Steering wheel for a vehicle, vehicle and electronic assembly

Abstract

Steering wheel (5) for a vehicle, wherein the steering wheel (5) comprises the following: - a steering wheel body with an earthing device designed to be connected to the vehicle mass, wherein the earthing device includes an earthing area on the body side, - at least one electronic assembly (40) attached to the steering wheel body, wherein the electronic assembly (40) comprises a plastic housing, an electronic component arranged in the plastic housing, a signal connection and an assembly-side grounding area (52), and - at least one electrically conductive and elastic contact element extending between the assembly-side grounding area (52) and the first body-side grounding area, wherein the electrically conductive and elastic contact element is under mechanical tension so that it transmits a force between the steering wheel body and the electronic assembly (40), where the electronic component has the assembly-side grounding area (52) from which the conductive and elastic contact element extends, and wherein the plastic housing has an opening (46) through which the conductive and elastic contact element or the first body-side grounding area extends.

Description

[0001] The invention relates to a steering wheel according to claim 1, a vehicle with such a steering wheel according to claim 15, and an electronic assembly for mounting on a steering wheel body to form such a steering wheel according to claim 16.

[0002] A steering wheel in a modern motor vehicle, particularly a passenger car, truck, bus, or similar vehicle, serves not only for steering the vehicle but also as a communication interface with switches, lighting elements, sensors, and the like. A steering wheel therefore comprises a steering wheel body and at least one electronic assembly attached to this steering wheel body. Such an electronic assembly includes an electronic component, usually housed in a casing. The steering wheel housing generally has a metal skeleton (usually magnesium), and this skeleton can be used as a grounding device or as part of a grounding system. In this case, the grounding device (especially the skeleton) is connected to the vehicle's chassis.

[0003] The electronic assembly must of course communicate with the vehicle's electronics, so the electronic assembly includes at least one signal connection that can be electrically connected to a wiring harness.

[0004] The electronic assembly often includes an assembly-side grounding point that must be connected to the vehicle chassis. In this case, the vehicle chassis's grounding system includes a chassis-side grounding point to which the assembly-side grounding point is connected. The connection between the assembly-side grounding point and the chassis-side grounding point is made by a grounding cable, which may be part of the wiring harness.

[0005] A large number of publications deal with the problem of grounding: DE 10 2017 217 334 B3 proposes a contact element intended for a vehicle steering wheel, which can also be used for grounding purposes.

[0006] DE 10 2014 201 577 A1 discloses a display unit for a vehicle in which several spring elements extend between a metal back cover and the grounding area of ​​a printed circuit board. A similar design is also disclosed in DE 102 05 816 A1, which describes a general electrical device with a metal housing and a printed circuit board arranged in the metal housing, wherein the grounding of the printed circuit board is effected via spring elements.

[0007] DE 102 53 853 A1 deals with the grounding of a vehicle component on a magnesium beam.

[0008] German patent DE 10 2013 114 791 A1 proposes grounding the gas generator of a driver's airbag module to a steering wheel housing by means of a spring assembly. In this arrangement, the spring assembly is not under tension when the driver's airbag module is not installed. When the driver's airbag module is installed on the steering wheel housing, the spring assembly is automatically tensioned, thus establishing contact between the airbag module's gas generator and a grounding point on the steering wheel housing. The grounding connection is therefore automatically established during the installation of the airbag module, without the need for any further assembly steps.

[0009] Based on this state of the art, it is an object of the invention to improve a steering wheel of the type described above, in particular the grounding of the electronic assembly.

[0010] This problem is solved by a steering wheel according to claim 1. A vehicle with such a steering wheel is defined in claim 15 and an electronic assembly suitable for mounting on a steering wheel body is defined in claim 16.

[0011] As with the steering wheel of DE 10 2013 114 791 A1, at least one electrically conductive and elastic contact element, usually a spring, is provided, extending between the assembly-side grounding area and the first body-side grounding area. This electrically conductive and elastic contact element is initially not pre-tensioned, but is placed under mechanical tension during the assembly of the electronic assembly onto the steering wheel body. During this assembly step, the electronic assembly is generally moved towards the steering wheel body, whereby the electrically conductive and elastic contact element is tensioned in such a way that a reliable grounding of the electronic assembly is "automatically" created during the mechanical assembly process.According to the invention, the electronic assembly further comprises a housing made of a plastic material in which the electronic component is located, and the assembly-side grounding area is provided directly on the electronic component, so that the housing does not participate in the grounding. Therefore, the housing has an opening through which the conductive and elastic contact element or the first body-side grounding area extends. The second alternative is generally preferred to ensure that the conductive and elastic contact element is not damaged before the electronic assembly is mounted on the steering wheel housing.

[0012] The embodiment of the invention has the following advantages: First, a separate assembly step for grounding is avoided, thus preventing the grounding from being forgotten and saving assembly time. Second, the risk of damage to the electronic component from static discharge is reduced, as grounding is ensured during mechanical assembly, which typically takes place before connecting the signal connector to the wiring harness or directly to ground via a dedicated cable. Finally, the grounding path is very short, reducing antenna effects that can cause EMC problems. Furthermore, space is saved on the fitting, as no additional grounding tab needs to be attached.

[0013] In a preferred embodiment, the conductive and elastic contact element is a leaf spring, one end of which is permanently connected to the assembly-side grounding area. This makes the assembly process even simpler and more reliable. In a less preferred embodiment, the spring is a coil spring.

[0014] As previously mentioned, the steering wheel's grounding system typically incorporates a metal frame. To improve the conductivity of the body-side grounding area, the steering wheel's grounding system may also include a rivet or screw attached to this frame. This rivet or screw may be coated to enhance electrical contact between the conductive and elastic contact element and the body-side contact area.

[0015] In most cases, the electronic component has a printed circuit board (PCB), and in this case, the assembly-side grounding area is a metallic surface area of ​​the PCB. Furthermore, the conductive and elastic contact element can be directly connected to this metallic surface.

[0016] In a relevant application of the invention, the electronic component can be an electronic control unit (ECU) comprising a controller, a micro-ECU, or a microprocessor. This ECU can, for example, control and / or receive signals from at least one further electrical and / or electronic assembly. The at least one further electrical and / or electronic assembly can, for example, be a manually operated switch, a lighting device mounted on the steering wheel, or a touch or proximity sensor. Often, it will be preferred that more than one further electrical and / or electronic assembly is provided, with all further electrical and / or electronic assemblies being controlled by the same ECU.

[0017] If the additional electrical and / or electronic component is a touch or proximity sensor, this sensor can be arranged, in particular, in a rim of the steering wheel and be in the form of a capacitor. It is known to also use the capacitor of such a touch or proximity sensor as a heating element for the steering wheel. In this case, the capacitor can be supplied with electrical energy by a switch controlled by the ECU when the steering wheel is in heating mode.

[0018] If any of the other electrical and / or electronic assemblies also need to be grounded, this grounding will often be done via a grounding cable connected to an additional body-side grounding area of ​​the grounding device, which is located away from the body-side grounding area to which the electrically conductive and elastic contact element is connected.

[0019] The invention will now be described in more detail with reference to a preferred embodiment and the figures. The figures show: Fig. 1 a skeleton of a steering wheel body, Fig. 2 the detail D1 from Fig. 1 in a perspective view, Fig. 3 an electronic assembly designed to be mounted on the hub of the in the Fig. 1 and Fig. to be mounted on the skeleton shown in the 2nd illustration, Fig. 4 a sub-assembly of a steering wheel, which includes the Fig. 1 skeleton depicted, which is in Fig. 3 shown electronic assembly and a cover that covers the rim of the skeleton, Fig. 5 a sectional view along the plane AA in Fig. 4, Fig. 6 essentially the in Fig. 5. The object shown, however in a highly schematic representation, so that only the most essential features of the invention are shown, and Fig. 7 a variation to the one in Fig. 6 shown.

[0020] Fig. Figure 1 shows the skeleton 10 of a steering wheel body. The skeleton 10 is made of metal, usually magnesium, and is therefore both mechanically stable and electrically conductive. Because the skeleton is electrically conductive, it also forms part of a grounding system for the steering wheel body, which is connected to the vehicle chassis. The connection to the vehicle chassis is not shown, as the skeleton 10 is depicted in an unassembled, preliminary state.

[0021] The skeleton 10 of the steering wheel body comprises a hub 12, spokes 14 and a rim 16. Of particular relevance to the invention is the hub 12, which is located in Fig. 2 is shown in more detail in an excerpt.

[0022] Especially from Fig. 2 It is evident that the hub 12 of the skeleton of the steering wheel body of this embodiment has projections 24 which are used for positioning and / or mounting an electronic assembly, which will later be used in particular with regard to Fig. 3 is described, are provided.

[0023] Other embodiments may also include other types of positioning and / or fastening elements.

[0024] The upper surface (that is, the surface facing the driver when the steering wheel is installed in a vehicle) comprises a raised portion 20. In the illustrated embodiment, a rivet 22 is attached to this raised portion 20. This rivet 22 is optional and serves primarily to create a surface that retains good conductivity over a long period of time. A screw or similar component could also be used instead of the rivet. According to the definitions chosen in this application, the rivet 22 (if present) constitutes part of the grounding arrangement of the steering wheel body, namely part of a first body-side grounding area. As mentioned, the rivet is optional, and it would also be possible for a region of the frame alone to form this first body-side grounding area.

[0025] Fig. Figure 3 shows the aforementioned electronic assembly 40. This electronic assembly 40 comprises a housing 42, which is at least partially made of at least one plastic material, such that the housing forms an electrically insulating enclosure for at least one electronic component located within the housing. As will be described later, this electronic component comprises at least one printed circuit board (PCB). A signal connection 54 is provided to connect the at least one electronic component located in the housing 42 to a cable harness.

[0026] The housing 42 includes receptacles 44 that fit the projections 24 of the hub 12. In this embodiment, the receptacles 44 are designed as through holes, so that after positioning the electronic assembly 40 on the hub 12, it can be fastened to the hub 12, for example, by means of screws that extend through the receptacles 44 into the projections, which are designed here as hollow cylinders. Alternative solutions for positioning and / or fastening the electronic assembly to the steering wheel are conceivable.

[0027] A key feature is that the housing 42, namely its base, has an opening 46 which in this embodiment has the form of a round hole. Fig. Figure 3 further shows that inside the housing 42, behind the opening 46, there is a spring 60 – here a leaf spring. This spring 60 forms an electrically conductive and elastic contact element. As will be described in detail later, this electrically conductive and elastic contact element extends from a component-side grounding area (in the illustrated embodiment, from the component-side grounding area of ​​a printed circuit board that forms part of the electronic component housed in the housing 42).

[0028] Fig. Figure 4 shows a sub-assembly 5 of a steering wheel, which forms the skeleton 10. Fig. 1, the electronic assembly 40 from Fig. 3 and a cover 30 that covers the edge of the skeleton 10. This cover 30 is usually made of foam, which is later covered with a trim (e.g., leather or imitation leather). Once the steering wheel is fully assembled, the electronic assembly 40 and, if applicable, parts of the spokes 14 may be covered by an airbag module.

[0029] The electronic component 50 arranged in housing 42 is, or at least comprises, a part of an electronic control unit (ECU) (usually a complete control unit) for further electrical and / or electronic assemblies that are part of the fully assembled steering wheel; these further electrical and / or electronic assemblies are in Fig. 4 not shown, in particular because in Fig. 4 shows only one subassembly.

[0030] During the mounting of the electronic assembly 40 on the hub 12, the raised part 20, together with the rivet 22 (if present) – the body-side grounding area – enters the housing 42 through the opening 46, so that the spring 60 is pressed against the body-side grounding area and a ground connection is "automatically" established between the electronic component (the circuit board 50) of the electronic assembly 40 and the steering wheel's grounding device (and thus the vehicle ground). In this state, the body-side grounding area, the spring 60, and the assembly-side grounding area are aligned with each other, and the spring is under mechanical tension, so that a permanent and stable mechanical and thus electrical connection is established between the spring and the body-side grounding area. This is, for example, Fig. Figure 5 shows the printed circuit board (PCB) 50 of the electronic component and its assembly-side grounding area 52, from which the spring 60 extends. In the illustrated embodiment, the spring 60 is attached to the assembly-side grounding area so that it cannot be lost during the assembly process.

[0031] Fig. Figure 6 shows essentially the same thing as Fig. 5, however, in a highly schematic representation, so that only the features relevant for grounding are visible. As in Fig. As indicated by 6, spring 60 could also be a coil spring (which is not preferred in most cases).

[0032] As from Fig.As can be seen in Figure 7, it would also be possible for the spring 60 to extend through the opening 46 instead of the body-side grounding area, but this is also not preferred in most cases, as there is a risk that the spring will be damaged before the electronic assembly is mounted on the steering wheel body.

[0033] The embodiment shown is a preferred embodiment, but alternatives may also be considered: The orientation of the electronic assembly may differ, and it may be located in any area of ​​the steering wheel where grounding can be achieved. The electronic assembly may also be screwed, snapped, or latched in various ways, as long as the grounding is effective. Reference symbol list 5 Steering wheel 10 Skeleton of the steering wheel body 12 hub 14 spokes 16 wreath 20 raised part of the skeleton 22 rivets 24 lead 30 Cover 40 electronic assembly 42 cases 44 shots for an advantage 46 Opening in the case base 50 Printed circuit board of the electronic assembly 52 component-side grounding area 54 Signal connection 60 springs

Claims

[1] Steering wheel (5) for a vehicle, wherein the steering wheel (5) comprises: - a steering wheel body with an earthing device designed to be connected to the vehicle mass, wherein the earthing device includes an earthing area on the body side, - at least one electronic assembly (40) attached to the steering wheel body, wherein the electronic assembly (40) comprises a plastic housing, an electronic component arranged in the plastic housing, a signal connection and an assembly-side grounding area (52), and - at least one electrically conductive and elastic contact element extending between the assembly-side grounding area (52) and the first body-side grounding area, wherein the electrically conductive and elastic contact element is under mechanical tension so that it transmits a force between the steering wheel body and the electronic assembly (40), where the electronic component has the assembly-side grounding area (52) from which the conductive and elastic contact element extends, and wherein the plastic housing has an opening (46) through which the conductive and elastic contact element or the first body-side grounding area extends. [2] Steering wheel (5) according to claim 1, wherein the electrically conductive and elastic element is a spring (60). [3] Steering wheel (5) according to claim 2, wherein the spring (60) is a coil spring or a leaf spring. [4] Steering wheel (5) according to one of the preceding claims, wherein the grounding device of the steering wheel body comprises a metal skeleton of the steering wheel (5). [5] Steering wheel (5) according to claim 4, wherein the grounding device of the steering wheel body further comprises a rivet (22) or a screw which is attached to the skeleton, wherein the rivet (22) or the screw forms at least a part of the body-side grounding area. [6] Steering wheel (5) according to one of the preceding claims, wherein the electronic component comprises a printed circuit board (30). [7] Steering wheel (5) according to claim 6, wherein the assembly-side grounding area (52) is a metallic surface area of ​​the printed circuit board (30). [8] Steering wheel (5) according to one of the preceding claims, wherein the electronic component comprises an ECU. [9] Steering wheel (5) according to claim 8, wherein the ECU controls and / or receives signals from at least one further electrical and / or electronic assembly selected from the group comprising: a manually operated switch, a lighting device arranged on the steering wheel and a touch or proximity sensor. [10] Steering wheel (5) according to claim 9, wherein the at least one further electrical and / or electronic assembly is grounded via a grounding cable. [11] Steering wheel (5) according to claim 10, wherein the grounding cable is connected to an additional body-side grounding area of ​​the grounding device which is located away from the first body-side grounding area. [12] Steering wheel (5) according to one of claims 9 to 11, wherein the steering wheel comprises at least one touch or proximity sensor which is controlled by the ECU and / or sends signals to the ECU, wherein the touch or proximity sensor is arranged in a rim of the steering wheel. [13] Steering wheel (5) according to claim 12, wherein the touch or proximity sensor is designed as a capacitor. [14] Steering wheel (5) according to claim 13, wherein the capacitor serves as a heating element for the steering wheel, wherein the capacitor is supplied with electrical energy by a switch which is controlled by the ECU when the steering wheel is in a heating mode. [15] Vehicle with a steering wheel (5), wherein the steering wheel (5) comprises: - a steering wheel body having an earthing device connected to the vehicle mass, wherein the earthing device has a body-side earthing area, - at least one electronic assembly attached to the steering wheel body, the electronic assembly comprising a plastic housing, an electronic component arranged in the plastic housing, a signal connection and an assembly-side grounding area electrically connected to the body-side grounding area, - at least one electrically conductive and elastic contact element extending between the grounding area of ​​the electronic assembly and the body-side grounding area, where the electronic component has the assembly-side grounding area from which the conductive and elastic contact element extends, and wherein the housing has an opening through which the conductive and elastic contact element or the first body-side grounding area extends. [16] Electronic assembly (40) designed for mounting on a steering wheel body to form a steering wheel according to any one of claims 1 to 14, wherein the assembly comprises a plastic housing and at least one electronic component located inside the housing, wherein: - the electronic component has a component-side grounding area, and - the housing has an opening that is aligned with the assembly-side grounding area. [17] Electronic assembly (40) according to claim 16, wherein the electronic component comprises a printed circuit board and wherein the assembly-side grounding area is a metallic surface area of ​​the printed circuit board.

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