JP2016054287A - Core and coil device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coil device that makes it possible to increase an inductance value per unit weight or inhibit heat generation due to core loss, by modifying an inductance value, to be more specific, shape.SOLUTION: A core 10 is a closed magnetic circuit core having a core body formed by pressure molding metal powder as a magnetic material or by pressure molding and sintering oxidation magnetic material. The core body has an irregular shape part 40 in which an inner-circumferential-side area S is larger than an outer-circumferential-side area S2 if a cut surface in a width direction extending from the inner circumference toward the outer circumference is sectioned by an intermediate line M between the inner circumference and the outer circumference. Preferably, in the cut surface of the irregular shape part 40, the maximum height Hmax on the inner-circumferential side from the intermediate line M is greater than the maximum height Hmax on the outer-circumferential side.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a core used in a coil device equipped in a rectifier circuit, a noise prevention circuit, a waveform shaping circuit, a resonance circuit, various switching circuits, etc. in an AC device such as a power supply circuit and an inverter, and a coil device using the same. It is.

  A coil device mounted on circuits of various AC devices is configured by winding a coil around an annular core. As the core, a so-called dust core obtained by press-molding metal powder as a magnetic material and a ferrite core formed by sintering an oxidized magnetic material after pressurization have been proposed. Then, winding is applied to the core via an insulator such as a bobbin or a resin coating to form a coil device.

  For example, Patent Document 1 discloses a coil device in which a core having a rectangular cross section is wound. By improving the material, the inductance value indicated by the AC magnetic permeability and DC superposition characteristics is increased, and the core loss is increased. Aims to reduce this.

JP 2003-249410 A

  The inventors studied to improve the inductance value of the coil device and reduce the core loss by improving the shape. As a result of diligent research, focusing on the fact that magnetic flux is concentrated on the inner circumference side where the magnetic path is short and the magnetic flux density decreases toward the outer circumference side in the annular core, especially the core with low magnetic permeability. Invented.

  An object of the present invention is to provide a core having a shape capable of increasing an inductance value, more specifically, an inductance value per unit weight or reducing core loss, and a coil device using the core. .

The core according to the present invention is:
A closed magnetic circuit core having a core body formed by pressing metal powder as a magnetic material or pressing and sintering an oxide magnetic material,
The core body has a deformed portion in which the inner circumferential area is larger than the outer circumferential area when a cut surface in the width direction from the inner circumference to the outer circumference is partitioned by an intermediate line between the inner circumference and the outer circumference.

  It is desirable that the cut surface of the deformed portion has a maximum height on the inner peripheral side with respect to the intermediate line higher than a maximum height on the outer peripheral side.

  The center of gravity of the cut surface of the deformed portion is preferably located on the inner peripheral side of the intermediate line.

  It is desirable that the cut surface of the deformed portion be chamfered at both edges in the height direction on the outer peripheral side.

  It is desirable that the cut surface of the deformed portion be chamfered with a chamfering amount that is smaller than the chamfering of both the height direction edges on the outer periphery side at both edges in the height direction on the inner periphery side.

  The core preferably has a permeability μ of 200 (CGS unit system: the same applies hereinafter) or less.

  The deformed portion may be the entire circumference of the core body.

  The deformed portion may be provided on a part of the core body.

  The deformed portion can be provided at least at a portion where the coil is wound.

Moreover, the coil device according to the present invention includes:
An insulating coating is applied to the core, and a coil is wound around at least a part of the deformed portion.

  According to the core according to the present invention, the deformed portion of the core body has a cross-sectional area and an inner diameter of the core by increasing the area on the inner peripheral side where the magnetic flux is large compared to the outer peripheral side where the magnetic flux is small. Because the effective magnetic path length can be shortened without changing the core, the inductance value per unit weight of the core can be improved, and the increase in the magnetic flux density on the inner circumference side can be suppressed, and the magnetic flux density in the cross section can be made uniform. Therefore, the core loss can be reduced.

FIG. 1 is a perspective view of a core according to an embodiment of the present invention. FIG. 2 is a plan view of the core of FIG. FIG. 3 is a cross-sectional view taken along line A-A ′ of FIG. 2. FIG. 4 is a plan view of a core according to another embodiment of the present invention. FIG. 5 is a cross-sectional view taken along line A-A ′ of FIG. 4. 6A and 6B are perspective views of a coil device according to an embodiment of the present invention, in which FIG. 6A is a perspective view of an invention example, and FIG. 6B is a perspective view of a comparative example. 7A and 7B are explanatory views showing the distribution of magnetic flux when the coil is energized. FIG. 7A is an explanatory view of an invention example, and FIG. 7B is an explanatory view of a comparative example. FIG. 8 is a perspective view of a core according to another embodiment of the present invention. FIG. 9 is a perspective view of a core according to another embodiment of the present invention. FIG. 10 is a perspective view of a core according to another embodiment of the present invention. FIG. 11 is a cross-sectional view of a core used in the coil device of the embodiment, in which FIG. 11 (a) is an invention example and FIG. 11 (b) is a comparative core. FIG. 12 is a graph showing DC superposition characteristics of the invention example and the comparative example.

  Hereinafter, a core 10 and a coil device 20 using the same according to an embodiment of the present invention will be described with reference to the drawings. The core 10 of the present invention can be used for a coil device 20 such as a choke coil or a reactor, for example.

  1 is an external perspective view of a core 10 (core body) according to an embodiment of the present invention, FIG. 2 is a plan view, and FIG. 3 is a cross-sectional view taken along line A-A ′ of FIG.

  The core 10 (core main body) according to the present invention is formed by pressure-molding or sintering after pressing a magnetic powder material. In the case of a core obtained by pressure molding (hereinafter referred to as “dust core”), the magnetic material may be iron, iron-silicon, iron-aluminum-silicon (so-called sendust), iron-nickel (so-called permalloy). Examples thereof include nickel-iron-molybdenum-based and iron-based amorphous materials. Magnetic material powder is mixed with powder using a resin such as silicon, acrylic or phenolic as a binder, and at the same time, the powder surface insulation is oxidized by heating or chemical treatment to reduce core loss. In many cases, a film is formed. In addition, in the case of a core sintered after pressure molding (hereinafter referred to as “sintered core”), a Mn—Zn ferrite core, a Ni—Zn ferrite core material, and the like can be exemplified.

  Among the magnetic materials, iron-aluminum-silicon-based (Sendust), iron-Si-based, and iron-based amorphous materials have high hardness, so that the powder of the magnetic material is not easily crushed during molding. There is an advantage that eddy current loss can be reduced. These materials are also cheaper than iron-nickel (permalloy).

  Among the cores 10, the present invention is particularly preferably applied to a dust core having a low magnetic permeability μ. The magnetic permeability μ of the dust core is about 40 to 200, and the magnetic permeability μ of the sintered core is about 2000 to 7000. The reason will be described later.

  The core 10 is formed in an annular shape as shown in FIG. The illustrated embodiment is an annular closed magnetic circuit (so-called toroidal core) in which an inner periphery and an outer periphery in which a window portion 12 is formed in the center are formed in a circular shape. The core 10 is not limited to an annular shape, but is an elliptical annular shape, a rectangular annular shape, another polygonal annular shape, or a teardrop-like annular closed magnetic circuit formed by connecting two substantially orthogonal straight portions by an annular portion. There may be. In addition, the core 10 may be a core having the above-described shape that forms a closed magnetic circuit by combining a plurality of cores (blocks). These will be described later with reference to FIGS. 8 to 10 as modified examples.

  The present invention is preferably applied to the core 10 in which the ratio between the inner diameter and the outer diameter, or the ratio between the inner circumference side circumference length and the outer circumference side circumference length is 1: 1.5 to 1: 2.0. Furthermore, it is preferable to apply to the core 10 having an outer diameter of 20 mm to 50 mm. The reason will be described later. Of course, it is also possible to apply to the core 10 having an outer diameter outside the above range.

  The core 10 can have a shape in which a gap is formed as needed or the formed gap is backfilled. For example, when inserting a pre-wound air-core coil into the core 10, a gap for inserting the air-core coil is formed in the core 10, and after inserting this air-core coil, if necessary Thus, the gap can be backfilled with a magnetic material or a non-magnetic structure.

  The core 10 is preferably integrally formed, but can also be formed from a plurality of divided blocks 42 and 42 as shown in the modified examples (FIGS. 8 to 10). The dividing direction can be appropriately selected such as parallel to the width direction and perpendicular to the height direction.

  The core 10 is subjected to insulation coating to ensure electrical insulation with the coil 30. For example, the insulating coating may be obtained by winding an insulating sheet or tape around the core 10, preparing a case with an insulating resin and housing the core 10, or insert-molding the core 10 with an insulating resin, It can be implemented by coating the core 10 with an insulating resin by a resin powder coating method or a coating method.

  As shown in FIGS. 1 to 3, the core 10 according to the present invention is characterized by its cross-sectional shape. More specifically, as shown in FIG. 3, when the core 10 is cut in the inner circumference, that is, in the width direction from the side of the window portion 12 formed inside the core 10 toward the outer circumference, And an intermediate line M between the outer periphery O and the deformed portion 40 having a shape in which the area S1 on the inner peripheral side is larger than the area S2 on the outer peripheral side. The illustrated deformed portion 40 is formed over the entire circumference of the core 10 (core body). The width direction means a surface that is orthogonal or substantially orthogonal to the inner peripheral surface of the core 10. That is, the width direction when the core 10 is annular is the radial direction, and when the core 10 has a straight portion, the direction perpendicular to the inner peripheral surface of the straight portion is the width direction. Moreover, when the core 10 has a curved part with a partially bent or different radius of curvature, it means a surface orthogonal or substantially orthogonal to the tangential direction.

  The deformed portion 40 of the core 10 preferably has a ratio of the area S1 on the inner peripheral side to the area S2 on the outer peripheral side in the cut surface of 1.1: 1 to 1.50: 1. : 1 to 1.37: 1 is more desirable.

  As described above, the deformed portion 40 can be chamfered at both edges in the height direction on the outer peripheral side of the core 10 in order to make the area S1 on the inner peripheral side of the core 10 larger than the area S2 on the outer peripheral side. . As shown in the cross-sectional view of FIG. 3, as the chamfering, a radius 14 having a large curvature radius is formed at the corner on the outer peripheral side of the core 10, or a straight or curved shape is formed on the outer peripheral side as shown in FIGS. A taper 16 can be formed. Further, the core 10 is formed such that the maximum height Hmax is located on the inner peripheral side of the intermediate line M, or the inner peripheral side average height is higher than the outer peripheral side average height. Also good. Furthermore, you may form so that the gravity center G of the cross section may be located in the inner peripheral side of the core 10. FIG. 3, the ratio of the area S1 on the inner peripheral side and the area S2 on the outer peripheral side in the cut surface of the deformed portion 40 is 1.15: 1.

  3 and 5, the inner peripheral surface of the core 10 is also chamfered at both edges in the height direction. In addition, the chamfering amount of both edges in the height direction on the inner peripheral side is set smaller than the chamfering amounts on both edges in the height direction on the outer peripheral side. More specifically, in FIG. 3, the inner peripheral side of the core 10 forms rounds 18 having a smaller radius of curvature than the rounds 14 on the outer peripheral side at both edges in the height direction. This improves the ease of winding of the coil 30 when manually winding or mechanically winding the coil 30, which will be described later, reduces the stress on the coil conductor insulation film, and increases the degree of adhesion between the coil 30 and the core 10. This is to reduce the DC resistance of the coil 30 by shortening the winding length with respect to the number of turns of the coil 30. In particular, in the case of manual winding, the DC resistance value varies greatly depending on the level of proficiency of the operator, but a certain level of suppression can be achieved.

  An insulating coating is formed on the core 10 having the above-described configuration, and the coil device 20 is produced by winding the coil 30 around all or at least a part of the deformed portion 40 as shown in FIG. The coil 30 can exemplify manual winding or mechanical winding. It is also possible to cut a part of the core 10 to form a gap, and to insert a previously wound air-core coil using the gap. As described above, the gap can be backfilled with a magnetic material or a non-magnetic structure.

  In the present invention, when the coil 30 is manually wound or mechanically wound, by forming a round 14 or a taper 16 as shown in FIGS. In comparison, the coil 30 can be tightly wound. In particular, when the coil 30 is manually wound, less tension is applied to the conducting wire, so that operator fatigue is reduced and working efficiency and the like can be improved. Moreover, the same effect can be obtained by forming the round 18 on the inner peripheral surface side of the core 10. And as above-mentioned, since winding length with respect to the winding number of the coil 30 can be shortened by these, the raise of the direct current | flow resistance of the coil 30 can be suppressed, and dispersion | variation can be suppressed.

  FIG. 7B shows the distribution of the magnetic flux density generated in the core 11 when the coil device 21 (FIG. 6B) in the core 11 of the comparative example is energized by an isodensity line MF. Referring to FIG. 7B, the distribution of the magnetic flux density of the core 11 is concentrated on the inner circumference I side, the outer circumference O side is sparse, and particularly, both end OS portions pass almost minute magnetic flux. I understand that there is no. Therefore, the both ends OS portion with a small magnetic flux density on the outer periphery O side of the core 11 is reduced, and the magnetic flux density on the inner periphery I side is reduced without increasing the weight of the magnetic material by utilizing the increase in the area S1 on the inner periphery I side. The magnetic flux density can be equalized as shown by the isodensity line MF of the magnetic flux density distribution shown in the invention example of FIG. 7A (the coil device 20 is FIG. 6A), and the core 10 can be increased in size and magnetic material. Can be wasted.

  As described above, the magnetic flux density of the core 10 of the invention example is distributed more on the inner circumference I side because the shape of the core 11 is annular, and the ratio of the inner circumference side circumference to the outer circumference side circumference length. This is probably because the difference is large. That is, in such a core 11, the magnetic flux density is concentrated not on the outer periphery O side of the core 11 having a long magnetic path but on the inner periphery I side having a short magnetic path. This tendency is prominent in dust cores with low magnetic permeability. In the case of an annular core having a small ratio (difference) between the inner circumference side circumference and the outer circumference side circumference, the effect of changing the areas of the inner circumference side and the outer circumference side as in the present invention is reduced.

  In the present invention, the magnetic flux density on the inner surface side of the core 10 can be reduced by increasing the area of the deformed portion 40 of the core 10 on the inner peripheral side of the cut surface compared to the outer peripheral side. Therefore, compared with a core having a rectangular cross section with the same cross-sectional area, the magnetic saturation due to the concentration of magnetic flux and the heat generation due to the core loss can be suppressed, and the inductance value per unit weight can be improved.

<Modification>
In the said embodiment, the core 10 (core main body) is produced by integral molding. However, as shown in FIG. 8, the core 10 can also be formed by joining a plurality of blocks 42, 42. By using such blocks 42, 42, molding can be performed more easily than in the integral molding. For example, the blocks 42, 42 can be manufactured by storing powder of magnetic material in a cylindrical mold having a cross-sectional shape corresponding to a cut surface and pressing from above and below.

  Moreover, in the said embodiment, the area of the inner peripheral side is enlarged compared with the outer peripheral side about the cut surface so that the deformed part 40 may be formed over the perimeter of the core 10. FIG. However, for example, in a core device used for a reactor, a coil may not be wound over the entire circumference of the core 10. In such a case, as shown in FIGS. 9 and 10, the blocks 42 and 42 of the coil winding portion 44 around which the coil is wound have a deformed portion in which the area on the inner peripheral side of the cut surface is larger than that on the outer peripheral side. 40, and the joint portion 46 around which the coil is not wound may employ a block 48 having a rectangular cut surface, that is, a shape having the same area on the inner peripheral side and the outer peripheral side. Since the block 48 having a rectangular cut surface is easier to form than the blocks 42 and 42 having a cut surface such as the deformed portion 40, the block 48 of the joint portion 46 is formed in a rectangular shape so as to be deformed over the entire circumference. Compared with the case where the blocks 42 and 42 (see FIG. 8) having the cut surface of the portion 40 are employed, the core 10 can be manufactured easily and inexpensively. Of course, the block 48 of the joint portion 46 can also be composed of a plurality of blocks.

  The core 10 shown in FIG. 8 to FIG. 10 can change the length of the coil winding portion 44 and the joint portion 46 by changing the number of the blocks 42 and the blocks 42 and 48. There is also an advantage that the degree can be increased.

  The powder of Sendust alloy composition was used as the magnetic material to form the dust core of the invention example (see FIG. 11 (a)) and the dust core of the comparative example (see FIG. 11 (b)). As the core, 157 g of a magnetic material having the same weight was used for both the inventive example and the comparative example.

Core, both the outer diameter 44.85Mm, inner diameter 25.2 mm (that is, the width 19.65Mm), the window area 4.99Cm ^2, the width direction of the cross-sectional area 2.46Cm ^2, volume is 27.06cm ^3. The core of the inventive example has a height of 30 mm, and the core of the comparative example has a height of 25 mm. See FIG. 11 for other dimensions. The difference in height is that the cross section of the comparative example is rectangular, whereas the core of the invention example has the same inner and outer diameter and cross sectional area, and the inner peripheral cross section S1 is larger than the outer peripheral cross section S2. Has occurred. The ratio of the area S1 on the inner circumference side to the area S2 on the outer circumference side of the core 10 shown in FIGS. 11 and 5 is 1.37: 1.

  The cores were each wound 36 times with an insulation-coated conductor wire having a thickness of 1.6 mm to form a coil device (choke coil) (invention example shown in FIG. 6 (a), comparative example shown in FIG. 6 (b)). ). The length of the conductive wire (coil) wound around each core was 2.94 m in the invention example and 2.99 m in the comparative example (see Table 1 described later). This means that the coil device of the invention example was able to wind the conductor wire in close contact with the core as compared with the coil device of the comparative example.

  About the produced coil apparatus of the example of an invention and a comparative example, HP4285A which is an LCR meter was used, and the initial inductance value (Ls) was measured at a frequency of 100 kHz. Moreover, DC resistance (Rdc) was measured using HIOKI3540 mΩHi-TESTER. The results are shown in Table 1.

  Referring to Table 1, it can be seen that the invention example has a higher initial inductance value than the comparative example. More specifically, the invention example has an initial inductance value that is about 6% higher than the comparative example. This is thought to be because the invention example was able to reduce the magnetic flux density and increase the inductance value without magnetic saturation by increasing the area S1 on the inner peripheral side where there was much magnetic flux in the cut surface of the deformed portion. It is done.

  In this example, the core weights of the inventive example and the comparative example are the same, so the initial inductance value per unit weight is also improved by about 6%.

  Further, in the invention example, since the taper 16 and the round 18 are formed on both edges of the outer circumference and the inner circumference in the height direction, the conductor can be wound in close contact with each other. The overall length of the coil) can be shortened. Thereby, it turns out that the direct current | flow resistance value (Rdc) originating in a coil is also small. Therefore, there is an advantage that the DC resistance loss of the coil device 20 can be reduced.

  With respect to the coil devices of the inventive example and the comparative example, a DC bias current of 0 A to 50 A was passed and the DC superposition characteristics were examined. The results are shown in Table 1 and FIG. Referring to the figure, it can be seen that the invention example has a higher inductance value than the comparative example. In particular, when the DC bias current is in the range of 0 A to 20 A, all exhibit particularly high inductance values as compared with the comparative example. This is also considered to be due to the fact that the magnetic path can be secured by increasing the area S1 on the inner peripheral side where the magnetic flux density is increased in the cut surface of the deformed portion, as in the above examples.

  Further, when the effective magnetic path length (l) of each coil device was calculated from the initial inductance value, it was shortened by about 6%. That is, according to the present invention, the effective magnetic path length serving as the center of gravity of the magnetic flux distribution is increased on the inner peripheral side of the core by increasing the area on the inner peripheral side and reducing the outer peripheral side in the cut surface of the core. You can see that it is close. On the other hand, in the comparative example, it is an intermediate position between the inner periphery and the outer periphery.

  Next, assuming a working state to measure the core loss in the invention example and the comparative example, the coil device of this example was energized with a high-frequency current of a triangular wave of 100 kHz, 10 Ap-p (effective value about 3 A), and the measurement result Is shown in Table 2.

In order to compare the core loss at the same magnetic flux density under the same conditions, it is necessary to make the inductance value the same in addition to the magnetizing force (the number of turns × current value), so the invention example has an initial inductance value of about 6%. In order to reduce the improvement and match with the comparative example, the winding is reduced by about 6% (Formula 1) by setting 1T winding from 36T to 35T, and the values are almost the same.
<Formula ^{1> (1-35 2/36 2} ) × 100%

  In addition, the core loss in Table 2 theoretically includes DC resistance loss and AC loss of the winding part. However, no direct current is applied in this measurement, and the conductor diameter including the DC resistance value. In addition, since the winding form is the same, it can be regarded as a core loss difference in the same magnetic material.

  According to Table 2, it can be seen that the core loss is clearly reduced in the inventive example compared to the comparative example. Thereby, compared with the comparative example core of the rectangular cross section with the same cross-sectional area, the invention example can reduce core loss by relaxing the concentration of magnetic flux, and can suppress heat generation as a result.

  The above description is for explaining the present invention, and should not be construed as limiting the invention described in the claims or limiting the scope thereof. Further, the configuration of each part of the present invention is not limited to the above-described embodiment, and various modifications can be made within the technical scope described in the claims.

10 Core 12 Window 14 R
16 Taper (peripheral side surface removal)
18 are
20 Coil device 30 Coil 40 Deformed section 42 Block (Deformed section)
44 Coil winding part

Claims (10)

A closed magnetic circuit core having a core body formed by pressing metal powder as a magnetic material or pressing and sintering an oxide magnetic material,
The core body has a deformed portion in which an area on the inner peripheral side is larger than an area on the outer peripheral side when a cut surface in a width direction from the inner periphery toward the outer periphery is partitioned by an intermediate line between the inner periphery and the outer periphery. Core to do. The cutting surface of the deformed portion has a maximum height on the inner peripheral side than the intermediate line, which is higher than a maximum height on the outer peripheral side.
The core according to claim 1. The center of gravity of the cut surface of the deformed portion is located on the inner peripheral side of the intermediate line,
The core according to claim 1 or 2. The cut surface of the deformed portion is chamfered on both edges in the height direction on the outer peripheral side,
The core according to any one of claims 1 to 3. The cut surface of the deformed portion is chamfered with a chamfering amount that is smaller than the chamfering of the height direction both edges on the outer peripheral side at both edges in the height direction on the inner peripheral side,
The core according to claim 4. The magnetic permeability μ is 200 or less.
The core according to any one of claims 1 to 5. The deformed portion is the entire circumference of the core body.
The core according to any one of claims 1 to 6. The deformed portion is provided in a part of the core body.
The core according to any one of claims 1 to 6. The deformed portion is provided at least in a portion around which the coil is wound.
The core according to claim 8. An insulating coating is applied to the core according to any one of claims 1 to 9, and a coil is wound.
Coil device.

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