JP6557527B2 - Reactor - Google Patents

Description

  The present invention relates to a reactor including a core and a coil wound around the core and the core.

  Reactors are used in various applications including drive systems for hybrid vehicles, electric vehicles, fuel cell vehicles, and the like. For example, as a reactor used in an in-vehicle booster circuit, after a coil is wound around a resin bobbin arranged around an annular core, these are housed in a metal case, and a filler is poured into the case. Many hardened ones are used (see, for example, Patent Document 1).

  As the coil, for example, in order to cope with a large current of 50 A or more, it is common to use a coil constituted by a rectangular wire. In order to suppress the winding space as much as possible, an edgewise coil is used as the coil.

JP 2011-124267 A

  As a conventional core, a ring-shaped core member using a U-shaped core member (hereinafter also referred to as a U-shaped core) has been used. For example, as shown in FIG. 12, a core formed by abutting both ends of two U-shaped cores, or a core that forms an annular shape by combining a U-shaped core and an I-shaped core has been used. When winding edgewise winding in such a core shape, it is necessary to bend the inner shape of the coil at four locations, which will increase the number of winding man-hours, and it is necessary to add equipment for that, Product cost increased.

  Further, as the current increases, the cross-sectional dimension of the rectangular wire constituting the coil also increases, and it is necessary to increase the bending of the coil in order to prevent damage to the insulation coating of the wire when performing edgewise winding. Therefore, the distance between the core and the coil inevitably increases. As a result, there has been a problem of an increase in the size of the reactor and an increase in loss due to an increase in DC resistance.

  The problem of the loss deterioration accompanying the increase in the product cost, the reactor physique, and the increase in DC resistance is partly because the U-shaped core was used as the core of the reactor.

  On the other hand, in the U-shaped core, the burden on the mold is great when molding, and the durability of the mold is lowered. That is, when a U-shaped core made of a dust core is formed, the pressing force per unit area applied to the magnetic powder constituting the dust core is two to three times that of the ferrite core. The burden of is great. In particular, as shown in FIG. 13, when a U-shaped core is molded, stress concentrates on the edge portion of the U-shape, so that the durability of the mold is reduced and crack C is generated. There was a case where it was damaged.

  Further, in order to produce a reactor core for high frequency applications, a powder magnetic core using hard magnetic powder is necessary. However, if the magnetic powder is hard, the moldability deteriorates and the productivity deteriorates.

  By the way, a magnetic flux is generated in the annular core by energizing the coil, and a closed magnetic path is formed by the magnetic flux passing through the core. This magnetic flux tends to pass inside the annular core. Therefore, the outer portion inside the annular core has a small amount of magnetic flux passing therethrough, and the contribution to the magnetic properties is small. In particular, a core portion around which a coil is not wound, that is, a so-called yoke portion, has a small contribution to the magnetic characteristics, which increases the weight, volume, and cost of the reactor.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to reduce the burden on the mold and improve productivity, and a core capable of reducing the physique and cost, It is to provide a reactor using the core.

The reactor according to the present invention is a core used for a reactor, in which a coil is wound around at least a part of a plurality of core members, and a pair of legs around which the coil is wound And a core having a pair of back surfaces connecting the pair of legs, and a coil wound around the legs of the core, and having the following configuration.
(1) Before Kiashi part is a dust core sectional shape has a cylindrical shape of circular or elliptical shape, formed of a material having a low iron loss than the rear portion, the rear portion, the cylindrical It has a notch part notched in the shape along the side surface of a leg part, and the side surface of the said column-shaped leg part is arrange | positioned along the said notch part, and comprises cyclic | annular shape.

The reactor according to the present invention is a core used for a reactor, in which a coil is wound around at least a part of a plurality of core members, and a pair of legs around which the coil is wound And a core having a pair of back surfaces connecting the pair of legs, and a coil wound around the legs of the core, and having the following configuration.
(2 ) The leg portion is a dust core having a cylindrical shape with a circular or elliptical cross-section, and is made of a material having a lower iron loss than the back portion , and the back portion is a substantially hexagonal flat plate And both end surfaces of the pair of leg portions are arranged so as to face the opposing surfaces of the pair of back surface portions to form an annular shape.

Moreover, the reactor of this invention may have at least any one of the following structures.
( 3 ) The leg portion has a circular or oval end surface exposed.
( 4 ) The said leg part is comprised including the magnetic powder whose Vickers hardness is 50 or more .
(5) The coil is configured by alpha winding, and the coil is mounted around the leg of the columnar shape.
(6) The leg portion has a higher density than the back surface portion.
(7) The powder magnetic core of the said leg part was comprised using Fe-Si alloy, Sendust, an amorphous alloy, or these 2 or more types of mixed powder as magnetic powder.
(8) The coil is made of a rectangular wire.
(9) A resin member that covers the core is provided, and a gap is formed between the leg portion and the back surface portion by the thickness of the resin member.

  ADVANTAGE OF THE INVENTION According to this invention, while reducing the burden on a metal mold | die and improving productivity, the core which can reduce a physique and cost, and the reactor using the core can be obtained.

It is a perspective view of the reactor which concerns on 1st Embodiment. It is a disassembled perspective view of the reactor which concerns on 1st Embodiment. It is a perspective view of the annular core concerning a 1st embodiment. It is a perspective view of the reactor which concerns on 2nd Embodiment. It is a disassembled perspective view of the reactor which concerns on 2nd Embodiment. It is a perspective view of the annular core which concerns on 2nd Embodiment. It is a figure which shows the modification of the back part which concerns on 2nd Embodiment. It is a table | surface which shows the stress evaluation to the metal mold | die in leg part shaping | molding. It is a perspective view of the annular core used for verification of the characteristic of a reactor. It is a table | surface which shows the characteristic of a reactor. It is a graph which shows the inductance characteristic of an Example and a comparative example. It is a perspective view of the cyclic | annular core comprised by the conventional U-shaped core. It is a figure for demonstrating the burden to the metal mold | die in a prior art.

  Hereinafter, a core according to an embodiment of the present invention and a reactor using the core will be described with reference to the drawings.

[1. First Embodiment]
[1-1. Constitution]
FIG. 1 is a perspective view of a reactor according to the present embodiment, and FIG. 2 is an exploded perspective view of the reactor according to the present embodiment.

  The reactor of the present embodiment is a large-capacity reactor used in, for example, a hybrid vehicle, an electric vehicle, a fuel cell vehicle drive system, and the like. The reactor is the main component of the electric circuit mounted on these automobiles. This electric circuit includes a semiconductor switching element such as an IGBT in addition to a reactor. The reactor converts the electrical energy supplied from the external power source into magnetic energy by turning on and off the semiconductor switching element at high speed, repeatedly stores and releases the energy, and suppresses current and voltage.

  As shown in FIGS. 1 and 2, the reactor includes an annular core 10, coils 5 a and 5 b mounted on a part of the outer periphery of the annular core 10, and covers the outer periphery of the annular core 10. 5b, and a resin member 20 that insulates 5b.

  FIG. 3 is a perspective view of the annular core 10. As shown in FIG.2 and FIG.3, the cyclic | annular core 10 consists of a some core member, and is comprised so that it may become cyclic | annular. As these core members, a pair of columnar leg portions 11 and a block-like back surface portion 12 connected to both ends of the leg portions 11 are provided. That is, the annular core 10 is arranged in an annular shape so that both end faces of the pair of leg portions 11 arranged in parallel face each other on the opposite surfaces of the back surface portion 12. In addition, although the leg part 11 and the back surface part 12 are connected via the resin member 20 in this embodiment, they may be connected via a spacer or may be connected so as to be in direct contact.

  The leg portion 11 has a columnar shape with a rounded peripheral surface. In the present embodiment, the leg portion 11 has a cylindrical shape. This cylindrical shape includes a case where the shape of the cross section perpendicular to the extending direction of the column is a circle or an ellipse. In other words, the cross-sectional shape orthogonal to the direction in which the column of the leg 11 extends does not have an edge portion where stress is concentrated. Coils 5 a and 5 b are wound around the leg portion 11, and when a current flows through the coils 5 a and 5 b, magnetic flux is generated in the leg portion 11.

  The leg 11 may be composed of a plurality of cylindrical powder magnetic cores. For example, a cylindrical shaft may be aligned and arranged with a predetermined gap.

  The back surface part 12 is a block-shaped core member, and is a flat hexagonal core member here. The coils 5 a and 5 b are not wound around the back surface portion 12. The back surface portion 12 is a core member through which the magnetic flux generated in the leg portion 11 passes, and is also referred to as a yoke portion. The approximate hexagonal shape includes a hexagonal shape and a hexagonal shape with rounded corners.

  As apparent from FIG. 3, the back surface portion 12 is configured such that the length in the height direction is longer than the diameter of the leg portion 11. The length in the height direction is the length of the back surface portion 12 in the z direction shown in FIG. 3 (symbol H in FIG. 3), and is also simply referred to as the height of the back surface portion 12 below. The length in the height direction of the back surface portion 12 will be described in detail. Since the back surface portion 12 is a portion through which the magnetic flux passes, it is necessary to secure a cross-sectional area thereof. For that purpose, it is necessary to lengthen the height of the back surface portion 12 or the thickness of the back surface portion 12 in the same direction as the extending direction of the leg portion 11, but the dead space of the coils 5a and 5b around the leg portion 11 is effective. From the viewpoint of utilization and overall size reduction, the thickness is not increased, but the height is made longer than the diameter of the legs 11 to ensure the core cross-sectional area. In addition, the thickness of the back surface part 12 said here means the length of the back surface part 12 of the same direction as the extension direction of the leg part 11, and this thickness direction and a height direction have a relationship orthogonal.

  Examples of the leg portion 11 and the back surface portion 12 will be described later in detail, but the leg portion 11 and the back surface portion 12 are made of a dust core. The dust core includes a magnetic powder having a Vickers hardness of 50 or more. Vickers hardness is one measure of the hardness of a substance and is defined by the ratio of the load to the sample and the surface area of the indentation. As the magnetic powder having a Vickers hardness of 50 or more, pure iron, Fe-3.5% Si alloy, Sendust, Fe-6.5% Si alloy, amorphous alloy, or a mixed powder of two or more of these is used. be able to. Moreover, as shown in the Example mentioned later, the leg part 11 may be comprised with the material of a lower iron loss than the back part 12. As shown in FIG. The leg portion 11 may have a higher density than the back surface portion 12. In terms of the above materials, pure iron, Fe-3.5% Si alloy, Fe-6.5% Si alloy, Sendust, and amorphous alloy have the lowest iron loss in this order.

  The resin member 20 is a member made of resin that covers the periphery of the annular core 10, and has a shape that follows the annular core 10. The resin member 20 includes a resin body 21 that covers the periphery of the leg portion 11 and a resin body 22 that covers the periphery of the back surface portion 12. As the resin constituting the resin member 20, for example, an epoxy resin, an unsaturated polyester resin, a urethane resin, BMC (Bulk Molding Compound), PPS (Polyphenylene Sulfide), PBT (Polybutylene Terephthalate), or the like can be used.

  Since the resin body 21 covers the periphery of the columnar leg portion 11, the shape thereof is a cylindrical shape. From both ends of the resin body 21, the circular end surfaces of the leg portions 11 are exposed. The resin body 22 has a shape that follows the back surface portion 12, and a housing portion 22 a is provided at a location where the leg portion 11 is connected. The accommodating part 22a is used as positioning of the leg part 11 at the time of a reactor assembly. That is, one end of the leg portion 11 is attached to the recessed portion of the accommodating portion 22a. A gap is provided between the leg portion 11 and the back surface portion 12 by the thickness of the resin body 22. Further, the resin body 22 is provided with an opening 22b from which a part of the back surface portion 12 is exposed.

  Examples of the method for manufacturing the resin bodies 21 and 22 include a molding method in which a resin is molded using the leg portions 11 and the back surface portion 12 as inserts.

  The coils 5a and 5b are conductive wires with insulation coating, and are constituted by alpha winding. Alpha winding is a method of winding an insulation-coated conductive wire so as to be laminated from the inside to the outside. The coils 5a and 5b may be edgewise coils. However, since the coils 5a and 5b of the present embodiment are alpha-wound, there are locations where the edgewise coils are bent at four locations with a rectangular cross section. On the other hand, the bending of the coils 5a and 5b is constant. The coils 5 a and 5 b are provided around the leg portion 11. That is, the coils 5a and 5b are attached by inserting the leg portions 11 into the air core portions of the coils 5a and 5b when the reactor is assembled. In the present embodiment, the coils 5a and 5b are made of rectangular wires, but may be made of round wires.

  Ends 50a and 50b of the coils 5a and 5b are drawn out, and the ends 50a and 50b are electrically connected to an external device such as an external power source. Here, the coils 5a and 5b are connected by a connecting wire made of the same material as that of the coils 5a and 5b, and the current flowing from either one of the end portions 50a and 50b is transferred to the outside from the other end portions 50a and 50b. leak. When the coils 5a and 5b are energized, a magnetic flux penetrating through the air cores of the coils 5a and 5b is generated.

[1-2. Manufacturing method of core member]
The manufacturing method of the column-shaped leg part 11 and the block-shaped back part 12 which comprise the cyclic | annular core 10 is demonstrated. The leg part 11 and the back part 12 consist of a dust core, and both are different in shape, and the manufacturing method is basically the same. Below, the manufacturing method of a powder magnetic core is demonstrated.

The manufacturing method of a dust core is roughly divided into the following steps.
(A) A mixing step in which a silicone resin is mixed with the magnetic powder to form an insulating film.
(B) A pressure forming step of pressure forming the mixture obtained in the mixing step.
(C) An annealing process for annealing the molded body obtained in the pressure molding process.

Hereinafter, each step will be described in detail.
(A) Mixing step In the mixing step, a silicone resin is mixed with the magnetic powder, and an insulating coating made of the silicone resin is formed on the surface of the magnetic powder.

  As the magnetic powder, a magnetic powder whose main component is a ferromagnetic element of a transition element such as Fe, Co, or Ni is used. In particular, magnetic powder containing Fe as a main component, and pure iron powder, Fe—Si alloy, Sendust alloy (Fe—Si—Al alloy), amorphous powder, or the like may be used. The magnetic powder containing Fe as a main component may contain Co or Al. As the magnetic powder, a mixed powder of a plurality of types of magnetic powders may be used. Examples thereof include mixed powders of pure iron powder and Fe-49Co-2V (permendur) powder, pure iron powder and Fe-3Si powder, sendust (Fe-9Si-6Al) powder and pure iron powder, and the like. The Vickers hardness of the magnetic powder used for the material of the dust core is preferably 50 or more.

  The particle size of the magnetic powder is 1 to 300 μm, preferably 20 to 200 μm. If it exceeds 300 μm, it is difficult to increase the density and reduce eddy current loss, and if it is less than 1 μm, it is difficult to reduce the hysteresis loss. Here, the “particle diameter” is a median diameter determined when classified by a sieve having a predetermined mesh size.

  The method for producing the magnetic powder is not particularly limited, but it may be processed into a spherical shape by a jet mill or the like after the powder is produced. In general, the magnetic properties are improved by using a spherical shape, but the anchor effect between the powders is lowered, and the mechanical strength is lowered, so that the use tends to be avoided. However, in this embodiment, since the shape of the leg portion 11 is a columnar shape, it can be pressed with a high pressure, so that a molded body with improved mechanical strength can be obtained even with a spherical magnetic powder. Can do.

  As the silicone resin, a thermosetting type that condenses and cures by heat and a room temperature curable type that cures at room temperature can be used. In the present embodiment, a thermosetting type is used in which crosslinking by siloxysan bond proceeds at about 70 to 300 ° C., and condensation and curing occur. As the silicone resin, resin-based, silane compound-based, rubber-based silicone, silicone powder, organically modified silicone oil, or a composite of at least two of these can be used. In particular, a straight silicone resin is preferable from the viewpoint of heat resistance, weather resistance, moisture resistance, electrical insulation, and ease of mixing.

  The adhesion amount of the silicone resin is preferably 0.01 to 1.0 wt% with respect to the magnetic powder. When the adhesion amount is less than 0.01 wt%, the insulating property is lowered and the electric resistance is lowered. If the adhesion amount is more than 1.0 wt%, the powder after heat drying tends to become lumpy, and the molded body after pressure molding is affected by springback because the film thickness of the silicone resin around the magnetic powder becomes large. Therefore, it is difficult to increase the density and cracks easily occur.

  After the mixing step, the magnetic powder is dried by heating. When the mixture obtained after this drying step is agglomerated and solidified, it may be crushed or crushed.

(B) Pressure molding process The mixture obtained after the mixing process is filled in a mold having a cavity having a predetermined shape, and the mixture is pressure molded by a press to produce a molded body. The cavity has a cylindrical shape when the leg portion 11 is manufactured, and a block shape when the back surface portion 12 is manufactured. For example, in the case of the leg part 11, it presses from the circular-shaped both end surfaces among the surfaces which comprise cylindrical shape. Therefore, both end surfaces of the molded body are flat.

  When filling the mixture into the mold, a lubricant may be added to the inner wall of the mold or the mixture. As the lubricant, metal soap such as zinc stearate, calcium stearate and lithium stearate, waxy or fatty material such as wax, ethylene bis-stearamide composition, silicone oil and the like can be used.

  The molding pressure for producing the molded body is preferably 1480 MPa or less from the viewpoint of mold life and productivity. In order to further strengthen the strength of the molded body, for example, a binder such as a low melting glass powder or water glass (sodium silicate) may be added to the mixture obtained after mixing.

(C) Annealing process An annealing process heat-processes the molded object obtained by the press-molding process. The annealing step is performed for the purpose of removing residual strain and residual stress in the molded body, and the annealing step can reduce the coercive force and hysteresis loss of the dust core.

  Residual strain is more effectively removed as the annealing temperature is higher, but even a heat-resistant silicone resin may cause partial breakdown in the insulating coating. Therefore, it is preferable to determine the annealing temperature in consideration of the heat resistance of the silicone resin and the thermal expansion of the magnetic powder. For example, if the annealing temperature is 500 to 800 ° C., it is possible to achieve both the removal of residual strain and the protection of the insulating coating of the silicone resin.

  In the annealing step, it is better to hold the molded body once in a temperature region where the lubricant decomposes before the temperature of the molded body reaches the annealing temperature. This is because when the temperature is rapidly increased to the annealing temperature, the decomposition gas of the lubricant is generated abruptly from the inside of the molded body, so that cracks are generated inside the molded body and the mechanical strength may be significantly reduced.

The annealing atmosphere is preferably a non-oxidizing atmosphere. For example, a vacuum atmosphere or an inert gas atmosphere. Examples of the inert gas atmosphere include H ₂ , N ₂ , and Ar atmospheres. By setting it as a non-oxidizing atmosphere, it can suppress that a powder magnetic core and the magnetic powder which comprises this are excessively oxidized, and a magnetic characteristic falls.

  The heating time in the annealing process is preferably 10 to 180 minutes in consideration of the effects and economics of the annealing process. More preferably, it is 30 to 90 minutes.

[1-3. Action / Effect]
(1) The core of the present embodiment is a core that is formed into a ring shape by a plurality of core members, the coils 5a and 5b are wound around at least a part thereof and used for the reactor, and the coils 5a and 5b are surrounded around the core. A pair of leg portions 11 around which a pair of legs 11 is wound, and a pair of back surface portions 12 connecting the pair of leg portions 11, and the leg portion 11 is a pressure having a circular or elliptical column shape. The back surface 12 is a substantially hexagonal flat plate, and the both end surfaces of the pair of leg portions 11 are arranged so as to face the opposite surfaces of the pair of back surface portions 12 to form an annular shape. did.

  Thereby, when producing the leg part 11, since the cross-sectional shape is rounded and there is no edge part, the stress to the mold is dispersed without being concentrated in one place, so the burden on the mold is reduced. While being able to reduce, the productivity of the annular core 10 can be improved. Moreover, since the leg part 11 around which the coil is wound is formed in a columnar shape, the coils 5a and 5b wound around the leg part 11 can be brought closer to the leg part 11, and the reactor size can be reduced.

  Furthermore, in the annular core 10, the magnetic flux tends to pass inside the annular core 10, and the contribution of the outer portion is small. In the present embodiment, since the back surface portion 12 is a substantially hexagonal flat plate, the amount of core usage for the four corners is reduced compared to the rectangular shape, so the weight, volume, and cost of the annular core 10 and the reactor are reduced. be able to.

(2) The leg portion 11 includes a magnetic powder having a Vickers hardness of 50 or more. Even if it does in this way, the moldability of the leg part 11 can be improved. That is, in general, when a hard magnetic powder is formed by pressing to form a powder magnetic core, the formability deteriorates by the amount of the hard magnetic powder. In the present embodiment, even if it is a hard magnetic powder having a Vickers hardness of 50 or more, since the shape of the leg portion 11 is a cylindrical shape, the stress due to pressing does not concentrate at a specific location, and pressing is performed at a high pressure. Can be molded, and the moldability can be improved.

(3) The reactor of this embodiment is provided with the annular core 10 provided with the leg portion 11 having a columnar shape, and the coils 5 a and 5 b wound around the leg portion 11 of the annular core 10. In particular, the coils 5 a and 5 b are configured by alpha winding, and the coils 5 a and 5 b are mounted around the columnar leg portion 11. The shape of the leg 11 around which the coils 5a and 5b are wound is a columnar shape, and the coils 5a and 5b are alpha-wound so that they can be arranged closer to the leg 11. Therefore, the size of the reactor can be reduced, and the coils 5a and 5b themselves are also reduced, so that the direct current resistance can be further reduced.

(4) Of the annular core 10, the legs 11 around which the coils 5 a and 5 b are wound have a higher density than the back surface portion 12 around which the coils 5 a and 5 b are not wound. A portion where the magnetic flux is generated is the leg portion 11 around which the coils 5a and 5b are wound, and the back surface portion 12 where the coils 5a and 5b are not wound only serves as a path through which the generated magnetic flux passes. Therefore, high inductance characteristics can be obtained while suppressing an increase in iron loss even if the leg portions 11 where the magnetic flux is generated are made high density and the back surface portion 12 where the magnetic flux is passed are made low density.

(5) The leg portion 11 is made of a material having a lower iron loss than the back surface portion 12. Thereby, the heat generation of the leg portion 11 can be reduced, and even when the coils 5a and 5b are wound around the leg portion 11 and the heat dissipation is deteriorated, the heat can be covered.

(6) The dust core of the leg portion 11 is configured using a Fe—Si alloy, Sendust, amorphous alloy, or a mixture of two or more of these as magnetic powder. Thereby, the reactor of a high frequency use can be obtained. That is, since the leg portion 11 has a cylindrical shape, the leg portion 11 can be configured using magnetic powder having a high Vickers hardness. Here, as shown in FIG. 8, the frequency band tends to increase as the Vickers hardness increases. Therefore, since a high Vickers hardness such as Fe-Si alloy, Sendust, amorphous alloy, or a mixed powder of two or more of these is used as the magnetic powder, a reactor for high frequency applications can be obtained. The high frequency referred to here is, for example, 20 kHz to 100 kHz.

(7) The coils 5a and 5b are made of rectangular wires. Thereby, the cross-sectional area of a wire is comparatively larger than a round wire etc., for example, and the reactor for a large current use can be obtained. Furthermore, the space factor can be increased compared to the round line, and the reactor can be downsized.

(8) The resin member 20 that covers the annular core 10 is provided, and a gap is formed between the leg portion 11 and the back surface portion 12 by the thickness of the resin member 20. Thereby, leakage of the magnetic flux of the coils 5a and 5b can be suppressed, and loss can be reduced. Further, since there is no need to provide a separate gap spacer, it is not necessary to attach the spacer when assembling the reactor, and assemblability can be improved.

[2. Second Embodiment]
[2-1. Constitution]
A second embodiment will be described with reference to FIGS. The basic configuration of the second embodiment is the same as that of the first embodiment. Therefore, only a different point from 1st Embodiment is demonstrated, the same code | symbol is attached | subjected about the same part as 1st Embodiment, and detailed description is abbreviate | omitted.

  FIG. 4 is a perspective view of the reactor of the second embodiment. FIG. 5 is an exploded perspective view of the reactor according to the second embodiment. FIG. 6 is a perspective view of the annular core of the second embodiment.

  In the second embodiment, the configuration of the annular core 10 is different. That is, the annular core 10 of the second embodiment has a pair of columnar legs 11 and a pair of back surfaces 13 sandwiched between them, and the shapes of the back surfaces 13 are different. As in the first embodiment, the leg 11 is a cylindrical powder magnetic core having a circular or elliptical cross section. The back surface portion 13 is in a block shape like the back surface portion 12 of the first embodiment, but the overall shape is a substantially rectangular shape, and a notch portion 13a that is notched so that the side portion is recessed inward is provided. Is provided. In the present embodiment, the cutout portion 13a has a shape that matches the shape of the outer peripheral surface of the leg portion 11, and has an arc shape.

  As a modification of the back surface portion 13, the notch portion 13a of the back surface portion 13 may be a circular opening 13b as shown in FIG. 7, and the leg portion 11 may be inserted into the opening 13b. In this case, the end surface of the leg part 11 is exposed from the opening 13b.

  The annular core 10 has an annular shape in which a back surface portion 13 is disposed along the side surfaces of a pair of parallel leg portions 11. In other words, the circular plane of the leg 11 is exposed to the outside. In addition, in FIG. 6, the notch part 13a of the back surface part 13 and the side surface of the leg part 11 are spaced apart. This is because the leg portion 11 is covered with the resin body 21 and the notch portion 13a of the back surface portion 13 is also covered with the resin body 24, and these portions have a thickness. However, you may make the side surface of the leg part 11 contact the notch part 13a directly.

  The resin member 20 includes a resin body 23 that covers the periphery of the leg portion 11 and a resin body 24 that covers the back surface portion 13. The resin body 23 is a member made of resin that covers the periphery of the leg portion 11, and the coils 5 a and 5 b are mounted around the resin body 23. The resin body 23 has a cylindrical shape like the resin body 21 of the first embodiment, and both ends thereof are open, and the circular plane of the leg portion 11 is exposed.

  The resin body 24 is provided with an opening 24 a into which the leg portion 11 is inserted and an opening 24 b through which the side surface of the back surface portion 13 is exposed. The opening 24 a has a circular shape following the cross-sectional shape of the leg 11, and is provided through the resin body 24. Therefore, when the end of the leg 11 covered with the resin body 23 is inserted into the opening 24a, the circular end surface of the leg 11 is exposed to the outside from the opening 24a.

  The resin member 20 functions as a gap between the end side surface of the leg portion 11 and the cutout portion 13 of the back surface portion 13. That is, the resin body 23 covers the leg portion 11 except for the end surface of the leg portion 11, and the resin thickness around the end portion of the leg portion 11 becomes an element constituting a gap with the back surface portion 13. 13 covers the notch 13 a, and the resin thickness of the portion covering the notch 13 a becomes an element constituting a gap with the end side surface of the leg 11. You may make it manage the gap between the leg part 11 and the notch part 13a only with either the resin body 23 or the resin body 24. FIG.

[2-2. Action / Effect]
(1) As for the core of this embodiment, the leg part 11 is a powder magnetic core which has a cylindrical shape whose cross-sectional shape is circular or elliptical, and the back surface part 13 followed the side surface of the cylindrical leg part 11. It has a cutout portion 13a cut out in a shape, and the side surface of the columnar leg portion 11 is arranged along the cutout portion 13a to form an annular shape.

  Thus, as in the first embodiment, when the leg portion 11 is manufactured, the cross-sectional shape is rounded and there is no edge portion, so that the stress on the mold can be prevented from being concentrated in one place. The burden on the mold can be reduced, and the productivity of the annular core 10 can be improved.

  Further, by providing the notch portion 13a, the back surface portion 13 further reduces the core usage of the outer portion of the annular core 10 with less magnetic flux passing therethrough than the back surface portion 12 of the first embodiment. Since the leg portion 11 can be arranged so as to bite into the back surface portion 13 as much as the cutout portion 13a is provided, the weight, volume, and cost of the annular core 10 and the reactor can be reduced. Furthermore, the weight, volume, and cost of the annular core 10 and the reactor can be reduced as compared with the back surface portion 13 provided with an opening in a flat plate shape as shown in FIG. Furthermore, the notch 13a can function as a positioning member for the leg 11.

(2) The leg portion 11 has a circular or elliptical end surface exposed to the outside. Thereby, in the columnar leg portion 11 in which magnetic flux is generated, heat generated by the iron loss can be efficiently released to the outside. For example, when a reactor using the core of the present embodiment is accommodated in a case made of a heat-dissipating material such as aluminum, it becomes possible to accommodate an exposed circular or elliptical end surface in contact with the case. , Heat dissipation can be improved.

  Moreover, the leg part 11 may be inserted into the opening 13b of the back surface part 13 shown in FIG. 7, and the circular or elliptical end face of the leg part 11 may be exposed to the outside. Thereby, as above-mentioned, heat dissipation can be improved.

[3. Example]
[3-1. Evaluation of stress on mold in leg molding]
The stress evaluation on the mold in the leg molding will be described. In the first and second embodiments, the shape of the leg portion 11 is a cylindrical shape. A sample of the columnar leg portion 11 (also referred to as “columnar core”) is manufactured through the above-described (a) mixing step, (b) pressure forming step, and (c) annealing step.

  In more detail, in the mixing step, the magnetic powder has an average particle diameter (D50) of 30 to 50 μm in the mixing step, and the magnetic powder as the main material of each sample is pure iron and Fe-3.5% Si alloy, respectively. Sendust, Fe-6.5% Si alloy, and amorphous alloy. The addition of the silicone resin was 0.8 wt% with respect to the magnetic powder.

  In the pressure molding step, the lubricant was Kenolube (manufactured by Höganäs), and the amount added was 0.5 wt% with respect to the mixture obtained in the mixing step. The molding pressure ratio when filling the mixture containing the lubricant into the mold cavity and pressurizing with a press to produce a cylindrical shaped body is as shown in FIG. In the order of 1.00, 1.20, 1.35, 1.50, and 2.00.

  A U-shaped core is used as a comparative example. The production conditions are the same as those for the cylindrical core sample. The U-shaped core differs from the cylindrical core only in shape, and the materials of the magnetic powder were pure iron, Fe-3.5% Si alloy, Sendust, Fe-6.5% Si alloy, and amorphous alloy, respectively.

  The specific resistance, Vickers hardness, and molding pressure ratio of each magnetic powder are shown in FIG. The molding pressure ratio is based on the pressure when molding the U-shaped core and the cylindrical core with pure iron. As shown in FIG. 8, there is a correlation between specific resistance, Vickers hardness, and molding pressure ratio. That is, as the specific resistance increases, that is, the iron loss decreases, the Vickers hardness increases. When the hardness of the magnetic powder is increased, the magnetic powder is not deformed even when pressed at the same pressure, so that the molding density is lowered, and the specific resistance and magnetic characteristics are lowered. Therefore, in order to increase the molding density, it is necessary to press at a high pressure, and cracks are likely to occur in the mold.

  It was verified by stress analysis whether cracks occurred in the mold from the maximum stress value on the mold. The maximum stress value is the maximum stress value applied to the mold when pressed at the pressure indicated by the molding pressure ratio shown in FIG. FIG. 8 shows the case where no crack occurs as “Good” and the case where a crack occurs as “NG”.

  As shown in FIG. 8, when producing a U-shaped core, when the magnetic powder is pure iron and Fe-3.5% Si alloy, cracks do not occur in the mold, but Sendust, Fe-6.5. In the case of% Si alloy or amorphous alloy, cracks occur in the mold. This is because, when a hard magnetic powder is used, the moldability deteriorates, and therefore, it cannot be molded unless it is pressed with a stronger force.

  On the other hand, the cylindrical core does not crack even when the magnetic powder is pure iron, Fe-3.5% Si alloy, Sendust, Fe-6.5% Si alloy, or amorphous alloy. That is, since the cross-sectional shape of the cylindrical core is circular, the stress applied to the mold is dispersed, so that it can be understood that the burden on the mold can be reduced.

  In general, the higher the frequency of the circuit in which the reactor is used, the greater the loss of the dust core. Therefore, it is necessary to use a magnetic powder having as low an iron loss characteristic as possible, in other words, a magnetic powder having a large specific resistance. However, as the specific resistance increases, the hardness of the magnetic powder increases, and the moldability deteriorates. There is. In order to improve the moldability, it is necessary to press with a larger pressure, so that the burden on the mold is large, causing damage.

  In the present embodiment, by making the shape of the leg portion 11 cylindrical, the stress on the mold during pressure molding is evenly distributed, thereby reducing the burden on the mold and improving the durability. Can do. In addition, since the leg portion 11 has a simple shape such as a columnar shape, it can be pressed evenly, so that there is little variation in molding and productivity can be improved.

[3-2. Reactor characteristics]
The characteristics of the reactor will be described. The reactor wound the coil around the annular core to produce a reactor. In the embodiment, as shown in FIG. 9, the annular core includes two cylindrical magnetic cores connected via a gap to form a leg portion 11, and the pair of leg portions 11 constitutes a pair of back surfaces. It was configured in an annular shape with the part 13 in between. In addition, the notch part 13a of the back part 13 and the side surface of the leg part 11 are contacting, and are gapless. In the comparative example, as shown in FIG. 12, the annular core is configured so that the legs of the two U-shaped cores face each other, and a gap is provided between the facing legs.

  The material of the leg part and the yoke part constituting the annular core is as shown in FIG. 10, and pure iron, Fe-3.5% Si alloy, or amorphous dust was used.

That is, in Example, the combination of the material and density of the leg part 11 and the back part 13 used as a yoke part is changed, and Example 1- Example 6 are shown in FIG. In Example 1, the legs 11 and the back part 13 were made of pure iron, and in Examples 2, 5, and 6, the legs 11 and the back part 13 were made of Fe-3.5% Si alloy. In Example 3, the leg part 11 was made of pure iron, and the back part 13 was made of an Fe-3.5% Si alloy, while Example 4 was made in the opposite way. Moreover, the leg part 11 of Example 5 and the back part 13 of Example 6 were made into high density, and it was set as standard density except these. Dense and is referred to herein, 6.99 g / cm ^3, and the standard density is 6.65 g / cm ^3.

  In Comparative Examples 1 to 3, the material of the leg part and the yoke part are the same, Comparative Example 1 is pure iron, Comparative Example 2 is an Fe-3.5% Si alloy, and Comparative Example 3 is amorphous dust.

The reactor design conditions were such that the following conditions were met.
・ Rated current: 67A
・ Input voltage: 300V
・ Output voltage: 520V
-Number of coil turns: 24 turns-Core cross-sectional area (U-shaped core leg, leg 11): 290mm ²
・ Gap (2 places): 1.5mm

The reactor preferably satisfies the following conditions.
・ Inductance: 28μH or more at0A / 16μH or more at360A
・ Drive frequency: 70kHz

  The L value, iron loss, reactor weight, and reactor volume were measured for the prepared reactor sample. These results are shown in FIG. The reactor weight is the total weight of the annular core and the coil. The reactor volume is the total volume of the annular core and the coil.

As shown in FIG. 10, as a whole, Examples 1 to 6 using columnar legs 11 are smaller in volume and lighter than Comparative Examples 1 to 3 using U-shaped cores. It can be confirmed that the size has been reduced. That is, the reactor volume is 117 cm ³ in Comparative Examples 1 to ³ , while 112 cm ³ in Examples 1 to 6. The reactor weight of Comparative Examples 1 and 2 is 389 g to 393 g, while Examples 1 to 6 are 375 g to 380 g. In addition, although the weight of the comparative example 3 is the lightest, it does not satisfy the design condition (28 μH or more at 0A / 16 μH or more at 360A).

  In Examples 1 to 6, the inductance value can satisfy the design condition (28 μH or more at 0A / 16 μH or more at 360A), and the iron loss is not inferior to that of Comparative Examples 1 to 3, but reaches a practical level. ing.

  The graph which shows the inductance characteristic of Examples 1-6 and Comparative Examples 1-3 is shown in FIG. The graph of FIG. 11 is a graph in which the horizontal axis represents current (A) and the vertical axis represents inductance (μH).

(Difference in the material of magnetic powder in the leg)
Example 4 uses a Fe-3.5% Si alloy, which is a material having a lower iron loss than the back part, in the leg part 11 as compared with Example 1, and as shown in FIG. It can be seen from Example 1 that the iron loss is low. Moreover, when Example 1 and Example 3 are compared, the Fe-3.5% Si alloy which is a low iron loss material is used for the back surface part 13. FIG. It turns out that the direction of Example 3 is excellent in the iron loss, maintaining an inductance value. That is, even if a material having a low magnetic permeability is used for the back surface portion 13 which is a simple magnetic flux path, an equivalent L value can be obtained. Furthermore, as in Example 3, by using a material with low magnetic permeability and low iron loss, loss can be reduced while maintaining an equivalent L value.

(Difference in density of magnetic powder on legs)
Comparing Example 2 and Example 5, the legs 11 of Example 5 have a higher density. It can be seen that Example 5 provides higher inductance characteristics while suppressing an increase in iron loss.

[4. Other Embodiments]
The present invention is not limited to the first and second embodiments and the above-described examples, and includes other embodiments described below. In addition, the present invention also includes a combination of at least any two of the first and second embodiments, the above-described examples, and the following other embodiments.

(1) In the first and second embodiments, the columnar core member is used as the leg portion 11, but the columnar cross-sectional shape is polygonal, and its apex portion is chamfered and formed round. May be. That is, it is only necessary that the peripheral surface of the columnar leg portion 11 has no edge. Even in such a case, the burden on the mold during molding can be reduced. For example, the number of vertices should be three or more. When the number of vertices is small, the degree of roundness is increased so as to eliminate the corner part, and when the number of vertices is large, the degree of roundness of the corner part is set as the stress level. You may make it small to such an extent that concentration is eased. Further, the cross-sectional shape of the leg portion 11 may include a straight line to the extent that stress concentration is eased.

(2) The leg portion 11 of the annular core 10 may be composed of a plurality of cylindrical core members. A plurality of core members may be directly connected with an adhesive, or may be connected via a spacer.

(3) In the first and second embodiments, the back surface portions 12 and 13 are powder magnetic cores, but a ferrite magnetic core or a laminated steel plate may be used.

5a, 5b Coil 10 Annular core 11 Leg 12 Back surface 13 Back surface 13a Notch 20 Resin member 21, 22 Resin body 22a Housing 22b Opening 23, 24 Resin body 24a, 24b Opening 50a, 50b End of coil Part

Claims (9)

A core that is formed into an annular shape by a plurality of core members, a coil is wound around at least a part of the core member, and is used for a reactor, and a pair of legs around which the coil is wound, and the pair of legs and a pair of rear portions connecting the parts, and core have a,
A coil wound around the leg of the core;
With
The leg part is a powder magnetic core having a circular or elliptical cylindrical shape in cross section, and is made of a material having a lower iron loss than the back part,
The back portion has a cutout portion cut out in a shape along a side surface of the columnar leg portion,
A side surface of the columnar leg portion is disposed along the notch portion to form an annular shape;
Reactor characterized by. A core that is formed into an annular shape by a plurality of core members, a coil is wound around at least a part of the core member, and is used for a reactor, and a pair of legs around which the coil is wound, and the pair of legs a pair of rear portions connecting the parts, and core have a,
A coil wound around the leg of the core;
With
The leg part is a powder magnetic core having a circular or elliptical cylindrical shape in cross section, and is made of a material having a lower iron loss than the back part,
The back portion is a substantially hexagonal flat plate,
Both end surfaces of the pair of leg portions are arranged so as to face opposite surfaces of the pair of back surface portions, and form an annular shape,
Reactor characterized by. The leg portion has a circular or oval end surface exposed;
The reactor according to claim 1. The leg portion includes a magnetic powder having a Vickers hardness of 50 or more;
The reactor of any one of Claims 1-3 characterized by these. The coil is composed of an alpha winding,
The coil is mounted around the columnar leg,
The reactor of any one of Claims 1-4 characterized by these. The legs are denser than the back;
The reactor of any one of Claims 1-5 characterized by these. The powder magnetic core of the leg part was configured using, as magnetic powder, an Fe-Si alloy, Sendust, amorphous alloy or a mixed powder of two or more of these,
Reactor according to any one of claims 1 to 6, wherein. The coil is composed of a rectangular wire;
Reactor according to any one of claims 1 to 7, characterized in. A resin member covering the core;
Between the leg portion and the back surface portion, a gap is formed by the thickness of the resin member,
Reactor according to any one of claims 1 to 8, wherein.

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