JPS63281415A - Formation of film of toroidal core and apparatus therefor - Google Patents

Abstract

PURPOSE:To enable positive and easy manufacturing without deteriorating the magnetic characteristics by applying at the time of hardening the resin a heat treatment wherein one surface of the core is heated while the other surface thereof is cooled, and then reversing the positions of both surfaces to apply the same heat treatment. CONSTITUTION:A core 1 is put in a thermostatic bath 4 or the like, and is heated to a predetermined temperature depending on a resin 5 to be used, or the temperature necessary for depositing the resin. Then, the resin powder is deposited by a fluidization dip method. Then one surface of the troidal core 1 is heated with a heater 3 such as nichrome-wire heater, infrared lamp or gas infrared heater, while the underside thereof is cooled by removing the heat with a cooling and holding base 2 [preferably to the melting point of the resin-(15 deg.C-20 deg.C)], forming a film. After forming the film with respect to one surface of the troidal core in the manner as described above, then by reversing the core 1 and iterating the above process also with respect to the other cooled surface, a film having a uniform thickness on the whole surface is formed which has no resin penetration between thin bands.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method and apparatus for forming a film on a toroidal core, and in particular to a method for forming an insulating film on the surface of a toroidal core used in a magnetic amplifier or choke coil. We will propose a coating forming method (mold curing method) and a coating forming apparatus used to carry out the method.

(Prior Art) In recent years, amorphous magnetic metal ribbons with excellent magnetic properties have come to be used in the fields of magnetic amplifiers and choke coils. Since this amorphous magnetic metal ribbon is obtained as a long thin strip (by ultra-quenching method), it is mostly used as a toroidal core.

Conventionally, a technique for shaping the external shape of the above-mentioned toroidal core; in particular, as a method for forming a film, a method is known in which a thin metal strip is wound and laminated into a susset, then sealed in a case, and then molded with resin (mold cure method). Ta. These external shaping operations (film formation) are necessary to provide the core with insulation properties, improve environmental resistance, and obtain a product that can withstand wire winding.

(Problems to be solved by the invention) The important points in producing the above toroidal core are:
When using an amorphous magnetic metal ribbon with excellent magnetic properties, it is important to prevent strain from being introduced into the ribbon that would cause deterioration of the magnetic properties.

Furthermore, it is an object of the present invention to provide a product that is easy to manufacture and inexpensive.

Therefore, each of the above-mentioned conventional techniques will be discussed below.

The first method is to use a case. In this method, when a wound and laminated toroidal core is enclosed in a case,
If sufficient care is taken to avoid adding distortion, the introduction of distortion will be extremely small and the magnetic properties will hardly be impaired. However, compared to the resin molding method described later, this method not only requires preparation of the case, but also has a smaller winding window because it is affected by the thickness of the case, making it difficult to perform so-called winding. In addition, case cracking sometimes occurs during winding, and furthermore, there are restrictions on use.

The second method is the resin molding method, which allows the thickness of the coating to be made thinner than the case encapsulation method.
Winding is easy, and there is no need to prepare extra parts, so it can be assembled relatively easily and at low cost. However, this method causes the resin to shrink during curing and introduces strain into the core body. It was difficult to apply this method to manufactured toroidal cores.

An object of the present invention is to overcome the drawbacks of the prior art described above, particularly the problems faced by the resin mold method.

(Means for Solving the Problems) To achieve the above-mentioned object, the present invention provides a method for coating the surface of a toroidal core with a resin and curing the resin, in which one side of the core is first heated while the other side is heated. Heat treatment is applied to cool the surface of the
A method for forming a film on a toroidal core, which is characterized in that the positions of both sides are then reversed and the same heat treatment is applied to cover the entire surface, is adopted as a means for solving the above problem.

In addition, in the above heat treatment, the heating temperature is set to be equal to or higher than the resin curing temperature, while the cooling temperature is set to a temperature lower than the resin melting point, preferably a temperature lower than the resin melting point of 20°C. The toroidal core body is formed by winding and laminating amorphous magnetic metal ribbons.

Furthermore, in carrying out the above method, the present invention provides a toroidal core film forming apparatus comprising a core holding stand that can be cooled by introducing a refrigerant, and a heater disposed above the holding stand; We decided to use

(Function) The present inventors investigated the magnetic properties of a core made by a conventional resin molding method. The purpose of this investigation is to find out whether the deterioration of core properties is due to the resin penetrating between the wound magnetic thin strips or due to the resin adhering to the outer periphery of the core.

The results of the experiment are shown in Figure 2.

FIG. 2-(a) is a diagram of the B-H loop before and after the heat treatment when the resin was not coated and cured and the heat treatment was performed under conditions of 100°c x 60 min, which are close to the curing conditions. In this case, almost no change in core properties is observed.

Figure 2 - fbl and (C1 are B when the resin is cured with a filler added to prevent the resin from penetrating during curing.
- The diagram of the H loop, and Figure 2 fdl and (e) are the results of examining the state of resin penetration inside the core after measurement.
b), (This is a diagram corresponding to c+. Although it is difficult to quantify the results, it is clear that the greater the apparent resin penetration, the more the B-H loop changes and the square characteristic of the loop is lost. The influence of resin penetration can be seen in the above two samples.The outer periphery of the above two types of samples was coated with resin in the same manner.

From the above experimental results, ■ Deterioration of the core magnetic properties is due to penetration of the resin between the ribbons, and ■ If only the outer periphery of the core is covered with resin while preventing penetration of the resin, the properties will deteriorate. New findings were obtained: After shaping, the material can withstand windings, etc., and its characteristics do not change even when subjected to shocks such as being dropped from a desk to the floor.

Based on these results, chicken [Th 1xo
-tropic) powder resin such as epoxy resin, for example: r GRADE NBP-3 manufactured by Sanko Resin Co., Ltd.
001 and "Sumilight Resin Pl'" manufactured by Sumitomo Durez Co., Ltd.
It can be seen that it is an important requirement to use 1-52194J or the like and to further prevent the resin from penetrating between the ribbons before curing.

Furthermore, when forming a film on a toroidal core, conventionally,
Since there is no suitable holding part during resin curing, a method of suspending the resin as shown in Figure 3 has been adopted, but such a method is not only complicated, but also causes damage to the resin during curing. Due to the flow, the uniformity of the film thickness may be lost and eccentricity may occur. Since such eccentricity applies non-uniform strain to the core, deterioration of magnetic properties is unavoidable.

Therefore, the present invention proposes a device as shown in FIG. The holding table 2 is configured such that a coolant, preferably cooling water, can be introduced into the holding table 2, and functions to cool one side of the toroidal core 1 placed thereon.

Further, the heater 3, preferably an infrared heater, acts to heat the other side of the toroidal core, and forms a film while suppressing penetration of the resin between the ribbons and preventing eccentricity. It is suitably used for.

Next, a method for forming a film on a toroidal core of the present invention using the above-mentioned apparatus will be explained based on FIG.

In FIG. 1, (al) is a core preheating process, in which the core 1 is placed in a constant temperature bath 4, etc., and heated to a predetermined temperature corresponding to the resin 5 to be used, that is, the temperature necessary to adhere the resin. It is a process.

In Figure 1, (bl is the resin coating process, fluidized dipping method (other methods include thermal spraying method, electrostatic dry spraying method, electrostatic dipping method,
This is a process of attaching resin powder using a spray method, cascade method, etc.).

(C) in Fig. 1 is a resin curing process, in which the upper surface of the toroidal core 1 is heated with a heater such as a nichrome wire heater, an infrared lamp, or a gas infrared heater, while the lower surface is cooled with a cooling holding table 2 to remove heat. [Preferably, the resin melting point - (
15°C to 20°C)] This is a step of forming a film.

After forming a film on one surface of the toroidal core as described above, the thin film is then formed on the other cooled surface by inverting the core 1 and repeating the steps (al to (C1) described above. Forms a film of uniform thickness on the entire surface without resin penetration.

(Example) This example was carried out using the apparatus shown in FIG. 1 (C1). A Kanthal wire heater was used as the heating device, and water was used as the refrigerant for cooling the holding table.

In order to control the curing temperature, the heating temperature was controlled by changing the power supply voltage.

Sumilight Resin PR, a thixotropic resin
-52194 is coated on the core through a preheating and painting process, and this is transferred to the above-mentioned equipment, where the upper surface is heated to about 150°C, while the lower surface is coated with the Sumilight resin PR-52194.
The temperature was controlled to be approximately 20°C lower than the melting point of. In this way, both sides of the core, that is, the entire surface, were coated with epoxy resin.

As a result of comparing the toroidal core thus obtained with the case-inserted core, as shown in Figure 4, the square characteristics of the loops B~ It was showing.

(Effects of the Invention) As can be seen from the above explanation and the results of the examples, according to the present invention, a toroidal core with high sensitivity and high performance can be manufactured reliably, easily, and at low cost without deteriorating the magnetic properties. It is possible to provide a device that can be used suitably for this purpose.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of the film forming method of the present invention, (al
is a preheating process, (bl is a painting process, fC) is a resin curing process, Figure 2 is a diagram showing the influence of presence or absence of resin penetration on magnetic properties, fa) is before and after heat treatment equivalent to resin curing, 0 )l, (C1 is the diagram of each B-H loop before and after resin curing, (dl and [el
Figure 3 is a perspective view of the toroidal core in a suspended state, showing the conventional resin mold curing method. FIG. 2 is a characteristic diagram showing a magnetization diagram obtained under an embodiment of the method of the present invention in comparison with a case-inserted core. 1... Core, 2... Holding stand, 3... Heater, 4...
... Constant temperature bath, 5... Resin.

Claims (1)

[Claims] 1. When coating the surface of the toroidal core with resin and curing it, heat treatment is first applied to heat one side of the core while cooling the other side, and then heat treatment is applied to both sides. A method for forming a film on a toroidal core, which is characterized by reversing the position and applying the same heat treatment to cover the entire surface. 2. The method according to claim 1, wherein in the heat treatment, the heating temperature is higher than the resin curing temperature, and the cooling temperature is lower than the melting point of the resin. 3. The method according to claim 1 or 2, characterized in that the cooling temperature is 20° C. or lower, which is the melting point of the resin. 4. The method according to any one of claims 1 to 3, wherein the toroidal core is made of a laminated material of an amorphous magnetic metal ribbon. 5. A toroidal core film forming device consisting of a core holding stand that can be cooled by introducing a refrigerant and a heater placed above the holding stand.