Control element with capacitive sensor technology for detecting approach and / or contact with improved reduction of temperature influence, its use and associated method for detection

Abstract

The invention relates to an operating element (1) with a control panel (2) and capacitive sensors (3) for detecting an approach and / or touch of the control panel (2) by an operator, wherein the capacitive sensors (3) have, on a side of the control panel (2) facing away from the operator, an electrode (S) and a counter electrode (S') for generating a measuring capacitance assigned to the capacitive control panel and an evaluation unit (ADC) that can be selectively connected electrically to the electrode (S), wherein the capacitive sensors (3) are designed to carry out a method with at least several steps in which the electrical potential that is established at the electrode (S) after a certain period of time, namely the first potential (U 1 ) or second potential (U 2) is determined; these steps i to viii are repeated several times in sequence, each forming a measuring cycle and after each measuring cycle, qualitative and / or quantitative determination of a change in a potential (U 1 ) and from the second potential (U 2 ) formed variable (ΔU) compared to an old variable (ΔU') previously determined in a previous, preferably the immediately preceding, measuring cycle by the capacitive sensor system, in order to detect the touch or approach to the control panel (2) positively or negatively by the capacitive sensor system (3) on the basis of the change and to output an associated detection result by the capacitive sensor system (3).

Description

[0001] The present invention relates to an operating element with capacitive sensors for detecting approach and / or contact with improved reduction of the temperature influence, its use, and an associated detection method. So-called touch-sensitive control panels are very popular for detecting user input on an operating element. Capacitive sensors are preferably used to detect touch because their sensing sensitivity is comparatively high and reliable. This capacitive sensor, assigned to the respective control panel, generally comprises at least one electrode and an associated evaluation unit. Conventional capacitive sensors contain expensive, special hardware components such as tilt oscillators and comparators. A sensor system that does not use such components is known, for example, from US Pat. No. 8,836,350 B2.In addition to electromagnetic interference, a problem that affects capacitive sensors but is comparatively easy to control, another problem arises in practice, which is caused by the temperature sensitivity of the sensors. In motor vehicles in particular, capacitive sensors are exposed to large temperature fluctuations, which leads to significant variations in the measuring capacitance assigned to the control panels and can lead to false detections of supposed user inputs, a process known as "ghost touch". For manufacturing reasons and due to simplified electrical contact, such measuring capacitances are implemented by metallic coatings forming one or more electrodes on a film substrate, which is typically arranged on the side of a panel facing away from the operator. Temperature-induced expansion and position changes cannot be completely suppressed mechanically.There is therefore a need to neutralise the change in measuring capacitance caused by the temperature change, which is also referred to here as temperature compensation.

[0002] Against this background, the present invention is based on the object of providing an operating element with capacitive sensors for detecting approach or contact, which, in addition to precise detection, ensures minimization of the temperature influence on the detection, is particularly cost-effective to implement, and is low in complexity. This object is achieved by an operating element having the features of claim 1 and by a method having the features of the independent claim. Further, particularly advantageous embodiments of the invention are disclosed in the respective subclaims.

[0003] It should be noted that the features listed individually in the following description can be combined with one another in any technically reasonable manner and demonstrate further embodiments of the invention. The description further characterizes and specifies the invention, particularly in conjunction with the figures.

[0004] It should also be noted that a conjunction "and / or" used hereinafter between two features and linking them together is always to be interpreted in such a way that in a first embodiment of the subject matter according to the invention only the first feature can be present, in a second embodiment only the second feature can be present and in a third embodiment both the first and the second feature can be present.

[0005] Furthermore, the term "approximately" used herein indicates a tolerance range that a person skilled in the art considers usual. In particular, the term "approximately" is understood to mean a tolerance range of the referenced size of up to a maximum of + / -20%, preferably up to a maximum of + / -10%.

[0006] Furthermore, within the meaning of the present invention, relative terms used herein with regard to a feature, such as "larger", "smaller", "higher", "lower" and the like, are always to be interpreted in such a way that manufacturing and / or implementation-related size deviations of the feature in question, which lie within the manufacturing / implementation tolerances defined for the respective manufacture or implementation of the feature in question, are not covered by the respective relative term.In other words, according to the definition applicable herein, a size of a feature is only to be regarded as “larger”, “smaller”, “higher”, “lower” and the like within the meaning of the present invention than a size of a comparison feature if the two compared sizes differ so significantly in their value that this difference in size certainly does not fall within the manufacturing / implementation-related tolerance range of the feature in question, but is the result of targeted action.

[0007] The invention relates to an operating element with a control panel and capacitive sensors for detecting an approach to the control panel by an operator as an operating input and / or a touch of the control panel by the operator, also as an operating input. According to the invention, the capacitive sensors have an electrode arranged on a side of the control panel facing away from the operator and a counter electrode, likewise arranged on the side of the control panel facing away from the operator, for generating a measuring capacitance associated with the capacitive control panel. The capacitive sensors have an evaluation unit that can be selectively electrically connected to the electrode for determining the potential present at the electrode. The evaluation unit preferably has an analog-to-digital converter for determining the measuring capacitance.Even more preferably, the evaluation unit, including the analog-to-digital converter, is an integrated component of a microcontroller, which, together with the electrodes forming the measuring capacitance, forms the capacitive sensor system. According to the invention, the capacitive sensor system is designed to carry out a method comprising at least the following steps.

[0008] In a first step, which is a first step of a sequence which is further formed from several steps described below and which together form a measuring cycle, the electrode is set to a predetermined electrical initial potential which is preferably lower in magnitude than the first and second potentials described below and most preferably corresponds to the ground potential.

[0009] In a second step following the first step, the electrode is charged, i.e. an electrical charge is applied to the electrode, and the counter electrode is simultaneously held at a first basic potential which is lower in magnitude than the potential at least finally applied to the electrode, both charging and holding, in each case for a predetermined, first period of time. The first basic potential preferably corresponds to the initial potential, usually preferably to the ground potential. “Holding” within the meaning of the invention does not necessarily mean keeping the potential strictly constant, but rather “holding” within the meaning of the invention can “imply” a smaller temporal variation in the relevant potential compared to “charging”, and “holding” preferably includes an average temporal fluctuation over the relevant step of less than 10%.

[0010] In a subsequent third step, the counter electrode is subjected to an influencing potential that differs from the first basic potential, for example the operating voltage of the previously described microcontroller, such that the influencing potential is greater in magnitude than the first basic potential of the first step and the potential at least finally applied to the electrode for a predetermined, second period of time.

[0011] In a fourth step within the second time period, at the latest before the end of the second time period, the evaluation unit is connected to the electrode previously insulated from the evaluation unit and a first electrical potential is determined by means of the evaluation unit connected to the electrode, which is established by the influencing potential applied to the counter electrode upon expiration of the second time period.

[0012] In a subsequent fifth step, the electrode is again adjusted to the predetermined electrical initial potential, which is preferably lower in magnitude than the first potential and the subsequently described second potential and corresponds, for example, to the ground potential, during which the counter electrode is maintained at the influencing potential.

[0013] In a subsequent sixth step, the electrode is charged, i.e., electrical charge is applied to the electrode and the counter electrode is simultaneously held at the influencing potential, i.e., charging and holding, for a predetermined, third period of time.

[0014] In the subsequent seventh step, the counter electrode is subjected to the first basic potential or a second basic potential which differs from the first basic potential and which is lower in magnitude than the potential which is at least finally applied to the electrode for a predetermined fourth period of time.

[0015] In an eighth step within the fourth time period, at the latest before the end of the fourth time period, the evaluation unit is connected to the electrode previously insulated from the evaluation unit and a second electrical potential is determined by the evaluation unit connected to the electrode, which is established by the first or second basic potential applied to the counter electrode at the end of the fourth time period.

[0016] According to the invention, the aforementioned steps from the first to eighth steps are repeated several times in the sequence of their numbering, with this sequence each constituting a measuring cycle. According to the invention, after each measuring cycle, a change in a variable formed from the first potential previously determined in the fourth step and from the second potential previously determined in the eighth step compared to a variable previously determined in a previous, preferably the immediately preceding, measuring cycle, referred to as the old variable, is qualitatively and / or quantitatively determined by the capacitive sensor system in order to detect contact with or approach to the control panel positively or negatively by the capacitive sensor system based on the change and to output an associated detection result by the capacitive sensor system.

[0017] The inventive design of the control element has the advantage that temperature influences on the measuring capacitance, which result, for example, from mechanical changes of the electrodes involved, such as expansion or change in position, can be reduced or eliminated by the double determination of the electrode potential, namely first and second potential, in one measuring cycle but with opposite polarity change of the counter potential of the counter electrode with respect to the electrode, namely once above the potential of the electrode and once below the potential of the electrode.

[0018] It has been shown that the temperature influence at best causes a change in the same direction in these potentials determined at the electrode, namely the first potential and the second potential, while the change in the two potentials determined in the fourth and eighth steps, namely the first potential and the second potential, caused by approaching and touching the control panel, is in the opposite direction, which means that the change in the quantity derived from the two previously determined potentials from the first and second potential improves the touch or approach detection by largely eliminating the temperature influence on the measuring capacity.

[0019] Preferably, the determined change in size compared to the old size is compared with a predetermined comparison change in order to detect the touch or approach to the control panel positively or negatively based on the comparison.

[0020] Even more preferably, a minimum change in the quantity detected from one measurement cycle to the next, which is below a specified amount, is used to subsequently adjust the specified comparison change. This procedure is referred to as baseline adjustment.

[0021] Preferably, the quantity is a difference between the first potential and the second potential, whereby a touch or an approach to the control panel is only positively detected as a predetermined comparison change when the value falls below a predetermined minimum difference.

[0022] The predetermined time period from the first to fourth time periods can be selected to be relatively short. For example, it can be a few microseconds, e.g., 1 µs to 2 µs, or 0.5 µs to 10 µs, e.g., 5 µs. For example, it can each be just a few clock cycles of the computing and storage unit used in the capacitive sensor technology. For example, the computing and storage unit or the microcontroller can be operated at a clock frequency of 64 MHz, so that the time period from the first to fourth time periods can also be in the range of a few nanoseconds, a few tens of nanoseconds, or a few hundred nanoseconds. It is understood that the shorter the respective time periods are determined, the more measuring cycles can be realized per time interval. However, it is also conceivable to vary at least one time period from the first to fourth time periods from one to a subsequent measuring cycle.Preferably, the first time period and the third time period are chosen to be the same.

[0023] Preferably, the second period and the fourth period are chosen to be the same.

[0024] According to a preferred embodiment, all the first, second, third and fourth time periods are chosen to be consistent.

[0025] The invention further relates to the use of the control element according to one of the previously described embodiments in a motor vehicle.

[0026] The invention further relates to a method for detecting an approach or touch of a control panel of a control element by an operator, comprising the following steps: In an initial preparation step, the control element with the control panel and capacitive sensors is prepared. The capacitive sensors of the provided control element have an electrode and a counter electrode on a side of the control panel facing away from the operator for generating a measuring capacitance associated with the capacitive control panel, as well as an evaluation unit that can be selectively electrically connected to the electrode.

[0027] In a first step, which is a first step of a sequence which is further formed from several steps described below and which together form a measuring cycle, the electrode is set to a predetermined electrical initial potential which is preferably lower in magnitude than the first and second potentials described below and most preferably corresponds to the ground potential.

[0028] In a second step following the first step, the electrode is charged, i.e. an electrical charge is applied to the electrode, and the counter electrode is simultaneously held at a first basic potential which is lower in magnitude than the potential at least finally applied to the electrode, both charging and holding, in each case for a predetermined, first period of time. The first basic potential preferably corresponds to the initial potential, usually preferably to the ground potential. “Holding” within the meaning of the invention does not necessarily mean keeping the potential strictly constant, but rather “holding” within the meaning of the invention can “imply” a smaller temporal variation in the relevant potential compared to “charging”, and “holding” preferably includes an average temporal fluctuation over the relevant step of less than 10%.

[0029] In a subsequent third step, the counter electrode is subjected to an influencing potential that differs from the first basic potential, for example the operating voltage of the previously described microcontroller, such that the influencing potential is greater in magnitude than the first basic potential of the first step and the potential at least finally applied to the electrode for a predetermined, second period of time.

[0030] In a fourth step within the second time period, at the latest before the end of the second time period, the evaluation unit is connected to the electrode previously insulated from the evaluation unit and a first electrical potential is determined by means of the evaluation unit connected to the electrode, which is established by the influencing potential applied to the counter electrode upon expiration of the second time period.

[0031] In a subsequent fifth step, the electrode is again adjusted to the predetermined electrical initial potential, which is preferably lower in magnitude than the first potential and the subsequently described second potential and corresponds, for example, to the ground potential, during which the counter electrode is maintained at the influencing potential.

[0032] In a subsequent sixth step, the electrode is charged, i.e., electrical charge is applied to the electrode and the counter electrode is simultaneously held at the influencing potential, i.e., charging and holding, for a predetermined, third period of time.

[0033] In the subsequent seventh step, the counter electrode is subjected to the first basic potential or a second basic potential which differs from the first basic potential and which is lower in magnitude than the potential which is at least finally applied to the electrode for a predetermined fourth period of time.

[0034] In an eighth step within the fourth time period, at the latest before the end of the fourth time period, the evaluation unit is connected to the electrode previously insulated from the evaluation unit and a second electrical potential is determined by the evaluation unit connected to the electrode, which is established by the first or second basic potential applied to the counter electrode at the end of the fourth time period.

[0035] According to the invention, the aforementioned steps from the first to the eighth step are repeated several times in the sequence of their numbering, with this sequence each constituting a measuring cycle. According to the invention, after each measuring cycle, a change in a variable formed from the first potential previously determined in the fourth step and from the second potential previously determined in the eighth step compared to an old variable previously determined in a previous, preferably the immediately preceding, measuring cycle is qualitatively and / or quantitatively determined by the capacitive sensor system in order to detect contact with or approach to the control panel positively or negatively by the capacitive sensor system based on the change and to output an associated detection result by the capacitive sensor system.

[0036] The inventive design of the method has the advantage that temperature influences on the measuring capacitance, which result, for example, from mechanical changes of the electrodes involved, such as expansion or change in position, and thus on the measuring capacitance, can be reduced or eliminated by the double determination of the electrode potential, namely first and second potential, in one measuring cycle but with opposite polarity change of the counter potential of the counter electrode with respect to the electrode, namely once above the potential of the electrode and once below the potential of the electrode.

[0037] It has been shown that the temperature influence at best causes a change in the same direction in these potentials determined at the electrode, namely the first potential and the second potential, while the change in the two potentials determined in the fourth and eighth steps, namely the first potential and the second potential, caused by approaching and touching the control panel, is in the opposite direction, which means that the change in the quantity derived from the two previously determined potentials from the first and second potential improves the touch or approach detection by largely eliminating the temperature influence on the measuring capacity.

[0038] Preferably, the determined change in size is compared with a predetermined comparison change in order to positively or negatively detect the touch or approach to the control panel based on the comparison.

[0039] Even more preferably, a minimum change in the quantity detected from one measurement cycle to the next, which is below a specified amount, is used to subsequently adjust the specified comparison change. This procedure is referred to as baseline adjustment.

[0040] Preferably, the quantity is a difference between the first potential and the second potential, whereby a touch or an approach to the control panel is only positively detected as a predetermined comparison change when the value falls below a predetermined minimum difference.

[0041] The predetermined time period from the first to fourth time periods can be selected to be relatively short. For example, it can be a few microseconds, e.g., 1 µs to 2 µs, or 0.5 µs to 10 µs, e.g., 5 µs. For example, it can each be just a few clock cycles of the computing and storage unit used in the capacitive sensor technology. For example, the computing and storage unit or the microcontroller can be operated at a clock frequency of 64 MHz, so that the time period from the first to fourth time periods can also be in the range of a few nanoseconds, a few tens of nanoseconds, or a few hundred nanoseconds. It is understood that the shorter the respective time periods are determined, the more measuring cycles can be realized per time interval. However, it is also conceivable to vary at least one time period from the first to fourth time periods from one to a subsequent measuring cycle.

[0042] Preferably, the first time period and the third time period are chosen to be the same.

[0043] Preferably, the second period and the fourth period are chosen to be the same.

[0044] According to a preferred embodiment, all the first, second, third and fourth time periods are chosen to be consistent.

[0045] Further features and advantages of the invention will become apparent from the following description of non-limiting embodiments of the invention, which are explained in more detail below with reference to the figures. These figures schematically show: Fig. 1 an embodiment of an operating element according to the invention; Fig. 2 a flowchart of an embodiment of the method or operating element according to the invention; Fig. 3 a diagram showing the temperature dependence of the electrode from Fig. 1 certain potentials U 1 and U 2 , Fig. 4 a flow chart with temperature change and a contact event to illustrate their effect on the variable ΔU determined by the method according to the invention.

[0046] In the different figures, parts that are equivalent in terms of their function are always provided with the same reference symbols, so that they are usually only described once.

[0047] Fig. 1 shows an embodiment of an operating element 1 for detecting a touch of an operating panel 2 and / or approach to the operating panel 2. The operating panel 2 is formed, for example, by a diaphragm covering the electrode S and counter electrode S' from the operator's perspective.

[0048] For detection, the control element 1 has a capacitive sensor 3, which comprises an electrode S arranged on a side of the control panel 2 facing away from the operator, and a counter electrode S' also arranged on the side of the control panel 2 facing away from the operator. Both electrodes S and S' are provided for generating a measuring capacitance assigned to the capacitive control panel. The electrode S and counter electrode S' are electrically insulated from one another and extend alongside one another, for example, in a meandering or forked manner, with the electrode S and the counter electrode S' being arranged in such an interwoven manner that gaps between one are filled by the other.

[0049] The capacitive sensor system 3 has an evaluation unit µC, here in the form of a microcontroller. This can be selectively electrically connected to the electrode S, among other things, to determine the potential present at the electrode S. Furthermore, the evaluation unit µC is also connected to the counter electrode S', is further fed from the supply potential Vcc, and has a connection to the ground potential. The evaluation unit µC is further configured to set the initial potential GND of the electrode S, to charge it, and to selectively set the first ground potential GND' or, if applicable, the second ground potential GND'', as well as the influencing potential Vcc of the counter electrode S'.

[0050] The sensor system 3 is designed to carry out the following steps, which are related to Fig. 2 are described below. Fig. 2 shows the temporal potential profile U(t) of the electrode S and the temporal potential profile, also referred to as counter potential U'(t), of the counter electrode S' over a measuring cycle formed by the steps i to viii described below, showing the case in which there is no contact or approach by the operator during the measuring cycle.

[0051] In a first step i, which is a first step of a sequence which is further formed from several steps ii to viii described below and which together form a measuring cycle, the electrode S is set to a predetermined electrical initial potential GND, which is preferably below the first potential U described below. 1 and second potential U 2 and usually corresponds preferentially to the ground potential.

[0052] In a step following the first step i, at time t 0beginning and at time t 1 In the second step ii, which ends, the electrode S is charged, ie electrical charge is applied to the electrode S, and the counter electrode S' is simultaneously held at a first ground potential GND', which is below the value at the electrode S at least finally, ie at the end time t 1 of the second step, both charging and holding, each for a predetermined, first period of time. Preferably, the first ground potential GND' corresponds to the initial potential GND of the electrode S, most preferably to the ground potential. "Holding" within the meaning of the invention preferably does not necessarily mean keeping it strictly constant; rather, "holding" within the meaning of the invention can imply a smaller temporal variation of the potential in question compared to "charging". Preferably, "holding" includes an average temporal fluctuation over the step in question of less than 10%.

[0053] In a second step ii at time t 1 In the subsequent third step iii, the counter electrode S' is subjected to an influencing potential VCC that differs from the first ground potential GND', for example the operating voltage of the previously described microcontroller as the evaluation unit µC for a second time period Δt 2 such that the influencing potential Vcc is higher in magnitude than the first ground potential GND' of the first step and that at the electrode S at least finally at this third step at time t 2 applied potential U(t 2 ) lies.

[0054] During or at the latest before the end of the second time period Δt 2 In a fourth step iv, the evaluation unit µC, which was previously isolated from the electrode S, is connected to the latter.

[0055] At the latest upon expiry of the second time period Δt 2 , i.e. at time t2 Furthermore, in the fourth step iv, a determination of an electrical first potential U is carried out which is established at the electrode S by the influencing potential Vcc applied to the counter electrode S'. 1 by means of the evaluation unit µC connected to the electrode S.

[0056] In a subsequent, at time t 2 beginning and at time t 3 In the fifth step v, which ends, the electrode S is again set to the predetermined electrical initial potential GND, which is preferably below the first potential U 1 and the second potential U described below 2 and corresponds, for example, to the ground potential, during which the counter electrode S' is maintained at the influencing potential Vcc.

[0057] In a subsequent, at time t 3 beginning and at time t 4In the sixth step vi, which ends, the electrode S is charged, ie electrical charge is applied to the electrode S and the counter electrode S' is simultaneously held at the influencing potential Vcc, i.e. charging and holding, for a predetermined, third time period Δt 3 .

[0058] In subsequent, at time t 4 beginning and at time t 5 ending seventh step vii is carried out for a predetermined fourth time period Δt 4 applying the first ground potential GND' or a second ground potential GND'' which is different from the first ground potential GND' and which is lower in magnitude than the potential U(t 5 ) lies.

[0059] During or at the latest before the end of the fourth period Δt 4In an eighth step viii, the evaluation unit µC is connected to the electrode S, which was previously isolated from the evaluation unit µC. At the latest when the fourth time period Δt 4 , i.e. at time t 5 Furthermore, a determination of an electrical second potential U which is established at the electrode S by the first ground potential GND' or second ground potential GND'' applied to the counter electrode S' 2 by the evaluation unit µC connected to the electrode S.

[0060] The aforementioned steps from the first step i to the eighth step viii are repeated several times in the sequence of their numbering, whereby this sequence forms a measurement cycle. After each measurement cycle, a qualitative and / or quantitative determination of a change in a potential U determined from the first potential U previously determined in the fourth step iv is carried out. 1 and from the second potential U previously determined in step viii2 formed variable ΔU compared to a previously determined in a previous, preferably the immediately preceding, measuring cycle, here referred to as the old variable, by the capacitive sensor system 3, in order to detect the touch or approach to the control panel 2 positively or negatively by the capacitive sensor system 3 based on the change in the variable ΔU compared to the old variable and to output an associated detection result by the capacitive sensor system 3. In the present embodiment, the variable ΔU is in each case a difference between the first potential U 1 and second potential U 2 , whereby a touch or an approach to the control panel 2 is only positively detected when a predetermined minimum difference is undershot as a predetermined comparison change.

[0061] The inventive design of the operating element 1 has the advantage that temperature influences on the measuring capacitance, which result, for example, from mechanical changes of the involved electrodes S, S', such as expansion or change in position, and thus from measuring capacitance, can be compensated for by the double determination of the electrode potential, namely the first potential U 1 and second potential U 2 , but in one measuring cycle with opposite polarity change of the counter-potential U'(t) applied to the counter-electrode S', namely influencing potential Vcc and at other times first ground potential GND' or second ground potential GND'', can be reduced or eliminated. It has been shown that the temperature influence can at best cause a rectified change in these potentials determined at the electrode S, namely the first potential U 1 and second potential U 2, while the change in the two potentials determined in the fourth and eighth steps, namely the first potential U 1 and the second potential U 2 , is opposite, which leads to the change in the two previously determined potentials from the first potential U 1 and second potential U 2 derived quantity ΔU improves contact or proximity detection by largely eliminating the temperature influence on the measuring capacity.

[0062] This shows Fig. 3 the dependence of the first potential U determined at the electrode S 1 and second potential U 2 , where a linear proportionality is assumed for simplicity, and T 2 >T 1 applies.

[0063] Fig. 4 shows the behavior of the two potentials determined at the electrode S, namely the first potential U determined in the fourth step iv 1 , the second potential U determined in step viii 2 and the derived quantity ΔU, obtained here by subtracting the two aforementioned values, on the one hand at contact B in the time interval t 6 <t<t 8 compared to non-contact in the time intervals t <t 6 and t>t 8 , which in Fig. 4 is marked by a crossed B. From time t 7 takes the temperature according to the Fig. 3 starting from T 1 to ultimately arrive well after time t 8 T 2 It can be seen that if there is no contact in the time intervals t <t 6 and t>t 8 the first potential U 1 (T 1 ) to ultimately U 1 (T 2) and the second potential U 2 undergoes a variation in the same direction and here approximately the same amount, namely also an increase of U 2 (T 1 ) to ultimately U 2 (T 2 ), so that the non-contact remains identifiable by the quantity ΔU essentially independent of temperature development. For the case of contact in the time interval t 6 <t<t 8 the dielectric influence of the operator's finger influences the measuring capacitance and, due to the different "polarity" of the counter potential U', there is an opposite change in the first potential U caused by the approach or contact. 1 and the second potential U 2 compared to non-contact, namely a lowering of U caused by contact 1 (T 1 ) on U* 1 (T 1), where the star represents the contact or approach situation, and an increase of U 2 (T 1 ) on U* 2 (T 1 ). The value ΔU* of the contact and approach situation differs not only significantly from ΔU of the non-contact situation due to the opposite change but also remains essentially unaffected by the temperature increase, as the further temporal development of ΔU* up to time t 8 shows. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 8 836 350 B2

[0001]

Claims

[1] Operating element (1) with control panel (2) and capacitive sensor system (3) for detecting an approach and / or touch of the control panel (2) by an operator, wherein the capacitive sensor system (3) has, on a side of the control panel (2) facing away from the operator, an electrode (S) and a counter electrode (S') for generating a measuring capacitance assigned to the capacitive control panel and an evaluation unit (µC) that can be selectively electrically connected to the electrode (S), wherein the capacitive sensor system (3) is designed to carry out a method with at least the following steps: i. Setting the electrode (S) to a predetermined initial electrical potential (GND); ii. subsequently charging the electrode (S) and simultaneously maintaining the counter electrode (S') at a first ground potential (GND'), which is below the potential at least finally applied to the electrode (S), in each case for a predetermined first time period (Δt1 ); iii. subsequently applying to the counter electrode (S') an influencing potential (Vcc) different from the first ground potential (GND') such that the influencing potential (Vcc) is higher in magnitude than the first ground potential (GND') and the potential at least finally applied to the electrode (S) for a predetermined second time period (Δt 2 ); iv. at the latest before the end of the second period (Δt 2 ) Connecting the evaluation unit (µC) to the electrode (S) and determining an influence potential (Vcc) which is generated by the counter electrode (S') at the end of the second time period (Δt 2 ) at the electrode (S) setting, electrical, first potential (U 1 ) by the evaluation unit (µC) connected to the electrode (S); v. subsequently setting the electrode (S) to the predetermined initial electrical potential (GND) while maintaining the influencing potential (Vcc) applied to the counter electrode (S'); vi. subsequent charging of the electrode (S) and simultaneous holding of the counter electrode (S') at the influence potential (Vcc) for a predetermined third time period (Δt 3 ), vii. subsequently applying the first ground potential (GND') or a second ground potential (GND'') different from the first ground potential (GND') to the counter electrode (S') for a predetermined fourth time period (Δt 4 ); viii. at the latest before the end of the fourth period (Δt 4) Connecting the evaluation unit (µC) to the electrode (S) and determining a first ground potential (GND') or second ground potential applied to the counter electrode (S') at the end of the fourth time period (Δt 4 ) at the electrode (S) setting, electrical, second potential (U 2 ) by the evaluation unit (µC); Repeating steps i to viii several times in sequence, each forming a measuring cycle and, after each measuring cycle, qualitatively and / or quantitatively determining a change in a potential (U 1 ) and from the second potential (U 2) formed variable (ΔU) compared to an old variable previously determined in a previous, preferably the immediately preceding, measuring cycle by the capacitive sensor system (3), in order to detect the contact or approach to the control panel (2) positively or negatively by the capacitive sensor system (3) on the basis of a change in the variable (ΔU) compared to the old variable and to output an associated detection result by the capacitive sensor system (3). [2] Operating element (1) according to the preceding claim, wherein the capacitive sensor system (3) is designed to compare the determined change in the variable (ΔU) compared to the old variable with a predetermined comparison change in order to positively or negatively detect the touching of the operating panel (2) or the approach to the operating panel (2) on the basis of the comparison. [3] Control element (1) according to the preceding claim, wherein a minimum change in the quantity (ΔU) from measuring cycle to measuring cycle which is below a predetermined amount is used for the subsequent adaptation of the predetermined comparison change. [4] Control element (1) according to one of the preceding claims, wherein the variable (ΔU) is a difference between the first and the first potential (U 1 ) and second potential (U 2 ) and a touch or approach to the control panel (2) is only positively detected when a predetermined minimum difference is undershot as a predetermined comparison change. [5] Control element (1) according to one of the preceding claims, wherein the evaluation unit (µC) comprises an analog-digital converter (ADC) which is selectively connected to the electrode (S). [6] Control element (1) according to one of the preceding claims, wherein the initial potential (GND) and the first ground potential (GND') correspond to a ground potential. [7] Control element (1) according to one of the preceding claims, wherein the first time period (Δt 1 ) and the third time period (Δt 3 ) are chosen consistently and / or the second time period (Δt 2 ) and the fourth time period (Δt 4 ) are chosen consistently. [8] Use of the control element (1) according to one of the preceding claims in a motor vehicle. [9] A method for detecting an approach and / or touch of a control panel (2) of a control element (1) by an operator, comprising an initial provision step in which the control element (1) is provided with the control panel (2) and capacitive sensor technology (3), and wherein the capacitive sensor technology (3) has, on a side of the control panel (2) facing away from the operator, an electrode (S) and a counter electrode (S') for generating a measuring capacitance associated with the capacitive control panel and an evaluation unit (µC) that can be selectively electrically connected to the electrode (S); further comprising the following steps: i. Setting the electrode (S) to a predetermined initial electrical potential (GND); ii. subsequently charging the electrode (S) and simultaneously maintaining the counter electrode (S') at a first ground potential (GND'), which is below the potential at least finally applied to the electrode (S), in each case for a predetermined first time period (Δt 1 ); iii. subsequently applying to the counter electrode (S') an influencing potential (Vcc) different from the first ground potential (GND') such that the influencing potential (Vcc) is higher in magnitude than the first ground potential (GND') and the potential at least finally applied to the electrode (S) for a predetermined second time period (Δt 2 ); iv. at the latest before the end of the second period (Δt 2 ) Connecting the evaluation unit (µC) to the electrode (S) and determining an influence potential (Vcc) which is generated by the counter electrode (S') at the end of the second time period (Δt 2) at the electrode (S) setting, electrical, first potential (U 1 ) by the evaluation unit (µC) connected to the electrode (S); v. subsequently setting the electrode (S) to the predetermined initial electrical potential (GND) while maintaining the influencing potential (Vcc) applied to the counter electrode (S'); vi. subsequent charging of the electrode (S) and simultaneous holding of the counter electrode (S') at the influence potential (Vcc) for a predetermined third time period (Δt 3 ), vii. subsequently applying the first ground potential (GND') or a second ground potential (GND'') different from the first ground potential (GND') to the counter electrode (S') for a predetermined fourth time period (Δt 4 ); viii. at the latest before the end of the fourth period (Δt 4 ) Connecting the evaluation unit (µC) to the electrode (S) and determining a first ground potential (GND') or second ground potential applied to the counter electrode (S') at the end of the fourth time period (Δt 4 ) at the electrode (S) setting, electrical, second potential (U 2 ) by the evaluation unit (µC); Repeating steps i to viii several times in sequence, each forming a measuring cycle and, after each measuring cycle, qualitatively and / or quantitatively determining a change in a potential (U 1 ) and from the second potential (U 2) formed variable (ΔU) compared to an old variable previously determined in a previous, preferably the immediately preceding, measuring cycle by the capacitive sensor system (3), in order to detect the contact or approach to the capacitive control panel (2) positively or negatively by the capacitive sensor system (3) on the basis of the change and to output an associated detection result by the capacitive sensor system (3). [10] Method according to the preceding claim, wherein the capacitive sensor system (3) is designed to compare the determined change in the variable (ΔU) compared to the old variable with a predetermined comparison change in order to positively or negatively detect the touching of the control panel (2) or the approach to the control panel (2) on the basis of the comparison. [11] Method according to the preceding claim, wherein a minimum change in the quantity (ΔU) from measuring cycle to measuring cycle which is below a predetermined amount is used for the subsequent adaptation of the predetermined comparison change. [12] Method according to one of the preceding claims 9 to 11, wherein the variable (ΔU) is a difference between the first potential (U 1 ) and second potential (U 2 ) and a touch of the control panel (2) or an approach to the control panel (2) is only positively detected when a predetermined minimum difference is undershot as a predetermined comparison change. [13] Method according to one of the preceding claims 9 to 12, wherein the evaluation unit (µC) has an analog-digital converter (ADC) for selective connection to the electrode (S). [14] Method according to one of the preceding claims 9 to 13, wherein the initial potential (GND) and the first ground potential (GND') correspond to a ground potential. [15] Method according to one of the preceding claims 9 to 14, wherein the first time period (Δt 1 ) and the third time period (Δt 3 ) are chosen consistently and / or the second time period (Δt 2 ) and the fourth time period (Δt 4 ) are chosen consistently.

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