JP2018170260A - Manufacturing method of insulated wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an insulated wire including an insulation film having a hole, the method capable of appropriately detecting a defect that potentially affects insulation properties thereof, thereby allowing a manufacture of the insulated wire with stable quality.SOLUTION: A manufacturing method of an insulated wire 1 includes: a step of preparing a conductor 10 having a linear shape; a step of obtaining an insulated wire 1 having the conductor 10 and an insulation film 20 covering the conductor 10; and a step of detecting a first capacitance between the insulated wire 1 and a first electrode 40 arranged outside in a diameter direction of the insulated wire 20 and facing an outer peripheral surface of the insulated wire 20, so as to inspect a formation state of the insulation film 20 according to a relation between porosity of the insulation film 20 and the first capacitance. The first electrode 40 includes a plurality of units 40a, 40b, 40c and 40d having a divided shape to be alienated with one another in a circumferential direction of the conductor in a cross section perpendicular to a longer direction of the conductor 10, and extending along the longer direction of the conductor 10.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for manufacturing an insulated wire.

  As an insulated wire, an insulated wire including a conductor and an insulating film formed on the outer peripheral side of the conductor is known. Such an insulated wire is required to suppress the occurrence of partial discharge. The partial discharge is a phenomenon in which if there is a defective portion in the insulating material, the electric field concentrates on the portion and a weak discharge is generated. When such partial discharge is repeatedly generated, the insulation is lowered and finally insulation failure occurs. Therefore, in addition to having excellent insulation properties and high mechanical properties, insulated wires are required to suppress the occurrence of partial discharge. In order to suppress the occurrence of partial discharge, it is effective to prepare an insulated wire having an insulating film with a low dielectric constant. As an insulated wire having an insulating film with a low dielectric constant, an insulated wire having an insulating film having pores on a conductor has been proposed (see, for example, Patent Document 1 and Patent Document 2).

Japanese Patent Laid-Open No. 2006-81563 JP 2016-110847 A

  In an insulated wire actually manufactured, a defect may occur in a part of the insulating film having pores. Such a defect may cause insulation failure. Among defects, it is difficult to detect the presence of a region called “low porosity portion”, which has no pores or has very few pores, from the appearance. A low porosity portion, particularly a non-porous portion where no void exists, may cause partial discharge. In addition, it is difficult to detect the presence of a defect in which a portion (thin portion) in which the insulating film becomes locally thin due to the swelling of the conductor from the appearance. If a thin portion exists in the insulating film, the insulating property decreases at that portion. In order to manufacture an insulated wire with stable quality, it is preferable to appropriately detect the presence of a low porosity portion and a thin portion and manage the quality of the insulating film.

  Therefore, it is possible to appropriately detect defects that can affect the insulation characteristics of insulated wires with an insulation film having pores, especially low porosity portions and thin portions, thereby producing stable quality insulated wires. An object of the present invention is to provide a method of manufacturing an insulated wire that can be performed.

  The method for manufacturing an insulated wire of the present application includes a step of preparing a conductor having a linear shape, and an insulating film made of an insulator and including a void inside so as to cover the outer peripheral surface of the conductor. The process of obtaining the insulated wire which has a conductor and the insulating film which coat | covers a conductor, the 1st electrode arrange | positioned on the radial direction outer side of an insulated wire so as to oppose the outer peripheral surface of an insulated wire, and an insulated wire, Detecting a first electrostatic capacity between the first and second electrodes, and inspecting a formation state of the insulating film based on a relationship between the first electrostatic capacity and a porosity of the insulating film. The first electrode has a shape divided so as to be separated from each other in the circumferential direction of the conductor in a cross section perpendicular to the longitudinal direction of the conductor, and includes a plurality of units extending along the longitudinal direction of the conductor.

  According to the above-described method for manufacturing an insulated wire, it is possible to appropriately detect defects, particularly low porosity portions and thin portions, which can affect the insulation properties of an insulated wire having an insulation film having pores, thereby It becomes possible to manufacture insulated wires with stable quality.

It is a cross-sectional schematic diagram which shows an example of an insulated wire. It is a block diagram for demonstrating the manufacturing process of an insulated wire. It is a flowchart which shows the procedure of the manufacturing method of an insulated wire. 4 is a schematic plan view showing an example of a structure of a test electrode in Embodiment 1. FIG. It is a schematic sectional drawing corresponding to the state which looked at the cross section in alignment with the line segment VV of FIG. 4 in the direction of the arrow. It is a schematic sectional drawing which shows the state of the low-porosity part in an insulating film. It is a schematic sectional drawing which shows the state of the thin part of an insulating film. It is a schematic sectional drawing which shows the state of the flaw defect on the surface of an insulating film. It is a schematic sectional drawing which shows the state of the hole defect of an insulating film. 5 is a schematic plan view showing an example of a structure of a test electrode in Embodiment 2. FIG. 10 is a schematic plan view showing an example of a structure of a test electrode in Embodiment 3. FIG. 6 is a schematic plan view showing an example of a structure of a test electrode in Embodiment 4. FIG.

[Description of Embodiment of Present Invention]
First, embodiments of the present invention will be listed and described. The method for manufacturing an insulated wire of the present application includes a step of preparing a conductor having a linear shape, and an insulating film made of an insulator and including a void inside so as to cover the outer peripheral surface of the conductor. The process of obtaining the insulated wire which has a conductor and the insulating film which coat | covers a conductor, the 1st electrode arrange | positioned on the radial direction outer side of an insulated wire so as to oppose the outer peripheral surface of an insulated wire, and an insulated wire, Detecting a first electrostatic capacity between the first and second electrodes, and inspecting a formation state of the insulating film based on a relationship between the first electrostatic capacity and a porosity of the insulating film. The first electrode has a shape divided so as to be separated from each other in the circumferential direction of the conductor in a cross section perpendicular to the longitudinal direction of the conductor, and includes a plurality of units extending along the longitudinal direction of the conductor.

  The dielectric constant of air is about 1.0. In contrast, the material constituting the insulating film has a dielectric constant different from that of air. Accordingly, when there are holes in the insulating film, the dielectric constant of the insulating film as a whole changes according to the existence ratio (porosity) of the holes in the insulating film. As a result of studies by the present inventors, it has been confirmed that there is a correlation between the capacitance between the electrode and the insulated wire and the porosity of the insulating film.

  According to the method for manufacturing an insulated wire of the present application, the first capacitance is detected in the step of inspecting the formation state of the insulating film by using the correlation described above, and the first capacitance and The formation state of the insulating film is inspected based on the relationship with the porosity of the insulating film. For example, if a defect such as a low-porosity part, a thin part, a scratch, or a hole is present in the insulating film, the capacitance between the electrode and the insulating film changes compared to that in a steady state. Therefore, the presence of a defect can be detected.

  Furthermore, in the method for manufacturing an insulated wire, the first electrode has a shape divided so as to be separated from each other in the circumferential direction of the conductor in a cross section perpendicular to the longitudinal direction of the conductor, and extends along the longitudinal direction of the conductor. Including multiple units. When the first electrode has such a shape, it is possible to finely specify the existence position of the defect in the circumferential direction of the insulated wire.

  In addition, defects that can be identified from the appearance of the insulation film, such as scratches and holes, can be detected by general defect inspection methods such as image analysis, but low-porosity parts and thin parts are detected only from the appearance. It is difficult. On the other hand, according to the manufacturing method of the insulated wire of the present application, by inspecting the formation state of the insulating film based on the relationship between the first capacitance and the porosity of the insulating film using the above-described electrode, In addition to scratches and holes, the presence of such a low porosity portion or thin portion can be detected. As a result, according to the method for manufacturing an insulated wire of the present application, it is possible to accurately detect a defect and to manufacture an insulated wire having a stable quality.

  The insulating film may include polyimide. An insulating film containing polyimide is excellent in insulation and heat resistance. Therefore, polyimide is suitable as a material constituting the insulating film.

  The step of inspecting the formation state of the insulating film is preferably performed online. By performing an on-line inspection of the step of inspecting the formation state of the insulating film, the insulated wire can be continuously manufactured, and the insulated wire can be obtained with high production efficiency. The state in which the inspection is performed online means a state in which the formation state of the insulating film is inspected continuously after the step of obtaining the insulated wire in a series of manufacturing processes.

  The method for manufacturing the insulated wire detects a second capacitance between the second electrode disposed on the radially outer side of the insulated wire and the insulated wire so as to face the outer peripheral surface of the insulated wire, You may further include the process of test | inspecting the formation state of an insulating film based on the relationship between a 1st electrostatic capacitance and a 2nd electrostatic capacitance, and the porosity of an insulating film. By performing inspection using a plurality of electrodes including the first electrode and the second electrode, it is possible to reduce erroneous detection of defects and detect defects with higher accuracy.

  In the method for manufacturing an insulated wire, the length of the second electrode along the longitudinal direction of the conductor may be different from that of the first electrode. By doing in this way, the 1st electrostatic capacity between the 1st electrode and an insulated wire and the 2nd electrostatic capacity between the 2nd electrode and an insulated wire are calculated, and based on them By comparing the inspection results (by taking the difference between the two), it becomes possible to detect a defect with higher accuracy.

  In the method for manufacturing an insulated wire, the second electrode has a shape divided so as to be separated from each other in the circumferential direction of the conductor in a cross section perpendicular to the longitudinal direction of the conductor, and extends along the longitudinal direction of the conductor. Multiple units may be included. When the second electrode has such a shape, it is possible to more precisely specify the position of the defect in the circumferential direction of the insulated wire.

[Details of the embodiment of the present invention]
Next, an embodiment of a method for manufacturing an insulated wire of the present application will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
[Insulated wire structure]
First, Embodiment 1 will be described with reference to FIGS. The cross-sectional schematic diagram of an example of the insulated wire 1 manufactured in the manufacturing method of the insulated wire of this application is shown in FIG. Referring to FIG. 1, an insulated wire 1 having a circular cross-sectional shape in a cross section perpendicular to the longitudinal direction of a conductor 10 having a linear shape includes a linear conductor 10 having a circular cross-sectional shape, and the conductor 10. And an insulating film 20 covering the conductor 10 so as to cover the outer peripheral surface. The insulating film 20 is made of an insulator containing an organic material. Further, the insulating film 20 includes pores 15 inside. Specifically, the insulating film 20 is formed in a state where a plurality (large number) of holes 15 are dispersed therein.

  Although it does not specifically limit as said organic material contained in an insulator, For example, if it is a thermosetting resin, polyimide (PI) and polyamideimide, if it is a thermoplastic resin, polyethersulfone (PES), polyetheretherketone ( PEEK). Especially, since it is excellent in insulation and heat resistance, it is preferable that the insulator which comprises the insulating film 20 contains a polyimide, and it is more preferable that 50 mass% or more of the insulator which comprises the insulating film 20 is a polyimide, It is particularly preferable that it consists of polyimide and inevitable impurities. For example, the insulating film 20 in the present embodiment is a polyimide film made of polyimide and unavoidable impurities. Referring to FIG. 1, insulating film 20 in the present embodiment includes voids 15 therein. The ratio of the total volume of the pores 15 (porosity) to the total volume of the insulating film 20 is, for example, 5% by volume to 80% by volume, preferably 10% by volume to 70% by volume, more preferably 25% by volume. % To 65% by volume. Since the dielectric constant is different between air and the material constituting the insulating film 20 such as polyimide, the dielectric constant of the insulating film 20 as a whole changes when the insulating film 20 has the holes 15. For example, polyimide has a higher dielectric constant (relative dielectric constant) than air. Therefore, when the insulating film 20 is made of polyimide, the insulating film 20 having the holes 15 makes it possible to obtain the insulating film 20 having a lower dielectric constant than the insulating film 20 having no holes 15.

  As shown in FIG. 1, the insulated wire 1 may have holes 15 in a state of being dispersed in the insulating film 20. Although not shown, the insulating film 20 may have a multilayer structure in which a solid layer and a porous layer having pores 15 are stacked on each other. In this case, the thickness of the solid layer and the thickness of the porous layer can be arbitrarily set according to necessary characteristics.

  Next, the flow of the method for manufacturing the insulated wire 1 according to the present embodiment will be described with reference to FIGS. FIG. 2 is a block diagram for explaining a manufacturing process of the insulated wire 1. FIG. 3 is a flowchart showing the procedure of the method for manufacturing the insulated wire 1. FIG. 4 is a schematic plan view showing an example of the structure of the inspection electrode in the first embodiment. FIG. 5 is a schematic cross-sectional view corresponding to a state in which a cross section taken along line VV in FIG. 4 is viewed in the direction of the arrow.

[Configuration of manufacturing equipment]
With reference to FIG. 2, the manufacturing apparatus 30 for the insulated wire 1 includes a conducting wire preparation unit 50, an insulating film forming unit 54, an inspection unit 53, and a winding unit 56. The conducting wire preparation unit 50 includes a strand supply unit 51 and a conductor processing unit 52. The strand supply unit 51 holds a metal strand such as a strand of copper that is a raw material of the conductor 10 and supplies the metal strand to the conductor processing unit 52. The conductor processing unit 52 is disposed downstream of the strand supply unit 51 and processes the metal strand supplied from the strand supply unit 51 into a desired shape and size. The conductor processing portion 52 includes a metal processing mold such as a die used for drawing (drawing), for example.

  The insulating film forming portion 54 is disposed on the downstream side of the conductor processing portion 52. The insulating film forming unit 54 includes, for example, a coating apparatus that coats the conductor 10 with a varnish that is a raw material of the insulating film 20, and a baking furnace that heats the coated varnish to form a polyimide film.

  The inspection unit 53 is disposed on the downstream side of the insulating film forming unit 54. The inspection unit 53 detects the first capacitance between the first main electrode 40 as the first electrode and the insulated wire 1, and the first capacitance and the porosity of the insulating film 20 are detected. Based on the relationship, the formation state of the insulating film 20 is inspected. Further, a second capacitance between the second main electrode 41 as the second electrode and the insulated wire 1 is detected, and the first capacitance and the second capacitance, and the insulating film 20 are detected. The formation state of the insulating film 20 may be inspected based on the relationship with the porosity. The inspection unit 53 includes a capacitance sensor 2 and a capacitance monitor 58. The capacitance sensor 2 includes a test electrode 55, a housing 44, and wiring connected to each electrode in the test electrode 55. When the insulated wire 1 passes through the capacitance sensor 2, the first capacitance and the second capacitance between the first main electrode 40 or the second main electrode 41 and the insulated wire 1 are detected. The

  The structure of the capacitance sensor 2 will be described with reference to FIGS. 2, 4 and 5. The capacitance sensor 2 includes a test electrode 55 and a housing 44. The inspection electrode 55 of the capacitance sensor 2 according to the first embodiment includes a first main electrode 40 as the first electrode, a second main electrode 41 as the second electrode, and a first guard electrode 42a. , Second guard electrode 42b and third guard electrode 42c. The housing 44 accommodates the first main electrode 40, the second main electrode 41, the first guard electrode 42a, the second guard electrode 42b, the third guard electrode 42c, and the wiring connected to each electrode. It has a shape that can be made.

  The structure of the inspection electrode 55 will be further described with reference to FIG. The first main electrode 40 has an arc shape that is divided into four parts so as to be separated from each other in the circumferential direction of the conductor 10 in a cross section perpendicular to the longitudinal direction of the conductor 10, and extends along the longitudinal direction of the conductor 10. It consists of four electrode units 40a, 40b, 40c, 40d. The second main electrode 41 also has a similar cross-sectional shape and extends along the longitudinal direction of the conductor 10 to four electrode units 41a, 41b, 41c, 41d (the electrode unit 41d is similar to the electrode unit 40d, It is located on the opposite side of the electrode unit 41b across the insulated wire 1 and is not shown). Each electrode unit of the first main electrode 40 and the second main electrode 41 is connected to a capacitance monitor 58 via wiring as shown in FIG. For convenience of explanation, illustration of wirings connected to the electrodes is omitted in FIG.

The length L ₄₀ of the first main electrode 40 along the longitudinal direction of the conductor 10 is different from the length L ₄₁ of the second main electrode 41 in the same direction. In FIG. 4, the length L ₄₁ of the second main electrode 41 is larger than the length L ₄₀ of the first main electrode 40.

  The first guard electrode 42 a is disposed on the upstream side in the longitudinal direction of the conductor 10 when viewed from the first main electrode 40. The second guard electrode 42 b is disposed between the first main electrode 40 and the second main electrode 41 along the longitudinal direction of the conductor 10. The third guard electrode 42 c is disposed on the downstream side in the longitudinal direction of the conductor 10 when viewed from the second main electrode 41. The first guard electrode 42a, the second guard electrode 42b, and the third guard electrode 42c alleviate the concentration of the electric field at the ends of the first main electrode 40 and the second main electrode 41, and the insulated wire 1 and the first main electrode 40. The first electrostatic capacity and the second electrostatic capacity generated between the second main electrode 41 and the second main electrode 41 are stably measured. The first guard electrode 42a, the second guard electrode 42b, and the third guard electrode 42c are connected to each other through a wiring. The first guard electrode 42a, the second guard electrode 42b, and the third guard electrode 42c are connected to the capacitance monitor 58 and the winding unit 56, and the winding unit 56, the first guard electrode 42a, the second guard electrode 42b, and It is grounded in the path between the third guard electrode 42c. That is, the first guard electrode 42a, the second guard electrode 42b, and the third guard electrode 42c are ground electrodes.

In the present embodiment, the first guard electrode 42a, the second guard electrode 42b, and the third guard electrode 42c have the same structure. That is, each guard electrode has a hollow cylindrical shape, and the lengths L _42a , L _42b , and L _42c of the guard electrodes along the longitudinal direction of the conductor 10 are the same. The main electrodes 40, 41 and the guard electrodes 42a, 42b, 42c are arranged with a gap G. The distance between the insulated wire 1 and each of the main electrodes 40 and 41 is appropriately set within a range in which the measured first capacitance and second capacitance are stable.

  The capacitance monitor 58 is connected to each electrode unit constituting the inspection electrode 55 of the capacitance sensor 2. The capacitance monitor 58 is grounded together with the first guard electrode 42a, the second guard electrode 42b, and the third guard electrode 42c through wiring. The capacitance monitor 58 displays the capacitance detected by the capacitance sensor 2 and records the capacitance in relation to the recording time or the inspection target position of the insulated wire 1. A normal location and a defective location in the insulated wire 1 can be distinguished from the variation in capacitance displayed or recorded on the capacitance monitor 58.

  The winding unit 56 is disposed on the downstream side of the inspection unit 53. The take-up unit 56 includes a take-up reel mounting unit in which a detachable take-up reel can be disposed, and winds the insulated wire 1 inspected by the inspection unit 53. The insulated wire 1 can be obtained in a wound state by detaching the take-up reel on which the insulated wire 1 is wound from the take-up reel mounting portion.

[Procedure for manufacturing method of insulated wire 1]
Next, with reference to FIGS. 1-9, the procedure of the manufacturing method of the insulated wire 1 is demonstrated. FIG. 6 is a schematic cross-sectional view showing a state of a low porosity portion defect in the insulating film 20. FIG. 7 is a schematic cross-sectional view showing the state of the thin portion of the insulating film 20. FIG. 8 is a schematic cross-sectional view showing a state of a flaw defect on the surface of the insulating film 20. FIG. 9 is a schematic cross-sectional view showing a state of hole defects in the insulating film 20.

In the method for manufacturing the insulated wire 1 according to the present embodiment, steps S10 to S30 shown in FIG. 3 are performed. With reference to FIG. 2 and FIG. 3, first, the conductor preparation part 50 prepares the linear conductor 10 having a circular cross-sectional shape (S10). Specifically, a metal strand such as a strand of copper held by the strand supply unit 51 is drawn out. Wire is fed in the direction of arrow D _1, is supplied to the conductor processing unit 52. The metal strand supplied from the strand supply section 51 is processed into a conductor 10 having a desired shape and size by drawing (drawing) using a die. The conductor 10 processed from the strand in the conductor processing portion 52 is sent to the insulating film forming portion 54.

  Next, the insulating film 20 is formed (S20). As shown in FIG. 1, the insulating film 20 is formed so as to cover the outer peripheral surface of the conductor 10 having a linear shape. The insulating film 20 is made of an insulator and includes pores 15 inside.

  As described above, the insulating film forming unit 54 includes a varnish coating device and a baking furnace. In the insulating film forming portion 54, the insulating film 20 is formed so as to cover the outer peripheral surface of the conductor 10 by the following procedure.

  First, the varnish is applied so as to cover the outer peripheral surface of the conductor 10 by passing the conductor 10 processed in the conductor processing section 52 through the varnish held in the coating apparatus. The varnish to be applied in the present embodiment is a polyimide precursor containing a mixture of a polyimide precursor and a thermal decomposition resin in an organic solvent. Next, when the coated coating film is heated in the baking furnace, the reaction from the polyimide precursor to the polyimide is promoted. Since polyimide is thermosetting, the coating is cured by heating. Further, the pyrolysis resin is decomposed and vaporized by heating. At this time, voids 15 are formed at locations where the thermally decomposable resin was present in the cured polyimide film. In this way, an insulating film 20 made of polyimide as an insulator and having a large number of holes 15 dispersed therein is formed so as to cover the outer peripheral surface of the conductor 10.

  Moreover, the insulating film 20 having a desired thickness can be formed by repeating the coating and heating cycle of the varnish as necessary.

Subsequent to step S20 for forming the insulating film 20, the obtained insulated wire 1 is inspected (S30). Insulation coating forming unit insulated wire 1 in which the insulating film 20 is formed at 54 is further fed in the direction of arrow D _1, the state of formation of the insulating coating 20 is inspected in the inspection unit 53.

  The inspection is performed by the capacitance sensor 2 and the capacitance monitor 58 as shown in FIG. Capacitance data detected by the inspection electrode 55 of the capacitance sensor 2 is transmitted to the capacitance monitor 58. The formation state of the insulating film 20 is inspected based on the relationship between the capacitance displayed on the capacitance monitor 58 and the porosity of the insulating film 20 investigated in advance.

  The inspection unit 53 detects the first capacitance between the first main electrode 40 as the first electrode and the insulated wire 1, and the first capacitance and the porosity of the insulating film 20 are detected. Based on the relationship, the formation state of the insulating film 20 is inspected. Further, a second capacitance between the second main electrode 41 as the second electrode and the insulated wire 1 is detected, and the first capacitance and the second capacitance, and the insulating film 20 are detected. The formation state of the insulating film 20 may be inspected based on the relationship with the porosity. In the present embodiment, the second electrostatic capacitance between the second main electrode 41 and the insulated wire 1 is detected, and the first electrostatic capacitance and the second electrostatic capacitance, and the insulating coating 20 The formation state of the insulating film 20 is inspected based on the relationship with the porosity. By detecting the first capacitance and the second capacitance in this manner and inspecting based on the relationship with the porosity of the insulating film 20, defects can be detected with higher accuracy.

  Specifically, the inspection is performed as follows. First, a voltage is applied to each electrode unit 40a, 40b, 40c, 40d of the first main electrode 40 and each electrode unit 41a, 41b, 41c, 41d of the second main electrode 41, and the first main electrode 40, the insulated wire 1 and A first capacitance between the second main electrode 41 and the insulated wire 1 is detected.

  Next, the formation state of the insulating film 20 is inspected based on the relationship between the detected first and second capacitances and the porosity of the insulating film 20. For example, in a state where the porosity of the insulating film 20 is stable, the detected capacitance shows a steady value. On the other hand, when there is a defect in the insulating film 20, the porosity varies, so the capacitance changes accordingly. Based on the change in the capacitance, the position of the defect is specified and recorded. In this way, the insulated wire 1 with stable quality can be manufactured.

  The insulated wire 1 in which the formation state of the insulating film 20 is inspected in the capacitance sensor 2 is then wound up in the winding portion 56. The wound insulated wire 1 may be a product with a recorded defect position, or the insulated wire 1 including the defect may be discarded without being a product. Further, only the defective part may be deleted based on the recorded position, and the remaining part may be the product.

  The above inspection is performed online. In the inspection performed online, the formation state of the insulating film 20 obtained in step S20 is inspected continuously from step S20 in the series of steps from step S10 to step S30. When the inspection is performed on-line, a series of flows from the wire supply unit 51 to the winding unit 56 shown in FIG. 4 are integrally performed without cutting the insulated wire 1.

  In the step of inspecting the formation state of the insulating film 20, the electrode units 40 a, 40 b, 40 c, 40 d of the first main electrode 40 and the second main electrode 41 are in a state where the inspection electrode 55 is immersed in water (not shown). A first electrostatic capacity and a second electrostatic capacity between the first main electrode 40 or the second main electrode 41 and the insulated wire 1 by applying a voltage to each electrode unit 41a, 41b, 41c, 41d. Is monitored by a capacitance monitor 58. The formation state of the insulating film 20 is inspected based on the relationship between the detected first electrostatic capacity and the second static electricity and the porosity of the insulating film 20.

  In the first embodiment, the first main electrode 40 has an arc shape that is divided into four so as to be separated from each other in the circumferential direction of the conductor 10 in a cross section perpendicular to the longitudinal direction of the conductor 10. It is comprised from four electrode units 41a, 41b, 41c, 41d extended along the longitudinal direction. Similarly, the second main electrode 41 is composed of four electrode units divided into four in the circumferential direction. By using the first main electrode 40 and the second main electrode 41 composed of the plurality of electrode units divided in the circumferential direction in this way, the position of the defect in the circumferential direction of the insulated wire 1 can be specified in detail. Is possible. Note that the number of the plurality of electrode units in the circumferential direction of the main electrode is not particularly limited to four. For example, a main electrode having an arbitrary number of electrode units of two or more in the circumferential direction, such as a main electrode having an electrode unit divided into two in the circumferential direction, can be selected as necessary.

  In the method of manufacturing the insulated wire 1 according to the first embodiment, it is possible to detect the low porosity portion 21 in the insulating film 20 as shown in FIG. The low porosity portion 21 is a portion of the insulating film 20 that has a significantly lower porosity and a lower proportion of the holes 15 than the average porosity of the insulating film 20 as a whole. In the low porosity portion 21, a portion where no pores 15 are present at all is called a non-porous portion. Such a low porosity portion 21, particularly a non-porous portion, can cause partial discharge. In order to manufacture the insulated wire 1 having stable quality, it is preferable to appropriately detect the presence of such a low porosity portion 21 and manage the quality of the insulating film 20.

  Furthermore, in the method for manufacturing the insulated wire 1 according to the first embodiment, it is also possible to detect the thin portion 22 in the insulating film 20 as shown in FIG. The thin portion 22 refers to a portion where the insulating film 20 is locally thin due to the swelling 12 of the conductor 10. When such a thin portion 22 exists, the insulating property is reduced in the thin portion 22. Therefore, in order to manufacture the insulated wire 1 with stable quality, it is preferable to appropriately detect the presence of such a thin portion 22 and manage the quality of the insulating film 20.

Further, defects that can be identified from the appearance of the insulating film 20 such as the scratch 23 on the surface of the insulating film 20 as shown in FIG. 8 and the hole 24 of the insulating film 20 as shown in FIG. It can also be detected by a defect inspection method. However, it is difficult to detect the low porosity portion 21 as shown in FIG. 6 and the thin portion 22 as shown in FIG. If it is possible to length L _D along the longitudinal direction of the conductor 10 is properly detect the low porosity portion 21 and the thin portion 22 of approximately 1 mm, it is possible to effectively detect a substantial harmful defects.

  In the first embodiment, the first main electrode 40 and the second main electrode 41 as described above are used as the main electrodes, and the first capacitance, the second capacitance, and the porosity of the insulating film 20 are used. By examining the formation state of the insulating film 20 based on the relationship, it is possible to detect the presence of the low porosity portion 21 and the thin portion 22 as well as the scratches 23 and the holes 24. As a result, according to the manufacturing method of the insulated wire 1 of the present application, it is possible to accurately detect defects and to manufacture the insulated wire 1 with stable quality.

In the first embodiment, the first main electrode 40 and the second main electrode 41 whose length along the longitudinal direction of the conductor 10 is approximately 10 mm or less, preferably 5 mm or less are used. The measured capacitance value is the average value of the entire first main electrode 40 or the average value of the entire second main electrode 41. Therefore, when the electrode is long along the longitudinal direction of the conductor 10, it is possible to detect a wide range, but since the capacitance value is averaged over the longitudinal direction, small defects can be detected with high sensitivity. Difficult to do. On the other hand, when the lengths L ₄₀ and L ₄₁ along the longitudinal direction of the conductor 10 of the first main electrode 40 and the second main electrode ₄₁ are 10 mm or less, a small defect that cannot be detected by an electrode that is long in the longitudinal direction. Can also be detected. The lower limit of the length of the first main electrode 40 and the second main electrode 41 is not particularly limited, but is, for example, 0.1 mm.

Further, the lengths L ₄₀ and L ₄₁ along the longitudinal direction of the conductor 10 of the first main electrode 40 and the second main electrode 41 are set to 10 mm or less, and the first capacitance, the second capacitance, and the insulating film By inspecting the formation state of the insulating film 20 based on the relationship with the porosity of 20, not only defects due to the scratches 23 and holes 24, or large-size defects, but also small defects, particularly the low porosity portion 21 and the thin wall It is possible to detect a defect caused by the portion 22.

  In the present embodiment, the first electrostatic capacitance and the second capacitance are obtained by using the capacitance sensor 2 including the inspection electrode 55 having a plurality of main electrodes, that is, the first main electrode 40 and the second main electrode 41. Measure the capacitance. By inspecting using multiple main electrodes in this way, verifying whether the inspection result of one main electrode includes a false detection of a defect in comparison with the inspection result of another main electrode Can do. As a result, it is possible to reduce erroneous detection of defects and detect defects with higher accuracy.

Further, the first main electrode 40 and the second main electrode 41 have different lengths. Therefore, by obtaining the first capacitance and the second capacitance measured using the two main electrodes, and comparing the inspection results based on them (by taking the difference between the two), it becomes narrower It is possible to inspect the formation state of the insulating film 20 in a wide range. That is, the first capacitance between the first main electrode 40 having the length L ₄₀ and the insulated wire 1 and the second main electrode 41 having the length L ₄₁ larger than the length L ₄₀ and the insulated wire. By calculating the second capacitance between the first and the second and comparing the inspection results based on the second capacitance (by taking the difference between the two), a substantial difference (L ₄₁ -L ₄₀ ) (for example, 1 mm) The formation state of the insulating film 20 corresponding to the range can be inspected.

  The porosity can be derived based on the relationship between the first capacitance (and the second capacitance) measured in this way and the porosity of the insulating film 20 investigated in advance. Specifically, the pores of the insulated wire 1 are compared by comparing a theoretical curve obtained by calculation, a calibration curve obtained using a standard substance, and a capacitance value of the insulated wire 1 obtained in the inspection process. The rate can be estimated. The defect can be detected by setting in advance a threshold value of the capacitance to be determined as a defect, which is obtained from the porosity to be detected as a defect. In addition to the relationship between the capacitance and the porosity, the relationship between the thickness and the capacitance can be referred to as necessary.

(Embodiment 2)
Next, Embodiment 2, which is another embodiment, will be described. FIG. 10 is a schematic plan view showing an example of the structure of the inspection electrode 55 in the second embodiment. The method of manufacturing the insulated wire 1 according to the present embodiment is basically performed in the same manner as in the first embodiment, and has the same effect. However, the inspection electrode 55 of the capacitance sensor 2 in the second embodiment is different from that in the first embodiment in that it includes one main electrode 60 and two guard electrodes 62a and 62b.

Referring to FIG. 10, the inspection electrode 55 includes a third main electrode 60 as a first electrode. The third main electrode 60 has the same structure as the first main electrode 40 according to the first embodiment. That is, the third main electrode 60 has an arc shape that is divided into four parts so as to be separated from each other in the circumferential direction of the conductor 10 in a cross section perpendicular to the longitudinal direction of the conductor 10, and along the longitudinal direction of the conductor 10. The four electrode units 60a, 60b, 60c and 60d (60d is not shown) are extended. The third main electrode 60 has a length L ₆₀ along the longitudinal direction of the conductor 10. The length L ₆₀ is 10 mm or less. Each electrode unit of the third main electrode 60 is connected to a capacitance monitor 58 (FIG. 2) via wiring. For convenience of explanation, in FIG. 10, illustration of wirings connected to the respective electrodes is omitted.

  A fourth guard electrode 62 a is disposed on the upstream side in the longitudinal direction of the conductor 10 when viewed from the third main electrode 60. A fifth guard electrode 62 b is disposed on the downstream side in the longitudinal direction of the conductor 10 when viewed from the third main electrode 60. Each of fourth guard electrode 62a and fifth guard electrode 62b has the same structure and the same function as each of first guard electrode 42a, second guard electrode 42b, and third guard electrode 42c according to the first embodiment. .

  In the step of inspecting the formation state of the insulating film 20, the first capacitance between the electrode units 60a, 60b, 60c, 60d of the third main electrode 60 and the insulated wire 1 is detected, and the first The formation state of the insulating film 20 is inspected based on the relationship between the capacitance and the porosity of the insulating film 20.

  According to the inspection unit 53 in the present embodiment, the third main electrode 60 is arranged in the circumferential direction of the conductor 10 in a cross section perpendicular to the longitudinal direction of the conductor 10, similarly to the first main electrode 40 and the second main electrode 41. It has an arcuate shape that is divided into four so as to be separated from each other, and includes four electrode units 60a, 60b, 60c, and 60d that extend along the longitudinal direction of the conductor 10. Therefore, it is possible to finely specify the existence position of the defect in the circumferential direction of the insulated wire 1.

Further, the length L ₆₀ along the longitudinal direction of the conductor 10 is sufficiently short as 10 mm or less. Therefore, as in the first embodiment, defects such as a small low porosity portion 21 and a thin portion 22 can be detected.

(Embodiment 3)
Next, the third embodiment which is another embodiment will be described. FIG. 11 is a schematic plan view showing an example of the structure of the inspection electrode 55 in the third embodiment. The method of manufacturing the insulated wire 1 according to the present embodiment is basically performed in the same manner as in the first embodiment, and has the same effect. However, the inspection electrode 55 of the capacitance sensor 2 in Embodiment 3, the case of the first embodiment in that the length _{L 71} of the length _{L 70} and a fifth main electrode 71 of the fourth main electrode 70 is more than 10mm Is different.

  Referring to FIG. 11, the inspection electrode 55 includes a fourth main electrode 70 as a first electrode and a fifth main electrode 71 as a second electrode. The fourth main electrode 70 has an arc shape that is divided into four so as to be separated from each other in the circumferential direction of the conductor 10 in a cross section perpendicular to the longitudinal direction of the conductor 10, and extends along the longitudinal direction of the conductor 10. The four electrode units 70a, 70b, 70c, and 70d (the electrode unit 70d is located on the opposite side of the electrode unit 70b across the insulated wire 1 as in the electrode unit 40d and is not shown). . The fifth main electrode 71 also has the same cross-sectional shape, and extends along the longitudinal direction of the conductor 10 to four electrode units 71a, 71b, 71c, 71d (the electrode unit 71d is similar to the electrode unit 40d, It is located on the opposite side of the electrode unit 71b with the insulated wire 1 in between and is not shown). Each electrode unit of the fourth main electrode 70 and the fifth main electrode 71 is connected to a capacitance monitor 58 (FIG. 2) via wiring. For convenience of explanation, illustration of wirings connected to the electrodes is omitted in FIG.

  A sixth guard electrode 72 a is arranged on the upstream side in the longitudinal direction of the conductor 10 when viewed from the fourth main electrode 70. A seventh guard electrode 72 b is disposed between the fourth main electrode 70 and the fifth main electrode 71 along the longitudinal direction of the conductor 10. An eighth guard electrode 72 c is disposed on the downstream side in the longitudinal direction of the conductor 10 when viewed from the fifth main electrode 71. Each of sixth guard electrode 72a, seventh guard electrode 72b, and eighth guard electrode 72c has the same structure as each of first guard electrode 42a, second guard electrode 42b, and third guard electrode 42c according to the first embodiment. And has the same function.

The length L ₇₀ of the fourth main electrode 70 along the longitudinal direction of the conductor 10 is different from the length L ₇₁ of the fifth main electrode 71 in the same direction. Although not particularly limited, the length L ₇₁ of the fifth main electrode 71 in FIG. 11 is 1.5 times the length L ₇₀ of the fourth main electrode 70.

  In the step of inspecting the formation state of the insulating film 20, a voltage is applied to each of the fourth main electrode 70 and the fifth main electrode 71 to insulate each electrode unit 70a, 70b, 70c, 70d of the fourth main electrode 70 from each other. A first capacitance between the electric wire 1 and a second capacitance between the electrode units 71a, 71b, 71c, 71d of the fifth main electrode 71 and the insulated electric wire 1 are detected.

  As shown in FIG. 11, the fourth main electrode 70 has an arc shape that is divided into four so as to be separated from each other in the circumferential direction of the conductor 10 in a cross section perpendicular to the longitudinal direction of the conductor 10. It is comprised from four electrode units 70a, 70b, 70c, 70d extended along a longitudinal direction. Similarly, the fifth main electrode 71 includes four electrode units 71a, 71b, 71c, and 71d that are divided into four in the circumferential direction. By using the fourth main electrode 70 and the fifth main electrode 71 composed of a plurality of electrode units divided in the circumferential direction in this way, the position of the defect in the circumferential direction of the insulated wire 1 can be specified in detail. Is possible.

  Further, in the present embodiment, the first electrostatic capacitance and the second capacitance are obtained by using the capacitance sensor 2 including the inspection electrode 55 having a plurality of main electrodes, that is, the fourth main electrode 70 and the fifth main electrode 71. Measure the capacitance. By inspecting using multiple main electrodes in this way, verifying whether the inspection result of one main electrode includes a false detection of a defect in comparison with the inspection result of another main electrode Can do. As a result, it is possible to reduce erroneous detection of defects and detect defects with higher accuracy.

Further, the fourth main electrode 70 and the fifth main electrode 71 have different lengths. Therefore, by obtaining the first capacitance and the second capacitance measured using the two main electrodes, and comparing the inspection results based on them (by taking the difference between the two), it becomes narrower It is possible to inspect the formation state of the insulating film 20 in a wide range. That is, the first electrostatic capacitance between the fourth main electrode 70 having the length L ₇₀ and the insulated wire 1, the fifth main electrode 71 having the length L ₇₁ larger than the length L _70, and the insulated wire By calculating the second capacitance between 1 and 1 and comparing the inspection results based on them (by taking the difference between the two), a substantial difference (L ₇₁ -L ₇₀ ) (for example, 1 mm) The formation state of the insulating film 20 corresponding to the range can be inspected.

(Embodiment 4)
Next, Embodiment 4, which is another embodiment, will be described. FIG. 12 is a schematic plan view showing an example of the structure of the inspection electrode 55 in the fourth embodiment. The method of manufacturing the insulated wire 1 according to the present embodiment is basically performed in the same manner as in the first embodiment, and has the same effect. However, the inspection electrode 55 of the capacitance sensor 2 according to the fourth embodiment has a point that the length L ₈₀ of the sixth main electrode 80 exceeds 10 mm, and the inspection electrode 55 has one main electrode (sixth main electrode) 80. The second embodiment is different from the first embodiment in that it includes two guard electrodes 82a and 82b.

Referring to FIG. 12, the inspection electrode 55 has a sixth main electrode 80 as a first electrode. The sixth main electrode 80 has the same structure as the first main electrode 40 according to the first embodiment. That is, the sixth main electrode 80 has an arc shape that is divided into four parts so as to be separated from each other in the circumferential direction of the conductor 10 in a cross section perpendicular to the longitudinal direction of the conductor 10, and along the longitudinal direction of the conductor 10. The four electrode units 80a, 80b, 80c, and 80d (80d is not shown) are extended. The sixth main electrode 80 has a length L ₈₀ along the longitudinal direction of the conductor 10. The length L ₈₀ exceeds 10 mm. Each electrode unit of the sixth main electrode 80 is connected to a capacitance monitor 58 (FIG. 2) via wiring. For convenience of explanation, in FIG. 12, illustration of wiring connected to each electrode is omitted.

  A ninth guard electrode 82a is disposed on the upstream side in the longitudinal direction of the conductor 10 when viewed from the sixth main electrode 80. A tenth guard electrode 82 b is disposed on the downstream side in the longitudinal direction of the conductor 10 when viewed from the sixth main electrode 80. Each of the ninth guard electrode 82a and the tenth guard electrode 82b has the same structure and the same function as each of the first guard electrode 42a, the second guard electrode 42b, and the third guard electrode 42c according to the first embodiment. .

  In the step of inspecting the formation state of the insulating film 20, a voltage is applied to the sixth main electrode 80, and the first unit between the electrode units 80 a, 80 b, 80 c, 80 d of the sixth main electrode 80 and the insulated wire 1 is applied. And the formation state of the insulating film 20 is inspected based on the relationship between the first capacitance and the porosity of the insulating film 20.

  Referring to FIG. 12, the sixth main electrode 80 as the first electrode in the present embodiment is divided into four so as to be separated from each other in the circumferential direction of the conductor 10 in a cross section perpendicular to the longitudinal direction of the conductor 10. It has a circular arc shape and is composed of four electrode units 80 a, 80 b, 80 c and 80 d extending along the longitudinal direction of the conductor 10. As described above, by using the sixth main electrode 80 composed of a plurality of electrode units divided in the circumferential direction, it is possible to finely specify the positions of defects in the circumferential direction of the insulated wire 1.

  In addition, in each said embodiment, although the manufacturing method of the linear insulated wire 1 which has a circular cross-sectional shape was demonstrated, the cross-sectional shape of the insulated wire 1 is not limited to these, Arbitrary squares, hexagons, etc. are arbitrary. It is also possible to obtain an insulated wire processed into a cross-sectional shape.

  In the above embodiment, the capacitance sensor 2 for detecting the capacitance is arranged at a position immediately before being taken up by the take-up unit 56. However, an apparatus for detecting the capacitance is arranged. The position is not limited to this position. For example, in the case where the insulating film 20 is formed by forming a plurality of insulating layers on the conductor 10, instead of the position immediately before being wound at the winding portion 56, or immediately before being wound at the winding portion 56. An inspection device such as the capacitance sensor 2 may be disposed at a position where the electrostatic capacitance can be detected at the intermediate stage before the insulating film 20 is completed.

  Moreover, in the said embodiment, although the length of each guard electrode along the longitudinal direction of the conductor 10 was the same, the said length of each guard electrode may each differ. In addition, the guard electrode can be omitted as long as it does not affect the detection of defects.

  In the said embodiment, although the insulating film 20 was formed by the method of heating the varnish coated on the surface of the conductor 10 in a baking furnace, the formation method of the insulating film 20 is not limited to this method. For example, the insulating film 20 can be formed by extrusion molding of a thermoplastic resin. As for the method for forming the holes 15, not only the method for forming the holes 15 utilizing decomposition of the thermally decomposable resin but also other methods can be used. For example, a phase separation method (a method of forming a pore by extracting and removing a solvent after a microphase separation from a homogeneous solution of a polymer and a solvent) or a supercritical method (a porous material is formed using a supercritical fluid) It is also possible to form the holes 15 in the insulating film 20 using the method.

  In the drawing, among the plurality of electrode units having an arc shape divided into four in the circumferential direction, the electrode units (electrode units 41d, 60d, 70d, 71d, and 80d) that are hidden behind other electrodes and cannot be illustrated. The illustration is omitted.

[Inspection example]
Next, based on the manufacturing method of the insulated wire 1 of this application, the example which actually measured the defect of the insulating film 20 with the capacitance sensor 2 is shown.

(Inspection example 1)
A defect-free insulated electric wire 1 having a conductor 10 and an insulating film 20 covering the conductor 10 was prepared. A hole having a square shape with a side of 0.5 mm is formed in the insulating film 20 and filled with an epoxy resin (dielectric constant of about 3.1) to artificially generate a low porosity portion. A measurement sample A having 21 was prepared. Similarly, a hole having a square shape with a side of 0.4 mm is formed in the insulating film 20 and the hole is filled with the same epoxy resin to artificially have the low porosity portion 21. Sample B was prepared.

  Whether or not the low porosity portion 21 of the measurement sample A and the measurement sample B is detected is inspected using the capacitance sensor 2 having the inspection electrode 55 according to the first embodiment. As a result, the low porosity portion 21 was detected for both the measurement sample A and the measurement sample B.

(Inspection example 2)
Whether or not the low porosity portion 21 of the measurement sample A and the measurement sample B is detected is inspected using the capacitance sensor 2 having the inspection electrode 55 according to the second embodiment. As a result, the low porosity portion 21 was detected for both the measurement sample A and the measurement sample B.

(Inspection example 3)
Whether or not the low porosity portion 21 of the measurement sample A and the measurement sample B is detected is inspected using the capacitance sensor 2 having the inspection electrode 55 according to the third embodiment. As a result, the low porosity portion 21 was detected for both the measurement sample A and the measurement sample B.

(Inspection example 4)
Whether or not the low porosity portion 21 of the measurement sample A and the measurement sample B is detected is inspected using the capacitance sensor 2 having the inspection electrode 55 according to the third embodiment. As a result, the low porosity portion 21 was detected for both the measurement sample A and the measurement sample B.

  As described above, in any of the inspection examples, the low porosity portion 21 having a square shape with a side of 0.5 mm in a plan view and the square shape with a side of 0.4 mm in a plan view. It was revealed that the low porosity portion 21 can be detected.

[Summary]
As described above, according to the method for manufacturing the insulated wire 1 of the present application, defects, particularly the low porosity portion 21 and the thin portion, of the insulated wire 1 including the insulating film 20 having the holes 15 can affect the insulation. 22 can be detected appropriately, and it becomes possible to manufacture the insulated wire 1 of the stable quality by it.

  It should be understood that the embodiments and inspection examples disclosed herein are illustrative in all respects and are not restrictive in any aspect. The scope of the present invention is defined by the terms of the claims, rather than the meaning described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The method for manufacturing an insulated wire of the present application can be applied particularly advantageously in a technical field that is an insulated wire having an insulating film having pores and requires an insulated wire with few defects.

DESCRIPTION OF SYMBOLS 1 Insulated electric wire 2 Capacitance sensor 10 Conductor 11 Swelling 15 Hole 20 Insulating film 21 Low-porosity part 22 Thin part 23 Scratch 24 Hole 40 1st main electrode 40a, 40b, 40c, 40d Electrode unit 41 2nd main electrode 41a, 41b , 41c, 41d Electrode unit 42a First guard electrode 42b Second guard electrode 42c Third guard electrode 44 Housing 50 Conductive wire preparation portion 51 Wire supply portion 52 Conductor processing portion 53 Inspection portion 54 Insulating film formation portion 55 Inspection electrode 56 Winding Taking part 58 Capacitance monitor 60 Third main electrodes 60a, 60b, 60c, 60d Electrode unit 62a Fourth guard electrode 62b Fifth guard electrode 70 Fourth main electrode 71 Fifth main electrode 72a Sixth guard electrode 72b Seventh guard electrode 72c The eighth guard electrode 80 The sixth main electrode 82a The ninth guard electrode 82b The tenth guard electrode

Claims (6)

Preparing a conductor having a linear shape;
An insulated wire comprising the conductor and the insulating film covering the conductor is obtained by forming an insulating film made of an insulator and including pores inside so as to cover the outer peripheral surface of the conductor. Process,
A first capacitance between the first electrode disposed radially outside the insulated wire and the insulated wire so as to face the outer peripheral surface of the insulated wire is detected, and the first static electricity is detected. Inspecting the formation state of the insulating film based on the relationship between the electric capacity and the porosity of the insulating film,
The first electrode has a shape divided so as to be separated from each other in the circumferential direction of the conductor in a cross section perpendicular to the longitudinal direction of the conductor, and includes a plurality of units extending along the longitudinal direction of the conductor. A method for manufacturing an insulated wire.   The method for manufacturing an insulated wire according to claim 1, wherein the insulating film includes polyimide.   The method for manufacturing an insulated wire according to claim 1, wherein the step of inspecting the formation state of the insulating film is performed online.   A second capacitance between the second electrode disposed radially outside the insulated wire so as to face the outer peripheral surface of the insulated wire and the insulated wire is detected, and the first static electricity is detected. 4. The method according to claim 1, further comprising a step of inspecting a formation state of the insulating film based on a relationship between a capacitance, the second capacitance, and a porosity of the insulating film. The manufacturing method of the insulated wire of description.   The method for manufacturing an insulated wire according to claim 4, wherein a length of the second electrode along a longitudinal direction of the conductor is different from that of the first electrode. The second electrode has a shape divided so as to be separated from each other in the circumferential direction of the conductor in a cross section perpendicular to the longitudinal direction of the conductor, and includes a plurality of units extending along the longitudinal direction of the conductor. The manufacturing method of the insulated wire of Claim 4 or Claim 5 containing.

Images