JP2023116224A - Magnetic core, and common mode choke coil using the same - Google Patents

Abstract

To provide a magnetic core capable of reducing size and amount of copper wire used while maintaining sufficient characteristics, and a toroidal coil using the magnetic core.SOLUTION: A magnetic core used in a common mode choke coil, is formed using nano crystal magnetic material. When the width in cross-sectional shape is a, the height is b, the core inner diameter is ID, and the effective cross-sectional area of core is Ae, b/a=1.0-1.3, and ID/√Ae=4.0-5.3 are satisfied.SELECTED DRAWING: Figure 1

Description

Applied for application of Article 30, Paragraph 2 of the Patent Act Nikkan Kogyo Shimbun February 1, 2022 morning edition

The present invention relates to a magnetic core and a common mode choke coil using the same, and more particularly to a magnetic core capable of maintaining performance while reducing winding length and a common mode choke coil using the same.

Conventionally, common mode choke coils have been widely used in power supply equipment such as AC adapters and home appliances as components for noise countermeasures. Toroidal ferrite cores are often used in such common mode choke coils because of their excellent balance between cost and performance. However, the ferrite core has a large inductance value, and when it is required that the magnetic saturation does not occur even if a DC current is superimposed, the size of the ferrite core must be increased in order to meet the requirement.

Therefore, Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-68364) proposes a small toroidal coil using a small ring core by changing the material of the magnetic body. That is, in this document, while bending a cylindrical coil formed by winding a conductive wire in advance into a ring shape, each of the divided ring cores is inserted into the hollow core portion of the cylindrical coil, and the divided surfaces are joined to form the ring core. A method for manufacturing a toroidal coil has been proposed. In particular, this document also discloses that the tubular coil is a rectangular tubular coil wound with a rectangular wire.

Also, conventionally, wire defects during winding on a magnetic core have been investigated. For example, in Patent Document 2 (Japanese Utility Model Laid-Open No. 1-153606), when the cross-sectional shape of a conventional core case is square, and a wire is wound around the outer peripheral surface, the wire is forced to bend at the excessive portion of the square. Focusing on the problem that defective parts such as pinholes and cracks are likely to occur due to strong hearing, the cross-sectional shape of the contact part between the wire wound around the outer peripheral surface of the case and the outer peripheral surface of the case is made circular or five. It has been proposed to use a vertex shape that is more than square.

Furthermore, in recent years, magnetic cores using nanocrystalline magnetic cores with excellent properties have also been developed and put into practical use. The nanocrystalline magnetic core has features such as high permeability, high saturation magnetic flux density, excellent temperature characteristics, and light weight. Due to these characteristics, the use of nanocrystalline magnetic cores makes it possible to improve the performance and reduce the size of common mode choke coils. For example, Patent Document 3 (Japanese Patent Application Laid-Open No. 2020-141041) discloses a coil component including a coil and a magnetic core, wherein the magnetic core has a laminate in which a plurality of soft magnetic layers are laminated, and the soft magnetic It proposes a coil component having a layer thickness of 10 μm or more and 30 μm or less, in which a structure composed of Fe-based nanocrystals is observed in the soft magnetic layer.

JP-A-2001-68364 Japanese Utility Model Laid-Open No. 1-153606 JP 2020-141041 A

As described above, Patent Document 1 proposes miniaturization of the toroidal coil by changing the material forming the magnetic core. However, this document aims to solve the problem by improving the manufacturing method, and does not consider the shape of the magnetic core itself. Therefore, the present invention provides a magnetic core and a toroidal coil using the magnetic core that can reduce the size of the toroidal coil and further reduce the amount of copper wire to be wound by reconsidering the shape of the magnetic core. This is one of the issues.

In addition, although Patent Literature 2 discusses defects that occur when a wire (copper wire, etc.) is wound around a magnetic core, characteristics such as inductance have not yet been fully investigated. Therefore, another object of the present invention is to provide a magnetic core capable of ensuring sufficient characteristics while realizing miniaturization and reducing the amount of copper wire used, and a toroidal coil using the same. and

In addition, Patent Document 3 proposes a coil component made of nanocrystals, but while the nanocrystal magnetic core has excellent characteristics, it is expensive due to reasons such as the manufacturing method, and is not widely used in general-purpose equipment. remains on scale. Therefore, in the present invention, although a nanocrystalline magnetic core is used as a magnetic core for a common mode choke coil, the cost is low, and the performance is the same as that of a common mode choke coil using a ferrite core, but the size is reduced. It is a further object to provide a common mode choke coil and a magnetic core for use therewith that can

In order to solve the above-mentioned problems, the present inventors conducted intensive studies, focused on magnetic saturation characteristics, core volume, inductance, and copper wire amount, and attempted to solve the problems.

That is, in the present invention, the magnetic core used in the common mode choke coil is formed using a nanocrystalline magnetic material, and has an effective cross-sectional area of Ae, a width of the cross-sectional shape, and a height of b , where the core inner diameter is ID, the ratio of a to b is b/a = 1.0 to 1.3, and the ratio of ID to √Ae is ID/√Ae = 4.0 to 5. .3 to provide a magnetic core.

The present invention also provides a common mode choke coil comprising a copper wire wound around the magnetic core. The copper wire wound around the magnetic core may be a round wire or a rectangular wire. Especially when a rectangular wire is used, the common mode choke coil may be wound around the magnetic core in an edgewise direction. can.

According to the present invention, there is provided a method for manufacturing a common mode choke coil according to the present invention, wherein a copper wire is automatically wound on a magnetic core comprising a laminated core formed by laminating the nanocrystalline alloy foils to form an annular body. A method for manufacturing a machine-wound common mode choke coil is provided.

The magnetic core used in the common mode choke coil according to the present invention is formed using a nanocrystalline magnetic material. is Ae, b/a=1.0-1.3 and ID/√Ae=4.0-5.3. As a result, it is possible to provide a magnetic core and a common mode choke coil using the magnetic core that can ensure sufficient characteristics while achieving miniaturization and reducing the amount of copper wire used. In particular, the magnetic core can achieve low cost by miniaturization while using a nanocrystalline magnetic core, and furthermore, it can be miniaturized while having the same performance as a common mode choke coil using a ferrite core. It is possible to provide a common mode choke coil and a magnetic core used therefor.

(A) perspective view, (B) front view, and (C) CC cross-sectional view showing the magnetic core according to the present embodiment Perspective view of a common mode choke coil formed by winding (A) a rectangular wire and (B) a round wire using the magnetic core of FIG. Graph of √Ae-ID in Example 2 Graph showing the results of Example 3

Hereinafter, a magnetic core according to the present embodiment and a common mode choke coil formed using the same will be specifically described with reference to the drawings. Particularly in this embodiment, the magnetic core is formed using a nanocrystalline magnetic material.

FIG. 1 shows (A) a front view, (B) a perspective view, and (C) a CC sectional view showing a magnetic core 10 according to the present embodiment. In particular, the magnetic core 10 according to this embodiment is formed in a toroidal shape, and its cross-sectional shape (CC cross-sectional shape) is formed to be substantially square. When the thickness of the magnetic core 10 is a, and the radial direction of the ring shape is the height b, the ratio (b/a) of the thickness a to the height b is 1.0 to 1.3. be able to.

In addition, the nanocrystalline magnetic material constituting the magnetic core is also called nanocrystal, ultramicrocrystalline alloy, ultramicrocrystalline soft magnetic alloy, etc., and is a soft magnetic material having nano-sized crystals in an amorphous (amorphous) alloy. provided as materials.

By winding a copper wire around the nanocrystalline magnetic core 10, a common mode choke coil 20 can be formed as shown in FIG. Copper wires having various cross-sectional shapes can be used as such copper wires, but rectangular copper wires having rectangular cross-sections are preferably used. This is because the space factor of the copper wire can be increased by using the rectangular copper wire, and the common mode choke coil 20 can be reduced in size and increased in current.

Also, the copper wire is preferably wound edgewise using an automatic winding machine.
Edgewise winding makes it possible to increase the number of copper wires that can be wound, that is, the number of turns of the coil, because the short side of the cross section of the copper wire is in contact with the core. In addition, automatic winding using a winding machine provides excellent high-frequency characteristics, and unlike a structure in which round wires are wound while piling up layers, it is possible to suppress the occurrence of layer short defects and achieve high quality. It is for

[Example 1]
In this embodiment, attention is focused on practical magnetic saturation characteristics as a common mode choke coil. That is, an experiment was conducted to confirm that a nanocrystalline magnetic core can obtain performance equivalent to that of a ferrite core even if the effective area Ae of the core is about 1/5.

Substituting the equations B=μH, H=NI/Le, and AL=μAe/Le into L=AL・N ² and arranging the equations yields the following equations. N is the number of turns of the coil, and Le is the magnetic path length of the core.
I=B・Ae・N/L
Assuming that the magnetic flux density at the time of magnetic saturation is Bm and the current at that time is Im, the above equation is as follows.
Im=Bm・Ae・N/Lleak
Here, Lleak is the inductance at magnetic saturation, that is, the leakage inductance.
By modifying this formula, Ae=Im・Lleak/Bm・N, the necessary core cross-sectional area Ae can be calculated. It can be confirmed that the effective cross-sectional area Ae of can be reduced.

Therefore, the saturation magnetic flux density of a ferrite core (permeability: μ7000, outer diameter: 47 mm, inner diameter: 27 mm, thickness: 15 mm) and a nanocrystalline magnetic core (permeability: μ36000, outer diameter: 40 mm, inner diameter: 28 mm, thickness: 6 mm) When Bm was actually measured, the following results were obtained. Note that the saturation magnetic flux density Bm is a value at 100°C. The results are shown in Table 1 below.

From the results in Table 1 above, when trying to obtain the same magnetic saturation current Im, if the number of turns N of the coil and the inductance Lleak at magnetic saturation are the same, the nanocrystalline magnetic core is about 1/5 that of the ferrite core. A cross-sectional area of . If the diameter of the core is the same, the cross-sectional area will be 1/5, and the volume of the core will also be 1/5. can be equivalent. That is, considering this example, even if the unit price per unit volume of the nanocrystalline magnetic core is about five times the unit price per unit volume of the ferrite core, the volume used can be reduced, resulting in an equivalent can be priced.
[Example 2]

In this example, in comparison with the ferrite core, the shape of the core that can make the core volume smaller, the amount of copper wire used can be reduced, and the saturation current can flow was investigated.
In the following, S is the geometric cross-sectional area (= vertical a × horizontal b), Ae is the effective cross-sectional area (= S × space factor δ), the space factor δ of the ferrite core is 0.97, and the nanocrystal core is 0.79.
In order to obtain the core inner diameter ID, the relationship between the core cross-sectional area Ae and the inner diameter window area Sid was examined.

When N copper wires pass through the core inner diameter window area (space area) Sid=π(ID/2) ² , the cross-sectional area s per copper wire is as follows.
s=n・Sid/N = π・n・(ID/2) ² /N
However, n is the area filling factor when the circle of the window area Sid of the core inner diameter is filled with the copper wire of the cross-sectional area s (n≈0.75 when the number of turns N=7 or more).

Using the permissible current density J of copper wire (generally J=10A/ ^mm2 ), the upper limit I of the current that can be passed through a single copper wire can be determined by the following formula. .
I = J・s = π・J・n・(ID/2) ² /N

On the other hand, the magnetic saturation current Im is given by Im=Bm·Ae·N/Lleak as described above. In order to allow this magnetic saturation current to flow, it is necessary to satisfy "Im≦I", so the following relationship must be satisfied.
Bm・Ae・N/Lleak ≤ πJn(ID/2) ² /N
{4・Bm・^N2 /(n・π・J・Lleak)}・Ae ≤ ^ID2
k√Ae ≤ ID
However, k = √{4·Bm·N ² /(n·π·J·Lleak)} (Formula 1)

This formula shows the relationship between core cross-sectional area Ae and core inner diameter ID from the viewpoint of saturation current. The larger the core cross-sectional area Ae, the larger the magnetic saturation current Im. It shows that the inner diameter ID of the core also increases due to the winding of the wire.

And if "k√Ae = ID", it shows that the magnetic saturation current Im can flow just right. If the slope k of the horizontal axis √Ae and the vertical axis ID is small and "k√Ae <ID", there is room for the magnetic saturation current Im to flow. However, since the characteristics of the core are saturated, it is wasted. If the slope k is large and "k√Ae>ID", the current that the core can flow cannot flow. Therefore, the slope k has certain upper and lower limits.
Therefore, in order to confirm the appropriate range of the slope k, calculation was performed using actual common mode choke coils based on actual measurements.
The name of each sample shown in Tables 1 and 2 below means "core type - number of turns - copper wire diameter (example: 240 → φ2.4)", and the magnetic core used in each sample is It is as follows.

[Nanocrystalline magnetic core]
NCS40-12-240: Magnetic core (relative magnetic permeability: μ36000, outer diameter: 40mm, inner diameter: 28mm, thickness: 6mm)
NCS40-19-150: Magnetic core (relative magnetic permeability: μ36000, outer diameter: 40mm, inner diameter: 28mm, thickness: 6mm)
NCS32-07-200: Magnetic core (relative magnetic permeability: μ36000, outer diameter: 32mm, inner diameter: 21mm, thickness: 5.5mm)
NCS32-13-150: Magnetic core (relative magnetic permeability: μ36000, outer diameter: 32mm, inner diameter: 21mm, thickness: 5.5mm)
NC29-10-180: Magnetic core (relative magnetic permeability: μ36000, outer diameter: 29mm, inner diameter: 20mm, thickness: 4.5mm)
Q26-10-150: Magnetic core (relative magnetic permeability: μ36000, outer diameter: 26mm, inner diameter: 18mm, thickness: 4mm)

〔Ferrite core〕
ADR47M-12-240: Magnetic core (permeability: μ7000, outer diameter: 47mm, inner diameter: 27mm, thickness: 15mm)
ADR-47-12-240: Magnetic core (permeability: μ5500, outer diameter: 47mm, inner diameter: 27mm, thickness: 15mm)
ADR38M-07-200: Magnetic core (permeability: μ7000, outer diameter: 38.1mm, inner diameter: 19mm, thickness: 12.7mm)
ADR31M-11-180: Magnetic core (permeability: μ7000, outer diameter: 31mm, inner diameter: 20mm, thickness: 15mm)
ADR25M-09-150: Magnetic core (permeability: μ7000, outer diameter: 25mm, inner diameter: 15mm, thickness: 12mm)

In Table 2, Bm: saturation magnetic flux density (T), N: number of turns of copper wire, J: maximum current density of copper wire (A/mm ² ), Lleak: leakage inductance (μH), n: occupancy of copper wire ratio, k: value of k obtained from the above formula 1, Ae: core cross-sectional area (mm ² ), ID: core inner diameter (mm)

In Table 3, Bm: saturation magnetic flux density (T), N: number of turns of copper wire, J: maximum current density of copper wire (A/mm ² ), Lleak: leakage inductance (μH), n: occupancy of copper wire ratio, k: value of k obtained from the above formula 1, Ae: core cross-sectional area (mm ² ), ID: core inner diameter (mm)

As shown in Tables 2 and 3 above, all magnetic cores satisfy the requirement of "k√Ae≦ID". Then, drawing a graph of "ID - √Ae" including other cores and calculating the slope ID/√Ae, in the case of ferrite cores, the slope ID/√Ae = 2.2, nano magnetic core (NC series), the slope ID/√Ae was 4.0 to 5.3 (see Fig. 3).

[Example 3]
Next, we examined the core size, inductance, and cost (amount of copper wire used). As a result, we found that the copper wire cost is the lowest when the aspect ratio of the core cross section is around 1.0 to 1.3.

A core with a higher inductance can reduce the number of turns required to obtain the same inductance L, and as a result, the amount of copper wire used for winding can be reduced. The required number of turns N can be expressed by the following equation, where AL is the induction coefficient of the core.
L=AL・^N2 =(μAe/Le)・^N2

Further, from the cross-sectional area S of the core and the aspect ratio b/a of the core cross-section, the length Ls of the copper wire that goes around the cross-section of the core can be obtained by the following formula.
Ls = 2(a+b)
Then, the necessary copper wire length L for the magnetic core can be obtained by "L=Ls·N".
In practice, this equation is set up and differentiated to find the minimum point, and the aspect ratio b/a of the cross section of the core that minimizes the required copper wire length L is found by numerical calculation.

That is, from the above formula "L = Ls N", the result "When the cross-sectional area S and the inner diameter ID are determined first, the minimum copper wire length is obtained when r = b/a = 1.3", and the same formula From this, "When the cross-sectional area S and the magnetic path length Le are determined first, the minimum copper wire length is obtained when r = b/a = 1.0". Furthermore, since r=1.0 (square) is desirable when considering automatic winding, the range of r=b/a=1 to 1.3. The results are shown in FIG.
In addition, the above formula is for winding the copper wire along the case, and when winding the copper wire in a circle by automatic winding, it becomes "Ls = √(a ² +b ² )・π", but the copper wire length is The minimum aspect ratio b/a is when r=1.2.

Based on the above results, the shape of the core that can reduce the volume of the core, reduce the amount of copper wire used, and allow the saturation current to flow is as follows.
The cross-sectional area Ae of the core is 1/5 that of ferrite with comparable saturation characteristics.
ID/√Ae = 4.0 to 5.3.
From the cross-sectional aspect ratio r=b/a=1.0 to 1.3 and S=ab, a=√(S/r), b=√(Sr),
Therefore, the core volume can be reduced, the amount of copper wire used can be reduced, and the core shape that can flow the same saturation current as the ferrite core has a core cross-sectional area that is 1/5 that of a ferrite core with equivalent performance. , b/a = 1.0 to 1.3, and ID/√Ae = 4.0 to 5.3.

The nanocrystalline magnetic core of the present invention has a cross-sectional width of a, a height of b, an inner diameter of the core of ID, and an effective cross-sectional area of the core of Ae. = 4.0 to 5.3, the core volume can be reduced, the amount of copper wire used can be reduced, and the magnetic core can have a core shape that allows saturation current to flow.

As a result, even though nanocrystalline magnetic cores are used as magnetic cores for common mode choke coils, the cost is low, and even though the performance is the same as common mode choke coils using ferrite cores, the size can be reduced. It is possible to provide a common mode choke coil and a magnetic core used therefor.

10 magnetic cores
20 Common mode choke coil

Claims (3)

A magnetic core used in a common mode choke coil,
It is formed using a nanocrystalline magnetic material,
A magnetic core where b/a = 1.0 to 1.3 and ID/√Ae = 4.0 to 5.3, where a is the width in the cross-sectional shape, b is the height, ID is the core inner diameter, and Ae is the effective cross-sectional area of the core. .
A common mode choke coil comprising the magnetic core according to claim 1 and a copper wire wound around the magnetic core.
A method for manufacturing a common mode choke coil according to claim 2,
A method of manufacturing a common mode choke coil, comprising winding a copper wire with an automatic winding machine to a magnetic core comprising a laminated core formed into an annular body by laminating the nanocrystalline alloy foils.