Wireless power reception device, wireless power supply system, and vehicle

Abstract

[Problem] To provide a device and the like with which it is possible to increase power supply efficiency. [Solution] One aspect of the present invention provides a wireless power reception device comprising a power reception waveguide and a tubular ring resonator. The power reception waveguide is configured to be capable of transmitting electromagnetic waves, and is disposed in the vicinity of the ring resonator. The ring resonator is capable of transmitting electromagnetic waves in the circumferential direction, transmits electromagnetic waves transmitted from a power transmission waveguide, which transmits electromagnetic waves, to the power reception waveguide when disposed in the vicinity of the power transmission waveguide, and is configured such that the length in the circumferential direction is longer than the wavelength when said electromagnetic waves are transmitted through the interior of the ring resonator.

Description

Wireless power receiving device, wireless power supply system, and vehicle

[0001] The present invention relates to a wireless power receiving device, a wireless power feeding system, and a vehicle.

[0002] Patent Document 1 discloses a technique for improving power supply efficiency by using a meandering conductor to shorten the wavelength of electromagnetic waves propagating within a power supply sheet.

[0003] International Publication No. 2021 / 075511

[0004] In order to avoid wasting the electromagnetic waves transmitted by the power transmission waveguide, high power supply efficiency to the wireless charging device is required.

[0005] In view of the above circumstances, the present invention provides a device and the like that can improve power supply efficiency.

[0006] According to one aspect of the present invention, there is provided a wireless power receiving device comprising a power receiving waveguide and a cylindrical ring resonator, wherein the power receiving waveguide is configured to be able to transmit electromagnetic waves and is arranged in the vicinity of the ring resonator, and the ring resonator is capable of transmitting electromagnetic waves in a circumferential direction and, when arranged in the vicinity of a power transmitting waveguide that transmits electromagnetic waves, transmits the electromagnetic waves transmitted from the power transmitting waveguide to the power receiving waveguide, and is configured so that the circumferential length of the electromagnetic waves is longer than the wavelength when transmitted inside the ring resonator.

[0007] With this configuration, it is possible to provide a device or the like that can improve power supply efficiency.

[0008] 1 is a diagram illustrating an example of a wireless power supply system; FIG. 1 is a diagram illustrating an enlarged view of the vicinity of a ring resonator; FIG. 2 is a diagram illustrating an enlarged view of a power transmission sheet; FIG. 3 is a diagram illustrating an enlarged view of an upper conductive layer; FIG. 4 is a diagram illustrating an example of a magnetic field generated by the power transmission sheet; FIG. 5 is a diagram illustrating an enlarged view of the ring resonator; FIG. 6 is a diagram illustrating an enlarged view of an outer circumferential conductive layer; FIG. 7 is a diagram illustrating an enlarged view of an inner circumferential conductive layer; FIG. 8 is a diagram illustrating an enlarged view of an upper conductive layer;

[0009] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0010] Incidentally, a program for realizing the software appearing in one embodiment may be provided as a non-transitory computer-readable recording medium, or may be provided so as to be downloadable from an external server, or may be provided so that the program is started on an external computer and its functions are realized on a client terminal (so-called cloud computing).

[0011] Furthermore, various information processing according to an embodiment may realize input and output corresponding to the input. Here, the form of information referenced in such information processing (hereinafter referred to as reference information) is not limited as long as an output is obtained as a result of the input. The reference information may be, for example, rule-based information such as a database, a lookup table, or a predetermined function (including a determination formula such as a regression formula constructed using a statistical method), a trained model that has previously learned the correlation between input and output, or a generative AI such as a large-scale language model or a visual language model that can output a desired result by inputting a prompt.

[0012] In one embodiment, the term "unit" may include, for example, a combination of hardware resources implemented by a circuit in the broad sense and software information processing that can be specifically realized by these hardware resources. In one embodiment, various information is handled, and this information is represented, for example, by physical values ​​of signal values ​​representing voltage or current, high or low signal values ​​as a binary bit set consisting of 0 or 1, or quantum superposition (so-called quantum bits), and communication and calculations can be performed on the circuit in the broad sense.

[0013] Furthermore, a circuit in a broad sense is a circuit realized by at least an appropriate combination of a circuit, circuitry, a processor, a memory, etc. The processor may be a general-purpose processor or a dedicated circuit. That is, it includes application specific integrated circuits (ASICs), programmable logic devices (e.g., simple programmable logic devices (SPLDs), complex programmable logic devices (CPLDs), and field programmable gate arrays (FPGAs)), etc.

[0014] <Embodiment> The configuration of a wireless power feeding system according to an embodiment will be described below. Fig. 1 is a diagram showing an example of a wireless power feeding system. The wireless power feeding system 1 shown in Fig. 1 is a system including a mechanism for supplying power contactlessly (wirelessly). In the example of Fig. 1, the wireless power feeding system 1 wirelessly supplies power from a power feeding unit 2 to a vehicle 7 and charges a battery 8 provided in the vehicle 7.

[0015] The wireless power feeding system 1 includes a power feeding unit 2 and a vehicle 7. The power feeding unit 2 is a unit that supplies power to a target device (vehicle 7 in the example of FIG. 1 ) by transmitting electromagnetic waves that can be converted into electric power. The power feeding unit 2 includes a power feeding section 3 and a power transmission sheet 30. The power feeding section 3 is connected to one end of the power transmission sheet 30 and is configured to be able to supply AC current of a predetermined frequency to the power transmission sheet 30. The predetermined frequency is preferably as low as possible to reduce losses due to propagation and radiation, and is, for example, on the order of several MHz to several hundred kHz.

[0016] The power transmission sheet 30 is a sheet-like component extending in the extension direction D31, and transmits electromagnetic waves EM in a transmission direction D34 along the extension direction D31 due to the action of an AC current supplied from the power supply unit 3. The transmission direction D34 is the direction from the end of the power transmission sheet 30 where the power supply unit 3 is connected to the opposite end. The configuration in which the AC current generates electromagnetic waves will be described in detail later.

[0017] The vehicle 7 includes a power receiving terminal 5, a battery 8, and a drive unit 9. The vehicle 7 is a vehicle that runs by generating driving force using electric power, such as an electric vehicle, a hybrid vehicle, an electric motorcycle, or an electric skater. The drive unit 9 is a power source, such as a motor, that is driven by the electric power stored in the battery 8. The power receiving terminal 5 is a terminal for receiving electric power supplied from the power transmitting sheet 30. The power receiving terminal 5 includes a ring resonator 10, a power receiving sheet 20, and two rectifiers 6.

[0018] The ring resonator 10 is provided so as to be located near the power transmission sheet 30 when the vehicle 7 moves to a position where it straddles the power transmission sheet 30. When the ring resonator 10 is located near the power transmission sheet 30, electromagnetic waves EM flowing through the power transmission sheet 30 are transmitted to the ring resonator 10. At this time, resonance of the electromagnetic waves EM (a phenomenon in which vibrations overlap and the amplitude increases) occurs inside the ring resonator 10. The electromagnetic waves EM are transmitted inside the ring resonator 10 and transmitted to the power receiving sheet 20.

[0019] The power receiving sheet 20 is a sheet equipped with a circuit that generates an AC current using the electromagnetic waves EM transmitted from the ring resonator 10, and two rectifiers 6 are connected to each of them. The power receiving sheet 20 supplies the generated AC current to one of the two rectifiers 6 (the rectifier 6 is determined depending on the orientation of the vehicle 7). The rectifier 6 converts the supplied AC current into a DC current and supplies the converted DC current to the battery 8. The battery 8 stores power using the supplied DC current. A charging circuit may be provided between the rectifier 6 and the battery 8 to improve the safety of power reception and the power supply efficiency.

[0020] 2 is an enlarged view of the vicinity of ring resonator 10. Ring resonator 10 is a cylindrical component formed with a length in a circumferential direction D11 of 500 mm and a length (i.e., width) in an axial direction D12 of 200 mm. Ring resonator 10 is fixed inside vehicle 7 with axial direction D12 oriented along the horizontal direction. Furthermore, ring resonator 10 is fixed at a position where the distance from power transmission sheet 30 is 11 mm when vehicle 7 moves to a position straddling power transmission sheet 30. Note that the sizes and lengths shown in FIG. 2 and other figures are merely examples and are not limiting.

[0021] The power receiving sheet 20 is a sheet-like component that extends in the extension direction D21 and is fixed with the extension direction D21 oriented horizontally. The power receiving sheet 20 has a length of 200 mm in the width direction D22 and is fixed vertically above the ring resonator 10 at a position where the gap between the power receiving sheet 20 and the ring resonator 10 is 11 mm. The power receiving sheet 20 is fixed with the extension direction D21 oriented perpendicular to the axial direction D12 of the ring resonator 10. A rectifier 6 is connected to both ends of the power receiving sheet 20 in the extension direction D21.

[0022] The power transmission sheet 30 is formed to have a length of 200 mm in the width direction D32, similar to the ring resonator 10 and the power reception sheet 20. Electromagnetic waves from the power transmission sheet 30 are most efficiently transmitted to the ring resonator 10 when the axial direction D12 of the ring resonator 10 is oriented perpendicular to the width direction D32 of the power transmission sheet 30 and the ring resonator 10 does not protrude from the space vertically above the power transmission sheet 30. Figure 2 shows such an arrangement in which electromagnetic waves from the power transmission sheet 30 are most efficiently transmitted to the ring resonator 10.

[0023] 3 is an enlarged view of the power transmission sheet 30. The power transmission sheet 30 includes a dielectric layer 31, an upper conductive layer 32, and a lower conductive layer 33. The power supply unit 3 shown in FIG. 1 is connected to one end of the upper conductive layer 32 and the lower conductive layer 33 in the extension direction D31, and a voltage is applied between the two layers. The other end of the upper conductive layer 32 and the lower conductive layer 33 in the extension direction D21 is electrically connected.

[0024] The dielectric layer 11 has a flat plate shape, and transmits electromagnetic waves in a transmission direction D34 by having an upper conductive layer 32 and a lower conductive layer 33 disposed in close contact on both sides of the thickness direction D33. The dielectric layer 31 may be made of a material with a low dielectric constant ε and high durability, such as polystyrene (dielectric constant ε = 2.4 to 2.6) or polypropylene (dielectric constant ε = 2.0 to 2.3). The dielectric layer 31 may be made of not only a dense material, but also a hollow structure made of a dielectric material, such as a dielectric foam or honeycomb structure.

[0025] The upper conductive layer 32 and the lower conductive layer 33 each have a conductor through which AC current supplied from the power supply unit 3 flows. These conductors may be made of a highly conductive material such as gold, silver, copper, aluminum, or iron.

[0026] Preferably, when laying the power transmission sheet 30 on a road surface or floor, an insulator several millimeters thick is placed over the surface to significantly reduce the absorption and scattering of electromagnetic waves when the power transmission sheet 30 comes into contact with a human body or other object.

[0027] The shapes of the conductors of the upper conductive layer 32 and the lower conductive layer 33 will be described with reference to FIG. 4 . FIG. 4 is an enlarged view of the upper conductive layer 32 and the lower conductive layer 33. The upper conductive layer 32 has a plurality of planar coils 321. Each of the plurality of planar coils 321 has a shape in which the length in the width direction D32 is longer than the length in the extension direction D31, and is arranged side by side in the extension direction D31. Each of the plurality of planar coils 321 is electrically connected to an adjacent planar coil 321, forming a circuit through which AC current supplied from the power supply unit 3 shown in FIG. 1 flows.

[0028] The lower conductive layer 33 has a plurality of planar coils 331. Each of the plurality of planar coils 331 has a length in the width direction D32 that is longer than the length in the extension direction D31, and is arranged side by side in the extension direction D31. The plurality of planar coils 331 are electrically connected to each other and form a circuit through which an AC current supplied from the power supply unit 3 shown in FIG. 1 flows. When an AC current flows through the upper conductive layer 32 and the lower conductive layer 33, the dielectric layer 31 transmits an electromagnetic wave. The wavelength λ of the electromagnetic wave transmitted by the dielectric layer 31 can be expressed by Equation 1.

[0029]

[0030] In Equation 1, L is the reactance of the upper conductive layer 32 and the lower conductive layer 33, C is the capacitance between the upper conductive layer 32 and the lower conductive layer 33, and ω is the angular frequency of the electromagnetic wave. As shown in Equation 1, the wavelength of the electromagnetic wave can be shortened by increasing the reactance L of the upper conductive layer 32 and the lower conductive layer 33 and the capacitance C between the upper conductive layer 32 and the lower conductive layer 33. Furthermore, the reactance L of the upper conductive layer 32 and the lower conductive layer 33 affects the strength of the magnetic field generated by the power transmission sheet 30; the greater the value of reactance L, the stronger the generated magnetic field.

[0031] 4, the upper conductive layer 32 and the lower conductive layer 33 have planar coils arranged side by side, which increases both the reactance L and the capacitance C, shortens the wavelength of the electromagnetic wave, and strengthens the generated magnetic field, compared to when meandering conductors are arranged. Furthermore, each planar coil 331 has an inverted shape of the planar coil 321, and is arranged such that the center of the extension direction D31 is offset from the center of the extension direction D31 of each planar coil 321.

[0032] Fig. 5 is a diagram showing an example of a magnetic field generated by power transmission sheet 30. The solid arrows in Fig. 5 represent some of the magnetic field lines of the magnetic field generated by planar coil 321, and the dashed arrows represent some of the magnetic field lines of the magnetic field generated by planar coil 331. The directions of the AC current supplied from power supply unit 3 are opposite in planar coil 321 and planar coil 331, but because planar coil 331 has an inverted shape of planar coil 321, the directions of the magnetic fields generated are the same.

[0033] 5 indicates the center of the magnetic field generated by planar coil 321, and arrow 33H indicates the center of the magnetic field generated by planar coil 331. As described above, by displacing the center of planar coil 331 in extension direction D31 from the center of planar coil 331 in extension direction D31 in a manner that is offset in extension direction D31, the positions of arrows 32H and 33H are offset, and therefore the intensity of the generated magnetic field is closer to being uniform compared to when these centers are aligned.

[0034] Next, the configuration of ring resonator 10 will be described. Fig. 6 is an enlarged view of ring resonator 10. Ring resonator 10 includes a dielectric layer 11, an outer circumferential conductive layer 12, and an inner circumferential conductive layer 13. Dielectric layer 11 has a cylindrical shape, and outer circumferential conductive layer 12 and inner circumferential conductive layer 13 are disposed in close contact with each other on both sides (the outer circumferential surface side and the inner circumferential surface side) in the thickness direction D13, thereby transmitting electromagnetic waves in a predetermined direction. The direction in which the electromagnetic waves are transmitted includes both a clockwise direction D111 and a counterclockwise direction D112 along the circumferential direction D11.

[0035] As the dielectric layer 11, it is preferable to appropriately use polystyrene (relative dielectric constant ε=2.4 to 2.6), polypropylene (relative dielectric constant ε=2.0 to 2.3), or the like, which have a low relative dielectric constant ε and high durability, similar to the dielectric layer 31. Furthermore, the dielectric layer 11 may be made of not only a dense material but also a hollow structure made of a dielectric material, such as a dielectric foam or a honeycomb structure.

[0036] The outer conductive layer 12 and the inner conductive layer 13 each have a conductor through which a current flows. These conductors may be made of a highly conductive material such as gold, silver, copper, aluminum, or iron. The shapes of the conductors in the outer conductive layer 12 and the inner conductive layer 13 will be described with reference to FIG. 7 .

[0037] 7 is an enlarged view of the outer circumferential conductive layer 12 and the inner circumferential conductive layer 13. The outer circumferential conductive layer 12 has a plurality of planar coils 121. Each of the plurality of planar coils 121 has a shape in which the length in the width direction D32 is longer than the length in the circumferential direction D11, and is arranged side by side in the circumferential direction D11. Each of the plurality of planar coils 121 is electrically connected to an adjacent planar coil 121 to form a closed circuit that makes one turn in the circumferential direction D11.

[0038] The inner circumferential conductive layer 13 has a plurality of planar coils 131. Each of the planar coils 131 has a length in the width direction D32 that is longer than its length in the circumferential direction D11, and is arranged side by side in the circumferential direction D11. Each of the planar coils 131 is electrically connected to an adjacent planar coil 131 to form a closed circuit that makes one turn in the circumferential direction D11. As in the example of FIG. 4 , the planar coils 131 have a shape that is an inverted version of the planar coil 121, and are arranged such that the center of each planar coil 131 in the circumferential direction D11 is offset from the center of each planar coil 121 in the circumferential direction D11.

[0039] Next, the configuration of the power receiving sheet 20 will be described. FIG. 8 is an enlarged view of the power receiving sheet 20. The power receiving sheet 20 includes a dielectric layer 21, an upper conductive layer 22, and a lower conductive layer 23. The dielectric layer 21 has a flat plate shape, and the upper conductive layer 22 and the lower conductive layer 23 are arranged in close contact on both sides of the dielectric layer 21 in the thickness direction D23, thereby transmitting electromagnetic waves in a predetermined direction. The direction in which the electromagnetic waves are transmitted includes both a first direction D211 along the extension direction D21 and a second direction D212 opposite to the first direction D211.

[0040] As the dielectric layer 21, it is preferable to appropriately use polystyrene (relative dielectric constant ε=2.4 to 2.6) or polypropylene (relative dielectric constant ε=2.0 to 2.3), which have a low relative dielectric constant ε and high durability, similar to the dielectric layer 31. Furthermore, the dielectric layer 21 may be made of not only a dense material but also a hollow structure made of a dielectric material, such as a dielectric foam or a honeycomb structure.

[0041] The upper conductive layer 22 and the lower conductive layer 23 each have a conductor through which a current flows. These conductors may be made of a highly conductive material such as gold, silver, copper, aluminum, or iron. The shapes of the conductors in the upper conductive layer 22 and the lower conductive layer 23 will be described with reference to FIG. 9 .

[0042] 9 is an enlarged view of the upper conductive layer 22 and the lower conductive layer 23. The upper conductive layer 22 has a plurality of planar coils 221. Each of the plurality of planar coils 221 has a shape in which the length in the width direction D32 is longer than the length in the extension direction D21, and is arranged side by side in the extension direction D21. Each of the plurality of planar coils 221 is electrically connected to an adjacent planar coil 221, forming a circuit through which a current flows.

[0043] The lower conductive layer 23 has a plurality of planar coils 231. Each of the planar coils 231 has a length in the width direction D32 that is longer than the length in the extension direction D21, and is arranged side by side in the extension direction D21. The planar coils 231 are electrically connected to adjacent planar coils 231 to form a circuit through which current flows. As in the example of FIG. 4 , the planar coils 231 have a shape that is an inverted version of the planar coil 221, and are arranged such that the center of the extension direction D21 is offset from the center of each planar coil 221 in the extension direction D21.

[0044] With the above-described configuration, the wireless power feeding system 1 transmits the electromagnetic waves transmitted by the power transmission sheet 30 to the power receiving sheet 20 via the ring resonator 10. The state of the electromagnetic waves at this time will be described with reference to FIG.

[0045] FIG. 10 is a diagram illustrating an example of electromagnetic wave transmission. FIG. 10 schematically illustrates the ring resonator 10, the power receiving sheet 20, and the power transmitting sheet 30 as viewed along the axial direction D12. Hereinafter, the end of the power transmitting sheet 30 to which the power feeding unit 3 is connected is referred to as "Port 1," the opposite end is referred to as "Port 2," one end of the power transmitting sheet 30 is referred to as "Port 3," and the opposite end is referred to as "Port 4." Rectifiers 6 are connected to both Port 3 and Port 4. In the example of FIG. 10 , the vehicle 7 is stopped with Port 3 located on the Port 1 side and Port 4 located on the Port 2 side.

[0046] 10A, transmission of electromagnetic waves EM inside the power transmission sheet 30 starts from Port 1, and in Fig. 10B, the electromagnetic waves EM reach an approach region C1 where the power transmission sheet 30 and the ring resonator 10 are closest to each other. Here, in the approach region C1, a phenomenon occurs in which the electromagnetic waves EM that have been transmitted inside the power transmission sheet 30 are transmitted to the ring resonator 10, and the transmitted electromagnetic waves EM are then transmitted inside the ring resonator 10. Such transmission of electromagnetic waves across different waveguides is also called transmission or uptake.

[0047] 10C, the electromagnetic waves EM transmitted inside the ring resonator 10 reach the approach region C2 where the ring resonator 10 and the power receiving sheet 20 are closest to each other. Here, in the approach region C2, similar to the approach region C1, a phenomenon occurs in which the electromagnetic waves EM transmitted inside the ring resonator 10 are transmitted to the power receiving sheet 20. At this time, the electromagnetic waves EM are transmitted in the direction of Port 3.

[0048] 10D, electromagnetic waves EM transmitted inside the power receiving sheet 20 reach Port 3 and are converted into direct current by the rectifier 6 shown in FIG. 1, which charges the battery 8. While power is being supplied from the power supply unit 3, the electromagnetic waves EM are transmitted via the power transmitting sheet 30, the ring resonator 10, and the power receiving sheet 20, and the battery 8 continues to be charged.

[0049] In the example of Fig. 10, the vehicle 7 is stopped so that Port 3 is on the same side as Port 1, but it may also be stopped in the opposite direction. This case will be described with reference to Fig. 11. Fig. 11 is a diagram showing another example of the manner in which electromagnetic waves are transmitted. In Fig. 11, unlike the example of Fig. 10, the vehicle 7 is stopped with Port 3 located on the Port 2 side and Port 4 located on the Port 1 side.

[0050] In Fig. 11(a), transmission of electromagnetic waves EM starts from Port 1 inside the power transmission sheet 30. In Fig. 11(b), the electromagnetic waves EM reach the approach region C1 and are absorbed by the ring resonator 10. In Fig. 11(c), the electromagnetic waves EM transmitted inside the ring resonator 10 reach the approach region C2 and are absorbed by the power receiving sheet 20. At this time, the electromagnetic waves EM are transmitted in the direction of Port 4, unlike the example in Fig. 10.

[0051] 11(d), electromagnetic waves EM transmitted through the inside of the power receiving sheet 20 reach Port 4 and are converted into direct current by the rectifier 6 shown in FIG. 1, thereby charging the battery 8. While power is being supplied from the power supply unit 3, the electromagnetic waves EM are transmitted via the power transmission sheet 30, the ring resonator 10, and the power receiving sheet 20, and the battery 8 continues to be charged. In this way, regardless of the orientation in which the vehicle 7 is stopped, shown in FIGS. 10 and 11, the power receiving terminal 5 can receive power from the power transmission sheet 30.

[0052] The inventors created the configuration of the wireless power supply system 1 using simulation software and simulated the output values ​​of each port. FIG. 12 is a diagram showing an example of the configuration used for the simulation. In the example shown in FIG. 12 , a ring resonator 10S, a power receiving sheet 20S, and a power transmission sheet 30S are used, each of which has a hexagonal coil sheet structure with an array of hexagonal planar coils, which differs from the planar coils shown in FIG. 7 and other figures. When the width of the sheet structure was set to 200 mm, the characteristic impedance was 100 Ω, and the wavelength within the sheet when transmitting electromagnetic waves of 6.78 MHz was approximately 1.3 m (common to the ring resonator 10S, the power receiving sheet 20S, and the power transmission sheet 30S).

[0053] The length of the ring resonator 10S in the circumferential direction D11 is 500 mm, as in the example of Fig. 2, and the gaps between the ring resonator 10S and the power receiving sheet 20S and the power transmission sheet 30S are also 11 mm, as in the example of Fig. 2. One end of the power transmission sheet 30S is called the incident port (Port 1), the other end is called the through port (Port 2), one end of the power receiving sheet 20S (the end on the incident port side) is called the drop port (Port 3), and the other end is called the add port (Port 4).

[0054] FIG. 13 is a diagram showing an example of the output of each port. In FIG. 13, the horizontal axis represents the frequency (MHz) of the electromagnetic wave EM, and the vertical axis represents the input / output ratio (ratio of input to output, measured in dB (decibels)). The closer the input / output ratio is to 0, the more electromagnetic waves are transmitted to that port. "S2,1" represents the input / output ratio of Port 2, and "S3,1" represents the input / output ratio of Port 3. The input / output ratio of S2,1 exhibited sharp peaks at 13.55 MHz ("1" in the diagram), 24.0 MHz ("2" in the diagram), around 31-32 MHz ("7" in the diagram), and around 41-42 MHz ("8" in the diagram).

[0055] On the other hand, the input / output ratio of S3,1 was high, at -1.36 dB at 20.65 MHz ("3" in the figure), -0.33 dB at 31.03 MHz ("5" in the figure), and -0.86 dB at 41.48 MHz ("6" in the figure). However, the input / output ratio decreased as the frequency increased above 41.48 MHz. Furthermore, the input / output ratio of S3,1 was approximately -2.0 dB at around 13 MHz ("9" in the figure), decreasing at lower frequencies.

[0056] From the above results, it is considered that when the frequency is lower than 13 MHz, the wavelength within the sheet becomes longer than the length in the circumferential direction D11 of the ring resonator 10S, resonance does not occur inside the ring resonator 10S, and electromagnetic waves do not transmit from the power transmission sheet 30S to the ring resonator 10S. Also, when the frequency is higher than 41.48 MHz, the wavelength becomes shorter than the length in the circumferential direction D11 of the planar coil, and the planar coil does not function as a coil, and similarly, electromagnetic waves do not transmit from the power transmission sheet 30S to the ring resonator 10S.

[0057] As described above, the power receiving terminal 5 includes the power receiving sheet 20 and the cylindrical ring resonator 10, and is an example of a wireless power receiving device that receives power wirelessly. In the example shown in Fig. 2 etc., the ring resonator 10 has a cylindrical shape. The power receiving sheet 20 is an example of a power receiving waveguide configured to be able to transmit electromagnetic waves, and is disposed near the ring resonator 10. In the example shown in Fig. 2 etc., the power receiving sheet 20 is disposed at a distance of 11 mm from the ring resonator 10.

[0058] The ring resonator 10 is configured to be able to transmit electromagnetic waves in the circumferential direction D11. When the ring resonator 10 is placed near the power transmission sheet 30, which is an example of a power transmission waveguide that transmits electromagnetic waves, the phenomenon described with reference to Fig. 10 and other figures occurs, and the ring resonator 10 transmits the electromagnetic waves transmitted from the power transmission sheet 30 to the power receiving sheet 20. In the example of Fig. 2 and other figures, when the ring resonator 10 is placed 11 mm away from the power transmission sheet 30, it absorbs the electromagnetic waves from the power transmission sheet 30 and transmits them to the power receiving sheet 20.

[0059] Furthermore, the ring resonator 10 is configured so that the length in the circumferential direction D11 is longer than the wavelength (hereinafter referred to as the "intra-ring wavelength") of the electromagnetic waves transmitted from the power transmission sheet 30 when they are transmitted inside the ring resonator 10. In the example of FIG. 2 etc., the electromagnetic waves transmitted from the power transmission sheet 30 to the ring resonator 10 have an intra-ring wavelength of 500 mm when transmitted inside the ring resonator 10, that is, a wavelength shorter than the length in the circumferential direction D11 of the ring resonator 10. This allows resonance to occur inside the ring resonator 10, allowing the ring resonator 10 to absorb the electromagnetic waves from the power transmission sheet 30. When resonance occurs inside the ring resonator 10, a high input / output ratio of approximately -0.2 to -1.36 dB can be achieved, as described in FIG. 13 .

[0060] For comparison, a case will be described in which a power receiving terminal equipped with a normal coil is used without using the ring resonator 10. FIG. 14 is a diagram showing a comparative example 1 of a power receiving terminal. FIG. 14 shows a resonant coil 10X and a power transmission sheet 30X. For the sake of explanation, the power transmission sheet 30X is assumed to be an infinitely long electromagnetic wave transmission path. In this case, the model is symmetrical with respect to the resonant coil 10X, and therefore it is not possible to absorb all of the electromagnetic waves EM1 transmitted by the power transmission sheet 30X.

[0061] To explain the reason, consider the case where a signal is input from the resonant coil 10X to the power transmission sheet 30X. When a signal is input from the resonant coil 10X, because the model is left-right symmetrical, the signal that enters the power transmission sheet 30X branches in two directions (signals indicated by electromagnetic waves EM2 and EM3 in the figure). Therefore, assuming that the system in Figure 14 is lossless, the signal that flows from the resonant coil 10X to the power transmission sheet 30X will be at most -3 dB. Here, the signal strength is the same for the outgoing and return signals, so even when a signal is input from port 1 of the power transmission sheet 30X, the signal that the resonant coil 10X can absorb will be at most -3 dB.

[0062] In a normal wireless power transfer system with no loss (using a coil with an infinite Q value), the efficiency is 100% (0 dB). However, power transfer using an infinitely long power transmission sheet 30X and resonant coil 10X always results in a symmetrical model, and as described above, only half of the power inside the power transmission sheet 30X can be extracted at most.

[0063] One possible method for increasing the power absorbed by the power transmission sheet 30X is to open or short one side of the waveguide to create an asymmetric model. Fig. 15 is a diagram showing a comparative example 2 of a power receiving terminal. Fig. 15 shows a resonance coil 10Y and a power transmission sheet 30Y. The power transmission sheet 30Y is configured so that the port 1 side is an infinitely long electromagnetic wave transmission path, but the opposite side has a termination TM1 (open or short).

[0064] 14 , when a signal (indicated by electromagnetic waves EM2 and EM3 in the figure) is input from resonance coil 10Y to power transmission sheet 30Y, the signal (indicated by electromagnetic wave EM3) that flows toward terminal end TM1 travels a length Lterm, is reflected by terminal end TM1, and returns (as a signal indicated by electromagnetic wave EM4). In other words, the signal returns with a phase shift corresponding to the length Lterm×2 that is transmitted through power transmission sheet 30Y, and then merges with the signal (indicated by electromagnetic wave EM2) that flows toward port 1. In the section between resonance coil 10Y and terminal end TM1, there are outgoing and returning waves, generating a standing wave.

[0065] If the signal flowing from resonant coil 10Y to port 1 and the signal flowing to termination TM1 and reflected by termination TM1 are in phase, the signals are added together, and all signals input from resonant coil 10Y to power transmission sheet 30Y reach port 1. At this time, resonant coil 10Y is located near the antinode of the standing wave. On the other hand, if these signals are out of phase, the signals cancel each other out, and no signal reaches port 1 (in this case, the signal itself cannot be input from resonant coil 10Y). At this time, resonant coil 10Y is located near the node of the standing wave.

[0066] As described above, even in the example of Figure 15, by setting Lterm to an appropriate length, power transmission between port 1 and resonant coil 10Y is possible with 100% efficiency in a lossless system. However, because the position of resonant coil 10Y can be changed arbitrarily, it is difficult to set Lterm to an appropriate length. One method is to switch between the antinode and node of the standing wave by switching termination TM1 between an open end and a short-circuit end. This avoids the risk of resonant coil 10Y entering a node and preventing power supply, but because Lterm is not set to an appropriate length, the signal input from port 1 does not necessarily reach resonant coil 10Y with high efficiency.

[0067] 2 and the like, it is possible to absorb electromagnetic waves from the power transmission sheet 30 with higher efficiency than the maximum efficiency of −3 dB in Comparative Example 1. Furthermore, using the ring resonator 10 eliminates the need to employ the complex configuration and control of Comparative Example 2. As described above, the wireless power feeding system 1 can improve power receiving efficiency with a simpler configuration than Comparative Examples 1 and 2.

[0068] In the wireless power supply system 1, the power receiving sheet 20 (an example of a power receiving waveguide) is configured to extend along a direction (extension direction D21) perpendicular to the axial direction D12 of the ring resonator 10. Note that "perpendicular" here is not limited to 90 degrees, but rather allows a range of, for example, about plus or minus 10 degrees. According to this embodiment, more electromagnetic waves can be transmitted to the power receiving sheet 20 (power receiving waveguide) than when the orientation of the power receiving sheet 20 is not within this range.

[0069] The ring resonator 10 also includes an outer circumferential conductive layer 12, which is an example of a first conductive layer, a dielectric layer 11, and an inner circumferential conductive layer 13, which is an example of a second conductive layer. The dielectric layer 11 is sandwiched between the outer circumferential conductive layer 12 and the inner circumferential conductive layer 13, thereby guiding electromagnetic waves in the circumferential direction D11. The outer circumferential conductive layer 12 includes a conductor shaped to shorten the wavelength of the electromagnetic waves. The outer circumferential conductive layer 12 includes, for example, a plurality of planar coils 121 arranged side by side in the circumferential direction D11, as shown in FIG. 7 .

[0070] The inner circumferential conductive layer 13 also includes a conductor disposed opposite the outer circumferential conductive layer 12 across the dielectric layer 11. The inner circumferential conductive layer 13 includes, for example, a plurality of planar coils 131 arranged side by side in the circumferential direction D11 shown in Fig. 7. These planar coils have a shape that increases the reactance of the outer circumferential conductive layer 12 and the inner circumferential conductive layer 13 and the capacitance between the outer circumferential conductive layer 12 and the inner circumferential conductive layer 13 compared to, for example, a case in which a meandering conductor is arranged, thereby shortening the wavelength of the electromagnetic wave as shown by the above equation (1).

[0071] As described above, the ring resonator 10 needs to be configured so that the length in the circumferential direction D11 is longer than the wavelength of the electromagnetic waves transmitted through the power transmission sheet 30. Therefore, by configuring the outer peripheral conductive layer 12 and the inner peripheral conductive layer 13 as described above, the wavelength of the electromagnetic waves transmitted through the ring resonator 10 is shortened compared to when the ring resonator 10 is configured with, for example, a meandering conductor, and the size of the ring resonator 10 can be reduced.

[0072] The power receiving sheet 20 also includes an upper conductive layer 22, which is an example of a third conductive layer, a dielectric layer 21, and a lower conductive layer 23, which is an example of a fourth conductive layer. The dielectric layer 21 is sandwiched between the upper conductive layer 22 and the lower conductive layer 23 to guide electromagnetic waves. The upper conductive layer 22 includes a conductor shaped to shorten the wavelength of the electromagnetic waves. The upper conductive layer 22 includes, for example, a plurality of planar coils 221 arranged side by side in the extension direction D21 shown in FIG. 9 . The lower conductive layer 23 includes a conductor disposed opposite the upper conductive layer 22 with the dielectric layer 21 sandwiched therebetween. The lower conductive layer 23 includes, for example, a plurality of planar coils 231 arranged side by side in the extension direction D21 shown in FIG. 9 .

[0073] These planar coils have a shape that increases the reactance of the upper conductive layer 22 and the lower conductive layer 23 and the capacitance between the upper conductive layer 22 and the lower conductive layer 23, as compared to when meander-shaped conductors are arranged, and shortens the wavelength of the electromagnetic wave as shown by the above equation 1. As a result, similar to the ring resonator 10, the size of the power receiving sheet 20 can be made smaller than when it is configured with meander-shaped conductors, for example.

[0074] The wireless power feeding system 1 also includes a power receiving terminal 5, which is an example of a wireless power receiving device, a power transmission sheet 30, and a power feeding unit 3, which is an example of an electromagnetic wave input device. The power feeding unit 3 inputs, to the power transmission sheet 30, electromagnetic waves having a wavelength equal to or shorter than the length in the circumferential direction D11 of the ring resonator 10. According to this aspect, the ring resonator 10 can absorb the electromagnetic waves, thereby improving power receiving efficiency compared to when the wavelength of the input electromagnetic waves is longer than the length in the circumferential direction D11 of the ring resonator 10.

[0075] The power transmission sheet 30 also includes an upper conductive layer 32, which is an example of a fifth conductive layer, a dielectric layer 31, and a lower conductive layer 33, which is an example of a sixth conductive layer. The dielectric layer 31 is sandwiched between the upper conductive layer 32 and the lower conductive layer 33 to guide electromagnetic waves. The upper conductive layer 32 includes a conductor shaped to shorten the wavelength of the electromagnetic waves. The upper conductive layer 32 includes, for example, a plurality of planar coils 321 arranged side by side in the extension direction D31 shown in FIG. 4 . The lower conductive layer 33 includes a conductor disposed opposite the upper conductive layer 32 with the dielectric layer 31 sandwiched therebetween. The lower conductive layer 33 includes, for example, a plurality of planar coils 331 arranged side by side in the extension direction D31 shown in FIG. 4 .

[0076] These planar coils have a shape that increases the reactance of the upper conductive layer 32 and the lower conductive layer 33 and the capacitance between the upper conductive layer 32 and the lower conductive layer 33, as compared to when meander-shaped conductors are arranged, and shortens the wavelength of the electromagnetic wave as shown by the above equation 1. As a result, similar to the ring resonator 10, the size of the power transmission sheet 30 can be made smaller than when it is configured with meander-shaped conductors, for example.

[0077] The vehicle 7 is also equipped with a power receiving terminal 5. The ring resonator 10 is provided at a height that puts it in the vicinity of the power transmission sheet 30 when the vehicle 7 is on the power transmission sheet 30. The vicinity of the power transmission sheet 30 is, for example, a position that is separated from the power transmission sheet 30 by the distance (11 mm) shown in FIG. 2 , but is not limited thereto and may be closer or farther than 11 mm. The distance that puts it in the vicinity of the power transmission sheet 30 is preferably, for example, equal to or less than half the length in the width direction D32 of the power transmission sheet 30. By stopping the vehicle 7 so that the ring resonator 10 and the power transmission sheet 30 are in the positional relationship shown in FIG. 2 , the power receiving efficiency can be improved in the same manner as described above.

[0078] <Other Modifications> The above-described embodiment of the wireless power supply system 1 is merely an example, and is not limited to this. For example, the shape of the ring resonator 10 is cylindrical in Fig. 2 and other figures, but is not limited to this. The shape may be an elliptical cylinder, a cylinder with a straight portion on the circumference like a track, or a rectangular cylinder (preferably with rounded corners).

[0079] The ring resonator 10 may have any shape as long as it is disposed between the power receiving sheet 20 and the power transmission sheet 30 and can resonate electromagnetic waves to transmit the electromagnetic waves from the power transmission sheet 30 to the power receiving sheet 20. Regardless of the shape of the ring resonator 10, in order to resonate electromagnetic waves therein, the length in the circumferential direction D11 needs to be longer than the intra-ring wavelength (the wavelength of the electromagnetic waves transmitted from the power transmission sheet 30 when transmitted inside the ring resonator 10). Furthermore, from the viewpoint of resonating electromagnetic waves therein, it is desirable that the length in the circumferential direction D11 of the ring resonator 10 be N times the intra-ring wavelength (N is a natural number).

[0080] Furthermore, the shapes of the conductors of the ring resonator 10, the power receiving sheet 20, and the power transmitting sheet 30 are not limited to those described in Figure 4 and other figures. For example, while each planar coil has a rectangular spiral shape in Figure 4 and other figures, it may have a square spiral shape, a circular spiral shape, an elliptical spiral shape, or another polygonal spiral shape. Furthermore, these conductors are not limited to a spiral shape, but may also have a meandering shape or the shape of a hex coil sheet in which hexagonal shapes are arranged as described in Figure 12. Furthermore, the conductors are not limited to planar coils. In short, any shape of conductor may be used as long as it shortens the wavelength of the electromagnetic wave.

[0081] Furthermore, in the ring resonator 10, the shapes and arrangements of the conductors of the outer peripheral conductive layer 12 and the inner peripheral conductive layer 13 are not limited to those shown in FIG. 7 . For example, in the inner peripheral conductive layer 13, the centers of the planar coils 131 in the circumferential direction D11 do not have to be offset from the centers of the planar coils 121 in the circumferential direction D11. Furthermore, the outer peripheral conductive layer 12 may have the same shape as that shown in FIG. 7 , and the inner peripheral conductive layer 13 may be a meandering-shaped or simply a plate-shaped conductor. Furthermore, the inner peripheral conductive layer 13 may have the same shape as that shown in FIG. 7 , and the outer peripheral conductive layer 12 may be a meandering-shaped or plate-shaped conductor. In short, it is sufficient that either the outer peripheral conductive layer 12 or the inner peripheral conductive layer 13 includes a conductor shaped to shorten the wavelength of electromagnetic waves. This also applies to the power receiving sheet 20 and the power transmission sheet 30.

[0082] Furthermore, although the shapes and arrangements of the conductors of the ring resonator 10, the power receiving sheet 20, and the power transmission sheet 30 are all common in the example shown in FIG. 4 and the like, they may be different from each other. Furthermore, although the widths of the ring resonator 10, the power receiving sheet 20, and the power transmission sheet 30 are all common in the example shown in FIG. 4 and the like, they may be different from each other. Furthermore, as described above, the length in the circumferential direction D11 of the ring resonator 10 may be shorter or longer than 500 mm shown in FIG. 2 as long as it is longer than the intra-ring wavelength. Furthermore, the length in the extension direction D21 of the power receiving sheet 20 is not particularly limited, and may be shorter or longer than the length shown in FIG. 2.

[0083] 1 and other examples, the rectifier 6 is connected to both ends of the power receiving sheet 20, but the rectifier 6 may be connected to only one end. In this case, when the vehicle 7 is parked with the end of the power receiving sheet 20 to which the rectifier 6 is connected facing the end to which the power supply unit 3 of the power transmission sheet 30 is connected, power is supplied to the rectifier 6 and the battery 8 is charged.

[0084] <Power Supply Experiment> The following describes a power supply experiment conducted by the inventor. Fig. 16 is a diagram showing a wireless power supply system 1a used in the power supply experiment. The wireless power supply system 1a includes a ring resonator 10a, a power receiving sheet 20a, and a power transmitting sheet 30a. The power receiving sheet 20a and the power transmitting sheet 30a are configured such that a plurality of coil elements, each formed by winding a thin coated conductor wire (polyester copper wire) in a coil shape, are arranged with half the coil elements offset from one another and connected in series, giving the sheet a ladder-like appearance.

[0085] Similar to the power receiving sheet 20a and the power transmitting sheet 30a, the ring resonator 10a is configured such that multiple coil elements, each formed by winding a thin coated conductor (polyester copper wire) into a coil shape, are arranged halfway between the coil elements and connected in series, with both ends connected to form a ring. The shape of the ring resonator 10a will be described with reference to FIG. 17.

[0086] 17 is a view of ring resonator 10a viewed in the axial direction D12a. Ring resonator 10a has two linear portions 14a and two semicircular portions 15a, which are connected to form a ring shape (a so-called racetrack shape). When viewed in the axial direction D12a, ring resonator 10a has a first dimension L14a in a first direction D14a that is longer than a second dimension L15a in a second direction D15a. In other words, the first direction D14a can be considered the longitudinal direction, and the second direction D15a can be considered the lateral direction. The second direction D15a is perpendicular to the first direction D14a.

[0087] 18 is a diagram showing the arrangement in power supply experiment 1. In power supply experiment 1, the ring resonator 10a is installed so that the first direction D14a (longitudinal direction) is aligned with the extension direction D31a of the power transmission sheet 30a (an example of a power transmission waveguide) and the extension direction D21a of the power receiving sheet 20a (a power receiving waveguide).

[0088] The dimensions of the power receiving sheet 20a and the power transmission sheet 30a are a width (short side = width length) of 220 mm and a length (longitudinal direction = length in the extension direction) of 500 mm. The dimensions of the ring resonator 10a are a width (short side = width direction) of 220 mm, a first dimension L14a of 350 mm, and a second dimension L15a of 170 mm. The number of turns of each coil element is 4. The dimensions of each coil element are 220 mm in the width direction and 100 mm in the arrangement direction (direction in which the coil elements are arranged).

[0089] The distance between the power transmission sheet 30a and the ring resonator 10a was 40 mm, and the distance between the power receiving sheet 20a and the ring resonator 10a was also 40 mm. In the experiment, a 40 mm distance was maintained using Styrofoam (registered trademark) (light blue polystyrene foam). The right-side terminations of both the power receiving sheet 20a and the power transmission sheet 30a were matched with a non-inductive load. Therefore, it is believed that there is almost no electromagnetic wave reflection at the terminations. Meanwhile, a signal input port and an output port were provided at the left-side termination, and the reflection coefficient and transmission coefficient for each frequency were measured using a vector network analyzer (device used: nanoVNA).

[0090] 19 is a diagram showing another arrangement in power supply experiment 2. In power supply experiment 2, ring resonator 10a is installed so that second direction D15a (short side direction) is aligned with extension direction D31a of power transmission sheet 30a (an example of a power transmission waveguide) and extension direction D21a of power receiving sheet 20a (a power receiving waveguide). In both of the arrangements shown in FIGS. 18 and 19, electromagnetic waves with a measurement frequency range of 75 to 150 kHz were input to power transmission sheet 30a.

[0091] Figure 20 shows the results of the power supply experiment. Figure 20 shows a graph with the vertical axis representing the transmission coefficient and the horizontal axis representing the frequency. In both power supply experiment 1 and power supply experiment 2, the transmission coefficient reached its maximum at approximately 114 kHz. This is thought to be because resonance occurred at 114 kHz, the outer circumference of ring resonator 10a was approximately 800 mm, and the wavelength of the waveguide was approximately 700 to 800 mm at 100 kHz, so the length of one circumference of ring resonator 10a matched the length of one wavelength at a frequency of 114 kHz.

[0092] The results of the above power supply experiments 1 and 2 show that resonance occurs and power supply efficiency is maximized when the length of one circumference of the ring resonator is equal to the length of one wavelength. Furthermore, it was found that when the ring resonator is arranged so that its longitudinal direction is aligned with the extension direction of the power transmission waveguide, as in power supply experiment 1, the power supply efficiency can be improved (by about three times in the above experiment) compared to when the ring resonator is arranged so that its lateral direction is aligned with the extension direction of the power transmission waveguide, as in power supply experiment 2.

[0093] In the above power supply experiment, the ring resonator had a so-called racetrack shape when viewed in the axial direction, but this is not limited to this. When viewed in the axial direction, the ring resonator may be circular, as shown in Figure 2, or may be elliptical or rectangular (with right-angled or rounded corners). Regardless of the shape, by arranging the ring resonator so that its longitudinal direction is aligned with the extension direction of the power transmission waveguide, the distance between the waveguide and the ring resonator becomes longer than when the short side is aligned with the extension direction, thereby improving power supply efficiency.

[0094] The wireless power supply system 1 and the like may be provided in the following aspects.

[0095] (1) A wireless power receiving device comprising a power receiving waveguide and a cylindrical ring resonator, wherein the power receiving waveguide is configured to be able to transmit electromagnetic waves and is arranged near the ring resonator, and the ring resonator is capable of transmitting electromagnetic waves in a circumferential direction and, when arranged near a power transmitting waveguide that transmits electromagnetic waves, transmits electromagnetic waves transmitted from the power transmitting waveguide to the power receiving waveguide, and is configured so that the circumferential length of the electromagnetic waves is longer than the wavelength when transmitted inside the ring resonator.

[0096] According to this aspect, it is possible to improve the power receiving efficiency.

[0097] (2) The wireless power receiving device according to (1) above, wherein the power receiving waveguide is configured to extend along a direction perpendicular to the axial direction of the ring resonator.

[0098] According to this aspect, a larger amount of electromagnetic waves can be transmitted to the power receiving waveguide.

[0099] (3) In the wireless power receiving device described in (1) above, the ring resonator comprises a first conductive layer, a dielectric layer, and a second conductive layer, the dielectric layer is sandwiched between the first conductive layer and the second conductive layer to guide electromagnetic waves in the circumferential direction, the first conductive layer includes a conductor shaped to shorten the wavelength of the electromagnetic waves, and the second conductive layer includes a conductor arranged in a position opposite the first conductive layer across the dielectric layer.

[0100] According to this embodiment, the size of the ring resonator can be reduced.

[0101] (4) A wireless power receiving device according to (1) above, wherein the power receiving waveguide comprises a third conductive layer, a dielectric layer, and a fourth conductive layer, the dielectric layer being sandwiched between the third conductive layer and the fourth conductive layer to guide electromagnetic waves, the third conductive layer including a conductor shaped to shorten the wavelength of the electromagnetic waves, and the fourth conductive layer including a conductor arranged in a position opposite the third conductive layer across the dielectric layer.

[0102] According to this aspect, the size of the power receiving waveguide can be reduced.

[0103] (5) A wireless power supply system comprising the wireless power receiving device according to any one of (1) to (4) above, a power transmission waveguide, and an electromagnetic wave input device, wherein the electromagnetic wave input device inputs an electromagnetic wave having a wavelength equal to or less than the circumferential length of the ring resonator to the power transmission waveguide.

[0104] According to this aspect, it is possible to improve the power receiving efficiency.

[0105] (6) In the wireless power receiving device described in (5) above, the ring resonator is installed so that its dimension in a first direction when viewed in the axial direction is longer than its dimension in a second direction perpendicular to the first direction, and the first direction is aligned with the extension direction of the power transmission waveguide.

[0106] According to this aspect, it is possible to improve the power supply efficiency.

[0107] (7) In the wireless power supply system described in (5) above, the power transmission waveguide includes a fifth conductive layer, a dielectric layer, and a sixth conductive layer, the dielectric layer guides electromagnetic waves by being sandwiched between the fifth conductive layer and the sixth conductive layer, the fifth conductive layer includes a conductor shaped to shorten the wavelength of the electromagnetic waves, and the sixth conductive layer includes a conductor arranged in a position opposite the fifth conductive layer with the dielectric layer in between.

[0108] According to this aspect, the size of the power transmission waveguide can be reduced.

[0109] (8) A vehicle equipped with the wireless power receiving device described in any one of (1) to (4) above, wherein the ring resonator is provided at a height that is close to the power transmission waveguide when the vehicle is above the power transmission waveguide.

[0110] According to this embodiment, it is possible to improve the power receiving efficiency. However, this is not necessarily the case.

[0111] Finally, while various embodiments of the present disclosure have been described, they are presented as examples and are not intended to limit the scope of the invention. The novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. Such embodiments and modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as defined in the claims.

[0112] 1: Wireless power feeding system, 2: Power feeding unit, 3: Power feeding section, 5: Power receiving terminal, 6: Rectifier, 7: Vehicle, 8: Battery, 9: Drive section, 10: Ring resonator, 11: Dielectric layer, 12: Outer conductive layer, 13: Inner conductive layer, 20: Power receiving sheet, 21: Dielectric layer, 22: Upper conductive layer, 23: Lower conductive layer, 30: Power transmitting sheet, 31: Dielectric layer, 32: Upper conductive layer, 33: Lower conductive layer, 121: Planar coil, 131: Planar coil, 221: Planar coil, 231: Planar coil, 321: Planar coil, 331: Planar coil

Claims

1. A wireless power receiving device comprising: a power receiving waveguide; and a cylindrical ring resonator; the power receiving waveguide is configured to be able to transmit electromagnetic waves and is arranged in the vicinity of the ring resonator; the ring resonator is capable of transmitting electromagnetic waves in a circumferential direction and, when arranged in the vicinity of a power transmitting waveguide that transmits electromagnetic waves, transmits the electromagnetic waves transmitted from the power transmitting waveguide to the power receiving waveguide, and is configured so that the circumferential length of the electromagnetic waves is longer than the wavelength when transmitted inside the ring resonator.

2. A wireless power receiving device according to claim 1, wherein the power receiving waveguide is configured to extend in a direction perpendicular to the axial direction of the ring resonator.

3. A wireless power receiving device according to claim 1, wherein the ring resonator comprises a first conductive layer, a dielectric layer, and a second conductive layer, the dielectric layer being sandwiched between the first conductive layer and the second conductive layer to guide electromagnetic waves in the circumferential direction, the first conductive layer including a conductor shaped to shorten the wavelength of the electromagnetic waves, and the second conductive layer including a conductor disposed in a position opposite the first conductive layer with the dielectric layer in between.

4. A wireless power receiving device comprising: the wireless power receiving waveguide according to claim 1; a third conductive layer, a dielectric layer, and a fourth conductive layer; the dielectric layer guides electromagnetic waves by being sandwiched between the third conductive layer and the fourth conductive layer; the third conductive layer includes a conductor shaped to shorten the wavelength of the electromagnetic waves; and the fourth conductive layer includes a conductor disposed in a position opposite the third conductive layer with the dielectric layer sandwiched therebetween.

5. A wireless power supply system comprising: a wireless power receiving device according to any one of claims 1 to 4; a power transmission waveguide; and an electromagnetic wave input device, wherein the electromagnetic wave input device inputs, into the power transmission waveguide, electromagnetic waves having a wavelength equal to or less than the circumferential length of the ring resonator.

6. A wireless power receiving device according to claim 5, wherein the ring resonator is installed so that the dimension in a first direction, as viewed in the axial direction, is longer than the dimension in a second direction perpendicular to the first direction, and the first direction is aligned with the extension direction of the power transmission waveguide.

7. A wireless power supply system according to claim 5, wherein the power transmission waveguide comprises a fifth conductive layer, a dielectric layer, and a sixth conductive layer, the dielectric layer is sandwiched between the fifth conductive layer and the sixth conductive layer to guide electromagnetic waves, the fifth conductive layer includes a conductor shaped to shorten the wavelength of the electromagnetic waves, and the sixth conductive layer includes a conductor disposed in a position opposite the fifth conductive layer with the dielectric layer sandwiched therebetween.

8. A vehicle equipped with a wireless power receiving device according to any one of claims 1 to 4, wherein the ring resonator is provided at a height that puts it in the vicinity of the power transmission waveguide when the vehicle is located above the power transmission waveguide.

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