Non-contact electric power transmission device and non-contact electric power supply system

Abstract

This non-contact electric power transmission device is characterized by comprising a housing, a coil that is disposed in the housing, a resonance capacitor that is disposed in the housing and electrically connected to the coil, a cable that is disposed outside the housing and electrically connected to the coil, and a frequency adjustment capacitor that is disposed outside the housing and is electrically connected to the cable.

Description

Wireless power transmission device and wireless power supply system

[0001] The present invention relates to a contactless power transmitting device and a contactless power supply system.

[0002] Conventionally, contactless power transfer has been known as a method for supplying power to a battery mounted on an electric vehicle. In contactless power transfer, power is supplied to the battery mounted on the electric vehicle by transmitting power from a power transmitting coil unit placed underground or above ground to a power receiving coil unit mounted on the electric vehicle. Patent Document 1 discloses a power transfer coil unit (contactless power transmission device) used for contactless power transfer.

[0003] JP 2014-233107 A

[0004] A contactless power supply device such as that described in Patent Document 1 may have a power transmission-side resonant circuit that resonates with a power receiving-side resonant circuit of a power receiving device. By utilizing the resonance phenomenon using such a resonant circuit, contactless power supply can be performed efficiently.

[0005] FIG. 1A is a schematic diagram of a contactless power supply system 1 that utilizes the above-described resonance phenomenon, and FIG. 1B is a schematic diagram showing the internal structure of a contactless power transmission device 10 included in the contactless power supply system 1. As shown in FIG. 1A, the contactless power supply system 1 includes a power source 2, a contactless power transmission device 10, and a contactless power receiving device 4. As shown in FIGS. 1A and 1B, the contactless power transmission device 10 includes a cable 11, a coil 12, a resonance capacitor 13, and a housing 14. The coil 12 and the resonance capacitor 13 form a resonance circuit. The contactless power receiving device 4 also includes a resonance circuit (not shown) formed by a coil and a resonance capacitor. These two resonance circuits have the same resonance frequency (e.g., 85 kHz).

[0006] In the contactless power supply system 1, when a current (AC) is passed from the power source 2 to the resonant circuit (coil 12 and resonant capacitor 13) of the contactless power transmitting device 10, a magnetic field oscillation occurs. This magnetic field oscillation is transmitted to the resonant circuit of the contactless power receiving device 4, which resonates at the same frequency, and a current flows in the resonant circuit of the contactless power receiving device 4. In this way, power can be efficiently supplied to the battery 5 of the electric vehicle 3.

[0007] 1A, the contactless power transmission device 10 is often buried underground (for example, in a moving power supply system, etc.). When the contactless power transmission device 10 is buried underground in this way, foreign objects such as screws and bolts present in the ground that affect the electric field and magnetic field may change the resonant frequency of the resonant circuit of the contactless power transmission device 10. When the resonant frequency changes in this way, the power supply efficiency decreases.

[0008] As a countermeasure in this case, it is conceivable to adjust the resonant frequency by changing the capacitance of the resonant capacitor 13 of the contactless power transmission device 10. However, because the resonant capacitor 13 is located underground, it is difficult to adjust the resonant frequency by changing the capacitance of the resonant capacitor 13.

[0009] An object of the present invention is to provide a contactless power transmission device capable of easily adjusting the resonant frequency, and a contactless power feeding system including the contactless power transmission device.

[0010] According to one aspect of the present invention for solving the above problem, there is provided a contactless power transmission device comprising: a housing; a coil arranged within the housing; a resonance capacitor arranged within the housing and electrically connected to the coil; a cable arranged outside the housing and electrically connected to the coil; and a frequency adjustment capacitor arranged outside the housing and electrically connected to the cable.

[0011] According to one 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.

[0012] According to the present invention, it is possible to provide a contactless power transmission device capable of easily adjusting the resonant frequency, and to provide a contactless power feeding system including the contactless power transmission device.

[0013] 1A and 1B are schematic diagrams of a conventional contactless power supply system. 2A and 2B are schematic diagrams of a contactless power supply system according to an embodiment. 3 is a perspective view of a portion of a contactless power transmission device that is buried underground. 4 is an exploded perspective view of a portion of a contactless power transmission device that is buried underground. 5A and 5B are schematic diagrams of a contactless power supply system according to a comparative example.

[0014] A contactless power supply system and a contactless power transmission device 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 are devices for contactlessly charging batteries mounted on electric vehicles, plug-in hybrid vehicles, and the like, for example. In this specification, the range of values ​​indicated by "to" includes both the upper and lower limits of the range.

[0015] [Contactless Power Supply System] Fig. 2A is a schematic diagram of a contactless power supply system 1 according to an embodiment. Fig. 2B is a schematic diagram showing the internal structure of a contactless power transmission device 10 of the contactless power supply system 1 shown in Fig. 2A. Fig. 3 is a perspective view of a portion of the contactless power transmission device 10 that is buried underground. Fig. 4 is an exploded perspective view of the portion of the contactless power transmission device 10 that is buried underground.

[0016] As shown in Fig. 2A, the contactless power supply system 1 includes a power source 2, a contactless power transmitting device 10, and a contactless power receiving device 4. As shown in Fig. 2B, the contactless power transmitting device 10 includes a cable 11, a coil 12, a resonance capacitor 13, and a housing 14, and further includes a frequency adjustment capacitor 15 (see comparison between Fig. 2B and Fig. 1B).

[0017] In the contactless power transmission device 10, the frequency adjustment capacitor 15 is disposed outside the housing 14 as shown in Fig. 2B. Moreover, as shown in Figs. 2A and 2B, the frequency adjustment capacitor 15 is preferably disposed on the ground. This makes it possible to easily adjust the resonant frequency of the resonant circuit of the contactless power transmission device 10 by adjusting the capacitance of the frequency adjustment capacitor 15 on the ground (for example, by replacing it with a capacitor having a different capacitance). Each component will be described in detail below.

[0018] (Power supply) The power supply 2 supplies electrical energy to the wireless power transmission device 10. In this embodiment, the power supply 2 is an AC power supply, and the current supplied to the circuit is AC. In this embodiment, the power supply 2 is placed on the ground and is electrically connected to a cable 11 having a detachable portion for a frequency adjustment capacitor 15.

[0019] (Housing) The housing 14 accommodates the coil 12 and the resonance capacitor 13. Preferably, the housing 14 can protect the accommodated coil 12 and the resonance capacitor 13 from the external environment. In this embodiment, the housing 14 is buried underground. Therefore, the housing 14 can protect the coil 12 and the resonance capacitor 13 underground. Specifically, the housing 14 preferably has a waterproof function. Furthermore, the coil 12 and the resonance capacitor 13 are preferably sealed with resin within the housing 14. This makes the coil 12 and the resonance capacitor 13 less susceptible to the effects of condensation and the like. It also improves insulation performance. The material of the housing 14 is not particularly limited as long as it can adequately protect the coil 12 and the resonance capacitor 13. Examples of materials for the housing 14 include polycarbonate, polypropylene, and polyphenylene sulfide (PPS). Examples of resins for sealing the coil 12 and the resonance capacitor 13 include silicone resin, epoxy resin, and urethane resin. From the viewpoint of heat resistance, silicone resins are preferred.

[0020] (Coil) The coil 12 is formed by winding a linear conductor. In this embodiment, the linear conductor is a Litz wire, and the Litz wire is wound in a spiral shape on a plane. As a result, in this embodiment, the outer shape of the coil 12 is a rectangular ring shape.

[0021] The basic design of the coil 12, such as the number of turns, may be adjusted appropriately to achieve the desired resonant frequency (e.g., 85 kHz) in relation to other components. As described above, in this embodiment, the coil 12 is sealed with resin. Therefore, the line voltage around the coil 12 does not pose a significant problem.

[0022] (Resonant Capacitor) The resonant capacitor 13 is electrically connected to the coil 12 and, together with the coil 12, constitutes a resonant circuit of the wireless power transmission device 10, generating a resonance phenomenon. The resonant frequency of the resonant circuit is determined primarily by the inductance of the coil 12 and the capacitance of the resonant capacitor 13. Therefore, the combined capacitance of the resonant capacitor 13 is set so that the resonant frequency of the resonant circuit of the wireless power transmission device 10 approaches a desired frequency (e.g., 85 kHz). Preferably, the combined capacitance of the resonant capacitor 13 is set so that the resonant frequency of the resonant circuit of the wireless power transmission device 10 becomes the desired frequency. The number of resonant capacitors 13 is not particularly limited and is set appropriately depending on the required combined capacitance, etc. In this embodiment, multiple resonant capacitors 13 are arranged on two capacitor substrates. The capacitor substrates on which the multiple resonant capacitors 13 are arranged are supported by pedestals and housed in a predetermined space within the housing 14. As described above, in this embodiment, the resonant capacitors 13 are sealed with resin within the housing 14. Therefore, the line voltage around the resonance capacitor 13 does not pose a significant problem.

[0023] The resonance capacitor 13 may be connected in parallel or in series to the coil 12. In this embodiment, the resonance capacitor 13 is arranged in series with the coil 12. That is, the resonance capacitor 13 is arranged between the coil 12 and the cable 11. More specifically, in this embodiment, the multiple resonance capacitors 13 are connected as follows between the two cables 11 and the coil 12 having both ends: That is, half of the multiple resonance capacitors 13 are connected in series between one end of the litz wire that constitutes the coil 12 and one of the two cables 11. Furthermore, the remaining half of the multiple resonance capacitors 13 are connected in series between the other end of the litz wire that constitutes the coil 12 and the other of the two cables 11.

[0024] In this embodiment, the resonance capacitor 13 is placed underground in a state where it is housed in a housing 14 together with the coil 12. Therefore, it is difficult to access the resonance capacitor 13, and it is difficult to change the capacitance once it has been selected.

[0025] (Frequency Adjustment Capacitor) The frequency adjustment capacitor 15 is a capacitor prepared separately from the resonance capacitor 13 and used to finely adjust the resonance frequency of the resonance circuit of the contactless power transmission device 10. As described above, the resonance frequency of the resonance circuit is determined mainly depending on the inductance of the coil 12 and the capacitance of the resonance capacitor 13. Therefore, the combined capacitance of the resonance capacitor 13 is set so that the resonance frequency of the resonance circuit of the contactless power transmission device 10 becomes a desired frequency (e.g., 85 kHz). However, the resonance frequency of the resonance circuit may change depending on the surrounding environment. In such cases, the frequency adjustment capacitor 15 is used to adjust the resonance frequency of the resonance circuit.

[0026] The frequency adjustment capacitor 15 is disposed outside the housing 14. Preferably, the frequency adjustment capacitor 15 is disposed on the ground. This allows workers to easily access the frequency adjustment capacitor 15, facilitating adjustment of the resonant frequency. The frequency adjustment capacitor 15 may be connected in series or in parallel with the coil 12. In this embodiment, the frequency adjustment capacitor 15 is connected in series with one of the two cables 11.

[0027] The combined capacitance of the frequency adjustment capacitors 15 is set so that the resonant frequency of the resonant circuit of the wireless power transmission device 10 is the desired frequency. Specifically, frequency adjustment capacitors 15 with optimal capacitance can be selected and installed depending on the change in resonant frequency. The combined capacitance of the frequency adjustment capacitors 15 is not particularly limited, but is, for example, approximately 10 nF to 15 nF. The number of frequency adjustment capacitors 15 is not particularly limited and is set appropriately depending on the required combined capacitance, etc. The combined capacitance of the frequency adjustment capacitors 15 is preferably smaller than the combined capacitance of the resonant capacitors 13. For example, the combined capacitance of the frequency adjustment capacitors 15 is preferably equal to or less than half the combined capacitance of the resonant capacitors. If the combined capacitance of the frequency adjustment capacitors 15 is larger than the combined capacitance of the resonant capacitors 13, the line voltage of the two cables 11 between the frequency adjustment capacitors 15 and the coil 12 (housing 14) may become high (e.g., exceed 600 V), potentially making it impossible to use a cable with a typical rated voltage (see the simulation results of Comparative Example 2 below).

[0028] The frequency adjustment capacitor 15 is preferably configured to be detachable from the cable 11. The mechanism for enabling detachment is not particularly limited, and for example, a known mechanism can be used. Configuring the frequency adjustment capacitor 15 to be detachable makes it easy to appropriately replace the frequency adjustment capacitor 15 with one having an optimal capacitance in accordance with changes in the resonant frequency. For example, a capacitor board on which one or more frequency adjustment capacitors 15 are arranged may be detachably attached to a board connection portion attached to the cable 11.

[0029] (Cables) In this embodiment, two cables 11 are arranged between the power source 2 and the coil 12. Specifically, one end of each of the two cables 11 is electrically connected to the power source 2, and the other end is electrically connected to the coil 12. This forms an electric circuit. There are no particular limitations on the type of cable 11, and it may be selected appropriately depending on factors such as the line voltage during use. In this embodiment, the rated voltage of the cable 11 is 600V.

[0030] [Simulation of Line Voltage] A simulation was performed to examine the line voltage of the contactless power transmission device 10 according to the embodiment. Specifically, as shown in FIG. 2B , points A to F were set in the contactless power transmission device 10 according to the embodiment, and the voltages (steady-state voltages) when a steady current was flowing between A and B, between C and D, between B and E, and between B and F were simulated. The combined capacitance of the resonant capacitors 13 between A and C was 103.71 nF, the combined capacitance of the resonant capacitors 13 between B and D was 103.71 nF, and the inductance of the coil 12 was 138.0 μH. The combined capacitances of the frequency adjustment capacitors 15 were 10 nF, 11 nF, 12 nF, and 13 nF.

[0031] Point A is the end of one of the two cables 11 (the cable 11 connected to the frequency adjustment capacitor 15) on the coil 12 side, and point B is the end of the other of the two cables 11 (the cable 11 not connected to the frequency adjustment capacitor 15) on the coil 12 side. Points A and B are both points on the cable 11. Therefore, the voltage between A and B must be equal to or less than the rated voltage of the cable 11. Point C is one end of the coil 12, and point D is the other end of the coil 12. One end of the coil 12 is connected to one cable 11 via half of the multiple resonance capacitors 13, and the other end of the coil 12 is connected to the other cable 11 via half of the multiple resonance capacitors 13. The multiple resonance capacitors 13 and the coil 12 are sealed with resin, and points C and D are also sealed with resin. Therefore, the voltage between C and D may be equal to or less than the rated voltage of the cable 11 or exceed the rated current. Point E is the end of one cable 11 on the frequency adjustment capacitor 15 side in the section between the power source 2 and the frequency adjustment capacitor 15, and point F is the end of the same cable 11 on the frequency adjustment capacitor 15 side in the section between the frequency adjustment capacitor 15 and the resonance capacitor 13. Points E and F are both points on the cable 11. Therefore, the voltage between B and E and the voltage between B and F are required to be equal to or less than the rated voltage of the cable 11.

[0032] As described above, the line voltages between A and B, between B and E, and between E and F are voltages between the cables 11. Therefore, the voltages between these points are required to be equal to or less than the rated voltage of the cable 11. In this embodiment, the rated voltage of the cable 11 is 600 V (0.6 kV), so the voltages between these points are required to be equal to or less than 600 V (0.6 kV). In contrast, the line voltage between C and D is the voltage between two points sealed with resin. Therefore, the voltage between C and D may be equal to or less than the rated voltage of the cable 11 or may exceed the rated current. In the simulation, the pass / fail judgment was made taking into account the difference in allowable voltage. The simulation results and pass / fail results are shown in Table 1.

[0033] For comparison, simulations were also performed to examine the line voltages of the contactless power transmission devices 10 of Comparative Examples 1 and 2, which do not have the frequency adjustment capacitor 15, as shown in FIGS. 5A and 5B . Specifically, in Comparative Example 1, points G to J were set in the contactless power transmission device 10 that does not have the frequency adjustment capacitor 15, as shown in FIG. 5A . In Comparative Example 2, points K to P were set in the contactless power transmission device 10 that does not have the frequency adjustment capacitor 15 and in which the resonance capacitor 13 is located outside the housing 14, as shown in FIG. 5B . In Comparative Example 1, steady-state voltages were simulated between G and H and between I and J. In Comparative Example 2, steady-state voltages were simulated between K and L, between M and N, and between O and P. In Comparative Example 1, points G and H are on the cable 11, so the voltage between G and H is required to be equal to or less than the rated voltage of the cable 11. On the other hand, points I and J are sealed with resin, so the voltage between I and J may exceed the rated voltage of the cable 11. Similarly, in Comparative Example 2, points K to P are all on cable 11, so the voltage at these points is required to be equal to or less than the rated voltage of cable 11. The simulation results and pass / fail judgment for Comparative Example 1 are shown in Table 2, and the simulation results and pass / fail judgment for Comparative Example 2 are shown in Table 3.

[0034]

[0035]

[0036]

[0037] As can be seen from Table 1, in the contactless power transmission device 10 according to the embodiment (FIG. 2B), the voltages between A and B, between B and E, and between B and F were equal to or less than the rated voltage (0.6 kV) of the cable 11 regardless of the capacitance of the frequency adjustment capacitor 15 used.

[0038] Similarly, as can be seen from Table 2, in the contactless power transmission device 10 according to Comparative Example 1 ( FIG. 5A ), the voltage between G and H was equal to or less than the rated voltage (0.6 kV) of the cable 11. However, since the resonance capacitor 13 is located inside the housing 14 and the frequency adjustment capacitor 15 is not located outside the housing 14, it has the disadvantage that it is difficult for an operator to adjust the resonance frequency.

[0039] In contrast, in the contactless power transmission device 10 according to Comparative Example 2 ( FIG. 5B ), the operator can easily adjust the resonant frequency because the resonant capacitor 13 is located outside the housing 14. However, as can be seen from Table 3, in the contactless power transmission device 10 according to Comparative Example 2, the voltages between M-N and between O-P exceeded the rated voltage (0.6 kV) of the cable 11.

[0040] From these simulation results, it was found that by placing the resonance capacitor 13 inside the housing 14, as in this embodiment, and also placing the frequency adjustment capacitor 15 outside the housing 14, it is possible to easily adjust the resonance frequency without creating the need to replace the cable 11 with one having a higher rated voltage.

[0041] <Effects> The contactless power supply device 10 according to this embodiment has the resonance capacitor 13 inside the housing 14, and also has the frequency adjustment capacitor 15 outside the housing 14. Therefore, even if the resonance frequency changes due to the external environment, the resonance frequency can be easily adjusted. Furthermore, the contactless power transmission device 10 according to this embodiment does not significantly change the line voltage of the cable 11 compared to a case where the contactless power transmission device 10 does not have the frequency adjustment capacitor 15, so there is no need to replace the cable 11 with one having a higher rated voltage.

[0042] The contactless power transmission device of the present invention is useful for contactless power supply to automobiles, for example.

[0043] REFERENCE SIGNS LIST 1 Wireless power supply system 2 Power source 3 Electric vehicle 4 Wireless power receiving device 5 Battery 10 Wireless power transmitting device 11 Cable 12 Coil 13 Resonant capacitor 14 Housing 15 Frequency adjustment capacitor

Claims

1. A contactless power transmission device comprising: a housing; a coil disposed within the housing; a resonance capacitor disposed within the housing and electrically connected to the coil; a cable disposed outside the housing and electrically connected to the coil; and a frequency adjustment capacitor disposed outside the housing and electrically connected to the cable.

2. A non-contact power transmission device according to claim 1, characterized in that the combined capacitance of the frequency adjustment capacitors is smaller than the combined capacitance of the resonance capacitors.

3. A non-contact power transmission device according to claim 1, characterized in that the combined capacitance of the frequency adjustment capacitors is 1 / 2 or less of the combined capacitance of the resonance capacitors.

4. A non-contact power transmission device according to claim 1, characterized in that the resonance capacitor is disposed between the coil and the cable.

5. A non-contact power transmission device according to claim 1, characterized in that the frequency adjustment capacitor is configured to be detachable from the cable.

6. A non-contact power transmission device according to claim 1, characterized in that the housing is placed underground, and the frequency adjustment capacitor is placed above ground.

7. A contactless power supply system comprising the contactless power transmission device according to any one of claims 1 to 6.

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