METHOD FOR FOREIGN OBJECT DETECTION FOR AN INDUCTION CHARGING DEVICE AND INDUCTION CHARGING DEVICE

Abstract

A method for foreign object detection for an induction charging device is described, including an oscillator circuit, in particular, for a hand-held power tool, a resonance frequency and an associated actual quality of the oscillator circuit being detected and the actual quality is subsequently compared to a setpoint quality as a function of the resonance frequency and a decision is made about the presence of a foreign object based on a defined setpoint quality range. The method provides that an internal temperature of induction charging device is detected, in particular, during the wireless energy transmission, and the actual quality is multiplied by a correction factor based on the internal temperature. Also, an induction charging device is described that includes an oscillator circuit and a control and regulating unit, as well as at least one temperature sensor for carrying out the method.

Claims

1.-8. (canceled)

9. A method for foreign object detection for an induction charging device including an oscillator circuit, comprising: detecting a resonance frequency and an associated actual quality of the oscillator circuit; subsequently comparing the actual quality to a setpoint quality as a function of the resonance frequency; determining whether a foreign object is present based on a defined setpoint quality range; detecting an internal temperature of the induction charging device; and multiplying the actual quality by a correction factor based on the internal temperature.

10. The method for foreign object detection as recited in claim 9, wherein the induction charging device is for a hand-held power tool.

11. The method for foreign object detection as recited in claim 9, wherein the detecting of the internal temperature is performed during a wireless energy transmission.

12. The method for foreign object detection as recited in claim 9, further comprising multiplying at least one of an upper limit and a lower limit of the setpoint quality range by an inverse of the correction factor.

13. The method for foreign object detection as recited in claim 9, further comprising: measuring a resistance of at least one charge coil; and deriving the correction factor from the measured resistance of the at least one charge coil.

14. The method for foreign object detection as recited in claim 9, further comprising calculating the correction factor based on the detected internal temperature.

15. The method for foreign object detection as recited in claim 9, wherein the correction factor for an average room temperature is standardized to a value of 1.0.

16. The method for foreign object detection as recited in claim 15, wherein the average room temperature is 25° C.

17. The method for foreign object detection as recited in claim 9, wherein a profile of the correction factor at higher internal temperatures above room temperature is leveled off relative to the detected temperature.

18. An induction charging device, comprising: an oscillator circuit; a control and regulating unit, wherein the control and regulating unit: detects a resonance frequency and an associated actual quality of the oscillator circuit, subsequently compares the actual quality to a setpoint quality as a function of the resonance frequency, and determines whether a foreign object is present based on a defined setpoint quality range; and at least one temperature sensor for detecting an internal temperature of the induction charging device, wherein the control and regulating unit multiplies the actual quality by a correction factor based on the internal temperature.

19. The induction charging device as recited in claim 18, wherein the induction charging device is for a hand-held power tool.

20. The induction charging device as recited in claim 18, wherein the detecting of the internal temperature is performed during a wireless energy transmission.

21. The induction charging device as recited in claim 18, wherein the at least one temperature sensor is situated neither directly on a charge coil of the oscillator circuit nor directly in a vicinity of power switch elements and other self-heating components of the induction charging device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 shows an induction charging device for carrying out the method according to the present invention for foreign object detection and a rechargeable battery device to be charged in a schematic representation.

[0013] FIG. 2 shows a relation table of a control and regulating unit of the induction charging device according to the related art in the form of a schematic diagram.

[0014] FIG. 3 shows a diagram of a first exemplary embodiment of the profile of a correction factor as a function of a detected internal temperature T of the induction charging device.

[0015] FIG. 4 shows a diagram of a second exemplary embodiment of the profile of the correction factor as a function of the detected internal temperature T of the induction charging device.

DETAILED DESCRIPTION

[0016] FIG. 1 shows an induction charging device 10 for carrying out the method according to the present invention for detecting a foreign object 11. FIG. 1 also shows a rechargeable battery device 12 to be charged for a hand-held power tool not shown. Induction charging device 10 forms the primary side of a charging system 14 and is provided to charge rechargeable battery device 12, which is designed as a hand-held power tool rechargeable battery or a hand-held power tool with integrated rechargeable battery. In principle, however, it would also be conceivable to charge other rechargeable battery devices that would be meaningful to those skilled in the art with induction charging device 10.

[0017] FIG. 1 shows induction charging device 10 and rechargeable battery device 12 to be charged in a charging operation. Rechargeable battery device 12 in this operation is placed on top of a housing 16 of induction charging device 10 and is wirelessly charged via at least one charge coil 18 of induction charging device 10. Induction charging device 10 includes a charging electronics unit 20, which in turn includes a control and regulating unit 22, as well as an oscillator circuit 24 having the at least one charge coil 18 and at least one capacitor 19, which is electrically connected to the at least one charge coil 18.

[0018] Control and regulating unit 22 of induction charging device 10 is provided to determine a resonance frequency f.sub.R and an associated actual quality Q.sub.I(f.sub.R). In addition, control and regulating unit 22 is provided to compare the actual quality Q.sub.I(f.sub.R) to a setpoint quality Q.sub.s(f.sub.R) as a function of resonance frequency f.sub.R. For this purpose, control and regulating unit 22 includes a memory 26, in which a relation table is stored, which contains a setpoint quality range q.sub.s having multiple setpoint qualities Q.sub.s(f.sub.R) for the ascertained resonance frequency f.sub.R (cf. in this regard also the following explanations with respect to FIG. 2).

[0019] During a charging operation of induction charging device 10, a foreign object detection is carried out at regular intervals. During the foreign object detection, it is checked whether one or multiple foreign objects 11 which could impair a charging operation, are situated between induction charging device 10 and rechargeable battery device 12 or are only on top of induction charging device 10 and/or put an operator or induction charging device 10 at risk. The foreign object detection takes place in accordance with a method described in the unpublished German application DE 10 2013 212 588 in such a way that resonance frequency f.sub.R and associated actual quality Q.sub.I(f.sub.R) are initially determined. Actual quality Q.sub.I(f.sub.R) is then compared to setpoint quality Q.sub.s(f.sub.R) as a function of resonance frequency f.sub.R in order to ultimately make a decision based on the defined setpoint quality range q.sub.s whether at least one foreign object 11 is present or not.

[0020] FIG. 2 shows the relation table of control and regulating unit 22 stored in memory 26 in the form of a schematic diagram, in which resonance frequency f.sub.R is plotted on the x-axis and quality Q is plotted on the y-axis. The diagram is divided into three ranges 30, 32, 34. A first range 30 is formed by a setpoint quality range q.sub.s for an operation with rechargeable battery device 12. If actual quality Q.sub.I(f.sub.R) is within an upper limit q.sub.so and a lower limit q.sub.su of range 30, it is assumed that no foreign object 11 is located in an area between induction charging device 10 and rechargeable battery device 12. It is further assumed that rechargeable battery device 12 rests on induction charging device 10 and is to be charged. A second range 32 is formed by a setpoint quality range q.sub.s for an operation without rechargeable battery device 12. If actual quality Q.sub.I(f.sub.R) lies within upper limit q.sub.so and lower limit q.sub.su of range 32, it is assumed that no foreign object 11 is situated on induction charging device 10. It is further assumed that no rechargeable battery device 12 is situated on top of induction charging device 10.

[0021] A third range 34, which encloses first range 30 and second range 32, is formed by an error range. If actual quality Q.sub.I(f.sub.R) is in this range 34, it is assumed that an arbitrary error is present or rechargeable battery device 12 is so poorly positioned relative to induction charging device 10 that a charging of rechargeable battery device 12 is not possible or possible only to a very limited extent. The error in this case may lie in induction charging device 10, in rechargeable battery device 12 as well as in the surroundings of charging system 14. Third range 34 includes two sub-ranges 34′, 34″. First sub-range 34′ of third range 34 is situated below lower limit q.sub.su of first range 30 in relation to quality Q. If actual quality Q.sub.I(f.sub.R) is within this first sub-range 34′, it is assumed that at least one foreign object 11 is located in an area between induction charging device 10 and rechargeable battery device 12. Second sub-range 34″ of third range 34 is situated below lower limit q.sub.su of second range 32 as related to quality Q. If actual quality Q.sub.I(f.sub.R) is within this second sub-range 34″, it is assumed that at least one foreign object 11 is situated on top of induction charging device 10.

[0022] However, the profile of actual quality Q.sub.I(f.sub.R) is also a function, of, among other things, temperature influences. Thus, actual quality Q.sub.I(f.sub.R) drops if internal temperature T of induction charging device 10 rises. Conversely, actual quality Q.sub.I(f.sub.R) increases as temperature values fall. This may be attributed mainly to the fact that the internal resistance of charge coil 18 increases as temperature T increases and decreases as temperature T decreases. However, other components of oscillator circuit 24 such as, for example, capacitors, may also have a corresponding temperature influence on actual quality Q.sub.I(f.sub.R). The temperature influences have an adverse impact on the accuracy of the foreign object detection. Thus, it is the object of the present invention to maintain actual quality Q.sub.I(f.sub.R) largely independent of such temperature influences.

[0023] According to the present invention, induction charging device 10 includes a temperature sensor 36 (see FIG. 1), which is connected to control and regulating unit 22, and which detects internal temperature T of induction charging device 10 in the vicinity of the at least one charge coil 18. In order to obtain a preferably accurate estimation of average internal temperature T of induction charging device 10 and oscillator circuit 24, temperature sensor 36 is situated preferably neither directly on charge coil 18 nor in the direct vicinity of power switch elements, or other self-heating components of induction charging device 10. In this way, it is possible to largely minimize or avoid distorting temperature influences of these components on the temperature detection, so that primarily the influence of internal temperature T of induction charging device 10 produced by the at least one charge coil 18, which in addition is stabilized by the mass of charge coil 18, may be taken into consideration.

[0024] The method according to the present invention for foreign object detection provides that internal temperature T of induction charging device 10 is detected, in particular, during the wireless energy transmission, and measured actual quality Q.sub.I(f.sub.R) is multiplied by a correction factor K based on internal temperature T. It is also provided to multiply upper limit q.sub.so and/or lower limit q.sub.su of setpoint quality range q.sub.s by the inverse 1/K of correction factor K. Correction factor K may be derived from the measured resistance of the at least one charge coil 18, since this correction factor—as previously mentioned—changes as a function of internal temperature T. Alternatively or in addition, it is possible to calculate correction factor K based on internal temperature T detected with temperature sensor 36.

[0025] In FIG. 3, the profile of correction factor K is depicted as a function of internal temperature T. Correction factor K increases nonlinearly within the operating range defined by temperature limits T.sub.min and T.sub.max as internal temperature T increases. T.sub.R refers to an average room temperature of, for example, 25° C., in which correction factor K is standardized to value K=1.0. However, other values such as, for example, 23° C. or 24.5° C. may also be stored as room temperature T.sub.R within memory 26 of control and regulating unit 22.

[0026] The sensitivity of the foreign object detection may be improved still further at higher values of internal temperature T via an adaptation of correction factor K according to FIG. 4. In this case, the profile of correction factor K corresponds to the profile from FIG. 3 up to somewhat above room temperature T.sub.R. At higher temperature values, however, the profile of correction factor K up to maximum temperature value T.sub.max levels off relative to the original profile depicted with dashed lines, which effectuates a compensation to a somewhat lesser extent of the temperature influences actually detected on the one hand, but which results in increased accuracy of the foreign object detection on the other hand.

[0027] Lastly, it should be noted that the exemplary embodiments of the present invention shown are limited neither to the curve profiles shown in the figures nor to the design of the inductive charging system according to FIG. 1.