WO2015028868A2

WO2015028868A2 - Power reception system, power transfer system, and vehicle

Info

Publication number: WO2015028868A2
Application number: PCT/IB2014/001622
Authority: WO
Inventors: Shinji Ichikawa
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2013-08-28
Filing date: 2014-08-26
Publication date: 2015-03-05
Anticipated expiration: 2016-02-28
Also published as: JP2015047013A; WO2015028868A3

Abstract

A power reception device includes a power reception coil and a magnetic member. The power reception coil is arranged on a bottom surface of a vehicle main body. The power reception coil is configured to receive power tirelessly from a power transfer coil in a state of facing the power transfer coil. The power reception coil is provided to surround a winding axis that extends in a first direction crossing a direction to face the power transfer coil. The magnetic member is arranged on the bottom surface of the vehicle main body. The magnetic member has a shape that extends in the first direction. The magnetic member is arranged adjacent to the power reception coil in a second direction crossing the first direction.

Description

POWER RECEPTION SYSTEM, POWER TRANSFER SYSTEM, AND VEHICLE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to a power reception device, a power transfer device, and a vehicle.

2. Description of Related Art

[0002] Japanese Patent Application Publication No. 2011-147213 (JP 2011-147213 A) discloses an invention relating to a power transfer system that transfers power wirelessly. In this system, a frequency of high frequency power and parameters on first and second coils are selected such that, when the high frequency power is transferred from the first coil to the second coil, the first and second coils resonate with each other in a state that currents in reverse directions from each other flow through the first and second coils. The bulletin describes that the intensity of a leakage electromagnetic field produced upon power transfer can be reduced by this system.

SUMMARY OF THE INVENTION

[0003] The present invention provides a power reception device, a power transfer device, and a vehicle that can reduce the intensity of a leakage electromagnetic field produced upon wireless power transfer.

[0004] A power reception device according to a first aspect of the present invention includes a power reception coil and a magnetic member. The power reception coil is arranged on a bottom surface of a vehicle main body. The power reception coil is configured to receive power wirelessly from a power transfer coil in a state of facing the power transfer coil. The power reception coil is provided to surround a winding axis that extends in a first direction crossing a direction to face the power transfer coil. The magnetic member is arranged on the bottom surface of the vehicle main body. The magnetic member has a shape that extends in the first direction. The magnetic member is arranged adjacent to the power reception coil in a second direction crossing the first direction.

[0005] A vehicle according to a second aspect of the present invention includes the vehicle main body and the power reception device. A center position of the power reception coil in the first direction is located on a front half of the vehicle main body. [0006] In the vehicle according to the second aspect of the present invention, the first direction may be the longitudinal direction of the vehicle main body. The second direction may be a width direction of the vehicle main body.

[0007] In the vehicle according to the second aspect of the present invention, the magnetic member may be provided on both of outer sides of the power reception coil in the width direction of the vehicle main body.

[0008] In the vehicle according to the second aspect of the present invention, the power reception coil may be wound around a core. A width dimension of the core may be larger than a sum of a width dimension of the magnetic member provided on the one outer side of the power reception coil and a width dimension of the magnetic member provided on the other outer side of the power reception coil in the width direction of the vehicle main body. In addition, the width dimension of the core may be smaller than the sum of the width dimension of the magnetic member provided on the one outer side of the power reception coil and the width dimension of the magnetic member provided on the other outer side of the power reception coil in the width direction of the vehicle main body.

[0009] In the vehicle according to the second aspect of the present invention, the power reception coil may be wound around a core. The distance between the magnetic member and the core may be shorter than a distance between the magnetic member and an outer edge section of the vehicle main body in the width direction of the vehicle main body.

[0010] In the vehicle according to the second aspect of the present invention, the power reception coil may be wound around a core. The distance between the magnetic member and the core may be longer than the distance between the magnetic member and the outer edge section of the vehicle main body in the width direction of the vehicle main body.

[0011] In the vehicle according to the second aspect of the present invention, the power reception coil may be wound around a core. The distance between the magnetic member and the core may be longer than the vehicle height of the vehicle main body in the width direction of the vehicle main body. In addition, the power reception device and the magnetic member may be provided between a pair of front wheels provided in the vehicle main body.

[0012] In the vehicle according to the second aspect of the present invention, the power reception device may include a case body that houses the power reception coil. The vehicle may further include an engine and an exhaust pipe connected to the engine. The case body may be arranged under the exhaust pipe so as to allow air to flow between the case body and the exhaust pipe. The power reception coil and the magnetic member may be arranged to overlap each other as viewed from a horizontal direction.

[0013] In the vehicle according to the second aspect of the present invention, the power reception device may be arranged between a first exhaust pipe and a second exhaust pipe provided on the bottom surface of the vehicle main body as viewed in a plane view of the bottom surface of the vehicle main body. The magnetic member may be arranged on an outer side of the first exhaust pipe and on an outer side of the second exhaust pipe as viewed in a plane view of the bottom surface of the vehicle main body.

[0014] In the vehicle according to the second aspect of the present invention, a difference between a natural frequency of the power transfer coil and a natural frequency of the power reception coil may be 10% or less of a natural frequency of the power reception coil.

[0015] In the vehicle according to the second aspect of the present invention, coupling coefficient of the power reception coil and the power transfer coil may be 0.3 or less. In addition, the power reception coil may receive power from the power transfer coil through at least one of a magnetic field that is formed between the power reception coil and the power transfer coil and oscillates at a specified frequency and an electric field that is formed between the power reception coil and the power transfer coil and oscillates at the specified frequency.

[0016] A power transfer device according to a third aspect of the present invention includes the power transfer coil and the magnetic member. The power transfer coil is configured to transfer power wirelessly to the power reception coil provided in the vehicle in a state of facing the power reception coil. The power transfer coil is provided to surround the winding axis that extends in a third direction crossing a direction to face the power reception coil. The magnetic member has a shape that extends in third direction. The magnetic member is arranged adjacent to the power transfer coil in the fourth direction crossing the third direction.

[0017] According to the present invention, a power reception device, a power transfer device, and a vehicle capable of reducing a leakage electromagnetic field that is generated when power is transferred wirelessly can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a schematic view of a power transfer system in a first embodiment;

FIG. 2 is a plan view of a vehicle including a power reception device in the first embodiment;

FIG. 3 is a bottom view of the vehicle including the power reception device in the first embodiment;

FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3;

FIG. 5 is a view of a magnetic member and the like that are seen from an arrow V direction in FIG. 4;

FIG. 6 is a partial bottom view of a bottom surface of the vehicle including the power reception device in the first embodiment;

FIG. 7 is a bottom view of another aspect of the magnetic member applicable to the first embodiment;

FIG. 8 is a bottom view of yet another aspect of the magnetic member applicable to the first embodiment;

FIG. 9 is a view of a simulation model of the power transfer system;

FIG. 10 is a graph for showing a relationship between the power transfer efficiency and a deviation of a natural frequency between a power transfer section and a power reception section;

FIG. 11 is a graph for showing a relationship between the power transfer efficiency and a frequency f3 of current supplied to a primary coil at a time when an air gap AG is changed in a state that a natural frequency fO is fixed;

FIG. 12 is a graph for showing a relationship between a distance from a current source or a magnetic current source and intensity of an electromagnetic field;

FIG. 13 is a plan view of a situation where the vehicle in the first embodiment is operated for parking;

FIG. 14 is a view of a situation around the power reception section when power is transferred in the power transfer system of the first embodiment;

FIG. 15 is a bottom view of the vehicle including a power reception device in a second embodiment;

FIG. 16 is a bottom view of the vehicle including a power reception device in a third embodiment;

FIG. 17 is a bottom view of the vehicle including a power reception device in a fourth embodiment; FIG. 18 is a bottom view of the vehicle including a power reception device in a fifth embodiment;

FIG. 19 is a plan view of a situation where the vehicle in a sixth embodiment is operated for parking;

FIG. 20 is a plan view of a situation where the vehicle in a modification of the sixth embodiment is operated for parking; and

FIG. 21 is a plan view of a situation where the vehicle in another modification of the sixth embodiment is operated for parking.

DETAILED DESCRIPTION OF EMBODIMENTS

[0019] Each embodiment based on the present invention will hereinafter be described with reference to the drawings. When the description of the each embodiment makes reference to the number, a quantity, and the like, the scope of the present invention is not necessarily limited to the number, a quantity, and the like, unless otherwise noted. In the each embodiment, same components and corresponding components are denoted by the same reference numerals, and the description thereof may not be repeated.

[0020] [First Embodiment] FIG. 1 is a schematic view of a power transfer system 1000 in a first embodiment. The power transfer system 1000 includes an external power supply apparatus 60 and an electric drive vehicle 10 (also referred to as a vehicle).

[0021] (External power, supply apparatus 60) The external power supply apparatus 60 includes a power transfer device 50, a high frequency power device 66, and a power transfer electronic control unit (ECU) 66C. The high frequency power device 66 is connected to an AC power supply 66E. The AC power supply 66E may be a commercial power supply or an independent power supply device. The power transfer device 50 is connected to the high frequency power device 66. The power transfer ECU 66C controls the drive of the high frequency power device 66 and the like.

[0022] The power transfer device 50 is provided in a parking space 52. The power transfer device 50 includes a power transfer section 300. The power transfer section 300 has a solenoid coil unit 64 and a capacitor 63 connected to the coil unit 64. The coil unit 64 includes a ferrite core 61, a power transfer coil 62 (primary coil), and a fixing member, which is not shown. The fixing member is plate shaped and made of a resin. The ferrite core 61 is housed in the fixing member. [0023] The power transfer coil 62 is wound around an outer peripheral surface of the fixing member described above, and is formed to surround a periphery of a winding axis, which is not shown (see a winding axis 01 in FIG. 13). The power transfer coil 62 has a floating capacitance. In the power transfer section 300, an electrical circuit is formed by the inductance of the power transfer coil 62, the floating capacitance of the power transfer coil 62, and the capacitance of the capacitor 63. The capacitor 63 is not an essential component and may be used upon necessity.

[0024] The power transfer ECU 66C includes a central processing unit (CPU), a memory, and an input/output buffer, receives a signal from each sensor or the like, outputs a control signal to each equipment, and controls the each equipment in the external power supply apparatus 60. The high frequency power device 66 is controlled by the control signal from the power transfer ECU 66C, and converts power received from the AC power supply 66E to high frequency power. The high frequency power device 66 supplies the converted high frequency power to the power transfer coil 62.

[0025] The power transfer coil 62 wirelessly transfers power to a power reception coil 22 in a power reception section 200 by electromagnetic induction. For the power transfer coil 62, the number of turns and a distance between the coils are appropriately set on the basis of a distance between the power transfer coil 62 and the power reception coil 22, frequencies of the power transfer coil 62 and the power reception coil 22, and the like such that a coupling coefficient (κ) and the like that indicate a degree of coupling between the power transfer coil 62 and the power reception coil 22 becomes an appropriate value.

[0026] An electromagnetic shield plate, which is not shown, is provided on an opposite side from a side that faces the electric drive vehicle 10 when seen from the coil unit 64. The electromagnetic shield plate has a flat plate shape. A rectangular aluminum plate that is 1 mm in thickness can be used as the electromagnetic shield plate, for example.

[0027] (Electric drive vehicle 10) The electric drive vehicle 10 includes an engine and a fuel cell, which are not shown, and functions as a hybrid vehicle. Instead, the electric drive vehicle 10 may function as a fuel cell vehicle as long as it is driven by a motor. In addition, the electric drive vehicle 10 may function as an electric vehicle as long as it is driven by a motor. In this embodiment, the vehicle is as a subject of power reception; however, the subject of power reception may be anything other than the vehicle. [0028] The electric drive vehicle 10 includes a vehicle main body 70 and a power reception device 11. In the vehicle main body 70, a vehicle electronic control unit (ECU) 12, a rectifier 13, a DC/DC converter 14, a battery 15, a power control unit 16, a motor unit 17, and the like are provided.

[0029] The power reception device 11 is arranged on a bottom surface of the vehicle main body 70 (a detail thereof will be described later). The power reception device 11 receives power from the power transfer device 50 wirelessly in a state that the electric drive vehicle 10 is parked in a specified position within the parking space 52 and that the power reception device 11 faces the power transfer device 50. The parking space 52 is provided with a wheel chock 52S and a parking line (not shown) that indicates a parking position and a parking area to assist in parking the electric drive vehicle 10 in the specified position.

[0030] The power reception device 11 includes the power reception section 200, magnetic members 81, 82 (which are not shown in FIG. 1 and will be described later with reference to FIG. 3 to FIG. 6), and a case body (not shown) for housing the power reception section 200. The power reception section 200 has a solenoid coil unit 24 and a capacitor 23 connected to the coil unit 24. The coil unit 24 includes a ferrite core 21, a power reception coil 22 (secondary coil), and a fixing member, which is not shown. The fixing member is plate shaped and made of a resin. The ferrite core 21 is housed in the fixing member.

[0031] The power reception coil 22 is wound around an outer peripheral surface of the fixing member described above, and is formed to surround a periphery of a winding axis, which is not shown (see a winding axis 02 in FIG. 2 and FIG. 3). The power reception coil 22 has a floating capacitance and is connected to the rectifier 13. In the power reception section 200, an electrical circuit is formed by the inductance of the power reception coil 22, the floating capacitance of the power reception coil 22, and the capacitance of the capacitor 23. The capacitor 23 is not an essential component and may be used upon necessity.

[0032] The DC/DC converter 14 is connected to the rectifier 13. The rectifier 13 converts AC current supplied from the power reception device 11 to DC current, and supplies the DC current to the DC/DC converter 14. The battery 15 is connected to the DC/DC converter 14. The DC/DC converter 14 adjusts voltage of the DC current supplied from the rectifier 13, and supplies the DC current to the battery 15. [0033] The vehicle ECU 12 controls the drive of the DC/DC converter 14, the power control unit 16, and the like. The DC/DC converter 14 is not an essential component and may be used upon necessity. If the DC/DC converter 14 is not used, a matching device may be provided between the power transfer device 50 and the high frequency power device 66 of the external power supply apparatus 60. This matching device matches the impedance, and thus can be used as a substitute for the DC/DC converter 14.

[0034] The power control unit 16 is connected to the battery 15. The motor unit 17 is connected to the power control unit 16. The power control unit 16 includes ^" a converter, which is not shown and connected to the battery 15, and an inverter, which is not shown and connected to the converter.

[0035] The converter adjusts (increases the voltage of) the DC current supplied from the battery 15, and supplies the DC current to the inverter. The inverter converts the DC current supplied from the converter to AC current, and supplies the AC current to the motor unit 17. The motor unit 17 includes a motor generator that functions as a generator, and a motor generator that functions as an electric motor. As the motor unit 17, a three-phase AC motor can be used, for example. The motor unit 17 is driven by the AC current, which is supplied from the inverter of the power control unit 16.

[0036] FIG. 2 is a plan view of the electric drive vehicle 10. FIG. 3 is a bottom view of the electric drive vehicle 10. In FIG. 2 and FIG. 3, "U" (FIG. 2) indicates upward U in a vertical direction. "D" (FIG. 3) indicates downward D in the vertical direction. "L" indicates a vehicle left direction L. "R" indicates a vehicle right direction R. "F" indicates a vehicle forward direction F. "B" indicates a vehicle backward direction B. These directions are also common in FIG. 4 to FIG. 8 and FIG. 13 to FIG. 21, which will be described later.

[0037] Referring to FIG. 2 and FIG. 3, the vehicle main body 70 of the electric drive vehicle 10 has a bottom surface 76 (FIG. 3). The power reception device 11 and the power reception section 200 included in the power reception device 11 are provided in the bottom surface 76 of the vehicle main body 70. The power reception section 200 is attached to the bottom surface 76 in a state that the power reception section 200 is housed in a case body 65 (FIG. 3) having a box shape.

[0038] The case body 65 includes a bottomed shield section that is opened downward D in the vertical direction and a lid section that closes a lower end opening of the shield section. The case body 65 is made of a metallic material such as copper. An electromagnetic shield plate, which is not shown, is provided on an opposite side from a side that faces the power transfer device 50 when seen from the case body 65. The electromagnetic shield plate has the flat plate shape. A rectangular aluminum plate that is 1 mm in thickness can be used as the electromagnetic shield plate, for example.

[0039] The bottom surface 76 has a center position PI. The center position PI is located at the center in a longitudinal direction (the vehicle forward direction F and the vehicle backward direction B) of the vehicle main body 70, and also located at the center of a width direction (the vehicle left direction L and the vehicle right direction R) of the vehicle main body 70. The electric drive vehicle 10 is provided with front wheels 19FR, 19FL aligned in the width direction of the electric drive vehicle 10 and back wheels 19BR, 19BL aligned in the width direction of the electric drive vehicle 10.

[0040] The bottom surface 76 of the electric drive vehicle 10 is a visible region of the vehicle main body 70 when the electric drive vehicle 10 is seen from a position that is downwardly separated from the ground in the vertical direction in a state that the wheels 19FL, 19FR, 19RL, 19RB contact the ground. A peripheral edge section of the bottom surface 76 includes a front edge section 34F, a back edge section 34B, a right outer edge section 34R, and a left outer edge section 34L. The bottom surface 76 of the vehicle main body 70 is a portion surrounded by the front edge section 34F, the back edge section 34B, the right outer edge section 34R, and the left outer edge section 34L.

[0041] The front edge section 34F is located on the vehicle forward direction F side of the front wheel 19FR and the front wheel 19FL. The right outer edge section 34R and the left outer edge section 34L are aligned in the width direction of the electric drive vehicle 10, and located between the front edge section 34F and the back edge section 34B. The back edge section 34B is located on the vehicle backward direction B side of the back wheel 19BR and the back wheel 19BL.

[0042] The bottom surface 76 of the electric drive vehicle 10 is provided with the magnetic members 81, 82, an exhaust pipe 68, a floor panel 69, a side member 67S, a cross member,, and the like. The floor panel 69 has a plate shape, and partitions the inside of the vehicle main body 70 and the outer side of the vehicle main body 70. The side member 67S and the cross member are arranged on a lower surface of the floor panel 69. [0043] The power reception device 11 is provided on the bottom surface 76 of the electric drive vehicle 10 in a state that the power reception device 11 is housed in the case body 65. The power reception device 11 of this embodiment is arranged on the vehicle forward direction F side of the center position PI. Any of various methods can be adopted to fix the power reception device 11 to the bottom surface 76. For example, the power reception device 11 can be fixed to the bottom surface 76 by suspending the power reception device 11 from the side member 67S or the cross member. Alternatively, the power reception device 11 may be fixed to the floor panel 69. In this embodiment, the power reception device 11 is arranged to partially overlap the exhaust pipe 68 when the bottom surface 76 of the vehicle main body 70 is seen in a plan view.

[0044] FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3. As shown in FIG. 4, the exhaust pipe 68 is arranged in a center tunnel 69T of the floor panel 69. The case body 65 of the power reception device 11 includes a top plate 65A made of copper and a lid member 65B made of a resin, and is arranged under the exhaust pipe 68 to face the exhaust pipe 68 with a space therebetween. The air can flow between the top plate 65A of the case body 65 and the exhaust pipe 68. Here, the air functions as a heat insulating layer. Thus, even if the exhaust pipe 68 is heated at a high temperature upon initiation of charging after traveling, for example, the heat of the exhaust pipe 68 is suppressed from being transferred to the power reception section 200.

[0045] FIG. 5 is a view of the magnetic member 82 and the like that are seen from an arrow V direction in FIG. 4. As shown in FIG. 5, when the power reception coil 22 of the power reception section 200 and the magnetic members 81, 82 are seen in a horizontal direction, the power reception coil 22 and each of the magnetic members 81, 82 are arranged to overlap each other. The power reception coil 22 and each of the magnetic members 81, 82 are not arranged to mismatch each other in a height direction. Thus, it is possible by the magnetic members 81, 82 to suppress leakage of the leakage electromagnetic field from the power reception coil 22 to the outer side of the vehicle.

[0046] FIG. 6 is a partial view of the bottom surface 76 of the vehicle main body 70. For convenience of the description, in FIG. 6, the case body 65 (see FIG. 3) for housing the power reception section 200 is not shown, and the power reception section 200 is shown in an exposed manner. As shown in FIG. 3, the power reception section 200 is actually housed in the case body 65. As described above, the power reception section 200 includes the ferrite core 21 and the power reception coil 22 (secondary coil). The power reception coil 22 is wound around the ferrite core 21 (more specifically, a fixing member, which is not shown and fixes the ferrite core 21).

[0047] The ferrite core 21 has a shape that extends along a direction in which a winding axis 02 of the power reception coil 22 extends. The winding axis 02 has a shape that extends linearly, and extends in a direction to cross (in this embodiment, a direction perpendicular to) a facing direction (an arrow Z direction in FIG. 1). The facing direction described here is a direction in which the power reception coil 22 faces the power transfer coil 62 (see FIG. 1). In this embodiment, that the winding axis 02 crosses the facing direction (Z direction) means that the winding axis 02 is perpendicular to or substantially perpendicular to the facing direction. A state of being substantially perpendicular includes a case of crossing in a state of being mismatched in a range of larger than 0° and up to 15°, for example, from a state of being perpendicular.

[0048] Preferably, the winding axis 02 may cross the facing direction (Z direction) in an angular range from 80° to 100°. More preferably, the winding axis 02 may cross the facing direction in an angular range from 85° to 95°. Optimally, the winding axis 02 may cross the facing direction at an angle of 90°. The facing direction in this embodiment is a direction orthogonal to a surface (the ground) of the parking space 52 (see FIG. 1), and the winding axis 02 extends in a parallel direction to the surface (ground) of the parking space 52. The power reception coil 22 is formed to surround a periphery of the winding axis 02.

[0049] For example, the power reception coil 22 is divided by a unit length from one end in a length direction of the power reception coil 22 to another end in the length direction of the power reception coil 22. At this time, the winding axis 02 of the power reception coil 22 described here is formed by drawing a line that passes through a curvature center point or the vicinity of the curvature center point of the power reception coil 22 per unit length. As a method of leading to the winding axis 02 as a virtual line from the curvature center point of the power reception coil 22 per unit length, various approximation methods can be raised, such as linear approximation, log approximation, and polynomial approximation.

[0050] The power reception section 200 (power reception device 11) has a center position P2. The center position P2 is a virtual point located on the winding axis 02 of the power reception coil 22, and is located at the center of the power reception coil 22 in a direction in which the winding axis 02 extends. The center position P2 is located at the center in a longitudinal direction of the power reception coil 22 when the power reception section 200 is seen in a plan view along the vertical direction. In other words, the center position P2 is located at the exact center between a portion of a coil wire of the power reception coil 22 that is located at an end in the direction in which the winding axis 02 extends (set as a first direction) and a portion of the coil wire of the power reception coil 22 that is located at another end in the direction in which the winding axis 02 extends (a second direction that is opposite from the first direction).

[0051] The power reception coil 22 of this embodiment is attached to the bottom surface 76 such that the center position P2 of the power reception coil 22 in the direction in which the winding axis 02 extends is located on the front side (the front half of the vehicle main body 70) in the vehicle main body 70 of the center position PI (FIG. 3) in the front/back direction of the vehicle main body 70. Furthermore, in this embodiment, the direction in which the winding axis 02 extends is parallel to the longitudinal direction of the vehicle main body 70.

[0052] It is intended in the power transfer system of this embodiment (see the power transfer system 1000 in FIG. 1) that the winding axis 02 of the power reception coil 22 is arranged parallel to the winding axis 01 of the power transfer coil 62 when the electric drive vehicle 10 is parked in the parking space 52 by using parking lines 41, 42 (see FIG. 13) and the like as marks.

[0053] The magnetic members 81, 82 arranged on the bottom surface 76 each have a shape that extends in a same direction as the direction in which the winding axis 02 of the power reception coil 22 extends. In this embodiment, each of the magnetic members 81, 82 has the shape just as described. However, the shape of each of the magnetic members 81, 82 is not limited to the shape just as described.

[0054] As shown in FIG. 7 and FIG. 8, the magnetic members 81, 82 may each be formed in an arcuate shape, for example. When the magnetic members 81, 82 are each formed in the arcuate shape, the magnetic members 81, 82 may be arranged such that curved portions of the magnetic members 81, 82 are projected toward lateral sides of the vehicle (see FIG. 7). Alternatively, the magnetic members 81, 82 may be arranged such that the curved portions of the magnetic members 81, 82 are projected toward the power reception section 200 side (see FIG. 8).

[0055] Referring again to FIG. 6, the magnetic members 81, 82 are arranged adjacent to the power reception coil 22 in a direction that crosses (in this embodiment, a direction perpendicular to) the direction in which the winding axis 02 extends. Being "adjacent" described here means that, for example, when the power reception coil 22 is projected in a direction perpendicular to the direction in which the winding axis 02 extends (in the horizontal direction), at least a portion of a projection image of the power reception coil 22 overlaps the magnetic members 81, 82.

[0056] The magnetic members 81, 82 are magnetically independent of each other. Thus, a magnetic member for magnetically connecting the magnetic member 81 and the magnetic member 82 is not provided. In other words, that the magnetic members 81, 82 are magnetically independent of each other means a state that a member for guiding a magnetic flux that enters one of the magnetic members 81, 82 to another of the magnetic members 81, 82 is not provided.

[0057] The magnetic members 81, 82 are each formed of a so-called ferromagnetic material such as ferrite, pressed iron power (dust core), amorphous (amorphous core), iron oxide, chromium oxide, or cobalt. When the magnetic members 81, 82 are manufactured, the magnetic members 81, 82 may each be manufactured by combining a plurality of divided ferrite bodies or the like, or may each be manufactured by a single ferrite body or the like.

[0058] The magnetic members 81, 82 of this embodiment each have a plate shape that extends linearly, and are arranged parallel to each other on both of the outer sides of the power reception section 200 in the width direction of the vehicle main body 70. The magnetic members 81, 82 are adjacent to the power reception coil 22 in the width direction of the vehicle main body 70 (the vehicle left direction L and the vehicle right direction R). The magnetic members 81, 82 may each have a curved plate shape.

[0059] A case where each of the magnetic members 81, 82 formed in the curved plate shape has a shape to extend in the same direction as the winding axis 02 of the power reception coil 22 includes, for example, a case where a linear line of the magnetic members 81, 82 that is approximated by any of the various approximation methods such as linear approximation, log approximation, and polynomial approximation extends in in the same direction as the winding axis 02 of the power reception coil 22. In this embodiment, the power reception device 11 includes the two magnetic members 81, 82. However, the power reception device 11 may only include either one of the magnetic members 81, 82.

[0060] Referring to FIG. 6, in this embodiment, a width dimension W21 of the ferrite core 21, around which the power reception coil 22 is wound, is larger than a sum of a width dimension W81 of the magnetic member 81, which is provided on the one outer side of the power reception coil 22, and a width dimension W82 of the magnetic member 82, which is provided on the other outer side of the power reception coil 22, in the width direction of the vehicle main body 70 (the vehicle left direction L and the vehicle right direction R). The width dimension W21 of the ferrite core 21 may be smaller than the sum of the width dimension W81 of the magnetic member 81 and the width dimension W82 of the magnetic member 82. The width dimensions W21, W81, W82 may be optimized in accordance with an effect of suppressing the leakage electromagnetic field, which is generated upon power transfer, or the like.

[0061] In the width direction of the vehicle main body 70 (the vehicle left direction L and the vehicle right direction R), a distance Wll between the magnetic member 81 and the ferrite core 21, around which the power reception coil 22 is wound, is shorter than a distance W13 between the magnetic member 81 and the right outer edge section 34R of the bottom surface 76 of the vehicle main body 70. In addition, in the width direction of the vehicle main body 70 (the vehicle left direction L and the vehicle right direction R), a distance W12 between the magnetic member 82 and the ferrite core 21, around which the power reception coil 22 is wound, is shorter than a distance W14 between the magnetic member 82 and the left outer edge section 34L of the bottom surface 76 of the vehicle main body 70.

[0062] However, the configuration is not limited to the above configuration. In the width direction of the vehicle main body 70 (the vehicle left direction L and the vehicle right direction R), the distance Wll between the magnetic member 81 and the ferrite core 21, around which the power reception coil 22 is wound, may be longer than the distance W13 between the magnetic member 81 and the right outer edge section 34R of the bottom surface 76 of the vehicle main body 70, or the distance Wll and the distance W13 may have a same value. In addition, in the width direction of the vehicle main body 70 (the vehicle left direction L and the vehicle right direction R), the distance W12 between the magnetic member 82 and the ferrite core 21, around which the power reception coil 22 is wound, may be longer than the distance W14 between the magnetic member 82 and the left outer edge section 34L of the bottom surface 76 of the vehicle main body 70, or the distance W12 and the distance W14 may have a same value.

[0063] In the longitudinal direction of the vehicle main body 70 (the vehicle forward direction F and the vehicle backward direction B), a length dimension L81 of the magnetic member 81 is preferably longer than a length dimension L21 of the ferrite core 21, around which the power reception coil 22 is wound. In addition, in the longitudinal direction of the vehicle main body 70 (the vehicle forward direction F and the vehicle backward direction B), a length dimension L82 of the magnetic member 82 is also preferably longer than the length dimension L21 of the ferrite core 21, around which the power reception coil 22 is wound. The width dimension W21 and the length dimension L21 of the ferrite core 21, the width dimension W81 and the length dimension L81 of the magnetic member 81, the width dimension W82 and the length dimension L82 of the magnetic member 82, and the distances Wll, W12, W13, W14 may appropriately be optimized in accordance with the arrangement of the each equipment provided on the bottom surface 76 of the vehicle main body 70.

[0064] (Principle of Power Transfer) After the alignment between the power reception section 200 and the power transfer section 300 is carried out, power is transferred between the power reception section 200 and the power transfer section 300. A description will be made on the principle of power transfer in this embodiment by using FIG. 9 to FIG. 12.

[0065] In the power transfer system according to this embodiment, a difference between a natural frequency of the power transfer section 300 (power transfer coil 62) and a natural frequency of the power reception section 200 (power reception coil 22) is 10% or less of the natural frequency of the power reception section 200 (power reception coil 22) or the power transfer section 300 (power transfer coil 62). The power transfer efficiency can be increased by setting the natural frequency of each of the power transfer section 300 and the power reception section 200 to fall within such a range. Meanwhile, if the difference of the natural frequency becomes larger than 10% of the natural frequency of the power reception section 200 or the power transfer section 300, the power transfer efficiency becomes lower than 10%, and a charging time of the battery 15 (FIG. 1) is extended.

[0066] Here, in a case where the capacitor 63 is not provided, the natural frequency of the power transfer section 300 (power transfer coil 62) means an oscillation frequency that is obtained when the electrical circuit, which is formed by the inductance of the power transfer coil 62 and the capacitance of the power transfer coil 62, freely oscillates. On the other hand, in a case where the capacitor 63 is provided, the natural frequency of the power transfer section 300 means an oscillation frequency that is obtained when the electrical circuit, which is formed by the capacitance of the power transfer coil 62, the capacitance of the capacitor 63, and the inductance of the power transfer coil 62, freely oscillates. In the electrical circuit just as described, the natural frequency that is obtained when a damping force and electric resistance are set to zero or set substantially to zero is also referred to as a resonance frequency of the power transfer section 300.

[0067] Similarly, in a case where the capacitor 23 is not provided, the natural frequency of the power reception section 200 (power reception coil 22) means an oscillation frequency that is obtained when the electrical circuit, which is formed by the inductance of the power reception coil 22 and the capacitance of the power reception coil 22, freely oscillates. On the other hand, in a case where the capacitor 23 is provided, the natural frequency of the power reception section 200 means an oscillation frequency that is obtained when the electrical circuit, which is formed by the capacitance of the power reception coil 22, the capacitance of the capacitor 23, and the inductance of the power reception coil 22, freely oscillates. In the electrical circuit just as described, the natural frequency that is obtained when the damping force and the electric resistance are set to zero or set substantially to zero is also referred to as a resonance frequency of the power reception section 200.

[0068] A description will be made on a result of a simulation in which a relationship between the difference in the natural frequency and the power transfer efficiency is analyzed by using FIG. 9 and FIG. 10. FIG. 9 is a view of a simulation model of the power transfer system. The power transfer system includes a power transfer device 190 and a power reception device 191. The power transfer device 190 includes a coil 192 (electromagnetic inductive coil) and a power transfer section 193. The power transfer section 193 has a coil 194 (primary coil) and a capacitor 195 provided in the coil 194. The power reception device 191 includes a power reception section 196 and a coil 197 (electromagnetic inductive coil). The power reception section 196 includes a coil 199 and a capacitor 198 connected to the coil 199 (secondary coil).

[0069] Here, the inductance of the coil 194 is set to an inductance Lt, and the capacitance of the capacitor 195 is set to a capacitance CI. In addition, the inductance of the coil 199 is set to an inductance Lr, and the capacitance of the capacitor 198 is set to a capacitance C2. If each parameter is set just as described, a natural frequency fl of the power transfer section 193 is expressed by the following equation (1), and a natural frequency f2 of the power reception section 196 is expressed by the following equation (2).

[0070] fl = l/{2jt(Lt x Cl)^{1 2}} ...(1) f2 = l/{27t(Lr x C2) ^1/2} ...(2)

Here, FIG. 10 shows a relationship between the power transfer efficiency and a deviation of the natural frequency between the power transfer section 193 and the power reception section 196 in a case where only the inductance Lt is changed while the inductance Lr and the capacitances CI, C2 are fixed. In this simulation, an adequate alignment relationship between the coil 194 and the coil 199 is in a fixed state, and the current supplied to the power transfer section 193 has a constant frequency.

[0071] In a graph shown in FIG. 10, a horizontal axis indicates the deviation of the natural frequency (%), and a vertical axis indicates the transfer efficiency (%) at the constant frequency. The deviation of the natural frequency (%) is expressed by the following equation (3).

[0072] The deviation of the natural frequency = {(f 1 - f2) /f2} x 100 (%)... (3)

As apparent from FIG. 10, when the deviation of the natural frequency (%) is ±0%, the power transfer efficiency approximates 100%. When the deviation of the natural frequency (%) is ±5%, the power transfer efficiency is 40%. When the deviation of the natural frequency (%) is ±10%, the power transfer efficiency is 10%. When the deviation of the natural frequency (%) is ±15%, the power transfer efficiency is 5%.

[0073] It is understood that the power transfer efficiency can be increased when the natural frequency of each of the power transfer section and the power reception section is set such that an absolute value of the deviation of the natural frequency (%) (the difference of the natural frequencies) falls within a range of 10% or less of the natural frequency of the power reception section 196. It is also understood that the power transfer efficiency can further be increased when the natural frequency of each of the power transfer section and the power reception section is set such that the absolute value of the deviation of the natural frequency (%) is 5% or less of the natural frequency of the power reception section 196. As simulation software, electromagnetic field analysis software (JMAG®: produced by JSOL Corporation) is adopted.

[0074] Next, an operation of the power transfer system according to this embodiment will be described. As described above, AC power is supplied from the high frequency power device 66 to the power transfer coil 62 (see FIG. 1 and the like). At this time, the power is supplied such that a frequency of AC current flowing through the power transfer coil 62 becomes a specified frequency. When the current at the specified frequency flows through the power transfer coil 62, an electromagnetic field that oscillates at the specified frequency is formed around the power transfer coil 62. [0075] The power reception coil 22 is arranged within a specified range from the power transfer coil 62. The power reception coil 22 receives the power from the electromagnetic field formed around the power transfer coil 62. In this embodiment, a so-called helical coil is adopted for each of the power reception coil 22 and the power transfer coil 62. A magnetic field and an electric field that oscillate at the specified frequency are formed around the power transfer coil 62, and the power reception coil 22 mainly receives the power from the magnetic field.

[0076] Here, a description will be made on the magnetic field of the specified frequency that is formed around the power transfer coil 62. "A magnetic field of a specified frequency" typically has a relationship with power transfer efficiency and a frequency of current supplied to the power transfer coil 62. A relationship between the power transfer efficiency and the frequency of the current supplied to the power transfer coil 62 will be described. The power transfer efficiency at a time when power is transferred from the power transfer coil 62 to the power reception coil 22 varies by various factors such as a distance between the power transfer coil 62 and the power reception coil 22. For example, the natural frequency (resonance frequency) of each of e power transfer section 300 and the power reception section 200 is set to a natural frequency fO, a frequency of current supplied to the power transfer coil 62 is set to a frequency f3, and an air gap between the power reception coil 22 and the power transfer coil 62 is set to an air gap AG.

[0077] FIG. 11 is a graph for showing a relationship between the power transfer efficiency and the frequency f3 of the current supplied to the power transfer coil 62 at a time when the air gap AG is changed in a state that the natural frequency fO is fixed. A horizontal axis in FIG. 11 indicates the frequency f3 of the current supplied to the power transfer coil 62, and a vertical axis in FIG. 11 indicates the power transfer efficiency (%).

[0078] An efficiency curve LL1 schematically indicates the relationship between the power transfer efficiency and the frequency f3 of the current supplied to the power transfer coil 62 at a time when the air gap AG is small. As indicated by the efficiency curve LL1, when the air gap AG is small, a peak of the power transfer efficiency is generated at frequencies f4, f5 (f4 < f5). When the air gap AG is increased, the two peaks, at which the power transfer efficiency is high, are changed to approach each other.

[0079] As indicated by an efficiency curve LL2, when the air gap AG is increased to be longer than a specified distance, the number of the peaks of the power transfer efficiency is reduced to one, and the peak of the power transfer efficiency is generated at a time when the frequency of the current supplied to the power transfer coil 62 is a frequency f6. When the air gap AG is further increased from a state of the efficiency curve LL2, as indicated by an efficiency curve LL3, the peak of the power transfer efficiency is reduced.

[0080] For example, a following first method is considered as a method of improving the power transfer efficiency. As the first method, it can be raised that the frequency of the current supplied to the power transfer coil 62 is set constant, and the capacitance of each of the capacitor 63 and the capacitor 23 is changed in accordance with the air gap AG, so as to change a characteristic of the power transfer efficiency between the power transfer section 300 and the power reception section 200. More specifically, the capacitance of each of the capacitor 63 and the capacitor 23 is adjusted in a state that the frequency of the current supplied to the power transfer coil 62 is set constant such that the power transfer efficiency reaches the peak.

In this method, the frequency of the current flowing through the power transfer coil 62 and the power reception coil 22 is constant regardless of the size of the air gap AG. As a method of changing the characteristic of the power transfer efficiency, a method of using the matching device provided between the power transfer device 50 and the high frequency power device 66, a method of using the DC/DC converter 14, or the like can also be adopted.

[0081] A second method is a method of adjusting the frequency of the current supplied to the power transfer coil 62 on the basis of the size of the air gap AG. For example, in FIG. 11, when the characteristic of the power transfer efficiency is as indicated by the efficiency curve LL1, the current at the frequency f4 or the frequency f5 is supplied to the power transfer coil 62. When a characteristic of the frequency is as indicated by the efficiency curves LL2, LL3, the current at the frequency f6 is supplied to the power transfer coil 62. In this case, the frequency of the current flowing through the power transfer coil 62 and the power reception coil 22 is changed in accordance with the size of the air gap AG.

[0082] In the first method, the frequency of the current flowing through the power transfer coil 62 is the fixed constant frequency. In the second method, the frequency of the current flowing through the power transfer coil 62 is the frequency that is appropriately changed in accordance with the size of the air gap AG. The current at the specified frequency, which is set to increase the power transfer efficiency by the first method, the second method, or the like, is supplied to the power transfer coil 62. Since the current at the specified frequency flows through the power transfer coil 62, the magnetic field (electromagnetic field) that oscillates at the specified frequency is formed around the power transfer coil 62.

[0083] The power reception section 200 receives the power from the power transfer section 300 through at least one of the magnetic field that oscillates at the specified frequency and the electric field that oscillates at the specified frequency, the magnetic field and the electric field being formed between the power reception section 200 and the power transfer section 300. Thus, the "magnetic field that oscillates at the specified frequency" is not necessarily limited to the magnetic field at the fixed frequency. In addition, the "electric field that oscillates at the specified frequency" is not necessarily limited to the electric field at the fixed frequency, either.

[0084] In the above example, the frequency of the current supplied to the power transfer coil 62 is set while the air gap AG is focused. However, since the power transfer efficiency is changed by another factor such as mismatching of the power transfer coil 62 and the power reception coil 22 in the horizontal direction, there is a case where the frequency of the current supplied to the power transfer coil 62 is adjusted on the basis of the other factor.

[0085] A description has been made on the example in which the helical coil is adopted for a resonance coil. Meanwhile, when an antenna such as a meander line is adopted for the resonance coil, the current at the specified frequency flows through the power transfer coil 62. Thus, the electric field at the specified frequency is formed around the power transfer coil 62. The power is transferred between the power transfer section 300 and the power reception section 200 through this electric field.

[0086] In the power transfer system according to this embodiment, a near field (an evanescent field) where a "static electromagnetic field" of the electromagnetic field is dominated is used to improve the power transfer efficiency and a power reception efficiency. FIG. 12 is a graph for showing a relationship between a distance from a current source or a magnetic current source and the intensity of the electromagnetic field. Referring to FIG. 12, the electromagnetic field is configured of three components. A curve kl represents a component that is inversely proportional to a distance from a wave source, and is referred to as a "radiated electromagnetic field". A curve k2 represents a component that is inversely proportional to the square of the distance from the wave source, and is referred to as an "inductive electromagnetic field". A curve k3 is a component that is inversely proportional to the cube of the distance from the wave source, and is referred to as the "static electromagnetic field". If a wavelength of the electromagnetic field is set to "λ", a distance with which the intensity of the "radiated electromagnetic field", that of the "inductive electromagnetic field", and that of the "static electromagnetic field" are substantially the same can be expressed as λ/2π.

[0087] The "static electromagnetic field" is a region where the intensity of an electromagnetic wave is abruptly reduced with an increase in the distance from the wave source. In the power transfer system according to this embodiment, the near field (evanescent field) where the "static electromagnetic field" is dominated is used to transfer energy (power). In other words, the power transfer section 300 and the power reception section 200 having the near-by natural frequencies (a pair of LC resonant coils, for example) are resonated in the near field where the "static electromagnetic field" is dominated. In this way, the energy (power) is transferred from the power transfer section 300 to the power reception section 200.

[0088] The energy is not propagated far away through the "static electromagnetic field". Thus, compared to the electromagnetic wave that transfers the energy (power) through the "radiated electromagnetic field" through which the energy is propagated far away, the power can be transferred with reduced energy loss by a resonance method. As described above, in this power transfer system, the power transfer section and the power reception section are resonated by the electromagnetic field, the power is transferred wirelessly between the power transfer section and the power reception section.

[0089] There is a case where such an electromagnetic field formed between the power reception section and the power transfer section is a near field resonance coupling field, for example. The coupling coefficient κ between the power transfer section and the power reception section is approximately 0.3 or less, for example, and is preferably 0.1 or less. As the coupling coefficient κ, an approximate range from 0.1 to 0.3 can also be adopted. However, the coupling coefficient κ is not limited to these values, but various values at which the favorable power transfer can be achieved may be adopted.

[0090] The coupling between the power transfer section 300 and the power reception section 200 in the power transfer in this embodiment is referred to as, for example, "magnetic resonance coupling", "magnetic field resonance coupling", "near field resonance coupling", "electromagnetic field resonance coupling", or "electric field resonance coupling". The "electromagnetic field resonance coupling" means coupling that includes all of the "magnetic resonance coupling", the "magnetic field resonance coupling", and the "electric field resonance coupling".

[0091] The coil-shaped antenna is adopted for the power transfer coil 62 of the power transfer section 300 and the power reception coil 22 of the power reception section 200 described in this specification. Thus, the power transfer section 300 and the power reception section 200 are mainly coupled to each other through the magnetic field, and the power transfer section 300 and the power reception section 200 are in a state of the "magnetic resonance coupling" or the "magnetic field resonance coupling".

[0092] As each of the power transfer coil 62 and the power reception coil 22, the antenna such as a meander line can be adopted, for example. In this case, the power transfer section 300 and the power reception section 200 are mainly coupled to each other through the electric field. At this time, the power transfer section 300 and the power reception section 200 are in a state of the "electric field resonance coupling". In this embodiment, just as described, the power is transferred wirelessly between the power reception section 200 and the power transfer section 300. When the power is transferred wirelessly just as described, the magnetic field is mainly formed between the power reception section 200 and the power transfer section 300. Thus, although the "intensity of the magnetic field" has been focused in the description of the above-described embodiment, the same operations and effects can be obtained even when the "intensity of the electric field" or the "intensity of the electromagnetic field" is focused.

[0093] (Power Transfer) Referring to FIG. 13, before the power is transferred between the power reception section 200 and the power transfer section 300, the electric drive vehicle 10 moves in the vehicle backward direction B along the parking line 41 and the parking line 42, and is stopped at a specified position between the parking line 41 and the parking line 42 in the parking space 52. The power reception section 200 and the power transfer section 300 are arranged to face each other with the air gap being provided therebetween. As described above, the coil unit of each of the power reception section 200 and the power transfer section 300 constitutes the solenoid coil unit.

[0094] When the power is transferred between the power reception section 200 and the power transfer section 300, the coil unit of the power reception section 200 and the coil unit of the power transfer section 300 are arranged to face each other, and the AC current at the specified frequency is supplied to the power transfer coil 62 of the power transfer section 300. The electromagnetic field that oscillates at the specified frequency is formed around the power transfer coil 62. A magnetic flux formed in this electromagnetic field has a so-called arch shape. The power reception coil 22 of the power reception section 200 receives the power from this electromagnetic field.

[0095] FIG. 14 is a view of a situation around the power reception section

200 when the power is transferred. When the power is transferred, the magnetic flux formed in the electromagnetic field includes a magnetic flux (leakage flux) that is not directly used for the power transfer in addition to a magnetic flux that is directly used for the power transfer. Generally, in a case where the power reception section and the power transfer section are relatively mismatched during the power transfer and the power reception, the power transfer efficiency tends to be reduced. In addition, generally speaking, in a case where the power reception section and the power transfer section each have a configuration capable of suppressing the reduction in the power transfer efficiency even when being mismatched, the leakage electromagnetic field (leakage flux) that is not directly used for the power transfer tends to be increased.

[0096] In this embodiment, such a characteristic that the power reception section 200 is easily magnetized due to the presence of the magnetic members 81, 82 is exerted, and a so-called bypass magnetic path is formed. Accordingly, a magnetic flux (an arrow DR) that intends to expand peripherally as the leakage electromagnetic field (leakage flux) is effectively reduced. According to the power transfer system 1000 that includes the power reception device 11 including the power reception section 200, the leakage electromagnetic field (leakage flux), which is generated upon power transfer, can be reduced. Therefore, fundamental wave emission can be reduced.

[0097] [Second Embodiment] In the first embodiment described above (see FIG. 3), the exhaust pipe 68 has a portion that extends along the center of the bottom surface 76 in the longitudinal direction of the vehicle main body 70. When the bottom surface 76 of the vehicle main body 70 is seen in the plan view, the power reception device 11 is arranged such that a portion of the power reception device 11 overlaps the exhaust pipe 68. The magnetic members 81, 82 are arranged both of the outer sides of the power reception device 11 in the width direction of the vehicle main body 70.

[0098] Referring to FIG. 15, the power reception device 11 and the magnetic members 81, 82 may be arranged between the pair of the front wheels 19FL, 19FR provided in the vehicle main body 70. In this embodiment, when the bottom surface 76 of the vehicle main body 70 is seen in the plan view, the power reception device 11 is arranged such that not the entire power reception device 11 overlaps the exhaust pipe 68. With such a configuration, the same operations and effects as those of the first embodiment described above can be obtained. In addition, since the magnetic members 81, 82 are each arranged in a position away from the exhaust pipe 68, it is also possible to suppress the magnetic members 81, 82 from being influenced by heat from the exhaust pipe 68.

[0099] [Third Embodiment] In the first embodiment described above (see FIG. 3), the magnetic members 81, 82 are arranged on the inner sides of the respective side members 67S in the width direction of the vehicle main body 70.

[0100] Referring to FIG. 16, the magnetic members 81, 82 may be arranged on the outer sides of the respective side members 67S in the width direction of the vehicle main body 70. In this embodiment, the magnetic member 81 is arranged adjacent to the right outer edge section 34R, and the magnetic member 82 is arranged adjacent to the left outer edge section 34L. With such a configuration, the same operations and effects as those of the first embodiment described above can be obtained. In addition, since the magnetic members 81, 82 are each arranged in the position away from the exhaust pipe 68, it is also possible to suppress the magnetic members 81, 82 from being influenced by the heat from the exhaust pipe 68.

[0101] [Fourth Embodiment] Referring to FIG. 17, in this embodiment, the bottom surface 76 of the vehicle main body 70 is provided with an exhaust pipe 68L (a first exhaust pipe) and an exhaust pipe 68R (a second exhaust pipe). When the bottom surface 76 of the vehicle main body 70 is seen in the plan view, the power reception device 11 is arranged between the exhaust pipe 68L and the exhaust pipe 68R. When the bottom surface 76 of the vehicle main body 70 is seen in the plan view, the power reception device 11 is arranged such that not the entire power reception device 11 overlaps the exhaust pipes 68L, 68R.

[0102] The magnetic member 81 is arranged on the outer side (a side in the vehicle right direction R) of the exhaust pipe 68R in the width direction of the vehicle main body 70, and the magnetic member 82 is arranged on the outer side (a side in the vehicle left direction L) of the exhaust pipe 68L in the width direction of the vehicle main body 70. With such a configuration, the same operations and effects as those of the first embodiment described above can be obtained.

[0103] Since the magnetic members 81, 82 are each arranged in the position away from the exhaust pipe 68, it is also possible to suppress the magnetic members 81, 82 from being influenced by the heat from the exhaust pipe 68. The magnetic member 81 may be arranged on the inner side (a side in the vehicle left direction L) of the exhaust pipe 68R in the width direction of the vehicle main body 70, and the magnetic member 82 may be arranged on the inner side (a side in the vehicle right direction R) of the exhaust pipe 68L in the width direction of the vehicle main body 70.

[0104] [Fifth Embodiment] Referring to FIG. 18, in the width direction (the vehicle left direction L and the vehicle right direction R) of the vehicle main body 70, it is preferred that the distance Wll between the magnetic member 81 and the ferrite core 21, around which the power reception coil 22 is wound, is longer than a vehicle height HH (minimum ground clearance, for example) of the vehicle main body 70. More preferably, the distance Wll may be set longer than the air gap between the power reception coil 22 and the power transfer coil 62.

[0105] Similarly, in the width direction (the vehicle left direction L and the vehicle right direction R) of the vehicle main body 70, it is preferred that the distance W12 between the magnetic member 82 and the ferrite core 21, around which the power reception coil 22 is wound, is longer than the vehicle height HH (minimum ground clearance, for example) of the vehicle main body 70. More preferably, the distance W12 may be set longer than the air gap between the power reception coil 22 and the power transfer coil 62.

[0106] According to such a configuration, when the power reception coil 22 and the power transfer coil 62 face each other in the height direction for charging, it is possible to suppress the magnetic flux from flowing to the sides of the magnetic members 81, 82, and thus is possible to keep the power transfer efficiency and the power reception efficiency high.

[0107] [Sixth Embodiment] Referring to FIG. 19, a magnetic member for reducing generation of the leakage flux may be provided in the parking space 52. In this embodiment, the power transfer device 50 includes magnetic members 43, 44. The magnetic member 43 is embedded so as to extend along the parking line 41, and the magnetic member 44 is embedded so as to extend along the parking line 42. The magnetic members 43, 44 each have a shape that extends in a same direction as the direction in which the winding axis 01 of the power transfer coil 62 in the power transfer section 300 extends.

[0108] The magnetic members 43, 44 are adjacent to the power transfer coil 62 in a direction that crosses the direction in which the winding axis 01 extends. Being "adjacent" described here means that, for example, when the power transfer coil 62 is projected in a direction perpendicular to the direction in which the winding axis 01 extends (in the horizontal direction), at least a portion of a projection image of the power transfer coil 62 overlaps the magnetic members 43, 44.

[0109] The magnetic members 43, 44 are also each formed of a so-called ferromagnetic material such as ferrite, pressed iron power (dust core), amorphous (amorphous core), iron oxide, chromium oxide, or cobalt. The magnetic members 43, 44 of this embodiment each have a plate shape that linearly extends, and are arranged parallel to each other on both of the outer sides of the power transfer section 300 in the width direction of the vehicle main body 70. The magnetic members 43, 44 may each have a curved plate shape.

[0110] (Modifications) Referring to FIG. 20, the magnetic member 43 may be arranged on the inner side of the parking line 41. The magnetic member 44 may be arranged on the inner side of the parking line 42. Since the magnetic members 43, 44 are arranged near the power transfer section 300, the further higher effects can be obtained. Referring to FIG. 21, the magnetic members 43, 44 may be provided on an inner wall surface of a garage 48. Accordingly, it is possible to further reduce a chance that the magnetic field is leaked to the outer side of the garage 48.

[0111] Each of the embodiments and modifications based on the present invention has been described so far. Note that each of the embodiments and modifications disclosed herein is merely illustrative in all respects and not restrictive. The technical scope of the present invention is defined by the claims, and intends to include all modifications falling within the claims and equivalents thereof.

[0112] The present invention can be applied to a power reception device, a power transfer device, and a vehicle.

Claims

1. A power reception device comprising:

a power reception coil arranged on a bottom surface of a vehicle main body, the power reception coil configured to receive power wirelessly from a power transfer coil in a state of facing the power transfer coil, and the power reception coil being provided to surround a winding axis extending in a first direction crossing a direction to face the power transfer coil; and

a magnetic member arranged on the bottom surface of the vehicle main body, the — magnetic member having a shape extending in the first direction, and the magnetic member being arranged adjacent to the power reception coil in a second direction crossing the first direction.

2. A vehicle comprising:

the vehicle main body; and

the power reception device according to claim 1 wherein

a center position of the power reception coil in the first direction is located on a front half of the vehicle main body.

3. The vehicle according to claim 2 wherein

the first direction is a longitudinal direction of the vehicle main body, and the second direction is a width direction of the vehicle main body.

4. The vehicle according to claim 3 wherein

the magnetic member is provided on both of outer sides of the power reception in the width direction of the vehicle main body.

5. The vehicle according to claim 4 wherein

the power reception coil is wound around a core, a width dimension of the core is larger than a sum of a width dimension of the magnetic member provided on one outer side of the power reception coil and a width dimension of the magnetic member provided on another outer side of the power reception coil in the width direction of the vehicle main body.

6. The vehicle according to claim 4 wherein the power reception coil is wound around a core, a width dimension of the core is smaller than a sum of a width dimension of the magnetic member provided on one outer side of the power reception coil and a width dimension of the magnetic member provided on another outer side of the power reception coil in the width direction of the vehicle main body.

7. The vehicle according to any one of claims 2 to 6 wherein

the power reception coil is wound around a core, a distance between the magnetic member and the core is shorter than a distance between the magnetic member and an outer edge section of the vehicle main body in a width direction of the vehicle main body.

8. The vehicle according to any one of claims 2 to 6 wherein

the power reception coil is wound around a core, a distance between the magnetic member and the core is longer than a distance between the magnetic member and an outer edge section of the vehicle main body in a width direction of the vehicle main body.

9. The vehicle according to any one of claims 2 to 6 wherein

the power reception coil is wound around a core, a distance between the magnetic member and the core is longer than a vehicle height of the vehicle main body in a width direction of the vehicle main body.

10. The vehicle according to any one of claims 2 to 9 wherein

the power reception device and the magnetic member are arranged between a pair of front wheels provided in the vehicle main body.

11. The vehicle according to any one of claims 2 to 9 further comprising:

an engine; and

an exhaust pipe connected to the engine, wherein

the power reception device includes a case body that houses the power reception coil, the case body is arranged under the exhaust pipe so as to allow air to flow between the case body and the exhaust pipe, and the power reception coil and the magnetic member are arranged to overlap each other as viewed from a horizontal direction.

12. The vehicle according to claim 4 wherein

the power reception device is arranged between a first exhaust pipe and a second exhaust pipe provided on the bottom surface of the vehicle main body as viewed in a plane view of the bottom surface of the vehicle main body, and the magnetic member is arranged on an outer side of the first exhaust pipe and on an outer side of the second exhaust pipe as viewed in a plane view of the bottom surface of the vehicle main body.

13. The vehicle according to any one of claims 2 to 12 wherein

a difference between a natural frequency of the power transfer coil and a natural frequency of the power reception coil is 10% or less of a natural frequency of the power reception coil.

14. The vehicle according to any one of claims 2 to 13 wherein

coupling coefficient of the power reception coil and the power transfer coil is 0.3 or less.

15. The vehicle according to any one of claims 2 to 14 wherein

the power reception coil is configured to receive power from the power transfer coil through at least one of a magnetic field that is formed between the power reception coil and the power transfer coil and oscillates at a specified frequency and an electric field that is formed between the power reception coil and the power transfer coil and oscillates at the specified frequency.

16. A power transfer device comprising:

a power transfer coil configured to transfer power wirelessly to a power reception coil provided in a vehicle in a state of facing the power reception coil, the power transfer coil being provided to surround a winding axis extending in a third direction crossing a direction to face the power reception coil; and

a magnetic member having a shape extending in the third direction, the magnetic member arranged adjacent to the power transfer coil in a fourth direction crossing the third direction.