Power transmission equipment

Abstract

To provide a power transmission device capable of simultaneously detecting foreign objects with high sensitivity and suppressing error detection.SOLUTION: A power transmission device of the embodiment performs power transmission without contact with a power reception device. The power transmission device includes a power transmission coil, a current detection circuit, and a control circuit. The current detection circuit measures the current value of the power transmission coil. The control circuit determines a standby current as a reference value during standby when power is not transferred to the power reception device, sets a value obtained by adding a certain value to a reference value, or a value obtained by adding a certain ratio to the reference value as a threshold for foreign object detection, and determines that there is a foreign object on the power transmission coil when the current value detected by the current detection circuit during standby is greater than or equal to the threshold value.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Embodiments of the present invention relate to a power transmission device.

Background Art

[0002] In recent years, systems have been devised that provide various services by mounting electronic devices on carts (mobile trolleys) such as shopping carts operated by users. A battery for supplying power to the electronic device is mounted on the cart. As a charging system for the battery mounted on the cart, a non-contact power transmission technology for non-contact power supply to the cart stored in the storage position is adopted. For example, in the power supply system, a power receiving coil is provided on the cart, and a power transmission coil for supplying power to the power receiving coil of the cart stored in the storage position is mounted at the storage position. Further, such non-contact power transmission technology is also used in fields other than carts.

[0003] In a device that performs non-contact power transmission, if power transmission is performed with a metal foreign object sandwiched between the power transmission coil and the power receiving coil, there is a problem that the metal foreign object generates heat.

[0004] Therefore, for example, a technique for detecting the presence of a metal foreign object by detecting an input current from an external power source and performing a comparison process with a preset foreign object determination threshold value is also known. Further, in order to enhance the safety against heat generation of the metal foreign object, if the foreign object determination threshold value is made as small as possible to increase the detection sensitivity of the metal foreign object, there is also a possibility that power transmission may not start due to false detection.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem that this invention aims to solve is to provide a power transmission device that can achieve both highly sensitive foreign object detection and suppression of false detections. [Means for solving the problem]

[0007] The power transmission device of this embodiment transmits power to a power receiving device without contact. The power transmission device comprises a power transmission circuit, a current detection circuit, and a control circuit. The power transmission circuit includes a power transmission coil. The current detection circuit measures the current value of the power transmission circuit. The control circuit determines the average value of the standby current measured a predetermined number of times at predetermined intervals during standby when power transmission is not being performed with the power receiving device, and sets a value obtained by adding a certain value to the reference value or by adding a certain ratio to the reference value as a foreign object detection threshold. If the current value detected by the current detection circuit during standby is equal to or greater than the threshold, the control circuit determines that there is a foreign object on the power transmission coil. When the control circuit enters a standby state after power-on, it sets the threshold for detecting foreign objects. [Brief explanation of the drawing]

[0008] [Figure 1] A perspective view showing the configuration of the power supply system according to the first embodiment. [Figure 2] A perspective view showing the configuration of the cart for the power supply system according to the first embodiment. [Figure 3] A block diagram showing the configuration of the control system of the power supply system according to the first embodiment. [Figure 4] A perspective view showing the configuration of the power receiving device and power transmitting device of the power supply system according to the first embodiment. [Figure 5] A flowchart showing an example of processing by a power transmission device in a power supply system according to the first embodiment. [Figure 6] A flowchart illustrating an example of the processing of a power transmission device in a power supply system according to the first embodiment, showing the process of setting a threshold for foreign object detection. [Figure 7] An explanatory diagram showing an example of the change in transmission current by the power transmission device of the power supply system according to the first embodiment. [Figure 8] An explanatory diagram showing an example of the change in transmission current by the power transmission device of the power supply system according to the first embodiment, and an example of the standby current for each power transmission device. [Figure 9] A perspective view showing the configuration of the power receiving device and power transmitting device of the power supply system according to the second embodiment. [Figure 10] A block diagram showing the configuration of the control system of the power supply system according to the second embodiment. [Figure 11] A perspective view showing the configuration of the power transmission device in the power supply system according to the third embodiment. [Figure 12] A block diagram showing the configuration of the control system of the power supply system according to the third embodiment. [Figure 13] A flowchart showing an example of the process for setting the threshold for foreign object detection in the power supply system according to the third embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, the power supply system 1 and power transmission device 35 according to the first embodiment will be described with reference to Figures 1 to 8. Figure 1 is a perspective view showing the configuration of the power supply system 1 according to the first embodiment, and Figure 2 is a perspective view of the cart 2 of the power supply system 1. Figure 3 is a block diagram showing the configuration of the control system of the power supply system 1. Figure 4 is a perspective view showing the configuration of the power receiving device 23 and the power transmission device 35. Figure 5 shows an example of power transmission processing by the power transmission device 35, and Figure 6 is a flowchart showing the setting process of the foreign object detection threshold T in the power transmission processing of the power transmission device 35. Figure 7 is an explanatory diagram showing an example of the change in power transmission current by the power transmission device 35, and Figure 8 is an explanatory diagram showing an example of the change in power transmission current for each power transmission device 35.

[0010] As shown in Figures 1 and 3, the power supply system 1 comprises a power receiving device 23 and a power transmitting device 35. The power receiving device 23 is provided, for example, on a cart 2. Multiple power transmitting devices 35 are provided, for example, on a cart base 3 that accommodates multiple carts 2. In the following description of embodiments, the power supply system 1 will describe an example in which the power receiving device 23 and power transmitting devices 35 are applied to a cart 2 and a cart base 3.

[0011] As shown in FIG. 1, the power supply system 1 includes a cart 2 having a power receiving device 23, and a cart base 3 on which a plurality of carts 2 are installed and having a power transmission device 35. In the cart base 3 having a plurality of power transmission devices 35 arranged in one direction, a plurality of carts 2 each having a power receiving device 23 are stored side by side in one direction, and the plurality of power transmission devices 35 and the plurality of power receiving devices 23 are arranged to face each other at a predetermined interval.

[0012] The cart 2 shown in FIG. 2 is a moving body, for example, a shopping cart. The cart 2 includes a frame 11, a basket part 12, casters 151 and 152, an electronic device 21, a battery box 223 provided with a battery 22 inside, and a power receiving device 23.

[0013] The frame 11 is configured by assembling a plurality of frame members extending in different directions. The frame 11 supports the basket part 12, the plurality of casters 151 and 152, various electronic devices 21, and the power receiving device 23 at predetermined positions.

[0014] The frame 11 includes, for example, a pair of left and right vertical frame parts 111, a lower frame part 112, a horizontal frame part 113, a handle part 114, and a mounting frame 115. The vertical frame part 111, the lower frame part 112, and the horizontal frame part 113 extend in directions intersecting each other.

[0015] The vertical frame part 111 includes a pair of main frames 1111 extending upward from the rear wheel caster 152, a pair of sub - frames 1112 provided on the rear side of the main frame 1111, and a pair of sub - frames 1113 provided on the front side of the main frame 1111. The vertical frame part 111 extends in the vertical direction behind the basket part 12, and the rear wheel caster 152 is arranged at the lower end part.

[0016] The lower frame part 112 includes a plurality of frame members arranged along the floor surface. The lower frame part 112 includes, for example, a pair of main frames 1121, a support frame 1123, a front connecting part 1124, and a mounting part 1125 provided below the support frame 1123. The main frame 1121 extends forward from the rear wheel caster 152 toward the front wheel caster 151.

[0017] The support frame 1123 is a frame member that extends downward from the lateral frame part 113, bends forward at a predetermined height, extends forward, and the front end part bends upward. The support frame 1123 is constituted by, for example, a U-shaped frame member that curves and folds back at the front. The support frame 1123 extends along a plane parallel to the floor surface inside the main frame 1121. The support frame 1123 constitutes a basket placement area on its upper side.

[0018] The front connecting part 1124 extends in the width direction at the front end part of the lower end of the cart 2 and connects the front ends of the pair of main frames 1121.

[0019] The mounting part 1125 has its upper end fixed to a predetermined position of the support frame 1123. The mounting part 1125 extends downward from the support frame 1123, bends backward at a predetermined height, and extends backward. The mounting part 1125 is a frame member for mounting the power receiving device 23. The mounting part 1125 extends along a plane parallel to the floor surface inside the main frame 1121 and constitutes a support surface for supporting the power receiving device 23 below the support frame 1123. For example, when the cart 2 is installed on the cart base 3, the mounting part 1125 is set to dimensions such that the power transmission device 35 provided on the cart base 3 and the power receiving device 23 provided on the mounting part 1125 are arranged to face each other at a predetermined interval.

[0020] The lateral frame part 113 includes a plurality of link frames 1131, 1132, 1133 that are spanned between the left and right vertical frame parts 111 and extend in the width direction.

[0021] The handle portion 114 is positioned above the rear end of the cart 2. The handle portion 114 is positioned continuously with the upper end of the vertical frame portion 111. For example, the handle portion 114 extends in the width direction.

[0022] The mounting frame 115 is connected to the vertical frame portion 111. The mounting frame 115 extends, for example, above one of the vertical frame portions 111 and supports various electronic devices 21.

[0023] In the frame 11, the cage section 12 is supported by the vertical frame section 111, and front wheel casters 151 and rear wheel casters 152 are provided at the front and rear ends of the lower frame section 112, which is located below the cage section 12. In addition, in the frame 11, a power receiving device 23 is provided on the mounting section 1125, which is a frame member arranged along the floor surface of the lower frame section 112. A battery box 223 is also provided on the vertical frame section 111. For example, the battery box 223 is supported by a pair of subframes 1112 of the vertical frame section 111.

[0024] Furthermore, in the lower frame section 112, the pair of main frames 1121 extend diagonally towards the center at the front, such that the distance between them in the width direction at the front becomes narrower. Therefore, the frame 11 is formed with a narrower width at the front and a wider width at the rear in the forward direction of the cart 2.

[0025] The basket section 12 is constructed in a box shape with an upward opening, for example, using perforated panel members or mesh-like wire members. The basket section 12 is formed to be able to accommodate goods or to accommodate a shopping basket for accumulating goods. The basket section 12 is positioned in front of the vertical frame section 111, at a height that is raised above the floor surface. The left and right sides of the rear end of the basket section 12 are supported by the vertical frame section 111.

[0026] The front caster 151 and rear caster 152 each include a wheel 153 that rotates in the direction of movement and a bracket portion 154 that rotatably supports the wheel 153. The bracket portion 154 is rotatably mounted to the frame 11. The cart 2 moves as the wheels 153 of the casters 151 and 152 rotate on the floor surface. In addition, the direction of travel of the cart 2 can be changed by rotating the bracket portion 154 of the casters 151 and 152.

[0027] Similar to the shape of the frame 11 and the basket section 12, the front casters 151 are positioned so that they are narrower in width from side to side than the rear casters 152. Therefore, when storing multiple carts 2 in a row, for example, the frame 11 of the rear cart 2 can be stored so that it overlaps with the frame 11 of the front cart 2.

[0028] The electronic device 21 is an information terminal such as a tablet device for providing information to the user, or a product reader for acquiring information on products selected by the user. The electronic device 21 is connected to a battery 22, for example, and is powered by the battery 22. The electronic device 21 may also be a charging device for charging electronic devices such as mobile phones, smartphones, and digital cameras owned by the user using the power from the battery 22.

[0029] In this embodiment, for example, the electronic device 21 is shown to include a tablet terminal 211 and a product reader 212. The tablet terminal 211 is a computer having a display unit equipped with a touch panel. The tablet terminal 211 is installed so that its display unit faces the user located on the handle unit 114 side. The tablet terminal 211 displays, for example, product information read by the product reader 212. The tablet terminal 211 may also perform settlement processing for products read by the product reader 212.

[0030] The product reader 212 is a device that reads product information. The product reader 212 may also have a display unit that displays the information of the product it has read. For example, the product reader 212 is an RFID tag reader that reads RFID tags attached to products that are placed in and taken out of the basket 12. Alternatively, the product reader 212 may be a scanner that reads product identification information such as barcodes attached to products.

[0031] Furthermore, the electronic device 21 may be an interface device for connecting a mobile device (smartphone, tablet, etc.) owned by the user, instead of the tablet device 211. The mobile device connected to the interface device as electronic device 21 may perform the same processing as the tablet device 211 described above. In addition, the interface device as electronic device 21 may charge the battery of the mobile device. Furthermore, the interface device as electronic device 21 may have a built-in battery 22, or it may connect to a separately provided battery 22.

[0032] The battery box 223 is mounted on the frame 11. The battery box 223 is fixed to and supported by a pair of subframes 1112 located, for example, below the opening / closing panel 121 of the basket section 12. The battery 22 is a power supply unit that supplies power to the electronic equipment 21 mounted on the cart 2, and comprises a charging circuit 221 and a secondary battery 222. The battery 22 is connected to a power receiving device 23 and is charged by the power receiving device 23.

[0033] The charging circuit 221 supplies power from the switching circuit 2324 of the power receiving device 23 to the secondary battery 222 as charging power (charging power). For example, the charging circuit 221 converts the power supplied from the switching circuit 2324 into a DC current (charging power) used to charge the secondary battery 222. That is, the charging circuit 221 converts the power from the switching circuit 2324 into charging power with predetermined current and voltage values ​​for charging the secondary battery 222 and supplies it to the secondary battery 222. The charging circuit 221 charges the secondary battery 222 with power from the power receiving device 23.

[0034] The secondary battery 222 is charged by the charging power supplied from the charging circuit 221. The secondary battery 222 is also connected to the electronic device 21 and supplies power to the electronic device 21.

[0035] The power receiving device 23 receives power transmitted wirelessly and supplies the received power to the electronic device 21 or the battery 22. The power receiving device 23 may also be configured to include an output terminal for supplying power to the electronic device 21. In this case, the battery 22 may be charged by the power supplied via the electronic device 21.

[0036] The power receiving device 23 is located at the bottom of the cart 2. The power receiving device 23 is positioned, for example, below the lower frame portion 112. When the cart is stored in the cart base 3, the power receiving device 23 faces one of the multiple power transmitting devices 35 provided on the cart base 3.

[0037] As shown in Figure 4, the power receiving device 23 includes, for example, a casing 230, a power receiving coil 231, and a power receiving board.

[0038] The casing 230 is, for example, a rectangular housing that houses the power receiving coil 231 and the power receiving board. The casing 230 is connected, for example, below the lower frame portion 112. Specifically, the casing 230 is fixed to the mounting portion 1125 of the lower frame portion 112.

[0039] The underside of the casing 230 is positioned on the cart 2 in a orientation that conforms to the floor surface on which the cart 2 travels. The casing 230 is shaped so that when multiple carts 2 are stacked and stored in a row on the cart base 3, the casing 230 does not overlap with the casing 230 of the power receiving devices 23 of adjacent carts 2 in the direction of travel. Furthermore, when multiple carts 2 are stacked and stored in a row on the cart base 3, the casing 230 is positioned so as not to overlap with or interfere with the power receiving devices 23 of adjacent carts 2 in the direction of travel.

[0040] The power receiving coil 231 is placed inside the casing 230. The power receiving coil 231 is, for example, a planar coil formed by winding Litz wire. Alternatively, the power receiving coil 231 is a planar coil in which a coil pattern, or winding, is formed on a printed circuit board. The power receiving coil 231 has, for example, a power receiving surface that is formed in a planar shape. The power receiving surface of the power receiving coil 231 is positioned facing the floor surface on which the cart 2 travels. Note that the power receiving coil 231 is not limited to a planar coil as long as it can transmit power to the power transmission device 35.

[0041] The receiving coil 231 electromagnetically couples with the transmitting coil 351 when the receiving device 23 faces the transmitting device 35. The receiving coil 231 generates an induced current due to the magnetic field output from the transmitting coil 351 of the transmitting device 35. The receiving coil 231 constitutes, for example, a receiving resonant circuit (resonant element).

[0042] Here, the receiving resonant circuit functions as an AC power source, for example, supplying AC power to the rectifier circuit 2322 connected to the receiving resonant circuit. For example, when using a magnetic field resonance method for power transmission, it is desirable that the resonant frequency of the receiving resonant circuit be the same as, or nearly the same as, the resonant frequency of the transmitting resonant circuit, which is composed of the transmitting coil 351 of the transmitting device 35 (described later). This improves the power transmission efficiency when the receiving resonant circuit and the transmitting resonant circuit are electromagnetically coupled. The receiving resonant circuit may also be configured to use an electromagnetic induction method for power transmission.

[0043] The power receiving board includes a rectifier circuit 2322, a voltage conversion circuit 2323, a switching circuit 2324, and a control circuit 2326. The power receiving board is configured with various processing circuits, including the rectifier circuit 2322, the voltage conversion circuit 2323, the switching circuit 2324, and the control circuit 2326, by mounting electronic components and wiring patterns, for example.

[0044] The rectifier circuit 2322 rectifies the AC power supplied from the receiving resonant circuit and converts it into DC power. The rectifier circuit 2322 includes, for example, a rectifier bridge composed of multiple diodes. A pair of input terminals of the rectifier bridge are connected to the receiving resonant circuit. The rectifier circuit 2322 outputs DC power from a pair of output terminals by full-wave rectifying the AC power supplied from the receiving resonant circuit. The rectifier circuit 2322 supplies the DC power to the voltage conversion circuit 2323.

[0045] The voltage conversion circuit 2323 converts the DC voltage output from the rectifier circuit 2322 into a desired DC voltage. For example, two voltage conversion circuits 2323 are provided. One voltage conversion circuit 2323 will be described as 23231 and the other as 23232. One voltage conversion circuit 23231 is connected, for example, to the rectifier circuit 2322 and the switching circuit 2324. One voltage conversion circuit 23231 converts the DC power supplied from the rectifier circuit 2322 into DC power with a voltage suitable for charging. The other voltage conversion circuit 23232 is connected to the rectifier circuit 2322 and the control circuit 2326. The other voltage conversion circuit 23232 converts the DC power supplied from the rectifier circuit 2322 into DC power suitable for operating the control circuit 2326.

[0046] The switching circuit 2324 switches the connection and disconnection of the voltage conversion circuit 23231 and the charging circuit 221. The switching circuit 2324 switches the connection and disconnection of the voltage conversion circuit 23231 and the charging circuit 221 based on a signal from the control circuit 2326, for example.

[0047] The control circuit 2326 controls the operation of the switching circuit 2324. The control circuit 2326 is a processing circuit. The control circuit 2326 includes, for example, a processor and memory. The processor performs arithmetic processing. The processor performs various processing based on the program and the data used in the program stored in the memory. The memory stores the program and the data used in the program, etc. The control circuit 2326 may be composed of a microcontroller and / or an oscillator circuit, etc.

[0048] As shown in Figures 1 and 2, cart 2 is stored in a cart base 3 located in a predetermined storage position. In Figures 1 and 2, multiple carts 2 are stored in the cart base 3 in a nested arrangement.

[0049] The cart base 3, which serves as a storage device for cart 2, comprises a guide base 31 as a base section, a cart gate 32, and a plurality of power transmission devices 35 supported by the guide base 31.

[0050] The guide base 31 includes a plate-shaped support base 311 that is laid at a predetermined storage position. The support base 311 has a plurality of guide rails 312 extending in one direction on its upper surface, and guide grooves 313 formed between the plurality of guide rails 312. The support base 311 also has protrusions and grooves that guide the storage positions of the plurality of carts 2. The guide base 31 guides the direction of travel of the carts 2 on the support base 311 by defining the movement of the front and rear wheels 153 with the guide rails 312 and guide grooves 313. The guide base 31 also supports a plurality of power transmission devices 35 at equal intervals.

[0051] The cart gate 32 comprises a pair of poles 322 erected from both sides of the guide base 31, and side bars 323 positioned at a predetermined height on both side edges of the guide base 31 and extending in one direction.

[0052] Multiple power transmission devices 35 are provided, for example, between a pair of guide grooves 313 in a guide base 31, which guides a pair of front wheels 153 of the cart 2. The multiple power transmission devices 35 are arranged in the direction of extension of the pair of guide grooves 313 in the guide base 31. Here, the direction of extension of the guide grooves 313 is the direction of travel of the cart 2 on the guide base 31. In other words, the direction of extension of the guide grooves 313 is the direction in which the multiple carts 2 are stacked on the guide base 31. The multiple power transmission devices 35 face the power receiving devices 23 of the multiple carts 2 that are stacked and stored on the cart base 3. The power transmission devices 35 transmit power to the power receiving devices 23 of the opposing carts 2 without contact.

[0053] As shown in Figure 4, the power transmission device 35 includes, for example, a casing 350, a power transmission coil 351, a power transmission board, and an AC adapter 354.

[0054] The casing 350 is formed, for example, in the shape of a rectangular box. The casing 350 houses the power transmission coil 351 and the power transmission board inside. The casing 350 faces the power receiving device 23 of the cart 2, which is housed in the cart base 3, at a predetermined distance apart. The distance between the casing 350 and the casing 230 of the power receiving device 23 is several millimeters, specifically, for example, 1 mm to 10 mm.

[0055] The power transmission coil 351 is, for example, a planar coil formed by winding Litz wire. Alternatively, the power transmission coil 351 is a planar coil in which a coil pattern, or windings, are formed on a printed circuit board. The power transmission coil 351 has, for example, a power transmission surface formed in a planar shape for transmitting power.

[0056] The power transmission surface of the power transmission coil 351 is positioned along the floor surface on which the cart 2 travels. The power transmission surface of the power transmission coil 351 is also positioned along the power receiving surface of the power receiving coil 231 housed in the cart base 3 and provided on the opposing cart 2. Each power transmission coil 351 of the multiple power transmission devices 35 is positioned opposite the power receiving coil 231 of each power receiving device 23 of the multiple carts 2 housed in the cart base 3.

[0057] When the power receiving device 23 and the power transmitting device 35 are facing each other, the power transmission coil 351 is electromagnetically coupled with the power receiving coil 231.

[0058] The power transmission coil 351 constitutes, for example, a power transmission resonant circuit (resonant element) as a power transmission unit.

[0059] Here, it is desirable that the resonant frequency of the power transmission resonant circuit, which is composed of the power transmission coil 351, be the same as, or approximately the same as, the oscillation frequency of the oscillation circuit of the control circuit 3528. This improves the power transmission efficiency when the power receiving resonant circuit and the power transmission resonant circuit are electromagnetically coupled. Note that the power transmission resonant circuit may also utilize an electromagnetic induction method for power transmission.

[0060] The power transmission board includes a power transmission circuit 3522, a voltage conversion circuit 3523, a switching circuit 3524, a current sensor 3526, a current detection circuit 3527, and a control circuit 3528. The power transmission board is configured with various processing circuits, including the power transmission circuit 3522, voltage conversion circuit 3523, switching circuit 3524, current sensor 3526, current detection circuit 3527, and control circuit 3528, by mounting electronic components and wiring patterns, for example.

[0061] The power transmission circuit 3522 generates power to be transmitted and supplies the generated power to the power transmission coil 351. For example, the power transmission circuit 3522 generates AC power as power to be transmitted by switching DC power supplied via an AC adapter 354 or the like, based on the control of the control circuit 3528. The power transmission coil 351 outputs power that the power receiving device 23 can receive according to the power to be transmitted supplied from the power transmission circuit 3522. The power transmission circuit 3522 generates AC power with a frequency that is the same as, or approximately the same as, the resonant frequency of the power transmission resonant circuit. The power transmission circuit 3522 has a switching element such as an FET. The power transmission circuit 3522 is switched on and off by the output of the oscillation circuit in the control circuit 3528. The power output from the power transmission circuit 3522 is transmitted to the power receiving device 23 using electromagnetic coupling such as electromagnetic induction or magnetic field resonance between the power transmission coil 351 and the power receiving coil 231.

[0062] The voltage conversion circuit 3523 converts the voltage of a DC power supply, such as an AC adapter 354 connected to a commercial power supply, into a desired DC voltage. Specifically, the voltage conversion circuit 3523 generates power to operate the control circuit 3528 and supplies it to the control circuit 3528.

[0063] The switching circuit 3524 switches between connecting and disconnecting the AC adapter 354 and the power transmission circuit 3522. Based on a control signal from the control circuit 3528, the switching circuit 3524 switches the power supply state from the power transmission device 35 to the power receiving device 23 by connecting or disconnecting the AC adapter 354 and the power transmission circuit 3522. For example, the switching circuit 3524 supplies either DC power at a voltage supplied from an external DC power source or DC power at a voltage stepped down by the voltage conversion circuit 3523 from the DC power supplied from the external DC power source to the power transmission circuit 3522. The switching circuit 3524 switches the DC power supplied to the power transmission circuit 3522 based on the control of the control circuit 3528.

[0064] The current sensor 3526 detects the DC current input to the power transmission circuit 3522. The current sensor 3526 is a small resistor connected between the switching circuit 3524 and the power transmission circuit 3522. The current sensor 3526 generates a potential (current detection signal) corresponding to the current transmitted from the switching circuit 3524 to the power transmission circuit 3522.

[0065] The current detection circuit 3527 amplifies the minute signal detected by the current sensor 3526 and outputs it to the control circuit 3528. The current detection circuit 3527 measures, for example, the current value input to the power transmission circuit 3522. The current value input to the power transmission circuit 3522 may be measured by the current sensor 3526, or by both the current sensor 3526 and the current detection circuit 3527.

[0066] The control circuit 3528 controls the operation of the power transmission circuit 3522. The control circuit 3528 is a processing circuit. The control circuit 3528 includes, for example, a processor and memory. The processor performs arithmetic processing. The processor performs various processing based on programs and data used in programs stored in memory. The memory stores programs and data used in programs, etc. The control circuit 3528 may be composed of a microcontroller and / or an oscillator circuit, etc.

[0067] For example, the control circuit 3528 controls the frequency of the AC power output from the power transmission circuit 3522, and controls the on / off operation of the power transmission circuit 3522. For example, the control circuit 3528 switches between a state in which a magnetic field is generated in the power transmission coil 351 (power transmission state) and a state in which a magnetic field is not generated in the power transmission coil 351 (standby state) by controlling the switching circuit 3524. Alternatively, the control circuit 3528 may be configured to intermittently generate a magnetic field in the power transmission coil 351 to change the timing of power transmission.

[0068] When power is supplied from the AC adapter 354 and the power is turned on, the control circuit 3528 measures the standby current in the standby state (standby time) of the power transmission unit after power is turned on using the current sensor 3526 and / or the current detection circuit 3527, and sets the measured current value as the reference value A. Alternatively, the control circuit 3528 measures the standby current in the standby state after the power supply to the power receiving device 23 has been stopped using the current sensor 3526 and / or the current detection circuit 3527, and sets the measured current value as the reference value A.

[0069] For example, the processor of the control circuit 3528 stores the set reference value A in memory. Specifically, the control circuit 3528 operates the power transmission unit with the same power supply voltage as the standby state, measures the power transmission current a predetermined number of times n at predetermined intervals s, calculates the average value, and sets this average value A as the reference value A.

[0070] For example, as shown in the explanatory diagram of the relationship between time and transmission current (power) in Figure 7, when power is turned on to the power transmission device 35 and the power transmission device 35 enters a standby state, a standby current, which is approximately the same as the reference value A, flows through the power transmission circuit 3522. At this time, since the current value of the standby current fluctuates within a predetermined range, the control circuit 3528 estimates the reference value A by measuring the current value a predetermined number of times n at predetermined intervals s and calculating the average value. Also, as shown in the explanatory diagram of the relationship between time and transmission current (power) in Figure 8, the standby current (reference value A) differs for each power transmission device 35, as shown by solid lines (1) to (3), depending on the variation in the characteristics of the power transmission device 35 and the installation environment of the power transmission device 35. For this reason, the reference value A is determined for each power transmission device 35. Here, (1) to (3) in Figure 8 are used for convenience to distinguish between three different power transmission devices 35. Furthermore, (1)A to (3)A in Figure 8 represent the current values ​​of each power transmission device 35 in the standby state (standby current, reference value A), and (1)T to (3)T represent the foreign object detection thresholds of each power transmission device 35.

[0071] The memory of the control circuit 3528 stores a predetermined interval s and a predetermined number of times n. Here, an example of a predetermined interval s is 0.5 seconds, and the predetermined number of times n is multiple, for example, 10 times. In this example, the control circuit 3528 measures the standby current 10 times at 0.5-second intervals, calculates the average value A of these measured current values, and stores the calculated average value A in memory as the reference value A.

[0072] Furthermore, when the power receiving device 23 is facing the power transmitting device 35, the control circuit 3528 performs an authentication process to confirm whether the power receiving device 23 is a legitimate power receiving device 23.

[0073] Furthermore, the control circuit 3528 performs a foreign object detection process to detect metallic foreign objects placed between the power transmission device 35 and the power receiving device 23.

[0074] Here, a metallic foreign object is defined as something that is made of metal material in part or all. Furthermore, the metallic foreign object is located between the power receiving device 23 and the power transmitting device 35, and is present on the power transmitting coil 351, and generates heat when the power transmitting coil 351 transmits power. Examples of metallic foreign objects include various items such as coins, metal pieces, paper or resin films with a metal film such as aluminum, clips, and hairpins.

[0075] For example, the memory of the control circuit 3528 stores a threshold value U, which is a predetermined value used to determine whether the calculated reference value A is normal or not. The control circuit 3528 determines that reference value A is normal if it is within the range of threshold value U, and determines that reference value A is abnormal if it is greater than threshold value U.

[0076] Furthermore, the control circuit 3528 sets a foreign object detection threshold T calculated based on the reference value A, which is a value greater than the reference value A and is assumed to occur when a metallic foreign object is present on the power transmission device 35. This setting process of the foreign object detection threshold T by the control circuit 3528 is performed during the standby state, for example, after power is turned on and before power is supplied to the power receiving device 23. An example of the foreign object detection threshold T is shown by a dashed line in Figure 7.

[0077] As a first setting process for the foreign object detection threshold T, the control circuit 3528 sets the foreign object detection threshold T based on the reference value (average value) A when, for example, the reference value A is determined to be normal. Furthermore, as shown in (1)A to (3)A in Figure 8, the reference value A is different for each power transmission device 35, so as shown in (1)T to (3)T in Figure 8, the control circuit 3528 of each power transmission device 35 sets the foreign object detection threshold T based on the reference value A of each power transmission device 35, based on the reference value A measured for each power transmission device 35.

[0078] As a specific example, the control circuit 3528 sets the current value A+α, which is the reference value A plus a constant value α, as the foreign object detection threshold T and stores it in memory. Another specific example is that the control circuit 3528 stores in memory the current value obtained by adding a constant ratio β to the reference value A as the foreign object detection threshold T. Here, the current value obtained by adding a constant ratio β to the reference value A is the value obtained by adding the value obtained by multiplying the reference value A by a constant ratio β to the reference value A (A+A·β). If the constant ratio β is 10% (0.1), the foreign object detection threshold T becomes A×1.1. The memory of the control circuit 3528 stores the constant value α and / or constant ratio β that set the foreign object detection threshold T based on the reference value A.

[0079] Furthermore, as a second setting process for the foreign object detection threshold T, the control circuit 3528, for example, if it determines that the reference value A is abnormal, sets a fixed value C, which is a predetermined value of a pre-set current value, as the foreign object detection threshold T and stores it in memory. Here, the fixed value C is a value greater than the reference value A and is a current value that is assumed to occur when a metal foreign object of a predetermined size is present on the power transmission device 35. Here, an example of a metal foreign object of a predetermined size is, for example, an iron piece about 20 mm square, but it is not limited to this example, and the current value set as the fixed value Cn is set appropriately based on the size and type of metal foreign object to be detected. As an example, the fixed value C is set to a value that takes into account the variation in standby current caused by variations in the power transmission device 35 and installation conditions, that is, a value that allows metal foreign objects to be detected on any of the power transmission devices 35. In the example shown in Figure 8, the fixed value C is set to a current value such that (1)T, and this fixed value C is used for all power transmission devices 35 so that foreign objects can be detected in the power transmission device 35 with the highest standby current (reference value A) (in Figure 8, (1)A).

[0080] As described above, the control circuit 3528 sets the foreign object detection threshold T based on a reference value A calculated for each power transmission device 35, or, if the reference value A is abnormal and unusable, sets a pre-set fixed value C.

[0081] The control circuit 3528 performs a foreign object detection process by comparing the foreign object detection threshold T set in the first or second setting process with the current value detected by the current sensor 3526 and / or the current detection circuit 3527, thereby detecting a foreign object. For example, as shown by the dashed line in Figure 7, when a metallic foreign object is placed on the power transmission device 35, the current value fluctuates by a larger value than the standby current. The control circuit 3528 determines that a metallic foreign object has been detected if the current value detected by the current sensor 3526 and / or the current detection circuit 3527 exceeds the threshold T and is different from a normal current value, such as when the power receiving device 23 has not been authenticated.

[0082] When the control circuit 3528 detects the presence of a metallic foreign object, it controls the switching circuit 3524 to stop power transmission by not generating a magnetic field in the power transmission coil 351, thereby preventing overheating of the metallic foreign object. Furthermore, when no metallic foreign object is detected and the power receiving device 23 is authenticated, the control circuit 3528 controls the switching circuit 3524 to generate a magnetic field in the power transmission coil 351 equivalent to the power transmission, and transmits power to the power receiving device 23.

[0083] As shown in Figure 7, after authentication of the power receiving device 23 is established and no foreign matter is detected, the control circuit 3528 transmits power from the power transmitting device 35 to the power receiving device 23 and proceeds to the charging operation.

[0084] As shown in these examples, the control circuit 3528 controls each component and performs various processes based on information such as various programs and parameters stored in memory.

[0085] The AC adapter 354 is located, for example, outside the casing 350 and connected to the power transmission board.

[0086] Next, an example of a control method for the power transmission device 35 of the power supply system 1 according to this embodiment will be described with reference to Figures 5 and 6. Figure 5 is a flowchart of a series of steps related to power transmission by the power transmission device 35, and Figure 6 is a flowchart related to setting the threshold for foreign object detection. In this embodiment, an example is shown in which authentication processing and foreign object detection processing are performed using the standby current, but the current for authentication and the current for foreign object detection may have different current values.

[0087] As shown in Figure 5, when the power transmission device 35 is powered on, the control circuit 3528 first performs a setting process to set a foreign object detection threshold T (ACT1). As shown in Figure 6, as part of the process to set the foreign object detection threshold T, the control circuit 3528 first takes in the current value and then calculates a reference value A, which is the average value (ACT11). Specifically, the control circuit 3528 measures the current value a predetermined number of times n at a predetermined interval s stored in memory, calculates the average value A from the measured current values, sets this average value A as the reference value A, and stores it in memory. Next, the control circuit 3528 compares the calculated reference value A with the threshold U stored in memory and determines whether the reference value A is normal as a current value for standby current (ACT12).

[0088] If the reference value A is normal (Yes in ACT12), the control circuit 3528 sets the current value obtained by adding a constant value α to the reference value A (A+α) as the foreign object detection threshold T, or sets the current value obtained by adding a constant ratio β to the reference value A (A+A·β) as the foreign object detection threshold T, and stores it in memory (ACT13).

[0089] If the reference value A is abnormal (No. in ACT12), the control circuit 3528 sets the fixed value C stored in memory as the foreign object detection threshold T and stores it in memory (ACT14). Through these processes from ACT11 to ACT14, the control circuit 3528 sets the foreign object detection threshold T as ACT1.

[0090] Next, the control circuit 3528 enters a standby state and performs foreign object detection processing until authentication processing is performed (ACT2). For example, in the standby state, the control circuit 3528 continues to supply power from the power transmission coil 351 at the standby current. Also, during the standby state, as part of the foreign object detection processing, the control circuit 3528 compares the current value detected by the current sensor 3526 and / or the current detection circuit 3527 with the set foreign object detection threshold T. If the current value detected by the current sensor 3526 and / or the current detection circuit 3527 does not exceed the foreign object detection threshold T, the control circuit 3528 continues in the standby state, assuming that no metallic foreign object has been detected. If the current value detected by the current sensor 3526 and / or the current detection circuit 3527 exceeds the foreign object detection threshold T, the control circuit 3528 determines that a metallic foreign object has been detected and, for example, stops power supply.

[0091] Next, when the power receiving device 23 faces the power transmitting device 35, the control circuit 3528 performs an authentication process to confirm whether or not it is the legitimate power receiving device 23 (ACT3). As part of the authentication process, for example, the control circuit 3528 performs authentication by using a load modulation method, for example, by performing load modulation corresponding to the ID at the power receiving unit and detecting a change in current corresponding to the ID on the power transmitting side. Alternatively, the control circuit 3528 may perform the authentication determination by querying and responding to the IDs of the power transmitting device and the power receiving device using wireless communication means such as wireless communication or infrared communication.

[0092] During the authentication process, if the control circuit 3528 determines that the power receiving device is a legitimate power receiving device (ACT4, Yes), it will supply power to the power receiving device 23 as normal and begin charging the secondary battery 222 (ACT5). As ACT5, the control circuit 3528 will supply power at a charging current value for a certain period of time. If it determines that the device is not the target power receiving device 23 (ACT4, No), the control circuit 3528 will return to the standby state of ACT2 without starting the normal power supply (charging) process.

[0093] For example, after starting charging in ACT5, the control circuit 3528 determines whether the charging termination condition has been met (ACT6). If the charging termination condition is met (Yes in ACT6), the control circuit 3528 stops power transmission as charging is complete (ACT7) and returns to the standby state of ACT2. If the charging termination condition is not met (No in ACT6), the control circuit 3528 continues the charging process. Here, the charging termination condition is either that the secondary battery 222 is fully charged, or that the power receiving device 23 has moved and the power receiving device 23 is no longer on the power transmitting device 35.

[0094] With the power transmission device 35 and power supply system 1 configured in this way, the foreign object detection threshold T for detecting metallic foreign objects can be set based on a reference value A measured from the standby current after power-on. Here, for example, the foreign object detection threshold T is either the reference value A plus a constant value α, or the reference value A plus a constant ratio β. As a result, the power transmission device 35 can set the foreign object detection threshold T to a current value slightly larger than the standby current when there are no metallic foreign objects in the standby state for each power transmission device 35. Therefore, regardless of variations in the performance and characteristics of each power transmission device 35 or the environment in which the power transmission device 35 is installed, the power transmission device 35 can perform highly sensitive foreign object detection and suppress false detection of metallic foreign objects.

[0095] This is because the standby current fluctuates depending on variations in the characteristics of the components that make up the power transmission device 35 (e.g., electronic components, coils, etc.) and the surrounding environment of the location where the power transmission device 35 is installed. Here, the surrounding environment of the location where the power transmission device 35 is installed refers to, for example, the material of the cart base 3 on which the power transmission device 35 is installed and the floor (iron, aluminum, wood, etc.). However, since the power transmission device 35 uses a foreign object detection threshold T obtained from a reference value A determined from actual measurements during standby states such as after power-on of each power transmission device 35 after installation, it becomes possible to detect foreign objects with high sensitivity and suppress false detection of metallic foreign objects.

[0096] Furthermore, by setting the average value A calculated from current values ​​detected a predetermined number of times at predetermined intervals s as the reference value A, it is possible to suppress variations in the reference value A due to fluctuating standby current. In other words, by assuming that the standby current fluctuates during standby and setting the average value A as the reference value A, it becomes unnecessary to set a foreign object detection threshold with a certain margin to avoid false detection of foreign objects. Therefore, the power transmission device 35 can detect metal foreign objects of small size or other types with small current changes without sacrificing foreign object detection sensitivity.

[0097] Furthermore, the power transmission device 35 compares the obtained reference value A with a threshold U to determine whether the reference value is normal or not, and if it determines that it is abnormal, it sets a fixed value C as the foreign object detection threshold T. This prevents the power transmission device 35 from setting the foreign object detection threshold T based on the reference value A, which has become a higher current value than normal due to the metal foreign object, when a metal foreign object is present on the power transmission device 35.

[0098] According to the power transmission device 35 and power supply system 1 of the above-described embodiment, by using a foreign object detection threshold T set based on a reference value A obtained from the standby current in the foreign object detection process, it is possible to achieve both highly sensitive foreign object detection and suppression of false detections.

[0099] Note that the power transmission device 35A and power supply system 1 are not limited to those exemplified in the embodiments described above. Next, the power transmission device 35 and power supply system 1 according to the second embodiment will be described with reference to Figures 9 to 10. In the power transmission device 35A and power supply system 1 according to the second embodiment, the same reference numerals are used for components similar to those in the power transmission device 35 and power supply system 1 according to the first embodiment described above, and their detailed descriptions are omitted.

[0100] Figure 9 is a perspective view showing the configuration of the power receiving device 23 and the power transmitting device 35A of the power supply system 1 according to the second embodiment, and Figure 10 is a block diagram showing the configuration of the control system of the power supply system 1 according to the second embodiment.

[0101] As shown in Figure 9, the power supply system 1 comprises a power receiving device 23 and a power transmitting device 35A. Multiple power transmitting devices 35A are provided, for example, on a cart base 3 that accommodates multiple carts 2.

[0102] Multiple power transmission devices 35A are provided, for example, between a pair of guide grooves 313 in a guide base 31, which guides a pair of front wheels 153 of the cart 2. The multiple power transmission devices 35A are arranged in the direction of extension of the pair of guide grooves 313 in the guide base 31. The multiple power transmission devices 35A face the power receiving devices 23 of the multiple carts 2 that are stacked and stored on the cart base 3. The power transmission devices 35A transmit power to the power receiving devices 23 of the opposing carts 2 without contact.

[0103] As shown in Figure 9, the power transmission device 35A includes, for example, a casing 350, a power transmission coil 351, a power transmission board, an AC adapter 354, and a switch 355.

[0104] Switch 355 is an external trigger. As shown in Figure 9, switch 355 is exposed on the outer surface of casing 350 and is configured to be operable from the outside. Switch 355 outputs the operated information as a signal to control circuit 3528. Switch 355 is a push switch that outputs a signal to control circuit 3528 when pressed, for example.

[0105] The control circuit 3528 then performs a setting process to set the foreign object detection threshold T when it receives a signal that the switch 355 has been operated. When the switch 355 is operated, the operator confirms that there are no metallic foreign objects on the casing 350 before operating the switch 355. In other words, when the operator operates the switch 355, the control circuit 3528 determines that the operator has confirmed that there are no metallic foreign objects on the casing 350 of the power transmission device 35, and sets the foreign object detection threshold T based on the calculated reference value A. For this reason, when setting the foreign object detection threshold T using the operation of the switch 355 as an external trigger, the control circuit 3528 does not perform the process of determining whether the reference value A in ACT12 is normal or not, or the process of setting the fixed value C in ACT14 to the foreign object detection threshold T, but only calculates the reference value A (ACT11) and then sets the foreign object detection threshold T based on the reference value A (ACT12).

[0106] With this configuration, the power transmission device 35A can use the operation of the switch 355 as a trigger to start setting the foreign object detection threshold T, and can perform the foreign object detection threshold T setting process after confirming that the power receiving device 23 is not facing the power transmission device 35A and that there are no metallic foreign objects on the power transmission device 35A. As a result, the power transmission device 35A can set the foreign object detection threshold T based on a normal reference value A, and in addition to the effect of achieving both highly sensitive foreign object detection and suppression of false detections, similar to the first embodiment described above, it is possible to set a reliable threshold.

[0107] Furthermore, the power transmission device 35A may be configured to perform the foreign object detection threshold setting process according to ACT11 to ACT14 of the first embodiment if the switch 355 is not operated for a predetermined time after power is turned on or after power is stopped to the power receiving device 23, and according to ACT11 and ACT13 of the second embodiment if the switch 355 is operated within the predetermined time.

[0108] Next, the power transmission device 35B and power supply system 1 according to the third embodiment will be described with reference to Figures 11 to 13. In the power transmission device 35B and power supply system 1 according to the third embodiment, the same reference numerals are used for components as in the power transmission device 35 and power supply system 1 according to the first embodiment and the power transmission device 35A and power supply system 1 according to the second embodiment, and their detailed descriptions are omitted.

[0109] Figure 11 is a perspective view showing the configuration of the power transmission device 35B of the power supply system 1 according to the third embodiment, Figure 12 is a block diagram showing the configuration of the control system of the power supply system 1 according to the third embodiment, and Figure 13 is a flowchart showing an example of the process for setting the foreign object detection threshold of the power supply system 1 according to the third embodiment.

[0110] As shown in Figure 11, the power supply system 1 comprises a power receiving device 23 and a power transmitting device 35B. The power receiving device 23 is provided, for example, on a cart 2. Multiple power transmitting devices 35B are provided, for example, on a cart base 3 that accommodates multiple carts 2.

[0111] Multiple power transmission devices 35B are provided, for example, between a pair of guide grooves 313 in a guide base 31, which guides a pair of front wheels 153 of the cart 2. The multiple power transmission devices 35B are arranged in the direction of extension of the pair of guide grooves 313 in the guide base 31. The multiple power transmission devices 35B face the power receiving devices 23 of the multiple carts 2 that are stacked and stored on the cart base 3. The power transmission devices 35B transmit power to the power receiving devices 23 of the opposing carts 2 in a non-contact manner.

[0112] As shown in Figure 12, the power transmission device 35B includes, for example, a casing 350, a power transmission coil 351, a power transmission board, an AC adapter 354, a switch 355, and a display device 356.

[0113] As shown in Figure 11, the casing 350 has a guide portion 3501 on its outer surface, in a part of the area where the power transmission coil 351 is provided. The guide portion 3501 is a mark that guides to a specific location, such as by printing, indentation, or a seal. In the foreign object detection threshold T setting process of the control circuit 3528, the guide portion 3501 guides the position where the metal test piece 90 for determining the foreign object detection threshold T is placed.

[0114] Switch 355 is an external trigger. As shown in Figure 11, switch 355 is exposed on the outer surface of casing 350 and is configured to be operable from the outside. Switch 355 outputs the operated information as a signal to control circuit 3528. Switch 355 is a push switch that outputs a signal to control circuit 3528 when pressed, for example.

[0115] The display device 356 displays or notifies information to the outside. As shown in Figure 11, the display device 356 is a display unit that is exposed on a part of the outer surface of the casing 350 so that the information can be seen from outside the casing 350. As shown in Figure 12, the display device 356 is connected to the control circuit 3528 and performs specific displays or notifications based on commands from the control circuit 3528. The display device 356 is, for example, an LED. The display device 356 is formed to emit light in multiple different colors. The display device 356 displays different information depending on the color displayed and the display method, such as lighting, extinguishing, and / or flashing. Note that the display device 356 is not limited to an LED, but may be a display or segment, etc.

[0116] When the control circuit 3528 receives a signal indicating that the switch 355 has been operated, it performs a setting process as ACT1 to set the foreign object detection threshold T. When the control circuit 3528 performs the setting process for the foreign object detection threshold T, it determines, for example, that the operation of the switch 355 triggers the artificial placement of a metal test piece 90 on the guide section 3501, resulting in a current value that is higher than the standby current. The control circuit 3528 then sets this detected current value, or a current value lower than this detected current value and higher than the standby current, as the foreign object detection threshold T.

[0117] The procedure for operating the switch 355 and placing the metal test piece 90 in the process of setting the foreign object detection threshold T is appropriately determined by the control method of the control circuit 3528. For example, the control may be such that when the operator operates the switch 355, or after the switch 355 is operated, the metal test piece 90 is placed on the guide section 3501 within a predetermined time. Alternatively, for example, the operator may confirm that the process of setting the foreign object detection threshold T is underway based on the display of the display device 356, and then operate the switch 355 after placing the metal test piece 90 on the guide section 3501.

[0118] Next, an example of the foreign object detection threshold setting process (ACT1) by the power transmission device 35B configured in this way will be explained using the flowchart in Figure 13. When the power is turned on, the control circuit 3528 starts setting the foreign object detection threshold T (ACT1). As a specific example, as shown in Figure 13, as part of the foreign object detection threshold T setting process, the control circuit 3528 first takes in the current value and then calculates the reference value A, which is the average value (ACT21). As a specific example, the control circuit 3528 measures the current value, which is the standby current, a predetermined number of times n at predetermined intervals s stored in memory, calculates the average value A from the measured current values, sets this average value A as the reference value A, and stores it in memory.

[0119] Next, the control circuit 3528 controls the display device 356 to inform the outside that the foreign object detection threshold T is being set, for example, by lighting or flashing an LED in a predetermined color (ACT22).

[0120] The operator performing the foreign object detection threshold T setting process places the metal test piece 90 on the guide section 3501 and operates the switch 355. When the control circuit 3528 receives a signal from the switch 355, it determines that the placement of the metal test piece 90 is complete, measures the current using the current sensor 3526 and / or the current detection circuit 3527, and detects a current value D that becomes the foreign object detection threshold T (ACT23). Here, the current value D is either the maximum value of the current detected within a predetermined period t, or the average value calculated from the current values ​​detected a predetermined number of times at a predetermined interval s. The memory of the control circuit 3528 stores a predetermined period t, a predetermined interval s, and / or a predetermined number of times n. In this embodiment, the predetermined interval s and predetermined number of times n may be the same as, or different from, the predetermined interval s and predetermined number of times n used to determine the reference value A.

[0121] The control circuit 3528 sets the calculated current value D to the foreign object detection threshold T (ACT23). Then, the control circuit 3528 controls the display device 356 to notify the outside that the setting of the foreign object detection threshold T is complete (ACT24). Here, the control circuit 3528 notifies the outside that the setting of the foreign object detection threshold T is complete by changing the display method of the display device 356 from that in ACT22. For example, in ACT24, the control circuit 3528 may turn off the LED or change the color of the LED. Then, the control circuit 3528 performs the processing from ACT2 onwards.

[0122] With this configuration, each power transmission device 35B can set a foreign object detection threshold T based on the metal test piece 90, making it possible to achieve both highly sensitive foreign object detection and suppression of false detections.

[0123] Since the target value of the foreign object detection threshold T can be set according to the shape and material of the metal test piece 90, the power transmission device 35 can set a foreign object detection threshold T that takes into account the size of the metal foreign object to be detected.

[0124] Furthermore, depending on the shape of the power transmission coil 351, the amount of heat generated by the metal foreign object may vary depending on its position on the power transmission coil 351, even if it is the same metal foreign object. In other words, the current flowing through the power transmission coil 351 may differ depending on the relative position between the metal foreign object and the power transmission coil 351. For this reason, by setting the position on the casing 350 where the guide section 3501 is displayed based on the current value flowing due to the metal foreign object, the threshold value when the metal test piece 90 is placed on the guide section 3501 can be managed, and the sensitivity can be set by the position where the guide section 3501 is installed. The position where the guide section 3501 is installed may be at the center of the power transmission coil 351, or it may be at a position offset from the center. Specifically, it may be at a position offset from the center of the power transmission coil 351, directly above the coil copper wire. Alternatively, the guide section 3501 may be installed at multiple locations where the amount of heat generated by the metal foreign object differs, and the position where the metal test piece 90 is placed can be selected by these multiple guide sections 3501 based on the foreign object detection threshold T to be set.

[0125] For example, the power transmission device 35B may be configured to determine a reference value A (ACT21) as part of the process for setting the foreign object detection threshold T (ACT1), and then, as shown in ACT12, determine whether the reference value A is normal as a current value for the standby current. In such a configuration, the control circuit 3528 may perform the processes from ACT22 onward if it determines that the reference value A is normal, and if it determines that the current value is abnormal, it may set a fixed value C to the foreign object detection threshold T as shown in ACT14.

[0126] Furthermore, for example, the power transmission device 35B may be configured to perform the foreign object detection threshold setting process according to ACT11 to ACT14 of the first embodiment if the switch 355 is not operated for a predetermined period of time after power is turned on or after power is stopped to the power receiving device 23, and if the switch 355 is operated within the predetermined period of time, it may perform the foreign object detection threshold T setting process using the metal test piece 90.

[0127] Furthermore, the power transmission device 35B may be configured to allow selection of either the foreign object detection threshold T setting process using the metal test piece 90 or the foreign object detection threshold T setting process of the second embodiment described above, based on signals input by different operating methods of the switch 355, for example, when the display device 356 is displaying information during the foreign object detection threshold T setting process. For example, when a signal corresponding to a short single operation of the switch 355 is input, the control circuit 3528 determines that the foreign object detection threshold T setting process using the metal test piece 90 of the third embodiment has been selected, and when signals corresponding to two short operations of the switch 355 are input, it determines that the foreign object detection threshold T setting process of the second embodiment has been selected. The control circuit 3528 may then be configured to perform the selected foreign object detection threshold T setting process.

[0128] In other words, the power transmission device according to the embodiment may be configured to perform any of the setting processes for the foreign object detection threshold T in each of the embodiments described above, or it may be configured to selectively perform all of the setting processes.

[0129] Furthermore, in the examples of the embodiments described above, the power receiving device 23 of the power supply system 1, which supplies power without contact, was described using a shopping cart as an example of a cart 2. However, the cart 2 on which the power receiving device 23 is mounted is not limited to a shopping cart; for example, it could be a picking cart used in a warehouse, etc. Also, as long as the power supply system 1 performs contactless power supply, the power receiving device 23 and the power transmitting device 35 can be applied to configurations other than the cart 2 and cart base 3.

[0130] According to the power transmission device and power supply system of at least one embodiment described above, by setting a foreign object detection threshold T based on a reference value A obtained from the standby current, it is possible to achieve both highly sensitive foreign object detection and suppression of false detections.

[0131] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. The following is a description equivalent to the invention described in the original claims of this application. [1] A power transmission device that transmits power to a power receiving device without contact, Transmission coil and A power transmission circuit that supplies the generated power to the power transmission coil, A current detection circuit that measures the current value input to the power transmission circuit, A control circuit determines that there is a foreign object on the power transmission coil when the power receiving device and the standby current during standby when no power transmission is being performed are used as a reference value, and a value obtained by adding a certain value to the reference value or by adding a certain ratio to the reference value is used as a foreign object detection threshold, and when the current value detected by the current detection circuit during standby is equal to or greater than the threshold, it is determined that there is a foreign object on the power transmission coil. A power transmission device equipped with the following features. [2] The power transmission device according to [1], wherein the control circuit measures the reference value after power is turned on and before power is supplied to the power receiving device. [3] Equipped with an external trigger, The power transmission device according to [1], wherein the control circuit determines the reference value and sets the foreign object detection threshold when the external trigger is operated during standby. [4] Equipped with a display unit that displays information indicating that threshold setting processing is in progress, The power transmission device according to any one of [1] to [3], wherein the control circuit measures the current value during standby, controls the display unit to display information on the display unit that the threshold setting process is in progress, and sets the current value measured during the threshold setting process as the threshold. [5] A power transmission device that transmits power to a power receiving device without contact, Transmission coil and A power transmission circuit that supplies the generated power to the power transmission coil, A current detection circuit that measures the current value input to the power transmission circuit, A display unit that shows information indicating that threshold setting processing is in progress, A control circuit measures the current value of the power receiving device and the standby state when power transmission is not being performed, controls the display unit to display information on the display unit indicating that the threshold setting process is in progress, and sets the current value measured during the threshold setting process as the threshold for foreign object detection. A power transmission device equipped with the following features. [Explanation of symbols]

[0132] 1...Power supply system, 2...Cart, 3...Cart base, 11...Frame, 12...Basket section, 21...Electronic equipment, 22...Battery, 23...Power receiving device, 31...Guide base, 32...Cart gate, 35, 35A, 35B...Power transmitting device, 90...Metal test piece, 111...Vertical frame section, 112...Lower frame section, 113...Horizontal frame section, 114...Handle section, 115...Mounting frame, 121...Opening / closing panel, 151...Front wheel caster, 152...Rear wheel caster, 153...Wheel, 154...Bracket section, 211...Tablet terminal, 212...Product reader, 221...Charging circuit, 222...Secondary battery, 223...Battery box, 230...Casing, 231...Power receiving coil, 311...Support base, 312...Guide Drail, 313... Guide groove, 322... Pole, 323... Side bar, 350... Casing, 351... Power transmission coil, 354... AC adapter, 1111... Main frame, 1112... Subframe, 1113... Subframe, 1121... Main frame, 1123... Support frame, 1124... Front connecting section, 1125... Mounting section, 1131... Link frame, 1132... Link frame, 1133... Link frame, 2322... Rectifier circuit, 2323... Voltage conversion circuit, 2324... Switching circuit, 2326... Control circuit, 3501... Guide section, 3522... Power transmission circuit, 3523... Voltage conversion circuit, 3524... Switching circuit, 3526... Current sensor, 3527... Current detection circuit, 3528... Control circuit.

Claims

1. A power transmission device that transmits power to a power receiving device without contact, Transmission coil and A power transmission circuit that supplies the generated power to the power transmission coil, A current detection circuit that measures the current value input to the power transmission circuit, A control circuit determines that there is a foreign object on the power transmission coil when the current detected by the current detection circuit during standby is greater than or equal to the threshold value, and the current value detected by the current detection circuit during standby is greater than or equal to the threshold value, and the power receiving device and the standby current during standby are measured a predetermined number of times at predetermined intervals, and the average value of the standby current is determined as a reference value, and the value obtained by adding a certain value to the reference value or a certain ratio is added to the reference value, and the control circuit determines that there is a foreign object on the power transmission coil, Equipped with, The control circuit is a power transmission device that sets the threshold for detecting foreign objects when it enters a standby state after power is turned on.

2. The power transmission device according to claim 1, wherein the control circuit measures the reference value after the power is turned on and before power is transmitted to the power receiving device.

3. Equipped with an external trigger, The power transmission device according to claim 1, wherein the control circuit determines the reference value and sets the foreign object detection threshold when the external trigger is operated during standby.

4. It includes a display unit that displays information indicating that threshold setting processing is in progress. The power transmission device according to any one of claims 1 to 3, wherein the control circuit measures the current value during standby, controls the display unit to display information on the display unit that the threshold setting process is in progress, and sets the current value measured during the threshold setting process as the threshold.

5. A power transmission device that transmits power to a power receiving device without contact, Transmission coil and A power transmission circuit that supplies the generated power to the power transmission coil, A current detection circuit that measures the current value input to the power transmission circuit, A display unit that shows information indicating that threshold setting processing is in progress, A control circuit measures the current value of the power receiving device and the standby state when power transmission is not being performed, controls the display unit to display information on the display unit indicating that the threshold setting process is in progress, and sets the current value measured during the threshold setting process as the threshold for foreign object detection. Equipped with, The control circuit is a power transmission device that sets the threshold for detecting foreign objects when it enters a standby state after power is turned on.

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