Capacitive sensor device, steering wheel, operating method, and vehicle

Abstract

The invention relates to a capacitive sensor device (10) for detecting the presence of a body part in a detection area of the sensor device (10), to a steering wheel (100) comprising a capacitive sensor device (10), to a method for operating a capacitive sensor device (10) or a steering wheel (100), and to a vehicle comprising a capacitive sensor device (10). The sensor device (10) comprises a first sensor electrode (11) having a first electrode portion (21), a second sensor electrode (13) having a second electrode portion (22), and a measuring device (30) for determining a measurement variable (UMess, IMess; B1-B2; B2-B1) based on a current difference (I1-I2; I2-I1) between a first current (I1) flowing in the first electrode portion (21) of the at least one first sensor electrode (11) and a second current (I2) flowing in the second electrode portion (22) of the second sensor electrode (13), wherein the measuring device (30) has an electronic coil (31), which is designed in such a way, and the first electrode portion (21) of the first sensor electrode (11) and the second electrode portion (22) of the second sensor electrode (13) are arranged and coupled to the coil (31) in each case at least partially relative to one another and relative to the coil (31), such that the measurement variable based on the current difference (I1-I2; I2-I1) is generated or generatable in the coil (31) using the current difference (I1-I2; I2-I1) between the first current (I1) flowing in the first electrode portion (21) and the second current (I2) flowing in the second electrode portion (22).

Description

TECHNICAL FIELD

[0001] The invention relates to a capacitive sensor device for recognizing the presence of a body part in a detection area of the sensor device, preferably for a steering wheel, in particular for recognizing the presence of a human hand in a grip area of a steering wheel. The sensor device comprises at least one first sensor electrode with an associated detection area and a first electrode portion, and a second sensor electrode with a second electrode portion; the at least one first sensor electrode and the second sensor electrode are separated from each other by a dielectric therebetween and form a first capacitive element, and the at least one first sensor electrode together with the surrounding environment further forms a second capacitive element; the sensor device further comprises a measuring device designed and configured to determine a measurement variable from a current difference between a first current flowing in the first electrode portion of the at least one first sensor electrode and a second current flowing in the second electrode portion of the second sensor electrode.

[0002] Furthermore, the invention relates to a steering wheel comprising such a sensor device, in particular for a motor vehicle.

[0003] Furthermore, the invention relates to a method for operating such a sensor device and / or a steering wheel comprising such a sensor device.

[0004] Furthermore, the invention relates to a vehicle, in particular comprising such a sensor device. BACKGROUND

[0005] Capacitive sensor devices of the general type configured to capture a change in capacitive coupling between a first electrode and a second electrode due to a human hand approaching the sensor device based on a current measurement are in principle known from the prior art, including for steering wheels or car seats, for example from FR 3 056 291, which patent document teaches to measure the absolute current between the second electrode and ground for this purpose.

[0006] Interfering influences, in particular from the outside, such as a changing ambient temperature of the sensor device or a changing air humidity in the environment, can lead to a change in capacitance and thus to a drift of the current measurement signal, i.e. a systematic deviation.

[0007] It is also known to determine or detect a change in capacitive coupling based on a current difference between the currents flowing in the two sensor electrodes, which is determined by first measuring each individual current and then determining the sought current difference from the individual currents. Determining the current difference enables a reduction in drift or even complete avoidance of drift. However, measuring the two individual currents before determining the current difference requires a correspondingly comprehensive and complex, and thus cost-intensive, measuring device. SUMMARY

[0008] Against this background, it is an object of the present application to provide an alternative, in particular improved, sensor device which requires only a relatively simple construction of the measuring means, but nevertheless has a low drift tendency and / or can be easily compensated for interfering variables.

[0009] Furthermore, it is an object of the present application to provide an alternative, in particular improved, steering wheel comprising a capacitive sensor device, an alternative, in particular improved, method for operating such a capacitive sensor device, and a vehicle comprising an alternative, in particular improved, sensor device.

[0010] According to the application, this object is achieved by a capacitive sensor device, a steering wheel, a method and a vehicle having the features according to the respective independent patent claim. Advantageous embodiments of the application are the subject of the dependent patent claims, the description and the drawings and will be explained in more detail below. The respective patent claim is incorporated by explicit reference into the content of the present description.

[0011] The capacitive sensor device according to the application is designed for recognizing the presence of a body part in a detection area of the sensor device, preferably for a steering wheel, in particular for recognizing the presence of a human hand in a gripping area of the steering wheel, i.e. in particular for "hands-on switch recognition". The sensor device comprises at least one first sensor electrode with an associated detection area and a first electrode portion, and a second sensor electrode with a second electrode portion. In this case, the at least one first sensor electrode and the second sensor electrode are separated from one another by a dielectric therebetween and form a first capacitive element. The at least one first sensor electrode, together with the surroundings, further forms a second capacitive element. The sensor device further comprises a measuring means which is designed and configured to determine a measurement variable which depends on a current difference between a first current flowing in the first electrode portion of the at least one first sensor electrode and a second current flowing in the second electrode portion of the second sensor electrode.

[0012] The capacitive sensor device according to the application is characterized in that the measuring means comprises an electronic coil with at least one winding, which coil is designed in such a way that the first electrode portion of the first sensor electrode and the second electrode portion of the second sensor electrode are at least partially arranged in each case relative to one another in such a way and in each case relative to the coil in such a way and coupled to the coil in such a way that the measurement variable which depends on the current difference between the first current flowing in the first electrode portion and the second current flowing in the second electrode portion is generable or generated in the coil by the current difference.

[0013] By means of the electronic coil, in a simple manner, a measurement variable dependent on the current difference between the currents flowing in the sensor electrode or its electrode sections, in particular proportional to the current difference, can be generated, which can be captured by means of a measuring device, which, for this purpose, particularly preferably comprises at least one suitable measuring unit, for example a voltage measuring unit, a current measuring unit and / or a magnetic flux measuring unit.

[0014] Since a measurement signal dependent on the current difference is generated, neither the individual currents have to be captured in a metrological manner nor is it necessary to form the difference by means of a complex circuit. Thus, compared to a configuration with a differential circuit, the number of components required to implement the sensor device according to the application can be significantly reduced. Furthermore, a sensor device can be provided which is, in principle, robust against common-mode interference, provided that it has a correspondingly suitable design and configuration.

[0015] In an advantageous configuration of the sensor device according to the application, the measuring device can further preferably, particularly preferably additionally, be designed and configured in dependence on a measurement variable generated and captured in the coil, i.e. measured, which has been generated in particular by means of or in dependence on the current difference between the first current flowing in the first electrode section and the second current flowing in the second electrode section, so that the absolute value of the current difference on which this measurement variable is based is determined and optionally also output.

[0016] The sensor device according to the application is in particular designed for use in a motor vehicle and can be designed, for example, in a steering wheel for a so-called "hands-on detection" or, for example, for a seat occupancy recognition device, which can recognize whether a seat is occupied by a person. Furthermore, numerous further application possibilities are conceivable.

[0017] Particularly preferably, the sensor device is designed here such that, in each case, the presence of a body part in the detection area of the at least one first sensor electrode causes a change in the capacitive coupling of the first sensor electrode to the surroundings, which is assignable to the at least one first sensor electrode, compared to a reference state in which no body part is present in the associated detection area. The change in the capacitive coupling of the first sensor electrode to the surroundings results in a change in the current flowing through the capacitive element formed by the first sensor electrode and the second sensor electrode, which in turn results in a change in the current in the second sensor electrode and thus in the current difference, which is proportional to the proximity, in particular to the distance between the body part and the first sensor electrode.

[0018] In this case, the first sensor electrode and the second sensor electrode are furthermore in particular not in direct electrical contact with one another, but are coupled to one another only via the dielectric located therebetween, and are furthermore coupled only indirectly, the second sensor electrode being preferably almost completely surrounded by the dielectric, in particular being completely remote from connections for contact with electrical conductors via which current can flow away.

[0019] In the case of the sensor device according to the application, the dielectric is here in particular selected such that a first capacitive element formed by the first sensor electrode, the dielectric and the second sensor electrode has a defined capacitance, in particular a capacitance in the range from 10 pF to 100 nF.

[0020] Here, the first electrode portion of the first sensor electrode and / or the second electrode portion of the second sensor electrode can in particular be an electrically conductive connection portion of the associated sensor electrode, for example in each case an electrical connection line of the associated sensor electrode. It is thus possible to provide a particularly simple sensor device which saves installation space, i.e. saves space, and does not require additional components, if appropriate only slightly longer and differently arranged connection lines.

[0021] An "electronic coil" within the meaning of the application is an electrical component which has at least one electrical conductor in the form of a winding, in particular with an input connection and an output connection, which is wound in such a way that a magnetic field is generated in the event of a current flow through the conductor; the at least one winding preferably comprises at least one complete turn, in particular a plurality of complete turns, the number of turns being particularly preferably selected in such a way and the remainder of the winding being particularly designed in such a way that the resultant inductance of the winding is adapted to capture a measurement variable dependent on a current difference with sufficient accuracy and to generate a corresponding measurement signal.

[0022] In some applications, a suitable inductance for the at least one winding of the coil can be, for example, L = 10 µH. However, alternatively, a suitable inductance can also be, for example, L = 1 µH, L = 20 µH, L = 30 µH, L = 50 µH, L = 100 µH or more, for example L = 500 µH, L = 600 µH or up to L = 10 000 µH, depending on the application. In this case, the suitability of the inductance value essentially depends on the properties of the other components of the sensor device, in particular any possible further inductances, in particular any possible further inductances coupled to the coil.

[0023] In this case, in the case of a sensor device according to the application, at least one winding of the electronic coil provided according to the application can in particular be a measuring winding, i.e. a winding which is used essentially for, in particular exclusively for, measuring, i.e. capturing, a variable which depends on the current difference and is to be determined. Alternatively, the aforementioned at least one winding can be a winding whose electrical conductor is additionally used for at least one further purpose, for example for feeding a current to an electrode, for example a reference current to a first sensor electrode and / or a heating current to a heating electrode, etc.

[0024] In this case, the coil of the sensor device according to the application or the coil of the measuring device of the sensor device according to the application can in principle be a hollow coil, i.e. an electronic coil without a coil core, or alternatively can comprise a coil core, in particular a magnetic or magnetizable core, a ferromagnetic core having proved to be particularly advantageous, in particular a permanent magnet core. The advantage of a coil with a core is that a stronger measurement signal can thereby be obtained, which has a favorable effect on the measurement accuracy.

[0025] In a further advantageous configuration of the sensor device according to the application, the sensor device is also designed and configured to identify, in particular depending on the determined measurement variable, the presence of a body part in a detection region of the sensor device, in particular the presence of a human hand in a grip region of a steering wheel; the sensor device in particular comprises an evaluation device for this purpose.

[0026] In a further advantageous configuration of the sensor device according to the application, the sensor device also comprises a current generation device, in particular at least one of the two sensor electrodes is electrically connectable or electrically connected to the current generation device, and a reference current can be applied to the at least one sensor electrode by means of the current generation device, in particular via the associated electrode portion of the sensor electrode.

[0027] In a further advantageous configuration of the sensor device according to the application, the current generation device is an AC current generation device and is in particular designed to generate an AC current as a reference current. This makes it possible to easily realize the desired current flow from the first sensor electrode through the first capacitive element into the other, second sensor electrode, thereby determining the change in capacitive coupling or said coupling to the surroundings.

[0028] In a particularly advantageous configuration of the capacitive sensor device according to the application, in particular, the first sensor electrode can be electrically connected or connected to the current generation device, and a reference current can be applied to the first sensor electrode, in which case, in particular, a measurement variable dependent on a current difference between the reference current flowing into the first sensor electrode and the measurement current flowing out of the second sensor electrode can be captured, preferably can be measured quantitatively by the measurement device, and the current difference, or the approach and / or touch, or the virtually no approach or contact, can be derived by the evaluation device.

[0029] In a particularly advantageous configuration of the capacitive sensor device according to the application, the measurement device is further designed and configured to determine, in particular, a measurement variable dependent on a current difference between a current flowing in the sensor electrode to which the reference current is applied and a measurement current flowing in the other sensor electrode, in particular, a measurement variable dependent on a current difference between the reference current flowing in the associated electrode portion of the sensor electrode to which the reference current is applied and the measurement current flowing in the associated electrode portion of the other sensor electrode.

[0030] If, apart from a deviation caused by a small, in particular unavoidable, loss, the reference current and the measurement current are equal or almost equal in magnitude, it can be assumed that no human body part is located in the detection area of the sensor device, that is, in particular, no approach and / or touch, since the entire reference current applied to one of the two sensor electrodes, preferably to the first sensor electrode, can flow away during operation or use of the sensor device according to the application only via the other one of the two sensor electrodes, preferably only via the second sensor electrode, which results in a measurement current of almost equal magnitude.

[0031] In contrast, if a human body part is present in the detection area of the sensor device, for example, if a human hand approaches and / or touches the steering wheel comprising the sensor device according to the application, in particular, approaches and / or touches the first sensor electrode, the first capacitance formed by the first sensor electrode and the surrounding environment changes. In addition, a capacitance is formed between the human body part and the first sensor electrode, via which the reference current, in particular at least a part thereof, can likewise flow away, similar to a so-called "fault current" in a residual current circuit breaker (RCCB). As a result, the current flowing away via the other sensor electrode, in particular the second sensor electrode, is reduced, and thus the measurement current, which can be captured by the measurement device, is reduced, and the current difference between the reference current and the measurement current increases when a human body part is present in the detection area of the sensor device.

[0032] In this case, the current difference between the reference current and the measurement current is proportional to the distance between the body part and the sensor electrode, such that in particular the characteristic of the presence (proximity, touch, constant position in the detection area, etc.) can be derived from the current difference value.

[0033] By evaluating the current difference between the currents flowing in the two sensor electrodes, in particular the current difference between the currents flowing in the first sensor electrode and the second sensor electrode, in particular by determining the difference between the current flowing into the first sensor electrode and the current flowing away via the second sensor electrode, in a manner similar to the case of a residual current circuit breaker, it is possible to eliminate system biases as far as possible, thus reducing or even avoiding the negative effects of system biases.

[0034] This makes it possible, for example, to also recognize a slow release of the steering wheel, which cannot be distinguished from a temperature-dependent system bias (i.e. a temperature-dependent drift of the current measurement value) in the case of sensor devices known from the prior art in which only the current measured in absolute terms is used as a basis for recognizing proximity and / or touch.

[0035] In this way, in the sensor device according to the application, in many cases it is possible to dispense with a shielding element, in particular a thermal shielding element, by means of which a temperature-dependent drift, in particular a temperature-dependent change in the capacitance between the first sensor electrode and the second sensor electrode, to which the magnitude of the current flowing away via the second sensor electrode is directly dependent, can be reduced. The sensor device according to the application thus makes it possible to provide a simpler, lighter and generally also more cost-effective sensor device, in particular a simpler, lighter and in many cases also more cost-effective steering wheel comprising a capacitive sensor device.

[0036] Furthermore, with the sensor device according to the application, in many cases it is possible to easily recognize system biases, in particular temperature drifts, i.e. by comparing the two current measurement values with an earlier, i.e. temporally preceding, current measurement value and / or one or more associated reference values. If, for example, both current measurement values are in principle higher than the value at the beginning of the respective measurement series or than the associated reference current measurement value, there is a high probability of a system bias, for example a temperature drift due to the sensor electrodes being heated by the sun.

[0037] In a further particularly advantageous configuration of the sensor device according to the application, the evaluation device is preferably configured to identify, from the current difference between the reference current and the measurement current, in particular from the determined measurement variable, whether a body part is present in the detection region of the sensor device, in particular whether a human hand is present in the gripping region of the steering wheel; the sensor device, in particular the evaluation device, is configured to identify whether a body part is present in the detection region of the sensor device (yes / no). In this way, so-called "hand-on-switch detection" can be implemented in an advantageous manner. The sensor device according to the application enables particularly precise "hand-on-switch detection", since some systematic deviations that typically occur during operation of a capacitive sensor device are reduced or eliminated.

[0038] It is particularly preferred that the evaluation device of the sensor device according to the application is further configured to specify whether, in each case, a body part is present in the detection region in a proximity or a contact or a position-invariant presence.

[0039] In a further possible and particularly advantageous configuration of the sensor device according to the application, the evaluation device is configured to determine, in particular if the presence of a body part in the detection region has been identified, a variable characterizing the presence of the body part in the detection region of the associated sensor electrode, preferably a variable characterizing the proximity and / or the touch, in particular a variable characterizing the proximity of a human hand to the gripping region of the steering wheel and / or the touch of a human hand to the gripping region of the steering wheel, from the determined measurement variable and from the current difference between the reference current and the measurement current, on the basis of which said measurement variable is formed, for example a distance and / or a position of the body part.

[0040] In this case, the evaluation device is particularly preferably in particular configured to determine, from the determined measurement variable, a distance between the body part and the at least one first sensor electrode and / or a defined reference datum, in particular a distance between a human hand and the gripping region of the steering wheel. To this end, the sensor device is preferably designed such that the measurement variable is proportional to the distance between the body part and the sensor device, in particular to the distance between the body part and the at least one first sensor electrode.

[0041] In one development of the sensor device according to the application, the first electrode portion and the second electrode portion are in particular designed and arranged relative to one another such that the current flowing in the first electrode portion and the current flowing in the second electrode portion flow in opposite directions at least in the region of the coil and / or generate opposite magnetic fluxes in the coil, in particular such that, in the reference state of the coil, the current flowing in the first electrode portion and the current flowing in the second electrode portion at least partially, in particular completely, cancel one another out at least in the region of influence of the coil, and / or such that the opposite magnetic fluxes generated in the coil at least partially, in particular completely, cancel one another out. This makes it possible to largely eliminate systematic deviations, in particular those caused by the reference current, and thus to reduce or even avoid the negative effects of systematic deviations.

[0042] In the meaning of the application, a "reference state" is understood to mean in particular a state in which no capacitively active input means are present in the detection region of the sensor device.

[0043] In one possible and advantageous configuration of the sensor device according to the application, the measurement variable that depends on the current difference and that is generable or generated in the coil is a voltage, in particular a voltage that is generable in at least one winding of the coil, and the measurement means comprise a voltage measurement unit for measuring said voltage. This makes the configuration of the measurement means particularly simple and thus cost-effective, so that a particularly simple and cost-effective sensor device can be provided.

[0044] To this end, it has proven particularly advantageous for the coil to be designed in particular such that the first electrode portion of the first sensor electrode and the second electrode portion of the second sensor electrode are arranged at least partially relative to one another and relative to the coil, respectively, such that, by means of a current difference between a first current flowing in the first electrode portion and a second current flowing in the second electrode portion, a voltage that depends on the current difference, in particular a voltage that is proportional to the current difference, is generable or generated in the coil, in particular in at least one winding of the coil; the measurement variable that depends on the current difference is in particular a voltage drop or an associated voltage drop on at least one winding of the electronic coil.

[0045] If the coil, in particular at least one winding of the coil, comprises a first connection contact and a second connection contact, a particularly simple and advantageous configuration of the measurement means for this purpose is produced, the voltage that is generable or generated in the coil or at least one winding thereof by means of a current difference between a first current flowing in the first electrode portion and a second current flowing in the second electrode portion being generable or generated between the first connection contact and the second connection contact of the coil.

[0046] In order to capture the voltage in at least one winding of the coil, in particular the voltage drop across the winding, the sensor device, in particular the measuring arrangement, preferably comprises a voltage measuring unit, in particular for measuring the voltage generated or dropped between the first connection contact and the second connection contact of the coil.

[0047] It is particularly preferred that the measuring arrangement is further designed and configured to determine, from the measured voltage that has been generated in the coil, in particular by means of the current difference between the first current flowing in the first electrode portion and the second current flowing in the second electrode portion, the current difference on which the voltage is based.

[0048] In one particularly advantageous configuration of the sensor device according to the application, for this purpose, the first electrode portion and / or the second electrode portion is / are at least partially located within the coil, i.e. in the space within the coil, or is / are at least partially arranged inside the coil.

[0049] By way of example, the first electrode portion and / or the second electrode portion can at least partially extend within the coil, or can at least partially be guided through the coil and / or can pass through the interior of the coil, inside.

[0050] In this case, depending on the geometry of the coil, the first electrode portion and / or the second electrode portion can at least partially extend adjacent to, in particular parallel to, the turns, or within the turns of the at least one winding.

[0051] In this case, the electronic coil of the sensor device according to the application may, for example, be a toroidal coil and may, in the circumferential direction, be wound in an almost closed manner, or may extend only over a portion of the circumference.

[0052] Alternatively, the coil can also be a right-cylindrical coil or a cubic coil, i.e. a coil having a cylindrical outer contour of the winding, or a coil having a cubic base of the winding, i.e. a rectangular or square base of the winding. In this case, the at least one winding can extend in the shape of a frame, in particular, for example, along a quadrangular frame, and can be designed to be opened or closed in the "circumferential direction" of the frame, i.e. over the entire circumference of the frame. However, in principle, other geometrical shapes are also possible.

[0053] In the case of a toroidal coil, for example a so-called ring coil, the first electrode portion and / or the second electrode portion can at least partially extend parallel to or along a geometric center axis or path of the at least one winding, i.e. parallel to or along an axis or path that extends along the geometric center of the at least one coil. For example, if the coil is a toroidal coil and the center of the ring forms the geometric center, the first electrode portion and / or the second electrode portion can at least partially extend in particular along or parallel to an axis that intersects the geometric center of the coil and is perpendicular to the ring plane in which the coil extends, in a manner similar to the so-called Rogowski coil known in principle from the prior art.

[0054] If a current flows through the electrode portions of the sensor electrodes, a magnetic flux is generated in the coil and in turn causes a voltage or a current to be generated in the at least one winding of the coil, the generated voltage or the generated current depending on the current difference in the electrode portions.

[0055] In one possible configuration, in particular if the coil is a hollow coil, the first electrode portion and / or the second electrode portion can at least partially also be guided alternatively inside the at least one winding, i.e. inside the turns, in particular along or parallel to a central axis of the turns. This is, however, more complex in terms of production, since the electrode portions are correspondingly more complex to arrange.

[0056] For example, if the coil is a straight coil, the first electrode portion and / or the second electrode portion can be guided inside the turns along a longitudinal axis in the coil (assuming that the coil is a hollow coil).

[0057] The advantage of a toroidal coil is that if the electrode portions are arranged at or close to or parallel to the geometric center axis, the distance of the windings, in particular the average distance of the windings, is almost constant with respect to the electrode portions, in contrast to, for example, a rectangular frame-shaped coil. Furthermore, in a toroidal coil, a more uniform magnetic flux, and thus a more uniform measurement variable, can be generated, whether there is a core or not. Thus, taking this into account, in many cases a higher signal quality of the measurement signal or measurement variable, and thus a higher measurement accuracy, can be achieved with a toroidal coil. A toroidal coil is therefore particularly advantageous.

[0058] In a further possible and advantageous configuration of the sensor device according to the application, the measurement variable that depends on the current difference and that can be generated or is generated in the coil is an electric current, in particular an electric current flowing in the at least one winding of the coil, the measurement device preferably comprising a current measurement unit for measuring said electric current.

[0059] To this end, it has proven particularly advantageous if the coil is designed in particular in such a way that the first electrode portion of the first sensor electrode and the second electrode portion of the second sensor electrode are arranged in each case relative to one another, in each case relative to the coil, and coupled to the coil in such a way that, by means of a current difference between a first current flowing in the first electrode portion and a second current flowing in the second electrode portion, a current, in particular proportional to the current difference, can be generated or is generated in the coil, in particular in at least one winding of the coil.

[0060] If the coil, in particular at least one winding of the coil, comprises a first connection contact and a second connection contact, a particularly simple and advantageous configuration of the measuring device for this purpose is produced; by means of a current difference flowing between the first connection contact and the second connection contact in the coil, a current can be generated or is generated in the coil or at least one winding.

[0061] In order to capture the current in at least one winding of the coil, the sensor device, in particular the measuring device, preferably comprises a current measurement unit, in particular for measuring the current flowing between the first connection contact and the second connection contact in the coil.

[0062] It is particularly preferred that the measuring device is further designed and configured to determine an absolute current difference from the measured current flowing in the coil, in particular in the at least one turn, on the basis of which the absolute current difference is based. This allows further evaluation and implementation of further functions.

[0063] In this case, the current as a measured variable can in principle be acquired instead of or in addition to the voltage as a measured variable. The additional capture enables plasticization in a simple manner, so that a higher functional reliability can be ensured. Depending on the configuration of the sensor device, this can be implemented in particular by means of only one further measurement unit, and in particular without further additional components in the coil region.

[0064] In order to capture the voltage and the current as measured variables, it has proven particularly advantageous if at least one winding of the coil is a measurement winding, in which case the voltage falling across the measurement winding and generated depending on the current difference can in particular be captured by means of a corresponding voltage measurement unit, and the current flowing in the measurement winding can be captured by means of a corresponding current measurement unit.

[0065] If a current flows through the winding formed by the electrode portions, a magnetic flux is generated in the coil, which in turn leads to the generation of a voltage or a current in the measurement winding, the generated voltage or current depending on the current difference in the electrode portions.

[0066] It is particularly advantageous if the electronic coil is configured as follows: At least one winding of the coil is a measurement winding, and the first electrode part and the second electrode part in each case form a further winding of the coil, the individual windings being coupled to one another, in particular magnetically, in particular via a common coil core. This makes it possible to provide an advantageous sensor device according to the application in a particularly simple manner.

[0067] It is particularly preferred if the first electrode part and the second electrode part in each case form a further winding, which in each case has a plurality of turns, the electrode parts or the turns formed thereby being arranged in particular such that the current or magnetic flux generated in the coil by the current flowing in the electrode parts cancel one another out at least in a reference state of the sensor device. This makes it possible to reduce or even completely eliminate systematic influences on the measurement variable caused by the current flowing in the electrode parts, which has an advantageous effect on the measurement accuracy and robustness of the sensor device.

[0068] One particularly advantageous configuration of such a sensor device can be implemented in particular by means of a toroidal coil having a magnetic or magnetizable core, in particular a ferromagnetic core, i.e. a ring-shaped coil, preferably comprising a ring-shaped permanent magnet core. The individual windings or their turns, i.e. the measurement winding and the further winding formed by the electrode parts, are in particular preferably in each case wound around this core, i.e. around the same core.

[0069] Due to the current flowing in the electrode parts, in particular due to the current difference resulting from the respective arrangement of the windings, a magnetic flux dependent on the current difference is generated in the coil core, which in turn results in a current dependent on the current difference in the measurement winding or a voltage dependent on this current difference, and this magnetic flux can be captured as a measurement variable.

[0070] Alternatively, the electrode parts can also in each case at least partially form a further winding of a further coil, in particular a winding of a secondary coil, which however (in a similar manner to the case of a transformer) is coupled to the coil having the measurement winding (primary coil) via a common magnetic or magnetizable core, in particular a common ferromagnetic core, such that a current or a voltage is generated in the core via the coil core dependent on the current difference of the electrode parts in the measurement winding, and this current or voltage can be captured as a measurement variable.

[0071] Here, the number of turns of the further winding is selected relative to the number of turns of the measurement winding, in particular such that a sufficiently accurate measurement can be made, in particular a sufficiently strong measurement signal is generated for reliable and accurate capture of the measurement variable. Here, the absolute inductance ratio of the individual windings relative to one another is of greatest importance.

[0072] In some cases, for example, if the measurement winding and the further winding formed by the two electrode parts each have approximately the same inductance, for example in each case approximately L = 10 µH, this is advantageous. However, alternatively, a suitable inductance can also be, for example, L = 20 µH, L = 30 µH, L = 50 µH, L = 100 µH or more, for example L = 500 µH, L = 600 µH or up to L = 1000 µH, depending on the application.

[0073] In a further possible and advantageous configuration of the sensor device according to the application, the measurement variable which can also be generated or is generated in the coil depending on the current difference can also be a magnetic flux, in particular a magnetic flux flowing in the coil, in particular a magnetic flux flowing in the core of the coil, in which case the measuring device in particular comprises a magnetic flux measuring unit, for example at least one Hall sensor, for measuring said magnetic flux. This configuration requires particularly few windings and is therefore particularly advantageous in terms of the number of components required.

[0074] In this case, the magnetic flux as measurement variable can in principle be acquired in addition to or instead of the voltage and / or the current as measurement variable. The additional capture enables plasticization in a simple manner and thus a higher functional reliability can be ensured. Depending on the configuration of the sensor device, this can be achieved in particular by means of a further measuring unit, for example a simple Hall sensor, and in particular without further additional components in the coil region.

[0075] In some cases, it is advantageous if the measuring device also comprises a measurement signal amplification device, for example a corresponding amplifier circuit, in order to be able to carry out a sufficiently precise evaluation, regardless of whether the captured measurement variable is a voltage, a current and / or a magnetic flux. In many cases, a simple signal amplification is sufficient.

[0076] In order to capture the magnetic flux as measurement variable by means of the coil or in the coil, it has proven to be particularly advantageous if the coil comprises at least one first winding, a second winding and a magnetic or magnetizable core, in particular a ferromagnetic core, the first winding being formed by the first electrode part and the second winding being formed by the second electrode part. An additional measurement winding is not absolutely necessary. For example, by means of a Hall sensor element, the magnetic flux depending on the current difference generated in the iron core can be tapped off or captured directly.

[0077] A particularly simple configuration of such a sensor device can be achieved, for example, by means of a toroidal coil having a toroidal but not completely closed magnetic ring core having a small air gap between its loop ends, into which said air gap a Hall sensor element projects in order to capture the resultant magnetic flux flowing through this air gap in the circumferential direction.

[0078] In another particularly advantageous possible configuration of the sensor device according to the application, the sensor device can in particular comprise a plurality of first sensor electrodes, each first sensor electrode having an associated detection area, for example as described in DE 10 2019 120 136.5, in which case the plurality of first sensor electrodes can be electrically insulated from one another and arranged or arrangeable in a manner distributed over the detection area of the sensor device, for example distributed over at least a portion of the gripping area of the steering wheel, or distributed over the entire gripping area of the steering wheel, and in particular each first sensor electrode can have a defined reference current applied thereto, each first sensor electrode is preferably assigned to one or more sectors, and the sensor device is in particular configured to identify the presence of a body part, in particular to identify the approach and / or touch of a human hand, sector by sector in each case, and if the presence of a body part has been identified in at least one sector, the sensor device is in particular preferably configured to determine therefrom in particular the position of said body part. Thereby, in a particularly simple manner, in particular with few additional components, a position determination can be achieved, which makes it possible to implement comprehensive functions, for example comprehensive driver assistance functions in a vehicle.

[0079] If a plurality of first sensor electrodes is provided and if the sensor device is configured to identify the presence of a body part sector by sector in each case, the position of a body part located in the detection area of the sensor electrodes can be determined in the capacitive coupling to the surroundings or from the respectively resulting current difference and a measurement variable dependent on said current difference, in particular from the captured ratio of change, which is assigned to the individual sensor electrodes of the plurality of first sensor electrodes. Depending on the subdivision and arrangement of the individual sensor electrodes, a corresponding spatial resolution is possible. For this purpose, in particular at least two first sensor electrodes are arranged in a manner intermeshing with one another in each case, in particular as described in DE 10 2014 117 823 or DE 10 2014 117 821, here reference is expressly made to advantageous sensor electrode structures for this purpose.

[0080] Furthermore, one or more second sensor electrodes can also be provided, for example as also described in DE 10 2019 120 136.5, here reference is expressly made to advantageous sensor electrode structures for this purpose.

[0081] By means of the plurality of first and / or second sensor electrodes, not only the position of the body part in the detection area of the sensor device can be determined, but also an inhomogeneous heating of the sensor device, for example due to inhomogeneous solar radiation, and the resulting inhomogeneous distribution of the systematic deviations, which cannot be identified by conventional, in particular single, temperature sensors and thus cannot be compensated, can be determined. Thus, by means of the sensor device according to the application with this configuration with a plurality of first and / or second sensor electrodes, the recognition accuracy can be further improved.

[0082] In a further particularly advantageous configuration of the sensor device according to the application, the sensor device, in particular the evaluation device, is further configured to compensate at least one interference variable, in particular at least one interference variable due to a parasitic capacitance which changes relatively little in relation to the capacitance in the presence of an approach and / or touch of the detection area, in particular of a body part, and / or an interference variable based on a temperature-dependent systematic deviation, in a computational manner.

[0083] In a further advantageous configuration of the sensor device according to the application, the sensor device, in particular the current generation device and / or the measurement device and / or the evaluation device, comprises one or more circuits, in particular discrete circuits and / or switching elements, for example one or more operational amplifiers and / or one or more filter devices (low-pass, high-pass, band-pass) and / or one or more resistors, at least one circuit being preferably an integrated circuit (IC), in particular an application-specific integrated circuit (ASIC), the ASIC being particularly advantageous, firstly due to the expected low current and secondly due to the realizable compact configuration which requires little space.

[0084] In a further particularly advantageous configuration of the sensor device according to the application, the sensor device is configured to output at least one sensor signal containing signal information which characterizes the presence, preferably the approach and / or touch, in particular the hand of a person touching and / or approaching a grip area of a steering wheel, of a body part in the detection area of the sensor device, for example a sensor signal with signal information about whether a body part is located in the detection area of the sensor device, if present, preferably at what position in the detection area and / or in particular how far away from the grip area, and / or whether said body part is approaching or leaving or contacting the grip area. This makes it possible to realize particularly advantageous and comprehensive functions, for example comprehensive driver assistance functions.

[0085] A steering wheel, in particular for a vehicle, comprising a capacitive sensor device according to the application, characterized in that it comprises a sensor device designed according to the application. With the sensor device according to the application, a "hands-on detection" can be realized particularly advantageously, in particular in a particularly simple manner and in a particularly precise manner.

[0086] In a particularly advantageous configuration of the steering wheel according to the application, the steering wheel here comprises a metallic, electrically conductive steering wheel rim core which is designed to extend circumferentially around the rotational axis of the steering wheel, which steering wheel rim core at least partially, in particular completely, forms the second sensor electrode. This results in a particularly compact steering wheel construction and requires few components, since generally each steering wheel usually has a corresponding steering wheel rim core.

[0087] Instead of the steering wheel rim core at least partially serving as the second sensor electrode, at least one further electrode can also be provided as a replacement or in addition to the steering wheel rim core as the second sensor electrode.

[0088] For optimum functioning of the sensor device, if the steering wheel rim core serves as the second sensor electrode, then in this case the core is almost completely surrounded by the dielectric, in particular completely remote from a connection for contact with an electrical conductor through which the (measuring) current can flow. In this case, upstream of the shunt point at which the current flowing from the second sensor electrode is shunted in order to obtain a measurement variable which depends on the current difference, the steering wheel rim core is in particular not in contact anywhere else than via the aforementioned one conductor through which the current can flow and / or with earth. That is to say, in other words, the steering wheel rim core or the corresponding second sensor electrode should not be in contact upstream of the shunt point in the direction of current flow with anything else, for example the vehicle earth (GND or 0 V), in particular the earth terminal of the vehicle battery, in order to ensure the correct (measuring) current.

[0089] Particularly preferably, the steering wheel also comprises a particularly closed outer covering, preferably made of leather and / or plastic, preferably having a grip region which extends in particular over almost the entire outer covering. In this case, the detection region can extend over the entire grip region of the steering wheel or only over a part of the grip region.

[0090] In a further advantageous configuration of the steering wheel according to the application, the at least one first sensor electrode is preferably arranged between the outer covering and the dielectric of the steering wheel in the radial direction, in which case, if the steering wheel comprises a plurality of first sensor electrodes, preferably all the first sensor electrodes are arranged in each case between the outer covering and the dielectric of the steering wheel. In this way, a particularly good recognition can be achieved.

[0091] In a further advantageous configuration of the steering wheel according to the application, the steering wheel comprises at least one heating electrode, in particular a heating pad, at least one first sensor electrode being at least partially or completely formed by the at least one heating electrode. This results in a particularly compact steering wheel construction and requires few components, since generally each steering wheel usually has a corresponding steering wheel rim core.

[0092] Instead of one or more heating electrodes at least partially serving as one or more first sensor electrodes, at least one further electrode can also be provided which serves exclusively as a heating electrode as an alternative or in addition to one or more first sensor electrodes.

[0093] In a particularly advantageous configuration of the steering wheel according to the application, the at least one heating electrode here comprises two connected heating electrode portions, in particular a first connected heating electrode portion and a second connected heating electrode portion; the two connected heating electrode portions are in each case designed in particular in such a way, arranged in each case relative to one another in such a way, and arranged in each case relative to the coil in such a way, and coupled to the coil in such a way, that the heating current flowing in the first connected heating electrode portion and the heating current flowing in the second connected heating electrode portion at least in the region of the coil flow in opposite directions and / or in each case generate magnetic fluxes of opposite direction, so that the influence on the measurement variable which depends on the current difference in the electrode portions of the sensor electrodes and which can be generated or is generated in the coil by the heating currents is reduced or avoided; in particular in such a way that, during heating of the coil, the current flowing in the first connected heating electrode portion and the current flowing in the second connected heating electrode portion at least in the region of the influence of the coil at least partially, preferably completely, cancel one another out in the reference state of the sensor device. This makes it possible to largely eliminate systematic deviations, in particular caused by the heating currents, so that the negative effects of systematic deviations are reduced or even avoided.

[0094] In this case, the connected heating electrode portions can in particular extend in the manner of the electrode portions described above. However, particularly preferably, the connected heating electrode portions here are in each case guided to the first and / or second electrode portions in a similar or identical manner. For example, if the electrode portions extend along a geometric centre axis, the connected heating electrode portions preferably likewise extend along or parallel to this axis.

[0095] In contrast, for example, if the first electrode portion and the second electrode portion form a further winding of the coil, the connected heating electrode portions particularly preferably likewise form a further winding of the coil or a winding of a further coil (secondary coil) which is magnetically coupled to the measurement winding (primary coil) by a common coil core.

[0096] Here, the number of turns of the connected heating electrode portions is in each case particularly preferably selected relative to the number of turns of the measurement winding and / or the number of turns of the further winding formed by the electrode portions, so that sufficiently precise measurements can be made, in particular a sufficiently strong measurement signal of the measurement variable is generated, at least one measurement signal can be further processed sufficiently precisely after amplification.

[0097] It appears to be advantageous if the ratio of the inductance of the winding formed by the connecting heating electrode portions to the inductance of the measuring winding and / or the inductance formed by the electrode portions is at least 10:1, in particular at least 50:1, for example 60:1, in particular up to 100:1; preferably the inductances formed by the two windings connecting the heating electrode portions are preferably approximately equal, in particular such that in the reference state, during the heating operation, the magnetic flux generated by the heating current in the coil, in particular in the coil core, cancels out.

[0098] In the case of a steering wheel according to the application, the first sensor electrode can also be formed at least partially or completely by the heating electrode, in which case the connecting heating electrode portions of the heating electrode can form the electrode portions of the first sensor electrode.

[0099] However, the connecting heating electrode portions can also be designed separately from the electrode portions. This has the advantage that, under certain prerequisites, which are assumed in the case of a suitable configuration of the sensor device, at the same time, i.e. during the heating period, a capacitive coupling can be determined, in particular a measurement variable can be captured.

[0100] In a further advantageous configuration of the steering wheel according to the application, the sensor device can comprise a plurality of first sensor electrodes, for example as also described in DE 10 2019 120 136.5, to which reference is also explicitly made in this respect.

[0101] In one particularly advantageous configuration of the steering wheel according to the application, the sensor device can also be configured in particular for determining the surrounding angle of a hand on the steering wheel and / or for determining the position of a hand on the steering wheel in the circumferential direction, for example as described in DE 10 2014 117 823 or DE 10 2014 117 821, which have already been cited and to which reference is also explicitly made here for a more detailed explanation in this respect.

[0102] The method according to the application for operating a sensor device according to the application and / or for operating a steering wheel according to the application, in particular for recognizing the presence of a body part in the detection area of the sensor device and / or the steering wheel, in particular for recognizing a human hand approaching and / or touching the sensor device and / or the steering wheel, is characterized by the following steps:

[0103] providing a sensor device, and

[0104] - determining, by means of a coil of a measuring device of the sensor device, a measurement variable which depends on the current difference between a first current flowing in a first electrode portion of at least one first sensor electrode and a second current flowing in a second electrode portion of a second sensor electrode.

[0105] The method according to the application makes it possible to achieve a high recognition accuracy in a particularly simple manner, in particular with only a small negative influence of system deviations occurring during the use of the sensor device.

[0106] Here, the coil is designed in such a way that the first electrode part of the first sensor electrode and the second electrode part of the second sensor electrode are arranged in each case at least partially in such a way with respect to one another and in each case in such a way with respect to the coil that a measurement variable dependent on the current difference, in particular proportional to the current difference, is generated in the coil by means of the current difference between the first current flowing in the first electrode part and the second current flowing in the second electrode part.

[0107] In a preferred embodiment of the method according to the application, in this case, in particular before and / or during the determination of the measurement variable, a reference current is applied to at least one first sensor electrode or the associated second sensor electrode, in particular in such a way that a current difference occurs between the reference current flowing in one sensor electrode, in particular the electrode part thereof, and the measurement current flowing in the other sensor electrode, in particular the electrode part thereof, and a measurement variable dependent on the current difference is generated.

[0108] In order to generate the reference current, in particular by means of a corresponding current generation device, in particular an AC voltage is applied to the sensor electrode pair comprising the first sensor electrode and the associated second sensor electrode.

[0109] In an advantageous embodiment of the method according to the application, the determined measurement variable is preferably used in at least one further step as a basis for checking whether a body part is located in the detection region of the sensor device, in particular in the detection region of the first sensor electrode; if the current difference on which the determined measurement variable depends is different, in particular significantly different, from zero, and / or if the absolute value of the measurement variable exceeds a defined threshold value, a body part is located in the detection region of the sensor device, in particular in the detection region of the associated first sensor electrode; if the current difference is zero or almost zero, i.e. the reference current and the measurement current are equal within the scope of the measurement accuracy, and / or the absolute value of the determined measurement variable is below a defined threshold value, no body part is located in the detection region. In this way, an evaluation which is particularly simple and thus requires few resources can be achieved.

[0110] In a further advantageous embodiment of the method according to the application, in particular, preferably in at least one further step, a variable is determined for characterizing the presence of a body part in the detection area of the associated sensor electrode from the determined measurement variable, preferably a variable for characterizing the approach and / or the touch, in particular a variable for characterizing the hand of a person approaching the gripping area of the steering wheel and / or the hand of a person touching the gripping area of the steering wheel.

[0111] In a further advantageous embodiment of the method according to the application, in this case, preferably, assuming that the sensor device is correspondingly configured for this purpose, the measurement variable is determined sector by sector, and in particular, in a further step, assuming that the presence of a body part in the detection area of the sensor device has been identified, the position of this body part in the detection area is determined therefrom. This makes it possible to realize particularly advantageous further functions, for example comprehensive driver assistance functions.

[0112] In a further advantageous embodiment of the method according to the application, in particular, preferably in at least one further step, assuming that the sensor device is correspondingly configured for this purpose, at least one compensation variable is determined for the purpose of at least partially compensating at least one interference variable, and at least one determined characteristic variable is calculated using the at least one determined compensation variable. This makes it possible to realize particularly precise identifications.

[0113] In a further advantageous embodiment of the method according to the application, in particular, preferably in at least one further step, assuming that the sensor device is correspondingly configured for this purpose, at least one further step comprises generating and outputting at least one sensor signal containing signal information for characterizing the presence of a body part, in particular a hand of a person, touching and / or approaching, preferably the gripping area of the steering wheel, in the detection area of the sensor device. This makes it possible to realize particularly advantageous further functions, for example comprehensive driver assistance functions.

[0114] In a further advantageous embodiment of the method according to the application, the measurement variable is determined during operation of the heating device, in particular while a heating current is applied to the heating electrode, in particular to the connected heating electrode portion. This results in particularly advantageous functions of the steering wheel according to the application.

[0115] The vehicle according to the application is characterized in that it comprises a sensor device according to the application and / or a steering wheel according to the application and / or is designed to carry out a method according to the application.

[0116] The preferred embodiments presented with respect to the sensor device according to the application and their advantages accordingly also apply to the steering wheel according to the application, the method according to the application and the method according to the application. BRIEF DESCRIPTION OF DRAWINGS

[0117] Other features of the invention will be apparent from the claims, the accompanying drawings, and the description thereof. All features and combinations thereof mentioned in the foregoing description, as well as features and combinations thereof mentioned in and / or shown individually in the accompanying drawings, may be used not only in the combinations specifically indicated, but also in other combinations, or individually, provided that they are technically feasible in principle in each case, i.e., achievable.

[0118] The invention will now be explained in more detail based on several non-limiting preferred exemplary embodiments and with reference to the accompanying drawings.

[0119] In the accompanying drawing, schematically:

[0120] Figure 1 A first exemplary embodiment of the steering wheel according to the invention is shown from the driver's perspective.

[0121] Figure 2 A cross-sectional view in the thickness direction is shown according to the invention. Figure 1 The steering wheel in the middle, the steering wheel having a sensor system according to the invention,

[0122] Figure 3 It shows Figure 1 and Figure 2 A schematic block diagram of a sensor device according to the present invention in a steering wheel.

[0123] Figure 4 The diagram shows the use of partial perspective and partial schematic diagram. Figure 3 The sensor device or device according to the present invention Figure 1 and Figure 2 A first exemplary embodiment of the measuring device for a steering wheel according to the present invention,

[0124] Figure 5 A second exemplary embodiment of the measuring device is shown in partial perspective and partial schematic diagram.

[0125] Figure 6 It shows about Figure 5 An exemplary block diagram of the measuring device,

[0126] Figure 7a A block diagram illustrating a third exemplary embodiment of the measuring device is shown.

[0127] Figure 7b It shows the use of Figure 7a An exemplary embodiment of the coil of the measuring device, and

[0128] Figure 8 Another exemplary embodiment of a coil for a measuring device of a sensor device according to the present invention is shown. DETAILED DESCRIPTION

[0129] Figure 1 A first exemplary embodiment of a steering wheel 100 for a vehicle according to the present application is shown from the perspective of a driver, and Figure 2 is shown Figure 1 in a cross-sectional view in the thickness direction. Figure 3 is depicted Figure 1 and Figure 2 a related schematic block diagram of a first exemplary embodiment of a sensor device 10 according to the present application in a steering wheel 100 of

[0130] An exemplary embodiment of a steering wheel 100 according to the present application as shown in Figures 1 to 3 includes a capacitive sensor device 10 according to the present application, which is designed for identifying the presence of a body part 16, in particular a hand or a finger 16, in a detection area of the sensor device 10, in particular for identifying the presence of a human hand 16 in a grip area 14 of the steering wheel 100.

[0131] The sensor device 10 includes a first sensor electrode 11 formed by a heating electrode 12 of a heating structure, and a second sensor electrode 13 formed by a metal and electrically conductive steering wheel rim core 13. Alternatively, the second sensor electrode 13 can also be formed by a metal wire braid in the steering wheel 100, which is preferably part of the heating structure.

[0132] In this case, the first sensor electrode 11 or the heating structure 12 extends completely circumferentially along a surrounding direction 17 (see Figure 1 and Figure 2 ), and also completely circumferentially along a circumferential direction 18 (see Figure 1 ), which is indicated by the reference arrows associated with the reference numerals 17 and 18.

[0133] In other words, in this exemplary embodiment, the first sensor electrode 11 and the heating structure 12 extend almost over the entire grip area 14 of the steering wheel rim surface, which is almost directly arranged under the cover 15, in particular under a steering wheel cover 15, for example a leather cover 15. In this case, the sensor electrode 11 and the heating structure 12 are embroidered on a support (here not more specifically designated) consisting of a thin material, as is generally known in the prior art.

[0134] The metal steering wheel rim core 13 arranged in the core region of the steering wheel rim forms the support structure of the steering wheel 100. The dielectric 9 is located radially outside the steering wheel rim core 13, i.e. in the outer region of the steering wheel rim core 13, through which the first sensor electrode 11 is separated from the second sensor electrode 13 or the steering wheel rim core 13 and forms a first capacitive element K1 (see Figure 3 ). Furthermore, the first sensor electrode 11 together with the surrounding environment forms a second capacitive element K2 (see Figure 3 ).

[0135] In this case, the recognition of an approaching and / or receding human hand (which is represented in Figure 2 by the finger tip 16) can be achieved by means of the capacitive sensor device 10 according to the so-called "capacitive principle", which is based on the fact that in the detection region of the sensor device 10, in particular in the detection region of the first sensor electrode 11, there is a human body part 16, for example a hand or a finger 16, and the approach and / or the distance of the human hand 16 from the sensor electrode 11 also causes a change in the capacitive coupling of the sensor electrode 11 to the surrounding environment, which in turn influences the capacitive coupling between the first sensor electrode 11 and the second sensor electrode 13 or the steering wheel rim core 13, which can be captured in a metrological manner.

[0136] The change in the capacitive coupling of the first sensor electrode 11 to the surrounding environment caused by the human body part 16, for example the finger 16, is represented in Figure 2 by the field line-like lines between the points on the sensor electrode 11. From the captured change in the capacitive coupling of the first sensor electrode 11 to the second sensor electrode 13, it is then possible to deduce the presence of a human hand or finger 16 in the detection region or the approach and / or the distance of the hand.

[0137] In order to capture the change in the capacitive coupling between the first sensor electrode 11 and the second sensor electrode 13 in a metrological manner, i.e. to capture the change in the capacitance of the first capacitive element K1, which occurs when, for example, a body part of the driver 60, such as a finger 16, is present in the detection area of the sensor device 10, the sensor device 10 according to the application also comprises a current generation means 20 by means of which a reference current I1 can be applied to the first sensor electrode 11 via a first electrode portion 21, which is an electrical line 21 ; the current generation means 20 comprises at least one AC current source and is designed to apply a corresponding AC voltage to the paired first and second sensor electrodes 11, 13, which has, for example, a potential difference of 5 volts, so that an AC current I1 as reference current I1 can be applied to the first sensor electrode 11. In this case, the AC current I1 can also be superimposed on a DC current, for example from the heating current Ih+, Ih-, and thus can only be an AC current component I1.

[0138] If no body part 16 is located in the detection area of the sensor device 10, the reference current I1, i.e. the AC current I1 or the AC current component I1, flows almost completely via the first capacitive element K1 into the steering wheel rim core 13 and out of this steering wheel rim core 13 via the electrode portion 22 of the second sensor electrode 13, which is likewise an electrical line 22, which in particular constitutes the only electrical contact of the second sensor electrode 13 or the steering wheel rim core 13, for example in the direction of contact, that is to say I2 ~ I1 holds.

[0139] In contrast, if a body part 16 is located in the detection area of the sensor device 10, a part of the reference current I1, in particular a so-called fault current component I3, flows away via the second capacitive element, in particular in the direction of contact. Thus, only a small part of the reference current I1 flows into the steering wheel rim core 13 via the first capacitive element K1 and out of this steering wheel rim core 13 via the electrode portion 22. That is to say, in this case I2 ~ I1 - I3 holds.

[0140] Thus, in the case of the sensor device 10 according to the application, it can be identified whether a body part 16 is located in the detection area of the sensor device 10 by determining the current difference between the reference current I1 flowing into the first sensor electrode 11 and the measurement current I2 flowing out of the second sensor electrode I2 or the steering wheel rim core 13, i.e. by I1 - I2 or I2 - I1, or by determining a measurement variable which depends on the current difference I1 - I2 or I2 - I1 in the electrode portions 21 and 22.

[0141] In order to capture the measurement variable, which can in principle be a voltage UMESS, a current IMESS and / or a magnetic flux BMESS = B1-B2 or BMESS = B2-B1 (see Figures 4 to 8 The sensor device 10 according to the application comprises corresponding measurement means 30, which comprise electronic coils 31 for this purpose, as will be explained in particular below with reference to Figures 4 to 8 which will be explained in more detail.

[0142] Furthermore, an evaluation device 40 is provided, which together with the current generation device 20 and the measurement means 30 forms part of a control device 50, which comprises in particular at least one IC, in particular at least one ASIC. In this exemplary embodiment of the sensor device 10 according to the application, the evaluation device 40 is configured here to specify, depending on the determined measurement variable, in particular in combination with a measurement value captured in time prior, whether a proximity or a touch or a position-invariant presence of a body part 16 in the detection area of the sensor device 10 is present respectively.

[0143] The sensor device 10 is designed here such that the measurement variable is proportional to the distance between the body part 16 and the at least one first sensor electrode 11 or between the gripping area 14 of the steering wheel 100 respectively. In particular, the evaluation device 40 is configured to determine the distance between the body part 16 and the at least one first sensor electrode 11 or between the gripping area 14 of the steering wheel 100 from the determined measurement variable or its value.

[0144] Furthermore, the evaluation device 40 is configured to extract the interference variable caused by the parasitic capacitance and the interference variable of the system deviation determined by the temperature in a computational manner, which is small with respect to the change in capacitance in the event of a presence, in particular a proximity and / or a touch, of a body part 16 in the detection area of the sensor device 10. The system deviation determined by the temperature can be obtained, for example, by comparing a current measurement variable value with a measurement variable value captured in time prior. The parasitic capacitance in the steering wheel 100 can be extracted in a computational manner, for example, with the aid of a compensation variable determined and stored for the respective steering wheel structure 100.

[0145] Furthermore, this example of the sensor device 10 according to the application is configured to output a plurality of sensor signals S1, S2,..., each of which contains signal information characterizing the presence of a body part 16 in the detection area of the sensor device, for example whether a body part 16 is located in the detection area of the sensor device and, if so, where in the detection area and how far away from the gripping area 14. This makes it possible to implement particularly advantageous and comprehensive functions, for example comprehensive driver assistance functions.

[0146] Figure 4A sensor device 10 for a steering wheel 100 according to the application is shown in a perspective view and partially in a schematic view Figure 3 A first exemplary embodiment of a measuring device 30 according to the application for a steering wheel 100 according to the application is shown in a perspective view and partially in a schematic view Figure 1 and Figure 2 A first exemplary embodiment of a measuring device 30 according to the application for a steering wheel 100 according to the application is shown in a perspective view and partially in a schematic view

[0147] In this case, the first electrode portion 21 or the electrical connection line 21 and the second electrode portion 22 or the electrical connection line 22 are designed in such a way and arranged relative to one another and relative to the coil 31 in such a way that the electrical current I1 flowing in the first electrode portion 21 and the electrical current I2 flowing in the second electrode portion 22 flow in opposite directions at least in the region of the coil 31 and generate opposite magnetic fluxes B1 and B2, respectively, in the coil 31, which are indicated by the respective arrows.

[0148] In this case, the two electrode portions 21 and 22 are in particular arranged in such a way that, in a reference state of the coil 31, i.e. when no finger 16 or the like is located in the detection region of the sensor device 10, the electrical current I1 flowing in the first electrode portion 21 and the electrical current I2 flowing in the second electrode portion 22 cancel one another out at least in the region of the coil 31 and the opposite magnetic fluxes B1 and B2, respectively, generated in the coil 31 by them cancel one another out.

[0149] In the case of this coil 31 or in the case of this measuring device for a sensor device 10 according to the application, the first electrode portion 21 and the second electrode portion 22 are at least partially located within the coil 31, the two electrode portions 21 and 22 being guided through the interior of the coil 31 and extending parallel to a central axis (not shown) through the geometrical center Z of the coil.

[0150] In this case, the coil 31 is designed in such a way that the measurement variable generated in the coil 31 depending on the electrical current difference is a voltage UMeSS generated in the winding 32. In order to capture this voltage UMeSS, the measuring device 30 comprises a respective voltage measurement unit 36.

[0151] If a current I1 or I2 flows through the respective electrode portion 21 or 22, a magnetic flux B1 and a magnetic flux B2 are generated in the core 33 of the coil 31 and, in this case, act in opposite directions; if there is a current difference I1 - I2 or I2 - I1, only a magnetic differential flux B1 - B2 or B2 - B1 remains. Otherwise, the magnetic fluxes B1 and B2 cancel each other out. The magnetic differential flux has the effect that a current flow or an electric current IMess (see Figure 6 ) is generated in the winding 32, which results in a voltage drop across the winding 32 that is proportional to the magnetic differential flux and thus also to the current difference and can be measured as a voltage IMess by means of the current measurement unit 36 via the connection contacts 32A and 32B.

[0152] Figure 5 A second exemplary embodiment of the measuring device 30 with the coil 31 is shown, with respect to which, in Figure 6 a corresponding block diagram is shown, the measuring device 30 is constructed in principle similarly to the measuring device 30 shown in Figure 4 and operates according to the same functional principle. Accordingly, in each case, functionally identical components have the same or identical reference numerals.

[0153] In contrast to the measuring device 30 shown in Figure 4 in each case, a connection portion 23 of the heating electrode 12 is provided next to the two electrode portions 21 and 22, said connection portion returns the electric current Ih- from the heating electrode 12 and is also guided through the coil 31 in order to compensate for the fault current component or heating current component Ih+ or Ih- that flows away via this connection portion 23. With this arrangement, Figure 4 The sensor device 10 according to the application in

[0154] In this example, the first electrode portion 21 of the first sensor electrode 11 and the first connection heating electrode portion at least partially jointly form, i.e. are formed by the same electrical conductor portion 21. However, this connection heating electrode portion 23 for returning the electric current Ih- from the heating electrode 12 is formed separately and is arranged with respect to the output connection heating electrode portion 21 and with respect to the coil 31 and is coupled to the coil 31 such that the electric currents Ih+ and Ih- flowing into the connection heating electrode portions 21 and 23 or the magnetic fluxes Bh+ and Bh- generated by said electric currents are likewise compensated for. This makes it possible, inter alia, to compensate for deviations caused by the heating electrode 12.

[0155] In this exemplary embodiment, in addition to the voltage measurement of the voltage UMESS, the measurement current IMESS flowing in the measurement winding 32 can also be captured as a measurement variable, whereby the measurement variable can be pulsed; for this purpose, the measurement device 30 additionally comprises a current measurement unit (not shown here).

[0156] Figure 7a A block diagram of a fourth exemplary embodiment of a measurement device 30 is shown, Figure 7b One possible exemplary embodiment of a coil 31 for such a measurement device 30 is shown, in which case neither of the electrode sections 21 and 22 is guided as a normal conductor through the coil, but rather each is designed to be an additional winding, i.e. in addition to the measurement winding 32, each additional winding having an associated inductance LI and L2. Likewise, the connection of the heating electrode sections 24 (output) and 23 (return) is designed separately in each case and in each case as a separate winding with inductances L3 and L4, the separate windings of the coil 31 being coupled to one another via the common coil core 33.

[0157] The connection of the heating electrode sections 23 and 24 can be electrically connected via the connection nodes 23B and 24B to the respective heating electrode areas 12 in the steering wheel 100, respectively. Likewise, the first electrode section 21 and the second electrode section 22 can be electrically connected via the "B" connection nodes 21 B and 22B to the respective associated sensor electrodes 11 and 13 at the steering wheel, respectively. A reference current II can be applied via the "A" connection node 21 A to the first electrode section 21 and can flow as a measurement current I2 to ground (GND) via the connection node 22A of the second electrode section 22.

[0158] Via the connection nodes 32A and 32B of the measurement winding 32, the measurement voltage UMESS falling across this measurement winding and / or the measurement current IMESS flowing in the measurement winding 32 can be captured or measured.

[0159] This measurement device 30 functions according to the same principle: the current difference II - I2 or I2 - II generated by the currents II and I2 flowing in the electrode sections 21 and 22 induces a magnetic differential flux B1 - B2 or B2 - B1 in the core 33, which results in the generation of a voltage UMESS dependent on the current difference and / or a current IMESS dependent on the current difference in the measurement winding 32, which can be measured by the respective measurement unit 36 as a measurement variable.

[0160] Since the connecting heating electrode portions 24 and 23 are also designed as further windings of the coil 31, they are correspondingly arranged to act in opposite directions, via which the reference current components I1' and I1" flowing through the connecting heating electrode portions 24 and 23 are also compensated, so that the measur able measurement variable actually only depends on the capacitive coupling between the ambient environment and the first sensor electrode 11.

[0161] Furthermore, the heating currents Ih+, Ih- flowing in the connecting portions 23 and 24 also cancel each other out in each case. The measurement device 30 thus also has the advantage that heating and measurement can also be carried out simultaneously, which is intended to be indicated by the closed switches SW1 and SW2 (see Figure 6 ) and Figure 7a is not shown in the figure. This is achieved, inter alia., by the individual configuration of the individual connecting portions 21, 22, 23 and 24 and their arrangement in each case relative to one another, relative to the coil 31 and relative to the core 33.

[0162] However, simultaneous measurement and heating is premised on a respective suitable coordination of the individual inductances L1 to L4, otherwise the magnetic flux generated by the heating current in the coil core 33 would become too strong and dominant, so that no measurement signal would occur which is reasonably usable or assessable for the measurement variable. Here, a ratio of L1 ≈ L2 ≈ L(32) and L3 ≈ L4 has proven to be valuable, in particular L3:L1 ≈ 60, in particular L3:L1 = 60, in which case L1, L2 and L(32) can be, for example, 10 µH and L3 and L4 can be, for example, 600 µH.

[0163] Figure 8 A further exemplary embodiment of the coil 31 of the measurement device 30 for a sensor device 10 according to the application is shown, in which case the measurement variable which depends on the current difference and which can be generated in the coil 31 is the magnetic flux, in particular the magnetic differential flux B1-B2 or B2-B1, in the coil 31 or its core 33, and the measurement device 30 comprises a magnetic flux measurement unit 36, in this case a Hall sensor 37 for measuring said magnetic differential flux.

[0164] According to the application, the coil 31 likewise comprises at least one winding, in particular a first winding 21 formed from a first electrode portion 21 and a second winding 22 formed from a second electrode portion 22, and a magnetic or magnetizable core 33. Furthermore, in each case, two heating windings 23 and 24 acting in opposite directions are also provided. The measurement winding is not necessary, however. This makes the construction of the measurement device 30 particularly simple and requires particularly few constituent components.

[0165] For example, as Figure 8As shown, a particularly simple configuration can be implemented using a toroidal coil 31 having a toroidal but not completely closed magnetic ring core 33 with a small air gap between its loop ends, into which air gap a Hall sensor element 37 projects in order to capture the resultant magnetic differential flux B1-B2 or B2-B1 flowing through this air gap in the circumferential direction.

[0166] In an advantageous embodiment of the method according to the application for operating the sensor device 10 according to the application and / or the steering wheel 100 according to the application, in particular for identifying the presence of a body part 16 in the detection region of the sensor device 10 and / or the steering wheel 100, in particular for identifying the approach and / or the touch of a human hand 16, the following steps are carried out:

[0167] - applying, by means of the current generation device 20, a reference current I1, which is an AC current, to the first sensor electrode 11, and

[0168] - capturing, in particular measuring, by means of the measuring device 30, a measurement variable which depends on the current difference between the reference current I1 flowing in the first sensor electrode 11 and the measurement current I2 flowing in the second sensor electrode 13 and generated in the coil 31, in which case this measurement variable can in particular be the voltage UMeSS falling across at least one winding 32 of the coil 31, the current IMess flowing through this winding or the magnetic flux in the coil 31.

[0169] In a further step, in the case of the steering wheel 100, the determined measurement variable can be used as a basis for checking whether a body part 16 is located in the detection region of the sensor device, in particular in the detection region of the first sensor electrode 11; if the determined measurement variable or the current difference I1-I2 or I2-I1 on which said determined measurement variable is based is particularly significantly different from zero, or the absolute value of the determined measurement variable exceeds a defined threshold value, a body part 16 is located in the detection region of the sensor device 10, in particular in the detection region of the associated first sensor electrode 11; if the determined measurement variable is almost zero or zero, i.e. if the reference current I1 and the measurement current I2 are equal within the scope of the measurement accuracy and unavoidable losses, and / or the absolute value of the determined measurement variable is below a defined threshold value, no body part 16 is located in the detection region.

[0170] In a further step, from the determined measurement variable, a characteristic variable of the presence of a body part 16 in the detection region of the associated sensor electrode 11 can be determined, for example a variable which characterizes the approach and / or the touch, for example the distance or the touch position.

[0171] Furthermore, in the evaluation device 40, for the purpose of at least partial compensation of the at least one disturbance variable, a compensation variable can be determined and / or at least one determined characteristic variable can be calculated using the at least one determined compensation variable.

[0172] Thereafter, a plurality of sensor signals S1, S2,... can preferably be generated and output, each containing signal information characterizing the presence of the body part 16 in the detection region of the sensor device, which can be used for other functions or systems, for example a driver assistance system.

[0173] List of reference signs:

[0174] 10 Sensor device according to the application

[0175] 100 Steering wheel according to the application

[0176] 9 Dielectric

[0177] 11 First sensor electrode

[0178] 12 Heating electrode

[0179] 13 Steering wheel rim core; second sensor electrode

[0180] 14 Grip region of the steering wheel

[0181] 15 Steering wheel cover (steering wheel cover)

[0182] 16 Finger of a human hand

[0183] 17 Surrounding direction

[0184] 18 Circumferential direction

[0185] 20 Current generation device

[0186] 21, 22 Electric line 23, 24

[0188] 21A, 21B Connection node

[0189] 22A, 22B

[0190] 23A, 23B

[0191] 24A, 24B

[0192] 32A, 32B

[0193] 30 Measuring device

[0194] 31 Coil

[0195] 32 (Measuring) winding

[0196] 33 coil core

[0197] 36 measuring unit (voltage measuring unit, current measuring unit, magnetic measuring unit)

[0198] 37 Hall sensor

[0199] 40 evaluation device

[0200] 50 control device

[0201] 60 driver

[0202] B1 magnetic flux generated by reference current

[0203] B2 magnetic flux generated by measuring current

[0204] Bh+ magnetic flux generated by current in the direction of the heating electrode

[0205] Bh- magnetic flux generated by current flowing back from the heating electrode

[0206] GND ground potential (ground)

[0207] I1 reference current

[0208] I1', I1" reference current component

[0209] I2 measuring current

[0210] I3 fault current

[0211] Ih+ current in the direction of the heating electrode

[0212] Ih- current flowing back from the heating electrode

[0213] IMess measuring current

[0214] K1 first capacitive element

[0215] K2 second capacitive element

[0216] L1 winding with an inductance

[0217] L2 winding with an inductance

[0218] L3 winding with an inductance

[0219] L4 winding with an inductance

[0220] S1, S2 control signal

[0221] SW1, SW2 switch

[0222] UMess measurement voltage

[0223] Center of the Z-coil.

Claims

1. A capacitive sensor device (10) for identifying the presence of a human body part (16) in a detection area of ​​the sensor device (10), The sensor device (10) includes: At least one first sensor electrode (11) has an associated detection area and a first electrode portion (21); and a second sensor electrode (13), having a second electrode portion (22), The at least one first sensor electrode (11) and the second sensor electrode (13) are separated from each other by a dielectric (9) therebetween and form a first capacitor element (K1), and the at least one first sensor electrode (11) together with the surrounding environment further forms a second capacitor element (K2). The sensor device (10) further includes a measuring device (30) designed and configured to determine a measurement variable (UMess, IMess; B1-B2; B2-B1) that depends on the current difference (I1-I2; I2-I1) between a first current (I1) flowing in a first electrode portion (21) of the at least one first sensor electrode (11) and a second current (I2) flowing in a second electrode portion (22) of the second sensor electrode (13). The measuring device (30) is characterized in that it includes an electronic coil (31) having at least one winding, the coil (31) being designed such that the first electrode portion (21) of the first sensor electrode (11) and the second electrode portion (22) of the second sensor electrode (13) are arranged relative to each other in such a way in each case, and relative to the coil (31) in such a way in each case, and coupled to the coil (31) in such a way that the current difference (I1-I2) depends on the first current (I1) flowing in the first electrode portion (21) and the second current (I2) flowing in the second electrode portion (22); The measured variables (UMess, IMess; B1-B2; B2-B1) of I2-I1 are generated or generated in the coil (31) by the current difference (I1-I2; I2-I1).

2. The sensor device (10) as described in claim 1, characterized in that, The sensor device (10) is also designed and configured to identify the presence of a human body part (16) in the detection area of ​​the sensor device (10) based on determined measurement variables (UMess, IMess; B1-B2; B2-B1), and the sensor device (10) includes an evaluation device (40) for this purpose.

3. The sensor device (10) as described in claim 1 or 2, characterized in that, The sensor device (10) further includes a current generating device (20), at least one of the two sensor electrodes (11, 13) is electrically connected or connected to the current generating device (20), and a reference current (I1) can be applied to at least one of the two sensor electrodes (11, 13) through the current generating device (20), wherein the current generating device (20) is an AC current generating device.

4. The sensor device (10) as described in claim 3, characterized in that, The measuring device (30) is also designed and configured to determine a measuring variable (UMess, IMess; B1-B2; B2-B1) that depends on the current difference (I1-I2; I2-I1) between the current (I1) flowing in the sensor electrode (11) to which the reference current (I1) is applied and the measuring current (I2) flowing in another sensor electrode (13).

5. The sensor device (10) as claimed in claim 1, characterized in that, The first electrode portion (21) and the second electrode portion (22) are designed and arranged relative to each other such that the current (I1) flowing in the first electrode portion (21) and the current (I2) flowing in the second electrode portion (22) flow in opposite directions at least in the region of the coil (31) and / or generate magnetic fluxes (B1, B2) in opposite directions in the coil (31).

6. The sensor device (10) as claimed in claim 1, characterized in that, The measured variable (UMess, IMess; B1-B2; B2-B1) that depends on the current difference (I1-I2; I2-I1) and can be generated or generated in the coil (31) is voltage (UMess), and the measuring device (30) includes a voltage measuring unit (36) for measuring the voltage (UMess).

7. The sensor device (10) as described in claim 6, characterized in that, The first electrode portion (21) and / or the second electrode portion (22) are at least partially located within the coil (31).

8. The sensor device (10) as claimed in claim 1, characterized in that, The measured variables (UMess, IMess; B1-B2) that can be generated or generated in the coil (31) depend on the current difference (I1-I2; I2-I1) and are generated or generated in the coil (31). B2-B1) is current (IMess), and the measuring device (30) includes a current measuring unit for measuring the current (IMess).

9. The sensor device (10) as described in claim 8, characterized in that, At least one winding (32) of the coil (31) is a measuring winding (32), and the first electrode portion (21) and the second electrode portion (22) respectively form another winding of the coil (31).

10. The sensor device (10) as claimed in claim 1, characterized in that, The measured variables (UMess, IMess; B1-B2) that can be generated or generated in the coil (31) depend on the current difference (I1-I2; I2-I1) and are generated or generated in the coil (31). B2-B1) is the magnetic flux (B1-B2; B2-B1), and the measuring device (30) includes a magnetic flux measuring unit (36; 37) for measuring the magnetic flux (B1-B2; B2-B1).

11. The sensor device (10) as claimed in claim 10, characterized in that, The coil (31) includes at least one first winding, a second winding and a magnetic or magnetizable core (33), the first winding being formed by the first electrode portion (21) and the second winding being formed by the second electrode portion (22).

12. A steering wheel (100) including a capacitive sensor device (10), characterized in that, The sensor device (10) is designed as described in any one of claims 1 to 11.

13. The steering wheel (100) as claimed in claim 12, characterized in that, The steering wheel (100) includes at least one heating electrode (12), the at least one heating electrode (12) including two connecting heating electrode portions (23, 24), and the two connecting heating electrode portions (23, 24) are designed in each case, and arranged relative to each other in each case, and arranged relative to the coil (31) in each case, and coupled to the coil (31) in such a way that the heating current (Ih+) flowing in the first connecting heating electrode portion (24) and the heating current (Ih-) flowing in the second connecting heating electrode portion (23) flow in opposite directions at least in the region of the coil (31) and / or generate magnetic flux (Bh+, Bh-) in opposite directions in each case, thereby causing the heating current (Ih+, Ih-) to affect the measured variables (UMess, IMess; B1-B2); The effects of B2-B1 are reduced or avoided, and the measured variable can be generated or generated in the coil (31) and depends on the current difference (I1-I2; I2-I1) in the electrode portions (21, 22) of the sensor electrodes (11, 13).

14. A method for operating the sensor device (10) as claimed in any one of claims 1 to 11, characterized by the following step: Provide sensor device (10), and The measurement variables (UMess, IMess; B1-B2; B2-B1) are determined by means of the coil (31) of the measuring device (30) of the sensor device (10), which depend on the current difference (I1-I2; I2-I1) between a first current (I1) flowing in the first electrode portion (21) of the at least one first sensor electrode (11) and a second current (I2) flowing in the second electrode portion (22) of the second sensor electrode (13).

15. A method for operating a steering wheel (100) as described in claim 12 or 13, characterized by the following step: Provide sensor device (10), and The measurement variables (UMess, IMess; B1-B2; B2-B1) are determined by means of the coil (31) of the measuring device (30) of the sensor device (10), which depend on the current difference (I1-I2; I2-I1) between a first current (I1) flowing in the first electrode portion (21) of the at least one first sensor electrode (11) and a second current (I2) flowing in the second electrode portion (22) of the second sensor electrode (13).

16. The method as described in claim 15, characterized in that, The steering wheel (100) includes a heating device, which depends on the current difference (I1-I2) between a first current (I1) flowing in a first electrode portion (21) of the at least one first sensor electrode (11) and a second current (I2) flowing in a second electrode portion (22) of the second sensor electrode (13). The determination of the measured variables (UMess, IMess; B1-B2; B2-B1) of I2-I1 is performed during the operation of the heating device.

17. A vehicle including a capacitive sensor device, characterized in that, The sensor device (10) is designed as described in any one of claims 1 to 11.

18. A vehicle comprising a steering wheel (100) as claimed in claim 12 or 13.

19. A vehicle including a capacitive sensor device, characterized in that, The vehicle is configured to perform the method as described in any one of claims 14-16.

Images