Non-contact charging system

Abstract

To provide a non-contact charging system capable of preventing radio wave interference from being generated by selecting a change destination on the basis of a Wi-Fi interference situation after the start of charging.SOLUTION: A non-contact charging system of the present invention performs charging to a battery electrically connected with an on-vehicle unit by transmitting power from a power transmission coil of a ground unit to a power reception coil of the on-vehicle unit installed in an electric vehicle in a non-contact manner. The ground unit comprises a ground side Wi-Fi machine for performing Wi-Fi communication with the on-vehicle unit. The on-vehicle unit comprises a vehicle side Wi-Fi machine for performing the Wi-Fi communication with the ground side Wi-Fi machine. The Wi-Fi communication is disconnected between the ground side Wi-Fi machine and the vehicle side Wi-Fi machine during charging due to radio wave interference, and the Wi-Fi communication is subsequently restarted on a Wi-Fi channel whose Wi-Fi disconnection rate is lowest from a past history, when restarting the Wi-Fi communication.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a wireless charging system. [Background technology]

[0002] Patent Document 1 discloses a communication control method in which a wireless LAN device monitors and records the interference situation of surrounding channels over a long period of time during normal operation, and based on this, constantly estimates the optimal channel to change to and prepares it as a candidate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-158485 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the Wi-Fi interference situation before the start of charging is considered, it may not be possible to select a change destination in consideration of the Wi-Fi interference situation after the start of charging.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a contactless charging system that can select a change destination based on the Wi-Fi interference situation after charging starts, thereby suppressing the occurrence of radio wave interference. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the contactless charging system of the present invention is a contactless charging system that contactlessly transmits power from a power transmitting coil of a ground unit to a power receiving coil of an on-board unit mounted on an electric vehicle, and charges a battery electrically connected to the on-board unit, wherein the ground unit has a ground-side Wi-Fi device for Wi-Fi communication with the on-board unit, and the on-board unit has a vehicle-side Wi-Fi device for Wi-Fi communication with the ground-side Wi-Fi device, and is characterized in that when Wi-Fi communication between the ground-side Wi-Fi device and the vehicle-side Wi-Fi device is disconnected due to radio wave interference during charging, and then when the Wi-Fi communication is reconnected, the Wi-Fi communication is resumed on a Wi-Fi channel with the lowest Wi-Fi disconnection rate based on past history. [Effects of the Invention]

[0007] The contactless charging system according to the present invention has an advantage that it is possible to select a change destination based on the Wi-Fi interference situation after charging starts, thereby suppressing the occurrence of radio wave interference. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a contactless charging system according to an embodiment. [Figure 2] FIG. 2 is a flowchart showing an example of control performed in the contactless charging system according to the embodiment. [Figure 3] Figure 3 is a graph showing the relationship between Wi-Fi disconnection rate and waiting time. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the contactless charging system according to the present invention will be described, but the present invention is not limited to the embodiment.

[0010] FIG. 1 is a diagram showing a schematic configuration of a contactless charging system 1 according to an embodiment.

[0011] The contactless charging system 1 according to the embodiment is made up of an electric vehicle 2 equipped with a contactless charging vehicle unit (VA) 3, and a contactless charging ground unit (GA) 4.

[0012] In addition to the contactless charging in-vehicle unit 3, the electric vehicle 2 is also provided with a charging control unit 21 capable of controlling the contactless charging in-vehicle unit 3 and the contactless charging ground unit 4, and a drive battery 22 that supplies power to the motor that is the drive source of the electric vehicle 2. The contactless charging in-vehicle unit 3 is equipped with a vehicle-side Wi-Fi device 31 for Wi-Fi communication with the ground-side Wi-Fi device 41 of the contactless charging ground unit 4, a vehicle-side control unit 32, a power receiving coil 33, and a GPS 34. The vehicle-side control unit 32 has a function of selecting a Wi-Fi channel for the vehicle-side Wi-Fi device 31.

[0013] The contactless charging ground unit 4 includes a ground-side Wi-Fi device 41 for Wi-Fi communication with the vehicle-side Wi-Fi device 31 of the contactless charging in-vehicle unit 3, a ground-side control unit 42, and a power transmission coil 43.

[0014] In the contactless charging system 1 according to the embodiment, power is transmitted contactlessly from the power transmission coil 43 of the contactless charging ground unit 4 to the power receiving coil 33 of the contactless charging on-board unit 3 mounted on the electric vehicle 2, and contactless charging can be performed to charge the driving battery 22 electrically connected to the contactless charging on-board unit 3.

[0015] During contactless charging, the ground-side Wi-Fi device 41 of the contactless charging ground unit 4 and the vehicle-side Wi-Fi device 31 of the contactless charging in-vehicle unit 3 communicate via Wi-Fi to execute processes such as starting and ending charging. If the Wi-Fi communication is disconnected due to an external factor such as radio wave interference during contactless charging, contactless charging is temporarily suspended, and then resumes when the Wi-Fi communication is reconnected. In the contactless charging system 1 according to the embodiment, when connecting Wi-Fi communication between the ground-side Wi-Fi device 41 and the vehicle-side Wi-Fi device 31, Wi-Fi communication is started using the Wi-Fi channel that had the lowest Wi-Fi disconnection rate during past contactless charging.

[0016] The Wi-Fi disconnection rate is the ratio of the accumulated time during which Wi-Fi was disconnected during wireless charging (accumulated Wi-Fi disconnection time) to the accumulated time of past charging (accumulated charging time) on a certain Wi-Fi channel. This Wi-Fi disconnection rate is then calculated for each Wi-Fi channel. Because the Wi-Fi disconnection rate is caused by radio wave interference with surrounding devices, it is calculated for each parking location and time of day. When selecting a Wi-Fi channel, the Wi-Fi channel with the lowest Wi-Fi disconnection rate is selected, taking into account the current parking location and time of day.

[0017] This makes it possible to select a Wi-Fi channel with the lowest risk of interference with the power transmitting coil 43, the power receiving coil 33, the control units 21, 32, and 42, various electronic circuits, or the navigation system (radio, television, and GPS 34) used by the driver, the car air conditioner, the smartphone (telephone and Bluetooth (registered trademark)), and radio waves emitted from peripheral devices of the electric vehicle 2, which operate after the start of contactless charging. This reduces the frequency of Wi-Fi disconnections during contactless charging, and as a result, prevents the charging time from becoming longer.

[0018] If Wi-Fi communication is disconnected during wireless charging, the device will wait a certain amount of time until it can reconnect on that Wi-Fi channel. This waiting time is set longer for Wi-Fi channels with a lower Wi-Fi disconnection rate. If the device is unable to reconnect after this waiting time has elapsed, it will attempt to connect on the Wi-Fi channel with the next lowest Wi-Fi disconnection rate. If it is unable to connect on any of the Wi-Fi channels, it will give up on recharging and terminate wireless charging.

[0019] This increases the likelihood of reconnecting on a Wi-Fi channel with a lower Wi-Fi disconnection rate, preventing the charging time from becoming too long after wireless charging is started again.

[0020] FIG. 2 is a flowchart showing an example of control performed in the contactless charging system 1 according to the embodiment.

[0021] In step S1, the Wi-Fi channel candidate with the smallest Wi-Fi disconnection rate ch[i] is selected. The Wi-Fi channel candidates are as follows: Before charging begins, all Wi-Fi channels are candidates. After that, Wi-Fi channels on which Wi-Fi communication has been disconnected and cannot be reconnected are excluded from the candidates. The Wi-Fi disconnection rate ch[i] refers to the i-th Wi-Fi channel. The subscript i ranges from 1 to the number of channels that each Wi-Fi device 31, 41 can handle. The Wi-Fi disconnection rate ch[i] is recorded for each vehicle position information and time obtained from the GPS 34. Here, the Wi-Fi channel with the smallest Wi-Fi disconnection rate is selected, taking into account the current GPS information and time.

[0022] In step S2, the radio wave interference level of the Wi-Fi channel selected in step S1 is checked. If the radio wave interference level is within a specified value (Yes in step S2), the process proceeds to step S3. On the other hand, if the radio wave interference level exceeds the specified value (No in step S2), the process proceeds to step S9. An index of the radio wave interference level is, for example, the commonly known SNR (Signal-to-Noise Ratio).

[0023] In step S3, Wi-Fi communication is established between the vehicle-side Wi-Fi device 31 of the non-contact charging in-vehicle unit 3 and the ground-side Wi-Fi device 41 of the non-contact charging ground unit 4.

[0024] In step S4, the vehicle-side Wi-Fi device 31 of the non-contact charging in-vehicle unit 3 instructs the ground-side Wi-Fi device 41 of the non-contact charging ground unit 4 to output power via Wi-Fi communication.

[0025] In step S5, the non-contact charging ground unit 4 outputs power from the power transmission coil 43 to perform non-contact charging.

[0026] In step S6, the control unit calculation cycle is added to the accumulated charging time ch[i]. The accumulated charging time ch[i] is the accumulated value of the past charging time for the currently selected Wi-Fi channel. The accumulated charging time ch[i] is recorded for each vehicle position information and time acquired from the GPS 34, and here the accumulated charging time ch[i] corresponding to the current vehicle position and current time is counted up.

[0027] In step S7, it is determined whether the drive battery 22 is fully charged. If the result of the full charge determination is that the drive battery 22 is fully charged (No in step S7), the process proceeds to step S15. On the other hand, if the drive battery 22 is not fully charged (Yes in step S7), the process proceeds to step S8.

[0028] In step S8, the Wi-Fi disconnection rate ch[i] corresponding to the current vehicle position and the current time is calculated using the formula: Wi-Fi disconnection rate ch[i] = accumulated Wi-Fi disconnection time ch[i] / accumulated charging time ch[i]. The accumulated Wi-Fi disconnection time ch[i] is the accumulated value of past Wi-Fi disconnection times for the currently selected Wi-Fi channel.

[0029] In step S9, the control unit calculation cycle is added to the Wi-Fi disconnection duration. The Wi-Fi disconnection duration is the duration of the currently occurring Wi-Fi disconnection, and is unrelated to past Wi-Fi disconnection durations.

[0030] In step S10, the control unit calculation cycle is added to the Wi-Fi disconnection time integrated value ch[i]. The Wi-Fi disconnection time integrated value ch[i] is recorded for each vehicle position information and time acquired from the GPS 34. In this example, the Wi-Fi disconnection time integrated value ch[i] corresponding to the current vehicle position and the current time is counted up.

[0031] In step S11, it is determined whether the Wi-Fi disconnection duration calculated in step S9 is longer than the standby time ch[i]. If the Wi-Fi disconnection duration is longer than the standby time ch[i] (Yes in step S11), the process proceeds to step S12. On the other hand, if the Wi-Fi disconnection duration is shorter than or equal to the standby time ch[i] (No in step S11), the process proceeds to step S8. Here, the standby time ch[i] refers to the upper limit of the standby time for the selected Wi-Fi channel, and as shown in FIG. 3, the standby time ch[i] is set longer for Wi-Fi channels with lower Wi-Fi disconnection rates.

[0032] In step S12, since the Wi-Fi has not been reconnected after waiting for a certain period of time, the current channel ch[i] is excluded from the Wi-Fi channel candidates as it is unlikely to be restored after that.

[0033] In step S13, the Wi-Fi disconnection duration is cleared.

[0034] In step S14, it is determined whether there are no more Wi-Fi channel candidates. If there are no more Wi-Fi channel candidates after eliminating the Wi-Fi channel candidates one by one in step S12 (Yes in step S14), the Wi-Fi reconnection is abandoned and the process proceeds to step S15. On the other hand, if there are still Wi-Fi channel candidates (No in step S14), the process proceeds to step S8 to retry the Wi-Fi connection.

[0035] In step S15, when the driving battery 22 is fully charged or when the Wi-Fi reconnection is abandoned, a charging end process is executed.

[0036] In the contactless charging system 1 according to the embodiment, the change destination can be selected based on the Wi-Fi interference situation after charging starts, thereby suppressing the occurrence of radio wave interference. [Explanation of symbols]

[0037] 1. Wireless charging system 2. Electric vehicles 3. Wireless charging vehicle unit 4. Wireless charging ground unit 21 Charging control unit 22 Drive battery 31 Vehicle Wi-Fi device 32 Vehicle side control unit 33 Receiving coil 34 GPS 41 Ground side Wi-Fi device 42 Ground control unit 43 Transmission coil

Claims

[Claim 1] A wireless charging system that transmits power contactlessly from a power transmitting coil of a ground unit to a power receiving coil of an on-board unit mounted on an electric vehicle, and charges a battery electrically connected to the on-board unit, the ground unit has a ground-side Wi-Fi device for Wi-Fi communication with the in-vehicle unit, the in-vehicle unit has a vehicle-side Wi-Fi device for Wi-Fi communication with the ground-side Wi-Fi device, A contactless charging system characterized in that Wi-Fi communication between the ground-side Wi-Fi device and the vehicle-side Wi-Fi device is disconnected due to radio wave interference during charging, and when the Wi-Fi communication is subsequently reconnected, the Wi-Fi communication is resumed on the Wi-Fi channel with the lowest Wi-Fi disconnection rate based on past history.

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