JP2017099055A - Power transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power transmission device capable of suppressing variations in detection accuracy depending on the position of metallic foreign matter.SOLUTION: A power transmission device 3 includes: a power transmission coil 21 that transmits electric power in a non-contact manner to a power reception coil provided outside; and a plurality of detection coils 26, 27 provided around the power transmission coil 21. At a center of the detection coils 26, 27, at least one of a low permeability member having a magnetic permeability lower than that of air and a reflection member reflecting a magnetic flux passing through the detection coil is provided so as to suppress variations in detection precision depending on the position of metallic foreign matter.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power transmission device including a foreign object detection coil.

  As proposed in Patent Documents 1 to 5 below, a non-contact power transmission system is known that transmits electric power from a power transmission device to a power reception device in a contactless manner using an electromagnetic field. In this non-contact power transmission system, when there is a metal foreign object between the power transmission apparatus and the power receiving apparatus during power transmission, the metal foreign object becomes high temperature. Therefore, a non-contact power transmission system including various metal foreign object detection devices has been proposed.

  For example, a power transmission device described in JP2013-27171A includes a power transmission coil and a Q value detection unit. The Q value detection unit includes a detection coil. When there is a metal foreign object around the detection coil, magnetic flux enters the metal foreign object, and an eddy current flows on the surface of the metal foreign object. The eddy current flows so that the incident magnetic flux decreases. As a result, the effective resistance of the detection coil increases. As the effective resistance of the coil increases, the Q value decreases.

  The Q value detection unit detects the presence or absence of a metallic foreign object by detecting a change in the Q value. And as a detection coil, the Solenoi coil is employ | adopted and it is provided in the center part of the power transmission apparatus.

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

  In general, when an alternating current is supplied to a circular coil, the magnetic flux density of the magnetic flux passing through the central portion of the circular coil becomes higher than the magnetic flux density of the magnetic flux passing through the inner peripheral edge of the circular coil.

  For this reason, in the detection coil described in JP2013-27171A, the magnetic flux density of the magnetic flux passing through the central portion of the detection coil is higher than the magnetic flux density of the magnetic flux passing through the inner peripheral edge of the detection coil.

  For this reason, the amount of variation in the Q value differs between the case where there is a metal foreign object at the center of the detection coil and the case where there is a metal foreign object at or near the inner peripheral edge of the detection coil. As a result, the detection accuracy varies depending on the position of the metal foreign object.

  The present invention has been made in view of the above problems, and an object thereof is to provide a power transmission device in which variation in detection accuracy due to the position of a metal foreign object is suppressed.

  In one aspect, a power transmission device according to the present invention includes a power transmission coil that transmits power in a non-contact manner to a power receiving coil provided outside, and a plurality of detection coils provided around the power transmission coil. At least one of a low-permeability member having a lower magnetic permeability than air and a reflecting member that reflects the magnetic flux passing through the detection coil is provided in the central portion.

  In the case where the reflecting member or the low magnetic permeability member is provided in the central portion of the coil, the amount of magnetic flux passing through the coil central portion is smaller than in the case where the reflecting member or the low magnetic permeability member is not provided. For this reason, it can suppress that a difference arises in the magnetic flux density of the magnetic flux which passes along the inner peripheral part of a coil, and the magnetic flux density of the magnetic flux which passes along the center part of a coil.

  As a result, variation in detection accuracy of the detection coil due to the position of the metal foreign object is suppressed.

  In another aspect, a power transmission device according to the present invention includes a power transmission coil that transmits power in a non-contact manner to a power receiving coil provided outside, and a detection coil provided around the power transmission coil. The detection coil includes a coil main body and a plurality of inner coils connected to the coil main body and provided at intervals on the inner periphery of the coil main body. When a current flows through the detection coil, the direction of the current flowing through the coil body and the direction of the current flowing through each inner coil are the same direction.

  According to said structure, when an electric current flows into a detection coil, magnetic flux will be formed with a coil main body and an inner side coil. Since multiple inner coils are provided on the inner periphery of the coil body, it is possible to suppress the difference between the magnetic flux density of the magnetic flux passing through the inner peripheral edge of the detection coil and the magnetic flux density of the magnetic flux passing through the center of the detection coil. can do.

  For this reason, it can suppress that the detection accuracy of a detection coil varies with the position of a metal foreign material.

  According to the power transmission device of the present invention, it is possible to suppress variation in detection accuracy due to the position of the metal foreign object.

It is a schematic diagram which shows a non-contact charging system typically. 2 is an exploded perspective view showing a power transmission device 3. FIG. 2 is a circuit diagram showing a circuit configuration of a foreign object detection device 11. FIG. 2 is a perspective view showing a reception coil 26 and a transmission coil 27. FIG. 3 is a plan view showing a receiving coil 26. FIG. 3 is a plan view showing a transmission coil 27. FIG. It is a top view which shows the transmission coil 27B which concerns on a comparative example. It is a top view which shows the receiving coil 26B which concerns on a comparative example. It is a top view which shows magnetic flux density distribution of 26 A of receiving coils at the time of a foreign material detection. 7 is a plan view showing a modification of the receiving coil 26. FIG. 6 is a plan view showing a receiving coil 26 according to Embodiment 2. FIG. It is a perspective view which shows the connection part of the inner side coil 63 and the coil main body 62. FIG. FIG. 6 is a plan view showing a transmission coil 27 according to the second embodiment. It is a top view which shows the transmission coil 27 containing the inner side coils 73 and 75. FIG.

(Embodiment 1)
FIG. 1 is a schematic diagram schematically showing a non-contact charging system. As shown in FIG. 1, the contactless charging system 1 includes a vehicle 2 including a power receiving device 5 and a battery 6, and a power transmitting device 3 that transmits power to the power receiving device 5 in a contactless manner. The power transmission device 3 receives power supply from the power source 4.

  The power receiving device 5 includes a power receiving unit, a filter that removes harmonic components from the AC current received by the power receiving unit, and a rectifier that converts AC power supplied from the filter into DC power. The power receiving unit includes a power receiving coil and a capacitor, and an LC resonator is formed. The Q value of this LC resonator is 100 or more. The battery 6 is supplied with DC power from the rectifier of the power receiving device 5.

  FIG. 2 is an exploded perspective view showing the power transmission device 3. As shown in FIG. 3, the power transmission device 3 includes a power transmission unit 10, a filter 13 connected to the power transmission unit 10, an inverter 14 connected to the filter 13, a foreign object detection device 11, a power transmission unit 10, and the like. And a case 12 housed inside. Furthermore, the power transmission device 3 includes a control unit 15 that controls driving of the foreign object detection device 11 and the inverter 14.

  The inverter 14 adjusts the frequency and voltage of the AC power supplied from the power supply 4 and supplies it to the filter 13. The filter 13 removes harmonic components from the supplied power and supplies the power to the power transmission unit 10.

  The power transmission unit 10 includes a ferrite 20, a power transmission coil 21 disposed on the upper surface of the ferrite 20, and a capacitor 22 connected to the power transmission coil 21. An LC resonator is formed by the power transmission coil 21 and the capacitor 22. The Q value of the LC resonator is 100 or more. The resonance frequency of the LC resonator substantially coincides with the resonance frequency of the LC resonator of the power receiving device 5.

  The power transmission coil 21 is a flat plate coil, and is formed by winding a coil wire so as to surround the periphery of a winding axis extending in the vertical direction.

  The case 12 includes a metal case main body 23 formed with an opening that opens upward, and a resin lid 24 provided so as to close the opening of the case main body 23. The case 12 houses the power transmission unit 10, the filter 13, the inverter 14, and the control unit 15.

  The foreign object detection device 11 includes an insulating plate 28, a plurality of receiving coils 26 disposed on the upper surface of the insulating plate 28, and a plurality of transmitting coils 27 disposed on the lower surface of the insulating plate 28. The plurality of receiving coils 26 are arranged in an array on the lower surface of the resin lid 24. Each transmission coil 27 is disposed below the reception coil 26.

  FIG. 3 is a circuit diagram showing a circuit configuration of the foreign object detection device 11. As shown in FIG. 3, the foreign object detection device 11 includes a transmission unit 30 and a reception unit 31. The transmission unit 30 includes an oscillator 32, a power amplifier 33 connected to the oscillator 32, a capacitor 34 connected to the power amplifier 33, a coil array 37 including a plurality of transmission coils 27, and a coil array 37. And multiplexers 35 and 36. For example, the oscillator 32 supplies an alternating current of several tens of MHz to the power amplifier 33.

  The coil array 37 is formed by a plurality of transmission coils 27 arranged in both the X direction and the Y direction. A plurality of common lines 38 are connected to the multiplexer 35, and a plurality of common lines 39 are also connected to the multiplexer 36.

  The multiplexer 35 connects one common wiring 38 to the capacitor 34 from the plurality of common wirings 38 based on a signal from the control unit 15.

  Similarly, the multiplexer 36 selects and grounds one common wiring 39 from the plurality of common wirings 39 based on the signal from the control unit 15.

  The plurality of common wirings 38 are arranged at intervals in the X direction, and each common wiring 38 extends in the Y direction and is connected to one end of a plurality of transmission coils 27 arranged in the Y direction. The common wiring 39 is arranged at intervals in the Y direction, and each common wiring 39 extends in the X direction and is connected to the other ends of the plurality of transmission coils 27 arranged in the X direction.

  The receiving unit 31 includes a coil array 40, multiplexers 41 and 42 connected to the coil array 40, a capacitor 43, a resistor 44, and a signal processing circuit 45.

  The coil array 40 is formed by a plurality of receiving coils 26 arranged in both the X direction and the Y direction.

  The multiplexer 41 is connected with a plurality of common wirings 46 arranged at intervals in the X direction. Each common wiring 46 extends in the Y direction and is connected to one end of the receiving coil 26 arranged in the Y direction. A plurality of common wirings 47 are connected to the multiplexer 42 at intervals in the Y direction. Each common wiring 47 extends in the X direction and is connected to the other end of the receiving coil 26 arranged in the X direction.

  The multiplexer 41 selects one common wiring 46 from the plurality of common wirings 46 based on the signal from the control unit 15 and connects it to the capacitor 43. Further, the multiplexer 42 also selects one common wiring 47 from the plurality of common wirings 47 based on the signal from the control unit 15 and grounds it.

  When the foreign matter detection is performed, the control unit 15 selects the transmission coil 27 in a time-sharing manner and supplies the current from the oscillator 32 to the selected transmission coil 27. Further, the control unit 15 connects the common wiring 46 and the common wiring 47 so as to select the reception coil 26 located above the selected transmission coil 27.

  FIG. 4 is a perspective view showing the reception coil 26 and the transmission coil 27. As shown in FIG. 4, the reception coil 26 is disposed in the unit coil 50, the unit coil 51 connected to the unit coil 50, the reflection member 52 disposed in the unit coil 50, and the unit coil 51. And the reflecting member 53.

  In addition, as the reflection members 52 and 53, metals, such as copper and iron, can be employ | adopted, for example.

  FIG. 5 is a plan view schematically showing the receiving coil 26. As shown in FIG. 5, the receiving coil 26 is formed by winding a coil wire 54. Here, the coil wire 54 is wound so as to form a part of the unit coil 51 in the process from the end 55 toward the end 56. Thereafter, the coil wire 54 is wound so as to form the unit coil 50, and then wound so as to form the remaining part of the unit coil 51. The winding direction of the unit coil 50 and the winding direction of the unit coil 51 are formed in opposite directions.

  The reflection member 52 is disposed at a position away from the inner peripheral edge of the unit coil 50 and is disposed at the center of the unit coil 50. The reflection member 53 is also provided at a position away from the inner peripheral edge of the unit coil 51, and is provided at the center of the unit coil 51.

  FIG. 6 is a plan view schematically showing the transmission coil 27. As shown in FIG. 6, the transmission coil 27 includes a unit coil 57 and a unit coil 58 connected to the unit coil 57, and the winding direction of the unit coil 57 and the winding direction of the unit coil 58 are It is formed to be in the opposite direction.

  The operation of the foreign object detection device 11 configured as described above will be described. The foreign object detection device 11 is activated even when the power transmission unit 10 is transmitting power toward the power reception device 5.

  During non-contact power transmission, an electromagnetic field is formed around the power transmission coil 21. Since the power transmission coil 21 is a flat plate coil, the magnetic flux from the power transmission coil 21 is emitted mainly in the vertical direction.

  As shown in FIG. 5 and the like, the winding direction of the unit coil 50 and the winding direction of the unit coil 51 are opposite to each other. For this reason, when the magnetic flux from the power transmission coil 21 passes through the unit coil 50 and the unit coil 51, the induced electromotive voltage generated in the unit coil 50 and the induced electromotive voltage generated in the unit coil 51 cancel each other. For this reason, it is suppressed that the receiving coil 26 receives the influence of the magnetic field by power transmission.

  When the foreign object detection device 11 is activated, in FIG. 3, the control unit 15 selects the transmission coil 27 in a time division manner and selects the reception coil 26 positioned above the selected transmission coil 27. .

  For example, if the transmission coil 27A and the reception coil 26A are selected, an alternating current from the oscillator 32 flows through the transmission coil 27A.

  Here, for example, as shown in FIG. 6, when the magnetic flux MF from the unit coil 57 flows in the direction from below to above, the magnetic flux MF from the unit coil 58 flows from above to below.

  As shown in FIG. 4, the magnetic flux MF from the unit coil 57 passes through the unit coil 50 of the receiving coil 26A, and then passes through the unit coil 51 and the unit coil 58.

  If there is a metal foreign object in the vicinity of the receiving coil 26A, the magnetic flux also enters the metal foreign object. When magnetic flux enters the metal foreign object, an eddy current flows on the surface of the metal foreign object, and a magnetic field is formed around the eddy current. This magnetic field is distributed so as to reduce the amount of magnetic flux incident on the metal foreign object.

  As a result, the amount of magnetic flux incident on the receiving coil 26A decreases, and the received voltage of the receiving coil 26A decreases. The signal processing circuit 45 stores the received voltage of the receiving coil 26A when there is no metallic foreign object as a reference value, and calculates the difference between this reference voltage and the detected received voltage of the receiving coil 26A. Then, the signal processing circuit 45 transmits the calculation result to the control unit 15. The control unit 15 determines the presence / absence of a metallic foreign object based on the received result.

Next, functions and effects of the reflecting member 52 and the reflecting member 53 will be described.
FIG. 7 is a plan view showing a transmission coil 27B according to a comparative example, and FIG. 8 is a plan view showing a reception coil 26B according to a comparative example. 7 and 8, regions R1 to R4 indicate the magnetic flux density distribution, and indicate that the magnetic flux density increases in the order from the region R4 to the region R3, the region R2, and the region R1.

  As shown in FIG. 7, the transmission coil 27B according to the comparative example and the transmission coil 27 according to the first embodiment have the same configuration. On the other hand, the receiving member 26B according to the comparative example is not provided with the reflecting member 52 and the reflecting member 53.

  As shown in FIG. 7, when the current from the oscillator 32 is supplied to the transmission coil 27B according to the comparative example, the magnetic flux increases from the inner peripheral edge of the unit coils 57B and 58B toward the center of the unit coils 57B and 58B. It can be seen that the density increases.

  Since the magnetic flux MF from the transmission coil 27B flows into the reception coil 26B, also in the unit coils 50B and 51B shown in FIG. 8, the magnetic flux density increases from the inner peripheral edge of the unit coils 50B and 51B toward the center. I understand that.

  In this comparative example, the case where the metal foreign object is in the center portion of the unit coil 50B of the receiving coil 26A and the case where it is in the vicinity of the inner peripheral edge portion of the unit coil 50B will be considered. The amount of magnetic flux incident on the metal foreign object is larger when there is a metal foreign object at the center of the unit coil 51B than when there is a metal foreign object near the inner peripheral edge of the unit coil 51B.

  Then, the amount of eddy current formed on the surface of the metal foreign object increases, and the amount of magnetic flux reflected by the metal foreign object increases.

  As a result, the voltage drop amount of the receiving coil 26B is greater when the metal foreign object is at the center of the unit coil 50B than when the metal foreign object is at the inner peripheral edge of the unit coil 50B.

  That is, there is a difference between the metal foreign object detection accuracy at the center of the unit coil 50B and the metal foreign object detection accuracy at the inner peripheral edge of the unit coil 50B.

  Similarly, the detection accuracy is higher in the central portion of the unit coil 51B than in the inner peripheral edge portion of the unit coil 51B.

  On the other hand, in the receiving coil 26A according to the first embodiment, as shown in FIG. 5, reflecting members 52 and 53 are provided.

  For this reason, even if a large amount of magnetic flux MF attempts to enter the central portion of the unit coils 50A and 51A in a state where no foreign matter is present, it is reflected by the reflecting members 52 and 53.

  As a result, the magnetic flux density of the magnetic flux MF that passes through the central part of the unit coils 50A and 51A and passes through the central part of the unit coils 50A and 51A and the inner peripheral edge of the unit coils 50A and 51A is not reflected by the reflective members 52 and 53. The magnetic flux density of the magnetic flux MF matches or approximates.

  FIG. 9 shows the magnetic flux density distribution of the receiving coil 26A at the time of foreign object detection. As shown in FIG. 9, it can be seen that the magnetic flux is distributed substantially uniformly in the receiving coil 26A.

  For this reason, it can suppress that a big difference arises in the detection accuracy in the center part of 26 A of receiving coils, and the detection accuracy of the inner peripheral part side of 26 A of receiving coils.

  As a result, in FIG. 2, the reception coil 26 and the transmission coil 27 formed as described above are arranged in an array, so that the accuracy of metal foreign object detection is uniform over substantially the entire top surface of the resin lid 24. Can be achieved.

  In the first embodiment, the example in which the reflecting members 52 and 53 are provided in the receiving coil 26 has been described. However, the reflecting member may be similarly disposed in the transmitting coil 27.

  Further, in the example shown in FIG. 5 and the like, the example in which the reflecting member is disposed in the receiving coil 26 has been described as a method for equalizing the magnetic flux density, but a low permeability member is disposed in place of the reflecting member. You may do it.

  FIG. 10 is a plan view showing a modification of the receiving coil 26. As shown in FIG. 10, the receiving coil 26 includes a low magnetic permeability member 80 provided in the central portion of the unit coil 50 and a low magnetic permeability member 81 provided in the central portion of the unit coil 51.

  The low magnetic permeability members 80 and 81 are made of a material having a magnetic permeability lower than that of air. For example, Teflon (registered trademark) can be used. The magnetic permeability of the low magnetic permeability members 80 and 81 is lower than that of air. For this reason, the magnetic flux density in the central part of the unit coils 50 and 51 is lower when the low magnetic permeability members 80 and 81 are provided than when the low magnetic permeability members 80 and 81 are not provided. . As a result, a difference between the magnetic flux density at the center of the unit coils 50 and 51 and the magnetic flux density at the inner peripheral edge of the unit coils 50 and 51 is suppressed. Thereby, it can suppress that the detection precision of the receiving coil 26 varies with the position where a metal foreign material is provided.

(Embodiment 2)
The power transmission apparatus according to the second embodiment will be described with reference to FIGS. Of the configurations shown in FIG. 11 and the like, the same or substantially the same configurations as those shown in FIGS. 1 to 10 may be denoted by the same reference numerals and description thereof may be omitted.

  FIG. 11 is a plan view showing the receiving coil 26 according to the second embodiment. As shown in FIG. 11, the receiving coil 26 includes a unit coil 60 and a unit coil 61 connected to the unit coil 60.

  The unit coil 60 includes a coil main body 62 and a plurality of inner coils 63 that are connected to the coil main body 62 and provided at intervals on the inner peripheral edge of the coil main body 62. The unit coil 61 also includes a coil body 64 and a plurality of inner coils 65 that are connected to the coil body 64 and provided at intervals on the inner periphery of the coil body 64.

  The diameter (opening area) of the inner coils 63 and 65 is smaller than the diameter (opening area) of the coil bodies 62 and 64.

  FIG. 12 is a perspective view showing a connection portion between the inner coil 63 and the coil main body 62. As shown in FIG. 12, the unit coil 60 includes a transition portion 66 that connects the inner coil 63 and the coil body 62.

  The inner coil 63 is formed at the tip of the portion 67 of the coil body 62, and the crossing portion 66 is connected to the terminal end of the inner coil 63. A portion 68 of the coil body 62 is connected to the end portion of the crossing portion 66.

  A crossing portion 66 is connected to each inner coil 63, and a coil body 62 is formed by the plurality of portions 67 and 68.

  Since the receiving coil 26 is thus formed, the winding direction of the coil body 62 and the winding direction of the inner coil 63 are the same direction.

  Note that the winding direction of the coil body 62 and the inner coil 63 is opposite to the winding direction of the coil body 64 and the inner coil 65.

  FIG. 13 is a plan view showing the transmission coil 27 according to the second embodiment. As shown in FIG. 13, the transmission coil 27 includes a unit coil 70 and a unit coil 71 connected to the unit coil 70. Note that the winding direction of the unit coil 70 and the winding direction of the unit coil 71 are opposite to each other.

  In FIG. 2, a plurality of receiving coils 26 shown in FIG. 11 are arranged, and a plurality of transmitting coils 27 shown in FIG. 13 are arranged.

  And when detecting the presence or absence of a metal foreign material, an alternating current is supplied to the transmission coil 27 shown in FIG. At this time, the magnetic flux density of the magnetic flux emitted from the central part of the unit coils 70 and 71 is higher than the magnetic flux density of the magnetic flux emitted from the inner peripheral edge of the unit coils 70 and 71.

  Therefore, in FIG. 11, the magnetic flux density of the magnetic flux passing through the central part of the unit coils 60 and 61 is higher than the magnetic flux density of the magnetic flux passing through the inner periphery of the unit coils 60 and 61.

  On the other hand, as shown in FIG. 11, the receiving coil 26 is formed with a plurality of inner coils 63, 65 along the inner peripheral edges of the coil bodies 62, 64.

  Therefore, the amount of voltage drop that occurs when there is a metal foreign object at the center of the unit coils 60 and 61 can be substantially matched with the amount of voltage drop that occurs when there is a metal foreign object on the inner coils 63 and 65. .

  As a result, it is possible to prevent the detection accuracy of the receiving coil 26 from varying depending on the position where the metal foreign object is provided.

  In the second embodiment, the example in which the inner coils 63 and 65 are arranged in the reception coil 26 has been described. However, the inner coil may be provided in the transmission coil 27.

  FIG. 14 is a plan view showing the transmission coil 27 including the inner coils 73 and 75. In the example shown in FIG. 14, the unit coil 70 includes a coil body 72 and a plurality of inner coils 73 connected to the coil body 72 and provided along the inner periphery of the coil body 72. The unit coil 71 includes a coil main body 74 and a plurality of inner coils 75 connected to the coil main body 74 and provided at intervals on the inner periphery of the coil main body 74.

  The winding direction of the coil body 72 and the winding direction of the inner coil 73 are the same direction, and the winding direction of the coil body 74 and the winding direction of the inner coil 75 are the same direction. And the winding direction of the coil main body 72 and the inner side coil 73 and the winding direction of the coil main body 74 and the inner side coil 75 are opposite directions.

  When an alternating current is supplied to the transmission coil 27 formed in this way, a magnetic flux is formed by the coil bodies 72 and 74 and the inner coils 73 and 75.

  For this reason, the magnetic flux density of the magnetic flux emitted from the center part of the unit coils 70 and 71 and the magnetic flux density of the magnetic flux emitted from the inner peripheral edge part of the unit coils 70 and 71 coincide with each other or substantially coincide with each other.

  Thus, the magnetic flux density of the magnetic flux emitted from the opening of the transmission coil 27 is substantially uniform over substantially the entire surface of the opening of the transmission coil 27.

  As a result, the magnetic flux interlinking the receiving coil 26 is uniformly distributed over substantially the entire surface of the opening of the receiving coil 26. For this reason, it can suppress that the detection accuracy of the receiving coil 26 varies depending on the position of the metal foreign object.

  In the first and second embodiments, the foreign object detection device 11 provided with the reception coil 26 and the transmission coil 27 has been described. However, the transmission coil 27 detects foreign objects without providing the reception coil 26. May be.

  In the foreign object detection device 11, an alternating current is supplied to the transmission coil 27 when the foreign object is detected. At this time, the frequency of the supplied alternating current is matched with the resonance frequency of the LC resonance circuit formed by the selected transmission coil 27 and the capacitor 34.

  When there is no metallic foreign material above or in the vicinity of the transmission coil 27, a current flows satisfactorily. On the other hand, if there is a metallic foreign object above or in the vicinity of the transmission coil 27, the effective resistance of the coil increases, and the capacitor 34 and the transmission coil 27 form an LCR resonance circuit. For this reason, a deviation occurs between the resonance frequency when there is a metal foreign object and the resonance frequency when there is no metal foreign object. As a result, the amount of current flowing through the transmission coil 27 is reduced. Therefore, metal foreign objects can be detected by detecting the amount of current with a current sensor.

  Thus, this invention is not restricted to the foreign material detection apparatus 11 provided with the transmission coil and the receiving coil, It can apply to various foreign material detection apparatuses.

  As mentioned above, although each embodiment based on this invention was described, the matter disclosed this time is an illustration and restrictive at no points. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be applied to a non-contact power transmission apparatus.

  DESCRIPTION OF SYMBOLS 1 Contactless charging system, 2 Vehicle, 3 Power transmission apparatus, 4 Power supply, 5 Power receiving apparatus, 6 Battery, 10 Power transmission part, 11 Foreign object detection apparatus, 12 Case, 13 Filter, 14 Inverter, 15 Control part, 20 Ferrite, 21 Power transmission Coil, 22, 34, 43 Capacitor, 23 Case body, 24 Resin lid, 26, 26A, 26B Receiver coil, 27, 27A, 27B Transmit coil, 28 Insulating plate, 30 Transmitter unit, 31 Receiver unit, 32 Oscillator, 33 Power Amplifier, 35, 36, 41, 42 Multiplexer, 37, 40 Coil array, 38, 39, 46, 47 Common wiring, 44 Resistance, 45 Signal processing circuit, 50, 50A, 50B, 51, 51A, 51B, 57, 57B , 58, 58B, 60, 61, 70, 71 Unit coil, 52, 53 Reflective member, 54 coil wire, 55, 56 end, 62, 64, 72, 74 coil body, 63, 65, 73, 75 inner coil.

Claims (2)

A power transmission coil for transmitting power in a non-contact manner to a power receiving coil provided outside;
A detection coil provided around the power transmission coil;
With
A power transmission device in which at least one of a low magnetic permeability member having a lower magnetic permeability than air and a reflective member that reflects a magnetic flux passing through the detection coil is provided in a central portion of the detection coil. A power transmission coil for transmitting power in a non-contact manner to a power receiving coil provided outside;
A detection coil provided around the power transmission coil;
With
The detection coil includes a coil body and an inner coil connected to the coil body and provided on the inner periphery of the coil body.
A power transmission device in which when a current flows through a detection coil, a current direction of a current flowing through the coil body is the same as a current direction of a current flowing through each inner coil.

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