Magnetic coil and wireless power supply device

Abstract

To improve heat dissipation in a magnetic coil including a coil and a magnetic composite material.SOLUTION: A magnetic coil includes a flat, planar coil in which wire is wound in a spiral shape and which has a first coil surface and a second coil surface that is the back side of the first coil surface, and a magnetic portion that covers the planar coil and is made of a magnetic composite material having a resin material and soft magnetic particles contained in the resin material, and at least the first surface that covers the first coil surface does not expose the soft magnetic particles.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to magnetic coils that include planar coils and magnetic composite materials. [Background technology]

[0002] Conventionally, Litz wire or flat coils have been used for wireless power supply coils in electric vehicles, and studies are being conducted to reduce AC resistance and achieve highly efficient power transmission. For example, in the technology described in Patent Document 1, a planar coil is enclosed in a holder containing resin and magnetic particles, suppressing magnetic eddy current loss and leakage flux of the holder. In the technology described in Patent Document 2, an adhesive layer is provided on the outer surface of a conductor used in the coil, and a magnetic powder layer is provided in which magnetic powder is fixed by the adhesive layer. In addition, in the technology described in Non-Patent Document 1, a magnetic composite material (also called a magnetic composite material) made by blending magnetic particles with silicone resin is used to form a magnetic layer on the surface of a flat coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7232960 [Patent Document 2] Japanese Patent Application Publication No. 2018-018585 [Non-patent literature]

[0004] [Non-Patent Document 1] Shun Endo, Takahiro Kasai, Takeshi Utsubo, Tsutomu Mizuno, "Lightweight and Efficient Wireless Power Transfer Coils Using Magnetically Coated Aluminum Plates," IEICE Technical Report, vol.117, no.383, WPT2017-66(2018-01), pp.59-64 Summary of the Invention [Problem to be solved by the invention]

[0005] When receiving power, the coil generates heat due to AC resistance. In the above patent and non-patent documents, the AC resistance is reduced by forming a magnetic layer, but the AC resistance still exists and generates heat. Therefore, there is a need to improve the heat dissipation performance of a magnetic coil that includes a coil and a magnetic composite material.

[0006] Such a problem relating to heat dissipation is a common problem for magnetic members including magnetic coils, wireless power supply devices including such magnetic members, and apparatuses using magnetic coils. [Means for solving the problem]

[0007] The present disclosure can be realized in the following forms. (1) According to one embodiment of the present disclosure, there is provided a magnetic coil comprising: a flat, planar coil formed by spirally winding a wire material and having a first coil surface and a second coil surface that is a reverse side of the first coil surface; and a magnetic part covering the planar coil, the magnetic part being made of a magnetic composite material having a resin material and soft magnetic particles contained in the resin material, wherein at least a first surface of the magnetic part that covers the first coil surface does not expose the soft magnetic particles.

[0008] With this type of magnetic coil, the soft magnetic particles are not exposed on the first surface of the magnetic part. The soft magnetic particles are made of metal and have a lower emissivity (also called emissivity) than resin materials, so the emissivity of the first surface can be improved compared to when the soft magnetic particles are exposed on the first surface. Heat dissipation by radiation is proportional to the fourth power of the absolute temperature, and heat can also be dissipated into the air, so improving the surface emissivity has a significant effect on improving heat dissipation. In other words, with this type of magnetic coil, heat dissipation by radiation on the first surface of the magnetic part can be increased, improving the cooling effect.

[0009] (2) In the magnetic coil of the above aspect, the soft magnetic particles may have an average particle size of 50 μm or less, which makes it possible to suppress eddy currents caused by changes in the magnetic field and the heat generated thereby.

[0010] (3) In the magnetic coil of the above embodiment, the thermal conductivity of the magnetic composite material may be 0.8 W / mK or more. In this case, the high thermal conductivity of the magnetic composite material can improve heat dissipation from the magnetic shielding layer on which the magnetic coil is provided on the magnetic part and from the heat sink joined to the magnetic shielding layer.

[0011] (4) In the magnetic coil of the above aspect, the thickness between the first surface and the first coil surface of the planar coil in the magnetic part may be 1 mm or less. This also reduces the thermal resistance of the magnetic part and improves heat dissipation from the magnetic shielding layer and the heat sink joined to the magnetic shielding layer.

[0012] (5) In the magnetic coil of the above embodiment, the cross-sectional shape of the wire of the planar coil may be substantially rectangular. In this way, compared with a planar coil using wire with a circular cross-sectional shape, the area facing the heat sink or space can be increased, and heat dissipation by heat transfer or radiation can be improved.

[0013] (6) According to another aspect of the present disclosure, there is provided a wireless power supply device. The wireless power supply device includes the magnetic coil of the above aspect and a circuit board electrically connected to the planar coil for supplying AC power to the planar coil or for supplying power generated by the planar coil to a load. The wireless power supply device of this aspect includes the magnetic coil of the above aspect, thereby improving the heat dissipation performance of the wireless power supply device.

[0014] The present disclosure can be realized in various forms other than those described above, such as a method for manufacturing a magnetic coil, a wireless power supply method using a magnetic coil, a vehicle using a magnetic coil, a moving body using a magnetic coil, etc. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an explanatory diagram conceptually showing a planar configuration of a magnetic coil according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is an explanatory diagram conceptually showing a cross-sectional configuration of a magnetic coil. [Figure 3] FIG. 2 is an explanatory diagram conceptually showing an enlarged cross-sectional configuration of a magnetic coil. [Figure 4] FIG. 10 is a diagram showing an example of the range of increase in coil temperature. [Figure 5] FIG. 10 is a diagram showing the relationship between the thickness of a magnetic layer and the resistance. [Figure 6] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a magnetic composite material. [Figure 7] FIG. 10 is a diagram showing the relationship between particle diameter and eddy current loss. [Figure 8] FIG. 2 is a diagram showing an example of particle size distribution of soft magnetic particles. [Figure 9] FIG. 10 is a diagram showing the results of SEM observation of a cross section of a magnetic part. [Figure 10] FIG. 2 is an explanatory diagram conceptually showing the configuration of a magnetic member. [Figure 11] FIG. 2 is a diagram showing the relationship between the content of soft magnetic powder and thermal conductivity. [Figure 12] 5A to 5C are explanatory diagrams showing an example of a manufacturing method of the magnetic coil of the present embodiment. [Figure 13] 1 is an explanatory diagram illustrating a schematic configuration of a wireless power supply system including a magnetic member including a magnetic coil. [Figure 14] FIG. 2 is an explanatory diagram schematically illustrating the arrangement of magnetic coils. [Figure 15] 10A and 10B are cross-sectional views illustrating an operation of wirelessly feeding power using the wireless power feeding system. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Embodiment> A. Magnetic coil configuration: FIG. 1 is an explanatory diagram conceptually illustrating the planar configuration of a magnetic coil 41 according to an embodiment of the present disclosure. The drawing shows mutually orthogonal X, Y, and Z axes to identify directions. For convenience, the positive Z-axis direction will be referred to as the upward direction, and the negative Z-axis direction will be referred to as the downward direction. As shown in the figure, the magnetic coil 41 includes a planar coil 42 formed by spirally wound wire 42L, and a magnetic portion 48 made of a magnetic composite material 10 and covering the planar coil 42. Temperature measurement positions, which will be described later, are also shown in FIG. 1.

[0017] The planar coil 42 is a plate-shaped coil made of metal such as aluminum or copper. The use of a planar coil (also called a plate-shaped coil) can contribute to weight reduction, thickness reduction, high efficiency power transmission, and reduction of the AC resistance of the coil. The magnetic composite material 10 includes a resin material 12 and soft magnetic particles 14 (described in detail below).

[0018] FIG. 2 is an explanatory diagram conceptually illustrating the cross-sectional configuration of magnetic coil 41. FIG. 2 shows the AA cross section in FIG. 1. Planar coil 42 is formed of a metal such as copper and has a flat plate shape with a first coil surface SC1 and a second coil surface SC2 that is the back surface of first coil surface SC1. Using a planar coil (also called a plate-shaped coil) can contribute to weight reduction, thinning, high power transmission efficiency, and reduced AC resistance of the coil. Magnetic portion 48 covers planar coil 42 and has a first surface S1 that covers first coil surface SC1 of planar coil 42 and a second surface S2 that covers second coil surface SC2 of planar coil 42.

[0019] In the example shown in Fig. 2, the cross-sectional shape of the wire 42L of the planar coil 42 is substantially rectangular. In other examples, the cross-sectional shape of the wire of the planar coil may be circular, elliptical, or polygonal, such as triangular, pentagonal, or hexagonal. When the cross-sectional shape of the wire 42L of the planar coil 42 is substantially rectangular, the area facing the heat sink or space can be increased compared to a planar coil using wire with a circular cross-sectional shape, thereby improving heat dissipation by heat transfer and radiation. The term "substantially" rectangular is a concept that includes rectangles with chamfered corners, etc.

[0020] FIG. 3 is an explanatory diagram conceptually illustrating an enlarged cross-sectional configuration of a magnetic coil 41. FIG. 3 shows an enlarged view of the X portion in FIG. 2. As shown in the figure, a magnetic composite material 10 includes a resin material 12 and soft magnetic particles 14 contained in the resin material 12. In the magnetic composite material 10 of this embodiment, the soft magnetic particles 14 are dispersed in the resin material 12 in the form of powder particles. As shown in FIG. 3, in the magnetic coil 41, the magnetic composite material 10 is filled between adjacent wires 42L. If the magnetic composite material 10 is not filled between adjacent wires 42L and air is introduced, the state of the magnetic field may change and the magnetic field may leak. However, in this configuration, the magnetic field leakage can be suppressed, and a decrease in power transmission efficiency can be suppressed.

[0021] Furthermore, the soft magnetic particles 14 are not exposed on at least the first surface S1 of the magnetic portion 48 of the magnetic coil 41. In the example shown in FIG.

[0022] As will be described in detail later, the soft magnetic particles 14 are made of metal and have a lower emissivity (also called emissivity) than the resin material 12. For example, the emissivities of iron, copper, and a resin material (elastomer) are as follows: Iron (unoxidized): 0.05 Copper (rough polish): 0.07 Copper (glossy): 0.02 Elastomer: 0.8 or higher

[0023] In the magnetic coil 41 of this embodiment, the first surface S1 of the magnetic portion 48 does not expose the soft magnetic particles 14, and therefore the emissivity of the first surface S1 can be improved compared to when the soft magnetic particles 14 are exposed. Heat dissipation by radiation is proportional to the fourth power of the absolute temperature, and heat can also be dissipated into the air, so improving the surface emissivity is highly effective in improving heat dissipation. In other words, with the magnetic coil of this embodiment, heat dissipation by radiation on the surface of the magnetic portion 48 can be increased, and the cooling effect can be improved. Arranging the first surface S1 of the magnetic coil 41 so that it is in contact with the air is preferable because heat dissipation by radiation can be improved.

[0024] FIG. 4 shows an example of the range of coil temperature rise. FIG. 4 shows the results of measuring temperature changes during charging in a wireless power supply device, as described below, constructed using the magnetic coil 41 of this embodiment, simulating a charging situation between a road surface and a vehicle. In this example, a 4.0 kW power was transmitted using a magnetic portion 48 with an unpolished surface (soft magnetic particles 14 not exposed on the surface) and a polished surface (soft magnetic particles 14 exposed on the surface), and the temperature rise from room temperature was measured. Here, the "inside" refers to the surface of the magnetic composite material 10 containing the innermost conductor of the spiral coil, and the "outside" refers to the surface of the magnetic composite material 10 containing the outermost conductor of the spiral coil. FIG. 1 shows an inner measurement point P1 and an outer measurement point P2. A known fluorescent optical fiber temperature sensor was used to measure the temperature.

[0025] When the surface of the magnetic part 48 was polished to smooth out the slight irregularities that occurred when the magnetic part 48 was formed, a temperature rise in the coil 42 was observed. Although polishing slightly reduced the thickness of the magnetic part 48, the temperature rise could not be explained solely by heat conduction from the coil 42 to the magnetic composite material 10. After careful investigation, we concluded that polishing exposed the polished surfaces of the soft magnetic particles 14 on the surface of the magnetic part 48, reducing the emissivity and heat dissipation by radiation, resulting in a further rise in the coil temperature. Conversely, covering the surface of the magnetic part 48 with resin increases the emissivity, improves heat dissipation by radiation, and enhances the cooling effect of the coil.

[0026] Whether the soft magnetic particles 14 are not exposed on the first surface S1 and the second surface S2 of the magnetic portion 48 of the magnetic coil 41 can be confirmed by observing backscattered electron images with a scanning electron microscope (SEM). In backscattered electron image observation, contrast is created due to differences in atomic number, making it possible to determine whether the particles are exposed or not. A magnification of 500x is preferable for observation, as this allows each soft magnetic particle to be observed to some extent, and also allows a fairly wide area to be observed at one time.

[0027] In the magnetic portion 48, the thickness t1 (FIG. 2) between the first surface S1 and the first coil surface SC1 of the planar coil 42 is not particularly limited, but is preferably 1 mm or less. 2 Since the thermal resistance is calculated as (K / W) = thickness (m) / thermal conductivity (W / mK), reducing the thickness reduces the thermal resistance. Also, the smaller the heat source, the easier the heat is transferred. Therefore, by making the thickness of the above-mentioned portion of the magnetic part 48 1 mm or less, when the magnetic coil 41 is provided with a magnetic sheet 18 and a heat sink 19 as shown in FIG. 10 (described later), the heat dissipation from the magnetic sheet 18 and the heat sink 19 can be improved. In addition, the thickness t2 (FIG. 2) between the second surface S2 and the second coil surface SC2 of the planar coil 42 in the magnetic part 48 is not particularly limited, but is preferably 1 mm or less. By making both the thickness t1 and the thickness t2 in the magnetic part 48 1 mm or less, the heat dissipation can be further improved. It is possible.

[0028] In the magnetic portion 48, the thickness t1 (FIG. 2) between the first surface S1 and the first coil surface SC1 of the planar coil 42 is not particularly limited, but is preferably 0.1 mm or more. This is because if the thickness t1 of the magnetic portion 48 is made too thin, the effect of reducing AC resistance becomes small.

[0029] FIG. 5 is a diagram showing the relationship between magnetic layer thickness and resistance. FIG. 5 shows the relationship at 85 kHz, which is the resonance frequency of magnetic field coupling type wireless power transfer. As shown in the figure, when the magnetic layer thickness is 0.4 mm, the AC resistance is 55 mΩ, which is the minimum. If the AC resistance is 66 mΩ, which is 1.2 times the minimum, as the reference, the magnetic layer thickness is preferably 0.1 mm or more. Note that FIG. 5 is also shown as FIG. 4 in the above-mentioned Non-Patent Document 1.

[0030] B. Composition of magnetic composite material: 6 is an explanatory diagram showing a schematic configuration of the magnetic composite material 10. The magnetic composite material 10 includes the resin material 12 and the soft magnetic particles 14 contained in the resin material 12, as described above.

[0031] The resin material 12 preferably has vibration-absorbing properties by itself, and examples thereof include elastomers such as natural rubber, butyl rubber, nitrile rubber, silicone rubber, polyurethane, and fluorine-based rubber. Among these, silicone rubber is particularly preferred due to its ease of mixing with the soft magnetic particles 14 (filler) and its high heat resistance, weather resistance, and adhesive properties. When silicone rubber is used as the resin material 12, the molecular weight between crosslinking points of the silicone rubber is preferably 20,000 or more in order to optimize the elongation and rubber hardness of the magnetic composite material 10. Using an elastomer as the resin material 12 can improve flexibility compared to using polycarbonate, polypropylene, epoxy resin, or phenolic resin. Furthermore, it can improve heat resistance and weather resistance compared to urethane. Resin materials other than elastomers may also be used as the resin material 12. For example, using polycarbonate or polypropylene can result in a magnetic composite material 10 with excellent shape stability, using urethane can result in a magnetic composite material 10 with excellent vibration absorption ability, and using epoxy resin or phenolic resin can result in a magnetic composite material 10 with excellent adhesiveness.

[0032] The soft magnetic particles 14 are preferably practical as a magnetic material in a frequency range of, for example, 50 to 100 kHz. This allows the magnetic composite material 10 to be suitably used in wireless power supply devices, as described below. The frequency range of 50 to 100 kHz is a frequency range in which high power transmission efficiency can be achieved in wireless power supply. From the perspective of applying the magnetic composite material 10 to a wireless power supply device, it is desirable that the soft magnetic particles 14 function well as a magnetic material, particularly in the 85 kHz band, which is the resonance frequency of magnetic field coupling type wireless power supply. The soft magnetic particles 14 can include, for example, at least one of a soft magnetic metal and a soft magnetic ferrite. The inclusion of such soft magnetic particles 14 allows the magnetic composite material 10 to function as a good magnetic material.

[0033] Examples of soft magnetic metals constituting the soft magnetic particles 14 include Fe-Si alloys, Fe-Si-Cr alloys, sendust (Fe-Si-Al alloys), and permalloy (Fe-Ni alloys). Examples of ferrites constituting the soft magnetic particles 14 include Ni-Zn ferrite (nickel zinc ferrite) and Mn-Zn ferrite (manganese zinc ferrite). Among these soft magnetic materials, Ni-Zn ferrite and Mn-Zn ferrite are particularly preferred because they have a large real part μ' of the complex relative permeability in the frequency range of 50 kHz to 100 kHz. The larger the real part μ' of the complex relative permeability, the greater the degree to which magnetic flux can be confined.

[0034] Furthermore, the shape of the powder particles that are the soft magnetic particles 14 is not particularly limited, but is preferably close to spherical in terms of enhancing the vibration absorption properties of the entire magnetic composite material 10. Specifically, the aspect ratio (major axis / minor axis) of the powder particles of the soft magnetic particles 14 is preferably 5 or less, and more preferably 3 or less, for example. Here, the "major axis" refers to the maximum value of the distance between two parallel lines when an image of a powder particle of the soft magnetic particles 14 projected in the vertical direction is sandwiched between the two lines, and the "minor axis" refers to the minimum value of the distance between the two lines.

[0035] Although there are no particular limitations on the average particle size of the soft magnetic particles 14, it is preferably 50 μm or less. This makes it possible to suppress eddy currents caused by changes in the magnetic field and the resulting heat generation. Furthermore, it is preferable that the average particle size of the soft magnetic particles 14 be 2 μm or more. If the average particle size is smaller than this, the surface area of ​​the soft magnetic particles increases relative to the volume when blended with the resin, causing the viscosity to increase and making it impossible to blend.

[0036] Fig. 7 is a diagram showing the relationship between particle diameter and eddy current loss. The example shown in Fig. 7 shows the results of evaluating eddy current loss by changing the particle diameter of the soft magnetic particles 14 as follows. In Fig. 7, when the eddy current loss is 20 kW / m 3 The following are marked as "○", and eddy current loss is 20kW / m 3A value greater than this was marked "X". Regarding the feasibility of blending soft magnetic particles, the state was evaluated when 60% by volume of soft magnetic particles was blended (equivalent to 90% by weight). When the resin blended with soft magnetic particles 14 was in a paste form and could be spread evenly, it was marked "O", and when it was not in a paste form and could not be spread evenly, it was marked "X". As an overall evaluation, if either the eddy current loss or the blending of soft magnetic particles was "x", it was marked "x", and if both were "o", it was marked "o". It is said that eddy current loss can be suppressed by reducing the particle size, but to estimate the specific size, electromagnetic field analysis using the finite element method was used. When evaluating the relationship between eddy current loss and particle size of soft magnetic particles 14 using electromagnetic field analysis, since it is difficult to perform electromagnetic field analysis on a group of fine particles with a particle size distribution, the particles were approximated with monodisperse cubic particles and an insulating coating was provided between the particles for evaluation. As a result, it was confirmed that eddy current loss with particle size decreases in proportion to the square of the particle size, and that eddy current loss can be reduced by reducing the particle size.

[0037] As shown in Figure 7, when the average particle size of the soft magnetic particles 14 is 60 μm or more, the eddy current loss becomes larger than 20, so it can be said that the average particle size of the soft magnetic particles 14 is preferably smaller than 60 μm, more preferably 50 μm or less, and even more preferably 40 μm or less.

[0038] The average particle size of the soft magnetic particles 14 was determined by measuring the particle size distribution using a wet particle size distribution measuring device, and the obtained D50 was taken as the average particle size. The average particle size of the soft magnetic particles 14 in the magnetic part 48 of the magnetic coil 41 can be calculated using an SEM (Scanning Electron Microscope) photograph. Specifically, the average particle size can be determined by the following method. A cross section of the magnetic part 48 of the magnetic coil 41 is photographed using an SEM, and 100 particles are randomly selected from the cross-sectional image. The cross-sectional area of ​​each particle is calculated as the ratio of the circularity (πr 2 After approximating the area ratio, the diameter (2r) of each particle was calculated. The area ratio for each diameter was calculated, and the diameter at which the cumulative frequency of the area ratio was 50% was defined as the average particle diameter.

[0039] 8 is a diagram showing an example of the particle size distribution of the soft magnetic particles 14. In FIG. 8, an amorphous alloy AW2-08 (88.5Fe 6.5Si 2.5Cr 2.5B, d=6.418 g / cm) manufactured by Epson Atmix is ​​used as an example of the soft magnetic particles 14. 3 ) particle size distribution. The upper part of Figure 8 shows the frequency (%), and the lower part shows the cumulative (%). As shown in the figure, D10 = 5.5, D50 = 12.9, and D90 = 29.2. The test conditions are as follows: Analyzer: Microtrac particle size distribution meter (wet laser analysis) Range: 0.02 to 2000 (μm) Measurement conditions: Dispersion: External homogenizer 3 minutes, Internal homogenizer 0 minutes, Ultrasonic bath 0 minutes Solvent: Ethanol Transmittance: Transmittance Sample refractive index: 3.26 Solvent refractive index: 1.36 Number of measurements: Average of 3 Calculation mode: MT3000II

[0040] Fig. 9 shows the results of SEM observation of a cross section of the magnetic part 48. The upper part of Fig. 9 shows a backscattered electron image at a magnification of 500 times, and the lower part shows a backscattered electron image at a magnification of 2000 times. In Fig. 9, amorphous alloy AW2-08 manufactured by Epson Atmix is ​​used as an example of the soft magnetic particles 14, and silicone rubber is used as the resin material.

[0041] Although the thermal conductivity of the magnetic composite material 10 is not particularly limited, it is preferably 0.8 W / mK or higher. The higher the thermal conductivity, the more preferable. When soft magnetic particles 14 are blended into the resin material 12, there is an upper limit to the amount of soft magnetic particles 14 blended in order to maintain flexibility and adhesiveness, and it is thought that the thermal conductivity that can be realistically achieved will be 10 W / mK or less.

[0042] 10 is an explanatory diagram conceptually illustrating the configuration of the magnetic member 58. The magnetic member 58 includes the magnetic coil 41 of this embodiment, a magnetic sheet 18, and a heat sink 19. The magnetic sheet 18 is a magnetic shielding layer that functions as a good magnetic material, and can be, for example, a metal sheet made of a soft magnetic metal or a ferrite sheet made of soft magnetic ferrite. The heat sink 19 is a heat dissipation component with a large surface area, and can be made of a metal with high thermal conductivity such as aluminum or copper.

[0043] 10 using the magnetic coil 41 of this embodiment, if the thermal conductivity of the magnetic composite material 10 is 0.8 W / mK or more, it is possible to improve the heat dissipation from the magnetic sheet 18 and the heat sink 19. The thermal conductivity of the magnetic composite material 10 can be adjusted by the type and amount of soft magnetic particles 14 added.

[0044] FIG. 11 is a diagram showing the relationship between the content of soft magnetic powder and thermal conductivity. In this example, the soft magnetic powder has an alloy composition of Fe-Si-Cr-B and a spherical shape. The measurement method is as follows. Silicone rubber as the resin material and an alloy as the soft magnetic powder were placed in a container at a specified volume fraction, and cured at 100°C for 10 hours and 150°C for 10 hours. After that, the product was removed and polished on both sides to remove any surface irregularities, producing a cured product with a diameter of 30 mm and a thickness of 10 mm. The thermal conductivity of both sides was then measured using a C-THERM TCi thermal conductivity measuring device.

[0045] C.Magnetic coil manufacturing method: Fig. 12 is an explanatory view showing an example of a manufacturing method for the magnetic coil 41 of this embodiment. Fig. 12 shows a cross section corresponding to Fig. 3 at step P116, which will be described later. In this manufacturing method, the following steps P102 to P118 are performed in order. (Step P102) A soft magnetic powder made of metal and a thermosetting resin are mixed to prepare a paste-like magnetic composite material 102. (Step P104) A resin material 104 containing no magnetic powder is prepared. (Step P106) A resin material 104 that does not contain magnetic powder is thinly spread. (Step P108) The magnetic composite material 102 is spread on the spread resin material 104. (Step P110) The coil 42 is placed on the magnetic composite material 102. (Step P112) The magnetic composite material 102 is applied between the coils 42, filling the gaps between the coils 42 so that no air bubbles remain. (Step P114) Then, the magnetic composite material 102 is applied to a predetermined thickness. (Step P116) Then, a thin layer of resin material 104 is applied. (Step P118) By heat curing, the coil covered with the magnetic composite material is completed. According to this magnetic coil manufacturing method, the magnetic coil 41 of this embodiment can be easily manufactured. However, the magnetic coil may be manufactured by other manufacturing methods. For example, the magnetic composite material 102 may be placed in a predetermined container, the planar coil 42 may be immersed in the magnetic composite material 102, and the planar coil 42 may be hardened by heating.

[0046] D: Wireless power supply system configuration: The magnetic coil 41 of this embodiment can be suitably used as a component of a wireless power supply system, for example. A wireless power supply system including a magnetic member including the magnetic coil 41 will be described below.

[0047] Fig. 13 is an explanatory diagram schematically illustrating the configuration of a wireless power feeding system 30 including a magnetic member including a magnetic coil 41. The wireless power feeding system 30 shown in Fig. 13 is a system that feeds power wirelessly by electromagnetic induction, and includes a wireless power feeding device 40 on the power receiving side and a wireless power feeding device 50 on the power transmitting side.

[0048] The wireless power transfer device 40 includes a magnetic member 58 having a magnetic coil 41 and a magnetic sheet 18, a circuit board 44, and a load 46. The magnetic coil 41 includes a planar coil 42 as a secondary coil on the power receiving side, and a magnetic composite material 10 covering the planar coil 42. The magnetic sheet 18 is a sheet that functions as a good magnetic material, and may be, for example, a metal sheet made of a soft magnetic metal or a ferrite sheet made of soft magnetic ferrite. In the example shown in FIG. 13 , the planar coil 42 is covered by the magnetic composite material 10 and is disposed on the back side of the magnetic sheet 18, with the portion hidden by the magnetic sheet 18 indicated by dashed lines. The circuit board 44 is electrically connected to the planar coil 42 and is provided to supply power generated by the planar coil 42 to the load 46. FIG. 13 shows, as an example, the wireless power transfer device 40 mounted on a vehicle (electric vehicle) 60. Vehicle 60 includes wireless power supply device 40 and a power storage device that stores power for driving vehicle 60. The power storage device corresponds to load 46 in FIG. 13 , and power generated in planar coil 42 is supplied to the power storage device via circuit board 44. Circuit board 44 includes a converter that converts the voltage when power is supplied from planar coil 42 to the power storage device into a voltage suitable for charging the power storage device. Note that, although load 46 in vehicle 60 is the power storage device, load 46 may also include a vehicle drive motor, allowing power to be directly supplied to the drive motor from wireless power supply device 40.

[0049] The wireless power supply device 50 includes a magnetic member 59 having a magnetic coil 51 and a magnetic sheet 18, a circuit board 54, and a power supply unit 56. The magnetic coil 51 includes a planar coil 52 as a primary coil on the power transmission side, and a magnetic composite material 10 covering the planar coil 52. In the example shown in FIG. 13 , the planar coil 52 is covered with the magnetic composite material 10, and the portion hidden by the magnetic composite material 10 is indicated by a dashed line. In the wireless power supply device 50, the magnetic coil 51 is disposed on the magnetic sheet 18. The circuit board 54 is electrically connected to the planar coil 52 and is provided to supply AC power to the planar coil 52. For example, as shown in FIG. 13 , when the power receiving wireless power supply device 40 is mounted on a vehicle 60, the wireless power supply device 50 may be installed at a specific location provided for power supply so as to be able to supply power to the vehicle 60 parked at the specific location. The circuit board 54 includes a converter that converts the voltage when power is supplied from the power supply device 56 to the planar coil 52 into a voltage suitable for power supply operation using the planar coil 52, and an inverter.

[0050] Fig. 14 is an explanatory diagram that schematically shows the arrangement of the magnetic coil 41 and the magnetic coil 51. Fig. 14 shows a cross section perpendicular to the plane direction of the magnetic coil 41 and the magnetic coil 51. As shown in the figure, the magnetic coil 41 and the magnetic coil 51 are arranged facing each other, and magnetic sheets 18 are arranged on the outside of the magnetic coil 41 and the magnetic coil 51, respectively.

[0051] FIG. 15 is a cross-sectional schematic diagram illustrating the operation of wireless power supply using the wireless power supply system 30. FIG. 15 shows an enlarged view of a portion of a cross section perpendicular to the plane direction of the magnetic coil 41 and the magnetic coil 51, corresponding to FIG. 3. In FIG. 15, the state of the magnetic flux during electromagnetic induction is indicated by a dashed line as magnetic flux 32. Also, in FIG. 15, the direction of the magnetic field lines is indicated by arrows. As shown in the figure, in the magnetic coil 41, the magnetic composite material 10 is filled between adjacent wire rods 42L of the planar coil 42. Similarly, in the magnetic coil 51, the magnetic composite material 10 is filled between adjacent wire rods 52L of the planar coil 52. Because the magnetic composite material 10 contains soft magnetic particles, when electromagnetic induction is performed using the primary coil (planar coil 52) and the secondary coil (planar coil 42) arranged opposite to each other, the spread of the magnetic field from the coil can be suppressed, and the mutual cancellation of magnetic fields generated between adjacent wire rods (proximity effect) can be suppressed. As a result, reduced AC resistance and improved power transmission efficiency can be achieved.

[0052] According to the wireless power supply device 40 of this embodiment, the first surface S1 covering the first coil surface SC1 includes the magnetic coil 41 on which the soft magnetic particles 14 are not exposed, thereby enhancing heat dissipation by radiation on the first surface S1 of the magnetic section 48 and improving the cooling effect. Similarly, in the wireless power supply device 50, heat dissipation by radiation on the S1 of the magnetic section 48 can be enhanced. In the wireless power supply device 40 and the wireless power supply device 50, if the second surface S2 is also configured so that the soft magnetic particles 14 are not exposed, heat dissipation by radiation can be further enhanced. As a result, performance degradation, malfunction, failure, etc. due to heat can be suppressed in the wireless power supply devices 40 and 50.

[0053] The magnetic coil 41 of the above-described embodiment may be used for purposes other than wireless power supply devices for electric vehicles, such as wireless power supply devices provided in aircraft, satellites, smartphones, tablet terminals, small home appliances, etc.

[0054] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0055] In the above embodiment, the magnetic coil 41 includes one planar coil 42, but two or more planar coils 42 may be stacked with the magnetic composite material 10 interposed therebetween. Even in such a configuration, at least the first surface covering the first coil surface of the magnetic part is configured so that the soft magnetic particles are not exposed, thereby improving heat dissipation from the first surface.

[0056] The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0057] The present disclosure can also be realized as the following application examples. [Application example 1] A magnetic coil, a flat, planar coil in which a wire is wound in a spiral shape and which has a first coil surface and a second coil surface that is the back surface of the first coil surface; a magnetic portion made of a magnetic composite material having a resin material and soft magnetic particles contained in the resin material, the magnetic portion covering the planar coil; Equipped with Among the surfaces of the magnetic part, at least a first surface covering the first coil surface does not expose the soft magnetic particles. Magnetic coil. [Application example 2] The magnetic coil according to Application Example 1, The average particle size of the soft magnetic particles is 50 μm or less. Magnetic coil. [Application example 3] The magnetic coil according to Application Example 1 or Application Example 2, The thermal conductivity of the magnetic composite material is 0.8 W / mK or more. Magnetic coil. [Application example 4] The magnetic coil according to any one of Application Examples 1 to 3, In the magnetic portion, a thickness between the first surface and the first coil surface of the planar coil is 1 mm or less. Magnetic coil. [Application example 5] The magnetic coil according to any one of Application Examples 1 to 4, The cross-sectional shape of the wire of the planar coil is approximately rectangular. Magnetic coil. [Application Example 6] A wireless power supply device, The magnetic coil according to any one of Application Examples 1 to 5, a circuit board electrically connected to the planar coil for supplying AC power to the planar coil or for supplying power generated by the planar coil to a load; characterized in that it comprises Wireless power supply device. [Explanation of symbols]

[0058] S1...Side 1 S2…Second side SC1: First coil surface SC2: Second coil surface 10...Magnetic composite material 12...Resin material 14...Soft magnetic particles 18...Magnetic sheet 19...heat sink 30...Wireless power supply system 32...Magnetic flux 40,50...Wireless power supply devices 41, 51...Magnetic coil 42, 52... Planar coil 42L,52L…Wire rod 44...Circuit board 46...Load 48...Magnetic part 50...Wireless power supply device 54...Circuit board 56...Power supply device 58, 59...Magnetic members 60...Vehicle 102...Magnetic composite material 104...Resin material

Claims

1. A magnetic coil, a flat, planar coil formed by spirally winding a wire material and having a first coil surface and a second coil surface that is a back surface of the first coil surface; a magnetic portion made of a magnetic composite material having a resin material and soft magnetic particles contained in the resin material, the magnetic portion covering the planar coil; Equipped with Among the surfaces of the magnetic part, at least a first surface covering the first coil surface does not expose the soft magnetic particles. Magnetic coil.

2. 2. The magnetic coil according to claim 1, The average particle size of the soft magnetic particles is 50 μm or less. Magnetic coil.

3. 2. The magnetic coil according to claim 1, The thermal conductivity of the magnetic composite material is 0.8 W / mK or more. Magnetic coil.

4. 2. The magnetic coil according to claim 1, In the magnetic portion, a thickness between the first surface and the first coil surface of the planar coil is 1 mm or less. Magnetic coil.

5. 2. The magnetic coil according to claim 1, The cross-sectional shape of the wire of the planar coil is approximately rectangular. Magnetic coil.

6. A wireless power supply device, The magnetic coil according to any one of claims 1 to 5; a circuit board electrically connected to the planar coil for supplying AC power to the planar coil or for supplying power generated by the planar coil to a load; characterized in that it comprises Wireless power supply device.

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