JP5598372B2 - Reactor and reactor manufacturing method - Google Patents

Description

  The present invention relates to a reactor used for a component part of a power conversion device such as a vehicle-mounted DC-DC converter.

  In a hybrid vehicle, a plug-in hybrid vehicle, an electric vehicle, and the like, a converter that performs a step-up operation or a step-down operation is required for driving a driving motor or charging a battery. Even in a fuel cell vehicle, the output of the fuel cell is boosted. One of the converter components is a reactor. Examples of the reactor include a form in which a pair of coils formed by winding a winding around the outer periphery of an annular magnetic core are arranged in parallel.

  Patent document 1 arrange | positions at the cylindrical inner core part inserted in the inside of one coil, the cylindrical outer core part arrange | positioned so that the outer periphery of the coil may be covered, and the both end surfaces of the coil. A reactor including a so-called pot-type core having an E-shaped cross-section having a pair of disk-shaped connecting core portions is disclosed. In the pot type core, the inner core portion and the outer core portion arranged concentrically are connected by the connecting core portion to form a closed magnetic circuit. Patent Document 1 also discloses that a small reactor can be obtained by reducing the cross-sectional area of the inner core portion by making the saturation magnetic flux density of the inner core portion higher than that of the outer core portion and the connecting core portion. .

JP 2009-033051 A

  For parts with a small installation space such as in-vehicle parts, it is desirable that the parts be small. Patent Document 1 discloses a magnetic core in which a plurality of divided pieces are joined and integrated with an adhesive. However, in consideration of further miniaturization, it is desirable to remove the adhesive as well. Patent Document 1 discloses a configuration in which the entire magnetic core is formed into a green compact, and the magnetic core is molded together with the powder material to form the magnetic core, thereby eliminating the need for an adhesive. However, when magnetic cores having partially different saturation magnetic flux densities are formed from a compacted body, it is necessary to perform the pressurization process in multiple stages depending on the shape of the magnetic core, leading to a reduction in productivity.

  In order to provide a reactor that is small and excellent in productivity, the present applicants propose to cover the outside of the coil with an exposed core portion formed of a mixture of a magnetic material and a resin. Thus, when a magnetic core is comprised by the mixture of a magnetic material and resin, the density of a magnetic material will produce a difference at the time of the hardening, and it may become difficult to implement | achieve an inductance as a design value.

  In order to solve such a problem, the present invention can easily achieve a desired inductance value even when an outer core portion that covers the outside of a coil is formed by a mixture of a magnetic material and a resin. Provide a reactor with excellent heat dissipation.

  A reactor provided by the present invention includes a coil, a core, and a case that accommodates the coil and the core, the core being an inner core portion disposed inside the coil, and an outer side of the coil. The outer core part is a reactor formed of a mixture of a magnetic material and a resin, and is substantially the same as the axial direction of the coil among the wall surfaces constituting the case. At least one of the parallel surfaces is configured as a cooling surface that is cooled from the outside, and the distribution of the density of the magnetic material in the outer core portion increases from the coil axis toward the cooling surface. It is a reactor characterized by the following distribution. The cooling surface may be the bottom surface of the case. However, when cooling a surface that is not the bottom surface, for example, the surface may be a side surface of the case that is substantially parallel to the axial direction of the coil. The term “substantially parallel” means, in a strict sense, a plane on a parallel side in a general sense in expressing the coil storage direction even if the direction is not parallel.

  In this reactor, the coil is arranged with the axial direction of the coil being substantially parallel to the cooling surface of the case, and the density of the magnetic material in the outer core portion is large on the cooling surface side of the case. Moreover, the outer peripheral surface of a coil is orient | assigned to the cooling surface of a case by arrange | positioning a coil with the end surface of a coil facing the side wall of a case. For this reason, it is easier to radiate heat from the cooling surface of the case than when the coil is arranged with the end surface of the coil facing the cooling surface of the case. When the coil is arranged so as to be in contact with the cooling surface, the cooling effect can be further exhibited.

  Moreover, in this reactor, the difference in the density of the magnetic material in the axial direction of the coil can be made smaller than in the direction perpendicular to the axial direction. For example, the coil is arranged with the axial direction of the coil substantially parallel to the bottom surface of the case, and the difference in density of the magnetic material in the outer core portion can be made smaller in the axial direction of the coil than in the direction along the side wall of the case. Thereby, the difference in the density of the magnetic material in the magnetic flux direction is reduced. A magnetic path is formed concentrating on a portion having a high density, but as a whole, an inductance as designed is easily realized.

  Here, the density of the magnetic material is an amount representing the density of the dispersion of the magnetic material dispersed in the mixture of the magnetic material and the resin (meaning the ratio of the whole of the magnetic material, not the density). Typically represented by the density of the mixture itself. In addition, it can be expressed by a volume ratio of the magnetic material in the resin, an area ratio in the cross section, or the like. Further, the bottom surface of the case refers to a surface in the direction corresponding to the bottom and bottom when filling and solidifying a mixture of a magnetic material and a resin, and the side wall refers to a surface erected in a substantially vertical direction from the bottom surface.

The difference in the density of the magnetic material in the outer core portion is obtained when the cooling surface side is compared with the cooling surface side when comparing the cooling surface side and the comparison surface, which is the lowest density surface. And 0% to 45% or less with reference to the above. This is because the density on the cooling surface side is high and the density on the comparison surface side is low, so that heat generated inside is concentrated on the cooling surface side, and heat dissipation efficiency is improved. For example, assuming a rectangular box case, the comparison surface is a surface (upper surface) that faces it when only one surface is used as a cooling surface (for example, a bottom surface) with high density. When both surfaces facing each other are used as cooling surfaces and the density of each surface is increased, the surface with the lowest density that is perpendicular to the surface is used as the comparison surface, and the average density of the surface is determined. And In addition, when a cylindrical case is assumed, in the case where the entire circumference of the cylindrical surface is cooled and the density is increased on the entire circumference of the cylindrical surface side, a plane which is a bottom surface and a top surface perpendicular thereto can be used as a comparison surface.

  In terms of improving heat dissipation, from the viewpoint of obtaining an effective effect of heat dissipation, the density difference is preferably 3% or more, and more preferably 5% or more. On the other hand, considering the weight difference between the magnetic material such as iron powder and the resin material, the maximum density difference can be about 75%, but if the density difference is 45% or more, the density is This is not preferable because the contribution of the outer core on the comparative surface side having a low level as a substantial magnetic substance is too low, and the size of the outer core becomes too large to obtain a desired inductance as a whole. From these points, the density difference is preferably 3% to 45%, more preferably 5% to 20%, and most preferably 10% to 20%.

  When the density difference of the magnetic material in the outer core portion is 3% or more when determined based on the maximum value of the density in one direction, the axial direction of the coil is made parallel to the direction in which the density difference is large. If the coil is arranged, the density difference in the magnetic flux direction becomes 3% or more, and it becomes difficult to realize a desired inductance value. That is, the coil is arranged with the axial direction of the coil substantially parallel to the cooling surface of the case, and the distribution of the density of the magnetic material increases from the axial center of the core toward the cooling surface. By making the density distribution small in the axial direction, it is possible to easily suppress a difference in density in the magnetic flux direction and obtain a desired inductance value.

  If the cooling surface of the case is configured to be forcibly cooled, the improvement of heat dissipation efficiency can be effectively exhibited. Forced cooling refers to all means for effectively radiating heat rather than natural air cooling in the case itself by means of a water cooling mechanism or heat radiating fins. The case cooling surface has such a structure capable of forced cooling, or has a structure (mounting structure, mounting surface, etc.) for thermal connection with a separately provided forced cooling mechanism, so that there is a difference in the density of magnetic materials. The effect of can be demonstrated.

  By making the saturation magnetic flux density higher in the inner core portion than in the outer core portion, it is possible to reduce the size of the entire reactor for obtaining a desired inductance. For this reason, it is preferable that an inner core part is made into a compacting body. In this case, since the heat generation density of the dust core is high, it is more effective to increase the cooling efficiency to the cooling surface side by adding a density difference to the mixture of the magnetic material and the resin constituting the outer core. .

  In this reactor, the case may have an inner wall surface formed in accordance with at least one of the outer shape of the coil and the inner core portion. In this case, the area of the inner wall surface facing the outer surface of the coil can be increased, and as a result, heat dissipation is further improved.

  In one embodiment of the reactor, a part of the outer peripheral surface of the coil is exposed from the outer core portion. Since the coil is arranged with the end face of the coil facing the side wall of the case, even when a part of the outer peripheral surface of the coil is exposed, the outer core part continues in the axial direction of the coil at the other part. Is secured. Since magnetic paths are concentrated on the bottom side of the case, for example, if the outer peripheral surface of the coil is exposed on the upper side of the case, the influence on the inductance value is particularly small. Therefore, it is possible to improve heat dissipation by exposing a part of the outer peripheral surface of the coil while realizing a desired inductance value. When the outer peripheral surface of the coil is exposed on the upper side of the case, magnetic flux leakage may occur in the air layer. Therefore, it is desirable to cover with a conductive material such as metal.

  The reactor may be provided with a support portion that supports the coil and the inner core portion at both ends protruding from the coil of the inner core portion. This support portion facilitates positioning of the coil within the case, and makes it easier to manufacture a reactor that achieves a desired inductance value. Further, the support portion can ensure insulation between the case and the coil. Moreover, the inner core portion and the bottom surface (cooling surface) of the case can be structurally continuous by the support portion, and heat can be easily radiated from the inner core portion to the bottom surface (cooling surface) of the case.

  Further, the present invention provides, as a reactor manufacturing method, a coil assembly including a coil, an inner core inserted into the coil, and a case including a cooling surface cooled from the outside. A housing step of housing the coil assembly in the case such that the cooling surface of the coil and the axial direction of the coil are substantially parallel, and a mixture including a magnetic material and a resin in a state where the cooling surface is a bottom surface A filling step for filling the case into the case, and a curing step for curing the filled mixture after the filling step, and the viscosity of the mixture is substantially minimized between the filling step and the curing step. The manufacturing method of the reactor which has the process hold | maintained at temperature is presented.

  As another manufacturing method, a coil assembly including a coil, an inner core inserted into the coil, and a case having a cooling surface cooled from the outside are prepared, and the cooling surface of the case Storing the coil assembly in the case so that the axial direction of the coil is substantially parallel, filling the case containing a mixture containing a magnetic material and a resin, and the filling Manufacturing a reactor having a curing step of curing the filled mixture after the step, and applying an external magnetic field so that the magnetic material moves to the cooling surface side in the filling step or after the filling step Present the method.

  Furthermore, a coil assembly including a coil, an inner core inserted through the coil, and a case having a cooling surface cooled from the outside are prepared, and the cooling surface of the case and the coil After the storing step of storing the coil assembly in the case so that the axial direction is substantially parallel, the filling step of filling the mixture containing the magnetic material and the resin in the case, and after the filling step, A reactor having a curing step of curing the filled mixture, and rotating the case so that a centrifugal force in a direction in which the magnetic material moves is generated on the cooling surface side in the filling step or after the filling step. The manufacturing method is presented. By setting it as such a manufacturing method, the reactor provided with the desired density difference can be obtained.

  According to the present invention, as described above, even when the outer core portion that covers the outside of the coil is formed by the mixture of the magnetic material and the resin, a desired inductance value is easily realized, and the reactor has excellent heat dissipation. Can be obtained.

The foregoing and other objects, features, and advantages of the present invention will become more apparent from embodiments described below with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same parts in different drawings.
It is a figure which shows the installation state of the reactor which concerns on embodiment of this invention. It is a perspective view which shows schematic structure of the reactor which concerns on this Embodiment. It is a figure for demonstrating the structural example of the reactor in which the inner wall surface of the case was formed in the non-similar shape with the outer wall surface. It is a figure which shows the structural example of the reactor which a part of outer peripheral surface of the coil exposed from the outer core part. It is a figure for demonstrating the structural example of the reactor which provided the support part of the coil in the case. It is a schematic diagram explaining the cross-sectional structure of the simulated reactor. It is the figure (the density difference exists, bottom side cooling) which expressed cross-sectional temperature distribution as a result of the simulation 1 by color distribution. It is the figure (there is a density difference, upper surface side cooling) which expressed cross-sectional temperature distribution as a result of the simulation 1 by color distribution. It is the figure (no density difference, bottom side cooling) which expressed cross-sectional temperature distribution as a result of the simulation 1 by color distribution. It is the figure (density difference 0%) which expressed cross-section temperature distribution as a result of the simulation 2 by color distribution. It is the figure (density difference 2%) which expressed cross-sectional temperature distribution as a result of the simulation 2 by color distribution. It is the figure (density difference 3%) which expressed cross-sectional temperature distribution as a result of the simulation 2 by color distribution. It is the figure (density difference 5%) which expressed cross-sectional temperature distribution as a result of the simulation 2 by color distribution. It is the figure (density difference 10%) which expressed cross-section temperature distribution as a result of the simulation 2 by color distribution. It is the figure (density difference 15%) which expressed cross-sectional temperature distribution as a result of the simulation 2 by color distribution. It is the figure (density difference 20%) which expressed cross-section temperature distribution as a result of the simulation 2 by color distribution. It is the figure (density difference 45%) which expressed cross-sectional temperature distribution as a result of the simulation 2 by color distribution. It is a schematic diagram explaining the formation method of the density difference by an external magnetic field. It is a schematic diagram explaining the formation method of the density difference by centrifugal force. It is a figure for demonstrating the structural example of the reactor formed so that a coil might contact the inner wall face of a case.

  FIG. 1 is a diagram showing an installation state of a reactor according to an embodiment of the present invention. Reactor 101 according to the present embodiment can be used as a component of a vehicle-mounted DC-DC converter. Reactor 101 is housed in an aluminum converter case 102 together with other components. In this embodiment, the reactor 101 includes a case 103 made of aluminum, for example, a box-lid shape, and is disposed in the converter case 102 by fixing the case 103 to the inner bottom surface 104 of the converter case 102 with a bolt. Yes. The bottom surface of the case 103 is in surface contact with the inner bottom surface 104 of the converter case 102.

  In an in-vehicle converter, a current of 100 amperes or more is normally applied, so that the reactor 101 generates high heat. In order to cool the reactor 101 and other components, cooling water 105 is introduced into the outer bottom surface of the converter case 102. Heat generated by the reactor 101 is transmitted to the converter case 102 via the bottom surface as the cooling surface of the case 103 and is dissipated by the cooling water 105.

  FIG. 2 is a diagram showing a schematic configuration of the reactor according to the present embodiment. The reactor 101 includes a coil 201, a core 204 having an inner core portion 202 disposed inside the coil 201, and an outer core portion 203 covering the outside of the coil 201. A case 103 provided in the reactor 101 accommodates the coil 201 and the core 204.

  In the reactor 101, the coil 201 is formed by spirally winding one continuous winding 201 w, and the axial direction 205 is disposed substantially parallel to the bottom surface of the case 103. Both ends of the winding 201w are connected to a semiconductor element of the converter and a battery. For the winding 201w, it is preferable to use a coated wire having an insulating coating made of an insulating material on the outer periphery of a conductor made of a conductive material such as copper or aluminum. Here, a covered rectangular wire whose conductor is made of a copper rectangular wire and whose insulating coating is made of enamel is used for the winding 201w. As the winding 201w, in addition to a conductor made of a rectangular wire, various shapes such as a circular shape and a polygonal shape can be used.

The reactor having the above-described configuration is used in applications where the energization conditions are, for example, a maximum current (direct current) of about 100 A to 1000 A, an average voltage of about 100 V to 1000 V, and a use frequency of about 5 kHz to 100 kHz, typically an electric vehicle or It can utilize suitably for the components of in-vehicle power converters, such as a hybrid car. In such applications, it is expected that an inductance satisfying 10 μH or more and 2 mH or less when DC current is 0 A and 10% or more of inductance when DC current is 0 A is preferably used. If the reactor and vehicle parts, reactor is preferably capacitance, including the case of 0.2 liters ⁽²⁰⁰ cm 3) to 0.8 liters (800 cm ³⁾ approximately. In this example, it is about 0.4 liter.

  The coil 201 forms one coil element, but a plurality of coil elements may be formed by one winding, and these coil elements may be accommodated in a case. The plurality of coil elements can be formed by separate windings instead of a single winding. By joining the ends of the windings by welding or the like, an integrated coil can be obtained. Examples of welding of separate windings include TIG welding, laser welding, and resistance welding. In addition, the ends of the windings may be joined to each other by crimping, cold welding, vibration welding, or the like.

  Both ends of the winding 201w forming the coil 201 are appropriately extended from the turn and drawn to the outside of the outer core portion 203, and the conductive portion such as copper or aluminum is exposed to the exposed conductor portion after the insulation coating is peeled off. A terminal member made of a conductive material is connected. The coil 201 is connected to a battery or the like through this terminal member. In addition to welding such as TIG welding, crimping or the like can be used to connect both ends of the winding 201w and the terminal member.

  The core 204 forms a closed magnetic circuit by integrating the inner core portion 202 and the outer core portion 203. In the present embodiment, the constituent material is different between the inner core portion 202 and the outer core portion 203, and the magnetic characteristics are different. Specifically, the inner core portion 202 has a higher saturation magnetic flux density than the outer core portion 203, and the outer core portion 203 has a lower magnetic permeability than the inner core portion 202.

  The inner core portion 202 has an outer shape along the shape of the inner peripheral surface of the coil 201 (each coil element when a plurality of coil elements are formed). Here, it has a cylindrical outer shape. You may have the external shape like the rectangular parallelepiped (track shape) in which the end surface shape rounded the angle | corner, and another external shape. The entire inner core portion 202 is composed of a powder compact, and no gap material, air gap, or adhesive material is interposed. However, the inner core portion is not limited to this, and the green compact may be divided into a plurality of cores and bonded with an adhesive. In this case, even if an adhesive is present, the adhesive does not substantially function as a gap. It is also possible to include a gap material in order to obtain a desired performance according to the design needs.

  The green compact is typically obtained by forming a soft magnetic powder having an insulating coating on the surface and firing it at a temperature lower than the heat resistance temperature of the insulating coating. A mixed powder in which a binder is appropriately mixed in addition to the soft magnetic powder can be used, or a powder having a coating made of a silicone resin or the like can be used as an insulating coating. The saturation magnetic flux density of the green compact can be changed by adjusting the material of the soft magnetic powder, the mixing ratio of the soft magnetic powder and the binder, the amount of various coatings, and the like. For example, a powder compact with a high saturation magnetic flux density can be obtained by using a soft magnetic powder with a high saturation magnetic flux density or by increasing the proportion of the soft magnetic material by reducing the blending amount of the binder. In addition, the saturation magnetic flux density tends to be increased by changing the molding pressure, specifically, by increasing the molding pressure. It is preferable to select a soft magnetic powder and adjust a molding pressure so as to obtain a desired saturation magnetic flux density.

  The soft magnetic powder is an iron group metal powder such as Fe, Co, Ni, Fe-based alloy powder such as Fe-Si, Fe-Ni, Fe-Al, Fe-Co, Fe-Cr, Fe-Si-Al, Or rare earth metal powder, ferrite powder, etc. can be used. In particular, the Fe-based alloy powder is easy to obtain a green compact with a high saturation magnetic flux density. Such a powder can be produced by an atomizing method (gas or water), a mechanical pulverization method, or the like. When a powder made of a nanocrystalline material having a nanosized crystal, preferably a powder made of an anisotropic nanocrystalline material, a compact with a high anisotropy and a low coercive force is obtained. For the insulating coating formed on the soft magnetic powder, for example, a phosphoric acid compound, a silicon compound, a zirconium compound, or a boron compound is used. As the binder, a thermoplastic resin, a non-thermoplastic resin, a higher fatty acid, or the like can be used. This binder disappears upon firing, or changes to an insulator such as silica. The compacted body is a case in which an insulating material such as an insulating film is present so that soft magnetic powders are insulated from each other, eddy current loss can be reduced, and high-frequency power is applied to the coil. However, the loss can be reduced.

  The inner core portion 202 includes not only the entirety of the inner core portion 202 disposed in the coil (element) but also a portion of the inner core portion 202 protruding from the coil (element). In the example shown in FIG. 2, the axial length of the coil 201 in the inner core portion 202 is larger than that of the coil 201, and both end portions of each inner core portion 202 protrude from the end surface of the coil 201. The length of the inner core portion 202 may be equal to the coil 201 or may be slightly shorter. When the length of the inner core portion 202 is equal to or greater than that of each coil 201, the magnetic flux generated by the coil 201 can be sufficiently passed through the inner core portion 202.

  In the present embodiment, outer core portion 203 is formed so as to cover substantially all of coil 201 and inner core portion 202. That is, the outer core portion 203 substantially covers the entire outer periphery of the coil 201, both end surfaces of the coil 201, and both end surfaces of the inner core portion 202. The inner core portion 202 and the outer core portion 203 are joined by the constituent resin of the outer core portion 203 without an adhesive. By the joining, the core 204 can be integrated without any gaps throughout.

  The outer core portion 203 has a rectangular parallelepiped outer shape that matches the inner wall surface of the case as a basic outer shape, but the shape of the outer core portion 203 is not particularly limited as long as a closed magnetic path can be formed. A part of the outer side of the coil 201 may be exposed without being covered with the outer core part 203.

  The entire outer core portion 203 can be formed of a mixture (molded and cured body) of a magnetic material and a resin. The molded cured body can typically be formed by injection molding or cast molding. In injection molding, soft magnetic powder (mixed powder with non-magnetic powder added if necessary) and fluid binder resin are usually mixed, and this mixed fluid is subjected to a predetermined pressure to form a mold ( Here, after being poured into the case 103) and molded, the binder resin is cured. In cast molding, a mixed fluid similar to that of injection molding is obtained, and then the mixed fluid is injected into a molding die (case 103) without applying pressure to be molded and cured. In any molding technique, a thermosetting resin such as an epoxy resin, a phenol resin, or a silicone resin can be suitably used as the binder resin. When a thermosetting resin is used as the binder resin, the molded body is heated to thermoset the resin. A normal temperature curable resin or a low temperature curable resin may be used as the binder resin. In this case, the molded body is allowed to stand at a normal temperature to a relatively low temperature to be cured. Since the molded hardened body contains a large amount of binder resin, which is a non-magnetic material, even if the same soft magnetic powder as that of the green compact is used, the saturation magnetic flux density is lower and the permeability is lower than that of the green compact. Become.

As the soft magnetic powder used for the outer core portion 203, the same soft magnetic powder as used for the inner core portion 202 described above can be used.
It is preferable to interpose an insulator at a location where the core 204 is in contact with the coil 201 in order to further improve the insulation between them. For example, an insulating tape is attached to the inner and outer peripheral surfaces of the coil 201, or insulating paper or an insulating sheet is disposed. A bobbin made of an insulating material may be disposed on the outer periphery of the inner core portion 202. As the bobbin constituent material, an insulating resin such as polyphenylene sulfide (PPS) resin, liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE) resin can be suitably used.

The typical density of the mixture of magnetic material and resin used in the present invention is about 3.0 to 5.5 g / cm ³ . In particular, when the resin material is an epoxy resin and the magnetic material is Fe, about 3.5 to 4.7 g / cm ³ , and the magnetic material is Fe-6.5Si (Fe-based alloy containing 6.5% by weight of Si). In this case, it is about 3.6 to 5.0 g / cm ^{3, and in the} case of Sendust (Fe—Al—Si alloy), it is about 3.6 to 5.0 g / cm ³ . Further, as typical dimensions, etc., the inner core if a powder compact of Fe powder, the density can be ^{6.5g / cm 3 ~7.8g / cm 3} . The dimensions are 10 mm to 70 mm in diameter and 20 mm to 120 mm in height when the core cross section is a circle. As for the coil, when the coil cross section is a circle, the inner diameter can be 20 mm to 80 mm, and the number of turns can be 30 to 70. When the outer core is a rectangular parallelepiped, one side can be about 60 mm to 100 mm, and when the case is a rectangular parallelepiped, one side can be about 60 to 100 mm.

  The above-described reactor can be manufactured, for example, by performing each step in the following order: storage step → filling step → curing step. Hereinafter, each step will be described.

  In the storing step, the coil 201 is stored in the case 103. When the inner core portion 202 is made of a compacted body as in this example, or is made of a material different from the outer core portion 203, such as when it is made of another electromagnetic steel plate, the coil 201 and the inner core portion 202 are Prepare and insert the inner core portion 202 into the coil 201 to produce an assembly of the coil 201 and the inner core portion 202. This assembly may be produced anytime before the next filling step. In addition, an insulator may be appropriately disposed between the coil 201 and the inner core portion 202 as described above. Then, the assembly is stored in the case 103. When the assembly is stored in the case 103, if the guide protrusion or the like is provided in the case 103, the assembly can be accurately placed at a predetermined position in the case 103.

  In the filling step, the case 103 is filled with a mixture containing the magnetic powder and the resin constituting the outer core portion 203. In the mixture of the magnetic powder and the resin (before the resin is cured), the magnetic permeability is about 20 to 60% by volume and the resin is about 40 to 80% by volume with respect to the entire mixture. 5 to 50 can be formed. For example, 40% by volume of pure iron powder having a phosphate coating on the magnetic powder, 60% by volume of bisphenol A type epoxy resin for the resin, and acid anhydride as a curing agent for the resin, respectively, are prepared. It may be formed and filled in the case 103. Further, after the filling, vacuuming is preferably performed as a deaeration process for removing voids in the mixture. It is preferable because voids in the mixture can be removed and desired magnetic characteristics of the outer core portion 203 can be easily obtained.

  In the curing step, the filled resin is cured. In this curing step, the temperature and time may be appropriately selected according to the type of resin to be cured. In this example, the first temperature was held at 80 ° C. for 2 hours before curing, then the curing temperature was maintained at the second temperature 120 ° C. for 2 hours, and the third temperature was maintained at 150 ° C. The resin was cured by allowing to stand for 5 hours.

  The first temperature is a temperature selected as the temperature at which the viscosity of the resin is lowest. After mixing the curing material, the viscosity of the resin before curing proceeds can be confirmed by changing the temperature and measuring under the same conditions. By setting it at such a temperature, the magnetic powder in the resin is likely to precipitate, and the density difference can be given. That is, the density difference of the mixture can be made between the bottom surface side and the top surface side. For this reason, the first temperature is preferably the temperature at which the viscosity of the resin becomes substantially minimum, ± 5 ° C. of the temperature at which the viscosity is lowest, and more preferably within ± 3 ° C.

  Furthermore, if the viscosity is low, the effect of easily defoaming bubbles in the resin is also obtained. Therefore, by maintaining the temperature at a temperature at which the viscosity is substantially minimum for a predetermined time, the mixture of the magnetic powder and resin after curing the resin As a feature, it is possible to obtain a feature that bubbles having a diameter of 300 μm or more are substantially absent. When an arbitrary cross section of 5 mm × 5 mm cross section of a mixture of magnetic powder and resin after resin curing is observed with an optical microscope, the average number of bubbles having a diameter of 200 μm or more is about 5 or more per cross section in the conventional method. Although bubbles having a diameter of 300 μm or more can also be found, in the present invention, the number of bubbles having a diameter of 200 μm or more is an average of 1 or less per cross section, and bubbles having a diameter of 300 μm or more were not found. Here, the diameter of the bubble is the diameter when the shape of the bubble that can be confirmed in the cross section is converted into a circle having the same area.

  Since there are few air bubbles in the mixture of the magnetic powder and resin after hardening, it can be set as the outer core which was further excellent in thermal conductivity. This is because resin and magnetic powder have higher thermal conductivity than bubbles, that is, air. Further, since the number of bubbles is small, the deviation from the designed magnetic characteristic distribution becomes small, and it becomes easy to realize desired characteristics. In particular, the presence of large bubbles is not preferable because the magnetic flux passes through the bubbles and unexpected magnetic flux line density occurs.

  The second temperature is a temperature for curing the resin. The third temperature is a temperature for increasing the crosslinking density of the resin. In particular, by selecting the first temperature based on knowledge obtained in advance, it is possible to arbitrarily form a density difference between the bottom surface and the top surface. What is necessary is just to select and hold | maintain the time required for hardening and bridge | crosslinking of resin for 2nd temperature and 3rd temperature.

  In the above, the step of holding for a predetermined time at the three heating temperatures of the first temperature, the second temperature, and the third temperature is used. However, heat resistance is not required so much, and there is a need to increase the crosslinking density of the resin. In the case where the temperature is low, it may be a process of holding for a predetermined time at a two-step heating temperature of only the first temperature and the second temperature. Alternatively, the second temperature may be omitted, and a process of holding for a predetermined time at a two-step heating temperature of only the first temperature and the third temperature may be performed. The holding time at the first temperature, which is the holding temperature before curing, is selected so that a desired density difference is obtained after grasping in advance the time when the sedimentation of the magnetic powder is almost saturated depending on the type of the magnetic powder in the resin. do it. In this example, since a desired density difference is obtained in about 2 hours, it was set as 2 hours as an example, but the holding time was 15 minutes to 3 in consideration of the viscosity of the resin, the kind and particle size of the magnetic powder, and the like. Choose from time.

  When using injection molding or cast molding, if not sintered, soft magnetic powder and nonmagnetic powder can be sintered by changing the blend of soft magnetic powder (or nonmagnetic powder) and binder resin. The magnetic permeability of the outer core portion can be adjusted by changing the blending of For example, when the blending amount of the soft magnetic powder is reduced, the magnetic permeability tends to decrease. The magnetic permeability of the outer core portion 203 may be adjusted so that the reactor 101 has a desired inductance.

  In such a reactor 101, the saturation magnetic flux density of the inner core portion 202 is higher than that of the outer core portion 203, so that the total magnetic flux passing through the inner core portion 202 is uniform with the same saturated core. When the total magnetic flux passing through the inner core of a typical magnetic core (uniform core) is the same, the cross-sectional area (surface through which the magnetic flux passes) of the inner core portion 202 may be made smaller than the cross-sectional area of the inner core of the uniform core. it can. By reducing the size of the inner core portion 202, the core 204 can be reduced in size, and as a result, the reactor 101 can be reduced in size. Further, the reactor 101 can have a desired inductance because the saturation magnetic flux density of the inner core portion 202 is high and the magnetic permeability of the outer core portion 203 is low.

  Furthermore, since the reactor 101 has no gap over the entire core 204, leakage magnetic flux at the gap does not affect the coil 201. It can be placed close to the surface. Therefore, the gap between the outer peripheral surface of the inner core portion 202 and the inner peripheral surface of the coil 201 can be reduced, and from this, the reactor 101 can be downsized.

  Further, when the reactor 101 is configured so as not to use any adhesive, it is excellent in productivity because a gap material joining step or the like is not required for forming the inner core portion 202. In particular, in the reactor 101, simultaneously with the formation of the outer core portion 203, the inner core portion 202 and the outer core portion 203 are joined by the constituent resin of the outer core portion 203 to form the core 204. As a result, the reactor 101 is manufactured. Therefore, the manufacturing process is simplified, and productivity is improved from this point.

  Further, in the reactor 101, the saturation magnetic flux density can be easily adjusted by forming the inner core portion 202 as a compact, and even a complicated three-dimensional shape can be easily formed. In addition, since the outer core portion 203 includes a resin component, protection from the external environment such as dust and corrosion and mechanical protection can be achieved. In particular, in the reactor 101, the entire coil 201 is covered with the outer core portion 203, whereby the outer core portion 203 can be easily formed and the coil 201 can be sufficiently protected. Thus, the reactor 101 has various advantages.

  Furthermore, the reactor 101 can easily achieve a desired inductance value even when the outer core portion 203 is formed of a mixture of a magnetic material and a resin as described above. When the outer core portion 203 is cured in the case 103, the magnetic material is distributed more on the bottom side of the case 103 due to gravity and less on the upper side of the case 103 according to the manufacturing method described above. For this reason, the density difference of the magnetic material becomes large in the direction 206 along the side wall of the case 103. For example, even when cured without intentional density difference, density differences of ± 1% or less, or less than ± 2% at most, can occur due to slight precipitation due to gravity and variations in density. When the end surface of the cylindrical coil 201 is directed to the bottom surface of the case 103 (the coil 201 is placed vertically in the case 103), a magnetic path is formed in the direction 206 in which the difference in the density of the magnetic material is large. As a result, it becomes difficult to achieve the inductance as designed. On the other hand, the difference in density of magnetic materials in the horizontal direction can be made considerably smaller than in the direction 206.

  The density of the magnetic material in one direction is, for example, each slice piece (excluding the volume of the coil 201 and the inner core part 202) when the outer core part 203 is sliced at a predetermined interval on a plane whose direction is the normal line. It can be evaluated by density measurement. In this case, the difference in the density of the magnetic material in one direction is obtained by using the minimum density and the maximum density among the density of each slice piece, with the maximum density as a reference (maximum density−minimum density). / Maximum density.

The measuring method of the density ρ can be obtained from the weight in air and the weight in water as follows. From the principle of Archimedes,
ρ = (ρw × Wair−ρair × Ww) / (Wair−Ww)
It becomes. Here, ρw is the density of water, ρair is the density of air, Ww is the weight in water, and Wair is the weight in air.
Since approximately ρw >> ρair, ρ≈ρw × Wair / (Wair−Ww)
And can.

  In the reactor 101, the axial direction 205 of the coil 201 is substantially parallel to the bottom surface of the case 103 in accordance with the direction in which the density difference is small, and the end surface of the coil 201 faces the side wall of the case 103 (coil 201 In the case 103). More magnetic material is distributed on the bottom side of the case 103, and a magnetic path is formed concentrating on that part, but the design as a whole without considering the density distribution of the magnetic material in the manufacturing process It becomes easy to realize the inductance according to the value. As a result, the manufacturing cost of the reactor 101 is reduced.

  The axial direction 205 of the coil 201 is preferably in the horizontal direction (or substantially parallel to the bottom surface of the case 103) from the filling step to the curing step, but the end surface of the cylindrical coil 201 faces the side wall of the case 103. If it is within the range, the difference in the density of the magnetic material in the direction of the magnetic flux can be suppressed as compared with the case where the end surface of the coil 201 is directed to the bottom surface of the case 103.

  Furthermore, by disposing the coil 201 such that the axial direction of the coil 201 is substantially parallel to the bottom surface of the case 103 and the end surface of the coil 201 faces the side wall of the case 103, the heat dissipation of the reactor 101 is improved. The outer core portion 203 formed from a mixture of a magnetic material and a resin has a lower thermal conductivity than the inner core portion 202 made of a green compact, and is heated by the coil 201 covered with the outer core portion 203. The reactor temperature tends to rise. When the coil 201 is arranged with the end surface of the coil 201 facing the bottom surface instead of the side wall of the case 103, the outer peripheral surface that occupies most of the outer surface of the coil 201 faces the side wall of the case 103. In this case, the heat generated from the coil 201 is mainly dissipated through a route from the inner core portion 202 to the bottom surface of the case 103 and a route from the outer core portion 203 and the side wall of the case 103 to the bottom surface. When heat is radiated along the path, the temperature of the entire reactor 101 is likely to rise.

  On the other hand, when the coil 201 is disposed with the end surface of the coil 201 facing the side wall of the case 103, the outer peripheral surface of the coil 201 faces the bottom surface of the case 103. Since the surface area of the coil 201 facing the bottom surface of the case 103 that is the cooling surface is increased, even when the coil 201 is covered by the outer core portion 203, the heat from the coil 201 is easily dissipated from the bottom surface of the case 103. Therefore, the reactor 101 can easily achieve a desired inductance value and can secure good heat dissipation.

  From this point of view, it is preferable that the outer peripheral surface of the coil 201 is in contact with the cooling surface of the case 103 or is in contact with an insulating material because heat dissipation is further improved. Although the outer core is substantially not present in the contact portion, there is no problem as a function of the outer core.

  FIG. 3 is a diagram for explaining a configuration example of the reactor in which the inner wall surface of the case is formed in a shape similar to the outer wall surface. In this example, the inner wall surface 301 of the case 103 has a substantially semi-elliptical cross section in accordance with the outer shape of the coil 201 and the inner core portion 202. Since the outer shape of the case 103 is a rectangular parallelepiped shape, the inner wall surface and the outer wall surface of the case 103 are not similar. An imaginary line 302 virtually shows the inner wall surface when formed in a rectangular parallelepiped shape similar to the outer wall surface of the case 103.

  As is apparent from the comparison between the inner wall surface 301 and the virtual line 302 in the figure, the inner wall surface 301 of the case 103 is formed in accordance with the outer shape of the coil 201 and the inner core portion 202 so that the inner wall surface of the case 103 is provided at various places. It is close to the coil 201 and the inner core portion 202 with little deviation. Compared with the case where the inner wall surface of the case 103 is formed in a similar shape to the outer wall surface, the surface area of the inner wall surface 301 facing the coil 201 and the inner core portion 202 within a certain distance can be increased. For this reason, it becomes easy to dissipate the heat from the coil 201 etc. from the inner wall surface 301, and the heat dissipation of a reactor is improved.

  The cross-sectional shape of the inner wall surface 301 is not limited to a substantially semi-elliptical shape, and may be a substantially semi-circular shape or other shapes in accordance with the outer shapes of the coil 201 and the inner core portion 202. Moreover, you may form the inner wall surface of a case according to the external shape of the coil 201, or the external shape of an inner core part.

  FIG. 4 is a diagram illustrating a configuration example of the reactor in which a part of the outer peripheral surface of the coil is exposed from the outer core portion. In this example, the inner wall surface 401 of the case 103 has a substantially semicircular cross section in accordance with the outer shapes of the coil 201 and the inner core portion 202. For this reason, the heat dissipation of a reactor improves with the shape of the inner wall surface 401 like the example of FIG. However, the inner wall surface of the case 103 may have other shapes.

  In the example of FIG. 4, a part of the outer peripheral surface 402 of the coil 201 is exposed from the outer core portion 203 on the upper side of the case 103. When the coil 201 is placed vertically in the case 103, if the coil 201 is exposed from the outer core portion 203, a portion where the outer core portion 203 does not exist is generated over the entire outer periphery of the coil 201. On the other hand, when the coil 201 is placed horizontally in the case 103, the outer core portion 203 continues in the axial direction 205 of the coil 201 at other portions even if a part of the outer peripheral surface 402 of the coil 201 is exposed. Therefore, a necessary magnetic path can be secured at a portion in the outer core portion 203 of the outer peripheral surface 402. Since magnetic paths are concentrated on the bottom surface side of the case 103, if the outer peripheral surface 402 of the coil 201 is exposed on the upper side of the case 103 in this way, the influence on the inductance value is particularly small, and the design value as a whole. This makes it easier to achieve the same inductance.

  If a part of the outer peripheral surface 402 of the coil 201 is exposed from the outer core part 203 on the upper side of the case 103, the heat of the coil 201 can be dissipated without passing through the outer core part 203. Since the upper side of the case 103 is farthest from the bottom surface of the case 103 which is a cooling surface, the temperature of that portion is likely to rise. By exposing a part of the outer peripheral surface 402 of the coil 201 on the upper side of the case 103, the heat dissipation of that part is enhanced. Therefore, the heat dissipation of the entire reactor can be further enhanced while ensuring a desired inductance value.

  In the example of FIGS. 3 and 4, the case 103 may have a lid that closes the upper portion thereof. If the upper part of the case 103 is closed with, for example, an aluminum lid, the outer core portion 203 and the upper surface of the coil 201 exposed from the outer core portion 203 can be brought into surface contact with the lid. In that case, the heat on the upper side of the reactor can be dissipated through the lid, the side wall of the case 103, and the path leading to the bottom surface as the cooling surface. For this reason, the heat dissipation of a reactor improves more. In addition to aluminum, other metal materials such as an aluminum alloy, and ceramics such as silicon nitride, alumina, aluminum nitride, boron nitride, and silicon carbide can be used as the material for the lid. Note that when the case is configured to be closed with a lid made of a conductive material, the insulation between the coil 201 and the lid is necessary.

  FIG. 5 is a diagram for explaining a configuration example of a reactor in which a coil support portion is provided in a case. In this example, the reactor includes a support portion 502 that supports the coil 201 and the inner core portion 202 at both end portions 501 protruding from the coil 201 of the inner core portion 202 on the inner bottom surface 503 of the case 103. The support portion 502 may be formed integrally with the case 103 main body, or may be formed separately from the case 103 main body and connected and fixed to the case 103 main body. The material of the support portion 502 may be the same material as the case 103 or a different material, and the same material as the case lid described above can be used for the support portion 502.

  Positioning of the coil 201 within the case 103 is facilitated by providing the support portion 502 in the case 103, in this example, the inner bottom surface 503 of the case 103. A reactor according to this example can be manufactured by filling the case 103 with the constituent material of the outer core portion 203 in a state where the coil 201 is placed on the support portion 502 and molding and curing the case. For this reason, manufacture of the reactor which implement | achieved the desired inductance value becomes easier.

  The support portion 502 contacts the inner core portion 202 at both end portions 501 protruding from the coil 201 of the inner core portion 202. The coil 201 is not in contact with the support portion 502. Further, since the support portion 502 is erected on the inner bottom surface 503 of the case 103, the coil 201 does not contact the inner bottom surface 503 of the case 103. Therefore, the insulation between the case 103 and the coil 201 is ensured only by placing the coil 201 on the support portion 502.

  The support portion 502 structurally connects the inner core portion 202 and the inner bottom surface 503 of the case 103. Heat can be dissipated from both end portions 501 of the inner core portion 202 to the bottom surface of the case 103 via the support portion 502. Therefore, by providing the support portion 502, the heat dissipation of the entire reactor can be further enhanced. If the insulation between the case 103 and the coil 201 is ensured, the heat radiation performance is improved as much as the inner bottom surface 503 of the case 103 and the coil 201 are brought close to each other.

  FIG. 20 is a diagram for explaining a configuration example of the reactor formed so that the coil contacts the inner wall surface of the case. FIG. 6 is a schematic diagram showing a state in which a coil 901 wound around a cylindrical inner core 901 is housed in a case 904 in a cross section perpendicular to the axial direction of the coil. Here, the density of the magnetic material in the outer core 903 made of a mixture of the magnetic material and the resin is represented by black dots. This example illustrates the case where both side walls and the bottom surface parallel to the axial direction of the coil of the case 904 are used as cooling surfaces, and the density of the magnetic material of the outer core is increased on the side wall surface and bottom surface side of the case 904. Yes. The effect of cooling can be further enhanced by contacting the coil with the inner wall surface of the case on the cooling surface side or via an insulator (not shown) such as a resin sheet or paint. In this example, there are three cooling surfaces, and an effect can be obtained when at least one of the cooling surfaces is in contact. Although FIG. 20 shows an example in which the two side surfaces are in contact with one side surface and the bottom surface, it is possible to configure all three surfaces, only the bottom surface, or only both side surfaces.

  Next, another manufacturing method for forming a density difference in the outer core portion will be described. FIG. 18 is a diagram for explaining a method of forming a density difference due to an external magnetic field. FIG. 18 schematically shows a reactor in which a coil assembly including a coil 702 and an inner core 701 is housed in a rectangular parallelepiped case 704 as a cross section of a plane perpendicular to the axial direction of the coil. After the case 704 is filled with a mixture 703 of a magnetic material and a resin, a permanent magnet 710 is disposed on the side surface of the case at a stage before curing. Thereby, the magnetic powder dispersed in the resin is attracted to the magnet, and the density of the magnetic powder on both side surfaces can be increased. By heat curing the resin in this state, it is possible to form a density difference. In this example, both side surfaces on the side where the density is increased are used as cooling surfaces.

  As yet another manufacturing method, FIG. 19 is a diagram for explaining a method of forming a density difference by centrifugal force. FIG. 19 schematically shows a reactor in which a coil assembly comprising a coil 802 and an inner core 801 is housed in a cylindrical case 804 as a cross section in the axial direction of the coil. After the case 804 is filled with the mixture 803 of the magnetic material and the resin, the case is placed on the turntable 810 and rotated before it is cured, thereby generating a centrifugal force. Thereby, the magnetic powder dispersed in the resin gathers on the cylindrical surface side of the cylindrical case 804, and the density of the magnetic powder on the cylindrical surface side can be increased. By heat curing the resin in this state, it is possible to form a density difference. In this example, a cylindrical surface with high density is used as a cooling surface and cooling is performed from the outside.

  The above-described embodiments do not limit the technical scope of the present invention, and various modifications and applications are possible within the scope of the present invention. For example, the reactor of the present invention can be applied not only to a vehicle-mounted converter but also to other power converters having a relatively high output such as an air conditioner converter. Furthermore, the end surface of the inner core portion may contact the side wall of the case. Since the end surface of the inner core portion is in contact with the side wall of the case, the heat dissipation of the reactor can be further enhanced.

  In the above-described embodiment, the present invention has been described with respect to the reactor in which the inner core portion is mainly composed of a compacted body. In addition, what consists of a laminated body which laminated | stacked the electromagnetic steel plate represented by the silicon steel plate can also be utilized as an inner core part. The magnetic steel sheet is easy to obtain a magnetic core having a high saturation magnetic flux density as compared with the green compact. Furthermore, in the reactor described above, the inner core portion has a higher saturation magnetic flux density than the outer core portion, and the outer core portion has a lower magnetic permeability than the inner core portion, but the reactor to which the present invention is applied is It is not limited to that example. For example, not only the outer core part but also the inner core part may be composed of a mixture of a magnetic material and a resin. In the case where the inner core portion and the outer core portion are both a mixture containing magnetic powder and resin, the filling process may be performed after only the coil is accommodated in the case. Even when only the coil is accommodated in the case, the subsequent filling step and curing step can be performed in the same manner as in the case where the coil and the inner core portion are accommodated.

[Formation of density difference]
Hereinafter, assuming that the cooling surface is the bottom surface, a formation example will be described on the premise of forming a density difference due to sedimentation of the magnetic material before curing to the bottom surface side. Accordingly, the cooling surface is the bottom surface, and the comparison surface, which is the surface different from the cooling surface side and has the lowest density, is the top surface. The density difference of the magnetic material can be set to a desired value depending on various conditions such as the curing conditions, the filling amount of the magnetic material, the particle diameter, and the type of the curing agent. Table 1 shows examples of formation. Commercially available pure iron powder was used as the magnetic material, and an epoxy resin (Mitsubishi Chemical (formerly Japan Epoxy Resin) bisphenol A type epoxy resin JER828) and a curing agent shown in the table were mixed without using other fillers and the like. The curing conditions were all the same, and heating was performed in the order of 80 ° C. for 2 hours, 120 ° C. for 2 hours, and 150 ° C. for 5 hours. A holding time of 2 hours at 80 ° C. is a time for which the precipitation of the magnetic material is almost saturated, and the density of the bottom surface side and the top surface side is sufficiently high. If the time is shorter, the difference can be reduced. Although slight precipitation proceeds during curing at 120 ° C., in this example, sufficient time at 80 ° C. is taken, and it is considered that there is almost no influence on the density difference.

  In Table 1, the height is the height of the filling portion serving as the outer core portion, that is, the distance from the case bottom to the top surface. The iron powder particle size range was measured by a laser diffraction / scattering method using an apparatus (Microtrack MT3300) manufactured by Nikkiso Co., Ltd. The iron powder filling amount is a volume ratio of iron powder to the entire mixture. The bottom surface side density and the density difference are measurement results after curing, and the sample was divided into five equal parts from the bottom surface side to the top surface side after curing, and the density of each part was calculated by the method described above. It can be confirmed that the density decreases from the bottom surface side toward the top surface side, and the bottom surface side density is the density at the bottom surface side most in the division and becomes the maximum density. The density difference was calculated by (bottom surface side density−top surface side density) / bottom surface side density.

  From the comparison of Example 1, Example 2, and Example 7, it can be seen that the density difference increases as the filling height increases. Moreover, it turns out from a comparison of Example 2, Example 3, and Example 4 that a density difference becomes large, so that there is much iron powder filling amount. Moreover, while Example 1 used iron powder having a particle size of 75 μm or less, Example 5 screened only 38 μm or less, and Example 6 screened only 38 to 75 μm. It can be seen that the smaller one contributes to the density difference. Further, Example 7 and Example 8 compare the difference in curing agent, and it is shown that the density difference can be changed also by selection of the curing agent.

[Simulation of heat dissipation effect 1]
Next, the result of having confirmed the difference in internal temperature by the density difference and the heat dissipation effect by simulation is shown. FIG. 6 shows a simulated reactor structure. A cylindrical inner core portion 602, a coil 601 wound around the outer periphery thereof, an outer core portion 603 that covers them entirely, and a case 604 that accommodates the whole are configured. The inner core portion 602 is a uniform compacted body core with a density of 7.27 g / cm ³ and has dimensions of 29.8 × 61 mm in height. In addition, the coil 601 has an inner diameter of 33.8 mm and is wound with 51 turns of a wire material having a thickness of 0.8 mm and a width of 9.0 mm. The outer shape of the case 604 is 91.2 × 74.2 × 60 mm.

The outer core portion 603 is a mixture of a magnetic material and a resin, and has an outer dimension of 87.2 × 70.2 × 56 mm. The outer core portion has a density difference equally divided into 10 from the bottom surface to the top surface. Table 2 shows the conditions of each part with a difference in density, vol% is the volume% of the magnetic material in each part of the outer core part, D is the density (g / cm ³ ) of each part, and μ is the relative permeability of each part. The magnetic susceptibility W represents the 10 kHz iron loss (magnetic flux density amplitude Bm = 0.1 T) (kW / m ³ ) of each part, and λ represents the thermal conductivity (W / mK) of each part. The saturation magnetic flux density of each part is between 0.8 and 1.1T.

  First simulation results are shown in FIGS. Based on the results of magnetic field analysis of loss for each of the coil, inner core, outer core, and case, they were treated as heat sources in thermal analysis. The driving frequency was 10 kHz, the energization condition was 45 A, and the temperature on the cooling side for forced cooling was 50 ° C. Each figure shows the cross-sectional temperature distribution as a relative color distribution. As for the color, red has the highest temperature, yellow, green, and blue become lower in order, and purple shows the lowest temperature. The lower side of the figure is the bottom side, and the upper side is the top side. 7 and 8 are based on the outer core of Table 2 above, and FIG. 9 is a uniform outer core with no density difference for comparison. In FIG. 7, the bottom of the figure is the bottom side (high density side), and the bottom side is forcibly cooled. In FIG. 8, the lower side of the figure is the bottom side (high density side), and the top side is forcibly cooled. FIG. 9 shows a case where the bottom surface side is forcibly cooled in the case of uniform density.

  When comparing the results of FIG. 7 and FIG. 8, the maximum temperature is 6 ° C. lower on the cooling surface on the higher density side (bottom side) than on the lower density side (upper surface side). It was confirmed that heat can be efficiently dissipated. In other words, it is effective to cool the high density side with a density difference.

  When comparing the results of FIG. 7 and FIG. 9, the difference in the maximum temperature is 3 ° C. even if cooling is performed in the same manner. It was confirmed that heat could be dissipated.

[Simulation of heat dissipation effect 2]
Next, in order to see the difference in cooling effect due to the difference in density of the outer core portion in more detail, the result of detailed simulation by changing the density difference is shown. The external dimensions of the reactor set as a simulation target are the same as those in the simulation 1 described above. As an outer core part, the density between the bottom side and the top side is set to 10 levels, and the density difference is changed to 0%, 2%, 3%, 5%, 10%, 15%, and 20%. From 1 to Analysis Example 7, the cross-sectional temperature distribution in each case was obtained, and the maximum temperature of each part was obtained to confirm the cooling effect. Table 3 shows the density (g / cm ³ ) set in each analysis example as simulation conditions, Table 4 shows thermal conductivity (W / mK), Table 5 shows relative permeability, and Table 6 shows iron loss (magnetic flux density). Amplitude Bm = 0.1T) (kW / m ³ ) is shown.

  10 to 17, the difference in cross-sectional temperature distribution obtained for analysis examples 1 to 8 is represented by color distribution. As is clear from the comparison of the figures, it can be seen that the greater the density difference, the greater the cooling effect, and the lower the temperature. Table 7 shows the maximum temperature in each of the inner core portion, the coil, the outer core portion, and the case, the overall maximum temperature, the loss of the entire reactor, and the coil DC current 0A (zero) for each analysis example of FIGS. This is a summary of the inductance of the entire reactor in the magnetic field. From Table 7, it can be seen that the overall maximum temperature is the inner core portion. If the density difference is 2%, the maximum temperature can be lowered by 0.5 ° C., and the cooling effect increases in order as the density difference increases, and if 20% is added, the maximum temperature can be lowered by 5.1 ° C.

  Thus, it was confirmed that the entire reactor can be effectively cooled by providing a difference in density between the outer core portions and cooling the bottom surface side, which is the higher density side, as the cooling surface. Although the manufacturing method by sedimentation of the magnetic powder on the bottom side has been shown as an example, the relationship between the cooling surface and the density difference is the same even when the density difference is given by another manufacturing method. The heat resistance temperature of the epoxy resin and the heat resistance temperature of the electronic components around the reactor are about 140 to 150 ° C., and the maximum temperature of each part of the reactor is not allowed to be higher than these heat resistance temperatures, which is a little compared with the heat resistance temperature. However, it is desirable to make it low. In addition, reducing the temperature also has the effect of reducing coil loss. Furthermore, although the cooling temperature is 50 ° C. here, it may be set to a temperature higher than 50 ° C. Therefore, it is desired that the temperature of each part of the reactor is made slightly lower than the heat-resistant temperature. Yes. Although the effect of cooling increases as the density difference increases, it is preferable that there is a density difference of 3% or more to produce an effect of more than 0.5 ° C. as a significant difference compared to the case where there is no density difference. It can be seen that 5% or more for the above and 10% or more is more preferable for 2 ° C or more. When focusing only on the temperature difference, it is preferable to further increase the density difference.

  On the other hand, when the density difference is increased, the inductance of the reactor as a whole is reduced. Inductance is proportional to the square of the number of coil turns and the cross-sectional area, and in order to obtain the same inductance, it is necessary to increase the number of turns of the coil or increase the cross-sectional area, and it is necessary to increase the size of the entire reactor. . In the case of the above simulation, in the case of Analysis Example 7 with a density difference of 20%, the inductance is reduced by 0.2% compared to Analysis Example 1. As a result of calculation from this viewpoint, in order to suppress the decrease in inductance to 1.5% or less, the density difference is preferably 45% or less, and in order to reduce to 0.2% or less, the density difference is 20% or less. It has been found that it is more preferable to do this. Moreover, if the density difference is increased, the loss of the entire reactor also increases. The allowable range of increase in loss for in-vehicle use is considered to be up to about 10%, and in order to suppress the increase in loss to 10% or less, the density difference is preferably 45% or less. Furthermore, in order to suppress the loss increase to 1.5% or less, it is preferable that the density difference is 20% or less.

The above description includes the following features.
(Supplementary Note 1) A coil, a core, and a case that accommodates the coil and the core, wherein the core includes an inner core portion disposed inside the coil, and a part or all of the outside of the coil. An outer core portion is covered, and the outer core portion is a reactor formed of a mixture of a magnetic material and a resin, and bubbles having a diameter of 300 μm or more exist in the mixture of the magnetic powder and the resin after the resin is cured. Reactor characterized by not. Since there are few air bubbles in the mixture of the magnetic powder and resin after hardening, it can be set as the outer core excellent in thermal conductivity. Further, since the number of bubbles is small, the deviation from the designed magnetic characteristic distribution becomes small, and it becomes easy to realize desired characteristics.
(Additional remark 2) Of the wall surfaces constituting the case, at least one of the surfaces substantially parallel to the axial direction of the coil is configured as a cooling surface cooled from the outside, and the magnetic material in the outer core portion is made of The reactor according to appendix 1, wherein the density distribution is a distribution that increases from the axis of the coil toward the cooling surface.
(Supplementary Note 3) A coil and a case having a cooling surface cooled from the outside are prepared, and the coil is placed in the case so that the cooling surface of the case and the axial direction of the coil are substantially parallel to each other. A storing step for storing, a filling step for filling the case with a mixture containing a magnetic material and a resin in a state where the cooling surface is the bottom surface, and a curing step for curing the filled mixture after the filling step. And a method of manufacturing a reactor, comprising a step of holding the mixture at a temperature at which the viscosity of the mixture is substantially minimized between the filling step and the curing step.

  The reactor of this invention can be utilized for the components of power converters, such as a converter mounted in vehicles, such as a hybrid vehicle, a plug-in hybrid vehicle, an electric vehicle, and a fuel cell vehicle, and an air conditioner.

DESCRIPTION OF SYMBOLS 101 Reactor 102 Converter case 103 Reactor case 201 Coil 201w Winding 202 Inner core part 203 Outer core part 204 Core 205 Coil axial direction 206 Direction along the side wall of the case 301, 401 Inner wall surface 402 Coil outer peripheral surface 501 End portions of coil 502 Support portion 503 Inner bottom surface of case 601 Coil 602 Inner core portion 603 Outer core portion 604 Case 701, 801, 901 Inner core 702, 802, 902 Coil 703, 803, 903 Mixture 704, 804, 904 Case 710 Permanent magnet 810 turntable

Claims (9)

A coil, a core, and a case that accommodates the coil and the core, wherein the core covers an inner core portion that is disposed inside the coil, and an outer core portion that covers a part or all of the outside of the coil. And the outer core part is a reactor formed of a mixture of a magnetic material and a resin,
Of the wall surfaces constituting the case, at least one surface substantially parallel to the axial direction of the coil is configured as a cooling surface cooled from the outside,
The reactor is characterized in that the distribution of the density of the magnetic material in the outer core portion is a distribution that increases from the axis of the coil toward the cooling surface.   The reactor according to claim 1, wherein the cooling surface is a surface other than a bottom surface of the case.   The reactor according to claim 1 or 2, wherein the difference in the density is more than 0% and 45% or less with respect to the cooling surface side.   The reactor according to claim 3, wherein the density difference is 3% or more.   The reactor of any one of Claims 1-4 arrange | positioned so that the said coil may contact | connect the said cooling surface.   The reactor according to any one of claims 1 to 5, wherein a part of the outer peripheral surface of the coil is exposed from the outer core portion. A coil assembly including a coil and an inner core inserted through the coil, and a case having a cooling surface cooled from the outside are prepared, and the cooling surface of the case and the axial direction of the coil are A storing step of storing the coil assembly in the case so as to be substantially parallel;
A filling step of filling the case with a mixture containing a magnetic material and a resin in a state where the cooling surface is a bottom surface;
After the filling step, it has a curing step of curing the filled mixture,
A method for producing a reactor, comprising a step of holding the mixture at a temperature at which the viscosity of the mixture is substantially minimized between the filling step and the curing step. A coil assembly including a coil and an inner core inserted through the coil, and a case having a cooling surface cooled from the outside are prepared, and the cooling surface of the case and the axial direction of the coil are A storing step of storing the coil assembly in the case so as to be substantially parallel;
A filling step of filling the case with a mixture containing a magnetic material and a resin;
After the filling step, it has a curing step of curing the filled mixture,
A method for manufacturing a reactor, wherein an external magnetic field is applied so that the magnetic material moves to the cooling surface side in the filling step or after the filling step. A coil assembly including a coil and an inner core inserted through the coil, and a case having a cooling surface cooled from the outside are prepared, and the cooling surface of the case and the axial direction of the coil are A storing step of storing the coil assembly in the case so as to be substantially parallel;
A filling step of filling the case with a mixture containing a magnetic material and a resin;
After the filling step, it has a curing step of curing the filled mixture,
A method for manufacturing a reactor, wherein the case is rotated so that a centrifugal force in a direction in which the magnetic material moves is generated on the cooling surface side in the filling step or after the filling step.