Insulated wire production device and insulated wire production method

Abstract

An insulated wire production device according to the present disclosure is for applying a varnish for forming an insulating layer to the outer circumferential surface of a linear conductor while running the conductor vertically upward along the longitudinal axis of the conductor, and comprises: a varnish tank that stores the varnish; a coating die into which the conductor that has passed through the varnish tank is inserted; and an upper surface member positioned between the varnish tank and the coating die. The upper portion of the varnish tank is closed by the upper surface member. The bottom surface of the varnish tank and the upper surface member have a through-hole through which the conductor penetrates.

Description

Insulated wire manufacturing apparatus and insulated wire manufacturing method

[0001] This disclosure relates to an insulated wire manufacturing apparatus and a method for manufacturing an insulated wire. This application claims priority to Japanese Application No. 2024-109924, filed on July 8, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] Insulated wires are known in which a linear conductor is coated with varnish (insulating paint). The insulated wires are manufactured by repeatedly applying and baking varnish to the outer surface of the linear conductor while the conductor is running in its axial direction until the insulating coating reaches a predetermined thickness.

[0003] Known manufacturing devices for such insulated wires include a vertical manufacturing device that includes an application unit that applies varnish to the surface of a running conductor and a heating unit that heats the conductor to which the varnish has been applied to form an insulating layer on the outer peripheral surface of the conductor (see Patent Document 1).

[0004] JP 2015-43305 A

[0005] The insulated wire manufacturing apparatus of the present disclosure is an insulated wire manufacturing apparatus that applies varnish for forming an insulating layer to the outer peripheral surface of a linear conductor while running the conductor vertically upward along the longitudinal axis of the conductor, and is equipped with a varnish tank that stores the varnish, an application die into which the conductor that has passed through the varnish tank is inserted, and an upper surface member located between the varnish tank and the application die, the upper part of the varnish tank being closed by the upper surface member, and the bottom surface of the varnish tank and the upper surface member having through holes that allow the conductor to pass through.

[0006] FIG. 1 is a schematic configuration diagram of an insulated electric wire manufacturing apparatus according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of a coating device of an insulated electric wire manufacturing apparatus according to a first embodiment of the present disclosure. FIG. 3 is a schematic cross-sectional view of a coating device of an insulated electric wire manufacturing apparatus according to a second embodiment of the present disclosure. FIG. 4 is a schematic cross-sectional view of a coating device of an insulated electric wire manufacturing apparatus according to a third embodiment of the present disclosure. FIG. 5 is a schematic cross-sectional view of a coating device of an insulated electric wire manufacturing apparatus according to a fourth embodiment of the present disclosure. FIG. 6 is a schematic cross-sectional view of a coating device of an insulated electric wire manufacturing apparatus according to a fifth embodiment of the present disclosure. FIG. 7 is a schematic cross-sectional view of a coating device of an insulated electric wire manufacturing apparatus according to a sixth embodiment of the present disclosure. FIG. 8 is a graph showing the relationship between the mass of filtered varnish and the filtration rate index in an insulated electric wire manufacturing apparatus according to an embodiment of the present disclosure.

[0007] In the conventional insulated wire manufacturing apparatus described above, the conductor is moved from below the varnish tank into the varnish tank and immersed in the varnish bath, thereby coating the outer surface of the conductor with varnish. The conductor then passes through a coating die, which adjusts the coating layer to a substantially uniform thickness. At this time, the varnish removed by the coating die is discharged downward and returned to the varnish tank. When the varnish removed by the coating die is returned to the varnish tank in this way, even if it solidifies through drying, it tends to remain as a solidified material in the varnish tank. If new varnish is applied to the conductor while this solidified material remains, there is a problem in that it affects the surface properties and elongation of the insulating layer formed on the conductor.

[0008] An object of the present disclosure is to provide an insulated wire manufacturing apparatus that can reduce the amount of varnish removed from a coating die that gets mixed into a varnish tank, thereby improving the properties of the insulating layer of the insulated wire to be manufactured.

[0009] According to the present disclosure, it is possible to reduce the amount of varnish removed from the coating die that gets mixed into the varnish tank, thereby improving the properties of the insulating layer of the insulated wire produced.

[0010] First, embodiments of the present disclosure will be listed and described.

[0011] (1) The insulated wire manufacturing apparatus of the present disclosure is an insulated wire manufacturing apparatus that applies varnish for forming an insulating layer to the outer peripheral surface of a linear conductor while running the conductor vertically upward along the longitudinal axis of the conductor, and includes a varnish tank for storing the varnish, an application die into which the conductor that has passed through the varnish tank is inserted, and an upper surface member located between the varnish tank and the application die, the upper part of the varnish tank being closed by the upper surface member, and the bottom surface of the varnish tank and the upper surface member having through holes for passing the conductor through.

[0012] In an insulated wire manufacturing apparatus that applies a varnish for forming an insulating layer to the outer peripheral surface of a linear conductor while the conductor is running vertically upward along the longitudinal axis of the conductor, the varnish tank is box-shaped and closed at the top by a top member, and the varnish tank has through holes in the bottom and top member that allow the conductor to pass through. Therefore, varnish removed by the coating die is discharged downward without mixing with the varnish stored in the varnish tank, and the removed varnish is not returned to the varnish tank. This reduces the amount of solidified varnish remaining in the varnish tank, even if the excess varnish removed by the coating die dries and solidifies. Therefore, the insulated wire manufacturing apparatus can form an insulating layer with reduced contamination of solidified material resulting from the solidification of the varnish removed by the coating die during manufacturing, thereby improving the properties of the insulating layer of the manufactured insulated wire.

[0013] (2) In the insulated wire manufacturing apparatus of (1), the varnish tank and the upper surface member are integrally formed. This configuration improves sealing performance and makes it easy to transport and install the varnish tank.

[0014] (3) In the above (1) or (2), the insulated wire manufacturing apparatus further includes a recovery tank capable of storing the varnish removed by the coating die. This configuration allows the removed varnish to be efficiently recovered. The varnish removed from the coating die and discharged downward can be received in the recovery tank. The removed varnish does not substantially mix with the varnish stored in the varnish tank.

[0015] (4) In the insulated wire manufacturing apparatus of (3), the bottom surface of the recovery tank may be located lower than the bottom surface of the varnish tank, and the recovery tank may have a through-pipe connecting the bottom surface of the varnish tank to the bottom surface of the recovery tank. By having the through-pipe connecting the bottom surface of the recovery tank to the bottom surface of the varnish tank, the varnish recovered in the recovery tank can be prevented from contacting the conductor. Therefore, it is possible to easily dispose of or reuse used varnish that contains a large amount of solidified material generated by solidification of excess varnish removed by the coating die after coating.

[0016] (5) In the above (3) or (4), the insulated wire manufacturing apparatus may further include a filter for filtering the varnish stored in the collection tank. By including a filter for filtering the varnish stored in the collection tank, the used varnish, which contains a large amount of solidified material resulting from the solidification of the excess varnish removed by the coating die, can be easily and compactly disposed of or reused.

[0017] (6) In any one of (3) to (5) above, the insulated wire manufacturing apparatus has a bottom surface of the collection tank that is inclined or curved so as to protrude vertically downward.

[0018] (7) In any of (3) to (6) above, the recovery tank has one or more discharge pipes for discharging the removed varnish in a lower end region of the bottom surface of the recovery tank. The lower end region may be the lowest region of the bottom surface. By having the configurations of (6) and (7), the removed varnish moves to the discharge pipes along the inclined or curved bottom surface after being recovered in the recovery tank, thereby enabling the removed varnish to be efficiently discharged.

[0019] (8) In the above (7), the recovery tank has a plurality of the discharge pipes. With this configuration, the removed varnish is efficiently discharged.

[0020] (9) In any one of (1) to (8) above, the varnish tank may further include one or more supply pipes for supplying varnish to the varnish tank. By including one or more supply pipes for supplying varnish to the varnish tank, the varnish can be efficiently supplied to the varnish tank.

[0021] (10) In the above (9), the varnish tank includes a plurality of the supply pipes. With this configuration, the varnish is efficiently supplied to the varnish tank.

[0022] (11) In any of the above (1) to (10), the side surface of the varnish tank may have an inclined surface or a curved surface that protrudes outward. By having the side surface of the varnish tank have an inclined surface or a curved surface that protrudes outward, the varnish removed from the coating die can be discharged downward more smoothly without being mixed with the varnish stored in the varnish tank.

[0023] (12) In any of the above (1) to (11), the upper surface member has an inclined surface or a curved surface that protrudes outward.

[0024] (13) In any one of (1) to (12) above, the upper surface member is inclined, and the through hole in the upper surface member is located in the upper end region. By having the configurations of (12) and (13), the removed varnish can be efficiently discharged along the upper surface of the upper surface member.

[0025] (14) The method for manufacturing an insulated wire according to the present disclosure includes applying a varnish for forming an insulating layer to an outer peripheral surface of a linear conductor while the conductor is running vertically upward along the longitudinal axis of the conductor, and includes the steps of applying the varnish stored in a varnish tank to the outer peripheral surface of the conductor, removing excess varnish adhering to the conductor after the applying step using an application die, and discharging the varnish removed in the removing step downward without mixing it with the varnish stored in the varnish tank.

[0026] The insulated wire manufacturing method includes a discharging step, whereby the varnish removed in the removing step is discharged downward without being mixed with the varnish stored in the varnish tank, and is therefore not returned to the varnish tank. This reduces the amount of varnish remaining in the varnish tank as a solid, even if the excess varnish removed by the coating die after coating dries and solidifies. Therefore, the insulated wire manufacturing method can reduce the amount of varnish removed from the coating die being mixed into the varnish tank, and can form an insulating layer that does not contain the solidified material that would result from the solidification of the excess varnish removed by the coating die, thereby improving the properties of the insulating layer of the manufactured insulated wire.

[0027] [Details of the embodiment of the present disclosure] An apparatus for manufacturing an insulated electric wire and a method for manufacturing an insulated electric wire according to an embodiment of the present disclosure will be described below with reference to the drawings.

[0028] <Insulated Wire Manufacturing Apparatus> [First Embodiment] An insulated wire manufacturing apparatus according to a first embodiment of the present disclosure is a vertical insulated wire manufacturing apparatus that applies a varnish for forming an insulating layer to the outer peripheral surface of a linear conductor while the conductor runs vertically upward along its longitudinal axis. Fig. 1 is a schematic diagram illustrating an insulated wire manufacturing apparatus 100 according to the first embodiment. As shown in Fig. 1 , the insulated wire manufacturing apparatus 100 includes a feed-out unit 4 that feeds a wound conductor 1 onto a first drum 6a, a pair of drums 6 (first drum 6a and second drum 6b) that are arranged vertically opposite each other and run the linear conductor 1 around one or more turns, an applicator 10 that applies varnish to the conductor 1 while the conductor runs vertically upward along its longitudinal axis, a drying and curing furnace 2 that dries and cures the applied varnish, and a winding unit 5 that winds up the conductor 1 with the insulating layer formed thereon, i.e., the insulated wire 7.

[0029] (Conductor) There are no particular limitations on the material or configuration of the conductor 1, but examples of the conductor that can be used include copper wire, tin-plated copper wire, aluminum wire, aluminum alloy wire, steel-core aluminum wire, copper fly wire, nickel-plated copper wire, silver-plated copper wire, and copper-clad aluminum wire. There are also no particular limitations on the cross-sectional shape of the conductor 1, and the conductor 1 can be a polygonal shape such as a circle (round wire), an oval, or a square (rectangular wire).

[0030] (Feed-Out Section) The feed-out section 4 feeds the conductor 1 wound on a reel onto the first drum 6a. The reel of the feed-out section 4 may be either a driven type or a non-driven type.

[0031] (Drum) The conductor 1 can be moved by, for example, a first drum 6a and a second drum 6b that transport the conductor 1 in the direction of the arrow shown in FIG. 1 . The first drum 6a is a feed member that supplies the conductor 1. The second drum 6b is a winding member that winds up the conductor 1 supplied from the first drum 6a. An insulating layer is formed on the outer peripheral surface of the conductor 1 by circling between the first drum 6a and the second drum 6b a certain number of times. The insulated wire 7 is finally wound around a winding section 5 provided downstream in the running direction of the conductor 1. The drum 6 can be made of a material such as metal or resin.

[0032] (Coating Device) The coating device 10 is a device that coats the outer peripheral surface of the conductor 1 with varnish for forming an insulating layer. FIG. 2 is a schematic cross-sectional view of the coating device 10 according to the first embodiment. As shown in FIG. 2, the coating device 10 includes a varnish tank 11 that stores a resin-containing varnish, a coating die 12 into which the conductor 1 that has passed through the varnish tank 11 is inserted, and an upper surface member 111 between the varnish tank 11 and the coating die 12. The varnish tank 11 and the upper surface member 111 may be integrally formed. The circumferential conductor 1 penetrates the bottom surface 113 of the varnish tank 11, and the insulating layer-forming varnish is applied to the outer peripheral surface of the conductor 1 that has passed through the varnish tank 11. The insulating layer-forming varnish applied to the outer peripheral surface of the conductor 1 is adjusted to a substantially uniform thickness by passing through the coating die 12. As a result, a conductor 8 having a coating film of a substantially uniform thickness is obtained.

[0033] <Varnish Tank> The varnish tank 11 stores varnish for forming an insulating layer. In the insulated wire manufacturing apparatus 100, the varnish tank 11 is box-shaped. The top of the varnish tank is closed by an upper surface member 111. The varnish tank 11 has a bottom surface 113 and a through hole in the top surface member 111 through which the conductor 1 passes. The varnish in the varnish tank 11 is applied to the outer peripheral surface of the conductor 1 passing through the through hole in the bottom surface 113. A valve (not shown) is provided in the through hole in the bottom surface 113 of the varnish tank 11 to prevent liquid from flowing out through the through hole in the bottom surface 113. The valve provided in the bottom surface 113 of the varnish tank 11 also prevents liquid from flowing in through the through hole. Hereinafter, excess varnish 18 refers to the varnish removed when the conductor 1 passes through the application die 12 after the varnish has been applied to the conductor 1. The removed varnish is discharged downward without mixing with the varnish stored in the varnish tank 11. A valve may or may not be provided in the through-hole in the upper surface member 111. If a valve is not provided, the backflow of varnish into the varnish tank 11 can be reduced or prevented by adjusting the flow rate and viscosity of the varnish. This reduces the amount of solidified excess varnish 18 remaining in the varnish tank 11, even when the excess varnish 18 dries and solidifies. Therefore, the insulated wire manufacturing apparatus 100 can reduce the amount of excess varnish 18 mixing into the varnish tank 11. Note that "reducing the amount of excess varnish 18 mixing into the varnish tank 11" includes a state in which the excess varnish 18 is substantially not contained in the varnish tank 11.

[0034] The shape of the varnish tank 11 is not particularly limited, as long as it is box-shaped and the top is closed by an upper surface member.

[0035] The varnish may be supplied to the varnish tank 11, for example, through a varnish supply pipe that communicates with the varnish tank 11. Alternatively, the upper surface member 111 of the varnish tank 11 may be provided so as to be openable and closable, and the varnish may be supplied from the top of the varnish tank 11.

[0036] The varnish used is a resin that constitutes the insulating layer dissolved in a solvent. There are no particular limitations on the resin, as long as it has high insulating properties and high heat resistance. For example, a varnish that uses polyimide, which has high adhesion to the conductor 1, as the resin component and N-methyl-pyrrolidone or the like as the solvent can be used. The content of the resin in the entire varnish containing the resin and solvent can be, for example, 10% by mass or more and 40% by mass or less. Other resins that can be used include polyamideimide and polyesterimide.

[0037] <Coating die> The coating die 12 adjusts the thickness of the varnish applied to the conductor 1. When the conductor 1 passes through the opening of the coating die 12, the opening comes into contact with the varnish, and the coating die 12 removes excess varnish 18, thereby adjusting the amount of varnish attached to the outer peripheral surface of the conductor 1 (i.e., the amount of varnish applied). This allows the coating film to be adjusted to a substantially uniform thickness.

[0038] (Drying and curing furnace) The drying and curing furnace 2 is provided downstream of the coating device 10 in the traveling direction of the conductor 1, and heats the conductor 1 after the varnish is coated. The drying and curing furnace 2 heats the conductor 1 after the varnish is coated, thereby evaporating the solvent and curing the varnish.

[0039] There are no particular limitations on the drying and curing furnace 2. As the drying and curing furnace 2, a furnace that uses heat generated by electric heating or combustion as an energy source to heat the conductor 1 by convection and radiation can be used.

[0040] As described above, the conductor 1 rotates between the first drum 6a and the second drum 6b a certain number of times, and passes through the coating device 10 and the drying and curing furnace 2 in this order each time it rotates.

[0041] (Winding Section) The winding section 5 pulls and winds the conductor 1 onto a reel. The tensile force of the winding section 5 causes the conductor 1 to circulate between the coating device 10 and the drying and curing furnace 2.

[0042] According to the insulated wire manufacturing apparatus 100 according to the first embodiment of the present disclosure, excess varnish 18 does not get mixed into the varnish stored in the varnish tank 11. The excess varnish 18 is discharged downward from the varnish tank 11 and is not returned to the varnish tank 11. As a result, even if the excess varnish 18 dries and solidifies, the solidified material is reduced from remaining in the varnish tank 11. Therefore, the insulated wire manufacturing apparatus can reduce the amount of excess varnish 18 getting mixed into the varnish tank 11. Furthermore, the insulated wire manufacturing apparatus can form an insulating layer that does not contain solidified material that is generated when the excess varnish 18 solidifies. As a result, the insulated wire manufacturing apparatus can manufacture an insulated wire 7 with improved insulating layer properties.

[0043] Second Embodiment The insulated wire manufacturing apparatus may further include a collection tank capable of storing excess varnish 18. FIG. 3 is a schematic cross-sectional view of the coating device 20 in an insulated wire manufacturing apparatus 120 according to a second embodiment of the present disclosure. As shown in FIG. 3, the bottom surface 153 of the collection tank 15 is located lower than the bottom surface 113 of the varnish tank 11, allowing excess varnish 18 to be stored. The insulated wire manufacturing apparatus 120 includes the collection tank 15 capable of storing excess varnish 18. The excess varnish 18 can be received by the collection tank 15 without being returned to the varnish tank 11. This makes it easy to dispose of or reuse used varnish that contains a large amount of solidified material resulting from the solidification of the excess varnish 18.

[0044] The recovery tank 15 is provided with a conductor through pipe 14. The conductor 1 passes through the inside of the conductor through pipe 14. The conductor through pipe 14 connects the bottom surface 113 of the varnish tank 11 to the bottom surface 153 of the recovery tank 15. The conductor through pipe 14 has a through hole in the bottom surface 153 of the recovery tank 15, and the conductor 1 is drawn out from the through hole. Since the recovery tank 15 has the conductor through pipe 14 connecting the bottom surface 113 of the varnish tank 11 to the bottom surface 153 of the recovery tank 15, it is possible to prevent excess varnish 18 recovered in the recovery tank 15 from coming into contact with the conductor 1.

[0045] 3, the collection tank 15 is trough-shaped. The opening area of ​​the opening of the collection tank 15 is larger than the cross-sectional area perpendicular to the running direction of the conductor 1 in the varnish tank 11. This allows excess varnish 18 discharged downward from the varnish tank 11 to be collected by the collection tank 15. In other words, the varnish tank 11 is enclosed by the outer frame of the collection tank 15 in a plan view of the collection tank. The clearance between the side surface 112 of the varnish tank 11 and the inner surface of the collection tank 15 is not particularly limited as long as it allows the excess varnish 18 to be collected, but it can be, for example, 5 mm or more and 1000 mm or less.

[0046] The recovery tank 15 has a discharge pipe 16 for discharging excess varnish 18. The varnish in the recovery tank 15 contains excess varnish 18, and the excess varnish 18 may contain solidified material that is generated when the varnish 18 solidifies due to drying. The provision of the discharge pipe 16 makes it easy to transfer the varnish containing the solidified material from the recovery tank 15 to another tank or to dispose of it.

[0047] [Third Embodiment] The insulated wire manufacturing apparatus may further include a filter for filtering the varnish stored in the collection tank, and may further include a supply pipe for supplying varnish to the varnish tank. The side of the varnish tank may have a curved surface that protrudes outward. FIG. 4 is a schematic cross-sectional view of the coating device 20 in an insulated wire manufacturing apparatus 150 according to a third embodiment of the present disclosure. As shown in FIG. 4, the insulated wire manufacturing apparatus 150 includes a box-shaped varnish tank 21 for storing varnish, a varnish supply pipe 29, and a coating die 12 into which the conductor 1 that has passed through the varnish tank 21 is inserted. The insulated wire manufacturing apparatus 150 also includes a collection tank 25. The recovery tank 25 differs from the insulated wire manufacturing apparatus 100 of the first embodiment in that it includes a conductor penetration tube 24 connecting the bottom surface 213 of the varnish tank 21 to the bottom surface 253 of the recovery tank 25 and through which the conductor 1 passes, and a filter 9 connected to a discharge tube 26 for discharging excess varnish 18. The conductor 1, the conductor 8 having a coating film, the coating die 12, and the excess varnish 18 are the same as those in the first embodiment, and therefore are designated by the same reference numerals and will not be described again. The conductor 8 having a coating film has a coating film that is adjusted to a uniform thickness. The insulated wire manufacturing apparatus 150 further includes a varnish supply tube 29, thereby efficiently supplying varnish to the varnish tank 21. Furthermore, the curved side surface 212 of the varnish tank 21 allows the excess varnish 18 to be more smoothly discharged downward without mixing with the varnish stored in the varnish tank 21. Furthermore, the excess varnish 18 collected in the collection tank 25 is sent by a pump (not shown) and filtered through the filter 9. In the insulated wire manufacturing apparatus 150, even when the excess varnish 18 solidifies due to drying, the excess varnish 18 is less likely to remain as a solidified material in the varnish tank 21, and by further providing the filter 9 that filters the excess varnish 18 collected in the collection tank 25, it is possible to easily and compactly dispose of or reuse used varnish that contains a large amount of solidified material resulting from the solidification of the excess varnish 18.

[0048] The filter 9 separates the excess varnish 18 collected in the collection tank 25 into a solid component and a filtrate. The filter material included in the filter 9 is not particularly limited, and any known filter material can be used. The filter material may be a depth filter or a screen filter, and may have pleats. Examples of filter material materials include polyamide, polyethylene, polypropylene, polyfluorocarbons such as polytetrafluoroethylene, polysulfone, cellulose, diatomaceous earth, polystyrene, and glass. The pore size of the filter 9 may be 1 μm or more and 1000 μm or less, from the viewpoint of improving the impurity removal efficiency. The method for installing the filter 9 is not particularly limited; for example, the filter 9 may be disposed in a pipe, or may be connected as a separate, independent filtering device.

[0049] Fourth Embodiment In an insulated electric wire manufacturing apparatus, the bottom surface of the collection tank may have a curved surface that protrudes downward, and the collection tank may have a discharge pipe in a lower end region of the bottom surface for discharging removed varnish. The lower end region may be the lowest part of the bottom surface. The insulated electric wire manufacturing apparatus may further include multiple supply pipes for supplying varnish to the varnish tank. FIG. 5 is a schematic cross-sectional view of the coating device 30 in an insulated electric wire manufacturing apparatus 200 according to a fourth embodiment of the present disclosure. As shown in FIG. 5, the insulated electric wire manufacturing apparatus 200 includes a box-shaped varnish tank 31 that stores varnish, a coating die 12 into which a conductor 1 that has passed through the varnish tank 31 is inserted, and supply pipes 38 and 39. The supply pipes 38 and 39 supply varnish to the varnish tank 31. The insulated electric wire manufacturing apparatus 200 also includes a collection tank 35. The collection tank 35 connects the bottom surface 313 of the varnish tank 31 with the bottom surface 353 of the collection tank 35 and has a conductor through-pipe 34 through which the conductor 1 passes. The bottom surface 353 of the collection tank 35 has a curved surface that protrudes downward, and the collection tank 35 has a discharge pipe 36 at the lower end region of the bottom surface 353 for discharging excess varnish 18. This lower end region may be the lowest part of the bottom surface. The conductor 1, the conductor 8 having a coating film, the coating die 12, and the excess varnish 18 are the same as those in the first embodiment, so they are designated by the same numbers and their description is omitted. The conductor 8 having a coating film has a coating film that is adjusted to a uniform thickness. In the insulated wire manufacturing apparatus 200, the bottom surface 353 of the collection tank 35 has a curved surface, and the collection tank 35 has a discharge pipe 36 at the lower end region of the bottom surface 353 for discharging excess varnish 18. Specifically, the bottom surface 353 of the collection tank 35 has an arcuate shape that protrudes downward toward the discharge pipe 36. As a result, after being collected in the collection tank 35, the excess varnish 18 moves along the bottom surface 353 to the discharge pipe 36, allowing the excess varnish 18 to be efficiently discharged. The insulated wire manufacturing apparatus 200 has the supply pipes 38 and 39, allowing the varnish to be efficiently supplied to the varnish tank 31. In the insulated wire manufacturing apparatus 200 as well, the excess varnish 18 is discharged downward without being mixed with the varnish stored in the varnish tank 31, and is not returned to the varnish tank 31.This reduces the amount of excess varnish 18 remaining as a solid in the varnish tank 31 even when the excess varnish 18 solidifies due to drying.

[0050] Fifth Embodiment In an insulated electric wire manufacturing apparatus, the bottom surface of the collection tank may have an inclined surface, and the collection tank may have a discharge pipe for discharging the removed varnish in a lower end region of the bottom surface. The lower end region may be the lowest part of the bottom surface. Furthermore, the side surface of the varnish tank may have an inclined surface. FIG. 6 is a schematic cross-sectional view of the coating device 40 in an insulated electric wire manufacturing apparatus 250 according to a fifth embodiment of the present disclosure. As shown in FIG. 6, the insulated electric wire manufacturing apparatus 250 includes a conical box-shaped varnish tank 41 for storing varnish, a varnish supply pipe 49, and a coating die 12 into which the conductor 1 that has passed through the varnish tank 41 is inserted. The insulated electric wire manufacturing apparatus 250 also includes a collection tank 45. The recovery tank 45 differs from the insulated wire manufacturing apparatus 100 of the first embodiment in that it has a conductor through-pipe 44 connecting the bottom surface 413 of the varnish tank 41 and the bottom surface 453 of the recovery tank 45 and through which the conductor 1 passes. The bottom surface 453 of the recovery tank 45 has an inclined surface, and the recovery tank 45 has a discharge pipe 46 at the lower end region of the bottom surface 453 for discharging excess varnish 18. The conductor 1, the conductor 8 having a coating film, the coating die 12, and the excess varnish 18 are the same as those in the first embodiment, and therefore are designated by the same reference numerals and will not be described again. The conductor 8 having a coating film has a coating film that is adjusted to a uniform thickness. In the insulated wire manufacturing apparatus 250, the bottom surface 453 of the recovery tank 45 is linearly inclined toward the discharge pipe 46 in a cross-sectional view. As a result, after being collected in the collection tank 45, the excess varnish 18 moves to the discharge pipe 46 along the bottom surface 453 that slopes linearly in cross section, so that the excess varnish 18 can be discharged downward more smoothly without mixing with the varnish stored in the varnish tank 41. Furthermore, the insulated wire manufacturing apparatus 250 further includes a supply pipe 49 that supplies varnish to the varnish tank 41, so that the varnish can be efficiently supplied to the varnish tank 41. In the insulated wire manufacturing apparatus 250, too, the excess varnish 18 is discharged downward without mixing with the varnish stored in the varnish tank 41, and the excess varnish 18 is not returned to the varnish tank 41. As a result, even if the excess varnish 18 solidifies due to drying, the excess varnish 18 is less likely to remain as a solid in the varnish tank 41.

[0051] Sixth Embodiment In an insulated electric wire manufacturing apparatus, the bottom surface of the collection tank may have an inclined surface, and the collection tank may have a plurality of discharge pipes for discharging removed varnish in a lower end region of the bottom surface. The lower end region may be the lowest part of the bottom surface. Alternatively, the top surface member may have an inclined surface. The top surface member is inclined so that the through holes in the top surface member are located in the upper end region. The upper end region may be the region of the top surface member 511 closest to the coating die 12. FIG. 7 is a schematic cross-sectional view of a coating device 60 in an insulated electric wire manufacturing apparatus 300 according to a sixth embodiment of the present disclosure. As shown in FIG. 7 , the insulated electric wire manufacturing apparatus 300 includes a varnish tank 51 having a box-like shape with a hexagonal cross section for storing varnish, a varnish supply pipe 59, and a coating die 12 into which the conductor 1 that has passed through the varnish tank 51 is inserted. The insulated electric wire manufacturing apparatus 300 also includes a collection tank 55. The recovery tank 55 connects the bottom surface 513 of the varnish tank 51 with the bottom surface 553 of the recovery tank 55, has a conductor through-pipe 54 through which the conductor 1 passes, and the bottom surface 553 of the recovery tank 55 has two inclined surfaces. The recovery tank 45 differs from the insulated wire manufacturing apparatus 100 of the first embodiment in that the recovery tank 45 has discharge pipes 56 and 57 for discharging excess varnish 18 at the two lower end regions of the bottom surface 453, respectively. The conductor 1, the conductor 8 having a coating film, the coating die 12, and the excess varnish 18 removed by the coating die 12 are the same as those in the first embodiment, and therefore are designated by the same numbers and will not be described again. The conductor 8 having a coating film has a coating film that is uniform in thickness. In the insulated wire manufacturing apparatus 300, after excess varnish 18 is collected in the collection tank 55, it moves toward the two discharge pipes 56 and 57 along the bottom surface 553, which has two linearly inclined surfaces in cross section, so that the removed excess varnish 18 can be efficiently discharged. The insulated wire manufacturing apparatus 300 also includes a supply pipe 59 that supplies varnish to the varnish tank 51, so that varnish can be efficiently supplied to the varnish tank 51. Furthermore, the upper surface member 511 of the varnish tank 51 may have an inclined surface and be hexagonal in cross section taken along the longitudinal axis of the conductor. Alternatively, the upper surface member 511 of the varnish tank 51 may have a curved surface that protrudes outward.At least one of these configurations allows the excess varnish 18 to be discharged downward more smoothly without being mixed with the varnish stored in the varnish tank 51. In the insulated wire manufacturing apparatus 300, the excess varnish 18 is also discharged downward without being mixed with the varnish stored in the varnish tank 51, and the excess varnish 18 is not returned to the varnish tank 51. As a result, even if the excess varnish 18 solidifies due to drying, it is less likely to remain as a solidified material in the varnish tank 51.

[0052] <Method for manufacturing insulated wire> A method for manufacturing an insulated wire includes coating an outer peripheral surface of a linear conductor with varnish for forming an insulating layer while the conductor is running vertically upward along the longitudinal axis of the conductor, and includes the steps of: coating the outer peripheral surface of the conductor with varnish stored in a varnish tank; removing excess varnish adhering to the conductor after the coating step using an application die; and discharging the varnish removed in the removing step downward without mixing it with the varnish stored in the varnish tank. The method for manufacturing an insulated wire can be performed using an insulated wire manufacturing apparatus.

[0053] The method for producing an insulated wire may further include a drying and curing step, a recovering step of the discharged varnish, and a filtering step of the recovered varnish.

[0054] In the coating process, the linear conductor is fed vertically upward along its longitudinal axis, and the outer peripheral surface of the conductor is coated with a varnish for forming an insulating layer. Specifically, the conductor is fed from the feed section, passes through a first drum, and is coated with a varnish stored in a varnish tank.

[0055] The conductor is inserted through a through hole in the bottom of the varnish tank and passes through the varnish stored in the varnish tank, whereby the varnish for forming an insulating layer is applied to the outer peripheral surface.

[0056] [Removing Step] In the removing step, excess varnish adhering to the conductor after the coating step is removed using a coating die. Specifically, the varnish coated on the outer peripheral surface of the conductor is adjusted to a substantially uniform thickness according to the diameter of the die hole by inserting the conductor into the coating die.

[0057] [Discharging step] In the discharging step, the removed varnish is discharged downward without being mixed with the varnish stored in the varnish tank. In this step, the varnish removed in the removing step is discharged downward without being mixed with the varnish stored in the varnish tank, so the removed varnish is not returned to the varnish tank. This reduces the amount of excess varnish remaining as a solid in the varnish tank, even if it solidifies due to drying.

[0058] [Recovering Step] In the recovering step, the varnish discharged in the discharging step is recovered. By providing a step of recovering the discharged varnish, it is possible to easily dispose of or reuse used varnish that contains a large amount of solidified material resulting from the solidification of the varnish removed by the coating die. In this step, a recovery tank is used to recover the varnish discharged downward without mixing it with the varnish stored in the varnish tank.

[0059] [Drying and curing process] In the drying and curing process, the varnish applied to the conductor is dried and cured in a drying and curing oven. Specifically, the conductor that has passed through the coating die is made to travel through the drying and curing oven. As a result, the solvent in the varnish applied to the conductor evaporates as it passes through the drying and curing oven, and the varnish dries and hardens. This hardens the resin contained in the varnish, forming an insulating layer on the outer peripheral surface of the conductor.

[0060] The steps from the application step to the drying and curing step may be repeated in this order.

[0061] [Filtering Step] In the filtering step, the varnish recovered in the recovering step may be filtered by solid-liquid separation using a filter. By further providing the filtering step in the method for producing an insulated electric wire, it is possible to easily and compactly dispose of or reuse used varnish that contains a large amount of solidified material generated by solidification of excess varnish.

[0062] Through the above steps, an insulating layer is formed on the outer peripheral surface of the conductor, and an insulated wire can be manufactured.

[0063] According to the insulated wire manufacturing method, the discharging step discharges the varnish removed in the removing step downward without mixing it with the varnish stored in the varnish tank, and therefore the varnish removed in the removing step is not returned to the varnish tank. As a result, even if the excess varnish solidifies due to drying, it is reduced from remaining as a solidified material in the varnish tank. Therefore, the insulated wire manufacturing method can reduce the varnish removed from the coating die from being mixed into the varnish tank and can form an insulating layer that does not contain solidified material that would result from the solidification of the excess varnish, thereby improving the properties of the insulating layer of the manufactured insulated wire.

[0064] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0065] In the above embodiment, the conductor is configured to pass through the same coating device and drying / curing oven for each revolution, but it may also be configured so that the conductor passes through different coating devices and drying / curing ovens for each revolution.

[0066] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0067] [Preparation of Varnish for Insulating Layer Formation] A polyimide-based insulating paint ("TONGTHERM 537-30" manufactured by ELANTAS) was prepared as a varnish for forming an insulating layer.

[0068] [Manufacturing Apparatus of the Example] The manufacturing apparatus shown in FIG. 3 was used as the manufacturing apparatus of the example.

[0069] [Comparative Example Manufacturing Apparatus] A conventional manufacturing apparatus in which the varnish removed by the coating die is returned to the varnish tank was used as the comparative example manufacturing apparatus. The other configurations of the apparatus were the same as those of the example manufacturing apparatus.

[0070] [Evaluation] (Amount of solidified material contained in varnish during production) The amount of solidified material contained in the varnish before the production equipment was put into operation, the varnish in the varnish tank of the comparative example, and the varnish tank of the example was measured by the following procedure.

[0071] Varnish was collected before the production equipment was operated, and the varnish in the varnish tank was collected after operating the comparative example (a production equipment with a conventional structure) and the example (the production equipment of this embodiment) for 5 days under the following conditions. Next, these varnishes were filtered (solid-liquid separation) using a measuring filter with a pore size of 30 μm, and the mass [g] of the filtered varnish (filtrate) was measured every minute to determine the filtration rate [g / min]. The more solids contained in the varnish, the smaller the mass of the filtered varnish (filtrate) and the lower the filtration rate. (Operating conditions) Varnish supply rate in the comparative example: 2 L / min Varnish supply rate in the example: 8 L / min Note that in the example, the varnish removed from the coating die was not returned to the varnish tank, so the varnish supply rate was adjusted so that the amount of varnish in the varnish tank was equivalent to that of the comparative example.

[0072] As shown in the following formula, the filtration rates of the varnishes before the production equipment was put into operation, the comparative examples, and the examples were normalized by the filtration rate in the first minute of each test to calculate a filtration rate index, and the calculated value was evaluated: Filtration rate index = (each filtration rate / filtration rate in the first minute of each test) x 100 Figure 8 shows a graph showing the relationship between the mass of filtered varnish and the filtration rate index for each test number.

[0073] As shown in the graph in Figure 8, when comparing the varnish before the production equipment was started, the varnish in the varnish tank of the Comparative Example, and the varnish tank of the Example, the varnish before the production equipment was started and the varnish in the varnish tank of the Example, which is the production equipment, both show a small decrease in the filtration rate index and a small amount of solidified material contained in the varnish, even when the mass of the filtered varnish increases.The varnish in the varnish tank of the Comparative Example, which is the conventional production equipment, shows a rapid decrease in the filtration rate index as the mass of the filtered varnish increases, and there is a large increase in solidified material caused by the solidification of the excess varnish removed by the application die.

[0074] The above results demonstrate that the insulated wire manufacturing apparatus of the present disclosure can reduce the contamination of the varnish removed from the coating die into the varnish tank.

[0075] REFERENCE SIGNS LIST 1 Conductor 2 Drying and curing furnace 4 Delivery section 5 Winding section 6 Drum 6a First drum 6b Second drum 7 Insulated wire 8 Conductor with coating film 9 Filter 10, 20, 30, 40, 50, 60 Coating device 11, 21, 31, 41, 51 Varnish tank 12 Coating die 14, 24, 34, 44, 54 Conductor penetration pipe 15, 25, 35, 45, 55 Recovery tank 16, 26, 36, 46, 56, 57 Discharge pipe 18 Excess varnish 29, 38, 39, 49, 59 Supply pipe 100, 120, 150, 200, 250, 300 Insulated wire manufacturing device 111, 211, 311, 411, 511 Upper surface member 112, 212, 312, 412, 512 Side surface of varnish tank 113, 213, 313, 413, 513 Bottom surface of varnish tank 153, 253, 353, 453, 553 Bottom surface of recovery tank

Claims

1. An insulated wire manufacturing apparatus that applies varnish to the outer peripheral surface of a linear conductor while the conductor is running vertically upward along the longitudinal axis of the conductor, for forming an insulating layer, the apparatus comprising: a varnish tank for storing the varnish; an application die into which the conductor that has passed through the varnish tank is inserted; and an upper surface member located between the varnish tank and the application die, the upper part of the varnish tank being closed by the upper surface member; and a bottom surface of the varnish tank and the upper surface member having through holes for passing the conductor through.

2. The insulated wire manufacturing apparatus according to claim 1, wherein the varnish tank and the upper surface member are integrally formed.

3. The insulated wire manufacturing apparatus according to claim 1 or 2, further comprising a recovery tank capable of storing the varnish removed by the coating die.

4. An insulated wire manufacturing apparatus as set forth in claim 3, wherein the bottom surface of the recovery tank is located lower than the bottom surface of the varnish tank, and the recovery tank has a through pipe connecting the bottom surface of the varnish tank with the bottom surface of the recovery tank.

5. The insulated wire manufacturing apparatus according to claim 3 or 4, further comprising a filter for filtering the varnish stored in the recovery tank.

6. An apparatus for manufacturing insulated electric wires according to any one of claims 3 to 5, wherein the bottom surface of the collection tank has an inclined surface or a curved surface that protrudes vertically downward.

7. An apparatus for manufacturing an insulated electric wire according to any one of claims 3 to 6, wherein the recovery tank has one or more discharge pipes at the lower end region of the bottom surface of the recovery tank for discharging the removed varnish.

8. The insulated wire manufacturing apparatus according to claim 7, wherein said recovery tank has a plurality of said discharge pipes.

9. An apparatus for manufacturing an insulated electric wire according to any one of claims 1 to 8, wherein the varnish tank further comprises one or more supply pipes for supplying varnish to the varnish tank.

10. The apparatus for manufacturing an insulated electric wire according to claim 9, wherein said varnish tank is provided with a plurality of said supply pipes.

11. An apparatus for manufacturing an insulated electric wire according to any one of claims 1 to 10, wherein the side surface of the varnish tank has an inclined surface or a curved surface that protrudes outward.

12. An insulated wire manufacturing apparatus according to any one of claims 1 to 11, wherein the upper surface member has an inclined surface or a curved surface that protrudes outward.

13. An apparatus for manufacturing an insulated electric wire according to any one of claims 1 to 12, wherein the upper surface member is inclined and the through hole in the upper surface member is located in an upper end region.

14. A method for manufacturing an insulated wire, comprising the steps of: applying varnish for forming an insulating layer to the outer peripheral surface of a linear conductor while the conductor is running vertically upward along the longitudinal axis of the conductor; applying the varnish stored in a varnish tank to the outer peripheral surface of the conductor; removing excess varnish adhering to the conductor after the applying step using an application die; and discharging the varnish removed in the removing step downward without mixing it with the varnish stored in the varnish tank.

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