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, and an inner surface facing the iron core, 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 side wall has a notch surface which is connected to the end face and the inner surface, and is farther from the iron core than the inner surface.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] International Publication No. 2018 / 092192 [Patent Document 2] Japanese Patent Application Publication No. 7-7124 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-164734 [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, 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 an inner face facing the iron core, the pair of coil units each having a central axis of the side wall located coaxially and the end faces facing each other with a gap in an axial direction along the central axis, and in at least one of the pair of coil units, the side wall is connected to the end face and the inner face and is spaced apart from the iron core relative to the inner face. , to reduce losses due to eddy currents Notched surface and an outer surface connected to the end surface and located opposite the inner surface, and in a radial direction intersecting the axial direction, the length from the iron core to the notched surface is greater than the length from the notched surface to the outer surface. [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] 5 is a schematic enlarged partial view showing a V portion in FIG. 2. FIG. [Figure 6] 6 is a schematic enlarged partial view showing a portion VI in FIG. 5. FIG. [Figure 7] FIG. 7 is a schematic partial enlarged view showing a notch portion of the first side wall. [Figure 8] FIG. 8 is a schematic partial enlarged view showing another example of a case provided in the coil unit. [Figure 9] FIG. 9 is a schematic partial enlarged view showing still another example of a case provided in the coil unit. [Figure 10] FIG. 10 is a diagram showing a comparative example of the contactless power transmission device of the first embodiment. [Figure 11] 11 is a schematic enlarged partial view showing part XI in FIG. 10. FIG. [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 the magnetic flux density at point A. [Figure 14] FIG. 14 is a diagram showing the analysis results of the magnetic flux density at point B. [Figure 15] FIG. 15 is a diagram for explaining the relationship between the width of the notch and eddy current loss. [Figure 16] FIG. 16 is a diagram showing the analysis results of the magnetic flux density at point A. [Figure 17] FIG. 17 is a diagram showing the analysis results of the magnetic flux density at point B. [Figure 18] FIG. 18 is a schematic partial cross-sectional view showing a contactless power transmission device according to a second embodiment. [Figure 19] 19 is a schematic enlarged partial view showing a portion XIX in FIG. 18. FIG. [Figure 20] FIG. 20 is a diagram for explaining the relationship between the height of the extension portion and eddy current loss. [Figure 21] FIG. 21 is a diagram showing the analysis results of the magnetic flux density at point A. [Figure 22] FIG. 22 is a diagram showing the analysis results of the magnetic flux density at point B. 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 clarity of explanation, the size and shape of each part may be changed from the actual embodiment and shown schematically in the drawings.

[0008] 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 be called a transformer or the like.

[0009] [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. FIG. 5 is a schematic partial enlarged view showing a portion V in FIG. 2. FIG. 6 is a schematic partial enlarged view showing a portion VI in FIG. 5. FIG. 7 is a schematic partial enlarged view showing a notch 81 of a first side wall 71.

[0010] 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").

[0011] 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.

[0012] 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.

[0013] Coil units 10A and 10B are formed in an annular shape. The central axis of coil unit 10A is positioned coaxially with the central axis of coil unit 10B. The central axes of coil units 10A and 10B are collectively referred to as central axis CX.

[0014] In the following description, the direction in which the central axis CX extends 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 (for example, perpendicular to) the axial direction X.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] The side wall 70 has a cylindrical first side wall 71 and a cylindrical second side wall 72. In this embodiment, the first side wall 71 and the second side wall 72 are formed in a cylindrical shape. 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. 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.

[0020] The side wall 70 has an end face 73 located on the opposite side to the bottom wall 21. The end face 73 is, for example, a surface parallel to the radial direction R. The end face 73 includes a first end face 74 of the first side wall 71 and a second end face 75 of the second side wall 72. The first end face 74 and the second end face 75 are located on the same plane perpendicular to the central axis CX.

[0021] 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 approximately 7 mm. The side wall 70 further has cutout portions 81 and 82. The cutout portions 81 and 82 are formed, for example, to have a rectangular cross-sectional shape.

[0022] The notch 81 is formed on one end side of the first side wall 71 located opposite the bottom wall 21. The notch 82 is formed on one end side of the second side wall 72 located opposite the bottom wall 21.

[0023] In this embodiment, the notches 81 and 82 are each formed over the entire circumference in the circumferential direction θ. The notch 81 faces the notch 82 in the radial direction R. For example, the notches 81 and 82 are formed by cutting out a portion of the first side wall 71 and the second side wall 72 on the iron core 30 side.

[0024] 2, in the coil unit 10B as well, notches 81, 82 are formed over the entire circumference in the circumferential direction θ in the first side wall 71 and the second side wall 72. In the axial direction X, the notches 81, 82 of the coil unit 10A face the notches 81, 82 of the coil unit 10B.

[0025] 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.

[0026] In the case 20, an annular storage portion 22 is formed by a bottom wall 21, a first side wall 71, and a second side wall 72. The cutout portions 81 and 82 are connected to the storage portion 22. A hollow shaft portion 23 is formed in the case 20. The bottom wall 21 has a flange portion 24 located outward in the radial direction R from the second side wall 72.

[0027] 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 (width) 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.

[0028] 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.

[0029] 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.

[0030] 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 all have the same length in the axial direction X. 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 31 of the core 30 located opposite the bottom 32. The first leg 33 has a peripheral surface 331 facing the case 20, and the second leg 34 has a peripheral surface 341 facing the case 20.

[0031] 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 FIG. 2, 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.

[0032] 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.

[0033] 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. 5, the peripheral surface 331 contacts the first side wall 71, and the peripheral surface 341 contacts the second side wall 72. In the axial direction X, the bottom portion 32 faces the bottom wall 21. In the radial direction R, the notch 81 faces one end of the first leg portion 33, and the notch 82 faces one end of the second leg portion 34.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] From another perspective, in the axial direction X, the first winding 51 of coil unit 10A has a different wire diameter than the first winding 51 of coil unit 10B, and the second winding 52 of coil unit 10A has a different wire diameter than the second winding 52 of coil unit 10B.

[0038] 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.

[0039] 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, for example, 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.

[0040] The length of the cover 60 in the axial direction X is, for example, approximately 2 to 3 mm. As shown in Fig. 2, the cover 60 has protrusions 61 formed on the inner edge 62 side and the outer edge 63 side, which overlap with the notches 81, 82. The protrusions 61 protrude from the cover 60 in the axial direction X and are formed along the circumferential direction θ.

[0041] The cover 60 is fixed to the case 20 by overlapping the protrusions 61 with the cutout portions 81 and 82, respectively. As another example, the cover 60 may be fixed to the case 20 with a fixing member such as an adhesive or a screw. The protrusions 61 may be formed only on the inner edge 62 side, or only on the outer edge 63 side. The cover 60 does not have to have the protrusions 61.

[0042] 2, the covers 60 face each other at a distance in the axial direction X. From another perspective, a gap G is located between the covers 60. The distance between the covers 60 in the axial direction X is, for example, about 2 mm.

[0043] Next, the shape of the second side wall 72 will be described with reference to FIG. The second side wall 72 further includes an inner surface 91, an outer surface 92, a notched surface 93, and a wall portion 83. In the example shown in Figure 6, the inner surface 91 and the outer surface 92 extend from the bottom wall 21 in the axial direction X with a uniform diameter.

[0044] The inner surface 91 faces the iron core 30 in the radial direction R. The inner surface 91 contacts the circumferential surface 341 of the second leg portion 34. The outer surface 92 is connected to the second end face 75 and is located on the opposite side of the inner surface 91 in the radial direction R.

[0045] As an example, the notched surface 93 is formed around the entire circumference in the circumferential direction θ of the second side wall 72. The notched surface 93 is connected to the second end face 75 and the inner surface 91, and is farther away from the second leg 34 of the iron core 30 in the radial direction R than the inner surface 91.

[0046] The cutout surface 93 has a first surface 931 connected to the second end surface 75 and a second surface 932 connecting the first surface 931 and the inner surface 91. In the example shown in Fig. 6, the first surface 931 is a surface parallel to the axial direction X and extends parallel to the second leg portion 34. The first surface 931 faces one end side of the second leg portion 34 and is not in contact with the iron core 30.

[0047] 6, the second surface 932 is a surface parallel to the radial direction R. In the axial direction X, the second surface 932 is located closer to the bottom wall 21 than the end face of the second leg 34. From another perspective, in the axial direction X, the length from the bottom wall 21 to the second surface 932 is shorter than the length from the bottom wall 21 to the end face of the second leg 34.

[0048] As an example, the angle formed by the first surface 931 and the second surface 932 is approximately 90 degrees. The wall portion 83 is located between the notched surface 93 and the outer surface 92, and surrounds one end side of the second leg portion 34. The notched portion 82 and the wall portion 83 are arranged in this order from the central axis CX side.

[0049] In FIG. 6, the length in the radial direction R from the iron core 30 (circumferential surface 341) to the first surface 931 is shown as width W1, and the length in the radial direction R from the first surface 931 to the outer surface 92 is shown as width W2. Width W1 corresponds to the width of the cutout portion 82 in the radial direction R, and width W2 corresponds to the width of the wall portion 83 in the radial direction R. In the example shown in FIG. 6, width W1 is approximately equal to width W2. As an example, widths W1 and W2 are approximately 5 mm.

[0050] In FIG. 6, the length of the first surface 931 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. Length L1 is equal to or less than length 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. As one example, length L1 is approximately 7.5 mm, and length L2 is approximately 50 mm.

[0051] 6, the protrusion 61 of the cover 60 is positioned in the cutout portion 82. In the radial direction R, a gap may be formed between the iron core 30 and the protrusion 61, and between the protrusion 61 and the wall portion 83.

[0052] In this embodiment, the first side wall 71 is configured similarly to the second side wall 72 . As shown in FIG. 7, the first side wall 71 further includes an inner surface 94, an outer surface 95, a notched surface 96, and a wall portion 84.

[0053] The inner surface 94 and the outer surface 95 extend with a uniform diameter from the bottom wall 21 in the axial direction X. The inner surface 94 faces the iron core 30 in the radial direction R. The inner surface 94 contacts the circumferential surface 331 of the first leg portion 33. The outer surface 95 is connected to the first end face 74 and is located on the opposite side of the inner surface 94 in the radial direction R.

[0054] As an example, the cutout surface 96 is formed around the entire circumference in the circumferential direction θ of the first side wall 71. The cutout surface 96 is connected to the first end surface 74 and the inner surface 94, and is farther away from the first leg portion 33 in the radial direction R than the inner surface 94.

[0055] The cutout surface 96 has a first surface 961 connected to the first end surface 74, and a second surface 962 connecting the first surface 961 and the inner surface 94. In the example shown in Fig. 7, the first surface 961 is a surface parallel to the axial direction X and extends parallel to the first leg 33. The first surface 961 faces one end side of the first leg 33 and is not in contact with the iron core 30.

[0056] 7, the second surface 962 is a surface parallel to the radial direction R. In the axial direction X, the second surface 962 is located closer to the bottom wall 21 than the end face of the first leg 33. From another perspective, in the axial direction X, the length from the bottom wall 21 to the second surface 962 is shorter than the length from the bottom wall 21 to the end face of the first leg 33. As an example, the angle formed by the first surface 961 and the second surface 962 is approximately 90 degrees.

[0057] The wall portion 84 is located between the cutout surface 96 and the outer surface 95, and surrounds one end side of the first leg portion 33. The cutout portion 81 and the wall portion 84 are arranged in this order from the central axis CX side. The protrusion 61 of the cover 60 is located in the cutout portion 81.

[0058] The length in the radial direction R from the iron core 30 (circumferential surface 331) to the first surface 961 is, for example, approximately equal to the width W1. The length in the radial direction R from the first surface 961 to the outer surface 95 is, for example, approximately equal to the width W2.

[0059] Hereinafter, the width of the cutout portions 81, 82 will be referred to as width W1, and the width of the wall portions 83, 84 will be referred to as width W2. The cutout portions 81, 82 are formed so that the widths W1, W2 are uniform in the circumferential direction θ. The length of the first surface 961 in the axial direction X is, for example, approximately equal to the length L1.

[0060] 8 and 9 are schematic partial enlarged views showing other examples of the case 20 included in the coil units 10A and 10B. In Fig. 8 and Fig. 9, a part of the second side wall 72 is shown enlarged.

[0061] In the example shown in FIG. 8, the width W1 is smaller than the width W2 (W1 < W2). As an example, the width W1 is about 1 mm and the width W2 is about 9 mm. As another example shown in FIG. 9, the width W1 is larger than the width W2 (W2 < W1). As an example, the width W1 is about 9 mm and the width W2 is about 1 mm. Each of the above-described shapes can also be applied to the first side wall 71.

[0062] FIG. 10 is a diagram showing a comparative example of the non-contact power transmission device 1 of the first embodiment. FIG. 11 is a schematic partial enlarged view showing a portion XI in FIG. 10. In FIG. 10, a partial cross section of the non-contact power transmission device 100 which is a comparative example is shown.

[0063] The non-contact power transmission device 100 includes a pair of coil units 10. The pair of coil units 10 is composed of a coil unit 10A and a coil unit 10B. The coil units 10A and 10B each include a case 200.

[0064] In the non-contact power transmission device 100, notch portions 81 and 82 are not formed in the case 200. Therefore, the first side wall 71 and the second side wall 72 do not have notch surfaces 93 and 96. The first side wall 71 has a corner portion 801 that contacts the first leg portion 33, and the second side wall 72 has a corner portion 802 that contacts the second leg portion 34.

[0065] Next, the eddy current generated in the case will be described. When a current flows through the winding 50 of the coil unit 10A, an eddy current that flows in the circumferential direction θ is generated in the case 200 due to the magnetic flux passing through the case 200. For example, eddy currents 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. Also in the coil unit 10B, an eddy current is generated in the side wall 70 of the case 200 due to the magnetic flux passing through the case 200. In the non-contact power transmission device, the eddy current can cause heat generation of the case, a decrease in the power transmission efficiency between the pair of coil units, and the like.

[0066] Next, the analysis results of the eddy current loss and leakage flux in this embodiment will be described. Fig. 12 is a diagram showing the analysis results of the eddy current loss and the reduction rate of the eddy current loss. In Fig. 12, the comparative example Figure 10 and Figure 11 The first shape corresponds to the contactless power transmission device 100 described with reference to FIGS. 1 and 2, and the second shape corresponds to the contactless power transmission device 1 described with reference to FIGS.

[0067] The eddy current loss indicates the loss due to eddy currents generated in the case. The reduction rate was calculated by using the comparative example as a reference and calculating the reduction rate of eddy current loss in the first shape. In the comparative example, the eddy current loss was 1596.7 W. In the first shape, the eddy current loss was 553.9 W, a reduction rate of 65.3%. Thus, by forming the cutouts 81 and 82 in the first side wall 71 and the second side wall 72 so as to have the cutout surfaces 93 and 96, the eddy current loss was reduced.

[0068] Fig. 13 is a diagram showing the analysis results of the magnetic flux density at point A. Fig. 14 is a diagram showing the analysis results of the magnetic flux density at point B. Fig. 13 shows the analysis of the magnetic flux density along the circumferential direction θ from point A (shown in Fig. 2) on one end side of the first side wall 71. Fig. 14 shows the analysis of the magnetic flux density along the circumferential direction θ from point B (shown in Fig. 2) on one end side of the second side wall 72.

[0069] For example, point A is located at a position approximately 150 mm away from the central axis CX in the radial direction R, and point B is located at a position approximately 550 mm away from the central axis CX in the radial direction R. The position of point A is an example of an external position on the first side wall 71 side outside the contactless power transmission device 1, and the position of point B is an example of an external position on the second side wall side outside the contactless power transmission device 1. In Fig. 13, the magnetic flux density of the first shape is larger than that of the comparative example, and in Fig. 14, the magnetic flux density of the first shape is smaller than that of the comparative example.

[0070] Next, we will explain eddy current loss and leakage flux leaking to the outside of the contactless power transmission device when the width W1 of the cutout portions 81, 82 is different. Fig. 15 is a diagram for explaining the relationship between the width W1 of the cutout portions 81, 82 and eddy current loss. Fig. 16 is a diagram showing the analysis results of the magnetic flux density at point A. Fig. 17 is a diagram showing the analysis results of the magnetic flux density at point B.

[0071] 15 to 17, the width of the first side wall 71 and the second side wall 72 is set to 10 mm, and the width W1 of the cutout portions 81, 82 is set to between 1 and 9 mm. Figures 16 and 17 show the analysis results for each width W1 of the cutout portions 81, 82. The angles in Figures 16 and 17 are angles from points A and B about the central axis CX.

[0072] 15, as the width W1 of the cutouts 81 and 82 increases, the eddy current loss gradually decreases, and when the width W1 of the cutouts 81 and 82 exceeds 8 mm, the eddy current loss increases. In other words, when the width W1 of the cutouts 81 and 82 is 8 mm, the eddy current loss is smallest.

[0073] 16, the magnetic flux density increased as the width W1 of the notches 81 and 82 increased. From another perspective, the leakage magnetic flux leaking to the outside of the contactless power transmission device 1 increases as the width W1 of the notches 81 and 82 increases. In FIG. 17, when the width W1 of the notches 81 and 82 is in the range of 4 to 7 mm (shown by mark C in FIG. 17), the magnetic flux density is smaller than the width W1 of the other notches 81 and 82.

[0074] According to the contactless power transmission device 1 of the present embodiment configured as described above, in the side walls 70 of the case 20, the first side wall 71 has a notched surface 96 that is farther away from the first leg 33 than the inner surface 94, and the second side wall 72 has a notched surface 93 that is farther away from the second leg 34 than the inner surface 91. From another perspective, the first side wall 71 and the second side wall 72 have notched portions 81, 82 formed therein.

[0075] As explained using Figure 12, by forming cutout portions 81, 82 in the first side wall 71 and the second side wall 72 so as to have cutout surfaces 93, 96, case 20 can suppress the generation of eddy currents and reduce eddy current losses more than case 200 provided in the contactless power transmission device 100 shown in the comparative example.

[0076] From another perspective, eddy current loss can be reduced by cutting out portions of first side wall 71 and second side wall 72 of case 20 that correspond to corners 801 and 802 described with reference to FIG.

[0077] By suppressing the generation of eddy currents in this way, 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.

[0078] As in the present embodiment, the generation of eddy currents can be suppressed by forming the notches 81, 82 in the first side wall 71 and the second side wall 72 of the coil unit 10A and the coil unit 10B, respectively. As a result, in the present embodiment, the decrease in power transmission efficiency can be further suppressed.

[0079] Furthermore, by enclosing one end side of the first leg 33 and one end side of the second leg 34 with the walls 83 and 84, it is possible to suppress leakage of magnetic flux to the outside of the contactless power transmission device 1. As a result, it is possible to suppress the influence (e.g., 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.

[0080] For example, in this embodiment, when the width of the side wall 70 is 10 mm, the width W1 of the cutout portions 81, 82 can be set to 4 to 7 mm to reduce eddy current loss and reduce the influence of leakage magnetic flux outside the second side wall 72 in the radial direction R. The width W1 of the cutout portions 81, 82 can be set appropriately with respect to, for example, a preset threshold value of the magnetic flux density of leakage magnetic flux outside the contactless power transmission device 1.

[0081] 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.

[0082] [Second embodiment] Fig. 18 is a schematic partial cross-sectional view showing a contactless power transmission device 1 of the second embodiment. Fig. 19 is a schematic partial enlarged view showing part XIX in Fig. 18. Fig. 19 shows a part of the second side wall 72 side of the coil units 10A, 10B. The contactless power transmission device 1 of the second embodiment differs from the first embodiment in the shape of the case 20.

[0083] In the iron core 30, the first leg 33 has a third end face 38 located opposite the bottom 32, and the second leg 34 has a fourth end face 39 located opposite the bottom 32. In the axial direction X, the third end face 38 is located on the same plane as the fourth end face 39.

[0084] 18 , in the axial direction X, the end face 73 of the case 20 is farther from the bottom wall 21 than the third end face 38 and the fourth end face 39. More specifically, in the axial direction X, the first end face 74 is farther from the bottom wall 21 than the third end face 38, and the second end face 75 is farther from the bottom wall 21 than the fourth end face 39.

[0085] The side wall 70 is formed so that the end face 73 of the case 20 is higher than the third end face 38 and the fourth end face 39 relative to the bottom wall 21. The first end face 74 and the second end face 75 are not located on the same plane as the third end face 38 and the fourth end face. In the example shown in Figures 18 and 19, the outer diameter of the cover 60 is smaller than the outer diameter of the second side wall 72, and the inner diameter of the cover 60 is larger than the inner diameter of the first side wall 71.

[0086] In the first side wall 71, the wall portion 84 has an extending portion 841 extending in the axial direction X from the third end face 38. In the second side wall 72, the wall portion 83 has an extending portion 831 extending in the axial direction X from the fourth end face 39.

[0087] 19, the length in the axial direction X from the fourth end face 39 to the second end face 75 is shown as height H1 of the extending portion 831. In the first side wall 71, the height of the extending portion 841, which is the length in the axial direction X from the third end face 38 to the first end face 74, is approximately equal to height H1 of the extending portion 831. Hereinafter, the height of the extending portions 831, 841 will be referred to as height H1. In the example shown in FIG. 19, height H1 is approximately 3.25 mm.

[0088] Fig. 20 is a diagram for explaining the relationship between the height H1 of the extension portions 831, 841 and eddy current loss. Fig. 21 is a diagram showing the analysis results of the magnetic flux density at point A. Fig. 22 is a diagram showing the analysis results of the magnetic flux density at point B. Figs. 20 and 20 show the analysis results for each height H1 of the extension portions 831, 841.

[0089] 21 and 22 are angles centered on the central axis CX from points A and B. A height of 0 mm in Figures 20 to 22 corresponds to the shape of case 20 described in the first embodiment. The widths W1 of cutout portions 81 and 82 at each height H1 are equal.

[0090] In Fig. 20, the eddy current loss gradually increased as the height H1 increased, and gradually decreased from the height H1 of 1.5 mm. In Fig. 21, the magnetic flux density decreased as the height H1 increased.

[0091] From another perspective, as the height H1 increases, the leakage magnetic flux leaking to the outside of the contactless power transmission device 1 decreases, thereby reducing the influence of the leakage magnetic flux outside the contactless power transmission device 1. In Fig. 22, as the height H1 increases, the magnetic flux density increases. From another perspective, as the height H1 increases, the leakage magnetic flux leaking to the outside of the contactless power transmission device 1 increases.

[0092] 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. The contactless power transmission device 1 of the second embodiment can adjust the influence of leakage magnetic flux to the outside of the contactless power transmission device 1 by forming the wall portions 83, 84 so as to have the extension portions 831, 841 on the first side wall 71 and the second side wall 72.

[0093] For example, by increasing the height H1 of the extension portion 841 in the first side wall 71, it is possible to reduce eddy current loss and the influence of leakage magnetic flux in the shaft portion 23. As one example, in the case 20, the first side wall 71 may form the wall portion 84 so that the extension portion 841 is higher than the extension portion 831. As another example, in the case 20, the first side wall 71 may form the wall portion 84 so that the extension portion 841 is included, and the second side wall 72 may form the wall portion 83 so that the extension portion 831 is not included.

[0094] As described above, according to each of the above-mentioned embodiments, by forming the cutout portions 81, 82 in the side wall 70 of the case 20 so as to have the cutout surfaces 93, 96 as described above, it is possible to provide a contactless power transmission device 1 that can suppress a decrease in power transmission efficiency.

[0095] 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.

[0096] In this embodiment, the side walls 70 of the coil unit 10A and the coil unit 10B have the cutout surfaces 93, 96, respectively, but the side walls 70 of at least one of the pair of coil units 10 may have the cutout surfaces 93, 96.

[0097] In this case, the side wall 70 of the coil unit 10A may have the notched surfaces 93, 96, or the side wall 70 of the coil unit 10B may have the notched surfaces 93, 96. 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.

[0098] In this embodiment, the first side wall 71 and the second side wall 72 have been described as having a cutout surface 96, and the second side wall 72 has a cutout surface 93. However, the first side wall 71 may have a cutout surface 96 and the second side wall 72 may not have a cutout surface 93, or the second side wall 72 may have a cutout surface 93 and the first side wall 71 may not have a cutout surface 96.

[0099] In this embodiment, the notched surfaces 93, 96 are formed all around the circumference in the circumferential direction θ, but the notched surfaces 93, 96 may be formed only on a portion of the circumference in the circumferential direction θ. The notched portions 81, 82 may be recessed down to the bottom wall 21. In this case, the side wall 70 is provided with a gap between it and the iron core 30. From another perspective, the side wall 70 does not contact the iron core 30.

[0100] The shapes and sizes of the cutouts 81 and 82 may be different from each other. For example, the cutout surfaces 93 and 96 may not have the second surfaces 932 and 962. In this case, the first surface 931 connects the second end surface 75 and the inner surface 91, and the first surface 961 connects the first end surface 74 and the inner surface 94.

[0101] For example, the first surfaces 931, 961 may be inclined surfaces that incline away from the central axis CX in the direction away from the bottom wall 21 in the axial direction X. The cutout surfaces 93, 96 may be formed to include a curved surface.

[0102] The width W1 of the cutout portions 81 and 82 does not have to be uniform in the circumferential direction θ. In this embodiment, the width of the cutout portion 81 is equal to the width of the cutout portion 82, but the width of the cutout portion 81 may be different from the width of the cutout portion 82.

[0103] The width of the notches 81, 82 can be set appropriately depending on the lengths of the first side wall 71 and the second side wall 72 in the radial direction R. The width of the protrusion 61 of the cover 60 changes depending on the width W1 of the notches 81, 82.

[0104] The notches 81 and 82 may be formed to have a plurality of steps. 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 the rotary type. [Explanation of symbols]

[0105] 1... non-contact power transmission device, 10... coil unit, 20... case, 21... bottom wall, 30... iron core, 50... winding, 70... side wall, 73... end face, 91... inner face, 93... notched face, 94... inner face, 96... notched face.

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 and an inner surface facing the iron core, 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 side wall is a notched surface connected to the end surface and the inner surface and spaced apart from the iron core more than the inner surface, for reducing loss due to eddy current; an outer surface connected to the end surface and located opposite the inner surface; and In a radial direction intersecting the axial direction, a length from the iron core to the notched surface is longer than a length from the notched surface to the outer surface. Contactless power transmission device.

2. The notched surface is formed on the entire circumference of the side wall in the circumferential direction about the central axis. The contactless power transmission device according to claim 1 .

3. The side walls of the pair of coil units each have the notched surface. 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 surrounding the first side wall, the iron core is located between the first side wall and the second side wall, At least one of the first side wall and the second side wall has the notched surface. The contactless power transmission device according to claim 1 .

5. the first side wall and the second side wall each have the notched surface; The contactless power transmission device according to claim 4 .

6. In the axial direction, the end face is farther from the bottom wall than an end face of the iron core located on the opposite side from the bottom wall. The contactless power transmission device according to claim 1 .

7. The side wall further has an extension portion extending in the axial direction beyond the end face of the iron core for adjusting leakage magnetic flux to the outside of the case; The extension portion is located between the cutout surface and the outer surface. The contactless power transmission device according to claim 6 .

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