Force or pressure sensor and method for providing a force or pressure sensor

Abstract

Force or pressure sensor (1), comprising: an electrically conductive layer (2), at least one electrically conductive surface element (3,3-x), a deformable insulating layer (4) between the electrically conductive layer (2) and the at least one electrically conductive surface element (3,3-x), and a measuring device (5), wherein the electrically conductive layer (2) is electrically connected to ground (6), and wherein the measuring device (5) is configured to detect and / or determine a change in self-capacitance at the at least one electrically conductive surface element (3,3-x) and, based on the detected and / or determined change in self-capacitance, to ascertain as a result (10,10-x) whether an actuation (20,20-x) of the force or pressure sensor (1) has taken place, and to generate and / or provide a signal (11,11-x) encoding the result (10,10-x), wherein the deformable insulating layer (4) is made of or comprises leather.

Description

[0001] The invention relates to a force or pressure sensor and a method for providing a force or pressure sensor.

[0002] Force sensors are used in modern motor vehicles. These often employ simple piezoelectric ceramics or strain gauges. Since the general aim is to place force sensors where the action (e.g., pressing a finger on a control element) occurs, it is desirable to design the force sensors to be as flat as possible.

[0003] A transparent pressure sensor and a manufacturing process for it are disclosed in US patent 2018 / 0209859A1. The transparent pressure sensor comprises several layers of transparent electrodes, at least one pressure-sensitive deformation layer between the transparent electrodes, and a metal oxide layer. Each layer of transparent electrodes consists of nanowires, and the metal oxide layer is arranged in a space between the nanowires.

[0004] DE 101 49 165 A1 describes a method for manufacturing a sensor element, in particular a switching element, with at least one carrier element having at least one conductive layer, which is covered with a charged or chargeable film and on which at least one electrode layer is placed. To connect the at least one carrier element with the at least one film and at least one electrode layer, the sensor element is to be heated, whereby the sensor element is to be exposed to an electric field before, during, or after heating.

[0005] US 2020 / 0141818A1 describes sensor devices and their methods. An exemplary sensor device comprises a capacitor and a sensor circuit. The capacitor includes a first substrate with a first electrode, a second substrate with a second electrode, and a dielectric layer. The dielectric layer has a plurality of dielectric structures arranged in a pattern, with the first and second electrodes separated by the dielectric layer and arranged with an overlap area. The sensor circuit is coupled to the capacitor and configured and arranged to detect normal and shear forces acting on the sensor device based on changes in capacitance resulting from changes in at least one of the following factors: the distance between the first and second electrodes and the overlap area of ​​the first and second electrodes.

[0006] German patent DE 10 2019 206 670 A1 describes a capacitive sensor system for the multimodal and / or location-selective measurement of forces, deformations, and / or object proximity, as well as a corresponding measurement method. The capacitive sensor system is used in the industrial, automotive, medical, sports, and leisure sectors.

[0007] The invention is based on the objective of creating and providing a force or pressure sensor that can be designed to be particularly flat and flexible.

[0008] The problem is solved according to the invention by a force or pressure sensor with the features of claim 1, a force or pressure sensor with the features of claim 9, and a method with the features of claim 10. Advantageous embodiments of the invention are set forth in the dependent claims.

[0009] In particular, a force or pressure sensor is provided, comprising an electrically conductive layer, at least one electrically conductive surface element, a deformable insulating layer between the electrically conductive layer and the at least one electrically conductive surface element, and a measuring device, wherein the electrically conductive layer is electrically connected to ground, and wherein the measuring device is configured to detect and / or determine a change in self-capacitance on the at least one electrically conductive surface element and, based on the detected and / or determined change in self-capacitance, to determine as a result whether actuation of the force or pressure sensor has taken place, and to generate and / or provide a signal encoding the result.

[0010] Furthermore, in particular a force or pressure sensor is created, comprising an electrically conductive layer, at least one electrically conductive surface element and a deformable insulating layer between the electrically conductive layer and the at least one electrically conductive surface element, wherein the force or pressure sensor is configured so that the electrically conductive layer can be electrically connected to ground and a change in self-capacitance at the at least one electrically conductive surface element can be detected and / or determined.

[0011] Furthermore, a method for providing a force or pressure sensor is provided in particular, wherein an electrically conductive layer connected to ground, at least one electrically conductive surface element and a deformable insulating layer between the electrically conductive layer and the at least one electrically conductive surface element are provided, and wherein a change in self-capacitance on the at least one electrically conductive surface element is detected and / or determined, and based on the detected and / or determined change in self-capacitance, it is determined as a result whether actuation of the force or pressure sensor has taken place, and wherein a signal encoding the result is generated and / or provided.

[0012] It is intended that the deformable insulating layer is made of leather or comprises leather.

[0013] The force or pressure sensor and the method enable the detection of force and / or pressure using a flat sensor. This is achieved by placing a deformable insulating layer between an electrically conductive layer connected to ground and at least one electrically conductive surface element. A change in the self-capacitance of the at least one electrically conductive surface element is detected and / or determined. Electric field lines emanating from electric charges located in the at least one electrically conductive surface element are cut off by the electrically conductive layer. However, deformation of the insulating layer through which the electric field lines pass can occur, leading to a change in the self-capacitance of the at least one electrically conductive surface element. Therefore, when the force or pressure sensor is actuated, for example by applying a force or pressure, the sensor's self-capacitance changes.When pressure is exerted on the electrically conductive layer and the deformable insulating layer is thereby deformed, this can be detected via the resulting change in self-capacitance at the at least one electrically conductive surface element. In particular, activation of the force or pressure sensor is detected when a change in self-capacitance exceeds a predefined threshold. Since self-capacitance measurement is very sensitive to external disturbances, the electrically conductive layer, which typically comes into contact with an actuating element (e.g., a user's finger), is electrically connected to ground, thus providing electrical shielding to the deformable insulating layer and the at least one electrically conductive surface element from the environment.In particular, it is further provided that one or more electrical lines necessary for detecting and / or determining the change in self-capacitance to the measuring device are also shielded, with one shield being electrically connected to ground.

[0014] One advantage of the force or pressure sensor and the method is that the force or pressure sensor can be very flat. This allows the force or pressure sensor to be positioned on surfaces without requiring much installation space. In particular, this makes it possible to functionalize almost any surface.

[0015] A change in self-capacity can be detected and / or determined, for example, by cyclically charging and discharging at least one surface element. In this process, charging and discharging times are specifically considered and evaluated. If these times (or the time constants for charging and / or discharging) change under otherwise constant conditions, then a change in self-capacity has occurred. This change in self-capacity can be detected and / or determined, for example, using a dedicated microcontroller circuit within the measuring device, such as those provided by Infineon Technologies AG.

[0016] In one embodiment, the measuring device is configured to determine, based on the detected and / or determined change in self-capacitance, a force and / or pressure acting on the force or pressure sensor, and to generate and / or provide a signal encoding the determined force and / or pressure. This allows not only the determination of whether actuation has occurred, but also the quantification of the actuation in terms of its magnitude. For this purpose, a function, characteristic curve, or map can be used, for example, to infer or determine the force and / or pressure acting on the force or pressure sensor based on a detected and / or determined change in self-capacitance.The function, characteristic curve or characteristic map can be determined, for example, by means of empirical test series and / or by means of simulation.

[0017] In one embodiment, the electrically conductive layer, the at least one electrically conductive surface element, and the deformable insulating layer are transparent. This allows the force or pressure sensor to be positioned in front of a graphically designed background, which can be detected through the force or pressure sensor. In particular, any surface can be functionalized without losing its optical appearance. "Transparent" here means, in particular, that imaging according to the laws of geometric optics is possible through the force or pressure sensor. This also allows for the provision of graphically designed control elements.

[0018] In one embodiment, a plurality of electrically conductive surface elements are provided, wherein the measuring device is configured to detect and / or determine a change in self-capacitance at each of the electrically conductive surface elements and, based on the respective detected and / or determined change in self-capacitance, to ascertain whether actuation of the respective surface element of the force or pressure sensor has occurred, and to generate and / or provide a signal encoding the respective result. This allows for the provision of control panels with multiple control elements. For example, these can be regularly or irregularly arranged arrays of control elements. It is particularly provided that the electrically conductive layer, the deformable insulating layer, and the multiple electrically conductive surface elements are transparent.This allows the control elements to be designed graphically, and the graphical design to be detected by the force or pressure sensor. The electrically conductive surface elements are arranged adjacent to each other, particularly within the same layer. The electrically conductive layer is particularly comprehensive, spanning and / or covering the majority of the electrically conductive surface elements.

[0019] In one embodiment, a further insulating layer is arranged on the at least one electrically conductive surface element, and another electrically conductive layer, connected to ground, is arranged on the opposite side of the further insulating layer. This further improves shielding from the environment. In particular, it reduces interference with the detection and / or determination of the change in self-capacitance caused by external influences. The further insulating layer and the further electrically conductive layer can also be transparent.

[0020] In one embodiment, the deformable insulating layer comprises silicone (in particular poly(organo)siloxane) and / or a deformable, cured, optically clear adhesive (OCA). This allows, in particular, the simple production of the deformable insulating layer by processing it in liquid form, which then cures. For example, polydimethylsiloxane (PDMS) can be used; this can be processed in liquid form and subsequently cured. An optically clear adhesive can, for example, be cured by UV radiation in such a way that it remains deformable even after curing.

[0021] In one embodiment, the electrically conductive layer and / or the at least one surface element is formed from or comprises one of the following materials: poly-3,4-ethylenedioxythiophene (PEDOT:PSS), indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATO), silver nanowires, disordered silver nanowires, silver nanowires and carbon nanotubes, carbon nanotubes, graphene, dodecacalcium heptaaluminate (DC12A7), or a metal mesh. Combinations of these materials can also be used (such as PEDOT:PSS and silver nanowires). In particular, this allows the electrodes to be made (optically) transparent.

[0022] In one embodiment, the deformable insulating layer comprises an injection-molded plastic. This allows surfaces, for example, interior surfaces of a motor vehicle, to be functionalized with different appearances using the force or pressure sensor, meaning they can be used, in particular, to detect forces. It can also be provided that the injection-molded plastic, through suitable additives, acquires an optical appearance such as aluminum, leather, wood, etc.

[0023] Further features for the design of the method result from the description of the various configurations of the force or pressure sensor. The advantages of the method are the same in each case as in the configurations of the force or pressure sensor.

[0024] The invention is explained in more detail below with reference to preferred embodiments and the figures. These show: Fig. 1 a schematic representation of an embodiment of the force or pressure sensor; Fig. 2 a schematic representation of another embodiment of the force or pressure sensor; Fig. 3 a schematic representation of another embodiment of the force or pressure sensor.

[0025] The Fig. Figure 1 shows a schematic representation of an embodiment of the force or pressure sensor 1. The force or pressure sensor 1 comprises an electrically conductive layer 2, (at least) one electrically conductive surface element 3, and a deformable insulating layer 4, which is arranged between the electrically conductive layer 2 and the electrically conductive surface element 3. Furthermore, the force or pressure sensor 1 includes, in particular, a measuring device 5. The electrically conductive layer 2 is electrically connected to ground 6.

[0026] The measuring device 5 is configured to detect and / or determine a change in self-capacitance of the electrically conductive surface element 3 and, based on the detected and / or determined change in self-capacitance, to ascertain as result 10 whether an actuation 20 of the force or pressure sensor 1 has occurred, and to generate and / or provide a signal 11 encoding the result 10. The actuation 20, which is schematically represented here by an arrow and is carried out, for example, by a user's finger, leads to a (local) change in the thickness of the deformable insulating layer 4, which in turn influences the electric field lines (not shown) emanating from the (at least one) electrically conductive surface element 3. Due to a change in the field lines, the self-capacitance of the (at least one) electrically conductive surface element 3 also changes, which is detected by the measuring device 5.The measured change in self-capacity can, for example, be compared with a predefined threshold value, whereby an activation event (20) is triggered if the predefined threshold value is exceeded. The result (10) or signal (11) can then be fed to a control unit, which, based on this, can execute an action.

[0027] For example, it may be possible to detect and / or determine the self-capacitance by cyclically charging and discharging the electrically conductive surface element 3 and, based on this, to determine the change in self-capacitance. In this context, changes in time constants during charging and discharging under otherwise identical conditions are particularly important. For example, the measuring device 5 may include a microcontroller configured for this purpose, which is set up to detect and / or determine the self-capacitance and / or the change in self-capacitance.

[0028] The measuring device 5 may be configured to determine a force 12 and / or a pressure 13 acting on the force or pressure sensor 1, based on the detected and / or determined change in self-capacity, and to generate and / or provide a signal 14 encoding the determined force 12 and / or the determined pressure 13. For this purpose, a function 7, a characteristic curve 8, or a characteristic map 9 may be stored in the measuring device 5, in which values ​​for a change in self-capacity are linked to values ​​for the force 12 and / or the pressure 13. Based on the detected and / or determined change in self-capacity, the measuring device 5 can then determine the force 12 and / or the pressure 13 using the function 7, the characteristic curve 8, or the characteristic map 9.Taking into account the area of ​​the electrically conductive surface element 3, the force 12 can in particular be converted into a pressure 13 and vice versa.

[0029] It can be provided that the electrically conductive layer 2, the at least one electrically conductive surface element 3 and the deformable insulating layer 4 are transparent.

[0030] In the Fig. Figure 2 shows a schematic representation of another embodiment of the force or pressure sensor 1. The embodiment is basically the same as that shown in Figure 2. Fig. The embodiment shown in Figure 1 is configured as follows; the same reference numerals denote the same features and terms. In this embodiment, a plurality of electrically conductive surface elements 3-x are provided, wherein the measuring device 5 is configured to detect and / or determine a change in self-capacitance at each of the electrically conductive surface elements 3-x and, based on the respective detected and / or determined change in self-capacitance, to determine as a result 10-x whether actuation 20-x of the respective surface element 3-x of the force or pressure sensor 1 has taken place, and to generate and / or provide a signal 11-x encoding the respective result 10-x. By way of example, the following are shown in the Fig. Figure 2 shows three electrically conductive surface elements 3-x, in each of which the measuring device 5 detects and / or determines a change in self-capacitance. Accordingly, a result 10-x, a signal 11-x, a force 12-x, a pressure 13-x, or a corresponding signal 14-x can be provided for each of the surface elements 3-x. The electrically conductive layer 2 is, in particular, formed over the entire surface, meaning that the electrically conductive layer 2 spans and / or continuously covers all surface elements 3-x without interruption.

[0031] It can be provided that a further insulating layer 15 is arranged on the at least one electrically conductive surface element 3, and that a further electrically conductive layer 16 is arranged on an opposite side of the further insulating layer 15, which is connected to ground 6. This embodiment is shown schematically in the Fig. 3 shown. The same reference symbols here denote the same characteristics and terms as in the Fig. 1 and Fig. 2. The further insulating layer 15 can, for example, be a printed circuit board (PCB), for instance made of polyethylene terephthalate (PET), on which the electrically conductive layer 2, the deformable insulating layer 4, and the (at least one) surface element 3 are arranged, as well as the further electrically conductive layer 16 on the opposite side. The further electrically conductive layer 16 can, for example, be made of or comprise a metal, or comprise one of the electrically conductive materials mentioned in the following paragraphs.

[0032] It may be provided that the deformable insulating layer 4 comprises silicone (especially poly(organo)siloxane) and / or a deformable cured optical clear adhesive (OCA).

[0033] The electrically conductive layer 2 and / or the (at least one) surface element 3 may be made of or comprise one of the following materials: poly-3,4-ethylenedioxythiophene (PEDOT:PSS), indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATO), silver nanowires, disordered silver nanowires, silver nanowires and carbon nanotubes, carbon nanotubes, graphene, dodecacalcium heptaaluminate (DC12A7), or a metal mesh. Combinations of these materials may also be used (such as PEDOT:PSS and silver nanowires).

[0034] It is intended that the deformable insulating layer 4 is made of leather or comprises leather.

[0035] It may be provided that the deformable insulating layer 4 comprises a sprayed plastic.

[0036] Embodiments of the method described in this disclosure result from the embodiments of the force or pressure sensor 1 described above. Reference symbol list 1 force or pressure sensor 2 electrically conductive layer 3, 3-x electrically conductive surface element 4 deformable insulating layer 5 Measuring device 6 Masse 7 Function 8 characteristic curve 9 characteristic map 10, 10-x result 11, 11-x Signal 12, 12-x force 13, 13-x print 14, 14-x Signal 15 additional insulating layers 16 additional electrically conductive layers 20, 20-x actuation

Claims

[1] Force or pressure sensor (1), comprising: an electrically conductive layer (2), at least one electrically conductive surface element (3,3-x), a deformable insulating layer (4) between the electrically conductive layer (2) and the at least one electrically conductive surface element (3,3-x), and a measuring device (5), wherein the electrically conductive layer (2) is electrically connected to ground (6), and wherein the measuring device (5) is configured to detect and / or determine a change in self-capacitance at the at least one electrically conductive surface element (3,3-x) and, based on the detected and / or determined change in self-capacitance, to ascertain as a result (10,10-x) whether an actuation (20,20-x) of the force or pressure sensor (1) has taken place, and to generate and / or provide a signal (11,11-x) encoding the result (10,10-x), wherein the deformable insulating layer (4) is made of or comprises leather. [2] Force or pressure sensor (1) according to claim 1, characterized by , that the measuring device (5) is configured to determine, based on the detected and / or determined change in self-capacity, a force (12,12-x) and / or a pressure (13,13-x) acting on the force or pressure sensor (1) and to generate and / or provide a signal (14,14-x) encoding the determined force (12,12-x) and / or the determined pressure (13,13-x). [3] Force or pressure sensor (1) according to claim 1 or 2, characterized by , that the electrically conductive layer (2), the at least one electrically conductive surface element (3,3-x) and the deformable insulating layer (4) are transparent. [4] Force or pressure sensor (1) according to any of the preceding claims, characterized by, that a plurality of electrically conductive surface elements (3,3-x) are present, wherein the measuring device (5) is configured to detect and / or determine a change in self-capacitance at each of the electrically conductive surface elements (3,3-x) and, starting from the respective detected and / or determined change in self-capacitance, to ascertain as a result (10,10-x) whether an actuation (20,20-x) of the respective surface element (3,3-x) of the force or pressure sensor (1) has taken place, and to generate and / or provide a signal (11,11-x) encoding the respective result (10,10-x). [5] Force or pressure sensor (1) according to any of the preceding claims, characterized by, that a further insulating layer (15) is arranged on the at least one electrically conductive surface element (3,3-x) and that a further electrically conductive layer (16) is arranged on an opposite side of the further insulating layer (15), which is connected to ground (6). [6] Force or pressure sensor (1) according to any of the preceding claims, characterized by , that the deformable insulating layer (4) comprises silicone and / or a deformable cured optically transparent adhesive. [7] Force or pressure sensor (1) according to any of the preceding claims, characterized by, that the electrically conductive layer (2) and / or the at least one surface element (3,3-x) is formed from or comprises one of the following materials: poly-3,4-ethylenedioxythiophene (PEDOT:PSS), indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATO), silver nanowires, disordered silver nanowires, silver nanowires and carbon nanotubes, carbon nanotubes, graphene, dodecacalcium heptaaluminate (DC12A7), metal mesh or a combination thereof. [8] Force or pressure sensor (1) according to any of the preceding claims, characterized by , that the deformable insulating layer (4) comprises a sprayed plastic. [9] Force or pressure sensor (1), comprising: an electrically conductive layer (2), at least one electrically conductive surface element (3,3-x), a deformable insulating layer (4) between the electrically conductive layer (2) and the at least one electrically conductive surface element (3,3-x), wherein the force or pressure sensor (1) is configured to allow the electrically conductive layer (2) to be electrically connected to ground (6) and to allow the detection and / or determination of a change in self-capacitance at the at least one electrically conductive surface element (3,3-x), wherein the deformable insulating layer (4) is made of or comprises leather. [10] Method for providing a force or pressure sensor (1), wherein an electrically conductive layer (2) connected to ground (6), at least one electrically conductive surface element (3, 3-x) and a deformable insulating layer (4) between the electrically conductive layer (2) and the at least one electrically conductive surface element (3, 3-x) are provided, and wherein a change in self-capacitance at the at least one electrically conductive surface element (2) is detected and / or determined, and based on the detected and / or determined change in self-capacitance, it is determined as a result (10, 10-x) whether an actuation (20, 20-x) of the force or pressure sensor (1) has taken place, and wherein a signal (11, 11-x) encoding the result (10, 10-x) is generated and / or provided, wherein the deformable insulating layer (4) is made of or comprises leather.

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