JPS5941290B2 - Resin molded electrical equipment coil - Google Patents

Description

[Detailed description of the invention] The present invention relates to resin molded electrical equipment coils.

Generally, a motor coil is wound with electric wire around a support such as an iron core, and then fixed together with electrically insulating varnish or the like. In recent years, electric motors have been applied to fields that require low armature inertia, such as control responsiveness, and ironless armature coils have been adopted. This ironless armature coil must be integrated in some way to provide rigidity as a rotating body. Generally, the coil is made into an integral rigid body by resin casting or injection molding. Thermoplastic resins do not have sufficient heat resistance, so thermosetting resins such as epoxy resins and unsaturated polyester resins are used, and casting or injection molding methods are used. However, as market demand for ironless core armature motors increased, with heavy load characteristics such as larger capacity, overcurrent, and high-temperature, high-speed rotation, it was inevitable that ironless armature motors would
It is necessary to have advanced properties such as burnout properties against overcurrent, heat-resistant mechanical properties against high-temperature and high-speed rotation, and dimensional stability. The present invention provides a resin-molded electrical equipment coil that has the above-mentioned heavy load characteristics, particularly excellent burnout resistance and heat resistance.

The main point is the combination of a molding material with excellent thermal conductivity and thermal expansion properties and an insulated wire with a buffer film that has a heat-resistant buffer film on the surface. The significant effect of the filler content in the molding material on the burnout time properties was surprisingly found. The configuration will be explained in detail below.
An overcurrent flows through the coil of an electrical device embedded in the molding material, causing the coil to burn out in a short period of time (generally refers to a state in which the coil has lost its original function due to a short circuit or disconnection).
The following four steps can be considered as the process leading to this.

(1) Electrical breakdown caused by the conductor generating heat due to overcurrent and the breakdown voltage of the wire's insulation coating decreasing at high temperatures.

(2) Electrical breakdown due to oxidative decomposition of the insulating film due to heat generated by the conductor, and a decrease in dielectric strength due to thermal decomposition.

(3) Due to the heat generated by the conductor, decomposition gas is generated from the insulation film, which causes cracks in the molding material in which the wire is embedded, and promotes oxidative decomposition of the insulation film.
Electrical breakdown similar to 2).

(4) Thermal expansion of the wire due to heat generated by the conductor, resulting in stress generation inside the molding material. The subsequent occurrence of cracks in the molding material promotes oxidative decomposition of the insulating film, leading to electrical breakdown similar to (2) below. In this case, the conductor swells from inside the insulation film itself because the surrounding molding material has not reached a high temperature.
It is placed under high stress due to swelling and compression of the molding material from the outside, further accelerating electrical breakdown. The above process shows that when the insulated wire is embedded in the molding material, the coil burnout characteristics are approximately 1.5 times as high in current value as when the insulated wire is alone, under the same burnout time. It is premised on facts that indicate the value.

Figure 1 shows a twisted pair of 0.5φ esterimide electric wires based on JISC3OO3, with a thickness of 1.4mm.
It was embedded in an epoxy molding material for low-pressure molding in the center of a plate with a width of 1 mm and 10 mu. A predetermined current is applied to one of the molded sheist pairs, and 10
Burnout is defined as the time when a leakage current of 100 mA flows under a condition of zero voltage applied, and the current application time is shown. The molded embedded product exhibits a value 10 to 100 times that of the non-molded product at a current density of around 150 A/Md. In other words, this shows that the burnout time greatly depends on the oxidative decomposition of the high-temperature insulating film due to air contact. In other words, it means the fact that the occurrence of cracks in the molding material determines the burnout time. From this, it is important to understand how heat-resistant cracking properties, especially heat shock properties (short-time boundary temperature properties) of the molding material are necessary for forming equipment coils that can withstand overcurrent, that is, have heat resistance. I've been considering whether there is one.

It has also been found that, depending on the filler used in the molding material, there is a certain filler content at which the thermal properties of the molding material are suddenly improved. Figure 2 shows the thermal conductivity and coefficient of thermal expansion when increasing the amount of silica filler, in which 85% by weight or more of the particle size distribution is within the particle size range of 1 to 20μ, to a high-flow epoxy resin. This shows the changes in

That is, it has been found that when the filler content exceeds approximately 75% by weight, the effects on both properties become significant. We were also able to discover the fact that these characteristics influence the burnout characteristics of the wire. Figure 3 shows the burnout time characteristics obtained using the same method as in Figure 1, using an ester imide wire coated with a heat-resistant buffer film of 10 to 14μ as a sheath pair with molding material inserted in the same way as in Figure 1. It is.
This figure also shows that the filler content of the molding material to be embedded is 7.
0 weight? Up to 75 weight? The filler effect is very different from the previous one, and it weighs almost 75%. We were able to see that it had a significant effect. Figure 3 also shows the case where an esterimide wire without a buffer film layer is embedded on the surface of the wire, but the reason why the filler effect is not seen is because the molded material contains a high amount of abrasive filler during molding. This is thought to be due to insulation deterioration due to the material flowing at high temperatures and high speeds damaging the wire's insulation film, and at the same time the wire's insulation film being subjected to the stress caused by the high pressure after the molding material is filled into the mold. It will be done.

This deterioration during the molding process was successfully solved by the action of a heat-resistant buffer film applied to the surface of the wire. This coating reduces mechanical damage during coil winding work, but above all, it eliminates wear and deterioration caused by the filler contained when the molding material is injected, which is impossible with conventional molding materials. The point is that it is possible to use a molding material containing 85% by weight of granular filler, and satisfactory results have been shown in terms of the burnout characteristics of the molded product. Therefore, the properties required for this film include abrasion resistance similar to that of thermoplastic resin in terms of workability, and after being embedded in a molding material, it has thermal decomposition resistance against overcurrent, and at the same time has insulation properties. It is located between the electric wire and the molding material and needs to act as a stress buffer. The main materials are phenoxy resin, polyether, and ester resin, which have flexibility and heat resistance like thermoplastic resins, and are modified with epoxy resin and isocyanate resin to impart heat-curing properties. We were able to obtain sufficient heat decomposition resistance and flexibility. FIG. 4 shows a study of the effect of the thickness of the buffer film on the electrical characteristics.

The sample was made into a twisted pair using a 0.5ψ bare copper wire coated with a buffer film in accordance with JISC3OO3.
Is this silica 82 weight? It is resin-molded using the contained epoxy molding material. Molding is performed at an injection pressure of 501<
g/d, molding temperature 155°C, and mold clamping time 3 minutes. The breakdown voltage characteristics indicate that a film thickness of 5 μm or more can sufficiently compensate for deterioration during molding operations. An example will be shown below.

An insulated wire with a core wire diameter of 0.76φ and a polyesterimide resin film of about 30μ is coated with polyether, ester resin (e.g., Epicron resin from Dainippon Ink Co., Ltd.), epoxy resin (e.g., Epicorte resin from Ciel Co., Ltd.), Approximately 10 μm of a resin modified by adding isocyanate resin (for example, Coronate AP manufactured by Nippon Polyurethane Industries, Ltd.) was applied as a buffer film to obtain an electric wire with a buffer film having a melting point of about 160°C.

This electric wire was laminated and wound to form a coreless armature coil.
90 weight based on particle size distribution? A resin-molded armature was obtained by integrally molding the coil with an epoxy resin molding material containing 82% by weight of silica having a particle size of 1 to 20 μm as a filler. The molding temperature was 150℃, the molding pressure was 50k9/d, the curing time was 5 minutes, and the molded product was 16"
A post-cure of C-5 hours was carried out. Using this armature, a commutator motor with an input of 500 W and a rated current of 15 A was obtained. When the rated load is attached to this motor, the starting inrush peak current is 90
A start/stop cycle was performed. As shown in Table 1, sufficiently satisfactory overcurrent characteristics were obtained. In addition, in the conventional product, an esterimide insulated wire is similarly made into an armature using an epoxy resin molding material with a filler content of 70% by weight.

As described above, the present invention, while conducting various studies on the influence of embedded molding materials on burnout characteristics, has discovered that a specific molding material exhibits a unique improvement in characteristics depending on its filling rate.
The problem that the highly filled molding material easily damages the coil during molding was solved by applying a heat-resistant buffer film to the wire surface, which improves overload characteristics, especially burnout characteristics due to overcurrent. We succeeded in obtaining an excellent resin-molded electrical equipment coil.

Note that the present invention is not limited to the armature described in the above embodiments,
It can also be applied to stationary equipment coils that require this type of overcurrent characteristic.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the burnout time as a function of the current flow of the coil when the insulated wire is embedded in the molding material and when it is not embedded, and Figure 2 shows the thermal conductivity and thermal expansion coefficient as a function of the filler content. FIG. 3 is a characteristic diagram showing burnout time versus filler content with and without a buffer film layer, and FIG. 4 is a characteristic diagram showing breakdown potential value versus buffer film thickness.

Claims (1)

[Claims] 1 A buffer that is mainly composed of phenoxy resin, polyether, or ester resin, modified with epoxy resin or isocyanate resin, and has a heat-resistant buffer layer on the surface of approximately 5μ or more as a stress buffer material that is made heat-curable. The coated insulated wire is wound multiple times to form a coil, and the particle size distribution is approximately 85% by weight or more from 1 to 20μ.
75% by weight of filler consisting of silica within the particle size range of
A resin molded electrical equipment coil characterized in that the coil is integrally molded with a resin molding material containing the above.