JP6856148B2 - Coil unit and power transmission device, power receiving device and wireless power transmission system using it - Google Patents

Description

The present invention relates to a structure of a coil unit preferably used in a wireless power transmission system. The present invention also relates to a power transmission device, a power receiving device, and a wireless power transmission system using such a coil unit.

Wireless power transmission technology, which transmits power without using a power cable or power cord, is attracting attention. Since wireless power transmission technology can wirelessly supply power from the power transmission side to the power reception side, it can be used for various transportation equipment such as trains, electric vehicles, automatic guided vehicles, home appliances, electronic equipment, wireless communication equipment, toys, and industrial equipment. It is expected to be applied to products.

In wireless power transmission technology, in order to extend the transmission distance, a power transmission method using a resonance phenomenon by a resonance circuit formed by connecting a capacitor to a coil is known.

In this power transmission method, the coil unit is miniaturized by integrating the coil and the capacitor. For example, Patent Document 1 discloses a coil unit in which a capacitor is arranged in a protruding support portion of a shield member.

Japanese Unexamined Patent Publication No. 2016-103612

However, in the technique disclosed in Patent Document 1, since the external dimension of the shield member is larger than the external dimension of the core member, the magnetic flux generated from the coil is likely to be interlinked with the shield member, and the shield member may generate heat. It was. Further, Patent Document 1 does not mention any exhaust heat of heat generated by passing an electric current through the coil, which may lead to damage to components of the coil unit such as a coil and a capacitor.

The present invention has been made in view of the above problems, and provides a coil unit capable of efficiently dissipating heat while suppressing heat generation, and a power transmission device, a power receiving device, and a wireless power transmission system using the same. With the goal.

In order to solve the above problems, the coil unit according to the present invention is arranged on a coil in which a lead wire is wound in a spiral shape, a capacitor electrically connected to the coil, and one end side of the coil in the coil axial direction. The magnetic material, the first metal shield arranged on the side opposite to the facing surface of the magnetic material with the coil, and the storage space of the capacitor arranged between the magnetic material and the first metal shield. The second metal shield is arranged so as to be thermally connected to the first metal shield, and the outer dimensions of the second metal shield are the outer dimensions of the magnetic material. It is characterized by being less than or equal to the size.

According to the present invention, since the second metal shield is equal to or smaller than the outer shape of the magnetic material, it is possible to prevent the magnetic flux generated from the coil from interlinking with the second metal shield to generate heat of the second metal shield. Further, when a current flows through the coil, the coil and the magnetic material generate heat, and the heat generated from the coil and the magnetic material during power transmission can be efficiently dissipated to the first metal shield side. Therefore, the heat generated in the coil unit can be efficiently dissipated while suppressing heat generation.

In the present invention, it is preferable that the second metal shield is arranged so as to be thermally connected to the magnetic material. As a result, the heat generated in the coil unit can be dissipated more efficiently.

In the present invention, the second metal shield preferably includes a flat plate portion arranged so as to face the magnetic material and a side wall connected to the flat plate portion and arranged around the capacitor. According to this configuration, not only the storage space of the capacitor can be secured by the simple configuration, but also the heat dissipation path of the coil and the magnetic material can be secured.

In the present invention, it is preferable that the tip end portion of the side wall from the flat plate portion toward the first metal shield is arranged so as to face the main surface of the first metal shield. As a result, even if the position of the first metal shield with respect to the second metal shield is displaced, the contact area between the first metal shield and the second metal shield can always be secured to prevent deterioration of heat dissipation.

In the present invention, it is preferable that an opening is provided in a part of the side wall, and the power cable connected to the coil or the capacitor is drawn out from the opening. According to this configuration, the terminals of the coil unit can be easily pulled out.

In the present invention, the second metal shield has an elongated planar shape in one direction when viewed from the coil axis direction, the coil axis of the coil faces in a substantially horizontal direction, and the opening is the second metal shield. It is preferable that the coil is provided on one end side in the longitudinal direction of the coil. According to this configuration, the coil unit can be made low in height in a system in which the coil surfaces are installed substantially vertically and power is transmitted in a substantially horizontal direction. Further, since the coil surface is substantially vertical, metal foreign matter does not adhere to the coil surface, and it is possible to avoid a decrease in power transmission efficiency due to the metal foreign matter and heat generation of the metal foreign matter. The coil shaft of the coil may be substantially horizontal, and is not required to be strictly horizontal. Therefore, the direction of the coil shaft may be within ± 10 degrees with respect to the horizontal shaft.

In the present invention, the second metal shield further includes a collar portion in which the tip end portion of the side wall is bent inward or outward, and the collar portion is thermally connected to the main surface of the first metal shield. It is preferable that they are arranged in such a manner. According to this configuration, the thermal resistance between the first metal shield and the second metal shield can be lowered to improve heat dissipation.

In the present invention, it is preferable that the second metal shield has an elongated planar shape in one direction when viewed from the coil axis direction, and the collar portion is provided along the longitudinal direction of the second metal shield. According to this configuration, the area of the collar portion can be secured as wide as possible, the thermal resistance of the collar portion can be lowered, and the heat dissipation can be improved.

In the present invention, it is preferable that the external dimension of the second metal shield viewed from the coil axial direction is equal to or larger than the external dimension of the coil. According to this configuration, the coil and the capacitor can be reliably supported on the main surface of the first metal shield, and a desired shielding effect and heat dissipation effect can be obtained.

In the present invention, it is preferable that the external dimensions of the first metal shield viewed from the coil axis direction are larger than the external dimensions of the second metal shield. According to this configuration, the heat dissipation of the entire coil unit can be improved.

In the present invention, it is preferable that a heat sink is provided on the side of the first metal shield opposite to the surface facing the second metal shield. As described above, the structure provided with the heat sink on the back surface of the first metal shield makes it possible to reduce the height of the coil unit and improve the power transmission efficiency, and to dissipate the heat generated in the coil unit more efficiently. This is especially advantageous in horizontal power transmission.

Further, the power transmission device according to the present invention is characterized by including a coil unit having the above-described characteristics of the present invention and an inverter circuit connected to the coil unit. According to the present invention, it is possible to provide a power transmission device capable of suppressing heat generation and reducing a leakage magnetic flux that largely orbits a region away from an opposing coil.

Further, the power receiving device according to the present invention is characterized by including a coil unit having the above-described characteristics of the present invention and a rectifier circuit connected to the coil unit. According to the present invention, it is possible to provide a power receiving device capable of suppressing heat generation and reducing a leakage magnetic flux that largely orbits a region away from an opposing coil.

Furthermore, the wireless power transmission system according to the present invention includes a power transmission device that wirelessly transmits power and a power reception device that wirelessly receives power transmitted from the power transmission device, and at least the power transmission device and the power reception device. One is characterized by including a coil unit having the characteristics of the present invention described above. According to the present invention, it is possible to provide a wireless power transmission system capable of suppressing heat generation and reducing a leakage magnetic flux that largely orbits a region away from an opposing coil.

According to the present invention, it is possible to provide a coil unit capable of efficiently dissipating heat while suppressing heat generation, and a power transmission device, a power receiving device, and a wireless power transmission system using the coil unit.

FIG. 1 is a block diagram showing a configuration of a wireless power transmission system according to a preferred embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the configuration of a coil unit according to the first embodiment of the present invention. FIG. 3 is a perspective view of the coil unit, showing a state in which the resin cover is removed. FIG. 4 is a perspective view of the coil unit and shows a state in which the resin cover is attached. FIG. 5 is a schematic cross-sectional view showing the configuration of the coil unit according to the second embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a configuration of a wireless power transmission system according to a preferred embodiment of the present invention.

As shown in FIG. 1, the wireless power transmission system 1 comprises a combination of a power transmission device 2 and a power reception device 3, and wirelessly transmits power from the power transmission device 2 to the power reception device 3.

The power transmission device 2 includes a DC power supply 4, a power transmission circuit 5 including an inverter circuit that converts a DC voltage supplied from the DC power supply 4 into an AC voltage of, for example, 100 kHz, and a power transmission coil 6a that generates an AC magnetic flux by the AC voltage. It includes a coil unit 10. The coil unit 10 according to the present embodiment constitutes an LC series resonance circuit in which capacitors 6b and 6c are connected in series at both ends of the transmission coil 6a, but it may be an LC parallel resonance circuit and is an LC series / parallel. It may be a resonance circuit. Further, the number of capacitors is not particularly limited, and a configuration in which only capacitors 6b are connected may be used.

The power receiving device 3 includes a coil unit 10 including a power receiving coil 7a that receives at least a part of the AC magnetic flux generated by the power transmitting coil 6a to generate an AC voltage, and a rectifier that converts the AC voltage generated in the power receiving coil 7a into a DC voltage. It includes a power receiving circuit 8 including a circuit. The rectifier circuit may include a smoothing function. The DC voltage output from the power receiving device 3 is supplied to the load 9. The coil unit 10 according to the present embodiment constitutes an LC series resonant circuit in which capacitors 7b and 7c are connected in series at both ends of the power receiving coil 7a, but it may be an LC parallel resonant circuit and LC series and parallel. It may be a resonance circuit. Further, the number of capacitors is not particularly limited, and a configuration in which only capacitors 7b are connected may be used.

FIG. 2 is a schematic cross-sectional view showing the configuration of the coil unit 10 used on the power transmission side and the power reception side. 3 and 4 are perspective views of the coil unit 10. In particular, FIG. 3 shows a state in which the resin cover 18 is removed, and FIG. 4 shows a state in which the resin cover 18 is attached. Note that FIG. 2 corresponds to a schematic cross-sectional view taken along the line AA of FIG.

As shown in FIGS. 2 to 4, the coil unit 10 includes a coil 11 in which a conducting wire is wound in a spiral shape, a capacitor 12 electrically connected to the coil 11 to form an LC resonance circuit, and a coil 11. A magnetic body 13 arranged on the back side of the magnetic body 13, a base shield 14 (first metal shield) arranged on the back side of the magnetic body 13, and a capacitor 12 arranged between the magnetic body 13 and the base shield 14. It is provided with a shield box 16 to be stored. The back surface side of the coil 11 _{means one end side of the coil shaft X 0} of the coil 11 in the extending direction and opposite to the main surface of the coil 11 facing the power transmission direction. Further, the back side of the magnetic body 13 means the side opposite to the facing surface of the magnetic body 13 with the coil 11.

The coil 11 corresponds to the coil 6a or 7a of FIG. The coil 11 is wound around a resin bobbin 17 and is housed in the resin cover 18. The coil 11 according to the present embodiment has a single-layer structure, but may have a multi-layer structure. The planar shape of the coil 11 is preferably an ellipse, an oval, or a substantially rectangular shape that is elongated in one direction, but may be a perfect circle or a substantially square shape.

The capacitor 12 corresponds to the capacitors 6b, 6c or 7b, 7c of FIG. The capacitor 12 is packaged together with the coil 11 to form a coil unit for power transmission. In this embodiment, the capacitor 12 is attached to the shield box 16, but may be attached to the base shield 14. Since the capacitor 12 is arranged on the back side of the coil 11 via the magnetic body 13 and the shield box 16, the metal parts (terminal electrodes, internal electrodes, etc.) of the capacitor 12 do not interfere with power transmission. A power cable 19 is connected to a pair of terminals of an LC resonance circuit composed of a coil 11 and a capacitor 12.

The magnetic body 13 is a sheet-shaped or plate-shaped member made of a magnetic material such as ferrite, and is provided so as to cover the entire back surface of the coil 11. The magnetic body 13 may be an aggregate of a plurality of magnetic pieces. In the present embodiment, the magnetic material 13 is attached to the back surface of the bobbin 17. By providing the magnetic body 13 on the back surface side of the coil 11 in this way, it is possible to secure a magnetic path having a magnetic flux φ interlinking with the coil 11 and improve the power transmission efficiency.

The base shield 14 is a metal support such as copper or aluminum having an outer dimension larger than that of the coil 11 or the magnetic body 13, and is provided to shield the leakage magnetic flux on the back surface side of the coil 11. A heat sink 20 is provided on the back side of the base shield 14 which is opposite to the surface facing the shield box 16. The heat sink 20 is composed of a plurality of extending fins 20a and a flat plate portion 20b provided with the plurality of fins 20a, and the flat plate portion 20b is connected to the back surface of the base shield 14. In a coil unit that handles a large amount of electric power, the amount of heat generated by the coil 11 and the magnetic body 13 is also very large. However, by forming the back surface of the base shield 14 on the side opposite to the power transmission direction of the coil 11 as a heat sink structure, the coil The heat dissipation of the unit 10 can be improved. In the present embodiment, the heat sink 20 is composed of a separate member from the base shield 14, but it is also possible to share the flat plate portion 20b of the base shield 14 and the heat sink 20 and integrally form both of them.

The shield box 16 is a substantially box-shaped metal frame provided on the back side of the coil 11 to secure a storage space for the capacitor 12. The shield box 16 according to the present embodiment is simply formed by bending a single metal plate such as a copper plate or an aluminum plate, and has a substantially rectangular parallelepiped outer shape. Specifically, in the shield box 16, the flat plate portion 16a arranged so as to face the back surface of the magnetic body 13, the side wall 16b extending from both ends in the width direction of the flat plate portion 16a, and the tip end portion of the side wall 16b are inside ( It has a collar portion 16c that is bent to the outside). Further, a storage port 16d for the capacitor 12 is provided on the back side of the shield box 16 facing the base shield 14. As described above, the shield box 16 according to the present embodiment has a planar shape elongated in one direction when viewed from the coil axis direction.

The flat plate portion 16a of the shield box 16 is in contact with the back surface of the magnetic body 13 directly or via an intermediate material such as a thermal compound, and is thermally connected to the magnetic body 13. Further, the flange portion 16c of the shield box 16 is in contact with the main surface 14a of the base shield 14 directly or via an intermediate material such as a thermal compound. With such a configuration, the flat plate portion 16a of the shield box 16 (second metal shield) is thermally connected to the base shield 14 (first metal shield) via the side wall 16b and the flange portion 16c. In particular, since the flat surface portion of the flange portion 16c faces the main surface of the base shield 14 and the base shield 14 and the shield box 16 are in surface contact with each other, heat transferability can be enhanced.

In the present embodiment, outside dimension of the flat plate portion 16a of the shielding box 16 as viewed from the traveling direction of the coil axis X ₀ (the second metal shield) is preferably not more than external dimensions of the magnetic member 13. That is, the contour of the flat plate portion 16a coincides with or fits inside the contour of the magnetic body 13, and is configured so as not to protrude outside the contour of the magnetic body 13. _{With such a configuration, since the magnetic flux φ e} emitted from the end portion 13e of the magnetic body 13 does not interlink with the flat plate portion 16a, heat generation of the flat plate portion 16a can be prevented.

The flat plate portion 16a of the magnetic body 13 and the shield box 16 may have a flat plate shape over the entire surface as shown in the drawing, or may have an opening in the center in accordance with the opening of the coil 11. It may have a shape in which a slit from to the outside is further formed. Also in this case, in order to prevent heat generation of the flat plate portion 16a, it is necessary that the contour of the opening of the flat plate portion 16a does not protrude outside the contour of the magnetic material 13.

As shown in FIG. 3, an opening 16e is provided in a part of the side wall 16b of the shield box 16 surrounding the periphery of the capacitor 12, and the power cable 19 connected to the coil 11 or the capacitor 12 has the opening 16e. It is pulled out from the outside of the shield box 16. The tips of the pair of power cables 19 are connected to the inverter circuit if the power transmission device 2 is used, or to the rectifier circuit if the power receiving device 3 is used.

The openings 16e are preferably provided at both ends of the shield box 16 in the longitudinal direction, and the power cable 19 is drawn out from either of the two openings 16e. In the method in which the coil surface is erected vertically to transmit power in a substantially horizontal direction, the height can be reduced by installing the coil unit 10 sideways, but on the side wall on one end side of the shield box 16 in the lateral direction. When the opening is provided, the height of the coil unit 10 is increased by the amount of the power cable 19 pulled out from one end side of the shield box 16 in the lateral direction. However, when the power cable 19 is pulled out from one end side in the longitudinal direction of the coil unit 10, the power cable 19 does not hinder the reduction of the height of the coil unit 10, and the height of the entire coil unit can be reduced. Become.

The side wall 16b and the flange portion 16c are preferably provided along the longitudinal direction of the shield box 16 (flat plate portion 16a). According to this structure, the cross-sectional area of the heat transfer path can be increased, and the area where the shield box 16 contacts the base shield 14 can be secured as wide as possible, thereby lowering the thermal resistance and improving the heat dissipation. Can be improved. Further, openings 16e can be provided at both ends of the shield box 16 in the longitudinal direction, and the power cable 19 can be pulled out from the side. Therefore, the coil unit 10 can be arranged sideways when the coil surface is vertically erected and power is transmitted in a substantially horizontal direction as shown in FIG. 3, and the height of the coil unit 10 can be reduced.

Coil axis X ₀ of the coil 11 is substantially horizontally oriented, the wireless power transmission system is preferably substantially the horizontal direction is performed in the power transmission. When the power transmission coil and the power reception coil are opposed to each other in the vertical direction to perform power transmission in the vertical direction, a metal foreign substance may continue to be on the upper surface of the upward coil, and the power transmission efficiency may be caused by the metal foreign substance. May decrease and power transmission may not be possible. However, when the coil surface is erected vertically and power is transmitted in a substantially horizontal direction, the metal that tends to adhere to the vertical coil surface falls from the coil surface, so that it is possible to avoid a decrease in power transmission efficiency. it can. It is also possible to avoid heat generation of metal foreign matter.

As described above, the coil unit 10 according to the present embodiment is generated from the coil 11 because the external dimensions of the shield box 16 (second metal shield) do not protrude outside the magnetic material 13 in a plan view. It is possible to prevent the magnetic flux emitted from the end portion of the magnetic body 13 from interlinking with the flat plate portion 16a, and it is possible to suppress the heat generation of the flat plate portion 16a due to the eddy current generated by the interlinking of the magnetic flux. Further, since the shield box 16 is thermally connected to the base shield 14 (first metal shield), the heat generated in the coil unit can be efficiently dissipated.

FIG. 5 is a schematic cross-sectional view showing the configuration of the coil unit according to the second embodiment of the present invention.

As shown in FIG. 5, a feature of the coil unit 10 according to the present embodiment is that it further includes a side shield 15 arranged so as to cover the periphery of the coil 11. The side shield 15 is integrally formed with the flat plate portion 21 parallel to the base shield 14 by bending a single metal plate such as a copper plate or an aluminum plate. The side shield 15 may be formed of a member different from the flat plate portion 21. The side shield 15 is arranged so as to be separated from the end portion 13e of the magnetic body 13 in the Y-axis direction, and the distance Ly (first distance) in the Y-axis direction from the magnetic body 13 to the side shield 15 is at least zero. Is also large, and is preferably larger than the distance from the center of the coil 11 to the closest lead wire portion on the innermost circumference of the coil 11. As a result, it is possible to shield the leakage magnetic flux that largely orbits the region away from the opposing coil while suppressing the shielding of the main magnetic flux that contributes to power transmission, thereby maintaining the desired power transmission efficiency and the leakage magnetic flux. Can be reduced.

Since the shield box 16 is provided between the magnetic body 13 and the base shield 14, the base shield 14 is also arranged apart from the magnetic body 13 in the X-axis direction (coil axis direction). That is, the distance Lx (second distance) in the X-axis direction from the reference plane SS including the back surface of the magnetic body 13 opposite to the coil 11 facing surface to the base shield 14 is larger than zero. The base shield 14 may be separated from the reference plane SS in the X-axis direction at least in the region between the end portion 13e of the magnetic body 13 and the side shield 15. With such a configuration, the main magnetic flux contributing to power transmission can be prevented from being shielded by the base shield 14. Therefore, it is possible to improve the power transmission efficiency while suppressing the heat generation of the base shield 14.

The length Lp of the projecting portion of the side shield 15 which projects forwardly of the extending direction of the coil axis X ₀ of the coil 11 than the magnetic body 13 is at least greater than zero, the side shield 15 from the end portion 13e of the magnetic member 13 It is preferable that the distance is shorter than the distance Ly in the Y-axis direction and shorter than the distance Lx from the magnetic material 13 to the base shield 14. Further, the distance Lx from the magnetic material 13 to the base shield 14 is shorter than the distance Ly from the end of the magnetic material 13 to the side shield 15, and is 0.6 times or more and less than 1 time (0.6Ly ≦ Lx < Ly) is preferable. According to such a configuration, the side shield 15 having an appropriate size can be provided at a position appropriately separated from the end portion 13e of the magnetic body 13. Therefore, it is possible to reduce the leakage magnetic flux that largely orbits the region away from the opposing coil while suppressing the shielding of the main magnetic flux that contributes to power transmission, and suppresses noise while maintaining the desired power transmission efficiency. Can be done. Further, not only the side shield 15 but also the base shield 14 can be provided at a position appropriately separated from the end portion 13e of the magnetic body 13. Therefore, it is possible to suppress an increase in the thickness of the coil unit while suppressing heat generation of the base shield 14.

Further, in the present embodiment, the base shield 14 is provided on the metal flat plate portion 21 integrated with the side shield 15, and the heat sink 20 is connected to the base shield 14 via the flat plate portion 21. Although the heat sink 20 is not in contact with the back surface of the base shield 14, it is thermally connected to the base shield 14 via the flat plate portion 21. Therefore, the heat generated by the coil 11 and the magnetic body 13 can be transferred to the heat sink 20 to improve the heat dissipation, and the same effect as that of the first embodiment can be obtained. In the present embodiment, the flat plate portion 21 is composed of a separate member from the base shield 14, but the base shield 14 and the flat plate portion 21 may be shared and both may be integrated.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention, and these are also the present invention. Needless to say, it is included in the range.

For example, in the above embodiment, the case where both the power transmitting device 2 and the power receiving device 3 are configured by using the coil unit 10 according to the present invention has been described, but the present invention is not limited to such a case. However, only one of the power transmitting device 2 and the power receiving device 3 may be configured by using the coil unit 10 according to the present invention.

Further, in the above embodiment, the shield box 16 has a collar portion 16c, but the collar portion 16c may be omitted. Further, the collar portion 16c is formed by being bent inward, but may be formed by being bent outward.

1 Wireless power transmission system 2 Transmission device 3 Power receiving device 4 DC power supply 5 Transmission circuit 6a Transmission coil 6b, 6c Capacitor 7a Power receiving coil 7b, 7c Capacitor 8 Power receiving circuit 9 Load 10 Coil unit 11 Coil 12 Capacitor 13 Magnetic material 13e Magnetic material End 14 Base shield 14a Base shield main surface 15 Side shield 16 Shield box 16a Flat plate 16b Side wall 16c Border 16d Capacitor storage 16e Opening 17 Bobbin 18 Resin cover 19 Power cable 20 Heat sink 20a Fin 20b Flat plate 21 Flat plate L x 2nd distance Ly 1st distance SS reference plane X ₀ coil axis φ, φ _e magnetic flux

Claims (14)

A coil in which the lead wire is spirally wound, and
The bobbin around which the coil is wound and
A capacitor that is electrically connected to the coil
A magnetic material arranged on one end side of the coil in the coil axial direction,
A first metal shield arranged on the side of the magnetic material opposite to the surface facing the coil,
A second metal shield, which is arranged between the magnetic material and the first metal shield and forms a storage space for the capacitor ,
The bobbin around which the coil is wound, the magnetic material, and a cover for accommodating the second metal shield are provided.
The second metal shield is arranged so as to be thermally connected to the first metal shield.
The external dimensions of the second metal shield as seen from the coil axis direction are equal to or smaller than the external dimensions of the magnetic material.
One of the bobbins covering one end side of the coil in the coil axis direction has an external dimension seen from the coil axis direction with respect to the other end of the bobbin covering the other end side of the coil in the coil axis direction. Has a large part,
The area of the one flange of the bobbin facing the magnetic material is larger than the area of the other collar of the bobbin.
A coil unit characterized in that the main surface of the other collar portion of the bobbin is in contact with the cover. The second metal shield is arranged so as to be thermally connected to the magnetic material.
The coil unit according to claim 1, wherein the area of the magnetic material facing the second metal shield is larger than the area of the other flange of the bobbin. The second metal shield is
A flat plate portion arranged so as to face the magnetic material and
Including a side wall connected to the flat plate portion and arranged around the capacitor.
The coil unit according to claim 1 or 2, wherein the area of the flat plate portion is larger than the area of the other flange portion of the bobbin. The coil unit according to claim 3, wherein the tip of the side wall from the flat plate portion toward the first metal shield is arranged so as to face the main surface of the first metal shield. An opening is provided in a part of the side wall.
The coil unit according to claim 3, wherein the coil or the power cable connected to the capacitor is drawn out from the opening. The second metal shield has an elongated planar shape in one direction when viewed from the coil axis direction.
The coil axis of the coil is oriented in a substantially horizontal direction.
The coil unit according to claim 5, wherein the opening is provided on one end side in the longitudinal direction of the second metal shield. The second metal shield further includes a collar portion in which the tip end portion of the side wall is bent inward or outward.
The coil unit according to any one of claims 3 to 6, wherein the collar portion is arranged so as to be thermally connected to the main surface of the first metal shield. The second metal shield has an elongated planar shape in one direction when viewed from the coil axis direction.
The coil unit according to claim 7, wherein the collar portion is provided along the longitudinal direction of the second metal shield. The external dimensions of the magnetic material, the second metal shield, and the one flange of the bobbin as viewed from the coil axis direction are the same.
The coil unit according to any one of claims 1 to 8, wherein the outer peripheral end faces of the magnetic material, the second metal shield, and the one of the bobbins are in contact with the inner wall surface of the cover. .. The coil unit according to any one of claims 1 to 9, wherein the external dimensions of the first metal shield viewed from the coil axis direction are larger than the external dimensions of the second metal shield. The coil unit according to any one of claims 1 to 10, wherein a heat sink is provided on the side of the first metal shield opposite to the surface facing the second metal shield. A power transmission device comprising the coil unit according to any one of claims 1 to 11 and an inverter circuit connected to the coil unit. A power receiving device comprising the coil unit according to any one of claims 1 to 11 and a rectifier circuit connected to the coil unit. A power transmission device for wirelessly transmitting electric power and a power receiving device for wirelessly receiving electric power transmitted from the power transmitting device are provided, and at least one of the power transmitting device and the power receiving device is any one of claims 1 to 11. A wireless power transmission system comprising the coil unit described in the section.

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