WO2022157837A1 - Power transmission device and power transfer system - Google Patents

Abstract

A plurality of sensor coils (120A) have an opening portion (123A), are disposed within the opening portion of a power transmission coil (211) when viewed from a first direction in which the coil axis of the power transmission coil (211) extends, and face a magnetic plate (212). A sensor coil (120B) has an opening portion (123B) and is disposed closer to the center of the power transmission coil (211) than the plurality of sensor coils (120A). When the area of the opening portion (123A) is denoted by S1, the number of turns of each of the plurality of sensor coils (120A) is denoted by N1, the area of the opening portion (123B) is denoted by S2, and the number of turns of the sensor coil (120B) is denoted by N2, the relationship of N1 × S1 < N2 × S2 is satisfied.

Description

Power transmission device and power transmission system

The present disclosure relates to a power transmission device and a power transmission system.

Wireless power transmission technology that transmits power wirelessly is attracting attention. Wireless power transmission technology can wirelessly transmit power from a power transmission device to a power reception device, so it is expected to be applied to various products such as transportation equipment such as trains and electric vehicles, home appliances, wireless communication equipment, and toys. Wireless power transmission technology uses a power transmitting coil and a power receiving coil that are coupled by magnetic flux to transmit power.

By the way, if there are foreign objects such as metal pieces in the vicinity of the power transmitting coil and the power receiving coil, various problems may occur. For example, such a foreign object may adversely affect power transmission from the power transmitting coil to the power receiving coil, or generate heat due to eddy current. Therefore, there is a demand for a foreign object detection device that appropriately detects a foreign object existing near the power transmitting coil and the power receiving coil.

Patent Document 1 describes a detection device that determines the presence or absence of a foreign object that generates heat due to magnetic flux from changes in electrical parameters of a magnetic coupling element, which is a detection coil, or a circuit that includes this magnetic coupling element. In the detection device described in Patent Document 1, a large number of detection coils of the same size are arranged in regions of two or more layers so that a dead region, which is a region in which a foreign object cannot be detected, does not occur between adjacent detection coils. there is Such a foreign object detection device is installed, for example, on a power transmission coil inside a power transmission device installed on a road surface.

JP 2013-192391 A

However, the magnetic flux density distribution based on the magnetic flux generated from the power transmission coil is not uniform around the power transmission coil. That is, there are positions with high magnetic flux density and positions with low magnetic flux density around the power transmission coil. For this reason, using a large number of detector coils of the same size as in the detector described in Patent Document 1 may not be preferable.

For example, if only a large number of sensing coils are used, a very high induced voltage is generated in the sensing coils placed at positions with high magnetic flux density. At this time, there is a possibility that a large induced current will flow through the sensing coil, causing the sensing coil to burn out, or that an overvoltage will be applied to the switch that selects the sensing coil to be used, causing the switch to break. On the other hand, if only a large number of small-sized detector coils are used, it is difficult to improve the foreign matter detection performance of the foreign matter detection apparatus as a whole. For this reason, there is a demand for a technique for preventing sensor coil burnout and the like while maintaining high detection performance in detecting foreign matter in wireless power transmission.

The present disclosure has been made in view of the above problems, and aims to prevent sensor coil burnout, etc., while maintaining high detection performance in foreign object detection in wireless power transmission.

In order to solve the above problems, a power transmission device according to an embodiment of the present disclosure includes:
a power transmission coil configured by winding a conductor wire and having an opening;
a magnetic body facing the power transmission coil;
a foreign object detection device,
The foreign matter detection device includes a plurality of sensor coils and a detection unit that detects a foreign matter present in a foreign matter detection area based on signals output from the plurality of sensor coils,
The plurality of sensor coils have a first sensor opening, and are arranged in the opening when viewed from a first direction in which the coil axis of the power transmission coil extends, and a plurality of first sensor coils facing the magnetic body. a sensor coil, and a second sensor coil having a second sensor opening and arranged closer to the center of the power transmission coil than the plurality of first sensor coils when viewed from the first direction,
The area of the first sensor opening is S1, the number of turns of each of the plurality of first sensor coils is N1, the area of the second sensor opening is S2, and the number of turns of the second sensor coil is N2. Then, the following formula (1) is satisfied.
N1×S1<N2×S2 (1)

According to the power transmission device with the above configuration, it is possible to prevent burnout of the sensor coil, etc., while maintaining high detection performance in foreign object detection in wireless power transmission.

Schematic configuration diagram of a power transmission system according to Embodiment 1 Layout diagram of the foreign object detection device according to the first embodiment 2 is a plan view of the detection coil unit according to Embodiment 1; FIG. FIG. 1 is a configuration diagram of a detection unit included in the foreign object detection device according to Embodiment 1. FIG. FIG. 4 is a diagram showing an equivalent circuit of a resonance circuit included in the detection coil unit according to Embodiment 1; 1 is a plan view of a power transmission coil unit according to Embodiment 1. FIG. Schematic diagram of cross section along line VII-VII in Fig. 3 FIG. 4 is a diagram showing the correspondence relationship among the magnetic flux density, the opening area, and the number of turns according to the first embodiment; Plan view of detection coil unit according to Embodiment 2 Schematic diagram of cross section along line XX in FIG. FIG. 10 is a diagram showing a correspondence relationship between magnetic flux density, opening area, and number of turns according to Embodiment 2; Schematic cross-sectional view of a detection coil unit according to Embodiment 3 Schematic cross-sectional view of a detection coil unit according to a fourth embodiment

A power transmission system according to an embodiment of the technology according to the present disclosure will be described below with reference to the drawings. In addition, in the following embodiment, the same code|symbol is attached|subjected to the same component. Also, the size ratios and shapes of the constituent elements shown in each drawing are not necessarily the same as in the actual implementation.

(Embodiment 1)
The power transmission system according to the present embodiment can be used to charge secondary batteries of various devices such as EVs (Electric Vehicles), mobile devices such as smartphones, and industrial devices. A case where the power transmission system charges an EV storage battery will be exemplified below.

FIG. 1 is a diagram showing a schematic configuration of a power transmission system 1000 used for charging a storage battery 500 provided in an electric vehicle 700. FIG. The electric vehicle 700 runs using a motor driven by electric power charged in a storage battery 500 such as a lithium ion battery or a lead storage battery as a power source.

As shown in FIG. 1, the power transmission system 1000 is a system that wirelessly transmits power from the power transmission device 200 to the power reception device 300 by magnetic coupling. The power transmission system 1000 includes a power transmission device 200 that wirelessly transmits power from an AC or DC commercial power supply 400 to an electric vehicle 700, and a power reception device 300 that receives the power transmitted by the power transmission device 200 and charges a storage battery 500. . In the following description, commercial power supply 400 is an AC power supply.

The power transmission device 200 is a device that wirelessly transmits power to the power reception device 300 by magnetic coupling. The power transmission device 200 includes a foreign object detection device 100 that detects foreign objects, a power transmission coil unit 210 that transmits AC power to the electric vehicle 700 , and a power supply device 220 that supplies AC power to the power transmission coil unit 210 . As shown in FIG. 2 , foreign object detection device 100 is arranged on power transmission coil unit 210 . In FIG. 2, the vertically upward axis is the Z-axis, the axis orthogonal to the Z-axis is the X-axis, and the axis orthogonal to the Z-axis and the X-axis is the Y-axis. A detailed description of the foreign object detection device 100 will be given later.

As shown in FIG. 2 , the power transmission coil unit 210 is supplied with AC power from a power supply device 220, and has a power transmission coil 211 that induces an alternating magnetic flux Φ. and a magnetic plate 212 for suppressing. The power transmission coil 211 is configured by spirally winding a conductive wire on a magnetic plate 212 . The power transmission coil 211 and the capacitors provided at both ends of the power transmission coil 211 constitute a resonance circuit, and an alternating magnetic flux Φ is induced by an alternating current flowing along with the application of an alternating voltage.

The magnetic plate 212 has a plate shape with a hole in the center and is made of a magnetic material. The magnetic plate 212 is, for example, a plate-like member made of ferrite, which is a composite oxide of iron oxide and metal. The magnetic plate 212 may be composed of an assembly of a plurality of individual pieces of magnetic material, and the plurality of individual pieces of magnetic material are arranged in a frame shape and formed to have an opening in the central portion. may

The power supply device 220 includes a power factor correction circuit that improves the power factor of the commercial AC power supplied by the commercial power supply 400 and an inverter circuit that generates the AC power to be supplied to the power transmission coil 211 . The power factor correction circuit rectifies and boosts AC power generated by commercial power supply 400, and converts it into DC power having a predetermined voltage value. The inverter circuit converts DC power generated by power conversion by the power factor correction circuit into AC power having a predetermined frequency. Power transmission device 200 is fixed, for example, to the floor of a parking lot.

The power receiving device 300 is a device that wirelessly receives power from the power transmitting device 200 by magnetic coupling. The power receiving device 300 includes a power receiving coil unit 310 that receives the AC power transmitted by the power transmitting device 200, and a rectifier circuit 320 that converts the AC power supplied from the power receiving coil unit 310 into DC power and supplies the DC power to the storage battery 500. Prepare.

As shown in FIG. 2, the power receiving coil unit 310 includes a power receiving coil 311 that induces an electromotive force in response to a change in the alternating magnetic flux Φ induced by the power transmitting coil 211, and a magnetic force generated by the power receiving coil 311 that passes through the magnetic force. and a magnetic plate 312 that suppresses loss. Power receiving coil 311 and capacitors provided at both ends of power receiving coil 311 form a resonance circuit. Power receiving coil 311 faces power transmitting coil 211 while electric vehicle 700 is stopped at a preset position. When the power transmission coil 211 receives power from the power supply device 220 and induces an alternating magnetic flux Φ, the alternating magnetic flux Φ interlinks with the power receiving coil 311 , thereby inducing an induced electromotive force in the power receiving coil 311 .

The magnetic plate 312 is a plate-shaped member with a hole in the center and is made of a magnetic material. The magnetic plate 312 is, for example, a plate-like member made of ferrite, which is a composite oxide of iron oxide and metal. The magnetic plate 312 may be composed of an assembly of a plurality of individual pieces of magnetic material, and the plurality of individual pieces of magnetic material are arranged in a frame shape and formed to have an opening in the central portion. may

The rectifier circuit 320 rectifies the electromotive force induced in the receiving coil 311 to generate DC power. The DC power generated by the rectifier circuit 320 is supplied to the storage battery 500 . Power receiving device 300 may include a charging circuit between rectifier circuit 320 and storage battery 500 that converts the DC power supplied from rectifier circuit 320 into DC power suitable for charging storage battery 500. good. The power receiving device 300 is fixed to the chassis of the electric vehicle 700, for example.

The terminal device 600 is a device that receives notification of the presence of a foreign object from the foreign object detection device 100 . Terminal device 600 is, for example, a smartphone owned by the owner of electric vehicle 700 . When the terminal device 600 receives notification of the presence of a foreign object from the foreign object detection apparatus 100, the terminal device 600 notifies the user of the presence of the foreign object through screen display, voice output, or the like.

The foreign object detection device 100 detects foreign objects existing in the detection target area. The detection target area is a target area for foreign matter detection, and is an area in which foreign matter can be detected. The detection target area is an area near power transmitting coil unit 210 and power receiving coil unit 310 and includes an area between power transmitting coil unit 210 and power receiving coil unit 310 . A foreign object is an object or a living body that is not necessary for power transmission.

If a foreign object is placed in the detection target area during power transmission, it may adversely affect power transmission or generate heat. Therefore, the foreign object detection apparatus 100 detects a foreign object existing in the detection target area and notifies the user that the foreign object has been detected. The user can receive this notification and remove the foreign matter. Various things such as metal pieces, people, and animals are assumed as the foreign matter. As shown in FIG. 2 , foreign object detection apparatus 100 includes detection coil unit 110 , detection section 150 , pulse generation section 160 , and notification section 170 .

The detection coil unit 110 is a unit that detects foreign matter. As shown in FIG. 3 , the detection coil unit 110 is formed in a flat plate shape and arranged on the power transmission coil unit 210 so as to overlap the power transmission coil 211 in plan view. 3 is a plan view of detection coil unit 110 arranged on power transmission coil unit 210. FIG. In order to facilitate understanding, FIG. 3 shows not only the detection coil unit 110 but also the power transmission coil 211 and the magnetic plate 212 included in the power transmission coil unit 210 .

The detection coil unit 110 includes a detection coil substrate 140 made of a magnetically permeable material typified by resin. A plurality of sensor coils 120A, a plurality of sensor coils 120B, a plurality of sensor coils 120C, and a plurality of sensor coils 120D are mounted on the detection coil substrate 140 . Sensor coil 120 is a general term for sensor coil 120A, sensor coil 120B, sensor coil 120C, and sensor coil 120D.

It should be noted that in FIG. 3, the sensor coils 120 arranged inside the detection coil substrate 140 are indicated by solid lines instead of dashed lines for easy understanding. Further, in FIG. 3, the reference numerals of the sensor coils 120 are omitted as appropriate. Also in the following drawings, reference numerals are appropriately omitted from the viewpoint of visibility. Each sensor coil 120, the detection section 150, and the pulse generation section 160 are connected by wiring (not shown).

The detection unit 150 determines whether or not a foreign object exists in the detection target area based on the output value of the sensor coil 120 excited by the application of the pulsed voltage. The pulse generating section 160 generates a pulse voltage for foreign object detection, selects the sensor coil 120 and applies it. When a foreign object is detected by the detection unit 150, the notification unit 170 notifies the user that the foreign object has been detected. For example, the notification unit 170 transmits information indicating that a foreign object has been detected to the terminal device 600 carried by the user.

Next, the configuration of the detection unit 150 will be described with reference to FIG. The detector 150 detects the foreign object 10 existing in the foreign object detection area based on the signals output from the plurality of sensor coils 120 . In other words, all of the plurality of sensor coils 120 are used to detect the foreign object 10 . Therefore, the detection unit 150 is connected to each of the plurality of sensor coils 120 via wiring.

The detection unit 150 is realized, for example, by a computer equipped with a CPU (Central Processing Unit), a memory, an A/D (Analog/Digital) converter, etc., and an operation program. The detection unit 150 functionally includes a detection control unit 151, a selection unit 152, a drive unit 153, an output value acquisition unit 154, a storage unit 155, a result output unit 156, and a power transmission control unit 157. Prepare.

The detection unit 150 selects one of the 20 sensor coils 120 using these components, turns on the switches 132 and 133 of the selected sensor coil 120, and switches on the unselected sensor coils 120. With the switches 132 and 133 turned off, the presence or absence of the foreign object 10 near the selected sensor coil 120 is detected. The detection unit 150 sequentially detects the presence or absence of such a foreign object for all the sensor coils 120 and outputs the detection result.

The detection control unit 151 controls each component included in the detection unit 150, detects the foreign object 10, outputs the detection result, and the like. The selection unit 152 selects one of all the sensor coils 120 under the control of the detection control unit 151 and controls the switch 132 and the switch 133 included in the selected sensor coil 120 to turn on. After the selection and on-control by the selection unit 152 are executed, the drive unit 153 drives the pulse generation unit 160 according to the control by the detection control unit 151 to cause the pulse generation unit 160 to generate a single pulse voltage. . This pulse-like voltage is applied to the resonance circuit formed in the selected sensor coil 120 via wiring. In addition, the voltage across the resonant circuit is led to the output value acquiring section 154 via wiring.

The equivalent circuit of the resonance circuit included in the detection coil unit 110 will be described below with reference to FIG. As shown in FIG. 5, the resonance circuit included in the detection coil unit 110 includes a sensor coil 120, a capacitor 131, a switch 132, and a switch 133. The sensor coil 120 has a conductor pattern wound one or more times about an axis parallel to the Z-axis.

One terminal of the sensor coil 120 is connected to one terminal of the switch 132, and is connected to one end of the pulse generator 160 via wiring. The other terminal of sensor coil 120 is connected to one terminal of capacitor 131 and one terminal of switch 133 . The other terminal of the switch 133 is connected to the other end of the pulse generator 160 via wiring. The other terminal of capacitor 131 is connected to the other terminal of switch 132 .

The switches 132 and 133 are controlled to be on or off under the control of the detection unit 150 via a control line (not shown). The ON state is a conducting state and the OFF state is a non-conducting state. The switch 132 has a function of switching states between the sensor coil 120 and the capacitor 131 . When switch 132 is turned on, sensor coil 120 and capacitor 131 form resonant circuit 130 . The switch 133 has a function of switching the state between this resonance circuit and the pulse generator 160 .

That is, when both the switch 132 and the switch 133 are turned on, the sensor coil 120 and the capacitor 131 form a resonant circuit, and a pulse voltage is applied to the resonant circuit from the pulse generator 160 through the wiring. be done. The voltage across the resonance circuit, that is, the voltage across the sensor coil 120 is led to the detection unit 150 via wiring. When switch 132 is turned off, sensor coil 120 and capacitor 131 do not form a resonant circuit. Also, when the switch 133 is turned off, the resonance circuit is electrically disconnected from the detection section 150 and the pulse generation section 160 .

FIG. 5 shows that a foreign object 10 exists near the resonant circuit. Assume that the switch 133 is closed and a pulse voltage is applied from the pulse generator 160 while the switch 132 is closed and the sensor coil 120 and the capacitor 131 form a resonant circuit. The voltage signal representing the voltage across the resonant circuit is an oscillating signal whose crest value gradually attenuates over time after the pulse voltage falls, that is, after the current to the sensor coil 120 is cut off. .

When the foreign object 10 exists near the sensor coil 120, the inductance of the sensor coil 120 changes. Therefore, when the foreign object 10 exists, the frequency of the vibration signal changes or the degree of attenuation of the vibration signal changes compared to when the foreign object 10 does not exist. The detection unit 150 determines the presence or absence of the foreign object 10 by detecting changes in the frequency of the vibration signal, changes in the degree of attenuation of the vibration signal, and the like.

The output value acquisition unit 154 acquires the output value of the selected sensor coil 120 from the vibration signal representing the voltage across the resonance circuit under the control of the detection control unit 151 . The output value acquired by the output value acquisition unit 154 can be adjusted as appropriate. For example, the output value can be the frequency of the vibration signal, the convergence time of the vibration signal, the magnitude of the amplitude of the vibration signal, and the like. The convergence time of the vibration signal is, for example, the time from when the pulse voltage is applied until the amplitude of the vibration signal falls below a predetermined amplitude. The magnitude of the amplitude of the vibration signal is, for example, the magnitude of the amplitude of the vibration signal when a predetermined time has passed since the pulse voltage was applied.

The storage unit 155 stores various data related to foreign matter detection processing executed by the foreign matter detection device 100 . For example, the storage unit 155 stores an output value, a reference value, a difference value, and a threshold. The output value is the output value acquired by the output value acquisition unit 154 . The reference value is the reference value of the output value. That is, the reference value is the output value obtained when the foreign object 10 does not exist near the sensor coil 120 . The reference value is obtained in advance through experiments, simulations, or the like, and stored in the storage unit 155 .

The difference value is the difference between the reference value, which is the output value obtained when the foreign object 10 is not present, and the currently obtained output value. That is, the difference value is the amount of change from the output value obtained when the foreign object 10 is not present. A small difference value means that there is a high possibility that the foreign object 10 does not exist, and a large difference value means that there is a high possibility that the foreign object 10 exists. The threshold is a threshold for determining the difference value. The threshold value is determined in advance in consideration of the expected magnitude of noise, the degree of change in the output value due to the presence or absence of the foreign object 10, and the like, and is stored in the storage unit 155, for example.

Note that the detection control unit 151 determines the presence or absence of the foreign object 10 based on the comparison result between the comparison target value based on the output value of the sensor coil 120 and the threshold. A comparison target value is a value to be compared with a threshold value, and specifically, a difference value between an output value and a reference value or a value based on this difference value. In this embodiment, the comparison target value is the difference value between the output value and the reference value. For example, the detection control unit 151 outputs a detection result indicating that the foreign object 10 is present when determining that the comparison target value exceeds the threshold for any one of the sensor coils 120 .

The result output unit 156 outputs the detection result by the detection control unit 151 according to the control by the detection control unit 151 . For example, when the detection control unit 151 determines that the foreign object 10 exists, the result output unit 156 instructs the notification unit 170 to notify that the foreign object 10 exists. Note that, upon receiving the notification from the detection control unit 151, the notification unit 170 transmits information indicating that a foreign object has been detected to the terminal device 600 possessed by the user. On the other hand, the terminal device 600 informs the user that a foreign object has been detected through screen display, voice output, or the like.

The power transmission control unit 157 controls power transmission from the power transmission coil unit 210 to the power reception coil unit 310 according to the control by the detection control unit 151 . When the detection control unit 151 determines that the foreign object 10 exists, the power transmission control unit 157 instructs the power supply device 220 to stop power transmission.

In the present embodiment, detection coil unit 110 is arranged above power transmission coil unit 210 . Magnetic flux for power transmission is generated from the power transmission coil 211 included in the power transmission coil unit 210 . The magnetic flux density distribution based on this magnetic flux is not uniform around power transmission coil 211 . In other words, there are positions with a high magnetic flux density and positions with a low magnetic flux density around the power transmission coil 211 . In addition, since the magnetic flux for power transmission changes with the passage of time, the magnetic flux density also changes with the passage of time. In the present embodiment, the maximum value of magnetic flux density based on the magnetic flux generated by power transmission coil 211 is simply referred to as magnetic flux density as appropriate.

Here, when the sensor coil 120 is placed at a position having a high magnetic flux density, the magnetic flux passing through the loop of the sensor coil 120 changes greatly over time during power transmission. Therefore, a high induced voltage is generated across the sensor coil 120 during power transmission. If the induced voltage is too high, an excessively large induced current may flow through the sensor coil 120 and the sensor coil 120 may burn out. Also, if the induced voltage is too high, an overvoltage is applied to the switch 132 that selects the state of the resonant circuit or the switch 133 that selects the sensor coil 120 to be used, and the switch 132 or the switch 133 may be damaged. be.

By the way, the sensor coil 120 having a large product of the opening area, which is the area of the opening of the sensor coil 120, and the number of turns of the sensor coil 120 basically has a high induced voltage generated at both ends of the sensor coil 120. The detection performance of detecting foreign matter 10 is high. On the other hand, the sensor coil 120 having a small product of the opening area and the number of turns basically has a low induced voltage across both ends of the sensor coil 120 and has a low detection performance for detecting a distant foreign object 10 . The number of turns is the number of loops forming the sensor coil 120 and the number of turns of the conductor wire.

Here, if all the sensor coils 120 of the detection coil unit 110 are sensor coils 120 with a large product of the opening area and the number of turns, too high induction will occur at both ends of the sensor coil 120 arranged at a position having a high magnetic flux density. There is a high possibility that a voltage will be generated and the sensor coil 120 will be burnt out. On the other hand, if all the sensor coils 120 included in the detection coil unit 110 are sensor coils 120 with a small product of the opening area and the number of turns, it is difficult to improve the detection performance of the foreign object detection device 100 as a whole. Further, when the outputs from all the sensor coils 120 are processed by the same circuit, a method of amplifying the output of the sensor coils 120 arranged at positions having a low magnetic flux density can be considered. However, in this method, it is necessary to provide an amplifier circuit in the foreign object detection device 100, which increases the cost.

Therefore, in the present embodiment, the sensor coil 120 is adopted according to the height of the magnetic flux density at the position where the sensor coil 120 is arranged. Specifically, in the present embodiment, the sensor coil 120 having a small product of the opening area and the number of turns is arranged at the position having a high magnetic flux density, and the sensor coil 120 having a small product of the opening area and the number of turns is arranged at the position having a low magnetic flux density. A sensor coil 120 having a large product of is arranged. According to such a configuration, it is possible to prevent burning of the sensor coil 120 while maintaining high detection performance.

Next, the distribution of magnetic flux density will be described with reference to FIG. FIG. 6 is a plan view of the power transmission coil unit 210. FIG. As shown in FIG. 6, the power transmission coil unit 210 has a magnetic plate 212 having an opening 212A and a power transmission coil 211 having an opening 211A smaller than the opening 212A. The power transmission coil 211 is arranged above the magnetic plate 212 so that the outer edge of the power transmission coil 211 is arranged inside the outer edge of the magnetic plate 212 and the entire opening 212A overlaps the opening 211A in plan view. be. Here, the area above power transmission coil unit 210 is classified into area A, area B, area C, and area D. FIG.

A region A is a region that overlaps with the opening 211A and does not overlap with the opening 212A in plan view. A region B is a region overlapping with the opening 211A and overlapping with the opening 212A in plan view. A region C is a region that overlaps with the conductor 211B included in the power transmission coil 211 and overlaps with the magnetic plate 212 in plan view. A region D is a region outside the conducting wire 211B overlapping the magnetic plate 212 in plan view. That is, the area A is an annular area in plan view. Region B is a region surrounded by region A in plan view. Region C is an annular region surrounding region A in plan view. Region D is an annular region surrounding region C in plan view.

Area A is an area where the magnetic flux generated by the power transmission coil 211 is collected by the magnetic plate 212, and thus has a very high magnetic flux density. The area B is an area that does not overlap with the magnetic plate 212 in plan view, and thus has a low magnetic flux density. The region C is a region that overlaps with the conductor 211B included in the power transmission coil 211 in plan view, and thus has a high magnetic flux density. The region D is a region that overlaps with the magnetic plate 212 in plan view, but is a region outside the power transmission coil 211 in plan view, and thus has a low magnetic flux density.

Therefore, in area A, the sensor coil 120 that can detect a small foreign object 10 is arranged, although the detection performance for detecting a distant foreign object 10 is low. Further, in the area B and the area D, sensor coils 120 with high detection performance for detecting a distant foreign object 10 are arranged. Further, in the area C, a sensor coil 120 that has a higher detection performance for detecting a distant foreign object 10 than the area A and that can detect a small foreign object 10 compared to the areas B and D is arranged. In this embodiment, as shown in FIG. 3, 16 sensor coils 120A are arranged in area A, two sensor coils 120B are arranged in area B, and 14 sensor coils 120C are arranged in area C. 18 sensor coils 120D are arranged in a region straddling the region C and the region D. As shown in FIG.

In this way, the detection performance of the sensor coils 120 arranged in each area is set according to the magnetic flux density of that area. For example, sensor coils 120 that have higher detection performance for detecting a distant foreign object 10 are arranged in areas where the magnetic flux density is low than in areas where the magnetic flux density is high. In other words, sensor coils 120 with higher detection performance for detecting foreign objects 10 at a farther distance are arranged in regions where the magnetic flux density is lower. On the other hand, sensor coils 120 having higher detection performance for detecting small foreign objects 10 are arranged in areas where the magnetic flux density is high than in areas where the magnetic flux density is low. In other words, sensor coils 120 with higher detection performance for detecting small foreign objects 10 are arranged in regions where the magnetic flux density is higher.

FIG. 7 is a schematic diagram of a cross section taken along line VII-VII in FIG. In addition to the cross section of the detection coil unit 110, FIG. 7 also shows a schematic diagram that schematically shows the cross section of the power transmission coil unit 210. As shown in FIG.

As shown in FIG. 7, the sensor coil 120A is a coil formed by winding a coil conductor 121A. The sensor coil 120A has an opening 123A that is an opening formed inside the coil conductor 121A. The sensor coil 120A is arranged in an opening 211A of the power transmission coil 211 and faces the magnetic plate 212 when viewed from the first direction in which the coil axis of the power transmission coil 211 extends. That is, the plurality of sensor coils 120A are annularly arranged at positions overlapping the opening 211A and the magnetic plate 212 when viewed from the first direction. Note that the first direction is the Z-axis direction.

Also, each of the plurality of sensor coils 120A has a substantially square shape when viewed from the first direction. A substantially rectangular shape is a concept that allows for slight differences from a perfect rectangular shape, and means that the shape as a whole is substantially rectangular. For example, a substantially rectangular shape is a concept that includes a shape in which the four corners of a perfect rectangular shape are rounded. Sensor coil 120A is an example of a first sensor coil. The opening 123A is an example of a first sensor opening.

The sensor coil 120B is a coil formed by winding a coil conductor 121B. The sensor coil 120B has an opening 123B that is an opening formed inside the coil conductor 121B. The sensor coil 120B is arranged closer to the center of the power transmission coil 211 than the plurality of sensor coils 120A when viewed from the first direction. That is, the sensor coil 120B is arranged inside the plurality of sensor coils 120A that are annularly arranged when viewed from the first direction. Moreover, the sensor coil 120B is arranged at a position overlapping the opening 211A and the opening 212A. Moreover, the sensor coil 120B has a substantially rectangular shape when viewed from the first direction. Sensor coil 120B is an example of a second sensor coil. The opening 123B is an example of a second sensor opening.

The sensor coil 120C is a coil formed by winding a coil conductor 121C. The sensor coil 120C has an opening 123C that is an opening formed inside the coil conductor 121C. The sensor coil 120C is arranged at a position overlapping with the conducting wire 211B of the power transmitting coil 211 when viewed from the first direction. That is, the plurality of sensor coils 120C are annularly arranged outside the plurality of annularly arranged sensor coils 120A when viewed from the first direction. Also, the sensor coil 120C has a substantially rectangular shape when viewed from the first direction. Sensor coil 120C is an example of a third sensor coil. The opening 123C is an example of a third sensor opening.

The sensor coil 120D is a coil formed by winding a coil conductor 121D. The sensor coil 120D has an opening 123D that is an opening formed inside the coil conductor 121D. The sensor coil 120D is arranged at a position farther from the center of the power transmission coil 211 than the plurality of sensor coils 120C when viewed from the first direction. That is, the plurality of sensor coils 120D are annularly arranged outside the plurality of annularly arranged sensor coils 120C when viewed from the first direction. Further, the sensor coil 120D is arranged at a position straddling a region overlapping with the conducting wire 211B and a region outside the conducting wire 211B when viewed from the first direction. Also, the sensor coil 120D has a substantially rectangular shape when viewed from the first direction. Sensor coil 120D is an example of a fourth sensor coil. The opening 123D is an example of a fourth sensor opening.

In the present embodiment, the area of the opening 123A is S1, the number of turns of each of the plurality of sensor coils 120A is N1, the area of the opening 123B is S2, the number of turns of the sensor coil 120B is N2, and the area of the opening 123C is S3, the number of turns of each of the plurality of sensor coils 120C is N3, the area of the opening 123D is S4, and the number of turns of each of the plurality of sensor coils 120D is N4, the following equations (1) and (2) ) and equation (3) are satisfied.
N1×S1<N2×S2 (1)
N3×S3<N2×S2 (2)
N3×S3<N4×S4 (3)

The product of the opening area, which is the area of the opening 123 of the sensor coil 120 , and the number of turns of the sensor coil 120 basically corresponds to the detection performance of the sensor coil 120 . Expression (1) is the detection performance that the sensor coil 120A arranged at a position having a higher magnetic flux density than the position where the sensor coil 120B is arranged detects the foreign object 10 farther than the sensor coil 120B. is low, but the detection performance for detecting a small foreign object 10 is high. That is, when the expression (1) is satisfied, the sensor coil 120A arranged at a position having a high magnetic flux density is prevented from being burnt out, and has a high detection performance for detecting a small foreign object 10. The sensor coil 120B arranged at a location having a higher detection performance for detecting a distant foreign object 10 is improved.

Expression (2) is the detection performance that the sensor coil 120C arranged at a position having a higher magnetic flux density than the position where the sensor coil 120B is arranged detects the foreign object 10 farther than the sensor coil 120B. is low, but the detection performance for detecting a small foreign object 10 is high. In other words, when the expression (2) is satisfied, the sensor coil 120C arranged at a position having a high magnetic flux density is prevented from being burnt out, and the detection performance of detecting a small foreign object 10 is improved. The sensor coil 120B arranged at a location having a higher detection performance for detecting a distant foreign object 10 is improved.

Expression (3) is the detection performance that the sensor coil 120C arranged at a position having a higher magnetic flux density than the position where the sensor coil 120D is arranged detects the foreign object 10 farther than the sensor coil 120D. is low, but the detection performance for detecting a small foreign object 10 is high. In other words, when the expression (3) is satisfied, the sensor coil 120C arranged at a position having a high magnetic flux density is suppressed in burnout, etc., and has a high detection performance for detecting a small foreign object 10. As for the sensor coil 120D arranged at the location where the sensor coil 120D is located, the detection performance of detecting the distant foreign object 10 is enhanced.

As described above, according to the present embodiment, it is possible to prevent burnout of the sensor coil 120 and the like while maintaining high detection performance in foreign object detection in wireless power transmission.

Further, in the present embodiment, the detection performance of the sensor coil 120 is adjusted by adjusting the opening area out of the opening area and the number of turns. Specifically, when viewed from the first direction, opening 123A is smaller than opening 123B. Also, when viewed from the first direction, the opening 123C is smaller than the opening 123B. In the present embodiment, the detection performance of sensor coil 120 is adjusted without limiting the number of turns of sensor coil 120A, the number of turns of sensor coil 120B, and the number of turns of sensor coil 120C. Therefore, according to the present embodiment, the sensor coil 120A, the sensor coil 120B, and the sensor coil 120C have a high degree of freedom in design.

Also, in the present embodiment, each of the plurality of sensor coils 120A is arranged at a position farther from the power transmission coil 211 than the sensor coil 120B in the first direction. That is, the layer in which each of the plurality of sensor coils 120A is arranged in the detection coil substrate 140 is farther from the power transmitting coil 211 than the layer in which the sensor coil 120B is arranged in the detection coil substrate 140 .

Here, the magnetic flux density of the magnetic flux generated by the power transmission coil 211 is basically lower the further away it is from the power transmission coil 211 . Therefore, in the above configuration, the increase in the magnetic flux density at the position where the sensor coil 120A is arranged is suppressed. That is, according to the present embodiment, an increase in the induced voltage induced in the sensor coil 120A is suppressed, and burnout of the sensor coil 120A is further suppressed.

Also, the sensor coil 120A can detect the foreign object 10 placed near the sensor coil 120A, but it is difficult to detect the foreign object 10 placed far from the sensor coil 120A. According to the present embodiment, since the sensor coil 120A is arranged closer to the foreign object 10 than the sensor coil 120B, efficient foreign object detection can be expected.

In addition, in the present embodiment, when the magnetic flux generated by the power transmission coil 211 interlinks with each of the plurality of sensor coils 120A, the voltage induced in each of the plurality of sensor coils 120A and the magnetic flux are applied to the sensor coil 120B. A voltage induced in the sensor coil 120B when the magnetic flux interlinks with the sensor coil 120C, a voltage induced in the sensor coil 120C when the magnetic flux interlinks with the sensor coil 120C, and a sensor coil 120D when the magnetic flux interlinks with the sensor coil 120D. The voltage induced in coil 120D is the same. The sameness is a concept that allows some degree of difference. For example, even if there is a difference of several percent to several tens of percent, it may be regarded as the same.

That is, in the present embodiment, the induced voltage induced in sensor coil 120A, the induced voltage induced in sensor coil 120B, the induced voltage induced in sensor coil 120C, and the induced voltage induced in sensor coil 120D are the same. The opening area and number of turns of each of sensor coil 120A, sensor coil 120B, sensor coil 120C, and sensor coil 120D are adjusted so as to be about the same.

A specific description will be given below with reference to FIG. FIG. 8 shows, for each type of sensor coil 120, the correspondence between the magnetic flux density at the position where the sensor coil 120 is arranged, the opening area that is the area of the opening 123 of the sensor coil 120, and the number of turns of the sensor coil 120. FIG. 4 is a diagram showing relationships;

Here, considering the detection performance of detecting a distant foreign object 10, the larger the product of the opening area and the number of turns, the better. However, if the product of the opening area and the number of turns is too large, the induced voltage induced in the sensor coil 120 due to the magnetic flux generated by the power transmission coil 211 will become too large, and the sensor coil 120 will burn out. Also, it is difficult to detect the foreign object 10 nearby. Therefore, the number of turns and the opening area of the sensor coil 120 are adjusted so that the induced voltage induced in the sensor coil 120 is constant regardless of the magnetic flux density at the position where the sensor coil 120 is arranged. That is, the product of the opening area and the number of turns is smaller for the sensor coil 120 arranged at a position where the magnetic flux density is higher.

For example, the magnetic flux density at the position where the sensor coil 120A is arranged is B1, the opening area of the sensor coil 120A is S1, and the number of turns of the sensor coil 120A is N1. Further, the magnetic flux density at the position where the sensor coil 120B is arranged is B2, the opening area of the sensor coil 120B is S2, and the number of turns of the sensor coil 120B is N2. Further, the magnetic flux density at the position where the sensor coil 120C is arranged is B3, the opening area of the sensor coil 120C is S3, and the number of turns of the sensor coil 120C is N3. Further, the magnetic flux density at the position where the sensor coil 120D is arranged is B4, the opening area of the sensor coil 120D is S4, and the number of turns of the sensor coil 120D is N4.

In this case, for example, based on B1, S1 and N1 are determined so that the induced voltage induced in the sensor coil 120A becomes a predetermined reference voltage. The reference voltage is, for example, the upper limit of the induced voltage at which burnout or the like is presumed not to occur. For example, when N1 is determined to be 2, S1 is determined so that the induced voltage becomes the reference voltage. In this embodiment, all the sensor coils 120 have the same number of turns, and N1=N2=N3=N4=2.

Also, when B2=B1/4, S2=S1×4. Also, when B3=B1/3, S3=S1×3. Also, when B4=B1/4, S4=S1×4. According to the present embodiment, it is possible to improve the detection performance of the foreign object detection apparatus 100 as a whole without causing burnout or the like in any of the sensor coils 120 .

In the present embodiment, the detection performance of sensor coil 120 is adjusted according to the height of the magnetic flux density at the position where sensor coil 120 is arranged. Specifically, the higher the magnetic flux density at the position where the sensor coil 120 is arranged, the smaller the product of the opening area and the number of turns is set. More specifically, the opening area and the number of turns are set for each of the plurality of sensor coils 120 so that the induced voltages induced in each of the plurality of sensor coils 120 are the same. According to the present embodiment, both improvement in detection performance and suppression of burnout of sensor coil 120 are achieved. In other words, according to the present embodiment, it is possible to prevent burnout of the sensor coil 120 and the like while maintaining high detection performance in foreign matter detection in wireless power transmission.

(Embodiment 2)
In the first embodiment, an example has been described in which the induced voltage induced in sensor coil 120 is adjusted by adjusting the opening area of sensor coil 120 . In this embodiment, an example in which the induced voltage induced in sensor coil 120 is adjusted by adjusting the number of turns of sensor coil 120 will be described. Note that the description of the same configuration and processing as in the first embodiment is omitted or simplified.

FIG. 9 shows a plan view of a detection coil unit 110A according to this embodiment. FIG. 10 shows a schematic diagram of a cross section taken along line XX in FIG. In order to facilitate understanding, FIG. 9 shows not only the detection coil unit 110 but also the power transmission coil 211 and the magnetic plate 212 included in the power transmission coil unit 210 . Also, in FIG. 9, the sensor coils 120 arranged inside the detection coil substrate 140 are indicated by solid lines instead of dashed lines for easy understanding. In order to facilitate understanding, FIG. 10 shows a schematic diagram schematically showing a cross section of the power transmission coil unit 210 in addition to the cross section of the detection coil unit 110A.

As shown in FIG. 9, the detection coil unit 110A has 8 sensor coils 120A, 1 sensor coil 120B, 14 sensor coils 120C, and 20 sensor coils 120D.

The sensor coil 120A has low detection performance for detecting a distant foreign object 10, but very high detection performance for detecting a small foreign object 10, and is arranged in the area A having a very high magnetic flux density. The sensor coil 120A is arranged in an opening 211A of the power transmission coil 211 and faces the magnetic plate 212 when viewed from the first direction. That is, the plurality of sensor coils 120A are annularly arranged at positions overlapping the opening 211A and the magnetic plate 212 when viewed from the first direction.

The sensor coil 120B has high detection performance for detecting a distant foreign object 10 and is arranged in a region B having a low magnetic flux density. The sensor coil 120B is arranged closer to the center of the power transmission coil 211 than the plurality of sensor coils 120A when viewed from the first direction. That is, the sensor coil 120B is arranged inside the plurality of sensor coils 120A that are annularly arranged when viewed from the first direction. Moreover, the sensor coil 120B is arranged at a position overlapping the opening 211A and the opening 212A.

The sensor coil 120C has low detection performance for detecting a distant foreign object 10, but high detection performance for detecting a small foreign object 10, and is arranged in a region C having a high magnetic flux density. The sensor coil 120C is arranged at a position overlapping with the conducting wire 211B of the power transmitting coil 211 when viewed from the first direction. That is, the plurality of sensor coils 120C are annularly arranged outside the plurality of annularly arranged sensor coils 120A when viewed from the first direction.

The sensor coil 120D has high detection performance for detecting a distant foreign object 10, and is generally arranged in a region straddling the region C having a high magnetic flux density and the region D having a low magnetic flux density. The sensor coil 120D is arranged at a position farther from the center of the power transmission coil 211 than the plurality of sensor coils 120C when viewed from the first direction. That is, the plurality of sensor coils 120D are annularly arranged outside the plurality of annularly arranged sensor coils 120C when viewed from the first direction.

Note that the sensor coil 120A, the sensor coil 120B, the sensor coil 120C, and the sensor coil 120D have a substantially rectangular shape when viewed from the first direction. Sensor coil 120A, sensor coil 120B, sensor coil 120C, and sensor coil 120D have openings 123 of the same size. In FIG. 10, the sizes of the openings 123 of the sensor coil 120 vary, but the actual sizes of the openings 123 of the sensor coil 120 are the same.

In the present embodiment, the number of turns of each of the plurality of sensor coils 120A and the number of turns of each of the plurality of sensor coils 120C are smaller than the number of turns of the sensor coil 120B. A specific description will be given below with reference to FIG. 11 . FIG. 11 shows the correspondence between the magnetic flux density at the position where the sensor coil 120 is arranged, the opening area that is the area of the opening 123 of the sensor coil 120, and the number of turns of the sensor coil 120 for each type of the sensor coil 120. FIG. 4 is a diagram showing relationships;

Considering the detection performance of detecting a distant foreign object 10, it is preferable that the product of the opening area and the number of turns is large. 120 may be damaged by burning or the like, and it is difficult to detect a foreign object 10 nearby. Therefore, in the present embodiment as well, the number of turns and the opening area are adjusted so that the induced voltage induced in sensor coil 120 is constant regardless of the magnetic flux density at the position where sensor coil 120 is arranged. . That is, the product of the opening area and the number of turns is smaller for the sensor coil 120 arranged at a position where the magnetic flux density is higher. In this embodiment, the induced voltage induced in the sensor coils 120 is adjusted by adjusting the number of turns, and all the sensor coils 120 have the same opening area.

For example, based on B1, S1 and N1 are determined so that the induced voltage induced in the sensor coil 120A becomes a predetermined reference voltage. For example, when N1 is determined to be 1, S1 is determined so that the induced voltage becomes the reference voltage. In this embodiment, all the sensor coils 120 have the same opening area, and S1=S2=S3=S4.

Also, when B2=B1/4, N2=N1×4=4. Also, when B3=B1/3, N3=N1×3=3. Also, when B4=B1/4, N4=N1×4=4. According to the present embodiment, it is possible to improve the detection performance of the foreign object detection apparatus 100 as a whole without causing burnout or the like in any of the sensor coils 120 .

In the present embodiment, the detection performance of sensor coil 120 is adjusted according to the height of the magnetic flux density at the position where sensor coil 120 is arranged. Therefore, according to the present embodiment, it is possible to prevent burning of the sensor coil 120, etc., while maintaining high detection performance in detecting a foreign object in wireless power transmission.

Note that in the present embodiment, all sensor coils 120 have the same opening area, and the detection performance of each sensor coil 120 is adjusted by adjusting the number of turns of each sensor coil 120 . Therefore, according to the present embodiment, an improvement in the degree of freedom in arranging the sensor coil 120 can be expected. For example, assume a case where a sensor coil 120 with high detection performance for detecting a distant foreign object 10 is arranged in a narrow place with a low magnetic flux density. In this case, it is difficult to dispose the sensor coil 120 with a large opening area and a small number of turns. However, in this case, the sensor coil 120 with a small opening area and a large number of turns can be arranged.

(Embodiment 3)
Embodiment 1 describes an example in which the position of sensor coil 120B in the first direction is the same as the position of sensor coil 120C in the first direction. In this embodiment, an example in which the position of sensor coil 120B in the first direction is different from the position of sensor coil 120C in the first direction will be described. Note that the description of the same configuration and processing as in the first and second embodiments will be omitted or simplified.

A front view of the detection coil unit 110B according to the present embodiment is the same as the front view shown in FIG. 3, so illustration is omitted. FIG. 12 shows a schematic diagram of a cross section of detection coil unit 110B according to the present embodiment. In order to facilitate understanding, FIG. 12 shows a schematic diagram schematically showing a cross section of the power transmission coil unit 210 in addition to the cross section of the detection coil unit 110B.

As shown in FIG. 12, in the present embodiment, each of the plurality of sensor coils 120A and each of the plurality of sensor coils 120C are arranged at positions farther from power transmitting coil 211 than sensor coil 120B in the first direction. It is In other words, the layer in which each of the plurality of sensor coils 120A and each of the plurality of sensor coils 120C are arranged in the detection coil substrate 140 is closer to the power transmission coil than the layer in which the sensor coil 120B is arranged in the detection coil substrate 140. Away from 211.

Here, the magnetic flux density of the magnetic flux generated by the power transmission coil 211 is basically lower at positions farther away from the power transmission coil 211 . Therefore, in the above configuration, the magnetic flux density at the position where the sensor coil 120A is arranged and the magnetic flux density at the position where the sensor coil 120C is arranged are prevented from becoming extremely high. That is, according to the present embodiment, the induced voltage induced in the sensor coil 120A and the induced voltage induced in the sensor coil 120C are prevented from becoming extremely high, and burning of the sensor coil 120A and the sensor coil 120C, etc. is further suppressed.

Also, the sensor coil 120A can detect the foreign object 10 placed near the sensor coil 120A, but it is extremely difficult to detect the foreign object 10 placed far from the sensor coil 120A. Also, the sensor coil 120C can detect a foreign object 10 placed near the sensor coil 120C, but it is difficult to detect a foreign object 10 placed far from the sensor coil 120C. According to the present embodiment, the sensor coil 120A and the sensor coil 120C are arranged closer to the foreign object 10 than the sensor coil 120B, so efficient foreign object detection can be expected.

(Embodiment 4)
Embodiment 3 has described an example in which the position of sensor coil 120A in the first direction is the same as the position of sensor coil 120C in the first direction. In this embodiment, an example will be described in which the position of sensor coil 120A in the first direction is different from the position of sensor coil 120C in the first direction. Note that the description of the same configuration and processing as in Embodiments 1-3 will be omitted or simplified.

A front view of the detection coil unit 110C according to the present embodiment is the same as the front view shown in FIG. 3, so illustration is omitted. FIG. 13 shows a schematic cross-sectional view of a detection coil unit 110C according to this embodiment. To facilitate understanding, FIG. 13 shows a schematic diagram schematically showing a cross section of the power transmission coil unit 210 in addition to the cross section of the detection coil unit 110C.

As shown in FIG. 13, in the present embodiment, each of the multiple sensor coils 120C is closer to the power transmission coil 211 than each of the multiple sensor coils 120A in the first direction, and is closer to the power transmission coil 211 than the sensor coil 120B. is placed away from That is, the layer in which each of the plurality of sensor coils 120C is arranged in the detection coil substrate 140 is closer to the power transmission coil 211 than the layer in which each of the plurality of sensor coils 120A is arranged in the detection coil substrate 140, and the detection coil In the substrate 140, the sensor coil 120B is farther from the power transmission coil 211 than the layer in which it is arranged.

Here, the magnetic flux density of the magnetic flux generated by the power transmission coil 211 is basically lower at positions farther away from the power transmission coil 211 . Therefore, in the above configuration, the magnetic flux density at the position where the sensor coil 120A is arranged is suppressed from becoming extremely high. Moreover, in the above configuration, the magnetic flux density at the position where the sensor coil 120C is arranged is suppressed to some extent from becoming extremely high. That is, according to the present embodiment, the induced voltage induced in sensor coil 120A is suppressed from becoming extremely high, and the induced voltage induced in sensor coil 120C is suppressed from becoming extremely high to some extent. and the sensor coil 120C are further suppressed.

Also, the sensor coil 120A can detect the foreign object 10 placed near the sensor coil 120A, but it is extremely difficult to detect the foreign object 10 placed far from the sensor coil 120A. Also, the sensor coil 120C can detect a foreign object 10 placed near the sensor coil 120C, but it is difficult to detect a foreign object 10 placed far from the sensor coil 120C. According to the present embodiment, since the sensor coil 120C is arranged further from the foreign object 10 than the sensor coil 120A and closer to the foreign object 10 than the sensor coil 120B, efficient foreign object detection can be expected.

(Modification)
Although the embodiments of the present disclosure have been described above, various modifications and applications are possible in carrying out the present disclosure. In the present disclosure, any part of the configurations, functions, and operations described in the above embodiments may be adopted. Further, in addition to the configurations, functions, and operations described above, additional configurations, functions, and operations may be employed in the present disclosure. Moreover, the above embodiments can be freely combined as appropriate. Also, the number of components described in the above embodiment can be adjusted as appropriate. Further, it goes without saying that materials, sizes, electrical characteristics, etc. that can be employed in the present disclosure are not limited to those shown in the above embodiments.

The position of each sensor coil 120 in the first direction is not limited to the examples described in Embodiments 1, 3, and 4, and can be adjusted as appropriate. For example, the position of the sensor coil 120A, the position of the sensor coil 120B, the position of the sensor coil 120C, and the position of the sensor coil 120D may all be the same in the first direction. Moreover, in the first direction, the position of the sensor coil 120A, the position of the sensor coil 120B, the position of the sensor coil 120C, and the position of the sensor coil 120D may all be different. In this case, it is preferable that the sensor coil 120 having a larger product of the opening area and the number of turns be arranged closer to the power transmission coil 211 in the first direction.

In the first embodiment, an example in which the sensor coil 120 has two turns has been described. The number of turns of the sensor coil 120 may be one, or three or more. Further, in Embodiment 1, an example in which the opening area is adjusted and the number of turns is not adjusted is described, and in Embodiment 2, an example in which the opening area is not adjusted and the number of turns is adjusted is described. Both the opening area and the number of turns may be adjusted. In this case, the sensor coil 120 having a larger product of the opening area and the number of turns is preferably arranged at a position where the magnetic flux density is lower.

In the first embodiment, an example has been described in which the opening area and the number of turns are adjusted so that the induced voltages induced in all the sensor coils 120 are the same. The induced voltages induced in all sensor coils 120 need not be the same. However, it is preferable to adjust the opening area and the number of turns so that the induced voltages induced in all the sensor coils 120 have as little difference as possible.

In Embodiments 1-4, an example in which foreign object detection device 100 includes four types of sensor coils 120, sensor coil 120A, sensor coil 120B, sensor coil 120C, and sensor coil 120D, has been described. Foreign object detection device 100 does not have to include these four types of sensor coils 120 . Foreign object detection device 100 may include at least two types of sensor coils 120 out of these four types of sensor coils 120 .

For example, the foreign object detection device 100 may include two types of sensor coils 120, a sensor coil 120A and a sensor coil 120B, or three types of sensor coils 120, a sensor coil 120A, a sensor coil 120B, and a sensor coil 120C. may be provided. Also, the number of sensor coils 120 of each type is not limited to the number described in the first and second embodiments.

In the first embodiment, an example in which the sensor coil 120 is driven by a self-exciting method in which the pulse-like voltage generated by the pulse generating section 160 under the control of the driving section 153 is used to drive the sensor coil 120 has been described. As a method for driving the sensor coil 120, a separate excitation method can be adopted. For example, it is possible to employ a separate excitation method in which the sensor coil 120 is driven using the magnetic flux generated by the power transmission coil 211 .

Various embodiments and modifications of the present disclosure are possible without departing from the broad spirit and scope of the present disclosure. In addition, the embodiments described above are for explaining the present disclosure, and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is indicated by the claims rather than the embodiments. Various modifications made within the scope of the claims and within the scope of equivalent disclosure are considered to be within the scope of the present disclosure.

10 Foreign object 100 Foreign object detection device 110, 110A, 110B, 110C Detection coil unit 120, 120A, 120B, 120C, 120D Sensor coil 121A, 121B, 121C, 121D Coil conductor 123, 123A, 123B, 123C, 123D, 211A, 212A Opening Unit 131 Capacitors 132, 133 Switch 140 Detection coil substrate 150 Detection unit 151 Detection control unit 152 Selection unit 153 Driving unit 154 Output value acquisition unit 155 Storage unit 156 Result output unit 157 Power transmission control unit 160 Pulse generation unit 170 Notification unit 200 Power transmission device 210 power transmission coil unit 211 power transmission coil 211B conducting wire 212 magnetic plate 213 metal plate 220 power supply device 300 power receiving device 310 power receiving coil unit 311 power receiving coil 312 magnetic plate 320 rectifier circuit 400 commercial power supply 500 storage battery 600 terminal device 700 electric vehicle 1000 electric power transmission system

Claims (15)

1. a power transmission coil configured by winding a conductor wire and having an opening;
   a magnetic body facing the power transmission coil;
   a foreign object detection device,
   The foreign matter detection device includes a plurality of sensor coils and a detection unit that detects a foreign matter present in a foreign matter detection area based on signals output from the plurality of sensor coils,
   The plurality of sensor coils have a first sensor opening, and are arranged in the opening when viewed from a first direction in which the coil axis of the power transmission coil extends, and a plurality of first sensor coils facing the magnetic body. a sensor coil, and a second sensor coil having a second sensor opening and arranged closer to the center of the power transmission coil than the plurality of first sensor coils when viewed from the first direction,
   The area of the first sensor opening is S1, the number of turns of each of the plurality of first sensor coils is N1, the area of the second sensor opening is S2, and the number of turns of the second sensor coil is N2. when N1×S1<N2×S2 is satisfied,
   transmission device.
2. when viewed from the first direction, the first sensor opening is smaller than the second sensor opening;
   The power transmission device according to claim 1 .
3. The number of turns of each of the plurality of first sensor coils is less than the number of turns of the second sensor coil,
   The power transmission device according to claim 1 or 2.
4. Each of the plurality of first sensor coils is arranged at a position farther from the power transmission coil than the second sensor coil in the first direction,
   The power transmission device according to any one of claims 1 to 3.
5. a voltage induced in each of the plurality of first sensor coils when the magnetic flux generated by the power transmission coil interlinks with each of the plurality of first sensor coils; and the magnetic flux interlinks with the second sensor coil. is the same as the voltage induced in the second sensor coil when
   The power transmission device according to any one of claims 1 to 4.
6. The plurality of first sensor coils are arranged annularly when viewed from the first direction,
   The power transmission device according to any one of claims 1 to 5.
7. Each of the plurality of first sensor coils and the second sensor coil have a substantially square shape when viewed from the first direction,
   The power transmission device according to any one of claims 1 to 6.
8. The plurality of sensor coils have a third sensor opening, and have a plurality of third sensor coils overlapping the conductor wire when viewed from the first direction,
   When the area of the third sensor opening is S3 and the number of turns of each of the plurality of third sensor coils is N3, N3×S3<N2×S2 is satisfied.
   The power transmission device according to any one of claims 1 to 7.
9. When viewed from the first direction, the first sensor opening and the third sensor opening are smaller than the second sensor opening,
   The power transmission device according to claim 8 .
10. The number of turns of each of the plurality of first sensor coils and the number of turns of each of the plurality of third sensor coils are less than the number of turns of the second sensor coil,
    The power transmission device according to claim 8 or 9.
11. Each of the plurality of first sensor coils and each of the plurality of third sensor coils are arranged at a position farther from the power transmission coil than the second sensor coil in the first direction,
    The power transmission device according to any one of claims 8 to 10.
12. a voltage induced in each of the plurality of first sensor coils when the magnetic flux generated by the power transmission coil interlinks with each of the plurality of first sensor coils; and the magnetic flux interlinks with the second sensor coil. and a voltage induced in each of the plurality of third sensor coils when the magnetic flux interlinks with each of the plurality of third sensor coils, are identical,
    The power transmission device according to any one of claims 8 to 11.
13. The plurality of sensor coils has a fourth sensor opening, and a plurality of fourth sensor coils arranged at a position farther from the center of the power transmission coil than the plurality of third sensor coils when viewed from the first direction. having a sensor coil,
    When the area of the fourth sensor opening is S4 and the number of turns of each of the plurality of fourth sensor coils is N4, N3×S3<N4×S4 is satisfied.
    The power transmission device according to any one of claims 8 to 12.
14. a voltage induced in each of the plurality of first sensor coils when the magnetic flux generated by the power transmission coil interlinks with each of the plurality of first sensor coils; and the magnetic flux interlinks with the second sensor coil. a voltage induced in each of the plurality of third sensor coils when the magnetic flux interlinks with each of the plurality of third sensor coils; and The voltage induced in each of the plurality of fourth sensor coils when the magnetic flux interlinks with each of the plurality of fourth sensor coils is the same.
    The power transmission device according to claim 13.
15. The power transmission device according to any one of claims 1 to 14;
    a power receiving device that receives power from the power transmitting device;
    power transmission system.

Images