JPH0590039A - Inductance element and magnetic core therefor - Google Patents

Abstract

PURPOSE:To provide an inductance element and a core in which a characteristic of a magnetic material is hard to be lowered even in a high frequency region. CONSTITUTION:A nonmagnetic body is inserted between plural magnetic thin films or magnetic thin bands 21 having a thickness of 5mum or less. They are laminated in a condition to form a core 2 in which both ends are opened. Alternatively, the core is formed with a sheet of magnetic thin film or magnetic thin band having a thickness of 5mum or less. This core 2 is housed within a bobbin 5 comprising a case 3 and a cover 4, and a coil is wound round the outer periphery of the bobbin 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductance element mainly used as a transformer or a choke for a switching power supply and a magnetic core thereof.

[0002]

2. Description of the Related Art A switching power supply device is widely used as a power supply device for various electric devices. In general,
A bulk magnetic core made of ferrite or the like and a plate-shaped magnetic material having a thickness of several hundred μm are used for the transformer and the choke of the switching power supply device. However, such a magnetic core has a large diamagnetic field coefficient when its both ends are open, and exhibits an effective magnetic permeability much smaller than the magnetic permeability of the material itself. Also, at high frequencies, the eddy current loss increases and the characteristics of the transformer and the inductance are remarkably deteriorated.
It could not be used in the Hz band region.

Therefore, conventionally, an inductance element in which a coil is wound around a magnetic core formed by laminating magnetic foil strips is known (see, for example, Japanese Patent Publication No. 3-55963). An example of the structure of this magnetic core is shown in FIG.

In FIG. 10, a magnetic core 50 is formed by laminating a large number of magnetic foil strips 51 in an insulated state from each other. The magnetic foil strip 51 is formed by applying a magnetic film 53 made of a magnetic material on the entire surface of a plate-shaped core material 52 made of a conductive material, and then coating an insulating film 54. The magnetic core 50 of this prior art is formed of a magnetic film 53 made of a magnetic material. Therefore, good inductance characteristics are exhibited even in a high frequency range.

[0005]

However, in the above prior art, since the magnetic foil strip 51 has the core material 52 made of a relatively thick (about 20 μm) conductive material, the magnetic film 53 made of a magnetic material. Even if the thickness is thin (about 3 μm), an eddy current is generated in the core material 52 in the frequency band where the skin depth is 20 μm or less. Therefore, the characteristics as a magnetic material are significantly deteriorated. The present invention has been made in view of the above conventional problems, and an object thereof is to provide an inductance element and a magnetic core for the inductance element in which the characteristics of the magnetic material are less likely to deteriorate even in a high frequency range.

[0006]

In order to achieve the above object, the magnetic core for inductance of the present invention has a thickness of 5 μm.
A plurality of magnetic thin films or magnetic ribbons having a size of m or less are stacked with a non-magnetic material interposed therebetween, and both ends are opened. The magnetic core may be formed of one magnetic thin film or magnetic ribbon having a thickness of 5 μm or less, and may have both ends open. The magnetic thin film refers to a magnetic film having a thickness of 1.0 μm or less, and the magnetic ribbon refers to a band-shaped magnetic material having a thickness of 1.0 μm to several hundreds of μm.

In the inductance element of the present invention, the magnetic core is housed in a bobbin for protection, and a coil is wound around the outer circumference of the bobbin. It is preferable that the bobbin is formed of a box-shaped case having a recess for accommodating the magnetic core, and a cover that abuts the opening end surface of the recess and covers the recess.

According to a fifth aspect of the inductance element, the secondary coil is wound close to the primary coil in a state where the magnetic core is stacked on the non-magnetic reinforcing plate.

[0009]

According to the present invention, the magnetic core for inductance has the non-magnetic material interposed between the magnetic thin film or the magnetic ribbon,
Alternatively, since it is formed of one magnetic thin film or magnetic ribbon and does not have a thick conductive core material, eddy current loss induced in the core material does not occur. Therefore, the loss due to the eddy current can be reduced up to the skin depth frequency band which is equal to or larger than the thickness of the magnetic thin film or the magnetic ribbon. As a result, good inductance characteristics can be obtained up to high frequencies.

Further, since the magnetic core formed by stacking the magnetic thin films or the magnetic ribbons is housed in the bobbin for protection, it is not necessary to provide a core member on the magnetic ribbons, so that the thickness of the magnetic core can be reduced.

Furthermore, when the cover is brought into contact with the opening end surface of the case to form the bobbin, the cover does not fall into the case, so that it is easy to protect the magnetic ribbon inside.

Further, by forming a thin magnetic thin film or magnetic ribbon in the longitudinal direction to increase the ratio of the length to the thickness of the magnetic ribbon, the demagnetizing factor of the magnetic core can be made extremely small. You can Therefore, the inductance of the coil wound above can be considered to be almost uniform at any position. That is, the magnetic core whose both ends are open and the magnetic core whose both ends are terminated perform the same action. Therefore, the coupling coefficient can be brought close to 1.0 without making the magnetic core into a closed loop.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of the present invention. In FIG. 1, a magnetic core 2 of an inductance element 1 such as a transformer is open at both ends, and a large number of magnetic ribbons 21 made of an amorphous alloy (amorphous alloy) made of a magnetic material are placed between them. It is configured by stacking with a magnetic body interposed. As the structure of the magnetic core 2,
As shown in FIG. 2A, each magnetic ribbon 21 may be coated with a highly elastic rubber-like insulator 22,
Alternatively, as shown in FIG. 2B, a separation film 23 made of an adhesive nonmagnetic material may be interposed between the magnetic ribbons 21.

In this embodiment, the magnetic core 2 is constructed by stacking 20 to several tens of magnetic ribbons 21 of about 3 μm. However, the magnetic core 2 may be configured by stacking a magnetic thin film having a thickness of 1.0 μm or less or a magnetic ribbon 21 having a thickness of 1.0 μm to 5.0 μm, or a single magnetic thin film or a magnetic ribbon 21. You may. Here, the separation film 23 to be inserted may be a conductive material. However, when the conductive separation film 23 is used, the thickness of the separation film 23 needs to be set thinner than the thickness of the magnetic ribbon 21 in order to reduce the eddy current loss.

The bobbin 5 shown in FIG. 1 includes a lower case 3 and a cover 4.
And protects the stacked magnetic cores 2. The lower case 3 has a box shape having a recess 30 for accommodating the magnetic core 2, and has bulk terminal portions 31 at both ends and a bottom plate 32.
And the two side plates 33 rising from the bottom plate 32 are integrally formed. Each terminal portion 31 is provided with a pair of L-shaped terminal pieces 36 forming the winding binding portion 34 and the surface mounting terminal 35 by insert molding. On the upper end surface 33a of the side plate 33 of the lower case 3, that is, on the opening end surface of the recess 30 in the lower case 3, a fitting recess 37 into which the cover 4 is fitted is formed. On the other hand, the cover 4 is made of a strip-shaped plate having a fitting convex portion 41, and
As shown in FIG. 5, the fitting convex portion 41 is fitted over the fitting concave portion 37, covers the upper end portion of the side plate 33 of the lower case 3, and covers the concave portion 30.

The lower case 3 and the cover 4 are
It is preferably composed of a non-magnetic material having a high thermal conductivity and a thermal conductivity of approximately 0.1 cal / cm · s · ° C or higher. As such a non-magnetic material, for example, ceramics such as zirconia and amylna can be used.

A coil 6 is wound around the bobbin 5 accommodating the magnetic core 2 (FIG. 1), as shown in FIG. Thickness T of bobbin 5 around which coil 6 is wound
Is thinner than the terminal portion 31, and
The coil 6 is set to be slightly thicker than the terminal portion 31 in a wound state.

Next, a method of manufacturing the inductance element 1 will be described. First, a magnetic material is applied to a base material by a plating method, a quenching method, or an evaporation method, and then the base material is peeled off or the base material is dissolved and removed.
The magnetic ribbon 21 of is obtained. Then, a fine powder of alumina or small diameter fine particles such as nylon balls dispersed in a liquid adhesive or silicon rubber is applied to the surface of the magnetic ribbon 21 to bond the magnetic ribbons 21. After the bonding, the laminated magnetic ribbons 21 are pressed to allow excess silicon rubber material to flow out, and uniform separation films 23 are formed between the magnetic ribbons 21 as shown in FIG. 2B. As a result, the magnetic core 2 accommodated in the bobbin 5 of FIG. 1 is obtained.

After that, the magnetic core 2 is dropped into the recess 30 of the lower case 3, the cover 4 is fitted into the lower case 3, and the magnetic core 2 is housed in the bobbin 5 of FIG. After this storage, as shown in FIG. 4, the coil 6 is wound around the outer circumference of the bobbin 5 to obtain the inductance element 1. The magnetic core 2 in FIG.
Only the both end portions 24 in the longitudinal direction L in the above may be adhered to the inner surface of the lower case 3.

In the above structure, the magnetic core 2 of the present invention is
Unlike the conventional example of FIG. 10, since the conductive thick core material 52 is not provided, eddy current loss induced in the core material 52 does not occur. Therefore, it is possible to reduce the loss due to the eddy current up to the skin depth frequency band which is equal to or larger than the thickness of the magnetic thin film or the magnetic ribbon 21 of FIG. As a result, good inductance characteristics can be obtained up to high frequencies.

By the way, if the magnetic film 53 is attached to the thick core material 52 by plating as in the conventional example of FIG. 10, unless the thermal expansion coefficients of the core material 52 and the magnetic film 53 are matched, the magnetic film 53. Since thermal stress is generated inside the magnetic material, the characteristics of the magnetic material cannot be fully obtained. In contrast to this, the present invention does not have a core material as shown in FIG. 2 and the non-magnetic body 22 to be inserted is rubber-like, so that the thermal stress generated in the magnetic ribbon 21 is extremely reduced. Can be made smaller. Therefore, the characteristics originally possessed by the magnetic material can be sufficiently obtained.

When the magnetic ribbon 21 is made of an amorphous alloy, if the coil is directly wound around the magnetic film 53 coated with the insulating film 54 as in the conventional example shown in FIG. As a result, stress is generated in the magnetic material, and the same problem as described above occurs. On the other hand, according to the present invention, since the magnetic core 2 is housed and protected in the bobbin 5 of FIG. 1, no stress is generated in the magnetic ribbon 21 constituting the magnetic core 2, so that the characteristics of the magnetic material can be sufficiently obtained. be able to.

Particularly, in this embodiment, since the convex portion 41 of the cover 4 abuts on the concave portion 37 of the upper end surface 33a of the lower case 3, by winding the coil 6 around the bobbin 5, it is possible to obtain the structure shown in FIG.
There is no possibility that the cover 4 of the above will fall into the lower case 3. Therefore, the magnetic ribbon 21 of FIG. 1 housed in the bobbin 5 can be protected.

By the way, the magnetic core 2 generates heat during switching. Here, in this embodiment, since the bobbin 5 is made of a non-magnetic material having a relatively high thermal conductivity, the heat of the magnetic core 2 is efficiently transferred to the outside via the bobbin 5 and the coil 6 (FIG. 4). Since it can be released, the power consumption can be increased. In order to enhance the heat dissipation effect, the cover 4 may be made of a conductive material having a high thermal conductivity and a thin material that does not cause skin depth.

In the above embodiment, the mounting terminals 35 are projected in the width direction W, but as shown in FIG.
5 may be projected in the longitudinal direction L. In addition, the terminal portion 31
Instead of projecting the L-shaped terminal piece 36 from the
As in (b), the terminal piece 36A made of a thick film may be integrally molded and embedded. Furthermore, as shown in FIG.
The terminal piece 36A made of a thick film may be provided at the end portion in the longitudinal direction L, and the terminal portion 31 may be provided in the longitudinal direction L with the tunnel-shaped groove 38 for passing the end portion of the coil 6. Needless to say, the present invention can be applied to a choke coil.

6 and 7 show a second embodiment of the present invention. In FIG. 6, the magnetic core 2 is the same as in FIG.
It has the same structure as the magnetic core 2 of (a) or (b). The magnetic ribbon 21 forming the magnetic core 2 in FIG. 6 has a large ratio of the length L1 to the thickness thereof, for example, the length L1 is 21 mm and the thickness is 3 μm. The magnetic core 2 is stacked on a non-magnetic reinforcing plate 7 made of plastic or ceramic. In this state,
As shown in FIG. 7, by winding the winding bundle 8 composed of the primary coil 6A and the secondary coil 6B into two spirals and winding it around the magnetic core 2, that is, by applying the bifilar winding to the magnetic core 2,
A transformer (inductance element) 1 is configured.
The width W1 of the reinforcing plate 7 is set to be slightly larger than the width W2 of the magnetic ribbon 21.

In the above structure, since the transformer 1 has a large ratio of the length L1 to the thickness of the magnetic ribbon 21 (for example, 7,000 times), the demagnetizing field coefficient of the magnetic core 2 becomes small, so that the magnetic flux generates magnetic flux. The magnetic flux passes through the magnetic core 2 with little leakage from the magnetic core 2. Therefore, the coupling coefficient can be brought close to 1.0 without forming a closed loop in the magnetic core 2. As a result, the size and weight of the transformer 1 can be reduced.

In the above embodiment, the winding bundle 8 is attached to the magnetic core 2.
Was wound with a bifilar, but is not necessarily limited to this. For example, as shown in FIG. 8, a secondary coil 6B may be wound around the outer periphery of the primary coil 6A,
Alternatively, as shown in FIG. 9, the primary coil 6A and the secondary coil 6B may be alternately wound, and the winding ratio may be set appropriately.

By the way, the ratio of the length L1 to the thickness of the magnetic ribbon 21 in FIG. 7 is preferably set to 1,000 times or more, but it is better to set it as large as possible.

Further, as in this embodiment, the reinforcing plate 7 is
When the number of sheets is one, by setting the width W1 of the reinforcing plate 7 to be slightly larger than the width W2 of the magnetic core 2, the stress generated in the magnetic core 2 by the tightening force of the coils 6A and 6B can be made relatively small.

In this embodiment, the reinforcing plate 7 is attached to the magnetic core 2.
One piece is provided on the lower surface of the magnetic core.
May be stacked above and below. When the reinforcing plates 7 are stacked above and below the magnetic core 2, the reinforcing plates 7 are stacked as in the first embodiment described above.
Since the magnetic core 2 can be protected by, no local stress is generated in the magnetic core 2. In this case, the width W1 of the reinforcing plate 7 is equal to the width W2 of the magnetic core 2.
May be set approximately equal to.

In the above embodiment, the magnetic core 2 is attached to the reinforcing plate 7.
Although the magnetic core 2 and the reinforcing plate 7 are not adhered only by being stacked on top of each other, the surface of the magnetic core 2 and the reinforcing plate 7 may be adhered to each other for easy assembly.

[0033]

As described above, according to the present invention, the magnetic core for inductance is stacked with a non-magnetic material interposed between the magnetic thin films or the magnetic ribbons, or one magnetic material. It is made of thin film or magnetic ribbon,
Since it does not have a thick conductive core material, eddy current loss induced in the core material does not occur, so good inductance characteristics can be obtained up to the skin depth frequency band that is greater than the thickness of the magnetic thin film or magnetic ribbon. be able to.

Further, since it has no core material, if the magnetic thin film or magnetic ribbon is laminated with an adhesive having flexibility, the expansion coefficient of the adhesive and that of the magnetic material are slightly different. Also, since the adhesive has flexibility, the stress generated in the magnetic material can be minimized, and therefore stable characteristics can be obtained even with temperature changes.

Further, when the cover is brought into contact with the opening end surface of the case of the bobbin, the cover does not fall into the case, so that it is easy to protect the magnetic ribbon inside.

The magnetic core is formed into a closed loop by winding the primary coil and the secondary coil close to each other in a state where the non-magnetic reinforcing plate is stacked on the magnetic core made of a thin and long magnetic ribbon. Even if the transformer is not provided, a transformer having a sufficient coupling coefficient can be obtained, so that the size and weight of the transformer can be reduced.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a bobbin and a magnetic core according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a magnetic ribbon.

FIG. 3 is a perspective view showing a bobbin.

FIG. 4 is a perspective view showing an inductance element.

FIG. 5 is a perspective view showing a modified example of the terminal portion.

FIG. 6 is a perspective view of a magnetic core showing a second embodiment of the present invention.

FIG. 7 is a perspective view of the transformer.

FIG. 8 is a plan view showing a modified example of the transformer.

FIG. 9 is a plan view showing another modification of the transformer.

FIG. 10 is an enlarged cross-sectional view showing a conventional magnetic core.

[Explanation of symbols]

1 ... Inductance element, 2 ... Magnetic core, 3 ... Case, 4 ...
Cover, 5 ... Bobbin, 6 ... Coil, 6A ... Primary coil,
6B: secondary coil, 7: reinforcing plate, 21 ... magnetic ribbon, 2
2, 23 ... Non-magnetic material, 30 ... Recess, 33a ... Open end face.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01F 17/04 F 7129-5E

Claims (5)

[Claims] 1. A magnetic core for an inductance element, which is formed by stacking a plurality of magnetic thin films or magnetic ribbons having a thickness of 5 μm or less with a non-magnetic material interposed therebetween, and opening both ends. 2. A magnetic core for an inductance element, which comprises one magnetic thin film or magnetic ribbon having a thickness of 5 μm or less and whose both ends are open. 3. An inductance element in which the magnetic core according to claim 1 or 2 is housed in a protective bobbin and a coil is wound around the outer circumference of the bobbin. 4. The bobbin according to claim 3, wherein the bobbin is formed of a box-shaped case having a recess for accommodating a magnetic core, and a cover that abuts an opening end surface of the recess and covers the recess. Inductance element. 5. An inductance element in which a secondary coil is wound close to a primary coil in a state where the magnetic core according to claim 1 or 2 is stacked on a non-magnetic reinforcing plate.