JP7518673B2 - Power transmission equipment - Google Patents

Description

The present invention relates to a power transmission device that transmits power to a device having a receiving coil by magnetic coupling.

Methods of supplying power to electrical and electronic devices through electromagnetic coupling can be broadly classified into the following two methods. The first is non-radiative power transmission, and the second is radiative power transmission. The first method mainly includes an electromagnetic induction method that uses the principles of a transformer at frequencies of about 100 kHz or less, and an electromagnetic coupling method that uses electromagnetic resonance in the near field (static energy stored in the near field) at frequencies of about several tens of MHz.

The methods disclosed in the following Patent Documents 1 and 2 are known as power transmission using the electromagnetic induction method. Patent Document 1 discloses a contactless charging device for a mobile terminal device, which supplies wireless power from a primary coil, receives the power with a secondary coil magnetically coupled to the primary coil, and charges a battery connected to the secondary coil. It is also disclosed that this device is provided with a shielding plate that shields the magnetic field generated by the primary coil and the secondary coil. Patent Document 2 discloses a contactless power supply device for an electric vehicle. It is also disclosed that this device is provided with a shielding member above the receiving coil to prevent leakage of magnetic flux. Patent Document 3 discloses a contactless power supply device for an electric vehicle, and discloses that a cancellation coil is provided to cancel leakage magnetic flux from the transmitting coil. In addition, the method disclosed in the following Patent Document 4 is known as an electromagnetic coupling method using electromagnetic resonance.

Patent Publication 2009-268334 Patent Publication 2016-103613 Patent Publication 2014-110726 Patent Publication 2011-205750

When transmitting power through non-contact magnetic coupling, the presence of leakage magnetic flux can lead to problems such as reduced power transmission efficiency and adverse effects on other devices. The technologies in Patent Documents 1 and 2 are based on the idea of magnetically shielding the magnetic flux so that it does not leak to the outside. Patent Document 3 is based on the idea of eliminating the leakage magnetic flux from the transmission coil by passing current through a cancellation coil.

However, the technology of Patent Document 1 provides shielding plates on the outside of the power transmission coil and the outside of the power receiving coil, and does not take into account leakage magnetic flux from the sides. In order to make it possible for a device having a power receiving coil to be detachable from a power transmission device having a power transmission coil, it is impossible to provide shielding in all directions, so the method of Patent Document 1 does not provide sufficient shielding. The method of Patent Document 2 only provides a shielding member on the upper side of the power receiving coil (opposite the power transmission coil) to prevent magnetic flux from leaking to the upper vehicle body side, but leakage still exists around the power receiving coil.

The method of Patent Document 3 is a method of passing a current of opposite phase to the current passing through the power transmission coil through a cancel coil to eliminate leakage magnetic flux due to the power transmission coil. In addition, the phase of the current flowing through the power receiving coil is detected and a current of the opposite phase is passed through the cancel coil to cancel the leakage magnetic flux due to the current flowing through the power receiving coil. In addition to a method of using an independent oscillator to pass a current of opposite phase to the current flowing through the power transmission coil or power receiving coil through the cancel coil, it has been proposed to set the connection direction of both coils so that a current of opposite phase flows. Furthermore, in order to reduce the coupling between the power transmission coil and its cancel coil and the coupling between the power receiving coil and its cancel coil, a conductor plate is provided between the power transmission coil and the power receiving coil and the corresponding cancel coil.

However, even if the cancellation coil disclosed in Patent Document 3 is used, it is difficult to eliminate the magnetic flux leaking to the outer side peripheral portion of the entire circumference of the plate-shaped power transmission coil without reducing the transmission efficiency.
The present invention has been made to solve this problem, and has an object to eliminate magnetic flux leaking to the side peripheral portion outside the entire circumference of a plate-shaped winding transmission coil without reducing transmission efficiency.

The present invention relates to a power transmission device that transmits power to an apparatus having a receiving coil by magnetic coupling, the power transmission device comprising: a flat plate facing the receiving coil; a power transmission coil arranged on the flat plate and wound into a flat shape that allows the generated AC magnetic flux to pass through the receiving coil; a shield arranged around the power transmission coil and attenuating the AC magnetic field; and a canceling coil wound around the shield on the side opposite to the side where the power transmission coil is arranged and for eliminating leakage magnetic flux when power is transmitted to the receiving coil, the canceling coil being connected in series with the power transmission coil so that the current flowing through the power transmission coil flows in a direction that eliminates the leakage magnetic flux, and the shielding has a wall surface perpendicular to the surface on which the power transmission coil is arranged .

In the present invention, the canceling coil may be connected in series with the power transmitting coil so that the current flowing through the power transmitting coil flows in a direction that eliminates the leakage magnetic flux. The power transmitting coil and the canceling coil may be separate and independent, and a current of a predetermined phase with respect to the current supplied to the power transmitting coil may be supplied to the canceling coil so as to eliminate the leakage magnetic flux. Furthermore, basically, the leakage magnetic flux is the leakage magnetic flux due to the power transmitting coil. However, it may also be something that eliminates the leakage magnetic flux due to the current flowing through the power receiving coil.

The canceling coil may be wound on any surface, but may be wound on a surface perpendicular to the surface on which the power transmitting coil is arranged. The canceling coil may be a flat coil wound on a surface parallel to the surface on which the power transmitting coil is arranged. The shielding body preferably has a wall surface perpendicular to the surface on which the power transmitting coil is arranged. The shielding body preferably has a ceiling portion covering the upper part of the canceling coil. Furthermore, the shielding body may be below the power transmitting coil and have a bottom surface portion extending in the direction of the power transmitting coil. The material of the flat plate on which the power transmitting coil is arranged may be any material, but is preferably a ferromagnetic material. It is preferable that a ferromagnetic material is arranged between the shielding body and the canceling coil. It is preferable that the shielding body is a non-magnetic conductor. It is preferable that the shielding body is a non-magnetic conductive material, such as aluminum, that transmits magnetic fields but attenuates AC magnetic fields due to eddy current loss. In other words, the shielding body functions to reduce the magnetic coupling between the power transmitting coil and the canceling coil.

In the above invention, the transmission method is arbitrary. For example, it may be an electromagnetic induction method (magnetic field coupling method) using a frequency range of several hundred kHz or less. It may be a method called an electromagnetic resonance method or a magnetic resonance transmission method using a frequency of about 10 MHz. A resonant circuit such as a capacitor or coil for resonance may be connected to the transmission coil. In addition, it is preferable that the axis of the power transmission coil and the axis of the cancellation coil are coaxial. It is preferable that the shield is arranged around the entire outer circumference of the side circumference of the power transmission coil, but it is not necessary that it is present in part of the circumference. The winding shape of the power transmission coil and the cancellation coil is arbitrary as long as it is formed in a flat shape such as a circle, a rectangle, or a rectangle with arc-shaped corners. The cancellation coil may be formed on a plane parallel to the formation surface of the power transmission coil, or on a perpendicular plane.

According to the present invention, the canceling coil and the shielding plate can attenuate the magnetic flux leaking to the outer peripheral portion of the entire circumference of the plate-shaped winding transmitting coil without reducing the transmission efficiency to the receiving coil.

1 is a cross-sectional view showing the overall configuration of a power transmitting device according to a first specific embodiment of the present invention and a power receiving device that receives the transmitted power. FIG. 2 is a plan view of the power transmitting device according to the first embodiment. 1 is a circuit diagram of a power transmitting device and a power receiving device that receives power from the power transmitting device according to a first embodiment. FIG. 4 is an explanatory diagram showing the positional relationship between a power transmitting coil and a power receiving coil used in a simulation of a magnetic field strength distribution in the first embodiment. FIG. 4 is a characteristic diagram showing the magnetic field strength distribution in the x-axis direction by the power transmitting device of the first embodiment. FIG. 11 is a circuit diagram of a power transmitting device according to a second embodiment and a power receiving device that receives power from the power transmitting device. FIG. 11 is a circuit diagram of a power transmitting device according to a third embodiment and a power receiving device that receives power from the power transmitting device. FIG. 13 is a configuration diagram showing a power transmitting device according to a fourth embodiment. FIG. 13 is a configuration diagram showing a power transmitting device according to a fifth embodiment.

Specific examples of the present invention will be described below with reference to the drawings, but the present invention is not limited to these examples.

1 is a cross-sectional view showing the relationship between a power transmission device 100 according to the first embodiment and a power receiving device 200 of a portable device to which power is transmitted by the power transmission device 100. FIG. 2 is a plan view of the power transmission device 100. A flat ferrite 2 is embedded on the upper surface 6a of a rectangular parallelepiped housing 6, and a power transmission coil 1 made of copper wire is arranged on the upper surface of the ferrite 2. The power transmission coil 1 is wound in a planar shape. The main surface through which the magnetic flux generated by the power transmission coil 1 penetrates vertically is positioned so as to face parallel to the main surface of the power receiving coil 7. The power transmission coil 1 may be wire-shaped or flat (tape-shaped). A metal body 3, which is a shielding body, is arranged to surround the entire periphery of the power transmission coil 1 and the ferrite 2. The material of the metal body is arbitrary, but aluminum is used in this embodiment. The metal body 3 electromagnetically induces the leakage magnetic flux between the transmitting coil 1 and the receiving coil 7 in the canceling coil 4, but attenuates the main magnetic flux generated by the transmitting coil 1, reducing the magnetic coupling between the transmitting coil 1 and the canceling coil 4 and reducing the mutual inductance between the two. This increases the coupling coefficient between the transmitting coil 1 and the receiving coil 7. Therefore, it is desirable for the metal body 3 to be a material that allows the leakage magnetic flux to pass through but attenuates the main magnetic flux through eddy current loss, and a material with low magnetic permeability but high conductivity is desirable.

The metal body 3 has a side wall portion 3a perpendicular to the main surface of the power transmission coil 1, a ceiling portion 3b, and a bottom portion 3c. The ceiling portion 3b is bent outward from the side wall portion 3a on the opposite side to the side where the power transmission coil 1 is disposed, and is formed parallel to the main surface of the power transmission coil 1. The bottom portion 3c is bent inward from the side wall portion 3a on the side where the power transmission coil 1 is present, and is formed parallel to the main surface of the power transmission coil 1. The bottom portion 3c extends downward near the side circumference of the ferrite 2.

Ferrite 5 is arranged in a rectangular frame shape on the outer surface of the side wall portion 3a of the metal body 3. A cancel coil 4 wound in a rectangular shape is arranged on the outer surface of the ferrite 5. The cancel coil 4 and ferrite 5 are covered at the top by the ceiling portion 3b of the metal body 3. The presence of the ceiling portion 3b more effectively suppresses the coupling between the power transmission coil 1 and the cancel coil 4. The ferrite 2, metal body 3, ferrite 5, and cancel coil 4 are molded together with the housing 6.

The power receiving device 200 has a housing 9, ferrite 8, a power receiving coil 7, a control device, a display device, etc. This power receiving device 200 is, for example, a mobile terminal such as a smartphone, or a battery that drives the mobile terminal. The power transmitting device 100 is a device for charging the battery of the mobile terminal. The power receiving device 200 is arranged in a non-contact and detachable manner with respect to the power transmitting device 100 so that the power receiving coil 7 faces the power transmitting coil 1 of the power transmitting device 100.

In FIG. 1, ferrite 2 of power transmission device 100 prevents magnetic flux generated by power transmission coil 1 from leaking to the opposite side of power reception device 200 (the lower side in the drawing). Similarly, ferrite 8 of power reception device 200 prevents magnetic flux generated by power reception coil 7 from leaking to the opposite side of power transmission device 100 (the upper side in the drawing). These ferrites 2 and 8 increase the coupling coefficient between power transmission coil 1 and power reception coil 7.

The metal body 5, which acts as a shield, is provided to reduce the coupling coefficient between the power transmission coil 1 and the canceling coil 4. The metal body 5 is provided to prevent or reduce the main magnetic flux that passes from the power transmission coil 1 to the power receiving coil 7 from passing through the canceling coil 4. The metal body 5 allows the leakage magnetic flux output by the power transmission coil 1 and the leakage magnetic flux output by the power receiving coil 7 to pass through the canceling coil 4.

3 is a circuit diagram of the power transmitting device 100 and the power receiving device 200. Power is supplied to the power transmitting coil ₁ and the canceling coil 4 from a high frequency power source 21. The capacitor C1 of the power transmitting device 100 and the capacitor _C2 of the power receiving device 200, together with the inductances of the power transmitting coil 1, the canceling coil 4, and the power receiving coil 7, are elements for realizing a resonant state with respect to the frequency of the high frequency power source 21 and increasing the Q value.

The canceling coil 4 and the power transmitting coil 1 are connected in series, and the same current flows through them. The power transmitting coil 1 and the canceling coil 4 are connected in series so that the direction of the magnetic flux generated by the power transmitting coil 1 and the direction of the magnetic flux generated by the canceling coil 4 are opposite. The load R of the power receiving device 200 is expressed as a resistor, but in reality it is a rectifier circuit and a battery. The transmitted power from the power transmitting device 100 is transmitted as an AC electromagnetic field from the power transmitting coil 1, received by the power receiving coil 7 in a non-contact manner, rectified, and charged into a battery for driving the mobile terminal device.

Next, the magnitude of leakage magnetic flux was determined by simulation. Figure 4 shows the positional relationship between the transmitting coil 1 and the receiving coil 7. An o-xyz coordinate system was set as shown in Figure 1. The origin is the center of the circle of the transmitting coil 1 in the xy plane, and the origin o is set at the midpoint of the distance between the main surface of the transmitting coil 1 and the main surface of the receiving coil 7 in the xz plane. In Figure 4, the x axis is set in the horizontal direction, the y axis is set in the height direction, and the z axis is set in the central axis direction. The coordinates (x, y, z) of the central axis of the transmitting coil 1 are (0, 0, -2.5), and the coordinates (x, y, z) of the central axis of the receiving coil 7 are (0, 5, 2.5). The unit is mm. The separation distance (distance between the main surfaces) between the transmitting coil 1 and the receiving coil 7 in the z-axis direction is 5 mm. The transmission power was 15 W, the frequency was 140 kHz, the transmission current of the power transmission coil 1 was 2.67 A, and the load current of the power receiving coil 7 was 1.42 A, with a 90 degree lead phase with respect to the transmission current. The ampere turn of the cancel coil 4 was 10 AT. That is, the number of turns was 3.75. The power transmission coil 1 and the power receiving coil 7 were set in the positional relationship shown in FIG. 4, and the magnetic field strength in the x-axis direction, i.e., the magnetic field strength at the coordinate (x, 0, 0), was simulated for two cases, one with the cancel coil 4 provided and one without it. The results are shown in FIG. 5. However, the origin 0 of the x-axis in FIG. 5 is 39.5 in the x-coordinate of the above coordinate system. In other words, the x-coordinate is taken as the x-coordinate of the outer periphery of the cancel coil 4, and the value is on the x-axis from the outer periphery toward the outside. It can be seen that the leakage magnetic flux is reduced by providing the cancel coil 4.

In the first embodiment, the power transmission coil 1 and the canceling coil 4 are connected in series so that a power transmission current flows through the canceling coil 4 in a direction that cancels the leakage magnetic flux of the power transmission coil 1. In other words, the two coils are connected so that the winding direction relative to the current is opposite. In contrast, in the present embodiment, as shown in FIG. 6, the power transmission coil 1 and the canceling coil 4 are not connected but are independent, and the power transmission coil 1 is driven by the high-frequency power supply 21a, and the canceling coil 4 is driven by the high-frequency power supply 21b. The phase of the output current of the high-frequency power supplies 21a and 21b is synchronized in opposite phases by the synchronizing circuit 23. The phase of the current relative to the power transmission current is controlled so that the current flowing through the canceling coil 4 cancels the magnetic flux penetrating the canceling coil 4. In this embodiment, unlike the first embodiment, the winding direction relative to the current of the power transmission coil 1 and the canceling coil 4 (the connection method of the polarity of both coils) is arbitrary.

In the first embodiment, the power transmission coil 1 and the canceling coil 4 are connected in series so that a power transmission current flows through the canceling coil 4 in a direction that cancels the leakage magnetic flux of the power transmission coil 1, and in the second embodiment, two independent high-frequency power sources are used so that a current of opposite phase to the power transmission current flowing through the power transmission coil 1 flows through the canceling coil 4. In contrast, in this embodiment, as shown in FIG. 7, the power transmission coil 1 and the canceling coil 4 are not connected but are independent, and the power transmission coil 1 is driven by the high-frequency power source 21a and the canceling coil 4 is driven by the high-frequency power source 21b. The phase of the output current of the high-frequency power source 21a and the high-frequency power source 21b is independently controlled by the phase control circuit 24. The phase of the current relative to the power transmission current is controlled so that the current flowing through the canceling coil 4 cancels the magnetic flux penetrating the canceling coil 4. This method also allows the leakage magnetic flux of the power transmission coil 1 to be eliminated by the canceling coil 4. In this method, the phase of the current passing through the cancel coil 4 is controlled independently of the phase of the transmission current through the transmission coil 1, so the combined magnetic flux of the leakage magnetic flux of the transmission coil 1 and the leakage magnetic flux of the receiving coil 7 can be eliminated by the cancel coil 4.

This embodiment is an example in which a different configuration of the shield is adopted. In this embodiment, the metal body 30, which is the shield, is configured in a rectangular frame shape as shown in FIG. 8(a). That is, the metal body 3 in the first embodiment has a ceiling portion 3b and a bottom portion 3c, but in the metal body 30 in this embodiment, the metal body 30 consists only of the side wall portion 3a of the first embodiment. As shown in FIGS. 8(a) and (b), a frame-shaped ferrite 5 is provided on the outer peripheral surface of the metal body 30, and a cancel coil 4 is wound around the outer peripheral surface of the ferrite 5. Note that the housing 6 in the first embodiment is not shown.

As shown in FIG. 9, in this embodiment, the metal body 31, which is a shield, has a rectangular frame shape, similar to that of the fourth embodiment. The metal body 31 is provided on a flat ferrite plate 2a. A planar canceling coil 4a is wound on the outside of the frame of the metal body 31 on the flat ferrite plate 2a. Therefore, the main surface of the flat power transmission coil 1 and the main surface of the flat canceling coil 4a are parallel to each other. The housing 6 in the first embodiment is not shown.

The present invention can be used in devices that supply power to the battery of devices such as mobile terminals in a non-contact manner.

Reference Signs List 1: power transmission coil 2, 5, 8: ferrite 7: power receiving coil 3, 30, 31: metal body 3a: side wall portion 3b: ceiling portion 3c: bottom portion 100: power transmission device

Claims (13)

In a power transmitting device that transmits power to a device having a power receiving coil by magnetic coupling,
A flat plate facing the receiving coil;
a power transmission coil wound in a flat shape disposed on the flat plate and passing a generated AC magnetic flux through the power receiving coil;
a shield disposed around the power transmission coil and configured to attenuate an AC magnetic field;
a cancel coil that is wound around the shield on a side opposite to the side where the power transmitting coil is disposed, and that cancels leakage magnetic flux when power is transmitted to the power receiving coil;
the canceling coil is connected in series with the power transmitting coil so that a current flowing through the power transmitting coil flows in a direction that cancels the leakage magnetic flux,
The shield has a wall surface perpendicular to the surface on which the power transmitting coil is disposed.
A power transmitting device comprising: In a power transmitting device that transmits power to a device having a power receiving coil by magnetic coupling,
A flat plate facing the receiving coil;
a power transmission coil wound in a flat shape disposed on the flat plate and passing a generated AC magnetic flux through the power receiving coil;
a shield disposed around the power transmission coil and configured to attenuate an AC magnetic field;
a cancel coil that is wound around the shield on a side opposite to the side where the power transmitting coil is disposed, and that cancels leakage magnetic flux when power is transmitted to the power receiving coil;
the canceling coil is connected in series with the power transmitting coil so that a current flowing through the power transmitting coil flows in a direction that cancels the leakage magnetic flux,
The shield has a ceiling portion that covers an upper portion of the cancel coil.
A power transmitting device comprising: In a power transmitting device that transmits power to a device having a power receiving coil by magnetic coupling,
A flat plate facing the receiving coil;
a power transmission coil wound in a flat shape disposed on the flat plate and passing a generated AC magnetic flux through the power receiving coil;
a shield disposed around the power transmission coil and configured to attenuate an AC magnetic field;
a cancel coil that is wound around the shield on a side opposite to the side where the power transmitting coil is disposed, and that cancels leakage magnetic flux when power is transmitted to the power receiving coil;
the canceling coil is connected in series with the power transmitting coil so that a current flowing through the power transmitting coil flows in a direction that cancels the leakage magnetic flux,
The shield is located below the power transmitting coil and has a bottom surface portion extending toward the power transmitting coil.
A power transmitting device comprising: In a power transmitting device that transmits power to a device having a power receiving coil by magnetic coupling,
A flat plate facing the receiving coil;
a power transmission coil wound in a flat shape disposed on the flat plate and passing a generated AC magnetic flux through the power receiving coil;
a shield disposed around the power transmission coil and configured to attenuate an AC magnetic field;
a cancel coil that is wound around the shield on a side opposite to the side where the power transmitting coil is disposed, and that cancels leakage magnetic flux when power is transmitted to the power receiving coil;
the canceling coil is connected in series with the power transmitting coil so that a current flowing through the power transmitting coil flows in a direction that cancels the leakage magnetic flux,
A ferromagnetic body is disposed between the shield and the cancel coil.
A power transmitting device comprising: 5. The power transmitting device according to claim 1, wherein the leakage magnetic flux is a leakage magnetic flux due to the power transmitting coil. 6. The power transmitting device according to claim 1, wherein the cancel coil is wound on a plane perpendicular to a plane on which the power transmitting coil is disposed. 6. The power transmitting device according to claim 1, wherein the cancel coil is a flat coil wound on a plane parallel to a plane on which the power transmitting coil is disposed. 5. The power transmitting device according to claim 2 , wherein the shielding body has a wall surface perpendicular to a surface on which the power transmitting coil is disposed. The power transmitting device according to claim 1 , 3 or 4 , wherein the shielding body has a ceiling portion covering an upper portion of the cancel coil. The power transmitting device according to claim 1 , 2 , or 4 , wherein the shield is located below the power transmitting coil and has a bottom surface portion extending in the direction of the power transmitting coil. The power transmitting device according to claim 1 , wherein the flat plate is made of a ferromagnetic material. 4. The power transmitting device according to claim 1, further comprising a ferromagnetic body disposed between the shield and the cancel coil. The power transmitting device according to claim 1 , wherein the shield is a non-magnetic conductor.

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