This invention relates generally to a molded steering wheel assembly.
Steering wheels for vehicles are well known. Some steering wheels include a circular rim connected by spokes to a central hub. Moving the rim turns the spokes and the central hub, which coveys torque to the vehicle's steering system. The steering wheel may include an airbag module mounting location near the central hub of the steering wheel.
Typical steering wheels maintain performance requirements, such as meeting certain strength requirements. Such requirements help ensure performance of the steering wheel under various conditions. As an example, some requirements are directed toward maintaining steering control over the vehicle under a wide range of events. Other requirements relate to the allowable deflection or bend when loaded.
Many steering wheels, especially molded steering wheels, require a support structure of a dissimilar material within the rim to meet the performance standards. Accordingly, some steering wheels overmold a cast metal armature with polyurethane to form the rim. The armature provides support and resists deflection, but undesirably increases the weight, cost, and complexity of the steering wheel. The step of overmolding the cast metal armature also complicates the assembly process. Other steering wheel support structures strengthen the airbag module mounting location for example.
An example steering wheel assembly includes an airbag module receiving surface generally defining a first plane. A lower portion includes a lower rim portion and the airbag module receiving surface. An upper portion includes an upper rim portion for covering the lower rim portion. The upper rim portion and the lower rim portion define a second plane spaced from said first plane where the upper rim portion contacts the lower rim portion. The lower portion may include an overmolded hub plate.
The steering wheel assembly may include an upper rim portion and a lower rim portion. An upper spoke portion secures to the upper rim portion, and a lower spoke portion secures to the lower rim portion. An airbag module mounting surface and the upper spoke portion define an airbag module receiving space.
An example method of assembling a steering wheel includes molding an upper rim portion together with an upper spoke portion and molding a lower rim portion together with a lower spoke portion and an airbag module mounting surface. The method also includes welding the upper rim portion to the lower rim portion.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
The present invention is more particularly described in the following description and examples that are intended to be illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. As used in the specification and in the claims, the term “comprising” may include the embodiments “consisting of” and “consisting essentially of.” All ranges disclosed herein are inclusive of the endpoints and are independently combinable. The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value; they are sufficiently imprecise to include values approximating these ranges and/or values.
As used herein, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially,” may not be limited to the precise value specified, in some cases. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value.
The present invention provides a steering wheel assembly that includes an airbag module. The airbag module includes a receiving surface generally defining a first plane. A lower portion includes a lower rim portion and the airbag module receiving surface. An upper portion includes an upper rim portion for covering the lower rim portion. The upper rim portion and the lower rim portion define a second plane spaced from said first plane where the upper rim portion contacts the lower rim portion. The lower portion may include an overmolded hub plate.
An example steering wheel assembly 10 includes an upper portion 14 and a lower portion 18. A driver airbag module 22 secures within an airbag module mounting space 26 defined by the upper portion 14 and the lower portion 18. A plurality of lower spokes 30 connect the airbag module mounting space 26 to a lower rim 34. A plurality of upper spokes 38 connect to an upper rim 42. The upper portion 14 and the lower portion 18 are injection molded of a high-strength thermoplastic material. A suitable thermoplastic material is deformable and absorbs energy during an impact event. Specifically, a suitable thermoplastic material has the properties of elastic deformation at low loads and plastic deformation at high loads. Low loads being characterized as those encountered during normal operation of a steering wheel, and high loads being characterized as severe abuse or impact events as defined under Federal Motor Vehicle Safety Standard 203. Further, in one embodiment, the thermoplastic material has a 20 percent stress to failure rating as measured by tensile testing in accordance with ASTM D-638. Examples of suitable thermoplastic materials include, but are not limited to, silicone modified polycarbonate, nylon, polyesters, polyphenylene oxide, polypropylene, mixtures thereof, and foamed materials thereof. In the exemplary embodiment, silicone modified polycarbonate, commercially available from SABIC Innovative Plastics under the trademark LEXAN® EXL, is used. The upper portion 14 and lower portion 18 are generally aligned relative a rotational axis extending through a vehicular steering column (not shown).
The airbag module mounting space 26 provides clearance for mounting an airbag module or similar safety accessory within the steering wheel assembly 10. The airbag module 22 mounts within the airbag module mounting space 26 adjacent a pair of airbag module receiving surfaces 28 that define a first plane generally transverse the rotational axis.
The bottom of the airbag module mounting space 26 includes a hub plate assembly 44 having a hub 46, as shown in
The general shape of the hub plate assembly 44 enhances the connection between the hub plate assembly 44 and the lower portion 18. As an example, the geometries of the example steering wheel assembly 10 prevent relative rotational movement between the hub plate assembly 44 and the lower portion 18.
Referring now to
In this example, the upper portion 14 and the lower portion 18 each include a plurality of molded strengthening ribs 66, as shown in
The upper portion 14 and the lower portion 18 contact each other along a second plane generally perpendicular to the steering column axis and spaced from the first plane defined by the airbag module mounting surfaces 28.
The steering wheel assembly 10 may be leather wrapped or painted. Other examples include finishing the steering wheel assembly 10 with an in-mold film or hydrographic design. The steering wheel assembly 10, when including a recyclable thermo-plastic, provides an eco-friendly design.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
This application claims priority to U.S. Provisional Application No. 60/928,475, which was filed on May 9, 2007.
Number | Date | Country | |
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60928475 | May 2007 | US |