Abstract:
An automobile including a front cross-member, an attachment element arranged at the rear of the cross-member, a bonnet that closes off an engine compartment and including one free edge, and a front bumper mounted in front of the front cross-member and including a central portion that extends as far as the bonnet and includes a tab for attaching to the attachment element. The attachment tab includes a frangible area, located to the front of the attachment area and capable of breaking, and the frangible area is arranged next to an empty space formed in the compartment, with a view to having the central portion of the bumper bend into the empty space when the frangible area breaks.

Description:
BACKGROUND 
     Most motor vehicles comprise a bonnet or hood in which the upper air inlet grille is formed. This air inlet grille is generally positioned between the front headlamps. The bumper or fender is positioned below the aforementioned air inlet grille. In the event of a frontal impact with a small-sized pedestrian, such as a child, for example, the head of the pedestrian strikes the bonnet, substantially, above the upper air inlet grille. The natural flexibility of the bonnet, which is made of sheet steel, is able to absorb part of the impact, through deformation of the bonnet. 
     However, for the last few years, and for reasons of style, motor vehicles have had very bulky front bumpers. These bumpers comprise a central part which rises up toward the bonnet, between the front headlamps. It is often this part of the bumper which bears the upper air inlet grille. The bonnet itself is shortened and its free edge is situated fairly high up between the headlamps. In the event of a frontal impact with a small-sized pedestrian, the head of the pedestrian strikes not the bonnet but the central part of the bumper. Bumpers of this type are made up of several components which, for functional reasons, are very rigid. Such bumpers can therefore seriously injure a pedestrian, particularly the head of a small-sized pedestrian. 
     BRIEF SUMMARY 
     It is an object of the present invention to propose a motor vehicle which comprises a bumper like the aforementioned one and which reduces the risk of serious injury in a collision with a pedestrian, particularly a pedestrian of small size. 
     With the object of solving this problem, the present invention proposes a motor vehicle comprising, in a known manner:
         a structure which comprises a front crossmember and which defines, behind said front crossmember, an engine compartment;   a fixing element, secured to said structure and arranged in said engine compartment;   a bonnet or hood which closes said engine compartment and has a free edge substantially parallel to said crossmember;   a front bumper or fender mounted in front of said front crossmember and which has a central part extending toward said bonnet, said central part having an upper portion delimited by a top edge which faces said free edge of the bonnet, said upper portion comprising a fixing tab which extends into said engine compartment and comprises an attachment region fixed to said fixing element.       

     According to the invention, and characteristically, said fixing tab comprises a frangible region, situated in front of said attachment region, and which is able to break when a force exceeding a given rupture value is applied to said frangible region, and said frangible region is arranged in the region of an empty space, formed in said compartment, by means of which contrivance, when said frangible region breaks, the central part of said bumper flexes into said empty space. 
     Such a vehicle is able to dissipate some of the kinetic energy of the impact in the breakage of the frangible region and in the deformation of the fixing tab. In addition, the Applicant Company has been able to demonstrate that such a structure is also capable of reducing contact forces (that is to say the force applied by that region of the vehicle that is in contact with the pedestrian&#39;s body, on the body of the pedestrian; this force being generated by the movement of the vehicle during the impact) which are lower and able to avoid serious trauma. Such a vehicle therefore proves to be particularly advantageous in reducing the risk of head injury, in an impact with a small-sized pedestrian whose head is liable to strike the bumper of the vehicle. 
     According to one embodiment, the central part comprises a reinforcement covered with a skin, and said reinforcement bears said fixing tab. The skin may be made of a relatively flexible material while the reinforcement is rigid. 
     The fixing tab may extend over the entire width of said central part in order to afford the latter optimal attachment. 
     The frangible region may be formed of a special material, the presence of perforations or the like which weakens the fixing tab. It may be obtained by any means capable of weakening the material of the fixing tab at a given point. According to one embodiment, the frangible region is formed of a reduction in thickness of said fixing tab. 
     Advantageously, said frangible region is positioned near said free edge of said bonnet, which allows the good deformation both of the bonnet and of the fixing tab, it being possible in effect for the head or other body part of the pedestrian to enter the engine compartment at the space created behind the bumper, without striking any rigid element that could cause injury. 
     According to one embodiment, the empty space corresponds substantially to the space which separates the internal face of said front bumper from said fixing element. 
     The depth of said empty space is, for example, comprised between 50 mm and 100 mm. 
     According to one particular embodiment, said central part comprises an air inlet grille. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other specifics and advantages of the invention will become apparent from the description given hereinafter of one particular embodiment of the invention, which is given by way of nonlimiting indication with reference to the attached drawings in which: 
         FIG. 1  depicts a perspective view of the vehicle according to the invention; 
         FIG. 2  depicts a view in longitudinal section of the front of the vehicle of  FIG. 1 ; 
         FIG. 3  depicts a partial view, in longitudinal section, of the front bumper embodiment depicted in  FIGS. 1 ,  2  and  4 ; and 
         FIG. 4  depicts a view in longitudinal section of the front of the vehicle of  FIG. 1  at the moment of impact with a small-sized pedestrian. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates one particular embodiment of a vehicle according to the invention. This vehicle comprises an engine compartment closed by a substantially horizontal bonnet  1 . The bonnet  1  is hinged in the region of the windscreen or windshield and has a free edge  11 , situated at the front of the vehicle. The vehicle comprises, on each side, a front headlamp  2  positioned substantially below the bonnet  1 . The vehicle is fitted at the front with a bumper or apron  3 . This apron  3  comprises, in its bottom part, a lower air inlet grille  31 . The apron  3  extends laterally to the vehicle, under the headlamps  2 . The apron  3  also has a central part  33  which extends between the front headlamps  2  of the vehicle, toward the free edge  11  of the bonnet  1 . The headlamps  2  are thus partially surrounded by the apron  3 . The central part  33  of the apron  3  has an upper portion, positioned between the headlamps  2  and which ends at a top edge  35  parallel to the free edge  11  of the bonnet  1 . The free edge  11  of the bonnet  1  is positioned near the top edge  35  of the apron  3  to form a continuous surface. An upper air inlet grille  37  is formed between the headlamps  2 , in the central part  33 . 
     With reference to  FIG. 2 , the vehicle comprises an engine compartment in which the radiators  51  and  52  are fixed. The radiators  51  and  52  are fixed, one in front of the other, on a radiator support  6  which is itself fixed to the chassis frame side rails (not depicted) of the structure of the vehicle. The support  6  extends above and below the radiators  51  and  52 . Because the radiator  51  which is positioned furthest forward in the engine compartment is not as tall as the other radiator, the support  6  comprises a vertical spacer piece  61  which serves to fix the top portion of the radiator  51 . The front ends of the chassis frame side rails (not depicted) are connected by a front crossmember  7 . The apron  3  comprises a reinforcement  8 , made of rigid plastic. This reinforcement  8  is covered with a skin  81 , made of flexible plastic, situated on the outside of the vehicle. A shock-absorbing element  10  is positioned in front of the front crossmember  7 . This shock-absorbing element extends along the entire length of the crossmember  7 . The lower air intake grille  31  is positioned under the crossmember  7  while the upper air inlet grille  37  is positioned above the crossmember  7 . 
     As  FIG. 2  depicts, the apron  3  comprises a fixing tab  83  that forms an integral part of the reinforcement  8  and that extends the top edge  35  of the apron. This fixing tab  83  extends into the engine compartment toward the radiator support  6 . The fixing tab  83  has a substantially horizontal attachment portion  85  situated forward of its free end. The fixing tab  83  extends transversally to the apron  3  over the entire width of the portion of the reinforcement  8  that is situated in the central part  33  of the apron  3 . The fixing of the attachment portion  85  of the fixing tab  83  does not limit the scope of the invention. The fixing tab  83  may be screwed or riveted to the radiator support  6 . The fixing tab  83  comprises a frangible region  87  which is positioned near the top edge  35  of the apron  3 , at the edge of the skin  81 . The bonnet  1  comprises a lining  12 , situated inside the engine compartment. The bonnet  1  is therefore hollow, giving it a certain degree of flexibility. 
     As  FIG. 2  depicts, an empty space is created under the fixing tab  83 . The fixing tab  83  and the upper portion of the central part  33  of the apron  3 , particularly the top edge  35 , can thus, when the frangible region breaks, as explained later on, bend into the engine compartment without striking any rigid element such as the radiator  51  which would cause them to deform and could inflict trauma on the struck pedestrian. The dimensions of this empty space are dependent on the size of the fixing tab  83  and on the material used for the reinforcement  8 . 
     By way of indication, the empty space may have a depth e, measured along the longitudinal dimension of the vehicle, of the order of 50 to 100 mm, and, for example, of the order of 80 mm. The depth e of the empty space corresponds to the distance which separates the internal face of the reinforcement  8  from the radiator support  6  and, more particularly, from the spacer piece  61  of this support  6 . 
       FIG. 3  depicts the frangible region  87  in greater detail. 
     The frangible region  87  corresponds to a line of reduction in thickness of the reinforcement  8 . This line extends across the entire width of the fixing tab  83 . The frangible region  87  is positioned under the skin  81 , substantially in the region of the edge of the latter which is situated in the engine compartment. The fixing tab  83  corresponds to the portion of the reinforcement  8  that protrudes beyond the skin  81  and extends into the engine compartment toward the radiators  51  and  52 . The skin  81  covers the reinforcement  8  on the external face of the apron  3  and, over a short length, enters the engine compartment at the top edge  35 , under the bonnet  1 . The frangible region  87  therefore corresponds to the edge of the fixing tab  83  which is connected to the reinforcement  8 . The frangible region forms a line or a strip parallel to the free edge  11  of the bonnet  1  and is situated near this free edge  11 . The effect of this arrangement will be explained in greater detail with reference to  FIG. 4 . 
     The skin  81  is made of a flexible plastic. The reinforcement  8  is formed of a more brittle and more rigid plastic. For example, it is possible to choose a plastic which breaks when its elongation reaches the order of 5 to 10%. 
     The way in which the invention works will now be explained with reference to  FIG. 4 . 
     In  FIG. 4 , dotted lines depict the position of the bonnet  1  and of the central part  33  of the apron  3  prior to the impact with a pedestrian. 
     When the head T of a small-sized pedestrian strikes the upper portion of the central part  33  of the apron  3 , the frangible region  87  breaks along the entire width of the fixing tab  83 , that is to say the entire width of the central part  33  of the apron  3 . The central part  33  of the apron  3  is therefore no longer fixed to the vehicle, particularly to the support  6 . It crumples, notably at its upper portion, flexing into the engine compartment, toward the bottom of the vehicle. The top edge  35  enters the engine compartment, forward of and above the radiator  51 , which is the furthest forward in the engine compartment. At the same time, the impact with the head T of the pedestrian causes the bonnet  1  to deform. The free edge  11  of the bonnet  1  enters the engine compartment and bends substantially toward the radiators  51  and  52 . Because the frangible region  87  is positioned near the free edge  11  of the bonnet  1 , it is directly subject to the impact with the head of the pedestrian and soon breaks. Moreover, this arrangement makes it possible to create two lips, one formed by the top edge  35  and the other by the free edge  11  of the bonnet  1 , which part under the effect of the impact, in the engine compartment, in the empty space formed under the fixing tab  83 . This affords effective protection to the head of the struck pedestrian. 
     As depicted in  FIG. 4 , when the deformation is at its maximum, the lining  12  of the bonnet  1  comes into contact with the radiator support  6  above the radiator  52 . The fixing tab keeps its attachment region  87 , fixed to the radiator support  6 . That portion of the fixing tab  83  that is situated forward of the attachment region bends toward the radiator  51 . 
     By way of indication, the deformation of the apron  3  and of the bonnet  1  causes the top edge  35  and the free edge  11  to move by a maximum amplitude P of the order of 10 mm. 
     In the impact with a pedestrian, the kinetic energy of the impact is dissipated, partly in the breakage of the frangible region  87 , and partly in the deformation both of the bonnet  1  and of the central part  33  of the apron  3 . Further, when the head T of the pedestrian is, as has been depicted in  FIG. 4 , resting against the top edge  35  of the apron  3  and on the free edge  11  of the bonnet  1 , contact forces are applied to the head T of the pedestrian throughout the length of time for which the vehicle is still in motion and the head T remains in contact with the aforementioned parts of the vehicle. The Applicant Company has observed that, not only is the kinetic energy of the impact effectively dissipated, as previously explained, but also the forces of contact, during the impact, can be reduced to a value of below 200 kg, which corresponds to the admissible limit for the cerebral skull. The central part  33  of the apron  3  of the invention is hard enough for normal use of the apron (that is to say protect the structure of the vehicle) and, because of the presence of the frangible region  87 , is also flexible enough not to cause serious traumatic injury to the head of a small-sized pedestrian.