Circuit arrangement for a steering wheel of a vehicle, method for operating a circuit arrangement, and steering wheel having a circuit arrangement

Abstract

The invention relates to a circuit arrangement (10) for a steering wheel (12) of a vehicle, to a method (55) for operating a circuit arrangement for a steering wheel (12) of a vehicle, and to a steering wheel (12) for a vehicle having a circuit arrangement (10). The steering wheel (12) has at least a conductive layer (16) and a skeleton structure (20). An intermediate layer capacitance (30) is formed between the conductive layer (16) and the skeleton structure (20), and a surrounding capacitance (32) is formed between the skeleton structure (20) and a vehicle frame part (34). The intermediate layer capacitance (30) and the surrounding capacitance (32) form a capacitive voltage divider for the conductive layer (16). The circuit arrangement (10) also has a voltage source (24), which can be coupled selectively to the skeleton structure (20) via a skeleton feed line (26). The skeleton feed line (26) has a resistance (38). The circuit arrangement (10) is at least configured to detect a first voltage value (V1) on the voltage source side of the resistance (38) of the skeleton feed line (26) and a second voltage value (V2) on the skeleton side of the resistance (38) of the skeleton feed line (26). A control device (22) of the circuit arrangement (10) is configured to detect a faulty skeleton feed line (26) depending on the surrounding capacitance (32) at least on the basis of the first and the second voltage value (V1, V2).

Description

[0001] Circuit arrangement for a steering wheel of a vehicle, method for operating a circuit arrangement and steering wheel with a circuit arrangement

[0002] The invention relates to a circuit arrangement for a steering wheel of a vehicle, a method for operating a circuit arrangement for a steering wheel of a vehicle and a steering wheel for a vehicle with a circuit arrangement.

[0003] Modern vehicle control systems, which, for example, perform autonomous or semi-autonomous driving functions, monitor whether a vehicle user wishes to make manual control inputs, for example, by activating a hand detection function with regard to the steering wheel (so-called hands-on / off detection (HOD), also known as a hand occupancy system). To ensure the detection mechanism, the steering wheel typically has multiple guide positions, allowing hand detection to be realized via capacitance measurement, since placing a hand on the steering wheel leads to a change in the relative capacitance ratios.

[0004] Previous steering wheels with HOD functionality have featured multiple conductive layers (see, for example, WO 2023 / 169827 A1), arranged within the steering wheel body. However, this makes the steering wheel structure complex and associated with relatively high manufacturing costs. It should be noted that, to form the desired shape, the steering wheel also has a skeleton structure, which typically comprises metal and is therefore conductive and serves as a component in the execution of the HOD functionality. Furthermore, the detection mechanisms required to reliably detect changes in capacitance ratios are also complex.

[0005] In addition, the steering wheel is constantly exposed to vibrations and movements. Therefore, in addition to the HOD functionality, a reliable detection mechanism for any damage to the underlying electrical circuits must be considered. For example, it may be that leads to conductive layers or other conductive layers, such as the skeleton structure, installed within the steering wheel are faulty. Reliable detection mechanisms must be provided for these faulty conditions.

[0006] The detection of faulty supply lines is made more difficult by the fact that variabilities in the capacitance ratios are caused by vibrations, movements and additional component deviations.

[0007] The invention is based on the object of eliminating or at least mitigating the disadvantages of the prior art. In particular, it is intended to create a way to manufacture a steering wheel cost-effectively while simultaneously enabling both reliable HOD functionality and error detection.

[0008] The problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are specified in the dependent patent claims and the following description, each of which, individually or in (sub)combination, may represent aspects of the invention. Individual aspects are presented with reference to devices, others with reference to methods. However, the features and advantages are to be transferred in a corresponding manner.

[0009] According to one aspect, a circuit arrangement for a steering wheel of a vehicle is provided. The steering wheel has at least one guide layer and a skeleton structure. An interlayer capacitance is formed between the guide layer and the skeleton structure, and an ambient capacitance is formed between the skeleton structure and a vehicle frame part.

[0010] The interlayer capacitance and the ambient capacitance form a capacitive voltage divider for the conducting layer.

[0011] The circuit arrangement further comprises a voltage source which can be selectively coupled to the skeleton structure via a skeleton supply line.

[0012] The skeleton lead has a resistance.

[0013] The circuit arrangement is configured at least to detect a first voltage value on the voltage source side of the resistance of the skeleton supply line and a second voltage value on the skeleton side of the resistance of the skeleton supply line. A control device of the circuit arrangement is configured to detect a faulty skeleton supply line based on the first and second voltage values ​​as a function of the ambient capacitance.

[0014] The capacitive voltage divider, taking the resistance of the skeleton lead into account, can create an effective detection mechanism for detecting a faulty skeleton lead. It should be noted that the applied partial voltages change due to the capacitive voltage divider. In particular, the interlayer capacitance is different between a defective skeleton connection and a functioning skeleton connection, so that the skeleton connection can be assessed as good or faulty based on the measured partial voltages. To do this, advantageously, only the voltage values ​​on the input and output sides—that is, on the voltage source side of the resistor and on the skeleton side of the resistor—need to be recorded and compared with the corresponding expected values.As a result, a simple, compact, but highly efficient and reliable mechanism is provided to detect a faulty, for example broken, skeleton lead.

[0015] The skeleton structure preferably forms a steering wheel skeleton. The skeleton structure is preferably made of a metallic material. For example, the skeleton structure can be made of an aluminum alloy and / or a magnesium alloy.

[0016] In some embodiments, the skeleton structure includes, for example, the steering wheel rim, which is connected to a steering wheel hub via spokes. The steering wheel rim, spokes, and hub can together form the steering wheel skeleton.

[0017] Optionally, the conductive layer forms at least one conductive conductor section. The conductive conductor section can be designed as a single line, a conductive grid, or the like. Particularly preferably, the conductive conductor section is integrated into a grip area of ​​the steering wheel device. For example, the conductive conductor section comprises a metallic line. Preferably, the conductive layer and the skeleton layer are arranged concentrically and / or in layers relative to one another in a cross-section.

[0018] The interlayer capacitance is designed as an intermediate storage capacitor between the conductive layer and the skeleton structure. The interlayer capacitance is generally (approximately) constant. A variance between different steering wheels may exist, for example, due to component deviations, but this can generally be neglected. The interlayer capacitance may be due to the fact that an electrically non-conductive material, such as a foam used to form the shape of the steering wheel, is arranged between the conductive layer and the skeleton structure.

[0019] In contrast, the ambient capacitance is formed between the skeleton structure and a (ideally infinitely distant) vehicle frame part.

[0020] Due to this arrangement, the skeleton structure influences both the interlayer capacitance and the ambient capacitance. Therefore, the interlayer capacitance and the ambient capacitance form a capacitive voltage divider for the conductive layer. In this regard, the ambient capacitance can also be viewed, in an alternative perspective, as the capacitance formed between the conductive layer and a vehicle frame part. The underlying detection mechanism for a faulty skeleton supply line is not affected by this, since in the latter, alternative perspective, the conductive layer influences both capacitances, i.e., the interlayer capacitance and the ambient capacitance. Therefore, in the alternative perspective, a voltage divider is also formed with respect to the conductive layer.

[0021] The resistance of the skeleton lead is understood here as a dedicated, separate resistor arranged within the skeleton lead. The resistance of the skeleton lead does not refer to the intrinsic conduction resistance of the electrical line of the skeleton lead itself. Rather, the resistance of the skeleton lead is to be viewed as a separate, predetermined component arranged specifically to provide the explained fault detection mechanism within the skeleton lead. In some embodiments, the resistance of the skeleton lead can be between 100 ohms ± 10% and 1 MOhm ± 10%, preferably between

[0022] 200 Ohm ± 10% and 500 kOhm ± 10%, more preferably between

[0023] 300 Ohm ± 10% and 100 kOhm ± 10%, more preferably between

[0024] 500 Ohm ± 10% and 10 kOhm ± 10%, more preferably between

[0025] 700 Ohm ± 10% and 5 kOhm ± 10%, more preferably between 800 Ohm ± 10% and 2 kOhm ± 10%, more preferably in particular 1 kOhm ± 10%.

[0026] The control device can have corresponding components for detecting voltage values, for example, at least one data processing device. The components of the control device can be at least partially digital or analog. In addition, the control device is coupled at least indirectly to the resistance of the skeleton supply line, in particular both on the voltage source side and the skeleton side. This means that the control device can detect the voltage values ​​on the voltage source side and the skeleton side of the resistance of the skeleton supply line independently of one another.

[0027] According to a further aspect, a method for operating a circuit arrangement for a steering wheel of a vehicle is also provided. The steering wheel has at least one guide layer and a skeleton structure. An interlayer capacitance is formed between the guide layer and the skeleton structure, and an ambient capacitance is formed between the skeleton structure and a vehicle frame part.

[0028] The interlayer capacitance and the ambient capacitance form a capacitive voltage divider for the conducting layer.

[0029] The circuit arrangement further comprises a voltage source which can be selectively coupled to the skeleton structure via a skeleton supply line.

[0030] The skeleton lead has a resistance.

[0031] The procedure includes at least the following steps:

[0032] A first voltage value is recorded on the voltage source side of the resistance of the skeleton lead.

[0033] A second voltage value is measured on the skeleton side of the resistance of the skeleton supply line. A faulty skeleton supply line is detected by a control device depending on the ambient capacitance based on at least the first voltage value and the second voltage value.

[0034] The advantages achieved by the previously explained circuit arrangement are also made possible in a corresponding manner by the method presented here.

[0035] By selectively coupling the skeleton structure to the voltage source, different phases can be defined with respect to the voltage source supply. This opens up the possibility of detecting specific voltage values ​​depending on the coupling to the voltage source. This simplifies the detection of a faulty skeleton supply line.

[0036] Optionally, the ambient capacitance is variable. This can be due to component properties variations. However, it can also be due to the movement and vibrations to which the steering wheel is exposed. Additionally, external influences can cause the ambient capacitance to vary. Due to the variability of the ambient capacitance, a robust detection mechanism for a faulty skeleton lead is necessary.

[0037] In some embodiments, the skeleton supply line can be selectively coupled to a vehicle ground. For example, a switching device can be provided and arranged such that an alternating galvanic conductance is formed between the skeleton structure and the switching device. Through the selective coupling, the skeleton supply line can be connected to a defined potential, at least in phases. If the skeleton supply line is coupled to the vehicle ground, the ambient capacitance in this case is zero due to the direct electrical coupling. This makes it possible to enforce certain operating states of the skeleton supply line, thus simplifying fault detection with regard to the skeleton supply line. Other operating states can be neglected. The alternating galvanic conductance provides the possibility of an additional fault detection mechanism.If the conductance remains constant despite actuation of the switching device, a fault condition exists. Optionally, the circuit arrangement is additionally configured at least to detect a third voltage value for the at least one conduction layer. This can be taken into account, in particular, as an additional method step in the method explained above. For example, the control device or a component coupled to the control device can again be used for this purpose. The control device is configured to detect a faulty skeleton supply line, additionally taking into account the third voltage value as a function of the variable ambient capacitance. In this case, in particular, the ambient capacitance can be variable, at least temporarily. The third voltage value simplifies the determination of a faulty skeleton supply line.

[0038] In some embodiments, the skeleton supply line is detected as faulty if the second voltage value exceeds a first voltage threshold and the third voltage value does not exceed a second voltage threshold. The second voltage threshold depends on the first voltage threshold, taking into account the capacitive voltage divider. Here, the capacitive voltage divider, which is formed by the interlayer capacitance and the ambient capacitance, can be used to determine expected values ​​that the second voltage value and the third voltage value must have in order for the skeleton supply line to be determined as fault-free. Conversely, corresponding voltage thresholds can be determined based on the capacitive voltage divider, which can be used to detect a faulty skeleton supply line.In other words, the voltage threshold values ​​are in a certain relationship to each other, which is determined by the capacitive voltage divider.

[0039] Preferably, appropriate tolerance ranges can be taken into account when determining the voltage threshold values.

[0040] For example, the detection of a faulty skeleton supply line can also be based on the corresponding voltage threshold conditions being met / not met for a number of acquisition cycles within a predefined time interval. This can prevent a single measurement, for example, based on a vibration, from immediately detecting the skeleton supply line as faulty.

[0041] Optionally, the control device is configured to bring the skeleton supply line into a first defined state, at least in a first phase, in which the skeleton supply line is decoupled from the voltage source and coupled to the vehicle ground.

[0042] Preferably, at the beginning of the process for operating the circuit arrangement, all voltage lines—that is, the skeleton supply line on both the voltage source side of the resistor and the skeleton side of the resistor (and thus also the skeleton structure) and the conductive layer—are coupled to ground. This ensures that all capacitors in the circuit arrangement are discharged and have a defined potential at the beginning of the process. This discharging process of the capacitors can also be part of the first phase.

[0043] The control device is then also configured to bring the skeleton supply line into a second defined state in a second phase, in which the skeleton supply line is decoupled from the vehicle ground and coupled to the voltage source. This defines a starting point for the method.

[0044] All subsequent voltage value measurements can then preferably be performed within a predetermined time interval t1. The time interval t1 can, in particular, be much smaller than the product of the resistance of the skeleton supply line and the capacitance of the interlayer capacitance. Thus, based on the corresponding time interval, it can be ensured that steady-state conditions have not yet been reached.

[0045] The circuit arrangement is thus configured such that the second voltage value is detected within the predetermined time interval after the start of the second phase. Selective coupling to the voltage source or the vehicle ground is typically ensured by switching devices. The control device controls the switching states of the switching devices. The switching processes cause fluctuations in the voltage amplitudes within the circuit arrangement. By considering a predetermined time interval after the start of a specific phase, in this case the second phase, it is possible to prevent the fluctuations caused by the switching processes from influencing the detection mechanism for the faulty skeleton supply line.

[0046] In addition, the predetermined time interval allows for defined configurations of the circuit arrangement to be taken into account. Since the value of the interlayer capacitance can be known in advance, the time interval can, for example, be selected such that a charge stored in the interlayer capacitance cannot have already fully built up (or dissipated). Ultimately, the time interval can be used to enable the detection of a faulty skeleton lead based on measured values, in particular with regard to the second voltage value, that correspond to a defined operating state of the circuit arrangement. It should be noted that the applied partial voltages change due to the capacitive voltage divider. This is exploited by the selective coupling within the phases.

[0047] In particular, the interlayer capacitance differs between a defective skeleton connection and a functioning skeleton connection, so that the skeleton connection can be assessed as good or faulty based on the measured partial voltages. This increases the reliability of the detection mechanism for detecting a faulty skeleton connection.

[0048] In some embodiments, the skeleton structure is electrically coupled to the vehicle frame part via a ground line. In this case, the ambient capacitance is zero, and the capacitive voltage divider is omitted. The control device of the circuit arrangement is configured in this case to detect a faulty skeleton supply line exclusively based on the first and second voltage values. This makes the detection mechanism for detecting a faulty skeleton supply line particularly compact. This means that a faulty skeleton supply line can be determined, in particular, independently of a voltage value detected with respect to the conductor position. In addition, this embodiment allows for a different topology, which may be desired for certain applications.Optionally, in this embodiment, which provides a separate ground line for the skeleton structure, a switching device is also arranged such that a changing galvanic conductance is established between the skeleton structure (via the skeleton supply line) and the vehicle frame part. This creates an additional fault detection mechanism and ensures that the skeleton supply line can be assessed for its integrity based on the changing galvanic conductance, even though the separate ground line is provided.

[0049] Preferably, according to the last-outlined embodiment, the skeleton supply line is detected as faulty if the second voltage value exceeds a minimum threshold. This demonstrates the compactness of the detection mechanism for detecting the faulty skeleton supply line. Only the second voltage value needs to be compared with a minimum threshold.

[0050] Preferably, the circuit arrangement has a single conductive layer. This makes the circuit arrangement, and thus the design of the steering wheel, particularly compact. As a result, manufacturing costs are low.

[0051] Optionally, at least one control layer is configured as a resistance heater and / or for hand recognition (HOD) of the steering wheel. This means that the control layer can also fulfill additional functionalities, for example, enabling autonomous or at least semi-autonomous driving functions, thus increasing comfort for the vehicle user.

[0052] Preferably, the HOD functionality is ensured based on the interlayer capacitance. With a capacitive hand detection device, the definition of the potential at the steering wheel skeleton, i.e., the skeleton structure, is important for reliable hand detection. The circuit arrangement explained here can reliably check the status of the skeleton supply line, thus ensuring the HOD function. For example, if the skeleton connection is assessed as faulty, the hand detection device (HOD function) can be classified as defective or inactive. This can be taken into account in downstream driving control systems. To implement the resistance heating, it can be provided that the conductive layer is supplied with a current, which is converted into thermal energy based on the conductive layer.

[0053] According to a further aspect, a steering wheel for a vehicle with a circuit arrangement as described above or with a circuit arrangement which can be operated according to a method as described above is also proposed.

[0054] According to an additional aspect, a vehicle with a steering wheel as previously explained is also provided.

[0055] The invention, as well as further advantageous embodiments and developments thereof, are described and explained in more detail below with reference to the example shown in the drawing. The features shown in the description and the drawing can be used individually or in any combination according to the invention. They show:

[0056] Fig. 1 is a schematic representation of a circuit arrangement for a steering wheel of a vehicle and a steering wheel according to embodiments of the invention,

[0057] Fig. 2 is a schematic representation of a circuit arrangement for a steering wheel of a vehicle and a steering wheel according to further embodiments of the invention, and

[0058] Fig. 3 is a schematic representation of a method for operating a circuit arrangement for a steering wheel of a vehicle according to embodiments of the invention.

[0059] All features disclosed below with reference to the exemplary embodiments and / or the accompanying figures can be combined alone or in any subcombination with features of the aspects of the present disclosure, including features of preferred embodiments, provided that the resulting combination of features is meaningful to a person skilled in the art. Fig. 1 shows a schematic representation of a circuit arrangement 10 for a steering wheel 12 of a vehicle and a steering wheel 12 according to embodiments of the invention. The steering wheel 12 is shown as a radial section through the steering wheel rim.

[0060] The structure of the steering wheel 12 is essentially determined by the circuit arrangement 10, at least with regard to the electrically conductive components.

[0061] According to this embodiment, the steering wheel comprises leather as the outer top layer 14. A conductive layer 16 is arranged beneath the top layer 14, which at least partially comprises an electrically conductive material. For example, the conductive layer 16 can be formed by an electrical conductor in the form of a two-dimensional conductor grid.

[0062] According to this embodiment, an electrically non-conductive layer 18, which here comprises a foam, is arranged adjacent to and below the conductive layer 16. The non-conductive layer 18 surrounds a skeleton structure 20, which also comprises an electrically conductive material, and acts as a dielectric between the conductive layer 16 and the skeleton structure 20.

[0063] The circuit arrangement 10 also includes a control device 22 which is coupled to both the guide layer 16 and the skeleton structure 20.

[0064] According to this embodiment, the control device 22 comprises a voltage source 24, which according to other examples may also be external to the control device 22.

[0065] The control device 22 is coupled to the skeleton structure 20 such that a skeleton supply line 26 can be used to couple the skeleton structure 20 to the voltage source 24. For this purpose, the skeleton supply line 26 is connected to a terminal 28 that is electrically conductively coupled to the skeleton structure 20.

[0066] The electrically non-conductive layer 18, which represents a dielectric between the conductive layer 16 and the skeleton structure 20, forms a capacitor, represented here as an interlayer capacitance 30 (interlayer capacitor), between the conductive layer 16 and the skeleton structure 20. Because the skeleton structure 20 is generally at least temporarily subjected to a voltage, an ambient capacitance 32 is formed between the skeleton structure 20 and the vehicle frame part 34 with respect to a (ideally infinitely distant) vehicle frame part 34. The ambient capacitance 32 generally varies over time, since, for example, the steering wheel 12 is subjected to vibrations and movements, and since the electrostatic conditions with respect to the vehicle frame part 34 can also change.As a result, in an alternative approach, a time-varying resistor 36 can be assumed to be formed between the skeleton structure 20 and the vehicle frame part 34. In this case, the resistor 36 is referred to as the second resistor R2.

[0067] The skeleton lead 26 has a dedicated, separately arranged first resistor 38, R1, which is arranged between the voltage source 24 and the interlayer capacitance 30.

[0068] The control device 22 is configured to detect a first voltage value 40 (also designated V1) on the voltage source side of the first resistor 38. Additionally, the control device 22 is also configured to detect a second voltage value 42 (also designated V2) on the skeleton side of the first resistor 38. For this purpose, the control device 22 can, for example, have corresponding measuring terminals that can be selectively coupled to the voltage source side and the skeleton parts of the first resistor 38, R1.

[0069] In order to be able to selectively couple the skeleton structure 20 and thus also the skeleton supply line 26 to the voltage source 24, a first switching device 46 is arranged between the voltage source 24 and the voltage source side of the first resistor 38, R1.

[0070] In addition, a second switching device 47 is arranged between the terminal 44 of the control device 22 and the voltage source side of the first resistor 38, R1.

[0071] This means that the first switching device 46 and the second switching device 47 are coupled to each other at a node 48 on the voltage source side of the first resistor 38, R1. At node 48, for example, the first voltage source-side voltage value 40, V1 can then be detected by selective coupling to a measuring terminal of the control device 22.

[0072] The control device 22 is configured to regulate the switching states of the switching devices 46, 47.

[0073] In addition, the control device 22 according to this embodiment comprises an analog-to-digital converter (ADC) 50, which is coupled on the one hand to the conductive layer 16 and on the other hand to the skeleton side of the first resistor 38, R1. For example, the ADC 50 can be coupled to a dedicated node 49, which is arranged on the skeleton side of the first resistor 38, R1, between the first resistor 38 and the interlayer capacitance 30. At node 49, the second voltage value 42, V2, can be detected using the ADC 50. In addition, the ADC 50 is also configured to detect a third voltage value V3 with respect to the conductive layer 16.

[0074] The detected voltage values ​​V1, V2, V3 are fed to a data processing device of the control device 22, which can determine, based on the detected measured values, whether the skeleton supply line 26 is faulty. This can take advantage of the fact that the interlayer capacitance 30 and the ambient capacitance 32 form a capacitive voltage divider for the conductive layer 16.

[0075] The voltage values ​​V1, V2, V3 can be recorded under certain operating conditions of the circuit arrangement 10.

[0076] In a first phase, the first switching device 46 can be open and the second switching device 47 can be closed. This means that the skeleton supply line 26 is not coupled to the voltage source 24, but exclusively to terminal 44 of the control device. In this first phase, using the control device 22 and, for example, terminal 44, the skeleton supply line 26 can additionally be coupled via a ground line 51 to a vehicle frame part 34, which, electrically speaking, represents a vehicle ground. This discharges the interlayer capacitance 30, since the stored charge flows to the vehicle ground in the form of the vehicle frame part 34 via terminal 44. The interlayer capacitance is thus brought to a defined potential, namely ground. In a second phase, the first switching device 46 can be closed and the second switching device 47 can be open.This means that the skeleton supply line 26 is coupled exclusively to the voltage source 24, but not to terminal 44 of the control device 22, and thus (actually) not to the vehicle frame part 34 either. In the second phase, the interlayer capacitance 30 can be at least partially charged with electrical charge provided by the voltage source 24. The charging behavior of the interlayer capacitance 30 depends directly on whether the skeleton supply line 26 is faulty or intact. This can be exploited here to assess whether the skeleton supply line 26 is faulty.

[0077] Since the skeleton supply line 26 and thus also the interlayer capacitance 30 are coupled to the voltage source 24 during the second phase, in particular the second voltage value 42, V2 and the third voltage value 50, V3 can be recorded during the second phase. A time interval can be taken into account so that the measured values ​​of the voltage values ​​42, 50, V2, V3 are recorded at a specific point in time or within a specific time interval after the start of the second phase. This defines a specific operating state that the circuit arrangement 10 should have at this point in time, provided the skeleton supply line 26 is not faulty. This enables the precise comparison of the measured values ​​of the voltage values ​​42, 50, V2, V3 with corresponding expected values, which can be taken into account in the evaluation, for example, by voltage threshold values ​​S1, S2.

[0078] Fig. 3 shows a schematic representation of a method 55 for operating a circuit arrangement 10 for a steering wheel 12 of a vehicle according to embodiments of the invention. Optional steps are shown in dashed lines.

[0079] Method 55 initially includes the optional step 56, in which all relevant voltage lines, in particular those of 40, V1, 42, V2, and 50, V3, are coupled to ground. This allows, in particular, the interlayer capacitance 30 to be discharged and ensures defined initial conditions for method 55.

[0080] The method then comprises the optional step 57 in which the node 48 at which the first voltage value 40, V1, is measured is first coupled to the voltage source 24, for example, for a predetermined time interval using the switching device 46.

[0081] The method 55 can then be configured such that the further steps 58, 60, 64, in which various voltage values ​​are detected, take place within a predetermined time interval t1 starting from the coupling to the voltage source 24. The time interval t1 is dimensioned such that it is much smaller than the product of the resistance value of the first resistor 38, R1 of the skeleton lead 26, and the capacitance value of the interlayer capacitance 30. This is indicated in Fig. 3 by the curved bracket. This can prevent stationary values ​​from being established during the voltage detection.

[0082] The method 55 then comprises step 58 in which a first voltage value 40, V1 is detected on the voltage source side of the first resistor 38, R1 of the skeleton lead 26.

[0083] In addition, the method 55 includes step 60 in which a second voltage value 42, V2 is detected on the skeleton side of the first resistor 38, R1 of the skeleton lead 26.

[0084] According to the embodiment of the circuit arrangement 10 shown in Fig. 1, the method 55 also includes the generally optional step 64 in which a third voltage value 50, V3 for the at least one conductive layer 16 is detected.

[0085] Step 60 and step 64 of method 55 are carried out in particular within a predetermined time interval after the start of the second phase, that is to say when the skeleton supply line 26 is not coupled to the terminal 44, but exclusively to the voltage source 24 using the switching devices 46, 47.

[0086] Finally, the method 55 also includes step 62 in which a faulty skeleton supply line 26 is detected by the control device 22 as a function of the ambient capacitance 32 based at least on the first voltage value 40, V1 and the second voltage value 42, V2.

[0087] As already explained, the coupling of the skeleton structure 20 to the vehicle frame part 34 can be described by means of a time-varying second resistor 36, R2. Depending on the relative resistance values ​​of the first resistor 38, R1 arranged within the skeleton supply line 26 and the time-varying second resistor 36, R2, the operating states schematically illustrated as A), B), and C) can then occur with respect to the measured values ​​of the voltage values ​​V1, V2, V3.

[0088] According to operating condition A), the first resistor 38, R1 can be (much) smaller than the second resistor 36, R2. In this case, the capacitive voltage divider formed by the interlayer capacitance 30 and the ambient capacitance 32 with respect to the conductive layer 16 results in the voltages applied to the skeleton lead 26 and the conductive layer 16, corresponding to the second voltage value 42, V2 and the third voltage value 50, V3, being (should be) in a specific relationship to one another, at least within the predetermined time interval within which the measured values ​​are recorded. The relationship is determined by the capacitive voltage divider. In this case, the second voltage value 42, V2 on the skeleton side of the first resistor 38, R1 is a factor greater than the third voltage value 50, V3 of the conductive layer 16.Accordingly, corresponding voltage thresholds, for example, a first voltage threshold S1 with respect to the second voltage value 42, V2, and a second voltage threshold S2 with respect to the third voltage value 50, V3, can be provided, based on which this situation can be assessed. If the respectively assigned voltage thresholds S1, S2 are exceeded by the respective voltage values ​​42, 50, V2, V3, the control device 22 can detect that operating state A) exists.

[0089] In operating state B), the first resistance 38, R1 is (much) greater than the second resistance 36, R2. This is the case, for example, when the skeleton supply line 26 is electrically coupled to the vehicle frame part 34 during the second phase. In this case, the interlayer capacitance 30 is discharged, and the electrical charge stored therein flows to the vehicle frame part 34 as vehicle ground. Since the skeleton supply line 26 is nevertheless coupled to the voltage source 24 during the second phase, the first voltage value 40, V1 is different from zero. In contrast, the second voltage value 42, V2 and the third voltage value 50, V3 are zero in this case. Thus, the presence of operating state B) can be determined, for example, by determining that neither the second voltage value 42, V2 exceeds the first voltage threshold value S1, nor that the third voltage value 50, V3 exceeds the second voltage threshold value S2.

[0090] In operating state C), the skeleton supply line 26 is faulty, for example, broken. In this case, the capacitive voltage divider has no effect on the conductive layer 16. This means that the third voltage value 50, V3 is zero in this case. Therefore, if it is determined that the third voltage value 50, V3 does not exceed its associated second voltage threshold value S2 and that, at the same time, the second voltage value 42, V2 exceeds its associated first voltage threshold value S1, the control device 22 can detect that a faulty skeleton supply line 26 is present. In this regard, the second voltage threshold value S2 is selected as a function of the first voltage threshold value S1, taking into account the capacitive voltage divider formed by the interlayer capacitance 30 and the ambient capacitance 32.

[0091] This allows all relevant operating states to be differentiated from one another with regard to the coupling of the skeleton structure to the vehicle frame part 34 and the integrity of the skeleton supply line 26. As a result, it is also possible to determine when the additional functions performed by the control system 16, such as resistance heating or a HOD function, can be considered as expected. In other words, it is possible to determine when the measurement signals underlying the HOD function can be trusted. This influences the execution of autonomous or semi-autonomous driving functions.

[0092] Fig. 2 shows a schematic representation of a circuit arrangement 10 for a steering wheel 12 of a vehicle and a steering wheel 12 according to further embodiments of the invention. Only the differences will be discussed here.

[0093] In contrast to the previously shown embodiments, the skeleton structure 20 is now permanently coupled to ground via the indexed ground line 52 and a separate ground connection 54. As a result, the ambient capacitance 32 is zero in this case. This means that no capacitive voltage divider is formed with respect to the conductive layer 16. This simplifies the determination of a faulty skeleton supply line 26. Operating state A) is not possible according to this embodiment.

[0094] Nevertheless, the galvanic conductance between the skeleton structure 20 and ground via the skeleton supply line 26 can be varied using the switching device 47. This ensures that the influence of the ground coupling can be taken into account when monitoring the skeleton supply line 26. The first voltage values ​​40, V1 and / or second voltage values ​​42, V2 can then be recorded with the switching device 47 open. The corresponding nodes at which the first and second voltage values ​​40, V1, 42, V2 are recorded can then be coupled exclusively to the skeleton structure 20.

[0095] As a result, a faulty skeleton supply line can be detected according to operating state C) of this embodiment exclusively based on the first voltage value 40, V1, and the second voltage value 42, V2. For this purpose, only the second voltage value 42, V2 is compared with its associated first voltage threshold value S1. If the second voltage value 42, V2 exceeds the first voltage threshold value S1, operating state C) corresponding to a faulty skeleton supply line 26 is present. Otherwise, an intact skeleton supply line 26 can be assumed.

[0096] Certain embodiments disclosed herein, in particular the respective module(s), use circuitry (e.g., one or more circuits) to implement standards, protocols, methods, or technologies disclosed herein, operatively couple two or more components, generate information, process information, analyze information, generate signals, encode / decode signals, convert signals, transmit and / or receive signals, control other devices, etc. Circuitry of any type may be used.

[0097] In one embodiment, a circuit (circuit) includes, among other things, one or more computing devices such as a processor (e.g., a microprocessor), a central processing unit (CPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a system on a chip (SoC), or the like, or any combination thereof, and may include discrete digital or analog circuit elements or electronics, or combinations thereof. In one embodiment, the circuit includes hardware circuit implementations (e.g., implementations in analog circuits, implementations in digital circuits, and the like, and combinations thereof).

[0098] In one embodiment, circuitry includes combinations of circuitry and computer program products with software or firmware instructions stored on one or more computer-readable memories that cooperate to cause a device to execute one or more of the protocols, methods, or technologies described herein. In one embodiment, the circuitry includes circuitry, such as microprocessors or portions of microprocessors, that require software, firmware, and the like to operate. In one embodiment, the circuitry includes one or more processors or portions thereof and the associated software, firmware, hardware, and the like.

[0099] In the present application, reference may be made to quantities and numbers. Unless expressly stated, such quantities and numbers are not to be considered limiting, but rather as examples of the possible quantities or numbers in the context of the present application. In this context, the term "plurality" may also be used in the present application to refer to a quantity or number. In this context, the term "plurality" means any number greater than one, e.g., two, three, four, five, etc. The terms "about," "approximately," "near," etc., mean plus or minus 5% of the stated value.

[0100] Although the disclosure has been illustrated and described with respect to one or more implementations, those skilled in the art will recognize equivalent changes and modifications upon reading and understanding this description and the accompanying drawings. Although a particular feature of the disclosure has been disclosed with respect to only one of several embodiments, that feature may be combined with one or more other features of the other embodiments as may be desired and advantageous for a given or particular application.

Claims

Patent claims 1. Circuit arrangement (10) for a steering wheel (12) of a vehicle, wherein the steering wheel (12) has at least one conductive layer (16) and a skeleton structure (20), an interlayer capacitance (30) is formed between the conductive layer (16) and the skeleton structure (20) and an ambient capacitance (32) is formed between the skeleton structure (20) and a vehicle frame part (34), the interlayer capacitance (30) and the ambient capacitance (32) form a capacitive voltage divider for the conductive layer (16), the circuit arrangement (10) further comprises a voltage source (24) which can be selectively coupled to the skeleton structure (20) via a skeleton supply line (26), the skeleton supply line (26) has a resistor (38), the circuit arrangement (10) is at least configured to generate a first voltage value (V1) on the voltage source side of the resistor (38) of the skeleton supply line (26) and a second voltage value (V2) on the skeleton side of the resistance (38) of the skeleton supply line (26),and wherein a control device (22) of the circuit arrangement (10) is configured to detect a faulty skeleton lead (26) as a function of the ambient capacitance (32) at least on the basis of the first and second voltage values (V1, V2).

2. Circuit arrangement (10) according to claim 1, characterized in that the ambient capacitance (32) is variable.

3. Circuit arrangement (10) according to claim 1 or 2, characterized in that the skeleton supply line (26) can be selectively coupled to a vehicle ground, so that an alternating galvanic conductance is formed between the skeleton structure (20) and the vehicle ground by means of a switching device (47).

4. Circuit arrangement (10) according to claim 3, characterized in that the circuit arrangement (10) is additionally at least configured to detect a third voltage value (V3) for the at least one conductive layer (16), and wherein the control device (22) is configured to detect a faulty skeleton lead (26) additionally taking into account the third voltage value (V3) as a function of the variable ambient capacitance (32).

5. Circuit arrangement (10) according to claim 4, characterized in that the skeleton supply line (26) is detected as faulty if the second voltage value (V2) exceeds a first voltage threshold value (S1) and the third voltage value (V3) does not exceed a second voltage threshold value (S2), wherein the second voltage threshold value (S2) depends on the first voltage threshold value (S1) taking into account the capacitive voltage divider.

6. Circuit arrangement (10) according to one of claims 3 to 5, characterized in that the control device (22) is set up to bring the skeleton supply line (26) into a first defined state, at least in a first phase, in which the skeleton supply line (26) is decoupled from the voltage source (24) and coupled to the vehicle ground, and to bring it into a second defined state, in which the skeleton supply line (26) is decoupled from the vehicle ground and coupled to the voltage source (24), and wherein the circuit arrangement (10) is set up such that the second voltage value (V2) is detected within a predetermined time interval after a start of the second phase.

7. Circuit arrangement (10) according to claim 1, characterized in that the skeleton structure (20) is electrically conductively coupled to the vehicle frame part (34) by means of a ground line (52), wherein the ambient capacitance (32) is zero in this case, and wherein the control device (22) of the circuit arrangement (10) is set up in this case to detect a faulty skeleton supply line (26) exclusively on the basis of the first and the second voltage value (V1, V2).

8. Circuit arrangement (10) according to claim 7, characterized in that a switching device (47) is arranged such that an alternating galvanic conductance between the skeleton structure (20) and the vehicle frame part (34).

9. Circuit arrangement (10) according to claim 7 or 8, characterized in that the skeleton supply line (26) is detected as faulty if the second voltage value (V2) exceeds a minimum threshold value.

10. Circuit arrangement (10) according to one of the preceding claims, characterized in that the circuit arrangement (10) has a single conductive layer (16).

11. Circuit arrangement (10) according to one of the preceding claims, characterized in that the at least one guide layer (16) is designed as a resistance heater and / or for hand recognition of the steering wheel (12).

12. A method (55) for operating a circuit arrangement (10) for a steering wheel (12) of a vehicle, wherein the steering wheel (12) has at least one conductive layer (16) and a skeleton structure (20), an interlayer capacitance (30) is formed between the conductive layer (16) and the skeleton structure (20), and an ambient capacitance (32) is formed between the skeleton structure (20) and a vehicle frame part (34), the interlayer capacitance (30) and the ambient capacitance (32) form a capacitive voltage divider for the conductive layer (16), the circuit arrangement (10) further comprises a voltage source (24) which can be selectively coupled to the skeleton structure (20) via a skeleton supply line (26), the skeleton supply line (26) has a resistor (38), and wherein the method (55) comprises at least the steps: Detecting a first voltage value (V1) on the voltage source side of the resistor (38) of the skeleton lead (26), Recording a second voltage value (V2) on the skeleton side of the resistance (38) of the skeleton lead (26), and Detecting a faulty skeleton supply line (26) as a function of the ambient capacitance (32) based on at least the first voltage value (V1) and the second voltage value (V2) by a control device (22).

13. The method (55) according to claim 12, characterized in that the skeleton structure (20) is electrically conductively coupled to the vehicle frame part (34) by means of a ground line (52), wherein the ambient capacitance (32) is zero in this case, and wherein the control device (22) of the circuit arrangement (10) detects a faulty skeleton supply line (26) in this case exclusively on the basis of the first and the second voltage value (V1, V2).

14. The method (55) according to claim 12, characterized in that the method (55) further comprises: Detecting a third voltage value (V3) for the at least one conductive layer (16), wherein the control device (22) detects a faulty skeleton supply line (26) additionally taking into account the third voltage value (V3), and wherein the ambient capacitance (32) is variable in this case.

15. Steering wheel (12) for a vehicle with a circuit arrangement (10) according to one of claims 1 to 11 or a circuit arrangement (10) which is operable according to a method (55) according to one of claims 12 to 14.

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