JPH0864051A - Resin molded electric equipment - Google Patents

Abstract

PURPOSE: To provide the resin molded electric equipment which is high in reliability of its crack resistance under any service environment by providing a cut-out section for the inner surface of an imbedding hole for imbedding a metal piece in a molded part. CONSTITUTION: In a molded part, a cavity 7 is provided, which forms a cut-out section in the inner surface of an imbedding hole 5 formed in the molded resin 3 for imbedding a metallic insert 1 consisting of an imbedded metal. This constitution thereby enables the molded resin 3 at the cavity 7 section to be deformed, remaining stresses taking place in the vicinity of the metallic insert 1, particularly remaining stressed produced in the circumferential direction can thereby be made low. Besides, an elastic body is provided in the surface axial direction of an imbedded metal in such a way as to be fairly higher in height than the outer circumferential surface of the imbedded metal, and it is so designed that the molded resin 3 in the elastic body can thereby be deformed for making remaining stresses low to the utmost in the vicinity of the imbedded metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-molded electric device having a metal insert such as a resin-molded bushing used in, for example, a closed switchboard.

[0002]

2. Description of the Related Art Most of resin-molded electric devices include metal inserts such as copper, aluminum and iron, or electronic parts.

Generally, the coefficient of thermal expansion of the conductors and electronic components to be embedded is smaller than that of the molding resin, and a crack is caused by a rapid thermal shock or thermal stress generated when exposed to an extremely low temperature below freezing. It is known to be easy. In particular, when using a relatively long conductor such as a resin mold bushing, cracks easily occur because the absolute amount of thermal stress in the conductor axial direction generated by the curing shrinkage of the mold resin and the difference in both thermal expansion coefficients increases. It's easy to do.

Therefore, conventionally, as shown in FIG. 5 as an example of a resin mold bushing, a stress relaxation layer made of a rubber-like elastic body 104 such as a flexible epoxy resin is provided around the conductor 105 in advance by casting. After that, the two-step molding method of molding again with the molding resin 101 is performed.

Regarding the molding of the long conductor 105, when the conductor 105 is directly molded as shown in the schematic diagram of the residual stress inside the molding resin in FIG. 6A, the residual stress remaining in the molding resin 101 is The larger the adhesive interface in the axial direction with the conductor 105 and the longer the conductor 105, the larger the absolute value of the residual stress becomes, and the more easily the crack develops. Therefore, as shown in FIG. 7, in order to prevent the conductor 105 from rotating or to fix it, a part of the knurl 106 or the like is processed,
A surface treatment is performed so that only that portion is adhered and the other portions are not adhered to the mold resin, thereby improving the movement of the mold resin 101 in the axial direction with respect to the conductor 105.

Another method is to add a flexibility-imparting agent or the like to the mold resin itself to improve the crack resistance of the mold resin itself.

[0007]

However, since the two-step molding method uses a mold for forming the rubber-like elastic body 104,
It is not mass-produced and the cost is high. Moreover, since silicone oil or a fluororesin-based mold release agent is applied to the mold in order to improve the mold releasability, a lot of trouble and careful handling are inevitable for removing these mold release agents.

Further, a part of the conductor 105 has a knurl 10
In the method of performing processing such as 6 and peeling off the other portion, since the bonding portion with the mold resin 101 is small, the conductor 10
When a load is applied to No. 5, the entire load is received by the mold resin 101 portion of the knurl 106, so that cracks easily occur due to stress concentration. In addition, a device using an insulating gas or insulating oil that requires airtightness is remarkably lacking in reliability.

In the latter method of adding a flexibility-imparting agent to the molding resin itself, which is another method, since the material used as the flexibility-imparting agent has a relatively low molecular weight such as polyethylene glycol, It itself has poor heat resistance, and its use in areas where thermal problems are required is limited. Especially in today's demand for miniaturization and large capacity of electric devices, thermal problems are inevitable.

The present invention has been made in view of the above,
The object is to provide a resin-molded electric device having high reliability in crack resistance under any use environment.

[0011]

In order to achieve the above object, the invention according to claim 1 is a resin-molded electric device having a cylindrical or columnar embedded metal in the center, and embedded for embedding the embedded metal. The gist is that a notch is provided on the inner surface of the hole.

According to a second aspect of the present invention, in a resin-molded electric device having a cylindrical or columnar embedded metal in the center thereof, in the surface axial direction of the embedded metal,
The gist is that the elastic body is provided so as to be higher than the outer peripheral surface of the embedded metal.

Further, the invention according to claim 3 is, in a resin-molded electric device having a cylindrical or columnar embedded metal in the center thereof, in which an elastic body is spirally provided on the surface of the embedded metal. To do.

According to a fourth aspect of the present invention, in a resin-molded electric device having a cylindrical or columnar embedded metal in the center thereof, the embedded metal is arranged in the circumferential direction so as to be higher than the outer peripheral surface of the embedded metal. The gist is to have an elastic body incorporated in the formed groove.

Further, the invention according to claim 5 is based on claim 2,
In the invention described in 3 or 4, the gist is that the elastic body is a rubber-like elastic body.

[0016]

Function: Mold resin 10 generated in the axial direction with respect to the conductor 105 when the cylindrical conductor 105 is resin-molded
As shown in FIG. 6 (a), the residual stress in 1 is that when the conductor 105 and the mold resin 101 are completely bonded,
It increases in proportion to the length of the conductor 105. Further, as the residual stress in the mold resin 101 generated in the circumferential direction with respect to the conductor 105 of the same model, as shown in FIG. 6B, the coefficient of thermal expansion of the mold resin 101 is larger than that of the conductor 105. It occurs concentrically with respect to the conductor 105. It is known that in any case, the maximum is in the vicinity of the conductor 105.

Therefore, according to the first aspect of the present invention, by providing a notch on the inner surface of the embedding hole formed in the mold resin for embedding the embedding metal, the deformation of the mold resin at the notch portion. The residual stress generated near the buried metal is minimized.

According to the present invention of claim 2,
By providing the elastic body in the surface axial direction of the embedded metal so as to be slightly higher than the outer peripheral surface of the embedded metal, the mold resin of the elastic portion can be deformed and residual stress generated near the embedded metal can be minimized. I'm making it small.

Further, according to the present invention as set forth in claim 3, by providing the elastic body in a spiral shape on the surface of the embedded metal, the mold resin of the elastic body portion can be deformed, and the elastic resin can be deformed near the embedded metal. The residual stress generated is minimized.

According to the present invention of claim 4,
By embedding the elastic body in the groove formed in the circumferential direction of the embedded metal so as to be slightly higher than the outer peripheral surface of the embedded metal, the mold resin of the elastic body portion can be deformed and generated near the embedded metal. Residual stress is minimized.

Particularly, by using a rubber-like elastic body as the elastic body as in the fifth aspect of the present invention, further reduction of the residual stress can be expected.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 (a) and 1 (b) are views showing the structure of a mold part used in a fuse holder or the like according to the first embodiment of the present invention. The feature is that a void 7 is formed in the inner surface of the embedding hole 5 formed in the mold resin 3 for embedding the metal insert 1 constituting the embedding metal.

The metal insert 1 is made of cylindrical brass having an outer diameter of about 25 mm, and the molding resin 3 is molded to a thickness of about 5 mm by injection molding using a phenol resin molding material.
A gap 7 having a height of about 0.5 mm and a width of 5 to 7 mm is formed in a part of the bonding interface between the mold resin 3 and the metal insert 1. Regarding the formation of the void 7, a jig having the same shape as that of the void 7 is attached to the mold, and the mold is devised so as to be removed at the time of releasing after the resin molding. Further, the jig as above may be integrally molded with the metal insert 1 and may be taken out after releasing from the mold. The jig as above has a suitable taper surface for facilitating removal. In addition, in FIG. 1, reference numeral 8 denotes a screw portion formed on the metal insert 1.

Therefore, according to the present embodiment, the mold resin can be deformed in the void portion, and the residual stress generated in the vicinity of the metal insert, especially the residual stress generated in the circumferential direction can be reduced. By the way, Table 1 shows
The result of the heat deterioration test of the molded component according to the present embodiment is shown.

[0026]

[Table 1] Phenolic resin is one of the molding materials that requires caution when used at high temperatures, because it shrinks more than epoxy resin due to heat deterioration. As shown in Table 1, by using the present invention, the generation of cracks is significantly improved even when shrinkage due to heating occurs.

FIG. 2 is a view showing the structure of the conductor 9 which constitutes the resin mold bushing according to the second embodiment of the present invention. The feature is that the groove 11 is provided in the conductor 9 forming the embedded metal, and the string-like rubber-like elastic body 13 is provided in the groove 11 so as to be slightly higher than the surface of the conductor 9. .

The conductor 9 having such a structure is made of an epoxy resin casting material (for example, Ciba Geigy Co., Ltd. of Japan).
Epoxy resin: Araldite GY260) as a main agent and a curing agent (for example, modified acid anhydride of Hitachi Chemical Co., Ltd.):
HN-2200) is added to a compound (for example, silica powder, for example, Crystallite A- of Tatsumori Co., Ltd.).
1) is added in an amount of about 50% or more of the total amount, and a tertiary amine such as BDMA is used as a curing accelerator in the composition.
It is embedded in the mold resin with a casting material containing a specified amount of.

Therefore, according to this embodiment, the mold resin can be deformed in the rubber-like elastic body portion, and the residual stress generated in the vicinity of the conductor, especially the residual stress generated in the circumferential direction can be reduced. Incidentally, the resin mold bushing according to the present example was subjected to a thermal shock test of 10 cycles of immersion in boiling water at 100 ° C. for 1 hour and immediately immersion in cold water at 0 to 2 ° C. for 1 hour, before and after that. As a result of investigating the partial discharge characteristics of No. 1, no abnormalities such as cracks were found in the appearance, and the partial discharge characteristics before and after the thermal shock test were hardly changed.

In the second embodiment, the rubber-like elastic body is provided in the groove, but as shown in FIG. 3, the groove is not provided on the surface of the conductor 9 and the rubber-like elastic body 13 is provided. Even if it is attached to the surface of the conductor 9 with an adhesive or the like,
Similar actions and effects can be obtained. When the rubber-like elastic body is attached to the conductor surface, the attachment shape may be, for example, a spiral shape, and the same action and effect can be obtained, particularly in the axial direction of the conductor. It is effective in relaxing the residual stress.

FIG. 4 is a view showing the structure of the conductor 15 which constitutes the resin mold bushing according to the third embodiment of the present invention. The feature is that a plurality of grooves 17 are provided in the circumferential direction of the conductor 15 (30 cm or more in length) that constitutes the embedded metal, and a ring-shaped rubber-like elastic body 19 is provided so as to be slightly higher than the surface of the conductor 15. It is included in the groove 17 part.

The conductor 15 having such a structure is used as the second
By embedding it in the molding resin with the casting material in the example of, it becomes possible to deform the molding resin in the rubber-like elastic body portion in the circumferential direction, and the residual stress generated in the axial direction is divided, so that the residual stress can be reduced. As a result, the residual stress generated particularly in the axial direction can be relaxed. Incidentally, regarding the resin mold bushing according to the present embodiment, after immersing it in boiling water at 100 ° C. for 1 hour,
Immediately after 10 cycles of a thermal shock test with 1 cycle of immersion in cold water of 0 to 2 ° C for 1 hour, the partial discharge characteristics before and after that were examined, and as a result, no abnormality such as cracks was observed in the appearance,
Almost no change was observed in the partial discharge characteristics before and after the thermal shock test.

[0033]

As described above, according to the first and second aspects.
According to the invention of claim 3, in particular, it is possible to relieve the residual stress generated in the circumferential direction of the embedded metal.
According to the invention, since the residual stress generated particularly in the axial direction of the embedded metal can be relaxed, it is possible to obtain high reliability in crack resistance under any use environment.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a mold component according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a conductor forming a resin mold bushing according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a modification of the second embodiment.

FIG. 4 is a diagram showing a structure of a conductor forming a resin mold bushing according to a third embodiment of the present invention.

FIG. 5 is a view showing a cross section of a conventional resin mold bushing.

FIG. 6 is a schematic diagram of residual strain generated on the mold resin side when a cylindrical conductor is resin-molded.

FIG. 7 is a view showing a cross section of a conventional resin mold bushing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal insert 3 Mold resin 5 Embedded hole 7 Void 8 Screw part 9 Conductor 11,17 Groove 13,19 Rubber-like elastic body 15 Conductor

Claims (5)

[Claims] 1. A resin-molded electric device having a cylindrical or columnar embedded metal in the center thereof, wherein a notch is provided in an inner surface of an embedded hole for embedding the embedded metal. 2. In a resin-molded electric device having a cylindrical or columnar embedded metal in the center thereof, an elastic body is provided so as to be higher than an outer peripheral surface of the embedded metal in a surface axial direction of the embedded metal. Characteristic resin-molded electrical equipment. 3. A resin-molded electric device having a cylindrical or columnar embedded metal in the center thereof, wherein an elastic body is spirally provided on the surface of the embedded metal. 4. A resin-molded electric device having a cylindrical or columnar embedded metal in the center thereof, which is incorporated in a groove formed in the circumferential direction of the embedded metal so as to be higher than the outer peripheral surface of the embedded metal. A resin-molded electric device having an elastic body. 5. The resin-molded electric device according to claim 2, wherein the elastic body is a rubber-like elastic body.