METHOD FOR WIRELESS ENERGY TRANSMISSION FROM AN ENERGY TRANSMISSION DEVICE TO A CONSUMER AND WIRELESS ENERGY TRANSMISSION DEVICE FOR CARRYING OUT THE METHOD

Abstract

A method is provided for a wireless, in particular inductive, energy transmission from an energy transmission device to a consumer, and in at least one method task, an interruption of the energy transmission from the energy transmission device to the consumer takes place in conjunction with a foreign object detection. The method provides that a cycle time of the method, and/or a duration and/or frequency of the foreign object detection is/are adapted in at least one method task as a function of a characteristic energy transmission variable of the wireless energy transmission.

Claims

1-20. (canceled)

21. A method for a wireless energy transmission from an energy transmission device to a consumer, the method comprising: performing an interruption of the energy transmission from the energy transmission device to the consumer in conjunction with a foreign object detection; and adapting a cycle time of the method, and/or a duration and/or frequency of the foreign object detection as a function of a characteristic energy transmission variable of the wireless energy transmission.

22. The method of claim 21, wherein in the adapting, a characteristic precision variable, in particular a number of discrete frequency points and/or a number of frequency sweep cycles of the foreign object detection, is adapted as a function of the characteristic energy transmission variable of the wireless energy transmission.

23. The method of claim 22, wherein it is differentiated between a standard foreign object detection, in particular at a cycle time of 1 to 10 seconds, and a rapid foreign object detection, in particular at a cycle time of less than 10 milliseconds, as a function of the number of discrete frequency points and/or the number of frequency sweep cycles.

24. The method of claim 23, wherein the foreign object detection is able to differentiate between at least a standby mode and an energy transmission mode of the wireless energy transmission, and a standard object detection is carried out in a change from the standby mode to the energy transmission mode, or the reverse.

25. The method of claim 23, wherein a rapid foreign object detection is carried out when the characteristic energy transmission variable has changed only slightly from one cycle to the next of the method, preferably by less than 10%.

26. The method of claim 21, wherein a subsequent communication between the energy transmission device and the consumer is allocated to the foreign object detection.

27. The method of claim 21, wherein the foreign object detection is suspended for a defined period of time as a function of an undershooting of an in particular lower limit value by the value of the characteristic energy transmission variable, until a change occurs or until the end of the energy transmission.

28. The method of claim 21, wherein the foreign object detection continues to be carried out and/or the cycle time is reduced as a function of an exceeding of an in particular upper limit value by a value of the characteristic energy transmission variable.

29. The method of claim 21, wherein the characteristic energy transmission variable is an electric power or a power gradient transmitted between the energy transmission device and the consumer, and the cycle time is reduced with a rising amplitude or rising gradient, and/or the duration and/or frequency of the foreign object detection is/are increased with a rising amplitude or rising gradient.

30. The method of claim 21, wherein the characteristic energy transmission variable is a temperature or a temperature gradient measured in the energy transmission device and/or the consumer, and the cycle time is reduced with a rising amplitude or rising gradient, and/or the duration and/or frequency of the foreign object detection is/are increased with a rising amplitude or a rising gradient.

31. The method of claim 21, wherein the characteristic energy transmission variable is an energy requirement of the consumer, and the cycle time is reduced with a rising energy requirement, and/or the duration and/or frequency of the foreign object detection is/are increased with an increased energy requirement.

32. The method of claim 21, wherein the characteristic energy transmission variable is a charge state of the consumer configured as a rechargeable energy store, and the cycle time is increased with a rising charge state, and/or the duration and/or the frequency of the foreign object detection is/are reduced with a rising charge state.

33. The method of claim 21, wherein the characteristic energy transmission variable is a gradient of an acquired actual quality, and the cycle time is reduced with a rising gradient, and/or the duration and/or the frequency of the foreign object detection is/are increased with a rising gradient.

34. The method of claim 21, wherein the characteristic energy transmission variable is a vibration or a vibration gradient measured in the energy transmission device and/or the consumer, and the cycle time is reduced with a rising amplitude or a rising gradient, and/or the duration and/or the frequency of the foreign object detection is/are increased with a rising amplitude or a rising gradient.

35. The method of claim 21, wherein the characteristic energy transmission variable is an electric current or a current gradient in the transmission coil of the energy transmission device, an electric voltage or a voltage gradient applied at the transmission coil and/or a temperature or a temperature gradient of the transmission coil, and the cycle time is reduced with a rising amplitude or a rising gradient, and/or the duration and/or frequency of the foreign object detection is/are increased with a rising amplitude or a rising gradient.

36. The method of claim 21, wherein the characteristic energy transmission variable is an accepted power or a power gradient of a power supply unit of the energy transmission device, and/or a supply voltage or a supply voltage gradient of the power supply unit of the energy transmission device, and the cycle time is reduced with a rising amplitude or a rising gradient, and/or the duration and/or frequency of the foreign object detection is/are increased with a rising amplitude or a rising gradient.

37. The method of claim 21, wherein the foreign object detection is carried out at an excitation voltage of a primary-side transmission coil of the energy transmission device of less than 10V, or between 2.5V and 5V.

38. A wireless energy transmission apparatus for providing a wireless energy transmission from the transmission apparatus to a consumer, comprising: a wireless energy transmission device configured to perform the following: performing an interruption of the energy transmission from the wireless energy transmission device to the consumer in conjunction with a foreign object detection; and adapting a cycle time of the method, and/or a duration and/or frequency of the foreign object detection as a function of a characteristic energy transmission variable of the wireless energy transmission; wherein the wireless energy transmission device is configured for a power range of the wirelessly to be transmitted energy within a lower power limit of 5 W and an upper power limit of 30 W or 15 W.

39. The wireless energy transmission device of claim 38, wherein the wireless energy transmission device is configured for a power range of the wirelessly to be transmitted energy within a lower power limit of 30 W and an upper power limit of 200 W or 65 W.

40. The wireless energy transmission device of claim 38, wherein the wireless energy transmission device is configured for a power range of the wirelessly to be transmitted energy above a lower power limit of 200 W or 2000 W.

41. The wireless energy transmission device of claim 38, wherein the wireless energy transmission device is inductive.

42. The method of claim 23, wherein a rapid foreign object detection is carried out when the characteristic energy transmission variable has changed only slightly from one cycle to the next of the method, by less than 5%.

43. The method of claim 23, wherein a rapid foreign object detection is carried out when the characteristic energy transmission variable has changed only slightly from one cycle to the next of the method, by less than 1%.

44. The method of claim 23, wherein the wireless energy transmission device is inductive.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a wireless energy transmission system having a primary energy transmission device and a secondary-side consumer, in a schematic representation.

[0037] FIG. 2 shows a schematic diagram of the different working ranges of the wireless energy transmission device.

[0038] FIG. 3 shows a program sequence of the method according to the present invention for a wireless energy transmission, in a schematic representation.

[0039] FIG. 4 shows a supplementary program sequence of the method according to the present invention for the wireless energy transmission, in a schematic representation.

DETAILED DESCRIPTION

[0040] FIG. 1 shows a wireless energy transmission system 10 in the form of an inductive charging system, which includes a primary energy transmission device 14 developed as a charging device 12, and a secondary-side consumer 18, developed as a rechargeable battery pack 16, for a handheld machine tool (not shown).

[0041] In the same way, however, consumer 18 may also be a rechargeable battery which is firmly integrated into the handheld machine tool. As mentioned in the introduction, however, the present invention is not restricted to inductive charging systems for handheld machine tools and their rechargeable batteries or battery packs. Instead, it may be used for a wide variety of wireless energy transmission types and for energy transmission and receiving devices for which a foreign object detection is useful or required. This may also include a wireless energy transmission based on an optical, acoustic and capacitive principle or one based on air flows or the like.

[0042] FIG. 1 shows rechargeable battery pack 16 placed on a topside of a housing 20 of wireless charging device 12. It is charged via at least one primary-side transmission coil integrated into charging device 12 and a secondary-side receiving coil (not shown) of wireless energy transmission system 10 integrated into rechargeable battery pack 16. Wireless energy transmission system 10 has a primary-side electronics unit 24 in charging device 12 for this purpose, which in turn includes an open-loop and closed-loop control unit 26 as well as an oscillating switching circuit 28 having transmission coil 22.

[0043] Open-loop and closed-loop control unit 26 of wireless energy transmission system 10 is provided to determine a resonant frequency f.sub.res and an associated actual quality Q.sub.act(f.sub.res). In addition, open-loop and closed-loop control unit 26 compares actual quality Q.sub.act to a setpoint quality Q.sub.tar(f.sub.res) as a function of the resonant frequency f.sub.res. Toward this end, open-loop and closed-loop control unit 26 includes a memory 30, which stores a setpoint quality range q.sub.tar having a plurality of setpoint qualities Q.sub.tar(f.sub.res) for ascertained resonant frequency f.sub.res (see also the following statements in connection with FIGS. 2 and 3).

[0044] During the wireless energy transmission, a foreign object detection is carried out at defined time intervals T.sub.cycle, such as every second, in which it is checked whether one or a plurality of foreign object(s) 32 that may have an adverse effect on the energy transmission and/or that could pose a safety risk is/are situated between energy transmission device 14 and consumer 18 or simply only on energy transmission device 14. The foreign object detection operates essentially in such a way that resonant frequency f.sub.res and associated actual quality Q.sub.actf.sub.res are determined to begin with, and actual quality Q.sub.act (f.sub.res ) is subsequently compared to setpoint quality Q.sub.tar (f.sub.res) as a function of resonant frequency f.sub.res. Finally, based on defined setpoint quality range q.sub.tar, a decision is made about the operating state of wireless energy transmission system 10 or energy transmission device 14.

[0045] The foreign object detection is carried out using an excitation voltage of primary-side transmission coil 22 of energy transmission device 14 of less than 10V, which may be between 2.5V and 5V. This allows the foreign object detection to be carried out at a negligible transmission power so that an energy transmission to the consumer is able to be avoided and a resulting faulty measurement of actual quality Q.sub.act (f.sub.res) may be prevented. In this way, consumer 18 also does not send any faulty data values to energy transmission device 14, e.g., an incorrect charge status of an accumulator to be charged, which could falsify a subsequent foreign object detection.

[0046] FIG. 2 shows setpoint quality ranges q.sub.tar stored in memory 30 of open-loop and closed-loop control unit 26 in the form of a schematic diagram in which resonant frequency f.sub.res is plotted on the abscissa and quality Q is plotted on the ordinate. The diagram is subdivided into three ranges 34, 36, 38 (38a, 38b). A first range 34 defines a setpoint quality range q.sub.tar for an operation using consumer 18. If actual quality Q.sub.act (f.sub.res) lies between an upper limit q.sub.tar_up and a lower limit q.sub.tar_lo of first range 34, then it is assumed that no foreign object 32 that has an effect on the energy transmission is situated on wireless energy transmission device 14. Moreover, a wireless energy transmission from energy transmission device 14 to consumer 18 is assumed in this range. A second range 36 defines a setpoint quality range q.sub.tar for a standby operation without an applied consumer 18. If actual quantity Q.sub.act (f.sub.res) lies between upper limit q.sub.tar_up and lower limit q.sub.tar_lo of second range 36, then it is assumed that neither a foreign object 32 nor a consumer 18 is situated on wireless energy transmission device 14.

[0047] A third range, which has two second subranges 38a, 38b, is formed by an error range. As a matter of principle, an error may lie in the wireless energy transmission system 10, in energy transmission device 14, in consumer 18 and also in an environment of energy transmission system 10. A first subrange 38a lies below lower limit q.sub.tar_lo of first range 34 in relation to quality Q, and a second subrange 38b lies below lower limit q.sub.tar_lo of second range 36. If actual quality Q.sub.act (f.sub.res) lies within first subrange 38a, it is assumed that at least one foreign object 32 is located on energy transmission device 14 or between energy transmission device 14 and consumer 18 in a region that has an effect on it during the energy transmission. Here, too, it may be assumed that a random fault has occurred, or that consumer 18 is positioned on wireless energy transmission device 14 in such an unfavorable position that an energy transmission is impossible or possible only with considerable restrictions. If actual quality Q.sub.act (f.sub.res) lies within second subrange 38b, then it is assumed that at least one foreign object 32 is situated on wireless energy transmission device 14 during the standby operation.

[0048] The following non-linear relationship, which may be gathered from FIG. 2, applies to the characteristic of actual quality Q.sub.act. If the distance between consumer 18 and energy transmission device 14 enlarges, then both resonant frequency f.sub.res and actual quality Q.sub.act (f.sub.res) increase. The same may be noticed when consumer 18 is shifted or positioned outside its optimal positionthe center of the at least one primary-side transmission coil 22 on the surface of energy transmission device 14regardless of the direction. These two cases describe quite frequently occurring scenarios. For example, a lateral offset of consumer 18 with respect to energy transmission device 14 has to be permitted because a user will normally not always be able to place the secondary-side receiving coil of consumer 18 in an exactly centered manner over the at least one transmission coil 22 of energy transmission device 14. This is particularly the case when energy transmission device 14 has a planar surface without mechanical guide aids for consumer 18 or ifas in the case of a vehicle to be chargedthe positions of the at least one primary-side transmission coil 22 and/or the at least one secondary-side receiving coil are not precisely known or able to be seen. In addition, in particular when consumer 18 is set down directly on energy transmission device 14, vertical tilting is conceivable as a result of foreign objects 32 between consumer 18 and energy transmission device 14.

[0049] FIG. 3 shows a program sequence of the method for a wireless energy transmission according to the present invention. After start 40, what is known as a power-on self-test (POST) of energy transmission device 14 is carried out in first step 42. Start 40 may take place automatically when consumer 18 is placed on energy transmission device 14, or when a button (not shown) on energy transmission device 14 and/or consumer 18 is operated. If the POST in step 42 was run through successfully, open-loop and closed-loop control unit 26 of energy transmission device 14 automatically initializes resonant frequency f res actual quality Q.sub.act (f.sub.res) and cycle period T.sub.cycle of the following method steps in a second step 44, with f.sub.res=f.sub.stdby, Q.sub.act,n (f.sub.res)=O and T.sub.cycle=T.sub.min, where f.sub.stdby describes a permissible resonant frequency in the standby operation (see FIG. 2), and T.sub.rain describes a minimum cycle period (e.g., 10 ms). Alternatively, it is also possible to initially set T.sub.cycle to T.sub.min=O.

[0050] In next step 46, an actual quality Q.sub.act,n+1 (f.sub.res) is initially measured for the initialized resonant frequency and then compared in fourth step 48 to initialized actual quality Q.sub.act,n (f.sub.res). Since there is no agreement between the initialized and the measured actual quantity immediately following the start of the method for the wireless energy transmission, this is followed in a fifth method step by a partial process, carried out by open-loop and closed-loop control unit 26 in the form of a frequency sweep, such that open-loop and closed-loop control unit 26 actuates a frequency unit (not shown) of primary-side electronics unit 24, the frequency unit being connected upstream from oscillating switching circuit 28. One skilled in the art is essentially familiar with the actuation of such an oscillating switching circuit for carrying out a frequency sweep. For this reason, no further details will be provided in this context.

[0051] To determine resonant frequency f res a resonance magnification at primary transmission coil 22 is detected in fifth step 50 during the frequency sweep. Using the amplitude ascertained at the location of the resonance magnification, actual quality Q.sub.act,n+1 (f.sub.res) is then able to be calculated in the known manner; the location of the resonance magnification corresponds to the ascertained frequency f.sub.res. In a seventh step 54, these two values are then compared to setpoint quality range q.sub.tar, which is stored in memory 30 of open-loop and closed-loop control unit 26 (step 52, see also FIG. 2).

[0052] If actual quality Q.sub.act,n+1 (f.sub.res) lies between the upper and the lower limit q.sub.tar_up, q.sub.tar_lo of first range 34 according to FIG. 2, then it may be assumed that no foreign object 32 that could affect the upcoming wireless energy transmission is located on wireless energy transmission device 14, so that the method for the wireless energy transmission runs through the following partial process 56, which is made up of four partial steps 56.1, 56.2, 56.3, 56.4, in which a communication between energy transmission device 14 and consumer 18 is established and checked. In first partial step 56.1, open-loop and closed-loop control unit 26 of energy transmission device 14 generates a synchronization pulse and transmits it to consumer 18, which may be via primary-side transmission coil 22 and the secondary-side receiving coil. Alternatively, some other wireless data transmission, e.g., via Bluetooth, optically, acoustically or the like, would also be conceivable for the communication between energy transmission device 14 and consumer 18. When the required received data Rx Data of consumer 18 are received in second partial step 56.2 by primary-side electronics unit 24 of energy transmission device 14 following the synchronization pulse, then the coupling between energy transmission device 14 and consumer 18 is able to be checked in third partial step 56.3. If the check of the coupling and the received data is successful, a decision is made in fourth partial step 56.4 to start the wireless energy transmission to consumer 18 according to an eighth step 58a. However, if the check is not successful, an error and/or a foreign object 32 is/are assumed in an alternative, eighth step 58c.

[0053] If actual quality Q.sub.act,n+1 (f.sub.res) lies between the upper and lower limit q.sub.tar_up, q.sub.tar_lo of second range 36 according to FIG. 2, then it is assumed that wireless energy transmission system 10 is in a standby operation and no foreign object 32 is present on wireless energy transmission device 14. The method for the wireless energy transmission thus jumps from sixth step 52 directly to a further, alternative eighth step 58b.

[0054] If the result between actual quality Q.sub.act,n+1 (f.sub.res) and setpoint quality Q.sub.act (f.sub.res) in sixth step 52 reveals that actual quality Q.sub.act,n+1 (f.sub.res) lies outside setpoint quality range q.sub.tar, then an error and/or an existing foreign object 32 is/are assumed in step 58c according to the above statements in connection with FIG. 2.

[0055] Starting from the three possible eighth steps 58a (operation for a wireless energy transmission, 58b (standby operation), 58c (error or foreign object is detected), a decision is made in a ninth method step 60 as to whether the adjusted cycle time T.sub.cycle has exceeded a maximum cycle time T.sub.max of one second, for example. T.sub.cycle defines a length of time between two consecutive passes through the method for the wireless energy transmission according to the present invention. On the other hand, steps 46 through 58 of the method for wireless energy transmission according to the present invention normally last only a few milliseconds and depend considerably on the processing power of primary-side open-loop and closed-loop control unit 26. As long as cycle time T.sub.cycle has not yet exceeded maximum cycle time T.sub.max in ninth step 60, it is increased to a specified value, successively or a single time, in a tenth step 62a. While cycling through steps 60 and 62a, the actual method for detecting the operating types and/or errors or foreign objects according to steps 46 through 58 has already been concluded so that the wireless energy transmission according to step 58a, the standby operation according to step 58b, or an interruption of the energy transmission or the standby operation according to step 58c is carried out as a function of the decision made in sixth step 54 until T.sub.cycle has exceeded maximum cycle time T.sub.max. A decision is then made in step 62b as to whether the method is to be repeated or terminated. In the case of a repeat, the currently stored actual quality Q.sub.act,.sub.n(f.sub.res) is set to the value of current actual quality Q.sub.act,n+1 (f.sub.res) of the past cycle in an eleventh step 64, and cycle time T.sub.cycle is set to minimum value T.sub.min. The method then begins anew with third step 46 and the measurement of a new actual quality Q.sub.act,n+1 (f.sub.res), in which the subsequent frequency sweep according to step 50 is omitted if the currently stored and new actual quality do not differ due to Q.sub.act,n+1 (f.sub.res)=Q Q.sub.act,n (f.sub.res).

[0056] If an error was determined in first step 42 during the POST or if a decision was made in eleventh step 64 not to repeat the cycle, then the method according to the present invention for the wireless energy transmission is stopped by final step 66.

[0057] Of particular importance for the method for the wireless energy transmission according to the present invention are the data Rx Data received in second partial step 56.2 of partial process 56 according to FIG. 4. In this context, the flow diagram illustrated in FIG. 4 shows only a section of the program sequence shown in FIG. 3, in which identical method steps have been provided with the same reference numerals in each case and seventh method step 54 was split up into two partial steps 54.1 and 54.2.

[0058] If actual quality Q.sub.act,n+1 (f.sub.res) lies between the upper and lower limit q.sub.tar_up, q.sub.tar_lo of second range 36 according to FIG. 2 in partial step 54.1, then it is assumed according to FIG. 3 that wireless energy transmission system 10 is in a standby operation and no foreign object 32 is situated on wireless energy transmission device 14. The method for the wireless energy transmission thus jumps directly to eighth step 58b from sixth step 52. However, if actual quality Q.sub.act,n+1 (f.sub.res) lies outside second range 36 in partial step 54.1, then it is checked in a following partial step 54.2 whether it lies between the upper and the lower limit q.sub.tar_up, q.sub.tar_lo of first range 34 according to FIG. 2. If this is not the case, then an error and/or a foreign object 32 is/are assumed in step 58c. In contrast, if actual quality Q.sub.act,n+1 (f.sub.res) corresponds to a setpoint quality Q.sub.tar (f.sub.res) of first range 34, then a communication to consumer 18 is built up in following partial process 56.

[0059] According to the present invention, in partial steps 56.5 and 56.6 as additional steps in comparison with FIG. 3, it is now provided to take a characteristic energy transmission variable into account for the following foreign object detection, the variable being derivable from the received data of consumer 18 Rx Data and/or data sensed in energy transmission device 14. The characteristic energy transmission variable in particular is a characteristic variable that characterizes, which may be in quantitative terms, an energy flow during the wireless energy transmission, in the case of an inductive energy transmission, in particular an electromagnetic energy flow, between energy transmission device 14 and consumer 18. For example, the characteristic energy transmission variable may be an electric power transmitted between energy transmission device 14 and consumer 18 or a power gradient; a temperature or a temperature gradient; a required energy requirement of consumer 18; a charge state of consumer 18, developed as a rechargeable energy store;

[0060] a gradient of acquired actual quality Q.sub.act,n+1 (f.sub.res); a vibration or a vibration gradient measured in the consumer; and/or an item of authenticating information regarding the right of consumer 18 to the wireless energy transmission.

[0061] Alternatively or additionally, however, electronics unit 24 of energy transmission device 14 may also include a sensor unit 68 which is connected to open-loop and closed-loop control unit 26 and provided for the continuous or quasi-continuous acquisition of the characteristic energy transmission variable. In this way, the acquisition may be undertaken both during the foreign object detection and during the wireless energy transmission, during the standby operation, or also during an interruption of the energy transmission as a result of a detected error and/or foreign object. A corresponding sensor unit 70 may additionally or alternatively also be required in consumer 18 for generating the above received data Rx Data (see FIG. 1). The sensor device may be made up of a wide variety of sensors such as a shunt resistance, a temperature probe, an acceleration sensor, a yaw rate sensor, and also an air pressure sensor, a moisture sensor or the like. Since one skilled in the art is quite familiar with corresponding sensors, no further description will be given here. The sensed characteristic energy transmission variable may thus involve an electric current or current gradient in transmission coil 22; an electric voltage or a voltage gradient applied at transmission coil 22; a temperature or a temperature gradient of transmission coil 22; an accepted power or a power gradient of a power supply unit of energy transmission device 14; a supply voltage or a supply voltage gradient of the power supply unit of energy transmission device 14, or the like. Also conceivable as a characteristic energy transmission variable is a measured vibration or a vibration gradient of energy transmission device 14.

[0062] In the same way, it would be conceivable to develop the characteristic energy transmission variable as a function of an installation location of energy transmission device 14, e.g., in a stationary form in a workshop or in mobile form in a vehicle.

[0063] For instance, the installation location is able to be determined based on the measured vibration or the measured vibration gradient of energy transmission device 14. It is also possible, however, to utilize existing speed and/or GPS data of a vehicle or the like toward this end.

[0064] To optimize the foreign object detection, different parameters for controlling the foreign object detection are able to be determined from the characteristic energy transmission variable with the aid of open-loop and/or closed-loop control unit 26. In at least one partial step 56.6, at least one characteristic precision variable, e.g. a number of discrete frequency points and/or a number of frequency sweep cycles (see step 50 in FIG. 3) of the foreign object detection is determined as a function of the at least one characteristic energy transmission variable. In addition, a duration and/or frequency, in particular a frequency of an execution of the foreign object detection during the wireless energy transmission, is able to be determined as a function of the at least one characteristic energy transmission variable. For example, the frequency during the wireless energy transmission at a medium transmission power, e.g., a transmission power of between 5 W and 10 W, may be reduced in comparison with a frequency during a wireless energy transmission at a high transmission power, e.g., a transmission power of more than 10 W. During a wireless energy transmission at a low transmission power, an execution of a foreign object detection may be dispensed with completely. In addition, in partial step 56.6, maximum cycle time T.sub.max and/or a length of time of the frequency sweep to be carried out in step 50 is/are able to be determined as a function of the at least one characteristic energy transmission variable.

[0065] Based on the measures specified in partial step 56.6, a decision is made in final partial step 56.7 whether the foreign object detection is able to be deactivated for a defined period of time or for the remaining energy transmission, and/or whether the limit values specified in step 56.6 of resonant frequency f.sub.res and actual quality Q.sub.act,n+1 (f.sub.res) inventive for the energy transmission process were complied with. If this is the case and if the foreign object detection was cycled through without an error, then the energy is able to be transmitted in step 58a in a wireless manner from energy transmission device 14 to consumer 18. However, if it was decided in partial step 56.7 that the limit values were exceeded or that the foreign object detection may not be suspended, then an error or an existing foreign object 32 is inferred according to step 58c, so that no further energy transmission takes place until the decision about the repeat of the cycle in step 62b.

[0066] Open-loop and/or closed-loop control unit 26 of energy transmission device 14 continuously monitors the energy transmission for irregularities as a function of cycle time T.sub.cycle. If open-loop and/or closed-loop control unit 26 detects a change in time, in particular an amplitude fluctuation and/or a gradient, of the characteristic energy transmission variable, then the energy transmission is interrupted and a renewed foreign object detection is initiated according to steps 60 through 64 illustrated in FIG. 3.

[0067] In partial step 56.7, the foreign object detection in partial step 56.7 is suspended for a defined period of time or until the end of the energy transmission as a function of an undershooting of an in particular lower limit value by a value of the characteristic energy transmission variable, this being done by increasing maximum cycle time T.sub.max correspondingly in partial step 56.6. In partial step 56.7 a decision is made as a function of an exceeding of an in particular upper limit value by a value of the characteristic energy transmission variable as to whether to carry on with the execution of the foreign object detection and/or to reduce maximum cycle time T.sub.max in partial step 56.6. In particular, the execution of the foreign object detection is suspended when a lower limit value of a transmission power is not attained, such as in a drop of the transmission power to a value of below 5 W. The foreign object detection resumes again when a specified limit value of the transmission power is exceeded.

[0068] It should finally also be pointed out that the illustrated exemplary embodiment is neither restricted to the FIGS. 1 through 4 nor to the mentioned power and voltage values. In particular, the present invention may also be used in wireless energy transmissions at transmission powers of considerably more than 10 W, e.g. for applications in kitchens or electric vehicles.