Coil device

Abstract

To reduce losses occurring in a conductor.SOLUTION: A coil device 1 includes: a plurality of conductors Wq connected in parallel to each other to an inverter 101 which is an external power device, and including a power transmission coil 10 which is twisted together and shaped so as to be able to form a part of a magnetic field coupling circuit; a plurality of current sensors HLq provided on each of the plurality of conductors Wq to obtain a plurality of measured current values Aq indicating a magnitude of an AC current flowing through each of the plurality of conductors Wq; and a plurality of variable inductors VLq provided on each of the plurality of conductors Wq to change the plurality of measured current values Aq.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a coil device. [Background technology]

[0002] A wireless power supply system is known as a system for charging an electric vehicle or receiving power from an electric vehicle. The wireless power supply system transmits or receives power between a coil device installed on the ground and a coil device installed in the vehicle without physical contact between the two. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-99323 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-297869 [Patent Document 3] JP 2016-9790 A Summary of the Invention [Problem to be solved by the invention]

[0004] The loss that occurs when transmitting or receiving power between coil-based contactless power transfer devices can increase due to several factors. For example, loss tends to increase when the position of the receiving coil is misaligned with the transmitting coil. Loss also tends to increase when there is a foreign object around the transmitting coil or receiving coil that affects the magnetic flux generated by these coils.

[0005] Although they are in technical fields different from contactless power transfer devices, Patent Documents 1 and 2 disclose techniques for reducing loss in devices that use coils. Patent Document 1 discloses a technique related to superconducting coils. The technique of Patent Document 1 reduces loss by appropriately setting the cross-sectional area of ​​each conductor. Patent Document 2 discloses a technique related to coils for induction heating devices. The technique of Patent Document 2 reduces loss by providing symmetry in the arrangement of multiple conductors.

[0006] The technologies in Patent Documents 1 and 2 focus on the loss caused by the configuration of the coil itself. In other words, the factors that cause the loss are predictable. However, misalignment between the transmitting coil and the receiving coil and the presence of foreign objects are external factors that are not caused by the configuration of the coil itself and cannot be predicted. However, there has been a demand for reducing power loss even when affected by these factors.

[0007] The present invention provides a coil device that reduces the power loss generated in the conductor. [Means for solving the problem]

[0008] A coil device according to one embodiment of the present invention comprises first to nth (n is an integer of 2 or greater) conducting wires which are connected in parallel to an external power device and include coil portions which are twisted together and shaped so as to form part of a magnetic field coupling circuit; first to nth current sensors which are provided on the first to nth conducting wires, respectively, and obtain first to nth current values ​​which indicate the magnitude of the alternating current flowing through the first to nth conducting wires, respectively; and first to nth variable inductors which are provided on the first to nth conducting wires, respectively, and vary the first to nth current values.

[0009] This coil device has first to n-th current sensors provided on first to n-th conductors including a coil portion. These first to n-th current sensors make it possible to determine whether or not there is a bias in the magnitude of the AC current caused by external factors unrelated to the components of the coil device. If there is a bias, the magnitude of the AC current in the first to n-th conductors can be changed using first to n-th variable inductors. This makes it possible to reduce power loss in the conductors due to the bias in the magnitude of the AC current.

[0010] The coil device further includes a first coupling end to which one end of each of the first to n-th conducting wires is coupled, and a second coupling end to which the other end of each of the first to n-th conducting wires is coupled. The conducting wires include a power transfer unit including a coil unit that contributes to contactless power transfer, a first coupling unit between the power transfer unit and the first coupling end and that does not contribute to contactless power transfer, and a second coupling unit between the power transfer unit and the second coupling end and that does not contribute to contactless power transfer. The current sensor may be provided in the first coupling unit or the second coupling unit, and the variable inductor may be provided in the first coupling unit or the second coupling unit. This configuration makes it possible to preferably determine whether or not there is a bias in the magnitude of the AC current. Furthermore, the magnitude of the AC current in the first to n-th conducting wires can be preferably changed.

[0011] The current sensor of the coil device may be provided on the first connecting part, and the variable inductor may be provided on the first connecting part, and the variable inductor may be provided between the power exchange part and the current sensor. This configuration also makes it possible to more effectively determine whether or not there is a bias in the magnitude of the AC current. Furthermore, the magnitude of the AC current in the first to nth conducting wires can be more effectively changed.

[0012] The current sensor of the coil device may be provided on the first connecting part, the variable inductor may be provided on the first connecting part, and the current sensor may be provided between the power transfer part and the variable inductor. This configuration also makes it possible to more effectively determine whether or not there is a bias in the magnitude of the AC current. Furthermore, the magnitude of the AC current in the first to nth conducting wires can be more effectively changed.

[0013] In the above coil device, one of the current sensor and the variable inductor may be provided at a first connection between the first coupling end and the power transfer unit, and the other of the current sensor and the variable inductor may be provided at a second connection between the second coupling end and the power transfer unit. This configuration also makes it possible to more effectively determine whether or not there is a bias in the magnitude of the AC current. Furthermore, the magnitude of the AC current in the first to nth conducting wires can be more effectively changed.

[0014] The coil device may further include a controller that receives first to n-th current values ​​from the first to n-th current sensors and provides first to n-th command values ​​that define the first to n-th inductances to the first to n-th variable inductors. With this configuration, the coil device can reduce power loss that occurs in the conductor due to unevenness in the magnitude of the AC current by itself, without relying on an external device.

[0015] The controller of the coil device may include a current value processing unit that determines whether or not there is a bias in the first to n-th current values, and an inductance setting unit that determines first to n-th command values ​​for adjusting the first to n-th inductances so as to reduce the bias in the first to n-th current values. With this configuration, it is possible to determine the first to n-th command values ​​for reducing the bias in the magnitude of the AC current. [Effects of the Invention]

[0016] According to the present invention, a coil device capable of reducing losses occurring in a conductor wire is provided. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing a contactless power supply system to which a coil device according to an embodiment is applied. [Figure 2] Fig. 2(a) is a plan view of a pair of coils with no misalignment. Fig. 2(b) is a side view of a pair of coils with no misalignment. Fig. 2(c) is a plan view of a pair of coils with misalignment. Fig. 2(d) is a side view of a pair of coils with misalignment. [Figure 3] FIG. 3 is a diagram for explaining various modes of misalignment. [Figure 4] FIG. 4 is a diagram illustrating the functional configuration of the power transmitting device and the power receiving device. [Figure 5] FIG. 5 is a diagram illustrating the physical configuration of the power transmitting device. [Figure 6] 6(a) and 6(b) are diagrams for explaining a variable inductor. [Figure 7] FIG. 7 is a functional block diagram of the controller. [Figure 8] FIG. 8 is a flowchart of a method for reducing current imbalance performed by the controller. [Figure 9] 9(a), 9(b), 9(c) and 9(d) are diagrams for explaining the steps of obtaining a plurality of current values. [Figure 10] FIG. 10 is a flow chart illustrating a variation of the method for reducing current bias performed by the controller. [Figure 11] FIG. 11 is a diagram showing the functional configuration of a power transmitting device and a power receiving device each including a coil device according to the second modification. [Figure 12] FIG. 12 is a diagram showing the functional configuration of a power transmitting device and a power receiving device each including a coil device according to the third modification. [Figure 13] FIG. 13 is a diagram showing the functional configuration of a power transmitting device and a power receiving device each including a coil device according to the fourth modification. [Figure 14]14(a), 14(b), 14(c), and 14(d) are diagrams for explaining modified examples of the step of obtaining a plurality of current values. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0019] 1, coil devices 1 and 2 are used, for example, as a power transmitting device 100 or a power receiving device 200 of a contactless power feeding system 900. The contactless power feeding system 900 charges a battery 202 mounted on a vehicle 300 such as an electric vehicle or a hybrid vehicle.

[0020] When the coil device 1 is used in the power transmission device 100, the coil device 1 as the power transmission device 100 is fixed to, for example, a road surface G. An external power supply is connected to the coil device 1 via a power transmission circuit, a rectifier circuit, etc. On the other hand, when the coil device 2 is used in the power receiving device 200, the coil device 2 as the power receiving device 200 is fixed to, for example, the chassis of the vehicle 300. A battery 202 is connected to the power receiving device 200 via a power receiving circuit, a charging circuit, etc.

[0021] The power transmitting device 100 and the power receiving device 200 face each other in the vertical direction, and the internal power transmitting coil 10 (coil portion) and power receiving coil 20 (coil portion) are magnetically coupled to form a magnetic field coupling circuit, thereby contactlessly feeding power from the power transmitting device 100 to the power receiving device 200. In other words, the power receiving device 200 receives power from the power transmitting device 100 in a contactless manner. The magnetic field coupling circuit may be a circuit that feeds power by a "magnetic field coupling method" or a "magnetic field resonance method." If only one of the power transmitting coil 10 or the power receiving coil 20 is present, a magnetic field coupling circuit is not formed.

[0022] Power transmission from the power transmitting device 100 to the power receiving device 200 is affected by magnetic coupling between the power transmitting coil 10 and the power receiving coil 20. For example, as shown in FIGS. 2(a) and 2(b), when the axis ZB of the power receiving coil 20 is aligned with the axis ZA of the power transmitting coil 10 (when the power transmitting coil and the power receiving coil are directly facing each other), power is transmitted effectively from the power transmitting coil 10 to the power receiving coil 20. On the other hand, as shown in FIGS. 2(c) and 2(d), when the axis ZB of the power receiving coil 20 is misaligned with the axis ZA of the power transmitting coil 10, power is not transmitted effectively from the power transmitting coil 10 to the power receiving coil 20. The states shown in FIGS. 2(c) and 2(d) are referred to as "misalignment." For ease of explanation, the distance from the axis ZA of the power transmitting coil 10 to the axis ZB of the power receiving coil 20 is defined as the "amount of misalignment." For example, when the vehicle 300 that is to receive power supply stops at a location that is shifted from a predetermined stopping position, the position of the power receiving coil 20 shifts relative to the power transmitting coil 10.

[0023] This positional deviation occurs in various situations. Fig. 3 illustrates an example in which positional deviation occurs in various situations and the amount of positional deviation is not uniform. For example, a period Ka is a period in which a vehicle 300 parked in a home garage is charged overnight using a power transmitting device 100 installed in the garage. At this time, because the vehicle 300 is parked in a misaligned position, the power receiving coil is misaligned with respect to the power transmitting coil 10 by a positional deviation amount Ma.

[0024] The period Kb is a period during which the vehicle 300 parked in a parking lot at the workplace during the daytime the following day is charged using the power transmitting device 100 installed in the parking lot at the workplace. At this time, the vehicle 300 is parked in a misaligned position, so the power receiving coil is misaligned by a positional deviation Mb with respect to the power transmitting coil 10. The positional deviation Mb at this time is smaller than the above-mentioned positional deviation Ma.

[0025] The period Kc is a period during the following night when the vehicle 300 parked in the garage at home is charged using the power transmitting device 100 installed in the garage. At this time, the vehicle 300 is parked in a misaligned position, and therefore the power receiving coil is misaligned by the positional deviation Mc with respect to the power transmitting coil 10. The positional deviation Mc at this time is larger than the above-mentioned positional deviation Ma during the night.

[0026] Then, the next day during the day, the period Kd is a period during which the vehicle 300 parked in the parking lot of a store visited for shopping is charged using the power transmitting device 100 installed in the parking lot of the store. At this time, the vehicle 300 is parked in a misaligned position, and the power receiving coil is misaligned by the positional misalignment amount Md with respect to the power transmitting coil 10. The positional misalignment amount Md at this time is slightly larger than the above-mentioned nighttime positional misalignment amount Ma.

[0027] When such a misalignment occurs, the efficiency of power transmission from the power transmitting device 100 to the power receiving device 200 decreases. In other words, power loss occurs during power transmission from the power transmitting device 100 to the power receiving device 200. The coil device 1 of this embodiment is adapted to various situations and amounts of misalignment shown in Fig. 3, and suppresses power loss that may occur during power transmission.

[0028] As shown in FIG. 4, the power transmitting device 100 includes an inverter 101 (external power device) and a coil device 1.

[0029] The inverter 101 receives a direct current, converts it into an alternating current of a frequency suitable for wireless power supply, and outputs it to the coil device 1. The inverter 101 may receive a direct current obtained by rectifying commercial alternating current transmitted from a power plant via a power grid using a rectifier and reducing voltage fluctuations using a smoothing circuit. The direct current received by the inverter 101 may be transformed to a predetermined voltage by a DC-DC converter. Alternatively, the direct current received by the inverter 101 may be transformed to a predetermined voltage by a DC-DC converter from a direct current obtained by a solar power generation facility. In the inverter 101, for example, the gate of an insulated gate bipolar transistor (IGBT) is driven by a pulse waveform generated by a microcomputer, and the IGBT is switched to modulate the direct current using pulse width modulation (PWM) to generate an alternating current. In the following description, the inverter 101 outputs a single-phase alternating current and has two output terminals.

[0030] The coil device 1 receives an AC current from the inverter 101 and generates a magnetic field. The coil device 1 transmits the power to the power receiving device 200 via a magnetic field coupling circuit formed between the coil device 1 and the coil device 2 of the power receiving device 200.

[0031] The coil device 1 has, as functional components, a power transfer unit F1 and a current balance adjustment unit F2. The power transfer unit F1 receives AC current from the inverter 101 to generate a magnetic field, and transmits power to the power receiving device 200 via a magnetic field coupling circuit. The current balance adjustment unit F2 adjusts the value of the AC current transmitted to the power transfer unit F1.

[0032] The power receiving device 200 has a coil device 2 and a rectifier 201 (external power device). Since the coil device 1 and the coil device 2 are magnetically coupled, an electromotive force is generated in the coil device 2 of the power receiving device 200 by the AC magnetic field generated by the coil device 1 of the power transmitting device 100. The coil device 2 sends the AC current generated by the electromotive force to the rectifier 201. The rectifier 201 obtains a DC current by rectifying the received AC current. The DC current output by the rectifier 201 is transformed to a predetermined voltage by a DC-DC converter and provided to the battery 202. The battery 202 is charged by the DC current. In the following description, it is assumed that the input of the rectifier 201 is a single-phase AC current and that it has two input terminals.

[0033] The coil device 1 included in the power transmitting device 100 will be described in further detail below.

[0034] 5, the coil device 1 has, as physical components, a first input / output end 11, a second input / output end 12, a first connecting end 13, a second connecting end 14, a first conducting wire W1, a second conducting wire W2, a third conducting wire W3, a fourth conducting wire W4, and a controller 15. Note that, although the coil device 1 of the embodiment has four conducting wires, the number of conducting wires is not limited to four. The coil device 1 may have two or more conducting wires.

[0035] In the following description, the first conductor W1, the second conductor W2, the third conductor W3, and the fourth conductor W4 may be collectively referred to as "plural conductors Wq." The subscripts of the reference numbers are numbers associated with the conductors in the description of this specification. For example, a subscript of "1" indicates the first conductor W1. The definitions of the subscripts are also used in the current sensors, variable inductors, current values, and command values ​​described below.

[0036] As mentioned above, power loss occurs when misalignment occurs between the transmitting coil 10 and the receiving coil 20. One cause of power loss is the imbalance of the current flowing through the multiple conductors Wq. "Imbalance" here refers to the current flowing through one conductor W being greater or less than the current flowing through the other conductors Wq. For example, if there is no imbalance in the current flowing through the multiple conductors Wq, the equivalent cross-sectional area of ​​the conductor through which the current flows is the sum of the cross-sectional areas of the multiple conductors Wq. On the other hand, if there is an imbalance in the current flowing through the multiple conductors Wq, the equivalent cross-sectional area of ​​the conductor through which the current flows approaches the cross-sectional area of ​​the conductor W through which the most current flows. If current flows through only one conductor W, the virtual cross-sectional area of ​​the conductor through which the current flows is the cross-sectional area of ​​the single conductor W. In other words, having four conductors is the same as having only one conductor. In other words, a large amount of current flows through the conductor W, which has a small cross-sectional area, generating a large amount of heat. This heat generation leads to a loss of power.

[0037] Therefore, each of the multiple conductors Wq is provided with a variable inductor whose inductance value can be changed in response to a command given by the controller 15. The controller 15 acquires the current value of the current flowing through each of the multiple conductors Wq. The controller 15 then adjusts the inductance values ​​of the multiple conductors Wq so that the current values ​​of the multiple conductors Wq become equal.

[0038] Specific components for suppressing power loss will be described in further detail.

[0039] The first input / output terminal 11 is connected to one of the output terminals of the inverter 101. The first coupling terminal 13 is connected to the first input / output terminal 11 via a conductor 16. In other words, all of the current received by the coil device 1 from the inverter 101 flows through the conductor 16 connecting the first input / output terminal 11 and the first coupling terminal 13. One end of each of the multiple conductors Wq is connected to the first coupling terminal 13. The other end of each of the multiple conductors Wq is connected to the second coupling terminal 14. In other words, the current flowing through the conductor 16 is divided and flows through each of the multiple conductors Wq. Therefore, the sum of the measured current values ​​Aq flowing through each of the multiple conductors Wq is the same as the current value flowing through the conductor 16.

[0040] The second coupling end 14 is connected to the second input / output end 12 via a conductor 17. That is, the value of the current flowing through the conductor 17 connecting the second input / output end 12 and the second coupling end 14 is the sum of the multiple measured current values ​​Aq flowing through the multiple conductors Wq. In other words, the value of the current flowing through the conductor 17 is the same as the value of the current flowing through the conductor 16. The second input / output end 12 is connected to the other output terminal of the inverter 101.

[0041] In the plurality of conducting wires Wq, a first connecting portion J1 is formed between the first connecting end portion 13 and the power transfer portion F1, which does not contribute to the non-contact transfer of power. Furthermore, in the plurality of conducting wires Wq, a second connecting portion J2 is formed between the second connecting end portion 14 and the power transfer portion F1, which does not contribute to the non-contact transfer of power. The definitions of the first connecting end portion 13, the first connecting portion J1, the second connecting end portion 14, and the second connecting portion J2 are not limited to those shown in FIG. 4 and the like. In FIG. 4, the portion indicated by the reference numeral "14" may be referred to as the "first connecting end portion," and the portion indicated by the reference numeral "J2" may be referred to as the "first connecting portion." Similarly, in FIG. 4, the portion indicated by the reference numeral "13" may be referred to as the "second connecting end portion," and the portion indicated by the reference numeral "J1" may be referred to as the "second connecting portion."

[0042] The first conductor W1 is provided with a first current sensor HL1 and a first variable inductor VL1. Similarly, the second conductor W2 is provided with a second current sensor HL2 and a second variable inductor VL2. The third conductor W3 is provided with a third current sensor HL3 and a third variable inductor VL3. The fourth conductor W4 is provided with a fourth current sensor HL4 and a fourth variable inductor VL4.

[0043] Like the multiple conductors Wq, the first current sensor HL1, the second current sensor HL2, the third current sensor HL3, and the fourth current sensor HL4 may be collectively referred to as the "multiple current sensors HLq." Furthermore, the first variable inductor VL1, the second variable inductor VL2, the third variable inductor VL3, and the fourth variable inductor VL4 may be collectively referred to as the "multiple variable inductors VLq."

[0044] The portion of each of the plurality of conductors Wq where the plurality of current sensors HLq and the plurality of variable inductors VLq are provided constitutes the current balance adjustment unit F2 described above. The portion of each of the plurality of conductors Wq where the plurality of current sensors HLq and the plurality of variable inductors VLq are provided does not constitute a coil unit and therefore does not function as a magnetic field coupling circuit. The portion of each of the plurality of conductors Wq where the plurality of current sensors HLq and the plurality of variable inductors VLq are provided is the first connecting unit J1 described above.

[0045] Furthermore, another portion of the plurality of conductors Wq is twisted together. Another portion of the twisted conductors Wq is wound as a whole in a coil shape. In other words, it constitutes the power transfer unit F1 described above. The power transfer unit F1 is connected to the second coupling end 14. The coil shape of the portion constituting the power transfer unit F1 is not particularly limited as long as it allows for contactless power transfer. The coil shape of the portion constituting the power transfer unit F1 can be a circular type, a solenoid type, a D type, or the like.

[0046] The multiple current sensors HLq are connected to the first coupling end 13. The first current sensor HL1 obtains a first measured current value A1 flowing through the first conducting wire W1. Similarly, the second current sensor HL2 obtains a second measured current value A2 flowing through the second conducting wire W2. The third current sensor HL3 obtains a third measured current value A3 flowing through the third conducting wire W3. The fourth current sensor HL4 obtains a fourth measured current value A4 flowing through the fourth conducting wire W4. The multiple current sensors HLq are connected to the controller 15 by wire or wirelessly. Each of the multiple current sensors HLq sends multiple measured current values ​​Aq to the controller 15.

[0047] The waveform of the current flowing through the multiple conductors Wq is an AC current that changes almost symmetrically between positive and negative at the frequency used for contactless power transfer. Furthermore, the current waveform is distorted from a sine wave because it contains harmonics caused by the switching of the inverter 101. Therefore, to reduce the measurement error of the current value, the sampling frequency of the multiple current sensors HLq is sufficiently higher than the frequency used for contactless power transfer. For example, the sampling frequency of the multiple current sensors HLq is approximately 10 to 100 times higher than the frequency used for contactless power transfer.

[0048] A plurality of measured current values ​​Aq obtained by a plurality of current sensors HLq, which are Hall elements as shown in FIG. 6(a) and the like, are provided to a controller 15, which then reads the provided plurality of measured current values ​​Aq. For example, the Hall elements may output analog voltages corresponding to the current values. In this case, the outputs of the plurality of current sensors HLq, which are Hall elements, may first be provided to a plurality of A / D converters. The A / D converters may then convert the analog voltages corresponding to the current values ​​into digital signals corresponding to the current values. The A / D converters may then provide the digital signals corresponding to the current values ​​to the controller 15.

[0049] The current is an alternating current and changes over time. Therefore, multiple measurement current values ​​Aq are measured simultaneously for each of the multiple conductors Wq. For example, if the Hall elements constituting multiple current sensors HLq output analog voltages corresponding to the current values, multiple A / D converters connected to each of the multiple current sensors HLq simultaneously perform the sample and hold operations that are performed by each of the multiple A / D converters.

[0050] Note that shunt resistors may be used as the multiple current sensors HLq. When shunt resistors are used as the multiple current sensors HLq, the potential difference across the shunt resistor is measured and divided by the resistance value of the shunt resistor to convert it into a current value.

[0051] As shown in FIGS. 6(a) and 6(b), an example of the plurality of current sensors HLq is a Hall sensor.

[0052] The multiple variable inductors VLq are connected in series with the multiple current sensors HLq, respectively. The current flowing through each of the multiple conductors Wq is an AC current. Therefore, the multiple variable inductors VLq, which have inductance, a type of complex impedance, generate a back electromotive force (back EMF) proportional to the AC frequency and inductance. The larger the back electromotive force, the more it reduces the current flowing through each of the multiple conductors Wq. The multiple variable inductors VLq are also connected to a controller 15 by wire or wirelessly. The inductance of each of the multiple variable inductors VLq can be set to a desired value according to multiple command values ​​Cq provided by the controller 15.

[0053] As shown in FIGS. 6(a) and 6(b), the first variable inductor VL1 has a coil body 181 and a movable shaft 182. The movable shaft 182 can expand and contract in its axial direction. The state of the shaft diameter of the movable shaft 182 inserted into the coil body 181 differs between the state in which the movable shaft 182 is contracted (see FIG. 6(a)) and the state in which the movable shaft 182 is extended (see FIG. 6(b)). As a result, the inductance when the movable shaft 182 is contracted (see FIG. 6(a)) differs from the inductance when the movable shaft 182 is extended (see FIG. 6(b)). While the variable inductor disclosed in Patent Document 3 has been exemplified, the present invention is not limited thereto, and any variable inductor whose inductance can be changed by providing a command value can also be used.

[0054] Some of the conductors Wq constituting the power transfer unit F1 are connected to the variable inductors VLq. Furthermore, some of the conductors Wq constituting the power transfer unit F1 are also connected to the second coupling end 14.

[0055] Next, the controller 15 will be described with reference to Fig. 7. As shown in Fig. 7, the controller 15 receives a plurality of measured current values ​​Aq from a plurality of current sensors HLq, respectively. Then, the controller 15 provides a plurality of command values ​​Cq to a plurality of variable inductors VLq.

[0056] Specifically, the controller 15 compares the multiple measured current values ​​Aq in the multiple conductors Wq, and then increases the inductance value of the conductor through which a relatively large current value flows among the multiple measured current values ​​Aq, and maintains the inductance value of the conductor through which a relatively small current value flows at a minimum value within an adjustable range.

[0057] The controller 15 repeats measuring the multiple measured current values ​​Aq and adjusting the inductance values ​​of the multiple conductors Wq until the multiple measured current values ​​Aq can be considered uniform, taking into account the error range. The controller 15 ends the adjustment of the inductance value when the multiple measured current values ​​Aq can be considered uniform, taking into account the error range. Ending the adjustment of the inductance value means maintaining the adjusted inductance value.

[0058] The above-described operation of the controller 15 can equalize the multiple measured current values ​​Aq in the multiple conductors Wq, thereby preventing current from concentrating in a specific conductor and reducing loss occurring in the multiple conductors Wq.

[0059] Furthermore, the operation of the above-described controller 15 uses only signals received from a sensor attached to the coil device 1. In other words, the operation of the controller 15 does not require the transmission and reception of information with the inverter 101, rectifier 201, etc. Therefore, the configuration for equalizing a plurality of measured current values ​​Aq can also be applied to the coil device 2 of the power receiving device 200. Furthermore, although the coil device 1 or the coil device 2 is installed in a location that is easily damaged by external impact, it is relatively easy to replace only the coil device 1 or the coil device 2 without replacing the inverter 101 or the rectifier 201.

[0060] The controller 15 is physically a computer including a processor P15 and a memory M15. The computer constituting the controller 15 may further include elements for performing necessary functions in addition to the processor P15 and the memory M15. For example, the controller 15 may include an input unit for receiving multiple measured current values ​​Aq and an output unit for providing command values ​​to multiple variable inductors VLq. The input unit and the output unit may be wired or wireless communication ports. The controller 15 executes a program stored in the memory M15. As a result, the controller 15 repeats the following operations: the processor P15 reads data from the memory M15, performs arithmetic processing on the data, and writes the arithmetic results to the memory M15. Through this series of operations, the controller 15 realizes the functional components shown in FIG. 7.

[0061] The controller 15 includes, as functional components, a current value input unit 151, a current value determination unit 152, a current value processing unit 153, an inductance setting unit 154, and a command value output unit 155. These functional components are realized by the processor P15 executing a predetermined program.

[0062] The controller 15 stores data for current balancing processing in the memory M15. The memory M15 here refers to a medium from which various data and information can be read and written. Examples of data stored in the memory M15 include a plurality of measured current values ​​Aq, a plurality of comparison current values ​​Pq, a maximum current value Amax, a plurality of command values ​​Cq, a maximum command value Cmax, and a current threshold Em. Other data and information may also be stored in the memory M15. n indicates the number of conductors. In this embodiment, n=4.

[0063] The current value input unit 151 receives a plurality of measured current values ​​Aq provided from a plurality of current sensors HLq. The specific contents of the operation of receiving the measured current values ​​Aq will be described later. The current value input unit 151 stores the received plurality of measured current values ​​Aq in the memory M15.

[0064] The current value determination unit 152 reads out a plurality of measured current values ​​Aq and a current threshold Em from the memory M15. The current value determination unit 152 compares the maximum value of the plurality of measured current values ​​Aq with the current threshold Em. This comparison is for determining whether the coil device 1 is transmitting or receiving power. The current value determination unit 152 writes the comparison result to the memory M15.

[0065] The current value processing unit 153 reads out a plurality of measured current values ​​Aq from the memory M15. The current value processing unit 153 determines whether the plurality of measured current values ​​Aq are approximately equal to one another. This determination is made to determine whether there is a bias in the plurality of measured current values ​​Aq flowing through the plurality of conductors Wq. The specific contents of the determination process will be described later. The current value processing unit 153 writes the determination result into the memory M15. In the description that follows, instead of the plurality of measured current values ​​Aq, the processing target will be a plurality of comparison current values ​​Pq converted from the plurality of measured current values ​​Aq.

[0066] The inductance setting unit 154 reads out a plurality of measured current values ​​Aq from the memory M15. The inductance setting unit 154 sets a plurality of command values ​​Cq based on the plurality of measured current values ​​Aq, which are biased. The specific details of the process of setting the plurality of command values ​​Cq will be described later. The inductance setting unit 154 writes the setting results into the memory M15. In the description below, instead of the plurality of measured current values ​​Aq, the processing target is a plurality of comparison current values ​​Pq converted from the plurality of measured current values ​​Aq.

[0067] The command value output unit 155 reads out a plurality of command values ​​Cq from the memory M15. The command value output unit 155 provides the plurality of command values ​​Cq to the plurality of variable inductors VLq, respectively. As a result, the inductance value of each of the variable inductors VLq becomes Dq.

[0068] <Methods for reducing losses in conductors> Next, a method for reducing losses occurring in the plurality of conductors Wq, executed by the controller 15, will be described with reference to the flowchart of FIG. 8. The controller 15 repeats steps S1 to S9 according to the flowchart shown in FIG. 8. Step S2 is an output process for issuing a command to the variable inductor and is always executed regardless of conditional branching. However, for example, step S2 may be executed once every 5 to 10 seconds. Steps S1 to S9 are started from a start step (S0) when the controller 15 is powered on. Steps S1 to S9 may also be executed from the start step (S0) every fixed time period (e.g., 30 minutes) based on a timer function provided in the controller 15. When execution starts from the start step (S0), the plurality of command values ​​Cq are all initialized to 1 in step S1. By repeating these steps S1 to S9, the imbalance in the current values ​​occurring in the plurality of conductors Wq is gradually eliminated.

[0069] First, the controller 15 sets all of the values ​​of a plurality of command values ​​Cq to “1” (S1). Specifically, the process is as follows. Here, a command value Ci (where i is 1≦i≦n) with a value of “1” is defined as minimizing the inductance value Di of the variable inductor VLi. Conversely, a command value Ci with a value of “0” is defined as maximizing the inductance value Di of the variable inductor VLi. In other words, the command value Ci (where i is 1≦i≦n) is a value between 0 and 1. Decreasing the command value Ci from 1 to 0 increases the inductance value Di. As will be described later, a feedback control operation is performed to change the command value C based on the measured current value. Therefore, the relationship between the command value C and the inductance value D of the variable inductor VL does not need to be linear as long as it is monotonic. The relationship between the command value and the inductance value may be different for each of the plurality of variable inductors VLq, and the relationship may change over time due to temperature changes, etc. First command value C1=1 Second command value C2=1 Third command value C3=1 Fourth command value C4=1

[0070] Next, the controller 15 provides the plurality of command values ​​Cq to the plurality of variable inductors VLq, respectively (S2).

[0071] Next, the controller 15 measures a plurality of measurement current values ​​Aq (S3). When measuring a plurality of measurement current values ​​Aq, it is desirable to increase the S / N ratio (signal to noise ratio). To increase the S / N ratio, the current values ​​are read at the timing of the peaks or valleys of the current waveform. For example, the current value reading operation is performed several times or more during one cycle of the current waveform. Then, only the largest current value may be used.

[0072] A specific example of the operation (S3) of measuring multiple measured current values ​​Aq will be described with reference to FIGS. 9(a), 9(b), 9(c), and 9(d). The frequency of the AC current used for wireless power transfer is denoted as "f." The time of one cycle of the AC current is denoted as "T." The time of one cycle is expressed as the reciprocal of the frequency (T=1 / f). The controller 15 then reads multiple measured current values ​​Aq at time intervals sufficiently shorter than the time (T). The sufficiently short time interval may be, for example, T / 10. In the examples of FIGS. 9(a), 9(b), 9(c), and 9(d), the operation of reading current values ​​five times during one cycle (T) is performed.

[0073] The five current values ​​obtained by the first current sensor HL1 attached to the first conducting wire W1 are referred to as current values ​​A11, A12, A13, A14, and A15, respectively. Similarly, the five current values ​​obtained by the second current sensor HL2 are referred to as current values ​​A21, A22, A23, A24, and A25, respectively. The five current values ​​obtained by the third current sensor HL3 are referred to as current values ​​A31, A32, A33, A34, and A35, respectively. The five current values ​​obtained by the fourth current sensor HL4 are referred to as current values ​​A41, A42, A43, A44, and A45, respectively.

[0074] Next, the controller 15 determines the maximum current value Amax and the comparative current value Pq from the plurality of measured current values ​​Aq (S4).

[0075] The current values ​​Aij (i = 1..4, j = 1..5) are compared with each other to extract the maximum value. In the examples of Figures 9(a), 9(b), 9(c), and 9(d), the current values ​​are read five times for each of the four conducting wires W1, W2, W3, and W4. Therefore, the number of obtained current values ​​Aij is 20 (= 4 × 5). These 20 current values ​​Aij are compared with each other to extract the maximum value. The current value Aij extracted as the maximum value is then set as the maximum current value Amax. In the examples of Figures 9(a), 9(b), 9(c), and 9(d), the current value A12 is set as the maximum current value Amax.

[0076] According to the above-described comparison operation, the current value at the timing when the current waveform has the maximum amplitude (in the example, the current value read for the second time) is extracted from the conductor through which the greatest current is flowing (in the example, the first conductor W1).

[0077] Then, for the comparison operation with the second to fourth current values ​​A2, A3, A4 flowing through the second to fourth conducting wires W2, W3, W4, the current values ​​A12, A22, A32, A42 read at the same timing as the maximum current value, that is, the current values ​​A12, A22, A32, A42 read in the second measurement in this example, are set as comparison current values ​​P1, P2, P3, P4. Specifically, this is as follows. Comparison current value P1 = current value A12 Comparison current value P2 = current value A22 Comparison current value P3 = current value A32 Comparison current value P4 = current value A42

[0078] The current flowing through the inverter 101 or the rectifier 201 is denoted as "I0." The current values ​​flowing through the multiple conductors Wq are denoted as "I1, I2, I3, I4," respectively. Then, the following equation is established. I0=I1+I2+I3+I4…(1) When power is being fed, the amplitude of the current I0 flowing through the inverter 101 is large. Therefore, at least one of the current values ​​I1, I2, I3, and I4 flowing through each of the multiple conductors Wq has a large amplitude. Therefore, according to the above procedure, if the current values ​​(Aij (i=1..4, j=1..5) in this example) measured at different times in the multiple conductors Wq are compared and the maximum current value is taken as the maximum current value Amax, the maximum current value Amax is large, and therefore the S / N ratio can be increased.

[0079] Next, the controller 15 determines whether the maximum current value Amax is zero (S5).

[0080] If the maximum current value Amax is zero (S5: YES), the controller 15 again executes step S1 of setting the plurality of command values ​​Cq to "1." The case where the maximum current value Amax is zero indicates that no power transmission operation is being performed from the power transmitting device 100 to the power receiving device 200. Specifically, examples of this state include a state before the power transmission operation is started, and a state where the power transmission operation was being performed but has stopped for some reason.

[0081] If the maximum current value Amax is not zero (S5: NO), the controller 15 performs the next step S6. If the maximum current value Amax is not zero, this means that a current is flowing through at least one of the multiple conductors Wq, and therefore power transmission from the power transmitting device 100 to the power receiving device 200 is being performed.

[0082] The determination of whether the maximum current value Amax is zero may be made by comparing the maximum current value Amax with a predetermined current threshold value Em. For example, the measurement error of the multiple current sensors HLq may be used as the predetermined current threshold value Em. Specifically, the maximum value of the measurement errors of the multiple current sensors HLq is denoted as "Em." Then, it is determined whether the maximum current value Amax is equal to or less than the current threshold value Em. For example, if the following formula is satisfied, the controller 15 determines that the maximum current value Amax is zero. Amax≦Em…(2)

[0083] Next, the controller 15 compares the multiple comparison current values ​​Pq with each other (S6). This comparison is for determining whether the multiple comparison current values ​​Pq are approximately equal, which is performed in the next step S7. For example, the controller 15 obtains the average value of the multiple comparison current values ​​Pq. Next, the controller 15 sets an allowable range of ±10% with the average value of the comparison current values ​​Pq as the center value. The comparison current values ​​Pi (where i is in the range of 1 to n) that fall within this allowable range are treated as equal to each other. In other words, the comparison current value Pj (where j is in the range of 1 to n, but is not the same value as i) that does not fall within the allowable range is not treated as equal to the comparison current value Pi that falls within the allowable range.

[0084] In step S6, the controller 15 determines whether each of the multiple comparison current values ​​Pq is within the allowable range. Specifically, the controller 15 obtains the average value of the multiple comparison current values ​​Pq described above, sets the allowable range, and determines whether the comparison current value Pq is within the allowable range. As a result of executing step S6, a tag indicating whether the multiple comparison current values ​​Pq are "within the allowable range" or "not within the allowable range" is attached to each of the multiple comparison current values ​​Pq.

[0085] Next, the controller 15 determines whether the multiple comparison current values ​​Pq are approximately equal (S7). Specifically, the controller 15 determines whether the tag indicating whether "within the allowable range" or "not within the allowable range" is "within the allowable range" for all of the multiple comparison current values ​​Pq. If all of the multiple comparison current values ​​Pq are "within the allowable range," the controller 15 determines that the multiple comparison current values ​​Pq are approximately equal (S7: YES). If at least one of the multiple comparison current values ​​Pq is "not within the allowable range," the controller 15 does not determine that the multiple comparison current values ​​Pq are approximately equal (S7: NO).

[0086] If the controller 15 determines that the multiple comparison current values ​​Pq are approximately equal (S7: YES), that is, there is no current imbalance in each of the multiple conductors Wq. In this state, there is no need to make adjustments to balance the currents. Therefore, there is no need to adjust the multiple inductance values. As a result, the controller 15 does not change the current content of the multiple command values ​​Cq. Then, the controller 15 again provides the multiple command values ​​Cq, with the content maintained, to each of the multiple variable inductors VLq (S2).

[0087] On the other hand, if the controller 15 does not determine that the multiple comparison current values ​​Pq are substantially equal (S7: NO), that is, a current imbalance occurs in the multiple conductors Wq. In this state, adjustments must be made to balance the currents. Therefore, steps S8 and S9 are executed to adjust the multiple inductance values.

[0088] If the multiple comparison current values ​​Pq are not approximately equal (S7: NO), the controller 15 first sets the maximum value of the multiple comparison current values ​​Pq as the maximum comparison current value Pmax (S8). For example, in the examples of Figures 9(a), 9(b), 9(c), and 9(d), the comparison current value P1 is set as the maximum comparison current value Pmax.

[0089] Next, the controller 15 sets a plurality of command values ​​Cq (S9). Specifically, the controller 15 decreases the first command value C1 by a predetermined adjustment value Δ so as to increase the inductance value of the first variable inductor VL1 of the first conducting wire W1 through which the maximum comparison current value Pmax flows. However, to prevent the first command value C1 from becoming negative, if the first command value C1 decreased by the adjustment value Δ becomes negative, the first command value C1 is set to 0. The adjustment value Δ is a small value set so as not to cause control to oscillate. The controller 15 does not change the contents of the second command value C2, the third command value C3, and the fourth command value C4.

[0090] The controller 15 then provides multiple command values ​​Cq to the multiple variable inductors VLq, respectively. Through the above procedure, for example, the first conductor W1, which had the largest current value, becomes slightly less conductive to AC current. In other words, the inductance of the first conductor W1, which had the largest current value, increases slightly. As a result, the current value flowing through the first conductor W1 decreases. Even if the inductance of the first conductor W1 increases, the current value flowing through the entire circuit system including the multiple conductors Wq does not increase or decrease. Therefore, the current value flowing through the second conductor W2, the third conductor W3, and the fourth conductor W4 increases by the amount of the decrease in the first conductor W1. By repeating the above procedure, the currents flowing through the multiple conductors Wq become more uniform.

[0091] <Action and effect> Contactless power transfer devices generate a magnetic field by passing an alternating current (AC) with a frequency ranging from several tens of kilohertz to several megahertz through a coil. When a coil's windings are made of a single conductor, the skin effect and proximity effect cause the current to concentrate in a portion of the conductor's cross section. This results in a situation similar to that of a thin conductor, resulting in increased loss. To address this issue, methods have been developed to ensure that current flows evenly through the multiple windings that make up the coil. For example, Patent Document 2 aims to equalize the resistance of each conductor by symmetrically arranging multiple conductors. The resistance of a conductor can also be referred to as complex impedance, which takes into account the influence of a magnetic field at the frequency used for contactless power transfer. Patent Document 1 discloses a method for setting the cross-sectional area of ​​each conductor to an appropriate value.

[0092] The skin effect and proximity effect occur when a current flowing through a magnetic field is subjected to a force. In contactless power transfer, a magnetic field for power transfer exists between the power transmitting coil and the power receiving coil, and the distribution of the strength and direction of the magnetic field for power transfer changes depending on the misalignment between the power transmitting coil and the power receiving coil. Therefore, even if the conductor arrangement shown in Patent Document 2 is adopted, if the power transmitting coil and the power receiving coil are misaligned, the power transfer efficiency may decrease. This is because, while current flows evenly through multiple conductors when the power transmitting coil and the power receiving coil are directly facing each other, if power is transferred when there is a misalignment, the current in each conductor becomes uneven, resulting in greater heat generation in the conductor through which more current flows. Furthermore, as the amount of misalignment changes, the state of current unevenness, i.e., which conductor the current is biased toward, also changes.

[0093] Furthermore, the distribution of the strength and direction of the magnetic field for power supply may change not only due to a change in the amount of misalignment, but also due to the influence of metal or magnetic material present near the power transmitting coil or the power receiving coil.

[0094] Therefore, the inventors of the present application have come up with the idea of ​​a coil device 1 that suppresses a decrease in power supply efficiency due to external factors that are difficult to predict.

[0095] The coil device 1 comprises a plurality of conductors Wq connected in parallel to each other to an inverter 101, which is an external power device, and including a power transmission coil 10 that is twisted together and shaped so as to be able to form part of a magnetic field coupling circuit; a plurality of current sensors HLq provided on each of the plurality of conductors Wq to obtain a plurality of measured current values ​​Aq indicating the magnitude of the AC current flowing through each of the plurality of conductors Wq; and a plurality of variable inductors VLq provided on each of the plurality of conductors Wq to change the plurality of measured current values ​​Aq.

[0096] In this coil device 1, multiple current sensors HLq are provided on multiple conductors Wq. These current sensors HLq make it possible to determine whether or not there is a bias in the magnitude of the AC current due to external factors unrelated to the components of the coil device 1. If a bias is present, the magnitude of the AC current in the multiple conductors Wq can be adjusted by changing the inductance of multiple variable inductors VLq. This makes it possible to reduce power loss in the conductors due to a bias in the magnitude of the AC current.

[0097] It should be noted that the mechanism for reducing losses generated in the multiple conductors Wq applied to the coil device 1 is not a substitute for the method disclosed in Patent Document 2. The mechanism for reducing losses generated in the multiple conductors Wq applied to the coil device 1 can be applied as an addition to the method disclosed in Patent Document 2 and the like. In other words, current imbalances caused by internal factors such as the shape of the coil are addressed using the method disclosed in Patent Document 2 and the like. The intention is to apply the mechanism for reducing losses generated in the multiple conductors Wq applied to the coil device 1 to current imbalances caused by external factors that cannot be addressed by the method disclosed in Patent Document 2 and the like.

[0098] The coil device 1 includes a first coupling end 13 to which one ends of a plurality of conductors Wq are coupled, and a second coupling end 14 to which the other ends of the plurality of conductors Wq are coupled. Each of the plurality of conductors Wq includes a power transfer unit F1 including a power transmission coil 10 that forms a magnetic field coupling circuit and contributes to contactless power transfer; a first coupling unit J1 between the power transfer unit F1 and the first coupling end 13 that does not contribute to contactless power transfer; and a second coupling unit J2 between the power transfer unit F1 and the second coupling end 14 that does not contribute to contactless power transfer. A current sensor HL is provided at the first coupling unit J1. A variable inductor VL is also provided at the first coupling unit J1. Because the first coupling unit J1 is not affected by the magnetic field associated with contactless power transfer, it is possible to prevent errors in the measured current value of the current sensor HL and deviations in the inductance of the variable inductor VL due to the influence of the magnetic field. Furthermore, the magnetic field caused by the contactless power transfer is prevented from being disturbed by the metal components included in the current sensor HL and the variable inductor VL. This configuration makes it possible to effectively determine whether or not there is a bias in the magnitude of the AC current. Furthermore, the magnitude of the AC current in the multiple conductors Wq can be effectively adjusted.

[0099] The variable inductor VL is provided between the power transfer unit F1 and the current sensor HL. This configuration makes it possible to more effectively determine whether or not there is a bias in the magnitude of the AC current. Furthermore, it is possible to more effectively adjust the magnitude of the AC current in the multiple conductors Wq.

[0100] The coil device 1 further includes a controller 15 that receives a plurality of measured current values ​​Aq from a plurality of current sensors HLq and provides a plurality of command values ​​Cq that define a plurality of inductance values ​​Dq to a plurality of variable inductors VLq. With this configuration, the coil device 1 can reduce power loss that occurs in the conductor W due to bias in the magnitude of the AC current, based only on information that can be measured within the coil device 1 without obtaining information from an external device.

[0101] The controller 15 includes a current value processing unit 153 that determines whether or not there is a bias in the multiple measured current values ​​Aq, and an inductance setting unit 154 that determines multiple command values ​​Cq for adjusting the multiple inductance values ​​Dq so as to reduce the bias in the multiple measured current values ​​Aq. With this configuration, it is possible to determine multiple command values ​​Cq for reducing the bias in the magnitude of the AC current.

[0102] <Modification> The present invention may be embodied in various forms, including the above-described embodiment, with various modifications and improvements based on the knowledge of those skilled in the art. Furthermore, modifications may be constructed by utilizing the technical matters described in the above-described embodiment. For example, modifications 1 to 7 relate to the current balance adjustment unit F2.

[0103] <Variation 1> In step S9 described above, the command value C to the variable inductor VL is decreased by the adjustment value Δ in order to increase the inductance value D. As a result of repeating this process, there is a possibility that all of the multiple command values ​​Cq will become smaller than 1. When all of the multiple command values ​​Cq are smaller than 1, this means that the inductance has become too large. Therefore, a process may be performed to increase the multiple command values ​​Cq while maintaining the relative magnitude relationship between the multiple command values ​​Cq.

[0104] In the flowchart shown in Fig. 10, steps S1 to S9 are the same as steps S1 to S9 in the embodiment. In the flowchart shown in Fig. 10, step S10 is an additional adjustment process for raising the multiple command values ​​Cq while maintaining the relative magnitude relationship among the multiple command values ​​Cq.

[0105] First, the controller 15 determines whether at least one of the multiple command values ​​Cq is "1" (S10a). If at least one of the multiple command values ​​Cq is "1," the inductance is not too large. Therefore, the multiple command values ​​Cq set in step S9 are provided to the multiple variable inductors VLq without performing additional adjustment of the multiple command values ​​Cq (S2). On the other hand, if all of the multiple command values ​​Cq are smaller than "1," the inductance is too large. Therefore, additional adjustment processing of the multiple command values ​​Cq shown in steps S10b and S10c is performed.

[0106] The controller 15 sets the maximum of the plurality of command values ​​Cq as the maximum command value Cmax (S10b). Next, the controller 15 uses the maximum command value Cmax to additionally correct the plurality of command values ​​Cq according to the following equation. Command value Ci after additional correction = Command value Ci before additional correction + (1 - maximum command value Cmax) ... (2) (where 1 ≦ i ≦ n) Since the multiple command values ​​Cq are increased by the same value, as a result of the additional correction calculation using equation (2), the relative magnitude relationship between the multiple command values ​​Cq remains unchanged, and the maximum command value can be raised to 1.

[0107] <Variation 2> FIG. 11 shows a contactless power transfer system 900A configured with a power transmitting device 100A including a coil device 1A according to Modification 2, and a power receiving device 200A including a coil device 2A. The coil devices 1A and 2A have a current balance adjustment unit F2A that has a configuration different from that of the embodiment. The variable inductor VLq that configures the current balance adjustment unit F2A is disposed between the first coupling end 13 and the current sensor HLq. In other words, the arrangement of the variable inductor VLq and the current sensor HLq is reversed compared to the current balance adjustment unit F2. This connection configuration can also achieve the same effects as the coil devices 1 and 2 according to the embodiment.

[0108] <Variation 3> 12 shows a contactless power transfer system 900B including a power transmitting device 100B including a coil device 1B according to Modification 3 and a power receiving device 200B including a coil device 2B. In the embodiment, the current sensor HLq and the variable inductor VLq are arranged at the first coupling portion J1 between the first coupling end portion 13 and the power transfer unit F1. For example, as shown in FIG. 12, the current sensor HLq may be arranged at the first coupling portion J1, and the variable inductor VLq may be arranged at the second coupling portion J2. That is, the current balance adjustment unit F2B includes the current sensor HLq provided at the first coupling portion J1 between the first coupling end portion 13 and the power transfer unit F1, and the variable inductor VLq provided at the second coupling portion J2 between the second coupling end portion 14 and the power transfer unit F1. Since neither the first connecting portion J1 nor the second connecting portion J2 is affected by the magnetic field associated with contactless power supply, it is possible to prevent errors in the measured current value of the current sensor HL or deviations in the inductance of the variable inductor VL due to the influence of the magnetic field. Furthermore, it is possible to prevent the magnetic field associated with contactless power supply from being disturbed by metal components included in the current sensor HL and the variable inductor VL. This connection configuration can also achieve the same effects as the coil devices 1 and 2 of the embodiments.

[0109] <Variation 4> 13 shows a contactless power transfer system 900C including a power transmitting device 100C including a coil device 1C according to Modification 4 and a power receiving device 200C including a coil device 2C. The current balance adjustment unit F2C of Modification 4 has the current sensor HLq and the variable inductor VLq arranged in reverse to the current balance adjustment unit F2B of Modification 3. As shown in FIG. 13, the variable inductor VLq may be arranged at the first coupling portion J1, and the current sensor HLq may be arranged at the second coupling portion J2. That is, the current balance adjustment unit F2C includes the variable inductor VLq provided at the first coupling portion J1 between the first coupling end portion 13 and the power transfer portion F1, and the current sensor HLq provided at the second coupling portion J2 between the second coupling end portion 14 and the power transfer portion F1. Since neither the first connecting portion J1 nor the second connecting portion J2 is affected by the magnetic field associated with contactless power supply, it is possible to prevent errors in the measured current value of the current sensor HL or deviations in the inductance of the variable inductor VL due to the influence of the magnetic field. Furthermore, it is possible to prevent the magnetic field associated with contactless power supply from being disturbed by metal components included in the current sensor HL and the variable inductor VL. This connection configuration can also achieve the same effects as the coil devices 1 and 2 of the embodiments.

[0110] <Variation 5> The adjustment value Δ does not have to be a predetermined fixed value, but may be a variable value. For example, the difference between the maximum and minimum values ​​of the multiple measured current values ​​Aq is indicated as the "difference current value Idiff." The adjustment value Δ may be determined based on this difference current value Idiff. For example, the function shown in the following equation may be used, in which the difference current value Idiff is the independent variable and the adjustment value Δ is the dependent variable. Δ=f(Idiff) (3) The function f may be such that the adjustment value Δ increases as the differential current value Idiff increases, and decreases as the differential current value Idiff decreases. That is, the change in the command value may be increased when the difference in the current values ​​of the multiple conductors Wq is large, and decreased when the difference in the current values ​​of the multiple conductors Wq is small. If the change in the command value is small, the change in inductance is small, and if the change in the command value is large, the change in inductance is large.

[0111] <Variation 6> In addition to setting the command value C to increase the inductance value D of the variable inductor VL arranged in the conductor W with the largest current value, the command value C may also be set to increase the inductance value D of the variable inductor VL arranged in a conductor W other than the conductor W with the largest current value. Assume that the measured current value A2 flowing through the second conductor W2 is the second largest. In this case, in addition to setting the command value C1 to increase the inductance value D1 of the variable inductor VL1 of the conductor W1 with the largest current value, a command value C2 to increase the inductance value D2 of the variable inductor VL2 of the conductor W2 with the second largest current value may be set. In this case, the amount of decrease in the command value C1 for the variable inductor VL1 of the conductor with the largest current value may be set to an adjustment value Δ, and the amount of decrease in the command value C2 for the variable inductor VL2 of the conductor with the second largest current value may be smaller than the adjustment value Δ.

[0112] <Variation 7> To improve the S / N ratio, the multiple measured current values ​​Aq may be obtained using a method different from that described in the embodiment. As shown in Figures 14(a), 14(b), 14(c), and 14(d), multiple measured current values ​​Aq are measured over multiple periods T. These average values ​​may then be used as each of the multiple measured current values ​​Aq. As shown in Figure 14(a), in graph G141 of the first measured current value A1, the average current value of the measured current value B11 obtained in the first measurement, the measured current value B12 obtained in the second measurement, the measured current value B13 obtained in the third measurement, and the measured current value B14 obtained in the fourth measurement may be used as the measured current value of the conductor W1. Similarly, in graphs G142, G143, and G144 of the second, third, and fourth current values ​​A2, A3, and A4, if the current values ​​obtained in the first measurement are B21, B31, and B41, the current values ​​obtained in the second measurement are B22, B32, and B42, the current values ​​obtained in the third measurement are B23, B33, and B43, and the current values ​​obtained in the fourth measurement are B24, B34, and B44, then the average current value of B21, B22, B23, and B24 can be taken as the measured current value of conductor W2, the average current value of B31, B32, B33, and B34 as the measured current value of conductor W3, and the average current value of B41, B42, B43, and B44 as the measured current value of conductor W4.

[0113] <Variation 8> As described above, the mechanism for reducing losses generated in the plurality of conductors Wq may be applied to the coil device 1 of the power transmitting device 100 and the coil device 2 of the power receiving device 200. In this case, the operation for reducing losses generated in the plurality of conductors Wq executed by the power transmitting device 100 and the operation for reducing losses generated in the plurality of conductors Wq executed by the power receiving device 200 can be executed independently. In other words, the control by the controller 15 of the coil device 1 constituting the power transmitting device 100 does not need to be synchronized with the control by the controller 15 of the coil device 2 constituting the power receiving device 200, and they may be independent of each other. When the configuration of the coil device 1 is applied to the coil device 2, the first input / output terminal 11 and the second input / output terminal 12 are connected to one and the other of the input terminals of the rectifier 201, instead of one and the other of the output terminals of the inverter 101. The control by the controller 15 of the power transmitting device 100 reduces losses generated in the plurality of conductors Wq constituting the coil device 1. The loss occurring in the plurality of conducting wires Wq that constitute the coil device 2 is reduced by the control of the controller 15 that constitutes the power receiving device 200.

[0114] Note that coil device 1 and coil device 2 do not need to have exactly the same configuration as long as they form a magnetic field coupling circuit and are capable of contactless power supply. For example, the number of conductors constituting coil device 1 and the number of conductors constituting coil device 2 may be the same or different. For example, the shape of power transmitting coil 10 constituting coil device 1 and the shape of power receiving coil 20 constituting coil device 2 may be the same or different.

[0115] Also, different modified examples may be applied to coil device 1 and coil device 2. For example, coil device 1 may have the configuration of the embodiment, and coil device 2 may have the configuration of modified example 2. Coil device 1 may have the configuration of modified example 4, and coil device 2 may have the configuration of modified example 3.

[0116] As shown in the embodiment, Modification 2, Modification 3, and Modification 4, the current sensors HL and variable inductors VL may be arranged in the same manner for all of the multiple conductors Wq, thereby facilitating the manufacture and maintenance of the coil device 1. Alternatively, the current sensors HL and variable inductors VL may be arranged differently for each of the multiple conductors Wq.

[0117] For example, in the first conducting wire W1, the current sensor HL1 and the variable inductor VL1 may be provided at the first connecting portion J1. As an example, the variable inductor VL1 may be provided between the power exchange unit F1 and the current sensor HL1. In the second conducting wire W2, the current sensor HL2 and the variable inductor VL2 may be provided at the first connecting portion J1. As an example, the current sensor HL2 may be provided between the power exchange unit F1 and the variable inductor VL2. In the third conducting wire W3, the current sensor HL3 may be provided at the first connecting portion J1. In contrast, the variable inductor VL3 may be provided at the second connecting portion J2. In the fourth conducting wire W4, the variable inductor VL4 may be provided at the first connecting portion J1. In contrast, the current sensor HL4 may be provided at the second connecting portion J2.

[0118] The above configuration may be adopted, for example, to avoid mechanical interference between one current sensor HL and another current sensor HL, between one variable inductor VL and another variable inductor VL, or between a current sensor HL and a variable inductor VL.

[0119] <Variation 9> The controller 15 of the coil device 1 constituting the power transmitting device 100 can perform an operation to reduce losses occurring in the plurality of conductors Wq by using only the current value in the coil device 1 constituting the power transmitting device 100. The same is true for the power receiving device 200. In other words, the controller 15 of the coil device 2 constituting the power receiving device 200 can perform an operation to reduce losses occurring in the plurality of conductors Wq by using only the current value in the coil device 2 constituting the power receiving device 200.

[0120] In the case of contactless power supply for automobiles, the coil of the power transmitting device 100 and the coil of the power receiving device 200 are separated by, for example, about 20 cm. With this distance, the magnetic field generated between the coil of the power transmitting device 100 and the coil of the power receiving device 200 is not determined by the current of each conductor. The magnetic field generated between the coil of the power transmitting device 100 and the coil of the power receiving device 200 is determined by the sum of the currents in the conductors (windings).

[0121] According to the mechanism for reducing losses occurring in the plurality of conductors Wq described above, the ratio of the currents flowing through the plurality of conductors Wq is changed, but the sum of the currents flowing through the plurality of conductors Wq is not changed. Therefore, the control by the controller 15 of the power transmitting device 100 and the control by the controller 15 of the power receiving device 200 do not interfere with each other. As a result, the control by the controller 15 of the power transmitting device 100 and the control by the controller 15 of the power receiving device 200 can be performed independently. [Explanation of symbols]

[0122] 1, 1A, 1B, 1C, 2, 2A, 2B, 2C Coil device 10 Transmission coil (coil part) 13 First coupling end 14 Second connecting end 15 Controller 101 Inverter (external power device) 153 Current value processing section 154 Inductance setting section 181 Coil body 20 Receiving coil (coil part) 201 Rectifier (external power device) F1 power transfer section J1 First connection J2 Second connection HL, HL1, HL2, HL3, HL4, HLq current sensors VL, VL1, VL2, VL3, VL4, VLq variable inductors W,W1,W2,W3,W4,Wq Conductor

Claims

1. first to n-th (n is an integer of 2 or more) conducting wires which are connected in parallel to an external power device, twisted together, and include coil portions shaped to be able to form part of a magnetic field coupling circuit; first to n-th current sensors provided on the first to n-th conducting wires, respectively, for obtaining first to n-th current values ​​indicating the magnitude of AC currents flowing through the first to n-th conducting wires, respectively; a coil device comprising: first to nth variable inductors provided in the first to nth conductors, respectively, for changing the first to nth current values.

2. a first coupling end portion to which one end of each of the first to n-th conducting wires is coupled; a second coupling end portion to which the other ends of the first to nth conducting wires are coupled; The conductive wire is a power transfer unit including the coil unit that contributes to contactless power transfer; a first connecting portion between the power transfer portion and the first coupling end portion, the first connecting portion not contributing to non-contact power transfer; a second connecting portion that is located between the power transfer portion and the second coupling end portion and does not contribute to contactless power transfer; the current sensor is provided on the first connecting portion or the second connecting portion, The coil device according to claim 1 , wherein the variable inductor is provided in the first connecting portion or the second connecting portion.

3. the current sensor is provided on the first connecting portion, the variable inductor is provided in the first coupling portion, The coil device according to claim 2 , wherein the variable inductor is provided between the power transfer unit and the current sensor.

4. the current sensor is provided on the first connecting portion, the variable inductor is provided in the first coupling portion, The coil device according to claim 2 , wherein the current sensor is provided between the power receiving unit and the variable inductor.

5. one of the current sensor and the variable inductor is provided on the first connecting portion; The coil device according to claim 2 , wherein the other of the current sensor and the variable inductor is provided on the second connecting portion.

6. The coil device according to any one of claims 1 to 5, further comprising a controller that receives the first to nth current values ​​from the first to nth current sensors and provides the first to nth command values ​​that define the first to nth inductances to the first to nth variable inductors.

7. The controller a current value processing unit that determines whether or not there is a bias in the first to n-th current values; an inductance setting unit that determines the first to nth command values ​​for adjusting the first to nth inductances so that bias in the first to nth current values ​​is reduced.

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