JP2000150282A - Core for chip coil and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily remove burrs by barrel finishing by forming a flank continuously entering the surface of a wound core toward the flange side by a specified length, and extended outward from the wound core in both directions perpendicular to the axis of the wound core. SOLUTION: A flank 21 is formed on a core 1 which flank continuously enters the surface of a wound core 2 toward the flange 3 side by a specified length and is extended in both directions perpendicular to the axis of the wound core 2. During press molding, burrs 81 and burrs 82 are formed on the wound core 2 and the flank 21, respectively, in the gap between a stamping die and a cavity die. A plurality of molded or sintered cores 1 are fed into a barrel and subjected to barrel finishing. At this time, the burrs 81 are completely protruded from the ridge of the core 1 to both ends in the direction of the length of the wound core 2 due to the presence of the flank 21, and other cores and abrasives are apt to collide with the burrs 81. Though the other burrs 82 may be sometimes left unremoved, they do not damage the covering layer of coil wires because of their relative positions. As a result, barrel finishing is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core for a chip-shaped coil comprising a core part around which a coil is wound and a pair of flange parts integrally formed at both ends of the core part, and a method of manufacturing the same. About.

[0002]

2. Description of the Related Art As a conventional core of this type and a method of manufacturing the same, for example, Japanese Patent Application Laid-Open No. 7-183126 discloses a core formed by winding a coil and one end integrally formed at both ends of the core. A chip-shaped coil core comprising a pair of flange portions, wherein a magnetic material powder filled in a die mold forming a substantially H-shaped concave portion is formed by pressing a flange with a press die forming a core portion. 2. Description of the Related Art There has been known a method in which press molding is performed integrally with a press die to be formed.

However, when the core is manufactured by press molding as described above, the magnetic material powder enters into the gap formed between the die mold and the press mold for molding the core, and the magnetic material powder extends along the axial direction of the core. Thin and sharp burrs are formed. Such burrs damage the coating layer of the coil wire when the coil wire is wound around the core, thereby reducing the reliability of the completed chip coil. Then, for example, Japanese Patent Application Laid-Open No. 9-27031
Japanese Patent Application Laid-Open No. 6-204, discloses a method of manufacturing a core in which a core formed by pressing and firing is subjected to barrel polishing to remove burrs.

[0004]

In the method of removing burrs formed on the core by barrel polishing, when burrs are removed by colliding cores in the barrel, the burrs are formed at the center of the core. Although the burrs formed can be removed, burrs formed over both ends of the core portion over the core portion and the flange portion are difficult to remove because other cores cannot enter the burrs.
If the abrasive having a smaller particle diameter than the core is put into the barrel together with the core and polished, the abrasive can reach the burrs formed over the core and the flange, but the burrs are formed due to the small particle diameter. Since the removing force is small, it is also difficult to completely remove burrs.

[0005] In view of the above problems, an object of the present invention is to provide a core capable of easily removing burrs which may damage a coil wire by barrel polishing, and a method of manufacturing the core.

[0006]

In order to solve the above-mentioned problems, a core for a chip-shaped coil according to the present invention comprises a core part around which a coil is wound and one end integrally formed at both ends of the core part. A chip-shaped coil core comprising a pair of flanges,
The core material powder filled in a die mold that forms a U-shaped recess, formed by press molding with a press mold that forms a core and a press mold that forms a flange,
A flank is formed continuously on the surface of the core portion to enter a predetermined length on the flange portion side and extends outward from the core portion toward both sides in a direction perpendicular to the axis of the core portion. .

[0007] A method of manufacturing a chip-shaped coil core is characterized in that the chip-shaped coil core includes a core portion around which the coil is wound and a pair of flange portions integrally formed at both ends of the core portion. Wherein a core material powder filled in a die mold for forming a substantially H-shaped recess is simultaneously formed in a press mold for forming a core portion and a press mold for forming a flange portion. In the press molding method, a press die for forming a core portion is formed into a predetermined length on the flange portion side continuously to the surface of the core portion, and is wound toward both sides in a direction perpendicular to the axis of the core portion. Providing a bulging portion that forms a flank that extends outward from the core, removing the core press-molded by the press die from the die, and removing at least burrs formed on the core by barrel polishing. It is characterized by.

In the conventional core, burrs are formed over the winding core and the flange, so that the burrs have high strength and are difficult to remove. However, when the above-mentioned flank is formed, the burrs generated by the core material powder entering the gap between the die mold and the press mold for press-molding the core are continuously formed from the core to the flank. It is formed. At that time, the burr formed on the core part is completely projected on the ridge line of the core to both ends in the longitudinal direction of the core part due to the presence of the flank. Therefore, when barrel polishing is performed, other cores or abrasives are likely to collide with burrs on the core, and burrs are easily removed. Further, even when an abrasive having a small particle diameter is mixed, burrs are easily removed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, reference numeral 1 denotes a core according to the present invention.
And a pair of flanges 3 integrally formed at both ends of the front end. The core is press-formed from a core material powder obtained by kneading and granulating a ceramic powder such as ferrite, alumina, or mullite and an appropriate binder, and then barrel-polished, and fired as necessary in a pre-process or a post-process of the barrel polishing. It is formed by doing. The overall length L of the core 1 is 1.85 mm, and the thickness D of the flange 3 is 0.475.
mm. The core 1 has a predetermined length (approximately 0.2 mm) continuous with the surface of the core portion 2 on the side of the flange portion 3, and the core extends toward both sides in a direction perpendicular to the axis of the core portion 2. The flank 21 is formed to extend outwardly by about 0.2 mm from the portion 2. In addition, a concave portion 31 to which the end 41 of the coil wire 4 is fixed is formed in at least one position on the peripheral surface of each flange portion 3. Silver, silver-platinum or copper is deposited on the peripheral surface of each flange 3 by plating or dipping, and furthermore, lead-
An external electrode conductive coating made of tin or the like is applied. Also,
The coil wire 4 is formed by covering a conductive wire having a wire diameter of about 50 to 100 μm with a coating layer formed of an insulator such as polyurethane or polyamide imide. Both ends 41 of the coil wire 4 are welded, thermocompressed, or ultrasonically welded to the concave portion 31 covered with the conductive film for external electrodes while being deformed flat. Thereafter, the coil wire 4 is covered with a resin in which a core material powder or the like is kneaded, and the resin portion is further covered with an exterior material to complete a chip-shaped coil.

As shown in FIGS. 3 and 4, the core 1 having the above-mentioned shape is substantially H-shaped and formed on a die 5 along a vertical direction.
Pressing dies 6 and 7 are inserted into the V-shaped mold hole 51 from above and below, and a core material powder obtained by kneading and granulating a ceramic powder such as ferrite powder and a binder is pressed into a pressing mold 6.7.
And press formed from above and below. Since the thickness in the pressing direction is greatly different between the core part 2 and the flange part 3, the amount of movement in the pressing direction between the press die 6 for press-forming the flange part 3 and the press die 7 for press-forming the core part 2 And the pressing force are set separately. On both ends of the press die 7, bulging portions 71 for forming the flank 21 are formed. In this way, the temporary molded product press-formed from the vertical direction by the two press dies 6 and 7 is taken out from the mold hole 51.

As shown in FIG. 5, a core 1 obtained by press molding according to the above configuration has a die 5
The kneaded core material powder enters into the gap formed between the core material and the press dies 6 and 7, and burrs 8.8a are generated. In particular, the burr 8 generated by the gap between the press die 7 and the die 5 includes a burr portion 81 formed on the core 2 and a burr portion 82 formed on the flank 21. When the coil wire 4 is wound around the core 2 as it is, the coating layer of the coil wire 4 is damaged by the burr portion 81. Therefore, in order to remove burrs, a large number of cores 1 after molding or firing are put into a barrel and barrel-polished. The cores 1 collide with each other in the barrel, and the burrs 8a protruding outward are immediately broken off and removed. Also, of the burrs 8 generated from the core 2 to the flank 21, the burrs 81 formed on the core 2
Is in a state of projecting completely on the ridge line of the core 1 to both ends in the length direction of the core 2 due to the presence of the flank 21. Therefore, other cores and abrasives easily collide with the burr portion 81,
Further, even if the number of times is small, if another core collides, the core is easily cut off. After the barrel polishing is completed, the burrs 8a and the burrs 81 are completely removed as shown in FIG.
The burr portion 82 is recessed, and the flank 21 and the flange portion 3
, And cannot be completely removed due to the high strength, and may remain as shown in the figure. However, since the burr portion 82 is substantially parallel to the winding direction of the coil wire 4 and is formed at the same position as the inner surface of the flange portion 3, the burr portion is formed when the coil wire 4 is wound around the core 2. There is no possibility that the coating 82 damages the coating layer of the coil wire 4.

By the way, as shown in FIG.
May be inclined so that the space above the flank 21 expands as the space away from the flank 21 increases. When the rising surface 21a is inclined in this manner, when the core 1 is barrel-polished using the abrasive, the abrasive is easily guided to the flank 21 by the rising surface 21a. Therefore, the chance of the abrasive colliding with the burrs of the winding core 2 is increased, and the burrs are easily removed.

[0013]

As is apparent from the above description, according to the present invention, the core formed by press-molding the core material powder has burrs that damage the coating of the coil wire wound around the core. The burr can be easily removed by barrel polishing.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a plan view showing a state where a coil wire is wound around a core;

FIG. 3 is a cross-sectional view illustrating a press forming step.

FIG. 4 is a sectional view taken along line IV-IV.

FIG. 5 is a partially enlarged view showing a state of burrs before barrel polishing.

FIG. 6 is a partially enlarged view showing a state of burrs after barrel polishing.

FIG. 7 is a perspective view showing the configuration of another embodiment of the core.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 (For chip-shaped coil) Core 2 Core part 3 Flange part 4 Coil wire 5 Die die 6 (For flange part) Press die 7 (For core part) Press die 8 Burr 21 Relief surface 71 Swelling part

Claims (2)

[Claims] 1. A chip-shaped coil core comprising a core portion around which a coil is wound and a pair of flange portions integrally formed at both ends of the core portion, wherein a substantially H-shaped concave portion is provided. The core material powder filled in a die mold is formed by press molding with a press mold for forming a core portion and a press mold for forming a flange portion. A flank extending a predetermined length into the flange portion side continuously from the core portion and extending outward from the core portion toward both sides in a direction perpendicular to the axis of the core portion. . 2. A method for manufacturing a chip-shaped coil core comprising a core part around which a coil is wound and a pair of flange parts integrally formed at both ends of the core part, the method comprising: In a method of simultaneously press-molding a core material powder filled in a die mold for forming a U-shaped concave portion with a press mold for forming a core portion and a press mold for forming a flange portion, The press die to be formed has a flank that extends a predetermined length into the flange side continuously to the surface of the core and extends outward from the core toward both sides at right angles to the axis of the core. After removing the core press-molded with the press mold from the die mold, the chip-shaped coil core is characterized in that at least burrs formed on the core portion are removed by barrel polishing. Production method.