Method for operating a wireless transmission device to recognize and avoid undesirable radiation of a high-frequency magnetic field

Abstract

The invention relates to a method for operating a wireless energy transmission device (1) for charging an energy storage device (2) of, for example, an electric vehicle, comprising at least one transmitting coil (4) suitable for inductive energy transmission with a transmitting coil control unit (5) and at least one receiving coil (6) suitable for energy transmission with a receiving coil control unit (7), further comprising at least one first measuring element (8) and a first measuring device (9) connected to the measuring element, wherein in a first step the magnetic field strength in an air gap (10) between the transmitting coil (4) and the receiving coil (6) is measured by the at least one measuring device (9) with the measuring element (8) and in a further step the transmitting coil control unit (5) takes into account the magnetic field strength values ​​measured by the measuring element (8) and sets an operating point of the energy transmission such that the efficiency of the energy transmission device (1) is maximized.

Description

Technical Field

[0001] The present invention relates to a method for operating a wireless energy transmission device for charging an energy storage device of an electric vehicle, for example, including a transmission coil suitable for inductive transmission of electrical energy and provided with a transmission coil control unit, wherein the inductive energy transmission device further includes a measurement device having a measurement element. Further, the inductive energy transmission device includes a reception coil suitable for inductive reception of electrical energy and provided with a reception coil control unit, and the inductive energy reception device further includes a measurement device having a measurement element. The measurement element, in cooperation with the first measurement device, measures the magnetic field strength of the alternating magnetic field within the air gap between the transmission coil and the reception coil. Based on the obtained measurement result, the operating point of the energy transmission device is set by the transmission coil control unit so as to maximize the efficiency of the energy transmission device, taking into account the magnetic field strength value measured by the measurement element.

Background Art

[0002] For wireless transmission of electrical energy to supply energy to electrical equipment and / or charge battery-powered equipment, there is a problem that part of the energy released is radiated into the surrounding space during inductive energy transmission. Only a part of the released energy is absorbed by the receiving side and converted back into electrical energy. The remaining part of the released energy is lost with respect to energy transmission and causes an undesirable impact on the environment of the wireless inductive energy transmission device.

[0003] European Patent No. 2332231 describes an inductive charger for inductively supplying energy to one or more battery-powered devices, each device including a secondary coil that is designed to surround a portion of a magnetic field and generate a current for charging the device's battery in response thereto, the charger including two or more pairs of primary coils arranged in a circular pattern, the circular pattern being provided to surround one or more secondary coils of the device and an AC power source provided to supply alternating current to the pairs of primary coils, the pairs of primary coils then being provided with alternating current to generate a rotating magnetic field between respective primary coils of the pairs of primary coils. The object of this invention is a universal inductive charger that can provide improved magnetic coupling, and thus improved efficiency, of a single primary side with a plurality of different secondary sides together with electrical energy.

[0004] A disadvantage of this prior art proposal is that European Patent No. 2332231 does not disclose any indication regarding a method for avoiding undesirable radiation. European Patent No. 2689512 describes a method for determining power loss in a system for inductive power transmission. The method includes a power transmitter that inductively transmits power to a power receiver via a transmission coil and a reception coil. For this purpose, the method includes the following steps: in one step, the power transmitter obtains reception power parameters transmitted from the power receiver; further, obtains timing information for timing adjustment transmitted from the power receiver so that the power transmitter can adjust the time for calculating the power loss during power transmission by the power receiver; then calculates the power loss corresponding to the obtained timing information and the received power parameters.

[0005] A disadvantage of this prior art proposal is that European Patent No. 2689512 also does not disclose any indication for avoiding undesirable radiation. This undesirable radiation, on the one hand, disadvantageously causes a reduction in the efficiency of the inductive energy transmission device, and on the other hand, also causes an undesirable heating of metal objects surrounding the inductive energy transmission device, and even more disadvantageously, also causes EMC interference to other devices. This EMC interference usually violates high-frequency regulations and must therefore be avoided at all costs. Moreover, governments around the world are currently paying special attention to electromagnetic compatibility. For example, in the parliamentary document 19 / 24557 of the German Bundestag, issues in EMC are recognized, especially against the background of the use of high frequencies and the increasing integration density. Violating the legal high-frequency regulations usually results in the device being shut down to protect other devices. Further restrictions may include, for example, banning the further market circulation of such devices. Additionally, significant costs must be expected if such restrictions or penalties are imposed by the regulatory authorities.

[0006] Therefore, there is a need for a method to reduce EMC interference radiation while improving the transmission efficiency.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] Therefore, an object of the present invention is to provide a method for reducing EMC interference radiation while improving the transmission efficiency.

Means for Solving the Problems

[0009] According to the present invention, this problem is solved by the subject matter of the independent claims. Advantageous developments of the present invention are apparent from the features of the dependent claims. The present invention relates to a method for operating a wireless energy transmission device having the features described in claim 1. According to the method of the present invention, in a first step, at least one measuring device measures the magnetic field strength in the air gap between the transmitting coil and the receiving coil using a measuring element. In a further step, the transmitting coil control unit sets the operating point of the energy transmission such that the efficiency of the energy transmission device is maximized, taking into account the magnetic field strength value measured by the measuring element. Here, the operating point can mean, for example, the setting of parameters characterizing the transmission, such as the current and voltage in the transmitting coil, especially the frequency, waveform, and possibly also the modulation type in some cases. Advantageously, the reduction of unwanted EMC interference radiation is related to the maximization of efficiency. Furthermore, by maximizing the efficiency, the consumption of electrical energy is reduced, and it is not necessary to limit the operation of the device to which the energy is supplied.

[0010] Advantageous developments of the method presented in the independent claims are possible by means of the means cited in the dependent claims. Furthermore, the method according to the present invention for operating a wireless energy transmission device in which the measuring device is directly connected to the transmitting coil control unit offers the great advantage that the operating point of the energy transmission can be set directly, taking into account the magnetic field strength value measured by the measuring element, without time delay due to further elements in the communication path.

[0011] Advantageously, the method according to the present invention for operating a wireless energy transmission device provided with a second measuring device and a second measuring element offers the advantage that it is not only one measuring element that can measure the magnetic field strength in the air gap between the transmission coils. Furthermore, advantageously, even if the measuring element fails, an independent redundant second measuring device is available, which ensures the operation of the energy transmission device, with a reduction in EMC interference radiation and at the same time an improvement in efficiency. Advantageously, the method according to the present invention can enable the operation of the wireless transmission device by means of the second measuring device, especially in an environment susceptible to EMI.

[0012] In the method according to the invention for operating a wireless energy transmission device, it is particularly advantageous when a first measuring device communicates with a second measuring device. This direct communication is advantageous in order to be able to detect measurement deviations. Thus, the measuring devices monitor each other, and this mutual monitoring provides the advantage that the method according to the invention enables the operation of the wireless transmission device even in an environment particularly susceptible to EMI.

[0013] In the method according to the invention for operating a wireless energy transmission device, it is advantageous if a first measuring device communicates with a second measuring device and, based on the exchange of measurement results, an improved operating point can be set with an increase in efficiency.

[0014] Particularly advantageously, the method according to the invention for operating a wireless energy transmission device comprising a second measuring device and a second measuring element provides the advantage that the regulations of radio regulations are monitored and complied with. Since radio regulations are still only unified at the regional level or, in part, at the national level, the method according to the invention provides the advantage that it can be easily adapted to the locally valid regulations. Particularly advantageously, the currently valid regulations for frequency regulation are selected by choosing a country or region. This device can be manufactured in a standard form and, by user selection, adapted to the regulations of radio regulations existing in the market. It is not necessary to manufacture and sell variations for each country.

[0015] Advantageously, the method according to the invention for operating a wireless energy transmission device comprising a second measuring device and a second measuring element provides the advantage that not only can the magnetic field strength in the air gap between the transmission coils be measured. It is advantageous to detect further emissions of the wireless energy transmission device using at least the second measuring device. These emissions can be caused, for example, by the power supply line to the coil or by a power electronics circuit and cannot be detected by measuring only the magnetic field in the air gap between the coils.

[0016] It is particularly advantageous to detect further emissions of an electrical device comprising a wireless energy transmission device using a second measuring device. Thus, the second measuring device can advantageously also detect and include in the evaluation emissions from capacitive and / or inductive components such as an electrically driven motor. Thereby, it is advantageously achieved that the electrical device monitors and complies with the regulations of the radio regulations as a whole. This overall monitoring offers the advantage that the method according to the invention enables reliable operation of the wireless transmission device even in an environment particularly susceptible to EMI.

[0017] Furthermore, the method according to the invention offers the great advantage that a change in the magnetic field strength in the air gap between the coils caused by interfering metal objects is detected by a first measuring device having a first measuring element and / or a second measuring device having a second measuring element. Advantageously, on the one hand, operating situations are recognized in which the efficiency is reduced by unwanted metal objects and, on the other hand, there is a risk that these objects are heated to an unacceptable degree.

[0018] Further features and advantages of the invention will become apparent to those skilled in the art from the following description of exemplary embodiments with reference to the accompanying drawings. However, these exemplary embodiments should not be construed as limiting the invention.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0020] All the figures are only schematic views of the method according to the present invention or the apparatus according to the present invention, and their components according to exemplary embodiments of the present invention. In the figures, the distance and size relationships are not drawn to a uniform scale. In the various figures, corresponding elements are given the same reference numerals.

[0021] Figure 1 shows a prior art wireless energy transmission device 1 comprising a transmitting coil 4 and a receiving coil 6 suitable for inductive energy transmission. Further, Figure 1 shows a transmitting coil control unit 5 and a receiving coil control unit 7. The transmitting coil 4 is connected to an energy source 13. The transmitting device of the wireless energy transmission device 1 is arranged spaced apart from the receiving device of the wireless energy transmission device 1 via an air gap 10. Between the transmitting coil 4 and the receiving coil 6, in addition to energy transmission, information transmission is also carried out. This information transmission can be carried out either by directly using the energy transmission of coils 4 and 6 at the energy transmission frequency (so-called in-band data transmission), or at different frequencies by coils 4 and 6 (so-called out-of-band data transmission). Similarly, other communication methods such as optical communication methods can also be used. The air gap 10 between the transmitting coil 4 and the receiving coil 6 is caused by the conditions of the device structure. Usually, since the transmitting coil 4 and the receiving coil 6 are each arranged within the device housing, even if the devices are arranged adjacent to each other without further separation, i.e., the housing walls are in contact, a distance between the transmitting coil 4 and the receiving coil 6 is already created by the wall thickness of the housing wall. On the other hand, when the transmitting coil 4 is incorporated, for example, in a table plate, a distance of the transmitting coil 4 with respect to the receiving coil 6 is created, which is determined by the thickness of the table plate and the wall thickness of the housing wall of the receiving device. This distance is usually always referred to as the air gap 10, not only when it is air as described by way of example, but also when, for example, the housing material or the wood of the table plate is within the so-called air gap 10. The consumer device supplied with electrical energy by the receiving coil 6 can be an electrical energy storage device or another consumer device, such as an electrical drive of a kitchen device or an electronic device. When the receiving coil 6 is optimally aligned with respect to the transmitting coil 4, it is possible to achieve an efficiency of the inductive transmission path well in excess of 90%. An unduly large air gap 10 and / or an insufficient alignment between the receiving coil 6 and the transmitting coil 4 result in a large increase in losses, which leads to a significant increase in undesirable radiation. Further, the air gap 10 may be enlarged, for example, by an object between the receiving coil 6 and the transmitting coil 4.

[0022] Figure 2 shows a wireless energy transmission device 1 similar to that of FIG. 1, supplemented by a first measurement element 8. This first measurement element 8 is independent of the transmission coil 4 used to transmit electrical energy. This additional first measurement element 8 is connected to a first measurement device 9. In this Figure 2, the measurement device 9 is part of the transmission coil control unit 5. The additional first measurement element 8 can be used in association with the measurement device 9 to provide information regarding the physical characteristics of energy transmission on the transmission side. For example, with a predetermined measurement signal, an alternating magnetic field with known physical characteristics can be generated. Here, if the first measurement element 8 measures the physical characteristics deviating therefrom, this indicates, for example, a conductive foreign object in the vicinity of the transmission coil 4. In this case, the use of the transmission coil 4 with a strong signal suitable for energy transmission causes undesirable heating of the conductive foreign object due to the generation of eddy currents. If this is not recognized, injuries or fires can occur. Especially when the transmission coil 4 is covered and incorporated within a table plate or a work plate, the arrangement of the inductive transmission coil 4 cannot be easily recognized. Turning on such a covered transmission coil 4 without monitoring it poses a great risk of heating, for example, inadvertently placed metallic objects, causing injuries and even fires. Furthermore, such objects significantly interfere with the wireless transmission of electrical energy, reducing the efficiency of the wireless energy transmission device. This results in an increase in undesirable radiation and thus usually exceeds the legally regulated limit values. These radio regulations cover the electromagnetic spectrum from 9 kHz to 275 GHz. At the international level, radio regulations are implemented by the ITU (International Telecommunication Union). At the regional level, radio regulations are implemented by intergovernmental organizations such as the CEPT (Conference of European Postal and Telecommunications Administrations). At the national level, for example, in the Federal Republic of Germany, radio regulations are implemented and enforced by the BnetzA (Federal Network Agency) commissioned by the Federal Ministry of Economics. Essentially, radio regulations include the use of the available spectrum and the allocation of usability to specific user groups. Along with this, the use by other user groups is prohibited.The monitoring of the use of available spectra is still within the jurisdiction of the Federal Network Agency in the Federal Republic of Germany, which identifies and sanctions unauthorized frequency users. This unauthorized frequency use can be deliberately committed by the intentional use of unassigned frequencies, but can also result from unwanted and / or unintentional electromagnetic field emissions. Unwanted, and in many cases unintentional, electromagnetic field emissions at unassigned frequencies lead to interference with other radio services at the assigned frequencies and are subject to sanctions. For this reason, the radiation of the magnetic field must always be limited so that no interference with other radio services within the assigned spectrum occurs. This can be achieved by the continuous detection of the magnetic field by means of an additional first measuring element 8 to which a first measuring device 9 is connected and the corresponding control of the wireless energy transmission device 1 by the transmission coil control unit 5.

[0023] The wireless energy transmission device 1 supplemented by the first measuring element 8 with the first measuring device 9 can deliver information on the magnetic field strength in the air gap 10 to the transmission coil control unit 5 by measuring the magnetic field strength in the air gap 10. Based on the measured magnetic field strength in the air gap 10, the transmission coil control unit 5 can control the transmission coil 4 so that the electromagnetic field radiation is reduced so that the efficiency of the wireless energy transmission device 1 is improved. The optimization of the efficiency of the wireless energy transmission device 1 corresponds, for example, to the so-called operating point AP shown in the data sheet. The non-fixed operating point AP has the advantage that it can be adjusted in accordance with the respective regulations, rather than simply changing uncontrollably due to external and other influences, such as those due to aging. This adjustment is particularly easy and efficient in the configuration shown in FIG. 2 because information on the physical state of the wireless transmission device is available using the first measuring element 8 by means of the first measuring device 9. These information are used at any time to readjust the operating point AP.

[0024] FIG. 3 shows a wireless energy transmission device 1 similar to FIGS. 1 and 2, and this wireless energy transmission device 1 also includes a second measurement element 11. The additional second measurement element 11, together with the second measurement device 12, is used to detect the generated alternating electromagnetic field. Generally, the additional second measurement element 11, together with the second measurement device 12, detects unwanted radiation emitted by the wireless energy transmission device 1. Further, the additional second measurement element 11, together with the second measurement device 12, is used to measure the alternating electromagnetic field radiated by other electrical devices, such as an electric motor, in addition to the wireless energy transmission device 1.

[0025] Therefore, information regarding the radiation behavior is available not only for the wireless energy transmission device 1 but also for the entire device. Information from the additional second measurement element 11 cooperating with the second measurement device 12 is useful for operating the entire device in accordance with the regulations, as it allows for the recognition of the radiation of an alternating electromagnetic field exceeding the regulated limit values and taking measures up to a complete shutdown of the wireless energy transmission device 1 and other electrical components. Therefore, the additional second measurement element 11, together with the second measurement device 12, also helps to recognize an increase in the radiation of the alternating electromagnetic field caused by malfunction and avoid non-compliant operation. This reliably prevents radio interference due to exceeding the legally regulated limit values and avoids sanctions due to operation of the device outside the allowable range.

[0026] Furthermore, unexpected changes can be identified by measuring the electromagnetic field of the wireless energy transmission device 1. Such an unexpected change in the electromagnetic field suggests the presence of a metallic object in the air gap 10 between the transmitting coil 4 and the receiving coil 6. Eddy currents are generated in such a metallic object by the electromagnetic field of the energy transmission, which leads to heating of the metallic object within the air gap 10 between the transmitting coil 4 and the receiving coil 6. Such heating can cause injury or fire and must therefore be avoided at all costs. When a so-called foreign object within the air gap 10 is recognized by continuous measurement of the electromagnetic field, the energy transmission is switched off, thus removing the danger.

Claims

1. A wireless energy transmission device (1) for charging an energy storage device (2) of an electric vehicle (3), comprising at least one transmission coil (4) suitable for inductive energy transmission and provided with a transmission coil control unit (5), and at least one reception coil (6) suitable for energy transmission and provided with a reception coil control unit (7), further comprising at least one first measurement element (8) and at least one first measurement device (9) connected to the first measurement element (8), wherein the method for operating the wireless energy transmission device (1) comprises: A. A first step (A) of measuring, using the first measurement element (8) via the at least one first measurement device (9), the magnetic field strength within an air gap (10) between the transmission coil (4) and the reception coil (6); B. A step (B) of setting an operating point (AP) of the energy transmission via the transmission coil control unit (5) such that the efficiency of the wireless energy transmission device (1) is maximized, taking into account the magnetic field strength value measured by the first measurement element (8); and the wireless energy transmission device (1) further comprises at least one second measurement device (12) provided with a second measurement element (11) connected to the reception coil control unit (7), and the at least one first measurement device (9) communicates directly with the at least one second measurement device (12) to detect a measurement deviation. A method for operating a wireless energy transmission device (1), characterized by the above.

2. A method for operating a wireless energy transmission device (1) according to claim 1, characterized in that the first measurement device (9) is connected to the transmission coil control unit (5).

3. The method for operating the wireless energy transmission device (1) according to claim 1, characterized in that both the transmission coil control unit (5) and the reception coil control unit (7) maximize the operating point (AP) of the energy transmission based on the communication between the first measurement device (9) and the second measurement device (12).

4. The method for operating the wireless energy transmission device (1) according to claim 1, characterized in that both the transmission coil control unit (5) and the reception coil control unit (7) set the operating point (AP) of the energy transmission so that the regulations of radio wave regulations are complied with based on the communication between the first measurement device (9) and the second measurement device (12).

5. The method for operating the wireless energy transmission device (1) according to claim 1, characterized in that the second measurement device (12) provided with the second measurement element (11) detects further radiation of the wireless energy transmission device (1).

6. The method for operating the wireless energy transmission device (1) according to claim 1, characterized in that the second measurement device (12) provided with the second measurement element (11) detects further radiation by an electrical device including the wireless energy transmission device (1) according to claim 1.

7. The method for operating the wireless energy transmission device (1) according to claim 1, characterized in that a change in the magnetic field strength in the air gap (10) caused by an interfering metal object is detected by the first measurement device (9) provided with the first measurement element (8) and / or the second measurement device (12) provided with the second measurement element (11).

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