JPH06208929A - Manufacture of core for transformer - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a core for transformer in which beating is prevented by eliminating the bonding face of the core while eliminating the influence of warp produced during the firing process of the core. CONSTITUTION:A core material is integrally molded into an item (as shown in fig. A or c) having no open end and can form a closed magnetic path. The molded item is then sintered 5, 21 and a part of sintered item (a part of magnetic path) is cut to form a gap G thus manufacturing cores 6, 22 for transformer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a transformer core used in manufacturing a ferrite core of a high frequency transformer such as a transformer for a switching power supply.

[0002]

2. Description of the Related Art FIG. 6 is an explanatory view of the prior art.
Inside, 1 is an E type core, 2 is a U type core, and 3 is an I type core.

Conventionally, various types of transformers have been used for high frequency transformers, but generally, ferrite cores have been used for these transformers. Hereinafter, such a ferrite core will be described.

§1: Description of EE type core When the EE type core is used as a core of a transformer, as shown in FIG. 6 (A), the E type core 1 having the same shape is used.
Are used in pairs.

When assembling the transformer, for example, the central leg portion of the E-shaped core 1 is inserted from both sides of a coil bobbin (not shown), and is abutted (joined) in the direction shown in FIG. 6B. ). After that, the two E-shaped cores 1,
Secure with adhesive tape.

In this case, two butted E-shaped cores 1
The magnetic path is formed by, but a gap G is provided in a part of the magnetic path in order to prevent magnetic saturation. For example, in this example, a gap G is provided between the central leg portions of the E-shaped core 1 (between the leg portions of the core located inside the coil bobbin).

Such an E-shaped core (ferrite core) 1
In the case of manufacturing, the E-shaped core sintered body is manufactured through a raw material processing step, a molding step, a firing step, and the like. afterwards,
The portion of the gap G was processed by polishing a part of the sintered body.

§2: Description of U-U type core When the U-U type core is used as the core of the transformer, as shown in FIG. 6C, the U-type core 2 having the same shape is used.
Are used in pairs.

When assembling the transformer, for example, one leg of the U-shaped core 2 is inserted from both sides of a coil bobbin (not shown), and they are butted in the direction shown in FIG. 6 (D). Then, the two U-shaped cores 2 are fixed with an adhesive tape or the like.

In this case, two butted U-shaped cores 2
The magnetic path is formed by, but a gap G is provided in a part of the magnetic path in order to prevent magnetic saturation. For example, in this example, a gap G is provided between one leg of the U-shaped core 2 (between the legs of the core located in the coil bobbin).

Such a U-shaped core (ferrite core) 2
Is manufactured in the same manner as in the case of the EE type core. . §3: Description of E-I type core When the E-I type core is used as a transformer core, as shown in FIG. 6 (E), the E-type core 1 and the I-type core 3 are combined. use.

Also in this case, a gap G is formed in a part of the magnetic path.
To form. The manufacturing method of the core is the same as that of the EE type core.

[0013]

SUMMARY OF THE INVENTION The above-mentioned conventional devices have the following problems. : The transformer core uses two cores butted against each other. In this condition, if current is applied to the transformer winding, 2
An electromagnetic force is applied to the abutting portion (joint surface) of the two cores, and a howling noise is generated.

The ferrite core is a sintered body produced through a firing process and the like. Therefore, the core shrinks during firing, and warpage occurs, for example. For this reason, when the two cores are abutted with each other, a gap is generated between the two cores on the joint surface, and the effective cross-sectional area of the joint surface (effective cross-sectional area of the magnetic path) is reduced. Therefore, the core cannot be used effectively.

An object of the present invention is to solve such a conventional problem, to eliminate the joint surface of the core, to prevent the howling noise, and to eliminate the influence of the warp generated by the firing process of the core.

[0016]

FIG. 1 is a diagram for explaining the principle of the present invention. In FIG. 1, the same parts as those in FIG. 6 are designated by the same reference numerals. Further, 5 is a "Japanese" shaped sintered body, 6 is a "Japanese" shaped core, 21 is a "B" shaped sintered body, and 22 is a "B" shaped core.

In order to solve the above problems, the present invention has the following configuration. After manufacturing a molded body integrally molded from the raw material of the core into a shape that does not have an open end and can form a closed magnetic circuit, and fire the molded body to manufacture sintered bodies 5 and 21, The transformer cores 6 and 22 are manufactured by cutting a part of the fired body (a part of the magnetic path) to form the gap G.

In the constitution, the molded body was formed into a "day" shape or a "b" shape.

[0019]

The operation of the present invention based on the above configuration will be described with reference to FIG. : When manufacturing a core for a transformer, in a "molding step", a molded body such as a "Japanese" shape or a "B" shape is manufactured. Gaps and the like are not formed in this molded body, and the molded body has no breaks.

After that, the molded body is fired to produce a sintered body. As this sintered body, as shown in FIG.
“E” shaped sintered body 5 shown in (E), or FIG.
The "B" shaped sintered body 21 shown in (C) is used.

Then, by cutting a part (a part of the magnetic path) of each of the sintered bodies 5 and 21, the gap G is formed.
To form. : A core (iron core) having a gap G can be manufactured as described above. As this core, the "Sun" -shaped core 6 shown in FIGS. 1 (B) and 1 (F), or the core shown in FIG.
It is the “square” -shaped core 22 shown in (D).

The core manufactured in this way is
With this core, it can be used as a transformer core (conventional transformer cores consisted of two cores). Moreover,
Since a transformer core with no joint surface can be realized, no growl noise is generated during use. Further, the work of assembling the core is unnecessary, and the workability of assembling the transformer is improved.

Further, the core after the firing is warped, but since the core of the present invention has no bonding surface, even if the warpage is generated, it is not affected by the warping.
The cross-sectional area of the core can be used effectively.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. (Explanation of the First Embodiment) FIGS. 2 to 4 are explanatory views (1 to 3) of the first embodiment of the present invention. In FIGS. 2 to 4, the same parts as FIGS. It is indicated by the same reference numeral. Further, 7 is a sheet coil body, 8 is an insulating sheet, 9 is an inner peripheral seal portion, 10 is an outer peripheral seal portion, 11 is a through hole, 12 is a sheet coil, 14 is a split coil bobbin, 15 is a coil, 1
6 is a collar, 17 is a gear, 18 is a wire, and 19 is a drive gear.

In this example, as an example of a ferrite core (iron core) for a high frequency transformer, an example of manufacturing a "day" character type core will be described. §1: Description of core manufacturing process ... See Fig. 2 As a manufacturing process of a ferrite core for a high frequency transformer (iron core), "raw material processing step", "forming step", "firing step", "processing step" , Etc., and the product (core) is completed through these steps. Hereinafter, each step will be described.

In the "raw material processing step", processing such as mixing of raw materials is performed, but since this step is the same as that of the prior art, the description is omitted. : In the "molding process", use the processed raw material and
Produce a letter-shaped compact. That is, a molded body that is integrally molded into a shape that does not have an open end and that can form a closed magnetic circuit (a shape without breaks) is manufactured.

Since the molding method is the same as that of the prior art, the description is omitted. : In the "firing process", the "Japanese" shaped body is fired to produce a sintered body. Note that the firing method is the same as that of the conventional technique, and therefore its description is omitted.

FIG. 2A shows a plan view of the "Japanese" shaped sintered body 5 manufactured in this step. : In the "machining step", a part of the leg portion (a part of the magnetic path) of the "Japanese" shaped sintered body 5 manufactured through the "firing step" is cut, so that FIG. The gap G as shown in FIG.

The gap G is for preventing magnetic saturation of the magnetic path, and the gap G having a predetermined gap length is provided at one position of the magnetic path (usually a part of the leg portion for winding). ).

By the above-mentioned steps, the "day" -shaped core (iron core) 6 having the gap G as shown in FIG.
Can be manufactured. The core manufactured in this way is a single core and can be used as a core of a transformer.

That is, a conventional EE type transformer core (using two E type cores as a set) can be constructed by one core. Moreover, a transformer core with no joint surface can be realized, and no growl noise is generated during use. Further, the work of assembling the core is unnecessary, and the workability of assembling the transformer is improved.

§2: Description of Warp of Core ... See FIG. 3 The influence of the core manufactured as described above on the warp of the core will be described with reference to FIG. For comparison, FIG. 3 also shows a conventional core.

By the way, when the core is manufactured, it is manufactured through the "firing process" as described above. For this reason, the molded body shrinks, and the core after firing is warped (there is also other distortion).

Therefore, for example, in the conventional core (EE type core) shown in FIG. 3A, when the two cores are abutted with each other, the joint surface is displaced due to the warp of the cores.
As a result, the actual cross-sectional area Wf of the core (Wf: the actual cross-sectional area of the core in the vicinity of the joint surface of both cores) cannot be effectively used, and the actually available cross-sectional area We of the core (We: The effective cross-sectional area of the joint surface becomes smaller (Wf> W
e).

On the other hand, in the core 6 of the first embodiment,
As shown in FIG. 3B, there is no joint surface. Therefore, even if warpage or the like occurs, the core cross-sectional area can be effectively utilized to the maximum (100%) without being affected by the warpage.

§3: Description of coil assembling process ...
See FIG. 4. When a transformer is assembled using the core 6 shown in FIG. 2B, a coil is incorporated into the core 6. In the coil assembling process, the assembling process is performed as follows.

Description of Example 1 of Assembling the Coil ...
-See Fig. 4 (A) and Fig. 4 (B). In this example, as a coil incorporated in the core 6,
The sheet coil 12 shown in (A) is used.

In the sheet coil 12, both sides of the sheet coil main body 7 in which a wire is wound in a spiral shape and a flat shape are sandwiched by an insulating sheet 8 and sandwiched between the sheet coil main body 7 and the inner peripheral portion of the sheet coil main body 7. At the position of the outer peripheral portion, the insulating sheets 8 on both sides are pressure-bonded and heat-melted to form the inner peripheral sealing portion 9 and the outer peripheral sealing portion 10.

Since the sheet coil 12 is mounted on the leg portion of the core of the transformer, the through hole 11 is formed inside the seal portion 9 on the inner circumference. A plurality of such sheet coils 12 are prepared, and as shown in FIG. 4B, each sheet coil 12 is provided with a gap G provided at the leg portion of the core 6.
It is inserted into the core 6 and incorporated into the core 6.

Description of coil assembly processing example 2
-See Fig. 4 (C), Fig. 4 (D), and Fig. 4 (E). In this example, when the coil 15 is incorporated in the core 6,
The split coil bobbin 14 shown in FIG.

The split coil bobbin 14 is divided into two bobbin pieces, and these bobbin pieces are combined to form a cylindrical bobbin. Further, a collar 16 is provided at both ends of each bobbin piece, and gear teeth are formed on the outer peripheral portion of the collar 16, and when two bobbin pieces are combined, both ends thereof are joined together. The collar 16 of the part serves as a gear 17.

When a coil is incorporated in the core 6, the coil shown in FIG.
As shown in (C), each bobbin piece of the split coil bobbin 14 is arranged around the leg portion (the leg portion provided with the gap G) of the core 6, and the two bobbin pieces are combined to form one bobbin piece. It is a cylindrical coil bobbin.

In this case, the two coil bobbin pieces are combined around the leg portion of the core 6 in a state where the split coil bobbin 14 can rotate. The gear 1 of the split coil bobbin 14 is connected to the drive gear 19 connected to the rotary shaft of the winding machine.
Engage 7

At this time, a part of the split coil bobbin 14 is
The tip of the wire 18 is fixed, and the drive gear 19 is fixed.
When is rotated, the wire 18 is wound and the coil 15 can be incorporated.

(Explanation of Second Embodiment) FIGS. 5A and 5B
FIG. 5B is an explanatory diagram of the second embodiment of the present invention, and FIG.
In FIGS. 5A and 5B, the same parts as those in FIGS. 1 to 4 are designated by the same reference numerals.

This example is an example of manufacturing a "square" type core. The manufacturing process of this core is similar to that of the first embodiment. However, in this example, in the "molding process",
Manufacture "B" shaped body. In addition, in the "firing process", the "B" shaped molded body is fired,
A square-shaped sintered body 21 as shown in (A) is manufactured.

In the "processing step", the "firing step"
By cutting a part of the "B" shaped sintered body 21 manufactured through the above, a gap G as shown in FIG. 5B is formed, and the "B" shaped core 22 is formed. To manufacture.

(Explanation of Third Embodiment) FIGS. 5 (C) and 5
FIG. 5D is an explanatory diagram of the third embodiment of the present invention, and FIG.
In (C) and FIG. 5 (D), the same components as those in FIGS. 1 to 4 are denoted by the same reference numerals.

This example is an example of manufacturing a "Japanese" character type core. In this case, in the "firing step", the "day" shaped sintered body 5 as shown in FIG. 5C is produced by firing the "day" shaped molded body.

Then, in the "processing step", the "firing step"
By cutting a part of the "Japanese" shaped sintered body 5 manufactured through the above process, a gap G as shown in FIG. 5D is formed, and the "Japanese" shaped core 6 is formed. To manufacture.

In this example, the position where the gap G is formed is different from that of the first embodiment, but the other structure is the same as that of the first embodiment. (Other Embodiments) Although the embodiments have been described above, the present invention can be implemented as follows.

The shape of the core is not limited to the "day" shape and the "b" shape, but is applicable to cores having other shapes. : The position of the gap G is not limited to the position in the above embodiment,
It may be provided at any position.

[0053]

As described above, the present invention has the following effects. : Since a transformer core without a joint surface can be realized, no growl noise is generated when the transformer operates.

A conventional core for transformer of EE type, UU type, EI type, etc. (using two cores as a set) can be constructed by one core. Therefore, the work of assembling the core is unnecessary, and the workability of assembling the transformer is improved.

Since the gap is formed by cutting after the firing process, even if the core is warped, the core cross-sectional area is always maximized (100%) without being affected by the warpage. Available.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an explanatory diagram 1 of the first embodiment.

FIG. 3 is an explanatory diagram 2 of the first embodiment.

FIG. 4 is an explanatory diagram 3 of the first embodiment.

FIG. 5 is an explanatory diagram of a second / third embodiment.

FIG. 6 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 5 “Day” shaped fired body 6 “Day” shaped core 21 “B” shaped fired body 22 “R” shaped core G Gap

Claims (2)

[Claims] 1. The core material is free of open ends, and
A molded body integrally molded into a shape capable of forming a closed magnetic circuit is manufactured, the molded body is fired to manufacture a sintered body (5, 21), and then a part of the fired body (5, 21). A method of manufacturing a transformer core, characterized in that the transformer core (6, 22) is manufactured by cutting (a part of the magnetic path) to form a gap (G). 2. The molded body is shaped like a "Japanese" or a "B"
The method for manufacturing a transformer core according to claim 1, wherein the transformer core is formed in a letter shape.