JP7207355B2 - wireless power transmission system - Google Patents

Description

The present invention relates to a wireless power transmission system for wireless power transmission. In particular, the present invention relates to power transmission by electromagnetic waves within a housing.

2. Description of the Related Art A technique is known in which power is transmitted by providing a transmission antenna and a reception antenna within a housing, forming a resonance mode within the housing, and transmitting electromagnetic waves at the resonance frequency.

Patent document 1 discloses that a power transmission unit and a power reception unit are entirely covered with a housing made of an electromagnetic wave reflecting material, a resonance mode is formed inside the housing, and the resonance frequency is set to the power transmission frequency. A wireless power transfer system that implements Further, it is described that an impedance variable probe having a shape such as a rod or a helical shape and having a variable reactance is provided on the inner wall surface of the housing to achieve impedance matching between the power transmission unit and the power reception unit.

Patent Literature 2 describes a system in which a resonator is provided in a closed space to form a resonance mode, and power is transmitted at the resonance frequency.

Patent Document 3 describes adjusting the resonance frequency of the waveguide by providing a tuning screw protruding inside the waveguide and adjusting the amount of projection by turning the tuning screw.

Non-Patent Document 1 describes that a transmitting antenna and a receiving antenna are provided in a rectangular parallelepiped box-shaped metal housing with one side open, and power transmission is performed by microwaves. is stated to improve.

JP 2019-41529 A U.S. Patent Application Publication No. 2018/0097402 WO 95/01658

Takuma Ikeda et al., ``Study on efficiency improvement by reception diversity of microwave wireless power transmission in closed metallic space'', IEICE Society Conference 2019

In Patent Documents 1 to 3 and Non-Patent Document 1, it is necessary to form a resonance mode in the housing. However, there are cases where the resonance mode cannot be formed depending on the size and shape of the housing. Moreover, even if the resonance mode can be formed, it is necessary to match the resonance frequency of the formed resonance mode with the frequency of the electromagnetic waves for power transmission and reception. However, the adjustment range of the resonance frequency is limited by the size and shape of the housing, the presence of conductive members in the housing, etc., and it has been difficult to transmit power using electromagnetic waves of a desired frequency.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to realize a wireless power transmission system capable of transmitting power at a desired frequency regardless of the shape and size of the housing.

The present invention has a transmitting antenna for transmitting electromagnetic waves of a predetermined frequency, a receiving antenna for receiving electromagnetic waves from the transmitting antenna, a relay for relaying power from the transmitting antenna to the receiving antenna, and an internal space. a transmitting antenna, a receiving antenna, and a housing in which a relay is arranged, the transmitting antenna and the relay, and the relay and the receiving antenna are electromagnetically coupled, and the relay and the housing have a distributed constant It is a wireless power transmission system characterized by forming a circuit and transmitting and relaying an electromagnetic wave through a relay .

The housing has a partition that separates the internal space into a side on which the transmitting antenna is arranged and a side on which the receiving antenna is arranged, the partition has a through hole penetrating the partition, and the relay penetrates It may be arranged through the hole from the internal space on the side where the transmitting antenna is arranged to the internal space on the side where the receiving antenna is arranged.

The distance between the inner wall surface of the housing and the relay may be 5 mm or more.

The intermediary may be separated into two or more parts.

An object made of a conductor is arranged in the internal space of the housing, and the distance between the object and the relay may be 5 mm or more.

According to the wireless power transmission system of the present invention, power can be transmitted at a desired frequency within a housing of any shape and size.

1 is a diagram showing the configuration of a wireless power transmission system according to a first embodiment; FIG. The figure which showed the structure of the wireless power transmission system of a modification. Graph of characteristic impedance Z0. The figure which showed the structure of the wireless power transmission system of a modification. The figure which showed the structure of the wireless power transmission system of a modification. 2 is a diagram showing a simplified model of the wireless power transmission system of Example 1. FIG. The figure which showed the equivalent circuit of a simple model. The graph which showed transmission efficiency |S21|. The graph which showed transmission efficiency |S21|. The figure which showed the analysis model of the wireless power transmission system of a comparative example. The graph which showed transmission efficiency |S21|. FIG. 2 is a diagram showing an analysis model of the wireless power transmission system of Example 1; The graph which showed transmission efficiency |S21|. FIG. 2 is a diagram showing an analysis model of the wireless power transmission system of Example 1; The graph which showed transmission efficiency |S21|. FIG. 2 is a diagram showing an analysis model of the wireless power transmission system of Example 1; The graph which showed transmission efficiency |S21|. FIG. 2 is a diagram showing an analysis model of the wireless power transmission system of Example 1; The graph which showed transmission efficiency |S21|. FIG. 2 is a diagram showing application of the wireless power transmission system of Example 1 to an electronic device; The figure which showed the structure of the wireless power transmission system of Example 2. FIG.

Specific examples of the present invention will be described below with reference to the drawings, but the present invention is not limited to the examples.

FIG. 1 is a diagram showing the configuration of a wireless power transmission system according to a first embodiment. As shown in FIG. 1 , the wireless power transmission system of Example 1 includes a transmitting antenna 10 , a receiving antenna 11 , a relay 12 and a housing 13 .

The transmitting antenna 10 is an antenna that radiates electromagnetic waves of a predetermined frequency, and the receiving antenna 11 is an antenna that receives electromagnetic waves of a predetermined frequency. Electric power is wirelessly transmitted by transmitting and receiving electromagnetic waves through the transmitting antenna 10 and the receiving antenna 11 . The transmitting antenna 10 and the receiving antenna 11 may be antennas of any shape, and may be linear antennas such as dipole antennas and monopole antennas, plate antennas, slot antennas, and the like. A magnetic field antenna such as a loop antenna may also be used.

The relay 12 relays electromagnetic waves from the transmitting antenna 10 to the receiving antenna 11 . The relay 12 is a linear conductor, one end of which is spaced near the transmitting antenna 10 and the other end of which is spaced near the receiving antenna 11 . For such arrangement, the relay 12 may be bent as appropriate. The transmitting antenna 10 and the relay 12, and the relay 12 and the receiving antenna 11 are electromagnetically joined, thereby enabling power transmission from the transmitting antenna 10 to the receiving antenna 11 with high efficiency. Here, the electromagnetic field coupling means any of electric field coupling, magnetic field coupling, and composite coupling of electric field and magnetic field. The inductance and capacitance of the transmitting antenna 10 and the receiving antenna 11 may be adjusted in order to electromagnetically bond the relay 12 to the transmitting antenna 10 and the receiving antenna 11 . For example, the antenna shape of the transmitting antenna 10 and the receiving antenna 11 can be modified, or a lumped constant element can be added.

Although the shape of the relay 12 is linear in the first embodiment, it may be of any shape as long as it can be electromagnetically bonded to the transmitting antenna 10 and the receiving antenna 11. For example, it may be flat or cylindrical. However, when the transmitting antenna 10 and the receiving antenna 11 are magnetic field antennas, the shape of the relay 12 may be looped.

Also, the distance between the relay 12 and the transmitting antenna 10 may be any distance as long as the relay 12 and the transmitting antenna 10 can be electromagnetically coupled. The same applies to the distance between the relay 12 and the receiving antenna 11 .

Further, the relay 12 does not need to be composed of one conductor, and may be separated into a plurality of conductors. Even in that case, if the relays 12 are electromagnetically coupled to each other, power can be relayed between the plurality of relays 12 and transmitted from the transmitting antenna 10 to the receiving antenna 11 . When the route from the transmitting antenna 10 to the receiving antenna 11 in the housing 13 is restricted, or when the position, size, etc. of the relay 12 are restricted by configuring the relay 12 by separating it into a plurality of pieces. Also in , it is possible to relay electric power. Also, by separating the relay 12 into a plurality of pieces, the shape of each relay 12 can be simplified. FIG. 2 shows an example in which the relay 12 is composed of two separated relays 12A and 12B. The relays 12A and 12B are linear conductors and are arranged in parallel with a predetermined distance therebetween.

Further, the material of the relay 12 does not have to be a conductor, and any material may be used as long as it can be electromagnetically coupled with the transmitting antenna 10 and the receiving antenna 11 . For example, it may be made of a resin material.

The housing 13 is made of a conductor and has a hollow rectangular parallelepiped shape. A transmitting antenna 10 , a receiving antenna 11 , and a relay 12 are arranged inside the housing 13 .

The distance between the inner wall surface of housing 13 and relay 12 is preferably 5 mm or more. The reason is as follows. The housing 13 and the relay 12 form a distributed constant circuit, the structure of which can be approximated to a microstrip line. Its characteristic impedance Z0 is as shown in the graph of FIG. Here, the distance from the inner wall surface of the housing 13 to the relay 12 is h, the thickness of the relay 12 is t, and the width is w. Also, the space between the inner wall surface of the housing 13 and the relay 12 has a relative permittivity εr=1. Also, w=t=0.5, 1, 2 mm.

As shown in FIG. 3, the characteristic impedance Z0 sharply increases when h=0 to 5 mm, but gently increases when h is 5 mm or more. In other words, if h is 5 mm or more, even if there is some variation in h, variation in the characteristic impedance Z0 is small. Therefore, stable and highly efficient wireless power transmission is possible even if there is some variation in the position, attitude, etc. of the relay 12 . Of course, if impedance matching is achieved between the transmitting antenna 10 and the receiving antenna 11, h may be less than 5 mm, and the inner wall surface of the housing 13 and the relay 12 may be in contact with each other.

In addition, although the housing 13 is made of a conductor in the first embodiment, it may be partially or wholly made of an insulator. For example, it may be made of a resin material. Further, the shape of the housing 13 does not have to be a rectangular parallelepiped, and any shape may be used as long as it has an internal space capable of containing the transmitting antenna 10, the receiving antenna 11, and the relay 12.

Further, a partition wall 14 made of a conductor may be provided in the housing 13 to separate the internal space between the side where the transmitting antenna 10 is arranged and the side where the receiving antenna 11 is arranged. In such a case, a through hole 15 is provided in the partition 14, and the relay 12 is passed through the through hole 15 so that the relay 12 is positioned in both the internal space on the transmitting side and the internal space on the receiving side. (See Figure 4). Even if the transmitting side and the receiving side are separated, power can be transmitted from the transmitting antenna 10 to the receiving antenna 11 via the relay 12 . The relay 12 may be in contact with the partition wall 14 or the side surface of the through hole 15 . Even if they are in contact with each other, it suffices if impedance matching is achieved between the transmitting antenna 10 and the receiving antenna 11 .

Further, an object 16 made of a conductor other than the transmitting antenna 10, the receiving antenna 11, and the relay 12 may be enclosed in the housing 13 (see FIG. 5). The shape and size of the object 16 can be arbitrarily set within a range in which the object 16 can be contained in the housing 13 and the distance between the object 16 and the intermediary body 12 can be sufficiently separated. If the distance between the object 16 and the relay 12 is sufficiently long, the fluctuation of the characteristic impedance Z0 of the relay 12 is small. It is preferable that the distance between the object 16 and the relay 12 is 5 mm or more.

Note that even when the object 16 and the relay 12 are not sufficiently separated or when the object 16 and the relay 12 are in contact with each other, the capacitance and inductance of the transmitting antenna 10 and the receiving antenna 11 are adjusted to obtain the impedance. By matching, highly efficient power transmission is possible.

As described above, in the wireless power transmission system of the first embodiment, since the relay 12 is electromagnetically coupled with the transmission antenna 10 and the reception antenna 11, highly efficient power transmission is possible. In addition, since the wireless power transmission system of the first embodiment does not use the formation of a resonance mode inside the housing 13 as in the conventional case, it is possible to transmit power at a desired frequency without being affected by the shape and size of the housing 13. can do.

Next, various simulation results regarding the wireless power transmission system of Example 1 will be described with reference to the drawings.

FIG. 6 is a simplified model of the wireless power transmission system of Example 1, and FIG. 7 is its equivalent circuit. As shown in FIGS. 6 and 7, the housing 13 is simplified by a flat housing wall, a transmitting antenna 10 and a receiving antenna 11 are provided on the housing wall, and a linear antenna is provided on the transmitting antenna 10 and the receiving antenna 11. A model provided with a relay 12 was used. It is assumed that the transmitting antenna 10 and the receiving antenna 11 are coupled to the relay body 12 by a stray capacitance C′, and the transmitting antenna 10 and the receiving antenna 11 have an inductance of L and a capacitance of C, and are composed of the relay body 12 and the housing wall. Z0 is the characteristic impedance of the distributed constant circuit. Also, Z1 is the impedance when the input side of the transmitting antenna 10 is viewed from the input port 1, and Z2 is the impedance when the output side is viewed from the output port 2 of the receiving antenna 11. FIG.

FIG. 8 is a graph showing the result of calculation of the transmission efficiency |S21| by simulation in the equivalent circuit of FIG. Here, the power transmission frequency is set to 3.5 GHz, C = 0.1 pF, L = 15 nH, C' = 0.07 pF, the length of the relay 12 is λ (about 70 mm in terms of 3.5 GHz), Z1 = Z2=50Ω. Also, Z0 was changed to 50, 200, and 400Ω. FIG. 8(a) is Z0=50Ω, FIG. 8(b) is Z0=200Ω, and FIG. 8(c) is Z0=400Ω. As a result of FIG. 8, it was found that at 3.5 GHz, high efficiency can be maintained even when Z0 is changed in the range of 200 to 400Ω.

FIG. 9 is a graph showing the result of calculating the transmission efficiency |S21| by simulation in the equivalent circuit of FIG. Z0 is set to 300Ω, and the length of the relay 12 is changed to 0.5λ, λ, and 2λ (approximately 35, 70, and 140 mm in terms of 3.5 GHz). Fig. 9(a) shows the case where the length of the relay 12 is 0.5λ, Fig. 9(b) shows λ, and Fig. 9(c) shows the case where the length is 2λ. Other settings are the same as in FIG. As shown in FIG. 9, the resonance frequency is changed by changing the length of the relay 12, but regardless of the length of the relay 12, the power transmission frequency of 3.5 GHz at which impedance matching is performed It was found that high efficiency can be maintained. This is because the characteristic impedance Z0 of the relay 12 does not change regardless of the length of the relay 12 . Moreover, from the results of FIGS. 8 and 9, it was found that highly efficient power transmission is possible even if there is some variation in the position, attitude, etc. of the relay 12 .

Next, we analyzed a more concrete model of the wireless power transmission system. FIG. 10 is an analytical model of a wireless power transmission system of a comparative example. The wireless power transmission system of the comparative example is obtained by omitting the relay 12 from the wireless power transmission system of the first embodiment. As shown in FIG. 10, the housing 13 is a rectangular parallelepiped box-shaped conductor of 43×18×152 mm. The transmitting antenna 10 and the receiving antenna 11 were L-shaped monopole antennas with a length of 19 mm, and the distance between the transmitting antenna 10 and the receiving antenna 11 was 140 mm. The line direction of the transmitting antenna 10 and the receiving antenna 11 is the longitudinal direction of the housing 13 .

FIG. 11 is a graph showing the result of calculating the transmission efficiency |S21| of the wireless power transmission system of the comparative example shown in FIG. 10 by simulation. As shown in FIG. 11, when the repeater 12 was not provided, the transmission efficiency |S21| was low and was -90 dB at 3.5 GHz.

Next, as shown in FIG. 12, an analysis model of the wireless power transmission system of Example 1 is obtained by adding the relay 12 to the analysis model of FIG. The relay 12 is a straight conductor and has lengths of 40, 80 and 140 mm. Impedance matching was performed at 3.5 GHz.

FIG. 13 is a graph showing the result of calculating the transmission efficiency |S21| of the wireless power transmission system of Example 1 shown in FIG. 12 by simulation. Fig. 13(a) shows a case where the length of the relay 12 is 40 mm, Fig. 13(b) shows a case where the length is 80 mm, and Fig. 13(c) shows a case where the length is 140 mm. As shown in FIG. 13 , the longer the relay 12 is, the more the resonance frequency changes, and the longer the relay 12 is, the more the resonance peak increases. Efficiency |S21| was high. As a result, it was found that the provision of the relay 12 enabled highly efficient power transmission. Moreover, since the characteristic impedance Z0 of the relay 12 does not depend on the line length, the transmission efficiency |S21| at 3.5 GHz was high even when the line length was changed.

Next, as shown in FIG. 14, in the analytical model of FIG. The size of the object 16 was 20×14×100 mm. Also, the distance between the object 16 and the relay 12 was set to 7.5 mm. The transmission efficiency |S21| was calculated for such a model. FIG. 15 is a graph showing the results of calculating the transmission efficiency |S21|. As shown in FIG. 15, it had a high transmission efficiency |S21| at the transmission frequency of 3.5 GHz. As a result, if the object 16 and the relay 12 are sufficiently separated from each other, even if the object 16 is inserted inside the housing 13, the characteristic impedance Z0 of the relay 12 fluctuates little, and highly efficient power transmission is possible. I understood it.

Next, as shown in FIG. 16, in the analysis model of FIG. 10, a partition wall 14 is provided at an intermediate position inside the housing 13 to separate the internal space into two, one on the transmitting antenna 10 side and the other on the receiving antenna 11 side. A through hole 15 was provided in the partition wall 14 to allow the relay 12 to pass therethrough, and the relay 12 was arranged from the internal space on the transmitting side to the internal space on the receiving side. The transmission efficiency |S21| was calculated for such a model. FIG. 17 is a graph showing the results of calculating the transmission efficiency |S21|. As shown in FIG. 17, it was found to have a high transmission efficiency |S21| at the transmission frequency of 3.5 GHz. As a result, it was found that highly efficient wireless power transmission is possible via the relay 12 even when the internal space is separated between the transmitting side and the receiving side by the partition wall 14 .

Next, as shown in FIG. 18, in the analysis model of FIG. 10, the relay body 12 was changed from one linear conductor to two linear conductors. The two conductors had a length of 80 mm and were arranged parallel to each other with a space therebetween. The transmission efficiency |S21| was calculated for such a model. FIG. 19 is a graph showing the results of calculating the transmission efficiency |S21|. As shown in FIG. 19, it was found to have a high transmission efficiency |S21| at the transmission frequency of 3.5 GHz. As a result, it was found that even if the relay 12 is separated into two pieces, if the relays 12 are electromagnetically coupled via the stray capacitance, wireless power transmission is possible via the relay 12 .

FIG. 21 is a diagram showing the configuration of the wireless power transmission system of the second embodiment. In the wireless power transmission system of the second embodiment, the transmission antenna 10, the reception antenna 11, and the relay 12 are helical in the wireless power transmission system of FIG. However, the central portion of the intermediate body 12 (the portion to be passed through the through hole 15 of the partition wall 14) remains straight so that it can be passed through even if the diameter of the through hole 15 is small. If the diameter of the through hole 15 is sufficiently large, the entire relay 12 may be helical.

By making the transmitting antenna 10, the receiving antenna 11, and the relay 12 helical as in the second embodiment, they can be made smaller. Therefore, it is possible to reduce the volume of the internal space of housing 13 being squeezed by transmitting antenna 10 , receiving antenna 11 and relay 12 .

(Modification)
In the wireless power transmission system of the present invention, the power transmission frequency can be set to any frequency, but a power transmission frequency of 1 GHz or higher is particularly suitable. Although it was difficult to efficiently transmit power wirelessly at 1 GHz or higher with the conventional method of forming a resonance mode in the housing, the present invention enables highly efficient power transmission even at such a frequency.

In the first and second embodiments, one transmitting antenna 10 and one receiving antenna 11 are used for one-to-one power transmission.

INDUSTRIAL APPLICABILITY The wireless power transmission system of the present invention is suitable for wireless power supply to a sensor or the like inside the housing of an electronic device. FIG. 20 shows an example in which the wireless power transmission system of the present invention is applied to electronic equipment. FIG. 20(a) shows various parts to be put into the housing 13 of the electronic device, and FIG.

As shown in FIG. 20, the receiving antenna 11 is provided on the substrate 100 . This substrate 100 is arranged on the bottom surface inside the housing 13 . Next, a plurality of objects 16 made of conductors are arranged inside the housing 13 . Next, the relay 12A made of a U-shaped linear conductor is attached to the side surface of the housing 13, and the relay 12A is arranged in the vicinity of the receiving antenna 11. FIG. Next, the partition 14 is inserted into the housing 13 to separate the space below the partition 14 on the receiving antenna 11 side from the space above the partition 14 . A through hole 15 is provided in the partition 14, and a relay 12B made of a U-shaped linear conductor is passed through the through hole 15. As shown in FIG. As a result, the relay 12B is arranged in the vicinity of the relay 12A. Furthermore, the substrate 101 is arranged on the partition wall 14 . A transmitting antenna 10 is provided on the substrate. Thereby, the transmitting antenna 10 is arranged in the vicinity of the relay 12B. After that, the housing 13 is sealed. Here, impedance matching is performed so that the transmitting antenna 10 and the relay 12B are electromagnetically coupled, the relay 12B and the relay 12A are electromagnetically coupled, and the relay 12A and the receiving antenna 11 are electromagnetically coupled. conduct.

As described above, power can be transmitted from the transmitting antenna 10 to the receiving antenna 11 via the relays 12A and 12B even in the electronic device housing 13 having a complicated internal space in which a plurality of objects 16 and partition walls 14 exist. can be done. In addition, since the relay 12 is separated into two relays 12A and 12B, power can be easily relayed even if the internal space of the housing 13 is complicated. It can be simplified.

INDUSTRIAL APPLICABILITY The present invention can be used for wireless power transmission within a housing of an electronic device or the like.

10: Transmitting Antenna 11: Receiving Antenna 12: Relay 13: Housing 14: Partition Wall 15: Through Hole 16: Object

Claims (5)

a transmission antenna for transmitting electromagnetic waves of a predetermined frequency;
a receiving antenna for receiving electromagnetic waves from the transmitting antenna;
a relay that relays power from the transmitting antenna to the receiving antenna;
a housing having an internal space in which the transmitting antenna, the receiving antenna, and the relay are arranged;
has
The transmitting antenna and the relay, and the relay and the receiving antenna are electromagnetically coupled,
The relay and the housing form a distributed constant circuit, and the relay propagates and relays an electromagnetic wave.
A wireless power transmission system characterized by: The housing has a partition that separates the internal space into a side on which the transmitting antenna is arranged and a side on which the receiving antenna is arranged,
The partition has a through hole penetrating through the partition,
The relay is arranged through the through hole from the internal space on the side where the transmitting antenna is arranged to the internal space on the side where the receiving antenna is arranged,
The wireless power transmission system according to claim 1, characterized in that: 3. The wireless power transmission system according to claim 1, wherein the distance between the inner wall surface of the housing and the relay is 5 mm or more. 4. The wireless power transmission system according to any one of claims 1 to 3, wherein the relay is separated into two or more parts. An object made of a conductor is arranged in the internal space of the housing,
5. The wireless power transmission system according to any one of claims 1 to 4, wherein the distance between the object and the relay is 5 mm or more.

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