Abstract:
The electricity supply device ( 100 ) supplies electricity using electromagnetic force and opposes an external electricity reception coil ( 153   a ). An electricity supply coil ( 102   a ) has a hollow section ( 102   b ), and has a spiral shape. A reader ( 103 ) has an antenna disposed in the projected space resulting from projecting the hollow section ( 102   b ) in the central axial direction of the electricity supply coil ( 102   a ) and at a position more separated from the electricity reception coil ( 153   a ) than the opposing surface that opposes the electricity reception coil ( 153   a ) and is of the electricity supply coil ( 102   a ), and ID data transmitted by an RF tag ( 154 ) installed proximally to the electricity reception coil ( 153   a ) is received and detected by the antenna. An electricity-supply-side control unit ( 104 ) determines the presence/absence of an electricity reception coil ( 153   a ) on the basis of the ID data detected by the reader ( 103 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a power supply apparatus and a power receiving apparatus for transmitting and receiving power in a wireless manner. 
       BACKGROUND ART 
       [0002]    Conventionally, there has been known a wireless charging system that charges a storage battery mounted on a vehicle using a power supply apparatus on the ground. In the wireless charging system, when power is supplied without a power supply coil and a power receiving coil being precisely positioned, a leakage magnetic field and unnecessary radiation increase. In this case, there is a problem of not being able to secure safety, for example, due to the malfunction of a pacemaker caused thereby. 
         [0003]    For the problem mentioned above, there has been known a wireless charging system that starts charging after guiding a vehicle to a power supply section (e.g., Patent Literature (hereinafter, referred to as “PTL 1”)). PTL 1 discloses that, when a vehicle is driven for parking at a position where a power receiving section of the vehicle faces a power supply section on the ground, the image of a positioning marker at the rear of a parking space is picked up with an onboard camera and the picked-up image is displayed on a display section to thereby guide the vehicle to the most appropriate position. A transmission section at the rear of the parking space transmits a reference position signal after the parking of the vehicle. Then, the power supply section starts supplying power when the reception level of the reference position signal received by a reception section of the vehicle is equal to or greater than a predetermined level. 
       CITATION LIST 
     Patent Literature 
     PTL 1 
     Japanese Patent Application Laid-Open No. 2010-226945 
     SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    In PTL 1, however, when a vehicle is parked obliquely relative to the parking space with the power receiving section and the power supply section facing each other, the reception section has a low reception level at the time of receiving the reference position signal from the transmission section at the rear of the parking space, and therefore the vehicle is not considered to be parked at the most appropriate position, making it impossible to start power supply. 
         [0005]    An object of the present invention is to provide a power supply apparatus and a power receiving apparatus capable of detecting that a power supply section and a power receiving section face each other, irrespective of the state of a stopped vehicle. 
       Solution to Problem 
       [0006]    The power supply apparatus of the present invention is a power supply apparatus that faces a power receiving coil located externally and that supplies power using an electromagnetic force, the apparatus including a spiral power supply coil that has a first hollow portion, a communication section that has an antenna disposed inside a projection space of the first hollow portion projected in a central axis direction of the power supply coil, the antenna being disposed at a position farther away from the power receiving coil than a facing surface of the power supply coil, the facing surface being a surface where the power supply coil faces the power receiving coil, the communication section receiving, via the antenna, and detecting an electromagnetic wave transmitted by a radio tag installed near the power receiving coil, and a control section that determines the presence or absence of the power receiving coil based on the electromagnetic wave detected by the communication section. 
         [0007]    The power receiving apparatus of the present invention is a power receiving apparatus that faces a power supply coil located externally and that receives power using an electromagnetic force, the apparatus including a spiral power receiving coil having a first hollow portion, and a radio tag disposed inside a projection space of the first hollow portion projected in a central axis direction of the power supply coil, the radio tag being disposed at a position farther away from the power receiving coil than a facing surface of the power supply coil, the facing surface being a surface where the power supply coil faces the power receiving coil, the radio tag transmitting an electromagnetic wave for detecting that the power supply coil and the power receiving coil face each other to a communication section provided for the power supply coil. 
       Advantageous Effects of Invention 
       [0008]    According to the present invention, it is possible to detect that a power supply section and a power receiving section face each other, irrespective of the state of a stopped vehicle. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is a block diagram illustrating the configuration of a power supply system according to Embodiment 1 of the present invention; 
           [0010]      FIG. 2  is a block diagram illustrating the configuration of a reader in Embodiment 1 of the present invention; 
           [0011]      FIGS. 3A and 3B  are diagrams illustrating the relative position between a power supply coil and the reader in Embodiment 1 of the present invention; 
           [0012]      FIGS. 4A and 4B  are diagrams illustrating the relative position between the reader and the power supply coil in Embodiment 1 of the present invention and the difference in electromagnetic fields and reception levels between  FIGS. 4A and 4B ; 
           [0013]      FIG. 5  is a diagram illustrating a preferred relative position between the power supply coil and the reader in Embodiment 1 of the present invention; 
           [0014]      FIG. 6  is a flow chart showing the operations of a power receiving apparatus according to Embodiment 1 of the present invention before power supply; 
           [0015]      FIG. 7  is a flow chart showing the operations of a power supply apparatus according to Embodiment 1 of the present invention before power supply; 
           [0016]      FIG. 8  is a flow chart showing the operations of the power supply apparatus according to Embodiment 1 of the present invention during power supply; 
           [0017]      FIGS. 9A and 9B  are diagrams illustrating the states of a parked vehicle in Embodiment 1 of the present invention; 
           [0018]      FIGS. 10A and 10B  are diagrams illustrating the variation of a communicable range depending on the position of the reader in Embodiment 1 of the present invention; 
           [0019]      FIG. 11  is a diagram illustrating the relative position between a power receiving coil and an RF tag in Embodiment 2 of the present invention; 
           [0020]      FIG. 12  is a flow chart showing the operations of a power receiving apparatus according to Embodiment 2 of the present invention before power supply; 
           [0021]      FIG. 13  is a flow chart showing the operations of a power supply apparatus according to Embodiment 2 of the present invention before power supply; 
           [0022]      FIG. 14  is a flow chart showing the operations of the power receiving apparatus according to Embodiment 2 of the present invention during power supply; 
           [0023]      FIG. 15  is a flow chart showing the operations of the power supply apparatus according to Embodiment 2 of the present invention during power supply; 
           [0024]      FIG. 16  is a diagram illustrating the configuration of a part of a power supply section in Embodiment 3 of the present invention; and 
           [0025]      FIGS. 17A and 17B  are diagrams illustrating the configuration of a part of a power supply section in Embodiment 4 of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0026]    Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 
       Embodiment 1 
     Configuration of Power Supply System 
       [0027]    The configuration of power supply system  10  in Embodiment 1 of the present invention will be described using  FIG. 1 . 
         [0028]    Power supply system  10  is mainly composed of power supply apparatus  100  and vehicle  150 . 
         [0029]    It is noted that  FIG. 1  illustrates the state capable of supplying power, in which power supply section  102  and power receiving section  153  face each other. 
         [0030]    Power supply apparatus  100  is installed on or buried in the ground so that power supply section  102  is exposed from ground G. Power supply apparatus  100  is provided, for example, in a parking space, and faces power receiving section  153  of vehicle  150  to supply power using an electromagnetic force during the parking of vehicle  150 . It is noted that the configuration of power supply apparatus  100  will be described hereinafter. 
         [0031]    Here, the phrase “power supply section  102  and power receiving section  153  face each other” means that power supply section  102  and power receiving section  153  face each other at a position where power can be supplied with predetermined or higher power supply efficiency. Specifically, it means that power supply coil  102   a  and power receiving coil  153   a  face each other at a position where power can be supplied with predetermined or higher power supply efficiency. 
         [0032]    Vehicle  150  is, for example, an automobile which runs on power of storage battery  155 , such as Plug-in Hybrid Electric Vehicle (PHEV) or Electric Vehicle (EV). It is noted that the detailed configuration of vehicle  150  will be described hereinafter. 
         [0033]    &lt;Configuration of Vehicle&gt; 
         [0034]    The configuration of vehicle  150  in Embodiment 1 of the present invention will be described using  FIG. 1 . 
         [0035]    Vehicle  150  is mainly composed of storage battery  155  and power receiving apparatus  160 . 
         [0036]    Storage battery  155  stores power supplied from power supply apparatus  100  through power receiving apparatus  160 . 
         [0037]    Power receiving apparatus  160  supplies the power supplied from power supply apparatus  100  to storage battery  155 . It is noted that the detailed configuration of power receiving apparatus  160  will be described hereinafter. 
         [0038]    &lt;Configuration of Power Supply Apparatus&gt; 
         [0039]    The configuration of power supply apparatus  100  according to Embodiment 1 of the present invention will be described using  FIG. 1 . 
         [0040]    Power supply apparatus  100  is mainly composed of power-supply-side communication section  101 , power supply section  102 , reader  103 , and power-supply-side control section  104 . 
         [0041]    Power-supply-side communication section  101  receives a power supply permission signal or power supply non-permission signal from vehicle-side communication section  152 . Power-supply-side communication section  101  outputs the received power supply permission signal or power supply non-permission signal to power-supply-side control section  104 . Power-supply-side communication section  101  transmits, to vehicle-side communication section  152 , a detection result which indicates that RF tag  154  and an antenna of reader  103  face each other, and which has been received from power-supply-side control section  104 . 
         [0042]    Power supply section  102  has spiral power supply coil  102   a . Power supply coil  102   a  is, for example, a planar spiral coil. Power supply coil  102   a  has hollow portion  102   b . Power supply coil  102   a  supplies power to power receiving coil  153   a  facing power supply coil  102   a , in accordance with the control of power-supply-side control section  104 . Power supply coil  102   a  supplies power, for example, by an electromagnetic induction system or a magnetic resonance system (also referred to as magnetic field resonance system). 
         [0043]    Reader  103  is disposed at a position farther away from power receiving coil  153   a  than a surface of power supply coil  102   a  where power supply coil  102   a  faces power receiving coil  153   a  (hereinafter, this surface is referred to as “facing surface”), such that an antenna (omitted in  FIG. 1 ) is positioned at the center of hollow portion  102   b  of power supply coil  102   a . Reader  103  detects whether or not it faces RF tag  154  by communicating with RF tag  154 . It is noted that the configuration and the disposition of reader  103  will be described hereinafter. The present embodiment takes an example of employing a single antenna for reader  103 . 
         [0044]    When a power supply permission signal is input from power-supply-side communication section  101 , and when a detection result indicating that reader  103  and RF tag  154  face each other is input from reader  103 , power-supply-side control section  104  determines the presence of power receiving coil  153   a  to permit power supply, and controls power supply section  102  to start the power supply. At that time, power-supply-side control section  104  outputs, to power-supply-side communication section  101 , a detection result indicating that RF tag  154  and the antenna of reader  103  face each other. When a power supply non-permission signal is input from power-supply-side communication section  101 , or when the detection result of reader  103  facing RF tag  154  is not input from reader  103 , power-supply-side control section  104  controls power supply section  102  not to start power supply or to stop power supply. 
         [0045]    &lt;Configuration of Power Receiving Apparatus&gt; 
         [0046]    The configuration of power receiving apparatus  160  according to Embodiment 1 of the present invention will be described using  FIG. 1 . 
         [0047]    Power receiving apparatus  160  is mainly composed of vehicle-side control section  151 , vehicle-side communication section  152 , power receiving section  153 , and RF tag  154 . 
         [0048]    Vehicle-side control section  151  controls vehicle-side communication section  152  and power receiving section  153  based on various input signals. When the detection result indicating that RF tag  154  and the antenna of reader  103  face each other is input from vehicle-side communication section  152 , vehicle-side control section  151  controls power receiving section  153  to start receiving power. When the detection result indicating that RF tag  154  and the antenna of reader  103  face each other is not input from vehicle-side communication section  152 , vehicle-side control section  151  controls power receiving section  153  not to start receiving power or to stop receiving power. 
         [0049]    Vehicle-side communication section  152  generates a power supply permission signal that permits power supply or a power supply non-permission signal that does not permit power supply in accordance with the control of vehicle-side control section  151 , and transmits the generated power supply permission signal or power supply non-permission signal to power supply apparatus  100 . Vehicle-side communication section  152  outputs, to vehicle-side control section  151 , a detection result indicating that RF tag  154  and the antenna of reader  103  face each other and received from power-supply-side communication section  101 . 
         [0050]    Power receiving section  153  has spiral power receiving coil  153   a . Power receiving section  153  has hollow portion  153   b . Power receiving coil  153   a  receives power from power supply coil  102   a  facing power receiving coil  153   a . Power receiving section  153  supplies the power supplied to power receiving coil  153   a  to storage battery  155  in accordance with the control of vehicle-side control section  151 . Power receiving section  153  is provided in such a state as to be exposed externally at the bottom of vehicle  150 . 
         [0051]    RF tag  154  is a radio tag, and is disposed at a position farther away from power supply coil  102   a  than a facing surface of power receiving coil  153   a  where power receiving coil  153   a  faces power supply coil  102   a , and at the center of hollow portion  153   b  of power receiving coil  153   a . It is noted that the disposition of RF tag  154  will be described hereinafter. The present embodiment takes an example of employing a single RF tag  154 . 
         [0052]    &lt;Configuration of Reader&gt; 
         [0053]    The configuration of reader  103  in Embodiment 1 of the present invention will be described using  FIG. 2 . 
         [0054]    Reader  103  is mainly composed of antenna  201 , transmission and reception section  202 , and control section  203 . 
         [0055]    Transmission and reception section  202  transmits a predetermined electromagnetic wave via antenna  201  in accordance with the control of control section  203 . Transmission and reception section  202  outputs a signal received via antenna  201  to control section  203 . 
         [0056]    Control section  203  controls transmission and reception section  202  to transmit an electromagnetic wave in accordance with the control of power-supply-side control section  104 . When a signal is input from transmission and reception section  202 , control section  203  determines whether or not the signal is from RF tag  154 . When the signal is from RF tag  154 , control section  203  outputs, to power-supply-side control section  104 , a detection result indicating that reader  103  and RF tag  154  face each other. Whether or not the signal is from RF tag  154  is determined by whether or not ID data unique to RF tag  154  is received. 
         [0057]    &lt;Disposition of Power Supply Coil and Reader&gt; 
         [0058]    The disposition of power supply coil  102   a  and reader  103  in Embodiment 1 of the present invention will be described using  FIGS. 3A and 3B . 
         [0059]      FIG. 3A  is a plan view of power supply coil  102   a  and reader  103 .  FIG. 3B  is a sectional view taken along line A-A of  FIG. 3A . 
         [0060]    In the present embodiment, reader  103  and RF tag  154  are passive RFIDs. That is, in the present embodiment, reader  103  transmits an electromagnetic wave to RF tag  154 , and RF tag  154  transmits the electromagnetic wave transmitted by reader  103  as a reflected wave, with ID data, for example, being superimposed thereon at the time of the transmission. The reason for disposing reader  103  as described above is to enhance position detection precision by narrowing the transmission range of an electromagnetic wave since reader  103  is a transmission side first to transmit the electromagnetic wave. 
         [0061]    As illustrated in  FIG. 3B , reader  103  is disposed such that antenna  201  is positioned inside a projection space of hollow portion  102   b  projected in central axis P direction (vertical direction in  FIG. 3B ) of power supply coil  102   a , and at a position farther away from power receiving coil  153   a  than facing surface  301  of power supply coil  102   a  to power receiving coil  153   a . Further, as illustrated in  FIG. 3A , reader  103  is disposed such that antenna  201  is positioned at the center of hollow portion  102   b  of power supply coil  102   a , when seen from the direction in which power supply coil  102   a  and power receiving coil  153   a  face each other (S 1  direction in  FIG. 3B ), which direction is parallel to the central axis P direction. It is noted that antenna  201  of reader  103  may be disposed at a position slightly deviated from the center of hollow portion  102   b  of power supply coil  102   a.    
         [0062]    Transmission and reception section  202  and control section  203  of reader  103  are preferably disposed at positions as far as possible from power supply coil  102   a  and power receiving coil  153   a.    
         [0063]    &lt;Relative Position Between Reader and Power Supply Coil and Difference in Electromagnetic Field and Reception Level&gt; 
         [0064]    The relative position between reader  103  and power supply coil  102   a  in Embodiment 1 of the present invention and the difference in electromagnetic fields and reception levels will be described using  FIGS. 4A and 4B . 
         [0065]      FIG. 4A  illustrates the relative position between conventional reader R 1  and power supply coil C 1  and the electromagnetic field and the reception level in the related art.  FIG. 4B  illustrates the relative position between reader  103  and power supply coil  102   a  and the electromagnetic field and the reception level in the present embodiment. 
         [0066]    As illustrated in  FIGS. 4A and 4B , in the present embodiment, reader  103  is disposed at a position farther away from power receiving coil  153   a  than facing surface  301  of power supply coil  102   a , which faces power receiving coil  153   a . This allows power supply coil  102   a  to function as a shield for shielding spreading of an electromagnetic wave transmitted from reader  103 . Accordingly, RF tag  154  can obtain a predetermined reception level in a narrower range than the related art. In addition, it is possible for an electromagnetic wave transmitted by reader  103  to have directionality. 
         [0067]    It is thereby possible for power-supply-side control section  104  to determine that power supply coil  102   a  and power receiving coil  153   a  face each other when reader  103  receives a signal from RF tag  154 , without setting a threshold. 
         [0068]    The widening of the reception level of reader  103  in the direction of chargeable range W 2  varies depending on the position of antenna  201  of reader  103 . Accordingly, power supply apparatus  100  may be designed to start power supply when the reception level is equal to or greater than a threshold by setting an optimum threshold depending on the position of antenna  201  of reader  103 . 
         [0069]    Further, referring to  FIG. 4B , power reception coil  153   a  can receive power supply in a range from a position at which central axis R of RF tag  154  and broken line S 1  overlap each other to a position at which central axis R of RF tag  154  and broken line S 2  overlap each other. Therefore, internal diameter d of power supply coil  102   a  is preferably equal to or greater than range W 3  (W 3 =W 2 /2). In this case, hollow portion  102   b  in which the influence of a magnetic field decreases during power supply overlaps power receiving coil  153   a , and thus it is possible to enhance the precision in determining whether or not power supply coil  102   a  and power receiving coil  153   a  face each other. 
         [0070]    Power supply coil  102   a  and reader  103  are preferably disposed to have the relative position as illustrated in  FIG. 5 . That is, power supply coil  102   a  and reader  103  are disposed such that virtual line L extending radially toward power receiving coil  153   a  from the center portion of reader  103  and passing through connection portion  303  between internal wall  302  of power supply coil  102   a  and facing surface  301  passes through connection portion  306  between facing surface  304  of power receiving coil  153   a , which faces power supply coil  102   a , and external wall  305  of power receiving coil  153   a . Thus, RF tag  154  cannot receive an electromagnetic wave transmitted from reader  103  until it enters the range of angle θ. Accordingly, power supply apparatus  100  is capable of supplying power, with power supply coil  102   a  and power receiving coil  153   a  being precisely positioned. 
         [0071]    &lt;Operation of Power Receiving Apparatus Before Power Supply&gt; 
         [0072]    The operations of power receiving apparatus  160  according to Embodiment 1 of the present invention before power supply will be described using  FIG. 6 . In  FIG. 6 , reader  103  and RF tag  154  are passive RFIDs. 
         [0073]    First, vehicle-side control section  151  determines whether or not the distance between power receiving coil  153   a  and power supply coil  102   a  is within a predetermined distance before power supply (step ST 501 ). For example, vehicle-side control section  151  determines whether or not the distance therebetween is within a predetermined distance based on the position of power supply apparatus  100  in the map information and on the current position information of vehicle  150  calculated from a signal from the GPS satellite, by utilizing a car navigation system, or the like. 
         [0074]    When the distance is not within the predetermined distance (step ST 501 : No), vehicle-side control section  151  repeats the processing of step ST 501 . 
         [0075]    On the other hand, when the distance is within the predetermined distance (step ST 501 : Yes), vehicle-side communication section  152  transmits a request for starting position detection (step ST 502 ). Here, the position detection means obtaining the detection result indicating that RF tag  154  and antenna  201  of reader  103  face each other. 
         [0076]    Next, vehicle-side control section  151  determines whether or not the guidance of vehicle  150  to power supply section  102  is completed (step ST 503 ). 
         [0077]    When the guidance of vehicle  150  to power supply section  102  is not completed (step ST 503 : No), vehicle-side control section  151  repeats the processing of step ST 503 . 
         [0078]    On the other hand, when the guidance of vehicle  150  to power supply section  102  is completed (step ST 503 : Yes), vehicle-side communication section  152  transmits a request for terminating position detection (step ST 504 ) to terminate the processing. 
         [0079]    &lt;Operation of Power Supply Apparatus Before Power Supply&gt; 
         [0080]    The operations of power supply apparatus  100  according to Embodiment 1 of the present invention before power supply will be described using  FIG. 7 . In  FIG. 7 , reader  103  and RF tag  154  are passive RFIDs. 
         [0081]    First, power-supply-side communication section  101  determines whether or not the request for starting position detection transmitted from vehicle-side communication section  152  is received (step ST 601 ). 
         [0082]    When power-supply-side communication section  101  does not receive the request for starting position detection (step ST 601 : No), the processing of step ST 601  is repeated. 
         [0083]    On the other hand, when power-supply-side communication section  101  receives the request for starting position detection (step ST 601 : Yes), power-supply-side control section  104  starts the operation of reader  103  (step ST 602 ). Thus, reader  103  transmits an electromagnetic wave. 
         [0084]    Further, power-supply-side communication section  101  determines whether or not the request for terminating position detection transmitted from vehicle-side communication section  152  is received (step ST 603 ). 
         [0085]    When power-supply-side communication section  101  does not receive the request for terminating position detection (step ST 603 : No), the processing of step ST 603  is repeated. 
         [0086]    On the other hand, when power-supply-side communication section  101  receives the request for terminating position detection (step ST 603 : Yes), reader  103  determines whether or not ID data of RF tag  154  is received (step ST 604 ). 
         [0087]    When reader  103  receives the ID data of RF tag  154  (step ST 604 : Yes), power-supply-side control section  104  sets a power supply permission flag (step ST 605 ). In this case, reader  103  receives the ID data from RF tag  154  present within chargeable range W 2  (see  FIG. 4B ). 
         [0088]    Then, power-supply-side control section  104  stops the operation of reader  103  (step ST 606 ) to terminate the processing. Thus, reader  103  stops the transmission of an electromagnetic wave. 
         [0089]    On the other hand, when reader  103  does not receive the ID data of RF tag  154  (step ST 604 : No), power-supply-side control section  104  skips the processing of step ST 605  to perform the processing of step ST 606 . 
         [0090]    &lt;Operation of Power Supply Apparatus During Power Supply&gt; 
         [0091]    The operations of power supply apparatus  100  according to Embodiment 1 of the present invention during power supply will be described using  FIG. 8 . In  FIG. 8 , reader  103  and RF tag  154  are passive RFIDs. 
         [0092]    First, power-supply-side control section  104  determines whether or not a power supply permission flag is set (step ST 701 ). 
         [0093]    When the power supply permission flag is not set in power-supply-side control section  104  (step ST 701 : No), power supply apparatus  100  terminates the processing. At that time, power supply apparatus  100  may notify vehicle  150  that power cannot be supplied. Vehicle  150  may be designed to inform a driver that parking should be redone when vehicle  150  is notified that power cannot be supplied. 
         [0094]    On the other hand, when the power supply permission flag is set (step ST 701 : Yes), power-supply-side control section  104  allows power supply section  102  to start power supply (step ST 702 ). 
         [0095]    Next, power-supply-side control section  104  starts the operation of reader  103  (step ST 703 ). Thus, reader  103  transmits an electromagnetic wave. 
         [0096]    Next, reader  103  determines whether or not the ID data of RF tag  154  is received (step ST 704 ). 
         [0097]    When reader  103  receives the ID data of RF tag  154  (step ST 704 : Yes), power-supply-side communication section  101  determines whether or not a request for stopping power supply is received (step ST 705 ). 
         [0098]    When power-supply-side communication section  101  does not receive the request for stopping power supply (step ST 705 : No), the operation returns to the processing of step ST 704 . 
         [0099]    On the other hand, when power-supply-side communication section  101  receives the request for stopping power supply (step ST 705 : Yes), power-supply-side control section  104  controls power supply section  102  to stop power supply (step ST 706 ). 
         [0100]    Further, when reader  103  does not receive the ID data of RF tag  154  (step ST 704 : No), power-supply-side control section  104  controls power supply section  102  to stop power supply (step ST 706 ). This situation occurs when RF tag  154  is not present within chargeable range W 2  (see  FIG. 4B ) any more, for example, as a result of vehicle  150  having been moved during power supply. 
         [0101]    Then, power-supply-side control section  104  stops the operation of reader  103  (step ST 707 ) to terminate the processing. 
         [0102]    &lt;Vehicle Parking Pattern&gt; 
         [0103]    The vehicle parking pattern in Embodiment 1 of the present invention will be described using  FIGS. 9A and 9B . 
         [0104]      FIG. 9A  illustrates a case in which vehicle  150  is parked along parking space  800 , and  FIG. 9B  illustrates a case in which vehicle  150  is parked obliquely in parking space  800 . 
         [0105]    In the case of normal parking state as illustrated in  FIG. 9A , power supply is possible in any of the related art and the present embodiment. During that time, power supply coil  102   a  and power receiving coil  153   a  face each other. 
         [0106]    On the other hand, when vehicle  150  is parked obliquely in parking space  800 , as illustrated in  FIG. 9B , vehicle-side communication section Q 2  and ground-side communication section Q 1  fail to face each other in the related art, thus making it impossible to establish communication, so that vehicle  150  is not considered to be parked at the most appropriate position for power supply. Accordingly, in the related art, power cannot be supplied despite the fact that power supply coil  102   a  and power receiving coil  153   a  face each other. In the present embodiment, the disposition of antenna  201  of reader  103  at the center of hollow portion  102   b  of power supply coil  102   a  and the disposition of the RF tag at the center of hollow portion  153   b  of power receiving coil  153   a  make it possible to establish communication between reader  103  and RF tag  154 , thus enabling power supply, even when vehicle  150  is parked obliquely in parking space  800 , as long as power supply coil  102   a  and power receiving coil  153   a  face each other. 
       Effects of Embodiment 1 
       [0107]    According to the present embodiment, it is possible to detect that the power supply section and the power receiving section face each other, irrespective of the state of a stopped vehicle, by disposing reader  103  such that antenna  201  is positioned inside a projection space of hollow portion  102   b  projected in central axis P direction of power supply coil  102   a , and at a position farther away from power receiving coil  153   a  than facing surface  301  of power supply coil  102   a , which faces power receiving coil  153   a.    
         [0108]    In the present embodiment, reader  103  is disposed such that antenna  201  is positioned inside a projection space of hollow portion  102   b  projected in central axis P direction of power supply coil  102   a , and at a position farther away from power receiving coil  153   a  than facing surface  301  of power supply coil  102   a , which faces power receiving coil  153   a . Thus, according to the present embodiment, it becomes possible to narrow the transmission range of an electromagnetic wave from reader  103 , which therefore enables power receiving coil  153   a  and power supply coil  102   a  to be precisely positioned. 
         [0109]    According to the present embodiment, the disposition of reader  103  at central axis P of power supply coil  102   a  and the disposition of RF tag  154  at the central axis of R of power receiving coil  153   a  allow a communicable range with RF tag  154  to be adjustable evenly, only by the adjustment of the distance of reader  103  from power receiving coil  153   a  in central axis P direction. For example, by making the distance between power receiving coil  153   a  and reader  103  in central axis P direction larger, it becomes possible to narrow the communicable range; and by making the above-mentioned distance smaller, it becomes possible to widen the communicable range. Since power supply coil  102   a  has a spiral shape, it is possible to adjust the communicable range evenly in any direction. 
         [0110]    Referring to  FIGS. 10A and 10B , when the distance of reader  103  from power receiving coil  153   a  in central axis P direction in  FIG. 10B  is larger than the distance in  FIG. 10A , angle θ 2  of the communicable range in  FIG. 10B  is smaller than angle θ 1  of the communicable range in  FIG. 10A  (θ 1 &gt;θ 2 ). That is, the communicable range in  FIG. 10B  can be narrower than that in  FIG. 10A . 
         [0111]    According to the present embodiment, reader  103  is provided on the power-supply-side and RF tag  154  excellent in durability is provided in vehicle  150 , and thus it is possible to provide a power supply system excellent in durability with less breakdown, or the like. 
         [0112]    According to the present embodiment, reader  103  is disposed at a position farther away from power supply coil  102   a , and thus it is possible to make a magnetic field generated from power supply coil  102   a  less influential in reader  103 . 
         [0113]    According to the present embodiment, when internal diameter d of power supply coil  102   a  is set equal to or greater than range W 3 , a half of the chargeable range, the hollow portion in which the influence of a magnetic field decreases overlaps power receiving coil  153   a  during power supply, so that it is possible to enhance the precision in determining whether or not power supply coil  102   a  and power receiving coil  153   a  face each other. 
       Variation of Embodiment 1 
       [0114]    While RF tag  154  is configured such that the bottom surface of RF tag  154  is positioned at a facing surface of power receiving coil  153   a  where power receiving coil  153   a  faces power supply coil  102   a  in the present embodiment, RF tag  154  may be disposed at a position farther away from power supply coil  102   a  than the facing surface of power receiving coil  153   a  which faces power supply coil  102   a , in the same manner as reader  103 . 
       Embodiment 2 
       [0115]    The configurations of a power supply system, a power supply apparatus and a power receiving apparatus according to Embodiment 2 of the present invention are the same as those in  FIGS. 1 to 3A  and  3 B, except the relative position between power supply coil  102   a  and reader  103  and the relative position between power receiving coil  153   a  and RF tag  154 , and thus descriptions thereof will be omitted. It is noted that, in the present embodiment, the same reference signs as those in the above-described Embodiment 1 are used to describe the respective components. 
         [0116]    &lt;Relative Position Between RF Tag and Power Receiving Coil&gt; 
         [0117]    The relative position between RF tag  154  and power receiving coil  153   a  in Embodiment 2 of the present invention will be described using  FIG. 11 . 
         [0118]    In the present embodiment, reader  103  and RF tag  154  are active RFIDs. That is, in the present embodiment, RF tag  154  has a built-in battery, and transmits an electromagnetic wave with, for example, ID data superimposed thereon to reader  103  on its own power. In the present embodiment, the reason for disposing RF tag  154  as described above is to enhance position detection precision by narrowing the transmission range of an electromagnetic wave since RF tag  154  is a transmission side to transmit the electromagnetic wave. 
         [0119]    As illustrated in  FIG. 11 , in the present embodiment, RF tag  154  is disposed at a position farther away from power supply coil  102   a  than facing surface  401  of power receiving coil  153   a , which faces power supply coil  102   a . This allows power receiving coil  153   a  to function as a shield for shielding spreading of an electromagnetic wave transmitted from RF tag  154 . Accordingly, reader  103  can obtain a predetermined reception level in a narrower range than the related art. In addition, it is possible for an electromagnetic wave transmitted by RF tag  154  to have directionality. 
         [0120]    &lt;Operation of Power Receiving Apparatus Before Power Supply&gt; 
         [0121]    The operations of power receiving apparatus  160  according to Embodiment 2 of the present invention before power supply will be described using  FIG. 12 . In  FIG. 12 , reader  103  and RF tag  154  are active RFIDs. 
         [0122]    First, vehicle-side control section  151  determines whether or not the distance between power receiving coil  153   a  and power supply coil  102   a  is within a predetermined distance before power supply (step ST 901 ). For example, vehicle-side control section  151  determines whether or not the distance therebetween is within a predetermined distance based on the position of power supply apparatus  100  in the map information and on the current position information of vehicle  150  calculated from a signal from the GPS satellite, by utilizing a car navigation system, or the like. 
         [0123]    When the distance is not within the predetermined distance (step ST 901 : No), vehicle-side control section  151  repeats the processing of step ST 901 . 
         [0124]    On the other hand, when the distance is within the predetermined distance (step ST 901 : Yes), vehicle-side communication section  152  transmits a signal for starting position detection (step ST 902 ). 
         [0125]    Next, vehicle-side control section  151  starts the operation of RF tag  154  (step ST 903 ). Thus, RF tag  154  transmits an electromagnetic wave. 
         [0126]    Next, vehicle-side control section  151  determines whether or not the guidance of vehicle  150  to power supply section  102  is completed (step ST 904 ). 
         [0127]    When the guidance of vehicle  150  to power supply section  102  is not completed (step ST 904 : No), vehicle-side control section  151  repeats the processing of step ST 904 . 
         [0128]    On the other hand, when the guidance of vehicle  150  to power supply section  102  is completed (step ST 904 : Yes), vehicle-side communication section  152  transmits a request for terminating position detection (step ST 905 ). 
         [0129]    Next, vehicle-side communication section  152  determines whether or not a response to terminating position detection transmitted from power-supply-side communication section  101  is received (step ST 906 ). 
         [0130]    When the response to terminating position detection is not received (step ST 906 : No), vehicle-side communication section  152  repeats the processing of step ST 906 . 
         [0131]    On the other hand, when the response to terminating position detection is received by vehicle-side communication section  152  (step ST 906 : Yes), vehicle-side control section  151  stops the operation of RF tag  154  (step ST 907 ) to terminate the processing. Thus, RF tag  154  stops the transmission of an electromagnetic wave. 
         [0132]    &lt;Operation of Power Supply Apparatus Before Power Supply&gt; 
         [0133]    The operations of power supply apparatus  100  according to Embodiment 2 of the present invention before power supply will be described using  FIG. 13 . In  FIG. 13 , reader  103  and RF tag  154  are active RFIDs. 
         [0134]    First, power-supply-side communication section  101  determines whether or not the signal for starting position detection transmitted from vehicle-side communication section  152  is received (step ST 1001 ). 
         [0135]    When the request for starting position detection is not received (step ST 1001 : No), power-supply-side communication section  101  repeats the processing of step ST 1001 . 
         [0136]    On the other hand, when the request for starting position detection is received by power-supply-side communication section  101  (step ST 1001 : Yes), power-supply-side control section  104  starts the operation of reader  103  (step ST 1002 ). This enables reader  103  to receive an electromagnetic wave transmitted from RF tag  154  when RF tag  154  is present within chargeable range W 2  (see  FIG. 4B ). 
         [0137]    Further, power-supply-side communication section  101  determines whether or not the request for terminating position detection transmitted from vehicle-side communication section  152  is received (step ST 1003 ). 
         [0138]    When the request for terminating position detection is not received (step ST 1003 : No), power-supply-side communication section  101  repeats the processing of step ST 1003 . 
         [0139]    On the other hand, when the request for terminating position detection is received by power-supply-side communication section  101  (step ST 1003 : Yes), reader  103  determines whether or not the ID data of RF tag  154  is received (step ST 1004 ). 
         [0140]    When the ID data of RF tag  154  is received by reader  103  (step ST 1004 : Yes), power-supply-side control section  104  sets a power supply permission flag (step ST 1005 ). In this case, reader  103  receives the ID data from RF tag  154  present within chargeable range W 2  (see  FIG. 4B ). 
         [0141]    Next, power-supply-side communication section  101  transmits a response to terminating position detection (step ST  1006 ). 
         [0142]    Then, power-supply-side control section  104  stops the operation of reader  103  (step ST 1007 ) to terminate the processing. 
         [0143]    On the other hand, when the ID data of RF tag  154  is not received by reader  103  (step ST 1004 : No), power-supply-side control section  104  skips the processing of step ST 1005  to perform the processing of step ST 1006 . 
         [0144]    &lt;Operation of Power Receiving Apparatus During Power Supply&gt; 
         [0145]    The operations of power receiving apparatus  160  according to Embodiment 2 of the present invention during power supply will be described using  FIG. 14 . 
         [0146]    First, power receiving section  153  receives power as a result of power supply section  102  starting power supply (step ST 1101 ). 
         [0147]    Next, vehicle-side communication section  152  transmits a signal for starting position detection (step ST 1102 ). 
         [0148]    Next, vehicle-side control section  151  starts the operation of RF tag  154  (step ST 1103 ). Thus, RF tag  154  transmits an electromagnetic wave. 
         [0149]    Next, vehicle-side control section  151  determines whether or not there is a request for stopping power supply (step ST 1104 ). 
         [0150]    When there is no request for stopping power supply (step ST 1104 : No), vehicle-side control section  151  repeats the processing of step ST 1104 . 
         [0151]    On the other hand, when there is a request for stopping power supply (step ST 1104 : Yes), vehicle-side communication section  152  transmits the request for stopping power supply (step ST 1105 ). 
         [0152]    Next, vehicle-side control section  151  stops the operation of RF tag  154  (step ST 1106 ) to terminate the processing. Thus, RF tag  154  stops the transmission of an electromagnetic wave. 
         [0153]    &lt;Operation of Power Supply Apparatus During Power Supply&gt; 
         [0154]    The operations of power supply apparatus  100  according to Embodiment 2 of the present invention during power supply will be described using  FIG. 15 . In  FIG. 15 , reader  103  and RF tag  154  are active RFIDs. 
         [0155]    First, power-supply-side control section  104  determines whether or not a power supply permission flag is set (step ST 1201 ). 
         [0156]    When the power supply permission flag is not set in power-supply-side control section  104  (step ST 1201 : No), power supply apparatus  100  terminates the processing. 
         [0157]    On the other hand, when the power supply permission flag is set (step ST 1201 : Yes), power-supply-side control section  104  allows power supply section  102  to start power supply (step ST 1202 ). 
         [0158]    Next, power-supply-side communication section  101  determines whether or not the signal for starting position detection transmitted from vehicle-side communication section  152  is received (step ST 1203 ). 
         [0159]    When the signal for starting position detection is not received (step ST 1203 : No), power-supply-side communication section  101  repeats the processing of step ST 1203 . 
         [0160]    On the other hand, when the signal for starting position detection is received by power-supply-side communication section  101  (step ST 1203 : Yes), power-supply-side control section  104  starts the operation of reader  103  (step ST 1204 ). This enables reader  103  to receive an electromagnetic wave transmitted from RF tag  154  when RF tag  154  is present within chargeable range W 2  (see  FIG. 4B ). 
         [0161]    Next, reader  103  determines whether or not the ID data of RF tag  154  is received (step ST 1205 ). 
         [0162]    When the ID data of RF tag  154  is received by reader  103  (step ST 1205 : Yes), power-supply-side communication section  101  determines whether or not a request for stopping power supply is received (step ST 1206 ). 
         [0163]    When power-supply-side communication section  101  does not receive the request for stopping power supply (step ST 1206 : No), the operation returns to the processing of step ST 1205 . 
         [0164]    On the other hand, when power-supply-side communication section  101  receives the request for stopping power supply (step ST 1206 : Yes), power-supply-side control section  104  controls power supply section  102  to stop power supply (step ST 1207 ). 
         [0165]    Further, when the ID data of RF tag  154  is not received by reader  103  (step ST 1205 : No), power-supply-side control section  104  controls power supply section  102  to stop power supply (step ST 1207 ). 
         [0166]    Then, power-supply-side control section  104  stops the operation of reader  103  (step ST 1208 ) to terminate the processing. 
       Effects of Embodiment 2 
       [0167]    According to the present embodiment, it is possible to detect that the power supply section and the power receiving section face each other, irrespective of the state of a stopped vehicle. 
         [0168]    In the present embodiment, RF tag  154  is disposed at a position farther away from power supply coil  102   a  than facing surface  401  of power receiving coil  153   a , and at the center of hollow portion  153   b  of power receiving coil  153   a . Thus, according to the present embodiment, it becomes possible to narrow the transmission range of an electromagnetic wave from RF tag  154 , which therefore enables power receiving coil  153   a  and power supply coil  102   a  to be precisely positioned. 
         [0169]    According to the present embodiment, reader  103  is provided on the power-supply-side and RF tag  154  excellent in durability is provided in vehicle  150 , and thus it is possible to provide a power supply system excellent in durability with less breakdown, or the like. 
         [0170]    According to the present embodiment, RF tag  154  is disposed at a position farther away from power receiving coil  153   a , and thus it is possible to make a magnetic field generated from power receiving coil  153   a  less influential in RF tag  154 . 
       Variation of Embodiment 2 
       [0171]    While reader  103  is designed such that the upper surface of reader  103  is positioned at a facing surface of power supply coil  102   a  where power supply coil  102   a  faces power receiving coil  153   a  in the present embodiment, reader  103  may be disposed at a position farther away from power receiving coil  153   a  than the facing surface of power supply coil  102   a  which faces power receiving coil  153   a , in the same manner as RF tag  154 . 
       Embodiment 3 
       [0172]    The configurations of a power supply system according to Embodiment 3 of the present invention are the same as those in  FIG. 1 , and thus the descriptions thereof will be omitted. 
         [0173]    &lt;Configuration of Power Supply Section&gt; 
         [0174]    The configuration of power supply section  1300  in Embodiment 3 of the present invention will be described using  FIG. 16 . It is noted that, in  FIG. 16 , the same reference signs are given to components having the same configurations as those in  FIGS. 1 ,  3 A and  3 B, and the descriptions thereof will be omitted. 
         [0175]    Power supply section  1300  is mainly composed of power supply coil  102   a , insulator  1301 , magnetic body  1302 , and mount  1303 . It is noted that, in  FIG. 16 , the description of a housing that houses power supply coil  102   a  is omitted. 
         [0176]    Power supply section  1300  is a laminate in which mount  1303 , magnetic body  1302 , insulator  1301 , and power supply coil  102   a  are laminated in this order. 
         [0177]    Insulator  1301  is provided between power supply coil  102   a  and magnetic body  1302  to insulate power supply coil  102   a  and magnetic body  1302  from each other. 
         [0178]    Magnetic body  1302  is provided between mount  1303  and insulator  1301  on the opposite surface side of facing surface  301  of power supply coil  102   a . Magnetic body  1302  is provided for allowing a magnetic field generated from power supply coil  102   a  during power supply to be stronger. Magnetic body  1302  is ferrite, for example. 
         [0179]    Mount  1303  is formed of an insulation material, and is provided between ground G and magnetic body  1302 . 
         [0180]    Antenna  201  of reader  103  is disposed at a position farther away from power receiving coil  153   a  than magnetic body  1302 . This allows reader  103  to be less susceptible to the magnetic field generated by providing magnetic body  1302 . Further, antenna  201  of reader  103  is preferably disposed to be closer to ground G than the magnetic field during power supply generated by providing magnetic body  1302 , the magnetic field being indicated by broken arrows. In this case, the height of mount  1303  from ground G is set such that gap H is formed between the bottom surface of magnetic body  1302  and the upper surface of reader  103 . It is noted that the configurations of reader  103  other than those described above are the same as those in the above-described Embodiment 1, and thus the descriptions thereof will be omitted. 
         [0181]    It is noted that the operations of power supply apparatus  100  and power receiving apparatus  160  in the present embodiment are the same as those in  FIGS. 6 to 8 , and thus the descriptions thereof will be omitted. 
       Effect of Embodiment 3 
       [0182]    According to the present embodiment, in addition to obtaining the above-described effects of Embodiment 1, providing antenna  201  of reader  103  to be closer to ground G than magnetic body  1302  can prevent antenna  201  from generating an electromotive voltage under the influence of a magnetic field occurring between power supply coil  102   a  and power receiving coil  153   a.    
         [0183]    Further, according to the present embodiment, it is possible to reduce the influence of a magnetic field on antenna  201 , and thus it is not necessary to provide reader  103  with a protection circuit against an electromotive voltage, thereby enabling inexpensive reader  103  to be used, which leads to reduction in manufacturing cost. 
       Variation of Embodiment 3 
       [0184]    While power supply section  1300  is provided with magnetic body  1302  in the present embodiment, the power receiving section may be provided with a magnetic body, and RF tag  154  may be disposed at a position farther away from the power supply coil than the magnetic body. In this case, the magnetic body is disposed near a side of a surface of power receiving coil  153   a  opposite to facing surface  401 . The operations of the power supply apparatus and the power receiving apparatus in this case are the same as those in  FIGS. 12 to 15 , and thus the descriptions thereof will be omitted. 
       Embodiment 4 
       [0185]    The configurations of a power supply system according to Embodiment 4 of the present invention are the same as those in  FIG. 1 , and thus the descriptions thereof will be omitted. 
         [0186]    &lt;Configuration of Power Supply Section&gt; 
         [0187]    The configuration of a power supply section in Embodiment 4 of the present invention will be described using  FIGS. 17A and 17B . It is noted that, in  FIGS. 17A and 17B , the same reference signs are given to components having the same configurations as those in  FIGS. 3A and 3B , so that the descriptions thereof will be omitted. 
         [0188]    The power supply section in the present embodiment has electromagnetic wave absorber  1501  that covers inner wall  302  of power supply coil  102   a , which defines hollow portion  102   b . Electromagnetic wave absorber  1501  absorbs an electromagnetic wave in a frequency band other than the frequency band used to transmit and/or receive between RF tag  154  and reader  103 . 
         [0189]    It is noted that the operations of power supply apparatus  100  and power receiving apparatus  160  in the present embodiment are the same as those in  FIGS. 6 to 8 , and thus the descriptions thereof will be omitted. 
       Effects of Embodiment 4 
       [0190]    In the present embodiment, electromagnetic wave absorber  1501  that covers the inner wall of power supply coil  102   a  is provided to absorb an electromagnetic wave in a frequency band other than the frequency band used to transmit and/or receive between RF tag  154  and reader  103 . Thus, according to the present embodiment, no electromagnetic field leaks toward the surrounding area, and thus it is possible to suppress harmful effects such as undesirably heating a metal object such as housing, in addition to obtaining the above-described effects of Embodiment 1. 
       Variation of Embodiment 4 
       [0191]    While electromagnetic wave absorber  1501  that covers the inner wall of power supply coil  102   a  is provided in the present embodiment, an electromagnetic wave absorber that covers the inner wall of power receiving coil  153   a  may be provided. The operations of the power supply apparatus and the power receiving apparatus in this case are the same as those in  FIGS. 12 to 15 , and thus the descriptions thereof will be omitted. 
       Variation Common to All Embodiments 
       [0192]    While reader  103  is provided on the ground side and RF tag  154  is provided in vehicle  150  in the above-described Embodiments 1 to 4, RF tag  154  may be provided on the ground side and reader  103  may be provided in vehicle  150 . In this case, whether or not power receiving coil  153   a  and power supply coil  102   a  face each other is determined in vehicle  150 . 
         [0193]    While reader  103  and RF tag  154  are used for position detection in the above-described Embodiments 1 to 4, an apparatus or a system for position detection other than reader  103  and RF tag  154  can be used. That is, in the above-described Embodiments 1 to 4, any system that can establish a mutual communication by radio communication using an electromagnetic wave is sufficient, and it is also possible to use a coil for near field communication (NFC) or position detection, other than the RF tag. The coils for NFC and position detection both correspond to a radio tag. At that time, an antenna of NFC or a coil for position detection is disposed at a position farther away from power supply coil  102   a  or power receiving coil  153   a  than a facing surface facing power supply coil  102   a  and power receiving coil  153   a , and at the center of hollow portion  102   b  of power supply coil  102   a  or hollow portion  153   b  of power receiving coil  153   a  when seen from the direction in which power supply coil  102   a  and power receiving coil  153   a  face each other. 
         [0194]    While description has been made assuming that a single RF tag  154  is provided in the above-described Embodiments 1 to 4, more than one RF tags  154  can be provided. For example, a plurality of RF tags  154  may be provided in hollow portion  153   b  of power receiving coil  153   a.    
         [0195]    The disclosure of Japanese Patent Application No. 2013-071863, filed on Mar. 29, 2013, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0196]    The power supply apparatus and the power receiving apparatus according to the present invention are suitable for use in transmitting and/or receiving power in a wireless manner. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  Power supply system 
           100  Power supply apparatus 
           101  Power-supply-side communication section 
           102  Power supply section 
           102   a  Power supply coil 
           102   b ,  153   b  Hollow portion 
           103  Reader 
           104  Power-supply-side control section 
           150  Vehicle 
           151  Vehicle-side control section 
           152  Vehicle-side communication section 
           153  Power receiving section 
           153   a  Power receiving coil 
           154  RF tag 
           155  Storage battery 
           160  Power receiving apparatus