Moving body of non-contact power transfer system, foreign matter detection method, and foreign matter detection program product

Abstract

This invention provides a mobile body, a foreign object detection method, and a foreign object detection program product for a non-contact power transmission system capable of accurately detecting foreign objects through a mobile body without relying on a ground-side unit. The vehicle (4) of the non-contact power transmission system (1) includes: a battery (BATT), a vehicle-side unit (40), a contactor (60) capable of switching the electrical connection or disconnection between the battery (BATT) and the vehicle-side unit (40), and a control device (50) including a processor (51). The vehicle-side unit (40) includes a vehicle-side coil (41), a power conversion device (43), and a smoothing capacitor (48). When the contactor disconnects the battery from the vehicle-side unit, the processor activates the power conversion device to perform a foreign object detection process that determines whether a metallic foreign object (100) exists between the vehicle-side unit and the ground-side unit (20).

Description

Technical Field

[0001] This invention relates to a non-contact power transmission system for non-contact power transmission between a mobile body-side unit and a ground-side unit, a method for detecting foreign objects, and a foreign object detection procedure product. Background Technology

[0002] In recent years, in order to ensure that more people have access to affordable, reliable and sustainable modern energy, research and development are underway to develop charging and power supply systems for mobile vehicles equipped with rechargeable batteries that can help improve energy efficiency. For example, Patent Document 1 describes a contactless power supply device for mobile vehicles, which includes a power supply coil disposed on the ground side and a power receiving coil disposed on the side of the mobile vehicle and facing the power supply coil through a gap, and supplies power from the power supply coil to the power receiving coil through electromagnetic induction.

[0003] The non-contact power supply device for a mobile body in Patent Document 1 supplies power for foreign object detection to the power supply coil when there are no metal foreign objects on the power supply coil, and calculates a standard value of power supply loss. It detects whether there are metal foreign objects on the power supply coil based on the difference between the measured value of power supply loss calculated by supplying power for foreign object detection to the power supply coil and the standard value.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5940784 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the technology described in Patent Document 1, communication between the vehicle side and the ground side is required to detect foreign objects. In such technology, foreign object detection is impossible when communication is poor. Therefore, a technology that does not require communication between the vehicle side and the ground side is desired. Specifically, a technology that can accurately detect foreign objects using a device on the vehicle side is desired.

[0009] This invention provides a non-contact power transmission system that can accurately detect foreign objects through a moving body without relying on a ground-side unit, a foreign object detection method, and a foreign object detection program product.

[0010] Methods for solving problems

[0011] This invention provides a mobile body for a contactless power transmission system. The contactless power transmission system performs contactless power transmission between a mobile body-side unit mounted on the mobile body and a ground-side unit disposed outside the mobile body.

[0012] The mobile body has:

[0013] Storage battery;

[0014] The mobile body side unit is electrically connected to the storage battery;

[0015] A switch, disposed between the battery and the mobile unit, is capable of switching the electrical connection or disconnection between the battery and the mobile unit; and

[0016] The control device includes a processor that controls the moving body side unit and the switch.

[0017] The mobile body side unit includes:

[0018] The movable body-side coil receives or supplies power to the ground-side coil disposed on the ground-side unit in a non-contact manner.

[0019] A power conversion device connected between the coil on the mobile body side and the battery, performing power conversion between DC power and AC power; and

[0020] An energy storage device is disposed between the power conversion device and the battery.

[0021] When the processor disconnects the battery from the mobile body unit via the switch, it activates the power conversion device to perform a foreign object detection process that determines whether there is a metallic foreign object between the mobile body unit and the ground unit.

[0022] The present invention also provides a foreign object detection method for a non-contact power transmission system, wherein the non-contact power transmission system performs non-contact power transmission between a mobile body-side unit mounted on a mobile body and a ground-side unit disposed outside the mobile body, wherein...

[0023] The mobile body includes: a battery; and a mobile body-side unit electrically connected to the battery.

[0024] The mobile body-side unit includes: a mobile body-side coil, which receives or transmits power to a ground-side coil disposed on the ground-side unit in a non-contact manner; a power conversion device connected between the mobile body-side coil and the battery, which converts power between DC power and AC power; and an energy storage device disposed between the power conversion device and the battery.

[0025] The foreign object detection method performs the following processing via a processor:

[0026] Before performing the contactless power transfer, disconnect the electrical connection between the battery and the mobile body-side unit; and

[0027] In the disconnected state where the battery is disconnected from the mobile body side unit, the power conversion device is activated to determine whether there is a metallic foreign object between the mobile body side unit and the ground side unit.

[0028] This invention also provides a foreign object detection program product for a contactless power transmission system, which includes a foreign object detection program. The contactless power transmission system performs contactless power transmission between a mobile body-side unit mounted on a mobile body and a ground-side unit disposed outside the mobile body.

[0029] The mobile body includes: a battery; and a mobile body-side unit electrically connected to the battery.

[0030] The mobile body-side unit includes: a mobile body-side coil, which receives or transmits power to a ground-side coil disposed on the ground-side unit in a non-contact manner; a power conversion device connected between the mobile body-side coil and the battery, which converts power between DC power and AC power; and an energy storage device disposed between the power conversion device and the battery.

[0031] The foreign object detection program causes the computer to perform the following processes:

[0032] Before performing the contactless power transfer, disconnect the electrical connection between the battery and the mobile body-side unit; and

[0033] In the disconnected state where the battery is disconnected from the mobile body side unit, the power conversion device is activated to determine whether there is a metallic foreign object between the mobile body side unit and the ground side unit.

[0034] Invention Effects

[0035] According to the present invention, foreign objects can be detected with high accuracy by means of a moving body without relying on a ground-side unit. Attached Figure Description

[0036] Figure 1 This is a schematic structural diagram of a contactless power transmission system according to an embodiment of the present invention.

[0037] Figure 2 This is a functional block diagram of a contactless power transmission system.

[0038] Figure 3 It is a circuit diagram that includes the battery, vehicle-side unit, and contactor installed in the vehicle.

[0039] Figure 4 This is a schematic side view of the ground-side unit and the vehicle-side unit.

[0040] Figure 5 This is a flowchart representing an example of a process executed by a processor.

[0041] Figure 6 yes Figure 5 The subsequent flowchart specifically represents the flowchart for foreign object detection and processing.

[0042] Figure 7 A flowchart illustrating a variation of the foreign object detection process.

[0043] Explanation of reference numerals in the attached figures

[0044] 1. Non-contact power transmission system

[0045] 4. Vehicles (mobile vehicles)

[0046] 20 Ground-side units

[0047] 40 Vehicle-side unit (moving body-side unit)

[0048] 43 Power conversion device

[0049] 48. Smoothing capacitor (energy storage device)

[0050] 49a Voltage sensor (voltage detection unit)

[0051] 49b Current sensor (current detection unit)

[0052] 50 Control devices

[0053] 51 processor (computer)

[0054] 60 Contactor (Switch)

[0055] 100 Foreign objects

[0056] BATT battery. Detailed Implementation

[0057] Hereinafter, an embodiment of the non-contact power transmission system, the foreign object detection method, and the foreign object detection program product of the present invention will be described based on the accompanying drawings. The drawings are viewed along the directions indicated by the reference numerals. Furthermore, in this specification and the like, for the sake of simplicity and clarity, the front of the vehicle is designated as Fr, the rear as Rr, the left as L, the right as R, the top as U, and the bottom as D in the drawings.

[0058] Figure 1This is a schematic structural diagram of a contactless power transmission system 1 according to an embodiment of the present invention. The contactless power transmission system 1 includes a ground-side device 2 equipped with a ground-side unit 20 and a vehicle 4 equipped with a vehicle-side unit 40. In the contactless power transmission system 1, contactless power transmission is performed between the ground-side unit 20 and the vehicle-side unit 40 by means of magnetic coupling between coils, for example, using magnetic field resonance or electromagnetic induction.

[0059] The contactless power transfer includes power transfer from the ground-side unit 20 to the vehicle-side unit 40 and power transfer from the vehicle-side unit 40 to the ground-side unit 20. The power transfer from the ground-side unit 20 to the vehicle-side unit 40 is equivalent to charging the battery BATT installed in the vehicle 4, and the power transfer from the vehicle-side unit 40 to the ground-side unit 20 is equivalent to supplying power from the battery BATT to the outside of the vehicle 4.

[0060] Ground-side equipment 2 is installed in designated parking spaces, etc. For example... Figure 2 As shown, the ground-side equipment 2 includes a ground-side unit 20, a communication device 27 capable of communicating with the vehicle 4, a control device 30 for controlling the ground-side unit 20, and a power supply device PS connected to an external power system such as a commercial power supply.

[0061] The ground-side unit 20 includes a ground-side coil 21 disposed on the ground, a resin pad 22 covering the ground-side coil 21, and a power conversion device 23 that converts AC power supplied from the power supply device PS into high-frequency AC power and supplies the converted high-frequency AC power to the ground-side coil 21. The shape of the ground-side coil 21 is, for example, circular when viewed from above, but is not limited to this, and may also be elliptical, square, rectangular, etc.

[0062] Communication device 27 is a communication interface for wireless communication with communication device 47 of vehicle 4. Wireless communication can use, for example, Wi-Fi (registered trademark), Bluetooth (registered trademark), etc.

[0063] The control device 30 includes, for example, a processor and a memory, for unified control of the ground-side equipment 2. The processor is configured as one or more circuits that combine circuit elements such as semiconductor elements. The memory functions as a storage unit and includes RAM (Random Access Memory) required for processor operation and ROM (Read Only Memory) for storing programs, data, etc.

[0064] Vehicle 4 is an electric vehicle capable of charging its battery BATT via external power supply, such as a battery-powered electric vehicle or a plug-in hybrid electric vehicle. When charging the battery BATT, the vehicle-side unit 40 receives power from the ground-side unit 20 in a contactless manner and stores the received power in the battery BATT. The battery BATT is, for example, a lithium-ion battery or a nickel-metal hydride battery. Vehicle 4 is configured to drive a motor MOT, which is powered by the power stored in the battery BATT. Vehicle 4 can also be configured to supply the power stored in the battery BATT to an external source. Specifically, vehicle 4 can also transmit power from the vehicle-side unit 40 to the ground-side unit 20 in a contactless manner.

[0065] Vehicle 4 has an automatic parking function that autonomously moves to and parks in a designated parking space. The automatic parking function operates, for example, based on requests from occupants. When the automatic parking function operates near a parking space where the ground-side unit 2 is located, vehicle 4 autonomously moves toward the target parking position. The parking position with the highest power transmission efficiency is the position where the centers of the ground-side unit 20 and the vehicle-side unit 40 coincide; vehicle 4 essentially sets this position with the highest power transmission efficiency as the target parking position and moves autonomously there.

[0066] like Figure 1 and Figure 2 As shown, vehicle 4 includes a battery BATT, a motor MOT as a drive source, a vehicle-side unit 40 electrically connected to the battery BATT, a contactor 60 disposed between the battery BATT and the vehicle-side unit 40, a sensor group 45, a notification device 46, a communication device 47, and a control device 50.

[0067] like Figure 3 As shown, the vehicle-side unit 40 includes a vehicle-side coil 41 that receives or supplies power to the ground-side coil 21 in a non-contact manner, and a resin gasket 42 covering the vehicle-side coil 41 (see reference). Figure 1 The system includes: a power conversion device 43 connecting the vehicle-side coil 41 and the battery BATT to convert DC power to AC power; a resonant circuit 44 connecting the vehicle-side coil 41 and the power conversion device 43; and a smoothing capacitor 48 disposed between the power conversion device 43 and the battery BATT. The shape of the vehicle-side coil 41 is, for example, circular when viewed from above, but is not limited to this; it can also be elliptical, square, rectangular, etc.

[0068] The power conversion device 43 includes, for example, an inverter forming a bridge circuit with four switching elements 431-434 connected in a two-phase bridge configuration. The multiple switching elements 431-434 are composed of paired upper arm elements (switching elements 431, 433) and lower arm elements (switching elements 432, 434) in each phase. Each switching element 431-434 is, for example, a power switching element such as an IGBT (Insulated Gate Bipolar Transistor), a FET (Field Effect Transistor), or, in the illustrated example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The drain current flowing between the drain and source terminals is controlled by a gate voltage applied between the gate and source terminals. In each switching element 431-434, a rectifier element is formed between the source and drain terminals; in the illustrated example, the rectifier element is a parasitic diode of the MOSFET.

[0069] The drain terminals of the switching elements 431 and 433, which are the upper arm elements, are connected to the positive electric field line 40p, and the source terminals of the switching elements 432 and 434, which are the lower arm elements, are connected to the negative electric field line 40n. The source terminals of the switching elements 431 and 433 and the drain terminals of the switching elements 432 and 434 are connected to the resonant circuit 44.

[0070] The resonant circuit 44 includes, for example, a resonant capacitor connected in series with the vehicle-side coil 41. When power is transmitted from the ground-side unit 20 to the vehicle-side unit 40, the vehicle-side coil 41 and the resonant circuit 44 constitute a receiving unit that receives power transmitted from the ground-side unit 20 in a non-contact manner. When power is transmitted from the vehicle-side unit 40 to the ground-side unit 20, the vehicle-side coil 41 and the resonant circuit 44 constitute a power supply unit that transmits power to the ground-side unit 20 in a non-contact manner.

[0071] The smoothing capacitor 48 is connected to the electric field line 40p on the positive side and the electric field line 40n on the negative side. The smoothing capacitor 48 smooths the voltage fluctuations caused by the switching operations of the switching elements 431-434, which are connected and disconnected. The smoothing capacitor 48 is an example of the energy storage device of the present invention.

[0072] The vehicle-side unit 40 also includes a voltage sensor 49a for detecting the voltage of the smoothing capacitor 48 and a current sensor 49b disposed between the power conversion device 43 and the smoothing capacitor 48 for detecting the current. Alternatively, in this embodiment, the vehicle-side unit 40 may not include the current sensor 49b.

[0073] Contactor 60 is configured to switch the electrical connection or disconnection between the battery BATT and the vehicle-side unit 40 via on / off control. Contactor 60 is located on the positive terminal side of the battery BATT. Contactor 60 is substantially open (open circuit state) except when performing non-contact power transmission. Contactor 60 is an example of the switch of the present invention.

[0074] return Figure 2 The sensor group 45 acquires various detection values ​​for the control of the vehicle 4. The sensor group 45 includes, for example, a camera (image sensor) and sonar for acquiring information about the surroundings of the vehicle 4. Furthermore, the sensor group 45 includes, for example, wheel sensors, positioning sensors, and steering angle sensors for acquiring state information about the vehicle 4. Additionally, the sensor group 45 may also include other sensors, such as radar and LiDAR (Light Detection and Ranging) for acquiring information about the surroundings of the vehicle 4.

[0075] The notification device 46 is the output destination of the notification processing of the control device 50, and notifies the occupants of the vehicle 4 of prescribed information. The notification device 46 may be, for example, a display (including a head-up display) or a speaker installed in the vehicle 4, and notifies the occupants of the prescribed information through images, sounds, etc. Alternatively, the notification device 46 may also be a user terminal owned by the occupants, such as a smartphone or tablet computer.

[0076] Communication device 47 is a communication interface for wireless communication with communication device 27 of ground-side equipment 2. Wireless communication can be achieved using, for example, Wi-Fi (registered trademark), Bluetooth (registered trademark), etc. In addition, communication device 47 can also conduct wireless communication via a network, such as "4G" or "5G".

[0077] The control device 50 is, for example, an ECU (Electronic Control Unit) that includes a processor 51 and a memory 52. ​​The processor 51 is configured as one or more circuits that combine circuit elements such as semiconductor elements. The memory 52 functions as a storage unit and includes RAM required for the operation of the processor 51 and ROM for storing programs, data, etc.

[0078] Next, refer to Figures 4-6The method for detecting metallic foreign objects 100 in the non-contact power transmission system 1 is described. When non-contact power transmission is performed with a foreign object 100 present between the ground-side unit 20 and the vehicle-side unit 40, eddy currents may be generated in the foreign object 100, causing heat and resulting in high temperatures. Furthermore, the heat generated by the foreign object 100 may increase power transmission losses. To ensure safety and reduce power transmission losses, it is necessary to remove the foreign object 100 before performing non-contact power transmission.

[0079] Sometimes a foreign object detector is installed on the ground-side unit 20. This foreign object detector is, for example, composed of a coil array in which multiple foreign object detection coils are distributed along a generally flat plane and are partially or entirely embedded in the gasket 22. The foreign object detector detects metallic foreign objects based on the changing patterns of oscillating waveform signals supplied from an oscillator to each foreign object detection coil.

[0080] The detection range of a foreign object detector composed of such a coil array is approximately tens of millimeters from the surface of the ground-side unit 20. When the foreign object 100 is located far from the surface of the ground-side unit 20, it is difficult for the foreign object 100 to be detected by the foreign object detector of the ground-side unit 20. For example, as Figure 4 As shown, when the foreign object 100 is attached to the gasket 42 of the vehicle side unit 40, it is difficult to detect the foreign object 100 by the foreign object detector of the ground side unit 20.

[0081] Furthermore, consider the case where the foreign object 100 is detected solely by the foreign object detector of the ground-side unit 20. For example, if communication between the ground-side equipment 2 and the vehicle 4 is poor due to a malfunction of the ground-side equipment 2, the vehicle 4 may be unable to detect the foreign object 100.

[0082] Therefore, the contactless power transmission system 1 of this embodiment has a structure that detects foreign objects 100 through a vehicle-side device without relying on the ground-side unit 20. Thus, even if the foreign object 100 is located far from the ground-side unit 20, the vehicle 4 can still detect it. Furthermore, even if communication between the ground-side device 2 and the vehicle 4 is poor, the vehicle 4 can still detect the foreign object 100.

[0083] Figure 5 and Figure 6 This is a flowchart illustrating an example of a process executed by processor 51. The flowchart shows the process in... Figure 6 The various processes shown are equivalent to foreign object detection processes. For example, the processes shown in the flowchart are executed after vehicle 4 has completed parking in the parking space and before vehicle-side unit 40 is coupled to ground-side unit 20.

[0084] The processor 51 first confirms that the vehicle-side unit 40 and the ground-side unit 20 are in a non-coupled state (step S1). In order to avoid being affected by the ground-side unit 20, it is preferable to perform foreign object detection processing before the vehicle-side unit 40 and the ground-side unit 20 are magnetically coupled, so the processor 51 first confirms that they are in a non-coupled state.

[0085] Processor 51 connects contactor 60 (closed state), electrically connecting battery BATT to vehicle-side unit 40 (step S2). At this time, processor 51 does not operate power conversion device 43. By connecting contactor 60, battery BATT is electrically connected to smoothing capacitor 48, and pre-charging is performed by accumulating charge in smoothing capacitor 48.

[0086] Processor 51 confirms the voltage of smoothing capacitor 48 (step S3). The voltage of smoothing capacitor 48 is the detected value detected by voltage sensor 49a. The voltage confirmed in step S3 is set as V1.

[0087] Processor 51 compares the voltage V1 of smoothing capacitor 48 with the threshold Va (step S4). If the voltage V1 is below the threshold Va (step S4: no), processor 51 returns to step S3 and monitors until the voltage V1 is greater than the threshold Va.

[0088] When voltage V1 is greater than threshold Va (step S4: Yes), processor 51 disconnects contactor 60 (open circuit state), electrically disconnecting battery BATT from vehicle-side unit 40 (step S5). In the disconnected state where battery BATT is disconnected from vehicle-side unit 40, processor 51 executes... Figure 7 The foreign object detection and processing shown.

[0089] Processor 51 confirms the voltage of smoothing capacitor 48 (step S11). The voltage of smoothing capacitor 48 is the detected value detected by voltage sensor 49a. The voltage confirmed in step S11 is set as V2.

[0090] The processor 51 activates the power conversion device 43 (step S12). Specifically, the processor 51 controls the switching of each switching element 431-434 on / off. The charge stored in the smoothing capacitor 48 is supplied to the vehicle-side coil 41 via the power conversion device 43 and the resonant circuit 44, generating a magnetic field around the vehicle-side coil 41.

[0091] Processor 51 determines whether a predetermined time has elapsed since the power conversion device 43 was started (step S13). Processor 51 continues to operate the power conversion device 43 until the predetermined time has elapsed.

[0092] After a predetermined time has elapsed (step S13: Yes), processor 51 confirms the voltage of smoothing capacitor 48 (step S14). The voltage of smoothing capacitor 48 is the detected value detected by voltage sensor 49a. The voltage confirmed in step S14 is set to V3.

[0093] Processor 51 compares the voltage V3 of smoothing capacitor 48 with a threshold Vb (step S15). The threshold Vb is, for example, a value calculated by collecting data on the voltage V3 when the foreign object 100 is present and when it is not present, and is pre-stored in memory 52.

[0094] In the presence of foreign object 100, eddy currents are generated in foreign object 100 due to the magnetic field generated around vehicle-side coil 41, and the losses in vehicle-side coil 41 increase. Therefore, the change (decrease) in voltage of smoothing capacitor 48 within a specified time is greater than in the case where foreign object 100 is not present.

[0095] When voltage V3 is greater than threshold Vb (step S15: Yes), the voltage change of smoothing capacitor 48 is small, so processor 51 determines that there is no foreign object 100 (step S16). After determining that there is no foreign object 100, processor 51 starts non-contact power transmission.

[0096] On the other hand, when the voltage V3 is below the threshold Vb (step S15: No), the voltage change of the smoothing capacitor 48 is large, so the processor 51 determines that a foreign object 100 is present (step S17). When the presence of a foreign object 100 is determined, the processor 51 notifies the occupant of the presence of the foreign object 100, for example, via the notification device 46. In this way, the foreign object 100 can be detected solely by the detection value of the voltage sensor 49a, eliminating the need for a large number of foreign object detection components.

[0097] In step S15, the processor 51 may also determine that there is a foreign object 100 when the change in voltage of the smoothing capacitor 48 after a specified time, specifically the difference between voltage V2 and voltage V3, is above a specified value.

[0098] As explained above, in the contactless power transmission system 1 according to this embodiment, the foreign object detection process is performed using the vehicle 4's devices, namely the vehicle-side coil 41 and the processor 51. Therefore, even when the foreign object 100 is located far from the ground-side unit 20 and cannot be detected by the foreign object detector of the ground-side unit 20, the vehicle 4 can still detect the foreign object 100. Furthermore, the vehicle 4 can detect the foreign object 100 even without communication with the ground-side device 2.

[0099] Furthermore, a contactor 60 is provided between the battery BATT and the vehicle-side unit 40. When the processor 51 disconnects the contactor 60, thus cutting off the connection between the battery BATT and the vehicle-side unit 40, it activates the power conversion device 43 to perform foreign object detection processing. This eliminates the influence of the battery BATT during foreign object detection processing. Specifically, when the voltage variation of the smoothing capacitor 48 is large, it is more likely that the cause is not due to fluctuations in the battery BATT voltage (which fluctuates according to margin) but rather to the presence of the foreign object 100. That is, the processor 51 can detect the foreign object 100 with high accuracy.

[0100] Furthermore, since the processor 51 performs foreign object detection processing before the vehicle-side unit 40 couples with the ground-side unit 20, it is more likely that the large voltage change in the smoothing capacitor 48 is caused by the presence of the foreign object 100 rather than the ground-side unit 20. That is, the processor 51 can detect the foreign object 100 with greater accuracy. Moreover, since no power is supplied from the vehicle-side unit 40 to the ground-side unit 20 during the foreign object detection processing, the processor 51 can detect the foreign object 100 with low power.

[0101] (Modified example)

[0102] Figure 7 This is a flowchart illustrating a modified example of foreign object detection processing performed by processor 51. The foreign object detection processing in this modified example also involves... Figure 5 The process is executed according to the flowchart shown, with the battery BATT disconnected from the vehicle-side unit 40.

[0103] Processor 51 confirms the voltage of smoothing capacitor 48 (step S21). The voltage of smoothing capacitor 48 is the detected value detected by voltage sensor 49a. The voltage confirmed in step S21 is set as V2.

[0104] The processor 51 activates the power conversion device 43 (step S22). Specifically, the processor 51 controls the switching of each switching element 431-434 on / off. The charge stored in the smoothing capacitor 48 is supplied to the vehicle-side coil 41 via the power conversion device 43 and the resonant circuit 44, generating a magnetic field around the vehicle-side coil 41.

[0105] Processor 51 confirms the voltage of smoothing capacitor 48 and the current detected by current sensor 49b (step S24). The voltage of smoothing capacitor 48 is the detected value detected by voltage sensor 49a. The voltage confirmed in step S24 is set as V3, and the current is set as I3.

[0106] Processor 51 calculates impedance Z based on voltage V3 and current I3, and compares impedance Z with threshold Za (step S25). Processor 51 can calculate impedance Z, for example, by dividing voltage V3 by current I3 (i.e., Z = V3 / I3). Threshold Za is a value calculated, for example, by collecting data on voltage V3 and current I3 in the presence and absence of foreign object 100, and is pre-stored in memory 52.

[0107] When the impedance Z is less than the threshold Za (step S25: yes), the processor 51 determines that there is no foreign object 100 (step S26).

[0108] When the impedance Z is above the threshold Za (step S25: no), it is presumed that the loss is increased due to the presence of foreign object 100, and the processor 51 determines that foreign object 100 is present (step S27).

[0109] The foreign object detection processing in the modified example can achieve the same effect as the foreign object detection processing in the previously described embodiment. Furthermore, in the modified example's foreign object detection processing, after the processor 51 activates the power conversion device 43 in step S22, it can determine the presence of the foreign object 100 without waiting for a predetermined time, thus shortening the processing time. Therefore, when the foreign object 100 is not present, non-contact power transmission can be initiated quickly after the vehicle 4 is parked.

[0110] The various processes described in the flowcharts of the above-described embodiments and variations can be implemented by a computer, specifically by processor 51, executing a pre-prepared program (i.e., the foreign object detection program of the present invention). This program is stored in a computer-readable storage medium and is executed by reading it from the storage medium. Furthermore, this program can be provided in the form of storage on a non-transitory storage medium such as flash memory, or it can be provided via a network.

[0111] The present invention has been described above with reference to the accompanying drawings, but the present invention is not limited to this embodiment. It is obvious that those skilled in the art will conceive of various modifications or alterations within the scope of the technical solution described, and it should be understood that these modifications and alterations also fall within the technical scope of the present invention. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the spirit of the invention.

[0112] For example, the mobile body of the present invention only needs to be able to transmit electricity to the ground-side unit 20 without contact, and is not limited to vehicles 4 such as battery-powered electric vehicles and plug-in hybrid vehicles as described above. The mobile body can be, for example, a two-wheeled vehicle, a work vehicle (which are other examples of vehicle 4), or an aircraft.

[0113] Furthermore, the determination in step S15 described above is performed after a predetermined time has elapsed since the power conversion device 43 was started to operate, but is not limited to this. For example, the processor 51 may also continuously monitor the voltage V3 (accumulated data) of the smoothing capacitor 48 after the power conversion device 43 has been started to operate. Moreover, the processor 51 may determine the presence of a foreign object 100 before the predetermined time has elapsed if the voltage V3 of the smoothing capacitor 48 falls below a threshold Vb within the predetermined time period, or if the change in the smoothing capacitor 48 exceeds a predetermined value within the predetermined time period.

[0114] At least the following items are described in this specification. The elements shown in parentheses are examples of components corresponding to the above embodiments, but are not intended to limit the scope.

[0115] (1) A mobile body of a contactless power transmission system (contactless power transmission system 1), wherein the contactless power transmission system performs contactless power transmission between a mobile body-side unit (vehicle-side unit 40) mounted on the mobile body (vehicle 4) and a ground-side unit (ground-side unit 20) disposed outside the mobile body, wherein,

[0116] The mobile body has:

[0117] Storage battery (BATT);

[0118] The mobile body side unit is electrically connected to the storage battery;

[0119] A switch (contactor 60), disposed between the battery and the mobile body-side unit, is capable of switching the electrical connection or disconnection between the battery and the mobile body-side unit; and

[0120] The control device (control device 50) includes a processor (processor 51) for controlling the movable body side unit and the switch.

[0121] The mobile body side unit includes:

[0122] The movable body-side coil receives or supplies power to the ground-side coil disposed on the ground-side unit in a non-contact manner.

[0123] A power conversion device (power conversion device 43) is connected between the coil on the moving body side and the battery to convert power between DC power and AC power; and

[0124] An energy storage device (smoothing capacitor 48) is disposed between the power conversion device and the battery.

[0125] When the processor disconnects the battery from the mobile body unit via the switch, it activates the power conversion device to perform a foreign object detection process to determine whether there is a metallic foreign object (foreign object 100) between the mobile body unit and the ground unit.

[0126] According to (1), a device capable of performing foreign object detection processing via a mobile body can be used without relying on a ground-side unit. Furthermore, a switch is provided between the battery and the mobile body-side unit, and the processor performs foreign object detection processing while the battery and the mobile body-side unit are electrically disconnected. Therefore, the influence of the battery can be eliminated in the foreign object detection processing, and foreign objects can be detected with good accuracy.

[0127] (2) The mobile body of the non-contact power transmission system according to (1), wherein,

[0128] The processor performs the foreign object detection process before the mobile body side unit is coupled to the ground side unit.

[0129] According to (2), foreign objects can be detected with good accuracy regardless of the influence of the ground-side unit. In addition, since no power is supplied from the moving body-side unit to the ground-side unit, foreign objects can be detected with low power.

[0130] (3) A mobile body according to the non-contact power transmission system described in (1) or (2), wherein,

[0131] The mobile body side unit also includes a voltage detection unit (voltage sensor 49a) for detecting the voltage of the storage device.

[0132] In the foreign object detection process, the processor determines whether the foreign object exists based on the detection result of the voltage detection unit.

[0133] According to (3), foreign objects can be detected without the need for a large number of foreign object detection components.

[0134] (4) The mobile body of the non-contact power transmission system according to (3), wherein,

[0135] In the foreign object detection process, if the voltage detected by the voltage detection unit is below a threshold during a predetermined period from the start of operation of the power conversion device or after the predetermined period, the processor determines that the foreign object is present.

[0136] According to (4), foreign objects can be detected based on the voltage of the storage device during a specified time period or after a specified time period.

[0137] (5) The mobile body of the non-contact power transmission system according to (3), wherein,

[0138] In the foreign object detection process, if the processor determines that the foreign object exists if the voltage change detected by the voltage detection unit is above a predetermined value during a predetermined period of time from when the power conversion device is started to operate or after the predetermined period of time has elapsed.

[0139] According to (5), foreign objects can be detected based on the change in voltage of the storage device within a specified time period or after a specified time.

[0140] (6) The mobile body of the non-contact power transmission system according to (3), wherein,

[0141] The mobile body side unit also includes a current detection unit (current sensor 49b) for detecting current, which is disposed between the power conversion device and the energy storage device.

[0142] In the foreign object detection process, the processor calculates the impedance based on the detection results of the voltage detection unit and the current detection unit, and determines that the foreign object exists if the impedance is above a threshold.

[0143] According to (6), the time for foreign object detection and processing can be shortened.

[0144] (7) A method for detecting foreign objects in a non-contact power transmission system, wherein the non-contact power transmission system performs non-contact power transmission between a mobile body-side unit mounted on a mobile body and a ground-side unit disposed outside the mobile body, wherein,

[0145] The mobile body includes: a battery; and a mobile body-side unit electrically connected to the battery.

[0146] The mobile body-side unit includes: a mobile body-side coil, which receives or transmits power to a ground-side coil disposed on the ground-side unit in a non-contact manner; a power conversion device connected between the mobile body-side coil and the battery, which converts power between DC power and AC power; and an energy storage device disposed between the power conversion device and the battery.

[0147] The foreign object detection method performs the following processing via a processor:

[0148] Before performing the contactless power transmission, disconnect the electrical connection between the battery and the mobile body-side unit (step S5); and

[0149] In the disconnected state where the battery is disconnected from the mobile body side unit, the power conversion device is operated (steps S12 and S22) to determine whether there is a metallic foreign object between the mobile body side unit and the ground side unit (steps S15 and S25).

[0150] According to (7), foreign object detection processing can be performed by the device of the mobile body without relying on the ground-side unit. In addition, foreign object detection processing is performed with the battery electrically disconnected from the mobile body-side unit, so the influence of the battery can be eliminated in the foreign object detection processing, and foreign objects can be detected with good accuracy.

[0151] (8) A foreign object detection program product for a contactless power transmission system, comprising a foreign object detection program, wherein the contactless power transmission system performs contactless power transmission between a mobile body-side unit mounted on a mobile body and a ground-side unit disposed outside the mobile body, wherein,

[0152] The mobile body includes: a battery; and a mobile body-side unit electrically connected to the battery.

[0153] The mobile body-side unit includes: a mobile body-side coil, which receives or transmits power to a ground-side coil disposed on the ground-side unit in a non-contact manner; a power conversion device connected between the mobile body-side coil and the battery, which converts power between DC power and AC power; and an energy storage device disposed between the power conversion device and the battery.

[0154] The foreign object detection program causes the computer (processor 51) to perform the following processes:

[0155] Before performing the contactless power transfer, disconnect the electrical connection between the battery and the mobile body-side unit; and

[0156] In the disconnected state where the battery is disconnected from the mobile body side unit, the power conversion device is activated to determine whether there is a metallic foreign object between the mobile body side unit and the ground side unit.

[0157] According to (8), foreign object detection processing can be performed by the device of the mobile body without relying on the ground-side unit. In addition, foreign object detection processing is performed with the battery electrically disconnected from the mobile body-side unit, so the influence of the battery can be eliminated in the foreign object detection processing, and foreign objects can be detected with good accuracy.

Claims

1. A mobile body for a contactless power transmission system, wherein the contactless power transmission system performs contactless power transmission between a mobile body-side unit mounted on the mobile body and a ground-side unit disposed outside the mobile body, wherein, The mobile body has: Storage battery; The mobile body side unit is electrically connected to the storage battery; A switch, disposed between the battery and the mobile unit, is capable of switching the electrical connection or disconnection between the battery and the mobile unit; and The control device includes a processor that controls the moving body side unit and the switch. The mobile body side unit includes: The movable body-side coil receives or supplies power to the ground-side coil disposed in the ground-side unit in a non-contact manner. A power conversion device is connected between the coil on the side of the mobile body and the battery to convert power between DC power and AC power. as well as An energy storage device is disposed between the power conversion device and the battery. When the processor disconnects the battery from the mobile body unit via the switch, it activates the power conversion device to perform a foreign object detection process that determines whether there is a metallic foreign object between the mobile body unit and the ground unit.

2. The mobile body of the non-contact power transmission system according to claim 1, wherein, The processor performs the foreign object detection process before the mobile body side unit is coupled to the ground side unit.

3. The mobile body of the contactless power transmission system according to claim 1 or 2, wherein, The mobile body side unit also includes a voltage detection unit for detecting the voltage of the energy storage device. In the foreign object detection process, the processor determines whether the foreign object exists based on the detection result of the voltage detection unit.

4. The mobile body of the non-contact power transmission system according to claim 3, wherein, In the foreign object detection process, if the voltage detected by the voltage detection unit is below a threshold during a predetermined period from the start of operation of the power conversion device or after the predetermined period, the processor determines that the foreign object is present.

5. The mobile body of the non-contact power transmission system according to claim 3, wherein, In the foreign object detection process, if the processor determines that the foreign object exists if the voltage change detected by the voltage detection unit is above a predetermined value during a predetermined period of time from when the power conversion device is started to operate or after the predetermined period of time has elapsed.

6. The mobile body of the non-contact power transmission system according to claim 3, wherein, The mobile body side unit also includes a current detection unit for detecting current, which is disposed between the power conversion device and the energy storage device. In the foreign object detection process, the processor calculates the impedance based on the detection results of the voltage detection unit and the current detection unit, and determines that the foreign object exists if the impedance is above a threshold.

7. A method for detecting foreign objects in a non-contact power transmission system, wherein the non-contact power transmission system performs non-contact power transmission between a mobile body-side unit mounted on a mobile body and a ground-side unit disposed outside the mobile body, wherein... The mobile body includes: a battery; and a mobile body-side unit electrically connected to the battery. The mobile body-side unit includes: a mobile body-side coil, which receives or transmits power to a ground-side coil disposed on the ground-side unit in a non-contact manner; a power conversion device connected between the mobile body-side coil and the battery, which converts power between DC power and AC power; and an energy storage device disposed between the power conversion device and the battery. The foreign object detection method performs the following processing via a processor: Before performing the contactless power transfer, disconnect the electrical connection between the battery and the mobile body-side unit; and In the disconnected state where the battery is disconnected from the mobile body side unit, the power conversion device is activated to determine whether there is a metallic foreign object between the mobile body side unit and the ground side unit.

8. A foreign object detection program product for a contactless power transmission system, comprising a foreign object detection program, wherein the contactless power transmission system performs contactless power transmission between a mobile body-side unit mounted on a mobile body and a ground-side unit disposed outside the mobile body, wherein... The mobile body includes: a battery; and a mobile body-side unit electrically connected to the battery. The mobile body-side unit includes: a mobile body-side coil, which receives or transmits power to a ground-side coil disposed on the ground-side unit in a non-contact manner; a power conversion device connected between the mobile body-side coil and the battery, which converts power between DC power and AC power; and an energy storage device disposed between the power conversion device and the battery. The foreign object detection program causes the computer to perform the following processes: Before performing the contactless power transfer, disconnect the electrical connection between the battery and the mobile body-side unit; and In the disconnected state where the battery is disconnected from the mobile body side unit, the power conversion device is activated to determine whether there is a metallic foreign object between the mobile body side unit and the ground side unit.

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