JP2007201203A - Reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reactor that is superior in producibility, heat dissipation properties, and low-noise properties. <P>SOLUTION: The reactor has a core 10 and a coil 40. The core 10 comprises an inner core 11 arranged inside the coil 40, an outer core 12 covering the outer periphery of the coil, a first linking core 13 jointed with one end side of the outer core 12, and a second linking core 14 joined to the other end side of the outer core 12 and the inner core 11. A gap (g) is formed by providing an air gap between the inner core 11 and the first linking core 13. The whole coil 40 is substantially covered by the outer core 12 and the first/second linking cores 13, 14. According to this constitution, efficient conduction of the heat generated from the coil to the core can be carried out, since the entire coil outer peripheral face is in contact with the core. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reactor. In particular, the present invention relates to a reactor excellent in manufacturability, heat dissipation and low noise.

  In recent years, hybrid vehicles and electric vehicles have been put into practical use from the viewpoint of protecting the global environment. A hybrid vehicle is a vehicle that includes an engine and a motor as drive sources and travels using one or both of them. Such a hybrid vehicle or the like includes a booster circuit in a power supply system to a motor. A reactor that can store electric energy as magnetic energy is used as one of the components of the booster circuit.

The reactor includes a coil and a core having a gap, and a closed magnetic circuit is formed in the core through the gap by excitation of the coil. A core of a typical reactor used in a booster circuit of a hybrid vehicle or the like is a ring-shaped core M as shown in FIG. 10 (Patent Document 1 as a document showing a similar core form, FIG. A plurality of core pieces as described above are combined. The core M has a U-shaped core pieces m _u pair having a rectangular end face, made I-shaped core piece m _{i 4} bracts, so that the U-shaped core pieces m _u is between the end face of each other facing arranged, side by side one by 2 I-shaped core piece m _i between the end faces, are formed by joining respectively. A conductive wire is wound around a part of the core M to form a coil C, and a current is passed through the coil C to form a closed magnetic circuit in the core M. The material constituting the core M is a ferromagnetic material such as an iron-based material such as silicon steel.

  In addition, the core M is provided with a gap in the magnetic path by arranging a spacer s at each joint portion of the core piece in order to avoid magnetic saturation. The inductance of the reactor is defined by the gap distance formed in the magnetic path. This gap distance needs to be maintained with high accuracy, and a plate made of a non-magnetic material having high hardness such as alumina is used for the spacer s.

  Further, the reactor is housed in a case in order to protect the conducting wire (coil) and facilitate mounting on the booster circuit. Specifically, after housing the reactor in the case, the case is filled with a sealing material made of resin such as urethane.

JP-A-8-111322

  However, the conventional reactor described above has the following problems.

(1) Inferior productivity of reactor.
Since alumina used for the reactor gap has high hardness, it is difficult to process it with high accuracy. For this reason, it takes time to adjust the gap distance using an alumina plate having a uniform thickness. These circumstances have also led to an increase in reactor manufacturing costs.

(2) It is difficult to suppress noise from the reactor.
The coil of the reactor vibrates due to the excitation, and the core and the spacer vibrate due to the electromagnetic attractive force accompanying the excitation at the joint portion or gap portion between the core pieces. This vibration generates noise from the reactor. In the technique described in Patent Document 1, noise is reduced by adhering abutting portions or gap portions between core constituent members with an adhesive having an adhesive strength of 100 kgf / cm ² . However, even with this technique, it is difficult to reduce the noise generated from the reactor to the required level.

(3) The heat dissipation efficiency of the reactor is low.
When a current flows through the reactor conductor (coil), the coil generates heat and becomes hot. The reactor is housed in a case, and the case is filled with a sealing material made of resin such as urethane, but such a sealing material has a lower thermal conductivity than metal. Therefore, when the coil generates heat, most of the heat is conducted to the core made of an iron-based material or the like that comes into contact with the coil. However, when the coil is wound around the ring-shaped core described above, the outer peripheral surface of the coil is exposed from the core, and only the inner peripheral surface of the coil is in contact with the core, and the contact area between the core and the coil is increased. I can't take it. As a result, efficient heat dissipation from the coil through the core is not possible.

  Moreover, there exists EI core currently disclosed by FIG. 13 of patent document 1 as a core of another shape from the ring-shaped core of FIG. The EI core is a combination of an E-shaped core piece and an I-shaped core piece. For example, when a coil is wound around the center leg portion of the E-shaped core piece, the outer peripheral surface of the coil can be brought into contact with the leg portions on both sides of the E-shaped core piece where the coil is not wound. The contact area between the core and the coil can be made larger than that of the core. However, even if an EI core is used as the reactor core, a substantial portion of the outer peripheral surface of the coil is always exposed from the core, and efficient heat dissipation from the outer peripheral surface of the coil through the core is difficult.

  And when the above-mentioned ring-shaped core and EI core are used for the core of the reactor, since a part of the outer peripheral surface of the coil is exposed from the core, from the viewpoint of protecting the conducting wire (coil), it is possible to dissipate heat. Cases and sealing materials that are obstructive factors must be used.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a reactor that can easily adjust the gap distance and has excellent manufacturability.

  Another object of the present invention is to provide a reactor excellent in low noise performance.

  Another object of the present invention is to provide a reactor having excellent heat dissipation.

  The reactor of the present invention includes a coil and a core having a gap, and a closed magnetic circuit is formed in the core through the gap by excitation of the coil. And this invention reactor has the following characteristics. The core includes an inner core disposed inside the coil, an outer core disposed outside the coil, a first connecting core joined to one end side of the outer core, and the other end side of the inner core and the outer core. It is comprised from the 2nd connection core to join. The gap is formed by providing a gap between the inner core and the first connecting core. The coil is substantially entirely covered by the outer core, the first connecting core, and the second connecting core.

  According to this configuration, the gap is formed as a gap without using an alumina plate or the like. Therefore, it is not necessary to process a difficult-to-process material with high accuracy when adjusting the gap distance, and the reactor can be easily manufactured.

  Further, according to this configuration, the entire outer peripheral surface of the coil can be brought into contact with the core, so that the contact area between the core and the coil can be maximized. Therefore, the reactor of the present invention can efficiently conduct the heat generated from the coil to the core and dissipate the heat in the entire core, and is excellent in heat dissipation.

  Further, the gap (air gap) and the coil are substantially covered by the core. Therefore, the reactor of the present invention can reduce noise by suppressing leakage of noise due to vibration of the coil or vibration of the core structural member in the gap portion to the outside of the core (reactor).

  Here, “the coil is substantially covered by the core” means that the coil is surrounded by the core except for a portion such as a groove or a hole provided in the core in order to draw the lead wire of the coil from the core. Means that.

  In the reactor of the present invention, the core constituent members of the inner core, the outer core, the first connecting core, and the second connecting core may be individually produced and joined, but a plurality of core constituent members are integrally formed. Is preferred. The following specific examples can be given as a combination of the core components formed integrally.

(A) The inner core, the outer core, and the second connecting core are integrally formed.
(B) The outer core and the first connecting core are integrally formed.
(C) The inner core and the second connecting core are integrally formed.

  Thus, if a several core structural member is formed integrally, the junction part between each core structural member can be decreased. Therefore, it is possible to prevent noise due to the vibration of the core constituent member at the joint. Further, even if noise is generated due to the vibration of the core constituent member in the gap portion, noise is less likely to leak from the joint portion to the outside of the core (reactor), so that noise can be further reduced.

  Each core constituent member of the reactor of the present invention is formed of a ferromagnetic material such as an iron-based material such as an electromagnetic steel plate, ferrite, or iron powder. And the said core is comprised by joining each core structural member formed with such a material with a volt | bolt, an adhesive agent, etc. FIG. For example, an epoxy resin or a urethane resin can be used as such an adhesive.

  On the other hand, it is preferable that at least one of the core constituent members as described above is formed of a compacted body. In particular, the integral formation of a plurality of core components can be performed using a compacting method or a sintering method. The green compact is preferable in that it has high dimensional accuracy and can also produce a three-dimensional shape. More specifically, it is manufactured by filling a powder material made of a ferromagnetic material such as iron powder or ferrite into a mold having a predetermined shape and performing pressure molding. Since the core constituent member made of the green compact has a smooth surface and is processed into a desired shape with high accuracy, it is possible to easily form an accurate gap distance.

  A rod-shaped body is typically used for the inner core. The cross-sectional shape of the inner core may be a polygon as well as a circle. A cylindrical body is typically used for the outer core. The cross-sectional contour shape of the outer core may be a polygon as well as a circle. Usually, an outer core having a cross-sectional contour shape corresponding to the cross-sectional shape of the inner core is used. On the other hand, a 1st connection core and a 2nd connection core are core structural members located in the edge part of an outer core, and the board | plate material of the shape corresponding to the cross-sectional outline shape of an outer core is normally utilized. For example, when the shape of the reactor is a prismatic shape, it is conceivable to form the inner core in a prismatic shape, the outer core in a rectangular tube shape, and the first connecting core and the second connecting core in a polygonal flat plate shape.

  The coils used for these reactors of the present invention are typically formed by winding a conductive wire having an insulating film. For example, a coil in which a round conductor having a circular cross section is spirally wound or a coil in which a rectangular conductor having a rectangular cross section is wound in a so-called edgewise manner can be used. The coil is preferably fixed to the core with an adhesive in order to reduce noise caused by vibration of the coil. For example, an epoxy resin or a urethane resin can be used as such an adhesive.

  In these reactors of the present invention, it is preferable that the cross-sectional areas of the inner core and the outer core are substantially equal in the core cross section orthogonal to the axial direction of the coil.

  According to this structure, the magnetic flux density of the magnetic flux which flows into an inner core and an outer core can be substantially equalized. Therefore, the reactor can be miniaturized with the miniaturization of the core by eliminating the portion with low magnetic flux density in the cross section of the core (the magnetic flux hardly flows) and making the magnetic flux density uniform.

  In the reactor according to the present invention, at least one of the first connecting core and the second connecting core is a magnetic flux distribution between the center side and the outer peripheral side in a region (fan-shaped portion) divided by an arbitrary central angle θ of the connecting core. It is preferable to make the thickness on the outer peripheral side thinner than the center side of the connecting core so that the thickness becomes uniform.

  According to this structure, the magnetic flux density of the magnetic flux which flows into the said connection core can be substantially equalized. Therefore, by eliminating the low magnetic flux density portion in the core cross section and making the magnetic flux density uniform, the reactor can be miniaturized with the miniaturization of the core.

  These reactors of the present invention preferably include an insulator at a portion where the coil and the core come into contact.

It is necessary to maintain insulation between the coil and the core. In particular, the insulation between the coil and the core is important in consideration of the case where a large current flows through the coil and the case where the insulation coating provided on the coil conductor is damaged. If an insulator is provided in the part where a coil and a core contact, between a coil and a core can be insulated more reliably. Examples of the insulating material forming the insulator include PPS (Poly Phenylene Sulfide polyphenylene sulfide) and LCP (Liquid
Resin such as Crystal Polymer (liquid crystal polymer). Further, an inorganic filler may be added to such a resin in order to better transfer the heat of the coil to the core. Examples of the inorganic filler include insulating materials such as glass (silicon dioxide), alumina (aluminum oxide), and titanium oxide. The amount of such inorganic filler added may be appropriately selected. It is easy to arrange such an insulator so as to be integrated by combining divided pieces, which is preferable.

  It is preferable that the reactor of the present invention constitutes the reactor main body by arranging a plurality of cores defined in the reactors as described above and arranging each of a plurality of coils formed in series in each core.

  Formed in series means formed from a series of conductive wires. According to this configuration, it is possible to store and release larger energy than a reactor using a single core. In addition, since a plurality of coils are formed in series, it is not necessary to connect the coils arranged in each core compared to the case where a plurality of coils are formed one by one and arranged in each core, The work process can be shortened.

  As described above, the reactor of the present invention can achieve the following effects.

  The reactor gap is formed as a gap without using an alumina plate or the like. Therefore, it is not necessary to process a difficult-to-process material with high accuracy when adjusting the gap distance, and the reactor can be easily manufactured.

  By maximizing the contact area between the core and the coil, the heat generated from the coil can be efficiently conducted to the core, the heat can be dissipated from the entire core, and a reactor with excellent heat dissipation can be obtained. .

  In addition, the gap (air gap) and the coil provided between the inner core and the second connecting core are covered with the entire core. With this configuration, the coil vibrates or the core constituent member vibrates in the gap portion. It is possible to reduce noise by suppressing leakage of noise caused by the leakage to the outside of the reactor.

  Furthermore, in the reactor of the present invention, the outer peripheral surface of the coil is not exposed from the core, and it is not necessary to provide a case for protecting the coil separately.

  In addition, in the reactor of the present invention, after arranging a plurality of cores, it is not necessary to connect the coils arranged in each core by arranging a plurality of coils formed in series in each core. In addition, since a larger amount of energy can be stored and discharged compared to a reactor using a single core, when the reactor of the present invention is used in a booster circuit such as a hybrid vehicle, the output of the motor can be further improved. it can.

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

  As shown in FIG. 1, the reactor of the present invention has a substantially cylindrical core 10. In addition, a coil 40 is accommodated in the core 10 as shown in FIG. Here, the core 10 includes an inner core 11, an outer core 12, a first connection core 13, and a second connection core 14. The core 10 is formed with a gap g composed of a gap.

  Each of the inner core 11, the outer core 12, the first connecting core 13, and the second connecting core 14 is individually manufactured by pressing a powder obtained by forming an insulating coating on an iron-based soft magnetic material.

  First, the inner core 11 is a round bar-shaped core disposed inside the coil 40. The height h1 of the inner core 11 is smaller than the height h2 of the outer core 12 described below. The gap g is formed using the difference in height.

  Next, the outer core 12 is a cylindrical core disposed outside the coil 40. Here, notches 12A and 12B (FIG. 1) penetrating the inner and outer peripheries are formed in a part of the upper end side and the lower end side of the outer core 12, and the notches 12A and 12B are used as end portions 50 of the conductors forming the coil 40. , 51 insertion holes. And this outer core 12 is coaxially arranged with the inner core 11, and between the inner core 11 and the outer core 12, the width of the flat conducting wire which constitutes the coil 40 so that the coil 40 mentioned later can be accommodated. Also, a slightly wider interval is formed.

  The first connecting core 13 and the second connecting core 14 are a pair of disk-shaped cores. The first connecting core 13 has a lid function in the core 10, and the second connecting core 14 has a bottom function in the core 10. Here, the lower end of the inner core 11 is joined to the second connecting core 14, and the upper end of the inner core 11 is not joined to the first connecting core 13, and a gap g is formed between the first connecting core 13 and the inner core 11. Yes. The upper end of the outer core 12 is joined to the first connecting core 13 and the lower end side is joined to the second connecting core 14.

  On the other hand, the gap g is a nonmagnetic part for adjusting the inductance of the reactor. The gap g is an air gap, and here, a single gap g is formed between the upper end surface of the inner core 11 and the first connecting core 13. The height of the inner core 11 and the outer core 12 is accurately formed by compacting so that the gap g has a predetermined dimension.

  Further, the coil 40 is configured by winding a conductive wire having an insulating coating in a spiral shape on the outer periphery of the inner core 11 and on the inner periphery of the outer core 12. Here, the coil 40 is formed by edgewise winding a rectangular copper wire having a cross section with an enamel coating. One end 50 of the conducting wire constituting the coil 40 is drawn out from the upper notch 12B to the outer periphery of the outer core 12 among the above-described notches, and one end 51 of the conducting wire is drawn from the lower notch 12A to the outer core 12 It is pulled out to the outer periphery.

  Such a reactor is assembled as shown in FIG.

  First, the second connecting core 14 is joined to the lower end of the inner core 11. This bonding may be performed using an adhesive or the like.

  Next, the coil 40 is fitted into the inner periphery of the outer core 12, and one end of the conducting wire constituting the coil 40 is fitted into the upper notch 12B (FIG. 1) and the other end of the conducting wire is fitted into the lower notch 12A (FIG. 1). . If necessary, the coil 40 is temporarily deformed by shifting the center of each turn of the coil 40, and the coil 40 is fitted into the outer core 12 and the conductor ends 50 and 51 are fitted into the notches 12A and 12B. May be performed.

  Subsequently, the outer core 12 to which the coil 40 is attached is joined onto the lower second connecting core 14. This bonding may be performed using an adhesive or the like. By this joining, the inner core 11, the coil 40, and the outer core 12 are held substantially concentrically.

  Finally, the first connecting core 13 is joined to the upper end surface of the outer core 12. This bonding may be performed using an adhesive or the like.

  The reactor assembled as described above, when the coil 40 is excited, as shown in FIG. 4, the closed magnetic circuit Φ connected to the inner core 11, the first connecting core 13, the outer core 12, the second connecting core 14, and the inner core 11. Form. At this time, for example, it is assumed that the magnetic flux flows in the direction of the arrow in FIG. More specifically, the magnetic flux generated in the inner core 11 flows from the inner core 11 into the central portion of the first connecting core 13 and 2) flows radially from the center side of the first connecting core 13 to the outer peripheral side. It flows into the outer core 12, 3) flows from the outer core 12 to the outer peripheral portion of the second connecting core 14, and 4) flows so as to converge from the outer peripheral side of the second connecting core 14 to the center side, and the center of the second connecting core 14 It flows into the inner core 11 from the part. At this time, if the cross-sectional area of the inner core 11 and the cross-sectional area of the outer core 12 are made substantially equal in the cross section of the core perpendicular to the axis of the coil 40, the magnetic flux density of the core 10 can be made substantially equal. And in this reactor, since each core structural member is accurately formed by compaction molding, it is necessary to prepare an alumina plate whose thickness is accurately controlled over a long time. The reactor can be efficiently manufactured.

  In addition, since the coil 40 is housed in the core 10 by using the core 10 having the shape described above, this reactor can reduce leakage of noise generated by vibration due to excitation of the coil 40 to the outside of the core 10, Low noise can be achieved.

  Further, by using the core 10 having such a shape, the coil 40 is substantially entirely covered by the core 10. That is, since the core 10 having excellent thermal conductivity is positioned on the outer periphery of the coil 40, a reactor having excellent heat dissipation can be obtained. In particular, if a heat radiating material (not shown) is brought into full contact with at least one of the upper and lower connecting cores 13 and 14, the reactor can be further improved in heat dissipation.

  In the above embodiment, the inner core, the first connecting core, the outer core, and the second connecting core are all formed separately and joined afterwards, but a plurality of these core constituent members are preliminarily compacted. Alternatively, it may be integrally formed. A modification is shown below. The description here will focus on the differences from the reactor of FIG.

<Modification 1>
The reactor of FIG. 5 shows an example in which the inner core 11, the outer core 12, and the second connecting core 14 are integrally formed. In this case, the number of constituent members of the core is two, and it is only necessary to join the integrally formed core portion and the first connecting core 13, which further improves manufacturability.

<Modification 2>
The reactor of FIG. 6 shows an example in which the inner core 11 and the second connecting core 14 are integrated, and the outer core 12 and the first connecting core 13 are integrally formed. Also in this case, the number of core constituent members is two, and it is only necessary to join the integrally formed core portions to each other, which further improves the manufacturability.

<Modification 3>
A modification will be described in which the distribution of magnetic flux in the first and second connection cores is made substantially uniform from the center side to the outer periphery side of these connection cores. In this modification, as shown in FIG. 7, in the longitudinal section of the first (second) connecting core 13 (14), a taper is formed so that the thickness becomes thinner toward the outer peripheral side. That is, the thickness t2 on the outer peripheral side is thinner than the thickness t1 on the center side.

  Consider the distribution of magnetic flux in the first (second) connecting core 13 (14) in FIG. When the thickness t of the core 13 (14) is constant in the region (fan portion) of the connecting core 13 (14) divided at an arbitrary central angle θ [radian], the cross-sectional area S1 (r1 away from the center) The area obtained by r1 × θ × t) and the sectional area S2 away from the center by r2 (area obtained by r2 × θ × t) satisfy S1 <S2 (where r1 <r2). Therefore, the magnetic flux density on the outer peripheral side (r2) of the connecting core 13 (14) is lower than the magnetic flux density on the central side (r1). Therefore, as shown in FIG. 7, if the thickness of the outer peripheral side is made thinner than the center side of the core 13 (14), the cross-sectional area of the core 13 (14) orthogonal to the magnetic flux can be made substantially equal.

<Modification 4>
The other reactor of the present invention forms a reactor body by arranging a plurality of cores used in the above-described reactor of the present invention and arranging a plurality of coils formed in series in each core. For example, FIG. 9 shows a case in which a reactor in which three cores 10 of the reactor of the present invention shown in FIG. 5 are arranged in parallel (arranged so that the axes of the three cores 10 are parallel) and three coils are connected in series is configured. I will explain. The reactor includes three cores 10 and three coils 41 to 43 formed in series. The coils 41 to 43 are housed in a space surrounded by the inner core 11, the outer core 12, and the second connecting core 14 of each core 10 so that the inner core 11 of each core 10 is disposed inside the coil. Is done. The coils 41 to 43 formed from a series of long conductive wires are formed as follows. The coil 41 is formed by winding a conducting wire from the top to the bottom, and is provided with a connecting portion 52 that connects the coil 41 and the coil. Next, the coil 42 is formed by winding a conductive wire from below to above, and a connecting portion 53 that connects the coil 42 and the coil 43 is provided. Further, the coil 43 is formed by winding a conducting wire from the top to the bottom. Although not shown, each outer core 12 of each core 10 has a notch, from which end portion 50 and connecting portion 52 of coil 41, connecting portions 52 and 53 of coil 42, coil 43 connecting portions 53 and end portions 51 are pulled out. When a current is passed through the coils 41 to 43 of such a reactor, a plurality of closed magnetic paths are formed in which the directions of magnetic flux passing through the inner cores 11 of the cores 10 are the same. The reactor shown in FIG. 9 can store and release larger energy as compared with the reactor using one core 10 as shown in FIG. Furthermore, it is also preferable that an engaging portion for connecting the cores 10 to each other is formed on the adjacent surface of the core.
When a plurality of cores 10 are arranged on the same axis and connected in series, the connecting cores existing between adjacent cores can be configured to serve as the first connecting core and the second connecting core. By arranging the cores in this way, the thickness of the connecting core can be reduced compared to the reactor using one core, and thus the reactor can be made smaller.

<Modification 5>
In addition, although not shown, a configuration in which an insulator is provided in a portion where the coil and the core come into contact may be employed. The insulator may be formed so as to cover the outer periphery of the coil before the coil is housed in the first connecting core, or may be disposed in advance on the surface of each core component member that contacts the coil. As this insulator, a thin molded product suitable for a gap formed between the coil and the core can be suitably used.

<Modification 6>
Further, although not shown, the form of the notches 12A and 12B in FIG. 1 may be changed. For example, if a slit connected from the upper end to the lower end of the outer core is provided, the reactor can be assembled smoothly only by inserting the coil directly in the axial direction of the outer core. After the coil is arranged inside the outer core, a strip made of resin or magnetic material is appropriately fitted into the open space of the slit and sealed.

  The reactor of the present invention can be used as a reactor used in a booster circuit such as a hybrid vehicle.

It is an external appearance perspective view of this invention reactor. It is a longitudinal cross-sectional view in the center vicinity of this invention reactor. It is a disassembled perspective view of this invention reactor. It is explanatory drawing of the closed magnetic circuit produced at the time of excitation of this invention reactor. It is a longitudinal cross-sectional view of the reactor of this invention in the modification 1. 6 is a longitudinal sectional view of a reactor of the present invention in Modification 2. FIG. 10 is a perspective view of a first (second) connecting core in Modification 3. FIG. It is explanatory drawing which shows the nonuniformity of distribution of the magnetic flux in a 1st (2nd) connection core. It is a disassembled perspective view of the reactor of this invention in the modification 4. It is a partial notch perspective view of the conventional reactor.

Explanation of symbols

10 core
11 Inner core 12 Outer core 12A, 12B Notch
13 First linked core 14 Second linked core
40, 41, 42, 43 Coil 50, 51 Coil end 52, 53 Coil connection
g gap Φ closed magnetic circuit M core C coil m _u U-shaped core mi _i I-shaped core s spacer

Claims (9)

A reactor comprising a coil and a core having a gap, and a closed magnetic circuit is formed in the core through the gap by excitation of the coil,
The core is
An inner core disposed inside the coil;
An outer core disposed outside the coil;
A first connecting core joined to one end of the outer core;
It is composed of a second connecting core that joins the other end side of the outer core and the inner core,
The gap is formed by providing a gap between the inner core and the first connecting core,
The reactor is characterized in that the coil is substantially entirely covered by an outer core, a first connecting core, and a second connecting core.   The reactor according to claim 1, wherein the inner core, the outer core, and the second connecting core are integrally formed.   The reactor according to claim 1, wherein the outer core and the first connecting core are integrally formed.   2. The reactor according to claim 1, wherein the inner core and the second connecting core are integrally formed.   The reactor according to any one of claims 1 to 4, wherein at least one of the inner core, the outer core, the first connection core, and the second connection core is a compacted body.   The reactor according to any one of claims 1 to 5, wherein in the core cross section orthogonal to the axial direction of the coil, the cross-sectional areas of the inner core and the outer core are substantially equal.   At least one of the first connection core and the second connection core is connected to the connection core so that the magnetic flux distribution between the center side and the outer periphery side is uniform in the region divided by the arbitrary central angle θ of the connection core. The reactor according to any one of claims 1 to 6, wherein the outer peripheral side is thinner than the center side.   The reactor according to any one of claims 1 to 7, wherein an insulator is interposed between the coil and the core.   A reactor in which a plurality of cores defined in the reactor according to claim 1 are arranged, and each of a plurality of coils formed in series is arranged in each core.

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