Shielded wire and conductive nonwoven fabric tape

Abstract

A shielded wire (1) is provided with an electric wire (10) and a conductive nonwoven fabric tape (20) wound around the electric wire. The conductive nonwoven fabric tape has a conductive nonwoven fabric (21) and an adhesive layer (22) disposed on one surface of the conductive nonwoven fabric, and has a lap part (L) wound so that the winding pitch is t / 3 or more and t / 2 or less with the width defined as t. The adhesive layer is arranged at a position different from the lap part, has an adhesive force of 2.0 N / 19 mm or more as measured by an adhesive force test according to JIS C2107, has a width of t / 10 or more, and has a thickness of 0.01 mm or more and a thickness of the conductive nonwoven fabric or less.

Description

Shielded wire and conductive nonwoven tape

[0001] The present invention relates to a shielded wire and a conductive nonwoven fabric tape.

[0002] Conventionally, a shielded electric wire has been proposed in which a conductive nonwoven fabric having a nonwoven fabric and a metal layer formed on the surface of the nonwoven fabric is arranged around the electric wire (see, for example, Patent Document 1). The shielded electric wire exhibits an electromagnetic shielding effect due to the metal layer of the conductive nonwoven fabric, and can be easily bent due to the excellent stretchability and compressibility of the nonwoven fabric. Furthermore, a conductive nonwoven fabric tape has been proposed which has a conductive nonwoven fabric and an adhesive layer laminated on one of the front and back surfaces of the conductive nonwoven fabric (see, for example, Patent Documents 2 and 3). The conductive nonwoven fabric tape can be attached around the electric wire using the adhesive layer.

[0003] Japanese Patent Publication No. 2019-075375 Japanese Patent Publication No. 2021-140950 Japanese Patent Publication No. 2021-103775

[0004] Incidentally, one example of the application method for applying a conductive nonwoven fabric tape around an electric wire described in Patent Documents 2 and 3 is a method (so-called longitudinal application) in which the conductive nonwoven fabric tape is applied to the electric wire while overlapping both ends of the conductive nonwoven fabric tape in the width direction, while being aligned with the electric wire so that the longitudinal direction of the conductive nonwoven fabric tape coincides with the axial direction of the electric wire. In a shielded electric wire manufactured by this application method, when the shielded electric wire is bent, the both ends of the conductive nonwoven fabric tape separate (hereinafter referred to as "opening of the lap portion") at the overlapping portion of the conductive nonwoven fabric tape, which is so-called., and this can reduce the shielding effect.

[0005] Another application method is a method (so-called spiral winding) in which the conductive nonwoven fabric tape is spirally wrapped around the electric wire while overlapping a portion of the conductive nonwoven fabric tape in the width direction. In a shielded electric wire manufactured using this application method, the lap portion has a spiral shape, so the lap portion is less likely to open when the shielded electric wire is bent, compared to a shielded electric wire manufactured using the above-mentioned vertical application method. However, the presence of an adhesive layer between the conductive nonwoven fabric tapes in the lap portion allows the conductive nonwoven fabric tape to form a spiral conductive path. Therefore, when the conductive path formed by the conductive nonwoven fabric tape is used as a return path for a signal current, as in a coaxial cable, the magnetic field generated by the signal current flowing through the electric wire and the magnetic field generated by the return current flowing through the conductive nonwoven fabric tape are less likely to cancel each other out, which may result in a reduced shielding effect compared to a shielded electric wire manufactured using the above-mentioned vertical application method.

[0006] One of the objects of the present invention is to provide a shielded electric wire and a conductive nonwoven fabric tape that have excellent shielding effect.

[0007] In a first aspect of the present invention, a shielded electric wire comprises an electric wire and a conductive nonwoven fabric tape spirally wound around the electric wire, wherein the conductive nonwoven fabric tape has a conductive nonwoven fabric and an adhesive layer disposed on one side of the conductive nonwoven fabric, and is spirally wound around the electric wire at a winding pitch of t / 3 to t / 2, where t is the width of the conductive nonwoven fabric tape, thereby forming a lap portion where parts of the conductive nonwoven fabric tape overlap each other, and the adhesive layer is disposed at a position different from the lap portion, and is configured so that the adhesive layer has an adhesive strength of 2.0 N / 19 mm or more as measured in an adhesion test in accordance with JIS C 2107, a width of t / 10 or more, and a thickness of 0.01 mm or more and equal to or less than the thickness of the conductive nonwoven fabric.

[0008] In a second aspect of the present invention, the conductive nonwoven fabric tape comprises a conductive nonwoven fabric and an adhesive layer arranged on one surface of the conductive nonwoven fabric, wherein the adhesive layer has an adhesive strength of 2.0 N / 19 mm or more as measured by an adhesive strength test in accordance with JIS C 2107, is arranged at an end of the width direction of the surface so that its width is t / 10 or more, where t is the width of the conductive nonwoven fabric tape, and has a thickness of 0.01 mm or more and equal to or less than the thickness of the conductive nonwoven fabric.

[0009] FIG. 1 is a perspective view showing a shielded electric wire according to an embodiment of the present invention. FIG. 2A is a schematic diagram showing a cross section of the conductive nonwoven fabric tape used in the shielded electric wire shown in FIG. 1 when the conductive nonwoven fabric tape is cut along a plane perpendicular to the longitudinal direction. FIG. 2B is an enlarged view of portion A in FIG. 2A. FIG. 2C is an enlarged view of portion B in FIG. 2B. FIG. 3 is a schematic diagram showing a cross section of the shielded electric wire (particularly the periphery of the conductive nonwoven fabric tape) when the shielded electric wire shown in FIG. 1 is cut along a plane parallel to the longitudinal direction. FIG. 4A is a schematic diagram showing the state of a magnetic field generated in a shielded electric wire prepared as a first reference example. FIG. 4B is a schematic diagram showing the state of a magnetic field generated in a shielded electric wire according to this embodiment. FIG. 5A is a schematic diagram showing the relationship between the thickness of the adhesive layer and the displacement of the conductive nonwoven fabric when the shielded electric wire is bent in a shielded electric wire prepared as a second reference example. FIG. 5B is a schematic diagram showing the relationship between the thickness of the adhesive layer and the displacement of the conductive nonwoven fabric when the shielded electric wire is bent in a shielded electric wire according to this embodiment. Fig. 6 is a graph showing the shielding performance of the shielded wire according to this embodiment and the shielded wires prepared as the third to fifth reference examples. Fig. 7 is a table showing details of the conductive nonwoven fabric tapes used in the examples and comparative examples. Fig. 8 is a first table showing test results of the examples and comparative examples. Fig. 9 is a second table showing test results of the examples and comparative examples. Fig. 10 is a third table showing test results of the examples and comparative examples.

[0010] The present invention will be described below in accordance with preferred embodiments. Note that the present invention is not limited to the embodiments shown below and can be modified as appropriate without departing from the spirit of the present invention. In addition, in the embodiments shown below, some components are omitted from illustration and description, but it goes without saying that publicly known or well-known technologies are applied as appropriate to the details of the omitted technologies within the scope of the content described below.

[0011] Fig. 1 is a perspective view showing a shielded electric wire 1 according to an embodiment of the present invention. As shown in Fig. 1, the shielded electric wire 1 according to this embodiment includes a single electric wire 10 and a conductive nonwoven fabric tape 20 wound spirally around the electric wire 10.

[0012] The electric wire 10 includes a conductor 11 made of, for example, copper, aluminum, or an alloy thereof, and an insulating sheath 12 that covers the conductor 11. In the example shown in FIG. 1 , the conductor 11 of the electric wire 10 is a stranded wire formed by twisting together multiple wires. However, the conductor 11 may also be a solid wire formed by a single wire. Also, multiple electric wires 10 may be provided. Furthermore, the sheath 12 is made of PVC (Polyvinyl Chloride), PP (Polypropylene), and PE (Polyethylene). However, the sheath 12 may also be made of silicone, polyurethane, nylon, etc.

[0013] Fig. 2A is a schematic diagram showing a cross section of the conductive nonwoven fabric tape 20 shown in Fig. 1 when the conductive nonwoven fabric tape 20 is cut along a plane perpendicular to the longitudinal direction. Fig. 2B is an enlarged view of portion A in Fig. 2A. Fig. 2C is an enlarged view of portion B in Fig. 2B. As shown in Fig. 2A, the conductive nonwoven fabric tape 20 includes a conductive nonwoven fabric 21 and an adhesive layer 22 provided on one surface (i.e., the front or back surface) of the conductive nonwoven fabric 21.

[0014] As shown in Figures 2B and 2C, the conductive nonwoven fabric 21 includes fibers 21a constituting the nonwoven fabric and plated portions 21b. The nonwoven fabric is a sheet-like member in which the fibers 21a are intertwined without being woven. As shown in Figures 2B and 2C, the nonwoven fabric has a structure in which the fibers 21a are arranged in multiple layers in the thickness direction due to manufacturing characteristics. The fibers 21a constituting the nonwoven fabric are made of, for example, polyethylene terephthalate (PET), polypropylene, nylon, acrylic, glass fiber, carbon fiber, aramid fiber, polyarylate fiber, etc.

[0015] The plated portion 21b is a conductive metal that coats the fibers 21a that make up the nonwoven fabric. The plated portion 21b is made of, for example, copper, nickel, tin, silver, or an alloy of these metals. The plated portion 21b may be formed in a single layer that covers the fibers 21a that make up the nonwoven fabric, or may be formed in a multi-layer structure. For example, the plated portion 21b may have a multi-layer structure in which a first layer made of copper is provided to cover the fibers 21a that make up the nonwoven fabric, and a second layer made of tin is provided to cover the first layer.

[0016] Fig. 3 is a schematic diagram showing a cross section of the shielded electric wire 1 (particularly the periphery of the conductive nonwoven fabric tape 20) when the shielded electric wire 1 shown in Fig. 1 is cut along a plane parallel to the longitudinal direction. As shown in Fig. 3, the adhesive layer 22 is disposed in a position different from the lap portion L when the conductive nonwoven fabric tape 20 is wrapped around the electric wire 10. Note that the lap portion L is a portion where parts of the conductive nonwoven fabric tape 20 overlap each other in the radial direction of the shielded electric wire 1, as shown in Fig. 3. In this embodiment, as shown in Fig. 3, the adhesive layer 22 is not interposed between adjacent conductive nonwoven fabrics 21 when the conductive nonwoven fabric tape 20 is spirally wrapped around the electric wire 10.

[0017] As shown in Fig. 2A , the adhesive layer 22 is disposed at one end in the width direction of the conductive nonwoven fabric 21. When the width of the conductive nonwoven fabric tape 20 (i.e., the width of the conductive nonwoven fabric 21) is t, the adhesive layer 22 is preferably disposed between the end 21c of the conductive nonwoven fabric 21 and a location a distance t / 2 from the end 21c (i.e., within the range indicated by t / 2 in Fig. 2A ). It is even more preferable that the adhesive layer 22 be disposed between the end 21c of the conductive nonwoven fabric 21 and a location a distance t / 3 from the end 21c (i.e., within the range indicated by t / 3 in Fig. 2A ).

[0018] As a result, when the conductive nonwoven fabric tape 20 is wrapped around the electric wire 10, in the former "preferred" example, if the width of the lap portion L is 1 / 2 or less of the width t of the conductive nonwoven fabric tape 20 (so-called half lap or less), the adhesive layer 22 can be positioned at a position different from the lap portion L; and in the latter "even more preferred" example, if the width of the lap portion L is 2 / 3 or less of the width t of the conductive nonwoven fabric tape 20 (so-called 2 / 3 lap or less), the adhesive layer 22 can be positioned at a position different from the lap portion L.

[0019] In particular, it is preferable that the adhesive layer 22 be arranged so that one end of the adhesive layer 22 is at the end 21c in the width direction of the conductive nonwoven fabric 21 and the other end of the adhesive layer 22 is within the above-mentioned range. This makes it easier to position the adhesive layer 22 in a position different from the wrapping portion L when the conductive nonwoven fabric tape 20 is wrapped around the electric wire 10.

[0020] The shielded wire 1 according to this embodiment has improved shielding performance compared to the first reference example (see FIG. 4A ) in which an adhesive layer is interposed between conductive nonwoven fabrics. The principle behind this is as follows.

[0021] Fig. 4A is a schematic diagram showing the magnetic field generated in a shielded electric wire prepared as a first reference example, and Fig. 4B is a schematic diagram showing the magnetic field generated in a shielded electric wire 1 according to this embodiment. As shown in Figs. 4A and 4B , when a current flows through the electric wire 10 in the direction of extension of the conductor 11 (rightward in this example), a magnetic field MF1 (dashed line) is generated around this current. On the other hand, when an adhesive layer 22 is interposed between the conductive nonwoven fabrics 21, the conductive nonwoven fabric tape 20 forms a spiral conductive path CP as in the first reference example shown in Fig. 4A . Therefore, for example, when the conductive nonwoven fabric 21 of the conductive nonwoven fabric tape 20 is used as a return path for a signal current, as in a coaxial cable, a return current flowing spirally from right to left through this conductive path CP generates a magnetic field MF2 (solid line) around the conductive nonwoven fabric 21. Because the direction of the magnetic field MF2 intersects but is not opposite to the direction of the magnetic field MF1, the magnetic field MF2 may not be able to sufficiently cancel out the magnetic field MF1. In contrast, when the adhesive layer 22 is located at a position other than the wrap portion L as shown in Fig. 3, the conductive nonwoven fabric 21 forms a tubular conductive path CP along the longitudinal direction of the electric wire 10 as shown in Fig. 4B. Therefore, a current flows linearly from right to left through the conductive path CP, generating a magnetic field MF2 (solid line) around the conductive nonwoven fabric 21. Because the direction of the magnetic field MF2 is opposite to the direction of the magnetic field MF1 (dashed line), the magnetic field MF2 can more efficiently cancel out the magnetic field MF1 compared to the first reference example.

[0022] In this way, in the shielded wire 1 according to this embodiment, the adhesive layer 22 is disposed at a position different from the wrap portion L, thereby improving the shielding performance.

[0023] Furthermore, in the shielded electric wire 1 according to this embodiment, the winding pitch of the conductive nonwoven fabric tape 20, the adhesive force, width w, and thickness AT of the adhesive layer 22 are determined as follows so that sufficient shielding performance is maintained even when the electric wire is bent (for example, when the shielded electric wire 1 is bent at a bent portion of the shielded electric wire 1 so that the shape of the surface on the inner side of the bend of the shielded electric wire 1 is an arc with a radius of 30 mm; hereinafter, this will be referred to as when an "R30 bend" is performed).

[0024] In the shielded electric wire 1 according to the present embodiment, when the width of the conductive nonwoven fabric tape 20 is t, the winding pitch of the conductive nonwoven fabric tape 20 is t / 3 or more and t / 2 or less. The winding pitch represents the length of the conductive nonwoven fabric tape 20 moving in the axial direction of the electric wire 10 when the conductive nonwoven fabric tape 20 is wound around the outer periphery of the electric wire 10 one full turn. The winding pitch corresponds to the width of the portion of the conductive nonwoven fabric tape 20 that is not the lap portion L. If the winding pitch is smaller than t / 3 (i.e., the width of the lap portion L is greater than 2t / 3), the winding of the conductive nonwoven fabric tape 20 may make the shielded electric wire 1 too stiff, possibly making bending of the shielded electric wire 1 (e.g., the above-mentioned R30 bend) difficult. If the winding pitch is larger than t / 2 (i.e., the width of the lap portion L is smaller than t / 2), the narrow width of the lap portion L may result in portions where the conductive nonwoven fabrics 21 do not overlap when bending at R30, potentially exposing the coating 12 of the electric wire 10.

[0025] The adhesive layer 22 is configured to have an adhesive strength of 2.0 N / 19 mm or more to a stainless steel plate (i.e., an SUS steel plate) as measured by an adhesive strength test in accordance with JIS C 2107. Experiments conducted by the inventors have shown that an adhesive layer 22 having such adhesive strength has an adhesive strength of 0.6 N / 19 mm or more to the coating 12 of the electric wire 10 (e.g., a coating 12 made of PVC, PP, PE, silicone, polyurethane, or nylon). Furthermore, the width w (see FIG. 2 ) of the adhesive layer 22 is t / 10 or more. By determining the adhesive strength and width w of the adhesive layer 22 as described above, displacement of the conductive nonwoven fabric tape 20 during bending with an R30 is less likely to occur.

[0026] Furthermore, the thickness AT of the adhesive layer 22 is equal to or greater than 0.01 mm and equal to or less than the thickness of the conductive nonwoven fabric 21. If the thickness AT of the adhesive layer 22 is equal to or greater than 0.01 mm, the adhesive layer 22 can be appropriately formed on the surface of the conductive nonwoven fabric 21 in terms of processing accuracy, etc., and if the thickness AT of the adhesive layer 22 is equal to or less than the thickness of the conductive nonwoven fabric 21, the conductive nonwoven fabrics 21 can be maintained in contact with each other at the wrap portion L during bending at R30, as will be described later, and the conductive path CP extending in the longitudinal direction of the shielded wire 1 can be maintained.

[0027] Fig. 5A is a schematic diagram showing the relationship between the thickness AT of the adhesive layer 122 and the displacement of the conductive nonwoven fabric 121 when the shielded wire is bent in a shielded wire prepared as a second reference example, and Fig. 5B is a schematic diagram showing the relationship between the thickness of the adhesive layer 22 and the displacement of the conductive nonwoven fabric 21 when the shielded wire 1 is bent in a shielded wire 1 according to the present embodiment. In the second reference example shown in Fig. 5A , the thickness AT of the adhesive layer 122 exceeds the thickness of the conductive nonwoven fabric 121. As a result, the conductive nonwoven fabric 121 is separated from the covering 12, and the contact pressure between the conductive nonwoven fabrics 121 tends to be lower due to the elasticity of the adhesive layer 122, etc. In addition, as shown in Fig. 5A , if the adhesive layer 122 is not interposed in the wrap portion L, the conductive nonwoven fabric tape rotates away from the covering 12 on the outer side of the bend when the shielded wire is bent. Here, in the second reference example shown in FIG. 5A, the thickness AT of the adhesive layer 122 exceeds the thickness of the conductive nonwoven fabric 121, so the amount of rotation of the conductive nonwoven fabric 121 during rotation tends to be large.

[0028] On the other hand, in the present embodiment shown in Fig. 5B , the thickness AT of the adhesive layer 22 is equal to or less than the thickness of the conductive nonwoven fabric 21. This tends to increase the contact pressure between the conductive nonwoven fabrics 21. In addition, as shown in Fig. 5B , when the shielded wire 1 according to this embodiment is bent, the conductive nonwoven fabric tape 20 rotates away from the covering 12 on the outer side of the bend, but the amount of this rotation also tends to be small. Therefore, by making the thickness AT of the adhesive layer 22 equal to or less than the thickness of the conductive nonwoven fabric 21 (more specifically, the smaller the thickness AT of the adhesive layer 22), the shielded wire 1 according to this embodiment can maintain contact between the conductive nonwoven fabrics 21 at the wrap portion L even when bent to an R30 angle, thereby maintaining the conductive path CP extending in the longitudinal direction of the shielded wire 1.

[0029] Fig. 6 is a graph showing the shielding performance of the shielded electric wire according to this embodiment and the shielded electric wires according to Reference Examples 3 to 5. Fig. 6 shows the shielding performance at the bent portion when bent at R30.

[0030] As a third reference example, a shielded electric wire was prepared in which a conductive nonwoven fabric was wrapped around an electric wire in a "longitudinal" manner. As a fourth reference example, a shielded electric wire was prepared in which a conductive nonwoven fabric tape, having an adhesive layer formed on the "entire surface" of one side of the conductive nonwoven fabric, was wrapped around the electric wire in a "spiral" manner (i.e., "half-wrapped") so that the width of the lapped portion was half the width of the conductive nonwoven fabric tape. As shown in Fig. 5, the shielding performance of the shielded electric wire of the fourth reference example was inferior to that of the shielded electric wire of the third reference example because a longitudinal conductive path was not formed.

[0031] In contrast, the shielded electric wire 1 according to this embodiment has the respective structures described above with reference to FIGS. 1 to 3. In the shielded electric wire 1, the conductive nonwoven fabric tape 20 is wrapped around the electric wire 10 in a half-wrap manner. The shielded electric wire 1 according to this embodiment has superior shielding performance compared to the shielded electric wires of the third and fourth reference examples. As a fifth reference example, a shielded electric wire was prepared in which a conductive nonwoven fabric tape "without" an adhesive layer (i.e., only conductive nonwoven fabric) was wrapped around the electric wire in a "half-wrap" manner. The shielded electric wire of the fifth reference example has shielding performance comparable to that of the shielded electric wire according to this embodiment, because the conductive nonwoven fabrics are unlikely to separate at the wrap portion even when bent at R30.

[0032] 6, when the frequency is 100 MHz or higher, the shielding performance of the shielded electric wire of the fifth reference example is inferior to that of the shielded electric wire of the present embodiment. This is because, in the fifth reference example, even if the conductive nonwoven fabrics are not completely separated in the wrap portion, small gaps are likely to occur between the conductive nonwoven fabrics when the shielded electric wire is bent, due to the absence of an adhesive layer. Furthermore, when the shielded electric wire of the fifth reference example is left in a bent state for a long period of time, the conductive nonwoven fabrics in the wrap portion gradually separate, which may significantly reduce the shielding performance.

[0033] Next, the relationship between the width t of the conductive nonwoven fabric tape, the width w of the adhesive layer, and the winding pitch and the shielding performance will be described with reference to Figures 8 to 10. In Examples 1 to 7 and Comparative Examples 1 to 8 shown in Figures 8 to 10, conductive nonwoven fabric tapes having the width t and the width w of the adhesive layer shown in Figures 8 to 10 were spirally wound around multiple types of electric wires with different conductor cross-sectional areas (specifically, multiple types of electric wires with conductor cross-sectional areas of 10 sq to 150 sq and outer diameters of 5.6 mm to 22.0 mm) at the winding pitch shown in Figures 8 to 10.

[0034] FIG. 7 is a table showing details of the conductive nonwoven fabric tapes used in Examples 1 to 7 and Comparative Examples 1 to 8. Specifically, the weight per unit area (basis weight) of the nonwoven fabric constituting the conductive nonwoven fabric is 85 g / m2 or more and 180 g / m2 or less. The thickness of the conductive nonwoven fabric is 0.25 mm or more and 0.55 mm or less. The plated portion of the conductive nonwoven fabric has a single-layer structure made of copper, or a multi-layer structure made of an inner layer made of copper and an outer layer made of nickel. The surface resistance value of the conductive nonwoven fabric is 2.0 mΩ / sq or more and 50 mΩ / sq or less. "mΩ / sq" is an abbreviation for "mΩ / square."

[0035] The adhesive strength of the adhesive layer (specifically, the adhesive strength to a SUS steel plate measured by an adhesive strength test in accordance with JIS C 2107) is 2.0 N / 19 mm or more and 14 N / 19 mm or less. The thickness of the adhesive layer is 0.02 mm or more and 0.08 mm or less. In each of Examples 1 to 7 and Comparative Examples 1 to 8, multiple samples satisfying the parameters shown in Figure 7 were prepared using the multiple types of electric wires described above, and the tests described below were performed using each of these multiple samples. Figures 8 to 10 show the results of these tests. Note that the test results shown in Figures 8 to 10 were commonly obtained in all tests using multiple samples. Note that, as described above, a conductive nonwoven fabric tape that exhibits an adhesive strength of 2.0 N / 19 mm or more to a SUS steel plate will exhibit an adhesive strength of 0.6 N / 19 mm or more to the coating of the electric wire used in the test.

[0036] A bending test was conducted in which the shielded electric wires according to Examples 1 to 7 and Comparative Examples 1 to 8 were repeatedly bent to R30 using a mandrel with a radius of 30 mm, and the shielded electric wires according to Examples 1 to 7 and Comparative Examples 1 to 8 were bent 90 degrees from a straight state and then returned to the straight state, 50,000 times at a speed of 60 rpm, assuming a state in which the shielded electric wires according to Examples 1 to 7 and Comparative Examples 1 to 8 were installed in a vehicle or the like and maintained in an R30 bent state for a long period of time.

[0037] Then, for Examples 1 to 7 and Comparative Examples 1 to 8, whether or not the conductive nonwoven fabric tape had peeled off from the electric wire after the bending test was observed, and the shielding performance of the shielded electric wire after the bending test was compared with the shielding performance of the shielded electric wire in which the conductive nonwoven fabric was attached vertically as in the third reference example.

[0038] As shown in Figure 8, the width t of the conductive nonwoven fabric tape is 20 mm in all of Examples 1 to 6 and Comparative Examples 1 to 3. The width w of the adhesive layer is 2 mm in Example 1, 4 mm in Example 2, 5 mm in Example 3, 7 mm in Example 4, 9 mm in Example 5, and 10 mm in Example 6. The width w of the adhesive layer is 1 mm in Comparative Example 1, 1.5 mm in Comparative Example 2, and 12 mm in Comparative Example 3. In Examples 1 to 6 and Comparative Examples 1 to 3, one end of the adhesive layer is located at the end of the conductive nonwoven fabric. In all of Examples 1 to 6 and Comparative Examples 1 to 3, the winding pitch of the conductive nonwoven fabric tape is t / 2 (= 10 mm).

[0039] In all of the above-mentioned samples, no peeling of the conductive nonwoven fabric tape occurred in the shielded electric wires of Examples 1 to 6. Furthermore, the shielding performance of the shielded electric wires of Examples 1 to 6 exceeded that of a shielded electric wire in which the conductive nonwoven fabric was attached longitudinally.

[0040] On the other hand, in Comparative Examples 1 and 2, the width w of the adhesive layer was small, making it difficult to maintain the state in which the conductive nonwoven fabric tape was wrapped around the electric wire, and peeling of the conductive nonwoven fabric tape occurred in the shielded electric wires of Comparative Examples 1 and 2. As a result, the shielding performance of the shielded electric wires of Comparative Examples 1 and 2 was lower than that of the shielded electric wire in which the conductive nonwoven fabric was attached vertically. In Comparative Example 3, the width w of the adhesive layer was large, so peeling of the conductive nonwoven fabric tape did not occur. However, because the width w of the adhesive layer was large, the adhesive layer was interposed between the conductive nonwoven fabrics in the lap portion, and therefore the shielding performance of the shielded electric wire of Comparative Example 3 was lower than that of the shielded electric wire in which the conductive nonwoven fabric was attached vertically.

[0041] Therefore, from Examples 1 to 6 and Comparative Examples 1 and 2, it was found that when the adhesive strength of the adhesive layer is 2.0 N / 19 mm or more against the SUS steel plate (in other words, 0.6 N / 19 mm or more against the electric wire), if the width w of the adhesive layer is 2 mm or more (i.e., t / 10 or more), peeling of the conductive nonwoven fabric tape does not occur, and the shielding performance is superior to that of a shielded electric wire in which the conductive nonwoven fabric is placed longitudinally. Furthermore, from Examples 1 to 6 and Comparative Example 3, it was found that when the adhesive layer is interposed between the conductive nonwoven fabrics in the wrap portion, a conductive path along the longitudinal direction of the shielded electric wire is not formed, and therefore the shielding performance is inferior to that of a shielded electric wire in which the conductive nonwoven fabric is placed longitudinally.

[0042] Next, as shown in Fig. 9, the width t of the conductive nonwoven fabric tape was 20 mm, and the width w of the adhesive layer was 5 mm in all of Examples 3 and 7 and Comparative Examples 4 and 5. The winding pitch of the conductive nonwoven fabric tape was t / 3 (≈6.67 mm) in Example 7, t / 2 (=10 mm) in Example 3, t / 4 (=5 mm) in Comparative Example 4, and t / 1.5 (≈13.3 mm) in Comparative Example 5. Note that in Examples 3 and 7 and Comparative Examples 4 and 5 shown in Fig. 9, one end of the adhesive layer was at the end of the conductive nonwoven fabric.

[0043] In all of the above-mentioned samples, no peeling of the conductive nonwoven fabric tape occurred in the shielded electric wires of Examples 3 and 7. Furthermore, the shielding performance of the shielded electric wires of Examples 3 and 7 exceeded that of the shielded electric wire in which the conductive nonwoven fabric was attached longitudinally.

[0044] The shielding performance of the shielded electric wire of Comparative Example 4 exceeded that of the shielded electric wire in which the conductive nonwoven fabric was attached longitudinally. However, the winding pitch of the shielded electric wire of Comparative Example 4 was too small, so it was difficult to even perform an R30 bend. In Comparative Example 5, the winding pitch was too large, so peeling of the conductive nonwoven fabric tape occurred. As a result, the shielding performance of the shielded electric wire of Comparative Example 5 was lower than that of the shielded electric wire in which the conductive nonwoven fabric was attached longitudinally.

[0045] Therefore, it was found from Examples 3 and 7 and Comparative Example 4 that it was difficult to perform an R30 bend when the winding pitch of the conductive nonwoven fabric tape was t / 4, but that it was possible to perform an R30 bend when the winding pitch of the conductive nonwoven fabric tape was t / 3 or more. Furthermore, it was found from Examples 3 and 7 and Comparative Example 5 that when the winding pitch of the conductive nonwoven fabric tape was t / 1.5, peeling of the conductive nonwoven fabric tape occurred during R30 bending, but when the winding pitch of the conductive nonwoven fabric tape was t / 2 or less, peeling of the conductive nonwoven fabric tape did not occur and a conductive path was formed along the longitudinal direction of the electric wire, resulting in better shielding performance than a shielded electric wire with a conductive nonwoven fabric attached longitudinally.

[0046] Next, as shown in Figure 10, in all of Example 6 and Comparative Examples 6 to 8, the width t of the conductive nonwoven fabric tape was 20 mm, and the width w of the adhesive layer was 10 mm. The winding pitch of the conductive nonwoven fabric tape was t / 2 (= 10 mm) in Example 6, t / 4 (= 5 mm) in Comparative Example 6, t / 3 (≈ 6.67 mm) in Comparative Example 7, and t / 1.5 (≈ 13.3 mm) in Comparative Example 8. Note that in Example 6 and Comparative Examples 6 to 8 shown in Figure 10, one end of the adhesive layer is at the end of the conductive nonwoven fabric.

[0047] In the shielded electric wire of Example 6, no peeling of the conductive nonwoven fabric tape occurred in any of the above-mentioned multiple samples, as described with reference to Fig. 8. Furthermore, the shielding performance of the shielded electric wire of Example 6 exceeded the shielding performance of the shielded electric wire in which the conductive nonwoven fabric was attached longitudinally.

[0048] The shielded electric wire of Comparative Example 6 had a winding pitch that was too small, making it difficult to bend to an R30. In Comparative Example 6, the width w of the adhesive layer was large, so the adhesive layer was interposed between the conductive nonwoven fabrics in the lap portion, and therefore the shielding performance of the shielded electric wire of Comparative Example 6 was lower than that of a shielded electric wire in which the conductive nonwoven fabric was attached vertically.

[0049] The shielded electric wire of Comparative Example 7 had an appropriate winding pitch, and therefore no peeling of the conductive nonwoven fabric tape occurred. However, in Comparative Example 7, the width w of the adhesive layer was large, and therefore the adhesive layer was interposed between the conductive nonwoven fabrics in the lap portion, and therefore the shielding performance of the shielded electric wire of Comparative Example 7 was lower than that of a shielded electric wire in which the conductive nonwoven fabric was attached vertically.

[0050] In Comparative Example 8, although no adhesive layer was interposed between the conductive nonwoven fabrics in the wrap portion, the winding pitch was too large, as in Comparative Example 5, and thus peeling of the conductive nonwoven fabric tape occurred, and the shielding performance of the shielded electric wire of Comparative Example 8 was lower than that of a shielded electric wire in which the conductive nonwoven fabric was attached vertically.

[0051] Therefore, Example 6 and Comparative Examples 6 to 8 revealed that R30 bending was difficult when the winding pitch of the conductive nonwoven fabric tape was t / 4, but R30 bending was possible when the winding pitch of the conductive nonwoven fabric tape was t / 3 or greater. Furthermore, Comparative Example 7 revealed that even when the winding pitch of the conductive nonwoven fabric tape was t / 3, shielding performance was reduced when an adhesive layer was interposed between the conductive nonwoven fabrics in the lap section. Furthermore, Example 6 and Comparative Examples 7 and 8 revealed that when the winding pitch of the conductive nonwoven fabric tape was t / 1.5, peeling of the conductive nonwoven fabric tape occurred during R30 bending, but when the winding pitch of the conductive nonwoven fabric tape was t / 2 or less, peeling of the conductive nonwoven fabric tape did not occur. In Example 6, where no adhesive layer was interposed between the conductive nonwoven fabrics in the lap section, a conductive path was formed along the longitudinal direction of the electric wire, and therefore, it was found that the shielding performance was superior to that of a shielded electric wire in which the conductive nonwoven fabric was placed longitudinally.

[0052] As described above, in the shielded wire 1 according to this embodiment using the conductive nonwoven fabric tape 20, the adhesive layer 22 is disposed at a position different from the wrap portion L, and therefore the conductive nonwoven fabrics 21 overlap each other in the wrap portion L, and the conductive nonwoven fabrics 21 form a conductive path CP along the longitudinal direction of the wire 10. This allows the shielded wire 1 to exhibit an appropriate shielding effect even when the conductive nonwoven fabric tape 20 is wound spirally.

[0053] Furthermore, in the shielded electric wire 1, the winding pitch is t / 3 or more and t / 2 or less, the width w of the adhesive layer 22 is t / 10 or more, the adhesive strength of the adhesive layer 22 is 2.0 N / 19 mm or more against the SUS steel plate (in other words, 0.6 N / 19 mm or more against the electric wire 10), and the thickness AT of the adhesive layer 22 is equal to or less than the thickness of the conductive nonwoven fabric 21. Therefore, displacement of the conductive nonwoven fabric tape 20 is unlikely to occur when bending at R30, and the conductive nonwoven fabrics 21 are maintained in contact with each other at the lap portion L, thereby preventing a decrease in shielding effectiveness. More specifically, because the width w and adhesive strength of the adhesive layer 22 satisfy the above ranges, displacement of the conductive nonwoven fabric tape 20 is unlikely to occur. Furthermore, because the winding pitch of the conductive nonwoven fabric tape 20 is t / 3 or more, bending of the shielded electric wire 1 is not hindered, and because the winding pitch of the conductive nonwoven fabric tape 20 is t / 2 or less, exposure of the coating 12 when bending the shielded electric wire 1 is also prevented. Furthermore, since the thickness AT of the adhesive layer 22 is equal to or less than the thickness of the conductive nonwoven fabric 21, the conductive nonwoven fabric tape 20 is less likely to move, and the conductive nonwoven fabrics 21 can be maintained in contact with each other. The thickness AT of the adhesive layer 22 is set to 0.01 mm or more in consideration of manufacturing difficulties.

[0054] As described above, the shielded wire 1 according to this embodiment has an excellent shielding effect.

[0055] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be adopted within the scope of the present invention. For example, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. are possible as appropriate. Furthermore, the material, shape, dimensions, number, location, etc. of each component in the above-described embodiments are arbitrary as long as they can achieve the present invention, and are not limited thereto.

[0056] 2 and the examples, one end of the adhesive layer 22 is located at the end 21c of the conductive nonwoven fabric 21. However, one end of the adhesive layer 22 may be located at a position away from the end 21c.

[0057] The shielded wire and conductive nonwoven fabric tape of the present invention have excellent shielding effect, and can be used, for example, as a wire harness to be mounted in an automobile or the like.

[0058] 1: Shielded electric wire 10: Electric wire 12: Covering portion 20: Conductive nonwoven fabric tape 21: Conductive nonwoven fabric 22: Adhesive layer AT: Thickness of adhesive layer L: Wrap portion t: Width of conductive nonwoven fabric tape w: Width of adhesive layer

Claims

1. A shielded electric wire comprising an electric wire and a conductive nonwoven fabric tape spirally wrapped around the electric wire, wherein the conductive nonwoven fabric tape has a conductive nonwoven fabric and an adhesive layer disposed on one side of the conductive nonwoven fabric, and is spirally wrapped around the electric wire at a winding pitch of t / 3 to t / 2, where t is the width of the conductive nonwoven fabric tape, to form a lap portion where parts of the conductive nonwoven fabric tape overlap each other, and the adhesive layer is disposed in a position different from the lap portion, and is configured so that the adhesive strength measured in an adhesion test conforming to JIS C 2107 is 2.0 N / 19 mm or more, the width is t / 10 or more, and the thickness is 0.01 mm or more and is equal to or less than the thickness of the conductive nonwoven fabric.

2. A conductive nonwoven fabric tape comprising a conductive nonwoven fabric and an adhesive layer arranged on one side of the conductive nonwoven fabric, wherein the adhesive layer has an adhesive strength of 2.0 N / 19 mm or more as measured in an adhesive strength test in accordance with JIS C 2107, is arranged at the end of the width direction of the surface so that its width is t / 10 or more, where t is the width of the conductive nonwoven fabric tape, and has a thickness of 0.01 mm or more and equal to or less than the thickness of the conductive nonwoven fabric.

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