JP3063557B2 - choke coil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a choke coil mainly used for removing noise flowing out of an electronic device or the like.

[0002]

2. Description of the Related Art In general, a common mode choke coil has a small amount of a normal mode leakage inductance component, and thus is effective for normal mode noise. Separately, it was necessary to take countermeasures against noise using a normal mode choke coil.

[0003] In the case of a common mode choke coil having a relatively large leakage inductance component in a normal mode, the leakage magnetic flux may have an adverse effect on peripheral circuits. For this reason, it is necessary to take measures such as applying a magnetic shield to the outer periphery of the common mode choke coil.

[0004]

The conventional choke coil cannot sufficiently remove both the common mode noise and the normal mode noise with a single choke coil, and therefore removes the common mode noise and the normal mode noise. For this purpose, two choke coils, that is, a common mode choke coil and a normal mode choke coil must be mounted on a printed circuit board or the like, and there is a problem that the area occupied by the printed circuit board or the like is large.

Further, providing a magnetic shield on the outer periphery of the choke coil also increases the cost of the choke coil. Therefore, an object of the present invention is to provide a choke coil having a sufficient noise removing effect on common mode noise and normal mode noise.

[0006]

In order to achieve the above object, a choke coil according to claim 1 of the present invention comprises:
(A) a pair of windings, (b) a rectangular cylindrical body provided with a hole having a circular cross section around which the pair of windings are wound, and at both ends and a center of the cylindrical body. A bobbin made of a magnetic material having a flange provided respectively and having a closed magnetic path surrounding each of the pair of windings; and (c) forming a closed magnetic path with one side inserted through a hole in the cylindrical body. (D) a cross section of one side of the magnetic core inserted into the hole of the cylindrical body is circular or square.

The choke coil according to a second aspect of the present invention is characterized in that the position of the hole provided in the rectangular cylindrical body is eccentric with respect to the rectangular cylindrical body. further,
In the choke coil according to claim 3 of the present invention, the thickness of the flange provided at the center of the rectangular cylindrical body is smaller than the thickness of the flange provided at both ends of the cylindrical body. It is characterized by being twice or more.

According to a fourth aspect of the present invention, in the choke coil according to the first aspect of the present invention, the choke coil is provided between the outer peripheral end surface of the flange provided at the center of the rectangular cylindrical body and the magnetic core within the opening of the magnetic core. Is larger than a gap formed between an outer peripheral end surface of a flange provided at both ends of the cylindrical body and the magnetic core.

[0009]

In the above construction, when a common mode noise current flows through a pair of windings, a magnetic flux is generated in each winding. The magnetic fluxes are added to each other and converted into thermal energy in the form of an eddy current loss and attenuated in the magnetic core forming the closed magnetic path. Thereby, the common mode noise current is removed. On the other hand, when a normal mode noise current flows through the pair of windings, a magnetic flux is generated in the windings. This magnetic flux goes around the closed magnetic path of the bobbin, is converted into thermal energy in the form of eddy current loss or the like, and is attenuated. Thereby, the normal mode noise current is removed.

In addition, since the cross section of one side of the magnetic core inserted into the hole of the bobbin is circular or square, the contact area between the magnetic core and the inner wall surface of the hole is reduced. Therefore, the magnetic resistance between the magnetic core and the bobbin increases, and the magnetic flux generated inside the bobbin due to the normal mode noise hardly leaks to the magnetic core. Further, in the choke coil according to the second aspect, since the bobbin has an eccentric hole with respect to the cylindrical body, the thickness of the cylindrical body of the bobbin in the opening of the magnetic core is small, and the thickness of the outside of the opening is small. The thickness of the cylindrical body of the bobbin is increased. Therefore, in the opening of the magnetic core, the area occupied by the bobbin is reduced, so that the area where the winding can be wound around the body of the bobbin is increased by that amount, and the normal mode and common mode inductances are reduced. Can be larger. Outside the opening of the magnetic core, the cross-sectional area of the magnetic path of the bobbin increases, so that the magnetic resistance of this magnetic path decreases and the inductance in the normal mode increases.

The choke coil according to claim 3 is
Since the thickness of the flange provided at the center of the cylindrical body is set to be at least twice the thickness of the flange provided at both ends,
The cross-sectional area of a magnetic path through which both magnetic fluxes generated by the pair of windings pass due to the normal mode noise increases, and the inductance of the normal mode increases. further,
In the choke coil according to the fourth aspect, in the opening of the magnetic core, the gap formed between the outer peripheral end surface of the flange provided at the center of the cylindrical body of the bobbin and the magnetic core is cylindrical. Because it is larger than the gap formed between the outer peripheral end face of the flange provided at both ends of the body and the magnetic core,
The magnetic resistance between the outer peripheral end surface of the flange provided at the center of the cylindrical body and the magnetic core is the magnetic resistance between the outer peripheral end of the flange provided at both ends of the cylindrical body and the magnetic core. The magnetic flux generated inside the bobbin due to the normal mode current is less likely to leak to the magnetic core.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a choke coil according to the present invention will be described below with reference to the accompanying drawings. 1 and 2
As shown in FIG. 1, the choke coil includes a bobbin 1 and a pair of windings 4 and 5 wound around the bobbin 1, respectively.
It is composed of two U-shaped magnetic cores 6 and 7. The bobbin 1 includes a tubular body 11, flanges 12, 13, 14 provided at both ends and a center of the body 11, and flanges 12 to 1.
4 and a lid 15 joined to the outer peripheral end surface of the cover 4.
The cross section of the cylindrical body 11 is rectangular, and is designed so that the area of the cross section is the largest within the limited outer dimensions of the choke coil. This is for increasing the cross-sectional area of the magnetic path through which the magnetic flux generated in the bobbin 1 due to the normal mode noise passes, and reducing the magnetic resistance of this magnetic path to obtain a large normal mode inductance.

The hole 11a of the cylindrical body 11 is provided eccentrically with respect to the body 11 toward the upper center. Hole 11a
Has a circular cross section. A guide groove 16 for the magnetic core is provided on the upper side surface of the flanges 12 and 13, and a terminal mount 17 is provided on the lower portion. Terminals 18 are implanted on the terminal mount 17. The lid 15 has a U-shaped cross section. After the windings 4 and 5 are wound around the body 11 of the bobbin 1, the lid 15 is joined to the outer peripheral end surfaces of the flanges 12 to 14 with an adhesive or the like.

As the material of the bobbin 1, an insulating magnetic material having a relative magnetic permeability of 1 or more (for example, two to several tens) is used. Specifically, a material obtained by kneading a Ni-Zn or Mn-Zn ferrite and a resin binder is used. The pair of windings 4 and 5 are respectively provided on the body 11 of the bobbin 1 and the flange 1.
4, and the start and end thereof are fixed to different terminals 18.

The magnetic cores 6 and 7 are connected to the body 11 of the bobbin 1.
And is joined in a state of being inserted into the hole 11a, thereby forming a square-shaped core. The magnetic cores 6 and 7 are disposed substantially vertically by the magnetic core guide grooves 16 provided on the bobbin 1. The lid 15 of the bobbin 1 is
7 is joined to the flanges 12 to 14 from the side opposite to the side where the 7 is provided. The cores 6 and 7 are preferably made of a material having a relative magnetic permeability of several thousands, specifically, ferrite or amorphous.

Further, the choke coil of this embodiment will be described in detail with reference to FIGS. Choke coil is body 1
Since the hole 11a is eccentric with respect to 1, the thickness t ₁ of the body 11 inside the opening 8 formed by the magnetic cores 6 and 7 is smaller than the thickness t ₂ of the body 11 outside the opening. . Therefore, in the opening 8 of the magnetic cores 6 and 7, the area occupied by the bobbin 1 is reduced, and the area where the windings 4 and 5 can be wound around the body 11 of the bobbin 1 is correspondingly increased. In addition, the normal mode and common mode inductances can be increased. Outside the openings of the magnetic cores 6 and 7, the cross-sectional area of the magnetic path of the bobbin 1 is increased, the magnetic resistance of the magnetic path is reduced, and the inductance in the normal mode is increased.

The eccentric position of the hole 11a is not limited to one eccentric with respect to the body 11 as shown in FIG. 3, but is eccentric in two directions, that is, obliquely from the center of the body 11. May be used. In FIG. 4, the bobbin 1 forms a closed magnetic path around the winding 4 by the left half of the body 11, the flange 12, the left half of the lid 15, and the flange 14.
1 and the right half of the flange 13 and the lid 15 and the flange 1
4 form a closed magnetic circuit that goes around the winding 5. The thickness t ₄ of the flange 14 is equal to the thickness t ₃ , t of the flanges 12 and 13.
_It is almost twice as large as ₅ . The flange portion 14 has a magnetic flux φ generated in the windings 4 and 5 by normal mode noise.
3 and φ4 (refer to FIG. 9) because the magnetic path passes through the magnetic path, so that it is necessary to increase the cross-sectional area of the magnetic path as compared with the magnetic paths of the other parts to obtain a large normal mode inductance. .

Further, in the inside 8 of the opening formed by the magnetic cores 6 and 7, the overhang dimension of the flange section 14 is set smaller than the overhang dimension of the flange sections 12 and 13.
Gap G ₂ formed between the outer peripheral end surface of the flange portion 14 and the magnetic core 6 is greater than the gap G ₁ formed between the outer peripheral end face and the magnetic core 6, 7 of the flange portions 12 and 13 Has become. Thereby, the magnetic resistance between the outer peripheral end surfaces of the flange portions 14 and the magnetic cores 6 and 7 becomes larger than the magnetic resistance between the outer peripheral end surfaces of the flange portions 12 and 13 and the magnetic cores 6 and 7. The magnetic fluxes φ3 and φ4 generated in the windings 4 and 5 due to the normal mode noise are hardly leaked from the bobbin 1 to the magnetic cores 6 and 7, and the saturation of the magnetic cores 6 and 7 is hardly caused. The effect on the removal characteristics is reduced.

The cross section of the portion of the magnetic cores 6, 7 inserted into the hole 11a of the bobbin 1 has a circular shape having a diameter slightly smaller than the diameter of the hole 11a. Are designed to have a small contact area. This is because the magnetic fluxes φ3 and φ4 generated in the windings 4 and 5 due to the normal mode noise hardly leak from the bobbin 1 to the magnetic cores 6 and 7, and the magnetic cores 6 and 7 are hardly saturated.

In this way, a choke coil that can sufficiently exhibit a noise removing effect on common mode noise and normal mode noise is obtained. FIG. 5 is an electric equivalent circuit diagram of the choke coil. Here, the common mode noise removing operation of the choke coil having the above configuration will be described with reference to FIGS.

As shown in FIG. 6, the choke coil is electrically connected to two signal lines provided between a power supply 20 and a load 21 such as an electronic device. A stray capacitance C1 is generated between the power supply 20 and the ground, and a stray capacitance C2 is generated between the load 21 and the ground. When common mode noise currents i ₁ and i ₂ flow in the two signal lines in the directions of arrows in the figure, magnetic fluxes φ 1 and φ 2 are generated in the windings 4 and 5 as shown in FIG. The magnetic fluxes φ1 and φ2 are added to each other and orbit inside the closed magnetic paths of the cores 6 and 7, and gradually attenuate without leaking to other parts. This is because the magnetic fluxes φ1 and φ2 are converted into thermal energy in the form of eddy current loss or the like. Thereby, the common mode noise currents i ₁ and i ₂ are reduced.

Next, the normal mode noise removing operation of the choke coil will be described with reference to FIGS. As shown in FIG. 8, the normal mode noise current i ₃
Flow through the two signal lines in the directions of the arrows in the figure, as shown in FIG. 9, magnetic fluxes φ3 and φ4 are generated in the windings 4 and 5. The magnetic fluxes φ3 and φ4 are converted into thermal energy in the form of eddy current loss and the like, and gradually attenuate while circulating in the closed magnetic circuit of the bobbin 1 without leaking. Thereby, the normal mode noise current i ₃ is reduced.

The choke coil according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the invention. The cross section of one side inserted into the bobbin of the magnetic core does not necessarily have to be circular, and may be, for example, a square, a triangle, or a polygon as shown in FIG. Is also good.

Further, a groove having an arbitrary shape may be provided on the outer peripheral end surface of the flange provided at the center of the cylindrical body of the bobbin, or the groove may not be provided. The thickness of this collar is 2
It may be twice or more. Further, the magnetic core may be a combination of two U-shaped cores or E-shaped cores, or a combination of a U-shaped core or E-shaped core with an I-shaped core. Alternatively, the core is not limited to a split type, but may be an integral type, for example, a Japanese character core or a square character core.

[0025]

As is apparent from the above description, according to the present invention, there is provided a bobbin made of a magnetic material having a closed magnetic path surrounding each of a pair of windings, and a closed magnetic path formed through the bobbin. Since a magnetic core is provided, the magnetic flux generated by the flow of the common mode noise current and the normal mode noise current through the pair of windings generates heat in the form of eddy current loss and the like in the magnetic core and the bobbin, respectively. It is converted to energy and attenuated, thereby removing common mode noise and normal mode noise. Further, since the magnetic flux does not leak out of the choke coil, a magnetic shield on the outer periphery of the choke coil is not required.

Further, since the cross section of one side of the magnetic core inserted into the hole of the bobbin is circular or square, the contact area between the magnetic core and the inner wall surface of the hole is reduced, and the inside of the bobbin is reduced due to normal mode noise. The magnetic flux generated in the magnetic material core hardly leaks. Also, since the position of the hole in the cylindrical body of the bobbin is eccentric with respect to the cylindrical body, the cross-sectional area of the magnetic path through which the magnetic flux generated in the bobbin by the normal mode noise passes increases, and this magnetic path has The magnetic resistance drops. Therefore, a large normal mode inductance can be obtained. Furthermore, since the ratio of the bobbin in the opening of the magnetic core forming the closed magnetic path is small, the winding can be wound more by that amount, and the normal mode and common mode inductances can be increased.

Further, the thickness of the flange provided at the center of the cylindrical body is set to be at least twice the thickness of the flange provided at both ends. The cross-sectional area of the magnetic path through which both the magnetic fluxes generated in the windings pass increases, and the normal mode inductance increases. Further, in the opening of the magnetic core, gaps formed between the outer peripheral end surface of the flange provided at the center of the cylindrical body of the bobbin and the magnetic core are provided at both ends of the cylindrical body. Since the gap is larger than the gap formed between the outer peripheral end face of the flange portion and the magnetic core, the magnetic flux generated inside the bobbin due to the normal mode noise hardly leaks to the magnetic core.

As a result, it is possible to obtain a choke coil that hardly saturates the magnetic flux due to the common mode noise and has a sufficient noise removing effect on the common mode noise and the normal mode noise.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a choke coil according to the present invention.

FIG. 2 is a side view of the choke coil shown in FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 1;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 2;

FIG. 5 is an electric equivalent circuit diagram of the choke coil shown in FIG.

FIG. 6 is an electric circuit diagram for explaining common mode noise removal by the choke coil shown in FIG. 1;

FIG. 7 is a magnetic circuit diagram for explaining common mode noise removal by the choke coil shown in FIG. 1;

8 is an electric circuit diagram for explaining normal mode noise removal by the choke coil shown in FIG.

FIG. 9 is a magnetic circuit diagram for explaining normal mode noise removal by the choke coil shown in FIG. 1;

FIG. 10 is a sectional view showing another embodiment.

[Explanation of symbols]

1 ... bobbins 4,5 ... windings 6 and 7 ... magnetic core 11 ... rectangular tube-shaped body portion 11a ... circular hole 12, 13, 14 ... flange portion 15 ... lid _{t 3, t 4, t 5} ... flange portion Thickness G ₁ , G ₂ ... gap

Continuation of front page (72) Inventor Tatsuyuki Yamada 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Murata Manufacturing Co., Ltd. (56) References JP-A-6-283359 (JP, A) Japanese Utility Model 4-70720 (JP, U) Japanese Utility Model Showa 58-51426 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 37/00 H01F 17/06

Claims (4)

(57) [Claims] 1. A pair of windings, a rectangular cylindrical body provided with a hole having a circular cross section around which the pair of windings are wound, and a pair of windings at both ends and a center of the cylindrical body, respectively. A bobbin made of a magnetic material having a provided flange portion and having a closed magnetic path surrounding each of the pair of windings; and a magnetic substance core having a closed magnetic path formed with one side inserted through a hole in the cylindrical body. Wherein the cross section of one side of the magnetic core inserted into the hole of the cylindrical body is circular or square. 2. The method according to claim 1, wherein the position of the hole provided in the rectangular cylindrical body is eccentric with respect to the rectangular cylindrical body.
The choke coil described. 3. The thickness of a flange provided at the center of the rectangular cylindrical body is at least twice the thickness of the flange provided at both ends of the cylindrical body. The choke coil according to claim 1, wherein 4. A gap formed between an outer peripheral end surface of a flange provided at a central portion of a rectangular cylindrical body and the magnetic core in an opening of the magnetic body core, the gap being formed by the cylindrical body. The choke coil according to claim 1, wherein the gap is larger than a gap formed between an outer peripheral end surface of a flange provided at both ends and the magnetic core.