JP2015065341A - Antenna coil and power transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna coil configured by suppressing a large scale while reducing stray capacitance produced between lines.SOLUTION: The antenna coil includes: an antenna frame 7 having a plurality of arms 72 disposed in a radial shape; a coil 41 having a part located on a transmission plane P1 side, which is one side of a radiation plane in the radiation direction of the arms 72 of the antenna frame 7, and alternately having a part located on the transmission plane P1 side and a part located on an anti-transmission plane P2 side opposite to the transmission plane P1, and having a conductor line 40 wound on the arms 72 in a flat spiral shape, and being held by the plurality of arms 72; and a shield member 8 disposed along the radial plane of the antenna frame 7 on the anti-transmission plane P2.

Description

  The present invention relates to an antenna coil for power transmission that performs wireless power feeding from a power feeding circuit to a power receiving circuit, and a power transmission system using the antenna coil.

  Mobile devices, personal information terminals (PDAs), electric assist bicycles, electric vehicles, hybrid vehicles, and other electric devices and electric devices that can be moved without being installed in one place can operate without being supplied with power from the outside. As described above, the battery has a power storage device such as a battery. In recent years, development of a technique for charging a power storage device mounted on such a device or apparatus has been advanced. In many cases, this charging is performed by, for example, connecting a charging port provided in a device or apparatus and a power supply apparatus with a cable or the like.

  However, in recent years, a technique for supplying power wirelessly without using such a cable, that is, contactless, has been attracting attention. In such wireless power transmission, power is transmitted via an antenna. For example, Japanese Patent Laying-Open No. 2012-89618 (Patent Document 1) discloses a non-contact power feeding device that transmits power between a primary coil and a secondary coil that have an air gap and are close to each other in a non-contact manner. (Claim 1, 16th, 26th paragraphs, FIG. 1 etc.). These primary coils and secondary coils have a flat planar structure. Specifically, these coils are configured by winding an insulated coil conductor in a spiral shape a plurality of times on the same plane.

  By the way, stray capacitance is generated in the radial direction of the coil lead wire thus wound, that is, between the wires. This stray capacitance becomes the impedance of the coil and increases the loss during power transmission. In Patent Document 1, in order to reduce such a stray capacitance, a gap is formed at intervals of a plurality of lines such as three or four on the plane. By increasing the distance between the lines, the stray capacitance is reduced. However, if the same number of turns is to be ensured, the diameter of the coil is increased by the amount of the gap, and the power feeding device tends to be enlarged. In addition, as illustrated in FIG. 1 of Patent Document 1, such a coil has a plurality of stages (here, a direction orthogonal to a reference plane on which the coil is wound flatly) (here, In some cases, there are two stages. The stray capacitance between the lines as described above also occurs in the axial direction, but this point is not taken into consideration in Patent Document 1.

JP 2012-89618 A

  In view of the above background, it is desired to provide an antenna coil that can be configured while suppressing the increase in size while reducing the stray capacitance generated between the lines.

In view of the above problems, the characteristic configuration of the antenna coil according to the present invention is as follows.
An antenna coil for power transmission that performs wireless power feeding from a power feeding circuit to a power receiving circuit,
An antenna frame having a plurality of radially arranged arms;
In the antenna frame, a portion located on the transmission surface side that is one side with respect to a radiation surface along the radiation direction of the arm, and a portion located on the non-transmission surface side that is opposite to the transmission surface; And a coil in which a conductor wire is wound in a flat spiral around the arm and held by the plurality of arms,
And a shield member disposed along the radiation surface of the antenna frame on the non-transmission surface.

  According to this configuration, since the coil is formed in a flat spiral shape, the antenna coil can be configured to be thin. In addition, the coil is configured by alternately having portions (conductor wires) located on the transmission surface side and portions (conductor wires) located on the non-transmission surface side. Therefore, for example, every time the conductor wire goes around the antenna frame, the surface (surface transmission surface side or anti-transmission surface side) through which the conductor wire passes through each arm or an arm group constituted by a plurality of adjacent arms is different. In addition, a conductor wire can be wound. As a result, in the arm or arm group, the effective length of the conductor wire adjacent in the radial direction of the coil (radiation direction of the arm) without a gap is reduced. Further, when the conductor wires are adjacent to each other with a gap, a distance equal to or larger than the wire diameter of the conductor wire is secured as the gap. Accordingly, stray capacitance generated between adjacent conductor lines is greatly suppressed.

  Furthermore, since the conductor wire exists on both the transmission surface side and the non-transmission surface side, the two-stage coil can be formed thin while providing a gap between the conductor wires. That is, the necessary number of turns can be ensured while suppressing an increase in the size of the coil in the radial direction. At this time, the conductor wire on the transmission surface side and the conductor wire on the non-transmission surface side do not overlap in the direction (axial direction) orthogonal to the transmission surface (and the anti-transmission surface). In this direction, a gap is also provided depending on the axial thickness of the antenna frame. Accordingly, stray capacitance between conductor lines adjacent in the axial direction can also be suppressed. Further, a shield member is provided on the side opposite to the transmission surface, and the diffusion of electromagnetic waves to spaces other than the transmission direction is suppressed. This shield member is disposed along the radiation surface of the antenna frame, and a thin antenna coil can be formed even when combined with a flat spiral coil. Thus, according to this configuration, it is possible to configure the antenna coil without increasing the size of the stray capacitance generated between the lines while suppressing the diffusion of the electromagnetic wave toward the non-transmission surface side.

  Here, it is preferable that the shield member is made of a magnetic material and has a diameter that is 1 to 1.5 times the outer diameter of the coil viewed from a direction orthogonal to the radiation surface of the coil. The shield member made of a magnetic material can satisfactorily shield or attenuate electromagnetic waves radiated to the non-transmission surface side. In consideration of tolerances during assembly and leakage of electromagnetic waves, it is preferable that the shield member has a diameter of at least one time larger than the coil diameter in order to shield and attenuate electromagnetic waves. Further, according to experiments by the inventors, the electrical characteristics are stabilized when the diameter of the shield member is about 1.5 times the outer diameter of the coil, and the effect obtained by providing the shield member at a higher magnification. The increase in is confirmed to be limited. Therefore, it is preferable that the diameter of the shield member is at least 1 to 1.5 times the diameter of the coil.

  The outer shape of the coil viewed from the direction orthogonal to the radiation surface is line symmetric with respect to each of two virtual straight lines that pass through the center of gravity of the outer shape and are orthogonal to each other, and is different from “1”. A shape having an aspect ratio is preferable. Since the coil has an aspect ratio different from “1” in this way, it absorbs a positional shift that occurs when the antenna coil provided in the power feeding circuit and the antenna coil provided in the power receiving circuit are opposed to each other, and is transmitted. Efficiency can be maintained.

  For example, when the antenna coil provided in the power feeding circuit is deflected long in the first direction and the antenna coil provided in the power receiving circuit is deflected long in the second direction orthogonal to the first direction on the same plane, Even if the antenna coil of the circuit is located at a position shifted along the first direction and faces the antenna coil of the power feeding circuit, a decrease in transmission efficiency is suppressed. That is, as one aspect, a power transmission system using the antenna coil according to the present invention for a power feeding antenna and a power receiving antenna includes the power feeding antenna in the power feeding circuit, and includes the power receiving antenna in the power receiving circuit. It is preferable that the power feeding antenna and the power receiving antenna are configured to have an aspect ratio such that the deflection direction is different by 90 degrees in a state of being opposed to each other for power transmission.

  By the way, if an antenna coil that can be downsized (thinned) in this way is applied, the power supply equipment can be configured on a small scale. As one aspect, the antenna coil according to the present invention is preferably a power feeding antenna provided in the power feeding circuit.

Block diagram schematically showing the configuration of the wireless power supply system Resonant circuit equivalent circuit diagram Plan view schematically showing the configuration of the antenna coil Enlarged side view schematically showing the relationship between conductor wire and arm Side view schematically showing configuration of antenna coil Graph showing an example of electrical characteristics of a coil with respect to the size of a shield member Graph showing an example of electrical characteristics of a coil with respect to the size of a shield member The figure which shows the example of the positional relationship of the antenna coil of the electric power feeding side and electric power receiving side at the time of electric power transmission The figure which shows the example of the electric power transmission in the vehicle

  Hereinafter, an embodiment of the present invention is a wireless power feeding system (power transmission system) that performs wireless power feeding (wireless power transmission) to a vehicle using electromagnetic resonance coupling (hereinafter, abbreviated as “magnetic field resonance” as appropriate). Will be described with reference to the drawings. As shown in FIG. 1, the wireless power feeding system 1 includes a power feeding system 2 installed in a power feeding facility and a power receiving system 3 mounted on the vehicle 9 side. In the present embodiment, for example, the power feeding system 2 is installed near the ground G if it is an outdoor facility, or near the floor surface if it is an indoor facility.

  As shown in FIG. 1, the power supply system 2 includes an AC power supply 21, a driver circuit 22, and a power supply side resonance circuit 25. The power supply side resonance circuit 25 includes a power supply side resonance coil 24 (power supply antenna). The power receiving system 3 includes a power receiving side resonance circuit 35, a rectifier circuit 32, and a power storage device 31. The power reception side resonance circuit 35 includes a power reception side resonance coil 34 (power reception antenna). The power supply side resonance circuit 25 and the power reception side resonance circuit 35 are resonance circuits having the same natural frequency (resonance frequency), and are collectively referred to as a resonance circuit 5. The power supply side resonance coil 24 and the power reception side resonance coil 34 are collectively referred to as a resonance coil or an antenna coil 4.

  The AC power supply 21 of the power supply system 2 is, for example, a power supply (system power supply) supplied from a commercial distribution network owned by an electric power company, and the frequency thereof is, for example, 50 Hz or 60 Hz. The driver circuit 22 is a circuit that converts the frequency of the system power supply of 50 Hz or 60 Hz into the resonance frequency of the power supply side resonance circuit 25 (resonance circuit 5), and is configured by a high frequency power supply circuit.

  The power storage device 31 of the power receiving system 3 is a DC power source that can be charged and discharged, and for example, a secondary battery or a capacitor such as lithium ion or nickel metal hydride is used. On the other hand, the power received by the power reception side resonance circuit 35 is AC power having the resonance frequency of the power reception side resonance circuit 35. The rectifier circuit 32 rectifies AC power having this resonance frequency into DC power. The driver circuit 22 and the power supply side resonance circuit 25 together or the entire power supply system 2 corresponds to a power supply circuit in a broad sense. The power supply side resonance circuit 25 corresponds to a power supply circuit in a narrow sense. Similarly, the power receiving side resonance circuit 35 and the rectifier circuit together or the entire power receiving system 3 corresponds to a power receiving circuit in a broad sense. The power receiving side resonance circuit 35 corresponds to a power receiving circuit in a narrow sense.

  The vehicle 9 is, for example, an electric vehicle driven by a rotating electrical machine 91 or a hybrid vehicle driven by an internal combustion engine (not shown) and the rotating electrical machine 91. The rotating electrical machine 91 is connected to the power storage device 31 via a rotating electrical machine drive device such as an inverter 92, for example. In the present embodiment, the rotating electrical machine 91 is, for example, a three-phase AC rotating electrical machine, and the rotating electrical machine driving device is configured with an inverter 92 that converts power between direct current and alternating current as a core. The rotating electrical machine 91 can function as an electric motor and a generator.

  The wireless power feeding system 1 is a system that resonates a pair of resonance circuits 5 (25, 35) via a magnetic field and feeds power via the magnetic field. As a “resonance” technique using “magnetism”, magnetic resonance imaging (MRI) often used in the medical field is known. However, whereas MRI uses the physical phenomenon of “magnetic resonance”, the “magnetic resonance power feeding device” in this embodiment does not use such a physical event. As described above, the two resonance circuits 5 are resonated via the “magnetic field”. Accordingly, here, the transmission method of the wireless power feeding system 1 that transmits power using resonance in a magnetic field, including clearly distinguishing from so-called MRI, is referred to as “electromagnetic resonance coupling method” or “magnetic resonance method”. Called. Further, this transmission method is different from the so-called “electromagnetic induction method”.

  As described above, the power supply side resonance circuit 25 and the power reception side resonance circuit 35 are circuits having the same resonance frequency. For example, when one of two tuning forks arranged apart from each other is vibrated in the air, the other tuning fork also vibrates in resonance with vibration propagated through the air. 25 and the power receiving resonance circuit 35 also resonate. More specifically, the power receiving side resonance circuit 35 resonates in resonance with the electromagnetic vibration propagated to the power receiving side resonance circuit 35 via the magnetic field generated by the resonance (electromagnetic vibration) of the power supply side resonance circuit 25 (electromagnetic). To vibrate).

  As one preferable aspect, the power supply side resonance circuit 25 and the power reception side resonance circuit 35 are configured as LC resonators. The resonance circuit 5 includes an antenna coil 4 having an inductance component “L” and a capacitor 6 having a capacitance component “C”, for example, as shown in the equivalent circuit of FIG.

  In the present embodiment, the antenna coil 4 for power transmission that wirelessly feeds power from the power feeding circuit to the power receiving circuit has a flat spiral wound on the conductor wire 40 on the antenna frame 7 having the radial arms 72 as schematically shown in FIG. The coil 41 wound in a shape is configured as a core. The antenna frame 7 is made of a material having a low dielectric loss tangent (tan δ) and a low dielectric constant, such as polypropylene, polycarbonate, polyethylene, or the like. As shown in FIG. 3, the antenna frame is configured to have a plurality of arms 72 arranged radially, and in this embodiment, an odd number of arms 72 are formed. The antenna frame 7 has a transmission surface P1 on one side with respect to the radiation surface along the radiation direction of the arm 72, and an anti-transmission surface P2 on the opposite side to the transmission surface P1.

  The conductor wire 40 is wound in a flat spiral around the antenna frame 7 and is held by a plurality of arms 72 to form a coil 41. The coil 41 is configured to alternately have portions (conductor wire 40) located on the transmission surface P1 side and portions (conductor wire 40) located on the non-transmission surface P2 side. In the present embodiment, as shown in FIGS. 3 and 4, the conductor wire 40 is wound so that the two arms 72 pass alternately on the transmission surface P1 side and the non-transmission surface P2 side. .

  As described above, in the present embodiment, an odd number of arms 72 are provided, and therefore, one shift of the arm 72 occurs each time the conductor wire 40 makes one round. Thereby, the effective length of the conductor wire 40 adjacent in the radial direction (radial direction of the arm 72) without a gap is reduced on the transmission surface P1 side and the non-transmission surface P2 side. When the conductor wires 40 are adjacent to each other with a gap, a distance equal to or larger than the diameter of the two conductor wires 40 is secured (see FIGS. 3 and 5). Accordingly, stray capacitance generated between adjacent conductor lines 40 is also greatly suppressed. As shown in FIG. 2, when the resonant circuit 5 is configured, if a stray capacitance is generated, the resonant frequency is also affected. Therefore, it is very useful to suppress stray capacitance.

  As shown in FIG. 5, the antenna coil 4 includes a shield member 8 arranged along the radiation surface of the antenna frame 7 on the non-transmission surface P2. The shield member 8 is made of a magnetic material, and shields or attenuates electromagnetic waves radiated toward the non-transmission surface P2 along a direction orthogonal to the radiation surface of the coil 41. For this reason, the shield member 8 has a diameter of the outer shape of the coil 41 (a shape formed by the conductor wire 40 positioned on the outermost side of the wound conductor wire 40) viewed from a direction orthogonal to the radiation surface of the coil 41. It is preferable that it has a diameter of at least 1 times.

  However, in consideration of tolerances during assembly and leakage of electromagnetic waves, the diameter of the shield member 8 is preferably set to be larger than one time with respect to the diameter of the coil 41. 6 and 7 show the relationship (electrical characteristics) between the ratio of the diameter of the shield member 8 to the outer diameter of the coil 41 and the inductance and ESR (equivalent series resistance) of the coil 41. FIG. 6 shows the characteristic on the long axis side of the track-shaped antenna coil 4, and FIG. 7 shows the characteristic on the short axis side. As shown in FIG. 3, the outer diameter of the coil 41 on the long axis side is “d1 × 2”, and the diameter of the shield member 8 is “d3 × 2”. Further, the outer diameter of the coil 41 on the short axis side is “d2 × 2”, and the diameter of the shield member 8 is “d4 × 2”.

  Referring to FIGS. 6 and 7, both the ratio of the diameter of the shield member 8 to the outer diameter of the coil 41 (d3 / d1, d4 / d2) is about “1.2”, and the change in characteristics is reduced. Most stable at around 5 ". That is, from the viewpoint of the stability of the electric characteristics, it can be said that the ratio of the diameter of the shield member 8 to the outer diameter of the coil 41 preferably satisfies at least about “1.2”. Further, even if this ratio is larger than “1.5”, the influence on the characteristics is small, so that the shield member 8 is unnecessarily enlarged. Therefore, it can be said that this ratio is preferably about "1.5" at most. That is, the diameter of the shield member 8 is 1 to 1.5 times the diameter of the coil 41 in consideration of the degree of shielding and attenuation of electromagnetic waves, electrical characteristics, installation space of the antenna coil 4, manufacturing cost, and the like. It is preferable to set a value of about 1.2 times, more preferably about 1.2 to 1.5 times.

  Incidentally, as illustrated in FIG. 3, in the present embodiment, the outer shape viewed from the direction orthogonal to the radiation surface of the coil 41 is not a circle but a shape having an aspect ratio. Here, the aspect ratio is an aspect ratio, and corresponds to a ratio of lengths of two line segments formed by crossing two virtual straight lines that pass through the center of gravity of the outer shape and are orthogonal to each other. (For example, “d1: d2”). The coil 41 of this embodiment has an outer shape whose aspect ratio is different from “1”. More specifically, the coil 41 according to the present embodiment has an outer shape viewed from a direction orthogonal to the radiation surface of the coil 41 and is symmetrical with respect to each of two virtual straight lines that pass through the center of gravity of the outer shape and are orthogonal to each other. Thus, the shape has an aspect ratio different from “1”.

  Since the coil 41 has an aspect ratio different from “1” as described above, a positional shift caused when the power supply side resonance coil 24 (power supply antenna) and the power reception side resonance coil 34 (power reception antenna) are opposed to each other. The transmission efficiency can be maintained by absorbing the above. In order to realize efficient power transmission, it is preferable that the power reception side resonance coil 34 is appropriately linked to the electromagnetic field generated by the power supply side resonance coil 24. At this time, it is preferable that the direction in which the amount assumed to cause positional deviation is large is the long axis of the power supply side resonance coil 24 (the direction in which it is deflected relatively long). Since there are more power supply side resonance coils 24 in the direction of deviation, the region where the power reception side resonance coil 34 is well linked to the electromagnetic field generated by the power supply side resonance coil 24 is large. Become. As one aspect, for example, as shown in FIG. 8, it is preferable that the power supply side resonance coil 24 be deflected long in the horizontal direction in the figure and the power reception side resonance coil 34 be deflected long in the vertical direction in the figure.

  At this time, it is more preferable that the length of the long axis of the power reception side resonance coil 34 corresponds to the length of the short axis of the power supply side resonance coil 24. More preferably, the center of gravity of the power reception side resonance coil 34 is located on the long axis of the power supply side resonance coil 24 when the long axis of the power reception side resonance coil 34 and the short axis of the power supply side resonance coil 24 are substantially the same. In this state, even if the power receiving side resonance coil 34 is displaced along the long axis of the power feeding side resonance coil 24, the power receiving side resonance coil 34 is sufficiently linked to the electromagnetic field generated by the power feeding side resonance coil 24. When the power reception side resonance coil 34 has completely entered the inside of the power supply side resonance coil 24, the electromagnetic field interlinked may decrease instead. Therefore, as shown in FIG. 8, when the deflection direction of the power supply side resonance coil 24 and the deflection direction of the power reception side resonance coil 34 are different by 90 degrees, the major axis of the power reception side resonance coil 34 and the power supply side It is preferable that the minor axis of the resonance coil 24 is substantially the same.

  In addition, since the power receiving system 3 is mounted on many devices, it is assumed that the number of the power receiving system 3 is larger than that of the power feeding system 2. In addition, since the power feeding system 2 is installed in the power feeding facility, the power receiving system 3 is mounted on a device, so that it is not preferable that the power receiving system 3 is enlarged. Therefore, here, the outer shape of the power supply side resonance coil 24 is illustrated as being larger than that of the power reception side resonance coil 34. However, the power reception side resonance coil 34 and the power supply side resonance coil 24 are naturally larger in size. The relationship may be reversed.

  That is, the feeding-side resonance coil 24 and the power-receiving-side resonance coil 34 have an aspect ratio in which the deflection direction is different by 90 degrees in a state of being opposed to each other, and one outer shape is the other outer shape at an ideal facing position. It is preferable that it is configured to have a size inscribed in It is preferable that the direction in which the coil 41 having a larger outer shape deflects longer (the long axis direction) is a direction in which the amount that is assumed to cause a positional shift is larger.

  Here, as shown in FIG. 9, a case is considered in which the power supply side resonance coil 24 is installed on the ground or the like, and the power reception side resonance coil 34 is installed in the vehicle 9. In order to efficiently transmit power to the vehicle 9, as described above, the power supply side resonance is performed so that the power reception side resonance coil 34 is linked to the electromagnetic field generated by the power supply side resonance coil 24. It is preferable that the coil 24 and the power receiving side resonance coil 34 face each other appropriately. As described with reference to FIG. 1, the power supply side resonance coil 24 is installed in the vicinity of the ground G if the power supply facility is an outdoor facility, and in the vicinity of the floor surface if it is an indoor facility. Therefore, the power reception side resonance coil 34 mounted on the vehicle 9 as a moving body is aligned with the fixed power supply side resonance coil 24.

  At this time, the front and rear direction of the vehicle 9 can be aligned by using a wheel stopper or the like. However, it is difficult to provide such a positioning mechanism in the width direction of the vehicle 9. Therefore, as illustrated in FIG. 9, it is preferable that the power supply side resonance coil 24 is arranged to be deflected long in the vehicle width direction, and the power reception side resonance coil 34 is arranged to be deflected long in the longitudinal direction of the vehicle in the drawing. .

[Other Embodiments]
Hereinafter, other embodiments of the present invention will be described. Note that the configuration of each embodiment described below is not limited to being applied independently, and can be applied in combination with the configuration of other embodiments as long as no contradiction arises.

(1) In the above description, the wireless power feeding system 1 (power transmission system) that performs wireless power feeding to the vehicle using electromagnetic resonance coupling (magnetic field resonance) has been described as an example. However, the transmission method is not limited to this method, and may be an electromagnetic induction method, for example.

(2) In the above, an odd number of arms 72 are provided, and the conductor wire 40 is wound so that the two arms 72 pass through the transmission surface P1 side and the non-transmission surface P2 side. Described as an example. That is, an arm group (in this case, an arm pair) is formed by two adjacent arms 72, and the conductor wire 40 passes through the transmission surface P1 side and the non-transmission surface P2 side alternately for each arm group. As an example, the configuration in which the is wound is described. However, this does not prevent the form in which an even number of arms 72 are provided, and the number of arms 72 constituting the arm group is not limited to “2”.

  For example, a natural number “k, n” is used, the number of arms 72 constituting the arm group is “k”, and the total number of arms 72 can be “k × n−1”. As for “−1”, since the total number of arms 72 may not be a multiple of “k”, if “k” is “2” or more, any value smaller than “k” is arbitrary. Can be set. Here, in the example of FIG. 3, “k = 2” and “n = 11”, and the total number of arms 72 is “21”. In the case of “k = 3” and “n = 7”, the total number of arms 72 is an even number “20”. Also in this case, every time the conductor wire 40 makes one turn, a shift of one arm 72 occurs, so that a gap can be provided between the conductor wires 40 adjacent in the radial direction of the coil 41. When “k = 1” and “n = 22”, the total number of arms 72 is “21”. In this case, the conductor wire 40 is wound so that the adjacent arm 72 passes alternately on the transmission surface P1 side and the non-transmission surface P2 side. Also in this case, every time the conductor wire 40 makes one turn, a shift of one arm 72 occurs, so that a gap can be provided between the conductor wires 40 adjacent in the radial direction of the coil 41.

  However, in the case of “k = 1”, a gap is likely to be generated between the adjacent conductor wires 40 in the radial direction of the coil 41. Therefore, when the outer shape of the coil 41 is the same, the case of “k = 2” In comparison, the number of turns is reduced. It is possible to reduce the line capacity by generating the gap. However, as described above, even when “k = 2”, the line capacity can be reduced by the way of winding. Therefore, in order to reduce the line capacitance while securing a sufficient number of turns for the outer shape of the coil 41, it is preferable to set “k = 2” as described above with reference to FIG. is there. However, when there is no problem even when the outer shape of the coil 41 is increased, or when there is no problem even when the number of turns is reduced, it is also a preferred embodiment to set “k = 1”. . Further, in the case of “k = 3”, the number of conductor wires 40 adjacent in the radial direction of the coil 41 without a gap is larger than that in the case of “k = 2”. Therefore, in order to suppress the line capacitance, it is preferable to set “k = 2”.

(3) In the above, the shield member 8 illustrated the form comprised with the plate-shaped magnetic body. However, the shield member 8 may be configured by a cancel coil that generates a magnetic flux that cancels the magnetic flux of the coil 41.

(4) In the above description, the wireless power feeding system 1 (power transmission system) that performs wireless power feeding to the vehicle has been described as an example. However, the wireless power supply system 1 can also be applied to applications such as supplying power to a mobile phone or a personal information terminal (PDA).

(5) In the above description, in the wireless power feeding system 1, an embodiment in which the antenna coil 4 according to the present invention is used as a power feeding antenna (power feeding side resonance coil 24) and a power receiving antenna (power reception side resonance coil 34) will be described as an example. did. However, the antenna coil 4 does not necessarily have to be used for both the power feeding antenna and the power receiving antenna. For example, only the power feeding antenna may be used as the antenna coil 4 according to the present invention.

(6) As illustrated in FIG. 3, each time the conductor wire 40 goes around, one arm 72 is displaced, and the effective length of the conductor wire 40 adjacent to the coil 41 in the radial direction is reduced. To do. Further, when the conductor wires 40 are adjacent to each other with a gap, a distance equal to or larger than the diameter of the two conductor wires 40 is secured. As shown in FIGS. 3 and 4, when the conductor wire 40 is wound so as to alternately pass through the transmission surface P1 side and the non-transmission surface P2 side every two arms 72, the transmission surface P1. The location where the conductor wire 40 advances from the non-transmission surface P2 side to the side of the transmission surface P2 is different from the location where the conductor wire 40 advances from the anti-transmission surface P2 side to the transmission surface P1 side. That is, the conductor line 40 moves between the transmission surface P1 and the non-transmission surface P2 between the adjacent arms 72 (between the arms), but the adjacent conductor lines 40 do not intersect between the same arms. . Accordingly, the conductor wire 40 can be wound around the conductor wire 40 by bending the conductor wire 40 in the radial direction so as to fill a gap having a distance equal to or larger than the diameter of the two conductor wires 40. In this case, the effect of reducing the line capacitance is limited, but the coil 41 can be further downsized.

  The present invention can be used for an antenna coil for power transmission that performs wireless power feeding from a power feeding circuit to a power receiving circuit.

1: Wireless power supply system (power transmission system)
4: Antenna coil 7: Antenna frame 8: Shield member 9: Vehicle 24: Power feeding side resonance coil (power feeding antenna)
34: Receiving side resonance coil (receiving antenna)
40: conductor wire 41: coil 72: arm P1: transmission surface P2: anti-transmission surface

Claims (5)

An antenna coil for power transmission that performs wireless power feeding from a power feeding circuit to a power receiving circuit,
An antenna frame having a plurality of radially arranged arms;
In the antenna frame, a portion located on the transmission surface side that is one side with respect to a radiation surface along the radiation direction of the arm, and a portion located on the non-transmission surface side that is opposite to the transmission surface; And a coil in which a conductor wire is wound in a flat spiral around the arm and held by the plurality of arms,
A shield member disposed along the radiation surface of the antenna frame at the anti-transmission surface;
An antenna coil comprising:   2. The antenna coil according to claim 1, wherein the shield member is made of a magnetic material, and has a diameter that is 1 to 1.5 times the diameter of the outer shape as viewed from a direction orthogonal to the radiation surface of the coil. .   The outer shape of the coil viewed from the direction perpendicular to the radiation surface is line symmetric with respect to each of two virtual straight lines that pass through the center of gravity of the outer shape and are orthogonal to each other, and has an aspect ratio different from “1”. The antenna coil according to claim 1, wherein the antenna coil has a shape having   The antenna coil according to claim 1, wherein the antenna coil is a power feeding antenna provided in the power feeding circuit. A power transmission system using the antenna coil according to claim 3 for a power feeding antenna and a power receiving antenna,
The power feeding antenna is provided in the power feeding circuit, the power receiving antenna is provided in the power receiving circuit,
The power transmission system, wherein the power feeding antenna and the power receiving antenna are configured to have an aspect ratio such that a deflection direction is different by 90 degrees in a state of being opposed to each other for power transmission.

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