Antenna device, wireless power transmission device, and wireless power transmission system

Abstract

This antenna device for wireless electric power transfer comprises two electrodes oriented perpendicularly to each other, a first coil connecting the two electrodes, and a second coil that is coupled to the first coil in an electromagnetic manner.

Description

[Technical Field]

[0001] The present invention relates to a technology for wirelessly transmitting power, and particularly to a technology that is effective when transmitting power wirelessly over a relatively long distance of several meters or more without using cables. [Background technology]

[0002] For example, as a method for wirelessly transmitting power between two points where it is difficult to lay a cable to supply power, prior art has proposed (1) a method using lasers, (2) a method using microwaves, (3) a method using magnetic field resonance or electric field resonance, and (4) a method using electromagnetic induction.

[0003] For example, Patent Document 1 discloses a method (3) that uses magnetic field resonance or electric field resonance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-60850 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional method (1) of wirelessly transmitting power between two points using a laser, power is transmitted using a linear beam, so power cannot be sent unless the other party is in a position where they can see it. There are limitations to its use, such as the need for no obstacles blocking the laser between the two parties to transmit power, and the need to track the laser beam to match the other party's position if the other party moves.

[0006] In the method (2) using microwaves, microwaves (radio waves) propagate while diffusing through space, so the transmission efficiency decreases as the distance increases.

[0007] Method (3) using magnetic field resonance or electric field resonance utilizes the resonance phenomenon caused by the resonance of the antennas on both the transmitting and receiving sides. Therefore, if the distance between the antennas changes (i.e., if the distance between the antennas is too close or too far), the resonance conditions are not met and the transmission efficiency decreases.

[0008] In the method (4) using electromagnetic induction, the transmission distance is short, so power can only be transmitted at a position where it is almost in contact.

[0009] The present invention has been made in view of the above points, and has an object to provide a technology for wirelessly transmitting power more efficiently than conventional technology. [Means for solving the problem]

[0010] According to the disclosed technology, two electrodes oriented perpendicular to each other, a first coil connecting the two electrodes; a second coil that is magnetically coupled to the first coil, The second coil is wound around the outside of the first coil without contacting the first coil. An antenna device for wireless power transmission is provided. [Effects of the Invention]

[0011] The disclosed technology provides a technology for wirelessly transmitting power more efficiently than conventional technology. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of a system for wireless power transmission using surface waves. [Figure 2] 1 is a diagram illustrating a configuration of an antenna device according to a first embodiment. [Figure 3] FIG. 2 is a diagram illustrating a configuration of a resonator. [Figure 4] 1 is a diagram illustrating a configuration of an antenna device according to a first embodiment. [Figure 5]1 is a diagram illustrating a configuration of a wireless power transmission system according to a first embodiment. [Figure 6] FIG. 10 is a diagram illustrating a configuration of an antenna device according to a second embodiment. [Figure 7] FIG. 10 is a diagram illustrating a configuration of an antenna device according to a second embodiment. [Figure 8] FIG. 10 is a diagram illustrating a configuration of a wireless power transmission system according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention (the present embodiment) will be described with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0014] (Outline of the embodiment) In this embodiment, wireless power transmission is performed using surface waves. That is, energy radiated from a power transmitting antenna is transmitted wirelessly to a power receiving antenna in the form of surface waves. Both the power transmitting and power receiving antennas can be antennas of the same shape that transmit and receive surface waves. The antennas may also be called "antenna devices."

[0015] A surface wave is an electromagnetic wave that propagates on a two-dimensional plane along the interface between two media with different dielectric constants. Because the power (energy) of a surface wave is concentrated near the interface and does not diffuse in the three-dimensional vertical direction, it can transmit power highly efficiently between antennas located near the interface.

[0016] Two media with different dielectric constants that form the interface through which surface waves propagate include "air and a metal floor," "air and the ground," "air and the sea surface," etc. For example, it is possible to efficiently transmit power wirelessly between devices placed on a metal-paneled floor in an office or factory.

[0017] An example of the configuration of a system that performs wireless power transmission using surface waves is shown in Fig. 1. As shown in Fig. 1, the system is equipped with a power transmitting antenna 100 and a power receiving antenna 200, which are antennas of the same shape that transmit and receive surface waves. In the example of Fig. 1, power is transmitted wirelessly from the power transmitting antenna 100 to the power receiving antenna 200 by the surface waves propagating along the interface between medium A and medium B, which are two media with different dielectric constants.

[0018] The structure of the antenna will be described in detail below using Examples 1 to 3.

[0019] Example 1 Generally, when an antenna resonates, it can generate both radio waves radiated into three-dimensional space and surface waves radiated within a two-dimensional plane. To increase the transmission efficiency of wireless power transmission on a two-dimensional plane, it is desirable for the antenna to reduce the radiation of radio waves into three-dimensional space and increase the radiation of surface waves on the two-dimensional plane.

[0020] In this embodiment, an antenna that reduces radiation of radio waves into three-dimensional space and increases radiation of surface waves on a two-dimensional plane is realized with the structure shown in FIG.

[0021] Fig. 2 is a diagram showing the configuration of the antenna of Example 1. Fig. 2 shows an image of a cross section of the antenna cut along a plane perpendicular to the plane of the electrodes.

[0022] As shown in FIG. 2, the antenna of the first embodiment includes an electrode 11 for emitting a surface wave to a medium (medium A) in front of it, and an electrode 12 for coupling with the floor (medium B).

[0023] Electrode 12 is placed parallel to the floor so as to face it directly, in order to couple strongly with medium B on the floor. Electrode 11 radiates surface waves in a direction parallel to the interface, so it is placed so as to face in a direction parallel to the interface (i.e., perpendicular to electrode 12, which is parallel to the floor). Note that "parallel" and "perpendicular" in this embodiment do not necessarily mean "parallel" and "perpendicular" in the strict sense. For example, a direction that deviates from "parallel" within a certain threshold value may also be considered "parallel." Furthermore, a direction that deviates from "perpendicular" within a certain threshold value may also be considered "perpendicular."

[0024] The electrodes 11 and 12 are connected by a coil (primary coil 13). A secondary coil 14 connected to a coaxial cable 15 is also provided.

[0025] Electrodes 11 and 12, and primary coil 13 form a resonator with a specific resonant frequency. The sizes of the electrodes and coil are adjusted so that the resonant frequency of this resonator matches the frequency of the transmitted high-frequency power source. Note that "matching" does not have to mean "matching" strictly. For example, even if the frequency deviates from "matching" within a certain threshold range, it may still be considered "matching."

[0026] Figure 3 shows a resonator formed by electrode 11, electrode 12, and primary coil 13. When the resonator shown in Figure 3 resonates, charge is stored in electrode 11 and electrode 12, increasing the voltage amplitude between electrode 11 and electrode 12 and creating a strong electric field around the electrodes.

[0027] Furthermore, a large current flows through the primary coil 13, and the amplitude of the current is maximum at the center of the primary coil 13.

[0028] At this time, by magnetically coupling the primary coil 13 and the secondary coil 14 without contact, it is possible to input or extract power to or from the resonator without affecting the resonant frequency of the resonator.

[0029] An example of the arrangement of the primary coil 13 and the secondary coil 14 is shown in Fig. 4. In the example shown in Fig. 4, the secondary coil 14 is wound around the primary coil 13, thereby enabling input and output of power to the resonator.

[0030] The antenna is connected to a power transmitting circuit or a power receiving circuit via a transmission line such as a coaxial cable 15. FIG. 5 shows a configuration example in which an antenna 100 is connected to a power transmitting circuit and an antenna 200 is connected to a power receiving circuit. Both the power transmitting circuit and the power receiving circuit may be called power transmitting and receiving circuits. A device including an antenna and a power transmitting and receiving circuit may be called a wireless power transmission device. A system including multiple wireless power transmission devices, as shown in FIG. 5, may be called a wireless power transmission system.

[0031] 5, the power transmitting circuit includes a matching circuit 101, an inverter 102, and a power supply 103. The power receiving circuit includes a matching circuit 201, a converter 202, and a load 203.

[0032] The matching circuit 101 of the power transmitting circuit performs impedance matching between the antenna 100 and the inverter 102. The matching circuit 201 of the power receiving circuit performs impedance matching between the antenna 200 and the converter 202. The matching circuits 101 and 201 can suppress reflections and improve the transmission efficiency of the entire wireless power transmission system.

[0033] Example 2 Next, a second embodiment will be described. When the resonator inside the antenna resonates, the electrodes at both ends become "resonance loops with the largest potential amplitude," and the area near the center of the resonator becomes "resonance nodes with the smallest potential amplitude." Therefore, as shown in Fig. 6, ground wire 16 of the coaxial cable for power supply may be connected to the position where the potential is zero and the resonance node occurs (the position between primary coil 13A and primary coil 13B).

[0034] This allows the ground potential of the resonator and the power transmission / reception circuit to match, improving transmission efficiency. Figure 7 shows the antenna shown in Figure 6 viewed from diagonally above.

[0035] Example 3 Next, a description will be given of Example 3. The antenna used in Example 3 may be the antenna described in Example 1 or the antenna described in Example 2.

[0036] Wireless power transmission technology using surface waves can confine power within a two-dimensional plane without diffusing it in the three-dimensional vertical direction, which has the advantage of higher transmission efficiency compared to conventional wireless power transmission technologies that transmit power in three-dimensional space.

[0037] Furthermore, because surface waves propagate along the interface between two media with different dielectric constants, there is also the advantage that the power transmission path can be bent along the interface when the interface is curved.

[0038] Figure 8 shows an example of a system configuration that takes advantage of the ability to bend the power transmission path along the interface. The system components are the same as those shown in Figure 5. The example in Figure 8 shows a case where the destination to which power is to be sent is on the horizon or beyond the horizon, and the two parties cannot see each other. Even in such a case, it is possible to send power from antenna 100 to antenna 200, which was not possible with conventional wireless power transmission technologies that use lasers or microwaves.

[0039] (Summary of the embodiment and its effects) As described above, in this embodiment, the antenna device for wireless power transmission is configured to include two electrodes oriented perpendicular to each other, a coil connecting them, and another coil that is magnetically coupled to the first coil, and is connected to a power transmission / reception circuit via the other coil.

[0040] The two electrodes and the coil connecting them form a resonator that resonates at the output frequency of the power transmission circuit for wireless power transmission. The resonator and the ground of the power transmission / reception circuit may be connected by a ground line.

[0041] According to the antenna device configured as above, radiation of radio waves into three-dimensional space can be suppressed, and surface waves propagating on a two-dimensional plane can be efficiently transmitted and received.

[0042] Furthermore, because the power is confined and transmitted on a two-dimensional plane, power can be transmitted more efficiently than with conventional wireless power transmission technologies that radiate power in three-dimensional spatial directions.

[0043] Furthermore, even if the interface through which the surface wave propagates is curved, the power also propagates while bending along the interface, so power transmission can be performed even if the other party is not in a position where they can be directly seen.

[0044] (Addendum) This specification discloses at least the antenna device, wireless power transmission device, and wireless power transmission system described in the following sections. (Section 1) Two electrodes oriented perpendicular to each other, a first coil connecting the two electrodes; a second coil that is magnetically coupled to the first coil; An antenna device for wireless power transmission comprising: (Section 2) The two electrodes and the first coil form a resonator that resonates at the output frequency of a power transmission / reception circuit for wireless power transmission. 2. The antenna device according to claim 1. (Section 3) The resonator and the ground of the power transmitting and receiving circuit are connected by a ground line. 3. The antenna device according to claim 2. (Section 4) The antenna device transmits power by surface waves or receives power transmitted by surface waves. 1. The antenna device according to claim 1, wherein the antenna device is a semiconductor integrated circuit. (Section 5) A wireless power transmission device comprising: the antenna device according to any one of claims 1 to 4; and a power transmission / reception circuit connected to the antenna device via the second coil in the antenna device. (Section 6) 10. A wireless power transmission system comprising: a wireless power transmission device on a power transmitting side that is the wireless power transmission device according to claim 5; and a wireless power transmission device on a power receiving side that is the wireless power transmission device according to claim 5.

[0045] Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0046] 11 electrodes 12 electrodes 13 Primary coil 14 Secondary coil 15 Coaxial Cable 16 Ground wire 100 Antennas 101 Matching circuit 102 Inverter 103 Power supply 200 Antennas 201 Matching circuit 202 Converter 203 Load

Claims

1. Two electrodes oriented perpendicular to each other, a first coil connecting the two electrodes; a second coil that is magnetically coupled to the first coil, The second coil is wound around the outside of the first coil without contacting the first coil. An antenna device for wireless power transmission.

2. Two electrodes oriented perpendicular to each other; a first coil connecting the two electrodes; a second coil that is magnetically coupled to the first coil; An antenna device for wireless power transmission, comprising: The two electrodes and the first coil form a resonator that resonates at the output frequency of a power transmission / reception circuit for wireless power transmission. Antenna device.

3. The resonator and the ground of the power transmitting and receiving circuit are connected by a ground line. The antenna device according to claim 2 .

4. The antenna device transmits power by surface waves or receives power transmitted by surface waves.

4. The antenna device according to claim 1, wherein the antenna device is a conductor.

5. A wireless power transmission device comprising: the antenna device according to claim 1 ; and a power transmission / reception circuit connected to the antenna device via the second coil of the antenna device.

6. A wireless power transmission system comprising: a power transmitting side wireless power transmission device that is the wireless power transmission device according to claim 5; and a power receiving side wireless power transmission device that is the wireless power transmission device according to claim 5.

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