Foreign matter detection device

A foreign matter detection device of the present invention is provided with a temperature detection means that detects a temperature distribution in a magnetic field that is formed by a power-supplying device that transmits power wirelessly to a power-receiving device; and a signal processor that, based on a detection result from the temperature detection means, detects a conductive foreign matter in the magnetic field.

TECHNICAL FIELD

The present invention relates to a foreign matter detection device.

BACKGROUND ART

In recent years, wireless power supply systems that supply power wirelessly to a battery mounted in a moving body such as a vehicle have been proposed. The wireless power supply systems are provided, for example, with a power-receiving coil mounted in the moving body and a power-supplying coil installed on the power supply side, and transmit electric power using a magnetic field that is formed by the power-supplying coil.

In the wireless power supply systems, it is known that if a foreign matter that is formed wholly or partly from an electrically conductive material such as metal or conductive plastic (i.e., a conductive foreign matter) intrudes between the power-receiving coil and the power-supplying coil, then a loss in energy occurs due to the heat generated by the conductive foreign matter, and there is a decrease in the transmission efficiency. To deal with this problem, for example, as is shown in Patent document 1, it has been proposed that countermeasures be devised that prevent a foreign matter from intruding between the power-receiving coil and the power-supplying coil.

DOCUMENTS OF RELATED ART

Patent Documents

SUMMARY OF THE INVENTION

Technical Problem

However, when a moving body such as a vehicle or the like is not present, it often happens that the power-supplying coil (or a cover covering the power-supplying coil) is left outside in an exposed state. Even if countermeasures such as those described above are devised, in some cases, it may be difficult to completely prevent the intrusion of a conductive foreign matter. As a consequence, to deal with an energy loss caused by the intrusion of a conductive foreign matter, there is a need to also consider how to devise countermeasures to limit the effects thereof to a minimum.

The present invention is conceived in view of the above-described problem and it is an object thereof to make it possible to quickly detect any reduction in transmission efficiency in a wireless power supply system that is caused by a conductive foreign matter.

Solution to the Problem

In order to solve the above-described problem, the present invention employs the following structure.

A first aspect of the present invention is a foreign matter detection device that includes: a temperature detection means that detects a temperature distribution in a magnetic field formed by a power-supplying device transmitting power wirelessly to a power-receiving device; and a signal processor that, based on a detection result from the temperature detection means, detects a conductive foreign matter in the magnetic field.

A second aspect of the present invention is the above-described first aspect, wherein the temperature detection means is provided with: an optical waveguide laid in the magnetic field; a light source unit that outputs detection light into the optical waveguide; and a light-receiving unit that receives the detection light through the optical waveguide.

A third aspect of the present invention is the above-described second aspect, wherein the optical waveguide is an optical fiber.

A fourth aspect of the present invention is the above-described third aspect, further including a supporting portion, wherein the power-supplying device is provided with a power-supplying coil and the power-supplying coil is provided in a parking space for a vehicle, and the supporting portion is located above the power-supplying coil, is formed from an insulating material and supports the optical fiber.

A fifth aspect of the present invention is the above-described fourth aspect, wherein the supporting portion is a sheet material that is formed from glass fibers and to whose bottom surface the optical fiber adheres.

A sixth aspect of the present invention is the above-described fifth aspect, wherein the light source unit and the light-receiving unit are located below a vehicle supporting surface of the parking space, and the supporting portion is positioned such that a top surface of the supporting portion is flush with the vehicle supporting surface.

A seventh aspect of the present invention is the above-described fourth aspect, wherein the supporting portion is formed from a plurality of flexible wire components.

An eighth aspect of the present invention is any of the above-described fourth through seventh aspects, wherein the optical fiber is laid such that, when viewed from above, the optical fiber has no overlapping portions.

A ninth aspect of the present invention is any of the above-described fourth through eighth aspects, wherein a plurality of the optical fibers are laid.

Effects of the Invention

A foreign matter detection device of the present invention is provided with a temperature detection means that detects the temperature distribution in a magnetic field formed by a power-supplying device. When a conductive foreign matter intrudes into the magnetic field, the conductive foreign matter generates heat due to the effects of the magnetic field. Thus a signal that shows the intrusion of the conductive foreign matter is contained in the detection result from the temperature detection device. Accordingly, by analyzing the detection result from the temperature detection device using a signal processor, it is possible to detect the presence of the conductive foreign matter. As a result, according to the present invention, when there is an intrusion of a conductive foreign matter, it is possible to quickly detect any reduction in transmission efficiency in a wireless power supply system that is caused by the conductive foreign matter.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment of a foreign matter detection device according to the present invention will be described with reference to the drawings. Note that, in the following drawings, the scale of each component has been modified in order to make each component appear in a recognizable size.

First Embodiment

FIG. 1is a view showing the schematic structure of a wireless power supply system1that incorporates a foreign matter detection device4of the present embodiment. As is shown in the drawing, the wireless power supply system1includes a power-supplying device2, a power-receiving device3, and the foreign matter detection device4.

The power-supplying device2is provided with a power source21, a rectifier circuit22, a power-supplying circuit23, a power-supplying coil24, and a power supply control unit25.

Output terminals of the power source21are connected to input terminals of the rectifier circuit22. The power source21is an AC power supply that supplies AC power, that is needed for the power supply to the power-receiving device3, to the rectifier circuit22. The power source21is a system power supply that supplies, for example, 200V or 400V three-phase AC power, or 100V single-phase AC power. Input terminals of the rectifier circuit22are connected to the power source21, while output terminals thereof are connected to the power-supplying circuit23. The rectifier circuit22rectifies the AC power supplied from the power source21into DC power which it then outputs from its output terminals.

Input terminals of the power-supplying circuit23are connected to the rectifier circuit22, while output terminals thereof are connected to both ends of the power-supplying coil24. The power-supplying circuit23is a type of inverter that is provided with the power-supplying coil24and with a resonance capacitor that forms part of a power supply-side resonance circuit. The power-supplying circuit23converts the frequency of DC power supplied from the rectifier circuit22into AC power having a higher frequency than the AC power of the power source21(i.e., into high-frequency power) based on control commands input from the power supply control unit25.

The power-supplying coil24is a helical coil having a predetermined coil diameter. The power-supplying coil24is installed in a parking space S for a vehicle M (seeFIG. 1) with the coil axis thereof aligned in an up-down direction (i.e., in a vertical direction), and either exposed on the ground surface or molded in an electrically insulating material such as plastic or the like. Note that, in the present embodiment, the power-supplying coil24is embedded in the ground (or in a mechanical-parking pallet) such that a top surface24aof the power-supplying coil24is flush with a vehicle-supporting surface S1of the parking space S (seeFIG. 2A). Moreover, in the present embodiment, the wires of the power-supplying coil24are wound in a circular shape when viewed from above, and the outer peripheral shape of the power-supplying coil24is circular (seeFIG. 2B).

The power supply-side resonance circuit that is provided with the above-described power-supplying coil24generates a magnetic field when it is supplied with high-frequency electric power. A power reception-side resonance circuit (described below) is made to resonate with the magnetic field, and power is transmitted wirelessly from the power-supplying coil24to a power-receiving coil31(described below).

The power supply control unit25is provided with a microprocessor and memory and the like, and is a software-type control device that functions based on a predetermined power supply program. The power supply control unit25is connected to the power-supplying circuit23, and controls the power-supplying circuit23based on the power supply program.

The power-receiving device3is mounted in the vehicle M, and is provided with the power-receiving coil31, a power-receiving circuit32, a charging circuit33, a battery34, and a power reception control unit35. Note that the vehicle M referred to here is an automobile that travels using electricity as a power source such as, for example, an electric vehicle or a hybrid vehicle, however, the present invention is also applicable to all devices in general that have a function of traveling using electricity as a power source such as automated guided vehicles.

The power-receiving coil31is a helical coil having a coil diameter that is substantially the same as that of the power-supplying coil24of the power-supplying device2, and is provided in a bottom portion of the vehicle M with the coil axis thereof extending in an up-down direction (i.e., in a vertical direction) such that it is able to face the power-supplying coil24. Both ends of the power-receiving coil31are connected to the power-receiving circuit32.

The power-receiving circuit32is connected to both ends of the power-receiving coil31, and output terminals thereof are connected to input terminals of the charging circuit33. The power-receiving circuit32is a type of rectifier circuit that is provided with the power-receiving coil31, and with a resonance capacitor that forms part of a power reception-side resonance circuit. The power-receiving circuit32converts AC power that has been transmitted to the power reception-side resonance circuit into DC power, and then supplies it to the charging circuit33. Note that the electrostatic capacity of the resonance capacitor of the power-receiving circuit32is set such that the resonance frequency of the power supply-side resonance circuit is the same as the resonance frequency of the power reception-side resonance circuit.

The input terminals of the charging circuit33are connected to the output terminals of the power-receiving circuit32, and the output terminals of the charging circuit33are connected to input terminals of the battery34. Power (i.e., DC power) supplied from the power-receiving circuit32charges the battery34. The battery34is a rechargeable battery (for example, a secondary battery such as a lithium ion battery or a nickel hydrogen battery), and supplies drive power to a travel motor or the like (not shown) that is mounted in the vehicle M.

The power reception control unit35is provided with a microprocessor and memory and the like, and is a software-type control device that functions based on a predetermined power reception control program. The power reception control unit35is connected to the charging circuit33, and controls the charging circuit33based on the power reception control program.

FIGS. 2A and 2Bare enlarged views that include the foreign matter detection device4.FIG. 2Ais a side view, whileFIG. 2Bis a top view. As is shown in these drawings, the foreign matter detection device4is provided with a glass sheet5(i.e., a supporting portion), a temperature detection unit6(i.e., a temperature detection means or a temperature detector), and a signal processing unit7(i.e., a signal processing means or a signal processor).

The glass sheet5is a sheet component that is formed from glass fibers, which are electrically insulating, and is provided on the vehicle-supporting surface S1of the parking space S so as to cover the power-supplying coil24from above. An optical fiber61(described below) adheres to a bottom surface5aof the glass sheet5such that the glass sheet5supports the optical fiber61. Namely, the foreign matter detection device4of the present embodiment is provided with the glass sheet5as a supporting portion that is formed from an insulating material that supports the optical fiber61, and is placed on top of the power-supplying coil24.

The temperature detection unit6is an optical fiber sensor that is formed from the optical fiber61(i.e., an optical waveguide), a light source unit62, and a light-receiving unit63. An input terminal of the optical fiber61is connected to the light source unit62, while an output terminal thereof is connected to the light-receiving unit63. As is shown inFIG. 2B, a portion between the input terminal and the output terminal is wound in a spiral configuration as it is laid out. Because the optical fiber61adheres to the bottom surface of the glass sheet5, it is placed between the power-supplying coil24and the power-receiving coil31(namely, in a magnetic field formed from the power-supplying coil24). Note that the optical fiber61is wound in a substantially circular shape such that, when viewed from above, the portion that is wound in a spiral shape is large enough to cover the entirety of the power-supplying coil24. In this way, by making the shape of the wound portion of the optical fiber61the same shape as the power-supplying coil24, when viewed from above, the optical fiber61can uniformly cover the power-supplying coil24without any portions thereof being provided unnecessarily.

The light source unit62is connected to the input terminal of the optical fiber61, and from the input terminal it emits detection light that enters the optical fiber61. The light-receiving unit63is connected to the output terminal of the optical fiber61and is also connected to an input terminal of the signal processing unit7. The light-receiving unit63receives the detection light emitted from the output terminal of the optical fiber61, converts it into an electrical signal and then outputs. As is shown inFIG. 2AandFIG. 2B, the light source unit62and the light-receiving unit63are placed at the sides of the power-supplying coil24such that they do not intrude into the space between the power-supplying coil24and the power-receiving coil31, namely, into the area where a strong magnetic field is generated between the power-supplying coil24and the power-receiving coil31when a wireless power supply operation is being conducted. If a heat source is present in the vicinity of the optical fiber61, the refractive index of the optical fiber61changes in localized portions depending on the temperature of the heat source. As a consequence, the frequency components of the detection light emitted from the output terminal of the optical fiber61change, so that, as a result, the output signal from the light-receiving unit63also changes in the temperature detection unit6. Accordingly, when a heat source is present in the vicinity of the optical fiber61, the temperature detection unit6outputs as a detection result an electrical signal that includes information showing the position of the heat source.

The signal processing unit7is connected to the temperature detection unit6and, based on a detection result output from the temperature detection unit6, detects the presence or non-presence of a conductive foreign matter within the magnetic field. The signal processing unit7analyzes output signals from the temperature detection unit6, and if information showing the heat source is contained therein, provides notification of this fact. The notification may take the form, for example, of a display on a display monitor (not shown), or a warning sound issued by an alarm device (not shown). Note that it is also possible for the signal processing unit7to be formed as an integral unit together with the power supply control unit25of the power-supplying device2.

Next, an operation of a wireless power supply system1which includes the foreign matter detection device4of the present embodiment having the above-described structure will be described.

The supply of power from the power-supplying device2to the power-receiving device3is started in the following manner. Namely, the vehicle M is parked in a predetermined position in the parking space S, and when the power-supplying coil24and the power-receiving coil31have been positioned facing each other, a control command instructing that the supply of power be started is input from the power supply control unit25to the power-supplying circuit23. When the control command is input into the power-supplying circuit23, power from the power source21that has been converted into DC power by the rectifier circuit22is converted into high-frequency power by the power-supplying circuit23, and magnetic field oscillation is formed in the power supply-side resonance circuit. When the magnetic field oscillation is formed in the power supply-side resonance circuit, the power-reception side resonance circuit resonates, and high-frequency power is transmitted from the power supply-side resonance circuit to the power reception-side resonance circuit.

After the high-frequency power transmitted to the power reception-side resonance circuit has been converted into DC power by the power-receiving circuit32and has been rectified, it is supplied to the battery34via the charging circuit33. The supplied power is then stored in the battery34. As a result, charging of the battery34takes place.

A case will now be considered in which a conductive foreign matter intrudes between the power-supplying coil24and the power-receiving coil31while power is being supplied wirelessly in the manner described above. In such a case, because the conductive foreign matter intrudes into the magnetic field formed by the power-supplying coil24(namely, by the power-supplying device2), an eddy current is generated in the conductive foreign matter as a result of the effects of the magnetic field, and it causes the conductive foreign matter to generate heat. When the conductive foreign matter generates heat in this manner, the refractive index of the optical fiber61changes in localized portions in the vicinity of the conductive foreign matter, and a detection result that include temperature information and position information about the heat source are output from the temperature detection unit6. The detection result is input into the signal processing unit7. The signal processing unit7then analyzes the detection result and, if information showing the heat source is contained therein, provides notification of this fact.

Next, the operation and effects of the foreign matter detection device4of the present embodiment that incorporates the above-described wireless power supply system1will be described.

According to the foreign matter detection device4of the present embodiment, there is provided the temperature detection unit6that detects the temperature in the magnetic field formed by the power-supplying coil24. When a conductive foreign matter intrudes into the magnetic field, the conductive foreign matter generates heat due to the effects of the magnetic field. Thus a signal showing the intrusion of the conductive foreign matter is contained in the detection result from the temperature detection unit6. In other words, according to the foreign matter detection device4of the present embodiment, a signal showing the presence or non-presence of a conductive foreign matter is acquired by the temperature detection unit6. Accordingly, as a result of the detection result from the temperature detection unit6being analyzed by the signal processing unit7, it is possible to detect the presence or non-presence of a conductive foreign matter. Accordingly, according to the foreign matter detection device4of the present embodiment, when there is an intrusion by a conductive foreign matter, it is possible to quickly detect any reduction in transmission efficiency that is caused by the conductive foreign matter.

Moreover, in the foreign matter detection device4of the present embodiment, the temperature detection unit6is formed from the optical fiber61that is laid in a magnetic field formed by the power-supplying coil24, the light source unit62that outputs detection light into the optical fiber61, and the light-receiving unit63that receives the detection light through the optical fiber61. According to the temperature detection unit6, it is possible to specify the temperature and position of a heat source simply by emitting detection light using the light source unit62, and then receiving the detection light using the light-receiving unit63. Accordingly, it is possible to specify the temperature and position of the heat source using a simple structure.

Moreover, in the foreign matter detection device4of the present embodiment, the optical fiber61is used as an optical waveguide in the temperature detection unit6. The optical fiber61is formed from an electrically insulating material. According to the temperature detection unit6which uses the optical fiber61, the optical fiber61is not affected by the magnetic field, and the transmission efficiency from the power-supplying coil24to the power-receiving coil31is not harmed by the temperature detection unit6. Moreover, the shape of the optical fiber61can be easily changed. It can be easily laid so as to conform to the shape of the power-supplying coil24, so that a foreign matter can be detected over the entire area of the power-supplying coil24without any overlap or any omission.

Moreover, because the light source unit62and the light-receiving unit63are located away from the space between the power-supplying coil24and the power-receiving coil31, that is, in areas where only a weak magnetic field is generated during the wireless supply of power, the magnetic field is prevented from being affected by the light source unit62and the light-receiving unit63and any reduction in the efficiency of the wireless power supply is also prevented. Furthermore, even if the light source unit62and the light-receiving unit63contain an electrically conductive material such as metal or the like, any heat generation that is caused by the action of the magnetic field during the wireless power supply is prevented.

Moreover, the foreign matter detection device4of the present embodiment is provided with the glass sheet5that is formed from glass fibers (i.e., an insulating material) that supports the optical fiber61. Because the glass sheet5is formed from an electrically insulating material in the form of glass fibers, even if it is placed within the magnetic field formed by the power-supplying coil24, it does not generate any heat and does not cause any reduction in the transmission efficiency. According to the foreign matter detection device4of the present embodiment, it is possible to support the optical fiber61without causing any deterioration in the transmission efficiency. Moreover, because the glass sheet5is formed from glass fibers, it is mechanically extremely strong. Therefore, for example, even if the vehicle or the like comes into contact with the glass sheet5, it is possible to prevent a heavy load being applied to the optical fiber61.

Second Embodiment

Next, a second embodiment of the present invention will be described. Note that in the description of the second embodiment, any description of portions thereof that are the same as in the above-described first embodiment is either omitted or simplified.

FIGS. 3A and 3Bare enlarged views that include a foreign matter detection device4A of the present embodiment.FIG. 3Ais a side view, whileFIG. 3Bis a top view. As is shown in these drawings, because the light source unit62and the light-receiving unit63are embedded into the foreign matter detection device4A of the present embodiment, they are positioned below the vehicle-supporting surface S1. Moreover, the top surface5bof the glass sheet5is flush with the vehicle-supporting surface S1.

According to the foreign matter detection device4A of the present embodiment in which the above-described structure is employed, it is possible for the foreign matter detection device4A to be installed without any portion thereof protruding above the vehicle-supporting surface S1. Thus the foreign matter detection device4A is prevented from coming into contact with the vehicle M.

Third Embodiment

Next, a third embodiment of the present invention will be described. Note that in the description of the third embodiment as well, any description of portions thereof that are the same as in the above-described first embodiment is either omitted or simplified.

FIGS. 4A and 4Bare enlarged views that include a foreign matter detection device4B of the present embodiment.FIG. 4Ais a side view, whileFIG. 4Bis a top view. As is shown in these drawings, the foreign matter detection device4B of the present embodiment is provided with three flexible wire components8(i.e., supporting portions) instead of the glass sheet5of the above-described first embodiment.

These wire components8are adhered to by the optical fiber61, and support the optical fiber61. The wire components8are formed from an electrically insulating material as the glass sheet5, and are also sufficiently heat resistant for them to not be damaged by a heat-generating conductive foreign matter. These wire components8can be formed, for example, from heat-resistant rubber.

According to the foreign matter detection device4B of the present embodiment which has the above-described structure, even if the vehicle M comes into contact with the wire components8, the wire components8flexibly deform, and the vehicle M can be prevented from being damaged. Furthermore, because the wire components8are flexible, after they have been deformed, they return to their original shape when the vehicle M moves away. Thus the position of the optical fiber61can be returned to its original location.

Note that, in the foregoing description, there are three wire components8, however, provided that they are able to support the optical fiber61, and are able to return to their original shape after having been pressed by the vehicle M, then the number of wire components8can be set to an optional number.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be described. Note that in the description of the fourth embodiment, any description of portions thereof that are the same as in the above-described first embodiment is either omitted or simplified.

FIG. 5Ais an enlarged top view that includes a foreign matter detection device4C of the present embodiment. As is shown in the drawing, in the foreign matter detection device4C of the present embodiment, the optical fiber61is laid out such that, when viewed from above, the optical fiber61has no overlapping portions.

If the optical fiber61is laid out such that it overlaps itself partway along its length, then when, for example, the vehicle M is driven onto the glass sheet5such that a heavy load is applied from above to the optical fiber61, then an even heavier load is applied locally to the overlapping portions, and there is a possibility that the performance of the optical fiber61will be reduced. In contrast, according to the foreign matter detection device4of the present embodiment, because the optical fiber61is laid out such that, when viewed from above, the optical fiber61has no overlapping portions, it is possible to prevent a heavy load from being applied to localized portions of the optical fiber61.

Fifth Embodiment

Next, a fifth embodiment of the present invention will be described. Note that in the description of the fifth embodiment, any description of portions thereof that are the same as in the above-described first embodiment is either omitted or simplified.

FIG. 5Bis an enlarged top view that includes a foreign matter detection device4D of the present embodiment. As is shown in the drawing, two temperature detecting units, namely, a temperature detecting unit6A and a temperature detecting unit6B are provided in the foreign matter detection device4D of the present embodiment.

As is shown inFIG. 5B, the optical fiber61A of the temperature detection unit6A and the optical fiber61B of the temperature detection unit6B are wound in a single wind. Moreover, the optical fiber61A of the temperature detection unit6A and the optical fiber61B of the temperature detection unit6B are placed such that, when viewed from above, their winding centers are mutually offset. Furthermore, in the foreign matter detection device4D of the present embodiment, the light source unit62A and the light-receiving unit63A of the temperature detection unit6A are located on one side of the power-supplying coil24(i.e., on the left side inFIG. 5B) when viewed from above, while the light source unit62B and the light-receiving unit63B of the temperature detection unit6B are located on the opposite side (i.e., on the right side inFIG. 5B) of the power-supplying coil24.

The foreign matter detection device4D of the present embodiment is provided with a plurality of temperature detection units (i.e., the temperature detection unit6A and the temperature detection unit6B). Namely, in the foreign matter detection device4D, a plurality of optical fibers (i.e., the optical fiber61A and the optical fiber61B) are laid down. Thus it is no longer necessary to cover the entire area of the power-supplying coil24with only a single optical fiber, and it is possible to reduce the number of winds in one optical fiber. As a result, the load on the optical fiber can be reduced.

Moreover, in the foreign matter detection device4D of the present embodiment, when viewed from above, the light source unit62A and the light-receiving unit63B of the one temperature detection unit6A are placed on one side of the power-supplying coil24, and the light source unit62B and the light-receiving unit63B of the other temperature detection unit6B are placed on the opposite side of the power-supplying coil24. In a case, for example, of damage occurring as a result of water entry or as a result of being struck by the vehicle, the locations affected by the damage do not extend over the entire periphery of the power-supplying coil24, and it may generally be assumed that the damage will be limited to only one side of the power-supplying coil24. Thus by placing the light source unit62A, the light-receiving unit63A, the light source unit62B, and the light-receiving unit63B in the above-described manner, it is possible to reduce the possibility of the light source units and light-receiving units of both temperature detection units being damaged at the same time. Accordingly, the foreign matter detection device4D of the present embodiment that employs the structure explained above has superior reliability.

For example, in the above-described embodiments, a structure is described in which the optical fiber61, the optical fiber61A, and the optical fiber61B (hereinafter, these will be abbreviated to ‘optical fibers61and the like’) are used as an optical waveguide. However, the present invention is not limited to this structure and it is also possible to use a plate-shaped or sheet-shaped optical waveguide.

Moreover, the supporting portion of the present invention may be formed from sheet-shaped rubber, and a structure may be employed in which the optical fibers61and the like are wound around the interior of the supporting portion. In this case, because the supporting portion and the optical fibers61and the like are integrated into a single unit, the handleability thereof is improved.

Moreover, in the above-described embodiments, a structure is described in which the optical fibers61and the like are wound out. However, the present invention is not limited to this structure and it is also possible for the optical fibers61and the like to meander. It is also possible for a plurality of rectilinear optical fibers to be laid out in parallel with each other or in a lattice configuration.

Moreover, in the above-described embodiments, a structure is described in which the optical fibers61and the like adhere to the bottom surface of the supporting portion (i.e., the glass sheet5and the wire components8). However, the present invention is not limited to this structure and it is also possible for the optical fibers61and the like to adhere to the top surface of the supporting portion. Moreover, it is also possible to eliminate the supporting portion and the optical fibers61and the like adhere directly to the top surface of the power-supplying coil24.

However, in such a case, because the optical fibers61and the like are exposed, it is desirable to implement measures to prevent the vehicle M from coming into contact with the optical fibers61and the like.

Moreover, in the above-described embodiments, a structure is described in which the optical fibers61and the like are wound within a horizontal plane. However, the present invention is not limited to this structure and it is also possible, for example, for the supporting portion (i.e., the glass sheet5) to be laid on an incline and for the optical fibers61and the like to be wound within the inclined plane. In such a case, because there is a high likelihood that a foreign matter will remain in lower portions of the inclined supporting portion, by placing the optical fibers61and the like close to each other in the lower portions of the supporting portion, it is possible to more precisely and reliably ascertain the position of the foreign matter.

Moreover, in the above-described embodiments, a structure is described in which the power-supplying coil24is wound in a substantially circular configuration, and the optical fibers61and the like are also wound in a substantially circular configuration in the same way. However, the present invention is not limited to this structure and if the power-supplying coil24is wound in a substantially square configuration, then it is desirable for the optical fibers61and the like to also be wound in a substantially square configuration in the same way.

Moreover, in the above-described embodiments, a structure is described in which the temperature within the magnetic field is detected using the optical fibers61and the like which are serving as an optical waveguide. However, the present invention is not limited to this structure and, for example, it is also possible to detect the temperature using an infrared camera that acquires an image of the area above the power-supplying coil24.

Moreover, in the above-described embodiments, it is also possible to provide an additional structure that raises and lowers the optical fibers61and the like. It becomes possible to lower the optical fibers and the like when the vehicle M is being moved, and to thereby prevent the optical fibers61and the like from coming into contact with the vehicle M.

Moreover, in the above-described embodiments, a structure is described in which the vehicle-supporting surface S1is the ground surface. However, it is not necessary for the vehicle-supporting surface S1to be the ground surface, and in an automated parking place and the like the top surface of the pallet forms the vehicle-supporting surface.

Moreover, in the above-described embodiment, a magnetic field resonance method is employed for the method of supplying power wirelessly, however, it is also possible to use another wireless power supply method such as an electromagnetic induction method and the like.

Moreover, the power-supplying coil24and the power-receiving coil31are not limited to helical coils. Provided that they enable power to be supplied wirelessly between the power-supplying coil24and the power-receiving coil31, then an arbitrary type and shape of coil such as a solenoid coil may be used, and the type, shape, and size of the both coils may be different.

INDUSTRIAL APPLICABILITY

The foreign matter detection device of the present invention makes it possible to rapidly detect any reduction in the transmission efficiency of a wireless power supply system that is caused by a conductive foreign matter.