VEHICLE ROOF WITH AT LEAST ONE ROOF ELEMENT AND A SHAPED HEADLINER ARRANGED AT A SPACE FROM THE ROOF ELEMENT, AND A METHOD FOR INCREASING THE ROOF BUCKLING RIGIDITY OF A VEHICLE ROOF

Description

[0001] The invention relates to a vehicle roof with at least one roof element and a molded headliner arranged at least partially spaced from the roof element, as well as a method for increasing roof buckling resistance. A vehicle is understood to mean, in particular, motor vehicles, and preferably passenger cars. However, the term is also intended to encompass other vehicles, in particular aircraft and watercraft.

[0002] During the product development of vehicles, especially motor vehicles, the vehicles must meet legal and / or manufacturer-specified specifications regarding roof buckling resistance. High roof buckling resistance leads to an improved quality perception among customers and, in practice, also results in greater resilience of the vehicle roof under snow loads or compressive loads, such as those that occur when polishing a vehicle roof. In general, it is desirable that the roof does not undergo plastic deformation under such practical loading conditions, and that the elastic deformation occurs without sudden buckling of the outer skin and is as minimal as possible.In practice, in addition to one or more relatively thin-walled roof panels forming the outer skin, roof stiffeners and / or roof bows (cross-roof beams made of sheet metal and secured to the roof panel with adhesive) are used, partially connected to the roof panels and arranged underneath them. The use of roof bows is cost-intensive due to the work steps required for series production and the associated plant technology.

[0003] FR 2 936 756 A1 discloses a vehicle roof which is formed from a roof panel made of metal or plastic forming the outer skin and a further inner roof element arranged at a distance from the roof panel at least towards the vehicle centre, wherein partially conical elements are arranged between the roof panel and the inner roof element in order to avoid vibrations of the roof panel and the further roof element.

[0004] EP 1 852 314 B1 discloses a vehicle trim element in the form of a plate-like headliner, wherein small spacer elements are foamed directly onto the side of the plate facing the vehicle body. These spacer elements have a length of 2 to 5 cm and, in the manner known from the prior art, serve to position the headliner relative to the vehicle body, in particular a roof panel of a motor vehicle, by locally filling the space between the headliner and the vehicle body in an area of ​​a maximum of 5 percent of the entire headliner. According to paragraph

[0005] of the description, these spacer elements do not fulfill any other technical tasks.

[0005] DE 202 00 835 U1 discloses an interior trim part, particularly in the form of a vehicle roof lining, which contributes to the rigidity of the vehicle's outer skin using simple means, allowing, for example, thinner metal sheets to be used for the outer skin. For this purpose, additional fastening points between the interior trim part and the outer skin are formed by detachable, essentially linear and / or planar fastening means. The fastening means should, in particular, be a removable adhesive by means of which fastening to the outer skin takes place.

[0006] The invention is based on the object of providing a vehicle roof with at least one roof element and a shaped headliner arranged at least partially at a distance from the roof element, as well as a method for increasing the roof buckling stiffness, by means of which the roof buckling stiffness can be increased locally in a simple and cost-effective manner.

[0007] The object is achieved according to the invention with the features of the independent claims. Further practical embodiments and advantages of the invention are described in conjunction with the dependent claims.

[0008] A vehicle roof according to the invention has at least one roof element and a shaped headliner arranged at a distance from the roof element. The roof element can be designed either as a single piece or in multiple pieces. In particular, the roof element and a roof panel manufactured as a single piece are used, which forms the outer skin of the roof and extends in the vehicle transverse direction (y-direction) over a large part of the vehicle width. In the case of a single-piece design, the roof panel forms the entire outer skin of the vehicle roof. In the vehicle roof according to the invention, at least one elastic tensioning spacer element is arranged under pressure between the shaped headliner and the roof element in order to increase the buckling stiffness of the vehicle roof, wherein the tensioning spacer element is compressed in the mounted state in the vehicle vertical direction (z-direction) by an excess of 0.5 mm to 5 mm."Compressively loaded" means that the clamping spacer element is manufactured prior to assembly in the area between the roof element and the headliner with an oversize Ü extending in the vertical direction of the vehicle (z-direction). This oversize is then elastically compressed during assembly and thus subjected to compressive stress. This actively supports the roof element, in particular a thin-walled roof panel, from the underside. This results in a particularly advantageous improvement in roof buckling resistance by means of material prestressing. The clamping spacer element is preferably designed to generate the greatest possible prestress in the roof element, in particular the roof panel, without the contour of the clamping spacer element being visible on the outside of the roof panel.

[0009] As already mentioned above, it is desirable to design the clamping spacer element in such a way that it generates the greatest possible prestress when installed, without negatively impacting the design of the roof element, in particular a thin-walled roof panel. To achieve this, it has proven advantageous, particularly in conjunction with clamping spacers made of polyurethane (PUR), if the clamping spacer element is compressed in the vehicle's vertical direction (z-direction) by an excess (Ü) of 0.5 mm to 5 mm when installed. Values ​​between 0.5 mm and 2 mm are particularly preferred, especially if the height of the spacer element in the installed state is within the ranges specified above, in particular between 10 mm and 30 mm.

[0010] Clamping spacers, particularly those made of PUR, are preferably firmly connected to at least one of the roof element or headliner, for example by welding to the headliner. This allows the headliner to be pre-assembled into a single unit with one or more clamping spacers and additional spacers, and the relative position of the spacers relative to the roof element can be ensured during subsequent assembly of the headliner. Alternatively or additionally, the connection can be made using a hot melt adhesive and / or a tape that is at least adhesive on one side or on both sides, particularly using a tape that is first covered with a protective film before use and then removed before assembly.

[0011] Tension spacers can be manufactured particularly easily and cost-effectively if they are cuboid-shaped or have another simple geometry. When such geometries are used in areas where the distance between the headliner and the roof element is not equal, the height of the tension spacer is designed so that the oversize at every point on the cuboid lies within a predetermined minimum and maximum overpressure, for example, between 1 mm and 2 mm. Preferably, a mediated height is then selected for the cuboid, ensuring compliance with the minimum and maximum overpressure.

[0012] In conjunction with the materials explained in more detail below, an oversize (Ü) of between 0.5 and 2 mm results in a particularly advantageous reinforcement effect without causing any visual impairment. This applies in particular if the oversize in the vertical direction amounts to a maximum of 20 percent of the smallest height of the clamping spacer element, preferably a maximum of 15 percent, and particularly preferably a maximum of 10 percent. With a (smallest) height of the clamping spacer element of approximately 13 mm, this results in an oversize of 2.6 mm at 20 percent and 1.95 mm at 15 percent.

[0013] A further advantage of using clamping spacers designed as described above is that, even in the event of significant temperature differences, no gap forms between the clamping spacer and the two elements (roof element and headliner), provided the prestressing is selected so that the prestressing is maintained even at the maximum distance between the headliner and roof element. Noise development, which could be caused by a gap forming between the clamping spacer and the two elements (roof element and headliner), is then eliminated.

[0014] The at least one elastic tensioning spacer element can be arranged, on the one hand - as explained above - between the shaped headliner and a roof panel or, on the other hand, between the shaped headliner and a roof stiffener, wherein the roof stiffener is in particular an intermediate element which supports the roof panel on the underside.

[0015] The at least one clamping spacer element is preferably made of a plastic or synthetic resin, in particular of a foam.

[0016] Materials made of polyurethane have proven particularly useful in this regard. Alternatively, or in addition to and independently of the material, materials which have a compressive strength of between 10 kPa and 30 kPa, preferably between 12 kPa and 28 kPa, and particularly preferably between 14 and 26 kPa, have proven suitable for clamping spacer elements. Materials with a bulk density of between 100 and 220 kg / m 3 have also proven advantageous, in particular those with a bulk density of between 120 and 200 kg / m 3 , preferably those with a bulk density of between 140 and 180 kg / m 3 , and more preferably those with a bulk density of between 150 and 170 kg / m 3 , i.e. 160 kg / m 3 + / - 10 kg / m 3 .

[0017] The invention relates in particular to a vehicle roof whose roof element and / or whose shaped headliner extend over a large part of the width of the vehicle roof of the corresponding vehicle. In this case, these are one-piece roof elements or roof sheets, in particular deep-drawn metal sheets or sheets produced by other forming (roof element) or sheets made from a type of plate, in particular from a fibrous material (shaped headliner). Since such elements usually have an area of ​​more than 1 m 2<, the risk of excessive elasticity of the roof element due to insufficient support or an excessively large hollow space between the roof element and the shaped headliner is particularly high. The invention is therefore particularly advantageous for vehicle roofs with an area of ​​more than 0.5 m 2<, preferably more than 0.8 m 2< and more preferably more than 1 m 2<.

[0018] Roof sheets within the meaning of the invention are understood to mean, in particular, roof sheets that have a maximum thickness of 1 mm, preferably a maximum thickness of 0.8 mm, and more preferably a maximum thickness of 0.75 mm or even a maximum thickness of 0.7 mm. Preferred thickness ranges of roof sheets for the invention are 0.3 mm to 1 mm, in particular 0.3 mm to 0.7 mm, and particularly preferably 0.4 mm to 0.7 mm.

[0019] In practice, in trial implementation of the invention, a height extending in the vertical direction of the vehicle (z-direction) has proven to be advantageous as a measure for the height of a clamping spacer element in the mounted state, which height is between 1 mm and 100 mm and in particular between 5 mm and 40 mm, preferably between 5 mm and 30 mm and particularly preferably between 5 mm and 20 mm.

[0020] To create the most uniform prestress possible in the area of ​​the clamping spacer between the headliner and the roof element, and thus prevent the clamping spacer from showing through in the area of ​​the outer skin, it is preferable if the upper surface of the clamping spacer facing the roof element is shaped to complement the roof element in the assembly area, and / or if the underside of the clamping spacer facing the headliner is shaped to complement the headliner in the assembly area. In this case, approximately the same compressive stress is created across the entire surface of the clamping spacer when compressed by the excess.

[0021] The invention also relates to a method for increasing the roof buckling stiffness of a vehicle roof with a roof element and a shaped headliner, wherein the method comprises the following method steps, which are carried out in the specified order and preferably on a vehicle which is under development at a vehicle manufacturer, i.e. whose design is still adaptable in the aspects relevant to the method steps, preferably at a very early stage of vehicle development, in particular with one of the first physically available prototype vehicles: a) Loading the vehicle roof to examine for weak points by applying a defined test force or a defined test pressure in the area of ​​at least one measuring point on the vehicle roof. Explanation: The weak points can either be points of elasticity where the roof can be elastically deformed beyond a certain maximum deformation path extending in the vertical direction of the vehicle, and / or they can be so-called spring dents, i.e. points where plastic deformation occurs in the vehicle roof when a certain force or pressure is applied. Such spring dents can be identified in the force-displacement diagram by the fact that the force curve decreases with increasing distance or by the fact that an inflection point can be identified in the force-displacement diagram.The loading is preferably carried out with a defined test force and with a defined test body, for example with a test body which has a predetermined shape, in particular a cylindrical head which consists of a predetermined material, in particular aluminum, and has a predetermined pressure surface, in particular a diameter of 70 mm, i.e. a pressure surface of approximately 3,850 mm2. The loading with the test body is preferably carried out normal to the surface, and it is further preferred if the test body is articulated so that it can follow any pivoting movement of the test surface. In particular, a 2 mm thick rubber plate with a hardness of 50 Shore A is used as a base for the test body. The rubber plate is arranged on the side of the test body facing the vehicle roof and thus comes into direct contact with the vehicle roof, in particular a roof panel.The rubber plate is intended to prevent the surface of the vehicle roof, in particular the paintwork, from being damaged by scratches or other marks. The vehicle roof is subjected to a specified test force, in particular a test force of 100 N, via the test specimen and the rubber plate attached to it. b) Creation of a force-displacement diagram during loading Explanation: In particular, the load is increased starting from an initial load (this can also be zero) up to a defined maximum force or a defined maximum pressure, and the force-displacement diagram is created from the recorded values, i.e. a corresponding measurement curve is plotted. The force-displacement diagram is preferably recorded using a force-displacement load cell that is functionally connected to the test specimen, which digitally records a specific number of measurement points and interpolates the measurement curve from this.c) Evaluation of the force-displacement diagram for weak points in the form of spring bumps (cracking frog effect) and / or an excessively large, intolerable elastic deformation path at the maximum force or maximum pressure or a force lower than the maximum force or a pressure lower than the maximum pressure. In particular, inflection points in the force-displacement diagram with a gradient < 0 can be regarded as intolerable, whereas inflection points with a gradient of approximately 0 and curves with a gradient that is always > 0 can be regarded as tolerable. A maximum permanent deformation for the vehicle roof can be specified, in particular to a value of <= 0.1 mm.Visible surfaces may also be considered intolerable. d) If a weak point is identified, insert at least one clamping spacer between the headliner and the roof element at the identified weak point, whereby the clamping spacer is compressed in the vehicle's vertical direction (z-direction) by an excess of 0.5 to 5 mm. Explanation: For this purpose, a clamping spacer in a standard size with the smallest possible dimensions is preferably used as the first clamping spacer. This is then successively enlarged according to the subsequent step until the desired effect is achieved.e) re-checking the roof buckling stiffness with the first spacer element or with the enlarged clamping spacer element and, if the roof buckling stiffness is still not satisfactory, enlarging the last checked clamping spacer element (in particular such that the upper surface facing the roof element and / or the underside facing the headliner is enlarged) and then repeating the two previous steps c) and d) until the result is satisfactory.

[0022] The method has the advantage that it enables weak points in the form of spring bulges or excessive elasticity of the roof element or roof sheet to be identified in a relatively simple and cost-effective manner and to be remedied by means of constructive, short-term measures.

[0023] In a practical embodiment of the method according to the invention, several measuring points are set off-center on a clamping spacer element where a weak point was previously identified. The measuring point with the qualitatively greatest weak point is then determined in order to enlarge the clamping spacer element only in the area of ​​this measuring point. If several measuring points have been determined, enlargement can be performed in the direction of all measuring points. Alternatively, enlargement can be performed successively in the direction of the measuring point where a weak point is still qualitatively most pronounced.

[0024] Reference is hereby made once again to the advantages described in connection with the vehicle roof. These are also achieved with the method, insofar as the method leads to a vehicle roof according to the invention.

[0025] Further practical embodiments of the invention are described below in conjunction with the drawings. They show: Fig. 1 a motor vehicle in a view from above with a plurality of measuring points MP1 to MP11 arranged on the vehicle roof, Fig. 2 a force-displacement diagram with all the Fig. 1 force-displacement curves assigned to the measuring points, which were determined before the modification according to the invention, Fig. 3 a modified headliner of a vehicle roof with a plurality of standard spacer elements and with two clamping spacer elements, Fig. 4 a force-displacement diagram with the Fig. 1entered measuring points MP4, MP6, MP8 and MP9 assigned force-displacement curves, which were determined after the modification according to the invention, Fig. 5 a schematic representation of a first roof arrangement according to the invention with a tensioning spacer element which is arranged between a shaped headliner and a roof element arranged further outwards in the form of a roof sheet, and Fig. 6 a schematic representation of a second roof arrangement according to the invention with a tensioning spacer element which is arranged between a shaped headliner and a roof element arranged further outwards in the form of a roof stiffener.

[0026] Figure 1 shows a motor vehicle 10 with a vehicle roof 12. A plurality of measuring points are arranged distributed over the vehicle roof 12, here a total of 13 measuring points, which are labeled MP1, MP2, MP3, MP4, MP5, MP6, MP7, MP7.1, MP7.2, MP8, MP9, MP10 and MP11.

[0027] The measuring points are selected locations on the vehicle roof 12 at which, as an example, the roof buckling stiffness of the roof 12 is measured. For this purpose, the vehicle roof 12 is loaded with a force F continuously increasing from 0 N to 100 N in the vertical direction of the vehicle from top to bottom, and during this time, the distance x in millimeters (mm) that the device by means of which the force is introduced into the vehicle roof 12 moves towards the vehicle interior is measured.

[0028] In the Figures 1 , 3 , 5 and 6 Coordinate systems are added in which the vehicle's longitudinal direction is marked with the x-direction, the vehicle's transverse direction with the y-direction and the vehicle's vertical direction with the z-direction.

[0029] Figure 2 shows the force-displacement diagrams for all measurement points. In this case, the following requirements are placed on the roof buckling stiffness: A) Under a load of 100 N, the distance the roof 12 moves toward the vehicle interior should be a maximum of 8 mm. This requirement is met for all measurement points. B) There should be no force drop in the entire force-displacement curve, i.e., a reduction in force with increasing displacement, because this effect leads to a so-called "spring bulge." This is undesirable.

[0030] In this case, a force drop occurs at the measuring points MP4, MP6, MP8 and MP9. An example is shown in Fig. 2 The travel range between approximately 1.5 mm and 2.7 mm is circled with a dashed line and marked with S because an undesirable force drop occurs in this travel range.

[0031] In order to meet requirement B for the measuring points MP4, MP6, MP8 and MP9, as described in Fig. 3is shown - on a shaped headliner 14, which is arranged on the side of the roof 12 facing the vehicle interior, in addition to a plurality of standard spacer elements 16, two clamping spacer elements 18 are also arranged.

[0032] In the Figures 5 and 6 Two different variants for the arrangement of clamping spacer elements 18 are shown.

[0033] In the variant according to Fig. 5 the clamping spacer element 18 is arranged between the headliner 14 and a roof element 20, here a roof sheet 22.

[0034] In the variant according to Fig. 6 the tensioning spacer element 18 is arranged between the shaped headliner 14 and a roof stiffener 24, which extends from the underside of the roof element 20, here again in the form of the roof sheet 22.

[0035] The clamping spacer element 18 has an oversize Ü in the unassembled state, which Figures 5 and 6is therefore recognizable and registered because the tensioning spacer element 18 in these figures is formed by the roof element 20 in the form of the roof sheet 22 ( Fig. 5 ) or in the state not subjected to pressure by the roof stiffener 24.

[0036] The invention may be varied within the scope of the claims and taking into account the knowledge of the person skilled in the art. List of reference symbols

[0037] 10Motor vehicle 12Vehicle roof 14Shaped headliner 16Standard spacer element 18Clamping spacer element 20Roof element 22Roof panel 24Roof stiffener ÜOversize MP1Measuring point MP2Measuring point MP3Measuring point MP4Measuring point MP5Measuring point MP6Measuring point MP7Measuring point MP7.1Measuring point MP7.2Measuring point MP8Measuring point MP9Measuring point MP10Measuring point MP11Measuring point

Claims

1. Vehicle roof comprising at least one roof element (20) and a shaped headliner (14) arranged at a distance from the roof element (20), characterized in that, in order to increase the vehicle roof buckling resistance, at least one resilient tensioning spacer element (18) is arranged under pressure between the shaped headliner (14) and the roof element (20), wherein, in the mounted state, the tensioning spacer element (18) is compressed in the vehicle vertical direction (z-direction) by an excess (Ü) of 0.5 mm to 5 mm.

2. Vehicle roof according to the preceding claim, characterized in that the at least one resilient tensioning spacer element (18) is arranged between the shaped headliner (14) and a roof panel (22) or between the shaped headliner (14) and a roof stiffening element (24).

3. Vehicle roof according to either of the preceding claims, characterized in that the at least one tensioning spacer element (18) is made of a plastics material or synthetic resin.

4. Vehicle roof according to the preceding claim, characterized in that the at least one tensioning spacer element (18) is made of a polyurethane and / or the material of the tensioning spacer element (18) has a compressive strength between 10 kPa and 30 kPa and / or has a bulk density between 100 and 220 kg / m 3.

5. Vehicle roof according to any of the preceding claims, characterized in that the roof element (20) and / or the shaped headliner (14) extend over a large part of the width of the vehicle roof (12).

6. Vehicle roof according to any of the preceding claims, characterized in that at least one tensioning spacer element (18), in the mounted state, has a height extending in the vehicle vertical direction (z-direction) of between 1 mm and 100 mm.

7. Vehicle roof according to any of the preceding claims, characterized in that the upper surface of the tensioning spacer element (18), which faces the roof element (20), has a shape which is complementary to the roof element (20) in the assembly region, and / or the lower surface of the tensioning spacer element (18), which faces the shaped headliner (14), has a shape which is complementary to the shaped headliner (14) in the assembly region.

8. Method for increasing the roof buckling resistance of a vehicle roof (12) comprising a roof element (20) and a shaped headliner (14), characterized by the following method steps: a) loading the vehicle roof (12) to examine for weak points, by applying a defined test force or a defined test pressure in the region of at least one measuring point (MP1-MP11) of the vehicle roof (12), b) creating a force-displacement diagram during the loading process, c) evaluating the force-displacement diagram for weak points in the form of oil canning and / or intolerable elastic deformation, d) if a weak point is identified, inserting at least one tensioning spacer element (18) between the headliner (14) and the roof element (20) at the identified weak point, wherein the tensioning spacer element (18) is compressed in the vehicle vertical direction (z-direction) by an excess (Ü) of 0.5 mm to 5 mm, e) checking the roof buckling resistance again with the first tensioning spacer element (16) in place or with the enlarged tensioning spacer element (18) in place and, if the roof buckling resistance is still not satisfactory, enlarging the last checked tensioning spacer element (18) and then repeating the two previous steps c) and d) until the result is satisfactory.

9. Method according to the preceding claim, characterized in that a plurality of measuring points (MP1-MP11) are each defined eccentrically on a spacer element (18), and any enlargement is carried out on the side of the clamping spacer element (18) where a weak point was previously identified.