Contactless power transmission device

Abstract

To provide a non-contact power transmission device which can suppress lowering of power transmission efficiency.SOLUTION: A non-contact power transmission device includes a pair of coil units each having a case having a cylindrical side wall and a bottom wall closing one end of the side wall, an iron core stored in the case, and a coil wound around the iron core. The side wall has an end face positioned at a side opposite to the bottom wall, in the pair of coil units, respective central axes of the side walls are positioned on the same axis, the end faces face each other at an interval in an axial direction along the central axes, and in at least one of the pair of coil units, the end face has a plurality of recesses which are aligned at an interval in a circumferential direction around the central axis.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a contactless power transmission device. [Background technology]

[0002] A contactless power transmission device is composed of, for example, a primary coil unit and a secondary coil unit. The primary and secondary coil units are arranged facing each other with a gap between them. Each of the primary and secondary coil units includes an iron core and a winding wound around the iron core. The contactless power transmission device can transmit power contactlessly between the primary and secondary coil units by using, for example, electromagnetic induction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-163273 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-149833 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-200174 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-20850 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of an embodiment of the present invention is to provide a contactless power transmission device that can suppress a decrease in power transmission efficiency. [Means for solving the problem]

[0005] According to an embodiment, a contactless power transmission device includes a case having a cylindrical side wall and a bottom wall closing one end of the side wall, and a pair of coil units each having an iron core housed in the case and a winding wound around the iron core. The side wall has an end face located opposite the bottom wall, and the pair of coil units are arranged such that the central axes of the side walls are coaxially positioned and the end faces face each other with a gap in between in an axial direction along the central axis, and in at least one of the pair of coil units, the end face is In order to adjust the area where leakage flux to the outside of the case occurs, In the circumferential direction around the central axis Unequally spaced It has a plurality of recesses arranged side by side. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic perspective view showing a contactless power transmission device according to a first embodiment. [Figure 2] FIG. 2 is a schematic perspective cross-sectional view showing the contactless power transmission device of the first embodiment. [Figure 3] FIG. 3 is a schematic perspective view showing a coil unit included in the contactless power transmission device of the first embodiment. [Figure 4] 4 is a schematic exploded perspective view of the coil unit shown in FIG. 3. FIG. [Figure 5] FIG. 5 is a schematic perspective view showing an example of a case provided in the coil unit of the first embodiment. [Figure 6] 6 is a schematic cross-sectional view of the case taken along line VI-VI in FIG. 5. FIG. [Figure 7] FIG. 7 is a schematic enlarged partial view showing a recess. [Figure 8] FIG. 8 is a schematic plan view of the case shown in FIG. [Figure 9] 9 is a schematic enlarged partial view showing part IX in FIG. 8. FIG. [Figure 10] FIG. 10 is a schematic perspective view showing another example of a case provided in the coil unit. [Figure 11] FIG. 11 is a diagram showing a comparative example of the contactless power transmission device of the first embodiment. [Figure 12]FIG. 12 is a diagram showing the analysis results of eddy current loss and the reduction rate of eddy current loss. [Figure 13] FIG. 13 is a diagram showing the analysis results of magnetic flux density in the vicinity of the first recessed portion. [Figure 14] FIG. 14 is a diagram showing the analysis results of magnetic flux density in the vicinity of the second recessed portion. [Figure 15] FIG. 15 is a diagram for explaining the relationship between eddy current loss and magnetic flux density in the first embodiment. [Figure 16] FIG. 16 is a schematic perspective view showing an example of a case provided in a coil unit in a contactless power transmission device according to the second embodiment. [Figure 17] FIG. 17 is a schematic perspective view showing another example of a case provided in the coil unit. [Figure 18] FIG. 18 is a diagram showing the analysis results of eddy current loss and the reduction rate of eddy current loss. [Figure 19] FIG. 19 is a diagram showing the analysis results of magnetic flux density in the vicinity of the first recessed portion. [Figure 20] FIG. 20 is a diagram showing the analysis results of magnetic flux density in the vicinity of the second recessed portion. [Figure 21] FIG. 21 is a schematic plan view showing an example of a case provided in a coil unit in a contactless power transmission device according to a third embodiment. [Figure 22] FIG. 22 is a diagram showing the analysis results of magnetic flux density in the vicinity of the second recessed portion. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the disclosure is merely an example, and the invention is not limited to the contents described in the following embodiments. Modifications that can be easily conceived by a person skilled in the art are naturally included in the scope of the disclosure. For clearer explanation, the size, shape, etc. of each part may be changed from the actual embodiment and shown schematically in the drawings. In each embodiment of the present invention, a rotary type contactless power transmission device is disclosed as an example of a contactless power transmission device. A contactless power transmission device may also be called a transformer, etc.

[0008] [First embodiment] Fig. 1 is a schematic perspective view showing a contactless power transmission device 1 of the first embodiment. Fig. 2 is a schematic perspective cross-sectional view showing the contactless power transmission device 1 of the first embodiment. Fig. 3 is a schematic perspective view showing a coil unit 10A included in the contactless power transmission device 1 of the first embodiment. Fig. 4 is a schematic exploded perspective view of the coil unit 10A shown in Fig. 3.

[0009] 1 and 2, the contactless power transmission device 1 includes a pair of coil units 10. The pair of coil units 10 includes a primary coil unit (hereinafter referred to as "coil unit 10A") and a secondary coil unit (hereinafter referred to as "coil unit 10B").

[0010] As an example, coil unit 10A corresponds to the power supply side, and coil unit 10B corresponds to the power receiving side. In this embodiment, for example, coil unit 10A is the fixed side provided in a fixed device, and coil unit 10B is the rotating side provided in a rotating device. Figure 3 shows coil unit 10A, which is the fixed side, as an example.

[0011] When current flows through the winding 50 (shown in FIG. 2) of the coil unit 10A, a voltage is generated in the winding 50 (shown in FIG. 2) of the coil unit 10B due to electromagnetic induction, and power is transmitted from the coil unit 10A to the coil unit 10B.

[0012] The coil units 10A and 10B are formed in an annular shape. The central axis of the coil unit 10A is coaxial with the central axis of the coil unit 10B. The central axes of the coil units 10A and 10B are collectively referred to as the central axis CX. In the following description, the extension direction of the central axis CX is defined as the axial direction X, the circumferential direction θ centered on the central axis CX, and the direction away from the central axis CX centered on the central axis CX is defined as the radial direction R. The axial direction X is a direction along the central axis CX, and the radial direction R is a direction intersecting (e.g., perpendicular to) the axial direction X.

[0013] Coil unit 10A faces coil unit 10B at a distance in the axial direction X. A gap G is formed between coil unit 10A and coil unit 10B. Coil unit 10B is provided so as to be rotatable about a central axis CX relative to coil unit 10A. Coil unit 10B has the same basic configuration as coil unit 10A. The following description will mainly focus on coil unit 10A.

[0014] 2 and 4, the coil unit 10A includes a case 20, an iron core 30 housed in the case 20, a bobbin 40, a winding 50, and a cover 60. The case 20, the iron core 30, the bobbin 40, the winding 50, and the cover 60 are arranged in this order along the axial direction X.

[0015] The case 20 is made of a metal material such as an aluminum alloy. The case 20 has a cylindrical side wall 70 centered on a central axis, and a bottom wall 21. The bottom wall 21 closes one end of the side wall 70 in the axial direction X. The central axis of the side wall 70 coincides with the central axis CX of the coil unit 10A.

[0016] The side wall 70 and the bottom wall 21 may be formed integrally or as separate members. When the side wall 70 and the bottom wall 21 are formed as separate members, the side wall 70 is connected to the bottom wall 21 by a fixing member such as an adhesive or a screw, for example.

[0017] The side wall 70 has a cylindrical first side wall 71, a cylindrical second side wall 72, and a plurality of recesses 80. In this embodiment, the first side wall 71 and the second side wall 72 are formed in a cylindrical shape. The first side wall 71 and the second side wall 72 each extend with a uniform diameter along the axial direction X. The length of the first side wall 71 in the axial direction X is approximately equal to the length of the second side wall 72 in the axial direction X.

[0018] The first side wall 71 is located on the inner side in the radial direction R, and the second side wall 72 is located on the outer side in the radial direction R. The second side wall 72 is spaced apart from the first side wall 71 in the radial direction R and surrounds the first side wall 71 from the outer side in the radial direction R.

[0019] The bottom wall 21 is formed in a disk shape centered on the central axis CX. The outer diameter of the bottom wall 21 is larger than the outer diameter of the second side wall 72, for example. A circular opening is formed in the center of the bottom wall 21 and centered on the central axis CX.

[0020] In the case 20, an annular housing portion 22 is formed by a bottom wall 21, a first side wall 71, and a second side wall 72. A hollow shaft portion 23 is formed inside the first side wall 71. The bottom wall 21 has a flange portion 24 located outward in the radial direction R from the second side wall 72.

[0021] As an example, coil unit 10A has an outer diameter of approximately 1100 mm, an inner diameter of approximately 400 mm, and a length in the axial direction X of approximately 70 mm. The length in the axial direction X of bottom wall 21 and the length in the radial direction R of first side wall 71 and second side wall 72 are approximately 10 mm. The length in the axial direction X of first side wall 71 and the length in the axial direction X of second side wall 72 are approximately 50 mm. Coil unit 10B is also the same size as coil unit 10A.

[0022] The iron core 30 is accommodated in the accommodation portion 22. The iron core 30 is made of a magnetic material such as ferrite. In the radial direction R, the iron core 30 is located between the first side wall 71 and the second side wall 72. The iron core 30 is fixed to the case 20 by, for example, an adhesive.

[0023] The iron core 30 has a cylindrical leg portion 31 centered on the central axis CX, and a bottom portion 32. The bottom portion 32 closes one end of the leg portion 31 in the axial direction X. The leg portion 31 is composed of a first leg portion 33, a second leg portion 34, and a third leg portion 35 between the first leg portion 33 and the second leg portion 34. In this embodiment, the first leg portion 33, the second leg portion 34, and the third leg portion 35 are formed in a cylindrical shape. The first leg portion 33 is located on the inner side in the radial direction R, and the second leg portion 34 is located on the outer side in the radial direction R.

[0024] The first leg 33, the second leg 34, and the third leg 35 each extend with a uniform diameter along the axial direction X. The first leg 33, the second leg 34, and the third leg 35 each have the same length in the axial direction X.

[0025] The iron core 30 has a first winding portion 36 formed by a bottom portion 32, a first leg portion 33, and a third leg portion 35, and a second winding portion 37 formed by the bottom portion 32, a second leg portion 34, and a third leg portion 35. In the example shown in Figures 2 and 4, the first winding portion 36 is larger than the second winding portion 37, but the first winding portion 36 may be smaller than the second winding portion 37, or the first winding portion 36 may be the same size as the second winding portion 37.

[0026] 2, the iron core 30 has an E-shaped cross section. The iron core 30 is provided in the housing portion 22 so as to open toward the side opposite to the bottom wall 21 in the axial direction X.

[0027] In the radial direction R, the first leg portion 33 faces the first side wall 71, and the second leg portion 34 faces the second side wall 72. In the example shown in Fig. 2, the first leg portion 33 contacts the first side wall 71, and the second leg portion 34 contacts the second side wall 72. In the axial direction X, the bottom portion 32 faces the bottom wall 21.

[0028] The bobbin 40 is made of a resin material. The bobbin 40 has a first bobbin 41 that covers the inner surface of the first winding portion 36 and a second bobbin 42 that covers the inner surface of the second winding portion 37. The winding 50 is wound around the iron core 30 in the circumferential direction θ. The winding 50 is made of a metal material such as copper or an aluminum alloy. Although not shown, for example, the winding 50 of the coil unit 10A is connected to a power supply that supplies electric power, and the winding 50 of the coil unit 10B is connected to an electrical load.

[0029] The winding 50 has a first winding 51 wound around the iron core 30 in the first winding section 36, and a second winding 52 wound around the iron core 30 in the second winding section 37. For example, the current flowing through the first winding 51 flows in the opposite direction to the current flowing through the second winding 52. In the example shown in FIG. 2, the first bobbin 41 is located between the first winding 51 and the iron core 30, and the second bobbin 42 is located between the second winding 52 and the iron core 30.

[0030] 2, the wire material forming winding 50 has a circular cross section. As an example, in coil unit 10A, the diameter of the wire material of first winding 51 is larger than the diameter of the wire material of second winding 52, and in coil unit 10B, the diameter of the wire material of first winding 51 is smaller than the diameter of the wire material of second winding 52.

[0031] From another perspective, in the axial direction X, the first winding 51 of coil unit 10A and the first winding 51 of coil unit 10B have different wire diameters, and the second winding 52 of coil unit 10A and the second winding 52 of coil unit 10B have different wire diameters.

[0032] The cover 60 prevents the winding 50, the bobbin 40, and the iron core 30 from falling out of the housing portion 22. In the example shown in FIGS. 2 and 4, the cover 60 is provided so as to overlap the side wall 70 and the housing portion 22 in the axial direction X. The cover 60 is formed of a resin material such as PPS or PEEK. The cover 60 is formed in the shape of a disk centered on the central axis CX. A circular opening centered on the central axis CX is formed in the center of the cover 60.

[0033] The outer diameter of the cover 60 is approximately equal to the outer diameter of the second side wall 72. The inner diameter of the cover 60 is approximately equal to the inner diameter of the first side wall 71. The inner diameter of the cover 60 corresponds to the diameter of the opening. The outer diameter of the cover 60 may be larger or smaller than the outer diameter of the second side wall 72. The inner diameter of the cover 60 may be larger or smaller than the inner diameter of the first side wall 71.

[0034] The length of the cover 60 in the axial direction X is, for example, approximately 2 to 3 mm. In the example shown in Fig. 2, the cover 60 has a plurality of protrusions 61 formed along an inner edge 62 and an outer edge 63, which overlap with a plurality of recesses 80.

[0035] The cover 60 is fixed to the case 20 by overlapping the multiple protrusions 61 with the multiple recesses 80. As another example, the cover 60 may be fixed to the case 20 with a fixing member such as an adhesive or screws. The number of the multiple protrusions 61 may be equal to or different from the number of the multiple recesses 80. The protrusions 61 may be formed only on the inner edge 62 side, or may be formed only on the outer edge 63 side. The cover 60 does not have to have the protrusions 61.

[0036] 2, the cover 60 of coil unit 10A and the cover 60 of coil unit 10B face each other with a gap in the axial direction X. From another perspective, a gap G is located between the cover 60 of coil unit 10A and the cover 60 of coil unit 10B. The gap between the cover 60 of coil unit 10A and the cover 60 of coil unit 10B in the axial direction X is, for example, about 2 mm.

[0037] Fig. 5 is a schematic perspective view showing an example of the case 20 included in the coil unit 10A of the first embodiment. Fig. 6 is a schematic cross-sectional view of the case 20 taken along line VI-VI in Fig. 5. Fig. 7 is a schematic partial enlarged view showing the recess 80. Fig. 8 is a schematic plan view of the case 20 shown in Fig. 5. Fig. 9 is a schematic partial enlarged view showing part IX in Fig. 8. Fig. 10 is a schematic perspective view showing another example of the case 20 included in the coil units 10A and 10B.

[0038] As described above, the case 20 has a side wall 70 composed of a first side wall 71 and a second side wall 72, and a bottom wall 21. The side wall 70 has an end face 73 located opposite the bottom wall 21. In the example shown in Fig. 2, in the axial direction X, the end face 73 is located on the same plane as the end face of the leg portion 31 of the iron core 30 located opposite the bottom portion 32. The end face 73 is a surface parallel to the radial direction R, for example.

[0039] The end surfaces 73 include a first end surface 74 included in the first side wall 71 and a second end surface 75 included in the second side wall 72. The first end surface 74 and the second end surface 75 are located on the same plane that is perpendicular to the central axis CX.

[0040] 2, in the axial direction X, the end face 73 of the coil unit 10A faces the end face 73 of the coil unit 10B with a gap therebetween. The gap between the end face 73 of the coil unit 10A and the end face 73 of the coil unit 10B in the axial direction X is, for example, about 7 mm. At the position shown in FIG. 2, the multiple recesses 80 of the coil unit 10A face the multiple recesses 80 of the coil unit 10B.

[0041] A plurality of recesses 80 are formed in the side wall 70. The recesses 80 are open toward the gap G. The recesses 80 are composed of a plurality of first recesses 81 and a plurality of second recesses 82. The first end surface 74 has a plurality of first recesses 81 arranged at intervals in the circumferential direction θ, and the second end surface 75 has a plurality of second recesses 82 arranged at intervals in the circumferential direction θ.

[0042] The first recess 81 and the second recess 82 are recessed toward the bottom wall 21 in the axial direction X. A first wall 83 is formed between adjacent first recesses 81, and a second wall 84 is formed between adjacent second recesses 82. In the radial direction R, the first recess 81 and the first wall 83 face one end side of the first leg 33, and the second recess 82 and the second wall 84 face one end side of the second leg 34.

[0043] 7 is a view of the second side wall 72 as viewed from the outside in the radial direction R. The second recess 82 has a pair of surfaces 801, 802 extending from the second end face 75 toward the bottom wall 21 in the axial direction X, and a connecting surface 803 extending in the circumferential direction θ. The surface 801 faces the surface 802 in the circumferential direction θ. The connecting surface 803 connects one ends of the pair of surfaces 801, 802 to each other. In this embodiment, the pair of surfaces 801, 802 are surfaces parallel to the axial direction X, and the connecting surface 803 is a surface parallel to the radial direction R.

[0044] In FIG. 7, the length of the pair of surfaces 801, 802 in the axial direction X is indicated as length L1, and the length of the second side wall 72 in the axial direction X is indicated as length L2. As shown in FIG. 7, length L1 is equal to or less than length L2 (L1≦L2). For example, length L1 is less than half of length L2. As another example, length L1 is less than one-fourth of length L2.

[0045] 7, the length L1 is smaller than the length of the connecting surface 803 in the circumferential direction θ. For example, the length L1 may be larger than the length of the connecting surface 803 in the circumferential direction θ.

[0046] In this embodiment, the first recess 81 is configured similarly to the second recess 82. The first recess 81 has a pair of surfaces 801, 802 extending in the axial direction X from the first end face 74 toward the bottom wall 21, and a connecting surface 803. The length in the axial direction X of the pair of surfaces 801, 802 of the first recess 81 is, for example, approximately equal to the length L1.

[0047] In this embodiment, the first recesses 81 and the second recesses 82 are arranged at equal intervals in the circumferential direction θ. Here, "arranged at equal intervals" means that the intervals between adjacent recesses 80 in the circumferential direction θ are equal. More specifically, the lengths of the first wall portions 83 in the circumferential direction θ are equal, and the lengths of the second wall portions 84 in the circumferential direction θ are equal. The lengths of the first wall portions 83 and the second wall portions 84 in the circumferential direction θ are the lengths from the surface 801 of one recess 80 to the surface 802 of another adjacent recess 80.

[0048] In this embodiment, the number of first recesses 81 is equal to the number of second recesses 82. In the example shown in Figures 5 to 9, the number of first recesses 81 and second recesses 82 is eight. The number of first recesses 81 and second recesses 82 is not limited to eight, and may be seven or less, or nine or more.

[0049] As shown in Fig. 10, for example, the number of first recesses 81 and second recesses 82 may each be 32. The first recesses 81 and second recesses 82 in Fig. 10 are configured similarly to the first recesses 81 and second recesses 82 in Fig. 5. As another example, the number of first recesses 81 and second recesses 82 may be 16 or 64.

[0050] 8, for example, the first recesses 81 and the second recesses 82 overlap with each other in the radial direction R. More specifically, the positions of the first recesses 81 and the second recesses 82 in the circumferential direction θ are equal to each other.

[0051] In this embodiment, the angle of the first recess 81 in the circumferential direction θ is different from the angle of the second recess 82 in the circumferential direction θ. Here, the angle is the angle from the surface 801 to the surface 802 in the circumferential direction θ. In Fig. 9, the angle of the first recess 81 in the circumferential direction θ is shown as angle θ1, and the angle of the second recess 82 in the circumferential direction θ is shown as angle θ2.

[0052] 9, angle θ1 is greater than angle θ2. As an example, angle θ1 is 5 degrees and angle θ2 is 2.5 degrees. Angle θ1 may be equal to angle θ2, or angle θ1 may be smaller than angle θ2.

[0053] From the perspective of the length in the circumferential direction θ, the length in the circumferential direction θ of the first recess 81 may be equal to the length in the circumferential direction θ of the second recess 82, or the length in the circumferential direction θ of the first recess 81 may be shorter or longer than the length in the circumferential direction θ of the second recess 82.

[0054] Fig. 11 is a diagram illustrating a comparative example of the contactless power transmission device 1 of the first embodiment. Fig. 11 illustrates a part of a cross section of the contactless power transmission device 100, which is the comparative example. The contactless power transmission device 100 includes a pair of coil units 10.

[0055] The pair of coil units 10 is composed of a coil unit 10A and a coil unit 10B. The coil units 10A and 10B include a case 200. In the contactless power transmission device 100, the case 200 does not have a plurality of recesses 80 formed therein.

[0056] Next, the eddy currents generated in the case will be explained using Figure 11. In Figure 11, the direction of current flow is indicated by marks S1 and S2. In the figure, mark S1 indicates the direction from the front to the back, and mark S2 indicates the direction from the back to the front.

[0057] In coil unit 10A, when a current flows through winding 50, magnetic flux penetrating case 200 generates eddy currents in case 200 that flow in the circumferential direction θ. The example shown in Fig. 11 shows eddy currents generated on the first end face 74 side of first side wall 71 and on the second end face 75 side of second side wall 72. The eddy current generated in first side wall 71 flows in the opposite direction to the current flowing through first winding 51, and the eddy current generated in second side wall 72 flows in the opposite direction to the current flowing through second winding 52.

[0058] In the coil unit 10B, magnetic flux penetrating the case 200 also generates eddy currents in the case 200. In the example shown in Fig. 11, eddy currents are shown flowing on the first end face 74 side of the first side wall 71 and on the second end face 75 side of the second side wall 72. In a contactless power transmission device, eddy currents can cause heat generation in the case and the like, and a decrease in the efficiency of power transmission between a pair of coil units.

[0059] Next, the analysis results of eddy current loss and leakage flux in this embodiment will be described. Fig. 12 is a diagram showing the analysis results of eddy current loss and the reduction rate of eddy current loss. The quantities in Fig. 12 correspond to the quantities of first recesses 81 and second recesses 82. The number of first recesses 81 is equal to the number of second recesses 82.

[0060] When the quantity is 0, it corresponds to the contactless power transmission device 100, which is a comparative example, described with reference to Fig. 11. When the quantity is 8, it corresponds to the contactless power transmission device 1 including the case 20 described with reference to Figs. 5 to 9, and when the quantity is 32, it corresponds to the contactless power transmission device 1 including the case 20 described with reference to Fig. 10.

[0061] The eddy current loss indicates the loss due to eddy currents generated in the case. The reduction rate is calculated based on a case where the quantity is 0, and is the reduction rate of eddy current loss for each number of first recesses 81 and second recesses 82. For each quantity, the length L1 of the pair of surfaces 801, 802 and the length in the circumferential direction θ of the connecting surface 803 in the first recesses 81 and second recesses 82 are equal.

[0062] When the quantity was 0, the eddy current loss was 1596.7 W. When the quantity was 8, the eddy current loss was 1480.8 W, a reduction rate of 7.3%. When the quantity was 16, the eddy current loss was 1309.7 W, a reduction rate of 18.0%. When the quantity was 32, the eddy current loss was 1197.7 W, a reduction rate of 25.0%. When the quantity was 64, the eddy current loss was 794.7 W, a reduction rate of 50.2%.

[0063] Fig. 13 is a diagram showing the analysis results of the magnetic flux density in the vicinity of the first recessed portion 81. Fig. 14 is a diagram showing the analysis results of the magnetic flux density in the vicinity of the second recessed portion 82. Fig. 13 shows the analysis of the magnetic flux density along the circumferential direction θ from point A (shown in Fig. 2) which is on the inside in the radial direction R of the first recessed portion 81, and Fig. 14 shows the analysis of the magnetic flux density along the circumferential direction θ from point B (shown in Fig. 2) which is on the outside in the radial direction R of the second recessed portion 82.

[0064] 12, the quantities in Figures 13 and 14 correspond to the quantities of first recesses 81 and second recesses 82. The angles in Figures 13 and 14 are angles from points A and B about the central axis CX.

[0065] In Figures 13 and 14, for example, the angle showing the maximum magnetic flux density for each quantity includes the angle at which the first recess 81 and the second recess 82 are formed in the circumferential direction θ, and the angle showing the minimum magnetic flux density for each quantity includes the angle at which the first wall portion 83 and the second wall portion 84 are formed in the circumferential direction θ.

[0066] In Figures 13 and 14, the area including the angle where the first recess 81 and the second recess 82 are formed corresponds to an area where the influence of leakage magnetic flux is large, and the area including the angle where the first wall portion 83 and the second wall portion 84 are formed corresponds to an area where the influence of leakage magnetic flux is small.

[0067] Fig. 15 is a diagram for explaining the relationship between eddy current loss and magnetic flux density in the first embodiment, showing the magnetic flux density at point A near the first recess 81 and the magnetic flux density at point B near the second recess 82.

[0068] 15, as the number of first recesses 81 and second recesses 82 increases, the eddy current loss decreases and the magnetic flux density increases. From another perspective, as the number of first recesses 81 and second recesses 82 increases, the leakage flux leaking to the outside of the case 20 increases. There is a trade-off between the reduction in eddy current loss and the increase in leakage flux.

[0069] According to the contactless power transmission device 1 of this embodiment configured as described above, the case 20 has a plurality of recesses 80. More specifically, a plurality of first recesses 81 are formed in the first end face 74 of the first side wall 71 and are spaced apart in the circumferential direction θ, and a plurality of second recesses 82 are formed in the second end face 75 of the second side wall 72 and are spaced apart in the circumferential direction θ.

[0070] The first recess 81 and the second recess 82 can block the path of eddy currents that are generated on the first end face 74 side of the first side wall 71 and the second end face 75 side of the second side wall 72. This makes it difficult for eddy currents to flow in the circumferential direction on the first end face 74 side of the first side wall 71 and the second end face 75 side of the second side wall 72 in the case 20, thereby reducing eddy current loss.

[0071] By making it difficult for eddy currents to flow, it is possible to suppress heat generation in the contactless power transmission device 1 and also to suppress a decrease in the efficiency of power transmission from the coil unit 10A to the coil unit 10B.

[0072] In this embodiment, by forming a plurality of recesses 80 in each of the side walls 70 of the coil unit 10A and the coil unit 10B, eddy current loss can be further reduced. In addition, by forming a first recess 81 and a second recess 82 in each of the first side wall 71 and the second side wall 72, eddy current loss can be further reduced. As a result, in this embodiment, the decrease in power transmission efficiency can be further suppressed.

[0073] Furthermore, the first wall portion 83 and the second wall portion 84 can prevent magnetic flux from leaking to the outside of the case 20. From another perspective, as described with reference to Figures 13 and 14, in the region including the angle at which the first wall portion 83 and the second wall portion 84 are formed, a region outside the case 20 that is less affected by leakage magnetic flux can be formed.

[0074] As a result, it is possible to suppress the influence (for example, heat generation) of leakage magnetic flux on peripheral devices provided outside the contactless power transmission device 1. The peripheral devices are, for example, metal parts such as cables.

[0075] In this embodiment, the recesses 80 are arranged at equal intervals in the circumferential direction θ. Therefore, regions that are heavily influenced by leakage magnetic flux and regions that are less influenced by leakage magnetic flux can be formed at equal intervals outside the contactless power transmission device 1. The number and size of the recesses 80 can be set appropriately, for example, based on a preset threshold value of the magnetic flux density of leakage magnetic flux outside the contactless power transmission device 1.

[0076] Next, other embodiments will be described. In the other embodiments described below, the same parts as those in the first embodiment described above will be given the same reference numerals as those in the first embodiment, and detailed descriptions thereof may be omitted or simplified.

[0077] [Second embodiment] Fig. 16 is a schematic perspective view showing an example of the case 20 included in the coil unit 10A in the contactless power transmission device 1 of the second embodiment. Fig. 17 is a schematic perspective view showing another example of the case 20 included in the coil unit 10A. The cases 20 in Figs. 16 and 17 can be applied to the coil units 10A and 10B, respectively. The contactless power transmission device 1 of the second embodiment differs from that of the first embodiment in the shape of the case 20.

[0078] 16 and 17, the number of first recesses 81 and second recesses 82 is 32. In the second embodiment, the first recesses 81 or the second recesses 82 are arranged at unequally spaced intervals in the circumferential direction θ.

[0079] In the example shown in Fig. 16, the first recesses 81 are arranged at uneven intervals in the circumferential direction θ, and the second recesses 82 are arranged at equal intervals in the circumferential direction θ. In Fig. 16, the first wall portion 83 has a first portion 85 and a second portion 86 that is longer in the circumferential direction θ than the first portion 85. The first recesses 81, the first portion 85, the first recesses 81, and the second portion 86 are arranged in this order in the circumferential direction θ. The first recesses 81 are arranged at uneven intervals in the circumferential direction θ due to the first portions 85 and the second portions 86.

[0080] For example, the length in the circumferential direction θ of the first portion 85 is smaller than the length in the circumferential direction θ of the first wall portion 83 in the case 20 described with reference to Fig. 10, and the length in the circumferential direction θ of the second portion 86 is larger than the length in the circumferential direction θ of the first wall portion 83 in the case 20 described with reference to Fig. 10. The lengths in the circumferential direction θ of the first portion 85 and the second portion 86 can be set as appropriate.

[0081] 17, the first recesses 81 are arranged at equal intervals in the circumferential direction θ, and the second recesses 82 are arranged at unequal intervals in the circumferential direction θ. In FIG. 17, the second wall portion 84 has a third portion 87 and a fourth portion 88 that is longer in the circumferential direction θ than the third portion 87. The second recesses 82, the third portion 87, the second recesses 82, and the fourth portion 88 are arranged in this order in the circumferential direction θ. The third portions 87 and the fourth portions 88 cause the second recesses 82 to be arranged at unequal intervals in the circumferential direction θ.

[0082] For example, the length in the circumferential direction θ of the third portion 87 is smaller than the length in the circumferential direction θ of the second wall portion 84 in the case 20 described with reference to Fig. 10, and the length in the circumferential direction θ of the fourth portion 88 is larger than the length in the circumferential direction θ of the second wall portion 84 in the case 20 described with reference to Fig. 10. The lengths in the circumferential direction θ of the third portion 87 and the fourth portion 88 can be set as appropriate.

[0083] Fig. 18 is a diagram showing the analysis results of eddy current loss and the reduction rate of eddy current loss. Fig. 18 shows contactless power transmission devices equipped with the cases described with reference to the respective figures. The comparative example is equipped with case 200 described with reference to Fig. 11, the first shape is equipped with case 20 described with reference to Fig. 10, the second shape is equipped with case 20 described with reference to Fig. 16, and the third shape is equipped with case 20 described with reference to Fig. 17. In the first shape, first recesses 81 and second recesses 82 are arranged at equal intervals in the circumferential direction θ.

[0084] The reduction rate of eddy current loss for each shape is calculated based on the comparative example. The number of first recesses 81 is equal to the number of second recesses 82. In each shape, the length L1 of a pair of surfaces 801, 802 and the length in the circumferential direction θ of the connecting surface 803 in the first recesses 81 and the second recesses 82 are equal.

[0085] In the comparative example, the eddy current loss was 1596.7 W. In the first shape, the eddy current loss was 1197.7 W, a reduction rate of 25.0%. In the second shape, the eddy current loss was 1193.2 W, a reduction rate of 25.3%. In the third shape, the eddy current loss was 1195.2 W, a reduction rate of 25.2%. This shows that the eddy current loss varies little depending on the shape.

[0086] Fig. 19 is a diagram showing the analysis results of the magnetic flux density in the vicinity of the first recess 81. Fig. 20 is a diagram showing the analysis results of the magnetic flux density in the vicinity of the second recess 82. Fig. 19 shows the analysis of the magnetic flux density along the circumferential direction θ on the inner side in the radial direction R of the first recess 81, and Fig. 20 shows the analysis of the magnetic flux density along the circumferential direction θ on the outer side in the radial direction R of the second recess 82. Fig. 20 shows a portion of the analysis results along the circumferential direction θ.

[0087] In Figures 19 and 20, the angle showing the maximum magnetic flux density for each shape includes the angle at which the first recess 81 and the second recess 82 are formed in the circumferential direction θ, and the angle showing the minimum magnetic flux density for each shape includes the angle at which the first wall portion 83 and the second wall portion 84 are formed in the circumferential direction θ.

[0088] In FIG. 19, the maximum magnetic flux density in the second shape is greater than the maximum magnetic flux density in the third shape, and the minimum magnetic flux density in the second shape is less than the minimum magnetic flux density in the third shape.

[0089] 20, the region in the third shape where the magnetic flux density is high is shown as region R1, and the region where the magnetic flux density is lower than region R1 is shown as region R2. Region R1 corresponds to the region where the influence of leakage magnetic flux is large, and region R2 corresponds to the region where the influence of leakage magnetic flux is small. By forming the second recesses 82 at unequal intervals in the circumferential direction θ, the size of region R1 and the size of region R2 are different in the third shape.

[0090] The angle at which the magnetic flux density is greatest in region R1 includes the angle at which the second recess 82 is formed in the circumferential direction θ. The angle at which the magnetic flux density is lowest in region R1 includes the angle at which the third portion 87 is formed in the circumferential direction θ. Region R2 includes the angle at which the fourth portion 88 is formed in the circumferential direction θ.

[0091] The second embodiment having the above-described configuration can also provide a contactless power transmission device 1 that can suppress a decrease in power transmission efficiency. In the second embodiment, by arranging the multiple recesses 80 at unequal intervals in the circumferential direction θ, it is possible to adjust the positions and sizes of the region where the influence of leakage magnetic flux to the outside of the contactless power transmission device 1 is large and the region where the influence of leakage magnetic flux is small.

[0092] For example, by arranging the second recesses 82 at uneven intervals as shown in Figure 17, the position and size of leakage magnetic flux generated radially outside the second side wall 72 can be adjusted, as explained using Figure 20.

[0093] 16 and 17, the number of recesses 80 is 32, but the number of recesses 80 is not limited to this. The first recesses 81 and the second recesses 82 may be arranged at unequal intervals in the circumferential direction θ. The position and size of leakage magnetic flux generated can be adjusted radially inward from the first side wall 71 and radially outward from the second side wall 72.

[0094] In addition, the first wall portion 83 may further have another portion whose length in the circumferential direction θ is different from that of the first portion 85 and the second portion 86, and the second wall portion 84 may further have another portion whose length in the circumferential direction θ is different from that of the third portion 87 and the fourth portion 88.

[0095] [Third embodiment] Fig. 21 is a schematic plan view showing an example of the case 20 included in the coil unit 10A in the contactless power transmission device 1 of the third embodiment. Fig. 21 shows the case 20 of the coil unit 10A, which is the fixed side.

[0096] Case 20 is formed with a portion P1 including a plurality of recesses 80 and a remaining portion P2. Portions P1 and P2 are each formed along the circumferential direction θ. In Fig. 21, the region of case 20 including portion P1 is shown as region R3, and the region of case 20 including portion P2 is shown as region R4.

[0097] 21, a metal part M, as an example of a peripheral device, is arranged in an area R4 outside the contactless power transmission device 1. From another perspective, the metal part M is arranged away from the portion P1.

[0098] In this embodiment, the size of portion P1 is approximately equal to the size of portion P2. In the example shown in Fig. 21, portions P1 and P2 are provided 180 degrees apart along the circumferential direction θ. Although not shown in Fig. 21, a plurality of first recesses 81 and a plurality of second recesses 82 are formed in portion P1. In portion P1, the plurality of first recesses 81 and the plurality of second recesses 82 may be arranged at equal intervals or at unequal intervals.

[0099] The positions and sizes of regions R3 and R4 can be adjusted depending on the positions and sizes of portions P1 and P2. For example, increasing the size of portion P1 increases region R3, and decreasing the size of portion P1 decreases region R3. The relationship between portion P2 and region R4 is similar to the relationship between portion P1 and region R3.

[0100] The positions and sizes of the portions P1 and P2 can be set as appropriate depending on the position, size, etc. of the metal part M disposed outside the contactless power transmission device 1. In the example shown in Fig. 21, by making the size of the portion P1 and the size of the portion P2 approximately equal, the size of the region R3 and the size of the region R4 become approximately equal.

[0101] Fig. 22 is a diagram showing the analysis results of the magnetic flux density in the vicinity of the second recess 82. Fig. 22 shows the analysis of the magnetic flux density on the outer side of the second recess 82 in the radial direction R along the circumferential direction θ.

[0102] 22, the angle at which the magnetic flux density is high overlaps with the angle at which portion P1 is formed in the circumferential direction θ, and the angle at which the magnetic flux density is low overlaps with the angle at which portion P2 is formed in the circumferential direction θ. Thus, region R3 including portion P1 corresponds to a region where the influence of leakage magnetic flux is large, and region R4 including portion P2 corresponds to a region where the influence of leakage magnetic flux is small.

[0103] The third embodiment having the above-described configuration can also provide a contactless power transmission device 1 that can suppress a decrease in power transmission efficiency. In the third embodiment, by forming the portion P1 and the portion P2 in the case 20, it is possible to form, outside the contactless power transmission device 1, a region R3 that is heavily influenced by leakage magnetic flux and a region R4 that is less influenced by leakage magnetic flux.

[0104] This makes it possible to suppress the influence of leakage magnetic flux on the metal part M arranged in the region R4. By forming the region R4 outside the contactless power transmission device 1 according to the position where the metal part M is arranged, it is possible to suppress, for example, heat generation in the metal part M due to the influence of leakage magnetic flux.

[0105] Furthermore, by providing portions P1 and P2 in the case 20 of the coil unit 10A, which is the fixed side, it is possible to effectively suppress the influence of leakage magnetic flux on the metal part M. Note that, although the present embodiment has been described with respect to the case 20 provided in the coil unit 10A, it is also applicable to the case 20 provided in the coil unit 10B.

[0106] As described above, according to each of the above-described embodiments, it is possible to provide a contactless power transmission device 1 that can suppress a decrease in power transmission efficiency by using the plurality of recesses 80 formed in the case 20.

[0107] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0108] In this embodiment, the coil unit 10A and the coil unit 10B each have a plurality of recesses 80, but in at least one of the pair of coil units 10, the end face 73 may have a plurality of recesses 80 arranged at intervals in the circumferential direction θ.

[0109] In this case, the end surface 73 of the side wall 70 of the coil unit 10A may have a plurality of recesses 80, or the end surface 73 of the side wall 70 of the coil unit 10B may have a plurality of recesses 80. Even in such a case, it is possible to provide a contactless power transmission device 1 that can suppress a decrease in power transmission efficiency.

[0110] In the present embodiment, the first end surface 74 of the first side wall 71 and the second side wall 72 has the first recess 81, and the second end surface 75 has the second recess 82. However, the end surface 73 of at least one of the first side wall 71 and the second side wall 72 may have a plurality of recesses 80. The number of first recesses 81 may be different from the number of second recesses 82. The number of first recesses 81 may be greater or less than the number of second recesses 82.

[0111] The recesses 80 may be formed so as to recess all the way to the bottom wall 21. The recesses 80 may have different shapes and sizes. As an example, the first recesses 81 may have different shapes, and the second recesses 82 may have different shapes. As another example, the shape of the first recesses 81 may be different from the shape of the second recesses 82.

[0112] For example, the recess 80 may have at least one curved surface among the pair of surfaces 801, 802 and the connecting surface 803. Although a rotary type contactless power transmission device has been disclosed as an example of a contactless power transmission device, the above-described embodiments can also be applied to contactless power transmission devices other than rotary types. [Explanation of symbols]

[0113] 1... non-contact power transmission device, 10... coil unit, 20... case, 21... bottom wall, 30... iron core, 50... winding, 70... side wall, 73... end surface, 80... recess.

Claims

1. a case having a cylindrical side wall and a bottom wall closing one end of the side wall, an iron core housed in the case, and a pair of coil units each having a winding wound around the iron core; The side wall has an end surface located opposite the bottom wall, The pair of coil units have the side walls with their central axes coaxially positioned, and the end faces thereof are spaced apart in an axial direction along the central axes, In at least one of the pair of coil units, the end surface has a plurality of recesses arranged at uneven intervals in a circumferential direction around the central axis in order to adjust a region in which leakage magnetic flux to the outside of the case occurs. Contactless power transmission device.

2. Each of the plurality of recesses has a pair of surfaces extending from the end surface toward the bottom wall in the axial direction, and a connecting surface connecting the pair of surfaces. The contactless power transmission device according to claim 1 .

3. the end surfaces of the pair of coil units each have the plurality of recesses; The contactless power transmission device according to claim 1 or 2.

4. The side wall includes a cylindrical first side wall and a cylindrical second side wall that is spaced apart in a radial direction intersecting the axial direction and surrounds the first side wall, the iron core is located between the first side wall and the second side wall, The end surface includes a first end surface provided on the first side wall and a second end surface provided on the second side wall, At least one of the first end surface and the second end surface has the plurality of recesses. The contactless power transmission device according to claim 1 .

5. The plurality of recesses include a plurality of first recesses formed in the first end face and arranged at intervals in the circumferential direction, and a plurality of second recesses formed in the second end face and arranged at intervals in the circumferential direction. The contactless power transmission device according to claim 4 .

6. The first recesses overlap with the second recesses in the radial direction. The contactless power transmission device according to claim 5 .

7. an angle of the first recess in the circumferential direction different from an angle of the second recess in the circumferential direction; The contactless power transmission device according to claim 5 or 6.

8. The side wall is a first portion located between two of the recesses arranged in the circumferential direction; a second portion located between two of the recesses aligned in the circumferential direction and having a length in the circumferential direction longer than that of the first portion, an area including the second portion is less affected by leakage magnetic flux to the outside of the case than an area including the first portion; The contactless power transmission device according to claim 1 .

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