WINDOW PANEL WITH CAPACITIVE SENSOR

Description

[0001] The invention relates to a composite disc with a capacitive sensor, a method for manufacturing the composite disc and its use.

[0002] Motor vehicle windshields are often equipped with a variety of functions. A windshield is typically a laminated glass, consisting of an inner pane, an outer pane, and an intermediate layer that bonds the two panes together. This intermediate layer contains a plastic, such as polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), and / or polyethylene terephthalate (PET). The windshield's functions are controlled by sensors, including a rain sensor that automatically detects rain on the windshield. The rain sensor automatically controls the windshield wipers based on the amount of rain or moisture detected on the windshield, without requiring any intervention from the driver.

[0003] The commonly used rain sensors are light sensors that use a photoelectric element to detect light rays. Light is coupled into a section of the windshield, reflected off the outer surface of the windshield by total internal reflection, and directed to the photoelectric element. The photoelectric element measures the light intensity and generates a corresponding signal. A change or decrease in this signal detects rain on the windshield and triggers the windshield wiper function. Such a rain sensor requires considerable space, particularly on the inside of the windshield. The individual components of the rain sensor extend into the interior of the vehicle.

[0004] Furthermore, capacitors used for rain sensors are known. These capacitors are typically stray-field capacitors mounted on a windshield, where the stray-field capacitance changes depending on the amount of rain present on the windshield. DE 102009029079 A1 discloses a stray-field capacitor comprising a centrally or eccentrically arranged reference electrode and a counter electrode. Both electrodes are arranged in a common electrode plane, with the counter electrode surrounding the reference electrode but being galvanically isolated from it. An electric field is generated between the reference electrode and at least one counter electrode, extending into a dielectric space outside the windshield. For this purpose, the electrodes are each connected to a positive and a negative terminal of a supply voltage source, respectively.Rain falling on the windshield alters the electric field and thus the capacitance of the stray field capacitor. Such a stray field capacitor requires complex installation on the windshield, restricts the driver's visibility as the number of electrodes on the laminated glass increases, and is prone to error messages when rain is detected. Furthermore, while such a stray field capacitor can indicate the presence of rain, it cannot measure its intensity.

[0005] US 8009053 B2 and DE 102008043610 A1 each disclose a composite pane according to the preamble of claim 1. Capacitive rain sensors are also known from WO 2007 / 009973 A1, US 2009 / 039901 A1 and US 6094981 A. The object of the present invention is to provide an improved composite pane that incorporates a sensor which can be easily and cost-effectively integrated into the window pane and which possesses a high degree of reliability and effectiveness.

[0006] The object of the present invention is achieved according to the invention by a composite disc with a capacitive sensor according to independent claim 1, and by a method for manufacturing the composite disc and its use according to claims 8 and 9. Preferred embodiments are described in the dependent claims.

[0007] The composite disc according to the invention has the features according to claim 1.

[0008] The laminated glass is designed to separate an interior space from its external environment. The laminated glass according to the invention comprises an inner pane and an outer pane. The inner pane is the pane that, when installed, faces the interior of the vehicle. The laminated glass is intended to separate the interior from the external environment through an opening, particularly a vehicle window opening. The outer pane is the pane that, when installed, faces the external environment of the vehicle. The laminated glass can be used in a variety of applications: In the case of a laminated glass used as a vehicle window, it can, for example, be a roof window, a windshield, a rear window, a side window, or any other glazing that defines the vehicle interior.The outer surface of the glass refers to the surface of the glass that faces outwards, away from the vehicle interior. The inner surface, therefore, refers to the surface of the glass that faces the vehicle interior.

[0009] The invention is based on the idea that sensor electronics mounted on a composite windscreen take up a lot of space and simultaneously obstruct the driver's view. The composite windscreen according to the invention, which incorporates a capacitor with two electrodes formed from a transparent, electrically conductive coating, allows the capacitor to be easily integrated into the composite windscreen. This does not impair the view through the composite windscreen, and the capacitor can therefore be positioned more easily and compactly on the composite windscreen. Space-saving integration of the sensor technology is particularly important in modern vehicles with complex windscreens.

[0010] The transparent, electrically conductive coating exhibits heat-reflective properties. Such a coating is a layer system containing a functional layer. The functional layer typically consists of an electrically conductive oxide (TCO), preferably indium tin oxide (ITO), fluorine-doped tin oxide (SnO₂:F), antimony-doped tin oxide (SnO₂:Sb), aluminum-doped zinc oxide (ZnO:Al), and / or gallium-doped zinc oxide (ZnO:Ga). The coating is electrically conductive and exhibits low absorption and low reflection in the visible spectral range, and therefore high transmission.The composite disc can have at least partially or fully the transparent, electrically conductive coating on an inner or outer surface of the inner disc, outer disc, intermediate layer or in the intermediate layer, wherein the capacitor and the electrodes are electrically separated from the coating by at least one coating-free dividing line.

[0011] Particularly advantageous electrodes according to the invention are provided for generating a sensor area on the composite disc, in particular an outer surface, within which moisture on the composite disc causes a change in capacitance. An electric field is generated between two electrodes of the capacitor, which extends into a space above the composite disc and defines the sensor area. The space above the composite disc can comprise air, water, or other contaminants and deposits. The arrangement of the sensor area on the composite disc ensures a rapid response of the sensor. The sensor area can be arranged in the upper section of the composite disc, preferably centrally.

[0012] In an advantageous embodiment, the sensor electronics are designed to generate a signal when moisture, including rain, is detected on the sensor surface. Advantageously, only one of the vehicle's windshield wiper systems is triggered if the sensor electronics have generated a corresponding signal.

[0013] The capacitive sensor can have one or more capacitors, in particular 2n and a maximum of 32 capacitors, with the sensor electronics designed to generate multiple signals and providing means for calculating a correlation between these signals. This allows the sensor electronics to reliably determine whether or not rain is present on the laminated windshield. This calculation of signal correlation is useful for applications where a meaningful signal for triggering the windshield wiper system is required within a short time. This is the case when rain begins to fall while driving and impairs the driver's visibility, requiring the windshield wiper system to respond quickly and reliably. This allows the system to distinguish between normal operation and rain.

[0014] The sensor electronics are designed to calculate autocorrelation and / or cross-correlation of the signals. A further improvement of the laminated windscreen with capacitive sensor is that the autocorrelation calculation provides a result indicating whether or not rain is present on the laminated windscreen. If the autocorrelation result is greater than 1, then rain is present. This determination triggers the windscreen wiper function. Cross-correlation allows for simple verification of rain presence with minimal technical effort, thus increasing resistance to dirt-related interference. The mathematical method of cross-correlation determines the similarity of two signals when they are time-shifted by a specific amount.

[0015] In a further advantageous embodiment of the invention, the electrodes are designed asymmetrically. The asymmetrical design of the electrodes avoids unwanted interference with electromagnetic fields generated by neighboring electrical conductors and devices.

[0016] To further improve the electromagnetic compatibility of the sensor, the electrodes have different surface areas.

[0017] A comb-shaped electrode has an elongated comb-like ridge on which numerous comb teeth are arranged. The comb teeth run parallel to each other and are positioned perpendicular to the ridge, thus creating a comb-like, toothed electrode. Surprisingly, it was found that this type of electrode design produces virtually no false signals; that is, the sensor electronics generate a switching signal even when there is no rain on the windshield.

[0018] Two comb-shaped electrodes interlock, offering the same advantage. Like the teeth of two combs, the electrode surfaces interlock, but remain insulated from each other by a dividing line. The electric field between the comb-shaped electrodes exhibits nearly parallel field lines in certain sections.

[0019] Furthermore, it has proven advantageous to arrange two comb-shaped electrodes ridge to ridge.

[0020] The laminated glass can be a vehicle windshield in which the electrodes are arranged on the surface of the outer or inner pane facing the interlayer. Alternatively or additionally, the electrodes can be arranged on or within the interlayer. The electrodes extend in a common plane of the laminated glass, in particular in a plane parallel to the outer surface of the outer pane. This creates an electric field between at least two electrodes, which penetrates the rainwater on the laminated glass.

[0021] In one possible embodiment, the windshield can have additional electrodes in different planes of the windshield. These electrodes serve to increase the precision of the measurement and, for example, to compensate for temperature effects such as capacitance drift caused by changes in the temperature of the glass and the PVB. Because these compensation electrodes are located in a different plane (preferably further away from the vehicle's exterior), the effect of rain on these structures is weaker, while temperature changes, especially when the vehicle is stationary, can still affect these sensor structures.

[0022] The laminated glass pane can have one or more capacitive sensors for detecting moisture, preferably rain. The sensors can be arranged along an edge of a wiper area of ​​the laminated glass pane.

[0023] The intermediate layer is preferably transparent. The intermediate layer preferably contains at least one plastic, preferably polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), and / or polyethylene terephthalate (PET). However, the intermediate layer can also contain, for example, polyurethane (PU), polypropylene (PP), polyacrylate, polyethylene (PE), polycarbonate (PC), polymethyl methacrylate, polyvinyl chloride, polyacetate resin, casting resins, acrylates, fluorinated ethylene propylene, polyvinyl fluoride, and / or ethylene tetrafluoroethylene, or copolymers or mixtures thereof. The intermediate layer can be formed by one or more films arranged one above the other. The intermediate layers are preferably thermoplastic and, after lamination, bond the inner pane, the outer pane, and any further intermediate layers together.

[0024] Another aspect of the invention comprises a method according to claim 8.

[0025] The application of the transparent, electrically conductive coating can be carried out by methods known per se, preferably by magnetic field-assisted cathode sputtering. This is particularly advantageous with regard to simple, fast, cost-effective and uniform coating of the discs. However, the transparent, electrically conductive coating can also be applied, for example, by vapor deposition, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD) or by wet chemical processes.

[0026] The removal of individual separation lines in the transparent, electrically conductive coating is preferably carried out using a laser beam. Methods for structuring thin metal films are known, for example, from EP 2200097 A1 or EP 2139049 A1. The width of the removal is preferably 10 µm to 1000 µm, particularly preferably 30 µm to 200 µm, and especially 70 µm to 140 µm. In this range, the laser beam achieves a particularly clean and residue-free removal of the coating. Removal using a laser beam is particularly advantageous because the removed lines are optically very inconspicuous and have little impact on the appearance and transparency. Removing a line with a width wider than that of a laser cut requires repeatedly scanning the line with the laser beam. Therefore, the process time and costs increase with increasing line width.Alternatively, the coating can be removed by mechanical removal as well as by chemical or physical etching.

[0027] Lamination, i.e., the bonding of the inner pane, intermediate layer, and outer pane, is preferably carried out under the influence of heat, vacuum, and / or pressure. Methods known per se for manufacturing a laminated pane can be used.

[0028] For example, so-called autoclave processes can be carried out at an elevated pressure of approximately 10 to 15 bar and temperatures of 130 to 145 °C for about two hours. Vacuum bag or vacuum ring processes, which are known per se, operate, for example, at approximately 200 mbar and 80 to 110 °C. The inner disc, the thermoplastic intermediate layer, and the outer disc can also be pressed together in a calender between at least one pair of rollers to form a disc. Systems of this type are known for the production of discs and typically have at least one heating tunnel upstream of a pressing unit. The temperature during the pressing process is, for example, between 40 to 150 °C. Combinations of calender and autoclave processes have proven particularly effective in practice. Alternatively, vacuum laminators can be used.These consist of one or more heated and evacuated chambers in which the inner and outer panes are laminated within, for example, about 60 minutes at reduced pressures of 0.01 mbar to 800 mbar and temperatures of 80°C to 170°C.

[0029] In the process according to the invention, the galvanic contacting of the transparent, electrically conductive coating can be carried out as a further process step by means of an electrical conductor connection. The galvanic contacting is preferably carried out by bonding with an electrically conductive adhesive, soldering and, in particular, ultrasonic soldering.

[0030] In galvanic contacting, it can be advantageous to first apply an electrically conductive contact layer to the transparent, electrically conductive coating, for example, by metallization or by printing with a metal-containing screen-printing paste followed by baking. This contact layer is particularly beneficial for achieving a low-resistance and corrosion-resistant connection between the conductive components of the transparent, electrically conductive coating and the other connection elements, such as foil conductors or round conductors.

[0031] Another aspect of the invention includes the use of the composite disc according to the invention with capacitive sensor for detecting moisture in means of transport for traffic on land, in the air or on water, in particular in motor vehicles, for example as a windshield or rear window.

[0032] The invention is explained in more detail below with reference to a drawing and exemplary embodiments. The drawing is a schematic representation and not to scale. The drawing does not limit the invention in any way.

[0033] They show: Figure 1 is a schematic top view of an embodiment of a composite disc according to the invention with a capacitive sensor; Figure 2 is a cross-sectional view along the section line AA'. Figure 1 Figure 3 shows an enlarged view of section Z from Figure 1 Figure 4 shows a first alternative representation of section Z from Figure 1 Figure 5, a second alternative representation of section Z from Figure 1 Figure 6, a third alternative representation of section Z from Figure 1 , which is not claimed in the patent claims, and Figure 7 a fourth alternative representation of section Z from Figure 1 , which is not claimed in the patent claims.

[0034] Figure 1 Figure 1 shows a top view of a composite glass pane 100 according to the invention, using a vehicle windshield as an example. The composite glass pane 100 has a capacitive sensor 3 in its upper section for detecting moisture on the composite glass pane 100. For the purposes of the invention, the term "moisture" denotes the degree of water presence on the composite glass pane 100 and also includes water in the form of rain. The capacitive sensor 3 measures a change in the dielectric constant or capacitance caused by the moisture or rain. For this purpose, the capacitive sensor 3 has at least one capacitor 5, which is connected via a terminal 8 to sensor electronics 14 located outside the composite glass pane 100.

[0035] The connection 8 is located at the outer edge of the composite disc 100. The distance to the outer edge is less than 10 cm, preferably approximately 0.5 cm. This allows the electrical contact of the connection, for example with a foil conductor, to be concealed under an optically inconspicuous black print or with a cover, for example a camera housing.

[0036] Furthermore, the capacitor 5 comprises three electrodes 10, 10', 10", each galvanically isolated from the others. The electrodes 10, 10', 10" are arranged in a common plane and capacitively coupled to each other. The electrodes generate a sensor area on an outer surface I of the composite disk, within which the moisture on the composite disk causes a change in capacitance.

[0037] The sensor electronics are designed to measure changes in capacitance and, depending on the measured value, to send a switching signal to a windshield wiper system. For this purpose, the capacitive sensor has several capacitors 5. The sensor electronics 14 are equipped with a microprocessor that calculates a cross-correlation and / or an autocorrelation of the signals to evaluate the values ​​transmitted by the capacitors 5. The calculation of the cross-correlation and / or the autocorrelation is continuously determined and monitored. Depending on a threshold value, the switching signal is forwarded to the windshield wiper system via the vehicle's CAN bus.

[0038] The output switching signals can be arbitrary and adapted to the requirements of the respective application. For example, a switching signal can represent a positive voltage, such as 12 V; no switching signal can represent 0 V; and another switching signal can represent +6 V. The switching signals can also correspond to the CAN_High and CAN_Low voltages common in a CAN bus and alternate around an intermediate voltage value. The switching signal can also be pulsed and / or digitally encoded.

[0039] During signal autocorrelation, a sensor reading from a capacitor is correlated with a sensor reading from the same capacitor at an earlier time. If a calculated autocorrelation coefficient is greater than a predefined threshold, a cross-correlation of two signals is determined. The two signals comprise at least a first signal corresponding to a sensor reading from a first capacitor and a second signal corresponding to a sensor reading from a second capacitor at the same time. The first signal is cross-correlated with the second signal. If the result of the cross-correlation is greater than a second threshold and not equal to one, the presence of rain on the windshield is assumed, and a corresponding switching signal, which controls the function of the windshield wipers, is transmitted to the windshield wiper system.

[0040] If the result of the cross-correlation is one, the presence of rain on the composite disc 100 is denied and no switching signal is generated.

[0041] Figure 2 presents a cross-section along the section line AA' perpendicular to the common plane of the electrodes Figure 1 The laminated glass 100 comprises at least an inner pane 1, an intermediate layer 2, and an outer pane 4. After final assembly in an installed position, the laminated glass 100 separates a vehicle interior from an external environment. The inner surface IV of the inner pane 1 is accessible from the interior, and the outer surface I of the outer pane 4 is accessible from the external environment of the vehicle. Furthermore, the outer pane 4 has an inner surface II, and the inner pane 1 has an outer surface III.

[0042] The inner pane 1 and the outer pane 4, for example, are made of soda-lime glass and were manufactured using the float process. The thickness d1 of the inner pane 1 is, for example, 2.1 mm. In principle, panes 1 and 4 can also have other thicknesses.

[0043] The intermediate layer 2 can be formed by one or more superimposed films, the thickness of which is preferably from 0.025 mm to 3 mm, typically 0.38 mm or 0.76 mm. The intermediate layers are preferably thermoplastic and, after lamination, bond the inner pane, the outer pane, and any further intermediate layers together. The intermediate layer 2 is a thermoplastic intermediate layer and consists, for example, of polyvinyl butyral (PVB). It has a thickness d2 of, for example, 0.76 mm.

[0044] The outer pane 4 has a transparent, electrically conductive coating 6 on its inner surface II. Table 1 shows three examples of transparent, electrically conductive coatings 6 with functional layers made of, for example, ITO. Each coating 6 of examples 1-3 consists of a layer stack of: outer pane 1 / adhesive layer / functional layer / barrier layer / antireflective layer. The thickness d 3 of the outer pane 4 is, for example, also 2.1 mm. Table 1 material thickness Example 1 Example 2 Example 3 Anti-reflective coating SiO2 :Al 45 nm 40 nm 80 nm Barrier layer Si 3 N 4 :Al 12 nm 20 nm 12 nm Functional layer ITO 120 nm 120 nm 120 nm Adhesive layer SiO2 :Al 30 nm 30 nm 40 nm Outer pane 4 or inner pane 1 Soda-lime glass

[0045] Figure 3 shows an enlarged view of section Z of the composite disc 100 from Figure 1with the capacitively coupled electrodes 10, 10', 10". The transparent, electrically conductive coating 6 is divided by a coating-free dividing line 7 into different, electrically isolated electrodes 10. In this example, electrically isolated means that the areas are galvanically separated from each other, i.e., that no direct current (DC) can flow between the areas.

[0046] In the Figure 3In the illustrated example, two electrodes 10' and 10" are electrically separated by a third electrode 10. Each electrode 10' and 10" is comb-shaped and consists of a comb back and several interlocking comb teeth. The width of a comb tooth and the comb back is approximately 1 mm in this example. The comb back is connected to a terminal 8. The terminal 8 has a rectangular shape with a width of, for example, 12 mm. The length of the comb back is approximately 48 mm. The third electrode 10 is separated from the remaining transparent, electrically conductive coating 6 by a dividing line 7. The third electrode 10 is rectangular and encompasses both electrodes 10' and 10". The third electrode 10 has a further terminal 8. This further terminal 8 can be positioned arbitrarily within the third electrode 10.In the example shown, it is located at the upper edge of the third electrode 10 at the upper edge of the composite disk 100. It is therefore visually inconspicuous.

[0047] The dividing line 7 has a width of, for example, only 100 µm and is introduced into the transparent, electrically conductive coating 6 by laser structuring. Dividing lines 7 with such a small width are barely perceptible and hardly impair the view through the laminated glass 100, which is particularly aesthetically pleasing and of special importance for driving safety, especially for use in the field of vision of vehicles.

[0048] Figures 4 to 7 show alternative representations of section Z from Figure 1 In Figure 4 and 5 Alternative forms of the comb-shaped electrodes 10' and 10" are shown. Figure 6 and 7show tulip-shaped configurations of the electrodes 10' and 10", which are not claimed in the patent claims. Reference symbol list:

[0049] 1 Inner pane 2 Intermediate layer 3 Capacitive sensor 4 Outer pane 5 Capacitor 6 Transparent, electrically conductive coating 7 Separation line 8 Connection 14 Sensor electronics 100 Composite pane d1, d2, d3 thickness A-A's section line Z's section I. Outer surface of the outer pane 4 II. Inner surface of the outer pane 4 III. Outer surface of the inner pane 1 IV. Inner surface of the inner pane 1

Claims

1. Composite pane (100) for separating an interior space from an external environment, comprising - an inner pane (1), with an outer surface (III) and an inner surface (IV), - an outer pane (4), with an outer surface (I) and an inner surface (II), and - an intermediate layer (2) that areally joins the inner surface (II) of the outer pane (2) to the outer surface (III) of the inner pane (1), - a, in the visible spectral range transparent, electrically conductive coating (6) at least partially or over its entire surface on an inner or outer surface of the inner pane (1), outer pane (4), intermediate layer (2) or in the intermediate layer (2), - a capacitive sensor (3) for detecting moisture having at least one capacitor (5) that is connected to an electronic sensor unit (14), which is provided for detecting a change in capacitance of the capacitor (5), wherein the at least one capacitor (5) has three electrodes (10, 10', 10") formed of the transparent, electrically conductive coating (6), which are capacitively coupled, wherein the electrodes (10, 10', 10") extend in a common plane of the composite pane (100) and the transparent, electrically conductive coating (6) is divided by two coating-free separating lines (7) into the electrodes (10, 10', 10") electrically isolated from one another, wherein two comb-shaped electrodes (10', 10") intermesh or two comb-shaped electrodes (10', 10") are arranged back to back, and wherein the two comb-shaped electrodes (10', 10") are electrically divided by a third electrode (10), wherein the third electrode (10) comprises both comb-shaped electrodes (10', 10") and is separated by a further separating line (Z) from the rest of the transparent, electrically conductive coating (6).

2. Composite pane (100) according to claim 1, characterized in that the electrodes (10, 10', 10") are provided for generating a sensor area on the composite pane, inside which the moisture on the composite pane causes a change in capacitance.

3. Composite pane (100) according to claim 2, characterized in that the electronic sensor unit (14) is provided for generating a signal when moisture is detected on the sensor area.

4. Composite pane (100) according to one of claims 1 through 3, characterized in that the capacitive sensor (3) includes a plurality of capacitors (5), wherein the electronic sensor unit (14) is provided for generating a plurality of signals and has means for calculating a correlation of the signals.

5. Composite pane (100) according to claim 4, characterized in that means of the sensor (3) are provided for calculating an autocorrelation and / or a cross-correlation of the signals.

6. Composite pane (100) according to one of claims 1 through 5, characterized in that the electrodes (10, 10', 10") have an asymmetric area.

7. Composite pane (100) according to one of claims 1 through 6, characterized in that the electrodes (10, 10', 10") have a different perimeter.

8. Method for producing a composite pane (100) according to one of claims 1 through 7, at least comprising: - applying a transparent, electrically conductive coating (6) at least partially or over its entire surface on an inner or outer surface of the inner pane (1), outer pane (4), intermediate layer (2) or in the intermediate layer (2) and introducing two separating lines (7), which electrically divide the transparent, electrically conductive coating (6) into three capacitively coupled electrodes (10, 10', 10"), preferably by laser patterning or by mechanical or chemical ablation, such that the electrodes (10, 10', 10") extend in a common plane of the composite pane (100) and the transparent, electrically conductive coating (6) is divided by two coating-free separating lines (7) into the electrodes (10, 10', 10") electrically isolated from one another, wherein two comb-shaped electrodes (10', 10") intermesh or two comb-shaped electrodes (10', 10") are arranged back to back, and wherein the two comb-shaped electrodes (10', 10") are electrically divided by a third electrode (10), wherein the third electrode (10) comprises both comb-shaped electrodes (10', 10") and is separated by a further separating line (Z) from the rest of the transparent, electrically conductive coating (6), and - producing a stack sequence comprising the inner pane (1), an intermediate layer (2), and an outer pane (4), wherein the intermediate layer (2) is arranged between the inner surface (II) of the outer pane (4) and the outer surface (III) of the inner pane (1), and laminating the stack sequence to form a composite pane (100).

9. Use of the composite pane (100) according to one of claims 1 through 7 in means of transportation for travel on land, in the air, or on water, in particular in motor vehicles, for example, as a windshield or rear window.