JP2010252497A - Radio power transfer device and radio power transfer method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute highly efficient power transfer in radio power transfer. <P>SOLUTION: In a radio power transfer device 1 transmitting power through magnetic-field resonance, a predetermined transmission/reception element, which is provided either to a power transmission unit 10 or to a power reception unit 20, is changed to change the transfer efficiency of power. Then, the transfer efficiency before/after the change is calculated, and the calculated transfer efficiency before the change is compared with that after the change to determine whether the transfer efficiency is attained or not after the change. This determining and changing process is repeated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to 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. As an automobile that travels using electric power, for example, there is a type that travels using electric power stored in a secondary battery. As a technique for charging a secondary battery mounted on an automobile, there is a technique for charging by receiving power from a power feeding unit provided on a traveling path in a non-contact manner (see, for example, Patent Document 1). In addition, as a technique for wirelessly transmitting power, there is a technique that sends power with high transmission efficiency to devices separated by magnetic resonance (see, for example, Patent Document 2).

JP 2008-120357 A JP 2008-301918 A

  Conventionally, there is a wireless power transmission technique by electromagnetic induction between coils. However, the electromagnetic induction power transmission method has the advantage that there is no need to expose the contacts on the power transmission side and the power reception side, but the transmission efficiency drops extremely as the coil interval becomes longer. In most cases, it was used in such a state.

  In addition to such an electromagnetic induction method, conventionally, there is a wireless power transmission technology that uses magnetic resonance (Magnetic Resonance, both magnetic resonance, magnetic resonance, and magnetic resonance) between coils having the same resonance frequency. In the power transmission method using magnetic field resonance, the coil interval can be made longer than in the electromagnetic induction method. However, in the power transmission method using magnetic resonance, the coil interval can be set more flexibly than electromagnetic induction, so the conditions under which high-efficiency power transmission can be performed differ depending on the coil interval between the power transmission coil and the power receiving coil. Therefore, it is considered difficult to perform efficient power transmission.

  In view of the above problems, an object of the present invention is to perform highly efficient power transmission in wireless power transmission.

  The present invention makes it possible to perform highly efficient power transmission in wireless power transmission by changing the power transmission / reception element that affects the transmission efficiency of power transmission using magnetic field resonance according to the transmission efficiency or the coil interval. did.

More specifically, the present invention is a wireless power transmission device that transmits electric power by generating magnetic field resonance between a power transmission unit including a power transmission coil and a power reception unit including a power reception coil, the power transmission unit and the power transmission unit A change unit that changes power transmission efficiency by changing a predetermined power transmission / reception element provided in any of the power reception units, and a transmission efficiency calculation unit that calculates transmission efficiency before and after the change by the change unit Determining means for determining whether the transmission efficiency has improved before and after the change by comparing the transmission efficiency before and after the change calculated by the transmission efficiency calculating means, It is a wireless power transmission apparatus that improves transmission efficiency by repeatedly performing the determination according to and the change by the changing means.

  Here, the predetermined power transmission / reception element refers to an element that affects transmission efficiency among elements used for power transmission in the wireless power transmission device. Examples of such elements include a load resistance, a transmission voltage, a coil configuration, a degree of coupling between coils, and the like, which will be described later. In the wireless power transmission device according to the present invention, the transmission efficiency is adjusted by changing the power transmission / reception element to perform high-efficiency power transmission. Note that the power transmission / reception element to be changed may be an element belonging to either side of the power transmission unit and the power reception unit.

  The wireless power transmission device according to the present invention further includes a transmission power acquisition unit that acquires power flowing in the power transmission coil, and a received power acquisition unit that acquires power flowing in the power reception coil, and calculates the transmission efficiency. The means may calculate the transmission efficiency by calculating a ratio of the received power to the acquired transmitted power.

  For example, the transmission power acquisition means can acquire transmission power from a transmission amplifier provided in the power transmission unit, and the received power acquisition means can acquire reception power from a rectifier circuit or the like provided in the power reception unit. .

  In addition, the present invention is a wireless power transmission device that transmits power by generating magnetic field resonance between a power transmission unit including a power transmission coil and a power reception unit including a power reception coil, the power transmission unit and the power reception unit By changing a predetermined power transmission / reception element provided in any of the above, the changing means for changing the power transmission efficiency, the coil interval between the power transmission coil and the power reception coil, and the relationship between the transmission efficiency and the transmission efficiency Information holding means for holding transmission efficiency information shown for each predetermined power transmission / reception element, and coil interval acquisition means for acquiring a coil interval between the power transmission coil and the power receiving coil, wherein the changing means is configured to transmit the transmission efficiency. The wireless power transmission apparatus refers to the information and changes the predetermined power transmission / reception element so that the transmission efficiency in the acquired coil interval is improved.

  The coil interval acquisition means can acquire the coil interval by, for example, a separately provided measuring instrument for measuring the coil interval. Various types of measuring instruments, such as those using radio wave or sound wave delay times, and those that perform surveying from images, can be employed. In addition, when the power receiving unit of the wireless power transmission device according to the present invention is mounted on a vehicle, information on the distance between the power receiving coil and the ground (power transmitting coil) is held in advance on the vehicle side (power receiving unit side). This information may be transmitted to the power transmission unit side. Further, the coil interval between the power receiving coil mounted on the vehicle and the ground power transmitting coil may be specified based on other information such as vehicle height information and vehicle type information held on the vehicle side. For example, the power transmission unit may receive vehicle type information transmitted from the power receiving unit, search a database, and acquire a standard coil interval of the vehicle type. Also in this case, the power transmission / reception element to which the change is applied may be an element belonging to either side of the power transmission unit and the power reception unit.

  Further, the transmission efficiency information held by the information holding means is obtained by changing the relationship between the coil interval between the power transmission coil and the power reception coil and the transmission efficiency at this coil interval, the power transmission / reception element (load resistance, power transmission voltage, Coil configuration, degree of coupling between coils, etc.). The transmission efficiency information is expressed in the form of, for example, a relational expression of the above parameters previously derived from the results of experiments or simulations, a map indicating the results of experiments or simulations, etc., and is connected to the controller of the power transmission unit or power reception unit. Held in the storage device. In the present invention, by referring to such transmission efficiency information, the acquired coil interval is substituted into the relational expression, or the transmission efficiency corresponding to the acquired coil interval is retrieved from the map, thereby obtaining the coil interval. Accordingly, the power transmission / reception element with high transmission efficiency can be changed.

  Further, the wireless power transmission device according to the present invention is a power transmission voltage control for controlling a voltage of a current flowing in the power transmission coil, and a power extraction means for making constant power extracted by a power supply target to which the power reception unit is connected. And the changing means may change the transmission efficiency by changing a voltage controlled by the power transmission voltage control means.

  In the case of including such extracted power adjustment means (for example, can be realized using a rectifier circuit and a DC / DC converter), when the received voltage changes according to the change in the transmission voltage, the power extracted from the power supply target is constant. The current flowing through the receiving coil changes. This can be regarded as a change in the apparent load resistance on the power receiving side. The change in the load resistance on the power receiving side affects the relationship between the coil interval and the transmission efficiency, and changes the transmission efficiency. That is, according to the present invention, it is possible to adjust the transmission efficiency by changing the transmission voltage by providing the extracted power adjusting means.

  Further, in the present invention, the power transmission coil selects any one of a first power transmission coil that receives power input from a power transmission amplifier, and electromagnetic induction from the first power transmission coil and the power transmission amplifier as a power input source. A second power transmission coil, and the power reception coil includes a first power reception coil through which a current flows by magnetic field resonance with the second power transmission coil, and a current by electromagnetic induction from the first power reception coil. A second power receiving coil through which the current flows, and the changing means changes the input source to the second power transmitting coil between the electromagnetic induction from the first power transmitting coil and the power transmitting amplifier, The transmission efficiency may be changed.

  Here, the first power transmission coil is a coil to which power is directly supplied from the power transmission amplifier. When a current is passed through the first power transmission coil by the power transmission amplifier, electromagnetic induction occurs between the first power transmission coil and the second power transmission coil, and a current flows through the second power transmission coil. And when an electric current flows into a 2nd power transmission coil by electromagnetic induction, magnetic field resonance will generate | occur | produce between a 2nd power transmission coil and a 1st power receiving coil, and an electric current will flow into a 1st power receiving coil. Furthermore, when a current flows through the first power receiving coil due to magnetic field resonance, electromagnetic induction occurs between the first power receiving coil and the second power receiving coil, and a current flows through the second power receiving coil. In the present invention, in such a configuration having coils of four different roles, the input source to the second power transmission coil is changed between “electromagnetic induction from the first power transmission coil” and “power transmission amplifier”. And a three-coil configuration having a second power transmission coil, a first power reception coil and a second power reception coil, and a four-coil configuration having a first power transmission coil, a second power transmission coil, a first power reception coil and a second power reception coil. The transmission efficiency is changed by switching.

  In the present invention, at least one of the power transmission coil and the power reception coil includes a magnetic field resonance coil for magnetic field resonance between the power transmission unit and the power reception unit, and a power between the magnetic field resonance coil and the magnetic field resonance coil. An electromagnetic induction coil that transmits or receives power by electromagnetic induction, and the changing means may change the transmission efficiency by changing a distance between the magnetic field resonance coil and the electromagnetic induction coil. Good.

  Here, the magnetic field resonance coil is a coil corresponding to the second power transmission coil and the first power reception coil, and the electromagnetic induction coil is a coil corresponding to the first power transmission coil and the second power reception coil. In the present invention, by changing the distance between the coils connected by electromagnetic induction on the power transmission side or the power reception side, the coupling degree between the coils is changed to change the transmission efficiency.

  Further, in the present invention, at least one of the power transmission coil and the power reception coil has a plurality of the electromagnetic induction coils having different diameters, and the changing unit uses the electromagnetic induction coil among the plurality of electromagnetic induction coils. The transmission efficiency may be changed by changing the electromagnetic induction coil.

  As a method of changing the distance between the coils, as described above, a method of changing the coil interval by moving the coils themselves is used in addition to a method of switching and using a plurality of coils having different diameters. May be.

  Furthermore, the present invention can be understood as a method executed by the wireless power transmission apparatus or a program executed by a computer that controls the wireless power transmission apparatus. Further, the present invention may be a program in which such a program is recorded on a recording medium readable by a computer, other devices, machines, or the like. Here, a computer-readable recording medium is a recording medium that stores information such as data and programs by electrical, magnetic, optical, mechanical, or chemical action and can be read from a computer or the like. Say.

  For example, in the present invention, a wireless power transmission device that transmits power by generating magnetic field resonance between a power transmission unit including a power transmission coil and a power reception unit including a power reception coil is any of the power transmission unit and the power reception unit. A change step for changing power transmission efficiency by changing a predetermined power transmission / reception element, a transmission efficiency calculation step for calculating transmission efficiency before and after the change in the change step, and the transmission efficiency calculation A step of determining whether or not the transmission efficiency has improved before and after the change by comparing the transmission efficiency before and after the change calculated in the step, and the determination in the determination step; In the wireless power transmission method, the transmission efficiency is improved by repeatedly executing the change in the change step.

  Further, the present invention provides a wireless power transmission device that transmits power by generating magnetic field resonance between a power transmission unit including a power transmission coil and a power reception unit including a power reception coil. The change step of changing the power transmission efficiency by changing the predetermined power transmission / reception element provided in FIG. 4 and the relationship between the coil interval and the transmission efficiency for each predetermined power transmission / reception element measured in advance are shown. An information holding step for holding transmission efficiency information and a coil interval obtaining step for obtaining a coil interval between the power transmission coil and the power receiving coil are executed. In the changing step, the transmission efficiency information is referred to and obtained. In the wireless power transmission method, the predetermined power transmission / reception element is changed so that transmission efficiency at the coil interval is improved.

  According to the present invention, it is possible to perform highly efficient power transmission in wireless power transmission.

It is a figure which shows the structure of the wireless power transmission system which concerns on embodiment. It is a figure which shows the structure of the power transmission coil and power receiving coil which are used in embodiment. It is a flowchart which shows the flow of the adjustment process of the transmission efficiency performed in the wireless power transmission system which concerns on embodiment. FIG. 3 is a diagram illustrating a result of simulating a relationship between a distance (coil interval) between a power transmission coil and a power reception coil and transmission efficiency for each load resistance in the four-coil configuration illustrated in FIG. 2. FIG. 3 is a diagram illustrating a result of simulating a relationship between a distance (coil interval) between a power transmission coil and a power reception coil and transmission efficiency for each power transmission frequency in the four-coil configuration illustrated in FIG. 2. It is a figure which shows the outline | summary of 4 coil structure in embodiment. It is a figure which shows the relationship between the frequency and the electric current which flow through a coil at the time of setting the space | interval of a 2nd power transmission coil and a 1st power receiving coil to 50 mm by 4 coil structure shown in FIG. It is a figure which shows the relationship between the frequency and the electric current which flow through a coil at the time of setting the space | interval of a 2nd power transmission coil and a 1st power receiving coil to 500 mm by 4 coil structure shown in FIG. It is a figure which shows the outline | summary of the 3 coil structure in embodiment. It is a figure which shows the relationship between the frequency and the electric current which flow through a coil at the time of setting the space | interval of a 2nd power transmission coil and a 1st power receiving coil to 50 mm by 3 coil structure shown in FIG. It is a figure which shows the relationship between the frequency when the space | interval of a 2nd power transmission coil and a 1st power receiving coil is 500 mm by 3 coil structure shown in FIG. 8, and the electric current which flows through a coil. It is a figure which shows the result of having simulated the relationship between the distance (coil space | interval) between a power transmission coil and a receiving coil and transmission efficiency for every coil structure. It is a figure which shows the outline | summary of a structure of the 1st power transmission coil and 2nd power transmission coil in embodiment. It is a figure which shows the result of having simulated the relationship between the distance (coil space | interval) between a power transmission coil and a receiving coil, and transmission efficiency for every 1st power transmission coil from which a diameter mutually differs shown in FIG. It is a figure which shows the outline | summary of the structure which enabled vertical movement of the 1st power transmission coil or the 2nd power transmission coil on the same axis | shaft. It is a figure which shows the coil structure at the time of enabling switching the number of use turns of a 1st power transmission coil or a 2nd power receiving coil. It is a figure which shows the flowchart which shows the flow of the adjustment process of the transmission efficiency performed in the wireless power transmission system which concerns on embodiment. It is a flowchart which shows the flow of the constant current charging process performed with progress of charge in the wireless power transmission system which concerns on embodiment. Figure comparing the state of eddy currents when only the metal plate is placed on the back side of the unit and the state of suppressing eddy currents when the magnetic shield sheet is placed on the metal plate on the back side of the unit It is. It is a figure which shows a mode that the magnetic shield sheet | seat was provided in the back surface of the power transmission coil installed in the ground, and the back surface of the receiving coil installed in a vehicle.

  Embodiments of a wireless power transmission apparatus and a wireless power transmission method according to the present invention will be described below with reference to the drawings. Note that the wireless power transmission system according to the present embodiment is a system for transmitting the power charged in the in-vehicle battery to the vehicle side. The power transmission unit is on the ground side where the vehicle stops, and the power reception unit is on the vehicle side. Is provided. However, the power transmission system according to the present invention is not limited to vehicle use, and can be applied to various devices using electric power, such as home appliances, information devices, and toys.

<Configuration of wireless power transmission system>
FIG. 1 is a diagram illustrating a configuration of a wireless power transmission system 1 according to the present embodiment. The wireless power transmission system 1 is roughly provided with two wireless power transmission devices, a power transmission unit 10 and a power reception unit 20. Among these, the power transmission unit 10 is provided on the ground side of a position where the vehicle stops (for example, a parking space), and includes a power transmission controller 17, a converter 13, a power transmission amplifier 14, a power transmission coil 15, a resonance control unit 16, an oscillation circuit 18, An antenna 11 and a data transmission / reception unit 12 are provided. Here, the power transmission coil 15 is opposed to the power reception coil 25 provided on the bottom surface of the vehicle at a position where the alignment is easy when the vehicle stops, such as a predetermined position based on the parking stop of the parking space. It is preferable to be provided.

The power transmission controller 17 is connected to a storage device and executes a control program to change the power transmission unit 10 into a changing unit, a transmission efficiency calculating unit, a determining unit, a transmitted power acquisition unit, an information holding unit, a coil interval acquisition unit, and It is a computer operated as the power transmission unit 10 provided with a power transmission voltage control means. The power transmission controller 17 sets the oscillation circuit 18, the resonance control unit according to the preset power transmission settings, the data transmission / reception unit 12 data transmission / reception result with the power reception unit 20, and the transmission power monitor result obtained from the power transmission amplifier 14. 16. Control the converter 13. The data transmission / reception unit 12 is a communication interface connected to the antenna 11 for wireless communication. Further, the converter 13 converts the supplied AC or DC power into a DC current and sends it to the power transmission amplifier 14. The output voltage from the converter 13 is controlled by the power transmission controller 17. Further, the power transmission amplifier 14 inputs the power transmitted from the converter 13 to the power transmission coil 15 at the frequency given from the oscillation circuit 18. Here, the frequency given by the oscillation circuit 18 is controlled by the power transmission controller 17.

  The resonance control unit 16 matches the resonance frequency of the power transmission unit 10 with the oscillation frequency of the oscillation circuit 18 by a method such as controlling the capacitance of the capacitor (capacitor) provided in the power transmission coil 15 in accordance with an instruction from the power transmission controller 17. Control to do. Further, the oscillation circuit 18 controls the frequency oscillated to the power transmission coil 15 to a predetermined value in accordance with an instruction from the power transmission controller 17.

  The power receiving unit 20 is provided in a vehicle and includes a power receiving controller 27, a power receiving coil 25, a resonance control unit 26, a rectifier circuit 28, a DC / DC converter 29, an antenna 21, and a data transmitting / receiving unit 22. Similar to the resonance control unit 16, the resonance control unit 26 controls the resonance frequency of the power reception unit 20 to coincide with the oscillation frequency of the oscillation circuit 18 in accordance with an instruction from the power reception controller 27. As a result, the resonance frequency of the power transmission unit 10 and the resonance frequency of the power reception unit 20 are controlled to coincide with each other, and wireless power transmission by magnetic field resonance is possible. Here, the power receiving coil 25 is preferably provided at a position on the bottom surface of the vehicle facing the power transmission unit 10 installed on the ground. The power receiving unit 20 is connected to the in-vehicle battery 33 via the in-vehicle charge / discharge control device 31. The charge / discharge control device 31 discharges electric power for driving the vehicle from the in-vehicle battery 33 in response to the accelerator operation, and when the brake is operated, the electric power generated by the motor 32 is supplied to the in-vehicle battery 33. Controlled to be charged.

  The power receiving controller 27 is connected to a storage device and executes a control program connected to the storage device, thereby changing the power receiving unit 20 to a changing unit, a transmission efficiency calculating unit, a determining unit, a received power acquiring unit, and an information holding unit. , A computer that is operated as a power receiving unit 20 including a coil interval acquisition unit and an extracted power adjustment unit. The power receiving controller 27 is configured according to the resonance control unit 26, the rectifying circuit, and the power receiving unit 27 according to the preset power receiving settings, the data transmission / reception result of the data transmitting / receiving unit 22 with the power transmitting unit 10, and the received power monitoring result obtained from the rectifying circuit 28 28 and DC / DC converter 29 are controlled. The data transmission / reception unit 22 is a communication interface connected to the antenna 21 for wireless communication. Further, a current flows through the power receiving coil 25 due to magnetic field resonance with the power transmitting coil 15. Here, the power reception controller 27 controls the resonance control unit 26 so that the resonance frequency of the power reception coil 25 matches that of the power transmission unit 10 in order to generate magnetic field resonance with the power transmission coil 15.

  The rectifier circuit 28 (AC / DC converter) and the DC / DC converter 29 can control the apparent load resistance on the power reception side by changing the voltage on the power transmission side by keeping the electric power taken out on the charge / discharge control side constant. . Details of the load resistance control process will be described later.

FIG. 2 is a diagram illustrating the configuration of the power transmission coil 15 and the power reception coil 25 used in the present embodiment. The coil shown in FIG. 2 is a coil having a four-coil configuration in which the first power transmission coil 15a and the second power transmission coil 15b are used as the power transmission coil 15, and the first power reception coil 25a and the second power reception coil 25b are used as the power reception coil 25. is there. Here, the first power transmission coil 15a is a two-turn coil having a diameter of 170 mm, the second power transmission coil 15b and the first power reception coil 25a are coils having a diameter of 250 mm and a tenth turn, and the second power reception coil 25b. Is a one-turn coil with a diameter of 157 mm.

  Here, the first power transmission coil 15 a is a coil to which power is directly supplied from the power transmission amplifier 14. When a current flows through the first power transmission coil 15a by the power transmission amplifier 14, electromagnetic induction occurs between the first power transmission coil 15a and the second power transmission coil 15b, and a current flows through the second power transmission coil 15b. Then, when a current flows through the second power transmission coil 15b by electromagnetic induction, magnetic field resonance occurs between the second power transmission coil 15b and the first power reception coil 25a whose resonance frequencies are matched, and a current flows through the first power reception coil 25a. Flows. Further, when a current flows through the first power receiving coil 25a due to magnetic field resonance, electromagnetic induction occurs between the first power receiving coil 25a and the second power receiving coil 25b, and a current flows through the second power receiving coil 25b. In the example illustrated in FIG. 2, a coil through which a current is directly supplied from the power transmission amplifier 14 and a coil directly connected to the load resistance on the power reception side (here, the first power transmission coil 15 a and the second power reception coil 25 b), and magnetic resonance The coils used for power transmission by the power transmission (here, the second power transmission coil 15b and the first power reception coil 25a) are not physically connected, but are connected by electromagnetic induction, thereby configuring the power transmission amplifier 14, the load resistance, and the like. However, the influence on the resonance frequency of the coil used for the magnetic field resonance is suppressed.

  In FIG. 2, as a representative example, a four-coil configuration of two coils on the power transmission side and two coils on the power reception side is illustrated, but the present invention is wireless based on magnetic field resonance between the power transmission coil 15 and the power reception coil 25. The present invention is applicable to a system using power transmission, and the number of coils is not limited to the above four-coil configuration. For example, a two-coil configuration including one power transmission side coil and one power receiving side coil may be employed, or a three coil configuration including one power transmission side coil and two power receiving side coils may be employed. The two coils on the power receiving side in the three-coil configuration are the first power receiving coil 25a and the second power receiving coil 25b that are connected by electromagnetic induction.

<Transmission efficiency adjustment processing>
FIG. 3 is a flowchart showing a flow of transmission efficiency adjustment processing performed in the wireless power transmission system 1 according to the present embodiment. In the processing shown in this flowchart, the power receiving coil 25 provided on the vehicle side and the power transmitting coil 15 provided in a parking lot or the like are aligned, and the processing for adjusting the resonance frequency is completed to prepare for power transmission. It is started when this is completed. Note that the specific contents and order of the processes shown in this flowchart are examples, and it is preferable that processes suitable for the embodiment are appropriately adopted as the process contents and order.

  In step S101, power transmission is started. The power transmission controller 17 controls the oscillation circuit 18 according to the preset contents or the result of communication with the power receiving side via the data transmission / reception units 12 and 22, and causes a current to flow through the coil at the determined frequency and voltage. Since this frequency is the resonance frequency of the power transmission unit 10 and the power reception unit 20, magnetic field resonance occurs between the power transmission coil 15 and the power reception coil 25 by this power transmission, and the power reception unit 20 can receive power. Thereafter, the process proceeds to step S102.

  In step S102, the transmission efficiency is calculated. At least one of the power transmission controller 17 and the power reception controller 27 (hereinafter simply referred to as “controllers 17 and 27”) indicates the ratio of the received power monitored by the rectifier circuit 28 to the transmitted power monitored by the power transmission amplifier 14. By calculating, the transmission efficiency is calculated. The power transmission controller 17 can acquire the received power from the power receiving unit 20 side via the data transmission / reception units 12 and 22. Further, the power receiving controller 27 can acquire the transmitted power from the power transmission unit 10 side via the data transmission / reception units 12 and 22. That is, the power transmission amplifier 14 and the controllers 17 and 27 correspond to the transmitted power acquisition means of the present invention, and the rectifier circuit 28 and the controllers 17 and 27 correspond to the received power acquisition means of the present invention. Thereafter, the process proceeds to step S103.

  In step S103, it is determined whether or not the transmission efficiency is sufficiently high. The controllers 17 and 27 determine whether or not the calculated transmission efficiency is equal to or higher than a predetermined target value. In the present embodiment, the target value of the transmission efficiency is set in advance to a value such as 80% or 70% based on the power that can be said to be sufficient for charging the in-vehicle battery 33. When it is determined that the transmission efficiency is equal to or higher than the target value, the transmission efficiency adjustment process shown in this flowchart ends, and thereafter, the power transmission process is continued until the charging of the in-vehicle battery 33 is completed. If it is determined that the transmission efficiency is less than the target value, the process proceeds to step S104.

  In step S104, the power transmission / reception element is changed. The controllers 17 and 27 change an element that affects the transmission efficiency in at least one of the power transmission unit 10 and the power reception unit 20, in other words, an element that changes the transmission efficiency by adding some change to the element. . Note that the power transmission / reception element change is performed so as to achieve the target transmission efficiency while feeding back the adjustment result in step S105 and subsequent steps. Also good. That is, even if it is difficult to predict whether the transmission efficiency is improved or decreased due to the change applied to the element, it may be changed in step S104. The result of the change made in step S104 is determined in the processing after step S105 described below. Here, the power transmission / reception element is an element that affects transmission efficiency among the elements used for power transmission in the wireless power transmission device, and the change of the power transmission / reception element is the control as such a power transmission / reception element. To change the target and control value. In this embodiment, the transmission efficiency is adjusted by controlling the apparent load resistance on the power receiving side, the transmission efficiency is adjusted by controlling the transmission frequency, the transmission efficiency is adjusted by changing the number of coils, and the coupling degree between the coils is changed. The transmission efficiency is adjusted by using at least one of the adjustment means of the adjustment of the transmission efficiency by. A specific method for adjusting transmission efficiency will be described later. Thereafter, the process proceeds to step S105.

  In steps S105 and S106, the transmission efficiency is calculated again, and it is determined whether or not the transmission efficiency has been improved. The specific method for calculating the transmission efficiency in step S105 is as described in step S102, and thus the description thereof is omitted. When the transmission efficiency is calculated, the controllers 17 and 27 compare the transmission efficiency before the transmission efficiency adjustment process calculated in step S102 with the transmission efficiency after the transmission efficiency adjustment process calculated in step S105. Thus, it is determined whether or not the transmission efficiency has improved as a result of the change of the power transmission / reception element executed in step S104. If it is determined that the transmission efficiency has not improved, the process proceeds to step S107. If it is determined that the transmission efficiency has improved, the process proceeds to step S108.

  In step S107, the power transmission / reception element is changed again. However, since the change of the power transmission / reception element in step S107 is an adjustment performed in response to the result of the change made in step S104 being unsatisfactory, the change to the power transmission / reception element made in step S104 It is preferable that a change in a direction different from the direction is performed. However, depending on the power transmission / reception elements to which changes are made, although the transmission efficiency once decreases, it is considered that the transmission efficiency may be improved by changing in the same direction. It may not be different from step S104. Thereafter, the process proceeds to step S105.

In step S108, it is determined whether or not the transmission efficiency is sufficiently high. Detailed processing contents of the transmission efficiency determination are substantially the same as those described in step S103, and thus description thereof is omitted. When it is determined that the transmission efficiency is equal to or higher than the target value, the transmission efficiency adjustment process shown in this flowchart ends, and thereafter, the power transmission process is continued until the charging of the in-vehicle battery 33 is completed. If it is determined that the transmission efficiency is less than the target value, the process proceeds to step S104.

  That is, in the process shown in this flowchart, the process of adjusting the transmission efficiency shown in steps S104 to S108 is repeated until a sufficiently high transmission efficiency is obtained. By performing the processing shown in this flowchart, according to the wireless power transmission system 1 according to the present embodiment, the distance between the coil on the power transmission side and the coil on the power reception side is particularly close without using an electric wire. Power transmission can be performed efficiently in a state that is not.

<Variations of transmission efficiency adjustment methods>
Hereinafter, a specific method for adjusting the transmission efficiency used in the power transmission system according to the present embodiment will be described. In the present embodiment, (1) adjustment of transmission efficiency by controlling the apparent load resistance on the power receiving side, (2) adjustment of transmission efficiency by controlling the transmission frequency, (3) adjustment of transmission efficiency by changing the number of coils, and (4) The transmission efficiency is adjusted using at least one of the adjustment means of the adjustment of the transmission efficiency by changing the coupling degree between the coils.

(1) Adjustment of transmission efficiency by control of apparent load resistance on power receiving side First, adjustment of transmission efficiency by control of apparent load resistance on the power receiving side will be described. The power receiving unit 20 according to the present embodiment includes a rectifier circuit 28 and a DC / DC converter 29 between the power receiving coil 25 and the in-vehicle battery 33. The rectifier circuit 28 and the DC / DC converter 29 are taken out by the in-vehicle battery 33 side. To maintain constant power. For this reason, when the power reception voltage of the power reception coil 25 changes with the change of the power transmission voltage by the power transmission unit 10, the apparent load resistance changes because the current flowing through the power reception coil 25 changes. For example, when the power transmission voltage is increased, the power reception voltage of the power reception coil 25 is increased, and the current flowing through the power reception coil 25 is decreased, so that the apparent load resistance is increased. That is, in this embodiment, the apparent load resistance with respect to the power receiving coil 25 can be changed by the rectifier circuit 28 and the DC / DC converter 29.

  FIG. 4 is a diagram illustrating a result of simulating a relationship between a distance (coil interval) between the power transmission coil 15 and the power reception coil 25 and transmission efficiency for each load resistance in the four-coil configuration illustrated in FIG. 2. . As can be seen from FIG. 4, the transmission efficiency at a certain distance changes by changing the load resistance. For example, in the example shown in FIG. 4, when the distance between the power transmission coil 15 and the power reception coil 25 is 200 mm and the load resistance is switched between 10Ω, 3.3Ω, and 33Ω, the load resistance is set to 10Ω. It can be seen that the best transmission efficiency can be obtained. Such a simulation result of the relationship between the coil interval and the transmission efficiency corresponding to the power transmission / reception element may be used as an auxiliary when determining the change direction of the power transmission / reception element in the feedback control. However, the change in the transmission efficiency according to the load resistance shown in FIG. 4 is an example obtained by simulation, and the relationship between the magnitude of the load resistance and the transmission efficiency changes depending on the embodiment. For this reason, in the implementation, the result of actual measurement using the wireless power transmission system 1 used in the implementation is the element to be changed (here, the load resistance or the transmission voltage on the power receiving side), the coil interval, and the transmission. Transmission efficiency information which is a relational expression or map with efficiency is held in a storage device connected to the controllers 17 and 27, and control is performed with reference to this. In the present embodiment, the storage device and the controllers 17 and 27 correspond to information holding means according to the present invention.

(2) Adjustment of transmission efficiency by control of power transmission frequency Next, adjustment of transmission efficiency by control of power transmission frequency will be described. When power transmission is performed using magnetic field resonance as used in this embodiment, the transmission efficiency with respect to the distance between the power transmission coil 15 and the power reception coil 25 changes by changing the power transmission frequency.

FIG. 5 is a diagram illustrating a result of simulating a relationship between a distance (coil interval) between the power transmission coil 15 and the power reception coil 25 and transmission efficiency for each power transmission frequency in the four-coil configuration illustrated in FIG. 2. . According to FIG. 5, it can be seen that the transmission efficiency at a certain distance changes by changing the power transmission frequency. For example, in the example shown in FIG. 5, when the interval between the power transmission coil 15 and the power reception coil 25 is 100 mm and the power transmission frequency is switched between 1 MHz, 0.5 MHz, and 2 MHz, the power transmission frequency is 2 MHz. It can be seen that the best transmission efficiency can be obtained. Such a simulation result of the relationship between the coil interval and the transmission efficiency corresponding to the power transmission / reception element may be used as an auxiliary when determining the change direction of the power transmission / reception element in the feedback control. However, the change in transmission efficiency according to the power transmission frequency shown in FIG. 5 is an example obtained by simulation, and the relationship between the magnitude of the power transmission frequency and the transmission efficiency varies depending on the embodiment. Therefore, in the implementation, the result of actual measurement using the wireless power transmission system 1 used in the implementation is a relational expression between the element to be changed (here, the transmission frequency), the coil interval, and the transmission efficiency, or The transmission efficiency information, which is a map, is held in a storage device connected to the controllers 17 and 27, and control is performed with reference to this.

(3) Adjustment of transmission efficiency by changing the number of coils Next, adjustment of transmission efficiency by changing the number of coils will be described. When power transmission is performed using magnetic field resonance as used in the present embodiment, the transmission efficiency with respect to the distance between the power transmission coil 15 and the power reception coil 25 is improved by changing the configuration of the power transmission coil 15 and the power reception coil 25. Change.

  FIG. 6 is a diagram showing an outline of a four-coil configuration in the present embodiment. Moreover, FIG. 7A is a figure which shows the relationship between the frequency and the electric current which flow through a coil when the space | interval of the 2nd power transmission coil 15b and the 1st power receiving coil 25a is 50 mm by 4 coil structure shown in FIG. FIG. 7B is a diagram illustrating a relationship between a frequency and a current flowing through the coil when the interval between the second power transmission coil 15b and the first power reception coil 25a is 500 mm in the four-coil configuration illustrated in FIG. In the example of FIGS. 7A and 7B, the resonance frequency is set to 1 MHz. According to FIG. 7A, when the coil interval is 50 mm (relatively small), a peak split occurs, and the current flowing through the first power transmission coil 15a at the resonance frequency (here 1 MHz) is large, that is, the output of the power source. It can be seen that the power loss at the resistor increases and the transmission efficiency decreases. On the other hand, according to FIG. 7B, when the coil interval is 500 mm (relatively large), no peak split occurs, and the current flowing through the first power transmission coil 15a at the resonance frequency (here 1 MHz) is small. It can be seen that the power loss at the output resistance of the power source is reduced and the transmission efficiency is increased.

  FIG. 8 is a diagram showing an outline of a three-coil configuration in the present embodiment. FIG. 9A is a diagram showing the relationship between the frequency and the current flowing through the coil when the interval between the second power transmission coil 15b and the first power reception coil 25a is 50 mm in the three-coil configuration shown in FIG. FIG. 9B is a diagram showing the relationship between the frequency and the current flowing through the coil when the interval between the second power transmission coil 15b and the first power reception coil 25a is 500 mm in the three-coil configuration shown in FIG. In the examples of FIGS. 9A and 9B, the resonance frequency is set to 1 MHz. According to FIG. 9A, when the coil interval is 50 mm (relatively small), a peak split occurs, and the current flowing through the second power transmission coil 15b is small at the resonance frequency (here, 1 MHz), that is, the output of the power source. It can be seen that the power loss at the resistor is reduced and the transmission efficiency is increased. On the other hand, according to FIG. 9B, when the coil interval is 500 mm (relatively large), no peak split occurs, and the current flowing through the second power transmission coil 15b at the resonance frequency (here 1 MHz) is large. It can be seen that the power loss at the output resistance of the power source increases and the transmission efficiency decreases.

FIG. 10 is a diagram illustrating a result of simulating a relationship between a distance (coil interval) between the power transmission coil 15 and the power reception coil 25 and transmission efficiency for each coil configuration. As can be seen from FIG. 10, as discussed with reference to FIGS. 7A, 7 </ b> B, 9 </ b> A, and 9 </ b> B, changing the coil configuration changes the transmission efficiency at a certain distance. For example, in the example shown in FIG. 10, when the interval between the power transmission coil 15 and the power reception coil 25 is 50 mm and the coil configuration is switched between the 4-coil configuration and the 3-coil configuration, the coil configuration is set to 3 coils. It can be seen that the best transmission efficiency can be obtained. On the other hand, when the coil configuration is switched with the interval between the power transmission coil 15 and the power reception coil 25 being 500 mm, the best transmission efficiency can be obtained when the coil configuration is 4 coils. Such a simulation result of the relationship between the coil interval and the transmission efficiency corresponding to the power transmission / reception element may be used as an auxiliary when determining the change direction of the power transmission / reception element in the feedback control. However, the change in the transmission efficiency according to the coil configuration shown in FIG. 10 is an example obtained by simulation, and the relationship between the size of the coil configuration and the transmission efficiency varies depending on the embodiment. For this reason, in the implementation, the result of actual measurement using the wireless power transmission system 1 used in the implementation is a relational expression between the element to be changed (here, the coil configuration), the coil interval, and the transmission efficiency, or The transmission efficiency information, which is a map, is held in a storage device connected to the controllers 17 and 27, and control is performed with reference to this.

(4) Adjustment of transmission efficiency by changing the degree of coupling between coils Next, adjustment of transmission efficiency by changing the degree of coupling between coils will be described. When power transmission is performed using magnetic field resonance as used in the present embodiment, between the first power transmission coil 15a and the second power transmission coil 15b, or between the first power reception coil 25a and the second power reception coil 25b. By changing the coupling degree, the transmission efficiency with respect to the distance between the power transmission coil 15 and the power reception coil 25 changes.

  FIG. 11 is a diagram showing an outline of the configuration of the first power transmission coil 15a and the second power transmission coil 15b in the present embodiment. In the example shown in FIG. 11, as the first power transmission coil 15a, three first power transmissions of a first power transmission coil 15a1 having a diameter of 157 mm, a first power transmission coil 15a2 having a diameter of 140 mm, and a first power transmission coil 15a3 having a diameter of 170 mm. Coils 15a1, 15a2, and 15a3 are provided in advance, and one of the three first power transmission coils 15a1, 15a2, and 15a3 is selected and used for power transmission under the control of the controllers 17 and 27. In the present embodiment, the degree of coupling between the first power transmission coils 15a1, 15a2, 15a3 and the second power transmission coil 15b is changed by selecting and using coils having different diameters. Note that the degree of coupling between the coils is generally stronger as the coil interval is closer. Moreover, in this embodiment, although it is supposed that the coupling | bonding degree of 1st power transmission coil 15a1, 15a2, 15a3 and the 2nd power transmission coil 15b will be changed by providing multiple types of 1st power transmission coil 15a1, 15a2, 15a3, diameter A plurality of second power receiving coils 25b may be provided to be selectable, and the degree of coupling between the first power receiving coil 25a and the second power receiving coil 25b may be changed.

12 simulates the relationship between the distance (coil interval) between the power transmission coil 15 and the power reception coil 25 and the transmission efficiency for each of the first power transmission coils 15a1, 15a2, and 15a3 having different diameters shown in FIG. It is a figure which shows the result. According to FIG. 12, it can be seen that the transmission efficiency at a certain distance changes by changing the diameters of the first power transmission coils 15a1, 15a2, and 15a3. For example, in the example illustrated in FIG. 12, the first power transmission coil 15a1 having a distance of 100 mm and a diameter of 157 mm, a first power transmission coil 15a2 having a diameter of 140 mm, and a first power coil having a diameter of 170 mm. It can be seen that when the three first power transmission coils 15a1, 15a2, and 15a3 of the single power transmission coil 15a3 are switched, the best transmission efficiency can be obtained when the first power transmission coil 15a3 having a diameter of 170 mm is used. Such a simulation result of the relationship between the coil interval and the transmission efficiency corresponding to the power transmission / reception element may be used as an auxiliary when determining the change direction of the power transmission / reception element in the feedback control. However, the change in transmission efficiency according to the diameters of the first power transmission coils 15a1, 15a2, and 15a3 shown in FIG. 12 is an example obtained by simulation, and depending on the embodiment, the first power transmission coils 15a1, 15a2, and 15a3. The relationship between the diameter and transmission efficiency varies. For this reason, in the implementation, the results of actual measurement using the wireless power transmission system 1 used in the implementation are changed elements (here, the diameters of the first power transmission coils 15a1, 15a2, and 15a3) and the coils. A relational expression or map between the interval and the transmission efficiency is held in a storage device connected to the controllers 17 and 27, and control is performed with reference to this.

  In order to change the degree of coupling between the coils, a method other than the method of preparing a plurality of coils having different diameters and changing the coil used as shown in FIG. 11 may be used. Hereinafter, a method of changing the degree of coupling between coils other than using a plurality of coils will be described with reference to FIGS. 13 and 14.

  FIG. 13 is a diagram showing an outline of a configuration in which the first power transmission coil 15a or the second power transmission coil 15b can be moved up and down on the same axis. According to the example shown in FIG. 13, the mutual inductance between the coils can be made variable by changing the distance between the first power transmission coil 15a and the second power transmission coil 15b. Even with such a configuration, it is possible to adjust the transmission efficiency by changing the degree of coupling between the first power transmission coil 15a and the second power transmission coil 15b. In the present embodiment, the degree of coupling between the first power transmission coil 15a and the second power transmission coil 15b is changed by allowing the first power transmission coil 15a or the second power transmission coil 15b to move up and down on the same axis. However, it is good also as changing the coupling | bonding degree of the 1st receiving coil 25a and the 2nd receiving coil 25b by enabling the 1st receiving coil 25a or the 2nd receiving coil 25b to move up and down on the same axis. Specifically, a drive device that can move the coil up and down on the same axis is connected to the coil, and the controllers 17 and 27 control the drive device, whereby the first power receiving coil 25a and the second power receiving coil 25a are connected. The degree of coupling with the power receiving coil 25b can be changed.

  FIG. 14 is a diagram illustrating a coil configuration when the number of turns used for the first power transmission coil 15a or the second power reception coil 25b can be switched. According to the example shown in FIG. 14, the first power transmission coil 15a or the second power receiving coil 25b is a coil having a plurality of turns (two turns in the example shown in FIG. 14), and the number of turns used is switched in the middle of the coil. The tap (center tap) 15c is provided, and the connection of the power transmission amplifier 14 or the load resistance is switched between the coil end and the center tap 15c based on the control by the controllers 17 and 27, so that the coil actually used can be changed. The number of turns can be switched. Even with such a configuration, the degree of coupling between the first power transmission coil 15a and the second power transmission coil 15b or the degree of coupling between the first power reception coil 25a and the second power reception coil 25b is changed, thereby improving the transmission efficiency. Can be adjusted. Note that the degree of coupling between the coils generally increases as the number of turns is increased.

<Transmission efficiency adjustment processing: 2>
In the transmission efficiency adjustment process described above, the transmission / reception element is changed while monitoring the transmission efficiency to obtain high transmission efficiency. However, the change of the transmission / reception element is controlled based on the coil interval. May be.

  FIG. 15 is a flowchart illustrating the flow of the transmission efficiency adjustment process performed in the wireless power transmission system 1 according to the present embodiment. The process shown in this flowchart is started when the power reception coil 25 provided on the vehicle side and the power transmission coil 15 provided in a parking lot or the like are aligned and preparation for power transmission is completed. Note that the specific contents and order of the processes shown in this flowchart are examples, and it is preferable that processes suitable for the embodiment are appropriately adopted as the process contents and order.

  In step S201, the coil interval is acquired. The controllers 17 and 27 acquire the coil interval between the power transmission coil 15 and the power reception coil 25. For example, the controllers 17 and 27 can acquire the coil interval by a measuring instrument (not shown) that measures a distance by a delay time of radio waves or sound waves or by a survey using a captured image. Alternatively, the power reception controller 27 on the vehicle side may hold information on the distance between the power reception coil 25 and the ground (power transmission coil 15) in advance, and transmit this information to the power transmission controller 17. The coil interval may be specified based on other information such as vehicle height information and vehicle type information held by the vehicle-side power receiving controller 27. For example, the power transmission controller 17 receives vehicle type information from the power receiving controller 27 via the data transmission / reception units 12 and 22, searches a database connected to the power transmission controller 17, and acquires a standard coil interval of the corresponding vehicle type. It is good. When the coil interval is acquired by any method, the process proceeds to step S202.

  In step S202 and step S203, the transmission efficiency information is referred to, and the change contents of the power transmission / reception element are determined. In the present embodiment, the transmission efficiency information is information indicating the relationship between the coil interval and the transmission efficiency, which is derived from the results of experiments and simulations in advance, for each power transmission / reception element, in the form of a relational expression or a map, It is held in a storage device connected to the controllers 17 and 27. More specifically, the storage device includes a coil for each power transmission / reception element described in FIG. 4, FIG. 5, FIG. 10, FIG. Transmission efficiency information that is a relational expression between the interval and the transmission efficiency or a control map (control table) is held. The control map is information including, for example, an optimal control value (contents of changing power transmission / reception elements) for each coil interval. Then, the controller 17 or 27 substitutes the coil interval acquired in step S201 into the relational expression, or searches the control map based on this coil interval, etc. Get the transmission efficiency for each. Then, the controllers 17 and 27 determine the change content that maximizes the transmission efficiency as the actual change content. Thereafter, the process proceeds to step S204.

  When determining the change contents using transmission efficiency information such as a relational expression or a control map (control table), even if the change contents are determined based on a plurality of parameters, It is possible to easily obtain the most preferable (highest efficiency) change contents. For example, when determining the change contents of the power transmission / reception element (for example, frequency) using the coil interval (first parameter) and the second parameter other than the coil interval, the controllers 17 and 27 are configured to change the coil interval (first parameter). Is used to obtain transmission efficiency Nax and Nay of frequencies x and y, which are control values corresponding to the coil interval a, and further using transmission efficiency information about the second parameter. The transmission efficiencies Nbx and Nby of the frequencies x and y, which are control values corresponding to the second parameter b, are acquired. Then, based on the acquired transmission efficiencies Nax and Nay and the transmission efficiencies Nbx and Nby, the controllers 17 and 27 determine the total transmission efficiencies (Nx = Nax * Nbx, Ny = Nay *) for each control value (frequency x, y). Nby) is calculated and compared, and the higher overall efficiency Nx, Ny of the frequencies x, y is determined as the change contents when the first parameter a and the second parameter b are obtained.

  In step S204, the power transmission / reception element is changed. The controllers 17 and 27 execute the power transmission / reception element changing process determined in step S203 in at least one of the power transmission unit 10 and the power reception unit 20. In the present embodiment, the transmission efficiency is adjusted by controlling the apparent load resistance on the power receiving side, the transmission efficiency is adjusted by controlling the transmission frequency, the transmission efficiency is adjusted by changing the number of coils, and between the coils described above. The transmission efficiency is adjusted by using at least one of the adjustment means among the adjustments of the transmission efficiency by changing the coupling degree. Thereafter, the processing shown in this flowchart ends.

<Transmission efficiency adjustment process as charging progresses>
The transmission efficiency adjustment process described with reference to FIG. 3 is a process for controlling the wireless power transmission system 1 so as to obtain a better transmission efficiency while monitoring the power transmission efficiency in the wireless power transmission. Since the wireless power transmission system 1 shown in the embodiment is a system for charging the in-vehicle battery 33, control for performing highly efficient charging may be performed in conjunction with the adjustment process illustrated in FIG. preferable. For example, depending on the type of battery used as the in-vehicle battery 33, conditions for maintaining high charging efficiency vary with the progress of charging. For example, in general, constant current charging is performed in a nickel metal hydride battery, charging is started at a constant current in a lithium ion battery, and constant current / constant voltage charging is performed while switching to constant voltage charging in the middle. For this reason, it is preferable to carry out appropriate current / voltage control in accordance with the type of battery to maintain high-efficiency charging.

  FIG. 16 is a flowchart showing a flow of constant current charging processing performed as charging progresses in the wireless power transmission system 1 according to the present embodiment. The processing shown in this flowchart is started when power transmission / reception by the wireless power transmission system 1 is started. Note that the specific contents and order of the processes shown in this flowchart are examples, and it is preferable that processes suitable for the embodiment are appropriately adopted as the process contents and order.

  First, the power receiving controller 27 acquires the voltage of the in-vehicle battery 33 (step S301). Generally, as charging progresses, the voltage of the battery increases. This means that the load resistance on the power receiving side has increased, and when the in-vehicle battery 33 is a battery that is charged with a constant current, the voltage required for constant current charging increases. The power reception controller 27 transmits the acquired voltage to the power transmission controller 17 via the data transmission / reception units 12 and 22 (step S302).

  The power transmission controller 17 receives the voltage of the in-vehicle battery 33 transmitted from the power reception controller 27 (step S302), and calculates a transmission voltage necessary for charging with a constant current based on the received in-vehicle battery 33 voltage. (Step S303). And the power transmission controller 17 makes the voltage to the power transmission coil 15 the calculated power transmission voltage by controlling the power transmission amplifier 14 (step S304). By performing such control, charging current becomes constant, and high-efficiency charging can be maintained in a battery in which constant current charging is performed or a battery in which constant current / constant voltage charging is performed.

  The power transmission voltage calculates the power to be received by the power receiving side based on the current charging voltage and a predetermined charging current on the power receiving side, and further calculates the power transmission side voltage that can be received by the power receiving side. Can be obtained. Moreover, the transmission voltage holds the result of actual measurement using the wireless power transmission system 1 used for implementation as a relational expression or map (transmission efficiency information) of the voltage, coil interval, and transmission efficiency on the power transmission side. And may be obtained by referring to this. In the example illustrated in FIG. 16, the power receiving controller 27 acquires only the charging voltage, transmits this to the power transmission controller 17, and the process of calculating the power transmission voltage is performed by the power transmission controller 17. The process for calculating the voltage may be performed by either the power reception controller 27 or the power transmission controller 17. For example, the power reception controller 27 calculates power necessary for constant current charging based on the charging voltage and transmits the power to the power transmission controller 17. The power transmission controller 17 calculates the power transmission voltage based on the necessary power transmitted from the power reception controller 27. It may be determined.

In the example shown in FIG. 16, the flow of processing when performing constant current charging has been described. However, the same method can be used when performing constant voltage charging or when performing rapid charging (increasing charging current). That is, by acquiring a charging voltage or charging current from the in-vehicle battery 33, calculating necessary current and voltage on the power transmission side, and controlling the power transmission side, constant voltage charging or quick charging can be performed. I can do it. That is, a change in voltage or current on the power receiving side can be regarded as a change in load resistance on the power receiving side, and can be handled by controlling the transmission voltage and current on the power transmission side.

  By the way, when the power transmission side unit and the power reception side unit for performing wireless power transmission are attached to the power reception side device and the power transmission side equipment, a magnetic body such as an iron plate may exist on the back side of the unit. For example, when a power receiving unit is installed in an automobile, a magnetic body (iron plate) such as a chassis or body of the automobile inevitably exists on the back surface of the power receiving unit. In this case, magnetism due to power transmission reaches the magnetic body, and eddy current is generated in the magnetic body. As a result, energy loss due to the eddy current is caused and power transmission efficiency is lowered.

  Therefore, in the present embodiment, a magnetic shield sheet is disposed in the vicinity of the coils on the power transmission side and the power reception side that perform wireless power transmission, specifically on the back surface. As this magnetic shield sheet, a synthetic rubber sheet containing a flat soft magnetic powder (for example, a flexible noise suppression sheet “DPR” manufactured by Daido Steel Co., Ltd.) or the like can be used. FIG. 17 shows how eddy currents are generated when only a metal plate is arranged on the back side of the unit, and how eddy currents are suppressed when a magnetic shield sheet is arranged on the metal plate on the back side of the unit. FIG.

  Specifically, for example, as shown in FIG. 18, the coils for power transmission and reception are arranged facing each other, the power transmission side is a magnetic shield sheet on the back of the power transmission coil, and the vehicle side which is the power reception side is the power reception coil, magnetic shield sheet, vehicle It is preferable to arrange in the order of (BODY). The size of the magnetic shield sheet is preferably sufficiently larger than the diameter of the coil so that the coil can be covered. In addition, the direction, arrangement, distance, and the like of the coil and the magnetic shield sheet are preferably set as appropriate while confirming through experiments, for example, in consideration of power transmission efficiency. Of course, in consideration of efficiency, it is preferable that the sheet bend (coil covering method), shape, thickness, size, and the like are appropriately designed through experiments and the like.

  In addition, according to such an embodiment, since the magnetism behind the magnetic shield sheet is shielded, it is also possible to obtain an effect that there is almost no influence of power transmission energy on the vehicle-side passengers and electronic devices receiving power. is there.

DESCRIPTION OF SYMBOLS 1 Wireless power transmission system 10 Power transmission unit 15 Power transmission coil 17 Power transmission controller 20 Power reception unit 25 Power reception coil 27 Power reception controller

Claims (9)

A wireless power transmission device that transmits electric power by generating magnetic field resonance between a power transmission unit including a power transmission coil and a power reception unit including a power reception coil,
Change means for changing power transmission efficiency by changing a predetermined power transmission / reception element provided in any one of the power transmission unit and the power reception unit;
Transmission efficiency calculating means for calculating transmission efficiency before and after the change by the changing means;
A determination means for determining whether or not the transmission efficiency has improved before and after the change by comparing the transmission efficiency before and after the change, calculated by the transmission efficiency calculation means,
A wireless power transmission apparatus that improves transmission efficiency by repeatedly performing determination by the determination unit and change by the change unit. Transmission power acquisition means for acquiring power flowing in the power transmission coil;
A received power acquisition means for acquiring power flowing in the power receiving coil,
The transmission efficiency calculation means calculates the transmission efficiency by calculating a ratio of received power to acquired transmission power.
The wireless power transmission device according to claim 1. A wireless power transmission device that transmits electric power by generating magnetic field resonance between a power transmission unit including a power transmission coil and a power reception unit including a power reception coil,
Change means for changing power transmission efficiency by changing a predetermined power transmission / reception element provided in any one of the power transmission unit and the power reception unit;
Information holding means for holding transmission efficiency information indicating a relationship between a coil interval between the power transmission coil and the power receiving coil and transmission efficiency for each of the predetermined power transmitting and receiving elements;
Coil interval acquisition means for acquiring a coil interval between the power transmission coil and the power receiving coil,
The said change means is a wireless power transmission apparatus which refers to the said transmission efficiency information and changes the said predetermined power transmission / reception element so that the transmission efficiency in the acquired coil space | interval may improve. Extracted power adjusting means for making constant the electric power extracted by the power supply target to which the power receiving unit is connected;
A power transmission voltage control means for controlling a voltage of a current flowing through the power transmission coil,
The changing means changes the transmission efficiency by changing a voltage controlled by the transmission voltage control means.
The wireless power transmission device according to any one of claims 1 to 3. The power transmission coil is:
A first power transmission coil for receiving power input from a power transmission amplifier;
As a power input source, and having a second power transmission coil capable of selecting either electromagnetic induction from the first power transmission coil and the power transmission amplifier,
The power receiving coil is
A first power receiving coil through which a current flows by magnetic field resonance with the second power transmitting coil;
A second power receiving coil through which current flows by electromagnetic induction from the first power receiving coil,
The changing means changes the transmission efficiency by changing the input source to the second power transmission coil between the electromagnetic induction from the first power transmission coil and the power transmission amplifier.
The wireless power transmission device according to any one of claims 1 to 3. At least one of the power transmission coil and the power reception coil is:
A magnetic field resonance coil for magnetic field resonance between the power transmission unit and the power reception unit;
An electromagnetic induction coil that transmits or receives electric power to or from the magnetic field resonance coil by electromagnetic induction;
The changing means changes the transmission efficiency by changing a distance between the magnetic field resonance coil and the electromagnetic induction coil.
The wireless power transmission device according to any one of claims 1 to 3. At least one of the power transmission coil and the power reception coil has a plurality of the electromagnetic induction coils having different diameters from each other,
The changing means changes the transmission efficiency by changing the electromagnetic induction coil to be used among the plurality of electromagnetic induction coils.
The wireless power transmission device according to claim 6. A wireless power transmission device that transmits power by generating magnetic field resonance between a power transmission unit including a power transmission coil and a power reception unit including a power reception coil,
Changing the power transmission efficiency by changing a predetermined power transmission / reception element provided in either the power transmission unit or the power reception unit;
A transmission efficiency calculation step of calculating transmission efficiency before and after the change in the change step;
A determination step of determining whether or not the transmission efficiency has improved before and after the change by comparing the transmission efficiency before and after the change calculated in the transmission efficiency calculation step; and
A wireless power transmission method in which transmission efficiency is improved by repeatedly executing the determination in the determination step and the change in the change step. A wireless power transmission device that transmits power by generating magnetic field resonance between a power transmission unit including a power transmission coil and a power reception unit including a power reception coil,
Changing the power transmission efficiency by changing a predetermined power transmission / reception element provided in either the power transmission unit or the power reception unit;
An information holding step for holding transmission efficiency information indicating a relationship between a coil interval and a transmission efficiency for each predetermined power transmission and reception element measured in advance;
Performing a coil interval acquisition step of acquiring a coil interval between the power transmission coil and the power receiving coil,
In the changing step, the transmission power information is referred to, and the predetermined power transmission / reception element is changed so that the transmission efficiency in the acquired coil interval is improved.

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