Power transmission device

Abstract

An inverter (1) and power transmission coils (51, 52) are connected in such a manner that when the respective switching switches (41, 42) of adjacent power transmission coils (51, 52) among a plurality of power transmission coils (5) arranged in the moving direction of a moving body (100) are turned on, currents flow in opposite directions to each other, and a difference between the currents flowing in the opposite directions is measured. By comparing the difference with a threshold value, it is possible to determine whether a power receiving coil (101) mounted on the moving body (100) is present on the power transmission coil (51).

Description

Technical Field

[0001] The present application relates to a power transmission device. Background Art

[0002] There is a contactless power supply technology that uses magnetic field coupling between two coils separated by a space to transmit power. In order to apply this contactless power supply technology to the power supply of mobile objects such as cars, elevators or factory handling equipment, various technical developments are underway. Among them, there is a technology for appropriately switching multiple coils arranged in the direction of travel of the mobile object and a technology involving a method for arranging the coils (for example, refer to Patent Document 1). Therefore, in order to achieve contactless power supply to the mobile object, multiple power transmission coils are arranged on the moving path, and the power transmission coils that transmit power to the power receiving coil mounted on the mobile object are switched in sequence according to the movement of the mobile object. In this case, it is necessary to detect on which of the multiple transmission coils the mobile object is located, or on which transmission coil the mobile object is not located.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 6221460 Summary of the Invention

[0006] Technical issues to be solved by the invention

[0007] As such detection means, there are methods such as those described in Patent Document 1, which use a camera to detect the position of the power receiving coil and determine whether the position of the power receiving coil is within the effective range of the power transmitting coil, or use an infrared sensor to directly detect the position of the moving body coil.

[0008] However, both camera-based and infrared sensor-based detection require additional detection equipment, such as cameras and infrared sensors, which increases costs due to the increased number of peripheral components. Furthermore, infrared sensors have difficulty distinguishing whether an object passing through their path is the receiving coil receiving power or another object.

[0009] The present application has been made to solve the above-mentioned problems, and provides a power transmission device capable of detecting the position of a power receiving coil without requiring an additional sensor.

[0010] Technical solutions to solve technical problems

[0011] The power transmission device disclosed in this application comprises:

[0012] Inverter, outputs AC power;

[0013] a plurality of power transmission coils connected to the inverter; and

[0014] Switching the switch to connect and disconnect the inverter and the power transmission coil;

[0015] This power transmission device performs contactless power supply between a power receiving coil mounted on a moving object and the power transmission coil, and is characterized by comprising:

[0016] a current sensor connected to the inverter and the power transmission coil so that currents flow in opposite directions when switches of adjacent power transmission coils among the plurality of power transmission coils arranged in the moving direction of the moving object are turned on, the current sensor measuring a difference between the currents flowing in the opposite directions; and

[0017] The control unit compares the measurement value of the current sensor with a threshold value to determine whether the power receiving coil is located above the power transmitting coil.

[0018] Effects of the Invention

[0019] According to the power transmission device disclosed in the present application, the position of the power receiving coil can be detected without an additional sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of the power transmission device according to Embodiment 1.

[0021] Figure 2 This is a diagram illustrating the hardware configuration of the control unit.

[0022] Figure 3 This is a diagram for explaining the path of current flowing through the power transmission coil of the power transmission device according to the first embodiment.

[0023] Figure 4 This is a flowchart illustrating the operation of the power transmission device according to the first embodiment.

[0024] Figure 5 This is a waveform diagram showing an example of the output voltage from the high-frequency inverter.

[0025] Figure 6 This diagram illustrates an example of the direction and magnitude of the current flowing through the current sensor.

[0026] Figure 7 This figure illustrates an example of the magnetic field generated in a power transmission coil.

[0027] Figure 8 This is a structural diagram of the power transmission device when the power receiving coil reaches above the power transmitting coil 51.

[0028] Figure 9This figure illustrates another example of the direction and magnitude of the current flowing through the current sensor.

[0029] Figure 10 This is a structural diagram of the power transmission device showing the switching state when rated power is output to the power transmission coil.

[0030] Figure 11 1 is a structural diagram of the power transmission device showing the switching state of the power receiving coil after passing through the power transmission coil 51.

[0031] Figure 12 This is a structural diagram of the power transmission device when the power receiving coil reaches above the power transmitting coil 52.

[0032] Figure 13 This is a structural diagram of a power transmission device according to Embodiment 2.

[0033] Figure 14 This is a structural diagram of a power transmission device according to Embodiment 3.

[0034] Figure 15 This is a flowchart showing an example of the operation of the power transmission device according to the fourth embodiment.

[0035] Figure 16 This is another flowchart showing an example of the operation of the power transmission device according to the fourth embodiment.

[0036] Reference numerals

[0037] 1: High-frequency inverter, 2: Inductor, 3: Capacitor, 4: Switch, 5: Transmission coil, 8, 10, 11: Current sensor, 9: Control unit, 100: Moving object, 101: Receiving coil DETAILED DESCRIPTION

[0038] The following describes preferred embodiments of the power transmission device of the present application with reference to the accompanying drawings. Identical or corresponding parts are denoted by the same reference numerals, and detailed description thereof is omitted. Similarly, in subsequent embodiments, duplicate descriptions of components denoted by the same reference numerals are omitted.

[0039] Implementation method 1.

[0040] <Basic Structure>

[0041] The basic structure of the power transmission device according to this embodiment will be described. Figure 1 This is a structural diagram showing the structure of the power transmission device of this embodiment. Although the case where three power transmission coils are connected is described here, the same implementation is possible even when four or more power transmission coils are connected.

[0042] The power transmission device includes a high-frequency inverter 1 with a bridge structure that outputs AC power, an inductor 2 connected to the output terminal of the high-frequency inverter 1, a capacitor 3 connected to the inductor 2, a switch unit 4 connected to the capacitor 3, a power transmission coil unit 5 connected to the switch unit 4, a current sensor 8, and a control unit 9. Arrows from the control unit 9 indicate control of the high-frequency inverter 1 and the switch unit 4.

[0043] Figure 2 The following figure shows an example of the hardware of the microcomputer in the control unit 9. It includes a processor 91 and a storage device 92. Although not shown, the storage device 92 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. The processor 91 performs operations, such as those described in detail below, by executing programs input from the storage device 92. In this case, the program is input from the auxiliary storage device to the processor 91 via the volatile storage device. Furthermore, the processor 91 can output data such as calculation results to the volatile storage device of the storage device 92, or store data in the auxiliary storage device via the volatile storage device.

[0044] In addition, the hardware in the control unit 9 may not be a microcomputer, but may be an ASIC (Application specific integrated circuit), an FPGA (Field Programmable Gate Array), a simple logic circuit, or a relay.

[0045] In addition Figure 1 In FIG. 4 , the switching unit 4 includes a plurality of switching switches 41, 42, and 43. The power transmission coil unit 5 includes a plurality of power transmission coils 51, 52, and 53, each of which is connected in series with the respective switching switches 41, 42, and 43. The current sensor 8 can measure the current flowing through the plurality of power transmission coils 51, 52, and 53 at once.

[0046] <Connection between Transmission Coil and Switch>

[0047] The power transmission coils 51 , 52 , and 53 are connected to the switch so that when the high-frequency inverter 1 outputs AC power, current flows in the same direction in the current paths closest to the adjacent power transmission coils. Figure 3 The direction of the current when the current is simultaneously passed through the power transmission coil 51 and the power transmission coil 52 is shown.

[0048] <Structure of Current Sensor>

[0049] Figure 1 or Figure 3The structure of the current sensor 8 that measures the current of the power transmission coil is as described below. When the two connection ends of the capacitor 3 are set as the H line (HLine) and the L line (L Line), the structure of the current sensor 8 can be as long as the H line and the L line are alternated according to the arrangement order of the power transmission coil. For example, the current sensor 8 is configured to measure the portion of the power transmission coil 51 connected to the L line, the portion of the power transmission coil 52 connected to the H line, and the portion of the power transmission coil 53 connected to the L line (configured in the order of L, H, L according to the arrangement order of the power transmission coils). Alternatively, it can be a structure that measures the current of the portion of the power transmission coil 51 connected to the H line, the portion of the power transmission coil 52 connected to the L line, and the portion of the power transmission coil 53 connected to the H line (configured in the order of H, L, H according to the arrangement order of the power transmission coils).

[0050] exist Figure 1 and Figure 3 The high-frequency inverter 1 includes a full-bridge circuit using four switching elements, but is not limited to this structure, and a half-bridge circuit or other circuit structures may also be used.

[0051] In addition, as each of the changeover switches 41 , 42 , and 43 constituting the changeover switch unit 4 , any of relay switches and semiconductor switches can be used.

[0052] <Basic Work>

[0053] Next refer to Figure 4 The basic operation of this embodiment is described with reference to the flowchart of FIG.

[0054] like Figure 1 As shown, control unit 9 first turns switches 41 and 42 on and switches 43 off (step S1). The two switches 41 and 42 that are turned on are connected to adjacent power transmission coils (here, power transmission coil 51 and power transmission coil 52) in the direction X of travel of moving object 100. High-frequency inverter 1 outputs power at regular intervals to detect power receiving coil 101 mounted on moving object 100. At this time, high-frequency inverter 1 outputs power lower than the rated power input (e.g., 1% of the rated power) (step S2). Figure 5 An example of a voltage waveform output from the high-frequency inverter 1 is shown.

[0055] Then, the current value Idet of the current sensor 8 is measured (step S3). If the moving object 100 does not have the power receiving coil 101, as shown in FIG. Figure 6 As shown, current flows in the power transmission coil 51 and the power transmission coil 52 in opposite directions, so the current sensor 8 does not detect a current exceeding the error.

[0056] In addition, Figure 7As shown, the magnetic fields generated by the currents flowing through the power transmission coils 51 and 52 are in a direction in which they cancel each other out as they move away from the portion exceeding approximately the diameter of the power transmission coils 51 and 52, and the leakage magnetic field strength decreases. Figure 7 In the figure, for the sake of simplicity and clarity, the ratio of the coil and the magnetic field is described as a ratio different from the actual ratio.

[0057] When the current detected by the current sensor 8 is sufficiently small, the control unit 9 determines that the power receiving coil 101 on the moving object 100 side is not located directly above the power transmitting coils 51, 52, and 53 (step S4). Figure 8 As shown in FIG. 1 , when the power receiving coil 101 mounted on the mobile object 100 enters the range where the power transmission coil 51 can supply power (in this embodiment, directly above the power transmission coil), the impedance of the power transmission coil 51 side and the impedance of the power transmission coil 52 side differ. As a result, the current flowing through the current sensor 8 also differs, as shown in FIG. Figure 9 The current shown flows. The order of the current paths connected to the power transmission coil is defined as node 01, node 02, and node 03. A large current flows through node 01, while a smaller current flows through node 02 compared to node 01. At node 03, no current flows because the switch is off. In this situation, a difference occurs in the current values between node 01 and node 02, and they do not cancel each other out. Consequently, the current sensor 8 detects the current value Idet. When the current value Idet is large enough to exceed the threshold value Ith pre-stored in the storage device 92 of the control unit 9, the control unit 9 determines that the power receiving coil 101 is mounted on the moving object 100 (step S5).

[0058] When the detection of the power receiving coil 101 is completed, Figure 10 As shown, the control unit 9 turns off the selector switch 42 (step S6). Since the selector switch 42 is turned off, power can only be supplied to the power transmission coil 51 magnetically coupled to the power reception coil 101. Thereafter, the high-frequency inverter 1 outputs the rated power according to the instruction from the control unit 9 (step S7).

[0059] After the power receiving coil 101 leaves the position directly above the power transmitting coil 51 due to the movement of the moving object 100, Figure 11 As shown, the switches 42 and 43 are turned on, and the switch 41 is turned off, so that current flows through the power transmission coils 52 and 53, and the power receiving coil 101 of the moving object 100 is detected in the same manner as above. Figure 12 In this way, the switch 43 is turned off.

[0060] Although the above is the operation when three power transmission coils are connected, even when four or more power transmission coils are connected, the same operation is performed except that the combination of the on and off switches is sequentially changed.

[0061] <Effects of this embodiment>

[0062] (1) By configuring a structure in which current flows simultaneously through two adjacent power transmission coils 51 and 52, and in which the current flows in a direction that cancels out the magnetic fields at a sufficient distance from the power transmission coils 51 and 52, leakage magnetic fields can be reduced. When detecting the power receiving coil 101 mounted on the mobile object 100, by intentionally flowing current through the two power transmission coils 51 and 52, leakage electromagnetic fields can be reduced.

[0063] (2) Furthermore, in this embodiment, current sensor 8 is configured to collectively measure the current flowing through each power transmission coil 51 to 53. This configuration allows only one current sensor 8 to be used for detecting the power receiving coil 101. Conventionally, it is necessary to prepare the same number of current sensors as the number of power transmission coils and to measure the current in each power transmission coil at all times. However, in this embodiment, there is no need to attach a current sensor to each power transmission coil, thus reducing the number of current sensors.

[0064] (3) Because the configuration is such that, in order to detect the power receiving coil 101, the same number of switches 41 to 43 and power transmitting coils 51 to 53 are provided, and a structure is provided in which two of the switches can be turned on and the other switches can be turned off, and the current flowing in the current paths of the adjacent power transmitting coils 51 and 52 is in opposite directions, when there is no power receiving coil 101 in the moving object 100, the current can always be zero or very small.

[0065] Implementation method 2.

[0066] <Structure>

[0067] Figure 13 This figure illustrates the basic structure of a power transmission device according to Embodiment 2. Current sensor 10 is located in the same location as current sensor 8. "Same location" here means a location capable of measuring the same current path as current sensor 8. Current sensor 10 also has a different resolution setting than current sensor 8, enabling it to measure larger currents than current sensor 8. Current sensor 10 is not used to detect receiving coil 101, but rather to transmit rated power after detection of receiving coil 101.

[0068] <Basic Work>

[0069] The basic operation of Embodiment 2 is the same as that described in Embodiment 1. Current sensor 8 detects current, and after determining that receiving coil 101 is located above transmitting coils 51-53, high-frequency inverter 1 outputs the rated high-frequency power. At this time, current sensor 10 is used to control the output power or output current from high-frequency inverter 1.

[0070] <Effects of Implementation Method 2>

[0071] Due to their resolution, current sensors have difficulty measuring both large and small currents. Therefore, as in Embodiment 1, when current sensor 8 is used for both detection of the receiving coil 101 and power control during rated output operation, the minimum measurable current value becomes larger than that of a current sensor designed for small currents. As a result, when detecting the receiving coil 101, a higher power needs to be supplied from the high-frequency inverter 1 to the power transmission coil than when using a current sensor designed for small currents, increasing the intensity of unnecessary leakage electromagnetic fields. For example, if the resolution of current sensor 8 is 8 bits and the maximum current value during power transmission is 100 amperes, the minimum current that can be measured by current sensor 8 is approximately 0.4 amperes. Therefore, when detecting the receiving coil 101, detection of the receiving coil 101 is impossible unless a current of 0.4 amperes or more is passed.

[0072] Therefore, by using current sensor 10 for power control at rated output, current sensor 8 used for detecting power receiving coil 101 can be configured to detect a smaller current than current sensor 10. This configuration has the following effects: the power supplied from high-frequency inverter 1 when detecting power receiving coil 101 can be reduced, thereby reducing leakage electromagnetic fields.

[0073] Implementation method 3.

[0074] <Structure>

[0075] Figure 14 This diagram shows a power transmission device according to Embodiment 3. In addition to current sensor 8, a current sensor 11 is also provided. Current sensor 11 is provided at a location capable of measuring the input current of high-frequency inverter 1. Current sensor 11 is not used to detect the power receiving coil 101 of moving object 100, but is used for power control during rated power transmission after detection of power receiving coil 101.

[0076] <Basic Work>

[0077] The basic operation of this embodiment is the same as that described in Embodiment 1. Current sensor 8 detects current, and after determining that power receiving coil 101 of moving object 100 is located above power transmitting coils 51-53, high-frequency inverter 1 outputs the rated high-frequency power. Current sensor 11 is used to control the output power or output current from high-frequency inverter 1.

[0078] <Effects of Implementation Method 3>

[0079] (1) As described in Embodiment 2, when only current sensor 8 is used to detect the power receiving coil 101 and control the transmission power, a technical problem arises due to the resolution of the current sensor. In contrast, by providing a current sensor 11 for power control in addition to current sensor 8 for detecting the power receiving coil 101, the power output from high-frequency inverter 1 can be reduced when detecting the power receiving coil 101 mounted on the moving object 100, thereby reducing the leakage magnetic field.

[0080] (2) Furthermore, since the current sensor 11 is provided at the current input portion of the high-frequency inverter 1, the effective power when transmitting the rated output can be controlled with high precision. In the second embodiment, since the output current of the high-frequency inverter 1 is measured, the error between the target value and the actual value of the transmission power may become large depending on the power factor of the output portion of the high-frequency inverter 1. In addition, although it is also possible to control the effective value of the transmission power by taking the power factor into consideration, calculations such as the phase difference between the output voltage and output current of the high-frequency inverter 1 become complicated. In contrast, in the present embodiment, the effective power can be actually measured by measuring the input current of the high-frequency inverter 1, and thus the aforementioned correction based on the power factor is unnecessary. This is effective when high-precision transmission power control is required for the mobile object 100. That is, by using the structure of the present embodiment, high-precision power control is easy even when the power factor is low.

[0081] Implementation method 4.

[0082] <Structure and Work>

[0083] The basic structure of the power transmission device of this embodiment is the same as that of Embodiment 1. This embodiment is characterized in that, in Embodiment 1, a value measured in advance by current sensor 8 is used as threshold value Ith stored in advance in storage device 92 .

[0084] That is, before the basic operation described in the first embodiment, Figure 15 The following work is recorded in.

[0085] When it is clear that the receiving coil 101 is not present, switches 41 and 42 are turned on and switch 43 is turned off (step S8). The high-frequency power used for receiving coil detection is then output from the high-frequency inverter 1 (step S9). The output of the current sensor 8 is measured (step S10), and the measured current value Ith01 is recorded in the storage device 92 (step S11). Next, switches 42 and 43 are turned on and switch 41 is turned off (step S12). The high-frequency power used for receiving coil detection is then output from the high-frequency inverter 1 (step S13). The output of the current sensor 8 is measured, and the measured current value (Ith02) is recorded in the storage device 92 (step S14).

[0086] If there are four or more power transmission coils, the above process is repeated, high-frequency current is passed simultaneously to two adjacent power transmission coils, and the current value (Ithx) measured by the current sensor 8 is recorded (step S15). The "x" in Ithx represents the number of power transmission coils starting from 01.

[0087] Next, Figure 16 As shown, the operation of Embodiment 1 is performed. Switches 41 and 42 are turned on, and switch 43 is turned off (step S1). The two switches 41 and 42 that are turned on are connected to power transmission coils 51 and 52 that are adjacent in the direction of travel X of the moving object 100. High-frequency inverter 1 outputs power to power transmission coils 51 and 52 at regular intervals to detect power receiving coil 101 (step S2).

[0088] The current value Idet measured by the current sensor 8 (step S3) is compared with the current value Ith01 stored in the storage device 92 (step S16). If the current value Idet is equal to or less than the current value Ith01, it is determined that the receiving coil 101 is not located above the power transmission coil 51, and detection of the receiving coil continues. If the current value Idet measured by the current sensor 8 is greater than the current value Ith01, it is determined that the receiving coil 101 is located above the power transmission coil 51 (step S17), the switch 42 is turned off (step S18), and the rated output to the receiving coil 101 is resumed from the power transmission coil 51 connected to the switched-on switch 41 (step S19). After the receiving coil 101 leaves the position directly above the transmitting coil 51, switches 42 and 43 are turned on, and switch 41 is turned off. The current value Idet for the subsequent transmitting coils 52 and 53 is compared with the recorded current value Ith02. The same operation as above is repeated for the number of transmitting coils x.

[0089] <Effects of Implementation 4>

[0090] The multiple power transmission coils 51-53 may have different inductance values due to manufacturing errors, different layout locations, or different distances from the power transmission coil layout location to the high-frequency inverter. In this case, even if a high-frequency current is passed through two adjacent power transmission coils 51 and 52 without the power receiving coil 101 directly above them, the current detected by the current sensor 8 may not be zero, and the current value detected may be different due to the difference in inductance. To eliminate this current value, screening and parameter adjustment can be performed during the production of the power transmission coils. However, this solution is laborious and increases costs. Using the method of this embodiment, even if there are differences in the inductance of the power transmission coils 51-53 or inductance errors caused by layout, the current value Ithx (in this embodiment, x = 01-03) measured when the power receiving coil 101 is absent is recorded, thereby improving the accuracy of determining whether the power receiving coil 101 is present.

[0091] This also makes it possible to improve the tolerance for errors in manufacturing the power transmission coil or the tolerance for changes in inductance value during layout.

[0092] Although the present application describes various exemplary embodiments and examples, the various features, forms, and functions described in one or more embodiments are not limited to application in specific embodiments, but can be applied to the embodiments alone or in various combinations.

[0093] Therefore, numerous variations not shown in the examples are contemplated within the technical scope disclosed in this specification, including, for example, variations, additions, or omissions of at least one component, and extraction and combination of at least one component with components of other embodiments.

Claims

1. A power transmission device comprising: Inverter, outputs AC power; a plurality of power transmission coils connected to the inverter; and Switching the switch to connect and disconnect the inverter and the power transmission coil; This power transmission device performs contactless power supply between a power receiving coil mounted on a moving object and the power transmission coil, and is characterized by comprising: a first current sensor connected to the inverter and the power transmission coil so that currents flow in opposite directions when switches of adjacent power transmission coils among the plurality of power transmission coils arranged in the moving direction of the moving object are turned on, the first current sensor measuring a difference between the currents flowing in the opposite directions; and The control unit compares the measurement value of the first current sensor with a threshold value to determine whether the power receiving coil is within a range where power can be supplied from the power transmitting coil.

2. The power transmission device according to claim 1, wherein: When the control unit determines that the power receiving coil is within a range where power can be supplied from the power transmitting coil, the control unit controls the power transmitting coil on the side of the adjacent power transmitting coils where the power receiving coil is not present to be disconnected from the inverter, and in order to supply power to the power receiving coil, power is supplied from the inverter to the power transmitting coil that is connected to the inverter.

3. The power transmission device according to claim 2, characterized in that The first current sensor further detects a current supplying electric power to a power transmission coil electrically connected to the inverter.

4. The power transmission device according to claim 2, wherein: The second current sensor is arranged at the same position as the first current sensor, the first current sensor is capable of measuring the difference of the current flowing in the opposite direction, and the second current sensor detects the current used to supply power to the power transmission coil connected to the inverter, and has a resolution different from that of the first current sensor.

5. The power transmission device according to claim 2, wherein: A third current sensor is provided for measuring an input current of the inverter to control a current when power is supplied to a power transmission coil connected to the inverter.

6. The power transmission device according to claim 1, wherein: The threshold value is a value obtained by measuring in advance the difference between currents flowing in opposite directions in adjacent power transmission coils when the power reception coil is not present.

Images