Composite cable

Abstract

To provide a fine-diameter composite cable with high durability to mechanical stress.SOLUTION: A composite cable 1 includes first to third wires 21-23 and a shielding layer 4. The shielding layer is composed of multiple shielding bare wires 40 spirally wound horizontally around the first to third wires 21-23. Each of the multiple shielding bare wires 40 has a bare wire diameter D40 of 0.035 mm or less and a break elongation rate of 4.0% or less. Tensile strength of the shielding bare wire 40 is 700 MPa or more. An inner diameter D4 of the shielding layer 4 is 0.65 mm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a composite cable including a shield layer formed of a plurality of shield strands helically transversely wound around a plurality of electric wires. [Background Art]

[0002] Conventionally, composite cables including a shield layer formed of a plurality of shield strands transversely wound around a plurality of electric wires have been used for various applications. For example, Patent Document 1 describes a multi-core cable suitably used as a cable for a USB interface. This multi-core cable includes an assembly formed by twisting a plurality of electric wires together, a shield layer in which metal strands made of a plurality of copper alloys are helically transversely wound on the outer side of the assembly, and a jacket covering the outer side of the shield layer. The outer diameter of the jacket is 3.5 mm to 6 mm. Each metal strand has an outer diameter of 0.03 mm to 0.09 mm, a tensile strength of 320 MPa to 450 MPa, and an elongation at break of 10% to 15%. It is stated that twist resistance is improved by the characteristics of these metal strands. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2019-061776 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] For example, in medical catheter cables used for endoscopes and the like, from the viewpoint of minimal invasiveness, there is a demand for an ultrafine composite cable having an outermost diameter of, for example, 1.0 mm or less. The inventors of the present invention have found that, in such a small-diameter composite cable, durability against mechanical stress can be improved by using a strand constituting the shield layer having characteristics different from those of conventional strands, and have arrived at the present invention.

[0005] In other words, the present invention aims to provide a small-diameter composite cable with high resistance to mechanical stress. [Means for solving the problem]

[0006] The present invention aims to solve the above problems by providing a composite cable comprising a plurality of electric wires and a shield layer consisting of a plurality of shielding strands spirally wound around the plurality of electric wires, wherein each of the plurality of shielding strands has a strand diameter of 0.035 mm or less and an elongation at break of 4.0% or less. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a small-diameter composite cable with high resistance to mechanical stress. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of a composite cable according to the first embodiment of the present invention. [Figure 2] This is an explanatory diagram showing the end of a composite cable with stepped stripping. [Figure 3] This is a conceptual diagram of a bending test. [Figure 4] This is a conceptual diagram of a torsion test. [Figure 5] This is a cross-sectional view of a composite cable according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0009] [First Embodiment] A first embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view of a composite cable 1 according to the first embodiment of the present invention. Figure 2 is an explanatory diagram showing the end of the composite cable 1 in a stepped state. The composite cable 1 is a medical cable inserted into the human body, for example, and is used more specifically as a probe cable, catheter cable, or endoscope cable.

[0010] The composite cable 1 comprises an assembly 2 formed by twisting together first to third electric wires 21 to 23, a tape member 3 spirally wound around the assembly 2, a shield layer 4 consisting of a plurality of shield wires 40 spirally wound horizontally around the assembly 2 and the tape member 3, and a sheath 5 covering the outer circumference of the shield layer 4. As shown in Figure 2, the twisting direction of the first to third electric wires 21 to 23 and the winding direction of the plurality of shield wires 40 are the same. Also, the winding direction of the tape member 3 is the same as the twisting direction of the first to third electric wires 21 to 23. In Figure 2, these twisting and winding directions are indicated by arrows A.

[0011] The sheath 5 is made of a fluororesin such as PFA and is formed on the outer circumference of the shield layer 4 by extrusion molding. The tape member 3 should preferably be made of a material that is slippery and has a low coefficient of friction with respect to the first to third electric wires 21-23 and the multiple shield strands 40. For example, a strip made of nonwoven fabric, paper, or a resin such as polyimide or PTFE (polytetrafluoroethylene) can be used. However, the tape member 3 may be omitted.

[0012] The outer diameter D1 of the composite cable 1 is preferably 1.0 mm or less, and more preferably 0.5 mm or less, in order to improve minimal invasiveness and reduce the burden on the patient. In this embodiment, the inner diameter D4 (lower diameter of the shield) of the shield layer 4 is 0.65 mm or less, and the strand diameter D of the shield strands 40 is 40 The size is 0.035 mm or less.

[0013] The first to third electric wires 21 to 23 are arranged so as to surround the central axis C1 of the composite cable 1. In the present embodiment, the first electric wire 21 and the second electric wire 22 are coaxial wires, and the third electric wire 23 is a simple wire. The first electric wire 21 and the second electric wire 22 include inner conductors 211, 221 formed by twisting a plurality of copper alloy wires, insulators 212, 222 covering the inner conductors 211, 221, outer conductors 213, 223 arranged on the outer periphery of the insulators 212, 222, and jackets 214, 224 covering the outer periphery of the outer conductors 213, 223. The third electric wire 23 includes an inner conductor 231 formed by twisting a plurality of copper alloy wires, and an insulator 232 covering the inner conductor 231.

[0014] The first electric wire 21 and the second electric wire 22 are used, for example, to transmit signals, and the third electric wire 23 is used, for example, to supply operating power to an electronic component inserted into a human body together with the composite cable 1. The shield layer 4 is electrically grounded, and suppresses electromagnetic waves that enter the assembly 2 from the outside of the composite cable 1 and electromagnetic waves radiated from the assembly 2 to the outside.

[0015] As an example, the outer diameter of the first electric wire 21, the outer diameter of the second electric wire 22, and the outer diameter of the third electric wire 23 are 0.15 mm. As an example, the inner diameter D4 of the shield layer 4 is 0.35 mm, and the wire diameter D of the shield element wire 40 40 is 0.025 mm, as an example. Note that if the shield element wire 40 is too thin, its strength decreases and it is prone to breakage, so the wire diameter D 40 is preferably 0.010 mm or more.

[0016] The shield element wire 40 is made of silver-plated copper alloy. Generally, examples of additive elements contained in a copper alloy include tin (Sn), nickel (Ni), magnesium (Mg), aluminum (Al), titanium (Ti), beryllium (Be), zirconium (Zr), cerium (Ce), manganese (Mn), silicon (Si), and yttrium (Y), and the properties of the copper alloy vary depending on the types and contents of these additive elements.

[0017] In this embodiment, the elongation at break of each shield wire 40 is 4.0% or less. This elongation at break is measured by a test method in accordance with JIS Z 2241 (Tensile Test Method for Metallic Materials), and is obtained by the calculation formula 100 × (L1 - L2) / L2, where L1 is the distance between gauge marks before the test and L2 is the distance between gauge marks at the time of break. The more desirable range for the elongation at break of a single shield wire 40 is 1.0% to 4.0%. In addition, the tensile strength of each shield wire 40 is 700 MPa or more. The tensile strength of the shield wire 40 can be measured in accordance with JIS C 3002 (Test Method for Copper and Aluminum Wires for Electrical Use).

[0018] Thus, in this embodiment, the shield strands 40 are made of a material that is less prone to stretching and has higher strength than, for example, the shield strands of the conventional cable described in Patent Document 1, thereby increasing durability against mechanical stress. In other words, in an ultra-fine composite cable 1 in which the inner diameter D4 of the shield layer 4 is, for example, 0.65 mm or less, it is necessary to use a small-diameter shield strand 40, while the distance from the central axis C1 to the shield strand 40 is short, so the amount of elongation when the composite cable 1 is twisted or bent is suppressed. In this embodiment, this point is taken into consideration, and durability against mechanical stress is increased by using a material that is less prone to stretching and has high strength as the shield strand 40.

[0019] Table 1 shows the evaluation results of bending tests and torsion tests performed on: composite cable 1 having the above configuration (Example), wherein the shield strands 40 have a strand diameter of 0.025 mm, an elongation at break of 3.3%, a tensile strength of 880 MPa, the number of shield strands 40 is 39, and the outer cable diameter D1 is 0.46 mm; a composite cable (Comparative Example 1), wherein the shield strands have a strand diameter of 0.05 mm, an elongation at break of 10%, a tensile strength of 320 MPa, the number of shield strands is 60, and the outer cable diameter is 1.26 mm; and a composite cable (Comparative Example 2), wherein the shield strands have a strand diameter of 0.05 mm, an elongation at break of 3.3%, a tensile strength of 880 MPa, the number of shield strands is 60, and the outer cable diameter is 1.26 mm. In the bending test and the torsion test, pass / fail judgment was performed with the passing number of cycles set to 150,000 cycles.

Table 1

[0020] As shown in FIG. 3, the bending test was carried out by suspending a weight with a load W of 100 gf from the lower end of a cable 10 as the test object, arranging bending jigs 100 having curved shapes on the left and right sides of the cable 10, and moving the cable 10 so as to apply bending at a predetermined bending angle X in the left-right direction along the bending jigs 100. The bending speed was set to 30 cycles / minute, with one reciprocation in the left-right direction counted as one cycle, and bending of the cable 10 was repeated. The resistance value of the shield layer between both ends of the cable 10 was measured after an appropriate number of cycles. When the resistance value measured during the bending test increased by 20% relative to the resistance value before the bending test (initial resistance value), it was considered that the shield layer had broken, and the number of bending cycles at that time was defined as the bending test life. For the Example, the bending angle X was set to 90°, and the bending radius R was set to 7.5 mm. For Comparative Example 1 and Comparative Example 2, the bending angle X was set to 90°, and the bending radius R was set to 5.0 mm.

[0021] In the torsion test, as shown in Figure 4, one end of the cable 10 under test is attached to a non-rotating fixed chuck 101, and another end, separated vertically above by a predetermined twist length L, is attached to a rotating chuck 102. A weight with a load W = 150 gf is suspended from the lower end of the cable 10. By rotating the rotating chuck 102 in this state, a twist of ±180 degrees is applied to the portion of the cable 10 between the fixed chuck 101 and the rotating chuck 102. The rotating chuck 102 is rotated +180 degrees and then returned to its original position, and then rotated -180 degrees and returned to its original position, in the order of arrows 10a, 10b, 10c, and 10d to complete one cycle. The twisting speed was set to 30 times / minute, and the number of twists was counted as one round trip in each direction. Then, the cable 10 was repeatedly twisted, and the resistance of the shield layer between both ends of the cable 10 was measured at appropriate intervals. When the resistance measured during the twisting test increased by 20% compared to the resistance before the twisting test (initial resistance), the shield layer was considered to have broken, and the number of twists at that point was defined as the lifespan of the twisting test. The twist length L was 200 mm for the example, and 180 mm for Comparative Example 1 and Comparative Example 2.

[0022] As is clear from the comparison between Comparative Example 1 and Comparative Example 2 in these test results, in a composite cable with an outer diameter of 1.26 mm, bending and twisting durability are improved by using shield wires made of a soft copper alloy with low tensile strength and high elongation at break. However, as is clear from the comparison between the Example and Comparative Example 2, even shield wires made of a hard copper alloy with high tensile strength and low elongation at break can provide sufficient bending and twisting durability when used in a thin composite cable with an outer diameter of 1.0 mm or less.

[0023] (Effects of the first embodiment) According to the embodiments described above, by constructing the shield layer 4 using multiple shield strands 40 having a strand diameter of 0.035 mm or less, a breaking elongation of 4.0% or less, and a tensile strength of 700 MPa or more, it is possible to provide a small-diameter composite cable 1 with high resistance to mechanical stress.

[0024] [Second Embodiment] Next, a second embodiment of the present invention will be described with reference to Figure 5. Figure 5 is a cross-sectional view of a composite cable 1A according to the second embodiment of the present invention. Similar to the composite cable 1 according to the first embodiment, the composite cable 1A is used, for example, as a medical cable inserted into the human body.

[0025] The composite cable 1A comprises an assembly 6 formed by twisting together first to sixth electric wires 61 to 66, a tape member 7 spirally wound around the assembly 2, a shield layer 8 consisting of a plurality of shield strands 80 spirally wound horizontally around the assembly 6 and the tape member 7, and a sheath 9 covering the outer circumference of the shield layer 4. The materials of the tape member 7 and the sheath 9 are the same as those of the tape member 3 and the sheath 5 in the first embodiment. The twisting direction of the first to sixth electric wires 61 to 66, the winding direction of the plurality of shield strands 80, and the winding direction of the tape member 7 are all the same.

[0026] In this embodiment, as an example, the cable outer diameter D 10 The diameter is 0.74 mm, the inner diameter D8 (lower diameter of the shield) of the shield layer 8 is 0.61 mm, and the strand diameter D of the shield strand 80 is 0.74 mm. 80 The thickness is 0.025 mm. The number of shielding strands 80 contained in the shielding layer 8 is 72.

[0027] The first to sixth wires 61 to 66 are arranged to surround the central axis C2 of the composite cable 1A. A fibrous interlining 60 is placed in the area surrounded by the first to sixth wires 61 to 66. The first wire 61, the fourth wire 64, and the fifth wire 65 are coaxial wires, while the second wire 62, the third wire 63, and the sixth wire 66 are simple wires. The outer diameter of the first to sixth wires 61 to 66 is, for example, 0.15 mm or more and 0.21 mm or less.

[0028] The shield wires 80, as in the first embodiment, are made of a silver-plated copper alloy and are spirally wound around the assembly 6 and the tape member 7. Each shield wire 80 has a breaking elongation of 3.3% or less and a tensile strength of 880 MPa or more. The method for measuring the breaking elongation and tensile strength is the same as in the first embodiment.

[0029] In the bending and twisting tests conducted on the composite cable 1A configured as described above, results exceeding the passing limit of 150,000 cycles were obtained in both cases. In other words, this second embodiment, like the first embodiment, can provide a small-diameter composite cable 1A with high durability against mechanical stress.

[0030] (Summary of the embodiments) Next, the technical concepts understood from the first and second embodiments described above will be described using the reference numerals and other symbols from the embodiments. However, the reference numerals in the following description are not limited to the components in the claims that are specifically shown in the embodiments.

[0031] [1] The system comprises a plurality of electric wires (21-23, 61-66) and a shield layer (4, 8) consisting of a plurality of shield strands (40, 80) spirally wound around the plurality of electric wires (21-23, 61-66), each of the plurality of shield strands (40, 80) having a strand diameter (D 40 , D 80 A composite cable (1, 1A) with a diameter of 0.035 mm or less and an elongation at break of 4.0% or less.

[0032] [2] The composite cable (1, 1A) described in [1] above, wherein the tensile strength of each of the plurality of shield wires (40, 80) is 700 MPa or more.

[0033] [3] The composite cable (1, 1A) described in [1] or [2] above, wherein the inner diameter (D4, D8) of the shield layer (4, 8) is 0.65 mm or less.

[0034] [4] The composite cable (1, 1A) described in [3] above, wherein the number of twists required for the shield layer (4, 8) to break when twisted in a twisting test is 150,000 or more.

[0035] [5] The composite cable (1, 1A) described in [3] above, wherein the number of times the shield layer (4, 8) is bent before it breaks when bent in a bending test is 150,000 or more.

[0036] [6] The composite cable (1, 1A) described in [1] above, wherein the twisting direction of the plurality of electric wires (21-23, 61-66) and the winding direction of the plurality of shield wires (40, 80) are the same.

[0037] Although embodiments of the present invention have been described above, the embodiments described above do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention.

[0038] Furthermore, the present invention can be implemented with appropriate modifications without departing from its spirit. For example, in the first and second embodiments, the use of composite cables 1 and 1A as medical cables was described, but the applications of composite cables 1 and 1A are not limited to this, and they can be used in various applications requiring a small diameter and high torsional and bending durability. Also, the configuration of the multiple wires in the bundle is not limited to those exemplified in Figures 1 and 5, and can be modified in various ways depending on the specifications of the composite cable. [Explanation of Symbols]

[0039] 1.1A…Composite cable 21~23,61~66...Electric wire 4,8…Shield layer 40, 80... Shielded wire

Claims

1. A bundle of three or more electric wires twisted together, a shield layer consisting of a plurality of shield wires spirally wound around the bundle, and a sheath covering the outer circumference of the shield layer, The cable outer diameter is 0.5 mm or less. Each of the aforementioned plurality of shielding strands has a strand diameter of 0.035 mm or less, a breaking elongation of 4.0% or less, and a tensile strength of 700 MPa or more. Composite cable.

2. At least one of the three or more electric wires is a coaxial wire having an inner conductor, an insulator covering the inner conductor, and an outer conductor arranged on the outer circumference of the insulator. The composite cable according to claim 1.

3. comprising a tape member spirally wrapped around the aggregate, The plurality of shielding wires are spirally wound horizontally around the assembly and the tape member. The composite cable according to claim 1 or 2.

4. In a torsion test, the number of twists required before the shield layer breaks is 150,000 or more. The composite cable according to claim 1 or 2.

5. In a bending test, the number of bending cycles until the shield layer breaks is 150,000 or more. The composite cable according to claim 1 or 2.

6. The twisting direction of the three or more electric wires, the winding direction of the tape member, and the winding direction of the multiple shield wires are the same. The composite cable according to claim 3.

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