Patent Application
20130200656
The present invention relates to a vehicle underbody panel assembly and a related method of manufacture.
Underbody panels have traditionally been utilized to protect a vehicle undercarriage from debris and moisture. In many such instances, underbody panels also attenuate vibration and noise, potentially providing a quieter ride in the car interior.
More recently, underbody panels have been shown to provide an appreciable decrease in vehicle drag. That is, underbody panels can reduce aerodynamic drag along the undercarriage, potentially increasing fuel efficiency over certain driving speeds. However, existing metal underbody panels can add undesired weight to a vehicle, offsetting any gains achieved by a reduction in drag, particularly at slow speeds.
Molded underbody panels have been offered as an alternative to metal underbody panels. For example, thermoplastic underbody panels are lightweight and generally inexpensive to manufacture and install. However, heat from an exhaust line or other underbody components can in some instances weaken, deform or even melt thermoplastic underbody panels, rendering such panels unsuitable for use in certain regions of a vehicle undercarriage.
The present invention provides an improved underbody panel assembly and a related method of manufacture. The underbody panel assembly includes an underbody panel coupled to a thermal shield having a plurality of expansion joints. The expansion joints are adapted to accommodate a lengthening or shortening of the thermal shield in response to a corresponding lengthening or shortening of the underbody panel. The related method includes the steps of providing an underbody panel, providing a thermal shield including a plurality of expansion joints, and joining the thermal shield to the underbody panel. The thermal shield can be joined to the underbody panel using a plurality of welds, with each weld being proximate an expansion joint.
According to one embodiment, the underbody panel assembly includes an underbody panel formed of a substantially rigid thermoplastic material. The underbody body panel may be generally shaped to reduce aerodynamic drag along the vehicle undercarriage, while also reducing vehicle noise. The thermal shield is supported along the underbody panel in regions proximate an exhaust, a muffler, a catalytic converter, or other heat source. The thermal shield is generally positioned to impede the flow of heat to the underbody panel. The thermal shield is optionally formed of strips of an insulating material, including for example compression molded polyethylene terephthalate (PET).
The underbody panel assembly optionally includes a plurality of preformed expansion joints in the thermal shield. The expansion joints can include one or more folds, pleats or gussets adapted to expand under tension with sufficient shape memory to contract when unloaded. Further optionally, the expansion joints can include V-shaped accordion folds or U-shaped corrugated folds in spaced apart intervals along the thermal shield. In these and other configurations, the expansion joints include fold lines running generally perpendicular to the thermal shield longitudinal axis. In addition, the sonic welds are generally offset, or closer to one adjacent expansion joint than to another adjacent expansion joint. The underbody panel assembly optionally includes only a single spot weld in the region between expansion joints. During heating and cooling cycles, the thermal shield remains generally flush against the underbody panel, while the expansion joints expand and contract in response to a thermal expansion and contraction of the underbody panel.
According to another embodiment, a method for manufacturing an underbody panel assembly includes vacuum molding a thermoplastic preform into an underbody panel, compression molding a PET preform into a thermal shield having a plurality of resilient expansion joints, and sonic welding the thermal shield to the underbody panel at regular or irregular intervals. The sonic welds are generally offset, being closer to one adjacent expansion joint than to another adjacent expansion joint. Optionally, each sonic weld is spaced apart from an expansion joint by less than one fourth of the distance separating successive expansion joints. Intermediate segments of the thermal shield generally rest flat against the underbody panel, and can extend around contoured or angled portions of the underbody panel.
The embodiments herein can provide an underbody panel assembly positionable along a vehicle undercarriage to improve fuel efficiency. Because the underbody panel assembly is adapted to withstand elevated temperatures from an exhaust line, for example, the underbody panel assembly can extend nearer to the exhaust line, thereby encompassing more of the vehicle undercarriage. The expansion joints can accommodate repeated lengthening and shortening of the thermal shield, which might otherwise irreversibly buckle or bow under the strain of an enlarged underbody panel.
These and other advantages and features of the present invention will be more fully understood and appreciated in view of the description of the current embodiments and the drawings.
The current embodiments relate to an underbody panel assembly including an underbody panel and a thermal shield, as well as methods for manufacturing the same.
Referring now to
As noted above, the underbody panel 12 is generally shaped to reduce drag and/or vehicle noise with minimal added weight. For example, the underbody panel 12 can be positioned immediately below a vehicle chassis while defining a major surface 18 that is substantially parallel to the road or other driving surface. The major surface 18 can terminate proximate a high temperature heat source, including for example an exhaust pipe, a catalytic converter, or a muffler. The major surface 18 is substantially planer in
Depending on the melting point of the selected thermoplastic material, radiant heat from an exhaust pipe (or other heat source) can thermally deform the underbody panel 12, potentially causing undesired pockets or bubbling. To maintain the structural integrity of the underbody panel 12, the thermal shield 14 is positioned to impede the flow of heat toward the underbody panel 12 and/or to reflect heat away from the underbody panel 12. As shown in
As also shown in
As noted above, the underbody panel assembly 10 is subject to a range of operating temperatures influenced, in part, by radiant heat from a nearby heat source and by ambient temperature variations. Under heating and cooling cycles, the underbody panel 12 and the thermal shield 14 expand and contract in proportion to their respective coefficient of thermal expansion. For example, the underbody panel 12 can expand by a greater amount or at a greater rate than the thermal shield 14 when exposed to an increasing temperature gradient. Because the underbody panel 12 and the thermal shield 14 are joined together, the thermal shield 14 can undergo tension between spot welds 24 during thermal expansion of the underbody panel 12. In order to minimize plastic deformation of the thermal shield 14 and the risk of welds failure, the expansion joints 16 absorb the expansion of the thermal shield 14 between spot welds 24. The expansion joints 16 return to their original shape during cooling cycles, caused by a shortening of the underbody panel 12 during cooling cycles. That is, the expansion 16 joints will return to their original state with sufficient shape memory for repeated expanding and contracting.
Referring again to
The underbody panel assembly 10 having been briefly described, a method for forming the underbody panel assembly 10 can be understood with reference to
With reference to the flow diagram of
The method of the present embodiment further includes forming the thermal shield 14 as described below in connection with the flow diagram of
Once the thermal shield 14 is removed from the compression mold, the thermal shield 14 is ready for attachment to the underbody panel 12. At step 56, the thermal shield 14 is spot welded to the underbody panel 12 at spaced apart portions of the thermal shield 14. Welding of the thermal shield 14 to the underbody panel 12 can be performed according to any suitable technique, including for example ultrasonic welding, radio frequency welding, and arc welding. The spot welds 24 are generally offset, i.e. closer to one adjacent expansion joint 16 than to another adjacent expansion joint 16. For example, a sonic weld 24 can be a distance X from a first adjacent expansion joint 16 and a distance 4X from a second adjacent expansion joint 16. Other multiples of X can also be utilized, include multiples of between 1.5 and 10, inclusive. Intermediate segments 22 generally rest flat against the underbody panel 12 in room temperature conditions. In addition, the cured thermal shield 14 can molded to conform to a specific contour of the underbody panel 12. As a result, the thermal shield 14 may also extend around corners or other non-planar surfaces of the underbody panel 12, and can continue along portions of the underbody panel 12 distal from high temperature heat sources.
To reiterate, step 56 includes introducing multiple welds 24 between the underbody panel 12 and the overlying thermal shield 14. Alternative attachment techniques can also be utilized, including rivets, pins, clips or screws, for example. In addition, the thermal shield 14 can include expansion joints 24 in some regions but not other regions. For example, the thermal shield 14 can include expansion joints 24 in regular intervals along predominantly straight sections, with minimal or perhaps no expansion joints 24 near curved or angled portions of the underbody panel 12. In addition, the expansion joints 24 can alternatively be formed in the thermal shield 14 after the curing process of step 52, including for example the manual introduction of a folds or gussets at regular or irregular intervals.
The completed underbody panel assembly 10 is positionable along a vehicle undercarriage 100 to improve fuel efficiency and noise reduction. For example, left and right side underbody panel assemblies 10 are positionable on either side of an exhaust line on a vehicle undercarriage. Because the thermal shield or liner 14 is adapted to withstand elevated temperatures from the exhaust line, the left and right side underbody panel assemblies 10 extend nearer to the exhaust line, thereby encompassing more of the vehicle underbody. As a result, underbody drag is reduced at high vehicle speeds, contributing to an overall increase in fuel efficiency. In addition, the expansion joints 16 accommodate repeated heating and cooling cycles, which might otherwise compromise the spot welds 24 and/or form gaps in the region between the underbody panel 12 and the thermal shield 14. The present invention can additionally utilize a minimal number of spot welds, while also saving material and manpower costs in the assembly of underbody panel assemblies 10. For illustrative purposes, the current embodiments are described in connection with an underbody panel, however, the present invention can be utilized in connection other protective panels, including for example the vehicle underhood. In these or other embodiments, the underbody panel 12 can additionally be formed of non-polymeric materials, including for example fiberglass or metals such as aluminum and aluminum alloy.
The above descriptions are those of the current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any reference to elements in the singular, for example, using the articles “a,” “an,” “the,” or “said,” is not to be construed as limiting the element to the singular.
