JP2014017916A - Radio power transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio power transmitter capable of significantly reducing deterioration in transmission efficiency even when changing a rotation angle of a direction of a reception side resonator.SOLUTION: A radio power transmitter 1 comprises: two power transmission side resonators 2x and 2y; a reception side resonator 3 which is smaller than the power transmission side resonators 2x and 2y and is movable; and a high frequency power supply 4. One power transmission side resonator 2x is excited by an output signal of the high frequency power supply 4, and another power transmission side resonator 2y is excited not by the high frequency power supply but by an electromagnetic field generated by the one power transmission side resonator 2x, which generates at least two natural resonance frequencies slightly differing from each other. Power is transmitted to the reception side resonator 3 by making the reception side resonator 3 resonate at the at least two natural resonance frequencies.

Description

  The present invention relates to a resonant coupling type wireless power transmission apparatus that performs wireless power transmission using non-radiated electromagnetic field coupling.

  Wireless power transmission includes magnetic induction method, resonant coupling method, radiated electromagnetic wave method, etc. Among them, the resonant coupling method performed using non-radiated electromagnetic field coupling is highly efficient and is about several meters in length. In recent years, it has attracted a great deal of attention because of its ability to transmit distance power.

  FIG. 8 is a diagram showing a basic configuration of a resonance type wireless power transmission apparatus. In the wireless power transmission device 101, the power supplied from the high frequency power source 104 is supplied to the power transmission side resonator 102 via the impedance matching means 105 such as a coupling loop, and is electromagnetically coupled with a coupling coefficient k corresponding to the transmission distance d. Is transmitted to the power receiving side resonator 103. Thereafter, electric power is supplied to the load 107 through the impedance matching means 106 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. For this reason, a resonator structure with a high unloaded Q value and a configuration in which the coupling coefficient k increases far away have been studied in detail. The coupling coefficient k in this case is a function that depends on the relative position and orientation between the power transmitting and receiving resonators.

  Therefore, despite the fact that the transmission line has been eliminated for wireless power transmission, the conventional wireless power transmission device has a relatively limited relative position and orientation between power transmitting and receiving resonators suitable for power transmission. In addition, the transmission efficiency tends to be greatly deteriorated when it is away from it.

  For this measure, wireless power transmission apparatuses have been proposed in which a plurality of power transmission side resonators are provided to reduce deterioration in transmission efficiency due to a change in the position or orientation of the power reception side resonator. Patent Document 1 is a wireless power transmission device that charges a vehicle, and a power transmission side resonator having high transmission efficiency among a plurality of power transmission side resonators provided in parallel according to the position of the power reception side resonator according to the stop position of the vehicle. Techniques for selecting are described. In Non-Patent Document 1, as shown in FIG. 9, the feeding phase difference between two power transmitting resonators 102 and 102 provided in parallel according to the direction of the power receiving resonator 103 is reversed by the controller 104 ′ from the same phase. A wireless power transmission device 101 ′ for switching to a phase is described. Reference numeral 105 denotes a transmission-side impedance matching means, reference numeral 106 denotes a reception-side impedance matching means, and reference numeral 107 denotes a load. More specifically, when the rotation angle θ in the direction of the power receiving side resonator 103 is −60 ° to 60 °, the phase is in phase, and when it is −90 ° to −60 ° and 60 ° to 90 °, the phase is reversed.

JP 2010-183812 A

Kenichiro Ogawa, 5 others, "Measurement of efficiency of power transmission coil array in magnetic resonance type wireless power transmission", 2010 IEICE Communication Society Conference, IEICE, 2010, B-1-2, p. 2

  However, the change in the direction of the power-receiving-side resonator cannot be handled by the technique described in Patent Document 1. Further, in the technique described in Non-Patent Document 1, only experimental values are disclosed in which the rotation angle of the direction of the power receiving resonator is changed at a specific position. Therefore, in order to fully enjoy the merit of wireless power transmission, there is a lot of room for development particularly for measures for reducing deterioration in transmission efficiency due to a change in the direction of the power-receiving-side resonator.

  The present invention has been made in view of such a reason, and an object of the present invention is to provide a wireless power transmission device that can significantly reduce deterioration in transmission efficiency even when the rotation angle of the direction of the power receiving resonator is changed. There is.

  To achieve the above object, the wireless power transmission device according to claim 1 includes a plurality of power transmission side resonators, at least one power reception side resonator that is smaller and movable than the power transmission side resonators, and at least And at least two of the power transmission side resonators are arranged so as to be substantially orthogonal to each other and electromagnetically coupled to each other, and two power transmission side resonances arranged so as to be substantially orthogonal to each other The power transmission side resonator is excited by the output signal of one high frequency power source, and the other power transmission side resonator is an electromagnetic field generated by one power transmission side resonator without depending on the high frequency power source. By being excited, at least two natural resonance frequencies having slightly different frequencies are generated, and the power receiving resonator is resonated with the at least two natural resonance frequencies, thereby supplying power to the power receiving resonator. Feature to transmit To.

  The wireless power transmission device according to claim 2 is the wireless power transmission device according to claim 1, wherein a frequency of an output signal of the one high-frequency power supply matches the at least two natural resonance frequencies. It can be switched.

  The wireless power transmission device according to claim 3 is the wireless power transmission device according to claim 2, wherein the at least two natural resonance frequencies are natural resonance frequencies corresponding to an odd mode and an even mode. The frequency of the output signal of each high frequency power source is switched so as to match the natural resonance frequency corresponding to the odd mode and the natural resonance frequency corresponding to the even mode.

  A wireless power transmission device according to a fourth aspect of the present invention is the wireless power transmission device according to any one of the first to third aspects, wherein the wireless power transmission device is substantially orthogonal to the two power transmission side resonators arranged so as to be substantially orthogonal to each other. Further, another power transmission side resonator is further arranged, and the another power transmission side resonator is excited by another excitation signal uncorrelated with the output signal of the one high frequency power source. .

  The wireless power transmission device according to claim 5 is the wireless power transmission device according to claim 4, wherein the another excitation signal temporally changes a phase difference with an output signal of the one high-frequency power source. It is characterized by.

  The wireless power transmission device according to claim 6 is the wireless power transmission device according to claim 4, wherein the other excitation signal has a frequency slightly different from an output signal of the one high-frequency power source. Features.

  According to the present invention, one power transmission side resonator of power transmission side resonators arranged so as to be substantially orthogonal to each other is excited by an output signal of one high frequency power source, and the other power transmission side resonator is driven by a high frequency power source. A wireless power transmission device capable of significantly reducing deterioration in transmission efficiency even when the rotational angle of the power receiving side resonator is changed by exciting with an electromagnetic field generated by one power transmitting side resonator be able to.

1 is a perspective view schematically showing a configuration of a wireless power transmission device according to an embodiment of the present invention. It is a top view which shows typically the structure of a wireless power transmission apparatus same as the above. It is explanatory drawing for demonstrating the natural resonance mode of a wireless power transmission apparatus same as the above. It is a top view explaining electric power reception in case the power transmission side resonator is one. It is a characteristic view which shows the characteristic of electric power reception in case the power transmission side resonator is one. It is a top view which shows the magnetic field vector of a wireless power transmission apparatus same as the above. It is a perspective view which shows typically the modification of a structure of the 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. It is a top view which shows typically another structure of the conventional wireless power transmission apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. A wireless power transmission device 1 according to an embodiment of the present invention is of a resonant coupling type, and includes two power transmission side resonators 2x and 2y as shown in FIGS. They are arranged so as to be substantially orthogonal to each other. In addition, the power receiving side resonator 3 is smaller and movable than the two power transmitting side resonators 2x and 2y. Moreover, it has one high frequency power supply 4 that outputs an output signal of high frequency AC power, and only one power transmission side resonator 2x of the two power transmission side resonators 2x and 2y is excited by the output signal. ing. The other power transmission side resonator 2y is excited by an electromagnetic field (non-radiated electromagnetic field) generated by the power transmission side resonator 2x as described later. Power is transmitted to the power receiving side resonator 3 from the two power transmitting side resonators 2x and 2y according to the transmission distances d and d '.

  The shapes of the power transmission side resonators 2x and 2y are not limited. For example, the power transmission side resonators 2x and 2y can be coils formed by winding an electric conductor in a flat and spiral shape.

  Specifically, the high-frequency power source 4 excites the power-transmission-side resonator 2x via the coupling loop 5 that performs impedance matching. The high-frequency power source 4 outputs the output signal to the coupling loop 5, and the coupling loop 5 is electromagnetically coupled to the power transmission side resonator 2x. In addition, about the power transmission side resonator 2y, the coupling loop for the excitation is not provided. The coupling loop 5 can be replaced with other known impedance matching means.

  The shape of the power receiving side resonator 3 is not limited. For example, the power receiving side resonator 3 can be a coil formed by winding an electric conductor in a planar and spiral shape. Further, in order to reduce the diameter, the electric conducting wire can be wound more densely than the coils of the power transmitting resonators 2x and 2y, or a capacitor can be connected between both ends of the coil.

  Specifically, the power receiving side resonator 3 supplies the received power to the load 7 through the coupling loop 6 that performs impedance matching. The coupling loop 6 is electromagnetically coupled to the power receiving side resonator 3. The load 7 is a circuit for exhibiting a required function of a device such as a communication terminal. The coupling loop 6 can be replaced by other known impedance matching means. In FIG. 2, the coupling loop 6 and the load 7 are omitted.

  With this configuration, in the wireless power transmission device 1, the power transmission side resonator 2 x excited by the high frequency power source 4 generates a non-radiated electromagnetic field in the surrounding area. Then, the power transmission side resonator 2y is excited by being coupled to the non-radiated electromagnetic field generated by the power transmission side resonator 2x. The power transmission side resonator 2y also generates a non-radiating electromagnetic field in the surrounding area. Near the two power transmission resonators 2x and 2y (for example, near the intersection of the center lines of the two power transmission resonators 2x and 2y), the non-radiated electromagnetic field from the power transmission resonator 2x and the power transmission resonator The electromagnetic field distribution of the non-radiated electromagnetic field obtained by combining the non-radiated electromagnetic field from 2y is obtained. Note that the power transmission side resonator 2y is excited by being coupled to the non-radiated electromagnetic field generated by the power transmission side resonator 2x without depending on the high-frequency power source, and thus is wasted due to interference with the power transmission side resonator 2x. No power is consumed.

  As shown in FIG. 3, such an electromagnetic field distribution is an electromagnetic field distribution having a plurality of natural resonance modes (in this figure, two natural resonance modes), and the frequency corresponding to each of the natural resonance modes is slightly increased. A plurality of different natural resonance frequencies are generated. The plurality of natural resonance modes are usually an odd mode in which the power transmission side resonator 2x and the power transmission side resonator 2y resonate in opposite phases if the power transmission side resonator 2x and the power transmission side resonator 2y have the same size and shape. This is an even mode that resonates in the same phase, and two natural resonance frequencies slightly different in frequency are generated as shown in FIG. The control of the plurality of natural resonance modes will be described in detail later. FIG. 3 shows a case where the power transmission side resonator 2y is coupled to the power transmission side resonator 2x having a natural resonance frequency of about 25.0 MHz when it is a single unit (when the power transmission side resonator 2y is not coupled). The two natural resonance frequencies are about 24.9 MHz and about 25.1 MHz. The vertical axis is the S parameter S21.

  The power receiving side resonator 3 has a shape, a size, or a structure that can resonate at any of two natural resonance frequencies in which electromagnetic field distribution is generated from the power transmitting side resonator 2x and the power transmitting side resonator 2y. If the power transmission side resonators 2x and 2y are arranged in a region near the power transmission side resonators 2x and 2y, coupling based on resonance is generated by the non-radiated electromagnetic field, and power is transmitted. The electric power transmitted to the power receiving side resonator 3 is supplied to the load 7.

  Next, the power transmission efficiency between the two power transmitting resonators 2x and 2y and the power receiving resonator 3 will be described. The coupling between the power transmission resonators 2x and 2y and the power reception resonator 3 is performed by both the electric field and the magnetic field, and the electric field depends on the winding direction of the coil of the power reception resonator 3 facing the power transmission resonators 2x and 2y. And the sum or difference of the two coupling degrees of the magnetic field. However, in general, electric field coupling is rapidly attenuated as the distance between the resonators increases, so that power transmission is mainly performed by magnetic field coupling. Therefore, the following description will focus on magnetic field coupling.

  First, for reference, the power transmission side resonator 2y is omitted and only the power transmission side resonator 2x is used. As shown in FIG. 4, the coupling when the power reception side resonator 3 is inclined with respect to the power transmission side resonator 2x is shown. Explain the change. The magnetic field vector is generated vertically from the power transmission side resonator 2x. FIG. 5 shows how the coupling coefficient k changes with respect to the rotation angle θ in the direction of the power-receiving-side resonator 3. The coupling coefficient k is normalized and shown. Curves a, b, and c are actually measured values when the distance d between the power transmission side resonator 2x and the power reception side resonator 3 is 7 cm, 8 cm, and 9 cm, respectively. The diameter of the power transmission side resonator 2x is 23 cm, and the diameter of the power reception side resonator 3 is 3.1 cm.

  It can be seen that the coupling coefficient k is maximum when facing the opposite direction (when the rotation angle θ in the direction of the power-receiving-side resonator 3 is 0 °), normalized by the value at that time, and approximated by a cosine curve. This indicates that the power receiving side resonator 3 receives the magnetic field vector emitted from the power transmitting side resonator 2x and distributed in parallel according to the projected area. Therefore, when the power receiving side resonator 3 has a large inclination, that is, the rotational angle θ of the direction, and the power receiving side resonator 3 is parallel to the magnetic field vector (the rotational angle θ of the direction of the power receiving side resonator 3 is 90 °), power is received. You can see that it becomes difficult.

  Next, a magnetic field vector in the wireless power transmission device 1 provided with the two power transmission side resonators 2x and 2y will be described. 6A shows an odd mode of the two resonance modes, and FIG. 6B shows a magnetic field vector when the power transmission side resonator 2x is excited at a frequency that matches the natural resonance frequency of the even mode. . When attention is paid to the vicinity of the intersection of the center lines of the two power transmission side resonators 2x and 2y in the figure (indicated by a broken line frame), the magnetic field vector is diagonally lower right in the odd mode of (a) and the even mode of (b). In FIG. 5, the direction is obliquely lower left, and it can be seen that the direction of the magnetic field vector is shifted by approximately 90 degrees between the odd mode and the even mode.

  Thus, if the direction of the magnetic field vector is deviated between the odd mode and the even mode, the rotation angle θ of the direction of the power-receiving-side resonator 3 changes and it is difficult to receive power from either the odd mode or the even mode. However, in other modes of the odd mode and the even mode, the power receiving side resonator 3 can easily receive power. Therefore, the wireless power transmission device 1 generates a mode suitable for the rotation angle θ in the direction of the power-receiving-side resonator 3 so that the change in the coupling coefficient k is very small even when the rotation angle θ is changed, and the transmission efficiency is increased. Therefore, the power receiving side resonator 3 can receive power satisfactorily.

  In order to generate a mode suitable for the rotation angle θ in the direction of the power-side resonator 3 between the odd mode and the even mode, the high-frequency power source 4 has a natural resonance whose output signal frequency (excitation frequency) corresponds to the odd mode. The frequency is switched to match the natural resonance frequency corresponding to the even mode. For example, the direction of the power-receiving-side resonator 3 is detected, and either the natural resonance frequency corresponding to the odd mode or the natural resonance frequency corresponding to the even mode is matched according to the rotation angle θ of the direction of the power-receiving side resonator 3. To be able to switch. Alternatively, regardless of the direction of the power-receiving-side resonator 3, it is possible to switch so that the natural resonance frequency corresponding to the odd mode and the natural resonance frequency corresponding to the even mode are alternately matched every predetermined time. is there.

  In addition, when the power transmission side resonator 2x and the power transmission side resonator 2y in the wireless power transmission device 1 have different shapes, sizes, or structures, the natural resonance mode generated by their electromagnetic coupling is an odd mode. There may be a mode other than the even mode, or more than two modes. Even in such a case, at least two natural resonance modes are controlled by switching so that the frequency of the output signal of the high-frequency power supply 4 matches the natural resonance frequency. In the same manner as described above, even if the direction of the magnetic field vector is shifted and the rotation angle θ of the direction of the power receiving side resonator 3 is changed, the deterioration of transmission efficiency can be greatly reduced, and the power receiving side resonator 3 can receive power well. It is possible to make it possible.

  Next, a wireless power transmission device 1 'obtained by modifying the wireless power transmission device 1 will be described. As shown in FIG. 7, in addition to the configuration of the wireless power transmission device 1, this wireless power transmission device 1 ′ includes another power transmission side resonator so as to be substantially orthogonal to the power transmission side resonator 2x and the power transmission side resonator 2y. 2z is further arranged. The power transmission side resonator 2z is excited by another excitation signal uncorrelated with the output signal of the high frequency power supply 4. As this other excitation signal, the output signal of the high-frequency power supply 4 'is used. The coupling loop 5z is electromagnetically coupled to the power transmission side resonator 2z, and the output signal of the high frequency power source 4 'is input to the coupling loop 5z. The coupling loop 5z can be replaced with other known impedance matching means.

  More specifically, whether the output signal (ie, another excitation signal) of the high frequency power supply 4 ′ is obtained by changing the phase difference with the output signal of the high frequency power supply 4 so as to be uncorrelated with the output signal of the high frequency power supply 4. Alternatively, the output signal of the high frequency power source 4 and the frequency are slightly different. In the case where the output signal of the high frequency power source 4 ′ is obtained by temporally changing the phase difference from the output signal of the high frequency power source 4, the high frequency power source 4 ′ generates a high frequency signal independently of the high frequency power source 4 or the high frequency power source. What is necessary is just to input the output signal of the high frequency power supply 4 to 4 ', and to change the phase temporally and to output it. When the output signal of the high frequency power supply 4 ′ is slightly different in frequency from the output signal of the frequency power supply 4, the high frequency power supply 4 ′ generates a high frequency signal independently of the high frequency power supply 4 and outputs the output signal as an AC power supply. What should I do?

  In such a wireless power transmission device 1 ′, similarly to the wireless power transmission device 1, the electromagnetic field distribution has an electromagnetic field distribution having a plurality of natural resonance modes in which the directions of the magnetic field vectors are deviated. A plurality of natural resonance frequencies corresponding to. In the electromagnetic field distribution in the wireless power transmission device 1 ′, the direction of the magnetic field vector further changes with time in a three-dimensional direction. Thereby, even when the power-receiving-side resonator 3 is changed in various directions in the three-dimensional direction, it is possible to reduce power transmission deterioration and to receive power satisfactorily.

  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 device 2x, 2y Power transmission side resonator 3 Power receiving side resonator 4 High frequency power supply 5 Transmission side coupling loop (impedance matching means)
6 Receiving side coupling loop (impedance matching means)
7 Load

Claims (6)

A plurality of power transmission side resonators;
At least one power receiving resonator that is smaller and movable than the power transmitting resonator;
And at least one high frequency power source,
At least two of the power transmission side resonators are arranged so as to be substantially orthogonal to each other and electromagnetically coupled,
The two power transmission side resonators arranged so as to be substantially orthogonal are:
One power transmission side resonator is excited by an output signal of one high frequency power source, and the other power transmission side resonator is excited by an electromagnetic field generated by one power transmission side resonator without depending on the high frequency power source. With that
Generating at least two natural resonance frequencies having slightly different frequencies, and resonating the power reception side resonator with the at least two natural resonance frequencies, thereby transmitting power to the power reception side resonator. Wireless power transmission device.   2. The wireless power transmission device according to claim 1, wherein the frequency of the output signal of the one high-frequency power source is switched to match the at least two natural resonance frequencies. The at least two natural resonance frequencies are natural resonance frequencies corresponding to an odd mode and an even mode,
The frequency of the output signal of the one high-frequency power source is switched so as to match a natural resonance frequency corresponding to the odd mode and a natural resonance frequency corresponding to the even mode. Wireless power transmission device. Further disposing another power transmission side resonator so as to be substantially orthogonal to the two power transmission side resonators disposed so as to be substantially orthogonal,
4. The radio according to claim 1, wherein the another power transmission side resonator is excited by another excitation signal that is uncorrelated with an output signal of the one high-frequency power source. Power transmission device.   The wireless power transmission device according to claim 4, wherein the another excitation signal temporally changes a phase difference with the output signal of the one high-frequency power source.   The wireless power transmission device according to claim 4, wherein the frequency of the another excitation signal is slightly different from that of the output signal of the one high-frequency power source.

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