Device for heating and fail-safe detection of touching contact with a surface

Abstract

The invention relates to a device (1) for heating and detecting touching contact with a surface (2), comprising a functional conductor (10) which is designed as a heating wire for heating the surface (2) and at the same time as a sensor element for detecting touching contact with the surface (2), wherein the functional conductor (10) has a first contact section (11) at a first end section and a second contact section (12) at a spaced-apart second end section, at which second contact section the functional conductor (10) can be electrically contacted (20) in order to heat the surface (2), further comprising an evaluation unit (20) which is in electric contact with the first contact section (11) and the second contact section (12) of the functional conductor (10) and is designed to sense, at the first contact section (11), a first sensor signal from which sensor signal the touching contact with the surface (2) can be determined, and to sense, at the second contact section (12), a second sensor signal from which the touching contact with the surface (2) can be determined.

Description

[0001] Marquardt GmbH

[0002] P 611 PCT WE / Kn

[0003] Device for heating and reliably detecting contact with a surface

[0004] Description:

[0005] The invention relates to a device for heating and detecting contact with a surface and an associated method.

[0006] Various devices are known in the prior art which can be used both for heating a surface and for touch detection, often having a functional conductor which serves as a heating wire during heating and as a sensor element during touch detection, so that two functions are fulfilled by such a functional conductor.

[0007] For example, it is known from publications DE 10 2021 122 593 A1 and DE 10 2021 122 610 A1 to connect the functional conductor alternately with a heating circuit and a sensor circuit, so that the heating and the detection of a touch do not occur simultaneously, but alternately.

[0008] Furthermore, it is known from the patent applications DE 10 2021 132 056 A1 and DE 10 2022 111 831 A1 to use the functional conductor simultaneously as a heating wire of a heating circuit and a sensor element of a sensor circuit, so that heating and the detection of a touch can take place simultaneously.

[0009] Further solutions for using a single functional conductor as a heating wire and sensor element are also known, for example, from documents DE 102019 124 293 A1 , DE 11 2018 005213 T5 , US 2012 / 0 326 735 A1 , US 2018 / 0 332 663 A1 and EP 2 028 078 A1.

[0010] The fundamental common feature of all these writings is that the functional conductor, when used as a sensor element, is connected to an evaluation unit and this unit provides a single sensor signal, so that the functional conductor and the evaluation unit form exactly one sensor.

[0011] Touch detection can be impaired by various interferences, such as electromagnetic interference (EMI), surface moisture, changing environmental conditions, or a faulty electrical connection of the functional conductor. Therefore, especially when using such devices for safety-related functions, a fail-safe and reliable touch detection system is advantageous.

[0012] It is already known from the aforementioned document DE 102022 111 831 A1 to use, in addition to the sensor formed by the functional conductor and the evaluation unit, a reference value which is detected by means of a separate sensor element, so that disturbances acting in the environment, which affect both the functional conductor and the separate

[0013] Sensor elements can be influenced, detected and, if necessary, compensated for.

[0014] However, in this case, disturbances or corresponding components of disturbances that directly and exclusively affect the functional conductor cannot be detected or compensated for.

[0015] Furthermore, the system is usually only intended to detect malfunctions or errors and compensate for the error or to switch off the device, without further monitoring or classifying the error or any resulting malfunction.

[0016] The invention is therefore based on the objective of overcoming the aforementioned disadvantages and providing a device and an associated method by which disturbances acting directly on the functional conductor can be detected.

[0017] This problem is solved by the device according to the main claim and by the method according to the dependent claim.

[0018] Regardless of whether heating and touch detection are to occur alternately or simultaneously, or whether additional measures for fault detection or fault compensation are planned, the

[0019] Functional conductors in the prior art are usually the sensor element of exactly one sensor.

[0020] According to the invention, a device for heating and detecting contact with a surface is proposed, in which the heating and detection of contact, i.e., the contact detection, can occur alternately or simultaneously. Such a device can be used, in particular, in a motor vehicle, preferably enabling the heating and contact detection of the steering wheel handle or a seat or backrest surface. According to the invention, the device includes a functional conductor that serves as a heating wire for heating the surface and simultaneously as a sensor element for detecting contact with the surface.The functional conductor preferably has exactly two end sections, wherein it has a first contact section at a first end section and a second contact section at a distance from the first end section, at which the functional conductor can be electrically contacted for heating the surface. For clarification, it should be noted that although the functional conductor can be arranged in a meandering pattern, it preferably extends linearly from the first end section to the second end section. According to the invention, the device further comprises an evaluation unit which is electrically contacted with the first contact section and the second contact section of the functional conductor and is configured to detect a first sensor signal at the first contact section, from which the contact of the surface can be determined, and to detect a second sensor signal at the second contact section, from which the contact of the surface can be determined.Since the evaluation unit thus captures two independent sensor signals, the evaluation unit forms a first sensor through the connection with the first contact section to the functional conductor and a second sensor through the connection with the second contact section to the functional conductor.

[0021] Consequently, the functional conductor serves not only as a heating wire or heating element and as a sensor element of a (first) sensor, but also as another sensor element of a further (second) sensor, so that both sensor signals generated by this can be evaluated separately and compared with each other.

[0022] It has been shown that a multitude of disturbances resulting from EMC radiation, environmental conditions and faulty contacting of the functional conductor lead to deviating sensor signals, so that such errors or disturbances can be detected from an evaluation of the first sensor signal and the second sensor signal and the sensor signals, i.e. the touch detection, can be made plausible.

[0023] According to an advantageous embodiment, the evaluation unit and the functional conductor form a first capacitive sensor by connecting the evaluation unit with the first contact section, and the evaluation unit and the functional conductor form a second capacitive sensor by connecting the evaluation unit with the second contact section, each of which is configured to detect an approach to the functional conductor and / or a touch of the surface.

[0024] According to the invention, the evaluation unit can comprise a single sensor circuit which is alternately connected by a switching element to the first contact section to form the first sensor and to the second contact section to form the second sensor. Accordingly, the sensor signals must be acquired alternately.

[0025] Alternatively, the evaluation unit can also have two, and in particular exactly two, sensor circuits, of which a first sensor circuit is permanently connected to the first contact section to form the first sensor, and a second sensor circuit is permanently connected to the second contact section to form the second sensor. Accordingly, the sensor signals can be acquired alternately or simultaneously.

[0026] According to an advantageous embodiment, it can further be provided that the evaluation unit is configured to detect the first sensor signal and the second sensor signal simultaneously and / or immediately consecutively, i.e. alternately, and after detection to determine a deviation of the first sensor signal and the second sensor signal from each other, wherein the deviation is preferably determined by forming a difference of the sensor signals and further, in particular, by forming an amount of the difference.

[0027] Based on this, it can further be provided that an error threshold is stored in the evaluation unit, or that the error threshold can be retrieved or determined by the evaluation unit, and that the evaluation unit is designed to detect an error in the detection of contact with the surface when the deviation exceeds the error threshold, or to assume that the deviation exceeding the error threshold is an error. If the two sensor signals deviate from each other beyond a tolerance defined by the error threshold, an error occurs, which leads to a disruption of the contact detection.

[0028] The error threshold specifies the maximum permissible measurement deviation or tolerance between the two sensor signals, preferably being set as a function of a touch detection threshold. For example, the error threshold can be greater than or equal to 50% of the touch detection threshold.

[0029] The touch detection threshold is the threshold against which the first and / or second sensor signal is compared to determine whether the surface has been touched, and this threshold depends on the specific application.

[0030] If a single error or a few errors occur, this is not yet considered a fault, and the sensor values ​​used to detect the error can be ignored for touch detection purposes. However, if the number of errors exceeds a fault threshold that may be stored in the evaluation unit, retrievable from it, or determined by it, a fault is detected or assumed, which can then be categorized.

[0031] The fault threshold can depend, in particular, on the measurement frequency and / or a maximum permissible time within which a predetermined number of errors may occur. For example, the fault threshold can be between 4 and 20.

[0032] Depending on the cause of errors or malfunctions, a fault may occur only once or briefly, so the resulting malfunction is only temporary. However, an error or errors may also be persistent or at least persist for a long period, resulting in a permanent malfunction. For example, brief EMC interference may only occur with individual measurements or sensor signals, meaning that an error is detected only once or briefly, and the resulting malfunction is temporary. However, a faulty functional conductor will lead to errors over a long period or permanently, making the malfunction permanent.Therefore, the evaluation unit is preferably designed to store the deviation and / or errors as historical data over time and to determine from this historical data whether a disturbance resulting from the errors is temporary or permanent. Such historical data can be represented, for example, by a history of values, time-based pairs of values, or a simple counter that can be incremented with each error and decremented or reset when no error is present.

[0033] Furthermore, temporary malfunctions can arise, for example, from fluctuations in the vehicle's electrical system, electromagnetic interference (EMI), or sudden, i.e., rapidly changing, environmental conditions. Besides a faulty functional conductor, permanent malfunctions can also generally result from a faulty connection or a permanently faulty control of a device, as well as from hardware defects.

[0034] For this purpose, a threshold value can be stored in the evaluation unit, i.e., saved, or retrievable by the evaluation unit. If a number of errors are detected, they are classified as temporary faults until the threshold value is exceeded, and as permanent faults once the threshold value is exceeded. The number of errors can be reset to 0 if the deviation falls below the error threshold, or reduced by a predetermined value, e.g., 1.

[0035] As with any sensor, the evaluation device is designed to detect the first and second sensor signals at a certain measurement frequency, wherein the evaluation device is preferably designed to detect the first sensor signal at a first measurement frequency and the second sensor signal at a second measurement frequency that differs from or is identical to the first measurement frequency, each of which is predetermined.

[0036] Based on this, the evaluation device can be designed to vary the first measurement frequency and / or the second measurement frequency in a predetermined manner and, in particular, following a respective predetermined course.

[0037] Although a separate device may be connected downstream for this purpose, the evaluation unit is preferably configured to determine whether the surface is touched from either the first or the second sensor signal, so that only one of the sensor signals, and in particular exactly one of the two sensor signals, is used for touch detection. Alternatively, instead of using exactly one sensor signal, the evaluation unit may be configured to determine whether the surface is touched from both the first and second sensor signals, in particular by calculating an average of the first and second sensor signals.

[0038] Regardless of whether only one sensor signal or both sensor signals are used for touch detection, it is preferably provided that the sensor signal(s) on which the deviation and, consequently, the error were based, are ignored by the evaluation unit during touch detection if an error is detected. Accordingly, the evaluation unit can be configured to determine the contact of the surface by evaluating the first sensor signal and / or the second sensor signal if the deviation of the sensor signals does not exceed the error threshold.

[0039] Another aspect of the invention relates to a method for heating a surface and, in particular, for simultaneously detecting contact between the surface and a device according to the invention. The method provides that the evaluation unit acquires the first sensor signal and the second sensor signal, determines a deviation between the sensor signals by calculating the difference between them, and compares this deviation with a predetermined error threshold. If the deviation exceeds the error threshold, an error is detected.

[0040] The method may further provide that the evaluation unit stores the deviation and / or the exceeding of the deviation above the error threshold as historical data over time and determines from this historical data whether a temporary or permanent fault exists. The features disclosed above may be combined in any way, provided this is technically feasible and they do not contradict each other.

[0041] Other advantageous embodiments of the invention are characterized in the dependent claims or are described in more detail below together with the description of the preferred embodiment of the invention with reference to the figures. The figures show:

[0042] Fig. 1 shows a circuit diagram of a device according to the invention;

[0043] Fig. 2 shows a method that can be carried out with the device according to Figure 1.

[0044] The figures are schematic examples.

[0045] Figure 1 shows a device 1 connected to a power supply for heating a surface 2 and detecting contact with the surface 2, wherein at least one switching element 3, i.e., where necessary, several switching elements 3, are connected upstream of the device 1 and at least one switching element 4, i.e., where necessary, several switching elements 4, are connected downstream.

[0046] The device 1 essentially comprises a functional conductor 10 and an evaluation unit 20. The evaluation unit 20 is connected to a first contact section 11 at a first end section of the functional conductor 10 and to a second contact section 12 at a second end section of the functional conductor 10, enabling sensor signal acquisition, wherein the two end sections of the functional conductor 10 are spaced apart from each other at opposite ends of the functional conductor.

[0047] By contacting the evaluation unit 20 with the first contact section 11, a first sensor is formed by the evaluation unit 20 and the functional conductor 10, whose sensor signal determined by the functional conductor 10 can be detected and evaluated by the evaluation unit 20 as the first sensor signal.

[0048] Furthermore, by contacting the evaluation unit 20 with the second contact section 12, a second sensor is formed by the evaluation unit 20 and the functional conductor 10, the sensor signal of which is determined by the functional conductor 10 and can be detected and evaluated by the evaluation unit 20 as a second sensor signal, wherein preferably each is a capacitive sensor.

[0049] From the two sensor signals, or even just one of the sensor signals, the evaluation unit can determine whether a user is approaching the functional conductor 10 or touching the surface 2.

[0050] However, various disturbances affecting the functional conductor 10 can lead to single or repeated and thus essentially permanent errors, which can be detected by comparing the two sensor signals, i.e., by comparing the first sensor signal with the second sensor signal, and can be ignored and categorized if contact with the surface is detected.

[0051] The representation in Figure 2 is based on a flowchart, wherein the device 1 shown in Figure 1 and in particular the evaluation unit 20 of the device 1 shown in Figure 1 can be configured to carry out such a procedure.

[0052] The steps are as follows:

[0053] A Start

[0054] B. Simultaneous or successive acquisition of a first measured value m1 of the first sensor signal and a second measured value m2 of the second sensor signal. Determining a deviation d by finding an absolute value of the difference between the first and second measured values ​​such that: d = |(m1 -m2)|

[0055] C Comparison of the deviation d with an error threshold f.

[0056] If the deviation d is less than the error threshold f, then there is no error and step E follows.

[0057] If the deviation d is greater than or equal to the error threshold f, then an error has occurred and step D follows.

[0058] The query is therefore: Is d < f? Yes Step E no Step D

[0059] D An error has occurred; a counter z for recording the number of errors or for recording the historical data of the error is incremented by 1.

[0060] E If no error has occurred, the counter z for recording the number of errors or for recording the historical data of the error is reduced by value 1 or set to value 0.

[0061] F Comparison of the numerator z with the value 0.

[0062] If the counter z equals 0, then no error or fault has occurred so far and step G follows.

[0063] If the counter z is not equal to 0, then errors or a malfunction already occurred and step H follows.

[0064] The query is therefore: Is z = 0? Yes Step G no Step HG: Performing touch detection, in particular by comparing the first sensor signal and / or second sensor signal with a threshold for touch detection.

[0065] H Comparison of the counter z with the disturbance threshold n.

[0066] If the counter z is less than the disturbance threshold n, then there is a single error or a small number of errors, but not yet a relevant disturbance. Step J follows.

[0067] If the counter z is greater than or equal to the disturbance threshold n, then a number of errors exists that classifies the errors as disturbances or relevant disturbances. Step H follows.

[0068] The query is therefore: Is z < n? Yes Step J no Step K

[0069] At least one error, but not yet a relevant malfunction, has occurred. The first sensor signal and the second sensor signal, or rather their current measured values, are ignored, and no touch detection based on them is performed.

[0070] K Comparison of the counter z with a limit value m to categorize into temporary and permanent disturbances.

[0071] If the counter z is less than the limit m, a temporary fault has occurred. Step L follows.

[0072] If the counter z is greater than or equal to the limit m, a permanent fault exists. Step M follows.

[0073] The query is therefore: Is z < m? yes Step L no Step ML: A temporary fault has occurred. The first sensor signal and the second sensor signal, or their current measured values, are ignored, and no touch detection based on them is performed.

[0074] M A permanent fault is present. The first sensor signal and the second sensor signal, or their current measured values, are ignored, and no touch detection based on them is performed.

[0075] If a permanent fault is detected, the procedure is terminated, but can be restarted at a later time, for example after a predetermined waiting period or a reset of the device.

Claims

Patent claims 1. Device (1) for heating and detecting contact with a surface (2), comprising a functional conductor (10) which is designed as a heating wire for heating the surface (2) and simultaneously as a sensor element for detecting contact with the surface (2), wherein the functional conductor (10) has a first contact section (11) at a first end section and a second contact section (12) at a spaced-apart second end section, at which the functional conductor (10) can be electrically contacted for heating the surface (2), further comprising an evaluation unit (20) which is electrically contacted with the first contact section (11) and the second contact section (12) of the functional conductor (10) and is designed to detect a first sensor signal at the first contact section (11) from which the contact with the surface (2) can be determined, and to detect a second sensor signal at the second contact section (12).from which the contact of the surface (2) can be determined.

2. Device according to claim 1, wherein the evaluation unit (20) and the functional conductor (10) form a first capacitive sensor by connecting the evaluation unit (20) with the first contact section (11), and the evaluation unit (20) and the functional conductor (10) form a second capacitive sensor by connecting the evaluation unit (20) with the second contact section (12), each of which is configured to detect an approach to the functional conductor (10) and / or a touch of the surface (2).

3. Device according to claim 1 or 2, wherein the evaluation unit (20) is configured to detect the first sensor signal and the second sensor signal simultaneously and / or immediately following one another and to determine a deviation of the first sensor signal and the second sensor signal from each other.

4. Device according to the preceding claim, wherein an error threshold is stored in the evaluation unit (20) or the error threshold can be retrieved by the evaluation unit (20) and the evaluation unit (20) is designed to detect an error in the detection of the contact of the surface (2) from an exceedance of the deviation above the error threshold.

5. Device according to one of the preceding claims 2 or 3, wherein the evaluation unit (20) is configured to store the deviation and / or the error as historical data over time and to determine from the historical data whether the errors are a temporary fault or a permanent fault.

6. Device according to one of the preceding claims, wherein the evaluation device (20) is configured to detect the first sensor signal with a first measurement frequency and the second sensor signal with a second measurement frequency that differs from or is identical to the first.

7. Device according to the preceding claim, wherein the evaluation device (20) is configured to vary the first measurement frequency and / or the second measurement frequency.

8. Device according to one of the preceding claims, wherein the evaluation unit (20) is configured to determine a contact of the surface (2) from the first sensor signal or the second sensor signal.

9. Device according to one of the preceding claims, wherein the evaluation unit (20) is configured to determine a contact of the surface (2) from the first sensor signal and the second sensor signal.

10. Method for heating a surface (2) and detecting contact of the surface (2) with a device (1) according to one of the preceding claims, wherein the evaluation unit (20) detects the first sensor signal and the second sensor signal, determines a deviation of the sensor signals from each other by forming a difference between the first sensor signal and the second sensor signal, and compares the deviation with a predetermined error threshold, wherein an error is present if the deviation exceeds the error threshold.

11. Method according to the preceding claim, wherein the evaluation unit (20) stores the deviation and / or the exceeding of the deviation above the error threshold as historical data over time and determines from a history of the historical data whether a temporary or permanent fault is present. * * * * *

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