Coil structure for wireless power supply device

Abstract

Provided is a high-performance coil structure, for a wireless power supply device, which enables increase in a transmission distance and has improved transmission power efficiency.　In the coil structure for the wireless power supply device, two spiral coils 31, 32 are coils having height differences and wound with a plurality of turns in substantially rectangular shapes or substantially annular shapes from the outer side toward the inner side, in a state of having height differences vertically (Z-axis direction) between the vicinity of the center in length of a magnetic body core 11 in the X-axis direction, which is a portion close to a solenoidal coil 33 and the vicinities of ends in length of the magnetic body core 11 in the X-axis direction, which are portions far from the solenoidal coil 33 such that the spiral coils are located: at the left and right (positive side and negative side in the X-axis direction) with respect to the solenoidal coil 33; above a magnetic flux (on the positive side in the Z-axis direction) that passes inside the magnetic body core 11 at the vicinity of the center in the X-axis direction; and below the magnetic flux (on the negative side in the Z-axis direction) that passes inside the magnetic body core 11 at the vicinities of the ends in the X-axis direction.

Description

Coil structure for wireless power supply device

[0001] The present invention relates to the structure of a power supply coil and / or a power receiving coil used in a wireless power supply device.

[0002] There are several known contactless wireless power transfer technologies, including electromagnetic induction and magnetic resonance. Of these, electromagnetic induction wireless power transfer technology is used, for example, to charge mobile phones, and has coils arranged one above the other, essentially acting as an electrical transformer, with electricity flowing when the power transfer coil and power receiving coil are tightly attached.

[0003] However, with electromagnetic induction wireless power transfer technology, it is not possible to create a large distance between the power transfer coil and the power receiving coil, and even a slight misalignment or separation between the power transfer coil and the power receiving coil makes charging and power transfer impossible, making it difficult to put into practical use.

[0004] Furthermore, magnetic resonance wireless power transfer technology was developed at a university in the United States around 2006-2007, and is close to being put to practical use because it allows for a greater distance between the power transfer coil and the power receiving coil compared to electromagnetic induction. However, it is sensitive to the fact that power cannot be transferred unless the distance between the power transfer coil and the power receiving coil is kept constant, and that power cannot be transferred if the coil is closer or farther than that distance, or if the coil is at an angle, making it difficult to put to practical use.

[0005] Currently, in wireless power feeders, a coil known as a "DD coil" or "double D coil," in which two coils are wound in a spiral shape on a magnetic plate, is known as a coil that can increase the transmission distance and have high magnetic flux generation efficiency (see, for example, FIG. 5 of Patent Document 1 and Patent Document 2). Furthermore, DD coils (double D coils) are used as the highest performance electromagnetic coils when transmitting large amounts of power, such as in wireless power feed to electric vehicles.

[0006] JP-T-2014-532296 A JP-A-2009-164293

[0007] When attempting to transmit large amounts of power using a wireless power transfer device, it is necessary to generate a large magnetic flux and to concentrate the magnetic flux in one direction toward the receiving coil. This is done to increase efficiency and to prevent leakage magnetic flux from adversely affecting people in the vicinity. In this case, even a slight increase in the coil's transmission efficiency (for example, 1%) can make a significant difference in the amount of heat generated, so there is a desire to improve efficiency even if only slightly. In other words, there is still a demand for high-performance coils that can achieve even greater transmission distances and higher transmission power efficiency than conventional DD coils (double D coils).

[0008] The present invention has been made to solve the above-mentioned problems, and aims to provide a higher performance coil structure in a wireless power supply device that can increase the transmission distance and improve the transmission power efficiency.

[0009] In order to achieve the above object, the present invention provides a coil structure for a wireless power supply device, the coil structure comprising a magnetic core having a substantially rectangular parallelepiped shape with a left-right length whose longest side is in the X-axis direction, a depth whose second longest side is in the Y-axis direction, and a top-bottom thickness whose shortest side is in the Z-axis direction, two spiral coils, and one solenoid coil, the one solenoid coil being a solenoid coil wound around the magnetic core a plurality of times only near the center of the length of the magnetic core in the X-axis direction, and the two spiral coils being wound on the left and right of the solenoid coil (around the center of the solenoid coil). The stepped spiral coil is wound multiple times from the outside to the inside in an approximately rectangular or annular shape, with steps formed above and below (in the Z-axis direction) near the center and near the ends in the X-axis direction, so that the magnetic core is positioned above (on the positive and negative sides in the X-axis direction) the magnetic flux passing through the interior of the magnetic core near the center of the X-axis length of the magnetic core, which is the part close to the solenoid coil, and is positioned below (on the negative side in the Z-axis direction) the magnetic flux passing through the interior of the magnetic core near the ends in the X-axis length of the magnetic core, which is the part farther from the solenoid coil.

[0010] According to the coil structure for a wireless power feeder of this invention, each spiral coil is provided with a step, and a solenoid coil is wound between these two spiral coils, which makes it possible to maintain a longer transmission distance between the power feeding coil and the power receiving coil, improve the transmission power efficiency, and provide a wireless power feeder with higher performance. Furthermore, because the spiral coil is provided with a step, the performance of the wireless power feeder is not reduced by the coil lead wires, and it is also possible to install a water-cooled pipe to cool the coil windings.

[0011] 1( a ) and 1 ( b ).

[0023] FIG. 1 is a schematic diagram showing four coil structures in total, including three conventional coil structures in a wireless power feeder and one coil structure considered as an applied type. It is an explanatory diagram comparing the performance (transmission distance and transmission power efficiency) of each of the four coil structures shown in FIG. 1. It is a diagram schematically showing a coil structure (basic type) for a wireless power feeder according to a first embodiment of the present invention. It is an explanatory diagram showing top, front, and bottom views of the coil structure for a wireless power feeder shown in FIG. 3. It is a schematic diagram showing an example of another possible variation based on the coil structure for a wireless power feeder shown in FIG. 3. It is a schematic diagram showing a simulation model for comparing the performance of coils in wireless power feeders. It is an explanatory diagram comparing the state of magnetic coupling in the coil structure for a wireless power feeder according to a first embodiment of the present invention with the state of magnetic coupling in a hybrid type shown in FIG. 1( d ). It is an explanatory diagram comparing the positional relationship between the magnetic flux and the coil in the coil structure for a wireless power feeder according to a first embodiment of the present invention with the positional relationship between the magnetic flux and the coil in the hybrid type shown in FIG. 1( d ). 1(c) 。 FIG. 1(c) is an explanatory diagram comparing a lead wire of a spiral coil in a coil structure for a wireless power feeder according to a first embodiment of the present invention with a lead wire of a conventional spiral coil shown in FIG. 1(c) . FIG. 1(c) is an explanatory diagram comparing an example of the arrangement of a water pipe for cooling the coil structure for a wireless power feeder according to a first embodiment of the present invention with the conventional coil structure shown in FIG. 1(c) . FIG. 1(c) is a diagram showing a specific example of the arrangement of a cooling water pipe in a coil structure for a wireless power feeder according to a first embodiment of the present invention. FIG. 1(c) is a schematic diagram showing the same three variations as in FIG. 5 . FIG. 1(c) is an explanatory diagram showing a method of making a coil structure for a wireless power feeder according to a second embodiment of the present invention. FIG. 1(c) is an explanatory diagram showing a method of winding a coil in a coil structure for a wireless power feeder according to a second embodiment of the present invention. FIG. 1(c) is an explanatory diagram showing a method of attaching a magnetic pole plate in a coil structure for a wireless power feeder according to a second embodiment of the present invention. FIG. 1(c) is an explanatory diagram showing the positional relationship between a magnetic flux passing through the inside of a ferrite core and a coil in the coil structures for wireless power feeders according to the first and second embodiments of the present invention.

[0012] The present invention relates to a structure of a power supply coil and / or a power receiving coil used in a wireless power supply device, i.e., a coil structure for a wireless power supply device. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0013] First, we will explain wireless power transfer technology. There are several known wireless power transfer technologies, such as electromagnetic induction and magnetic resonance. Of these, electromagnetic induction wireless power transfer technology is used, for example, to charge mobile phones. In this technology, the coils are arranged one above the other, and, based on the same principle as a transformer, power can be transferred only when the distance (transmission distance) between the power transfer coil and the power receiving coil is very short.

[0014] However, with electromagnetic induction wireless power transfer technology, the transmission distance is short, at just a few millimeters, so the distance between the power transfer coil and the power receiving coil cannot be large. Furthermore, even a slight misalignment or separation between the power transfer coil and the power receiving coil makes charging and power transfer impossible. In other words, because it is sensitive to misalignment, it is difficult to put into practical use.

[0015] Furthermore, magnetic resonance wireless power transfer technology has a long transmission distance of several centimeters to several meters, which means that the distance between the power supply coil and the power receiving coil can be greater than with electromagnetic induction, and it is close to being put to practical use. However, power cannot be transferred unless the distance between the power supply coil and the power receiving coil is kept constant, and if the coils are closer or further away than that distance, or if they are at an angle, the transmission efficiency decreases and the required power cannot be sent. In other words, this method is also vulnerable to positional misalignment, which again makes it difficult to put to practical use.

[0016] Furthermore, for example, Patent Document 1 discloses a coil known as a "DD coil" or "double D coil," which is made by winding two coils in a spiral shape on a magnetic plate, as a wireless power supply device that increases the transmission distance and has high magnetic flux generation efficiency.

[0017] However, when attempting to transmit large amounts of power using a wireless power transfer device, it is necessary to generate a large magnetic flux and to concentrate the magnetic flux in one direction toward the receiving coil. This is done to increase efficiency and to prevent leakage magnetic flux from adversely affecting people in the vicinity. In this case, even a slight increase in the coil's transmission efficiency (for example, 1%) can make a significant difference in the amount of heat generated, so there is a demand for even slight improvements in efficiency. In other words, there is still a demand for high-performance coils that have even greater transmission distances and higher transmission power efficiency than conventional DD coils (double D coils).

[0018] Therefore, first, the applicant of the present application conducted an experiment to compare the transmission distance and transmission power efficiency of existing coil structures in wireless power feeders. Figure 1 is a schematic diagram showing a total of four coil structures in wireless power feeders, including three conventional coil structures and one coil structure considered as an applied type.

[0019] 1(a) shows a coil structure in which a spiral coil 21 (spiral coil 21) is arranged on top of a ferrite core 1, which is a magnetic material, and is one type of conventional coil structure in wireless power feeders, which will be referred to as a "single spiral type." This single spiral type coil structure is used, for example, in wireless power feeders for charging mobile information terminals such as smartphones.

[0020] FIG. 1(b) shows a coil structure in which a ferrite core 1, which is a magnetic material, is used as an axis, and a coil 22 (solenoid coil 22) is wound around the axis in a solenoid shape. This is also one type of conventional coil structure in a wireless power supply device, and this coil structure will be called a "solenoid type."

[0021] 1(c) shows a coil structure in which spiral coils 23 and 24 (planar spiral coils 23, 24 constituting a double spiral) are arranged on top of a ferrite core 1, which is a magnetic material. This is also a type of conventional coil structure in wireless power transfer devices, but this coil structure will be referred to as a "double spiral type." This double spiral type coil structure is the same as the DD coil (double D coil) disclosed in Patent Document 1, for example.

[0022] FIG. 1(d) shows a coil structure in which, similar to the double spiral type of FIG. 1(c), two spiral coils, 25 and 26 (planar spiral coils 25, 26 constituting a double spiral), are arranged a short distance apart on top of a ferrite core 1, which is a magnetic material, and a solenoid coil 27 (solenoid coil 27) is arranged between the two coils 25, 26, wound around the ferrite core 1 as an axis, similar to FIG. 1(b).

[0023] The coil structure in Figure 1(d) is a coil structure that the applicant of the present application has devised as an applied type, and this coil structure will be called a "hybrid type." In other words, the three coil structures in Figures 1(a) to 1(c) are conventional coil structures that are already in use, while Figure 1(d) is a coil structure that the applicant of the present application has devised as an applied type.

[0024] Figure 2 is an explanatory diagram comparing the performance (transmission distance and transmission power efficiency) of each of the four coil structures shown in Figure 1. The symbols in Figure 2 are relative evaluations, with the symbols ◎, ○, △, and × being used to indicate the best performance.

[0025] As shown in Figure 2, the single-spiral coil structure in Figure 1(a) has a short transmission distance (×) and can only supply power in close proximity, but has good power transmission efficiency (○). Conversely, the solenoid coil structure in Figure 1(b) has no problems even when the transmission distance is quite long (◎), but its power transmission efficiency is not very good (△). On the other hand, the double-spiral coil structure in Figure 1(c) can withstand a relatively long transmission distance (○) and has good power transmission efficiency (○).

[0026] However, in the case of the hybrid coil structure shown in Figure 1(d), the transmission distance was quite long without any problems (◎), and the transmission power efficiency was also quite high (◎). These results show that a hybrid coil structure that combines a double spiral type and a solenoid type can provide a higher transmission distance than the conventional DD coil (double D coil), and a high-performance coil with higher transmission power efficiency.

[0027] The present invention proposes a higher performance coil structure that further evolves the coil structure shown in FIG. 1(d) and that can achieve a longer transmission distance and higher power transmission efficiency in a wireless power feeder than the double spiral coil structure (conventional DD coil (double D coil)) shown in FIG. 1(c) and the hybrid coil structure shown in FIG. 1(d).

[0028] Embodiment 1. Fig. 3 is a diagram schematically illustrating a coil structure (basic type) for a wireless power feeder according to embodiment 1 of the present invention. The schematic diagram shown in Fig. 3 does not illustrate a resin former (see Fig. 12 described later) for winding the coil, and only illustrates a ferrite core (magnetic core) which is a magnetic material and the coil winding. Fig. 4 is an explanatory diagram illustrating a top view, a front view, and a bottom view of the coil structure for the wireless power feeder shown in Fig. 3, with Fig. 4(b) being a front view as seen from the direction of arrow A in Fig. 3, Fig. 4(a) being a top view as seen from directly above, and Fig. 4(c) being a bottom view as seen from below.

[0029] As shown in Figures 3 and 4, the coil structure for the wireless power supply device of this invention is a coil structure in which two spiral coils 31, 32 (stepped spiral coils 31, 32 forming a double spiral) are wound diagonally from top to bottom around a ferrite core (magnetic core) 11, which is a magnetic material, and the two coils 31, 32 are arranged a short distance apart, and one solenoid-shaped coil 33 (solenoid coil 33) is arranged between the two coils 31, 32, wound around the ferrite core 11 as its axis.

[0030] To explain in more detail, as shown in Fig. 3, the ferrite core 11 is a magnetic body having a substantially rectangular parallelepiped shape, with the longest side being the left-right length in the X-axis direction, the second longest side being the depth in the Y-axis direction, and the shortest side being the top-bottom thickness in the Z-axis direction. Note that the directions of the X-axis, Y-axis, and Z-axis are shown only in Fig. 3 and omitted in other figures, but the X-axis, Y-axis, and Z-axis are defined in the other figures in the same way as in Fig. 3. In other words, the descriptions of top and bottom, such as top and bottom, refer to the plus and minus sides in the Z-axis direction.

[0031] Furthermore, the use of "approximately rectangular parallelepiped-shaped magnetic material" means that the material does not have to be strictly rectangular as long as it appears to be roughly rectangular overall, such as if each corner of the rectangular parallelepiped is slightly rounded, or if the intersecting edges are slightly diagonal rather than at right angles.

[0032] 3 and 4, the coil structure for the wireless power feeder according to the first embodiment of the present invention includes at least a ferrite core 11, two spiral coils 31 and 32, and one solenoid coil 33. In the first embodiment, the two spiral coils 31 and 32 and the solenoid coil 33 are described as being formed by a single coil winding, but the present invention is not limited to this.

[0033] Here, two spiral coils 31, 32 form a double spiral, and in Figures 3 and 4, coil 31 is located on the left side and coil 32 is located on the right side. The left coil 31 is stepped in the Z-axis direction so that the inner side (the side closest to the right coil 32) of the coil 31 is located above the ferrite core 11 (the positive side in the Z-axis direction) and the outer side (the side farthest from the right coil 32) is located below the ferrite core 11 (the negative side in the Z-axis direction). The right coil 32 is stepped in the Z-axis direction so that the inner side (the side closest to the left coil 31) of the coil 32 is located above the ferrite core 11 (the positive side in the Z-axis direction) and the outer side (the side farthest from the left coil 31) is located near the bottom of the ferrite core 11 (the negative side in the Z-axis direction).

[0034] These two stepped spiral coils 31, 32 are arranged at a slight distance in the X-axis direction, and one solenoid coil 33 is arranged between these two spiral coils 31, 32, wound multiple times around the ferrite core 11 as its axis so that the coils do not overlap in the Y-axis and Z-axis directions.

[0035] As a result, as can be seen from Figure 4(b), the coil structure for the wireless power feeder of the present invention has a spiral coil 31 wound diagonally from the upper part near the center to the lower left end of the ferrite core 11, which is a magnetic material, a spiral coil 32 wound diagonally from the upper part near the center to the lower right end of the ferrite core 11, and a solenoid coil 33 wound around (from top to bottom) the ferrite core 11 as its axis between the two coils 31, 32. Furthermore, the spiral coils 31, 32 are wound multiple times from the outside to the inside in a substantially rectangular or circular shape so that the coils do not overlap in the Z-axis direction. The coil winding method will be described later with reference to Figure 14.

[0036] Furthermore, the use of "approximately" in "approximately square or approximately circular" means that even if the coil is wound around in a square shape, due to the thickness of the coil, it will not be a perfect square but will be a square with slightly rounded corners (approximately square), and also that even if the coil is wound around in a circular shape, it does not have to be a perfect circle, and it is fine if it is somewhat close to an ellipse, and it means that it is sufficient if the coil is wound around from the outside to the inside multiple times, resulting in an overall approximately square or approximately circular shape.

[0037] Also, although the solenoid coil 33 is described here as being wound in multiple rows only in the X-axis direction and in only one row in the Y-axis and Z-axis directions without overlapping coils, it may also be wound in two or three overlapping layers on the Y-axis and Z-axis depending on the overall size of the coil and the influence of the output voltage value, etc. In other words, the solenoid coil 33 may be "only one row in the X-axis direction and multiple rows (multiple rows) in the Y-axis and Z-axis directions," or "multiple rows (multiple rows) in the X-axis direction and only one row in the Y-axis and Z-axis directions," or "multiple rows (multiple rows) in the X-axis direction and multiple rows (multiple rows) in the Y-axis and Z-axis directions."

[0038] That is, the solenoid coil 33 may be wound in any manner as long as it is wound multiple times around the ferrite core 11 only near the center of the ferrite core 11 in the X-axis direction. The spiral coils 31 and 32 may also overlap in the Z-axis direction. However, overlapping the coils in layers can cause problems such as insulation breakdown, which can lead to breakdowns and other problems, and an increase in the overall thickness of the coil can shorten the transmission distance. Therefore, it is desirable to wind both the solenoid coil 33 and the spiral coils 31 and 32 as shown in the embodiment of the present invention.

[0039] In this way, the single solenoid coil 33 is a solenoid coil wound multiple times around the ferrite core 11 only near the center of the length of the ferrite core 11 in the X-axis direction. The two spiral coils 31, 32 are stepped spiral coils wound multiple times from the outside to the inside in a substantially rectangular or circular shape with steps formed in the top and bottom (Z-axis direction) near the center and near the ends in the X-axis direction, so that the spiral coils 31, 32 are arranged on the left and right of the solenoid coil 33 (i.e., on the left and right of the solenoid coil 33, on the positive and negative sides of the X-axis direction around the solenoid coil 33), and are arranged at the top of the ferrite core 11 (the positive side in the Z-axis direction) near the portion close to the solenoid coil 33, i.e., near the center of the length of the ferrite core 11 in the X-axis direction, and are arranged at the bottom of the ferrite core 11 (the negative side in the Z-axis direction) near the end of the length of the ferrite core 11 in the X-axis direction.

[0040] In this first embodiment, the two spiral coils 31, 32 are described as being arranged symmetrically with respect to the solenoid coil 33 on the left and right sides of the solenoid coil 33 (on the positive and negative sides in the X-axis direction, with the solenoid coil 33 as the center), but they do not need to be completely symmetrical as long as they are arranged on the left and right sides of the solenoid coil 33. For example, the spiral coils 31 and 32 may have different numbers of coil turns, or may have a substantially rectangular or annular shape.

[0041] In addition, the following description will be given assuming that a coil structure for a wireless power supply device is configured by winding one coil around one of two spiral coils (here, spiral coil 32), the solenoid coil 33, and the other of the two spiral coils (here, spiral coil 31) in this order, but instead of connecting three coils in series, it is also possible to connect two spiral coils 31 and 32 in parallel and connect the solenoid coil 33 directly to them. Details of this coil winding method will be described in the second embodiment described below.

[0042] As mentioned above, the three coils may be connected in any manner (parallel or series), but it is important that the direction of the current flowing through the coils be such that the magnetic fluxes generated by the three coils (the two spiral coils 31 and 32 and the solenoid coil 33 between them) reinforce each other, as shown in Figure 5. The three coils are bound together and energized so as to observe this principle. As a result, as shown in Figure 5, all of the coils located in the upper part of the ferrite core 11 are wound so that the current flows in the same direction, and all of the coils located in the lower part of the ferrite core 11 are wound so that the current flows in the same direction (but in the opposite direction to that of the coils located in the upper part).

[0043] Fig. 5 is a schematic diagram showing one example of another possible variation based on the coil structure for the wireless power feeder shown in Fig. 3. The three variations shown in Fig. 5 differ only in the length of the ferrite core 11 in the left-right direction (X-axis direction).

[0044] Figure 5(a-1) is the same as Figure 3, and Figure 5(a-2) is a cross-sectional view of the cross section of the dashed line in Figure 5(a-1) as viewed from the direction of arrow A. Here, an x ​​mark inside a circle on the cross section of the coil indicates that the direction of the current flowing through the coil is the same as that of arrow A (from the front to the back in the example of Figure 5(a-2)), and a ● mark inside a circle indicates that the direction of the current flowing through the coil is opposite to that of arrow A (from the back to the front in the example of Figure 5(a-2)).

[0045] 5(a-2), the magnetic flux (magnetic lines of force) in this coil structure is indicated by dashed arrows. In order to form such a circular magnetic flux, the coils arranged relative to the ferrite core 11 must be arranged such that all the coils arranged above the ferrite core 11 are wound so that current flows in the same direction, and all the coils arranged below the ferrite core 11 are wound so that current flows in the same direction (but in the opposite direction to the coils arranged above).

[0046] 5(b-1) and 5(c-1) have a slightly different structure from that of FIG. 5(a-1). FIG. 5(b-2) is a cross-sectional view of the dashed line portion of FIG. 5(b-1) as seen from the direction of arrow A, and FIG. 5(c-2) is a cross-sectional view of the dashed line portion of FIG. 5(c-1) as seen from the direction of arrow A.

[0047] As shown in Fig. 5(b-1), the length of the ferrite core 11 in the left-right direction (X-axis direction) is slightly shorter than that of the ferrite core 11 in Fig. 5(a-1) (see Fig. 5(b-2)). Also, in Fig. 5(c-1), the length of the ferrite core 11 in the left-right direction (X-axis direction) is even slightly shorter than that of the ferrite core 11 in Fig. 5(b-1) (see Fig. 5(c-2)).

[0048] Here, it will be explained that the coil structure for the wireless power feeder shown in FIGS. 3 to 5 in the first embodiment of the present invention can achieve a longer transmission distance and higher power transmission efficiency than the double spiral coil structure (conventional DD coil (double D coil)) shown in FIG. 1(c) or the hybrid coil structure shown in FIG. 1(d).

[0049] In a wireless power feeder, the transmission distance between the power supply coil and the power receiving coil can be long because the magnetic coupling coefficient k is large, and the transmission efficiency is high because the Q value, which represents the quality factor of the coil, is high. In other words, the product (k x Q) of the magnetic coupling coefficient k and the quality factor Q value of the coil is the figure of merit of the coil.

[0050] Fig. 6 is a schematic diagram showing a simulation model for comparing the performance of coils in wireless power feeders. In the experiments and simulations actually performed using the simulation model shown in Fig. 6, copper was used as the material for the coil, and soft ferrite, which is a soft magnetic material, was used as the material for the ferrite core (magnetic body). However, when the frequency is low (for example, 10 kHz or less), a silicon steel plate, an iron-based microcrystalline plate, an iron-based amorphous alloy plate, or the like may also be used.

[0051] Figure 6(a) is a modified example of the hybrid coil structure shown in Figure 1(d), and uses a ferrite core 10 that is slightly shorter in the depth direction (Y-axis direction) of the ferrite core 1 compared to Figure 1(d). The length of the ferrite core 10 in the left-right direction (X-axis direction) is 300 mm, the thickness of the ferrite core 10 in the Z-axis direction is 10 mm, the frequency is 50 kHz, the coil wire diameter is 3.83 mm, the number of turns of the two opposing spiral coils 25, 26 is 8, the length is 2.79 m, and the number of turns of the solenoid coil 27 is 5, the length is 0.877 m.

[0052] 6(b) shows the coil structure according to the first embodiment of the present invention shown in Fig. 3 and Fig. 5(a-1), in which the length of the ferrite core 11 in the left-right direction (X-axis direction) is 300 mm, the thickness of the ferrite core 11 in the Z-axis direction is 10 mm, the frequency is 50 kHz, the coil wire diameter is 3.83 mm, the number of turns of the solenoid coil 33 is 5, the length is 0.877 m, and the number of turns of the two pairs of opposing spiral coils 31, 32 is 8, which are the same as those shown in Fig. 6(a), but the length of the two pairs of opposing spiral coils 31, 32 is 3.17 m. This is because the stepped spiral coils 31, 32 are longer than the spiral coils 25, 26 shown in Fig. 6(a).

[0053] Here, if the voltage on the power supply side is V1, the voltage on the power receiving side is V2, the number of coil turns on the power supply side is N1, and the number of coil turns on the power receiving side is N2, the magnetic coupling coefficient k can be expressed by the formula k = (V2 / V1) x (N1 / N2). A simulation was performed by applying each value to this formula.

[0054] As a result, in the case of the coil structure shown in Fig. 6(a), the magnetic coupling coefficient k was 0.187, the coil quality factor Q value was 1090, and k × Q was 204. On the other hand, in the case of the coil structure shown in Fig. 6(b), the magnetic coupling coefficient k was 0.191, the coil quality factor Q value was 1529, and k × Q was 292. In other words, it was confirmed by calculation that the coil structure according to the first embodiment of the present invention can maintain a longer transmission distance between the power supply coil and the power receiving coil, improve transmission power efficiency, and provide a higher performance wireless power feeder.

[0055] 6(c) is a modified example of the hybrid coil structure shown in FIG. 6(a), in which the length of the ferrite core 10 in the left-right direction (X-axis direction) is slightly shorter than that of FIG. 6(a). Here, the length of the ferrite core 10 in the left-right direction (X-axis direction) shown in FIG. 6(c) is 270 mm, the thickness of the ferrite core 10 in the Z-axis direction is 10 mm, the frequency is 50 kHz, the coil wire diameter is 3.83 mm, the number of turns of the two opposing spiral coils 25, 26 is 8, the length is 2.79 m, and the number of turns of the solenoid coil 27 is 5, the length is 0.877 m. In other words, compared to FIG. 6(a), everything is the same except for the length of the ferrite core 10 in the left-right direction.

[0056] On the other hand, Figure 6(d) shows the coil structure of the first embodiment of the present invention shown in Figure 5(b-1), in which the length of the ferrite core 11 in the left-right direction (X-axis direction) is 270 mm. The thickness of the ferrite core 11 in the Z-axis direction is 10 mm, the frequency is 50 kHz, the coil wire diameter is 3.83 mm, the solenoid coil 33 has 5 turns, its length is 0.877 m, and the two opposing sets of spiral coils 31, 32 each have 8 turns, which are the same as those shown in Figure 6(c), but the length of the two opposing sets of spiral coils 31, 32 is 3.17 m. In other words, compared to Figure 6(c), everything is the same except for the length of the ferrite core 11 in the left-right direction.

[0057] In the case of the coil structure shown in Fig. 6(c), the magnetic coupling coefficient k was 0.184, the coil quality factor Q value was 1088, and k × Q was 201. On the other hand, in the case of the coil structure shown in Fig. 6(d), the magnetic coupling coefficient k was 0.184, the coil quality factor Q value was 1276, and k × Q was 235. Even in this case, it was confirmed by calculation that the coil structure according to the first embodiment of the present invention can provide a wireless power feeder with higher performance.

[0058] In this way, simulations and experiments were also carried out to check the transmission distance and transmission power efficiency for the coil structure variation shown in Fig. 5, i.e., the case where the ferrite core 11 was used in which both ends in the X-axis direction of the ferrite core 11 were cut to shorten the length in the left-right direction (X-axis direction), and it was confirmed that these structures also had sufficiently high performance. It was also confirmed that higher performance could be achieved by adjusting the length of the ferrite core in the left-right direction (X-axis direction) in this way.

[0059] These experiments and simulations were conducted not only for a wireless power feeder in which both the power feeder coil and the power receiving coil had the coil structure for a wireless power feeder according to embodiment 1 of the present invention, but also for a wireless power feeder in which only one of the power feeder coil or the power receiving coil had the coil structure for a wireless power feeder according to embodiment 1 of the present invention, and it was confirmed that even in these cases, higher performance was achieved.

[0060] However, if both the power supply coil and the power receiving coil have the coil structure for the wireless power supply device according to the first embodiment of the present invention, not only can higher performance be achieved, but there is also an advantage in terms of magnetic coupling.

[0061] Here, regarding the magnetic coupling of the coil structure for a wireless power feeder, the advantages of using the coil structure for a wireless power feeder according to the first embodiment of the present invention, as shown in FIGS. 3 to 5 , for the power feeder coil and the power receiver coil are explained, over the double spiral coil structure (conventional DD coil (double D coil)) shown in FIG. 1( c) and the hybrid coil structure shown in FIG. 1( d).

[0062] 7A and 7B are explanatory diagrams comparing the magnetic coupling state of the coil structure for the wireless power feeder according to the first embodiment of the present invention with the magnetic coupling state of the hybrid type shown in Fig. 1D. Fig. 7A is a diagram showing an example of the arrangement of two coils, the power supply coil and the power receiving coil of the hybrid type shown in Fig. 1D, and corresponds to Fig. 6A, but shows a state in which the positions of the two coils are misaligned. In this case, the opposing visible portions of the surface (top surface) of the ferrite core 1 (hereinafter referred to as "magnetic poles") can be used for magnetic coupling, but as shown in Fig. 7A, only the center of each coil in the left-right direction (the longitudinal direction of the ferrite core 1) can be used as a magnetic pole, and the magnetic flux loop generated between the two coils is within the range indicated by the dashed arrows in Fig. 7A.

[0063] On the other hand, Figure 7(b) is a diagram showing an example of the coil structure for the wireless power feeder according to the first embodiment of the present invention, in which two coils, a power supply coil and a power receiving coil, are arranged. However, as in Figure 7(a), the two coils are misaligned, and corresponds to Figure 6(b). Figures 7(a) and 7(b) correspond to Figures 6(a) and 6(b), so it may be easier to understand by looking at Figures 6(a) and 6(b). It can be seen that the magnetic poles, which are the portions of the ferrite cores 11 that are seen facing each other from the surface (top surface) of each coil, are longer in the longitudinal direction (X-axis direction) of the coils in Figure 7(b) than in Figure 7(a). In this case, the length that can tolerate misalignment of the two coils in the longitudinal direction (X-axis direction) is extended, and therefore, if the magnetic poles are longer, the length that can tolerate misalignment is also extended. That is, as in the magnetic flux loop indicated by the dashed arrow in FIG. 7B, the entire length of the ferrite core 11 (up to the end in the longitudinal direction (X-axis direction)) can be used for magnetic coupling, which has the advantage of being resistant to misalignment of the coil.

[0064] Furthermore, the fact that the coil structure for a wireless power feeder according to the first embodiment of the present invention is more resistant to transmission distance and positional misalignment than conventional coils will be explained below from the relationship between the direction of magnetic flux and the arrangement of the coils. Fig. 8 is an explanatory diagram comparing the positional relationship between the magnetic flux and the coils in the coil structure for a wireless power feeder according to the first embodiment of the present invention with the positional relationship between the magnetic flux and the coils in the hybrid type coil structure shown in Fig. 1(d).

[0065] Figure 8(a) shows the positional relationship between the magnetic flux and coils in the hybrid coil structure shown in Figure 1(d), similar to Figure 5(a-2), using a cross-sectional view of the dashed-dotted line portion of Figure 5(a-1) as viewed from the direction of arrow A. Here, the dashed arrows indicate the magnetic flux, and the coils with a ● mark inside a circle on both the left and right ends, i.e., spiral coils in which current flows from the back to the front of the figure, are all located above the magnetic flux passing through the ferrite core 1 (arrow indicated by the thick dashed line), i.e., on the positive side of the Z-axis direction.

[0066] On the other hand, Fig. 8(b) shows the positional relationship between magnetic flux and coils in the coil structure for a wireless power feeder according to the first embodiment of the present invention, similar to Fig. 5(a-2), using a cross-sectional view of the part enclosed by the dashed dotted line in Fig. 5(a-1) as viewed from the direction of arrow A. Here, similar to Fig. 8(a), the dashed arrows indicate magnetic flux, but in Fig. 8(b), the coils marked with a ● mark inside a circle on both the left and right ends, i.e., the spiral coils through which current flows from the back to the front of the figure, are all positioned below the magnetic flux (arrow indicated by the thick dashed line) passing through the inside of the ferrite core 11, i.e., on the negative side of the Z-axis direction.

[0067] When comparing Figures 8(a) and 8(b), as can be seen from the difference in the size of the magnetic flux (magnetic lines of force) indicated by the dashed arrows, in the case of a coil arrangement such as that shown in Figure 8(a), the spiral coil itself obstructs and narrows the magnetic flux outlet (magnetic pole). However, by arranging the coils at both ends of the spiral coil lower (on the negative side of the Z-axis) than the magnetic flux passing through the inside of the ferrite core 11 (indicated by the arrows with thick dashed lines), as shown in Figure 8(b), the magnetic flux outlet (magnetic pole) can be made wider, which has the advantage of improving resistance to transmission distance and positional misalignment of the two coils.

[0068] That is, in the above explanation, the two spiral coils 31, 32 are arranged on the left and right of the solenoid coil 33 (i.e., on the positive and negative sides in the X-axis direction around the solenoid coil 33), and are arranged at the top of the ferrite core 11 (the positive side in the Z-axis direction) in the part close to the solenoid coil 33, i.e., near the center of the length of the ferrite core 11 in the X-axis direction, and are arranged at the bottom of the ferrite core 11 (the negative side in the Z-axis direction) in the part far from the solenoid coil 33, i.e., near the ends of the length of the ferrite core 11 in the X-axis direction, so that the spiral coils are arranged in the

[0069] The two spiral coils 31, 32 are stepped spiral coils wound multiple times from the outside to the inside in an approximately rectangular or annular shape, with steps formed above and below (in the Z-axis direction) near the center and near the ends in the X-axis direction, so that they are positioned on the left and right sides of the solenoid coil 33 (on the positive and negative sides in the X-axis direction, centered on the solenoid coil 33), higher than the magnetic flux passing through the inside of the ferrite core 11 near the center of the X-axis length of the ferrite core 11, which is the part close to the solenoid coil 33, and lower than the magnetic flux passing through the inside of the ferrite core 11 near the ends in the X-axis length of the ferrite core 11, which is the part farther from the solenoid coil 33, (on the negative side in the Z-axis direction).

[0070] Also, with regard to the lead wires of the spiral coils 31 and 32, it will be explained that the coil structure for the wireless power feeder according to the first embodiment of the present invention shown in FIGS. 3 to 5 allows the wires to be drawn without shortening the transmission distance, compared to the double spiral coil structure (conventional DD coil (double D coil)) shown in FIG. 1(c) or the hybrid coil structure shown in FIG. 1(d).

[0071] In the case of the double spiral coil structure shown in FIG. 1(c) (a conventional DD coil (double D coil)) and the hybrid coil structure shown in FIG. 1(d), two spiral coils (23 and 24, or 25 and 26) are wound on the top (positive side in the Z-axis direction) of the ferrite core 1, which is a magnetic material. In other words, two planar spiral coils (23 and 24, or 25 and 26) are arranged on the top (positive side in the Z-axis direction) of the ferrite core 1. Therefore, in order to draw these coil windings to the outside, it was necessary to take the time and effort to pass the wires above the spiral coils to increase the overall thickness, or to divide the ferrite core and devise a way to wind the coils so that the wires can pass between the spiral coils without changing the overall thickness.

[0072] However, in the coil structure for a wireless power feeder of the present invention shown in Figures 3 to 5, the stepped spiral coils 31, 32 can be drawn out to the outside using the thick portion of the ferrite core 11 in the Z-axis direction, so there is no need to increase the thickness of the entire coil structure and there is no need to devise a way to wind the coil, so it is possible to draw the coil windings out to the outside without shortening the transmission distance and without requiring much effort.

[0073] 9A and 9B are explanatory diagrams comparing the lead wires of the spiral coil of the coil structure for the wireless power feeder according to the first embodiment of the present invention with the lead wires of the coil of the conventional double-spiral coil structure shown in Fig. 1C. Fig. 9A is a front view of a cross section of the conventional double-spiral coil structure shown in Fig. 1C, taken near the center in the Y-axis direction, and Fig. 9B is a front view of a cross section of the coil structure shown in Fig. 3 and Fig. 5A-1, taken near the center in the Y-axis direction, with the solenoid coil 33 omitted, for comparison with Fig. 9A. That is, Fig. 9B is a front view of a cross section taken along the dashed dotted line in Fig. 5A-1, taken from the direction of arrow A, with only the solenoid coil 33 omitted.

[0074] As shown in Figure 9(a), in the case of a conventional double spiral coil structure, two spiral coils 23, 24 are wound around the top (positive side in the Z-axis direction) of a ferrite core 1, which is a magnetic material, and therefore, the lead wires 41, 42 that lead these coil windings to the outside pass even further above the spiral coils 23, 24 (positive side in the Z-axis direction).

[0075] For example, if the outer diameter of the winding is 10 mm and there are no lead wires 41, 42, and the transmission distance is 10 cm (= 100 mm), in the case of Figure 9(a), the lead wires will necessarily overlap with the windings of the spiral coils 23, 24, shortening the transmission distance by the amount of the outer diameter of the windings. In this example, the transmission distance becomes 100 mm - (winding outer diameter 10 mm + winding outer diameter 10 mm) = 80 mm, which reduces 10 cm to 8 cm, which has a significant impact. In this way, the lead wires and the windings of the spiral coils 23, 24 overlap, increasing the thickness of the entire coil structure, which has the disadvantage of shortening the transmission distance.

[0076] 9(b), in the case of the coil structure for the wireless power feeder according to the first embodiment of the present invention, two stepped spiral coils 31, 32 are wound diagonally around the upper part (positive side in the Z-axis direction) and lower part (negative side in the Z-axis direction) of the ferrite core 11, and therefore lead wires 51, 52 that lead these coil windings to the outside can use the thick part in the Z-axis direction of the ferrite core 11. As a result, even when lead wires are drawn from the coil windings, the thickness of the entire coil structure does not change, and therefore there is an advantage that the wires can be drawn without shortening the transmission distance, that is, the transmission distance can be maintained long.

[0077] Furthermore, with regard to cooling of the coil winding of the coil structure for a wireless power feeder, the coil structure for a wireless power feeder shown in FIGS. 3 to 5 according to the first embodiment of the present invention is superior to the double spiral coil structure (conventional DD coil (double D coil)) shown in FIG. 1( c) and the hybrid coil structure shown in FIG. 1( d).

[0078] In actual operation (continuous operation), the coil windings need to be cooled by water or air, but with the current double spiral coil structure (conventional DD coil (double D coil)) shown in Figure 1(c) or the hybrid coil structure shown in Figure 1(d), cooling the coil windings is difficult in itself. Because the ferrite core has very poor thermal conductivity, cooling the ferrite core does not cool the coil windings, so the coil windings need to be cooled directly, but with the conventional coil structures shown in Figures 1(c) and 1(d), there is no way to directly access the coil windings.

[0079] 10A and 10B are explanatory diagrams comparing an example of the arrangement of water pipes for cooling the coil structure for the wireless power feeder according to the first embodiment of the present invention with the conventional coil structure shown in Fig. 1C. Fig. 10A is a diagram showing an example of the arrangement of two coils, a power supply coil and a power receiving coil, for the double-spiral coil structure shown in Fig. 1C. However, the spiral coils 23 and 24 cannot be accessed from the back side of the ferrite core 1, and the spiral coils 23 and 24 are a transmission space, so if a cooling water pipe or the like were to be installed, the actual transmission distance would be shortened. Therefore, a cooling water pipe cannot be installed.

[0080] On the other hand, FIG. 10(b) is a diagram showing an example of a coil structure for a wireless power feeder according to the first embodiment of the present invention, in which two coils, a power feed coil and a power receiving coil, are arranged, and water-cooled pipes 61 (61-1, 61-2, 61-3) are shown in bold only in the lower coil (power receiving coil) in FIG. 10(b).

[0081] In the coil structure for the wireless power feeder according to the first embodiment of the present invention, as shown in Fig. 10(b), the spiral coils 31 and 32 have steps, which makes it possible to place cooling water pipes at the positions of the water-cooled pipes 61-1, 61-2, and 61-3 indicated by the thick lines. Note that the dashed thick lines indicate the portions that pass behind and are not visible.

[0082] 11A and 11B are diagrams showing a specific example of the arrangement of cooling water pipes in the coil structure for a wireless power feeder according to the first embodiment of the present invention. Fig. 11A is a diagram showing either the power supply coil or the power receiving coil as viewed from the front (top) side, and Fig. 11B is a diagram showing the same as viewed from the back (bottom) side. A thick line indicates a water-cooled pipe 61, and arrows indicate the direction of the cold water flowing through it. Note that, in this diagram, the thick dashed line indicates the portion that passes behind and is not visible.

[0083] Although specific coil winding methods and the lead wires of the coil windings will be described later, in the first place, because bundling coil windings makes it difficult for heat to escape, as mentioned above, the coil windings will be described here as being wound in a single row without being bundled. The coil structure for a wireless power feeder according to the first embodiment of the present invention has the advantage that it is also possible to cool the coil windings by arranging a water-cooled pipe 61 for cooling the coil windings, as shown in Figures 10 and 11.

[0084] As described above, according to the coil structure for a wireless power feeder in embodiment 1 of the present invention, each of the spiral coils 31, 32 is provided with a step, and the solenoid coil 33 is wound between these two spiral coils 31, 32, so that the transmission distance between the power feeding coil and the power receiving coil can be maintained longer, the transmission power efficiency can be increased, and a higher performance wireless power feeder can be achieved. Furthermore, because the spiral coils 31, 32 are provided with a step, the performance of the wireless power feeder is not reduced by the coil lead wires, and further, it is possible to arrange a water-cooled pipe for cooling the coil windings.

[0085] As shown in Figure 5 of the first embodiment, there are various variations in the length of the ferrite core (magnetic core) which is a magnetic material in the left-right direction (X-axis direction), and it was confirmed that any of the structures had sufficiently high performance (long transmission distance and high transmission power efficiency). It was also confirmed that even higher performance could be achieved by adjusting the length of this ferrite core in the left-right direction (X-axis direction).

[0086] However, since it is impossible to know which length (length in the X-axis direction) of ferrite core to use as the magnetic body will provide the best performance without actually trying it, it was not possible to confirm which of the ferrite cores shown in Figures 5(a-1), (b-1), and (c-1) should be used before winding the spiral coils 31 and 32.

[0087] Here, we will explain the adjustment of the resonant frequency, which is considered important in wireless power transfer devices. Ferrite materials and capacitors have variations in their characteristics, making it difficult to adjust the resonant frequency of the resonant circuits (power supply resonant circuit, power receiving resonant circuit) to a specified value. Possible methods for adjusting the resonant frequency include adjusting the number of turns of the coil (power supply coil, power receiving coil) and adjusting the capacitance of the capacitor. However, adjusting the number of turns of the coil requires work such as unwinding and rewinding the coil after winding the wire, which is difficult for manufactured products. Furthermore, even if we try to adopt the method of adjusting the capacitance of the capacitor, it is difficult to adjust the capacitance of the capacitor because capacitors only have a standard capacitance.

[0088] As a means of solving this problem, the resonant frequency can be changed by using ferrite cores with different lengths in the left-right direction (X-axis direction), as shown in Figures 5(a-1), (b-1), and (c-1). However, as mentioned above, even if you find after winding the coil that it would have been better if it were a little longer or a little shorter, it is difficult to make adjustments.

[0089] Therefore, as shown in Fig. 12, it was considered to make it possible to attach magnetic pole plates 13 to a ferrite base (magnetic base) 12 having the same length (length in the X-axis direction) as the ferrite core (magnetic core) 11 shown in Fig. 5(c-1). That is, in this second embodiment, the ferrite core 11 is made up of a ferrite base 12 having substantially the same shape as the ferrite core 11, and two magnetic pole plates 13 that can be attached to the ferrite base 12. Also, in Fig. 12, the two magnetic pole plates 13 will be described as being thinner than the thickness (thickness in the Z-axis direction) of the ferrite base 12.

[0090] 12 is a schematic diagram showing the coil structure for a wireless power feeder according to the second embodiment of the present invention, with the same three variations as in FIG. 5. For the sake of explanation, the coil windings (spiral coils 31, 32 and solenoid coil 33) are not shown, and only the winding forms 81, 82, and 71 for the respective coils, the ferrite base 12, and the magnetic pole plate 13 are shown. These winding forms 81, 82, and 71 will be described later with reference to FIG.

[0091] In all of Figures 12(a), (b), and (c), the ferrite base 12 used has the shortest length in the left-right direction (X-axis direction) as shown in Figures 5(c-1) and (c-2), but magnetic pole plates 13 of different lengths (lengths in the X-axis direction) are attached to the top of the ferrite base 12 (on the positive side in the Z-axis direction).

[0092] In other words, in Figure 12(a), the two magnetic pole plates 13 are attached so that when the ferrite base 12 and the two magnetic pole plates 13 are combined, the length is the same as the length in the left-right direction (X-axis direction) of the ferrite core 11 in Figures 5(a-1) and (a-2); in Figure 12(b), the two magnetic pole plates 13 are attached so that when the ferrite base 12 and the two magnetic pole plates 13 are combined, the length is the same as the length in the left-right direction (X-axis direction) of the ferrite core 11 in Figures 5(b-1) and (b-2); and in Figure 12(c), the two magnetic pole plates 13 are attached so that when the ferrite base 12 and the two magnetic pole plates 13 are combined, the length is the same as the length in the left-right direction (X-axis direction) of the ferrite core 11 in Figures 5(c-1) and (c-2).

[0093] 12(a), (b), and (c), two magnetic pole plates are attached corresponding to the two spiral coils 31 and 32, respectively, and are configured to be attached after the spiral coils 31 and 32 are wound on the upper part (positive side in the Z-axis direction) of the ferrite base 12. In the example shown in FIG. 12, three types of magnetic pole plates 13 are prepared, each differing only in length in the X-axis direction, and the magnetic pole plate 13 attached to the ferrite base 12 can be replaced with an appropriate size from the three types. In each of the examples shown in FIGS. 12(a), (b), and (c), the two magnetic pole plates 13 are the same size, but they do not necessarily have to be the same size because the two magnetic pole plates may not be the same size (not bilaterally symmetrical).

[0094] 12(a), (b), and (c) have been described as an example, the number of types of magnetic pole plates 13 is not limited to three. If multiple types of magnetic pole plates 13 with different sizes only in the length in the X-axis direction are prepared, the resonant frequency can be adjusted by replacing the magnetic pole plate 13 attached to the ferrite base 12 with one of the multiple types with an appropriate size. Furthermore, because magnetic pole plates can be easily cut and adjusted, there is no need to prepare multiple types; it is sufficient if magnetic pole plates 13 of different sizes can be attached to the ferrite base 12.

[0095] Furthermore, although not shown, the two magnetic pole plates 13 may be attachable to the left and right ends (the end side surface on the positive side and the end side on the negative side in the X-axis direction) of the ferrite base 12, rather than to the top (the positive side in the Z-axis direction) of the ferrite base 12. Even in this case, the two magnetic pole plates are attached to the left and right ends (the end side surface on the positive side and the end side on the negative side in the X-axis direction) of the ferrite base 12, respectively, and are configured to be attachable after the spiral coils 31 and 32 are wound on the left and right ends (the end side surface on the positive side and the end side on the negative side in the X-axis direction) of the ferrite base 12. Note that even in this case, the two magnetic pole plates 13 do not need to be the same size.

[0096] As described above, in the first embodiment, experiments were also conducted using a ferrite core 11 in which both ends in the X-axis direction of the ferrite core 11 were shaved to shorten the length in the left-right direction (X-axis direction), and the transmission distance and transmission power efficiency were confirmed, and it was confirmed that these structures also had sufficiently high performance. In the second embodiment, experiments were conducted by attaching magnetic pole plates 13 that differed only in size in the left-right direction (X-axis direction) to the ferrite base 12, and by changing the length of the attached magnetic pole plates 13, the transmission distance and transmission power efficiency were confirmed, and it was confirmed that, similar to the first embodiment, sufficiently high performance was achieved. It was also confirmed that higher performance could be achieved by adjusting the left-right direction (X-axis direction) length of the magnetic pole plates 13 attached to the top (positive side in the Z-axis direction) or left and right ends (positive and negative end side faces in the X-axis direction) of the ferrite base 12 in this way.

[0097] Furthermore, in the case of the coil structure shown in this embodiment 2, the magnetic pole plates 13 can be attached after the coil windings (spiral coils 31, 32, solenoid coil 33) have been wound around the ferrite base 12, which has the additional advantage that the resonant frequency can be adjusted by attaching magnetic pole plates 13 of a more optimal length in accordance with variations in the characteristics of the ferrite core consisting of the ferrite base 12 and two magnetic pole plates 13. In other words, it is precisely because of the coil structure in this embodiment of the present invention that the resonant frequency can be adjusted by attaching magnetic pole plates 13 of different sizes (lengths in the X-axis direction).

[0098] Here, we will explain how to make the coil structures in the first and second embodiments of the present invention, including the fact that an actual wireless power supply device requires a resin winding former for winding the coil. Note that the coil structure in the first embodiment is also almost the same in terms of how to make the coil structure, as the only difference is whether or not the magnetic pole plate 13 is finally attached to the ferrite base 12.

[0099] 13A and 13B are explanatory diagrams showing a method for fabricating a coil structure for a wireless power feeder according to a second embodiment of the present invention. First, as shown in FIG. 13A, a resin coil former 71 for the solenoid coil 33 is attached to the center (center in the X-axis direction) of the ferrite base 12. Next, as shown in FIG. 13B, resin coil formers 81 and 82 for the two stepped spiral coils 31 and 32 are attached to both sides of the ferrite base 12. FIG. 13C is a front view of FIG. 13B as viewed from the direction of arrow A, and FIG. 13D is a view of FIG. 13B as viewed from the back (bottom side).

[0100] Then, a coil winding is wound around this. The method of winding this coil will be described later with reference to Fig. 14. Finally, as shown in Fig. 13(e), magnetic pole plates 13 are attached to the top (positive side in the Z-axis direction) or left and right ends (positive and negative end side faces in the X-axis direction) of the ferrite base 12. This completes the coil structure for a wireless power feeder according to the second embodiment of the present invention.

[0101] Next, a method of winding the coil before the step shown in Fig. 13(e) will be described. Fig. 14 is an explanatory diagram showing a method of winding the coil in the coil structure for a wireless power feeder according to the second embodiment of the present invention.

[0102] 14(a), the spiral coil 32 is first wound from the outer portion at the bottom right of the figure, i.e., the portion indicated by the arrow [1], onto the resin winding form 82, and is wound from the outside to the inside in a generally rectangular or circular shape. Then, since the end of the stepped spiral coil 32 on the right side is the innermost portion of the lower stepped portion on the right side, the spiral coil is passed from there, as indicated by the arrow [2], over the diagonal coil winding and through the back side of the resin winding form 82 in the higher stepped portion (portion indicated by the dashed arrow [3]), and then the winding of the solenoid coil 33 begins.

[0103] The solenoid coil 33 is wound starting from arrow [4], around the resin solenoid coil former 71 attached to the ferrite base 12, from right to left in the figure, and finally, when it finishes winding at the part indicated by arrow [5], it passes diagonally around the back side of the resin coil former 81 to the bottom left as shown by dashed arrow [6] in Figure 14(b) (see Figure 14(d) described later), and then starts winding the spiral coil 31 onto the resin coil former 81 from the bottom left (see arrow [7] in the figure). The spiral coils 31 and 32 are wound so that the coils are wound in opposite directions.

[0104] Then, as with the spiral coil 32, the coil is wound from the outside to the inside in a generally square or circular shape, and the end of the left-side stepped spiral coil 31 is the innermost part of the lowest step on the left side, so the coil winding is simply pulled out from there as shown by arrow [8] in Figure 14(c) and finished. Figure 14(d) is a view from the back (bottom side) of the resin winding forms 81, 82 showing the state after the coil winding has been wound in this way.

[0105] As explained in Fig. 14 , once the coil winding is complete, the magnetic pole plate 13 is attached, completing the coil structure for a wireless power feeder according to embodiment 2 of the present invention. Fig. 15 is an explanatory diagram showing how to attach the magnetic pole plate of the coil structure for a wireless power feeder according to embodiment 2 of the present invention. In Fig. 15 as well, an example will be explained in which the magnetic pole plate 13 is attached to the top of the ferrite base 12 (on the positive side in the Z-axis direction).

[0106] Fig. 15(a) shows the state before the magnetic pole plate 13 is attached to the ferrite base 12, Fig. 15(b) shows the state after the magnetic pole plate 13 has been attached with a length (length in the X-axis direction) similar to that shown in Fig. 12(b), and Fig. 15(c) shows the state after the magnetic pole plate 13 that is the longest in the X-axis direction has been attached, similar to that shown in Fig. 12(a). The magnetic pole plate 13 may be attached using double-sided tape, for example.

[0107] Here, the length of the magnetic pole plate 13 in the X-axis direction was gradually changed and the resonance frequency of the wireless power feeder was compared, and it was found that extending the magnetic pole plate 13 by 1 cm lowered the resonance frequency by approximately 1 kHz. As a result, by adjusting the length of the magnetic pole plate 13 after winding the coil winding, it is possible to absorb individual differences between parts, so if the magnetic pole plate 13 is attached after winding the coil winding is completed, it will be possible to use it in a state with the highest performance.

[0108] Figure 16 is an explanatory diagram showing the positional relationship between the magnetic flux passing through the inside of the ferrite core and the coil in the coil structure for the wireless power feeder according to each of Embodiments 1 and 2 of the present invention. Figures 16(a) and 16(b) correspond to Embodiment 1, and Figures 16(c) and 16(d) correspond to Embodiment 2. Figure 16(a) is a diagram of the exact same structure as Figure 5(c-2), except that dashed arrows indicating the magnetic flux passing through the inside of the ferrite core 11 have been added. Note that although the magnetic flux flows as shown in Figures 5(a-2) and 8, Figure 16 only shows the magnetic flux passing through the inside of the ferrite core 11.

[0109] 16(a) and 16(b), the spiral coils 31 and 32 are arranged below the magnetic flux passing through the ferrite core 11 (on the negative side in the Z-axis direction) in the portion far from the solenoid coil 33 (near the end of the ferrite core 11 in the X-axis direction), but the only difference is that the positions are slightly different up and down. In other words, in Fig. 16(a), the coils at both ends are arranged completely below the ferrite core 11 (on the negative side in the Z-axis direction), but in Fig. 16(b), the coils are not arranged completely below the ferrite core 11 but slightly higher than in Fig. 16(a). This illustration is intended to explain that even such an arrangement falls within the coil structure of the present invention as long as it is arranged below the magnetic flux passing through the ferrite core 11 (on the negative side in the Z-axis direction).

[0110] Similarly, in both Figures 16(c) and 16(d), the spiral coils 31 and 32 are arranged below (on the negative side in the Z-axis direction) the magnetic flux passing through the ferrite base 12 (i.e., the ferrite core 11) in the portion far from the solenoid coil 33 (near the end of the ferrite base 12 in the X-axis direction), but the only difference is that the positions are slightly different up and down. That is, in Figure 16(c), the coils at both ends are arranged completely below (on the negative side in the Z-axis direction) the ferrite core 11, but in Figure 16(d), they are not arranged completely below the ferrite core 11, but are arranged slightly higher than in Figure 16(c). However, in this case too, they are arranged below (on the negative side in the Z-axis direction) the magnetic flux passing through the ferrite core 11.

[0111] As described above, in the case of the coil structure for the wireless power feeder in the second embodiment, as in the first embodiment, the two spiral coils 31, 32 are stepped spiral coils wound multiple times from the outside to the inside in an approximately rectangular or annular shape with steps formed above and below (in the Z-axis direction) near the center and near the ends in the X-axis direction so that they are arranged on the left and right sides of the solenoid coil 33 (on the positive and negative sides in the X-axis direction around the solenoid coil 33), and are arranged above (on the positive side in the Z-axis direction) the magnetic flux passing through the inside of the ferrite core 11 in the part close to the solenoid coil 33 (near the center of the length of the ferrite core 11 in the X-axis direction), and are arranged below (on the negative side in the Z-axis direction) the magnetic flux passing through the inside of the ferrite core 11 in the part far from the solenoid coil 33 (near the ends of the length of the ferrite core 11 in the X-axis direction).

[0112] As described above, according to the coil structure for a wireless power feeder in embodiment 2 of the present invention, similarly to embodiment 1, each of the spiral coils 31, 32 is provided with a step, and the solenoid coil 33 is wound between these two spiral coils 31, 32, so that it is possible to maintain a longer transmission distance between the power feeding coil and the power receiving coil, improve the efficiency of transmitted power, and provide a wireless power feeder with higher performance. Furthermore, because the spiral coils 31, 32 are provided with a step, the performance of the wireless power feeder is not reduced by the coil lead wires, and furthermore, it is possible to arrange a water-cooled pipe for cooling the coil windings.

[0113] Furthermore, according to the second embodiment, after the coil winding is wound, the length of the two magnetic pole plates 13 attached to the ferrite base 12 in the left-right direction (X-axis direction) can be adjusted, which has the further advantage that the resonant frequency can be adjusted by attaching magnetic pole plates 13 of a more optimal length in accordance with variations in the characteristics of the ferrite core consisting of the ferrite base 12 and the two magnetic pole plates 13.

[0114] It should be noted that within the scope of the present invention, the embodiments may be freely combined, or any of the components of the embodiments may be modified, or any of the components of the embodiments may be omitted.

[0115] The coil structure for a wireless power feeder of the present invention can be applied as a coil structure for wireless power feeders in various fields requiring wireless power feed, such as electronic devices and electric vehicles.

[0116] REFERENCE SIGNS LIST 1, 10, 11 Ferrite core (magnetic material) 12 Ferrite base (magnetic material base) 13 Magnetic pole plate 21 Spiral coil 22, 27, 33 Solenoid coil 23, 24, 25, 26 Planar spiral coil constituting double spiral 31, 32 Stepped spiral coil constituting double spiral 41, 42, 51, 52 Lead wire of coil winding 61, 61-1, 61-2, 61-3 Water-cooled tube 71 Winding form for solenoid coil 33 81, 82 Winding form for stepped spiral coils 31, 32

Claims

1. A coil structure for a wireless power supply device, wherein the coil structure has left and right lengths with the X-axis direction being the longest side, a depth with the Y-axis direction being the second-longest side, and upper and lower thicknesses with the Z-axis direction being the shortest side, and includes a substantially rectangular parallelepiped-shaped magnetic core, two spiral coils, and one solenoid coil. The one solenoid coil is a solenoid coil wound around the magnetic core a plurality of times only near the center of the length of the magnetic core in the X-axis direction. The two spiral coils are arranged on the left and right (the plus side and the minus side in the X-axis direction centered on the solenoid coil) with respect to the solenoid coil, and near the center of the length of the magnetic core in the X-axis direction, which is a portion close to the solenoid coil, they are arranged above (the plus side in the Z-axis direction) the magnetic flux passing through the inside of the magnetic core, and near the ends of the length of the magnetic core in the X-axis direction, which is a portion far from the solenoid coil, they are arranged below (the minus side in the Z-axis direction) the magnetic flux passing through the inside of the magnetic core. They are stepped spiral coils wound a plurality of times in a substantially square shape or a substantially annular shape from the outside to the inside with steps in the up and down (Z-axis direction) between the vicinity of the center and the vicinity of the ends in the X-axis direction. A coil structure for a wireless power supply device, characterized by the above.

2. The magnetic core of the coil structure for a wireless power supply device according to claim 1, which is composed of a magnetic base having substantially the same shape as the magnetic core and two magnetic pole plates attachable to the magnetic base. Each of the two magnetic pole plates corresponds to each of the two spiral coils and is configured to be attachable to the upper part (the plus side in the Z-axis direction) or the left and right ends (the end side surfaces on the plus side and the minus side in the X-axis direction) of the magnetic base after the two spiral coils are wound.

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