Shielding material and wire harness

Abstract

To provide a shielding material that does not contain metal foil, and a wire harness that includes such a shielding material.SOLUTION: A shielding material 1 includes a porous resin 10 in which a skeleton 11 made of a resin material forms a three-dimensional mesh structure, and a metal layer 12 that covers the surface of the skeleton 11 of the porous resin 10. A wire harness includes a group of electric wires including at least one communication electric wire, and the shielding material 1 that covers at least a portion of the surface of the group of electric wires.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a shielding material and a wire harness. [Background technology]

[0002] In communication electric wires used in fields such as automobiles, metal foil, i.e., sheet-like shielding material including a continuous metal layer, is sometimes used as a shielding material to reduce the intrusion of external noise and the emission of external noise. Such shielding materials are typically made of metal foil made of Cu, Al, or alloys containing these metals, such as the metal foil shield used in the shielded electric wire disclosed in Patent Document 1. Alternatively, shielding materials in which metal foil is bonded to a base sheet made of a resin material such as polyethylene terephthalate (PET) are also used.

[0003] When a sheet-like shielding material is used for noise shielding of communication cables, the shielding material may be arranged to cover the outer periphery of a core wire constituting a single communication cable, as described in Patent Document 1. Alternatively, in a wire harness having a group of electric wires including multiple electric wires, the shielding material may be arranged to cover the outside of the group of electric wires. For example, as disclosed in Patent Document 2, a wire harness is known in which multiple electric wires are fixed by sewing or welding to the surface of a sheet material made of a resin sheet or nonwoven fabric, with the aim of assembling multiple electric wires while maintaining space saving in the vertical direction. Although Patent Document 2 does not describe incorporating a shielding material into a wire harness, when the multiple electric wires constituting the wire harness include a communication electric wire, it is desirable to provide noise shielding for the communication electric wire. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-146850 [Patent Document 2] Japanese Patent Application Publication No. 2018-196174 Summary of the Invention [Problem to be solved by the invention]

[0005] When a shielding material having a metal foil, such as that disclosed in Patent Document 1, is placed on a communication wire or a wire harness, the metal foil is configured as a continuous metal, which may prevent the shielding material from being used conveniently. For example, the inclusion of metal foil increases the specific gravity of the shielding material, and the need to connect the metal foil to ground potential complicates the structure and processing steps of the wire or wire harness. It is desirable to develop a shielding material that does not contain metal foil.

[0006] Therefore, an object of the present invention is to provide a shielding material that does not contain metal foil and a wire harness that includes such a shielding material. [Means for solving the problem]

[0007] The shielding material of the present disclosure has a porous resin in which a skeleton made of a resin material forms a three-dimensional network structure, and a metal layer that covers the surface of the skeleton of the porous resin.

[0008] The wire harness of the present disclosure includes a group of electric wires including at least one communication electric wire, and the shielding material that covers at least a portion of a surface of the group of electric wires. [Effects of the Invention]

[0009] The shielding material and wire harness of the present disclosure are a shielding material that does not contain metal foil, and a wire harness that includes such a shielding material. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating the structure of a shielding material according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is an enlarged view showing the area indicated by the oval in FIG. [Figure 3] 3 is a plan view showing a wire harness according to an embodiment of the present disclosure, in which components are gradually removed from an end portion. [Figure 4] Figure 4 shows an electron microscope image of an actual cross section of the shielding material. DETAILED DESCRIPTION OF THE INVENTION

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

[0012] [1] The shielding material according to the present disclosure comprises a porous resin having a skeleton made of a resin material that forms a three-dimensional mesh structure, and a metal layer that covers the surface of the skeleton of the porous resin.

[0013] The above-mentioned shielding material includes a metal layer, which functions as a shielding material for shielding electrical noise in components such as communication cables and wire harnesses. This metal layer does not take the form of a continuous metal foil, but is formed by coating the surface of a porous resin skeleton having a three-dimensional mesh structure, and the metal layer itself also forms a three-dimensional mesh structure. In this shielding material, multiple metal layers are superimposed along the thickness direction via the resin skeleton or air spaces between the skeletons. Each of these metal layers undergoes multiple reflections of electromagnetic waves and the generation of eddy currents, resulting in high noise shielding performance. Because the metal layer is formed by coating the porous resin skeleton, this shielding material tends to have a lower specific gravity than shielding materials containing metal foil. Furthermore, due to its high noise shielding performance, it is possible to maintain sufficient noise shielding performance without connecting the shielding material to ground potential, thereby eliminating the need for a connection structure that would be required for connecting to ground potential.

[0014] [2] In the above aspect [1], the porous resin may be a foamed resin. In a foamed resin, a continuous skeleton forms a highly isotropic three-dimensional network structure. Therefore, by using a foamed resin to form a shielding material, a network in which metal layers are connected three-dimensionally is formed with high isotropy in the shielding material, and the shielding material exhibits high noise shielding performance against electromagnetic waves incident along various directions, including the thickness direction.

[0015] [3] In the above aspect [2], the porous resin may be composed of a foamed polyurethane resin. A foamed polyurethane resin can form a three-dimensional network structure with high isotropy and stability. This allows the shielding material to achieve particularly high noise-shielding performance and structural stability.

[0016] [4] In any one of the above aspects [1] to [3], the metal layer may cover 50% or more of the surface area of the skeleton of the porous resin, thereby ensuring a sufficiently large amount of metal contained in the shielding material, and thereby providing the shielding material with particularly high noise shielding performance.

[0017] [5] In any one of the above aspects [1] to [4], it is preferable that two or more of the metal layers are arranged along the thickness direction of the shielding material. In this case, multiple metal layers are superimposed in various locations of the shielding material via a resin skeleton or an air layer, and electromagnetic waves are attenuated in each of the metal layers, thereby achieving particularly high noise shielding performance in the shielding material.

[0018] [6] In any one of the above aspects [1] to [5], the metal layer may have a thickness of 3 μm or more, so that the metal layer effectively attenuates electromagnetic waves, thereby achieving high noise shielding performance in the shielding material.

[0019] [7] A wire harness according to the present disclosure includes a group of electric wires including at least one communication electric wire, and a shielding material according to any one of the above aspects [1] to [6] that covers at least a portion of the surface of the group of electric wires.

[0020] As described above, the shielding material of the present disclosure has a structure in which the surface of a skeleton of a porous resin having a three-dimensional mesh structure is coated with a metal layer, thereby providing high noise shielding performance without including a continuous metal foil. By covering a group of electric wires with this shielding material to form a wire harness, high noise shielding performance is exerted on the communication electric wires included in the group of electric wires. Even when a group of electric wires includes multiple communication electric wires, noise shielding can be applied to all of the communication electric wires at once. In the shielding material, the porous resin formed into a sheet or the like functions as a substrate. Therefore, when the shielding material is placed over the group of electric wires, the shielding material is easy to handle and the structure in which the group of electric wires is covered with the shielding material can be stably maintained.

[0021] [8] In the aspect [7] above, the wire harness may further include a substrate, each of the electric wires constituting the electric wire group being fixed to the substrate, and the shielding material covering the surface of the electric wire group and fixed to the substrate. In this case, the wire harness has a structure in which each of the electric wires constituting the electric wire group is fixed to the substrate and the surface of the electric wire group is covered with the shielding material, thereby achieving high space-saving properties for the entire wire harness. Furthermore, when the electric wire group includes multiple communication electric wires, noise shielding can be easily performed on the multiple communication electric wires collectively.

[0022] [9] In the above aspect [7] or [8], the wire harness may not have a ground wire that connects the metal layer of the shielding material to a ground potential. As described above, the shielding material of the present disclosure has high noise shielding performance, and can maintain high noise shielding performance even without connecting the metal layer to a ground potential. By omitting the connection to a ground potential, the structure of the entire wire harness is simplified, and components and processing steps that would be required if a connection to a ground potential were made can be eliminated.

[0023] [Details of the embodiments of the present disclosure] Hereinafter, a shielding material and a wire harness according to an embodiment of the present disclosure will be described in detail with reference to the drawings. The wire harness according to an embodiment of the present disclosure is configured as an example of a component including the shielding material according to an embodiment of the present disclosure.

[0024] <Shielding material> First, a description will be given of a shielding material 1 according to an embodiment of the present disclosure. Figures 1 and 2 schematically show a cross-sectional state of a shielding material 1 according to an embodiment of the present disclosure. Figure 1 shows a wide area, and Figure 2 shows an enlarged view of the area surrounded by an ellipse in Figure 1.

[0025] The shielding material 1 according to this embodiment has a porous resin 10 and a metal layer 12. In the porous resin 10, a skeleton 11 made of a resin material forms a three-dimensional network structure. That is, the skeleton 11 made of a resin material extends three-dimensionally to form a network, and has air layers A between the skeletons 11 as spaces (air bubbles) containing air.

[0026] The porous resin 10 is not specifically limited in type as long as it has a three-dimensional network structure, i.e., a structure including a skeleton 11 made of a resin material and an air layer A surrounded by the skeleton 11. Examples of types of porous resin 10 include foamed resin and resin nonwoven fabric. Foamed resin is a three-dimensionally connected network structure of resin material containing air bubbles. On the other hand, resin nonwoven fabric is an aggregate of many discontinuous resin fibers, with air trapped between the resin fibers. Of these, it is particularly preferable for the porous resin 10 to be configured as a foamed resin, and Figures 1 and 2 are also shown assuming a foamed resin.

[0027] 1 and 2, the skeleton 11 of the porous resin 10 is shown schematically as a structure of continuous hexagonal structures, but the specific structure of the skeleton 11 is not particularly limited. However, as shown in Fig. 4, which is an electron microscope photograph of a cross section of a shielding material actually formed using a foamed resin, the actual skeleton 11 also has a structure that can be approximated as a continuous hexagon or polygons close to it.

[0028] The type of resin constituting the porous resin 10 is not particularly limited, and examples thereof include polyethylene resins such as polyethylene terephthalate (PET), chlorine-based resins such as polyvinyl chloride (PVC), polyolefin resins such as polyethylene (PE) and polypropylene (PP), melamine resins, polyimide resins, and polyurethane resins. When the porous resin 10 is formed as a foamed resin, it is preferable to form the porous resin 10 from a polyethylene resin or a polyurethane resin. Foamed polyurethane resins are particularly suitable because they have excellent foaming properties and can easily form a highly isotropic and stable three-dimensional network structure. The resin material constituting the skeleton of the porous resin 10 may contain additives in addition to the organic polymer. The thickness of the skeleton 11 in the porous resin 10, i.e., the thickness of each of the skeletons 11 arranged at various locations along the thickness direction of the entire shielding material 1 (the thickness of each of the upper skeleton a and the lower skeleton b in FIG. 2), is not particularly limited, but a range of 10 μm or more and 100 μm or less can be exemplified. Furthermore, the pore size in skeleton 11 is preferably 100 μm or more and 800 μm or less, and the porosity is preferably 90% or more and 98% or less. Porous resin 10 functions as a base that determines the overall shape of shielding material 1, and the overall shape of porous resin 10 may be set as desired depending on the expected use of shielding material 1, etc. When shielding material 1 is used in a wire harness, which will be described later, forming porous resin 10 into a sheet shape will provide great convenience in covering the components to be shielded with shielding material 1.

[0029] In the shielding material 1, the metal layer 12 is configured as a metal layer that covers the surface of the skeleton 11 that constitutes the porous resin 10. In other words, the metal layer 12 is formed as a layer that covers at least a portion of the outer peripheral surface of the mesh-like skeleton 11 of the porous resin 10, which corresponds to the edge that surrounds the air layer A. The metal layer 12 may be formed only in a portion of the outer peripheral surface of the skeleton 11 of the porous resin 10, but the most preferred form is one in which the metal layer 12 is formed over the entire outer peripheral surface of the skeleton 11, except for areas where the metal layer 12 is inevitably not formed, as shown in FIG.

[0030] The type of metal constituting the metal layer 12 is not particularly limited. Suitable examples of the metal constituting the metal layer 12 include Ni, Cu, Al, Fe, and alloys of these metals. Among these, from the viewpoints of high noise shielding performance and ease of forming the metal layer 12, it is preferable to form the metal layer 12 from Ni or a Ni-based alloy, or Cu or a Cu-based alloy. The metal layer 12 is preferably formed from a single metal layer, but may also be formed by laminating layers of multiple metals. The metal layer 12 may directly coat the surface of the skeleton 11 of the porous resin 10, or another type of layer, such as a conductive layer made of conductive carbon, may be formed between the metal layer 12 and the surface of the skeleton 11. It is preferable that the shielding material 1 does not include other types of layers, such as metal foil or resin film, outside the structure in which the metal layer 12 coats the surface of the skeleton 11 of the porous resin 10.

[0031] In the shielding material 1 according to this embodiment, a metal layer 12 is formed on the surface of the skeleton 11 of the porous resin 10. As shown in the enlarged view of FIG. 2, a plurality of metal layers 12 are superimposed with a skeleton 11 made of a dielectric or an air layer A interposed therebetween. In the region shown in FIG. 2, of the two skeletons 11 shown as layers, two metal layers 12 (c, d) respectively covering the top and bottom of the upper skeleton 11 (a) and two metal layers 12 (e, f) respectively covering the top and bottom of the lower skeleton 11 (b) - a total of four metal layers 12 superimposed in the thickness direction. In other words, in the region shown in FIG. 2, a superimposed structure is formed from top to bottom in the order of air layer A → metal layer 12 → skeleton 11 → metal layer 12 → air layer A → metal layer 12 → skeleton 11 → metal layer 12 → air layer A. The metal layers 12 overlapping each other at different positions in the thickness direction are interconnected and electrically continuous via the regions that cover the portions of the skeleton 11 of the porous resin 10 that extend in the thickness direction. In other words, the mesh structure of the metal layers 12 has three-dimensional conductivity in all directions, including the surface direction and thickness direction of the shielding material 1.

[0032] The shielding material 1 according to this embodiment exhibits noise shielding properties due to the inclusion of the metal layer 12. In other words, when the shielding material 1 is used to cover a target component, such as an electric wire, the shielding material 1 attenuates electromagnetic waves entering the target component from the outside, thereby suppressing noise generation in the target component, and attenuates electromagnetic waves emitted from the target component to the outside, thereby preventing the emitted electromagnetic waves from causing external noise. The attenuation of electromagnetic waves occurs due to multiple reflections of the electromagnetic waves in the metal layer 12 and the generation of eddy currents. As described above, the shielding material 1 has a structure in which multiple metal layers 12 are superimposed with the framework 11 or air layer A made of a resin material interposed therebetween. This allows for the attenuation of electromagnetic waves, accompanied by multiple reflections and the generation of eddy currents, in each of the superimposed metal layers 12. Therefore, electromagnetic waves are significantly attenuated along the thickness direction of the shielding material 1, and the transmission of electromagnetic waves is highly efficiently suppressed throughout the shielding material 1, resulting in high noise shielding performance.

[0033] Thus, the shielding material 1 according to this embodiment has a structure in which the surface of the skeleton 11 of the porous resin 10 is coated with the metal layer 12, thereby exhibiting high noise shielding performance even without a metal continuum in which the metal is uniformly continuous in the plane and thickness directions, as in metal foil. Rather, as described above, each of the multiple metal layers 12 stacked with the dielectric skeleton 11 or air layer A sandwiched between them contributes to electromagnetic wave attenuation due to multiple reflections and the generation of eddy currents, thereby achieving higher noise shielding performance than when metal foil is used. Therefore, to achieve the desired noise shielding performance, the shielding material 1 can be constructed using a smaller total amount of metal than when metal foil is used. The shielding material 1 is constructed using porous resin 10, which has a lower specific gravity than the metal layer 12, as the base, and the shielding material 1 can be constructed using such a small amount of metal, making it easier to keep the specific gravity low in the shielding material 1 according to this embodiment. Furthermore, the absence of a metal continuum, such as metal foil, allows the shielding material 1 to have high flexibility. Furthermore, even if the same amount of metal is used to construct the shielding material 1 as when metal foil is used, the surface area of the metal layer 12 is increased by using the porous resin 10 as the base. The thickness of the shielding material 1 as a whole can also be increased. These increases in surface area and thickness also contribute to improving the noise shielding performance of the shielding material 1.

[0034] Furthermore, the shielding material 1 according to this embodiment exhibits excellent noise shielding performance, allowing it to maintain high noise shielding performance even without connecting it to ground potential. Not connecting the shielding material 1 to ground potential eliminates the components and processing steps required for ground connection, reducing component and processing costs. Conventionally, when a shielding material with metal foil is attached to a component such as an electric wire or a wire harness, a ground wire is attached to the metal foil via a connecting member such as a terminal and then connected to ground potential. However, this method requires costs for the ground wire and connecting member, requires labor from the worker during installation, and also poses safety issues due to the use of sharp members. However, by omitting the ground connection in the shielding material 1 according to this embodiment, these factors can be eliminated. Even if a ground connection is performed, the configuration of the connecting member and its installation process can be simplified.

[0035] In the shielding material 1 according to this embodiment, the thickness of the metal layer 12 and the area of the region where the metal layer 12 covers the porous resin 10 are not particularly limited. However, it is preferable that the thickness of the metal layer 12 covering each portion of the skeleton 11 of the porous resin 10 (in FIG. 2, the thickness of each of the metal layers c, d, e, and f formed on the surface of the upper skeleton a and the lower skeleton b) be 3 μm or more, further 5 μm or more, or even 10 μm or more. This allows the shielding material 1 to achieve particularly high noise shielding performance. Although there is no particular upper limit for the thickness of the metal layer 12, it is preferable that it be 30 μm or less from the viewpoints of avoiding the use of excessive amounts of metal and increasing the flexibility of the shielding material 1. The thickness of the metal layer 12 can be evaluated by observing the cross section of the shielding material 1 with an electron microscope and averaging the thicknesses of the metal layer 12 formed in each portion in the observed image. When calculating the average, regions on the surface of the skeleton 11 of the porous resin 10 where the metal layer 12 is not formed, i.e., regions where the metal layer 12 has no thickness, are not taken into account. When the shielding material 1 is formed in a sheet form, the thickness of the shielding material 1 as a whole is not particularly limited, but from the viewpoint of achieving both high noise shielding performance and flexibility, examples of the thickness include a range of 100 μm or more and 2000 μm or less.

[0036] The area of the region where the porous resin 10 is covered with the metal layer 12 can be defined by the metal layer area ratio. Here, the metal layer area ratio refers to the ratio of the area of the region covered by the metal layer 12 to the surface area of the skeleton 11 constituting the porous resin 10. In the shielding material 1 according to this embodiment, the metal layer area ratio is preferably 50% or more, further 60% or more, or even 70% or more. In this case, when a sufficient amount of metal is contained in the shielding material 1, the shielding material 1 exhibits particularly high noise shielding performance. The larger the metal layer area ratio, the more preferable it is, and no upper limit is particularly specified. The metal layer area ratio can be determined by measuring the total length (skeleton length) of the skeleton 11 of the network-connected porous resin 10 in an observation image obtained by observing the cross section of the shielding material 1 with an electron microscope, measuring the total length (covering length) of the region of the skeleton 11 covered with the metal layer 12, and calculating the ratio of the covering length to the skeleton length. If the metal layer area ratio is less than 100%, there will be areas on the surface of the skeleton 11 of the porous resin 10 that are not covered with the metal layer 12, but from the viewpoint of preventing leakage of electromagnetic waves, it is preferable that, except for unavoidable areas, no areas where the metal layer 12 is not formed at any position along the thickness direction of the shielding material 1 are formed at any position in the in-plane direction of the shielding material 1. In other words, it is preferable that the metal layer 12 is formed at any position in the thickness direction throughout the entire in-plane area of the shielding material 1.

[0037] As described above, in the shielding material 1 according to this embodiment, multiple metal layers 12 are stacked with the framework 11 layer or the air layer A interposed therebetween to enhance noise shielding performance. To fully achieve this effect, the number of metal layers 12 stacked in this manner along the thickness direction of the shielding material 1 is preferably two or more, more preferably four or more, or even eight or more. As described above, the region shown in FIG. 2 has four metal layers 12. While there is no particular upper limit on the number of metal layers 12, it is preferable to limit it to, for example, 16 or less in order to avoid using excessive amounts of metal and to increase the flexibility of the shielding material 1. The number of metal layers 12 can be determined by counting the number of metal layers 12 stacked in the thickness direction in an image of a cross section of the shielding material 1 observed with an electron microscope and averaging the number of layers in each portion in the surface direction. The number of layers of the skeleton 11 and the air layer A is not particularly specified, but in order to effectively utilize the attenuation of electromagnetic waves due to multiple reflections, there must be two or more layers of the skeleton 11 and three or more layers of the air layer A. The number of layers of the air layer A includes the air layers present on the outer side in the thickness direction of the shielding material 1 as a whole.

[0038] In the shielding material 1 according to this embodiment, it is the metal layer 12 that contributes to noise shielding, and the porous resin 10 does not directly contribute to noise shielding. However, the porous resin 10 functions as a base for the entire shielding material 1, and serves to improve the stability of the shape maintenance and handleability of the shielding material 1 as a whole, as well as contribute to stably maintaining the structure in which the shielding material 1 is arranged in a component that includes the shielding material 1, such as a wire harness, which will be described later. Furthermore, as described above, the porous resin 10 serves to stably maintain the microstructure in which multiple metal layers 12 are superimposed via the skeleton 11 or the air layer A. From this perspective, the shielding material 1 according to this embodiment is likely to exhibit higher noise shielding performance than a porous metal body in which a three-dimensional network structure is formed using only metal.

[0039] As described above, either a resin nonwoven fabric or a resin foam can be used as the porous resin 10, but a resin foam is preferred. The reason is as follows: In a resin foam, the resin material branches at short intervals, forming a three-dimensional, continuous network structure. Therefore, the metal layer 12 formed on the surface of the resin skeleton 11 also forms a highly isotropic network structure in all directions, including the in-plane and thickness directions, and exhibits high conductivity in all directions. This allows the metal layer 12 to exhibit high noise shielding performance regardless of the direction of incident electromagnetic waves. In contrast, a resin nonwoven fabric is merely a collection of linear fibers, and the three-dimensional connection of the skeleton 11 may not be sufficient. In the case of a sheet-like resin nonwoven fabric, the connection of the skeleton 11 is relatively strong in the in-plane direction, but tends to be weak in the thickness direction. In other words, the isotropy of resin skeleton 11 is low, and the three-dimensional isotropy of metal layer 12 formed on the surface of skeleton 11 is also low, making the conductivity in the thickness direction lower than in the surface direction. This causes anisotropy in the noise shielding performance, and it may be difficult to obtain high shielding performance against electromagnetic waves that penetrate in the thickness direction.

[0040] The shielding material 1 according to this embodiment can be manufactured by forming a metal layer 12 on the surface of the skeleton 11 of the porous resin 10. For example, the metal layer 12 can be formed on the surface of the skeleton 11 of the porous resin 10 by a plating method. The plating can be performed by electrolytic plating or electroless plating, but electrolytic plating is preferable from the viewpoint of manufacturing efficiency, etc. In this case, prior to forming the metal layer 12, a conductive layer containing a conductive material such as conductive carbon can be formed on the surface of the skeleton 11 of the porous resin 10 by coating, impregnation, etc., and then electrolytic plating can be performed.

[0041] The use of the shielding material 1 according to this embodiment is not particularly limited, and it may be used to cover various components and devices that require noise shielding. Suitable uses include signal transmission components such as communication wires and wire harnesses. When used in communication wires, the sheet-like shielding material 1 may be disposed around the outer periphery of a core wire that contains one or more insulated wires and is responsible for signal transmission. Use in wire harnesses will be described in detail below. When using the shielding material 1 according to this embodiment for various uses, since the shielding material 1 according to this embodiment alone exhibits high noise shielding performance, it is preferable to use it alone as a noise shielding member without combining it with other types of noise shielding material, such as one that includes metal foil or one that includes braided thin metal wires. Furthermore, the shielding material 1 may be used while connected to ground potential, but as explained above, it is preferable to use it without connecting it to ground potential because high noise shielding performance can be maintained even without connecting it to ground potential.

[0042] <Wire harness> Next, a wire harness according to an embodiment of the present disclosure will be described as an example of a component incorporating the above-described shielding material 1. Fig. 3 shows a plan view of a wire harness 5 according to an embodiment of the present disclosure.

[0043] A wire harness 5 according to an embodiment of the present disclosure includes an electric wire group 2 including at least one communication electric wire, and includes a shielding material 1 according to an embodiment of the present disclosure covering at least a portion of the surface of the electric wire group 2. The configuration of the electric wires in the electric wire group 2 and the configuration of the shielding material 1 covering the electric wire group 2 are not particularly limited, and an example is a configuration in which the shielding material 1 is arranged to cover the entire outer periphery of the electric wire group 2 formed by bundling multiple electric wires. However, here, as a preferred specific example of the structure of the wire harness 5, a configuration in which the shielding material 1 covers the surface of the electric wire group 2 formed by arranging multiple electric wires in parallel, as shown in FIG. 3, will be described.

[0044] The wire harness 5 shown in Fig. 3 includes a group of electric wires 2, a shielding material 1 according to an embodiment of the present disclosure, and a substrate 3. Fig. 3 shows the end of the wire harness 5, with the insulating coatings 21b of the insulated electric wires 21 that make up the shielding material 1 and the group of electric wires 2 gradually removed.

[0045] The electric wire group 2 constituting the wire harness 5 includes at least one communication electric wire 20. The electric wire group 2 may be composed of only the communication electric wire 20, or may include other types of electric wires in addition to the communication electric wire 20. However, preferably, the electric wire group 2 includes a plurality of communication electric wires 20, and more preferably, all of the electric wires constituting the electric wire group 2 are communication electric wires 20. The type of communication electric wire 20 is not particularly limited, but at least one, preferably all of the communication electric wires 20 included in the electric wire group 2 are configured as parallel electric wires. A parallel electric wire is a communication electric wire in which a pair of insulated electric wires 21, each having an insulating coating 21b formed on the outer periphery of a conductor 21a, are arranged with their axes aligned. In the illustrated embodiment, the electric wire group 2 is composed of two (two sets) of communication electric wires 20, and each of the two communication electric wires 20 is configured as a parallel electric wire. It is preferable that each of the communication electric wires 20 constituting the electric wire group 2 does not have a noise shielding member such as a metal member surrounding the outer periphery of the signal wire (core wire).

[0046] Each electric wire constituting the electric wire group 2 is fixed to the base material 3. That is, each electric wire is arranged horizontally with its axial direction aligned in parallel, and each is fixed to the surface of the base material 3. The base material 3 not only serves to bundle the multiple electric wires constituting the electric wire group 2 together, but also functions as a buffer member that prevents damage to each electric wire constituting the electric wire group 2 due to physical stimuli such as contact between the electric wire group 2 and components on which the wire harness 5 is installed, such as metal components that make up an automobile.

[0047] The base material 3 is not particularly limited in type as long as it has a surface on which the communication wires 20 and other electric wires constituting the electric wire group 2 can be aligned and fixed. However, from the viewpoint of ensuring the routing of the wire harness 5, it is preferable that the base material 3 be a sheet, i.e., a flexible planar member. Examples of the sheet material that can be used include fabrics such as woven fabrics, nonwoven fabrics, and knitted fabrics, and resin sheets. The method for fixing the electric wire group 2 to the base material 3 is not particularly limited, and examples include fusion bonding, sewing, bonding using adhesives or pressure-sensitive adhesives, and fixing using fixing members such as fasteners. Among these, from the viewpoints of secure fixation, space-saving, and the reduction in the number of fixing members required, it is preferable to fix the electric wires constituting the electric wire group 2 to the base material 3 by fusion bonding. Using a nonwoven fabric as the base material 3 facilitates strong and easy fixing of the electric wires using fusion bonding. Furthermore, a high cushioning effect is obtained. The material for the base material 3 is not particularly limited, and various resin materials such as various polyethylene resins, chlorine-based resins, polyolefin resins, etc. The base material 3 may be formed by combining a plurality of materials.

[0048] In the wire harness 5, the sheet-like shielding material 1 according to the embodiment of the present disclosure is disposed so as to cover the surface of the electric wire group 2, i.e., the surface (top surface) of all the electric wires constituting the electric wire group 2. The shielding material 1 is fixed to the base material 3 on both sides of the electric wire group 2 in the width direction (the vertical direction in FIG. 3 ). The shielding material 1 can be fixed to the base material 3 by adhesion using an adhesive tape, a pressure-sensitive adhesive tape, an adhesive, a pressure-sensitive adhesive, or the like, as appropriate. Alternatively, the shielding material 1 may be fixed by sewing, fusing at a location where the porous resin 10 is exposed, or the like. The shielding material 1 does not particularly need to have a front or back, and the orientation of the surface is not particularly specified when it is disposed to cover the electric wire group 2 in the wire harness 5. The wire harness 5 according to the present embodiment may be provided with a ground wire for connecting the metal layer 12 of the shielding material 1 to a ground potential and a connecting member for attaching the ground wire to the shielding material 1, but it is preferable to configure it without these.

[0049] The wire harness 5 according to this embodiment has a plurality of electric wires constituting the electric wire group 2 arranged side by side and each fixed to the base material 3, resulting in a wire harness with excellent space-saving properties in the vertical direction. Furthermore, the surface of the electric wire group 2 is covered with the shielding material 1, and the shielding material 1 serves as a noise shield for the communication electric wires 20 included in the electric wire group 2. That is, the shielding material 1 shields electromagnetic waves originating from outside the wire harness 5, suppressing noise generation in the communication electric wires 20, and shields electromagnetic waves emitted from the communication electric wires 20 to the outside, preventing the emitted electromagnetic waves from causing noise externally. As described above, the shielding material 1 has a structure in which the surface of the skeleton 11 of the porous resin 10 is covered with the metal layer 12, thereby exhibiting high noise-shielding performance. Furthermore, the high noise-shielding performance can be maintained even if the shielding material 1 is not connected to a ground potential.

[0050] In this embodiment, even if the group of electric wires 20 includes multiple communication electric wires 20, the common sheet-like shielding material 1 can collectively provide noise shielding for the multiple communication electric wires 20. Therefore, the increase in the height and width dimensions of the wire harness 5 due to noise shielding is limited to the dimensions required to arrange the sheet of shielding material 1. Therefore, compared to when a noise shielding member is individually provided for each communication electric wire 20, the space-saving nature of the wire harness 5 can be maintained at a high level. Furthermore, the labor and cost required for noise shielding can be reduced. In particular, when the communication electric wires 20 are parallel electric wires, the wire harness 5 can be more space-saving in the height direction than when a twisted electric wire is formed by twisting a pair of insulated electric wires together, and the wire harness 5 can be easily fixed to the substrate 3 by fusion bonding or the like. The cost required for twisting the insulated electric wires 21 can also be reduced. On the other hand, parallel electric wires are prone to common noise because they do not have the twisted structure of twisted electric wires. However, by including the shielding material 1 in the wire harness 5, the effects of common noise in parallel electric wires can be reduced, making the wire harness 5 suitable for use in electrical communications inside automobiles, etc. The greater the number of electric wires included in the group of electric wires 2, including the communication electric wires 20, the greater the space-saving effect and labor- and cost-reducing effect of using the sheet-like shielding material 1. For example, a particularly high effect can be achieved when the group of electric wires 2 includes six or more (six pairs), or even eight or more (eight pairs), of communication electric wires 20, such as parallel electric wires. [Example]

[0051] Examples are shown below. However, the present invention is not limited to these examples. Here, the relationship between the configuration of the shielding material and the noise shielding performance in a wire harness was investigated.

[0052] <Sample preparation> First, a shielding material was prepared. Specifically, a sheet of foamed polyurethane resin was impregnated with a conductive paint containing carbon black to form a conductive layer on the surface of the resin skeleton. A metal layer made of Ni or Cu was then formed on the surface by electroplating. By varying the pore size and porosity of the foamed polyurethane resin used, the type of metal, and the electroplating conditions (metal concentration in the plating solution, current density, temperature, current supply method, etc.), multiple shielding materials with different configurations were prepared as samples 1 to 12. For comparison, shielding materials were also prepared as samples 21 and 22, in which metal foils made of Cu and Al, respectively, were bonded to a PET sheet, which served as the resin skeleton.

[0053] Next, a wire harness was fabricated using each of the shielding materials prepared above. As shown in Figure 3, a group of eight communication wires (eight sets) each configured as parallel wires was fixed to a substrate. The surfaces of the group of wires were then covered with one of the shielding materials prepared above, which was then fixed to the substrate on both sides in the width direction. Here, the insulated wires constituting each parallel wire were made of a conductor with a cross-sectional area of 0.5 mm. 2 The shielding material had a conductor outer diameter of 0.85 mm and an electric wire outer diameter of 1.25 mm. The base material was a material made by bonding PVC and nonwoven fabric. In the wire harness, no ground wire was placed to connect the shielding material to the ground potential. In addition, a wire harness in which the electric wires were not covered with a shielding material was also prepared as sample 23.

[0054] <Evaluation method> The structures of the shielding materials of Samples 1 to 12 were evaluated. Specifically, each shielding material was cut in the thickness direction, and the cross section was observed using a scanning electron microscope (SEM). The obtained SEM images were analyzed to evaluate the thickness of the porous resin skeleton, the thickness of the metal layer, the metal layer area ratio, and the number of superimposed layers. The thicknesses of the skeleton and metal layer were evaluated by measuring the thickness of the resin skeleton and the thickness of the metal layer formed on the surface of the resin skeleton at each point in the SEM image and averaging the measured values at each point. When evaluating the thickness of the metal layer, we ignored the areas on the surface of the porous resin skeleton where the metal layer was not formed and focused only on the areas where the metal layer was formed, and averaged them. The metal layer area ratio was calculated by measuring the total length of the porous resin skeleton (skeleton length) in the SEM image and the total length of the area of the skeleton covered with the metal layer (covering length) and calculating the ratio of the covering length to the skeleton length. The number of layers was determined by counting the number of air layers, skeletal layers, and metal layers superimposed in the thickness direction in the SEM image and averaging the number of layers obtained for each part in the surface direction. The number of air layers was counted including the air layers present on the outer side in the thickness direction of the entire shielding material.

[0055] Furthermore, the noise shielding performance of the shielding materials was evaluated for wire harnesses fabricated using each shielding material. The evaluation was performed by measuring radiated emissions using the antenna irradiation method (ALSE method) in accordance with the CISPR25 standard of the International Special Committee on Radio Interference (CISPR). Specifically, a sample wire harness was prepared with eight communication wires (eight pairs) arranged as parallel wires, each with a length of 1.2 m. At both ends of each section, a 5.4 m section was formed in which a pair of insulated wires constituting each communication wire was twisted together. The sample was placed in an anechoic chamber, and a rod antenna was installed 1.0 m to the side of the center of the parallel wire section. An electrical signal with a frequency of 0.53 to 1.8 MHz was input to each communication wire constituting the wire harness, and the noise radiation was measured using the rod antenna. The twisted insulated wire section contributed little to noise radiation.

[0056] The noise radiation level was measured using peak values from eight (eight pairs) of communication cables. In other words, the maximum peak value in the frequency range of 0.53 to 1.8 MHz was recorded as the noise radiation level. The lower the noise radiation level, the higher the noise shielding performance of the shielding material. When the noise radiation level exceeded 56 dBμV / m, the limit for Class 3 in the MW band (frequency 0.53 to 1.8 MHz) of CISPR25, the noise shielding performance was rated as low (B). On the other hand, when the noise radiation level was 56 dBμV / m or less, the noise shielding performance was rated as high (A). Furthermore, when the noise radiation level was 48 dBμV / m or less, the limit for Class 4 in CISPR25, the noise shielding performance was rated as especially high (A+).

[0057] <Test Results> Figure 4 shows a representative cross-sectional SEM image of Sample 1. Table 1 below shows the configuration of the shielding material obtained based on the analysis of the SEM images for Samples 1 to 12, as well as the noise radiation measured for Samples 1 to 12 and 21 to 23, and the evaluation results of the noise shielding performance. The thickness of the porous resin skeleton constituting the shielding material was 50 μm in all Samples 1 to 12. The overall thickness of the sheet-like shielding material was 800 μm in all Samples 1 to 12.

[0058] [Table 1]

[0059] The SEM image in Figure 4 confirms the shape of the porous resin skeleton, which forms a network structure. Furthermore, the areas where the metal layer is formed are indicated by gray lines in the image, and it can be seen that the metal layer is formed along the network structure of the porous resin. The metal layer also forms a three-dimensional network structure, reflecting the network structure of the porous resin.

[0060] According to Table 1, Sample 23, which does not have a shielding material in the wire harness, has a noise emission level exceeding 56 dBμV / m. In contrast, Samples 1 to 12, which have a shielding material with a metal layer on the surface of the porous resin skeleton, all have noise emission levels of 56 dBμV / m or less, achieving high noise shielding performance. This confirms that by providing noise shielding by covering multiple communication electric wires, each configured as parallel wires, collectively with a shielding material with a metal layer on the surface of the porous resin skeleton, it is possible to achieve sufficiently high noise shielding performance for each communication electric wire.

[0061] Comparing Samples 1 to 12, which use shielding materials with a metal layer on the surface of a porous resin skeleton, with Samples 21 and 22, which use shielding materials with a continuous metal foil, the former exhibit noise shielding performance equivalent to or even higher than the latter. In particular, Samples 11 and 21 both use Cu as the metal, and the total thickness of the Cu layer is similar—8 μm (2 μm × 4 layers) for Sample 11 and 9 μm for Sample 21—but Sample 11 is slightly thinner. Comparing the noise radiation levels of Sample 11 and Sample 21, Sample 11 exhibits lower noise radiation and exhibits higher noise shielding performance. In other words, it can be seen that using a shielding material with a metal layer formed on the surface of a porous resin skeleton can achieve higher noise shielding performance with the same or less metal content than a shielding material with metal foil.

[0062] Here, Samples 1 to 12, which use shielding materials with a metal layer on the surface of a porous resin skeleton, include those using Ni (Samples 1 to 6) and those using Cu (Samples 7 to 12) as the metal constituting the metal layer. Regardless of the metal used, if the metal layer thickness, metal layer area ratio, and number of metal layers are similar, roughly the same amount of noise radiation is obtained. For example, Sample 2 and Sample 8 show such a relationship. From these results, it can be said that high noise shielding performance can be obtained whether Ni or Cu is used as the metal layer.

[0063] Samples 3 and 5 have roughly the same metal layer area ratio and the same number of layers, but the thicknesses of the metal layers are different. Comparing the noise shielding performance of these samples, sample 3, with its thicker metal layer, exhibits lower noise radiation. Samples 2 and 6 have similar metal layer thicknesses, but differ in their metal layer area ratios and numbers of layers. A similar relationship exists between samples 8 and 12. Comparing the noise shielding performance of these pairs, samples 2 and 8, with their higher metal layer area ratios and number of metal layers, exhibit lower noise radiation than samples 6 and 12, with their lower metal layer area ratios and numbers of metal layers. In particular, samples 1 to 4 and 7 to 10, with metal layer thicknesses of 3 μm or more, metal layer area ratios of 50% or more, and two or more metal layers, exhibited particularly high noise shielding performance, rated A+, with noise radiation suppressed to 48 dBμV / m or less.

[0064] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention. [Explanation of symbols]

[0065] 1 Shielding material 10 Porous resin 11 (Porous resin) skeleton 12 metal layer 2 wire group 20. Telecommunication wires 21 Insulated wire 21a conductor 21b Insulation coating 3 Base material 5. Wire harness A Air layer a,b Each layer of the skeleton c~f Each metal layer

Claims

1. a porous resin having a skeleton made of a resin material that forms a three-dimensional network structure; a metal layer covering the surface of the skeleton of the porous resin.

2. The shielding material according to claim 1 , wherein the porous resin is made of a foamed resin.

3. The shielding material according to claim 2 , wherein the porous resin is made of a foamed polyurethane resin.

4. The shielding material according to claim 1 , wherein the metal layer covers 50% or more of the surface area of the skeleton of the porous resin.

5. The shielding material according to claim 1 , wherein two or more metal layers are arranged along the thickness direction of the shielding material.

6. The shielding material of claim 1 , wherein the metal layer has a thickness of 3 μm or more.

7. a group of wires including at least one communication wire; A wire harness comprising: the shielding material according to claim 1 , which covers at least a portion of a surface of the group of electric wires.

8. The wire harness further has a base material, Each of the electric wires constituting the electric wire group is fixed to the base material, The wire harness according to claim 7 , wherein the shielding material covers a surface of the group of electric wires and is fixed to the base material.

9. The wire harness according to claim 7 , which does not include a ground wire that connects the metal layer of the shielding material to a ground potential.

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