CN113450946A

CN113450946A - Enameled wire

Info

Publication number: CN113450946A
Application number: CN202110168093.9A
Authority: CN
Inventors: 西甫; 牛渡刚真; 本田祐树; 安藤郁美
Original assignee: Hitachi Metals Ltd
Current assignee: Proterial Ltd
Priority date: 2020-03-27
Filing date: 2021-02-07
Publication date: 2021-09-28
Also published as: JP2021157964A; JP7326203B2

Abstract

The invention provides an enameled wire with excellent deformation resistance, wherein an insulating coating containing a hollow hole is arranged on a conductor. Provided are enameled wires (1, 2) which are provided with a conductor (10) and insulating coatings (11, 21) which are provided around the conductor (10) and have voids (111, 213), and which have a deformation rate of less than 10%. The deformation ratio is determined by the equation of (2 nd displacement amount-1 st displacement amount) × 100/(film thickness of the insulating film × 2).

Description

Enameled wire

Technical Field

The present invention relates to an enamel wire.

Background

Conventionally, there is known an insulated wire including a conductor provided with an insulating film made of polyimide having a hole in order to suppress occurrence of partial discharge (see, for example, patent document 1). Since air has a lower relative dielectric constant than polyimide, the insulating film having voids has a lower relative dielectric constant than an insulating film having no voids, and partial discharge of the insulated wire can be effectively suppressed. In the insulated wire described in patent document 1, the porosity of the insulating film is set in a wide range of, for example, 5 vol% to 80 vol%.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2018-170261

Disclosure of Invention

Problems to be solved by the invention

However, if the insulating film has voids, the insulating film is easily deformed (the deformation resistance is lowered).

Accordingly, an object of the present invention is to provide an enameled wire having excellent deformation resistance, which includes an insulating film having a void on a conductor.

Means for solving the problems

In order to solve the above problems, the present invention provides an enameled wire including a conductor and an insulating film provided around the conductor and having a void, wherein a deformation ratio obtained by the following formula 1 is less than 10%.

Formula 1: (2 nd displacement-1 st displacement) × 100/(film thickness of the insulating film × 2)

1 st displacement amount: a difference between a position of an end surface of a cylindrical jig in a vertical direction when a force (initial value) directed vertically downward is applied to the sample stage by the jig by bringing the end surface of the jig into contact with an upper surface of the sample stage from vertically above at 22 to 23 ℃ and a position of the end surface of the jig in the vertical direction when the force is applied for 10 minutes,

displacement amount 2: a difference between a position of the end surface of the jig in a vertical direction when a force (initial value) directed vertically downward is applied to the enameled wire by the jig, and a position of the end surface of the jig in a vertical direction when the force is applied for 10 minutes,

force directed vertically downward: force increasing at an increasing rate of 98 mN/min with an initial value of 5mN

Effects of the invention

According to the present invention, an enameled wire having an insulating coating film containing voids on a conductor and having excellent deformation resistance can be provided.

Drawings

Fig. 1(a) and 1(b) are cross-sectional views of an enamel wire according to an embodiment of the present invention, the cross-sectional views being perpendicular to the longitudinal direction.

Fig. 2 is a schematic view showing a case where a deformation ratio of the enamel wire is measured.

Fig. 3 is a graph showing an example of the measurement result of the deformation ratio of the enamel wire.

FIG. 4 is a graph showing the relationship between the porosity and the deformation ratio of samples A to J.

Description of the symbols

1. 2: enamelled wires; 10: a conductor; 11. 21: an insulating film; 211: layer 1; 212: layer 2.

Detailed Description

[ embodiment ]

Fig. 1(a) is a cross-sectional view of an enamel wire 1 according to an embodiment of the present invention, which is perpendicular to the longitudinal direction. The enamel wire 1 includes a conductor 10 and an insulating film 11 provided around the conductor 10 and having a void 111, and has a deformation ratio of less than 10%. The deformation ratio is as described below.

The conductor 10 is a wire-shaped metal wire made of a conductive material such as copper, a copper alloy, aluminum, or an aluminum alloy, and is, for example, a copper wire made of oxygen-free copper or low-oxygen copper. The configuration of the conductor 10 is not limited to this, and for example, a wire plated with a metal such as nickel on the outer periphery of a metal wire may be used as the conductor 10. The cross-sectional shape of the conductor 10 perpendicular to the longitudinal direction shown in fig. 1(a) and 1(b) is circular, but is not limited thereto, and may be, for example, a square.

The insulating film 11 is formed using a polyimide coating material containing a foaming agent such as tetraethylene glycol dimethyl ether as a precursor. For example, a polyimide coating containing a foaming agent is applied to the surface of the conductor 10, and the coated conductor is heated in a furnace at 300 to 500 ℃. The above operation was repeated a plurality of times to obtain an insulating film 11 made of polyimide. The thickness of the insulating film 11 is, for example, 30 μm or more and 200 μm or less.

Here, if the polyimide coating material is heated in an oven, the solvent is removed to perform imidization of the polyamic acid, and the blowing agent is volatilized (for example, at a temperature of 275 ℃ or higher in the case of a blowing agent composed of tetraethylene glycol dimethyl ether) or thermally decomposed (for example, at a temperature of 230 ℃ or higher in the case of a blowing agent composed of polymethyl methacrylate polymer fine particles) when heated at a temperature higher than the boiling point and decomposition starting temperature of the blowing agent, thereby forming a polyimide containing voids. The foaming agent is added to the polyimide coating material in an amount ranging from 1phr to 300phr, for example, with respect to the amount of the resin contained in the polyimide coating material. When the foaming agent is added in such an amount, it is effective to appropriately adjust the porosity of the pores 111 formed in the insulating film 11.

As the polyimide coating material which is a precursor of the insulating film 11, for example, a polyimide coating material which is a polyamic acid solution in which a diamine component composed of 4, 4' -diaminodiphenyl ether and an acid component composed of pyromellitic dianhydride are dissolved in DMAc (dimethylacetamide) as a solvent (hereinafter referred to as a 1 st polyimide coating material) can be used.

In order to increase the partial discharge inception voltage of the enamel wire 1 particularly, for example, 4,4 '-diaminodiphenyl ether and pyromellitic dianhydride, as well as 3, 4' -diaminodiphenyl ether, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, 4,4 '-bis (4-aminophenoxy) biphenyl, 2-bis { 4- (4-aminophenoxy) phenyl } propane, 2-bis { 4- (4-aminophenoxy) phenyl } hexafluoropropane and the like, 4, 4' -oxydiphthalic anhydride, 2-bis (3, 4-anhydrodicarboxyl) -hexafluoropropane, 3 ', 4, 4' -benzophenonetetracarboxylic dianhydride, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride and the like, which are diamine components, may be dissolved in DMAc, may be used, A polyimide paint as a polyamic acid solution (hereinafter referred to as a 2 nd polyimide paint).

When the insulating film 11 is formed from the 2 nd polyimide varnish, the dielectric constant of the insulating film 11 is lower than that when the insulating film 11 is formed from the 1 st polyimide varnish, and therefore, the partial discharge starting voltage of the enamel wire 1 can be increased. Further, when the insulating film 11 is formed directly around the conductor with the 2 nd polyimide coating material, the peeling of the insulating film 11 can be suppressed as compared with the case where the insulating film 11 is formed directly around the conductor with the 1 st polyimide coating material.

As the foaming agent contained in the polyimide coating material, a high boiling point solvent such as tetraethylene glycol dimethyl ether or polymer fine particles such as polymethyl methacrylate which are volatilized or thermally decomposed by a heat treatment in a furnace to form the pores 111 in the insulating film 11 can be used. Alternatively, the pores 111 may be formed by mixing a polyimide coating with a thermally expandable microcapsule instead of the high-boiling point solvent or the polymer fine particles. In this case, when the polyimide coating applied to the outer periphery of the conductor 10 is heated in the furnace, the thermally expandable microcapsules contained in the polyimide coating expand or foam, and the insulating film 11 containing the pores 111 is formed. The hollow 111 may be formed by mixing a hollow filler with a polyimide coating. In this case, the hollow portion inside the hollow filler becomes the hollow hole 111 included in the insulating film 11.

Fig. 1(b) is a cross-sectional view of the enamel wire 2 according to the embodiment of the present invention, which is perpendicular to the longitudinal direction. The enamel wire 2 includes a conductor 10 and an insulating film 21 made of polyimide provided around the conductor 10 and having a void 213, and has a deformation ratio of less than 10%. The deformation ratio is more preferably 1% to 8%.

The insulating film 21 has a 1 st layer 211 in contact with the conductor 10 and a 2 nd layer 212 provided outside the 1 st layer 211. The relative dielectric constant of the 1 st layer 211 is preferably lower than that of the 2 nd layer 212. Further, the 1 st layer 211 in contact with the conductor 10 is preferably high in adhesion to the conductor 10. If the adhesion of the 1 st layer 211 to the conductor 10 is high, the insulation film 21 can be prevented from peeling off from the conductor 10 by using the 1 st layer 211 as an inner layer and causing adhesion to the conductor 10.

When the 2 nd layer 212 is formed of a polyimide coating (for example, the 1 st polyimide coating) having a higher relative dielectric constant than the 1 st layer 211, the following advantages are obtained: compared to the 1 st layer 211 (for example, the 1 st layer 211 made of the 2 nd polyimide coating material), the voids 213 can be easily formed by a foaming agent (the void ratio can be easily increased), and the insulating film 21 can be produced at a low cost. Therefore, by using the 1 st layer 211 and the 2 nd layer 212 in combination, the insulating film 21 can be easily prevented from peeling off from the conductor 10 to form the void 213, and the relative permittivity and cost can be adjusted to a desired range.

The 1 st layer 211 and the 2 nd layer 212 can be formed using, for example, the 2 nd polyimide coating and the 1 st polyimide coating, respectively, as precursors. The thickness of the entire insulating film 21 is, for example, 30 μm or more and 200 μm or less.

As in the case where insulating film 11 has voids 111, insulating film 21 may have voids 213, including at least one of 1

st layer

211 and 2 nd layer 212. As described above, since the void 213 is more easily formed in the 2 nd layer 212 than in the 1 st layer 211, when the void 213 is formed in one of the 1 st layer 211 and the 2 nd layer 212, it is preferable to form the void 213 in the 2 nd layer 212.

As described above, the insulating film 11 of the enamel wire 1 and the insulating film 21 of the enamel wire 2 have the

pores

111 and 213, respectively. The relative dielectric constant of the portions of the

voids

111, 213 is lower than that of polyimide. Therefore, the

voids

111 and 213 of the insulating

films

11 and 21 lower the relative dielectric constants of the insulating

films

11 and 21, thereby increasing the partial discharge inception voltages of the

enamel wires

1 and 2.

In the present embodiment, in order to make the mechanical strength of the insulating

films

11 and 21 less likely to decrease, the porosity of the insulating

films

11 and 21 is preferably set within a range in which the deformation ratio of the

enamel wire

1 or 2 is less than 10%. For example, the porosity of the insulating

films

11 and 21 is preferably set to less than 25% in the range where the deformation ratio of the

enamel wires

1 and 2 is less than 10%.

If the porosity of the insulating

films

11 and 21 is too high, the insulating

films

11 and 21 are easily deformed during processing. At this time, the

pores

111 and 213 of the insulating

films

11 and 21 may collapse, and the original quality (relative permittivity) may not be exhibited. In order to suppress collapse of the

voids

111, 213 and to make the insulating

films

11, 21 less likely to deform, the void ratio is preferably less than 25%. The porosity of the insulating

films

11 and 21 is calculated by the following formula (1).

[ number 1]

Here, ρ₁Specific gravity, ρ, of the insulating

films

11, 21 in the absence of the

voids

111, 213₂The specific gravity of the insulating

films

11 and 21 including the

pores

111 and 213. The specific gravity of the insulating film 21 refers to the specific gravity of the entire insulating film 21 including the 1 st layer 211 and the 2 nd layer 212.

In addition, by using a polyimide constituting the insulating film 11 of the enamel wire 1 and the insulating film 21 of the enamel wire 2, which has a low relative permittivity, it is easy to suppress the porosity and reduce the permittivity. That is, it is easy to suppress a decrease in the mechanical strength of the insulating

films

11 and 21 and to reduce the dielectric constant. For example, the relative dielectric constant of the insulating

films

11 and 21 is preferably 3 or less. The relative permittivity of insulating film 21 refers to the relative permittivity of the entire insulating film 21 including layer 1 211 and layer 2 212.

Fig. 2 is a schematic view showing a case where the deformation ratio of the enamel wire 1 is measured. Hereinafter, a method of measuring the deformation ratio of the enamel wire 1 will be described with reference to fig. 2. The deformation ratio of the enamel wire 2 can be measured by the same method as the method for measuring the deformation ratio of the enamel wire 1 described below.

First, the end face of the jig 42 was brought into direct contact with the upper surface of the sample table 41 made of quartz disposed in a TMA furnace (a furnace of a thermomechanical analyzer) from the vertically upper side at 22 to 23 ℃. In a state where the end face of the jig 42 is brought into direct contact with the upper surface of the sample stage 41, a force F directed vertically downward is applied to the sample stage by the jig 42 for 10 minutes. The magnitude of the vertically downward force F increased at an initial value of 5mN at an increasing rate of 98 mN/min. The force F after 10 minutes from the start of the increase was 985 mN.

At this time, the difference between the position (height) of the end surface of the jig 42 in the vertical direction when a force F of 5mN (initial value) directed vertically downward is applied by the jig 42 and the end surface of the jig 42 is brought into contact with the upper surface of the sample stage 41 (initial state) and the position (height) of the end surface of the jig 42 in the vertical direction when 10 minutes have elapsed since the downward force F started to be applied to the upper surface of the sample stage 41 is defined as the 1 st displacement amount. That is, the 1 st displacement amount is an absolute value of a difference between a position of an end surface of the jig 42 in contact with the sample stage 41 when a force F (initial value) directed vertically downward is applied to the upper surface of the sample stage 41 by the jig 42 and a position in the vertical direction of the end surface of the jig 42 in contact with the sample stage 41 when the force F is applied for 10 minutes.

Next, as shown in fig. 2, the enamel wire 1 is disposed in a state of being laid on the upper surface of a sample table 41 made of quartz disposed in a TMA furnace (a furnace of a thermomechanical analyzer) under a condition of 22 to 23 ℃. Here, the lateral arrangement means that the length direction of the enamel wire 1 is arranged parallel to the upper surface of the sample stage 41. Next, a force F directed vertically downward was applied for 10 minutes while the end surface of the cylindrical jig (quartz probe) 42 was in contact with the enamel wire 1 laid on the upper surface of the sample stage 41 from vertically above. The magnitude of the vertically downward force F increased at an initial value of 5mN at an increasing rate of 98 mN/min. The force F was 985mN 10 minutes after the start of the increase.

At this time, the difference between the position (height) of the end surface of the jig 42 in the vertical direction in a state (initial state) where 5mN (initial value) of the force F directed vertically downward is applied by the jig 42 and the position (height) of the end surface of the jig 42 in the vertical direction in a state (initial state) where the force F directed vertically downward with respect to the enamel wire 1 starts to increase at the above-described rate of increase and 10 minutes has elapsed is defined as the 2 nd displacement amount. That is, the 2 nd displacement amount is an absolute value of a difference between a position of the end surface of the jig 42 in contact with the enamel wire 1 when a force F (initial value) directed vertically downward is applied to the enamel wire 1 by the jig 42 and a position of the end surface of the jig 42 in contact with the enamel wire 1 in the vertical direction when the force F is applied for 10 minutes.

After the 2 nd displacement is measured, the force F is released and the enamel wire 1 is removed from the sample stand 41.

Then, the deformation ratio of the enamel wire 1 is determined by the equation (2 nd displacement amount-1 st displacement amount) × 100/(film thickness of the insulating coating 11 × 2). Here, the unit of the 1 st displacement amount, the 2 nd displacement amount, and the film thickness of the insulating film 11 is the same. The film thickness is the thickness of the insulating film 11. When the enamel wire 2 is used as a sample, the film thickness is the thickness of the entire insulating film 21.

The deformation ratios of the

enamel wires

1 and 2 were evaluated by using the average value of the measured values of the plurality of deformation ratios obtained by 3 or more measurements. That is, when the deformation ratio of the

enamel wires

1 and 2 is measured 3 times or more and the average value of the obtained plurality of measured values is less than 10%, it is judged that the deformation ratio of the

enamel wires

1 and 2 is less than 10%.

Fig. 3 is a graph showing an example of the measurement result of the deformation ratio of the enamel wire 1. The "load" in fig. 3 is a straight line indicating a temporal change in the force (the magnitude of the force F directed vertically downward when the component directed vertically upward is positive) of the enameled wire 1 brought into contact with the jig 42 or the upper surface of the sample stage 41. The "control group" in fig. 3 indicates a temporal change in the amount of displacement of the end surface of the jig 42 in the vertical direction, which is obtained when the end surface of the jig 42 is brought into direct contact with the upper surface of the sample table 41 and measurement for obtaining the 1 st displacement amount is performed.

In addition, "sample 1" in fig. 3 shows a temporal change in the amount of displacement of the end surface of the jig 42 in the vertical direction, which is obtained when the end surface of the jig 42 is brought into direct contact with the enamel wire 1 having the insulating film 11 made of the 2 nd polyimide varnish to measure the 2 nd displacement amount.

In the measurement of the deformation ratio referred to in FIG. 3, the enamel wire 1, which is cut into a length of 5mm using a copper wire having a diameter of 0.8mm as the conductor 10, is used. In sample 1, the insulating film 11 made of the 2 nd polyimide coating material had a film thickness of 33.5 μm. The deformation ratio at this time was about 8.4%.

Table 1 below shows the deformation ratios of 10 types of enameled wires (enameled wire 1 or enameled wire 2), the porosity of the insulating coating, and the thickness of the insulating coating, which are different in the material constituting the insulating coating (insulating coating 11 or insulating coating 21). Each of the test pieces was a test piece having a copper wire of 0.8mm in diameter as the conductor 10 and cut into a length of 5 mm.

[ Table 1]

Here, the polyimide "a" in table 1 is composed of the 2 nd polyimide paint, and the polyimide "b" is composed of the 1 st polyimide paint.

In Table 1, blowing agent "d" is a high boiling point solvent, and blowing agent "e" is fine polymer particles (particle diameter: 1 μm).

Samples B to E, I to J correspond to the enamel wire 1, and the insulating film thereof corresponds to the insulating film 11. The insulating film 11 of samples B to E, I to J was formed by repeatedly applying the 2 nd polyimide paint containing a foaming agent 15 times. The insulating film of sample a was formed by repeatedly applying the 2 nd polyimide paint containing no foaming agent 15 times.

Sample F, G, H corresponds to enameled wire 2, and its insulating coating corresponds to insulating coating 21 composed of 1

st layer

211 and 2 nd layer 212. The polyimide "a/b" of sample F, G, H in Table 1 indicates that the materials of the 1 st layer 211 and the 2 nd layer 212 are "a" and "b", respectively. The 1 st layer 211 of sample G was formed by repeatedly applying 2 times a polyimide coating material doped with a foaming agent, and the 1 st layer 211 of sample F, H was formed by repeatedly applying 2 times a polyimide coating material containing no foaming agent. Further, layer 2 212 of sample F, G, H was formed by repeatedly applying 13 times a polyimide coating incorporating a blowing agent. Blowing agent "d" of sample F, G, H in Table 1 is the blowing agent contained in the polyimide coating of layer 2 212.

The average value of the deformation ratios of samples a to J in table 1 is a value obtained by 3 measurements.

The porosity of the insulating film of each sample in table 1 is the porosity of the entire insulating film calculated by using the above formula (1). The porosity of the insulating film 21 of sample F, G, H is the porosity of the entire insulating film 21 composed of the 1 st layer 211 and the 2 nd layer 212 calculated by the above formula (1).

FIG. 4 is a graph showing the relationship between the porosity and the deformation ratio of samples A to J. Each point on the graph represents an average value of deformation ratios at each void ratio. Fig. 4 shows that the deformation ratios of the enamel wires are not greatly different, but are approximately less than 10% in samples B to H in which the porosity of the insulating film is less than 25%. It is clear from Table 1 that the samples B to H containing a blowing agent have the same deformation ratios as those of the sample A containing no blowing agent. That is, it is found that the enamel wires (samples B to H) having the insulating film containing the voids formed on the outer periphery of the conductor have the same deformation ratio as the enamel wire (sample a) having the insulating film containing no voids formed on the outer periphery of the conductor.

(effects of the embodiment)

According to the embodiments of the present invention described above, the enamel wire satisfies the predetermined deformation ratio in order to increase the partial discharge inception voltage of the enamel wire, to use the insulating coating containing the voids, and to suppress the decrease in the mechanical strength of the insulating coating. Thus, an enameled wire having an insulating coating containing voids on a conductor and having excellent partial discharge resistance and deformation resistance can be provided.

(summary of the embodiments)

Next, the technical idea grasped from the above-described embodiments will be described with reference to the symbols and the like in the embodiments. However, the reference numerals and the like in the following description do not limit the components in the claims to those specifically shown in the embodiments.

[1] An enameled wire (1, 2) is provided with a conductor (10) and insulating films (11, 21) which are provided around the conductor (10) and have holes (111, 213), and the deformation rate determined by the following formula (1) is less than 10%.

1 st displacement amount: the end face of a cylindrical jig (42) is brought into contact with the upper surface of a sample stage (41) from vertically above at 22 to 23 ℃, and the difference between the position of the end face of the jig (42) in the vertical direction when a force (F) directed vertically downward (initial value) is applied to the sample stage (41) by the jig and the position of the end face of the jig (42) in the vertical direction when the force (F) is applied for 10 minutes,

displacement amount 2: the end face of a jig (42) is brought into contact with the enameled wires (1, 2) horizontally placed on the upper surface of a sample table (41) from the vertically upper side under the condition of 22 to 23 ℃, and the difference between the position of the end face of the jig (42) in the vertical direction when a force (F) directed vertically downward is applied to the enameled wires (1, 2) by the jig (42) (initial value) and the position of the end face of the jig (42) in the vertical direction when the force (F) is applied for 10 minutes,

force (F) directed vertically downward: a force increasing at an increasing rate of 98 mN/min with 5mN as an initial value.

[2] The enameled wire (1, 2) according to the above [1], wherein the insulating film (11, 21) has a porosity of less than 25%.

[3] The enameled wire (1, 2) according to the above [1] or [2], wherein the insulating film (11, 21) is formed of polyimide.

The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and can be implemented by being appropriately modified within the scope not departing from the gist of the present invention.

The embodiments described above are not intended to limit the invention according to the claims. Further, it should be noted that not all combinations of the features described in the embodiments are essential to the method for solving the problem of the invention.

Claims

1. An enameled wire comprising a conductor and an insulating coating provided around the conductor and having holes,

The deformation rate obtained by the following formula 1 is less than 10%:

Formula 1: Deformation rate (%)=(second displacement amount−first displacement amount)×100/(film thickness of the insulating film×2)

First displacement amount: The end face of the cylindrical jig was brought into contact with the upper surface of the sample stage from vertically above under the condition of 22 to 23°C, and a vertical downward direction was applied to the sample stage with the jig. The difference between the position of the end face of the jig in the vertical direction when the force (initial value) and the position of the end face of the jig in the vertical direction when the force was applied for 10 minutes,

Second displacement amount: under the condition of 22 to 23°C, the end face of the jig is brought into contact with the enameled wire lying on the upper surface of the sample stage from the vertical above, and the enameled wire is applied with the jig to the enameled wire in the vertical direction. The difference between the position of the end face of the jig in the vertical direction when a square force (initial value) is applied, and the position of the end face of the jig in the vertical direction when the force is applied for 10 minutes,

The force toward the vertical downward direction: the force increased at an increase rate of 98 mN/min with an initial value of 5 mN.

2 . The enameled wire according to claim 1 , wherein the porosity of the insulating film is less than 25%. 3 .

3. The enameled wire according to claim 1 or 2, wherein the insulating coating is made of polyimide.