JP3419337B2 - Method of firing magnetic core - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of firing a magnetic core, and more particularly, to a method of firing a flat ring-shaped magnetic core used as a core of a noise removing component or the like. About. 2. Description of the Related Art A flat ring-shaped magnetic core 21 as shown in FIG. 5 is known as a core of a noise removing component or the like. The magnetic core 21 removes high-frequency noise propagating through the signal line by inserting a signal line such as a flat cable into the flat through hole 22. The magnetic core 21
The long side dimension L of the cross section is 10 to 100 mm, the short side dimension T is 1 to 10 mm, and the short side dimension t of the through hole 22 is 0.3 to 0.3 mm.
Those having dimensions in the range of 8 mm are often used. As a method for sintering the magnetic core 21, for example, a method as shown in FIG. 5 is generally known. [0005] That is, in the firing method shown in FIG. 5, a flat ring-shaped molded body 21 made of a ferrite material having a flat through hole 22 is opened at one end so that the axial direction of the through hole 22 is vertical. This is a method in which the surface is set inside a firing container (not shown) and fired. At this time, the flat ring-shaped molded bodies 21 are arranged so as to be separated from each other, and are designed so that the adjacent flat ring-shaped molded bodies 21 do not stick to each other during firing. This is because if the formed bodies 21 stick together, a chemical reaction occurs between them, and defects such as chipping or cracking occur when the bonded formed body 21 is removed by applying a mechanical impact force. [0004] In the conventional method of firing a magnetic core, when the size of the molded body 21 is large, the molded body 21 is set up vertically in a firing container at a distance. The work was relatively easy. Further, even when a slight vibration or impact is applied, the flat ring-shaped molded body 21 does not tilt, and problems such as the adjacent flat ring-shaped molded bodies 21 sticking to each other during firing are unlikely to occur. However, in recent years, due to the thinning and miniaturization of the magnetic core, firing of the small-sized flat ring-shaped molded body 21 in a state of being vertically erected is increasing. In this case, there is a problem that the work of vertically standing the small flat ring-shaped molded bodies 21 with a small size apart from each other is complicated and troublesome. Also, if the size of the flat ring-shaped molded body 21 is small, even if a slight vibration is applied, the flat ring-shaped molded body 21 is inclined and comes into contact with the adjacent flat ring-shaped molded body 21 to cause a chemical reaction between them. There is a problem that sticking or chipping occurs, cracks and the like that are difficult to detect from the appearance occur, and the yield rate decreases and product reliability decreases. An object of the present invention is to provide a method for firing a magnetic core which can be fired with high reliability and which is excellent in mass productivity. [0007] In order to achieve the above object, a method for firing a magnetic core according to the present invention comprises the steps of: providing a surface of a plurality of flat ring-shaped molded bodies made of a magnetic material;
A powder made of an organic material including one having a diameter of 1000 μm or less is applied , and the plurality of flat ring-shaped molded bodies are brought close to each other such that the axial direction of the flat through-holes of the flat ring-shaped molded body is vertical. after aligning, with firing the flat ring-shaped molded product while interposing the powder between flat ring-shaped molded bodies adjacent to each other, the powder by the sintering
The organic materials that make up the body are vaporized . According to the above method, the powder applied to the surface of the flat ring-shaped molded product functions as a spacer by being interposed between adjacent flat ring-shaped molded products. Therefore,
The flat ring-shaped moldings can be stacked and set, which facilitates the setting operation. Then, when the flat ring-shaped molded body is fired, the adjacent flat ring-shaped molded bodies do not come into direct contact with each other, and the problem that a reaction occurs between them and sticking or chipping occurs is solved. Embodiments of a method for firing a magnetic core according to the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, a plurality of flat ring-shaped moldings 1 are prepared. The flat ring-shaped molded body 1 is formed by molding magnetic material powder such as ferrite kneaded with a binder or the like into a flat ring shape having flat through holes 2. Each of the flat ring-shaped molded bodies 1 is laid so that the axial direction of the through hole 2 is horizontal. Next, as shown by an arrow A in FIG. 1, the powder is sprinkled evenly over the flat ring-shaped molded body 1. The powder contains particles having a particle size of 1000 μm or less, and is made of an organic material or an inorganic material. As the organic material, a material that evaporates in the firing step is preferable, and specifically, a polyvinyl alcohol-based or cellulose-based synthetic resin material, or a natural organic material such as flour or potato starch is used. As the inorganic material, a material that does not chemically react with the flat ring-shaped molded body 1 in the firing step is preferable, and specifically, alumina, zirconia, or the like is used. If the particle size of the powder exceeds 1000 μm, the powder and the flat ring-shaped molded product 1 become less compatible with each other. Easily fall off the surface of the flat ring-shaped molded body 1,
The workability of setting the flat ring-shaped molded body 1 is reduced. However, for powder having a particle size exceeding 1000 μm, 10
By mixing those having a particle size of not more than 00 μm, the above-mentioned decrease in workability is improved. On the other hand, powder having a particle size of 20 μm or less has a slightly inferior function as a spacer for preventing the flat ring-shaped molded product 1 from sticking to each other, but has a light mechanical impact on the flat ring-shaped molded product 1 attached to each other. By giving
It can be easily separated. Next, as shown in FIG. 2, the powder is sprinkled and the flat ring-shaped compact 1 having the powder adhered to the surface is formed.
Are stacked in a fixed number with their axial directions aligned horizontally.
Powder is interposed between the flat ring-shaped molded bodies 1 in the stacked state. Thereafter, as shown in FIG. 3, the flat ring-shaped compacts 1 are maintained in a stacked state, and the respective axes are oriented vertically, so that inorganic powder that does not chemically react with the flat ring-shaped compacts 1 (for example, high purity (Alumina powder or zirconia powder) are arranged and arranged inside a firing container (not shown). Depending on the shape of the flat ring-shaped molded body 1 and the material of the firing container, it may not be necessary to spread the inorganic powder in the firing container. Thereafter, as shown in FIG. 4, a bar 3 of high-purity alumina or zirconia is attached to the side surface of the flat ring-shaped molded body 1 so as to prevent the flat ring-shaped molded body 1 standing upright from falling down. The flat ring-shaped molded body 1 set in this way is fired in a firing furnace. Thus, a magnetic core obtained by firing the flat ring-shaped molded body 1 is obtained. The powder applied to the surface of the flat ring-shaped molded product 1 by the above firing method functions as a spacer by being interposed between the adjacent flat ring-shaped molded products 1.
Therefore, the flat ring-shaped molded bodies 1 can be stacked and set, and the setting operation becomes easy. And
When the flat ring-shaped molded product 1 is fired, the adjacent flat ring-shaped molded products 1 do not come into direct contact with each other, and a problem that a reaction occurs between them and sticking or chipping occurs can be solved. . It should be noted that the present invention is not limited to the above-described embodiment, and may have various configurations within the scope of the present invention. For example, in the above embodiment, the powder is sprinkled on the flat ring-shaped compact, but the powder may be forcibly adhered to the flat ring-shaped compact by spraying or the like. EXAMPLE Long dimension L = 22.8 mm, short dimension T =
It has an outer dimension of 2.8 mm, length = 12.0 mm, and the long side dimension of the through hole 2 = 18.7 mm, the short side dimension t =
A 0.7 mm flat ring-shaped molded product 1 (see FIG. 1) was prepared. The flat ring-shaped molded body 1 is made of a NiZn-based ferrite material. Various powders shown in Table 1 below were prepared as powders. Then, after laying the flat ring-shaped molded body 1 so that the axial direction of the through hole 2 is horizontal,
Each powder shown in Table 1 from above was placed in a net container and sprinkled evenly. Next, the flat ring-shaped molded product 1 is interposed with the sprinkled powder so that each axial direction is vertical.
Piled up. After that, the flat ring-shaped molded product 1 is placed in a firing container covered with zirconia powder for 32 rows per line.
The pieces were arranged in five rows, and a bar 3 made of zirconia was attached. In this way, 30 samples (4800 flat ring-shaped molded bodies 1) of firing containers in each of which the flat ring-shaped molded bodies 1 were set were prepared and fired in an electric furnace at 1000 to 1200 ° C. Table 1 shows the evaluation results of the sticking occurrence rate and the defective rate of the magnetic core after firing (Examples 1 to 8). For comparison, Table 1 also shows the evaluation results of the magnetic cores fired by the conventional firing method (Comparative Example). [Table 1] In Table 1, when the calcined product was prepared using the cellulosic powder of Example 3, and the average particle size of Example 8 was 40 μm.
When baking was performed using high-purity alumina powder of m, the magnetic cores of 15% and 14% respectively adhered to each other. However, in both cases, when a light mechanical shock is applied to the attached magnetic cores, the magnetic cores can be easily separated, the quality thereof has reached a passing level, and the defect rate is 0%.
%Met. As is clear from the above description, according to the present invention, the powder applied to the surface of the flat ring-shaped compact is interposed between the adjacent flat ring-shaped compacts. To function as a spacer. Therefore, the flat ring-shaped molded bodies can be stacked and set, and the setting operation becomes easy. Then, when the flat ring-shaped molded body is fired, the adjacent flat ring-shaped molded bodies do not come into direct contact with each other, and a reaction between them or a problem of sticking or chipping can be solved. . As a result, not only can the magnetic core be fired efficiently with high reliability, but also the yield rate can be significantly improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing one embodiment of a method for firing a magnetic core according to the present invention. FIG. 2 is a perspective view showing a step following the step shown in FIG. 1; FIG. 3 is an explanatory view showing a step following FIG. 2; FIG. 4 is an exemplary perspective view showing a step following FIG. 3; FIG. 5 is a perspective view showing a conventional method for firing a magnetic core. [Description of Signs] 1 ... Flat ring-shaped molded body 2 ... Flat through hole 3 ... Bar

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-145101 (JP, A) JP-A-3-199168 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 41/02

Claims (1)

(57) [Claims 1] The surface of a plurality of flat ring-shaped molded bodies made of a magnetic material includes those having a particle diameter of 1000 μm or less.
A powder made of an organic material is applied, and a plurality of the flat ring-shaped molded bodies are arranged close to each other so that the axial direction of the flat through-holes of the flat ring-shaped molded body is vertical, and then adjacent to each other. While firing the flat ring-shaped molded body with the powder interposed between the flat ring-shaped molded bodies ,
A method for sintering a magnetic core, wherein the organic material constituting the powder is vaporized by the sintering.