Abstract:
The invention relates to a shock absorber for protection against side impact on a motor vehicle, which absorber is made of fiber material and has a cross-sectional profile comprising at least first, second, third and fourth flanks, wherein two consecutive flanks extend in opposite directions, respectively.

Description:
BACKGROUND  
       [0001]     The invention relates to a shock absorber made of fiber material and a vehicle door comprising a shock absorber of this type as well as method for producing a shock absorber.  
         [0002]     From the state of the art, various shock absorbers are known to protect against vehicle side impact. Shock absorbers of this type are also referred to as impact absorbers. Impact absorbers are typically made of polyurethane (PU) foam, expanded polypropylene (EPP) or polystyrene (PS).  
         [0003]     From EP 0 683 072 B1, a shock absorber made of compressed and formed fiber is known. This shock absorber has the shape of a stepped pyramid, wherein the individual pyramid steps form shearing zones.  
         [0004]     From DE 44 17 835 A1, a shock absorber is known, which is configured as an impact pot, in which the energy absorption is effected via a plurality of chronologically successive shearing processes of the absorber material during impact. The shock absorber in particular has the shape of a terrace arrangement or a stepped pyramid.  
         [0005]     Furthermore, from DE 699 12 789 T2, an absorber for motor vehicle bumpers and motor vehicle linings is known, which is made of natural or synthetic resin material or composite material. Energy absorption here is provided by a plurality of cup-shaped cells, which have a thin-walled construction with a circular cross-section.  
         [0006]     From DE 101 25 987 A1, a side wall with side wall impact protection in a vehicle is known. In this patent, a deformation element is described, which comprises a deformation profile that has on its long side at least two steps in the vehicle longitudinal direction.  
         [0007]     DE 296 07 664 U1 discloses a vehicle door with an assembly carrier, which in conjunction with functional elements, such as window lift mechanisms, door locking mechanisms, speakers and cables, forms a completely assembled modular installation unit. The assembly carrier is made of dimensionally stable fiber composite material, which has increased inner friction and greater impact resistance and therefore guarantees improved energy absorption in the event of a side impact.  
       SUMMARY OF THE INVENTION  
       [0008]     It is the object of the invention to create a shock absorber, particularly for installation in a motor vehicle door, made of fiber material, which offers improved side impact protection for the vehicle passengers.  
         [0009]     In accordance with one or more aspects of the present invention, a shock absorber for protection against side impact onto a motor vehicle may be made of a fiber material, and have a cross-sectional profile comprising: at least first, second, third and fourth flanks extending from a base plane at an angle of about 25 to 90 degrees; two consecutive flanks extending in opposite directions, respectively, where a single upper plateau, which is smaller than the base plane, connects to the flanks, which plateau comprises at least one indentation extending to the base plane.  
         [0010]     The invention creates a shock absorber for protection against side impact on a motor vehicle. The shock absorber is made of fiber material and has a cross-sectional profile comprising at least first, second, third and fourth flanks, wherein two consecutive flanks extend in opposite directions, respectively. The flanks extend from a base plane at an angle between 25 and 90 degrees and form an upper plateau, which is comparatively smaller than the base plane. This plateau comprises at least one indentation, which extends substantially to the base plane.  
         [0011]     As a result of this structure of the shock absorber, even high side impact forces can be absorbed, which at a load of over 3,000 Newtons, for example, result in compression of the shock absorber.  
         [0012]     According to a preferred embodiment of the invention, a natural fiber molding material, preferably a ligneous fiber material, is used to produce the shock absorber. It is preferable if a ligneous fiber mat is shaped into the correct form by pressing or deep-drawing. The use of a ligneous fiber material is particularly advantageous because no sharp edges form, even when the shock absorber is deformed and compressed during side impact. As a result of the material properties of the ligneous fiber material, the shock absorber is rather compressed similar to cardboard and folded to absorb the impact energy.  
         [0013]     According to one embodiment of the invention, the first flank, meaning the outside wall of the shock absorber, has an angle of inclination of about 25 to 90 degrees, preferably between about 30 and 75 degrees, particularly about 45 degrees to the base plane.  
         [0014]     According to a further embodiment of the invention, the inside radii, particularly the inside radii of abutting flanks, are selected as large as possible and measure at least about 5 millimeters, preferably at least about 10 millimeters, to limit the development of stress peaks on the inside radii when stress is applied on the shock absorber.  
         [0015]     According to one preferred embodiment of the invention, the fiber material has a thickness of about 1 to 3 millimeters, preferably approximately 1.8 millimeters after it has been shaped as desired by means of hot-pressing or deep-drawing.  
         [0016]     According to a further embodiment of the invention, the shock absorber circumscribes a base surface with edge lengths between about 20 and 40 centimeters, preferably a square surface with edge lengths of about 30 centimeters.  
         [0017]     According to a further embodiment of the invention, the shock absorber measures between about 2 and 8 centimeters, and preferably about 6 centimeters, in height.  
         [0018]     According to a further embodiment of the invention, the shock absorber has at least one indentation. The indentation can have various profiles in its cross-section, for example it can have substantially circular, triangular, square, polygonal or other profile shapes.  
         [0019]     According to a further embodiment of the invention, the shock absorber has, for example, two or four indentations. It is preferable if a bar extends between two adjoining indentations. Depending on the desired rigidity of the shock absorber, the bar may extend substantially parallel to the base plane of the shock absorber or in an arched shape, particularly concave to the base plane. This concave bar provides the impact absorber with a lower stress level than an impact absorber without lowered bar.  
         [0020]     According to a further embodiment of the invention, the indentation extends to the base plane. This has the advantage that the indentation can be supported by the inside of the vehicle door, for example, during side impact so that the shock absorber is only irreversibly deformed at relatively high side impact forces.  
         [0021]     According to a further embodiment of the invention, the indentation comprises a convex or concave region. It is preferable if the concave region extends to the height of the shock absorber, resulting in a prop effect on the opposing inside of the vehicle door during side impact.  
         [0022]     In a further aspect, the invention relates to a motor vehicle door comprising an outside metal sheet and an inside molding. A shock absorber according to the invention is disposed between the outside metal sheet and the inside molding. The absorber is preferably disposed such that the base plane thereof extends substantially in the vertical direction. Furthermore, the base plane is preferably provided opposite the inside molding, so that the indentation extends in the direction of the vehicle interior.  
         [0023]     The impact absorber proposed here can be used in all conceivable applications for the protection of vehicle passengers (hip, thorax, abdomen, head (moldings), knees, etc.).  
         [0024]     According to a further embodiment, the shock absorber is made of a natural fiber mat. The mat can have one or more layers.  
         [0025]     To produce a shock absorber, a fiber mat is inserted in a tool with a cross-sectional profile having at least first, second, third and fourth flanks, wherein two consecutive flanks each extend in opposite directions. By moving the tool pieces toward each other, the fiber mat is shaped into the desired form by means of hot-pressing or deep-drawing. It is preferable if a polypropylene mixture, for example, is mixed with the fiber mat, which mixture comprises resin for bonding the fibers, thus providing the fiber mat with a dimensionally stable shape as a result of the bonding process. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0026]     The invention will be explained in more detail hereinafter with reference to the drawings, wherein:  
         [0027]      FIG. 1  is a perspective view of a shock absorber with a cylindrical indentation,  
         [0028]      FIG. 2  is a perspective view of a shock absorber with two triangular indentations,  
         [0029]      FIG. 3  is a perspective view of a shock absorber with four indentations, each having a polygonal cross-section,  
         [0030]      FIG. 4  is a perspective view of a shock absorber with a convex region in the indentation,  
         [0031]      FIG. 5  is a perspective view of a shock absorber with two pyramidal indentations,  
         [0032]      FIG. 6  is a top view of the shock absorber according to  FIG. 5  as well as a view of a cross-section,  
         [0033]      FIG. 7  is a further perspective illustration of the shock absorber according to  FIGS. 5 and 6 ,  
         [0034]      FIG. 8  is part of a tool for hot-pressing a fiber mat to produce the shock absorber according to  FIGS. 5, 6  and  7 ,  
         [0035]      FIG. 9  is the tool according to  FIG. 8  with a fiber mat applied before the pressing operation,  
         [0036]      FIG. 10  shows the fiber mat cut open along a bar of the shock absorber after the pressing operation,  
         [0037]      FIG. 11  is an alternative embodiment of the shock absorber according to  FIGS. 5, 6  and  7  with an arched bar as well as a sectional view, and  
         [0038]      FIG. 12  is a schematic illustration of a motor vehicle door. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0039]      FIG. 1  shows a shock absorber  100 , which is made of fiber material and comprises a wall extending in various directions, for example along the cross-section  102 .  
         [0040]     Starting from a base  104  of the shock absorber  100 , the wall—following the cross-section  102  in the direction of the arrow—extends in the outer wall region  106  with an upwardly inclining flank. After reaching the upper plateau  108  of the wall, the wall slopes downward along an inner wall region  110  in a substantially cylindrical indentation  112  to the bottom  114  of the wall.  
         [0041]     Starting from the bottom  114 , the wall then inclines again upward along the cross-section  102  along the inner wall region  116 , which is opposite the inner wall region  110 , to the upper plateau  108 . From there, the wall slopes downward again along the outer wall region  118  thereof opposite the outer wall region  106  to the base  104 .  
         [0042]     As a result of the consecutive outer wall region  106 , the inner wall region  110 , the inner wall region  116  and the outer wall region  118  along the cross-section  102  consequently four consecutive flanks are created. Two consecutive flanks, respectively, extend in opposite directions.  
         [0043]     For example, the outer wall region  106  inclines upward at an angle, while the inner wall region  110  slopes downward perpendicularly. The outer wall region  106  and the inner wall region  110  thus extend in opposite directions. The same applies to the inner wall region  110  and the inner wall region  116 , which extends substantially vertically upward, meaning in the opposite direction of the inner wall region  110 .  
         [0044]     The same applies to the inner wall region  116  and the outer wall region  118  following it, which outer wall region extends at an angle downward, meaning in the opposite direction of the perpendicularly upwardly extending inner wall region  116 . The shock absorber  100  therefore has a zigzag-shaped cross-sectional profile along its cross-section  102 , in which profile alternately ascending and descending flanks are incorporated.  
         [0045]     This has the advantage that the shock absorber  100  has relatively high mechanical stability. If a relatively small side impact force is applied on the shock absorber, the shock absorber  100  is therefore resilient. It is only at high side impact forces that the shock absorber  100  is compressed irreversibly and folded.  
         [0046]     It is particularly advantageous if the bottom  114  is roughly on the same plane as the base  104 . This enlarges the support surface of the shock absorber  100  and consequently its ability to withstand side impact forces.  
         [0047]     It is preferable if the shock absorber  100  is made of a ligneous fiber material. This has the advantage that even in the event that the shock absorber  100  should fold no sharp or protruding edges develop when a side impact force is applied. The risk of secondary injuries will then be accordingly low.  
         [0048]     To improve production feasibility, the inside radii are selected as large as possible, for example about 5 mm, preferably greater than about 10 mm.  
         [0049]     The angles of inclination of the outer wall regions  104  and  118  can vary within a wide range. For example, an angle of inclination of the outer wall region  106  in relation to the base  104  in the range of about 25 to 90 degrees, preferably between about 30 and 75 degrees, particularly about 45 degrees can be selected. In the embodiment used here according to  FIG. 1 , the angle of inclination of the flank formed by the outer wall region  106  is about 60 degrees in relation to the base plane of the shock absorber.  
         [0050]      FIG. 2  shows a further embodiment of a shock absorber  200 . The shock absorber  200  is structured similarly to the shock absorber  100 . Contrary to the shock absorber  100 , the shock absorber  200  comprises two indentations  212 , which each have a triangular cross-section. Also the indentations  212  preferably extend to the base plane of the shock absorber  200 .  
         [0051]     Between the indentations  212 , a cross-bar  214  is provided on the upper plateau of the shock absorber  200 .  
         [0052]      FIG. 3  shows a further embodiment of a shock absorber  300 , which is again structured similarly to the shock absorbers  100  and  200  according to  FIGS. 1 and 2 . The shock absorber  300  has four indentations  312 , which each have a polygonal cross-section.  
         [0053]      FIG. 4  shows a further embodiment of a shock absorber  400 , which is again structured similarly to the shock absorbers  100 ,  200  and  300  according to  FIGS. 1, 2  and  3 . The shock absorber  400  has an indentation  412 , which has a substantially square cross-section. The bottom  414  of the indentation  412  preferably extends to the plane of the base  404  of the shock absorber  400 . The bottom  414  frames a concave region  420 , which extends from the bottom  414  preferably to the height of the apex  422  of the shock absorber  400 .  
         [0054]      FIG. 5  shows a further shock absorber  500 , which is again structured similarly to the shock absorbers  100 ,  200 ,  300  and  400  according to  FIGS. 1, 2 ,  3  and  4 .  
         [0055]     The shock absorber  500  comprises two pyramidal indentations  512 , wherein the tips of the pyramidal indentations  512  preferably extend to the plane defined by the base  504  of the shock absorber  500 . In the embodiment illustrated here, the indentations  512  each have tetrahedral shapes, however different pyramidal shapes are also possible. A cross-bar  514  extends between the two indentations  512 . The cross-bar preferably extends at the height of the apex  522  and therefore parallel to the base plane of the shock absorber  500 .  
         [0056]     The outer wall region  506  of the shock absorber  500  preferably has an angle of inclination of about 45 degrees to the base plane, which is defined by the base  504 .  
         [0057]      FIG. 6  shows a top view of the shock absorber  500  according to  FIG. 5  as well as sectional view along the section A-A. As  FIG. 6  illustrates, the tips of the pyramids  524  of the tetrahedral indentations  512  extend to the base plane  526  defined by the base  506  of the shock absorber  500 .  
         [0058]     The base  506  of the shock absorber  500  preferably has edge lengths ranging between 20 and 40 centimeters, particularly approximately 30 centimeters. The height of the shock absorber  500  from the base plane  526  to the apex  522  is preferably between 4 and 10 centimeters, particularly approximately 6 centimeters.  
         [0059]      FIG. 7  shows the shock absorber according to  FIGS. 5 and 6  in a further perspective illustration.  
         [0060]      FIG. 8  shows part of a tool  600 , which can be used to produce the shock absorber  500  as it is shown in  FIGS. 5, 6  and  7 . For this purpose, the tool  600  has the inner contour desired for the shape of the shock absorber  500 . To produce the shock absorber  500 , a fiber mat  602  is placed on the tool  600 , as is shown in  FIG. 9 . The fiber mat is preferably made of ligneous fibers, to which polypropylene has been mixed.  
         [0061]     The fiber mat  602  is shaped to the desired form by means of the tool  600  in a hot-pressing operation.  
         [0062]     The pressing or deep-drawing operation is performed, for example, at a tool temperature of 220° C., a pressing force of 60 bar and a pressing time of about 20 seconds.  
         [0063]      FIG. 10  shows the pressed fiber mat  602 , which has been cut along the cross-bar  514  for demonstration purposes.  
         [0064]      FIG. 11  shows a top view of an alternative embodiment of the shock absorber  500 . Contrary to the embodiment according to  FIGS. 5, 6 ,  7  and  10 , the shock absorber  500  according to  FIG. 11  has a concavely arched bar  514  in relation to the base plane  526 . At the center, the bar  514  is therefore lower than the apex  522  by a distance  528 .  
         [0065]     Contrary to the embodiment according to  FIG. 6 , the tips of the pyramids  524  do not extend all the way to the base plane  526 .  
         [0066]      FIG. 12  shows a schematic illustration of one embodiment of a motor vehicle door  730  according to the invention. The motor vehicle door  730  comprises a window  732 . Below the door rail  734 , a shock absorber according to the invention is provided, such as the shock absorber  500 . The base plane defined by the base  506  of the shock absorber  500  is disposed opposite an inside molding part  736  of the motor vehicle door  730 , so that the base plane extends substantially in the vertical direction.  
         [0067]     Below the shock absorber  500 , a shock absorber  738  is provided. The shock absorber  738  is made of polyurethane foam, for example, and has a higher rigidity than the shock absorber  500 . The shock absorber  738 , however, can also be an accordingly rigidly dimensioned embodiment of a shock absorber according to the invention.  
         [0068]     The shock absorber  738  is disposed approximately at the height of the pelvis  740  of a person  742  who is sitting on the vehicle seat  744 . The shock absorber  500  disposed above the shock absorber  738 , on the other hand, is provided at about the height of the thorax and/or abdomen  746  of the person  742 . Between the outside metal sheet  748  of the door  730  and the inside molding part  736  of the door  730 , the shock absorbers  500  and  738  are disposed on top of each other.  
         [0069]     In the event of a side impact, this offers the advantage that the person  742  is first moved away from the deforming motor vehicle door  730  in the direction of the vehicle center by the shock absorber  738 . In the event of further deformation of the motor vehicle door  730 , the shock absorber  500  then above all protects the thorax/abdomen  746  of the person  742  from severe injuries.  
         [0070]     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.  
       REFERENCE NUMERAL LIST  
       [0071]      100  shock absorber  
         [0072]      102  cross-section  
         [0073]      104  base  
         [0074]      106  outer wall region  
         [0075]      108  upper plateau  
         [0076]      110  inner wall region  
         [0077]      112  cylindrical indentation  
         [0078]      114  bottom  
         [0079]      116  inner wall region  
         [0080]      118  outer wall region  
         [0081]      200  shock absorber  
         [0082]      212  indentation  
         [0083]      214  cross-bar  
         [0084]      300  shock absorber  
         [0085]      312  indentation  
         [0086]      400  shock absorber  
         [0087]      404  base  
         [0088]      412  indentation  
         [0089]      414  bottom  
         [0090]      420  convex region  
         [0091]      422  apex  
         [0092]      500  shock absorber  
         [0093]      504  base  
         [0094]      506  outer wall region  
         [0095]      512  indentation  
         [0096]      514  cross-bar  
         [0097]      522  apex  
         [0098]      524  tip of pyramid  
         [0099]      526  base plane  
         [0100]      528  distance  
         [0101]      600  tool  
         [0102]      602  fiber mat  
         [0103]      730  motor vehicle door  
         [0104]      732  window  
         [0105]      734  door rail  
         [0106]      736  inside molding part  
         [0107]      738  shock absorber  
         [0108]      740  pelvis  
         [0109]      742  person  
         [0110]      744  vehicle seat  
         [0111]      746  thorax/abdomen  
         [0112]      748  outside metal sheet