Manufacturing method of stranded wire

Abstract

Provided is a method for producing a twisted wire that can be made up of only an outer layer made up of 20 or more wires under compression or low compression, and a method for producing twisted wire that can produce multiple types of twisted wires from a preliminary twisted wire. [Solution] A method for manufacturing a stranded wire, comprising the steps of: forming a pre-stranded wire 1 having an outer layer 2 formed by arranging a plurality of element wires 12 on the same circumference; an inner layer 6 formed of one or more layers 3, 4 in which element wires 13, 14 are arranged on the same circumference inside the outer layer 2; and forming a hollow portion 5 inside the inner layer 6; cutting the pre-stranded wire 1 to a predetermined length; pulling out and removing one element wire 14 constituting the innermost layer 4; and then removing all or some of the other element wires 14 constituting the innermost layer 4. Alternatively, one element wire 13 constituting a layer 3 constituting the next layer inside the innermost layer 4 may then be pulled out and removed; and then all of the other element wires 13 constituting that layer 3 may be removed.

Description

[Technical field]

[0001] The present invention relates to a method for producing a stranded wire. [Background technology]

[0002] In recent years, in the electric wire market, from the viewpoint of making electric wires and cables thinner, lighter, and more functional, there has been a demand for stranded wires in which the cross section is closer to circular and the outer layer is made of wires of the same diameter arranged on the same circumference so as to have a hollow portion on the inside (for example, Patent Document 1, Figure 2).

[0003] It is composed of a single outer layer made up of wires that make up the outer layer, with a hollow space formed inside. In order to stabilize the shape of this twisted wire, the wires are compressed from the outside at a compression rate of about 10%, and adjacent wires are configured to abut against each other.

[0004] Also, as shown in FIG. 1 of Patent Document 1, for example, a stranded wire is known in which the outer layer is made up of a plurality of layers and a hollow portion is formed inside the outer layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2000-057852 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the wires constituting the outer layer described in Patent Document 1 are compressed and deformed from the outside, causing distortion toward the central axis, resulting in an oval shape rather than a perfect circle, making it difficult to precisely manufacture the inner diameter of the hollow portion at a value close to the design value. Also, in order to make the inner diameter of the hollow portion close to the design value, the wires constituting the outer layer must be compressed at a compression rate of 10% or more, since the shape of the outer layer cannot be stabilized unless the wires constituting the outer layer are compressed.

[0007] In addition, due to the stability of the shape of a stranded wire consisting of only one outer layer with a hollow space formed inside, the maximum number of wires that could be manufactured was limited to 20.

[0008] In addition, the stranded wire having one or more outer layers as described in Patent Document 1 is desired to have various outer and inner diameters depending on the intended use, etc. There is a problem in that the costs, etc., become high if all the different types are manufactured and stored.

[0009] Therefore, if it were possible to produce a plurality of types of wire from one type of pre-stranded wire, it would be desirable to reduce the manufacturing cost.

[0010] Furthermore, when the twisted wire shown in FIG. 1 of Patent Document 1 is used for audio purposes, the number of strands that make up the inner layer can be changed to tune how the sound is heard in the audio device. However, there is a problem in that it is difficult to compare multiple types of twisted wire because of the cost of prototyping the twisted wire.

[0011] Therefore, an object of the present invention is to provide a method for manufacturing a stranded wire that can solve the various problems described above by manufacturing a pre-stranded wire, cutting it to a specified length, and then pulling out the wires that make up the inner layer. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides a pre-stranded wire having an outer layer formed by arranging a plurality of wires on the same circumference, and an inner layer formed of one or more layers of wires on the same circumference inside the outer layer, the pre-stranded wire having a hollow portion formed inside the inner layer, the pre-stranded wire being cut to a predetermined length, and then: This is a method for manufacturing a stranded wire, characterized in that one wire constituting the innermost layer is pulled out and removed, and then all other wires constituting the innermost layer are removed.

[0013] In addition, a pre-stranded wire is formed having an outer layer formed by arranging a plurality of wires on the same circumference, and an inner layer formed of one or more layers of wires arranged on the same circumference inside the outer layer, and a hollow portion is formed inside the inner layer, and the pre-stranded wire is cut to a predetermined length, and then One of the wires constituting the innermost layer may be pulled out and removed, and then the wires adjacent to that wire may be successively removed, thereby removing a portion of all the wires constituting the innermost layer.

[0014] The inner layer is made up of a plurality of layers, After removing all the other wires that make up the innermost layer, After one of the wires constituting the layer immediately outside the innermost layer is pulled out and removed, all of the other wires constituting that layer may be removed.

[0015] The wires constituting the outer layer are formed to have the same diameter as the wires constituting the outermost layer of the inner layer, and the diameter of the wires constituting the outermost layer of the inner layer is smaller than the diameter of the wires constituting the inner layer. The number of wires constituting the outer layer may be seven or more greater than the number of wires constituting each of the inner layers.

[0016] The stranding direction of the wires constituting the inner layer may be different from the stranding direction of the wires constituting the outer layer.

[0017] The twist direction of the wires constituting the inner layer is the same as the twist direction of the wires constituting the outer layer, The twist pitch of the wires constituting the inner layer may be different from the twist pitch of the wires constituting the outer layer. Effect of the Invention

[0018] According to the present invention, by removing one of the wires constituting the inner layer and then removing all or some of the wires located circumferentially therefrom, it is possible to construct the stranded wire without compressing it or with a low compression ratio, and it is possible to precisely manufacture the outer diameter of the stranded wire and the inner diameter of the hollow portion.

[0019] In addition, multiple types of stranded wires can be manufactured from one type of pre-stranded wire, which reduces manufacturing costs.

[0020] Furthermore, when the stranded wire is used for acoustic applications, the number of strands constituting the inner layer can be easily varied, allowing comparisons of different stranded wires to be made easily. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a cross-sectional view of a pre-stranded wire according to the first embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view of an example of a stranded wire according to a first embodiment of the present invention. [Diagram 3] FIG. 4 is a cross-sectional view of another example of the stranded wire according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view of another example of the stranded wire according to the first embodiment of the present invention. [Diagram 5] FIG. 11 is a cross-sectional view of a pre-stranded wire according to a fourth embodiment of the present invention. [Figure 6] FIG. 11 is a cross-sectional view of an example of a stranded wire according to a fourth embodiment of the present invention. [Figure 7] FIG. 11 is a cross-sectional view of another example of the stranded wire according to the fourth embodiment of the present invention. [Figure 8] FIG. 11 is a cross-sectional view of a pre-stranded wire according to a fifth embodiment of the present invention. [Figure 9] FIG. 11 is a cross-sectional view of an example of a stranded wire according to a fifth embodiment of the present invention. [Figure 10] FIG. 11 is a cross-sectional view of another example of the stranded wire according to the fifth embodiment of the present invention. [Figure 11] FIG. 13 is a cross-sectional view of an example of a pre-stranded wire according to a sixth embodiment of the present invention. [Figure 12] FIG. 13 is a cross-sectional view of an example of a stranded wire according to a sixth embodiment of the present invention. [Figure 13] FIG. 13 is a cross-sectional view of another example of the stranded wire according to the sixth embodiment of the present invention. [Figure 14] FIG. 13 is a cross-sectional view of another example of the pre-stranded wire according to the sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The present invention will be described with reference to the drawings. The stranded wire produced by the method of the present invention can be used as a stranded conductor for electric wires and cables, a catheter tube for medical treatment, a guide wire for passing through blood vessels, an operating wire for endoscopes, and other medical wires.

[0023] [Example 1] A pre-stranded wire used in the manufacture of the stranded wire according to the first embodiment will be described.

[0024] FIG. 1 is a cross-sectional view of a pre-stranded wire 1 according to a first embodiment of the present invention, cut in a direction perpendicular to the axial direction, and the oblique lines indicating the cross sections of the individual wires are omitted to avoid complicating the drawing.

[0025] As shown in Fig. 1, the pre-stranded wire 1 is composed of three layers: an outer layer 2 located radially outward from its center, a first inner layer 3 provided on the outer layer 2 radially inward from the center of the pre-stranded wire 1, and a second inner layer 4 provided on the first inner layer 3 radially inward from the center of the pre-stranded wire 1. A hollow portion 5 is formed on the second inner layer 4 radially inward from the center of the pre-stranded wire 1. The pre-stranded wire 1 is composed of one outer layer 2 and an inner layer 6 composed of two layers, the first inner layer 3 and the second inner layer 4.

[0026] The outer layer 2 is composed of an outer layer wire 12, the first inner layer 3 is composed of a first inner layer wire 13, the second inner layer 4 is composed of a second inner layer wire 14, and the preliminary stranded wire 1 is composed of three types of wires 12, 13, 14. The outer layer wire 12 constituting the outer layer 2, the first inner layer wire 13 constituting the first inner layer 3, and the second inner layer wire 14 constituting the second inner layer 4 are twisted in the same direction.

[0027] The preliminary stranded wire 1 is formed so that the twist pitch of the outer layer wire 12 constituting the outer layer 2 is the same as the twist pitch of the first inner layer wire 13 constituting the first inner layer 3 and the second inner layer wire 14 constituting the second inner layer 4.

[0028] The outer layer wires 12, the first inner layer wires 13, and the second inner layer wires 14 each include 24 wires.

[0029] When a stranded wire is used as a stranded wire conductor, the wire material that forms the base of each of the strands 12, 13, 14 can be, for example, copper wire such as bare copper wire, oxygen-free copper wire, linear crystal oxygen-free copper wire, single crystal high-purity oxygen-free copper wire, copper wire plated with tin, nickel, silver, etc., aluminum wire, various alloy wires, and wires with an insulating coating such as enameled wire, Litz wire, formal wire, etc.

[0030] When the stranded wire is used for medical wire, the wire material that forms the base of each of the strands 12, 13, 14 may be, for example, hard copper wire, alloy wire, nickel wire, stainless steel wire, titanium wire, or the like.

[0031] As will be described later, the second inner layer wire 14 is formed to have a strength that allows the second inner layer wire 14 to be pulled out from the preliminary strand 1 without breaking midway.

[0032] The wires 12, 13, and 14 may be made of the same material or different materials.

[0033] 1, the outer layer 2 is configured by arranging 24 outer layer wires 12 on the same circumference. The outer layer 2 is configured by outer layer wires 12 that are circular in cross section and all have the same diameter, and the outer layer wires 12, 12 adjacent in the circumferential direction about the center of the pre-stranded wire 1 are arranged so as to abut on each other over the entire axial direction or part of the axial direction.

[0034] As shown in Fig. 1, the first inner layer 3 is configured by arranging 24 first inner layer lines 13 on the same circumference. The first inner layer 3 is configured of first inner layer lines 13 that are circular in cross section and all have the same diameter.

[0035] The first inner layer wire 13 is disposed so as to abut the adjacent outer layer wires 12, 12 over the entire axial direction or over a portion of the axial direction in an inner valley portion 15 formed by the adjacent outer layer wires 12, 12 in the circumferential direction about the center of the preliminary strand 1. The diameter d2 of the first inner layer wire 13 is formed to be smaller than the diameter d1 of the outer layer wire 12.

[0036] 1, the second inner layer 4 is configured by arranging 24 second inner layer wires 14 on the same circumference. The second inner layer 4 is configured by second inner layer wires 14 that are circular in cross section and all have the same diameter, and adjacent second inner layer wires 14, 14 in the circumferential direction about the center of the pre-stranded wire 1 are arranged so as to abut on each other over the entire axial direction or part of the axial direction.

[0037] The second inner layer wire 14 is disposed so as to abut the adjacent first inner layer wires 13, 13 over the entire axial direction or over a portion of the axial direction in an inner valley portion 16 formed by the adjacent first inner layer wires 13, 13 in the circumferential direction about the center of the preliminary strand 1. The diameter d3 of the second inner layer wire 14 is formed smaller than the diameter d2 of the first inner layer wire 13.

[0038] In the present embodiment 1, the wires 12, 13, and 14 having the relationships d1=1.255×d2 and d3=0.797×d2 were used.

[0039] In addition, the cross-sectional shape of the pre-stranded wire 1 is substantially circular, that is, the distances L1 from the center of the pre-stranded wire 1 to the outermost ends of the outer layer wires 12 constituting the outer layer 2 are substantially uniform. The distances L2 from the center of the pre-stranded wire 1 to the outermost ends of the first inner layer wires 13 constituting the first inner layer 3 are substantially uniform, and the distances L3 from the center of the pre-stranded wire 1 to the outermost ends of the second inner layer wires 14 constituting the second inner layer 4 are substantially uniform.

[0040] Next, a method for producing the stranded wire will be described.

[0041] First, the preliminary strand 1 is cut to a predetermined axial length.

[0042] Next, one second inner layer wire 14 constituting the second inner layer 4 located on the innermost side of the preliminary stranded wire 1 is pulled out. As a result, the other second inner layer wires 14 constituting the second inner layer 4 tend to collapse into the hollow portion 5, making it easier to pull out the other second inner layer wires 14.

[0043] Next, the other second inner layer wires 14 constituting the second inner layer 4 are successively pulled out, and all the second inner layer wires 14 constituting the second inner layer 4 are pulled out, so that only the outer layer 2 and the first inner layer 3 remain, as shown in Fig. 2. The second inner layer wires 14 may be pulled out one by one, or multiple wires may be pulled out at once.

[0044] Next, one of the first inner layer wires 13 constituting the first inner layer 3 located one layer outside the innermost layer is pulled out. This makes it easier for the other first inner layer wires 13 constituting the first inner layer 3 to collapse into the hollow portion 5, making it easier to pull out the other first inner layer wires 13.

[0045] Next, the other first inner layer wires 13 constituting the first inner layer 3 are successively pulled out, and all of the first inner layer wires 13 constituting the first inner layer 3 are pulled out, resulting in a stranded wire 20 having only one outer layer 2, as shown in Fig. 3. The first inner layer wires 13 may be pulled out one by one, or multiple wires may be pulled out at a time.

[0046] Alternatively, the other first inner layer wires 13 constituting the first inner layer 3 may not be pulled out, and a stranded wire 19 consisting of the outer layer 2 and the first inner layer 3 may be formed as shown in FIG.

[0047] Since the stranded wires 19, 20 of the present invention have the above-mentioned structure, they provide the following functions and effects.

[0048] By making the outer shape of the stranded wires 19, 20 approximately circular without compressing it, the elongation value of each strand 12, 13 is reduced to a small extent, and physical properties such as flexibility and suppleness are not impaired, allowing the physical properties to be maintained.

[0049] Furthermore, the stranded wire 20 can be constructed from only one outer layer 2 having 20 or more outer layer wires 12 (24 wires), which is difficult to manufacture using conventional techniques, and can maintain its shape stably.

[0050] In addition, because the stranded wire 20 can be formed with only one outer layer 2 without compressing the outer layer wire 12, the outer diameter of the stranded wire 20 and the inner diameter of its internal hollow portion can be set to values ​​close to the design values, resulting in a stranded wire 20 with high dimensional accuracy. Similarly, the stranded wire 19, which is composed of two layers, the outer layer 2 and the first inner layer 3, can also be formed with high dimensional accuracy.

[0051] Furthermore, the preliminary strand 1 may be used as the strand 18 as it is, and by using the manufacturing method of the present invention, three types of strands 18, 19, and 20 can be obtained from the preliminary strand 1, thereby reducing manufacturing costs.

[0052] In the above-mentioned Example 1, all of the second inner layer wires 14 constituting the second inner layer 4 are pulled out, but the stranded wire 18A may be configured such that, after one second inner layer wire 14 constituting the second inner layer 4 is pulled out from the preliminary stranded wire 1, the second inner layer wires 14 adjacent to the pulled out second inner layer wire 14 are pulled out one by one, leaving a plurality of second inner layer wires 14 as shown in Fig. 4. In this way, when the stranded wire 18A is used as an audio cable or the like, the way in which sound is heard in an audio device can be easily tuned by changing the configuration of the stranded wire 18A.

[0053] [Example 2] As long as an arrangement similar to that of the pre-stranded wire 1 of Example 1 can be formed, the pre-stranded wire 1 can be formed using wires having any diameter other than the wires having the diameters described in Example 1, so long as the diameter d2 of the first inner layer wire 13 is smaller than the diameter d1 of the outer layer wire 12 and the diameter d3 of the second inner layer wire 14 is smaller than the diameter d2 of the first inner layer wire 13. In addition, the pre-stranded wire 1 may be compressed from the outside of the outer layer 2, which is the outermost layer, by a compression die or the like. The pre-stranded wire 1 can be stably formed at a compression rate lower than that of the prior art.

[0054] This compression causes the outer periphery of the outer layer wire 12 constituting the outer layer 2 to be compressed and deformed, making the outer shapes of the pre-stranded wire 1 and the stranded wires 19, 20 closer to a perfect circle. Compression using a compression die or the like may be performed when the pre-stranded wire 1 is manufactured, or may be performed after the pre-stranded wire 1 is manufactured. The compression rate can be set arbitrarily, but even if a compression rate lower than that of the above-mentioned conventional technology is used, the stranded wires 18A, 19, 20 can be formed in a stable shape.

[0055] The other structure is similar to that of the first embodiment, and therefore the description will be omitted.

[0056] In the second embodiment as well, the same effects as those in the first embodiment can be achieved.

[0057] [Example 3] In the above-mentioned Examples 1 and 2, the preliminary stranded wire 1 is configured with 24 outer layer wires 12, 24 first inner layer wires 13, and 24 second inner layer wires 14, but the numbers of the outer layer wires 12, 13, and 14 can be set to any numbers as long as the numbers of the outer layer wires 12, the first inner layer wires 13, and the second inner layer wires 14 are the same.

[0058] The outer layer 2 is composed of outer layer lines 12 of the same diameter, the first inner layer 3 is composed of first inner layer lines 13 of the same diameter, and the second inner layer 4 is composed of second inner layer lines 14 of the same diameter.

[0059] The outer layer wire 12, the first inner layer wire 13 and the second inner layer wire 14 are arranged in the same regularity as in the first and second embodiments.

[0060] The other structure is similar to that of the first and second embodiments, and therefore the description thereof will be omitted.

[0061] In the third embodiment as well, the same effects as those in the first and second embodiments can be achieved.

[0062] [Example 4] In the above-mentioned first to third embodiments, the preliminary stranded wire 1 is constituted by the same number of the outer layer wire 12, the first inner layer wire 13, and the second inner layer wire 14, respectively, but the outer layer wire 12, the first inner layer wire 13, and the second inner layer wire 14 may be constituted by different numbers of wires, respectively. The first inner layer wire and the second inner layer wire are each constituted by the same number of wires. Also, the outer layer is constituted by outer layer wires of the same diameter, the first inner layer is constituted by first inner layer wires of the same diameter, and the second inner layer is constituted by second inner layer wires of the same diameter.

[0063] 5, the preliminary stranded wire 27 may be formed such that the outer layer 21 is composed of 22 outer layer wires 21a, the first inner layer 22 is composed of 15 first inner layer wires 22a, and the second inner layer 23 is composed of 15 second inner layer wires 23a, and the hollow portion 25 is formed inside the inner layer 24. By using the strands 42a, 43a, 44a in which the relationships d1=0.964×d2 and d3=0.694×d2 are satisfied, the cross-sectional shape of the preliminary stranded wire 27 can be made substantially circular with no compression or a low compression ratio.

[0064] Using this preliminary stranded wire 27, stranded wires 28 and 29 as shown in Fig. 6 and Fig. 7 can be obtained by the same manufacturing method as in the above-mentioned embodiment 1. Moreover, the preliminary stranded wire 27 can be made into a stranded wire 30.

[0065] The other structures are the same as those in the first to third embodiments, and therefore the description thereof will be omitted.

[0066] In this fourth embodiment as well, the same effects as those in the first to fourth embodiments can be achieved.

[0067] [Example 5] In the above-mentioned Examples 1 to 4, the outer layer 2, 21 constituting the preliminary stranded wire 1, 27 is constituted by one kind of outer layer wire 12, 21a, but the outer layer may be constituted by a plurality of kinds of outer layer wires having different diameters. The number of wires constituting each layer of the inner layer is the same, and the wires constituting each layer are constituted by wires having the same outer diameter.

[0068] 8, the outer layer 31 may be composed of 10 first outer layer wires 31a and 20 second outer layer wires 31b, the inner layer 34 may be composed of a first inner layer 32 composed of 10 first inner layer wires 32a and a second inner layer 33 composed of 10 second inner layer wires 33a, and a hollow portion 35 may be formed inside the inner layer 34 to form a preliminary stranded wire 37. The first outer layer wire 31a is formed thicker than the second outer layer wire 31b.

[0069] 8, the outer layer 31 is configured by arranging first outer layer lines 31a at a distance in the circumferential direction, and arranging two second outer layer lines 31b, 31b in the circumferential direction between the first outer layer lines 31a, 31a adjacent in the circumferential direction. The first outer layer line 31a and the second outer layer line 31b are arranged on the same circumference so that their outer edges are located on the same circumference.

[0070] Adjacent outer layer wires 31a, 31b (31a, 31a) are disposed so as to abut on each other over the entire axial direction or over a portion of the axial direction.

[0071] As shown in FIG. 8, the first inner layer line 32a is located on the inside between adjacent first outer layer lines 31a, 31a, and is arranged so as to abut the two first outer layer lines 31a, 31a and the two second outer layer lines 31b, 31b over the entire axial direction or over part of the axial direction.

[0072] Assuming that the inner diameter of the first outer layer wire 31a is d11 and the inner diameter of the second outer layer wire 31b is d12, by using the individual wires 31a, 31b, 32a, 33a in which the relationships d11=0.630×d2, d12=0.400×d2, and d3=0.575×d2 are satisfied, the cross-sectional shape of the preliminary strand 37 can be made substantially circular without compression or with a low compression ratio.

[0073] 9 and 10 can be obtained by using this preliminary stranded wire 37 and the same manufacturing method as in the above-mentioned embodiment 1. The preliminary stranded wire 37 can also be made into a stranded wire 40.

[0074] The other structures are the same as those in the first to fourth embodiments, and therefore the description thereof will be omitted.

[0075] In this fifth embodiment as well, the same effects as those in the first to fourth embodiments can be achieved.

[0076] [Example 6] In the above-mentioned Examples 1 to 5, the twisting direction of the wires 12, 21a, 31a, 31b constituting the outer layers 2, 21, 31 of the preliminary stranded wires 1, 27, 37 is the same as the twisting direction of the wires 13, 14, 23a, 24a, 33a, 34a constituting each of the layers 3, 4, 22, 23, 33, 34 constituting the inner layers 6, 24, 34. However, in the preliminary stranded wire of the present embodiment, the twisting direction of the wires constituting the outer layer is different from the twisting direction of the wires constituting each of the inner layers.

[0077] The number of wires constituting the outer layer is seven or more than the number of wires constituting each of the inner layers.

[0078] For example, as shown in Fig. 11, the pre-stranded wire 41 is composed of three layers: an outer layer 42 located at the outermost position in the radial direction from the center of the pre-stranded wire 41, a first inner layer 43 provided on the outer layer 42 radially inward from the center of the pre-stranded wire 41, and a second inner layer 44 provided on the first inner layer 43 radially inward from the center of the pre-stranded wire 41. A hollow portion 45 is formed on the second inner layer 44 radially inward from the center of the pre-stranded wire 41. The pre-stranded wire 41 is composed of one outer layer 42 and an inner layer 46 composed of two layers, the first inner layer 43 and the second inner layer 44. There are 38 outer layer wires 42a, and 15 first inner layer wires 43a and 15 second inner layer wires 44a.

[0079] The outer layer 42 is composed of an outer layer wire 42a, the first inner layer 43 is composed of a first inner layer wire 43a, the second inner layer 44 is composed of a second inner layer wire 44a, and the preliminary stranded wire 41 is composed of three types of wires 42a, 43a, and 44a. The twisting direction of the outer layer wire 42a constituting the outer layer 42 is different from the twisting direction of the first inner layer wire 43a constituting the first inner layer 43 and the second inner layer wire 44a constituting the second inner layer 44.

[0080] The twist pitch of the outer layer wire 42a constituting the outer layer 42 may be the same as or different from the twist pitch of the first inner layer wire 43a constituting the first inner layer 43 and the second inner layer wire 44a constituting the second inner layer 44.

[0081] The outer layer wire 42a is disposed so as not to drop into the valley portion 47 between the circumferentially adjacent first inner layer wires 43a, 43a, that is, so as not to abut against the outer surface of the first inner layer wire 43a at the valley portion 47.

[0082] As a result, the imaginary circle formed by the radially inner edge of the pre-stranded wire 41 in each outer layer wire 42a and the imaginary circle formed by the radially outer edge of the pre-stranded wire 41 in each first inner layer wire 43a are substantially the same. In other words, the contact portion between the radially inner edge of the pre-stranded wire 41 in each outer layer wire 42a and the radially outer edge of the pre-stranded wire 41 in the first inner layer wire 43a is located on the same circumference.

[0083] The diameter d2 of the first inner layer wire 43a is larger than the diameter d1 of the outer layer wire 42a.

[0084] By using the wires 42a, 43a, and 44a in which the relationships d1=0.523×d2 and d3=0.694×d2 are satisfied, the cross-sectional shape of the pre-stranded wire 37 can be made substantially circular without compression or with a low compression rate.

[0085] Next, a method for producing the pre-stranded wire 41 will be described.

[0086] First, an inner layer 46 consisting of two layers, a first inner layer 43 and a second inner layer 44, is formed so as to have a hollow portion 45 in the center. Next, an outer layer 42 is formed on the outside of the inner layer 46 so as to have a twist direction different from the twist direction of the inner layer 46, thereby forming a preliminary stranded wire 41.

[0087] Using this preliminary stranded wire 41, stranded wires 51 and 52 as shown in Fig. 12 and Fig. 13 can be obtained by the same manufacturing method as in the above-mentioned embodiment 1. Also, the preliminary stranded wire 37 can be made into a stranded wire 53.

[0088] Alternatively, as shown in FIG. 14, a preliminary strand 61 may be formed with 49 outer layer wires 42a, and 20 first inner layer wires 43a and 20 second inner layer wires 44a.

[0089] By using the strands 42a, 43a, and 44a in which the relationships d1=0.506×d2 and d3=0.760×d2 are satisfied, the cross-sectional shape of the pre-stranded wire 61 can be made substantially circular without compression or with a low compression rate.

[0090] The other structures are the same as those in the first to fifth embodiments, and therefore the description thereof will be omitted.

[0091] In this sixth embodiment as well, the same effects as those in the first to fifth embodiments can be achieved.

[0092] [Example 7] In the above-mentioned Example 6, the twist direction of the strands 42a constituting the outer layer 42 of the preliminary stranded wire 41 was different from the twist direction of the strands 43a, 44a constituting each layer 43, 44 constituting the inner layer 46. However, in the present example, the twist direction of the strands of the strands of the outer layer and the twist direction of the strands of the strands of each layer constituting the inner layer are the same, and the twist pitch of the strands of the strands of the outer layer and the twist pitch of the strands of the strands of each layer constituting the inner layer are different.

[0093] The other structure is the same as that of the sixth embodiment, and therefore the description thereof will be omitted.

[0094] In the seventh embodiment as well, the same effects as those in the sixth embodiment can be achieved.

[0095] [Example 8] In the above-mentioned Examples 1 to 7, the preliminary stranded wires 1, 27, 37, 41, 61 are constituted by the outer layer 2, 21, 31, 42, and the inner layer 6, 24, 34, 46 which is constituted by two layers, that is, the first inner layer 3, 22, 32, 43 and the second inner layer 4, 23, 33, 44, but the inner layer may be constituted by one layer or three or more layers. The number of wires constituting each inner layer is the same for all layers constituting the inner layers.

[0096] The other structures are the same as those in the first to seventh embodiments, and therefore the description thereof will be omitted.

[0097] In this eighth embodiment as well, the same effects as those in the first to seventh embodiments can be achieved. [Explanation of symbols]

[0098] 1,27,37,41,61 Pre-stranded wire 2,21,31,42 outer layer 5 Hollow part 6,24,34,46 Inner layer 18,18A,19,20,28,29,30,38,39,40,51,52,53 stranded wire

Claims

1. A pre-stranded wire is formed having an outer layer formed by arranging a plurality of wires on the same circumference, and an inner layer formed of one or more layers of wires arranged on the same circumference inside the outer layer, and a hollow portion is formed inside the inner layer. The pre-stranded wire is then cut to a predetermined length, A method for producing a stranded wire, comprising the steps of: pulling out and removing one element wire constituting the innermost layer; and then removing all other element wires constituting the innermost layer.

2. A pre-stranded wire is formed having an outer layer formed by arranging a plurality of wires on the same circumference, and an inner layer formed of one or more layers of wires arranged on the same circumference inside the outer layer, and a hollow portion is formed inside the inner layer, and the pre-stranded wire is cut to a predetermined length, This method for manufacturing a stranded wire is characterized in that one wire constituting the innermost layer is pulled out and removed, and then the wires adjacent to that wire are sequentially removed, thereby removing a portion of the wires of all the wires constituting the innermost layer.

3. The inner layer is composed of a plurality of layers, After removing all the other wires that make up the innermost layer, 2. The method for producing a stranded wire according to claim 1, wherein after one wire constituting the layer immediately outside the innermost layer is pulled out and removed, all other wires constituting that layer are removed.

4. The wires constituting the outer layer are formed to have the same diameter and are smaller in diameter than the wires constituting the outermost layer of the inner layer, 4. The method for producing a stranded wire according to claim 1, wherein the number of strands constituting the outer layer is at least seven more than the number of strands constituting each of the inner layers.

5. 5. The method for producing a stranded wire according to claim 4, wherein the stranding direction of the wires constituting the inner layer is different from the stranding direction of the wires constituting the outer layer.

6. the twisting direction of the wires constituting the inner layer is the same as the twisting direction of the wires constituting the outer layer; 5. The method for producing a stranded wire according to claim 4, wherein the twist pitch of the wires constituting the inner layer is different from the twist pitch of the wires constituting the outer layer.

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