Patent Application
20050186413
This application claims priority to German Patent Application No. 10 2004 008 718.0, which was filed on Feb. 23, 2004.
The present invention relates to a vehicle body panel, and a method of manufacturing the vehicle body panel.
Vehicle body panels are connected to a vehicle frame to define an outer skin of a vehicle in a final assembled condition. One example of a vehicle body panel is a roof module that defines almost an entire vehicle roof. The roof module is a composite structure that is preferably attached on a roof frame by bonding. Other vehicle body panels include e.g. flaps, doors, fenders, and bumpers.
Vehicle body panels may be produced to have an excellent surface quality by using a thin, deep-drawn plastic sheet that is dyed throughout, and which is provided with a foam backing on a rear side. For a liquid plastic material to adhere to the plastic sheet, the plastic sheet is flame-treated immediately before attaching the foam backing. During the flame-treatment, a gas flame is swept over the rear side to “activate” the plastic sheet. During activation, molecular chains at a surface of the plastic sheet are broken up. Oxygen and hydroxyl groups will attach to the broken-up molecular chains. At the same time, surfaces on the plastic sheet are cleaned and a micro-roughening is performed, which also provides for a better connection between the plastic sheet and a polyurethane (PU) material.
In addition, a previously non-polar surface of the plastic sheet is polarized to a certain degree, and wettability is increased. In such a flame-treatment, it is known to admix a vaporizable silicon compound to a combustible gas/air mixture, which is referred to as a “silica-coating technique.”
Flame-treatment, or silica-coating where appropriate, is a method step that involves high reject rates. These high reject rates are due to high degrees of extension that occur in the deep-drawing process, and the associated stretching of the plastic sheet, during the flame-treatment or the silica-coating process, in which the plastic sheet tends to be very easily damaged. Moreover, the flame-treatment is typically a manual process where desired low reject rates are achievable only with very experienced staff.
It is the object of the invention to improve a method of manufacturing a vehicle body panel that produces a higher process reliability, in addition to overcoming the other deficiencies mentioned above.
A method for manufacturing a vehicle body panel includes flame-treating a rear side of a plastic sheet that defines at least a portion of an outer skin of a vehicle, plastically reshaping the plastic sheet, and providing the rear side of the plastic sheet with a foam backing or an injection-molded backing.
In the method according to the invention, the plastic sheet is flame-treated before it is plastically reshaped, that is, usually before a deep-drawing process. In this state, the plastic sheet is more even than after the reshaping process. Further, the plastic sheet is preferably flat and of a constant material thickness (approx. 0.5 to 1.5 mm) so that no portions with high degrees of extension are present, and the flame-treatment can be performed more easily and more uniformly. Surprisingly, it is found that activation of the plastic sheet, as achieved by the flame-treatment, is not reversed during reshaping. The method according to the invention renders it possible to reduce reject rates; furthermore, the use of a very simple automated flame-treatment step provides easy documentability of this method step, by which a manufacturer is able to provide written evidence that all method steps have been fulfilled in producing the product.
One example embodiment provides for a silica-coating of the rear side of the plastic sheet, which is attained by admixing a vaporizable silicon compound, in particular silanes or an organic silicon compound such as organosilanes. An extremely thin layer of a silicon compound, particularly in a form of a silicon oxide SiOx (were x is about 2), is deposited on the rear side of the plastic sheet. This thin layer, which is only a few nanometers thick, has a certain roughness and increases adhesive surface tension. It also acts as a diffusion barrier layer.
In one example, the rear side of the plastic sheet has the foam backing across an entire surface area. In this example, the plastic sheet is also provided with the layer of the silicon compound across the entire surface area. A liquid PU material is preferably applied to provide the foam backing.
The invention also relates to a vehicle body panel having a deep-drawn plastic sheet provided with a foam backing or an injection-molded backing of a PU material wherein the vehicle body panel defines part of the outer skin of the vehicle. Applied on the rear side of the plastic sheet is a thin layer of a silicon compound, in particular SiOx. The PU material adjoins this thin layer.
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 method of manufacturing the roof module 10 will now be explained with reference to
Prior to the plastic sheet 14 being plastically reshaped, the plastic sheet 14, which is substantially flat, is first flame-treated. To this end, a burner 16 is moved along the rear side 18 of the plastic sheet 14 and produces a flame that is denoted by reference numeral 22. The burner 16 utilizes a vaporizable silicon compound, in particular silanes or a vaporizable organo-silicon compound, which is admixed to a combustible gas/air mixture in a metering valve 20.
In the flame-treatment, a silicon compound is deposited on the rear side 18 in the form of a layer 24 of SiOx, with x being approximately 2. The layer 24 has a thickness of a few nanometers. In
In the next method step, the plastic sheet 14, which has been activated by the flame-treatment, is placed in a deep-drawing die 26, where the plastic sheet 14 is plastically reshaped.
Finally, after deep-drawing, the plastic sheet 14 is placed in a foaming die 28 where a liquid PU material 30 is applied onto a rear side of the layer 24, which covers an entire rear side 18 of the plastic sheet 14. Then the foaming die 28 is closed and the PU material 30 expands. This process, often referred to as “back-foaming,” provides a foam backing directly to the layer 24.
The method steps shown in
The finished body panel shown in
In addition to applying liquid PU material 30 onto the rear side 18 of the plastic sheet 14, glass fiber sections are preferably incorporated into the plastic layer during application in a process referred to as a LFI (long fiber injection) process.
In place of the process of providing a foam backing as shown in
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 008 718.0 | Feb 2004 | DE | national |
