JP7175807B2 - inductor device - Google Patents

Description

The present invention relates to inductor devices.

In a PFC (Power Factor Correction) circuit, a converter circuit, an inverter circuit, etc., miniaturization of inductors and capacitors has been attempted. In order to miniaturize the inductor, it is required to reduce the size of the winding and core, but the reduction of these sizes tends to increase the amount of heat generated by the inductor. Therefore, in order to enable continuous use of a miniaturized inductor, it is important to improve the heat dissipation of the inductor.

In order to improve heat dissipation, Patent Document 1 below, for example, discloses a reactor in which an inductor is housed in a case having a bottom plate portion and side wall portions and the case is fixed to a cooling base. In addition, Patent Document 1 discloses that a heat dissipation layer is provided on the bottom plate, that the case is formed of a metal material such as aluminum in order to increase thermal conductivity, and that the sealing resin enclosed in the case has thermal conductivity. Also disclosed is the inclusion of fillers that are superior in

Japanese Patent No. 5597106

By the way, as described in Patent Document 1, when the entire side wall of the case is made of a metal material such as aluminum, eddy currents generated in the side wall of the winding flow around the side wall. As a result, it has become clear that the eddy current loss in the case increases, leading to a decrease in the magnetic properties (eg, inductance value) of the inductor. In order to compensate for the deterioration of the magnetic properties, it is necessary to take countermeasures such as increasing the number of windings of the inductor or enlarging the core size.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an inductor device in which the eddy current loss of the case is reduced while suppressing deterioration in heat dissipation.

In order to solve the above problems, the present invention provides an inductor having an annular polygonal core and a winding wound through an inner space of the polygonal core; and a case rising from the bottom and having sidewalls surrounding the inductor, wherein the inductor is arranged such that the winding axis is parallel to the bottom and the core is parallel to the bottom An insulating portion made of an insulating non-magnetic material and an insulating portion formed of an insulating non-magnetic material and having a heat resistance higher than that of the insulating portion are provided on the side wall portion of the case along the direction of circling around the inductor. A high heat conductive portion made of a non-magnetic material having a high conductivity is alternately arranged , and the insulating portion is arranged so as to face the corners of the polygonal core .

With such a configuration, since the eddy current generation region in the side wall is electrically separated by the insulating portion, no eddy current that circulates around the inductor is generated in the side wall. As a result, eddy current loss in the case can be reduced, and a decrease in the magnetic properties (eg, inductance value) of the inductor can be minimized. Moreover, since heat is radiated from the inductor by the high thermal conductivity portion, the heat radiation performance of the inductor device can be ensured.

It is preferable to arrange the high thermal conductivity portion in a region facing the outer peripheral surface of the winding. As a result, the high thermal conductivity portion faces the outer peripheral surface of the winding, which generates a large amount of heat, so that the heat generated in the winding can be quickly dissipated via the high thermal conductivity portion.

If the inductor is placed in the case with the winding axis perpendicular to the bottom, the core will be close to the bottom, and the heat dissipation path from the winding will be through the core. rate will be governed. Therefore, in order to improve the heat dissipation, it is necessary to review the material of the core. In addition, the heat generated in the upper part of the winding reaches the bottom via the lower part of the winding and the core, and the heat travels longer distance (thermal resistance is large), so the temperature rise in the upper part of the winding is remarkable. becomes. On the other hand, if the inductor is arranged so that the winding axis is parallel to the bottom, the heat generated by the winding is dissipated via the high thermal conductivity portion and the bottom without passing through the core. In addition, since the distance from each part of the winding to the bottom in the direction of the winding axis is made uniform, the heat dissipation at each part can be made uniform. Therefore, it is possible to uniform the width of temperature rise in each part and suppress variations in magnetic characteristics.

It is preferable that the bottom portion and the side wall portion are formed as separate members, and the bottom portion and the side wall portion are fixed by fitting a convex portion formed on one of them with a concave portion formed on the other. This simplifies the work of joining the bottom portion and the side wall portion, thereby reducing the cost.

It is preferable to provide rounded portions at the corners of the projections. With such a configuration, the pushing direction when pushing the convex portion into the concave portion is guided, so that the work of fitting the convex portion and the concave portion becomes easy.

It is preferable to provide relief in the recess. With such a configuration, the relief portion absorbs the plastic flow that accompanies the press-fitting of the convex portion, so that the convex portion and the concave portion are brought into surface contact to prevent the occurrence of a gap therebetween. Moreover, when using an adhesive, the relief part becomes an adhesive pool. Therefore, the bonding strength between the convex portion and the concave portion can be increased.

By attaching two windings having the same magnetic flux generating direction to the core, the inductor device can be used as a coupled inductor in which the two windings are magnetically coupled.

The inductor device described above is suitable for use in an interleaved circuit.

ADVANTAGE OF THE INVENTION According to this invention, the inductor apparatus which reduced the eddy current loss of a case can be provided, suppressing the fall of heat dissipation.

It is a perspective view which shows the assembly procedure of the inductor apparatus concerning 1st embodiment. 1 is a plan view of an inductor device; FIG. FIG. 3 is a cross-sectional view taken along line XX of FIG. 2; FIG. 11 is a perspective view showing another embodiment of a case for use with an inductor device; 4 is a circuit diagram showing an interleave circuit; FIG. It is a perspective view which shows the fixing structure of a bottom part and a coil|winding opposing part. (a) is a front view of the fixing structure of the bottom portion and the winding facing portion viewed from direction P in FIG. 6, and (b) is a bottom view of the bottom portion viewed from direction Q in FIG. (a) is a front view of the fixing structure of the bottom portion and the winding facing portion viewed from direction P in FIG. 6, and (b) is a bottom view of the bottom portion viewed from direction Q in FIG. (a) is a front view of the fixing structure of the bottom portion and the winding facing portion viewed from direction P in FIG. 6, and (b) is a bottom view of the bottom portion viewed from direction Q in FIG. (a) is a front view of the fixing structure of the bottom portion and the winding facing portion viewed from direction P in FIG. 6, and (b) is a bottom view of the bottom portion viewed from direction Q in FIG. 4 is a table showing measurement results of Confirmation Test 1. FIG. 4 is a table showing the measurement results of Confirmation Test 2;

A first embodiment of an inductor device according to the present invention will be described below with reference to FIGS. 1 to 3. FIG.

FIG. 1 is a perspective view showing the procedure for assembling the inductor device 1. FIG. 2 is a plan view of the inductor device 1 after assembly, and FIG. 3 is a cross-sectional view taken along line XX of FIG.
As shown in FIGS. 1 and 2, the inductor device 1 of this embodiment has an inductor 2 and a case 5 that accommodates the inductor 2 .

As shown in FIGS. 1 and 2, the inductor 2 has a core 21 and two windings 22 attached to the core 21 . The core 21 is made of, for example, a dust core. A powder magnetic core is made by coating soft magnetic metal powder made of pure iron, amorphous, soft magnetic alloy, nanocrystal, etc. Manufactured by annealing.

The core 21 forms a closed magnetic circuit and is formed in an annular shape such as a polygon . In this embodiment, the core 21 formed in a substantially rectangular shape is exemplified. As shown in FIG. 2, the core 21 of the present embodiment includes two U-shaped core members 21a and 21b each having two legs 211 and a connecting portion 212 bridging between one ends of the legs 211. It is manufactured by arranging the end surfaces of the legs 211 in abutting manner and integrating the two by bonding or the like. A tapered chamfered portion 213 is formed on the outer surface of the region of the core 21 that will be the corner portion. The windings 22 are wound around the outer circumferences of the connecting portions 212 of the cores 21 and 21b. The winding is performed so as to pass through the inner space 23 of the polygonal core 21 . In FIG. 2, the core 21 is formed in an endless annular shape, but the core 21 may be provided with an air gap.

The shape of the core members 21a and 21b is arbitrary, and an I-shaped core member can be used instead of the U-shaped one. Moreover, the form of the core 21 is arbitrary, and a rod-shaped core or a pot-shaped core can also be adopted. Furthermore, the number of windings 22 is also arbitrary, and one or three or more windings 22 can be attached to the core 21 .

As shown in FIG. 1 , the case 5 has a flat bottom portion 51 and side wall portions 52 rising from the bottom portion 51 . One end of the case 5 is closed with a bottom portion 51 and the other end is open. The inductor 2 is housed in the case 5 , and the inductor 2 is oriented such that its winding axis O is parallel to the inner bottom surface 511 of the bottom portion 51 . Also, the windings 22 and the bottom portion 51 are arranged in a direction in which the distance is constant. The case 5 holding the inductor 2 is brought into contact with the base member 3 (see FIG. 3) for heat dissipation made of a water-cooled plate or the like on the outer bottom surface of the bottom portion 51, and is attached to the base member 3 by appropriate means such as screwing or bonding. Fixed.

The side wall portion 52 of the case 5 is arranged so as to surround the entire circumference of the inductor 2 . The side wall portion 52 of this embodiment is formed in a polygonal tubular shape corresponding to the shape of the core 21 . The side wall portion 52 has a winding facing portion 52 a facing the outer peripheral surface of the winding 22 and a core facing portion 52 b facing the core 21 . The core facing portion 52 b has a portion 52 b 1 facing the leg portion 211 of the core 21 and a portion 52 b 2 facing the chamfered portion 213 of the core 21 . Between the winding facing portion 52a and the core facing portion 52b, a restricting surface 53 projecting to face the end surface of the winding 22 is formed. As shown in FIG. 2, the winding 22 is arranged between two regulation surfaces 53 facing each other with the winding facing portion 52a therebetween.

As shown in FIG. 3, the case 5 is filled with an insulating sealing resin 4 (illustration of the sealing resin 4 is omitted in FIGS. 1 and 2). A gap is formed between the core 21 and the winding 22 and each inner surface of the case 5 , and the gap is filled with the sealing resin 4 . Specifically, both the core 21 and the windings 22 are in a state of non-contact with both the bottom portion 51 and the side wall portion 52 of the case 5, and the gap between them is filled with the sealing resin 4. As shown in FIG. The sealing resin 4 provides insulation between the core 21 and the case 5 and insulation between the windings 22 and the case 5 . A bobbin made of an insulating material such as resin may be interposed between the outer peripheral surface of the core 21 and the inner peripheral surface of the winding 22 in order to ensure insulation between the core 21 and the winding 22 .

The bottom portion 51 of the case 5 is made of a non-magnetic material such as aluminum (including aluminum alloy) having a higher thermal conductivity than at least the insulating portion A, which will be described later, in order to ensure heat dissipation. Although illustration is omitted, the opening of the side wall portion 52 (the opening on the side opposite to the sealing side of the bottom portion 51) can be covered with a top plate. The top plate can be made of a material that has similar properties as the bottom portion 51 .

As shown in FIGS. 1 and 2, the side wall portion 52 of the case 5 has an insulating portion A (indicated by a dotted pattern) formed of an insulating non-magnetic material along the direction of winding around the inductor 2 . ) and a high thermal conductivity portion B (indicated by no pattern) made of a non-magnetic material having a thermal conductivity higher than that of the insulating portion A are alternately provided. For example, the insulating portion A can be made of a resin material, and the high thermal conductivity portion B can be made of aluminum (including aluminum alloy). The insulating portion A can also be made of ceramic or glass. Non-magnetic metal materials can be widely used as the material of the high thermal conductivity portion B. In addition to aluminum, for example, magnesium (including magnesium alloys), copper (including copper alloys), and silver (including silver alloys). Alternatively, a non-magnetic steel material (for example, austenitic stainless steel such as SUS304) can be used. The high thermal conductivity portion B formed of the materials described above usually also has high electrical conductivity. The bottom portion 51 and the top plate, which have already been described, can also be made of any of the materials listed as the material of the high thermal conductivity portion B.

In this embodiment, of the core facing portion 52b, a region 52b2 facing the chamfered portion 213 of the core 21 is formed of the insulating portion A, and a region 52b1 facing the leg shaft 211 is formed of the high thermal conductivity portion B. Further, the winding-facing portion 52a is formed of the high thermal conductivity portion B. As shown in FIG. The insulating portion A is formed over the entire length of the side wall portion 52 in the height direction.

As described above, the case 5 of the present embodiment has the side wall portion 52 along the direction of winding around the inductor 2 and the insulating portion A (made of resin, for example) made of an insulating and non-magnetic material. It is characterized by a hybrid structure in which high thermal conductivity portions B made of a material having magnetism and high thermal conductivity (made of metal, for example) are alternately arranged.

With such a configuration, an eddy current generation region in the side wall portion 52 is electrically separated by the insulating portion A, so that an eddy current that circulates around the inductor 2 is not generated in the side wall portion 52 . Therefore, the eddy current loss in the case 5 can be reduced, and the deterioration of the magnetic properties (for example, the inductance value) of the inductor 2 can be minimized.

In addition, since the winding facing portion 52a formed of the high thermal conductivity portion B faces the outer peripheral surface of the winding 3 which generates a large amount of heat, the heat generated in the winding 3 is dissipated through the winding facing portion 52a and the bottom portion. The heat is quickly radiated to the base member 3 via 51 . Therefore, the heat dissipation of the inductor device 1 can be improved, and the problem of heat dissipation when the inductor 2 is miniaturized can be avoided. In order to obtain the above effects, the thermal conductivity of the high thermal conductivity portion B is preferably 10 W/(m·K) or more.

In general, in the polygonal core 21, the leakage magnetic flux tends to increase at the corners (regions around the chamfered portion 213). Therefore, it is possible to suppress the generation of eddy currents due to leakage flux at the corners, and from this point also, it is possible to reduce the eddy current loss. On the other hand, since the amount of heat generated at the corners of the core 21 is not so large, even if the insulating portions A with low thermal conductivity are opposed to the corners, the deterioration of heat dissipation can be minimized.

As already mentioned, the core 21 can be provided with an air gap. is preferred.

When the inductor 2 is arranged in the case 5 with the winding axis O orthogonal to the bottom portion 51, the core 21 is close to the bottom portion 51, and the heat radiation path from the winding 22 is through the core 21. Heat dissipation of the wire 22 is governed by the thermal conductivity of the core 21 . Therefore, in order to improve the heat dissipation, it is necessary to reconsider the material of the core 32, which lowers the degree of freedom in selecting the core material. In addition, the heat generated in the upper portion of the winding 22 reaches the bottom portion 51 via the lower portion of the winding and the core 21, and the heat travels longer (the thermal resistance is greater). The temperature rise becomes noticeable. On the other hand, if the inductor 2 is arranged so that the winding axis O is parallel to the bottom portion 51, the heat generated in the winding 22 does not pass through the core 21, but passes through the high thermal conductivity portion B and the bottom portion 51 to the base. Heat is radiated to the member 3 . In addition, since the distance from each part of the winding 22 to the bottom part 51 in the direction of the winding axis O is made uniform, heat dissipation can be made uniform at each part of the winding. Therefore, it is possible to uniform the width of temperature rise in each part and suppress variations in magnetic characteristics.

A second embodiment of the inductor device 1 is shown in FIG. In this second embodiment, the core facing portion 52b is entirely formed of the insulating portion A. As shown in FIG. That is, of the core facing portion 52b, a region 52b1 facing the leg portions 211 (see FIGS. 1 and 2) of the core members 21a and 21b and a region 52b2 facing the chamfered portion 213 are formed integrally with the insulating portion A. . The configuration of the second embodiment can also obtain the same effect as the first embodiment.

The inductor 2 described above can be used as a coupled inductor by connecting the two windings 22 so that the directions of magnetic flux generation with respect to direct current are the same. This coupled inductor 2 is suitable for use in a multi-phase (FIG. 5 illustrates the two-phase case) interleaved circuit shown in FIG. The interleave circuit is a circuit in which a power source is divided into a plurality of systems, a phase difference is given to currents of respective phases by switching elements Q1 and Q2, and ripples and the like are canceled out. Since the coupled inductor 2 has a large leakage magnetic flux, the reduction of eddy current loss is an important issue, but by using the inductor device 1 of this embodiment, the eddy current loss can be reduced while ensuring high heat dissipation. becomes possible.

Since the insulating portion A forming the side wall portion 52 is made of a material different from that of the bottom portion 51, both are formed of separate members. The fixing of the insulating portion A to the bottom portion 51 can be performed by adhesion, ultrasonic welding, or the like. Alternatively, the bottom portion 51 and the insulating portion A can be integrated by insert molding the insulating portion A into the bottom portion 51 .

The bottom portion 51 and the high thermal conductivity portion B can be made of the same material (eg, aluminum alloy). In this case, it is possible to form the bottom portion 51 and the high thermal conductivity portion B integrally by, for example, casting or press working. On the other hand, when the bottom portion 51 and the high thermal conductivity portion B are made of different materials, or when it is preferable to use the same material for both as separate members for some reason, the bottom portion 51 and the high thermal conductivity portion B It is necessary to consider a fixed structure. For example, it is conceivable to use screws as the fixing structure, but in this case, processing of screw holes is required, and the number of assembly steps increases, so there is a problem that the cost of the inductor device 1 increases.

In order to solve the above problems, when fixing the bottom portion 51 and the high thermal conductivity portion B, which are separate members, as shown in FIG. It is desirable to fix by fitting 61 with a recess 62 formed on the other side. In this case, the high thermal conductivity portion B can be fixed to the bottom portion 51 by press-fitting the convex portion 61 into the concave portion 62, or by press-fitting or fitting them together with an adhesive interposed. With this fixing structure, post-processing for forming screw holes is not required, and the number of assembly man-hours can be reduced, so that the cost of the inductor device 1 can be reduced.

Hereinafter, an embodiment of this fixing structure will be described with reference to FIGS. . 7A, 7B, 7A, and 10A, 10A and 10A, 10A and 10A, 10B, and 10A, 10B, 10A, 10B, 10C, and 10D are views of the state immediately before the convex portion 61 and the concave portion 62 are fitted together, as seen from direction P in FIG. 6B is a view of the bottom portion 51 before fitting as seen from the direction Q in FIG.

As shown in FIGS. 7(a) and 7(b), a convex portion 61 and a concave portion 62 are formed at the end of one member (for example, the bottom portion 51). 62 and projection 61 are formed at the end of the other member (for example, winding facing portion 52a). The protruding direction of the convex portion 61 formed on one member and the depth direction of the concave portion 62 formed on the other member and fitted with the convex portion 61 are orthogonal to each other. As already described, the winding facing portion 52a is attached to the bottom portion 51 by press-fitting the protrusion 61 of one member into the recess 62 of the other member, or by press-fitting or fitting them together with an adhesive interposed therebetween. can be fixed

In FIGS. 8A and 8B, arc-shaped rounded portions 63 are provided at the corners of the convex portion 61 . By providing the convex portion 61 with the rounded portion 63 in this manner, the direction of pushing the convex portion 61 into the concave portion 62 is guided, so that the convex portion 61 and the concave portion 62 can be easily fitted.

In FIGS. 9A and 9B, an arc-shaped relief portion 64 is provided at the corner of the recess 62 . By providing the relief portion 64 in the concave portion 62 in this way, the plastic flow caused by the press-fitting of the convex portion 61 is absorbed by the relief portion 64, so that the convex portion 61 and the concave portion 62 are brought into surface contact to form a gap between them. occurrence can be prevented. Moreover, when using an adhesive, the escape portion 64 serves as an adhesive reservoir. Therefore, the bonding strength between the convex portion 61 and the concave portion 62 can be increased.

In FIGS. 10A and 10B, the convex portion 61 is provided with the rounded portion 63 and the concave portion 62 is provided with the escape portion 64 . Accordingly, both the effect of providing the rounded portion 63 and the effect of providing the relief portion 64 can be enjoyed.

The fixing structure described above can be applied between each portion of the side wall portion 52 formed of the high thermal conductivity portion B and the bottom portion 51 . Therefore, in the first embodiment shown in FIGS. 1 to 3, the region 52b1 of the side wall portion 52 facing the leg shaft 211 of the core facing portion 52b can be fixed to the bottom portion 51 with a similar fixing structure. Alternatively, the insulating portion A can be fixed to the bottom portion 51 by a similar fixing structure.

[Confirmation test 1]
In order to confirm the effect of the inductor device 1 described in the above description of the embodiment, the inductance value (L value) and the heat dissipation (ΔT) of Examples 1 and 2 using different cases 5 and Comparative Examples 1 and 2 were measured. A test was conducted to measure the Example 1 uses the case 5 of the first embodiment shown in FIGS. 1 to 3, and Example 2 uses the case 5 of the second embodiment shown in FIG. Comparative Example 1 uses a case in which the side wall portion 52 is entirely made of resin, and Comparative Example 2 uses a case in which the side wall portion 52 is entirely made of metal (aluminum alloy). Except for the side wall portion 52, the structure of the case 5 and the structure of the inductor 2 are common to the first and second comparative examples and the first and second examples.

This confirmation test is performed by passing a sinusoidal alternating current in which a direct current is superimposed on each winding 22 of the inductor 2 . The inductor 2 is generally connected in series, and the average value of the inductance is the L value. The superimposed current is 30 A and the frequency is 50 kHz. Also, the heat dissipation (ΔT) is evaluated by the maximum temperature (average value) of the inductor 2 . The iron loss is 44 W, the copper loss is 92.1 W, the aluminum loss is 8.5 W, and the ambient temperature is 105°C.

FIG. 11 shows the measured values of L and ΔT, and the rate of change of each measured value with Comparative Example 1 as the reference. As is clear from FIG. 11, in Comparative Example 2, compared with Comparative Example 1, the heat dissipation property is good, but the attenuation of the inductance value is remarkable. This is thought to be due to an increase in eddy current loss due to eddy currents circulating around the side wall. On the other hand, in Examples 1 and 2, although inferior to Comparative Example 2, it is possible to obtain practically sufficiently high heat dissipation compared to Comparative Example 1, and the attenuation of the L value is at a level that does not cause any particular problem. understood to be suppressed.

[Confirmation test 2]
Next, the inductors of Comparative Examples 1 and 2 and Examples 1 and 2 were used as coupled inductors in the two-phase interleaved circuit shown in FIG. 5, and the ripple width ΔI during boosting operation was measured. Here, the ripple width ΔI can be expressed as ΔI=voltage V×duty ratio d/(inductance L×frequency f). The duty ratio d is the ratio of the ON time during switching in the booster circuit. A voltage V of +250 to -550 V, a frequency f of 50 kHz, and an average current of 30 A were aimed at in the test. FIG. 12 shows the measured values of ΔI and the rate of change of the measured values with Comparative Example 1 as the reference.

In general, the smaller the ripple width (ΔI), the better the characteristics of the inductor. As is clear from FIG. 12, in Comparative Example 2, the ripple width sharply increases compared to Comparative Example 1, and therefore Comparative Example 2 is considered unsuitable for use in an interleave circuit. On the other hand, in Examples 1 and 2, a ripple width equivalent to that of Comparative Example 1 was obtained, and it can be understood that they are suitable for use as a coupled inductor in an interleave circuit.

The inductor device 1 described above can be widely used, for example, in PFC (power factor correction) circuits, converter circuits, transformer applications (whether step-down or step-up) in inverter circuits, inverter applications, converter applications, and the like. . It can also be used as a solenoid or transformer.

1 Inductor device 2 Inductor 3 Base member 4 Sealing resin 5 Case 21 Core 21a Core member 21b Core member 22 Winding 51 Bottom 52 Side wall 61 Projection 62 Concavity 63 Radial portion 64 Relief portion A Insulation portion B High thermal conductivity portion O Winding line axis

Claims (7)

an inductor having a ring-shaped polygonal core and a winding wound through an inner space of the polygonal core ; An inductor device comprising a case having a sidewall portion surrounding the periphery,
arranging the inductor so that the winding axis is parallel to the bottom and the core is annular on a plane parallel to the bottom;
An insulating portion made of an insulating non-magnetic material and a non-magnetic material having a thermal conductivity higher than that of the insulating portion are formed on the side wall portion of the case along the direction of winding around the inductor. Alternating with high heat conduction parts ,
An inductor device , wherein the insulating portion is arranged so as to face corners of the polygonal core . 2. The inductor device according to claim 1, wherein the high thermal conductivity portion is arranged in a region facing the outer peripheral surface of the winding. 3. The inductor according to claim 1, wherein the bottom portion and the side wall portion are separate members, and the bottom portion and the side wall portion are fixed by fitting a convex portion formed on one of them with a concave portion formed on the other. Device. 4. The inductor device according to claim 3 , wherein rounded portions are provided at the corners of the projections. 5. The inductor device according to claim 3 , wherein the recess is provided with a relief portion. The inductor device according to any one of claims 1 to 5 , wherein the core is provided with two windings having the same magnetic flux generating direction. 7. The inductor device of claim 6 used in an interleaved circuit.

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