JP2017055529A - Power transmission device, power reception device and non-contact power transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an incorrect detection of a foreign object by the change of transmission power, while maintaining the detection accuracy of a foreign object, which exists between a power transmission coil and a power reception coil, as high as possible.SOLUTION: A control device executes first determination processing and second determination processing. The first determination processing determines that a foreign object exists if a difference between first and second induction voltages, which are respectively generated at two coils for foreign object detection among a plurality of coils for foreign object detection, is a predetermined first value or greater. The second determination processing determines that a foreign object exists if the variation of a value, which indicates an induction voltage generated at one of the plurality of coils for foreign object detection, is a predetermined second value or greater. The control device executes the first determination processing when a condition to determine a stable state of power which is transmitted from the power transmission coil to the power reception coil indicates instability, whereas executes the second determination processing if the above condition indicates stability.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power transmission device, a power reception device, and a non-contact power transmission system, and more particularly to a power transmission device, a power reception device, and a non-contact power transmission system that detect a foreign object existing between the power transmission device and the power reception device.

  Conventionally, a non-contact power transmission system that performs non-contact power transmission from a power transmission device to a power reception device is known (see Patent Documents 1 to 6). In such a non-contact power transmission system, it is assumed that a foreign object (an object that should not exist) enters between the power transmission device and the power receiving device, and it is necessary to detect the foreign material appropriately. For example, Japanese Patent Laying-Open No. 2013-27171 (Patent Document 6) discloses a detection device that can accurately detect a metal foreign object even during power transmission from a power transmission device to a power reception device. This detection device detects a metallic foreign object existing between the power transmission device and the power reception device by using a change in the Q value of the resonance circuit including the coil.

JP2013-154815A JP2013-146154A JP2013-146148A JP 2013-110822 A JP 2013-126327 A JP2013-27171A

  In the detection device disclosed in Patent Document 6, the coil for measuring the Q value may be a power feeding coil. Even when the Q value measuring coil is provided separately from the power feeding coil, it is the same size as the power feeding coil. It is assumed that In this case, there is a possibility that foreign matters smaller than the power feeding coil (power transmission coil) may not be detected with high accuracy.

  In order to detect a foreign object smaller than the power transmission coil with high accuracy, a plurality of foreign object detection coils smaller than the power transmission coil may be provided. Depending on the presence or absence of foreign matter between the power transmission coil and the power reception coil, the power reception state of at least one of the plurality of foreign matter detection coils changes. Therefore, for example, foreign matter detection can be performed by monitoring temporal changes in the power receiving state in each of the plurality of foreign matter detection coils.

  However, if foreign object detection is performed by monitoring temporal changes in the power reception state of the foreign object detection coil, the power reception state of the foreign object detection coil is changed when the magnitude of power transmitted by the power transmission coil changes abruptly. It may change and falsely detect foreign objects. The above Patent Documents 1 to 6 do not disclose any problem of such foreign object erroneous detection and its solution.

  The present invention has been made to solve such a problem, and its object is to change the transmission power while maintaining the detection accuracy of a foreign object existing between the power transmission coil and the power reception coil as high as possible. It is providing the power transmission apparatus, power receiving apparatus, and non-contact electric power transmission system which can suppress the erroneous detection of the foreign material by.

  A power transmission device according to an aspect of the present invention includes a power transmission coil, a foreign object detection coil, and a control device. The power transmission coil is configured to transmit power to the power reception coil of the power reception device in a contactless manner. The plurality of foreign object detection coils are arranged along the upper surface of the power transmission coil above the power transmission coil, assuming that the power transmission coil transmits power to the power reception coil located above the power transmission coil. The control device executes a first determination process and a second determination process. In the first determination process, when a difference between the first and second induced voltages generated in two of the plurality of foreign matter detection coils is greater than or equal to a first predetermined value, the presence of foreign matter is determined. This is a process for determining. The second determination process is a process for determining that a foreign object is present when the amount of change in the value indicating the induced voltage generated in any of the plurality of foreign object detection coils is equal to or greater than a second predetermined value. The control device executes the first determination process when the condition for determining the stable state of the power transmitted from the power transmission coil to the power reception coil indicates instability, and performs the second determination when the condition indicates stability. Execute the judgment process.

  A power reception device according to another aspect of the present invention includes a power reception coil, a plurality of foreign object detection coils, and a control device. The power reception coil is configured to receive power in a non-contact manner from the power transmission coil of the power transmission device. The plurality of foreign object detection coils are disposed along the lower surface of the power receiving coil under the power receiving coil, as the power receiving coil receives power from the power transmitting coil positioned below the power receiving coil. The control device executes a first determination process and a second determination process. In the first determination process, when a foreign object exists when the difference between the first and second induced voltages respectively generated in two foreign object detection coils among the plurality of foreign object detection coils is equal to or greater than a first predetermined value. This is a process for determining. The second determination process is a process for determining that a foreign object is present when the amount of change in the value indicating the induced voltage generated in any of the plurality of foreign object detection coils is equal to or greater than a second predetermined value. The control device executes the first determination process when the condition for determining the stable state of the power transmitted from the power transmission coil to the power reception coil indicates instability, and performs the second determination when the condition indicates stability. Execute the judgment process.

  A contactless power transmission system according to another aspect of the present invention includes a power transmission device and a power reception device. This non-contact power transmission system includes a power reception coil, a power transmission coil, a plurality of foreign object detection coils, and a control device. The power reception coil is configured to receive power from the power transmission device in a contactless manner. The power transmission coil is configured to transmit power to the power receiving coil in a contactless manner. The plurality of foreign matter detection coils are assumed to transmit power to a power receiving coil located above the power transmission coil, and are arranged along the upper surface of the power transmission coil above the power transmission coil or on the lower surface of the power reception coil below the power reception coil. Arranged along. The control device executes a first determination process and a second determination process. In the first determination process, when a foreign object exists when the difference between the first and second induced voltages respectively generated in two foreign object detection coils among the plurality of foreign object detection coils is equal to or greater than a first predetermined value. This is a process for determining. The second determination process is a process for determining that a foreign object is present when the amount of change in the value indicating the induced voltage generated in any of the plurality of foreign object detection coils is equal to or greater than a second predetermined value. The control device executes the first determination process when the condition for determining the stable state of the power transmitted from the power transmission coil to the power reception coil indicates instability, and performs the second determination when the condition indicates stability. Execute the judgment process.

  The interval at which the value indicating the power reception state of each of the two different foreign object detection coils is detected is shorter than the interval at which the value indicating the power reception state of the same foreign object detection coil is detected. Therefore, the first determination process is less susceptible to the change in the transmission power than the second determination process. On the other hand, the value indicating the power reception state of the foreign object detection coil slightly changes because, for example, the magnetic flux density of the transmitted power differs depending on the location of the foreign object detection coil. Therefore, the accuracy of foreign object detection is higher in the second determination process for comparing the power reception states of the same foreign object detection coils than in the first determination process. In each of the above inventions, the first determination process is performed when the power transmitted from the power transmission coil to the power reception coil is unstable, and the second determination process is performed when the power is stable. Is done. That is, when the power is unstable, the first determination process that is not easily affected by the change in the transmission power is executed, and when the power is stable, the second determination process with high accuracy is executed. . As a result, according to each of the above-described inventions, it is possible to suppress the foreign object detection due to the change in the transmitted power while maintaining the detection accuracy of the foreign object existing between the power transmission coil and the power receiving coil as high as possible.

  According to the present invention, a power transmitting device, a power receiving device, and a power receiving device capable of suppressing erroneous detection of a foreign material due to a change in transmitted power while maintaining as high a detection accuracy of a foreign material existing between a power transmitting coil and a power receiving coil as possible. A contactless power transmission system can be provided.

1 is a schematic configuration diagram of a contactless power transmission system according to a first embodiment. It is a disassembled perspective view of a power transmission unit. It is a perspective view of the coil pair comprised by the 1st coil and the 2nd coil. It is the figure which showed the electrical structure of the foreign material detector. It is a figure for demonstrating the order in which alternating voltage is applied to each 1st coil of a foreign material detector. It is a flowchart which shows the specific procedure of a foreign material detection process. 6 is an exploded perspective view of a power receiving unit according to Embodiment 2. FIG. It is the figure which showed the electrical structure of the foreign material detector. It is a figure which shows the 1st coil and 2nd coil of the figure eight shape in other embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, a plurality of embodiments will be described. However, it is planned from the beginning of the application to appropriately combine the configurations described in the embodiments. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

(Embodiment 1)
<Configuration of contactless power transmission system>
1 is a schematic configuration diagram of a contactless power transmission system to which a power transmission device according to Embodiment 1 of the present invention is applied. In the figure, an arrow D indicates a downward vertical direction, and an arrow U indicates an upward vertical direction. These are the same in FIGS.

  Referring to FIG. 1, non-contact power transmission system 1000 includes a vehicle 100 and a power transmission device 300. Vehicle 100 includes a power reception unit 200, and power reception unit 200 includes a power reception coil (not shown). The power receiving coil of the power receiving unit 200 is configured to receive power from the power transmitting device 300 in a contactless manner. In vehicle 100, the power received by power receiving unit 200 is supplied to a power storage device (not shown). Vehicle 100 can travel by generating travel driving force from the power of the power storage device.

  The power transmission device 300 includes an AC power source 330, a power transmission unit 400, and a control device 485. The AC power source 330 is connected to the power transmission unit 400 and supplies AC power to the power transmission unit 400. The power transmission unit 400 includes a power transmission coil (not shown). The power transmission coil forms a magnetic field by receiving supply of AC power from the AC power supply 330, and contacts the power reception coil of the power reception unit 200 via the formed magnetic field in a non-contact manner. Power transmission. The number of turns of the conducting wire in the power transmission coil is appropriately designed so that the distance between the power transmission coil and the power reception coil, the Q value (for example, Q ≧ 100), and the coupling coefficient κ are increased. The control device 485 will be described later with reference to FIG.

<Configuration of power transmission unit>
FIG. 2 is an exploded perspective view of the power transmission unit 400 shown in FIG. Referring to FIG. 2, power transmission unit 400 includes a power transmission coil 410, a housing 430, a foreign object detector 460, and a resonance capacitor (not shown) arranged in the arrow D direction with respect to power transmission coil 410. Power transmission coil 410 includes a core 440 and a conductive wire 450 wound around core 440. As an example, the core 440 is made of ferrite. The power transmission coil 410 and a resonance capacitor (not shown) are accommodated in the housing 430. The housing 430 includes a shield 432 and a lid member 434.

  If there is a foreign object (an object that should not exist) between the power transmission unit 400 and the power receiving unit 200 (FIG. 1), the foreign object generates heat during power transmission from the power transmitting coil 410 to the power receiving coil of the power receiving unit 200, Transmission efficiency is reduced. The foreign object detector 460 detects such a foreign object when the foreign object exists between the power transmission unit 400 and the power receiving unit 200 (FIG. 1). As a foreign material, a metal piece, such as a drink can and money, and an animal are assumed, for example.

  Foreign object detector 460 includes a plurality of first coils 468 and a plurality of second coils 478. The plurality of first coils 468 and the plurality of second coils 478 are provided above the power transmission coil 410 (in the direction of the arrow U), and are disposed on the inner surface of the lid member 434 in the first embodiment. The plurality of second coils 478 are provided corresponding to the plurality of first coils 468, and each first coil 468 and each second coil 478 have the same size and shape. Each second coil 478 is arranged to face the corresponding first coil 468 and constitutes a coil pair together with the corresponding first coil 468. A plurality of coil pairs corresponding to the number of the plurality of first coils 468 (the plurality of second coils 478) are arranged in a matrix on the inner surface of the lid member 434. With such a coil pair having an outer shape smaller than that of the power transmission coil 410, even a small foreign object that cannot be detected by a change in the power reception state of the power reception unit 200 can be detected.

  Note that the foreign matter may exist above the coil pair, not between the first coil 468 and the second coil 478 constituting the coil pair. Even in such a case, the first coil 468 is present due to the presence of the foreign matter. And the second coil 478 change the coupling coefficient. As a result, the power receiving state of the second coil 478 changes. Therefore, a foreign object can be detected based on the power receiving state of the second coil 478. The power receiving state of the second coil 478 is typically an induced voltage generated in the second coil 478, but may be an induced current or induced power generated in the second coil 478.

  FIG. 3 is a perspective view of a coil pair constituted by the first coil 468 and the second coil 478. Referring to FIG. 3, each of first coil 468 and second coil 478 has a rectangular shape. The second coil 478 is disposed to face the corresponding first coil 468.

  When a detection AC voltage is applied to the first coil 468, the first coil 468 forms a detection magnetic field AR1. Then, an induced voltage is generated by the detection magnetic field AR1 in the second coil 478 arranged to face the first coil 468. At this time, if a foreign object exists in the vicinity of the coil pair, the magnetic field for detection AR1 is affected by the foreign object, the coupling coefficient between the first coils 468 and 478 changes, and the power receiving state of the second coil 478 changes.

  FIG. 4 is a diagram showing an electrical configuration of foreign object detector 460 shown in FIG. Referring to FIG. 4, in addition to the plurality of first coils 468 and the plurality of second coils 478, the foreign object detector 460 includes an oscillator 461, a power amplifier 462, a resonance capacitor 463, multiplexers 464, 465, A plurality of common wirings 466 and 467 are included. Foreign object detector 460 further includes a signal processing circuit 471, a resonance capacitor 472, a resonance resistor 473, multiplexers 474 and 475, and a plurality of common wires 476 and 477.

  For convenience of explanation, the plurality of first coils 468 and the plurality of second coils 478 are illustrated apart from each other, but actually, as described with reference to FIG. Are arranged to face the corresponding first coil 468 and constitute a coil pair with the corresponding first coil 468. Moreover, in this Embodiment 1, although the structure by which 16 coil pairs are provided is shown as an example, the number of coil pairs is not limited to this.

  In the power transmission device according to the first embodiment, multiplexers 464, 465, 474, and 475 provide one first coil 468 to which a detection AC voltage is applied among a plurality of first coils 468, and the detection AC. A pair (coil pair) with one second coil 478 corresponding to the first coil 468 to which the voltage is applied is sequentially switched. This will be specifically described below.

  The oscillator 461 generates a signal having an arbitrary frequency (for example, 13.56 MHz), and the signal is amplified by the power amplifier 462. The AC voltage for detecting foreign matter output from the power amplifier 462 is input to the multiplexer 464 through the resonance capacitor 463. The multiplexer 464 is connected to the resonance capacitor 463, the control device 485, and the four common wires 466. On the other hand, the multiplexer 465 is connected to the ground line, the control device 485, and the four common wires 467.

  Each common wire 466 is connected to one terminal of four first coils 468. Each common wiring 467 is connected to the other terminal of the four first coils 468. The multiplexer 464 outputs an AC voltage to any one of the four common wirings 466 in accordance with a switching command from the control device 485. The multiplexer 465 conducts any one of the four common wirings 467 to the ground line in accordance with a switching command from the control device 485.

  The plurality of first coils 468 are arranged in a 4 × 4 matrix. The AC voltage from the multiplexer 464 is applied to one of the 16 first coils 468 at a certain timing by the multiplexer 464 and the multiplexer 465. The first coil 468 to which the AC voltage is applied is determined according to a switching command given from the control device 485 to the multiplexers 464 and 465. Each first coil 468 forms a detection magnetic field when a detection AC voltage is applied.

  On the other hand, the plurality of second coils 478 are also arranged in a 4 × 4 matrix. The multiplexer 474 is connected to the resonance capacitor 472, the control device 485, and the four common wires 476. The multiplexer 475 is connected to the ground line, the control device 485, and the four common wires 477. Each common wiring 476 is connected to one terminal of four second coils 478. Each common wiring 477 is connected to the other terminal of the four second coils 478. The signal processing circuit 471 is connected to the resonance capacitor 472 and the resonance resistor 473. The resonance resistor 473 is provided in order to realize power transmission that is robust against a frequency shift.

  When an AC voltage is applied to any of the 16 first coils 468, the first coil 468 forms a magnetic field for detection. The second coil 478 arranged to face the first coil 468 generates an induced voltage by the detection magnetic field formed by the first coil 468. The second coil 478 is specified in advance according to a switching command sent from the control device 485 to the multiplexers 474 and 475.

  The induced voltage generated in the second coil 478 corresponding to the first coil 468 to which the AC voltage for detection is applied is passed through the multiplexer 474, the resonance capacitor 472, and the resonance resistor 473 (for example, an AC / DC circuit). ). The signal processing circuit 471 converts the voltage received from the resonant capacitor 472 into a signal suitable for reception by the control device 485 and outputs the signal to the control device 485.

  When a foreign object exists in the vicinity of the first coil 468 and the second coil 478, the magnetic field formed around the first coil 468 and the second coil 478 interlinks with the foreign object, so that the second The power receiving state of the coil 478 changes.

  The power transmission unit 400 according to the first embodiment can execute two types of determination processes as determination processes for foreign object detection. Specifically, the power transmission unit 400 can execute a first determination process and a second determination process. In the first embodiment, the induced voltage generated in each second coil 478 is detected in order, and the detection of the induced voltage generated in all the second coils 478 is one cycle, and this cycle is repeated.

  The first determination process is a determination process that determines that there is a foreign object when the difference between the induced voltages generated in the two second coils 478 is equal to or greater than a second predetermined value in the same cycle. For example, in the first determination process, the difference between induced voltages generated in two adjacent second coils 478 is sequentially calculated for each second coil 478.

  The second determination process is that a foreign object exists when the difference between the induced voltage generated in the second coil 478 and the induced voltage generated in the same second coil 478 one cycle before is equal to or greater than a first predetermined value. This is a determination process for determining. The second determination process is executed by sequentially calculating the difference from the induced voltage one cycle before in each second coil 478.

<Suppression of influence of transmission power change in foreign object detection>
According to the power transmission unit 400 configured as described above, it is possible to determine intrusion of a foreign object by monitoring temporal changes in the power reception state in each of the plurality of second coils 478 (second determination process). . However, if the intrusion of foreign matter is determined by always monitoring the temporal change in the power reception state of the second coil 478, the second coil 478 is changed when the magnitude of the power transmitted by the power transmission coil 410 changes abruptly. There is a possibility that the power receiving state of the battery will change and foreign objects will be erroneously detected.

  In power transmission device 300 according to the first embodiment, control device 485 selectively uses the first determination process and the second determination process. The first determination process determines that there is a foreign object when the difference between the values indicating the power reception states (inductive voltages) of the two second coils 478 among the plurality of second coils 478 is equal to or greater than a first predetermined value. It is processing to do. The second determination process is a process of determining that a foreign object is present when the amount of change in the value indicating the power reception state of any of the plurality of second coils 478 is equal to or greater than a second predetermined value. Then, the control device executes the first determination process when the condition for determining the stable state of the transmission power by the power transmission coil indicates instability, and performs the second determination process when the condition indicates stability. Run.

  The interval at which the value indicating the power reception state of each of the two different second coils 478 is detected is shorter than the interval at which the value indicating the power reception state of the same second coil 478 is detected. Therefore, the first determination process is less susceptible to the change in the transmission power than the second determination process. On the other hand, the value indicating the power reception state of the second coil 478 slightly changes because, for example, the magnetic flux density of the transmitted power differs depending on the location of the second coil 478 and the like. Therefore, the second determination process for comparing the power reception states of the same second coil 478 has higher foreign object detection accuracy than the first determination process. In power transmission device 300 according to the first embodiment, the first determination process is executed when the transmission power is unstable, and the second determination process is executed when the transmission power is stable. . That is, when the transmitted power is unstable, a determination process that is not easily affected by changes in the transmitted power is executed, and when the transmitted power is stable, a highly accurate determination process is executed. As a result, according to the power transmission device 300 according to the first embodiment, erroneous detection of foreign matter due to changes in transmitted power is performed while maintaining the detection accuracy of foreign matter existing between the power transmission unit 400 and the power receiving unit 200 as high as possible. Can be suppressed.

  Next, the control device 485 executes the first determination process when the fluctuation range of the transmission power is large, and details the reason why the second determination process is executed when the fluctuation range of the transmission power is small. explain.

  FIG. 5 is a diagram for explaining the order in which an AC voltage is applied to each first coil 468 of foreign object detector 460. Referring to FIG. 5, in the first embodiment, control device 485 controls multiplexers 464 and 465 to apply an alternating voltage in the order of first coils 468 (A) to 468 (P). When an AC voltage is applied to the first coil 468 (P), the control device 485 again controls the multiplexers 464 and 465 so as to apply the AC voltage in order from the first coil 468 (A).

  Since such control is performed, in this Embodiment 1, in order to compare the receiving voltage in the same 2nd coil 478, it waits until 1 cycle passes. As a result, if the transmission power suddenly increases before the power reception voltage after one cycle in the same second coil 478 is detected, the power reception voltage after one cycle also increases abruptly, and foreign matter is erroneously detected. It can happen. That is, it can be said that the second determination process for comparing the received voltage of the same second coil 478 is easily influenced by a sudden change in the transmitted power.

  On the other hand, for example, if the received voltage of the second coil 478 (A) and the received voltage of the second coil 478 (B) are compared (first determination process), the time lag in detecting the received voltage is one cycle. This is shorter than the time required and shorter than the second determination process. Therefore, it can be said that the first determination process is less affected by the rapid change in the transmission power than the second determination process. Here, in the first determination process, the received voltages of the two adjacent second coils 478 do not necessarily have to be compared. For example, the received voltages of two second coils 478 having the same sum of the wiring lengths from each of the multiplexers 474 and 475 may be compared. For example, the second coil 478 (B) and the second coil 478 (E) may be compared, or the second coil 478 (H) and the second coil 478 (N) may be compared. . This is because it is considered that when the sum of the wiring lengths from each of the multiplexers 474 and 475 is closer, the resistance value caused by the common wirings 476 and 477 is also closer, and a receiving voltage close to that when receiving the same magnetic flux is generated. .

  However, in the first determination process, since the received voltage of the same second coil 478 is not compared as in the second determination process, the foreign object detection accuracy is lower than that in the second determination process. To do. For example, the magnitude of the magnetic flux density of the magnetic field received by the two second coils 478 from the power transmission coil 410 varies depending on the arrangement location of the two second coils 478 to be compared. Therefore, a difference in the received voltage generated in each of the two second coils 478 may occur due to the difference in magnetic flux density. Further, a difference in resistance value caused by the common wirings 476 and 477 may cause a difference in received voltage generated in each of the two second coils 478. Since the foreign matter can be erroneously detected due to the difference in the received voltage caused by such a cause other than the foreign matter, the first determination process is less accurate than the second determination process.

  Therefore, in power transmission device 300 according to the first embodiment, control device 485 executes the first determination process when the conditions for determining the stable state of transmitted power indicate instability, and the above conditions indicate stability. In this case, the second determination process is executed. Therefore, according to the power transmission device 300 according to the first embodiment, the detection accuracy of the foreign matter existing between the power transmission unit 400 and the power receiving unit 200 is kept as high as possible, and the erroneous detection of the foreign matter due to the change in the transmission power is suppressed. can do. Next, a specific procedure of the foreign object detection process in the first embodiment will be described.

<Foreign matter detection processing>
FIG. 6 is a flowchart showing a specific procedure of foreign object detection processing in the first embodiment. Referring to FIG. 6, control device 485 determines whether or not the power transmitted by power transmission coil 410 is stable (step S100).

  For example, whether or not it is within a predetermined time from the start of power transmission may be a condition for determining the stable state of the transmitted power. In this case, the control device 485 determines that the transmission power is unstable because the transmission power is not stable at the start of power transmission by the power transmission device 300, and the transmission power is stable after the predetermined time has elapsed. It is determined that Further, for example, the above condition may be whether or not a function for limiting the target value of transmitted power to a predetermined value or less is enabled. In this case, when the function is enabled, the control device 485 determines that the transmission power is unstable because the transmission power may be drastically reduced. When the function is invalid, Since it is considered that the transmitted power does not change rapidly, it is determined that the transmitted power is stable. Further, for example, the above condition may be whether or not the fluctuation range of the effective value of the transmission power is equal to or greater than a predetermined value. In this case, the control device 485 monitors the fluctuation range of the effective value of the transmission power, determines that the transmission power is unstable when the fluctuation range of the effective value of the transmission power is equal to or greater than a predetermined value, When the fluctuation range of the transmission power is less than a predetermined value, it is determined that the transmission power is stable.

  If it is determined that the transmitted power is stable (YES in step S100), priority can be given to the accuracy of foreign object detection, and therefore the control device 485 changes the amount of received voltage of each of the plurality of second coils 478. In accordance with (temporal differential value), it is determined whether or not a foreign object exists between the power transmission unit 400 and the power reception unit 200. Specifically, control device 485 determines that there is a foreign object between power transmission unit 400 and power reception unit 200 when the amount of change in power reception voltage is equal to or greater than a first predetermined value (step S110).

  If it is determined that the transmission power is not stable (NO in step S100), the control device 485 needs to suppress the influence of the change in the transmission power, so that the control device 485 has two second coils out of the plurality of second coils 478. It is determined whether there is a foreign object between the power transmission unit 400 and the power reception unit 200 according to the difference (spatial differential value) of the power reception voltage 478. Specifically, the control device 485 sequentially compares the power reception voltages of two adjacent second coils 478 among the plurality of second coils 478, and when the difference is equal to or greater than a second predetermined value, the power transmission unit It is determined that there is a foreign object between 400 and the power receiving unit 200 (step S120).

  As described above, in power transmission device 300 according to the first embodiment, control device 485 executes the first determination process when the condition for determining the stable state of transmitted power indicates instability, and the above condition is stable. The second determination process is executed when Therefore, according to the power transmission device 300 according to the first embodiment, the detection accuracy of the foreign matter existing between the power transmission unit 400 and the power receiving unit 200 is kept as high as possible, and the erroneous detection of the foreign matter due to the change in the transmission power is suppressed. can do.

(Embodiment 2)
In the first embodiment, foreign object detector 460 is provided on the power transmission unit 400 side. In the second embodiment, the foreign object detector is provided on the power receiving unit side. Hereinafter, the configuration of the power receiving unit in the second embodiment will be described.

<Configuration of power receiving unit>
FIG. 7 is an exploded perspective view of power reception unit 200A in the second embodiment. Referring to FIG. 7, power reception unit 200 </ b> A includes power reception coil 210, housing 230, foreign object detector 560, and a resonance capacitor (not shown) arranged in the arrow U direction with respect to power reception coil 210. The power receiving coil 210 includes a core 240 and a conductive wire 250 wound around the core 240. The housing 230 includes a shield 232 and a lid member 234.

  Foreign object detector 560 includes a plurality of first coils 568 and a plurality of second coils 578. The plurality of first coils 568 and the plurality of second coils 578 are provided below the power receiving coil 210 (in the direction of arrow D), and are disposed on the inner surface of the lid member 234 in the second embodiment.

  FIG. 8 is a diagram showing an electrical configuration of foreign object detector 560 shown in FIG. Referring to FIG. 8, foreign object detector 560 to control device 585 correspond to foreign object detector 460 to control device 485 (FIG. 4) and have equivalent functions.

  That is, in the second embodiment, the first determination process is performed when the difference between the values indicating the induced voltages generated in at least two second coils 578 among the plurality of second coils 578 is equal to or greater than the first predetermined value. In addition, it is a process for determining that there is a foreign object. The second determination process is a process of determining that a foreign object is present when the amount of change in the value indicating the induced voltage generated in any of the plurality of second coils 578 is equal to or greater than a second predetermined value. Then, the control device 585 executes the first determination process when the condition for determining the stable state of the received power indicates instability, and executes the second determination process when the condition indicates stability. . According to vehicle 100 according to the second embodiment, it is possible to suppress erroneous detection of foreign matters due to changes in transmitted power while maintaining the detection accuracy of foreign matters existing between power transmission unit and power receiving unit 200A as high as possible. .

(Other embodiments)
As described above, the first and second embodiments have been described as the embodiments of the present invention. However, the present invention is not necessarily limited to these embodiments. Here, an example of another embodiment will be described.

  In the first and second embodiments, rectangular coils are used as the first coil (468, 568) and the second coil (478, 578). However, the shape of the first coil and the second coil is not necessarily limited to such an example. For example, the first coil and the second coil may be configured in an eight-letter shape. FIG. 9 is a diagram showing an eight-shaped first coil and a second coil when a foreign object detector is provided on the power transmission unit side. Even in this case, the foreign object detector may be provided on the power receiving unit side. Referring to FIG. 9, first coil 468a corresponds to first coil 468 (FIG. 3), and second coil 478a corresponds to second coil 478 (FIG. 3).

  When a detection AC voltage is applied to the first coil 468a, the first coil 468a forms a detection magnetic field AR2. Then, an induced voltage is generated by the detection magnetic field AR2 in the second coil 478a disposed to face the first coil 468a. Here, during the power transmission between the power transmission unit 400 and the power reception unit 200, each coil receives a magnetic flux (arrow AR3) in the same direction. An induced voltage can be generated in each coil by the magnetic flux AR3, but the induced voltage generated in the first coil 468b is canceled by the induced voltage generated in the first coil 468c. Therefore, no induced voltage is generated in the first coil 468a in total. The same applies to the second coil 478a. Even if the second coil 478a receives the magnetic flux AR3, no induced voltage is generated in the second coil 478a in total. Therefore, by setting it as such a coil shape, the influence on the foreign material detector of the magnetic field formed by the power transmission coil 410 at the time of the electric power transmission from the power transmission unit 400 to the power receiving unit 200 can be suppressed.

  In the first and second embodiments, the first coil and the second coil are used to detect the foreign matter. However, the configuration for detecting a foreign object is not necessarily limited to such a configuration. For example, a configuration in which only the second coil (478, 578) is used without using the first coil (468, 568) may be used. In this case, the first determination process and the second determination process are executed based on the received voltages of the plurality of second coils that are caused by the transmitted power. Thereby, the foreign material detection which suppressed the influence by the change of transmitted power is realizable with few members.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 Vehicle, 200, 200A Power receiving unit, 210 Power receiving coil, 230, 430 Housing, 232, 432 Shield, 234, 434 Lid member, 240, 440 Core, 250, 450 Conductor, 300 Power transmission device, 330 AC power source, 400 Power transmission Unit, 410 Power transmission coil, 460 Foreign object detector, 461 Oscillator, 462 Power amplifier, 463,472 Resonant capacitor, 464, 465, 474, 475 Multiplexer, 466, 467, 476, 477 Common wiring, 468, 468A to 468P First Coil, 471 signal processing circuit, 473 resonance resistance, 478, 478A to 478P second coil, 485 controller, 1000 non-contact power transmission system.

Claims (3)

A power transmission coil configured to contactlessly transmit power to a power reception coil of a power reception device;
As the power transmission coil to transmit power to the power reception coil located above the power transmission coil, a plurality of foreign matter detection coils disposed along the upper surface of the power transmission coil above the power transmission coil,
A control device that executes the first determination process and the second determination process;
In the first determination process, when a difference between the first and second induced voltages generated in two of the plurality of foreign matter detection coils is greater than or equal to a first predetermined value, the foreign matter is detected. It is a process to determine that it exists,
The second determination process is a process of determining that a foreign substance is present when a change amount of a value indicating an induced voltage generated in any of the plurality of foreign object detection coils is equal to or greater than a second predetermined value.
The control device executes the first determination process when a condition for determining a stable state of power transmitted from the power transmission coil to the power reception coil indicates instability, and when the condition indicates stability A power transmission device that executes the second determination process. A power receiving coil configured to receive power from the power transmitting coil of the power transmitting device in a contactless manner;
As the power receiving coil that receives power from the power transmitting coil located below the power receiving coil, a plurality of foreign matter detecting coils disposed along the lower surface of the power receiving coil below the power receiving coil;
A control device that executes the first determination process and the second determination process;
In the first determination process, when a difference between the first and second induced voltages generated in two of the plurality of foreign matter detection coils is greater than or equal to a first predetermined value, the foreign matter is detected. It is a process to determine that it exists,
The second determination process is a process of determining that a foreign substance is present when a change amount of a value indicating an induced voltage generated in any of the plurality of foreign object detection coils is equal to or greater than a second predetermined value.
The control device executes the first determination process when a condition for determining a stable state of power transmitted from the power transmission coil to the power reception coil indicates instability, and when the condition indicates stability A power receiving apparatus that executes the second determination process. A non-contact power transmission system including a power transmission device and a power reception device,
A power receiving coil configured to receive power from the power transmitting device in a contactless manner;
A power transmission coil configured to contactlessly transmit power to the power reception coil;
The power transmission coil transmits power to the power reception coil located above the power transmission coil, along the upper surface of the power transmission coil above the power transmission coil, or along the lower surface of the power reception coil below the power reception coil. A plurality of foreign object detection coils arranged,
A control device that executes the first determination process and the second determination process;
In the first determination process, when a difference between the first and second induced voltages generated in two of the plurality of foreign matter detection coils is greater than or equal to a first predetermined value, the foreign matter is detected. It is a process to determine that it exists,
The second determination process is a process of determining that a foreign substance is present when a change amount of a value indicating an induced voltage generated in any of the plurality of foreign object detection coils is equal to or greater than a second predetermined value.
The control device executes the first determination process when a condition for determining a stable state of power transmitted from the power transmission coil to the power reception coil indicates instability, and when the condition indicates stability A non-contact power transmission system that executes the second determination process.

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