Coil device

A coil device of solenoid type includes a coil portion having a bobbin and a conductive wire wound around the bobbin, a housing for accommodating the coil portion, and at least one fastener for fastening the bobbin and the housing. The conductive wire includes a plurality of extending portions extending along a wound wire direction on the bobbin and having gaps in a winding axis direction, and the coil portion includes an enlarged portion in which a gap between extending portions adjacent to each other in the winding axis direction is wider than a gap between other extending portions. The fastener is provided in the enlarged portion.

TECHNICAL FIELD

The present disclosure relates to a coil device.

BACKGROUND ART

A wireless power transfer system includes a power transmission coil device and a power reception coil device, and implements wireless power transmission using electromagnetic induction, magnetic resonance, etc. between coils. Each of the coil devices has a coil and ferrite therein. The coil device is surrounded by a housing. For example, the housing includes a protective cover and an aluminum plate. For example, the wireless power transfer system is applied to a power feeding system of an electric vehicle. In this case, the power reception coil device is installed in the vehicle.

Technologies disclosed in Patent Literatures 1, 2, and 3 are known. In an apparatus disclosed in Patent Literature 1, an in-vehicle transducer corresponding to a power reception coil device is installed in a vehicle (chassis). Alternatively, the in-vehicle transducer is installed to protrude downward on a lower surface of a vehicle body. In an apparatus disclosed in Patent Literature 2, a bobbin that supports a secondary self-resonant coil corresponding to a power reception coil is attached to a vehicle by a fixing member connected to a flange portion thereof.

In an apparatus disclosed in Patent Literature 3, an aluminum substrate of a power reception unit is fixed to a lower portion of a moving body by a non-magnetic bolt through a bolt hole. An aluminum substrate of a power feeding unit is fixed to a road surface, etc. by a non-magnetic bolt through a bolt hole. A protective cover made of polycarbonate is fixed to the substrate by a non-magnetic bolt through a bolt hole. A spacer is provided between the protective cover and an insulating plate, and strength of the protective cover is increased by the spacer.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

In a solenoid coil disclosed in Patent Literature 1, a bobbin around which a conductive wire is wound (a ferrite housing portion in the apparatus of Patent Literature 1) is disposed to extend in a flat plate shape between a protective cover and an aluminum plate. A plurality of slot-shaped grooves is formed in the bobbin, and the conductive wire is disposed in the grooves. In this configuration, the conductive wire wound around the bobbin has a plurality of parallel linear portions on each of a surface side and a rear surface side of the bobbin. Therefore, the conductive wire is present over the entire area of the bobbin disposed between the protective cover and the aluminum plate.

A spacer disclosed in Patent Literature 3 is known to be provided to increase strength of a housing. However, there is difficulty in applying the spacer to a solenoid coil in which a conductive wire is present over the entire are of a bobbin. Increasing strength of the housing is an issue in a coil device that employs the solenoid coil.

An object of the present disclosure is to provide a coil device of solenoid type capable of increasing strength of a housing.

Solution to Problem

A coil device of solenoid type according to an aspect of the present disclosure includes a coil portion having a bobbin and a conductive wire wound around the bobbin, a housing for accommodating the coil portion, and at least one fastener for fastening the bobbin and the housing, wherein the conductive wire includes a plurality of extending portions extending along a wound wire direction on the bobbin and having gaps in a winding axis direction, the coil portion includes an enlarged portion in which a gap between extending portions adjacent to each other in the winding axis direction is wider than a gap between other extending portions, and the fastener is provided in the enlarged portion.

According to this coil device, the housing is accommodated in the coil portion that includes the bobbin. The plurality of extending portions extending in the wound wire direction on the bobbin has gaps in the winding axis direction. The enlarged portion in which the gap between the extending portions adjacent to each other is wider than the gap between other extending portions is provided in the coil portion. The at least one fastener is provided in the enlarged portion. The bobbin and the housing are fastened by the fastener. The gap between the extending portions is wide in the enlarged portion, and thus interference in the extending portion by the fastener is avoided. Therefore, strength of the housing may be increased in the coil device of solenoid type.

In some embodiments, the coil portion further includes a magnetic member disposed inside the bobbin. In this case, power efficiency is increased.

In some embodiments, the housing includes a first housing member facing a first surface of the coil portion having a flat plate shape, and a second housing member fixed to the first housing member to face a second surface on an opposite side from the first surface. In this case, strength of the housing may be increased by fastening the bobbin and at least one of the first housing member and the second housing member by the fastener.

In some embodiments, the bobbin includes a first winding plate disposed between the first housing member and the magnetic member, and a second winding plate disposed between the second housing member and the magnetic member, and the fastener penetrates through the magnetic member and fastens the first winding plate and the second winding plate. In this case, the magnetic member is provided between the first housing member and the second housing member. The fastener penetrates through the magnetic member, and the first winding plate and the second winding plate are fastened, and thus the housing is more strongly fixed to the bobbin.

In some embodiments, a hole portion is provided in the magnetic member, the first winding plate has a protrusion protruding to an inside of the hole portion, and the fastener includes a flange portion contacting the protrusion of the first winding plate from a side of the first housing member, a shaft portion formed on a distal end side of the flange portion to penetrate through the first winding plate, the magnetic member, and the second winding plate, and a distal end portion formed on a distal end side of the shaft portion and screwed to the second housing member. In this case, the protrusion of the first winding plate is pressed against the second winding plate and the second housing member by the fastener. The first winding plate and the second winding plate are more strongly fastened. The magnetic member is sandwiched between and held by the first winding plate and the second winding plate. The magnetic member may be fragile. However, according to the above configuration, strength of the magnetic member may be increased.

In some embodiments, the fastener includes a first screw member in which the flange portion, the shaft portion, and the distal end portion are integrally formed, and a second screw member penetrating through the first housing member to be screwed to the shaft portion. In this case, first, the protrusion of the first winding plate is pressed against the second winding plate and the second housing member by the first screw member. The first housing member is fastened to the first winding plate, the second winding plate, and the second housing member, which are integrated with one another, by the second screw member. In this way, the fastener may be reliably and easily provided by performing fastening in two discrete steps.

In some embodiments, the fastener penetrates through the housing. Fastening using the fastener is performed from the outside of the housing, and thus the fastener may be reliably and easily provided.

In some embodiments, the fastener includes a first combined member integrally provided in the first housing member to protrude toward the second housing member, and a second combined member integrally provided in the second housing member to protrude toward the first housing member, and at least one of the first combined member and the second combined member is disposed inside the coil portion, and the first combined member and the second combined member are combined together. In this case, the fastener does not penetrate through the housing, and thus a seal around the fastener is not needed.

In some embodiments, the conductive wire of the coil portion includes a first extending portion and a second extending portion extending to both sides of the fastener in the winding axis direction to form the enlarged portion, a distance between the fastener and the second extending portion is smaller than a distance between the fastener and the first extending portion, and a gap between the second extending portion and a third extending portion adjacent to the second extending portion in the winding axis direction is narrower than a gap between other extending portions. According to this configuration, the fastener is positioned nearer to the second extending portion between the first extending portion and the second extending portion. The gap between the second extending portion and the third extending portion is narrower than the gap between the other extending portions. Thus, a gap between extending portions (that is, a position of the conductive wire) may not be changed in a portion other than the enlarged portion in which the fastener is provided. Therefore, an influence on a magnetic field may be made as small as possible.

In some embodiments, the fastener is provided in a central region of the bobbin in the wound wire direction and the winding axis direction. In this case, strength of the housing is increased at a position corresponding to the central region of the bobbin. The housing is relatively easily bent at the position corresponding to the central region of the bobbin. Therefore, strength of the housing is further improved.

In some embodiments, the fastener is provided in a central region of the housing in the wound wire direction and the winding axis direction. In this case, strength of the housing is increased at a position corresponding to the central region of the housing. The housing is relatively easily bent in the central region. Therefore, strength of the housing is further improved.

In some embodiments, the fastener is provided in a region in which a decrease in power efficiency due to provision of the fastener is less than or equal to 0.1%. In this case, an influence on power efficiency by the fastener may be made as small as possible.

In some embodiments, the fastener is provided in a region in which a magnetic flux density in the coil portion is lower than a magnetic flux density in another region. In this case, an influence on a magnetic flux by the fastener may be made as small as possible.

In some embodiments, the at least one fastener includes a plurality of fasteners, and the plurality of fasteners are arranged along the winding axis direction.

In some embodiments, the at least one fastener includes a plurality of fasteners, and the plurality of fasteners are arranged along the wound wire direction.

Effects

According to some embodiments of the present disclosure, strength of a housing may be increased in a coil device of solenoid type.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described with reference to drawings. The same reference numeral will be applied to the same component in description of the drawings, and repeated description will be omitted.

A wireless power transfer system1to which a coil device of the present embodiment is applied will be described with reference toFIG. 1. The wireless power transfer system1is a system for feeding power from a power transmitter2to a power receiver3. For example, the power transmitter2and the power receiver3are separated from each other in a vertical direction. For example, the power transmitter2is installed in a parking lot, etc. For example, the power receiver3is installed in an electric vehicle EV. The wireless power transfer system1is configured to feed power to the EV arriving at the parking lot, etc. using a magnetic resonance scheme, an electromagnetic induction scheme, etc.

The power transmitter2includes a power transmission coil device4for wireless power transfer provided to protrude upward from a road surface of the parking lot, etc. For example, the power transmission coil device4has a shape of a flat rectangular parallelepiped or frustum. The power transmitter2generates desired AC power from a DC power source or an AC power source to send the generated AC power to the power receiver3, and further includes a controller, an inverter, etc. (not illustrated). For example, the power receiver3includes a power reception coil device5for wireless power transfer attached to a bottom surface of a vehicle body (chassis, etc.) of an EV to face the power transmission coil device4. For example, the power reception coil device5has a shape of a flat rectangular parallelepiped or frustum. The power receiver3receives power from the power transmitter2to feed power to a load (e.g., a battery), and further includes a controller, a rectifier, etc. (not illustrated). Hereinafter, the power transmission coil device4and the power reception coil device5will be referred to as a coil device4and a coil device5, respectively.

The coil device5will be described with reference toFIG. 1andFIG. 2. The coil device5generates an induced current when a magnetic flux generated by the power transmission coil device4interlinks with the coil device5. The coil device5corresponds to a solenoid type. The coil device5includes a flat plate-shaped coil portion C that generates an induced current and a housing10that accommodates the coil portion C.

For example, the housing10, which has a shape of a flat rectangular parallelepiped, includes a base (second housing member)12and a protective cover (first housing member)11that forms an accommodation space between the protective cover11and the base12(seeFIG. 3AandFIG. 3B). The protective cover11faces a surface (first surface) C1of the coil portion C. The base12faces a rear surface (second surface on the opposite side from the first surface) C2of the coil portion C. When the coil device5is installed in the EV, for example, the base12is fixed to the vehicle body side. The protective cover11faces the coil device4. That is, the base12is disposed above the coil portion C, and the protective cover11is disposed below the coil portion C while the coil device5is installed in the EV. For example, the base12and the protective cover11are made of resin. Alternatively, the base12, which does not face the coil device4, may be formed using a non-magnetic or conductive material (e.g., aluminum).

The base12is a portion fixed to the vehicle body of the EV. For example, the base12is fixed to the vehicle body by four screw members15at four corner portions. The base12, which has a rectangular shape, includes a rectangular-shaped accommodating depression12aslightly smaller than an external form thereof. The coil portion C is accommodated in the accommodating depression12a, and is fixed to the base12by a screw member such as a screw. An insulation sheet may be inserted between the coil portion C and the base12.

For example, the protective cover11, which has a rectangular shape, is fixed to the base12by four screw members14through four screw holes13at edges of the base12. A gap G (seeFIG. 4) is formed between the protective cover11and the coil portion C substantially over the entire region of the surface C1of the coil portion C. A fastener16described below is provided at a center of the protective cover11. A seat11band a through-hole11cfor providing the fastener16are formed in the protective cover11. The protective cover11protrudes to the coil portion C side in a portion in which the through-hole11cis formed. The above-described gap G extends between the protective cover11and the coil portion C in a region excluding the portion in which the through-hole11cis formed. The protective cover11may be flat over the entire region rather than protruding to the coil portion C side in the portion in which the through-hole11cis formed.

As illustrated inFIG. 2,FIG. 3AandFIG. 3B, the coil portion C includes a conductive wire30corresponding to a litz wire, and a flat plate-shaped bobbin20around which the conductive wire30is wound. The bobbin20includes a rectangular-shaped first winding plate21disposed on the surface C1side, and a rectangular-shaped second winding plate22disposed on the rear surface C2side. The first winding plate21and the second winding plate22are formed using the same material (e.g., a polyphenylene sulfide resin).

A ferrite plate (magnetic member)23is disposed between the first winding plate21and the second winding plate22. That is, the ferrite plate23is disposed inside the bobbin20. In plan view, a shape and a size of the ferrite plate23are substantially equal to or smaller than shapes and sizes of the first winding plate21and the second winding plate22. The ferrite plate23is sandwiched between and held by the first winding plate21and the second winding plate22. The first winding plate21is disposed between the ferrite plate23and the protective cover11. The second winding plate22is disposed between the ferrite plate23and the base12.

For example, a plurality of groove portions21bextending in a long-side direction of the coil portion C is formed in the first winding plate21. The plurality of groove portions21bis parallel to each other. A cross-sectional shape of the plurality of groove portions21bperpendicular to the long-side direction corresponds to a rectangular shape in which one side on the protective cover11side is open. The groove portion21bis recessed with respect to a surface21aof the first winding plate21, and has a predetermined depth.

For example, a plurality of groove portions22bextending in the long-side direction of the coil portion C is formed in the second winding plate22. The plurality of groove portions22bis parallel to each other. A cross-sectional shape of the plurality of groove portions22bperpendicular to the long-side direction corresponds to a rectangular shape in which one side on the base12side is open. The groove portion22bis recessed with respect to a surface22aof the second winding plate22, and has a predetermined depth.

The first winding plate21, the ferrite plate23, and the second winding plate22described above are integrated with one another, and are wound with the conductive wire30. More specifically, the conductive wire30is disposed inside the groove portion21band the groove portion22b. As illustrated inFIG. 3AandFIG. 3B, in the coil portion C, a position at which the groove portion21bis provided and a position at which the surface22ais provided are different from each other in a short-side direction of the coil portion C. In other words, the groove portion21band the groove portion22bare not aligned in the vertical direction (a direction perpendicular to the surface C1of the coil portion C, that is, a plate thickness direction of the first winding plate21and the second winding plate22).

According to the above configuration, the conductive wire30wound around the bobbin20includes a plurality of surface-side extending portions31extending on the first winding plate21and a plurality of rear surface-side extending portions32extending on the second winding plate22. The long-side direction of the coil portion C is equal to a wound wire direction of the conductive wire30, and the short-side direction of the coil portion C is equal to a winding axis direction of the conductive wire30. The wound wire direction and the winding axis direction are orthogonal to (intersect with) each other. The conductive wire30extends in a direction which is inclined with respect to the vertical direction on an end surface of the bobbin20in the wound wire direction. The respective surface-side extending portions31and the respective rear surface-side extending portions32are not aligned in the vertical direction. The surface-side extending portions31and the rear surface-side extending portions32are provided in a vertically diagonal shape (in zigzag) when viewed in the wound wire direction (seeFIG. 3AandFIG. 3B). When the conductive wire30is disposed as described above, portions of the conductive wire30are separated from each other as much as possible, and an insulation distance is ensured in the coil portion C.

A more detailed description will be given of the surface-side extending portions31and the rear surface-side extending portions32with reference toFIG. 3A,FIG. 3BandFIG. 4. The conductive wire30includes the plurality of surface-side extending portions31extending along the wound wire direction on the first winding plate21. The plurality of surface-side extending portions31has linear shapes, and is parallel to each other. The surface-side extending portions31include a plurality of first extending portions31alined up at equal intervals in the winding axis direction, and one second extending portion31band one third extending portion31cin which a gap between surface-side extending portions31adjacent to each other in the winding axis direction is different from that in the first extending portions31a.

As illustrated inFIG. 3B, a distance between centers, that is, a pitch of two first extending portions31aand31ais a first pitch P1. A pitch of the second extending portion31band a first extending portion31aadjacent to the second extending portion31bis a second pitch P2. The second pitch P2is larger than the first pitch P1. When distances between the surface-side extending portions31are compared, pitches may be used for the comparison as described above, or gaps between the surface-side extending portions31may be used for the comparison as illustrated inFIG. 4. A gap between the first extending portions31aand31a, that is, a distance between two inner end surfaces facing each other in the winding axis direction is a first gap D1. A gap between the second extending portion31band the first extending portion31aadjacent to the second extending portion31bis a second gap D2. The second gap D2is larger than the first gap D1.

The coil portion C includes an enlarged portion35in which the second gap D2between the first extending portion31aand the second extending portion31badjacent to each other in the winding axis direction is wider than a gap between another first extending portion31aand another first extending portion31a. In other words, while the first gap D1between the first extending portion31aand the first extending portion31aadjacent to each other is uniform in a plurality of portions of the coil portion C, the second gap D2between the first extending portion31aand the second extending portion31badjacent to each other is different from the first gap D1. When the enlarged portion35is provided, a pitch of the conductive wire30is non-uniform as a whole of the surface-side extending portions31. The enlarged portion35may not be formed on the surface C1of the coil portion C by the surface-side extending portions31, and may be formed on the rear surface C2by the rear surface-side extending portions32as illustrated inFIG. 4.

As illustrated inFIG. 3B, a pitch of the second extending portion31band the third extending portion31cadjacent to the second extending portion31bis a third pitch P3. The third pitch P3is smaller than the first pitch P1. As illustrated inFIG. 4, a gap between the second extending portion31band the third extending portion31cadjacent to the second extending portion31bis a third gap D3. The third gap D3is smaller than the first gap D1.

As illustrated inFIGS. 2 to 5, in the coil portion C, only a position of the second extending portion31bamong the surface-side extending portions31is shifted (leaned) to one side in the winding axis direction.FIG. 4illustrates positions of the extending portions using a virtual line when the conductive wire30is wound at all equal pitches without providing the enlarged portion35. As illustrated inFIG. 4using the virtual line, the second gap D2is twice or more as large as the first gap D1. The fastener16capable of increasing strength of the protective cover11is provided in the enlarged portion35in which a pitch of the conductive wire30is enlarged. A hole portion26in which the fastener16is provided is formed between the first extending portion31aand the second extending portion31bin the bobbin20of the coil portion C. According to this arrangement, interference in the conductive wire30by the fastener16is avoided.

As illustrated inFIG. 3AandFIG. 3B, the conductive wire30includes the plurality of rear surface-side extending portions32extending along the wound wire direction on the second winding plate22. The plurality of rear surface-side extending portions32has linear shapes, and is parallel to each other. The rear surface-side extending portions32include a plurality of first extending portions32alined up at equal intervals in the winding axis direction. A distance between centers, that is, a pitch of two extending portions32aand32ais a first pitch P1. As illustrated inFIG. 4, a gap between the extending portions32aand32a, that is, a distance between two inner end surfaces facing each other in the winding axis direction is a first gap D1. In this way, the first gap D1between the extending portion32aand the extending portion32aadjacent to each other is uniform in the coil portion C.

The enlarged portion35is a portion in which “a gap between extending portions adjacent to each other in the winding axis direction is wider than a gap between other extending portions”. Herein, when “the gap between the other extending portions” is calculated, various schemes are considered. For example, when most extending portions have the first gap D1between the first extending portions31aand31ain the coil portion C as described above, the first gap D1may be set as a standard. When gaps between adjacent extending portions are different from each other (or a dispersion is present), an average of gaps at a plurality of points may be calculated, and a portion, in which a gap is wider than the average, may be set as an enlarged portion. An exposed surface of the bobbin20formed between adjacent extending portions (e.g., an area per unit length in the wound wire direction) may be calculated, and a portion, in which an exposed surface is larger than that of another portion, may be set as an enlarged portion. An average of exposed areas of the bobbin20at a plurality of points may be calculated, and a portion, in which an exposed area is larger than the average, may be set as an enlarged portion.

As illustrated inFIG. 3B, symmetry between the surface-side extending portions31and the rear surface-side extending portions32is maintained in the coil portion C except for the second extending portion31bof the surface-side extending portions31. The plurality of first extending portions31a, the second extending portion31b, and the third extending portion31ccorrespond to the plurality of rear surface-side extending portions32, and a relationship of a vertically diagonal shape (a zigzag positional relation) is maintained.

A detailed description will be given of the fastener16with reference toFIG. 4andFIG. 5. As illustrated inFIG. 5, the fastener16is provided in a first central region A1which is a central region of the bobbin20in the wound wire direction and the winding axis direction. In other words, the fastener16is provided at an intersection point of first diagonal lines L1and L1, that is, a central point of the bobbin20.

The fastener16may be provided inside the first central region A1, a center of which corresponds to the intersection point of first diagonal lines L1and L1of the bobbin20. The fastener16may be provided in a second central region A2which is a central region of the housing10(that is, the protective cover11or the base12) in the wound wire direction and the winding axis direction. In other words, the fastener16may be provided at an intersection point of second diagonal lines L2and L2, that is, a central point of the base12, or may be provided inside the second central region A2, a center of which corresponds to the intersection point.

As illustrated inFIG. 4, the fastener16is provided along the vertical direction. The fastener16is orthogonal to the wound wire direction and the winding axis direction. The fastener16penetrates through the protective cover11, the first winding plate21, the ferrite plate23, and the second winding plate22. A distal end portion17cof the fastener16does not penetrate through the base12, and terminates inside the base12. More specifically, the fastener16includes a first screw member17screwed to the base12and a second screw member18screwed to the first screw member17. Each of the first screw member17and the second screw member18is made of a non-magnetic material. The first screw member17and the second screw member18may be non-magnetic or magnetic. The fastener16strongly fastens the protective cover11, the first winding plate21, the ferrite plate23, the second winding plate22, and the base12using two (a plurality of) screw members. In addition, when the first screw member17and the second screw member18are made of a material having a thermal conductivity, a portion of heat of the ferrite plate23heated by wireless power transfer is successively transferred to a seat21c, the first screw member17, and the second screw member18, and is released to the outside from a head portion18a. In particular, when the first screw member17and the second screw member18are made of a material having a high thermal conductivity (e.g., metal), heat release effect is improved.

For example, a circular hole portion23ais provided at a position corresponding to the fastener16in the ferrite plate23. The first winding plate21includes a cylindrical seat (protrusion)21cthat protrudes to the inside of the hole portion23a. The hole portion23amay be a rectangle. A circular through-hole21dis provided at a center of the seat21c. A through-hole22cthat communicates with the through-hole21dis formed in the second winding plate22. The seat21cof the first winding plate21is disposed inside the hole portion23aof the ferrite plate23. A rear surface of the seat21ccontacts the second winding plate22.

The first screw member17includes a disc-shaped flange portion17athat contacts the seat21cof the first winding plate21from the protective cover11side, a shaft portion17bformed on a distal end side of the flange portion17ato penetrate through the first winding plate21, the ferrite plate23, and the second winding plate22, and the distal end portion17cformed on a distal end side of the shaft portion17band screwed to the base12. The shaft portion17bis disposed inside the through-hole21dand the through-hole22c. A female screw and a screw insertion hole to which the second screw member18may be screwed are formed in the shaft portion17b. The flange portion17a, the shaft portion17b, and the distal end portion17care integrally formed. The hole portion26of the coil portion C described above (seeFIG. 2) includes the through-hole21d, the hole portion23a, and the through-hole22c.

The second screw member18includes the head portion18awith which a rotating tool, etc. can be engaged, a shaft portion18bformed on a distal end side of the head portion18ato penetrate through the protective cover11, and a distal end portion18cscrewed to the shaft portion17bof the first screw member17. The shaft portion18bis disposed inside the through-hole11cof the protective cover11. The head portion18a, the shaft portion18b, and the distal end portion18care integrally formed.

A seal member is appropriately provided between the protective cover11and the flange portion17a. A cylindrical member19is provided between the shaft portion18bof the second screw member18and the seat11bof the protective cover11.

When fastening is performed using the fastener16, the second winding plate22in which the through-hole22cis provided, the ferrite plate23in which the hole portion23ais provided, and the first winding plate21in which the through-hole21dis provided are superposed. The first winding plate21, the ferrite plate23, the second winding plate22, and the base12are fastened by screwing the first screw member17in the base12. The flange portion17aimmobilizes the seat21cof the first winding plate21on the base12side. In this way, the seat21cis pressed against the second winding plate22, the ferrite plate23sandwiched between the first winding plate21and the second winding plate22is fixed. Then, the seat11bof the protective cover11is superposed on the seat21cof the first winding plate21through the flange portion17a. The protective cover11is fastened to the first winding plate21, the ferrite plate23, the second winding plate22, and the base12by screwing the second screw member18in the base12. The protective cover11is supported by the base12and the coil portion C (bobbin20) through the flange portion17aof the fastener16.

The seat11bof the protective cover11is recessed from the end surface11aand formed in a cylindrical shape. A cylindrical space S is formed in a recessed portion of the seat11b. The head portion18aof the second screw member18is accommodated in the space S. An upper end surface of the head portion18ais positioned on the base12side from the end surface11a. That is, the head portion18ais installed on the base12side from the end surface11aof the protective cover11. As illustrated inFIG. 1, the protective cover11is disposed on a lower side in a state in which the coil device5is installed in the EV. When the head portion18aof the fastener16is positioned on the base12side from the end surface11aof the protective cover11(that is, a lower end surface of the coil device5), a position of a lowermost end (that is, a minimum height) of the coil device5may be prevented from being lowered by the fastener16. In this way, it is possible to avoid touching an object by the head portion18aof the fastener16when the EV is driven or stopped.

According to the coil device5of the present embodiment, the housing10is accommodated in the coil portion C that includes the bobbin20and the ferrite plate23. The plurality of surface-side extending portions31and rear surface-side extending portions32extending in the wound wire direction on the bobbin20have gaps in the winding axis direction. The enlarged portion35, in which the second gap D2between the first extending portion31aand the second extending portion31badjacent to each other is wider than the first gap D1between other first extending portions31aand31a, is provided in the coil portion C. The fastener16is provided in the enlarged portion35. The bobbin20and the housing10are fastened by the fastener16. The gap between the first extending portion31aand the second extending portion31bis wide in the enlarged portion35, and thus it is possible to avoid interfering in the surface-side extending portions31and the rear surface-side extending portions32by the fastener16(seeFIG. 4). Strength of the housing10is increased in the coil device5of solenoid type.

The housing10includes the protective cover11and the base12. Strength of the housing10is increased by fastening the bobbin20and both the protective cover11and the base12using the fastener16.

The ferrite plate23is provided between the protective cover11and the base12. The fastener16penetrates the ferrite plate23to fasten the protective cover11and the base12. Therefore, the housing10is more strongly fixed to the bobbin20. Further, movement of the ferrite plate23in the wound wire direction and the winding axis direction is regulated.

The seat11bof the protective cover11is pressed against the second winding plate22and the base12by the fastener16. Therefore, the first winding plate21and the second winding plate22are more strongly fastened. The ferrite plate23is sandwiched between and held by the first winding plate21and the second winding plate22. In general, the ferrite plate23may be fragile. However, according to the above-described configuration, strength of the ferrite plate23is increased.

The fastener16includes two members corresponding to the first screw member17and the second screw member18. First, the seat21cof the first winding plate21is pressed against the second winding plate22and the base12by the first screw member17. The protective cover11is fastened to the first winding plate21, the second winding plate22, and the base12, which are integrated with one another, by the second screw member18. In this way, the fastener16may be reliably and easily provided by performing fastening in two discrete steps.

Since the fastener16penetrates through the housing10, fastening using the fastener16may be easily performed from the outside of the housing10. Therefore, the fastener16may be reliably and easily provided.

The fastener16is positioned nearer to the second extending portion31bbetween the first extending portion31aand the second extending portion31b. The third gap D3between the second extending portion31band the third extending portion31cis narrower than the first gap D1between the other first extending portions31aand31a. Thus, a gap between the surface-side extending portions31(that is, a position of the conductive wire30) may not be changed or adjusted in a portion other than the enlarged portion35in which the fastener16is provided. Therefore, an influence on a magnetic field is minimized. It is possible to minimize a variation of a magnetic field distribution due to a magnetic flux leakage with respect to a magnetic field distribution generated by the coil portion C around which the conductive wire is wound at the first pitch P1in a whole area.

Since the fastener16is provided in the first central region A1of the bobbin20in the wound wire direction and the winding axis direction, strength of the housing10is increased at a position corresponding to the first central region A1of the bobbin20. When the fastener16is not provided, the housing10is relatively easily bent at a position corresponding to the second central region A2of the bobbin20. Strength of housing10is further improved by the fastener16.

Even when the fastener16is provided in the second central region A2of the housing10in the wound wire direction and the winding axis direction, strength of the housing10is increased at a position corresponding to the second central region A2of the housing10. When the fastener16is not provided, the housing10is relatively easily bent in the second central region A2. Strength of housing10is further improved by the fastener16.

The coil device5has advantageous effect in contrast with the above respective conventional art documents. In the above Patent Literature 1, there is no examination of a scheme of attaching the power reception coil device to the outside of the vehicle. When the power reception coil device is installed inside the vehicle, the power reception coil device is supported by the chassis. However, it is unclear how to suspend the power reception coil device when the power reception coil device is installed to be exposed to the outside of the chassis of the vehicle. In general, as a distance between the power transmission coil device and the power reception coil device decreases, transmitting efficiency increases. Thus, there is a great need to attach the power reception coil device to the outside of the chassis of the vehicle. In this regard, according to the coil device5of the present embodiment, the base12is fixed to the outside of the chassis. When the protective cover11facing the power transmission coil device4is made of a non-magnetic material, for example, resin, a magnetic flux generated by the coil device4is not affected. Therefore, efficient wireless power transfer is achieved. Further, when a non-magnetic and non-conducting material is used for the protective cover11, power efficiency of wireless power transfer may be further increased. When the base12facing the vehicle body side is made of a non-magnetic and conductive material, structural strength of the coil device5may be improved while suppressing an influence on a magnetic field distribution between the coil device4and the coil device5. In addition, the non-magnetic and conductive base12functions as a magnetic shielding, and thus magnetic fluxes heading the coil devices4and5increase, and power efficiency may be improved.

In the above Patent Literature 2, an outer circumferential portion of the bobbin is attached to the vehicle, and thus a central region is not fixed. For this reason, there is concern that a central region may be easily bent and broken, thereby causing damage due to external impact even when the power reception coil device of Patent Literature 1 is attached as in Patent Literature 2. In addition, the power reception coil device is subjected to thermal strain due to power reception, or receives a vibration of the vehicle. The central region, which is not fixed, is easily affected by a force generated in these circumstances. In this regard, according to the coil device5of the present embodiment, strength of the central region of the housing10is increased, and the above-mentioned problem is solved.

The above Patent Literature 3 discloses that a central region of the substrate is bolted. However, only the substrate is fixed, and the protective cover is not fixed. For this reason, a central region of the protective cover is bent similarly to Patent Literature 2. In addition, Patent Literature 2 mentions a spacer for ensuring strength of the protective cover. However, when the power reception unit is attached backward, and the protective cover is bent, a gap is generated between the spacer and the protective cover. Thus, there is difficulty in ensuring strength of the protective cover. In this regard, in the coil device5of the present embodiment, the housing10and the bobbin20are fastened by the fastener16, and thus strength of the housing10is ensured.

Originally, the bolt or the spacer may be provided in the central region of the power reception unit as in Patent Literature 3 since the coil has a circular shape in which a space is present in the central region. There is difficulty in employing a scheme of Patent Literature 3 in a solenoid coil as in Patent Literature 1 in which a conductive wire is wound around a central region. In addition, a cross-sectional view of the power reception coil device is given in FIG. 7 of Patent Literature 1, and conductive wire positions of an upper ferrite housing portion and a lower ferrite housing portion are matched with each other. Thus, the bolt may be vertically inserted so as not to interfere in the conductive wire. However, a pitch of the conductive wire may not be longer than a width of the bolt. As disclosed in Patent Literature 2 (paragraph 0025), when the conductive wire is sparsely and densely wound, there are problems of heating due to an eddy current in a dense part and a magnetic flux leakage in a sparse part, and thus the conductive wire is preferably wound at equal intervals. For this reason, when the pitch of the conductive wire is set to be wider than the width of the bolt, the power reception coil device increases in size as a whole. However, the power reception coil device is required to be reduced in size due to a characteristic that the power reception coil device is installed in a vehicle in which an installation position is restricted. In addition, the conductive wire needs to be densely wound to improve transmitting efficiency. For this reason, there is difficulty in setting all pitches of the conductive wire to be wider than the width of the bolt. Further, positions of the conductive wire are provided in a diagonal shape rather than being vertically matched in many cases in terms of ensuring an insulation distance (necessity of separating pieces of the conductive wire as much as possible) (see the surface-side extending portions31and the rear surface-side extending portions32illustrated inFIG. 16). In this case, one of upper and lower pitches of the conductive wire (a gap between the surface-side extending portions31and31) includes a position of another conductive wire position (the rear surface-side extending portion32), and thus there is difficulty in inserting a bolt116such that the conductive wire is not interfered. In this regard, in the coil device5of the present embodiment, the above-mentioned various problems are overcome.

The present disclosure is not limited to the above-described embodiment. The present invention includes various modifications. In the above embodiment, a description has been given of a mode in which arrangement of the fastener16is determined based on the first central region A1of the bobbin20or the second central region A2of the housing10. However, arrangement of the fastener16may be determined based on another criterion.

For example, as illustrated inFIG. 6A, arrangement of the fastener16may be determined based on a viewpoint on a magnetic flux. In the bobbin20, regions FS and FS in which a magnetic flux is strong are formed at both end portions in the winding axis direction. Regions FM and FM in which a magnetic flux is moderate are formed at both end portions in the wound wire direction. A magnetic flux is relatively weak in a central region FW in the winding axis direction and the wound wire direction except for the region FS and the region FM. In some modes, one or a plurality of fasteners16may be disposed in the region FM in which the magnetic flux is weak.

A description will be given of a specific range of the region FW in which the magnetic flux is weak. The regions FS and FS in which the magnetic flux is strong are regions corresponding to 20% to 40% of a whole length of the coil portion C in the winding axis direction from both end portions of the coil portion C. The regions FM and FM in which the magnetic flux is moderate are regions corresponding to 20% to 40% of a whole length of the coil portion C in the wound wire direction from both end portions of the coil portion C. Therefore, for example, the region FW in which the magnetic flux is weak corresponds to a region in a range of 20% to 60% in the middle in the winding axis direction and a region in a range of 20% to 60% in the middle in the winding axis direction.

When a determination scheme based on the viewpoint on the magnetic flux is described from another point of view, the fastener16may be provided in a region in which a decrease in power efficiency due to provision of the fastener16is less than or equal to 0.1%. Power efficiency refers to a ratio of power at a certain place inside the power receiver3to power at a certain place inside the power transmitter2. For example, power efficiency refers a ratio of power of an output of a rectifier of the power receiver3to power of an input of an inverter of the power transmitter2. In this case, an influence on power efficiency by the fastener16may be made as small as possible. When the determination scheme based on the viewpoint on the magnetic flux is described from another different point of view, the fastener16may be provided in a region in which a magnetic flux density in the coil portion C is lower than that in another region. In this case, an influence on a magnetic flux by the fastener16may be made as small as possible. An average magnetic flux density in a plurality of regions may be calculated, and the fastener16may be provided in a region in which a magnetic flux density is lower than the average. The fastener16may be provided in a region in which a magnetic flux density is lowest.

As illustrated inFIG. 6B, arrangement of the fastener16may be determined based on a viewpoint on strength. In some modes, one or a plurality of fasteners16may be provided in a rectangular-shaped region A3extending in a short-side direction of the bobbin20(that is, the winding axis direction) in which the intersection point of the first diagonal lines L1and L1of the bobbin20is set as a center.

As illustrated inFIG. 7, one or a plurality of fasteners16may be provided in a region A4where the region FW in which the magnetic flux is weak overlaps the rectangular-shaped region A3.

As illustrated inFIG. 8, an enlarged portion35A may be provided by providing fourth extending portions31dand31d, a gap of which is widened only in a part in the wound wire direction. In this coil portion CA, the fourth extending portion31d, which is curved in an arc, is provided in a middle portion of a first extending portion31ahaving a linear shape. The enlarged portion35A is provided in the first central region A1(seeFIG. 5). The fastener16is provided in the enlarged portion35A. In other words, the enlarged portion35A is provided to circle around the fastener16.

As illustrated inFIG. 9A, for example, it is possible to have a coil portion CB in which fifth extending portions31eand31eare provided on the first winding plate21. Here, the fifth extending portions31eand31ehave a pitch which is twice as large as (an integer multiple) of the first pitch P1between the first extending portions31aand31a. In this case, when an enlarged portion35B is provided, the number of turns in the first winding plate21is decreased to be smaller than the number of turns in the second winding plate22. As illustrated inFIG. 9B, symmetry between the surface-side extending portions31and the rear surface-side extending portions32is not maintained.

As illustrated inFIG. 10, it is possible to employ a mode in which a fastener is divided into two parts corresponding to a fastener16C on the protective cover11side and a fastener16C on the base12side. An enlarged portion35C is configured similarly to the enlarged portion35B illustrated inFIG. 9A. In this case, the two fasteners16C are provided from the outside of the housing10. The fastener16C on the protective cover11side penetrates through the protective cover11, and does not penetrate through the ferrite plate23. The fastener16C on the base12side penetrates through the base12, and does not penetrate through the ferrite plate23. In other words, a distal end of the fastener16C terminates inside the first winding plate21or the second winding plate22. A seal member is provided between the fastener16C on the protective cover11side and the protective cover11. A seal member is provided between the fastener16C on the base12side and the base12.

As illustrated inFIG. 11, it is possible to employ a mode in which a fastener is divided into two parts corresponding to a fastener16D on the protective cover11side and a fastener16D on the base12side. An enlarged portion35D is configured similarly to the enlarged portion35B illustrated inFIG. 9A. In this case, the two fasteners16D and16D are provided from the inside of the bobbin20(that is, the ferrite plate23side of the first winding plate21and the ferrite plate23side of the second winding plate22). The fastener16D on the protective cover11side does not penetrate through the protective cover11and the ferrite plate23. The fastener16D on the base12side does not penetrate through the base12and the ferrite plate23. In other words, a base end of the fastener16D does not protrude from a surface of the first winding plate21or the second winding plate22on the ferrite plate23side. A distal end of the fastener16D on the protective cover11side terminates inside the protective cover11. A distal end of the fastener16D on the base12side terminates inside the base12. A seal member is not needed between the fastener16D on the protective cover11side and the protective cover11. A seal member is not needed between the fastener16D on the base12side and the base12.

As illustrated inFIG. 12, it is possible to employ a mode in which two fasteners16E and16E are provided on the protective cover11side. The fasteners16E and16E are obliquely disposed with respect to a virtual plane which is perpendicular to the winding axis direction. The fasteners16E and16E form an angle with respect to the virtual plane which is perpendicular to the winding axis direction. The fasteners16E and16E are provided to avoid interference by a surface-side extending portion31and an extending portion32aon the base12side close to each other. The fasteners16E and16E penetrate through the protective cover11and the ferrite plate23. Distal ends of the fasteners16E and16E terminate inside the base12. A seal member is provided between the fasteners16E and16E and the protective cover11.

As illustrated inFIG. 13, it is possible to employ a mode in which a plurality of miniaturized screw members is used.FIG. 13illustrates a case in which four fasteners16F are provided. A thickness (diameter) of each of the fasteners16F may be appropriately changed. For example, one medium-sized fastener16F is used on the protective cover11side to fasten the protective cover11and the first winding plate21. The second winding plate22and the ferrite plate23are fastened by two small-sized fasteners16F and16F on the base12side. Further, the base12and the second winding plate22are fastened by one small-sized fastener16F. A seal member is provided between the fastener16F and the protective cover11or the base12only when the fastener16F penetrates through the protective cover11or the base12. The “middle-sized fastener” and the “small-sized fastener” correspond to thicknesses (diameters) when the one fastener16illustrated inFIG. 3AandFIG. 3Bis set as a criterion. When a plurality of middle-sized or small-sized fasteners is used, an influence on a magnetic field distribution may be reduced.

As illustrated inFIG. 14, a key structure may be provided inside the protective cover11and the base12. That is, a fastener16G includes a first combined member11gintegrally provided with a protective cover11G to protrude toward a base12G, and a second combined member12gintegrally provided with the base12G to protrude toward the protective cover11G. At least one of the first combined member llg and the second combined member12gis disposed inside a coil portion CG. In other words, at least one of the first combined member11gand the second combined member12gintersects with (enters) the coil portion CG. The first combined member11gand the second combined member12gare combined together. More specifically, the fastener16G is configured such that a distal end of the first combined member11gfits into a depression of a distal end of the second combined member12g. As the protective cover11G is further pressed against the base12G fastening strength between the first combined member11gand the second combined member12gincreases. In this case, the fastener16G is integrally provided with a housing10G, and does not penetrate through the housing10G, and thus a seal around the fastener16G is not needed.

As illustrated inFIG. 15A, two (a plurality of) fasteners16H may be arranged along the winding axis direction. In this case, for example, two enlarged portions35H, in which a gap between parallel surface-side extending portions31is widened, are provided in a coil portion CH. The fasteners16H are provided in the respective enlarged portions35H. In this case, the fasteners16H and16H may be provided in point symmetry about the intersection point of the first diagonal lines L1and L1, that is, the central point of the bobbin20(seeFIG. 5). In this way, loads applied to both the fasteners16H and16H may be easily balanced, and thus strength of the protective cover may be easily increased.

As illustrated inFIG. 15B, two (a plurality of) fasteners16J may be arranged along the wound wire direction. In this case, for example, two enlarged portions35J that circle around the fasteners16J are provided in a coil portion CJ by bending middle portions of linear-shaped surface-side extending portions31in arcs. The fasteners16J are provided in the respective enlarged portions35J. In this case, the fasteners16J and16J are provided in point symmetry about the intersection point of the first diagonal lines L1and L1, that is, the central point of the bobbin20(seeFIG. 5). In addition, if only a position of the second extending portion31bamong the surface-side extending portions31is shifted to one side in the winding axis direction as inFIG. 5, the plurality of fasteners16J may be provided even when a plurality of enlarged portions35is not provided unlike the mode ofFIG. 15A. When the number of enlarged portions35is suppressed, it is possible to suppress a magnetic flux leakage from between pitches due to the enlarged portions35.

If a plurality of fasteners is provided as described above, sizes of the fasteners may be determined such that a surface area of a surface through which magnetic fluxes of the fasteners pass is the same as a surface area obtained when one fastener16is provided. When a surface area of a surface through which magnetic fluxes pass is prevented from increasing, a demerit due to a plurality of fasteners is excluded.

In the above embodiment, a description has been given on a case in which the groove portion21band the groove portion22bare formed on the first winding plate21and the second winding plate22. However, the present invention is not limited to this case. The conductive wire30may extend on a surface of a flat winding plate without forming a groove portion on the winding plate.

The present invention is not limited to a case in which the distal end portion17cof the fastener16does not penetrate through the base12, and the distal end portion17cmay penetrate through the base12. For example, the distal end portion17cpenetrating through the base12is screwed to the vehicle body, and the coil device5is more strongly installed in the vehicle body.

In the above embodiment, a description has been given on a case in which an enlarged portion is provided only on the protective cover11side or both the protective cover11side and the base12side. However, the present invention is not limited to this case. For example, the enlarged portion may be provided only on the base12side.

The present invention is not limited to a case in which the bobbin20is disposed on the base12such that the first central region A1and the second central region A2do not fully overlap each other (seeFIG. 5). For example, the bobbin20may be disposed on the base12such that a center of the bobbin20overlaps a center of the base12.

In the above embodiment, a description has been given on a case in which a magnetic member is the ferrite plate23. However, the magnetic member is not restricted to the ferrite plate23. The magnetic member may be made of another magnetic material (e.g., a silicon steel plate, an amorphous magnetic alloy, and a magnet). In particular, the magnetic member may be made of a soft magnetic material (e.g., ferrite, a silicon steel plate, and an amorphous magnetic alloy) in terms of improving power efficiency. In addition, a component disposed inside the bobbin20is not restricted to the magnetic member, and may correspond to a reinforcing material that fills a portion or a whole of a cavity inside the bobbin20to ensure strength of the coil portion C. Further, the present invention is not limited to a case in which the magnetic member or the reinforcing material is disposed inside the bobbin20. The coil portion C may be an air-core coil in which the inside of the bobbin20remains as a cavity.

The above embodiment gives an example in which the litz wire is used as the conductive wire30. However, the present invention is not limited thereto. A conductive wire other than the litz wire may be used as long as the conductive wire functions as a coil device for wireless power transfer. For example, a type, a figure, a form, a material, a configuration, a shape, and a dimension of the conductive wire30are arbitrarily selected.

In the above embodiment, a description has been given on a case in which the present disclosure is applied to the coil device5. However, the present invention is not limited thereto. The present disclosure may be applied to the power transmission coil device4. In addition, in the above embodiment, a description has been given on a case in which the coil device of the present disclosure is applied to the wireless power transfer system. However, a system to which the coil device is applied is not restricted to the wireless power transfer system. For example, the coil device of the present disclosure may be applied to an induction heating system or an eddy current flaw detection system.

In the above embodiment (in particular, the mode ofFIG. 4), a description has been given on a case in which the fastener16includes the first screw member17and the second screw member18as a detailed description of the fastener16. However, the present invention is not limited thereto. For example, a cylindrical member having the same flange portion as the flange portion17amay be employed in place of the first screw member17. In this case, the shaft portion18bof the second screw member18has a shape extended to an extent to penetrate through the cylindrical member, and the distal end portion18cis screwed to the base12rather than the shaft portion17bof the first screw member17.

INDUSTRIAL APPLICABILITY

According to some embodiments of the present disclosure, strength of a housing may be increased in a coil device of solenoid type.