Patent Application
20180186411
The invention relates to an automotive body shell comprising a composite underbody component being made of fibre reinforced plastic material, namely carbon-fibre-reinforced plastic material (CFRP) and rocker panels connected to the composite underbody component at outer sides thereof. The invention also relates to a method for producing such an automotive body shell.
WO 2011/128081 A1 was published on 20 Oct. 2011 in the name of Roding Automobile GmbH. It describes an automobile body shell with a very stiff passenger cell having a floor part made from carbon-fibre-reinforced plastic material. The floor part is provided with lateral rocker panels which are adhesively bonded to the side skirt sections of the floor part to increase the stiffness during impact. The rocker panels are made from carbon-fibre-reinforced plastic material. One problem is that said structure is not appropriate for large scale production and the thereto related test procedures.
It is a object of the invention to provide an automobile body shell which is suitable for cost-saving mass production.
An embodiment of the automobile body shell comprises at least one rocker panel which is at least partially made of ductile material, preferably of metallic material, such as steel and/or aluminium and/or a similar material. Alternatively or in addition the rocker panels can be filled with energy absorbing material such as a energy absorbing foam. Thereby a stiff load bearing passenger cell arranged at the inside is combined with at least one rocker panel forming part of a crush zone for absorbing deformation energy. By the invention described herein a body shell comprising the above mentioned energy absorbing elements is suitable to be integrated in large scale mass production.
Carbon-fibre-reinforced plastic material has a higher strength, a lower elongation at break and thereby a higher bending and torsional stiffness can be achieved compared to most metallic materials including steel and aluminium that are commonly used for automobile body shells. On the other hand, a very high stiffness may be of disadvantage in view of crash situations where kinetic impact energy has to be absorbed, e.g. by deformation energy. By using ductile material, e.g. such as metallic material, for the rocker panels and non-ductile material, such as carbon-fibre-reinforced plastic material, at least for certain load bearing parts of the underbody component, the automobile body shell can be optimized in both respects, namely in obtaining a stiff passenger cell in combination with rocker panels which can more effectively deform under impact forces. The deformation is thereby concentrated in the rocker panels whereas the composite underbody component keeps almost undeformed up to a certain level. Under normal conditions, the rocker panels can form part of the load bearing structure.
Accordingly, for an automobile body shell having a stiff load bearing passenger cell and a crush zone, it is preferred to use a composite underbody component made at least partially of carbon-fibre-reinforced plastic material as a stiffening part of the passenger cell and the rocker panels as a part of the crush zone. On the other hand, if the underbody structure of the passenger cell and the rocker panels are both made from metallic material, as this is actually most common in the art, the passenger cell may suffer considerable deformations in crash situations unless it is significantly reinforced.
The difference is considerable: for example, an Euro NCAP polecrash with 29 km/h produces 90 mm less deformation of the passenger cell if a composite underbody component according to the invention is used compared to a common underbody structure made from metallic material. The invention accordingly ensures more passenger survival space what course also applies for front or rear impacts if there are metallic crushing elements provided as well.
An automobile body shell according to the invention normally comprises an underbody component being made of fibre-reinforced plastic material, and at least one rocker panel interconnected to the underbody component at outer sides thereof, extending in longitudinal direction of the underbody component. The at least one rocker panel is in transversal direction (transverse to the driving direction) designed in a more deformable manner (compared to the underbody component) such that impact energy occurring in said lateral direction is absorbed by deformation of the rocker panels. The rocker panels are mechanically interconnected to the underbody component. They preferably form part of the load bearing structure of the automobile body shell and thereby contribute to the stiffness of the overall structure, i.e. the automobile body shell. The underbody component normally comprises at least one crossmember extending in transversal direction foreseen to receive the load in transversal direction and distribute it within the structure of the underbody component. Good results may be achieved if the at least one crossmember is mechanically interconnected to the at least one rocker panel. If appropriate the rocker panels arranged on each side of the underbody component can be interconnected to each other via the front and/or the back of the underbody component. The fibre-reinforced plastic material of the underbody component preferably comprises carbon fibres and/or kevlar fibres and/or glass fibres and/or metallic fibres and/or natural fibres. The at least one rocker panel may comprise an outer shell. Very good results may be achieved if the outer shell is at least partially made of ductile sheet metal and/or composite material. Depending on the field of application the outer shell may comprise several layers of sheet metal and/or composite material. In a preferred variation the outer shell of the at least one rocker panel has in transversal direction an in principle a C-shaped cross-section. The outer shell of the at least one rocker panel may have in transversal direction a multi-cell cross-section. The outer shell of the at least one rocker panel may comprise at least one drainage, e.g. in the form of one or several holes or openings. If appropriate the drainage can be closed after production. The at least one rocker panel may comprise foam material and/or honeycomb for absorbing impact energy during impact. The foam material and/or honeycomb material is preferably arranged between the underbody component and an outer shell of the at least one rocker panel. The foam material and/or honeycomb material may at least during impact form at least one support between the underbody component and an outer shell of the at least one rocker panel.
In an embodiment of the invention the composite underbody component at least essentially extents over the area of the passenger cell. It is even preferred that the composite underbody component does at least not essentially extend beyond the area of the passenger cell in the horizontal direction and not beyond the height of the middle tunnel in the vertical direction. Thereby the composite underbody component is a somewhat large part that can replace several tens of metallic parts that are assembled in common BIW metallic structures for building up the floor panel of the passenger cell. The effort for assembling the several tens of parts is saved of course as well. On the other hand, the composite underbody component of the invention is small enough that it can be produced in a simple form by a RTM process. The composite underbody component may even be in one piece and/or may be free of cavities and/or may be free of undercuts. This allows to use a high/speed low cost RTM injection process and cost effective/high speed preform and resin technologies. The preform may be preassembled in one or only a pieces as well.
In a preferred variation of the invention the composite underbody component is primarily made of a carbon-fibre-reinforced plastic material (CFRP) produced by a RTM process. It is free of cavities and at least almost free of undercuts so that it can be molded as a monolithic piece in one step in a two-part or at least a three-part form. If appropriate the mold may comprise one or several sliders in the case that an undercut needs to be formed.
In metallic constructions critical tolerances can only be achieved after the assembly of their parts by machining. Components in carbon-fibre-reinforced plastic material do have much less tolerances and lower variation, thus reducing the necessary amount of post-machining. This is in particular the case if the composite underbody component is in one piece.
All this, separately or in combination, renders the automotive body shell as described herein suitable for an even automated large scale production. The increased precision and higher automation helps to compensate price differences between carbon-fibre-reinforced plastic material and traditional metallic materials. Other than in monocoque designs where the passenger cabin is completely or at least predominantly made in one piece from carbon-fibre-reinforced plastic material, the composite underbody component of the invention can be designed suitable for use in existing standardized production lines being actually adapted for processing metallic parts.
By automotive body shell according to the invention made from a combination of fibre reinforced material on the inside and ductile rocker panels on the outside, in comparison with even light metallic materials a considerable reduction in weight and a significant increase in safety may be realized. For example, just for the floor part of the passenger cell an advantage in weight of about 30 kg (50%) can be obtained in comparison with a conventional steel construction, wherein this percentage even increases above average with increasing demands in the stiffness of the passenger cell.
Further in comparison with metallic materials, the higher stiffness of the composite underbody component and the passenger cell as a whole also provides a higher introduction rigidity towards vibrational exitations at the connections points to the movable vehicle components resulting in an enhanced noise comfort.
Depending on the field of application, the underbody component has a trough shaped structures comprising a at least one crossmember extending in a transversal direction and a bottom. Alternatively or in addition the underbody component may comprise at least one crossmember extending in longitudinal direction. The at least one crossmember preferably has an open cross section which during production in a forming tool may be demolded from the top and/or from the bottom in vertical direction, i.e. which does not comprise any hindering undercut. Good results may be achieved if the at least one crossmember is forming a tunnel in the lengthwise and/or transversal direction. A crosswise arrangement of several crossmembers results in a high stability and low weight of the underbody component. For automobiles provided with an electric drive the underbody component may be provided with at least one trough shaped structure for receiving a battery pack. This trough could be closed by a covering part also made form carbon-fibre-reinforced plastic material. Embedded in such a trough the battery pack would be well protected against damages by deformation in crash situations.
Carbon-fibre-reinforced plastic material behave like relatively precious metals due to the electrochemical properties of the carbon. This has so far limited the application of carbon-fibre-reinforced plastic material in automotive applications because metallic parts in contact with such material may undergo strong corrosion in a short time. If required, the invention solves this problem by providing a layer of insulating material between connection faces of a composite underbody component and a rocker panels made from ductile metal at which connection faces composite underbody component and the rocker panels are connected to each other. The layer provides a galvanic isolation between the carbon-fibre-reinforced plastic material of the composite underbody component and the metallic material of the rocker panels. This may as well apply to other metallic parts which are connected to the composite underbody component such as front end side rails, a bulkhead, a front seat cross member, a rear seat cross member and/or A, B and/or C pillar inners.
An underbody component made from fibre reinforced plastic material in combination with rocker panel according to the invention normally comprises one or several first connection faces arranged in sequence or parallel to each other along an outer edge of the underbody component.
Depending on the field of application, the fibre-reinforced plastic material of the underbody component may comprise carbon fibres and/or glass fibres and/or metallic fibres and/or natural fibres or a combination thereof.
According to the state of the art automobile body shells or so called Bodies in White are treated after their assembly in a cathodic dip painting process. The fibre-reinforced plastic material used for the composite underbody component therefore has the property to withstand such a cathodic dip painting process with a temperature of least 180° C. during at least 30 min. In addition, the carbon-fibre-reinforced plastic material shall not contaminate the ingredients of the cathodic bath.
As well according to the state of the art various parts of automobile body shells or so called Bodies in White are connected to each other by adhesive bonding techniques. In view of that, in a further preferred embodiment, the layer providing the galvanic isolation is an adhesive material which also provides an adhesive bond between the composite underbody component and the rocker panels. Thereby the one layer provides a advantageously a function.
Adhesives used for automobile body shells usually achieve their final bonding strength by curing at elevated temperatures. The adhesive used for the insolating layer preferably obtains its final bonding strength under the temperature conditions that prevail in the above mentioned cathodic dip painting process. The adhesive may be a structural adhesive which is a heat cured (at 180° C.), fracture-toughened epoxy adhesive and which is capable of bonding oily galvanized steel. At least for handling the automobile body shell prior to the cathodic dip painting, i.e. as long the adhesive is not yet cured, the composite underbody component and the at least one rocker panel may be attached to each other by mechanical means. Possible techniques include punch riveting and/or high speed joining and/or steel flow forming screws and/or clips. In case of a greater thermal extension of the metallic material of the rocker panels in comparison to the fibre-reinforced plastic material of the underbody component, beads may be foreseen in the rocker panels along the connection faces in particular between the possible mechanical fixation positions.
In view of the above described galvanic isolation by providing a isolating layer the between mutual faces of the composite underbody component and the rocker panels, a method for producing an automobile body shell according to the invention is characterized by the following steps:
It is to be understood that both the foregoing general description and the following detailed description present embodiments, and are intended to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings are included to pro-vide a further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments, and together with the description serve to explain the principles and operation of the concepts disclosed.
The herein described invention will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the invention described in the appended claims. The drawings are showing:
Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.
Referring now to the accompanying drawings wherein like reference numerals denote like elements through the various views, one exemplary embodiment of an automobile body shell is shown in
The underbody component 20 is in the shown variation symmetrically shaped with regard to a plane (extending in the x-z-directions) along centre line CL and includes a tunnel 21 in the form of an inverted channel longitudinally extending between a front end wall structure 22 and a rear end wall structure 23. If present, the middle tunnel 21 can be foreseen to receive a drive shaft. Alternatively or in addition, the tunnel 21 can be foreseen to receive a battery, e.g. in case of an electric drive.
A first and a second cross member 24, 25 extend transversely between the tunnel 21 and lateral side wall structures 26 to which the rocker panels 30 are interconnected as described herein. The first and the second crossmembers 24, 25 are having an open cross-section facing downward such that they can easily be demolded during production. Other shapes are possible. The first and the second crossmembers 24, 25 serve among others as reinforcing rails in the transverse direction avoiding unwanted deformation (collapse) of the underbody component e.g. during side impact. The underbody component furthermore comprises a bottom 35 which extends between the side wall structures 26 and if present, the crossmembers 24, 25, respectively the tunnel 21, if present.
Interconnected to the side wall structures 26 are rocker panels 30, commonly also referred to a “rocker outer”, which extend longitudinally (x-direction, respectively driving direction) almost in parallel to the tunnel 21 along the side walls 26. In the drawings further parts are visible, which are interconnected with the underbody component 20. Among others, two front end side rails 40, a bulkhead 50, at least one faceplate 60, a rear seat cross member 70, and a rear seatback member 80 are visible. As it can be seen the front end side rails 40 extend into the bottom 35 of the underbody component 20. At least one faceplate 60 can be foreseen to form a closed box-like structure to increase stability and stiffness of the overall structure 20.
As can be seen from
The composite underbody component 20 is preferably made of one or several composite materials, e.g. carbon-fibre-reinforced plastic material (CFRP), and is produced by a RTM process. For easy production it should be kept free of cavities and undercuts which can not be demolded. Thereby it can be molded as a monolithic piece with high precision in one step in a two-part or at least a three-part mold. If required, one or several inserts can be placed in the mold before curing of the composite material.
Rocker panels 30 as shown here are made of a ductile material by deep drawing, e.g. by deep drawing of sheet metal such as steel and/or aluminium. The sheet metal of the rocker panels 30 is forming a shell 33 having an in principle C-shaped cross section. If required, patches or tapes (both not shown in detail) of composite material can be applied locally or over the whole shell 33 for specific reinforcement. This may as well be the case for the other mentioned parts 40-90.
The underbody component 20 is provided, at least in the area of its side wall structures 26 but preferably all around its circumference with one or several first connection faces 27 arranged in sequence or parallel to each other. Corresponding second connection faces 31 are provided at least the rocker panels 30.
For compensating different thermal extension e.g. of the carbon-fibre-reinforced plastic material of the underbody component 20 on the one hand and metallic material of the rocker panels 30 on the other hand, the rocker panels may be provided with beads 32. The beads 32 can be arranged between the mechanical connection points, if present. With regard to the interconnection between the underbody component 20 and the other parts 40-90, that what has been described with respect to the galvanic isolation, the adhesive bonding, the at least provisional mechanical connection and the thermal extension, may also apply to such other parts.
The rocker panels 30 are in transversal direction (y-direction, transverse to the driving direction x) constructed in a more deformable manner compared to the underbody component 20 such that deformation energy occurring in said lateral direction during impact is absorbed primarily by deformation of the rocker panels 30. The rocker panels 30 are mechanically interconnected to the underbody component 20 by first and second faces 27, 31. They preferably form part of the load bearing structure of the automobile body shell 10 and thereby contribute to the stiffness of the overall structure, i.e. the automobile body shell 10.
The underbody component 20 normally comprises at least one crossmember 24, 25 which extend in transversal direction (y-direction) foreseen to receive at least part of the load in transversal direction and distribute it within the structure of the underbody component 20. Good results may be achieved if, as shown here. the at least one crossmember 24, 25 is mechanically interconnected to the at least one rocker panel 30 in a mounted position.
The rocker panels 30 of the shown variation comprise an outer shell 33. Very good results may be achieved if the outer shell is at least partially made of ductile sheet metal and/or composite material. Depending on the field of application the outer shell may comprise several layers of sheet metal and/or composite material. In a preferred variation the outer shell of the at least one rocker panel has in transversal direction an in principle a C-shaped cross-section. The outer shell 33 may comprise at least one drainage, e.g. in the form of one or several holes or openings. If appropriate the drainage can be closed after production. The rocker panels may comprise foam material and/or honeycomb for absorbing impact energy during impact. The foam material and/or honeycomb material is preferably arranged between the underbody component and an outer shell of the at least one rocker panel. The foam material and/or honeycomb material may at least during impact form at least one support between the underbody component and an outer shell of the at least one rocker panel. An underbody component 20 made from fibre reinforced plastic material in combination with rocker panel according to the invention normally comprises one or several first connection faces 27 arranged in sequence or parallel to each other adjacent an outer edge of the underbody component 20. In
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 invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01341/15 | Sep 2015 | CH | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/071783 | 9/15/2016 | WO | 00 |
