Power transmission equipment

Abstract

To provide a power-transmitting device capable of suppressing magnetic field leakage of a power-transmitting coil while suppressing an increase in outer shape and weight, with a simple structure thereof.SOLUTION: A power-transmitting device 1 comprises a power-transmitting part 2 provided with a power-transmitting coil 20, and a metallic housing 3 having a peripheral wall 30 that surrounds the power-transmitting part 2. A shield part 5 projecting toward an inner side of the peripheral wall 30 is integrated with a top end part 30t located on an arrangement side of a power-receiving coil 90 out of the peripheral wall 30.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a power transmission device for wirelessly charging an electronic device.

Background Art

[0002] In recent years, power transmission devices for wirelessly charging electronic devices typified by electric vehicles, electric bicycles, and portable information terminals such as smartphones and tablets by electromagnetic coupling have been proposed. As power transmission methods in this type of power transmission device, non-radiative methods and radiative methods are known. Among these, as non-radiative power transmission methods, those using magnetic field coupling including electromagnetic induction and magnetic field resonance, or electric field coupling are known. As radiative power transmission methods, those using electromagnetic wave energy such as microwaves and laser waves are known.

[0003] Currently, it is common to adopt a non-radiative method as the power transmission method of the power transmission device. In this type of non-radiative power transmission device, power is generally supplied from the power transmission coil side to the power reception coil side by using electromagnetic induction or magnetic field resonance between the power transmission coil and the power reception coil (see, for example, Patent Documents 1 to 4).

[0004] Patent Document 1 introduces a non-radiative power transmission device that wirelessly charges a power reception coil (secondary side core) from a power transmission coil (primary side core), and thereby charges a battery cell electrically connected to the power reception coil. Patent Documents 2 and 3 also introduce non-radiative power transmission devices for supplying power to an electric vehicle. Patent Document 4 introduces a non-radiative power transmission device using electromagnetic resonance between a power transmission coil and a power reception coil.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] Incidentally, when power is supplied to electronic equipment using various power transmission devices that utilize electromagnetic induction or magnetic field resonance as described above, magnetic field leakage may occur from the gap between the transmitting coil and the receiving coil. This magnetic field leakage can cause a decrease in power transmission efficiency between the transmitting and receiving coils, and furthermore, the leakage flux may adversely affect other electronic equipment.

[0007] To suppress the magnetic field leakage described above, for example, Patent Document 1 introduces a technique for shielding the magnetic fields generated in the primary and secondary cores with shielding plates. Patent Document 2 introduces a technique for suppressing magnetic field leakage by a shielding member installed above the power receiving coil. Patent Document 3 introduces a technique for canceling leakage flux from the power transmitting coil with a cancellation coil.

[0008] However, the mechanisms for suppressing magnetic field leakage in the above-mentioned technologies are either structurally complex or have large external dimensions and mass. As a result, there are problems such as increased manufacturing costs for power transmission equipment including such mechanisms, or excessive external dimensions and mass of the power transmission equipment. This invention was made in consideration of the above circumstances, and aims to solve the problem of providing a power transmission device that has a simple structure and can suppress magnetic field leakage from the power transmission coil while suppressing an excessive increase in its external shape and mass. [Means for solving the problem]

[0009] The power transmission device of the present invention, which solves the above problems, It comprises a power transmission unit including a power transmission coil, and a housing having a metal peripheral wall surrounding the power transmission unit, A power transmission device wherein a metal shielding portion protruding inward from the peripheral wall is integrated into the top end of the peripheral wall located on the side where the power receiving coil is arranged. [Effects of the Invention]

[0010] The power transmission device of the present invention has a simple structure and can suppress magnetic field leakage from the power transmission coil while suppressing excessive increases in its external size and mass. [Brief explanation of the drawing]

[0011] [Figure 1] This is an explanatory diagram illustrating the relationship between the power transmission device and the power receiving coil in Example 1. [Figure 2] This is a schematic diagram illustrating the power transmission device of Example 1 as viewed from the top end of the peripheral wall. [Figure 3] This is a schematic diagram illustrating the appearance of the power transmission device of Example 1 when it is cut in the thickness direction. [Figure 4] This is an explanatory diagram illustrating a metal pattern for suppressing magnetic field leakage in the power transmission device of Example 1. [Figure 5] This is an explanatory diagram that schematically illustrates the results of Evaluation 1. [Figure 6] This is an explanatory diagram that schematically illustrates the results of Evaluation 2. [Modes for carrying out the invention]

[0012] The embodiments for carrying out the present invention are described below. Unless otherwise specified, the numerical range "a to b" described herein includes the lower limit a and the upper limit b. The numerical range can be constructed by arbitrarily combining these upper and lower limits, as well as the numerical values ​​listed in the examples, etc. Furthermore, the upper and lower limits can be arbitrarily selected from within the numerical range.

[0013] The power transmission device of the present invention includes a power transmission unit and a housing. The power transmission unit includes a power transmission coil and has a metal peripheral wall surrounding the power transmission unit. The power transmission device has a side where the power receiving coil is disposed, that is, the side where the power receiving coil is disposed (referred to as the power receiving coil disposition side in this specification). A shielding portion protruding toward the inside of the peripheral wall is integrally formed at the top end portion of the peripheral wall located on the power receiving coil disposition side.

[0014] Here, when power is transmitted from the power transmission coil of the power transmission device to the power receiving coil of the electronic device, a part of the magnetic flux created by the power transmission coil becomes a so-called leakage magnetic flux that does not link with the power receiving coil. A part of the leakage magnetic flux heads toward the inside of the housing, and another part heads toward the outside of the housing via the top end portion of the peripheral wall.

[0015] In the power transmission device of the present invention, a shielding portion protruding toward the inside of the peripheral wall is integrally formed at the top end portion of the peripheral wall. Therefore, in the power transmission device of the present invention, at least a part of the leakage magnetic flux heading toward the outside of the housing via the top end portion of the peripheral wall is shielded by the shielding portion, and the spread of the magnetic field to the outside in the radial direction of the power transmission coil and outside the housing is suppressed. That is, according to the power transmission device of the present invention, it is possible to suppress the magnetic field leakage of the power transmission coil. Further, the shielding portion in the power transmission device of the present invention is only integrally formed at the top end portion of the peripheral wall and protrudes toward the inside of the peripheral wall, and has a very simple structure. Therefore, the power transmission device of the present invention itself also has a simple structure, and its outer shape and mass do not increase excessively. Therefore, the power transmission device of the present invention can be said to be a power transmission device that has a simple structure and can suppress the magnetic field leakage of the power transmission coil while suppressing excessive increase in its outer shape and mass.

[0016] Hereinafter, the power transmission device of the present invention will be specifically described.

[0017] The power transmission device of the present invention includes a power transmission unit and a housing. Among these, the power transmission unit essentially includes a power transmission coil and may include auxiliary members of a general power transmission device together with the power transmission coil. The power transmission coil may be any device that can perform non-radiative power supply through electromagnetic induction or magnetic field resonance with a power receiving coil mounted on an electronic device to be powered. The power transmission coil may be referred to as a primary coil in some cases, and the power receiving coil may be referred to as a secondary coil in some cases.

[0018] As a sub-member that can constitute a power transmission unit together with the power transmission coil, various known ones such as lead wires connected to the power transmission coil may be included. In the power transmission device of the present invention, it is particularly preferable that the power transmission unit includes, as the sub-member, a magnetic member for shielding magnetic flux directed from the power transmission coil to the side opposite to the power receiving coil and a magnetic field spreading to the opposite side.

[0019] As the magnetic member included in the power transmission unit, for example, those containing general magnetic materials represented by ferrite, sendust, and carbonyl iron may be used. The magnetic member may be composed of these magnetic materials, but considering cost and handling properties, it is preferable to use those in which the magnetic material is kneaded into a base material such as silicon or rubber.

[0020] The magnetic member preferably constitutes the surface on the non-arrangement side of the power receiving coil in the power transmission unit, that is, the bottom surface of the power transmission unit. The shape of the magnetic member is not particularly limited, but considering that it widely covers the surface on the non-arrangement side of the power receiving coil in the power transmission coil, that is, the bottom surface of the power transmission coil, and weight reduction, a thin shape such as a sheet shape, a film shape, or a tape shape is preferable. Considering the handling property of the power transmission unit during the manufacture of the power transmission device or the like, it is particularly preferable that the magnetic member is integrated with the bottom surface of the power transmission coil by a method such as adhesion.

[0021] As previously described, the enclosure includes a metal peripheral wall and a metal shielding section. The metals used for the peripheral wall and shielding section may be the same or different. Furthermore, the metals constituting parts of the peripheral wall and shielding section may be different from the metals constituting other parts. In addition, the metals constituting the peripheral wall and shielding section may be individual metals or alloys. As the metals constituting the peripheral wall and shielding section, it is possible to select materials commonly used in magnetic shielding.

[0022] The peripheral wall surrounds the aforementioned power transmission coil and has an end on the power transmission coil side and an end on the power receiving coil side. The end of the peripheral wall on the power transmission coil side is called the bottom end of the peripheral wall. The end of the peripheral wall on the power receiving coil side is the top end as previously described.

[0023] As previously mentioned, the peripheral wall only needs to be roughly cylindrical in shape to surround the power transmission coil; it may be cylindrical, rectangular, or any other shape. The positional relationship between the power transmission coil and the peripheral wall is also not particularly limited; the power transmission coil may be placed in the center of the peripheral wall, or it may be positioned towards the end of the peripheral wall. The height of the peripheral wall, i.e., the length of the peripheral wall in the top-to-bottom direction, can be set appropriately according to the size of the transmission coil and the positional relationship between the transmission coil and the receiving coil, and is not particularly limited. The thickness of the peripheral wall, i.e., the length of the peripheral wall in the inside-to-outside direction, is also not particularly limited.

[0024] The shielding portion only needs to be integrated with the top end of the peripheral wall, and it is particularly preferable that it be present around the entire circumference of the peripheral wall, but it may also be present only in a part of the peripheral wall in the circumferential direction. Even when the shielding portion is present only in a part of the peripheral wall in the circumferential direction, it is possible to suppress the magnetic field leakage of the power transmission coil in that part.

[0025] Furthermore, when the peripheral wall is rectangular, it is particularly preferable that the shielding portion be provided along two or more sides of the peripheral wall. In this case, it is preferable to position the power transmission coil off-center on the side where the shielding portion is provided, rather than in the center of the peripheral wall. This brings the shielding portion closer to the power transmission coil, making it possible to further reduce the magnetic field leakage from the power transmission coil as described above.

[0026] The shielding portion only needs to protrude from the top of the peripheral wall toward the inside of the peripheral wall, in other words toward the radially inward direction of the peripheral wall, and its shape is not particularly limited. For example, the shielding portion may be flat, curved, or have other shapes such as columnar or eaves. Furthermore, if the shielding portion protrudes close to the power transmission coil surrounded by the peripheral wall, there is the advantage of being able to further suppress magnetic field leakage from the power transmission coil. The preferred range for the protruding length Le of the shielding portion will be described in detail in the Examples section.

[0027] The housing may be roughly cylindrical in shape, consisting of a peripheral wall surrounding the power transmission coil and a shielding portion integrated with the peripheral wall, or it may be box-shaped in addition to having at least one of a bottom cover portion covering the bottom end of the peripheral wall and a top cover portion covering the top end of the peripheral wall. Considering the need to isolate the power transmission coil housed inside the housing from the outside world, it is preferable for the housing to have either the bottom cover portion or the cover portion, and it is particularly preferable to have both the bottom cover portion and the top cover portion. The material of the bottom cover portion and the top cover portion may be metal or not, but in order to suppress magnetic field leakage from the power transmission coil, it is preferable that at least a part of the bottom cover portion and the top cover portion be metal.

[0028] The bottom cover and top cover described above may be simple metal plates, but it is preferable that they be substrates on which a metal pattern having a predetermined function is provided. The metal pattern may be a circuit pattern for a power transmission device, but it is preferable that it includes a metal pattern for suppressing magnetic field leakage.

[0029] In this case, the transmitting coil generates electromagnetic waves at frequencies outside the frequency range used for electromagnetic induction with the receiving coil (e.g., 100kHz to 200kHz). These electromagnetic waves outside the frequency range may interfere with electromagnetic induction and magnetic field resonance between the transmitting and receiving coils, potentially hindering efficient power transmission.

[0030] For this reason, it is particularly preferable to provide a magnetic field leakage suppression metal pattern on the top cover portion, which is positioned between the power transmission coil and the power receiving coil of the electronic device. This pattern has a filtering effect against electromagnetic waves outside the above frequency range generated by the power transmission coil and suppresses the leakage of such electromagnetic waves to the power receiving coil. Furthermore, among electromagnetic waves outside the above frequency range, the frequency range of 200 kHz and above is used for GPS, digital audio, FM radio, etc. For this reason, it is particularly preferable that the magnetic field leakage suppression metal pattern has a filtering effect that suppresses the leakage of electromagnetic waves in the frequency range of 200 kHz and above. While any known metal pattern can be used for suppressing magnetic field leakage, a comb-shaped pattern, as described in the embodiments below, is preferably used.

[0031] When the above-mentioned metal pattern for suppressing magnetic field leakage is provided on the top cover, it is preferable to provide a shielding portion made of the metal pattern in the region of the top cover radially outward from the metal pattern for suppressing magnetic field leakage. In this case, the shielding portion can be brought into contact with the peripheral wall by attaching the top cover to the peripheral wall, which has the advantage of allowing the housing with the shielding portion to be manufactured easily and inexpensively. The metal pattern for suppressing magnetic field leakage and the shielding portion can be placed at a distance from each other, and they may be close together or far apart. Furthermore, even if the above-mentioned magnetic field leakage suppression metal pattern is not provided on the top cover, if a shielding portion made of a metal pattern is provided in the radially outer region of the top cover, there is a similar advantage in that a housing with a shielding portion can be manufactured easily and inexpensively.

[0032] The power transmission device of the present invention will be described below with specific examples.

[0033] (Example 1) The power transmission device of Example 1 is installed inside a vehicle and is for charging a portable information terminal. Figure 1 shows a schematic diagram illustrating the relationship between the power transmission device and the receiving coil of Example 1. Figure 2 shows a schematic diagram illustrating the power transmission device of Example 1 as seen from the top end of the peripheral wall. Figure 3 shows a schematic diagram illustrating the power transmission device of Example 1 as seen when cut in the thickness direction. Figure 4 shows a schematic diagram illustrating the metal pattern for suppressing magnetic field leakage in the power transmission device of Example 1. Figure 5 shows a schematic diagram illustrating the results of Evaluation 1. Figure 6 shows a schematic diagram illustrating the results of Evaluation 2.

[0034] As shown in Figures 1 to 3, the power transmission device 1 of Example 1 comprises a power transmission unit 2 and a housing 3.

[0035] The power transmission unit 2 comprises a power transmission coil 20, a magnetic member 21, and lead wires (not shown). The lead wires are attached to the power transmission coil 20 and connected to a power source (not shown). The magnetic member 21 is made of silicone rubber mixed with ferrite powder and is in the form of a sheet. As shown in Figures 1 and 3, the magnetic member 21 is bonded to the bottom surface 20b of the power transmission coil 20 and covers the power transmission coil 20 from the bottom surface 20b side.

[0036] The housing 3 has a peripheral wall 30, a bottom cover portion 35, and a top cover portion 4.

[0037] The peripheral wall 30 is made of aluminum, has a rectangular tubular shape, and its axis is oriented in the direction of the power transmission coil 20-power reception coil 90, that is, in the z direction in Figures 1 and 3. It can also be said that the top and bottom ends of the peripheral wall 30 are open. The receiving coil 90 is included in the electronic equipment 9 and is mounted on the top cover 4 of the power transmission device 1 to receive power from the power transmission coil 20.

[0038] A plate-shaped bottom cover portion 35 made of aluminum is integrated with the bottom end portion 30b of the peripheral wall 30. The bottom cover portion 35 closes the inside and outside of the peripheral wall 30 on the bottom end portion 30b side of the peripheral wall 30. The power transmission unit 2 is fixed to the peripheral wall 30 slightly towards the top end 30t side of the bottom cover 35. The power transmission unit 2 has the power transmission coil 20 facing the top and the magnetic member 21 facing the bottom.

[0039] A plate-shaped top cover portion 4 is integrated into the top end 30t of the peripheral wall 30. The top cover portion 4 is a printed circuit board on which two types of metal patterns are formed on the substrate 41.

[0040] One of the metal patterns formed on the top cover portion 4 is a metal pattern 40 for suppressing magnetic field leakage, and is formed in the radially inner region of the top cover portion 4. The other of the metal patterns formed on the top cover portion 4 is a shielding portion 5, and is formed in the radially outer region of the top cover portion 4. The magnetic field leakage suppression metal pattern 40 is made of a conductive metal material and is connected to lead wires (not shown), and is powered by a power supply (not shown) via these lead wires. The shielding portion 5, on the other hand, is made of the same aluminum as the peripheral wall 30 and is not connected to a power supply.

[0041] As shown in Figure 4, the metal pattern 40 for suppressing magnetic field leakage consists of linear patterns 40p arranged at intervals and connected in a comb-like manner. The width of each linear pattern 40p and the spacing between adjacent patterns 40p are both approximately 5 mil (approximately 0.125 mm).

[0042] As shown in Figures 1 and 2, the top cover portion 4 is substantially rectangular in shape, and the shielding portion 5 formed in the radially outer region of the top cover portion 4 is also substantially rectangular in shape. The width of the shielding portion 5, that is, the length of the shielding portion 5 in the radially inner-outer direction of the top cover portion 4, was 3.5 mm.

[0043] As shown in Figure 3, the top cover portion 4 is integrated with the top edge 30t of the peripheral wall 30, with the shielding portion 5 and the magnetic field leakage suppression metal pattern 40 facing downwards. The shielding portion 5 faces the peripheral wall 30. The top cover portion 4 is fastened to the top edge 30t of the peripheral wall 30 by screws (not shown), thereby integrating the shielding portion 5 with the top edge 30t of the peripheral wall 30. Furthermore, the width of the shielding portion 5 is greater than the thickness of the peripheral wall 30, and the shielding portion 5 protrudes inward from the peripheral wall 30 as shown in Figure 3. The width of the shielding portion 5 can be said to be the protruding length Le of the shielding portion 5 (see Figure 3).

[0044] As shown in Figure 3, the top end 30t of the peripheral wall 30 extends further toward the receiving coil 90 than the transmitting coil 20, so it can be said that the shielding portion 5 is located further toward the top end of the peripheral wall 30 than the transmitting coil 20.

[0045] In the power transmission device 1 of Example 1, the thickness of the shielding portion 5 was 0.5 mm, the thickness of the peripheral wall 30 was 1.5 mm, and the distance H between the power transmission coil 20 and the power receiving coil 90 was 5.0 mm. In addition, the length Lp from the bottom surface 2b of the power transmission portion 2 to the top end 30t of the peripheral wall 30 was 3.7 mm, the protruding length Le of the shielding portion 5 was 3.5 mm, and the shortest distance Lx between the outer peripheral end of the power transmission coil 20 or magnetic member 21 and the peripheral wall 30 was 0.7 mm. Therefore, the relationship between Lx, Lp, and Le satisfies Lx < (Lp + Le).

[0046] Here, in order to more efficiently suppress magnetic field leakage from the power transmission coil 20, it is considered desirable that the relationship between Lx, Lp, and Le satisfy Lx < (Lp + Le). This is because the magnetic field leakage generated in the power transmission coil 20 is efficiently blocked by the peripheral wall 30 and the shielding part 5.

[0047] As previously described, the relationship between Lx, Lp, and Le in the power transmission device 1 of Example 1 satisfies Lx < (Lp + Le). Therefore, it can be said that the power transmission device 1 of Example 1 can efficiently shield magnetic field leakage from the power transmission coil 20.

[0048] [Rating 1] As comparative example power transmission device 1, a device substantially identical to power transmission device 1 of Example 1 was prepared, except that it lacked the shielding section 5. The magnetic field generated during power transmission was evaluated by simulation for the power transmission device 1 of Example 1 and the power transmission device 1 of the Comparative Example. The results are shown in Figure 5.

[0049] As shown in Figure 5, in the power transmission device 1 of Example 1 and Comparative Example, a magnetic field is generated between the power transmission coil 20 and the power receiving coil 90, and a portion of this magnetic field leaks outward from the space between the power transmission coil 20 and the power receiving coil 90, that is, towards the peripheral wall 30.

[0050] However, the magnetic field lf generated in each power transmission device 1 and leaked to the peripheral wall 30 side is reduced, especially in the power transmission device 1 of Example 1, on the forward side in the x direction, i.e., on the peripheral wall 30 side facing the power transmission coil 20, compared to the power transmission device 1 of the comparative example. This can be presumed to be because the magnetic field lf was blocked by the shielding portion 5 provided at the top end 30t of the peripheral wall 30. From this result, it can be seen that magnetic field leakage can be suppressed by the power transmission device 1 of the present invention, which has a shielding portion 5 provided at the top end 30t of the peripheral wall 30.

[0051] [Rating 2] As reference power transmission devices 1 for evaluation, three levels were prepared: one with a length Lp of 2.35 mm (Lp2.35), one with a length Lp of 3.7 mm (Lp3.7), and one with a length Lp of 5 mm (Lp5), from the bottom surface 2b of the power transmission unit 2 to the top end 30t of the peripheral wall 30. Each reference power transmission device 1 is substantially the same as the power transmission device 1 of Example 1, except for the values ​​of Lp and Le. For each of these reference power transmission devices 1, the average magnetic field strength formed when the protruding length Le of the shielding section 5 was varied was calculated by simulation. The results are shown in Figure 6.

[0052] The "average magnetic field strength" mentioned above is calculated by obtaining the magnetic field strength at the outermost part of the top end 30t of the peripheral wall 30 (indicated as L0 in Figure 3) for each reference power transmission device 1 (Lp2.35, Lp3.7, and Lp5) over the entire length of one side of the peripheral wall 30, and then calculating the average value. The vertical axis in Figure 6 represents the average value of the magnetic field strength for each reference power transmission device 1 as a ratio, with the case where the protruding length Le of the shielding part 5 is 0 mm set to 1. The same applies to evaluation 3 described later.

[0053] As shown in Figure 6, the magnetic field strength in each power transmission device 1 changes in relation to the protruding length Le of the shielding portion 5. More specifically, the magnetic field strength decreases as Le increases until the protruding length Le of the shielding portion 5 reaches a predetermined length. The value of Le that minimizes the magnetic field strength, that is, the value of Le that minimizes magnetic field leakage, differs depending on the length Lp from the bottom surface 2b of the power transmission unit 2 to the top end 30t of the peripheral wall 30, that is, the height of the peripheral wall 30 between the power transmission unit 2 and the power receiving coil 90. If Lp is large, the protruding length Le of the shielding portion 5 required to minimize the magnetic field strength becomes smaller. Although not included in the items of this evaluation 2, Lp and Le are naturally related to the shortest distance Lx between the outer peripheral end of the power transmission coil 20 or magnetic member 21 and the peripheral wall 30. In other words, if Lx is large, that is, if the peripheral wall 30 is far from the power transmission unit 2, it is necessary to increase the height Lp of the peripheral wall 30 and / or the protruding length Le of the shielding part 5 in order to suppress magnetic field leakage from the power transmission unit 2. These results support the validity of the above-mentioned relationship Lx < (Lp + Le). For reference, if the protruding length Le of the shielding portion 5 exceeds a predetermined length, the magnetic field strength increases again. This is presumed to be because the magnetic field blocked by the shielding portion 5 becomes turbulent. However, in reality, it is presumed that the presence of the shielding portion 5 keeps this turbulent magnetic field inside the shielding portion 5.

[0054] Here, as shown in Figure 6, at the point where the magnetic field strength in each power transmission device 1 is minimum (indicated by the arrow in Figure 6), the sum of Lp and Le is approximately 7. From this finding, the inventors of the present invention hypothesized that the dimensional relationship of each part in each power transmission device 1 is involved in the effect of suppressing magnetic field leakage.

[0055] [Rating 3] As reference power transmission devices 1 for evaluation, various values ​​were prepared for the length Lp from the bottom surface 2b of the power transmission unit 2 to the top end 30t of the peripheral wall 30, the shortest distance Lx between the outer peripheral end of the power transmission coil 20 or magnetic member 21 and the peripheral wall 30, and the distance H between the power transmission coil 20 and the power receiving coil 90. For each of these reference power transmission devices 1, the average magnetic field strength formed when the protruding length Le of the shielding part 5 was varied was calculated by simulation, and the protruding length Le of the shielding part 5 at the point where the magnetic field strength was minimized was determined. The relationship between this Le value and the dimensions of each part described above was then evaluated. The results are shown in Table 1.

[0056] [Table 1]

[0057] As shown in Table 1, in all cases, the relationship between Le at the point where the magnetic field strength is minimized and the dimensions of each part, (Lp+Le-Lx) / H, falls within a predetermined range. More specifically, (Lp+Le-Lx) / H is within the range of 0.35 to 0.55, more preferably within the range of 0.4 to 0.51. From these results, it can be said that in order to minimize the magnetic field strength, it is preferable to set the relationship between the dimensions of each part within the range of 0.35 ≤ (Lp+Le-Lx) / H ≤ 0.55, and more preferably within the range of 0.4 ≤ (Lp+Le-Lx) / H ≤ 0.51.

[0058] The present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications without departing from the spirit of the invention. Furthermore, each component shown in this specification, including the embodiments, can be arbitrarily extracted and combined to implement the invention. [Explanation of Symbols]

[0059] 1: Power transmission equipment 2: Power transmission section 20: Power transmission coil 21: Magnetic material 2b: Bottom of the power transmission section 3: Cabinet 30: Peripheral wall 30t: Top end of peripheral wall 4: Lid part 40: Metal pattern for suppressing magnetic field leakage 5: Shield part Lp: Length from the bottom of the power transmission section to the top of the surrounding wall. Le: Protrusion length of the shielding portion Lx: The shortest distance between the outer edge of the power transmission coil or magnetic member and the peripheral wall. 90: Power receiving coil

Claims

1. It comprises a power transmission unit including a power transmission coil, and a housing having a metal peripheral wall surrounding the power transmission unit, A power transmission device wherein a metal shielding portion protruding inward from the peripheral wall is integrated into the top end of the peripheral wall located on the side where the power receiving coil is arranged.

2. The power transmission unit further includes a magnetic member superimposed on the power transmission coil, The power transmission device according to claim 1, wherein the relationship between the length Lp from the bottom surface of the power transmission unit located on the side where the power receiving coil is not positioned to the top end of the peripheral wall, the protruding length Le of the shielding portion, and the shortest distance Lx between the outer peripheral end of the power transmission coil or the magnetic member and the peripheral wall is Lx < (Lp + Le).

3. The power transmission device according to claim 2, wherein the relationship between Lp, Le, Lx, and the distance H between the power transmission coil and the power receiving coil is within the range of 0.41 ≤ (Lp + Le - Lx) / H ≤ 0.

5.

4. The peripheral wall has a cover portion that is integrated with the top end and covers the power transmission unit from the top side, The shielding portion is provided in the radially outer region of the lid portion. The power transmission device according to any one of claims 1 to 3, wherein a metal pattern for suppressing magnetic field leakage is provided in the radially inner region of the lid.

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