Abstract:
The invention relates to a motor vehicle part including a light unit support possessing an initial “operational” position in which the light unit is held at a given height on the vehicle. The light unit support also is configured to take up a second “depressed” configuration on being subjected to a vertical force that is substantially equal to that of an impact with the head of a pedestrian, in which second configuration the light unit is located lower down relative to the vehicle.

Description:
BACKGROUND 
     1. Field of Invention 
     The present invention relates to a motor vehicle part including light unit support means. 
     2. Description of Related Art 
     In the state of the art, in particular from EP 1 577 610, a light unit is already known that is arranged on a vehicle in such a manner as to damp impacts of medium intensity with other vehicles (known as “insurance” or “repairable” impacts), or else with the hip of a pedestrian, where such impacts are directed mainly in the travel direction of the vehicle (generally referred to as the X direction). That light unit is provided with fastenings that break on being subjected to high levels of stress in the X direction, thereby allowing the light unit to move backwards. Thus, the light unit is not damaged by the impact and can easily be repaired. In addition, it does not constitute a dangerous “hard” point in the event of an impact with the hip of a pedestrian. 
     It is also known that attempts are being made to protect the heads of pedestrians in the event of an impact with the zone covering the front fender and the light unit, referred to as the “head” zone. For this purpose, it is desired to provide a zone that becomes depressed in the vertical direction (generally referred to as the Z direction) that does not have a hard point so as to allow a head to move down over a certain distance during an impact. 
     The state of the art already discloses a fender support capable of damping such an impact, known as a “head impact”, as described in particular in publications FR 2 855 810 or DE 10 347 810. 
     SUMMARY 
     The problem lies in there being no known way of dealing with a head impact against a vehicle in which the fender covers the light unit. The light unit constitutes a hard point, such that even if the fender can become depressed by using the prior art support, the light unit remains dangerous for the head of a pedestrian. 
     The present invention seeks to provide a part for supporting a light unit and that is capable of dealing with a head impact, regardless of the configuration of the front of the vehicle. 
     To this end, the invention provides a motor vehicle part including means for supporting a light unit, these light unit support means possessing an initial, so-called “operating” configuration in which the light unit is held at a given height on the vehicle, the part being characterized in that the light unit support means are also capable of taking up a second, so-called “depressed” configuration on being subjected to a vertical force substantially equal to that of an impact with the head of a pedestrian, in which second configuration the light unit is lower down relative to the vehicle. 
     The invention provides a support part that acts as a support for the light unit when in its operating configuration, while nevertheless also protecting a pedestrian by moving down over a certain distance under drive from the head of the pedestrian. The light unit thus no longer constitutes a dangerous hard point. 
     The term “vertical force” is used to mean a force directed in the direction that is conventionally vertical relative to the vehicle, referred to as the Z direction. The value of this force in accordance with the invention, which is substantially equal to the force of an impact against the head of a pedestrian, lies in the range 250 kilograms (kg) to 900 kg, and preferably in the range 300 kg to 600 kg. Advantageously, the support means also take up a depressed configuration under the effect of a force that is vertical in part only, i.e. a force that comprises not only a component in the vertical direction, but also a component in the longitudinal direction of the vehicle, referred to as the X direction, and/or in the transverse direction, referred to as the Y direction. Such a part is thus capable of handling not only a head impact, but also a “hip” impact. 
     The term “light unit support means” is used to cover means capable of supporting the light unit, at least in part. In general, the light unit is supported via three or four points. The second configuration of the support means may be the result of one or two of these points rupturing, and of rotation alone about the other points. It may also result from all of the points. 
     The term “light unit” covers an assembly comprising optical glazing, a housing, and optical and lighting components. For simplification purposes, the term “light unit” may designate one or another of the above parts or the assembly thereof. 
     In a preferred embodiment, the part further includes means for supporting a fender of the vehicle, said means possessing an initial, operating configuration in which the fender is held at a given altitude, and also being capable of taking up a second, depressed configuration on being subjected to a vertical force substantially equal to that from an impact with the head of a pedestrian, in which second configuration the fender occupies a lower position. 
     Thus, in the event of a head impact, the fender support means no longer constitute a hard point for the pedestrian. This embodiment is particularly advantageous for vehicles where the fender covers the light unit. Furthermore, instead of using two distinct support parts for the light unit and for the fender, each of which is provided with its own means for fastening to the structure of the vehicle, a common part is used for performing support functions both for the light unit and for the fender, such that the configuration of the front unit of the vehicle is simplified, in particular because the means for fastening to the structure are common. 
     Preferably, the part is provided with fusible means arranged to hold the means for supporting the light unit and/or the fender in their operating configuration. These means are fusible in the vertical direction, i.e. they are capable of breaking or of deactivating under the effect of a vertical force, and thus of enabling the support means for the light unit and/or the fender to take up their depressed configuration. 
     Advantageously, the fusible means are means that are deformable in buckling or in folding, or means that break in shear. 
     Preferably, the fusible means are constituted by means for fastening the part to a structural part of the vehicle. 
     The term “structural part of the vehicle” is used to mean a rigid part belonging to the chassis or the body-in-white of the vehicle, such as a low or high longitudinal member, a cross-member, or an upright of a front panel, a strut of the body carrying hinges for a vehicle door or for a hood, a frame member around a recess, a structural wheel arch, etc. 
     Preferably, the part further includes means for positioning the light unit or a member supporting the light unit, means for positioning the fender, means for positioning a bumper skin, and/or also means for positioning a hood. Thus, in addition to its semi-structural function, the part performs a function of putting various bodywork parts into reference positions relative to one another, said parts being situated specifically in a zone that requires particular attention from the point of view of making parts flush and putting them properly into position. 
     It is particularly advantageous for the part to include in particular means for positioning two adjacent bodywork parts relative to each other, since said means serve to act directly on the two facing edges that are to be positioned so as to position those edges relative to each other. The support can thus be provided with direct-thrust positioning means for the fender and for the light unit so as to provide control over positioning between the top edge of the light unit glazing and the edge of the fender that is best in terms of clearance and surfaces that are flush. 
     Preferably, the part also provides an anti-indentation function for the fender. For example, it matches substantially the inside shape of the fender, thus making it possible to use a fender that is relatively flexible and thin, e.g. made of plastics material, of aluminum, or of steel, and without it being necessary to apply reinforcement in the fender. 
     Advantageously, the part is adapted to support the fender during a step during which the vehicle is painted or subjected to cataphoresis, thus enabling the part to be mounted on the vehicle before the fender is mounted, and then enabling it to support the fender during subsequent assembly steps. 
     A part of the invention may also present one or more of the following characteristics:
         The part includes means for fastening to two structural parts of the vehicle, namely a front vertical upright and a side rail of the bodywork.   The means for supporting the light unit and/or the fender are arranged in such a manner as to conserve their operating configuration(s) under the effect of a force substantially equal to that of the weight of a sitting person or to vibration during operation of the vehicle. In other words, the fusible means are strong enough to support some minimum force, e.g. 50 kilograms weight (kg), imparting the stiffness needed to enable the part to operate, while being capable of breaking or of being deactivated under the effect of a force exceeding a certain threshold.   The means for supporting the light unit and/or the fender are capable of taking up two depressed configurations, depending on whether they are subjected to a vertical force equal to that of an impact with the head of a pedestrian of adult size or of child size.   The part extends over the major fraction of a so-called pedestrian head impact zone, constituted by top portions of the fender and of light unit.   The part is shaped so as to free access to the light unit in order to change a bulb.   The part includes adjustable fastener means for the light unit, so as to enable the light unit (or at least its glazing or its housing) to be positioned relative to the remainder of the vehicle prior to being secured finally in place for operation on the vehicle.   The part includes hood abutments.   The part is made of a thermoplastic material of the polyamide type that can withstand 200° C., and possibly associated with metal reinforcement by overmolding. Alternatively, it is made of a thermosetting resin of the sheet molding compound (SMC) type, or of the type sold under the trademark AMC 3600 (adapted molding compound).       

     The invention also provides an assembly comprising a light unit and a part as defined above, in which the part is made integrally with the housing of the light unit. 
     Optionally, the means for supporting the fender are formed on the light unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       The invention can be better understood on reading the following description given purely by way of example and made with reference to the accompanying drawings, in which: 
         FIG. 1  is a diagram of a motor vehicle front; 
         FIG. 2  is a diagram of a vehicle front structural portion including a part constituting a first embodiment of the invention; 
         FIG. 3  is a diagram showing fusible means formed on the part of  FIG. 2 ; 
         FIG. 4  is a section view of the  FIG. 2  part, supporting a light unit and a fender; 
         FIG. 5  is a perspective diagram of a part constituting a second embodiment of the invention; 
         FIG. 6  is a diagram of a part constituting a third embodiment of the invention; 
         FIG. 7  is a diagram of fusible means suitable for being formed on a part of the invention; and 
         FIG. 8  is a perspective diagram of fusible means arranged on a part of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     A part of the invention serves to protect a pedestrian who has been hit by a vehicle and whose head  10  is liable to strike a zone  12  of a motor vehicle front that is referred to as the “head” zone, as shown in  FIG. 1 . 
     In the event of an impact, the zone  12  is subjected to a force that is essentially vertical, represented by arrow  17  and directed along the Z direction. This force may also have components in the X and Y directions, i.e. it might be directed obliquely relative to the vehicle. 
     The zone is constituted by the top portion of a fender  14  that covers a light unit  16 . While the vehicle is in operation, the fender  14  and the light unit  16  are maintained at a given height on the vehicle, referred to as the operating height, i.e. the  height as shown in  FIG. 1 . 
     The light unit is supported by a semi-structural part  18  of the invention shown in  FIG. 2 , constituting a support for the light unit  16  and the fender  14  (not shown). 
     The unit  16  may optionally be supported by the part  18  via a support member that is secured to the part  18 . When suitably positioned relative to the other parts of the bodywork, this support member (not shown) serves to enable the light unit to be put into place and removed without it being necessary for it to be re-positioned. 
     The part  18  also constitutes a support for the front fender  14  of the vehicle. More particularly, it includes fender support means  22  that are constituted by the top portion of the part  18 . 
     The part  18  is secured to two structural parts of the vehicle, namely a front vertical upright  24  secured to a longitudinal member  26 , and a side rail  28  of the body. 
     The part  18  is secured to the upright  24  by fusible means  30 . These means  30  are arranged to hold the part  18  in an initial, operating configuration in which the light unit  16  and the fender  14  are held at their operating heights. 
     These means  30  may be constituted by a stud, as shown in  FIG. 3 , that is hollow and in the form of a pyramid of square base  32  and top  34 , with side surfaces  36  that are pre-slit. By means of these slits  38 , the surfaces  36  can buckle in the directions represented by arrows  40  in the event of the stud being subjected to a certain amount of vertical force in the Z direction. 
     In the event of a head impact, the zone  12 , and consequently the stud  30 , are both subjected to a force that is sufficient to cause the walls  36  to buckle. The height of the stud decreases, thereby lowering the part  18  that is secured to its top  34 , so that the part  18  then occupies a depressed configuration in which the heights of the light unit  16  and of the fender  14  are lower than their operating heights. This difference in height increases the distance over which energy can be absorbed prior to striking a structural part of the vehicle. 
     In a variant shown in  FIG. 8 , the part  18  comprises a bottom portion  84  secured to the upright  24  in a contact zone  82 . The bottom portion  84  is a channel-section bar, having two side flanges  86  and  86 ′. 
     In this configuration, the means  30  comprise constrictions in thickness  88  in the side flanges  86  and  86 ′ associated with notches  90  at the top ends of each of the constrictions. These fusible means  30  are situated in a so-called zone of “weakness” formed at the periphery of the contact zone  82 . 
     In the event of a head impact, the part  18  is subjected essentially to a downwardly-directed vertical force. The forces then concentrate in the zone of “weakness” at the periphery of the contact zone  82 , which contact zone is held rigidly in place on the upright  24 . 
     The force to which the side flanges  86  and  86 ′ are subjected in the region of the constriction  88  in thickness is sufficient for a break starter to be created by shear in the vicinity of the notch  90 . This causes the bottom portion  84  to break in the zone of weakness, and thus reduces the height of the light unit  16 , since it is no longer supported by the upright  24  and thus by the body. 
     Fusible means other than those described could be envisaged. For example, a part arranged in a “concertina” configuration in the Z direction could be provided between the part  18  and the upright  24 , so as to be capable of reducing its height under the action of a vertical force. 
     Fusible means  42  may also be provided on the other end of the part  18  that is secured to the side rail  28 ; 
     The part  18  also carries means  44  for directly positioning the light unit  16  and the fender  14 , as can be seen more precisely in  FIG. 4 . 
     These positioning means  44  comprise a groove  46  enabling a portion  48  of the light unit housing that is situated in the vicinity of the optical glazing  50  to be positioned. In the vicinity of the groove  46 , the means  44  comprises a rib  52  receiving the top edge  54  of the fender. As can be seen in the figure, the top edge  54  of the fender and that of the glazing  50  are correctly positioned flush with minimum clearance, by the means  44 . 
     In another embodiment shown in  FIG. 5 , a part  60  of the invention is constituted by a strip  62  along which there is secured the top edge of the fender. The light unit  64  is also secured to the strip  62 . It may be molded integrally with the strip  62 . Nevertheless, it is preferable to provide adjustable fastenings between the light unit and the strip  62  so as to enable the light unit to be positioned on the vehicle prior to finally setting its operating height. 
     The part  60  constitutes a support for the light unit  64  and for the fender. It matches substantially the inside top shape of the fender, so as to perform an anti-indentation function. 
     It may take up a depressed configuration when subjected to a vertical force equal to that of an impact with the head of a pedestrian. In such a configuration, the light unit and the fender are to be found at a lower height. 
     This depressed configuration is obtained by virtue of fusible means provided by the shape of the strip  62  which is constituted by a hollow tube that is capable of deforming by buckling. The strip  62  may also be Z-shaped, as shown diagrammatically in  FIG. 7 , and it may be provided with gussets  66  capable of buckling under the action of a vertical force. 
     In another embodiment of the invention shown in  FIG. 6 , a part  70  of the invention includes means  72  for supporting the light unit  74 , which in turn carries means  76  for supporting the fender  78 . The light unit  74  is covered in part by the hood  79  of the vehicle. A portion  80  of the part  70  is fusible in the event of a head impact. If the impact takes place more particularly on the outer portion of the fender, the portion  80  becomes pushed in, such that the outer portion of the light unit  74  can pivot relative to a portion  82  of the part  70  and thus move downwards. 
     In a second embodiment shown in  FIG. 8 , the part  18  is of a shape similar to that of the part shown in  FIG. 2 , and it is placed in the motor vehicle in the same manner. The part  18  includes a bottom portion  84  that is in contact with the upright  24  in a contact zone  82  that is situated in the bottom portion  84  of the part  18 , with the upright  24 . The bottom portion  84  is a channel-section member with two side flanges  86  and  86 ′. 
     In this embodiment, the means  30  comprise a constriction  88  in the thickness of each of the side flanges  86  and  86 ′, together with associated notches  90  at the top edges of the flanges in the contact  82 . These fusible means  30  are situated in a so-called zone of “weakness” situated at the periphery of the contact zone  82 . 
     In the event of a head impact, the part  18  is subjected to a downwardly-directed vertical force. Forces then become concentrated at the periphery of the contact zone  82  since it is held rigidly by the upright  24 . 
     The shear force to which the side flanges  84  and  86  are subjected in the vicinity of the constrictions  88  in thickness in this location is sufficient to create a rupture starter in the vicinity of the notches  90 . This causes the bottom portion  84  to rupture in the zone of weakness, thereby causing the light unit to move downwards, since it is no longer supported by the body via the upright. 
     Finally, it should be observed that the invention is not limited to the embodiments described above.