Power supply cable

Abstract

To provide a power supply cable allowing efficient transmission of electric power while suppressing transmission loss and heat generation in a specific high-frequency band.SOLUTION: A power supply cable is used in a high-frequency band of an HF band, and includes a plurality of conductors formed with a thickness based on a skin effect corresponding to the high-frequency band, and insulators that individually insulate and cover the plurality of conductors.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a power cable. [Background technology]

[0002] For example, a technology is known for transmitting power using litz wire, which is made by twisting together multiple thin conductors, as a power transmission cable for contactless power supply to electronic devices, electric mobility, etc. By using litz wire, high-frequency current can be passed with relatively low resistance, even when the current flows unevenly near the surface of each conductor. This makes it possible to suppress power loss and heat generation even in the high-frequency range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-080441 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as the number of required conductors increases, the manufacturing cost of Litz wire increases. Furthermore, when Litz wire is used in high-frequency bands, it is difficult to obtain the effect of increasing the surface area due to the proximity effect. Therefore, conventional techniques have room for improvement in terms of suppressing transmission loss and heat generation in the high-frequency band where the skin effect becomes a problem.

[0005] Therefore, this embodiment provides a power cable that can efficiently transmit power in a specific high frequency band region by suppressing transmission loss and heat generation. [Means for solving the problem]

[0006] The power cable of the embodiment is a power cable used in the high frequency band of the HF band, and includes a plurality of conductors formed with a thickness based on the skin effect corresponding to the high frequency band, and an insulator that insulates each of the plurality of conductors. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating an example of application of a power cable according to a first embodiment; FIG. [Figure 2] FIG. 1 is a plan view showing an example of the configuration of a power cable according to a first embodiment; [Figure 3] 3 is a cross-sectional view of the power cable according to the first embodiment taken along line X3-X3 in FIG. 2. [Figure 4] 10 is a cross-sectional view showing another example of the metal layer of the power cable according to the first embodiment. [Figure 5] FIG. 10 is a plan view showing an example of the configuration of a plurality of conductors in a power cable according to a second embodiment; [Figure 6] FIG. 10 is a cross-sectional view showing an example of the configuration of a power cable according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, several embodiments will be described with reference to the drawings. In each embodiment, substantially the same components are designated by the same reference numerals, and their description will be omitted. Furthermore, in each drawing, for the sake of convenience, the dimensions of each component may be enlarged as necessary, and the dimensional ratios between each component may not necessarily be the same as in reality.

[0009] 1 can be used to supply power from an AC power source 80, such as a high-frequency power supply, to a power transmission device 91 of a contactless power supply device 90. The contactless power supply device 90 uses magnetic coupling between the power transmission device 91 and the power receiving device 92 to transmit and receive power contactlessly to a mobile object M on which the power receiving device 92 is mounted. Note that the power cable 1 can also be used for purposes other than supplying power to the power transmission device 91.

[0010] The power cable 1 is used in the high frequency band of 3 MHz to 30 MHz, the so-called HF band, and carries high-frequency current. The power cable 1 is designed to be easily bent, for example, in the longitudinal direction. As shown in FIG. 2, the power cable 1 is provided with an input connector 2 on the primary side for connection to an AC power source 80, and an output connector 3 on the secondary side for connection to a power transmission device 91. The types of the connectors 2 and 3 can be selected as desired depending on the device to be connected.

[0011] The power cable 1 comprises a plurality of conductors 10, an insulator 20, a metal layer 30, and a plurality of resonance elements 40. The thickness of the portion of the power cable 1 comprised of the plurality of conductors 10, the insulator 20, and the metal layer 30 is set to a few millimeters or less. The plurality of conductors 10 are arranged parallel to one another along the longitudinal direction of the power cable 1. That is, the power cable 1 comprises two conductors 10 for supplying power. The currents flowing through the two conductors 10 are in opposite directions. As shown in FIG. 3, the plurality of conductors 10 overlap in the thickness direction of the power cable 1. The cross section of the conductor 10 is formed into a wide, approximately rectangular shape that is long in the short direction of the power cable 1. That is, the conductor 10 is formed so as to have a large surface area. The cross-sectional shape of the conductor 10 is not limited to a rectangular shape, and it may be formed into an elliptical shape or the like.

[0012] The conductor 10 is formed with a thickness based on the skin effect corresponding to the high frequency band in which the power cable 1 is used. In this case, the conductor 10 is formed with a thickness at least twice the skin effect corresponding to the high frequency band in which the power cable 1 is used. The skin effect refers to a phenomenon in which, when an AC current flows through the conductor 10, the current concentrates on the surface of the conductor 10, and the current becomes less likely to flow as it moves away from the surface of the conductor 10 and approaches the center of the conductor 10. The conductor 10 is formed of a highly conductive metal, such as copper foil, and has a thickness of, for example, approximately several tens to several hundreds of micrometers. When copper foil is used for the conductor 10, the conductor 10 can be formed, for example, by patterning the copper foil by etching.

[0013] The insulator 20 is made of a resin having electrical insulating properties and flexibility, such as polyimide. The insulator 20 can be made of, for example, a flexible substrate. The insulator 20 insulates each of the conductors 10. In other words, the conductors 10 face each other with the insulator 20 in between. The power cable 1 has electrical insulating properties and flexibility because the conductors 10 are integrally covered with the insulator 20.

[0014] The metal layer 30 is made of a conductive material such as copper or a copper alloy. The metal layer 30 covers the periphery of the insulator 20. In other words, the metal layer 30 is located outside the multiple conductors 10. As shown in FIG. 3, the metal layer 30 covers, for example, the entire periphery of the insulator 20. In this case, the metal layer 30 forms the outer surface of the power cable 1. Note that the periphery of the metal layer 30 of the power cable 1 may be covered with a sheath (not shown) or the like.

[0015] Furthermore, the metal layer 30 may be configured to partially cover the periphery of the insulator 20, as shown in Fig. 4. In the example of Fig. 4, the metal layer 30 includes a pair of layers 301 and 302 and a conductive portion 303. The pair of layers 301 and 302 are formed, for example, in a planar shape and are respectively arranged on the front and back sides of the power cable 1 along the longitudinal direction of the power cable 1. The conductive portion 303 is formed, for example, by a through hole, and connects the pair of layers 301 and 302 to each other.

[0016] On the primary side of the power cable 1, the metal layer 30 is connected to the outer periphery of the input connector 2. The metal layer 30 is provided over substantially the entire length of the power cable 1. In other words, the metal layer 30 is formed in an elongated shape. This allows the metal layer 30 to form a waveguide structure. Therefore, by using the elongated metal layer 30, the power cable 1 can efficiently transmit high-frequency current. Furthermore, when harmonics flow into the power cable 1 from the power transmission device 91, the metal layer 30 can attenuate the harmonics. This makes it possible to suppress external radiation of the harmonics.

[0017] As shown in Figure 2, the multiple resonance elements 40 are connected between the input connector 2 and the multiple conductors 10, respectively. The resonance elements 40 are covered with a metal layer 30. The resonance elements 40 are formed, for example, from capacitors, and form the power cable 1 as a resonance circuit. Even if the shape of the power cable 1, such as its length or width, is changed, the resonance elements 40 can suppress changes in the resonance characteristics.

[0018] Furthermore, on the secondary side of the power cable 1, the multiple conductors 10 are electrically connected to an output connector 3. Furthermore, the output connector 3 is attached to a connecting portion 51. The connecting portion 51 is made of a conductive material such as a metal. The metal layer 30 is formed to extend to the connecting portion 51.

[0019] According to the embodiment described above, the power cable 1 is used in the high frequency band of the HF band. The power cable 1 includes a plurality of conductors 10 and an insulator 20. The plurality of conductors 10 are formed with a thickness based on the skin effect corresponding to the high frequency band. The insulator 20 insulates each of the plurality of conductors 10. This makes it possible to suppress transmission loss and heat generation and transmit power efficiently in the specific high frequency band region where the skin effect becomes a problem.

[0020] Furthermore, the conductor 10 is formed to a thickness at least twice the skin effect compatible with high frequency bands, which allows for efficient power transmission while efficiently suppressing the influence of conductor loss due to the skin effect.

[0021] The power cable 1 further includes a metal layer 30 that covers the insulator 20. This ensures shielding performance that suppresses noise radiation by the metal layer 30, thereby blocking noise generation from the power cable 1. This improves the reliability of the power cable 1.

[0022] The power cable 1 also includes a resonance element 40 that forms a resonance circuit on the primary side. This allows the same resonance characteristics to be obtained even if the shape of the power cable 1 is changed. This makes it possible to prevent the transmission characteristics from changing in a specific high frequency band even when the power cable 1 is connected to the power transmission device 91 of the contactless power feeding device 90.

[0023] (Second embodiment) Next, a second embodiment will be described with reference to FIG. 5. In this second embodiment, the structure of the multiple conductors 10 differs from that of the first embodiment. In this embodiment, the multiple conductors 10 are arranged crossing each other along the extension direction, i.e., the longitudinal direction, of the power cable 1. In other words, the multiple conductors 10 are configured to be twisted together. In this embodiment, the multiple conductors 10 are configured by multiple conductor bodies 11. The multiple conductor bodies 11 are connected to each other at their longitudinal ends.

[0024] The multiple conductor bodies 11 are connected via conductive parts 12 such as through holes formed in the insulator 20, so that their arrangement alternates between the front and back sides along the longitudinal direction of the power cable 1. When viewed from the short side of the power cable 1, the magnetic fields generated in the spaces S formed between adjacent conductor bodies 11 are in opposite directions along the longitudinal direction of the power cable 1.

[0025] The second embodiment can also achieve the same effects as the first embodiment. In addition, since the magnetic fields generated between the conductors 10 are opposite in direction, the magnetic fields can cancel each other out, thereby suppressing noise generation.

[0026] (Third embodiment) Next, a third embodiment will be described with reference to FIG. 6. In this third embodiment, the arrangement of the multiple conductors 10 differs from that of the first embodiment. In this embodiment, the multiple conductors 10 are arranged side by side in the short direction of the power cable 1, with a predetermined gap between them. Intermediate members 13 are provided on both sides of the multiple conductors 10 in the short direction. The intermediate members 13 are formed, for example, from a highly conductive metal, such as copper foil. The thickness of the intermediate members 13 is set to be approximately the same as the thickness of the conductors 10.

[0027] In this embodiment, a pair of insulators 20 are provided so as to sandwich the multiple conductors 10 in the thickness direction of each conductor. That is, the pair of insulators 20 cover the front and back surfaces of the conductors 10, which are part of the outer surface of the conductors 10. Furthermore, layers 301 and 302 constituting the metal layer 30 are provided on the front and back surfaces of the pair of insulators 20, respectively. As shown in FIG. 6 , the layers 301 and 302 are connected to each other by a conductive portion 303. In this case, the conductive portion 303 extends through the intermediate member 13 in the thickness direction.

[0028] The third embodiment can also achieve the same effects as the first embodiment. Furthermore, by arranging the multiple conductors 10 side by side, the cross-sectional structure of the power cable 1 can be simplified compared to when the multiple conductors 10 are arranged in the thickness direction. This improves the manufacturability of the power cable 1.

[0029] The metal layer 30 is not limited to a configuration including the layers 301 and 302, and may be configured to cover the surfaces of the pair of insulators 20 other than the surface facing the conductor 10, thereby forming the outer surface of the power cable 1. In this case, the power cable 1 can be configured without the intermediate member 13 and the conductive portion 303.

[0030] The above-described embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0031] 1...power cable, 10...conductor, 20...insulator

Claims

1. A power cable used in the high frequency band of the HF band, a plurality of conductors formed with a thickness based on the skin effect corresponding to the high frequency band; and an insulator that insulates each of the plurality of conductors. power cable.

2. A power cable used in the high frequency band of the HF band, a plurality of conductors formed to a thickness based on the skin effect corresponding to the high frequency band and arranged side by side in a short direction of the power cable; and an insulator disposed so as to sandwich the plurality of conductors in the thickness direction of the conductors. power cable.

3. The conductor is formed to have a thickness at least twice the skin effect corresponding to the high frequency band.

3. The power cable according to claim 1 or 2.

4. Further comprising a metal layer covering the insulator.

3. The power cable according to claim 1 or 2.

5. The plurality of conductors are arranged to cross each other along the extension direction of the power cable. The power cable of claim 1 .

6. Further provided is a resonant element that forms a resonant circuit on the primary side.

3. The power cable according to claim 1 or 2.

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