Contactless power transmission device

Abstract

To provide a non-contact power transmission device which can reduce eddy current loss generated in a metallic case.SOLUTION: A non-contact power transmission device includes: a primary side configuration part having a cylindrical primary iron core, primary winding that is wound inside the primary iron core and to which power is supplied, a metal primary side case that stores the primary iron core, and a resin primary side cap that seals the primary iron core and the primary winding in the primary side case; and a secondary side configuration part having a secondary iron core, secondary winding, a secondary side case and a secondary side cap corresponding to the respective components of the primary side configuration part, wherein the primary side configuration part and the secondary side configuration part are arranged so as to face each other at a gap, and lengths of axial end faces of the cylinders of the primary side case and the secondary side case are set to be shorter than lengths of the axial end faces of the primary iron core and the secondary iron core.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an apparatus for transmitting power from a primary side to a secondary side in a contactless manner. [Background technology]

[0002] In a configuration where power is supplied to a rotating part through contact, the lifespan of the parts is shortened due to wear, and periodic maintenance and part replacement are necessary. Therefore, as in Patent Document 1, for example, a device has been devised that transmits power from the primary side to the secondary side in a non-contact manner by configuring the transformer as a rotating type. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-50640 Summary of the Invention [Problem to be solved by the invention]

[0004] An example of the configuration of the above-described device will be described with reference to Figs. 19 to 24. Fig. 19 is a perspective view of rotary transformer 1. Rotary transformer 1 is an axial gap type and is composed of primary side component 10 and secondary side component 30. Primary side component 10 is the fixed side, and secondary side component 30 is the rotating side. Fig. 20 is a perspective view of primary side component 10, and Fig. 21 is an exploded perspective view of primary side component 10.

[0005] The primary side component 10 includes a case 11, a core 12 which is a primary iron core, a bobbin 13, a coil 14, and a cap 15. The case 11 is a hollow, disk-shaped metal, such as aluminum, with an inner wall 16 and an outer wall 17 extending from the inner and outer periphery of the disk, respectively. The core 12 is a hollow, disk-shaped or short cylinder made of ferrite. A partition wall 18 extends between the inner and outer periphery of the core 12, with the inner side of the partition wall 18 forming an inner coil housing section 19 and the outer side forming an outer coil housing section 20.

[0006] The bobbin 13 is made of resin, and is placed in the core 12 with the coil 14 wound around the bobbin 13. The coil 14 includes an inner coil 21 and an outer coil 22, with the inner coil 21 housed in the inner coil housing portion 19 of the core 12 and the outer coil 22 housed in the outer coil housing portion 19. The cap 15 is made of resin and has a hollow disk shape, and seals the case 11, which houses the core 12 together with the coil 14, from above in the figure.

[0007] 22 is a perspective view showing a vertical cross-sectional side of rotary transformer 1. Secondary side component 30 has a configuration that is approximately symmetrical to primary side component 10, and components corresponding to primary side component 10 are assigned reference numerals in the 30 to 40 range. Note that the conductor wire of primary side inner coil 21 has a larger diameter than the conductor wire of outer coil 22, but the conductor wire of secondary side inner coil 41 has a smaller diameter than the conductor wire of outer coil 42.

[0008] 23 is a circuit diagram of a rotary transformer 1. The inner coil 21 and outer coil 22 of the primary side component 10 are connected in parallel to an AC power supply P. The inner coil 41 and outer coil 42 of the secondary side component 30 are connected to load resistors 43 and 44, respectively. The inner coil 21 and outer coil 22 may also be connected in series to the AC power supply P.

[0009] In rotary transformer 1 configured as described above, an analysis of eddy current loss density was performed when AC current was passed through primary side component 10 to transmit power to the secondary side and then supplied from secondary side component 30. FIG. 24 shows the dimensions of rotary transformer 1 analyzed. The frequency of the current passed through primary side component 10 was 10 kHz, with a current value of 20 A on the low current side and 100 A on the high current side. As a result, it was found that eddy current loss was concentrated near the gap between primary side component 10 and secondary side component 30 on outer walls 17 and 37 of primary side case 11 and secondary side case 31, as shown in FIG. 25. Therefore, a contactless power transmission device capable of reducing eddy current loss occurring in a metal case is provided. [Means for solving the problem]

[0010] The contactless power transmission device of the embodiment includes a cylindrical primary core, a primary winding wound inside the primary core and supplied with power; a metal primary case that accommodates the primary core; a primary-side component including a resin primary-side cap that seals the primary core and the primary winding within the primary-side case; a secondary-side component part having a secondary core, a secondary winding, a secondary-side case, and a secondary-side cap corresponding to each component of the primary-side component part, In a wireless power transmission device in which the primary side component and the secondary side component are arranged opposite each other with a gap therebetween, The lengths of the axial end faces of the cylinders of the primary case and the secondary case are set shorter than the lengths of the coaxial end faces of the primary core and the secondary core, respectively. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing a vertical cross-sectional side of a rotary transformer according to a first embodiment. [Figure 2] FIG. 1 is a perspective view showing a longitudinal section of a rotary transformer having a conventional configuration. [Figure 3]FIG. 1 is a diagram showing a state in which eddy current loss occurs in the rotary transformer of the first embodiment. [Figure 4] A diagram showing the occurrence of eddy current loss in a conventional rotary transformer. [Figure 5] Diagram showing the flow of magnetic flux in the longitudinal section of a rotary transformer [Figure 6] A diagram showing the difference in the axial length of the outer wall of the primary case, which is shorter than the axial length of the outer wall of the core, by changing the difference in the axial length. [Figure 7] FIG. 1 shows the state of eddy current loss when the above difference dimension is changed. [Figure 8] A graph showing the results shown in Figure 7. [Figure 9] A diagram showing the temperature of each part measured at an outside temperature of 25°C according to each difference dimension. [Figure 10] Diagram showing the state when the radial width of the core is changed from the standard to 1 / 2 and 3 / 2 times the standard. [Figure 11] 11 is a diagram showing the occurrence of eddy current loss when the size of the difference is changed for each state shown in FIG. [Figure 12] A graph showing the results shown in Figure 11. [Figure 13] Diagram showing the state when the radial width of the case is changed from the standard to 1 / 2 and 3 / 2 times the standard. [Figure 14] 14 is a diagram showing the state of eddy current loss when the size of the difference is changed for each state shown in FIG. [Figure 15] A graph showing the results shown in Figure 14 [Figure 16] Diagram showing the state when the axial width of the case is changed from the standard to 1 / 2 and 3 / 2 times the standard. [Figure 17] 17 is a diagram showing the state of eddy current loss when the size of the difference is changed for each state shown in FIG. [Figure 18] A graph showing the results shown in Figure 17. [Figure 19] Perspective view of a conventional rotary transformer [Figure 20] Perspective view of the primary side components [Figure 21] Exploded perspective view of the primary side components [Figure 22] A perspective view showing a vertical cross-sectional side view of a rotary transformer [Figure 23] Diagram showing the circuit configuration of a rotary transformer [Figure 24] Diagram showing the dimensions of the rotary transformer used for analysis [Figure 25] Diagram showing the occurrence of eddy current loss DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment will be described below with reference to FIGS. 1 to 18. As shown in FIG. 1, a rotary transformer 1A, which is a contactless power transmission device of this embodiment, differs from a conventional rotary transformer 1 in the shapes of its primary and secondary cases and primary and secondary caps. As shown enlarged in FIG. 2, in rotary transformer 1, the axial length of outer wall 17 of primary case 11 coincides with the axial length of the outer wall of core 12. The same is true for secondary case 31. The axial direction refers to the direction along the central axis of each disk, i.e., the up-and-down direction in the drawing.

[0013] In contrast, in rotary transformer 1A, the axial length of outer wall 17A of primary case 11A is shorter than the axial length of the outer wall of core 12, 5 mm shorter in the example shown in FIG. 1. Similarly, inner wall 16 is also 5 mm shorter than the axial length of the inner wall of core 12. The same is true for secondary case 37A. Comparing the eddy current losses of the two, in rotary transformer 1, as shown in FIG. 4, the total for cases 11A and 31A is 183.1 W, while in rotary transformer 1A, as shown in FIG. 3, the total for cases 11A and 31A is 55.0 W, a 70% reduction in loss. Note that caps are not shown in FIGS. 1 to 4.

[0014] As shown in Figures 5 and 6, analysis was performed on cases where the difference in axial length between the outer wall 17A of the primary case 11A and the outer wall 12 was 2.5 mm, 5.0 mm, and 20.0 mm. As shown in Figures 7 and 8, eddy current loss decreased sharply when the difference was 2.5 mm and 5.0 mm. Figure 9 also shows the temperatures measured at various locations at an outside temperature of 25°C for each difference in axial length.

[0015] For ease of explanation, only the secondary cap 35A is shown in Fig. 6. As the axial length of the outer wall 37A of the secondary case 31A becomes shorter, the end of the secondary cap 35A is bent in the axial direction to prevent the end of the core 32 from being exposed. This is also true for the primary cap 15A.

[0016] The following Figures 10 to 12, 13 to 15, and 16 to 18 show the results of analyzing eddy current loss when the radial width of cores 12 and 32, the radial width of cases 11A and 31A, and the axial length of cases 11A and 31A are changed, respectively. The "distances" in Figures 11, 14, and 17 correspond to the above-mentioned difference dimensions.

[0017] As shown in Figures 10 to 12, when the radial width of the core is changed from the standard to 1 / 2 or 3 / 2 times that standard, the rate of loss reduction becomes small when the difference in dimension is about 7.5 mm. The same tendency is observed when the radial width of the case is changed from the standard to 1 / 2 or 3 / 2 times that standard, as shown in Figures 13 to 15, and when the axial width of the case is changed from the standard 40 mm to 20 mm (1 / 2 times that standard) or 60 mm (3 / 2 times that standard), as shown in Figures 16 to 18.

[0018] These results show that, regardless of the axial length of cases 11A and 31A, eddy current loss can be reduced by approximately 80% by setting the difference to 7.5 mm or more. However, the larger the difference, the greater the radial leakage magnetic field. Therefore, the difference can be set appropriately depending on the environment in which rotary transformer 1A is used, as long as it does not affect the operation of surrounding electronic devices, etc.

[0019] As described above, according to this embodiment, rotary transformer 1A comprises primary side component 10A having primary side core 12, winding 14 wound inside core 12 and supplied with power, metal primary side case 11A that houses core 12, and resin primary side cap 15A that seals core 12 and winding 14 within primary side case 11A, and secondary side component 30A having secondary side core 32, winding 34, secondary side case 31A, and secondary side cap 35A that correspond to the respective components of primary side component 10A.

[0020] Rotary transformer 1A is configured by arranging primary side component 10A and secondary side component 30A opposite each other with a gap between them. The lengths of the axial end faces of primary side case 11A and secondary side case 30A are set shorter than the lengths of the coaxial end faces of cores 12 and 32, respectively. This prevents magnetic flux from concentrating and reduces eddy current loss. Setting the difference in the lengths of the axial end faces to 7.5 mm or more further reduces eddy current loss.

[0021] Furthermore, bobbins 13 and 33 are disposed between core 12 and winding 14, and between core 32 and winding 34, respectively, thereby further improving the insulation of windings 14 and 34. Furthermore, the ends of primary cap 15A and secondary cap 35A are shaped to cover the exposed end faces of cores 12 and 32, respectively, thereby preventing foreign matter from entering the gaps.

[0022] Furthermore, by configuring the secondary side component 30A to rotate relative to the fixed side primary side component 10A around the central axis of the cylindrical core 12, power can be transmitted to the rotating side secondary side component 30A in a non-contact manner.

[0023] In addition, the primary winding 14 supplies power to an inner coil 21 and an outer coil 22 that are divided into two parts by the core 12 inside the core 12, and the secondary winding 34 similarly has an inner coil 41 and an outer coil 42 that are divided into two parts by the core 32, so that output can be supplied to two loads simultaneously.

[0024] (Other embodiments) The difference does not necessarily have to be set to 7.5 mm or more. The frequency and current value of the AC current flowing through the primary winding may be changed as appropriate. The bobbins may be arranged as needed. Three or more sets of primary and secondary coils may be provided. The secondary component does not necessarily have to be the rotating component. The application of the contactless power supply device is not limited to rotary radar.

[0025] 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 novel 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, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0026] In the drawings, 1A indicates a rotary transformer, 10A indicates a primary component, 11A indicates a primary case, 12 indicates a primary core, 15A indicates a primary cap, 17A indicates an outer wall, 30A indicates a secondary component, 31A indicates a secondary case, 32 indicates a secondary core, and 35A indicates a secondary cap.

Claims

1. a cylindrical primary core; a primary winding wound inside the primary core and supplied with power; a metal primary case that accommodates the primary core; a primary-side component including a resin primary-side cap that seals the primary core and the primary winding within the primary-side case; a secondary-side component part having a secondary core, a secondary winding, a secondary-side case, and a secondary-side cap corresponding to each component of the primary-side component part, In a wireless power transmission device in which the primary side component and the secondary side component are arranged opposite each other with a gap therebetween, A contactless power transmission device in which the length of the axial end faces of the cylinders of the primary case and the secondary case is set shorter than the length of the coaxial end faces of the primary iron core and the secondary iron core, respectively.

2. 2. A contactless power transmission device as described in claim 1, wherein the difference in length between the axial end faces of the primary iron core and the primary side case and the difference in length between the axial end faces of the secondary iron core and the secondary side case are set to 7.5 mm or more.

3. 3. The contactless power transmission device according to claim 1, further comprising a primary side bobbin and a secondary side bobbin made of resin, respectively, between the primary core and the primary winding and between the secondary core and the secondary winding.

4. 4. A contactless power transmission device according to claim 1, wherein the end shapes of the primary side cap and the secondary side cap are formed so as to cover the portions of the coaxial end faces of the primary core and the secondary core that are exposed to the outside.

5. The contactless power transmission device according to claim 1 , wherein the secondary side component rotates around a central axis of the cylindrical secondary core.

6. The primary winding is supplied with power in a state where it is divided into multiple sections by the primary core inside the primary core, The contactless power transmission device according to claim 1 , wherein the secondary winding is also divided into a plurality of sections by the secondary core, and has the same number of outputs as the divided sections.

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