Piezo switching element

Abstract

Piezo switching element comprising: - a housing (10) with a base part (19), - a cover plate (11), - a carrier (30) with a piezo element (35), - a capacitive sensor with at least one sensor electrode (33), - the base part (19) is designed as a spring-movable coupling means (20) and comprises a contacting element (24) and a coupling element (26), - wherein the coupling element (26) protrudes from the coupling means (20) in the shape of a base and - wherein the coupling element (26) is coupled to the cover plate (11), - wherein the contacting element (24) protrudes in a base-like manner on a side of the coupling means (20) opposite the coupling element (26), - wherein the contacting element (24) is coupled to the piezo element (35), - wherein an external force (F) on a user-facing side (8) of the cover plate (11) can be transmitted by means of the coupling means (20) to the piezo element (35) to generate a piezo signal corresponding to this force (F), - wherein the cover plate (11) has a transmission area (15), - wherein the presence of an actuating means on the user-facing side (8) of the cover plate (11) in the transmission area (15) is detectable by the capacitive sensor to generate a corresponding sensor signal, wherein the at least one sensor electrode (33) of the capacitive sensor is arranged between the cover plate (11) and the coupling means (20), and - wherein the at least one sensor electrode (33) is designed as a circular ring-shaped component which is arranged around the coupling element (26).

Description

[0001] The present invention relates to a piezo switching element.

[0002] Piezo switching elements are known in various designs from the prior art and comprise at least one piezo element. Such piezo switching elements serve to convert a force exerted on a piezo element into a switching signal. Typically, a piezo switching element evaluation is provided, which evaluates a voltage output by the piezo element upon application of a force.

[0003] Such a piezo switching element is known from DE 43 32 927 C2, in which a contact carrier is overmolded with housing parts, with one of the housing parts serving as a carrier for a piezo element and an electronic component. The housing parts connected via contact carriers are folded together and locked together. Furthermore, this document discloses a piezo switching element in which a base-like plastic carrier serves as the housing and carries a carrier film with conductor tracks and contact surfaces, as well as the piezo element and the electronic component. The carrier film thus assembled is folded around the plastic carrier.

[0004] The piezo switching elements known from DE 43 32 927 C2 are, on the one hand, complex to manufacture. In particular, the complex assembly process leads to high manufacturing costs and high scrap rates.

[0005] Furthermore, these known piezo switching elements are relatively insensitive, as a certain threshold value, which is determined by the circuit processing the piezo signals, must first be exceeded. Furthermore, the circuits used in these devices merely amplify the piezo signal, which can lead to unwanted switching behavior due to unwanted external mechanical influences.

[0006] From DE 10 2009 012 475 A1, a piezo switching element is already known which has a simple and compact design and realizes a defined pressure point, so that the piezo switching element can have a very high sensitivity.

[0007] A disadvantage of this state of the art is that the known piezo switching elements are not suitable for use in hygienically sensitive areas or areas at risk from heavy contamination, since the piezo switching elements must be directly exposed to the external force in order to achieve the desired high sensitivity.

[0008] DE 10 2019 110 399 therefore presents a piezo switching element with a cover plate. An external force exerted on the cover plate is transmitted to the piezo element to generate a corresponding signal.

[0009] The external force can be applied, for example, by pressing with a finger or another actuating element. Many applications require that a control signal be generated only when the external force is applied within a specific transmission range of the cover plate.

[0010] With regard to the teaching disclosed in DE 10 2019 110 399, it has proven disadvantageous that an external force can be transmitted to the piezo element and a corresponding signal can be generated even if the external force acts on the cover plate outside the transmission range.

[0011] Further sensor devices are known from US 2018 / 0334018 A1, DE 10 2013 007 008 A1 and DE 10 2012 005 708 A1.

[0012] The invention is therefore based on the object of providing an improved piezo switching element which expediently eliminates the disadvantages of the piezo switching elements known from the prior art and in particular only generates a control signal when the external force is applied in a defined transmission range.

[0013] Furthermore, the object is to provide a piezo switching element that is suitable for use in hygienically sensitive areas or areas at risk from heavy contamination and that can be cleaned easily and hygienically in accordance with the requirements without leaving residues, in particular biological contamination.

[0014] The task is also to provide a piezo switching element that is easy to manufacture.

[0015] These objects are achieved according to the invention by a piezo switching element having the features of patent claim 1 or 2.

[0016] Advantageous embodiments and further developments of the invention are specified in the dependent claims.

[0017] The piezo switching element according to the invention comprises a housing, a cover plate with a user-facing side and a user-remote side, a carrier with a piezo element and a coupling means held on the housing, as well as a capacitive sensor with at least one sensor electrode. The coupling means comprises a contacting element and a coupling element, wherein the coupling element is coupled to the cover plate, wherein the contacting element is coupled to the piezo element, and wherein an external force on the user-remote side of the cover plate can be transmitted to the piezo element by means of the coupling means to generate a piezo signal corresponding to this force.The housing, the contact element, and the carrier are preferably arranged on the side of the cover plate facing away from the user. The external force acting on the cover plate on the side facing the user can elastically deform the cover plate in the region of the contact element. The resulting displacement can be transmitted to the coupling means by means of the coupling element and further to the piezo element by means of the contact element. In response to the acting external force, the piezo element can output a voltage that can be evaluated by a logic element.

[0018] In addition, the cover plate has a transmission range, wherein the presence of an actuating means on the side of the cover plate facing the user can be detected in the transmission range by the capacitive sensor to generate a corresponding sensor signal. Detection can be carried out using a field spanned across the at least one sensor electrode, which field can be influenced by the approach of an actuating means. Actuating means can be, for example, a finger of an operator or a pen. The transmission range is preferably defined in that, within the transmission range, both the external force can be transmitted to the piezo element and the presence of an actuating means can be detected by the capacitive sensor. In particular, the extent of the transmission range can thus be determined by appropriate configuration of the capacitive sensor.Preferably, the transmission range is designed symmetrically, wherein the transmission range is particularly preferably designed symmetrically about the longitudinal axis in which the piezo element, the contacting element and the coupling element are arranged.

[0019] The cover plate can be made of any material, preferably glass, whereby the piezo switching element according to the invention can have an easy-care and dirt-resistant and durable surface, which can also protect the sensitive piezo element and the capacitive sensor from foreign substances.

[0020] This makes it possible to provide a piezo switching element with a particularly simple design, which on the one hand meets the requirements during use and on the other hand also has a reliable switching behavior with a defined pressure point and a high sensitivity.

[0021] In a further development of the invention, the piezo switching element has a logic element that is electrically coupled to the piezo element and the capacitive sensor and is configured to evaluate the piezo signal and the sensor signal and to generate a control signal that triggers a switching operation. The logic element is preferably formed by an electronic component, in particular a microprocessor. The logic element can preferably evaluate the piezo signal and the sensor signal with regard to their time-level curve on the basis of predetermined parameters and compare them with one another. A control signal is preferably only generated if the evaluation indicates that an actuating means was also present in the transmission area when the external force was applied.Even if the application of an external force outside the transmission range generates a piezo signal which, viewed alone, indicates actuation of the piezo switching element, a corresponding control signal is preferably not generated if there is no sensor signal indicating the presence of an actuating means. The probability of inadvertent generation of a control signal, particularly due to the application of an external force outside the transmission range, can thereby be significantly reduced. The logic element can therefore be configured such that a control signal is generated even with a small external force - provided that an actuating means is present in the transmission range. A particular advantage here can be that no measures are required to infer actuation within the transmission range based solely on the characteristics of the piezo signal.In particular, complex machining of the cover plate to reduce its local stiffness and improve power transmission in the transmission area can be dispensed with.

[0022] In a further development of the invention, the rigidity of the cover plate is locally reduced in the transmission area. This allows for improved transmission behavior of the cover plate when an external force is applied. The improved transmission behavior reduces the sensitivity or the pressure required to actuate the piezo switching element. The reduction in rigidity can be achieved by reducing the mechanical modulus of elasticity, by selecting the appropriate material, or by changing the shape of the cover plate in the transmission area.

[0023] It has also proven advantageous if the cover plate has a recess in the transmission area on the side facing the user, wherein the recess is particularly preferably aligned coaxially with the coupling element. In particular, it has proven advantageous for the recess on the side facing the user to be visually perceptible to the user. A user can thus immediately recognize that the transmission area is located in the area of ​​the recess. The recess on the side facing the user can preferably be designed as a symmetrical recess, for example, as a finger or grip recess.

[0024] The recess can also be arranged on the side of the cover plate facing away from the user. Thus, the housing of the piezo switching element can be at least partially recessed into the side of the cover plate facing away from the user, thereby reducing the installation space of the piezo switching element. In one embodiment, the cover plate can have a recess on both the side facing the user and the side facing away from the user.

[0025] Preferably, the recess is designed such that the thickness t of the cover plate has a local minimum in the transmission region. The local minimum is preferably arranged coaxially with the coupling element in the longitudinal axis and accordingly lies on the longitudinal axis. It has proven advantageous if the cover plate is as thin as possible and as thick as necessary in the transmission region. On the one hand, a sufficiently reduced stiffness in the transmission region should enable the actuation of the piezo switching element without the need for significant force, and on the other hand, the strength of the cover plate must be ensured with sufficient reliability.

[0026] Depending on the configuration of the logic element, the piezo switching element can have different functionalities. For example, the piezo switching element can act as a switch or as a button. In both configurations, it is preferably first checked whether a piezo signal and a sensor signal are present that indicate the application of an external force and the presence of an actuating element. If both conditions are met, a one-time, short-term control signal is preferably generated in the switch configuration. In the button configuration, a control signal can also be generated if both conditions are met. However, it can also be checked whether the sensor signal continues to indicate the presence of an actuating element. The control signal is preferably generated as long as the sensor signal indicates the presence of an actuating element.

[0027] The logic element is preferably arranged on the carrier, preferably on the side of the carrier opposite the piezo element. Particularly preferably, the carrier is designed as a printed circuit board, which may additionally have conductor tracks and vias connecting both sides of the circuit board. In addition to the logic element, the circuit board may have other electronic components.

[0028] Furthermore, the logic element can be arranged at a location spaced apart from the piezo switching element instead of directly on it. Particularly when using multiple piezo switching elements according to the invention, several of the existing piezo switching elements can have a common logic element. This allows for a simpler structure of the overall system comprising multiple piezo switching elements.

[0029] According to one embodiment of the invention, the at least one sensor electrode of the capacitive sensor is arranged between the cover plate and the coupling means. Furthermore, the at least one sensor electrode is preferably designed as a flat element. As a result, the at least one sensor electrode is arranged close to the cover plate, allowing the capacitive sensor to exhibit high sensitivity with respect to the presence of actuating means on the side of the cover plate facing the user.

[0030] Furthermore, it is advantageous if a cavity is formed between the coupling means and the piezoelectric element and / or between the coupling means and the cover plate. Within the cavity(ies), the coupling means can be elastically deflected, deformed, or displaced by an external force, thereby ensuring unhindered transmission of the displacement from the cover plate to the piezoelectric element upon actuation by a user. Particularly preferably, the at least one sensor electrode of the capacitive sensor is arranged in the cavity between the coupling means and the cover plate.

[0031] According to both embodiments of the invention, the coupling element is base-shaped and is operatively connected to the cover plate. The coupling element preferably protrudes from the coupling means in a base- or pin-shaped manner along a longitudinal axis and is in constant operative contact with the cover plate. The coupling element can be connected to the cover plate, in particular by a material connection. According to one embodiment of the invention, the at least one sensor electrode is designed as a circular ring-shaped component arranged around the coupling element. This allows the coupling element to be arranged centrally in the transmission area. If the external force is exerted on the cover plate by an actuating means in the area of ​​the coupling element, a corresponding piezo signal and a corresponding sensor signal can be generated simultaneously.

[0032] According to one of the inventive embodiments of the present invention, the contacting element is aligned with the piezo element in a base-like manner and is preferably in continuous operative connection with the piezo element. The contacting element protrudes along the longitudinal axis on the side of the coupling means opposite the coupling element, preferably in a base-like or pin-like manner, and contacts the piezo element as precisely as possible, thereby achieving high sensitivity and a defined pressure point.

[0033] It is particularly preferred if the coupling means is flexibly elastic and / or is held on the housing in a flexibly elastic manner. The contacting element and / or the coupling element can be, or particularly preferably can be, arranged centrally on the coupling means.

[0034] A further advantageous embodiment of the present invention provides that the contacting element and the coupling element are aligned coaxially with each other. Due to the coaxial arrangement along the longitudinal axis, which preferably forms a line of symmetry of the coupling means, a one-dimensional stress state can be transmitted through the contacting element and the coupling element.

[0035] The housing of the piezo switching element preferably has a diameter D in the range of 10 mm ≤ D ≤ 50 mm. Furthermore, the thickness t of the cover plate in the transmission area is preferably selected depending on the material selected for the cover plate. For example, the thickness t of a glass cover plate is preferably t ≤ 4 mm, and for a plastic cover plate, t ≤ 8 mm. Furthermore, the ratio of the diameter D of the piezo switching element to the thickness t of the cover plate is preferably greater than or equal to 10, i.e., D / t ≥ 10.

[0036] A further advantageous embodiment of the present invention provides that the cover plate is a multilayer cover plate and / or that the cover plate is made of glass, glass ceramic, ceramic, plastic, or a sandwich composite of the aforementioned materials. Furthermore, other materials or any other desired material combinations can be used. It has proven advantageous if the layers of a multilayer cover plate are bonded to one another, in particular by means of an adhesive bond.

[0037] A further feature of the present invention provides that the housing is cylindrical and has a front-end base portion. It is particularly preferred if the housing is cup-shaped with a front-end base portion, wherein "cylindrical" is used here and below in the sense that the cylinder has congruent end surfaces.

[0038] It is particularly advantageous to arrange the carrier with the piezo element in the region of the bottom part of the housing so that the piezo element is in direct operative connection with the contacting element. Furthermore, according to one embodiment of the invention, the bottom part of the housing is designed as the coupling means, thus allowing the housing to be manufactured cost-effectively in a single piece. The housing can preferably be manufactured from a plastic material using an injection molding process.

[0039] According to one embodiment of the present invention, the housing has a frontal and at least partially circumferential edge, the free end of which lies in a common plane with the free end of the coupling element. The circumferential edge can serve as a support surface for the housing on the cover plate. Furthermore, the circumferential edge forms the cavity between the coupling means and the cover plate, thereby enabling the resilient design of the coupling means.

[0040] The housing can be attached to the cover plate in any desired manner, with the housing preferably being connected to the cover plate by means of a material-to-material connection, in particular by gluing or ultrasonic welding. Alternatively, a detachable connection, in particular a screw connection, can be used to connect the housing to the cover plate. Other positive and / or non-positive connections can also be used to attach the housing to the cover plate, for example, plug-in, clamp-on, or snap-in connections.

[0041] Furthermore, it has proven advantageous if the carrier rests with its peripheral surface against an inner surface of the housing. The positive fit between the carrier and the preferably cylindrical inner surface of the housing transverse to the longitudinal axis allows for a tight seal with respect to the cavity in which the piezo element is arranged.

[0042] It has also proven advantageous if the side of the housing facing away from the cover plate, or the side facing away from the user, is at least partially sealed with a potting compound. The potting compound can secure the carrier in the housing.

[0043] It has also proven advantageous if the housing and / or the coupling element are connected to the carrier.

[0044] A further aspect of the present invention relates to the use of the piezo switching element according to the invention in a human-machine interface.

[0045] An embodiment of the invention is explained with reference to the following figures. It shows: Fig. 1 a schematic and highly simplified representation of an embodiment of a piezo switching element according to the invention, Fig. 2 a flow diagram illustrating the operation of a piezo switching element according to the invention in switch configuration, and Fig. 3 a flow diagram illustrating the operation of a piezo switching element according to the invention in button configuration.

[0046] For the sake of clarity, not all reference symbols are used in every figure.

[0047] The sectional view according to Fig. Figure 1 shows the piezo switching element 1 according to the invention, which is arranged along a longitudinal axis 5. The piezo switching element 1 comprises a housing 10, a cover plate 11, a carrier 30 with a piezo element 35, a capacitive sensor with a sensor electrode 33, and a coupling means 20. Furthermore, the piezo switching element 1 can comprise a logic element 32, which is electrically connected to the piezo element 35 and the sensor electrode 33 of the capacitive sensor and is configured to evaluate a piezo signal output by the piezo element 35 and a sensor signal output by the capacitive sensor and to generate a control signal that triggers a switching operation.

[0048] The cover plate 11 has a side 8 facing the user and a side 9 facing away from the user and is preferably made of glass, a ceramic, a glass ceramic, a plastic, or a metallic material. The cover plate 11 has a thickness t, which can be selected arbitrarily, but is small compared to the dimensions in a plane parallel to the side 8 facing the user. Typical thicknesses t of the cover plate 11 are 10 mm > t > 0.5 mm, with both larger and smaller thicknesses t being possible and not subject to any restrictions. The cover plate 11 is - as shown - preferably oriented perpendicular to the longitudinal axis 5.

[0049] The housing 10 is arranged coaxially to the longitudinal axis 5 and can have a hollow cylindrical cross-section. Fig. 1, the housing 10 is U-shaped or cup-shaped with a base part 19 and encloses a space with its inner surface 13. The housing 10 has a first side which faces the cover plate 11 and a second side which faces away from the cover plate 11. The second side of the housing 10 is an open end through which the space within the housing 10 is accessible, wherein the housing 10 extends from the open end over the region of the base part 19 to a circumferential edge 18. In the region of the base part 19, on the side facing the open end, an annular shoulder 14 is formed which forms a shoulder-shaped stop in the direction of the longitudinal axis 5. The annular shoulder 14 surrounds or surrounds a second cavity 12b.

[0050] The edge 18 projects in the direction of the longitudinal axis 5 from the area of ​​the base part 19 and projects beyond the base part 19 to form a first cavity 12a between the cover plate 11 and the base part 19.

[0051] The base part 19 is designed as a spring-movable coupling means 20, wherein the base part 19 is preferably designed rotationally symmetrical about the longitudinal axis 5 and has, on the one hand, a coupling element 26 and, on the other hand, a contacting element 24, which each protrude in opposite directions coaxially to the longitudinal axis 5 in the form of a base.

[0052] The carrier 30 with the piezo element 35 is inserted into the space enclosed by the inner surface 13, wherein the carrier 30 is inserted into the U-shaped or cup-shaped housing 10 such that the piezo element 35 is arranged on the side facing the base part 19 and the carrier 30 can rest against the annular shoulder 14. The shape and size of the carrier 30 preferably correspond to the cross-section of the space, whereby the position of the carrier 30 relative to the longitudinal axis 5 is predetermined and the piezo element 35 can be arranged coaxially to the longitudinal axis 5. The carrier 30 or the piezo element 35, the annular shoulder 14 and the base part 19 enclose the second cavity 12b.

[0053] The coupling means 20 or the base part 19 can be resiliently deflected within the first cavity 12a and the second cavity 12b.

[0054] The sensor electrode 33 of the capacitive sensor is arranged between the side 9 of the cover plate 11 facing away from the user and the coupling means 20, preferably within the first cavity 12a. The sensor electrode 33 is designed as a flat, circular element that surrounds the base-shaped coupling element 26. An electric field is generated by the sensor electrode 33. If the electric field changes, particularly due to the presence of an actuating means, such as a finger, a corresponding sensor signal can be output from the capacitive sensor to the logic element 32.

[0055] On the side of the plate-shaped carrier 30 facing away from the piezo element 35, a logic element 32 can be arranged, which is electrically coupled to the piezo element 35 and the capacitive sensor and is configured to evaluate the piezo signals of the piezo element 35 and the sensor signals of the capacitive sensor and to generate a control signal. The logic element 32 is preferably designed as an electronic component, particularly preferably as a microcontroller.

[0056] The housing 10 is arranged on the cover plate 11 in such a way that, on the one hand, the coupling element 26 is in operative connection or operative contact with the cover plate 11 and, on the other hand, the contacting element 24 is in operative connection or operative contact with the piezo element 35.

[0057] An external force F, which in the embodiment is only shown for illustration purposes, Fig. 1 by means of an arrow, leads to an elastic deformation of the cover plate 11, wherein the deformation acts on the piezo element 35 by means of the coupling means 20 resiliently supported on the housing 10. Due to the deformation, a piezo signal in the form of a voltage is output by the piezo element 35.

[0058] The area in which both the presence of an actuating means can be detected by the capacitive sensor and the external force F can be transmitted to the piezo element 35 is referred to as the transmission area 15. Due to the central arrangement of the coupling element 26 in the center of the sensor electrode 33, the actuation of the piezo switching element can be detected particularly reliably.

[0059] The piezo signal and the sensor signal can be evaluated by the logic element 32 and translated into a corresponding control signal. Preferably, a control signal is only generated when the external force F acts on the cover plate 11 in the transmission area 15 and an actuating element is present.

[0060] The Fig. 2 and Fig. 3 illustrate two possible operating modes of the piezo switching element 1 with different configurations of the logic element 32.

[0061] In Fig. Figure 2 shows the operation of the piezo switching element 1 in switch configuration 40. After starting the piezo switching element 1 in method step 41, the first step in step 42 is to check whether the piezo signal indicates an actuation of the piezo element 35, i.e., the action of an external force F on the piezo element 35. The test in step 42 is carried out until the piezo element 35 outputs a piezo signal that indicates the action of an external force F. In this case, the logic element 32 proceeds to the next method step 43, in which it is checked whether the capacitive field is active. Activity of the capacitive field is detected when the capacitive sensor, using the sensor electrode 33, detects the presence of an actuating means in the transmission area 15 and generates a corresponding sensor signal.If no activity of the capacitive field is detected in step 43, the logic element 32 jumps back to method step 42. If activity of the capacitive field is detected in step 43, step 44 is subsequently executed, in which a control signal for changing a switching state is generated.

[0062] Fig. 3 shows the operation of a piezo switching element 1 in button configuration 50. After starting (method step 51), a check is carried out in step 52 to determine whether the piezo element 35 is actuated, i.e., whether a piezo signal is present that indicates the action of an external force F on the piezo element 35. Step 52 is executed until actuation of the piezo element 35 is detected. If this is the case, the next step 53 checks whether there is any activity in the capacitive field. If this check is negative, the logic element 32 jumps back to step 52. If activity in the capacitive field is detected in step 53, a control signal for activating a switching state ("switching state on") is generated in step 54. The activity of the capacitive field is then further checked in step 55. The activation of the switching state (“Switching state On”) remains as long as the test in step 55 produces a positive result.No further verification of the piezo signal takes place. The application of an external force F to the piezo element 35 is therefore only required to initialize the "switching state on." To maintain this state, the presence of an actuating element in the transmission area 15 is sufficient. If no further activity of the capacitive field is detected, a control signal is generated in step 56 to deactivate a switching state ("switching state off"). The logic element then returns to step 52.

[0063] By showing the two exemplary configurations of the logic element 32 in the Fig. 2 and Fig. 3 particularly illustrates that in the switch configuration 40 ( Fig. 2) the duration of the actuation of the piezo switching element 1 is irrelevant. As soon as the actuation has been detected once by positive results in both step 42 and step 43, a control signal is generated to change a switching state. In the button configuration 50, however, after the initial detection of an external force F (step 52) and the presence of an actuating means (step 53), a further check of the sensor signal and thus of the capacitive field takes place (step 55). The "switching state On" is maintained until no more activity of the capacitive field is detected in step 55. Thus, in the button configuration 50, the actuation duration influences the generation of the control signal. Using a lamp as an example, a possible application scenario for the two Fig. 2 and Fig.3 presented configurations: While the switch configuration 40 can be used to switch the lamp on and off, the button configuration 50 is particularly suitable for implementing a dimming function. List of reference symbols 1 piezo switching element 5 Longitudinal axis 8 user-facing page of 11 9 user-facing page of 11 10 housings 11 Cover plate 12a first cavity 12b second cavity 14 paragraph 15 Transmission range 18 rand 19 Base part 20 coupling agents 24 Contact element 26 Coupling element 30 carriers 31 circuit board 32 logic element 33 Sensor electrode 35 Piezo element 40 switch configuration 41-44 Procedure steps for switch configuration 50 button configuration 51-56 Procedure steps for button configuration F external force t Thickness of the cover plate

Claims

[1] Piezo switching element comprising: - a housing (10) with a base part (19), - a cover plate (11), - a carrier (30) with a piezo element (35), - a capacitive sensor with at least one sensor electrode (33), - the base part (19) is designed as a spring-movable coupling means (20) and comprises a contacting element (24) and a coupling element (26), - wherein the coupling element (26) protrudes from the coupling means (20) in the shape of a base and - wherein the coupling element (26) is coupled to the cover plate (11), - wherein the contacting element (24) protrudes in a base-like manner on a side of the coupling means (20) opposite the coupling element (26), - wherein the contacting element (24) is coupled to the piezo element (35), - wherein an external force (F) on a user-facing side (8) of the cover plate (11) can be transmitted by means of the coupling means (20) to the piezo element (35) to generate a piezo signal corresponding to this force (F), - wherein the cover plate (11) has a transmission area (15), - wherein the presence of an actuating means on the user-facing side (8) of the cover plate (11) in the transmission area (15) is detectable by the capacitive sensor to generate a corresponding sensor signal, wherein the at least one sensor electrode (33) of the capacitive sensor is arranged between the cover plate (11) and the coupling means (20), and - wherein the at least one sensor electrode (33) is designed as a circular ring-shaped component which is arranged around the coupling element (26). [2] Piezo switching element comprising: - a housing (10), - a cover plate (11), - a carrier (30) with a piezo element (35), - a coupling means (20) comprising a contacting element (24) and a coupling element (26), and - a capacitive sensor with at least one sensor electrode (33), - wherein the coupling element (26) is coupled to the cover plate (11), - wherein the contacting element (24) is coupled to the piezo element (35), - wherein an external force (F) on a user-facing side (8) of the cover plate (11) can be transmitted by means of the coupling means (20) to the piezo element (35) to generate a piezo signal corresponding to this force (F), - wherein the cover plate (11) has a transmission area (15), and - where the presence of an actuating means on the user-facing side (8) of the cover plate (11) in the transmission area (15) can be detected by the capacitive sensor to generate a corresponding sensor signal, characterized by , that - the housing (10) has an end-side and at least partially circumferential edge (18), the free end of which lies in a common plane with a free end of the coupling element (26), which is of base-shaped design. [3] Piezo switching element according to claim 1 or 2, characterized by that the piezo switching element (1) has a logic element (32) which is electrically coupled to the piezo element (35) and the capacitive sensor and is configured to evaluate the piezo signal and the sensor signal and to generate a control signal. [4] Piezo switching element according to claim 3, characterized by that the logic element (32) is arranged on the carrier (30). [5] Piezo switching element according to one of the preceding claims, characterized bythat the carrier (30) is designed as a printed circuit board (31). [6] Piezo switching element according to one of the preceding claims characterized by that a cavity (12a, 12b) is formed between the coupling means (20) and the piezo element (35) and / or between the coupling means (20) and the cover plate (11) for the resilient formation of the coupling means (20). [7] Piezo switching element according to one of the preceding claims, characterized by that the contacting element (24) is aligned in a base-like manner with the piezo element (35) and is in operative connection with the piezo element (35). [8] Piezo switching element according to one of the preceding claims, characterized by that the coupling means (20) is flexurally elastic and / or is resiliently supported on the housing (10). [9] Piezo switching element according to one of the preceding claims, characterized bythat the cover plate (11) is a multi-layer cover plate (11) and / or consists of glass, glass ceramic or plastic. [10] Piezo switching element according to claim 1, characterized by that the housing (10) is cylindrical with the front-side base part (19). [11] Piezo switching element according to one of the preceding claims, characterized by that the carrier (30) rests with its peripheral surface on an inner surface (13) of the housing (10).

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