Operating a steering device

Abstract

The invention relates to a method for operating a steering device (1), wherein at least one heating element (3) of a steering handle (2) of the steering device (1) is subjected to an electric heating current on the basis of a heating operation, and during a sensor operation, an electrical capacitance (4) is detected between at least two sensor electrodes (5, 6) of a sensor element (7) of the steering handle (2) of the steering device (1) in order to determine a manual actuation of the steering handle (2). According to the invention, during an impedance detection operation, the electrical impedance (8) between the at least two sensor electrodes (5, 6) of the sensor element (7) is detected at least outside the sensor operation, a moisture on the steering handle (2) being determined on the basis of the detected impedance (8).

Description

[0001] 2023PF03008

[0002] 1

[0003] Operating a steering device

[0004] The invention relates to a method for operating a steering device, wherein, in sensor mode, an electrical capacitance between at least two sensor electrodes of a sensor element of the steering handle of the steering device is detected in order to determine manual operation of the steering handle. Furthermore, the invention relates to a steering device for a motor vehicle comprising a steering handle, at least one sensor element arranged on the steering handle having at least two sensor electrodes, and an operating unit electrically coupled to at least one sensor element, configured to detect an electrical capacitance between the at least two sensor electrodes in sensor mode in order to determine manual operation of the steering handle. Finally, the invention also relates to an operating unit of the steering device and a motor vehicle with at least one steering device.

[0005] Generic methods, steering devices and operating equipment therefor, as well as motor vehicles of this type, are extensively known from the prior art, for example from US11,613,293 B2. This patent discloses a capacitive detection device for a motor vehicle for detecting the presence of a person near or in contact with a vehicle component. This device can be used, in particular, to detect the presence of a driver's hands on a steering wheel. For this purpose, the steering wheel has a capacitive sensor element connected to a capacitive detection device.

[0006] Steering wheels are often also equipped with a heating device, which has one or more heating elements integrated into the steering wheel handle. These heating elements can be supplied with an electric current as needed, so that a surface of the steering wheel handle reaches a predetermined desired temperature. This predetermined temperature is usually set slightly lower than the surface temperature of the user's hand. 2023PF03008

[0007] 2

[0008] Capacitive touch sensors, also known as capacitive sensor elements, are devices that allow manual activation to be detected based on capacitive properties. This is achieved, among other things, by exploiting the fact that a capacitive sensor element changes its electrical capacitance depending on its proximity to a human body part, particularly a hand or finger. To detect this manual activation, the sensor element is at least temporarily, or at least partially, electrically coupled to an evaluation unit, allowing for appropriate evaluation to determine whether manual activation of the sensor element has occurred.

[0009] Within the context of this disclosure, the term "manual actuation" is understood to encompass not only actual contact between the body part and the capacitive sensor element or sensor device, but also the approach of the body part to it. Direct contact is therefore not strictly necessary. However, due to the proximity between the body part and the sensor element, the evaluation unit can determine or detect such actuation. According to a specification or configuration of the sensor device, sensor element, or evaluation unit, such an approach of a person's body part can be defined as manual actuation.For example, an actuation can be detected at a distance of one or more millimeters from the capacitive sensor element, for example less than 5 mm, preferably less than 1 mm. However, it is also possible that only direct contact of the steering handle in the area of ​​the capacitive sensor element is considered a manual actuation.

[0010] In this context, WO 2009 / 151 904 A2, for example, discloses a touch sensor based on a capacitive voltage divider. However, this teaching has proven inaccurate and prone to interference in practical applications, particularly in motor vehicles, especially in the area of ​​hands-on device (HoD) functionality, such as in the area of ​​a vehicle's steering wheel. Effects due to long-term influences, atmospheric influences such as temperature and especially humidity, and / or similar factors that can affect the function of the capacitive sensor element have proven particularly problematic. 2023PF03008

[0011] 3

[0012] The invention is therefore based on the objective of improving the functionality of a capacitive sensor element, particularly in heated steering handles.

[0013] The invention proposes a method, a steering device, an operating unit and a motor vehicle according to the independent claims as a solution.

[0014] Advantageous further training opportunities arise from the characteristics of the dependent requirements.

[0015] With regard to a generic method, the invention particularly proposes that, in an impedance detection mode, at least outside of sensor operation, an electrical impedance between the at least two sensor electrodes of the sensor element is detected, whereby a moisture content of the steering handle is determined depending on the detected impedance.

[0016] With regard to a steering device of the generic type, the invention particularly proposes that the operating unit is configured to detect an electrical impedance between the two sensor electrodes of the at least one sensor element in an impedance detection mode, at least outside of sensor operation, and to determine a moisture level of the steering handle depending on the detected impedance.

[0017] With regard to a generic operating unit, the invention particularly proposes that the operating unit is configured to detect an electrical impedance between the two sensor electrodes of the at least one sensor element in an impedance detection mode, at least outside of sensor operation, and to determine a moisture level of the steering handle depending on the detected impedance.

[0018] With regard to a motor vehicle of the generic type, the invention specifically proposes that the steering device be designed according to the invention.

[0019] The invention is based, among other things, on the idea that the function of a generic capacitive sensor element can be significantly improved if moisture is present in the area of ​​the sensor element. It has been found with the invention that moisture can have a considerable influence on the reliability and accuracy of the sensor element's function. This influence can be...2023PF03008

[0020] 4

[0021] The invention takes into account the known humidity level, thus significantly improving the evaluation functionality with regard to detecting the electrical capacitance between the at least two sensor electrodes and, consequently, determining the manual actuation. Here, the invention utilizes, among other things, the effect that the electrical conductivity between the at least two sensor electrodes can change due to humidity. This change can be determined by detecting the impedance between the at least two sensor electrodes. Since, in particular, the electrical conductivity between the sensor electrodes depends on the degree of humidity of the electrical material between the sensor electrodes, the degree of humidity can be determined based on this.The level of humidity can then be taken into account during the evaluation, as humidity can naturally also influence the dielectric constant of the material between the sensor electrodes. Overall, this results in improved functionality with regard to determining manual actuation. This functionality can, for example, be controlled by an operating unit of the steering device. The operating unit can be configured, for instance, to control the sensor operation, and in particular to evaluate a sensor signal from the sensor element in order to determine manual actuation.

[0022] Preferably, a heating element of the steering handle of the steering device is supplied with an electric heating current depending on a heating operation.

[0023] Preferably, the steering handle has at least one heating element by means of which the steering handle can be heated. Preferably, the at least one heating element is arranged on the steering handle. In heating mode, the at least one heating element can heat the steering handle by supplying it with an electric heating current. The at least one heating element can, for example, be electrically coupled to the operating unit of the steering device. The operating unit can, for example, be configured to supply the at least one heating element with the heating current during heating mode. The operating unit can, for example, be configured to control both the heating mode and the sensor mode.

[0024] Furthermore, additional effects can be achieved in combination with heating operation, because heating operation makes it possible to keep the sensor element at a predefined temperature level. This allows for additional influences beyond just 2023PF03008

[0025] 5

[0026] The effects are reduced not only due to humidity, but also due to temperature.

[0027] According to an advantageous embodiment, it is proposed that the impedance be measured within a predetermined measurement period. This measurement period is preferably selected such that short-term changes, for example, due to variations in manual operation or the like, have as little impact as possible. The measurement period can, for example, consist of several sub-periods spaced apart in time. This is particularly advantageous when the invention is used in the intended operation of the vehicle, where manual steering operation is also to be measured. The measurement of steering hand movements is preferably performed in short time intervals, which follow each other at relatively short intervals. The sub-periods can be arranged between the periods used to measure manual operation.A predetermined number of partial periods can be evaluated together to determine the humidity. Therefore, the invention need not only be used outside of normal ferry operations, but can also be used during them.

[0028] Furthermore, it is proposed that a first of at least two sensor electrodes be arranged between an actuating surface of the steering handle and a second of at least two sensor electrodes, wherein the first sensor electrode is supplied with a predetermined reference potential to detect the impedance. Preferably, the predetermined reference potential can be the vehicle mass of the motor vehicle or the like. This allows the first sensor electrode to act like a shield, so that the effects of any manual actuation of the steering handle on the humidity measurement can be reduced, if not completely avoided. The actuating surface of the steering handle can, for example, be wheel-shaped like a steering wheel, in particular having a torus or tire shape, which is mechanically coupled to a rotational axis of the steering device by means of one or more spokes.

[0029] Preferably, the second sensor electrode also serves as a heating element, and a shielding electrode is arranged between the first and second sensor electrodes, wherein the first and second sensor electrodes are connected in parallel to detect the impedance, and the impedance between the parallel-connected sensor electrodes and the 2023PF03008

[0030] 6

[0031] The sensor electrode is detected. Preferably, the two sensor electrodes are electrically connected to an electrical reference potential such as the vehicle ground or the like.

[0032] It is further proposed that the steering handle have an electrically conductive support frame that serves as one of at least two sensor electrodes, with the impedance between the support frame and the other sensor electrode being measured. In the simplest case, only one separate sensor electrode is required, because the steering handle's support frame can form the at least one second sensor electrode. This allows for a particularly simple implementation of sensor functionality.

[0033] Preferably, to measure the impedance, the support frame is disconnected from an electrical reference potential, and the other sensor electrode is coupled to this electrical reference potential. This has the advantage that the effects of manual steering operation can be reduced or even avoided. The support frame is typically made of an electrically conductive material such as metal, particularly steel, and is electrically connected to the vehicle's chassis due to its design. To perform the sensing function, the support frame is electrically disconnected from the reference potential, and at least one other sensor electrode is coupled to it. This ensures reliable impedance measurement.

[0034] Furthermore, it is proposed that at least the sensor operation and the impedance measurement operation switch in a time-division multiplex. This ensures that the associated evaluation functionalities do not significantly influence or interfere with each other. At the same time, it creates the possibility not only to reliably determine manual actuation but also to simultaneously determine humidity. The functionality of the invention can thus be further improved.

[0035] Furthermore, it is proposed that the electrical capacitance measurement in sensor mode be dependent on the humidity determined in impedance measurement mode. In particular, it can be provided that the operating unit takes into account a humidity value measured in impedance measurement mode for the evaluation when measuring electrical capacitance. This allows for the simple determination of the 2023PF03008

[0036] 7

[0037] The reliability of the sensor element's functionality is improved. In particular, the invention requires no additional hardware.

[0038] According to a further provision, it is proposed that the operating unit has at least one reference impedance for measuring the electrical capacitance, wherein the at least one reference impedance is adjusted depending on the humidity determined during impedance measurement. This takes into account that the operating unit uses a reference impedance to measure the electrical capacitance of the sensor element. For example, the reference impedance can be part of a bridge circuit used to measure the electrical capacitance of the sensor element. Depending on the determined humidity value, the operating unit can adjust or set the value of the reference impedance. This allows changes in humidity during normal operation to be taken into account, thus improving the overall long-term operation of the steering system.

[0039] In particular, the at least two sensor electrodes are coupled to a common reference potential for parallel connection. In this way, a simple parallel connection can be achieved while simultaneously ensuring reliable potential application.

[0040] It is further proposed that the operating unit include a switching unit to which the at least one sensor element and at least one heating element of the steering handle are connected. This allows for combined operation of the sensor element and the heating element using the operating unit. Depending on the switching state of the unit, the operating unit can connect the heating element to the heating current and / or the sensor element to an evaluation unit. A switching state can also be provided in which the sensor element can be connected to an impedance detection unit. This proves particularly advantageous if the at least one heating element is implemented at least partially by means of the at least one sensor element, especially if the at least one heating element is provided at least partially by a sensor electrode of the at least one sensor element.The operating unit can be used to implement and / or control heating, sensor, and / or impedance sensing operations. The switching elements can be electronic components, such as transistors in switching mode, programmable terminals of a computer unit, and / or the like. 2023PF03008.

[0041] 8

[0042] The switching unit can have one or more switching elements by means of which respective switching states can be realized in order to assume corresponding switching states.

[0043] The advantages and effects described for the method according to the invention also apply to the steering device, the operating unit, and the motor vehicle according to the invention, and vice versa. In particular, method features can therefore also be formulated as device features, or vice versa.

[0044] Further features of the invention are evident from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations without departing from the scope of the invention. Thus, embodiments that are not explicitly shown and explained in the figures, but which can be derived and generated from the explained embodiments by separate combinations of features, are also to be considered as encompassed and disclosed by the invention. Embodiments and combinations of features that do not exhibit all the features of an originally formulated independent claim are also to be considered disclosed.Furthermore, embodiments and combinations of features, in particular those set out above, are to be considered disclosed which go beyond or deviate from the combinations of features set out in the cross-references of the claims.

[0045] For use cases or application situations that may arise during the procedure and are not explicitly described here, it may be provided that, according to the procedure, an error message and / or a request for user feedback is issued and / or a default setting and / or a predetermined initial state is set.

[0046] This shows:

[0047] Fig. 1 shows a schematic block representation of a steering device of a motor vehicle with a steering wheel, a heating element arranged on the steering wheel and a 2023PF03008 connected to the heating element.

[0048] 9

[0049] Operating unit, wherein the heating element serves as a sensor electrode of a sensor element,

[0050] Fig. 2 shows a schematic representation of a section of another steering wheel with a sensor element having two sensor electrodes according to a first embodiment,

[0051] Fig. 3 shows a schematic circuit diagram of the impedance of the sensor element according to Fig. 2.

[0052] Fig. 4 shows a schematic representation as in Fig. 2, in which, according to a second embodiment, a shielding electrode is provided in addition to two sensor electrodes.

[0053] Fig. 5 shows a schematic representation like Fig. 2, in which an operating unit is connected to the steering wheel.

[0054] Fig. 6 shows a schematic representation like Fig. 4, in which, according to a third embodiment, an electronic component is provided.

[0055] Fig. 7 shows a schematic representation like Fig. 6, in which an electrical NTC resistor is provided as the electronic component.

[0056] Fig. 8 shows a schematic circuit diagram for the third embodiment according to Fig. 7.

[0057] Fig. 9 shows a schematic representation like Fig. 4, in which, according to a fourth embodiment, a support frame of the steering wheel is taken into account for impedance measurement, and

[0058] Fig. 10 is a schematic representation like Fig. 4, in which, according to the second embodiment, the operating unit with connection impedances is shown.

[0059] Fig. 1 shows a schematic block diagram of a steering device 1 of a motor vehicle (not shown) with a steering wheel 2 as the steering handle. A heating element 3 is arranged on the steering wheel 2, which in turn is connected to an operating unit 16. The operating unit 16 has a switching unit 17, to which the 2023PF03008

[0060] 10

[0061] Heating element 3 is connected. A heating energy source 18 and a sensor unit 19 are also connected to the switching unit 17. Both the sensor unit 19 and the heating energy source 18, as well as the switching unit 17, are in communication connection with a control unit 20 of the operating unit 16, which controls the functionality of the units connected to the operating unit 16.

[0062] The control unit 20 can, among other things, control the switching state of the switching unit 17, so that the heating element 3 can be coupled to the heating energy source 18 in heating mode. The heating energy source 18 provides an electric heating current that supplies the heating element 3, so that heat can be generated in the steering wheel 2 by means of the heating element 3. This determines the heating mode.

[0063] Furthermore, the switching unit 17 can couple the heating element 3 with the sensor unit 19, the sensor unit 19 being configured to detect an electrical capacitance between the heating element 3 and a support frame 13 of the steering wheel 3. By detecting the electrical capacitance 4 (Fig. 2), manual operation of the steering wheel 2 by a user can be determined in the sensor mode thus established. In this operating state, the heating element 3 therefore serves as a sensor electrode.

[0064] The design according to Fig. 1 proves problematic insofar as moisture can penetrate the steering wheel 2, for example, into a layered structure of the steering wheel 2. This is generally relatively unproblematic for heating operation. However, the moisture proves problematic with regard to sensor operation, particularly when the electrical capacitance 4 is to be measured. Due to the comparatively high relative dielectric constant, the penetrating moisture is disruptive because it can significantly alter the measured value of the electrical capacitance. This affects the evaluation by the sensor unit 19 and can, for example, lead to the sensor unit 19 determining from the measured values ​​of the electrical capacitance 4 that the steering wheel 2 is being manually operated by the user continuously, even though no operation is actually taking place.

[0065] Fig. 2 shows a schematic representation of a section of the steering wheel 2 according to Fig.

[0066] 1, where the sensor element 7 is shown with two sensor electrodes 5, 6. The sensor electrodes 5, 6 are each electrically conductive plates arranged within an insulating material 21 of the steering wheel 2. The sensor electrodes 5, 6 are spaced apart from each other by a distance d. Between the 2023PF03008

[0067] 11

[0068] An electric field forms at sensor electrodes 5, 6, at least during sensor operation, thereby creating the electrical capacitance 4. Fig. 3 shows a schematic circuit diagram of an impedance 8 of the sensor element 7 according to Fig.

[0069] 2 according to the type of an equivalent circuit diagram. It can be seen that the impedance 8 is formed by a parallel connection of an electrical resistance 9 and the electrical capacitance 4. The electrical resistance 9 represents an insulation resistance between the sensor electrodes 5, 6 of the insulating material 21. In the case of a substantially plate-shaped arrangement according to Fig. 2, the following relationship results approximately:

[0070] C = (e * A / d

[0071] where C represents a value of the electrical capacitance, £ a dielectric constant of the insulating material 21 , A a plate area and d a distance between the plates.

[0072] If the insulating material 21 is essentially moisture-free, the electrical resistance will be very high, for example, one or more GQ units. However, if moisture has penetrated the steering wheel 2, particularly the insulating material 21, the moisture reduces the properties of the insulating material, and the electrical resistance 9 will decrease depending on the moisture content. With respect to the arrangement shown in Fig. 2, the electrical resistance can be as follows:

[0073] R = p * b / A

[0074] where R is a value of the electrical resistance 9, p is a specific electrical resistance of the insulating material 21, b is a length, which in this case is formed by the distance d between the sensor electrodes 5, 6, and A is an area of ​​the sensor electrodes 5, 6. If the specific electrical resistance of the insulating material 21 changes due to the ingress of moisture, the value of the electrical resistance 9 changes accordingly. The moisture can thus lead to an undesired leakage current between the two sensor electrodes 5, 6. It may be advantageous to take the leakage current into account when evaluating the sensor during operation.

[0075] Fig. 4 shows a schematic representation, as in Fig. 2, of a first embodiment of a steering device 1, which is designed to determine the moisture content of the steering wheel 2 and, in particular, to take this into account in sensor operation. For this purpose, 2023PF03008

[0076] 12

[0077] The operating unit 16 is extended by an impedance determination unit 22, which is also connected to the switching unit 17. Furthermore, a vehicle ground 11 is connected to the switching unit 17 as a reference potential. The steering wheel 12 has a layered structure as shown in Figure 23. The innermost layer of the steering wheel 2 is the support frame 13, which is surrounded by a foam layer 24. One of the sensor electrodes, namely sensor electrode 6, is arranged on the foam layer 24. This is indicated by reference numeral 25 in the layered structure 23. This is followed by a layer 26 of insulating material 21, on which a shielding electrode 12 is arranged as layer 27. Layer 27 is followed by another layer 28 of insulating material 21, to which a layer 29 is attached, forming the sensor electrode 5.Layer 29 is followed by an elastic foam layer 30, which is formed by a surface material, such as leather, as layer 31. Layer 31 also provides an actuation surface 10 of the steering wheel 2, which the user can grasp and operate.

[0078] Figure 4 shows that, among other things, electrical capacitances 4 form between the shielding electrode 12 and the sensor electrodes 5, 6. In sensor mode, the sensor unit 19 is electrically connected to the shielding electrode 12 and the sensor electrode 5 via switching elements 32, 33 of the switching unit 17, so that manual operation of the steering wheel 2 can be determined based on the measurement of the electrical capacitance 4. Switching elements 34, 35, 36 of the switching unit 17 are in the open state during sensor mode, thus ensuring reliable sensor functionality. A switching element 37 of the switching unit 17 can be in the switched-on state as needed, so that the sensor electrode 6, which can also serve as a heating element 3, can be supplied with a heating current from the heating current source 18. The switching states of the switching elements 32 to 37 are controlled accordingly by the control unit 20.

[0079] To measure the impedance, switching elements 32, 33, and 37 of switching unit 17 are switched to the open or off state, respectively. Simultaneously, switching elements 34, 35, and 36 of switching unit 17 are switched on. Using the impedance measuring unit 22, the value of the electrical capacitance 4 between the shield electrode 12 and the sensor electrodes 5 and 6 can now be determined. As previously explained, a humidity value can be determined from the measured impedance. This humidity value can be further evaluated and transmitted to the sensor unit 19, which adjusts its functionality depending on the value of the 2023PF03008.

[0080] 13

[0081] It adjusts the humidity. This makes it possible to achieve reliable function even with varying humidity.

[0082] Fig. 5 shows, in a schematic representation similar to Fig. 4, a second embodiment of a steering wheel 2, which is connected to an operating unit 16. The embodiment according to Fig. 5 is based on the embodiment according to Fig. 4, therefore only the differences will be explained below. In contrast to the embodiment according to Fig. 4, the embodiment according to Fig. 5 features a simplified layer structure 23 of the steering wheel 2. Instead of layers 25 to 29, a layer 38 is now provided, which simultaneously forms the heating element 3 and a sensor electrode 5 as an integral component. A further sensor electrode 6 is formed by the support frame 13.

[0083] This significantly simplifies the construction process.

[0084] At the same time, the operating unit 16 is adapted accordingly and includes a control unit 33 in which the desired functions are implemented. In sensor mode, switching elements 40 and 41 are in the on state (closed), and switching elements 39 and 42 are in the off state (open), so that the electrical capacitance 4 can be detected by the control unit 33. In heating mode, on the other hand, switching elements 39 and 42 are in the on state (closed), whereas switching elements 40 and 41 are in the off state (open), so that the heating current can flow and heat the steering wheel 12. The further evaluation functionality corresponds to that explained previously, and therefore reference is made to the corresponding descriptions.

[0085] Fig. 6 shows a further schematic representation as in Fig. 5 according to a third embodiment, in which an additional electronic component 14 is provided. The electronic component can be a sensor element such as a temperature sensor, an integrated circuit, or the like. The layer structure 23 of the steering wheel 2 corresponds to the layer structure 23 of the steering wheel 2 according to the second embodiment as shown in Fig. 5. In contrast to the second embodiment according to Fig. 5, this third embodiment includes the electronic component 14, which is connected via a connecting line 15 to an impedance detection unit 22, as already explained with reference to Fig. 4, for which reason reference is made to the corresponding descriptions. The function of the control unit 33 essentially corresponds to that already explained for the second embodiment according to Fig. 5, for which reason reference is made to the corresponding descriptions. 2023PF03008

[0086] 14

[0087] Reference is made to the following. To detect the impedance 8 between the connecting line 15 and the sensor electrodes 5, 6 or the heating element 3, the switching elements 44, 45 of the switching unit 17 are closed, while the switching element 43 of the switching unit 17 is switched to the open switching state. This results in the conditions shown in Fig.

[0088] The electrical capacitances 4 shown in the diagram are effective. In this way, the impedance of the arrangement can be determined using the impedance detection unit 22. The detected impedance can then be evaluated by the control unit 33 to determine the humidity. The humidity determined in this way can be taken into account for the further functionality of the control unit 33, in particular within the context of sensing operation.

[0089] Fig. 7 shows, in a further schematic representation as in Fig. 6, a modification of the third embodiment according to Fig. 6, in which an NTC resistor 46 is now provided instead of the electronic component 14. In particular, the connecting leads 15 of the NTC resistor 46 cause an electrical capacitance, thus creating a possibility to detect moisture. The impedance formed thereby can be determined as follows:

[0090] NTC = RNTC ~ j / ü) ^NTC

[0091] CNTC can be determined from the aforementioned equation because RNTC can be measured. The connecting leads 15 are connected to a capacitance measuring unit 47, which is in communication with the control unit 33. By suitable evaluation, the humidity can also be determined here, and the function of the sensor operation can be adjusted depending on the humidity determined in this way.

[0092] Fig. 8 shows a schematic circuit diagram of the third embodiment based on Fig. 7. It can be seen that the sensor electrodes 5, 6 and the heating element 3 are visible, and that the NTC resistor 46 is connected to a microcontroller 49 so that, with the aid of a reference capacitor CREF and a reference resistor RREF, the impedance can be determined. Reference numeral 48 denotes an impedance sensing unit, which is also connected to the NTC resistor 46. The impedance sensing unit 48 communicates with the microprocessor 49. The microcontroller 49 can be part of the control unit 33. 2023PF03008

[0093] 15

[0094] Fig. 9 shows a further schematic representation similar to Fig. 4 according to a fourth embodiment, which is based on the embodiment shown in Fig. 4, and for which further reference is made to the corresponding explanations. The embodiment shown in Fig. 9 differs from the embodiment shown in Fig. 4 in that no shielding electrode 12 is provided. Instead, two sensor electrodes 5, 6 are provided, which serve both as sensor electrodes and as heating elements. The function of the switching unit 17 essentially corresponds to that already explained with regard to Fig. 4. Only the switching element 37 is omitted compared to the embodiment shown in Fig. 4, because the control unit 33 is provided instead of the heating current source 18 and the sensor unit 19. Otherwise, the functionality essentially corresponds to that already explained with regard to the previous embodiments.Basically, the switching element 36 can also be omitted if the function of the support frame 13 is not required for evaluation.

[0095] Fig. 10 shows a schematic circuit diagram of the first embodiment according to Fig. 4, in which the operating unit 16 is shown with the respective connection impedances for the sensor electrodes 5, 6 and the shielding electrode 12. The function has already been explained with reference to Fig. 4, so reference is made to the corresponding explanations.

[0096] The exemplary embodiments serve solely to illustrate the invention and are not intended to limit it.

Claims

2023PF03008 16 Patent claims 1. Method for operating a steering device (1), wherein in sensor operation an electrical capacitance (4) between at least two sensor electrodes (5, 6) of a sensor element (7) of a steering handle (2) of the steering device (1) is detected in order to determine manual operation of the steering handle (2), characterized in that in impedance detection operation at least outside of sensor operation an electrical impedance (8) between the at least two sensor electrodes (5, 6) of the sensor element (7) is detected, wherein depending on the detected impedance (8) a moisture content of the steering handle (2) is determined.

2. Method according to claim 1 , characterized in that the impedance (8) is measured within a specified impedance measurement period.

3. Method according to any one of the preceding claims, characterized in that a first of the at least two sensor electrodes (5) is arranged between an actuating surface (10) of the steering handle (2) and a second of the at least two sensor electrodes (6), wherein the first sensor electrode (5) is supplied with a predetermined reference potential (11) to detect the impedance (8).

4. Method according to claim 3, characterized in that the second sensor electrode (6) additionally serves as a heating element and a shielding electrode (12) is arranged between the first and the second sensor electrodes (5, 6), wherein the first and the second sensor electrodes (5, 6) are connected in parallel to detect the impedance (8) and the impedance (8) between the parallel-connected sensor electrodes (5, 6) and the shielding electrode (12) is detected. 2023PF03008 17 5. Method according to any one of the preceding claims, characterized in that the steering handle (2) has an electrically conductive support frame (13) which serves as one of the at least two sensor electrodes, wherein the impedance (8) between the support frame (13) and the other of the sensor electrodes (5, 6) is detected.

6. Method according to claim 5, characterized in that, in order to detect the impedance (8), the support frame (13) is separated from an electrical reference potential (11) and the other of the sensor electrodes (5, 6) is coupled to the electrical reference potential (11).

7. Method according to any of the preceding claims, characterized in that at least the sensor operation and the impedance detection operation switch in a time multiplex.

8. Method according to any one of the preceding claims, characterized in that the steering handle (2) has an electronic component (14) which is arranged between the at least two sensor electrodes (5, 6), wherein the at least two sensor electrodes (5, 6) are connected in parallel to detect the impedance (8) and the impedance (8) is detected between at least one electrical connection (15) of the electronic component (14) and the parallel-connected sensor electrodes (5, 6), wherein in particular the at least two sensor electrodes (5, 6) are coupled to a common reference potential (11) for parallel connection.

9. Method according to any one of the preceding claims, characterized in that the detection of the electrical capacitance (4) in sensor operation is dependent on the humidity determined in impedance detection operation.

10. Method according to any one of the preceding claims, characterized in that an operating unit (16) has at least one reference impedance for measuring the electrical capacitance (4), wherein the at least one reference impedance is set depending on the humidity determined in impedance measurement mode. 2023PF03008 18 11. Steering device (1) for a motor vehicle, comprising a steering handle (2), at least one sensor element (7) arranged on the steering handle (2) which has at least two sensor electrodes (5, 6), and an operating unit (10) electrically coupled to the at least one sensor element (7), which is configured to detect an electrical capacitance (4) between the at least two sensor electrodes (5, 6) in sensor mode in order to determine manual operation of the steering handle (2), characterized in that the operating unit (16) is configured to detect an electrical impedance (8) between the two sensor electrodes (5, 6) of the at least one sensor element (7) in an impedance detection mode, at least outside of sensor operation, and to determine a moisture content of the steering handle (2) depending on the detected impedance (8).

12. Steering device according to claim 12, characterized in that the operating unit (16) is further configured to control at least the sensor operation depending on the determined humidity.

13. Steering device according to claim 13, characterized in that the operating unit (16) has a switching unit (17) to which the at least one sensor element (7) and at least one heating element (3) of the steering handle (2) are connected.

14. Operating unit (16) of the steering device (1) according to one of claims 11 to 13.

15. Motor vehicle with at least one steering device (1), characterized in that the steering device (1) is designed according to one of claims 11 to 13.

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