Cable

Abstract

To provide a multi-core cable that is easy to bend and easily maintains its shape in a bent state.SOLUTION: A cable 1 comprises a plurality of wires 2, each having an insulator 22 that covers the circumference of a conductor 21, and a sheath 7 that covers the circumference of an assembled core 4 that is configured by twisting the plurality of wires 2 in two or more layers. In the assembled core 4, adjacent wires 2 are in contact with each other on the surface of insulator 4. The insulator 22 has a surface roughness Sdr of 1.0 or more, and a surface roughness Spc of 3000 mm-1 or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cable. [Background technology]

[0002] In devices that use many electric wires, such as industrial robots, multiple cables are bundled together to reduce weight and improve ease of handling. For this reason, multi-core cables in which many electric wires are collectively covered with a sheath have come into widespread use in recent years. Prior art document information related to the invention of this application includes Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-73741 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a multi-core cable using many electric wires as described above, the outer diameter becomes large, making it difficult to bend the cable. In addition, in a multi-core cable using many electric wires as described above, the restoring force that tries to return the cable to a straight shape when the cable is bent becomes too high, making it difficult to maintain the cable in a bent state. For example, when wiring the cable, the cable needs to be carried in a state where it is wound with a small bending radius, but a cable with too high restoring force makes it difficult to wind the cable with a small bending radius, which reduces the workability during wiring and the freedom of wiring layout.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a multi-core cable that is easy to bend and that easily maintains its shape in a bent state. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a sheath that covers the periphery of an assembly core formed by twisting together a plurality of electric wires having an insulator that covers the periphery of a conductor, the plurality of electric wires being twisted together in two or more layers, the assembly core being configured such that adjacent electric wires are in contact with each other on the surface of the insulator, and the insulator has a surface roughness Sdr of 1.0 or more and a surface roughness Spc of 3000 mm or less. -1 That is all, a cable is provided. Effect of the Invention

[0007] According to the present invention, it is possible to provide a multi-core cable that is easy to bend and that easily maintains its shape in a bent state. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a cable according to an embodiment of the present invention. [Diagram 2] 1A is a micrograph of the surface of the insulator in the electric wire of the example, and FIG. 1B is a micrograph of the surface of the insulator in the electric wire of the comparative example. [Diagram 3] FIG. 13 is a diagram showing the measurement results of the amount of deflection. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Embodiment Mode] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0010] 1 is a cross-sectional view perpendicular to the longitudinal direction of a cable 1 according to this embodiment. The cable 1 is used, for example, for wiring that connects an industrial robot and a control panel.

[0011] The cable 1 includes a plurality of electric wires 2, a binding layer 5 provided around an aggregate core 4 formed by twisting the plurality of electric wires 2 together in two or more layers, a shielding layer 6 consisting of a braided shield provided around the binding layer 5, and a sheath 7 covering the shielding layer 6.

[0012] (wire 2) The electric wire 2 is an insulated electric wire having a conductor 21 and an insulator 22 covering the conductor 21. The conductor 21 is a bunched stranded wire formed by bunching and twisting a plurality of metal strands. The metal strands are made of copper or a copper alloy. The metal strands may be made of aluminum or an aluminum alloy.

[0013] If the insulator 22 is hard, the contact area between adjacent electric wires 2 is small, and the electric wires 2 are easily moved relative to each other in the longitudinal direction, making it easier to bend the cable 1. However, if the insulator 22 is hard, the restoring property to return to a straight shape is high, making it difficult to maintain the cable 1 in a bent state. On the other hand, if the insulator 22 is soft, the restoring property is reduced and it is easier to maintain the cable 1 in a bent state, but the contact area of ​​the parts where the adjacent electric wires 2 contact each other at the insulator 22 is large, making it difficult for the electric wires 2 to move relative to each other, making it difficult to bend the cable 1. Therefore, in this embodiment, a relatively soft material is used as the insulator 22 to make it easier to maintain the cable 1 in a bent state, and the outer circumferential surface of the insulator 22 is made to have a predetermined surface roughness to make it easy to slide, making it easier for the electric wires 2 to move relative to each other and making it easier to bend the cable 1.

[0014] More specifically, in the cable 1 according to the present embodiment, the insulator 22 constituting the electric wire 2 has a surface roughness Sdr of 1.0 or more and a surface roughness Spc of 3000 mm. -1 That's all. Surface roughness Sdr is the ratio of the surface area to the area of ​​the measurement region, and is also called the developed area ratio of the interface. The larger the surface roughness Sdr, the greater the gradient of the surface irregularities. Surface roughness Spc is the arithmetic mean of the curvature of the convex parts of the surface, and is also called the arithmetic mean curvature of the peaks. The larger the surface roughness Spc, the sharper the tips of the convex parts. The measurement methods for these surface roughness Sdr and Spc are as specified in ISO25178.

[0015] The surface roughness Sdr of the insulator 22 is 1.0 or more, and the surface roughness Spc is 3000 mm -1 By doing so, a large number of fine irregularities are formed on the surface of the insulator 22, so that the contact area of ​​the surface of the insulator 22 when the electric wires 2 are brought into contact with each other on the surface of the insulator 22 can be reduced, and the frictional force can be reduced. As a result, even if the electric wires 2 are arranged closely together, the electric wires 2 can easily move relative to each other in the longitudinal direction, and the cable 1 can be easily bent. In particular, even if the cable 1 is not bent and the multiple electric wires 2 are closely arranged so that they are in surface contact with each other on the surface of the insulator 22, the cable 1 can be easily bent. The surface roughness of the insulator 22 can be appropriately adjusted by adjusting the manufacturing conditions such as the temperature during extrusion molding, or by adjusting the amount of plasticizer and additives used in the insulator 22. The arithmetic mean roughness Sa of the insulator 22 is preferably 1.5 μm or more and 3.0 μm or less, more preferably 1.7 μm or more and 2.7 μm or less.

[0016] The Shore A hardness of the insulator 22 is preferably 77 or more and 93 or less. By making the Shore A hardness of the insulator 22 77 or more, the insulator 22 is not too soft, so that the twisted electric wires 2 can be prevented from being excessively crushed. By preventing the electric wires 2 from being excessively crushed, the above-mentioned effect of making the portions where the surfaces of the insulators 22 contact each other have the predetermined surface roughness Sdr, Spc can be easily obtained. Furthermore, by making the Shore A hardness of the insulator 22 93 or less, the insulator 22 does not become too hard, so that the repulsive force between the twisted electric wires 2 at the portions where they contact each other can be prevented from becoming strong. This makes it easier to maintain the bent shape when the cable 1 is bent and processed or wired (i.e., it is difficult for the cable 1 to naturally return to a state close to a straight line from the bent state). More preferably, the Shore A hardness of the insulator 22 is 80 or more and 90 or less, and even more preferably, 85 or more and 90 or less. In this embodiment, a resin composition containing a PVC (polyvinyl chloride) resin as a base resin is used as the insulator 22. The Shore A hardness of the insulator 22 can be measured by a durometer hardness test method (type A) in accordance with JIS K7125.

[0017] (Collective Core 4) The assembly core 4 is configured by twisting a plurality of electric wires 2 in two or more layers around a central spacer 3 provided at the center of the cable. Here, 8, 14, and 20 electric wires 2 are twisted together in order from the radially inner side, and an assembly core 4 with a three-layer structure is configured using 42 electric wires 2. Here, a case is shown in which all of the 42 electric wires 2 have the same configuration, but the assembly core 4 may include electric wires 2 with different configurations such as outer diameters. The total number of electric wires 2 that configure the assembly core 4 is, for example, 20 or more.

[0018] Since stress is concentrated at the center of the cable 1 when the cable 1 is bent, it is preferable not to place the electric wire 2 at the center of the cable, and it is preferable to use the central insert 3. In a cross section perpendicular to the longitudinal direction of the cable 1, the cross-sectional area of ​​the central insert 3 is preferably larger than the cross-sectional area of ​​one electric wire 2. This makes it difficult for the stress concentrated at the center of the cable when the cable 1 is bent to be applied to the multiple electric wires 2 constituting the layer closest to the central insert 3. In this embodiment, a fiber insert made of staple fiber (staple fiber) is used as the central insert 3. However, this is not limited to this, and a fiber insert made of a material other than staple fiber may be used, and for example, a solid linear body consisting of only the insulator 22 in the electric wire 2 excluding the conductor 21 can be used as the central insert 3. This allows, for example, the outer diameter of the linear body and the electric wire 2 to be the same, making it possible to facilitate handling during manufacturing and design of the cable outer diameter. In addition, for example, a hollow tube may be used as the central insert 3 placed at the center of the cable. The tube used for the central insert 3 is made of resin such as polyvinyl chloride resin or nylon. This makes it possible to make the cable 1 easier to bend while preventing the arrangement of the electric wires 2 from being disturbed when the cable 1 is bent. A covering layer made of fibers such as staple fiber or a covering layer made of resin such as polyvinyl chloride resin may be provided to cover the periphery of the tube. The covering layer provided around the central insert 3 made of a tube can serve as a buffer layer between the central insert 3 and the electric wires 2 when the cable 1 is bent.

[0019] In the collective core 4, a filler made of a solid or a tube may be disposed between the electric wires 2 arranged along the circumferential direction of the cable in order to easily maintain the cross-sectional shape of the cable 1 when the cable 1 is bent. The filler disposed between the electric wires 2 is made of a resin such as polyvinyl chloride or polyurethane, and its outer diameter is preferably 0.9 to 1.1 times the outer diameter of the electric wires 2.

[0020] It is desirable that the twist direction of the multiple electric wires 2 constituting the collective core 4 is the same in all layers. This makes it easier to bend the cable 1 and easier to maintain the bent state. For example, if the twist directions of the electric wires 2 in adjacent layers are made different and alternate, a repulsive force is generated between the layers, making the cable 1 slightly more difficult to bend and more difficult to maintain the bent state because the cable 1 has a higher tendency to return to a straight shape. The twist direction of the electric wires 2 in each layer is the direction in which the electric wires 2 rotate from one end to the other end when viewed from one end of the cable 1.

[0021] (Bind layer 5) The bind layer 5 is provided around the aggregate core 4 and is in contact with the outer peripheral surface of the aggregate core 4. The bind layer 5 is a layer that serves to prevent the aggregate core 4 from untwisting, and is formed by winding a tape member spirally around the aggregate core 4.

[0022] In this embodiment, since the cable 1 includes the shield layer 6 made of a braided shield, in order to suppress the clamping of the collective core 4 by the shield layer 6 and maintain the ease of bending of the cable 1, it is preferable to use a tape member with cushioning properties for the bind layer 5. Specifically, it is preferable to use a foam tape having a foam layer made of a foamed resin, or a nonwoven fabric tape, as the tape member for the bind layer 5. In particular, when a foam tape is used as the tape member for the bind layer 5, the cushioning effect can be enhanced compared to a nonwoven fabric tape. Therefore, when the bind layer 5 is made of a tape member made of a foam tape, it is possible to make the cable 1 easier to bend than when the bind layer 5 is made of a tape member made of a nonwoven fabric tape.

[0023] As the foam tape, a tape made of foamed polypropylene, which is relatively difficult to crush, may be used. The foam tape does not have to be entirely foamed, and may have a structure in which a non-foamed layer and a foamed layer are laminated, or may have a structure in which foamed layers with different foaming degrees are laminated. By making the foam tape into a multi-layer structure, the cushioning properties of the bind layer 5 can be adjusted. This makes it possible to adjust the bendability of the cable 1 by the bind layer 5. In addition, in this embodiment, the bind layer 5 is one layer, but multiple bind layers 5 may be provided between the assembly core 4 and the shield layer 6. When multiple bind layers 5 are provided, a structure in which a bind layer 5 made of a foamed polypropylene tape is extruded and coated with a resin made of foamed polypropylene may be provided around the bind layer 5.

[0024] The winding direction of the tape member in the binding layer 5 is different from the twisting direction of the electric wires 2 in the assembly core 4. This makes it possible to maintain the arrangement of the electric wires 2 in the assembly core 4 without collapse. However, in this case, the bendability of the cable 1 is slightly impaired, so in a cable 1 that is particularly required to be easy to bend, the winding direction of the tape member in the binding layer 5 may be different from the twisting direction of the electric wires 2 in the assembly core 4. Note that the winding direction of the tape member is the direction in which the tape member rotates from one end to the other end when viewed from one end of the cable 1.

[0025] (Shield layer 6) The shield layer 6 is made of a braided shield formed by braiding a plurality of metal wires. The metal wires used for the shield layer 6 can be made of copper, a copper alloy, aluminum, or an aluminum alloy. In this embodiment, the bind layer 5 that is the base of the shield layer 6 serves as a cushion layer (buffer layer), and can reduce stress applied to the shield layer 6 and the collective core 4 when the cable 1 is bent. As a result, breakage of the metal wires of the shield layer 6 can be suppressed, and damage to the electric wires 2 that constitute the collective core 4 can be suppressed. The shield layer 6 may be omitted depending on the use of the cable 1, etc.

[0026] (Sheath 7) The sheath 7 is made of, for example, PVC (polyvinyl chloride) or the like. In this embodiment, since the collective core 4 contains a large number of electric wires 2, such as 42 wires 2, the outer diameter of the sheath 7, i.e., the outer diameter of the cable 1, is large, 15 mm or more. In this way, in a thick cable 1 having an outer diameter of 15 mm or more, particularly an outer diameter of 20 mm or more, the above-mentioned problems (problems of being difficult to bend and difficult to maintain in a bent state) are likely to occur, and the above-mentioned effects can be easily obtained by making the insulator 22 have the predetermined surface roughness Sdr, Spc. In other words, this embodiment is particularly suitable for a cable 1 having an outer diameter of 15 mm or more, particularly an outer diameter of 20 mm or more.

[0027] (Surface roughness verification) The insulator 22 was formed by extrusion coating a resin composition containing polyvinyl chloride resin as a base resin directly on the conductor 21, and the electric wire 2 of the example and the comparative example was produced. In the example and the comparative example, the surface properties of the insulator 22 were appropriately adjusted by adjusting the amount of plasticizer and additives in the resin composition, and the surface roughness of the insulator 22 was measured. Here, the surface roughness was measured twice for both the example and the comparative example. In addition, the arithmetic mean roughness Sa, the developed area ratio Sdr of the interface, and the arithmetic mean curvature Spc of the peak were measured as the surface roughness. The results are summarized in Table 1. In addition, micrographs of the surface of the insulator 22 of the example and the comparative example are shown in Figs. 2(a) and (b). The surface roughness of the insulator 22 was measured for the entire surface area (measurement area: length: about 540 μm, width: about 720 μm) of the insulator 22 shown in Figs. 2(a) and (b) using a laser microscope (Keyence Corporation, VK-X3000).

[0028] [Table 1]

[0029] As shown in Table 1, when comparing the surface roughness of the insulator 22 between the example and the comparative example, it can be seen that the arithmetic mean roughness Sa is equivalent, but both Sdr and Spc are larger in the example than in the comparative example. In addition, when comparing the appearance of the surface of the insulator 22, the surface of the insulator 22 of the electric wire 2 of the comparative example is glossy, whereas the surface of the insulator 22 of the electric wire 2 of the example is not glossy. And, as can be seen by comparing Figs. 2(a) and (b), it was confirmed that a large number of finely pointed irregularities are formed on the surface of the insulator 22 in the example compared to the comparative example. It is considered that these fine irregularities can reduce the contact area when the insulators 22 are brought into contact with each other, thereby reducing friction. In addition, when the Shore A hardness of the insulator 22 of the electric wire 2 of the example and the comparative example was measured by the durometer hardness test method (type A) conforming to JIS K7125, it was 89 in the example and 81 in the comparative example. The hardness of the insulator 22 of the example is slightly higher than that of the comparative example.

[0030] (Verification of ease of bending) Next, cables 1 of Examples 1 to 3 were produced by varying the material of the tape member used in the binding layer 5 and the twisting direction of the electric wires 2 in the aggregate core 4, and a deflection test was performed. In the cables 1 of Examples 1 to 3, the aggregate core 4 was formed using 42 electric wires 2 of the Examples shown in Table 1. In the deflection test, the cable 1 was extended horizontally to a length of 300 mm from the end of a base for fixing the cable 1, a predetermined weight was attached to the tip of the cable 1, and the deflection amount 30 seconds after the start of the test (i.e., the vertical distance from the surface of the base to the tip of the cable) was measured. In Example 1, a foam tape was used for the binding layer 5, and the twisting direction of the electric wires 2 in each layer of the aggregate core 4 was the same direction. In Example 2, a foam tape was used for the binding layer 5, and the twisting direction of the electric wires 2 in the aggregate core 4 was set to be different in adjacent layers (alternate layers). In Example 3, a nonwoven fabric tape was used for the binding layer 5, and the twisting direction of the electric wires 2 in each layer of the aggregate core 4 was the same. Moreover, an aggregate core 4 was formed using 42 electric wires 2 of the comparative example shown in Table 1, and a cable was produced in which a nonwoven fabric tape was used for the binding layer 5 and the twisting direction of the electric wires 2 in each layer of the aggregate core 4 was the same, as in Example 3, and a deflection test was performed in the same manner as in Examples 1 to 3. The results are summarized in FIG. 3.

[0031] As shown in Fig. 3, it is understood that Examples 1 to 3 according to the present invention have a larger amount of deflection than the Comparative Example, and are easier to bend. Also, Examples 1 and 2, in which a foam tape is used for the bind layer 5, have a larger amount of deflection than Example 3, in which a nonwoven fabric tape is used for the bind layer 5, and it was confirmed that the use of a foam tape for the bind layer 5 makes it easier to bend. Furthermore, when Example 1 and Example 2 are compared, it was confirmed that it is easier to bend and easier to maintain the bent state when the twist direction of the electric wires 2 in the aggregate core 4 is the same in all layers. (Functions and Effects of the Embodiments)

[0032] As described above, in the cable 1 according to the present embodiment, the insulator 22 constituting the electric wire 2 has a surface roughness Sdr of 1.0 or more and a surface roughness Spc of 3000 mm or less. -1This is the end of the story. As a result, the contact area at the contact portion between the electric wires 2 (i.e., the contact portion on the surface of the insulator 22) becomes smaller, and the frictional force becomes smaller, so that the electric wires 2 can easily move relative to each other in the longitudinal direction even if a relatively soft insulator 22 is used. As a result, even a multi-core cable 1 in which many electric wires 2 are arranged closely together can be easily bent and can easily maintain its shape in a bent state.

[0033] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiment will be described by using the reference numerals and the like in the embodiment. However, the reference numerals and the like in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiment.

[0034] [1] A plurality of electric wires (2) having an insulator (22) covering the periphery of a conductor (21), and a sheath (7) covering the periphery of an aggregate core (4) formed by twisting the plurality of electric wires (2) together in two or more layers, wherein the aggregate core (4) is configured such that adjacent electric wires (2) are in contact with each other on the surface of the insulator (22), and the insulator (22) has a surface roughness Sdr of 1.0 or more and a surface roughness Spc of 3000 mm -1 That's all for cable (1).

[0035] [2] The cable (1) according to [1], wherein the Shore A hardness of the insulator (22) is 77 or more and 93 or less.

[0036] [3] The cable (1) described in [1], further comprising a bind layer (5) between the aggregate core (4) and the sheath (7), the bind layer (5) being configured by wrapping a foam tape having a foam layer made of a foamed resin or a nonwoven tape around the aggregate core (4).

[0037] [4] The cable (1) according to [1], wherein the twist direction of the plurality of electric wires (2) constituting the assembly core (4) is the same in all layers.

[0038] [5] The cable (1) described in [1], wherein the collective core (4) is configured by twisting the plurality of electric wires (2) in two or more layers around a central insert (3) provided at the center of the cable.

[0039] (Additional Note) Although the embodiment of the present invention has been described above, the invention according to the claims is not limited to the embodiment described above. It should be noted that not all of the combinations of features described in the embodiment are essential to the means for solving the problems of the invention. The present invention can be modified appropriately without departing from the spirit of the invention. [Explanation of symbols]

[0040] 1…Cable 2...Electric wire 21...Conductor 22...Insulator 3…Central intervention 4. Collective Core 5…Binding layer 6…Shield layer 7…Sheath

Claims

1. A plurality of electric wires each having an insulator covering a conductor; and a sheath covering the collective core formed by twisting the plurality of electric wires in two or more layers, In the collective core, adjacent electric wires are in contact with each other on a surface of the insulator, The insulator has a surface roughness Sdr of 1.0 or more and a surface roughness Spc of 3000 mm －１ That's all. cable.

2. The Shore A hardness of the insulator is 77 or more and 93 or less.

2. The cable of claim 1.

3. a binding layer between the aggregate core and the sheath; The bind layer is configured by wrapping a foam tape having a foam layer made of a foamed resin or a nonwoven fabric tape around the aggregate core.

2. The cable of claim 1.

4. The twist direction of the plurality of electric wires constituting the collective core is the same in all layers.

2. The cable of claim 1.

5. The core assembly is configured by twisting the plurality of electric wires in two or more layers around a central core provided at the center of the cable.

2. The cable of claim 1.

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