JP3353915B2 - Composite ferrite core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a composite ferrite core,
More specifically, the present invention relates to a composite ferrite core used for a power transformer and an inductor or a high-frequency signal transformer and an inductor. For example, EMC EMI
It is applied to a shielding material and a shielding method.

[0002]

2. Description of the Related Art Conventional ferrite cores are usually manufactured by a sintering method as in the case of ceramics and the like, without any other manufacturing method, and almost all have a single composition. Recently, products obtained by simply dispersing ferrite or the like in a resin have been produced as products. However, there is no single-composition single-particle composition in which a plurality of fine particles are dispersed as described above. As the switching frequency of a switching power supply or the like increases, there is a demand for a transformer or the like that can operate at high power with low loss in a high frequency region. However, conventional materials that can handle high frequencies in principle have not been suitable for high power. Further, noise generated due to operation in a high frequency region increases with loss, which is not preferable in terms of EMC and EMI.

[0003]

An object of the present invention is to provide a composite ferrite core used for a transformer and an inductor operable in a high frequency region and with high power, and to achieve a low loss. It is an object of the present invention to provide a transformer and an inductor with low noise generation.

[0004]

To achieve the above object, the present invention provides (1)
Ni-Zn ferrite material is provided inside, and Mn-
Providing Zn ferrite; (2) providing a layer having a continuous composition at the boundary between the two layers; and (3) providing the Ni-Zn ferrite material and Mn-Zn
The ferrite material is characterized in that fine particles are dispersed in a support material such as plastic, and (4) the ferrite material is used for a transformer or an inductor. Hereinafter, an embodiment of the present invention will be described.

FIG. 1 is a structural view of a transformer for explaining an embodiment (claim 1) of a composite ferrite core according to the present invention. FIG. 1 (a) is a sectional view and FIG. 1 (b) is a top view. is there. In the figure, 1 is a bonding surface of the upper and lower cores, 2 is a bonding portion for bonding, 3 is a secondary winding, 4 is an insulating spacer, 5 is a primary winding,
6 is a Ni-Zn layer, 7 is a Mn-Zn layer, 8 is a ferrite core, 9 is a secondary winding end, and 10 is a primary winding end. FIG.
In the example of the transformer, the primary side is 10 turns, 2
The next side shows an example of three turns.

[0006] The primary winding 5 and the secondary winding 3 are interposed by an insulating spacer 4, and each winding is formed by molding a normal winding or a copper foil on an insulating sheet formed by a printing method or the like. Become. The ferrite core 8 is formed by doubly bonding a material once manufactured by a sintering method. At this time, an adhesive or an adhesive in which ferrite fine particles are dispersed is used for joining, so that leakage of magnetic flux during joining is reduced. In the present invention, Ni-Zn ferrite 6 having excellent high-frequency characteristics is used for the inner core, and Mn-Zn ferrite 7 having a large saturation magnetic flux density is used for the outer core. The Mn-Zn ferrite 7 forms a ferrite core. Further, in order to obtain a similar core structure, a binder and Mn-
Using a mixture of Zn ferrite fine particles and a binder and Ni-Zn ferrite fine particles, placing a mixture of binder and Ni-Zn ferrite fine particles inside, and disposing a mixture of binder and Mn-Zn ferrite outside, and then firing It is possible to manufacture by doing. In addition, each ferrite fine particle after calcination,
It is obtained by means such as grinding.

For example, in a high-frequency region exceeding 3 MHz, the Ni-Zn layer 6 functions as a magnetic flux flow path, and the degree of magnetic flux increases during large power transmission, and only when the saturation magnetic flux density of the Ni-Zn ferrite 6 approaches, Mn-Zn layer 7
The magnetic flux starts to flow through. Since the concentration of the magnetic flux is greater toward the inside, Ni-Zn with a small loss up to a relatively saturated region
The layer 6 carries the magnetic flux up to the saturation region, and the larger magnetic flux carries only the extra magnetic flux. At a low saturation magnetic flux density, the Mn-Zn layer 7 with a small loss carries the magnetic flux. In a high-frequency region exceeding 3 MHz as compared with the case of a layer, a core that bears a magnetic flux accompanying large power transmission can be realized.

FIG. 2 is a diagram showing another embodiment (claim 2) of a multiple ferrite core according to the present invention, showing an example of a transformer as in FIG. The next side shows an example of one turn. In the figure, 11 is a joint surface between the upper and lower cores, 12 is a secondary winding (one turn per layer), 13 is an insulating spacer, 14 is a conducting wire, 15 is a covering resin portion, 16 is a multi-parallel line (one layer), 17 Is the primary winding (4 turns, 4 turns), 18
Is a boundary intermediate layer, 19 is a Mn-Zn layer, 20 is Ni-Zn
The layer 21 is a ferrite core.

In order for the Ni—Zn layer 20 and the Mn—Zn layer 19 to be magnetically well-coupled, specifically, the saturation magnetic flux density of each layer changes gradually and the magnetic permeability changes continuously. It is necessary to make the flow of the magnetic flux between the layers smooth up to the saturation magnetic flux density area of each layer, so that the saturation area of the magnetic flux is less likely to be formed between the layers and bears the magnetic flux associated with high power transmission. be able to.

FIGS. 3 (a) to 3 (d) are views showing the steps of manufacturing the ferrite core in FIG. After forming the winding portion in the same manner as in FIG. 1, the ferrite core portion is formed as follows. In the step (a), a sintered precursor having a Ni—Zn composition is prepared. In the step (b), a sintering precursor having a Mn-Zn composition is formed outside the Ni-Zn composition produced in the step (a). In the step (c), the Ni—Zn composition prepared in the step (a) and the step (b)
To combine the Mn-Zn composition created in the above. In the step (d), the combined Ni-Zn composition and Mn-Zn composition are sintered (lower ferrite core) to complete. That is,
As shown in FIGS. 3A to 3D, the core is, for example,
The sintering is carried out by dividing, sintering a Ni-Zn composition inside, and sintering a Mn-Zn composition outside. At this time, a ferrite precursor having a composition intermediate between the two is arranged in the boundary region, so that the magnetic coupling of both layers is good after sintering. It is intended to prevent the occurrence of cracks and the like after knotting.

FIG. 4 is a view showing still another embodiment (claim 3) of a multiple ferrite core according to the present invention. As in FIG. 1, an example of a transformer is shown.
The next side shows an example of two turns. In the figure, 22 is a secondary winding (1 layer 2 turns), 23 is a conductor, 24 is an insulating film, 25 is a spiral type winding (12 turns), 26 is a primary winding (3 layers 12 turns). Reference numeral 27 denotes a Mn-Zn ferrite fine particle region, 28 denotes an intermediate region, 29 denotes a Ni-Zn ferrite fine particle region, 30 denotes a resin forming air, and 31 denotes an insulating spacer. For the windings 22 and 25, an example is shown in which a spiral conductive foil is used on an insulating film formed by a photolithographic method.

FIGS. 5 (a) to 5 (e) are views showing the steps of manufacturing the ferrite core in FIG. In the step (a), first, a resin solution containing a solvent obtained by fractionating ferrite fine particles having a Mn-Zn composition is prepared. In the step (b), a resin solution containing a solvent in which the ferrite fine particles of the Ni—Zn composition are fractionated is prepared. In the step (c), a mold is prepared, and a resin solution having an outer Mn-Zn composition is injected and solidified. In the step (d), the ferrite resin having the Mn-Zn composition solidified in the step (c) is used as an outer mold, and a new mold is prepared inside, and a ferrite resin solution having a Ni-Zn composition is injected. In the step (e), the ferrite resin solution of the Ni—Zn composition injected in the step (d) is solidified to complete the process. If the mold and the injection conditions are selected, it is possible to form a core having a Mn-Zn ferrite resin on the outside, a Ni-Zn ferrite resin on the inside, and a resin having a resin in which both ferrite fine particles are mixed in an intermediate layer. it can.

[0013]

As apparent from the above description, the present invention has the following effects. (1) An effect corresponding to claim 1; for example, even in a high-frequency region exceeding 3 MHz, the Ni-Zn layer works effectively as a flow path of magnetic flux, and the degree of magnetic flux is increased at the time of large power transmission, so that saturation of Ni-Zn ferrite is achieved. Mn-Zn outside only when approaching magnetic flux density
Magnetic flux flows through the layers. Since the concentration of the magnetic flux is larger on the inner side, Ni-Z with less loss up to a relatively saturated region.
The n layer carries the magnetic flux up to the saturation region, and the larger magnetic flux carries only the extra magnetic flux.At a low saturation magnetic flux density, the Mn-Zn layer with less loss carries the magnetic flux. In the high-frequency region exceeding 3 MHz as compared with the case of the above, a core that bears a magnetic flux associated with large power transmission can be realized. Also, in the case of the planar core type shown in the figure, there are few winding parts exposed in the space, so it is effective for noise countermeasures such as reducing leakage magnetic flux, but the core is not easily saturated. For this reason, it is effective in reducing noise. (2) An effect corresponding to claim 2;
In order for the n-Zn layer to be magnetically satisfactorily coupled, specifically, it is necessary that the saturation magnetic flux density of each layer gradually changes and that the magnetic permeability continuously changes. Since the flow of magnetic flux between the layers is smooth up to the saturation magnetic flux density area of each layer, it is more difficult to create a magnetic flux saturation area between each layer, and it can carry the magnetic flux associated with high power transmission. It is possible to realize a core, a transformer, and an inductor that are effective in reducing the noise because of, for example, difficulty in saturation. (3) An effect corresponding to claim 3; in addition to the above-mentioned effect, there is an easy manufacturing method. As compared with the above-described example, the degree of freedom of the core shape is increased due to the molding method of plastic or the like, which is advantageous in terms of cost due to easiness of the production method. In addition, since the dispersion ratio of the appropriate magnetic fine particles and the dispersion support material can be selected, the value of the magnetic permeability and the saturation magnetic flux density can be selected separately from the ferrite specific value, and it is optimal according to the required magnetic flux density such as the thickness of the ferrite core Design can be done. Further, by further mixing metal fine particles such as copper in the dispersing material,
In the region exceeding 0 MHz, a core that realizes a further low magnetic flux leakage can be manufactured, and noise reduction can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of a composite ferrite core according to the present invention.

FIG. 2 is a view showing another embodiment of the composite ferrite core according to the present invention.

FIG. 3 is a view showing a manufacturing process of the ferrite core in FIG. 2;

FIG. 4 is a view showing still another embodiment of the composite ferrite core according to the present invention.

FIG. 5 is a view showing a manufacturing process of the ferrite core in FIG. 4;

[Explanation of symbols]

1. Joint surface of upper and lower cores, 2. Joint portion by adhesion, 3. 2.
Secondary winding, 4 ... insulating spacer, 5 ... primary winding, 6 ... Ni-
Zn layer, 7 ... Mn-Zn layer, 8 ... ferrite core, 9 ...
Secondary winding end, 10 ... primary winding end.

Continuation of the front page (56) References JP-A-4-318906 (JP, A) JP-A-5-121244 (JP, A) JP-A-4-4602 (JP, A) JP-A-3-150815 (JP) JP-A-2-158107 (JP, A) JP-A-4-28497 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 27/24 H01F 1/34 H01F 27/255

Claims (4)

(57) [Claims] An Ni-Zn ferrite material is provided inside,
A composite ferrite core characterized by providing Mn-Zn ferrite on the outside. 2. The composite ferrite core according to claim 1, wherein a layer having a continuous composition is provided at a boundary between said two layers. 3. The Ni—Zn ferrite material and Mn—
The composite ferrite core according to claim 1, wherein the Zn ferrite material has fine particles dispersed in a support material such as plastic. 4. The composite ferrite core according to claim 1, wherein the composite ferrite core is used for a transformer or an inductor.