Steering wheel with adaptive capacitive touch recognition and motor vehicle

Abstract

Steering wheel (1) for a motor vehicle, comprising: a steering wheel hub (3) designed for detachable attachment to a steering shaft (12) of the motor vehicle; a steering wheel rim (2) fixed to the steering wheel hub (3); at least one electrode (4) integrated into the steering wheel rim (2) for capacitive detection of a touch of the steering wheel rim (2); an electrically conductive connection (5) between the electrode (4) and an evaluation electronics (6) arranged outside the steering wheel (1) in order to apply an electrical measuring potential to the electrode (4) via the electrically conductive connection (5) for touch detection and to detect a touch of the steering wheel rim (2) as a function of at least one predetermined parameter based on an associated change in measuring capacitance; characterized in that a non-volatile data storage device (10) arranged on or in the steering wheel (1), in which at least one of the parameters is stored, and a reading unit (7) arranged outside the steering wheel (1) and in data-transmitting communication with the evaluation electronics (6), which is designed to read the non-volatile data storage device (10) and to transmit the at least one parameter to the evaluation electronics (6), are provided.

Description

[0001] The invention relates to a steering wheel with capacitive touch detection. Steering wheels have evolved from simple input devices for manual steering inputs to a motor vehicle's steering system. In addition to steering a motor vehicle, they now also serve to provide touch-based inputs, including gesture inputs, for controlling other vehicle components. Furthermore, they are designed to monitor the driver's steering control, for example, while driving the vehicle, but especially when transitioning to and from an autonomous driving mode. A grip detection system for steering wheels is known from DE 10 2010 035 940 B4. A piezoresistive layer is arranged around the circumference of the steering wheel rim, which reacts to the force exerted by the driver when gripping the steering wheel.If this system detects an anomaly, such as a cramped hand position, the sensor signals can trigger the engine to shut off or initiate braking. These force-applying devices have the disadvantage of requiring a relatively large installation space, making it difficult to achieve detection covering the entire steering wheel rim. In contrast, capacitive detection has proven advantageous, as it allows not only touch detection on the surface of the steering wheel rim but also proximity detection before surface contact occurs. By simplifying the design of the electrodes used, spatially resolved touch detection can be achieved while saving installation space.A further advantage of capacitive touch detection integrated into the steering wheel is that many steering wheels are equipped with electric steering wheel heating, and the existing electrical equipment can thus be used, at least partially, for capacitive touch detection. A disadvantage of capacitive touch detection is that, due to space constraints, the evaluation electronics are usually located outside the steering wheel. Furthermore, if the steering wheel is replaced, for example, due to a change in the permittivity of the steering wheel rim materials, the touch detection system must be painstakingly recalibrated to the new steering wheel to ensure reliable touch detection. A steering wheel according to the preamble of claim 1 is known from DE 10 2019 203 633 A1.

[0002] Against this background, there was a need for a solution in which a steering wheel with capacitive touch detection and an external evaluation unit could be replaced easily, in particular without multiple calibration procedures. This problem is solved by a steering wheel according to claim 1. An equally advantageous arrangement and a corresponding motor vehicle are each the subject of the dependent claims. Advantageous embodiments are each the subject of the dependent claims. The description, especially in conjunction with the figures, further characterizes and specifies the invention.

[0003] The invention relates to a steering wheel for a motor vehicle. The term "motor vehicle" is intended to also include a software-based simulation of a motor vehicle, in which the steering wheel serves as an input device for effecting a virtual steering movement of a simulated motor vehicle. Generally, it is a component of a motor vehicle's steering system, with which the driver effects a change in the direction of the real or virtual motor vehicle by turning the steering wheel, for example, by changing the steering position of one or more of the vehicle's wheels. The steering wheel according to the invention has a steering wheel hub designed for detachable attachment to a steering shaft of the motor vehicle. For example, a screw connection is provided between the steering shaft and the steering wheel hub. For example, the screw connection is covered by a shock absorber. According to the invention, a steering wheel rim fixed to the steering wheel hub is also provided.For example, the steering wheel rim is ring-shaped or alternatively designed as one or more ring segments. The steering wheel rim is fixed to the steering wheel hub, for example, by one or more steering wheel spokes. According to the invention, at least one electrode integrated into the steering wheel rim is provided for the capacitive detection of a touch to the steering wheel rim. Furthermore, according to the invention, an electrically conductive connection is provided between the electrode and evaluation electronics arranged outside the steering wheel in order to supply the electrode with an electrical measuring potential for touch detection via the electrically conductive connection and to detect a touch to the steering wheel rim based on an associated change in measuring capacitance and depending on a predetermined parameter. The function of the capacitive touch detection is based, for example, on the change in the electric field in the environment in front of the electrode (active zone).The evaluation electronics, for example, feature an RC oscillator circuit. During application of the measuring potential, the capacitance between the electrode and the electrical ground potential is measured. Instead of ground potential, a counter electrode with a corresponding ground or counter potential can also be used. As a metallic or non-metallic material approaches the electrode, particularly when touching the steering wheel rim, the capacitance increases and thus affects the oscillation amplitude of the RC oscillator. This change causes a downstream trigger stage to "flip" and change its output state, thereby positively detecting a touch. The sensitivity of the evaluation electronics can generally be adjusted by selecting the switching distance.The switching distance of capacitive touch detection varies with the permittivity constant and the conductivity of the approaching material, as well as with the effective area of ​​the approaching body compared to the electrode area. However, this is only partially true in the steering wheel situation. Furthermore, the switching distance depends on the installation conditions, i.e., the materials surrounding the electrode on the steering wheel rim, such as whether it is made of genuine leather, synthetic leather, wood, or similar materials. For example, the switching distance is determined by a parameter related to the permittivity of the steering wheel rim material and / or by a parameter related to the geometry and position of the electrode within the steering wheel rim.

[0004] According to the invention, a non-volatile data storage device is further provided, arranged on or in the steering wheel, in which at least one of the parameters, such as the parameter associated with the electrical permittivity constant of the steering wheel rim material, is stored. According to the invention, the non-volatile data storage device is read by a reading unit arranged outside the steering wheel and in data-transmitting communication with the evaluation electronics in order to transmit the at least one parameter to the evaluation electronics, so that the latter can, for example, adapt the detection in subsequent evaluation steps using the stored parameter. For example, the reading unit, the data storage device, and the evaluation electronics communicate via a data connection designed as a bus system, such as a CAN bus.

[0005] Preferably, at least the electrode and the data storage device are arranged on a common substrate. The substrate is preferably a film or a fabric.

[0006] Preferably, the electrode is formed by a heating wire from a steering wheel heater. For example, the heating operation is carried out by applying a pulse-width modulated heating current to the heating wire, while the touch detection takes place during a dead time of this application.

[0007] For example, the reading unit and the non-volatile data storage device are connected by a data line. However, wireless reading of the data storage device is preferred, in which a transponder is provided on or in the steering wheel, which is electrically connected to the data storage device and communicates wirelessly with the reading unit. For example, the wireless communication between the transponder and the reading unit uses Radio Frequency Identification (RFID) technology in active or passive configuration, Near Field Communication (NFC) technology, Bluetooth® technology, or WiFi technology. Preferably, the transponder is also arranged on the aforementioned substrate.

[0008] Preferably, both the transponder and the non-volatile data storage device are integrated into the steering wheel rim.

[0009] The invention further relates to an arrangement comprising a steering wheel in one of the previously described configurations and evaluation electronics and a reading unit arranged outside the steering wheel. For example, the evaluation electronics and the reading unit are arranged behind a steering column cover or a panel of the dashboard or center console of the motor vehicle.

[0010] The invention further relates to a motor vehicle with the arrangement described above or to the use of the described arrangement in a motor vehicle.

[0011] The invention is explained in more detail with reference to the following figure. The figure is to be understood as merely exemplary and represents only one preferred embodiment. It shows: Fig. 1 a schematic representation of an embodiment of the arrangement according to the invention.

[0012] Fig. Figure 1 shows an embodiment of the arrangement according to the invention. The arrangement according to the invention comprises a steering wheel 1, a reading unit 7 arranged outside the steering wheel 1, and evaluation electronics 6 arranged outside the steering wheel 1. The reading unit 7 is in data-transmitting communication with the evaluation electronics 6. In the Fig. 1. An unspecified data line is provided for this purpose. However, this transmission can also be wireless.

[0013] The steering wheel 1 has a steering wheel hub 3 for detachably attaching the steering wheel 1 to a steering shaft 12 of a motor vehicle (not shown). The steering wheel 1 also has an annular steering wheel rim 2, which is supported on the steering wheel hub 3 by several spokes 11. The surface of the steering wheel rim 2 serves as a gripping surface for steering inputs by a motor vehicle operator, who is also referred to as the driver. An electrode 4 is arranged beneath the surface of the steering wheel rim 2 and thus integrated into the steering wheel rim 2. The electrode 4 extends along the steering wheel rim 2 in the circumferential direction corresponding to the direction of rotation of the steering wheel 1. The electrode 4 is supplied with a measuring potential via an electrically conductive connection 5 by the evaluation electronics 6. The electrically conductive connection 5 includes, for example, a sliding contact provided in the area of ​​the steering wheel hub 3.

[0014] In this embodiment, electrode 4 is formed by a heating wire from a steering wheel heater (not shown), which is supplied with a pulse-width modulated heating current. During the dead time of this heating current, electrode 4 is available for touch detection. Based on a corresponding change in measuring capacitance and depending on a predefined parameter, the evaluation electronics 6 detect a touch of the steering wheel rim 2. The function of the capacitive touch detection is based, for example, on the change in the electric field in the area in front of electrode 4, more precisely in the region of the surface of the steering wheel rim 2. The evaluation electronics 6, for example, have an RC oscillator circuit. During the application of the measuring potential, the capacitance between electrode 4 and the electrical ground potential is measured.Instead of a ground potential, a counter electrode with a corresponding ground or counter potential can alternatively be provided. When the driver's hand approaches electrode 4, particularly when touching the steering wheel rim 2, the capacitance increases and thus influences the oscillation amplitude of the RC oscillator. This change causes a downstream trigger stage belonging to the evaluation electronics 6 to "flip" and change its output state, thereby positively detecting a touch. The sensitivity of the evaluation electronics 6 can generally be adjusted by selecting the switching distance. The switching distance of the capacitive touch detection varies with the permittivity constant and the conductivity of the approaching material, as well as with the effective area of ​​the approaching body compared to the electrode area, although this is only partially true in the steering wheel situation.However, the switching distance also depends on the installation conditions, i.e., the materials of the steering wheel rim 2 surrounding the electrode 4, such as whether it is made of genuine leather, imitation leather, wood, or similar materials. For example, the switching distance is determined by a parameter related to the permittivity of the steering wheel rim 2 material and / or by a parameter related to the geometry and position of the electrode within the steering wheel rim 2.

[0015] Therefore, according to the invention, a non-volatile data storage device 10 is further provided, arranged on or in the steering wheel 1, here also arranged in the steering wheel rim 2, in which at least one of the parameters, such as the parameter associated with the electrical permittivity constant of the steering wheel rim material, is stored. This non-volatile data storage device 10 is read by the reading unit 7, which is arranged outside the steering wheel 1 and is in data-transmitting communication with the evaluation electronics 6, in order to transmit the at least one parameter to the evaluation electronics 6, so that the latter can, for example, in the evaluation steps following the readout, adapt the detection using the stored and read parameter.In this embodiment, wireless reading of the non-volatile data storage device 10 is provided by means of a transponder 9 arranged on or in the steering wheel 1, which is electrically connected to the non-volatile data storage device 10 and wherein the transponder 9 communicates wirelessly with the reading unit 7. For example, the wireless communication between the transponder 9 and the reading unit 7 uses Radio Frequency Identification (RFID) technology in active or passive form, Near Field Communication (NFC) technology, Bluetooth® technology or WiFi technology. The electrode 4, the non-volatile storage device 10 and the transponder 9 are, for example, mounted on a common surface in . Fig. 1 substrate not shown.

Claims

[1] Steering wheel (1) for a motor vehicle, comprising: a steering wheel hub (3) designed for detachable attachment to a steering shaft (12) of the motor vehicle; a steering wheel rim (2) fixed to the steering wheel hub (3); at least one electrode (4) integrated into the steering wheel rim (2) for capacitive detection of a touch of the steering wheel rim (2); an electrically conductive connection (5) between the electrode (4) and an evaluation electronics (6) arranged outside the steering wheel (1) in order to apply an electrical measuring potential to the electrode (4) via the electrically conductive connection (5) for touch detection and to detect a touch of the steering wheel rim (2) as a function of at least one predetermined parameter based on an associated change in measuring capacitance; characterized by, that a non-volatile data storage device (10) arranged on or in the steering wheel (1), in which at least one of the parameters is stored, and a reading unit (7) arranged outside the steering wheel (1) and in data-transmitting communication with the evaluation electronics (6), which is designed to read the non-volatile data storage device (10) and to transmit the at least one parameter to the evaluation electronics (6), are provided. [2] Steering wheel (1) according to claim 1, wherein the electrode (4) and the data storage device (10) are arranged on a common substrate. [3] Steering wheel (1) according to the preceding claim, wherein the substrate is a film or a fabric. [4] Steering wheel (1) according to one of the preceding claims, wherein electrode (4) is formed by a heating wire of a steering wheel heater. [5] Steering wheel (1) according to one of the preceding claims, wherein the data storage device (10) is read wirelessly by the reading unit (7) via a transponder (9) arranged on the steering wheel. [6] Steering wheel (1) according to the preceding claim, wherein the transponder (9) is further arranged on the substrate. [7] Steering wheel (1) according to one of the two preceding claims, wherein the transponder (9) and the non-volatile data storage device (10) are arranged in the steering wheel rim (2). [8] Motor vehicle with an arrangement according to the preceding claim.

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