A device consisting of a steering wheel with electrodes and an evaluation unit, and related motor vehicles.

Abstract

The present invention relates to an apparatus (1) for a motor vehicle, comprising a steering wheel (2) having electrodes (6) and an evaluation electronics (3) electrically connected to the electrodes (6); wherein the steering wheel (2) has a steering wheel rim (5) and a conductive steering wheel core (4); the steering wheel core (4) is electrically connected to a first ground connection (11); the evaluation electronics (3) is designed to apply an electrical measurement potential to the electrodes (6) to detect a touch on the steering wheel rim (5) based on a change in the measurement capacitance formed between the electrodes (6) and the steering wheel core (4); a conductive connection line (15) is provided between the electrodes (6) and the steering wheel core (4), which is high resistance when a measurement potential is applied to the electrode side and low resistance when an overvoltage occurs on the electrode side, so that in the latter case the overvoltage is released to the first ground connection (11) through the steering wheel core (4); and a motor vehicle having the above-described apparatus.

Description

Technical Field

[0001] The present invention relates to an apparatus comprising a steering wheel and an evaluation electronic device having electrodes for capacitive touch detection, the evaluation electronic device being conductively connected to the electrodes for detecting touches on the steering wheel, particularly on the steering wheel rim. Background Technology

[0002] The steering wheel has evolved from a simple input device for providing manual steering input on the steering components of a motor vehicle to a multifunctional input unit that may also have steering control monitoring capabilities. Therefore, in addition to controlling the direction of the motor vehicle, it is also used to provide touch-based input via gesture input to control other components of the motor vehicle. Furthermore, it is increasingly designed to monitor the steering control of the motor vehicle driver, for example, while driving the motor vehicle, but particularly when switching to and from the motor vehicle's automatic driving state. Touch detection is performed regularly by establishing a measuring capacitance between an electrode and a first ground connection connected to the vehicle ground. A disadvantage of capacitive touch detection is its susceptibility to overvoltages, i.e., voltages, especially transient voltages, where the maximum voltage exceeds the value of the measuring potential used for touch detection by one or more orders of magnitude. This can lead to interruption of touch input or even damage to the evaluation electronics. Therefore, it is known to protect the evaluation electronics from overvoltages on the input side connected to the electrode by a protection circuit, wherein the protection circuit has at least one overvoltage discharge element disposed in the electrical connection between the input side or the electrode and the vehicle ground. This protection circuit ensures that unwanted overvoltages electrically connected to the input side of the electrode are discharged toward the vehicle ground. In this scenario, under standard protection circuitry, an overvoltage reaching the associated second ground connection, through which the evaluation electronics are typically "grounded" with minimal loss, results in a potential shift between the first and second ground connections. This shift occurs because the first and second ground connections are spatially separated and isolated from each other via metal body housing portions and / or frame portions that can be considered electrical conductors. These temporary potential shifts between the first and second ground connections can lead to unpredictable interruptions in the evaluation electronics' ability to assess or detect touch, such as intolerable false detections, particularly when monitoring a motor vehicle driver's steering control, or when the driver switches from autonomous driving to steering control, or vice versa. Summary of the Invention

[0003] Against the aforementioned background, a technical solution is needed in which the device includes a steering wheel having electrodes for capacitive touch detection; and an evaluation electronics device for detecting touches on the steering wheel, the evaluation electronics device being conductively connected to the electrodes, the device better preventing coupling overvoltages on the electrode side. This objective is achieved by a device consisting of a steering wheel with electrodes and an evaluation unit. Motor vehicles are also the subject of the parallel claims. In each case, the advantageous configuration is the subject of the dependent claims. It should be noted that the features individually listed in the claims can be combined with each other in any technically meaningful manner, demonstrating further configurations of the invention. This specification, in particular in conjunction with the accompanying drawings, additionally describes and defines the invention.

[0004] This invention relates to an apparatus for a motor vehicle, comprising a steering wheel having electrodes, and evaluation electronics protected against electrical overvoltage. In this context, the term "motor vehicle" should also include software-supported simulations of the motor vehicle, wherein the steering wheel forms an input device for realizing virtual steering movements of the simulated motor vehicle. Generally, the steering wheel is a component of the motor vehicle's steering system, by which the driver changes the direction of the real or virtual motor vehicle, wherein one or more wheels of the motor vehicle change their steering position.

[0005] According to the invention, an evaluation unit is electrically connected to one or more electrodes for capacitive detection of touches on the steering wheel. According to the invention, the steering wheel has a steering wheel rim and a conductive steering wheel core for fixing to a steering wheel shaft on a motor vehicle. The steering wheel core is made of, for example, metal or a metal alloy and forms a steering wheel hub for releasably fastening to the steering shaft of the motor vehicle. For example, a threaded connection is provided between the steering shaft and the steering wheel hub. For example, a screw connection is covered by a shock absorber. For example, the steering wheel rim is designed as annular or alternatively as one or more annular segments. For example, the steering wheel core extends from the steering wheel hub through steering wheel spokes to the steering wheel rim, thereby fixing the steering wheel rim to the steering wheel hub, for example, through one or more steering wheel spokes. For example, electrodes are integrated into the steering wheel rim.

[0006] According to the present invention, the steering wheel core is electrically connected to a first ground connection via a first ohmic resistor.

[0007] According to the invention, an evaluation electronics device, as part of the apparatus, is designed to apply an electrical measurement potential to electrodes for touch detection, so as to detect a touch on the steering wheel rim based on a change in the measurement capacitance formed between the electrodes and the steering wheel core. According to the invention, the evaluation electronics device is further conductively connected to a second ground connection.

[0008] The term "second connection" here means that it is different, i.e., not the first connection. According to the invention, the first and second grounding connections are arranged spatially separate from each other and are electrically connected via grounding paths, such that they preferably define or seek a common grounding potential.

[0009] According to the invention, a connecting wire is provided between the electrode and the steering wheel core, the connecting wire having an overvoltage discharge element such that when a measuring potential is applied to the electrode side, the connecting wire is high-resistance, i.e., it has the effect of impeding or preferably blocking the current flow between the electrode and the steering wheel core; and when an overvoltage occurs on the electrode side, the connecting wire is low-resistance, i.e., it allows currently, preferably unimpeded, current to flow between them, so that in the latter case, the overvoltage is discharged from the electrode to the first ground connection through the steering wheel core. For example, the difference between the low-resistance and high-resistance states is more than one, preferably more than three orders of magnitude (ohms). The difference between the overvoltage and the measuring potential is, for example, more than one, preferably more than three orders of magnitude (volts).

[0010] As a result of the technical solution according to the invention, the overvoltage is first conducted to the first ground connection via a first ohmic resistor so that it reaches the evaluation unit via the ground path. This reduces the voltage drop at the first ohmic resistor by at least a certain amount, meaning that no potential shift due to the overvoltage occurs or is at least reduced at the second ground connection. The reduced potential (if any) generated by the overvoltage discharge is applied to the ground connection of the evaluation electronics. Therefore, touch detection of the evaluation electronics does not need to be interrupted in the event of an overvoltage, and is not interrupted. Capacitive touch detection functionality is based, for example, on changes in the electric field in the environment in front of the electrode (active region). The evaluation electronics has, for example, an RC oscillator circuit. When a measurement potential is applied, the capacitance between the measurement electrode and the ground potential is measured. Instead of the measurement potential, a specially provided reverse electrode with a corresponding ground potential can also be provided. The capacitance increases due to the proximity of metallic or non-metallic materials to the electrode, particularly when contacting the steering wheel rim, thus affecting the oscillation amplitude of the RC oscillator. This change causes the downstream trigger stage to "flip" and change its output state, thereby actively detecting the touch. Therefore, the ground potential shift at the evaluation electronics due to overvoltage has a disastrous effect on touch detection.

[0011] The overvoltage discharge element can be part of a multi-component electronic circuit that establishes an electrical connection between the electrodes and the steering wheel core. The overvoltage discharge element located in the electrical connection between the electrodes and the steering wheel core is preferably a diode, such as a transient absorption Zener diode or a transient voltage suppression diode. The overvoltage discharge element is preferably spatially arranged closer to the evaluation electronics than the steering wheel core.

[0012] According to a preferred embodiment, the steering wheel core is also connected to a second ground connection via a capacitor. This has the advantage that the potential applied to the steering wheel core is stable when the measuring capacitance is applied to the electrode, or when the measuring capacitance changes; and when used as a measuring electrode, i.e., outside of overvoltage discharge of the overvoltage discharge element, the electromagnetic interaction between the steering wheel core and the electrode is minimized. A second ohmic resistor (whose ohmic resistance is greater than that of the first ohmic resistor) is preferably connected in parallel with the capacitor to form an RC element. The second ohmic resistor is chosen to be larger to ensure a larger discharge current between the steering wheel core and the first ground connection in the event of overvoltage and discharge.

[0013] The first ohmic resistance is preferably in the range of 500Ω to 10kΩ, and more preferably in the range of 800Ω to 1.2kΩ.

[0014] The overvoltage is preferably conducted to the first ground connection via the steering wheel shaft. The first ohmic resistance is preferably formed substantially by the contact resistance in the bearing region of the steering wheel shaft. For example, the first ohmic resistance can be defined as the average resistance of the steering wheel over the entire adjustment path from one steering shift to the opposite steering shift.

[0015] According to the invention, the first grounding connection and the second grounding connection do not overlap in space, and are preferably arranged such that they are visible to each other at a minimum spatial distance of 0.5m.

[0016] Preferably, the first and second grounding connections are electrically connected with potential equalization (i.e., having almost zero resistance and thus defining a common ground potential), or preferably electrically connected with low resistance (i.e. having at most one or two ohmic resistances) through a grounding path.

[0017] According to one configuration, at least one of the first and second grounding connections is formed by a separable electromechanical connection device, such as a separable force-fit connection device. Preferably, both the first and second grounding connections are formed by a disconnectable connection device, such as a disconnectable force-fit connection device.

[0018] The electrodes are preferably formed from the heating wire of the steering wheel heating device. For example, heating is performed by applying a pulse-width modulated heating current to the heating wire, while touch detection is performed during the pauses in the current application.

[0019] The evaluation electronics and overvoltage discharge components are preferably located outside the steering wheel. As an example, the evaluation electronics and reader unit are located behind the screen of the steering column cover, instrument panel, or center console of the motor vehicle.

[0020] The present invention also relates to a motor vehicle having the device of one of the foregoing embodiments. In this case, the conductive grounding path between the first grounding connection and the second grounding connection is at least partially formed by the vehicle body shell and / or frame. Attached Figure Description

[0021] The invention will be explained in more detail with the aid of the following accompanying drawings. In this context, the drawings should be understood as merely exemplary and, in each case, only variations of preferred embodiments are shown.

[0022] Figure 1 A schematic diagram of a first embodiment of the device of the present invention is shown;

[0023] Figure 2 A schematic diagram of a second embodiment of the device of the present invention is shown. Detailed Implementation

[0024] Figure 1 An embodiment of the device 1 of the present invention is shown. The device 1 of the present invention includes a steering wheel 2 and an evaluation electronics 3 disposed outside the steering wheel 2. The evaluation electronics 3 is protected from overvoltage on the input side by an overvoltage discharge element 13, which is also disposed outside the steering wheel 2. The evaluation electronics 3 is designed to perform capacitive detection of touches on the steering wheel 2, and the measurement input of the evaluation electronics 3 is therefore via an input resistor R. E It is electrically connected to the electrode 6 disposed on or in the steering wheel 2.

[0025] The steering wheel 2 is shown only partially in the accompanying drawings and not in detail. It has a conductive steering wheel core 4, preferably made of metal or a metal alloy, and is fixed to a steering wheel shaft 9 of a motor vehicle (not shown). The steering wheel core 4 forms a steering wheel hub 8, which is used to fix to the steering wheel shaft 9 and electrically connect to a first ground connection 11. The first ground connection 11 is formed by a disconnectable, force-fit electromechanical connection for establishing an electrical connection with the vehicle body shell or frame. The steering wheel core 4 extends on at least one steering wheel spoke 7 to a steering wheel rim 5, which is part of the steering wheel 2. The steering wheel core 4 forms an inner skeleton, stabilizing the steering wheel rim 5, and is surrounded by a plastic, leather, or wood shell. The steering wheel rim 5 is designed, for example, in the form of an annular shape or at least an annular segment, and forms a gripping surface for the driver of the motor vehicle, whose touch will be detected. Within the housing of the steering wheel rim 5, an electrode 6 extending circumferentially along the steering wheel rim 5 is provided. This electrode 6 is electrically insulated relative to the steering wheel core 4, except for the connection wire 15 (described below) used for voltage discharge. Those skilled in the art will understand that, depending on the desired detection result, multiple electrodes, such as an electrode array, may also be provided to enable spatially resolved touch detection, for example, on the touch surface of the steering wheel rim 5.

[0026] In this embodiment, electrode 6 is formed from the heating wire of a steering wheel heating system (not shown), which applies a pulse-width modulated heating current to the heating wire, and electrode 6 can be used for touch detection during the stagnation time of the heating current. A measurement potential is applied to electrode 6 by evaluation electronics 3 via conductive connection 16. In addition to the electrical connection 16 to electrode 6, evaluation electronics 3 is also connected to a power supply voltage V and, through its ground output, to a second ground connection 12, which is formed by a disconnectable, force-fit electromechanical connection device for establishing an electrical connection to the vehicle body shell or the vehicle frame.

[0027] The evaluation electronics 3 detects a touch on the steering wheel rim 5 based on a change in the measured capacitance formed between electrode 6 and steering wheel core 4, which is conductively connected to the first ground connection 11. The capacitive touch detection function is based, for example, on a change in the electric field in the environment around electrode 6, more precisely, on a change in the electric field in the surface area of ​​steering wheel rim 5. The evaluation electronics 3 has, for example, an RC oscillator circuit. During the application of the measured potential, the capacitance between the measured electrode 6 and the reverse electrode (in this case, steering wheel core 4) is applied to it, thus applying a ground potential. As the driver's hand approaches electrode 6, especially when touching steering wheel rim 5, the capacitance increases, thus affecting the oscillation amplitude of the RC oscillator. This change causes a downstream trigger stage, as part of the evaluation electronics 3, to "flip" and change its output state, thereby actively detecting the touch and outputting the detection result via digital output 10, for example, as part of a bus system such as a CAN bus. The sensitivity of the evaluation electronics 3 can typically be set by selecting the switching distance. Therefore, a ground potential shift at the evaluation electronics due to overvoltage at the second ground connection has a disastrous effect on touch detection.

[0028] A connecting wire 15 is provided between electrode 6 and steering wheel core 4. This connecting wire has an overvoltage discharge element 13, such that when a measuring potential is applied to the electrode side, the connecting wire is high-resistance, i.e., it has the effect of impeding or preferably blocking the flow of current, and when an overvoltage occurs on the electrode side, the connecting wire is low-resistance, i.e., it allows the flow of current, preferably unimpeded, so that the overvoltage can be conducted to the steering wheel core 4 in the latter case. For example, the difference between the low-resistance and high-resistance states is more than one, preferably more than three orders of magnitude (ohms). The difference between the overvoltage and the measuring potential is, for example, more than one, preferably more than three orders of magnitude (volts). Since the steering wheel core 4 is also conductively connected to a first ground connection 11 via a first ohmic resistor R, the overvoltage discharges at the first ground connection 11 and the voltage drop at the first resistor R is reduced before it reaches the second ground connection 12 of the evaluation electronics 3 via a common ground wire 14, which is implemented, for example, through the vehicle body shell (not shown) or the vehicle frame (not shown). The additional resistance R generated by the distance greater than 0.5m between the first grounding connection 11 and the second grounding connection 12 M For example, it can have a supporting function in the range of 0.01 to 99.99 ohms. The first ohmic resistance R is preferably in the range of 500Ω to 10kΩ, and more preferably in the range of 800Ω to 1.2kΩ. Overvoltage is conducted here to the first ground connection 11 via the steering wheel shaft 9. The first ohmic resistance R is essentially formed by the contact resistance in the bearing (not shown) region of the steering wheel shaft 9. The first ohmic resistance can be defined, for example, as the average resistance of the steering wheel 2 over the entire adjustment path from one steering shift to the opposite steering shift.

[0029] As a result of the technical solution according to the present invention, the overvoltage is first conducted to the first ground connection 11 through the first ohmic resistor R so that it reaches the evaluation unit 3 through the ground path 14, thereby reducing the overvoltage at least through the voltage drop at the first ohmic resistor R. This means that the potential shift caused by the overvoltage at the second ground connection 12 will not occur, or at least be reduced, and the at least reduced potential (if any) generated by the discharge of the overvoltage is applied to the ground output of the evaluation electronic device 3.

[0030] Figure 2 A second embodiment of the device 1 of the present invention is shown. Here, the steering wheel core 4 is also connected to the second ground connection 12 via a capacitor C. This has the advantage that the potential applied to the steering wheel core 4 is stabilized when the measuring capacitance is applied to the electrode 6, or when the measuring capacitance changes, and the electromagnetic interaction between the steering wheel core 4 and the electrode 6 is minimized when used as a measuring electrode, i.e., outside of the overvoltage discharge of the overvoltage discharge element. A second ohmic resistor R has a resistance greater than the first ohmic resistor R. S Preferably, it is connected in parallel with capacitor C to form an RC element. The second ohmic resistor R S A larger value is selected to ensure a larger discharge current between the steering wheel core 4 and the first ground connection 11 in the event of overvoltage and discharge.

Claims

1. An apparatus (1) for a motor vehicle, comprising a steering wheel (2) having electrodes (6) and an evaluation electronics (3) protected against overvoltage and conductively connected to the electrodes (6) for capacitive detection of a touch on the steering wheel (2); wherein the steering wheel (2) has a steering wheel rim (5) and a conductive steering wheel core (4) for attachment to a steering wheel shaft (9); wherein the steering wheel core (4) is conductively connected to a first ground connection (11) via a first ohmic resistor (R); wherein the evaluation electronics (3) is configured to apply an electrical measurement potential to the electrodes (6) for touch detection to detect a touch on the steering wheel rim (5) based on a change in the measurement capacitance formed between the electrodes (6) and the steering wheel core (4); The evaluation electronics (3) is further conductively connected to a second ground connection (12); wherein the first ground connection (11) and the second ground connection (12) are arranged spatially separate from each other and are conductively connected via a grounding path (14); A connecting line (15) with an overvoltage discharge element (13) is provided between the electrode (6) and the steering wheel core (4), such that the connecting line (15) is high resistance when a measurement potential is applied to the electrode side and low resistance when an overvoltage occurs on the electrode side, so that the overvoltage is released to the first ground connection (11) through the steering wheel core (4) in the latter case.

2. The apparatus (1) according to claim 1, characterized in that, The overvoltage discharge element (13) is a diode.

3. The apparatus (1) according to claim 2, characterized in that, The diode is a transient absorption Zener diode or a transient voltage suppressor diode.

4. The apparatus (1) according to claim 1, characterized in that, The steering wheel core (4) is also connected to the second ground connection (12) via a capacitor (C).

5. The apparatus (1) according to claim 4, characterized in that, Second ohmic resistor (R) S The second ohmic resistor (R) is connected in parallel with the capacitor (C). S The resistance of the first ohmic resistor (R) is greater than the resistance of the second ohmic resistor (R).

6. The apparatus (1) according to claim 1, characterized in that, The resistance of the first ohmic resistor (R) is in the range of 500Ω to 10kΩ.

7. The apparatus (1) according to any one of claims 1-6, characterized in that, The overvoltage is conducted to the first ground connection (11) via the steering wheel shaft (9).

8. The apparatus (1) according to any one of claims 1-6, characterized in that, The first ohmic resistor (R) is formed by the contact resistance in the bearing region of the steering wheel shaft (9).

9. The apparatus (1) according to any one of claims 1-6, characterized in that, The first grounding connection (11) and the second grounding connection (12) are arranged such that they are visible to each other at a minimum spatial distance of 0.5m.

10. The apparatus (1) according to claim 9, characterized in that, The first grounding connection (11) and the second grounding connection (12) are connected to a potential-equalized conductive ground, thereby defining a common ground potential through the grounding path (14).

11. The apparatus (1) according to claim 10, characterized in that, The first ground connection (11) and the second ground connection (12) are connected to a potential-equalized conductive ground, thereby defining a low resistance (R) through the grounding path (14). M ).

12. The apparatus (1) according to any one of claims 1-6, characterized in that, Both the first grounding connection (11) and the second grounding connection (12) are formed by disconnectable electromechanical connection devices.

13. The apparatus (1) according to any one of claims 1-6, characterized in that, The electrode (6) is formed from the heating wire of the steering wheel heating device.

14. The apparatus (1) according to any one of claims 1-6, characterized in that, The evaluation electronics (3) and the overvoltage discharge element (13) are arranged outside the steering wheel (2).

15. A motor vehicle having the device (1) according to any one of claims 1-14, wherein, The grounding path between the first grounding connection and the second grounding connection is formed at least in part by the vehicle body shell and / or frame.

Images