Electric field type wireless power transmission system

Abstract

To provide an electric field type wireless power transmission system with high transmission efficiency.SOLUTION: An electric field type wireless power transmission system is constituted by matching magnetic paths of a first power transmission side coil L11 and a second power transmission side coil L12 constituting a power transmission side coil L1 with each other, and matching magnetic paths of a first power reception side coil L21 and a second power reception side coil L22 constituting a power reception side coil L2 with each other. A litz wire constitutes a winding L5 of the power transmission side coil L1 and / or the power reception side coil L2. The power transmission side coil L1 and / or the power reception side coil L2 are air-core coils.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an electric field type wireless power transmission system.

Background Art

[0002] In recent years, with the popularization of mobile phones, electric vehicles, etc., the development of wireless power transmission systems that supply power wirelessly has been actively carried out. As an example of a document describing this type of technology, there is Patent Document 1. Patent Document 1 describes that in a wireless power transmission method using a magnetic field, a power supply unit includes an inverter circuit that converts a DC voltage into an AC voltage, a control circuit that controls the inverter circuit, and a capacitor that forms a resonance circuit together with the power feeding coil.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of transmitting large power, the coils constituting the resonance circuit have problems such as heat generation due to iron loss, copper loss, and an increase in resistance. In particular, in electric field type wireless power transmission, since two coils for resonance are required, there is room for improvement from the viewpoints of improving transmission efficiency and suppressing heat generation.

[0005] The present invention provides an electric field type wireless power transmission system with high transmission efficiency and suppressed heat generation.

Means for Solving the Problems

[0006] The electric field type wireless power transmission system according to the present invention is configured such that the magnetic paths of a first power transmission side coil and a second power transmission side coil constituting the power transmission side coil coincide, and the magnetic paths of a first power reception side coil and a second power reception side coil constituting the power reception side coil coincide.

Effect of the Invention

[0007] According to the present invention, an electric field type wireless power transmission system with high transmission efficiency and suppressed heat generation can be obtained.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 4

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Figure 8

Modes for Carrying Out the Invention

[0009] Hereinafter, the electric field type wireless power transmission system according to the embodiment of the present invention will be described with reference to the drawings. In each figure, the same reference numerals are given to the same components.

[0010] (Embodiment 1) Hereinafter, the electric field type wireless power transmission system S according to Embodiment 1 will be described with reference to FIGS. 1 and 2.

[0011] As shown in FIG. 1, the electric field type wireless power transmission system S according to an embodiment of the present invention includes a wireless power transmission device 1 and a wireless power reception device 2. A power transmission side reactance adjustment circuit 31, a power transmission side coupler main body part 301, a power reception side coupler main body part 302, and a power reception side reactance adjustment circuit 32 constitute a coupler 3.

[0012] First, the configuration of the wireless power transmission device 1 will be described. The wireless power transmission device 1 includes a power supply main body 41, a boosting unit 6, a power transmission side reactance adjustment circuit 31, and a power transmission side coupler main body part 301. The power sent out from the power supply main body 41 is boosted by the boosting unit 6. The boosting unit 6 boosts the voltage output from the power supply and converts it into a voltage suitable for power transmission. The boosted power is transmitted to the power transmission side coupler main body part 301 via the power transmission side reactance adjustment circuit 31. The transmitted power is wirelessly transmitted from the power transmission side coupler main body part 301 to the wireless power reception device 2.

[0013] The configuration of the wireless power reception device 2 will be described. The wireless power reception device 2 includes a power reception side coupler main body part 302, a power reception side reactance adjustment circuit 32, a step-down unit 8, and a rectification circuit 9, and is connected to a load 5. The power reception side coupler main body part 302 transmits power by wireless transmission from the power transmission side coupler main body part 301. The power received by the power reception side coupler main body part 302 is transmitted to the load 5 via the power reception side reactance adjustment circuit 32, the step-down unit 8, and the rectification circuit 9. The step-down unit 8 converts the transmitted voltage into a voltage suitable for the circuit. The rectification circuit 9 converts the power transmitted in alternating current into direct current. The load 5 is, for example, a storage battery and is adopted in industrial equipment, portable electronic devices, etc. Examples of industrial equipment include electric vehicles, and examples of portable electronic devices include laptop computers, smartphones, portable music players, etc.

[0014] FIG. 2 is a schematic diagram of the circuit configuration of the electric field type wireless power transmission system S according to an embodiment of the present invention. The first power transmission side flat electrode 11 and the second power transmission side flat electrode 12 shown in FIG. 2 are held by the power transmission side coupler main body 301, and the first power reception side flat electrode 21 and the second power reception side flat electrode 22 are held by the power reception side coupler main body 302. In this embodiment, the coupler 3 is constituted by the power transmission side coupler main body 301 and the power reception side coupler main body 302.

[0015] A first capacitance Cm1 is formed between the first power transmission side flat electrode 11 and the first power reception side flat electrode 21, and a second capacitance Cm2 is formed between the second power transmission side flat electrode 12 and the second power reception side flat electrode 22. A first stray capacitance C11 associated with the formation of an electric field is formed between the first power transmission side flat electrode 11 and the second power transmission side flat electrode 12, and a second stray capacitance C21 associated with the formation of an electric field is formed between the first power reception side flat electrode 21 and the second power reception side flat electrode 22.

[0016] The first power transmission side flat electrode 11 is connected to one terminal 401 on the power transmission side of the power supply main body 41 through the first transmission line 101 on the power transmission side and the first power transmission side coil L11 in this order. The second power transmission side flat electrode 12 is connected to the other terminal 402 on the power transmission side of the power supply main body 41 through the second transmission line 102 on the power transmission side and the second power transmission side coil L12 in this order. The first transmission line 101 on the power transmission side and the second transmission line 102 on the power transmission side are connected through the capacitor C12 on the power transmission side. The first power transmission side coil L11, the second power transmission side coil L12, and the capacitor C12 on the power transmission side form a power transmission side reactance adjustment circuit 31.

[0017] The first power receiving side flat plate electrode 21 is connected to one terminal 501 on the power receiving side of the load 5 through the first transmission line 201 and the first power receiving side coil L21 on the power receiving side in this order. The second power receiving side flat plate electrode 22 is connected to the other terminal 502 on the power receiving side of the load through the second transmission line 202 and the second power receiving side coil L22 on the power receiving side in this order. The first transmission line 201 on the power receiving side and the second transmission line 202 on the power receiving side are connected through a capacitor C22 on the power receiving side. The first power receiving side coil L21, the second power receiving side coil L22, and the capacitor C22 on the power receiving side form a power receiving side reactance adjustment circuit 32.

[0018] As described above, the capacitive coupling type wireless power transmission method in which a coil and a capacitor are provided with respect to the coupler is called the electric field method.

[0019] Alternating current is transmitted from the power supply main body 41 shown in FIG. 2. Electric charges are stored in or discharged from the first capacitor Cm1 and the second capacitor Cm2, whereby power is transmitted. Power is transmitted to the wireless power receiving device 2 through the first capacitor Cm1 and the second capacitor Cm2, and power is supplied to the load 5.

[0020] The magnetic paths of the first power transmission side coil L11 and the second power transmission side coil L12 coincide, and the magnetic paths of the first power receiving side coil L21 and the second power receiving side coil L22 that constitute the power receiving side coil also coincide. The coincidence of the magnetic paths here does not necessarily mean that the magnetic paths completely coincide. The coincidence of the magnetic paths means that the magnetic fields of a pair of coils overlap, the magnetic field of one coil affects the other coil, the magnetic field of the other coil affects one coil, and a pair of coils form a coupled inductor.

[0021] The first power transmission side coil L11 and the second power transmission side coil L12 form a coupled inductor with opposite phases. Similarly, the first power receiving side coil L21 and the second power receiving side coil L22 form a coupled inductor with opposite phases. In FIG. 2, this relationship is shown by arranging dots indicating phases at point-symmetric positions.

[0022] The first power transmission side coil L11 and the second power transmission side coil L12 are air-core coils, and solenoid coils, spiral coils, etc. are concentrically arranged so that their magnetic paths coincide. It is also possible to use an iron core. In this case, two coils are wound around the same iron core so that their magnetic paths coincide.

[0023] Figure 3 shows the influence of the coupling degree between the first power transmission side coil L11 and the second power transmission side coil L12 on the power transmission transmittance. As shown in Figure 3, for example, when the inductances of the first power transmission side coil L11 and the second power transmission side coil L12 are fixed at 10 μH and the coupling degree K is changed to 0, 0.5, and 1, the transmittance improves. When the coupling degree between the first power transmission side coil L11 and the second power transmission side coil L12 increases, in order to achieve the same transmittance, the inductances of the first power transmission side coil L11 and the second power transmission side coil L12 can be kept small. For example, when the coupling degree is 1, compared with the case where the coupling degree is 0, that is, when they are completely separated, the first power transmission side coil L11 and the second power transmission side coil L12 produce the same effect with half the inductance. As shown in Figure 3, for example, the case where the inductance of the first power transmission side coil L11 and the second power transmission side coil L12 is 20 μH and the coupling degree K is 0, and the case where the inductance of the first power transmission side coil L11 and the second power transmission side coil L12 is 10 μH and the coupling degree K is 1 show the same transmittance. Therefore, the first power transmission side coil L11 and the second power transmission side coil L12 can be made smaller and lighter. Also, the number of turns of the first power transmission side coil L11 and the second power transmission side coil L12 can be reduced, and the copper loss can be suppressed. Also, in the case of an air core, since there is no need to use an iron core, the iron loss can be suppressed.

[0024] Regarding the first power receiving coil L21 and the second power receiving coil L22, similar to the power transmitting side, they are air-core coils. The magnetic paths are made to coincide, and the windings of the first power receiving coil L21 and the second power receiving coil L22 are adjusted so that the voltage fluctuations are out of phase. When the degree of coupling between the first power receiving coil L21 and the second power receiving coil L22 increases, the inductances of the first power receiving coil L21 and the second power receiving coil L22 can be kept small. When the degree of coupling is 1, compared with the case where the degree of coupling is 0, that is, when they are completely separated, the first power receiving coil L21 and the second power receiving coil L22 produce the same effect with half the inductance. Therefore, the first power receiving coil L21 and the second power receiving coil L22 can be made smaller and lighter. Also, the number of turns of the first power receiving coil L21 and the second power receiving coil L22 can be reduced, and the copper loss can be suppressed. Also, since there is no need to use an iron core, the iron loss can be suppressed.

[0025] (Embodiment 2) FIG. 4 shows, as a second embodiment, an embodiment of the first power transmitting coil L11 adopting an air-core coil configuration. On one side of the oval-shaped flat plate L3, the first cylinder L4a, the second cylinder L4b, and the third cylinder L4c are erected on the vertices of a triangle. Similarly, on the other side of the oval-shaped flat plate L3, the fourth cylinder L4d, the fifth cylinder L4e, and the sixth cylinder L4f are erected on the vertices of a triangle, and the winding L5 is wound so as to enclose these as supports. For example, ebonite resin constitutes these first to sixth cylinders. Similarly, for the second power transmitting coil L12, on one side of the oval-shaped flat plate L3, the first cylinder L4a, the second cylinder L4b, and the third cylinder L4c are erected on the vertices of a triangle. Similarly, on the other side of the oval-shaped flat plate L3, the fourth cylinder L4d, the fifth cylinder L4e, and the sixth cylinder L4f are erected on the vertices of a triangle, and the winding L5 is wound so as to enclose these as supports. In the second power transmitting coil L12, the direction in which the winding L5 is wound and the number of turns of the winding L5 are the same as those of the first power transmitting coil L11.

[0026] As shown in Fig. 5, the first power transmission side coil L11 and the second power transmission side coil L12 are stacked vertically to form the power transmission side coil L1, which constitutes a coupling inductance. The magnetic field generated from the first power transmission side coil L11 passes through the core of the second power transmission side coil L12, and a current flows as the second power transmission side coil L12 tries to cancel it. Conversely, the magnetic field generated from the second power transmission side coil L12 passes through the core of the first power transmission side coil L11, and a current flows as the first power transmission side coil L11 tries to cancel it. As a result, in the first power transmission side coil L11 and the second power transmission side coil L12, the winding L5 is wound in the same direction, a reverse voltage is generated, and the phase is reversed.

[0027] The first modification is shown in Fig. 6. One oval-shaped flat plate L3 has one first cylinder L6a of the first modification standing upright, and the other oval-shaped flat plate L3 has one second cylinder L6b of the first modification standing upright. The winding L5 is wound so as to enclose these two cylinders as supports. For example, ebonite resin constitutes the first cylinder L6a of the first modification and the second cylinder L6b of the first modification.

[0028] The first cylinder L6a of the first modification has a larger volume and is heavier than the total of the first cylinder L4a, the second cylinder L4b, and the third cylinder L4c according to the second embodiment of the present invention. In the second embodiment, compared with the first modification, the volume of the cylinders existing inside the first power transmission side coil L11, that is, the core part, is smaller, and a decrease in efficiency due to the dielectric tangent with the magnetic flux generated inside the first power transmission side coil L11 is prevented. Further, in the second embodiment, compared with the first modification, the first power transmission side coil L11 generates heat, but the contact area between the first cylinder L4a, the second cylinder L4b, the third cylinder L4c, and the winding L5 is small, and heat dissipation is easy. Furthermore, air flows through the hollow space constituting the air core coil, and since the surface area of the first cylinder L4a, the second cylinder L4b, and the third cylinder L4c is large, the heat dissipation property is high. As a result, an increase in temperature is suppressed. Also, since the total volume of the cylinders is small, the material cost can be kept low. (Embodiment 3)

[0029] In the electric-field type wireless power transmission system S according to the present embodiment, although it is also possible to use a single wire or a stranded wire as the wire material of the windings of the first power transmission side coil L11, the second power transmission side coil L12, the first power reception side coil L21, and the second power reception side coil L22, in the third embodiment, a litz wire is used as the winding of the coil.

[0030] Fig. 7 shows the simulation results of the relationship between the Q values of the first power transmission side coil L11 and the second power transmission side coil L12 and the transmittance of the power transmission side coupler main body 301. The horizontal axis represents the power transmission frequency. The higher the Q values of the first power transmission side coil L11 and the second power transmission side coil L12, the better the transmittance in Fig. 7, that is, the higher the transmission efficiency, when the Q value is 300.

[0031] The frequency band available for the electric-field type wireless power transmission system S is assigned to the 400 kHz band. In this region, when a single wire or a stranded wire is used, there are many losses due to the skin effect and generally the Q value of the coil is low. On the other hand, as shown in Fig. 8, the inventors have found that the Q value of the coil is significantly improved by adopting a litz wire. When the power transmission frequency is 450 kHz, for example, the coil performance is improved (Q value = 254) by adopting a litz wire as compared with a coil (Q value = 233) wound with a single wire around an iron dust core.

[0032] Based on this, in the electric-field type wireless power transmission system S according to the present embodiment, litz wires are respectively used as the wire materials of the windings of the first power transmission side coil L11, the second power transmission side coil L12, the first power reception side coil L21, and the second power reception side coil L22. The skin effect is suppressed more than that of a single wire or a stranded wire, the AC resistance is reduced, and the loss of the coil is suppressed to be small. Furthermore, higher Q values can be obtained by using a core of Mn·Zn (Q value = 262) or an air core (Q value = 426) for the coil.

[0033] When using Litz wire for each of the first power transmission side coil L11, the second power transmission side coil L12, the first power reception side coil L21, and the second power reception side coil L22, and adopting an iron dust, MnZn, and air core coil configuration as each core, the wireless power transmission efficiency is 94.6% when adopting an iron dust core, 94.8% when adopting MnZn, and 96.6% when adopting an air core coil configuration. Higher wireless power transmission efficiency can be obtained by adopting an air core coil configuration.

[0034] According to the electric field type wireless power transmission system S according to the embodiment described above, the following effects can be obtained.

[0035] An electric field type wireless power transmission system S, in which the magnetic paths of the first power reception side coil L21 and the second power reception side coil L22 constituting the power reception side coil L2 coincide, and the magnetic paths of the first power transmission side coil L11 and the second power transmission side coil L12 constituting the power transmission side coil L1 coincide.

[0036] Thereby, high transmission efficiency can be obtained and heat generation can be suppressed.

[0037] An electric field type wireless power transmission system S, in which the Litz wire constitutes the winding of the power transmission side coil L1 and / or the power reception side coil L2.

[0038] Thereby, the skin effect can be suppressed and high transmission efficiency can be obtained.

[0039] An electric field type wireless power transmission system S, in which the power transmission side coil L1 and / or the power reception side coil L2 is an air core coil.

[0040] Thereby, iron loss can be suppressed and high transmission efficiency can be obtained.

[0041] An electric field type wireless power transmission system S, in which the winding L5 of the air core coil is wound so as to include three or more columns L4.

[0042] As a result, the volume of the support column is reduced, thereby preventing a decrease in efficiency due to the dielectric tangent with the magnetic flux caused by the support column, and as a result, high transmission efficiency can be obtained.

[0043] An electric field type wireless power transmission system S, wherein the phases of the coupling inductors composed of the first power receiving coil L21 and the second power receiving coil L22 are opposite phases, and the phases of the coupling inductors composed of the first power transmitting coil L11 and the second power transmitting coil L12 are opposite phases.

[0044] As a result, the number of turns of the coil can be reduced, and copper loss can be suppressed. In addition, since there is no need to use an iron core, iron loss can be suppressed.

[0045] The present disclosure can be implemented in various embodiments and modifications without departing from the broad spirit and scope of the present invention. Further, the above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims rather than the embodiments. And various modifications made within the scope of the claims and within the scope of the meaning of the disclosure equivalent thereto are considered to be within the scope of the present invention.

Explanation of Reference Numerals

[0046] 1 Wireless power transmission device, 2 Wireless power reception device, 3 Coupler, 5 Load, 6 Boosting unit, L1 Power transmission side coil, L11 First power transmission side coil, L12 Second power transmission side coil, L2 Power reception side coil, L21 First power reception side coil, L22 Second power reception side coil, L5 Winding, S Wireless power transmission system

Claims

1. An electric field type wireless power transmission system that transmits power by capacitive coupling between a first power transmission side flat electrode and a second power transmission side flat electrode, and a first power reception side flat electrode and a second power reception side flat electrode, wherein a magnetic path of a first power transmission side coil and a second power transmission side coil, which are respectively connected to the first power transmission side flat electrode and the second power transmission side flat electrode to form a power transmission side coil, coincides, and a magnetic path of a first power reception side coil and a second power reception side coil, which are respectively connected to the first power reception side flat electrode and the second power reception side flat electrode to form a power reception side coil, coincides, wherein the power transmission side coil and / or the power reception side coil is an air-core coil, and the winding of the air-core coil is wound so as to include three or more struts electric field type wireless power transmission system.

2. A litz wire constitutes the winding of the power transmission side coil and / or the power reception side coil The electric field type wireless power transmission system according to claim 1.

3. The phase of the coupling inductor formed by the first power reception side coil and the second power reception side coil is an opposite phase, and the phase of the coupling inductor formed by the first power transmission side coil and the second power transmission side coil is an opposite phase The electric field type wireless power transmission system according to claim 1 or 2.

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