JPH0222258Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a casting mold for a resin molded coil for a transformer. As shown in Fig. 1, this type of conventional casting mold consists of an outer mold 1 for the outer circumferential surface and an inner mold 2 for the inner circumferential surface and the bottom surface. When a cooling duct is provided between them, a pair of arc-shaped duct molds 3 are used. By the way, when a primary coil 4 and a secondary coil 5 are inserted into these molds as shown in Fig. 2, and a resin 6 is injected and hardened to make a resin molded coil, the heat generated when the resin hardens This causes a temperature difference inside the mold resin as shown in the graph. In other words, since the outer peripheral surface has a large area in contact with the outside air and there is natural convection, its temperature T ₁
is the lowest, and since the inner surface has a smaller area than the outer surface and there is almost no natural convection, its temperature T ₂
is higher than T ₁ , and the intermediate temperature T ₃ is the highest. When T ₁ is 80°C, T ₂ is 90°C and T ₃ is 110°C, and the temperature difference Δt between T ₁ and T ₃ is 30 degrees. This temperature difference Δt becomes even larger as the coil becomes larger.

If a large temperature difference occurs inside the resin during curing, the curing and shrinkage of the resin will become uneven, generating complex internal stresses and causing cracks in the molded resin. Further, even if no cracks occur during resin molding, internal stress remains, so there is a risk that cracks may occur during use. In order to prevent the occurrence of cracks, it is effective to make the internal temperature uniform during resin molding, and for this purpose, the curing reaction of the resin can be slowed down by heating at a low temperature for a long time. Manufacturing time increases and productivity decreases. The effect of this low-temperature, long-time heating is limited and cannot be applied to large resin molded coils. As a result, an expensive resin that does not cause cracks must be used.

The purpose of the present invention is to solve the above-mentioned problems.A heat pipe is attached to the inner mold and the duct mold, and the heat generated inside the resin molded coil is transferred to the outside by the heat pipe. It is intended to be derived and dissipated. As shown in Fig. 3, the heat pipe is made by forming an adsorption layer 8 made of a porous material (wick) with capillary action on the inner surface of a sealed metal tube 7 made of a metal with good thermal conductivity such as copper or aluminum. heat transfer liquid 9
(water, fluorocarbons, alcohol, etc.), one end of which is the heat collection part A (evaporation part), and the other end of which is the heat radiation part B (condensation part).
That is. 10 is a heat collecting plate made of a metal with good heat conduction, and 11 is a heat radiating plate. When the heat collecting portion A is heated by the heat collected by the heat collecting plate 10, the heat medium liquid 9 evaporates and moves inside the sealed metal tube 7 in the direction of the arrow a. The vapor of the heat medium that has reached the heat radiation part B is absorbed by the heat radiation plate 11, condensed and liquefied, and flows back to the heat collection part A along the adsorption layer 8 as shown by the arrow b. The heat transport capacity of this heat pipe is more than two orders of magnitude greater than that of copper or aluminum, which have high thermal conductivity, and more than four orders of magnitude greater than that of resin.

An embodiment of the present invention will be described with reference to FIGS. 4 to 7. FIG. 4 shows an embodiment in which a heat collecting part A of a heat pipe is attached to the inner surface of the inner mold 2. In this case, the inner mold 2 becomes a heat collecting plate of a heat pipe. FIG. 5 shows an example in which the inner mold 2 itself is used as the heat collecting part of a heat pipe, that is, the inner mold 2 is formed by the heat collecting part A of the heat pipe. FIG. 6 shows an embodiment of the present invention in which the duct mold 3 is formed by the heat collecting part A of a heat pipe. Note that this duct mold 3 may be constructed by drilling a hole in the duct mold and inserting the heat collecting part A of the heat pipe as in the embodiment shown in FIG.
Outer mold 1 is effectively cooled naturally, so
The vertical outer mold shown in the figure is used as is, but a heat pipe may be attached if necessary.

The temperature distribution inside the resin molded coil when using the mold of the present invention is as shown in the graph of Figure 7. When the temperature of T ₁ is 80℃, T ₂ is 81℃, and T ₃ is 81℃.
can be set to 83℃ and Δt to about 5deg, making the temperature distribution inside the resin molded coil almost uniform. Therefore, it is possible to prevent cracks from occurring when the resin is cured for the reasons mentioned above, and since almost no internal stress remains in the cured resin, there is no risk of cracks occurring during use. do not have. Even if the curing temperature of the resin is increased, the temperature distribution can be made uniform, so the curing time can be shortened and the productivity of resin molded coils can be improved. It is possible to obtain a resin-molded coil that is electrically and mechanically stable and has excellent heat resistance.

[Brief explanation of drawings]

Figure 1: A perspective view of a conventional casting mold for resin-molded coils, Figure 2: A sectional view of the mold shown in Figure 1 during use, Figure 3: An explanatory diagram of the structure of a heat pipe, Figure 4
Figures, Figure 5: A perspective view of an embodiment of the casting mold of the invention, Figure 6: A perspective view of an embodiment of the duct mold of the invention, Figure 7: During use of the mold of the invention. Cross-sectional view. Symbol, 1...Outer mold, 2...Inner mold, 3...Duct mold, 4...Primary coil, 5...Secondary coil, 6...Resin, 7...Sealed metal tube (heat pipe), 8...Adsorption layer , 9... Heat medium liquid, 10... Heat collecting plate, 11... Heat sink, A... Heat collecting section, B... Heat dissipating section.

Claims (1)

[Scope of utility model registration request] In a casting mold consisting of an outer mold for the outer peripheral surface, an inner mold for the inner peripheral surface and the bottom surface, and a duct mold, the inner mold and the duct mold are formed of a heat collecting plate of a heat pipe or the like. A casting mold for a resin molded coil that itself forms a heat collecting part.