JPH0797706B2 - Sealing structure for electrical equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sealing structure for electrical equipment such as solenoids, transformers, and semiconductor devices.

(Prior Art) A solenoid is incorporated in a solenoid valve as a driving means of a spool, or is used as an actuator by the solenoid itself. In general, in order to facilitate waterproofing, dustproofing, insulation, and attachment at a predetermined position, as shown in FIG. 1, the periphery of a yoke 3 having a coil bobbin 2 wound with a coil 1 is sealed with resin. A casing 4 is formed. Conventionally, the sealing by the resin is performed in order to smoothly dissipate the heat generated in the coil 1 and to prevent the intrusion of moisture, the yoke 3
The resin was fixed to the yoke 3 by filling a thermosetting resin in the periphery of the and then heating and curing.

In addition to solenoids, electrical equipment such as transformers and semiconductor elements are also sealed with a resin for waterproofing, dustproofing, and insulation.

(Problems to be Solved by the Invention) However, in the above-described conventional products, the use of the solenoid may cause cracks in the resin casing 4 to impair the insulating property. As a cause of this, a steel plate or a silicon steel plate is used as a material of the yoke 3 enclosed in the casing 4 and galvanized or the like is applied for rust prevention, but since it is formed by a press or the like, there are many notches. It is conceivable that a stress concentration occurs in the notch portion due to a difference in thermal expansion between the yoke 3 and the casing 4 due to heat generation of the coil when the solenoid is used, and a crack is generated in the casing 4. Therefore, it is considered that cracks generated in the casing 4 can be prevented by using the materials of the yoke 3 and the casing 4 having the same coefficient of thermal expansion. It is impossible to make the same.

In addition, the same problem occurs in other electric devices and the like that adopt a resin sealing structure such as a transformer.

The present invention has been made in view of the conventional problems described above, and an object thereof is to prevent the occurrence of cracks due to use when a metal part such as a yoke is sealed with a resin around the periphery. To provide a resin sealing structure such as.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a resin film is formed by electrodeposition coating on the surface of a metal component that causes thermal expansion during use, and the metal component is a thermosetting resin. It was sealed with. As the electrodeposition coating, both anion electrodeposition coating and cation electrodeposition coating can be adopted, but cation electrodeposition coating is preferable. Further, as the thermosetting resin for sealing, an epoxy resin is preferable from the viewpoints of operability in curing and molding, less shrinkage during curing, mechanical strength, electrical insulation, chemical resistance and the like.

(Function) Since the film formed by electrodeposition coating on the surface of the metal component has high adhesion with the metal, for example, even when the yoke as the metal component causes thermal expansion due to heat generation of the coil when the solenoid is used, The close contact with the yoke surface is maintained. In addition, since the film formed by electrodeposition coating is resin, it has a higher affinity for the thermosetting resin used as the sealing material than the conventional metal plating layer, and was formed by electrodeposition coating. Adhesion between the film and the thermosetting resin used for the sealing material is increased. Therefore, the internal pressing force generated by the difference in the coefficient of thermal expansion between the metal component and the sealing resin due to the heat generated when using an electric device such as a solenoid is absorbed by the entire adhesion surface between the coating film and the sealing resin, causing cracks. Is prevented from occurring.

(Example) The present invention will be described in more detail with reference to examples and test examples embodied in a solenoid. A yoke for assembling a coil having an outer diameter of 18.5 mm and a coil size of 26 mm was subjected to cationic electrodeposition coating to form an electrodeposition coating film on its surface. Epoxy resin with amino group introduced is the main resin for electrodeposition coating,
A conventional cationic electrodeposition coating material containing a blocked isocyanate resin was used as a curing agent. After assembling the coil to this yoke, it was sealed with an epoxy resin in the same manner as in the prior art to manufacture a rectangular parallelepiped test sample S shown in FIG. Further, as a comparative sample, a similar sample S was manufactured by using a yoke not subjected to electrodeposition coating. Then, a temperature cycle test was carried out on these samples under the following conditions, and it was checked for each cycle whether or not a crack had occurred.

Hold the sample in a constant temperature bath at -25 ℃ for 2 hours, and then let it stand at room temperature for 30 hours.
One cycle is completed by leaving it for a minute, then putting it in a constant temperature bath at 70 ° C. for 2 hours and then leaving it at room temperature again for 30 minutes.

No cracks were observed in the samples that had been electrodeposited even after the completion of 15 cycles, whereas the samples without electrodeposition were observed after the completion of one cycle in Figs. 3 (a) and (b). Occurrence of crack C was observed as shown in FIG. In addition, the sample after 15 cycles was checked for disconnection and insulation, but no abnormality was found. Further, the thickness of the electrodeposition coating film on the surface of the yoke was almost the same as the thickness of the conventional rust preventive plating, and the magnetic efficiency did not decrease due to the increase in magnetic resistance.

Next, a test was conducted to examine the adhesion between the epoxy resin and the electrodeposition coating film. As shown in FIG. 4, the test method was as follows: a film 6 formed by electrodeposition coating was formed on the surface of a metal fitting 5 made of carbon steel (S45C), and a washer 7 was embedded between both metal fittings 5 as a starting point for damage. The epoxy resin 8 was cured to prepare a sample for a tensile test, and the sample was subjected to a tensile test at a tensile speed of 5 mm / min with a tensile tester for 50 tons to examine the breaking strength and the location of the broken portion. In addition, both the cation electrodeposition coating and the anion electrodeposition coating were performed as the electrodeposition coating, and the same test was performed for the comparative sample whose surface was galvanized and the melamine baking coating was applied. It was The number of samples was 3 in each case. The test results are shown in the table.

In the case of the sample in which the film was formed on the surface of the metal fitting 5 by galvanizing or baking coating with melamine, peeling occurred from the interface between the plated portion and the resin or the interface between the metal and the film only by pulling the sample by hand. On the other hand, when a film is formed by cationic electrodeposition coating, fracture occurs at the epoxy resin part, and the strength is equivalent to the calculated value of the epoxy resin fracture (notched) strength of 190 Kg / cm ² This proves that the adhesion between the coating film and the metal and the adhesion between the cationic electrodeposition coating film and the epoxy resin are extremely strong. Also, in the case of anion electrodeposition coating film, unlike the case of cation electrodeposition coating, fracture occurs at the interface between the electrodeposition coating film and epoxy resin, and the adhesion between the electrodeposition coating film and epoxy resin is It is weaker than the case of coating, but has practically sufficient strength.

In addition, although an example in which the epoxy resin is used as the sealing resin has been described in the above-described embodiment, a thermosetting resin other than the epoxy resin may be used. Further, it may be applied to a sealing structure for transformers other than solenoids and other electric devices such as semiconductor devices.

(Effects of the Invention) As described in detail above, according to the present invention, the adhesion of the sealing resin and the electrodeposition coating film by the action of the electrodeposition coating film formed on the surface of the metal component that causes thermal expansion during use. Is improved,
For example, resistance to heat shock due to heat generation of the coil when using a solenoid as an electric device is increased, cracks and the like are reliably prevented, and waterproof,
Moisture resistance and insulation are also improved, and the rust prevention effect on exposed parts of metal parts is also enhanced. Further, since it is possible to prevent the occurrence of cracks and the like only by the resin film formed by electrodeposition coating, it is possible to make the electric device and the like sealed with the resin compact.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a solenoid sealing structure, FIG. 2 is a schematic perspective view of a heat shock test sample, FIG. 3 (a),
(B) is a schematic perspective view showing the positions of cracks generated in the comparative sample by the heat shock test, and FIG. 4 is a cross-sectional view of the tensile strength measurement sample. Coil 1, yoke 3, casing 4.

Claims (1)

[Claims] 1. Electricity characterized by forming a resin film by electrodeposition coating on the surface of a metal part (3) which undergoes thermal expansion during use, and sealing the metal part (3) with a thermosetting resin. Sealing structure for equipment.