JP6729464B2 - Magnetic core, coil unit and wireless power transmission unit - Google Patents

Description

The present invention relates to a magnetic core, a coil unit and a wireless power transmission unit.

A technique for transmitting electric power without using a power cord, that is, a so-called wireless electric power transmission technique is drawing attention. Since wireless power transmission technology can supply power from a power feeding device to a power receiving device in a contactless manner, it is applied to various products such as moving bodies such as trains and electric cars, home appliances, electronic devices, wireless communication devices, and toys. Is expected.

In a device used for wireless power transmission, in order to realize high power transmission efficiency, thinness and light weight, and high output transmission, for example, the structure of a conductor member or winding forming a coil included in a coil unit, the structure of a magnetic material The structure and material have been studied (for example, Patent Document 1).

For example, as shown in Patent Document 1, ferrite is often used as a magnetic material. However, in the case of mobile devices such as automobiles or mobile devices such as smartphones, vibration and impact are applied to the device, so it is desirable that the magnetic material has high vibration resistance and shock resistance, but ferrite is a typical ceramic. Yes easily damaged.
In mobile devices such as automobiles or mobile devices such as smartphones, it is desired to make them thinner and lighter, but if they are made thinner, they will be more easily damaged.Ferrite has a low saturation magnetic flux density, especially in devices with high output. Has a limit in thinning due to magnetic saturation.

Patent Document 2 discloses a magnetic core for wireless power transmission, which has high impact resistance and is not damaged by an impact such as a drop. However, the disclosed magnetic core for wireless power transmission is a ferrite resin composition molded body and has a low magnetic permeability of 5 to 15, and since ferrite is used, the saturation magnetic flux density is low. Due to the low magnetic permeability, it is necessary to increase the number of coil windings in order to increase the inductance. Particularly in a high-power device, as the number of coil turns increases, copper loss becomes very large and efficiency decreases. Also, since the saturation magnetic flux density is low, a large magnetic core cross-sectional area is required for use in high-power equipment, which is not suitable for downsizing equipment.

In thinning non-contact transmission equipment, it is desirable that the magnetic material has a high saturation magnetic flux density so that magnetic saturation does not occur even if the magnetic core is thinned. A metal-based soft magnetic material is known as a soft magnetic material having a high saturation magnetic flux density, but the metal-based soft magnetic material has an extremely low electric resistivity, and when used as a magnetic core for wireless power transmission, eddy current causes There is a problem that the loss is very large and the efficiency is reduced.

As a method of reducing the effect of eddy current loss and improving efficiency, a magnetic core using a soft magnetic ribbon divided into a plurality of small pieces is disclosed as in Patent Document 3. Further, Patent Document 4 discloses a structure for reducing the eddy current loss, suppressing the decrease in magnetic permeability as much as possible, and improving the scattering of small pieces which is a problem when dividing the small pieces. It should be noted that the division into small pieces or division of small pieces is performed for the purpose of reducing eddy current loss due to a change in magnetic flux density in the Z direction, which is a direction orthogonal to the XY plane, when the coil surface is the XY plane.
The magnetic cores disclosed in Patent Documents 3 and 4 are very thin because the saturation magnetic flux density of the magnetic body is large, and have improved eddy current loss, which was a problem of metal-based soft magnetic materials. It is suitable for high efficiency and high transmission efficiency. However, the magnetic layer has a very small thickness of 30 μm, and magnetic saturation occurs in high-power transmission, so that the output that can be transmitted is limited.

In order to prevent magnetic saturation in high power transmission, it is effective to laminate a plurality of soft magnetic ribbons. As such a structure, a magnetic sheet obtained by laminating a plurality of soft magnetic ribbons by using a double-sided tape is disclosed in Patent Document 5. It is disclosed.

JP 2012-70557 A International Publication No. 2015/064694 Japanese Patent No. 4836749 JP, 2011-134959, A Japanese Patent Publication No. 2015-505166

In the structure in which the double-sided tape is laminated, which is disclosed in Patent Document 5, the magnetic layer is thicker than that in which the double-sided tape is not laminated, and magnetic saturation is less likely to occur even in high-power transmission. However, since there is a non-magnetic adhesive layer for each soft magnetic ribbon, there is a problem that the magnetic core becomes thicker by the thickness thereof. Further, since the double-sided tape used in Patent Document 5 is very expensive, there is a problem that the price of the magnetic core becomes high.

In order to solve this problem, if the adhesive layer disposed between the soft magnetic ribbons is not used, the soft magnetic ribbons come into direct contact with each other, and the two soft magnetic ribbons that are in direct contact with each other are soft. Those skilled in the art expect that the magnetic ribbon becomes thicker, that is, the cross-sectional area in the thickness direction becomes larger, so that the eddy current becomes larger than that when the adhesive layer is provided. Also, if there is no adhesive layer at all, the small piece will move freely, the shape as a magnetic core cannot be maintained, and even if the outer periphery is wrapped with a protective layer, if there is no adhesive layer, A person skilled in the art would expect that since the small pieces move freely inside the protective layer, the magnetic material may be biased and the characteristics may be adversely affected.

The present inventor has proposed a magnetic core provided with a plurality of soft magnetic ribbons, and a magnetic core not provided with an adhesive layer between some soft magnetic ribbons among the plurality of soft magnetic ribbons. The inventors arrived at the present invention by earnestly studying the results, which overturned the common sense of those skilled in the art that characteristics equivalent to those of a magnetic core provided with an adhesive layer between all soft magnetic ribbons were obtained. ..

The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic core, a coil unit, and a wireless power transmission unit that have a low cost structure.

To solve the above problems, the following means are provided.
(1) A magnetic core according to one aspect of the present invention is a magnetic core including a laminated body including a plurality of soft magnetic ribbons divided into small pieces and an adhesive layer provided between adjacent soft magnetic ribbons. Then, at least one pair of soft magnetic ribbons that are in contact with each other without an adhesive layer is provided in the laminate.

(2) In the above aspect, an adhesive layer may be provided on at least one surface of each soft magnetic ribbon.

(3) In the above aspect, a value obtained by dividing the number of layers of the adhesive layer by the number of layers of the soft magnetic ribbon may be 0.75 or less.

(4) A coil unit according to one aspect of the present invention includes the magnetic core according to the above aspect and a coil arranged on the magnetic core.

(5) A wireless power transmission unit according to one aspect of the present invention includes the coil unit according to the above aspect.

According to the present invention, it is possible to provide a magnetic core, a coil unit, and a wireless power transmission unit in which the number of adhesive layers is reduced as compared with the related art.

1A is a schematic sectional view of a magnetic core according to an embodiment of the present invention, and FIG. 1B is a schematic sectional view of a conventional magnetic core. (A) is a schematic cross-sectional view showing an example of the magnetic core of the present invention, (b) is a schematic cross-sectional view showing an example of the magnetic core of the present invention, and (c) is an example of the magnetic core of the present invention. 2D is a schematic sectional view showing an example of the magnetic core of the present invention, and FIG. 3E is a schematic sectional view showing an example of the magnetic core of the present invention. (A) is a side surface schematic diagram of the coil unit concerning one embodiment of the present invention, and (b) is a top view of the coil unit seen from the coil side. It is a coil unit concerning other embodiments, and is a top view of the coil unit seen from the coil side. It is a side surface schematic diagram of the wireless electric power transmission unit concerning one embodiment of the present invention which used the coil unit concerning one embodiment of the present invention as an electric power receiving coil unit and an electric power transmitting coil unit. FIG. 9 is a schematic side view of a wireless power transmission unit according to another embodiment of the present invention, which uses a coil unit according to another embodiment of the present invention as a power receiving coil unit and a power transmitting coil unit. FIG. 6 is a schematic cross-sectional view for explaining the manufacturing method of the example. 7 is a graph showing the magnitude of power transmission efficiency η in Examples and Comparative Examples. It is a graph which shows the temperature rise of a magnetic core at the time of power transmission efficiency measurement of an Example and a comparative example.

Hereinafter, the present embodiment will be described in detail with reference to the drawings. In the drawings used in the following description, in order to make the features of the present invention easy to understand, there are cases where features are enlarged for the sake of convenience, and the dimensional ratios of the respective components may be different from the actual ones. is there. The materials, dimensions, and the like exemplified in the following description are merely examples, and the present invention is not limited to them, and can be appropriately modified and implemented within the scope of the effects of the present invention.

[Magnetic core]
FIG. 1A is a schematic sectional view of a magnetic core according to one embodiment, and FIG. 1B is a schematic sectional view of a conventional magnetic core.
The magnetic core 10 shown in FIG. 1A is a laminated body M including a plurality of soft magnetic ribbons 1a to 1j divided into small pieces and adhesive layers 2a to 2e between adjacent soft magnetic ribbons. The magnetic core 10 including the soft magnetic ribbon 1b and the soft magnetic ribbon 1c, and the soft magnetic ribbon 1d and the soft magnetic layer, as a pair of the soft magnetic ribbons that are in contact with each other in the laminated body M without an adhesive layer. Four sets of a thin ribbon 1e, a soft magnetic thin strip 1f, a soft magnetic thin strip 1g, a soft magnetic thin strip 1h and a soft magnetic thin strip 1i are provided.
The magnetic core 10 shown in FIG. 1 includes protective films 3a and 3b on the upper surface and the lower surface of the laminated body, respectively.
The magnetic core of the present invention has the soft magnetic ribbon and the adhesive layer as the main members, like the ordinary magnetic core, but may include other components within the range that the effects of the present invention are exhibited. The magnetic core of the present invention comprises a soft magnetic ribbon and an adhesive layer when it is not provided with other components.

In the magnetic core of the present invention, at least one of the pair of adjacent soft magnetic ribbons is in contact without an adhesive layer. In other words, the magnetic core of the present invention does not have an adhesive layer between all adjacent soft magnetic ribbons, but may not have an adhesive layer between adjacent soft magnetic ribbons.
That is, in the case of the magnetic core 10 shown in FIG. 1, the adhesive layer 2a is provided between the soft magnetic ribbon 1a and the soft magnetic ribbon 1b, and between the soft magnetic ribbon 1c and the soft magnetic ribbon 1d. Has an adhesive layer 2b, an adhesive layer 2c between the soft magnetic ribbon 1e and the soft magnetic ribbon 1f, and an adhesive layer 2d between the soft magnetic ribbon 1g and the soft magnetic ribbon 1h. Although the adhesive layer 2e is provided between the soft magnetic ribbon 1i and the soft magnetic ribbon 1j, the soft magnetic ribbon 1d and the soft magnetic ribbon 1d are provided between the soft magnetic ribbon 1b and the soft magnetic ribbon 1c. There is no adhesive layer between the thin ribbon 1e, between the soft magnetic thin strip 1f and the soft magnetic thin strip 1g, and between the soft magnetic thin strip 1h and the soft magnetic thin strip 1i.
When there is no adhesive layer between adjacent soft magnetic ribbons, the adjacent soft magnetic ribbons are in contact with each other. The magnetic core 10 shown in FIG. 1 has four pairs of soft magnetic ribbons that are in contact with each other without an adhesive layer.

The magnetic core of the present invention has a low-cost structure including a pair of soft magnetic ribbons that are in contact with each other without an adhesive layer.
According to the magnetic core of the present invention, the cost can be reduced by reducing the number of adhesive layers, and the core can be thinned while maintaining the same function as the conventional one by reducing the thickness of the adhesive layer. The effect that the eddy current loss in the direction is reduced, and further the increase in the loss in the plane parallel direction of the laminated portion without the adhesive layer can be suppressed.

On the other hand, in the conventional magnetic core, as shown in FIG. 1B, between the soft magnetic ribbons of the ten soft magnetic ribbons 1Aa to 1Aj forming the laminated body MA together with the adhesive layers 2Aa to 2Aj. All of them have a bonding layer.
That is, the adhesive layer 2Aa is provided between the soft magnetic ribbon 1Aa and the soft magnetic ribbon 1Ab, and the adhesive layer 2Ab is provided between the soft magnetic ribbon 1Ab and the soft magnetic ribbon 1Ac. An adhesive layer 2Ac is provided between the ribbon 1Ac and the soft magnetic ribbon 1Ad, and an adhesive layer 2Ad is provided between the soft magnetic ribbon 1Ad and the soft magnetic ribbon 1Ae. An adhesive layer 2Ae is provided between the soft magnetic ribbon 1Af and an adhesive layer 2Af between the soft magnetic ribbon 1Af and the soft magnetic ribbon 1Ag, and the soft magnetic ribbon 1Ag and the soft magnetic ribbon are provided. The adhesive layer 2Ag is provided between the soft magnetic ribbon 1Ah and the soft magnetic ribbon 1Ai, and the adhesive layer 2Ah is provided between the soft magnetic ribbon 1Ah and the soft magnetic ribbon 1Ai. Has an adhesive layer 2Ai.

An adhesive layer is preferably provided on at least one surface (upper surface or lower surface) of each soft magnetic ribbon.
This is because if the adhesive layer is provided on at least one surface of the soft magnetic ribbon, the small pieces of the soft magnetic ribbon are fixed by the adhesive layer, so that the characteristics are stable.

A value obtained by dividing the number of adhesive layers by the number of soft magnetic ribbons is preferably 0.75 or less.
With such a configuration, the number of adhesive layers is considerably smaller than that of the conventional configuration, and the cost reduction effect is large.
The lower limit of the value obtained by dividing the number of adhesive layers by the number of soft magnetic ribbons can be set to 0.5.

In the case of the magnetic core 10 shown in FIG. 1A, the number of adhesive layers is 5 and the number of soft magnetic ribbons is 10. Therefore, the number of adhesive layers is equal to the number of soft magnetic ribbons. The value divided by the number of layers is 0.5.

FIG. 2 shows an example of the magnetic core of the present invention and an example of the magnetic core not of the present invention. In all the examples of the magnetic core shown in FIG. 2, the protective layer 3 surrounds the outer side of the laminated body including the soft magnetic ribbon and the adhesive layer.
As the protective layer 3, an aramid film, a PET film, a polyimide film, a PPS film or the like can be used.

As the soft magnetic ribbon for the magnetic core, a known material can be used, for example, an amorphous alloy, a microcrystalline alloy, a magnetic alloy such as permalloy, or the like can be used. The amorphous alloy material includes, for example, an Fe-based amorphous soft magnetic material and a Co-based amorphous material, and the microcrystalline alloy material includes, for example, an Fe-based nanocrystalline soft magnetic material. There is something.

As the adhesive layer, a known adhesive layer can be used, and examples thereof include those in which an acrylic adhesive is applied to the surface of a PET film, and those in which a silicone adhesive is applied to a polyester film.

The magnetic core shown in FIG. 2A is a case where the soft magnetic ribbon has 6 layers and the adhesive layers have 3 layers, and there is no adhesive layer on either the upper surface or the lower surface of the laminated body, It is an example of having an adhesive layer between matching soft magnetic ribbons, in which a pair of soft magnetic ribbons having an adhesive layer between them and a pair of soft magnetic ribbons having no adhesive layer between them are alternately arranged. is there. This example is the magnetic core of the present invention because it has two pairs of soft magnetic ribbons having no adhesive layer between them. In this example, the value obtained by dividing the number of adhesive layers by the number of soft magnetic ribbons is 0.5.

In the magnetic core shown in FIG. 2B, the examples on the left side and the example on the right side each have five soft magnetic ribbons and three adhesive layers.
In the example on the left side, a pair of soft magnetic ribbons that have an adhesive layer on one end surface (upper surface) of the laminate and have an adhesive layer between them alternate with a pair of soft magnetic ribbons that do not have an adhesive layer between them. This is the case when arranging in. This example is the magnetic core of the present invention because it has two pairs of soft magnetic ribbons having no adhesive layer between them. In this example, the value obtained by dividing the number of adhesive layers by the number of soft magnetic ribbons is 0.6.
On the other hand, the example on the right side does not have an adhesive layer on either end face of the upper and lower surfaces of the laminate, and in the order from the upper side, a pair of soft magnetic ribbons having an adhesive layer between them, and no adhesive layer between them. This is a case where a pair of soft magnetic ribbons, a pair of soft magnetic ribbons having an adhesive layer between them, and a pair of soft magnetic ribbons having an adhesive layer between them are arranged. This example is a magnetic core of the present invention because it has one pair of soft magnetic ribbons having no adhesive layer between them. In this example, the value obtained by dividing the number of adhesive layers by the number of soft magnetic ribbons is 0.6.

The magnetic core shown in FIG. 2C has four layers of soft magnetic ribbons in both the left and right examples, while the left example has two adhesive layers, while the right example has four layers. The adhesive layer is three layers.
The example on the left is an example in which no adhesive layer is provided on either the upper surface or the lower surface of the laminate, and an adhesive layer is provided between adjacent soft magnetic ribbons. This is a case where pairs and pairs of soft magnetic ribbons having no adhesive layer are alternately arranged. This example is a magnetic core of the present invention because it has one pair of soft magnetic ribbons having no adhesive layer between them. In this example, the value obtained by dividing the number of adhesive layers by the number of soft magnetic ribbons is 0.5.
On the other hand, the example on the right side has a pair of soft magnetic ribbons having an adhesive layer on each of the upper and lower end faces of the laminate and having no adhesive layer between them, and a soft magnetic ribbon having an adhesive layer between them. This is a case where pairs are arranged alternately. This example is the magnetic core of the present invention because it has two pairs of soft magnetic ribbons having no adhesive layer between them. In this example, the value obtained by dividing the number of adhesive layers by the number of soft magnetic ribbons is 0.75.

The magnetic core shown in FIG. 2D is a case where the soft magnetic ribbon has three layers and the adhesive layer has two layers, and the adhesive layer is provided on one end surface (lower surface) of the laminate, and the adhesive layer is provided between them. In this case, a pair of soft magnetic ribbons having a and a pair of soft magnetic ribbons having no adhesive layer between them are alternately arranged. This example is a magnetic core of the present invention because it has one pair of soft magnetic ribbons having no adhesive layer between them. In this example, the value obtained by dividing the number of adhesive layers by the number of soft magnetic ribbons is 0.67.

The magnetic core shown in FIG. 2E is a case where the soft magnetic ribbon has two layers and the adhesive layer has two layers.
This example is a magnetic core of the present invention because it has an adhesive layer on each of the upper and lower end faces of the laminate and one pair of soft magnetic ribbons having no adhesive layer between them. In this example, the value obtained by dividing the number of adhesive layers by the number of soft magnetic ribbons is one.

The magnetic core of the present invention may include other layers as long as the effects of the present invention are exhibited. Other layers include, for example, the above-described protective films 3a and 3b, and a heat conductive sheet for efficiently dissipating heat generated in the magnetic core.

[Coil unit]
FIG. 3A is a schematic side view of the coil unit according to the embodiment, and FIG. 3B is a plan view of the coil unit seen from the coil side.
The coil unit 100 shown in FIG. 3 includes a magnetic core 10 and a coil 20 arranged on the magnetic core 10.
The coil unit 100 shown in FIG. 3 can be used as both a power receiving coil unit and a power transmitting coil unit.

FIG. 4 is a coil unit according to another embodiment, and is a plan view of the coil unit viewed from the coil side.
The coil unit 101 shown in FIG. 4 includes a magnetic core 10 and a coil 21 arranged on the magnetic core 10. Compared with the coil unit shown in FIG. 3, it is different in that the coil is rectangular.

According to the coil unit of the present invention, there is an effect that the wireless power transmission unit can be made thin and lightweight while suppressing an increase in cost.

[Wireless power transmission unit]
FIG. 5 is a schematic side view of a wireless power transmission unit using the coil unit according to the embodiment as a power reception coil unit and a power transmission coil unit. In the figure, the power reception coil unit and the power transmission coil are included in the wireless power transmission unit. Only units are shown. Other components of the wireless power transmission unit include, for example, a power supply, an amplifier unit including an inverter, a power receiving unit including a rectifier, a charging unit for charging the received electricity to a storage battery, or a voltage suitable for a device. There is a DCDC converter for doing so.
The wireless power transmission unit 200 shown in FIG. 5 includes a power transmission coil unit 210 including the magnetic core 10 and the power transmission coil 20, and a power receiving coil unit 220 including the magnetic core 30 and the power receiving coil 40.

FIG. 6 is a schematic side view of a wireless power transmission unit that uses a coil unit according to another embodiment as a power reception coil unit and a power transmission coil unit. Only the coil unit is shown.
A wireless power transmission unit 300 shown in FIG. 6 includes a power transmission coil unit 310 including a bobbin 11, a magnetic core 12, a metal shield 13 and a power transmission coil 20, and a power reception including a bobbin 31, a magnetic core 32, a metal shield 33 and a power reception coil 40. And a coil unit 320.
This embodiment differs from the embodiment shown in FIG. 5 in that the power transmission coil unit 310 includes the bobbin 12 and the metal shield 13, and similarly, the power receiving coil unit 320 includes the bobbin 32 and the metal shield 33.
The bobbin is a resin component for winding the coil cleanly, and the metal shield is a metal plate for blocking the leakage magnetic flux so as not to affect peripheral devices.

Although the embodiments of the present invention have been described in detail above with reference to the drawings, the configurations and combinations thereof in each of the embodiments are examples, and addition and omission of the configurations are not departing from the scope of the present invention. , Substitutions, and other changes are possible.

"Example"
1. Production of Magnetic Core A method for producing the magnetic core will be described with reference to FIG. 7. The following (1) to (3) correspond to (1) to (3) in FIG.
(1) First, a nanocrystal soft magnetic ribbon having a thickness of about 20 μm that has been preheated is adhered to one side of a PET film (5 μm in which the PET film and the adhesive are combined together) having a thickness of 5 μm coated with an adhesive on both sides. Then, a magnetic sheet (a structure in which a nanocrystal soft magnetic thin strip was attached to a PET film having an adhesive layer coated on one side as an adhesive layer, the size of which is 150 mm×150 mm) was prepared.
(2) Next, the nanocrystalline soft magnetic ribbon of the magnetic sheet with the nanocrystalline soft magnetic ribbon adhered to both sides is subjected to a knurled surface treatment as a fragmentation treatment to obtain a fragmented magnetic strip. A sheet was prepared.
(3) Next, the entire surface of the laminated body in which five pieces of the diced magnetic sheets were laminated was wrapped with an aramid film having a thickness of about 5 μm as a protective layer to form a magnetic core.
In this case, the value obtained by dividing the number of adhesive layers by the number of soft magnetic ribbons is 0.5.

2. Evaluation (1) Inductance of coil The obtained magnetic core was arranged in a planar spiral coil of 22 turns, and the inductance of the coil was measured using an LCR meter.
(2) Transmission efficiency (output power/input power) η
A wireless power transmission device including a power transmission unit including a DC power supply, an amplifier unit, a resonance capacitor, and a power transmission coil unit, and a power reception unit including a power reception coil unit, a resonance capacitor, a rectifying/smoothing circuit, and an electronic load. A ferrite plate having a thickness of 1.5 mm is used as the magnetic core of the unit, and a power transmitting coil unit and a power receiving coil unit that use the magnetic core of the first embodiment as the magnetic core of the power receiving coil unit are opposed to each other with a coil-to-coil distance of 60 mm. Then, the transmission efficiency η (100×(output power/input power)) when 250 W of power was received by wireless power transmission was measured.
The input power and the output power were measured using a power meter (Yokogawa WT210).
(3) Temperature of magnetic core during measurement of power transmission efficiency During measurement of power transmission efficiency, a thermocouple was attached to the magnetic core of the power receiving coil to measure the temperature rise of the magnetic core.

The evaluation results are shown in Table 1 and FIGS. 8 and 9. The power transmission efficiency η is (output power/input power)×100, and the temperature increase ΔT is the core temperature−room temperature.

"Comparative example"
The magnetic core of the comparative example was manufactured as follows.
A pre-heat treated nanocrystalline soft magnetic ribbon of about 20 μm in thickness was adhered to both sides of a PET film having a thickness of 5 μm, which was applied to both sides, and then the adhesive was applied to both sides in order. PET film (adhesive layer (second layer)), nanocrystalline soft magnetic ribbon (third layer), adhesive layer (third layer), nanocrystalline soft magnetic ribbon (fourth layer), adhesive layer (four layers) Eye), nanocrystalline soft magnetic ribbon (fifth sheet), adhesive layer (fifth layer), nanocrystalline soft magnetic ribbon (sixth sheet), adhesive layer (sixth layer), nanocrystalline soft magnetic ribbon ( 7th), adhesive layer (7th layer), nanocrystalline soft magnetic ribbon (8th), adhesive layer (8th layer), nanocrystalline soft magnetic ribbon (9th), adhesive layer (9th layer) Eye), a nanocrystal soft magnetic ribbon (10th sheet) was laminated to produce a laminated body, and thereafter, this laminated body was subjected to the same fragmentation treatment as in the example to obtain a nanocrystal soft magnetic ribbon. A magnetic core was obtained by wrapping the entire surface of the diced laminate with a protective layer similar to that of the example to form an integrated body.
The comparative example also has the same number of nanocrystalline soft magnetic ribbons (the number of layers) as the example, but differs from the example in that an adhesive layer is provided between all the pairs of nanocrystalline soft magnetic ribbons.
Similarly, in the comparative example, the temperature of the magnetic core was measured when measuring the inductance of the coil and the power transmission efficiency ((output power/input power)×100) power transmission efficiency.

As shown in Table 1, FIG. 8 and FIG. 9, in the example, the coil inductance, the power transmission efficiency η by the power transmission coil unit and the power receiving coil unit, and the temperature rise of the magnetic core during the measurement of the power transmission efficiency are all of the conventional structure. It was confirmed that it was almost the same as the comparative example. That is, it was confirmed that the example has a lower cost structure than the conventional structure, but has substantially the same characteristics as the comparative example of the conventional structure.

1a-1j Soft magnetic ribbon 2a-2e Adhesive layer 3,3a,3b Protective film 10,12,30,32 Magnetic core 20,21,40, Coil 100,101 Coil unit 200,300 Wireless power transmission unit 210,310 Power transmitting coil unit 220, 320 Power receiving coil unit Laminated body M

Claims (5)

A magnetic core including a laminate including a plurality of soft magnetic ribbons divided into small pieces and an adhesive layer between adjacent soft magnetic ribbons,
A magnetic core comprising at least one pair of soft magnetic ribbons which are in contact with each other without an adhesive layer in the laminate. The magnetic core according to claim 1, wherein an adhesive layer is provided on at least one surface of each soft magnetic ribbon. The magnetic core according to claim 1, wherein a value obtained by dividing the number of layers of the adhesive layer by the number of layers of the soft magnetic ribbon is 0.75 or less. A coil unit comprising the magnetic core according to claim 1, and a coil arranged on the magnetic core. A wireless power transmission unit comprising the coil unit according to claim 4.

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