Lead wire, non-contact power transmission device, and non-contact power supply system

Abstract

A lead wire (12) according to the present invention is characterized by comprising: a first conductor foil (12a) extending along an extending direction of the lead wire (12); a second conductor foil (12b) extending side-by-side with the first conductor foil (12a) along the extending direction of the lead wire (12); and an insulator (12c) disposed between the first conductor foil (12a) and the second conductor foil (12b).

Description

Lead wire, non-contact power transmission device and non-contact power supply system

[0001] The present invention relates to a lead wire, a contactless power transmission device having the lead wire, and a contactless power supply system having the contactless power transmission device.

[0002] Conventionally, contactless power transfer has been known. In contactless power transfer, a coil on a power receiving side generates electric power by the action of a coil on a power transmitting side. A battery is connected to the coil on the power receiving side, and electric power is stored in the battery. Patent Document 1 discloses a power transfer coil unit (contactless power transfer device) used in contactless power transfer.

[0003] JP 2014-233107 A

[0004] In a contactless power transfer device such as that described in Patent Document 1, a lead wire (power cable) is used to transmit power from an AC power source (high-frequency power source) to a coil. To reduce AC resistance, a litz wire, which is made by twisting multiple thin enameled wires, is often used as the lead wire. Because the enameled wires that make up the litz wire are thin, they can suppress an increase in conductor resistance due to the skin effect when AC current is passed through them. Furthermore, because the litz wire is made up of multiple twisted enameled wires, they can suppress an increase in conductor resistance due to the proximity effect.

[0005] The above-mentioned litz wire is manufactured, for example, using polyurethane copper wire (enameled wire), which is a conductor wire with a diameter of 0.1 mm coated with polyurethane, as follows: First, multiple enameled wires are twisted together. Next, the twisted wires are twisted in multiple stages to obtain the litz wire. As described above, multiple twisting steps are required to obtain litz wire suitable for lead wire, resulting in high manufacturing costs. Furthermore, to connect the litz wire to a coil or AC power source, the enamel coating of many enameled wires must be removed, necessitating special terminal processing (for example, fusing, which generates heat with a large current).

[0006] An object of the present invention is to provide a lead wire that can suppress an increase in AC resistance and that is excellent in manufacturing cost and ease of terminal processing, a non-contact power transmission device having the lead wire, and a non-contact power supply system having the non-contact power transmission device.

[0007] According to one aspect of the present invention for solving the above problem, there is provided a lead wire, characterized in that it has: a first conductor foil extending along the extension direction of the lead wire; a second conductor foil extending alongside the first conductor foil along the extension direction of the lead wire; and an insulator arranged between the first conductor foil and the second conductor foil.

[0008] According to another aspect of the present invention for solving the above problem, there is provided a contactless power transmission device comprising: an AC power supply; a coil unit; and a lead wire electrically connecting the AC power supply and the coil unit, wherein the lead wire is the lead wire described above.

[0009] According to another aspect of the present invention for solving the above problem, there is provided a contactless power supply system including the contactless power transmission device described above.

[0010] According to the present invention, it is possible to provide a lead wire that can suppress an increase in AC resistance and that is excellent in manufacturing cost and ease of terminal processing, a wireless power transmission device having the lead wire, and a wireless power supply system having the wireless power transmission device.

[0011] Fig. 1A is a schematic diagram of a contactless power supply system according to an embodiment, and Fig. 1B is a schematic diagram of a contactless power transmission device. Figs. 2A and 2B are cross-sectional views of lead wires according to an embodiment. Fig. 3 is a graph showing the relationship between frequency and conductor resistance. Fig. 4 is a partially enlarged graph of the graph in Fig. 3.

[0012] A contactless power supply system, a contactless power transmission device, and a lead wire according to an embodiment of the present invention will be described below. However, the embodiment described below is merely an example, and the present invention is not limited thereto. The contactless power supply system and the contactless power transmission device of the present invention can be used, for example, to charge batteries mounted on electric vehicles, plug-in hybrid vehicles, etc. in a contactless manner. In this specification, the range of values ​​indicated by "to" includes both the upper and lower limits of the range.

[0013] [Contactless Power Supply System] Fig. 1A is a schematic diagram showing a state in which power is being contactlessly supplied to a battery 3 of an electric vehicle 2 using a contactless power supply system 1 according to the present embodiment. Fig. 1B is a schematic diagram showing the internal structure of a contactless power transmitting device 10 included in the contactless power supply system 1 shown in Fig. 1A.

[0014] 1A and 1B, a contactless power transmission device 10 includes a power source 11, lead wires 12, and a coil unit 13. In the contactless power transmission device 10, a current supplied from the power source 11 flows through the lead wires 12 and then to the coil unit 13. Due to the action of the coil unit 13 through which the current flows, a current is generated in the coil 4 for receiving power provided in the electric vehicle 2, and power is supplied contactlessly to the battery 3 provided in the electric vehicle 2.

[0015] (Contactless Power Transmission Device) The contactless power transmission device 10 included in the contactless power supply system 1 will be described below. As described above, the contactless power transmission device 10 includes the power source 11, the lead wire 12, and the coil unit 13. Here, the lead wire 12 according to this embodiment does not include a Litz wire but includes a conductor foil. Details of the lead wire 12 will be described later. Each component of the contactless power transmission device 10 will be described below.

[0016] <Power Supply> The power supply 11 is an electrical energy source for the contactless power transmission device 10. In the present embodiment, the power supply 11 is an AC power supply, and the current supplied to the circuit is AC. From the viewpoint of efficient power supply, the power supply 11 preferably supplies AC current at the resonant frequency of the contactless power supply system 1. When the contactless power transmission device 10 is used in the contactless power supply system 1 of the electric vehicle 2, the resonant frequency is generally around 85 kHz (80 kHz to 90 kHz). Therefore, the power supply 11 is preferably capable of supplying AC current of around 85 kHz (80 kHz to 90 kHz), and more preferably capable of supplying AC current of 85 kHz.

[0017] <Lead Wire> As shown in Fig. 1B, the lead wire 12 is electrically connected to the power source 11 and the coil unit 13 to form a circuit. Fig. 2A is a cross-sectional view of such a lead wire 12, specifically, a cross-sectional view taken along line A-A in Fig. 1B.

[0018] 1B and 2A, the lead wire 12 has a first conductor foil 12a, a second conductor foil 12b, and an insulator 12c disposed between the first conductor foil 12a and the second conductor foil 12b. In this embodiment, the lead wire 12 further has a sheath 12d. Each of these will be described below.

[0019] The first conductor foil 12a and the second conductor foil 12b are conductors of the lead wire 12. In this specification, "conductor foil" refers to a plate-shaped conductor. The length (length in the extension direction of the lead wire) and width (length in the direction perpendicular to the extension direction and thickness direction of the lead wire) of the conductor foil are greater than the thickness of the conductor foil. The first conductor foil 12a and the second conductor foil 12b may be made of any conductive material (conductor), such as a metal. Examples of metals include copper and copper alloys. In this embodiment, the material of the first conductor foil 12a and the second conductor foil 12b is copper. That is, the first conductor foil 12a and the second conductor foil 12b are copper foils. Furthermore, the surfaces of the first conductor foil 12a and the second conductor foil 12b are smooth.

[0020] The first conductor foil 12a and the second conductor foil 12b extend along the extension direction of the lead wire 12. The first conductor foil 12a and the second conductor foil 12b are arranged side by side so that one of their two main surfaces faces each other. Here, "main surfaces" refers to the two relatively large surfaces of the conductor foil (the front surface and the back surface). The main surfaces are surfaces that are perpendicular to the thickness direction of the conductor foil and extend in the width and length directions of the conductor foil.

[0021] The distance between the first conductor foil 12a and the second conductor foil 12b arranged side by side as described above (the distance between the two opposing principal surfaces) is preferably set so that an increase in AC resistance when an AC current is passed through them can be suppressed by the proximity effect. From this perspective, the distance between the first conductor foil 12a and the second conductor foil 12b is preferably 1.5 mm or less. On the other hand, if the distance between the first conductor foil 12a and the second conductor foil 12b is too close, the possibility of a short circuit occurring increases. From this perspective, the distance between the first conductor foil 12a and the second conductor foil 12b is preferably, for example, 0.5 mm or more.

[0022] The thicknesses of the first conductor foil 12a and the second conductor foil 12b are preferably set so as to suppress an increase in AC resistance due to the skin effect when an AC current is passed through them. The skin effect increases as the frequency of the AC current increases, resulting in increased resistance. The thicknesses of the first conductor foil 12a and the second conductor foil 12b may be set appropriately depending on the frequency of the AC current. For example, when the wireless power transmission device 10 is used to charge an electric vehicle, the power source 11 passes an AC current with a frequency of approximately 85 kHz (e.g., 80 kHz to 90 Hz), which is the resonant frequency. When a current with a frequency of approximately 85 kHz is passed through the copper foil, the skin depth is 0.227 mm. Note that the skin depth is the depth at which the current passing through the copper foil is 37% of the surface of the copper foil through which the maximum current flows. Therefore, to suppress the skin effect, the thicknesses of the first conductor foil 12a and the second conductor foil 12b are preferably set to, for example, 0.5 mm or less. On the other hand, if the foil is too thin, the cross-sectional area becomes small, making it difficult for current to flow. From this perspective, it is preferable that the thickness of each of the first conductor foil 12a and the second conductor foil 12b is, for example, 0.1 mm or more.

[0023] There are no particular limitations on the width of each of the first conductor foil 12 a and the second conductor foil 12 b. The upper limit of each of the widths of the first conductor foil 12 a and the second conductor foil 12 b is, for example, 100 mm or less, and the lower limit of each of the widths is, for example, 10 mm or more.

[0024] There are no particular limitations on the manner in which the first conductor foil 12a and the second conductor foil 12b are electrically connected to the power source 11 and the coil unit 13. For example, as shown in Fig. 1B, one end of each of the first conductor foil 12a and the second conductor foil 12b may be connected to a connection terminal of the power source 11 via a rivet 6, and the other end of each of the first conductor foil 12a and the second conductor foil 12b may be connected to a connection terminal of the coil unit 13 via a rivet 6. Alternatively, for example, holes may be drilled in the first conductor foil 12a and the second conductor foil 12b, and the first conductor foil 12a and the second conductor foil 12b may be screwed to the connection terminal.

[0025] The insulator 12c is disposed between the first conductor foil 12a and the second conductor foil 12b, and performs an insulating function to prevent a short circuit between the first conductor foil 12a and the second conductor foil 12b. There are no particular limitations on the insulator 12c as long as it can perform this function.

[0026] 2A, in this embodiment, the first conductor foil 12a, the insulator 12c, and the second conductor foil 12b are stacked in this order, so that the insulator 12c is disposed between the first conductor foil 12a and the second conductor foil 12b. The insulator 12c is plate-shaped and extends in the direction in which the lead wire 12 extends.

[0027] As shown in FIG. 2A , the width of the insulator 12c is longer than the width of the first conductor foil 12a and the width of the second conductor foil. As a result, when the three components are stacked, the insulator 12c has ends that extend beyond the first conductor foil 12a and the second conductor foil 12b in the width direction. Two more insulators 12c are stacked sandwiching the three components. The sandwiched insulator 12c is also longer in the width direction than the first conductor foil 12a and the second conductor foil 12b, and has ends that extend beyond the width direction. The ends of the two sandwiched insulators 12c are bonded to the end of the insulator 12c positioned between the first conductor foil 12a and the second conductor foil 12b. In this manner, the first conductor foil 12a and the second conductor foil 12b covered with the insulator 12c can be obtained. The method for bonding the ends of the insulators 12c is not particularly limited. Examples of bonding methods include bonding using an adhesive, heat sealing, ultrasonic welding, and the like.

[0028] The manner in which the insulator 12c is disposed between the first conductor foil 12a and the second conductor foil 12b is not limited to the example shown in Figure 2A above, and may be, for example, as shown in Figure 2B. That is, as shown in Figure 2B, the peripheries of the first conductor foil 12a and the second conductor foil 12b are each coated with the insulator 12c. Then, the first conductor foil 12a and the second conductor foil 12b coated with the insulator 12c are stacked. In this manner, the insulator 12c may be disposed between the first conductor foil 12a and the second conductor foil 12b.

[0029] The insulator 12c may be formed by extrusion molding or by attaching tape.

[0030] The material of the insulator 12c is not particularly limited as long as it can perform an insulating function. Examples of the material of the insulator 12c include resin. Examples of the resin include thermoplastic resin. Examples of the material of the insulator 12c include polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP).

[0031] The thickness of the insulator 12c disposed between the first conductor foil 12a and the second conductor foil 12b is preferably a thickness that generates a proximity effect between the first conductor foil 12a and the second conductor foil 12b. From this perspective, the thickness of the insulator 12c disposed between the first conductor foil 12a and the second conductor foil 12b is preferably 1.0 mm or less. On the other hand, if the thickness of the insulator 12c is too thin, sufficient insulating function may not be obtained. From this perspective, the thickness of the insulator 12c is preferably 0.1 mm or more.

[0032] The sheath 12d covers the first conductor foil 12a, the second conductor foil 12b, and the insulator 12c. The sheath 12d has an optional configuration and may or may not be present. In this embodiment, the lead wire 12 has the sheath 12d. The lead wire 12 covered with the sheath 12d is used as a lead cable.

[0033] The sheath 12d extends in the direction in which the lead wire 12 extends. The material of the sheath 12d is preferably insulating. Examples of the material of the sheath 12d include resin. Examples of the resin include thermoplastic resin. The material of the sheath 12d may be the same as the material of the insulator 12c.

[0034] <Coil Unit> The coil unit 13 is electrically connected to the lead wire 12. When a current is supplied to the coil unit 13 via the lead wire 12, a magnetic field is generated in the coil 13a of the coil unit 13, and the generated magnetic field acts on the coil 4 for receiving power, generating a current.

[0035] 1B, in this embodiment, the coil unit 13 includes a coil 13a, a capacitor 13b, and a housing 13c. Each of these will be described below.

[0036] The coil 13a is formed by winding a linear conductor. In this embodiment, the linear conductor is an enameled wire, and the enameled wire is wound in a plane.

[0037] The basic design of the coil 13a, such as the number of turns, may be adjusted appropriately so as to achieve a desired resonance frequency (e.g., 85 kHz) in relation to other components. In this embodiment, the coil 13a is sealed with resin within the housing 13c.

[0038] The capacitor 13b is electrically connected to the coil 13a and, together with the coil 13a, constitutes a resonant circuit of the contactless power transmission device 10, generating a resonance phenomenon. The resonant frequency of the resonant circuit is determined primarily by the inductance of the coil 13a and the capacitance of the capacitor 13b. Therefore, it is preferable to set the combined capacitance of the capacitors 13b so that the resonant frequency of the resonant circuit of the contactless power transmission device 10 approaches a desired frequency (e.g., 85 kHz). The number of capacitors 13b is not particularly limited and is set appropriately depending on the required combined capacitance, etc. In this embodiment, multiple capacitors 13b are arranged on two substrates, respectively. The substrates on which the multiple capacitors 13b are arranged are supported by a base and housed in a predetermined space within the housing 13c.

[0039] Capacitor 13b may be connected in parallel or in series to coil 13a. In the present embodiment, capacitor 13b is arranged in series with lead wire 12 and coil 13a. That is, capacitor 13b is arranged between coil 13a and each of first conductor foil 12a and second conductor foil 12b.

[0040] <Housing> The housing 13c accommodates the coil 13a and the capacitor 13b. It is preferable that the housing 13c can protect the accommodated coil 13a and the resonance capacitor 13b from the external environment. In this embodiment, the coil unit 13 is buried underground. Therefore, it is preferable that the housing 13c can protect the coil 13a and the capacitor 13b underground. Specifically, it is preferable that the housing 13c has a waterproof function. It is also preferable that the coil 13a and the capacitor 13b are sealed with resin within the housing 13c. This makes the coil 13a and the capacitor 13b less susceptible to the effects of condensation and the like. It also improves insulation performance.

[0041] The material of the housing 13c is not particularly limited as long as it can adequately protect the coil 13a and the capacitor 13b. Examples of materials for the housing 13c include polycarbonate, polypropylene, and polyphenylene sulfide (PPS). Examples of resins that seal the coil 13a and the capacitor 13b include silicone resin, epoxy resin, and urethane resin. From the viewpoint of heat resistance, silicone resin is preferred.

[0042] (Effects) The lead wire 12 according to this embodiment includes the first conductor foil 12a and the second conductor foil 12b as conductors, but does not include a litz wire. This eliminates the disadvantages of using a litz wire as a conductor, such as the need for cumbersome twisting during manufacturing and special terminal processing during connection. Furthermore, by using the first conductor foil 12a and the second conductor foil 12b, the skin effect can be reduced while utilizing the proximity effect to suppress increases in AC resistance. Furthermore, the insulator 12c can be easily removed, easily exposing the first conductor foil 12a and the second conductor foil 12b, facilitating electrical connection. Furthermore, when installed in a power supply system, the lead wire 12 can be installed as a single lead wire 12 (or a single lead cable if the sheath 12d is included), enabling terminal processing on-site.

[0043] An experiment was conducted to examine the difference in resistance to AC current between a conductor foil and a litz wire. The conductor foil was a copper foil with a thickness of 0.3 mm, a width of 50 mm, and a length of 2 m. The litz wire was a 2-m-long litz wire made by twisting together 2,000 enameled wires with a diameter of 0.1 mm. Specifically, the litz wire was obtained by twisting several wires together and then twisting them in multiple stages.

[0044] The copper foil was covered with a 0.5 mm thick resin tape to form an insulator, thereby obtaining a coated copper foil. The resin tape was made of polyethylene. The coated copper foil was folded at the center in the longitudinal direction, and two coated copper foils were overlapped so that they were in contact with each other to obtain the lead wire of Sample 1. In this lead wire of Sample 1, a 1 mm thick insulator derived from two 0.5 mm thick tapes was placed between the two copper foils (see Figure 2B). Furthermore, the coated copper foil was folded at the center in the longitudinal direction, and two coated copper foils were overlapped with a 100 mm thick polystyrene foam plate placed between the two coated copper foils to obtain the lead wire of Sample 2. In this lead wire of Sample 2, a 101 mm thick insulator derived from two 0.5 mm thick tapes and a 100 mm thick polystyrene foam plate was placed between the two copper foils.

[0045] On the other hand, for comparison, a lead wire having a litz wire was obtained as follows: The above litz wire was bent in the center in the longitudinal direction, with the distance between the two bent litz wires being 1 mm, to obtain the lead wire of Sample 3. The above litz wire was also bent in the center in the longitudinal direction, with a 100 mm thick polystyrene foam plate placed between the two bent litz wires, to obtain the lead wire of Sample 4.

[0046] A power supply was connected to both ends of the lead wires of Samples 1 to 4 obtained as described above, and the conductor resistance was measured when an AC current with a frequency of 0 to 2000 kHz was passed through them. The measurement results for conductor resistance are shown in the graph in Figure 3. As can be seen from the graph in Figure 3, the lead wires of Samples 1 and 2, which used copper foil as the conductor, had lower conductor resistance than the lead wires of Samples 3 and 4, which used lead wire as the conductor. In particular, the difference in conductor resistance between Samples 1 and 2 and Samples 3 and 4 increased as the frequency increased. This is presumably because the copper foil is thin, suppressing the skin effect, in which high-frequency current concentrates on the surface of the conductor, thereby suppressing an increase in resistance. Furthermore, it is presumed that the proximity effect is achieved because the copper foils are arranged side by side.

[0047] The graph in Figure 4 is a partially enlarged version of the graph in Figure 3, and shows the conductor resistance at frequencies of 0 to 200 kHz. As can be seen from Figure 4, Sample 2, which uses copper foil as the conductor and has a distance of 100 mm between the two copper foils, has a higher resistance at frequencies of approximately 120 kHz or less than Samples 3 and 4, which use litz wire. From this, it is thought that when using conductor foil as the conductor and passing an AC current at a frequency of 120 kHz or less, the distance between the two copper foils is preferably less than 100 mm, and more preferably 1.5 mm or less.

[0048] The lead wire, contactless power transmission device, and contactless power supply system of the present invention can be used, for example, for contactless power supply in automobiles. Furthermore, the lead wire of the present invention may be used for purposes other than contactless power supply systems, and can be used in various devices that require a power supply.

[0049] REFERENCE SIGNS LIST 1 Wireless power supply system 2 Electric vehicle 3 Battery 4, 13a Coil 6 Rivet 10 Wireless power transmission device 11 Power source 12 Lead wire 12a First conductive foil 12b Second conductive foil 12c Insulator 12d Sheath 13 Coil unit 13b Capacitor 13c Housing

Claims

1. A lead wire comprising: a first conductor foil extending in an extension direction; a second conductor foil extending alongside the first conductor foil in the extension direction; and an insulator disposed between the first conductor foil and the second conductor foil.

2. A lead wire as claimed in claim 1, characterized in that the insulator is disposed between one main surface of the first conductor foil and one main surface of the second conductor foil.

3. The lead wire according to claim 1, wherein the first conductive foil, the insulator, and the second conductive foil are laminated.

4. A lead wire according to claim 1, characterized in that the thickness of each of the first conductor foil and the second conductor foil is 0.1 mm to 0.5 mm.

5. A lead wire according to claim 1, characterized in that the distance between the first conductive foil and the second conductive foil is 0.5 mm to 1.5 mm.

6. The lead wire according to claim 1, characterized in that the conductor foil is a copper foil.

7. A contactless power transmission device comprising: an AC power supply; a coil unit; and a lead wire that electrically connects the AC power supply and the coil unit, wherein the lead wire is the lead wire described in any one of claims 1 to 6.

8. A contactless power transmission device according to claim 7, characterized in that the frequency of the AC power supply is 80 to 90 kHz.

9. A contactless power supply system comprising the contactless power transmission device according to claim 7.

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