JP7649776B2 - Insulated wire manufacturing method and insulated wire manufacturing device - Google Patents

Description

The present disclosure relates to a method and an apparatus for producing an insulated wire.
This application claims priority based on Japanese Application No. 2020-040494 filed on March 10, 2020, and incorporates by reference all of the contents of the above-mentioned Japanese application.

There is known an insulated electric wire in which a linear conductor is coated with insulating paint (varnish). This insulated electric wire is manufactured by repeatedly applying and baking varnish to the outer surface of the linear conductor while running the conductor in its axial direction until the insulating coating reaches a predetermined thickness.

A hot air circulation type baking device is generally used to apply and bake this varnish (see, for example, JP-A-9-35556 and JP-A-2003-187658).

Japanese Patent Application Publication No. 9-35556 JP 2003-187658 A

A method for manufacturing an insulated wire according to one aspect of the present disclosure includes the steps of: applying a varnish containing an insulating material and a solvent to a linear conductor while running the conductor in its axial direction; heating the varnish applied in the applying step while maintaining the temperature below the boiling point of the solvent; evaporating the solvent after the heating step while maintaining the temperature difference between the temperature of the varnish and the boiling point of the solvent; and hardening the insulating material after the evaporating step.

An insulated wire manufacturing apparatus according to another aspect of the present disclosure includes an application section that applies a varnish containing an insulating material and a solvent to a linear conductor while running the conductor in its axial direction, a first induction heater that is installed downstream of the application section in the running direction of the conductor and is capable of heating the varnish, and a second induction heater that is installed downstream of the first induction heater in the running direction of the conductor and is capable of hardening the insulating material contained in the varnish, and the first induction heater and the second induction heater are arranged at a distance from each other.

An insulated wire manufacturing apparatus according to yet another aspect of the present disclosure includes one or more first manufacturing units and one or more second manufacturing units arranged in series from the upstream side to the downstream side in the running direction of a linear conductor running in an axial direction, and a control unit that controls the first manufacturing unit and the second manufacturing unit, wherein the first manufacturing unit and the second manufacturing unit each have an application unit that applies a varnish containing an insulating material and a solvent to the conductor while running the conductor, and a first heating unit that is installed downstream of the application unit in the running direction of the conductor and is capable of heating the varnish, and the first manufacturing unit further has a second heating unit that is installed at the most downstream side in the running direction of the conductor and is capable of hardening the insulating material contained in the varnish, and the control unit controls the first heating unit to raise the temperature of the varnish while maintaining it at a temperature below the boiling point of the solvent, and controls the second heating unit to harden the insulating material.

FIG. 1 is a flow diagram illustrating a method for producing an insulated wire according to one embodiment of the present disclosure. FIG. 2 is a schematic configuration diagram of an apparatus for manufacturing an insulated electric wire according to one embodiment of the present disclosure. FIG. 3 is a schematic diagram showing the relative positions of the coating unit, the first induction heater, and the second induction heater of the insulated electric wire manufacturing apparatus of FIG. FIG. 4 is a schematic diagram showing a detailed configuration of the coating device in the coating section of FIG. FIG. 5 is a schematic diagram of an insulated electric wire manufacturing apparatus according to an embodiment different from that shown in FIG. FIG. 6 is a schematic diagram showing the layout relationship of the first production unit, the second production unit, and the control unit of the insulated electric wire production apparatus of FIG.

[Problem to be solved by this disclosure]
In a method for manufacturing an insulated electric wire using a hot air circulation type baking device, the conductor is heated relatively gently by heat transfer from the hot air to manufacture the insulated electric wire. Although this conventional manufacturing method can prevent the varnish from foaming, the heating is gentle, so the manufacturing process takes time and the manufacturing efficiency is low.

The present disclosure has been made based on the above-mentioned circumstances, and aims to provide an insulated electric wire manufacturing method and an insulated electric wire manufacturing apparatus that improves manufacturing efficiency while suppressing foaming of the varnish.

[Effects of the present disclosure]
The insulated electric wire manufacturing method and insulated electric wire manufacturing apparatus according to the present disclosure can enhance manufacturing efficiency while suppressing foaming of varnish.

[Description of the embodiments of the present disclosure]
A method for manufacturing an insulated wire according to one aspect of the present disclosure includes a step of applying a varnish containing an insulating material and a solvent to a linear conductor while running the conductor in its axial direction, a step of heating the varnish applied in the applying step while maintaining the temperature below the boiling point of the solvent, a step of evaporating the solvent after the heating step while maintaining a temperature difference between the temperature of the varnish and the boiling point of the solvent, and a step of hardening the insulating material after the evaporating step.

In the insulated wire manufacturing method, the varnish applied to the conductor is heated while being maintained at a temperature below its boiling point, and then the solvent is evaporated while maintaining the temperature difference from the boiling point. By using such a temperature profile, the insulated wire manufacturing method can prevent foaming of the varnish. Furthermore, in the insulated wire manufacturing method, the heating rate in the temperature raising process can be increased to shorten the time it takes for the solvent to evaporate, thereby improving manufacturing efficiency.

In the above-mentioned temperature increasing process, it is preferable to heat the conductor using an induction heater. By using an induction heater for heating in the above-mentioned process, the heating speed can be easily increased, thereby further improving manufacturing efficiency.

In the hardening process, the conductor may be heated using an induction heater. By using an induction heater for heating in the process, the heating speed can be easily increased, further improving manufacturing efficiency.

The evaporation of the solvent in the evaporation process may be performed using residual heat from the conductor heated in the heating process. In this way, the evaporation of the solvent in the evaporation process may be performed using residual heat from the conductor heated in the heating process, thereby reducing manufacturing costs.

An insulated wire manufacturing apparatus according to another aspect of the present disclosure includes an application section that applies a varnish containing an insulating material and a solvent to a linear conductor while running the conductor in its axial direction, a first induction heater that is installed downstream of the application section in the running direction of the conductor and is capable of heating the varnish, and a second induction heater that is installed downstream of the first induction heater in the running direction of the conductor and is capable of hardening the insulating material contained in the varnish, and the first induction heater and the second induction heater are arranged at a distance from each other.

The insulated wire manufacturing apparatus can heat the varnish applied to the conductor using the first induction heater while maintaining the temperature below the boiling point of the solvent. Furthermore, in the insulated wire manufacturing apparatus, when the varnish heated by the first induction heater passes through the space between the first induction heater and the second induction heater, the solvent can be evaporated by the residual heat of the conductor. Furthermore, in the insulated wire manufacturing apparatus, the insulating material from which the solvent has evaporated can be hardened by the second induction heater. Therefore, by using the insulated wire manufacturing apparatus, it is possible to increase manufacturing efficiency while suppressing foaming of the varnish.

The distance between the first induction heater and the second induction heater is preferably 50 cm or more. By setting the distance between the first induction heater and the second induction heater to the lower limit or more, the solvent contained in the varnish can be evaporated more reliably.

An insulated wire manufacturing apparatus according to yet another aspect of the present disclosure includes one or more first manufacturing units and one or more second manufacturing units arranged in series from the upstream side to the downstream side in the running direction of a linear conductor running in an axial direction, and a control unit that controls the first manufacturing unit and the second manufacturing unit, wherein the first manufacturing unit and the second manufacturing unit each have an application unit that applies a varnish containing an insulating material and a solvent to the conductor while running the conductor, and a first heating unit that is installed downstream of the application unit in the running direction of the conductor and is capable of heating the varnish, and the first manufacturing unit further has a second heating unit that is installed at the most downstream side in the running direction of the conductor and is capable of hardening the insulating material contained in the varnish, and the control unit controls the first heating unit to raise the temperature of the varnish while maintaining it at a temperature below the boiling point of the solvent, and controls the second heating unit to harden the insulating material.

In the insulated wire manufacturing apparatus, the control unit increases the heating rate while suppressing foaming of the varnish in the first heating unit of the first manufacturing unit and the second manufacturing unit, thereby shortening the time it takes for the solvent to evaporate. In addition, the insulated wire manufacturing apparatus is capable of supplying an optimal amount of heat to the conductor by arranging in series a first manufacturing unit having a second heating unit that hardens the insulating material contained in the varnish, and a second manufacturing unit that does not have a second heating unit. Therefore, the insulated wire manufacturing apparatus is capable of reducing power consumption while increasing manufacturing efficiency.

At least one of the first heating section and the second heating section of the first manufacturing unit may be an induction heater. By using an induction heater as at least one of the first heating section and the second heating section of the first manufacturing unit, the heating speed can be easily increased, the travel distance of the conductor can be shortened, the manufacturing device for the insulated electric wire can be made smaller, and manufacturing efficiency can be further improved.

The first manufacturing unit and the second manufacturing unit are each installed downstream of the first heating unit in the running direction of the conductor and have a third heating unit capable of evaporating the solvent, and the control unit controls the third heating unit so as to evaporate the solvent while maintaining the temperature difference between the temperature of the varnish and the boiling point of the solvent in the first heating unit. By providing the third heating unit in this way and evaporating the solvent while maintaining the temperature difference between the temperature of the varnish and the boiling point of the solvent in the first heating unit, the manufacturing efficiency can be further improved.

The first manufacturing unit may be disposed at the most downstream side in the running direction of the conductor. By disposing the first manufacturing unit at the most downstream side in the running direction of the conductor in this manner, the insulating material can be cured last, making it easier to ensure the stability of the quality of the manufactured insulated wire.

The first manufacturing unit may be disposed at the most upstream side in the running direction of the conductor. By disposing the first manufacturing unit at the most upstream side in the running direction of the conductor in this manner, the insulating material can be hardened first, which makes it easier to increase the adhesion between the conductor and the insulating material.

It is preferable to have a first manufacturing unit group consisting of one or two of the first manufacturing units, and a second manufacturing unit group consisting of one or more of the second manufacturing units and arranged consecutively to the first manufacturing unit group. By arranging one or two first manufacturing units discretely in this manner, it is easy to improve the uniformity of the quality in the thickness direction of the manufactured insulated electric wire while reducing power consumption.

The "boiling point" of a solvent refers to the boiling point at 101.3 kPa (1 atmosphere). In the case of varnish, the boiling temperature changes depending on the concentration of the insulating material dissolved in the solvent, causing a so-called boiling point rise, and the "boiling point" of the solvent refers to the temperature at which this boiling point rise occurs. In other words, the "boiling point" of the solvent changes depending on the concentration of the varnish.

[Details of the embodiment of the present disclosure]
Hereinafter, an insulated electric wire manufacturing method and an insulated electric wire manufacturing apparatus according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

First Embodiment
The method for producing an insulated wire shown in Fig. 1 includes a step S1 of applying a varnish containing an insulating material and a solvent to a linear conductor while running the conductor in its axial direction, a step S2 of increasing the temperature of the varnish while maintaining the temperature below the boiling point of the solvent after the applying step, a step S3 of evaporating the solvent while maintaining a temperature difference between the temperature of the varnish and the boiling point of the solvent after the heating step, and a step S4 of curing the insulating material after the evaporating step. The method for producing an insulated wire can be performed using an insulated wire production apparatus which is itself an embodiment of the present disclosure, as shown in Fig. 2.

<Insulated wire manufacturing equipment>
The insulated wire manufacturing apparatus 1 shown in FIG. 2 includes a pair of drums 10 (first drum 10a and second drum 10b) arranged in parallel and running a linear conductor W that is wound around one or more times, an application unit 20 that applies a varnish containing an insulating material and a solvent to the linear conductor W while running the conductor W in its axial direction, a first induction heater 30 that is installed downstream of the application unit 20 in the running direction of the conductor W and is capable of heating the varnish, a second induction heater 40 that is installed downstream of the first induction heater 30 in the running direction of the conductor W and is capable of hardening the insulating material contained in the varnish, a delivery unit 50 that delivers the conductor W to the first drum 10a, and a winding unit 60 that winds up the conductor W on which an insulating layer has been formed, i.e., the insulated wire.

(conductor)
The material and configuration of the conductor W are not particularly limited, but examples thereof 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, copper-clad aluminum wire, etc. The cross-sectional shape of the conductor W is not particularly limited, and may be a polygonal shape such as a circle (round wire), an ellipse, or a square (rectangular wire).

(Sending section)
The delivery unit 50 delivers the conductor W wound on the reel to the first drum 10a. The reel of the delivery unit 50 may be driven or non-driven. When the reel of the delivery unit 50 is driven, it is preferable to control the driving of the delivery unit 50 so that excessive slack or tension is not generated in the conductor W between the delivery unit 50 and the first drum 10a. A known motor such as a servo motor or a stepping motor can be used to drive the delivery unit 50.

(drum)
The first drum 10a and the second drum 10b are arranged facing each other in the vertical direction with the coating unit 20, the first induction heater 30, and the second induction heater 40 in between, with the first drum 10a arranged on the lower side and the second drum 10b arranged on the upper side. The first drum 10a and the second drum 10b rotate the conductor W. The first drum 10a and the second drum 10b extend in a direction perpendicular to the paper surface of FIG. 2, and the position where the conductor W is applied is shifted at a fixed interval toward the back side of the paper surface in the axial direction of the drum 10 for each rotation, so that the conductor W can be rotated. The conductor W, which has been rotated a fixed number of times between the first drum 10a and the second drum 10b and has an insulating layer formed on its surface, i.e., the insulated electric wire, is finally wound up by the winding unit 60 provided downstream in the running direction of the conductor W. The drum 10 can be made of metal, resin, or the like. The first drum 10a is a driving drum and is driven to rotate by a driving unit (not shown). The second drum 10b is supported so as to be freely rotatable, and rotates as the conductor W travels.

An example configuration of the coating section 20, the first induction heater 30 and the second induction heater 40, which are sandwiched between the first drum 10a and the second drum 10b, is shown in Figure 3.

As described above, the conductor W rotates between the first drum 10a and the second drum 10b a certain number of times, passing through the coating device 21 and the first induction heater 30 provided in the coating section 20 in that order each time. In addition, in the insulated wire manufacturing apparatus shown in FIG. 3, the conductor W is configured to pass through the coating device 21 and the first induction heater 30 in the coating section 20 three times in succession before passing through the second induction heater 40.

In the insulated wire manufacturing apparatus 1, the varnish applied by the applicator 21 is dried by heating and evaporating the solvent in the varnish by the first induction heater 30, and the insulating material contained in the varnish is heated and hardened by the second induction heater 40. In this case, the time required for hardening can be shortened by configuring the application and drying of the conductor W to be repeated a certain number of times by the applicator 21 and the first induction heater 30 as described above, and then hardening by the second induction heater 40. This makes it possible to improve the manufacturing capacity of insulated wires while preventing deterioration of the insulation properties of the insulating layer.

In Fig. 3, the coating section 20 is configured so that the conductor W passes through a different coating device 21 for each revolution, but if the same type and concentration of varnish is to be applied, for example, the conductor W may be configured to pass through the same coating device 21 for each revolution. Also, a configuration may be provided in which multiple coating devices 21 are provided, the number of which is less than the number of revolutions of the conductor W, and the conductor W passes through one coating device 21 once or multiple times.

3, the insulated wire manufacturing apparatus 1 is configured so that the conductor W passes through the same first induction heater 30 for each revolution, but if temperature control is performed for each revolution, for example, the conductor W can be configured to pass through a different first induction heater 30 for each revolution. Also, a configuration may be provided in which the number of first induction heaters 30 is fewer than the number of revolutions of the conductor W, and the conductor W passes through one first induction heater 30 once or multiple times.

(Applying part)
4, the coating device 21 provided in the coating section 20 coats varnish on the outer peripheral surface of the conductor W revolving around the first drum 10a and the second drum 10b. The coating device 21 includes a varnish tank 21a for storing varnish, and a coating die 21b that is provided downstream of the varnish tank 21a in the traveling direction of the conductor W and through which the conductor W that has passed through the varnish tank 21a is inserted.

A through hole is provided at the bottom of the varnish tank 21a to allow the conductor W to pass through, and the varnish from the varnish tank 21a is applied to the outer surface of the conductor W that passes through the through hole. If the conductor W passes through one application device 21 multiple times, the through holes are arranged at the desired intervals for the number of passes so that the conductor W can easily rotate around.

The varnish applied to the outer peripheral surface of the conductor W is adjusted to a substantially uniform thickness according to the diameter of the die hole by inserting the conductor W through the coating die 21b. This coating die 21b is provided for each revolution of the conductor W, regardless of the number of times the conductor W passes through one coating device 21. In other words, the same number of coating dies 21b as the number of times the conductor W passes through are provided. The diameter of the die hole of the coating die 21b is made larger for coating dies 21b located downstream in the running direction of the conductor W. By gradually increasing the diameter of the coating die 21b toward the downstream side in this way, the coating formed on the outer peripheral surface of the conductor W is gradually made thicker, and an insulating layer of a constant thickness can be formed.

Therefore, the number of coating dies 21b is determined based on the thickness of the insulating layer formed per time and the total thickness of the insulating layer required. The number of revolutions of the conductor W can be the same as the number of coating dies 21b.

The varnish used is a solution of the resin (insulating material) that constitutes the insulating layer in a solvent. There are no particular limitations on the constituent resin, so long as it has high insulating properties and high heat resistance. Specific examples include polyimide, polyamideimide, polyesterimide, etc. Also, examples of the solvent that can be used include pyrrolidone, cresol, etc.

(First induction heater)
The first induction heater 30 directly heats the conductor W by using an electromagnetic induction current generated in the conductor W by a change in a magnetic field (AC magnetic field). The frequency of the first induction heater 30 (the frequency of the current for generating the AC magnetic field) is appropriately determined from the viewpoints of heating efficiency and equipment costs, and can be, for example, 10 kHz or more and 10 MHz or less.

In induction heating, the magnetic field becomes stronger in proportion to the magnitude of the current flowing through the coil to generate the magnetic field, and the current induced in the conductor W also becomes larger in proportion to the strength of the magnetic field. Since the amount of heat generated by the conductor W is proportional to the square of this induced current, the first induction heater 30 can heat the conductor W in proportion to the square of the current flowing through the coil to generate the magnetic field. Therefore, by increasing the current so as to generate heat proportional to the required running speed, the conductor W can be heated as required without increasing the distance that the conductor W passes through the inside of the first induction heater 30 (the heating distance of the first induction heater 30). In addition, because it is direct heating, the heating temperature is less likely to be restricted due to the heat resistance of the equipment.

The first induction heater 30 can also be configured to have multiple heating regions that can independently control the heating temperature of the conductor W. By having multiple heating regions in this way, it becomes possible to finely control the heating temperature.

(Second induction heater)
As the second induction heater 40, a heater similar to the first induction heater 30 can be used.

The first induction heater 30 and the second induction heater 40 are arranged at a distance from each other. The distance between the first induction heater 30 and the second induction heater 40 (distance D in FIG. 3) is set to a distance sufficient to complete the evaporation of the solvent by the residual heat of the conductor W sent out from the first induction heater 30.

Specifically, the lower limit of the distance D between the first induction heater 30 and the second induction heater 40 is preferably 50 cm, and more preferably 1 m. By setting the distance D between the first induction heater 30 and the second induction heater 40 to the lower limit or more, the solvent contained in the varnish can be evaporated more reliably. On the other hand, the upper limit of the distance D is not particularly limited, but if the distance D is made large, the efficiency of evaporation of the solvent decreases and the overall length of the device becomes long, making the device unnecessarily large. Therefore, the upper limit is set to, for example, 5 m.

The evaporation efficiency of the solvent can be improved by blowing air with an appropriate speed and direction in the area between the first induction heater 30 and the second induction heater 40. The air direction is preferably perpendicular to the axial direction of the conductor W.

The upper limit of the wind speed is preferably 3 m/s. By setting the wind direction and wind speed as described above, the efficiency of solvent evaporation can be increased while suppressing an increase in the energy required for blowing the wind. The lower limit of the wind speed is not particularly limited, and it is also possible to set it to 0 m/s, i.e., no wind is blown.

The lower limit of the temperature of the air (air temperature) is preferably 10°C, more preferably 20°C. On the other hand, the upper limit of the air temperature is preferably 200°C, more preferably 180°C, and even more preferably 150°C. If the air temperature is below the lower limit, the conductor W may become too cold and the solvent may not evaporate sufficiently. Conversely, if the air temperature exceeds the upper limit, the solvent may be heated too much by the air temperature and exceed its boiling point, or energy may be unnecessarily increased. From the viewpoint of energy consumption, the air temperature may be room temperature, that is, a natural temperature without heating.

(Winding section)
The winding unit 60 pulls the conductor W and winds it on the reel. The tensile force of the winding unit 60 causes the conductor W to rotate between the coating unit 20, the first induction heater 30, and the second induction heater 40. A known motor such as a servo motor or a stepping motor can be used to drive the winding unit 60.

<Coating process>
In the coating step S1, a linear conductor W is caused to travel in its axial direction, and a varnish containing an insulating material and a solvent is applied to the conductor W. Specifically, the conductor W is sent out from the sending section 50, passed through the first drum 10a, and caused to travel through the coating device 21.

The conductor W is inserted from a through hole at the bottom of the varnish tank 21a, and passes through the varnish stored in the varnish tank 21a, so that the insulating varnish is applied to the outer peripheral surface of the conductor W. The varnish applied to the outer peripheral surface of the conductor W is adjusted to a substantially uniform thickness according to the diameter of the die hole by inserting the conductor W through the application die 21b.

<Temperature increasing step>
In the temperature increasing step S2, the temperature of the varnish applied in the application step S1 is increased while being maintained at a temperature lower than the boiling point of the solvent in the varnish. This is continued until the temperature of the varnish and the conductor W after the temperature increase reaches a desired value.

In the method for manufacturing the insulating device, the conductor W is heated using the first induction heater 30 in the heating step S2. Specifically, the conductor W that has passed through the coating die 21b is made to run through the first induction heater 30. By using the first induction heater 30 for heating in the heating step S2 in this way, the heating speed can be easily increased, further improving the manufacturing efficiency of the insulated wire.

The temperature of the varnish and conductor W after heating is preferably closer to the boiling point of the solvent, but still below the boiling point. The upper limit of the temperature difference between the temperature of the conductor W after heating and the boiling point of the solvent is preferably 10°C, and more preferably 7°C. If the temperature difference exceeds the upper limit, the evaporation efficiency of the solvent may decrease. On the other hand, the lower limit of the temperature difference is not particularly limited and may be 0°C, but is preferably 5°C so as to absorb temperature control errors.

The lower limit of the average heating rate of the varnish and conductor W is preferably 50°C/sec, and more preferably 100°C/sec. In this way, by setting the average heating rate of the varnish and conductor W to be equal to or higher than the lower limit, the manufacturing efficiency of the insulated wire can be further improved. On the other hand, the upper limit of the average heating rate of the varnish and conductor W is not particularly limited, but is set to, for example, 500°C/sec from the viewpoint of controllability and energy efficiency.

<Evaporation process>
In the evaporation step S3, the solvent is evaporated while maintaining the temperature difference between the temperature of the varnish and the boiling point of the solvent after the temperature increasing step S2. This step is continued until the solvent has completely evaporated (e.g., the residual solvent in the varnish is preferably 3% by mass or less, more preferably 1% by mass or less).

In the method for manufacturing an insulated electric wire, the evaporation of the solvent in the evaporation step S3 is performed using the residual heat of the conductor W heated in the heating step S2. In other words, this step is performed in the space between the first induction heater 30 and the second induction heater 40. By thus evaporating the solvent in the evaporation step S3 using the residual heat of the conductor W heated in the heating step S2, the manufacturing cost can be reduced.

Strictly speaking, the temperature difference between the temperature of the varnish and the boiling point of the solvent increases slightly as the solvent evaporates due to the residual heat of the conductor W, but the magnitude of this increase is small due to the specific heat of the conductor W, and the temperature difference is substantially maintained. Here, the temperature difference being "substantially maintained" means that the change in temperature difference is 5°C or less, preferably 3°C or less, and more preferably 1°C or less. This temperature difference can be controlled by the distance D between the first induction heater 30 and the second induction heater 40, or, in the case of blowing air, by the air direction, air speed, and air temperature.

<Curing step>
In the curing step S4, the insulating material is cured after the evaporating step S3.

In the manufacturing method of the insulating device, the conductor W is heated using the second induction heater 40 in the hardening step S4. This heating hardens the insulating material. Specifically, the conductor W that has passed through the space between the first induction heater 30 and the second induction heater 40 is made to run through the second induction heater 40. By using the second induction heater 40 for heating in the hardening step S4 in this way, the heating speed can be easily increased, further improving the manufacturing efficiency of the insulated wire.

This causes the resin (insulating material) contained in the varnish after the solvent has evaporated in evaporation step S3 to harden, forming an insulating coating around the outer periphery of the conductor W.

The temperature of the conductor W in the hardening process S4 is a temperature at which the resin contained in the varnish can be hardened, for example, 150°C or higher and 600°C or lower.

In addition, the application process S1, the heating process S2, the evaporation process S3 and the hardening process S4 may be repeated in this order.

Through the above steps, an insulating layer is formed around the outer periphery of the conductor W, and an insulated electric wire can be manufactured.

<Advantages>
In the method for producing an insulated electric wire, the varnish applied to the conductor W is heated while being maintained at a temperature below its boiling point, and then the solvent is evaporated while maintaining a temperature difference from the boiling point. In the method for producing an insulated electric wire, such a temperature profile can suppress foaming of the varnish. In addition, in the method for producing an insulated electric wire, the time until the solvent evaporates can be shortened by increasing the heating rate in the temperature increasing step S2, thereby improving production efficiency.

The insulated wire manufacturing apparatus 1 can heat the varnish applied to the conductor W using the first induction heater 30 while maintaining the temperature below the boiling point of the solvent. In addition, in the insulated wire manufacturing apparatus 1, when the varnish heated by the first induction heater 30 passes through the space between the first induction heater 30 and the second induction heater 40, the solvent can be evaporated by the residual heat of the conductor W. Furthermore, in the insulated wire manufacturing apparatus 1, the insulating material from which the solvent has evaporated can be hardened by the second induction heater 40. Therefore, by using the insulated wire manufacturing apparatus 1, it is possible to increase manufacturing efficiency while suppressing foaming of the varnish.

Second Embodiment
The insulated wire manufacturing apparatus 2 shown in Figures 5 and 6 includes a pair of drums 10 (first drum 10a and second drum 10b) arranged in parallel and running a linear conductor W that is suspended in one or more revolutions, a plurality of first manufacturing unit groups 70 and a plurality of second manufacturing unit groups 80 that are arranged in series from the upstream side to the downstream side in the running direction of the linear conductor W running in the axial direction, a control unit 90 that controls the first manufacturing unit 70a included in the first manufacturing unit group 70 and the second manufacturing unit 80a included in the second manufacturing unit group 80, a sending unit 50 that sends out the conductor W to the first drum 10a, and a winding unit 60 that winds up the conductor W with an insulating layer formed thereon, i.e., the insulated wire.

<Conductor, drum, delivery section, winding section>
The conductor W, the drum 10, the delivery section 50 and the winding section 60 are similar to those of the insulated electric wire manufacturing apparatus 1 of the first embodiment, and therefore the same reference numerals are used and detailed description thereof will be omitted.

<Coating section>
Each of the first production unit 70a and the second production unit 80a has a coating unit 20 that coats the conductor W with a varnish containing an insulating material and a solvent while the conductor W is traveling. The coating unit 20 can be configured in the same manner as the insulated electric wire production apparatus 1 of the first embodiment, and therefore the same reference numerals are used and detailed description is omitted. Note that the coating unit 20 may be provided in common to all of the first production units 70a and the second production units 80a, as shown in FIG. 6, or may be provided for each production unit.

<Heating section>
6, the first manufacturing unit 70a has a first heating section 71 that is installed downstream of the coating section 20 in the running direction of the conductor W and is capable of heating the varnish, a second heating section 72 that is installed at the most downstream side in the running direction of the conductor W and is capable of hardening the insulating material contained in the varnish, and a third heating section 73 that is installed downstream of the first heating section 71 in the running direction of the conductor W and is capable of evaporating the solvent. In other words, the first manufacturing unit 70a has the coating section 20, the first heating section 71, the third heating section 73, and the second heating section 72 in this order toward the downstream side in the running direction of the conductor W.

6, the second manufacturing unit 80a is installed downstream of the application unit 20 in the running direction of the conductor W and has a first heating unit 81 capable of heating the varnish, and a third heating unit 83 installed downstream of the first heating unit 81 in the running direction of the conductor W and capable of evaporating the solvent. In other words, the second manufacturing unit 80a has the application unit 20, the first heating unit 81, and the third heating unit 83 in this order toward the downstream side in the running direction of the conductor W.

The heaters used in the first heating section 71, the second heating section 72 and the third heating section 73 of the first manufacturing unit 70a and the first heating section 81 and the third heating section 83 of the second manufacturing unit 80a are not particularly limited, and various heaters such as heating furnaces and induction heaters can be used.

At least one of the first heating section 71 and the second heating section 72 of the first manufacturing unit 70a may be an induction heater. By using an induction heater for at least one of the first heating section 71 and the second heating section 72 of the first manufacturing unit 70a in this manner, the heating speed can be easily increased, so that the travel distance of the conductor W can be shortened, the insulated wire manufacturing apparatus 2 can be made smaller, and manufacturing efficiency can be further improved.

In addition, the first heating section 81 of the second production unit 80a may be an induction heater. By using an induction heater as the first heating section 81 of the second production unit 80a in this manner, the heating speed can be easily increased, so that the travel distance of the conductor W can be shortened, the insulated wire production device 2 can be made smaller, and production efficiency can be further improved.

In particular, by using induction heaters for both the first heating section 71 and the second heating section 72 of the first manufacturing unit 70a and the first heating section 81 of the second manufacturing unit 80a, manufacturing efficiency can be further improved.

On the other hand, the third heating section 73 of the first manufacturing unit 70a and the third heating section 83 of the second manufacturing unit 80a may be a heating furnace. The third heating section aims to evaporate the solvent, and heats the conductor W so that its temperature is constant while it passes through the third heating section. By making the third heating section a heating furnace, it is possible to easily control the temperature to be constant.

Note that each heating section does not necessarily have to be of the same type. For example, the first heating section 71 of the first manufacturing unit 70a may use a heater of a different type depending on the unit.

<Control Unit>
The control unit 90 controls the first heating unit 71 of the first production unit 70a and the first heating unit 81 of the second production unit 80a to raise the temperature of the varnish while maintaining it at a temperature below the boiling point of the solvent, and controls the second heating unit 72 of the first production unit 70a to harden the insulating material. The control unit 90 also controls the third heating unit 73 of the first production unit 70a and the third heating unit 83 of the second production unit 80a to evaporate the solvent while maintaining the temperature difference between the temperature of the varnish and the boiling point of the solvent in the first heating unit.

The control unit 90 can be configured, for example, by a temperature measuring device installed in each heating unit and a controller that adjusts the output of each heating unit based on the measurement results of the temperature measuring device.

<Arrangement of First Manufacturing Unit and Second Manufacturing Unit>
6, the insulated wire manufacturing apparatus 2 has a first manufacturing unit group 70 composed of one or two first manufacturing units 70a, and a second manufacturing unit group 80 composed of one or more second manufacturing units 80a and arranged contiguous to the first manufacturing unit group 70. By discretely arranging one or two first manufacturing units 70a in this manner, it is possible to reduce power consumption while easily improving the uniformity of quality in the thickness direction of the manufactured insulated wire.

The insulated wire manufacturing apparatus 2 shown in Figure 6 has a plurality of first manufacturing unit groups 70 and a plurality of second manufacturing unit groups 80, but the number of first manufacturing unit groups 70 and second manufacturing unit groups 80 may be one. Also, in the insulated wire manufacturing apparatus 2 shown in Figure 6, the number of first manufacturing unit 70a included in each of the first manufacturing unit groups 70 is one, but the number of first manufacturing units 70a may be two, or a mixture of one and two. Below, a description will be given based on the configuration of the insulated wire manufacturing apparatus 2 shown in Figure 6.

It is preferable that the number of second manufacturing units 80a included in the second manufacturing unit group 80 is more than one, and more preferably is greater than the number of first manufacturing units 70a in the adjacent first manufacturing unit group 70. This results in a relatively small number of first manufacturing units 70a, thereby enabling low power consumption.

The lower limit of the number of second manufacturing units 80a in the second manufacturing unit group 80 is preferably 2, and more preferably 3. On the other hand, the upper limit of the number is preferably 10, and more preferably 5. If the number is less than the lower limit, the effect of reducing power consumption may be insufficient. Conversely, if the number exceeds the upper limit, the uniformity of quality in the thickness direction of the insulated wire may decrease.

In addition, it is preferable that the number of second manufacturing units 80a in the second manufacturing unit group 80 is the same. By arranging the number of second manufacturing units 80a in this manner, the uniformity of the quality of the insulated electric wire in the thickness direction can be further improved.

The first manufacturing unit 70a is preferably arranged at the most downstream side in the running direction of the conductor W. In other words, the first manufacturing unit group 70 is preferably arranged at the most downstream side in the running direction of the conductor W. By arranging the first manufacturing unit 70a at the most downstream side in the running direction of the conductor W in this manner, the insulating material can be hardened last, making it easier to ensure the stability of the quality of the manufactured insulated wire.

In addition, the first manufacturing unit 70a is preferably arranged at the most upstream side in the running direction of the conductor W. In other words, the first manufacturing unit group 70 is preferably arranged at the most upstream side in the running direction of the conductor W. By arranging the first manufacturing unit 70a at the most upstream side in the running direction of the conductor W in this manner, the insulating material can be hardened first, making it easier to increase the adhesion between the conductor W and the insulating material.

<Method of manufacturing insulated wire>
Using the insulated wire manufacturing apparatus 2, an insulated wire can be manufactured by the insulated wire manufacturing method shown in Fig. 1. That is, the insulated wire manufacturing method includes a step S1 of applying a varnish containing an insulating material and a solvent to a linear conductor W while running the conductor W in its axial direction, a step S2 of raising the temperature of the varnish applied in the applying step while maintaining the temperature below the boiling point of the solvent, a step S3 of evaporating the solvent after the heating step while maintaining the temperature difference between the temperature of the varnish and the boiling point of the solvent, and a step S4 of curing the insulating material after the evaporating step.

(Coating process)
The coating step S1 is performed in the coating sections 20 of the first production unit 70a and the second production unit 80a. This step can be performed in the same manner as the coating step S1 in the first embodiment.

(Temperature increasing process)
The temperature increasing step S2 is performed in the first heating section 71 of the first production unit 70a and the first heating section 81 of the second production unit 80a. At this time, the control section 90 controls the first heating section so as to increase the temperature of the varnish while maintaining the temperature below the boiling point of the solvent in the varnish.

The temperature and average heating rate of the varnish and conductor W after heating can be the same as in heating process S2 of the first embodiment.

(Evaporation process)
The evaporation step S3 is performed in the third heating section 73 of the first production unit 70a and the third heating section 83 of the second production unit 80a. At this time, the control section 90 controls the third heating section so as to evaporate the solvent while maintaining the temperature difference between the temperature of the varnish and the boiling point of the solvent in the first heating section.

In the second manufacturing unit 80a, after the evaporation process S3, the conductor W is moved to the next manufacturing unit (the first manufacturing unit 70a or the second manufacturing unit 80a). That is, in the second manufacturing unit 80a, the application process S1, the heating process S2, and the evaporation process S3 are repeated. By repeating these processes, the insulating material can be laminated uniformly on the conductor W.

(Curing process)
In the first manufacturing unit 70a, the evaporation step S3 is followed by the curing step S4. This step is performed by the second heating section 72. At this time, the control section 90 controls the second heating section 72 so as to cure the insulating material.

This causes the resin (insulating material) contained in the varnish after the solvent has evaporated in evaporation step S3 to harden, forming an insulating coating around the outer periphery of the conductor W.

The temperature of the conductor W in the hardening process S4 is a temperature at which the resin contained in the varnish can be hardened, for example, 150°C or higher and 600°C or lower.

Through the above process, hardened insulation layers are sequentially stacked around the outer periphery of the conductor W each time it passes through the first manufacturing unit 70a, thereby producing an insulated electric wire.

<Advantages>
In the insulated wire manufacturing apparatus 2, the control unit 90 increases the heating rate while suppressing foaming of the varnish in the first heating units of the first manufacturing unit 70a and the second manufacturing unit 80a, thereby shortening the time it takes for the solvent to evaporate. In addition, the insulated wire manufacturing apparatus 2 is capable of supplying an optimal amount of heat to the conductor W by arranging in series the first manufacturing unit 70a having the second heating unit 72 that hardens the insulating material contained in the varnish, and the second manufacturing unit 80a having no second heating unit. Therefore, the insulated wire manufacturing apparatus 2 can reduce power consumption while increasing manufacturing efficiency.

In addition, by providing a third heating section in the first production unit 70a and the second production unit 80a, the solvent can be evaporated while maintaining the temperature difference between the temperature of the varnish and the boiling point of the solvent in the first heating section, thereby further improving production efficiency.

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

In the above first embodiment, an induction heater is used for heating in the temperature increasing process and the hardening process, but it is also intended by this disclosure that a heating device other than an induction heater is used for one or both of these processes.

In the first embodiment, the solvent is evaporated in the evaporation step by using the residual heat of the conductor heated in the heating step. However, the solvent may be evaporated while controlling the temperature by a heat retaining device or a heating device. In this case, the temperature difference between the temperature of the varnish and the boiling point of the solvent may be gradually reduced within a range that does not exceed the boiling point of the solvent. In other words, the varnish and the conductor may be gently heated in the evaporation step. When the varnish and the conductor are gently heated, the average heating rate is made smaller than the average heating rate of the varnish and the conductor in the heating step. Specifically, the average heating rate of the varnish and the conductor in the evaporation step is preferably 1/10 or less, more preferably 1/20 or less, of the average heating rate of the varnish and the conductor in the heating step. Even when the varnish is heated gently in this way, the present disclosure is effective as long as the temperature of the varnish is maintained at a temperature lower than the boiling point of the solvent.

In the second embodiment, the first and second manufacturing units each have a third heating unit, but some or all of the first and second manufacturing units may not have a third heating unit. For example, a first manufacturing unit without a third heating unit may have a configuration in which the first and second heating units are spaced apart from each other, and the distance between the first and second heating units is sufficient to complete evaporation of the solvent by the residual heat of the conductor sent out from the first heating unit.

In the above second embodiment, the configuration of the insulated electric wire manufacturing apparatus shown in Fig. 6 has been described, but the present disclosure is not limited to the configuration of the insulated electric wire manufacturing apparatus shown in Fig. 6. For example, three or more first manufacturing units may be consecutively provided.

Alternatively, the insulated wire manufacturing apparatus may have three or more first manufacturing units and three or more second manufacturing units, with one of the first manufacturing units being arranged on the most downstream side in the running direction of the conductor, one of the second manufacturing units being arranged on the most upstream side in the running direction of the conductor, and the same number of the second manufacturing units being arranged between adjacent first manufacturing units. This configuration can further improve manufacturing efficiency. In this configuration, one or more second manufacturing units are arranged upstream of the most upstream first manufacturing unit. The number of second manufacturing units arranged upstream of the most upstream first manufacturing unit may be different from the number of second manufacturing units arranged between adjacent first manufacturing units, and is preferably small.

The insulated wire manufacturing apparatus may be configured such that one or more first manufacturing units are arranged on the most upstream side in the running direction of the conductor, and only the second manufacturing unit is arranged downstream of the one or more first manufacturing units. This configuration makes it easier to improve adhesion between the conductor and the insulating material. Specifically, the basic characteristics of the insulated wire can be determined mainly by the amount of heat of the second manufacturing unit, and the adhesion between the conductor and the insulating material can be improved by the first manufacturing unit arranged on the most upstream side, that is, the first manufacturing unit that heats the insulating material on the side in contact with the conductor. The number of the first manufacturing units is preferably 1 or 2, from the viewpoint of improving adhesion while reducing power consumption.

The insulated wire manufacturing apparatus may be configured such that one or more first manufacturing units are arranged at the most downstream side in the running direction of the conductor, and only the second manufacturing unit is arranged upstream of the one or more first manufacturing units. This configuration makes it easier to increase the flexibility of the manufactured insulated wire. Specifically, the basic characteristics of the insulated wire can be determined mainly by the amount of heat generated by the second manufacturing unit, and the flexibility of the conductor can be increased by heating with the first manufacturing unit arranged at the most downstream side. The number of first manufacturing units arranged is preferably 1 or 2, from the viewpoint of increasing adhesion while reducing power consumption.

Reference Signs List 1, 2 Manufacturing apparatus for insulated electric wire 10 Drum 10a First drum 10b Second drum 20 Coating section 21 Coating device 21a Varnish tank 21b Coating die 30 First induction heater 40 Second induction heater 50 Delivery section 60 Winding section 70 First manufacturing unit group 70a First manufacturing unit 71 First heating section 72 Second heating section 73 Third heating section 80 Second manufacturing unit group 80a Second manufacturing unit 81 First heating section 83 Third heating section 90 Control section W Conductor

Claims (12)

A step of applying a varnish containing an insulating material and a solvent to a linear conductor while the conductor is traveling in its axial direction;
a step of increasing the temperature of the varnish applied in the applying step while maintaining the temperature at a temperature lower than the boiling point of the solvent;
a step of evaporating the solvent while maintaining a temperature difference between the temperature of the varnish and the boiling point of the solvent after the heating step;
and a step of curing the insulating material after the evaporating step. The method for manufacturing an insulated electric wire according to claim 1, wherein the conductor is heated using an induction heater in the heating process. The method for manufacturing an insulated electric wire according to claim 1 or 2, wherein the conductor is heated using an induction heater in the hardening process. The method for manufacturing an insulated electric wire according to claim 1, claim 2 or claim 3, wherein the evaporation of the solvent in the evaporation step is performed using residual heat of the conductor heated in the heating step. an applicator that applies a varnish containing an insulating material and a solvent to a linear conductor while the linear conductor is traveling in its axial direction;
a first induction heater that is installed downstream of the coating unit in a running direction of the conductor and that heats the varnish while maintaining the temperature of the varnish at a temperature lower than the boiling point of the solvent ;
a second induction heater that is disposed downstream of the first induction heater in the running direction of the conductor and is capable of hardening an insulating material contained in the varnish,
The first induction heater and the second induction heater are disposed apart from each other,
an insulated wire manufacturing apparatus that evaporates the solvent in a region between the first induction heater and the second induction heater while maintaining a temperature difference between a temperature of the varnish and a boiling point of the solvent . The insulated wire manufacturing apparatus according to claim 5, wherein the distance between the first induction heater and the second induction heater is 50 cm or more. One or more first production units and one or more second production units arranged in series from the upstream side to the downstream side in the running direction of a linear conductor running in an axial direction;
a control unit that controls the first manufacturing unit and the second manufacturing unit,
The first manufacturing unit and the second manufacturing unit each include a coating unit that coats the conductor with a varnish containing an insulating material and a solvent while the conductor is traveling;
a first heating unit that is installed downstream of the coating unit in the running direction of the conductor and is capable of heating the varnish;
the first production unit is provided on the most downstream side in the running direction of the conductor, and further includes a second heating unit capable of curing an insulating material contained in the varnish;
The control unit controls the first heating unit to raise the temperature of the varnish while maintaining the temperature below the boiling point of the solvent in the varnish, and controls the second heating unit to evaporate the solvent downstream of the first induction heating unit while maintaining a temperature difference between the temperature of the varnish and the boiling point of the solvent, and then to harden the insulating material. The insulated electric wire manufacturing apparatus according to claim 7, wherein at least one of the first heating section and the second heating section of the first manufacturing unit is an induction heater. the first manufacturing unit and the second manufacturing unit each have a third heating unit that is installed downstream of the first heating unit in a running direction of the conductor and is capable of evaporating the solvent;
9. The apparatus for manufacturing an insulated electric wire according to claim 7, wherein the control unit controls the third heating unit so as to evaporate the solvent while maintaining a temperature difference between a temperature of the varnish and a boiling point of the solvent in the first heating unit. The insulated wire manufacturing apparatus according to claim 7, claim 8 or claim 9, wherein the first manufacturing unit is disposed at the most downstream side in the running direction of the conductor. The insulated wire manufacturing apparatus according to any one of claims 7 to 10, wherein the first manufacturing unit is disposed on the most upstream side in the running direction of the conductor. A first manufacturing unit group consisting of one or two of the first manufacturing units;
12. The apparatus for manufacturing an insulated electric wire according to claim 7, further comprising: a second manufacturing unit group configured with one or more of the second manufacturing units and arranged adjacent to the first manufacturing unit group.

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