JPS61197076A - Method of coating resin on magnetic body - Google Patents

Abstract

PURPOSE:To maintain practically magnetic characteristics before coating by coating a resin at a temp. below the room temp. when at least a part of the titled magnetic recording body is coated with a resinous material. CONSTITUTION:At least a part of a magnetic body (e.g., an amorphous magnetic material) is coated with a resinous material such as a photoresist. In the resin- coating method, the resin is coated at a temp. below the room temp. Consequently, the deterioration in the magnetic characteristic due to the compressive stress of the resin is controlled even after the resin is coated on the magnetic body and the magnetic characteristics (e.g., iron loss, coercive force, initial permeability, etc.) before coating can be practically maintained.

Description

[Detailed Description of the Invention] [Technical Field] This invention relates to a magnetic material used as a magnetic core for magnetic heads, transformers, current transformers, etc. [Background Art] Soft materials such as silicon steel plates, ferrite, permalloy, etc. Magnetic materials have high magnetic permeability and are often used, for example, in the magnetic cores of transformers. BACKGROUND ART Magnetic materials have traditionally been coated with resin (usually molded in a mold) using a hardening agent for the purpose of material retention, material protection, and insulation. In this case, a thermosetting resin material is used, and it is known that this coating reduces the basic magnetic properties necessary for a magnetic core, such as decreasing magnetic permeability and increasing iron loss. ing. This phenomenon is particularly noticeable in magnetic materials with large magnetostriction.

Recently, amorphous materials have been attracting attention as soft magnetic materials, but magnetic materials with large magnetostriction such as Fe-based amorphous (e.g. Fe 79B + aS i s) I materials have the above-mentioned magnetic properties. Significant deterioration.

For example, when winding an Fe-based amorphous magnetic ribbon, impregnating and coating it with resin, including the gaps, and cutting it to manufacture cut cores, etc., the magnetic properties of the magnetic material after the resin hardens are different from those before the resin coating. It also deteriorates.

It has been pointed out that the main cause of the deterioration of magnetic properties as described above is the stress generated when the coating resin hardens and contracts. There are two reasons for the generation of this stress.

The first reason is shrinkage stress that occurs when the resin solidifies. Before the resin hardens and solidifies, it is in a liquid state, and only after solidification does it become solid and coat the magnetic material.During this solidification, the volume of the resin shrinks significantly, but the magnetic material The volume of the body hardly changes, and the magnetic body itself ends up receiving compressive stress from the hardened and solidified resin.

The second reason is compressive stress based on the difference in thermal expansion coefficient between the resin and the magnetic material after the resin is cured and solidified. Comparing the coefficient of thermal expansion of the resin after solidification and that of the magnetic material, the coefficient of thermal expansion of the resin is generally larger (the coefficient may differ by one order of magnitude or more depending on the combination). Therefore, when the resin solidifies at a high temperature and then reaches room temperature, the resin contracts more due to the difference in expansion coefficients, and the magnetic material itself ends up receiving compressive stress from the resin. . Therefore, in the case of thermosetting resin, the above two compressive stresses are applied to the magnetic material in an overlapping manner. For example, in grain-oriented silicon steel sheets, iron loss increases, especially as the strength of compressive stress increases.
Magnetostriction increases, making it undesirable as a magnetic core. In order to solve this problem, it is known that using a type of resin that hardens and solidifies in a relatively low temperature range of above room temperature and below about 50° C. has a certain effect. However, depending on the magnetic material and the like to which the resin coating is applied, it is still insufficient for practical use.

[Purpose of the invention]

This invention solves the above-mentioned problems and provides a method for coating a magnetic body with resin, which prevents deterioration of magnetic properties due to compressive stress of the resin even after the magnetic body is coated with resin, and substantially maintains the magnetic properties before coating. The purpose is to

[Disclosure of the invention]

In order to achieve this object, the present invention provides a method for coating a magnetic body with resin, in which at least a part of the magnetic body is coated with a resin material, and is characterized in that the resin coating is carried out at a temperature lower than room temperature. The gist of this paper is a method of coating a magnetic material with resin.

As a result of extensive research including various experiments, this invention has found that if a thermosetting resin that hardens and solidifies in a relatively low temperature range is used, the compressive stress caused by the second reason is eliminated, but the compressive stress caused by the first reason is eliminated. This is based on the discovery that the compressive stress due to the above reasons does not disappear, and the deterioration of magnetic properties becomes extremely small when the coating resin is cured and solidified at a temperature lower than room temperature and then brought to room temperature. This is presumably due to the following reasons.

As mentioned above, the thermal expansion coefficient of the coated resin is considerably larger than that of the magnetic material, so when the temperature drops, the coated resin contracts and compressive stress is generated, but conversely, the temperature rises. In this case, since the elongation of the coated resin is greater, tensile stress is applied to the magnetic material. Therefore, if a resin coating is applied at a temperature lower than room temperature and then allowed to rise to room temperature, the compressive stress generated during resin curing and solidification and the tensile stress accompanying the temperature rise will cancel each other out, resulting in a magnetic material. The compressive stress applied to the
Deterioration of magnetic properties can be prevented. Curing the resin at low temperatures can be easily achieved by using a two-component thermal curable resin or a photoreactive curable resin (for example, an ultraviolet curable resin).

In addition, in this invention, in the case of resin coating, not only the case where the surface of a single magnetic substance is coated with resin,
It is possible to impregnate resin into the voids of a thin plate-shaped magnetic material that is wound or laminated, and then harden only the impregnated portion to maintain the wound or laminated state, or to completely mold the entire magnetic material formed into a coiled wire. It also includes cases where the

In addition, it is placed under a temperature lower than room temperature (because it is necessary, a low-temperature state is usually created by forced cooling means.

Next, we will examine the results of examining changes in various magnetic properties for an example in which a magnetic core made by winding magnetic ribbons of various magnetic materials was coated with resin according to the present invention, and a comparative example in which the resin was coated by a conventional method. It is shown in Table 1.

The resin coating conditions and measurement conditions are as follows [Condition A
) After the resin was coated and solidified at -10°C, the temperature was raised to room temperature and the characteristics were measured. A two-part curable resin was used as the resin. This [condition A] is a condition for implementing the method of this invention.

[Condition B] After the resin was coated and solidified at 20° C., the characteristics were measured in that state. A two-part curable resin was used as the resin. This [condition B] is a condition for implementing the conventional method.

[Condition C] After the resin was coated and solidified at 120°C, it was cooled to room temperature and the characteristics were measured. As the resin, a one-liquid curable resin was used. This [condition C] is a condition for implementing another conventional method.

Note that the resins used are all epoxy-based.

The types of magnetic materials and the types of magnetic properties measured are as follows.

(Type A) Fe-based amorphous (composition Fe79BI63
i,) to calculate the high frequency iron loss (20KH2, 3KGaus
s) was measured.

[Species [B] Fe-based amorphous (composition F'eta13+
commercial frequency iron loss (60H2, 10KG
a u s s) was measured.

[Type C] Fe-Ni amorphous (composition FeaoN
l 3sM Oa B +s) and the coercive force Hc (
(measured with direct current).

(Type D) Co-based amorphous (composition Co=sFes
The initial permeability μi (20K
H2) was measured.

[Type E] Using permalloy, the coercive force Hc (measured with direct current) was measured.

(Left below) As is clear from the results in Table 1, in terms of basic magnetic properties such as iron loss, coercive force, and initial magnetic permeability, the example of condition A according to the method of this invention has the best magnetic properties before and after resin coating. There are few changes.

〔Effect of the invention〕

As described in detail above, the present invention covers all or part of a magnetic material with a resin material at a temperature lower than room temperature. Therefore, when the obtained magnetic material is used, for example, in the magnetic core of a transformer, it is possible to prevent temperature rise than before due to the reduction in iron loss, and to realize a highly efficient transformer.

Agent Patent Attorney Takehiko Rei Matsumoto ``45 Yami Ne Hosho 1 ((0 Shoulder υ 1, Incident Indication Relationship with 1985 Sacrifice Wall No. 035645 Incident Patent Application Colonel Address 1048 Kadoma, Kadoma City, Osaka Prefecture given name
Name (583) Matsushita Electric Works Co., Ltd. Representative #E Warmsmith Sadao Fujii 4, Agent 6, Specification subject to amendment 78 Contents of amendment (1) Deleted "Magnetism" in the second line of page 5 of the specification do.

Claims (8)

[Claims] (1) A resin coating method for a magnetic body in which at least a part of the magnetic body is coated with a resin material, characterized in that the resin coating is carried out at a temperature lower than room temperature. Method. (2) A method for coating a magnetic material with resin according to claim 1, wherein the magnetic material is a magnetic core. (3) A method for coating a magnetic material with resin according to claim 1 or 2, wherein the magnetic core is formed by winding a thin plate of magnetic alloy. (4) A method of coating a magnetic material with resin according to claim 1 or 2, wherein the magnetic core is formed by laminating thin plates of magnetic metal. (5) A method for coating a magnetic body with resin according to any one of claims 1 to 4, wherein the magnetic body is formed of an amorphous magnetic material. (6) A method for coating a magnetic material with resin according to any one of claims 1 to 5, wherein the resin material is a photocurable resin. (7) A method for coating a magnetic material with resin according to any one of claims 1 to 6, wherein the low-temperature state is created by forced cooling means. (8) Claim 1 in which the low temperature is a low temperature of 0°C or lower
A method for coating a magnetic material with a resin according to any one of Items 1 to 7.