JP2522432B2 - High voltage transformer manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a high-voltage transformer, and more particularly, to a high-voltage transformer having excellent thermal conductivity and greatly improved crack resistance, which is suitable as an electric device. Manufacturing method.

[Conventional technology]

Conventionally, as a method of manufacturing a high-voltage transformer, an epoxy resin composition in which a coil, a circuit component and the like are set in a plastic case, and an acid anhydride and a curing accelerator or an amine compound are mixed in a uniform mixture of an epoxy resin and an inorganic filler. There is known a potting method of injecting and curing under normal pressure or vacuum.

However, in this method, there is a limit to the amount of the inorganic filler to be mixed in terms of viscosity during mixing and injection workability,
For example, the weight ratio of the epoxy resin composition to the filler of 1.0 is limited to 0.4. Therefore, there is a drawback that the product price becomes high. In addition, since volume contraction occurs when the epoxy resin composition cures, cracks occur in the cured product, peeling and cracking easily occur in the built-in coil and parts or case, and the thermal conductivity is poor There is a problem that the temperature of the equipment becomes high and the temperature to be used is limited. Furthermore, since the injection work is performed after the epoxy resin composition and the inorganic filler are mixed and defoamed under vacuum, it is necessary to use one having a long curing time of the epoxy resin composition, and the curing time after injection also becomes long. There is a limit to the rationalization of work processes and energy saving.

[Problems to be Solved by the Invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a method of manufacturing a high-voltage transformer excellent in curability, crack resistance and thermal conductivity.

[Means for solving the problem]

The present invention, after filling a filler having an average particle size of 100 μm or more in a case in which parts for a high-voltage transformer are stored,
The present invention relates to a method for producing a high-voltage transformer, which comprises injecting and curing an epoxy resin composition containing an epoxy resin and a curing agent or an epoxy resin composition containing an epoxy resin, a curing agent and a filler having an average particle size of 50 μm or less.

The filler having an average particle size of 100 μm or more (hereinafter referred to as filler (A)) used in the present invention is filled in the case in which the coil and the parts are housed before the epoxy resin composition is injected. Preferred average particle size is 200-2000μ
m. The average particle diameter is measured according to JIS Z 2602-1976. If the average particle size is less than 100 μm, the particles are fine and the voids between the particles are small, so that when the epoxy resin composition is injected, unimpregnated parts remain, the thermal conductivity decreases, and the insulating property is impaired. Further, since the filler (A) is unevenly filled between the parts, the linear expansion coefficient of the entire transformer becomes non-uniform, and peeling or cracks occur around the coil and the parts during the heat cycle.

The type of the filler (A) is not particularly limited and, for example, silica sand, silica, alumina, clay mica, glass beads and the like are used. This commercial product is Pearl Sand 4
No., Pearl Sand No. 6, Mikawa Sisand V-3 (trade name of Tochu Co., Ltd.), Morundum-A (Showa Denko KK), GB-A
G, GB-AC, GB-B (manufactured by Toshiba Ballotini) and the like can be mentioned. These can be used in combination.

The filler having an average particle diameter of 50 μm or less (hereinafter referred to as filler (B)) used in the present invention is used by mixing with the epoxy resin composition. A preferable average particle size is 5
20 μm. The average particle size is calculated based on the sedigraph (MICROM
ERI-TICS). The average particle size is 5
When it exceeds 0 μm, the filler (B) precipitates quickly during storage of the epoxy resin composition, and the desired epoxy resin composition cannot be obtained. Moreover, when the epoxy resin composition is injected onto the filler (A), unimpregnated portions remain, the thermal conductivity is lowered, and the insulating property is impaired. Furthermore, since the filler (B) is unevenly filled between the parts, the linear expansion coefficient of the entire transformer becomes non-uniform, and peeling and cracks occur around the coil and parts during the heat cycle.

Examples of the filler (B) include crystalline silica, fused silica, hydrated alumina, alumina oxide, talc, calcium carbonate, mica, glass beads, magnesium hydroxide,
Clay or the like is used. This commercially available product is CRT-AA, C
RT-D, RD-8 (manufactured by Tatsumori), C-303H, C-315H, C
Examples include −308 (Sumitomo Chemical Co., Ltd.) and SL-700 (Takehara Chemical Co., Ltd.). These can be used in combination.

The epoxy resin used in the present invention has at least one epoxy group in one molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, polyglycidyl polyhydric alcohol. Esters and the like can be used. Although these resins are not particularly limited, those which are liquid at room temperature are preferable, and commercially available products are Epicoat 82
8 (Shell Chemical Co., Ltd. trade name), GY-260 (Ciba Geigy Co., Ltd. trade name), DER-331 (Dow Chemical Co., Ltd. trade name) and the like. These can be used in combination.

As the curing agent used in the present invention, an acid anhydride, a curing accelerator, or an amine compound is used.

The above-mentioned acid anhydride is not particularly limited, but those which are liquid at room temperature are preferable, and for example, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylendomethylenephthalic acid, dodecenylphthalic anhydride and the like are used. Examples of commercially available products include HN-2200 (trade name, manufactured by Hitachi Chemical Co., Ltd.) and QH-200 (trade name, manufactured by Nippon Zeon Co., Ltd.). These can be used in combination. The amount of the acid anhydride is preferably 50 to 150 parts by weight based on 100 parts by weight of the epoxy resin.

Examples of the acid anhydride curing accelerator include 2-ethyl-4-methylimidazole and 1-cyanoethyl-4-
Imidazole and its derivatives such as methylimidazole and 1-benzyl-2-ethylimidazole, and tertiary such as trisdimethylaminophenol and benzinemethylamine
Primary amines and the like are used. 2E4MZ as a commercial product
(Trade name manufactured by Shikoku Kasei), BDMA (trade name manufactured by Kao), and the like. The compounding amount of the curing accelerator is preferably 0.1 to 5.0 parts by weight per 100 parts by weight of the acid anhydride.

Examples of the amine compound include aromatic polyamines and modified products thereof, and aliphatic polyamines and modified products thereof. For example, an addition product of diaminodiphenylmethane and an epoxy resin is used. As commercial products, EH-520 (product name manufactured by Asahi Denka Co., Ltd.), EH-551 (product name manufactured by ADEKA Co., Ltd.), Ancamine 2
007 (manufactured by Anchor Chemical Co.) and the like. These can be used in combination. The content of the amino compound is preferably 5 to 50 parts by weight with respect to 100 parts by weight of the epoxy resin.

In the epoxy resin composition containing the epoxy resin and the curing agent or the epoxy resin composition containing the filler (B) therein, red phosphorus, hexabromobenzene, dibromophenyl glycidyl ether, dibromocresyl glycidyl ether, and ternary trifluorobenzene may be added, if necessary. Flame retardants such as antimony oxide, red iron oxide, ferric oxide, carbon, coloring agents such as titanium white, silane coupling agents, defoaming agents such as silicone agents, diluents such as monoglycidyl ether, diglycidyl ether, etc. It can be mixed.

The high-voltage transformer obtained in the present invention includes, for example, a transformer in which electronic parts and electric parts are housed in a plastic or metal case, an electric device such as a solenoid coil, an electromagnetic clutch, a ballast, an igniter, an ignition, a regulator, a ceramic substrate, and a printed circuit board. Examples include electric equipment having a built-in circuit board such as.

〔Example〕

Hereinafter, the present invention will be described with reference to examples. "Parts" in the following examples means parts by weight.

(1) Average particle size of filler (A): JIS Z 2602-19
The particle size distribution was measured according to 76 “Method for testing particle size distribution of foundry sand”, and the particle size with a cumulative weight% of 50% by weight was taken as the average particle size.

(2) Average particle diameter of filler (B): Cedigraph 5000
ET (manufactured by Shimadzu Corporation) is used and the start particle size is 50 μm.
As a filler (B) at a concentration of about 8% by weight to an aqueous solution of 0.1% by weight sodium hexametaphosphate, ultrasonic cleaning is performed for 20 minutes as a preliminary dispersion, and the particle size distribution is measured. (3) Model impregnation rate: A polyethylene beaker having a diameter of 50 mm is filled while vibrating the filler (A) and then weighed to obtain the weight (W ₀ g) of the filler (A). Next, the epoxy resin composition is injected and left under reduced pressure of 10 mmHg for 10 minutes, and cured at 80 ° C. for 3 hours at normal pressure. Then, the cured product was taken out from the polyethylene beaker, the weight (W ₁ g) of the filler (A) separated from the cured product without impregnating the lower epoxy resin composition was calculated, and the model impregnation property was calculated from the following formula.

The model impregnation rate is obtained by determining the rate of the epoxy resin composition impregnated in the filler (A). If the filler (A) in the non-impregnated portion is small, the model impregnation rate is high and the impregnation property is excellent. .

(4) Thermal conductivity: Fill a polyethylene beaker with a diameter of 50 mm while vibrating the filler (A). Next, inject the epoxy resin composition, leave it under a reduced pressure of 10 mmHg for 10 minutes, and cure at atmospheric pressure and 80 ° C. for 3 hours to prepare a disc-shaped test piece with a diameter of 50 mm and a thickness of 10 mm, and heat it. The thermal conductivity (cal / cm · sec · ° C) was determined with a conductivity meter (Dynatech).

(5) Crack resistance: A test piece was prepared by casting in the same manner as in (3), and the test piece was tested according to the crack resistance test of JIS C 2105 “Testing method for solvent-free liquid resin for electrical insulation”.
The number of crack test pieces was five, and a predetermined cooling / heating cycle was performed. The presence or absence of cracks was confirmed for each cycle, and the number of cycles in which cracks occurred first was described.

(6) Coefficient of linear expansion: 5 mm using a test piece for measuring thermal conductivity
A test piece of × 5 mm × 2 mm was cut out, and the coefficient of linear expansion (° C. ⁻¹ ) was determined using a TMA thermophysical tester (manufactured by Rigaku Corporation).

(7) Impregnation into model transformer: A coil made of modified polyphenylene oxide bobbin (10 slits) wound with 250 mm of urethane wire for each 250 turns and parts such as resistors are placed in a case made of the same material as the bobbin. The stored model transformer is dried at 100 ° C. for 1 hour and then filled into the filler (A) while vibrating. Next, the epoxy resin composition is injected, left for 10 minutes under a reduced pressure of 10 mmHg, returned to normal pressure and cured at 80 ° C. for 3 hours. Then, the model transformer was cut, and the state of impregnation into the coil and the gap between the components and the state of impregnation of the epoxy resin composition into the filler (A) were observed as follows.

◯: The gap between the coil and the component was impregnated with the epoxy resin composition, and the filler (A) was impregnated with the epoxy resin composition.

Δ: The gap between the coil and the part or the filler (A) is not impregnated with the epoxy resin composition.

X: The epoxy resin composition is not impregnated into the gap between the coil and the part and the filler (A).

Table 1 shows the trade names (manufacturing companies), compositions, and average particle diameters of the filler (A) and the filler (B) used in Examples and Comparative Examples.

Examples 1 to 3 Filler (A) and filler (B) having the composition shown in Table 2
A test piece was prepared by the above-described test method using an epoxy resin composition not containing, and each property was examined. The results are shown in Table 2. In all cases, the model impregnation property and the model transformer impregnation property were good, the thermal conductivity was high, the linear expansion coefficient was small, and the crack resistance was also good. It was

Examples 4 to 6 Filler (A) and filler (B) having the composition shown in Table 2
Using the epoxy resin composition containing, a test piece was prepared by the above-mentioned test method, and each property was examined. The results are shown in Table 2. In all cases, the model impregnation property and the model transformer impregnation property were good, the thermal conductivity was high, the linear expansion coefficient was small, and the crack resistance was also good. It was

Comparative Example 1 A test piece was prepared in the same manner as in Example 4 except that the filler (A) was not used, and the characteristics thereof were examined. The results are shown in Table 2. The thermal conductivity was low, the crack resistance was poor, and the linear expansion coefficient was also high.

Comparative Example 2 A test piece was prepared in the same manner as in Comparative Example 1 except that the amount of H-32 used as the filler (B) was changed to 350 g, and the characteristics thereof were examined. The results are shown in Table 2, but the impregnability of the coil and the component gap in the model transformer was poor.

Comparative Example 3 A test piece was prepared in the same manner as in Example 4 except that EC-H (average particle size: 150 μm) was used as the filler (B), and its characteristics were examined. The result is the second
As shown in the table, the model impregnation property and the model transformer impregnation property were inferior, the coefficient of linear expansion varied greatly, and the crack resistance was inferior.

Comparative Example 4 A test piece was prepared by shaking with Example 6 except that EC-40 (average particle size: 40 μm) was used as the filler (A), and its characteristics were examined. The result is the second
As shown in the table, the model impregnation property and the model transformer impregnation property were inferior, the coefficient of linear expansion varied greatly, and the crack resistance was inferior.

EFFECT OF THE INVENTION According to the production method of the present invention, the filler (A) in the case is uniformly and sufficiently impregnated with the epoxy resin composition,
There are no bubbles in the cured product, and a high-voltage transformer can be obtained that is in close contact with parts, elements, substrates, etc. The impregnating property and the adhesiveness are almost the same as those obtained by the conventional potting method, that is, the method in which the epoxy resin composition and the filler are mixed in advance and then injected into the case and cured. Further, according to the method of the present invention, since the total amount of filler can be increased, the total cost can be reduced, the curing shrinkage during curing is small, and the thermal conductivity of the cured product and the cracking property during the heat cycle are improved. However, the performance of the high voltage transformer is significantly improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasunori Okada 4-13-1, Higashimachi, Hitachi City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Yamazaki Plant (56) References JP-A-54-3264 (JP, A) Special Features Kai 54-3289 (JP, A) JP 54-66451 (JP, A)

Claims (1)

(57) [Claims] 1. A case in which high-voltage transformer parts are housed is filled with a filler having an average particle size of 100 μm or more,
A method for producing a high-voltage transformer, which comprises injecting and curing an epoxy resin composition containing an epoxy resin and a curing agent or an epoxy resin composition containing an epoxy resin, a curing agent and a filler having an average particle diameter of 50 μm or less.