Method for determining a temperature of a switchable window in a vehicle and device for carrying out the method

Abstract

Method for determining a temperature of a transparency-variable, switchable pane (4) having a transparency-variable layer arranged between two transparent electrically conductive contact layers for switching the same, comprising: (a) applying (100) an electrical reference voltage to the two contact layers; (f) separating (200) one of the contact layers from the provided reference voltage at a predetermined first time (t1); (g) measuring (300) a value of the residual voltage still remaining between the two contact layers during a discharge of the two contact layers through the transparency-variable layer at at least one second time point (t2) following the predetermined first time point (t1) and spaced apart in time from the same; (h) determining (400) a value of a parameter representing the discharge from the measurement, (i) Determining (500) a first value of the temperature of the switchable disc (4) from the determined value for the parameter using an assignment rule between the parameter and the temperature by a control unit.

Description

Technical area:

[0001] The present invention relates to a method for determining a temperature of a switchable window in a vehicle and a device, or glass window device, for carrying out the method. Technical background:

[0002] Switchable or intelligent glass (smart glass) is increasingly being used not only in buildings but also in vehicles, for example as privacy screens, for shading or in the context of ambient light applications, etc. In this application, vehicles are understood to include motor vehicles, including cars and commercial vehicles, construction machinery, aircraft, or ships, etc.

[0003] Switchable glass is typically provided in a laminated glass structure, in which two glass plates sandwich a film containing a transparency-variable layer coated on both sides with contact layers that serve as surface electrodes. The transparency-variable layer can comprise, for example, a material made of LC (liquid crystal), PDLC (polymer dispersed liquid crystal), or SPD (suspended particle device). When a voltage is applied, such materials change their optical properties, for example, from transparent to opaque and vice versa.

[0004] In the case of PDLC, for example, the liquid crystals enclosed in a solid polymer matrix align when a certain voltage is applied (corresponding to an ON state), allowing incident light to pass directly between the crystals and making the switchable glass transparent. When the voltage is switched off, the liquid crystals randomly reorient themselves, causing the incident light to scatter and thus interrupting the light transmission. In this case, the switchable glass becomes opaque or milky.

[0005] The functionality of SPD is similar to that of LC or PDLC. Here, the liquid in which rod-shaped SPD nanoparticles are suspended is an organic gel, specifically a non-aqueous, electrically resistant liquid with a polymer stabilizer dissolved in it, which reduces the tendency of the particles to agglomerate, thus dispersing them and keeping them suspended. When no voltage is applied, SPD still has low light transmittance and exhibits a blue tint. When a voltage is applied, the blue tint disappears (no more color), and the material becomes entirely translucent.

[0006] The materials mentioned for the transparency-variable layer can change their optical properties depending on the applied voltage. In this way, the light transmittance can be adjusted by applying a suitable voltage to the relevant contact layers. Typically, a switchable glass pane is operated with an alternating current, since direct current components can have a detrimental effect on the material in the long term. Control to achieve a specific light transmittance can be achieved by adjusting the amplitude and / or frequency, or by adjusting the duty cycle in pulse-width modulation.

[0007] It is known, however, that the relationship between the optical properties of the material of the transparency-variable layer and the applied voltage also depends on the temperature. If only the "on" (e.g. transparent) and "off" (e.g. opaque) states are required, a voltage value can be selected for both states that can achieve the desired limiting case (opaque or fully transparent) for all considered temperature values. However, things become more difficult if a user requires a specific value for partial transmittance. Without further measures, the control system would select a voltage value depending on the desired transmittance value based on a mapping between voltage values ​​and light transmittance values. This voltage value would then achieve a completely different result in terms of the actual light transmittance depending on the temperature.

[0008] Because this is known, sensors, e.g. NTC-based sensors, are regularly installed in vehicles, for example. These allow the measurement or determination of a temperature on or near the relevant glass panes. Based on the measured temperature, the voltage value to be set can be adjusted so that, for example, a deviation of the temperature from a reference value can be compensated. However, the implementation of one or even several independent temperature sensors in switchable panes can entail increased material costs and a high cabling effort. Furthermore, such sensors are usually located on the edge of a pane of glass (or, in the case of several switchable panes of glass, on another pane of glass in the vehicle) and therefore may not represent the current temperature regime in the layer with variable transparency. With the result that, despite the use of sensors, incorrect light transmittance is achieved.

[0009] DE 10 2017 213 302 B3 describes a method for determining a temperature in a switchable disk. The method involves measuring the current consumption within the respective contact layers. For this purpose, a specified voltage is applied to one or both contact layers between two points within the contact layers. The current flows depending on the respective voltage and the temperature-dependent resistance. The temperature can then be derived from the latter. The advantage is that the temperature can be determined in situ, thus providing more reliable values ​​than methods for determining the temperature using sensors.

[0010] However, to avoid current flow through the intermediate, variable-transparency layer, the measurement must be performed symmetrically in both contact layers with the same voltage. This, however, requires a neutral, discharged state of the capacitor formed by the contact layers. Therefore, a measurement during operation, e.g., during a cyclic discharge phase, which would otherwise be appropriate, is not feasible, so the measurement would entail a disruption to operation.

[0011] Alternatively, DE 10 2017 213 302 B3 proposes measuring the temperature-dependent impedance inherent in the layer arrangement of the contact layers and the transparency-variable layer sandwiched between them to determine the temperature. However, it remains unclear how the measurement could be performed, what design measures could be used to achieve this, and whether this would be done during operation or not. Description of the invention:

[0012] The present invention is therefore based on the object of providing a method for determining a temperature of the switchable pane and in particular of the transparency-variable layer as well as a corresponding device in which the effort and costs are kept low on the one hand and on the other hand the integration into the ongoing operation of the switchable pane is simplified.

[0013] According to various aspects of the invention, a method is proposed for determining the temperature of a switchable, transparency-variable pane. The pane has a layer of variable transparency arranged between two transparent, electrically conductive contact layers for switching the layer. The two contact layers serve as contact or surface electrodes, with the aid of which an electrical voltage can be applied across the layer of variable transparency. In particular, the contact layers can be provided for this purpose with connection areas for contacting lines, with which a power supply can be achieved, for example, from a control unit.

[0014] According to one embodiment, the switchable disc or the transparency-variable layer can be formed from a PDLC material, an LC material, or an SPD material. PDLC or LC are preferred. Furthermore, the two contact layers can be formed from a material comprising indium tin oxide (ITO), which is itself transparent so as not to impair the light transmission of the disc. However, other similar materials are also possible.

[0015] According to the method, an electrical reference voltage provided by a control unit is first applied to the two contact layers. The control unit can, for example, comprise a microcontroller and a memory. The microcontroller can, for example, carry out the measurement described below and evaluate it to determine the temperature of the pane. The same or a different microcontroller can be used to output a control signal during normal operation, which is, for example, converted in a known manner by a digital-to-analog converter element into an analog signal and then amplified by an amplifier element. The amplified signal can be used to periodically recharge the switchable pane during normal operation in order to control the light transmittance. The amplifier element can, for example, have a half-bridge operated by an operational amplifier.Other designs for controlling the switchable disc are also possible.

[0016] The reference voltage applied to the contact layers can be a voltage provided by a power source, such as a vehicle battery or a converter connected downstream of it, or a predefined maximum operating voltage resulting from the output control signal. However, lower reference voltages can also be set using this control signal, and the magnitude of the reference voltage is essentially arbitrary, as long as the components are not damaged (upper limit) or the level is so low that a subsequently determined decay curve can no longer be measured with sufficient resolution (lower limit).

[0017] The application of the reference voltage can coincide with the application of a voltage applied during normal operation. It is important that the value of this voltage or of the reference voltage is known for the subsequent determination or characterization of a decay curve in order to be able to compare it with subsequently measured values ​​of a residual voltage. Furthermore, it is preferred that the applied reference voltage is kept constant for a period of time before a separation of one of the contact layers from the voltage supply takes place, as will be described below. This prevents any charge transfer processes from still being ongoing at the time of separation. Instead, the capacitor formed from the contact layers is essentially charged according to the reference voltage. The time constant for charging τ = Rs C is calculated from the capacitor (C) formed by the two contact layers and the resistance Rs of the contact layers.For example, the minimum time period for applying the constant reference voltage can be a factor of 2, preferably a factor of 5, more preferably a factor of 10 of this time constant.

[0018] Next, the above-mentioned separation of at least one of the charged contact layers from the provided reference voltage at a predetermined first time follows. As a result, a discharge of the contact layers acting as capacitors can now only occur via the intermediate layer of variable transparency, which, as an ohmic resistor, allows a current to flow. The separation can be achieved by an additional switch in the circuitry of the amplifier circuit. If necessary, a high-impedance voltage divider is also connected in parallel to measure the respective voltage. The influence of the parallel voltage divider can be calculated out.

[0019] According to the Fig. In the equivalent circuit diagram shown in Figure 1, which shows the arrangement of the two contact layers and the intermediate transparency-variable layer, the capacitor formed by the two contact layers, charged according to the reference voltage, can discharge via the intermediate transparency-variable layer. The rate of discharge is temperature-dependent, because both the capacitance of the two contact layers and the ohmic resistance of the transparency-variable layer can depend on the temperature. Thus, the invention exploits the fact that the temperature can be inferred from determining the discharge rate.

[0020] For this purpose, a value of the remaining voltage between the two contact layers during a discharge of the two contact layers, hereinafter referred to as the residual voltage, is next measured through the transparency-variable layer at at least one second point in time, subsequent to and spaced apart from the predetermined first point in time. Ideally, the discharge curve corresponds to an exponentially declining curve. The discharge curve characterizing the discharge is uniquely defined by the reference voltage and the residual voltage measured at at least one further point in time.

[0021] To quantify the discharge curve in a parameter, a characteristic value can be determined, where the parameter represents the discharge.

[0022] For example, the parameter can be the time constant τ = Rp · C of the capacitor (C) formed by the two contact layers and the resistance (Rp) formed by the transparency-variable layer. From the two measured values ​​for the two points in time, the discharge curve can be determined and the time after which the residual voltage has dropped to a factor of 1 / e can be calculated. This time corresponds to the time constant.

[0023] Alternatively, according to another embodiment, the voltage value measured at a fixed second point in time can be used as a parameter, whereby the measured value is equal to the value of the parameter.

[0024] According to a further alternative, a time can be determined which is required until the voltage has dropped to a factor (less than 1) of the original reference voltage. The voltage measurement can be supported here by a circuit measuring arrangement with a comparator which compares the measured voltage with a corresponding reference voltage which corresponds to the factor. The factor can be 1 / e, for example, which corresponds directly to the time constant, but other factors are also possible. The time period until the measured voltage value falls below the reference voltage can be measured or determined by a timer. In this embodiment, the time period is the parameter representing the discharge.

[0025] The aspect of the invention further provides that a first value of the temperature of the switchable disc is determined from the value determined for the parameter (e.g. the time constant, the dropped voltage at the second time, the time until a reference voltage is reached, etc.) by the control unit on the basis of an assignment rule between the parameter and the temperature.

[0026] The assignment rule can be, for example, a table, optionally with interpolation, an approximate equation determined from a fit, an algorithm, and / or even a Cl scheme applied by the control unit. The assignment rule assigns a (first) temperature value to the value for the parameter.

[0027] It should be noted that a high-impedance voltage divider, if provided, for measuring the respective voltage between the contact layers contributes to the discharge curve. This can be calculated out or taken into account accordingly in the assignment table.

[0028] The aspects of the invention proposed here advantageously measure the electrical properties of the contact layers and even of the transparency-variable layer itself, each of which is temperature-dependent. This enables precise on-site temperature determination in real time. Furthermore, these aspects enable good integration into normal operating procedures because cyclical charge reversal phases, which occur anyway, can be used for the measurement.

[0029] According to embodiments, measuring the value of the residual voltage remaining during a discharge of the two contact layers may involve the second time being predetermined and specified. The value of the parameter may be calculated from the measured voltage or identified with it.

[0030] Alternatively, measuring the voltage can include specifying a residual voltage value that is reduced by a factor compared to the reference voltage. From a repeated or continuous measurement of the residual voltage, a second point in time is determined, up to which point the measured residual voltage has fallen to the reduced voltage value. The value of the parameter can then be calculated from the time interval between the first point in time and the second point in time or identified with this. According to a further embodiment of the method, the control unit receives a second value of an ambient temperature via a measurement by a temperature sensor, at least in the event that two or more possible temperature values ​​can be determined based on the determined value of the discharge parameter from the assignment rule. This proposed solution solves a particular problem that, for example,the time constant mentioned as the parameter representing the discharge for the mentioned common materials of the transparency-variable layer such as PDLC over the range of temperatures possible in vehicles (e.g. -40°C to +80°C) may, under certain circumstances, very roughly viewed, have the shape of a downward-opening parabola or bell, with the result that one value for the parameter can be assigned two or possibly even three temperature values. However, the shape of the time constant over the temperature depends on the transparency-variable layer used or the corresponding film material. With the help of a (second) temperature value, possibly only roughly measured in an area surrounding the switchable pane by a temperature sensor, it is possible to differentiate in which sub-range of the temperature scale the assignment rule should be applied, so that only a (now exact) first temperature value comes into question.In order not to conflict with the aim of the invention to achieve a saving in effort and costs by omitting temperature sensors on or near the switchable windows, a temperature sensor which is usually always present in the relevant ECU of the vehicle can preferably be used for this purpose.

[0031] This second temperature value can now be compared with the possible values ​​determined from the assignment rule. Depending on the comparison, one of the possible values ​​determined from the assignment rule is selected as the valid first temperature value in this embodiment.

[0032] A further embodiment provides that the control unit, based on the now determined temperature, calculates and outputs a control signal for setting a predetermined light transmittance of the pane as a function of the first temperature value. In other words, the voltage swing is adjusted so that temperature deviations or changes are compensated for to set a desired light transmittance. For example, the effect can be compensated by varying the applied voltage generated by the control unit (e.g., the ECU), namely by varying its amplitude and shape (rectangular, sawtooth, sinusoidal, trapezoidal) and / or frequency as a function of temperature and time (age and / or number of switching cycles).

[0033] A further embodiment provides that the separation of one of the two contact layers from the provided voltage is carried out by means of an additional switch which is not part of an amplifier circuit for the charge reversal of the contact layers composing the capacitor.

[0034] A further aspect of the present invention provides a glass pane device for a switchable, variable-transparency pane, wherein the glass pane device comprises a control device configured to carry out the method as outlined above. This achieves the same advantages as described above. The control device can also be part of an ECU.

[0035] Overall, the aspects and embodiments of the method and device presented here ensure consistent optical properties of the switchable glazing across the application temperature range and also the vehicle age or service life for the user.

[0036] The invention is particularly designed for use in vehicles, for example, in glass roofs, windows, or windshields or rear windows of motor vehicles, or even in partitions in taxis or buses between the driver and passenger compartment. As mentioned at the beginning, it is also applicable in trucks, construction machinery, ships, or aircraft, etc. – wherever a transparent (i.e., see-through) and an opaque (i.e., non-transparent) state is required or desired by a customer. Short description of the drawings:

[0037] The invention is explained below by way of example with reference to the following figures.

[0038] They show: Fig. 1 shows a schematic circuit diagram of an overview of a very simplified disk device 2 according to an embodiment; Fig. 2 a diagram showing the transmission of the switchable disc 4 over the applied voltage U for three different temperatures (-10°C, 0°C, 20°C); Fig. 3 shows in a schematic diagram the course of the capacitance of a capacitor C consisting of two contact layers and the resistance Rp of the intermediate transparency-variable layer in a switchable disc over a relevant temperature range; Fig. 4 shows discharge curves for a switchable disk 4, recorded in a diagram for 9 different temperatures between -40 °C and +100 °C according to the invention, with the residual voltage schematically plotted against time; Fig. 5 in a diagram that consists of Fig. 4 time constants derived for each of the 9 curves plotted against temperature; Fig. 6 shows a flow chart of a method for determining the temperature of a switchable pane according to an embodiment. Detailed description of preferred embodiments:

[0039] In the following description of the drawings, identical reference numerals designate identical or comparable components. The features of the invention disclosed in the above description, in the drawings, and in the claims may be essential for the implementation of the invention, both individually and in any combination.

[0040] In the Fig. Figure 1 shows a schematic circuit diagram of a very simplified glass pane device 2, which can be used to implement a method according to an exemplary embodiment. The pane device 2 has a switchable pane 4, which is shown in the circuit diagram only in the form of an equivalent circuit diagram as an RC element.

[0041] The switchable disc 4 comprises an arrangement of two contact layers and an intermediate, variable-transparency layer. The two contact layers, together with the intermediate, variable-transparency layer, form a capacitor C. A current can flow between the two contact layers through the intermediate, variable-transparency layer. Therefore, the variable-transparency layer forms a resistor Rp, which is connected in parallel with the capacitor C in the equivalent circuit, as it enables bridging. Furthermore, the contact layers themselves have a resistor Rs, which is connected in series with the capacitor C. Connections (not shown) on the two contact layers enable the application of a voltage.

[0042] In this embodiment, the switchable pane (also referred to as foil) or the transparency-variable layer comprises a PDLC material. The two contact layers are formed from a material comprising indium tin oxide (ITO), which is itself transparent so as not to impair the light transmission of the pane.

[0043] Furthermore, the glass pane device 2 has a control unit 6, which has a first analog amplifier 8 and a second analog amplifier 10. For the sake of simplicity, only the two analog amplifiers 8, 10 of the control unit 6 are shown in the figure. It is understood that this type of representation does not entail any restriction with regard to the control unit 6. Rather, other components not described here can also be part of the control unit 6. The switchable pane 4 is connected between an output OUT of the first analog amplifier 8 and an output COM of the second analog amplifier 10.

[0044] The control unit 6 controls the switchable disc 4 with a control voltage composed of a first AC signal, which is amplified by the first analog amplifier 8, and a second AC signal, which is amplified by the second analog amplifier 10. The first AC signal is preferably electrically phase-shifted by 180° from the second AC signal.

[0045] A measuring device 12 for measuring a discharge or residual voltage in the capacitor C is connected between the output OUT of the first analog amplifier 8 and one of the two terminals of the switchable disc 4. The measuring device 12 comprises a voltage divider 14 having two series-connected resistors, which is connected on one side to the terminal of the switchable disc 4 or to one of the two contact layers, and on the other side to ground or ground potential. A center tap between the two series-connected resistors of the voltage divider 14 is connected to a measuring unit 16, which measures an applied voltage V SENSE The voltage V SENSE is in a fixed relationship, defined by the voltage divider, to the remaining residual voltage in the capacitor. Therefore, the measuring unit or device also directly detects the residual voltage.

[0046] The measuring device 12 further includes an electronic switch 18. The electronic switch 18 can be actuated by a control device 20, which is also connected to the measuring unit 16. The electronic switch 18 can be switched on and off. This allows the switchable disc 4 to be completely disconnected from a voltage applied by the control unit 6 or to be supplied with it.

[0047] With this design, the measuring unit 18 can track a discharge of the capacitor C by measuring the voltage drop VSENSE across the voltage divider 14 starting at a first time t1, at which the control device 20 has opened the electronic switch 18. Beforehand, the control device can have charged the capacitor C with the switch closed for a minimum period of time, e.g., with a direct voltage to a reference voltage UREF, for example 60V in the non-limiting embodiment. For this purpose, the control device can also be connected to the control unit 6 or to another controller controlling it, in order to enable a defined charging of the capacitor C. By determining the temporal discharge curve, a temperature prevailing directly in the switchable disk 4 can be determined according to the embodiment of the invention, as described below.

[0048] The Fig. Figure 2 shows a diagram in which the transmission or light transmittance of the switchable pane 4 is plotted against the applied voltage U for three different temperatures (-10°C, 0°C, 20°C). A temperature dependence is clearly evident in that a range in which only partial darkening can be achieved (transmission ≤ 0, but also ≤ 1) extends over different voltage intervals. For example, compensation for this effect can be initiated by detecting the temperature according to the invention, for example by adjusting the assignment of voltages to the desired transmittances depending on the temperature.

[0049] The Fig. Figure 3 shows a schematic diagram of the capacitance of a capacitor C from the two contact layers and the resistance Rp of the intermediate, variable-transparency layer over a temperature range relevant to the application (vehicles), including the freezing point. This fact is utilized by the exemplary embodiment. The capacitance of the capacitor C from the two contact layers and the resistance Rp of the intermediate, variable-transparency layer form an RC element with a time constant τ = Rp · C. This time constant is reflected in the discharge curve measured according to the exemplary embodiment; it is the time in which the residual voltage remaining in the capacitor has fallen from the reference voltage to a value of 1 / e.

[0050] The Fig. Figure 4 shows a diagram of theoretically determined discharge curves for a specific switchable disk 4 for nine different temperatures between -40°C and +100°C, with the residual voltage plotted schematically against time. The reference voltage U REF For example, the discharge curve recorded at T = 60 °C is shown in the diagram as an example of the time constant τ = Rp · C (approximately 0.01 s). The residual voltage here is only slightly more than 20 V (= 60 V / e).

[0051] According to an alternative method provided in the embodiment, starting from the first time t1, at which the switchable disc 4 is switched off by the switch 18 from the reference voltage U REF is separated, a time interval is measured until a second time t2, at which the residual voltage U has fallen to a value which is smaller by a predetermined factor than the reference voltage U REF, for example, a factor of 1 / e. This time interval, determined by measurement (a timer (not shown) may additionally be provided, e.g., in the measuring device 12 or in the control device 20), is a parameter derived from the residual voltage measurement, which is characteristic of the discharge or the discharge curve.

[0052] The Fig. 5 shows in a diagram the Fig. 4 time constants derived from the 9 curves, plotted against temperature. Under certain circumstances, a continuous curve may result, sometimes in the form of a downward-opening parabola. Based on this diagram, an assignment rule can be established in advance through theory or experiment, for example, in the form of a table or a mathematical function, which assigns a temperature to the parameter values ​​(in the example, the measured time interval).

[0053] If, using the method according to the invention, a time interval is measured between the first time t1 and the second time t2, which is as in Fig. 4 is approximately 0.01 s (10 ms), the diagram shows the Fig. 5 a horizontal line at the corresponding point. However, due to the parabolic shape, the assignment is not unambiguous: for the parameter determined from the measurement (time interval), an assignment can be found either to T = -24 °C or to T = +57 °C. For this purpose, the control device 20, which can also be an ECU, for example, can have access to a temperature sensor already provided elsewhere, which allows reliable discrimination between a higher temperature range and a lower temperature range. In this way, the correct temperature can be detected and used for further control of the glass pane device.

[0054] The Fig.6 shows a flow chart of an exemplary sequence of the method for determining the temperature of a switchable pane according to an embodiment.

[0055] In step 100, an electrical reference voltage U REF applied to the two contact layers.

[0056] In step 200, one of the contact layers is separated from the provided reference voltage at a predetermined first time t1.

[0057] In step 300, a value of the residual voltage still remaining between the two contact layers during a discharge of the two contact layers is measured by the transparency-variable layer at at least one second time t2 following the predetermined first time t1 and spaced apart from it.

[0058] In step 400, a value of a parameter representing the discharge is determined from the measurement, for example a time interval as described above, or a residual voltage measured at a fixed second time point can also be used as such as a parameter, etc.

[0059] In step 500, a first value of the temperature of the switchable disc 4 is determined from the determined value for the parameter using an assignment rule between the parameter and the temperature by a control unit. List of reference symbols 2 glass pane device 4 switchable discs 6 Control unit 8 first analog amplifier 10 second analog amplifier 12 Measuring device 14 voltage dividers 16 measuring units 18 electronic switches 20 Control device 100 Applying a reference voltage to contact layers 200 Separating the contact layers from the reference voltage 300 Measuring the voltage or discharge current between contact layers 400 Determining a parameter value representing the discharge from the measured values 500 Determining a temperature from the parameter value using an assignment rule QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2017 213 302 B3 [0009, 0011]

Claims

[1] Method for determining a temperature of a transparency-variable, switchable pane (4) having a transparency-variable layer arranged between two transparent electrically conductive contact layers for switching the same, comprising: (a) applying (100) an electrical reference voltage to the two contact layers; (b) separating (200) one of the contact layers from the provided reference voltage at a predetermined first time (t1); (c) measuring (300) a value of the residual voltage still remaining between the two contact layers during a discharge of the two contact layers through the transparency-variable layer at at least one second time point (t2) following the predetermined first time point (t1) and spaced apart in time from the same; (d) determining (400) a value of a parameter representing the discharge from the measurement, (e) Determining (500) a first value of the temperature of the switchable disc (4) from the determined value for the parameter using an assignment rule between the parameter and the temperature by a control unit. [2] Method according to claim 1, wherein the parameter is the electrical discharge of a capacitor (C) formed by the two contact layers via a resistor (R) formed by the transparency-variable layer p ) represents. [3] Method according to claim 2, wherein the parameter is the time constant τ = R p ·C of the capacitor (C) formed by the two contact layers and the resistor formed by the transparency-variable layer (R p ) is. [4] Method according to one of claims 1 to 3, wherein measuring includes specifying the predetermined second time (t2) at which the residual voltage is measured, wherein the value of the parameter is calculated from the measured residual voltage or is identified with it; or which includes specifying a voltage value reduced by a factor compared to the reference voltage, wherein a second point in time is determined from a repeated or continuous measurement of the residual voltage, up to which point the measured residual voltage has fallen to the reduced voltage value, wherein the value of the parameter is calculated from the time interval between the first point in time and the second point in time or is identified with this. [5] Method according to one of claims 1 to 4, wherein the control unit (20): at least in the event that two or more possible values ​​of the temperature can be determined on the basis of the determined value of the discharge parameter from the assignment rule, a second value of a temperature of an environment is obtained via a measurement by a temperature sensor, compares this second temperature value with the possible values ​​determined from the assignment rule, and Depending on the comparison, one of the possible values ​​determined from the assignment rule is selected as the valid first value of the temperature. [6] The method according to any one of claims 1 to 5, wherein the transparency-variable layer is formed from a PDLC material, an LC material or an SPD material. [7] Method according to one of claims 1 to 6, wherein the two contact layers are formed from a material comprising indium tin oxide (ITO). [8] Method according to one of claims 1 to 7, wherein a control signal for setting a predetermined light transmittance of the pane (4) is calculated and output as a function of the first value of the temperature. [9] Method according to one of claims 1 to 8, wherein steps (a) - (e) are carried out during a cyclic charge reversal in a discharge phase of the switchable disc. [10] Method according to one of claims 1 to 9, wherein the separation of a contact layer from the provided reference voltage is carried out by means of an additional electronic switch (18) which is not part of an amplifier circuit for the charge reversal of the contact layers composing the capacitor. [11] Glass pane device (2) with a transparency-variable, switchable pane (4), wherein the glass pane device (2) has a control unit (20) which is designed to carry out a method according to one of the preceding claims.

Images