Sensor arrangement, door handle and rear trim module

Abstract

Sensor arrangement (11) comprising a sensor (13), in particular a capacitive sensor, and a cover layer (15) arranged above the sensor (13), the cover layer having a metallization (17) facing away from the sensor (13), wherein the metallization (17) is at least partially permeable such that an object (27) in a detection area (25) of the sensor (13) can be detected by the sensor (13) without contact through the cover layer (15), characterized in that the metallization (17) has electrically isolated metallization islands (33) which are non-conductively connected to each other, wherein the lateral dimensions of the metallization islands (33) and the areas between the metallization islands (33) are dimensioned such that the metallization (17) formed by the metallization islands (33) is perceived by the human eye as a continuous, planar metallization layer.

Description

The present invention relates to a sensor arrangement comprising a sensor and a cover layer arranged above the sensor, the cover layer having a metallization facing away from the sensor. The sensor is, in particular, a capacitive sensor. Such sensor arrangements are generally known and are used, for example, as electrical operating switches on motor vehicles, whereby a manual deformation of the cover layer triggers, for example, the unlocking of a door lock of the vehicle. The metallization of the surface layer primarily serves aesthetic purposes, giving the outer surface of the layer, especially in visible areas, an appealing appearance. Depending on the optical properties of the metallization, the surface layer can appear particularly robust and elegant, and can optionally blend harmoniously into the environment of the sensor assembly. This is especially desirable for vehicles whose bodywork has a metallic or metallic-looking exterior surface. Furthermore, if the sensor assembly is to be used as an operating switch, the metallization can possess tactile properties that are perceived as higher quality than those of plastics. A significant disadvantage of metallization lies in its electrically shielding effect, which can lead to a substantial impairment of the functionality of a sensor located beneath the coating. In particular, the shielding effect of the metallization can impair a sensor that is intended to detect an object through the coating without the object touching it. For example, the metallization can shield a capacitive proximity sensor, which, due to a change in capacitance, could theoretically detect an object located close to the sensor without contact (i.e., without touching the coating), to such an extent that it no longer functions reliably.This problem will be explained in more detail below using the example of a sensor designed as a capacitive proximity switch, which is designed to measure a change in the alternating electric field in the vicinity of a sensor electrode. The basic principle of such a proximity sensor is that a metallic or non-metallic object is brought into close proximity to the sensor electrode, causing a change in capacitance between the sensor electrode and a reference potential, particularly ground. If the change in capacitance exceeds a predetermined threshold, the proximity sensor detects the object that caused the change in capacitance. If a conductive object, especially a metal surface, is located between the sensor electrode and the object to be detected, the electric field of the sensor electrode induces an electric field in the metal surface that opposes the electric field of the sensor electrode (sensor field). Thus, the induced field weakens the sensor field necessary for object detection.The strength of the induced field depends, among other things, on the sensor field and the dimensions of the metal surface in which the field is induced. Typically, the dimensions of the metal surface have a significant influence on the attenuation of the sensor field and thus on the shielding effect of the metal surface. Traditionally, a top layer, for example made of plastic, is metallized by electroplating. The shielding effect of the resulting metallization is usually so strong that a proximity sensor located beneath the top layer no longer triggers reliably when an object is brought into close proximity to the sensor and the metallized top layer is positioned between the sensor and the object. A sensor arrangement according to the preamble of claim 1 is known from the company publications “OC Oerlikon Corporation AG: This is Oerlikon - A sustainable alternative to electroplating. Issue 3 / 2014. Pfäffikon, Switzerland, 2014. pp. 1-2” or “Oerlikon Balzers Coating AG: ePD & INUBIA I: Chrome looking plastic metallisation on a new level. Issue 14 / 05. Balzers, Liechtenstein, 2014, pp. 1-8.” The present invention is based on the objective of creating a sensor arrangement of the type mentioned above that enables more reliable contactless object detection. This problem is solved by a sensor arrangement having the features of claim 1. According to the invention, it has been recognized that the shielding effect of the metallization can be reduced by certain features, described below by way of example, such that, in particular, a capacitive sensor can reliably detect an object within a detection area assigned to the sensor through the top layer by having metallization islands which are non-conductively connected to one another, wherein the lateral dimensions of the islands and the areas between the islands are dimensioned such that the metallization formed by the islands is perceived by the human eye as a continuous, planar metallization layer. Due to the metallization islands being isolated from one another, the metallization in the areas between the islands is particularly permeable to electric fields. The electrical insulation of the islands contributes to the fact that no opposing field is present in the islands or between them.The metallization is induced, which effectively hinders the penetration of the sensor field. This eliminates the need for moving parts, especially switching elements, to detect conventional manual operation. Advantageous embodiments of the invention are described in the dependent claims, the description and the drawings. The thickness of the metallization is preferably no more than a few hundred nm, and particularly preferably no more than 200 nm. This ensures that the electric field emanating from the sensor can penetrate the metallization with only minimal attenuation, meaning that an opposing electric field induced in the metallization does not completely cancel out the sensor field. The metallization is preferably at least 100 nm thick, so that it is optically recognizable as such and forms a continuous, opaque metal surface. Furthermore, a minimum thickness can also ensure that the metallization is perceived haptically as a "solid" metallized surface, for example, when touched with a finger. According to one exemplary embodiment, the metallization has a varying thickness. This ensures, on the one hand, that the electrical sensor field can penetrate if the metallization has a sufficiently thin thickness, at least in some areas. On the other hand, the metallization can have a greater thickness in other areas, so that, for example, it completely obscures a substrate of the top layer onto which it is applied, and is robust against external influences. Additionally or alternatively, the metallization can have at least one hole. Furthermore, holes in the metallization can improve its electrical penetration properties to such an extent that a sensor can detect an object even more reliably and without contact through the top layer within the sensor's detection area. According to a further preferred embodiment, the metallization is at least partially transparent and / or opaque on one side. In this way, a light source arranged on the sensor side can emit light through the surface layer. At the same time, the light source is concealed by the metallization in such a way that it is not visible from the outside, at least when inactive. In other words, the metallization can be semipermeable, i.e., it is opaque and at least subjectively opaque on one side and transparent on the other. This can be achieved, for example, by introducing holes into the metallization that do not exceed a predetermined diameter, so that the metallization is perceived by the human eye as a continuous surface, but is simultaneously transparent to light on at least one side.The metallization can also be frequency-selective and transparent, meaning it filters light within a predetermined frequency range. Alternatively, the metallization can be transparent on both sides and not opaque. For example, it may be desirable for the color of the substrate to which the metallization is applied to be visible through the metallization, while the metallization merely creates a metallic sheen, such as a chrome look. A sensor array with a semipermeable metallization can be used, for example, in areas of a vehicle where the top layer is visibly exposed and needs to be illuminated, such as to improve its location in the dark. For this purpose, the sensor array can be equipped with a sensor-side light source. Depending on the light source's intensity and the sensor array's configuration, it can perform a variety of functions on the vehicle, such as providing illumination of the area in front of the vehicle and / or the license plate. The metallization can be applied to a substrate of the top layer using a physical vapor deposition (PVD) process, in particular a magnetron sputtering process. Such a process ensures that the metallization does not exceed a predetermined thickness, as described above. Furthermore, when using such a process, isolated islands and / or holes can be defined during the metallization application itself, eliminating the need for an additional process step. A primer layer can be applied between the metallization and the substrate to compensate for manufacturing irregularities in the substrate and to provide the smoothest and most durable base layer possible for the metallization. Such a primer can thus contribute to a particularly uniform metallization and a visually smooth, clean surface. The primer layer preferably consists of a UV-resistant lacquer and has a thickness in the range of a few tens of micrometers, e.g., 15 micrometers. Furthermore, the primer layer can be transparent to avoid affecting the color of the substrate. This is particularly advantageous if the metallization is not opaque from the outside. According to a preferred embodiment, the metallization is at least partially covered by a protective layer. For example, the metallization in a particularly exposed area or even completely coated with a UV lacquer to protect it from external influences and improve its durability. Preferably, the protective layer is transparent so that at least the color properties of the metallization remain unaffected. Additionally, the protective layer can improve the optical properties of the metallization, for example, by being designed as a glossy or matte lacquer. Furthermore, the protective layer can be so thin that the tactile properties of the metallization are also preserved. Preferably, the protective layer has a thickness in the range of a few tens of micrometers, e.g., 15 micrometers. Advantageously, the metallization is chromium- and / or nickel-free. In particular, the metallization does not contain any multivalent chromium, thus ensuring freedom from chromium(VI) and compliance with legal guidelines such as the ELV, RoHS, and WEEE directives. According to another preferred embodiment, the metallization includes indium, which can contribute to the metallization having a high-quality appearance and, in particular, looking like chromium or chromium-like, without containing chromium. According to one embodiment, the surface layer of the sensor assembly is plastically deformable. This allows for further improvement of the haptic properties of the surface layer and / or the metallization. Furthermore, the reliability of the sensor can be improved by enabling object detection even through plastic deformation of the surface layer, i.e., under pressure. In addition to a capacitive sensor, a resistive pressure sensor can also be provided, for example, which, in the event of a failure or temporary malfunction of the capacitive sensor, at least enables force-based detection of the object. The sensor assembly can advantageously be integrated into a door handle or rear trim module of a motor vehicle, such that the metallized cover layer forms a button, at least for unlocking a door or tailgate lock. Naturally, when an object, such as a finger, approaches the button or when the button is touched, other functions of the motor vehicle can also be triggered, such as activating the approach lighting ("coming-home function"). The sensor assembly offers particular advantages when used in a door handle or rear trim module, as it completely eliminates the need for conventional, movable buttons, which are often subject to significant wear and tear in motor vehicles due to use and weather conditions. Of course, a movable button can still be provided, for example, to...to be able to manually unlock a door or tailgate lock in accident-related emergencies. The invention is described below by way of example with reference to advantageous embodiments and the accompanying drawings. The drawings show: Fig. 1 a cross-sectional view of a sensor arrangement according to one embodiment; Fig. 2 a cross-sectional view of a sensor arrangement according to another embodiment; Fig. 3 a top view of a sensor arrangement according to another embodiment; Fig. 4 a cross-sectional view of the sensor arrangement of Fig. 3; Fig. 5 a top view of a sensor arrangement according to another embodiment; Fig. 6 a cross-sectional view of the sensor arrangement of Fig. 5; and Fig. 7 a cross-sectional view of a sensor arrangement in a rear trim module of a motor vehicle. Fig. 1 shows a cross-sectional view of a sensor arrangement 11, which comprises a capacitive sensor 13 and a cover layer 15. The cover layer 15 has a metallization 17 with a thickness 18 in the range of a few hundred nm, in the present embodiment 170 nm. The exact structure of the top layer 15 is as follows. A plastic substrate 19 serves as the base layer, which is covered with a transparent primer layer 21. The metallization 17 is applied to the primer layer 21 over a surface area using a magnetron sputtering process and covered with a transparent protective layer 23. A detection area 25 is assigned to the sensor 13, within which the sensor 13 can detect objects, e.g., a finger 27. Due to its small thickness 18, the metallization 17 is permeable to an invisible electric field emitted by the sensor 13. This means that the metallization 17 provides such minimal shielding to the sensor 13 that the finger 27, located within the detection area 25, can be detected by the sensor 13 without the finger 27 having to touch or press into the cover layer 15. Detection is enabled by a change in capacitance caused by the finger 27 at a sensor electrode of the sensor 13 (not shown). Fig. 2 shows another embodiment of a sensor arrangement 11, which is similar to the sensor arrangement 11 shown in Fig. 1. In contrast to Fig. 1, the metallization 17 of Fig. 2 has a varying thickness, i.e., the metallization 17 has a wave profile with peaks 29 and valleys 31. In the region of the valleys 31, the metallization 17, with a thickness in the range of 80 nm to 120 nm, here 100 nm, is so thin that the electric field emitted by the sensor 13 for the detection of objects can penetrate at least in the region of the valleys 31 without significant impairment. Figure 3 shows a top view of another embodiment of a sensor arrangement 11, showing only an exemplary, greatly enlarged section of an outer surface 35 of the cover layer 15. The metallization 17 is applied in sections or interrupted layers and not as a continuous surface as in Figures 1 and 2. Specifically, the metallization 17 in Figure 3 has metallization islands 33 which are not conductively connected to each other; that is, the areas between the islands 33 are free of metallization. Fig. 4 shows a cross-sectional view of the sensor arrangement from Fig. 3 along line IV-IV'. As shown in Fig. 4, the islands 33 have a substantially constant thickness 18, which, as before, can be in the range of a few hundred nm. No metallization 17 extends between the islands 33, allowing the electric field emitted by the sensor 13 to pass through the areas between the islands 33 with particularly low loss. The islands 33 and the areas between them are coated with the protective layer 23. The lateral dimensions of the islands 33 and the areas between them are such that the metallization 17 formed by the islands 33 is perceived by the human eye as a continuous, planar metallization layer, although some color of the substrate 19 shines through the metallization 17.For example, when applying the metallization 17, the ratio of the area of ​​the islands 33 to the area between the islands 33 can be set to a value that is, for example, in the range of 1:1 to 100:1. Fig. 5 shows a top view of a sensor arrangement 11, which differs from the sensor arrangement 11 shown in Figs. 3 and 4 in that the metallization 17 is fundamentally continuous, i.e., without islands, and is interrupted only by holes 37. The holes 37 are arranged here purely by way of example along a straight line, but can also have any other suitable arrangement. Fig. 6 shows a cross-sectional view along the line VI-VI' shown in Fig. 5. The electric field emitted by the sensor 13 can penetrate the top layer 15 particularly easily through the holes 37 and thus detect an object through the top layer 15. The number and dimensions of the holes 37 are defined such that the metallization 17 is perceived by a user as a continuous, flat metal surface. Fig. 7 shows a cross-sectional view of a section of a rear trim module 38, which is provided on a tailgate (not shown) of a passenger car (not shown). The cover layer 15 is designed according to one of the embodiments shown in Figs. 1, 2, 3, 4, 5 to 6. In addition to the sensor 13, a light source 39 is provided, which is designed to illuminate a license plate 41 of the passenger car through the cover layer 15 and simultaneously illuminate the cover layer in such a way that it is perceptible from the outside as a luminous surface. However, the contours of the light source 39 are not visible from the outside. When switched off, the light source 39 is completely invisible to the human eye through the cover layer 15.The cover layer 15 forms a button 43 for unlocking the tailgate, whereby, as described above, simply approaching the button 43 is sufficient to unlock the tailgate. Additionally, a capacitive pressure sensor (not shown) is provided, which reacts only to a deformation of the cover layer 15 due to contact with the button 43. In accordance with the application of the rear trim module 38 described above, the sensor arrangement 11 can also be used on an exterior door handle (not shown). Instead of the license plate light, the light source 39 can provide approach lighting. Furthermore, additional light sources 39 can also be provided to illuminate the top layer in different colors or intensity levels. For example, if the sensor 13 successfully detects a finger 27, an optical confirmation signal in the form of a color change or increased light intensity can be output. This allows for a particularly high level of user experience and overall user experience. Reference symbol list 11 Sensor arrangement 13 Capacitance sensor 15 Top layer 17 Metallization 18 Thickness 19 Substrate 21 Primer layer 23 Protective layer 25 Detection area 27 Finger 29 Peak 31 Valley 33 Island 35 Outer surface 37 Hole 38 Rear trim module 39 Light source 41 License plate 43 Button

Claims

Sensor arrangement (11) comprising a sensor (13), in particular a capacitive sensor, and a cover layer (15) arranged above the sensor (13), the cover layer having a metallization (17) facing away from the sensor (13), wherein the metallization (17) is at least partially permeable such that an object (27) in a detection area (25) of the sensor (13) can be detected by the sensor (13) without contact through the cover layer (15), characterized in that the metallization (17) has electrically isolated metallization islands (33) which are non-conductively connected to each other, wherein the lateral dimensions of the metallization islands (33) and the areas between the metallization islands (33) are dimensioned such that the metallization (17) formed by the metallization islands (33) is perceived by the human eye as a continuous, planar metallization layer. Sensor arrangement (11) according to claim 1, characterized in that a maximum thickness (18) of the metallization (17) does not exceed a few hundred nanometers, in particular two hundred nanometers. Sensor arrangement (11) according to claim 1 or 2, characterized in that the metallization (17) has a varying thickness (18). Sensor arrangement (11) according to at least one of the preceding claims, characterized in that the metallization (17) has at least one hole (37). Sensor arrangement (11) according to at least one of the preceding claims, characterized in that the metallization (17) is at least partially transparent to light on one side and / or opaque. Sensor arrangement (11) according to at least one of the preceding claims, characterized in that a primer layer (21) is provided between the metallization (17) and a substrate (19) of the top layer (15). Sensor arrangement (11) according to at least one of the preceding claims, characterized in that the metallization (17) is at least partially covered by a protective layer (23). Sensor arrangement (11) according to at least one of the preceding claims, characterized in that the metallization (17) is chromium and / or nickel free. Sensor arrangement (11) according to at least one of the preceding claims, characterized in that the metallization (17) comprises indium. Sensor arrangement (11) according to at least one of the preceding claims, characterized in that the cover layer (15) of the sensor arrangement (11) is plastically deformable. Door handle, in particular exterior door handle of a motor vehicle, with a sensor arrangement (11) according to at least one of the preceding claims, wherein the cover layer (15) of the sensor arrangement (11) forms a button at least for unlocking a door lock of the motor vehicle. Rear trim module for a motor vehicle with a sensor arrangement (11) according to at least one of claims 1 to 10 wherein the cover layer (15) of the sensor arrangement (11) forms a button at least for unlocking a tailgate lock of the motor vehicle.

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