Method for detecting foreign objects in an induction charging device

Abstract

A method for detecting foreign objects in an induction charging device, with the aid of at least one control and/or regulating unit of the induction charging device, includes: ascertaining a resonance frequency; determining an actual quality at the resonance frequency; and comparing the actual quality to a setpoint quality which is a function of a resonance frequency.

Claims

1. A method for detecting foreign objects in an induction charging device, comprising: ascertaining in a first method step, using a control unit of the induction charging device, a resonance frequency at an oscillator component of the induction charging device; determining in a second method step, using the control unit, an actual quality at the resonance frequency; and comparing in a third method step, using the control unit, the determined actual quality at the resonance frequency to a setpoint quality which is a function of the resonance frequency.

2. The method as recited in claim 1, wherein a frequency run is carried out in the first method step for ascertaining the resonance frequency.

3. The method as recited in claim 2, wherein in the first method step for ascertaining the resonance frequency, a resonance step-up is detected at the oscillator component during the frequency run.

4. The method as recited in claim 3, wherein in the second method step for determining the actual quality, at least one of (i) the detected resonance step-up at the oscillator component and (ii) an excitatory voltage is processed.

5. The method as recited in claim 2, wherein: in the first method step for ascertaining the resonance frequency, at least one of a value of a resonance step-up at an oscillator component and a value of an excitatory voltage is detected during the frequency run; and in the second method step, at least one of the value of the resonance step-up at the oscillator component at the resonance frequency and the value of the excitatory voltage at the resonance frequency is used to determine the actual quality.

6. The method as recited in claim 5, wherein in the third method step, the determined actual quality at the resonance frequency is compared to a setpoint quality range which is a function of the resonance frequency.

7. The method as recited in claim 6, further comprising: evaluating in a fourth method step, using the control unit, the results of the first through third method steps to make at least one decision as a function of the evaluation.

8. The method as recited in claim 7, wherein in the fourth method step, at least one decision is made with regard to at least one of an operating state of the induction charging device and a presence of a foreign object in the induction charging device.

9. The method as recited in claim 8, wherein at least the first method step is carried out periodically at regular intervals.

10. The method as recited in claim 1, further comprising: detecting the presence of a foreign object based on results of the comparing.

11. An induction charging device, comprising: a control unit including a processor and configured to perform the following: ascertain, in a first method step, a resonance frequency at an oscillator component of the induction charging device; determine, in a second method step, an actual quality at the resonance frequency; and compare, in a third method step, the determined actual quality to a setpoint quality which is a function of the resonance frequency.

12. The induction charging device as recited in claim 11, wherein the control unit has at least one memory unit storing at least one relation table which assigns at least one setpoint quality to an associated resonance frequency.

13. The induction charging device as recited in claim 11, wherein the control unit is further configured to detect the presence of a foreign object based on results of the comparison.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic representation of an induction charging device for carrying out a method according to the present invention for detecting foreign objects and of a battery device to be charged.

(2) FIG. 2 shows a schematic representation of a program flow chart of the method according to the present invention for detecting foreign objects in the induction charging device.

(3) FIG. 3 shows a schematic diagram of an exemplary time curve of an amplitude of a frequency at an oscillator component and of an excitatory voltage during a first method step.

(4) FIG. 4 shows a relation table of the control and regulating unit of the induction charging device in the form of a schematic diagram.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 shows an induction charging device 10 for carrying out a method for detecting foreign objects according to the present invention. Furthermore, FIG. 1 shows a battery device 30 to be charged. Induction charging device 10 is formed by a hand tool battery induction charging device. Induction charging device 10 forms the primary side of a charging system 32. Induction charging device 10 is provided for charging hand tool batteries or handheld power tools having an integrated battery. Battery device 30 to be charged is formed by a hand tool battery. However, it would basically also be conceivable to charge other batteries which appear reasonable to those skilled in the art with the aid of induction charging device 10. FIG. 1 shows induction charging device 10 and battery device 30 to be charged during a charging operation. Here, battery device 30 is positioned on an upper side of a housing 34 of induction charging device 10 and is charged wirelessly via a charging coil 36 of induction charging device 10.

(6) Induction charging device 10 has a control and regulating unit 12. Induction charging device 10 has a charging electronic unit 38 which includes control and regulating unit 12. Furthermore, charging electronic unit 38 has an oscillator circuit 40. Oscillator circuit 40 includes charging coil 36. Control and regulating unit 12 of induction charging device 10 is provided in a first method step 14 for ascertaining a resonance frequency f. Furthermore, control and regulating unit 12 is provided in a second method step 16 for determining an actual quality Q.sub.i at resonance frequency f. Moreover, control and regulating unit 12 is provided in a third method step 18 for comparing actual quality Q.sub.i to setpoint quality Q.sub.s which is a function of resonance frequency f.

(7) Control and regulating unit 12 has a memory unit 28. A relation table which assigns multiple setpoint qualities Q.sub.s to a resonance frequency f is stored in memory unit 28. The relation table assigns a setpoint quality range q.sub.s to a resonance frequency f.

(8) A detection of foreign objects is carried out at regular intervals during a charging operation of induction charging device 10. During the detection of foreign objects, it is checked whether foreign objects which could impair a charging operation are present between induction charging device 10 and battery device 30 or simply only on induction charging device 10 or endanger a user or induction charging device 10. The detection of foreign objects takes place using a method for detecting foreign objects in induction charging device 10 with the aid of control and regulating unit 12 of induction charging device 10.

(9) FIG. 2 shows a program flow chart of the method according to the present invention for detecting foreign objects. A start 42 of the method is in this case parallel to a start of the charging operation. In a first method step 14 of the method, a resonance frequency f is ascertained. To ascertain resonance frequency f, a frequency run is carried out in first method step 14. The frequency run is carried out in a first operation 44. The frequency run is carried out by control and regulating unit 12 which controls a frequency unit which is not illustrated here in greater detail. The frequency unit forms a part of charging electronic unit 38 and is electrically connected upstream from oscillator circuit 40. The frequency unit which is not illustrated here in greater detail and oscillator circuit 40 which is not illustrated here in greater detail 40 form a half-bridge. The frequency unit has two switches which are controlled by control and regulating unit 12. In order to ascertain resonance frequency f, a resonance step-up A is detected at a oscillator component 20 during the frequency run in first method step 14. A resonance step-up A is detected at charging coil 36. In a second operation 46 which is carried out in parallel to first operation 44, an amplitude characteristic Y.sub.f of a frequency of oscillator component 20 is recorded during the frequency run. Furthermore, an excitatory voltage U.sub.a is measured and recorded during the frequency run in second operation 46. In a third operation 48 of first method step 14, which follows first operation 44 and second operation 46, a resonance frequency f is determined. For this purpose, a resonance step-up A of amplitude characteristic Y.sub.f of the frequency of charging coil 36 is determined during second operation 46. At the point in time of resonance step-up A of charging coil 36, the frequency run of control and regulating unit 12 has passed resonance frequency f.

(10) Subsequently, an actual quality Q.sub.i at resonance frequency f is determined in a second method step 16. Here, actual quality Q.sub.i of charging coil 36 is determined when charging coil 36 is excited with a resonance frequency f. In second method step 16, resonance step-up A at oscillator component 20 and an excitatory voltage U.sub.a are detected for ascertaining actual quality Q.sub.i. In order to determine actual quality Q.sub.i, a value of resonance step-up A of oscillator component 20 and a value of excitatory voltage U.sub.a at resonance frequency f are retrieved from second operation 46 in a fourth operation 50 of second method step 16. The values are used to compute an actual quality Q.sub.i at resonance frequency f in fourth operation 50. Accordingly, in first method step 14, a value of a resonance step-up A at oscillator component 20 and values of an excitatory voltage U.sub.a are detected during the frequency run, and in second method step 16, the value of resonance step-up A at oscillator component 20 and a value of excitatory voltage U.sub.a at resonance frequency f are used to ascertain actual quality Q.sub.i.

(11) In a third method step 18, actual quality Q.sub.i is compared to a setpoint quality Q.sub.s which is a function of a resonance frequency f. In third method step 18, actual quality Q.sub.i is compared to a setpoint quality range q.sub.s which is a function of resonance frequency f. In a fifth operation 52 of third method step 18, computed actual quality Q.sub.i is compared to a setpoint quality range q.sub.s which is a function of resonance frequency f. For this purpose, a setpoint quality range q.sub.s which is a function of resonance frequency f is read out in a sixth operation 54 of third method step 18. Setpoint quality range q.sub.s is read out from the relation table which is stored in memory unit 28 of control and regulating unit 12. In the relation table, every possible resonance frequency f is assigned a setpoint quality range q.sub.s in which a quality Q may move at this frequency f and also move at this resonance frequency f under normal conditions. In sixth operation 54, a setpoint quality range q.sub.s is read out which is associated with resonance frequency f determined in third operation 48. Actual quality Q.sub.i is compared to this read-out setpoint quality range q.sub.s in fifth operation 52.

(12) Subsequently, in a fourth method step 22, the results of preceding method steps 14, 16, 18 are evaluated and multiple decisions 24, 26 are made as a function thereof. Decisions 24, 26 are each formed from Yes/No decisions. In fourth method step 22, decisions 24, 26 are made with regard to an operating state and with regard to a presence of a foreign object. In a first decision 24 of fourth method step 22, which follows fifth operation 52, it is checked whether actual quality Q.sub.i is within setpoint quality range q.sub.s in fifth operation 52. First decision 24 forms a branch in the program flow chart. In first decision 24, a decision is made with regard to a presence of a foreign object. If actual quality Q.sub.i is within setpoint quality range q.sub.s, it is assumed that there is no foreign body in an area between induction charging device 10 and battery device 30 or simply only on induction charging device 10. If actual quality Q.sub.i is outside of setpoint quality range q.sub.s, it is assumed that there is a foreign body in an area between induction charging device 10 and battery device 30 or simply only on induction charging device 10.

(13) If actual quality Q.sub.i is now within setpoint quality range q.sub.s during first decision 24, first decision 24 is followed by second decision 26. During second decision 26, resonance frequency f is checked which was measured in third operation 48. Here, it is checked whether a resonance frequency f is involved such as the one present during a charging operation. For this purpose, resonance frequency f is compared to a charging resonance frequency range f.sub.L which is stored in memory unit 28 of control and regulating unit 12. If resonance frequency f is within charging resonance frequency range f.sub.L, it is assumed that a battery device 30 is present on induction charging device 10 and battery device 30 is to be charged. If resonance frequency f is outside of charging resonance frequency range f.sub.L, it is assumed that no battery device 30 is present on induction charging device 10 or battery device 30 is fully charged. If during second decision 26 resonance frequency f is now within charging resonance frequency range f.sub.L, a charging operation is started in a seventh operation 56 of fourth method step 22 or a charging operation is normally continued. If during second decision 26 resonance frequency f is now outside of charging resonance frequency range f.sub.L, a stand-by operation is started in an eighth operation 58 of fourth method step 22 or a stand-by operation is continued.

(14) The four method steps 14, 16, 18, 22 are repeated after seventh operation 56 or after eighth operation 58. First operation 44 of first method step 14 is restarted after a break 60 after seventh operation 56 or after eighth operation 58 of fourth method step 22. In this case, the four method steps 14, 16, 18, 22 are carried out intermittently at regular intervals. The four method steps 14, 16, 18, 22 are carried out together once every second. The four method steps 14, 16, 18, 22 have a total duration of 100 ms. Another total duration which appears reasonable to those skilled in the art or another repetition duration which appears reasonable to those skilled in the art is, however, also basically conceivable.

(15) If actual quality Q.sub.i is now outside of setpoint quality range q.sub.s during first decision 24, a charging operation is stopped in a ninth operation 62 of fourth method step 22. An output 64 subsequently follows which outputs a message to a user that a foreign object is present on induction charging device 10. In this way, a user may be given the possibility of inspecting induction charging device 10 for foreign objects. After output 64, the method for detecting foreign objects and the charging operation are stopped by a stop 66. In this way, the risk of damaging induction charging device 10 may be avoided. Now, a user must actively restart a charging operation and thus the method for detecting foreign objects. However, it would also be basically conceivable, as illustrated by a dashed line, that the four method steps 14, 16, 18, 22 are repeated after output 64 and the process is restarted with first operation 44 of first method step 14. Thereby, a switching on by a user could be avoided after a detection of a foreign object, whereby the frequency run of first operation 44 could heat up the foreign object at least slightly.

(16) FIG. 3 shows an exemplary time curve of the amplitude of the frequency at oscillator component 20 during the frequency run of first method step 14. FIG. 3 shows amplitude characteristic Y.sub.f of the frequency at oscillator component 20 during the frequency run of first method step 14. Furthermore, FIG. 3 shows an exemplary time curve of excitatory voltage U.sub.a during the frequency run of first method step 14. Amplitude characteristic Y.sub.f and excitatory voltage U.sub.a are illustrated in the same diagram. In the diagram, the time is plotted on an x axis and a voltage is plotted on a y axis. The two maximum turning points of amplitude characteristic Y.sub.f each represent a resonance step-up A. In this case, the second maximum turning point is reached by reactivation using resonance frequency f. The reactivation using resonance frequency f is basically not absolutely necessary. Excitatory voltage U.sub.a drops towards resonance step-up A due to the increased load.

(17) FIG. 4 shows a relation table of control and regulating unit 12 of induction charging device 10 in the form of a schematic diagram. In the diagram, the frequency is plotted on an x axis and a quality is plotted on a y axis. In this case, the diagram is divided into three areas 68, 70, 72. A first area 68 is formed from a setpoint range for an operation using battery device 30. If actual quality Q.sub.i is in this area 68 in relation to resonance frequency f, it is assumed that no foreign body is present in an area between induction charging device 10 and battery device 30. Furthermore, it is assumed that a battery device 30 is present on induction charging device 10 and battery device 30 is to be charged. A second area 70 is formed from a setpoint range for an operation without battery device 30. If actual quality Q.sub.i is in this area 70 in relation to resonance frequency f, it is assumed that no foreign body is present on induction charging device 10. Furthermore, it is assumed that no battery device 30 is present on induction charging device 10 or battery device 30 is fully charged. A third area 72 which surrounds first area 68 and second area 70 is formed from an error range. If actual quality Q.sub.i is in this area 72 in relation to resonance frequency f, it is assumed that any arbitrary type of error is present or battery device 30 is positioned so poorly with regard to induction charging device 10 that charging of battery device 30 is not possible or is only possible to a very limited extent. The error may be present in induction charging device 10, in battery device 30, as well as in the surroundings of charging system 32. Third subarea 72 has two subareas 72, 72. In this case, first subarea 72 of third subarea 72 is situated below first area 68 with regard to a quality. If actual quality Q.sub.i is in this first subarea 72 in relation to resonance frequency f, actual quality Q.sub.i in relation to resonance frequency f is below setpoint quality range q.sub.s in relation to resonance frequency f. Accordingly, it is assumed that a foreign body is present in an area between induction charging device 10 and battery device 30. In this case, second subarea 72 of third subarea 72 is situated below second area 70 with regard to a quality. If actual quality Q.sub.i is in this second subarea 72 in relation to resonance frequency f, actual quality Q.sub.i in relation to resonance frequency f is below setpoint quality range q.sub.s in relation to resonance frequency f. Accordingly, it is assumed that a foreign body is present on induction charging device 10.