I. Field of the Invention
The present invention relates to vehicle doorbeams.
II. Description of the Art
Vehicle doorbeams are widely used in the automotive industry to enhance the impact strength of vehicle doors and thereby enhance safety. Vehicle manufacturers desire to make vehicles safer for passengers and to improve fuel efficiency. Therefore, doorbeams must strike a balance between strength to resist impacts and reduced weight to increase fuel efficiency.
One method to increase the strength of the beam is to increase the thickness of the material from which the beam is fabricated. This improves passenger safety but also increases the weight of the beam, thereby decreasing fuel efficiency.
Another technique for increasing beam strength is to add extra reinforcing pieces of metal to the doorbeam as illustrated in U.S. Pat. No. 5,277,469 issued Jan. 11, 1994 to Klippel. These reinforcements add weight to the beam. The reinforcements also increase the complexity, cost, and required labor to fabricate the beam.
Another technique for increasing beam strength is to make the doorbeam out of lightweight, high-strength alloys. While the alloys are relatively lightweight, they are expensive to manufacture. Another technique for increasing beam strength is to fabricate the entire beam of a lightweight material, such as aluminum, with a relatively thick cross section and wall thickness. This approach eliminates most of the weight savings. These beams are also difficult and expensive to manufacture, difficult to adapt between different doors, and hard to fit within narrow profile doors.
Other methods include fabricating the doorbeam with special geometric cross sections such as trapezoids and ellipses as seen in U.S. Pat. No. 6,020,039 issued Feb. 1, 2000, to Cline et al. Other beams are filled with a composite material in an attempt to improve impact strength. All these beams are difficult, expensive and time consuming to manufacture. They are also difficult to adapt among various doors on different makes and models of vehicles.
The aforementioned problems are overcome in the present application wherein a one-piece doorbeam is rollformed from a continuous web of stock having a varying thickness profile across its lateral extent. More specifically, a web has stock at least two different thicknesses across its width; and the web is rolled into a tubular shape and welded along the resulting seam.
The present invention has a variety of advantages over prior techniques. First, the beam provides thicker walls where needed to increase passenger safety and thinner walls elsewhere to save weight. Second, the complete beam may be fabricated as a single piece without additional pieces, expensive alloys, composite fillers or unusual cross sections. Consequently, the beam is relatively labor-efficient and inexpensive, while providing the necessary strength and desired weight. The beam is also easily adaptable between vehicles by changing the overall length of the resultant rollformed segments.
These and other objects, advantages and features of the invention will be more fully understood and appreciated by reference to the detailed description of the preferred embodiments and the drawings.