Sensor device and method for manufacturing a vehicle door handle with a sensor device

Abstract

The invention relates to a sensor device (1), for example for a motor vehicle. The sensor assembly comprises a circuit board (2) with a sensor electrode (3), a cover plate (4) with a sensing area (6), and optionally a spacer (5, 5'). A cavity (H) is formed between the sensor electrode (3) and the cover plate (4). A control and evaluation unit (7) is provided to enable functionality. The cover plate (4) is coupled to the control and evaluation unit (7), with which the electrical potential level of the cover plate (4) can be switched. The sensor electrode shown can detect a pressure actuation performed by an operator (B) on the outer part (A). Furthermore, a method for manufacturing a vehicle door handle is presented.

Description

[0001] The invention relates to a sensor device that can be used, for example, in applications in motor vehicles. In particular, applications in motor vehicle door handles are possible. The invention further relates to a method for manufacturing a motor vehicle door handle with a sensor device.

[0002] The sensor device, which is the subject of the present invention, provides a capacitive detection system. Capacitive detection systems for approach detection are known in practice.

[0003] A measurement principle for detecting an approach or actuation of a switch is based on determining a capacitance or a quantity dependent on the capacitance, or on the change in the capacitance or a quantity dependent on the capacitance.

[0004] Commercially available sensors exist that feature a sensor electrode to which a thin, electrically conductive—especially metallic—pressure element is attached, which is at ground potential during sensor operation. Such sensors are referred to in practice, for example, as "metal over capacitive" sensors. One example of such a sensor is the AN1325 from Microchip (see, for example, the link accessed on the filing date: https: / / wwl.microchip.com / downloads / en / Appnotes / 01325A.pdf). In such a sensor, the pressure element and the sensor electrode form a capacitor. This capacitor can ideally be considered a parallel-plate capacitor, and therefore its capacitance changes in a known manner, exactly or approximately inversely, with changes in the distance between the sensor electrode and the pressure element.Determining the capacitance or changes in capacitance, possibly indirectly via the measurement of a capacitance-dependent quantity, can therefore serve as the basis for detecting pressure on the pressure element. Such systems are subsequently referred to as metallically covered pressure sensors.

[0005] Metal-encased pressure sensors offer numerous advantages. For example, they are easy to clean and therefore well-suited for use in demanding environments, such as in the medical field, food processing, or as part of a motor vehicle with partial exposure to the elements and thus to environmental influences like precipitation. The metallic casing also effectively prevents or at least limits contamination by dust, dirt, or penetrating liquids. Furthermore, the presence of a metallic casing provides an excellent foundation for a sensor with a high-quality appearance.

[0006] A further advantage of metal-covered pressure sensors arises from the fact that, due to the sensitive dependence of the capacitance on the distance of the metal cover from the sensor (by a factor of 1 / d), pressure actuations can be detected even with low pressure forces and consequently small deflections of the cover plate, especially with appropriately dimensioned small distances. Compared to similarly powerful systems, such as piezoelectric or inductive sensors, a metal-covered pressure sensor based on capacitance measurement has the additional advantage of requiring less complexity in component manufacturing, thus keeping costs comparatively low.

[0007] Modern vehicles and their operating systems require increasingly complex and flexible customization options.

[0008] The invention is therefore based on the objective of providing an improved sensor device whose functionality is based on the detection of capacities or changes in capacities or on quantities dependent on them.

[0009] The problem is solved by a sensor device having the features of claim 1. The problem is further solved by a method for manufacturing a vehicle door handle having the features of claim 14.

[0010] A sensor device is proposed. The sensor device could, for example, be intended for use in a motor vehicle.

[0011] The sensor device indicates: - a circuit board with a sensor electrode, as well as - a cover plate that is both mechanically flexible and electrically conductive.

[0012] The cover plate serves to protect the circuit board from the outside of the sensor device, i.e., from the side facing away from the sensor electrode. The cover plate can be, for example, a thin metallic plate, such as one between 0.05 mm and 1 mm thick. The combination of material, such as a metallic material like stainless steel, and its thinness provides the desired balance of mechanical flexibility and electrical conductivity. The mechanical flexibility allows the cover plate to be pressed down with an operator's finger, reducing its distance from the sensor electrode, and it returns to its original position when the finger is removed.The precise dimensioning of the interplay between material, thickness of the cover plate and distance of the cover plate from the sensor electrode must be selected by the implementing specialist depending on the specific application and the desired properties, for example with regard to the sensitivity of the sensor device. This is, however, easily possible since the basic parameters are immediately apparent; the material must deflect sufficiently in typical operating scenarios without touching the sensor electrode, and return to its initial position after the end of the touching.

[0013] The cover plate provides a sensing area for pressure actuation detection. This means that the cover plate has an area where pressure can be applied as described above, thereby reducing the distance to the sensor electrode. This functionality enables the basic principle of the metal-covered pressure sensor: Pressing within the sensing area, by reducing the distance between the cover plate and the pressure sensor, increases the capacitance of the capacitor formed by the sensor electrode and the cover plate. Consequently, when a capacitance-dependent value is measured, it differs from the value measured when the sensor is not under pressure, thus indicating that pressure has been applied.

[0014] Air is preferably used as the dielectric between the sensor electrode and the cover plate.

[0015] To maintain the sensing area at a defined distance from the sensor electrode when not pressed, it is preferably fixed by one or more spacers at a defined distance from the circuit board. The spacers are thus arranged between the circuit board and the cover plate such that the distance between the circuit board and the cover plate corresponds to the height of the spacer(s). The spacer leaves a free cavity between the cover plate and the sensor electrode in the area of ​​the sensing area, so that the distance between the cover plate and the circuit board can be reduced by pressing the sensing area.

[0016] According to the invention, the sensor electrode is coupled with a control and evaluation device in order to determine a quantity dependent on the capacitance of the sensor electrode relative to the cover plate, in order to detect a pressure actuation in the sensing range from the determined quantity.

[0017] The control and evaluation unit can, for example, be an arrangement of coupled control and evaluation units; however, it can also be designed as an integrated circuit. In particular, the control and evaluation unit can be implemented as a microcontroller coupled to the sensor electrode. As a possible alternative, the control and evaluation unit can be arranged on the circuit board of the sensor device.

[0018] Determining the value dependent on the capacitance of the sensor electrode relative to the cover plate can be carried out using one of the usual procedures known to those skilled in the art. For example, it may be possible to record the number of clocked discharge cycles or the discharge duration as the value dependent on the capacitance of the sensor electrode relative to the cover plate, as is known, for example, from DE 196 17 038 A1. Another possible procedure for evaluation by determining a value dependent on the capacitance of the electrode relative to the cover plate could, for example, involve charging a sample / hold capacitor of an ADC input of a microcontroller, which is coupled to the sensor electrode, to a known voltage, then discharging the unknown capacitance of the sensor to 0 V, and finally connecting the sample / hold capacitor and the sensor electrode.The resulting voltage across the total capacitance of the sensor electrode and sample / hold capacitance is then measured and converted into a digital value by the ADC; its magnitude is then a direct measure of the capacitance of the sensor electrode, and depending on this magnitude, it can be concluded whether or not pressure actuation of the sensing range is taking place.

[0019] According to the invention, the sensor device presented here is provided in that the cover plate is coupled to the control and evaluation unit, with which the sensor electrode is also coupled, wherein, according to the invention, the control and evaluation unit is configured to switch the electrical potential level of the cover plate.

[0020] In contrast to the aforementioned known pressure sensors, where a metallic cover plate is at a fixed potential, particularly ground potential, the innovation presented here is that the cover plate can be set to a specifically variable electrical potential. Thus, the electrical potential of the cover plate can be adjusted by selective switching via the control and evaluation unit, thereby allowing the characteristics of the sensor to be precisely controlled. This previously unknown approach makes it possible to adapt the existing components of the sensor to different functionalities depending on the control signal from the control and evaluation unit, without requiring complex structural modifications.The question of which functionality is used at which time can be specifically influenced by appropriate programming of the control and evaluation unit and can therefore be implemented without major effort and in a cost-efficient manner.

[0021] According to an advantageous embodiment of the sensor device, it can be provided, for example, that the control and evaluation device is set up in a pressure actuation detection mode, switches the electrical potential level of the cover plate to ground potential or to a predetermined reference potential, and detects the pressure actuation in the sensing range at the potential level of the cover plate switched to ground potential or a predetermined reference potential by determining the quantity that depends on the capacitance of the sensor electrode relative to the cover plate.Accordingly, at least one mode of the control and evaluation device is provided in which the functionality described above is achieved by deriving the charge carriers present on the cover plate or by setting it to a predetermined potential level, according to which the control and evaluation device can evaluate a capacitance of the sensor electrode relative to the cover plate or a quantity dependent on the capacitance of the sensor electrode relative to the cover plate in order to detect, by determining the capacitance or the quantity dependent on the capacitance of the sensor electrode relative to the cover plate, whether or not pressure actuation is present in the sensing range.

[0022] Particularly preferred is the control and evaluation unit configured, either alternatively or additionally, to switch the cover plate as a proximity detection electrode in a proximity detection mode. This means that the control and evaluation unit coupled to the cover plate determines the capacitance of the cover plate relative to the environment. This determination of the capacitance of the cover plate relative to the environment is performed particularly when the sensing range is not activated, so that a change in the capacitance of the cover plate relative to the environment indicates a change in the environment, for example, the approach of an operator's hand.The cover plate is thus temporarily used like a proximity detection electrode known to those skilled in the art and evaluated for the detection of approaches, compared to the known proximity detection electrode only with the difference that the proximity detection electrode can be switched to ground potential or to a predetermined reference potential outside the proximity detection mode, as described above, and thereby temporarily loses its functionality as a proximity detection electrode and is instead used as a provision for a sensing range in a pressure actuation detection.

[0023] The evaluation of the capacity or of a cover plate connected as a proximity detection electrode can be carried out in any way known to those skilled in the art, for example by determining charging cycles with known charge quantities or by determining discharging cycles to discharge capacities of known size or by determining discharge periods.

[0024] According to a preferred further development, it can be provided that the control and evaluation device is set up to switch the sensor electrode arranged on the circuit board to a potential-free state, i.e., floating state, in a proximity detection mode, in order to facilitate proximity detection through the cover plate.

[0025] According to an advantageous further development, a second sensor electrode can also be arranged on the circuit board. The second sensor electrode is preferably located further away from the cover plate than the first sensor electrode. For example, the first sensor electrode can be arranged on a first surface of the circuit board facing the cover plate, and the second sensor electrode can be arranged on a second surface of the circuit board facing away from the cover plate. This provides a multi-layered circuit board with various sensors that, depending on the circuit configuration, can provide different functionalities. Preferably, the second sensor electrode is also coupled to the control and evaluation unit.

[0026] For example, the control and evaluation unit coupled to the second sensor electrode may be configured to switch the second sensor electrode to a ground potential in a proximity detection mode. In such a case, where the second sensor electrode is switched to a ground potential and the first sensor electrode is floating (i.e., at no potential), the cover plate, switched in proximity detection mode, can be used to effectively create a detection range for the proximity electrode oriented upwards, i.e., in the space away from the cover plate.

[0027] The control and evaluation device is particularly preferably configured to alternate the circuitry of the sensor electrode and the cover plate between a pressure actuation detection mode and a proximity detection mode in temporal multiplex operation.

[0028] According to a further advantageous embodiment, the control and evaluation unit is configured to operate the cover plate in proximity detection mode during normal operation. Furthermore, a pressure actuation mode is activated after the cover plate, configured as a proximity electrode, has detected an approach. In this case, the operation of the pressure actuation mode can be specifically made dependent on the detected proximity indicating a high probability that an operator has approached the sensor device with the intention of activating it. This approach has the advantage that for the majority of the time, only the proximity detection mode, and not the pressure actuation mode, is active, thus reducing energy consumption.For example, it may be provided that the evaluation of the proximity electrode is only carried out at a comparatively low frequency, for example in the range of 0.01-5 Hz, which has proven to be a practical frequency in many operating scenarios.

[0029] In an alternative, further developed embodiment, the control and evaluation unit can be configured to operate the cover plate in proximity detection mode during normal operation, with the activation of the pressure actuation mode occurring at a first frequency per unit of time. This alternative implementation further provides that, when the cover plate, configured as a proximity electrode, detects an approach, the activation of the pressure actuation mode is triggered at a second frequency per unit of time, the second frequency being higher than the first. Unlike the first implementation, the pressure actuation mode is not completely deactivated during normal operation; it is merely operated with a lower evaluation frequency.

[0030] According to a further advantageous embodiment of the sensor device, the control and evaluation unit can be configured to classify a detected pressure actuation as plausibly detected only if at least one proximity detection, preferably a minimum number of proximity detections stored in the control and evaluation unit, has been recorded within a defined maximum time period before the detected pressure actuation. This means that a pressure actuation triggers a function, for example on a vehicle on which the sensor device is located, only if, in addition to the detected pressure actuation, a further condition is met, namely the condition that the proximity detection occurred within a defined maximum time period before the pressure actuation.Detecting a pressure actuation, and consequently triggering a function, necessarily requires that a change in capacitance be detected in two different detection modes, using the sensor electrode and the cover plate with two different sensors. This change must indicate both a proximity and a pressure actuation. This process validates the detected pressure actuation, allowing for the exclusion of pressure actuations caused by anomalies. Furthermore, a pressure actuation that occurred without proximity, for example, due to hail or rain, can be reliably distinguished from an intended pressure actuation, as only the latter requires prior proximity via the cover plate in proximity detection mode.This can be implemented, for example, by starting a timer in the control and evaluation unit upon detection of an approach. This timer runs until the end of the maximum time period, or at least until the end of the maximum time period. The control and evaluation unit only accepts a pressure actuation detected by the sensor electrode as plausible if this actuation occurred before the end of the maximum time period. Furthermore, the control and evaluation unit can be configured, for example, to issue a release signal—which can be used, for instance, by a central control unit of a vehicle to trigger a function—as soon as a pressure actuation is recognized as plausible. A pressure actuation that could not be confirmed as plausible by the end of the maximum time period can be rejected as implausible and without consequence.

[0031] According to a further advantageous embodiment of the sensor device, the spacer is an incompressible film, for example made of polyester, or a PCB. The acronym PCB stands for printed circuit board, which serves as a substrate for electronic components and can be made, for example, of thin circuit boards, fiberglass boards, Teflon, aluminum oxide, or generally of a ceramic material. Circuit boards made of polyester film can also be used. The thickness of the incompressible film or PCB is preferably less than 2 mm, and particularly preferably less than 1 mm.

[0032] Another aspect of the invention relates to a method for manufacturing a vehicle door handle with a sensor device. Such a method comprises, in particular, the following steps: A sensor device of the type mentioned above, or one of its further developments, is positioned in a cavity of the vehicle door handle. The sensor device is positioned within the cavity such that the cover plate faces an inner wall of the cavity, the corresponding outer surface of which is an outer button-press area of ​​the vehicle door handle. A gap remains between the cover plate and the cavity, which has the advantage that the positioning of the sensor device within the cavity can be carried out without tight manufacturing tolerances, thus promoting cost-effective production. The sensor device is fixed at this point, for example, by means of a suitable plug-in system, by gluing, or by potting with a potting compound, preferably a hardening compound, and made of, for example, a plastic. - Subsequently, any remaining gap between the cover plate and the inner wall is filled with a hardening, electrically non-conductive potting compound of high mechanical hardness. A suitable potting compound, for example, must possess sufficient mechanical hardness to transmit pressure in the sensing area, through the hardened potting compound and into the sensing area on the sensor's cover plate. An epoxy resin, for instance, could be used as a suitable potting compound.

[0033] Further details, features and advantages of the subject matter of the invention will become apparent from the following description in conjunction with the drawings, in which exemplary embodiments of the invention are shown.

[0034] It is understood that the features explained above and below can be used not only in the combination specified, but also in other combinations with each other or on their own.

[0035] They show: Fig. 1: an exemplary embodiment of a sensor device; Fig. 2: another embodiment of a sensor device; Fig. 3: A representation of a vehicle door handle to illustrate a method for manufacturing the vehicle door handle.

[0036] Fig. A sensor device 1 can be removed from Figure 1. This can be used, for example, to detect proximity and pressure actuation in automotive applications.

[0037] The sensor device 1 comprises a circuit board 2, which has a metallic sensor electrode 3 on one of its surfaces. The metallic sensor electrode 3 can be a conductive plate, but it can also be implemented as a conductor printed on the circuit board. The sensor electrode 3 is coupled to a control and evaluation unit 7, which can, for example, be implemented as a microcontroller.

[0038] A mechanically flexible and electrically conductive cover plate 4 is arranged at a defined distance from the sensor electrode 3. The cover plate 4 serves to cover the circuit board 2, including the sensor electrode mounted on the circuit board, from an external aspect A of the sensor device 1. The cover plate 4 also provides a sensing area 6 that can be used by an operator B for pressure actuation detection. The cover plate 4 and the sensing area 6 are fixed at a defined distance from the circuit board 2 by spacers 5, 5'. The spacer 5, 5' is, for example, an incompressible film or a PCB, preferably with a thickness of less than 2 mm, and particularly preferably with a thickness of less than 1 mm.

[0039] A cavity H is maintained between the sensing area 6 of the cover plate 4 and the sensor electrode 3, which reduces the distance between the cover plate 4 and the circuit board 2 when the sensing area 6 is pressed. The resulting change in the capacitance of the assembly consisting of the sensor electrode 3 and the cover plate 4 is detected by the control and evaluation unit 7 and used to recognize a press action. This occurs in a mode where the cover plate is at a fixed potential, preferably ground potential. The cover plate 4, like the sensor electrode 2, is coupled to the control and evaluation unit 7, and the potential of the cover plate 4 can be switched by means of the control and evaluation unit 7.

[0040] Because the potential of the cover plate is variable, the sensor device 7 can be operated both as a proximity sensor and as a pressure actuation sensor.

[0041] The sensor device, which is in the Fig. The one shown in 2 differs from the one in Fig. The embodiment shown in Figure 1 differs in that a second sensor electrode is arranged on the surface of the circuit board 2 that is repelled by the cover plate 4, and this second sensor electrode is also coupled to the control and evaluation unit 7. Thus, a multi-layer circuit board is present, which has sensor electrodes that can be connected in different ways, for example, in multiplex operation.

[0042] Fig. Figure 3 shows a representation of a vehicle door handle 9, from which a method for manufacturing the vehicle door handle can be traced, which has a sensor device 1, as is the case, for example, in Fig. 1 or in Fig.Figure 2 illustrates this. To manufacture such a vehicle door handle 9, a procedure can be used, for example, which begins with the provision of a vehicle door handle body 9'. The vehicle door handle body 9' has a cavity 10. A sensor device 1 is positioned within the cavity 10. The sensor device 1 is positioned within the cavity 10 such that the cover plate 4 faces an inner wall 11' corresponding to an outer pressure-sensitive area 11 of the vehicle door handle. At the point on the vehicle door handle 9 where actuation by pressure occurs, i.e., the pressure-sensitive area 11, the area of ​​the wall is located whose inner side, i.e., inner wall 11', is then oriented frontally to the cover plate 4, and the cover plate 4 is oriented frontally to the inner wall 11'.Within the vehicle door handle 9, the sensor device 1 is fixed at the described position, for example by gluing or snapping it into appropriately provided locking clips. To enable the transmission of a pressure actuation occurring in the tactile pressure area 11 to the cover plate, a sufficiently rigid mechanical coupling between the inner wall 11' and the cover plate 4 is required. To achieve this, the remaining gap between the cover plate 4 and the inner wall 11' is filled with a hardening, electrically non-conductive potting compound 12 of high mechanical hardness, for example, an epoxy resin. QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 196 17 038 A1

[0018]

Claims

[1] Sensor device (1), preferably for a motor vehicle, comprising a circuit board (2) with a sensor electrode (3), a cover plate (4) which is both mechanically flexible and electrically conductive, for covering the circuit board (2) towards an exterior of the sensor device (1), wherein the cover plate (4) provides a sensing area (6) for pressure actuation detection, wherein the sensing area is designed to reduce the distance between the cover plate (4) and the circuit board (2) when the sensing area (6) is pressed, wherein the sensor electrode (3) is coupled to a control and evaluation device (7) for determining a variable dependent on the capacitance of the sensor electrode (3) relative to the cover plate (4), wherein the cover plate (4) is coupled to the control and evaluation device (7), and the control and evaluation device (7) is configured to switch the electrical potential level of the cover plate (4). [2] Sensor device (1) according to claim 1, wherein the sensing area (6) is fixed at a defined distance from the circuit board (2) by means of a spacer (5, 5') or a plurality of spacers (5, 5') such that when the sensing area (6) is actuated by pressure, the distance between the cover plate (4) and the circuit board (2) is reduced. [3] Sensor device (1) according to claim 1 or claim 2, wherein the control and evaluation device (7) is configured in a pressure actuation detection mode to switch the electrical potential level of the cover plate (4) to ground potential or a predetermined reference potential, and to detect the pressure actuation in the sensing area (6) by determining the quantity dependent on the capacitance of the sensor electrode (3) with respect to the cover plate (4) when the potential level of the cover plate (4) is switched to ground potential or a predetermined reference potential. [4] Sensor device (1) according to one of claims 1 to 3, wherein the control and evaluation device (7) is arranged to switch the cover plate (4) as a capacitive proximity detection electrode in a proximity detection mode. [5] Sensor device (1) according to claim 4, wherein the control and evaluation device (7) is arranged to switch the sensor electrode (3) arranged on the circuit board (2) to a potential-free state, that is to say "floating", in a proximity detection mode. [6] Sensor device (1) according to claim 4, wherein the control and evaluation device (7) is arranged to switch the sensor electrode (3) arranged on the circuit board (2) to a ground potential in a proximity detection mode. [7] Sensor device (1) according to one of the preceding claims, wherein a second sensor electrode (8) is arranged on the circuit board (2). [8] Sensor device (1) according to claim 7, wherein the second sensor electrode (8) is spaced further from the cover plate (4) than the first sensor electrode (3). [9] Sensor device (1) according to claim 7 or claim 8, wherein the control and evaluation device (7) is arranged to switch the second sensor electrode (8) to a ground potential in a proximity detection mode. [10] Sensor device (1) according to one of claims 4 to 9, wherein the control and evaluation device (7) is arranged to alternate the wiring of the sensor electrode and the cover plate (4) between a pressure actuation detection mode and a proximity detection mode in time multiplex operation. [11] Sensor device (1) according to one of claims 4 to 10, wherein the control and evaluation device (7) is configured to operate the cover plate (4) in the proximity detection mode during regular operation and to activate the pressure actuation mode after the cover plate (4) connected as a proximity electrode has detected an approach, or the control and evaluation device (7) is configured, in regular operation, to switch the cover plate (4) into the proximity detection mode when the pressure actuation mode is switched on at a first frequency per unit of time, and to switch the pressure actuation mode on at a second frequency per unit of time after the cover plate (4) switched as a proximity electrode has detected an approach, wherein the second frequency per unit of time is greater than the first frequency per unit of time. [12] Sensor device (1) according to one of claims 4 to 11, wherein the control and evaluation device (7) is configured to define a detected pressure actuation as a plausibility-detected pressure actuation only under the condition that at least one proximity detection, preferably a minimum number of proximity detections stored on the control and evaluation device (7), was detected within a specified maximum period before the detected pressure actuation, and otherwise the detected pressure actuation is rejected as a non-plausibility-detected pressure actuation. [13] Sensor device (1) according to one of the preceding claims, wherein the spacer (5, 5') is an incompressible film or a PCB, preferably with a thickness of less than 2 mm, particularly preferably with a thickness of less than 1 mm. [14] Method for producing a vehicle door handle (9) with a sensor device (1) according to one of the preceding claims, comprising the steps: - Providing a vehicle door handle body (9') with a cavity (10); - positioning the sensor device (1) in the cavity (10) of the vehicle door handle body with alignment of the cover plate (4) to an inner wall (11') corresponding to an outer key pressure area (11) of the vehicle door handle and then fixing the sensor device (1); - Filling a remaining gap between the cover plate (4) and the inner wall (11') with a hardening, electrically non-conductive casting material (12) of high mechanical hardness. [15] Method according to claim 14, characterized by that the potting material (12) is an epoxy resin.

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