JP2019071762A - Method for controlling power transmitting device for radio power transmission system, method for detecting foreign matter and power transmitting device - Google Patents

Abstract

To easily remove a metallic foreign matter located near a power transmission coil.SOLUTION: A method for controlling a power transmitting device to detect a metallic foreign matter comprises: a power transmission coil which outputs power with a power reception coil; a thermal sensor which measures a surface temperature of the foreign matter on the power transmission coil. The method, making the power transmission coil output the power and the thermal sensor measure the temperature of the metallic foreign matter, before the power reception coil and the power transmission coil are electromagnetically coupled and before a mobile body having the power reception coil and the power transmission coil are superimposed, transmits a signal which indicates presence of the metallic foreign matter to the receiving devices capable of receiving the signal except the transmission device when the measured surface temperature of the metallic foreign matter is equal to or more than a threshold.SELECTED DRAWING: Figure 5

Description

  The present disclosure relates to a control method of a power transmission device in a wireless power transmission system, a foreign object detection method, and a power transmission device.

  A wireless power transmission system used for a mobile object such as a vehicle electromagnetically couples a power transmission coil included in a power transmission device and a power reception coil included in a power reception device to transmit power from the power transmission coil to the power reception coil. At that time, if a metal foreign object such as an empty can or a coin is present between the power transmission coil and the power reception coil, the surface temperature of the metal foreign object may increase due to the magnetic field generated from the power transmission coil at the time of power transmission. In addition, the presence of a metal foreign object between both coils causes a problem that wireless charging can not be performed normally. Therefore, various techniques for detecting such metallic foreign matter have been proposed.

  Patent Document 1 discloses a method in which a camera is installed on the bottom of a vehicle and a metal foreign object is detected by the camera in a state in which a power transmission coil and a power reception coil face each other. When it is determined that the metal foreign object is present between the power transmission coil and the power reception coil, power transmission from the power transmission coil to the power reception coil is stopped.

  Patent document 2 transmits information obtained by the secondary voltage detection unit and the secondary current detection unit provided in the terminal on the power reception side from the terminal to the main body, and the main body is supplied to the feed oscillation unit based on the information. Discloses a method of controlling power supply to a terminal by determining whether the primary current value is an overcurrent or not. It is disclosed that even when a metal foreign object is present between the power feeding side and the power receiving side, the power feeding operation can be stopped before the metal foreign object generates heat.

JP 2013-192411 A JP 2001-275280

  In the above-mentioned prior art, a metal foreign object is detected in the state where a power transmission coil and a receiving coil have opposed. However, in such a system, it is necessary to move the vehicle from the parking position once, for example, in order to remove foreign metal present under the vehicle. The present disclosure provides a novel method that can solve such problems.

A foreign matter detection method according to an aspect of the present disclosure is
The power transmission device
An inverter circuit that generates power;
A power transmission coil for outputting electric power to a power reception coil of the mobile unit;
A thermal sensor that measures the surface temperature of metal foreign matter on the power transmission coil;
A power transmission control circuit for controlling the power output from the power transmission coil in the inverter circuit;
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the movable body and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold, a signal indicating the presence of the metal foreign object is transmitted from the power transmission device to a receiver having a function of receiving the signal other than the power transmission device.

A foreign matter removal method according to another aspect of the present disclosure is
The power transmission device
An inverter circuit that generates power;
A power transmission coil for outputting electric power to a power reception coil of the mobile unit;
A thermal sensor that detects the surface temperature of metal foreign matter on the power transmission coil;
A foreign matter removal mechanism,
A power transmission control circuit for controlling the power output from the power transmission coil in the inverter circuit;
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the movable body and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold value, the foreign object removing mechanism is made to execute the foreign object removing operation.

  The above general or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a storage medium. Alternatively, the present invention may be realized by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

  According to an aspect of the present disclosure, before a receiving coil and a transmitting coil are electromagnetically coupled, and before a moving body having the receiving coil and the transmitting coil overlap, a metal foreign object located in the vicinity of the transmitting coil Can be detected. Therefore, foreign matter can be quickly removed, and non-contact power transmission can be started normally and quickly.

FIG. 1 is a view schematically showing an example of a wireless power transmission system for supplying power to a mobile unit 200 wirelessly. FIG. 2 shows an example of a situation in which a metal foreign object is present on the power transmission coil. FIG. 3 shows an example of a situation where the mobile unit 200 and the power transmission coil 110 overlap. FIG. 4 is a flowchart illustrating the basic operation performed by the power transmission device in an aspect. FIG. 5 is a flowchart showing the basic operation performed by the power transmission device in another aspect. FIG. 6 is a flowchart showing an example of the operation of removing metal foreign matter by the foreign matter removing mechanism provided in at least one of the power transmission device and the moving object. FIG. 7 is a perspective view schematically showing a configuration of a wireless power transmission system in an exemplary embodiment 1 of the present disclosure. FIG. 8 is a block diagram showing the configuration of the wireless power transmission system in the present embodiment. FIG. 9 is a flowchart showing a basic flow of the operation performed by the power transmission control circuit 150. FIG. 10 is a flowchart showing a more detailed example of the operation of the power transmission control circuit 150. FIG. 11A is a view showing an example of an equivalent circuit of the power transmission coil 110 and the power reception coil 210. FIG. 11B is a diagram illustrating another example of the equivalent circuit of the power transmission coil 110 and the power reception coil 210. FIG. 12 is a diagram for explaining a variation of the arrangement of the power transmission coil 110. As shown in FIG. FIG. 13A shows an example in which the power transmission coil 110 is disposed along the road surface. FIG. 13B shows an example in which the power transmission coil 110 is disposed on the wall surface orthogonal to the road surface. FIG. 14 is a view schematically showing another example of the power transmission coil 110 and the power reception coil 210. As shown in FIG. FIG. 15A shows a configuration example of a full bridge inverter circuit 160. As shown in FIG. FIG. 15B shows a configuration example of the half bridge inverter circuit 160. FIG. 16A is a schematic view of the wireless power transmission system in an example as viewed from the side of the mobile unit 200. FIG. 16B is a schematic view of the system as viewed from the front of the movable body 200. FIG. 17 is a diagram showing an application example of the wireless power transmission system of the present embodiment. FIG. 18A is a diagram illustrating an example of a configuration of a wireless power transmission system in an exemplary embodiment 2 of the present disclosure. FIG. 18B is a flowchart showing the basic operation of the power transmission control circuit 150 in the second embodiment. FIG. 19 is a view showing an image of a flow of removing the foreign object 400 after the position of the metal foreign object 400 on the power transmission coil is confirmed by the display. FIG. 20 is a flowchart illustrating another example of the operation in the second embodiment. FIG. 21 is a flowchart illustrating another example of the operation in the second embodiment. FIG. 22 is a diagram illustrating still another example of the operation in the second embodiment. FIG. 23 is a diagram illustrating still another example of the operation in the second embodiment. FIG. 24 is a diagram illustrating still another example of the operation in the second embodiment. FIG. 25 is a diagram illustrating still another example of the operation in the second embodiment. FIG. 26 is a diagram illustrating still another example of the operation in the second embodiment. FIG. 27 is a diagram illustrating still another example of the operation in the second embodiment. FIG. 28 is a diagram illustrating still another example of the operation in the second embodiment. FIG. 29 is a diagram illustrating still another example of the operation in the second embodiment. FIG. 30 is a diagram illustrating still another example of the operation in the second embodiment.

(Findings that formed the basis of this disclosure)
Before describing the embodiments of the present disclosure, the findings underlying the present disclosure will be described.

  FIG. 1 is a view schematically showing an example of a wireless power transmission system for supplying power to a mobile unit 200 wirelessly. In this wireless power transmission system, power is wirelessly transmitted from the power transmission coil 110 disposed along the road surface to the power reception coil 210 disposed on the bottom surface of the moving body 200. The moving body 200 is a vehicle driven by an electric motor in this example. The moving body 200 may be, for example, a vehicle such as a bus, a car, a train, an automated guided vehicle (AGV) or the like, but may be a movable object other than the vehicle.

  FIG. 1 shows XYZ coordinates indicating X, Y, Z directions orthogonal to one another. The following description uses the illustrated XYZ coordinates. The traveling direction of the moving body 200 is Y direction, the direction perpendicular to the road surface is Z direction, and the direction perpendicular to the Y direction and the Z direction is X direction. Note that the orientation of the structure shown in the drawings of the present disclosure is set in consideration of the ease of explanation, and does not limit the orientation when the embodiment of the present disclosure is actually implemented. In addition, the shape and size of all or a part of the structure shown in the drawings do not limit the actual shape and size.

  The wireless power transmission system includes a power transmission device and a power reception device. The power transmission device converts the power supplied from the external power supply 300 into AC power of a frequency and voltage suitable for power transmission and outputs the power, a power transmission coil 110 connected to the power transmission circuit 120, and And a thermal sensor 130 (see FIG. 3). The power transmission circuit 120 has components such as an inverter circuit and a power transmission control circuit which are not shown. The power transmission circuit 120 and the power supply 300 may be embedded, for example, under the road surface. The power receiving device is provided to the mobile unit 200. The power receiving device includes components such as a rectifier circuit (not shown) and a power reception control circuit in addition to the power receiving coil 210.

  In this wireless power transmission system, when the mobile unit 200 moves to above the power transmission area 105 and the power transmission coil 110 and the power reception coil 210 face each other, power transmission starts. The power transmission area 105 is an area where the power transmission coil 110 is disposed, and is an area where the power reception coil 210 can be electromagnetically coupled to the power transmission coil 110. The power transmission control circuit included in the power transmission circuit 120 causes the inverter circuit to generate, for example, high frequency AC power, and controls the output of the AC power from the inverter circuit to the power transmission coil 110. That is, the power transmission control circuit 150 causes the inverter circuit to control the AC power output from the power transmission coil 110.

  The power transmission coil 110 generates a magnetic field in the surrounding space by the supplied AC power. The alternating current may simply be called power. The power receiving coil 210 is magnetically coupled to the power transmitting coil 110 by its magnetic field, and receives at least a portion of the transmitted power (energy). The power receiving coil 210 supplies the received power to a load (such as a secondary battery) in the mobile unit 200 via a rectifier circuit (not shown). Thereby, charging and feeding to the moving body 200 are performed.

  However, if the metal foreign object 400 exists on or near the power transmission coil 110, the metal foreign object 400 is heated at the time of power transmission, causing a safety problem. Therefore, various techniques for detecting such metallic foreign matters at the time of power transmission and preventing heating have been proposed up to now.

  For example, Patent Document 1 mentioned above discloses a system for detecting a metal foreign object by a camera mounted on the bottom of a vehicle. According to Patent Document 1, in response to a request for starting contactless power transfer, the metal foreign object detection area above the external coil is imaged by the camera. If it is determined that there is no metallic foreign object based on the image obtained by this imaging, during the non-contact power transfer, the presence or absence of the metallic foreign object in the metallic foreign matter detection region is determined based on the temperature measured by the temperature sensor. Is done. Moreover, the above-mentioned patent document 2 transmits the information obtained by the secondary voltage detection part and the secondary current detection part which were provided in the terminal which is a receiving side from a terminal to a main body, and a main body is based on the said information A method is disclosed to control the power supply to the terminal by determining whether the primary current value to the feed oscillation unit is an overcurrent or not. According to Patent Document 2, even when a metal foreign object is present between the power feeding side and the power receiving side, the power feeding operation can be stopped before the metal foreign substance abnormally generates heat. Besides these techniques, for example, there is also a method of detecting a metal foreign object by detecting an increase in feed loss.

  However, in any of these conventional techniques, detection of a metal foreign object is possible only when the power transmission coil and the power reception coil face each other. That is, a metal foreign object is detected in the state where a vehicle is located on a power transmission coil. Therefore, it is difficult to remove metal foreign matter without moving the vehicle. Further, as in Patent Document 1, in a system in which a metal foreign object is detected by a camera, there is also a problem that it is difficult to determine whether the foreign object on the power transmission coil is, for example, a copper coin or mud. In a general camera, when soil or the like covers a metal foreign object, it is difficult to detect the metal foreign object from above the soil.

  The present inventors found the above problems, and examined a configuration for solving the problems. The present inventors perform preliminary power transmission for metal foreign object detection before the mobile object is located on the power transmission coil, and measure the temperature near the power transmission coil and the power transmission coil with a thermal sensor, so that the metal foreign object I thought that I could detect When detecting a metal foreign object, stopping or reducing the output of power from the power transmission coil, transmitting a signal indicating the presence of the metal foreign object to an external device, or causing the power transmission device to execute a foreign object removing operation This makes it possible to remove the metal foreign matter safely or easily.

  Based on the above consideration, the present inventors have arrived at each aspect of the present disclosure described below.

A control method of a power transmission device according to an aspect of the present disclosure is:
A transmitting coil for outputting power to the receiving coil;
A thermal sensor that measures the surface temperature of metal foreign matter on the power transmission coil;
A method of controlling a power transmission device comprising
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the moving body having the power reception coil and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
If the measured surface temperature of the metal foreign object is equal to or higher than a threshold value, the power transmission coil is caused to decrease or stop the output of power.

According to the above aspect, the control method is
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the moving body having the power reception coil and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
If the measured surface temperature of the metal foreign object is equal to or higher than a threshold value, the power transmission coil is caused to decrease or stop the output of power.

  By this, before the moving body having the power receiving coil and the power transmitting coil overlap, a metal foreign object can be detected, and when the metal foreign object is detected, the power transmission coil reduces the output of power, or Stop it. For this reason, the temperature rise of a metal foreign material can be prevented beforehand. In particular, if the power transmission is stopped before the movable body overlaps the power transmission coil and the movable body is also stopped, it is possible to easily remove the metal foreign matter.

  A cover usually provided on the power transmission coil has deposits such as mud or tire marks, and it may be difficult to identify the presence or absence of metal foreign matter with a normal camera. In addition, in a dark situation such as night, it is more difficult for a normal camera to identify the presence or absence of metal foreign matter. According to the above aspect of the present disclosure, by intentionally raising the surface temperature of the metal foreign object, the metal foreign object can be reliably detected, and therefore the above problem can be solved.

  The first power output from the power transmission coil for metal foreign object detection and the second power for power transmission from the power transmission coil to the power reception coil may be different. In one example, the first power is set to a value smaller than the second power. In a system applied to charge a small device such as a portable terminal, since the power output from the power transmission coil is about several W, the power output from the power transmission coil and the power for detecting a metal foreign object Even if they are equal, metallic foreign matter does not become abnormally hot. However, in a system in which a large amount of power (for example, several kw to several hundreds of kw) is output from a power transmission coil, such as a system for supplying power to a vehicle, the temperature of metallic foreign matter rises rapidly, which is very dangerous. . Therefore, it is effective to make the first power for metal foreign object detection smaller than the second power for power transmission. As a result, when the metal foreign matter is detected, it is possible to prevent the temperature of the metal foreign matter from rising rapidly. The first power may be set, for example, to less than one tenth of the second power. In another example, the first power may be set to less than one hundredth of the second power.

  Generally, the calorific value of the metallic foreign matter changes depending on the material or shape of the metallic foreign matter and the frequency of the power transmitted from the power transmission coil 110 to the power receiving coil 210. Preferably, the frequency of the first power and the frequency of the second power are the same. As a result, before transmitting the second power from the power transmission coil 110 to the power receiving coil 210, the metal foreign object is heated by the first power having the same frequency as the second power, so the heat generation of the metal foreign object by the second power is predicted in advance it can. Even when the magnitude of the first power is equal to the magnitude of the second power, it is preferable that the frequency of the first power and the frequency of the second power be the same frequency.

  As used herein, "mobile" is not limited to a vehicle but refers to any mobile object driven by electrical power. A mobile includes, for example, an electric vehicle provided with an electric motor and one or more wheels. Such a vehicle may be, for example, an Automated Guided Vehicle (AGV), such as the aforementioned transfer robot, or an electric vehicle (EV), an electric cart. The "mobile" in the present disclosure also includes a movable object having no wheel. For example, a biped robot, an unmanned aerial vehicle (UAV, so-called drone) such as a multicopter, and a man-powered electric aircraft are also included in the "mobile".

  In the present specification, "a metal foreign object on a power transmission coil" means a metal foreign object present at a position that can be heated by a magnetic field generated from the power transmission coil. For example, FIG. 2 shows an example of a situation in which a metal foreign object is present on the power transmission coil. In the example of FIG. 2, the power transmission coil 110 is embedded under the road surface, and the metal foreign object 400 is arrange | positioned on the road surface. Arrows in FIG. 2 schematically show a part of magnetic force lines. Even if the metal foreign object 400 is not located immediately above the power transmission coil 110 as in this example, the metal foreign object 400 can be heated by the magnetic field from the power transmission coil 110. The larger the power to be transmitted, the wider the range in which the metal foreign object 400 can be heated. In the present specification, even if the metal foreign object 400 is not located immediately above the power transmission coil 110, the metal foreign object 400 is located on the power transmission coil if the surface temperature of the metal foreign object 400 rises. It shall be. When a metallic foreign matter is present, the area where the surface temperature rises may be referred to as the "target area".

  “The mobile unit having the power receiving coil and the power transmission coil overlap” means that at least a part of the mobile unit having the power receiving coil is located in the area facing the area where the power transmission coil is provided. For example, when the power transmission coil is a flat coil and is disposed along a flat surface such as a road surface or a wall surface, if the moving body overlaps the power transmission coil when viewed from the direction perpendicular to the surface, It can be said that the moving body having a coil and the power transmission coil overlap.

  FIG. 3 shows an example of a situation where the mobile unit 200 and the power transmission coil 110 overlap. In this example, only a part of the mobile unit 200 (the tip of the body of the vehicle) is located in the area facing the area where the power transmission coil 110 is located. In this state, the power receiving coil 210 does not overlap with the power transmitting coil 110, but the mobile unit 200 overlaps with the power transmitting coil 110. In an embodiment of the present disclosure, the power transmission device intentionally heats the metal foreign object 400 and causes the thermal sensor 130 to detect the metal foreign object 400 before such a state occurs. Furthermore, the power transmission device stops or reduces the output power from the power transmission coil 110 when the metal foreign object 400 is detected. This makes it possible to remove the metal foreign object 400 safely and easily.

  It is determined using the thermal sensor 130 or another position sensor whether or not the mobile unit 200 and the power transmission coil 110 overlap. In the example shown in FIG. 3, the thermal sensor 130 detects not only the metal foreign substance 400 but also the position of the moving body 200. The thermal sensor 130 may include, for example, an image sensor that acquires an infrared image near the power transmission coil 110. From the infrared image, in addition to the presence or absence of the metal foreign substance 400, the position of the moving body 200 can also be detected. The power transmission device may include a position sensor that detects the position of the mobile unit 200 in addition to the thermal sensor 130. Such a position sensor may be, for example, a visible light camera, a distance measuring device that measures the distance between the power transmission coil 110 and the moving object 200, and a sensor using GPS. Each sensor is provided at a position where the presence or absence of metal foreign object 400 and the relative position of mobile unit 200 with respect to power transmission coil 110 can be detected with high accuracy.

  FIG. 4 is a flow chart showing the basic operation performed by the power transmission device in the above aspect. This operation is performed by the power transmission control circuit (included in the power transmission circuit 120) that controls the operation of the power transmission device. First, in step S101, the power transmission control circuit causes the power transmission coil to output power before the movable body overlaps the power transmission coil.

  Here, in the specification and drawings of the present disclosure, the phrase “allowing the power transmission coil to output power before the mobile overlaps the power transmission coil” refers to “the mobile having the power receiving coil is the power receiving coil,” as described later. It is an expression equivalent to the meaning of "allowing the power transmission coil to output power before moving to a position where it can be electromagnetically coupled to the power transmission coil and before the mobile body overlaps the power transmission coil. The above expression may be applied to other embodiments.

  Next, in step S102, the power transmission control circuit causes the thermal sensor to start measuring the surface temperature of the metal foreign object. This measurement may be performed, for example, based on the distribution of the temperature in the target area near the power transmission coil. In other words, the power transmission control circuit causes the thermal sensor to monitor the temperature distribution in the target area near the power transmission coil. If a point where the temperature exceeds the threshold is detected in the target area, it can be determined that a metallic foreign matter is present at that point. If it is determined in step S103 that the surface temperature of the metal foreign object is equal to or higher than the threshold value, the power transmission control circuit reduces or stops the output of power from the power transmission coil in step S104.

  If it is determined in step S103 that the surface temperature of the metal foreign object is less than the threshold value, the power transmission control circuit executes the operation of step S103 again. For example, the power transmission control circuit determines in step S103 until transmission of the power requested by the mobile object is completed or until a predetermined time has elapsed from the time (T1) at which the power transmission control circuit causes the power transmission coil to output power. repeat. The transmission control circuit executes the operation of step S104 after the transmission of the power requested by the moving body is completed or after a predetermined time has elapsed from the time (T1) at which the transmission control circuit causes the transmission coil to output the power. . The predetermined time may be set to, for example, a time until the mobile unit overlaps the power transmission coil or longer than a time (T1) at which the power transmission control circuit causes the power transmission coil to output power. The predetermined time may be set to a standard time required to charge the battery mounted on the mobile unit. The predetermined time is not particularly limited as long as it starts from a time (for example, a time earlier than T1 or a time later than T1) related to the time (T1) at which the power transmission coil outputs power.

  By the above operation, it is possible to prevent the heating of the metal foreign matter in advance.

  In the above embodiment, when the surface temperature of the metal foreign matter is equal to or higher than the threshold, it is determined that the metal foreign matter is present, but the following method may be used. First, the power transmission control circuit causes the thermal sensor to measure the surface temperature of the metal foreign matter before the moving body approaches the power transmission coil. The measured temperature is referred to as "measured temperature 1". Next, the power transmission control circuit causes the power transmission coil to output electric power and causes the thermal sensor to measure the surface temperature of the metal foreign substance before the moving body having the power reception coil and the power transmission coil overlap. The measured temperature is referred to as "measured temperature 2". If the difference between the measured temperature 1 and the measured temperature 2 is equal to or greater than the threshold, the power transmission control circuit may determine that there is a metal foreign object.

A foreign matter detection method according to another aspect of the present disclosure is
The power transmission device
An inverter circuit that generates power;
A power transmission coil for outputting electric power to a power reception coil of the mobile unit;
A thermal sensor that measures the surface temperature of metal foreign matter on the power transmission coil;
A power transmission control circuit for controlling the power output from the power transmission coil in the inverter circuit;
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the movable body and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold, a signal indicating the presence of the metal foreign object is transmitted from the power transmission device to a receiver having a function of receiving the signal other than the power transmission device.

  According to the above aspect, the foreign matter detection method has a function of receiving the signal indicating the presence of the metal foreign matter other than the power transmission device when the measured surface temperature of the metal foreign matter is equal to or higher than a threshold. Send to the receiver. In the present specification and drawings of the present disclosure, "a receiver having a function of receiving the signal" may be referred to as "another device".

  Thus, when a metallic foreign matter is detected, the party can be notified of the presence of the metallic foreign matter via another device. The “other device”, which is a transmission destination of a signal indicating the presence of a metal foreign object, controls, for example, an information device mounted on a mobile, an information device owned by a user of a mobile or a manager, or a power transmission device It may be a controller. The “other device” may include, for example, a car navigation system, a smartphone, a tablet computer, a mobile (for example, a vehicle or a robot), or a computer (or a controller) mounted on a control device that controls a power transmission device. Based on the transmitted signal, the user or manager of the mobile body can notice the presence of the metallic foreign matter and can promptly take action to remove the metallic foreign matter. If the power transmission device is installed at, for example, a parking lot and controlled by a system of a manager's office or a central monitoring room, the "other device" may be a controller (controller) in the system. Based on the transmitted signal, the administrator of the power transmission device can grasp the presence of the metal foreign object and promptly take action such as dispatching a cleaning worker to remove the metal foreign object.

The “signal indicating the presence of the metallic foreign matter” may include information indicating the position of the metallic foreign matter on the power transmission coil, in addition to the information indicating the presence or absence of the metallic foreign matter. The position of the metallic foreign matter may be measured by a thermal sensor or other sensor. The power transmission control circuit in the power transmission device may transmit, for example, information indicating the relative positional relationship between the power transmission coil and the metal foreign object to another device such as a smartphone, when the metal foreign object is detected. The device that has received the information may display, for example, an image indicating the relative positional relationship between the power transmission coil and the metal foreign object on the display. According to such an aspect, the party can easily identify the position of the metal foreign object based on the displayed image and can quickly remove the detected metal foreign object.

  That is, in the foreign matter detection method according to the above aspect, when the measured surface temperature of the metal foreign matter is equal to or higher than the threshold value, the presence of the metal foreign matter from the power transmission device to the reception device having the function of receiving the signal other than the power transmission device. Send a signal indicating. The foreign object detection method is executed by, for example, a power transmission control circuit of a power transmission device. The foreign object detection method is executed, for example, by the power transmission control circuit of the power transmission device included in the wireless power transmission system. The above foreign matter detection method may be applied to other embodiments.

  FIG. 5 is a flowchart showing the basic operation performed by the power transmission device in this aspect. This operation is performed by the power transmission control circuit that controls the operation of the power transmission device. The operations of steps S111 to S113 are the same as the operations of steps S101 to S103 in FIG. In the example of FIG. 5, when it is determined that a metal foreign object is present, the power transmission control circuit transmits a signal indicating the presence of the foreign object to another device other than the power transmission device (step S114).

  As a result, the party can be notified of the presence of the metal foreign substance through another device that has received the signal, and rapid foreign substance removal becomes possible.

  In the example shown in FIG. 5, the power transmission stop or the output power reduction operation in step S104 of FIG. 4 may be performed together. As a result, it is possible to obtain both the effect of suppressing the heating of the metal foreign object and the effect of notifying the party of the presence of the foreign object.

  In the embodiment of the present disclosure, the detected foreign matter may be removed by a foreign matter removing mechanism provided in at least one of the power transmission device and the moving body. The "foreign matter removing mechanism" means any mechanism capable of removing foreign matter located in the vicinity of the power transmission coil. The foreign matter includes a foreign matter containing metal and a foreign matter not containing metal. Foreign matter containing metal is called metallic foreign matter. The power transmission device may include, for example, a foreign matter removing mechanism that changes the tilt by lifting a part of the cover covering the power transmission coil and drops the foreign matter to slide. Another example of the foreign matter removal mechanism may be a mechanism that sweeps out foreign matter using a wiper or a brush provided on the bottom of a moving body (for example, a vehicle) or a power transmission device. In addition, for example, a mechanism that blows a strong wind by a compressor to blow away foreign substances or sucks in foreign substances by a strong suction force can be used as the foreign substance removal mechanism. Examples of such foreign matter removal mechanisms are disclosed, for example, in Japanese Patent Application Laid-Open Nos. 2013-48511 and 2013-59239 (or US Patent Application Publication No. 2014/239735). The disclosure content of these documents is incorporated in its entirety into the specification of the present disclosure.

  FIG. 6 is a flowchart showing an example of the operation of removing metal foreign matter by the foreign matter removing mechanism provided in at least one of the power transmission device and the moving object. The operations in steps S121 to S123 in FIG. 6 are the same as the operations in steps S101 to S103 in FIG. In the example of FIG. 6, when a metal foreign object is detected, the power transmission control circuit causes the foreign object removing mechanism in the power transmission device and / or the moving object to execute the foreign object removing operation (step S124). Thereby, it is possible to remove metal foreign matters quickly.

  Hereinafter, more specific embodiments of the present disclosure will be described. However, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters and redundant description of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. It is noted that the inventors provide the attached drawings and the following description so that those skilled in the art can fully understand the present disclosure, and intend to limit the claimed subject matter by these is not. In the following description, the same or similar components are given the same reference numerals.

(Embodiment 1)
FIG. 7 is a perspective view schematically showing a configuration of a wireless power transmission system in an exemplary embodiment 1 of the present disclosure. The wireless power transfer system is used for powering an electric vehicle on a road, for example, a road or a parking lot. The wireless power transmission system includes a power transmission device and a mobile unit 200. The power transmission device includes a power transmission circuit 120, a power transmission coil 110, a thermal sensor 130, and a position sensor 140. In the present embodiment, the thermal sensor 130 and the position sensor 140 are disposed above the power transmission area 105 (under the roof). The thermal sensor 130 and the power transmission circuit 120 and the position sensor 140 and the power transmission circuit 120 are wirelessly connected. Thus, the power transmission device may be a collection of spatially separated components. The thermal sensor 130 and the power transmission circuit 120 and the position sensor 140 and the power transmission circuit 120 may be connected by wire.

  The mobile unit 200 is a vehicle such as a bus, for example, and includes a power receiving coil 210 on the bottom surface.

  FIG. 8 is a block diagram showing the configuration of the wireless power transmission system in the present embodiment. The power transmission device 100 includes a communication circuit 170 in addition to the power transmission coil 110, the power transmission circuit 120, the thermal sensor 130, and the position sensor 140 described above. The power transmission circuit 120 includes an inverter circuit 160 and a power transmission control circuit 150. The inverter circuit 160 is connected between the external power supply 300 and the power transmission coil 110. The inverter circuit 160 converts DC power supplied from the power supply 300 into AC power and supplies the AC power to the power transmission coil 110. The power transmission control circuit 150 controls the inverter circuit 160, the communication circuit 170, the thermal sensor 130, and the position sensor 140. The power transmission control circuit 150 controls conduction / non-conduction of a plurality of switching elements in the inverter circuit 160, for example, to output AC power of a desired frequency and voltage. The communication circuit 170 transmits and receives signals to and from the communication circuit 270 in the mobile unit 200. The thermal sensor 130 detects metal foreign matter in the vicinity of the power transmission coil 110. The position sensor 140 serves to measure the position of the metallic foreign matter and further to measure the position of the moving body 200.

  The moving body 200 includes a power receiving coil 210, a rectifier circuit 220, a power receiving control circuit 230, a secondary battery 240, a communication circuit 270, an electric motor 260, and a motor inverter 250. The rectifier circuit 220 is connected to the power receiving coil 210, converts AC power output from the power receiving coil 210 into DC power, and outputs the DC power. The electric motor 260 is a motor for driving the moving body 200, and is driven by, for example, three-phase AC power. The motor inverter 250 converts the supplied DC power into three-phase AC power and supplies it to the electric motor 260. Power reception control circuit 230 performs control of charging secondary battery 240 with DC power output from rectification circuit 220 and control of motor inverter 250 and communication circuit 270.

  When the storage amount of the secondary battery 240 decreases, the moving body 200 in the present embodiment approaches the power transmission area 105 in which the power transmission coil 110 is disposed for charging. When the metal foreign object 400 is not detected in the vicinity of the power transmission coil 110, the power transmission control circuit 150 drives the inverter circuit 160 to start power transmission. The power transmitted by magnetic field coupling between power transmission coil 110 and power reception coil 210 is stored in secondary battery 240. When charging of the secondary battery 240 is completed, the moving body 200 drives the motor 260 by the power stored in the secondary battery 240 to resume traveling.

  However, as shown in FIG. 7, when the metal foreign matter 400 is present in the vicinity of the power transmission coil 110, the metal foreign matter 400 is heated and is dangerous. Therefore, the power transmission device 100 according to the present embodiment detects the metal foreign object 400 using the thermal sensor 130 before the moving body 200 reaches the area on the power transmission coil 110. And when the metal foreign material 400 is detected, the power transmission from the power transmission coil 110 is stopped or output power is reduced.

  The thermal sensor 130 can be realized, for example, by the same configuration as an infrared camera. The thermal sensor 130 measures the temperature of the target area by detecting the amount of infrared light emitted from the object, for example, by one or more detectors sensitive to infrared light. The above measurement method by the thermal sensor 130 is also called infrared thermography. If the thermal sensor 130 is a single detector (including a photodiode, for example), the entire object is measured. When the thermal sensor 130 is implemented by an image sensor such as a two-dimensional CCD or CMOS, it is preferable because the temperature distribution of the object can be measured in two dimensions.

  In the example shown in FIG. 7, the information on the temperature measured by the thermal sensor 130 is wirelessly sent to the power transmission control circuit 150.

  In the present embodiment, in addition to the thermal sensor 130, a position sensor 140 is further provided. The position sensor 140 measures the position of the mobile unit 200 using, for example, light, radio waves, pressure, sound waves and the like. The position sensor 140 may be, for example, a normal image sensor or a distance measuring device such as a TOF sensor. Position sensor 140 may also be a pressure sensitive sensor. Such a pressure sensor may be disposed on the path of the mobile unit 200. In the present embodiment, the position sensor 140 is disposed independently of the thermal sensor 130, but these may be realized by one sensor. For example, the thermal sensor 130 may double as the function of the position sensor 140.

  Hereinafter, with reference to FIG. 9, the operation in the present embodiment will be described in more detail.

  FIG. 9 is a flowchart showing a basic flow of the operation performed by the power transmission control circuit 150. The power transmission control circuit 150 causes the power transmission coil 110 to output weak power (first power) before the moving body 200 overlaps the power transmission coil 110 (step S151). Next, the power transmission control circuit 150 causes the thermal sensor 130 to measure the temperature of the target area including the power transmission coil 110 (step S152). Step S152 is the same operation as step S102 in FIG. If there is a place where the temperature is equal to or higher than a predetermined threshold value in the target area, it can be determined that the metal foreign object 400 exists in the place (step S153). This threshold may be set, for example, to a value of 50 degrees Celsius or more and 100 degrees or less. For example, temperatures may be set such as 60 degrees, 70 degrees, 80 degrees, or 90 degrees. The presence or absence of the metallic foreign matter may be determined based on the difference between the surface temperature before power transmission and the surface temperature after power transmission. In this case, the value of the temperature difference (for example, 10 degrees) is the threshold. If the power transmission control circuit 150 determines that the metal foreign object 400 is present, the power transmission control circuit 150 stops or reduces the output of power (first power) from the power transmission coil 110 by stopping control of the inverter circuit 160 or changing the switching timing ( Step S154).

  In step S151, it is determined whether the mobile unit 200 overlaps the power transmission coil 110 or not. This determination is made based on the output from the position sensor 140. The power transmission control circuit 150 constantly monitors the relative positional relationship between the power transmission coil 110 and the mobile unit 200 based on the output from the position sensor 140. If it is determined that the distance between the moving body 200 and the power transmission coil 110 is shorter than a predetermined distance, the power transmission control circuit 150 controls the inverter circuit 160 to cause the power transmission coil 110 to output the first power. Thereby, detection of the metal foreign object 400 by the thermal sensor 130 becomes possible.

  FIG. 10 is a flowchart showing a more detailed example of the operation of the power transmission control circuit 150. The power transmission control circuit 150 determines whether the mobile unit 200 overlaps the power transmission coil 110 based on the output from the position sensor 140 (step S200). Here, the meaning of "determining whether the mobile unit 200 overlaps the power transmission coil 110" means that the mobile unit and the power transmission coil overlap before the power receiving coil and the power transmission coil are electromagnetically coupled. It means that "judge". If this determination is NO, as described above, the power transmission control circuit 150 causes the power transmission coil 110 to output the first power (step S201). Next, the power transmission control circuit 150 causes the thermal sensor 130 to measure the temperature of the target area of the power transmission coil 110 (step S202). Then, it is determined whether there is a portion where the temperature is equal to or higher than the threshold (step S203). If this determination is YES, the power transmission control circuit 150 stops or reduces the output of the first power from the power transmission coil 110 (step S204). If the determination in step S203 is NO, the process returns to step S200, and steps S200 to S203 are repeated until the moving body having the power receiving coil overlaps the power transmitting coil or a metal foreign object is detected. In addition, the timing which detects a metal foreign material may be regular, and may be irregular.

  If it is determined in step S200 that the moving body 200 overlaps the power transmission coil 110, the power transmission control circuit 150 determines whether the power receiving coil 210 faces the power transmission coil 110 (step S210). If this determination is YES, the power transmission control circuit 150 causes the power transmission coil 110 to output the second power (step S211). This starts charging. As described above, the second power is larger than the first power for detecting foreign matter. The second power may be set to, for example, 10 times or more, and in one example, 100 times or more of the first power. The second power may be set, for example, to a value in the range of several kW to several hundred kW. On the other hand, the first power can be set to, for example, a value within the range of several tens of watts to several tens of kW. When the charging is completed in step S212, the power transmission control circuit 150 stops the control of the inverter circuit 160 to cause the power transmission coil 110 to stop outputting the second power (step S213). By the above operation, charging of the mobile unit 200 is completed.

  As described above, in the present embodiment, when the surface temperature of the metal foreign object detected by the thermal sensor 130 is equal to or higher than the threshold, the power transmission control circuit 150 causes the power transmission coil 110 to stop the output of power or output power. Reduce. In addition, when the metallic foreign matter is not detected and the moving body moves to a position where the power receiving coil 210 can be electromagnetically coupled to the power transmitting coil 110, the power transmitting coil 110 is caused to output the second power. According to such an operation, before performing power transmission to the moving body 200, a metal foreign object can be found in advance, and the metal foreign object can be removed safely.

  That is, according to the control method of the present embodiment, power transmission is performed before the mobile body having the power reception coil moves to a position where the power reception coil and the power transmission coil can be electromagnetically coupled and before the mobile body overlaps the power transmission coil. The power is output to the coil, the surface temperature of the metal foreign object is measured by the thermal sensor, and when the measured surface temperature of the metal foreign object is equal to or higher than the threshold, the power transmission coil is decreased or stopped.

  The control method is executed by, for example, a power transmission control circuit included in the power transmission device. The control method is executed, for example, by the power transmission control circuit of the power transmission device of the wireless power transmission system. The above control method may be applied to other embodiments.

  Next, each component in the present embodiment will be described in more detail.

  FIG. 11A is a view showing an example of an equivalent circuit of the power transmission coil 110 and the power reception coil 210. As shown, each coil 110, 120 functions as a resonant circuit having an inductance component and a capacitance component. By setting the resonance frequencies of the coils 110 and 120 to close values, power can be transmitted with high efficiency. AC power is supplied to the power transmission coil 110 from the inverter circuit 160. Electric power is transmitted to the power receiving coil 210 by the magnetic field generated from the power transmission coil by this AC power. In this example, both the transmitting coil 110 and the receiving coil 210 function as a series resonant circuit.

  FIG. 11B is a diagram illustrating another example of the equivalent circuit of the power transmission coil 110 and the power reception coil 210. In this example, the power transmission coil 110 functions as a series resonance circuit, and the power reception coil 210 functions as a parallel resonance circuit. In addition to these examples, the power transmission coil 110 may function as a parallel resonance circuit, and the power reception coil 210 may function as a series resonance circuit.

  Each coil may be, for example, a flat coil or a laminated coil, or a winding coil using a copper wire, a litz wire, or a twist wire. Each capacitance component in the resonant circuit may be realized by the parasitic capacitance of each coil, or a capacitor having, for example, a chip shape or a lead shape may be separately provided.

  The resonant frequency f0 of the resonant circuit is typically set to coincide with the transmission frequency f during power transmission. The resonant frequency f0 of each of the resonant circuits may not exactly match the transmission frequency f. Each resonance frequency f0 may be set, for example, to a value within the range of about 50 to 150% of the transmission frequency f. The transmission frequency f may be set to, for example, 50 Hz to 300 GHz, more preferably 20 kHz to 10 GHz, still more preferably 20 kHz to 20 MHz, and still more preferably 20 kHz to 7 MHz.

  Although a resonant circuit is used in the present embodiment, an electromagnetic induction method that does not use resonance or a method that uses microwaves may be used.

  FIG. 12 is a diagram for explaining a variation of the arrangement of the surface (upper surface) of the power transmission coil 110. Three variations are shown in FIG. In any of these examples, the power transmission coil 110 is covered with a cover member 112 made of, for example, a resin. In the example of (a) of FIG. 12, the surface of the power transmission coil 110 is arrange | positioned on the road surface. In the example of FIG. 12B, the surface of the power transmission coil 110 is disposed at a height substantially equal to the road surface. In the example of (c) of FIG. 12, the surface of the power transmission coil 110 is arrange | positioned under the road surface. The arrangement of the surface of power transmission coil 110 may be any of these arrangements. Also, the surface of the resin cover member 112 may be disposed above the road surface, at a height approximately equal to the road surface, and at any position below the road surface.

  In the present embodiment, the power transmission coil 110 is disposed along the road surface, but may be disposed along a surface (for example, a wall surface) other than the road surface.

  13A and 13B are diagrams showing an arrangement example of the power transmission coil 110 and the power reception coil 210. FIG. FIG. 13A shows an example in which the power transmission coil 110 is disposed along the road surface. Such a configuration is suitable for feeding power to a vehicle such as an electric vehicle having the power receiving coil 210 on the bottom surface as in the present embodiment. On the other hand, FIG. 13B shows an example in which the power transmission coil 110 is disposed on a wall surface intersecting (orthogonally in the illustrated example) the road surface. In such an example, the power receiving coil 210 may also be provided on the surface intersecting the wall surface (for example, the side surface of the moving body 200). Thus, the power transmission coil 110 and the power reception coil 210 do not have to be disposed parallel to the road surface.

  FIG. 14 is a view schematically showing another example of the power transmission coil 110 and the power reception coil 210. As shown in FIG. In this example, the power transmission coil 110 and the power reception coil 210 are respectively configured by windings wound around the magnetic members 190 and 290. The two magnetic members 190, 290 have symmetrical shapes, and the end faces of the two opposite ends face each other. Such a structure also enables power transmission using electromagnetic induction (magnetic field coupling). The two magnetic members 190 and 290 may have an asymmetrical shape.

  15A and 15B are diagrams showing configuration examples of the inverter circuit 160. FIG. FIG. 15A shows a configuration example of a full bridge inverter circuit 160. As shown in FIG. In this example, the power transmission control circuit 150 controls the on / off of the four switching elements S1 to S4 included in the inverter circuit 160 to set the input DC power to the desired frequency f and voltage V (effective value). Convert to AC power. FIG. 15B shows a configuration example of the half bridge inverter circuit 160. In this example, the power transmission control circuit 150 controls the on / off of the two switching elements S1 and S2 included in the inverter circuit 160 to set the input DC power to the desired frequency f and voltage V (effective value). Convert to AC power. The inverter circuit 160 may have a structure different from that shown in FIGS. 15A and 15B. For example, an oscillation circuit such as class E may be used.

  The power transmission control circuit 150 and the power reception control circuit 230 may be realized by a circuit including a processor and a memory, such as a microcontroller unit (MCU). By executing the computer program stored in the memory, various controls can be performed. The power transmission control circuit 150 and the power reception control circuit 230 may be configured by dedicated hardware configured to execute the operation of the present embodiment.

  The communication circuits 170 and 270 can transmit and receive signals using, for example, known wireless communication technology, optical communication technology, or modulation technology (such as frequency modulation or amplitude modulation). The communication method by the communication circuits 170 and 270 is arbitrary and is not limited to a specific method.

  The electric motor 260 may be a three phase alternating current driven motor, such as a permanent magnet synchronous motor or an induction motor. The motor 260 may be another type of motor such as a direct current motor. In that case, a motor drive circuit according to the structure of the motor 260 is used instead of the motor inverter 250 which is a three-phase inverter circuit.

  Power supply 300 may be any power supply that outputs DC power. The power supply 300 is, for example, a commercial power supply, a primary battery, a secondary battery, a solar battery, a fuel cell, a USB (Universal Serial Bus) power supply, a high-capacity capacitor (for example, an electric double layer capacitor), voltage conversion connected to a commercial power supply. It may be any power source such as

  Secondary battery 240 may be any secondary battery such as, for example, a lithium ion battery, a nickel hydrogen battery, or a lead battery. Instead of the secondary battery 240, a large capacity capacitor (for example, an electric double layer capacitor or the like) may be used.

  Next, an exemplary arrangement of the thermal sensor 130 and the position sensor 140 will be described with reference to FIGS. 16A and 16B. FIG. 16A is a schematic view of the wireless power transmission system in an example as viewed from the side of the mobile unit 200. FIG. 16B is a schematic view of the system as viewed from the front of the movable body 200. As shown to FIG. 16A, the thermal sensor 130 and the position sensor 140 in this example are arrange | positioned rather than the position of the power transmission coil 110 in the front side (front) of the mobile body 200. As shown in FIG. By arranging in this manner, it is possible to detect the metal foreign object and the moving body 200 until immediately before the moving body 200 overlaps the power transmission coil 110. Further, as shown in FIG. 16B, the thermal sensor 130 and the position sensor 140 (not shown) are provided such that the coordinate in the X direction substantially coincides with the center of the moving body 200 or the center of the power transmission coil 110. Such an arrangement is suitable for more accurately measuring the position of the foreign object and the moving body 200.

  FIG. 17 is a diagram showing an application example of the wireless power transmission system of the present embodiment. In this example, a wireless power transfer system is utilized for a three-dimensional parking lot. A thermal sensor 130 is disposed on the ceiling of each floor of the three-dimensional parking lot. Although not shown in FIG. 17, a position sensor 140 is also disposed on the ceiling of each floor. A power transmission coil 110 is disposed on the floor of each floor. Since the thermal sensor 130 and the position sensor 140 are disposed at a position higher than the moving body 200, it is easy to detect the metallic foreign matter and the moving body 200. Thus, the wireless power transmission system of this embodiment is suitable for a parking lot with a roof as shown in FIG.

  In FIG. 17, when the mobile unit 200 parks backward, the thermal sensor 130 may be disposed behind the mobile unit 200.

Second Embodiment
Next, a wireless power transmission system in an exemplary embodiment 2 of the present disclosure will be described. The wireless power transmission system according to the present embodiment is different from that of the first embodiment in that when a metal foreign object is detected, the presence of the metal foreign object is notified to devices other than the power transmission device. Such an operation can notify the party of the presence of the metallic foreign matter, and can quickly remove the metallic foreign matter. There are a great many variations in the operation of the present embodiment after notifying other devices of the presence of the metallic foreign matter. The main ones of these variations will be described below. In the following examples of the present embodiment, similarly to the first embodiment, control may be performed to stop power transmission or reduce output power when a metal foreign object is detected. The configurations of the power transmission device 100 and the mobile unit 200 in the present embodiment are basically the same as the configurations of the first embodiment. However, in the present embodiment, at least one of the power transmission device 100 and the mobile unit 200 may include the aforementioned “foreign substance removing mechanism”. FIG. 18A is a diagram showing an example of such a configuration. In this example, the power transmission device 100 and the mobile unit 200 have the foreign matter removing mechanisms 180 and 280, respectively. The structures of these foreign matter removing mechanisms 180 and 280 are various as described above, and any structure capable of removing the foreign matter can be adopted.

  FIG. 18B is a flowchart showing the basic operation of the power transmission control circuit 150 in the present embodiment. Steps S301 to S303 are the same as the operations of steps S151 to S153 in FIG. In this example, when a metal foreign object is detected, the power transmission control circuit 150 transmits a signal indicating the presence or position of the metal foreign object to another device other than the power transmission apparatus 100 in step S304. The thermal sensor 130 can specify the position of the metallic foreign matter on the transmission coil based on the measured temperature distribution. The other device may be, for example, a smartphone of a driver of the mobile unit 200 or a device such as a car navigation system mounted on the mobile unit 200. Another device may be a server computer in a manager's office or a central monitoring room that manages the power transmission device 100. The device that has received the signal indicating the presence of the metal foreign object causes, for example, the display to display an image indicating the presence of the metal foreign object. As a result, for example, the driver of the mobile unit 200 or the administrator of the power transmission apparatus 100 (sometimes referred to collectively as the "party") notices the presence of the metal foreign object, removes the metal foreign object by itself, or Can be dispatched and removed. Thus, power transmission can be safely started.

  FIG. 19 is a view showing an image of a flow of removing the metal foreign object 400 after the position of the metal foreign object 400 on the power transmission coil is confirmed by the display. As shown in FIG. 19, an image capable of grasping the positional relationship between the power transmission coil 110 and the metal foreign object 400 may be displayed on the display of another device. The party can remove the metal foreign substance 400 while looking at this screen. In addition, the hand of the person who is going to remove a foreign material is also displayed on FIG. Such display of the hand may or may not actually be displayed.

  Since the surface temperature of the metallic foreign matter 400 may be high, a tool may be used to remove the metallic foreign matter 400 to prevent burns.

  Subsequently, an example in which at least one of the power transmission device 100 and the mobile unit 200 performs the foreign matter removing operation will be described. As described above, at least one of the power transmission device 100 and the mobile unit 200 may have a foreign matter removal mechanism. When the surface temperature of the metal foreign object measured by the thermal sensor 130 is equal to or higher than the threshold value, the power transmission control circuit 150 in the power transmission device 100 performs the foreign substance removing operation on the foreign substance removing mechanism in at least one of the power transmitting device 100 and the moving body 200. Let Hereinafter, specific examples will be described.

  FIG. 20 is a flowchart showing another example of the operation in this embodiment. In this example, the moving body 200 includes the above-described foreign matter removing mechanism, and executes the operation of removing the foreign matter. When the moving body 200 approaches the position where it approaches the power transmission coil 110 (step S331), the power supply of the power transmission device 100 is turned on (step S332). Then, the power transmission control circuit 150 causes the power transmission coil to output power (step S333). Next, the power transmission control circuit 150 measures the surface temperature of the metal foreign object by the thermal sensor (step S334). And it is judged whether temperature is more than a threshold (step S335). If this determination is YES, the power transmission control circuit 150 notifies the communication circuit 170 of a signal indicating the presence of the metal foreign object to the moving body 200 (step S336). When the mobile unit 200 receives this notification (step S 337), the mobile unit 200 moves to the vicinity of the power transmission coil 110 and executes the foreign matter removing operation (step S 338). The foreign matter removing operation may be, for example, an operation of sweeping out foreign matter with a wiper or a brush provided on the bottom surface of the moving body 200, blowing away by strong wind, or sucking in the foreign matter as described above. After the foreign matter removing operation is completed, the noncontact charging process described in the first embodiment is performed (step S339).

  FIG. 21 is a flowchart showing another example of the operation in this embodiment. In this example, the power transmission device 100 includes the above-described foreign matter removing mechanism, and executes the operation of removing the foreign matter. The operations from step S341 to step S345 are the same as the operations from step S331 to step S335 in FIG. When the metallic foreign matter is detected, in step S346, the power transmission control circuit 150 causes the foreign matter removing mechanism to execute the foreign matter removing operation (step S346). As described above, the foreign matter removing operation may be an operation of sweeping out foreign matter with, for example, a wiper or a brush provided in the vicinity of the power transmission coil 110, blowing away with strong wind, or tilting the cover of the power transmission coil 110. Accordingly, when the metal foreign matter is removed, the power transmission control circuit 150 notifies of a signal indicating that the metal foreign matter removal is completed (step S347). When mobile unit 200 receives this notification (step S348), the non-contact charging process is started (step S349).

  FIG. 22 is a diagram showing still another example of the operation in the present embodiment. The operations from steps S351 to S358 in this example are the same as the operations from steps S331 to S338 in the example of FIG. The difference is that the moving body 200 detects the presence or absence of a metal foreign substance in step S359 after performing the foreign substance removing operation. There are cases where metal foreign matter can not be completely removed by performing the foreign matter removal operation only once. Therefore, in this example, after the foreign matter removal operation, the presence or absence of the metal foreign matter is confirmed, and if the metal foreign matter is not removed, the foreign matter removal operation is executed again (step S360). Foreign metal detection by the mobile unit 200 can be performed, for example, by measuring the efficiency of power transmission. For example, after the foreign matter removal operation is performed, power transmission is performed on a trial basis, and it can be determined that a metallic foreign matter is present when the transmission efficiency is greatly reduced compared to the efficiency in the normal operation. In step S360, when removal of the metal foreign matter is confirmed, a non-contact charging process is performed (step S361). If it is determined YES in step S360 even if the processes of steps S358 to S360 are repeated a plurality of times, the power reception control circuit 230 or the power transmission control circuit 150 transmits a signal indicating that metal foreign matter can not be removed, such as a smartphone registered in advance. It may be sent to another device. Thereby, the parties can be notified of the presence of the metallic foreign matter.

  FIG. 23 is a diagram showing still another example of the operation in the present embodiment. The operations from steps S371 to S377 in this example are the same as the operations from steps S351 to S357 in the example of FIG. In this example, after the power transmission device 100 performs the foreign matter removing operation, the metal foreign matter detecting operation is performed, and the foreign matter removing operation is repeated until the metal foreign matter is completely removed (steps S378 to S380). The confirmation of the removal of the metal foreign matter in steps S379 and S380 may be performed based on the reduction rate of the power transfer efficiency as described above. When the removal of the foreign matter is confirmed, the power transmission apparatus 100 notifies the mobile body 200 of a signal indicating that the foreign matter removal is completed (step S381). After the mobile unit 200 receives this notification (step S382), a noncontact charging process is performed (step S383). If it is determined YES in step S380 even if the processes of steps S378 to S380 are repeated a plurality of times, the power transmission control circuit 150 transmits a signal to the effect that metal foreign matter can not be removed to another device such as a smartphone registered in advance. You may Thereby, the parties can be notified of the presence of the metallic foreign matter. As described above, the power transmission control circuit 150 may detect whether or not the metal foreign substance is actually removed after the foreign substance removing operation is performed, and may transmit a signal indicating the detection result to another device.

  In the examples of FIGS. 20 to 23, only one of the power transmission device 100 and the moving body 200 performs the foreign matter detection operation, but both the power transmission device 100 and the moving body 200 may perform the foreign matter detection operation. Hereinafter, an example of such an operation will be described.

  FIG. 24 is a diagram showing still another example of the operation in the present embodiment. The operations from steps S401 to S410 in this example are the same as the operations from steps S351 to S360 in the example of FIG. In this example, the moving body 200 first performs the foreign matter removing operation (step S408). Thereafter, the power reception control circuit 230 in the mobile unit 200 confirms whether or not the metal foreign matter has been removed normally (steps S409 and S410). When removal of the metal foreign material can not be confirmed, a signal to that effect is transmitted to the power transmission device 100, and the power transmission device 100 performs the foreign material removal operation (step S411). Then, the power transmission device 100 confirms whether the metal foreign matter has been removed normally (steps S412 and S413). When removal of the metal foreign object is confirmed, the non-contact charging process is started (step S414). If the removal of the metal foreign object is not confirmed, the power transmission control circuit 150 transmits a signal (warning) to the other device to the effect that the metal foreign object could not be removed (step S415). Thereafter, removal of the metal foreign matter is performed manually.

  FIG. 25 is a diagram showing still another example of the operation in the present embodiment. In this example, the power transmission device 100 performs the foreign matter removing operation first (step S428), and when the metallic foreign matter can not be removed still, the moving body 200 performs the foreign matter removing operation (step S431). If the metal foreign object is not removed even by the foreign object removing operation of the moving body 200 (YES in step S433), a warning is sent to the other devices than the power transmission device 100 (step S435). The other points are the same as the operation in FIG.

  As in the examples shown in FIGS. 24 and 25, each of the power transmission device 100 and the mobile unit 200 can have a foreign matter removal mechanism. The power transmission control circuit 150 in the power transmission apparatus 100 causes the foreign substance removal mechanism in one of the power transmission apparatus 100 and the moving body 200 to execute the foreign substance removal operation when the measured surface temperature of the metal foreign substance is equal to or higher than the threshold. After the foreign matter removing operation is performed, the power transmission control circuit 150 detects whether or not the metal foreign matter is actually removed. Then, when the metal foreign matter is not removed, the foreign matter removing mechanism in the other of the power transmission device 100 and the moving body 200 is caused to execute another foreign matter removing operation. Such an operation can more reliably remove metal foreign matter.

  FIG. 26 is a diagram showing still another example of the operation in the present embodiment. In this example, when the surface temperature of the metal foreign object is equal to or higher than the threshold, the power transmission control circuit 150 transmits the position information of the metal foreign object on the power transmission coil to another device (for example, a smartphone, a car navigation system, or It transmits to the server computer in the monitoring room (step S446). When receiving the position information, the other device displays an image indicating the position information of the foreign matter on the power transmission coil on the display (step S 447). Thereby, the user or the manager can recognize the presence of the metal foreign matter and the position on the power transmission coil. In this example, the user can issue a command to turn off the power transmission apparatus 100 or a command to decrease the power output, for example, via a smartphone or other device such as a car navigation system. In step S448, when such a command is received, the other device transmits, to the power transmission device 100, a signal to turn off the power or a signal to decrease the output of power (step S449). In response to the signal, the power transmission control circuit 150 in the power transmission apparatus 100 turns off the power (stops the output power) or reduces the output power (step S450). This can prevent further heating of the metallic foreign matter. Thereafter, metal foreign matter is removed manually or the like (step S451).

  FIG. 27 is a diagram showing still another example of the operation in the present embodiment. In the operation in this example, the moving body 200 performs the foreign matter removing operation as in the operation shown in FIG. The difference from the example of FIG. 22 is that the power transmitting apparatus 100 notifies the mobile unit 200 of positional information of the metallic foreign object on the power transmission coil (step S 486), and the mobile unit 200 aligns the power transmission coil 110 and the power receiving coil 210. After performing (steps S488 and S489), the foreign matter removing operation is performed based on the position information of the metallic foreign matter on the power transmission coil (step S490). If removal of the metal foreign matter is not confirmed, the other device is warned. (Step S494). The operations in steps S481 to S486, S491, S492, and S493 are the same as the corresponding steps in FIG. Here, the alignment between the power transmission coil 110 and the power reception coil 210 in steps S 488 and S 489 is an operation for moving the power reception coil 210 and the power transmission coil 110 by moving the moving body 200. As a result, in the subsequent step S 490, the metal foreign matter is easily removed based on the position information of the metal foreign matter on the power transmission coil. The foreign matter removing mechanism in the moving body 200 reliably removes the metal foreign matter by selectively sweeping out or suctioning a region where the metal foreign matter is presumed to exist, based on the position information of the metal foreign matter on the power transmission coil. It is possible to improve the quality.

  FIG. 28 is a diagram showing still another example of the operation in the present embodiment. In this example, not the mobile unit 200 but the power transmission device 100 removes metal foreign matter based on the position information (step S510). Except for this point, the operation is the same as that shown in FIG. In this example, the foreign matter removing mechanism in the power transmission device 100 performs the foreign matter removing operation mainly on the area where the metal foreign matter is estimated to exist, based on the position information of the metal foreign matter on the power transmission coil. Thereby, the certainty of the removal of the metal foreign matter can be improved.

  FIG. 29 is a diagram showing still another example of the operation in the present embodiment. In this example, the foreign matter removing operation is performed on both the power transmission device 100 and the moving body 200. First, the moving body 200 performs the foreign matter removing operation by the same operation as the operation in FIG. 27 (step S530). If the metal foreign object can not be removed also by this operation (YES in step S531), the power transmitting apparatus 100 performs the foreign object removing operation based on the position information (step S532). If the metal foreign object is still not removed, the power transmission device 100 transmits a warning to the other device (step S535). The other operations are similar to the corresponding operations in FIG.

  FIG. 30 is a diagram showing still another example of the operation in the present embodiment. Also in this example, the foreign matter removing operation is performed in both the power transmission device 100 and the moving body 200. First, the power transmission device 100 performs the foreign matter removing operation by the same operation as the operation in FIG. 28 (step S560). If the metallic foreign matter can not be removed also by this operation (YES in step S561), the moving body 200 performs the foreign matter removing operation based on the position information (step S562). If the metallic foreign matter is still not removed, the mobile unit 200 transmits a warning to the other device (step S565). The other operations are similar to the corresponding operations in FIG.

  As described above, in the present embodiment, after the metal foreign object is detected by the thermal sensor 130, a signal indicating the presence of the metal foreign object is transmitted to another device other than the power transmission device 100. Thereby, for example, it becomes easy for the mobile body 200 to remove the metal foreign matter or to remove the metal foreign matter manually. As described above, each of the power transmission device 100 and the mobile unit 200 can also perform the foreign matter removing operation in a complementary manner. Thereby, the metal foreign matter can be reliably removed.

  As described above, the present disclosure includes the wireless power transmission devices described in the following items.

[Item 1]
A transmitting coil for outputting power to the receiving coil;
A thermal sensor that measures the surface temperature of metal foreign matter on the power transmission coil;
A method of controlling a power transmission device comprising
Before the moving body having the receiving coil moves to a position where the receiving coil and the power transmitting coil can be electromagnetically coupled, and before the moving body having the receiving coil and the power transmitting coil overlap with each other Make the transmitting coil output power,
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold value, the power transmission coil is caused to decrease or stop the output of power;
Control method.

[Item 2]
The power output from the power transmission coil includes a first power for detection of the metal foreign object and a second power for power transmission from the power transmission coil to the power reception coil.
The first power is smaller than the second power,
Causing the power transmission coil to output the first power before the moving body and the power transmission coil overlap;
Causing the thermal sensor to measure the surface temperature of the metal foreign substance while the first power is being output;
When the measured surface temperature of the metal foreign object is equal to or higher than the threshold value, the power transmission coil is caused to reduce the output of power or to stop it.
The control method according to item 1.

[Item 3]
The item (1) or (2), wherein after the moving object moves to a position where the power receiving coil can electromagnetically couple with the power transmission coil without the metal foreign object being detected, the second power is output to the power transmission coil. Control method.

[Item 4]
The power transmission apparatus further includes a position sensor that measures the distance between the mobile unit and the power transmission coil or the position of the mobile unit.
It is determined based on the measurement result of the position sensor that the mobile unit and the power transmission coil do not overlap.
The control method according to any one of items 1 to 3.

[Item 5]
A transmitting coil for outputting power to the receiving coil;
A thermal sensor that measures the surface temperature of metal foreign matter on the power transmission coil;
A power transmission control circuit that controls power output from the power transmission coil;
Power transmission device provided with
The power transmission control circuit is
Before the moving body having the receiving coil moves to a position where the receiving coil and the power transmitting coil can be electromagnetically coupled, and before the moving body having the receiving coil and the power transmitting coil overlap with each other Make the transmitting coil output power,
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold value, the power transmission coil is caused to decrease or stop the output of power;
Power transmission device.

[Item 6]
The power output from the power transmission coil includes a first power for detection of the metal foreign object and a second power for power transmission from the power transmission coil to the power reception coil.
The first power is smaller than the second power,
The power transmission control circuit is
Causing the power transmission coil to output the first power before the moving body and the power transmission coil overlap;
Causing the thermal sensor to measure the surface temperature of the foreign metal while the first power is being output;
When the measured surface temperature of the metal foreign object is equal to or higher than the threshold value, the power transmission coil is caused to reduce the output of power from the power or to stop it.
The power transmission device according to item 5.

[Item 7]
The power transmission control circuit causes the power transmission coil to output the second power when the moving object moves to a position where the power receiving coil can be electromagnetically coupled to the power transmission coil without detecting the metal foreign object. The power transmission device according to any of items 5 or 6.

[Item 8]
It further comprises a position sensor that measures the distance between the mobile unit and the power transmission coil, or the position of the mobile unit,
The power transmission control circuit determines that the mobile unit and the power transmission coil do not overlap based on the measurement result of the position sensor.
The power transmission device according to any one of Items 5 to 7.

[Item 9]
A foreign object detection method for detecting a metal foreign object, comprising
The power transmission device
An inverter circuit that generates power;
A power transmission coil for outputting electric power to a power reception coil of the mobile unit;
A thermal sensor that measures the surface temperature of metal foreign matter on the power transmission coil;
A power transmission control circuit for controlling the power output from the power transmission coil in the inverter circuit;
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the movable body and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold, a signal indicating the presence of the metal foreign object is transmitted from the power transmission device to a receiver having a function of receiving the signal other than the power transmission device.
Foreign object detection method.

[Item 10]
The foreign matter detection method according to Item 9, wherein the signal indicating the presence of the metal foreign matter includes position information of the metal foreign matter.

[Item 11]
The power output from the power transmission coil includes a first power for detection of the metal foreign object and a second power for power transmission from the power transmission coil to the power reception coil.
The first power is smaller than the second power,
The power transmission coil is caused to output the first power before the moving body having the power reception coil and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the foreign metal while the first power is being output;
The foreign matter detection method according to item 9 or 10.

[Item 12]
The power transmission apparatus further includes a position sensor that measures the distance between the mobile unit and the power transmission coil or the position of the mobile unit.
It is determined that the power receiving coil and the power transmitting coil do not overlap based on the measurement result of the position sensor.
The foreign material detection method according to any one of items 9 to 11.

[Item 13]
In any of the items 9 to 12, the receiving device is an information device mounted on the moving body, an information device owned by a user or a manager of the moving body, or a control device for controlling the power transmission device. Foreign substance detection method described.

[Item 14]
The foreign object detection method according to any one of items 9 to 13, wherein the reception device includes a car navigation system, a smartphone, a tablet computer, a vehicle, a robot, or a controller mounted on a control device that controls the power transmission device.

[Item 15]
At least one of the power transmission device and the moving body has a foreign matter removing mechanism,
When the measured surface temperature of the metal foreign object is equal to or higher than the threshold value, the foreign object removing mechanism in the at least one of the power transmission device and the moving object is caused to execute a foreign object removing operation.
The foreign material detection method according to any one of items 9 to 14.

[Item 16]
The foreign substance detection according to any one of items 9 to 15, which detects whether the metal foreign substance is actually removed after the foreign substance removing operation is performed, and transmits a signal indicating a detection result to the receiving device. Method.

[Item 17]
Each of the power transmission device and the moving body has a foreign matter removing mechanism,
When the measured surface temperature of the metal foreign object is equal to or higher than the threshold value, the foreign object removing mechanism in one of the power transmission device and the moving object is caused to execute a foreign object removing operation.
After the foreign matter removing operation is performed, it is detected whether the metal foreign matter is actually removed or not.
When the metal foreign matter is not removed, the other foreign matter removing operation is performed by the foreign matter removing mechanism in the other of the power transmission device and the movable body.
The foreign material detection method according to any one of items 9 to 16.

[Item 18]
If the detected surface temperature of the metal foreign object is equal to or higher than the threshold value, the power transmission coil is caused to decrease or stop the output of power;
The foreign material detection method according to any one of items 9 to 17.

[Item 19]
After the power transmission device transmits a first signal indicating the presence of the metallic foreign matter to the receiving device,
Receiving the first signal at the receiving device;
The receiver transmits a second signal to the power transmission device to reduce or stop the power;
When the power transmission device receives the second signal, the power transmission device reduces or stops the power.
The foreign material detection method according to any one of items 9 to 18.

  After transmitting a signal indicating the presence of the metal foreign object to the receiving device, and then receiving from the receiving device a command to decrease the output of the power from the power transmission coil or a command to stop the transmission, the power transmission coil 19. The foreign matter detection method according to any one of items 9 to 18, which reduces or stops the output.

[Item 20]
The power transmission device
An inverter circuit that generates power;
A power transmission coil for outputting electric power to a power reception coil of the mobile unit;
A thermal sensor that measures the surface temperature of metal foreign matter on the power transmission coil;
A power transmission control circuit for controlling the power output from the power transmission coil in the inverter circuit;
The power transmission control circuit is
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the movable body and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold, a signal indicating the presence of the metal foreign object is transmitted from the power transmission device to a receiver having a function of receiving the signal other than the power transmission device.
Power transmission device.

[Item 21]
A foreign object detection method for detecting a metal foreign object, comprising
The power transmission device
An inverter circuit that generates power;
A power transmission coil for outputting electric power to a power reception coil of the mobile unit;
A thermal sensor that detects the surface temperature of metal foreign matter on the power transmission coil;
A foreign matter removal mechanism,
A power transmission control circuit for controlling the power output from the power transmission coil in the inverter circuit;
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the movable body and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold value, the foreign object removing mechanism is made to execute a foreign object removing operation.
Foreign matter removal method.

[Item 22]
The foreign matter removing method according to Item 21, which detects whether or not the metal foreign matter is actually removed after the foreign matter removing operation is performed, and transmits a signal indicating a detection result to a receiving device other than the power transmitting device. .

  The technology of the present disclosure can be applied to any application that wirelessly feeds a mobile object such as a vehicle. For example, it can be used to supply power to mobiles on a road, a parking lot, or a factory.

100 power transmission device 105 power transmission area 110 power transmission coil 112 cover 120 power transmission circuit 130 thermal sensor 140 position sensor 150 power transmission control circuit 160 inverter circuit 170 power transmission communication circuit 180 foreign object removing mechanism 190 magnetic body 200 moving body 210 power receiving coil 220 rectification circuit 230 power reception Control circuit 240 Secondary battery 250 Motor inverter 260 Electric motor 270 Power receiving communication circuit 280 Foreign matter removal mechanism 290 Magnetic body 300 Power source 400 Metal foreign matter

Claims (14)

A foreign object detection method for detecting a metal foreign object, comprising
The power transmission device
An inverter circuit that generates power;
A power transmission coil for outputting electric power to a power reception coil of the mobile unit;
A thermal sensor that measures the surface temperature of metal foreign matter on the power transmission coil;
A power transmission control circuit for controlling the power output from the power transmission coil in the inverter circuit;
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the movable body and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold, a signal indicating the presence of the metal foreign object is transmitted from the power transmission device to a receiver having a function of receiving the signal other than the power transmission device.
Foreign object detection method.   The foreign matter detection method according to claim 1, wherein the signal indicating the presence of the metal foreign matter includes position information of the metal foreign matter. The power output from the power transmission coil includes a first power for detection of the metal foreign object and a second power for power transmission from the power transmission coil to the power reception coil.
The first power is smaller than the second power,
The power transmission coil is caused to output the first power before the moving body having the power reception coil and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the foreign metal while the first power is being output;
The foreign matter detection method according to claim 1 or 2. The power transmission apparatus further includes a position sensor that measures the distance between the mobile unit and the power transmission coil or the position of the mobile unit.
It is determined that the power receiving coil and the power transmitting coil do not overlap based on the measurement result of the position sensor.
The foreign material detection method according to any one of claims 1 to 3.   5. The control apparatus according to claim 1, wherein the receiving device is an information device mounted on the mobile object, an information device owned by a user or an administrator of the mobile object, or a control device that controls the power transmission device. The foreign matter detection method according to any one of the items.   The said receiving device is a car navigation system, a smart phone, a tablet computer, a vehicle, a robot, or the controller mounted in the control apparatus which controls the said power transmission apparatus of any one of Claims 1-5. Foreign object detection method. At least one of the power transmission device and the moving body has a foreign matter removing mechanism,
When the measured surface temperature of the metal foreign object is equal to or higher than the threshold value, the foreign object removing mechanism in the at least one of the power transmission device and the moving object is caused to execute a foreign object removing operation.
The foreign material detection method according to any one of claims 1 to 6.   The foreign matter detection method according to claim 7, wherein after the foreign matter removal operation is performed, it is detected whether or not the metal foreign matter is actually removed, and a signal indicating a detection result is transmitted to the receiving device. Each of the power transmission device and the moving body has a foreign matter removing mechanism,
When the measured surface temperature of the metal foreign object is equal to or higher than the threshold value, the foreign object removing mechanism in one of the power transmission device and the moving object is caused to execute a foreign object removing operation.
After the foreign matter removing operation is performed, it is detected whether the metal foreign matter is actually removed or not.
When the metal foreign matter is not removed, the other foreign matter removing operation is performed by the foreign matter removing mechanism in the other of the power transmission device and the movable body.
The foreign material detection method according to any one of claims 1 to 8. If the detected surface temperature of the metal foreign object is equal to or higher than the threshold value, the power transmission coil is caused to decrease or stop the output of power;
The foreign material detection method according to any one of claims 1 to 9. After the power transmission device transmits a first signal indicating the presence of the metallic foreign matter to the receiving device,
Receiving the first signal at the receiving device;
The receiver transmits a second signal to the power transmission device to reduce or stop the power;
When the power transmission device receives the second signal, the power transmission device reduces or stops the power.
The foreign material detection method according to any one of claims 1 to 9. The power transmission device
An inverter circuit that generates power;
A power transmission coil for outputting electric power to a power reception coil of the mobile unit;
A thermal sensor that measures the surface temperature of metal foreign matter on the power transmission coil;
A power transmission control circuit for controlling the power output from the power transmission coil in the inverter circuit;
The power transmission control circuit is
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the movable body and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold, a signal indicating the presence of the metal foreign object is transmitted from the power transmission device to a receiver having a function of receiving the signal other than the power transmission device.
Power transmission device. A foreign object detection method for detecting a metal foreign object, comprising
The power transmission device
An inverter circuit that generates power;
A power transmission coil for outputting electric power to a power reception coil of the mobile unit;
A thermal sensor that detects the surface temperature of metal foreign matter on the power transmission coil;
A foreign matter removal mechanism,
A power transmission control circuit for controlling the power output from the power transmission coil in the inverter circuit;
The power transmission coil is caused to output power before the power reception coil and the power transmission coil are electromagnetically coupled and before the movable body and the power transmission coil overlap.
Causing the thermal sensor to measure the surface temperature of the metallic foreign matter;
When the measured surface temperature of the metal foreign object is equal to or higher than a threshold value, the foreign object removing mechanism is made to execute a foreign object removing operation.
Foreign matter removal method.   The foreign matter removal method according to claim 13, wherein after the foreign matter removal operation is performed, whether or not the metal foreign matter is actually removed is detected, and a signal indicating a detection result is transmitted to a receiver other than the power transmission device. Method.

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