Magnetic sheet, magnetic member, wireless power supply device, and vehicle

Abstract

To improve the vibration resistance of a magnetic sheet.SOLUTION: A magnetic sheet comprises an elastomer, and a soft magnetic body contained in the elastomer, wherein a loss coefficient tanδ obtained through dynamic viscoelasticity measurement at a room temperature within a frequency range of 1 to 110 Hz is 0.05 or more, and an imaginary part μ" of a complex relative magnetic permeability in a frequency range of 50 to 100 kHz is 2.0 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a magnetic sheet, a magnetic member, a wireless power supply device, and a vehicle. [Background technology]

[0002] Conventionally, as one type of magnetic sheet, a ferrite structure processed into a sheet shape is known. Such magnetic sheets are known to be used in various electronic devices by utilizing their properties of shielding or absorbing magnetic flux. For example, in a wireless power supply device, a magnetic sheet is disposed on the outside of a power transmission coil and a power receiving coil, thereby suppressing the spread of magnetic lines during power supply and efficiently converging the magnetic lines, thereby improving power transmission efficiency. As a magnetic sheet made of ferrite, for example, a magnetic sheet is known that is manufactured by dividing a sintered ferrite plate into a plurality of ferrite pieces and supporting the divided ferrite pieces on a support sheet using an adhesive or the like. With such a configuration, flexibility is imparted to the magnetic sheet made of ferrite, which is a brittle material, to suppress cracking of the magnetic sheet (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-150105 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, even if the magnetic sheet is made using ferrite pieces obtained by dividing a ferrite plate as described above, when a device such as a wireless power supply device including the magnetic sheet is subjected to larger vibrations, such as when the device is mounted on an electric vehicle or the like as a device for supplying power to a battery, the magnetic sheet may crack, and further improvement in vibration resistance of the magnetic sheet has been desired. Such problems related to vibration resistance are not limited to cases where a magnetic sheet is made using ferrite or where a magnetic sheet is used for a wireless power supply device, but are common problems when a magnetic sheet is used in an environment affected by vibration. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms. (1) According to one embodiment of the present disclosure, there is provided a magnetic sheet comprising an elastomer and a soft magnetic material contained in the elastomer, and having a loss factor tan δ of 0.05 or more as measured by dynamic viscoelasticity measurement at room temperature in a frequency range of 1 Hz to 110 Hz, and an imaginary part μ" of complex relative permeability of 2.0 or less in a frequency range of 50 kHz to 100 kHz. According to the magnetic sheet of this embodiment, the loss coefficient tan δ measured by dynamic viscoelasticity measurement at room temperature in the frequency range of 1 Hz to 110 Hz is 0.05 or more, so that the impact absorption ability of the magnetic sheet can be ensured when vibrations of about 1 Hz to 110 Hz are applied to the magnetic sheet. Therefore, damage to the magnetic sheet caused by impacts from vibrations and damage to electronic devices and the like arranged adjacent to the magnetic sheet caused by damage to the magnetic sheet can be suppressed. Furthermore, the imaginary part μ" of the complex relative permeability in the frequency range of 50 kHz to 100 kHz is 2.0 or less, so that the magnetic loss of the magnetic sheet in the frequency range of 50 kHz to 100 kHz can be suppressed. (2) In the magnetic sheet of the above embodiment, the storage modulus measured by dynamic viscoelasticity measurement at room temperature in the frequency range of 1 Hz to 110 Hz may be 200 MPa or less. With such a configuration, the lower the storage modulus, the more difficult it becomes to preserve (store) energy in response to displacement in the magnetic sheet, and the stored energy can be prevented from connecting to repulsion energy, etc., thereby improving the impact absorption ability of the magnetic sheet. (3) In the magnetic sheet of the above embodiment, the elongation rate at room temperature may be 30% or more. With such a configuration, it is possible to ensure the flexibility of the magnetic sheet, and even if the magnetic sheet is used by overlapping a member having a significantly different thermal expansion coefficient from that of the magnetic sheet, it is easy to make the magnetic sheet follow the thermal expansion of such a member. (4) In the magnetic sheet of the above embodiment, the rubber hardness measured with a type A durometer defined in JIS K 6235-3:2012 may be equal to or less than 80. With such a configuration, the degree to which the magnetic sheet can flexibly deform in response to an impact is increased, thereby improving the impact absorption ability of the magnetic sheet. (5) In the magnetic sheet of the above aspect, the soft magnetic body may include at least one of a metal and a ferrite. With such a configuration, it is easy to ensure that the magnetic sheet functions as a magnetic body. (6) In the magnetic sheet of the above aspect, the elastomer may be silicone rubber. With this configuration, it is easy to ensure the heat resistance and weather resistance of the magnetic sheet. (7) In the magnetic sheet of the above embodiment, the peak of the imaginary part μ″ of the complex relative permeability may be 150 kHz or higher. With such a configuration, when a device including the magnetic sheet is used in a frequency range of, for example, 50 kHz to 100 kHz, the effect of suppressing magnetic loss of the magnetic sheet can be enhanced. (8) In the magnetic sheet of the above embodiment, the real part μ′ of the complex relative permeability in the frequency range of 50 kHz to 100 kHz may be equal to or greater than 5. With this configuration, the magnetic sheet can function well as a magnetic body in the above frequency band. (9) According to another aspect of the present disclosure, there is provided a magnetic member comprising: the magnetic sheet according to any one of (1) to (8); and a planar coil disposed on the magnetic sheet, the planar coil having a wire wound in a spiral shape. According to the magnetic member of this embodiment, by providing the magnetic sheet described above, it is possible to improve the vibration resistance of the magnetic member. (10) According to yet another aspect of the present disclosure, there is provided a wireless power supply device including the magnetic sheet according to any one of (1) to (8), a planar coil arranged on the magnetic sheet and having a wire wound in a spiral shape, and a circuit board electrically connected to the planar coil for supplying AC power to the planar coil or supplying power generated by the planar coil to a load. According to the wireless power supply device of this embodiment, by including the magnetic sheet described above, it is possible to improve the vibration resistance of the wireless power supply device. (11) According to yet another aspect of the present disclosure, there is provided a vehicle including a power storage device configured to store power for driving the vehicle, and the wireless power supply device according to (10), wherein the circuit board supplies the power generated by the planar coil to the power storage device. According to the vehicle of this configuration, even if vibrations are applied to the wireless power supply device as the vehicle travels, damage to the wireless power supply device caused by the vibrations can be suppressed. The present disclosure may be realized in various forms other than those described above, for example, in the form of a method for manufacturing a magnetic sheet, a wireless power supply method using a magnetic sheet, etc. [Brief description of the drawings]

[0006] [Figure 1] 1 is a schematic cross-sectional view showing a schematic configuration of a magnetic sheet according to an embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a magnetic sheet including a soft magnetic material whose particles are spherical. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing a magnetic sheet including a soft magnetic material having flat particles. [Figure 4] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a wireless power supply system. [Diagram 5] FIG. 4 is a schematic cross-sectional view for explaining an operation of wireless power supply. [Figure 6] FIG. 4 is an explanatory diagram illustrating a specific configuration of a magnetic sheet. [Figure 7] FIG. 11 is an explanatory diagram showing all the measured values ​​related to the performance of each sample. [Figure 8] FIG. 4 is an explanatory diagram showing a summary of evaluation results for the magnetic sheet. [Figure 9] FIG. 3 is an explanatory diagram showing the loss factor tan δ at frequencies from 0.1 Hz to 110 Hz. [Figure 10] FIG. 2 is an explanatory diagram showing values ​​of storage elastic modulus at frequencies from 0.1 Hz to 110 Hz. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] FIG. 1 is an explanatory diagram showing a schematic configuration of a magnetic sheet 10 according to an embodiment of the present disclosure. The magnetic sheet 10 includes an elastomer 12 and a soft magnetic material 14 contained in the elastomer 12. In the magnetic sheet 10 of this embodiment, the soft magnetic material 14 is dispersed in the elastomer 12 in the form of powder particles. As will be described later, the magnetic sheet 10 of this embodiment is characterized in that it is particularly excellent in vibration resistance (shock resistance). First, the overall configuration of the magnetic sheet 10 will be described below.

[0008] The elastomer 12 preferably has vibration absorbing properties by itself, and examples of such materials include natural rubber, butyl rubber, nitrile rubber, silicone rubber, polyurethane, etc. Among these, silicone rubber is particularly preferable because of its ease of mixing with the soft magnetic material 14 (filler) and its high heat resistance and weather resistance. When using silicone rubber as the elastomer 12, the molecular weight of the silicone rubber is preferably 20,000 or more from the viewpoint of optimizing the elongation and rubber hardness of the magnetic sheet 10.

[0009] It is desirable that the soft magnetic body 14 is practical as a magnetic body in a frequency range of, for example, 50 to 100 kHz. This allows the magnetic sheet 10 to be suitably used in a wireless power supply device, as described below. The frequency range of 50 to 100 kHz is a frequency range in which high power transmission efficiency can be obtained in wireless power supply. From the viewpoint of applying the magnetic sheet 10 to a wireless power supply device, it is desirable that the soft magnetic body 14 functions well as a magnetic body, particularly in the 85 kHz band. The soft magnetic body 14 can include, for example, at least one of a soft magnetic metal and a soft magnetic ferrite. By including such a soft magnetic body 14, the magnetic sheet 10 can function as a good magnetic body.

[0010] Examples of soft magnetic metals constituting the soft magnetic body 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 body 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 preferable from the viewpoint of having a large real part μ' of the complex relative permeability in the frequency range of 50 kHz to 100 kHz.

[0011] In addition, the shape of the powder particles of the soft magnetic material 14 is preferably close to spherical in terms of increasing the vibration absorption of the entire magnetic sheet 10. Specifically, the aspect ratio (major axis / minor axis) of the powder particles of the soft magnetic material 14 is preferably 5 or less, and more preferably 3 or less, for example. Here, the above-mentioned "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 material 14 projected in the vertical direction is sandwiched between two parallel lines, and the "minor axis" refers to the minimum value of the distance between the two lines. The effect of the particle shape of the soft magnetic material 14 on the absorption of vibration and shock by the magnetic sheet 10 will be further described below.

[0012] FIG. 2 is a schematic cross-sectional view showing the state of a magnetic sheet 10a having soft magnetic material 14a whose particle shape is spherical, and FIG. 3 is a schematic cross-sectional view showing the state of a magnetic sheet 10b having soft magnetic material 14b whose particle shape is flat. FIG. 2 and FIG. 3 show the state in which an object 20 collides with each magnetic sheet and applies an impact to the magnetic sheet. In general, when an impact is applied to a sheet made of an elastomer, the impact is absorbed by the deformation of the elastomer. As shown in FIG. 2 and FIG. 3, when an impact is applied to a magnetic sheet containing an elastomer and a soft magnetic material (filler), the impact is absorbed by the rearrangement of the filler due to the impact and the deformation of the elastomer 12 present between the fillers. After the impact is applied in this way, the magnetic sheet tries to return to its original shape.

[0013] Here, when the filler has a nearly spherical shape as shown in Fig. 2, the filler that receives an impact can disperse the impact to other adjacent fillers, and as a result, the amount of deformation of the elastomer 12 existing around these fillers also increases, making it easier to absorb a larger impact. In Fig. 2, the dashed arrows indicate how the impact is dispersed from the impacted filler to the surrounding fillers.

[0014] In contrast, when the filler has a flat shape as shown in FIG. 3, the filler behaves as a metal or ceramic plate when it receives an impact. In FIG. 3, the outline arrow indicates how the impact is transmitted into the magnetic sheet 10b. When the filler has a flat shape, the deformation of the elastomer 12 due to the impact is small, and part of the applied impact becomes a repulsive force, and part of the impact remains in the magnetic sheet as a residual stress. Therefore, in order to improve the impact resistance (vibration resistance) of the magnetic sheet 10, it is preferable that the particle shape of the soft magnetic material 14 is close to a sphere. As described above, the degree to which the impact is converted into a repulsive force in the magnetic sheet and the degree to which the impact remains in the magnetic sheet as a residual stress increases as the storage modulus of the magnetic sheet increases. Therefore, even when a flat soft magnetic material 14 is used as the filler, it is possible to ensure the impact resistance and vibration resistance of the magnetic sheet by suppressing the storage modulus of the magnetic sheet. The storage modulus of the magnetic sheet 10 will be described in detail later.

[0015] When the soft magnetic body 14 is made of a metal and the particle shape of the soft magnetic body 14 is close to a sphere, the particle size of the soft magnetic body 14 is preferably 10 μm or more from the viewpoint of increasing the real part μ' of the complex relative magnetic permeability. From the viewpoint of shifting the peak of the imaginary part μ" of the complex relative magnetic permeability of the magnetic sheet 10 to the high frequency side, which will be described later, the particle size of the soft magnetic body 14 is preferably 50 μm or less, more preferably 45 μm or less, and even more preferably 40 μm or less. Furthermore, when the soft magnetic body 14 has a flat shape and, for example, the aspect ratio exceeds 5, for the same reason as when the particle shape is spherical, the long side of the powder particle of the soft magnetic body 14 is preferably 20 μm or more, and the short side is preferably 1 μm or more. The long side of the powder particle of the soft magnetic body 14 is preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 80 μm or less. Furthermore, The side is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. In the case where the soft magnetic body 14 has a flat shape, the powder particles of the soft magnetic body 14 are oriented in the elastomer 12, so that the powder particles of the soft magnetic body 14 are more preferably spherical in particle shape from the viewpoint of ensuring the flexibility of the magnetic sheet in addition to the viewpoint of ensuring the impact resistance (vibration resistance) described above. In the case where the soft magnetic body 14 is made of ferrite, unlike the case where the soft magnetic body 14 is made of metal, there is no preferred particle size range of the soft magnetic body 14 from the viewpoint of increasing the real component μ' of the complex relative permeability due to the high electrical resistance of ferrite. The particle size may be smaller than the thickness of the magnetic sheet 10.

[0016] Furthermore, the loss factor tan δ (hereinafter also simply referred to as "loss factor tan δ") of the magnetic sheet 10 measured by dynamic viscoelasticity at room temperature in the frequency range of 1 Hz to 110 Hz may be 0.05 or more, and more preferably 0.1 or more. The value of the loss factor tan δ of the magnetic sheet 10 can be said to be the degree to which the energy of an impact can be converted into other energy, for example, and the larger the loss factor tan δ, the higher the impact absorption ability of the magnetic sheet 10. Therefore, by setting the value of the loss factor tan δ of the magnetic sheet 10 within the above range, it is possible to prevent damage to the magnetic sheet 10 when vibrations of a frequency of about 1 Hz to 110 Hz are applied, and to prevent damage to electronic devices adjacent to the magnetic sheet 10 due to the damage to the magnetic sheet 10.

[0017] In the magnetic sheet 10, the storage modulus (hereinafter also simply referred to as "storage modulus") measured by dynamic viscoelasticity measurement at room temperature in the frequency range of 1 Hz to 110 Hz is preferably 200 MPa or less, more preferably 100 MPa or less, and even more preferably 50 MPa or less. The storage modulus is one of the parameters that indicates the hardness that contributes to the impact absorption capacity of the magnetic sheet 10, which is a viscoelastic body, and in order to ensure the impact absorption capacity of the magnetic sheet 10, it is desirable for the storage modulus to be low. In other words, the lower the storage modulus, the more difficult it is to preserve (store) energy against displacement in the magnetic sheet 10. And since the energy stored in the magnetic sheet 10 leads to repulsive energy against impact, it can be said that a low storage modulus increases the impact absorption capacity of the magnetic sheet 10.

[0018] In the magnetic sheet 10, the rubber hardness measured by a type A durometer defined in JIS K 6235-3:2012 (hereinafter, simply referred to as "rubber hardness") is preferably 80 or less, more preferably 70 or less, and even more preferably 60 or less. The rubber hardness is one of the parameters that indicates the hardness that contributes to the shock absorbing ability of the magnetic sheet 10, which is an elastic body, and the lower the rubber hardness, the more flexibly the magnetic sheet 10 can deform in response to an impact, so that a lower rubber hardness is desirable in order to ensure the shock absorbing ability of the magnetic sheet 10. However, if the rubber hardness of the magnetic sheet 10 is excessively low, the magnetic sheet 10 may lack strength, so the rubber hardness is preferably 10 or more.

[0019] It is desirable that the magnetic sheet 10 has an elongation rate at room temperature (hereinafter, simply referred to as "elongation rate") of 30% or more. This ensures the flexibility of the magnetic sheet 10. By ensuring the flexibility of the magnetic sheet 10, for example, when the magnetic sheet 10 is used integrated with a member having a large thermal expansion coefficient, such as a metal member (for example, when the magnetic sheet 10 is integrated with a coil to form a magnetic member as described below), the magnetic sheet 10 can easily follow the thermal expansion of the metal member when the temperature rises.

[0020] The loss factor tan δ, storage modulus, rubber hardness, and elongation of the magnetic sheet 10 described above can be adjusted, for example, by the crosslink density of the elastomer 12, the molecular weight of the elastomer 12, the amount of the soft magnetic material 14 added to the magnetic sheet 10, the particle shape of the soft magnetic material 14, and the like. For example, when the crosslink density of the elastomer 12 is lowered, the loss factor tan δ and elongation tend to increase, and the storage modulus and rubber hardness tend to decrease. When the molecular weight of the elastomer 12 is increased, the loss factor tan δ and elongation tend to increase, and the storage modulus and rubber hardness tend to decrease. When the amount of the soft magnetic material 14 added to the magnetic sheet 10 is reduced, the loss factor tan δ and elongation tend to increase, and the storage modulus and rubber hardness tend to decrease. However, when the amount of the soft magnetic material 14 added to the magnetic sheet 10 is reduced, the magnetic properties of the magnetic sheet 10 are reduced, so from the viewpoint of ensuring the magnetic properties of the magnetic sheet 10, it is not desirable to reduce the amount of the soft magnetic material 14 added. Furthermore, when the particle shape of the soft magnetic material 14 is closer to a sphere, the loss factor tan δ and the elongation rate tend to increase, and the storage modulus and rubber hardness tend to decrease.

[0021] In magnetic sheet 10, the imaginary part μ" of the complex relative permeability in the frequency range of 50 kHz to 100 kHz (hereinafter also referred to simply as the "imaginary part μ") may be 2.0 or less, more preferably 1.0 or less, and even more preferably 0.5 or less. In this way, by suppressing the imaginary part μ" of the complex relative permeability, it is possible to suppress magnetic loss in magnetic sheet 10. Therefore, for example, when magnetic sheet 10 is applied to a wireless power supply device as described below and made to function as a transformer component in the frequency range of 50 kHz to 100 kHz, the power supply efficiency of the wireless power supply device can be improved by suppressing magnetic loss.

[0022] In such a magnetic sheet 10, it is desirable that the peak of the imaginary part μ" be 150 kHz or higher. With such a configuration, the effect of suppressing magnetic loss of the magnetic sheet 10 can be enhanced when a device including the magnetic sheet 10 is used in a frequency range of, for example, 50 kHz to 100 kHz. The peak of the imaginary part μ" can be shifted to the higher frequency side by making the particle size of the soft magnetic material 14 smaller or by covering the powder particles of the soft magnetic material 14 with resin. In addition, increasing the degree of dispersion of the powder particles of the soft magnetic material 14 in the magnetic sheet 10 can also contribute to the shift of the peak of the imaginary part μ".

[0023] In the magnetic sheet 10, the real part μ' of the complex relative permeability in the frequency range of 50 kHz to 100 kHz (hereinafter, also referred to simply as the "real part μ'") is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more. In this way, the magnetic sheet 10 can function well as a magnetic body in the above frequency band. The value of such a real part μ' can be adjusted by the type of soft magnetic material constituting the soft magnetic body 14, and can be increased by increasing the particle size of the soft magnetic body 14 or by increasing the amount of the soft magnetic body 14 added to the magnetic sheet 10. In addition, when using a soft magnetic body 14 whose particle shape is flat, the soft magnetic body 14 is oriented and the major axis of the flat shape approaches parallel to the sheet surface, so that the real part μ' of the magnetic sheet 10 can be increased in the plane parallel to the sheet surface. In addition, by reducing the particle size of the soft magnetic body 14, it is possible to maintain a high value of the real part μ' even in a higher frequency band.

[0024] According to the magnetic sheet 10 of the present embodiment configured as described above, the loss coefficient tan δ measured by dynamic viscoelasticity measurement at room temperature in the frequency range of 1 Hz to 110 Hz is 0.05 or more, so that when vibrations of a frequency of about 1 Hz to 110 Hz are applied to the magnetic sheet 10, the shock absorbing ability of the magnetic sheet 10 can be ensured. Therefore, damage to the magnetic sheet 10 caused by shocks due to vibrations, and damage to electronic devices adjacent to the magnetic sheet 10 caused by damage to the magnetic sheet 10, can be suppressed. Furthermore, according to the magnetic sheet 10 of the present embodiment, the imaginary part μ" of the complex relative permeability in the frequency range of 50 kHz to 100 kHz is 2.0 or less, so that the magnetic loss of the magnetic sheet 10 in the frequency range of 50 kHz to 100 kHz can be suppressed.

[0025] The magnetic sheet 10 of this embodiment can be suitably used, for example, as a component of a wireless power supply system. The wireless power supply system including the magnetic sheet 10 will be described below.

[0026] Fig. 4 is an explanatory diagram that illustrates a schematic configuration of a wireless power supply system 30 including a magnetic sheet 10. The wireless power supply system 30 illustrated in Fig. 4 is a system that supplies power wirelessly by electromagnetic induction, and includes a wireless power supply device 40 on the power receiving side and a wireless power supply device 50 on the power transmitting side.

[0027] The wireless power supply device 40 includes a magnetic member 41 including a magnetic sheet 10 and a secondary coil 42 on the power receiving side, which is a planar coil formed by winding a wire in a spiral shape and is disposed on the magnetic sheet 10. In FIG. 4, the secondary coil 42 is disposed on the back side of the magnetic sheet 10, and the portion hidden by the magnetic sheet 10 is indicated by a dashed line. The wireless power supply device 40 further includes a circuit board 44 electrically connected to the secondary coil 42 for supplying power generated in the secondary coil 42 to a load 46, in addition to the magnetic member 41. FIG. 4 shows, as an example, a state in which the wireless power supply device 40 is mounted on a vehicle (electric vehicle) 60. The vehicle 60 includes the wireless power supply device 40 and a power storage device that stores power for driving the vehicle 60. The power storage device corresponds to the load 46 in FIG. 4, and power generated in the secondary coil 42 is supplied to the power storage device via the circuit board 44. The circuit board 44 includes a converter that converts the voltage when power is supplied from the secondary coil 42 to the power storage device into a voltage suitable for charging the power storage device. In the vehicle 60, the load 46 is a power storage device, but the load 46 may further include a drive motor of the vehicle, so that the wireless power supply device 40 can directly supply power to the drive motor.

[0028] The wireless power supply device 50 includes a magnetic member 51 including a magnetic sheet 10 and a power transmission side primary coil 52 arranged on the magnetic sheet 10 and being a planar coil in which a wire is wound in a spiral shape. In addition to the magnetic member 51, the wireless power supply device 50 further includes a circuit board 54 electrically connected to the primary coil 52 for supplying AC power to the primary coil 52. For example, when the wireless power supply device 40 on the power receiving side is mounted on a vehicle 60 as shown in FIG. 4, 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 a voltage when power is supplied from a power supply device 56 to the primary coil 52 into a voltage suitable for power supply operation using the primary coil 52, and an inverter.

[0029] In addition, in the magnetic member 41 and the magnetic member 51, the secondary coil 42 or the primary coil 52 can be integrated with the magnetic sheet 10 by, for example, adhering the magnetic sheet 10 and the above-mentioned coil while the soft magnetic material such as silicone rubber constituting the magnetic sheet 10 is in an uncured state, and then curing the soft magnetic material. Alternatively, the above-mentioned coil may be disposed on the magnetic sheet 10 after the magnetic material constituting the magnetic sheet 10 is cured.

[0030] FIG. 5 is a schematic cross-sectional view for explaining the operation of wirelessly feeding power using a wireless power feeding system 30 including a wireless power feeding device 40 on the power receiving side and a wireless power feeding device 50 on the power transmitting side. FIG. 5 shows a cross section perpendicular to the plane direction of the magnetic member 41 and the magnetic member 51. In FIG. 5, the state of the magnetic flux during electromagnetic induction is shown by a broken line as magnetic flux 32. When electromagnetic induction is performed using a primary coil and a secondary coil arranged opposite to each other, if the magnetic sheet 10 is not arranged, the magnetic flux spreads to the outside of the primary coil and the secondary coil. However, by arranging the magnetic sheet 10 on the outside of each of the primary coil 52 and the secondary coil 42 as shown in FIG. 5, the magnetic flux can be converged around the primary coil 52 and the secondary coil 42 along the magnetic sheet 10, thereby ensuring power feeding efficiency.

[0031] As described above, the performance of converging magnetic flux is improved by suppressing the value of the imaginary part μ" of the complex relative permeability of magnetic sheet 10. For example, when a magnetic sheet comprising a soft magnetic material and an elastomer is used as a radio wave absorber, it is possible to improve the performance as a radio wave absorber by increasing the value of the imaginary part μ" in the frequency band used, increasing magnetic loss, and releasing the energy of radio waves as heat. Therefore, the property of magnetic sheet 10 of this embodiment, in which the value of the imaginary part μ" is suppressed, can be said to be a characteristic unique to magnetic sheets that are suitable for converging magnetic flux as described above.

[0032] Furthermore, since the magnetic sheet 10 including the soft magnetic body 14 has excellent magnetic shielding properties, it is possible to prevent the relatively high-frequency magnetic flux transmitted from the primary coil 52 in the wireless power supply device 40 from penetrating the magnetic sheet 10. Therefore, in the case where the wireless power supply device 40 includes, for example, a metal housing that houses the magnetic member 41, it is possible to prevent the magnetic flux transmitted from the primary coil 52 from reaching the housing. In addition, it is possible to prevent a decrease in power transmission efficiency and excessive heat generation caused by eddy currents generated in the metal housing by the magnetic flux that reaches the metal housing.

[0033] As described above, when the wireless power supply system 30 is configured using the magnetic sheet 10, the vibration resistance of the wireless power supply device 40 and the wireless power supply device 50 can be improved, and damage to the magnetic sheet 10 can be suppressed even when the wireless power supply device 40 and the wireless power supply device 50 are subjected to an impact. Here, the frequency of vibration when a car is running is generally considered to be about several Hz to 200 Hz. Therefore, by setting the loss coefficient tan δ of the magnetic sheet 10 by dynamic viscoelasticity measurement at room temperature in the frequency range of 1 Hz to 110 Hz to the above-mentioned value, when the magnetic sheet 10 is mounted on a vehicle and used as described above, the vibration absorption performance of the magnetic sheet 10 can be ensured and damage to the magnetic sheet 10 caused by vibration can be suppressed. In addition, by providing the magnetic sheet 10 with excellent vibration resistance in the wireless power supply device 50 on the power transmission side, damage to the magnetic sheet 10 caused by vibration can be suppressed even when an impact is applied due to vibration when the vehicle enters and exits for power supply, for example.

[0034] The magnetic sheet 10 of the above embodiment may be used for purposes other than the wireless power supply device of an electric vehicle. For example, it may be used in a wireless power supply device provided in a smartphone, a tablet terminal, or a small home appliance. When used in a wireless power supply device provided in an apparatus to which vibration is applied similarly to an electric vehicle, the magnetic sheet 10 can achieve the same effect due to its excellent vibration resistance. EXAMPLES

[0035] FIG. 6 is an explanatory diagram showing the specific configurations (constituent materials and additive amounts) of eleven types of magnetic sheets from sample S1 to sample S11. FIG. 7 is an explanatory diagram showing the measured values ​​relating to the performance of sample S1 to sample S11. FIG. 8 is an explanatory diagram showing the evaluation results of the magnetic sheets of sample S1 to sample S11. The configuration and manufacturing method of each sample, and the results of evaluating the performance are explained below. Each sample differs in the type of material used, the mixing ratio of the materials, and the manufacturing method. Samples S9 to S11 are comparative examples that do not satisfy the conditions related to the magnetic sheet 10 described in the embodiment.

[0036] <Preparation of each sample> [Samples S1-S8] Using silicone resin with the molecular weight shown in FIG. 6 and soft magnetic filler with the particle size shown in FIG. 6 and the type shown in FIG. 6, the magnetic sheets of samples S1 to S8 were produced by setting the amount of filler added to the ratio shown in FIG. 6. FIG. 6 also shows the rough aspect ratio of the soft magnetic filler used in samples S1 to S8 and sample S9 described later. Specifically, as a method for producing samples S1 to S8, a predetermined amount of soft magnetic filler was added to silicone resin having a vinyl group as a functional group, and the mixture was mixed with a stirrer using a stirring blade and a three-roll mill to obtain a paste. Here, only the paste of sample S1 became highly viscous, so toluene was added as a solvent. A silane coupling agent, a crosslinking agent, and a metal catalyst were added to these pastes and mixed thoroughly. The obtained paste was formed into a sheet with a thickness of 2 mm by a doctor blade method, and heat-cured at a temperature of 100°C or higher to obtain a magnetic sheet as each sample.

[0037] [Sample S9] A soft magnetic filler (Mn-Zn ferrite) was added to the liquid epoxy resin at 50% by volume, and mixed with a stirrer using a stirring blade and a three-roll mill to obtain a paste. An epoxy hardener was added to this paste and mixed thoroughly. The paste to which the hardener was added was molded into a sheet of 2 mm thickness by the doctor blade method, and cured at a temperature of 60°C or less to obtain the magnetic sheet of sample S9.

[0038] [Samples S10, S11] For samples S10 and S11, ferrite tiles were prepared and the obtained ferrite tiles were attached to a PET (polyethylene terephthalate) film to prepare a magnetic sheet. Sample S10 used Ni-Zn ferrite tiles, and sample S11 used Mn-Zn ferrite tiles. Specifically, the raw materials iron oxide, nickel oxide, zinc oxide, and manganese oxide were mixed to the desired composition ratio and wet-mixed in a ball mill. The mixed powder was dried and then calcined at a temperature of 600°C or higher. The obtained powder was pulverized in a wet ball mill, and a binder was added and mixed to obtain a slurry. The obtained slurry was granulated by a spray-drying method to form a granular shape, and then press-molded to a thickness of 2 mm and a square of 10 mm. The obtained molded body was degreased and then fired at a temperature of 1000°C or higher while adjusting the oxygen partial pressure, and a large number of ferrite tiles were prepared for each sample. These ferrite tiles were arranged two-dimensionally at equal intervals, and after applying an adhesive, they were attached to a PET film in a vacuum. PET films were attached to both sides of the tile to create magnetic sheets for samples S10 and S11.

[0039] When carrying out the measurements described below, test pieces of a size suitable for the measurements were prepared for each sample by cutting, molding, or press molding, depending on the sample.

[0040] <Derivation of complex relative permeability> Complex permeability was measured using a microstrip line and a vector network analyzer in the range of 1 kHz to 1 MHz, and an E4991B impedance analyzer (Keysight Technologies) in the range of 1 MHz to 1 GHz. The samples were plate-shaped or ring-shaped. In Figure 7, the real part μ' of the complex relative permeability is shown as the minimum value of the real part in the frequency range of 50 kHz to 100 kHz. The imaginary part μ" of the complex relative permeability is shown as the maximum value of the imaginary part in the frequency range of 50 kHz to 100 kHz.

[0041] <Measurement of elongation rate> The elongation was measured at room temperature using a tensile tester (Shimadzu Autograph (AG-IS)). Specifically, each sample was cut into a rectangular test piece with a width of 1 cm and a length of 7 cm, and a tensile test was performed on the middle part with a length of 3 cm, with the test piece held at a position 2 cm from both ends by a jig. Each test piece was pulled until it broke, and the elongation was calculated by subtracting the original sample length (the middle length of 3 cm in the above sample) from the sample length at the time of breakage, and then dividing the result by the original sample length. For samples S10 and S11, the ferrite tile and the PET film were evaluated separately, and the smaller value was selected.

[0042] <Rubber hardness measurement> The rubber hardness was measured using a type A durometer as specified in JIS K 6235-3:2012.

[0043] <Derivation of storage modulus and loss factor tan δ> The storage modulus and loss modulus were measured at frequencies from 0.1 Hz to 110 Hz by dynamic viscoelasticity measurement, and the loss factor tan δ was calculated from the obtained values. For samples S10 and S11, the above measurements were performed on the PET film, which is responsible for flexibility, of the ferrite tile and the PET film.

[0044] FIG. 9 is an explanatory diagram showing the values ​​of the loss factor tan δ of samples S6 to S8 and S10 at frequencies of 0.1 Hz to 110 Hz, and FIG. 10 is an explanatory diagram showing the values ​​of the storage modulus of samples S6 to S8 and S10 at frequencies of 0.1 Hz to 110 Hz. In FIG. 8, the minimum value of the loss factor tan δ obtained by dynamic viscoelasticity measurement at room temperature in the frequency range of 1 Hz to 110 Hz is shown as the loss factor tan δ of each sample. In FIG. 7, the minimum value of the loss factor tan δ obtained by dynamic viscoelasticity measurement at room temperature in the frequency range of 1 Hz to 110 Hz is shown as the loss factor tan δ of each sample. In addition, the maximum value of the storage modulus obtained by dynamic viscoelasticity measurement at room temperature in the frequency range of 1 Hz to 110 Hz is shown as the storage modulus of each sample.

[0045] <Evaluation method> As shown in FIG. 8, each item was evaluated by comparing with the standard value. For the "loss factor tan δ", if the value of the loss factor tan δ of each sample was 0.05 or more, it was marked as "○", and if it was less than 0.05, it was marked as "×". For the "storage modulus", if the storage modulus of each sample was 200 MPa or less, it was marked as "○", and if it exceeded 200 MPa, it was marked as "×". For the "elongation", if the elongation of each sample was 30% or more, it was marked as "○", and if it was less than 30%, it was marked as "×". For the "rubber hardness", if the rubber hardness of each sample was 80 or less, it was marked as "○", and if it exceeded 80, it was marked as "×". For the "μ"", if the imaginary part μ" of the complex relative permeability of each sample in the frequency range of 50 kHz to 100 kHz was 2.0 or less, it was marked as "○", and if it exceeded 2.0, it was marked as "×". For "μ" peak, if the peak of the imaginary part μ" of the complex relative permeability of each sample was 150 kHz or higher, it was marked as "○", and if it was less than 150 kHz, it was marked as "×". For "μ'", if the real part μ' of the complex relative permeability in the frequency range of 50 kHz to 100 kHz of each sample was 5 or higher, it was marked as "○", and if it was less than 5, it was marked as "×".

[0046] Fig. 8 further shows the results of the overall evaluation. The "overall evaluation" was marked as "X" when the main evaluation item related to vibration resistance, which is the basic performance of the magnetic sheet of the present disclosure, i.e., the "loss coefficient tan δ", was marked as "X". In addition, when the overall evaluation was other than "X", and there were no remaining evaluation items marked as "X", it was marked as "◎", when there was one evaluation item marked as "X", it was marked as "○", and when there were two or more evaluation items marked as "X", it was marked as "△".

[0047] <Evaluation Results> As shown in Figures 6 to 8, in order to increase the value of the loss coefficient tan δ and ensure the vibration resistance of the magnetic sheet, it was confirmed that it is important to incorporate a soft magnetic material into the resin material and to use an elastomer such as silicone rubber as the resin material (compare samples S1 to S8 with samples S9 to S11). It was also confirmed that by making the shape of the powder particles of the soft magnetic material closer to a sphere rather than a flat shape, it is possible to reduce the storage modulus and rubber hardness, improve vibration resistance, increase the elongation rate, and shift the peak of the imaginary part μ" of the complex relative permeability to the higher frequency side (comparison of samples S3 to S8 with samples S1 to S2). It was also confirmed that by increasing the molecular weight of the elastomer, the elongation rate of the magnetic sheet can be increased (comparison of samples S3 to S6 with samples S1, S2, S7, and S8). Furthermore, it was confirmed that the less the amount of filler added, the more the storage modulus and rubber hardness can be reduced and the elongation rate can be increased, but the smaller the real part μ' of the complex relative permeability in the frequency range of 50 kHz to 100 kHz becomes, and the magnetic properties deteriorate (comparison of samples S2 with S1, comparison of samples S3 with S4, comparison of samples S5 with S6, comparison of samples S7 with S8).

[0048] The present disclosure is not limited to the above-mentioned embodiments, etc., and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in each form described in the Summary of the Invention column can be appropriately replaced or combined in order to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0049] The present disclosure can also be realized in the following forms. [Application example 1] A magnetic sheet comprising: The magnetic bearing comprises an elastomer and a soft magnetic material contained in the elastomer, The loss factor tan δ measured at room temperature in a dynamic viscoelasticity measurement in the frequency range of 1 Hz to 110 Hz is 0.05 or more; The imaginary part μ" of the complex relative permeability in the frequency range of 50 kHz to 100 kHz is 2.0 or less. Magnetic sheet. [Application example 2] The magnetic sheet according to Application Example 1, The storage modulus measured by dynamic viscoelasticity measurement at room temperature in the frequency range of 1 Hz to 110 Hz is 200 MPa or less. Magnetic sheet. [Application example 3] The magnetic sheet according to Application Example 1 or 2, It is characterized by having an elongation rate of 30% or more at room temperature. Magnetic sheet. [Application example 4] The magnetic sheet according to any one of Application Examples 1 to 3, The rubber hardness measured by a type A durometer specified in JIS K 6235-3:2012 is 80 or less. Magnetic sheet. [Application example 5] A magnetic sheet according to any one of Application Examples 1 to 4, The soft magnetic material contains at least one of a metal and a ferrite. Magnetic sheet. [Application Example 6] A magnetic sheet according to any one of Application Examples 1 to 5, The elastomer is silicone rubber. Magnetic sheet. [Application Example 7] A magnetic sheet according to any one of Application Examples 1 to 6, The imaginary part μ" of the complex relative permeability has a peak of 150 kHz or higher. Magnetic sheet. [Application Example 8] A magnetic sheet according to any one of Application Examples 1 to 7, The real part μ' of the complex relative permeability in the frequency range of 50 kHz to 100 kHz is 5 or more. Magnetic sheet. [Application Example 9] A magnetic sheet according to any one of Application Examples 1 to 8, a planar coil disposed on the magnetic sheet and having a wire wound in a spiral shape; A magnetic member comprising: [Example 10] A magnetic sheet according to any one of Application Examples 1 to 8, a planar coil disposed on the magnetic sheet and having a wire wound in a spiral shape; 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; A wireless power supply device comprising: [Application Example 11] A vehicle, a storage battery that stores power for driving the vehicle; The wireless power supply device according to Application Example 10, Equipped with The circuit board supplies the power generated by the planar coil to the capacitor. vehicle. [Explanation of symbols]

[0050] 10, 10a, 10b...Magnetic sheet 12...Elastomer 14,14a,14b...Soft magnetic material 20…object 30...Wireless power supply system 32…Magnetic flux 40,50...Wireless power supply devices 41, 51...Magnetic member 42…Secondary coil 44,54…Circuit board 46…Load 52…Primary coil 56...Power supply device 60…Vehicle

Claims

1. A magnetic sheet, The magnetic bearing comprises an elastomer and a soft magnetic material contained in the elastomer, the soft magnetic material includes at least one of a metal and a ferrite, the elastomer is silicone rubber, The loss factor tan δ measured at room temperature in a dynamic viscoelasticity measurement range of 1 Hz to 110 Hz is 0.05 or more; The imaginary part μ″ of the complex relative permeability in the frequency range of 50 kHz to 100 kHz is 2.0 or less, The storage modulus measured by dynamic viscoelasticity measurement at room temperature in the frequency range of 1 Hz to 110 Hz is 200 MPa or less. Magnetic sheet.

2. The magnetic sheet according to claim 1 , The elongation at room temperature is 30% or more. Magnetic sheet.

3. The magnetic sheet according to claim 1 , The rubber hardness measured by a type A durometer specified in JIS K 6235-3:2012 is 80 or less. Magnetic sheet.

4. The magnetic sheet according to claim 1 , The peak of the imaginary part μ″ of the complex relative permeability is 150 kHz or higher. Magnetic sheet.

5. The magnetic sheet according to claim 1 , The real part μ' of the complex relative permeability in the frequency range of 50 kHz to 100 kHz is 5 or more. Magnetic sheet.

6. A magnetic sheet according to any one of claims 1 to 5, a planar coil disposed on the magnetic sheet and having a wire wound in a spiral shape; A magnetic member comprising:

7. A magnetic sheet according to any one of claims 1 to 5, a planar coil disposed on the magnetic sheet and having a wire wound in a spiral shape; 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; A wireless power supply device comprising:

8. A vehicle, a storage battery that stores power for driving the vehicle; The wireless power supply device according to claim 7 ; Equipped with The circuit board supplies the power generated by the planar coil to the capacitor. vehicle.

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