JP2017092071A - Inductance element and evaluation method for inductance element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inductance element comprising a magnetic core which is configured by joining two cores, and optimizing operation, and an evaluation method therefor.SOLUTION: A product of a ratio of a minimum magnetic path cross-sectional area of a first core and a minimum magnetic path cross-sectional area of a second core and magnetic permeability of the second core is defined as a criterion of evaluation and an inductor performance index (μH A/T mm) of an inductance element using a plurality of magnetic cores is evaluated. The product is made equal to or greater than 18 and equal to or smaller than 80 as a result, thereby obtaining the inductance element improved in performance.SELECTED DRAWING: Figure 10

Description

  The present invention relates to an inductance element used as, for example, a choke coil in a switching power supply and an inductance element evaluation method.

  In recent electronic devices, in order to drive various devices, a high-efficiency switching power source that supplies an appropriate power source is often installed for each device as a load.

  Computers and servers with high-performance CPUs and SOCs, or communication devices such as mobile devices and smartphones use highly integrated devices for high-speed and high-speed processing, and the supply current to these devices increases. doing. Therefore, as a switching power supply, it is necessary to increase the switching frequency, and it is also necessary to be able to cope with a large current.

  In order to enable a switching power supply for driving a DC device to operate stably even with a large current, it is necessary to use an inductor element that can operate stably even when the DC superimposed current becomes a large current.

The inductance element according to the power conversion switching power supply, direct current flows inductor current superimposed, in operation of the switching power supply, the relationship between the inductor voltage V _L, and the inductance value L, the inductor current I _L, V _L = L · (dI _L / dt).

From this relationship, given the large DC bias currents, the core is magnetically saturated, the inductance value L of the inductance element is reduced, the increase (dI L / _dt) is increased ripple current [Delta] I _L flowing through the inductor Will bring. Such core is rapidly magnetically saturated with respect to an increase in DC bias current, when the decrease in the inductance value occurs, a rapid increase in the ripple current [Delta] I _L is damage to the power supply device, the power supply and it May cause damage such as burning of the equipment in which is installed.

  Therefore, it is desirable to have a characteristic that does not cause a sudden drop from the specified inductance value even when an unexpected increase in the inductor current occurs.

  A conventional inductance element using a core formed of ferrite forms a gap at the joint between two cores, and suppresses a decrease in the inductance value L when a large DC superimposed current is applied. Furthermore, by increasing the gap width, so-called DC superposition characteristics can be improved.

  In addition, recent power supply devices are required to increase the switching frequency in order to reduce the size, etc. In addition to operating the inductance value lower by widening the gap, the number of turns of the coil of the inductance element is reduced. It is also required to reduce the core volume.

  However, in this case, a high-frequency magnetic field leaks from a widely formed gap, and this leakage magnetic field affects other devices and wiring that are close to each other. Furthermore, the leakage magnetic field from the gap causes an eddy current in its own winding of the inductance element and causes an increase in AC resistance (ACR).

Next, the following patent documents 1, 2, and 3 describe inventions related to conventional inductors.
FIG. 26A shows a cross-sectional view of the inductor 30 described in Patent Document 1, and FIG. 26B shows a bottom view of the metal dust core 32 as seen from the joint surface side. The inductor 30 combines the Mn—Zn ferrite core 31 having a high magnetic permeability and the metal dust core 32 having a high saturation magnetic flux density, thereby reducing the number of turns of the coil 33 without deteriorating the DC superimposed saturation current characteristic. DC resistance can be reduced. In addition, a coil 33 is wound around the center leg 32a of the metal dust core 32, and the metal dust core 32 and the Mn—Zn ferrite core 31 are joined, and a substantial gap is formed in the hatched portion in FIG. Ga and Gb are formed.

  In Patent Document 2, a ferrite having a high magnetic permeability and a low iron loss at a high frequency is used as a first magnetic core, and a saturation magnetic flux is lower as a second magnetic core than the first magnetic core. An inductance element using a metal magnetic material having a high density and excellent direct current superposition characteristics is described. Further, in paragraphs (0036) and (0037) of Patent Document 2, there is a problem that an inductance is reduced when an attempt is made to improve DC superposition characteristics by providing a gap. In order to solve this problem, It has been described that by performing mutual complementation between the first magnetic core and the second magnetic core, the direct current superimposition characteristics are improved, and a decrease in inductance can be suppressed.

  Patent Document 3 describes an inductor having a first ferrite bead core and a second core having a lower magnetic permeability, as in Patent Document 2. By configuring the two cores so that the magnetic flux passes through them, magnetic saturation of the cores under a large direct current is avoided.

JP 2005-228897 A Japanese Patent No. 3818465 European published patent EP1498915A1

  As described in Patent Literature 1, Patent Literature 2, and Patent Literature 3, an inductance element using a core made of ferrite having a high magnetic permeability and a dust core having a high saturation magnetic flux density conflicts with each other. Since it has characteristics, it is difficult to combine both cores in an optimal state, and a method for efficiently obtaining the optimum values of both cores has not been established.

  Next, as described above, in the inductance element, the leakage magnetic field from the gap of the magnetic core causes an eddy current in the winding of the inductance element, thereby increasing the AC resistance (ACR).

  In this regard, in the inductor described in Patent Document 1, since the coil 33 is wound around the outer periphery of the center leg 32 a, the substantial gap Gb formed in the center leg 32 a extends along the inner periphery of the coil 33. However, the substantial gaps Ga and Ga formed linearly on the leg portions on both sides of the magnetic core are located away from the outer peripheral surface of the coil 33 wound in a circle. Is formed. Therefore, this structure originally has less influence on the eddy current.

  On the other hand, the inductors described in Patent Document 2 and Patent Document 3 have a junction gap that is a junction of two magnetic cores along the coil conductor in the magnetic core. Although the degree of influence of the leakage magnetic field on the coil is different, it is necessary to take measures against the influence of the leakage magnetic field from the gap.

  Further, in this type of inductor, even if the nonmagnetic layer intended to form a desired gap width is not actively interposed at the junction of two magnetic cores, the surface roughness of the junction In addition, it is inevitable that a substantial gap exists in the bonding of the magnetic core due to the interposition of the bonding material for bonding between the cores. However, in the inductors described in Patent Document 2 and Patent Document 3, no countermeasure is taken to eliminate the harmful effects caused by the existence of such a substantial gap.

  The present invention solves the above-described conventional problems, and an object thereof is to provide an inductance element having a structure in which a desired inductance value can be easily obtained, a direct current superposition characteristic is excellent, and a current value that can be passed is kept high. It is said.

  In addition, the present invention provides an inductance element evaluation method capable of efficiently evaluating an inductance element having a structure that makes it easy to obtain a desired inductance value, has excellent DC superposition characteristics, and can maintain a high current value that can be passed. It is intended to provide.

The present invention provides an inductance element in which a conductor is housed inside a magnetic core.
The magnetic core includes a first core made of a magnetic material, and a second core made of a magnetic material having a permeability lower than that of the first core and a DC superposition characteristic superior to that of the first core. It is formed by joining the core,
The product of the minimum magnetic path cross-sectional ratio obtained by (the minimum magnetic path cross-sectional area of the second core / the minimum magnetic path cross-sectional area of the first core) and the magnetic permeability of the second core is 18 or more and 80 or less. It is characterized by being set to.

  The inductance element of the present invention has an inductor performance index of 15 or more, which is a value calculated per unit volume of the product of the initial inductance per unit number of turns and the magnetomotive force when the DC superposition characteristic has a predetermined ratio. It is preferable.

In the inductance element of the present invention, it is preferable that the magnetic permeability of the first core is 1000 or more, and the magnetic permeability of the second core is 100 or less.
In the inductance element of the present invention, for example, the second core is a dust core.

  In the inductance element of the present invention, the gap between the magnetic core and the conductor is located in the magnetic core at a position close to the joint gap between the first core and the second core. It is preferable that the ratio of (core-coil gap / joining gap) is 1 or more.

  Furthermore, in the inductance element of the present invention, the junction gap is preferably 50 μm or less.

  The width of the bonding gap is preferably as small as possible. In calculation, when the bonding gap is zero, the ratio of (core-coil gap / bonding gap) is infinite. However, even if the junction gap is made as small as possible, the surface roughness of the opposing surface at the junction between the first core and the second core, or the thickness when an adhesive layer is interposed, etc. Therefore, there may be a minimum effective gap width. Such a substantial effective gap width is usually about 5 μm. In this case, the ratio of (core-coil gap / joining gap) may be about 20 or less.

  Furthermore, in the inductance element of the present invention, the conductor has a rectangular cross-sectional area, and the core-coil gap is formed along at least one side surface of the conductor.

Next, the present invention provides a first core made of a magnetic material, and a first core made of a magnetic material having a lower magnetic permeability than the first core and a DC superimposition characteristic superior to that of the first core. In an evaluation method of an inductance element in which a conductor is housed inside a magnetic core formed by joining two cores,
(1) Obtain the product of the minimum magnetic path cross-sectional ratio obtained by (the minimum magnetic path cross-sectional area of the second core / the minimum magnetic path cross-sectional area of the first core) and the permeability of the second core;
The direct current superposition characteristics of the inductance are evaluated in relation to the product of (1).

In addition, the evaluation method of the inductance element of the present invention is:
(2) The initial inductance per unit number of turns of the conductor is evaluated in relation to the product obtained in (1),
(3) The magnetomotive force when the DC superimposition characteristic becomes a predetermined ratio is evaluated in relation to the product obtained in (1).

Furthermore, the evaluation method of the inductance element of the present invention is:
(4) The inductor performance index, which is a value obtained by calculating the product of the initial inductance per unit winding number of the conductor and the magnetomotive force when the DC superimposition characteristic is a predetermined ratio, per unit volume is (1) The evaluation is based on the relationship with the product obtained in.

  The present invention relates to an inductance element using a magnetic core in which two types of cores are combined, and a minimum magnetic path cross section obtained by (the minimum magnetic path cross section of the second core / the minimum magnetic path cross section of the first core). Paying attention to the product of the ratio and the magnetic permeability of the second core, and setting the value of this product to a value between 18 and 80, the desired inductance value is shown, the direct current superposition characteristics are excellent, and the current that can pass It is possible to increase the amount.

  Furthermore, by setting the ratio of (core-coil gap / joining gap) to 1 or more, the influence of leakage magnetic flux from the joining cap on the conductor is suppressed, and the AC resistance value is kept low even for high-frequency currents. Is possible.

  In the inductance element evaluation method of the present invention, the minimum magnetic path cross-sectional ratio obtained by the minimum magnetic path cross-sectional area of the second core / the minimum magnetic path cross-sectional area of the first core) and the magnetic permeability of the second core. By using parameters that have not been used so far, such as the product of, high-performance inductance elements can be easily evaluated and designed.

The top view of the inductance element of the 1st Embodiment of this invention, Sectional drawing which cut | disconnected the inductance element shown in FIG. 1 by the II-II line | wire, It is sectional drawing which cut | disconnected the inductance element shown in FIG. 1 by the III-III line | wire, (A) (B) (C) shows what changed the height dimension of the 1st core and the 2nd core, (A) is a plan view of the inductance element of the second embodiment of the present invention, (B) is a cross-sectional view of the inductance element shown in (A) cut along line BB, A diagram showing the relationship between the ratio of the junction gap of the magnetic core and the core-coil gap and the increase ratio of the AC resistance, When the ratio of (core-coil gap / joining gap) is 10, the permeability of the first core is 2500, and the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is changed. A diagram showing the change in inductance with increasing current, When the ratio of (core-coil gap / joining gap) is 10, the permeability of the first core is 2500, and the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is changed. A diagram showing the rate of change of inductance with respect to current increase, When the ratio of (core-coil gap / junction gap) is 10 and the permeability of the first core is 2500, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core, A diagram showing a change in initial inductance (AL0) per unit number of turns, When the ratio of (core-coil gap / junction gap) is 10 and the permeability of the first core is 2500, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core, A diagram showing changes in magnetomotive force (N · Isat) when ΔL is 30%, When the ratio of (core-coil gap / junction gap) is 10 and the permeability of the first core is 2500, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core, A diagram showing a change in an inductor performance index which is a value calculated per unit volume by a product of an initial inductance per unit winding (AL0) and a magnetomotive force (N · Isat) when ΔL is 30%, When the ratio of (core-coil gap / joining gap) is 10, the permeability of the first core is 1000, and the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is changed. A diagram showing the change in inductance with increasing current, When the ratio of (core-coil gap / joining gap) is 10, the permeability of the first core is 1000, and the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is changed. A diagram showing the rate of change of inductance with respect to current increase, When the ratio of (core-coil gap / junction gap) is 10 and the permeability of the first core is 1000, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core, A diagram showing a change in initial inductance (AL0) per unit number of turns, When the ratio of (core-coil gap / junction gap) is 10 and the permeability of the first core is 1000, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core, A diagram showing changes in magnetomotive force (N · Isat) when ΔL is 30%, When the ratio of (core-coil gap / junction gap) is 10 and the permeability of the first core is 1000, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core, A diagram showing a change in an inductor performance index which is a value calculated per unit volume by a product of an initial inductance per unit winding (AL0) and a magnetomotive force (N · Isat) when ΔL is 30%, When the ratio of (core-coil gap / joining gap) is 10, the permeability of the first core is 5000, and the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is changed. A diagram showing the change in inductance with increasing current, When the ratio of (core-coil gap / joining gap) is 10, the permeability of the first core is 5000, and the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is changed. A diagram showing the rate of change of inductance with respect to current increase, When the ratio of (core-coil gap / junction gap) is 10 and the permeability of the first core is 5000, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core, A diagram showing a change in initial inductance (AL0) per unit number of turns, When the ratio of (core-coil gap / junction gap) is 10 and the permeability of the first core is 5000, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core, A diagram showing changes in magnetomotive force (N · Isat) when ΔL is 30%, When the ratio of (core-coil gap / junction gap) is 10 and the permeability of the first core is 5000, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core, A diagram showing a change in an inductor figure of merit that is a product of an initial inductance per unit winding (AL0) and a magnetomotive force (N · Isat) when ΔL is 30%; When the ratio of (core-coil gap / joining gap) is 1, the permeability of the first core is 2500, and the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is changed. A diagram showing the change in inductance with increasing current, When the ratio of (core-coil gap / joining gap) is 1, the permeability of the first core is 2500, and the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is changed. A diagram showing the rate of change of inductance with respect to current increase, When the ratio of (core-coil gap / joining gap) is 1 and the permeability of the first core is 2500, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is A diagram showing a change in initial inductance (AL0) per unit number of turns, When the ratio of (core-coil gap / joining gap) is 1 and the permeability of the first core is 2500, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is A diagram showing changes in magnetomotive force (N · Isat) when ΔL is 30%, When the ratio of (core-coil gap / joining gap) is 1 and the permeability of the first core is 2500, the change in the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core is A diagram showing a change in an inductor performance index which is a value calculated per unit volume by a product of an initial inductance per unit winding (AL0) and a magnetomotive force (N · Isat) when ΔL is 30%, (A) (B) is explanatory drawing of the prior art described in patent document 1

<Inductance element structure>
The inductance element 10 according to the first embodiment of the present invention shown in FIGS. 1 to 3 includes a first core 1 and a second core 2, and the first core 1 and the second core 2. Are joined to form a magnetic core C.

  A groove 1a having a rectangular cross section and extending linearly is formed on the upper surface of the first core 1, and a conductor 3 is accommodated in the groove 1a. As shown in FIG. 2, the conductor 3 has a main body 3 a housed in the groove 1 a, exposed portions 3 b and 3 b extending in the height direction on both the left and right sides of the magnetic core C, and the bottom of the first core 1. It has a pair of terminal parts 3c and 3c arranged along.

  The conductor 3 is formed of a conductive metal wire such as copper that extends in a straight line. After the main body portion 3a is housed in the groove 1a, the exposed portions 3b and 3b and the terminal portion are bent by bending both ends. 3c and 3c are integrally formed.

  The 2nd core 2 is flat plate shape, and the 2nd core 2 is joined to the part in which the groove | channel 1a of the upper surface of the 1st core 1 is not formed through the contact bonding layer. Or the 1st core 1 and the 2nd core 2 are joined by winding the outer peripheral part with a tape etc. When the adhesive layer is used, the adhesive layer is formed of a nonmagnetic material such as a glass material, an inorganic material, or an organic material.

  As a result, joint gaps G1 and G1 where the first core 1 and the second core 2 are joined exist on both sides of the groove 1a. The widths of the bonding gaps G1 and G1 are the surface roughness of the bonding surfaces of the cores of the first core 1 and the second core 2, and the adhesive layer when an adhesive layer is interposed in the bonding portion. Depends on the thickness etc. In FIG. 3A, the gap width (gap length) of the junction gaps G1 and G1 is indicated by δ1.

  As shown in each of the cross-sectional views of FIGS. 3A, 3B, and 3C, there is a core-coil gap between the left and right side surfaces of the conductor 3 having a rectangular cross section and the inner wall surface of the groove 1a. G2 and G2 exist. As shown in FIG. 1, since the groove 1a and the main body 3a of the conductor 3 extend linearly, the gap width (gap length) along the entire length of both sides of the main body 3a inside the magnetic core C. Core-coil gaps G2 and G2 having a width of δ2 are formed. The core-coil gaps G2 and G2 exist along the bonding gaps G1 and G1, and as shown in FIG. 3, each of the core-coil gaps G2 and G2 is inside the core of the bonding gaps G1 and G1. It exists continuously with the end of the.

FIG. 4 shows an inductance element 20 according to the second embodiment of the present invention.
The inductance element 20 includes a first core 1 and a second core 2 joined to form a magnetic core C. A circular groove 1a is formed in the upper portion of the first core 1, and the conductor 3 is accommodated in the groove 1a. As shown in FIG. 4A, the conductor 3 is integrally formed with a main body portion 3d formed in a ring shape and a pair of terminal portions 3e, 3e extending to the outside of the magnetic core C.

  As shown in FIG. 4B, a joint gap G3 is formed on the outer peripheral side of the groove 1a at the joint portion between the first core 1 and the second core 2, and is joined on the inner peripheral side of the groove 1a. A gap G4 is formed.

  A core-coil gap G5 exists between the main body 3d and the inner wall surface of the groove 1a along the outer peripheral side surface of the main body 3d of the conductor 3, and the inner periphery of the main body 3d of the conductor 3 is present. A core-coil gap G6 exists between the main body 3d and the inner wall surface of the groove 1a along the side surface. The core-coil gap G5 and the core-coil gap G6 exist along the entire circumference of the outer edge and the inner edge of the ring-shaped main body 3d. The core-coil gap G5 exists close to the end of the bonding gap G3, and the core-coil gap G6 exists close to the end of the bonding gap G4.

  In each embodiment, the first core 1 is an oxide magnetic material having high magnetic permeability and low iron loss in a high frequency band, and is formed of a ferrite material such as Mn—Zn ferrite. The second core 2 has a magnetic permeability lower than that of the first core 1, but has a higher saturation magnetization (saturation magnetic flux density) than that of the first core 1, and is made of a magnetic metal material having excellent direct current superposition characteristics. Yes. For example, the second core is a dust core, which is formed by using a magnetic metal powder of an Fe-Si-B amorphous material, and formed by a compacting method, or an Fe-PC-C amorphous material. It is formed by a compacting method using magnetic metal powder as a material.

  The permeability of the first core 1 is 1000 or more and preferably 5000 or less, and the permeability of the second core 2 is 100 or less, preferably 20 or more, and more preferably 50 or less.

<Gap width>
The inductance element 10 of the first embodiment and the inductance element 20 of the second embodiment prevent a decrease in initial inductance by maintaining a high magnetic permeability by the first core 1, and the second core 2 The saturation magnetism is increased to improve the DC superimposition characteristics, so that the decrease in inductance when the DC superimposition current increases can be suppressed.

  Since the direct current superimposition characteristic can be improved by using the second core 2, the direct current superimposition characteristic is improved by increasing the gap width of the core and generating a leakage magnetic field like an inductance element using a conventional ferrite core. It becomes unnecessary to use such a method.

  Therefore, in the inductance elements 10 and 20, the gap widths of the junction gaps G1, G3, and G4 between the first core 1 and the second core 2 can be made as small as possible. As a result, the junction gap G1, The leakage magnetic field from G3 and G4 to the outside can be reduced, and adverse effects on peripheral devices and peripheral parts when used in a high frequency band can be reduced. Further, by reducing the gap width of the junction gaps G1, G3, G4, it is possible to prevent the initial inductance from being lowered.

  When the size of one side of the magnetic core C of the inductance elements 10 and 20 is a small size of 10 mm or less, the gap width of the junction gaps G1, G3, and G4 of the first core 1 and the second core 2 Is preferably 100 μm or less, more preferably 50 μm or less. The bonding gaps G1, G3, and G4 are effective due to the roughness of the bonding surface where the first core and the second core are bonded, or when an adhesive layer is interposed on the bonding surface. The lower limit of the gap width is about 5 μm to 10 μm.

  The inductance element 10 according to the first embodiment shown in FIG. 1 to FIG. 3 is continuous with the inner end of the joint gap G1 between the first core 1 and the second core 2, and the inside of the magnetic core C. There is a core-coil gap G2. The side surface of the conductor 3 is close to and opposed to the inner end of the bonding gap G1. Therefore, when an AC current is applied to the conductor 3 and an AC magnetic field is induced inside the magnetic core C, a leakage magnetic field from the inner end of the junction gap G1 acts on the main body 3a of the conductor 3, and the conductor 3 An eddy current is likely to be generated inside. As a result, an alternating current is likely to collect on the surface of the conductor 3 due to the so-called skin effect, resulting in an increase in alternating current resistance (ACR).

  In particular, as shown in FIG. 1, in the small inductance element 10, when the core-coil gap G2 is formed at a close distance along substantially the entire length of both side surfaces of the main body 3a of the conductor 3, the skin effect is a conductor. 3 of the main body 3a, and the increase in the AC resistance is increased.

  This is the same also in the inductance element 20 of the second embodiment shown in FIG. 4, and the core-coil gap G5 exists continuously at the inner end of the junction gap G3, and the end of the junction gap G4. And the core-coil gaps G5 and G6 extend along substantially the entire circumference of the outer peripheral side surface and the inner peripheral side surface of the ring-shaped main body 3d of the conductor 3. Existing. Therefore, also in the inductance element 20, the leakage magnetic flux from the junction gaps G <b> 3 and G <b> 4 tends to affect the conductor 3, and the problem that the AC resistance increases due to the eddy current loss inside the conductor 3 is likely to occur.

  FIG. 5 shows the result of simulating the influence of the bonding gap between the cores on the conductor.

  This simulation uses the inductance element 10 of the first embodiment shown in FIGS. 1 to 3 as a model. The gap width δ2 of the core-coil gap G2 was fixed to 100 μm, and the gap width δ1 of the bonding gap G1 was changed to 50 μm, 100 μm, 200 μm, and 300 μm. The cross-sectional shape of the conductor 3 was 1.4 mm long and 1.5 mm wide. And the change of alternating current resistance when the alternating current of 0.3 MHz, 0.6 MHz, 0.9 MHz, and 1.2 MHz was given to the conductor 3 was calculated | required.

  5 indicates the ratio of (gap width δ2 of the core-coil gap G2) / (gap width δ1 of the bonding gap G1), and the vertical axis indicates (when the conductor 3 is disposed in the magnetic core C). (Increase amount of AC resistance) / (AC resistance of the conductor 3 when the magnetic core C is not provided). For example, the vertical axis of 0.2 is compared with the AC resistance of the conductor 3 when the magnetic core C is not provided because the magnetic field C leaks from the junction gap G1 because the conductor 3 is placed in the magnetic core C. This means that the AC resistance has increased by 20%.

  From FIG. 5, when the ratio of (gap width δ2 of core-coil gap G2) / (gap width δ1 of junction gap G1) is 1 or more, the increase in AC resistance is 20% even in a high frequency band of about 1.2 MHz. It becomes possible to suppress to less than. If the ratio is 2 or more, the increase in AC resistance due to the leakage magnetic field from the junction gap G1 can be reduced to almost zero. Therefore, the ratio is more preferably 2 or more.

  However, if the gap width δ2 of the core-coil gap G2 is excessively increased, the cross-sectional area of the main body 3a of the conductor 3 is decreased, and the resistance value is further increased. Therefore, the ratio of δ2 / δ1 is preferably 20 or less.

  In order to prevent a reduction in the cross-sectional area of the main body portion 3a of the conductor 3 so that the gap width δ2 does not increase when the ratio of (gap width δ2 / gap width δ1) is 1 or more and 20 or less, the junction gap G1 It is necessary to make the gap width δ1 of the above as small as possible. In addition, by reducing the gap width δ1, it is possible to suppress a decrease in the initial inductance value (inductance value when no current is applied) of the inductance element 10, and to improve the performance of the inductance element 10.

A preferable range of the gap width δ1 of the bonding gap G1 is 100 μm or less, and more preferably 50 μm or less.
The width dimension of the bonding gap G1 is preferably as small as possible.

  However, the effective gap width δ1 is approximately 5 μm or more by being formed of the surface roughness of the facing surface where the core 1 and the core 2 are bonded, or the adhesive layer interposed in the bonding portion of the facing surface. Considering this, it is preferable that the ratio of (gap width δ2 / gap width δ1) is substantially 20 or less.

  Therefore, in order to suppress an increase in AC resistance and to suppress a decrease in the cross-sectional area of the main body 3a of the conductor 3 and an increase in the resistance value, as described above, the ratio of δ2 / δ1 is 20 or more. Or less, more preferably 2 or more and 20 or less.

  In other words, when the gap width δ1 of the junction gap G1 is 5 μm or more and the ratio of (gap width δ2 / gap width δ1) is 1 or more and 20 or less, an increase in AC resistance is suppressed even in a high frequency band. In addition, it is possible to suppress a decrease in the initial inductance value of the inductance element 10, and even if the control of the roughness of the joint surface between the core 1 and the core 2 and the dimensional accuracy of the gap width δ1 of the joint gap G1 is eased, mass production of the inductance element is possible. Can be facilitated.

  The preferable range of the ratio is the same in the inductance element 20 of the second embodiment shown in FIG.

<Appropriate value of magnetic core C structure>
In the inductance element 10 of the first embodiment and the inductance element 20 of the second embodiment, the bonding gaps G1, G3, and G4 between the cores and the core-coil gaps G2, G5, and G6 inside the magnetic core are properly set. By setting to, the increase in AC resistance can be suppressed and the initial inductance can be kept high, but the magnetic path cross section of the first core 1 and the second core 2 and the permeability of the second core are appropriate. By setting to, the inductor performance index, which is a value calculated per unit volume of the product of the initial inductance per unit winding and the magnetomotive force when the DC superimposition characteristic becomes a predetermined ratio, is maintained at a high value. It becomes possible.

  An evaluation method of the present invention for obtaining an inductor performance index and an inductance element having a high inductance performance index obtained as a result of the calculation will be described below as an example.

  In the following embodiments, the inductance element 10 shown in FIGS. 1 to 3 is modeled, but the same applies to the inductance element 20 shown in FIG.

  The inductance element 10 as a model of the embodiment has a longitudinal dimension H of 6.8 mm, a width dimension L1 of 6.8 mm, and a length dimension L2 shown in FIG. 1 of 6.8 mm in the cross section of the magnetic core C shown in FIG. It is. The cross-section of the conductor 3 is rectangular, the vertical dimension in FIG. 3 is 1.4 mm, and the horizontal dimension in FIG. 3 is 1.5 mm.

  Table 1 below shows that when the position of the conductor 3 in the magnetic core C is changed in the height direction, as shown in FIGS. The calculated value of the minimum magnetic path cross-sectional ratio obtained by (minimum magnetic path cross-sectional area / minimum magnetic path cross-sectional area of the first core) is described in units of%. This minimum magnetic path section ratio has the following meaning.

  As shown in FIGS. 3A and 3B, when the thickness dimension Wb below the groove 1a of the first core 1 is larger than the thickness dimension Ws on both the left and right sides of the groove 1a. The minimum magnetic path cross-sectional area of the first core 1 is obtained by Ws × L2. Since the minimum magnetic path cross-sectional area of the second core 2 is Wu × L2 when the thickness dimension is Wu, the minimum magnetic path cross-sectional ratio in this case is Wu / Ws × 100 (%).

  As shown in FIG. 3C, when the thickness dimension Wb below the groove 1a of the first core 1 becomes smaller than the thickness dimension Ws on the side of the groove 1a, the first core 1 The minimum magnetic path cross-sectional area is Wb × L2. Since the minimum magnetic path cross-sectional area of the second core 2 is Wu × L2, the minimum magnetic path cross-sectional ratio in this case is Wu / Wb × 100 (%).

  In the rightmost column of Table 1, the product of the minimum magnetic path cross-sectional ratio and the permeability of the second core 2 is further shown. In the example, the magnetic permeability of the second core is three types, “30”, “40”, and “60”.

<Example 1>
In Example 1, the magnetic permeability of the first core 1 was fixed to 2500. Further, the gap width δ1 of the joint gap G1 between the first core 1 and the second core 2 was set to 10 μm. By reducing the gap width δ1 to 10 μm, even if the gap width δ2 of the core-coil gap G2 is increased to 100 μm by design, a sufficiently large cross-sectional area of the main body 3a of the conductor 3 can be secured, and the cross-section is lowered. It is possible to prevent an increase in resistance value due to. Therefore, the ratio of (gap width δ2 / gap width δ1) can be set to 10.

  In FIG. 6, the horizontal axis indicates the direct current Idc (A), and the vertical axis indicates the change in the inductance L. In the inside of the graph, the change of what was extracted from the configuration of the plurality of types of magnetic cores C described in Table 1 is shown. In the extracted magnetic core C, “permeability μ of the second core × minimum magnetic path section ratio = product” is “μ60 × 180% = 108”, “μ40 × 180% = 72”, “μ30 × 180% = 54 ”,“ μ60 × 80% = 48 ”,“ μ40 × 80% = 32 ”,“ μ30 × 80% = 24 ”, and“ μ40 × 20% = 8 ”.

  7, the horizontal axis indicates the direct current Idc (A), and the vertical axis indicates (inductance change amount (decrease amount)) ΔL / (initial inductance L0) for the same magnetic core C as illustrated in FIG. ).

  As shown in FIG. 6, the initial inductance L0 increases as the value of “permeability μ of the second core × minimum magnetic path cross section ratio = product” increases, but as shown in FIG. The reduction rate of the inductance L is remarkably increased, and the direct current superimposition characteristic is deteriorated. Further, the smaller the value of “permeability μ of the second core × minimum magnetic path cross section ratio = product”, the lower the initial inductance L0. However, the decrease in the inductance L due to the increase in current is suppressed, and the DC superposition characteristics are reduced. Become good.

  As shown in FIGS. 6 and 7, the magnetic core C having various permeability in various shapes by using the value of “permeability μ of the second core × minimum magnetic path section ratio = product” as a parameter. On the other hand, the direct current superposition characteristics of the inductance change can be evaluated on the same scale.

  In FIG. 8, the horizontal axis indicates “permeability μ of the second core × minimum magnetic path section ratio = product”, and the vertical axis indicates the initial inductance AL0 per unit number of turns of the conductor. In FIG. 8, AL0 obtained for 7 × 3 = 21 types of magnetic cores C shown in Table 1 is plotted. With this AL0, the characteristics of the magnetic core can be known regardless of the number of turns of the conductor.

From FIG. 8, it can be evaluated that the initial inductance AL0 per unit number of turns increases as “permeability μ of the second core × minimum magnetic path section ratio = product” increases. In order to set the initial inductance AL0 per unit number of turns to 100 μH / T ² or more, it is necessary to set “the magnetic permeability μ of the second core × the minimum magnetic path section ratio = product” to 18 or more. T is the number of turns of the conductor (coil).

  In FIG. 9, the horizontal axis indicates “permeability μ of the second core × minimum magnetic path cross section ratio = product”, and the vertical axis indicates the magnetomotive force (N · Isat) multiplied by the number of windings of the conductor of the inductance element. Is shown. N is a numerical value indicating the number of turns T of the conductor, and is “1” in the embodiment. In FIG. 7, “Isat” means a DC current Idc that flows through each inductance element when the rate of decrease in inductance ΔL / L0 due to DC superposition is 30%.

  From FIG. 9, it can be evaluated that the magnetomotive force (N · Isat) multiplied by the number of windings of the conductor decreases as “permeability μ of the second core × minimum magnetic path section ratio = product” increases. In order to set N · Isat to 30 A / T or more, it is necessary to set “permeability μ of second core × minimum magnetic path section ratio = product” to 80 or less.

  In FIG. 10, the horizontal axis indicates “permeability μ of the second core × minimum magnetic path section ratio = product”, and the vertical axis indicates the product of the AL0 and the magnetomotive force (N · Isat) as the magnetic core C. The value divided by the volume of is shown as the inductor performance index.

Also from FIG. 10, when “the magnetic permeability μ of the second core × the minimum magnetic path section ratio = product” is set to 18 or more and 80 or less, the AL0 and the magnetomotive force (N · Isat) per unit volume of the magnetic core C are set. ), That is, the inductor performance index can be set to 15 (μH · A / T · mm ³ ) or more.

  As described above, regardless of the shape of the magnetic core C and the ratio of the sizes of the first core 1 and the second core 2, the permeability of the second core is further improved. Regardless of the value of the magnetic permeability, the value of “permeability μ of the second core × minimum magnetic path cross section ratio = product” is obtained, and the value of this product is used as a parameter, so that the characteristics of the inductance element can be determined. It becomes possible to evaluate. Further, by calculating the inductor performance index shown in FIG. 10, it is possible to standardize and evaluate the individual performance of the inductance element by comparing with “the permeability μ of the second core × the minimum magnetic path section ratio = product”. It becomes like this.

  As a result of this evaluation, the characteristic of the inductance element can be improved by setting “the permeability μ of the second core × the minimum magnetic path section ratio = product” to 18 or more and 80 or less.

<Example 2>
In Example 2, the magnetic permeability of the first core 1 was fixed to 1000. Further, the gap width δ1 of the junction gap G1 between the first core 1 and the second core 2 was set to 10 μm. Therefore, the gap width δ2 of the core-coil gap G2 can be set to 100 μm, and the gap width ratio δ2 / δ1 can be set to 10.

  11 is the same evaluation diagram as FIG. 6, FIG. 12 is the same evaluation diagram as FIG. 7, FIG. 13 is the same evaluation diagram as FIG. 8, FIG. 14 is the same evaluation diagram as FIG. It is the same evaluation diagram.

  In the second embodiment, by setting the magnetic permeability of the first core 1 to 1000, the total magnetic resistance of the magnetic core C is increased by 2% compared to the first embodiment, and the initial inductance L0 is increased in all the magnetic cores C. Is reduced by 2%, and the DC superposition characteristics are improved by 1%.

  Also in this case, as shown in FIGS. 13 to 15, the characteristic of the inductance element is improved by setting “the permeability μ of the second core × the minimum magnetic path cross section ratio = product” to 18 or more and 80 or less. be able to.

<Example 3>
In Example 3, the magnetic permeability of the first core 1 was fixed to 5000. Further, the gap width δ1 of the junction gap G1 between the first core 1 and the second core 2 was set to 10 μm. Therefore, the gap width δ2 of the core-coil gap G2 can be set to 100 μm, and the gap width ratio δ2 / δ1 can be set to 10.

  16 is the same evaluation diagram as FIG. 6, FIG. 17 is the same evaluation diagram as FIG. 7, FIG. 18 is the same evaluation diagram as FIG. 8, FIG. 19 is the same evaluation diagram as FIG. It is the same evaluation diagram.

  In the third embodiment, by setting the magnetic permeability of the first core 1 to 5000, the total magnetic resistance of the magnetic core C is reduced by 1% compared to the first embodiment, and the initial inductance L0 is reduced in all the magnetic cores C. Increase by 1%. Therefore, the direct current superimposition characteristic is deteriorated by 1%.

  Also in this case, as shown in FIGS. 18 to 20, the characteristic of the inductance element is improved by setting “the permeability μ of the second core × the minimum magnetic path section ratio = product” to 18 or more and 80 or less. be able to.

  When Example 1, Example 2, and Example 3 are compared, the evaluation of the magnetic core C based on “the magnetic permeability μ of the second core × the minimum magnetic path section ratio = product” is substantially the same. This is because when the magnetic permeability of the first core 1 is 1000 or more and 5000 or less, and the magnetic permeability of the second core 2 is 100 or less, preferably 50 or less, the first core 1 and the second core 2 This is because the change in the magnetic permeability of the entire magnetic core C is mainly determined by the magnetic permeability of the second core 2.

  Therefore, even if the magnetic permeability of the first core 1 changes greatly, the magnetic core C can be evaluated on the basis of “the magnetic permeability μ of the second core × the minimum magnetic path section ratio = product”.

<Example 4>
In Example 4, the magnetic permeability of the first core 1 was fixed to 2500. Further, the gap width δ1 of the junction gap G1 between the first core 1 and the second core 2 was set to 30 μm. In this case, if the gap width δ2 of the core-coil gap G2 is 30 μm, the gap width ratio δ2 / δ1 can be set to 1.

  21 is the same evaluation diagram as FIG. 6, FIG. 22 is the same evaluation diagram as FIG. 7, FIG. 23 is the same evaluation diagram as FIG. 8, FIG. 24 is the same evaluation diagram as FIG. It is the same evaluation diagram.

  In Example 4, by increasing the gap width δ2 of the junction gap G1 to 30 μm, the total magnetic resistance of the magnetic core C is increased by 20% compared to Example 1, and the initial inductance L0 is 20 in all the magnetic cores C. %Decrease. Therefore, the direct current superimposition characteristic can be improved by 20%.

  As shown in FIGS. 23 to 25, the magnetic resistance in Example 4 is larger than that in Example 1, but “the permeability μ of the second core × the minimum magnetic path section ratio = product” is 18 or more. By setting it to 80 or less, the characteristics of the inductance element can be improved. The initial inductance AL0 per unit number of turns shown in FIG. 23, the magnetomotive force shown in FIG. 24, and the inductor performance index shown in FIG. , 2, 3.

DESCRIPTION OF SYMBOLS 1 1st core 1a Groove 2 2nd core 3 Conductor 10,20 Inductance element G1, G3, G4 Junction gap G2, G5, G6 Core-coil gap | gap (delta) 1, (delta) 2 Gap width

Claims (11)

In the inductance element in which the conductor is housed inside the magnetic core,
The magnetic core includes a first core made of a magnetic material, and a second core made of a magnetic material having a permeability lower than that of the first core and a DC superposition characteristic superior to that of the first core. It is formed by joining the core,
The product of the minimum magnetic path cross-sectional ratio obtained by (the minimum magnetic path cross-sectional area of the second core / the minimum magnetic path cross-sectional area of the first core) and the magnetic permeability of the second core is 18 or more and 80 or less. An inductance element characterized by being set to   2. The inductor according to claim 1, wherein an inductor performance index that is a value obtained by calculating a product of an initial inductance per unit winding number and a magnetomotive force when the DC superimposition characteristic is a predetermined ratio per unit volume is 15 or more. element.   The inductance element according to claim 1 or 2, wherein the magnetic permeability of the first core is 1000 or more, and the magnetic permeability of the second core is 100 or less.   The inductance element according to claim 1, wherein the second core is a dust core. Inside the magnetic core, a core-coil gap between the magnetic core and the conductor is formed along the conductor at a position close to a bonding gap between the first core and the second core. Has been
The inductance element according to claim 1, wherein a ratio of (core-coil gap / junction gap) is 1 or more.   The inductance element according to claim 5, wherein a ratio of (core-coil gap / junction gap) is 20 or less.   The inductance element according to claim 5, wherein the junction gap is 50 μm or less.   The inductance element according to claim 5, wherein the conductor has a rectangular cross-sectional area, and the core-coil gap is formed along at least one side surface of the conductor. A first core made of a magnetic material is joined to a second core made of a magnetic material having a lower magnetic permeability than the first core and a DC superimposition characteristic superior to that of the first core. In the evaluation method of the inductance element in which the conductor is housed inside the magnetic core formed by
(1) Obtain the product of the minimum magnetic path cross-sectional ratio obtained by (the minimum magnetic path cross-sectional area of the second core / the minimum magnetic path cross-sectional area of the first core) and the permeability of the second core;
A method for evaluating an inductance element, wherein the direct current superimposition characteristic of inductance is evaluated in relation to the product of (1). (2) The initial inductance per unit number of turns of the conductor is evaluated in relation to the product obtained in (1),
(3) The inductance element evaluation method according to claim 9, wherein the magnetomotive force when the direct current superimposition characteristic becomes a predetermined ratio is evaluated in relation to the product obtained in (1). (4) The inductor performance index is a value obtained by calculating the product of the initial inductance per unit winding number of the conductor and the magnetomotive force when the DC superimposition characteristic is a predetermined ratio per unit volume, according to (1) The method for evaluating an inductance element according to claim 9, wherein the evaluation is performed in relation to the obtained product.

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