Power transmission coil structure and power transmission device having the same

Abstract

The present invention provides a power transmission coil structure and a power transmission device having the same. The power transmission coil structure can suppress the proximity effect generated between the wires of the coil, and effectively gather the magnetic flux generated from the coil to improve the transmission efficiency. The power transmission coil structure

Description

[Technical Field]

[0001] The present invention relates to a power transmission coil structure for supplying or receiving power and a power transmission device having the same. [Previous Technology]

[0002] In recent years, there has been anticipation for power transmission devices utilizing electromagnetic induction to charge the batteries of vehicles such as electric vehicles and plug-in hybrid electric vehicles. Typically, a power transmission device includes a power supply coil and a power receiving coil. Power is transmitted by flowing a high-frequency alternating current through the power supply coil and receiving a high-frequency magnetic field generated at that time. In recent years, to meet the requirement of overall thinness in such power transmission devices, various schemes have been proposed using coils formed by winding multiple coil wires in a spiral shape.

[0003] Typically, in such coils, because multiple coil wires are close to each other, eddy currents are generated between adjacent wires by the magnetic field formed by the wires, causing a proximity effect. As a result, at high frequencies, the resistance of the coil increases, leading to increased eddy current losses, and thus a tendency for the transmission efficiency of the power transmission device to decrease. Therefore, for example, Patent Document 1 proposes a power transmission device to suppress the decrease in transmission efficiency. Specifically, in Patent Document 1, at least one magnetic layer, including a magnetic layer located on at least one surface of the secondary receiving coil, a shielding layer for blocking electromagnetic noise, and a heat insulation layer, is integrally stacked on the secondary receiving coil, and the magnetic layer is embedded in the gaps between the strands of the secondary receiving coil. As a result, good transmission efficiency can be ensured in the power transmission device.

[0004] Furthermore, Patent Document 2 discloses a power transmission device comprising a receiving coil and a green compact made of magnetic material powder. This power transmission device is configured such that the receiving coil is embedded in the magnetic material powder, and the density of the green compact near the receiving coil differs from that of the surrounding compact, thereby increasing the permeability of the high-density green compact. Prior Art Documents Patent Documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-294385; Patent Document 2: Japanese Patent Application Publication No. 2009-5474 [Summary of the Invention]

[0006] -The problem that the invention aims to solve-

[0007] In the case of the power transmission device shown in Patent Documents 1 and 2, as described above, a good transmission efficiency can be ensured by burying a magnetic layer in the gap between the coil wires. However, there is still a need for a power transmission device that can further improve the transmission efficiency. For this purpose, a coil structure that can suppress the proximity effect between adjacent coil wires and effectively concentrate the magnetic flux generated from the coil is required.

[0008] The present invention has been made in view of the above-mentioned problems, and its object is to provide a power transmission coil structure and a power transmission device having the same, wherein the power transmission coil structure can suppress eddy current losses caused by the proximity effect between the coil's conductors, and effectively concentrate the magnetic flux generated from the coil, thereby improving transmission efficiency. -Solution to the problem-

[0009] In order to achieve the above objective, in the present invention, a coil is disposed on the surface of a magnetic body, and another magnetic body with a relative permeability greater than that of the magnetic body is disposed around it.

[0010] Specifically, the power transmission coil structure of the present invention is a power transmission coil structure for receiving or supplying power, characterized in that the power transmission coil structure includes: a first magnetic body in the shape of a flat plate; a second magnetic body, including a central magnetic body disposed at the center of the surface of the first magnetic body and an outer peripheral magnetic body disposed at the outer periphery of the surface of the first magnetic body; a third magnetic body disposed between the central magnetic body and the outer peripheral magnetic body; and a coil disposed on the surface of the third magnetic body and wound around the central magnetic body. The second magnetic body has a relative permeability that is more than three times higher than that of the third magnetic body.

[0011] According to the power transmission coil structure of the present invention, by arranging a coil on the surface of a third magnetic body disposed between the central magnetic body and the outer peripheral magnetic body, and by having a third magnetic body between adjacent coil wires, the proximity effect caused by eddy currents generated between adjacent coil wires can be suppressed. This reduces the coil resistance and suppresses the increase in eddy current losses. Furthermore, in the power transmission coil structure of the present invention, since the second magnetic body has a relative permeability more than three times higher than the third magnetic body, magnetic bodies with high relative permeability are arranged on the inner and outer sides of the coil, creating a difference in relative permeability between the inner and outer sides of the coil and the coil wires. This suppresses the diffusion of magnetic flux generated from the coil, thereby concentrating the magnetic flux to the inner side of the coil. Therefore, according to the power transmission coil structure of the present invention, eddy current losses caused by proximity effects generated between coil wires are suppressed, and magnetic flux generated from the coil is effectively concentrated, resulting in excellent transmission efficiency.

[0012] In the power transmission coil structure of the present invention, preferably, the relative permeability of the third magnetic body is greater than 1 and less than or equal to 10.

[0013] As a result, a difference in relative permeability will be generated between the wires of the coil and around the coil, thereby enabling the concentration of magnetic flux generated from the coil.

[0014] In the power transmission coil structure of the present invention, preferably, in the thickness direction of the first magnetic body, the outer peripheral magnetic body protrudes more than the third magnetic body.

[0015] As a result, since the diffusion of magnetic flux generated from the coil can be suppressed, the magnetic flux generated from the coil can be more effectively concentrated to the inside of the coil.

[0016] In addition, another object of the present invention is a power transmission device, characterized in that the power transmission device has any of the above-described power transmission coil structures.

[0017] Because such a power transmission device possesses the power transmission coil structure described above, it can suppress the proximity effect between coil conductors and suppress eddy current losses in the coil, and can also effectively concentrate the magnetic flux generated from the coil, thus achieving excellent transmission efficiency. -Effects of the Invention-

[0018] According to the power transmission coil structure of the present invention, the proximity effect caused by eddy currents generated between coil conductors can be suppressed, and the magnetic flux generated from the coil can be effectively concentrated to improve the transmission efficiency of the power transmission device.

Implementation Method

[0020] Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. In the drawings, illustrations of external connection terminals are omitted. The following description of preferred embodiments is merely illustrative and is not intended to limit the present invention, its applicable methods, or its uses.

[0021] First, a power transmission coil structure 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a top view of the power transmission coil structure 1 viewed from the top surface side, and FIG. 2 shows a cross-section along line II-II in FIG. 1. As shown in FIGS. 1 and 2, the power transmission coil structure 1 according to this embodiment has a flat first magnetic body 10 disposed on the surface of a substrate 2 made of a conductive material such as aluminum, and a second magnetic body 20 disposed on the surface of the first magnetic body 10. Specifically, the second magnetic body 20 is composed of a central magnetic body 21 and an outer peripheral magnetic body 22. The central magnetic body 21 is disposed at the center of the surface of the first magnetic body 10, and the outer peripheral magnetic body 22 is disposed at the outer periphery of the surface of the first magnetic body 10. A third magnetic body 30 is disposed between the central magnetic body 21 and the outer peripheral magnetic body 22, and a coil 40 formed around the central magnetic body 21 is disposed on the surface of the third magnetic body 30. As shown in FIG. 1, the coil 40 is wound at approximately a right angle along the shape of the outer peripheral magnetic body 22. It should be noted that in Figure 2, the coil 40 is arranged flush with the surface of the third magnetic body 30, but this is not a limitation. It is acceptable as long as the entire circumference or at least a portion of the coil 40 is disposed within a recess formed on the surface of the third magnetic body 30, allowing the entire coil 40 to be seen from the upper surface. Furthermore, although the cross-sectional shape of the coil 40 is represented by a rectangle, it is not limited to a rectangle and can also be circular or other polygonal. Additionally, the number of turns and the winding direction of the coil 40 are not particularly limited. Furthermore, a through-hole for connecting the coil wire pattern to an external terminal may also be provided on the first magnetic body 10.

[0022] The magnetic materials used for the first magnetic body 10 and the second magnetic body 20 are not particularly limited. For example, Mn-Zn ferrite, Ni-Zn ferrite, metallic amorphous magnetic material, ribbon nanocrystal alloy magnetic material, etc. can be used. The first magnetic body 10 and the second magnetic body 20 can be integrally formed or made as independent components.

[0023] The magnetic material used as the third magnetic body 30 is not particularly limited, and for example, a resin compound of Mn-Zn ferrite powder or Ni-Zn ferrite powder can be used. In this embodiment, since the coil 40 is disposed on the surface of the third magnetic body 30, the irregularities are formed along the shape of the coil wire, for example, by casting.

[0024] The magnetic material used in this embodiment is preferably a soft magnetic material with a large real part (μ') and a small imaginary part (μ") of permeability at the frequency used. Preferably, it is a sintered sheet of a metal-based soft magnetic powder mixed with resin and formed into a sheet, a spinel-based magnetic ferrite, or a flexible composite magnetic sheet with a resin film attached to the sintered sheet. When used in the frequency band around 100kHz, such as for EV contactless power supply applications, it is preferably a Mn-Zn ferrite or a Ni-Zn ferrite.

[0025] The magnetic material used in this embodiment is preferably capable of withstanding both high and low temperature environments. Therefore, it is preferable to use a thermosetting resin together with the aforementioned magnetic material material such as ferrite to form the magnetic material used in this embodiment. The thermosetting resin is, for example, polyurethane resin, silicone resin, epoxy resin, etc., but is not limited thereto.

[0026] There are no particular limitations on the material used for coil 40. For example, conductive materials such as silver, copper, or silver-containing alloys can be used. Coil 40 is formed into a flat plate shape. When using wire, it can be a rectangular wire, a round wire, or a Litz wire made of multiple strands twisted together.

[0027] In the power transmission coil structure 1 according to this embodiment, as described above, a third magnetic body 30 is provided between the central magnetic body 21 and the outer peripheral magnetic body 22. In particular, the relative permeability of the second magnetic body 20, which is composed of the central magnetic body 21 and the outer peripheral magnetic body 22, is more than three times the relative permeability of the third magnetic body 30. This suppresses the diffusion of magnetic flux generated from the coil 40 and concentrates the magnetic flux within the coil 40. Therefore, the transmission efficiency of the power transmission device can be improved. In this embodiment, the relative permeability of the second magnetic body 20 is preferably more than 50 times the relative permeability of the third magnetic body 30, and more preferably more than 100 times. It should be noted that as long as the relative permeability of the second magnetic body meets the above range, the relative permeabilities of the central magnetic body 21 and the outer peripheral magnetic body 22 can be different. Furthermore, the relative permeability of the second magnetic body 20 is preferably less than or equal to the relative permeability of the first magnetic body 10.

[0028] In this embodiment, the first magnetic body 10 and the second magnetic body 20 have a high magnetic material content, while the third magnetic body 30 has a low magnetic material content. Therefore, the relative permeability of the third magnetic body 30 is adjusted to be less than one-third of the relative permeability of the first magnetic body 10 and the second magnetic body 20.

[0029] In this embodiment, the relative permeability of the third magnetic body 30 is preferably greater than 1 and less than or equal to 10. As a result, a difference in relative permeability is generated between the wires of the coil 40 and around the coil 40, thereby effectively concentrating the magnetic flux generated from the coil 40.

[0030] In this embodiment, preferably, in the thickness direction of the first magnetic body 10, the outer peripheral magnetic body 22 is formed to protrude beyond the third magnetic body 30. This suppresses the diffusion of magnetic flux generated from the coil 40, thus allowing the magnetic flux generated from the coil 40 to be more effectively concentrated inside the coil 40.

[0031] In another embodiment of the present invention, the first magnetic body 10, the second magnetic body 20 and the third magnetic body 30 may be magnetic bodies with different compositions and different relative permeabilities, and the content of the magnetic bodies may be the same.

[0032] Another embodiment of the present invention is a power transmission device having the above-described power transmission coil structure. In addition to the power transmission coil structure, the power transmission device also includes external terminals for connection to other external devices, a power supply for supplying current to the conductors, etc. Because this power transmission device has the above-described power transmission coil structure, as described above, the proximity effect caused by eddy currents between the coil conductors can be suppressed, and the magnetic flux generated from the coil can be effectively concentrated, thus ensuring good transmission efficiency of the power transmission device.

[0033] Next, the manufacturing method of the power transmission coil structure will be described. First, the first magnetic body 10 and the second magnetic body 20 are processed into the desired shape and disposed on the surface of the substrate 2. More specifically, a shaped body is formed on the surface of the substrate 2 by using a method of sintering a sintered body of magnetic powder formed by pressing and shaping, a method of mixing pre-burnt magnetic powder with resin and processing it into a predetermined shape and then sintering it, or a method of mixing sintered magnetic powder with resin and processing it into a predetermined shape, etc., consisting of a flat first magnetic body 10 as shown in FIG1 and a second magnetic body 20 including a central magnetic body 21 and an outer peripheral magnetic body 22 respectively disposed in the central part and the outer peripheral part of the first magnetic body 10. Here, the shaped body consisting of the first magnetic body 10 and the second magnetic body 20 can be integrally formed or formed as independent components.

[0034] Next, a third magnetic body 30 is formed between the central magnetic body 21 and the outer peripheral magnetic body 22 disposed on the surface of the first magnetic body 10. Specifically, Mn-Zn ferrite powder or Ni-Zn ferrite powder is mixed with resin (epoxy resin, polyurethane resin, silicone resin, etc.), and the irregularities are formed along the wire shape of the coil 40 described later by means of, for example, casting. For example, in order to form a spiral coil 40 surrounding the central magnetic body 21, it is preferable to form the spiral recess on the third magnetic body 30. In this embodiment, the first magnetic body 10 and the second magnetic body 20 have a structure with a higher magnetic body content, and the third magnetic body 30 has a structure with a lower magnetic body content. As a result, the relative permeability of the first magnetic body 10 and the second magnetic body 20 is adjusted to be more than three times the relative permeability of the third magnetic body 30.

[0035] Next, a coil 40 is disposed on the surface of the third magnetic body 30. As shown in FIG1, the coil 40 is wound around the central magnetic body 21 and bent at approximately a right angle along the shape of the outer peripheral magnetic body 22. For example, as described above, a spiral-shaped recess is pre-made on the surface of the third magnetic body 30, and then the coil 40 is disposed by forming the coil 40 in the recess. Through the above steps, the power transmission coil structure 1 shown in FIG1 is obtained.

[0036] As described above, according to the power transmission coil structure 1 of this embodiment, the coil 40 is disposed on the surface of the third magnetic body 30, and the third magnetic body exists between adjacent coil wires, thereby suppressing the proximity effect caused by eddy currents generated between adjacent coil wires. As a result, the resistance of the coil 40 can be reduced, and the increase of eddy current loss can be suppressed. Furthermore, since the second magnetic body 20 has a relative permeability that is more than three times higher than that of the third magnetic body 30, a difference in relative permeability is generated between the inner and outer sides of the coil 40 and the coil wires, thereby suppressing the diffusion of magnetic flux generated from the coil 40. As a result, the magnetic flux can be concentrated inside the coil 40. Therefore, according to the power transmission coil structure 1 of the present invention, the proximity effect caused by eddy currents generated between the wires of the coil 40 can be suppressed, the magnetic flux generated from the coil 40 can be effectively concentrated, and the transmission efficiency of the power transmission device can be improved. Embodiment

[0037] Hereinafter, embodiments and comparative examples of the present invention will be described. These embodiments are examples of the present invention and do not limit the scope of the present invention. In this embodiment, as shown below, various power transmission coil structures within the scope of the present invention and power transmission coil structures outside the scope of the present invention are fabricated, and the transmission efficiency when using each coil structure is evaluated.

[0038] Example 1: The pressed and sintered Mn-Zn ferrite sintered body was machined into a specified shape to form a sintered body having the first and second magnetic body structures shown in FIG. 2. Next, Mn-Zn ferrite powder was mixed with a two-component epoxy resin to achieve a Mn-Zn ferrite powder content of 50% by weight, and then cast to form concave and convex shapes corresponding to the shape of the coil wire, forming a third magnetic body between the central magnetic body and the outer peripheral magnetic body of the second magnetic body. Then, a coil was formed on the third magnetic body using Litz wire to manufacture a power transmission coil structure.

[0039] Example 2: 80% by weight of Mn-Zn ferrite powder, 10% by weight of cellulose resin, and the balance water were mixed and extruded into sheets using a vacuum extrusion molding machine. The sheets were then processed into a specified shape and sintered to form a sintered body having the first and second magnetic body structures shown in FIG. 2. Then, as in Example 1, a third magnetic body was combined with a coil to manufacture a power transmission coil structure.

[0040] Example 3: The pressed and sintered Mn-Zn ferrite sintered body was cut into a specified shape to form the first magnetic body with the structure shown in Figure 2. Additionally, Mn-Zn ferrite powder was mixed with silicone resin to achieve a Mn-Zn ferrite content of 80% by weight, processed into sheets, and then further processed into specified shapes to form the second magnetic body with the structure shown in Figure 2. Then, similar to Example 1, the third magnetic body was combined with a coil to manufacture a power transmission coil structure.

[0041] Example 4: A Mn-Zn ferrite sintered body, formed by pressing and sintering powder, is machined into a predetermined shape to form a first magnetic body with the structure shown in FIG2. Additionally, a Ni-Zn ferrite sintered body, formed by pressing and sintering powder, is machined into a predetermined shape to form a second magnetic body with the structure shown in FIG2. Then, similar to Example 1, a third magnetic body is combined with a coil to manufacture a power transmission coil structure.

[0042] Example 5: Fe-based amorphous soft magnetic material was made into sheets, and the sheets, which were stacked into a specified shape, were cut to form the first magnetic body and the second magnetic body with the structure shown in Figure 2. Then, in the same manner as in Example 1, the third magnetic body was combined with a coil to manufacture a power transmission coil structure.

[0043] Example 6: Nanocrystalline soft magnetic material is made into sheets, and the sheets stacked into a specified shape are cut to form the first magnetic body and the second magnetic body with the structure shown in FIG2. Then, in the same manner as in Example 1, the third magnetic body is combined with a coil to manufacture a power transmission coil structure.

[0044] Comparative Example 1: A first magnetic body is formed from a Mn-Zn ferrite sintered body formed by pressing and sintering, and a third magnetic body part is processed using vinyl chloride resin as a non-magnetic body. A second magnetic body is not provided, and a power transmission coil structure is manufactured.

[0045] Comparative Example 2: A first magnetic body and a second magnetic body were formed in the same manner as in Example 1. The third magnetic body portion was processed using vinyl chloride resin, which is a non-magnetic body, to manufacture an electric transmission coil structure.

[0046] Comparative Example 3: A first magnetic body with the structure shown in FIG2 was formed from a Mn-Zn ferrite sintered body formed by pressing and sintering powder. The second magnetic body structure shown in FIG2 was formed using the material and method for forming the third magnetic body in Example 1. The third magnetic body was processed in the same way as in Example 1 to manufacture a power transmission coil structure.

[0047] Comparative Example 4: A first magnetic body with the structure shown in Figure 2 was formed from a sintered Mn-Zn ferrite body formed by pressing and sintering powder. Mn-Zn ferrite powder was mixed with a two-component epoxy resin to make the content of Mn-Zn ferrite powder after mixing reach 50% by weight, forming a second magnetic body with the structure shown in Figure 2. 10% by weight of Mn-Zn ferrite powder was mixed with a two-component epoxy resin and cast to form concave and convex shapes corresponding to the shape of the coil wire, forming a third magnetic body with the structure shown in Figure 2, thus manufacturing a power transmission coil structure.

[0048] The relative permeability was determined using an impedance analyzer. In this determination, the same magnetic material as that used in the examples and comparative examples was used to prepare a ring-shaped sample with an outer core diameter of 31.9 mm, an inner core diameter of 18.9 mm, and a core height of 5.41 mm. 1 mm copper wire was wound around the sample 22 times, and the relative permeability was measured.

[0049] Measurement of Transmission Efficiency: The power supply coil adopted the coil structure of Comparative Example 1, and the receiving coil adopted the coil structure manufactured in each embodiment and comparative example. Power converted to AC by the inverter circuit was input to the power supply coil side, and the power received by the receiving coil was measured to evaluate the transmission efficiency. The evaluation is expressed as follows: when the transmission efficiency of the coil structure of Comparative Example 1 is used for both the power supply coil and the receiving coil, it is set to 100, and the ratio of the transmission efficiency of each embodiment and comparative example to that efficiency is given.

[0050] Table 1 shows the measurement results of the relative permeability of the first magnetic body, the second magnetic body and the third magnetic body in each embodiment and comparative example, as well as the evaluation results of the transmission efficiency of the coil structure in each embodiment and comparative example.

[0051] Table 1 Relative permeability (μ') Transmission efficiency (ratio to Comparative Example 1) First magnetic body Second magnetic body Third magnetic body η Example 1 3400 3400 5 121 Example 2 2000 2000 5 113 Example 3 3400 20 5 109 Example 4 3400 400 5 111 Example 5 6000 6000 5 113 Example 6 9000 9000 5 116 Comparative Example 1 3400 - 1 100 Comparative Example 2 3400 3400 1 103 Comparative Example 3 3400 5 5 104 Comparative Example 4 3400 5 2 103

[0052] As shown in Table 1, it is evident that compared to the coil structures in the comparative examples where the second magnetic body 20 is not configured or where the relative permeability of the second magnetic body 20 is less than three times the relative permeability of the third magnetic body 30, the coil structures in each embodiment where the relative permeability of the second magnetic body 20 is more than three times that of the third magnetic body 30 improve transmission efficiency. Therefore, when using the power transmission coil structures of each embodiment, the magnetic flux generated from the coil can be effectively concentrated, ensuring good transmission efficiency when applied to power transmission devices.

[0053] As described above, the power transmission coil structure of the present invention can suppress the proximity effect caused by eddy currents between coil conductors and effectively concentrate the magnetic flux generated from the coil, thereby improving the transmission efficiency of the power transmission device, which is very useful. [Simplified Explanation of the Diagram]

[0019] FIG1 is a top view of a power transmission coil structure according to an embodiment of the present invention, viewed from the top surface side. FIG2 is a cross-sectional view of a power transmission coil structure according to an embodiment of the present invention at line II-II in FIG1.

Claims

1. A power transmission coil structure, which is used for receiving or supplying power, wherein, The power transmission coil structure includes: a first magnetic body in the shape of a flat plate; a second magnetic body including a central magnetic body disposed at the center of the surface of the first magnetic body and an outer peripheral magnetic body disposed at the outer periphery of the surface of the first magnetic body; a third magnetic body disposed between the central magnetic body and the outer peripheral magnetic body; and a coil disposed on the surface of the third magnetic body and wound around the central magnetic body; the second magnetic body has a relative permeability that is more than three times higher than that of the third magnetic body.

2. The power transmission coil structure as described in claim 1, wherein, The relative permeability of the third magnetic material is greater than 1 and less than or equal to 10.

3. The power transmission coil structure as requested in item 1 or 2, wherein, In the thickness direction of the first magnetic body, the outer peripheral magnetic body protrudes more than the third magnetic body.

4. A power transmission device, wherein, The power transmission device has a power transmission coil structure as described in any of claims 1 to 3.

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