Reactor

A reactor is provided with a coil including a winding portion, and a magnetic core including an inner core portion to be arranged inside the winding portion and an outer core portion to be arranged outside the winding portion. The magnetic core includes a communication hole penetrating through the outer core portion and leading to the inner core portion, and a coupling shaft made of a composite material filled into the communication hole and coupling the inner core portion and the outer core portion. The composite material is obtained by dispersing a soft magnetic powder in a resin.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase of PCT application No. PCT/JP2019/046467, filed on 27 Nov. 2019, which claims priority from Japanese patent application No. 2018-226542, filed on 3 Dec. 2018, all of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a reactor.

BACKGROUND

For example, a reactor including a coil having a winding portion formed by winding a winding wire and a magnetic core for forming a closed magnetic path is disclosed in Patent Document 1. The magnetic core of this reactor can be divided into an inner core portion to be arranged inside the winding portion and an outer core portion to be arranged outside the winding portion. In Patent Document 1, the magnetic core is formed by coupling the inner core portion formed by assembling a plurality of core pieces independent of each other and gap members and core pieces forming the outer core portion by bolt members.

PRIOR ART DOCUMENT

Patent Document

Patent Document 1: JP 3195212 U

SUMMARY OF THE INVENTION

Problems to be Solved

The present disclosure is directed to a reactor with a coil including a winding portion, and a magnetic core including an inner core portion to be arranged inside the winding portion and an outer core portion to be arranged outside the winding portion, wherein the magnetic core includes a communication hole penetrating through the outer core portion and leading to the inner core portion, and a coupling shaft made of a composite material filled into the communication hole, the coupling shaft coupling the inner core portion and the outer core portion, and the composite material is obtained by dispersing a soft magnetic powder in a resin.

DETAILED DESCRIPTION TO EXECUTE THE INVENTION

Technical Problem

According to the configuration of Patent Document 1, the plurality of core pieces can be accurately coupled. Further, since the bolt members for coupling the core pieces are arranged to penetrate through all the core pieces and not arranged outside the coil, the enlargement of the reactor due to the bolt members can be suppressed. However, in the configuration of Patent Document 1, there is room for improvement in productivity and magnetic properties may be reduced.

Firstly, since the inner core portion is composed of the plurality of core pieces and the gap members, through holes have to be provided in each core piece and each gap member. Further, an operation of aligning the core pieces and the gap members and an operation of aligning the bolt members with the through holes of the respective members and passing the bolt members through the members are cumbersome.

Secondly, in the configuration of Patent Document 1, the bolt members are arranged in parts serving as the magnetic path and magnetic properties of the reactor are not good. This is because the material of the bolt members of Patent Document 1 is thought to be selected in consideration of tightening strength by the bolt members, but not in consideration of the magnetic properties of the reactor.

Accordingly, one object of the present disclosure is to provide a reactor which is excellent in magnetic properties and can be manufactured with good productivity in a simple procedure.

Effect of Present Disclosure

The reactor of the present disclosure is excellent in magnetic properties and can be manufactured with good productivity in a simple procedure.

Description of Embodiments of Present Disclosure

First, embodiments of the present disclosure are listed and described.<1> A reactor according to an embodiment is provided with a coil including a winding portion, and a magnetic core including an inner core portion to be arranged inside the winding portion and an outer core portion to be arranged outside the winding portion, wherein the magnetic core includes a communication hole penetrating through the outer core portion and leading to the inner core portion, and a coupling shaft made of a composite material filled into the communication hole, the coupling shaft coupling the inner core portion and the outer core portion, and the composite material is obtained by dispersing a soft magnetic powder in a resin.

In the case of manufacturing the reactor having the above configuration, the inner core portion and the outer core portion are aligned and the composite material is filled into the communication hole penetrating through the outer core portion and leading to the inner core portion. As a result, the softened resin of the composite material adheres to the communication hole, the communication hole and the coupling shaft made of the composite material are fused over entire lengths while hardly forming any clearance therebetween, and the outer core portion and the inner core portion are coupled by the coupling shaft. As just described, according to the configuration of the above reactor, the reactor is completed only by filling the composite material into the communication hole, wherefore the productivity of the reactor is improved.

In the reactor having the above configuration, magnetic properties required for the reactor are hardly reduced. This is because a reduction in the magnetic properties required for the magnetic core of the reactor is suppressed since the coupling shaft for coupling the inner core portion and the outer core portion is made of the composite material.<2> As one mode of the reactor according to the embodiment, each of the inner core portion and the outer core portion may be an integrated body having an undivided structure.

Each of the inner core portion and the outer core portion may be an assembly of divided pieces. However, if each of the inner core portion and the outer core portion is an integrated body having an undivided structure, the inner core portion and the outer core portion are easily aligned when the reactor is manufactured. As a result, the productivity of the reactor is improved.<3> As one mode of the reactor according to the embodiment, the coupling shaft may include a retaining portion to be hooked to an inner peripheral surface of the communication hole in an axial direction thereof.

By forming the retaining portion on the coupling shaft, the coupling shaft is less likely to be mechanically detached from the magnetic core. As a result, the inner core portion and the outer core portion can be more firmly coupled by the coupling shaft. The configuration of the retaining portion is not particularly limited. For example, the retaining portion may be formed by thread-like irregularities formed on the outer peripheral surface of the coupling shaft.<4> As one mode of the reactor of <3> above, the coupling shaft may include a protruding portion protruding in a direction intersecting the axial direction, and the retaining portion may be formed by the protruding portion.

If the retaining portion is formed by the protruding portion protruding in the direction intersecting the axial direction of the coupling shaft, the detachment of the coupling shaft from the magnetic core can be reliably prevented. The protruding portion may be, for example, a thick shaft portion making a transverse cross-sectional area of the coupling shaft locally large. Further, the protruding portion may be, for example, a crossing shaft intersecting the axial direction of the coupling shaft.<5> As one mode of the reactor of <3> or <4> above, the retaining portion may be formed inside the outer core portion.

By forming the retaining portion of the coupling shaft inside the outer core portion, the detachment of the outer core portion from the inner core portion can be effectively suppressed.<6> As one mode of the reactor of <5> above, the retaining portion may also be formed inside the inner core portion.

By also forming the retaining portion of the coupling shaft inside the inner core portion, the inner core portion and the outer core portion can be more firmly coupled.<7> As one mode of the reactor of <4> above, the protruding portion may be formed over the outer core portion and the inner core portion.

By forming the protruding portion over the outer core portion and the inner core portion, an increase in the loss of the reactor can be suppressed. In the reactor of this example in which the outer core portion and the inner core portion are coupled by the coupling shaft, a clearance (air gap) may be formed in a boundary of the both core portions. If the air gap is formed in the boundary, magnetic fluxes leak from that air gap and the loss of the reactor increases. In contrast, if the protruding portion is formed over the both core portions, a facing area of the both core portions is reduced by the protruding portion. As a result, the air gap is less likely to be formed in the boundary of the both core portions, wherefore an increase in the loss of the reactor can be suppressed.<8> As one mode of the reactor according to the embodiment, the inner core portion may be made of a composite material obtained by dispersing a soft magnetic powder in a resin.

Since containing the resin, the composite material is better in machinability than a powder compact formed by pressure-molding a soft magnetic powder. Since particularly the inner core portion may be formed with a communication hole having a complicated shape as shown in embodiments to be described later, it is preferred to form the inner core portion of the composite material excellent in machinability.

By constituting the inner core portion by the composite material, the magnetic properties of the entire reactor are easily adjusted. This is because the magnetic properties of the composite material are easily adjusted by adjusting the content of the soft magnetic powder of the composite material. Particularly, if each of the inner core portion and the outer core portion is an independent molded body, a room for interposing a gap member is only present between the inner core portion and the outer core portion and it is difficult to adjust the magnetic properties of the entire reactor. In contrast to this configuration, it is effective to constitute the inner core portion by the composite material.<9> As one mode of the reactor according to the embodiment, the outer core portion may be constituted by a powder compact made of a soft magnetic powder.

The content of the soft magnetic powder of the powder compact is easily increased, and the saturation magnetic flux density and relative magnetic permeability of the powder compact are easily enhanced by increasing this content. Particularly, if the inner core portion is a composite material and the outer core portion is a powder compact, it is possible to obtain a reactor having highly excellent magnetic properties.

DETAILS OF EMBODIMENTS OF PRESENT DISCLOSURE

Hereinafter, embodiments of a reactor of the present disclosure are described in detail with reference to the drawings. The same components are denoted by the same reference signs in the drawings. Note that the present invention is not limited to configurations shown in the embodiments and is intended to be represented by claims and include all changes in the scope of claims and in the meaning and scope of equivalents.

First Embodiment

The configuration of a reactor1is described on the basis ofFIGS.1and2in a first embodiment. The reactor1shown inFIG.1is configured by assembling a coil2, a magnetic core3and holding members4. The magnetic core3includes inner core portions31and outer core portions32. One of features of this reactor1is that each of the inner and outer core portions31,32is an integrated body having an undivided structure and the inner and outer core portions31,32are coupled by coupling shafts5made of a composite material. Each component provided in the reactor1is described in detail below.

The coil2of this embodiment includes a pair of winding portions2A,2B and a coupling portion2R coupling the both winding portions2A,2B as shown inFIG.1. The respective winding portions2A,2B are formed into a hollow tubular shape having the same number of turns and the same winding direction, and arranged in parallel so that axial directions thereof are parallel. Although the coil2is manufactured by coupling the winding portions2A,2B made of separate winding wires2win this example, the coil2can also be manufactured by one winding wire2w.

Each winding portion2A,2B of this embodiment is formed into a rectangular tube shape. The winding portion2A,2B in the form of a rectangular tube is a winding portion with end surfaces having a rectangular shape (including a square shape) with rounded corners. Of course, the winding portions2A,2B may be formed into a hollow cylindrical shape. The hollow cylindrical winding portion is a winding portion with end surfaces having a closed curved surface shape (elliptical shape, true circular shape, race track shape, etc.).

The coil2including the winding portions2A,2B can be made of coated wires each including a conductor such as a flat rectangular wire or round wire made of a conductive material such as copper, aluminum, magnesium or an alloy of one of these and an insulation coating made of an insulating material and provided on the outer periphery of the conductor. In this embodiment, each winding portion2A,2B is formed by winding a coated flat rectangular wire including a conductor in the form of a flat rectangular wire (winding wire2w) made of copper and an insulation coating made of enamel (typically, polyamide-imide) in an edge-wise manner.

Both end parts2a,2bof the coil2are pulled out from the winding portions2A,2B and connected to unillustrated terminal members. The insulation coating such as enamel is striped in the both end parts2a,2b. An external device such as a power supply for supplying power to the coil2is connected via these terminal members.

The magnetic core3includes the inner core portions31,31to be respectively arranged inside the winding portions2A,2B and the outer core portions32,32for forming a closed magnetic path together with the inner core portions31,31. The magnetic core3of this example has a gap-less structure in which no gap member is arranged between the inner core portions31and the outer core portions32, but may be structured to include gap members.

The inner core portions31are parts extending along axial directions of the winding portions2A,2B of the coil2, out of the magnetic core3. In this example, both end parts of the parts of the magnetic core3extending along the axial directions of the winding portions2A,2B project from end surfaces of the winding portions2A,2B (FIG.2). Those projecting parts are also parts of the inner core portions31. End parts of the inner core portions31projecting from the winding portions2A,2B are inserted into through holes40of the holding members4to be described later.

The shape of the inner core portion31is not particularly limited as long as conforming to the inner shape of the winding portion2A (2B). The inner core portion31of this example is substantially in the form of a rectangular parallelepiped. This inner core portion31is an integrated body having an undivided structure, which is one of factors facilitating the assembling of the reactor1. Unlike this example, the inner core portion31can also be configured by assembling a plurality of divided cores. Further, the inner core portion31can be configured by interposing gap plates between the divided cores.

An end surface31ein the axial direction of the inner core portion31is in contact with an inner surface32eof the outer core portion32to be described later (FIG.2). An adhesive may be present between the end surface31eand the inner surface32eor may not be present. This is because the inner core portion31and the outer core portion32are coupled by the coupling shaft5as described later. On the other hand, a peripheral surface31sexcept the end surface31e, out of the outer peripheral surface of the inner core portion31, is facing the inner peripheral surface of the winding portion2A,2B, but held at a position separated from the inner peripheral surface without contacting the inner peripheral surface. This is because the inner core portion31and the winding portion2A,2B are both mechanically engaged with the holding members4to be described later and relative positions of the inner core portion31and the winding portion2A,2B are determined.

The inner core portion31of this example further includes an inner core hole61. The inner core hole61of this example is a through hole penetrating through the inner core portion31in the axial direction. The inner core hole61has an inner peripheral surface shape uniform in an axial direction thereof. This inner core hole61constitutes a part of a communication hole6to be described later. The coupling shaft5made of the composite material is arranged inside the inner core hole61. The composite material can be a constituent material of the magnetic core3as described later. Thus, a part of the coupling shaft5arranged inside the inner core hole61may be considered as a part of the inner core portion31.

The inner core hole61of this example has a circular transverse cross-sectional shape orthogonal to the axial direction thereof. The transverse cross-sectional shape of the inner core hole61is not particularly limited and may be, for example, a polygonal shape such as a rectangular shape or a pentagonal shape. Further, an axis of the inner core hole61of this example coincides with an axis of the inner core portion31. Unlike this example, the inner core hole61may be inclined with respect to the axial direction of the inner core portion31.

A transverse cross-sectional area of the inner core hole61is not particularly limited. For example, when a transverse cross-sectional area of the inner core portion31is 100%, the transverse cross-sectional area of the inner core hole61may be 5% or more and 30% or less. Further, the transverse cross-sectional area of the inner core hole61with respect to the inner core portion31is preferably 10% or more and 25% or less and more preferably 10% or more and 20% or less.

The inner core hole61can be formed by a mold when the inner core portion31is molded. The inner core hole61can also be formed by machining. In this case, the inner core hole61can be formed by boring the end surface31eby a drill or the like after the inner core portion31is molded.

The outer core portion32is a part of the magnetic core3to be arranged outside the winding portions2A,2B (FIG.1). The shape of the outer core portion32is not particularly limited as long as linking the end parts of the pair of inner core portions31,31. The outer core portion32of this example is a rectangular parallelepiped block body, but may be substantially dome-shaped or U-shaped in a top view. This outer core portion32is an integrated body having an undivided structure, which is one of factors facilitating the assembling of the reactor1. Unlike this example, the outer core portion32can also be configured by assembling a plurality of divided cores.

The outer core portion32has the inner surface32efacing the end surfaces of the winding portions2A,2B of the coil2, an outer surface32oopposite to the inner surface32eand a peripheral surface32s. The inner and outer surfaces32e,32oare flat surfaces parallel to each other. Out of the peripheral surface32s, upper and lower surfaces are flat surfaces parallel to each other and orthogonal to the inner and outer surfaces32e,32o. Further, out of the peripheral surface32s, two side surfaces are also flat surfaces parallel to each other and orthogonal to the inner and outer surfaces32e,32o.

The outer core portion32of this example further includes outer core holes62extending coaxially with the inner core holes61. The outer core hole62of this example is a through hole having one end side open in the outer surface32oand the other end side open in the inner surface32e. Two outer core holes62are provided in one outer core portion32. That is, four outer core holes62are provided in the entire reactor1.

The outer core hole62of this example is a substantially T-shaped hole composed of a first hole portion h1on the side of the inner core portion31and a second hole portion h2on the side of the outer surface32o. The first hole portion h1is a hole having the same inner peripheral surface shape and cross-sectional area as the inner core hole61. On the other hand, the second hole portion h2is a hole having a larger cross-sectional area than the first hole portion h1. The cross-sectional area mentioned here is an area of a transverse cross-section orthogonal to an axial direction of the outer core hole62(communication hole6). Unlike this example, the cross-sectional area of the first hole portion h1may be smaller or larger than that of the inner core hole61.

The coupling shaft5made of the composite material is also arranged inside the outer core hole62. Accordingly, a part of the coupling shaft5arranged inside the outer core hole62may be considered as a part of the outer core portion32.

The inner and outer core portions31,32can be constituted by powder compacts formed by pressure-molding a raw material powder containing a soft magnetic powder or compacts made of a composite material obtained by dispersing a soft magnetic powder in a resin. Besides, the core portions31,32can be hybrid cores formed by covering the outer peripheries of powder compacts with a composite material. Further, the core portions31,32may be compacts made of a composite material in which gap plates of alumina or the like are embedded or may be mold cores formed by coupling core pieces and gap plates and covering the outer peripheries of the coupled assembly with a resin.

A powder compact can be manufactured by filling a raw material powder into a mold and pressurizing the filled raw material powder. Because of its manufacturing method, the content of a soft magnetic powder is easily increased in the powder compact. For example, the content of the soft magnetic powder in the powder compact can be more than 80% by volume and further equal to or more than 85% by volume. Thus, if powder compacts are used, the core portions31,32having a high saturation magnetic flux density and a high relative magnetic permeability are easily obtained. For example, the relative magnetic permeability of the powder compact can be set to 50 or more and 500 or less and further 200 or more and 500 or less.

The soft magnetic powder of the powder compact is an aggregate of soft magnetic particles made of an iron group metal such as iron or an alloy thereof (Fe—Si alloy, Fe—Ni alloy or the like). Insulation coatings made of phosphate may be formed on the surfaces of the soft magnetic particles. Further, a lubricant and the like may be contained in the raw material powder.

On the other hand, a compact made of a composite material can be manufactured by filling a mixture of a soft magnetic powder and an uncured resin into a mold and curing the resin. Because of its manufacturing method, the content of the soft magnetic powder is easily adjusted in the composite material. For example, the content of the soft magnetic powder in the composite material can be set to 30% by volume or more and 80% by volume or less. The content of the magnetic powder is preferably 50% by volume or more, 60% by volume or more and 70% by volume or more in terms of improving saturation magnetic flux density and heat dissipation. Further, the content of the magnetic powder is preferably set to 75% by volume or less in terms of improving fluidity in a manufacturing process. The relative magnetic permeability of the compact made of the composite material is easily reduced if a filling rate of the soft magnetic powder is adjusted to be low. For example, the relative magnetic permeability of the compact made of the composite material can be set to 5 or more and 50 or less and further 20 or more and 50 or less.

The same soft magnetic powder usable in the powder compact can be used as the soft magnetic powder of the composite material. On the other hand, examples of the resin contained in the composite material include thermosetting resins, thermoplastic resins, room temperature curing resins and low temperature curing resins. The thermosetting resin is, for example, an unsaturated polyester resin, an epoxy resin, a urethane resin or a silicone resin. The thermoplastic resin is, for example, a polyphenylene sulfide resin, a polytetrafluoroethylene resin, a liquid crystal polymer, a polyamide resin such as nylon 6 or nylon 66, a polybutylene terephthalate resin or an acrylonitrile-butadiene-styrene resin. Besides, a BMC (Bulk Molding Compound) in which calcium carbonate and glass fibers are mixed in an unsaturated polyester, millable-type silicone rubber, millable-type urethane rubber and the like can also be utilized. The heat dissipation of the above composite material is further enhanced if a non-magnetic and non-metal powder (filler) such as alumina or silica is contained in addition to the soft magnetic powder and the resin. The content of the non-magnetic and non-metal powder may be set to 0.2% by mass or more and 20% by mass or less, further 0.3% by mass or more and 15% by mass or less, and furthermore 0.5% by mass or more and 10% by mass or less.

The holding member4shown inFIG.2is a member interposed between the end surfaces of the winding portions2A,2B of the coil2and the inner surface32eof the outer core portion32of the magnetic core3for holding the end surfaces in the axial direction of the winding portions2A,2B and the outer core portion32. The holding member4is typically made of an insulating material such as a polyphenylene sulfide resin. The holding member4functions as an insulating member between the coil2and the magnetic core3and a positioning member for the inner core portions31and the outer core portions32with respect to the winding portions2A,2B. Two holding members4of this example have the same shape. Thus, a mold for manufacturing the holding members4can be used in common, wherefore the productivity of the holding members4is excellent. The holding members4can also be omitted.

The holding member4includes a pair of through holes40,40, a pair of core supporting portions41, a pair of coil accommodating portions42and one core accommodating portion43. The through holes40penetrate through the holding member4in a thickness direction, and the end parts of the inner core portions31are inserted into these through holes40. The core supporting portions41are tubular pieces projecting from the inner peripheral surfaces of the respective through holes40toward the inner core portions31to support the inner core portions31. The coil accommodating portions42(FIG.2) are recesses extending along the end surfaces of the respective winding portions2A,2B and formed to surround the core supporting portions41, and the end surfaces of the respective winding portions2A,2B and the vicinities thereof are fit therein. The core accommodating portion43is formed by recessing a part of a surface of the holding member4on the side of the outer core portion32in the thickness direction, and the inner surface32eof the outer core portion32and the vicinity thereof are fit therein. The end surfaces31eof the inner core portions31fit into the through holes40of the holding member4project from the bottom surface of the core accommodating portion43(FIG.3). Thus, the end surfaces31eof the inner core portions31and the inner surface32eof the outer core portion32are in contact.

The reactor1of this example is provided with two coupling shafts5. One coupling shaft5couples the left outer core portion32, the inner core portion31accommodated in the winding portion2A and the right outer core portion32inFIG.2. The other coupling shaft5couples the left outer core portion32, the inner core portion31accommodated in the winding portion2B and the right outer core portion32. The coupling shaft5is made of the composite material filled into the communication hole6. Thus, the outer peripheral shape of the coupling shaft5matches the inner peripheral shape of the communication hole6. The resin contained in the composite material constituting the coupling shaft5is fused to the inner peripheral surface of the communication hole6in filling the composite material into the communication hole6. Thus, the communication hole6and the coupling shaft5are held in close contact over entire lengths while hardly forming any clearance therebetween, and the outer core portions32and the inner core portion31are coupled by the coupling shaft5.

The communication hole6of this example is formed by connecting the inner core hole61and the outer core holes62as already described. Thus, the communication hole6penetrates through one outer core portion32, the inner core portion31and the other outer core portion32. Both end parts of this communication hole6serve as the second hole portions h2(parts of the outer core holes62) having a larger cross-sectional area than other parts. Thus, the coupling shaft5made of the composite material filled into the communication hole6is composed of a thin shaft portion50and thick shaft portions51. The thin shaft portion50is a part corresponding to the first hole portions h1of the outer core holes62and the inner core hole61. On the other hand, the thick shaft portions51are parts corresponding to the second hole portions h2of the outer core portions62. An end surface of the thick shaft portion51is flush with the outer surface32oof the outer core portion32. The thick shaft portion51is a protruding portion further protruding than the thin shaft portion50in a direction intersecting an axial direction of the coupling shaft5. An end surface of this thick shaft portion51on the side of the inner surface32eis in contact with a step between the first and second hole portions h1, h2in the communication hole6. That is, the thick shaft portion51functions as a retaining portion to be hooked to the inner peripheral surface of the communication hole6in the axial direction of the coupling shaft5to prevent the detachment of the coupling shaft5from the magnetic core3. As a result, the inner core portion31and the outer core portions32can be firmly coupled by the coupling shaft5. In this example, the outer core portion32is sandwiched by the thick shaft portion51of the coupling shaft5and the end surface31eof the inner core portion31, so that the outer core portion32is not disengaged from the inner core portion31. According to the configuration of this example, the inner core portions31and the outer core portions32can be directly coupled without any additional component other than the coupling shafts5.

The composition of the composite material constituting the coupling shafts5can be appropriately selected. If parts of the magnetic core3, e.g. the inner core portions31, are constituted by the composite material, the composition of the composite material constituting the coupling shafts5may be the same as or different from that of the composite material constituting the inner core portions31. If the compositions of the coupling shafts5and the inner core portions31are the same, nonuniformity in magnetic properties of the inner core portions31including the coupling shafts5can be suppressed.

If the composition of the coupling shafts5and that of the inner core portions31are different, a resin content of the coupling shafts5can be made more than that of the inner core portions31. By doing so, the composite material is easily filled into the communication holes6. In that case, it is preferred to prevent the content of the soft magnetic powder of the coupling shafts5from becoming excessively low in order to suppress a reduction in the magnetic properties of the coupling shafts5. For example, the resin content of the coupling shafts5may be set to 50% by volume or more and 60% by volume or less, and the content of the soft magnetic powder may be set to 40% by volume or more and 50% by volume or less. On the other hand, the resin content of the coupling shafts5may be less than that of the inner core portions31. This configuration is, namely, a configuration for making the content of the soft magnetic powder of the coupling shafts5more than that of the soft magnetic powder of the inner core portions31. Since the coupling shafts5are located in centers of magnetic paths in the inner core portions31, the magnetic properties of the magnetic core3can be improved by improving the magnetic properties of the coupling shafts5. For example, the resin content of the coupling shafts5may be set to 30% by volume or more and 40% by volume or less, and the content of the soft magnetic powder may be set to 60% by volume or more and 70% by volume or less.

In filling the composite material into the communication hole6, the composite material may be filled only from one end side of the communication hole6or may be filled from one end side and the other end side.

Use Mode

The reactor1of this example can be utilized as a constituent member of a power conversion device such as a bidirectional DC-DC converter to be installed in an electrically driven vehicle such as a hybrid vehicle, an electric vehicle or a fuel cell vehicle. The reactor1of this example can be used in a state immersed in a liquid refrigerant. The liquid refrigerant is not particularly limited, but ATF (Automatic Transmission Fluid) or the like can be utilized as the liquid refrigerant in the case of utilizing the reactor1in a hybrid vehicle. Besides, fluorine-based inactive liquids such as Fluorinert (registered trademark), chlorofluorocarbon refrigerants such as HCFC-123 and HFC-134a, alcohol-based refrigerants such as methanol and alcohol, ketone-based refrigerants such as acetone and the like can be utilized as the liquid refrigerant. Since the winding portions2A,2B are exposed to outside in the reactor1of this example, the winding portions2A,2B are directly brought into contact with the refrigerant in the case of cooling the reactor1by the refrigerant such as the liquid refrigerant. Thus, the reactor1of this example is excellent in heat dissipation.

Effects

The reactor1of this example can be manufactured with good productivity in a simple procedure. This is because the inner core portions31and the outer core portions32are easily aligned when the reactor1is manufactured since both the inner core portions31and the outer core portions32are integrated bodies having an undivided structure. Further, if the inner core portions31and the outer core portions32are aligned and the composite material is filled into the communication holes6penetrating through the outer core portions32and the inner core portions31, the resin of the composite material is fused to the communication holes6. As a result, the communication holes6and the coupling shafts5made of the composite material are held in close contact over the entire lengths while hardly forming any clearance therebetween, and the outer core portions32and the inner core portions31are coupled by the coupling shafts5. The completion of the reactor1only by filling the composite material into the communication holes6also contributes to an improvement in the productivity of the reactor1.

Further, in the reactor1of this example, a reduction in magnetic properties required for the reactor1is unlikely to occur. This is because a reduction in magnetic properties required for the magnetic core3of the reactor1is suppressed since the coupling shafts5coupling the inner core portions31and the outer core portions32is made of the composite material.

Second Embodiment

In a second embodiment, a reactor1in which communication holes6communicating with outer core portions32and inner core portions31are formed into a T shape is described on the basis ofFIG.3.

As shown inFIG.3, the reactor1of this example includes four independent communication holes61. Each communication hole6functions to couple one inner core portion31and one outer core portion32.

The communication hole6of this example is composed of an inner core hole61and an outer core hole62. The shape of the outer core hole62is the same as in the first embodiment. On the other hand, the inner core hole61is formed into a substantially T shape by being composed of a third hole portion h3and a fourth hole portion h4. The third hole portion h3is a short hole having an inner shape matching the first hole portion h1of the outer core hole62. The fourth hole portion h4is a hole extending in a direction intersecting the third hole portion h3and open in a peripheral surface31sof the inner core portion31. The fourth hole portion h4of this example extends in the direction orthogonal to an axial direction of the third hole portion h3(i.e. axial direction of the inner core portion31). Openings of the fourth hole portion h4are entirely covered by a core supporting portion41of a holding member4.

The substantially T-shaped inner core hole61is, for example, formed as follows. First, the fourth hole portion h4penetrating through the peripheral surface31sof the inner core portion31is formed by a drill or the like. Subsequently, cutting is performed from an end surface31eof the inner core portion31in the axial direction of the inner core portion31by the drill or the like to form the third hole portion h3leading to the fourth hole portion h4. If the inner core portion31is made of a composite material, the both hole portions h3, h4can be formed, using a mold core to be removed in the axial direction of the inner core portion31and a mold core to be removed in an orthogonal direction.

If the composite material is filled from a position of the communication hole6open in an outer surface32o, the composite material enters the fourth hole portion h4via the third hole portion h3from the outer core hole62, and a part having entered the fourth hole portion h4becomes a protruding portion (retaining portion) of a coupling shaft5. At this time, since the openings of the fourth hole portion h4are covered by the core supporting portion41, the composite material does not leak to the inside of winding portion2A,2B and a core accommodating portion43from the openings of the fourth hole portion h4.

The reactor1of this example can also obtain effects similar to those of the reactor1of the first embodiment. Further, according to the reactor1of this example, since the coupling shaft5is hardly removed from the inner core portion31, the inner core portion31and the outer core portion32can be more firmly coupled.

Third Embodiment

In a third embodiment, a reactor1in which retaining portions formed in inner core holes61are formed by thread-like irregularities is described on the basis ofFIG.4.

As shown inFIG.4, the reactor1of this example includes four independent communication holes6. An outer core hole62of the communication hole6of this example is the same as in the first embodiment. On the other hand, internal thread-like irregularities are formed on the inner peripheral surface of an inner core hole61. Thus, if a composite material is filled into the communication hole6, the outer periphery of a part arranged in the inner core hole61, out of a thin shaft portion50of the coupling shaft5, becomes a screw-shaped portion5m. This screw-shaped portion5mis hooked to the uneven inner peripheral surface of the inner core hole61and functions as a retaining portion of the coupling shaft5.

Here, the threaded inner peripheral surface of the inner core hole61can be formed by being processed by a tap or the like. Besides, if the inner core portion31is formed of the composite material, the threaded shape can also be formed by using an externally threaded mold core. In this case, the inner core hole61having the threaded inner peripheral surface is formed by removing the core from the inner core portion31while rotating the mold core.

The reactor1of this example can also obtain effects similar to those of the reactor1of the first embodiment. The reactor1of this example has an advantage that the inner core holes61are relatively easily formed.

The screw-shaped portion5mmay be formed over the entire length of the coupling shaft5as a modification of this example.

Fourth Embodiment

In a fourth embodiment, a reactor1in which protruding portions (thick shaft portions51) of coupling shafts5are formed over outer core portions32and inner core portions31is described on the basis ofFIG.5.

As shown inFIG.5, a communication hole6into which the coupling shaft5of this example is fit penetrates through one outer core portion32, the inner core portion31and the other outer core portion32, similarly to the reactor1of the first embodiment. In an outer core hole62, a cross-sectional area of a first hole portion h1on the side of the inner core portion31is larger than that of a second hole portion h2on the side of an outer surface32o. On the other hand, an inner core hole61is composed of a fifth hole portion h5extending substantially over the entire length in an axial direction of the inner core portion31and sixth hole portions h6formed on one and the other ends of the fifth hole portion h5. The inner peripheral surface shape and cross-sectional area of the fifth hole portion h5are the same as those of the second hole portions h2. The inner peripheral surface shape and cross-sectional area of the sixth hole portions h6are the same as those of the first hole portions h1.

The inner core hole61and the outer core holes62shaped as described above are, for example, formed as follows. First, a through hole is formed in the inner core portion31(outer core portions32) by a thin drill. Subsequently, short holes are formed in end surface s31e(inner surfaces32e) by a thick drill. In this case, the hole formed by the thin drill becomes the fifth hole portion h5(second hole portions h2) and the holes formed by the thick drill become the sixth hole portions h6(first hole portions h1).

The coupling shaft5made of the composite material fit into the communication hole6includes two thick shaft portions51at intermediate axial positions of the thin shaft portion50. The thick shaft portion51is constituted by the composite material filled into a space formed by the first hole portion h1and the sixth hole portion h6. Thus, the thick shaft portion51is formed over the inner core portion31and the outer core portion32.

According to the reactor1of this example, an effect of being able to reduce leakage magnetic fluxes from boundaries between the inner core portions31and the outer core portions32can be obtained in addition to effects similar to those of the reactor1of the first embodiment. In this example, the end surface31eof the inner core portion31and the inner surface32eof the outer core portion32are in contact. However, if fine irregularities are present in the end surface31eand the inner surface32e, a plurality of local gaps may be formed between the end surface31eand the inner surface32e. If a transverse cross-sectional area of the thick shaft portion51is increased, the number of the local gaps can be reduced since an area of parts of the end surface31eand the inner surface32efacing each other can be reduced. As a result, the leakage magnetic fluxes of the reactor1can be reduced and magnetic loss of the reactor1can be reduced.

Other Embodiments

The reactor1may be manufactured with the configurations relating to the coupling shafts5of the first to fourth embodiments appropriately combined. For example, internal thread-like irregularities may be formed on the inner peripheral surface of the inner core holes61of the first embodiment shown inFIG.2. Further, in the configuration of the fourth embodiment, the thick shaft portions51may be formed also on the side of the outer surfaces32oof the outer core portions32. By combining a plurality of configurations relating to the coupling shafts5, the inner core portions31and the outer core portions32are possibly more firmly coupled.

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