Detection device for a steering wheel of a motor vehicle, steering wheel having a detection device, and method

Abstract

The invention relates to a detection device (6) for a steering wheel (2) of a motor vehicle (1) for detecting at least part of a hand (4) in a gripping region of the steering wheel (2), and to the steering wheel (2) and a method. The detection device (6) comprises at least one electrode (10) and / or at least one group (11) of electrodes (10) and a measuring device (14). The measuring device (14) is designed to measure an input (15) and an output (16) of the at least one electrode (10) and / or of the at least one group (11) of electrodes (10) in a parallel manner, thus increasing a detection sensitivity of the detection device (6), at least for a predefined period of time.

Description

[0001] Detection device for a steering wheel of a motor vehicle, steering wheel with a detection device and method

[0002] The invention relates to a detection device for a steering wheel of a motor vehicle for detecting at least part of a hand within a gripping area of ​​the steering wheel. The invention also relates to a steering wheel with such a detection device and a method for detecting a hand on a steering wheel with such a detection device.

[0003] A motor vehicle may have a steering wheel into which a detection device is integrated. The detection device is designed to determine whether or not a user of the motor vehicle is currently touching the steering wheel with at least part of a hand or is gripping it with at least one hand. The detection device can therefore provide a hand recognition function, which can alternatively be referred to as hands-on detection (HOD). Checking whether the user is touching the steering wheel with at least part of their hand or is gripping the steering wheel with at least their hand can be carried out, for example, to determine whether the user is ready to resume manual steering of the motor vehicle if the steering of the motor vehicle is currently being carried out by an at least partially automatic, in particular fully automatic function, for example a driver assistance system.The user is therefore preferably a driver of the motor vehicle.

[0004] The detection device can be designed as a capacitive detection device. It typically has a capacitive sensor. The capacitive sensor comprises at least one electrode or group of electrodes. The at least one electrode or group of electrodes can, for example, be designed as a mat arranged around a steering wheel skeleton. Using the mat and thus using the at least one electrode or group of electrodes, a heating function for the steering wheel can also be implemented, for example. The heating function can, for example, specify and implement an increase in the temperature of the steering wheel to a predetermined target temperature.

[0005] If the detection device has a plurality of electrodes, for example, it typically switches back and forth between them and checks are carried out at a specific time for exactly one of the electrodes to determine whether or not at least part of the user's hand is located within its detection range. For this purpose, the detection device has, for example, a plurality of different interfaces, whereby one interface per electrode or several interfaces per electrode can be provided. Measurement information is then recorded one after the other at each of the interfaces. If it is determined for the plurality of interfaces that at least part of the user's hand is located within the gripping range of the steering wheel, the hand recognition is evaluated as successful, for example.

[0006] However, such a detection device is often not designed to detect only individual fingers within the reach of the steering wheel, since the measurement information acquired at each interface is difficult to distinguish from the underlying surface, for example, due to components of the steering wheel. The detection device should therefore be operated differently to also detect individual fingers within the reach of the steering wheel.

[0007] It is the object of the invention to provide a detection device for a steering wheel of a motor vehicle which has a high detection sensitivity.

[0008] The problem is solved by the subject matter of the independent patent claims.

[0009] A first aspect of the invention relates to a detection device for a steering wheel of a motor vehicle for detecting at least part of a hand within a gripping area of ​​the steering wheel. Thus, the detection device can detect whether, for example, a driver of the motor vehicle or another occupant of the motor vehicle is touching the steering wheel with individual fingers of their hand or, for example, is gripping it with at least one hand, in particular with both hands. The gripping area is to be understood as a detection area of ​​the detection device, which preferably comprises a surface of a steering wheel rim of the steering wheel. The person touching the steering wheel is referred to below as the user.

[0010] The detection device comprises at least one electrode and / or at least one group of electrodes and a measuring device. According to the invention, the detection device can therefore have only a single electrode. Alternatively or additionally, it is possible for the detection device to comprise multiple electrodes, i.e., for it to have multiple individual electrodes, a group of electrodes, and / or multiple groups of electrodes. The measuring device is designed to measure an input and an output of the at least one electrode and / or of the at least one group of electrodes in parallel. With parallel measuring, simultaneous measuring takes place. If the detection device comprises the only electrode, the measuring device is designed to measure the input and the output of the only electrode in parallel and thus simultaneously.If the detection device has at least one group of electrodes, the measuring device is designed to measure the input and the output of the at least one group of electrodes in parallel and thus simultaneously. This has the effect of increasing the detection sensitivity of the detection device at least for a predetermined period of time. The predetermined period of time is the period of time in which the input and output are measured in parallel. In the case of a single electrode, the input and output can be two different ends of the electrode, which are arranged at opposite ends of the electrode. The input and output can alternatively be referred to as the first and second interfaces of the at least one electrode or of the at least one group of electrodes.

[0011] During measurement, for example, an impedance is measured as measurement data or measurement information, wherein the detection device has the measured impedance. The impedance, in particular a capacitive component of the impedance, is therefore preferably measured simultaneously at two different locations within the detection device. The impedance drops particularly at the input or output of the electrode compared to a reference point of an electronic circuit of the detection device. Since measurements are taken simultaneously at the input and output, simultaneously recorded measurement data or measurement information can be evaluated together, so that, for example, a capacitive component of the impedance measured at a specific point in time is essentially measured twice. The total recorded impedance is therefore essentially doubled.Essentially, in the sense of the invention, deviations of less than 1 percent, 3 percent, 5 percent, 10 percent, in particular 20 percent between the measured data or of a doubled value. Because more measurement data or measurement information is available, a weaker signal can be detected than by means of a detection device that measures the electrode or group of electrodes one after the other and thus serially at the input and output. In this way, the desired increase in detection sensitivity is achieved more reliably and easily. A detection device for a steering wheel of a motor vehicle is therefore provided which has a high detection sensitivity. An advantageous embodiment provides that the measuring device is designed to add input information measured during measurement at the input and output information measured during measurement at the output to form a total information item.The measuring device is also designed to evaluate the total information to detect at least part of the hand. The input information and the output information can alternatively be referred to as first interface information and second interface information, respectively. If, for example, input information of 20 picofarads is measured for a hand grasping the steering wheel during a measurement at the input, the total information is essentially 40 picofarads, since the input information or the output information is essentially doubled, since the output information or the input information is also measured and taken into account. This is particularly relevant when only individual fingers are touching the steering wheel. For three individual fingers, for example, input information of 4 picofarads is typically measured. The total information is then essentially 8 picofarads.This clearly shows that, in order to recognize individual fingers of the hand, adding the input and output information together to form the total information contributes to their recognition. This is reliably achieved by approximately doubling the measurement data or measurement information.

[0012] A further embodiment provides that the detection device has a first electrode and a second electrode. The measuring device is designed to measure the first electrode as input information and the second electrode as output information. It is therefore not necessary to measure the input and output of a single electrode; instead, each individual electrode can be measured exactly once, thus providing either the input information or the output information. However, here too, two pieces of measurement data or measurement information are recorded in parallel and added together, so that here too an increase in the measurement data or the measurement information is achieved. This can be applied analogously to a first group of electrodes and a second group of electrodes as an alternative or additional embodiment of the detection device.

[0013] An additional embodiment provides that the detection device comprises a plurality of second electrodes. The measuring device is designed to measure the respective second electrode as respective output information and to add the input information with the plurality of output information to form the total information. If, for example, more than two electrodes are provided, in particular three or four electrodes, the impedance, in particular the capacitive component of the impedance, can be measured simultaneously for each of the electrodes. All measurement data obtained in this way are summed in order to obtain a particularly high overall and thus easily evaluated total information. The described detection device is therefore not limited to exactly one input and output, but can be expanded as desired. It is thus adaptable to a wide variety of electrode configurations and designs.Alternatively or additionally, it is possible for more than two groups of electrodes to be provided, the design otherwise being analogous to that described for multiple electrodes.

[0014] Furthermore, one embodiment provides for a switch to be arranged at the input and output, such that the detection device is designed to individually measure the input and output of the at least one electrode and / or the at least one group of electrodes. It can therefore be provided that an electronic switch, in particular a multiplex switch, is provided at least at the input and at the output. This can be controlled in such a way that, for example, only the input information is measured when the switch arranged at the input is closed, whereas no output information is measured if the switch arranged at the output is closed at the same time. Subsequently, for example, when the switch at the output is closed and the switch at the input is open, the output information can be measured individually and thus without input information being measured at the same time.Such a single acquisition is suitable, for example, for location-dependent measurement of the respective electrode and / or group of electrodes. It can then be determined specifically where the part of the hand or the entire hand is located on the steering wheel.

[0015] For this purpose, it is preferable to switch at least temporarily from a parallel mode, in which measurements are taken in parallel at the input and output, to a serial mode, in which measurements are taken sequentially at the input and output and thus serially, in order to be able to carry out the location-dependent measurement.

[0016] In this context, one embodiment provides that the measuring device is configured to measure each electrode and / or group of electrodes individually by appropriately controlling the individual switches and to determine position information by evaluating the measurement data or measurement information acquired in this process. This information describes a position of at least part of the hand within the gripping range of the steering wheel.It is therefore possible, for example, that if the measurement data or measurement information for the first electrode or group of electrodes, i.e., for example, the input information, indicates that the user is touching the steering wheel with their hand, but the measurement data or measurement information for the second electrode or group of electrodes, i.e., for example, the output information, indicates that the user is not touching the steering wheel, it is determined that the hand is probably only in the area of ​​the first electrode and not in the area of ​​the second electrode. If, for example, the electrodes or groups of electrodes are arranged on opposite sides around the steering wheel skeleton, this indicates that the hand is not gripping the steering wheel, but is only touching one side and / or, in particular, is supporting itself on one side of the steering wheel.This information can be further evaluated by the function, in particular the driver assistance system, if necessary. This allows details about the position of at least part of the hand within the gripping area of ​​the steering wheel to be obtained, in particular to distinguish between a wraparound grip and a one-sided touch.

[0017] An additional embodiment provides that the measuring device is designed to vary a frequency of an alternating voltage applied to the electrode or group of electrodes after the parallel measurement of the input and output of the electrode or group of electrodes. It is also designed to repeat the parallel measurement at the varied frequency and, by evaluating the repeated parallel measurement, to determine whether or not detection of at least part of the hand in the gripping area of ​​the steering wheel can be confirmed by evaluating the previously performed parallel measurement. Thus, the input information and the output information can be measured in parallel, the frequency of a signal applied to the electrode can then be changed, and the parallel measurement can be repeated at the input and output.If these two consecutive parallel measurements yield the same results regarding the detection of at least part of the hand within the reach of the steering wheel, the repeated measurement confirms the first measurement. This confirmation can, for example, be a prerequisite for providing the detection of at least part of the hand within the reach of the steering wheel to the function, such as the driver assistance system of the motor vehicle.

[0018] However, if the two parallel measurements yield different results, it can be concluded that the first or second parallel measurement may have been a false detection. Preferably, another parallel measurement is then performed. Ultimately, this provides a reliable means of confirming the results of the hand detection function for the steering wheel.

[0019] It is assumed here that the detection device is operated with alternating current. The detection device can therefore have an alternating voltage source. Alternatively or additionally, the alternating voltage source is assigned to the steering wheel and / or the motor vehicle in which the steering wheel is located and provides energy for the detection device. In the case of the hand in the gripping range of the steering wheel, at least one capacitance of the electrode or group of electrodes changes. This change is described by the measurement data or the measurement information, i.e., by the input information and the output information.

[0020] Preferably, the described variation of the applied alternating voltage only occurs if the first parallel measurement determined that a hand was within the reach of the steering wheel. Alternatively or additionally, it is possible for the parallel measurement to be performed repeatedly, especially continuously, and thus repeated.

[0021] In a further exemplary embodiment, it is provided that the measuring device is designed to measure background information that can always be measured without at least part of the hand being arranged in the gripping area of ​​the steering wheel. By selecting at least one component of the detection device, in particular a protective element, the background information is kept smaller than a predetermined limit. It is therefore provided that, for example, by selecting the components used and in particular added protective elements, the background information, i.e. a background that results, for example, from the steering wheel alone without electrodes or other capacitances of electronic components, is kept so small that it lies below the predetermined limit. The limit can be, for example, 180 picofarads. Higher or lower background information is possible.Ultimately, this has the advantage that, with the smallest possible background information, which is smaller than the existing threshold value, the detection range for the measurement data or the measurement information until saturation is reached is particularly large compared to a larger background information. This allows the hand, or at least part of it, to still be reliably detected despite, for example, essentially doubling the input and output information for the total information. This further increases the sensitivity of the detection device.

[0022] An additional embodiment provides that the measuring device is designed to measure the electrode or group of electrodes by performing a voltage and / or current measurement at least by means of an analog-to-digital converter and to evaluate the measurement data acquired thereby. Thus, an analog-to-digital converter (ADC) can be provided as a component and thus part of the detection device. The analog-to-digital converter is designed to perform a voltage and / or current measurement and subsequently provide the input information and / or the output information. This is a particularly cost-effective and simple embodiment of the measuring device.

[0023] Alternatively or additionally, one embodiment may provide for the measuring device to be configured to acquire and evaluate time information for measuring the electrode or group of electrodes, wherein the time information describes how long it takes for a given current source to reach a given voltage. This example assumes that a current source, i.e., an energy source, is fixedly specified for the detection device, so that, for a given target voltage, it is possible to wait to see how long it takes until this voltage has actually been built up. Based on this time, the magnitude of the input information and / or output information can be determined.

[0024] Furthermore, an alternative or additional embodiment provides that the measuring device is configured to output a frequency signal for measuring the electrode and / or group of electrodes and to detect and evaluate any resulting phase shift. The frequency is specified, for example, by the AC voltage source, i.e., the energy source. Ultimately, this check determines how the current flowing through the detection device reacts with respect to the phase shift and what value the phase shift assumes. This is another reliable option for designing the measuring device.

[0025] Ultimately, there are numerous possibilities for how the measuring device can measure the electrode and / or group of electrodes. The detection device is therefore versatile in this regard. Another aspect of the invention relates to a steering wheel with a detection device as described above. The steering wheel is preferably installed in a motor vehicle.

[0026] An embodiment of the steering wheel according to the invention provides that the respective electrode is arranged on at least a partial region of an inner side of the steering wheel, which faces a steering wheel hub of the steering wheel. Alternatively or additionally, the respective electrode is arranged on at least a partial region of an outer side of the steering wheel opposite the inner side. Alternatively or additionally, the electrode is arranged on at least a partial region of an underside of the steering wheel, which faces a steering column of the steering wheel. Alternatively or additionally, the electrode is arranged on at least a partial region of an upper side of the steering wheel opposite the underside. In other words, the electrode can be arranged at the front or rear (top side or bottom side) when viewed from above the steering wheel and / or outside or inside (outside or inside) when viewed in a radial direction starting from the steering wheel hub.Several zones can be formed, each with two electrodes or groups of electrodes arranged opposite each other. Each zone covers, for example, a quarter of the steering wheel rim. An electrode or group of electrodes can extend over two adjacent zones and partially overlap with two other electrodes or groups of electrodes. For example, there need not be an electrode that extends over the entire inside, the entire outside, the entire underside and / or the entire top side of the steering wheel, but it can only extend over part of the corresponding side. Ultimately, numerous different arrangements of individual and multiple electrodes or groups of electrodes are possible on the steering wheel. The arrangement of the electrodes or groups of electrodes is therefore particularly versatile.

[0027] The electrode or group of electrodes can be integrated into a heating mat or a detection mat and arranged, for example, around a steering wheel core. This can be separated from the steering wheel core, for example, by a dielectric material.

[0028] According to an additional embodiment of the steering wheel according to the invention, the steering wheel is provided with a control device. The control device is designed to control the electrode and / or group of electrodes in a first operating mode for heating the steering wheel. The control device is also designed to control the electrode and / or group of electrodes in a second operating mode for detecting at least part of a hand in the gripping area of ​​the steering wheel. The two operating modes can be activated or are activated alternately.

[0029] Preferably, in the first operating mode, the switches at the input and output of the electrode or group of electrodes are open. In addition, a switching device can be provided which is designed to switch between the first operating mode and the second operating mode. For example, a time interval for which the first operating mode is activated can be dependent on a desired temperature change of the steering wheel, which is to be changed by heating the steering wheel. The second operating mode typically comprises a time interval in the range of milliseconds, in particular between 100 milliseconds and 500 milliseconds. This time interval is selected in particular depending on how long it takes until at least one and preferably several measurements of the electrode or group of electrodes have been carried out.It is preferably provided that at least two parallel measurements can be performed to verify the result of the first measurement before switching back to the first operating mode. Ultimately, the detection of at least part of the hand within the gripping area of ​​the steering wheel is not performed continuously while the steering wheel's heating function is activated; instead, these two steering wheel functions alternate.

[0030] A further aspect of the invention relates to a motor vehicle with such a steering wheel. The motor vehicle is, for example, a passenger car, a truck, a bus, a motorcycle, and / or a moped.

[0031] The invention further relates to a method for detecting a hand on a steering wheel using a detection device. The detection device comprises at least one electrode and / or at least one group of electrodes and a measuring device. Using the measuring device, an input and an output of the at least one electrode and / or the at least one group of electrodes are measured in parallel, thereby increasing the detection sensitivity of the detection device, at least for a predetermined period of time.

[0032] A further aspect of the invention relates to a control device for a steering wheel of a motor vehicle. The control device is designed to control the measuring device and / or further components of the detection device, in particular to carry out the described method. The control device has a processor device. The processor device can have at least one microprocessor and / or at least one microcontroller and / or at least one FPGA (Field Programmable Gate Array) and / or at least one DSP (Digital Signal Processor). Furthermore, the processor device can have program code, which can alternatively be referred to as a computer program product. The program code can be stored in a data memory of the processor device.

[0033] A further aspect of the invention relates to a computer program product. The computer program product is a computer program. The computer program product comprises instructions that, when executed by a computer, such as the steering wheel control devices, cause the computer to perform the corresponding steps of the method according to the invention, in particular relating to the measuring device of the detection device.

[0034] The exemplary embodiments described in connection with the detection device according to the invention or the steering wheel according to the invention, individually and in combination with one another, apply accordingly, to the extent applicable, to the method according to the invention, the motor vehicle according to the invention, the control device according to the invention, and the computer program product according to the invention. The invention encompasses combinations of the described exemplary embodiments.

[0035] Showing:

[0036] Fig. 1 is a schematic representation of a motor vehicle with a steering wheel;

[0037] Fig. 2 is a schematic representation of a detection device for a steering wheel of a motor vehicle;

[0038] Fig. 3 is a schematic representation of a measurement data curve of a detection device for a steering wheel;

[0039] Fig. 4 is a schematic representation of an arrangement of electrodes of a detection device for a steering wheel; Fig. 5 is a schematic representation of an alternative arrangement of the electrodes of a detection device for a steering wheel; and

[0040] Fig. 6 shows a schematic representation of a signal flow graph of a method for operating a detection device for a steering wheel.

[0041] Fig. 1 shows a section of the interior of a motor vehicle 1. The motor vehicle 1 has a steering wheel 2. A user 3, i.e., a driver or passenger, is located in the motor vehicle 1. The user 3 currently grips the steering wheel 2 with a right hand 4 on one side of the steering wheel. On the opposite side, the user touches the steering wheel 2 with individual fingers 5, here, for example, with three fingers 5, of a left hand 4. The sides are arranged opposite one another in a transverse direction of the steering wheel 2 (y-direction).

[0042] The steering wheel 2 has a detection device 6. This can be used to detect that the right hand 4 is completely within the gripping range of the steering wheel 2 and that part of the left hand 4, here with three fingers 5, is within the gripping range of the steering wheel 2.

[0043] Fig. 2 shows the detection device 6 in more detail. The detection device 6 has, for example, a single electrode 10. Alternatively or additionally, it has a single group 11 of electrodes 10. Sketched here as an example, the detection device 6 has a first electrode 12 and a second electrode 13, i.e., a total of two electrodes 10. These are arranged side by side here. Alternatively or additionally, the detection device 6 can have two or more groups 11 of electrodes 10 and / or more than two electrodes 10.

[0044] The detection device 6 has a measuring device 14. This is designed to measure an input 15 and an output 16 of the electrode 10 and / or the group 11 of electrodes 10 in parallel, such that a detection sensitivity of the detection device 6 is increased. In this case, it is increased at least for a predetermined period of time in which the parallel measuring takes place. Parallel measuring here means that measurements are taken at the input 15 and at the output 16 simultaneously and thus simultaneously. An impedance is preferably measured as measurement data or measurement information, since the detection device 6 is preferably operated with an alternating voltage and thus has an impedance. A capacitive component of the impedance is preferably measured. In the following examples, only the capacitive component and thus the measured electrical capacitance are described.

[0045] The input 15 and the output 16 can alternatively be referred to as the first interface and the second interface, respectively, or as the first end and the second end of the electrode 10 or the group 11 of electrodes 10. If the first electrode 12 and the second electrode 13 are provided, the first electrode 12 can be measured at the input 15 and the second electrode 13 at the output 16. In this case, therefore, not the input 15 and the output 16 of a single electrode 10 are measured, but rather the two electrodes 12, 13 individually, yet simultaneously, since they are parallel.

[0046] When measuring at input 15, input information 17 is measured. When measuring at output 16, output information 18 is measured. These two are given, for example, as capacitive components of the impedance. Using the measuring device 14, the input information 17 and the output information 18 are added to form a total information 19. This is thus essentially twice as large as, for example, the input information 17 or the output information 18 alone. The total information 19 can be evaluated to recognize at least part of the hand 4. If three fingers 5 touch the steering wheel 2, this can be recorded, for example, as input information 17 and / or output information 18 of 4 picofarads each. The total information 19 is approximately 8 picofarads in this example.If the user 3 grips the steering wheel 2 with their entire hand 4, the input information 17 or the output information 18 can be approximately 20 picofarads. The total information 19 can then be approximately 40 picofarads. This clearly increases the detection sensitivity of the detection device 6, since, compared to sequentially capturing the input information 17 and the output information 18, essentially doubled values ​​are provided and evaluated as the total information 19. "Substantial" within the meaning of the invention refers to an inaccuracy of, for example, less than 1 percent, 3 percent, 5 percent, 10 percent, in particular 20 percent.If several electrodes 10 or groups 11 of electrodes 10 are provided, other than the two electrodes 12, 13 sketched here as an example, several output information items 18 can be recorded, so that, for example, the input information 17 and the several output information items 18 can be added together to form the total information 19.

[0047] A switch 20 can be arranged at each input 15 and output 16. The detection device 6 is designed to individually measure the input 15 and the output 16 of the electrode 10 and / or the group 11 of electrodes 10 by controlling the respective switch 20 accordingly. The input information 17 and the output information 18 can therefore be acquired one after the other without these two pieces of information being added together. By appropriately controlling the individual switches 20, each electrode 10 and / or group 11 of electrodes 10 can be measured individually. By evaluating the measurement data or measurement information acquired in this way, position information can be determined that describes a position of at least part of the hand 4 in the gripping range of the steering wheel 2. The position depends on how the individual electrodes 10 or groups 11 of electrodes 10 are arranged.

[0048] Fig. 2 also shows a control device 21. This is designed to control the switches 20 and / or the measuring device 14. The control device 21 can also be designed to evaluate data provided by the measuring device 14, such as the overall information 19. For example, the control device 21 preferably determines the position information. The control device 21 can be a component of the steering wheel 2 and / or the motor vehicle 1.

[0049] Fig. 3 shows an example of a measurement curve 22. In Fig. 3, time is plotted on an x-axis and the capacitive component of the impedance or a capacitance, abbreviated here with the letter C, is plotted on a y-axis. It is clear, on the one hand, that the measurement curve 22 experiences saturation 23 above a certain capacitance or a certain capacitive component of the impedance. In addition, there is background information 24, which is predetermined, for example, by parts or components of the steering wheel 2. The background information 24 describes a background or substrate that is always detected by the measuring device 14. It can be provided that the background information 24 is reduced here to the reduced background information 25. The reduced background information 25 is, for example, smaller than a predetermined limit value.The background information 24, 25 is always detected when at least no part of the hand 4 is located within the gripping range of the steering wheel 2. The reduction of the background information 24 shown here to the reduced background information 25 below the predetermined limit value is achieved by selecting at least one component of the detection device 6, in particular by a protective element as at least one component. Thus, the particularly low reduced background information 25 is ultimately achieved through appropriate design of the detection device 6 and its individual components. If the total information 19, which is greater than the input information 17 and / or output information 18 alone, is also taken into account, the already described high sensitivity of the detection device 6 is achieved and, moreover, a measuring range up to saturation 23 is increased.

[0050] Various configurations are possible with regard to the measuring device 14. The measuring device 14 can be designed to carry out a voltage and / or current measurement at least by means of an analog-to-digital converter for measuring the electrode 10 and / or the group 11 of electrodes 10 and to evaluate the measurement data or measurement information acquired in this way. Alternatively or additionally, it can be designed to acquire and evaluate time information for measuring the electrode 10 and / or the group 11 of electrodes 10, wherein the time information describes how long it takes for a predetermined voltage to be reached with a predetermined current source. Alternatively or additionally, the measuring device is designed to output a frequency signal for measuring the electrode 10 and / or the group 11 of electrodes 10 and to acquire and evaluate any resulting phase shift.The phase shift then occurs, for example, in the electrode 10 or the group 11 of electrodes 10.

[0051] Fig. 4 shows a possible arrangement of electrodes 10 in the steering wheel 2. Here, an electrode 10 is arranged on an inner side 31 of the steering wheel 2, wherein the inner side 31 faces a steering wheel hub 30 of the steering wheel 2. The steering wheel hub 30 is located in the region of a center point of the steering wheel 2, in particular the steering wheel rim of the steering wheel 2. Alternatively or additionally, the electrode 10 can be arranged at least in a partial region of an outer side 32 of the steering wheel 2 opposite the inner side 31. Preferably, a configuration is selected in which, for example, the electrode 10 arranged on the inner side 31 is the first electrode 12 and the electrode 10 arranged on the outer side 32 is the second electrode 13, or vice versa.

[0052] Fig. 5 outlines a further embodiment in which an electrode 10 is arranged on an underside 35 of the steering wheel 2, which underside faces a steering column 33 of the steering wheel 2. In a plan view of the steering wheel 2 outlined here, the steering column 33 is located below the steering wheel 2 and is therefore outlined with dashed lines. In addition, an electrode 10 can be arranged on an upper side 34 of the steering wheel 2 opposite the underside 35. Combinations of the described arrangements are generally possible. It can also be provided that the electrode 10 only ever covers a partial area of ​​the inner side 31, the outer side 32, the upper side 34 and / or the underside 35. The electrodes 10 can partially overlap one another. Any combinations and arrangements of the electrodes 10 are possible.

[0053] Fig. 6 shows a method for detecting at least part of a hand 4 on a steering wheel 2 using a detection device 6. In a method step S1, parallel measuring takes place at the input 15 and output 16, i.e., the input information 17 and the output information 18 are measured and thus recorded by the measuring device 14. In a method step S2, the input information 17 and the output information 18 are added to the total information 19, and this is evaluated to provide hand recognition information 40 that describes whether or not the user 3 is touching the steering wheel 2 with at least part of their hand 4. Here, it is assumed that, for example, it is detected that the user 3 is currently touching the steering wheel 2 with at least part of their hand 4.

[0054] In a method step S3, an alternating voltage applied to the electrode 10 and / or group 11 of electrodes 10, which is provided by an alternating voltage source, can be varied. This alternating voltage variation 41 occurs with respect to a frequency. The parallel measurement is therefore carried out again at a different frequency, so that the input information 17' and the output information 18' are measured again at the varied frequency. In a method step S4, the repeatedly acquired input information 17 and output information 18 can be added to form a new total information 19', and then a new hand recognition information 40' can be determined. If the previously determined hand recognition information 40 and the new hand recognition information 40' determined during repeated measurements match, this is considered a determination that the detection of at least part of the hand 4 in the gripping range of the steering wheel 2 has been confirmed.

[0055] In a method step S6, the hand recognition information 40 can then be considered as confirmed and, for example, made available, in particular for a driver assistance system or another function of the motor vehicle 1. If the checking results in the determination that the previously performed parallel measurement was not confirmed, method step S1 can, for example, be carried out again.

[0056] It should also be noted that the electrode 10 and / or the group 11 of electrodes 10 can typically also be controlled for a heating function of the steering wheel 2, i.e., there is a first operating mode in which the electrode 10 and / or group 11 of electrodes 10 is controlled by the control device 21 to heat the steering wheel 2. In a different second operating mode, the electrode 10 and / or the group 11 of electrodes 10 are controlled to detect at least part of the hand 4 in the gripping area of ​​the steering wheel 2, i.e., for the hand detection function. The two operating modes are activated alternately, for example, for predetermined time intervals. Therefore, the steering wheel 2 cannot be heated and the hand detection function provided at the same time; instead, these two functions alternate with one another.

[0057] Overall, the examples demonstrate hands-on and hands-off detection (hand recognition function) with improved resolution. Currently, measurements are performed at individual interfaces (input 15 and output 16) to ensure that the analog-to-digital converter measurement does not reach saturation 23. For example, a single hand leads to an increase in system capacitance of 20 picofarads. This capacitance is measured and displayed at both interfaces. Therefore, the minimum capacitance that can be measured is 4 picofarads (roughly equivalent to three fingers 5). Setting a reference offset (background information 24, 25) to a lower value and leaving both interfaces active results in a larger jump when a hand 4 touches the steering wheel 2 (twice 20 picofarads), thereby improving the system's sensitivity.This procedure can also help to check whether the hand 4 has been detected or not by adding a third option to check the touch of the steering wheel 2.

Claims

Patent claims 1. Detection device (6) for a steering wheel (2) of a motor vehicle (1) for detecting at least part of a hand (4) in a gripping area of ​​the steering wheel (2), comprising at least one electrode (10) and / or at least one group (11) of electrodes (10) and a measuring device (14) which is designed to measure an input (15) and an output (16) of the at least one electrode (10) and / or the at least one group (11) of electrodes (10) in parallel, such that a detection sensitivity of the detection device (6) is increased at least for a predetermined period of time.

2. Detection device (6) according to claim 1, wherein the measuring device (14) is designed to add an input information (17) measured during measurement at the input (15) and an output information (18) measured during measurement at the output (16) to form a total information (19) and to evaluate the total information (19) for recognizing at least part of the hand (4).

3. Detection device (6) according to claim 2, wherein the detection device (6) comprises a first electrode (12) and a second electrode (13) and the measuring device (14) is designed to measure the first electrode (12) as input information (17) and the second electrode (13) as output information (18).

4. Detection device (6) according to claim 3, wherein the detection device (6) comprises a plurality of second electrodes (13) and the measuring device (14) is designed to measure the respective second electrode (13) as the respective output information (18) and to add the input information (17) with the plurality of output information (18) to the total information (19).

5. Detection device (6) according to one of the preceding claims, wherein a switch (20) is arranged at the input (15) and output (16) so that the Detection device (6) is designed to connect the input (15) and the output (16) of the electrode (10) and / or the group (11) of electrodes (10) to be measured individually.

6. Detection device (6) according to one of claims 3 or 4 and claim 5, wherein the measuring device (14) is designed to measure each electrode (10) and / or group (11) of electrodes (10) individually by appropriately controlling the individual switches (20) and to determine position information by evaluating measurement data acquired in the process, which describes a position of at least part of the hand (4) in the gripping area of ​​the steering wheel (2).

7. Detection device (6) according to one of the preceding claims, wherein the measuring device (14) is designed, after the parallel measurement of the input (15) and the output (16) of the electrode (10) and / or the group (11) of electrodes (10), to vary a frequency of an alternating voltage applied to the electrode (10) and / or the group (11) of electrodes (10), to repeat the parallel measurement at the varied frequency and to determine by evaluating the repeated parallel measurement whether or not a detection of at least part of the hand (4) in the gripping area of ​​the steering wheel (2) can be confirmed by evaluating the previously carried out parallel measurement.

8. Detection device (6) according to one of the preceding claims, wherein the measuring device (14) is designed to measure background information (24, 25) which is always measurable without at least the part of the hand (4) being arranged in the gripping area of ​​the steering wheel (2), wherein by selecting at least one component, in particular a protective element, of the detection device (6), the background information (24, 25) is smaller than a predetermined limit value.

9. Detection device (6) according to one of the preceding claims, wherein the measuring device (14) is designed to carry out a voltage and / or current measurement for measuring the electrode (10) and / or group (11) of electrodes (10) at least by means of an analog-digital converter and to evaluate the measurement data acquired thereby.

10. Detection device (6) according to one of the preceding claims, wherein the measuring device (14) is designed to detect and evaluate time information for measuring the electrode (10) and / or group (11) of electrodes (10), which time information describes how long it takes for a given current source to reach a given voltage.

11. Detection device (6) according to one of the preceding claims, wherein the measuring device (14) is designed to output a frequency signal for measuring the electrode (10) and / or group (11) of electrodes (10) and to detect and evaluate a phase shift occurring thereafter.

12. Steering wheel (2) with a detection device (6) according to one of the preceding claims.

13. Steering wheel (2) according to claim 12, wherein the respective electrode (10) is arranged on at least a partial region of an inner side (31) of the steering wheel (2) facing a steering wheel hub (30) of the steering wheel (2); and / or on at least a partial region of an outer side (32) of the steering wheel (2) opposite the inner side (31); and / or on at least a partial region of an underside (35) of the steering wheel (2) facing a steering column (33) of the steering wheel (2); and / or on at least a partial region of an upper side (34) of the steering wheel (2) opposite the underside (35).

14. Steering wheel (2) according to claim 12 or 13, wherein the steering wheel (2) has a control device (21) which is designed to control the electrode (10) and / or group (11) of electrodes (10) in a first operating mode for heating the steering wheel (2) and in a second operating mode for detecting at least part of a hand (4) in a gripping area of ​​the steering wheel (2), wherein the two operating modes are activated alternately.

15. Method for detecting at least part of a hand (4) on a steering wheel (2) with a detection device (6) which comprises at least one electrode (10) and / or at least one group (11) of electrodes (10) and a measuring device (14), wherein by means of the measuring device (14) an input (15) and an output (16) of the at least one electrode (10) and / or of the at least one group (11) of electrodes (10) are measured in parallel, so that a Detection sensitivity of the detection device (6) is increased at least for a predetermined period of time.

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