JPH02125404A - Magnetic core and manufacture thereof - Google Patents

Abstract

PURPOSE:To eliminate waste of material, to obviate the damage of a molded form in manufacturing steps, and to obtain a magnetic core having a low cost and an accurate recess by integrally molding an auxiliary molded form capable of dissolving or baking to be lost and magnetic powder, and baking it. CONSTITUTION:Auxiliary molded form 4 corresponding to an arbitrary shape to be formed, made, for example, of wax, etc., due to substance capable of baking to be lost by baking or substance capable of dissolving to be lost with solvent is molded previously. Then, a columnar punch 3 is inserted into the through hole of a die and filled with magnetic powder R is filled, a lower punch 3 is punched down, the form 4 is inserted, the punch 3 is further moved down and filled with the powder R, an upper punch 2 is moved down to be inserted into the hole of the die 1; and material are integrally molded by the pressures of the punches 2, 3. When the thus molded form is heated to 150 deg.C, wax is melted out. It is further baked at 1200 deg.C to obtain the drum core of ferrite magnetic material.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetic core and a method for manufacturing the same.

[Prior Art] A typical manufacturing method conventionally used to manufacture magnetic cores, such as ferrite drum cores (Fig. 4), is shown in Figs. 2a to 2a.
The explanation will be as follows based on FIGS. 2C and 3.

First, a magnetic powder raw material R containing ferric oxide as a main component and containing nickel, cobalt, etc., and a mold M consisting of a die 1, an upper bunch 2, and a lower bunch 3 are prepared. Figure 2a shows a state in which the lower bunch 3 is inserted into the lower side of the through hole of the die 1, and the powder filling space formed by the upper surface of the lower bunch 3 and the through hole of the die 1 is filled with the magnetic powder raw material R. show. 2nd b
The figure shows that the upper punch 2 is then lowered and inserted into the through hole of the die 1, and the upper punch 2 and lower punch 3 are used to R
The state in which the molded body R' is formed by applying pressure is shown.

Next, in FIG. 2C, the upper punch 2 rises, the upper surface of the lower bunch 3 rises to the upper surface of the die 1, and a columnar molded body R' is formed.
It shows the state in which the is pushed upward from the through hole of the die 1. In this manner, a columnar molded body R' is obtained according to the procedure shown in FIGS. 2a to 2C.

After obtaining the columnar molded body R' as above, a circumferential band-shaped recess is formed in the center of the circumferential surface.

Thus, for example, the diameter of the upper and lower flanges is 17.5 mm and the thickness is 1.75 mm, as shown in FIGS. 4 and 5.
m+e, the diameter of the central winding core a is 7.0*os, and the width of the winding groove C of the winding core is 14. After forming a ferrite drum core molded body R' of hm by cutting, the drum core is manufactured by firing.

[Problems to be Solved by the Invention] In the above-mentioned conventional method, the molded body obtained by press-molding the raw material powder and the organic binder is cut by, for example, a cutting machine to form the concave portion. The processed material is discarded as cutting waste.

As mentioned above, ferrite materials contain relatively expensive raw material powders such as nickel and cobalt, and as compacts become larger, more materials are cut and discarded, making them expensive. Apart from this, there is a need to reduce the size of the drum core, such as cutting the thickness of the flange to 0.3 degrees or less, or reducing the winding groove in the winding core. When it is necessary to cut the width of C to 0.4 mm or less, a large stress is applied locally to the press-formed body during cutting, and the molded body is easily damaged, causing damage to the flange and winding core. The probability of damage increases,
There was a problem in that the yield of molded products with thin flanges and narrow grooves was poor.

An object of the present invention is to provide a magnetic core and a method for manufacturing the same that can solve the above problems by integrally molding and firing an auxiliary molded body that can be melted or burned away and magnetic powder. .

[Means for Solving the Problems] The gist of the means for solving the problems is, firstly, by forming a recess of an arbitrary shape on the surface of an object, which is integrally molded and fired with an auxiliary molded body that can be melted or burned away. The second aspect of the invention is to provide a magnetic core having at least a part thereof, and secondly, a material that can be burned out by firing.
Alternatively, an auxiliary molded body of any shape made of a substance that can be dissolved (dissolved and removed) by solvent treatment is combined with a part of the molded body to form a compacted powder body, and the molded body is treated with a solvent to dissolve it. After removing the possible parts, the parts are fired or fired immediately to burn out the auxiliary molded body and fired at the same time to obtain a sintered magnetic core having a recessed part of any desired shape. The purpose is to provide a method.

[Function] In the molding space of the die, an auxiliary molded body of any desired shape made of a substance that can be burnt out by firing or a substance that can be dissolved by solvent treatment is placed in the desired concave part of the product. After the raw material powder is arranged in a corresponding manner, the molding space of the die is filled with pressure molding, and then the molded body is immersed in, for example, an organic solvent to melt away the auxiliary molded body, and then fired. When the auxiliary compact is a material that can be burned out by firing, the compact is fired as it is to obtain a sintered compact, so there is no waste of material powder, and there is no need to mechanically process the compact. Since there is no need to perform sintering, it is now possible to create a sintered body that has four fine parts precisely in the desired shape without damaging the brittle compacted compact.

[Example-1] An example of the present invention will be described with reference to FIGS. 1a to 1d. First, the diameter is 17. ioam, inner diameter 7.0mm, thickness 1
Pre-shape the wax into a shape of 4.0m+*. Next, as shown in FIG. 1a, the columnar lower punch 3 is inserted into the through hole of the die 1 and filled with magnetic powder R, and then the lower punch 3 is pulled down as shown in FIG. 1b to form the wax auxiliary molded body 4. 1C, lower the lower punch 3 to fill it with magnetic powder R, lower the upper punch 2 as shown in Figure 1D, insert it into the through hole of the die 1, and then lower the upper punch 3 as shown in Figure 1D. It was pressurized with the lower punch 3 and molded into one piece.

The molded body thus formed had an outer diameter of 17.5 m.
, a columnar body with a height of 17.5++*, and a wax thickness of 1
4.0 mm, and its inner diameter was 7.0+n. When this molded body is heated at a temperature of 150°C, the wax melts and
It was further fired at a temperature of 1200°C to obtain a drum core of ferrite magnetic material. The diameter of the drum core is 15.0m
+*, the height is 15.0mm, and the flange thickness is
It was 1.5 m+i, and the diameter of the winding core was 6.0 fins.

[Example-2] Example-1 except that a resin (PVA) was used instead of the wax auxiliary molded body, and the integrally molded body was fired as it was at a temperature of 1200°C. -1
A magnetic core having a similar shape and size was obtained in the same manner as described above.

[Example 3] In Example 1, the binder of the raw material powder was replaced with PVA and Metroose was used, the wax auxiliary molded body was replaced with boric acid, and these were integrally molded. Thereafter, a drum core having the same shape and size was obtained in the same manner as in Example 1, except that the core was immersed in water, the portion formed with boric acid was removed, and then fired.

[Example-4] Outer diameter 1.72+n, inner diameter 0.57+a as auxiliary molded body
The procedure was the same as in Example-1, except that a ring with a diameter of 0.8 mm and a thickness of 0.8 mm was formed, and a columnar molded body with an outer diameter of 1.72 mm and a height of 1.72 mm was formed and fired. A drum core with a diameter of 1.5+n1, a height of 1.5+nm, a flange thickness of 0.4 mm, and a core diameter of 0.51 mm was manufactured.

In the above embodiments, a drum core was explained as an example, but the technical scope of the present invention should not be limited thereto. Needless to say, it can be widely applied to forming compacted magnetic cores.

[Effects of the Invention] According to the present invention, instead of subjecting a brittle molded body to mechanical processing such as cutting, it can be heated or immersed in a solvent and then fired, or simply fired as it is, thereby forming a molded body having four parts such as grooves. Since the molded body can be processed, there is no waste of material and there is no chance of the molded body being damaged during the manufacturing process. In addition, it becomes easier to process grooves, etc., which are impossible with mechanical cutting, and this greatly contributes to the manufacturing technology of magnetic cores with inexpensive and highly accurate recesses.

[Brief explanation of the drawing]

Figures 1a to 1d show that according to the method of the present invention, an auxiliary molded body that can be burnt out is first formed, and then a magnetic powder molding mold is filled, and this is integrally molded with magnetic powder to embed the auxiliary molded body. FIG. 4 is a schematic cross-sectional view showing the state of forming a compacted powder body in each step. FIGS. 2a to 2c are schematic cross-sectional views showing each step of forming a green compact of magnetic powder by a conventional method. Figure 3 shows how the magnetic powder molded product formed by the method shown in Figures 2a to 2C is processed using a grindstone such as a centerless grinder to create a recess in the center of the cylindrical wall of the sintered molded product. FIG. FIG. 4 is a perspective view of the four-part molded article shown in FIG. 3 which has been ground using the conventional method. FIG. 5 is a sectional view of the molded body shown in FIG. 4. 6 to 8 are perspective views of three other examples of sintered parts with recesses that can be produced by the method of the invention. FIG. 9 and FIG. 1O are cross-sectional views of two further examples of sintered parts having recesses that can be manufactured by the method of the present invention. The symbols in the figure represent the following, respectively. 1... Dice 2... Upper bunch 3...
・Lower punch 4...Auxiliary compact 5...Whetstone R...Magnetic powder R'...Magnetic powder compact

Claims (4)

[Claims] (1) A magnetic core characterized in that it is a fired molded body having a concave portion of an arbitrary shape on at least a portion of the object surface. (2) The magnetic core according to claim 1, wherein the width of the recessed portion is smaller than 0.3 mm. (3) The magnetic core according to claim 1 or 2, which is not mechanically processed before or after firing. (4) Molding an auxiliary molded body of any shape made of a substance that can be completely removed by heating or solvent treatment, embedding it inside the molded body so that it fills the desired recess, and combining it with the auxiliary molded body. Forming an integrated powder compact,
The compacted compact is heated or treated with a solvent to remove the auxiliary compact and then fired, or the compact is fired as it is without heating or solvent treated to burn out the auxiliary compact and at the same time. A method of manufacturing a magnetic core, which consists of firing.