Coated conductive wire and multi-core cable

Abstract

A coated conductive wire according to one embodiment of the present disclosure comprises a conductor part and a coating part. The coating part covers the conductor part. The conductor part is formed by twisting together a plurality of strands. The conductor part includes a conductor. The conductor is adjacent to the coating part. A direction in which the conductor part extends is defined as a Z direction. In the conductor, the half-value width is 15.5 mm or less. The half-value width is calculated from a histogram of the twist pitch in the Z direction of the conductor.

Description

Insulated conductors and multi-core cables

[0001] The present disclosure relates to a coated conductor wire and a multi-core cable. This application claims priority to Japanese Patent Application No. 2023-099060, filed on June 16, 2023. The entire contents of said Japanese Patent Application are incorporated herein by reference.

[0002] Conventionally, a multi-core cable including a conductor formed by twisting together a plurality of wires and a covering portion that covers the conductor has been known (see, for example, International Publication No. 2017 / 056278). The conductor formed by twisting together a plurality of wires is manufactured using, for example, a bobbin-fixed manufacturing device or a bobbin-rotating manufacturing device (see, for example, Japanese Patent Application Laid-Open Nos. 2006-328603 and 4-075733).

[0003] International Publication No. 2017 / 056278 Japanese Patent Application Laid-Open No. 2006-328603 Japanese Patent Application Laid-Open No. 4-075733

[0004] The covered conductor wire of the present disclosure includes a conductor portion and a covering portion. The covering portion covers the conductor portion. The conductor portion is formed by twisting together a plurality of wires. The conductor portion includes a conductor. The conductor is adjacent to the covering portion. The direction in which the conductor portion extends is defined as the Z direction. The conductor has a half-width of 15.5 mm or less. The half-width is calculated from a histogram of the twist pitch of the conductor in the Z direction.

[0005] FIG. 1 is a cross-sectional view of a multi-core cable according to the present embodiment. FIG. 2 is a cross-sectional view of a covered conductor in the multi-core cable according to the present embodiment. FIG. 3 is a cross-sectional view of a covered conductor in the multi-core cable according to the present embodiment. FIG. 4 is a cross-sectional view of a conductor in the multi-core cable according to the present embodiment. FIG. 5 is a schematic cross-sectional view of a conductor for explaining a method for calculating the twist pitch of the wires. FIG. 6 is a schematic distribution diagram for explaining a histogram of the twist pitch. FIG. 7A is a schematic diagram showing an apparatus for manufacturing a conductor in which multiple wires of the multi-core cable according to the present embodiment are twisted together. FIG. 7B is a schematic diagram showing an apparatus for manufacturing a multi-core cable according to the present embodiment. FIG. 8 is a diagram showing the configuration of a quality evaluation system 40 for a multi-core cable. FIG. 9 is a diagram showing the configuration of a learning device 60. FIG. 10 is a diagram showing an example of a convolutional neural network according to the present embodiment. FIG. 11 is a diagram showing the configuration of a processed image generation device 50. FIG. 12A is a diagram showing a tomographic image input to the neural network. FIG. 12B is an enlarged view of the rectangular area in FIG. 12A. FIG. 13A is a diagram showing a processed image when the filter size is {f1=5, f2=1, f3=5}. FIG. 13B is an enlarged view of the area shown by the rectangle in FIG. 13A. FIG. 14A is a diagram showing a processed image when the filter size is {f1=10, f2=1, f3=5}. FIG. 14B is an enlarged view of the area shown by the rectangle in FIG. 14A. FIG. 15A is a diagram showing a processed image when the filter size is {f1=15, f2=1, f3=5}. FIG. 15B is an enlarged view of the area shown by the rectangle in FIG. 15A. FIG. 16A is a diagram showing a processed image when the filter size is {f1=25, f2=1, f3=5}. FIG. 16B is an enlarged view of the area shown by the rectangle in FIG. 16A. FIG. 17A is a diagram showing a processed image when the filter size is {f1=35, f2=1, f3=5}. Fig. 17B is an enlarged view of the area represented by the rectangle in Fig. 17A. Fig. 18A is a view showing a processed image when the filter size is {f1=45, f2=1, f3=5}. Fig. 18B is an enlarged view of the area represented by the rectangle in Fig. 18A. Fig. 19A is a view showing a processed image when the filter size is {f1=55, f2=1, f3=5}.FIG. 19B is an enlarged view of the area represented by the rectangle in FIG. 19A. FIG. 20A is a view showing a processed image when the filter size is {f1=35, f2=1, f3=15}. FIG. 20B is an enlarged view of the area represented by the rectangle in FIG. 20A. FIG. 21A is a view showing a processed image when the filter size is {f1=35, f2=5, f3=15}. FIG. 21B is an enlarged view of the area represented by the rectangle in FIG. 21A. FIG. 22A is a view showing a processed image when the filter size is {f1=35, f2=15, f3=15}. FIG. 22B is an enlarged view of the area represented by the rectangle in FIG. 22A. FIG. 23A is a view showing a processed image when the filter size is {f1=35, f2=1, f3=5}. FIG. 23B is an enlarged view of the area represented by the rectangle in FIG. 23A. FIG. 24A is a diagram showing a processed image when the filter size is {f1=35, f2=1, f3=10}. FIG. 24B is an enlarged view of the area shown by the rectangle in FIG. 24A. FIG. 25A is a diagram showing a processed image when the filter size is {f1=35, f2=1, f3=15}. FIG. 25B is an enlarged view of the area shown by the rectangle in FIG. 25A. FIG. 26A is a diagram showing a processed image when the filter size is {f1=35, f2=1, f3=25}. FIG. 26B is an enlarged view of the area shown by the rectangle in FIG. 26A. FIG. 27A is a diagram showing a processed image when the filter size is {f1=35, f2=1, f3=45}. FIG. 27B is an enlarged view of the area shown by the rectangle in FIG. 27A. FIG. 28A is a diagram showing a processed image when the filter sizes are {f1 = 35, f2 = 1, f3 = 55}. FIG. 28B is an enlarged view of the rectangular area in FIG. 28A. FIG. 29 is a diagram showing appropriate and optimal values ​​for the number of filters and filter size of the convolutional neural network in FIG. 10. FIG. 30 is a diagram showing the configuration of a center position detection device 70. FIG. 31 is a diagram showing the configuration of an index calculation device 80. FIG. 32 is a diagram showing an example of connection of the center positions of the cross sections of the wires. FIG. 33 is a diagram showing example trajectory data of each wire. FIG. 34 is a diagram for explaining a first twist pitch. FIG. 35 is a diagram for explaining a second twist pitch. FIG. 36 is a diagram for explaining a third twist pitch.Fig. 37 is a diagram for explaining the first twist pitch. Fig. 38 is a flowchart showing the operating procedure during learning. Fig. 39 is a flowchart showing the quality evaluation procedure for a multi-core cable. Fig. 40 is a flowchart showing the procedure for detecting the center position in step S202. Fig. 41 is a diagram showing a configuration in which the functions of multi-core cable quality evaluation system 40 are realized using software. Fig. 42 is a schematic diagram showing an apparatus for manufacturing a conductor in which multiple wires of the multi-core cables relating to samples 9 and 10 are twisted together.

[0006] [Problem to be Solved by the Present Disclosure] Conventionally, multi-core cables connected to sensors used in anti-lock brake systems (ABS) or the like, or to electric parking brakes (EPB) or the like, can be bent in complex ways as actuators are driven, etc. Therefore, there is a demand for improved bending resistance of multi-core cables.

[0007] The present disclosure has been made to solve the above-mentioned problems. More specifically, it provides a covered conductor wire and a multi-core cable with improved bending resistance. [Advantages of the present disclosure] According to the present disclosure, a covered conductor wire and a multi-core cable with improved bending resistance can be obtained.

[0008] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0009] (1) An image generation method according to one aspect of the present disclosure includes the steps of: acquiring a tomographic image of a cross section perpendicular to a longitudinal direction of an object including a plurality of rod-shaped materials or a plurality of rod-shaped hollows; and generating, from the acquired tomographic image, an image in which the pixels in the cross section of the materials or hollows in the acquired tomographic image are bright at the center and the pixels gradually become darker in the radial direction of the cross section of the materials or hollows, using a trained model that generates an image from the tomographic image in which the pixels in the cross section of the materials or hollows in the acquired tomographic image are bright at the center and the pixels gradually become darker in the radial direction of the cross section of the materials or hollows. This makes it possible to generate an image that is easy to separate into single materials or hollows when multiple materials or hollows are in contact.

[0010] (2) In the image generation method described in (1) above, the trained model is configured by a convolutional neural network with three convolutional layers. The trained model can be generated by a convolutional neural network with three convolutional layers that has high learning ability and is efficient.

[0011] (3) In the image generation method of (2) above, the size of one side of the filter (kernel size) of the first-stage convolutional layer is the number of pixels corresponding to a size between 0.88 and 2.64 times the diameter of the cross section of the material or hollow. This allows the processing capacity of the first-stage convolutional layer to be appropriately set.

[0012] (4) In the image generation method of (2) above, the size of one side of the filter in the third-stage convolutional layer is the number of pixels corresponding to a size between 0.59 and 1.47 times the diameter of the cross section of the material or hollow. This allows the processing capacity of the third-stage convolutional layer to be appropriately set.

[0013] (5) A quality evaluation method for a multi-core cable according to one aspect of the present disclosure includes the steps of generating a tomographic image and generating an image as described in any one of (1) to (4) above, wherein the step of acquiring the tomographic image includes acquiring a tomographic image of a cross section perpendicular to the longitudinal direction of a multi-core cable including a plurality of wires, and the step of generating an image includes generating, for each of the tomographic images of the plurality of cross sections of the multi-core cable, an image in which a pixel at the center of the cross section of the wire in the tomographic image is bright and the pixels gradually become darker in a radial direction of the cross section of the wire. The quality evaluation method for a multi-core cable further includes the steps of detecting center positions of the cross sections of the wires from the generated images, determining trajectories of the wires by connecting the center positions of the cross sections of the wires in the plurality of cross sections, and calculating, based on the trajectories of the wires, an index representing the twist pitch of the wires, or calculating, based on the trajectories of the plurality of wires, an index representing the twist pitch of an assembly in which a plurality of wires are twisted together. This allows an image to be generated that shows that multiple wires are likely to be separated into a single wire when they are in contact, and the twist pitch can be calculated with high accuracy using the center position of the wire.

[0014] (6) In the method for evaluating the quality of a multi-core cable according to (5), the step of detecting the center position includes a step of binarizing the obtained image, thereby making it possible to appropriately separate an image that is likely to be separated into single strands into single strands.

[0015] (7) The method for evaluating the quality of a multi-core cable according to (5) above further comprises a step of calculating statistics of an index representing the twist pitch. The statistics representing the twist pitch can be used to evaluate the quality of the multi-core cable.

[0016] (8) In the method for evaluating the quality of a multi-core cable according to (7), the statistical quantity of the index representing the twist pitch is the half-width of the frequency calculated from a histogram of the index representing the twist pitch. The quality of the multi-core cable can be evaluated based on whether the twist pitch varies widely as the statistical quantity of the index.

[0017] (9) A covered conductor according to one aspect of the present disclosure includes a conductor portion and a covering portion. The covering portion covers the conductor portion. The conductor portion is formed by twisting together a plurality of wires. The conductor portion includes a conductor. The conductor is adjacent to the covering portion. The direction in which the conductor portion extends is defined as the Z direction. The conductor has a half-width of 15.5 mm or less. The half-width is calculated from a histogram of the twist pitch of the conductor in the Z direction.

[0018] (10) In the coated conductor of (9) above, when two cross sections perpendicular to the Z direction and spaced apart from each other in the Z direction are considered, the twist pitch may be calculated based on the amount of displacement of the relative positions of the wires between the two cross sections in a relative coordinate system. The relative coordinate system may have the center of gravity of the conductor in the cross section as its origin.

[0019] (11) In the coated conductor of (10) above, the distance between the two cross sections may be 1 mm.

[0020] (12) In the coated conductor of (10) or (11) above, the histogram may be created from the amount of displacement of the relative positions of each of the plurality of strands.

[0021] (13) In the coated conductor of (9) to (12) above, the histogram may be created for a portion of the conductor that is 50 mm long in the Z direction.

[0022] (14) In the coated conductor according to any one of (9) to (13), the conductor may include a first outer conductor and a second outer conductor. The histogram may be created from the twist pitches of the first outer conductor and the second outer conductor.

[0023] (15) In the coated conductor of any one of (9) to (14) above, the conductor portion may include an inner conductor. The inner conductor may be disposed apart from the coating portion.

[0024] (16) A multi-core cable according to one aspect of the present disclosure may include the coated conductor according to any one of (9) to (15) above.

[0025] [Details of the embodiment of the present disclosure] <Configuration of multi-core cable> Fig. 1 is a cross-sectional view of a multi-core cable 1 according to the present embodiment. As shown in Fig. 1, the multi-core cable 1 according to the embodiment of the present disclosure is, for example, a multi-core cable 1 connected to a sensor used in a vehicle's ABS or an electric parking brake, and mainly includes a plurality of covered conductor wires 2 and a sheath layer 30. The covered conductor wires 2 are surrounded by the sheath layer 30. The plurality of covered conductor wires 2 are composed of two covered conductor wires 2a and two covered conductor wires 2b. The number of covered conductor wires 2 is not particularly limited. The multi-core cable 1 may include at least one of the covered conductor wires 2a and the covered conductor wire 2b. The number of covered conductor wires 2a may be three or more, or may be one. The number of covered conductor wires 2b may be three or more, or may be one. The number of covered conductor wires 2b may be zero.

[0026] Here, the direction in which the multi-core cable 1 extends is defined as the Z direction (the Z direction shown in FIG. 1 ). Directions perpendicular to the Z direction are defined as the X direction and the Y direction. The X direction is perpendicular to the Y direction. The cross section shown in FIG. 1 is a plane perpendicular to the Z direction.

[0027] <Sheath Layer> The sheath layer 30 may have a two-layer structure. Specifically, the sheath layer 30 includes an outer sheath layer 31 and an inner sheath layer 32. The two coated conductor wires 2 a and the two coated conductor wires 2 b are surrounded by the outer sheath layer 31. The inner sheath layer 32 is disposed inside the outer sheath layer 31. Specifically, the inner sheath layer 32 covers the outer circumference of each of the two coated conductor wires 2 a and the two coated conductor wires 2 a so as to fill the space between the outer sheath layer 31 and the coated conductor wires 2 b.

[0028] Any flexible synthetic resin may be used as the main component of the inner sheath layer 32. The material constituting the inner sheath layer 32 may be, for example, a polyolefin such as polyethylene or EVA (Ethylene-Vinyl Acetate), a polyurethane elastomer, or a polyester elastomer.

[0029] The outer sheath layer 31 may be mainly made of a synthetic resin having excellent flame retardancy and abrasion resistance, such as polyurethane.

[0030] 1 , in a cross section of the multi-core cable 1 in the Z direction, the outer sheath layer 31 has an annular shape. The inner sheath layer 32 is connected to the inner circumferential surface of the outer sheath layer 31. In other words, the outer periphery 32a of the inner sheath layer 32 has a circular shape.

[0031] The minimum distance from the outer periphery 32a of the inner sheath layer 32 to the coated conductor wire 2 is preferably 0.3 mm, more preferably 0.4 mm. The maximum distance from the outer periphery 32a of the inner sheath layer 32 to the coated conductor wire 2 is preferably 0.9 mm, more preferably 0.8 mm. The minimum outer diameter of the inner sheath layer 32 is preferably 6.0 mm, more preferably 7.3 mm. The maximum outer diameter of the inner sheath layer 32 is preferably 10 mm, more preferably 9.3 mm.

[0032] The thickness of the outer sheath layer 31 is preferably 0.3 mm or more and 0.7 mm or less. A tape member such as paper may be wound between the sheath layer 30 and the coated conductor wire 2a as a restraining member.

[0033] <Coated Conductor> Fig. 2 is a cross-sectional view of a coated conductor 2a in the multi-core cable 1 according to the present embodiment. Fig. 3 is a cross-sectional view of a coated conductor 2b in the multi-core cable 1 according to the present embodiment.

[0034] 2, the covered conductor wire 2a includes a conductor portion 4 and a covering portion 22. The covering portion 22 covers the conductor portion 4. The conductor portion 4 is formed by twisting together a plurality of wires 5. The conductor portion 4 may have any configuration as long as it includes a conductor 21 adjacent to the covering portion 22.

[0035] 2 , the conductor portion 4 includes an outer conductor 21 a and an inner conductor 21 b. The outer conductor 21 a is adjacent to the coating portion 22. The inner conductor 21 b is not adjacent to the coating portion 22. In other words, the inner conductor 21 b is disposed away from the coating portion 22.

[0036] The outer conductor 21a includes a first outer conductor 21a1, a second outer conductor 21a2, a third outer conductor 21a3, a fourth outer conductor 21a4, a fifth outer conductor 21a5, and a sixth outer conductor 21a6. The outer conductors 21a are arranged around the inner conductor 21b, on the outer side of the inner conductor 21b. That is, the first outer conductor 21a1, the second outer conductor 21a2, the third outer conductor 21a3, the fourth outer conductor 21a4, the fifth outer conductor 21a5, and the sixth outer conductor 21a6 are arranged in a circular arrangement surrounding the inner conductor 21b. In this manner, the coated conductor 2a may include multiple outer conductors 21a and inner conductors 21b. On the other hand, as shown in FIG. 3, in the coated conductor 2b, the conductor portion 4 may be composed of only one conductor 21.

[0037] The covering portion 22 is laminated on the outer periphery of the conductor portion 4 to cover the conductor portion 4. As shown in Figures 2 and 3, the cross-sectional shape of the covering portion 22 is annular. The thickness of the covering portion 22 is not particularly limited, but is, for example, 0.1 mm or more and 5 mm or less.

[0038] The coating 22 may be made of any insulating material. Therefore, the coating 22 may be formed from a composition primarily composed of a synthetic resin. While there are no particular limitations on the material as long as it is insulating, the primary component of the coating 22 is preferably a copolymer of ethylene and an α-olefin from the viewpoint of flex resistance. The coating 22 may contain additives such as a flame retardant, a flame retardant aid, an antioxidant, a lubricant, a colorant, a reflectivity imparting agent, a masking agent, a processing stabilizer, and a plasticizer. Furthermore, the coating 22 may contain resins other than the above-mentioned primary component resin.

[0039] The lower limit of the product C×E (unit: MPa / K) of the linear expansion coefficient C of the coating 22 from 25°C to -35°C and the modulus of elasticity E at -35°C is 0.01 MPa / K. Meanwhile, the upper limit of the product C×E is 0.9 MPa / K. The upper limit of the product C×E is preferably 0.7 MPa / K, more preferably 0.6 MPa / K. If the product C×E is smaller than the lower limit, the mechanical properties of the coating 22, such as strength, may be insufficient. On the other hand, if the product C×E exceeds the upper limit, the coating 22 becomes less likely to deform at low temperatures. Therefore, the bending resistance of the coated conductor 2 at low temperatures may be reduced. The product C×E can be adjusted by adjusting the α-olefin content, the content ratio of the main component resin, etc.

[0040] The lower limit of the linear expansion coefficient C (unit: / K) of the coating 22 from 25°C to -35°C is preferably 1 x 10-5 / K, more preferably 1 x 10-4 / K. On the other hand, the upper limit of the linear expansion coefficient C of the coating 22 is preferably 2.5 x 10-4 / K, more preferably 2 x 10-4 / K. If the linear expansion coefficient C of the coating 22 is less than the lower limit, the mechanical properties of the coating 22, such as strength, may be insufficient. On the other hand, if the linear expansion coefficient C of the coating 22 exceeds the upper limit, the coating 22 becomes less likely to deform at low temperatures. As a result, the bending resistance of the coated conductor 2a at low temperatures may be reduced.

[0041] The lower limit of the elastic modulus E (unit: MPa) of the covering portion 22 at −35° C. is preferably 1000 MPa, more preferably 2000 MPa. On the other hand, the upper limit of the elastic modulus E of the covering portion 22 is preferably 3500 MPa, more preferably 3000 MPa. If the elastic modulus E of the covering portion 22 is less than the lower limit, the mechanical properties of the covering portion 22, such as strength, may be insufficient. On the other hand, if the elastic modulus E of the covering portion 22 exceeds the upper limit, the covering portion 22 becomes less likely to deform at low temperatures, and the bending resistance of the covered conductor 2a at low temperatures may be reduced.

[0042] The linear expansion coefficient C is a linear expansion coefficient measured in accordance with the test method for dynamic mechanical properties described in JIS-K7244-4 (1999). The linear expansion coefficient C is a value calculated from the dimensional change of a thin plate with respect to a temperature change using a viscoelasticity measuring device (for example, "DVA-220" manufactured by IT Measurement Control Co., Ltd.). The elastic modulus E is a value measured in accordance with the test method for dynamic mechanical properties described in JIS-K7244-4 (1999). The elastic modulus E is a value of the storage elastic modulus measured using a viscoelasticity measuring device (for example, "DVA-220" manufactured by IT Measurement Control Co., Ltd.).

[0043] Fig. 4 is a cross-sectional view of the conductor portion 4 in the multi-core cable 1 according to this embodiment. As shown in Fig. 4, the conductor portion 4 is formed by twisting together a plurality of wires 5 at a constant pitch (twist pitch P). The wires 5 only need to be electrically conductive. Therefore, the material constituting the wires 5 is not particularly limited, and may be, for example, a copper wire, a copper alloy wire, an aluminum wire, or an aluminum alloy wire.

[0044] In this embodiment, the number of element wires 5 included in one conductor portion 4 is 72. The covered conductor wire 2a includes six outer conductors 21a and one inner conductor 21b. Therefore, the covered conductor wire 2a includes 504 element wires 5. The number of element wires 5 may be changed appropriately depending on the application of the multi-core cable 1, the diameter of the element wires 5, etc. The lower limit of the number of element wires 5 included in one covered conductor wire 2 is preferably 196, and more preferably 294. On the other hand, the upper limit of the number of element wires 5 included in one covered conductor wire 2 is preferably 2,450, and more preferably 2,000.

[0045] The lower limit of the diameter of the wire 5 is preferably 40 μm, more preferably 50 μm, and even more preferably 60 μm, while the upper limit of the diameter of the wire 5 is preferably 100 μm, and more preferably 90 μm.

[0046] In a cross section of the conductor 4 perpendicular to the Z direction, the lower limit of the area ratio of the void regions between the multiple strands 5 is 5%, more preferably 6%, and even more preferably 8%. On the other hand, the upper limit of the area ratio of the void regions is 20%, more preferably 19%, and even more preferably 18%. If the area ratio of the void regions is less than the lower limit, large bending stresses are likely to be locally applied to the strands 5 when the multi-core cable 1 is bent. This may result in a decrease in the bending resistance of the multi-core cable 1. On the other hand, if the area ratio of the void regions exceeds the upper limit, the extrusion moldability of the coating 22 decreases. As a result, the roundness of the coated conductor wire 2 and the adhesion between the coating 22 and the conductor 4 may decrease. In other words, when the conductor 4 is exposed at the end of the coated conductor wire 2, the conductor 4 is more likely to move relative to the coating 22. This may result in a decrease in terminal workability. Furthermore, the coated conductor wire 2 may be more susceptible to deformation and water infiltration.

[0047] The area occupied by the gap regions between the strands 5 is calculated by subtracting the total cross-sectional area of ​​the strands 5 from the area of ​​the portion surrounded by the gap 22 (the cross-sectional area of ​​the conductor 4, including the gap between the gap 22 and the conductor 4 and the gap between the strands 5) using a photograph of a cross section of the coated conductor 2, which includes the conductor 4 and the coating 22 that coats the conductor 4. Specifically, the area occupied by the gap regions can be calculated by, for example, binarizing the shading of the cross-sectional photograph into strands and gaps, and then performing image processing to determine the area of ​​the gaps. This image processing can be performed by, for example, using software such as "Paint Shop Pro" to convert the image into two shades of gray, visually checking to set a threshold value so that the boundaries of the strands 5 are correctly distinguished, and then calculating the area proportion of each binarized region using a histogram.

[0048] Here, a method for calculating the twist pitch P will be described. FIG. 5 is a schematic cross-sectional view of a conductor illustrating a method for calculating the twist pitch P of the wires 5. Here, a method for calculating the twist pitch P of any wire 5 included in the conductor 4 will be described. First, a quality evaluation system 40 for the multicore cable 1, which will be described later, identifies center positions O01A-O72A of each of the multiple wires 5 on cross section A at any position in the Z direction. The coordinates of the center positions O01A-O72A of the wires 5 on cross section A are expressed as relative positions in a relative coordinate system VA, whose origin is the center position OA of the conductor 4 on cross section A. The center position OA of the conductor 4 is determined from the center positions O01A-O72A of each of the multiple wires 5 included in the conductor 4. Specifically, the center positions O01A-O72A of each of the multiple wires 5 are regarded as the center of gravity of each of the multiple wires 5 on cross section A. Assuming that each of the multiple wires 5 has the same cross-sectional area, the center of gravity of the multiple wires 5 as a whole is determined as the center of gravity of the conductor portion 4 based on the center of gravity positions of the multiple wires 5. This center of gravity position of the conductor portion 4 on cross section A is regarded as the center position OA of the conductor portion 4 on cross section A. The coordinates of the center position of each of the multiple wires 5 are determined using a relative coordinate system VA with the center position OA of the conductor portion 4 determined in this way as the origin. In this way, the coordinates of the center position of each of the multiple wires 5 on the cross section at an arbitrary position in the Z direction are determined.

[0049] Next, central positions O01B to O72B of the plurality of wires 5 are identified in cross section B using a method similar to that used to identify the central position of the wire 5 in cross section A. Cross section B is a cross section located adjacent to cross section A in the Z direction (i.e., different from cross section A). The coordinates of the central positions O01B to O72B of the wires 5 in cross section B are expressed as relative positions in a relative coordinate system VB whose origin is the central position OB of the conductor portion 4 in cross section B. As in the case of cross section A, the central position OB of the conductor portion 4 is determined from the central positions O01B to O72B of each of the plurality of wires 5 included in the conductor portion 4.

[0050] 5 shows the center position 001A of one wire 5 in cross section A and the center position 001B of one wire 5 in cross section B, assuming that the relative coordinate system VB has been translated so that the origin (center position OB) of the relative coordinate system VB coincides with the origin (center position OA) of the relative coordinate system VA. In other words, in FIG. 5, the center position O01A of the wire 5 in cross section A and the center position O01B of the wire 5 in cross section B are virtually shown on the same plane.

[0051] As shown in Figure 5, the circumferential displacement dθ1 of the wires 5 is determined around the center position OA (OB) of the conductor portion 4. The twist pitch P of the wires 5 is calculated by P = l × 360 / dθ, where l is the distance between cross-section A and cross-section B in the Z direction. In this way, when two cross-sections spaced apart in the Z direction are considered, the twist pitch P for the portion of the wires 5 located between the two cross-sections is calculated based on the displacement dθ1 of the relative position of the wires 5 between the two cross-sections in a relative coordinate system with the center of gravity of the conductor portion 4 at the origin. In other words, by setting multiple cross-sections at short intervals in the Z direction for one wire 5, the twist pitch P (local twist pitch P) for each portion of the wire 5 located between two adjacent cross-sections among the multiple cross-sections can be determined.

[0052] Next, a histogram of the twist pitch P in the Z direction will be described. FIG. 6 is a schematic distribution diagram illustrating a histogram of the twist pitch P of the conductor portion 4. In FIG. 6, the horizontal axis represents the twist pitch P (unit: mm) described above, and the vertical axis represents the frequency (unit: pieces). The series range of the twist pitch P may be set at 1 mm intervals, for example. Furthermore, the lower limit of the series range of the twist pitch P may be set as the class value of the twist pitch P. Specifically, in a series range of the twist pitch P from 0 mm to less than 1 mm, the class value of the twist pitch P may be set to 0 mm. In a series range of the twist pitch P from 1 mm to less than 2 mm, the class value of the twist pitch P may be set to 1 mm. In a series range of the twist pitch P from 2 mm to less than 3 mm, the class value of the pitch P may be set to 2 mm. Note that the frequency depends on the number of data points of the twist pitch P calculated below. As shown in FIG. 6, F1 represents the frequency at the mode of the twist pitch P. F2 is a frequency equivalent to half the value of frequency F1. The twist pitch P corresponding to frequency F2 may be calculated by interpolating the frequencies in the class values ​​of two adjacent twist pitches P. For example, if frequency F2 corresponds to 50, the number of frequencies at a class value of 1 mm is 40, and the number of frequencies at a class value of 2 mm is 70, the twist pitch P corresponding to frequency F2 of 50 is calculated to be 1.3 mm (rounded to one decimal place). There are two twist pitches P corresponding to frequency F2 calculated in this way. The half-value width W is the difference between the twist pitches P at these two points. In this way, the half-value width W is calculated.

[0053] The number of data points for creating a histogram of the twist pitch P is determined based on the distance between the two cross sections and the length in the Z direction of the conductor 21 to be measured.

[0054] When the distance l between the two cross sections is 1 mm, the histogram may be calculated, for example, for a portion of the conductor 4 that is 50 mm long in the Z direction. In this case, the number of data points for the twist pitch P of one wire 5 is 50. When it is desired to expand the measurement target area of ​​the wire 5 in the Z direction, the length of the conductor 4 in the Z direction to be measured may be increased. The histogram may be calculated for a portion of the conductor 4 that is 100 mm long in the Z direction. In this case, the number of data points for the twist pitch P of one wire 5 is 100. Increasing the number of data points in this way makes it possible to create a histogram that more accurately reflects the degree of variation in the twist pitch P in the Z direction.

[0055] The distance l between the two cross sections may be reduced. For example, when the length of the conductor 4 in the Z direction is 50 mm, the distance l between the two cross sections may be 0.1 mm. In this case, the number of data points for the twist pitch P of one wire 5 is 500. Increasing the number of data points in this way makes it possible to create a histogram that reflects with higher accuracy the local variation in the twist pitch P in the Z direction. In other words, the twist pitch P of the conductor 4 in the narrower Z direction is reflected in the histogram. In this way, the distance l between the two cross sections and the length of the conductor 4 in the Z direction may be adjusted to set any number of data points.

[0056] The histogram may reflect not only the variation in the Z direction but also the variation in the twist pitch P among the multiple wires 5. Specifically, the histogram may be calculated from the displacements dθ1 to dθ72 of the relative positions of the multiple wires 5. A single conductor 4 includes multiple wires 5. Therefore, the local twist pitch P may be calculated for each of the multiple wires 5. If the twist pitch P of each of the multiple wires 5 is included in the number of data points, the histogram can reflect the variation in the twist pitch P among the multiple wires 5 included in a single conductor 4.

[0057] When the coated conductor wire 2a includes multiple conductor portions 4, the histogram may reflect variations in the twist pitch P of the wires 5 included in each of the multiple conductor portions 4. Specifically, the first outer conductor 21a1, the second outer conductor 21a2, the third outer conductor 21a3, the fourth outer conductor 21a4, the fifth outer conductor 21a5, and the sixth outer conductor 21a6 each include multiple wires 5. Therefore, the twist pitch P of the wires 5 included in each conductor portion 4 may be calculated individually. If the twist pitch P of the wires 5 included in each conductor portion 4 is included in the number of data points, the histogram can reflect variations in the twist pitch P of the wires 5 included in the multiple conductor portions 4. In this way, a histogram can be created that also reflects variations in the twist pitch P of the wires 5 among the multiple conductor portions 4.

[0058] Here, a feature of the coated conductor wire 2 according to the first embodiment is that the half-value width W calculated from a histogram of the twist pitch P of the wires 5 in the conductor 21 is 15.5 mm or less. The less frequently regions in the coated conductor wire 2 have a locally large twist pitch P, the more improved the bending resistance of the coated conductor wire 2. In particular, a small half-value width W of the twist pitch P means that the twist pitch P varies less. In other words, a small half-value width W of the twist pitch P of the wires 5 reduces the frequency of regions in the wires 5 where the twist pitch P is locally large.

[0059] Furthermore, when the multi-core cable 1 is bent, a greater bending stress is applied to the outer conductor 21a than to the inner conductor 21b. Therefore, the half width W of the twist pitch P of the element wires 5 in the outer conductor 21a has a greater effect on the bending resistance of the multi-core cable 1 than the half width W of the twist pitch P of the element wires 5 in the inner conductor 21b.

[0060] (Method of manufacturing a multi-core cable) Fig. 7A is a schematic diagram showing an apparatus for manufacturing a conductor 21 formed by twisting together a plurality of wires 5 of a multi-core cable 1 according to this embodiment. The conductor 21 formed by twisting together a plurality of wires 5 can be manufactured using the bobbin-fixed manufacturing apparatus shown in Fig. 7A. As shown in Fig. 7A, the apparatus for manufacturing the conductor 21 mainly includes a plurality of rollers 100-105, a plurality of supply reels 200, a batten 300, a die 400, an arm 600, and a winding unit 700. The plurality of supply reels 200 are installed so as to be fixed to the floor.

[0061] The supply reel 200 is a bobbin around which the wires 5 are wound. The wires 5 are supplied by the rotation of the supply reel 200, which is fixed to the floor. As shown in FIG. 7A , the wires 5 wound around the supply reel 200 are supplied to the mesh plate 300 via rollers 100 to 105. The mesh plate 300 has, for example, a circular planar shape. The mesh plate 300 has multiple guide holes (not shown). The number of guide holes corresponds to the number of wires 5 to be twisted. The multiple guide holes are formed so as to be distributed around the center of the mesh plate 300, preferably at equal intervals. The multiple wires 5 are then fed toward the die 400 by passing through each guide hole and being distributed around the center of the mesh plate 300.

[0062] The strands 5 dispersed by the mesh plate 300 are then gathered in the die 400. The strands 5 gathered in the die 400 are twisted together by the twisting roller 500. The twisted strands 5 are supplied to the winding unit 700 along the arm 600. The arm 600 is driven to rotate in the rotation direction R (shown in FIG. 7A ). The twisted strands 5 are then wound and accommodated in the winding unit 700. In this manner, the conductor 21 is manufactured in which a plurality of strands 5 are twisted together.

[0063] The half-value width W of the twist pitch P can be changed by the pass line ratio L. The distance from the twist roller 500 to the closest supply reel 201 of the multiple supply reels 200 is defined as pass line L1. The distance from the twist roller 500 to the farthest supply reel 203 of the multiple supply reels 200 is defined as pass line L2. The pass line ratio L is calculated by L2 / L1. The pass lines L1 and L2 correspond to the length of the wire 5 along the transport path of the wire 5 from the supply reels 201 and 203 to the twist roller 500. The pass line ratio can be adjusted by changing the position of the twist roller 500 (twist point). The pass line ratio may be reduced by adjusting the relative positions of the multiple supply reels 200 with respect to the twist roller 500 and the arrangement of the rollers 101 to 105. As a result, the half-value width W of the twist pitch P of the wire 5 can be reduced, as described below.

[0064] 7B is a schematic diagram showing an apparatus for manufacturing multi-core cable 1 according to this embodiment. Multi-core cable 1 can be manufactured using the apparatus for manufacturing multi-core cable 1 shown in FIG. 7B. The apparatus for manufacturing multi-core cable 1 mainly includes a plurality of conductor supply reels 801, a twisting unit 802, an inner sheath layer covering unit 803, a storage unit 803a, an outer sheath layer covering unit 804, a storage unit 804a, a cooling unit 805, and a winding unit 806.

[0065] The conductor supply reel 801 is, for example, a bobbin around which the conductor 21 is wound. The conductor supply reel 801 may be the winding unit 700 shown in Fig. 7A. The conductors 21 wound around each of the multiple conductor supply reels 801 are supplied to a twisting unit 802. The multiple conductors 21 are twisted together in the twisting unit 802 to form the conductor portion 4.

[0066] The conductor 4 is supplied to the inner sheath layer covering portion 803. The inner sheath layer covering portion 803 extrudes the resin stored in the storage portion 803a to the outside of the conductor 4. In this way, the inner sheath layer 32 is formed on the outside of the conductor 4.

[0067] The conductor portion 4 on which the inner sheath layer 32 is formed is supplied to the outer sheath layer covering portion 804. The outer sheath layer covering portion 804 extrudes the resin stored in the storage portion 804a to the outside of the inner sheath layer 32. In this way, the outer sheath layer 31 is formed on the outside of the inner sheath layer 32.

[0068] The conductor portion 4 on which the outer sheath layer 31 is formed is supplied to the cooling portion 805. The supplied conductor portion 4 is cooled in the cooling portion 805, whereby the sheath layer 30 formed from the inner sheath layer 32 and the outer sheath layer 31 is hardened. In this manner, the multi-core cable 1 is manufactured. The multi-core cable 1 is supplied to the winding portion 806, and is wound and accommodated in the winding portion 806.

[0069] <Effects> The coated conductor wire 2 according to the present disclosure includes a conductor portion 4 and a coating portion 22. The coating portion 22 coats the conductor portion 4. The conductor portion 4 is formed by twisting together a plurality of wires 5. The conductor portion 4 includes a conductor 21. The conductor 21 is adjacent to the coating portion 22. The direction in which the conductor portion 4 extends is defined as the Z direction. The conductor 21 has a half-width W of 15.5 mm or less. The half-width W is calculated from a histogram of the twist pitch P of the conductor in the Z direction.

[0070] This reduces the frequency of occurrence of regions with locally large twist pitch P in the wires 5. As a result, the coated conductor wire 2 has improved bending resistance. The multi-core cable 1 including the coated conductor wire 2 can also have improved bending resistance.

[0071] When two cross sections of the coated conductor 2 are considered, which are perpendicular to the Z direction and spaced apart from each other in the Z direction, the twist pitch P may be calculated based on the displacement of the relative positions of the wires 5 between the two cross sections in a relative coordinate system. The relative coordinate system may have the origin at the center of gravity of the conductor in the cross section (the center positions OA and OB of the conductor portion 4). In this way, the local twist pitch P of the wires 5 included in the coated conductor 2 can be calculated.

[0072] In the coated conductor 2, the distance 1 between the two cross sections may be 1 mm. In this way, a histogram of the twist pitch P can be created based on a sufficient number of data points. In addition, the twist pitch P of the portion of the conductor 21 that is narrower in the Z direction is reflected in the histogram.

[0073] In the coated conductor 2, the histogram may be created for a portion of the conductor 21 that is 50 mm long in the Z direction. In this way, a histogram of the twist pitch P can be created based on a sufficient number of data points.

[0074] In the coated conductor wire 2, the histogram may be created from the displacement dθ of the relative position of each of the plurality of element wires 5. In this way, the histogram can reflect not only the variation in the twist pitch P in the Z direction of a single element wire 5, but also the variation in the twist pitch P among the plurality of element wires 5 included in one conductor 21.

[0075] In the coated conductor 2a, the conductor 21 may include a first outer conductor 21a1 and a second outer conductor 21a2. The histogram may be created from the twist pitch P of each of the first outer conductor 21a1 and the second outer conductor 21a2. In this way, a histogram including the variation in the twist pitch P of the wires 5 among the multiple conductors 21 can be created.

[0076] In the coated conductor wire 2a, the conductor portion 4 may include an inner conductor 21b. The inner conductor 21b may be disposed away from the coating portion 22. In this manner, the twist pitch P of the wires 5 in the outer conductor 21a and the twist pitch P of the wires 5 in the inner conductor 21b can be reflected in the histogram.

[0077] The multi-core cable 1 according to the present disclosure may include any of the above-described covered conductor wires 2. In this way, a multi-core cable 1 with improved bending resistance can be obtained.

[0078] In order to verify the effects of the coated conductor wire 2 a according to the present embodiment, the following test was carried out. Specifically, for a sample of a multi-core cable having the configuration shown in Fig. 1, the correlation between the half-width W and the pull-out force, the bending resistance, and the frequency of abnormal spark points was evaluated.

[0079] <Test Subjects> Table 1 shows the configuration of multi-core cables 1 including coated conductor wires 2a for Samples 1 to 10, as well as the pull-out force, bending resistance, and frequency of spark abnormalities for each sample. The specific configuration of the multi-core cables 1 for Samples 1 to 10 is described below. The multi-core cables 1 for Samples 1 to 8 are composed of two coated conductor wires 2a, two coated conductor wires 2b, and a sheath layer 30. Two coated conductor wires 2a and two coated conductor wires 2b are twisted together to form a core. The sheath layer 30 is extruded around the core. The sheath layer 30 includes an outer sheath layer 31 and an inner sheath layer 32. The inner sheath layer 32 is primarily made of cross-linked polyolefin. The minimum thickness of the inner sheath layer 32 is 0.45 mm. The outer diameter of the inner sheath layer 32 is 7.4 mm. The outer sheath layer 31 is primarily made of flame-retardant cross-linked polyurethane. The thickness of the outer sheath layer 31 is 0.5 mm. The outer diameter of the outer sheath layer 31 is 8.4 mm. The resin component of the sheath layer 30 was cross-linked by electron beam irradiation at 180 kGy. The coated conductor wire 2a has a conductor portion 4 and a coating portion 22. The conductor portion 4 is composed of six outer conductors 21a and one inner conductor 21b twisted together. The outer diameter of the conductor portion 4 is 2.4 mm. The coating portion 22 is formed by extruding an insulating layer-forming structure around the conductor portion 4. The outer diameter of the coating portion 22 is 3 mm. The coating portion 22 was irradiated with electron beam irradiation at 60 kGy to cross-link the resin component. The conductor portion 4 is composed of six outer conductors 21a and one inner conductor 21b twisted together, each of which is composed of 72 strands 5. The diameter of the strands 5 is 80 μm. The coated conductor 2b is composed of a conductor 21 and a coating 22. The outer diameter of the conductor 21 is 0.72 mm. The coating 22 is formed by extruding a cross-linked flame-retardant polyolefin around the outer periphery of the conductor 21. The outer diameter of the coating 22 is 1.45 mm. The conductor 21 is composed of 60 strands 5 twisted together. The diameter of the strands 5 is 80 μm. The multicore cables 1 of Samples 1 to 8 are multicore cables 1 formed from conductors 21 manufactured using the bobbin-fixed manufacturing apparatus shown in FIG. 7A.The multi-core cables 1 of Samples 9 and 10 are multi-core cables 1 formed from conductors 21 manufactured using the bobbin rotation type manufacturing apparatus shown in FIG.

[0080] Fig. 42 is a schematic diagram showing an apparatus for manufacturing conductor 21 formed by twisting together multiple strands 5 of multi-core cables 1 according to Samples 9 and 10. Multi-core cables 1 according to Samples 9 and 10 can be formed from conductor 21 manufactured using the bobbin rotation type manufacturing apparatus shown in Fig. 42. As shown in Fig. 42, the apparatus for manufacturing conductor 21 formed by twisting together multiple strands 5 of multi-core cables 1 according to Samples 9 and 10 mainly includes multiple supply reels 210, a batten 310, a die 410, and a cradle 211. As shown in Fig. 42, multiple supply reels 210 are fixed to cradle 211 so as to be arranged circumferentially about central axis A1.

[0081] The supply reel 210 is a bobbin around which the wire 5 is wound. The cradle 211 rotates about a central axis A1. The supply reel 210, which is fixed to the cradle 211, revolves about the central axis A1, thereby supplying the wire 5. As shown in FIG. 42 , the plurality of wires 5 wound around the supply reel 210 are supplied toward a die 410 via a mesh plate 310. The mesh plate 310 rotates in synchronization with the cradle 211. The plurality of wires 5 are gathered in the die 410 and twisted together.

[0082] As shown in Figure 42, in a bobbin rotation type manufacturing apparatus, the pass line is the distance L10 from the supply reel 210 to the die 410. The multiple supply reels 210 are arranged on the circumference of a center axis A1. Therefore, the distance L10 from each of the multiple supply reels 210 to the die 410 is equal to each other. Therefore, the pass line ratio L is 1. Sample 9 is a multi-core cable 1 manufactured by a method substantially similar to the method disclosed in Japanese Patent Application Laid-Open No. 2006-328603. Sample 10 is a multi-core cable 1 manufactured by a method substantially similar to the method disclosed in Japanese Patent Application Laid-Open No. 4-075733.

[0083]

[0084] As shown in Table 1, the test subjects were multicore cables 1 including ten types of coated conductor wires 2a, Samples 1 to 10. Samples 1, 2, 3, 4, 9, and 10 are comparative examples. Samples 5 to 8 are examples. The half-value width W of the twist pitch P of the outer conductor 21a in the coated conductor wires 2a of Samples 1, 2, 3, 4, 9, and 10 was 16 mm or more. In particular, the half-value width W of the twist pitch P of the outer conductor 21a in the coated conductor wires 2a of Samples 9 and 10, which were manufactured using a bobbin rotation manufacturing device, was 18 mm or more. On the other hand, the half-value width W of the twist pitch P of the outer conductor 21a in the coated conductor wires 2a of Samples 5 to 8 was 15.5 mm or less.

[0085] When a conductor 21 formed by twisting together a plurality of wires 5 of a multi-core cable 1 is manufactured using a bobbin rotation type manufacturing apparatus such as that shown in Fig. 42, centrifugal force is applied to the wires 5 as the bobbin revolves, causing runout, even if the pass line ratio L is 1. On the other hand, when a conductor 21 formed by twisting together a plurality of wires 5 of a multi-core cable 1 is manufactured using a fixed bobbin type manufacturing apparatus such as that shown in Fig. 7A, the bobbin does not revolve, so runout does not occur in the wires 5. Therefore, the half width W of the twist pitch P of the outer conductor 21a of Samples 1 to 4 manufactured using the fixed bobbin type manufacturing apparatus is smaller than the half width W of the twist pitch P of the outer conductor 21a of Samples 9 and 10 manufactured using the fixed bobbin type manufacturing apparatus.

[0086] As shown in Table 1, the median twist pitch P of the coated conductor wires 2a of Samples 1 to 10 is 26.0 or more and 26.5 or less. In other words, there is no significant difference between the median twist pitches P of the coated conductor wires 2a of Samples 1 to 10. The median twist pitch P refers to the value of the twist pitch P that is exactly in the middle when the data points are sorted in ascending order from the smallest to the largest number when calculating a histogram. When the number of data points is even, the median is the average value of the two middle-ranked points.

[0087] In the coated conductor wires 2a of Samples 1 to 10, the coefficient of linear expansion C of the coating 22 is 2.0×10 / K. In the coated conductor wires 2a of Samples 1 to 10, the modulus of elasticity E of the coating 22 is 2800 MPa. That is, in the coated conductor wires 2a of Samples 1 to 10, the product C×E is 0.56 MPa / K, respectively.

[0088] <Test Method> The method for measuring the pull-out force of the coating 22 will be described. For the coated conductor wires 2a of Samples 1 to 10, the coating 22 was removed in the Z direction, leaving 50 mm of the coating 22 exposed, to expose the conductor 4. Next, a metal plate (5 mm thick) with a hole whose inner diameter was larger than that of the conductor 4 and smaller than the outer diameter of the coating 22 was prepared. The conductor 4 was passed through the hole in the metal plate, and the metal plate was fixed and the conductor 21 was pulled up at a speed of 200 mm / min. During this process, the coating 22 was caught on the metal plate and could not be pulled up, and only the conductor 21 was pulled out of the coating 22. The force required to pull out a 50 mm long conductor 21 from a 50 mm long coating 22 was measured, and the maximum value was taken as the pull-out force. The results are shown in Table 1. The pull-out force is preferably 20 N or greater.

[0089] Next, a method for measuring the number of flexing times of the multi-core cable 1 will be described. The flex resistance of the multi-core cable 1 was evaluated based on the number of flexing times. Specifically, two mandrels with a diameter of 60 mm were prepared, arranged horizontally and parallel to each other. Then, the multi-core cables 1 of Samples 1 to 8 were passed vertically between the two mandrels. The multi-core cable 1 was bent horizontally by 90° so that the upper end of the multi-core cable 1 abutted against the upper side of one of the mandrels. Then, the multi-core cable 1 was bent in the opposite direction by 90° so that the upper end of the multi-core cable 1 abutted against the upper side of the other mandrel. This operation was repeated. The test conditions were as follows: a downward load of 2 kg was applied to the lower end of the multi-core cable 1, the temperature was −30°C, and the flexing rate was 60 times / min. In this test, the number of flexing times until the multi-core cable 1 broke (became unable to conduct electricity) was measured. The results are shown in Table 1. The flexing time is preferably 27,000 or more.

[0090] Next, a method for measuring the frequency of abnormal spark points using a spark test will be described. The spark test is performed during the extrusion process in which the coating 22 is formed around the outer periphery of the conductor 4. The frequency of abnormal spark points is the number of pinholes and exposed conductor portions detected per 1 mm (megameter) of the coated conductor 2a. A spark tester (HB15F) manufactured by Clinton was used for the spark test. The set voltage of the spark tester was 5 kV. The frequency of abnormal spark points is preferably 0.1 times / mm or less.

[0091] <Evaluation> In samples 1, 3, 5, 7, 9, and 10, which have a porosity of 4%, the pull-out force of the covering portion 22 is 70 N. In samples 2, 4, 6, and 8, which have a porosity of 20%, the pull-out force of the covering portion 22 is 20 N. In other words, it can be seen that the smaller the porosity, the smaller the pull-out force of the covering portion 22. In other words, as described above, it can be seen that a larger porosity reduces the adhesion between the covering portion 22 and the conductor portion 4. Note that the pull-out force of the covering portion 22 in samples 1 to 10 is 20 N or more in all cases.

[0092] As shown in Table 1, the number of flexures in Sample 2 is greater than the number of flexures in Sample 1. The half-width W in Sample 2 is the same as the half-width W in Sample 1. On the other hand, the porosity in Sample 2 is greater than that in Sample 1. This result shows that the number of flexures is greater when the porosity of the conductive portion is smaller. Table 1 shows that the above result occurs when comparing samples with the same half-width W but different porosities. For example, the above result is shown by comparing Sample 3 with Sample 4, Sample 5 with Sample 6, and Sample 7 with Sample 8.

[0093] From a similar perspective, the frequency of spark abnormal points in Sample 2 is slightly higher than that in Sample 1. Table 1 shows that the above result is obtained when comparing samples with the same half-width W but different porosities.

[0094] As shown in Table 1, the number of flexions in Sample 5 is greater than that in Sample 1. The porosity in Sample 5 is the same as that in Sample 1. Meanwhile, the half-width W in Sample 5 is smaller than that in Sample 1. From these results, it can be seen that a smaller half-width W corresponds to a larger number of flexions. In other words, Table 1 shows that the above results are obtained when comparing samples with the same porosity but different half-width W. For example, the above results are demonstrated by comparing Sample 2 with Sample 6, Sample 3 with Sample 7, and Sample 4 with Sample 8. In particular, the number of flexions in Samples 5 to 8, which are examples, is 27,000 or more. Note that the number of flexions in Samples 9 and 10, which were manufactured using a bobbin rotation type manufacturing apparatus, is 5,000 or less. This is because the half-width W in Samples 9 and 10, which were manufactured using a bobbin rotation type manufacturing apparatus, is large.

[0095] As shown in Table 1, the frequency of abnormal spark points in Sample 5 is lower than that in Sample 1. The porosity in Sample 5 is the same as that in Sample 1. Meanwhile, the half-width W in Sample 5 is smaller than that in Sample 1. From these results, it can be seen that a smaller half-width W results in a lower frequency of abnormal spark points. In other words, Table 1 shows that the above results are obtained when comparing samples with the same porosity but different half-width W. For example, the above results are demonstrated by comparing Sample 2 with Sample 6, Sample 3 with Sample 7, and Sample 4 with Sample 8. In particular, the frequencies of abnormal spark points in Samples 5 to 8, which are examples, are all 0.1 times / Mm or less. On the other hand, the frequencies of abnormal spark points in Samples 1, 2, 3, 4, 9, and 10, which are comparative examples, are all greater than 0.1 times / Mm. In particular, the frequencies of abnormal spark points in Samples 9 and 10, which were manufactured using a bobbin rotation type manufacturing apparatus, are all greater than 1.0 times / Mm. This is because the half-value width W of Samples 9 and 10, which were manufactured using the bobbin rotation type manufacturing apparatus, was large.

[0096] From the above results, the half-value width W of the twist pitch P of the outer conductor 21a is smaller in the multi-core cable 1 formed from the conductor 21 manufactured by the bobbin fixed type manufacturing equipment than in the multi-core cable 1 formed from the conductor 21 manufactured by the bobbin rotation type manufacturing equipment.

[0097] Furthermore, the smaller the half-value width W, the smaller the number of flexing times, and in particular, if the half-value width W is 15.5 mm or less, the number of flexing times will be 27,000 or more. In other words, if the half-value width W is small, the flex resistance will be improved.

[0098] Furthermore, the smaller the half-value width W, the lower the frequency of spark abnormal points. In particular, if the half-value width W is 15.5 mm or less, the frequency of spark abnormal points is 0.1 times / mm or less. In other words, if the half-value width W is small, the occurrence of pinholes in the coating 22 of the coated conductor wire 2 a is suppressed.

[0099] Furthermore, the smaller the porosity, the greater the number of bending times. In other words, a smaller porosity improves bending resistance. Similarly, the smaller the porosity, the lower the frequency of spark abnormal points. In other words, a smaller porosity suppresses the occurrence of pinholes in the coating 22 of the coated conductor 2a.

[0100] The configuration of a multi-core cable quality evaluation system 40 will be described with reference to Fig. 8. The multi-core cable quality evaluation system 40 includes a processed image generation device 50, a learning device 60, a trained model storage device 41, a center position detection device 70, and an index calculation device 80.

[0101] The learning device 60 generates a trained model that generates a processed image of a tomographic image from a tomographic image of a cross section perpendicular to the longitudinal direction of a multi-core cable including multiple wires. The processed image of the tomographic image is an image in which pixels at the center of the wires in the tomographic image are bright and the pixels gradually become darker in the radial direction of the cross section of the wires.

[0102] The processed image generating device 50 generates a processed image from the acquired tomographic image using the trained model.

[0103] The trained model storage device 41 stores the trained model. The center position detection device 70 detects the center position of the wire included in the processed image.

[0104] The index calculation device 80 calculates an index representing the twist pitch of the wire based on the trajectory of the wire obtained from the center position of the wire in a plurality of processed images.

[0105] The configuration of the learning device 60 will be described with reference to Fig. 9. The learning device 60 includes a data acquisition unit 61, a learning data generation unit 62, and a model generation unit 63.

[0106] The data acquisition unit 61 acquires a tomographic image of a cross section perpendicular to the longitudinal direction of a multi-core cable including a plurality of wires.

[0107] Based on user operation, the learning data generation unit 62 generates a processed image from a tomographic image in which the pixels at the center of each wire in the tomographic image are bright and the pixels gradually become darker in the radial direction of the cross section of each wire. The learning data generation unit 62 uses one tomographic image as input data and generates learning data using a processed image generated from that tomographic image as training data. The learning data generation unit 62 generates multiple pieces of learning data by using multiple tomographic images or parts of tomographic images. Specifically, while viewing the tomographic image, the user places circles of a certain diameter at the position of each wire in the tomographic image. For each placed circle, the learning data generation unit 62 generates a processed image in which the center of the circle is brightest (highest pixel value), gradually becomes darker along the radial direction of the wire, and is darkest on the circumference (pixel value 0). The pixel values ​​of the processed image consist only of the pixel values ​​of the circle and do not include the pixel values ​​of the original tomographic image.

[0108] If the training data is an image in which the pixel values ​​are constant across the entire circle, rather than a processed image as in this embodiment, the binarization process described below may fail to cut two touching wires. On the other hand, if the training data is an image in which only one point at the center of the wire has a constant pixel value, learning becomes difficult. This is because the training may be performed to generate an image in which the error from the training data is small and all pixel values ​​are 0.

[0109] The model generation unit 63 uses multiple pieces of training data to generate a trained model that generates a processed image from a tomographic image in which the pixel at the center of the cross section of the wire in the tomographic image is bright and the pixels gradually become darker in the radial direction of the cross section of the wire. Specifically, the model generation unit 63 inputs input data to the first-stage convolutional layer CV1 of the neural network in Figure 10 and learns the coefficients of filters FL1, FL2, and FL3 so as to reduce the sum of squares of the error between the data output from the third-stage convolutional layer CV3 and the training data. The model generation unit 63 stores the generated trained model in the trained model storage device 41.

[0110] The configuration of the processed image generating device 50 will be described with reference to Fig. 11. The processed image generating device 50 includes a data acquiring unit 51 and an image generating unit 52.

[0111] The data acquisition unit 51 acquires a tomographic image of a cross section perpendicular to the longitudinal direction of a multi-core cable including a plurality of wires.

[0112] The image generation unit 52 uses the trained model stored in the trained model storage device 41 to generate a processed image from the acquired tomographic image in which the pixel at the center of the cross section of each wire in the tomographic image is bright and the pixels gradually become darker in the radial direction of the cross section of each wire. Specifically, the image generation unit 52 inputs the tomographic image to the first-stage convolutional layer CV1 of the trained neural network of Fig. 10 and outputs data output from the third-stage convolutional layer CV3 as a processed image.

[0113] Next, experimental results are shown when the filter size of the neural network is changed. Fig. 12A shows a tomographic image input to the neural network. Fig. 12B is an enlarged view of the rectangular area in Fig. 12A.

[0114] 13A to 19A are diagrams showing processed images when the filter size f1 of the first-stage convolutional layer CV1 is changed.

[0115] FIG. 13A shows a processed image output from the neural network when the filter size is {f1=5, f2=1, f3=5}. FIG. 13B shows an enlarged view of the rectangular area in FIG. 13A. FIG. 14A shows a processed image output from the neural network when the filter size is {f1=10, f2=1, f3=5}. FIG. 14B shows an enlarged view of the rectangular area in FIG. 14A. FIG. 15A shows a processed image output from the neural network when the filter size is {f1=15, f2=1, f3=5}. FIG. 15B shows an enlarged view of the rectangular area in FIG. 15A. FIG. 16A shows a processed image output from the neural network when the filter size is {f1=25, f2=1, f3=5}. FIG. 16B shows an enlarged view of the rectangular area in FIG. 16A. FIG. 17A shows a processed image output from the neural network when the filter size is {f1=35, f2=1, f3=5}. FIG. 17B shows an enlarged view of the rectangular area in FIG. 17A. FIG. 18A shows a processed image output from the neural network when the filter size is {f1=45, f2=1, f3=5}. FIG. 18B shows an enlarged view of the rectangular area in FIG. 18A. FIG. 19A shows a processed image output from the neural network when the filter size is {f1=55, f2=1, f3=5}. FIG. 19B shows an enlarged view of the rectangular area in FIG. 19A.

[0116] 20A to 22A are diagrams showing processed images when the filter size f2 of the second-stage convolutional layer CV2 is changed.

[0117] FIG. 20A shows a processed image output from the neural network when the filter size is {f1=35, f2=1, f3=15}. FIG. 20B shows an enlarged view of the rectangular area in FIG. 20A. FIG. 21A shows a processed image output from the neural network when the filter size is {f1=35, f2=5, f3=15}. FIG. 21B shows an enlarged view of the rectangular area in FIG. 21A. FIG. 22A shows a processed image output from the neural network when the filter size is {f1=35, f2=15, f3=15}. FIG. 22B shows an enlarged view of the rectangular area in FIG. 22A.

[0118] 23A to 28A are diagrams showing processed images when the filter size f3 of the third-stage convolutional layer CV3 is changed.

[0119] FIG. 23A shows a processed image output from the neural network when the filter size is {f1=35, f2=1, f3=5}. FIG. 23B shows an enlarged view of the rectangular area in FIG. 23A. FIG. 24A shows a processed image output from the neural network when the filter size is {f1=35, f2=1, f3=10}. FIG. 24B shows an enlarged view of the rectangular area in FIG. 24A. FIG. 25A shows a processed image output from the neural network when the filter size is {f1=35, f2=1, f3=15}. FIG. 25B shows an enlarged view of the rectangular area in FIG. 25A. FIG. 26A shows a processed image output from the neural network when the filter size is {f1=35, f2=1, f3=25}. FIG. 26B shows an enlarged view of the rectangular area in FIG. 26A. Fig. 27A shows a processed image output from the neural network when the filter size is {f1 = 35, f2 = 1, f3 = 45}. Fig. 27B shows an enlarged view of the rectangular area in Fig. 27A. Fig. 28A shows a processed image output from the neural network when the filter size is {f1 = 35, f2 = 1, f3 = 55}. Fig. 28B shows an enlarged view of the rectangular area in Fig. 28A.

[0120] Based on the above results, appropriate and optimal values ​​for the number of filters and filter size of the convolutional neural network of FIG. 10 will be described with reference to FIG.

[0121] The number n1 (number of channels) of filters FL1 in the first-stage convolutional layer CV1 is set to 128. The size f1 of one side of filters FL1 in the first-stage convolutional layer CV1 is set to 15 to 45 pixels. Furthermore, the size f1 of one side may be set to 35 pixels. The number n2 (number of channels) of filters FL2 in the second-stage convolutional layer CV2 is set to 64 pixels. The size f2 of one side of filters FL2 in the second-stage convolutional layer CV2 is set to 1, 5, or 15 pixels. The size f3 of one side of filters FL3 in the third-stage convolutional layer CV3 is set to 10 to 25 pixels. Furthermore, the size f3 of one side may be set to 15 pixels.

[0122] The diameter d of the wire in the tomographic image is represented by 17 pixels in the original image shown in Fig. 12A. The above-mentioned appropriate value and optimal value based on the diameter d are as follows:

[0123] The size of one side of FL1, 15 to 45 pixels, corresponds to 0.88 to 2.64 times the diameter d of the wire. The size of one side of FL1, 35 pixels, corresponds to 2.06 times the diameter d of the wire. The first-stage filter is responsible for extracting local features from the original image. Generally, to determine whether a wire is present at a certain point in an image, it is necessary to look around that point and determine the area equivalent to one to several wires. The fact that a filter equivalent to about two wires is optimal supports this fact. On the other hand, if the filter is made too large, information from an area that is unnecessarily wide for determining whether a wire is present will be taken in, and the accuracy of the conversion will not improve, or will tend to decrease.

[0124] The side sizes of 1, 5, and 15 pixels for FL2 correspond to 0.06, 0.29, and 0.88 times the diameter d of the wire. The second-stage filter is responsible for understanding the interrelationships between multiple feature maps of the image extracted by the first-stage filter. If the image features extracted by the first-stage filter are sufficiently good, high accuracy can be achieved even with a filter size of 1, that is, without incorporating in-plane information. In some cases, when combining image features extracted by the first-stage filter, bundling feature values ​​slightly shifted in the in-plane direction can result in higher conversion accuracy.

[0125] The size of one side of FL3, 10 to 25 pixels, corresponds to 0.59 to 1.47 times the diameter d of the wire. The size of one side of FL3, 15 pixels, corresponds to 0.88 times the diameter d of the wire. The third-stage filter is responsible for generating an image in which the wires are not touching each other, based on the image features compiled by the second-stage filter. Ideally, it is necessary to generate a large number of shapes about the size of the wire, with a bright center and gradually darkening toward the ends of the wire. Therefore, when referencing the features, comprehensively incorporating information from an area about the size of the wire from that point makes it possible to more accurately determine whether the point is the center of the wire or is far from the center of the wire. Therefore, it makes sense to set the size of f3 to the diameter of the wire, or at least the radius of the wire.

[0126] 30, the configuration of the center position detection device 70 will be described. The center position detection device 70 includes a binarization unit 71, a segmentation unit 72, a distance conversion unit 73, a wire region detection unit 74, and a center detection unit 75.

[0127] The binarization unit 71 binarizes the processed image. The segmentation unit 72 detects a plurality of regions in which the same pixel value is continuous from the binarized image.

[0128] The distance transform unit 73 generates a distance-transformed image for each region. The wire region detection unit 74 generates partial regions by binarizing the distance-transformed image of each region using an adaptive threshold. The wire region detection unit 74 selects an appropriate threshold based on the number of partial regions. Specifically, for each region, the wire region detection unit 74 determines the number of partial regions in which pixels having a first pixel value are consecutive in the binarized distance-transformed image as a count value. The wire region detection unit 74 acquires multiple count values ​​for each region by sequentially increasing the threshold value TH from an initial value until the count value decreases. If the ratio R of the threshold value TH at which the maximum count value among the multiple count values ​​is equal to or greater than a reference value, the wire region detection unit 74 determines the number of partial regions included in the binarized distance-transformed image generated using one of the multiple threshold values ​​TH at which the count value is maximum as the number of wires.

[0129] The center detector 75 detects the position of any pixel in the partial region (for example, the position of the pixel with the highest pixel value) as the center position of the wire.

[0130] The configuration of the index calculation device 80 will be described with reference to Fig. 31. The index calculation device 80 includes a trajectory data generation unit 81, a twist pitch calculation unit 82, a histogram creation unit 83, and a statistics calculation unit 84.

[0131] It is assumed that N processed images RI(i) are generated from N tomographic images X(i) by the processed image generating device 50, where i=1 to N.

[0132] As shown in Figure 32, the trajectory data generation unit 81 connects the center position of the cross section of each wire included in the processed image RI(i) to the closest center position of the cross section of multiple wires included in the processed image RI(i+1), thereby obtaining trajectory data for each wire, as shown in Figure 33.

[0133] In this specification, determining the trajectory of the wire does not mean determining the actual trajectory of the wire itself, but rather determining the coordinates of both ends of each of a plurality of consecutive line segments that approximate the actual trajectory of the wire.

[0134] Here, L ｉ(i=1 to LN) represents the longitudinal position of the multi-core cable, and (X, Y) represents the center position of the cross section of the wire.

[0135] The trajectory of the wire is L ｉ The center position (X, Y) and L ｉ＋１ The center position (X, Y) of the LN-1 coordinate system is approximated by a line segment connecting the center position (X, Y) of the LN-1 coordinate system. ｉ and L ｉ＋１ The interval between the first and second electrodes may be, for example, 10 to 100 μm. LN may be, for example, 3,000 to 5,000.

[0136] The twist pitch calculation unit 82 calculates the first twist pitch, the second twist pitch, the third twist pitch, and the fourth twist pitch as follows: The third twist pitch and the fourth twist pitch are twist pitches of the wires, and the first twist pitch and the second twist pitch are twist pitches of an assembly in which multiple wires are twisted together.

[0137] The twist pitch calculation unit 82 calculates the position L ｉ (i = 1 to LN-1) are selected every K positions. The selected longitudinal position is Z ｉ (i = 1 to N-1). Z ｉ =L Ｋ×ｉ However, N = LN / K. Z ｉ and Z ｉ＋１ The interval between the first and second electrodes may be, for example, 1 mm. N may be, for example, 51.

[0138] FIG. 34 is a diagram for explaining the first twist pitch. ｉ In the cross section of the coated conductor wire 2a, the center of gravity of the central positions of all the wires included in the coated conductor wire 2a is O ｉ (1) The center of gravity of all the wires included in the other coated conductor wire 2a is O ｉ (2). The center of gravity of the central positions of all the wires included in the two coated conductor wires 2a is O ｉ Let's say.

[0139] Z ｉ In the cross section of ｉ and O ｉ (j) (j = 1 to 2) The angle between the line segment connecting these points and the X axis is θｉ Let (j). Z ｉ＋１ In the cross section of ｉ＋１ and O ｉ＋１ (j) (j = 1 to 2) The angle between the line segment connecting these points and the X axis is θ ｉ＋１ The twist pitch calculation unit 82 calculates the following value.

[0140] dθ ｉ (j) = θ ｉ＋１ (j)-θ ｉ (j) PT ｉ (j) = 360 / dθ ｉ (j) For i = 1 to N-1, j = 1 to 2, PT ｉ (j) is the first index. The number of samples of the first index is (N-1)×2.

[0141] FIG. 35 is a diagram for explaining the second twist pitch. ｉ In the cross section of the outer conductor included in one of the coated conductor wires 2a, the positions of the centers of gravity of all the wires included in the outer conductor 21a1 are defined as P ｉ (1, 1), and the center of gravity of all the wires included in the outer conductor 21a2 is P ｉ (1, 2), the center of gravity position of all the wires included in the outer conductor 21a3 is P ｉ (1, 3), the center of gravity of all the wires included in the outer conductor 21a4 is P ｉ (1, 4), the center of gravity of all the wires included in the outer conductor 21a5 is P ｉ (1, 5), the center of gravity of all the wires included in the outer conductor 21a6 is P ｉ The center of gravity of the central positions of all the wires included in the outer conductors 21a1, 21a2, 21a3, 21a4, 21a5, and 21a6 is P ｉ (1)

[0142] In the cross section of Zi, the center of gravity of the outer conductor included in the other coated conductor 2a is defined as follows: ｉ (2, 1), and the center of gravity of all the wires included in the outer conductor 21a2 is P ｉ (2, 2), the center of gravity of all the wires included in the outer conductor 21a3 is P ｉ(2, 3), the center of gravity of all the wires included in the outer conductor 21a4 is P ｉ (2, 4), the center of gravity of all the wires included in the outer conductor 21a5 is P ｉ (2, 5), the center of gravity of all the wires included in the outer conductor 21a6 is P ｉ The center of gravity of the central positions of all the wires included in the outer conductors 21a1, 21a2, 21a3, 21a4, 21a5, and 21a6 is P ｉ (2)

[0143] Z ｉ In the cross section of P ｉ (j) and P ｉ The angle between the line segment connecting (j, k) (j = 1 to 2, k = 1 to 6) and the X axis is θ ｉ Let (j, k). Z ｉ＋１ In the cross section of P ｉ＋１ (j) and P ｉ＋１ The angle between the line segment connecting (j, k) (j = 1 to 2, k = 1 to 6) and the X axis is θ ｉ＋１ (j, k). The twist pitch calculation unit 82 calculates the following values.

[0144] dθ ｉ (j, k) = θ ｉ＋１ (j, k)-θ ｉ (j, k) PT ｉ (j,k)=360 / dθ ｉ (j, k) i = 1 to N-1, j = 1 to 2, k = 1 to 6, PT ｉ (j, k) is the second index. The number of samples of the second index is (N-1) x 2 x 6.

[0145] FIG. 36 is a diagram for explaining the third twist pitch. ｉ In the cross section of the outer conductor included in one of the coated conductor wires 2a, the center of gravity of the M wires included in the outer conductor 21al (k=1 to 6) is defined as P ｉ (1, k), and the center position of each wire included in the outer conductor 21al (k=1 to 6) is P ｉ Let (1, k, m) (m = 1 to M).

[0146] In the cross section of Zi, the center of gravity of the M wires included in the outer conductor 21al (k=1 to 6) is defined as P ｉ (2, k), and the center position of each wire included in the outer conductor 21al (k=1 to 6) is P ｉ Let (2, k, m) (m = 1 to M).

[0147] Z ｉ In the cross section of P ｉ (j, k) and P ｉ The angle between the line segment connecting (j, k, m) (j = 1 to 2, k = 1 to 6, m = 1 to M) and the X axis is θ ｉ Let (j, k, m). Z ｉ＋１ In the cross section of P ｉ＋１ (j, l) and P ｉ＋１ The angle between the line segment connecting (j, k, m) (j = 1 to 2, k = 1 to 6, m = 1 to M) and the X axis is θ ｉ＋１ (j, k, m). The twist pitch calculation unit 82 calculates the following values.

[0148] dθ ｉ (j, k, m) = θ ｉ＋１ (j, k, m)-θ ｉ (j, k, m) PT ｉ (j, k, m) = 360 / dθ ｉ (j, k, m) i = 1 to N-1, j = 1 to 2, k = 1 to 6, m = 1 to M, PT ｉ (j, k, m) is the third index. The number of samples of the third index is (N-1) x 2 x 6 x M.

[0149] FIG. 37 is a diagram for explaining the fourth twist pitch. ｉ In the cross section of the inner conductor 21b included in one of the coated conductor wires 2a, the center of gravity of the M strands included in the inner conductor 21b is defined as S ｉ (1) The center position of each wire included in the inner conductor 21b is S ｉ Let (1, m) (m = 1 to M).

[0150] Z ｉIn the cross section of the other coated conductor 2a, the inner conductor 21b included in the other coated conductor 2a is defined as follows: The center of gravity of the M strands included in the inner conductor 21b is defined as S ｉ (2) The center position of each wire included in the inner conductor 21b is S ｉ Let (2, m) (m = 1 to M).

[0151] Z ｉ In the cross section of S ｉ (j) and S ｉ The angle between the line segment connecting (j, m) (j = 1 to 2, m = 1 to M) and the X axis is θ ｉ Let (j, m) be Z. ｉ＋１ In the cross section of S ｉ＋１ (j) and S ｉ＋１ The angle between the line segment connecting (j, m) (j = 1 to 2, m = 1 to M) and the X axis is θ ｉ＋１ (j, m). The twist pitch calculation unit 82 calculates the following values.

[0152] dθ ｉ (j, m) = θ ｉ＋１ (j, m)-θ ｉ (j, m) PT ｉ (j, m)=360 / dθ ｉ (j, m) For i = 1 to N-1, j = 1 to 2, m = 1 to M, PT ｉ (j, m) is the fourth index. The number of samples of the fourth index is (N-1) x 2 x M.

[0153] The statistics calculation unit 84 calculates statistics of the indices using the histogram of the calculated indices. The statistics may be, for example, the mean, median, variance, standard deviation, or decile of the indices. The statistics may also be the half-width of the frequency calculated from the histogram of the indices.

[0154] The operation procedure during learning will be described with reference to Fig. 38. In step S101, the data acquisition unit 61 acquires a tomographic image of a cross section perpendicular to the longitudinal direction of a multi-core cable including a plurality of wires.

[0155] In step S102, the learning data generation unit 62 generates a processed image from the tomographic image based on a user's operation, in which pixels at the center of the wire in the tomographic image are bright and the pixels gradually become darker in the radial direction of the cross section of the wire. The learning data generation unit 62 uses one tomographic image as input data and generates multiple pieces of learning data using processed images generated from that tomographic image as training data.

[0156] In step S103, the model generation unit 63 uses multiple pieces of training data to generate a trained model that generates a processed image from the tomographic image in which the pixels at the center of the cross section of the wire in the tomographic image are bright and the pixels gradually become darker in the radial direction of the cross section of the wire. The model generation unit 63 stores the generated trained model in the trained model storage device 41.

[0157] The quality evaluation procedure for a multi-core cable will be described with reference to Fig. 39. In step S201, the data acquisition unit 51 of the processed image generation device 50 acquires a tomographic image of the cross section of a multi-core cable including a plurality of wires.

[0158] In step S202, the image generation unit 52 of the processed image generation device 50 uses the trained model stored in the trained model memory device 41 to generate a processed image from the tomographic image acquired in step S201 in which the pixels at the center of the cross section of each wire in the tomographic image are bright and the pixels gradually become darker in the radial direction of the cross section of each wire.

[0159] In step S203, the center position detection device 70 detects the center position of each wire from the processed image.

[0160] In step S204, the trajectory data generating unit 81 of the index calculation device 80 generates trajectory data of each wire by connecting the center positions of each wire in the multiple processed images.

[0161] In step S205, the twist pitch calculation unit 82 of the index calculation device 80 calculates an index representing the twist pitch of each wire or an index representing the twist pitch of an assembly in which multiple wires are twisted together, based on the trajectory data of each wire. Specifically, the twist pitch calculation unit 82 calculates at least one of a first index, a second index, a third index, and a fourth index.

[0162] In step S206, the histogram creation unit 83 of the index calculation device 80 creates a histogram of the calculated index.

[0163] In step S207, the statistics calculation unit 84 of the index calculation device 80 calculates statistics of the calculated index using a histogram.

[0164] The procedure for detecting the center position in step S202 will be described with reference to Fig. 40. In step S301, the binarization unit 71 binarizes the processed image to generate a first binarized image made up of a plurality of pixels having a first pixel value (for example, 1) or a second pixel value (for example, 0).

[0165] In step S302, the segmentation unit 72 detects regions in the first binarized image where pixels having a first pixel value are continuous.

[0166] In step S303, the distance conversion unit 73 calculates the shortest distance from a pixel having a first pixel value (corresponding to a candidate area where a strand exists) in each area to a pixel having a second pixel value (corresponding to a candidate area where a strand does not exist).

[0167] In step S304, the distance transforming unit 73 generates a distance transformed image for each region, in which the pixel value is the shortest distance.

[0168] In step S305, the wire region detection unit 74 sets the threshold value TH to an initial value for each region.

[0169] In step S306, the wire region detection unit 74 binarizes the distance transformation image for each region based on the threshold value TH to generate a binarized distance transformation image consisting of multiple pixels with a first pixel value (1) or a second pixel value (0).

[0170] In step S307, the strand region detection unit 74 obtains, for each region, the number of partial regions in which pixels having the first pixel value (1) contained in the binarized distance transformed image are continuous, as a count value.

[0171] In step S308, if the count value changes to decrease, the process proceeds to step S310, and if the count value does not change to decrease, the process proceeds to step S309.

[0172] In step S309, the wire region detection unit 74 increases the threshold value TH by the step size ΔdTH, and then the process returns to step S305.

[0173] In step S310, the element wire region detection unit 74 calculates, for each region, the ratio R of the number of threshold values ​​TH at which the maximum count value among the multiple count values ​​is reached to the number of all the set threshold values ​​TH.

[0174] In step S311, if the ratio R for each region is equal to or greater than the reference value, the process proceeds to step S312.

[0175] In step S312, the strand region detection unit 74 determines that the number of one or more partial regions generated by one of multiple thresholds (for example, the maximum threshold, the minimum threshold, or the average value of both) when the count value is maximum for each region is the number of strands.

[0176] In step S313, the center detection unit 75 detects the position of one of the pixels in one or more partial regions as the center position of the wire. For example, the center detection unit 75 may detect the position of the pixel in the partial region whose pixel value in the distance transformation image is maximum, or the position of the pixel at the center of gravity of the partial region, as the center position of the wire.

[0177] In the above embodiment, the quality evaluation system 40 for multi-core cables generates a processed image from a cross-sectional image of a multi-core cable perpendicular to the longitudinal direction, the cross-sectional image including multiple strands, in which pixels at the center of the strands in the cross-sectional image are bright and the pixels gradually become darker in the radial direction of the cross-sectional image of the strands, and evaluates the quality of the multi-core cable using the processed image. However, the quality evaluation is not limited to multi-core cables. More strictly, the above-described method can be applied to any object whose presence can be recognized by some change in brightness in the cross-sectional image of the original cross-sectional image. The quality evaluation system 40 may also generate a processed image from a cross-sectional image of an object perpendicular to the longitudinal direction, the cross-sectional image including multiple rod-shaped materials, or a cross-sectional image of an object perpendicular to the longitudinal direction, the cross-sectional image being bright at the center of the cross-sectional image of the materials or hollows, and the pixels gradually become darker in the radial direction of the cross-sectional image of the materials or hollows, and evaluate the quality of the object using the processed image.

[0178] A configuration for implementing the functions of the multi-core cable quality evaluation system 40 using software will be described with reference to Fig. 41. The multi-core cable quality evaluation system 40 includes a processor 502 and a memory 501 connected to a bus 503. The functions described in the above embodiment are implemented by the processor 502 executing a program stored in the memory 501.

[0179] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The basic scope of the present disclosure is defined by the claims, not by the above-described embodiments, and is intended to include any modifications within the scope of the claims and meanings equivalent to the claims.

[0180] 1 Multi-core cable, 2, 2a, 2b Coated conductor, 4 Conductor portion, 5 Wire, 21 Conductor, 21a Outer conductor, 21a1 First outer conductor, 21a2 Second outer conductor, 21a3 Third outer conductor, 21a4 Fourth outer conductor, 21a5 Fifth outer conductor, 21a6 Sixth outer conductor, 21b Inner conductor, 22 Covering portion, 30 Sheath layer, 31 Outer sheath layer, 32 Inner sheath layer, 32a Outer periphery, 100, 101, 102, 103, 104, 105 Roller, 200, 201, 202, 203, 210 Supply reel, 211 Cradle, 300, 310 Mesh plate, 400, 410 Die, 500 Applying roller, 600 Arm, 700 Winding unit, 801 conductor supply reel, 802 twisting unit, 803 inner sheath layer covering unit, 804 outer sheath layer covering unit, 803a, 804a storage unit, 805 cooling unit, 806 winding unit, A, B cross section, C linear expansion coefficient, E elastic modulus, C × E product, F1, F2 frequency, L pass line ratio, L1, L2, L10 pass line, O01A, O01B, O72A, O72B, OA, OB center of gravity position, P twist pitch, A1 central axis, VA, VB relative coordinate system, W half width, dθ displacement amount, l distance between cross sections, 40 quality evaluation system, 41 trained model storage device, 50 processed image generation device, 51, 61 data acquisition unit, 52 image generation unit, 60 learning device, 62 Learning data generation unit, 63 model generation unit, 70 center position detection device, 71 binarization unit, 72 segmentation unit, 73 distance conversion unit, 74 wire region detection unit, 75 center detection unit, 80 index calculation device, 81 trajectory data generation unit, 82 pitch calculation unit, 83 histogram creation unit, 84 statistics calculation unit, 501 memory, 502 processor, 503 bus, CV1, CV2, CV3 convolution layer, FL1, FL2, FL3 filter.

Claims

1. A coated conductor comprising a conductor portion and a coating portion that coats the conductor portion, the conductor portion being formed by twisting together a plurality of wires, the conductor portion including a conductor adjacent to the coating portion, wherein, when the direction in which the conductor portion extends is the Z direction, a half-value width calculated from a histogram of the twist pitch of the conductor in the Z direction is 15.5 mm or less.

2. The coated conductor according to claim 1, wherein, when two cross sections perpendicular to the Z direction and spaced apart from each other in the Z direction are considered, the twist pitch is calculated based on the amount of displacement of the relative position of the wires between the two cross sections in a relative coordinate system whose origin is the center of gravity of the conductor in the two cross sections.

3. The coated conductor according to claim 2, wherein the distance between the two cross sections is 1 mm.

4. The coated conductor according to claim 2 or 3, wherein the histogram is created from the amount of displacement of the relative position for each of the plurality of strands.

5. The coated conductor according to any one of claims 1 to 4, wherein the histogram is created for a portion of the conductor having a length of 50 mm in the Z direction.

6. The coated conductor according to any one of claims 1 to 5, wherein the conductor includes a first outer conductor and a second outer conductor, and the histogram is created from the twist pitch in each of the first outer conductor and the second outer conductor.

7. The coated conductor according to any one of claims 1 to 6, wherein the conductor portion includes an inner conductor, and the inner conductor is disposed apart from the coating portion.

8. A multi-core cable comprising a coated conductor according to any one of claims 1 to 7.

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