Shielding material and wire harness

Abstract

Provided are a shielding material that does not include any metal foil and a wire harness comprising the shielding material.　The shielding material 1 includes: a porous resin 10 in which a skeleton 11 formed from a resin material forms a three-dimensional network structure; and a metal layer 12 covering the surface of the skeleton 11 of the porous resin 10. The wire harness includes: an electrical wire group including at least one electrical wire for communication; and the shielding material 1, which covers at least part of the surface of the electrical wire group.

Description

Shielding and Wire Harnesses

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

[0002] In communication electric wires used in fields such as automobiles, metal foil, i.e., sheet-like shielding materials including a planar continuous metal layer, are sometimes used as shielding materials 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 a base sheet made of a resin material such as polyethylene terephthalate (PET) and a metal foil are bonded together are also used.

[0003] When a sheet-like shielding material is used for noise shielding of communication wires, the shielding material may be arranged to cover the outer periphery of a core wire constituting a single communication wire, 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, for the purpose 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.

[0004] JP 2009-146850 A JP 2018-196174 A

[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 a 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 include 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.

[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] Moreover, a wire harness according to 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.

[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.

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

[0011] [Description of 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 has 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, planar 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 attenuation of electromagnetic waves accompanied by 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 aspect of [1] above, 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 each direction, 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 at various locations on 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 electromagnetic waves are effectively attenuated in the metal layer, 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 a 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 wire harness as a whole. 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 embodiment of the present disclosure] The shielding material and the 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 as an example of a component including the shielding material according to the embodiment of the present disclosure.

[0024] <Shielding material> First, a shielding material 1 according to one embodiment of the present disclosure will be described. Figures 1 and 2 schematically show the cross-sectional state of the shielding material 1 according to one embodiment of the present disclosure. Figure 1 shows a wide area state, 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 includes 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 air layers A are present 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 the porous resin 10 include foamed resin and resin nonwoven fabric. Foamed resin is a three-dimensionally connected network structure of a resin material in which air bubbles are trapped. On the other hand, resin nonwoven fabric is an aggregate of many discontinuous resin fibers, with air trapped between the resin fibers. It is particularly preferable that the porous resin 10 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 there are no particular limitations on the specific structure of the skeleton 11. 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 series of hexagons or polygons close to hexagons.

[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. Polyurethane foamed resins are particularly suitable for use because of their excellent foaming properties, which facilitate the formation of 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 in various locations along the thickness direction of the entire shielding material 1 (the thickness 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 diameter in the 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. The porous resin 10 functions as a base that defines the overall shape of the shielding material 1, and the overall shape of the porous resin 10 may be set as desired depending on the expected use of the shielding material 1. When the shielding material 1 is used in a wire harness, which will be described later, for example, forming the porous resin 10 into a sheet shape makes it highly convenient to cover the components to be shielded with the 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. That is, 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, 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 other types of layers, 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 have other types of layers, such as metal foil or resin film, outside the structure in which the surface of the skeleton 11 of the porous resin 10 is coated with the metal layer 12.

[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, and 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-layer skeleton 11 shown, a total of four metal layers 12 are superimposed in the thickness direction: two metal layers 12 (c, d) covering the top and bottom of the upper skeleton 11 (a), and two metal layers 12 (e, f) covering the top and bottom of the lower skeleton 11 (b). 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 penetrating the target component from the outside, thereby suppressing noise generation in the target component, and also attenuates electromagnetic waves emitted from the target component to the outside, thereby preventing the emitted electromagnetic waves from causing noise externally. 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, to occur in each of the superimposed multiple 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] As described above, 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 including 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 superimposed with the dielectric skeleton 11 or air layer A sandwiched between them contributes to the attenuation of electromagnetic waves due to multiple reflections of electromagnetic waves 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. Because the shielding material 1 is constructed using the 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, the specific gravity of the shielding material 1 according to this embodiment can be easily kept low. 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 the shielding material 1 to ground potential. Not connecting the shielding material 1 to ground potential eliminates the components and processing steps required for ground connection, thereby reducing component and processing costs. Conventionally, when a shielding material with metal foil is placed on 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 of 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 of the porous resin 10 covered by 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. Thus, by containing a sufficient amount of metal in the shielding material 1, the shielding material 1 exhibits particularly high noise shielding performance. The higher 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 a 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%, a region that is not covered with the metal layer 12 will be generated on part of the surface of the skeleton 11 of the porous resin 10, but from the viewpoint of preventing leakage of electromagnetic waves, it is preferable that, except for unavoidable areas, no region in which the metal layer 12 is formed at any position along the thickness direction of the shielding material 1 is 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 over 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 superimposed with the framework 11 layer or the air layer A interposed therebetween, thereby enhancing noise shielding performance. To fully obtain this effect, the number of metal layers 12 thus superimposed 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, in the region shown in FIG. 2 , the number of metal layers 12 is four. While there is no particular upper limit on the number of metal layers 12, it is preferable to limit the number to, for example, 16 or less in order to avoid using an excessive amount 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 superimposed 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, the skeleton 11 needs to have two or more layers and the air layer A needs to have three or more layers (including the air layer present on the outer side in the thickness direction of the shielding material as a whole). Note that the number of layers of the air layer A includes the air layer 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 is not directly involved in noise shielding. However, the porous resin 10 functions as a base for the entire shielding material 1, and plays a role in improving the stability of shape maintenance and handleability of the shielding material 1 as a whole, as well as contributing 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 plays a role in stably maintaining 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 may 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 direction and the thickness direction, and exhibits high conductivity in all directions. This allows the metal layer 12 to exhibit high noise shielding performance regardless of the direction of incidence of 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 resin skeleton 11 has low isotropy, and the metal layer 12 formed on the surface of the skeleton 11 also has low three-dimensional isotropy, 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 may be formed on the surface of the skeleton 11 of the porous resin 10 by a plating method. The plating may 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 may be formed on the surface of the skeleton 11 of the porous resin 10 by coating, impregnation, or the like, and then electrolytic plating may be performed.

[0041] The use of the shielding material 1 according to the present 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 the present embodiment for various uses, the shielding material 1 according to the present embodiment exhibits high noise shielding performance even when used alone, and therefore is preferably used alone as a noise shielding member without using other types of noise shielding material, such as those including metal foil or braided thin metal wires. Furthermore, the shielding material 1 may be used while connected to ground potential, but as described above, high noise shielding performance can be maintained even without being connected to ground potential, so it is preferable to use it without connecting 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 a plurality of 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 a plurality of 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 constitute the shielding material 1 and the group of electric wires 2 being removed in stages.

[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 plurality of electric wires constituting the electric wire group 2 together, but also functions as a buffer member that suppresses damage to each electric wire constituting the electric wire group 2 due to physical stimulation such as contact between the electric wire group 2 and components on which the wire harness 5 is installed, such as metal components that constitute 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 body, i.e., a flexible planar member. Examples of the sheet body that can be used include fabrics such as woven fabrics, nonwoven fabrics, and knitted fabrics, and resin sheets. The method of fixing the electric wire group 2 to the base material 3 is not particularly limited, and examples include fusion bonding, sewing, bonding using an adhesive or pressure-sensitive adhesive, and fixing using a fixing member such as a fastener. Among these, from the viewpoints of secure fixation, space-saving, and the number of parts required for fixation, 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 makes it easy to fix the electric wires firmly and easily using fusion bonding. Furthermore, a high cushioning effect is obtained. The material of 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 surfaces (top surfaces) of all the electric wires constituting the electric wire group 2. The shielding material 1 is fixed to the substrate 3 on both sides in the width direction of the electric wire group 2 (the vertical direction in FIG. 3 ). The shielding material 1 can be fixed to the substrate 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] In the wire harness 5 according to this embodiment, the multiple electric wires constituting the electric wire group 2 are arranged side by side and each is fixed to the substrate 3, resulting in a wire harness that is highly space-saving in the height direction (the direction in which the substrate 3, the electric wire group 2, and the shielding material 1 are stacked). Furthermore, because the surface of the electric wire group 2 is covered with the shielding material 1, 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, noise shielding can be performed collectively for the multiple communication electric wires 20 using the common sheet-like shielding material 1. Therefore, the increase in the height and width dimensions of the wire harness 5 due to noise shielding is limited to the dimensions necessary to arrange the sheet of shielding material 1. Therefore, compared to when noise shielding members are 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 a twisted structure like twisted electric wires. However, by including the shielding material 1 in the wire harness 5, the influence of common noise in the parallel electric wires can be reduced, making it possible to suitably use the wire harness 5 for electrical communications inside automobiles, etc. The greater the number of electric wires included in the electric wire group 2, including the communication electric wires 20, the greater the effect of improving space saving and reducing labor and costs by using the sheet-like shielding material 1. For example, a particularly high effect can be obtained when the electric wire group 2 includes six or more (six sets) or even eight or more (eight sets) of communication electric wires 20, such as parallel electric wires.

[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, shielding materials were prepared. Specifically, a sheet-shaped polyurethane foam was impregnated with a conductive paint containing carbon black to form a conductive layer on the surface of the resin skeleton. Furthermore, a metal layer made of Ni or Cu was formed on the surface by electroplating. By varying the pore size and porosity of the polyurethane foam used, the type of metal, and the plating conditions during electroplating (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 corresponding to 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, and the wires were 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. A forming material made by bonding PVC and nonwoven fabric was used as the substrate. In the wire harness, no ground wire connecting the shielding material to a ground potential was placed. 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 each superimposed layer. The thicknesses of the skeleton and the 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 in each part of the SEM image and averaging the measured values ​​for each part. When evaluating the thickness of the metal layer, the area on the surface of the porous resin skeleton where no metal layer was formed was ignored, and only the area where the metal layer was formed was averaged. 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 material 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, the wire harness was prepared as a sample, with a 1.2-m-long section in which eight (eight pairs) communication wires were arranged as parallel wires. At both ends of each section, a 5.4-m-long 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 then input to each communication wire constituting the wire harness, and the noise radiation level was measured using the rod antenna. The twisted insulated wire section barely contributed to noise radiation.

[0056] The noise radiation level was measured using peak values ​​from eight (eight sets) 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 smaller 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 corresponding to Class 3 of the CISPR25 MW band (frequency 0.53 to 1.8 MHz), 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 corresponding to Class 4 of CISPR25, the noise shielding performance was rated as particularly high (A+).

[0057] <Test Results> Figure 4 shows a representative SEM image of the cross section 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 of Samples 1 to 12. The overall thickness of the sheet-like shielding material was 800 μm in all of Samples 1 to 12.

[0058]

[0059] The SEM image in Figure 4 confirms the shape of the porous resin skeleton forming 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 skeleton 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 radiation level exceeding 56 dBμV / m. In contrast, Samples 1 to 12, which have a shielding material having a metal layer on the surface of the porous resin skeleton, all have noise radiation levels suppressed to 56 dBμV / m or less, achieving high noise shielding performance. This confirms that by providing noise shielding by collectively covering multiple communication electric wires, each configured as parallel electric wires, with a shielding material having 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] Here, comparing Samples 1 to 12, which use shielding materials having a metal layer on the surface of a porous resin skeleton, with Samples 21 and 22, which use shielding materials having 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 8 μm (2 μm × 4 layers) for Sample 11 and 9 μm for Sample 21, which are similar, but Sample 11 is slightly thinner. Comparing the noise radiation levels of Sample 11 and Sample 21, Sample 11 exhibits lower noise radiation levels and exhibits higher noise shielding performance. In other words, it can be seen that using a shielding material with a structure in which a metal layer is 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 having metal foil.

[0062] Here, among Samples 1 to 12, which use shielding materials having a metal layer on the surface of a porous resin skeleton, there are those using Ni (Samples 1 to 6) and those using Cu (Samples 7 to 12) as the metal constituting the metal layer, but regardless of the metal used, if the 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 have 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 approximately 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, which has a thicker metal layer, exhibits lower noise radiation. Samples 2 and 6 have similar metal layer thicknesses, but differ in metal layer area ratio and number of metal layers. Samples 8 and 12 have a similar relationship. Comparing the noise shielding performance of these pairs, Samples 2 and 8, which have a higher metal layer area ratio and number of metal layers, exhibit lower noise radiation than Samples 6 and 12, which have a lower metal layer area ratio and number of metal layers. In particular, Samples 1 to 4 and 7 to 10, which have 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.

[0065] REFERENCE SIGNS LIST 1 Shielding material 10 Porous resin 11 Skeleton (of porous resin) 12 Metal layer 2 Group of electric wires 20 Communication electric wire 21 Insulated electric wire 21a Conductor 21b Insulating coating 3 Base material 5 Wire harness A Air layer a, b Each layer of the skeleton c to f Each metal layer

Claims

1. A shielding material having a porous resin in which a skeleton made of a resin material forms a three-dimensional network structure, and 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 according to claim 1, wherein the metal layer has a thickness of 3 μm or more.

7. A wire harness having a wire group including at least one communication wire, and the shielding material according to any one of claims 1 to 6 covering at least a part of the surface of the wire group.

8. The wire harness according to claim 7, further having a base material, each wire constituting the wire group being fixed to the base material, and the shielding material covering the surface of the wire group and being fixed to the base material.

9. The wire harness according to claim 7, not having a ground wire connecting the metal layer of the shielding material to a ground potential.

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