Patent Application
20150217821
This disclosure relates to a method of manufacturing a vehicle body by initially welding aluminum components in precise geometrical alignment and subsequently joining the components with cold-formed joining processes.
Individual parts or sub-assemblies are assembled in a “framing operation” for vehicle bodies that are comprised primarily of steel with resistance spot welds to establish the dimensional relationship between the components and sub-assemblies. Spot welding equipment is flexible and can be used to form welds in a variety of different applications with variations in the thickness of parts and the number of panels to be joined by the weld, or part stack-up. Vehicle bodies may be assembled in a framing operation where major sub-assemblies (e.g. a front end sub-assembly, a right side sub-assembly, a left side sub-assembly, a roof sub-assembly, an underbody sub-assembly and a rear end sub-assembly) are placed in fixtures and then welded together to set the geometry of the vehicle. After the geometry is set, “respot” welds are formed along the length of the joints between the major sub-assemblies adding structural joints to strengthen the assembly.
Interest in using alternative materials to steel has driven the development of aluminum-intensive vehicles as the automotive industry continues to focus on reducing the weight of vehicles to meet customer quality expectations and fuel economy standards. Joining methods for aluminum intensive vehicles rely predominantly on self-piercing riveting processes. Self-piercing rivets provide high strength joints and excellent durability performance. Riveting multiple joints with a single rivet gun increases the utilization of the rivet gun in particular where multiple joints are formed along a lengthy seam between two sub-assemblies that have the same gauge and panel stack-up. In addition to self-piercing rivets, clinch joints may be formed to join adjacent parts in aluminum intensive vehicles. In some cases, aluminum parts may be welded together but the lower strength and reduced durability of aluminum welds compared to self-piercing rivets can limit the applicability of such welds for vehicle body applications.
Design requirements associated with each major sub-assembly may be significantly different. Some sub-assemblies may require higher durability and fatigue requirements, while other sub-assemblies may be joined together with a view to absorbing impacts during collisions. Designing vehicle body structures to meet these different design requirements results in the use of different sheet metal gauges and alloys in each sub-assembly.
Self-piercing rivets require specific rivet geometry and die geometry that often must be changed if the gauge of the material or number of panels to be joined varies. In framing operations for major sub-assemblies, there are large variations in sheet metal stack-ups and material gauges. Since one self-piercing rivet tool can be used for only a limited range of joints between major sub-assemblies, many additional robots and self-piercing rivet tools must be used to accommodate the wide range of part thicknesses and stack-ups encountered in framing operations to set the geometry of the major sub-assemblies.
This disclosure is directed to solving the above problems and other problems as summarized below.
A method of manufacturing a vehicle body is disclosed that is performed in which the geometry of the vehicle body is set by placing the major sub-assemblies together in fixtures and selectively spot welding together a plurality of aluminum panels that make up the major sub-assemblies. As referred to in this disclosure, the major sub-assemblies include a front end sub-assembly, a right side sub-assembly, a left side sub-assembly, a roof sub-assembly, an underbody sub-assembly, and a rear end sub-assembly. The welds used to geometry set are “manufacturing welds” that are primarily used to set the geometry but are not necessarily sufficient for structural strength and durability. The joints between adjacent major sub-assemblies are subsequently joined together with cold-formed joints such as self-piercing rivets or clinch joints or a combination of self-piercing rivets and clinch joints that provide strong joints required for structural integrity.
The method of manufacturing may further include setting the geometry of the major sub-assemblies by assembling aluminum panels making up the major sub-assemblies in a fixture and spot welding the panels together at spaced locations. After setting the geometry with aluminum spot welds, the panels are joined with self-piercing rivets and clinch joints or a combination of self-piercing rivets and clinch joints to establish structural joints within the major sub-assemblies.
According to one aspect of this disclosure, a method is disclosed for manufacturing a vehicle body that comprises placing a plurality of sub-assemblies together in alignment in a series of fixtures to frame the vehicle. The sub-assemblies are welded together at spaced locations with resistance spot welds. Each of the sub-assemblies is then joined together with each adjacent sub-assembly with cold-formed joints, for example self-piercing rivets and clinch joints.
According to other aspects of this disclosure, the plurality of sub-assemblies may include a front end sub-assembly, a right side sub-assembly, a left side sub-assembly, a roof sub-assembly, an underbody sub-assembly and a rear end sub-assembly. A first one of the sub-assemblies may include a first plurality of aluminum panels that are welded to a second plurality of aluminum panels of a second one of the sub-assemblies. The number of panels in the first plurality of panels may be different than the number of panels in the second plurality of panels. The thickness of panels stacked in the first plurality of panels may be different than the thickness of panels stacked in the second plurality of panels.
The method may further comprise assembling a plurality of aluminum panels together, welding the panels in a specified geometric setting with resistance spot welds, and joining the panels together between the welds with cold-formed joints to form one of the sub-assemblies.
According to other aspects of this disclosure relating to the latter method, a first one of the sub-assemblies may include a first plurality of aluminum panels that are welded to a second plurality of aluminum panels of a second one of the sub-assemblies. The number of panels in the first plurality of panels may different than the number of panels in the second plurality of panels because of the versatility and flexibility of welding tools. A geometry setting weld may be effective even if the thickness of panels stacked in the first plurality of panels is different than the thickness of panels stacked in the second plurality of panels.
The above aspects of this disclosure and other aspects are described below in greater detail with reference to the attached drawings.
A detailed description of the illustrated embodiments of the present invention is provided below. The disclosed embodiments are examples of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed in this application are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to practice the invention.
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Welding aluminum can be difficult and the strength of a welded joint may not be sufficient to meet the structural design requirements. One advantage of welding over self-piercing rivets is that the weld tooling is more flexible. The same weld gun may be used to join parts including different numbers of panels in the stack-up and also may be used to join parts having different material thicknesses or gauges. For example, the same weld gun or type of weld gun tooling may be used to join a front end sub-assembly and also may be used to assemble body sides and underbody or roof sub-assemblies that have different types of aluminum alloys and material gauges.
Rivets provide increased strength and may be better suited to meet design requirements for a front end sub-assembly being joined to the vehicle body because they offer high strength, durability and can meet fatigue requirements. Moreover, self-piercing riveted joints offer high dynamic strength which may be advantageous in body side sub-assemblies which must be joined in such a way that they meet side impact crash requirements.
Clinch joints may be used to reduce costs where less joint strength is required. The use of self-piercing rivets are better suited to joints that include three or possibly four panels that are joined together. Cold-formed joints are sensitive to materials and the gauges of the panels involved in a given joint. A given self-piercing rivet gun or clinch tool may be used to form many joints where a region of similar panel combinations of a set of sub-assemblies is to be joined.
The resistance spot weld joints used for geometry setting may be classified as “manufacturing welds” that are added for manufacturing purposes to facilitate setting the geometry of the parts to be assembled. Joints that are required to meet structural requirements in the vehicle body may then be inserted as cold-formed joints, such as self-piercing rivets and clinch joints. These joints may be formed in groups where the same parts are to be joined in one area and can be used to meet exacting structural requirements of the vehicle body.
The disclosed method provides advantages over prior art assembly manufacturing techniques because it enables greater flexibility in geometry setting operations. This added flexibility reduces production tooling costs and reduces the investment in robots and other tooling used in assembly operations.
While specific embodiments are described above, it is not intended that these embodiments describe all possible forms of the disclosed apparatus and method. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure as claimed. The features of various implementing embodiments may be combined to form further embodiments of the disclosed concepts.
