JPH05175065A - Manufacture of soft ferrite - Google Patents

Abstract

PURPOSE:To prevent that a soft ferrite core which has been stacked on the uppermost stage is deteriorated in its baking operation by a method wherein a ceramic sheet is placed on the uppermost surface of a soft ferrite molded body. CONSTITUTION:A zirconia sheet 3 is placid on a molded body 1; this assembly is baked. Thereby, the magnetic characteristic of an upper-stage core is improved. The obtained magnetic characteristic depends on the material of a ceramic which is placed at the upper part. However, when especially zirconia is used, its level which is not different at all from that of a lower-stage core is obtained. Consequently, a soft ferrite can be baked without deteriorating the magnetic property of a baked ferrite core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a soft ferrite, which is used as a soft magnetic material for high frequencies, and which contains, as one constituent, zinc such as Mn-Zn and Ni-Zn.

[0002]

2. Description of the Prior Art Soft ferrites such as Mn-Zn and Ni-Zn are generally formed by mixing raw material oxides, calcination, pulverization and granulation, molding them into a desired shape and finally heating them at a high temperature. It is manufactured by firing under appropriate temperature and atmospheric conditions. Firing is generally performed in a pusher-type continuous furnace, but in order to increase the firing efficiency, it is often the case that ferrite molded bodies are stacked on a ceramic plate in multiple stages and fired. .

[0003]

However, of the ferrite cores stacked and fired in a plurality of stages, the uppermost core in particular has a problem in that the magnetic characteristics are significantly inferior to those of the lower cores. there were. Therefore, when it is required to strictly control the material variation of the fired product within a narrow range, the ferrite core loaded on the uppermost stage may even cause a decrease in yield.

The present invention is intended to solve the above-mentioned problems, and proposes a method for producing soft ferrite in which deterioration of the soft ferrite core loaded on the uppermost stage during firing is prevented.

[0005]

According to the present invention, when a soft ferrite molded body is stacked on a ceramic plate in one or a plurality of stages and fired, a ceramic plate is placed on the uppermost surface of the molded body. In the method for producing soft ferrite, which is characterized in that it is placed, a zirconia-based ceramic plate is desirable as the ceramic plate to be placed on the uppermost surface of the molded body.

[0006]

As a result of various studies on the above problems, the inventors of the present invention place a ceramic plate on the upper surface of the uppermost loading core of the soft ferrite moldings loaded in a plurality of steps and fire it. By doing so, it was found that the magnetic properties of the fired core can be made equal to those of the core below it. The present invention can be applied to a high magnetic permeability material in which initial magnetic permeability is important and a low loss material in which iron loss value is important.

Further, the effect is large or small depending on the material of the ceramic to be placed, and zirconia-based ceramics are preferable, but the material is not particularly limited. The reason why the above effect is obtained is not entirely clear at this time, but the diffusion of Zn into the atmosphere during firing is suppressed, or the cooling rate of the core top surface is relaxed during cooling after firing. Finally, it is conceivable to reduce residual stress remaining in the core.

As is apparent from the above, the application of the present invention is not limited to the case where a plurality of ferrite molded bodies are stacked, but is also effective when a single stage is stacked. The effects obtained by applying the present invention will be specifically described below with reference to examples.

[0009]

【Example】

Fe ₂ O ₃ as Example 1 final composition: 52.3 mol%, MnO: 36.1 mol%, ZnO: blending SiO _2, CaO, and Nb ₂ O ₅ and TiO ₂ as an additive to the raw material of 11.6 mol% and made basic composition The material was then processed in the usual manner to form a toroidal core with an outer diameter of 36 mm.

When these molded bodies are stacked and fired in two stages, firing is carried out by a normal method in which nothing is placed on the molded body as shown in FIG. 1 and as shown in FIG. The characteristics of the sintered body were measured and compared when the zirconia plate and the alumina plate were placed on the top and fired. About the obtained fired core, 100kHz, 200mT, 100
Table 1 shows the results of measuring the iron loss value at ° C.

As is clear from Table 1, the magnetic properties of the upper core of the present invention are significantly improved in comparison with the comparative example of the conventional method. The obtained magnetic properties depend on the material of the ceramics placed on the upper part, but when zirconia is used, the magnetic properties are at the same level as the lower core.

[0012]

[Table 1]

Example 2 As a final composition, Fe ₂ O ₃ : 53.0 mol%, MnO: 26.9 mol% and ZnO: 20.1 mol% were added to the raw materials of the basic composition, and SiO ₂ , CaO, Nb ₂ O ₅ and The material containing Bi ₂ O ₃ was treated by a method commonly used in the art and molded into a toroidal core having an outer diameter of 36 mm.

When firing these molded bodies, they were fired in the same manner as in Example 1, and the results of measuring the initial magnetic permeability at 100 kHz are shown in Table 2. It can be seen from Table 2 that the improvement effect of the present invention is remarkable also for the high magnetic permeability material. The obtained magnetic characteristics depend on the material of the ceramics placed on the upper part, but when zirconia is used, the magnetic properties are at the same level as the lower core.

[0015]

[Table 2]

Example 3 Table 3 shows the results of treating in exactly the same manner as in Example 2 except that the cells were stacked in one layer. From Table 3, it can be seen that the improving effect of the present invention is remarkable.

[0017]

[Table 3]

[0018]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, when one or more soft ferrite compacts are stacked and fired,
By placing a ceramic plate on the surface of the uppermost core of the molded body, it was possible to fire soft ferrite without causing deterioration of the magnetic properties of the fired ferrite core.

[Brief description of drawings]

FIG. 1 is a view showing a conventional loading state of a floorboard and a toroidal core during firing.

FIG. 2 is a diagram showing a loading state of a floorboard and a toroidal core during firing of the present invention.

[Explanation of symbols]

 1 Ferrite core 2 Setter 3 Plate to be placed on the core

Claims (2)

[Claims] 1. When the soft ferrite molded body is stacked on a ceramic plate in one or more stages and fired, the ceramic plate is placed on the uppermost surface of the molded body. Method for manufacturing soft ferrite. 2. The method for producing soft ferrite according to claim 1, wherein the ceramic plate placed on the uppermost surface of the molded body is zirconia ceramics.