Abstract:
A frontal structure is provided for a motor vehicle. The frontal structure includes, but is not limited to a support structure, to which a radiator is fastened and on which a bumper girder is mounted in front of the radiator in such a manner that it yields backward toward the radiator in case of an impact. The fastening of the radiator to the support structure is formed by a frame, in which the radiator is retained and which is in turn anchored to the support structure via connection elements which detach if a maximum force is exceeded. The frame is adapted to the form of the bumper girder and the radiator to come into contact with the bumper girder earlier than the radiator in case of yielding backward of the bumper girder.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to German Patent Application No. 102007020914.4, filed May 4, 2007, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a frontal structure for a motor vehicle. 
     BACKGROUND 
     A frontal structure for a motor vehicle generally comprises a support structure, to which the radiator, engine, and other parts are fastened, as well as a bumper girder installed in front. The radiator is generally mounted in front of the engine block to be effectively cooled by travel wind. To make the vehicle as a whole is as compact as possible, an effort is made to make the distance between bumper girder and radiator, on one hand, and between radiator and engine block, on the other hand, as small as possible. However, the disadvantage results there from are that if the vehicle is involved in an impact, there is a high probability of damage to the radiator, so that costly repairs are necessary even in the event of a light impact. 
     In view of the foregoing, at least one object of the present invention is to specify a frontal structure for a motor vehicle, in which, in spite of a compact construction, the radiator is protected well from damage in the event of an impact. In addition, other objects, desirable features, and characteristics will become apparent from the subsequent summary, detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background. 
     SUMMARY 
     The at least one object and other objects, desirable features, and characteristics are achieved in that, in a frontal structure having a support structure, to which a radiator is fastened and a bumper girder is mounted in front of the radiator in such a manner that it yields backward toward the radiator in the event of an impact, the fastening of the radiator to the support structure is formed by a frame, in which the radiator is retained and which is in turn anchored on the support structure via connection elements which detach if a maximum force is exceeded, and the frame is adapted to the form of the bumper girder and the radiator to come into contact with the bumper earlier than the radiator if the bumper girder yields backward. The connection elements are detached in that the bumper girder yielding backward exerts force on the frame, and the frame may yield backward as a whole together with the radiator lying protected therein. A free space lying behind the radiator, which is not available for permanent placement of the radiator therein, may thus be made useful for protecting it, because the possibility exists that the engine or parts connected thereto will temporarily penetrate into this free space because of oscillations of the engine in relation to the support structure. 
     According to an embodiment, the connection elements are destructible by exceeding the maximum force. In particular, the connection elements may be implemented as pins which may be sheared off. However, the use of connection elements which yield elastically if the maximum force is exceeded, without thus being destroyed, is also conceivable. 
     To ensure that the frame is hit earlier by the bumper girder yielding backward than the radiator, the frame may be provided with vertical ribs projecting toward the bumper girder. In particular, these ribs may laterally border the radiator. 
     Furthermore, it is expedient if the frame is anchored on the support structure via a group of lower connection elements and a group of upper connection elements, and if the connection elements of one of the groups detach, the other group of connection elements defines an axis around which the radiator is pivotable. This allows in particular the usage of a free space whose depth is not constant over the vertical extension of the radiator. 
     A heat transfer line extends between the radiator and the support structure, preferably adjacent to the axis. The heat transfer line is thus essentially only subjected to a torsion load if the radiator yields backward, but not to a strong shear load, which could result in tearing of the line. 
     To fix the location of the pivot axis, one of the groups of connection elements is preferably designed to detach earlier than the other group under a force exerted by the bumper girder on the frame. 
     The depth of the free space behind the radiator is then expediently deeper at the height of the group of connection elements detaching earlier than at the height of the group detaching later. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
         FIG. 1  shows a schematic side view of a frontal structure according to the invention; 
         FIG. 2  shows a horizontal section through the frontal structure; 
         FIG. 3  shows a vertical section through the frontal structure; 
         FIG. 4  shows a section analogous to  FIG. 3  after an impact according to a first embodiment; 
         FIG. 5  shows a section analogous to  FIG. 3  after an impact according to a second embodiment; and 
         FIG. 6  shows a detail of a detachable connection between the frame of the radiator and the support structure. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. 
       FIG. 1  shows a schematic side view of a frontal structure according to the an embodiment for a motor vehicle. The chassis of the motor vehicle comprises two longitudinal girders  1  rigidly connected to one another, one of which is partially shown in  FIG. 1 . A front axle  2 , which supports an engine  3  and a driveshaft  4  driven thereby, is mounted elastically on the longitudinal girders  1 . 
     The front ends of the two longitudinal girders  1  are connected to one another by a traverse  5  running below the longitudinal girders and by a support part  6  extending above them. A transverse bow  7  of the support part  6 , which is curved or C-shaped in a top view, is supported on the longitudinal girders  1  by vertical legs  8  and is used as a support for an engine hood (not shown in the figure). 
     The longitudinal girders  1  each terminate at a vertical plate  9 , on which, approximately in horizontal extension of the longitudinal girders  1 , a bumper cross member  11  is fastened via crash boxes  10 . An auxiliary girder  12  mounted below the bumper cross member  11  on the plates  9  is used to support the bumper (not shown in the figure), which is mounted covering the bumper girder  11  and the auxiliary girder  12  at the lower leg height of a typical pedestrian. 
     A radiator frame  13  is attached between the two plates  9  within a curve circumscribed by the bumper cross member  11 . The radiator frame  13  is an essentially rectangular structure, open at the front and rear, made of profile, in whose interior a radiator  14  (not visible in  FIG. 1 ) is mounted (see  FIG. 2 , for example). The radiator  14  comprises, in a way known to those skilled in the art and therefore not shown in detail, one or more heat exchangers, one of which is connected via hose lines to the engine  3  to have coolant water of the engine flowing through it, as well as one or, if necessary, multiple fans. 
       FIG. 2  shows a horizontal section through the frontal structure along the line identified by II in  FIG. 1 . It may be seen in this figure that the two lateral flanks  15  of the rectangular radiator frame  13  project significantly wider toward the bumper cross member  11  than the lower flank  16  of the frame  13  and the radiator  14  itself. It is thus ensured that even if, for example, an impact having partial overlap has the result that the bumper cross member  11  buckles centrally, the projecting edges of the lateral flanks  15  come into contact with the bumper cross member  11  yielding backward earlier than the radiator  14  and thus the radiator frame  13  is displaced to the rear together with the radiator  14 . 
       FIG. 3  shows a vertical section through the frontal structure according to an embodiment in a section along the plane III from  FIG. 2 . Anchoring pins  17 ,  18  may be seen in this section, which each project in pairs from the lower flank  16  and/or the upper flank  19  of the frame  13  and engage in holes of the traverse  5  and/or the transverse bow  7 . The anchoring pins  17 ,  18  may be plastic pins, for example, which are anchored in the aligned holes of the flanks  16 ,  19  and/or the traverse  5  and the support part  6  and whose material strength is selected in such a manner that they shear off if the bumper cross member  11  hits against the front edge of the flanks  15 , without leaving damage on the radiator frame  13 , the traverse  5 , or the support part  6 . 
     Depending on how the strength of the anchoring pins  17 ,  18  or other, similar connection elements between the radiator frame  13  and the support structure is dimensioned, different scenarios result if the radiator frame  13  is displaced by the bumper cross member  11  yielding backward. If both the upper and also the lower anchoring pins  18  and  17  are easily destructible, the moment of inertia of the radiator  14  and its frame  13  has the result that the pins  17 ,  18  are sheared off simultaneously and frame  13  and radiator  14  are displaced to the rear, toward the engine  3 , while essentially maintaining their orientation in space. This may be an expedient solution if, as in the illustration of  FIG. 1 , the free space  20  present between radiator  14  and engine  3  has a depth remaining essentially uniform over the height of the radiator  14 . 
       FIG. 4  shows a section analogous to  FIG. 3  of another embodiment, in which the free space  20  has a depth increasing from top to bottom in the normal state before an impact. The bumper cross member  11  is displaced back by an impact from the position shown as a dashed outline into the position shown by solid lines with compression of the crash boxes  10  (not shown in the figure) and has sheared off the lower anchoring pins  17  at the same time. The radiator frame  13  is pivoted around an axis essentially defined by the engagement of the upper anchoring pins  18  in the support part  6 . A hose connection, via which coolant water circulates between the radiator  14  and engine  3 , as shown in the figure by dashed outlines  21 , is led out on a lateral flank  15  of the frame  13  adjacent to the upper anchoring pins  17 . Therefore, the danger that the coolant water line will be damaged by the yielding backward of the radiator  14  is very low. There is therefore quite a high probability that in the event of an impact which is not too strong, which has not resulted in a deformation of the longitudinal girder  1 , the vehicle will still be capable of movement and may reach a service station under its own power, with a still functioning cooling system. 
       FIG. 5  shows the case opposite to  FIG. 4 , in which the depth of the free space  20  decreases from top to bottom. To use the free space  20  effectively, it is therefore necessary here for the upper anchoring pins  18  to be sheared off while the lower anchoring pins  17  remain intact. Because the height difference between the upper cross member  11  and the lower anchoring pins  17  is less than between the bumper cross member  11  and the upper anchoring pins  18 , the lower anchoring pins  17  are subjected to a higher strain upon impact then the upper. Therefore, to implement the tilting of the radiator  14  around an axis defined by the lower anchoring pins  17  as shown in  FIG. 5 , they must have a significantly higher carrying capacity than the upper anchoring pins  18 . 
     In this embodiment, the coolant water line  21  is led out of the radiator frame  13  adjacent to the lower flank  16  to minimize the danger the coolant water line  21  will be sheared off. 
     While up to this point only the case of a connection of the radiator frame  13  to the support structure via pins which may be sheared off has been observed, there are, of course, numerous other possibilities for fastening the radiator frame  13  to the support structure in such a manner that it may yield to the pressure of the bumper cross member  11  yielding backward without receiving damage.  FIG. 6  shows an example of a top view of a fraction of the traverse  5  or the support part  6  according to such an alternative having two leaf springs  22  fastened thereon, which hold one anchoring pin  17  or  18  of the radiator frame  13  between them. If the radiator frame  13  is subjected to a sufficient force, acting to the right in  FIG. 6 , the leaf springs  22  are driven apart and the anchoring pin  17 ,  18  comes free without being damaged. The possibility exists of fixing the radiator frame  14  again by simply pressing the anchoring pin  17  or  18  back between the leaf springs  22 . 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment or embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.