Coil Unit

Abstract

To provide a coil unit that can improve a coupling coefficient by increasing output density and reducing unwanted radiation in non-contact power transmission.SOLUTION: A coil unit includes a power reception unit 15 and a control unit 17 of a power reception device 4, which are installed in a vehicle. The power reception unit 15 includes a secondary coil and a secondary capacitor connected in series. The secondary coil receives AC power transmitted from a power transmission device 2 without contact. The secondary coil generates a conducting current in the opposite phase to a primary coil when receiving the AC power transmitted from the primary coil of the power transmission device 2 without contact. The capacity of the secondary capacitor is set according to a high-frequency side resonance point RPH of two resonance points corresponding to the secondary coil and the secondary capacitor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a coil unit. [Background technology]

[0002] In recent years, research and development has been conducted into charging vehicles equipped with secondary batteries that contribute to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy. Conventionally, in a contactless power transfer system that supplies power from outside the vehicle to the vehicle by contactless power transfer, a configuration is known that reduces leakage magnetic flux (i.e., magnetic flux other than the main magnetic flux that links with the power transmitting coil and the power receiving coil) between a power transmitting coil outside the vehicle and a power receiving coil in the vehicle (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-234496 A [Patent Document 2] JP 2014-193013 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology related to charging and supplying power to a vehicle equipped with a secondary battery, it is desirable to improve the output and efficiency of charging and supplying power. For example, in the contactless power transfer system of the above-mentioned conventional technology, it is desirable to increase the output density and suppress the generation of unnecessary radiation to improve the coupling coefficient without requiring changes to the vehicle shape such as lowering the ground clearance.

[0005] The present invention aims to provide a coil unit capable of improving the coupling coefficient by increasing the output density and reducing unnecessary radiation in contactless power transmission, thereby contributing to energy efficiency. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the above object, the present invention employs the following aspects. (1): A coil unit according to one aspect of the present invention (e.g., coil unit 10 in the embodiment) includes a coil (e.g., secondary coil 15a in the embodiment) that generates a current of opposite phase to a power transmission side coil (e.g., primary coil 8a in the embodiment) of a power transmission device (e.g., power transmission device 2 in the embodiment) when receiving AC power transmitted contactlessly from the power transmission side coil (e.g., primary coil 8a in the embodiment).

[0007] (2) In the coil unit described in (1) above, the winding direction of the coil may be set to be opposite to the winding direction of the power transmission side coil when viewed from the same predetermined direction.

[0008] (3): The coil unit described in (1) or (2) above includes a resonance capacitor (e.g., secondary side capacitor 15c in the embodiment) connected in series to the coil, and the capacitance of the capacitor may be set according to the higher frequency resonance point (e.g., resonance point RPH in the embodiment) of two resonance points corresponding to the coil and the capacitor.

[0009] (4): The coil unit described in (3) above may be provided with a control device (e.g., control device 17 in the embodiment) that sets the frequency corresponding to the resonance point on the high frequency side to a required frequency for power transmission by the power transmission device. Effect of the Invention

[0010] According to the above (1), by providing a coil that generates a current of opposite phase to the power transmission coil, it is possible to shift the phase due to the magnetic field coupling and the electric field coupling, and to suppress the cancellation of the magnetic field coupling coefficient and the electric field coupling coefficient. By suppressing the reduction of the coupling coefficient due to the electric field coupling, it is possible to improve the output density. For example, compared to a case where a coil that generates an in-phase current to the power transmitting coil is provided, it is possible to suppress a decrease in the coupling coefficient that occurs with an increase in the gap between the power transmitting coil and the coil, thereby improving the coupling coefficient. Furthermore, it is possible to suppress an increase in the magnetic flux density in the power transmitting coil and around the coil due to unnecessary radiation.

[0011] In the above case (2), a coil that generates a current having a reverse phase to the power transmitting coil can be easily provided.

[0012] In the case of (3) above, compared to, for example, a case where the capacitance of the capacitor is set according to the anti-resonance point, it is possible to suppress the occurrence of leakage flux that inhibits the main magnetic flux, and to suppress the decrease in the magnetic flux transmitted to the coil. By suppressing the decrease in the coupling coefficient due to leakage flux, it is possible to improve the output density.

[0013] In the above case (4), the coupling coefficient can be improved by increasing the power density and reducing unnecessary radiation in contactless power transmission. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing a configuration of a contactless power transfer system including a coil unit according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the configuration of a power transmitting unit and a power receiving unit of a contactless power transfer system according to an embodiment of the present invention. [Diagram 3] 2 is a perspective view showing a primary coil of a power transmitting device and a secondary coil of a power receiving device according to an embodiment of the present invention; FIG. [Figure 4] FIG. 4 is a graph showing an example of the correspondence relationship between impedance and frequency in the coil unit according to the embodiment of the present invention. [Diagram 5] FIG. 11 is a graph showing an example of actual measurements of the relationship between impedance and phase and frequency in the coil unit according to the embodiment of the present invention. [Figure 6] 4A to 4C are diagrams showing examples of magnetic flux density distribution in the coil unit according to the embodiment of the present invention and a first comparative example. [Figure 7] FIG. 11 is a graph showing an example of the correspondence relationship between the coupling coefficient k and the gap between the primary coil and the secondary coil in each of the coil unit according to the embodiment of the present invention and the second comparative example. [Figure 8] 6A and 6B are diagrams showing examples of magnetic flux density distribution in the coil unit according to the embodiment of the present invention and a second comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a coil unit according to an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a diagram showing the configuration of a contactless power transfer system 1 including a coil unit 10 according to an embodiment. Fig. 2 is a diagram showing the configurations of a power transmitting unit 8 and a power receiving unit 15 of the contactless power transfer system 1 according to the embodiment. The coil unit 10 of the embodiment constitutes a part of a contactless power transfer system 1 that supplies power from the outside of a moving body such as a vehicle to the moving body by contactless power transfer. The coil unit 10 of the embodiment is mounted on a moving body such as a vehicle. The vehicle is, for example, an electric vehicle such as an electric car, a hybrid vehicle, or a fuel cell vehicle.

[0016] (Non-contact power transmission system) As shown in FIG. 1, a contactless power transfer system 1 according to the embodiment includes, for example, a power transmitting device 2 installed on a vehicle's running path, and a drive control device 3 and a power receiving device 4 mounted on the vehicle.

[0017] The power transmission device 2 includes, for example, a power supply unit 6, a power transmission power conversion unit 7, and a power transmission unit 8. Note that the power transmission device 2 may include at least a plurality of power transmission units 8 in a predetermined power transmission section on a road along which the vehicle travels. The power supply unit 6 includes, for example, an AC power supply such as a commercial power supply, an AC-DC converter that converts the AC power into DC power, and a power smoothing capacitor. The power supply unit 6 converts the AC power supplied from the AC power supply into DC power by the AC-DC converter.

[0018] The transmission power conversion unit 7 includes, for example, an inverter that converts DC power into AC power. The inverter of the transmission power conversion unit 7 includes, for example, a bridge circuit formed by a plurality of switching elements and rectifying elements that are bridge-connected in two phases, and a voltage smoothing capacitor. Each switching element is, for example, a transistor such as a SiC (Silicon Carbide) MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The multiple switching elements are high-side arm and low-side arm transistors that form a pair in each phase. The rectifying element is, for example, a free wheel diode connected in parallel to each transistor. The voltage smoothing capacitor is connected in parallel to the bridge circuit.

[0019] The power transmitting unit 8 transmits power by changing a high-frequency magnetic field, for example, by magnetic field coupling such as magnetic resonance or electromagnetic induction. As shown in Fig. 2, the power transmitting unit 8 includes a resonant circuit formed by a primary coil 8a, a primary resistor 8b, and a primary capacitor 8c connected in series. The power transmitting unit 8 includes a sensor such as a current sensor that detects a current It flowing through the resonant circuit.

[0020] For example, the power transmission device 2 transmits power to the power receiving device 4 of the vehicle by controlling the on (conduction) and off (cutoff) switching of each switching element of the transmission power conversion unit 7 in accordance with a preset drive frequency or information on a desired frequency received from the power receiving device 4.

[0021] 1, the drive control device 3 of the vehicle includes, for example, a power storage device 11, a storage voltage converter 12, a power converter 13, and a rotating electric machine 14. The power receiving device 4 of the vehicle includes, for example, a power receiving unit 15 and a received power converter 16. The drive control device 3 and the power receiving device 4 include, for example, a common control device 17. For example, in the case of an electric vehicle or the like that is driven using the power storage device 11 as a power source, the drive control device 3 does not need to include the storage voltage conversion unit 12. For example, in the case of a hybrid vehicle or the like that is driven using the power storage device 11 and an internal combustion engine as a power source, the drive control device 3 may include the storage voltage conversion unit 12.

[0022] The power storage device 11 is connected to a storage voltage converter 12. The power storage device 11 is charged by electric power transmitted in a non-contact manner from a power transmission device 2 outside the vehicle. The power storage device 11 exchanges electric power with a rotating electric machine 14 via the storage voltage converter 12 and a power converter 13. The power storage device 11 includes a battery, such as a lithium ion battery, a current sensor that detects the current of the battery, and a voltage sensor that detects the voltage of the battery. For example, in an electric vehicle or the like that does not include the storage voltage conversion unit 12, the power storage device 11 is connected to the power conversion unit 13 and the received power conversion unit 16, which will be described later.

[0023] The storage voltage conversion unit 12 is connected to the power conversion unit 13 and the received power conversion unit 16. The storage voltage conversion unit 12 includes, for example, a voltage controller that performs bidirectional voltage conversion of step-up and step-down. The voltage controller converts input power and output power by bidirectional voltage conversion when charging and discharging the power storage device 11. The voltage controller of the storage voltage conversion unit 12 includes, for example, a pair of first reactors, a first element module, and a capacitor for voltage smoothing.

[0024] The pair of first reactors are magnetically coupled to each other with opposite polarity to form a composite reactor, and are connected to a connection point between the high-side arm and the low-side arm of each phase of the first element module. The first element module includes a first bridge circuit formed by a plurality of switching elements and rectifier elements that are bridge-connected in, for example, two phases. Each switching element is, for example, a transistor such as a SiC MOSFET. The plurality of switching elements are high-side arm and low-side arm transistors that form a pair in each phase. The rectifier element is, for example, a free wheel diode connected in parallel to each transistor. A voltage smoothing capacitor is connected in parallel to the power storage device 11. The storage voltage converter 12 includes a resistor and a transistor connected in series to a first bridge circuit in parallel.

[0025] A pair of first reactors and a first element module of the voltage controller perform voltage conversion by so-called two-phase interleaving, in which one cycle of switching control of a first-phase transistor and one cycle of switching control of a second-phase transistor among two-phase transistors connected to a pair of first reactors are shifted from each other by half a cycle.

[0026] The power conversion unit 13 is connected to a rotating electric machine 14. The power conversion unit 13 includes, for example, a power converter that converts between DC power and AC power. The power converter includes, for example, a second element module and a voltage smoothing capacitor. The second element module includes, for example, a second bridge circuit formed by a plurality of switching elements and rectifier elements bridge-connected in three phases. Each switching element is, for example, a transistor such as a SiC MOSFET. The plurality of switching elements are high-side arm and low-side arm transistors that form a pair in each phase. The rectifier element is, for example, a freewheeling diode connected in parallel to each transistor. A voltage smoothing capacitor is connected in parallel to the second bridge circuit.

[0027] The second element module controls the operation of the rotating electrical machine 14 by power transfer. For example, when the rotating electrical machine 14 is in power running mode, the second element module converts the DC power input from the DC terminals of the positive and negative electrodes into three-phase AC power, and supplies the three-phase AC power from the three-phase AC terminals to the rotating electrical machine 14. The second element module generates a rotational driving force by sequentially commutating the energization of the three-phase stator windings of the rotating electrical machine 14. For example, when the rotating electrical machine 14 is in regeneration mode, the second element module converts the three-phase AC power input from the three-phase stator windings into DC power by driving the on (conducting) and off (blocking) of the switching elements of each phase synchronized with the rotation of the rotating electrical machine 14. The second element module can supply the DC power converted from the three-phase AC power to the power storage device 11 via the power storage voltage conversion unit 12.

[0028] The rotating electrical machine 14 is, for example, a three-phase AC brushless DC motor provided for driving the vehicle. The rotating electrical machine 14 includes a rotor having a permanent magnet for field and a stator having three-phase stator windings for generating a rotating magnetic field for rotating the rotor. The three-phase stator windings are connected to the three-phase AC terminals of the power conversion unit 13. The rotating electrical machine 14 generates a rotational driving force by performing a power running operation with the power supplied from the power conversion unit 13. For example, when the rotating electrical machine 14 can be connected to the vehicle wheels, the rotating electrical machine 14 generates a driving force for running by performing a power running operation with the power supplied from the power conversion unit 13. The rotating electrical machine 14 may generate generated power by performing a regeneration operation with the rotational power input from the vehicle wheel side. When the rotating electrical machine 14 can be connected to the internal combustion engine of the vehicle, the rotating electrical machine 14 may generate electricity by the power of the internal combustion engine.

[0029] The power receiving unit 15 is connected to the receiving power conversion unit 16. The power receiving unit 15 receives power by a change in a high-frequency magnetic field transmitted from the power transmitting unit 8, for example, by magnetic field coupling such as magnetic resonance or electromagnetic induction. As shown in Fig. 2, the power receiving unit 15 includes a resonant circuit formed by, for example, a secondary side coil 15a, a secondary side resistor 15b, and a secondary side capacitor 15c connected in series. The power receiving unit 15 includes a sensor such as a current sensor that detects a current Ir flowing through the resonant circuit.

[0030] The receiving power conversion unit 16 shown in Fig. 1 is connected to the power conversion unit 13. The receiving power conversion unit 16 includes a so-called full-bridgeless (or bridgeless and totem-pole) power factor correction (PFC) circuit that converts AC power into DC power. The so-called bridgeless PFC is a PFC that does not include a bridge rectifier made of multiple bridge-connected diodes, and the so-called totem-pole PFC is a PFC that includes a pair of switching elements of the same conductivity type that are connected in series in the same direction (totem-pole connection).

[0031] The receiving power conversion unit 16 includes, for example, a third bridge circuit formed by a plurality of switching elements and rectifying elements bridge-connected in two phases, and a voltage smoothing capacitor. Each switching element is, for example, a transistor such as a SiC MOSFET. The plurality of switching elements are high-side arm and low-side arm transistors that form a pair in each phase. The rectifying element is, for example, a free wheel diode connected in parallel to each transistor. The voltage smoothing capacitor is connected in parallel to the third bridge circuit.

[0032] For example, a power receiving device 4 equipped with a power receiving unit 15 and a power receiving power conversion unit 16 receives power transmitted from the power transmitting device 2 by controlling the on (conducting) and off (cutting) switching of each switching element of the power receiving power conversion unit 16 in accordance with information on the frequency of power transmission by the power transmitting device 2.

[0033] The control device 17 comprehensively controls, for example, the drive control device 3 and the power receiving device 4 of the vehicle. The control device 17 is a software function unit that functions when a processor such as a CPU (Central Processing Unit) executes a predetermined program. The software function unit is an ECU that includes a processor such as a CPU, a ROM (Read Only Memory) that stores programs, a RAM (Random Access Memory) that temporarily stores data, and electronic circuits such as a timer. At least a part of the control device 17 may be an integrated circuit such as an LSI (Large Scale Integration).

[0034] The control device 17 generates, for example, control signals indicating the timing for driving each switching element on (conducting) and off (cutting), and generates gate signals for actually driving each switching element on and off based on the control signals. For example, the control device 17 controls the switching of each switching element of the power receiving device 4 to rectify the AC power received from the power transmitting device 2 into DC power, while improving the power factors of the input voltage and the input current.

[0035] For example, the control device 17 controls the output according to the target output by a synchronous rectification operation that synchronously drives a plurality of switching elements of the power receiving device 4 to be turned on and off, and a short-circuit operation that short-circuits the secondary coil 15a. For example, the control device 17 controls the synchronous rectification operation according to the magnitude and phase of a current generated in the power receiving unit 15 by the power transmitted from the power transmitting device 2, i.e., a current Ir flowing through the secondary coil 15a. The control device 17 controls the multiple switching elements of the power receiving power conversion unit 16 by soft switching of so-called zero voltage switching (ZVS). In zero voltage switching (ZVS), each switching element is turned on (switched from an off state to an on state) after the voltage across both ends is made zero by discharging the output capacitance (parasitic capacitance) in the off state during the dead time period of each phase. For example, the control device 17 controls the short-circuit operation by continuing the zero voltage switching (ZVS) synchronous rectification operation in the high side arm of each phase of the receiving power conversion unit 16 while turning on only the low side arm of each phase.

[0036] For example, the control device 17 sets the frequency (required frequency) required for power transmission by the power transmission device 2 based on the vehicle's ground clearance related to the distance between the primary coil 8a and the secondary coil 15a and the mounting layout of the power receiving device 4 on the vehicle, the state of power transmission between the power transmission device 2 and the power receiving device 4, the desired efficiency and output (power) of the power transmission, etc. The control device 17 transmits the required frequency to the power transmitting device 2 through appropriate communication between the power transmitting device 2 and the vehicle. The communication between the power transmitting device 2 and the vehicle is, for example, communication based on an induced voltage between the coils 8a, 15a of the power transmitting device 2 and the power receiving device 4, or wireless communication by a communication device additionally provided in each of the power transmitting device 2 and the vehicle.

[0037] The coil unit 10 of the embodiment includes, for example, a power receiving section 15 of a power receiving device 4 mounted on a vehicle, and a control device 17. FIG. 3 is a perspective view showing the primary coil 8a of the power transmitting device 2 and the secondary coil 15a of the power receiving device 4 in the embodiment. 3, when viewed from a predetermined same direction F, the winding direction of the secondary coil 15a of the power receiving device 4 is set to be opposite to the winding direction of the primary coil 8a of the power transmitting device 2. The predetermined same direction F is, for example, a direction in which the primary coil 8a and the secondary coil 15a face each other. In other words, the primary coil 8a of the power transmitting device 2 and the secondary coil 15a of the power receiving device 4 are arranged to generate currents of opposite phases to each other during power transmission.

[0038] Fig. 4 is a graph showing an example of the correspondence relationship between impedance Z and frequency in the coil unit 10 of the embodiment. The solid line shown in Fig. 4 represents the case where there is an optimal load resistance at which the efficiency of power transmission is maximized, and the dashed line represents the case where there is no load resistance. 4, the frequency characteristic of impedance Z in the coil unit 10 of the embodiment has two resonance points corresponding to the resonance circuit formed by the secondary coil 15a, secondary resistor 15b, and secondary capacitor 15c connected in series to the power receiving device 4. The resonance point RPL where the impedance Z is minimum on the low frequency side indicates an in-phase resonance mode, and the resonance point RPH where the impedance Z is minimum on the high frequency side indicates an anti-phase resonance mode. Between the two resonance points RPL and RPH, the anti-resonance point ARP where the impedance Z is maximum indicates switching between the in-phase resonance mode and the anti-phase resonance mode.

[0039] The capacitance of the secondary capacitor 15c in the coil unit 10 is, for example, a frequency (frequency of the high frequency mode) f hi is set to be the required frequency of the power transmitting device 2. For example, as shown in the following formula (1), the frequency f hi and the natural frequency f of each of the primary coil 8a and the secondary coil 15a. 0 is expressed by a coupling coefficient k between the primary coil 8a and the secondary coil 15a. The natural frequency f0 is set to a predetermined frequency such as 85 kHz.

[0040]

number

[0041] Based on the above formula (1), the resonance point is set to the frequency f hi In order to match this, the capacitance C1 of the primary side capacitor 8c and the capacitance C2 of the secondary side capacitor 15c are set as shown in the following formula (2). In the following formula (2), the capacitances C1 and C2 are set according to the frequency f hi and the self-inductance L of the primary coil 8a 1 and the self-inductance L of the secondary coil 15a. 2 and a coupling coefficient k between the primary coil 8a and the secondary coil 15a. The control device 17 detects a frequency f corresponding to the resonance point RPH on the higher frequency side of the two resonance points RPL and RPH in the frequency characteristic of the impedance Z. hi is set as the required frequency for power transmission by the power transmitting device 2.

[0042]

number

[0043] Fig. 5 is a graph showing an example of measurements of the relationship between impedance and phase and frequency in the coil unit 10 of the embodiment. The impedance and phase shown in Fig. 5 can be obtained by measuring the current Ir flowing through the resonant circuit of the power receiving unit 15, for example, with a shunt resistor having a predetermined resistance value (for example, 1 Ω). As shown in Figure 5, the frequency of the high-frequency mode, f hi It can be seen that the phase difference is zero and the impedance is minimal at this point, that is, this is the resonance point.

[0044] 6 is a diagram showing an example of magnetic flux density distribution (magnetic flux density distribution in a cross section parallel to the opposing direction of the primary coil 8a and the secondary coil 15a) in each of the coil unit 10 of the embodiment and the first comparative example. In the coil unit 10 of the embodiment, the capacitance of the secondary capacitor 15c is set to a capacitance C2 corresponding to the resonance point RPH on the high frequency side. In the first comparative example, the capacitance of the secondary capacitor 15c is set to a capacitance corresponding to the anti-resonance point ARP. 6, for example, in the vicinity area A of the primary coil 8a, in the first comparative example, leakage flux that cancels the main magnetic flux occurs, and the magnetic flux transmitted to the secondary coil 15a is reduced. In contrast, in the embodiment, the occurrence of leakage flux that inhibits the main magnetic flux is suppressed, and the reduction in the magnetic flux transmitted to the secondary coil 15a is suppressed.

[0045] Fig. 7 is a graph showing an example of the correspondence relationship between the coupling coefficient k and the gap between the primary coil 8a and the secondary coil 15a in each of the coil unit 10 of the embodiment and the second comparative example. Fig. 8 is a diagram showing an example of the magnetic flux density distribution (magnetic flux density distribution in a cross section parallel to the opposing direction of the primary coil 8a and the secondary coil 15a) in each of the coil unit 10 of the embodiment and the second comparative example. In the coil unit 10 of the embodiment, the primary coil 8a of the power transmitting device 2 and the secondary coil 15a of the power receiving device 4 are arranged in a so-called differential type so as to generate currents of opposite phases when transmitting power. In the second modified example, the primary coil 8a of the power transmitting device 2 and the secondary coil 15a of the power receiving device 4 are arranged in a so-called sum type so as to generate currents of the same phase when transmitting power. In the second modified example, the winding direction of the secondary coil 15a of the power receiving device 4 is set to be the same as the winding direction of the primary coil 8a of the power transmitting device 2 when viewed from a predetermined same direction such as an opposing direction.

[0046] As shown in FIG. 7, in the embodiment, it is found that the decrease in the coupling coefficient k accompanying an increase in the gap between the primary coil 8a and the secondary coil 15a is suppressed compared to the second modified example. As shown in the following formula (3), the coupling coefficient k between the primary coil 8a and the secondary coil 15a is expressed by the difference between the magnetic coupling coefficient km and the electric field coupling coefficient kc. In the embodiment, the mutual cancellation of the coupling coefficients km and kc is suppressed by shifting the phase of the magnetic field coupling and the electric field coupling in a differential manner, and the reduction of the coupling coefficient k due to the electric field coupling is suppressed.

[0047]

number

[0048] 8, for example, in the peripheral region B of the primary coil 8a and the secondary coil 15a, it is recognized that the peripheral magnetic flux density increases due to unnecessary radiation in the second comparative example. In contrast, in the embodiment, it is recognized that the increase in the peripheral magnetic flux density is suppressed by reducing the unnecessary radiation.

[0049] As described above, according to the coil unit 10 of the embodiment, by providing the secondary coil 15a that generates a current of opposite phase to the primary coil 8a, it is possible to shift the phase due to the magnetic field coupling and the electric field coupling, and to suppress the cancellation of the magnetic field coupling coefficient km and the electric field coupling coefficient kc. By suppressing the reduction of the coupling coefficient k due to the electric field coupling, it is possible to improve the output density. For example, compared to a case where a secondary coil that generates a current of the same phase as the primary coil 8a is provided, it is possible to suppress a decrease in the coupling coefficient k that accompanies an increase in the gap between the primary coil 8a and the secondary coil 15a, and to improve the coupling coefficient k. Furthermore, it is possible to suppress an increase in the magnetic flux density around the primary coil 8a and the secondary coil 15a due to unnecessary radiation.

[0050] When viewed from the same specified direction F, the winding direction of the secondary coil 15a of the power receiving device 4 is set in the opposite direction to the winding direction of the primary coil 8a of the power transmitting device 2, thereby making it easy to provide a secondary coil 15a that generates an opposite-phase current flowing through the primary coil 8a.

[0051] The capacitance of the secondary side capacitor 15c is set to a capacitance C2 corresponding to the higher frequency resonance point RPH of the two resonance points RPL, RPH in the frequency characteristic of the impedance Z, thereby making it possible to suppress the occurrence of leakage flux that inhibits the main magnetic flux, compared to, for example, a case in which the capacitance of the secondary side capacitor 15c is set according to the anti-resonance point ARP. By suppressing the decrease in the coupling coefficient k due to leakage flux and suppressing the decrease in the magnetic flux transmitted to the secondary side coil 15a, the output density can be improved. By providing a control device 17 that sets the frequency corresponding to the resonance point RPH on the high frequency side to the required frequency for power transmission by the power transmission device 2, the coupling coefficient k can be improved by increasing the output density in contactless power transmission and reducing unnecessary radiation.

[0052] (Modification) Modifications of the embodiment will be described below. Note that the same parts as those in the above-described embodiment will be denoted by the same reference numerals and descriptions thereof will be omitted or simplified. In the above-described embodiment, the contactless power transfer system 1 includes the storage voltage converter 12 that converts the input and output power of the power storage device 11. However, the present invention is not limited to this, and the storage voltage converter 12 may be omitted. For example, in the case of a hybrid vehicle that is powered by an electric storage device 11 and an internal combustion engine, the drive control device 3 is provided with a storage voltage conversion unit 12, whereas in the case of an electric vehicle that is powered by an electric storage device 11, the drive control device 3 does not need to be provided with the storage voltage conversion unit 12.

[0053] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims, as well as the scope and spirit of the invention. [Explanation of symbols]

[0054] 1...non-contact power transfer system, 2...power transmission device, 3...drive control device, 4...power receiving device, 6...power supply unit, 7...transmission power conversion unit, 8...power transmission unit, 8a...primary side coil (transmission side coil), 10...coil unit, 11...power storage device, 12...storage voltage conversion unit, 13...power conversion unit, 14...rotating electric machine, 15...power receiving unit, 15a...secondary side coil (coil), 15c...secondary side capacitor (capacitor), 16...receiving power conversion unit, 17...control device.

Claims

1. A resonant circuit mounted on a vehicle, the resonant circuit including: a coil that generates a current of a reverse phase in a power transmission side coil when receiving AC power transmitted contactlessly from a power transmission side coil of a power transmission device; and a capacitor connected in series with the coil; A control device; Equipped with the resonant circuit has a first resonance point on a low frequency side showing an in-phase resonance mode, a second resonance point on a high frequency side showing an anti-phase resonance mode, and an anti-resonant point showing a maximum impedance between the in-phase resonance mode and the anti-phase resonance mode, the control device sets a frequency corresponding to the second resonance point among the first resonance point, the second resonance point, and the anti-resonance point as a required frequency for power transmission by the power transmitting device. Coil unit.

2. When viewed from the same predetermined direction, the winding direction of the coil is set to be opposite to the winding direction of the power transmission coil. The coil unit according to claim 1 .

3. The capacitance of the capacitor is set in accordance with the second resonance point. The coil unit according to claim 1 or 2.

4. The requested frequency is transmitted to the power transmission device by communication between the power transmission device and the vehicle. The coil unit according to claim 1 or 2.

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