INPUT DEVICE FOR A MOTOR VEHICLE WITH VOLTAGE-BASED FAULT DETECTION

Description

[0001] The invention relates to an input device for safety-relevant functions of a motor vehicle. The input device comprises a switching element having a switching contact with a first terminal and a mating contact with a second terminal. When the input device is actuated, the switching contact is made contact with the mating contact. The input device also comprises a first resistor and a first and a second power supply terminal, via which an operating voltage for the input device can be provided. The first power supply terminal is connected to one of the terminals of the switching element, and the second power supply terminal is connected to the other terminal of the switching element via the first resistor.Furthermore, the input device has a measuring node located between the first resistor and the respective terminal of the switching element, and which is connected to a measuring terminal. This allows an actuation-dependent voltage to be detected via the measuring terminal, which depends on the actuation of the input device.

[0002] Input devices with corresponding switching elements are already known in the prior art. For example, US 6,423,918 B1 discloses an input device with a switching element that has a dome- or cup-shaped switching contact which, when actuated, is brought into contact with a mating contact on a printed circuit board. The dome- or cup-shaped switching contact is held on the printed circuit board by retaining elements.

[0003] US Patent 7,825,345 B1 discloses an input device in the form of a microswitch that can be actuated from the rear. For this purpose, the microswitch has a dome- or cup-shaped switching element in its housing, which, when actuated, is brought into contact with a mating contact in the housing. The respective contacts are connected to terminals provided on the outside of the microswitch housing.

[0004] US patent 2014 / 0144765 A1 discloses an input device with a switching element comprising a dome- or cup-shaped switching contact that, when actuated, is brought into contact with a mating contact on a printed circuit board. The dome- or cup-shaped switching contact is held on the printed circuit board by retaining elements.

[0005] EP 2 001 034 A2 discloses an input device with a switching element that has a switching contact which, when actuated, is brought into contact with a mating contact on a printed circuit board. The switching contact is connected via an electrode to a first power supply terminal, and the mating contact is connected via a first resistor to a second power supply terminal. The voltage drop across the resistor is measured and serves as a measure of the actuation of the input device. Another input device is known from DE-A-102017113905.

[0006] A disadvantage of the aforementioned state of the art is that a fault in the switching contact cannot be detected clearly and reliably, since, for example, a broken switching contact cannot be distinguished from a failure to actuate the input device. Consequently, such input devices cannot be used in safety-critical applications, such as autonomous driving.

[0007] Therefore, the object of the invention is to further develop the generic input devices in such a way that they meet higher safety standards and are thus usable for safety-relevant applications in motor vehicles.

[0008] This problem is solved by the solution according to the characterizing part of claim 1.

[0009] For the purposes of this invention, a fault in the switching contact is understood to mean a break in the switching contact and / or any change in the resistance of the switching contact that leads to a voltage at the measuring node that is distinguishable from the switching states. This applies in particular if the fault described above occurs in the area of ​​the switching contact between the first and third terminals. In this case, the electrical connection between the first and third terminals is affected by the fault.

[0010] In an advantageous embodiment of the input device according to the invention, an evaluation circuit is provided which detects the voltage at the measuring node via the measuring connection, thereby enabling the detection of actuation of the input device and / or a fault in the switching contact. This has the advantage that the various voltages at the measuring node can be detected and evaluated accordingly, so that the state of the input device can be unambiguously determined. A further advantage of evaluation circuits is that they can process the information further, for example by a controller or an electronic control unit, which can be part of the evaluation circuit, in order to trigger corresponding functions in the vehicle or to issue appropriate warnings.

[0011] Alternatively or additionally, the input device according to the invention can be designed with a dome- or cup-shaped switching contact, and preferably with the first and third connections located on opposite sides of the dome- or cup-shaped switching contact. This has the advantage that the dome- or cup-shaped switching contact can generate passive haptic feedback to the actuator when actuated.

[0012] Due to its dome- or cup-shaped form, the metallic switching contact exhibits a non-linear deformation property under constantly increasing actuation force, similar to a snap-action mechanism. This means that the switching contact only yields abruptly at a specific pressure point when actuated, resulting in corresponding haptic feedback to the actuator. After the switching contact is released, it returns to its initial state.

[0013] Furthermore, the arrangement of the first and third connections on opposite areas of the dome- or cup-shaped switching contact has the advantage of improving the fault detection of the input device according to the invention. This is because this measure maximizes or at least enlarges the area of ​​the switching contact between the connections, so that any faults within this area can be detected.

[0014] In a further advantageous embodiment of the input device according to the invention, the switching contact is formed in a planar form. Preferably, the first and third connections are located adjacent to an edge or in opposing areas of the planar switching contact. The planar contact can be elastic and / or embossed to generate haptic feedback for the actuator. The embossing can also provide a non-linear deformation characteristic with a constantly increasing actuating force, similar to a snap disc or a click mechanism.

[0015] Furthermore, the arrangement of the first and third connections on opposite areas of the planar switching contact has the advantage of improving the fault detection of the input device according to the invention. This is because this measure maximizes or at least enlarges the area of ​​the switching contact between the connections, so that any faults within this area can be detected.

[0016] Alternatively or additionally, the input device according to the invention can be provided with a third resistor between the first power supply terminal and the respective terminal of the switching element, so that the respective terminal of the switching element is connected to the first power supply terminal via the third resistor. This additional resistor allows the actuation of the switching contact to be detected by means of an actuation-dependent voltage that differs from the operating voltage or from one of the operating voltage potentials. This further improves the reliability of the input device according to the invention, since the actuation can now be distinguished from a short circuit of the measuring terminal to one of the operating voltage potentials in the event of a fault.

[0017] In a further advantageous embodiment of the input device according to the invention, the second power supply terminal is connected to a positive operating voltage and the first power supply terminal is connected to a reference potential, preferably ground, of the input device. This measure allows the operating voltage to be provided in a simple manner. Alternatively, the first power supply terminal can also be connected to a positive operating voltage and the second power supply terminal to a reference potential, preferably ground, of the input device.

[0018] Alternatively or additionally, the input device according to the invention can be provided such that, in the unactuated state of the input device, an actuation-dependent voltage can be detected at the measuring node, which results from the voltage divider ratio between the first resistor and the second resistor and preferably the third resistor. The actuation-dependent voltage in the unactuated state is calculated as follows, with U₁ as the actuation-dependent voltage, UB as the positive operating voltage, R₁ as the first resistor, R₂ as the second resistor and R₃ as the third resistor: U 1 = U B ∗ R 2 R 2 + R 1 (If R 1 on U B is located and without R 3) or U 1 = U B ∗ R 1 R 2 + R 1 (If R 1 on Masse is located and without R 3) or U 1 = U B ∗ R 2 + R 3 R 2 + R 1 + R 3 (If R 1 on U B is located and with R 3) or U 1 = U B ∗ R 1 R 2 + R 1 + R 3 (If R 1 on Masse is located and with R 3)

[0019] This has the advantage that the actuation-dependent voltage differs significantly from the actuation state or the fault state, thus increasing the safety of the input device according to the invention.

[0020] In a further advantageous embodiment of the input device according to the invention, an actuation-dependent voltage can be detected at the measuring node when the input device is actuated. This voltage corresponds to the voltage or potential of the first power supply connection or results from the voltage divider ratio between the first resistor and the third resistor. The actuation-dependent voltage in the actuated state is calculated as follows, with U₁ as the actuation-dependent voltage, UB as the positive operating voltage, R₁ as the first resistor, R₂ as the second resistor, and R₃ as the third resistor: U 1 = Masse (If R 1 on U B is located and without R 3) or U 1 = U B (IfR 1 on Masse is located and without R 3) or U 1 = U B ∗ R 3 R 1 + R 3 (If R 1 on U B is located and with R 3) or U 1 = U B ∗ R 1 R 1 + R 3 (If R 1 on Masse is located and with R 3)

[0021] This has the advantage that the actuation-dependent voltage differs significantly from the unactuated state or the fault state, thus increasing the safety of the input device according to the invention.

[0022] In a further advantageous embodiment of the input device according to the invention, in the event of a fault in the switching contact, preferably in the event of a break in the switching contact, particularly between the first and third terminals of the switching contact, and preferably when the switching contact is not actuated, a fault voltage can be detected at the measuring node, which corresponds to the voltage or potential of the second power supply terminal. The fault voltage is calculated as follows, with U₂ as the fault voltage, UB as the positive operating voltage, R₁ as the first resistor, R₂ as the second resistor, and R₃ as the third resistor: U 2 = U B (If R 1 on U B is located and without R 3) or U 2 = Masse (If R 1 on Masse is located and without R 3) or U 2 = U B (If R 1 on U B is located and with R 3) or U 2 = Masse (If R 1 on Masse is located and withR 3)

[0023] This has the advantage that the fault voltage differs significantly from the unactuated state or the actuated state, thus increasing the safety of the input device according to the invention.

[0024] In a further advantageous embodiment of the input device according to the invention, the evaluation unit comprises an analog-to-digital converter, so that the detected actuation-dependent voltage can be converted into a digital value and processed digitally. Digital values ​​of measured voltages are particularly insensitive to interference, thus further increasing the safety of the input device according to the invention. Furthermore, digital values ​​can be processed particularly effectively, for example, to perform plausibility checks, which in turn further enhances the safety of the input device according to the invention.

[0025] Alternatively or additionally, the input device according to the invention can be provided such that, when the input device is actuated, the contact between the switching contact and the mating contact is galvanically or electrically conductive. This means that the switching contact and the mating contact are positioned relative to each other in such a way that an electrically conductive connection is established between them. In particular, this refers to a direct electrical contact between the switching contact and the mating contact. This type of contact advantageously creates a reliable connection that delivers clearly distinguishable voltage values ​​at the measuring node.

[0026] In a particularly advantageous embodiment of the input device according to the invention, the contact between the switching contact and the mating contact is resistive or capacitive when the input device is actuated. According to the first alternative, this means that the contact between the switching contact and the mating contact is made via a resistive element, such as a resistive material or a corresponding coating. This has the advantage that an additional resistive element is introduced during actuation, which interacts with the second resistor and thus provides particularly reliable and distinguishable voltage values ​​at the measuring node.

[0027] According to the second alternative, contact can also be made via a capacitive element, for example a capacitor, so that when an alternating voltage is used as the operating voltage and the device is actuated accordingly, the transition between the switching contact and the mating contact becomes low-resistance. This also advantageously provides reliably distinguishable voltage values ​​at the measuring node.

[0028] Alternatively or additionally, in the input device according to the invention, the switching element and the resistors are arranged on a printed circuit board, and preferably at least the first and third connections are implemented as solder points on the printed circuit board. This measure allows the input device according to the invention to be provided in a particularly compact design.

[0029] In a further advantageous embodiment of the input device according to the invention, the dome- or cup-shaped switching contact is soldered to the solder points for the first and third connections, and the mating contact is provided between these two solder points on the circuit board. This measure allows the dome- or cup-shaped switching contact to be advantageously supported on the circuit board in order to provide haptic feedback to the actuator, similar to a snap disc. The mating contact arranged between the solder points ensures reliable contact between the switching contact and the mating contact during actuation, as well as a compact design for the input device according to the invention.

[0030] In a further advantageous embodiment of the input device according to the invention, additional support points for the dome- or cup-shaped switching contact are provided, which are preferably designed as solder points. This ensures that the dome- or cup-shaped switching contact is held particularly securely on the circuit board, thus improving the overall safety of the input device according to the invention.

[0031] The invention will now be explained in more detail with reference to preferred embodiments, in particular with reference to the accompanying drawings. These show Fig. 1a schematically shows the circuit diagram of a first advantageous embodiment of the input device according to the invention in the unactuated state of the switching element, Fig. 1b schematically shows the circuit diagram of the first advantageous embodiment of the input device according to the invention in the unactuated state of the switching element, Fig. 1c schematically shows the circuit diagram of the first advantageous embodiment of the input device according to the invention in the event of a fault in the switching element, Fig. 2a schematically shows the circuit diagram of a second advantageous embodiment of the input device according to the invention in the unactuated state of the switching element, Fig. 2b schematically shows the circuit diagram of the second advantageous embodiment of the input device according to the invention in the unactuated state of the switching element, Fig. 2c schematically shows the circuit diagram of the second advantageous embodiment of the input device according to the invention in the event of a fault in the switching element.Fig. 3a schematically the circuit diagram of a third advantageous embodiment of the input device according to the invention in the unactuated state of the switching element, Fig. 3b schematically the circuit diagram of the third advantageous embodiment of the input device according to the invention in the unactuated state of the switching element, Fig. 3c schematically the circuit diagram of the third advantageous embodiment of the input device according to the invention in the event of a fault in the switching element, Fig. 4a schematically the circuit diagram of a fourth advantageous embodiment of the input device according to the invention in the unactuated state of the switching element, Fig. 4b schematically the circuit diagram of the fourth advantageous embodiment of the input device according to the invention in the unactuated state of the switching element, Fig. 4c schematically the circuit diagram of the fourth advantageous embodiment of the input device according to the invention in the event of a fault in the switching element, Fig.Fig. 5 schematically a fifth advantageous embodiment of the input device according to the invention with a printed circuit board, Fig. 5 a sectional view through the printed circuit board of the input device according to the fifth embodiment, Fig. 6 schematically a sixth advantageous embodiment of the input device according to the invention with a printed circuit board, and Fig. 6 a sectional view through the printed circuit board of the input device according to the sixth embodiment.

[0032] Fig. 1a Figure 1 schematically shows the circuit diagram of a first advantageous embodiment of the input device (1) according to the invention in its unactuated state. The input device (1) has a switching element (2) with a dome- or cup-shaped switching contact (3) which can be contacted by a mating contact (5) when actuated. The switching element (2) has a first terminal (4) on the dome- or cup-shaped switching contact (3), to which a first resistor (9) is connected to a second voltage supply terminal (8). In this example, the operating voltage UB applied here is positive. Between the first resistor (9) and the first terminal (4) of the switching element (2) is a measuring node (10) on which a measuring terminal (11) is provided for tapping an actuation-dependent voltage U1.

[0033] A second terminal (6) of the switching element (2) is provided at the mating contact (5). This second terminal (6) connects the mating contact (5) to a first power supply terminal (7). In this example, the first power supply terminal (7) is connected to the reference potential of the input device (1) according to the invention, which is ground or ground potential. Furthermore, the switching element (2) has a third terminal (12), which is provided at the switching contact (3) on the opposite side of the first terminal (4). A second resistor (13) is connected between the second and third terminals (6, 12).

[0034] In the unactuated state of the input device (1) according to the invention, or when the switching element (2) is not actuated, an actuation-dependent voltage U1 can be tapped at the measuring terminal (11), which results from the voltage divider ratio between the first resistor (9) and the second resistor (13). The following relationship applies, with U1 being the actuation-dependent voltage, UB being the positive operating voltage, R1 being the first resistor, and R2 being the second resistor: U 1 = U B ∗ R 2 R 2 + R 1

[0035] This voltage U 1 is, as will be shown, clearly distinguishable from the voltages of the other states of the input device (1) according to the invention, so that the non-activation of the input device (1) according to the invention is clearly recognizable.

[0036] This shows Fig. 1b the input device (1) according to the embodiment shown above Fig. 1a This corresponds to the input device according to the invention now being in an actuated state. The switching element (2) was actuated by a force F acting on the switching contact (3). Due to the action of the force F and the design of the switching element (2) with a dome- or cup-shaped switching contact (3), the switching contact (3) is deformed and is electrically connected or contacted with the mating contact (5). The corresponding deformation of the switching contact (3) additionally generates haptic feedback for the actuator.

[0037] Actuation bridges or short-circuits the second resistor (13) between the second terminal (6) and the third terminal (12) of the switching element (2), and the measuring node (10) is directly connected to the opposite contact (5) or to the second terminal (6) of the switching element (2). In this embodiment, the second terminal (6) is connected to the first power supply terminal (7), which is at the reference potential of the input device (1) according to the invention, which is ground or ground potential. Thus, the measuring node (10) is also at ground, so that the following actuation-dependent voltage U1 can be measured at the measuring terminal (11): U 1 = Masse

[0038] This voltage U1 is also clearly distinguishable from the voltages of the other states of the input device (1) according to the invention. Thus, the actuation of the input device (1) according to the invention is clearly identifiable.

[0039] The Fig. 1c shows the input device (1) according to the embodiment shown in the invention. Fig. 1a , whereby a fault has now occurred at the switching contact (3) of the switching element (2). The input device (1) according to the invention is therefore in a fault state. The fault comprises a break (19) of the switching contact (3) between the first terminal (4) and the third terminal (12) of the switching element (2).

[0040] This interrupts the connection of the first terminal (4) to the other terminals (6, 12) of the switching element (2), so that the measuring node (10) is always at the potential of the second power supply terminal (8), which here is the operating voltage UB. Therefore, the following fault voltage U₂ can be measured at the measuring terminal (11): U 2 = U B

[0041] This voltage U2 is also clearly distinguishable from the voltages of the other states of the input device (1) according to the invention. Therefore, the fault condition of the input device (1) according to the invention is also clearly identifiable.

[0042] The Fig. 2a shows a further embodiment of the input device according to the invention (1). This example is essentially based on the embodiment according to Fig. 1a The first resistor (9) is now arranged between the first power supply terminal (7) and the second terminal (6) of the switching element (2), instead of between the second power supply terminal (8) and the first terminal (4) of the switching element (2). Accordingly, the measuring node (10) with the measuring terminal (11) is now provided between the second terminal (6) of the switching element (2) and the first resistor (9). Furthermore, the first terminal (4) of the switching element (2) is now directly connected to the second power supply terminal (8). In this example, the first power supply terminal (7) is connected to the reference potential, here ground, of the input device (1) according to the invention. The second power supply terminal (8) is connected to a positive operating voltage UB.

[0043] In the unactuated state of the input device (1) according to this second embodiment, or when the switching element (2) is not actuated, an actuation-dependent voltage U1 can be tapped at the measuring terminal (11), which results from the voltage divider ratio between the first resistor (9) and the second resistor (13). The following relationship applies, with U1 being the actuation-dependent voltage, UB being the positive operating voltage, R1 being the first resistor, and R2 being the second resistor: U 1 = U B ∗ R 2 R 2 + R 1

[0044] This voltage U1 is clearly distinguishable from the voltages of the other states of the input device (1) according to this second embodiment. Thus, the non-activation of the input device (1) according to the invention is clearly identifiable.

[0045] The Fig. 2b Figure 1 shows the input device (1) according to the second embodiment, which is now in an actuated state. The switching element (2) was actuated by a force F acting on the switching contact (3). Due to the action of the force F and the design of the switching element (2) with a dome- or cup-shaped switching contact (3), the switching contact (3) is deformed and is electrically connected or contacted with the mating contact (5).

[0046] This bridges or short-circuits the second resistor (13) between the second terminal (6) and the third terminal (12) of the switching element (2), and the measuring node (10) is directly connected to the first terminal (4) of the switching element (2). Since the first terminal (4) is connected to the second power supply terminal (8), which is at the positive operating voltage potential, the measuring node (10) is also at the positive operating voltage potential, so that the following actuation-dependent voltage U1 can be measured at the measuring terminal (11): U 1 = U B

[0047] This voltage U1 is also clearly distinguishable from the voltages of the other states of the input device (1) according to this second embodiment. The actuation of the input device (1) according to the invention is therefore also clearly identifiable.

[0048] The Fig. 2c shows the input device (1) according to the second embodiment. Fig. 2a , whereby a fault has now occurred at the switching contact (3) of the switching element (2). The input device (1) according to the invention is therefore in a fault state. The fault comprises a break (19) of the switching contact (3) between the first terminal (4) and the third terminal (12) of the switching element (2).

[0049] This interrupts the connection of the first terminal (4) to the other terminals (6, 12) of the switching element (2), so that the measuring node (10) is now at the potential of the first power supply terminal (7), which corresponds to the reference potential here. Therefore, the following fault voltage U₂ can be measured at the measuring terminal (11): U 2 = Masse

[0050] This voltage U2 is also clearly distinguishable from the voltages of the other states of the input device (1) according to the second embodiment. Thus, the fault condition of the input device (1) according to the invention is also clearly identifiable.

[0051] The Fig. 3a Figure 1 shows a third embodiment of the input device according to the invention. This example is essentially based on the embodiment shown in Figure 2. Fig. 1a , wherein a third resistor (15) is now provided. The third resistor (15) is connected or arranged between the second terminal (6) of the switching element (2) and the first power supply terminal (7). In this example, the first power supply terminal (7) is also connected to the reference potential, here ground, of the input device (1) according to the invention, and the second power supply terminal (8) is connected to a positive operating voltage UB.

[0052] In the unactuated state of the input device (1) according to this third embodiment, or when the switching element (2) is not actuated, an actuation-dependent voltage U1 can be tapped at the measuring terminal (11), which results from the voltage divider ratio between the first resistor (9), the second resistor (13), and the third resistor (15). The following relationship applies, with U1 being the actuation-dependent voltage, UB being the positive operating voltage, R1 being the first resistor, R2 being the second resistor, and R3 being the third resistor: U 1 = U B ∗ R 2 + R 3 R 2 + R 1 + R 3

[0053] This voltage U 1 is clearly distinguishable from the voltages of the other states of the input device (1) according to the third embodiment and thus the non-activation of the input device (1) according to the invention is clearly recognizable.

[0054] The Fig. 3b Figure 1 shows the input device (1) according to the third embodiment, which is now in an actuated state. The switching element (2) was actuated by a force F acting on the switching contact (3). Due to the action of the force F and the design of the switching element (2) with a dome- or cup-shaped switching contact (3), the switching contact (3) is deformed and is electrically connected or contacted with the mating contact (5).

[0055] This bridges or short-circuits the second resistor (13) between the second terminal (6) and the third terminal (12) of the switching element (2), and the measuring node (10) is directly connected to the second terminal (4) of the switching element (2). Thus, the measuring node (10) is now located between the first resistor (9) and the third resistor (15), so that the following actuation-dependent voltage U1 can be measured at the measuring terminal (11): U 1 = U B ∗ R 3 R 1 + R 3

[0056] This voltage U 1 is also clearly distinguishable from the other states of the input device (1) according to this embodiment and thus the actuation of the input device (1) according to the invention is clearly recognizable.

[0057] The Fig. 3c shows the input device (1) according to the third embodiment. Fig. 3a , whereby a fault has now occurred at the switching contact (3) of the switching element (2). The input device (1) according to the invention is therefore in a fault state. The fault comprises a break (19) of the switching contact (3) between the first terminal (4) and the third terminal (12) of the switching element (2).

[0058] This interrupts the connection between the first terminal (4) and the other terminals (6, 12) of the switching element (2), so that the measuring node (10) is always at the potential of the second power supply terminal (8), which corresponds here to the positive operating voltage. Therefore, the following fault voltage U₂ can be measured at the measuring terminal (11): U 2 = U B

[0059] This voltage U2 is also clearly distinguishable from the voltages of the other states of the input device (1) according to the third embodiment. Thus, the fault condition of the input device (1) according to the invention is also clearly identifiable.

[0060] The Fig. 4a Figure 1 shows a fourth embodiment of the input device according to the invention. This example is essentially based on the embodiment shown in Figure 2. Fig. 2a , wherein a third resistor (15) is now provided. The third resistor (15) is connected or arranged between the first terminal (4) of the switching element (2) and the second power supply terminal (8). In this example, the first power supply terminal (7) is also connected to the reference potential, here ground, of the input device (1) according to the invention, and the second power supply terminal (8) is connected to a positive operating voltage UB.

[0061] In the unactuated state of the input device (1) according to this fourth embodiment, or when the switching element (2) is not actuated, an actuation-dependent voltage U1 can be tapped at the measuring terminal (11), which results from the voltage divider ratio between the first resistor (9), the second resistor (13), and the third resistor (15). The following relationship applies, with U1 being the actuation-dependent voltage, UB being the positive operating voltage, R1 being the first resistor, R2 being the second resistor, and R3 being the third resistor: U 1 = U B ∗ R 1 R 2 + R 1 + R 3

[0062] This voltage U 1 is clearly distinguishable from the voltages of the other states of the input device (1) according to this embodiment and thus the non-activation of the input device (1) according to the invention is clearly recognizable.

[0063] The Fig. 4b Figure 1 shows the input device (1) according to the fourth embodiment, which is now in an actuated state. The switching element (2) was actuated by a force F acting on the switching contact (3). Due to the action of the force F and the design of the switching element (2) with a dome- or cup-shaped switching contact (3), the switching contact (3) is deformed and is electrically connected or contacted with the mating contact (5).

[0064] This bridges or short-circuits the second resistor (13) between the second terminal (6) and the third terminal (12) of the switching element (2), and the measuring node (10) is directly connected to the first terminal (4) of the switching element (2). Thus, the measuring node (10) is now located between the first resistor (9) and the third resistor (15), so that the following actuation-dependent voltage U1 can be measured at the measuring terminal (11): U 1 = U B ∗ R 1 R 1 + R 3

[0065] This voltage U 1 is also clearly distinguishable from the voltages of the other states of the input device (1) according to this embodiment and thus the actuation of the input device (1) according to the invention is clearly recognizable.

[0066] The Fig. 4c shows the input device (1) according to the fourth embodiment. Fig. 4a , whereby a fault has now occurred at the switching contact (3) of the switching element (2). The input device (1) according to the invention is therefore in a fault state. The fault comprises a break (19) of the switching contact (3) between the first terminal (4) and the third terminal (12) of the switching element (2).

[0067] This interrupts the connection between the first terminal (4) and the other terminals (6, 12) of the switching element (2), so that the measuring node (10) is always at the potential of the first power supply terminal (7), which corresponds to the reference potential here. Therefore, the following fault voltage U₂ can be measured at the measuring terminal (11): U 2 = Masse

[0068] This voltage U2 is also clearly distinguishable from the voltages of the other states of the input device (1) according to the fourth embodiment. Thus, the fault condition of the input device (1) according to the invention is also clearly identifiable.

[0069] Fig. 5a Figure 1 schematically shows a fifth embodiment of the input device (1) according to the invention, wherein the circuit of the input device (1) according to the invention is shown on a printed circuit board (16). The circuit essentially corresponds to the embodiment according to Figure 1. Fig. 3a , where the reference numerals for the respective components are identical. A repetition of the respective components is omitted, as they are completely analogous to the embodiment shown in the example. Fig. 3a are.

[0070] The switching contact (3) is dome- or cup-shaped and is arranged on the circuit board (16). The switching element (2) is provided with two terminals (4, 12) on the circuit board (16) in the form of solder points (17). Additional solder points (17) on the circuit board (16) serve as mounting points (18) for the switching contact (3). This allows the switching contact (3) to deform when actuated, generating haptic feedback to the actuator. This action closes a contact between the switching contact (3) and the mating contact (5), which is located centrally below the switching contact (3).

[0071] The contact order will be reviewed again in the Fig. 5b clarifies which is a sectional view through the section axis AA' of the Fig. 5a The dome- or cup-shaped form of the switching contact (3) is illustrated here, with the switching contact (3) being attached to the solder points (17), which also serve as terminals (4, 12) of the switching element (2). The mating contact (5) is arranged centrally below the dome- or cup-shaped switching contact (3). Fig. 5b show the input device (1) according to the fifth embodiment in the unactuated state.

[0072] Fig. 6a Figure 1 schematically shows a sixth embodiment of the input device (1) according to the invention, wherein the circuit of the input device (1) according to the invention is shown on a printed circuit board (16). The circuit essentially corresponds to the embodiment according to Figure 1. Fig. 3a , where the reference numerals for the respective components are identical. A repetition of the respective components is omitted, as they are completely analogous to the embodiment shown in the example. Fig. 3a are.

[0073] The switching contact (2) is a flat surface and is arranged on the circuit board (16). For this purpose, the switching element (2) is provided with two terminals (4, 12), which are implemented as solder points (17) on the circuit board (16). The switching contact (3) of the switching element (2) is spring-loaded to close the contact between the switching contact (3) and the mating contact (5) in the manner of a push button. The flat switching contact (3) also has a slot (20), so that the switching contact (3) has two separate connection areas, to which the first terminal (4) and the third terminal (12) are provided.

[0074] The contact order will be reviewed again in the Fig. 6b clarifies which is a sectional view through the section axis BB' of the Fig. 6a The planar shape of the switching contact (3) is illustrated here, with the switching contact (3) being attached to the solder point (17), which also serves as the connection (4) of the switching element (2). The mating contact (5) is located near the end region of the switching contact (3) on the circuit board (16), so that when actuated, the switching contact (3) moves towards the mating contact (5) until the contact is closed. Fig. 6b The input device (1) according to the sixth embodiment is shown in the unactuated state.

Claims

1. Input device (1) for safety-relevant functions of a motor vehicle, having a switching element (2), which has a switching contact (3) with a first connection (4) and a mating contact (5) with a second connection (6), wherein the switching contact (3) is able to make contact with the mating contact (5) when the input device (1) is actuated, having a first resistor (9), with a first and a second voltage supply connection (7, 8) via which an operating voltage for the input device (1) is able to be provided, wherein the first voltage supply connection (7) is connected to one of the connections (4, 6) of the switching element (2) and the second voltage supply connection (8) is connected via the first resistor (9) to the respective other connection (4, 6) of the switching element (2), having a measuring node (10) that is provided between the first resistor (9) and the respective connection (4, 6) of the switching element (2) and that is connected to a measuring connection (11), such that an actuation-dependent voltage (U1), which is dependent on the actuation of the input device (1), is able to be recorded via the measuring connection (11), characterized in that the switching element (2) has a third connection (12) that is connected to the switching contact (3), wherein a second resistor (13) is provided, which is connected to the second and third connections (6, 12) of the switching element (2) and is connected between the second and third connections (6, 12) such that, in the event of a fault of the switching contact (2), which affects the electrical connection between the first and third connections (4, 12), preferably in the event of a break (19) of the switching contact (3), a fault voltage (U2) is able to be recorded at the measuring node (10) via the measuring connection (11) and is able to be distinguished from the actuation-dependent voltage (U1).

2. Input device (1) according to Claim 1, wherein an evaluation circuit (14) is provided, which records the voltage at the measuring node (10) via the measuring connection (11) and as a result is able to detect an actuation of the input device (1) and / or a fault of the switching contact (3).

3. Input device (1) according to either of Claims 1 and 2, wherein the switching contact (3) is rounded or dome-shaped and preferably the first and third connections (4, 12) are provided in opposite regions of the rounded or dome-shaped switching contact (3).

4. Input device (1) according to either of Claims 1 and 2, wherein the switching contact (3) is of planar design and preferably the first and third connections (4, 12) are provided adjacent to an edge or in opposite regions of the planar switching contact (3).

5. Input device (1) according to one of the preceding claims, wherein a third resistor (15) is provided between the first voltage supply connection (7) and the respective connection (4, 6) of the switching element (2) such that the respective connection (4, 6) of the switching element (2) is connected to the first voltage supply connection via the third resistor (15).

6. Input device (1) according to one of the preceding claims, wherein the second voltage supply connection (8) is connected to a positive operating voltage and the first voltage supply connection (7) is connected to a reference potential of the input device (1), preferably ground.

7. Input device (1) according to one of the preceding claims, wherein, in the unactuated state of the input device (1), an actuation-dependent voltage (U1), which results from the voltage divider ratio between the first resistor (9) and the second resistor (13) and preferably the third resistor (15) is able to be recorded at the measuring node (10).

8. Input device (1) according to one of the preceding claims, wherein, in the actuated state of the input device (1), an actuation-dependent voltage (U1), which corresponds to the voltage or the potential of the first voltage supply connection (7) or results from the voltage divider ratio between the first resistor (9) and the third resistor (15), is able to be recorded at the measuring node (10).

9. Input device (1) according to one of the preceding claims, wherein, in the event of a fault of the switching contact (3), preferably in the event of a break (19) of the switching contact (3), a fault voltage (U2), which corresponds to the voltage or the potential of the second voltage supply connection (8) is able to be recorded at the measuring node (10).

10. Input device (1) according to one of the preceding claims, wherein the evaluation unit (14) comprises an analogue-to-digital converter such that the recorded voltage is able to be converted into a digital value and digitally processed.

11. Input device (1) according to one of the preceding claims, wherein, when the input device (1) is actuated, the contact between the switching contact (3) and the mating contact (5) is galvanically or electrically conductive.

12. Input device (1) according to one of Claims 1 to 10, wherein, when the input device (1) is actuated, the contact between the switching contact (3) and the mating contact (5) is resistive or capacitive.

13. Input device (1) according to one of the preceding claims, wherein the switching element (2) and the resistors (9, 13, 15) are arranged on a printed circuit board (16) and preferably at least the first and third connections (4, 12) are embodied as solder points (17) on the printed circuit board (16).

14. Input device (1) according to Claim 13, wherein the rounded or dome-shaped switching contact (3) is soldered to the solder points (17) for the first and third connections (4, 12) and the mating contact (5) is provided between these two solder points (17) on the printed circuit board (16).

15. Input device (1) according to Claim 14, wherein further support points (18) for the rounded or dome-shaped switching contact (3) are provided on the printed circuit board (16) and are preferably embodied as solder points (17).