JP7802566B2 - Contactless power transmission device - Google Patents

Description

An embodiment of the present invention relates to a contactless power transmission device.

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. The primary and secondary coil units each include an iron core and a winding wound around the iron core. A contactless power transmission device can transmit power contactlessly between the primary and secondary coil units by using, for example, electromagnetic induction.

Japanese Patent Application Publication No. 6-163273 JP 2015-149833 A Japanese Patent Application Laid-Open No. 2009-200174 Japanese Patent Application Laid-Open No. 2005-20850

An objective of an embodiment of the present invention is to provide a contactless power transmission device that can suppress a decrease in power transmission efficiency.

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, the pair of coil units are coaxially positioned with the central axes of the side walls, and the end faces face each other at an interval in an axial direction along the central axis, and in at least one of the pair of coil units, the end face has a plurality of recesses arranged at unequal intervals in a circumferential direction around the central axis to adjust a region where leakage magnetic flux to the outside of the case is generated .

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

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.

[First embodiment]
Fig. 1 is a schematic perspective view showing a contactless power transmission device 1 of a 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.

As shown in Figures 1 and 2, the contactless power transmission device 1 includes a pair of coil units 10. The pair of coil units 10 is composed of a primary coil unit (hereinafter referred to as "coil unit 10A") and a secondary coil unit (hereinafter referred to as "coil unit 10B").

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 installed in a fixed device, and coil unit 10B is the rotating side installed in a rotating device. Figure 3 shows coil unit 10A, which is the fixed side, as an example.

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

Coil units 10A and 10B are formed in an annular shape. The central axis of coil unit 10A is coaxial with the central axis of coil unit 10B. The central axes of coil unit 10A and coil unit 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 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.

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 rotatable about 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.

As shown in Figures 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, iron core 30, bobbin 40, winding 50, and cover 60 are arranged in this order along the axial direction X.

The case 20 is formed from 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.

The side wall 70 and the bottom wall 21 may be formed integrally or as separate members. If 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.

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.

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.

The bottom wall 21 is formed in a circular plate 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 centered on the central axis CX is formed in the center of the bottom wall 21.

The case 20 has a bottom wall 21, a first side wall 71, and a second side wall 72 that form an annular storage section 22. A hollow shaft section 23 is formed inside the first side wall 71. The bottom wall 21 has a flange section 24 that is located radially outward of the second side wall 72.

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 the bottom wall 21 and the length in the radial direction R of the first side wall 71 and the second side wall 72 are approximately 10 mm. The length in the axial direction X of the first side wall 71 and the length in the axial direction X of the second side wall 72 are approximately 50 mm. Coil unit 10B is the same size as coil unit 10A.

The iron core 30 is housed in the housing 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, for example, with an adhesive.

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 located 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.

The first leg 33, second leg 34, and third leg 35 each extend with a uniform diameter along the axial direction X. The lengths of the first leg 33, second leg 34, and third leg 35 in the axial direction X are all equal.

The iron core 30 has a first winding portion 36 formed by the bottom portion 32, the first leg portion 33, and the third leg portion 35, and a second winding portion 37 formed by the bottom portion 32, the second leg portion 34, and the 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.

In the example shown in Figure 2, the iron core 30 has an E-shaped cross section. The iron core 30 is installed in the housing 22 so that it opens toward the side opposite the bottom wall 21 in the axial direction X.

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

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 coil unit 10A is connected to a power supply that supplies power, and the winding 50 of coil unit 10B is connected to an electrical load.

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 Figure 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.

In the example shown in Figure 2, the wire forming the winding 50 has a circular cross-sectional shape. As an example, in coil unit 10A, the diameter of the wire of the first winding 51 is larger than the diameter of the wire of the second winding 52, and in coil unit 10B, the diameter of the wire of the first winding 51 is smaller than the diameter of the wire of the second winding 52.

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.

The cover 60 prevents the winding 50, bobbin 40, and iron core 30 from falling out of the housing portion 22. In the example shown in Figures 2 and 4, the cover 60 is arranged to overlap the side wall 70 and the housing portion 22 in the axial direction X. The cover 60 is made 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.

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.

The length of the cover 60 in the axial direction X is, for example, approximately 2 to 3 mm. In the example shown in Figure 2, the cover 60 has multiple protrusions 61 formed along its inner edge 62 and outer edge 63 that overlap with multiple recesses 80.

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 the same as or different from the number of the multiple recesses 80. The protrusions 61 may be formed only on the inner edge 62 side, or only on the outer edge 63 side. The cover 60 may not have any protrusions 61.

As shown in FIG. 2, the cover 60 of coil unit 10A and the cover 60 of coil unit 10B face each other at a distance 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 distance between the cover 60 of coil unit 10A and the cover 60 of coil unit 10B in the axial direction X is, for example, approximately 2 mm.

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

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 Figure 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, for example, a surface parallel to the radial direction R.

The end surface 73 includes a first end surface 74 on the first side wall 71 and a second end surface 75 on the second side wall 72. The first end surface 74 and the second end surface 75 are located on the same plane perpendicular to the central axis CX.

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

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 spaced apart in the circumferential direction θ, and the second end surface 75 has a plurality of second recesses 82 spaced apart in the circumferential direction θ.

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

Figure 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. Surface 801 faces surface 802 in the circumferential direction θ. The connecting surface 803 connects one end of the pair of surfaces 801, 802. 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.

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

As an example, length L1 is approximately 7.5 mm, and length L2 is approximately 50 mm. In the example shown in FIG. 7, length L1 is smaller than the length of connection surface 803 in the circumferential direction θ. For example, length L1 may be larger than the length of connection surface 803 in the circumferential direction θ.

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 surface 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.

In this embodiment, the first recesses 81 and the second recesses 82 are arranged at equal intervals in the circumferential direction θ. "Arranged at equal intervals" here 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 the adjacent recess 80.

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.

As shown in FIG. 10, for example, the number of first recesses 81 and second recesses 82 may be 32 each. 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.

As shown in FIG. 8 , for example, the first recesses 81 and the second recesses 82 overlap in the radial direction R. More specifically, the position of the first recesses 81 in the circumferential direction θ is equal to the position of the second recesses 82 in the circumferential direction θ.

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 surface 801 to surface 802 in the circumferential direction θ. In Figure 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.

In the example shown in FIG. 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.

In terms 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.

Figure 11 is a diagram showing a comparative example of the contactless power transmission device 1 of the first embodiment. Figure 11 shows a portion of a cross section of the contactless power transmission device 100, which is a comparative example. The contactless power transmission device 100 has a pair of coil units 10.

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

Next, we will use Figure 11 to explain the eddy currents that occur in the case. 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.

In coil unit 10A, when 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 Figure 11 shows eddy currents generated on the first end face 74 side of first side wall 71 and 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.

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

Next, the analysis results of eddy current loss and leakage flux in this embodiment will be described. Figure 12 shows the analysis results of eddy current loss and the eddy current loss reduction rate. The quantities in Figure 12 correspond to the number of first recesses 81 and second recesses 82. The number of first recesses 81 is equal to the number of second recesses 82.

When the quantity is 0, it corresponds to the contactless power transmission device 100, which is a comparative example, described using Figure 11. When the quantity is 8, it corresponds to the contactless power transmission device 1 equipped with the case 20 described using Figures 5 to 9, and when the quantity is 32, it corresponds to the contactless power transmission device 1 equipped with the case 20 described using Figure 10.

Eddy current loss indicates the loss due to eddy currents generated in the case. The reduction rate is calculated based on a quantity of 0 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 θ of the circumferential direction of the connecting surface 803 in the first recesses 81 and second recesses 82 are equal.

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%.

Figure 13 shows the analysis results of the magnetic flux density near the first recess 81. Figure 14 shows the analysis results of the magnetic flux density near the second recess 82. Figure 13 shows an analysis of the magnetic flux density along the circumferential direction θ from point A (shown in Figure 2) radially inward from the first recess 81 in the radial direction R, while Figure 14 shows an analysis of the magnetic flux density along the circumferential direction θ from point B (shown in Figure 2) radially outward from the second recess 82 in the radial direction R.

As with Figure 12, the numbers in Figures 13 and 14 correspond to the number 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.

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.

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.

Figure 15 is a diagram illustrating the relationship between eddy current loss and magnetic flux density in the first embodiment. Figure 15 shows 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.

In Figure 15, as the number of first recesses 81 and second recesses 82 increases, eddy current loss decreases and magnetic flux density increases. From another perspective, as the number of first recesses 81 and second recesses 82 increases, the leakage magnetic flux leaking to the outside of the case 20 increases. There is a trade-off between reduced eddy current loss and increased leakage magnetic flux.

In 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 on the first end surface 74 of the first side wall 71 and spaced apart in the circumferential direction θ, and a plurality of second recesses 82 are formed on the second end surface 75 of the second side wall 72 and spaced apart in the circumferential direction θ.

The first recess 81 and the second recess 82 block the path of eddy currents that occur 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 circumferentially 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.

By making it difficult for eddy currents to flow, heat generation in the contactless power transfer device 1 can be suppressed, and a decrease in the efficiency of power transfer from coil unit 10A to coil unit 10B can be suppressed.

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

Furthermore, the first wall portion 83 and the second wall portion 84 can prevent magnetic flux from leaking outside the case 20. From another perspective, as explained using Figures 13 and 14, in the area including the angle formed by the first wall portion 83 and the second wall portion 84, an area outside the case 20 where the influence of leakage magnetic flux is small can be formed.

As a result, the effects of leakage magnetic flux (e.g., heat generation) on peripheral devices installed outside the contactless power transmission device 1 can be suppressed. Peripheral devices are, for example, metal components such as cables.

In this embodiment, the multiple recesses 80 are arranged at equal intervals in the circumferential direction θ. Therefore, areas where the influence of leakage magnetic flux is large and areas where the influence of leakage magnetic flux is small can be formed at equal intervals outside the contactless power transmission device 1. The number and size of the multiple recesses 80 can be set appropriately, for example, based on a preset threshold value for the magnetic flux density of leakage magnetic flux outside the contactless power transmission device 1.

Next, other embodiments will be described. Note that in the other embodiments described below, parts that are the same as those in the first embodiment described above will be given the same reference numerals as in the first embodiment, and detailed descriptions of these parts may be omitted or simplified.

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 Fig. 16 and Fig. 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.

In the example shown in Figures 16 and 17, the number of first recesses 81 and second recesses 82 is 32 each. In the second embodiment, the first recesses 81 or second recesses 82 are arranged at uneven intervals in the circumferential direction θ.

In the example shown in Figure 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 Figure 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, first portion 85, first recesses 81, and 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 second portions 86.

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 Figure 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 Figure 10. The lengths in the circumferential direction θ of the first portion 85 and the second portion 86 can be set as appropriate.

In the example shown in Figure 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 Figure 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. Due to the third portions 87 and the fourth portions 88, the second recesses 82 are arranged at unequal intervals in the circumferential direction θ.

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 Figure 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 Figure 10. The lengths in the circumferential direction θ of the third portion 87 and the fourth portion 88 can be set as appropriate.

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

The reduction rate of eddy current loss for each shape was calculated using the comparative example as a reference. The number of first recesses 81 is equal to the number of second recesses 82. For each shape, the length L1 of the pair of surfaces 801, 802 and the length θ of the connecting surface 803 in the circumferential direction are equal for the first recesses 81 and the second recesses 82.

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 eddy current loss varies little between shapes.

Figure 19 shows the analysis results of the magnetic flux density near the first recess 81. Figure 20 shows the analysis results of the magnetic flux density near the second recess 82. Figure 19 shows an analysis of the magnetic flux density along the circumferential direction θ radially inward from the first recess 81, while Figure 20 shows an analysis of the magnetic flux density along the circumferential direction θ radially outward from the second recess 82. Figure 20 shows a portion of the analysis results along the circumferential direction θ.

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

In Figure 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.

In Figure 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.

The angle showing the maximum magnetic flux density in region R1 includes the angle in the circumferential direction θ at which the second recess 82 is formed. The angle showing the minimum magnetic flux density in region R1 includes the angle in the circumferential direction θ at which the third portion 87 is formed. Region R2 includes the angle in the circumferential direction θ at which the fourth portion 88 is formed.

The second embodiment with the above-described configuration also provides a contactless power transmission device 1 that can suppress a decrease in power transmission efficiency. In the second embodiment, by arranging multiple recesses 80 at uneven intervals in the circumferential direction θ, it is possible to adjust the position and size of areas where the influence of leakage magnetic flux to the outside of the contactless power transmission device 1 is large and areas where the influence of leakage magnetic flux is small.

For example, by arranging the second recesses 82 at uneven intervals as shown in Figure 17, it is possible to adjust the position and size of leakage magnetic flux generated radially outside the second side wall 72 in the radial direction R, as explained using Figure 20.

Note that while the number of recesses 80 in Figures 16 and 17 is 32, 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 can be adjusted radially inward from the first side wall 71 and radially outward from the second side wall 72.

The first wall portion 83 may further include another portion whose length in the circumferential direction θ differs from the first portion 85 and the second portion 86, and the second wall portion 84 may further include another portion whose length in the circumferential direction θ differs from the third portion 87 and the fourth portion 88.

[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.

The case 20 is formed with a portion P1 including multiple recesses 80 and a remaining portion P2. Portions P1 and P2 are each formed along the circumferential direction θ. In Figure 21, the region of the case 20 including portion P1 is shown as region R3, and the region of the case 20 including portion P2 is shown as region R4.

In the example shown in FIG. 21, a metal part M, an example of a peripheral device, is arranged in region R4 outside the contactless power transmission device 1. From another perspective, the metal part M is arranged away from portion P1.

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 arranged 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 second recesses 82 may be arranged at equal intervals or at unequal intervals.

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

The positions and sizes of portions P1 and P2 can be set appropriately depending on the position and size of the metal component M placed outside the contactless power transmission device 1. In the example shown in FIG. 21, by making the sizes of portions P1 and P2 approximately equal, the sizes of regions R3 and R4 become approximately equal.

Figure 22 shows the analysis results of the magnetic flux density near the second recess 82. Figure 22 shows the magnetic flux density outside the second recess 82 in the radial direction R, analyzed along the circumferential direction θ.

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

The third embodiment, configured as described above, also provides a contactless power transmission device 1 that can suppress a decrease in power transmission efficiency. In the third embodiment, by forming portions P1 and P2 on the case 20, it is possible to form a region R3 outside the contactless power transmission device 1 that is heavily influenced by leakage magnetic flux and a region R4 that is less influenced by leakage magnetic flux.

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

Furthermore, by providing portions P1 and P2 in the case 20 of coil unit 10A, which is the fixed side, the effect of leakage magnetic flux on the metal part M can be effectively suppressed. Note that while this embodiment has been described with reference to the case 20 provided in coil unit 10A, it can also be applied to the case 20 provided in coil unit 10B.

As explained above, according to each of the above-described embodiments, a contactless power transmission device 1 can be provided that is capable of suppressing a decrease in power transmission efficiency by using multiple recesses 80 formed in the case 20.

While 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 a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope of the invention and its equivalents as set forth in the claims, as well as within the scope and spirit of the invention.

In this embodiment, the coil unit 10A and the coil unit 10B each have multiple recesses 80, but the end surface 73 of at least one of the pair of coil units 10 may have multiple recesses 80 spaced apart in the circumferential direction θ.

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

In this embodiment, the first end surface 74 of the first side wall 71 and the second side wall 72 has a first recess 81, and the second end surface 75 has a 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 multiple recesses 80. The number of first recesses 81 may differ 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.

The multiple 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 one 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.

For example, at least one of the pair of surfaces 801, 802 and the connecting surface 803 of the recess 80 may be curved. Note that while 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.

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 (8)

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