JP6893815B2 - Manufacturing method of insulated wire - Google Patents

Description

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

As an insulated wire, an insulated wire having a conductor and an insulating film formed on the outer peripheral side of the conductor is known. In such an insulated wire, it is required to suppress the occurrence of partial discharge. Partial discharge is a phenomenon in which when there is a defect in the insulating material, an electric field is concentrated on that part and a weak discharge occurs. If such partial discharge occurs repeatedly, the insulating property is lowered and finally the insulation is poor. Therefore, the insulated wire is required to have excellent insulating properties and high mechanical properties, and 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 having a low dielectric constant. As an insulating wire having an insulating film having a low dielectric constant, an insulated wire having an insulating film having holes on the conductor has been proposed (see, for example, Patent Document 1 and Patent Document 2).

Japanese Unexamined Patent Publication No. 2016-81563 Japanese Unexamined Patent Publication No. 2016-110847

In the actually manufactured insulated wire, a defect may occur in a part of the insulating film having holes. Such defects may cause poor insulation. Among the defects, it is difficult to detect the presence of the defect from the appearance, particularly in a region called a low porosity portion where there are no voids or there are very few voids. A low porosity portion, particularly a non-pore portion having no pores, can cause partial discharge even if the size in a plan view is as small as about 1 mm square. In addition, it is difficult to detect the presence of a defect in which the insulating film is locally thinned (thinned portion) due to the swelling of the conductor from the appearance. If a thin portion is present in the insulating film, the insulating property is lowered in that portion. In order to produce an insulated wire having stable quality, it is preferable to appropriately detect the presence of a low porosity portion and a thin portion and control the quality of the insulating film.

Therefore, it is possible to appropriately detect defects that may affect the insulation characteristics of an insulated wire having an insulating film having pores, particularly fine low porosity parts and thin parts, thereby providing stable quality insulation. One of the purposes is to provide a method for manufacturing an insulated electric wire that enables the manufacture of an electric wire.

The method for manufacturing an insulated wire of the present application is a step of preparing a conductor having a linear shape, and forming an insulating film made of an insulator and containing holes inside so as to cover the outer peripheral surface of the conductor. A step of obtaining an insulated wire having a conductor and an insulating film covering the conductor, a first electrode arranged on the radial outer side of the insulated wire so as to face the outer peripheral surface of the insulated wire, and an insulated wire. Includes a step of detecting a first capacitance between the two and inspecting the state of formation of the insulating coating based on the relationship between the first capacitance and the porosity of the insulating coating. The length of the electrode along the longitudinal direction of the conductor is 0.1 mm or more and 2 mm or less.

According to the above-mentioned method for manufacturing an insulated wire, it is possible to appropriately detect defects that may affect the insulating property of the insulated wire having an insulating film having pores, particularly fine low porosity portion and thin portion. As a result, it becomes possible to manufacture an insulated wire of stable quality.

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

[Explanation of Embodiments of the Invention]
First, embodiments of the present invention will be listed and described. The method for manufacturing an insulated wire of the present application is a step of preparing a conductor having a linear shape, and forming an insulating film made of an insulator and containing holes inside so as to cover the outer peripheral surface of the conductor. A step of obtaining an insulated wire having a conductor and an insulating film covering the conductor, a first electrode arranged on the radial outer side of the insulated wire so as to face the outer peripheral surface of the insulated wire, and an insulated wire. Includes a step of detecting a first capacitance between the two and inspecting the state of formation of the insulating coating based on the relationship between the first capacitance and the porosity of the insulating coating. At this time, the length of the first electrode along the longitudinal direction of the conductor is 0.1 mm or more and 2 mm or less.

The dielectric constant of air is about 1.0. On the other hand, the material constituting the insulating film has a dielectric constant different from that of air. Therefore, if there are vacancies in the insulating film, the dielectric constant of the insulating film as a whole changes according to the abundance ratio (porosity) of the vacancies in the insulating film. As a result of the examination by the present inventors, it was 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 utilizing the above correlation, and the first capacitance is combined with the first capacitance. The state of formation of the insulating film is inspected based on the relationship with the porosity of the insulating film. For example, if the insulating film has defects such as low porosity, thin parts, scratches, and holes, the capacitance between the electrode and the insulating film changes as compared with the steady state. Therefore, when a defect exists, its existence can be detected.

Further, the length of the electrode along the longitudinal direction of the conductor is 0.1 mm or more and 2 mm or less. The value of the capacitance obtained in the above inspection step is an average value along the longitudinal direction of the electrode. When long electrodes are used along the longitudinal direction of the conductor, it is possible to detect a wide range, but the capacitance value is averaged over the longitudinal direction of the electrode, so it is sensitive to minute defects. Difficult to detect well. On the other hand, by setting the length of the electrode along the longitudinal direction of the conductor to 2 mm or less, it is possible to detect even minute defects that cannot be detected by the electrode long in the longitudinal direction. On the other hand, if the length of the electrode along the longitudinal direction of the conductor is too short, the measurement range becomes narrow and the capacitance fluctuates greatly according to the difference in the local state of the insulating film. Defect detection becomes difficult. By setting the length of the electrode along the longitudinal direction of the conductor to 0.1 mm or more, it is possible to detect defects with high accuracy.

Defects such as scratches and holes that can be identified from the appearance of the insulating film can also be detected by a general defect inspection method such as image analysis, but thin parts and fine low porosity parts can be detected only from the appearance. Is difficult to detect. On the other hand, according to the method for manufacturing an insulated wire of the present application, the state of formation of the insulating film is inspected based on the relationship between the first capacitance and the porosity of the insulating film using the above-mentioned electrodes. Not only scratches and holes, but also the presence of such thin parts and fine low porosity parts can be detected. As a result, according to the method for manufacturing an insulated wire of the present application, defects can be accurately detected, and an insulated wire of stable quality can be manufactured.

The insulating film may contain polyimide. The insulating film containing polyimide is excellent in insulating property and heat resistance. Therefore, polyimide is suitable as a material for forming an insulating film.

The step of inspecting the formation state of the insulating film is preferably performed online. By inspecting the process of inspecting the formation state of the insulating film online, it is possible to continuously manufacture the insulated electric wire, and it is possible to obtain the insulated electric wire with high production efficiency. The state of performing the inspection online means a state of inspecting the formation state of the insulating film continuously in the process of obtaining the insulated wire in a series of manufacturing processes.

In the method for manufacturing an insulated wire, the first electrode includes a plurality of units having a shape divided so as to be separated from each other in a cross section perpendicular to the longitudinal direction of the conductor and extending along the longitudinal direction of the conductor. But it may be. When the first electrode has such a shape, it is possible to specify the position of the defect in the circumferential direction of the insulated wire in detail.

The method for manufacturing an insulated wire detects a second capacitance between a second electrode arranged radially outside the insulated wire so as to face the outer peripheral surface of the insulated wire and the insulated wire. A step of inspecting the formation state of the insulating film based on the relationship between the first capacitance and the second capacitance and the pore ratio of the insulating film may be further included. By performing the inspection using a plurality of electrodes including the first electrode and the second electrode, erroneous detection of defects can be reduced and defects can be detected more accurately.

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 so, the first capacitance between the first electrode and the insulated wire and the second capacitance between the second electrode and the insulated wire are obtained and based on them. By comparing the inspection results (by taking the difference between the two), it is possible to detect defects with higher accuracy.

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

[Details of Embodiments of the present invention]
Next, an embodiment of the method for manufacturing an insulated wire of the present application will be described with reference to the drawings. In the drawings below, the same or corresponding parts are given the same reference number and the explanation is not repeated.

(Embodiment 1)
[Structure of insulated wire]
First, the first embodiment will be described with reference to FIGS. 1 to 9. FIG. 1 shows a schematic cross-sectional view of an example of an insulated wire 1 manufactured by the method for manufacturing an insulated wire of the present application. With reference to FIG. 1, the insulated wire 1 having a circular cross-sectional shape in a cross section perpendicular to the longitudinal direction of the conductor 10 having a linear shape includes the linear conductor 10 having a circular cross-sectional shape and the conductor 10. An insulating film 20 that covers the conductor 10 so as to cover the outer peripheral surface of the conductor 10 is provided. The insulating film 20 is made of an insulator containing an organic material. Further, the insulating film 20 includes holes 15 inside. Specifically, the insulating film 20 is formed in a state in which a plurality (many) of pores 15 are dispersed therein.

The organic material contained in the insulator is not particularly limited. For example, if it is a thermosetting resin, it is polyimide (PI) or polyamide-imide, and if it is a thermoplastic resin, it is polyethersulfone (PES) or polyetheretherketone (). PEEK) and the like. Among them, the insulator constituting the insulating film 20 preferably contains polyimide, and more preferably 50% by mass or more of the insulator constituting the insulating film 20 is polyimide because of its excellent insulating property and heat resistance. It is particularly preferably composed of polyimide and unavoidable impurities. For example, the insulating film 20 in the present embodiment is a polyimide film composed of polyimide and unavoidable impurities. With reference to FIG. 1, the insulating film 20 in the present embodiment includes holes 15 inside thereof. The ratio (porosity) of the total volume of the pores 15 to the total volume of the insulating film 20 is, for example, 5% by volume or more and 80% by volume or less, preferably 10% by volume or more and 70% by volume or less, and more preferably 25 volumes. % Or more and 65% by volume or less. Since the dielectric constant of the material constituting the insulating film 20 such as polyimide and air is different, the dielectric constant of the insulating film 20 as a whole changes when the insulating film 20 has pores 15. For example, polyimide has a higher dielectric constant (relative permittivity) than air. Therefore, when the insulating film 20 is made of polyimide, since the insulating film 20 has holes 15, it is possible to obtain an 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 the insulating film 20. Further, 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 laminated 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 the required characteristics.

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

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

The insulating film forming portion 54 is arranged on the downstream side of the conductor processing portion 52. The insulating film forming portion 54 includes, for example, a coating device for coating the conductor 10 with a varnish as a raw material for the insulating film 20, and a baking furnace for heating the coated varnish to form a polyimide film.

The inspection unit 53 is arranged 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 determines the first capacitance and the porosity of the insulating film 20. The state of formation of the insulating film 20 is inspected based on the above relationship. Further, the second capacitance between the second main electrode 41 as the second electrode and the insulated wire 1 is detected, and the first capacitance, the second capacitance, and the insulating film 20 are detected. The state of formation of the insulating film 20 may be inspected based on the relationship with the pore ratio of. The inspection unit 53 includes a capacitance sensor 2 and a capacitance monitor 58. The capacitance sensor 2 includes an inspection electrode 55, a housing 44, and wiring connected to each electrode in the inspection electrode 55. As 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. To.

The structure of the capacitance sensor 2 will be described with reference to FIGS. 2, 4 and 5. The capacitance sensor 2 includes an inspection electrode 55 and a housing 44. The inspection electrode 55 of the capacitance sensor 2 according to the first embodiment includes the first main electrode 40 as the first electrode, the second main electrode 41 as the second electrode, and the first guard electrode 42a. , The second guard electrode 42b and the third guard electrode 42c are included. 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 formed.

The structure of the inspection electrode 55 will be further described with reference to FIG. The first main electrode 40 has an arcuate shape divided into four in the circumferential direction so as to be separated from each other in a cross section perpendicular to the longitudinal direction of the conductor 10, and four extending along the longitudinal direction of the conductor 10. It is composed of electrode units 40a, 40b, 40c, and 40d. The second main electrode 41 also has a similar cross-sectional shape, and is composed of four electrode units extending along the longitudinal direction of the conductor 10 (not shown). The four electrode units 40a, 40b, 40c, 40d of the first main electrode 40 (and the four electrode units 41a, 41b, 41c, 41d (not shown) of the second main electrode 41) are shown in FIG. As described above, each of them is connected to the capacitance monitor 58 via wiring. For convenience of explanation, in FIG. 4, the wiring connected to each electrode is not shown.

_{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. Specifically, the length L ₄₀ of the first main electrode 40 is 1 mm, and the length L ₄₁ of the second main electrode 41 is 1.5 mm. In the step of inspecting the formation state of the insulating film 20, a voltage is applied to each of the first main electrode 40 and the second main electrode 41, and the first capacitance between the first main electrode 40 and the insulated wire 1 is applied. The capacitance and the second capacitance between the second main electrode 41 and the insulated wire 1 are detected.

The first guard electrode 42a is arranged on the upstream side in the longitudinal direction of the conductor 10 when viewed from the first main electrode 40. The second guard electrode 42b is arranged between the first main electrode 40 and the second main electrode 41 along the longitudinal direction of the conductor 10. The third guard electrode 42c is arranged 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 relax 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. It is installed to stably measure the numerical values of the first capacitance and the second capacitance generated between the and the second main electrode 41. The first guard electrode 42a, the second guard electrode 42b, and the third guard electrode 42c are connected to each other via wiring. Further, 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 portion 56, and the winding portion 56, the first guard electrode 42a, the second guard electrode 42b, and the winding portion 56 are connected. It is grounded in the path between it and 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. Along the longitudinal direction of the conductor 10, the length _{L 42a} of the first guard electrode 42a, the length _{L 42c} of the second length _{L 42b} of the guard electrode 42b, and the third guard electrode 42c, is a 5mm or less than 100mm, respectively is there.

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 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 distance G between the main electrodes 40 and 41 and the guard electrodes 42a, 42b and 42c is set to be approximately 2 mm or more and 5 mm or less. The distance between the insulated wire 1 and the main electrodes 40 and 41 is appropriately set within a range in which the measured first capacitance and the second capacitance are stable.

The capacitance monitor 58 is connected to each electrode unit constituting the inspection electrode 55 of the capacitance sensor 2. Further, 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. From the fluctuation of the capacitance displayed or recorded on the capacitance monitor 58, it is possible to distinguish between a normal portion and a defective portion in the insulated wire 1.

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

In the above embodiment, the first guard electrode 42a, the second guard electrode 42b, and the third guard electrode 42c are used, but these guard electrodes may be replaced with ordinary electrodes (secondary electrodes). The length of the auxiliary electrode along the longitudinal direction of the conductor 10 is not particularly limited, but is usually set to be longer than _{the length L 40 of the first main electrode and the length L 41 of} the second main electrode.

[Procedure of manufacturing method of insulated wire 1]
Next, the procedure of the manufacturing method of the insulated wire 1 will be described with reference to FIGS. 1 to 9. FIG. 6 is a schematic cross-sectional view showing a state of defects in the low porosity portion in the insulating film. FIG. 7 is a schematic cross-sectional view showing a state of a thin portion of the insulating film 20. FIG. 8 is a schematic cross-sectional view showing a state of scratches and defects 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, the steps S10 to S30 shown in FIG. 3 are carried out. With reference to FIGS. 2 and 3, first, the conductor preparation unit 50 prepares a linear conductor 10 having a circular cross-sectional shape (S10). Specifically, a metal wire such as a copper wire held by the wire 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 wire supplied from the wire supply unit 51 is processed into a conductor 10 having a desired shape and size by drawing (drawing) with a die. The conductor 10 processed from the wire 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 holes 15 inside. The insulating film 20 including the pores 15 inside is formed as follows.

As described above, the insulating film forming portion 54 includes a varnish coating device and a baking furnace. In the insulating film forming portion 54, the insulating film 20 is formed on the surface of the conductor 10 by the following procedure.

First, the conductor 10 processed by the conductor processing portion 52 passes through the varnish held in the coating device, so that the varnish is coated so as to cover the outer peripheral surface of the conductor 10. The varnish coated in the present embodiment is a polyimide precursor containing a mixture of a polyimide precursor and a pyrolysis resin in an organic solvent. Next, when the coated coating film is heated in the baking oven, the reaction from the polyimide precursor to the polyimide is promoted. Since polyimide is thermosetting, the coating film is cured by heating. In addition, the pyrolysis resin is decomposed and vaporized by heating. At this time, pores 15 are formed in the cured film of polyimide where the thermosetting resin was present. In this way, an insulating film 20 made of polyimide as an insulator and having a large number of pores 15 dispersed inside is formed so as to cover the outer peripheral surface of the conductor 10.

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

Following 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. The 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 determines the first capacitance and the porosity of the insulating film 20. The state of formation of the insulating film 20 is inspected based on the above relationship. Further, the second capacitance between the second main electrode 41 as the second electrode and the insulated wire 1 is detected, and the first capacitance, the second capacitance, and the insulating film 20 are detected. The state of formation of the insulating film 20 may be inspected based on the relationship with the pore ratio of. In the present embodiment, the second capacitance between the second main electrode 41 and the insulated wire 1 is detected, and the first capacitance, the second capacitance, and the insulating film 20 are formed. The state of formation of the insulating film 20 is inspected based on the relationship with the porosity. By doing so, defects can be detected with higher accuracy.

Specifically, the inspection is performed as follows. First, a voltage is applied to each of the first main electrode 40 and the second main electrode 41, the first capacitance between the first main electrode 40 and the insulated wire 1, and the second main electrode 41 and the insulated wire 1 The second capacitance between and is detected. At this time, for example, an operational amplifier is used so that there is no difference between the potentials of the first main electrode 40 and the second main electrode 41 and the potentials of the guard electrodes 42a, 42b, and 42c. Capacitance can be detected.

Next, the formation state of the insulating film 20 is inspected based on the relationship between the detected first capacitance and the second capacitance and the porosity of the insulating film 20. For example, when the porosity of the insulating film 20 is stable, the detected capacitance shows a steady value. On the other hand, when the insulating film 20 has a defect, the porosity fluctuates, so that the capacitance also changes accordingly. The location of the defect is identified and recorded based on the change in capacitance. In this way, the insulated wire 1 having stable quality can be manufactured.

The insulated wire 1 whose forming state of the insulating film 20 is inspected by the capacitance sensor 2 is then wound by the winding portion 56. The wound insulated wire 1 may be used as a product in a state where the defect position is recorded, or the insulated wire 1 containing a defect may be discarded without being made into a product. Further, only the defective part may be deleted based on the recorded position, and the rest may be used as a product.

The above tests are done online. In the online inspection, in a series of steps from steps S10 to S30, the formation state of the insulating film 20 obtained in step S20 is inspected following the step S20. Further, when the inspection is performed online, 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, a voltage is applied to the first main electrode 40 and the second main electrode 41 while the inspection electrode 55 is immersed in water, and the first main electrode 40 or the second main electrode is inspected. The first capacitance and the second capacitance between the 41 and the insulated wire 1 are monitored by the capacitance monitor 58.

In the first embodiment, the first main electrode 40 and the second main electrode 41 having a length of 0.1 mm or more and 2 mm or less along the longitudinal direction of the conductor 10 are used. The value of the capacitance to be measured 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, minute defects can be sensitively detected. Difficult to detect. _{On the other hand, by setting the lengths L 40} and L ₄₁ of the first main electrode 40 and the second main electrode 41 along the longitudinal direction of the conductor 10 to 2 mm or less, fine particles that cannot be detected by the electrodes long in the longitudinal direction can be detected. Defects can also be detected. _{Further, by setting the lengths L 40} and L ₄₁ of the first main electrode 40 and the second main electrode 41 along the longitudinal direction of the conductor 10 to 0.1 mm or more, it is possible to detect defects with high accuracy. ..

In the method for 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 in which the porosity is significantly lower than the average porosity of the entire insulating film 20 and the proportion of the pores 15 is small. Among the low porosity portions 21, a portion in which no pores 15 exist is called a non-pore portion. Such a low porosity portion 21, particularly a non-porosity portion, can cause partial discharge even if the size is as small as 1 mm square in a plan view. In order to manufacture an insulated wire 1 having stable quality, it is preferable to appropriately detect the presence of such a low porosity portion 21 and control the quality of the insulating film 20.

Further, in the method for manufacturing the insulated wire 1 according to the first embodiment, it is possible to detect the thin portion 22 in the insulating film 20 as shown in FIG. 7. The thin portion 22 refers to a portion where the insulating film 20 is locally thinned due to the swelling 12 of the conductor 10. If such a thin portion 22 is present, the insulating property is lowered in the thin portion 22. Therefore, in order to manufacture an insulated wire having stable quality, it is preferable to appropriately detect the presence of such a thin portion 22 and control the quality of the insulating film 20.

Further, defects that can be identified from the appearance of the insulating film 20 such as scratches 23 on the surface of the insulating film 20 as shown in FIG. 8 and holes 24 of the insulating film 20 as shown in FIG. 9 are generally found by image analysis or the like. 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. 7 only from the appearance. 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 inspecting the formation state of the insulating film 20 based on the relationship with, it is possible to detect the presence of not only the scratch 23 and the hole 24 but also such a fine low porosity portion 21 and the thin portion 22. .. As a result, according to the method for manufacturing the insulated wire 1 of the present application, defects can be accurately detected, and the insulated wire 1 of stable quality can be manufactured.

_{In this way, the lengths L 40} and L ₄₁ of the first main electrode 40 and the second main electrode 41 along the longitudinal direction of the conductor 10 are set to 2 mm or less, and the first capacitance and the second capacitance are set to 2 mm or less. By inspecting the formation state of the insulating film 20 based on the relationship between the insulation film 20 and the porosity of the insulating film 20, not only defects due to scratches 23 and holes 24 or large defects but also fine low porosity portions 21 and , It is possible to detect a defect due to the thin portion 22. _{Further, by setting the lengths L 40} and L ₄₁ along the longitudinal direction of the conductor 10 to 0.1 mm or more, it is possible to detect defects with high accuracy. As a result, according to the method for manufacturing the insulated wire 1 of the present application, it is possible to manufacture the insulated wire 1 having stable quality by controlling the porosity.

Further, as shown in FIG. 4, in the first embodiment, the first main electrode 40 has an arcuate shape divided into four in the circumferential direction so as to be separated from each other in a cross section perpendicular to the longitudinal direction of the conductor 10. It is composed of four electrode units 41a, 41b, 41c, and 41d that have and extend along the longitudinal direction of the conductor 10. Similarly, the second main electrode 41 is also 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 a plurality of electrode units divided in the circumferential direction in this way, the location of defects in the circumferential direction of the insulated wire 1 can also be specified in detail. Is possible. The number of the plurality of electrode units in the circumferential direction of the main electrode is not particularly limited to four. A main electrode having an arbitrary number of two or more electrode units in the circumferential direction, such as a main electrode having an electrode unit divided into two in the circumferential direction, can be selected as needed.

Further, in the first embodiment, the capacitance sensor 2 is provided with an inspection electrode 55 having a plurality of main electrodes, that is, a first main electrode 40 and a second main electrode 41 having different lengths along the longitudinal direction of the conductor 10. The first capacitance and the second capacitance are measured using. By performing the inspection using a plurality of main electrodes in this way, it is possible to verify whether or not the inspection result of one main electrode includes a false detection of a defect by comparing with the inspection result of another main electrode. Can be done. As a result, erroneous detection of defects can be reduced, and defects can be detected more accurately.

Further, by comparing the inspection results measured using the plurality of main electrodes having different lengths in this way, it is possible to inspect the formation state of the insulating film 20 in a narrower range. That is, the first capacitance between the first main electrode 40 having a _{length L 40 of 1 mm and the insulated wire 1 and the second main electrode 41 having a length L 41} of 1.5 mm and the insulated wire 1 By obtaining the second capacitance between them and comparing the inspection results based on them (by taking the difference between the two), more accurate defect detection becomes possible.

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

(Embodiment 2)
Next, the second embodiment, 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 according to the second embodiment. The method for manufacturing the insulated wire 1 according to the present embodiment is basically the same as that of 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 the case of the first embodiment in that it is composed of one main electrode 60 and two guard electrodes 62a and 62b.

With reference to FIG. 10, the third main electrode 60 as the first electrode in the present embodiment has the same structure as the first main electrode 40 according to the first embodiment. That is, the third main electrode 60 has an arcuate shape divided into four in the circumferential direction so as to be separated from each other in a cross section perpendicular to the longitudinal direction of the conductor 10, and extends along the longitudinal direction of the conductor 10. It is composed of four electrode units 60a, 60b, 60c, and 60d (60d is not shown). _{The length L 60} of the third main electrode 60 along the longitudinal direction of the conductor 10 is 1 mm, which is within the range of 0.1 mm or more and 2 mm or less.

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

According to the inspection unit 53 in the present embodiment, although it is not possible to compare the inspection results using a plurality of main electrodes having different lengths as in the first embodiment, the length along the longitudinal direction of the conductor 10 L ₆₀ is sufficiently short as 1 mm. Therefore, as in the first embodiment, defects such as the fine low porosity portion 21 and the thin portion 22 can be detected.

Further, the third main electrode 60, like the first main electrode 40 and the second main electrode 41, has an arcuate shape divided into four in the circumferential direction so as to be separated from each other in a cross section perpendicular to the longitudinal direction of the conductor 10. It is composed of four electrode units 60a, 60b, 60c, and 60d that have and extend along the longitudinal direction of the conductor 10. Therefore, it is possible to specify in detail the position of the defect in the circumferential direction of the insulated wire 1.

(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 according to the third embodiment. The method for manufacturing the insulated wire 1 according to the present embodiment is basically the same as that of the first embodiment, and has the same effect. However, the inspection electrode 55 of the capacitance sensor 2 according to the third embodiment has a ring shape in which two main electrodes 70 and 71 are continuously connected in the circumferential direction in a cross section perpendicular to the longitudinal direction of the conductor 10. It is different from the case of the first embodiment in that it has.

_{With reference to FIG. 11, the length L 70} in the longitudinal direction of the conductor 10 of the fourth main electrode 70 as the first electrode in the present embodiment is the length of the first main electrode 40 according to the first embodiment. It is 1 mm like the _{L 40. Further, in the present embodiment, the longitudinal length L 71} of the conductor 10 of the fifth main electrode 71 as the second electrode is the longitudinal length of the conductor 10 of the second main electrode 41 according to the first embodiment. It is 1.5 mm like the _{L 41.} Both the length L ₇₀ and the length L ₇₁ are within the range of 0.1 mm or more and 2 mm or less.

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

According to the inspection electrode 55 in the present embodiment, although it is difficult to specify the location of the defect in the circumferential direction of the insulated wire 1 in detail as in the first embodiment, the fourth main electrode 70 of the insulated wire 1 has a defect. _{The length L 70} along the longitudinal direction of the conductor 10 is sufficiently short as 1 mm. Therefore, as in the first embodiment, defects such as the fine low porosity portion 21 and the thin portion 22 can be detected. _{Further, since the length L 70 of} the fourth main electrode 70 along the longitudinal direction of the conductor 10 is 0.1 mm or more, it is possible to detect defects with high accuracy.

The inspection electrode 55 in the present embodiment has a plurality of main electrodes (fourth main electrode 70 and fifth main electrode 71). Therefore, the first capacitance and the second capacitance measured using the two main electrodes are obtained, and the inspection results based on them are compared (by taking the difference between the two) to make it 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 fourth main electrode 70 having a _{length L 70 of 1 mm and the insulated wire 1 and the fifth main electrode 71 having a length L 71} of 1.5 mm and the insulated wire 1 By obtaining the second capacitance between them and comparing the inspection results based on them (by taking the difference between the two), the formation state of the insulating film 20 substantially corresponding to the range of 0.5 mm can be obtained. Can be inspected.

(Embodiment 4)
Next, the fourth embodiment, 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 according to the fourth embodiment. The method for manufacturing the insulated wire 1 according to the present embodiment is basically the same as that of 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 ring shape in which the main electrode 80 is continuously connected in the circumferential direction in a cross section perpendicular to the longitudinal direction of the conductor 10. , And the inspection electrode 55 is different from the case of the first embodiment in that it is composed of one main electrode 80 and two guard electrodes 82a and 82b.

Referring to FIG. 12, in this embodiment, the longitudinal length L ₈₀ of the conductor 10 of the sixth main electrode 80 as a first electrode, the first main electrode 40 according to the first embodiment, The length of the conductor 10 in the longitudinal direction _{is 1 mm, which is the same as that of L 40,} and is within the range of 0.1 mm or more and 2 mm or less.

The ninth guard electrode 82a is arranged on the upstream side in the longitudinal direction of the conductor 10 when viewed from the sixth main electrode 80. The tenth guard electrode 82b is arranged 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 the first guard electrode 42a, the second guard electrode 42b, and the third guard electrode 42c according to the first embodiment.

In the inspection electrode 55 according to the present embodiment, the length L ₈₀ of the sixth main electrode 80 along the longitudinal direction of the conductor 10 is sufficiently short as 1 mm. Therefore, although it is difficult to specify the location of the defect in the circumferential direction of the insulated wire 1 in detail as in the first embodiment, or to inspect a finer range as in the case of comparing the inspection results using a plurality of electrodes. As in the first embodiment, defects such as a fine low porosity portion 21 and a thin portion 22 can be detected. _{Further, since the length L 80} of the sixth main electrode 80 along the longitudinal direction of the conductor 10 is 0.1 mm or more, it is possible to detect defects with high accuracy.

In each of the above embodiments, the method of manufacturing the linear insulated wire 1 having a circular cross-sectional shape has been described, but the cross-sectional shape of the insulated wire 1 is not limited to these, and any arbitrary shape such as a quadrangle or a hexagon can be used. It is also possible to obtain an insulated wire processed into a cross-sectional shape.

Further, in the above embodiment, only an example in which the lengths of the first main electrode 40 and the second main electrode 41 along the longitudinal direction of the conductor 10 are 1 mm or 1.5 mm, respectively, is shown, but the lengths are 0. It is not particularly limited as long as it is within the range of 1 mm or more and 2 mm or less. When having a plurality of main electrodes, at least one of the above lengths may be in the range of 0.1 mm or more and 2 mm or less.

Further, in the above embodiment, the capacitance sensor 2 for detecting the capacitance is arranged at the position immediately before being wound by the winding unit 56, but a device for detecting the capacitance is arranged. The position is not limited to this position. For example, when the insulating film 20 is formed by forming a plurality of layers of insulating layers on the conductor 10, instead of the position immediately before being wound by the winding portion 56, or immediately before being wound by the winding portion 56. In addition to the position of, an inspection device such as a capacitance sensor 2 may be arranged at a position where the capacitance can be detected at the stage of the intermediate body before the insulating film 20 is completed.

Further, in the above embodiment, the length of each guard electrode along the longitudinal direction of the conductor 10 is the same, but the length of each guard electrode may be different. Further, the guard electrode can be omitted as long as it does not affect the detection of defects.

In the above embodiment, the insulating film 20 is formed by a method of heating the varnish coated on the surface of the conductor 10 in a baking furnace, but the method of forming 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. Further, as the method for forming the pores 15, not only the method for forming the pores 15 using the decomposition of the thermally decomposable resin but also other methods can be used. For example, a phase separation method (a method of forming a porous body by extracting and removing a solvent after microphase separation from a uniform solution of a polymer and a solvent) or a supercritical method (a method of forming a porous body using a supercritical fluid). It is also possible to form the pores 15 in the insulating film 20 by using the method).

[Inspection example]
Next, an example in which the defect of the insulating film 20 is actually measured by the capacitance sensor 2 based on the manufacturing method of the insulated wire 1 of the present application will be shown.

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

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

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

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

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

As described above, in each of the inspection examples, the low porosity portion 21 has a square shape with a side of 0.5 mm when viewed in a plane, and the square shape has a side of 0.4 mm when viewed in a plane. It has become clear 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 that may affect the insulating property of the insulated wire 1 having the insulating film 20 having the pores 15, particularly the fine low porosity portion 21 and , The thin portion 22 can be appropriately detected, whereby the insulated wire 1 having stable quality can be manufactured.

It should be understood that the embodiments and test examples disclosed this time are exemplary in all respects and are not restrictive in any way. The scope of the present invention is not defined as described above, but is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

The method for manufacturing an insulated wire of the present application is an insulated wire provided with an insulating film having holes, and can be particularly advantageously applied in a technical field in which an insulated wire having few defects is required.

1 Insulated wire 2 Capacitance sensor 10 Conductor 11 Bulge 15 Vacancy 20 Insulation film 21 Low pore ratio part 22 Thin part 23 Scratch 24 Hole 40 1st main electrode 40a, 40b, 40c, 40d Electrode unit 41 2nd main electrode 42a 1st Guard electrode 42b 2nd guard electrode 42c 3rd guard electrode 44 Housing 50 Conductor preparation part 51 Wire supply part 52 Conductor processing part 53 Inspection part 54 Insulation film forming part 55 Inspection electrode 56 Winding part 58 Capacitance monitor 60 Third main Electrodes 60a, 60b, 60c, 60d Electrode unit 62a 4th guard electrode 62b 5th guard electrode 70 4th main electrode 71 5th main electrode 72a 6th guard electrode 72b 7th guard electrode 72c 8th guard electrode 80 6th main electrode 82a 9th guard electrode 82b 10th guard electrode

Claims (5)

The process of preparing a conductor with a linear shape and
So as to cover the outer peripheral side surface of the conductor, an insulating material, by forming an insulating skin layer containing voids therein, an insulated wire having said conductor, and said insulating skin layer to cover the conductive And the process of getting
It is arranged on the outer side in the radial direction of the insulated wire so as to face the outer peripheral surface of the insulated wire, has a shape divided so as to be separated from each other in a cross section perpendicular to the longitudinal direction of the conductor, and has a shape divided so as to be separated from each other in the longitudinal direction of the conductor. The first capacitance between the first electrode including a plurality of electrode units extending along the above and the insulating electric wire is detected, and the first capacitance and the pore ratio of the insulating film are determined. Including the step of inspecting the formation state of the insulating film based on the relationship of
A method for manufacturing an insulated electric wire, wherein the length of the first electrode along the longitudinal direction of the conductor is 0.1 mm or more and 2 mm or less. The method for manufacturing an insulated electric wire according to claim 1, wherein the insulating film contains polyimide. The method for manufacturing an insulated electric wire according to claim 1 or 2, wherein the step of inspecting the formation state of the insulating film is performed online. Wherein it is located radially outwardly of the insulated wire so as to face the outer peripheral surface of the insulated wire, and a second electrode disposed downstream from the first electrode, the second between the insulated wire The step of detecting the capacitance and inspecting the formation state of the insulating film based on the relationship between the first capacitance and the second capacitance and the pore ratio of the insulating film is further included. The method for manufacturing an insulated wire according to any one of claims 1 to 3. The second electrode has a shape divided so as to be separated from each other in a cross section perpendicular to the longitudinal direction of the conductor, and includes a plurality of electrode units extending along the longitudinal direction of the conductor. 4. The method for manufacturing an insulated wire according to 4.

Images