ES2775211T3 - Production method of an annular magnetic core made with Fe-based nanocrystalline soft magnetic alloy and production method of a magnetic device comprising the same - Google Patents

Abstract

Production method of an annular magnetic core that comprises winding a soft, nanocrystalline, Fe-based magnetic alloy tape, in which part of the Fe is replaced with Ni and / or Co, and heat treating the tape in a magnetic field of 1,000 A / m or higher applied in a tape width direction at a temperature equal to or higher than a crystallization initiation temperature with a temperature rise rate of 5 ° C / minute or lower; wherein said Fe-based nanocrystalline soft magnetic alloy tape comprises Ni and / or Co from 4 to 6 atomic%, from 0.1 to 2 atomic% Cu, from 0.1 to 4 atomic% Nb, 10 to 11.5 atomic% Si, and 9.2 to 10 atomic% B, and wherein said Fe-based nanocrystalline soft magnetic alloy ribbon comprises more than 75.5 atomic% in total of Fe and Ni and / or Co.

Description

DESCRIPTION

Production method of an annular magnetic core made of Fe-based nanocrystalline soft magnetic alloy and production method of a magnetic device comprising the same

Field of the invention

The present invention relates to a method of producing an annular magnetic core used, for example, in a noise filter, etc., arranged between a power supply and an electronic device in order to suppress noise in a large current, and a method of producing a magnetic device comprising the same.

Background of the invention

In an electronic circuit comprising a power supply 201, an inverter 202, an electronic device 203, and so on, as shown in Fig. 9, noises such as a high-frequency switching noise generated from the conversion part are produced. from the power source 201, a high voltage pulse noise generated from the electronic device 203, for example a motor, etc., causing malfunctions. To avoid such noises, a noise filter 10 is arranged between the power supply 201 and the inverter 202 and the electronic device 203.

Fig. 10 shows the general structure of a noise filter 10 for a three-phase power supply. This noise filter 10 comprises interface capacitors C11, C12, C13, C21, C22, C23 to reduce normal mode noise, a common mode choke 5 to reduce common mode noise, and capacitors C31, C32, C33 connected to ground, between input terminals 101a on the power supply side and output terminals 101b on the electronic device side. To suppress noise in the normal way, a choke coil may be arranged in series with the path of each power source.

Fig. 11 shows an example of common mode choke coils 5. This common mode choke coil 5 comprises, as described in JP 2000-340437 A, for example, an annular magnetic core 1 formed by Mn-Zn ferrite, an amorphous Fe-Si-B alloy, an alloy soft magnetic, Fe-Si-B nanocrystalline, etc., and pluralities of coils 7a, 7b, 7c wound around the annular magnetic core 1. The coil can be of bifilar winding. The common mode choke 5 has a high impedance for the common mode noise of the power supply circuit, attenuating the common mode noise of the power supply by means of the inductance of the coils 7a, 7b, 7c and the capacitors C31, C32, C33 connected to ground, and attenuating the noise in the normal way in the input terminals by means of the interface capacitors C11, C12, C13 connected between the input terminals, the interface capacitors C21, C22, C23 connected between the output terminals, and the leakage inductance of each coil, thus preventing noise from the power supply and electronic devices from interacting with each other. Since noise suppression according to a VCCI or CISPR standard determines, for example, the noise limit of conducted emissions ( noise terminal voltage) in a frequency band from 150 kHz to 30 MHz, noise filters are required to reduce high-voltage noise, as well as noise over a wide frequency range. To suppress high voltage noise, the saturation magnetic flux density of the magnetic material used for the cores of the common mode chokes is important. To suppress noise in a wide frequency band, the permeability of the magnetic material and its frequency characteristics are important.

JP 7-74419 B discloses an Fe-based soft magnetic alloy having a composition represented by the general formula (Fe-i-aMa) ¹⁰⁰ -xYz-aCuxSiYBzM'a, where M is Co and / or Ni, M 'is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo, a, x, y, z and satisfy 0 <a <0.5, 0.1 <x <3, 0 <y <30, 0 <z <25, 5 <yz <30, and 0.1 <a <30; at least 50% of its structure being occupied by fine crystalline grains having a mean grade size of 100 nm or less, the balance being substantially amorphous. This soft, Fe-based magnetic alloy has high permeability at high frequencies, although it is easily magnetically saturated with a high current, thus it may not be able to perform well for choke coils. When a magnetic core becomes magnetically saturated with a high current, its permeability is reduced, resulting in low inductance. Therefore, when used for a noise filter, common mode noise and normal mode noise are less attenuated. When the magnetic core is provided with a magnetic air gap

in the core are increased, and magnetic flux leaks from the magnetic gap.

JP 2006-525655 A discloses a magnetic core formed by an ultra-fine crystalline alloy having a specific permeability p of 500 to 15,000, a saturation magnetostriction X of less than 15 ppm, and characteristics of intensive operation in a linear loop of BH and in AC and DC; at least 50% of the ultrafine crystalline alloy being occupied by fine crystal particles having a mean grain size of 100 nm or less; and the ultrafine crystalline alloy having a composition represented by the general formula of FeaCobNicCudMcSifBgXh, where M is at least one of V, Nb, Ta, Ti, Mo, W, Zr, Cr, Mn and Hf, X is P, Ge , C and unavoidable impurities, and expressing a, b, c, d, e, f, g and h in atomic%, and fulfilling the conditions of 0 <b <40, 2 <c <20, 0.5 <d <2, 1 <e <6, 6.5 <f <18, 5 <g <14, 5 <bc <45, abcdef = 100, and h <5. However, it has been observed that magnetic cores presenting the compositions specifically described in JP 2006-525655 A suffer from the problem that a high specific permeability of AC pr cannot be easily maintained in a DC magnetic field of 150 A / m or higher.

DE 102011 002114 A1 discloses a core wound from Fe-Cu-Nb-Si-B ribbons with up to 5% substitution of Fe by Ni or Co. The core is heated above the temperature of crystallization and is oriented by high fields in the direction of the width of the belt, without specifying heating rates.

Object of the invention

Accordingly, it is an object of the present invention to provide a method of producing an annular magnetic core capable of maintaining high permeability even at high current with a high resistance to magnetic saturation, and a method of producing such a magnetic device such as a choke coil, etc., exhibiting excellent noise reduction effect.

Presentation of the invention

The annular magnetic core produced with the method of the present invention is formed by a soft, nanocrystalline magnetic alloy, based on Fe, in which part of the Fe is substituted with Ni and / or Co, and which has a specific permeability of AC pr ¹⁰⁰ k ( ⁵⁰ ) of 4,000 or higher at a frequency of 100 kHz and a magnetic field intensity Dc of 50 A / m;

a specific permeability of AC pr ¹⁰⁰ k ( ¹⁵⁰ ) of 2,500 or higher at a frequency of 100 kHz and a DC magnetic field intensity of 150 A / m; and

the maximum permeability pMax of 8,000 or less, and a B ⁴⁰⁰ magnetic flux density of 1.3 T or greater at a DC magnetic field intensity of 400 A / m.

The above annular magnetic core preferably has a specific permeability of AC pr ¹⁰ k ( ¹⁵⁰ ) of 4,000 or higher at a frequency of 10 kHz and a magnetic field intensity of DC 150 A / m, and a specific permeability of AC pr- i ⁰ k ( ²⁰⁰ ) of 2,000 or higher at a frequency of 10 kHz and a DC magnetic field strength of 200 A / m.

The method of the present invention is specified in claim 1.

The above Fe-based nanocrystalline soft magnetic alloy is preferably in the form of a ribbon up to 10-25 µm thick. More preferably, the above tape has a thickness of up to 14/25 pm. The magnetic device produced according to the present invention comprises the above annular magnetic core contained in a resin casing, part of the annular magnetic core being fixed with an adhesive. In the first example, a conductor penetrates through a hollow part of the annular magnetic core. In the second example, a conductor is wound around the annular magnetic core. The conductor is a conductive metallic wire or a busbar.

Brief description of the drawings

Fig. 1 is a perspective view showing an example of the annular magnetic cores produced according to the present invention (Example 1).

Fig. 2 is a graph showing a B-H DC loop of the annular magnetic core of Example 1.

Fig. 3 is a graph showing the relationship between the specific permeability of AC pr and the magnetic field intensity in the annular magnetic core of Example 1.

Fig. 4 is a graph showing the frequency characteristics of the AC pr specific permeability in the annular magnetic core of Example 1.

Fig. 5 is a graph showing the frequency characteristics of the impedance in the choke of Example 2.

Fig. 6 is a graph showing the characteristics of the inductance with DC current overlap in the choke coils of Example 2 and Comparative Example 1.

Fig. 7 is a perspective view showing an example of a triphasic common mode choke. Fig. 8 is a graph showing the frequency characteristics of impedance and inductance in the three-phase common mode choke of Example 3.

Fig. 9 is a block diagram showing a circuit comprising a noise filter arranged between a power supply and an electronic device.

Fig. 10 is a view showing an example of the circuit structures of a noise filter for a three-phase power supply.

Fig. 11 (a) is a front view showing an example of common mode choke coils.

Fig. 11 (b) is a front view showing another example of common mode choke coils.

FIG. 12 is a schematic, exploded, perspective view showing an annular magnetic core disposed in an insulating core shell.

Description of the preferred embodiments

The embodiments produced in accordance with the present invention will now be explained in detail with reference to the accompanying drawings, without intending to limit the present invention to them. The explanations of each embodiment will apply to other embodiments unless otherwise mentioned.

[1] Fe-based, nanocrystalline, soft magnetic alloy

A soft, nanocrystalline, Fe-based magnetic alloy used in the annular magnetic core produced according to the present invention has a composition in which part of the Fe is substituted with Ni and / or Co. To have the desired characteristics of BH, it preferably has a composition represented by the general formula of Fe ^a (Ni, Co) ^b Cu ^c Nb ^d Si ^e B ^f (atomic%), where 75.5 <ab, 4 <b <6.0 , 1 <c <2, 0.1 <d <4, 10 <e <11.5, 9.2 <f <10, and abcdef = 100, except for impurities. In the above formula, (Ni, Co) means Ni and / or Co.

(1) Fe, and Ni and / or Co

Fe is an element that dominates a saturation magnetic flux density Bs. To achieve a B400 magnetic flux density of 1.3 T or higher at a DC magnetic field intensity of 400 A / m, Fe and Ni and / or Co they are more than 75.5 atomic% in total.

Substitution of part of the Fe for ni and / or Co can increase the induction magnetic anisotropy. Consequently, a heat treatment in a magnetic field can intentionally lower the specific permeability without drastically reducing the saturation magnetic flux density, thereby endowing the alloy with resistance to magnetic saturation at a large current. In addition, the addition of Ni and / or Co reduces the losses in the Pcv core. The amount of Ni and / or Co added is between 4 and 6 atomic%. More than 6 atomic% Ni and / or Co causes the permeability to be greatly reduced, making it difficult to achieve a specific permeability of AC pr100 ^{k (} 50 ⁾ of 4,000 or more at a frequency of 100 kHz and a DC magnetic field intensity of 50 A / m, and a specific permeability of AC pr100 ^{k (} 150 ⁾ of 2,500 or higher at a frequency of 100 kHz and a DC magnetic field intensity of 150 A / m. To obtain the required impedance, the number of windings must be increased, making it unsuitable for a choke. The internal permeability is obtained by applying a magnetic field in a direction perpendicular to the magnetic path of the magnetic core (width direction of the alloy) during heat treatment.

Since Ni causes the saturation magnetic flux density Bs to be reduced, the addition of only more than 6 atomic% Ni makes it difficult to achieve a B400 magnetic flux density of 1.3 T or greater.

Since Ni is more effective than Co in steepening the B-H curve (reduction of specific permeability) in a range of 6 atomic% or less, the amount of Co added can be reduced.

Co causes the saturation magnetic flux density Bs to increase slightly, but is cost-effective as it is more expensive than Ni. With Co to which Ni has been added, the reduction of the saturation magnetic flux density Bs is preferably suppressed depending on the percentage of Co. Cu is a necessary element to precipitate fine crystalline grains by heat treatment. Less than 0.1 atomic% Cu makes it difficult to obtain fine crystalline grains with an average crystalline grain size of 100 nm or less, occupying 50% or more by volume of the alloy structure. In addition, more than 2 atomic% Cu makes a heat-pretreated amorphous alloy tape brittle, complicating winding and punching. Accordingly, the amount of Cu added is preferably 0.1 to 2 atomic%, more preferably 0.5 to 1.5 atomic%.

Nb contributes to the precipitation of fine crystalline grains together with Cu. With less than 0.1 atomic% Nb, the above effect is not sufficiently achieved. On the other hand, not even more than 4 atomic% of Nb considerably changes the effect of precipitation of fine crystalline grains, but reduces the amounts of other metallic elements due to their content, probably deteriorating the magnetic properties. Accordingly, the amount of Nb added is preferably 0.1 to 4 atomic%, more preferably 1 to 3.5 atomic%. Part or all of Nb can be replaced with an element that has the same function as that of Nb, such as Ti, Zr, Hf, Mo, W or Ta.

Both Si and B are constituent elements of amorphous phases. With 8 atomic% or more Si, the amorphous phase is stably formed by quenching, resulting in low Hc coercivity and low Pcv core loss. However, more than 12 atomic% of Si causes the saturation magnetic flux density Bs to decrease. Induction magnetic anisotropy is influenced by the amount of Si in crystalline Fe grains having a bcc structure. Consequently, the amount of Si added is 10 to 11.5 atomic%.

With 9 atomic% or more of B, the amorphous phase is stably formed by quenching, resulting in a uniform nanocrystalline phase after heat treatment. However, more than 12 atomic% of B causes the saturation magnetic flux density Bs to be reduced. To avoid permeability saturation over a wide range of frequencies in a large current (in a strong magnetic field), the amount of B added is 9.2 to 10 atomic%. Preferably, the total amount of Si and B is 22 atomic% or less, more preferably 21 atomic% or less.

[2] Fe-based, nanocrystalline, soft magnetic alloy tape

The Fe-based, nanocrystalline, soft magnetic alloy tape is preferably up to 10-25 µm thick. With a thickness less than 10 pm, the tape not only has insufficient mechanical strength, which easily results in breakage during handling, but also has high coercivity Hc. With a thickness greater than 25 pm, the tape does not have an amorphous structure stably, experiencing large losses due to eddy currents. Without taking eddy current losses into account, the tape preferably has a thickness of up to 14-25 pm.

Fig. 1 shows an example of annular magnetic cores 1 produced in accordance with the present invention, which is obtained by winding the Fe-based, nanocrystalline soft magnetic alloy ribbon 100. Apart from the wound magnetic core shown in Fig. 1, A magnetic core can be obtained by punching the tape into a donut shape, and laminating pluralities of the tapes into a donut shape. The annular magnetic core 1 is not limited to a circular shape, but can have a racing circuit shape, a rectangular shape, and so on.

[3] Production method of the annular magnetic core

(1) Production of Fe-based nanocrystalline soft magnetic alloy tape

To obtain a Fe-based nanocrystalline soft magnetic alloy tape, first, for example, an alloy melt having a predetermined composition is quenched, by means of a known single-roll method, in order to form an amorphous Fe-based alloy ribbon having a thickness of 10 pm or somewhat more at about 30 pm, preferably 10-25 pm, more preferably 14-25 pm. The Fe-based amorphous alloy ribbon may partially contain fine crystalline grains in the structure. The Fe-based amorphous alloy ribbon is wound or rolled to form an annular magnetic core. In this case, the tapes are preferably insulated.

(2) Heat treatment in magnetic field

The resulting annular magnetic core is heat treated in a magnetic field at a temperature equal to or higher than the crystallization initiation temperature for 10 minutes or more, in an atmosphere of inert gas such as nitrogen gas, or in air, to obtain a annular magnetic core of a soft, nanocrystalline, Fe-based magnetic alloy, 50% by volume or more of its structure being occupied by fine Fe-bcc crystalline grains having an average crystalline grain size of 100 nm or less. The precipitation temperature of crystalline Fe-bcc grains (crystallization initiation temperature) is approximately 480 to 560 ° C, although it is variable depending on the composition of the Fe-based, nanocrystalline, soft magnetic alloy. Crystallization start is a heat generation start temperature measured by differential scanning calorimetry. When compound phases, such as Fe2B, etc., precipitate, the coercivity Hc increases, losing constancy of permeability. Accordingly, the upper limit of the heat treatment temperature is preferably a temperature up to which no compound phases precipitate.

In heat treatment in a magnetic field, temperature and holding time are important. Since the amount of Si in crystalline Fe grains having a bcc structure is influenced by induction magnetic anisotropy, Si should be sufficiently dissolved in Fe during crystallization. Accordingly, the holding time of the highest temperature is preferably 10 minutes or more. A lower heat treatment temperature requires a longer holding time. Considering productivity, the upper limit is preferably 60 minutes.

When a heat treatment is applied in a magnetic field in a direction perpendicular to the magnetic path of the annular magnetic core (tape width direction), the BH curve is tilted with improved linearity, resulting in low specific permeability, a low quadrature ratio, and excellent permeability constancy. Heat treatment in a magnetic field per se is a known method as disclosed, for example, in JP 7-74419 B. To saturate the alloy, a magnetic field of 1,000 A / m or higher is applied.

In a premature stage of crystallization, Si does not dissolve sufficiently in a solid solution, failing to induce anisotropy. However, as more Si dissolves, anisotropy is induced more rapidly. Therefore, it is preferable to start by applying a magnetic field at a temperature lower than the crystallization temperature.

The rate of temperature rise until reaching the maintenance temperature from the start of the application of a magnetic field is 5 ° C / minute or less. Too high a temperature rise rate causes premature crystallization due to the heat generated by crystallization. Although anisotropy can be induced after crystallization, it is insufficient compared to that obtained during crystallization. Also, crystallization can end with insufficient Si dissolved. To obtain a sufficient induction of anisotropy, the rate of temperature rise is more preferably less than 1 ° C / minute.

[4] Characteristics of the annular magnetic core

As a result of investigations to solve problems that occur when Fe-based, nanocrystalline soft magnetic alloy is used for a magnetic device (particularly a choke coil), in order to obtain excellent effects in terms of pressure noise while maintaining excellent magnetic properties, such as a high saturation magnetic flux density, low losses and low magnetostriction, it has been observed that (a) the specific permeability of AC | jr100 ^{k (} 50 ⁾ at a frequency of 100 kHz and a magnetic field intensity ^d C of 50 A / m should be 4,000 or higher, which (b) the specific permeability of AC jr- ⁱ 00 ^{k (} 150 ⁾ at a frequency of 100 kHz and a magnetic field intensity 150 A / m DC should be 2,500 or higher, and that (c) the maximum permeability j ^Max should be 8,000 or higher, and the B400 magnetic flux density should be 1.3 T or higher, at an intensity magnetic field co DC 400 A / m.

The specific permeability of AC jr is the permeability determined from the effective self-inductance of a coil having a magnetic core with a closed magnetic path with negligible magnetic flux leaks, by means of the following formula (1):

jr = (L x C1) / (j ⁰ x N ² ) ... (1),

L: Effective self-inductance (H),

N: Winding number,

J0: Permeability of vacuum (4 xnx 10 ^'7 ), and

C1: Constant of the magnetic core (mm ^-1 ).

The effective self-inductance L was measured with an LCR meter (4284A available from Agilent Technologies, Inc.), and an impedance / gain phase analyzer (4194A available from Agilent Technologies, Inc.).

The relationship between magnetic field and specific permeability pr was determined by measuring inductance with DC current overlap using a combination of a 428A CLR meter and a bias current source (42841A available from Agilent Technologies, Inc.) capable of providing an overlapping DC current of up to 20 A. The specific AC permeability pr was determined from the effective self-inductance L at a predetermined frequency (eg 100 kHz) by means of the above formula (1). The bias current I that generates a predetermined DC magnetic field strength H (for example, 50 A / m) was determined by the following formula (2):

H = 1 x N / Le ... (2),

H: DC magnetic field strength (A / m),

I: Polarization current (A),

N: Winding number, and

Le: Mean linear length (m).

The frequency characteristics of the AC pr specific permeability were measured with an operating magnetic field of 0.05 A / m and a frequency of 10 kHz to 10 MHz, by means of a 4194A gain phase / impedance analyzer. Maximum permeability p ^Max , B400 magnetic flux density, and Hc coercivity at a DC magnetic field intensity of 400 A / m were measured with a DC magnetization tester (SK-110 available from METRON, Inc.) .

Considering an overcurrent containing noise, the present invention requires specific permeabilities of AC pr- ⁱ 00 ^{k (} 50 ⁾ and pr- ⁱ 00 ^{k (} 150 ⁾ of 4,000 or more and 2,500 or more, respectively, at a frequency of 100 kHz and DC magnetic field strengths of 50 A / m and 150 A / m. With the specific permeability of AC pr- ⁱ 00 ^{k (} 50 ⁾ of 4,000 or higher and the specific permeability of AC pr100 ^{k (} 150 ⁾ of 2,500 or higher, the reduction of the common mode noise attenuation performance and the noise are suppressed. normally due to the decrease in permeability, making it possible to obtain an excellent noise suppression effect. The specific permeability of AC prm ⁽ 150 ⁾ at a frequency of 10 kHz and a DC magnetic field intensity of 150 A / m is more preferably 4,000 or higher, and the specific permeability of AC prm ⁽ 200 ⁾ at a frequency 10 kHz and a DC magnetic field strength of 200 A / m is more preferably 2,000 or higher.

When the maximum permeability p ^Max is 8,000 or less, and the B400 magnetic flux density is 1.3 T or more, at a DC magnetic field intensity of 400 A / m, the high-voltage noise is reduced, and the It avoids magnetic saturation even with a large current generated by an increase in transient current peaks, thus avoiding an extreme decrease in inductance.

Since the Fe-based nanocrystalline soft magnetic alloy used in the annular magnetic core produced in accordance with the present invention has a higher permeability than that of other magnetic materials at high frequencies, a noise filter that makes The use of a magnetic device (choke coil) comprising the annular magnetic core of the present invention is also excellent, not only in reducing high voltage noise, but also in reducing noise in bands. wide frequency.

[5] Magnetic device

The magnetic device produced according to the present invention is obtained (a) by penetrating conductors through a hollow part of an annular magnetic core, or (b) by winding conductors around an annular magnetic core, after the previous core ring magnet is contained in an insulating core shell or is provided with an insulating coating. Fig. 11 (a) shows a three-phase common-mode choke comprising three conductors a, b, c penetrating through an annular magnetic core 5 ', as an example of magnetic devices comprising conductors penetrating through a hollow part of the annular magnetic core. Fig. 11 (b) shows a three-phase common mode choke comprising three conductors a, b, c wound around an annular magnetic core 5 ', as an example of magnetic devices comprising conductors wound around a core ring magnetic. Fig. 12 shows the annular magnetic core 5 'contained in an insulating core shell made up of an upper shell 11 and a lower shell 12.

The present invention will be explained in more detail by the following Examples without any intention of limiting the scope of the invention.

Example 1

According to the method of the single roller, a melt having a composition of Fe7 ^{or 7NÍ5, or} Cu ^or 8Nb2,8Si ^{io, g} B ^g, 8 (atomic%) it was rapidly quenched by ejection from a nozzle onto a roll of copper rotating at a high speed, to obtain alloy ribbons 53 mm wide with a thickness of up to 16 µm, 18 µm and 23 µm, respectively. These alloy ribbons were confirmed by X-ray diffraction measurement to have a substantially amorphous structure. The crystallization temperature Tx of this alloy measured by differential scanning calorimetry was 490 ° C.

Each tape was cut to obtain two 25mm wide tapes. Each of the tapes was wound to obtain a toroidal core (gap factor: 0.9) having an outer diameter of 24.5mm, an inner diameter of 21mm, and a height / width of 25mm. Each of the toroidal cores was placed in a controlled heat treatment furnace under a nitrogen atmosphere, and was subjected to a heat treatment comprising a temperature rise from 420 ° C to the highest temperature of 550 ° C at a speed 0.54 ° C / minute, remaining at the highest temperature for 20 minutes, and then allowing it to cool in the furnace, thereby obtaining a toroidal core of the soft, nanocrystalline magnetic alloy, based on Fe, shown in Fig. 1. While the temperature was raised and the highest temperature was maintained, a magnetic field of 280 kA / m was applied to the annular magnetic core in the direction of height (direction of width of tape). By heat treatment in a magnetic field, substantially 70% by volume fine crystalline grains having a mean grain size of 100 nm or less were formed on all tapes.

Each of the annular magnetic cores was enclosed in an insulating casing, provided with 10 winding turns on the primary side and 10 winding turns on the secondary side, to measure the maximum permeability j ^Max , the magnetic flux density B400, the Hc coercivity, and the quadrature ratio at 25 ° C, by means of a SK-110 DC magnetization testing machine. The results are shown in Table 1. As a typical example, a DC BH loop of an annular magnetic core of a tape with a thickness of 16 µm is shown in Fig. 2.

Each of the annular magnetic cores was enclosed in an insulating casing and provided with 10 winding turns to determine the relationship of the specific permeability of AC jr with respect to a magnetic field Dc (intensity: 50 A / m, 150 A / m and 200 A / m) at frequencies of 10 kHz and 100 kHz, and at 25 ° C, by means of a 4284A LCR meter. Table 1 shows the specific permeability of AC jr 100 ^{k (} 50 ⁾ at a frequency of 100 kHz and a DC magnetic field intensity of 50 A / m, the specific permeability of AC jr 100 ^{k (} 150 ⁾ at a frequency of 100 kHz and a DC magnetic field strength of 150 A / m, the specific permeability of AC jr 10 ^{k (} 150 ⁾ at a frequency of 10 kHz and a DC magnetic field strength of 150 A / m, and the specific permeability of AC jrm ⁽ 200 ⁾ at a frequency of 10 kHz and a DC magnetic field strength of 200 A / m. Fig. 3 shows the relationship between the specific permeability of AC jr and the intensity of the magnetic field (frequency: 10 kHz) in the annular magnetic core of a 16 jr thick tape.

Each of the annular magnetic cores (Samples 1 to 5) was enclosed in an insulating casing and provided with 1 winding turn, to measure the specific permeability of AC jrm and jr 100 ^k at a voltage amplitude of 0.5 Vrms, at frequencies of 10-100 kHz, and at a temperature of 25 ° C, by means of a 4194A gain phase / impedance analyzer. A frequency f50 was also measured, at which the specific permeability jr corresponding to 50% of the specific permeability jr10k at a frequency of 10 kHz was obtained. The results are shown in Table 1. Fig. 4 shows the frequency characteristics of the specific permeability jr of a 16 µm thick tape.

Table 1-1

Table 1-2

Note: (1) the maximum permeability at a DC magnetic field intensity of 400 A / m.

(2) Measured at a frequency of 10 kHz and a DC magnetic field strength of 150 A / m.

(3) Measured at a frequency of 10 kHz and a DC magnetic field strength of 200 A / m.

(4) Measured at a frequency of 100 kHz and a DC magnetic field strength of 50 A / m.

(5) Measured at a frequency of 100 kHz and a DC magnetic field strength of 150 A / m.

Table 1-3

It is clear that the annular magnetic core produced in accordance with the present invention has a small quadrature ratio, an excellent permeability constancy, and a small variation of AC specific permeability with frequency, while maintaining a high magnetic flux density. It also has a specific permeability of AC jr ¹⁰⁰ k ( ⁵⁰ ) of 4,000 or higher at a frequency of 100 kHz and a DC magnetic field intensity of 50 A / m, a specific permeability of AC jr ¹⁰ k ( ¹⁵⁰ ) of 4,000 or greater than a frequency of 10 kHz and a DC magnetic field strength of 150 A / m, a specific permeability of AC | jr ¹⁰⁰ k ( ¹⁵⁰ ) of 2,500 or greater at a frequency of 100 kHz and a DC magnetic field strength of 150 A / m, and a specific permeability of AC jrm ( ²⁰⁰ ) of 2,000 or higher at a frequency of 10 kHz and a DC magnetic field intensity of 200 A / m. Thus, the annular magnetic core produced in accordance with the present invention has a high AC specific permeability in a range from a low magnetic field to a high magnetic field. In addition, the annular magnetic core formed with the thin tape has excellent frequency characteristics, with less reduction in AC specific permeability.

Comparative Example 1

A ribbon (thickness: 18 jm) of a soft, nanocrystalline, Fe-based magnetic alloy (FT-3KL from Hitachi Metals, Ltd.) was shaped into a toroidal core with an outer diameter of 36.0 mm, a diameter inside 17.5 mm and 25 mm wide, and loaded into a casing, around which 8 turns of enameled wire with a diameter of 2.5 mm were wound to produce a choke coil.

Example 2

The tape (thickness: 18 µm) produced in Example 1 was shaped into a toroidal core with an outer diameter of 36.0 mm, an inner diameter of 17.5 mm, and a width of 25 mm, and was loaded into a casing, around which 17 turns of enameled wire with a diameter of 2.5 mm were wound to produce a choke coil. In Fig. 5 the impedance of the choke coil is shown. As is clear from Fig. 5, the choke of Example 2 exhibited excellent impedance performance in a range from a low frequency to a high frequency.

The chokes of Example 2 and Comparative Example 1 were evaluated for the characteristics of inductance with superposition of a DC current. The results are shown in Fig. 6. As is clear from Fig. 6, the choke coil of Example 2 was better than the corresponding one of Comparative Example 1 in terms of inductance characteristics with DC current overlap.

Example 3

The tape (thickness: 18 µm) produced in Example 1 was shaped into a toroidal core with an outer diameter of 17.8 mm, an inner diameter of 13.8 mm, and a width of 25 mm, which is was then used to produce a three-phase common mode choke coil shown in Fig. 7. The annular magnetic core was inserted into an insulating shell 6, into which a central divider plate 8 was inserted to divide regions of the winding. A 3-turn winding 7a, 7b, 7c of each phase was formed by winding an enameled wire with a diameter of 2.5 mm. The frequency characteristics for impedance and inductance in the three-phase common mode choke are shown in Fig. 8. In the figure, a solid line indicates inductance, and a broken line indicates impedance. As clear from Fig. 8, the three-phase common mode choke of Example 3 exhibited excellent impedance performance from a low frequency band to a high frequency band.

Example 4

The three-phase common mode choke produced in Example 2 was used to produce a noise filter shown in Fig. 9. The resulting noise filter exhibited excellent attenuation to low-frequency noise, high-frequency noise, and high-frequency noise. Impulse noise, as well as a significant reduction in noise from conducted emissions in a wide frequency range from 150 kHz to 30 MHz.

Example 5

Each of the alloy melts having the composition (atomic%) shown in Table 2 was shaped into a tape with a thickness of 16 µm and a width of 53 mm, in the same way as in Example 1 Each of the tapes was cut into two 25mm wide tapes. Each of the tapes was wound to obtain a toroidal core (space factor: 0.9) with an outer diameter of 24.5mm, an inner diameter of 21mm, and a width of 25mm. Each of the toroidal cores was subjected to the same magnetic field heat treatment as in Example 1, to obtain a toroidal core of a soft, nanocrystalline Fe-based magnetic alloy. The specific permeabilities of AC jr-iook ( ⁵⁰ ), jr-iook ( ¹⁵⁰ ), jrm ( ¹⁵⁰ ) and jrmpoo) of each toroidal core were measured in the same way as in Example 1. The results are shown in Table 2.

Table 2-1

Table 2-2

Note: (1) - (4) Same as Notes (2) - (5) under Table 1-2.

As is clear from Table 2, good AC specific permeability characteristics were obtained particularly when B was in a range of 9.32 to 9.78 atomic%.

Effect of the invention

Since the annular magnetic core produced according to the present invention is resistant to magnetic saturation, maintaining high permeability at large current, it exhibits high performance in voltage noise reduction and excellent impulse attenuation characteristics, suitable for small, lightweight shock filters to reduce noise over a wide frequency band. Furthermore, it does not require a necessary magnetic gap when using a soft, nanocrystalline Fe-based magnetic alloy which has high permeability, resulting in the reduced number of processing steps. Furthermore, it advantageously does not undergo the change of characteristics by magnetostriction, unlike amorphous alloys based on Fe.

Claims (6)

1. Production method of an annular magnetic core comprising winding a soft, nanocrystalline, Fe-based magnetic alloy tape, in which part of the Fe is substituted with Ni and / or Co, and heat treating the tape in a magnetic field 1,000 A / m or greater applied in a tape width direction at a temperature equal to or greater than a crystallization initiation temperature with a temperature rise rate of 5 ° C / minute or less; wherein said Fe-based nanocrystalline soft magnetic alloy tape comprises Ni and / or Co from 4 to 6 atomic%, from 0.1 to 2 atomic% Cu, from 0.1 to 4 atomic% Nb, 10 to 11.5 atomic% Si, and 9.2 to 10 atomic% B, and wherein said Fe-based nanocrystalline soft magnetic alloy ribbon comprises more than 75.5 atomic% in total of Fe and Ni and / or Co. 2. Production method of an annular magnetic core according to claim 1, wherein said Fe-based nanocrystalline soft magnetic alloy tape has a thickness of 10 to 25 pm. 3. Production method of an annular magnetic core according to claim 2, wherein said Fe-based nanocrystalline soft magnetic alloy tape has a thickness of 14 to 25 pm. 4. Production method of a magnetic device comprising the annular magnetic core produced by the method set forth in any one of claims 1 to 3 in a resin housing, part of said annular magnetic core being fixed with an adhesive. 5. Production method of a magnetic device according to claim 4, wherein a conductor penetrates through a hollow part of said annular magnetic core. 6. Method of producing a magnetic device according to claim 4, wherein a conductor is wound around said annular magnetic core.