JPH04304601A - Magnetic material and induction electromagnetic apparatus - Google Patents

Abstract

PURPOSE:To provide a magnetic material whose permeability and magnetic flux density are sufficiently elevated while minimizing the eddy current loss in the case of being used at high frequencies, and an induction electromagnetic apparatus like a transformer or a chock wherein this is used as its core. CONSTITUTION:This is a magnetic material where the gap between each second magnetic powder 5 is stopped with the first magnetic powder 3 by mixing the second magnetic powder 5 of high permeability larger in particle diameter than the above magnetic powder 3 in the solution where the first magnetic powder 3 being superfine particles are dispersed in a dispersant 2, and the surface of the above first magnetic powder 3 is covered with a surfaceactive agent 4, and the fellow particles of the first magnetic powder 3 do not contact with each other. By molding a coil 6 with this magnetic material, it is made an induction electromagnetic apparatus.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic materials used in a wide frequency range from low frequencies to high frequencies, and induction electromagnetic devices such as transformers and chokes made using the magnetic materials.

0002

BACKGROUND OF THE INVENTION For example, ferrite is one of the conventionally known magnetic materials for high frequencies. In this ferrite, in order to reduce loss due to eddy current when used at high frequencies, it is possible to reduce the crystal structure by mixing impurities during sintering, but the smaller the crystal structure, the more The magnetic permeability cannot be made sufficiently high due to the combination of the increased influence of the insulating film covering the ferrite particles and the increased demagnetizing field coefficient considering the shape of the particles. Furthermore, due to the material properties of ferrite itself, the maximum magnetic flux density Bm is a relatively small value of about 4500 to 5000 G (Gauss), making it difficult to obtain a sufficient magnetic material for high frequencies.

[0003] Another conventionally known magnetic material is a ribbon of amorphous material. By manufacturing this amorphous thin strip to a thickness of several microns, it is possible to obtain a product with excellent magnetic permeability in a relatively wide frequency range from several hundred KHz to several MHz, and with low iron loss. When trying to actually use it, it cannot be processed into any shape, and there are restrictions on the shape it can be used in. That is, since the magnetic field of a ribbon has directionality, when the ribbon is punched into a desired shape, distortion occurs and the magnetic properties deteriorate. In addition, annealing or the like is required to eliminate the distortion, resulting in low productivity and high costs. Therefore, in the case of thin strips such as amorphous, there are no other ways to use them than by winding them in a toroidal shape.
There is a drawback in practical use that it is technically difficult to process and use it into a free shape, both technically and cost-wise.

It has also been known to compress magnetic powder and use it as a high frequency material. Even in this case, if the magnetic powder is made smaller in an attempt to reduce loss due to eddy currents at high frequencies, the magnetic permeability cannot be made sufficiently high due to the influence of the insulating coating covering each powder and the demagnetizing field. Conversely, increasing the size of the magnetic powder increases loss due to eddy currents. Therefore, when compressing the magnetic powder to increase the space factor in order to increase the magnetic permeability, the insulating coating of the magnetic powder is broken and the eddy current loss increases.

Furthermore, attempts have been made to stack thin films formed by vapor deposition techniques, but in this case, a large cross-sectional area is required when used as a magnetic material for high frequency and high power applications. However, in order to increase the cross-sectional area by stacking thin films, it is necessary to repeat the process of inserting an insulating layer for each layer under vacuum conditions, making the manufacturing process extremely complicated and expensive, making it impractical. Missing. Furthermore, due to the necessity of lamination, it is virtually impossible to manufacture the device in a shape other than a plate shape, and the degree of freedom in shape is also reduced.

Furthermore, a technique is also known in which a magnetic powder material with high magnetic permeability and high magnetic flux density is hardened with an adhesive such as an epoxy resin. However, in this case, the gap between the magnetic powders is simply filled with a resin with low magnetic permeability, so it is not much different from the situation where air gaps remain between the magnetic powders, and as a result, the magnetic permeability can be increased. I can't.

The present invention was made in view of the above circumstances, and its main purpose is to provide a magnetic material with sufficiently high magnetic permeability and magnetic flux density while minimizing eddy current loss when used at high frequencies. It is said that

Another object of the present invention is to provide products such as transformers and chokes that have high magnetic permeability and magnetic flux density, have excellent heat dissipation properties, and can be miniaturized by improving the space factor. The purpose of the present invention is to provide an induction electromagnetic device.

[0009]

[Means for Solving the Problems] In order to achieve the above object, a magnetic material according to the invention of claim 1 of this application is prepared by dispersing a first magnetic powder, which is an ultrafine particle, in a dispersant. A second magnetic powder having a larger particle size and high magnetic permeability than the first magnetic powder is used.
The first magnetic powder is mixed with magnetic powder, and the surface of the first magnetic powder is covered with a surfactant, so that the particles are not in direct contact with each other.

Further, in the magnetic material according to the second aspect of the invention, in a solution in which first magnetic powder, which is an ultrafine particle, is dispersed in a curable dispersant, there are more particles than the first magnetic powder. A second magnetic powder having a large diameter and high magnetic permeability is mixed and hardened.

[0011] Further, according to the invention of claim 3, an induction electromagnetic device such as a transformer or a choke made of the above magnetic material comprises a coil having an insulating film formed on its surface and the magnetic material of claim 1. is enclosed in a case, and a core is formed of the magnetic material.

[0012]Furthermore, according to a fourth aspect of the invention, an induction electromagnetic device such as a transformer or a choke using the above magnetic material includes a coil having an insulating film formed on the surface of the magnetic material according to claim 2. is molded, and the core is formed of this magnetic material.

[0013] The first magnetic powder used in this invention is as follows:
In addition to manganese-zinc ferrite powder, ferrite containing manganese, iron, nickel, copper, magnesium, etc., iron nitride, or metal materials such as nickel and cobalt can be used, and the particle size is usually 10 Å to 5000 Å. , and the relative magnetic permeability μ is 5 or more, for example 5 to 200.
It is.

Further, as the second magnetic powder used in the present invention, pure iron, permalloy, ferrite, amorphous material, sendust, silica steel, etc. can be used, and the particle size is 1
It is preferable that the magnetic flux density B is about 100 μm to about 100 μm, the relative magnetic permeability μ is 1000 or more, and the magnetic flux density B is about several thousand to 30000 G. Further, the second magnetic powder may be spherical, plate-like, fibrous, or acicular, but plate-like, fibrous, and acicular are preferable in that the demagnetizing field is small.

[0015] In addition, the dispersants used in this invention include those that do not have hardening properties such as petroleum-based kerosene, paraffin, or water, thermosetting resins, two-component adhesives, and those that do not have hardening properties such as petroleum-based kerosene, paraffin, or water. There are general-purpose adhesives that harden and those that have hardening properties, such as plastic monomers such as acrylic monomers that do not have adhesive properties. As the thermosetting resin, monomers such as urea resin, melamine resin, phenol resin, epoxy resin, unsaturated polyester resin, polycarbonate resin, alkyd resin, or urethane resin can be used. Further, as the two-component adhesive, for example, an epoxy resin consisting of Epicoat 808 (manufactured by Shell) and an amine hardening agent can be used. Moreover, polycarbonate-based allyl diglycol carbonate can be used as a dispersant having a lower viscosity than the epoxy resin.

Furthermore, the surfactant used in this invention varies depending on the dispersant used, but when the dispersant is an epoxy resin, β...(3,4 epoxycyclohexyl)ethyltrimethoxylane or γ- Silane coupling agents such as glycidoxypropyltrimethoxylane can be used, and titanium coupling agents can also be used. When allyl diglycol carbonate is used as a dispersant, γ-aminopropyltriethoxysilane can be used as a surfactant.

[0017]

[Operation] The magnetic material according to the invention of claim 1 is characterized in that a second magnetic powder having a particle size larger than that of the first magnetic powder and having a high magnetic permeability is added to a solution in which a first magnetic powder, which is an ultrafine particle, is dispersed. is mixed in, so the gap formed between the second magnetic powder is different from that of the first magnetic powder.
Since it is filled with magnetic powder, magnetic permeability and magnetic flux density can be increased. Moreover, since the surface of the first magnetic powder intercalated between the second magnetic powders is covered with a surfactant,
The state is similar to that in which an insulating film is formed between the second magnetic powders, and an increase in eddy current loss due to dielectric breakdown is also suppressed.

Further, in the magnetic material according to the second aspect of the invention, a solution obtained by dispersing first magnetic powder, which is an ultrafine particle, in a curable dispersant is used as the solution. Magnetic materials of any shape can be easily created by simply pouring the material into a mold and allowing it to solidify. In other words, it is possible to freely select the shape of the magnetic body with high magnetic permeability and high magnetic flux density depending on its use.

Further, according to the induction electromagnetic device according to the invention of claim 3, a coil having an insulating film formed on the surface and the magnetic material of claim 1 are enclosed in a case, and the core is formed by the magnetic material. Since the coil and the magnetic material (core) with good thermal conductivity are in direct contact with each other via the insulating film, this is different from the conventional type where there is an air layer or coil bobbin between the coil and the core. Compared to this, it is possible to significantly increase the heat dissipation coefficient of induction electromagnetic devices such as transformers and chokes, thereby improving heat dissipation. Further, by appropriately shaping the case, the dead space between the coil and the core can be reduced, the space factor can be further increased, and downsizing can be achieved. In other words, in conventional induction electromagnetic devices in which a coil is attached to the outer periphery of the core, the coil bulges out relative to the core, and a dead space is created around the bulged coil. By making the case cylindrical, for example, dead space can be eliminated, and the size can be reduced accordingly.

Furthermore, according to the induction electromagnetic device according to the invention of claim 4, the coil having an insulating film formed on the surface has the structure of claim 2.
The core is formed by molding a magnetic material, so simply by molding the magnetic material onto the coil, the magnetic material with good thermal conductivity will enter the gaps between the coils and solidify. , the heat dissipation performance is improved by increasing the heat dissipation coefficient, and the size is reduced by increasing the space factor.

[0021]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. First, a magnetic material using spherical second magnetic powder will be described. In FIG. 1, 1 is a magnetic fluid;
As clearly shown in FIG. 2, this magnetic fluid 1 has a dispersant 2 containing a surfactant 4 that has an affinity for the dispersant 2 and the first magnetic powder 3, which is an ultrafine particle. It is made by dispersing the powder 3 at a high concentration and is in the form of a solution. That is, the magnetic fluid 1 uses the dispersant 2 as a medium to disperse the first magnetic powder 3 forming the magnetic fluid 1, and the first magnetic powder 3 is dispersed in the magnetic fluid 1.
The surface of the magnetic powder 3 is covered with the surfactant 4 to prevent the particles from coming into direct contact with each other. The particle size of the first magnetic powder 3 that can form the magnetic fluid 1 is usually 10 Å to 500 Å.
It is. Further, the relative magnetic permeability μ of the magnetic fluid 1 varies depending on the material of the first magnetic powder 3, but is usually 5 to 200.

In FIG. 1, 5 is a second magnetic powder, and this second magnetic powder 5 has a particle size of about 1 to 100 μm, a relative permeability μ of 1000 or more, and a magnetic flux density B of several thousand to 300 μm.
00G, and by mixing this second magnetic powder 5 into the above-mentioned magnetic fluid 1, the magnetic fluid 1 containing the first magnetic powder 3 is interposed in the gap between the second magnetic powders 5 having a large particle size. I'm letting you do it. Note that the particle size of the second magnetic powder 5 is selected depending on the frequency used. For example, it is selected to reduce the eddy current loss, such as 5 μm for 1 MHz and 1 μm for 10 MHz.

Next, a method for manufacturing the above magnetic material will be explained. As shown in FIG. 3(a), a second magnetic powder 5 of, for example, iron-based amorphous, cobalt-based amorphous, or pure iron is mixed into the magnetic fluid 1, and then ultrasonic vibrations are applied to the mixed liquid. Add. As a result, the second magnetic powder 5
The second magnetic powders 5 in the magnetic fluid 1 settle and are naturally aligned as shown in FIG. 3(b) so that the positional potential of is the lowest, and the space factor becomes high.

In the magnetic material manufactured as described above, the magnetic permeability μ of the precipitation region X shown in FIG. 3(b) is high;
Since the magnetic flux density Bm is also large, this precipitated region X is used as a magnetic material.

By the way, in the magnetic material obtained as described above, the gap formed between the second magnetic powders 5 having the characteristics of high magnetic permeability and high magnetic flux density is filled with the magnetic fluid 1. This magnetic fluid 1 is a ferrite magnetic fluid, with relative magnetic permeability μ=6 to 10 and maximum magnetic flux density Bm=40.
0 to 500G, in the case of iron nitride magnetic fluid, relative magnetic permeability μ = 180 to 200, maximum magnetic flux density Bm = 1800G
becomes. For example, when a magnetic fluid 1 with a relative magnetic permeability μ=180 is interposed, at low magnetic flux density where the magnetic fluid 1 is not magnetically saturated, the gap is essentially compressed to 1/180. This increases the magnetic permeability of the entire material even more than when a resin adhesive is interposed in the gap.

Furthermore, since the surface of the second magnetic powder 5 is also covered with an insulating film and a surfactant, an increase in eddy current loss due to dielectric breakdown between the second magnetic powders 5 is also suppressed. Eddy current loss can be minimized when used at high frequencies. Moreover, whether to put the magnetic material 1 in the case,
Alternatively, when a curable dispersant is used, a magnetic material of any shape with high magnetic permeability can be obtained by pouring the magnetic material 1 into a mold or the like.

Next, magnetic materials according to other embodiments of the present invention will be explained. This embodiment shows an example in which plate-shaped, needle-shaped or fibrous powder is used as the second magnetic powder 5, and in the magnetic fluid 1, for example, plate-shaped powder such as iron-based amorphous or cobalt-based amorphous powder, etc. A needle-like or fibrous second magnetic powder 5 is mixed. In this mixed state, Figure 4
As shown in (a), the second magnetic powder 5 is randomly oriented, and by applying ultrasonic vibration to it,
So that the positional potential of the second magnetic powder 5 is the lowest,
The second magnetic powder 5 in the magnetic fluid 1 settles, as shown in FIG. 4(b).
They are arranged in a stacked state as shown in the figure, and the space factor is increased.

This embodiment is similar to the above embodiment, and as shown in FIG. A magnetic material filled with a magnetic fluid 1 of high magnetic permeability, high magnetic permeability, high magnetic flux density, and low eddy current loss when used at high frequencies can be obtained.

In particular, it is possible to increase the space factor by using the plate-shaped, needle-shaped or fibrous second magnetic powder 5 and stacking it in the magnetic fluid 1. Since the demagnetizing field coefficient is smaller than that of the second magnetic powder and the second magnetic powder is easily magnetized in the direction of the lines of magnetic force from the outside, the magnetic permeability can be further increased than when the second magnetic powder is spherical. Furthermore, unlike the spherical powder, as shown in FIG. 6, the contact area between the upper and lower surfaces of the second magnetic powders 5 increases, so the magnetic resistance in the vertical direction decreases by the increase in the contact area. Therefore, for example, in the path of the magnetic flux H shown in FIG. Due to the lamination effect of the second magnetic powder 5 in the laminated state, the magnetic flux moves to 5D and 5D.
The magnetic flux H itself selects and passes a place where the magnetic resistance is small, and as a result, the overall magnetic resistance becomes smaller and higher, and high magnetic permeability is obtained.

FIG. 7 shows an example of an induction ceramic manufactured using the above magnetic material. This embodiment is applied to a high frequency transformer. In FIG. 7, 6A, 6B
are air-core coils on the primary side and the secondary side, and the peripheries thereof and the outer peripheries of the lead wires 11A and 11B are tightly covered with an insulator 7 such as an epoxy resin film without any gaps. With the air-core coils 6A and 6B placed in a mold 8, the magnetic material 9 using a hardening dispersant is molded in the mold 8.
After curing, the mold is removed to form a high-frequency transformer having an appearance as shown in FIG. 8, in which a core 10 is formed of the magnetic material 9.

In the high frequency transformer manufactured as described above, the coils 6A, 6B and the core 10 made of a magnetic material with good thermal conductivity are in direct contact with each other through the insulator 7, and there is a conventional transformer between them. There is no air layer or coil bobbin as seen in the coils 6A and 6B.
The heat generated can be efficiently released to the outside,
Heat dissipation can be improved. Further, since there is almost no dead space 13 around the bulging coil 12 as seen in the conventional transformer shown in FIG. 9, the space factor can be improved and the transformer can be made smaller.

Furthermore, FIG. 10 shows another embodiment of an induction electromagnetic device manufactured using the above magnetic material. This embodiment is applied to a high frequency choke. In FIG. 10, reference numeral 6 denotes an air-core coil, and the other configurations are the same as those of the high-frequency transformer shown in FIG. 7, so the same reference numerals are given to the corresponding parts and the explanation will be omitted. With the air-core coil 6 placed in a case 15 made of a material such as aluminum or synthetic resin, a magnetic material 9A using a non-hardening dispersant is injected into the case 15, and the case is A lid 15a is attached to the top of the container 15 to enclose it.

[0033] Also in the choke shown in Fig. 10,
Similar to the transformer shown in FIG. 7, heat dissipation can be improved, and the choke can be made smaller by improving the space factor. In particular, since the magnetic material 9A is in a fluid state and has high thermal conductivity, the heat radiation coefficient becomes extremely large.

[0034] In each of the above examples, the particle size is 1
Although the description has been made using the magnetic fluid 1 made by dispersing the first magnetic powder 3 in the range of 0 Å to 500 Å, it is not necessary to use a complete magnetic fluid. The powder 3 is in an independent form with its surface covered by a surfactant 4 and the distance between the particles is maintained, and magnetic powders do not aggregate together to form large clusters. Any material may be used as long as it can sufficiently fill the gap between the magnetic powders 5. For example, in the case of ferrite powder, ferrite powder with a particle size of 500 Å to 5000 Å can also be used as the first magnetic powder 3 because it can maintain the above-mentioned independent form and has high magnetic permeability. For high frequency applications, if ferrite powder with a particle size of 50 Å to 100 Å is used, it will be in a super para state and the iron loss (hysteresis loss) will be zero, so an ideal state will be obtained from an energy standpoint.

A test example in which the present invention was applied to the choke shown in FIG. 10 will be described below. Test example 1:
As shown in FIG. 11(a), the inductance was measured with the coil 6 left with an air core, and the result was 5.4 μH. Test Example 2: As shown in Figure 11(b), pure iron powder with a particle size of 5 μm (corresponding to the second magnetic powder) was used as the magnetic powder, and this was dissolved with chlorinated paraffin (dispersant) to form a paste. The inductance of the coil 6 was measured by placing it in a container 18, and the inductance was found to be 14.2.
It was μH. Test example 3: As shown in FIG. 11(c),
A ferrite magnetic fluid with a relative magnetic permeability μ=6 was placed in a container 18, the coil 6 was inserted into this magnetic fluid, and the inductance was measured and found to be 18.7 μH. Test example 4
(corresponding to the present invention): As shown in Fig. 11(d), pure iron powder with a particle size of 5 μm is mixed into a ferrite magnetic fluid with a relative magnetic permeability μ = 6, and the coil 6 is inserted into this. As a result of measuring the inductance, it was 26 μH.

As is clear from the above test examples, as in the present invention, a magnetic solution in which a second magnetic powder having a larger particle size is mixed into a solution containing a first magnetic powder, which is an ultrafine particle, It was discovered that by using these materials, it was possible to obtain high magnetic permeability that could not be obtained with each magnetic powder alone.

[0037]

As described above, according to the invention of claim 1 of this application, a magnetic material with high magnetic permeability and high magnetic flux density can be obtained. In particular, as in the invention of claim 2, by using a solution containing the first magnetic powder in which the first magnetic powder, which is an ultrafine particle, is dispersed in a curable dispersant, high permeability can be obtained. It becomes possible to freely select the shape of the magnetic material with high magnetic flux density and magnetic flux density according to its application, and the range of its application can be expanded.

Further, according to the electromagnetic inductor according to the third and fourth aspects of the invention, since the core is formed of the magnetic material described in the first or second aspect, the coil and the magnetic material with good thermal conductivity are connected to each other. (core) are in direct contact with each other through the insulating film, so the heat dissipation coefficient can be significantly increased and heat dissipation performance can be improved. Further, by reducing the dead space between the coil and the core and increasing the space factor, it is possible to realize downsizing.

[Brief explanation of drawings]

FIG. 1 is an enlarged view showing the conceptual structure of a spherical magnetic material according to the present invention.

FIG. 2 is an enlarged view showing the conceptual structure of a magnetic fluid.

FIG. 3 is a process diagram showing a method for manufacturing a magnetic material of the present invention.

FIG. 4 is a process diagram showing a method for manufacturing a magnetic material according to another embodiment of the present invention.

FIG. 5 is an enlarged view of a portion of the magnetic material produced according to FIG. 4;

FIG. 6 is an explanatory diagram of a magnetic flux path in the magnetic material of FIG. 4;

FIG. 7 is a longitudinal sectional view of a high frequency transformer showing an embodiment of the induction electromagnetic device of the present invention.

8 is an external perspective view of FIG. 7. FIG.

FIG. 9 is a perspective view showing a conventional general transformer.

FIG. 10 is a longitudinal cross-sectional view of a choke showing an embodiment of the induction electromagnetic device of the present invention.

FIG. 11 is a schematic diagram showing a test example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Magnetic fluid, 2... Dispersant, 3... First magnetic powder, 4... Surfactant, 5... Second magnetic powder, 6, 6A, 6B... Air core coil, 8... Type, 9... Magnetic material, 10... Core, 15...case.

Claims (4)

[Claims] [Claim 1] A second magnetic powder having a particle size larger than that of the first magnetic powder and having a high magnetic permeability is mixed into a solution obtained by dispersing a first magnetic powder which is an ultrafine particle in a dispersant. The first magnetic powder is a magnetic material whose surface is covered with a surfactant so that the particles are not in direct contact with each other. 2. A second magnetic powder having a particle size larger than that of the first magnetic powder and having a high magnetic permeability is added to a solution obtained by dispersing a first magnetic powder, which is an ultrafine particle, in a dispersant having curability. The first magnetic powder is a magnetic material in which the surface of the first magnetic powder is covered with a surfactant and the particles are not in direct contact with each other. 3. An induction electromagnetic device in which a coil having an insulating film formed on its surface and the magnetic material according to claim 1 are enclosed in a case, and a core is formed by the magnetic material. 4. An induction electromagnetic device in which the magnetic material according to claim 2 is molded onto a coil having an insulating film formed on its surface, and a core is formed of this magnetic material.