Matching circuit for wireless power receiving device

Abstract

To provide a matching circuit of a wireless feeding power reception device capable of being miniaturized and reduced in weight without reducing power supply efficiency.SOLUTION: A matching circuit 1 of a wireless feeding power reception device mounted on an electric vehicle connected with a first reception electrode 17a and a second reception electrode 17b comprises a plurality of metal rod-like bodies 19, and a plurality of first coil units 21 to a metal core of which a plurality of ring-shaped ferrite cores are attached in the form of a rosary. The plurality of metal rod-like bodies 19 and the plurality of first coil units 21 are aligned in the long direction to be arranged in line in parallel and the ends are electrically connected in series to form an impedance.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a matching circuit of a power receiving device for wireless power supply.

Background Art

[0002] For moving bodies such as electric vehicles (EVs) and robots, when they move, power is wirelessly supplied to the moving body by the energy of an electric field generated between a power transmission electrode connected to a high-frequency power source (a device that converts power from DC to high frequency) and a power receiving electrode mounted on the moving body. In the case of such wireless power supply by an electric field coupling method, it is necessary to optimize the impedance of the entire wireless power supply system by a transmission-side matching circuit between the high-frequency power source and the power transmission electrode and a reception-side matching circuit between the power receiving electrode and the rectifier circuit to improve the transmission efficiency.

[0003] In addition, when the moving body on which the power receiving device including the matching circuit is mounted is an automobile traveling on a public road, ensuring the minimum ground clearance becomes an issue. In the "Notification on Specifying Details of Road Transport Vehicle Safety Standards <Section 3> Article 163" determined by the Ministry of Land, Infrastructure, Transport and Tourism, it is stipulated that "the ground clearance on the entire surface is 9 cm or more." The minimum ground clearance of commercially available small and medium-sized EVs is, for example, about 14 cm to 15 cm. To comply with the ordinance, the power receiving device mounted on the bottom of the moving body needs to be made as thin as about 5 cm. In addition to this issue of thinning, miniaturization and weight reduction are required from the viewpoints of device capabilities and mounting performance.

[0004] Patent Document 1 discloses a wireless power supply system in which a power reception-side matching circuit unit and a resonance circuit unit are provided in a power transmission-side device. In this wireless power supply system, in the resonance circuit unit, the electrical capacitance between the power transmission electrode unit and the power reception electrode unit and the capacitance between the pair of power transmission electrode units are canceled out, and it is realized that the space between the power transmission electrode unit and the power reception electrode unit is an electrically equivalent transmission path. That is, in Patent Document 1, by providing the power reception-side matching circuit in the power transmission-side device, miniaturization and weight reduction of the power reception-side device are achieved.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-045013 [Patent Document 2] Japanese Patent Publication No. 2016-058839 [Non-patent literature]

[0006] [Non-Patent Document 1] Takehiro Imura et al., "Proposal of a Mean Line Antenna for Contactless Power Transmission," 2008 IEICE Communications Society Conference, September 2008, B-9-1 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the wireless power transmission system described in Patent Document 1, the electrical capacitance between the transmitting electrode and the receiving electrode is assumed to be a constant value if the distance between the transmitting and receiving electrodes, and the electrical constants (dielectric constant, permeability, etc.) of the space and materials surrounding the electrodes are constant. However, in reality, it fluctuates depending on the distance between the electrodes and differences in the environment. Therefore, it is not canceled out by this resonant circuit alone, and it cannot be considered an assumed equivalent transmission path, which may lead to a decrease in transmission efficiency. Furthermore, not limited to Patent Document 1, the receiving device mounted on a mobile body is composed of active elements such as coil elements and capacitor elements. Therefore, as the power received increases, the size of the active elements increases. In particular, the coil element becomes especially large as the power increases, as it causes magnetic saturation.

[0008] This invention has been made in view of the circumstances described above, and the problem that this invention aims to solve is to provide a matching circuit for a wireless power supply receiving device that can be miniaturized and lightened without reducing power supply efficiency. [Means for solving the problem]

[0009] To solve the above problems, the present invention employs the following means. In other words, the matching circuit of the present invention is a matching circuit for a wireless power supply receiving device mounted on an electric vehicle, which is connected to a first power receiving electrode and a second power receiving electrode, and comprises a plurality of metal rod-shaped bodies and a plurality of first coil units in which a plurality of ring-shaped ferrite cores are attached in a bead-like manner to a metal core, wherein the plurality of metal rod-shaped bodies and the plurality of first coil units are aligned in parallel with their longitudinal orientations and their ends are connected in series to form an impedance.

[0010] According to the present invention, by arranging a plurality of metal rod-shaped bodies and a plurality of first coil units in parallel and connecting their ends in series to form an impedance, the matching circuit can be made smaller and lighter.

[0011] In one embodiment of the present invention, the plurality of metal rod-shaped bodies and the plurality of first coil units are arranged to be interchangeable with one another. According to this embodiment, the multiple metal rod-shaped bodies and the multiple first coil units are interchangeable, making it easy to adjust the impedance.

[0012] In one embodiment of the present invention, a second coil unit is provided, in which copper wire is wound around a ring-shaped ferrite core. According to this embodiment, the matching circuit is constructed using a second coil unit in which copper wire is wound around a ring-shaped ferrite core, so that the matching circuit can be constructed with appropriate components while satisfying the requirements of miniaturization and weight reduction.

[0013] In one embodiment of the present invention, the circuit, which includes the plurality of metal rod-shaped bodies, the plurality of first coil units, and the second coil unit, is arranged symmetrically on the first power receiving electrode side and the second power receiving electrode side. According to this aspect, since the matching circuits by each component member are symmetrically arranged on the first power receiving electrode side and the second power receiving electrode side, the impedance can be properly matched to suppress a decrease in power feeding efficiency.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a matching circuit for a power receiving device for wireless power feeding that can be miniaturized and lightened without reducing the power feeding efficiency.

Brief Description of the Drawings

[0015] [Figure 1] It is a schematic diagram for explaining the outline of a wireless power feeding system in which the matching circuit of the power receiving device of the present invention is used. [Figure 2] It is a schematic projection view showing the configuration of the matching circuit of the power receiving device according to an embodiment of the present invention. [Figure 3] It is an enlarged perspective view of the main part of FIG. 2. [Figure 4] It is a schematic diagram showing the configuration of the first coil unit according to an embodiment of the present invention. [Figure 5] It is a schematic diagram showing the configuration of the second coil unit according to an embodiment of the present invention. [Figure 6] It is a model diagram for explaining the electrical characteristics according to the meander shape of the matching circuit according to an embodiment of the present invention. [Figure 7] It is an equivalent circuit of a wireless power feeding system including the matching circuit according to an embodiment of the present invention. [Figure 8] It is a diagram showing the structure of a variable matching circuit in a conventional example. [Figure 9] It is a diagram showing the structure of a matching circuit in a conventional example.

Mode for Carrying Out the Invention

[0016] <Wireless Power Feeding System> First, a wireless power feeding system using an electric field coupling method in which the present invention is used as a matching circuit of a power receiving device will be described. Figure 1 is a schematic diagram illustrating the general outline of a wireless power supply system utilizing the matching circuit of the power receiving device of the present invention. As shown in the figure, the wireless power supply system 10 includes a high-frequency power supply 11, a power transmission matching circuit 13, and a power transmission electrode 15 on the power transmission side. The power receiving side includes a matching circuit 1, a rectifier circuit 7, a load 9, and a power receiving electrode 17. The matching circuit 1, rectifier circuit 7, and load 9 are mounted on a mobile body 3 such as an electric vehicle. Here, the load 9 includes on-board equipment such as a DC / DC converter and a battery, and the power transmitted from the matching circuit 1 is supplied to the battery via the DC / DC converter, etc. The power transmission electrode 15 is installed on a road 5 over which the mobile body 3 travels. The power receiving electrode 17 is positioned at the bottom of the mobile body 3 to receive power from the power transmission electrode 15. The components on the power receiving side and the power transmission side are connected by cables, etc.

[0017] The transmitting electrode 15 is assumed to be several meters to several hundred meters in length. The receiving electrode 17 is less than 5 meters in length, and it is assumed that the relative positions of the transmitting and receiving electrodes 15 and 17 will change as it moves along the transmitting electrode 15.

[0018] High-frequency energy (6.78 MHz and 13.56 MHz are assumed in this invention, but technically wireless power transfer is possible with frequencies of approximately 100 kHz or higher) is transmitted to the transmitting electrode 15 connected to the high-frequency power supply 11, generating an electromagnetic field in the surrounding area. When the receiving electrode 17 opposes the transmitting electrode 15, the electric field between the transmitting and receiving electrodes 15 and 17 enables contactless power transmission. Furthermore, by connecting the receiving electrode 17 to the rectifier circuit 7 (a device that converts high-frequency energy into DC), it becomes possible to charge the battery (load 9) of the mobile unit 3.

[0019] The matching circuit 1 and the transmitting side rectifier circuit 13, installed on the transmitting side (road 5) and the receiving side (mobile body 3), play a role in optimizing the impedance of the transmission path of the high-frequency power supply, coupling system (transmitting electrode 15 and receiving electrode 17), and rectifier circuit 7, and are essential devices for improving the transmission efficiency of wireless power transfer.

[0020] <Embodiment> The matching circuit of the wireless power receiving device according to the present invention will be described below with reference to the attached drawings. Figure 2 is a schematic projection showing the configuration of the matching circuit of the power receiving device according to an embodiment of the present invention. Figure 2(a) is a front view, (b) is a bottom view, and (c) is a left side view. Figure 3 is an enlarged view of the main part of Figure 2(a). As shown in Figure 3, the matching circuit 1 of the wireless power receiving device according to this embodiment is a matching circuit 1 of a wireless power receiving device mounted on an electric vehicle, connected to a first receiving electrode 17a and a second receiving electrode 17b. The matching circuit 1 comprises a plurality of metal rod-shaped bodies 19, a plurality of first coil units 21, and a second coil unit 23. As shown in Figure 2(b), the matching circuit 1 is provided in a shielded box 33 with its potential set to ground. Figures 2 and 3 depict the inside of the shielded box 33 in order to explain its internal configuration. Matching circuit 1 is connected to the first receiving electrode 17a and the second receiving electrode 17b, with wires 31a and 31b as input terminals. These wires 31a and 31b are metal wires of the same length, thickness, and material, preferably 10 cm or less in length. This length is determined by comprehensively considering various conditions, including the distance between the road 5 (and transmission electrodes) and the receiving electrodes 17a and 17b, and the distance to the bottom surface 33a of the shield box which serves as the receiving-side ground, as shown in Figure 2(b). Matching circuit 1 is also connected to a rectifier circuit (not shown) with wires 31c and 31d as output terminals.

[0021] Figure 4 is a schematic diagram showing the configuration of the first coil unit 21. As shown in the figure, the first coil unit 21 has a configuration in which multiple ring-shaped ferrite cores 21b are attached in a bead-like fashion to a metal core 21a. In Figure 4, two ferrite cores 21b are shown to illustrate the structure, but in reality, as shown in Figure 3, the ferrite cores 21b are attached so as to cover the entire metal core 21a, thus forming the first coil unit 21. The metal core 21a is a metal wire or metal pipe (non-magnetic metal such as copper, aluminum, silver, gold, tin, or SUS304) with a diameter of 3 cm or less. The ferrite cores are ring-shaped with an inner diameter of 3 cm or less and an outer diameter of 5 cm or less. The metal rod-shaped body 19 and the metal core 21a may be the same.

[0022] As shown in Figure 3, the multiple metal rods 19 and the multiple first coil units 21 are supported by a coil support 27. The multiple metal rods 19 and the multiple first coil units 21 are aligned parallel to each other with their longitudinal orientations aligned, and their ends are electrically connected in series to form an impedance. In Figure 3, the metal rods 19, the first coil units 21, and the metal rods 19 and the first coil units 21 are electrically connected via a connecting plate 29. In Figure 3, impedances L1, L1, and L3 are formed by the multiple metal rods 19 and the multiple first coil units 21. Here, the multiple metal rods 19 and the multiple first coil units 21 are provided to be interchangeable with each other. The impedances L1, L1, and L3 can be adjusted by replacing the metal rods 19 with the first coil units 21, or by replacing the first coil units 21 with the metal rods 19. Here, L1 and L2 are impedances formed symmetrically on the left and right sides. L3 is formed symmetrically on the left and right sides.

[0023] In Figure 3, impedance L1, one end of the first coil unit 21 below L1 is connected to power receiving electrodes 17a and 17b, and a series connection is started from the other end, resulting in an 8-stage connection. Of the 8 stages, 6 are the first coil unit 21 and 2 are metal rod-shaped bodies 19 made of copper pipe. Here, as mentioned above, the first coil unit 21 and the metal rod-shaped bodies 19 are connected by a connecting plate 29 made of metal. The first coil unit 21, the metal rod-shaped bodies 19 and the connecting plate 29 are supported by a coil support 27 and fixed insulated inside the shield box 33. The power receiving electrodes 17a and 17b are insulated from the shield box 33 and fixed via insulators 25.

[0024] Figure 5 is a schematic diagram showing the configuration of the second coil unit 23. The second coil unit 23 is configured by winding copper wire around a ring-shaped ferrite core 23b. In this embodiment, flat rectangular copper wire 23a is used as the copper wire. In this embodiment, copper is used as the material for the metal wire wound around the ring-shaped ferrite core 23b, but it is not limited to this, and any non-magnetic conductor material such as gold, silver, or tin may be used instead of copper. The second coil unit 23 is fixed to the substrate 23c together with the substrate wiring 23d using solder 23f. The second coil unit 23 is also electrically connected to the external wiring 23e, 23e via solder 23g, 23g. The second coil unit 23 constitutes impedances L2, L2 in Figure 3.

[0025] As shown in Figure 3, the matching circuit 1, which includes impedances L1, L1, L2, L2, and L3, is arranged symmetrically in relation to the first receiving electrode 19a and the second receiving electrode 19b.

[0026] The arrangement of the metal rod-shaped bodies 19 and the first coil unit 21 constituting L1, L1, and L3, as shown in Figure 3, is called a meander shape (meander line). Patent Document 2 and Non-Patent Document 1 disclose methods for analyzing and calculating impedance in such a meander line. Figure 6 is a schematic diagram showing the electrical characteristics modeled after this meander line. Figure 6(a) shows the overall shape model, Figure 6(b) shows a model with the resistive component and capacitive reactance separated, and Figure 6(c) shows a model with the inductive reactance separated. In this model, a meander line with length L in the longitudinal direction and width W in the transverse direction is assumed. From these dimensions L and W, and parameters such as the distance a between lines and the width b of the lines, the resistive component and capacitive reactance component shown in Figure 6(b) and the inductive reactance component shown in Figure 6(c) can be derived using the methods described in Patent Document 2 and Non-Patent Document 1.

[0027] In fact, in this embodiment, the inductive reactance X is achieved by constructing a receiving-side matching circuit using the following elements as parameters. L Adjust. (1) Diameter a [mm] of the metal wire or metal pipe used in the first coil unit 21 (2) Material and shape of ferrite core (mainly inner diameter and outer diameter) (3) Number of ferrite core connections (4) Metal wire or metal pipe, length W [mm] of the first coil unit 21 (5) Metal wire or metal pipe, number of connections n of the first coil unit 21 (number of meander-shaped stages and connection ratio) (6) Metal wire or metal pipe, spacing b [mm] between each stage of the first coil unit 21 (7) Length L determined by a[mm], b[mm] and the number of connections n

[0028] Figure 7 is an equivalent circuit showing the overall configuration of the wireless power supply system 10. On the transmitting side, a high-frequency power supply 11, a transmitting-side matching circuit 13, a first transmitting electrode 15a, and a second transmitting electrode 15b are arranged. On the receiving side, a first receiving electrode 17a, a second receiving electrode 17b, a matching circuit 1, a rectifier circuit 7, and a load 9 are arranged opposite the first transmitting electrode 15a and the second transmitting electrode 15b. The equivalent circuit including L1, L1, L2, L2, and L3 in Figure 3 is shown as matching circuit 1 in Figure 7. Here, C is the parasitic capacitance between lines calculated from the meander line analysis. In this embodiment, a capacitance unit is not provided, but it may be added as needed.

[0029] As described above, the matching circuit 1 of the wireless power supply receiving device in this embodiment comprises a plurality of metal rod-shaped bodies 19 and a plurality of first coil units 21 in which a plurality of ring-shaped ferrite cores 21b are attached in a bead-like manner to a metal core 21a. The plurality of metal rod-shaped bodies 19 and the plurality of first coil units 21 are arranged in a meander shape to form an impedance. In addition, a second coil unit 23 in which a flat copper wire 23a constituting the inductance is wound around a ring-shaped ferrite core 23b is also used, making it possible to make the impedance unit including the inductance thinner, smaller, and lighter.

[0030] Figure 8 shows the structure of a conventional variable matching circuit 100, and Figure 9 shows the structure of a conventional matching circuit 110. As shown in the figures, in the conventional example, the coil L constituting the inductance uses a coil made by winding metal wire and metal pipe in a solenoid shape to obtain the desired inductance. Because these coils are solenoid shaped, they require a large thickness. In the present invention, such a coil L is not used, and the inductance is obtained by a plurality of metal rod-shaped bodies 19, a plurality of first coil units 21, and a second coil unit 23, making it possible to make the circuit thinner. As the inductance components become thinner, the power supply unit also becomes thinner. This makes it easier to attach to the bottom of the mobile unit. Therefore, it is possible to provide a matching circuit for a wireless power supply receiving device that can be miniaturized and lightened without reducing power supply efficiency by using components with desired circuit constants.

[0031] The metal rod-shaped body 19 and the first coil unit 21 are mutually interchangeable, making it easy to adjust the impedance by replacing them. Furthermore, the circuit including multiple metal rod-shaped bodies 19, multiple first coil units 21, and second coil unit 23 is arranged symmetrically on the first power receiving electrode 19a side and the second power receiving electrode 19b side, thus achieving a configuration that minimizes the reduction in power supply efficiency as a matching circuit. In addition, the first coil unit 21 and second coil unit 23 used as inductance do not require the metal wire and metal pipe to be processed into a spiral shape, as shown in coil L in Figures 8 and 9, making them easy to manufacture and allowing them to be constructed to the same dimensions with high precision as they do not have complex shapes. Therefore, it is possible to contribute to improved symmetry.

[0032] In this embodiment, a circuit using units L1, L1, L2, L2, and L3 was used as the matching circuit 1, but the invention is not limited to this, and other circuit configurations can be realized using a metal rod-shaped body 19, a first coil unit 21, and a second coil unit 23. Therefore, in addition to the above embodiment, it is possible to select or change the configurations listed above as appropriate, as long as it does not depart from the spirit of the present invention. [Explanation of Symbols]

[0033] 1. Matching circuit for wireless power supply receiving device 17a First receiving electrode 17b Second receiving electrode 19 Metal rod-shaped body 21 First coil unit 21a metal core 21b Ferrite core 23 Second coil unit 23a copper wire (flat copper wire) 23b Ring-shaped ferrite core

Claims

1. A matching circuit for a wireless power supply receiving device mounted on an electric vehicle, which is connected to a first power receiving electrode and a second power receiving electrode, Multiple metal rod-shaped bodies, It comprises a plurality of first coil units, each having multiple ring-shaped ferrite cores attached in a bead-like fashion to a metal core, A matching circuit for a wireless power supply receiving device, wherein the plurality of metal rod-shaped bodies and the plurality of first coil units are aligned parallel to each other with their longitudinal orientations aligned, and their ends are connected in series to form an impedance.

2. Matching circuit for wireless power receiving device according to claim 1, wherein the plurality of metal rod-shaped bodies and the plurality of first coil units are arranged to be interchangeable with one another.

3. Matching circuit for a wireless power supply receiving device according to claim 1 or 2, comprising a second coil unit in which copper wire is wound around a ring-shaped ferrite core.

4. Matching circuit for wireless power supply receiving device according to claim 3, wherein the circuit including the plurality of metal rod-shaped bodies, the plurality of first coil units, and the second coil unit is arranged symmetrically on the first power receiving electrode side and the second power receiving electrode side.

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