be exemplified:

[0027] The material constituting the insulating coating 12 is not particularly limited, and the insulating coating 12 can be formed using various organic polymers. Examples of the organic polymer constituting the insulating coating 12 include polyolefins such as polyethylene and polypropylene, halogen-based polymers such as polyvinyl chloride, engineering plastics such as polystyrene, polytetrafluoroethylene, and polyphenylene sulfide, various elastomers, rubber, and the like. Only one type of organic polymer may be used, or two or more types may be used in combination by mixing, laminating, or the like. The organic polymer may be crosslinked or foamed. In addition to the organic polymer material, the insulating coating 12 may contain additives such as a flame retardant as appropriate.

[0028] In the signal wire 10, the thickness of the insulating coating 12 is not particularly limited, but may be 0.1 mm or more and 0.3 mm or less at a portion other than between the conductors 11, 11. In the signal wire 10, the insulating coating 12 has a portion covering the outer periphery of one conductor 11 and a portion covering the outer periphery of the other conductor 11, and may have any specific shape and be formed by any method as long as these two portions are integrally continuous. For example, a two-core integrated electric wire may be formed by arranging two insulated electric wires provided with an insulating coating that covers the entire outer periphery of one conductor 11, contacting them side by side, and fusing the contact portion of the two insulated electric wires. However, from the viewpoint of structural stability of the signal wire 10, it is preferable to integrally extrude a coating material that occupies the portion between the conductors 11, 11 and the outer periphery of the pair of conductors 11, 11 arranged in parallel to form the insulating coating 12.

[0029] The overall external shape of the signal wire 10 is not particularly limited, but as shown in the cross-sectional view of FIG. 2, it is preferable that the outer peripheral surface of the insulating coating 12 has a region of a substantially arc shape reflecting the shape of the conductors 11, 11, which are substantially circular in cross section. That is, it is preferable that the outer edge of the insulating coating 12 has a substantially arc shape except for the portion between the pair of conductors 11, 11 in the cross section, and that the upper and lower outer edges of the insulating coating 12 have a shape that is constricted inward (10a in the figure) at the position between the pair of conductors 11, 11. By providing this constricted portion 10a, it becomes easier to twist the signal wire 10 configured as a two-core integrated electric wire. The twist pitch of the signal wire 10 is not particularly limited, but from the viewpoint of suitability as a communication electric wire, a range of 5 mm or more and 50 mm or less can be exemplified.

[0030] The sheath 20 is provided on the communication electric cable 1 as a covering member that covers the outer periphery of the signal wire 10. The sheath 20 integrally covers the entire periphery of the signal wire 10. It is preferable that the sheath 20 is in close contact with the entire outer periphery of the signal wire 10, except for a portion where a gap inevitably occurs between the signal wire 10 and the sheath 20.

[0031] The material of the sheath 20 is not particularly limited, and the same materials as those listed for the insulating coating 12 of the signal line 10 can be applied. That is, the sheath 20 can be made of organic polymers such as polyolefins such as polyethylene and polypropylene, halogen-based polymers such as polyvinyl chloride, engineering plastics such as polystyrene, polytetrafluoroethylene, and polyphenylene sulfide, various elastomers, and rubber. The organic polymers may be used alone or in combination of two or more types by mixing, laminating, etc. The organic polymers may be crosslinked or foamed. In addition to the organic polymer material, the sheath 20 may contain additives such as flame retardants as appropriate. As described above, it is preferable not to provide other members between the signal line 10 and the sheath 20, but it is also preferable to form the sheath 20 after disposing a release agent containing an inorganic powder material such as talc around the outer periphery of the signal line 10.

[0032] The sheath 20 has a highly smooth outer peripheral surface. Specifically, the smoothness of the surface along the parallel direction (horizontal direction) of the pair of conductors 11, 11 is higher on the outer peripheral surface of the sheath 20 than that of the outer peripheral surface of the signal wire 10. That is, in a cross section, the smoothness of the upper and lower outer edges of the sheath 20 is higher than that of the upper and lower outer edges of the signal wire 10 located inside the sheath 20. In other words, the height difference at the outer edge is smaller on the upper and lower outer edges of the sheath 20 than that of the upper and lower outer edges of the signal wire 10. As described above, the constricted portion 10a is generated at the location between the pair of conductors 11, 11 on the outer peripheral surface of the signal wire 10, but the outer peripheral surface of the sheath 20 does not have such an unevenness such as a structure in which the upper and lower outer edges are constricted inward, or only an unevenness structure shallower than the constricted portion 10a of the signal wire 10 is provided. The specific degree of smoothness of the outer peripheral surface of the sheath 20 is not particularly limited, but it is preferable that the height difference between the upper and lower outer edges of the sheath 20 in the cross section (the distance in the vertical direction between the outermost and innermost points of each outer edge) be 30% or less of the height difference between the upper and lower outer edges of the signal wire 10. Also, it is preferable that the height difference between the upper and lower outer edges of the sheath 20 in the cross section be 10% or less of the height (dimension in the vertical direction) of the signal wire 10. The smoother the outer peripheral surface of the sheath 20, the more preferable it is, and there is no particular lower limit set for these numerical values.

[0033] Since the outer peripheral surface of the sheath 20 has high smoothness on the upper and lower surfaces, as will be described later in detail with respect to the wire harness 3, the contact area of ​​the communication wire 1 with the surface of an external member such as the substrate 30 can be secured larger than when the sheath 20 is not provided around the signal wire 10 or when the outer peripheral surface of the sheath 20 has low smoothness. When the communication wire 1 is fixed to the external member at the contact point, the strength and stability of the fixation can be increased. In addition, the communication wire 1 can be fixed with high uniformity at the points near each of the pair of conductors 11, 11, and the symmetry between the pair of conductors 11, 11 can be easily maintained. As an effect of the strength, stability, and uniformity of the fixation, the twisted structure of the signal wire 10 is less likely to loosen even when the communication wire 1 is fixed to the external member. As a result, the communication wire 1 can stably maintain communication-related characteristics such as characteristic impedance and obtain high noise resistance. In the first place, the effect of providing the sheath 20 around the outer periphery of the signal wire 10 is to suppress loosening of the twisted structure of the signal wire 10. Since the sheath 20 has a smooth outer periphery, it is highly effective in suppressing loosening of the signal wire 10 even when the communication electric wire 1 is fixed to an external member.

[0034] As described above, the sheath 20 is not particularly limited in terms of its specific thickness or shape as long as the upper and lower surfaces of the outer peripheral surface have an outer peripheral shape that is smoother than the upper and lower surfaces of the signal line 10. However, the thickness is preferably 0.1 mm or more on average from the viewpoint of effectively fulfilling the role of the sheath 20, such as smoothing the outer peripheral surface of the communication cable 1 as a whole. On the other hand, from the viewpoint of ensuring space saving of the communication cable 1, it is preferable that the thickness is 0.5 mm or less on average. As for the shape of the sheath 20, it is preferable that the outer edge of the sheath 20 has sides along the parallel direction in the cross section, that is, the upper and lower outer edges of the sheath 20, especially the lower outer edge, extend linearly along the horizontal direction. Furthermore, it is preferable that the upper and lower outer edges are parallel to each other. In this way, the upper and lower outer edges of the sheath 20 extend linearly along the horizontal direction in the cross section, which means that the outer peripheral surface of the sheath 20 has a surface that can be approximated to a plane along the parallel direction of the conductors 11, 11, and the effect of the smoothness of the sheath 20, such as improving fixation to an external member, can be enhanced. In particular, it is preferable that the cross-sectional shape of the sheath 20 has an outer shape that is rectangular or has a rectangular shape with chamfered (rounded) corners, as shown in Fig. 2. Then, when the communication electric wire 1 is arranged next to other electric wires (including the same type of communication electric wire 1) in the wire harness 3 etc. described below, the distance between adjacent electric wires can be clearly defined by the length of the sides of the rectangle.

[0035] <Wire harness configuration> Next, a wire harness according to an embodiment of the present disclosure will be described. Fig. 4 shows a plan view of a wire harness 3 according to an embodiment of the present disclosure. Fig. 5 shows a cross section of the wire harness 3 in a vicinity of where the communication wire 1 is arranged, cut perpendicularly to the axial direction of the communication wire 1. As in Fig. 1, Fig. 4 also shows the end portion excluding the sheath 20 of the communication wire 1.

[0036] The wire harness 3 according to the present embodiment includes the communication electric wire 1 according to the embodiment of the present disclosure described above and a substrate 30. The communication electric wire 1 is fixed to the substrate 30 on a surface along the parallel direction (lateral direction) of the conductors 11, 11, specifically, on the lower surface. The wire harness 3 may include only one or more communication electric wires 1 according to the embodiment of the present disclosure. In the embodiment shown in FIG. 4, the wire harness 3 includes two communication electric wires 1. The wire harness 3 may include other types of electric wires 5 in addition to the communication electric wire 1 according to the embodiment of the present disclosure. When the wire harness 3 includes a plurality of electric wires 1, 5 including the communication electric wire 1 of the present disclosure, it is preferable that the plurality of electric wires 1, 5 are arranged with their axial directions parallel to each other and fixed to a common substrate 30.

[0037] The base material 30 is not particularly limited in type as long as it has a surface on which the communication electric wire 1 and other types of electric wires 5 can be aligned and fixed as necessary. However, from the viewpoint of ensuring the routing of the wire harness 3, it is preferable that the base material 30 is made of a sheet body, that is, a planar member having flexibility. As the sheet body, fabrics such as woven fabric, nonwoven fabric, knitted fabric, resin sheets, etc. can be used. The method of fixing the electric wires 1 and 5 including the communication electric wire 1 to the base material 30 is not particularly limited, and examples of the fixing methods include fusion, sewing, adhesion using an adhesive or a pressure sensitive adhesive, and fixing using a fixing member such as a fastener. Among them, from the viewpoints of the reliability of fixing, space saving, and the small number of members required for fixing, it is preferable to fix the communication electric wire 1 by fusion. If a nonwoven fabric is used as the base material 30, it is easy to fix the communication electric wire 1 firmly and easily by using fusion. When the communication electric cable 1 is fixed to the nonwoven fabric by fusion, the fusion may result in the communication electric cable 1 sinking deeply into the surface of the nonwoven fabric. However, from the viewpoint of not impairing the characteristics of the base material 30 and from the viewpoint of obtaining a large effect of increasing the fixing strength by the sheath 20, it is preferable to keep the contact depth, that is, the length by which the position of the contact part between the communication electric cable 1 and the base material 30 sinks downward from the surrounding surface of the base material 30, to 10% or less of the thickness of the sheath 20 and 0.02 mm or less.

[0038] The material of the substrate 30 is not particularly limited, but when fusion is used to fix the communication wire 1, it is preferable that the substrate 30 and the sheath 20 of the communication wire 1 contain the same type of organic polymer. Here, "containing the same type of organic polymer" refers to the organic polymer contained in each material containing the same type of monomer unit. It is preferable that the organic polymer constituting the substrate 30 and the organic polymer constituting the sheath 20 of the communication wire 1 are the same. In these cases, it is easy to increase the strength of fixation by fusion between the communication wire 1 and the substrate 30. In addition, since the same or similar additives are often added to the same type of organic polymer, the transfer of additives such as plasticizers and the associated material denaturation are unlikely to occur between the substrate 30 and the sheath 20 of the communication wire 1 through the fusion part. For example, a preferred example can be given of a form in which polyvinyl chloride (PVC) is used as both the organic polymer constituting the substrate 30 and the organic polymer constituting the sheath 20 of the communication wire 1. In many cases, a plasticizer is added to PVC, and if both the base material 30 and the sheath 20 are made of PVC containing a plasticizer, migration of the plasticizer through the fused portion is unlikely to occur.

[0039] As described above, in the wire harness 3 according to the present embodiment, the communication electric wire 1, which has the sheath 20 with a lower surface smoothness higher than that of the signal wire 10, is fixed by contacting the lower surface of the communication electric wire 1 with the base material 30. Since the lower surface of the sheath 20 has high smoothness, the communication electric wire 1 comes into contact with the base material 30 over a large area and is fixed thereto, compared with the case where the signal wire 10, which is not covered with the sheath 20 on the outer periphery, is directly fixed to the base material 30 or the case where the lower surface of the sheath 20 has low smoothness. In particular, if the lower surface of the sheath 20 is configured as a flat surface, the entire lower surface can come into contact with the surface of the base material 30 in a flat manner and be fixed thereto. This provides the wire harness 3 in which the signal wire 10 is firmly fixed to the base material 30 over a large area. As a result, even when the wire harness 3 is used while being bent or used for a long period of time, the state in which the signal wire 10 is fixed to the base material 30 can be stably maintained.

[0040] If the signal wire 10 is fixed directly to the substrate 30 without being covered with the sheath 20, as described above, the conductors 11, 11 have a substantially circular cross section, and therefore the outer peripheral surface of the signal wire 10, including the constricted portion 10a, is exposed, making it difficult to ensure a large contact area with the substrate 30. In this case, the twisted structure of the signal wire 10 may gradually loosen when the wire harness is used while being bent or when it is used for a long period of time. In addition, as shown in FIG. 6, the signal wire 10 is fixed to the substrate 30 only below one of the pair of conductors 11 (the conductor 11 on the left side in the figure), and the signal wire 10 is not fixed to the substrate 30 or the fixing strength is low below the other conductor 11. In this way, a state in which the fixing points and / or fixing strengths based on each conductor 11 are not uniform between the pair of conductors 11, 11 is likely to occur at least in a part of the axial direction of the communication electric wire. When this state occurs, the twisted structure of the signal line 10 becomes more likely to loosen. Also, the symmetry between the pair of conductors 11, 11 becomes more likely to decrease. When the twisted structure of the signal line 10 becomes loose, the distance between the pair of conductors 11, 11 changes, and the characteristics related to communication of the signal line 10, such as the characteristic impedance, become unstable. Furthermore, when the symmetry between the pair of conductors 11, 11 decreases, common mode noise increases and noise resistance decreases.

[0041] In contrast, in the wire harness 3 according to the present embodiment, the outer periphery of the signal wire 10 is covered with the sheath 20 to form the communication wire 1, and the communication wire 1 is firmly fixed to the substrate 30 by the smooth outer periphery of the sheath 20. Therefore, even when the wire harness 3 is bent or used for a long period of time, the twisted structure of the signal wire 10 is unlikely to loosen. As a result, the inter-wire distance between the pair of conductors 11, 11 is stably maintained, and the symmetry between the pair of conductors 11, 11 is also highly maintained. Since the signal wire 10 has a structure in which a two-core integrated electric wire is twisted, the signal wire 10 itself has excellent properties in terms of maintaining the inter-wire distance and symmetry between the pair of conductors 11, 11. However, by forming the sheath 20 and fixing the sheath 20 to the substrate 30 using the smooth surface of the sheath 20, the inherent properties of the signal wire 10 can be effectively used as properties of the wire harness 3. By stably maintaining the distance between the pair of conductors 11, 11, it is possible to stably maintain communication-related characteristics such as characteristic impedance in the communication electric cable 1. Furthermore, by maintaining a high degree of symmetry between the pair of conductors 11, 11, common mode noise is less likely to occur, and high noise resistance is obtained.

[0042] <Estimation of fixing strength of communication cables> Here, the change in the fixing strength of the communication electric wire to the substrate 30 due to the presence or absence of the sheath 20 is estimated by calculation. For the estimation, a model shown in the cross section in Figures 7A and 7B was used. 2 or 0.13 mm 2The signal wire 10 was prepared by arranging two conductors 11 each having a circular cross section and a conductor cross-sectional area of ​​0.35 mm, and integrally providing an insulating coating 12 on the outer periphery of the conductors 11. The distance between the conductors 11, 11 was 0.35 mm, and the thickness of the insulating coating 12 was 0.2 mm in the region other than between the conductors. In the model without a sheath shown in FIG. 7A, the signal wire 10 was used as a communication wire. On the other hand, in the model with a sheath shown in FIG. 7B, the signal wire 10 was used as a communication wire by providing a sheath 20 on the top and bottom of the signal wire 10. In reality, the sheath 20 surrounds the entire outer periphery of the signal wire 10, but here, in order to simplify the model, the sheath 20 was provided only on the top and bottom of the signal wire 10. Specifically, the sheath 20 was structured to fill the upper and lower narrowed portions of the signal wire 10 so that the outer edge of the sheath 20 constitutes a tangent to the signal wire 10.

[0043] A model was set in which the above two types of communication electric wires were fixed to the substrate 30 at their lower surfaces. That is, the substrate 30, which was assumed to be a nonwoven fabric, was placed below each communication electric wire, and contact was made at a contact depth of 0.01 mm. Then, as shown by the thick line in the figure, the length of the contact point where the substrate 30 and the surface of the communication electric wire were in contact was geometrically calculated as the contact distance. Note that the contact depth of 0.01 mm is close to the contact depth actually observed when a conventional insulated electric wire with a generally circular cross section was fused to a nonwoven fabric. When calculating the contact distance, each contact point shown by the thick line in the figure was decomposed into a straight line portion and a curved portion, and the curved portion was approximated to an elliptical arc to calculate its length.

[0044] Furthermore, the fixing strength between the communication electric wire and the substrate 30 was estimated for each model. 2 The fixing strength for each configuration was estimated in proportion to the contact distance, with the fixing strength in this case being set at 1. The fact that a proportional relationship exists between the contact distance and the fixing strength was confirmed by a preliminary test in which the fusion strength was measured by changing the conductor cross-sectional area for a conventional configuration in which a generally circular insulated electric wire was fused to a nonwoven fabric.

[0045] Table 1 below summarizes the calculated conductor cross-sectional area, contact distance, and fixing strength for a communication electric cable without a sheath 20 and for a communication electric cable with a sheath 20.

[0046] [Table 1]

[0047] According to Table 1, it is confirmed that for any conductor cross-sectional area, the contact area between the communication electric wire and the substrate 30 is larger and the fixing strength is also larger when the sheath 20 is provided than when the sheath 20 is not provided. 2 In the case of 1.7 times, the conductor cross-sectional area is 0.13 mm 2 In the case of conductor with a larger cross-sectional area, the increase in the fixing strength due to the installation of the sheath 20 is greater.

[0048] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0049] 1. Communication wires 10 Signal wire (two-core integrated wire) 10a Neck 11 Conductor 11a Bare wire 12 Insulation coating 20 Sheath 3. Wire Harness 30 Base material 5 Other types of wires

Claims

1. A signal line including a pair of conductors and an insulating coating that integrally covers the outer periphery of the pair of conductors; a sheath that covers an outer periphery of the signal line; the signal wire is configured such that an entire assembly including the pair of conductors and the insulating coating is twisted, and the pair of conductors cross each other in a spiral shape with the insulating coating sandwiched therebetween; a surface smoothness along a direction in which the pair of conductors are arranged in parallel is higher on the outer peripheral surface of the sheath than on the outer peripheral surface of the signal wire;

2. 2. The communication electric wire according to claim 1, wherein in a cross section of the communication electric wire cut perpendicular to an axial direction, an outer edge of the sheath has a side along the parallel direction.

3. 3. The communication electric wire according to claim 2, wherein in a cross section of the communication electric wire cut perpendicular to an axial direction, the sheath has an outer shape that is rectangular or has a rectangular shape with chamfered corners.

4. The communication wire according to any one of claims 1 to 3, A substrate, The communication electric wires are fixed to the base material on a surface along the parallel direction.

5. The substrate is made of a nonwoven fabric, The wire harness according to claim 4 , wherein the communication wire is fixed to the base material by fusion bonding.

6. The wire harness according to claim 4 , wherein the substrate and the sheath contain the same kind of organic polymer and are fused to each other.

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