JP2014003773A - Wireless power transmission apparatus and wireless power transmission method - Google Patents

Abstract

A wireless power transmission device capable of improving power transmission efficiency by improving a no-load Q value and increasing a possible power transmission distance.
A wireless power transmission device includes a power transmission side resonator and a power reception side resonator that are coupled to coupling terminals, and an electromagnetic field is transmitted from the power transmission side resonator to the power reception side resonator. The power transmission side resonator 2 and the power reception side resonator 3 are constituted by dielectric resonators, and shielding cases 21 and 31 having openings 21a and 31a through which electromagnetic fields partially pass. The coupling terminals 22 and 32 that are covered and coupled to each other are electrically connected to the outside of the shielding cases 21 and 31.
[Selection] Figure 1

Description

  The present invention relates to a wireless power transmission apparatus and a wireless power transmission system that wirelessly transmit power.

  Wireless power transmission includes a magnetic induction system, a resonant coupling system, and a radiated electromagnetic wave system. Among these, the resonance type coupling method using non-radiated electromagnetic field coupling is near-medium distance power transmission, but if there is a power receiving side, the power on the power transmission side is transmitted according to the coupling with it, High power transmission efficiency can be obtained. Therefore, the resonance type coupling method has attracted much attention in recent years.

  FIG. 6 is a diagram showing a basic configuration of a conventional resonance coupling type wireless power transmission apparatus. In the wireless power transmission apparatus 101, the power supplied from the outside (high-frequency AC power) is configured by winding a metal conductor in a coil shape via a coupling terminal 122 including impedance matching means 122a such as a coupling loop. It is supplied to the resonator 102. The power is electromagnetically coupled with a coupling coefficient k corresponding to the transmission distance s between the power transmitting resonator 102 and the power receiving resonator 103, and the power receiving side configured by winding a metal conductor in a coil shape. It is transmitted to the resonator 103. Thereafter, power is supplied to an external load through a coupling terminal 132 that also includes impedance matching means 132a such as a coupling loop. It is known that the maximum power transmission efficiency at this time is determined by the product of the coupling coefficient k between the resonators and the no-load Q value indicating the goodness of the resonators.

  In order to further improve the power transmission efficiency, various structures have been proposed conventionally. For example, in Patent Literature 1, another inductor or capacitor is disposed between the impedance matching unit and the power transmission side resonator or between the power reception side resonator and the impedance matching unit to increase the unloaded Q value. Is described. In Patent Document 2, the coiled metal conductors of the power transmission side resonator and the power reception side resonator are sandwiched and supported by two dielectrics having different dielectric constants, and the dielectric having the lower dielectric constant is supported. It is described that the power transmission efficiency is improved by making the body face the other resonator.

JP 2011-142724 A JP 2011-211792 A

  However, in the conventional wireless power transmission apparatus including Patent Document 1 and Patent Document 2, the power transmission side resonator and the power reception side resonator are configured by winding a metal conductor (usually a copper wire) in a coil shape, Because of the resistance loss determined by the electrical conductivity, there is a limit to the improvement of the no-load Q value. For example, the unloaded Q value in this case is on the order of several hundred to one thousand at most.

  In addition, since the coupling coefficient k in the resonance-type wireless power transmission device is determined by the interaction with the non-radiated electromagnetic field in the vicinity of the power receiving side resonator, the power transmission side resonator and the power receiving side resonator When the distance between them increases, it is inevitable that the distance decreases exponentially, and there is a limit to the distance at which power can be transmitted.

  The present invention has been made in view of the above-mentioned reasons, and an object of the present invention is to improve the power transmission efficiency by improving the no-load Q value and to increase the power transmission possible distance. An object of the present invention is to provide a wireless power transmission device that can be used.

  To achieve the above object, a wireless power transmission device according to claim 1 includes a power transmission side resonator and a power reception side resonator coupled to a coupling terminal, and the power reception side resonator is connected to the power reception side resonator. In the wireless power transmission apparatus for transmitting power using an electromagnetic field, at least one of the power transmission side resonator and the power reception side resonator is configured by a dielectric resonator, and an opening through which the electromagnetic field passes partially The coupling terminal which is covered and coupled by the shielding case having an electrical connection is electrically connected to the outside of the shielding case.

The wireless power transmission device according to claim 2 is the wireless power transmission device according to claim 1, wherein at least one of the power transmission side resonator and the power reception side resonator is a TE _01δ type dielectric resonator. It is characterized by being.

  The wireless power transmission device according to claim 3 is the wireless power transmission device according to claim 1 or 2, wherein at least one of the power transmission side resonator and the power reception side resonator is a ceramic dielectric resonance. It is a vessel.

  The wireless power transmission device according to claim 4 is the wireless power transmission device according to any one of claims 1 to 3, wherein the wireless power transmission device covers at least one of the power transmission side resonator and the power reception side resonator. The shielding case is a metal hexahedron, and the opening of the shielding case is formed by opening a part of one surface of the hexahedron.

  The wireless power transmission system according to claim 5 includes a power transmission side resonator and a power reception side resonator coupled to a coupling terminal, and uses the electromagnetic field to transmit power from the power transmission side resonator to the power reception side resonator. In the wireless power transmission system, at least one of the power transmission side resonator and the power reception side resonator is covered with a shielding case having an opening through which an electromagnetic field passes, and a coupling terminal to be coupled is shielded. In addition to being electrically connected to the outside of the case, power transmission is mainly performed by coupling of non-radiated electromagnetic fields at short and medium distances, and power transmission is performed mainly by coupling of radiated electromagnetic fields at long distances. Features.

  According to the wireless power transmission device of the present invention, since at least one of the power transmission side resonator and the power reception side resonator is composed of the dielectric resonator, the loss in the resonator is greatly reduced, and the no-load Q The value can be improved and the power transmission efficiency can be improved. In addition, when one of the above is a power transmission side resonator, it is covered with a shielding case having an opening in part, and by suppressing the radiated electromagnetic field to an appropriate amount and adding it to the non-radiated electromagnetic field, If one of the above is a power-receiving-side resonator, it is covered with a shielding case that has an opening in part, and it is easy to receive power even when the electromagnetic field is a radiated electromagnetic field, thereby increasing the distance at which power can be transmitted. can do. In addition, according to the wireless power transmission system of the present invention, optimum power transmission is mainly performed by combining non-radiated electromagnetic fields at short and middle distances, and to some extent by coupling of radiated electromagnetic fields mainly at long distances ( Since (at least the minimum) power transmission is performed, it is possible to increase the power transmission possible distance while maintaining the power transmission efficiency in the near and middle distances.

It is a perspective view which shows the structure of the wireless power transmission apparatus which concerns on embodiment of this invention. It is a perspective view which shows the power transmission side resonator (and power receiving side resonator) of the wireless power transmission apparatus same as the above. It is a characteristic view about the no-load Q value of the power transmission side resonator (and power receiving side resonator) of a wireless power transmission apparatus same as the above. It is a perspective view which shows the modification of a structure of the wireless power transmission apparatus same as the above. It is a characteristic view about the product of the no-load Q value and the coupling coefficient k of a wireless power transmission apparatus same as the above. It is a top view which shows typically the structure of the conventional wireless power transmission apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. As shown in FIG. 1, the wireless power transmission device 1 according to the embodiment of the present invention includes a power transmission side resonator 2 and a power reception side resonator 3, and generates an electromagnetic field from the power transmission side resonator 2 to the power reception side resonator 3. Used to transmit power. The power transmission side resonator 2 and the power reception side resonator 3 are respectively coupled to coupling terminals 22 and 32 described later. In the wireless power transmission device 1, the structure of the power transmission side resonator 2 and the structure in the vicinity thereof, and the structure of the power reception side resonator 3 and the structure in the vicinity thereof are substantially the same.

  The power transmission side resonator 2 is composed of a dielectric resonator. The dielectric resonator is not limited in material as long as the dielectric loss tangent (tan δ) is low, but is preferably made of ceramic. The lower the dielectric loss tangent, the higher the unloaded Q value. Ceramics having a very low dielectric loss tangent are already known.

The shape and size of the power transmission side resonator 2 correspond to the resonance frequency and resonance mode to be used. In this embodiment shown in FIG. 1, since it is a TE _01δ type dielectric resonator that uses the TE _01δ mode as a resonance mode, it has a cylindrical shape with a hollow in the vicinity of the central axis. The resonant frequency can be, for example, about 2.4 GHz. As shown in FIG. 2, the electric field distribution in this case is generated and distributed in the circumferential direction of the cylindrical electric field vector, and the magnetic field vector is orthogonal to the electric field vector inside and outside the power transmission resonator 2. Occur and distribute. In addition, the resonance frequency and resonance mode to be used, and the shape and size of the power transmission side resonator 2 according to the resonance frequency are not limited, and various ones can be applied according to desired characteristics. .

  The power transmission side resonator 2 is covered with a shielding case 21. The shielding case 21 has an opening 21a through which an electromagnetic field passes. The shielding case 21 covers almost the entire power transmission resonator 2 except for the opening 21a. Specifically, the shielding case 21 is a metal hexahedron (a rectangular parallelepiped or a cube), and the opening 21a is a part of one surface of the hexahedron that is opened. Further, the opening 21 a is provided at a position between the power transmission side resonator 2 and the power reception side resonator 3. In addition, in FIG. 1, the inside is drawn through the shielding case 21 (and a shielding case 31 described later).

  The shielding case 21 confines a radiated electromagnetic field (electromagnetic wave) in a portion other than the opening 21a. The power transmission side resonator 2 formed of a dielectric resonator generates a large amount of a radiated electromagnetic field together with a non-radiated electromagnetic field. Therefore, if the radiated electromagnetic field is not confined, electric power (energy) is radiated to the surroundings and no load Q This is because the value drops sharply.

  A non-radiated electromagnetic field and a radiated electromagnetic field pass through the opening 21 a of the shielding case 21. The shape and size of the opening 21a of the shielding case 21 are determined so as to suppress the radiation electromagnetic field to an appropriate amount. The amount of the electromagnetic field including the non-radiated electromagnetic field and the radiated electromagnetic field passing through the opening 21a depends on not only the size (area) of the opening 21a but also the shape thereof, as shown in the experimental results described later.

  The power transmission side resonator 2 is coupled to the coupling terminal 22 as described above, and the coupling terminal 22 is electrically connected to the outside of the shielding case 21. Specifically, the coupling terminal 22 is provided inside the shielding case 21 and is electrically connected to the coupling loop 22a coupled to the power transmission side resonator 2 by a magnetic field or the like, and the coupling loop 22a. External terminal portion 22b to which AC power) can be supplied.

  The power transmission side resonator 2 is held so as not to contact the shielding case 21 by a support base 23 having a lower dielectric constant. The support base 23 can be made of ceramic.

  Such a power transmission side resonator 2 is excited by external power via the coupling terminal 22 and generates a non-radiated electromagnetic field and a radiated electromagnetic field. The power transmission side resonator 2 can use a material having a very low dielectric loss tangent, such as ceramics, so that the loss can be remarkably reduced and the unloaded Q value can be improved (for example, on the order of several tens of thousands). Is possible. As a result, power transmission efficiency can be improved.

  Further, the power transmission side resonator 2 can increase the distance in which power can be transmitted by adding an appropriate amount of the radiated electromagnetic field to the non-radiated electromagnetic field. When the power-receiving-side resonator 3 is located at a near / medium distance where the non-radiated electromagnetic field is strong, the power-receiving resonator 3 can be coupled to the non-radiated electromagnetic field mainly to perform optimal (high power transmission efficiency) power transmission. When the power-receiving-side resonator 3 is located at a long distance where the non-radiated electromagnetic field is weak, it is mainly coupled to the radiated electromagnetic field propagating there, so that a certain amount (at least minimum) of power transmission is possible. Become. As a result, the possible distance for power transmission can be increased.

  Next, the power receiving side resonator 3 will be described. As described above, the power receiving side resonator 3 has substantially the same structure as that of the power transmitting side resonator 2, and the structure in the vicinity of the power receiving side resonator 3 is substantially the same as that in the vicinity of the power transmitting side resonator 2. Structure. That is, the power receiving side resonator 3 is configured by a dielectric resonator similar to the power transmitting side resonator 2, and is covered with a shielding case 31 similar to the shielding case 21. The shielding case 31 has an opening 31a similar to the opening 21a. The opening 31 a is provided at a position between the power transmission side resonator 2 and the power reception side resonator 3. The power receiving side resonator 3 is coupled to a coupling terminal 32 similar to the coupling terminal 22. The coupling terminal 32 includes a coupling loop 32a similar to the coupling loop 22a, and an external terminal portion 32b that is similar to the external terminal portion 22b and can output electric power (high-frequency AC power) to the outside. The power receiving side resonator 3 is held by a support base 33 similar to the support base 23.

  Power is transmitted to the power receiving side resonator 3 using a non-radiated electromagnetic field or a radiated electromagnetic field according to the distance from the power transmitting side resonator 2. The power transmitted to the power receiving resonator 3 is supplied to an external load via the coupling terminal 32. The load is a circuit for performing a required function of a device such as a communication terminal. Similarly to the power transmission side resonator 2, the power reception side resonator 3 can use a material having a very low dielectric loss tangent, such as ceramic, to significantly reduce the loss and improve the no-load Q value (for example, , In the order of tens of thousands). As a result, power transmission efficiency can be improved.

  Further, the power receiving side resonator 3 covers the dielectric resonator with a shielding case 31 having a part of the opening 31a, thereby making it easy to receive an appropriate amount even when the electromagnetic field for power transmission is a radiated electromagnetic field. As a result, the possible distance for power transmission can be increased.

Next, simulations and sample experiments by the inventors will be described. Both the power transmission side resonator 2 and the power reception side resonator 3 have a cylindrical shape hollowed out in the vicinity of the central axis. . Further, the TE _01δ mode having a resonance frequency of about 2.4 GHz is used as the resonance mode. Both the shielding case 21 and the shielding case 31 are metal hexahedrons, and the surfaces on which the openings 21a and 31a are formed face each other. One side where the openings 21a and 31a of the shielding cases 21 and 31 are formed has side lengths C and C ′ of 50 mm in the same direction as the cylindrical longitudinal direction of the power transmission side resonator 2 and the power reception side resonator 3. The side lengths D and D ′ in the direction perpendicular thereto are set to 80 mm. The lengths E and E ′ in the direction perpendicular to the one surface are 80 mm.

  FIG. 3 shows the aperture ratio (area ratio) of the opening 21a (or 31a) with respect to one surface of the shielding case 21 (or 31) with respect to the unloaded Q value (Qu) of the power transmitting resonator 2 (or the power receiving resonator 3). It is the result of the simulation experiment which shows the relationship with). A curve a (solid line) in FIG. 3 is shown in FIG. 1 in which one side of the shielding case 21 (or 31) that is 100% open is covered with two metal plates that are long in the horizontal direction and the upper end and lower end are closed. In this way, the opening 21a (or 31a) is formed. Curve b (dashed line) is a 100% open surface of the shielding case 21 (or 31), with two metal plates that are long in the vertical direction closed at the left and right ends, as shown in FIG. This is a case where the portion 21a (or 31a) is formed. In curve a, as the aperture ratio is decreased, the load Q value is increased and increased to about 20,000. From this, it can be seen that radiation is suppressed by shortening the length of the opening in the direction of the magnetic field vector, and a high unloaded Q value is obtained. On the other hand, the curve b shows no significant change.

  FIG. 5 is a result of simulation and sample experiment showing a change with respect to the distance s ′ between the shielding case 21 and the shielding case 31 with respect to the product (k · Qu) of the unloaded Q value (Qu) and the coupling coefficient k. The curve c (dashed line) and the curve d (solid line) in FIG. 5A each have an opening ratio of the opening 21a with respect to one surface of the shielding case 21 (and an opening ratio of the opening 31a with respect to one surface of the shielding case 31). This is a simulation and sample experiment. A curve e (dashed line) and a curve f (solid line) in FIG. 5B each close the upper end and the lower end with two metal plates that are long in the horizontal direction, and the opening 21 a with respect to one surface of the shielding case 21. This is a simulation and sample experiment when the aperture ratio (and the aperture ratio of the opening 31a with respect to one surface of the shielding case 31) is 64%.

  According to this experimental result, as the distance s ′ between the shielding case 21 and the shielding case 31 increases, the value of the product of the no-load Q value Qu and the coupling coefficient k decreases rapidly, but the distance s ′ is approximately 2 to 2. From 3cm, the slope of the decrease becomes gentle. This indicates that transmission by coupling of non-radiated electromagnetic fields is mainly performed when the distance s ′ is approximately 2 to 3 cm, whereas transmission by coupling of radiated electromagnetic fields is mainly performed at distances s ′ or more. As a result, it can be seen that the possible distance for power transmission can be increased.

  Note that such a wireless power transmission device 1 leaves only one of the power transmission side resonator 2 and the power reception side resonator 3 and the structure in the vicinity thereof, and the other resonator and the structure in the vicinity thereof in the other. It may be possible to replace it with a structure. When only the power transmission side resonator 2 is left, as described above, the no-load Q value of the power transmission side resonator 2 can be improved, and the power transmission efficiency can be improved. And the radiated electromagnetic field can be used to increase the distance in which power can be transmitted. Further, when only the power receiving resonator 3 is left, as described above, the no-load Q value of the power receiving resonator 3 can be improved, and the power transmission efficiency can be improved. Even when the electromagnetic field is a radiated electromagnetic field, it is possible to increase the distance in which power can be transmitted by making it easy to receive an appropriate amount.

  In addition, the wireless power transmission method by the wireless power transmission device 1 as described above, that is, optimal power transmission is mainly performed by combining non-radiated electromagnetic fields at short and medium distances, and radiation electromagnetic fields mainly at long distances. A method of performing a certain amount (at least minimum) of power transmission by coupling is a very useful method capable of increasing a power transmission possible distance while maintaining near-medium distance power transmission efficiency. In order to realize this method, dielectric resonators are used for the power transmission side resonator 2 and the power reception side resonator 3, but both power transmission by coupling of non-radiated electromagnetic fields and power transmission by coupling of radiated electromagnetic fields can be performed. For example, other resonators can be used in some cases. In any case, at least one of the power transmission side resonator 2 and the power reception side resonator 3 is covered by the shielding case 21 (or 31) and coupled to the coupling terminal 22 (or 32). preferable.

  The wireless power transmission device according to the embodiment of the present invention has been described above. However, the present invention is not limited to that described in the above-described embodiment, and various modifications within the scope of the matters described in the claims. Design changes are possible.

DESCRIPTION OF SYMBOLS 1 Wireless power transmission apparatus 2 Power transmission side resonator 21 Power transmission side shielding case 21a Power transmission side shielding case opening 22 Power transmission side coupling terminal 23 Power transmission side support base 3 Power reception side resonator 31 Power reception side shielding case 31a Power reception Side shielding case opening 32 receiving side coupling terminal 33 receiving side support base

Claims (5)

In a wireless power transmission device including a power transmission side resonator and a power reception side resonator coupled to a coupling terminal, and transmitting power from the power transmission side resonator to the power reception side resonator using an electromagnetic field.
At least one of the power transmission side resonator and the power reception side resonator is formed of a dielectric resonator, and is covered with a shielding case having an opening part through which an electromagnetic field passes, and a coupling terminal to be coupled is A wireless power transmission device, wherein the wireless power transmission device is electrically connected to the outside of the shielding case. 2. The wireless power transmission device according to claim 1, wherein at least one of the power transmission side resonator and the power reception side resonator is a TE _01δ type dielectric resonator.   The wireless power transmission device according to claim 1, wherein at least one of the power transmission side resonator and the power reception side resonator is a ceramic dielectric resonator.   The shielding case covering at least one of the power transmission side resonator and the power reception side resonator is a metal hexahedron, and the opening of the shielding case opens a part of one surface of the hexahedron. The wireless power transmission device according to claim 1, wherein the wireless power transmission device is a wireless power transmission device. In a wireless power transmission system including a power transmission side resonator and a power reception side resonator coupled to a coupling terminal, and transmitting power from the power transmission side resonator to the power reception side resonator using an electromagnetic field,
At least one of the power transmission side resonator and the power reception side resonator is covered with a shielding case having an opening through which an electromagnetic field passes, and a coupling terminal to be coupled is electrically connected to the outside of the shielding case. Wireless power transmission system characterized in that power is transmitted mainly by coupling of non-radiated electromagnetic fields at short and medium distances, and power transmission is performed mainly by coupling of radiated electromagnetic fields at long distances. .

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