JPH0265107A - Core for inductor and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent burr from being produced and obtain a balun transformer free from imperfect insulation in the insulation coating of a winding by chamfering the edges of the wall of a through hole roundly by barrel polishing when an inductor core is formed by inserting a lead wire into a ferrite core having at least one through hole. CONSTITUTION:An admixture of Ni-Zn ferrite magnetic powder and a binder is packed into a shaping metallic mold to form a shaped body 2 having for example two through holes 1 and sintered. The sintered body is put into an octagonal rotation barrel and rotated while water is added to chamfer the edges of the walls of the through holes 1 roundly. Thereby the coating is not torn even if a covered wire is wound through the holes 1 to make a balun transformer free from imperfect insulation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an inductor core having at least one through hole and a method for manufacturing the same.

(Prior Art) Conventionally, a balun transformer has been used as a transformer for matching a television antenna and a television receiver. As shown in FIG. 6, this balun transformer usually uses a columnar ferrite core b having a pair of through holes a as the core, and a polyurethane-coated parallel conducting wire C is inserted into the through hole a. It is manufactured by winding it around a ferrite core b. In order to prevent the insulating coating of the conductive wire from breaking at the edges of the core b, a mold is used in which the edge forming portion of the molding mold is filled in advance, and the surfaces of the molded body are perpendicular to each other as shown in Figure 6. The edge portion formed by this process is cut at a plane that intersects several planes at an angle of approximately 45 degrees to make the edge angle obtuse.

(Problem to be Solved by the Invention) However, due to the tolerance of the mold, protruding pieces, so-called "bumps", are formed at the edges of the obtuse angle portions of the core.

Therefore, a balun transformer using such a core has a problem in that the insulation coating of the winding is likely to be damaged, resulting in poor insulation.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inductor core and a manufacturing method thereof that solve the above-mentioned problems of balun transformers and other inductors.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the inductor core of the present invention is a ferrite core having at least one through hole, and a conductive wire is inserted through the through hole. An inductor core wound around a ferrite core is characterized in that at least an edge of the through hole of the ferrite core is formed into an arc shape by barrel polishing, It is characterized in that the tip portion of the protrusion formed on the edge and protruding from the end face of the core is formed into an arc shape by barrel polishing. The above-mentioned method for manufacturing an inductor core includes filling a mold with a mixture of ferrite magnetic powder and a binder and applying pressure to form a molded body having at least one through hole, and after firing the molded body, The fired body has a diameter of 1 to 5 of the diameter of the through hole.
It is characterized by barrel polishing using media with twice the diameter, and after filling a mold with a mixture of ferrite magnetic powder and a binder and applying pressure to form a molded body having at least one through hole. , the molded body is barrel-polished using a combustible media having a diameter equal to or smaller than the diameter of the through-hole of the molded body, and then fired.

(Function) At least the edge of the through-hole of the ferrite core or the tip of the protrusion that protrudes from the core end face formed at the edge of the through-hole is formed into an arc shape by barrel polishing, so that it can be inserted into the through-hole. When the conductor wire is wound around a ferrite core, the insulation coating of the conductor wire will not be torn.

The barrel polishing is performed after or before firing the ferrite core molded body.

When polishing after firing, use hard media such as alumina or glass. If the diameter of the media is less than the diameter of the through-hole of the fired body, the effect of polishing the edge of the through-hole will be improved, but the media will clog the through-hole and the conductor will not be able to pass through. If the diameter exceeds 5 times, the edges of the outer peripheral surface of the fired body will be polished faster than the edges of the through-hole, and even if polished until the outer shape of the fired body is damaged, the through-hole will not be polished. The edges of the edges are not polished enough.

When polishing before firing, the molded body is brittle and will easily break if subjected to extreme impact, so avoid using grain flour, coconut shell,
Use soft media such as resin beads.

When the media is in the form of granules or powder, it easily enters the through-hole, and the edge of the through-hole is polished at approximately the same speed as the edge of the outer peripheral surface of the molded body. Media may clog the through holes, but if fired as is, the media will easily burn and disappear, so there is no problem.

If the media is too fine, for example (1. It's about the same size.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

[Example 1] After filling a mold with a mixture of N1-Zn ferrite magnetic powder and a binder and applying pressure to form a molded body 2 having two through holes 1.1 as shown in the first figure, The molded body 2 was fired.

An example of a fired body is length 6.0 and width 3.0. Ommq height
The diameter of the through hole is 0.6 mm.

The fired body and alumina media with a diameter of 2.0 to 2.5 mm (3.3 to 4.2 times the diameter of the through hole) were mixed in a ratio of 1 = 4 and heated in a hexagonal rotating barrel. (inner volume: 1 liter), water was added thereto, and barrel polishing was performed for 20 minutes by rotating at a rotational speed of 29 rpm. As a result, the second
A polished sintered body 2' was obtained as shown in the figure.

When this was observed using a scanning electron microscope, the edges were polished as shown in the third figure.

One end of this fired body 2' is held by an arm 3 whose one end is rotatably supported as shown in the fourth figure, and a polyurethane-covered conductive wire 4 with a diameter of 0.5 mm is passed through one through hole 1. A load 5 of 500 g is applied to the terminal, the arm 3 is rotated 90 degrees to the left from vertically downward, returned to its original position, and then the arm 3 is rotated 90 degrees to the right and returned to the halo, which is defined as a - cycle. This was repeated and the number of times the conductive wire 4 was broken was recorded as a disconnection test.

As a result of conducting a disconnection test on 10 cores, the number of times the conducting wire 4 was disconnected was at least 8 times, and the average was 9.8 times.

Next, a similar disconnection test was conducted with the load too low, and the minimum number of times was 3, and the average number of times was 3.9.

[Example 2] As a molded body, as shown in FIGS. 5(A) and (B),
A protrusion 6 protruding from the end surface of the molded body 2 at the edge of the through hole 1
Barrel polishing was performed under the same conditions as in Example 1 using the same molded body 2 as shown in the first figure except that .

For a load of 500 g, the minimum number of times was 6 times, with an average number of 9.2 times, and for a load of 1000 g, the minimum number of times was 2 times, and the average number of times was 3 times. As can be seen from this disconnection test, the tip of the protrusion 6 is likely to be barrel-polished into an arc shape.

[Example 3] Instead of the alumina media in the order of diameter 2, 0 m+s to 2.5 in Example 1, the diameter was 2.7 mm to 3.0 m.
The procedure was carried out in the same manner as in Example 1, except that alumina media with a diameter of m (4.5 to 5.0 times the diameter of the through hole) was used. As a result, the number of cuts was at least 6 for a load of 500 g. , the average number of times was 7.6.

For a load of 1000 g, the minimum number of times was 2 times, and the average number of times was 3.2 times.

[Example 4] Instead of the alumina media with a diameter of 2.0 to 2.5 mm in Example 1, a media with a diameter of 0.6 to 1.2 mm (1.0 to 2.0 times the diameter of the through hole) was used. ) was carried out in the same manner as in Example 1, except that the alumina media of 500
The number of cuts for a load of g is at least 7 times, and the average number of cuts is 8 times.
．． It was 5 times.

For a load of 1000 g, the minimum number of tests was 2 times, and the average number of tests was 3.4 times.

[Example 5] The molded body 2 shown in the first figure is placed in a vibrating barrel using corn flour as a media and without using water, and the molded body 2 is set at a vibration frequency of 1.
Barrel polishing was performed in the same manner as in Example 1, except that vibration was performed at 50 rpm and an amplitude of 3 m+s, and then firing was performed under the same conditions as in Example 1.

For a load of 500 g, the minimum number of cuts was 9 times, and the average number of cuts was 1000 times, and for a load of 1000 g, the minimum number of cuts was 4 times, and the average number of cuts was 4.3 times.

[Comparative Example 1] Instead of the alumina media with a diameter of 2.0+++n to 2.5 mm in Example 1, media with a diameter of 3.5 mm to 2.5 mm were used.
The same procedure as in Example 1 was performed except that alumina media with a diameter of 4.0 mm (5.8 to 6.7 times the diameter of the through hole) was used. As a result, the number of cuts was at least 3 for a load of 500 g. , the average number of times was 5.1.

For a load of 1000 fr, the minimum number of times was 1, and the average number of times was 1.1.

[Comparative Example 2] Instead of the alumina media with a diameter of 2.0 to 2.5 mm+ in Example 1, alumina media with a diameter of 0.2 to 0.5 +++ m was used.
The procedure was carried out in the same manner as in Example 1, except that alumina media (0.3 to 0.8 times the diameter of the through hole) was used.
Out of 1000 cores subjected to barrel polishing, the through holes of 31 cores were clogged with media, and the conductor could not be passed through.

However, the number of cuts is at least 6 times for a load of 500g.
The average number of times was 7.9. For a load of 1000 g, the minimum number of times was 2 times and the average number of times was 3.7 times.

[Conventional Example] The same procedure as in Example 1 was carried out except that the wire was wound without barrel polishing. As a result, the number of cuts was at least 3 for a load of 500 g, and the average number of cuts was 5.2. Ta.

For a load of 1000 g, the minimum number of tests was once, and the average number of tests was 1.2 times.

The table shows the results of the disconnection test for the example described above.

However, 0 in the table is the minimum number of times during measurement.

(Effects of the Invention) Since the present invention has the above-described configuration, it has the following effects.

According to the core for an inductor according to the first and second aspects of the present invention, poor insulation of the conductive wire wound around the core is significantly improved compared to the conventional core.

According to the method for manufacturing an inductor core according to claims 3 and 4, the through hole of the core is not clogged with media and the conducting wire cannot be passed through the through hole, and the outer shape of the core is not damaged. The edge of the end edge of the through-hole of the core or the tip portion of the protrusion that projects from the core end face formed on the end edge can be polished without polishing.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a molded inductor core, Fig. 2 is a sectional view of an example of the inductor core of the present invention, Fig. 3 is an enlarged view of its edge, and Fig. 4 is a conductor wire breakage test. 5(A) and (B) are cross-sectional views of the molded body used in the inductor core of the present invention, and FIG. 6 is a cross-sectional view of a part of the core, with some conductors omitted. FIG. 2 is a side view of a conventional balun transformer. 1...Through hole 2...Molded body 2'...Sintered body 6...Protrusion permission application Taiyo Yuden Kitamura Co., Ltd. - ・ -(!' and 3 others)

Claims (4)

[Claims] 1. A ferrite core having at least one through hole, in which a conductive wire is wound around the ferrite core by passing through the through hole; An inductor core characterized by being formed into an arc shape. 2. A ferrite core having at least one through hole, the core for an inductor having a conductive wire inserted into the through hole and wound around the ferrite core, wherein the ferrite core is formed at least at an edge of the through hole. A core for an inductor, characterized in that a tip of a protrusion protruding from an end face of the core is formed into an arc shape by barrel polishing. 3. A mixture of ferrite magnetic powder and a binder is filled into a mold and pressurized to form a molded body having at least one through hole, and after firing the molded body, the fired body is A method for manufacturing an inductor core, the method comprising barrel polishing using media with a diameter 1 to 5 times the diameter. 4. After filling a mold with a mixture of ferrite magnetic powder and a binder and applying pressure to form a molded body having at least one through hole, the molded body is combustible and has a diameter smaller than the diameter of the through hole of the molded body. 1. A method for producing an inductor core, the method comprising barrel polishing using a media having a diameter of , followed by firing.