JPH11195534A - Core, transformer and inductor for inductive element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core for an inductive element which reduces a core loss in a high frequency band and reduces thickness of its form, to provide a transformer which reduces core loss and avoids the deterioration of power transmitting efficiency, and to provide an inductor which reduces the core loss. SOLUTION: A system adopts a core 22 for an inductive element, consisting of a base core 23 and a cover core 24 comprising Mn-Zn ferrite which is larger than 5 μm average crystal grain diameter obtained by granulate-molding Mn-Zn ferrite material power and then baking, a transformer 21 consisting of a conductor board for a transformer 25 inserted between these cores 23 and 24, and the inductor consisting of a conductor board for the inductor 49 inserted between these cores 23 and 24.

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. 13A, an inductor 1 is of a printed circuit board type, and a core 2 for an inductive element is provided.
, 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. Each of the rectangular parallelepiped projections 5, 5,... Of the base core 6 is formed at the same height. As shown in FIG. 13A, the side surfaces 13 and 13 of the two rectangular projections 5 and 5 are provided on the base core 6.
And a concave portion 10 partitioned by the base portion 4. In the case of the shape shown in FIG.
Since there are nine cuboid projections 5, 5,..., The number is twelve. Further, the core 2 for the inductive element is provided with a cover core 7 made of a plate-like magnetic material. Printed circuit board 3
Are made of an insulating plate 3a made of a glass epoxy material or the like, and holes 12, 12 ... through which the rectangular parallelepiped protrusions 5, 5 ... of the base core 6 penetrate are formed in the insulating plate 3a.

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 recesses 10, 10,.... Conductor 1
Both ends 11a of one are connected to another electronic circuit. 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. 13B, the inductor 1 is applied to the conductor 11 by the two rectangular parallelepiped projections 5, 5 defining the recesses 10, 10, the base 4 and the cover core 7. Independent closed magnetic paths for passing magnetic flux generated by the applied voltage are formed. This is referred to as unit cores 15, 15,... (Within the dashed-dotted line frame). Since twelve concave portions 10 are provided, the number of unit cores 15 is also twelve. 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.

The ferrite material is generally excellent in workability, and the base core 6 can be easily manufactured by putting the ferrite powder into a mold having a predetermined shape and firing it, or processing a block of the ferrite material with a grindstone or the like. can do. However, in the inductor 1 manufactured using the conventional ferrite material, there is a problem that 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. Further, when a transformer is manufactured using a conventional ferrite material, the core loss of the core 2 for the inductive element increases when an alternating current in a high frequency band is applied, and the power transmission efficiency decreases. was there. 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 made of Mn—Zn ferrite having an average crystal grain size of 5 μm or less obtained by granulating, molding and firing, and has a plate-shaped base portion and two or more protrudingly provided from one surface of the base portion. The base core includes a columnar projection, and a plate-shaped cover core. The base core and the cover core are joined to an upper surface of the columnar projection of the base core and a bottom surface of the cover core. And at least one unit core is formed by the base portion, the two or more columnar projections, and the cover core.

Further, the core for an inductive element of the present invention is the core for an inductive element described above, wherein an area S1 of one surface of the base portion and a total area S2 of an upper surface of the columnar projection are provided. Is characterized by 2 ≦ S1 / S2 ≦ 16. Furthermore, the core for an inductive element according to claim 3 is the core for an inductive element according to the above, wherein 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 μm, the performance coefficient is 50 to 300 at 1 MHz, and the frequency at which the performance coefficient 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 for an inductive element, an insulating plate having a hole through which the columnar protrusion of the base core is penetrated, and one or both surfaces of the insulating plate. And a transformer conductor plate having the primary and secondary conductors provided. The transformer according to the present invention is the transformer described above, wherein the transformer conductor plate has the primary conductor and the secondary conductor arranged in a zigzag shape along the hole, and The direction of the current path is arranged so as to be orthogonal to the current path of the primary conductor, and the conductor plate for the transformer allows the base core and the cover core to pass through the hole by penetrating the columnar projection. And the primary conductor and the secondary conductor are arranged in the unit core. A transformer according to the present invention is the transformer described above, wherein at least two or more secondary conductors are formed on the conductor plate for the transformer.

An inductor according to the present invention is formed on one or both sides of the core for an inductive element described above, an insulating plate having a hole through which the columnar protrusion of the base core penetrates, and one or both surfaces of the insulating plate. And a conductor plate for an inductor having a conductor formed. The inductor of the present invention is the inductor according to the above, wherein the conductor plate for the inductor is configured such that the conductor is arranged in a zigzag along the hole, and the conductor plate for the inductor is formed in the hole. By penetrating the columnar projection, the base core and the cover core are arranged so as to be sandwiched between the base core and the cover core, and the conductor is arranged in the unit core. .

[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 has a Mn-
Base core 23 made of Zn ferrite and Mn-Zn
It is composed of a cover core 24 made of ferrite and a conductor plate 25 for a transformer.

As shown in FIGS. 2A to 2C, the base core 23 includes a plate-like base portion 26, and a plurality of columnar protrusions 27 projecting from one surface of the base portion 26 at a predetermined interval.
27... In FIG. 2a, the cross sections of the columnar protrusions 27, 27... Are substantially square and substantially triangular, but the present invention is not limited to this.
It may be polygonal, circular, or elliptical. Are formed so that the heights of the columnar protrusions 27 are the same. If the heights are not the same, it is not preferable because not all the columnar projections 27 can be joined to the bottom surface 29 of the cover core 24 at the time of joining to the cover core 24 described later. Also, the base core 23 has side surfaces 27a, 27 of two adjacent columnar projections 27, 27 facing each other.
a and a concave portion 30 partitioned by the base portion 26. The columnar projections 27, 27...
Are provided, two adjacent columnar projections 27,
There are 72 concave portions 30, 30 ... between 27 ...

As shown in FIG. 2A, the area S1 of one 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 surfaces 28, 28 of the columnar projections 27, 27.
The total area S2 of... Is a triangular shape having 28 square pillar-shaped projections and half the square area on each side of the base core, where z is the length of one side of the upper surface 28 of the pillar-shaped projection 27. There columnar projections 14, since the pillar projection of the triangle is one of the area of a quarter of a square in the four corners of the base core is ^{four, S2 = 28z 2 + 14 /} 2z 2 + 4 / 4z 2 = 3
6z ² . At this time, the ratio between S1 and S2 is 2 ≦ S
It is preferable that 1 / S2 ≦ 16. S1 / S2 is 2
If it is less than the above, the cross-sectional area of the closed magnetic path of the base 26 becomes extremely small, which is not preferable. Also, S1 / S2 is 16
If it is more than the above, the cross-sectional area of the closed magnetic path of the columnar projections 27, 27.

As shown in FIGS. 3A to 3C, the cover core 24 of the core 2 for the inductive element has a plate shape.

As shown in FIGS. 5A to 5D, columnar projections 27, 2
An insulating plate 32 having holes 31 through which holes 7 are penetrated, and a primary conductor 33 formed on one surface of the insulating plate 32
And secondary conductors 34, 35, 36 formed on the other surface. In addition, the primary conductor 33 and the secondary conductor 3
4, 35, 36 are arranged in a zigzag along the edges of the holes 31, 31,..., And the direction of the current path of the secondary conductors 34, 35, 36 is orthogonal to the current path of the primary conductor 33. Are arranged as follows. Further, the primary conductor 33 and the secondary conductor 3
An insulating layer (not shown) is formed on the layers 4, 35, and 36 to maintain insulation between the cores 22 for the inductive element. Further, the primary conductor 33 is connected to an external conductor (not shown) via a primary terminal 33a. Also, the secondary conductors 34, 35, 36 are connected to the secondary terminals 34a, 35a, 36a.
The secondary conductors 34, 35, 36 are connected to each other by a conductor 34b so as to be parallel to each other, and are connected to an external conductor (not shown).

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 conductors 34, 35, 36 are formed by forming copper foil on the insulating plate 32 in the figure.
The present invention is not limited to this, and a copper plate, a copper wire, or the like is preferably selected according to the amount of power applied to the transformer. Further, as the insulating layer formed on the primary conductor 33 and the secondary conductors 34, 35, 36, 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 formed by, for example, forming a pattern of the primary conductor 33 and the secondary conductors 34, 35, and 36 on a multilayer printed circuit board by etching, and then forming the hole 3
Are easily created by piercing 1, 31,.

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, first, the conductor plate 25 for the transformer is provided with the columnar projections 27 in the holes 31, 31.
27 are mounted on the upper surface of the base core 23 by penetrating them. Next, the cover core 24 is moved to its bottom surface 29.
Are mounted on the transformer conductor plate 25 by joining the columnar projections 27, 27,. In this manner, 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 the primary conductor 33
And the secondary conductors 34, 35, 36 are arranged in the recesses 30, 30,. Also, the base core 23 and the cover core 24
Are integrated to form a core 22 for an inductive element. 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.

A gap is provided between the upper surfaces 28, 28 of the columnar projections 27 of the base core 23 and the bottom surface 29 of the cover core 24 for the purpose of suppressing magnetic saturation, adjusting the inductance value, and the like. You can also. 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 as small a dielectric property 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, and can be appropriately selected from these and used.

As shown in FIG. 4A, a magnetic flux generated by a voltage applied to a primary conductor 33 is formed on a core 22 for an inductive element by a base portion 26, columnar projections 27, 27. An independent closed magnetic path is formed for each passage. This is called unit core 37, 37 ...
(Within the dashed line frame). Since 72 concave portions 30 are provided, the number of unit cores 37 is also 72. Therefore, the core 22 for the inductive element has a form in which one or more unit cores 37 are arranged in the same plane.

The primary conductor 33 and the secondary conductors 34, 35, 3
6 are arranged in the unit cores 37, 37,.
The inductive element 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. The primary conductor 33 and the secondary conductors 34, 35, 36 are magnetically coupled by unit cores 37, 37,.
The primary conductor 33 acts as a primary winding of the transformer, and the secondary conductors 34, 35, 36 act as secondary windings of the transformer.

The primary conductor 33 and the secondary conductors 34, 35, 3
When 6 is arranged in the plurality of unit cores 37, 37,..., The obtained inductance becomes equivalently large. Therefore, if a large inductance value is required, the primary conductor 33 and the secondary conductors 34, 35,
36 may be arranged. In the case of this transformer 21, the primary conductor 33 is arranged in series with 72 unit cores 37. Also, the secondary conductors 34, 35, 36
Four unit cores 37 are arranged in series, and the secondary conductors 3
4, 35 and 36 are connected in parallel. Therefore, the step-up ratio of this transformer 21 is: primary: secondary = 72: 24 =
3: 1.

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 crystal grain size of 5 µm or less, obtained by granulating and molding a Zn ferrite raw material powder and then calcining in a temperature range of a stable region in which a shrinkage rate by calcining is stable. This Mn-Zn ferrite
In the composition of mol%, Fe ₂ O ₃ is 52 to 55, ZnO
Is 5 to 20, and MnO is 25 to 40.
Further, as additives, CaO, Ta ₂ O ₅ , SiO ₂ , T
iO ₂ or the like may be one that was 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 amount of CaO added is 0.02 to 0.25 mol in order to reduce the core loss of 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.

[0033] 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 700 ° C. or lower, the reduction reaction does not proceed and the additive does not form a solid solution, so that core loss cannot be reduced.
On the other hand, if the firing temperature is 930 ° C. or higher, the growth of the particle diameter proceeds excessively, and the characteristics deteriorate.

Next, this Mn-Zn ferrite raw material powder is granulated and placed in a mold having an internal 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 FIGS.
By forming grooves in the form of a lattice with a grindstone or the like on the block-shaped Mn-Zn ferrite obtained by molding and firing to form the concave portions 30, 30 ... and the columnar protrusions 27, 27 ..., or Mn is added to a mold having an inner shape of the core 23.
-It can be obtained by filling and firing the raw material powder of Zn ferrite.

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 may be prepared by a coprecipitation method for generating a hydroxide, in addition to the hydrothermal synthesis method. . Also, a core 2 for an inductive element
In order to obtain No. ₂ , a dry method in which fine powders of Fe ₂ O ₃ , ZnO, and MnO are mixed, molded, and fired may be used.

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.
Further, the base core 23 having a complicated shape can be easily manufactured.

The core 22 for the inductive element includes a base core 23 having a base portion 26 and two or more columnar protrusions 27 protruding from one surface of the base portion 26, a plate-shaped cover core. When the base core and the cover core are integrated, a large number of unit cores are formed, so that it is possible to manufacture an inductive element whose shape can be reduced. Also, in the above-described core 22 for the inductive element, the ratio of the area S1 of one surface of the base portion 26 to the total area S2 of the upper surfaces 28 of the columnar projections 27, 27. Since it is 16, the sectional area of the closed magnetic path of the unit core can be made appropriate.

The core 22 for the inductive element described above is
Its composition is mol% and Fe_TwoO_Three: 52 to 55, Zn
O: 5 to 20; MnO: 25 to 40;
Density is 97% or more, average crystal grain size is 1.3 to 3.0 μm
Further, the core loss of the Mn-Zn ferrite is
200 to 500 kW / m under the conditions of 1 MHz and 50 mT
^Three, The coefficient of performance is 50 to 300 at 1 MHz,
The frequency showing the large value is in the range of 0.2 to 2 MHz
Inductive element with low core loss in high frequency band
Can be made.

The above-described transformer 21 is a transformer conductor having an inductive element core 22, a primary conductor 33 and secondary conductors 34, 35, 36 formed on one or both surfaces of an insulating plate 32. Since the transformer conductor plate 25 can be easily manufactured by etching a printed circuit board or the like, the manufacturing cost of the transformer 21 can be greatly reduced. The transformer 21 is provided between the base core 22 and the cover core 23, and the
5, the manufacturing process can be simplified and the manufacturing cost can be reduced. Further, the above-described transformer 21
Means that the secondary conductors 34, 35, 36 are
5, the step-up ratio of the transformer 21 can be easily changed. Furthermore, since the above-described transformer 21 includes the core for the inductive element according to the present invention, core loss in a high-frequency band is small, and a decrease in power transmission efficiency can be prevented.

6a to 6c show another example of a base core 39 in which the columnar projections 38 have a circular cross section. 7a to 7d show holes 40, 40... Having a circular shape, and primary and secondary conductors 41 and 42 formed in a zigzag shape along the edges of the holes 40, 40. A conductor plate 45 for a transformer comprising:
Is shown. This transformer conductor plate 45 is attached to the base core 39.
A transformer (not shown) is formed by being disposed between the cover core 24 and the cover core 24. In such a transformer (not shown), the flow of the magnetic flux between the base core 39 and the primary conductor 33 and the secondary conductors 34, 35, 36 becomes good, the leakage magnetic flux is small, and the power transmission efficiency is reduced. More can be prevented. Such a base core 39
Can be obtained by filling a raw material powder of Mn—Zn ferrite into a mold having a predetermined shape and firing.

FIGS. 8A to 8D show an insulating plate 47 in which holes 46, 46... For penetrating the columnar projections 27, 27 of the base core 23 are formed. 5 shows an inductor conductor plate 49 including a conductor 48 arranged. The conductor plate 49 for the inductor is connected to the base core 23 which is the core 22 for the inductive element and the cover core 2.
4 to form an inductor (not shown). That is, first, the conductor plate 49 for the inductor is inserted into the holes 46, 46,.
27 are penetrated to be placed on the upper surface of the base core 23. Next, the cover core 24 is mounted on the conductor plate 49 for an inductor by joining the bottom surface 29 thereof and the upper surfaces 28 of the columnar projections 27, 27.
Thus, in the inductor (not shown),
An inductor conductor plate 49 is arranged so as to be sandwiched between the base core 23 and the cover core 24, and the conductor 4
8 are arranged in the recesses 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 is disposed on the unit cores 37, 37,.
7 is an inductive element that generates inductance determined by the cross-sectional area of the magnetic path, the magnetic permeability of the magnetic material, and the like. Conductor 4
When 8 is arranged 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-described inductor (not shown) has an Mn-
Since the core 22 for the inductive element made of Zn ferrite is provided, core loss in a high frequency band can be reduced, and the shape can be reduced. Also,
By arranging the inductor conductor plate 49 so as to be sandwiched between the base core 23 and the cover core 24, an inductor (not shown) can be manufactured. Therefore, the inductor can be easily manufactured, and the manufacturing cost can be reduced. Can be lower.

[0045]

EXAMPLES (Example) The composition is 53.6 mol of Fe ₂ O ₃ .
%, ZnO 7.1 mol%, MnO 39.3 mol
% Of an acrylic polymer as an organic binder is added to a raw material powder of Mn-Zn ferrite obtained by a hydrothermal synthesis method which is a CIP molding at 196 MPa.
Sintering at 1050 ° C. for 4 hours in vacuum to obtain Mn—Zn having an average crystal grain size of 2.2 μm.
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.

Next, from the obtained fired body, a width of 34 mm
After cutting out a block of Mn-Zn ferrite having a length of 68 mm and a height of 2.1 mm, grooves having a width of 4 mm and a depth of 1.3 mm are provided in a lattice shape with a gap of 4 mm on the surface of the block with a grindstone or the like. As shown in FIG. 2, a cubic columnar protrusion having a side length of 4 mm and a height of 1.3 mm was formed to produce a base core. A block of MnZn ferrite having a size of 34 mm in width, 68 mm in length, and 0.9 mm in height was cut out from the obtained fired body to obtain a cover core. Further, a 2 mm wide primary conductor and a secondary conductor as shown in FIG. 4 are etched on both sides of a multilayer printed circuit board made of glass epoxy resin and copper foil having a width of 40 mm, a length of 74 mm, and a thickness of 1.2 mm. And a hole was perforated at a position corresponding to the columnar projection of the base core to produce a transformer conductor plate. Further, by joining the base core and the cover core with the transformer conductor plate sandwiched therebetween, the overall size as shown in FIG.
m, a transformer having a length of 74 mm and a height of 3.0 mm.

Comparative Example 1 Composition of Fe ₂ O ₃ was 54.5 m
ol%, ZnO 15 mol%, MnO 30.5 mol
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 of 1%, CIP molding is performed at 196 MPa for 180 seconds, and then at 1300 ° C. in a mixed gas of oxygen and nitrogen. For 8 hours to obtain a fired body of Mn—Zn ferrite having an average crystal grain size of 10 μm. From this fired body,
Ring shape for core loss measurement (outer diameter 10 mm, inner diameter 6 m
m, thickness 1.5 mm) A sample was cut out. Further, a transformer was assembled in the same manner as in the example except that this fired body was used.

(Comparative Example 2) Composition: Fe ₂ O ₃ of 54.5 m
ol%, 6.5 mol% of ZnO, 39 mol of MnO
% Of an Mn-Zn ferrite raw material powder having an average crystal grain size of 1 [mu] m obtained by a dry method, and then adding an appropriate amount of an acrylic polymer as an organic binder, performing CIP molding at 196 MPa for 180 seconds, and then adding oxygen and nitrogen. By firing at 1200 ° C. for 4 hours in a mixed gas, a fired Mn—Zn ferrite having an average crystal grain size of 5 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. Further, a transformer was assembled in the same manner as in the example except that this fired body was used.

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. 9 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. 10 shows the measurement results.
a and FIG. 10b. FIG. 10a shows a frequency of 1 MH
The relationship between the holding temperature of Mn-Zn ferrite and the core loss under the conditions where z and Bm are 50 mT is shown. Mn of Example
-Zn ferrite was obtained in Comparative Examples 1 and 2 at any temperature.
It can be seen that the core loss is much lower than that of Mn-Zn ferrite. Further, FIG. 10b shows that Bm · f is 25 × 1
The relationship between the frequency of the sine wave alternating current and the core loss when the temperature is set to 0 ³ T · Hz and the installation temperature is set to 80 ° C is shown. Mn of Example
-Zn ferrite has a larger core loss in a low frequency band (0.1 to 0.3 MHz) but a smaller core loss in a high frequency band (0.3 to 1.5 MHz) as compared with Comparative Examples 1 and 2. It turns out that it is advantageous in a high frequency band. Therefore, when the inductive element is manufactured using the Mn-Zn ferrite of the example, it is expected that the characteristics in the high frequency band are good.

Next, the characteristics of the transformers of the embodiment and comparative examples 1 and 2 will be described. 11 is equivalent to the release of the transformer secondary conductor, including the time of applying a sine AC wave current of 10 ⁰ to 10 ³ kHz frequency range in the primary conductor, the equivalent inductance L, and copper loss and core loss Resistance R, coefficient of performance Q
(= ΩL / R). The measurement used the impedance analyzer. In FIG. 11B, the transformer of the example has a smaller equivalent resistance in a high frequency band of 10 kHz or more than the transformer of the comparative example. FIG.
In the transformer of the embodiment, the coefficient of performance is 0.2 M
It shows a maximum value near 250 at around 250 Hz.
In the transformer of No. 2, the frequency at which the maximum value of the performance coefficient is 0.
09 to 0.1 MHz, which is lower than the embodiment, and the coefficient of performance itself is about 120 to 160, which is lower than the embodiment. Further, FIG.
In 1a, the transformer of the example has an equivalent inductance value substantially equal to the transformers of Comparative Examples 1 and 2.

In FIG. 12, a load resistor is connected to the terminal of the secondary winding of the transformer of the embodiment, a sine AC voltage (33 V) having a frequency of 500 kHz is input to the primary winding of the transformer, and the secondary winding is connected. The measurement result of the power transfer efficiency with respect to the output voltage when the output voltage from the line is fixed at about 10 V is shown. 12, when the output current is about 0.7 A, that is, when the output power is about 7 W, the power transfer efficiency exceeds 90%, and the power transfer efficiency increases as the output current increases. Especially,
When the output current is 3 A, that is, when the output power is 30 W,
The power transmission efficiency is 95.2%. in this way,
It can be seen that the transformers of the examples exhibit high power transmission efficiency despite being thin.

From the above results, the transformer of the present invention has a small core loss in a high frequency band even though it is thin,
It was found that the power transmission efficiency was good.

[0054]

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 made of Zn ferrite and having a base portion and two or more columnar protrusions protruding from one surface of the base portion; and a cover core having a substantially rectangular shape in plan view and a predetermined thickness. Since the base core and the cover core are integrated and the unit core is formed, it is possible to produce an inductive element that has a small core loss in a high-frequency band and can have a thin shape. it can. Further, a base core having a complicated shape 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 columnar projections is 2 ≦ S1 / S2 ≦ 16. The cross-sectional area of the road can be made appropriate.

Further, the core for the inductive element of the present invention has a composition of mol%, Fe ₂ O ₃ : 52 to 55, ZnO:
5 to 20, MnO: 25 to 40, the relative density is 97% or more, and the average crystal grain size is 1.3 to 3.0 μm.
m, the coefficient of performance is 50 to 300 at 1 MHz,
Since the frequency at which the coefficient of performance has the maximum value is in the range of 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, and the conductor plate for a transformer 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. Further, in the transformer of the present invention, since at least two secondary conductors are formed on the transformer conductor plate, the step-up ratio of the transformer can be easily changed.

The inductor of the present invention comprises the core for the inductive element of the present invention and a conductor plate for the inductor having a conductor, and the conductor plate for the inductor is sandwiched between the base core and the 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 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. 7 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. 8 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. 9 is a graph showing a relationship between a firing temperature and a shrinkage rate of a Mn—Zn ferrite fired body according to an embodiment of the present invention.

FIG. 10 is a diagram for explaining the characteristics of the Mn—Zn ferrite according to the embodiment of the present invention.
It is a figure which shows the relationship between the holding temperature of Zn ferrite and core loss, and b is a figure which shows the relationship between the frequency and core loss of Mn-Zn ferrite.

FIG. 11 is a diagram for explaining characteristics of a transformer having a core for an inductive element according to an embodiment of the present invention, in which “a” indicates a relationship between a frequency of a current input to the transformer and an equivalent inductance; B is a diagram showing the relationship between the frequency of the current input to the transformer and the equivalent resistance,
c is a diagram showing the relationship between the frequency of the current input to the transformer and the coefficient of performance.

FIG. 12 is a diagram showing the power transmission efficiency of a transformer having a core for an inductive element according to an embodiment of the present invention.

FIG. 13 is a view showing a conventional inductor having a core for an inductive element, where 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 27 columnar projection 28 upper surface of columnar projection 29 bottom surface of cover core 30 concave portion 31 hole 32 insulating plate 33 primary conductor 34 secondary Conductor 35 Secondary conductor 36 Secondary conductor 48 Conductor 49 Conductor plate for inductor

 ──────────────────────────────────────────────────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,
A base core made of Mn—Zn ferrite having an average crystal grain size of 5 μm or less obtained by firing after molding, and having a plate-shaped base portion and two or more columnar protrusions protruding from one surface of the base portion; The base core and the cover core are integrated by joining the upper surface of the columnar protrusion of the base core and the bottom surface of the cover core, A core for an inductive element, wherein one or more unit cores are formed by the base portion, the two or more columnar projections, and the cover core. 2. The core for an inductive element according to claim 1, wherein a ratio of an area S1 of one surface of the base portion to a total area S2 of an upper surface of the columnar projection is 2 ≦ S1 / S2. ≤16
A core for an inductive element, characterized in that: 3. The core for an inductive element according to claim 1, wherein the composition of the Mn—Zn ferrite is mo.
In _{l%, Fe 2 O 3:} 52~55 ZnO: 5~20 MnO: core for the inductive element, characterized in that 25 to 40. 4. The core for an inductive element according to claim 1, wherein the relative density of the Mn—Zn ferrite is 97% or more, and the average crystal grain size is 1.3 or more.
3.0 μm, and the coefficient of performance is 50 to 300 at 1 MHz.
And the frequency at which the coefficient of performance has the maximum value is 0.2 to 2M.
A core for an inductive element, which is in the range of Hz. 5. The core for an inductive element according to claim 1, an insulating plate having a hole through which the columnar protrusion of the base core penetrates, and one surface of the insulating plate or A transformer comprising: a transformer conductor plate having a primary conductor and a secondary conductor formed on both surfaces. 6. The transformer according to claim 5, wherein in the transformer conductor plate, the primary conductor and the secondary conductor are arranged in a zigzag shape along the hole. The direction of the current path is arranged so as to be orthogonal to the current path of the primary conductor, and the base plate and the cover core are formed by allowing the transformer conductor plate to penetrate the columnar projection through the hole. Wherein the primary conductor and the secondary conductor are arranged in the unit core. 7. The transformer according to claim 5, wherein at least two or more secondary conductors are formed on the conductor plate for the transformer. 8. An inductive element core according to any one of claims 1 to 4, an insulating plate having a hole through which said columnar projection of said base core penetrates, and one surface of said insulating plate or An inductor comprising: a conductor plate for an inductor having conductors formed on both surfaces. 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 columnar projection through the hole, thereby forming the base core and the cover. An inductor, which is arranged to be sandwiched between a core and the conductor, and wherein the conductor is arranged in the unit core.