Method for manufacturing insulated wire, method for detecting defective part, and manufacturing system for insulated wire

Abstract

Provided are a method for manufacturing an insulated wire, a method for detecting a defective portion, and a manufacturing system for an insulated wire, which can obtain an insulated wire while detecting a defective portion of a conductor or a defective portion generated closer to the conductor side of an insulating film with higher accuracy. 【Solution means】A method for manufacturing an insulated wire having a conductor and an insulating film covering the outer periphery of the conductor, comprising: An application and baking step of providing an insulating film of a multilayer insulating layer by repeatedly forming an insulating layer by applying and baking a resin varnish on the outer periphery of the conductor; A detection step of detecting a defective portion generated in the conductor or the insulating layer, in parallel with the repetition of the formation of the insulating layer by applying and baking the resin varnish. A method for manufacturing an insulated wire.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an insulated wire, a method for detecting a defective portion, and a manufacturing system for an insulated wire.

Background Art

[0002] If there are defects in the conductor or insulating film of an insulated wire, insulation failure occurs at the defective portion. Therefore, the manufactured insulated wire is inspected before shipment to identify and mark the defective portion, and if necessary, the area having the defective portion is removed and then shipped.

[0003] As a method for accurately detecting surface defects of a rectangular enameled wire, for example, Patent Document 1 discloses a method including: irradiating bright-field imaging light onto the flat surface and corner surface of a rectangular enameled wire moving in the longitudinal direction, and imaging bright-field images of the flat surface and the corner surface; irradiating dark-field imaging light along the longitudinal direction of the rectangular enameled wire, and imaging dark-field images of the flat surface and the corner surface; and determining the presence or absence of defects on the flat surface and the corner surface from the bright-field images and the dark-field images. Further, Patent Document 2 discloses an invention of a film defect detection device for an enameled wire, including: a contact member that contacts the surface of the enameled film of the enameled wire linearly moving in a certain direction and is displaced according to the height of a film abnormality generated on the surface of the enameled film; and a displacement meter that acquires the amount by which the contact member is displaced.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Rotating electrical machines such as motors are manufactured, for example, by shortening (segmenting) insulated electric wires and then bending them into hairpin shapes to form segment coils, and inserting these segment coils into slots of a stator (stator) core. When using an insulated electric wire by bending it in this way, insulation failure may occur at the bent or curved portions due to minute defects that are difficult to detect in the state of the insulated electric wire before bending (linear state). Further, as a result of the studies by the present inventors, among the defects of the insulated electric wire, conductor defects and defects existing on the conductor side (more inside) in the thickness direction of the insulating film (insulating film defects on the side closer to the conductor) are likely to cause insulation failure due to bending, while it has become clear that defects on the surface or near the surface of the insulating film do not significantly affect insulation failure. Fig. 1 shows a graph of the relationship between the position in the thickness direction of the defective portion and the insulation breakdown voltage, focusing on the defective portion of the insulating film. As shown in Fig. 1, the closer the position of the defective portion in the insulating film is to the inside (the left side of the graph in Fig. 1), the lower the insulation breakdown voltage. Therefore, it is considered that by detecting more accurately the defects occurring more inside the insulating film and conductor defects in particular, insulation failure that is likely to be manifested by bending or the like can be avoided more efficiently. Referring to Patent Documents 1 and 2 from the above viewpoint, since the techniques described in Patent Documents 1 and 2 are methods for inspecting the appearance of the finished product of enameled wire, it is difficult to detect internal defects that do not appear on the appearance. For example, a method of detecting insulation failure by applying a voltage to the manufactured insulated electric wire and measuring the leakage current can also be considered. However, in order to detect without leakage even defects occurring on the conductor side of the insulating film of the finished insulated electric wire (insulated electric wire having a sufficiently thick insulating film) and conductor defects, it is necessary to apply a very high voltage, which may also cause damage to the insulating film and over-detection.

[0006] An object of the present invention is to provide a method for manufacturing an insulated electric wire, a method for detecting a defective portion, and a manufacturing system for an insulated electric wire that can obtain an insulated electric wire while detecting a defective portion of a conductor and a defective portion occurring on the conductor side of an insulating film with higher accuracy.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that in the production of insulated electric wires, by detecting defective portions in parallel with the repetition of the formation of an insulating layer by applying and baking a resin varnish for forming an insulating film (enamel layer), it is possible to more accurately detect conductor defects and defects on the conductor side of the insulating film, and by marking the defective portions or removing the region having the defective portions if necessary, it is possible to efficiently avoid the use of insulated electric wires that are likely to cause insulation failure due to bending or the like. The present invention has been further studied based on these findings and has been completed.

[0008] That is, the above problems of the present invention have been solved by the following means. [1] A method for manufacturing an insulated electric wire having a conductor and an insulating film covering the outer periphery of the conductor, a coating and baking step of repeatedly forming an insulating layer by applying and baking a resin varnish on the outer periphery of the conductor to provide an insulating film of a multilayer insulating layer; and a detection step of detecting defective portions generated in the conductor or the insulating layer in parallel with the repetition of the formation of the insulating layer by applying and baking the resin varnish. A method for manufacturing an insulated electric wire. [2] The method for manufacturing an insulated electric wire according to [1], wherein in the detection step, the defective portions are detected by measuring leakage current. [3] The method for manufacturing an insulated electric wire according to [1] or [2], wherein in the detection step, the defective portions are detected two or more times during the repetition of the formation of the insulating layer by applying and baking. [4] The method for manufacturing an insulated electric wire according to any one of [1] to [3], wherein in the detection step, the first detection of the defective portions is performed when the thickness of the entire insulating layer is 5 to 90 μm. [5] The method for manufacturing an insulated electric wire according to any one of [1] to [4], wherein the thickness of the insulating film is 25 μm or more. [6] In the production of an insulated wire having a conductor and an insulating film covering the outer periphery of the conductor, when providing an insulating film of a multilayer insulating layer by repeatedly forming an insulating layer by applying and baking a resin varnish on the outer periphery of the conductor, a method for detecting a defective portion, including detecting a defective portion generated in the conductor or the insulating layer in parallel with the repetition of the formation of the insulating layer by applying and baking the resin varnish. 〔7〕 An insulated wire manufacturing system having a conductor and an insulating film covering the outer periphery of the conductor, an application and baking device that repeatedly forms an insulating layer by applying and baking a resin varnish on the outer periphery of the conductor, and a detector that detects a defective portion generated in the conductor or the insulating layer in parallel with the repetition of the formation of the insulating layer by applying and baking the resin varnish. An insulated wire manufacturing system. 〔8〕 The insulated wire manufacturing system according to 〔7〕, wherein the detector is a spark tester. 〔9〕 The insulated wire manufacturing system according to 〔7〕 or 〔8〕, having two or more of the detectors.

Effect of the Invention

[0009] According to the method for manufacturing an insulated wire, the method for detecting a defective portion, and the insulated wire manufacturing system of the present invention, a defective portion of the insulated wire can be detected with higher accuracy.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

[0011] In the present invention or in this specification, when simply referring to an "insulating layer", it means a layer (enamel layer) formed by performing application and baking of a resin varnish once. In the present invention, an insulating layer formed by repeating application and baking of the same resin varnish a plurality of times is regarded as a multi-layer insulating layer. That is, whether the resin varnishes are the same or different, a layer formed by one application and baking is counted as one insulating layer. In other words, when application and baking are repeated, a multi-layer insulating layer in which the same number of insulating layers as the number of repetitions is laminated is formed. In this specification, the shape of the insulated wire including the conductor and the insulating film in a cross-sectional shape orthogonal to the longitudinal direction of the insulated wire may be simply referred to as the cross-sectional shape. The cross-sectional shape in the present invention is not merely that only the cut surface has a specific shape, but the cross-sectional shape is continuously connected in the longitudinal direction of the entire insulated wire. Unless otherwise specified, for any portion in the longitudinal direction of the insulated wire, the cross-sectional shape orthogonal to this direction is substantially the same. In this specification, a numerical range represented using "~" means a range including the numerical values described before and after it as the lower limit value and the upper limit value.

[0012] [Method for Manufacturing Insulated Wire] In one embodiment, the present invention provides a method for producing an insulated wire (hereinafter, also referred to as the "production method of the present invention"). The production method of the present invention is a method for producing an insulated wire having a conductor and an insulating coating covering the outer periphery of the conductor, and includes a coating / baking step of providing an insulating coating of a multilayer insulating layer by repeatedly forming an insulating layer by coating / baking a resin varnish on the outer periphery of the conductor, and a detection step of detecting a defect (also simply referred to as a defect) occurring in the conductor or the insulating layer in parallel with the repeated formation of the insulating layer by coating / baking the resin varnish. In other words, the method for producing an insulated wire includes a detection step of detecting a defect occurring in the conductor or the insulating layer during the repeated coating / baking of the resin varnish on the outer periphery of the conductor. The insulating coating is a multilayer insulating layer (multilayer enamel layer) formed by repeatedly coating / baking a resin varnish. In the manufacturing method of the present invention, defects are detected in parallel with the repeated formation of insulating layers by coating and baking resin varnish (i.e., defects are detected during the formation of the insulating coating), making it possible to accurately detect defects in the insulated wire that may become apparent through bending or other processes.

[0013] In the present invention and this specification, the term "defective portion" of an insulated wire refers to a portion that may cause poor insulation. Examples of such defective portions include surface defects (chips, peeling) of the conductor, internal defects of the conductor, bubbles in the insulating coating (insulating layer), inclusion of foreign matter (gel of resin varnish, carbonized coating, fibers, metal, sand dust, etc.) in the insulating coating (insulating layer), and scratches on the surface of the conductor or insulating coating (insulating layer) (such as scratches due to contact with contact parts). Examples of the internal defects of the conductor include cracks such as fissures, cracks caused by blowholes (or pinholes), and surface swellings.

[0014] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments except as defined in the present invention. Figure 2 is an explanatory diagram schematically showing a state in which a varnish coating device 101 and a baking furnace 102 for applying and baking a resin varnish, a roller 103, and a detector 104 (104A, 104B1, 104B2, 104C) for detecting defective portions of an insulated wire are provided in a manufacturing system 100 of an insulated wire used in the manufacturing method of the present invention. In the resin varnish application and baking process, the resin varnish is applied onto the outer periphery of the conductor 201 by the varnish coating device 101 and then baked in the subsequent baking furnace 102 to form an insulating layer. By repeating this application and baking operation a plurality of times, an insulating film of a multilayer insulating layer is formed. In an example shown in Figure 2, a manufacturing system 100 of an insulated wire that repeats the application and baking operation 12 times (including the first pass line to the twelfth pass line) is shown. In the manufacturing method of the present invention, detection of defective portions is performed in parallel with repetition of formation of the insulating layer by the application and baking of the resin varnish. In an example shown in Figure 2, application and baking of the resin varnish are performed on the front side of the manufacturing system 100, and detection of defective portions of the insulated wire is performed on the back side. Also, the four detectors 104 for detecting the defective portions are respectively provided such that one (detector 104A) is on the third pass line, two (detectors 104B1, 104B2) are on the sixth pass line, and one (detector 104C) straddles the ninth to eleventh pass lines. That is, by detecting defective portions at an appropriate timing in parallel with repetition of formation of the insulating layer by the application and baking of the resin varnish, high detection accuracy for defective portions can be achieved.

[0015] Figure 3 is a cross-sectional view schematically showing a configuration example of an insulated wire 200 manufactured by the manufacturing method of the insulated wire of the present invention. The insulated wire 200 has a conductor 201 and an insulating film 202 that is in contact with the conductor 201 and covers the circumferential surface of the conductor 201. In Figure 3, the conductor 201 is a conductor (flat conductor) having a rectangular cross-sectional shape orthogonal to the longitudinal direction. The insulating film 202 is a multilayer insulating layer in which a plurality of insulating layers 203 formed by application and baking of a resin varnish are laminated. Note that in Figure 3, a part of the boundary between the insulating layers 203 is shown with omission. The cross-sectional shape of the insulating wire 200 is preferably similar to that of the conductor 201. Among them, it is particularly preferable that the shape of the entire insulating film 202, that is, the cross-sectional shape of the insulating film 202 on the outermost surface on the side opposite to the conductor 201 is similar to that of the conductor 201. Note that the similar shape is not limited to a perfect similar shape, and a substantially similar shape may be sufficient.

[0016] In the manufacturing method of the present invention, as the conductor used for the insulating wire, those conventionally used as the conductor of the insulating wire can be used. For example, metal conductors such as copper wires and aluminum wires can be mentioned. The cross-sectional shape perpendicular to the longitudinal direction of the conductor used in the manufacturing method of the present invention is not particularly limited. For example, conductors having a circular or rectangular (square, rectangular (flat angle shape)) cross-sectional shape can be mentioned. In the present invention, a conductor having a rectangular cross-sectional shape is preferable, and a flat angle conductor is more preferable. A conductor having a rectangular cross-sectional shape has a higher occupancy rate with respect to the slot of the stator core compared to a conductor having a circular cross-sectional shape. Therefore, it is preferable for applications such as incorporating a large number of insulating wires into a certain narrow space.

[0017] The characteristic configuration of the manufacturing method of the present invention will be described in more detail below.

[0018] <Coating and baking process> The manufacturing method of the present invention has a coating and baking process in which an operation of applying and baking a resin varnish on the outer periphery of the conductor is repeated a plurality of times, and an insulating film of a multilayer insulating layer is formed on the outer periphery of the conductor by this process. The method of applying the resin varnish on the conductor may be a conventional method. For example, in a varnish coating device, a method using a die having a shape similar to the conductor shape, or when the cross-sectional shape of the conductor is rectangular, a method using a die called a "universal die" formed in a grid shape can be mentioned. The conductor coated with the resin varnish is baked in a baking furnace by a conventional method. Specific baking conditions depend on the shape of the baking furnace used, etc., but if it is a natural convection vertical furnace of about 10 m, it can be achieved by setting the passing time to 10 to 90 seconds at a furnace temperature of 400 to 650 °C.

[0019] The number of repetitions of the application and baking of the resin varnish for forming the insulating film is not particularly limited and can be appropriately set so as to satisfy the provisions of the present invention. In the present invention, the "number of repetitions of application and baking" is synonymous with the number of layers of the multilayer insulating layer. For example, the number of repetitions of application and baking can be 10 or more, 12 or more, or 15 or more. Also, the number of repetitions can be 35 or less, 30 or less, or 25 or less. If the number of repetitions is shown in a preferable range, it is preferably 10 to 35 times, more preferably 12 to 30 times, and even more preferably 15 to 25 times. Similarly, the number of layers of the insulating layer constituting the insulating film can be 10 or more, 12 or more, or 15 or more. Also, the number of layers can be 35 or less, 30 or less, or 25 or less. If the number of layers is shown in a preferable range, it is preferably 10 to 35, more preferably 12 to 30, and even more preferably 15 to 25. Note that the same resin varnish can be used for all the insulating layers, or different types of resin varnishes can be used for each insulating layer for the application and baking.

[0020] In the manufacturing method of the present invention, the coating and baking operation of the resin varnish is preferably carried out such that the thickness of the formed insulating film (the total thickness of the multilayer insulating layer in the finished product) is 25 μm or more, more preferably 30 μm or more, still more preferably 40 μm or more, still more preferably 50 μm or more, and still more preferably 60 μm or more. Also, the coating and baking operation of the resin varnish is preferably carried out such that the thickness of the formed insulating film is 230 μm or less, more preferably 200 μm or less, still more preferably 170 μm or less, and still more preferably 140 μm or less. When the thickness of the formed insulating film is shown within a preferable range, it is preferably 25 to 230 μm, more preferably 30 to 230 μm, still more preferably 40 to 200 μm, still more preferably 50 to 170 μm, and still more preferably 60 to 140 μm. The thickness of the insulating film is measured by 16-point measurement. The 16-point measurement is a commonly used measurement method in this field, and the specific measurement method is described in the pamphlet of International Publication No. 2013 / 073397.

[0021] The insulating layer is an enamel layer formed by applying a resin varnish containing an insulating resin (insulating polymer) onto a conductor and baking it. For the formation of this enamel layer, a resin that can be used for the formation of the enamel layer can be appropriately applied according to the purpose. The resin type can be either a thermosetting resin or a thermoplastic resin, and the insulating layer is preferably an enamel layer formed by curing a thermosetting resin. Examples of the thermosetting resin that can be used for the formation of the enamel layer include polyimide (PI), polyamideimide (PAI), polyurethane, thermosetting polyester (PEst), H-type polyester (HPE), polybenzimidazole, polyesterimide (PEsI), melamine resin, and epoxy resin, etc., and one or more of these can be used.

[0022] Examples of the organic solvent (organic solvent) for varnishing the resin contained in the resin varnish include amide solvents such as N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), and N,N-dimethylformamide (DMF); urea solvents such as N,N-dimethylethyleneurea, N,N-dimethylpropyleneurea, and tetramethylurea; lactone solvents such as γ-butyrolactone and γ-caprolactone; carbonate solvents such as propylene carbonate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate, n-butyl acetate, butyl cellosolve acetate, butyl carbitol acetate, ethyl cellosolve acetate, and ethyl carbitol acetate; glyme solvents such as diglyme, triglyme, and tetraglyme; hydrocarbon solvents such as toluene, xylene, and cyclohexane; phenol solvents such as cresol, phenol, and halogenated phenol; sulfone solvents such as sulfolane; and dimethyl sulfoxide (DMSO). Among them, from the viewpoint of varnish stability due to hydrogen bonding with the resin, the organic solvent is preferably an aprotic solvent, preferably contains DMAc and / or NMP, and more preferably is DMAc and / or NMP. In addition, only one type of the above organic solvent or the like may be used alone, or two or more types may be used in combination.

[0023] The resin varnish may optionally contain various additives such as adhesion aids, foaming agents for bubble formation, antioxidants, antistatic agents, ultraviolet light absorbers, light stabilizers, fluorescent brighteners, pigments, dyes, compatibilizers, lubricants, reinforcing agents, flame retardants, crosslinking agents, crosslinking assistants, plasticizers, thickeners, thinners, and elastomers. Further, the resin varnish may contain inorganic fine particles within a range that does not affect the properties. Examples of such inorganic fine particles include zinc oxide, titanium oxide, tin oxide, silicon carbide, and strontium titanate.

[0024] <Detection Step> The manufacturing method of the present invention has a detection step of detecting a defective portion generated in the conductor or the insulating layer in parallel with the repetition of forming an insulating layer by applying and baking a resin varnish. Note that "detecting a defective portion generated in the conductor or the insulating layer in parallel with the repetition of forming an insulating layer by applying and baking a resin varnish" means that, for example, when the application and baking operations of the resin varnish are repeated n times, at least once during that period (that is, from after the first application and baking operation to before the nth application and baking operation), a defective portion of the insulated wire is detected.

[0025] The number of times of detecting the defective portion of the insulated wire can be appropriately set according to the thickness of the insulating film to be formed, the number of layers of the insulating layer, etc. The detection of the defective portion performed during the repetition of forming an insulating layer by applying and baking the resin varnish is preferably performed two or more times, more preferably three or more times, even more preferably four or more times, and even more preferably five or more times during the repetition of forming an insulating layer by applying and baking the resin varnish. For example, in an example shown in FIG. 2, detection is performed once on the 3rd pass line, twice on the 6th pass line, and once each on the 9th to 11th pass lines, and the number of times of detection during the repetition of forming an insulating layer by applying and baking the resin varnish is six times. Note that when the detection of the defective portion is performed multiple times as described above, the detection method for each defective portion may be the same method, or different methods may be combined. When the detection of the defective portion is performed multiple times, the defective portion may be detected multiple times on the same pass line, may be detected multiple times across different pass lines, or may be detected multiple times on the same pass line and further detected multiple times across different pass lines. For example, in an example shown in FIG. 2, detection is performed twice on the 6th pass line, and detection is performed across the 3rd, 6th, 9th to 11th pass lines.

[0026] In the detection step, the thickness of the entire insulating layer at the time of the first detection is not particularly limited, and the first detection can be performed at a desired timing according to the purpose. For example, the thickness of the entire insulating layer at the time of the first detection is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more, and may be 30 μm or more, or may be 40 μm or more. Further, the thickness is preferably 90 μm or less, more preferably 80 μm or less, and still more preferably 70 μm or less. When the thickness is shown in a preferable range, it is preferably 5 to 90 μm, more preferably 10 to 90 μm, still more preferably 20 to 90 μm, and may be 30 to 80 μm, or may be 40 to 70 μm. By performing the first detection of the defective portion when the thickness of the entire insulating layer is within the above thickness range, defects in the conductor and defects generated in the insulating layer on the conductor side of the insulating film can be detected more accurately. Further, when the detection of the defective portion is performed a plurality of times, each detection after the second time is preferably performed when the thickness increases by 3 to 20 μm, more preferably when the thickness increases by 4 to 15 μm, and still more preferably when the thickness increases by 5 to 10 μm from the thickness of the entire insulating layer at the time of the immediately preceding detection. For example, when the thickness of the entire insulating layer at the time of the first detection is 50 μm, the second detection can be performed when the thickness of the entire insulating layer is preferably in the range of 53 to 70 μm, more preferably in the range of 54 to 65 μm, and still more preferably in the range of 55 to 60 μm. It is also preferable to perform the first detection when the thickness of the entire insulating layer at the time of detection is in the range of 1 / 3 or more and 2 / 3 or less of the thickness of the insulating film at the completion of the insulated wire, and it is also preferable to perform the first detection when the thickness is in the range of 1 / 2 or more and 2 / 3 or less.

[0027] The method for detecting the defective portion is not particularly limited. For example, it includes leakage current measurement, image inspection, ultrasonic inspection, partial discharge inception voltage (PDIV) measurement, corona discharge measurement, eddy current flaw detection measurement, laser outer measurement, contact measurement, etc. Among them, it is preferable to detect the defective portion of the insulated wire by leakage current measurement. In leakage current measurement, it can be determined that there is a defective portion at the location where the leakage current is measured. Examples of the device used for leakage current measurement include a spark tester (manufactured by Shin-Toyo Kiki Co., Ltd., DSE Test Solutions Co., Ltd.). Note that it is known per se to apply these measuring devices (detection devices) to detect defective portions in the insulated wire of a finished product. The characteristic technical viewpoint of the present invention lies in that the inventors recognized the problems in the conventional methods of detecting defective portions by these measuring devices and set new problems, and the characteristic technical element of the present invention is that the above new problems are solved by devising the detection timing as described above. Also, as in the example shown in FIG. 2, when two detections are performed on the sixth pass line, for example, the first detection (detection by the detector 104B1) may be detection by a spark tester and the second detection (detection by the detector 104B2) may be detection by image inspection, or the first detection may be detection by image inspection and the second detection may be detection by a spark tester. In the former case, the shape of the defective portion (insulation failure location) that has sparked by the spark tester can be recorded and confirmed, and in the latter case, minute defective portions that could not be detected by the image sensor can be detected by the spark tester. In addition, by performing analysis processing using artificial intelligence (AI) on the data (such as image data, etc.) obtained by the above detection method, the oversight of defective portions can be reduced, and the defective portions can be detected with higher accuracy.

[0028] When detecting a defective part of an insulated wire by measuring leakage current, the measurement conditions can be appropriately set according to the purpose. For example, the applied voltage is preferably 500 V or more, more preferably 2 kV or more, and even more preferably 4 kV or more. Also, from the viewpoint of reducing damage to the insulating film, the voltage is preferably less than 10 kV, more preferably 8 kV or less, and even more preferably 6 kV or less. Further, when detecting a defective part, if the overall thickness of the insulating layer is thin, the applied voltage may be set low, and if the overall thickness of the insulating layer is thick, the applied voltage may be set high. Also, in leakage current measurement, it can also be set such that when the detected current value exceeds a certain value (threshold value), it indicates the presence of a defective part. Such a threshold value can be appropriately set according to the applied voltage and the type of insulated wire (type of conductor and insulating layer, thickness of insulating layer, etc.).

[0029] In the manufacturing method of the present invention, an example of the case where the detection of a defective part is performed by measuring leakage current is schematically shown in FIG. 4. In the insulated wire 200 shown in FIG. 4, the defective part 204 exists at a position close to the conductor of the insulating film 202. As shown in FIG. 4(a), when detecting the defective part 204 with respect to the completed insulated wire 200, since the thickness of the insulating film 202 is sufficiently thick, the defective part 204 cannot be detected only by applying a certain voltage (a voltage that does not damage the insulating film) with the spark tester 300. In FIG. 4(a), it is necessary to apply a high voltage to detect the defective part 204 with respect to the completed insulated wire 200, and in that case, the insulating film 202 may be damaged. On the other hand, as in the manufacturing method of the present invention shown in FIG. 4(b), when performing leakage current measurement during the formation of the insulating film 202, since the overall thickness of the insulating layer 203 is thin, the defective part 204 can be detected only by applying a low voltage, and damage to the insulating film 202 can also be suppressed. Further, even if the application and baking operations of the resin varnish are repeated later and the overall thickness of the insulating layer 203 becomes thick, since the leakage current is measured at the same position due to the spark generation location 205 (starting from the spark generation location 205), the defective part 204 can be detected without applying a high voltage to the completed insulated wire 200.

[0030] In the manufacturing method of the present invention, it is preferable that the defective portions of the insulated wire (the insulated wire after the formation of the insulating film) are also detected even after the coating and baking process of the resin varnish (after all the repetitions of the formation of the insulating layer by coating and baking the resin varnish). The detection of the defective portions after the coating and baking process may be performed on the pass line after the last coating and baking operation of the resin varnish, and can also be performed at any timing such as after winding the finished insulated wire or before shipment. By detecting the defective portions of the insulated wire after the coating and baking process of the resin varnish, the defective portions can be surely specified on the surface of the insulated wire, markings can be made at the positions of the defective portions, and if necessary, the regions having the defective portions can be removed in advance and shipped. As the method for detecting the defective portions of the insulated wire after the formation of the insulating film, the method described above can be applied as a method for detecting the defective portions in parallel with the repetition of the formation of the insulating layer by coating and baking the resin varnish, and it is preferable to carry out a combination of a plurality of detection methods. Further, it is preferable that the plurality of detection methods include the same detection method as the method for detecting the defective portions in parallel with the repetition of the formation of the insulating layer by coating and baking the resin varnish. For example, the detection method for detecting the defective portions in parallel with the repetition of the formation of the insulating layer by coating and baking the resin varnish can be leakage current measurement, and the detection method for the defective portions of the insulated wire after the formation of the insulating film can be a combination of leakage current measurement, image inspection, and laser outer side measurement.

[0031] The manufacturing method of the present invention may have steps that are usually performed in the manufacturing method of insulated wires, in addition to the above coating and baking process and detection process. Examples of such steps include a wire drawing process, an annealing process, a lubricant coating process, a winding process, etc. Further, it may have a marking process for recording the positions of the defective portions and a removing process for removing the regions having the defective portions.

[0032] [Defect Detection Method] Relating to the manufacturing method of the present invention described above, the present invention provides, in one embodiment, a method for detecting defects occurring in a conductor or an insulating layer in the manufacture of an insulated wire (the detection method of the present invention). That is, according to the present invention: In the manufacture of an insulated wire having a conductor and an insulating film covering the outer periphery of the conductor, when providing an insulating film of a multi-layer insulating layer by repeatedly forming an insulating layer by applying and baking a resin varnish on the outer periphery of the conductor, a method for detecting defects occurring in the conductor or the insulating layer is provided, including detecting the defects occurring in the conductor or the insulating layer in parallel with the repeated formation of the insulating layer by applying and baking the resin varnish. In the detection method of the present invention, the method of repeatedly forming an insulating layer by applying and baking a resin varnish to provide an insulating film of a multi-layer insulating layer, and the method of detecting defects occurring in the conductor or the insulating layer in parallel with the repeated formation of the insulating layer by applying and baking the resin varnish are as described in the manufacturing method of the present invention, and the preferred forms are also the same. That is, the matters described in the manufacturing method of the present invention can be directly applied to the detection method of the present invention. Furthermore, the present invention provides, in one embodiment, a method for manufacturing an insulated wire, including marking and / or removing the defects detected by the above detection method.

[0033] [Manufacturing System for Insulated Wire] The present invention provides, in another embodiment, a manufacturing system for an insulated wire (hereinafter, also referred to as "the manufacturing system of the present invention"). The manufacturing system of the present invention is a manufacturing system for an insulated wire having a conductor and an insulating film covering the outer periphery of the conductor, and includes a coating and baking device that repeatedly forms an insulating layer by applying and baking a resin varnish on the outer periphery of the conductor, and a detector that detects defects occurring in the conductor or the insulating layer in parallel with the repeated formation of the insulating layer by applying and baking the resin varnish. The manufacturing system of the present invention is a system suitable for implementing the manufacturing method of the present invention described above.

[0034] In the manufacturing system of the present invention, the coating and baking apparatus includes at least a varnish coating apparatus for applying a resin varnish and a baking furnace. The coating and baking apparatus can adopt those generally used in the manufacture of insulated electric wires. Also, the number of pass lines provided in the coating and baking apparatus can be appropriately set according to the number of layers of the insulating layer of the insulated electric wire to be manufactured. For example, in an example shown in FIG. 2, the manufacturing system 100 of the present invention has 12 pass lines from the first pass line to the twelfth pass line.

[0035] In the manufacturing system of the present invention, it is preferable that the detector is incorporated in the coating and baking apparatus. More specifically, it is preferably provided between the baking furnace and the varnish coating apparatus, which are arranged in the coating and baking apparatus. The manufacturing system of the present invention preferably has a plurality (two or more) of detectors (or detection units). For example, in an example shown in FIG. 2, the manufacturing system 100 of the present invention has a total of four detectors 104, including one (detector 104A) on the third pass line, two (detectors 104B1 and 104B2) on the sixth pass line, and one (detector 104C) straddling the ninth to eleventh pass lines. In the detector 104C, each detection unit for detecting a defective portion is provided on the ninth to eleventh pass lines, respectively.

[0036] In the manufacturing system of the present invention, since a defective portion is detected for the insulating wire during the formation of the insulating film, at least one detector is provided on at least one of the pass lines excluding the final pass line. The manufacturing system of the present invention preferably has two or more pass lines provided with at least one detector, more preferably has three or more pass lines provided with at least one detector, even more preferably has four or more pass lines provided with at least one detector, and even more preferably has five or more pass lines provided with at least one detector. Also, the number of detectors provided on the same pass line is preferably two or more, may be three or more, may be four or more, or may be five or more. By providing a plurality of detectors on the same pass line, overlooking of defective portions can be reduced. Note that the plurality of detectors may be the same detector or may be a combination of different detectors.

[0037] In the manufacturing system of the present invention, the first detector (the detector that first detects a defective portion) is provided on the pass line between the baking furnace and the varnish coating device when the thickness of the entire insulating layer is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. Also, the thickness may be 30 μm or more or 40 μm or more. Further, the thickness is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less. When the thickness is shown within a preferable range, it is preferably 5 to 90 μm, more preferably 10 to 90 μm, even more preferably 20 to 90 μm, may be 30 to 80 μm, or may be 40 to 70 μm. Further, when a plurality of detectors are provided, the second and subsequent detectors are preferably provided on the pass line between the baking furnace and the varnish coating device when the thickness of the entire insulating layer has increased by preferably 3 to 20 μm, more preferably 4 to 15 μm, and even more preferably 5 to 10 μm from the thickness of the entire insulating layer at the immediately preceding detector. Further, the installation position of the first detector can be set such that, based on the thickness of the insulating film at the completion of the insulated wire, the thickness of the entire insulating layer at the installation position of the first detector is 1 / 3 or more and 2 / 3 or less, or 1 / 2 or more and 2 / 3 or less of the thickness of the insulating film.

[0038] The type of the detector is not particularly limited. For example, a spark tester for measuring leakage current, an appearance inspection device for acquiring an image, an ultrasonic generator, a partial discharge inception voltage (PDIV) measuring device, a corona discharge measuring device, an eddy current flaw detection measuring device, a laser outer measuring device, a contact type measuring device, etc. may be mentioned. Among them, a spark tester is preferable. Further, a computer or the like for analyzing and recording a detection signal may be provided along with the detector. The computer may be capable of executing data processing by artificial intelligence (AI). Also, as in an example shown in FIG. 2, when two detectors (104B1, 104B2) are provided on the sixth pass line, for example, the first detector (detector 104B1) may be a spark tester and the next detector (detector 104B2) may be an appearance inspection device, or the first detector (detector 104B1) may be an appearance inspection device and the next detector (detector 104B2) may be a spark tester. In the former case, the shape of the defective portion (insulation defective portion) that has sparked by the spark tester can be recorded and confirmed, and in the latter case, minute defective portions that could not be detected by the image sensor can be detected by the spark tester.

[0039] The manufacturing system of the present invention, independently of the repetition of forming the insulating layer by applying and baking the resin varnish, further has a detector (hereinafter, in order to distinguish such a detector from a detector that detects defective parts in parallel with the repetition of forming the insulating layer by applying and baking the resin varnish, also referred to as the "final detector") for detecting defective parts of the insulated wire after forming the insulating film. The final detector may be provided on the pass line after the application and baking operation of the last resin varnish, and can be provided at any position, such as after winding the finished insulated wire or before shipment. By detecting defective parts for the insulated wire after the repetition of forming the insulating layer by applying and baking the resin varnish, defective parts can be surely specified on the surface of the insulated wire, markings can also be made at the positions of the defective parts, and further, if necessary, the area having the defective parts can also be removed. As the above-mentioned final detector, the detectors described above can be used, and it is preferable to use a combination of a plurality of detectors. Further, it is preferable that the plurality of detectors include the same type of detector as the detector that detects defective parts in parallel with the repetition of forming the insulating layer by applying and baking the resin varnish. For example, the detector that detects defective parts in parallel with the repetition of forming the insulating layer by applying and baking the resin varnish is a spark tester, and the final detector can be a combination of a spark tester, an appearance inspection device, and a laser outer measurement device.

[0040] The manufacturing system of the present invention can have the same configuration as a normal insulated wire manufacturing system except that it has a coating and baking device for repeating the formation of the insulating layer by applying and baking the resin varnish, and a detector for detecting defective parts in parallel with the repetition of the formation of the insulating layer by applying and baking the resin varnish. For example, in addition to the above coating and baking device and detector, it may have a cleaning device, a drying device, a cooling device, a straightening device, an extrusion device, etc. Further, it may be provided with a marking device for recording the position of the defective part and a removing device for removing the area having the defective part. Furthermore, the manufacturing system of the present invention may be provided with a recording device or the like for recording the position and state of the defective parts detected by the detector.

Example

[0041] It is considered that those skilled in the art can fully understand the problems of the present invention and the means for solving them from the above description. Hereinafter, the present invention will be described with reference to specific examples for supplementary purposes.

[0042] [Evaluation of Detection Rate of Foaming] <Example 1> As the conductor, a conductor (copper wire) having a rectangular cross-section was used. Using a die in which the outer shape of the cross-section of the innermost insulating layer in contact with the conductor is similar to the conductor cross-section shape, a polyimide resin varnish (manufactured by Essex Solutions) was applied to the surface of the conductor, and baking was performed for 60 seconds in a baking furnace with a furnace length of 15 m set at 550°C. The wire speed was 15 m / min. This coating and baking were performed 17 times in total to form an insulating film (thickness: 60 μm) composed of 17 layers of polyimide insulating layers. In parallel with the repetition of the formation of the insulating layer by the above-described application and baking of the resin varnish, a spark tester (manufactured by Shinto Instruments Co., Ltd.) was installed at a position where the thickness of the entire insulating layer during manufacturing became the thickness shown in Table 1 below, and a voltage of 4 kV was applied to cause a spark at the defective part.

[0043] (Evaluation Method) Regarding 2000 m of the insulated electric wire (finished product) obtained by the manufacturing method of Example 1, the defective part was caused to spark again under the same conditions (applied voltage 4 kV), and the defect at the position where the spark occurred was identified visually or with a magnifying glass. Then, a voltage of 10 kV was applied by the spark tester to forcibly cause a spark at the fine defective parts. The defect at each position where the spark occurred was identified by cutting the insulated electric wire at that position and observing it with a microscope. The number of foaming among the defects detected under each applied condition was counted, the detection rate was calculated by the following (Formula 1), and evaluation was performed based on the following evaluation criteria. The results are shown in Table 1 below. Detection rate (%): [Number of foaming detected at 4 kV applied] / [Number of foaming detected at 10 kV applied] × 100 ··· (Formula 1) -Evaluation Criteria- ◎: Detection rate is 95% or more 〇: Detection rate is 80% or more and less than 95% △: Detection rate is 50% or more and less than 80% ×: Detection rate is less than 50%

[0044] <Examples 2 to 4, Comparative Example 1> Insulated wires were manufactured in the same manner as in Example 1, except that the thickness of the insulating film, the number of insulating layers, the number of detectors, and the total thickness of the insulating layers at the positions of the respective detectors were as described in Table 1 below (Examples 2 to 4). For each of the obtained insulated wires, the detection rate was evaluated in the same manner as described above. The results are shown in Table 1 below. Also, for the insulated wires obtained by the manufacturing method of Comparative Example 1, which was the same as in Example 1 except that the thickness of the insulating film and the number of insulating layers were as described in Table 1 below and further no detection of defective portions was performed during the manufacturing stage of the insulated wire, the detection rate was evaluated in the same manner as described above. The results are shown in Table 1 below.

[0045] [Evaluation of Detection Rate of Foreign Matter Entrance] <Examples 5 to 7, Comparative Examples 2 and 3> Insulated wires were manufactured in the same manner as in Example 1, except that the thickness of the insulating film, the number of insulating layers, the number of detectors, and the total thickness of the insulating layers at the positions of the respective detectors were as described in Table 2 below (Examples 5 to 7). For each of the obtained insulated wires, after causing a spark at the defective portion in the same manner as described above, the defects were identified, and the number of foreign matter entrances among the identified defects was counted to evaluate the detection rate. Regarding the calculation method and evaluation criteria of the detection rate, it was the same as described above except that the number of foreign matter entrances was used instead of the number of foams. The results are shown in Table 2 below. Also, for each of the insulated wires obtained by the manufacturing methods of Comparative Examples 2 and 3, which were the same as in Example 1 except that the thickness of the insulating film and the number of insulating layers were as described in Table 2 below and further no detection of defective portions was performed during the manufacturing stage of the insulated wire, the detection rate of foreign matter entrance was evaluated in the same manner as in Examples 5 to 7. The results are shown in Table 2 below.

[0046] [Evaluation of Detection Rate of Conductor Defects] <Examples 8 to 10, Comparative Example 4> An insulating electric wire was manufactured in the same manner as in Example 1, except that the thickness of the insulating film, the number of insulating layers, the number of detectors, and the thickness of the entire insulating layer at the position of each detector were as described in Table 3 below (Examples 8 to 10). For each of the obtained insulating electric wires, after causing a defect portion to spark in the same manner as above, the defect was identified, and the number of conductor defects (surface flaws and internal defects of the conductor) among the identified defects was counted to evaluate the detection rate. Regarding the calculation method and evaluation criteria of the detection rate, it was the same as above, except that the number of conductor defects was used instead of the number of foams. The results are shown in Table 3 below. Also, an insulating electric wire was obtained by the manufacturing method of Comparative Example 4, which was the same as in Example 1 except that the thickness of the insulating film and the number of insulating layers were as described in Table 3 below, and further, detection of defect portions was not performed during the manufacturing stage of the insulating electric wire. For this insulating electric wire, the detection rate of conductor defects was evaluated in the same manner as in Examples 8 to 10. The results are shown in Table 3 below.

[0047]

Table 1

[0048]

Table 2

[0049]

Table 3

[0050] From Tables 1 to 3 above, for each insulating electric wire obtained by the manufacturing methods of Comparative Examples 1 to 4, where the thickness of the insulating film was 60 μm, 100 μm, and 130 μm and defect portions were not detected during the manufacturing process, as a result of detecting defect portions in the completed insulating electric wire, it was shown that the detection rate was low for any of the defects of foaming, foreign matter inclusion, and conductor defects. The reason was considered that in Comparative Examples 1 to 4, as shown in Fig. 4(a), defect portions were not detected during the manufacturing process, so there were no spark generation locations in the insulating film, and defects or conductor defects generated inside the insulating film could not be detected by the final detector. In contrast, in the manufacturing process, for each insulated wire obtained by the manufacturing methods of Examples 1 to 10 in which detection of defective parts was performed in parallel with repetition of formation of an insulating layer by application and baking of a resin varnish, as a result of detecting defective parts in the completed insulated wire, it was revealed that all showed a high detection rate (Tables 1 to 3). The reason is that in Examples 1 to 10, as shown in Fig. 4(b), since there are spark generation locations in the insulating film, a new spark is generated due to the spark generation locations in the detection by the final detector, and it was considered that the detection could be enabled regardless of the position in the thickness direction of the defective part.

Explanation of Signs

[0051] 100 Manufacturing system of insulated wire 101 Varnish coating device 102 Baking furnace 103 Roller 104, 104A, 104B1, 104B2, 104C Detector 200 Insulated wire 201 Conductor 202 Insulating film 203 Insulating layer 204 Defective part 205 Spark generation location 300 Spark tester

Claims

1. A method for manufacturing an insulated wire having a conductor and an insulating film covering the outer periphery of the conductor, comprising: a coating and baking step of repeatedly forming an insulating layer by applying and baking a resin varnish on the outer periphery of the conductor to provide an insulating film of a multi-layer insulating layer; a detection step of detecting a defective portion generated in the conductor or the insulating layer in parallel with the repetition of forming the insulating layer by applying and baking the resin varnish. A method for manufacturing an insulated wire.

2. The method for manufacturing an insulated wire according to claim 1, wherein in the detection step, the defective portion is detected by measuring a leakage current.

3. The method for manufacturing an insulated wire according to claim 1 or 2, wherein in the detection step, the defective portion is detected two or more times during the repetition of forming the insulating layer by applying and baking.

4. The method for manufacturing an insulated wire according to claim 1 or 2, wherein in the detection step, the first detection of the defective portion is performed when the thickness of the entire insulating layer is 5 to 90 μm.

5. The method for manufacturing an insulated wire according to claim 1 or 2, wherein the thickness of the insulating film is 25 μm or more.

6. In the manufacture of an insulated wire having a conductor and an insulating film covering the outer periphery of the conductor, when repeatedly forming an insulating layer by applying and baking a resin varnish on the outer periphery of the conductor to provide an insulating film of a multi-layer insulating layer, a method for detecting a defective portion, comprising detecting a defective portion generated in the conductor or the insulating layer in parallel with the repetition of forming the insulating layer by applying and baking the resin varnish.

7. An insulated wire manufacturing system having a conductor and an insulating film covering the outer periphery of the conductor, comprising: a coating and baking device for repeatedly forming an insulating layer by applying and baking a resin varnish on the outer periphery of the conductor; a detector for detecting a defective portion generated in the conductor or the insulating layer in parallel with the repetition of forming the insulating layer by applying and baking the resin varnish. An insulated wire manufacturing system.

8. The insulated wire manufacturing system according to claim 7, wherein the detector is a spark tester.

9. The insulated wire manufacturing system according to claim 7 or 8, having two or more of the detectors.

Images