JP2014116543A - Antenna and wireless power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique of easy-to-manufacture wireless power supply which enhances power transmission efficiency.SOLUTION: In a power transmission or reception antenna for wireless power supply, a conductor of circular cross section is formed in a planar spiral-shape having an air-core 26. The diameter ratio Di/Do of the innermost diameter Di and the outermost diameter Do of the planar spiral-shaped conductor falls within a range of 0.36-0.45. The gap between the conductors of n-th turn and (n+1)th turn of the antenna falls within a range of 0.5d-1.5d, where d is the diameter of the conductor.

Description

  The present invention relates to an antenna and a wireless power feeding apparatus including the antenna.

  The non-contact type power supply device for an automobile described in Patent Document 1 has an electric supply stand provided with a first coil, a power supply, a power supply control device, and a supply command unit on the ground, and the vehicle has a second power supply stand. A coil, charge control circuit, and battery are installed. This non-contact power supply device outputs a control signal from the power supply control device to the supply power source by operating a supply command unit of the electricity supply stand, supplies an alternating excitation current from the supply power source to the first coil, and induces magnetic flux Is generated. The induction induced electromotive force induced in the second coil by the induced magnetic flux is converted into direct current by the charge control circuit, and the obtained direct current is supplied to the battery for charging.

  The coil unit for a non-contact power transmission device described in Patent Document 2 has a substantially disk-shaped coil, and the coil is wound around a tape-shaped conductor member so that the wide surfaces of the conductor members face each other. Formed.

  Each of the secondary self-resonant coil and the primary self-resonant coil described in Patent Document 3 includes a coil conductor that forms a spiral coil and an insulating resin. The resin is coated on the coil conductor in a tapered shape so that the thickness increases as the end of the coil conductor is closer.

  The resonance coil described in Patent Document 4 is formed in a spiral shape, and is used to transmit power to the counterpart coil by a resonance phenomenon. The resonance coil includes a coil conductor in which a certain axial gap between conductors is provided between winding portions, and a covering member that covers the surface of the coil conductor.

JP-A-8-23890 JP 2011-142177 A JP 2010-73885 A JP 2012-134250 A

  In the technique described in Patent Document 2, since a tape-shaped conductor member is opposed, a capacitor is formed, resistance is increased, and power transmission efficiency may be reduced. In the techniques described in Patent Document 3 and Patent Document 4, since the coil is formed in a spiral shape, it is difficult to process the coil on the vehicle or the ground.

  The present invention has been made in view of such problems, and an object thereof is to provide a wireless power feeding technique that can be easily manufactured and enhances power transmission efficiency.

  In order to solve the above-described problems, an antenna according to an aspect of the present invention is an antenna for power transmission or reception for wireless power feeding, and is formed of a conducting wire having a circular cross section in a plane spiral shape having an air core, The inner / outer diameter ratio Di / Do between the innermost diameter Di and the outermost diameter Do of the planar spiral conductor is within the range of 0.36 to 0.45.

  According to this aspect, by forming the antenna in a planar spiral shape, the antenna can be processed more easily than the spiral shape, and can be easily attached to the vehicle or the ground. Moreover, the conducting wire having a circular cross section is inexpensive, and the manufacturing cost can be suppressed. Moreover, by forming an air core and forming the inner / outer diameter ratio Di / Do so as to be within the range of 0.36 to 0.45, the power transmission efficiency can be increased.

  According to this invention, it can manufacture easily and can improve power transmission efficiency.

It is a figure which shows the structure of the wireless electric power feeding using the electric power feeder of embodiment. It is a figure for demonstrating the power transmission antenna of embodiment. It is a figure which shows the comparison of the impedance of the some lead wire material in an antenna. It is a figure which shows the power transmission efficiency according to the inner-outer diameter ratio of the antenna formed with the flat wire. It is a figure which shows the relationship between the inner-outer diameter ratio of a 1st antenna, and power transmission efficiency. It is a figure which shows the relationship between the inner-outer diameter ratio of a 2nd antenna, and power transmission efficiency. It is a figure which shows the relationship between the inner-outer diameter ratio of a 3rd antenna, and power transmission efficiency. FIG. 8 is a diagram obtained by integrating the measurement results shown in FIGS. 5 to 7 and showing the relationship between the inner / outer diameter ratio of the antenna and the power transmission efficiency. It is a figure for demonstrating the power transmission antenna of a modification. It is a figure which shows the relationship between the clearance gap between the conducting wires in each antenna, and power transmission efficiency. It is a figure for demonstrating the electric power feeder of a modification. It is a fragmentary sectional view of the power transmission antenna of a modification. It is a front view of the power transmission antenna of another modification.

  FIG. 1 is a diagram illustrating a configuration of wireless power feeding using the power feeding device 10 of the embodiment. A power feeding device 10 is embedded in the ground, and a power receiving device 22 that receives a power signal transmitted from the power feeding device 10 is provided below the vehicle 11. The power feeding device 10 is installed in a gas station or a parking lot. The wireless power feeding according to the present invention is executed by an electromagnetic resonance method or an electromagnetic induction method. In the embodiment, the wireless power feeding will be described using an electromagnetic resonance method.

  The power feeding device 10 includes a power transmission antenna 12, a control unit 14, and a power supply unit (not shown) connected to the control unit 14. The control unit 14 controls power transmission from the power transmission antenna 12. For example, the control unit 14 receives a command signal indicating the start of power transmission from an external device (not shown) and starts power transmission. The external device has an interface operated by the driver of the vehicle 11, and sends a command signal indicating the start of power transmission to the control unit 14 when the driver presses a power transmission start button on the interface.

  The power receiving device 22 includes a power receiving antenna 16, a charging control unit 18, and a battery 20. The power receiving antenna 16 receives the power signal transmitted from the power transmitting antenna 12. The charging control unit 18 converts the received power from alternating current to direct current, and controls charging to the battery 20. The charge control unit 18 detects the amount of charge of the battery 20 and displays the amount of charge on the driver. When the driver determines that the charged amount of the battery 20 is sufficient, the driver instructs the stop of power transmission from the interface of the external device, and the control unit 14 receives a command signal indicating the stop of power transmission from the external device, and stops power transmission. In this way, wireless power feeding is executed.

  Drawing 2 is a figure for explaining power transmission antenna 12 of an embodiment. 2A is a front view of the power transmission antenna 12, FIG. 2B is a sectional view of the power transmission antenna 12 along the line AA shown in FIG. 2A, and FIG. It is the elements on larger scale of the power transmission antenna 12 shown to 2 (b). It should be noted that the same or equivalent components and members shown in the following drawings are denoted by the same reference numerals, and redundant description will be omitted as appropriate.

  The conductor of the power transmission antenna 12 is provided with an insulating coating, but the coating is not shown in FIG. Moreover, the winding number of the power transmission antenna 12 is not limited to the aspect to show in figure, It may be more than the winding number shown in FIG. The first terminal 28 on the inner diameter side and the second terminal 30 on the outer diameter side of the power transmission antenna 12 are connected to the control unit 14. In the wireless power feeding of the vehicle, for example, a voltage of 300 V and a current of 10 A are used for the power transmission antenna 12. Therefore, the conducting wire of the power transmission antenna 12 needs to have a certain size, and a conducting wire having a diameter of 2.0 mm to 3.5 mm is used.

  The power transmission antenna 12 has a single layer and is formed in a plane spiral shape. As shown in FIG.2 (c), the conducting wire of the power transmission antenna 12 is not a stranded wire (Litz wire) but one single wire, and a cross section is a circular round wire. It is formed of a metal wire such as copper, aluminum, or copper alloy as a conductive wire material. Copper alloy includes copper clad aluminum (hereinafter referred to as “CCA”). Alternatively, a wiring material such as graphene, which is a carbon material having conductivity, or indium tin oxide of a transparent conductive film may be used. A single wire having a circular cross section is less expensive than a stranded wire. Moreover, the rigidity of an antenna can be made high by forming with a single wire. Moreover, by forming it in a planar shape, it can be easily attached to the lower part of the vehicle and installed on the ground. By forming it with a single layer, the antenna can be made thinner.

  The power transmission antenna 12 has an air core 26 formed at the center. The inner / outer diameter ratio Di / Do between the innermost diameter Di and the outermost diameter Do shown in FIG. 2 is 0.45. By forming the air core 26, the air core portion can also improve power transmission efficiency as compared with an antenna wound with a conductive wire. The innermost diameter Di is measured from the first terminal 28, the outermost diameter Do is measured from the second terminal 30, and the position of the connection terminal to the control unit 14 is used as a reference for the innermost diameter and the outermost diameter.

  Moreover, as shown in FIG.2 (c), a clearance gap is provided in the conducting wire of the nth roll and the (n + 1) th roll. n is a natural number, and the first volume starts from the first terminal 28. By securing the gap between the conductive wires, the effect of eddy current can be suppressed and the power transmission efficiency can be improved as compared with a flat spiral antenna having a close winding. Note that the thickness of the outer coating is not included between the gaps of the conductive wires. An insulating material is provided between the line gaps of the conductive wires to maintain the distance.

  The inter-line gap 32 between the first winding conductor 12a and the second winding conductor 12b is the same as the inter-line gap 34 between the second winding conductor 12b and the third winding conductor 12c. In the power transmission antenna 12, the gaps between the n-th and (n + 1) -th lead wires are equal. This facilitates processing.

  FIG. 3 shows a comparison of impedances of a plurality of conductor materials in the antenna. It is the result of having measured the impedance of each antenna at the time of changing a frequency using the antenna formed with each of aluminum, CCA, and copper. Aluminum antennas and CCA antennas are cheaper and lighter than copper antennas and are suitable for mounting in vehicles.

  The measurement results at 20 Hz (Hertz) and 200 Hz show that the impedance of the copper antenna is low, and is deviated from the aluminum antenna and the CCA antenna. On the other hand, in the measurement results at 2 kHz (kilohertz), 20 kHz, and 200 kHz, the impedance of each antenna is a close value. Therefore, if a frequency between 2 kHz and 200 kHz is used for wireless power feeding, performance close to that of a copper antenna can be obtained even when an aluminum antenna and a CCA antenna are used. By using an aluminum antenna and a CCA antenna, the cost can be reduced and the weight can be reduced compared to a copper antenna. Furthermore, at 20 kHz to 200 kHz, the copper antenna and the CCA antenna showed equivalent impedance. That is, if a frequency between 20 kHz and 200 kHz is used for wireless power feeding, even if a CCA antenna is used, performance equivalent to that of a copper antenna can be obtained.

  FIG. 4 shows the power transmission efficiency according to the inner / outer diameter ratio of the antenna formed by a rectangular wire. The experimental results shown in FIG. 4 show how the power transmission efficiency changes according to the inner / outer diameter ratio using a rectangular antenna in which a rectangular wire is formed in a single layer plane spiral shape. The cross section of the flat wire is rectangular, and the flat antenna is wound so that the surfaces with long sides are adjacent.

  The experimental method will be described. A flat antenna is wound in a spiral shape by tightly winding a single covered flat wire. The tight winding has almost no gap between the n-th and (n + 1) -th lead wires. In the flat-angle antenna in this experiment, a gap between the lines was generated by about 0.6 mm due to the spring back after the tight winding. The width of one flat wire, that is, the radial width of the flat wire after being wound is 2 mm.

  First, a rectangular antenna having almost no air core was prepared, and the air core was enlarged by cutting from the end on the inner diameter side to change the inner / outer diameter ratio. The inner diameter is changed and the outer diameter is constant. The power transmission efficiency was calculated by detecting the power supplied to the antenna on the power transmission side and the power received from the antenna on the power receiving side using a vector network analyzer and comparing the supplied power and the received power. The antenna on the power transmission side and the antenna on the power reception side are measured with the same acrylic plate sandwiched between them, and the distance between the two antennas is always kept constant at 20 cm. The antenna on the power transmission side and the power reception side are the same. This method of detecting power transmission efficiency is common to detection of power transmission efficiency of other antennas described below.

  The inventor has obtained knowledge that there is a peak in power transmission efficiency near the inner / outer diameter ratio of 0.5 from the experimental results. On the other hand, with a rectangular antenna, the power transmission efficiency is 73% at the maximum, and does not increase. This is considered to be due to the fact that the use of a flat wire causes the gap between the flat wires to function like a capacitor, and the impedance increases due to an increase in capacitors, and the inventor changed the flat wire to a round wire. The relationship between the inner / outer diameter ratio and the power transmission efficiency was measured for the antenna formed by the round wire.

  FIG. 5 shows the relationship between the inner / outer diameter ratio of the first antenna and the power transmission efficiency. The conducting wire of the first antenna is a round wire, and its diameter φ is 3.1 mm. The first antenna is formed by a round wire in a single layer plane spiral shape and wound by close winding, and the gap between the wires is uniformly 0.3 mm. The frequency is 100 kHz, and the inductance of any antenna is in the range of 364 to 368 μH (muhenry).

  The corner points shown in FIG. 5 are the measurement results of the first antenna made of copper, and the round points are the measurement results of the first antenna made of aluminum. The inventor measured the power transmission efficiency at an inner / outer diameter ratio of 0.5 with reference to the peak of the power transmission efficiency in FIG. All the measurement results were as low as 63 to 67%. The inventor considered that the low power transmission efficiency was caused by tight winding, and finished measuring the first antenna.

  FIG. 6 shows the relationship between the inner / outer diameter ratio of the second antenna and the power transmission efficiency. The conducting wire of the second antenna is a round wire, and its diameter φ is 2.7 mm. The second antenna is formed by a round wire in a single layer plane spiral shape, and the gap between the lines is 1.7 mm evenly. The frequency is 100 kHz, and the inductance of any antenna is in the range of 335 to 356 μH. Inductance decreases as the inner diameter side conductor is cut.

  The corner points shown in FIG. 6 are the measurement results of the second antenna made of copper, and the round points are the measurement results of the second antenna made of CCA. Since the power transmission efficiency decreased at the inner / outer diameter ratio of 0.465, the inventor considered that the peak of the power transmission efficiency was exhibited at the inner / outer diameter ratio of 0.45, and the measurement of the second antenna was finished. In FIG. 6, when the inner / outer diameter ratio is increased, the measurement results are reversed between copper and CCA. In other words, the CCA second antenna has a better power transmission efficiency than the copper second antenna with an inner / outer diameter ratio of 0.465.

  In addition, the square antenna shown in FIG. 4 shows a peak of power transmission efficiency near the inner / outer diameter ratio of 0.5, whereas the second antenna with a round line shows the peak of power transmission efficiency in both the copper antenna and the CCA antenna. Since it is in the vicinity of 0.45, the inventor has obtained knowledge that the peak of power transmission efficiency is smaller than the inner / outer diameter ratio 0.5 shown in FIG. In addition, the power transmission efficiency is improved to 86 to 89% by increasing the gap between the conductors compared to the first antenna of the closely wound winding.

  FIG. 7 shows the relationship between the inner / outer diameter ratio of the third antenna and the power transmission efficiency. The conducting wire of the third antenna is a round wire, and its diameter φ is 3.1 mm. The third antenna is formed in a single layer plane spiral shape by a round wire, and the gap between the lines is uniformly 2.5 mm. The corner points shown in FIG. 7 are the measurement results of the third antenna made of copper, the black circle points are the measurement results of the third antenna made of CCA, and the white circle points are the measurement results of the third antenna made of aluminum. The frequency is 100 kHz, the inductance of the copper and aluminum antennas is in the range of 383 to 413 μH, and the inductance of the third CCA antenna is in the range of 298 to 307 μH.

  The copper third antenna has a peak near the inner / outer diameter ratio of 0.41, the CCA third antenna has a peak near the inner / outer diameter ratio of 0.43, and the aluminum third antenna has an inner / outer diameter ratio of near 0.39. Shows a peak. Since the third antenna has a larger inter-line gap than the second antenna shown in FIG. 6, the power transmission efficiency is very high in the range of 95 to 97% regardless of whether the antenna is made of copper, aluminum, or CCA. Therefore, both materials are suitable for practical use in terms of power transmission efficiency.

  FIG. 8 integrates the measurement results shown in FIGS. 5 to 7 and shows the relationship between the inner and outer diameter ratio of the antenna and the power transmission efficiency. Each of the first to third antennas shown in FIGS. 5 to 7 is a round spiral and has a plane spiral shape, and an air core is formed at the center.

  It is preferable that the inner / outer diameter ratio Di / Do of a plane spiral conductor wire having a power transmission efficiency of 90% or more falls within a range from 0.36 (R1) to 0.45 (R4). Thereby, the power transmission efficiency of a planar spiral antenna with a round wire can be improved.

  More preferably, the inner / outer diameter ratio Di / Do of a plane spiral conductor wire with a power transmission efficiency of 95% or more is preferably in the range of 0.363 (R2) to 0.42 (R3). Thereby, the power transmission efficiency of a planar spiral antenna with a round wire can be further increased.

  FIG. 9 is a diagram for explaining a power transmission antenna 24 according to a modification. 9A is a front view of the power transmission antenna 24, FIG. 9B is a cross-sectional view of the power transmission antenna 24 along the line AA shown in FIG. 9A, and FIG. It is the elements on larger scale of the power transmission antenna 24 shown to 9 (b).

  The conductor of the power transmission antenna 24 is provided with an insulating coating, but the coating is not shown in FIG. The first terminal 38 on the inner diameter side and the second terminal 40 on the outer diameter side of the power transmission antenna 24 are connected to the control unit 14. The power transmission antenna 24 is a single layer and is formed in a plane spiral shape. As shown in FIG. 9C, the conducting wire of the power transmission antenna 24 is a single single wire, and the cross section is a circular round wire.

  The power transmission antenna 24 has an air core 36 formed at the center. The inner / outer diameter ratio Di / Do between the innermost diameter Di and the outermost diameter Do shown in FIG. 9 is 0.45. As shown in FIG. 9C, a gap is provided between the n-th and (n + 1) -th lead wires. The first volume starts from the first terminal 38.

  A gap 42 between the first wire 24a and the second wire 24b is larger than the gap on the outer diameter side of the wire 24b. The inter-line gap 42 is larger than the inter-line gap 44 between the second winding conductor 24b and the third winding conductor 24c, and decreases toward the outer diameter side. The inter-line gaps 52 between the seventh winding conductor 24e and the sixth winding conductor 24d on the outermost diameter side are the smallest among the inter-line gaps 42, 44, 46, 48, 50, 52. Thereby, power transmission efficiency can be improved by enlarging the gap between the lines where the influence of the proximity effect is strong while suppressing an increase in the diameter of the power transmission antenna 24.

  When the total number of turns of the power transmission antenna 24 is m, the average value between the line gaps on the inner diameter side from (m + 1) / 2 turns is larger than the average value between the line gaps on the outer diameter side from (m + 1) / 2 turns. m is a natural number of 5 or more. Since the average value between the line gaps on the inner diameter side from the (m + 1) / 2 roll is m = 7 in FIG. 9, it is the average value of the three line gaps 42, 44, 46, and (m + 1) / 2 The average value between the line gaps on the outer diameter side of the winding is the average value of the three line gaps 48, 50, 52. When m is an even number, (m + 1) / 2 is rounded up. Further, as a modification, when m is an even number, if it is the 2.5th winding, it is divided into an inner diameter side and an outer diameter side with reference to a position rotated 2.5 times on the conducting wire from the first terminal 38, You may calculate the average value of a clearance, respectively.

  The gap between the lines of the power transmission antenna 24 is set to 1.5 d or less as the diameter d of the conducting wire. In a wireless power supply for a vehicle, the diameter d of the conductive wire needs to be increased to some extent so as to withstand high current and high voltage. For this reason, if the gap between the lines is set to 1.5 d or more, the outer diameter Do of the power transmission antenna 24 becomes too large, which may not be suitable for mounting a vehicle. In order to further reduce the size of the power transmission antenna 24, the gap between the lines of the power transmission antenna 24 may be determined to be smaller than the diameter d of the conducting wire. Moreover, the diameter of the power transmission antenna 24 can be easily mounted on a normal vehicle by setting it to 1.5 m or less.

  FIG. 10 shows the relationship between the gap between the conductors of each antenna and the power transmission efficiency. The inter-line gap shown on the horizontal axis is a ratio to the diameter d of the conducting wire. The line gap L1 is a plot of the measurement results shown in FIG. 5, the line gap L2 is a plot of the measurement results shown in FIG. 6, and the line gap L3 is shown in FIG. The measurement results are plotted.

  As shown in FIG. 10, when the gap between the lines is increased, the power transmission efficiency is increased and saturated. In the inter-line gap L4, the power transmission efficiency is saturated at about 98%. Even if the line gap is increased beyond the line gap L4, the effect of the proximity effect is only reduced, and the power transmission efficiency remains saturated.

  The gap between the conductors of the n-th and (n + 1) -th conductors where the power transmission efficiency is 85% or more is 0.5d or more (d: the diameter of the conductor). Thereby, the power transmission efficiency of the antenna can be increased.

  The gap between the n-th and (n + 1) -th lead wires where the power transmission efficiency is 90% or more is 0.63d or more. Thereby, the power transmission efficiency of the antenna can be further increased.

  FIG. 11 is a diagram for explaining a power supply device 84 according to a modification. The power feeding device 84 includes a power transmission antenna 82 having a first coil 60 and a second coil 62 wound in a plane spiral shape, a switching circuit 78, and a control unit 80.

  The control unit 80 controls energization to the power transmission antenna 82 via the switching circuit 78. The switching circuit 78 is connected to the input terminal and the output terminal 70 of the first coil 60 and the input terminal 72 and the output terminal 74 of the second coil 62, and connects the first coil 60 and the second coil 62. Is provided.

  The first coil 60 has a first input terminal 64, a second input terminal 66 and a third input terminal 68 connected to different positions of the antenna, and an output terminal 70. Both terminals are connected to the control unit 80 via the switching circuit 78. The switching circuit 78 can switch energization to a desired input terminal in accordance with an instruction from the control unit 80.

  The length of the conducting wire from the first input terminal 64 to the output terminal 70 is longer than the length from the second input terminal 66 to the output terminal 70, and the inductance also decreases according to the difference. That is, when the first input terminal 64 is energized, the inductance applied to the first coil 60 is greater than when the second input terminal 66 is energized.

  The resonance frequency decreases as the inductance increases. That is, the control unit 80 can change the frequency of the power signal output from the antenna by selectively energizing any of the plurality of input terminals. Thereby, when the resonance frequency of the power receiving device 22 differs depending on the vehicle type, the frequency of the power feeding device 84 can be appropriately changed according to the resonance frequency of the power receiving device 22.

  In the antenna from the first input terminal 64 to the output terminal 70 and the antenna from the third input terminal 68 to the output terminal 70, the position of the outermost diameter of the antenna substantially changes and the inner / outer diameter ratio changes. . Here, the position of each input terminal is set so that the inner / outer diameter ratio Di / Do of the conducting wire falls within the range of 0.36 (R1) to 0.45 (R4). Thereby, high power transmission efficiency can be maintained when the position of the input terminal is changed.

  The control unit 80 holds in advance frequency information when the first input terminal 64, the second input terminal 66, and the third input terminal 68 are energized. And the control part 80 will select the input terminal according to the information of resonance frequency, if the command signal which shows the power transmission start, and the information of the resonance frequency of the power receiving apparatus 22, and will make the frequency of the electric power signal to output into a resonance frequency. After matching, start power transmission. Thereby, the versatility of the electric power feeder 84 can be improved.

  The switching circuit 78 switches the first coil 60 and the second coil 62 to serial connection or parallel connection. Assuming that the inductances of the first coil 60 and the second coil 62 are the same L, the inductance of the power transmission antenna 82 is 2L in the serial connection, and the inductance of the power transmission antenna 82 is L / 2 in the parallel connection. Accordingly, the resonance frequency changes greatly between the series connection and the parallel connection, and the change in the resonance frequency becomes larger than when the input terminal of the first coil 60 is changed. By combining the change in series / parallel connection and the change in the input terminal of the first coil 60, the range of frequencies that can be changed is expanded, and the versatility of the power supply device 84 can be further enhanced.

  As described above, the control unit 80 changes the frequency of the power signal output from the power transmission antenna 82 by the switching control of the switching circuit 78. Thereby, the versatility of the electric power feeder 84 can be improved. Further, the impedance can be easily changed by changing the resonance frequency by changing the capacitor.

  In the example of FIG. 11, a mode in which the input terminals of the first coil 60 are provided at a plurality of different positions is shown, but the present invention is not limited to this mode. A plurality of output terminals of the first coil 60 may be provided and arranged at different positions.

  FIG. 12 is a partial cross-sectional view of a power transmission antenna 86 of another modification. In the power transmission antenna 86, the first coil 88 and the second coil 90 wound in a plane spiral shape are stacked in two layers, and the cross sections of the two layers of conductors are staggered. A gap 89 between adjacent conductors is fixed. By the staggered arrangement, the gaps 89 between the conducting wires can be efficiently opened. The gap 89 between the conducting wires is within a range of 0.5d to 1.5d.

  The first coil 88 and the second coil 90 are hardened by a resin material 92. The first coil 88 and the second coil 90 are connected in series connection or parallel connection. By superimposing the two coils, the diameter of the power transmission antenna 86 can be made smaller than that of the single-layer power transmission antenna.

  FIG. 13 is a front view of a power transmission antenna 112 of another modification. The power transmission antenna 112 is formed in an octagonal plane spiral shape and has an air core 126 in the center. The cross section of the conducting wire of the power transmission antenna 112 is circular.

  The polygonal spiral power transmission antenna 112 having a hexagonal shape or more, more preferably an octagonal shape or more, can obtain substantially the same effect as the circular spiral power transmission antenna 12 when viewed from the front. The polygonal spiral power transmission antenna 112 can be easily formed by being bent.

  The inner / outer diameter ratio Di / Do between the innermost diameter Di and the outermost diameter Do of the power transmission antenna 112 is preferably within a range of 0.36 to 0.45. Thereby, the power transmission efficiency of a planar spiral antenna can be improved. More preferably, the inner / outer diameter ratio Di / Do of the planar spiral conductor is preferably in the range of 0.363 (R2) to 0.42 (R3). Thereby, the power transmission efficiency of the planar spiral antenna can be further increased.

  Further, the gap between the n-th and (n + 1) -th lead wires is 0.5d or more, more preferably 0.63d or more. Thereby, the power transmission efficiency of the antenna can be increased.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added to the embodiments based on the knowledge of those skilled in the art. Examples may also be included within the scope of the present invention. Moreover, it is also possible to combine each modification.

  The configuration of the power transmitting antenna described in the embodiment can be applied to a power receiving antenna.

  DESCRIPTION OF SYMBOLS 10 Electric power feeder, 12 Power transmission antenna, 14 Control part, 16 Power receiving antenna, 18 Charging control part, 20 Battery, 22 Power receiving apparatus, 24 Power transmission antenna, 26 Air core, 60 1st coil, 62 2nd coil, 64 1st input Terminal, 66 second input terminal, 68 third input terminal, 70 output terminal, 72 input terminal, 74 output terminal, 78 switching circuit, 80 control unit, 82 power transmission antenna, 84 power feeding device, 86 power transmission antenna.

Claims (7)

An antenna for power transmission or reception for wireless power feeding,
A conductor having a circular cross section is formed into a plane spiral shape having an air core,
The antenna characterized in that the inner / outer diameter ratio Di / Do between the innermost diameter Di and the outermost diameter Do of the conducting wire having a plane spiral shape falls within a range of 0.36 to 0.45. 2. The antenna according to claim 1, wherein a gap between the conductors of the nth and (n + 1) th windings is within a range of 0.5d to 1.5d as a diameter d of the conductor.
n is a natural number.   The antenna according to claim 1 or 2, wherein the inner / outer diameter ratio Di / Do falls within a range of 0.363 to 0.42.   The antenna according to claim 1, wherein the conducting wire is a single wire.   The antenna according to any one of claims 1 to 4, wherein the conductive wires wound in a planar spiral shape are stacked in a plurality of layers, and cross sections of the conductive wires in a plurality of layers are staggered. A wireless power feeder having the antenna according to any one of claims 1 to 5,
The antenna for transmitting power;
A control unit for controlling power transmission from the antenna;
A terminal on the input side or output side connected to the control unit, and a plurality of terminals connected to different positions of the antenna, and
The wireless power feeder, wherein the control unit changes the frequency of a power signal output from the antenna by selectively energizing any of the plurality of terminals. The antenna is
A plurality of planar spiral coils;
A switching circuit that is provided in a connecting portion that connects the coils to each other, and that switches the coils to a serial connection or a parallel connection;
The wireless power feeding apparatus according to claim 6, wherein the control unit changes a frequency of a power signal output from the antenna by switching control of the switching circuit.

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