cable

Abstract

To provide a cable capable of improving durability to U-shaped bending motion.SOLUTION: A cable 1 includes an internal conductor 3, an insulator 4 for coating the internal conductor 3, and a cushion member 2 arranged on the inner peripheral side of the internal conductor 3, and deformable in a cable radial direction by force from the internal conductor 3. The internal conductor 3 is formed by laminating, in the cable radial direction, multiple conductor layers 31 formed by twisting multiple bundled stranded wires 321, 331.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, cables for moving parts have been used as cables wired to moving parts of industrial robots, etc. The cables for moving parts are repeatedly bent or twisted as the moving parts move, which can repeatedly generate stress.

[0003] Therefore, Patent Document 1 discloses a cable for movable parts that is designed to improve durability against repeated bending or twisting. The cable for movable parts described in Patent Document 1 includes a tension member, a conductor made of multiple conductive wires twisted around the tension member, and an insulator that covers the conductor. The cable for movable parts described in Patent Document 1 improves the flexibility of the cable for movable parts by forming a gap between the insulator and the conductor, thereby improving durability against repeated bending or twisting. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-51947 Summary of the Invention [Problem to be solved by the invention]

[0005] The cable for a movable part described in Patent Document 1 has room for improvement in terms of durability against bending.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a cable that can improve durability against bending. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a cable comprising: a cushion member; an inner conductor arranged on the outer periphery of the cushion member; and an insulator covering the inner conductor from the outer periphery, wherein the cushion member is configured to be deformable in the cable radial direction by a force from the inner conductor, and the inner conductor is formed by laminating multiple conductor layers in the cable radial direction, each conductor layer being made by twisting together a plurality of bunched stranded wires. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a cable that can improve durability against bending. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a cross section perpendicular to the longitudinal direction of a cable according to an embodiment; [Figure 2] 2 is an enlarged view of a portion of FIG. 1 extending from the outer conductor toward the inner circumference. [Figure 3] FIG. 3 is an enlarged view of the area surrounded by the two-dot chain line in FIG. 2. [Figure 4] FIG. 10 is a schematic diagram for explaining a U-shaped bending test according to an experimental example. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Embodiment Mode] An embodiment of the present invention will be described with reference to Figures 1 to 3. The embodiment described below is shown as a preferred specific example for carrying out the present invention, and although various technically preferable technical matters are specifically exemplified, the technical scope of the present invention is not limited to this specific embodiment.

[0011] (Moving part cable 1) Fig. 1 is a cross-sectional view perpendicular to the longitudinal direction of a cable for movable part 1 according to this embodiment. Fig. 2 is an enlarged view of a region from an outer conductor 5 to an inner peripheral side in Fig. 1.

[0012] The cable for movable part 1 is used, for example, as a cable wired to a movable part of an industrial robot that manufactures semiconductor devices, etc. The cable for movable part 1 may be bent into a U-shape and laid inside a Cableveyor (registered trademark) that houses the cable for movable part 1. When the industrial robot has a movable part in which a Cableveyor (registered trademark) is arranged, the movable part, for example, repeats sliding motions up to 10 million times along the longitudinal direction of the Cableveyor (registered trademark) with the Cableveyor (registered trademark) bent into a U-shape. As the Cableveyor (registered trademark) slides, the cable for movable part 1 wired inside the Cableveyor (registered trademark) is subjected to repeated U-shaped bending motions. Therefore, the cable for movable part 1 is required to be durable against repeated U-shaped bending motions. The bending radius of the U-shaped bent portion of the cable for movable part 1 is, for example, 10 times or more the outer diameter of the cable for movable part 1. Furthermore, when the cable for movable section 1 is repeatedly subjected to U-shaped bending motions, a voltage of, for example, 3000 V or more is applied to the inner conductor 3 provided within the cable for movable section 1, and a current of, for example, 60 A or more is passed through it. When the cable for movable section 1 is subjected to such a high voltage and a high current, repeated U-shaped bending motions impose a large load on the insulator 4 constituting the cable for movable section 1. If the load causes cracks or the like in the insulator 4, dielectric breakdown of the insulator 4 may become more likely. In consideration of the above circumstances, the cable for movable section 1 according to this embodiment is devised to improve durability against U-shaped bending motions and to suppress dielectric breakdown of the insulator 4. The cable for movable section 1 will now be described in detail.

[0013] 1 , the cable for movable part 1 includes, in order from the inner periphery, a cushion member 2, an inner conductor 3, an insulator 4, an outer conductor 5, a tape 6, a jacket 7, a shielding layer 8, and a sheath 9. Hereinafter, the term "longitudinal direction of the cable" refers to the longitudinal direction of the cable for movable part 1, and the term "diametric direction of the cable" refers to the radial direction of the cable for movable part 1.

[0014] The cushion member 2 is a wire rod elongated in the cable longitudinal direction and configured to be deformable under the force from the inner conductor 3. For example, when the cable for movable section 1 is bent in a U-shape, the cushion member 2 is pushed by the force from the inner conductor 3 and deforms in the cable radial direction. This reduces stress concentration on the inner conductor 3 or the insulator 4 when the cable for movable section 1 is bent in a U-shape, thereby reducing the risk of breakage of the inner conductor 3 or cracks in the insulator 4. This improves the durability of the cable for movable section 1 against U-shape bending and suppresses dielectric breakdown of the insulator 4. In this embodiment, the cushion member 2 is made of a plurality of staple fiber yarns. Each staple fiber yarn can be made of a single yarn having a count of 10 to 60, for example. The cushion member 2 is made by bundling or twisting these staple fiber yarns. In this case, the cushion member 2 may be made by bundling or twisting multiple single staple fiber yarns, or by bundling or twisting multiple paired yarns formed by twisting a pair of staple fiber yarns. When the cushion member 2 is constructed by bundling or twisting together a large number of paired yarns each made up of a pair of staple yarns, it is easy to obtain the effect of improving the durability of the movable part cable 1 against the U-shaped bending motion described above. For example, the cushion member 2 may be constructed from a paired yarn made up of two twisted staple yarns made up of any of 10, 20, 40, and 60 count staple yarns. Note that the staple yarn that constitutes the cushion member 2 should preferably have an elongation of 10% or more. The elongation of the staple yarn can be measured by a test method based on JIS L 1095.

[0015] The cushion member 2 is arranged to fill the space on the inner periphery side of the inner conductor 3. That is, as shown in FIG. 1 , the cushion member 2 is arranged so as to contact the entire inner surface of the bunched strands 321 that make up the inner conductor 3, and is also arranged without gaps in the recesses formed at the contact points between adjacent bunched strands 321. Furthermore, when the movable section cable 1 bends in a U-shape, the cushion member 2 deforms in the cable radial direction following the deformation of the space on the inner periphery side of the inner conductor 3. The cushion member 2 is preferably arranged to fill the space on the inner periphery side of the inner conductor 3 even during the above-mentioned deformation in the cable radial direction. This facilitates the improvement of durability against the above-mentioned U-shape bending. From the viewpoint of improving the cushioning performance of the cushion member 2, it is preferable that the cushion member 2 include a large number of thin staple yarns. In this embodiment, the number of staple yarns in the cushion member 2 is greater than the number of strands 30 in each bunched strand 321, 331 that make up the inner conductor 3. This facilitates the improvement of the cushioning performance of the cushion member 2. Although the cushion member 2 can be made of fibers other than staple fiber, it is preferable to use staple fiber from the viewpoint of improving cushioning performance.

[0016] In a cross section of the cable for movable part 1 perpendicular to the longitudinal direction of the cable, the area of ​​the region surrounded by the inner conductor layer 31 (i.e., the region where the cushion member 2 is disposed) is larger than the cross-sectional area of ​​each of the bunched strands 321, 331 (described below) that constitute the inner conductor 3. In other words, the cross-sectional area of ​​the cushion member 2 is larger than the cross-sectional area of ​​each of the bunched strands 321, 331. This improves the cushioning performance of the cushion member 2 when the cable for movable part 1 repeatedly undergoes U-shaped bending. This improves the durability of the cable for movable part 1 against U-shaped bending. The cross-sectional areas of the cushion member 2 and the bunched strands 321, 331 can be determined, for example, by photographing a cross section of the cable for movable part 1 perpendicular to the longitudinal direction using a scanning electron microscope (SEM) at a magnification that captures the entire cushion member 2 and the inner conductor 3, and then analyzing the obtained SEM image.

[0017] The inner conductor 3 is formed by laminating two conductor layers 31 radially of the cable, each conductor layer being formed by helically twisting together a plurality of bunched strands 321, 331. Hereinafter, the inner conductor layer 31 disposed in contact with the cushion member 2 will be referred to as the inner conductor layer 32, and the outer conductor layer 31 disposed in contact with the inner surface of the insulator 4 will be referred to as the outer conductor layer 33; when no distinction is made between these layers, they will simply be referred to as conductor layer 31. The inner conductor 3 may be formed by laminating three or more conductor layers 31.

[0018] The inner conductor layer 32 is formed by twisting six bunched strands 321 around the outer periphery of the cushion member 2. The outer conductor layer 33 is formed by twisting twelve bunched strands 331 around the outer periphery of the inner conductor layer 32. Note that the number of bunched strands 321 constituting the inner conductor layer 32 and the number of bunched strands 331 constituting the outer conductor layer 33 are not limited to those described above. It is preferable that the number of bunched strands 321 constituting the inner conductor layer 32 is smaller than the number of bunched strands 331 constituting the outer conductor layer 33.

[0019] Here, the twist direction of each of the bunched strands 321, 331 constituting the internal conductor 3 is referred to as the child twist direction, and the direction in which the multiple bunched strands 321 are twisted together in the inner conductor layer 32 and the direction in which the multiple bunched strands 331 are twisted together in the outer conductor layer 33 are referred to as the parent twist direction. In Fig. 2 , the parent twist direction of each conductor layer 31 is indicated by a dashed arrow on each conductor layer 31. The child twist direction of each bunched strand 321 constituting the inner conductor layer 32 is indicated by a dashed arrow on one of the bunched strands 321. The child twist direction of each bunched strand 331 constituting the outer conductor layer 33 is indicated by a dashed arrow on one of the bunched strands 331. In this embodiment, the parent twist direction of the inner conductor layer 32 and the parent twist direction of the outer conductor layer 33 are the same. Furthermore, in each of the inner conductor layer 32 and the outer conductor layer 33, the child twist direction and the parent twist direction are opposite to each other. As shown in FIGS. 1 and 2 , the inner conductor layer 32 and the outer conductor layer 33 of the inner conductor 3 are preferably parent-twisted with a gap between two adjacent bunched strands 321 arranged at predetermined positions and two adjacent bunched strands 331 arranged around them. The inner conductor 3 is preferably parent-twisted with a gap S between two adjacent bunched strands 331 and the insulator 4. This allows the bunched strands 321, 331 to deform and escape into the gaps as the cushion member 2 deforms in the cable radial direction when the cable for movable part 1 is bent in a U-shape. This improves the durability of the cable for movable part 1 against U-shape bending.

[0020] The inner conductor layer 32 is formed to be flatter in the cable radial direction than the outer conductor layer 33. That is, in a cross section of the movable section cable 1 perpendicular to the cable longitudinal direction, the width W1 of the bunched strands 321 that has the smallest cable radial width among the multiple bunched strands 321 that make up the inner conductor layer 32 is smaller than the width W2 of the bunched strands 331 that has the smallest cable radial width among the multiple bunched strands 331 that make up the outer conductor layer 33. Here, the cable radial width of each bunched strand 321, 331 refers to the cable radial length from the innermost end position to the outermost end position of each bunched strand 321, 331. For convenience, in FIGS. 1 and 2, the shapes of the bunched strands 321 that make up the inner conductor layer 32 are depicted as the same shape, and the shapes of the bunched strands 331 that make up the outer conductor layer 33 are depicted as the same shape (including symmetric shapes). 1 and 2, the multiple bunched strands 321 constituting the inner conductor layer 32 have the same width in the cable radial direction, so width W1 is the width in the cable radial direction of each bunched strand 321. The same applies to the outer conductor layer 33. However, in reality, it is expected that the multiple bunched strands 321 constituting the inner conductor layer 32 will have different widths in the cable radial direction, and in such a case, width W1 is the width of the bunched strand 321 with the smallest width in the cable radial direction among the multiple bunched strands 321. The same applies to width W2.

[0021] 3 is an enlarged view of the area surrounded by the two-dot chain line in FIG. 2. The bunched strands 321, 331 that make up the inner conductor 3 are formed by twisting together a large number of thin strands 30, each having a diameter of, for example, 0.20 mm or less. By configuring the bunched strands 321, 331 from a large number of thin strands 30, for example, when the movable section cable 1 is bent in a U-shape, the bunched strands 321, 331 deform to escape into the tiny gaps between the bunched strands 321, 331, thereby dispersing stress generated within the movable section cable 1. The number of strands 30 that make up each bunched strand 321, 331 is preferably 100 or more, and more preferably 150 or more. In this embodiment, the 18 bunched strands 321, 331 that make up the inner conductor 3 each have the same number of strands 30 and the same diameter. The strands 30 of the bunched strands 321, 331 are made of conductor wires (metal wires), such as annealed copper wires, tin-plated annealed copper wires, copper alloy wires, aluminum wires, or aluminum alloy wires. The bunched strands 321 and the bunched strands 331 may be made of wires of different metals. For example, the multiple bunched strands 321 making up the inner conductor layer 32 may be made of wires made of aluminum wires or aluminum alloy wires, and the multiple bunched strands 331 making up the outer conductor layer 33 may be made of wires made of annealed copper wires or copper alloy wires. By using an inner conductor 3 in which the bunched strands 321 and the bunched strands 331 are made of wires of different metals, the amount of copper used can be reduced, and a cable 1 with a small diameter can be achieved.

[0022] The insulator 4 covers the inner conductor 3 from the outer periphery. The insulator 4 is formed by forming an electrically insulating resin into a cylindrical shape by non-solid extrusion (tube extrusion). Forming the insulator 4 by non-solid extrusion forms gaps S between adjacent bunched strands 331 in the outer conductor layer 33 and surrounded by the insulator 4. The formation of the gaps S makes it easier for each strand 30 of the inner conductor 3 to move into the gaps S within the insulator 4 as the cushion member 2 deforms in the cable radial direction. In other words, when the cable for movable part 1 is bent in a U-shape, the inner conductor 3 is more likely to deform in the cable radial direction so that the strands 30 appropriately escape into the gaps S. This makes it possible to reduce stress generated in the inner conductor 3, thereby improving the durability of the cable for movable part 1 against U-shape bending.

[0023] The insulator 4 is preferably arranged so as not to press the inner conductor 3 in the cable radial direction as much as possible, and is desirably arranged so that the insulator 4 and the inner conductor 3 are relatively movable in the cable longitudinal direction. For example, when the cable for movable part 1 is straightened and the end of the inner conductor 3 is pulled from the end of the insulator 4 in the cable longitudinal direction, it is sufficient that the inner conductor 3 is movable in the cable longitudinal direction relative to the insulator 4.

[0024] In this embodiment, the insulator 4 is made of fluororesin. As shown in FIG. 2 , the thickness T of the insulator 4 is smaller than the diameter of each of the bunched strands 321, 331 constituting the inner conductor 3. The diameter of each of the bunched strands 321, 331 constituting the inner conductor 3 here refers to the diameter of a circumscribed circle of the bunched strands 321, 331 twisted together into a substantially circular shape before parent twisting (i.e., the unflattened bunched strands 321, 331). The diameter of the bunched strands 321, 331 can be theoretically calculated based on the diameter and number of strands 30 constituting the bunched strands 321, 331, or can be obtained by directly measuring the diameter of each of the bunched strands 321, 331 before parent twisting. In this embodiment, the thickness T of the insulator 4 is smaller than the width W1 of the multiple bunched strands 321 constituting the inner conductor layer 32 and the width W2 of the multiple bunched strands 331 constituting the outer conductor layer 33. Furthermore, the thickness T of the insulator 4 is smaller than both the thickness of the jacket 7 and the thickness of the sheath 9. In particular, in this embodiment, the thickness T of the insulator 4 is smaller than both half the thickness of the jacket 7 and half the thickness of the sheath 9. This improves the durability of the cable for movable part 1 against U-shaped bending motion.

[0025] The outer conductor 5 covers the outer periphery of the insulator 4. The outer conductor 5 is formed by horizontally winding a plurality of bunched strands 51 around the outer periphery of the insulator 4. In FIG. 2 , the horizontal winding direction of the outer conductor 5 is indicated by dashed arrows on the plurality of bunched strands 51, and the twist direction of each bunched strand 51 in the outer conductor 5 is indicated by a dashed arrow on one bunched strand 51. The horizontal winding direction of the outer conductor 5 is the same as the parent twist direction of the inner conductor layer 32 and the parent twist direction of the outer conductor layer 33. The twist direction of each bunched strand 51 constituting the outer conductor 5 is the same as the horizontal winding direction of the outer conductor 5 and is opposite to the child twist direction of the bunched strands 321 constituting the inner conductor layer 32 and the child twist direction of the bunched strands 331 constituting the outer conductor layer 33.

[0026] The number of bunched strands 51 constituting the outer conductor 5 is the same as the total number of bunched strands 321, 331 constituting the inner conductor 3 (18 in this embodiment). The diameter and number of strands 50 in each bunched strand 51 constituting the outer conductor 5 are the same as the diameter and number of strands 30 in each bunched strand 321, 331 constituting the inner conductor 3. In a cross section of the movable section cable 1 perpendicular to the cable longitudinal direction, the cross-sectional area of ​​the outer conductor 5 is equal to that of the inner conductor 3. Although the cross-sectional areas of the outer conductor 5 and the inner conductor 3 are designed to be the same, even if they differ slightly due to manufacturing errors or the like, the cross-sectional area of ​​the outer conductor 5 is considered to be equal to that of the inner conductor 3. For example, in a case where the inner conductor 3 is connected to the positive pole of an external power supply and the outer conductor 5 is connected to the negative pole of the external power supply, it is preferable to make the electrical resistance values ​​of the inner conductor 3 and the outer conductor 5 the same. The strands 50 of the bunched strands 51 of the outer conductor 5 are made of conductive wire such as annealed copper wire, tin-plated annealed copper wire, copper alloy wire, or the like.

[0027] The tape 6 is wound spirally around the outer periphery of the outer conductor 5. For example, a paper tape, a resin tape, or the like can be used as the tape 6. The tape 6 serves to prevent the outer conductor 5 from unwinding after the outer conductor 5 is wound around the outer periphery of the insulator 4.

[0028] The jacket 7 covers the outer periphery of the tape 6. The jacket 7 is made of an electrically insulating resin such as PVC (polyvinyl chloride) formed into a cylindrical shape.

[0029] The shielding layer 8 covers the outer periphery of the jacket 7. In this embodiment, the shielding layer 8 is made of a braided shield formed by braiding a plurality of wires. The wires used for the shielding layer 8 are conductors such as annealed copper wires, tin-plated annealed copper wires, and copper alloy wires. By providing an additional shielding layer 8 on the outer periphery of the outer conductor 5, it is possible to improve the shielding characteristics against external electromagnetic noise. Note that the shielding layer 8 may not be a braided shield, but may instead be made of a plurality of bunched stranded wires wound helically across the conductor, as in the outer conductor 5.

[0030] The sheath 9 covers the outer periphery of the shield layer 8. The sheath 9 is made of an electrically insulating resin such as PVC formed into a cylindrical shape.

[0031] (Actions and Effects of the Embodiments) The cable for movable section 1 of this embodiment includes a cushion member 2 disposed on the inner periphery of the inner conductor 3 and capable of deforming in the cable radial direction when a force is applied from the inner conductor 3. This allows the inner conductor 3 to deform toward the cushion member 2 when the cable for movable section 1 is bent into a U shape, thereby reducing stress on the inner conductor 3. As a result, the durability of the cable for movable section 1 against U-shaped bending can be improved. Furthermore, since the inner conductor 3 is more likely to deform toward the cushion member 2, the load on the insulator 4 is reduced, thereby suppressing dielectric breakdown of the insulator 4. For example, even when the cable is bent into a U shape under conditions in which a voltage of 3000 V or more is applied and a current of 60 A or more is passed, dielectric breakdown of the insulator 4 can be suppressed. Furthermore, the inner conductor 3 is formed by laminating multiple conductor layers 31, each layer being formed in the cable radial direction, the conductor layers 31 being formed by twisting together multiple bunched strands 321, 331. This allows the bunched strands 321, 331 of each conductor layer 31 to deform more freely in the cable radial and circumferential directions when the cable for movable section 1 is bent in a U shape, and the stress of the inner conductor 3 is more easily distributed to the bunched strands 321, 331 of each conductor layer 31. As a result, the durability of the cable for movable section 1 against U-shaped bending can be improved, and the load on the insulator 4 can be reduced, preventing dielectric breakdown of the insulator 4.

[0032] The cushion member 2 also has a plurality of staple fiber yarns. By forming the cushion member 2 from staple fiber yarns, the cushioning performance of the cushion member 2 is significantly improved compared to when the cushion member 2 is formed from other fibers (e.g., aramid fiber, carbon fiber, polyamide fiber) or the like.

[0033] Furthermore, the cushion member 2 contains more staple yarns than the number of wires 30 of each of the bunched strands 321, 331 that make up the internal conductor 3. In order to increase the number of staple yarns, the thickness of the staple yarns needs to be thin. In this embodiment, by using a large number of relatively thin staple yarns with counts of 10 to 60, the cushioning performance of the cushion member 2 can be further improved.

[0034] Moreover, each of the bunched strands 321, 331 constituting the inner conductor 3 is formed by twisting together 100 or more strands 30. By forming each of the bunched strands 321, 331 constituting the inner conductor 3 from a large number of strands 30 in this way, the inner conductor 3 becomes more likely to deform when the cable for movable part 1 is bent in a U shape.

[0035] Furthermore, in a cross section of the movable part cable 1 perpendicular to the cable longitudinal direction, the width W1 of the bunched strand 321 having the smallest cable radial width among the multiple bunched strands 321 constituting the inner conductor layer 32 is smaller than the width W2 of the smallest cable radial width among the multiple bunched strands 331 constituting the conductor layer 31 other than the inner conductor layer 32 (the outer conductor layer 33 in this embodiment). Here, because the outer conductor layer 33 is twisted with the inner conductor layer 32 from its outer periphery, the inner conductor layer 32 is more susceptible to pressure in the cable radial direction than the outer conductor layer 33. Therefore, the inner conductor layer 32, which is more susceptible to pressure in the cable radial direction among the multiple conductor layers 31, is flattened compared to the other conductor layers 31, thereby effectively alleviating stress occurring in the inner conductor layer 32, which is more susceptible to pressure.

[0036] Furthermore, the twisting directions (parent twisting directions) of the multiple bunched strands 321, 331 between adjacent conductor layers 31 (i.e., the inner conductor layer 32 and the outer conductor layer 33) are the same. Therefore, the bunched strands 321 constituting the inner conductor layer 32 can deform to wedge between adjacent bunched strands 331 in the outer conductor layer 33, and the bunched strands 331 constituting the outer conductor layer 33 can deform to wedge between adjacent bunched strands 321 in the inner conductor layer 32. Therefore, the inner conductor 3 is more easily deformed when the movable part cable 1 is bent in a U-shape.

[0037] The cable further includes an outer conductor 5 that covers the outer periphery of the insulator 4, and the outer conductor 5 is formed by laterally winding a plurality of bunched strands 51. By forming the outer conductor 5 by laterally winding a plurality of bunched strands 51 in this way, the outer conductor 5 is more likely to deform when the cable for movable section 1 is bent in a U shape. This reduces stress generated in the outer conductor 5 and prevents excessive strain from being placed on the insulator 4 surrounded by the outer conductor 5 and the inner conductor 3, thereby preventing dielectric breakdown.

[0038] Furthermore, the spiral winding direction of the bunched strands 51 in the outer conductor 5 is the same as the twisting direction (parent twisting direction) of the bunched strands 321, 331 in each of the conductor layers 31. This makes it easy to improve the productivity of the cable 1 for a movable part.

[0039] Furthermore, in a cross section perpendicular to the longitudinal direction of the cable for movable part 1, the cross-sectional area of ​​the outer conductor 5 is equal to the cross-sectional area of ​​the inner conductor 3. Therefore, the electrical resistance values ​​of the inner conductor 3 and the outer conductor 5 can be made uniform.

[0040] The insulator 4 is made of fluororesin, and the thickness T of the insulator 4 is smaller than the diameter of each of the bunched strands 321, 331 that make up the inner conductor 3. Therefore, the insulator 4 ensures electrical insulation between the inner conductor 3 and the outer conductor 5, and the flexibility of the insulator 4 is improved, thereby improving the flexibility of the cable for movable part 1 as a whole.

[0041] As described above, according to this embodiment, it is possible to provide a cable that can improve durability against bending.

[0042] [Experimental Example] A sample 100 having the same configuration as the cable for a movable part described in the embodiment was prepared and subjected to a U-shaped bending test. In the U-shaped bending test, as shown in Fig. 4, one end of the sample 100 was fixed to a reference part 11, and the other end of the sample 100 was bent into a U-shape with a curvature radius R (60 mm) that was approximately three times the outer diameter (approximately 20 mm) of the sample 100 and fixed to a sliding part 12. The sliding part 12 was slid relative to the reference part 11 so that the stroke length L was 300 mm. The other end of the sample 100 was slid in the direction of arrow A in the figure by the stroke length L, and then slid in the direction of arrow B by the stroke length L, which constituted one cycle. The sliding operation was performed 7.5 million times at a speed of 60 times / min. The radius of curvature R of sample 100 (cable for moving parts) in this test (i.e., approximately three times the outer diameter of sample 100) is assumed to be smaller than the radius of curvature of the bent part of the cable for moving parts when the cable for moving parts is actually used for applications such as industrial robots. In other words, the test conditions in this experimental example are stricter than the usage conditions when the cable is actually wired into a device as a cable for moving parts.

[0043] As a result of the U-shaped bending test, even when sample 100 was subjected to 7.5 million repeated U-shaped bending operations, no breakage occurred inside sample 100. In other words, it was found that the cable for a movable part having the configuration described in the embodiment has high durability against repeated U-shaped bending operations.

[0044] Furthermore, even when a similar U-shaped bending test was performed with the bending radius of the sample 100 set to 300 mm and the sliding movement was performed 10 million times, no fracture occurred inside the sample 100.

[0045] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiments will be described by using the reference numerals and the like in the embodiments. 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 embodiments.

[0046] [1] A cable (1) comprising: a cushion member (2); an inner conductor (3) disposed on the outer periphery of the cushion member (2); and an insulator (4) covering the inner conductor (3) from the outer periphery, wherein the cushion member (2) is configured to be deformable in a cable radial direction by a force from the inner conductor (3), and the inner conductor (3) is formed by laminating, in a cable radial direction, a plurality of conductor layers (31) each formed by twisting together a plurality of bunched stranded wires (321, 331).

[0047] [2] The cable according to [1], wherein the cross-sectional area of ​​the cushion member in a cross section perpendicular to the longitudinal direction of the cable is larger than the cross-sectional area of ​​each of the bunched strands that make up the inner conductor.

[0048] [3] The cable (1) according to [1] or [2], wherein the cushion member (2) has a plurality of staple fibers.

[0049] [4] The cable (1) according to [3], wherein the cushion member (2) has a number of the staple yarns greater than the number of strands (30) of each of the bunched strands (321, 331) constituting the inner conductor (3).

[0050] [5] The cable (1) according to any one of [1] to [4], wherein each of the bunched strands (321, 331) constituting the inner conductor (3) is formed by twisting together 100 or more strands (30).

[0051] [6] The cable (1) according to any one of [1] to [5], wherein, when the conductor layer (31) located at the innermost end among the plurality of conductor layers (31) is defined as an inner conductor layer (32), in a cross section perpendicular to the cable longitudinal direction, the width (W1) of the bunched stranded wire (321) constituting the inner conductor layer (32) that has the smallest width in the cable radial direction among the plurality of bunched stranded wires (321) constituting the inner conductor layer (32) is smaller than the width (W2) of the bunched stranded wire (331) constituting the conductor layer (31) other than the inner conductor layer (32).

[0052] [7] The cable (1) according to any one of [1] to [6], wherein the twist directions of the plurality of bunched strands (321, 331) of the adjacent conductor layers (31) are the same.

[0053] [8] The cable (1) according to any one of [1] to [7], further comprising an outer conductor (5) covering the outer periphery of the insulator (4), the outer conductor (5) being formed by horizontally winding a plurality of bunched stranded wires (51).

[0054] [9] The cable (1) according to [8], wherein the transverse winding direction of the plurality of bunched strands (51) in the outer conductor (5) and the twisting direction of the plurality of bunched strands (321, 331) in each of the plurality of conductor layers (31) are the same.

[0055]

[10] The cable (1) according to [9], wherein the cross-sectional area of ​​the outer conductor (5) is equal to the cross-sectional area of ​​the inner conductor (3) in a cross section perpendicular to the longitudinal direction of the cable.

[0056]

[11] The cable (1) according to any one of [1] to

[10] , wherein the insulator (4) is made of a fluororesin, and the thickness (T) of the insulator (4) is smaller than the diameter of each of the bunched strands (321, 331) constituting the inner conductor (3).

[0057] (Addendum) Although the embodiments of the present invention have been described above, the invention according to the claims is not limited to the above-described embodiments. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention. Furthermore, the present invention can be appropriately modified and implemented within the scope of its spirit. [Explanation of symbols]

[0058] 1...Cable 2...Cushion member 3...Inner conductor 30...Elemental wire 31...Conductor layer 32...Inner conductor layer 33...Outer conductor layer 321...Inner conductor layer stranded wire 331...Outer conductor layer bunched strand 4...Insulator 5...Outer conductor 51...Outer conductor strand T: Insulator thickness

Claims

1. A cushion member; an inner conductor disposed on the outer periphery of the cushion member; an insulator that covers the inner conductor from an outer periphery side, A cable in which a voltage of 3000 V or more is applied to the inner conductor and a current of 60 A or more is passed through the inner conductor while the cable is repeatedly subjected to U-shaped bending motions, the cushion member is configured to be deformable in a cable radial direction by a force from the inner conductor, the inner conductor is formed by laminating two layers in the cable radial direction, including an inner conductor layer made by twisting together a plurality of bunched strands and in contact with the cushion member, and an outer conductor layer made by twisting together a plurality of bunched strands and in contact with the insulator, the inner conductor layer and the outer conductor layer have the same twist direction of the plurality of bunched strands; the plurality of bunched strands constituting the inner conductor layer and the plurality of bunched strands constituting the outer conductor layer are formed flat in the cable radial direction, the bunched strands constituting the inner conductor layer are deformed so as to fit into adjacent bunched strands in the outer conductor layer with gaps between them; cable.

2. In a cross section perpendicular to the longitudinal direction of the cable, the cross-sectional area of ​​the cushion member is larger than the cross-sectional area of ​​each of the bunched strands constituting the inner conductor. The cable of claim 1 .

3. The cushion member has a plurality of staple fibers.

3. The cable according to claim 1 or 2.

4. the cushion member has a number of staple fibers greater than the number of strands of each of the bunched stranded wires that constitute the inner conductor; 4. The cable of claim 3.

5. Each bunched strand constituting the inner conductor is formed by twisting together 100 or more strands. A cable according to any one of claims 1 to 4.

6. In a cross section perpendicular to the longitudinal direction of the cable, the width of the bunched stranded wire having the smallest width in the cable radial direction among the plurality of bunched stranded wires constituting the inner conductor layer is smaller than the width of the bunched stranded wire having the smallest width in the cable radial direction among the plurality of bunched stranded wires constituting the outer conductor layer. A cable according to any one of claims 1 to 5.

7. The inner conductor and the insulator are configured to be relatively movable in the cable longitudinal direction. A cable according to any one of claims 1 to 6.

8. Further, an outer conductor is provided to cover an outer periphery of the insulator, the outer conductor is formed by laterally winding a plurality of bunched stranded wires; A cable according to any one of claims 1 to 7.

9. a spiral winding direction of the plurality of bunched strands in the outer conductor and a twisting direction of the plurality of bunched strands in each of the inner conductor layer and the outer conductor layer are the same direction.

9. The cable of claim 8.

10. In a cross section perpendicular to the longitudinal direction of the cable, the cross-sectional area of ​​the outer conductor is equal to the cross-sectional area of ​​the inner conductor.

10. The cable of claim 9.

11. The insulator is made of fluororesin, the thickness of the insulator is smaller than the diameter of each of the bunched strands constituting the inner conductor; A cable according to any one of claims 1 to 10.

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