JPH06327199A - Formation of film - Google Patents

Abstract

PURPOSE:To make an insulator film executed between a winding and a metal part thin while its insulating and pressure-resistant performance is being maintained by a method wherein the surface of a metal for an electronic component having a burr is electrodeposition-coated with an electrodeposition paint which contains an emulsion or the like and its coating film is baked. CONSTITUTION:The surface of a metal for an electronic component having a burr is electrodeposition-coated with a specific electrodeposition paint which is composed of at least an emulsion, a gel fine-particle dispersed liquid and a pigment paste. The emulsion contains an epoxy resin or the like whose number-average molecular weight is 1000 to 3000, which is provided with one or more epoxy groups on the average per molecule and which contains a bisphenol A residual group. The gel fine-particle dispersed liquid contains 20 to 50 pts.wt., in terms of a solid portion, of a methylolphenol component whose number-average molecular weight is 200 to 1000. In addition, the pigment paste contains 50 to 70 pts.wt. of a pigment in terms of a solid portion. The electrodeposition paint is baked under a definite condition, and an insulating film having an average film thickness of 20 to 100mum is formed. Consequently, the tip of the burr cannot be exposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a coating on a metal surface for burrs having an electronic component, and more particularly to forming an insulating coating on the surface of an electronic component having a structure in which a winding is housed in a slot of a metal portion having burrs. Relates to a method of forming.

[0002]

2. Description of the Related Art An electronic component having a structure in which a winding is housed in a slot of a metal portion, such as a rotor core for a motor, has an insulating treatment between the winding and the metal portion in order to avoid a short circuit between the conductive portion and the metal portion of the winding. It is common to apply.

FIG. 1 schematically shows the shape of a conventional rotor core for a motor as viewed from above. Figure 1
In the above, a rotor core having three slot portions is illustrated, but not limited to three, there are of course those having four or more slot portions, and there are various shapes. Depending on the size of the motor, for example, the thickness is about 0.35m
A plurality of rotor core thin pieces each having a diameter of about 40 mm and a shape of FIG. 1 are stacked to form a rotor core 2, and a conductor wire is wound around the slot portion 6. The rotor core 2 rotates about the rotating shaft 1 in the direction of arrow (e).

FIG. 2 is a schematic sectional view of the slot 6 portion of the rotor core 2 in FIG. 1 taken along the line dd '. A plurality of rotor core thin pieces 2'are stacked, and an insulating coating 8 is formed around them. A winding (not shown) is provided around the insulating coating 8. If the punching burr 3 is exposed here, the coating of the winding is damaged at the tip of the punching burr 3 during the winding process, causing a short circuit between the winding and the rotor core 2. Therefore, on the surface of the rotor core 2, PBT, PET,
An insulating coating 8 which is a molded product of thermoplastic resin such as PPS or PA (thickness is 100 μm or more which is a molding limit thickness) is attached.

Alternatively, such an insulating coating 8 is formed by coating the surface of an electronic component with a method such as powder coating or electrodeposition coating and baking. However, whichever coating method is used, when conventional paint baking is performed using a conventional paint, when the film thickness of the coating film is thin, as shown in FIG. The scale 10 caused by the surface tension of the coating material is generated at the tip of the coating. As a result, the tip of the punching burr 3 is exposed, and insulation between the winding as the motor and the rotor core cannot be ensured.

As described above, in order to prevent the exposure of the punching burr tip and to prevent the short circuit between the winding and the rotor core due to the penetration of the insulating film of the conducting wire due to the winding treatment, a relatively short length of about 100 to 200 μm. Requires a thick film.

[0007]

However, such a thick film has a drawback that a large proportion of the insulating film occupies the inner volume of the slot portion 6. In order to make the motor lighter, thinner, shorter, smaller, and more powerful, it is desired to reduce the thickness of the insulating coating applied between the winding and the rotor core 2.

Further, when the blast treatment for deburring is performed, not only is it disadvantageous in terms of cost, but in comparison with the case where the blast treatment is not performed due to the change in the magnetic characteristics of the core 2,
It has a drawback that the generated torque is reduced by 5% or more.

The present invention has been made in view of the above circumstances, and is intended for electronic parts which have burrs when an insulating film is formed between a winding and a metal part of an electronic part used for a motor or the like to prevent a short circuit. An object of the present invention is to provide a film forming method capable of forming a thin film insulating film of 100 μm or less without exposing the burr tip even on a metal surface.

[0010]

In order to achieve the above-mentioned object, the present invention has at least (A) a number average molecular weight of 1,000 to 3,000 on the surface of a metal for electronic parts having burrs and an average of 1 or more per molecule. A bisphenol A residue-containing epoxy resin having an epoxy group or a derivative thereof and an amino group-containing polymer, which is a reaction product of a monovalent secondary amine, are contained in an amount of 60 to 80 parts by weight in terms of solid content, and a blocked isocyanate crosslinking agent. Emulsion containing 20 to 40 parts by weight in terms of solid content, (B) number average molecular weight of 200 to
20 to 50 parts by weight of 1000 methylolphenol compound in terms of solid content, and number average molecular weight 1000 to 30
00 amine-added polybutadiene resin is converted into solid content 50
To 80 parts by weight of a gel fine particle dispersion, and (C) a pigment containing 50 to 70 parts by weight of solid content, and a pigment dispersion resin containing 5 to 15 parts by weight of solid content. The paste is (A) / (B) / in terms of solid content
(C) = 1 / 0.18 to 0.72 / 0.5 to 0.9: The electrodeposition coating composition is electrodeposited, the coating film is baked, and the average film thickness is 20 to 100 µm. The insulating film is formed by the method.

The coating material used in the film forming method of the present invention comprises at least an emulsion, a gel particle dispersion and a pigment paste. The resin component of the emulsion used in the electrodeposition coating composition of the present invention comprises a cationic resin and a blocked isocyanate crosslinking agent.

The cation resin has a number average molecular weight of 1,000 to
Bisphenol A residue-containing epoxy resin having an average of 1 or more epoxy groups per molecule at 3000, and an amino group which is a reaction product of an esterified product, an etherified product, an imidized product thereof and a monovalent secondary amine It is a contained polymer. This cationic resin is 60 to 8 when the total emulsion resin component is 100 parts by weight in terms of solid content.
0 parts by weight is contained. If it is less than 60 parts by weight, the corrosion resistance will be reduced, and if it is more than 80 parts by weight, the strength of the coating film will be insufficient.

On the other hand, the blocked isocyanate cross-linking agent is prepared by converting isocyanates into alcohols, oximes, amines,
Blocked with phenols. Isocyanates include aromatic isocyanates such as 2,
4- or 2,6-tolylene diisocyanate, m-
Alternatively, p-phenylene diisocyanate or aliphatic isocyanate such as hexamethylene diisocyanate may be used.

Blocking agents for isocyanates include aliphatic or aromatic monoalcohols such as methanol, ethanol, butanol, 2-ethylhexanol or benzyl alcohol, oximes such as methyl ethyl ketone oxime or methyl isobutyl ketone oxime, amines such as Dimethylamine or dimethylethanolamine, or phenols,
Examples include phenol and methylphenol.

When the amount of the blocked isocyanate is less than 20 parts by weight based on the total solid content of 100 parts by weight, the curing is insufficient, and when it exceeds 40 parts by weight, the coating stability is deteriorated due to insufficient water solubility. So do 2
The amount is 0 to 40 parts by weight.

The emulsion used in the present invention is prepared by neutralizing a predetermined amount of a cationic resin and a blocked isocyanate with an acid in an aqueous medium and emulsifying.
The gel particle solution used in the electrodeposition coating composition of the present invention comprises a methylol compound and an amine-added polybutadiene resin.

The methylolphenol compound is obtained by reacting phenols with formaldehyde and has a number average molecular weight of 200 to 1000. Specifically, it is a resol type phenol resin such as Taconol 720721 manufactured by Arakawa Chemical Industry Co., Ltd. Gunei Chemical Industry WP
551, WP201, or the like, or a phenol ether compound can be used.

The compounding amount of the methylolphenol compound is
When the total amount of the gel particle dispersion is 100 parts by weight in terms of solid content, if the amount is less than 20 parts by weight, the curing of the coating film will be insufficient, and if it exceeds 50 parts by weight, the corrosion resistance will decrease, so the amount is set to 20 to 50 parts by weight.

As the amine-added polybutadiene resin,
Number average molecular weight 1000-3000, 1,2 bond 30-1
It is obtained by epoxidizing a polybutadiene resin of 00% with peracetic acid and adding an amine. As such a resin, for example, C-1800- manufactured by Nippon Petrochemical Industry Co., Ltd.
6, 5, etc. can be used. When the total amount of the gel particle dispersion is 100 parts by weight in terms of solid content, the amount of the amine-added polybutadiene resin is less than 50 parts by weight, the stability of the gel particles decreases due to insufficient water solubility, and when the amount exceeds 80 parts by weight, the particles become particles. Since the edge covering property is deteriorated due to insufficient gelation inside, it is 50 to 80 parts by weight.

The gel fine particle dispersion is obtained as an emulsion by adding glacial acetic acid to a predetermined amount of the methylolphenol compound and the amine-added polybutadiene resin, stirring the mixture sufficiently, and adding deionized water thereto to emulsify.

The pigment paste used in the electrodeposition coating composition of the present invention comprises a pigment dispersion resin and a pigment. The pigment-dispersed resin component functions to coat the pigment particles and to cationize the pigment particles, and examples thereof include a quaternary ammonium resin.

The pigment is usually a color pigment having a particle size of 20 μm or less,
A rust preventive pigment and an extender pigment may be appropriately used. As the color pigment, for example, carbon black or titanium dioxide can be used. Examples of the rust preventive pigment include strontium chromate and basic lead silicate. Examples of extender pigment components include aluminum silicate and calcium carbonate.

As the pigment composition, it is preferable to add 10 to 80 parts by weight of an extender pigment when the total amount of the pigment components is 100 parts by weight. If it is 10 parts by weight or less, the edge covering property is not effective, and if it is 80 parts by weight or more, the smoothness of the coated surface is significantly reduced. Among them, aluminum silicate having a flat particle shape is effective in improving the edge coverage because it controls the viscosity of the coating film during baking and melting.

The pigment paste is prepared by adding deionized water to the above pigment-dispersed resin and pigment, stirring and mixing with a disper for about 1 hour, adding glass beads to this mixture, and dispersing with a sand mill to a particle size of 20 μm or less. To be done.

The pigment is used in an amount of 50 to 70 parts by weight in terms of solid content. If the amount is too small, the film hardness will be insufficient, and if it is too large, the coating film becomes brittle. Pigment dispersion resin is 5
Use 15 parts by weight. If it is less than 5 parts by weight, the pigment cannot be uniformly coated with the resin. Also, if more than 15 parts by weight is added, there is no effect of adding any more, and the economic disadvantage becomes large.

The paint used in the electrodeposition coating of the present invention comprises the above emulsion, pigment paste and gel particle dispersion liquid mixed with deionized water. The mixing method is not particularly limited as long as each solution can be uniformly mixed, but at the time of mixing, the emulsion, the pigment paste, and the gel particle dispersion liquid are sampled, and deionized water is added while gently stirring so as not to foam. To prepare.

The mixing ratio of each solution of emulsion, pigment paste and gel particle dispersion is 50 to 90 parts by weight of pigment paste and 18 to 72 parts by weight of gel particle dispersion based on 100 parts by weight of solid content. is there. By increasing the melt viscosity at the time of baking with this composition, the flow of the paint in the edge portion is suppressed, and the edge cover property is remarkably improved. Especially, the gel particle dispersion is
The effect is large when 0 to 60 parts by weight is blended. If the amount of the gel particle dispersion is less than 18 parts by weight, the edge covering property is remarkably deteriorated, and if the amount is more than 72 parts by weight, the smoothness of the coated surface is significantly deteriorated and the winding is hindered. Further, if the proportion of the pigment paste is increased too much, the coating film becomes brittle, the Erichsen value becomes small, and voids tend to increase.

By adjusting the composition of the electrodeposition coating material to the above-mentioned conditions, the coating film should have good adhesion to an object having an Erichsen value of 40 mm or more and rigidity enough to withstand the high pressure generated at the tip of the punching burr during the winding process. It can be given at the same time.
The Erichsen value is JIS-K-5400, 8.2.
It is a value measured by the test method described in the paragraph, and is a value suitable for representing the adhesion of the coating film to the substrate and the flexibility of the coating film itself.

Using the coating material obtained as described above, electronic parts with burrs are subjected to cationic electrodeposition coating. Cationic electrodeposition coating involves immersing an electronic component, which is the object to be coated, in the electrodeposition coating material, with the object side as the cathode (-) and the electrode plate installed in the diaphragm chamber in the electrodeposition tank as the anode (+). It is a coating method in which a direct current is applied to the substrate to deposit a film on the charged object to be coated.

The cationic electrodeposition coating method is not particularly limited, and a known method can be applied using the coating material obtained above. The specific conditions for the electrodeposition coating should be appropriately set in accordance with the type, shape, size, type of paint, etc. of the electronic component as the article to be coated. However, in the present invention, the coating film after electrodeposition baking has an average of 20 to 1
Even when a film thickness of 00 μm, especially 30 to 60 μm is formed, it is possible to prevent thinning of the burr portion and the accompanying short circuit between the metal portion and the winding.

According to the present invention, it is possible to reduce the film thickness of the insulator provided between the electronic component winding and the metal portion while maintaining the dielectric strength performance, and accordingly increase the effective area of the winding.
It is possible to realize light, thin, short and compact electronic components.

When the coating film thickness is made thicker than 100 μm, there is a problem that the effective area of the winding is remarkably reduced.
If the thickness is less than 20 μm, it is impossible to effectively prevent a short circuit between the metal part and the winding part. In the present invention, the coating film thickness is the average of the thicknesses represented by (b) in FIG. 2, and the portion (a) of the coating film thickness at the edge portion in FIG. 2 is not taken into consideration.

Next, the electrodeposition coating film is dried and baked. Drying is effective in removing the solvent, hydrogen gas, and water present in the electrodeposition coating film from the film, and preventing the formation of voids or pinholes in the coating film during the subsequent baking. The drying condition is performed by placing the coating film in a temperature environment of about 60 ° C. to below the boiling point of water. If the time left under the temperature atmosphere shown on the left is too short, hydrogen gas, solvent, and water present in the coating film before baking and curing will not be sufficiently removed,
Voids or pinholes are likely to occur in the coating film in the baking process after drying. The longer the time, the higher the drying effect, but it is not preferable in terms of production. Therefore, the drying time should be appropriately set so that the above problem does not occur, and normally about 1 to 3 minutes is sufficient.

After drying, baking is performed. For baking, the temperature is raised from the final temperature after drying to a predetermined baking temperature. During this temperature rising period, the emulsion resin component melts and softens,
At this time, the gel fine particle resin component exists in the film in the form of solid particles. Therefore, even if the emulsion resin component is melted, its flow is suppressed, and the drooping of the molten resin and the thinning of the resin particularly in the burred portion of the electronic component are prevented. From the viewpoint of productivity, the heating up to the baking temperature is usually 10
The time is not more than 5 minutes, preferably about 5 minutes, but if the temperature rising time is prolonged, the edge cover property is further improved.

When the predetermined baking temperature is reached, the temperature is maintained for a certain period of time to complete the baking of the emulsion resin. Although the baking conditions depend on the type of paint, 135
It is performed in a step of about 20 to 40 minutes under an atmosphere of about 195 ° C. The film after electrodeposition coating has a certain degree of hardness by itself, and is a resin film that is not deformed even if it is touched with a hand. By baking this film, it is further hardened to form a hard film, and the adhesive force with the electronic component base material is further enhanced. If the baking is set more slowly than the above conditions, the curing of the coating cannot be sufficiently achieved, and the embrittlement of the coating becomes too severe.

The electronic component to which the method of forming a coating film of the present invention can be applied, as long as it is a metal component formed by punching and having a burr and having a structure in which the winding is housed in the slot portion of the metal portion. The present invention can also be applied to, and is particularly suitable for a rotor core for a motor or a core for a transformer.

In the present invention, since it is not necessary to remove the punching burr generated during the manufacturing of the metal part by the blasting process or the like, it is possible to prevent defects such as deformation of the metal part due to the blast pressure, and there is no need for the blasting process. The process becomes possible.

When the present invention is applied to a rotor core for a motor, the film thickness of the insulating film between the winding and the metal portion can be reduced, and accordingly, the effective area of the winding can be increased or the motor can be made lighter and thinner. realizable.

The coating film after the baking treatment had a surface roughness (see FIG. 2).
It is formed as an orange peeling-shaped unevenness of 5 to 20 μm as represented by c), and the friction coefficient between the winding and the metal part at the time of winding treatment is increased to prevent the winding from slipping. Very effective as a base material for windings.

The rotor core for a motor used in the present invention is not subjected to secondary processing such as blasting after the punching step. For such a rotor core, the edge coverage of the coating film is 50% at the punched burr tip of the rotor core.
Or more, preferably 70% or more. The edge coverage is a / b × 100 from a and b shown in FIG.
Is expressed as. When the coating film is formed to a thickness of 20 μm, which is the minimum film thickness required for the coating film of the present invention, the edge coverage ratio of 50% is between the coated conductive wire conductive portion and the metal portion at the tip of the punching burr of the metal portion for electronic parts. Minimum required withstand voltage 7
It is a value that guarantees a coating film thickness of 10 μm at the tip of a punching burr satisfying 50V. Further, the edge coverage is improved by reducing the temperature rising rate near the point where the viscosity of the coating film before curing is lowered during baking. Here, the lowering point of the viscosity of the coating film before curing means the temperature reaching point at which the emulsion resin component starts to melt.

The edge coverage is improved by increasing the proportion of pigment having poor flowability during baking in the pigment component. Further, the edge coverage ratio is improved by reducing the blending amount of the solvent to the extent that there is no problem in the performance of the paint.

The electrodeposition coating formed according to the present invention is formed on an insulating treated metal column having a cross section of 2.25 mm × 1.0 mm.
Electrodeposition coating is applied so that the winding trace depth generated in the coating film when a 0.18 conductor wire is wound in four layers with a tension of 150 g is 20 μm or less, preferably 10 μm or less.
By doing so, the surface of the rotor core is completely covered with punching burrs generated during core manufacturing, and a high-performance insulating coating with a uniform and low film thickness that can withstand the high pressure generated at the tip of the punching burrs during the winding process is obtained. It is a thing. The winding trace depth of 20 μm is a critical coating film deformation value for imparting a hardness that enables aligned winding without causing any trouble in the rewinding process.

Further, the present invention can be applied to a transformer which is one of transformer electronic components. The conventional transformer is shown in Fig. 4.
As shown in (a), the punching burrs formed on the core 11 are completely covered with a bobbin 14 on which an insulating tape 17, a thermoplastic resin such as PET, PBT, nylon, or a thermosetting resin such as phenol is formed and processed. Then, the bobbin 14 is further provided with the primary winding 12 and the secondary winding 13, and the outer circumference thereof is covered with the insulating case 15 and the insulating tape 16.
The insulation between 13 and the core 11 was secured. When the film forming method of the present invention is applied to such a transformer, an insulator (bobbin film thickness of 1 mm or more in the conventional insulation treatment) applied between the primary winding 12 and the secondary winding 13 and the core 11 is formed. It is possible to reduce the thickness, and, like the motor rotor core, a transformer can be made lighter, thinner, shorter, and smaller, and the power of the transformer capacity can be increased.

[0044]

EXAMPLES The present invention will be described in more detail with reference to examples. Pigment paste contained in the electrodeposition coating composition of the present invention,
The emulsion and gel particle dispersions were prepared as follows. (Production of pigment paste) Quaternary ammonium resin varnish 192 parts by weight carbon black 9 parts by weight titanium dioxide 318 parts by weight basic lead silicate 27 parts by weight kaolin 101 parts by weight dibutyltin oxide 1 part by weight deionized water 318 parts by weight Based on the formulation, deionized water was added to the quaternary ammonium resin varnish to dissolve it, then the pigment and dibutyltin oxide were added, and the mixture was stirred with a disper for 1 hour. Glass beads were added to this mixture and dispersed to 15 μm or less by a sand mill, and the glass beads were separated by filtration. (Emulsion) (1) Production of Aminated Epoxy Resin 1000 parts by weight of diglycidyl ether of bisphenol A (epoxy equivalent 910) was dissolved in 463 parts by weight of thielen glycol monoethyl ether while maintaining the temperature at 70 ° C. under stirring. 80.3 parts by weight of diethylamine was added and reacted at 100 ° C. for 2 hours to obtain an aqueous aminated epoxy resin.

(2) Production of Blocked Isocyanate Crosslinking Agent Toluenediisocyanate (2,4-
To 174 parts by weight of 80/20 mixture of toluene diisocyanate / 2,6 toluene diisocyanate: TDI), 87 parts by weight of methyl ethyl ketone oxime was gradually added dropwise while keeping the reaction temperature at 50 ° C. or lower by external cooling to obtain a half-blocked isocyanate. .

Then, 45 parts by weight of trimethylolpropane and 0.05 parts by weight of dibutyltin dilaurate were added and the reaction was carried out at 120 ° C. for 90 minutes. The obtained reaction product was diluted with 131 parts by weight of ethylene glycol monoethyl ether to obtain an aqueous blocked isocyanate.

220 parts by weight of the above-mentioned aminated epoxy resin,
After 146 parts by weight of the blocked isocyanate and 4.8 parts by weight of glacial acetic acid were neutralized, the mixture was diluted with 342 parts by weight of deionized water to obtain an emulsion having a nonvolatile content of about 36%. (Gel Fine Particle Dispersion) (1) Production of amine-added polybutadiene resin Polybutadiene (B-2000, Nisseki Co., number average molecular weight 2000, 1,2 bond 65%) is epoxidized using peracetic acid to contain oxirane oxygen. An amount of 6.4% epoxidized polybutadiene was produced.

1000 g of this epoxidized polybutadiene
And 354 g of ethyl cellosolve were charged into the autoclave, 62.1 g of dimethylamine was added, and the temperature was 150 ° C.
And reacted for 5 hours. Unreacted amine was distilled off to prepare an amine-added polybutadiene resin solution.

The amine value of the resulting amine-added polybutadiene resin solution was 120 mmol / 100 g (solid content). The nonvolatile content was 75%. (2) Production of gel fine particle dispersion Amine-added polybutadiene resin 100 parts by weight (solid content 75%) Tamanol 722 (* 1) 33.3 parts by weight (solid content 25%) Glacial acetic acid 2.8 parts by weight Deionized water 363 9.3 parts by weight * 1 Resol type phenol resin manufactured by Arakawa Chemical Industry Co., Ltd. To 3 parts by weight of Tamanol 722 and 2.8 parts by weight of glacial acetic acid are added to 100 parts by weight of the amine-added polybutadiene resin obtained above. Stir well. To this, 363.9 parts by weight of deionized water was added and emulsified.

A part of the obtained emulsified solution was taken and added to 100 times amount of tetrahydrofuran, and it was transparently dissolved. Here, ethyl cellosolve contained in the amine-added polybutadiene resin was removed, and then the emulsified solution obtained above was kept at 95 ° C. for 6 hours and cooled to obtain a cationic gel fine particle dispersion.

This cationic gel fine particle dispersion liquid did not dissolve transparently in tetrahydrofuran and became cloudy. Next, dip a tin plate into a gel particle dispersion liquid with a nonvolatile content of 10%,
After air-drying and drying under reduced pressure at room temperature, observation with an electron microscope revealed fine particles having a particle diameter of 100 nm or less. (Example 1) Preparation of electrodeposition paint 112 parts by weight of pigment paste (solid content 6
1.6 parts by weight) 278 parts by weight of emulsion (solid content 100
75 parts by weight (solid content: 18 parts by weight)
Parts by weight) deionized water 433 parts by weight (solid content-
(Parts by weight) were mixed by stirring to prepare an electrodeposition coating composition.

20φ for hard disk using the above paint
The rotor core of the spindle motor (sample number (N) = 10) was electrodeposited. After electrodeposition coating, in the water-drying oven,
The mixture was heated from room temperature to 100 ° C. for about 2 minutes and from 100 ° C. to 160 ° C. for about 5 minutes, drained and dried, and subsequently baked in a baking furnace at 160 ° C. for 25 minutes.

The electrodeposition coating film formed as described above completely covered the burrs and had the following characteristics. Average film thickness: 50 μm, edge coverage on the rotor core surface: 70% or more, winding trace depth: 8 μm or less (cross section 2.2
Φ0.1 on a 5 mm x 1.0 mm insulated metal prism
When 8 conductors were wound into 4 layers with a tension of 150 g) For comparison, an insulating coating film was formed by powder coating by a conventional method on the same rotor core as above. The results are summarized in Table 1 below.

[0054]

[Table 1]

As is apparent from Table 1, when the present invention is used, the same withstand voltage performance can be obtained.
Can be reduced to (Example 2) In this example, the same coating material as in Example 1 was used except that it was applied to the rotor core of a 38φ spindle motor for floppy disks (N = 10). It was painted and baked.

For comparison, except that the power core U paint for general electric equipment, Power Top U Excel 200 (manufactured by Nippon Paint Co., Ltd.) was used for the rotor core (for φ38 spindle motor (N = 10)) which was subjected to the blast treatment for removing the punching burr. Then, electrodeposition coating (film thickness 50 μm) was performed in the same manner as in Example 1.

Both rotor cores obtained above have the same specifications (winding diameter 0.17 mm, winding number 100, winding tension 1
50 g) was applied and the minimum starting torque, maximum starting torque and average starting torque were measured. The results are shown in Table 2.

[0058]

[Table 2]

As is clear from Table 2, even if the specifications are the same, the generated torque is improved by 5% or more by using the present invention.
For comparison, a rotor core (for φ38 spindle motor (N = 10)) that has not been subjected to blasting to remove punching burrs is powder-coated by the conventional method (film thickness: 200μ).
m) was performed.

The rotor core obtained as described above and the wound rotor core obtained in this embodiment were wire-coated with a diameter of 0.17 mm and a number of turns of 80.
Finished to the same specifications. The obtained rotor core was incorporated into a motor, and the relationship between torque, rotation speed and current was measured. The results are shown in Fig. 5. In FIG. 5, the solid line indicates the result of the motor incorporating the rotor core to which the present invention is applied, and the dotted line indicates the result of the motor incorporating the rotor core to which the powder coating of the conventional method is applied.

As is clear from FIG. 5, it was found that the starting torque could be improved even with the same specifications. This is because the distance between the winding and the rotor core is reduced as the insulator thickness is reduced, the electromagnetic air gap is reduced, and the motor efficiency is improved.

Further, when an attempt was made to wind the slot portions of both rotor cores obtained as described above so that the rotor thickness would be a set value (constant), the product of the present invention was found to have one winding having a diameter of 0.18 mm.
Although it was possible to make 00 turns, in the conventional method, the winding having a diameter of 0.17 mm could only make 80 turns.

The rotor core thus obtained was incorporated into a motor,
The relationship between torque, rotation speed and current was measured. The results are shown in Fig. 6. In FIG. 6, the solid line indicates the result of the motor incorporating the rotor core to which the present invention is applied, and the dotted line indicates the result of the motor incorporating the rotor core to which the conventional method is applied.

As is apparent from FIG. 6, the starting torque and the generated torque T-current 1 characteristics are remarkably improved, and the motor power-up or power saving is achieved. The insulating film thickness applied between the winding wire and the rotor core 2 can be increased from 200 μm to 50 μm in the case of powder coating by the conventional method, and the effective area of the winding wire can be significantly increased. This is because it is possible to increase the winding diameter and the number of windings. (Example 3) The core surface was electrodeposited and baked in the same manner as in Example 1 except that the rotor core of the autofocus spindle motor was used.

The insulating film thickness applied between the winding and the rotor core 2 can be set to 130 μm to 20 μm in the case of the conventional insulator (POM, manufactured by Polyplastics Co., Ltd.). This significantly increased the effective area of the winding.

FIG. 7 shows the relationship with the dielectric strength characteristics when the motor has the same specifications as a motor provided with an insulator having an insulator thickness of 130 μm. As is clear from FIG. 7, the withstand voltage between the winding and the rotor core has been improved about twice, and the large power specifications can be achieved while maintaining the motor dimensions.
It can be seen that even with a film thickness of 20 μm, the same withstand voltage as that of the insulator of 130 μm can be achieved. (Example 4) A rotor core of a 38φ spindle motor for a floppy disk was prepared in the same manner as in Example 1 except that an electrodeposition paint prepared by blending a pigment paste, an emulsion, a gel particle dispersion and deionized water as shown in Table 3 below was used. The surface was coated with a coating thickness of 50 μm.

Table 3 shows the relationship between the blending ratio and the edge coverage, the presence / absence of voids, the Erichsen value (mm), the withstand voltage (V) and the practicality. In Table 3,
The presence or absence of voids was ranked as follows.

◯: The surface after baking was visually observed, and no pinhole was observed. (Triangle | delta): Although the surface after baking is visually observed and pinhole generation is observed, there is no problem in practicality.

X: The surface after baking was visually observed, and pinholes were severely generated, which was not practical. The practicality was ranked as follows.

◯: It has a withstand voltage higher than 800V. X: The withstand voltage is 800 V or less. In the following, withstand voltage means the average withstand voltage.

[0071]

[Table 3]

From Table 3, as the blending ratio of the gel fine particle dispersion increases, the edge coverage improves and the winding-
It can be seen that the dielectric strength between the rotor cores is improved. On the other hand, the amount of voids generated in the coating film increases with an increase in the proportion of gel particles dispersed and mixed. This is because the melt viscosity of the coating film increases as the blending ratio of the gel particle dispersion increases, so that the efficiency of discharging hydrogen gas, solvent, and water present in the coating film before curing during baking decreases. The increase in the generation of voids promotes the formation of a porous structure in the coating film, and as a result, the strength of the coating film is reduced and the withstand voltage between the winding and the rotor core is reduced. If the proportion of pigment paste is increased too much, the coating becomes brittle, the Erichsen value decreases, and the voids increase, while
If the proportion of the pigment paste is too small, the edge covering property will deteriorate. (Example 5) A rotor core for a φ38 spindle motor (N) was prepared in the same manner as in Example 1 except that the coating material described in Example 1 was used and the temperature in the baking furnace was set as shown in Table 4 below. = 10) The surface was coated so that the coating thickness would be 50 μm. The results are shown in Table 4. The ranking in the table is synonymous with that in Table 3.

[0073]

[Table 4]

It can be seen from Table 4 above that the coating film has the following properties as the temperature inside the baking oven increases. Edge coverage is reduced.

Since the Erichsen value decreases, the coating film becomes brittle. Occurrence of pinholes increases. The coating strength is improved because the winding trace depth is reduced. (Embodiment 6) A case where the present invention is applied to a 1 W transformer which is an example of an electronic component will be described with reference to FIG. Reference numeral 18 denotes an insulating coating applied to the core 11 and having a film thickness of 50 μm, to which the present invention is applied. As shown in FIG.
It is possible to omit the conventional mounting of the insulating case 15 and the insulating tapes 16 and 17, and the bobbin 14 is also equipped with the primary winding 12
-It is possible to have an extremely simple structure only for ensuring insulation between the secondary windings 13.

Therefore, the effective area of the winding is significantly increased,
The effective area ratio with respect to the slot portion is significantly improved from 52.9% (conventional insulation treatment) to 85.2% (present invention). As a result, the transformer can be made extremely light, thin, short, and compact, or the transformation capability can be increased.

[0077]

According to the present invention, it is possible to reduce the film thickness of the insulator applied between the winding and the metal portion while maintaining the withstand voltage performance even in the case of electronic parts having burrs. Along with that, it is possible to increase the effective area of the winding and to reduce the size, weight, and size of electronic components.

[Brief description of drawings]

FIG. 1 is a plan view for explaining the concept of a motor rotor core.

2 is a schematic cross-sectional view taken along the line dd 'of the rotor core of FIG. 1 which has been surface-insulated according to the present invention.

FIG. 3A is a schematic partial cross-sectional view of a conventional surface-insulated rotor core (with burrs). FIG. 3B is a schematic partial cross-sectional view of a conventional surface-insulated rotor core (deburred).

FIG. 4A is a cross-sectional view of a core having a conventional surface insulation treatment applied to the core. FIG. 4B is a cross-sectional view of a transformer core showing another embodiment of the present invention.

FIG. 5: Characteristic comparison diagram of φ38 spindle motor

FIG. 6 is a characteristic comparison diagram of φ38 spindle motor.

[Fig. 7] Insulation film thickness-dielectric strength (between winding and rotor core) characteristic diagram of autofocus spindle motor

[Explanation of symbols]

 1 Rotating Shaft 2 Rotor Core 3 Punching Burr 6 Slot 8 Electrodeposition Insulation Film 11 Core 12 Primary Winding 13 Secondary Winding 14 Bobbin 18 Electrodeposition Insulation Film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuguo Inazawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Within

Claims (5)

[Claims] 1. A bisphenol A residue-containing epoxy resin having at least (A) a number average molecular weight of 1,000 to 3,000 and an average of one or more epoxy groups per molecule, or a derivative thereof, on the surface of a metal for electronic parts having burrs. An emulsion containing an amino group-containing polymer, which is a reaction product with a monovalent secondary amine, in an amount of 60 to 80 parts by weight in terms of solid content, and a blocked isocyanate crosslinking agent in an amount of 20 to 40 parts by weight in terms of solid content. (B) 20 to 50 parts by weight of a methylolphenol compound having a number average molecular weight of 200 to 1000 in terms of solid content, and 50 to 80 parts by weight of an amine-added polybutadiene resin having a number average molecular weight of 1000 to 3000 in terms of solid content. 50 to 70 parts by weight of the pigment fine particle dispersion liquid (C) in terms of solid content, and the pigment dispersion resin A pigment paste containing 5 to 15 parts by weight in terms of form is (A) / (B) /
(C) = 1 / 0.18 to 0.72 / 0.5 to 0.9: The electrodeposition coating composition is electrodeposited, the coating film is baked, and the average film thickness is 20 to 100 µm. A method for forming a coating film, which comprises forming the insulating coating film. 2. The film forming method according to claim 1, wherein the electronic component is a rotor core for a motor. 3. The method for forming a coating film according to claim 1, wherein the electronic component is a transformer core. 4. An electrodeposition coating film is subjected to a drying step at a temperature of 60 ° C. to a temperature lower than the boiling point of water and then to a baking step.
3. The method for forming a coating film according to any one of 3 above. 5. The baking is performed at 135 ° C. to 195 ° C. for 20 to 20 ° C.
The coating film forming method according to claim 1, which is performed for 40 minutes.