JP5759716B2 - Wireless power transmission system - Google Patents

Description

  The present invention relates to a technique for supplying power to a battery mounted on a moving body by wireless power transmission.

  In the field of land transportation, research and development of automobiles that run on electric power has been actively conducted due to concerns about air pollution and depletion of fossil fuels. One technique for supplying power to an electric vehicle is a wireless power transmission technique that does not use a power cord or a power transmission cable. In the wireless power transmission technology, wireless power transmission is realized by using an electromagnetic induction action or a magnetic field resonance action between a power transmission coil provided in the power transmission apparatus and a power reception coil provided in the power reception apparatus.

  When performing wireless power transmission, electromagnetic waves may leak from the power transmission coil and the power reception coil. In order to block and absorb this unnecessary electromagnetic wave that leaks, a metal shield is disposed on the surface opposite to the opposing surface of the power transmission coil and the power reception coil. Since a large amount of magnetic flux passes through the space between the metal shield and the coil disposed on the surface opposite to the opposing surface of the power transmission coil and the power reception coil, an eddy current is generated on the metal shield. Due to the generation of eddy currents, the metal shield generates heat, which may cause unnecessary energy consumption and reduce power transmission efficiency.

  In order to prevent a decrease in power transmission efficiency due to the generation of eddy current, a magnetic path is formed by arranging a non-conductive magnetic plate between the coil and the metal shield so that eddy current is not generated by the metal shield. There is also a method, for example, used in a charging device such as a domestic electric razor. However, since the magnetic material is an expensive material, the cost is increased. Further, for example, when ferrite or the like is used as a magnetic material, there is a problem that it is difficult to handle because it is weak against impact and easily broken.

JP 2009-200194 A International Publication No. 2007/122788

  In view of the above problems, an object of the present invention is to provide a wireless power transmission system, a power receiving device, and a power transmitting device that can suppress a decrease in power transmission efficiency at a lower cost.

  In order to solve the above-described problems, the present invention includes the following means in a power transmission device that performs power transmission by wireless power transmission. That is, the present invention is a power transmission device that transmits power to a power receiving device disposed oppositely by wireless power transmission, the power transmission coil that transmits power to a power receiving coil provided in the power receiving device, and the power transmission coil. The power transmission device includes a conductive first shield plate disposed on a surface opposite to the surface facing the power receiving device and having at least one slit formed therein.

  In addition, the present invention is a power receiving device that receives power from a power transmitting device arranged oppositely by wireless power transmission, the power receiving coil that receives power from a power transmitting coil provided in the power transmitting device, and the power receiving device The coil is a power receiving device including a conductive shield plate disposed on a surface opposite to the surface facing the power transmission device of the coil and having at least one slit formed therein.

  The present invention can also be understood as a wireless power transmission system. The present invention is arranged on the opposite surface side of the power transmission coil that transmits power to the power reception coil provided in the power reception device disposed opposite to the surface facing the power reception device of the power transmission coil. A conductive shield plate formed with at least one slit, and a power receiving coil that receives power from the power transmitting coil provided in the power transmitting device arranged oppositely, and A wireless power transmission system comprising: a power receiving device that is disposed on a surface opposite to a surface facing the power transmitting device of the power receiving coil, and includes a conductive shield plate having at least one slit formed therein. It is.

  In the power transmission device, the first shield plate is formed by forming at least one slit on the conductive first shield plate disposed on the surface opposite to the surface facing the power receiving device of the power transmission coil. Generation of the above eddy current can be suppressed. When an overcurrent is generated on the conductive shield plate, the shield plate generates heat and unnecessary energy consumption occurs, resulting in a reduction in power transmission efficiency. However, in the power transmission device of the present invention, since the slit is formed in the conductive first shield plate, generation of eddy current can be suppressed. Thereby, the heat generation of the shield plate can be suppressed, and the power transmission device of the present invention can suppress a decrease in power transmission efficiency. The conductive shield plate may be, for example, a metal plate such as aluminum, copper, or iron, or a plate formed of carbon fiber. Such a material of the conductive first shield plate is cheaper than the magnetic material, and thus the price of the power transmission device can be kept low.

  Also, in the power receiving device, at least one slit is formed on the conductive shield plate disposed on the surface opposite to the surface facing the power transmitting device of the power receiving coil, so that on the shield plate. Generation of eddy current can be suppressed. Thereby, the heat generation of the shield plate can be suppressed, and the power receiving device of the present invention can suppress a decrease in power transmission efficiency.

  In addition, the power transmission device has at least one slit disposed on the surface of the first shield plate opposite to the surface on which the power transmission coil is disposed so as not to contact the first shield plate. You may make it further contain the formed electroconductive 2nd shield board.

  Further, the second shield plate in the power transmission device may be arranged so that the first shield plate and the slit do not overlap. Thereby, since the magnetic flux (electromagnetic wave) leaked from the slit of the first shield plate is absorbed by the second shield plate, leakage of unnecessary electromagnetic waves to the outside can be reduced. Further, the second shield plate in the power transmission device may be formed with slits having the same arrangement, shape, and size as the slits of the first shield plate.

  In addition, each slit of the first and second shield plates in the power transmission device has a length in the radial direction of the power transmission coil from the inner radial position of the innermost coil of the power transmission coil to the outermost coil. It is good also to the outer radial position.

  The means for solving the problems in the present invention can be combined as much as possible.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the power transmission efficiency of wireless power transmission can be suppressed more cheaply in a wireless power transmission system, a power receiving apparatus, and a power transmission apparatus.

It is a figure which shows an example of the use of the wireless power transmission system which concerns on 1st Embodiment. It is a figure which shows the structure of the wireless power transmission system which concerns on 1st Embodiment. It is sectional drawing of the structural example of the coil case for power transmission which concerns on 1st Embodiment, and the coil case for power reception. FIG. 4 is a diagram in which a power transmission coil and a metal shield and a part of a power reception coil and a metal shield shown in FIG. 3 are extracted. It is a figure which shows the example of the metal shield in the coil case for power transmission shown by FIG. 3, and the metal shield in the coil case for power reception. It is sectional drawing which shows the structure of the coil case for power transmission in 2nd Embodiment, and the coil case for power reception. FIG. 7 is a diagram in which a part of a power transmission coil and two metal shields, a power reception coil and two metal shields shown in FIG. 6 are extracted. It is a figure which shows the two metal shields in the coil case for power transmission shown by FIG. 6, and the two metal shields in the coil case for power reception. It is the schematic when the coil case for power transmission in the modification of 2nd Embodiment is seen from the top. It is AA sectional drawing of the coil case for power transmission shown by FIG. It is a figure which shows the example of the simulation result of the relationship between the models 1-5 of a wireless power transmission system, and power transmission efficiency. It is a figure which shows the example of the simulation result of the relationship between the distance from the center of a coil, and electric field strength about each of the models 1, 3 to 5 of a wireless power transmission system. It is a figure which shows the model 1 of a wireless power transmission system. It is a figure which shows the model 2 of a wireless power transmission system. It is a figure which shows the model 3 of a wireless power transmission system.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a wireless power transmission system according to the present invention will be exemplarily described in detail based on the drawings. Note that the dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the technical scope of the invention only to those unless otherwise specified. .

<First Embodiment>
FIG. 1 is a diagram illustrating an example of the use of the wireless power transmission system according to the first embodiment. The wireless power transmission system is a system for transmitting electric power charged in the in-vehicle battery to the electric vehicle 30 wirelessly. The power transmission unit (power transmission device) 10 is provided on the ground side where the vehicle stops, and the power reception unit (power reception device) 20 is provided on the vehicle side.

  FIG. 2 is a diagram illustrating a configuration of the wireless power transmission system 1 according to the first embodiment. The wireless power transmission system 1 includes a power transmission device 10 and a power reception device 20 roughly.

  In the first embodiment, the power transmission device 10 is provided on the ground side at a position (for example, a parking space) where the electric vehicle 30 stops. The power transmission device 10 includes a communication antenna 11, a transmission / reception unit 12, a high frequency power source 13, a power transmission coil 15, and a power transmission controller 17 that controls them.

In the first embodiment, the power receiving device 20 is provided at the lower part of the vehicle body of the electric vehicle 30. The electric vehicle 30 is an automobile that travels using electric power as a main power source or an auxiliary power source, and includes a power control unit (hereinafter also referred to as “PCU (Power Control Unit)”) 31, a motor 32 for moving the vehicle forward or backward, The battery 33 for supplying power to the motor 32 and the power receiving device 20 are mounted. The battery 33 is a rechargeable DC power source, and can include, for example, a secondary battery such as lithium ion or nickel metal hydride, and a large capacity capacitor or the like can be appropriately employed.

  The power receiving device 20 includes a communication antenna 21, a transmission / reception unit 22, a power receiving coil 25, a rectifier circuit 28, a DC / DC converter 29, and a power receiving controller 27 for controlling them.

  The power transmission device 10 and the power reception device 20 transmit power by cooperating as follows. When the electric vehicle 30 equipped with the power receiving device 20 is parked at the position where the power transmitting device 10 is installed and the power transmitting coil 15 and the power receiving coil 25 are in a predetermined facing relationship, the power transmitting controller 17 and the power receiving controller 27 transmit and receive each. Communicate with each other via the unit. The transmission / reception unit 12 and the transmission / reception unit 22 are communication interfaces for performing wireless communication with each other.

  When the power reception controller 27 detects that there is an empty remaining amount of the battery 33 via the PCU 31, the power reception controller 27 transmits data indicating that power transmission is requested to the power transmission device 10 via the transmission / reception unit 22. The power transmission controller 17 that has acquired data to request power transmission from the power receiving device 20 via the transmission / reception unit 12 causes the high-frequency power supply 13 to output high-frequency power of, for example, about 1 MHz to several tens MHz, and causes the power transmission coil 15 to output the power. Supply.

  The power transmission coil 15 includes a primary coil 15a and a power transmission resonance coil 15b. The primary coil 15 a is connected to the high frequency power supply 13, and power is directly supplied from the high frequency power supply 13. The primary coil 15a is disposed concentrically with the power transmission resonance coil 15b, and is magnetically coupled to the power transmission resonance coil 15b by electromagnetic induction. When a current supplied from the high-frequency power source 13 flows through the primary coil 15a, electromagnetic induction occurs between the primary coil 15a and the power transmission side resonance coil 15b. As a result, an electromotive force is induced in the power transmission resonance coil 15b, whereby a current flows in the power transmission resonance coil 15b.

  On the other hand, on the power receiving device 20 side, the power receiving coil 25 includes a secondary coil 25a and a power receiving resonance coil 25b. The secondary coil 25a is disposed concentrically with the power reception resonance coil 25b and is magnetically coupled to the power reception resonance coil 25b by electromagnetic induction. Here, the power transmission side resonance coil 15b and the power reception side resonance coil 25b are provided with variable capacitors 16 and 26 for adjusting the resonance frequency, respectively. The power transmission controller 17 and the power reception controller 27 cooperatively control the variable capacitors 16 and 26 so that the resonance frequencies of the power transmission side resonance coil 15b and the power reception side resonance coil 25b are matched.

  When a high frequency current flows through the power transmission side resonance coil 15b due to induction of electromotive force by electromagnetic induction, magnetic field resonance occurs between the power transmission side resonance coil 15b and the power reception side resonance coil 25b whose resonance frequencies are matched, and power reception side resonance occurs. A current also flows through the coil 25b. When a current flows through the power receiving resonance coil 25b, electromagnetic induction occurs between the power receiving resonance coil 25b and the secondary coil 25a. As a result, an electromotive force is induced in the secondary coil 25a, and a current flows through the secondary coil 25a.

The secondary coil 25a takes out the electric power received by the power receiving resonance coil 25b by electromagnetic induction and outputs it to the rectifier circuit 28. The rectifier circuit 28 rectifies the AC power extracted by the secondary coil 25a. The DC / DC converter 29 converts the power rectified by the rectifier circuit 28 into a voltage level of the battery 33 based on the control signal from the power receiving controller 27 and outputs the voltage to the battery 33. The battery 33 stores power supplied from the DC / DC converter 29 and also stores regenerative power generated by the motor 32. The battery 33 supplies the stored electric power to the PCU 31. In the case of receiving power from the power transmission device 20 while the electric vehicle 30 is traveling (in this case, the power transmission device 20 may be disposed above or on the side of the electric vehicle 30, for example), DC / DC The converter 29 can also convert the power rectified by the rectifier circuit 28 into a system voltage and supply it directly to the PCU 31.

The PCU 31 drives the motor 32 with electric power output from the battery 33 or directly supplied from the DC / DC converter 29. Further, the PCU 31 rectifies the regenerative power generated by the motor 32 and outputs the rectified power to the battery 33 to charge the battery 33. The motor 32 is driven by the PCU 31 to generate a vehicle driving force and output it to the driving wheels. Further, the motor 32 generates electric power by kinetic energy received from driving wheels or an engine (not shown), and outputs the obtained regenerative power to the PCU 31. The PCU 31 is controlled by a vehicle ECU (Electronic Control Unit) (not shown) of the electric vehicle 30.
The vehicle ECU is a central control device that controls the PCU 31 based on the traveling state of the vehicle and the state of charge of the battery 33 when the electric vehicle 30 is traveling.

  As described above, in the wireless power transmission system 1 according to the first embodiment, power is transmitted from the power transmission device 10 to the power reception device 20 wirelessly using the magnetic field resonance generated between the power transmission device 10 and the power reception device 20. To do. The power received by the power receiving device 20 is supplied to the battery 33 and the like that are comprehensively shown as a load resistance after the rectifier circuit 28.

  In the wireless power transmission system 1, a coil to which power is directly supplied from the high-frequency power source 13 and a coil directly connected to the load resistance on the power receiving side (here, the primary coil 15 a and the secondary coil 25 a), and power transmission by magnetic resonance. The coils (here, the power transmission side resonance coil 15b and the power reception side resonance coil 25b) used in the above are not physically connected but are connected by electromagnetic induction, so that they are used for magnetic field resonance depending on the configuration of the high frequency power supply 13, load resistance, and the like. An adverse effect on the resonance frequency of the coil is suppressed.

  FIG. 3 is a cross-sectional view of a configuration example of a power transmission coil case and a power reception coil case according to the first embodiment. On the power transmission device 10 side, a power transmission coil 15 (primary coil 15 a and power transmission resonance coil 15 b) is housed in a power transmission coil case 150. On the other hand, on the power receiving device 20 side, a power receiving coil 25 (secondary coil 25a, power receiving resonance coil 25b) is housed in a power receiving coil case 250. In addition, FIG. 3 has shown the longitudinal cross-section structure of the coil case for power transmission, and the coil case for power reception.

  When wireless power transmission from the power transmission device 10 using the magnetic field resonance to the power reception device 20 is performed, the power transmission coil case 150 and the power reception coil case 250 are opposed to each other as illustrated in FIGS. 1 to 3. Become. In the example shown in FIG. 3, the power transmission coil case 150 and the power reception coil case 250 are formed in a rectangular parallelepiped shape. However, the present invention is not limited to this, and other shapes such as a cylindrical shape are appropriately adopted. It doesn't matter.

  The power transmission coil case 150 includes a top plate 151, a bottom plate 152, and a peripheral wall 153. Here, the top plate 151 is a surface that faces (opposites) the power receiving device 20 (the power receiving coil 25) during wireless power transmission. Hereinafter, this surface is referred to as a “front surface”. The bottom plate 152 is a surface facing the top plate 151, and this surface is hereinafter referred to as a “rear surface”. In FIG. 3, the power transmission coil case 150 is indicated by a dotted line.

In the power transmission coil case 150, a metal shield 155 is installed as a shield member between the bottom plate 152 and the power transmission coil 15. The metal shield 155 is a conductive metal plate such as aluminum, copper, or iron. Metal shield 15
Instead of 5, carbon fiber may be used as the shield member. A connector 156 is disposed on the bottom plate 152 of the power transmission coil case 150. The connector 156 is connected to the primary coil 15a. The connector 156 is connected to the high frequency power supply 13 via a wiring cable. That is, the primary coil 15 a and the high frequency power supply 13 are connected via the connector 156.

  The power receiving coil case 250 includes a top plate 251, a bottom plate 252, and a peripheral wall 253, similarly to the power transmitting coil case. The top plate 251 is a surface that faces (opposites) the power transmission device 10 (the power transmission coil 15) during wireless power transmission. Hereinafter, this surface is referred to as a “front surface”. The bottom plate 252 is a surface facing the top plate 251, and this surface is hereinafter referred to as a “back surface”. In FIG. 3, the power receiving coil case 250 is indicated by a dotted line.

  The power receiving coil case 250 is also provided with a metal shield 255 similar to that of the power transmitting coil case 150. That is, the metal shield 255 is disposed between the bottom plate 252 of the power receiving coil case 250 and the power receiving coil 25. The metal shield 255 is equivalent to the metal shield 155 in the power transmission coil case 150.

  A connector 256 is disposed on the bottom plate 252 of the power receiving coil case 250. The connector 256 is connected to the secondary coil 25a. The connector 256 is connected to the rectifier circuit 28 via a wiring cable, and the secondary coil 25a and the rectifier circuit 28 are connected via the connector 256.

  Each of the metal shields 155 and 255 absorbs and blocks electromagnetic waves that are to leak outside, that is, electromagnetic waves that have not contributed to wireless power transmission, when power is transmitted wirelessly from the power transmission device 10 to the power reception device 20. The leakage of electromagnetic waves that did not contribute to the outside is suppressed.

  In the first embodiment, the metal shield 155 accommodated in the power transmission coil case 150 and the metal shield 255 accommodated in the power reception coil case 250 are each formed in a disk shape. However, the present invention is not limited to this, and the metal shields 155 and 255 only have to have an area that fits in the coil case and covers the power transmission coil 15 or the power reception coil 25.

  FIG. 4 is a diagram in which a part of the power transmission coil 15 and the metal shield 155 and a part of the power reception coil 25 and the metal shield 255 shown in FIG. 3 are extracted. The metal shield 155 is disposed so that the center position of the power shield coil 15 is matched. Similarly, the metal shield 255 is disposed so that the center position of the metal shield 255 matches the power receiving coil 25. The metal shields 155 and 255 each have a plurality of slits 155SL and 255SL in the circumferential direction of the coil that is a predetermined distance away from the center. Each slit passes through the metal shields 155 and 255.

  FIG. 5 is a diagram illustrating an example of the metal shield 155 in the power transmission coil case 150 and the metal shield 255 in the power reception coil case 250 shown in FIG. 3. In FIG. 5, each metal shield 155, 255 is a disc and has 36 slits. Each of the 36 slits has the same shape and the same size. These 36 slits are arranged at equal intervals at a predetermined distance from the reference point with the centers of the metal shields 155 and 255 as the reference point. In other words, each of the 36 slits is arranged at a position on the radiation that spreads equally from the centers of the metal shields 155 and 255 by a predetermined distance from the center. However, the present invention is not limited to this, and the slits may be arranged at unequal intervals in the circumferential direction of the coil.

In addition, the slits are arranged inside the innermost coil of the primary coil 15a or the secondary coil 25a when the metal shields 155 and 255 are arranged so that their centers coincide with the primary coil 15a or the secondary coil 25a, respectively. It is preferable to extend from the radial position to the outer radial position of the outermost coil of the power transmission side resonance coil 15b or the power reception side resonance coil 25b. The shape of each slit may be a rectangle, or may be a shape in which the width on the center side of the coil is narrow and the width increases as the distance from the center increases. The number of slits formed on the metal shield is not limited to 36.

  Since the slits exist in the metal shields 155 and 255, the flow of eddy currents on the metal shields 155 and 255 can be divided, and the generation of eddy currents can be suppressed. By suppressing the generation of eddy current, heat generation of the metal shields 155 and 255 can be suppressed, and a decrease in power transmission efficiency can be suppressed.

  Further, since the slits are present in the metal shields 155 and 255, the generation of overcurrent can be suppressed and the power transmission efficiency can be maintained without using a magnetic plate, so that the cost can be reduced.

Second Embodiment
FIG. 6 is a cross-sectional view illustrating configurations of a power transmission coil case and a power reception coil case in the second embodiment. The components already described are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the second embodiment, in the power transmission coil case 150, the two metal shields 155a and 155b are arranged on the back surface of the power transmission coil 15 so as not to contact each other. In the second embodiment, both of the metal shields 155a and 155b have the same arrangement, the same number, and the same shape of slits. Further, both of the metal shields 155a and 155b are the same as the metal shield 155 of the first embodiment. However, the present invention is not limited to this, and the metal shields 155a and 155b may have slits in different arrangements. It should be noted that both slits of the metal shields 155a and 155b have the same arrangement when the center of the metal shield is the reference point, the arrangement of the slits relative to the reference point is the same, or between the slits Indicates that the relationship is the same.

  Similarly, in the power receiving coil case 250, two metal shields 255 a and 255 b are arranged on the back surface of the power receiving coil 25. In the second embodiment, both of the metal shields 255a and 255b have the same arrangement, the same number, and the same shape of slits. The metal shields 255a and 255b are the same as the metal shields 155a and 155b of the power transmission coil case 150. However, the present invention is not limited to this, and the metal shields 255a and 255b may have slits in different arrangements, or may be different from the metal shields 155a and 155b of the power transmission coil case 150.

  FIG. 7 is a diagram in which a part of the power transmission coil 15 and the metal shields 155a and 155b and the power reception coil 25 and the metal shields 255a and 255b shown in FIG. 6 are extracted. FIG. 8 is a diagram showing metal shields 155a and 155b in power transmission coil case 150 and metal shields 255a and 255b in power reception coil case 250 shown in FIG. The metal shields 155a and 155b in the power transmission coil case 150 are arranged so that the center position of the metal shields 155a and 155b matches. Furthermore, the metal shields 155a and 155b are arranged so that the slits of each of them do not overlap.

  Similarly, the metal shields 255a and 255b in the power receiving coil case 250 are arranged so that the center positions of the metal shields 255a and 255b are matched. Furthermore, the metal shields 255a and 255b are arranged so that the slits of the metal shields 255a and 255b do not overlap each other.

  In this way, in the power transmission device 10 and the power receiving device 20, the two metal shields having the slits are arranged so that the slits do not overlap. Thereby, for example, the magnetic shield 155b disposed on the back surface of the metal shield 155a can absorb and block the magnetic flux leaking from the slit 155aSL of the metal shield 155a disposed on the back surface of the power transmission coil 15. Leakage can be reduced. Similarly to the first embodiment, since the metal shield 155b that absorbs the magnetic flux leaking from the metal shield 155a also has a slit, generation of eddy current can be suppressed also in the metal shield 155b. By suppressing the generation of eddy current, heat generation of the metal shields 155a and 155b can be suppressed, and as a result, a decrease in power transmission efficiency can be prevented. The power receiving device 20 also has the same effect as the power transmission device 10. In the second embodiment, two metal shields are provided on the back surface of the coil. However, the present invention is not limited to this, and three or more metal shields may be provided. However, two sheets are suitable for reducing the weight and cost of the apparatus.

<Modification of Second Embodiment>
As a modification of the second embodiment, a power transmission device and a power reception device that can adjust the overlapping degree of the slits of the two metal shields will be described.

  FIG. 9 is a schematic view when a coil case for power transmission according to a modification of the second embodiment is viewed from above. In FIG. 9, only the metal shield 155c, the adjustment dial 157, and the idler gears 158a and 158b included in the power transmission coil case 150 are extracted and shown.

  The metal shield 155c is a metal shield used in place of the metal shield 155b in FIGS. The metal shield 155c is disposed on the back surface of the metal shield 155a (not shown) disposed on the back surface of the power transmission coil 15. The metal shield 155c has a plurality of slits similarly to the metal shield 155a. The circumference of the metal shield 155c is a saw shape, and the metal shield 155c is a gear.

  The adjustment dial 157 has a gear (not shown) that meshes with the metal shield 155c. The idler gears 158a and 158b are gears that mesh with the metal shield 155c and assist the rotation of the metal shield 155c. The metal shield 155c rotates to the left and right according to the left / right twist of the adjustment dial 157 by the adjustment person in the device manufacturing factory, the adjustment person in the apparatus installation company, or the user, and the metal shield 155a (not shown). It is possible to adjust the overlapping degree of the slits.

  10 is a cross-sectional view taken along line AA of the power transmission coil case shown in FIG. 9. The power transmission coil 15b is fixed by insulating members 158a and 158b. A metal shield 155a is disposed next to the insulating member 158b. An insulating member 158c is disposed between the metal shield 155a and the metal shield 155c. A metal shield 155 c in the form of a gear is arranged so as to mesh with the gear of the adjustment dial 157. Since the metal shield 155c is rotated by the adjustment dial 157, the user can adjust the overlapping state of the slits of the metal shield 155a and the metal shield 155c. The adjustment dial 157 may be configured to rotate using a motor or the like as a drive source, and the leakage magnetic flux is detected by a sensor, and the motor is set in an appropriate state (leakage magnetic flux minimum state) according to the detected value. It is also possible to control so that

<Simulation>
FIG. 11 is a diagram illustrating an example of a simulation result of a relationship between models 1 to 5 of the wireless power transmission system and power transmission efficiency. FIG. 12 is a diagram illustrating an example of a simulation result of the relationship between the distance from the center of the coil and the electric field strength for each of the models 1, 3 to 5 of the wireless power transmission system. FIG. 13 is a diagram illustrating a model 1 of the wireless power transmission system. FIG. 14 is a diagram illustrating a model 2 of the wireless power transmission system. FIG. 15 is a diagram illustrating a model 3 of the wireless power transmission system.

  In the model 1 of the wireless power transmission system shown in FIG. 14, both the power transmitting device 10 and the power receiving device 20 have magnetic plates 159 and 259 disposed on the back surfaces of the power transmitting coil 15 and the power receiving coil 25, respectively. This is a model in which metal shields 155x and 255x having no slits are arranged on the back surfaces of 159 and 259.

  The model 2 of the wireless power transmission system illustrated in FIG. 14 is a coil-only model in which both the power transmission device 10 and the power reception device 20 do not have a shield.

  In the model 3 of the wireless power transmission system shown in FIG. 15, only the metal shields 155x and 255x that do not have slits are arranged on the back surfaces of the power transmission coil 15 and the power reception coil 25 in both the power transmission device 10 and the power reception device 20. Model.

  The model 4 of the wireless power transmission system includes the metal shields 155 and 255 having slits on the back surfaces of the power transmission coil 15 and the power reception coil 25 in the power transmission device 10 and the power reception device 20 described in the first embodiment. Is a model (see FIG. 4). The model 5 of the wireless power transmission system includes two metal shields having slits on the back surfaces of the power transmission coil 15 and the power reception coil 25 in the power transmission device 10 and the power reception device 20 described in the second embodiment. 155a, 155b, 255a, 255b is a model (see FIG. 7) arranged so that the slits do not overlap.

  The simulation results shown in FIGS. 11 and 12 show the results when the distance between the coil and the shield on the back surface is set to be the same in models 1 and 3-5.

  As shown in the relationship between each model in FIG. 11 and the power transmission efficiency, in the case of model 3 (only a metal shield without slits), in the case of model 1 (with magnetic plate and metal shield) and model 2 (without shield) Therefore, the power transmission efficiency of 90% or more is 30% or less. On the other hand, in the case of model 4 (one slit metal shield) and model 5 (two slit metal shields), the power transmission efficiency is corrected to 85% or more. Also, model 4 (one slit metal shield) is approximately 1% better in power transmission efficiency than model 5 (two slit metal shields).

  As shown in FIG. 12, for example, at a position 30 m away from the center of the coil in the radial direction, model 4 (one slit metal shield) is almost identical to model 1 (magnetic plate and non-slit metal shield). The electric field strength can be suppressed to the same extent. In addition, model 5 (two slit metal shields) can suppress the electric field strength more than model 4 (one slit metal shield), and is shown to have the highest electromagnetic wave leakage prevention effect.

  From the above, the models 4 and 5 using the slit metal shield described in the first embodiment and the second embodiment suppress the generation of eddy current on the metal shield without using the magnetic plate, Heat generation of the metal shield can be suppressed, and a decrease in power transmission efficiency can be suppressed. In addition, the models 4 and 5 can suppress the electric field strength to be almost equal to or higher than the model 1 using the magnetic material plate and the metal shield without slits without using the magnetic material plate.

  The metal shield can be conductive and nonmagnetic. Thereby, a relatively lightweight material such as aluminum can be used. In addition, wireless power transmission applied to vehicles generates strong electromagnetic waves because the distance between power transmission and reception is long and the power is large compared to household items such as electric razors. Generation can be suppressed.

  The embodiment described above is an example for explaining the present invention, and various modifications can be made without departing from the spirit of the present invention. For example, in the embodiments, a wireless power transmission system, a power transmission device, and a power reception device that perform wireless power transmission using magnetic field resonance have been described. However, the present invention is not limited to this, and slits are provided on the back surfaces of the power transmission coil and the power reception coil. By arranging the metal shield, it can be applied to a power transmission device, a power reception device, and a wireless power transmission system that perform wireless power transmission using electromagnetic induction.

  In addition, for example, in the configuration examples up to the above, the case where the power transmission coil is buried in the ground and the power is transmitted to the vehicle side is described as an example, but the present invention transmits power in the lateral direction with the power transmission device embedded in the wall, It is also possible to transmit power downward using a power transmission device embedded in the ceiling. In addition, the power receiving device, the power transmitting device, and the wireless power transmission system according to the present invention are not limited to the above-described embodiment, and can include combinations thereof as much as possible. In addition, the wireless power transmission system according to the present invention is not limited to a vehicle application, and can be applied to various devices using power, such as home appliances, information devices, and toys.

DESCRIPTION OF SYMBOLS 1 Wireless power transmission system 10 Power transmission device 15 Power transmission coil 15a Primary coil 15b Power transmission side resonance coil 150 Power transmission coil case 155 Slit metal shield 155a Slit metal shield 155b Slit metal shield 155c Slit metal shield 155x Metal without slit Shield 20 Power receiving device 25 Power receiving coil 25a Secondary coil 25b Power receiving resonance coil 250 Power receiving coil case 255 Slit metal shield 255a Slit metal shield 255b Slit metal shield 255c Slit metal shield 255x Slit metal shield

Claims (1)

A power transmission coil that transmits power to a power reception coil provided in a power reception device disposed oppositely; and
A conductive first shield plate disposed on a surface opposite to the surface facing the power receiving device of the power transmission coil, and having at least one slit formed thereon;
Conductive material in which at least one slit is formed on the surface of the first shield plate opposite to the surface where the coil for power transmission is disposed so as not to contact the first shield plate. A third shield plate;
A power transmission device including:
A power receiving coil that receives power from the power transmitting coil provided in the power transmitting device disposed oppositely; and
A conductive second shield plate disposed on a surface opposite to the surface facing the power transmission device of the power receiving coil, and having at least one slit formed thereon;
Conductive material in which at least one slit is formed on the surface opposite to the surface on which the power receiving coil is disposed on the second shield plate so as not to contact the second shield plate. A fourth shield plate;
A power receiving device including
The slits of the first shield plate and the third shield plate are arranged so that the radial length of the power transmission coil is changed from the radial position inside the innermost coil of the power transmission coil to the outermost coil. Length according to the distance to the outer radial position,
The slits of the second shield plate and the fourth shield plate are arranged so that the radial length of the power receiving coil is changed from the inner radial position of the innermost coil of the power receiving coil to the outermost coil. The length depends on the distance to the outer radial position.
Wireless power transmission system.

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