JPH02285613A - Composite magnetic core - Google Patents

Abstract

PURPOSE:To make it possible to improve the permeability of the entire composite magnetic core by a method wherein the degree of magnetic resistance at the junction part of cores is lowered by mutually adhering the junction surface of the cores using a bonding agent containing magnetic powder. CONSTITUTION:In the composite magnetic core with which a closed magnetic circuit will be formed by assembling a plurality of cores 1 and 1, the junction surfaces of the cores 1 and 1 are adhered with each other using a bonding agent 8 containing magnetic powder. For example, a winding 3 is wound on a bobbin 2 made of resin, metal or metal oxide powder is compression-molded, a pair of U-shaped sintered magnetic cores 1 and 1 are fitted from both sides of the bobbin 2, a closed magnetic circuit is formed by coupling said both ends with each other, and a small type transformer is constituted. When both ends of the cores 1 and 1 are coupled in the case as above-mentioned, the coupling surfaces, namely, both end parts of the cores to be butt-together are bonded with a bonding agent 8. The bonding agent is formed by dispersing the ferrite powder having high permeability into the resin such as epoxy resin and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a composite magnetic core in which molded cores are joined to form a closed magnetic path.

[Prior Art] A composite magnetic core in which a closed magnetic circuit is formed by combining molded cores is used, for example, in a small transformer as shown in FIG.

The small transformer shown in Fig. 5 consists of a bobbin 2 made of resin, a winding 3, and a pair of U-shaped cores 11 made of compression-molded metal or oxidized metal powder and fired magnets 11. , 1 are fitted into the bobbin 2 from both sides, and both ends are tightly joined to form a mouth-shaped closed magnetic path.

In this case, in the conventional composite magnetic core, the pair of cores 1.1 are sandwiched from both sides by metal U-shaped spring pieces 4 having spring properties to join the cores 1.1.

[Problems to be Solved by the Invention] The end faces of the core 1, (2) to be joined are carefully (
Although the core 1.1 is manufactured to be smooth, due to variations in the roughness of the particles forming the core 1.1, it is difficult to say that the mating surfaces will be in perfect contact with each other on the entire surface. . In addition, since the core 1.1 itself often has fine holes, even if the end faces of the core L1 are sufficiently polished and butted, for example, as shown in FIG.
It is unavoidable to include.

In addition, since a closed magnetic path is formed by sandwiching the metal spring pieces 4, gaps are likely to form on the joint surfaces due to variations in the elasticity of the spring pieces 4.

If voids 711119 or gaps as described above occur on the bonding surface of the core 1.1, the presence of these cavities 9 and gaps will unavoidably reduce the magnetic permeability between the cores 1.1, resulting in a high magnetic permeability. There has been a problem that it is not possible to provide a composite magnetic core having the following characteristics.3.An object of the present invention is to provide a commercially available composite magnetic core that solves the above-mentioned conventional problems.

[Means for solving the problem] That is, the gist of the present invention for achieving the above object is as follows:
In a composite magnetic core in which a plurality of cores 1 and 2 are combined to form a closed magnetic path, the joint surfaces of the cores 1 and 2 are bonded to each other with an adhesive 9 containing magnetic powder.

[Function] In the above-described composite magnetic core according to the present invention, when a plurality of cores 1,゛1
The adhesive 9 containing the L magnetic powder is filled into spaces such as cavities 9 and gaps formed in the openings of the bonding surfaces of , (2). As a result, the magnetic resistance at the joint portion 7 of the core 1.1 becomes low, and the magnetic permeability of the entire composite magnetic core is improved.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a small transformer. As already mentioned, this small I-lance consists of a bobbin 2 made of resin, a winding 3, and a pair of U-shaped magnetic materials made of metal or oxidized metal powder formed into wires and fired. A shaped core 1.1 is fitted into the bobbin 2 from both sides, and both ends thereof are joined together to form a closed magnetic path.

In the present invention, when joining the ends of the cores 1 and 2, the joining surfaces, that is, the ends of the core 1.1 to be butted together are bonded with an adhesive 8. This adhesive 8 is made by dispersing ferrite magnetic powder with low magnetic permeability in a resin such as epoxy resin. FIGS. 2 and 3 show schematic cross-sectional views of the joint 7 of the cores 1 and 1. 1118, as shown in FIG. 2, a cavity 9 or the like is formed at the joint 7 between the core 1 and (2), but according to the present invention, a transparent W! An adhesive 8 containing a high magnetic powder is filled.

FIG. 4 shows a hobbin core 11 having a disc-shaped base,
This is an embodiment in which the present invention is applied to a composite magnetic core formed by joining a cap-shaped core 10 whose lower surface is open.

In this case, the periphery of the base of the hobbin core 11 and the bottom edge of the cap-shaped core 10 are bonded together with an adhesive 8 containing magnetic powder.

Next, a specific example will be described in which the present invention is applied to a composite magnetic core constituted by a pair of U-shaped cores 1 and (2) as shown in FIG.

Made of Mn-Zn based ferrite magnetic material with a magnetic permeability of 5500, the thickness is 5.2 mm x 2.7 m rrh width 8
．． 5mm5 Height 12.0 U-shaped core 1.1
I prepared a pair of

On the other hand, M n with a particle size of 0.3 to 5 μm and a magnetic permeability of 10,000
-Z n-based Ferrai I magnetic powder was dispersed in an epoxy resin to prepare an adhesive 8 containing magnetic powder.

Next? The adhesive 8 is applied to the area where the pair of cores 1.1 are to be joined, and ultrasonic vibrations are applied from both ends of the cores 1.1 to press the contact surfaces of the cores 1 and I to close the magnet. A composite magnetic core was constructed to form a channel.

The magnetic permeability of the composite magnetic core constructed in this way is 3000
Met.

On the other hand, for comparison with the above example, core 1. I without using the adhesive 8 as described above.
As shown in the figure, a composite magnetic core was constructed in which cores I and I were sandwiched and joined from both ends using metal U-shaped spring pieces 4. The magnetic permeability of this composite magnetic core was 2000.

[Effect] As explained above, according to the present invention, the space formed on the bonding surface of the core 1.1 is filled with the adhesive 9 containing magnetic powder with high magnetic permeability, thereby making it possible to The magnetic resistance of the entire magnetic core is lowered, and magnetic permeability is improved.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a composite magnetic core according to an embodiment of the present invention incorporated into a small transformer, and FIG. 2 is an enlarged cross-sectional view schematically showing the state of the core joint of a conventional composite magnetic core. Figure 3 is an enlarged sectional view schematically showing the state of the core joint of a composite magnetic core in an embodiment of the present invention, and Figure 4 is a partially cutaway diagram showing another embodiment of the present invention. FIG. 5 is a perspective view of a conventional example in which a composite magnetic core is incorporated into a small transformer. 1.1-0.11... Core 7... Core joint
8...Adhesive

Claims (1)

[Claims] A composite magnetic core in which a plurality of cores 1, 1 are combined to form a closed magnetic path, and the joint surfaces of the cores 1, 1 are bonded to each other with an adhesive 9 containing magnetic powder. core.