JP2014195364A - Wireless power transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless power transmission system capable of enhancing a power transmission efficiency from a transmission-side apparatus to a power incoming-side apparatus by controlling the distribution of non-radiation electromagnetic fields from the transmission-side apparatus.SOLUTION: The wireless power transmission system 1, wirelessly transmitting electric power from a transmission-side apparatus 2 to a power incoming apparatus 3 using non-radiation electromagnetic fields, includes a dielectric substance or an inductor 4 of magnetic material which refracts non-radiation electromagnetic fields from the transmission-side apparatus 2, guides the electromagnetic fields toward the power incoming-side apparatus 3, or controls the distribution of non-radiation electromagnetic fields.

Description

  The present invention relates to a wireless power transmission system that performs wireless power transmission using a non-radiated electromagnetic field.

  Electromagnetic fields can be classified into radiated electromagnetic fields (electromagnetic waves) and non-radiated electromagnetic fields (evanescent fields). Wireless power transmission systems using non-radiated electromagnetic fields include a coupled resonator type, an electromagnetic induction type, and a capacitive coupling type.

  For example, the coupled resonator type wireless power transmission system is capable of highly efficient power transmission even if there is a certain distance from the power transmission side resonator of the power transmission side device to the power reception side resonator of the power reception side device. It has attracted a lot of attention. Various proposals have been made so far for the coupled resonator type wireless power transmission system. For example, Patent Document 1 discloses a basic configuration of a wireless power transmission system that performs power transmission by causing resonance in a resonator such as a loop conductor provided in both a transmission side device and a reception side device. Have been described. In Patent Literature 2, in a wireless power transmission system that performs power transmission by causing resonance between a coil of a power transmission side resonator and a coil of a power reception side resonator, a distance between the power transmission side resonator and the power reception side resonator is set. What detects and changes the resonance frequency based on it is described.

Special table 2009-501510 JP 2010-239769 A

  However, a non-radiated electromagnetic field is distributed around the power transmission side device in a space other than the specific space where the power reception side device is expected to exist. In spaces other than the specific space, energy loss occurs not a little, which contributes to a reduction in power transmission efficiency from the power transmission side device to the power reception side device. Conventionally proposed wireless power transmission systems including Patent Documents 1 and 2 do not consider controlling the distribution of non-radiated electromagnetic fields.

  The present invention has been made in view of such a reason, and its purpose is to increase the power transmission efficiency from the power transmission side device to the power reception side device by controlling the distribution of the non-radiated electromagnetic field from the power transmission side device. An object of the present invention is to provide a wireless power transmission system that can be used.

  To achieve the above object, the wireless power transmission system according to claim 1 is a wireless power transmission system that wirelessly transmits power from a power transmission side device to a power reception side device using a non-radiated electromagnetic field. An inductor is provided that refracts a non-radiated electromagnetic field from the device and guides it toward the power receiving device.

  A wireless power transmission system according to a second aspect is the wireless power transmission system according to the first aspect, wherein the inductor is made of a dielectric or magnetic material.

  The wireless power transmission system according to claim 3 is the wireless power transmission system according to claim 1 or 2, wherein the power transmission side device has a power transmission side resonator, and the power reception side device is a power reception side resonator. And transmitting power by causing resonance in the power transmission side resonator and the power reception side resonator.

  The wireless power transmission system according to claim 4 is the wireless power transmission system according to any one of claims 1 to 3, wherein the inductor extends in a direction of a central axis of the power transmission side device. It is characterized by that.

  The wireless power transmission system according to claim 5 is the wireless power transmission system according to any one of claims 1 to 3, wherein the inductor is bent.

  The wireless power transmission system according to a sixth aspect is the wireless power transmission system according to any one of the first to third aspects, wherein the inductor is a concave lens.

  The wireless power transmission system according to claim 7 is the wireless power transmission system according to any one of claims 1 to 6, wherein the inductor induces a non-radiated electromagnetic field using water. And

  The wireless power transmission system according to claim 8 is the wireless power transmission system according to claim 7, wherein the inductor is at least in a portion of the water facing the power transmission side device and the power reception side device. It is characterized by the addition of salt.

  The wireless power transmission system according to claim 9 is the wireless power transmission system according to claim 7 or 8, wherein the inductor is at least a portion of water facing the power transmission side device and the power reception side device. The salinity of is in the range of 0.1 wt% to 2 wt%.

  The wireless power transmission system according to claim 10 is the wireless power transmission system according to claim 7, wherein the inductor has a salinity of water in a portion facing at least the power transmission side device and the power reception side device. The concentration is in the range of 0.0001% by weight or less.

  The wireless power transmission system according to claim 11 is the wireless power transmission system according to any one of claims 1 to 6, wherein the inductor uses a ferrite to induce a non-radiated electromagnetic field. And

  According to the wireless power transmission system of the present invention, the inductor induces a non-radiated electromagnetic field, that is, controls the distribution of the non-radiated electromagnetic field, thereby increasing the power transmission efficiency from the power transmission side device to the power reception side device. Is possible.

1 is a block diagram of a configuration of a wireless power transmission system according to an embodiment of the present invention. The power transmission side apparatus of a radio | wireless power transmission system same as the above is shown, (a) is a typical perspective view, (b) is a schematic front view of the power transmission side resonator which comprises a power transmission side apparatus. The power receiving side apparatus of a wireless power transmission system same as the above is shown, (a) is a schematic perspective view, and (b) is a schematic front view of a power receiving side resonator constituting the power receiving side apparatus. 2A and 2B show the state of refraction at the boundary of different media, where FIG. 3A shows the state of an electric field at the boundary of a medium having a different dielectric constant, and FIG. It is the block diagram which showed typically the electric lines of force of the electric field of the non-radiation electromagnetic field of a wireless power transmission system same as the above. It is a block diagram which shows the structure of the experiment which used the inductor as the dielectric material in the wireless power transmission system same as the above. It is a characteristic figure of the coupling coefficient of the experiment which used the inductor as the dielectric material in the wireless power transmission system same as the above. It is a characteristic diagram of the transmittance | permeability of the experiment which used the inductor as the dielectric material in the wireless power transmission system same as the above. It is a characteristic figure of the unloaded Q value of the experiment which used the inductor as the dielectric material in the wireless power transmission system same as the above. It is a block diagram of other composition of a wireless power transmission system same as the above. It is a block diagram of the further another structure of a wireless power transmission system same as the above. It is a block diagram which shows the structure of the experiment which used the inductor as the magnetic body in the wireless power transmission system same as the above. It is a characteristic figure of the coupling coefficient of the experiment which used the inductor as the magnetic body in the wireless power transmission system same as the above.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The wireless power transmission system 1 according to the embodiment of the present invention is a coupled resonator type, and wirelessly transmits power from the power transmission side device 2 to the power reception side device 3 using a non-radiation electromagnetic field as shown in FIG. It is a system to do. What should be noted in the wireless power transmission system 1 is that it includes an inductor 4 that refracts a non-radiated electromagnetic field from the power transmission side device 2 and guides it toward the power reception side device 3.

  The power transmission side device 2 has a power transmission side resonator 21. As shown in FIG. 2, the power transmission side resonator 21 may be a coil formed by winding an electric conductor in a flat and spiral shape, that is, a spiral coil. The power transmission side resonator 21 is excited by a signal from the high frequency power source 23 through an impedance matching unit 22 that performs impedance matching. The impedance matching means 22 can typically use a coupling loop that electromagnetically couples to the power transmission side resonator 21, but may be in other forms (for example, one that is directly connected to the power transmission side resonator 21). Good. In FIG. 2, both ends of the spiral coil are open, but it is also possible to connect a capacitor between them in order to control the electric field.

  The power receiving side device 3 has a power receiving side resonator 31. The power receiving side resonator 31 can be a spiral coil as shown in FIG. The electric power transmitted to the power receiving resonator 31 is supplied to the load 33 via the impedance matching means 32 that performs impedance matching. The load 33 is a circuit for a required function of the device such as a charging circuit of a portable device in the communication field. The impedance matching unit 32 can typically use a coupling loop that electromagnetically couples to the power receiving resonator 31, but may be in another form (for example, directly connected to the power receiving resonator 31). Good. In addition, in each figure, although the power receiving side apparatus 3 is drawn with the substantially same magnitude | size as the power transmission side apparatus 2, the magnitude | size of the power receiving side apparatus 3 is not limited and may be smaller than the power transmission side apparatus 2. Many. In FIG. 3, both ends of the spiral coil are open, but it is also possible to connect a capacitor between them in order to control the electric field.

  The inductor 4 can be made of a dielectric material or a magnetic material. This inductor 4 utilizes refraction of a non-radiated electromagnetic field. As described above, the electromagnetic field can be classified into a radiated electromagnetic field and a non-radiated electromagnetic field.

  For reference, the refraction of the radiated electromagnetic field will be described first. The refraction of the radiated electromagnetic field has been studied for a long time. For example, a well-known convex lens that converges light is widely used in society. The principle of refraction of the radiated electromagnetic field is called Snell's law, and is a law that regulates the traveling direction of electromagnetic waves. Snell's law is expressed by the following equation.

This equation has a dielectric constant epsilon _1, the permeability mu ₁ of the medium and the dielectric constant epsilon _2, the boundary of the magnetic permeability mu ₂ of the medium, the dielectric constant epsilon _1, the electromagnetic wave is at an angle theta ₁ a permeability mu ₁ medium side The incident light is incident on the medium side having the dielectric constant ε ₂ and the magnetic permeability μ ₂ at an angle θ ₂ .

  However, Snell's law is irrelevant for refraction of non-radiating electromagnetic fields. In general, the law is derived for the refraction of electric and magnetic fields as follows.

At the boundary between the medium having the dielectric constant ε _{1 and} the medium having the dielectric constant ε ₂ as shown in FIG. 4A, the electric field and the electric flux density in each medium are expressed by the following equations from Maxwell's equations.

  From this, the law of refraction of the electric field is derived as follows.

This equation is for a case where an electric field (lines of electric force) enters from the medium side having a dielectric constant ε _{1 at} an angle θ ₁ and exits to the medium side having a dielectric constant ε ₂ at an angle θ ₂ .

Thus, the electric field is refracted at the boundary of different media. Here, it should be noted that when the expression (3) is compared with the expression (1), the positions of ε ₁ and ε ₂ are opposite in the numerator and the denominator. Thus, assuming that ε ₁ > ε ₂ , Snell's law is θ ₁ <θ ₂ , whereas θ ₁ > θ _{2 in} refraction of the electric field. That is, the direction of refraction of the electric field is opposite to the direction of refraction of Snell's law.

Further, at the boundary between the medium with magnetic permeability μ _{1 and} the medium with magnetic permeability μ ₂ , the magnetic field and magnetic flux density in each medium are expressed by the following equations from Maxwell's equations.

  From this, the law of refraction of the magnetic field is derived as follows.

This equation is for a case where a magnetic field (magnetic field line) of a non-radiated electromagnetic field enters at an angle θ ₁ from the medium side of the magnetic permeability μ ₁ and exits to the medium side of the magnetic permeability μ ₂ at an angle θ ₂ .

Thus, the magnetic field is refracted at the boundary of different media. Here, it should be noted that when the expression (5) is compared with the expression (1), the positions of μ ₁ and μ ₂ are opposite in the numerator and the denominator. Thus, when μ ₁ > μ ₂ , θ ₁ <θ ₂ in the radiated electromagnetic field, whereas θ ₁ > θ _{2 in} the refraction of the magnetic field. That is, the direction of refraction of the magnetic field is opposite to the direction of refraction of the radiated electromagnetic field.

  Therefore, Snell's law does not hold for non-radiating electromagnetic fields, and the law of electric field refraction expressed by the above formula (3) and the law of magnetic field refraction expressed by the above (5) hold. By utilizing the fact that the law of refraction of the electric field and the law of refraction of the magnetic field are established, the inductor 4 can be configured by a dielectric or a magnetic material as follows.

  First, the dielectric inductor 4 will be described.

  As shown in FIG. 1, the dielectric inductor 4 is disposed between the power transmission side device 2 and the power reception side device 3, and has a shape extended in the direction of the central axis z of the power transmission side device 2. Yes. The central axis z of the power transmission side device 2 is the central axis of the spiral of the power transmission side resonator 21. At the boundary between the dielectric inductor 4 and the surrounding air, refraction of the electric field of the non-radiating electromagnetic field occurs due to the difference in dielectric constant. Then, by utilizing the refraction, as shown in FIG. 5, the electric field of the non-radiated electromagnetic field is induced in the inductor 4 from the power transmission side device 2 toward the power reception side device 3 without being diverged. be able to. In FIG. 5, the electric lines of force of the electric field of the non-radiated electromagnetic field are schematically shown by broken lines.

  Next, an experiment of the wireless power transmission system 1 using the dielectric inductor 4 will be described. Each of the power transmission side resonator 21 of the power transmission side device 2 and the power reception side resonator 31 of the power reception side device 3 uses a spiral coil having a diameter of about 30 cm by winding an electric wire having a wire diameter of about 1 mm. The power transmission side resonator 21 and the power reception side resonator 31 are opposed to each other at a distance of about 50 cm, and as shown in FIG. A container 41 made of polyethylene terephthalate having a substantially rectangular parallelepiped shape was placed with water. A container 41 having a length in the central axis z direction of less than 10 cm, a vertical direction of about 8.5 cm, and a height of about 30 cm was used.

  FIG. 7 shows a change in the coupling coefficient between the power transmission side resonator 21 and the power reception side resonator 31. FIG. 8 shows a change in transmittance indicating the efficiency of power transmission from the power transmission side resonator 21 to the power reception side resonator 31. The horizontal axis of FIG.7 and FIG.8 is the number of the containers 41 which put water. Tap water was used as the water, and the container 41 containing the water was arranged symmetrically from the center toward the end. The power transmission side resonator 21 has about 100 turns clockwise (see FIG. 2) when viewed from the impedance matching means 22 of the power transmission side device 2. Curves a, c, d in FIG. 7 and curves e, g, h in FIG. 8 are approximately counterclockwise (see FIG. 3) when the power-receiving-side resonator 31 is viewed from the impedance matching means 22 of the power-transmission-side device 2. This is a characteristic of 100 rolls. A curve b in FIG. 7 and a curve f in FIG. 8 are characteristics of the power-receiving-side resonator 31 having about 100 turns clockwise as viewed from the impedance matching unit 22 of the power-transmission-side device 2. The curves a and b in FIG. 7 and the curves e and f in FIG. 8 are only water in the containers 41 (containers arranged at both ends of the container row) facing the power transmission side resonator 21 and the power reception side resonator 31. 0.45% by weight of salt was added to the remaining water in the remaining container 41. A curve c in FIG. 7 and a curve g in FIG. 8 are obtained by adding 0.45% by weight of salt to the water in all the containers 41. Curve d in FIG. 7 and curve h in FIG. 8 are all still tap water.

  In the curve a in FIG. 7 and the curve e in FIG. 8, the coupling coefficient increases as the number of containers 41 containing water increases, that is, the longer the dielectric inductor 4 is extended in the direction of the central axis z, The transmittance is also increasing. In the curve b of FIG. 7 and the curve f of FIG. 8, when the number of containers 41 containing water is increased, the coupling coefficient is lowered and the transmittance is also lowered. In the curve c of FIG. 7 and the curve g of FIG. 8, when the number of containers 41 filled with water is increased, the coupling coefficient is increased in substantially the same manner as the curve a described above (substantially overlapping the curve a) and transmitted. The rate rises more steeply than the curve e above. In the curve d of FIG. 7 and the curve h of FIG. 8, when the number of containers 41 containing water is increased, the coupling coefficient increases, but the transmittance is less than five containers 41 containing water, that is, four containers. Until it becomes, it rises as the number increases, and when it becomes 5, it falls.

  When all of the water in the container 41 containing water remains tap water, the transmittance decreases when the number of the containers 41 containing water reaches five is close to the power transmission side resonator 21 and the power reception side resonator 31. This is because the container 41 filled with tap water facing the lowering of the unloaded Q value. FIG. 9 shows a change in the unloaded Q value with respect to the salinity concentration of the container 41 containing the adjacent water. The horizontal axis represents the salinity concentration expressed logarithmically. A curve i, a curve j, a curve k, a curve l, a curve m, a curve n, a curve o, a curve p, a curve q, and a curve r are respectively a power transmission side resonator 21 (and a power reception side resonator 31) and water adjacent thereto. The distance between the container 41 and the container 41 is 0, 0.5 cm, 1 cm, 1.5 cm, 2 cm, 3 cm, 4 cm, 5 cm, 7 cm, 10 cm. Although tap water (tap water to which no salt is added) has a salinity of about 0.003% by weight, it can be seen that the no-load Q value is very low near this salinity. Further, although there is some variation depending on the distance between the power transmitting resonator 21 (and the power receiving resonator 31) and the container 41 containing water adjacent thereto, the salt concentration is 0.1 wt% to 2 wt%. It can be seen that a high unloaded Q value can be obtained locally if the amount is in the range of 1, and a high unloaded Q value can be obtained if the salinity concentration is in the range of 0.0001% by weight or less. In general, the salt concentration of physiological saline is about 0.9% by weight, and pure water or distilled water has a salt concentration of 0.0001% by weight or less.

  From this experiment, in particular, from the curves a and c in FIG. 7 and the curves e and g in FIG. 8, the dielectric inductor 4 between the power transmission side device 2 and the power reception side device 3 is elongated in the direction of the central axis z. It can be seen that the coupling coefficient can be increased and the transmittance can be increased as the amount is increased. Further, water can be used as a dielectric for inducing a non-radiating electromagnetic field, and at least a portion of the water facing the power transmission side device 2 and the power reception side device 3 can have a high unloaded Q value. In addition, it is preferable to use a material to which an appropriate amount of salt has been added or a material from which salt has been removed as much as possible. In particular, the salinity concentration of the water in that portion is preferably in the range of 0.1 wt% to 2 wt%, or in the range of 0.0001 wt% or less.

  Such a dielectric inductor 4 may be bent as shown in FIG. 10 instead of being extended in the direction of the central axis z. This is because the inductor 4 can guide the electric field of the non-radiated electromagnetic field from the power transmitting side device 2 toward the power receiving side device 3 without causing the electric field of the non-radiated electromagnetic field to diverge in the inductor 4.

  In addition, the dielectric inductor 4 may be composed of a dielectric concave lens 42 as shown in FIG. The reason for the concave lens is that, as described above, the direction of refraction of the electric field of the non-radiated electromagnetic field is opposite to the direction of refraction of the radiated electromagnetic field. The direction of the central axis of the concave lens 42 is not limited to that corresponding to the direction of the central axis z of the power transmission side device 2 (see FIG. 11), and may be tilted therefrom.

  Next, the magnetic inductor 4 will be described.

  As shown in FIG. 1, the magnetic inductor 4 is disposed between the power transmission side device 2 and the power reception side device 3 and is extended in the direction of the central axis z of the power transmission side device 2. It can be a shape. The central axis z of the power transmission side device 2 is the central axis of the spiral of the power transmission side resonator 21. At the boundary between the magnetic inductor 4 and the surrounding air, refraction of the magnetic field of the non-radiated electromagnetic field occurs due to the difference in magnetic permeability. By utilizing the refraction, the magnetic field of the non-radiated electromagnetic field can be guided from the power transmission side device 2 toward the power reception side device 3 without being diverged in the inductor 4.

  Next, an experiment of the wireless power transmission system 1 using the magnetic inductor 4 will be described. Each of the power transmission side resonator 21 of the power transmission side device 2 and the power reception side resonator 31 of the power reception side device 3 is a spiral coil having a diameter of about 10 cm by winding about 10 turns of an electric wire having a wire diameter of about 1 mm. A capacitor with a capacitance of 68 pF was connected between both ends. The power transmission side resonator 21 and the power reception side resonator 31 are opposed to each other with a distance of about 10 cm, and as shown in FIG. 12, the length of the magnetic substance inductor 4 in the central axis z direction is between them. A ferrite plate 43 having a height of 2.4 cm, a height of 2.4 cm, and a thickness of 0.1 cm was disposed.

  A curve s in FIG. 13 shows a change in the coupling coefficient between the power transmission side resonator 21 and the power reception side resonator 31. The horizontal axis in FIG. 13 represents the number of ferrite plates 43. In the curve s, the coupling coefficient increases as the number of ferrite plates increases, that is, the longer the magnetic inductor 4 is extended in the direction of the central axis z.

  From this experiment, ferrite can be used as a magnetic body for inducing a non-radiated electromagnetic field, and the magnetic inductor 4 between the power transmission side device 2 and the power reception side device 3 is placed in the direction of the central axis z. It can be seen that the longer the stretching, the higher the coupling coefficient.

  Such a magnetic inductor 4 is bent in the same manner as the dielectric inductor 4 shown in FIGS. 10 and 11, instead of being elongated in the direction of the central axis z. Alternatively, it may be constituted by a magnetic concave lens 42. The reason for the concave lens is that, as described above, the direction of refraction of the magnetic field of the non-radiated electromagnetic field is opposite to the direction of refraction of the radiated electromagnetic field.

  As described above, in the wireless power transmission system 1, the inductor 4 induces a non-radiated electromagnetic field, that is, controls the distribution of the non-radiated electromagnetic field, thereby transmitting power from the power transmission side device 2 to the power reception side device 3. Efficiency can be increased. In addition, in such a wireless power transmission system 1, the inductor 4 may be installed simultaneously with the installation of the power transmission side device 2, or in order to improve the power transmission efficiency from the power transmission side device 2 to the power reception side device 3. The inductor 4 may be installed ad hoc later.

  The wireless power transmission system 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. For example, the wireless power transmission system 1 is not limited to the coupled resonator type, but can be applied to other wireless power transmission systems using a non-radiated electromagnetic field (for example, an electromagnetic induction type or a capacitive coupling type). Further, the inductor 4 can be made of a metal regardless of a dielectric or a magnetic material as long as it can induce a non-radiated electromagnetic field.

DESCRIPTION OF SYMBOLS 1 Wireless power transmission system 2 Power transmission side apparatus 21 Power transmission side resonator which comprises power transmission side apparatus 2 22 Impedance matching means which comprises power transmission side apparatus 2 23 High frequency power supply 3 Power reception side apparatus 31 Power reception side resonance which comprises power reception side apparatus 3 32 Impedance matching means constituting power receiving side device 3 Load 4 Inductor

Claims (11)

In a wireless power transmission system that wirelessly transmits power from a power transmission side device to a power reception side device using a non-radiated electromagnetic field,
A wireless power transmission system comprising an inductor that refracts a non-radiated electromagnetic field from the power transmission side device and guides it toward the power reception side device. The wireless power transmission system according to claim 1,
The wireless power transmission system, wherein the inductor is made of a dielectric material or a magnetic material. The wireless power transmission system according to claim 1 or 2,
The power transmission side device has a power transmission side resonator, and the power reception side device has a power reception side resonator;
A wireless power transmission system, wherein power transmission is performed by causing resonance between the power transmission side resonator and the power reception side resonator. The wireless power transmission system according to any one of claims 1 to 3,
The wireless power transmission system according to claim 1, wherein the inductor extends in a direction of a central axis of the power transmission side device. The wireless power transmission system according to any one of claims 1 to 3,
The wireless power transmission system according to claim 1, wherein the inductor is bent. The wireless power transmission system according to any one of claims 1 to 3,
The wireless power transmission system according to claim 1, wherein the inductor is a concave lens. The wireless power transmission system according to any one of claims 1 to 6,
The wireless power transmission system according to claim 1, wherein the inductor induces a non-radiated electromagnetic field using water. The wireless power transmission system according to claim 7,
The wireless power transmission system according to claim 1, wherein the inductor has salt added to at least a portion of water facing the power transmission side device and the power reception side device. The wireless power transmission system according to claim 7 or 8,
The inductor has a salt concentration of water in a range of 0.1 wt% to 2 wt% at least in a portion facing the power transmitting side device and the power receiving side device. system. The wireless power transmission system according to claim 7,
The wireless power transmission system according to claim 1, wherein the inductor has a salinity concentration of water at least in a portion facing the power transmission side device and the power reception side device in a range of 0.0001% by weight or less. The wireless power transmission system according to any one of claims 1 to 6,
The wireless power transmission system according to claim 1, wherein the inductor uses a ferrite to induce a non-radiated electromagnetic field.

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