cable

Abstract

To provide a cable that allows for improved resistance to bending.SOLUTION: A cable is provided with a cable core 3 including one or more electric wires 2, a shield layer 5 provided to cover around the cable core 3 and composed of a laterally wound shield formed by winding metal wire strands helically, and a sheath 6 provided to cover around the shield layer 5. The metal wire strands are semi-hard copper alloy wires, and P / PD, which is the ratio of the winding pitch P in the laterally wound shield to the pitch diameter PD of the shield layer 5, is less than 9.9.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] For example, a conventional cable includes a cable core (aggregate core) in which multiple signal lines and power lines are twisted together, a tape member arranged spirally around the cable core, a shielding layer arranged around the tape member, and a sheath arranged around the shielding layer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-143015 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, cables used for internal wiring in small industrial robots and for medical applications such as endoscopes are repeatedly bent or twisted. Furthermore, cables used for internal wiring in automobiles and small electronic devices are sometimes bent into shapes appropriate for the wiring location. Therefore, there is a demand for improved durability, particularly when the cable is used while being bent.

[0005] Therefore, an object of the present invention is to provide a cable that can improve resistance to bending. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention provides a cable comprising: a cable core having one or more electric wires; a shielding layer formed by a spirally wound metal wire shield and arranged to cover the cable core; and a sheath arranged to cover the shielding layer, wherein the metal wire is a semi-rigid copper alloy wire, and P / PD, which is the ratio of the winding pitch P of the spirally wound shield to the core diameter PD of the shielding layer, is less than 9.9. [Effects of the Invention]

[0007] According to the present invention, a cable capable of improving resistance to bending can be provided. [Brief explanation 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. [Figure 2] FIG. 1 is a diagram illustrating a bending test. DETAILED DESCRIPTION OF THE INVENTION

[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 according to this embodiment. Cable 1 is used, for example, as internal wiring for small industrial robots or as a medical cable for endoscopes and other applications where bending and twisting are required.

[0011] The cable 1 includes a cable core 3 having one or more electric wires 2, a shield layer 5 arranged to cover the periphery of the cable core 3 and consisting of a horizontally wound shield formed by spirally winding metal wires, and a sheath 6 arranged to cover the periphery of the shield layer 5.

[0012] (wire 2) The cable core 3 includes, as the electric wires 2, a plurality of first electric wires 21 and a plurality of second electric wires 22 arranged so as to surround the periphery of the plurality of first electric wires 21. Note that, in the cable core 3, the electric wires 2 may be constituted only by the first electric wires 21. Also, in the cable core 3, the electric wires 2 may be constituted only by the second electric wires 22. Also, in the cable core 3, the electric wires 2 may be a twisted pair wire formed by twisting two insulated electric wires together.

[0013] The first electric wire 21 is an insulated electric wire having a conductor 211 and an insulator 212 provided to cover the periphery of the conductor 211. In this embodiment, the first electric wire 21 is used as a power line for supplying power. Note that the cable 1 shown in FIG. 1 has a structure in which only four first electric wires 21 are arranged on approximately the same circumference around the center of the cable, but this is not limiting. For example, the cable 1 may have a structure in which multiple first electric wires 21 and a signal line for signal transmission (e.g., a coaxial cable such as the second electric wire 22) are arranged on approximately the same circumference around the center of the cable. In this case, it is preferable that the signal line has an outer diameter equivalent to that of the first electric wire 21. This allows the outer diameter of the cable 1 to be reduced by arranging the first electric wires 21 as power lines and the signal line on the same circumference.

[0014] The conductor 211 of the first electric wire 21 is composed of multiple element wires. The conductor 211 is made of, for example, a stranded conductor in which multiple element wires made of metal wires are twisted together in a bunched or concentric twist state. The element wires used for the conductor 211 are preferably metal wires with a small diameter, for example, an outer diameter of 0.01 mm to 0.03 mm. Furthermore, the element wires used for the conductor 211 are preferably metal wires made of a copper alloy wire such as a Cu-Ag alloy so as to maintain strength even when they are small in diameter. The outer diameter of the conductor 211 is preferably 0.10 mm to 0.30 mm. The insulator 212 is preferably made of a fluororesin such as PFA (perfluoroalkyl vinyl ether copolymer), which can maintain desired insulating performance even with a thin thickness. The insulator 212 may be made of two or more insulating layers stacked together. In this case, for example, the insulating layer of insulator 212 that contacts the outer surface of conductor 211 may be made of a resin such as polypropylene or polyethylene, and the insulating layer provided around this insulating layer may be made of a fluororesin. When insulator 212 is made of a laminate of insulating layers as described above, it becomes easier to adjust the thickness of insulator 212 and the mechanical properties of first electric wire 21, such as flexibility and abrasion resistance.

[0015] The second electric wire 22 is a coaxial wire having an inner conductor 221, an inner insulator 222 provided to surround the inner conductor 221, an outer conductor 223 provided to surround the inner insulator 222, and an outer insulator 224 provided to surround the outer conductor 223. In this embodiment, the second electric wire 22 is used as a signal line for signal transmission. That is, the cable 1 is a composite cable including a plurality of first electric wires 21 serving as power lines and a plurality of second electric wires 22 serving as signal lines. Note that the cable 1 shown in FIG. 1 has a structure in which only eight second electric wires 22 are arranged on approximately the same circumference around the center of the cable, but this is not limiting. For example, the cable 1 may have a structure in which a plurality of second electric wires 22 and a power supply line (e.g., an insulated electric wire like the first electric wire 21) for power supply are arranged on approximately the same circumference around the center of the cable. In this case, it is preferable that the power supply line has an outer diameter equivalent to that of the second electric wire 22. Since the power line and the second electric wire 22 have the same outer diameter, in a structure in which the second electric wire 22 as a signal line and the power line are arranged on approximately the same circumference around the center of the cable, excess gaps inside the cable 1 can be reduced, and the outer diameter of the cable 1 can be made thinner.

[0016] The inner conductor 221 of the second electric wire 22 is a stranded conductor formed by twisting together multiple metal wire strands in a bunched or concentric twisted state. The outer conductor 223 is a spirally wound shield formed by spirally winding metal wire strands around the inner insulator 222. The outer conductor 223 may also be a braided shield formed by braiding multiple metal wire strands. The wires used for the inner conductor 221 and the outer conductor 223 are preferably thin metal wires with an outer diameter of, for example, 0.01 mm to 0.03 mm. The inner conductor 221 and the outer conductor 223 are preferably made of copper alloy wires such as Cu-Ag alloy or Cu-Sn-In alloy to maintain strength even with a small diameter. The inner insulator 222 and the outer insulator 224 are preferably made of fluororesin such as PFA, which can provide desired insulating performance even with a thin thickness. When the outer insulator 224 is made of a fluororesin, it is possible to reduce abrasion due to contact between the first electric wire 21 and the second electric wire 22. The inner insulator 222 may be made of two or more laminated insulating layers. In this case, for example, the insulating layer in contact with the inner conductor 221 may be made of a fluororesin, and the insulating layer provided around this may be made of a resin other than a fluororesin (for example, a resin such as polypropylene or polyethylene). When the inner insulator 222 is made of two or more laminated insulating layers as described above, cracks are less likely to occur in the inner insulator 222 when the cable 1 is bent or twisted, and therefore breakage of the second electric wire 22 can be suppressed.

[0017] (Cable core 3) The cable core 3 has an inner layer portion 31 in which a plurality of (four here) first electric wires 21 are twisted together, and an outer layer portion 32 in which a plurality of (eight here) second electric wires 22 are twisted around the inner layer portion 31. In the present embodiment, the cable core 3 includes a total of 12 electric wires 2. However, the number of electric wires 2 included in the cable core 3 (the number of first electric wires 21 and the number of second electric wires 22) is not limited to this, and may be, for example, 8 to 16 in total. The number of second electric wires 22 is preferably greater than the number of first electric wires 21. More specifically, the number of second electric wires 22 is preferably two to three times the number of first electric wires 21. As a result, adjacent second electric wires 22, adjacent first electric wires 21, and adjacent second electric wires 22 and first electric wires 21 are arranged to come into contact with each other. Therefore, in the cable 1, when the second electric wires 22 have a larger outer diameter than the first electric wires 21, excess space within the cable core 3 can be eliminated, and the diameter of the cable 1 can be reduced.

[0018] When the cable core 3 is composed of a first electric wire 21 and a second electric wire 22, the first electric wire 21, which has a smaller outer diameter than the second electric wire 22, is arranged in the inner layer portion 31, and the second electric wire 22, which has a larger outer diameter than the first electric wire 21, is arranged in the outer layer portion 32. This allows the cable 1 to be made thinner and also improves bending resistance and twisting resistance. Note that if the cable core 3 is arranged, for example, such that the second electric wire 22, which has a larger outer diameter, is arranged in the inner layer portion 31, and the first electric wire 21, which has a smaller outer diameter, is arranged in the outer layer portion 32, stress will concentrate on the first electric wire 21, which has a smaller outer diameter than the second electric wire 22, when the cable 1 is bent or twisted, making it more likely to break. Furthermore, more wasted space will be created between the electric wires 2 (particularly between the first electric wires 21), which will lead to an increase in the diameter of the entire cable 1.

[0019] In this embodiment, a tensile strength fiber 7 is disposed at the center of the cable (the central portion in a cross section perpendicular to the longitudinal direction of the cable), and a plurality of first electric wires 21 are twisted around this tensile strength fiber 7 to form the inner layer portion 31. The tensile strength fiber 7 may be made of, for example, aramid fiber. This makes it easier to reduce the diameter of the cable 1 in this embodiment compared to a structure in which a thread-like filler such as staple fiber or jute is disposed at the center of the cable. Note that the cable 1 does not necessarily need to have a tensile strength fiber 7 disposed at the center of the cable.

[0020] (Tape member 4) The cable 1 includes a tape member 4 wound spirally around the cable core 3. The tape member 4 serves to prevent the cable core 3 from untwisting. For example, a resin tape made of a resin such as polyimide can be used as the tape member 4. Alternatively, for example, a metal foil tape in which a metal foil made of aluminum, copper, or the like is laminated onto a resin tape can be used as the tape member 4. From the viewpoint of increasing the flexibility of the cable 1, it is preferable that such a tape member 4 be wound in the same direction as the twisting direction of the multiple electric wires 2 constituting the cable core 3.

[0021] (Sheath 6) A shielding layer 5 is provided so as to cover the periphery of the tape member 4, and a sheath 6 is provided so as to cover the periphery of the shielding layer 5. Details of the shielding layer 5 will be described later.

[0022] The sheath 6 protects the shielding layer 5 and the cable core 3. To reduce the diameter of the cable 1, it is desirable that the thickness of the sheath 6 be as thin as possible, and is set to less than 0.20 mm. More desirably, the thickness of the sheath 6 is 0.06 mm or more but less than 0.20 mm, and even more desirably, 0.06 mm or more but less than 0.16 mm. A thickness of the sheath 6 of 0.06 mm or more ensures the strength of the sheath 6, thereby preventing cracks from occurring in the sheath 6 when repeatedly bent and twisted. Furthermore, a thickness of the sheath 6 of less than 0.20 mm, and even more desirably, less than 0.16 mm, prevents the cable 1 from becoming too large in diameter. In the present invention, the "thickness of the sheath 6" refers to the average thickness of the sheath 6 determined by the test method specified in JIS C 3005 at a cross section of the cable 1 shown in FIG. 1 at any location in the longitudinal direction.

[0023] The outer diameter of the sheath 6, i.e., the maximum outer diameter of the cable 1 (hereinafter also referred to as the maximum outer diameter of the sheath 6), is 2.0 mm or less. More preferably, it is 1.0 mm or more and 2.0 mm or less. This enables the cable 1 to be wired in very narrow spaces. For the sheath 6, it is preferable to use a fluororesin such as PFA that can be formed to the thickness of the sheath 6 described above. Note that in the present invention, the "maximum outer diameter of the cable 1" does not mean a specific point where the outer diameter is largest in the longitudinal direction of the cable 1, but means the outer diameter of the cable 1 at a portion where the outer diameter of the sheath 6 is largest in the cross section of the cable 1 at any point in the longitudinal direction as shown in Figure 1. The outer diameter of the cable 1 can be determined based on the test method specified in JISC3005.

[0024] Although the sheath 6 has a single layer structure in this embodiment, it may have a two-layer structure consisting of an inner layer and an outer layer. In this case, the inner layer should be a layer that enhances heat dissipation, and may be made of, for example, a resin composition in which a heat dissipation filler is contained in a base resin (fluororesin).

[0025] Furthermore, the cable 1 preferably has projections and recesses along the circumferential direction at predetermined positions on the outer surface of the sheath 6. For example, as shown in Fig. 1, the outer surface of the cable 1 preferably has recesses 61 at predetermined positions in the circumferential direction. By having such projections and recesses, the cable 1 can be more easily wired in a space-saving wiring section than when the outer surface of the sheath 6 is smoothly curved along the circumferential direction of the cable (i.e., when the outer shape of the sheath 6 in a cross section perpendicular to the longitudinal direction of the cable is circular).

[0026] (Shield layer 5) The shielding layer 5 is a horizontally wound shield formed by spirally winding metal wires around the tape member 4. For example, if the shielding layer 5 is formed of a braided shield made of braided metal wires, the metal wires may rub against each other due to repeated bending of the cable 1, particularly when using thin metal wires, which may easily cause the metal wires to break. In contrast, by forming the shielding layer 5 with a horizontally wound shield as in the present embodiment, it is possible to suppress the friction between the metal wires when the cable 1 is bent, thereby improving the bending resistance. Furthermore, if the shielding layer 5 is formed with a braided shield, the thickness of the shielding layer 5 increases due to the overlapping of the metal wires, which results in a large outer diameter of the cable 1. However, by forming the shielding layer 5 with a horizontally wound shield as in the present embodiment, it is possible to suppress the overlapping of the metal wires, thereby making it possible to reduce the thickness of the shielding layer 5 and maintain a small outer diameter of the cable 1.

[0027] (Metal wires used in shield layer 5) In this embodiment, semi-hard copper alloy wires are used as the metal wires used in the shield layer 5. Examples of such metal wires include semi-hard copper-silver alloy wires containing 1% to 3% silver, with the remainder consisting of copper and unavoidable impurities. The metal wires may be other than semi-hard copper-silver alloy wires. For example, semi-hard copper alloy wires containing 0.01% to 0.50% chromium, zirconium, magnesium, indium, tin, etc., with the remainder consisting of copper and unavoidable impurities (e.g., Cu—Cr alloy, Cu—Zr alloy, Cu—Mg alloy, Cu—Sn alloy, Cu—Sn—In alloy, Cu—In alloy, etc.) may be used. Semi-hard copper alloy wires have a tensile strength of 350 MPa to 500 MPa and an elongation of 5% to less than 10%. Generally, hard copper alloy wires have an elongation of less than 5%, while soft copper alloy wires have an elongation of 10% or more. The "elongation" and "tensile strength" referred to here mean the "elongation at break" and "tensile strength" determined by the test method specified in JIS Z2241.

[0028] By using semi-hard copper alloy wires as the metal wires of the shielding layer 5, the tensile strength of the metal wires increases, improving the bending resistance of the shielding layer 5. This is because, when the cable 1 is bent, tensile strain is applied to the surface of the metal wires on the outside of the bend, and the higher the tensile strength of the metal wires, the higher the yield stress at which plastic deformation begins (0.2% proof stress in the case of copper), and the smaller the amount of plastic deformation. In other words, metal wires with higher tensile strength accumulate less strain due to repeated bending, so they can be bent more times before breaking, improving bending resistance.

[0029] Furthermore, if the elongation of the metal wires used in the shield layer 5 is too small, the bending resistance of the shield layer 5 will also decrease. However, by using semi-hard copper-silver alloy wires as the metal wires of the shield layer 5, the decrease in bending resistance due to the influence of elongation can be suppressed. However, the inventors' investigations have revealed that if the elongation is too large, the strength will also decrease and bending resistance will also decrease. Therefore, it is more desirable that the elongation of the metal wires used in the shield layer 5 be less than 10%. In this way, by using semi-hard copper alloy wires that combine relatively high tensile strength and elongation (tensile strength of 350 MPa to 500 MPa and elongation of 5% to less than 10%) as the metal wires of the shield layer 5, the bending resistance of the shield layer 5 can be improved. Note that the above-mentioned functions and effects are particularly easily obtained when semi-hard copper-silver alloy wires that have a tensile strength of 350 MPa to 500 MPa and an elongation of 5% to less than 10% are used as the metal wires.

[0030] In this embodiment, very thin metal wires are used, and if the copper used contains a large amount of impurities, breaks are likely to occur starting from the impurities. Therefore, it is more desirable to use copper alloy wires with a copper purity of 99.99% or more as the metal wires used in the shielding layer 5. Furthermore, it is more desirable for the metal wires used in the shielding layer 5 to have a conductivity of 85% or more IACS or more. This can improve heat dissipation.

[0031] The semi-hard copper alloy wire used as the metal wire can be obtained by heating a hard copper alloy wire (tensile strength of 800 MPa or more, elongation of 1% or more) at a specified temperature (500°C or more and 650°C or less) for a short time of 1.5 seconds or less.

[0032] (winding pitch P of shield layer 5) Furthermore, in this embodiment, the winding pitch P of the shield layer 5 made of a horizontally wound shield is set so that P / PD, which is the ratio of the winding pitch P to the layer core diameter PD of the shield layer 5, is less than 9.9. In this embodiment, P / PD is set to be 6.6 or more and less than 9.9. The winding pitch P is the interval along the cable longitudinal direction between points at the same circumferential position in any metal wire constituting the shield layer 5.

[0033] Furthermore, the layer core diameter PD of the shield layer 5 means the diameter of a circle passing through the center of the shield layer 5 (the center of the metal wire) in a cross section perpendicular to the longitudinal direction of the cable. The layer core diameter PD of the shield layer 5 can be calculated by adding together the maximum outer diameter of the cable core 3, twice the thickness of the tape member 4, and twice the radius of the metal wire. Note that the "maximum outer diameter of the cable core 3" does not mean a specific point where the outer diameter is largest in the longitudinal direction of the cable core 3, but means the outer diameter of the cable core 3 at a portion where the outer diameter is largest in a cross section of an arbitrary point in the longitudinal direction of the cable 1 shown in FIG. 1.

[0034] In this embodiment, the core diameter PD of the shield layer 5 is set to 1.36 mm. In this case, the winding pitch P may be set to 9 mm or more and less than 13.5 mm.

[0035] If the winding pitch P of the spiral wound shield is made too large, the metal wires will be arranged nearly parallel to the longitudinal direction of the cable, which increases the bending strain imposed on the metal wires when the cable is bent, reducing the winding pitch P of the spiral wound shield, or more specifically, by making P / PD less than 9.9, it is possible to reduce the strain accumulated in the metal wires when the cable is repeatedly bent, thereby improving bending resistance.

[0036] Furthermore, when the core diameter PD of the shield layer 5 is 1.36 mm, by setting the winding pitch P of the metal wire in the shield layer 5 to 10 mm or more and less than 13.5 mm, that is, by setting P / PD to 7.3 or more and less than 9.9, it is possible to maintain the resistance to bending described above while also improving the resistance to repeated twisting, i.e., twisting resistance.

[0037] (Outer diameter of metal wire used in shield layer 5) In conventional cables, when the sheath provided on the outermost layer of the cable is thinned to a thickness of less than 0.20 mm in order to reduce the diameter (i.e., to make the maximum outer diameter of the sheath 2.0 mm or less), cracks can occur in the sheath when the cable is repeatedly bent or twisted. The inventors of the present invention have found that when the cable is repeatedly twisted, undulations occur in the shielding layer in a portion of the cable's longitudinal direction, causing breaks in the metal wires that make up the shielding layer in the undulated portion. Furthermore, they have found that the broken portion of the shielding layer rubs against the sheath in contact with the broken portion due to twisting, causing wear on the sheath and resulting in cracks in the sheath. The inventors have found that the occurrence of such undulations in the shielding layer is due to the fact that when the outer diameters of the multiple metal wires constituting the shielding layer have a predetermined outer diameter, the shielding layer falls together with the tape member toward the cable core side (in Figure 1, the valley between the second electric wires 22 adjacent in the circumferential direction), creating a gap between the tape member and the sheath.

[0038] Therefore, in the cable 1 according to the present embodiment, when the maximum outer diameter of the sheath 6 is set to 2.0 mm or less, the outer diameter of the metal wires used in the shielding layer 5 is set to be between 1 / 2 and 1 time the thickness of the sheath 6. By setting the outer diameter of the metal wires to 1 / 2 or more times the thickness of the sheath 6, it is possible to prevent the rigidity of the metal wires from becoming too low. This prevents the metal wires from dropping together with the tape member 4 into the cable core 3 (in the valleys between the circumferentially adjacent second electric wires 22) and creating gaps between the tape member 4 and the sheath 6 when the cable 1 is repeatedly twisted. As a result, it is possible to prevent undulation in the shielding layer 5, which can prevent breakage of the shielding layer 5 due to undulation, and also to prevent cracks in the sheath 6 due to friction with the broken portion of the shielding layer 5. Furthermore, by setting the outer diameter of the metal wires to 1 / 2 or more times the thickness of the sheath 6, it is possible to prevent problems such as a decrease in the strength of the metal wires and increased susceptibility to breakage. In the present invention, the "outer diameter of the metal wires" refers to the average value of the diameters of the metal wires that make up the shielding layer 5 measured by the test method specified in JIS C3002.

[0039] Furthermore, for example, if the outer diameter of the metal wire exceeds one time the thickness of the sheath 6, the metal wire will have a high rigidity, and after being stretched by twisting in one direction, the metal wire will not be able to absorb the stretch when twisted in the other direction, resulting in kinking and the risk of breaking the metal wire. By making the outer diameter of the metal wire less than one time the thickness of the sheath 6 as in this embodiment, it is possible to prevent such breakage of the metal wire and also to prevent cracks in the sheath 6 due to friction with the broken part of the shielding layer 5.

[0040] When the maximum outer diameter of cable 1 (i.e., the maximum outer diameter of sheath 6) is set to 2.0 mm or less as in this embodiment, it is desirable that the thickness of sheath 6 be 0.06 mm or more and less than 0.16 mm as described above. Accordingly, it is desirable that the outer diameter of the metal wires used in shielding layer 5 be 0.03 mm or more and less than 0.16 mm.

[0041] (Bending test) A prototype cable 1 was fabricated and subjected to a bending test. In the bending test, as shown in Figure 2, a weight with a load W = 100 gf was suspended from the lower end of the sample cable 1. A bending jig 80, which curved left and right, was attached to the cable 1. The cable 1 was repeatedly bent left and right along the bending jig 80 at angles between ±90° and ±150°. The bending radius (bending radius) R was set to 7.5 times or less the outer diameter of the cable 1 (outer diameter: approximately 1.6 mm). The bending speed was set to 30 times per minute. Each round of bending in the left and right directions was counted as one bending. The cable 1 was then repeatedly bent, and the appearance of the sheath 6 was observed after each bending to check for cracks. If no cracks were observed in the sheath 6 after 150,000 bending cycles or more, the test was evaluated as passing (◯). If cracks were observed in the sheath 6, the test was evaluated as failing (×). Furthermore, the resistance after 150,000 bending cycles was measured, and the rate of increase in resistance from the initial resistance was calculated. A calculated resistance increase rate of less than 20% was evaluated as pass (◯), and a rate of 20% or more was evaluated as fail (×). Three samples were used, and in the evaluation of sheath cracking and resistance increase rate, if any of the three samples failed, it was evaluated as failing, and only if all three samples passed was it evaluated as passing.

[0042] The sample cables 1 used were those of Example 1, in which the shield layer 5 was composed of a spirally wound shield made of semi-hard copper alloy wire, with the spirally wound shield having a winding pitch P of 9.5 mm (P / PD = 7.0) and Example 2, in which the winding pitch P was 11.5 mm (P / PD = 8.5). In the cables 1 of Examples 1 and 2, the metal wires of the shield layer 5 were semi-hard copper-silver alloy wires (tensile strength: approximately 400 MPa, elongation: 8% to 9%) containing 2% silver and the remainder copper and unavoidable impurities. The thickness of the shield layer 5 (outer diameter of the metal wires) was approximately 0.05 mm, the core diameter PD of the shield layer 5 was 1.36 mm, the thickness of the sheath 6 was approximately 0.08 mm, and the outer diameter of the cable 1 was approximately 1.6 mm.

[0043] Furthermore, cables were prepared as Comparative Example 1 with a winding pitch P of 13.5 mm (P / PD = 9.9) and Comparative Example 2 with a winding pitch P of 15.0 mm (P / PD = 11.0), and were subjected to bending tests in the same manner as for Cable 1 in Examples 1 and 2. The cables in Comparative Examples 1 and 2 had the same configuration as Cable 1 in Examples 1 and 2, except that the winding pitch P was changed.

[0044] Furthermore, Conventional Example 1, in which the shield layer was constructed of a braided shield and the braid pitch was 10.8 mm, and Conventional Example 2, in which the braid pitch was 16.6 mm, were prepared, and a bending test was conducted in the same manner as for Cable 1 in Examples 1 and 2. In the cables of Conventional Examples 1 and 2, the braided shield had a thickness of approximately 0.03 mm, and the shield layer had a layer core diameter PD of 1.38 mm. The metal wires constituting the braided shield were soft copper alloy wires (tensile strength: approximately 370 MPa, elongation: 12% to 13%) containing 0.19% tin, 0.2% indium, and the remainder copper and unavoidable impurities. The bending test results for the cables of Examples 1 and 2, Comparative Examples 1 and 2, and Conventional Examples 1 and 2 are summarized in Table 1.

[0045] [Table 1]

[0046] As shown in Table 1, in Comparative Examples 1 and 2, in which the winding pitch P was increased to 13.5 mm or more and P / PD was 9.9 or more, the resistance increase rate was 20% or more, and the resistance increase rate was unacceptable. Furthermore, in Conventional Examples 1 and 2, which used a braided shield, it was confirmed that cracks occurred in the sheath. In contrast, in Examples 1 and 2, in which the winding pitch P was less than 13.5 mm and P / PD was less than 9.9, it was confirmed that both the resistance increase rate and sheath cracking passed the test.

[0047] The results in Table 1 confirm that by using semi-hard copper alloy wires as the metal wires used in the shielding layer 5 and setting the P / PD to less than 9.9, it is possible to reduce the rate of increase in resistance due to repeated bending and suppress the occurrence of cracks in the sheath 6, thereby improving the durability of the cable 1 when repeatedly bent. That is, according to this embodiment, in a left-right bending test of ±90 degrees or more, the increase in resistance of the metal wires constituting the shielding layer 5 after at least 150,000 repeated bendings is less than 20% of the initial resistance value, and no cracks occur in the sheath 6, making it possible to realize a highly flexible cable 1.

[0048] (Actions and Effects of the Embodiments) As described above, the cable 1 according to this embodiment includes the cable core 3 having one or more electric wires 2, the shielding layer 5 which is arranged to cover the cable core 3 and is made of a spirally wound metal wire shield, and the sheath 6 which is arranged to cover the shielding layer 5, the metal wire used in the shielding layer 5 is a semi-rigid copper alloy wire, and the ratio P / PD of the winding pitch P of the spirally wound shield to the core diameter PD of the shielding layer 5 is less than 9.9.

[0049] With this configuration, a highly flexible cable 1 can be realized in which, in a left-right bending test of ±90 degrees or more, the resistance of the metal wires constituting the shielding layer 5 increases by less than 20% of the initial resistance value after at least 150,000 repeated bendings, and no cracks occur in the sheath 6. In other words, according to this embodiment, a cable 1 with improved durability against repeated bending can be realized.

[0050] Furthermore, in cable 1 according to the present embodiment, the outer diameter of the metal wires constituting shield layer 5, which is a spirally wound shield, is set to between 1 / 2 and 1 time the thickness of sheath 6. As a result, even when the maximum outer diameter of sheath 6 is set to 2.0 mm or less, which is a small cable outer diameter, and the thickness of sheath 6 is set to less than 0.20 mm, it is possible to prevent breaks in shield layer 5 due to repeated twisting and to prevent cracks in sheath 6 due to friction with the broken portion. In other words, according to the present embodiment, cable 1 can be realized in which sheath 6 is thin and has a small diameter, and in which cracks are less likely to occur in sheath 6 due to repeated twisting.

[0051] (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.

[0052] [1] A cable (1) comprising: a cable core (3) having one or more electric wires (2); a shield layer (5) arranged to surround the cable core (3) and consisting of a spirally wound shield of metal wires; and a sheath (6) arranged to surround the shield layer (5), wherein the metal wires are semi-rigid copper alloy wires, and the ratio P / PD of the winding pitch P of the spirally wound shield to the core diameter PD of the shield layer (5) is less than 9.9.

[0053] [2] The cable (1) according to [1], wherein the metal wire is a semi-hard copper-silver alloy wire containing 1% to 3% of silver, with the remainder being copper and unavoidable impurities.

[0054] [3] The cable (1) according to [1] or [2], wherein the metal wires have a tensile strength of 350 MPa or more and 500 MPa or less, and an elongation of 5% or more and less than 10%.

[0055] [4] The cable (1) according to any one of [1] to [3], wherein the P / PD is equal to or greater than 7.3 and less than 9.9.

[0056] [5] The cable (1) according to any one of [1] to [4], wherein the cable core (3) includes, as the electric wires (2), a plurality of first electric wires (21) and a plurality of second electric wires (22) having an outer diameter larger than that of the first electric wires (21), and the cable core (3) has an inner layer portion (31) in which the plurality of first electric wires (21) are twisted together, and an outer layer portion (32) in which the plurality of second electric wires (22) are twisted around the inner layer portion (31).

[0057] [6] The cable (1) described in [5], wherein the first electric wire (21) is an insulated electric wire having a conductor (211) and an insulator (212) arranged to cover the periphery of the conductor (211), and the second electric wire (22) is a coaxial wire having an inner conductor (221), an inner insulator (222) arranged to cover the periphery of the inner conductor (221), an outer conductor (223) arranged to cover the periphery of the inner insulator (222), and an outer insulator (224) arranged to cover the periphery of the outer conductor (223).

[0058] Although the embodiments of the present invention have been described above, the invention according to the claims is not limited to the embodiments described above. 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.

[0059] The present invention can be appropriately modified and implemented without departing from the spirit and scope of the present invention. For example, in the above embodiment, the cable core 3 includes a plurality of electric wires 2, but the present invention is not limited to this. The cable core 3 may be formed of a single electric wire 2. In this case, the cable 1 may be a coaxial cable in which a shield layer 5 and a sheath 6 are sequentially provided around a single insulated electric wire. [Explanation of symbols]

[0060] 1...Cable 2...Electric wire 21...First electric wire 211...conductor 212...Insulator 22...Second electric wire 221...Inner conductor 222...Inner insulator 223...Outer conductor 224...Outer insulator 3...Cable core 31...Inner layer 32…Outer layer part 4...Tape member 5...Shield layer 6...Sheath 7...Tensile strength fiber

Claims

1. A cable core including a plurality of first electric wires and a plurality of second electric wires having an outer diameter larger than that of the first electric wires, the cable core having an inner layer portion in which the plurality of first electric wires are twisted together, and an outer layer portion in which the plurality of second electric wires are twisted together around the inner layer portion; a shield layer provided to cover the cable core and made of a spirally wound shield formed by winding metal wires in a spiral shape; a sheath provided to cover the periphery of the shielding layer, The metal wire is a semi-hard copper alloy wire having a tensile strength of 350 MPa or more and 500 MPa or less and an elongation of 5% or more and less than 10%, The metal wire is a semi-hard copper-silver alloy wire containing 1% or more and 3% or less of silver, with the remainder being copper and unavoidable impurities, a ratio P / PD of a winding pitch P of the spiral wound shield to a layer diameter PD of the shield layer is 7.3 or more and less than 9.9; cable.

2. The maximum outer diameter of the sheath is 2.0 mm or less, The outer diameter of the metal wire is between 1 / 2 and 1 times the thickness of the sheath. The cable of claim 1 .

3. The first electric wire is an insulated electric wire having a conductor and an insulator provided so as to cover the conductor, the second electric wire is a coaxial wire having an inner conductor, an inner insulator provided to cover the periphery of the inner conductor, an outer conductor provided to cover the periphery of the inner insulator, and an outer insulator provided to cover the periphery of the outer conductor, The cable of claim 1 .

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