JPH11214221A - Core, transformer, and inductor for inductive element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core for thine inductive element with a small core loss in a high-frequency range, to provide a transformer with a small core loss in a high-frequency range and no drop in power transfer efficiency, and to provide an inductor with a small core loss in a high-frequency range. SOLUTION: A core 22 for an inductive element formed of a base core 23 and a cover core 24 comprising Mn-Zn ferrite of average crystal particle size 5 μm or less which is obtained by preparing Mn-Zn ferrite raw material powder and molding it before sintering, a transformer 21 constituted of a transformer conductor plate 25 sandwiched between the base core 23 and the cover core 24, and an inductor constituted of an inductor conductor plate 49 sandwiched between the base core 23 and the cover core 24 are employed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductive element used for various electronic devices, and more particularly to a core for an inductive element and a transformer and an inductor including the core for the inductive element. is there.

[0002]

2. Description of the Related Art An inductive element such as a transformer for stepping up or stepping down a voltage or converting a current flow rate and an inductor acting as a self-inductance are indispensable for various electronic devices. Recently, there has been an increasing demand for downsizing and thinning of electronic devices. Accordingly, there has been a problem that inductive elements incorporated in these electronic devices must be downsized and thinned.

As means for solving the above-mentioned problems of miniaturization and thinning of the inductive element, there has been proposed a core for an inductive element which is thinner than a conventional EI core, toroidal core or the like. An inductor using this inductive element core will be described with reference to the drawings.

As shown in FIG. 10A, an inductor 1 is of a printed circuit board type, and a core 2 for an inductive element is used.
, A printed circuit board 3, and a conductive wire 11.
The core 2 for the inductive element includes a plate-like base portion 4 and rectangular parallelepiped protrusions 5, 5... Protruding from one surface of the base portion 4 at regular intervals in three rows and three rows. A base core 6 made of a body is provided. Base core 6
Are formed at the same height. As shown in FIG. 10A, the base core 6 is provided with a groove 10 defined by the side surfaces 13 and 13 of the two rectangular parallelepiped projections 5 and 5 and the base portion 4. In the case of the shape shown in FIG. 10A, the number of the grooves 10 is 12, since there are nine rectangular projections 5, 5,....
Further, the core 2 for the inductive element is provided with a cover core 7 made of a plate-like magnetic material. The printed circuit board 3
It is made of an insulating plate 3a such as a glass epoxy material,
The rectangular parallelepiped projections 5, 5 of the base core 6 are provided on the insulating plate 3a.
Are perforated.

In the inductor 1, the conductor 11 and the printed board 3 are arranged so as to be sandwiched between the base core 6 and the cover core 7. That is, the conductor 11 made of a metal wire is placed on the base core 6 so as to be inserted through the twelve grooves 10, 10,.... Conductor 11
Are connected to other electronic circuits. Next, the printed circuit board 3 is placed on the upper surface of the base core 6 by passing the rectangular parallelepiped projections 5, 5,... Of the base core 6 through the holes 12, 12,. Further, the cover core 7 has a rectangular parallelepiped projection 5 penetrating the printed circuit board 3,
5 are mounted on the printed circuit board 3 by bonding the upper surfaces 8, 8.

As shown in FIG. 10B, a conductor 1 is formed on the inductor 1 by two rectangular parallelepiped projections 5, 5 defining the grooves 10, 10, the base 4 and the cover core 7.
Each of them has an independent closed magnetic path for passing a magnetic flux generated by the voltage applied to the element. This is referred to as unit cores 15, 15,... (Within the dashed-dotted line frame). Groove 10
Are provided, the number of unit cores 15 is also 12
Individual. Therefore, the core 2 for an inductive element has a form in which a plurality of unit cores 15 are arranged in the same plane. The conductor 11 becomes an inductive element that generates an inductance determined by the cross-sectional area of the magnetic path of the unit core 15 and the magnetic permeability of the magnetic material when inserted into the unit core 15. When the conductor 11 is inserted through the plurality of unit cores 15, 15,..., The obtained inductance value equivalently increases. Therefore, if a large inductance value is needed,
The conductor 11 may be inserted through a large number of unit cores 15, 15,.

The two conductors 11 are connected to the core 2 for the inductive element.
Can be formed into a transformer in which one conductor 11 becomes a primary winding and the other conductor 11 becomes a secondary winding.

According to the above-described core 2 for an inductive element, the unit core 15 is arranged on one surface of the base core 6, so that the shape can be made thin. The number of the unit cores 15 can be easily increased or decreased by increasing or decreasing the number of the rectangular projections 5, 5,. Furthermore, the core 2 for an inductive element can be used as an inductor or a transformer by adjusting the number of conductors.

According to the inductor 1 described above, since the core 2 for the inductive element is provided, the shape can be reduced. Further, in the inductor 1 described above, one or more unit cores 15 provided in the core 2 for the inductive element are provided.
A predetermined inductance can be generated by the conductor 11 inserted into the unit core 15.
In addition, the inductor 1 described above adjusts the number of the unit cores 15 of the unit cores 15 into which the conductive wires 11 are inserted, so that
That is, the inductance can be easily adjusted by inserting the conductive wire 11 into only a part of the unit core 15.

[0010]

The core 2 for the inductive element described above is made of a ferrite material such as Mn-Zn ferrite or Ni-Zn ferrite having high magnetic permeability and saturation magnetic flux density, or a material such as Permalloy. Metal materials such as Sendust and amorphous alloys have been used.

However, in the inductor 1 manufactured using the conventional ferrite material, there is a problem that the core loss of the inductive element core 2 increases when an alternating current in a high frequency band is applied. Further, when a transformer is manufactured using a conventional ferrite material, the core loss of the core 2 for the inductive element increases when a sine wave alternating current in a high frequency band is applied, and the power transmission efficiency decreases. There was a problem that. In addition, when the base core is manufactured using a metal material, the shape of the base core 6 is complicated, so that it is difficult to form the base core. Even if the base core 6 can be formed, it is difficult to make the shape thin. There was a problem that.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a core for an inductive element having a small core loss in a high-frequency band and a thin shape. It is an object of the present invention to provide a transformer with a small core loss and no reduction in power transmission efficiency, and further provide an inductor with a small core loss in a high frequency band.

[0013]

In order to achieve the above object, the present invention employs the following constitution.

The core for the inductive element of the present invention is made of Mn-Z
An n-ferrite raw material powder is granulated, molded and fired after being formed, and has a base core and a cover core of Mn—Zn ferrite having an average crystal grain size of 5 μm or less, and at least the base core and the cover core On one surface, a plurality of protrusions are arranged substantially in parallel with a predetermined interval therebetween, and the base core and the cover core are overlapped via the protrusions, and the base core and the cover core are overlapped with each other. 2
One or more unit cores are formed by the protrusions and the cover core. The core for the inductive element of the present invention is obtained by granulating and shaping the Mn-Zn ferrite raw material powder, and then sintering the resulting powder to obtain an average crystal grain size of 5 μm.
It comprises a base core and a cover core of the following Mn-Zn ferrite, and at least one surface of the base core and the cover core, a band-like projection group including a plurality of projections, a predetermined projection between each other. The base core and the cover core are superimposed via the projection group and are substantially parallel to each other at intervals.
One or more unit cores are formed by the protrusions and the cover core.

The core for an inductive element according to the present invention is the core for an inductive element described above, wherein an area S1 of one surface of the base core or the cover core and a total area of an upper surface of the protrusion are provided. When the ratio to the area S2 is 1.1 ≦ S1 / S2 ≦ 5.
5 is characterized. Further, the core for the inductive element of the present invention is a core for the inductive element described above,
The Mn-Zn ferrite preferably has a composition of at _{mol%, Fe 2 O 3:} 52~55 ZnO: 5~20 MnO: characterized in that it is a 25 to 40. Furthermore, the core for an inductive element of the present invention is the core for an inductive element described above, wherein the relative density of the Mn-Zn ferrite is 97% or more and the average crystal grain size is 1.3 to 3%. 0.0 μm, and the coefficient of performance is 1M
The frequency is 50 to 300 in Hz, and the frequency at which the coefficient of performance has the maximum value is in the range of 0.2 to 2 MHz.

According to a second aspect of the present invention, there is provided a transformer comprising: a core for an inductive element as described above; an insulating plate having a hole for allowing the projection of the base core to pass therethrough; and one or both surfaces of the insulating plate. And a conductor plate for a transformer having a primary conductor and a secondary conductor. Further, the transformer of the present invention is the transformer according to the above, wherein the transformer conductor plate is configured such that the primary conductor and the secondary conductor are arranged in a zigzag along the hole. A transformer conductor plate is disposed so as to be sandwiched between the base core and the cover core by penetrating the projection through the hole, and the primary conductor and the secondary conductor are connected to the unit core. It is characterized in that it is configured to be arranged inside.

According to the present invention, there is provided an inductor comprising: a core for an inductive element as described above; an insulating plate having a hole through which the projection of the base core penetrates; and one or both surfaces of the insulating plate. And a conductor plate for an inductor having a conductor. Further, the inductor of the present invention is the inductor described above, wherein the conductor plate for the inductor is configured such that the conductors are arranged in a zigzag along the hole, and the conductor plate for the inductor is configured as By penetrating the projection through the hole, it is arranged so as to be sandwiched between the base core and the cover core, and the conductor is arranged in the unit core. I do.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1A to 1D, a transformer 21 includes a core 22 for an inductive element, Mn-Z.
It comprises a base core 23 made of n-ferrite, a cover core 24 made of Mn-Zn ferrite, and a conductor plate 25 for a transformer.

As shown in FIGS. 2A to 2C, the base core 23 has a rectangular plate-like base portion 26 and a base portion 26.
27a or 27b extending along the short direction of the projections 27a, 27b,.
a are arranged side by side at a substantially constant interval. The shapes of the projections 27a, 27a, 27b,... Are, for example, rectangular parallelepiped as shown in FIG. Also, the base 26
Are formed such that the area of the upper surface 28a of the two protrusions 27a at both ends in the longitudinal direction is approximately one half of the area of the upper surface 28b of the other protrusions 27b. ing. Further, the projections 27a, 27a, 2
7b are formed so as to have the same height. If the heights are not the same, it is not preferable because all the projections 27a, 27a, 27b,... Cannot be joined to the bottom surface 29 of the cover core 24 at the time of joining to the cover core 24 described later. The base portion 26 and the cover core 24 may be made parallel by providing a convex portion on the side and abutting on the protrusions 27a, 27a, 27b. Further, the base core 23 is provided with grooves 30, 30... Defined by the protrusions 27 a, 27 b or the side surfaces 27 c, 27 c of the protrusions 27 b, 27 b and the base 26. Since twelve projections 27a, 27a, 27b are provided in this figure, two projections 27 adjacent to each other are provided.
There are 11 grooves 30, 30 ... between a, 27a, 27b ... .. Have the same width.

As shown in FIG. 2A, the area S1 of the surface of the base portion 26 is given by S1 = xy, where x is the length of the longitudinal side of the base core 23 and y is the length of the other side.
Becomes Also, the upper surface 2 of the projections 27a, 27a, 27b.
The total area S2 of 8a, 28a, 28b,... Is given by z where the width of the upper surface 28b of the projection 27b is z, and there are 10 projections 27b and 2 projections 27a.
(1 / 2z) = 11yz. S1 and S2 at this time
Is preferably 1.1 ≦ S1 / S2 ≦ 5.5. When S1 / S2 is less than 1.1, each groove 30,
The width of 30 is extremely small, which is not preferable. When S1 / S2 exceeds 5.5, the protrusions 27a, 27
Since the sectional areas of the closed magnetic paths a, 27b,... become extremely small, it is not preferable.

FIG. 6 shows another base core 51. The base core 51 has a rectangular plate-like base portion 5.
2 and a plurality of protrusions 54a, 54 formed of a plurality of protrusions 53a, 53b.
a, 54b... and the projection groups 54a, 54a,
Are arranged side by side at a substantially constant interval. The shapes of the projections 53a, 53b are, for example, rectangular parallelepiped as shown in FIG. The base 52
Are formed so that the area of the upper surface 55a of the projections 53a at both ends in the longitudinal direction is approximately one half of the area of the upper surface 55b of the other projections 53b. Furthermore,
The projections 53a, 53b are formed so as to have the same height. If the heights are not the same, all the projections 27a, 27
a, 27b... cannot be joined to the bottom surface 29 of the cover core 24, which is not preferable.
The base portion 26 and the cover core 24 may be made parallel by providing a convex portion on the side and abutting on the protrusions 27a, 27a, 27b. Further, the base core 51 is provided with grooves 56, 56 between the projections 53a, 53b. The projection groups 54a, 54b,... Are provided 12 in this figure, so that two adjacent projection groups 54a, 54b,
There are 11 grooves 56, 56 ... between 4a, 54b ... Also, the widths of the grooves 56 are the same.

As shown in FIGS. 3A to 3C, the cover core 24 of the core 22 for the inductive element has a plate shape.

As shown in FIGS. 5A to 5D, the projections 27a, 27a of the base core 23 are provided on the conductor plate 25 for the transformer.
a, 27b... penetrate therethrough.
An insulating plate 32 is provided with holes 1b, a primary conductor 33 formed on one surface of the insulating plate 32, and a secondary conductor 34 formed on the other surface. Slots 31a, 31a, 3
1b, the size and position of the protrusions 27a, 27a,
27b are perforated so as to correspond to the shape and position of the upper surfaces 28a, 28a, 28b. The primary conductor 3
The third and secondary conductors 34 are elongated holes 31a, 31a, 31b,.
Are arranged in a zigzag shape along the edge of. Furthermore, 1
An insulating layer (not shown) is formed on the secondary conductor 33 and the secondary conductor 34 in order to maintain insulation from the core 22 for the inductive element. Further, the primary conductor 33 and the secondary conductor 3
4 is connected to an external conductor (not shown) via a primary terminal 33a and a secondary terminal 34a.

The insulating plate 32 is made of a material having high insulating properties, such as a glass epoxy material, a paper epoxy material, and a phenol resin.
The primary conductor 33 and the secondary conductor 34 are formed by forming a copper foil on the insulating plate 32 in the drawing, but the present invention is not limited to this. Is preferably selected. Further, the primary conductors 33 and 2
As the insulating layer formed on the next conductor 34, a material such as a glass epoxy material, a paper epoxy material, and a phenol resin is used. The transformer conductor plate 25 having such a structure is
For example, after the patterns of the primary conductor 33 and the secondary conductor 34 are formed on the multilayer printed circuit board by performing an etching process, the holes 31a, 31a, 31b,.

As shown in FIGS. 1A to 1C, the transformer conductor plate 25 is disposed so as to be sandwiched between the base core 23 and the cover core 24. That is, the transformer conductor plate 25 is first placed on the upper surface of the base core 23 by passing the projections 27a, 27a, 27b... Through the long holes 31a, 31a, 31b. Next, the cover core 24 is fixed to the bottom surface 29 and the protrusion 27 of the base core 23.
a, 27a, 27b,... upper surfaces 28a, 28a, 28b,.
Are mounted on the conductor plate 25 for a transformer. Thus, in the transformer 21, the conductor plate 25 for the transformer is arranged so as to be sandwiched between the base core 23 and the cover core 24, and
A secondary conductor 33 and a secondary conductor 34 are arranged in the grooves 30, 30. Further, the core 22 for the inductive element is formed by integrating the base core 23 and the cover core 24. The connection between the base core 23 and the cover core 24 may be performed, for example, by bonding with an adhesive or the like, or by sandwiching with a metal leaf spring or the like.

The protrusions 27a, 27a, 2
7b ... and the upper surface 28a, 28a, 28b ... and the cover core 2
A gap may be provided between the base 4 and the bottom surface 29 for the purpose of suppressing magnetic saturation and adjusting the inductance value. This gap is formed by sandwiching an insulating material such as a resin. As the insulating material used for the gap, a resin or the like having a dielectric constant as small as possible is preferable, and a film of polyimide, polyvinyl chloride, polystyrene, polyester, fluororesin, epoxy resin or the like is optimal. These resins have sufficiently small dielectric constants in the range of 2 to 4,
Any of these can be appropriately selected and used.

As shown in FIG. 4A, the core 22 for the inductive element has a base 26 and projections 27a, 27a, 27b.
, And the cover core 24 form independent closed magnetic paths for passing magnetic flux generated by the voltage applied to the primary conductor 33. This is the unit core 37,
37... (Within the dashed-dotted line frame). Since eleven grooves 30 are provided, the number of unit cores 37 is also eleven. Therefore, the core 22 for the inductive element is composed of one or more unit cores 3.
7, 37... Are arranged in the same plane.

The primary conductor 33 and the secondary conductor 34 are arranged on the unit cores 37, 37,.
The inductive element generates an inductance determined by the cross-sectional area of the magnetic path of 7, 37... And the magnetic permeability of the magnetic material. The primary conductor 33 and the secondary conductor 34 include a unit core 37,
37 are magnetically coupled by a primary conductor 33
Act as a primary winding of the transformer, and the secondary conductor 34 acts as a secondary winding of the transformer.

When the primary conductor 33 and the secondary conductor 34 are arranged on the plurality of unit cores 37, 37, the obtained inductance is equivalently increased. Therefore, if a large inductance value is required, a large number of unit cores 37, 37.
The primary conductor 33 and the secondary conductor 34 may be arranged at the same time.
In the case of this transformer 21, a primary conductor 33 and a secondary conductor are arranged in series with eleven unit cores 37, 37. Therefore, the step-up ratio of this transformer 21 is primary: 2
Next = 11: 11 = 1: 1: 1. The transformer 21 is 2
If the next conductor 34 is arranged only in five unit cores 37, for example, primary: secondary = 11: 5, and a step-down type transformer is obtained. Also, the secondary conductor 34 is laminated via an insulating material,
If arranged on a total of 22 unit cores, primary: secondary = 1
1: 22 = 1: 2, resulting in a step-up type transformer. Thus, in the transformer of the present invention, the primary conductor 33
Alternatively, by appropriately changing the arrangement of the secondary conductor 34 with respect to the unit core 37, a transformer having an arbitrary step-up / step-down ratio can be formed, so that the degree of freedom in circuit design is large.

The core 22 for the inductive element of the present invention is made of Mn.
-It is made of Mn-Zn ferrite having an average particle size of 5 µm or less, obtained by granulating and molding a Zn ferrite raw material powder, and then firing in a temperature range of a stable region where a shrinkage rate by firing is stable. The Mn-Zn ferrite preferably has a composition of at mol%, Fe ₂ O ₃ is 52 to 55, ZnO is 5
-20 and MnO of 25-40. As additives, CaO, Ta ₂ O ₅ , SiO ₂ , Ti
O ₂ or the like may be added.

Fe ₂ O ₃ , ZnO, M used in the present invention
The Mn-Zn ferrite raw material powder composed of nO is preferably manufactured by a hydrothermal synthesis method. Here, the hydrothermal synthesis method is a kind of solution method in powder synthesis from a liquid phase, and is known as a method for producing powder in which formation of coarse fixed particles is relatively small, and an alkaline suspension is used. It is to produce powder particles by water treatment under high temperature and high pressure. In this method, two or more compounds such as a solution and a solid oxide participate in the reaction, and a desired compound is synthesized. When the reaction occurs in this manner, one of the compounds is present as a solution. Alkali metal ions are frequently used. To produce a Mn-Zn ferrite raw material powder by hydrothermal synthesis, for example, first, Mn, Zn, F
An aqueous metal compound solution containing a predetermined amount of e is prepared. As the compound of these elements, various water-soluble compounds can be used, but chlorides and nitrates are preferably used. Then, for example, NaOH, KOH,
An aqueous solution such as aqueous ammonia is contacted and mixed to form an alkaline suspension. Next, this alkali suspension is placed in a pressure vessel such as an autoclave and subjected to a hydrothermal reaction at 120 to 250 ° C. to generate a ferrite precipitate. Then, the obtained ferrite precipitate is dried to obtain a desired raw material powder.

As additives, CaO, Ta ₂ O ₅ ,
When SiO ₂ , TiO _2, or the like is added, these additives suppress grain growth of ferrite to reduce overcurrent loss,
It has the effect of suppressing core loss. In addition, the solid solution of these additional elements in the ferrite main component solid phase also has the effect of reducing lattice defects in ferrite and reducing core loss. The additive is added by mixing an appropriate amount when adjusting the aqueous metal compound solution.

When CaO is added to the raw material powder, the content of the CaO in the ferrite should be 0.02 to 0.25 mol in order to reduce the core loss of the Mn-Zn ferrite.
%. If the amount of CaO is too large, the magnetic properties such as initial permeability deteriorate, so that the amount of CaO is particularly large.
The range of 02 to 0.2 mol% is more preferable. Ta ₂ O ₅
Is preferably added to the raw material powder such that the content in the ferrite is 0.02 to 0.35 mol% in order to reduce the core loss of the Mn-Zn ferrite. The addition amount of the case of adding SiO ₂ in the raw material powder, in order to reduce the core loss of the Mn-Zn ferrite, preferably as content in the ferrite becomes 0~0.3mol%. When TiO ₂ is added to the raw material powder, the content of ferrite is 0.1% in order to reduce the core loss of Mn—Zn ferrite.
It is preferable to set it to 1.5 mol%. Ti
If the amount of O ₂ is too large, the magnetic properties such as initial permeability deteriorate, so the range of 0.1 to 1.3 mol% is more preferable.

The additive element is sufficiently dissolved in ferrite,
For the purpose of promoting a certain degree of grain growth, the obtained raw material powder may be calcined in a reducing atmosphere. The term “reducing atmosphere” used herein refers to an atmosphere in which a reduction reaction occurs in ferrite, such as a nitrogen atmosphere, a vacuum, or an argon atmosphere. The calcining temperature is preferably in the range of 700 to 930 ° C, more preferably in the range of 850 to 930 ° C. If the calcination temperature is lower than 700 ° C., the reduction reaction does not proceed and the additive does not form a solid solution, so that the core loss cannot be reduced. On the other hand, if the calcination temperature exceeds 930 ° C., the growth of the crystal grain size proceeds excessively, and the characteristics deteriorate.

Next, this Mn-Zn ferrite raw material powder is granulated and put into a mold having an inner mold of a desired shape and molded. Granulation is performed by adding a small amount of organic binder and adding
This was performed by passing through a 00 mesh sieve to produce a powder without aggregation. Further, after the raw material powder is made into a slurry by adding water, drying and granulation are simultaneously performed using a spray drier, so that a hollow granular powder can be produced.

By firing the obtained compact, desired Mn-Zn ferrite is obtained. The firing temperature at this time is preferably in a temperature range of a region where the shrinkage ratio is stable. Here, the shrinkage rate is defined as the length of the molded body before firing, L
₀ , when the length changed by firing is ΔL, ΔL
/ L ₀ (%) was measured. As the firing temperature is increased, the shrinkage increases, but it is approximately 900 to 113.
The shrinkage rate becomes constant in the temperature range of 0 ° C. This temperature range is referred to as a temperature range of a region where the shrinkage rate is stable. This 900
Within a temperature range of １1130 ° C., the shrinkage does not change even with a change in temperature. Further, when the firing temperature is increased to 1130 ° C. or more, the shrinkage rate decreases. If the firing temperature is 900 ° C. or lower, the density of the sintered body is not sufficient, and the core loss increases, which is not preferable. On the other hand, if the firing temperature is 1130 ° C. or higher, core loss is increased due to rapid growth of crystal grains, which is not preferable. 900 to 113 at which the shrinkage rate becomes constant
In the temperature range of 0 ° C., the average crystal grain size of the crystal grains can be suppressed to 5 μm or less, and the relative density of the sintered body becomes 95%.
% Or more, so that core loss can be significantly reduced. More preferably, firing is performed at a temperature at which the average crystal grain size of the Mn-Zn ferrite is 1.3 to 3.0 m. Mn—Zn ferrite has an average crystal grain size of 5 μm or less, and more preferably 1.3 to 3.0 μm.
Then, core loss in a high frequency band can be significantly reduced.

The base core 23 shown in FIG. 2A to FIG.
The block-like Mn-Zn ferrite obtained by molding and sintering is used to form grooves 30, 30,.
By forming 7a, 27b ... or
It can be obtained by filling a raw material powder of Mn-Zn ferrite into a mold having an inner shape of the base core 23 and firing it.

When the core 22 for an inductive element using such Mn-Zn ferrite is used as the transformer 21, the core loss is 200 MHz at 1 MHz and 50 mT.
５００500 kW / m ³ and the coefficient of performance is 50 at 1 MHz.
And the frequency at which the coefficient of performance has the maximum value is in the range of 0.2 to 2 MHz. In addition, as long as the average crystal grain size of the raw material powder of Mn-Zn ferrite can be suppressed to a small value, the raw material powder may be produced by a coprecipitation method for generating a hydroxide, in addition to the hydrothermal synthesis method. . Also, the core 22 for the inductive element
May be obtained by a dry method in which fine powders of Fe ₂ O ₃ , ZnO and MnO are mixed, molded and fired.

The above-mentioned core 22 for the inductive element has an average crystal grain size of 5 μm obtained by granulating, molding and firing the Mn—Zn ferrite raw material powder obtained by the hydrothermal synthesis method.
Since it is composed of the following Mn-Zn ferrite,
Core loss in a high frequency band can be reduced.

The above-described core 22 for an inductive element includes a base portion 26 and two or more protrusions 27a, 27a protruding from one surface of the base portion 26 along one direction of the base portion 26.
27b ... or a plurality of protrusions 53a, 53a, 53b ...
, And a cover core 24 having a substantially rectangular shape in a plan view and a predetermined thickness, and the base core 2 is provided with a plurality of protrusion groups 54a, 54a, 54b.
Since the unit cores 37 are formed in large numbers when the cover core 24 is integrated with the cover cores 51, 51, an inductive element whose shape can be made thin can be manufactured. In addition, the above-described base core 23 or base core 51
Are formed by a plurality of protrusions 27a, 27a, 27b...
Are arranged along the longitudinal direction of the base portion 26, and a large number of cubic projections 5, 5,... Unlike the protruded one, the shape is simpler than the base core 6 of the conventional example, so that the base core 23 or the base core 51 can be easily manufactured. In addition, the above-described inductive element core 22 can increase the effective cross-sectional area of the magnetic flux in the unit cores 37, 37... Can be generated. The core 22 for the inductive element described above has an area S1 on the surface of the base portion 26.
And the upper surfaces 28a, 28 of the protrusions 27a, 27a, 27b,.
a, 28b... with the total area S2 is 1.1 ≦ S1 / S.
Since 2 ≦ 5.5, the sectional area of the closed magnetic path of the unit cores 37, 37... Can be made appropriate. In addition, since the base core 23 and the base core 51 of the core 22 for the inductive element described above are provided with the protrusions 27a, 27a or the protrusion groups 54a, 54a at both ends, the leakage magnetic flux can be reduced. .

The core 22 for the inductive element described above is
Its composition in _{mol%, Fe 2 O 3:} 52~55, Zn
O: 5 to 20, MnO: 25 to 40, and a relative density of 97% or more and an average crystal grain size of 1.3 to 3.0 μm
And the core loss of the Mn-Zn ferrite is 1M
Hz, 200-500 kW / m ³ under the condition of 50 mT,
Since the frequency at which the coefficient of performance is 1 MHz is 50 to 300 and the frequency at which the coefficient of performance is the maximum is 0.2 to 2 MHz, an inductive element having a small core loss in a high frequency band can be manufactured.

The above-described transformer 21 includes a core 22 for an inductive element and a conductor plate 25 for a transformer having a primary conductor 33 and a secondary conductor 34 formed on one or both surfaces of an insulating plate 32. The conductor plate 25 for the transformer.
Can be easily manufactured by etching a printed circuit board or the like, so that the manufacturing cost of the transformer 21 can be greatly reduced. Further, since the transformer 21 can be manufactured only by sandwiching the transformer conductor plate 25 between the base core 23 or the base core 51 and the cover core 24, the manufacturing process can be simplified and the manufacturing cost can be reduced. Furthermore, since the above-described transformer 21 includes the core 22 for an inductive element according to the present invention, core loss in a high-frequency band is small, and a reduction in power transmission efficiency can be prevented.

FIGS. 7A to 7D show elongated holes 46 through which the projections 27a, 27a, 27b.
a, 46a, 46b,... and an insulating plate 47 having a perforated hole, and a conductor 48 disposed on one surface of the insulating plate 47 along the edges of the long holes 46a, 46a, 46b,. 49 is shown. This inductor conductor plate 4
By arranging 9 so as to be sandwiched between a base core 23 which is a core 22 for an inductive element and a cover core 24, an inductor (not shown) is formed. That is, first, the conductor plate 49 for the inductor is inserted into the long holes 46a, 46a.
are mounted on the upper surface of the base core 23 by penetrating the projections 27a, 27a, 27b. Next, the cover core 24 is attached to the bottom surface 29 and the protrusions 27a,
The upper surfaces 28a, 28a, 28b,... Of 7a, 27b,. In this manner, in the inductor (not shown), the conductor plate 49 for the inductor is arranged so as to be sandwiched between the base core 23 and the cover core 24, and
A conductor 48 is arranged in the groove 30, 30... Further, the core 22 for the inductive element is formed by integrating the base core 23 and the cover core 24. The conductor 48
By being arranged in the unit cores 37, 37, it becomes an inductive element that generates an inductance determined by the cross-sectional area of the magnetic path of the unit core 37 and the magnetic permeability of the magnetic material. When the conductor 48 is disposed on the plurality of unit cores 37, 37,.
The obtained inductance becomes equivalently large. Therefore, if a large inductance value is required, the conductor 48 may be provided on a large number of unit cores 37, 37.

The above-mentioned inductor (not shown) is a core 2 for an inductive element made of the above-mentioned Mn-Zn ferrite.
2, the core loss in the high frequency band can be reduced and the shape can be made thin. Further, the conductor plate 49 for the inductor is connected to the base core 23.
Since the inductor (not shown) can be manufactured by being sandwiched between the cover core 24 and the cover core 24, the inductor can be easily manufactured and the manufacturing cost can be reduced.

[0045]

EXAMPLE The composition was 53.6 mol% of Fe ₂ O ₃ and ZnO
After adding an appropriate amount of an acrylic polymer as an organic binder to a raw material powder of Mn—Zn ferrite obtained by a hydrothermal synthesis method having 7.1 mol% and MnO of 39.3 mol%, CIP molding was performed at 196 MPa for 180 seconds. ,
Thereafter, by firing at 1050 ° C. for 4 hours in a vacuum, a fired body of Mn—Zn ferrite having an average crystal grain size of 2.2 μm was obtained. From this fired body, a ring-shaped (outer diameter 10 mm, inner diameter 6 mm, thickness 1.5 mm) sample for core loss measurement was cut out.

[0046]

[Comparative Example 1] The composition was 54.5 mol% of Fe ₂ O ₃ and Zn
After adding an appropriate amount of an acrylic polymer as an organic binder to the raw material powder of Mn—Zn ferrite obtained by a dry method in which O is 15 mol% and MnO is 30.5 mol%, CIP molding is performed at 196 MPa for 180 seconds. Mn-Zn having an average crystal grain size of 10 μm by firing at 1300 ° C. for 8 hours in a mixed gas of oxygen and nitrogen.
A ferrite fired body was obtained. From the fired body, a ring shape (outer diameter 10 mm, inner diameter 6 mm, thickness 1.
5 mm) A sample was cut out.

[0047]

Comparative Example 2 The composition was 54.5 mol% of Fe ₂ O ₃ and Zn
Mn—Zn having an average crystal grain size of 1 μm obtained by a dry method in which O is 39 mol% and MnO is 6.5 mol%
After adding an appropriate amount of an acrylic polymer as an organic binder to the raw material powder of ferrite, CIP molding is performed at 196 MPa.
For 180 seconds, and then in oxygen-nitrogen mixed gas for 1 second.
By firing at 200 ° C for 4 hours, the average crystal grain size is 5μ.
m was obtained. From this fired body, a ring-shaped (outer diameter 10 mm, inner diameter 6 mm, thickness 1.5 mm) sample for core loss measurement was cut out.

The Mn− obtained in Examples and Comparative Examples 1 and 2
The relationship between the firing temperature and the shrinkage rate of the Zn ferrite fired body was examined. The shrinkage rate is the length of the fired body before firing as L ₀ ,
When the length changed by firing is ΔL, ΔL / L
₀ (%) was measured. FIG. 8 shows the measurement results. In the fired body of the example, the shrinkage rate increases as the firing temperature increases, and a stable region in which the shrinkage rate is stable in the range of 1000 to 1200 ° C. This is presumably because the variation in the average crystal grain size of the crystal grains of the fired body of the example is small, and the crystal grains shrink simultaneously as the firing temperature increases.
Therefore, the core for the inductive element manufactured from the Mn-Zn ferrite fired body of the example has a small average crystal diameter of crystal grains and small variation, and the relative density of the fired body is increased, so that the core loss is expected to be reduced. Is done. On the other hand, in the fired bodies of Comparative Examples 1 and 2, even when the firing temperature was increased, the increase in shrinkage was not remarkable as in the examples, and no stable region was observed. Therefore, the variation in the average crystal grain size of the crystal grains is large, and the relative density is small, so that the core loss is expected to increase.

The core loss was measured using the ring-shaped sample for core loss measurement obtained in Example and Comparative Examples 1 and 2.
To measure the core loss, use a magnetometer (manufactured by Ryowa Electronics Co., Ltd., M
MS 0375-2.1B) was used. FIG. 9A shows the measurement results.
And FIG. 9B. FIG. 9A shows a frequency of 1 MHz, Bm
2 shows the relationship between the holding temperature of Mn-Zn ferrite and the core loss under the condition that the temperature is 50 mT. The Mn-Zn ferrites of the Examples are different from those of Comparative Examples 1 and 2 at any temperature.
It can be seen that the core loss is much lower than that of Zn ferrite. Further, FIG. 9B shows that Bm · f is 25 × 10 ³ TH
z shows the relationship between the frequency of the sine wave alternating current and the core loss when the installation temperature is 80 ° C. The Mn—Zn ferrite of the example has a lower frequency band (0.
Although the core loss is large at 1 to 0.3 MHz), the core loss is small at a high frequency band (0.3 to 1.5 MHz), which is advantageous in a high frequency band.

Therefore, when a core for an inductive element is manufactured from the Mn-Zn ferrite of the example and a transformer, an inductor, and the like are manufactured using the core for the inductive element, the characteristics in a high frequency band are good. It is expected to be. In particular, when a transformer is manufactured using this inductive element core, the equivalent resistance in the high frequency band decreases, the maximum value of the performance coefficient increases, and the frequency at which the performance coefficient reaches the maximum value is shifted to the high frequency side. Expected to shift. It is also expected that the power transfer efficiency will be good.

[0051]

As described above in detail, the core for the inductive element of the present invention has a Mn having an average crystal grain size of 5 μm or less.
A base core comprising a Zn ferrite, and having a base portion and two or more protrusions or protrusion groups projecting from one surface of the base portion, and a cover core; and the base core and the cover core are integrated. In addition, since the unit core is formed, it is possible to manufacture an inductive element that has a small core loss in a high-frequency band and can have a thin shape. Further, the base core can be easily manufactured. Further, in the core for an inductive element of the present invention, the ratio of the area S1 of one surface of the base portion to the total area S2 of the upper surface of the projection is 1.1 ≦ S1 / S2 ≦ 5.5. The cross-sectional area of the magnetic path of the core can be made appropriate.

The core for the inductive element of the present invention has a composition of mol%, Fe ₂ O ₃ : 52 to 55, ZnO:
5-20, MnO: 25-40, the relative density is 97% or more, the average crystal grain size is 1.3-3.0 μm, and the Mn-Zn ferrite has a core loss of 1M.
Hz, 200-500 kW / m ³ under the condition of 50 mT,
Since the frequency at which the coefficient of performance is 1 MHz is 50 to 300 and the frequency at which the coefficient of performance is the maximum is 0.2 to 2 MHz, an inductive element having a small core loss in a high frequency band can be manufactured.

The transformer of the present invention comprises a core for an inductive element of the present invention and a conductor plate for a transformer having a primary conductor and a secondary conductor. The transformer conductor plate comprises a base core and a cover core. Since the transformer is disposed so as to be sandwiched between them, the transformer can be easily manufactured. Further, it is possible to obtain a transformer in which core loss in a high frequency band is small and power transmission efficiency does not decrease. Further, the shape of the transformer can be reduced.

The inductor of the present invention comprises a core for an inductive element of the present invention and a conductor plate for an inductor having a conductor. The conductor plate for an inductor is sandwiched between a base core and a cover core. Since they are arranged, the inductor can be easily manufactured. Further, an inductor having a small core loss in a high frequency band can be obtained. Further, the shape of the inductor can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a transformer having a core for an inductive element according to an embodiment of the present invention, wherein A is a plan view, B is a side view, C is a front view, D is a rear view.

FIG. 2 is a diagram showing a base core of a core for an inductive element according to an embodiment of the present invention, wherein A is a plan view;
B is a side view and C is a front view.

FIG. 3 is a view showing a cover core of a core for an inductive element according to an embodiment of the present invention, wherein A is a plan view,
B is a side view and C is a front view.

FIG. 4 is a view showing a core for an inductive element according to an embodiment of the present invention, wherein A is a plan view, B is a side view, and C is a front view.

FIG. 5 is a view showing a transformer conductor plate of a transformer having a core for an inductive element according to an embodiment of the present invention, wherein A is a plan view, B is a side view, and C is It is a front view and D is a rear view.

FIG. 6 is a view showing a base core of a core for an inductive element according to an embodiment of the present invention, wherein A is a plan view;
B is a side view and C is a front view.

FIG. 7 is a view showing an inductor conductor plate of an inductor having an inductive element core according to an embodiment of the present invention, wherein A is a plan view, B is a side view, and C is It is a front view and D is a rear view.

FIG. 8 is a graph showing a relationship between a firing temperature and a shrinkage ratio of a fired Mn—Zn ferrite according to an embodiment of the present invention.

FIG. 9 is a diagram for explaining the characteristics of the Mn—Zn ferrite according to the embodiment of the present invention, where A is Mn—Z;
It is a figure which shows the relationship between the holding temperature of n ferrite and core loss, and B is a figure which shows the relationship between the frequency of Mn-Zn ferrite and core loss.

FIG. 10 is a diagram showing a conventional inductor having a core for an inductive element, wherein A is an exploded perspective view of the inductor, and B is a plan view of the core for the inductive element.

[Explanation of symbols]

 Reference Signs List 21 transformer 22 core for inductive element 23 base core 24 cover core 25 conductor plate for transformer 26 base portion 27a protrusion 27b protrusion 28a upper surface of protrusion 28b upper surface of protrusion 29 bottom surface of cover core 30 groove 31a long hole 31b long hole 32 insulation Plate 33 Primary conductor 34 Secondary conductor 48 Conductor 49 Conductor plate for inductor 51 Base core 52 Base portion 53a Projection 53b Projection 54a Projection group 54b Projection group 56 Groove

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akihiro Makino 1-7 Yukitani Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Toshitaka Minamisawa 1163 Shimosei Plane, Inari-cho, Nagano City, Nagano Japan Radio Co., Ltd.

Claims (9)

[Claims] Claims: 1. Mn-Zn ferrite raw material powder is granulated,
It comprises a base core and a cover core of Mn—Zn ferrite having an average crystal grain size of 5 μm or less obtained by molding and firing, and a plurality of projections on at least one surface of the base core and the cover core. The base core and the cover core are superimposed via the protrusion, and the base core, the two or more protrusions, and the cover A core for an inductive element, wherein at least one unit core is formed by the core. 2. Mn-Zn ferrite raw material powder is granulated,
It comprises a base core and a cover core of Mn—Zn ferrite having an average crystal grain size of 5 μm or less obtained by molding and firing, and a plurality of projections on at least one surface of the base core and the cover core. Band-like projections are arranged substantially in parallel with a predetermined interval therebetween, and the base core and the cover core are overlapped with each other via the projections, and the base core and A core for an inductive element, wherein one or more unit cores are formed by the two or more protrusions and the cover core. 3. The core for an inductive element according to claim 1, wherein an area S1 of one surface of the base core or the cover core and a total area S of an upper surface of the protrusion are provided.
2. A core for an inductive element, wherein the ratio to 2 is 1.1 ≦ S1 / S2 ≦ 5.5. 4. The core for an inductive element according to claim 1, wherein the Mn—Zn ferrite comprises:
Its composition in _{mol%, Fe 2 O 3:} 52~55 ZnO: 5~20 MnO: core for the inductive element, characterized in that 25 to 40. 5. The core for an inductive element according to claim 1, wherein the Mn—Zn ferrite has a relative density of 97% or more and an average crystal grain size of 1.3 to 3. 0μ
m, the coefficient of performance is 50 to 300 at 1 MHz,
A core for an inductive element, wherein a frequency at which a coefficient of performance has a maximum value is in a range of 0.2 to 2 MHz. 6. A core for an inductive element according to claim 1, an insulating plate having a hole through which said projection of said base core penetrates, and one or both surfaces of said insulating plate. And a transformer conductor plate including a primary conductor and a secondary conductor formed in the transformer. 7. The transformer according to claim 6, wherein the transformer conductor plate is configured by arranging the primary conductor and the secondary conductor in a zigzag shape along the hole. A conductor plate is disposed so as to be interposed between the base core and the cover core by penetrating the projection through the hole, and the primary conductor and the secondary conductor are disposed in the unit core. A transformer configured to be arranged in a transformer. 8. An inductive element core according to claim 1, an insulating plate having a hole through which said projection of said base core penetrates, and one or both surfaces of said insulating plate. And a conductor plate for an inductor having a conductor formed on the inductor. 9. The inductor according to claim 8, wherein:
The conductor plate for inductor is configured such that the conductor is arranged in a zigzag along the hole, and the conductor plate for inductor penetrates the protrusion through the hole, thereby forming the base core and the cover core. And the conductor is arranged so as to be sandwiched between the unit core and the conductor.