JP2005302598A - Enameled wire and insulating coating used for it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive enameled wire with high reliability of an insulating coating in the vicinity of a welding part in welding; and to provide an insulating coating used for it. <P>SOLUTION: This enameled wire 10 has an insulating coating composed of at least two insulating layers around a conductor 11. The enameled wire is so formed that the innermost insulating layer 13 immediately above the conductor 11 is formed of a polyimide coating; the outermost insulating layer 14 is formed of a polyamide-imide coating; and adhesion strength between the conductor 11 and the insulting layer 13 is set above 40 g/mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an enameled wire used for an electric device such as a motor or a transformer and an insulating paint used therefor.

  Generally, an enameled wire is provided with an insulating film made of an insulating paint around a conductor. When using this enameled wire to make an electrical device such as a motor or a transformer, it is generally formed by winding the enameled wire continuously in a coil shape around the motor core (magnetic core) slot, Alternatively, a method in which an enameled wire wound in a coil shape is fitted and inserted into a slot of the core has been the mainstream.

  On the other hand, in the case of enameled wire with a large cross-sectional area (thick size) or enameled wire with a flat rectangular conductor, the enameled wire is not continuously wound to form a long coil with a large number of turns. A method has been proposed in which a plurality of small short-diameter coils are formed, and the enameled wire ends of these small-diameter coils are welded together to form a long coil. The coil formed in this way is used for a coil of an electric device that is small and requires a high-density magnetic flux, for example, a coil of an automobile generator or the like.

  For coils such as automobile generators, double-coated wires with a polyesterimide insulation film formed around the conductor and a polyamideimide insulation film around the polyesterimide insulation film, or polyamideimide around the conductor Single-coated wires with an insulating film are mainly used. In some cases, double-coated wires with a polyimide insulation film formed around the conductor and a polyamide-imide insulation film around the polyimide insulation film to improve heat resistance and mechanical strength are also used. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 5-130759

  By the way, in a coil of an automobile generator or the like, when welding the enameled wire terminal of each of the short coils described above, it is a mainstream to use an electric welding method such as TIG welding or fusing.

  When performing TIG welding or fusing, the welded portion of each coil is heated to 1084 ° C. or higher, which is the melting point of copper, in order to dissolve copper. Since this heat is also transmitted to the insulating film in the vicinity of the welded portion, the insulating film is also rapidly heated.

  At this time, in the conventional double-coated wire made of the polyesterimide and polyamideimide insulating film and the single-coated wire made of the polyamideimide film, the insulating film is thermally decomposed and gas is generated due to the high temperature caused by welding. The moisture absorbed in the insulating film and the solvent component remaining (residual) in the film after the baking of the insulating film are rapidly vaporized. As a result, the insulating film is pushed up from the surface of the conductor by these pyrolysis gas and vaporized gas, and is peeled off from the conductor and floats (hereinafter referred to as film floating), or foaming called a blister occurs. Therefore, there is a problem that the reliability of the electrical equipment is lowered.

  On the other hand, a double-coated wire composed of a polyimide resin film and a polyamideimide resin film, which have higher heat resistance than those of the polyesterimide resin and polyamideimide resin, is expensive and therefore becomes an expensive enameled wire. There was a problem. Moreover, since the adhesion between the conductor and the insulating film is poor, there is a problem that the film is liable to float.

  An object of the present invention, which was created in view of the above circumstances, is to provide an enameled wire with high reliability of an insulating film in the vicinity of a welded portion at the time of terminal welding and an insulating paint used therefor.

  In order to achieve the above object, the enameled wire according to the present invention is an enameled wire having an insulating film composed of at least two insulating layers around a conductor, wherein the innermost insulating layer directly above the conductor is a polyimide film, The outer insulating layer is composed of a polyamideimide film, and the adhesion strength between the conductor and the innermost insulating layer is 40 g / mm or more.

Here, it is preferable that the linear expansion coefficient of the innermost insulating layer at 300 to 400 ° C. is 5 × 10 ⁻⁴ / ° C. or less. Moreover, it is preferable to comprise an innermost insulating layer with mixed resin formed by mixing at least 0.1 part by weight of an adhesion improver with 100 parts by weight of polyimide resin. Furthermore, it is preferable that the ratio between the thickness of the innermost insulating layer and the thickness of the entire insulating film is 0.05 or more.

  On the other hand, the insulating paint used for the enameled wire according to the present invention is an insulating paint constituting the enameled wire insulating layer, and as a resin component of the insulating paint, at least 0.1 part by weight of 100 parts by weight of polyimide resin is adhered. It contains a mixed resin formed by mixing a property improver.

  Moreover, the insulating paint used for the enameled wire according to the present invention is an insulating paint constituting the insulating layer of the enameled wire, and the adhesion strength between the conductor of the enameled wire and the insulating layer is 40 g / mm or more as a resin component of the insulating paint. Preferably, it includes a mixed resin obtained by mixing a polyimide resin and an adhesion improver at a predetermined ratio.

  According to the present invention, when an end of an enameled wire is welded, an excellent effect is obtained that good heat resistance and weldability can be obtained in an insulating film near the welded portion.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings.

  When the present inventors welded the end of an enameled wire, as a result of earnest research to suppress film floating and blister generation in the vicinity of the weld, the following was found.

  (1) As a material constituting the insulating film, it is necessary to use a material that has high heat resistance and is difficult to be thermally decomposed. Examples of such a material include polyimide (hereinafter referred to as PI) and polyamideimide (hereinafter referred to as PAI). In particular, for the innermost insulating layer directly on the conductor having the largest heat load, the PI resin having the highest heat resistance is optimal. For the outermost insulating layer, a PAI resin that has high heat resistance and is less likely to be damaged when subjected to processing such as winding is optimal.

  (2) It is necessary to use a material having a high adhesion strength to the conductor as the material constituting the insulating film. This is because when the adhesion strength between the conductor and the insulating film is higher than the force (or the lifting force) at which the insulating film peels from the conductor, film floating and blister generation can be suppressed.

  (3) As a material constituting the insulating film, it is necessary to use a material having a small thermal deformation at a high temperature, that is, a material having a small coefficient of linear expansion. This is because when the insulating film receives rapid heat during welding, the smaller the thermal deformation, the more the film floating and blister generation can be suppressed.

  As described above, based on (1) to (3), as a result of further investigations by the present inventors, the insulating film as the outermost layer is less likely to be damaged when subjected to processing such as winding, We have found that PAI with excellent scratch resistance and the innermost insulating film, PI, which has a high adhesion strength to the conductor, can be used to suppress film floating and blistering. It was.

  A cross-sectional view of an enameled wire according to a preferred embodiment of the present invention is shown in FIG.

  As shown in FIG. 1, the enameled wire 10 according to the present embodiment has an insulating film composed of at least two insulating layers 13 and 14 around a conductor 11 (two layers in FIG. 1). is there. More specifically, the insulating film is provided immediately above the conductor 11, and the PI resin film whose adhesion strength to the conductor 11 is adjusted to 40 g / mm or more, preferably 70 g / mm or more, more preferably 85 g / mm or more. And an outer layer (outermost insulating layer) 14 formed of a PAI resin film. The inner layer 13 and the outer layer 14 are formed integrally (or substantially integrally). In order to further improve the adhesion (integration) between the inner layer 13 and the outer layer 14, an adhesion improving layer (not shown) may be provided between the inner layer 13 and the outer layer 14.

  In the enameled wire 10 according to the present embodiment, it is preferable that the adhesion strength between the conductor 11 and the insulating film (inner layer 13) is stronger (higher). This is because the higher the adhesion strength between the conductor 11 and the inner layer 13, the greater the effect of suppressing the generation of blisters. However, when an insulating film made of a single PI resin is formed around the conductor 11, it is difficult to ensure an adhesion strength of 40 g / mm or more. Therefore, in order to improve the adhesion strength between the conductor 11 and the inner layer 13 to 40 g / mm or more, an additive called an adhesion improver is added and mixed in the insulating coating of PI resin constituting the inner layer 13 immediately above the conductor 11. Is done. The reason why the adhesion strength between the conductor 11 and the inner layer 13 is 40 g / mm or more is that when the adhesion strength is less than 40 g / mm, the effect of suppressing the floating of the insulating film and the generation of blisters is reduced.

The adhesion improver is not particularly limited as long as it has an effect of improving the adhesion strength between the conductor 11 and the inner layer 13, for example,
Melamine resins such as butylated melamine resin,
Amines such as trialkylamine,
Mercaptans such as mercaptobenzimidazole,
Polycarbodiimide resins,
Etc. Two or more types of adhesion improvers may be added in combination.

  The ratio of addition of the adhesion improver to the PI resin content of the insulating paint is sufficient to obtain the effect of improving adhesion, and the stability of the insulating paint, the linear expansion coefficient of the inner layer 13, the flexibility of the enameled wire 10, etc. There is no particular limitation as long as it does not adversely affect the characteristics. For example, when a butylated melamine resin is used as an adhesion improver, it may be added at least 0.1 parts by weight, preferably 0.3 parts by weight or more, more preferably 0.6 parts by weight or more with respect to 100 parts by weight of the PI resin.

The linear expansion coefficient of the inner layer 13 at 300 ° C. to 400 ° C. is 5 × 10 ⁻⁴ / ° C. or less, preferably 2.5 × 10 ⁻⁴ / ° C. or less. The reason why the linear expansion coefficient at 300 to 400 ° C is set to 5 × 10 ^-4 / ° C or less is that when the linear expansion coefficient is greater than 5 × 10 ^-4 / ° C, the insulation film floats and blisters are suppressed. This is because the effect is reduced.

  Further, the ratio between the layer thickness of the inner layer 13 and the layer thickness of the entire insulating film (inner layer 13 + outer layer 14) is not particularly specified, but is 0.05 or more, preferably 0.10 or more, more preferably 0.15 or more. In this case, if the ratio of the layer thickness of the inner layer 13 to the layer thickness of the whole insulating film is smaller than 0.05, for example, if the layer thickness of the inner layer 13 is smaller than 2 μm, the effect of suppressing film floating and blistering is reduced. Because.

The mixed resin of the PI resin constituting the inner layer 13 and the adhesion improver referred to in this embodiment can produce an insulating film having an adhesion strength between the conductor 11 and the insulating film (inner layer 13) of 40 g / mm or more. It is. The mixed resin is more preferably capable of producing an insulating film having a linear expansion coefficient of 5 × 10 ⁻⁴ / ° C. or less at 300 ° C. to 400 ° C. Further, it is more preferable that the mixed resin is capable of producing an extremely thin insulating film having a layer thickness of about 2 μm. The inner layer 13 is an insulating film formed by applying and baking this insulating resin paint on the conductor 11.

  Insulating paint of PI resin referred to in this embodiment is usually a polyamic acid solution in the state of paint, and after this solution is applied to a conductor, it is squeezed with a die to make the coating thickness uniform, and then applied to a baking furnace. By firing, the polyamic acid is closed and a PI resin insulating film is formed. As the PI resin insulating paint, a paint obtained by reacting an aromatic tetracarboxylic dianhydride and an aromatic diamine in a polar solvent is most common, and the chemical structure of PI is not particularly specified. Absent.

A typical aromatic tetracarboxylic dianhydride is:
Pyromellitic dianhydride,
Examples include benzophenone tetracarboxylic dianhydride.

Typical aromatic diamines are:
4,4′-diaminodiphenylmethane,
4,4'-diaminodiphenyl ether and the like.

  Examples of commercially available PI resin insulating paints include Pyre ML manufactured by DuPont and Trenys # 3000 manufactured by Toray.

  On the other hand, as the PAI resin insulating paint referred to in the present embodiment, a paint obtained by heating and reacting trimellitic anhydride and 4,4′-diphenylmethane diisocyanate in a polar solvent is most common. The chemical structure of PAI is not particularly specified.

  Examples of commercially available PAI resin insulation paints include HI-404 and HI-406 manufactured by Hitachi Chemical.

  As a constituent material of the conductor 11, any material that is conventionally used as an enameled wire conductor can be applied, and although not particularly limited, Cu or a Cu alloy is preferable. Further, the cross-sectional shape of the conductor 11 is not particularly limited, and may be any one such as a circular conductor or a flat conductor. Furthermore, the cross-sectional area (size) of the conductor 11 is not particularly limited, and any conductor that is conventionally used as an enameled wire conductor can be applied.

  Next, the operation of the present embodiment will be described.

The enameled wire 10 according to the present embodiment includes an inner layer 13 made of PI resin and having an adhesion strength with respect to the conductor 11 adjusted to 40 g / mm or more as an insulating film, and an outer layer 14 made of a PAI film. ing. The linear expansion coefficient of the inner layer 13 at 300 ° C. to 400 ° C. is adjusted to 5 × 10 ⁻⁴ / ° C. or less. As a result, the insulating film has a high adhesion strength to the conductor 11, has high heat resistance, is difficult to be thermally decomposed, and reduces thermal deformation at high temperatures. As a result, when the ends of the enameled wire 10 are welded together, the insulating film is thermally decomposed due to the high temperature associated with the welding to generate gas, or even after moisture or moisture absorbed in the insulating film is baked. Even if the solvent component that remains (residual) vaporizes abruptly, it is possible to suppress film floating and blister generation in the insulating film near the weld.

  Therefore, a plurality of short small-diameter coils having a small number of turns are formed by using the enameled wire 10 according to the present embodiment, and the enameled wire terminals of these small-diameter coils are welded and joined together to form a long coil. In electrical equipment, high reliability can be obtained.

  As described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various other things are assumed.

  Next, although this invention is demonstrated based on an Example, this invention is not limited to this Example.

(Example 1)
1 part by weight of adhesion improver A (butylated melamine resin) was added to 100 parts by weight of the resin content of polyimide a (Trenice # 3000, manufactured by Toray Industries, Inc .; hereinafter referred to as PIa) to obtain an insulating paint. .

  After applying this insulating paint on a rectangular copper conductor with a conductor size of 1.5 x 2.5 mm and a chamfer radius of R part of 0.6 mm, it is baked in a hot air circulation type solid baking furnace, and the film thickness is 10 μm. An inner layer insulating film was provided. A polyamideimide (HI-404, manufactured by Hitachi Chemical Co., Ltd .; hereinafter referred to as PAI) coating was applied around the inner insulating film and then baked to provide an outer insulating film with a film thickness of 30 μm. . Thereby, a two-layer heat-resistant enameled wire having a total thickness of 40 μm was produced.

(Example 2)
A two-layer heat-resistant enamel wire was produced in the same manner as in Example 1 except that polyimide b (Pyre ML, manufactured by DuPont; hereinafter referred to as PIb) paint was used instead of the PIa paint.

Example 3
Pyromellitic dianhydride as the acid component and 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenyl ether as the diamine component in a solvent (2-methylpyrrolidone) in a molar ratio of 2 to 1 to 1 Dissolved in. This solution was stirred and reacted to prepare a polyimide c (hereinafter referred to as PIc) paint.

  A two-layer heat-resistant enameled wire was produced in the same manner as in Example 1 except that PIc paint was used instead of PIa paint.

Example 4
A two-layer heat-resistant enameled wire was produced in the same manner as in Example 1 except that the thickness of the inner insulating film was 5 μm and the thickness of the outer insulating film was 35 μm.

(Example 5)
A two-layer heat-resistant enameled wire was produced in the same manner as in Example 1 except that the thickness of the inner insulating film was 2 μm and the thickness of the outer insulating film was 38 μm.

Example 6
A two-layer heat-resistant enameled wire was produced in the same manner as in Example 1 except that the blending ratio of the adhesion improver A to 100 parts by weight of the PIa paint was 0.5 parts by weight.

(Example 7)
A two-layer heat-resistant enameled wire was prepared in the same manner as in Example 1 except that the blending ratio of the adhesion improver A with respect to 100 parts by weight of the resin of the PIa paint was 0.2 parts by weight.

(Example 8)
A two-layer heat-resistant enamel wire was produced in the same manner as in Example 1 except that the adhesion improver B (mercaptobenzimidazole) was used instead of the adhesion improver A.

(Comparative Example 1)
A two-layer heat-resistant enameled wire is formed in the same manner as in Example 1 except that the adhesion improver A is not added at all to the insulating coating constituting the inner insulating film, that is, the resin component of the inner insulating film is composed of PIa alone. Produced.

(Comparative Example 2)
As in Example 1, except that the insulating paint constituting the inner layer insulating film is a paint obtained by adding 1 part by weight of the adhesion improver A to 100 parts by weight of the resin content of the PAI paint of Example 1. A two-layer heat-resistant enameled wire was produced.

  For each of the enameled wires of Examples 1 to 8 and Comparative Examples 1 and 2, the adhesion strength between the conductor and the insulating film (inner layer) was determined.

  The adhesion strength between the conductor and the insulating film was measured by the following method. First, after each enamel wire was manufactured, a sample piece having a length of about 5 cm was cut from each enamel wire. Thereafter, two cuts extending in the longitudinal direction of the sample piece were formed at intervals of 1 mm on the insulating film on the upper surface or the lower surface (one of the wider surfaces) of each sample piece using a cutter or the like. The longitudinal ends of the insulating film between the cuts were peeled from the conductor using tweezers or the like to form a grip allowance. Thereafter, each sample piece was fixed to a jig, the gripping margin was sandwiched between chucks, and the insulating film was further peeled from the conductor using a Tensilon universal testing machine. At this time, the peel strength (adhesion strength) when the insulating film was peeled off with a length of 1 mm was measured.

  Moreover, about each enamel wire of Examples 1-8 and Comparative Examples 1 and 2, the linear expansion coefficient in 300-400 degreeC of the inner layer was calculated | required.

  Specifically, first, after coating (applying) the insulating paint constituting each inner layer on a glass plate, using a thermostatic bath, 80 ° C. × 20 minutes, 200 ° C. × 20 minutes, 300 ° C. × 10 minutes Each insulating coating was cured by heating with a heat history of 30 μm to produce an insulating film having a thickness of 30 μm. After each insulating film is mounted on a jig so that the width is 2 mm and the length between chucks is 20 mm, the insulating film is stretched using a thermomechanical analysis measuring device under the conditions of a tensile load of 48 mN and a heating rate of 10 ° C./min. Was measured, and the average linear expansion coefficient from 300 ° C. to 400 ° C. was measured.

  Furthermore, the external appearance evaluation after TIG welding was performed about each enameled wire of Examples 1-8 and Comparative Examples 1 and 2.

  Appearance evaluation after TIG welding was performed by the following method. First, after each enamel wire was manufactured, each enamel wire was allowed to stand in a constant temperature and humidity chamber of 40 ° C.-95% RH for 30 minutes in consideration of variations due to the environment at the time of evaluation. After that, within 10 minutes after taking out each enamel wire from the thermo-hygrostat, each sample piece of about 5 cm length is cut out from each enamel wire, and 4.5 mm long from one end of each sample piece. The insulating film was peeled off. Place 2.5 mm from the end of one end of each sample piece with a chrome-copper ground rod with a cross-sectional dimension of 1.5 mm x 2.0 mm, and place 1.25 mm from the end of one end of each sample piece. In addition, the tip position of the welding torch was aligned and energized by a TIG welder. The energization conditions were an energization current of 40 A and an energization time of 0.5 seconds.

  Appearance is evaluated by visually observing the surface in the vicinity of the current-carrying part of each sample piece after energization, and the film floating or blister generation is almost unobservable, and the length of the film floating in the longitudinal direction of the sample piece is less than 4 mm Thus, foams (blisters) with a diameter of less than 1 mm and a small number of foams of 5 or less were considered to be good, and those with more film floating or blistering were considered bad.

  Table 1 shows the adhesion strength between the conductor and the insulating film, the measurement results of the linear expansion coefficient of the inner layer, and the appearance evaluation results after TIG welding.

  As shown in Table 1, each enameled wire of Examples 1 to 8 comprises an inner layer of an insulating film composed of a PI resin and an adhesion improver.

Thus, the adhesion strength between the conductor and the insulating film of each enameled wire of Examples 1 to 8 was 45 to 124 g / mm, and all satisfied the specified range (40 g / mm or more). In addition, the linear expansion coefficient at 300 ° C. to 400 ° C. of the inner layer in each of the enamel wires in Examples 1 to 8 is 5.9 × 10 ⁻⁵ / ° C. to 1.8 × 10 ⁻⁴ / ° C., both of which are in the specified range (5 × 10 5 ^-4 / ° C or less). In particular, by comparing the enamel wires of Examples 1 and 4 to 8 with the enamel wire of Comparative Example 1, the adhesion strength is increased and the linear expansion coefficient is further reduced by the addition of the adhesion improver. I was able to confirm.

In addition, each of the enamel wires of Examples 1 to 5 and 8 had very good adhesion strength between the conductor and the insulating film of 70 g / mm or more. Furthermore, each enamel wire of Examples 1, 2, 4 to 8 had a very good linear expansion coefficient at 300 ° C. to 400 ° C. of 9.0 × 10 ⁻⁵ / ° C. or less. Therefore, the enameled wires of Examples 1, 2, 4, 5, and 8 are more preferable because both the adhesion strength and the linear expansion coefficient are very good. For this reason, the adhesion strength between the conductor and the insulating film is more preferably 80 g / mm or more.

  As a result, each of the enamel wires of Examples 1 to 8 has sufficiently high adhesion strength in the vicinity of the welded portion, sufficient heat resistance, difficult to be thermally decomposed, and difficult to thermally deform at high temperatures. The appearance after TIG welding was good or almost good.

On the other hand, the enameled wire of Comparative Example 1 in which the inner layer of the insulating film is composed of PIa alone without mixing the adhesion improver has a linear expansion coefficient of 9.1 × 10 ⁻⁵ / ° C. at 300 to 400 ° C. Although the specified range was satisfied, the adhesion strength was 35 g / mm, which was less than the specified range. As a result, although the insulation film of the enameled wire of Comparative Example 1 has sufficient heat resistance, the adhesion strength is insufficient, so that the film floats and blisters are generated during welding, and the appearance after TIG welding is It was bad.

In addition, the enamel wire of Comparative Example 2 in which the adhesion improver was added to the PAI resin instead of the PI resin as the base resin of the inner layer had an adhesion strength of 58 g / mm, which satisfied the specified range, but was 300 to 400 ° C. The linear expansion coefficient was 7.2 × 10 ⁻⁴ / ° C., which was larger than the specified range. As a result, although the enamel wire insulation film of Comparative Example 2 has sufficient adhesion strength, it uses a PAI resin that is inferior in heat resistance to the PI resin. Thermal deformation was large, and film floating and blistering occurred during welding, and the appearance after TIG welding was poor.

It is a cross-sectional view of an enameled wire according to a preferred embodiment of the present invention.

Explanation of symbols

10 Enamelled wire 11 Conductor 13 Inner layer (innermost insulating layer)
14 Outer layer (outermost insulating layer)

Claims (6)

  In an enameled wire having an insulating film composed of at least two insulating layers around a conductor, the innermost insulating layer directly above the conductor is a polyimide film, and the outermost insulating layer is a polyamideimide film, An enameled wire having an adhesion strength with an inner insulating layer of 40 g / mm or more. The enameled wire according to claim 1, wherein the innermost insulating layer has a coefficient of linear expansion at 300 to 400 ° C of 5 × 10 ^-4 / ° C or less.   The enameled wire according to claim 1 or 2, wherein the innermost insulating layer is composed of a mixed resin obtained by mixing at least 0.1 parts by weight of an adhesion improver with 100 parts by weight of a polyimide resin.   The enameled wire according to any one of claims 1 to 3, wherein a ratio of a layer thickness of the innermost insulating layer to a layer thickness of the entire insulating film is 0.05 or more.   The insulating paint constituting the enameled wire insulating layer includes a mixed resin obtained by mixing at least 0.1 part by weight of an adhesion improver with 100 parts by weight of polyimide resin as a resin component of the insulating paint. Insulating paint used for characteristic enameled wire. In the insulating paint constituting the enameled wire insulating layer, a polyimide resin and an adhesion improver are used as a resin component of the insulating paint so that the adhesion strength between the enameled wire conductor and the insulating layer is 40 g / mm or more. Insulating paint used for enameled wire, characterized by containing a mixed resin mixed at a ratio.

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