JPS6221252B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to transformers for various electrical devices including flyback transformers for televisions. Conventionally, in a transformer, an outer shell case is attached to two concentrically arranged split-wound coil bobbins, and both coils are integrally molded with a thermosetting resin as an insulating filling material within the outer shell case. The bobbin and outer case are generally made of molding resin such as polycarbonate, polyphenylene oxide, diallyl phthalate, and polybutylene terephthalate, and the insulating filling material is made of epoxy resin. , silicone rubber, unsaturated polyester resin, polybutadiene resin, and other thermosetting resins for casting impregnation are used. However, plastics generally have poor adhesive strength, and the moldability of the bobbin and outer case is improved by containing a mold release agent in the resin or by applying a mold release agent to the mold surface. Therefore, the adhesion between the bobbin, the outer shell case, and the insulating filling material is extremely poor. For this reason, the shrinkage stress when the insulation filling material hardens and the linear expansion coefficient (hereinafter referred to as
When a transformer is subjected to thermal stress due to a difference in expansion coefficient (simply referred to as the coefficient of expansion) or mechanical thermal shock is applied to the transformer from the outside, the joints can easily separate, causing damage between the high-voltage split-wound coils or between the high-voltage coil and the low-voltage coil. Corona discharge is becoming more likely to occur during this period. Also,
Characteristics change as moisture in the atmosphere penetrates into the separated parts, and furthermore, if such a transformer is actually shut down repeatedly,
Linear expansion and contraction occurs, and peeling between the filling material and the bobbin material grows, which further deteriorates the corona resistance and leads to dielectric breakdown. In particular, unsaturated polyester resins are low in cost, have large curing shrinkage, and have low adhesive strength, making them easy to peel off, making their use difficult. The object of the present invention is that even when unsaturated polyester resin is used as an insulating filler material,
The purpose is to provide a transformer that is maintained in good adhesiveness between the bobbin, the outer shell case, and the insulating filling material. For this purpose, the present invention makes the expansion coefficient of the low-voltage coil bobbin arranged at the innermost circumference smaller than that of the insulation filling material, and also makes the expansion coefficient of the outer shell case as the outermost circumference smaller than that of the insulation filling material. It is designed to be larger than the expansion coefficient of the material. Hereinafter, one embodiment of the transformer according to the present invention will be described in detail with reference to the accompanying drawings. Figures 1 and 2 show the plane and longitudinal section of the transformer taken along the line A-A', respectively. be. According to this, in the figure, 1 is a high voltage coil wound around a divided high voltage coil bobbin 3, one end of which is taken out from the top, and the other end taken out from the bottom. Reference numeral 2 designates a low-voltage coil wound around a divided bobbin 4 for low-voltage coils, and both ends of the coil are taken out from the top. These high-voltage coil 1 and low-voltage coil 2 are arranged concentrically at a predetermined distance B, and are housed in an outer shell case 6. In this case, the low-voltage coil split bobbin 4 and the high-voltage coil split hobbin 3 are fixed at the bottom of the outer shell case 6 by a plurality of plate pieces 7, and the low-voltage coil split bobbin 4 is also attached to the outer shell case 6 at its lower end. The parts are fixed. As a result, a space C is formed between the low-voltage coil split bobbin 4 and the outer shell case 6. This space C is filled with an insulating filling material 5 such as epoxy resin, which causes the split bobbins 3 and 4 and the coils 2 and 1 wound around them to be molded inside the outer shell case 6. The transformer obtained is as follows. In addition, 8 and 9 indicate the coil ends of the high voltage coil 1, 10 and 11 indicate the coil ends of the low voltage coil 2, and 13 indicates the iron core ( core). Now, the insulation method using the insulating filling material 5 in a transformer is not a special method, but the filling material such as epoxy resin is sufficiently mechanically kneaded, stirred and degassed at 3 to 5 mmHg, and then heated at 5 to 10 mmHg. This is injected into the space C formed in the outer shell case 6 using a vacuum device (not shown). After this, the pressure is returned to atmospheric pressure and the material is heated and cured. Here, materials for the bobbin and case that can be applied in this example include thermoplastic resins such as polycarbonate, polyphenylene oxide, and polyester, and thermoplastic resins such as epoxy, unsaturated polyester, diallyl phthalate, silicone, phenol, melamine, and urea. Curable resins or these with organic or inorganic fillers added. In this case, fillers include silica, calcium carbonate, alumina, zircon,
Inorganic particulate fillers such as calcium sulfate glass, and inorganic and organic fibrous materials such as glass, carbon, nylon, tetron, aromatic polyamide, and boron are suitable. By changing the amount of filler added, these materials can ^be
The expansion coefficient can be changed within the range of . In addition, epoxy resin,
Thermosetting resins such as unsaturated polyester resins, diallylphthalate polybutadiene, and silicones,
Alternatively, an organic or inorganic filler may be added to these materials, and the filler used here may be the same as that used for the bobbin and case material. By changing the amount of filler added, these materials can be made into
The expansion coefficient can be changed within a range of 7×10 ^-5 /°C. In the transformer shown in the figure, the separation between the bobbin and the filling material, which causes corona discharge, is caused by the curing shrinkage force due to the volumetric shrinkage of the insulating filling material as it hardens, and by the curing shrinkage force of each bobbin, outer shell case, This is caused by thermal stress due to the difference in coefficient of thermal expansion among the four filling materials. The former method of reducing curing shrinkage force is achieved by using epoxy resins with low shrinkage rates or low shrinkage unsaturated polyester resins, but the latter method of reducing thermal stress is achieved by reducing the expansion coefficient of the filler material. Consideration is being given to increasing the adhesive strength. but,
No particular consideration has been given to the combination with bobbin or case materials. It is known that it is better that the expansion coefficients of the split winding coil bobbin, that is, the high voltage coil split bobbin 3 and the filling material 5, which are partially arranged between the filling materials, are the same.
The reality is that for the innermost bobbin, that is, the low-voltage coil divided bobbin 4 and the outer shell case 6, filler materials with a small expansion coefficient are generally used. However, if we consider in detail the mechanism by which peeling occurs, which causes dielectric breakdown, peeling does not occur at the curing temperature where the filling material hardens; for example, in the transformer shown in this example, the curing temperature is 60 It was found that this phenomenon occurs when the temperature decreases from 120°C to room temperature or -20°C, or when this temperature cycle is repeated. During this temperature change, thermal stress is generated due to the difference in expansion coefficient between each coil bobbin, outer shell case, and filling material.
While almost no thermal stress occurs at a curing temperature of 120°C, it does occur when the temperature decreases. More specifically, it has been found that peeling is likely to occur when the thermal stress caused by this temperature drop becomes tensile stress at the interface between the low-voltage coil split bobbin 4, the outer shell case 6, and the filling material 5. . Therefore, in the present invention, peeling is prevented by changing the combination of expansion coefficients so that the thermal stress when the temperature decreases becomes compressive stress at the interface between the bobbin 4, the outer shell case 6, and the filling material 5. This is what I am trying to do. Now, Table 1 shows compounding examples when epoxy resin and unsaturated polyester resin are used as insulating filler materials used in the examples of the present invention, and Tables 2 and 3 show them. Experimental data using this is shown together with comparative examples.

【table】

【table】

[Table] Table 2 uses epoxy resin as the filling material, and Table 3 uses unsaturated polyester resin as the filling material, and the combinations of the expansion coefficients of the bobbin and outer shell case made by injection molding polycarbonate are used. This shows the results of the experiment. In this experiment, these samples were held at a temperature (+) of 100° C. for 2 hours and then at a temperature (-) of 50° C. for 2 hours. One cycle was a thermal shock test in which five cycles were conducted. After this, in 60℃95%R,H
After leaving it for 1000 hours, it was cut and dyed using penetrant tester "Nippon Red Check" (Taiyo Bussan KK).
As a result of the flaw detection test, as shown in Table 2,
When epoxy resin was used as a filler, it was confirmed that no peeling occurred in all of the Examples. Furthermore, as shown in Table 3, when unsaturated polyester resin is used as a filler, the second
As in the case in the table, no peeling occurred in any of the Examples, but it was confirmed that peeling occurred in all Comparative Examples. As explained above, in the present invention, the expansion coefficient of the low-voltage coil divided bobbin disposed on the innermost circumference side is smaller than the expansion coefficient of the insulation filling material, and the expansion coefficient of the outer shell case as the outermost circumference is smaller than the expansion coefficient of the insulation filling material. The expansion coefficient is preferably larger than that of the insulating filling material. Therefore, since the expansion coefficient of the outer shell case is larger than that of the others, compressive stress is effectively generated at each interface when the temperature decreases. That is, no peeling phenomenon occurs between the constituent materials, and a transformer superior in breakdown voltage characteristics to conventional transformers can be obtained. Further, even if an inexpensive filling insulating material is used, no peeling phenomenon occurs between the component materials, so an economical effect can also be obtained.

[Brief explanation of the drawing]

The attached drawings are for explaining the structure of a transformer showing one embodiment of the present invention, and FIG. 1 is a plan view thereof, and FIG.
FIG. 1... High voltage split winding coil, 2... Low voltage split winding coil, 3... Split bobbin for high voltage coil, 4... Split bobbin for low voltage coil, 5... Insulating filling material, 6... Outer shell case.

Claims (1)

[Claims] 1. On the innermost side of the outer shell case as the outermost periphery, there is a bobbin on which a low voltage coil is wound in parts, and between the bobbin and the above outer shell case there is a bobbin that is not in contact with the bobbin and the outer shell case. The two bobbins are insulated and molded within the case by filling the inner space of the outer shell case with an insulating material while the bobbins each having a high-voltage coil wound therein are disposed. In the transformer, assuming that the expansion coefficient of the bobbin on which the high-voltage coil is wound in sections is almost the same as the expansion coefficient of the insulating material, and the expansion coefficient of the bobbin on which the low-voltage coil is wound in sections is smaller than the expansion coefficient of the insulating material, A transformer characterized by a structure in which the expansion coefficient of the outer shell case is set larger than the expansion coefficient of the material.