Electrically sensitive control element

Abstract

Method with a sensor (40) for detecting the operating intention of an operator on at least one operating element (100) with a base body (55) facing the operator made of metal and / or of a galvanizable plastic which is at least partially provided with a metallic coating (10) on at least one front side, wherein the method comprises the following steps: - Arranging at least one exciter / receiver coil system (1.3) of the sensor (40) on a rear side of the base body (55), - cyclic injection of an excitation current (1.4) into at least one excitation coil (1.1) which is suitable to induce a DC voltage waveform (6.1) or at least a voltage waveform similar to a DC voltage waveform in at least one receiver coil (1.2) in an initial state, and detection of a voltage waveform (1.5) of the receiver coil (1.2), - Evaluating the voltage of the voltage curve (1.5) of the receiver coil (1.2) in an initiation mode in which a crystalline structure of the metallic base body (55) and / or the metallic coating (10) is analyzed and stored by the measuring system (5.5), wherein the control element (100) is also in an initial state and is not operated, - Evaluating the voltage of the voltage curve (1.5) of the receiver coil (1.2) in an operating mode in which the control element (100) is operable, wherein, for its operation, the control element (100) is touched by the operator at least at one position and, in addition, pressure is exerted on the control element (100) that alters, in particular deforms, the crystalline structure of the metallic base body (55) and / or the metallic coating (10), and which may have different pressure values. - Determine whether the crystalline structure of the metallic base body (55) and / or the metallic coating (10) corresponds to that of the initial state of the control element (100) in the non-operated case, and determine a pressure-value-dependent operating intention in the case of operation.

Description

Field of invention

[0001] The present invention relates to a method according to claim 1 with a sensor that forwards signals to a measuring system for evaluation, for detecting the operating intention of an operator at at least one control element having a base body made of metal and / or of a galvanizable plastic facing the operator and provided with a metallic coating. The invention further relates to a sensor according to claim 8, which functions based on the method according to the invention, and a control element for the sensor according to claim 13.

[0002] When this application refers to a "metallic coating", it refers to a metallic coating per se or to a metallic coating applied to a substrate by electroplating of metal.

[0003] When this application refers to "galvanizable plastic", it means a plastic that is suitable for being coated at least at one point with a metallic layer produced by electroplating to create a metallic surface, i.e., it is coatable. State of the art

[0004] Operating elements, for example in the form of push buttons or rotary switches, such as those found in motor vehicles or in the white goods sector (i.e., household appliances), are often formed from a base body manufactured using injection molding. This base body can be coated with a metallic layer, provided the plastic meets the necessary requirements. This coating generally has a layered structure, typically consisting of a copper layer, followed by a nickel layer, and finally a chromium layer. A chemically deposited nickel or copper layer is usually applied beforehand and then reinforced. The chromium layer is then the visible surface, providing both the visual and tactile impression of metal. Despite this, the plastic base body allows the operating element to be lightweight and versatile in its design, e.g.,for mechanical adaptation to electrical switches that carry the control element in the installed state.

[0005] A key development step in such control elements involved selectively coating the surface, so that individual areas of the base body were not provided with a metallic surface. This selective coating allows for the creation of symbols on the surface of the control element and, if the base body is transparent in that area, also enables backlighting of the control element for improved visibility at night. Such control elements are known in motor vehicles and are used as rotary switches and push buttons.

[0006] From DE 10 2017 125 446 A1, an operating element and a method for its manufacture are known. The operating element has a base body made of plastic with a visible side and a back side. The base body comprises at least one electroplated plastic component. The visible side has an electroplated metal layer applied to it, which covers part of the visible side and defines at least one unplated, exposed area on the visible side. The base body carries at least one touch-sensitive sensor element in the exposed area, wherein a layer of the electroplated plastic component is provided between the visible side and the sensor element, covering the sensor element on its surface. The effect of the touch-sensitive sensor element is limited to the at least one unplated, exposed area.

[0007] DE 10 2020 105 312 A1 describes an operating element and a method for its manufacture. The operating element has a visible side and a back side, and a base body made of plastic, which includes at least one electroplated plastic component. The visible side has an electroplated metal layer applied to it, which covers at least part of the visible side, and the base body carries at least one touch-sensitive sensor arrangement on its back side. The sensor arrangement is, among other things, a pressure-sensitive sensor arrangement. The pressure acting on the sensor is generated indirectly via the base body, so that these must form a connected unit.

[0008] With the aforementioned previously used touch-sensitive, capacitive sensor elements / arrangements, incorrect operation can occur, for example, in the case of a control element that extends across a surface, such as a touchpad. This happens when simply swiping the sensor across the surface to a desired target point, intended to trigger a function, is interpreted as an operation, resulting in the unintended activation of a function. Furthermore, the sensor is directly connected to the control element's base, meaning that a failure of either the control element or the sensor always necessitates replacing the entire control element. Additionally, an electrical connection between the base and the vehicle's electronics is required. These designs also result in significant installation effort and design limitations due to the rear-mounted sensor.

[0009] From EP 3 829 065 A1, a capacitive sensor device and a method for detecting the approach or position of an object are known. A measuring electrode is driven by a control device with a voltage derived from a supply voltage, thereby generating an electric field emanating from the measuring electrode within the sensor's active area. A switching device, actuated by the control device, is operatively connected to the measuring electrode to generate the electric field. An evaluation device is provided for assessing the changes generated by the measuring electrode due to the movement or presence of the object within the sensor's active area. An inductor is arranged between the voltage source and the switching device.The control unit is configured to control the switching device in such a way that, due to the inductance, a feedback pulse with high-frequency spectral components is generated when the current is switched off. This feedback pulse generates a voltage at the measuring electrode that is higher than the supply voltage. At least one charge storage device and at least one charge leakage resistor are connected downstream of the at least one measuring electrode. These are configured to allow the charge present after a feedback pulse to be detected by the evaluation unit of a microcontroller, thus creating a sensitive, capacitive proximity or position sensor.

[0010] According to DE 10 2007 048 402 A1, an operating unit and a method trigger a function as a result of an object approaching. A first sensor surface provides a first sensor output value when the object approaches. It is at least partially surrounded by at least one further sensor surface, which provides a further sensor output value when the object approaches. An evaluation device evaluates these sensor output values ​​to generate output information for triggering the function. For this purpose, the sensor surfaces are arranged and controlled such that the approach angle of the object can be determined as a criterion for generating the output information as a result of the sensor output values.

[0011] From DE 10 2018 120 912 A1, a measuring arrangement and a method for the inductive analysis of metallic objects are known, comprising a coil arrangement with an excitation coil that can be excited by means of an excitation current and at least one receiver coil, which are inductively coupled to each other. An output signal of the measuring arrangement is evaluated by means of an evaluation unit. Means for generating a ramp-shaped signal of an excitation voltage are provided, wherein a control device regulates the current at the base of the excitation coil such that a ramp-shaped excitation current is generated. This method, also known as Deep Field Analysis (DFA), provides an inductive analysis or detection method in which temperature influences on the coil system have no effect and which enables a spectral analysis of the inductive properties of the metal to be analyzed in a wide frequency range. (see WO 2020 / 025608 A1, which belongs to the patent family)

[0012] WO 2016 / 037 597 A1 discloses a sensor element of an inductive proximity or distance sensor, comprising a coil assembly with at least one excitation coil and at least one receiving coil, and provided with an electrically conductive shield that includes a shielding cup surrounding the coil assembly laterally and on the rear side, as well as a method for operating the sensor element. The sensor element is characterized in that the shield further comprises a flange provided on the front side of the sensor element, which is electrically connected to the shielding cup and completely encloses the coil assembly.

[0013] The invention is therefore based on the objective of providing a method for a control element, a sensor for a control element and a control element, by which operating intentions are recognized and thus malfunctions when operating the control element are prevented. Description of the invention

[0014] This problem is solved by a method with the features of claim 1. This method comprises a sensor for detecting the operating intention of an operator at at least one operating element having a base body made of metal and / or a galvanizable plastic, which is at least partially provided with a metallic coating on at least one front side. the procedure includes the following steps: - Arranging at least one exciter / receiver coil system of the sensor on a rear side of the base body, - cyclically injecting an excitation current into at least one excitation coil, which is suitable to induce a DC voltage waveform or at least a voltage waveform similar to a DC voltage waveform in at least one receiver coil in an initial state, and detecting a voltage of the receiver coil, - Evaluating the voltage of the receiver coil in an initiation mode in which a crystalline structure of the metallic base body and / or the metallic coating is analyzed and stored by the measuring system, with the control element also being in an initial state and not being operated, - Evaluating the voltage of the receiver coil in an operating mode in which the control element is operable, wherein, for its operation, the control element is touched by the operator at least at one position and, in addition, pressure is exerted on the control element that alters, in particular deforms, the crystalline structure of the metallic base body and / or the metallic coating, and which may have different pressure values, and thereby - Determine whether the crystalline structure of the metallic base body and / or the metallic coating corresponds to that of the initial state of the control element when not in use, and determine a pressure-value-dependent operating intention when in use.

[0015] The method advantageously recognizes operating intentions and thus prevents malfunctions when operating the control element. At the same time, an electrical connection between the control element and any electronics associated with the vehicle's electronics can be omitted if necessary. This is primarily because the measurement of the structural change in the crystalline structure due to pressure can be recorded separately from an approach by evaluating a curve profile, which will be explained in more detail below.

[0016] Secondly, the problem is solved by a sensor with the features of claim 8, which functions based on the method according to the invention. The sensor for a control element has a base body made of metal and / or a galvanizable plastic, which is at least partially provided with a metallic coating on at least one front side. An excitation / receiver coil system is preferably arranged non-positively on a rear side of the base body. A generator system is connected to the at least one excitation coil and is suitable for generating an excitation current for injection into the at least one excitation coil, which is suitable for inducing a DC voltage waveform or at least a voltage waveform similar to a DC voltage waveform, in particular without metallic influence, in the at least one receiver coil when the excitation / receiver coil system is in an initial state.A measuring system is connected to at least one receiver coil and is capable of analyzing the voltage of the at least one receiver coil, wherein the sensor is capable of performing the steps of the method. By implementing the method in the sensor according to the invention for a control element, operating intentions are advantageously detected, thus preventing malfunctions when operating the control element. At the same time, an electrical connection between the control element and electronics associated with the vehicle electronics can be dispensed with if required. Furthermore, mechanical damage to the control element can be detected, and its maintenance can be facilitated.

[0017] Thirdly, the problem is solved by an operating element with the features of claim 13. This is an operating element with a base body made of metal and / or a galvanizable plastic for a sensor, wherein the base body is at least partially provided with a metallic coating on at least one front side as an operating point.

[0018] In its initial state, the exciter / receiver coil system is preferably not influenced by any other metallic objects besides the metallic base body and the metallic coating, if applicable. However, this is not essential, as such influences are taken into account by storing the initial state. Simultaneously, an initial state of the crystalline structure of the base body and / or the metallic coating is analyzed and stored, allowing for the detection of any changes in state that deviate from it. Preferably, this also allows for the detection of mechanical damage to the control element as a deviation from the initial state.

[0019] Advantageous further developments are the subject of the dependent patent claims.

[0020] In a preferred embodiment of the method, the sensor is arranged with or without a gap to the base body. Direct contact between the sensor and the control element is not necessary, depending on the desired overall height. Mounting the sensor with a gap advantageously provides shock isolation between the control element and the sensor. Furthermore, additional separating elements can be provided between the sensor and the control element.

[0021] Preferably, the reliability of the method can be increased by advantageously recording and using for evaluation the crystalline structure and / or layer thicknesses of individual layers of the metallic coating. Recording individual layer thicknesses allows for a clearer differentiation between cases of operation, non-operation, and overpainting.

[0022] In a further preferred embodiment that advantageously improves the safety of the method, if a difference is detected between the crystalline structure determined in operating mode and the crystalline structure stored in initiation mode during a period of non-use of the control element, damage to the control element is inferred, and a corresponding message is issued to a system superior to the measuring system and / or to an operator. This allows for faster detection, if necessary, of whether the system was installed without damage or was subsequently damaged, for example, in an accident, if several buttons are possibly deformed or cracked, even if not visibly.

[0023] In another preferred embodiment of the method, which improves the safety of the method, in operating mode, by differentiating the pressure-value-dependent operating intention during operation of the control element, it is possible to determine whether the control element was pressed at a planar position of the control element with a pressure reaching or exceeding a predetermined pressure value to trigger a predetermined function, whether the control element was pressed at the planar position of the control element with a pressure below the predetermined pressure value to trigger another predetermined function, or whether only an approach, such as a light pressure or, if further sensors detect an approach, to the control element at the planar position of the control element, took place.This advantageously allows for a desired distinction between a "search" without operation, a "select" with light pressure, and an "activate" with higher pressure.

[0024] In a preferred embodiment of the sensor that facilitates the operation of the control element, at least one LED is arranged on the sensor's circuit board, which is suitable for search and function illumination of the control element. Advantageously, this can be used to switch on the search and function illumination when the operator approaches the control element, for example, by lightly pressing it, or when another sensor detects approach to the control element.

[0025] In another preferred embodiment of the sensor which facilitates the integration of the sensor, the generator and measuring system arranged on the circuit board of the sensor is part of a higher-level system or the higher-level system is arranged on the circuit board in addition to the generator and measuring system.

[0026] In a preferred embodiment of the control element that facilitates its operation, the electroplatable plastic of the base body comprises transparent, translucent, and / or non-transparent plastic material. This is particularly advantageous when the base body is backlit, for example, when line and / or symbol areas are to be selectively illuminated and / or other areas are to remain unilluminated.

[0027] In a preferred embodiment of the control element which improves the properties of the control element, the electroplatable plastic of the base body of the control element comprises acrylonitrile butadiene styrene (ABS), ABS / PC blends, polyamides (PA) and / or polycarbonate (PC) or also an electroplatable film made of PC and ABS.

[0028] In another preferred embodiment of the control element which improves the properties of the control element, the metallic coating has a layer structure comprising a copper and / or a nickel and / or a chromium layer.

[0029] In a further preferred embodiment of the control element, which improves its properties, the metallic coating completely encloses the base body. Advantageously, this leads to greater stability, increased protection against external influences, and / or a better appearance.

[0030] In a preferred embodiment of the control element which facilitates its operation, the metallic coating has at least one recess to advantageously display, for example, markings or operating instructions on the operating side.

[0031] In a further preferred embodiment of the control element, which facilitates its operation, a line and / or symbol area extending to the base body is recessed into at least one recess. Particularly with backlighting, the symbols can thus advantageously be provided with an illuminated border or be illuminated themselves.

[0032] In a preferred embodiment that facilitates the operation of the control element, the line and / or symbol area extends to a height below or above the surface of the metallic coating, or exactly to this level. This allows for different haptic effects to be achieved depending on the requirements.

[0033] In a preferred embodiment of the control element that facilitates operation, the line and / or symbol area is made of polycarbonate (PC). Alternatively, symbols can be printed and / or laser-etched onto an ABS surface.

[0034] The features listed individually in the patent claims can be combined in a technologically meaningful way and can be supplemented by explanatory facts from the description and by details from the figures, showing further embodiment variants of the invention.

[0035] The invention will now be explained in more detail using an exemplary embodiment. The figures shown are: Fig. 1 a circuit of a measuring system from the state of the art with an integrated coil system, Fig. 2 a coil pair of the measuring system, Fig. 3. Time-dependent voltage waveforms at the first operational amplifier (comparator) and at the transmitting coil within the measuring system, Fig. 4. Time-dependent voltage waveforms at the receiver coil and of the current through a current measuring point connected in series with the excitation coil, represented by the voltage across a feedpoint resistor, within the measuring system without metal influence, Fig. 5 different time profiles of the voltage of the output signal of the measuring system for different types of metal, Fig. 6a-f different embodiments of control elements with a sensor according to the invention, Fig. 7a a signal waveform of the output signal of the measuring system with a metallic coating present, Fig. 7b Signal waveforms of the output signal under structural change and distance change, Fig. 8a, Fig. 8b a section through a control element when structural changes occur and when the distance changes due to user operation. Description of preferred embodiments

[0036] Before the invention is described in detail, it should be noted that it is not limited to the respective components of the device or the respective process steps, as these components and processes can vary. The terms used here are intended solely to describe particular embodiments and are not used restrictively. Furthermore, where the singular or indefinite articles are used in the description or in the claims, this also refers to the plural of these elements, unless the overall context clearly indicates otherwise.

[0037] The control element according to the invention uses a sensor based on a measuring system operating according to the Deep Field Analysis (DFA) method, as described in PCT patent application WO 2020 / 025608 A1. The inductive measuring system operating according to the DFA method consists of a simple coil system, preferably a coil pair, and electronics that, compared to known measuring methods for metallic proximity, are composed of only a few components. Furthermore, this method offers a sensitive measuring system for measuring structural changes in the metallic body, such as those that occur under pressure or slight deformation. The following section will begin by describing how the already known method works.

[0038] Fig. Figure 1 schematically shows a measuring system operating according to this method and Fig. 2 a coil system used therein, comprising an excitation coil and a receiver coil.

[0039] The coil system 1.3 of the measuring system according to Fig. 2 consists of at least two coils, which are preferably aligned parallel to each other. One of the two coils acts as an excitation coil 1.1, into which an excitation current 1.4 is fed, and the other as a receiver coil 1.2, at which a voltage waveform 1.5 of the receiver coil 1.2 can be detected. The coil system 1.3 shown consists of one excitation coil 1.1 and one receiver coil 1.2; however, several excitation coils and receiver coils can also be used, particularly if several control elements are used.

[0040] In the simplest case, the coil system consists of a winding body with two bifilar-wound coils. Coil systems are also possible in which the receiver coil 1.2 and the excitation coil 1.1 are arranged directly next to each other or even nested within each other. The number of turns in the excitation coil 1.1 and the receiver coil 1.2 can also differ. Preferably, the excitation coil has fewer turns but a larger conductor thickness. Since only a few turns (5-20) are sufficient, printed coils can easily be used.

[0041] However, it is also possible, especially if temperature independence is not critical, to work with a coil system 1.3 that comprises only one coil, which serves simultaneously as the excitation coil and the receiver coil. This can also be done, for example, with an alternating voltage as the excitation voltage.

[0042] In contrast to classical inductive measuring systems, the excitation coil 1.1 is not excited with a sine or square wave signal or a square wave pulse, but by a direct current, preferably starting from zero and rising uniformly in the form of a ramp, as represented by the curve of the excitation voltage 2.5 in Fig. 3.

[0043] Assuming the ramp-shaped excitation voltage 2.5 is applied directly to the feed terminal 2.2 of the excitation coil 1.1, the current through the excitation coil does not follow the voltage curve of the excitation voltage 2.5 immediately, but with a time delay, due to self-induction. This becomes apparent when the excitation coil 1.1 is connected in series with a current measuring point, such as a feedpoint resistor 2.3 at the feedpoint of the excitation coil 1.1, at which the excitation coil current is measured as a result of the resulting voltage 2.4. Fig. Figure 3 illustrates this. The excitation voltage curve 2.5 corresponds to the ramped voltage increase at the feed point 2.2, while curve 4.1 shows the resulting voltage, measured as the voltage value at the feed point resistor 2.3. (For clarity, the voltages at the excitation coil and the receiver coil are not shown proportionally).

[0044] To ensure that the excitation current 1.4 follows the specified curve of the excitation voltage 2.5 exactly, this is supplied to a non-inverting input 3.3 of a first operational amplifier (comparator) 3.1 ( Fig. 1) Its output supplies the input terminal 2.2 of the excitation coil 1.1 with a suitable excitation voltage. In principle, any excitation voltage is possible, as long as a suitable evaluation reflects the detection of the magnetic field build-up. Furthermore, the inverting input is located at the current measuring point, i.e., in Fig. 1 is connected to the feedpoint resistor 2.3 and receives the voltage 2.4 of the feedpoint resistor 2.3. Through this measure, the excitation current 1.4 is actively controlled and now corresponds exactly to the curve of the excitation voltage 2.5, whereby the excitation voltage 4.2 generated by the operational amplifier 3.2 builds up quickly at the start of the ramp in order to first overcome the self-inductance of the excitation coil 1.1, and then transitions into a range of the output voltage parallel to the excitation voltage 2.5.

[0045] The at least one excitation coil 1.1 is connected in series with the current measuring point. The current flowing into the at least one excitation coil 1.1 increases continuously during a measurement interval from an initial state, which is controlled by a control loop via the current at the current measuring point. The excitation coil 1.1 is energized with the ramp-like increasing current, thereby generating a magnetic field with a temporally increasing effective range. If a metallic object is present within the effective range of the magnetic field, this field dynamically penetrates the metallic object with increasing intensity during the measurement interval, thereby transferring energy to the metallic object. Preferably, this allows the current flowing in the excitation coil 1.1 to be modulated by the metallic object during the measurement interval.Current measuring points at other locations are also possible, provided they are preferably connected in series with the excitation coil.

[0046] This provides means for generating a ramp-shaped voltage signal of the excitation voltage 2.5 as a specification for a ramp-shaped current through the excitation coil 1.1. The described control device regulates the current at the current measuring point, in the exemplary embodiment at the base of the excitation coil 1.1, such that a ramp-shaped excitation current 1.4 is generated, which is modulated by a metallic object 1.6 and affects the change in the excitation voltage.

[0047] Preferably, the control device regulates the current at the feed point of the excitation coil 1.1 such that a steadily increasing excitation current 1.4 is generated in the feed point resistance, wherein the influence of the metallic object 1.6 during the ramp-like increase of the excitation current 1.4 changes the magnitude of the excitation voltage. In particular, this influence is based on the type of metal of the metallic object 1.6, which will be discussed in more detail below. Considering the influence of the control device in Fig. 3 exactly, it turns out that the means for generating a ramp-shaped voltage signal of the excitation voltage 2.5 at the beginning of the ramp-shaped rise initially generate a steep rise 4.2 of the excitation voltage compared to the ramp-shaped rise.

[0048] The voltage 3.2 generated at the feed point 2.2 preferably rises sharply at the start of the ramp before transitioning into a linear range and following the curve of the excitation voltage 2.5. In a preferred embodiment, the voltage at the feed point resistor 2.3 thus follows the curve of the specified excitation voltage 2.5 precisely. The voltage rise 4.2 counteracts the self-inductance of the excitation coil 1.1, leading to a linear increase in the coil current. This results in a gradual build-up of the magnetic field that penetrates the metallic object 1.6.

[0049] This measuring principle is based on the idea that in a series circuit, the same current always flows through the excitation coil. This current, which flows through at least one excitation coil (or multiple excitation coils in the case of multiple control elements), generates a ramp-like magnetic field, a "magnetic field ramp." When a metallic object enters the influence or effective area of ​​this magnetic field ramp, energy is transferred to it. Because a magnetic field ramp is present, the magnetic field penetrates the metallic object dynamically with increasing penetration depth. If the current in the series circuit is measured and regulated to the ramp-like current, the resulting voltage curve can be used as a measurement curve for detecting the metallic object.However, due to the dynamic penetration of the magnetic field, this measurement curve also contains information about the structure and composition of the metallic object.

[0050] This measure also eliminates temperature influences on the coil system, which would otherwise manifest as a change in the ohmic winding resistance and thus the inductance or quality factor of the coil, since the excitation current 1.4 directly follows the predetermined voltage curve of the excitation voltage 2.5. This also applies if the curve of the excitation voltage 2.5 is not chosen to be linear and / or if it is deliberately modified, for example, to achieve metal filtering. Since the regulated current through the excitation coil 1.1 determines the magnetic field, this field is no longer temperature-dependent due to the measure described above, which involves changing the coil resistance.

[0051] Receiver coil 1.2 and excitation coil 1.1 can also use a common ferrite core, preferably a shell core closed on one side.

[0052] If the excitation coil 1.1 is supplied with a ramp-shaped current 6.2, as results at the current measuring point, e.g., at the feedpoint resistor 2.3, due to the specified excitation voltage 2.5, a pure DC voltage waveform 6.1 is formed in the receiver coil 1.2 according to Fig. 4 for the time of the ramp-up. Since temporal changes in a DC voltage level are particularly easy to detect, this measurement method offers significant advantages over conventional measurement methods, e.g., with sinusoidal excitation. The change in this DC voltage over time when metal is approached or when a base body of the galvanized plastic layer changes due to the influence of external forces can then be evaluated. Complete temperature insensitivity is achieved when no current flows in the receiver coil 1.2. This means that if one end of the receiver coil 1.2 is connected to GND, the resulting voltage is simply tapped at the other end with a very high impedance.

[0053] Preferably, the input resistance of the subsequent circuit should be in the megaohm range. This ensures that no significant current flows in the receiver coil 1.2 and therefore temperature-related resistance changes in the receiver winding cannot have any effect.

[0054] The measuring system is completed after Fig. 1 by a clock generator 5.1, which provides a start clock, e.g., every 100 ms, for a ramp generator 5.2 that generates the ramp. With each start clock, the ramp generator 5.2 starts and delivers the ramp signal, e.g., 10 µs long, as an excitation voltage to the first operational amplifier (comparator) 3.1, which ensures that a current flows through the excitation coil 1.1 according to the excitation voltage. The measurement is thus repeated periodically, e.g., every 100 ms, whereby the coil system 1.3 exerts a magnetically induced interaction on a metallic object 1.6.

[0055] Circuits that generate a ramp-shaped signal are known to those skilled in the art, so they will not be discussed in more detail here.

[0056] Power transistors can also be connected downstream of the first operational amplifier (comparator) 3.1 to generate a high ramp current. Furthermore, the second operational amplifier 5.3, configured as a voltage follower (impedance converter), can also be used as an amplifier. However, with a suitable ramp current and an appropriate number of turns, the evaluable voltage at the receiver coil can be several volts, so that no further amplification is necessary and this voltage or voltage curve can be fed directly to the A / D converter of a microcontroller for evaluation. The evaluation of the output voltage of the second operational amplifier (impedance converter) 5.3 can be performed, for example, using a signal processor or microcontroller as a measurement system 5.5.

[0057] The control and evaluation of the excitation and reception signals can also be performed using a microcontroller. In this case, the measurement system is particularly simple, as it essentially requires only a high-impedance input of an analog-to-digital converter (ADC) or an operational amplifier configured as an impedance converter, and current control, e.g., via a feedpoint resistor as the current sensing point. Furthermore, the coil system is implemented as a printed circuit board to enable a temperature-stable and cost-effective measurement method. All signal inputs and outputs can be implemented via corresponding analog or digital inputs of the microcontroller.

[0058] The following curve progressions according to Fig. Five values ​​were determined in practice using the following circuit configuration: Excitation coil 1.1 and receiver coil 1.2 each had 10 turns, printed bifilar, D=10 mm. The maximum current at the end of the ramp was 50 mA. The voltage of the DC voltage waveform 6.1 across the receiver coil 1.2, without any metal influence, had a value of 1.8 Vpp. The ramp length was 5 µs. The distance 1.7 ( Fig. 2) of the coil system to the metal surface of the metallic object 1.6 was 1.5 mm.

[0059] When metal influences the coil system 1.3 of the measuring system, the amplitude response of the output signal 5.4 changes, i.e., according to the [document / reference] in [reference]. Fig. 4. Curve 6.1 shown. While it is strictly linear without metal influence and has the character of a direct current voltage, it deviates from the curve shown at predetermined points depending on the type of metal or composition of different metals.

[0060] Fig. Figure 5 illustrates this. The DC voltage curve 6.1 shows the output signal 5.4 without metal influence. Deviations of the value towards higher voltages indicate ferromagnetic materials. Paramagnetic or diamagnetic materials change the voltage curve towards lower values.

[0061] The essential information about ferromagnetic materials is therefore contained primarily in the voltage level of the output signal 5.4 at low frequencies, i.e., at the end of the curve, and to a lesser extent in the signal rise and the subsequent shape of the curve. Paramagnetic and diamagnetic materials exhibit their magnetic interaction particularly in the high-frequency range, i.e., in the signal rise region, while in the low-frequency range they approach the value of the DC voltage curve 6.1. The curves shown above the main curve represent an identical ferromagnetic metal type, each with a greater thickness, as they increase in distance from the main curve. The curves shown below the main curve represent an identical paramagnetic and diamagnetic metal type, each with a greater thickness, as they increase in distance from the main curve.

[0062] Without metal influence, the output signal 5.4 essentially resembles a DC voltage during the ramp-up. With metal influence, as dictated by the arrangement as a button, a curve is generated. This is stored and serves as the value for the unpressed button. Pressing on this button or contacting this area causes a minimal structural change in the metal, which, however, according to Fig. 7b causes a large change in the curve of the received amplitude.

[0063] The shape of the ramp, and thus also any shape altered by surrounding metal, can be modified to mask the surrounding metals. The curves generated for a specific metal or metal alloy can, for example, be stored in a database, and by comparing them to the stored curves, the material being analyzed can then be examined for damage, incorrect processing, or position.

[0064] Furthermore, for example, by Fourier analysis of the output signal 5.4, three arbitrarily arranged coating layers of metals (e.g. nickel, copper, chromium, etc.) can be determined with regard to their order as well as the total coating thickness and the individual coating layer thicknesses.

[0065] As mentioned earlier, the plastics used in control elements, such as acrylonitrile butadiene styrene (ABS), PC / ABS blends, polyamide (PA), or polycarbonate (PC), are coated with a metallic layer. This layered structure generally consists of a copper layer, followed by a nickel layer, and finally a chromium layer. Nickel exhibits ferromagnetic properties, copper diamagnetic properties, and chromium, depending on factors such as temperature, can be antiferromagnetic or paramagnetic. These properties can be used in the process to analyze the metals used, their condition, and / or their layer thickness. In particular, the stress distribution of the materials changes when operated by a user.

[0066] At the same time, this measurement method can of course also be used to examine materials for specific changes in their crystalline structure due to stress (compression, strain) or to detect hairline cracks or material defects.

[0067] Specifically, these properties of the measuring method are used in the present invention to detect pressure on, or contact with, a control element, which can vary depending on the operator's intention. For example, the pressure will be relatively low if the operator simply moves their finger across the control element. Conversely, the pressure will be higher if they want to select a function at a specific position. Additionally, the measuring method can also detect whether the control element has mechanical damage.

[0068] A first part of the invention relates to a method with a sensor 40 for detecting the operating intention of an operator at least one operating element 100 with a base body 55 made of metal and / or of a galvanizable plastic, as exemplified in the Fig. Figures 6a-6f, which are at least partially provided with a metallic coating 10 on at least one front side, comprise the following steps: - Arranging at least one exciter / receiver coil system 1.3 of the sensor 40 on a rear side of the base body 55, - cyclic injection of an excitation current 1.4 into at least one excitation coil 1.1, which is suitable to induce a DC voltage waveform 6.1 or at least a voltage waveform similar to a DC voltage waveform in at least one receiver coil 1.2 in an initial state, and detection of a voltage waveform 1.5 of the receiver coil 1.2, - Evaluating the voltage of the voltage curve 1.5 of the receiver coil 1.2 in an initiation mode in which a crystalline structure of the metallic base body 55 and / or the metallic coating 10 is analyzed and stored by the measuring system 5.5, wherein the control element 100 is also in an initial state and is not operated, - Evaluating the voltage of the voltage curve 1.5 of the receiver coil 1.2 in an operating mode in which the control element 100 is operable, wherein, for its operation, the control element 100 is touched by the operator at least at one position and, in addition, pressure is exerted on the control element 100 that alters, in particular deforms, the crystalline structure of the metallic base body 55 and / or the metallic coating 10 and which may have different pressure values, and thereby - Determine whether the crystalline structure of the metallic base body 55 and / or the metallic coating 10 corresponds to that of the initial state of the operating element 100 in the non-operated case, and determine a pressure-value-dependent operating intention in the case of operation.

[0069] By implementing the DFA method in the inventive method for an operating element 100, malfunctions during operation of the operating element 100 are advantageously prevented, mechanical damage to the operating element 100 is detected, and its maintenance is facilitated. It is completely irrelevant whether the base body 55 is made of metal and / or a galvanizable plastic. It is also irrelevant whether pressure is applied directly to the metallic base body 55 or to the metallic coating. With a base body 55 made of metal, operation can also occur at a flat position of the operating element 100 where no metallic coating has been applied, but rather, for example, a plastic layer. In this case, pressure on the plastic layer is transferred to the metallic base body.In any case, the method is able to analyze a change in the crystalline structure of the metallic substrate and / or the metallic coating.

[0070] In a first embodiment of the method that advantageously facilitates the maintenance of the control element 100, the sensor 40 can preferably be arranged with or without a gap to the base body. Direct contact between the sensor 40 and the control element 100 is possible depending on the overall height, but not necessary. Installing the sensor with a gap, for example, decouples damage caused by mechanical impacts on the control element 100 from the sensor 40. This also makes it possible, for example, to place an additional separating element between the sensor 40 and the control element 100 to protect it from contamination.

[0071] To advantageously improve the safety of the process, if a difference is detected between the crystalline structure determined in operating mode and the crystalline structure stored in initiation mode during a period of inactivity of the control element 100, damage to the control element 100 can preferably be inferred. Based on this, a corresponding message can be issued to a system superior to the measuring system 5.5 and / or to an operator. This allows, for example, the detection of hairline cracks, other mechanical damage, or temperature changes in the control element.During periods of inactivity, the crystalline structure of the metallic base body 55 and / or the metallic coating 10 is analyzed and compared with the stored values ​​of the crystalline structure of the metallic base body 55 and / or the metallic coating 10, which was originally in an intact initial state. Damage, for example caused by the use of the operating element 100, can thus be reliably detected and reported to the higher-level system and / or the operator.

[0072] The measuring system itself is temperature-independent. However, the control element 100 and the coating's layer system are not. Accordingly, the initial signal will change with temperature, for example, when a vehicle heats up. This can be accounted for by a calibration cycle in the "unattended state" every x seconds.

[0073] Preferably, the sensor is detachably connected to the control element. This advantageously allows, for example, the easy replacement of the control element 100 during maintenance of the device in which the control element 100 is installed. This is particularly the case when the sensor is preferably detachably connected to the control element.

[0074] Preferably, in operating mode, by differentiating the pressure-value-dependent operating intention during operation of the control element 100, one of the following operating intentions can be deduced: whether the control element 100 was pressed at a planar position of the control element 100 with a pressure reaching or exceeding a predetermined pressure value to trigger a predetermined function; or whether the control element 100 was pressed at the planar position of the control element 100 with a pressure below the predetermined pressure value to trigger another predetermined function; or whether only an approach to the control element 100, such as a light pressure, or, if further sensors detect an approach to the control element 100, at the planar position of the control element 100, has taken place.

[0075] A predetermined pressure value allows for a clear distinction between the user's intention when operating control element 100 at a specific point on the control element. Light pressure below the predetermined pressure value, for example, while a finger or stylus is moved across the control element 100, can indicate, for instance, changing the volume or brightness. Stronger pressure, at least at the predetermined pressure value, can, however, indicate an on / off function. This advantageously allows for a desired differentiation between "searching" without operation, "selecting" with light pressure, and "activating" with stronger pressure.

[0076] The different pressure values ​​and their corresponding positions on the control element 100 are analyzed by the system and transmitted to a higher-level system, which then translates them into specific actions. For example, the detection of a pressure value can indicate that an operator is approaching without pressing the control element. This could then be used, for instance, to activate auxiliary lighting for operating the control element. These steps can advantageously improve the safety of the process.

[0077] Any geometric control area can be considered as a planar position, which can include both point-like and line-like control areas (sliders), but also other geometric shapes of control areas.

[0078] A second part of the invention is a sensor 40 for a control element 100 ( Fig. 6a-6f) with a base body 55 made of metal and / or a galvanizable plastic, which is at least partially provided with a metallic coating 10 on at least one front side. Such a sensor need not necessarily consist of only one coil arrangement. It can also comprise several coil arrangements. Likewise, such a sensor can cover any geometric control areas, which can include both point-like and line-like control areas (sliders), as well as other geometric shapes of control areas.

[0079] At least one exciter / receiver coil system 1.3, preferably arranged on a printed circuit board 45, is provided, which is preferably detachably mounted on a rear side of the base body 55. A generator system is connected to the exciter coil 1.1 and is suitable for generating an excitation current 1.4 for injection into the exciter coil 1.1, which is suitable for inducing a DC voltage waveform 6.1, or at least a voltage waveform similar to a DC voltage waveform, in the receiver coil 1.2 when the exciter / receiver coil system 1.3 is in an initial state. Preferably, the exciter / receiver coil system 1.3 is influenced in the initial state, although the base body 55 or the electroplatable plastic may also be present in the initial state. A measuring system 5.5 is connected to the receiver coil 1.1 and is suitable for measuring a voltage of a voltage waveform 1.5 of the receiver coil 1.1.2 to analyze, wherein the generator system and the measuring system 5.5 can be arranged either on the circuit board 45 or remotely from it, and wherein the sensor 40 is suitable to perform the steps of the procedure described above.

[0080] By implementing the DFA method in the sensor 40 according to the invention for a control element 100, operating intentions are advantageously detected, thus preventing malfunctions when operating the control element 100. Furthermore, mechanical damage to the control element 100 can be detected, and its maintenance facilitated. It is completely irrelevant whether the base body 55 is made of metal and / or a galvanizable plastic. It is also irrelevant whether operation and / or pressure is applied directly to the metallic base body 55 and / or to the metallic coating 10. In any case, a change in the crystalline structure is analyzed.

[0081] The sensor can be used, for example, as in Fig. The generator system is set up as shown in Figure 1. In this case, it would consist of the clock generator 5.1, the ramp generator 5.2, the first operational amplifier (comparator) 3.1, and the feedpoint resistor 2.3 as the current measuring point. The second operational amplifier (impedance converter) 5.3 is optional and can also be integrated into the measuring system 5.5.

[0082] In an advantageous embodiment that facilitates the operation of the control element 100, at least one LED can be arranged on the circuit board 45 of the sensor 40, which is suitable for search and function illumination of the control element 100. This can be used, for example, in conjunction with the detection of a pressure change of the metallic base body 55 and / or the metallic coating 10, to switch on the search and function illumination when the operator approaches the control element, e.g., with a light pressure, or when another sensor detects an approach.

[0083] In a further embodiment of the sensor 40 that advantageously facilitates its integration, the generator and measuring system 5.5 arranged on the circuit board 45 of the sensor 40 can be part of a higher-level system, or the higher-level system can be arranged on the circuit board in addition to the generator and measuring system 5.5. The first case can be advantageous, for example, in more complex systems / larger devices or machines, such as in a motor vehicle, while the second case is preferably used in less complex systems / smaller devices or machines.

[0084] A third part of the invention comprises a control element 100 with a base body 55 made of metal and / or a galvanizable plastic, which is at least partially provided with a metallic coating 10 on at least one front side, for a sensor 40. Fig. Figures 6a-6f show 100 such control elements.

[0085] As in Fig. As shown in Figures 6a-6f, the sensor 40 is, for example, located on the circuit board 45 and on a housing / support part 50, spaced behind the plastic base body 55. It could also be in direct contact with the base body 55. In all illustrated embodiments of the control element 100, it is possible to apply line and / or symbol areas directly to the metallic surface using an optional laser etching process.

[0086] Preferably, the electroplatable plastic of the base body 55 comprises transparent, translucent, and / or opaque plastic material, which is used as needed for specific purposes. This is particularly advantageous when backlighting the base body 55, for example, if line and / or symbol areas on the control element 100 are to be selectively illuminated and / or other areas are not to be illuminated. In this case, for example, lighting can be arranged on the circuit board 45.

[0087] Preferably, the electroplatable plastic of the base body 55 of the control element 100 comprises acrylonitrile butadiene styrene (ABS), ABS / PC blends, polyamide (PA) and / or polycarbonate (PC), or an electroplatable film made of PC and ABS. ABS plastics are generally non-transparent but translucent, while PC plastics are generally usable in a transparent form.

[0088] In another embodiment that advantageously improves the properties of the control element 100, the metallic coating 10 has a layered structure comprising a copper and / or a nickel and / or a chromium layer. The chromium layer is then the visible surface, which has both the visual and tactile appearance of metal. Nevertheless, due to the plastic base body, the control element 100 is lightweight and can be designed in a variety of ways, e.g., for mechanical adaptation to electrical switches that support the control element 100 in its installed state.

[0089] If required, the metallic coating 10 can completely enclose the base body 55. This can be useful, for example, if greater stability of the plastic base body 55 or a higher level of protection against external influences is needed.

[0090] In principle, to facilitate operation, the metallic coating 10 can have at least one recess 70. This can be used, for example, to display line and / or symbol areas on the operating side.

[0091] Preferably, a line and / or symbol area extending to the base body 55 is recessed into at least one recess 70. Particularly with backlighting of the base body 55, if it is made of, for example, transparent plastic such as PC, the symbols can be provided with a luminous border or, if the line and / or symbol areas are made of transparent plastic, they can be illuminated themselves.

[0092] The line and / or symbol area can be designed as desired. It can extend to a height below or above the surface of the metallic coating 10, or exactly to this level. This can be used to achieve particularly desired haptic effects that enable intuitive recognition of the respective control element 100.

[0093] In a final embodiment of the control element 100 that advantageously facilitates its operation, the line and / or symbol area is made of polycarbonate (PC). As already mentioned, this can be used to directly illuminate the line and / or symbol areas.

[0094] Fig. Figures 6a-6f show different variants of control element 100. Fig. Figure 6a shows, for example, a base body 55 made of an ABS component 20, which is completely surrounded by a metallic coating 10. However, instead of the base body 55 made of the ABS component 20, a metallic base body 55 could also be used. In this case, the metallic coating 10 could even be omitted entirely.

[0095] In Fig. 6b the base body 55 consists of a PC component 30 over which an ABS component 20 is arranged, which are at least partially covered by the metallic coating.

[0096] In Fig. In 6c, an additional area of ​​the metallic coating 10 has been laser-cut to allow for the possible placement of a pre-produced line and / or symbol area in the resulting recess 70.

[0097] In Fig. In contrast, in 6d the line and / or symbol area has been directly injected as PC component 80. This can be transparent or translucent.

[0098] The Fig. 6e has a base body 55 made of a PC component 30 with an ABS / PC film 25 arranged over it, which carries a metallic coating 10 that partially surrounds it. Here too, an area of ​​the metallic coating 10 was laser-cut to create a recess 70 for a line and / or symbol area.

[0099] In Fig. In contrast, 6f has no recess 70 in the metallic coating, but it is also possible here to apply line and / or symbol areas directly onto the metallic surface by means of an optional annealing laser.

[0100] Fig. Figure 7a shows an example of the output signal 7.2 when a metallic coating 10 is located in front of the coil system 1.3 and the sensor 40. For better orientation, in Fig. 7 again the voltage curve 6.1 at the output of the receiver coil without metal influence and the associated curve 6.2 of the voltage at the feedpoint resistor 2.3 resulting from a ramp-shaped current, i.e. the ramp specification shown.

[0101] To understand and better illustrate the differences between general metal approximation and a structural change in the metal, in Fig. 7b the output signal 7.2 resulting from the influence of metal at the output of the receiver coil 1.2 is calculated to form a straight line 7.4.

[0102] In the case of a structural change, such as that caused by material stress, line 7.4 changes to curve 7.6 in such a way that essentially only the signal components at the start of the ramp change, in this case, for example, only in the first µs. The structural change in the metal, i.e., the material stress, can be caused, for example, by localized pressure, as occurs in Fig. Figure 8a shows the "indentation" under the fingertip (8.2). This is neither visible nor perceptible, yet the signal change from straight line (7.4) to curve (7.6) is clearly measurable.

[0103] However, if the metallized surface with metallic coating approaches operating range 90 in general, as is the case in Fig. As shown in 8b, the line 7.4 changes to the signal curve 7.5.

[0104] Thus, a general change in distance can be clearly distinguished from a localized structural change. This is important if the metallized surface is not rigidly connected to the base body 55 and the coil system, and changes in distance are to be expected, e.g., due to manufacturing tolerances or temperature influences.

[0105] The magnitude of the change from straight line 7.4 to curve 7.6 depends on the respective finger pressure, and various actions can be triggered by appropriate software evaluation at different pressures. Reference symbol list 1.1 Excitation coil 1.2 Receiver coil 1.3 Coil system 1.4 Excitation current through the excitation coil 1.5 detectable receiver coil voltage curve 1.6 metallic object 1.7 Distance between coil system and metallic object 2.2 Power supply connection of the excitation coil 2.3 Foot point resistance 2.4 Voltage at the feedpoint resistor 2.5 Ramp-shaped excitation voltage at the output of the ramp generator 3.1 First operational amplifier (comparator) 3.2 Output voltage of 3.1 3.3 Non-inverting input from 3.1 4.1 Resultant current at 2.2, measured as voltage waveform at 2.3 4.2 Excitation voltage waveform generated by the operational amplifier (comparator) 5.1 Clock Generator 5.2 Ramp Generator 5.3 Second operational amplifier (impedance converter) 5.4 Output voltage from 5.3 5.5 Measurement system 6.1 Voltage curve at the output of the receiver coil or from 5.3 6.2 Voltage curve at 2.3 resulting from a ramp-shaped current 7.2 Output signal 7.4 Straight 7.5 Signal waveform 7.6 Curve 8.2 Fingertip 10 metallic coating 20 ABS components 25 ABS / PC film 30 PC components 40 Sensor 45 circuit board 50 Housing / Carrier part 55 Basic body 60 Optional starting laser 70 Cutout for line / symbol area 80 line / symbol area made of PC-injected material 90 operating area 100 Control element

Claims

[1] Method with a sensor (40) for detecting the operating intention of an operator on at least one operating element (100) having a base body (55) facing the operator made of metal and / or of a galvanizable plastic which is at least partially provided with a metallic coating (10) on at least one front side, wherein the method comprises the following steps: - Arranging at least one exciter / receiver coil system (1.3) of the sensor (40) on a rear side of the base body (55), - cyclic injection of an excitation current (1.4) into at least one excitation coil (1.1) which is suitable to induce a DC voltage waveform (6.1) or at least a voltage waveform similar to a DC voltage waveform in at least one receiver coil (1.2) in an initial state, and detection of a voltage waveform (1.5) of the receiver coil (1.2), - Evaluating the voltage of the voltage curve (1.5) of the receiver coil (1.2) in an initiation mode in which a crystalline structure of the metallic base body (55) and / or the metallic coating (10) is analyzed and stored by the measuring system (5.5), wherein the control element (100) is also in an initial state and is not operated, - Evaluating the voltage of the voltage curve (1.5) of the receiver coil (1.2) in an operating mode in which the control element (100) is operable, wherein, for its operation, the control element (100) is touched by the operator at least at one position and, in addition, pressure is exerted on the control element (100) that alters, in particular deforms, the crystalline structure of the metallic base body (55) and / or the metallic coating (10), and which may have different pressure values. - Determine whether the crystalline structure of the metallic base body (55) and / or the metallic coating (10) corresponds to that of the initial state of the control element (100) in the non-operated case, and determine a pressure-value-dependent operating intention in the case of operation. [2] Method according to claim 1, wherein in the exciter / receiver coil system (1.3) of the sensor (40) the exciter coil (1.1) is arranged separately from the receiver coil (1.2). [3] Method according to claim 1 or 2, wherein the exciter / receiver coil system (1.3) of the sensor (40) is detachably arranged on a rear side of the base body (55). [4] Method according to one of the preceding claims, wherein the sensor (40) is arranged with or without a distance to the base body (55). [5] Method according to one of the preceding claims, wherein the crystalline structure and / or layer thicknesses of individual layers of the metallic coating (10) are detected and used for evaluation. [6] Method according to one of the preceding claims, wherein, upon detection of a difference between the crystalline structure determined in operating mode and the crystalline structure stored in initiation mode during a period of non-operation of the control element (100), damage to the control element (100) and / or a temperature change is inferred and a corresponding message is issued to a system superior to the measuring system (5.5) and / or to the operator. [7] Method according to one of the preceding claims, wherein in operating mode, by differentiating the pressure-value-dependent operating intention during the operation of the control element (100), at least one of the following operating intentions is inferred, namely whether the control element (100) was pressed at a planar position of the control element (100) with a pressure reaching or exceeding a predetermined pressure value to trigger a predetermined function, or whether the control element (100) was pressed at the planar position of the control element (100) with a pressure below the predetermined pressure value to trigger another predetermined function, or whether only an approach, which may be detected by further sensors, to the control element (100) at the planar position of the control element (100) has taken place. [8] Sensor (40) for an operating element (100) with a base body (55) made of metal and / or of a galvanizable plastic, wherein the base body (55) is at least partially provided with a metallic coating (10) on at least one front side, comprising - at least one exciter / receiver coil system (1.3) arranged on a rear side of the base body (55), - a generator system connected to at least one excitation coil (1.1) and capable of generating an excitation current (1.4) for injection into the at least one excitation coil (1.1), capable of producing a DC voltage waveform (6.1) or at least a voltage waveform similar to a DC voltage waveform in the at least one receiver coil (1.2) when the excitation / receiver coil system (1.3) is in an initial state, - a measuring system (5.5) to which at least one receiver coil (1.2) is connected and is suitable for analyzing a voltage of a voltage waveform (1.5) of the at least one receiver coil (1.2), wherein the sensor (40) is suitable to perform the steps of the method according to any one of claims 1 to 7. [9] Sensor (40) according to claim 8, wherein an exciter coil (1.1) and a receiver coil (1.2) are provided in the exciter / receiver coil system (1.3). [10] Sensor (40) according to claim 8 or 9, wherein the exciter / receiver coil system (1.3) of the sensor (40) is detachably arranged on a rear side of the base body (55). [11] Sensor (40) according to one of claims 8 to 10, wherein at least one LED is arranged on the circuit board (45) of the sensor (40) which is suitable for search and function illumination of the control element (100). [12] Sensor (40) according to one of claims 8 to 11, wherein the generator and measuring system (5.5) arranged on a printed circuit board (45) of the sensor (40) is part of a higher-level system or the higher-level system is arranged on the printed circuit board in addition to the generator and measuring system (5.5). [13] Control element (100) with a base body (55) made of metal and / or of a galvanizable plastic, which is at least partially provided with a metallic coating (10) on at least one front side, for a sensor (40) according to one of claims 8 to 11. [14] Control element (100) according to claim 13, wherein the electroplatable plastic of the base body (55) comprises acrylonitrile butadiene styrene (ABS), ABS / PC blends, polyamides (PA) and / or polycarbonate (PC) or also an electroplatable film made of PC and ABS. [15] Control element (100) according to claim 13 or 14, wherein the metallic coating (10) has a layer structure comprising a copper and / or a nickel and / or a chromium layer. [16] Control element (100) according to one of claims 13 to 15, wherein the metallic coating (10) completely encloses the base body (55). [17] Control element (100) according to one of claims 13 to 16, wherein the metallic coating (10) has at least one recess (70), wherein preferably a line and / or symbol area extending to the base body (55) is embedded in the at least one recess (70). [18] Control element (100) according to claim 17, wherein the line and / or symbol area extends to a height below or above the surface of the metallic coating (10) or exactly to it.

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