JP2020047721A - Inductor installation structure - Google Patents

Abstract

To provide an inductor installation structure that can enhance the heat dissipation of an inductor.SOLUTION: A core 2 of an inductor 1 includes an inner core 21 around which a winding 3 is wound, an outer core 22 which is on the outer diameter side of the inner core 21 and faces the outer periphery of the winding 3 via a gap, and an opening 2a. The outer core 22 and the opening 2a are provided along the circumferential direction of a winding axis O. The inductor 1 is arranged such that the direction of the winding axis O is parallel to an inductor installation surface 7a with the opening 2a facing the inductor installation surface 7a. A heat dissipating member 6 made of a non-magnetic material having a thermal conductivity of 0.5 W/(m K) or more is arranged between the inductor installation surface 7a and the outer peripheral surface of the winding 3 facing through the opening 2a.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an inductor installation structure.

  2. Description of the Related Art In recent years, power conversion circuits of transportation equipment (for example, hybrid cars, electric vehicles, fuel cell vehicles, etc.) and electronic equipment (for example, smartphones, personal computers, etc.) incorporating a storage battery have been reduced in size and weight while maintaining high output, that is, high power conversion circuits. Power density is required.

  Various inductors are used in the above-described power conversion circuit as a transformer application, an inverter application, or a converter application. When a UU type core is used as the core of the inductor, the magnetic flux path is limited to one direction, so that it is difficult to reduce the size of the inductor. On the other hand, an inner core that winds a winding, such as a P-type core, an EP-type core, or a PQ-type core, and an outer core that is on the outer diameter side of the inner core and faces the outer periphery of the winding. When a core having a core is used, a large number of magnetic flux paths are formed in the core, so that the ratio of the core in the space volume can be increased as compared with the UU core. Therefore, it is possible to reduce the size and weight of the inductor and to increase the power density of the power conversion circuit.

  By the way, in order to suppress heat generation during operation, the inductor is usually installed in contact with a cooling plate. When installing the inductor on the cooling plate, for example, as described in Patent Document 1 below, the inductor is arranged on the cooling plate so that the winding axis direction is orthogonal to the surface of the cooling plate. General.

JP-A-2015-103538

  In a core such as a P-type, an EP-type, or a PQ-type, there is a flat connection core that connects an inner core and an outer core. When this type of inductor is arranged in a direction in which the winding axis direction is orthogonal to the cooling plate as described in Patent Document 1, the connecting core comes into contact with the cooling plate. In this case, since the heat radiation path of the winding passes through the core, the heat radiation of the winding follows the thermal conductivity of the core. Therefore, in order to enhance the heat radiation, it is necessary to review the material of the core, and it is difficult to improve the heat radiation.

  In particular, the heat generated at the upper part of the winding away from the cooling plate reaches the cooling plate via the lower part of the winding and the core, and the heat transfer distance becomes longer (higher thermal resistance). In addition, since heat propagates in the direction of lower thermal resistance, the windings are usually formed of copper wire with high thermal conductivity (low thermal resistance), and heat is transferred in the winding direction of the copper wire. Propagate. Therefore, the heat transfer distance is further increased, and the temperature rise in the upper part of the winding tends to be promoted.

  Therefore, an object of the present invention is to provide an installation structure that can enhance the heat dissipation of the inductor.

  In order to solve the above problems, the present invention is a structure for installing an inductor including a core and a winding on an inductor installation surface, wherein the core has an inner core wound with the winding, An outer core, which is on the outer diameter side of the inner core and faces the outer periphery of the winding via a gap, and an opening, wherein the outer core and the opening are provided along the circumferential direction of the winding axis. The inductor is arranged so that the opening is opposed to the inductor installation surface, the direction of the winding axis is parallel to the inductor installation surface, and the outer peripheral surface of the winding facing through the opening. And a heat dissipating member made of a non-magnetic material having a thermal conductivity of 0.5 W / (m · K) or more is disposed between the heat sink and the inductor mounting surface.

  As described above, the use of the core having the inner core around which the winding is wound and the outer core located on the outer diameter side of the inner core and facing the outer periphery of the winding with a gap therebetween allows the magnetic flux path to be increased. Many are formed. Therefore, the size of the inductor can be reduced by increasing the ratio of the core to the space volume.

  Assuming such a core structure, an outer core and an opening are provided along the circumferential direction of the winding axis, and the inductor is arranged such that the opening of the core is opposed to the inductor installation surface, and the direction of the winding axis is parallel to the inductor installation surface. If a heat dissipating member made of a non-magnetic material having high thermal conductivity is provided between the outer peripheral surface of the winding and the inductor mounting surface that face each other through the opening, heat generated by the winding can be obtained. Most of them propagate to the inductor installation surface via a heat radiating member having high thermal conductivity without passing through the core. Therefore, the heat radiation effect can be enhanced and the temperature rise of the winding can be suppressed. In addition, since the distance between each part of the winding in the direction of the winding axis and the surface on which the inductor is installed is made uniform, the heat radiation at each part can be made uniform. Therefore, the temperature rise width of each part can be made uniform, and the variation in magnetic characteristics can be suppressed. By improving the heat dissipation, it is not necessary to provide a separate component for heat dissipation (such as a heat sink), so that the overall size of the inductor can be reduced.

  When the heat dissipating member is arranged over the entire circumference in the circumferential direction of the winding shaft, a peripheral circuit of the eddy current is formed, so that the temperature of the heat dissipating member increases due to electromagnetic induction. In addition, since the magnetic flux changes to an eddy current, the circulating magnetic flux decreases, and the inductance value of the inductor greatly decreases. In order to avoid this, it is preferable to dispose the heat radiating member only in a partial region in the circumferential direction of the winding axis.

  It is preferable that, of the heat radiating member, a surface facing the outer peripheral surface of the winding is formed in a shape along the outer peripheral surface of the winding. Thereby, the heat generated in each part in the circumferential direction of the winding is evenly transmitted to the heat radiating member, so that the heat radiation in the circumferential direction of the winding can be made uniform. In addition, the surface of the heat dissipating member through which heat propagates from each part in the circumferential direction of the winding can be enlarged, and heat dissipation can be improved.

  By interposing a sealing material made of an insulating material between the heat radiating member and the outer periphery of the winding, insulation between the winding and the heat radiating member can be reliably performed.

  By interposing a sealing material made of an insulating material between the outer core and the outer periphery of the winding, insulation between the winding and the outer core can be reliably performed.

  By arranging the inductor directly on the inductor mounting surface without using a case, a case irrelevant to the magnetic characteristics can be omitted, so that the size of the inductor can be reduced. In addition, a rise in the temperature of the case can be prevented.

  ADVANTAGE OF THE INVENTION According to the installation structure of the inductor of this invention, the heat dissipation of an inductor can be improved.

It is a perspective view which shows the installation structure of the inductor 1 concerning this embodiment. It is sectional drawing in the plane orthogonal to winding axis O containing XX in FIG. It is a perspective view which shows the shape of only the core 2. It is sectional drawing which shows the reference example of an inductor installation structure. It is a perspective view in the confirmation test which shows the comparative example of the inductor installation structure. It is sectional drawing which shows the reference example in a confirmation test. 7 is a table showing the results of confirmation test 1. 9 is a table showing the results of confirmation test 2.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an installation structure of the inductor 1, and FIG. 2 is a cross-sectional view including a line XX in FIG.
As shown in FIGS. 1 and 2, the inductor 1 according to the present embodiment has a core 2, a winding 3, a sealing member 5, and a heat radiation member 6.

  FIG. 3 is a perspective view showing the shape of only the core 2 (showing a state in which the winding 3, a bobbin 4, a sealing material 5, and a heat radiating member 6 described later have been removed from the inductor 1). As shown in FIG. 3, the core 2 of the present embodiment has a shape corresponding to the PQ type.

  As shown in FIG. 3, the core 2 includes an axial inner core 21, an outer core 22 disposed on the outer diameter side of the inner core 21, and a connection core 23 connecting the inner core 21 and the outer core 22. Have. The outer core 22 of the present embodiment has a rectangular flat plate shape, and is arranged in parallel with the winding axis O at a position 180 ° opposite to the inner core 21. The distance between the inner surface of each outer core 22 and the winding axis O is equal. One connecting core 23 is arranged between the two outer cores 22 at one end in the winding axis O direction in a manner orthogonal to the two outer cores 22, and between the other end of the two outer cores 22 in the winding axis O direction. The other connecting core 23 is arranged orthogonal to the outer cores 22. Each of the two connection cores 23 has a rectangular flat plate shape.

  In the core 2, a region not covered by the outer core 22 in the circumferential direction around the winding axis O is an opening 2 a without a core. That is, the core 2 has two outer cores 22 and two openings 2a alternately along the circumferential direction of the winding axis O. Therefore, the core 2 (except for the inner core 21) of the present embodiment has a rectangular cylindrical shape with both ends opened. As shown in FIG. 1, the width W of the opening 2a is equal to or larger than the total length of the winding 3 in the direction of the winding axis O, and the outer peripheral surface of the winding 3 is opened over the entire length in the direction of the winding axis O. It is exposed in the portion 2a.

  Both end surfaces of the inner core 2 are brought into contact with the connection core 23. The core 2 has no air gap.

  The core 2 is manufactured, for example, by compression molding soft magnetic powder and then performing an annealing process. As the soft magnetic powder, a soft magnetic powder with an insulating coating obtained by coating an insulating coating made of a resin or the like on a soft magnetic metal powder of a pure iron type, an amorphous type, a soft magnetic alloy type, a nanocrystalline type, or the like can be used. The initial magnetic permeability (meaning the relative magnetic permeability at a magnetic field of 0 A / m) of the core using the soft magnetic powder with the insulating coating is preferably 30 or more and 200 or less.

  As the material of the core 2, in addition to using only the above-described soft magnetic powder, a composite material having a soft magnetic powder and a resin powder can be used as needed. The composite material can be formed by injection molding, which makes it easier to form the outer core 22 and the connecting core 23 integrally. In order to prevent a local temperature rise of the core 2, it is preferable that the thermal conductivity of the core 2 be 1.2 W / (m · K) or more. The inner core 21, the outer core 22, and the connection core 23 are preferably formed of the same material, but may be formed of different materials as needed.

  As shown in FIG. 2, the winding 3 is wound around the outer periphery of the inner core 21. At this time, the outer peripheral surface of the winding 3 is on the inner diameter side of the outer core 22, and the outer peripheral surface of the winding 3 is opposed to the inner surface of the outer core 22 via a gap. A bobbin 4 made of an insulating material such as resin is interposed between the inner circumference of the winding 3 and the outer circumference of the inner core 21. The diameter of the winding 3 is smaller than the distance between the inner surfaces of the outer cores 22 and smaller than the height H of the outer core 22 and the connecting core 23. Accordingly, there are gaps between the outer peripheral surface of the winding 3 and the inner surfaces of the outer cores 22 and between the outer peripheral surface of the winding 3 and an imaginary plane in contact with the lower ends of the outer cores 22.

  In the inductor 1 described above, for example, after each of the divided bodies of the core 2 divided by the line L in FIG. 3 are integrally formed, the previously wound winding 3 is inserted into the outer periphery of the half of the inner core 21, Thereafter, the two divided bodies can be manufactured by integrating them by means such as bonding. Of course, the manufacturing procedure of the inductor 1 is not limited to this. For example, after the entire core 2 including the inner core 21, the outer core 2, and the connection core 23 is integrally formed, the winding 3 is wound around the inner core 21. The inductor 1 may be manufactured. In any case, each part (the inner core 21, the outer core 22, and the connection core 23) of the core 2 is molded using a mold before the winding 3 is mounted.

  The heat dissipating member 6 is arranged on the inner periphery of the opening 2a on one side of the core 2 (the lower side in FIG. 2). The heat radiating member 6 is arranged over the entire length of the winding 3 in the direction of the winding axis O in a region including at least the shortest distance between the outer peripheral surface of the winding 3 and an inductor installation surface 7a described later. In the present embodiment, the heat radiating member 6 that fits into the inner periphery of the opening 2a of the core 2 and closes the opening 2a of the core 2 is exemplified. The heat radiating member 6 is fixed to the core 2 by, for example, press-fitting the inner surfaces of the outer core 22 and the connection core 23. The facing surface 6 a of the heat radiating member 6 that faces the outer peripheral surface of the winding 3 is formed in a shape along the outer peripheral surface of the winding 3. In the present embodiment, the outer peripheral surface of the winding 3 is formed in a cylindrical shape, and accordingly, the facing surface 6a of the heat radiation member 6 is formed in a concave cylindrical shape. There is an arc-shaped gap between the outer peripheral surface of the winding 3 and the facing surface 6 a of the heat radiating member 6.

  The heat radiating member 6 is not disposed over the entire circumference of the winding 3 in the circumferential direction. If the heat radiating member 6 is arranged over the entire circumference of the winding 3 (see FIG. 6), a eddy current peripheral circuit is formed in the heat radiating member 6, so that the temperature of the heat radiating member 6 rises due to electromagnetic induction. In order to avoid this, the heat radiating member 6 is arranged only in a partial area in the circumferential direction of the winding 3 (specifically, an area smaller than a half circumference of the winding 3).

  The heat radiation member 6 is formed of a non-magnetic material. Further, the heat radiating member 6 has a function of radiating heat generated in the winding 3 to the inductor installation surface 7a. Therefore, the heat radiation member 6 is formed of a material having a high thermal conductivity, specifically, a material having a thermal conductivity of 0.5 W / (m · K) or more. As described above, non-magnetic materials having a thermal conductivity of 0.5 W / (m · K) or more and usable as a material of the heat radiation member 6 include aluminum (including an aluminum alloy), stainless steel, and copper (copper). Alloys) and ceramics (including aluminum nitride, alumina and the like). Among them, it is preferable to use an aluminum alloy because of its excellent thermal conductivity, low cost and light weight.

  After assembling the assembly including the core 2, the windings 3, and the heat radiating member 6 in this manner, the sealing material 5 made of an insulating material such as resin is inserted through another opening 2a that is not closed by the heat radiating member 6. And supplied to the internal space of the core 2. At this time, since the opening 2a on the side where the heat dissipating member 6 is disposed is closed by the heat dissipating member 6, the molten sealing material 5 supplied to the inner space of the core 2 does not leak out of the core 2. Absent. Thereby, the mold structure for supplying the sealing material 5 can be simplified.

  By supplying the sealing material 5 inside the core 2 in this manner, as shown in FIG. 2, between the outer peripheral surface of the winding 3 and the inner surface of the outer core 22, and between the outer peripheral surface of the winding 3 and the heat radiating member. The gap between the first and second opposed surfaces 6 a is filled with the sealing material 5. By solidifying the filled sealing material 5, insulation between the winding 3 and the outer core 22, and between the winding 3 and the heat radiating member 6 are provided. In the opening 2a on the upper side of the drawing that does not face the inductor installation surface 7a, since insulation from other devices does not matter, a part of the winding 3 in the circumferential direction may be exposed from the sealing material 5. Absent. Of course, if it is necessary to ensure insulation, it is preferable to completely cover the winding 3 with the sealing material 5 also on the opening 2a side on the upper side of the drawing.

  The inductor 1 completed through the above steps is placed on the inductor installation surface 7a provided on the water-cooled cooling plate 7 and the like, and is fixed to the inductor installation surface 7a using fixing means such as a bracket or an adhesive. . When the inductor 1 is installed, as shown in FIG. 2, the opening 2a on the side closed by the heat radiating member 6 is opposed to the inductor installation surface 7a, and the core 2 is positioned such that the direction of the winding axis O and the inductor installation surface 7a. Arrange them in a parallel direction.

  In the present embodiment, as described above, the outer core 22 and the opening 2a are provided along the circumferential direction of the winding axis O. In addition, the inductor 1 is arranged such that the direction of the winding axis O is parallel to the inductor mounting surface 7a with the opening 2a facing the inductor mounting surface 7a, and between the inductor mounting surface 7a and the winding 3. The core 2 does not exist (especially in the region of the shortest distance between the winding 3 and the inductor installation surface 7a). Therefore, much of the heat generated in the winding 3 propagates to the inductor installation surface 7 a via the heat radiation member 6 having high thermal conductivity without passing through the core 2. Therefore, it is possible to enhance the heat radiation effect and suppress the temperature rise of the winding 3.

  In addition, since the distance from each part of the winding to the inductor installation surface 7a in the direction of the winding axis O is made uniform, the heat radiation in each part can be made uniform. Therefore, the temperature rise width of each part can be made uniform, and variations in the magnetic characteristics of the winding 3 can be suppressed. By improving the heat dissipation, it is not necessary to install another component for heat dissipation, so that the overall size of the inductor 1 can be reduced. Furthermore, since the material of the core 2 is not restricted from the viewpoint of heat dissipation, the degree of freedom in selecting the material of the core 2 can be increased.

  In addition, of the heat radiating member 6, the facing surface 6 a facing the outer peripheral surface of the winding 3 is formed in a shape (cylindrical surface shape) along the contour of the outer peripheral surface of the winding 3. The heat generated in each part in the circumferential direction can be evenly transmitted to the heat radiating member 6. Therefore, it is possible to make the heat dissipation uniform in the circumferential direction of the winding 3.

  The core 2 of the present embodiment includes an inner core 21 around which the winding 3 is wound, and an outer core 22 facing the outer periphery of the winding 3 on the outer diameter side of the inner core 21. As a result, the size of the inductor 1 can be reduced by increasing the number of magnetic flux paths. The present invention has found that in this type of core structure, it is a problem to secure heat radiation, and in order to solve the problem, the structure of the inductor 1 and the installation structure of the inductor 1 are devised to improve the heat dissipation. This achieves improved heat dissipation along with miniaturization.

  In order to make the above operation and effect more remarkable, an intervening hole is provided between the winding 3 and the heat radiating member 6 so that heat can be smoothly conducted from the winding 3 to the inductor installation surface 7a. It is preferable that the sealing material 5 is formed of a material having as high a thermal conductivity as possible.

FIG. 4 is a cross-sectional view showing a reference example of the installation structure of the inductor.
As shown in the figure, it is conceivable to house an inductor 1 ′ having a core 2 ′ and a winding 3 ′ in a case 8. However, this requires the use of Case 8, which is unrelated to the improvement of the magnetic characteristics, and is therefore not preferable for achieving high power density. Another problem is that the case 8 serves as a magnetic flux path and an eddy current is generated in the case 8 to generate heat. On the other hand, by arranging the inductor 1 directly on the inductor installation surface 7a without using the case 8 as in the present embodiment, the size of the inductor 1 can be reduced and the power density of the circuit can be increased. At the same time, a decrease in efficiency due to heat generation in case 8 can be avoided.

  When the installation structure of FIG. 4 is adopted, for example, after winding the winding 3 ′ around the inner core 21 ′, the soft magnetic powder is supplied into the case 8 and the case 8 is used as a mold. It is also possible to form portions 22 'and 23' corresponding to the outer core and the connecting core. However, with this installation structure, a gap cannot be secured between the winding 3 'and the outer core equivalent portion 22'. Therefore, a sealing material (reference numeral 5 in FIG. 2) cannot be disposed between the winding 3 'and the outer core equivalent portion 22', and insulation between the winding 3 'and the core 2' becomes insufficient. . By providing a gap between the outer core 22 and the winding 3 as in the present embodiment, it is possible to arrange the sealing material 5 in the gap, and to reliably insulate the winding 3 and the core 2. Can be.

  Hereinafter, in order to confirm the effects of the present invention, tests for measuring the amount of temperature rise in the winding 3 and the core 2 of the operating inductor 1 were performed on Examples 1, 2 and Comparative Example (confirmation test 1). . The test conditions and results will be described.

[Test target]
As Example 1, the inductor and the installation structure shown in FIGS. The heat radiation member 6 is formed of an aluminum alloy. In Example 2, the inductor 1 of Example 1 was used in which the heat radiation member was changed from an aluminum alloy to stainless steel (SUS403) having high corrosion resistance. As shown in FIG. 5, the comparative example has a structure in which the inductor 1 having the same structure as that of the first embodiment is arranged on the inductor mounting surface 7a such that the winding axis O is orthogonal to the inductor mounting surface 7a. I have. The heat conductivity of the aluminum alloy heat radiating member 6 used in Example 1 is 230 W / (m · K), and the heat conductivity of the stainless steel heat radiating member 6 is 26 W / (m · K). is there.

[Test method]
In the indoor environment, the temperature of the lower surface of the cooling plate 7 (the upper surface becomes the inductor installation surface 7a) is fixed at 50 ° C., and the heating value of the winding 3 during energization is 60 W and the heating value of the core 2 is 30 ° C. The temperature (average temperature) of the winding 3 and the core 2 when the temperature reached the temperature equilibrium was measured.

  The result of confirmation test 1 is shown in FIG. FIG. 7 is a table summarizing the results of measuring the temperature rise (average value) at 50 ° C. for each of the winding 3 and the core 2. As is clear from FIG. 7, it was confirmed that Examples 1 and 2 can reduce the temperature rise of each part of the inductor as compared with the comparative example. Therefore, it was confirmed that Examples 1 and 2 had higher heat radiation properties than Comparative Examples. Further, it was also confirmed that the temperature rise of Example 1 was smaller than that of Example 2. Therefore, it has been clarified that the use of the heat radiating member 6 having a higher thermal conductivity can suppress the temperature rise of the inductor 1.

  Next, as confirmation test 2, a test for measuring the magnetic characteristics of the inductor was performed on Example 1 in Confirmation Test 1 and Reference Examples 1 and 2 described below. Reference Example 1 has no heat radiating member 6 in Example 1, and Reference Example 2 has a heat radiating member 6 ′ made of an aluminum alloy formed over the entire circumference of the winding 3 as shown in FIG. It is. Each example was placed on the cooling plate 7 and the inductance value was measured by applying a sine wave alternating current in which a DC current was superimposed on each inductor 1 while cooling the inductors 1 as in the confirmation test 1.

  The result of confirmation test 2 is shown in FIG. From FIG. 8, in the first embodiment in which the heat radiating member 6 is disposed only in a part of the circumferential direction of the winding 3, the decrease in the inductance value is very small as compared with the reference example 1 without the heat radiating member. In the reference example 2 in which the coils were arranged over the entire circumference in the circumferential direction of the winding 3, the inductance value was extremely reduced. This is considered to be due to the fact that the magnetic flux changes to eddy current in the circulating heat dissipating member and the magnetic flux is lost. Therefore, it is preferable to dispose the heat radiating member 6 only in a part of the circumferential direction of the winding 3.

  The inductors described above can be used, for example, for power transformation applications (both step-down and step-up) in PFC (power factor correction) circuits, converter circuits, inverter circuits, etc., inverter applications, converter applications, and the like.

REFERENCE SIGNS LIST 1 inductor 2 core 2a opening 3 winding 4 bobbin 5 sealing material 6 heat radiating member 6a facing surface 7 cooling plate 7a inductor mounting surface 22 outer core 23 connecting core

Claims (6)

A structure for installing an inductor including a core and a winding on an inductor installation surface,
The core has an inner core around which the winding is wound, an outer core which is on the outer diameter side of the inner core, faces the outer periphery of the winding with a gap therebetween, and an opening, and has a winding shaft. The outer core and the opening are provided along a circumferential direction of,
The inductor, the opening portion is opposed to the inductor installation surface, the direction of the winding axis is arranged in a direction parallel to the inductor installation surface,
A heat dissipating member made of a non-magnetic material having a thermal conductivity of 0.5 W / (m · K) or more is arranged between the outer peripheral surface of the winding facing the opening and the inductor mounting surface. The installation structure of the inductor.   2. The inductor installation structure according to claim 1, wherein the heat radiating member is disposed only in a part of a circumferential direction of the winding axis. 3.   The installation structure of the inductor according to claim 1, wherein a surface of the heat radiation member facing the outer peripheral surface of the winding is formed along the outer peripheral surface of the winding.   The installation structure of the inductor according to any one of claims 1 to 3, wherein a sealing material made of an insulating material is interposed between the heat radiation member and the outer periphery of the winding.   The inductor installation structure according to any one of claims 1 to 4, wherein a sealing material made of an insulating material is interposed between the outer core and the outer periphery of the winding.   The inductor installation structure according to any one of claims 1 to 5, wherein the inductor is directly arranged on the inductor installation surface without using a case.

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