Abstract:
The invention relates to a system for deviating part of an external panel of a motor vehicle, during an accident to reduce the impact energy of a person colliding with deviated part of the external panel. The part is displaced in a deviation direction that is opposite to that of an impact direction of the person. The system includes a device for deviating the part. The device is engaged at least at one point on the part and permits a displacement of the part in the impact direction, if a person collides with the part.

Description:
BACKGROUND 
     The invention relates to an arrangement for deflecting part of the external paneling of a motor vehicle in the event of a crash. 
     The deflection of part of the external paneling of the motor vehicle toward the outside in the event of a crash is intended to dissipate the impact energy of a person (e.g., a pedestrian or cyclist) in a controlled manner. The impact energy of the person is dissipated by movement of the deflected part in a deflecting direction that is counter to an impact direction of the person, thereby reducing the likelihood of the person coming into contact with rigid motor vehicle elements positioned behind the external paneling, such as, for example, an engine block. To this end, a typical arrangement comprises a device for deflecting the part of the external paneling, which device acts on at least one point of this part and which, during the impact of a person, permits a movement of this part counter to the deflecting direction, thereby dissipating impact energy. 
     An arrangement of this type is disclosed, for example, in WO 01/23 225 A1 (incorporated by reference herein), which describes a device for raising the engine hood of a motor vehicle in the event of crash, which can be detected by a pre-crash sensor. The sensor triggers a raising of the engine hood if it detects a directly imminent, unavoidable accident. A person impacting against the engine hood, as a consequence of this accident, is protected (by the raising of the engine hood) from coming into contact with the engine block situated under the hood. 
     As the impact of a person against the engine hood (and the associated impact forces) leads to a movement of the engine hood counter to the deflecting direction (i.e. the impact and associated forces lead to a counter deflection of the engine hood toward the engine block), energy may be dissipated in a controlled manner. As a result, the risk of injury is reduced in comparison with a direct impact against a rigid part of the motor vehicle. 
     However, a problem with this arrangement is that the impact of a person against the external paneling of a motor vehicle (e.g., against the engine hood thereof) frequently takes place in a number of steps. For example, during the usual kinematic sequence of a collision between a pedestrian and vehicle, the impact of the pedestrian&#39;s head against the engine hood is generally preceded by an impact of the pedestrian&#39;s upper body. The impact of the upper body (and its associated impact energy) may result in the previously deflected engine hood being lowered back against the engine block. As a result, there may no longer sufficient protective potential for the subsequent impact of the head. However, it is the protection of the head of a person (e.g., pedestrian or cyclist) colliding with the vehicle that is of particular importance. 
     SUMMARY 
     The embodiments of the invention described herein improve upon the conventional arrangement by accounting for multiple impact stages. As a result, the invention accounts for and dissipates, for example, the impact energy of a pedestrian&#39;s head after accounting for and dissipating, for example, the impact energy of the pedestrian&#39;s upper body. 
     In accordance therewith, the deflecting device serving for deflecting part of the external paneling of the motor vehicle can be controlled as a function of the location, the time and/or the direction of the impact in such a manner that, as a function of the instant of the impact (after the triggering of the deflecting device or after a preceding first impact) against the part of the external paneling and/or as a function of the location of the impact against the deflected part of the external paneling and/or as a function of the direction of the impact against the deflected part of the external paneling, the deflecting device permits or does not permit a movement of the part of the external paneling counter to the deflecting direction. 
     This makes it possible to control the deflecting device as a function of experimental values concerning the time sequence of the impact of the upper body of a person, on the one hand, and of his head, on the other hand, and as a function of experimental values concerning the location and the direction of the impact of the upper body, on the one hand, and of the head, on the other hand, in such a manner that it permits a movement counter to the deflecting direction specifically at the moment when, according to the available experimental values, the head of a person situated outside the vehicle is striking against the deflected part of the external paneling of the vehicle, for example against a deflected engine hood. 
     On account of the mobility and deformability of the deflected part of the external paneling, the feature according to which the deflecting device permits or does not permit a movement of the part of the external paneling counter to the deflecting direction is not absolutely to be understood within the meaning of either a movement of the external paneling taking place or alternatively no movement thereof at all taking place. On the contrary, depending on the severity of the impact, a certain movement is imposed on the system even in those cases in which no movement per se of the external paneling counter to the deflecting direction is to take place. Rather, the crucial factor for the feature is for the deflecting device to be controlled in such a manner that, under given conditions (as a function of the instant, the location and the direction of the impact), opens up the possibility of a movement of the part of the external paneling counter to the deflecting direction or opposes this movement in order as far as possible to prevent it. 
     The solution according to the invention firstly provides, by part of the external paneling being deflected, a deformation distance in order to dissipate the energy transmitted by the head of a pedestrian or a cyclist to the external paneling to an acceptable level without his head coming into contact with rigid vehicle parts situated behind the external paneling, such as, for example, the engine block. In this case, the effect achieved by controlling the deflecting device is that this deformation distance is not already used up during an impact of the upper body that precedes the impact of the head. On the contrary, the available deformation distance is not as far as possible to be reduced during an impact of the upper body that precedes the impact of the head. 
     An accident which leads to the deflecting device being activated can be detected by a contact sensor or a proximity sensor (pre-crash sensor). Upon detection of an accident, the corresponding sensor produces a signal causing the deflecting device to deflect the corresponding part of the motor vehicle outward. In this case, the activation of the deflecting device and the impact of the head must not coincide in time. This causes correspondingly short deflecting times. To this end, the corresponding part of the external paneling of the motor vehicle, for example the engine hood, is to be designed in such a manner that it can be brought into the deflected position (protective position) without permanent deformation. On the other hand, the external paneling must not, however, be of such rigid design that the load limit values of the head are exceeded solely because of the rigidity of the external paneling. 
     In particular, the external paneling has to be of sufficiently flexible design even in the region of the points on which the deflecting device acts, so that the load limit values for the head are not exceeded. 
     Overall, the arrangement according to the invention results in a uniform and low loading of the head during the impact against part of the external paneling of a motor vehicle, in order to avoid serious head injuries. 
     To control the deflecting device as a function of the instant of the impact, provision may be made for the deflecting device to permit a movement of the deflected part of the external paneling counter to the deflecting direction only after a specified period of time has elapsed since the activation of the deflecting device by the force with which the deflecting device acts on the deflected part of the external paneling being time-controlled. The control takes place here in such a manner that the force with which the deflecting device acts on the external paneling decreases with time after the deflection of the part of the external paneling. This means that, upon an impact of the upper body of a person directly after part of the external paneling has been deflected, the force applied by the deflecting device is still sufficiently large in order to prevent a restoring movement of the part of the external paneling. During the subsequent impact of the head, the force has decreased sufficiently now for it to be possible for energy to be dissipated in a controlled manner by the part of the external paneling moving counter to the deflecting direction and therefore counter to the direction of action of the pressure. 
     To this end, use may be made of a deflecting device which deflects the part of the external paneling which is to be deflected under the action of the pressure of a fluid, in particular of a gas, the pressure of the fluid being time-controlled and decreasing after the deflection of the part of the external paneling, thus enabling the part of the external paneling to move counter to the pressure of the fluid. 
     The pressure of the fluid acting on the deflected part of the external paneling can be reduced, for example, by some of the fluid being discharged by corresponding outflow openings being provided for discharging the fluid. In addition, the size of these outflow openings may be controllable in order to be able to set the pressure of the fluid in a specific manner as a function of the time. 
     The triggering of the deflecting device may take place, for example, pyrotechnically, it furthermore also being possible for the production or release of a gas used for deflecting the external paneling to take place pyrotechnically. 
     According to one embodiment, the deflecting device comprises an element which can be filled with fluid to produce the pressure, for example an inflatable airbag, which acts on the part of the external paneling that is to be deflected. According to another embodiment, the deflecting device has a piston (e.g. guided in a cylinder) which acts on the part of the external paneling which is to be deflected and is moved, for example, by means of a pressure produced by a fluid. 
     According to another variant of the time control of the deflecting device, the deflecting device can be locked in such a manner that, in the locked state, it does not permit any movement of the deflected part of the external paneling counter to the deflecting device, the locking being releasable by the impact of a body part (e.g. the upper body) of a person against the external paneling, so that, upon a further impact (e.g. of the head), the deflected part of the external paneling can move counter to the deflecting direction. The locking may take place, for example, by means of a hook which is released owing to the force produced upon a first impact. 
     According to a further variant of the invention, the deflecting device permits a movement of the deflected part of the external paneling counter to the deflecting direction Only upon the impact of a body part of a person within a certain region of this part. This region is selected in such a manner that it precisely encompasses those points of the part of the external paneling against which, according to the available experimental values, the head of a pedestrian or of a cyclist impacts during a typical accident sequence. 
     In one preferred embodiment, that region encompasses in particular those points of the external paneling on which the deflecting device acts. To this end, the deflecting device may act on the external paneling via an elastically or plastically deformable element. The corresponding element may also be of multipart design, with the result that the deformability is achieved by the movement of two components of the element with respect to each other, for example by the movement of a piston in a cylinder. 
     When a person impacts against the external paneling of the motor vehicle in the environment of the elastically or plastically deformable element, said element is deformed in such a manner that the deflected part of the external paneling can move counter to the deflecting direction (with deformation of each element). 
     The deformable element can be formed, for example, by a spring-elastic element, by a flexible coupling element of the deflecting device (e.g. in the form of a flexible traction means) or by a telescopic element (e.g. in the form of a piston guided in a cylinder). 
     As an alternative or in addition to a deformable element, provision may be made for the deflecting device to be of reversible or at least partially reversible design, so that, upon the impact of a body part of a person (within a certain region of the external paneling), those elements of the deflecting device which serve for deflecting the external paneling directly permit the part of the external paneling to move counter to the deflecting device. 
     According to a further variant of the invention, the deflecting device permits a movement of the deflected part of the external paneling counter to the deflecting direction only if the impact of a body part of a person against the external paneling takes place along a certain, specifiable directional region (corresponding to a specified region of possible force application directions). 
     This may be achieved, for example, by the use of a deformation element which can be deformed only upon an impact with a force application direction within the specified solid angle region. According to another embodiment with a reversible or partially reversible deflecting device, the latter, on account of its reversibility, only permits a movement of the external paneling if the force exerted on the deflecting device has a direction which lies within the specified directional region. 
     For deflecting part of the external paneling of the motor vehicle, the deflecting device may have, for example, a lever mechanism with at least one pivotable lever. On the other hand, the deflecting device may comprise a movably guided traction means which is tightened for the deflection of part of the external paneling. 
     In order to permit a movement of the deflected part of the external paneling counter to the deflecting direction, the pivotably mounted lever of the deflecting device is pivoted in the opposite direction and the part of the external paneling that is to be moved is moved counter to the tensioning of the traction means. In this case, the pivotable lever and the traction means may be arranged and designed in such a manner that a movement of the deflected part of the external paneling counter to the deflecting direction is possible only if the force exerted by the impact of a body part (in particular the head) of a person acts on the deflected part in a certain subregion and/or with a certain direction. 
     In a corresponding manner, provision may also be made, in the case of part of the external paneling being deflected by means of a piston, for the piston to be arranged in such a manner and to be guided in such a manner that a movement of the deflected part counter to the deflecting direction is possible only upon an impact against a certain region of the deflected part and/or upon a certain force application direction. 
     In a development of the invention, the deflecting device is coupled to an elastic element which pretensions the deflecting device in the deflecting direction. Furthermore, a locking element is provided which opposes a deflection of the corresponding part of the external paneling by the deflecting device and which, in the event of a crash, can be unlocked either under control by a sensor or by the force produced during the impact of a person. 
     The solution according to the invention can be used particularly advantageously for deflecting (raising) a flap of a motor vehicle, for example the engine hood or the trunk flap, in the event of a crash, in which case the application point of the deflection device is preferably to be arranged in the region of that end of the corresponding flap which is on the passenger compartment side. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below. 
         FIG. 1   a  shows a schematic illustration of an arrangement for raising an engine hood by means of an inflatable airbag; 
         FIG. 1   b  shows the arrangement from  FIG. 1   a  after the raising of the engine hood; 
         FIG. 2   a  shows a schematic illustration of an arrangement for raising an engine hood by means of a piston which can be moved by gas pressure; 
         FIG. 2   b  shows the arrangement from  FIG. 2   a  after the raising of the engine hood; 
         FIG. 3   a  shows a modification of the exemplary embodiment from  FIG. 2   a;    
         FIG. 3   b  shows the arrangement from  FIG. 3   a  after the raising of the engine hood; 
         FIG. 4   a  shows a schematic illustration of an arrangement for raising an engine hood using a traction means; 
         FIG. 4   b  shows the arrangement from  FIG. 4   a  after the raising of the engine hood; 
         FIG. 5   a  shows a development of the exemplary embodiment from  FIG. 4   a;    
         FIG. 5   b  shows the arrangement from  FIG. 5   a  after the raising of the engine hood; 
         FIG. 6   a  shows a schematic illustration of an arrangement for raising an engine hood using a pivot lever and a spring acting thereon; 
         FIG. 6   b  shows the arrangement from  FIG. 6   a  after the raising of the engine hood; 
         FIG. 7  shows a schematic illustration of an arrangement for raising an engine hood using a lever system; 
         FIG. 8   a  shows a schematic illustration of an arrangement for raising an engine hood using a pivotably mounted piston; 
         FIG. 8   b  shows the arrangement according to  FIG. 8   a  after the raising of the engine hood; 
         FIG. 9   a  shows a schematic illustration of an arrangement for raising the outer side of an engine hood by means of an inflatable airbag; 
         FIG. 9   b  shows the arrangement from  FIG. 9   a  after the raising of the engine hood; 
         FIG. 10  shows a schematic illustration of an arrangement for raising an engine hood using an airbag which additionally covers regions of a motor vehicle that are adjacent to the engine hood; 
         FIG. 11  shows a schematic illustration of an arrangement for raising an engine hood using an airbag which extends along the outer edges of the engine hood; 
         FIG. 12   a  shows a hinge for an engine hood for use in one of the arrangements according to  FIGS. 1   a  to  11 ; 
         FIG. 12   b  shows the hinge according to  FIG. 12   a  after the raising of an engine hood. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1   a  schematically shows an engine hood M of a motor vehicle in the region of its rear end H, i.e. in the region of its end facing the passenger cell, in particular the windshield. 
     In the region of an end H of the engine hood M, which is at the rear in the direction of travel and faces the passenger cell, a deflecting device  1  is arranged between a load-bearing structure T of the motor vehicle and the engine hood M. The deflecting device  1  can be used to raise the engine hood M in the event of a crash, to provide a deformation distance s (shown in  FIG. 1   b ) for a person, e.g. a pedestrian or a cyclist, impacting against the engine hood M as a consequence of the accident. The deflecting device  1  includes an airbag  10 , which is arranged on the load-bearing structure T of the motor vehicle. The airbag  10  can be inflated by means of a gas generator  12  and, in the folded state (shown in  FIG. 1   a ), extends between the load-bearing structure T and the engine hood M. Arranged on the engine hood M above the airbag  10  is a force transmission element  15  via which the airbag  10  can act on the engine hood M. 
     If, by means of a “pre-crash sensor” in the form of a proximity sensor, a directly imminent, unavoidable accident is identified or if, by means of a contact sensor, an accident which is already taking place is identified, then the deflecting device  1  is triggered by the gas generator  12  being ignited. The gas generator  12  produces a gas by means of a pyrotechnic charge and/or releases an already stored gas which flows into the airbag  10 , so that the latter is inflated and is deployed. 
     When the airbag  10  is inflated, it presses (via the force transmission element  15 ) against at least part of the engine hood M, so that the part is raised in a deviation direction a, as illustrated in  FIG. 1   b . In the completely inflated state of the airbag  10 , the engine hood M is raised in the region of its rear end H by a defined distance s in relation to its starting position illustrated in  FIG. 1   a . This distance s defines the deformation distance that is available to a person (e.g., a pedestrian or cyclist) impacting against the engine hood M as a consequence of an accident. As a result, the impact energy of the person impacting the hood M in an impacting direction (which is counter to the deviation direction) can be dissipated in a controlled manner. Moreover, the likelihood of the person coming directly into contact with rigid vehicle parts (which may be situated behind the engine hood M, such as, for example, the engine block) is reduced. 
     To this end, the engine hood M should be sufficiently stable, so that it can be raised, without being damaged, by means of an airbag  10 , which can be inflated very rapidly within milliseconds. In addition, the engine hood M should be sufficiently flexible, so that an impacting person does not sustain severe injuries due to the rigidity of the engine hood M. 
     Immediately after the inflation of the airbag  10 , the airbag  10  (as a result of the gas pressure existing in the airbag  10 ) forms an element that keeps the engine hood M stable in the raised position. Upon impact of a person against the engine hood M, the airbag  10  initially yields only to a small extent such that a substantial movement of the engine hood M counter to the deflecting direction a of the engine hood is not possible. That is to say, a first impact of a body part (e.g., an upper body) of the person involved in the accident against the engine hood M immediately after the upward deflection of the engine hood M by inflation of the airbag  10  does not result in the engine hood M being moved counter to the deflecting direction a. As a result, the energy of the initial impact is not substantially dissipated in a controlled manner. However, the deformation distance s is still available for a later, second impact (as hereafter described) and, therefore, the deformation distance is available to dissipated the energy of the second impact in a controlled manner. 
     During a later, second impact, a movement of the engine hood M counter to its deflecting direction a is made possible by the fact that the airbag  10  has vent openings as are known, for example, in the case of airbag modules for protecting vehicle occupants, through which the gas which has flowed from the gas generator  12  into the airbag  10  can be discharged again into the surroundings. By this means, the pressure within the airbag  10  decreases, so that during a later impact, e.g. of the head of a person, against the engine hood M, a considerably lower pressure opposes a movement of the engine hood M counter to the deflecting direction a. The engine hood M can then move counter to the deflecting direction a under the action of the force of the impact, in which case impact energy is now dissipated in a controlled manner and an injury to the head impacting against the engine hood M is prevented. 
     In this connection, it should be noted that even upon the first impact of the person with his upper body against the engine hood M, the deflecting device nevertheless still fulfills a second main function, namely of protecting the person against coming directly into contact with rigid vehicle parts placed below the engine hood M, such as, for example, the engine block. 
     As a result, the arrangement illustrated in  FIGS. 1   a  and  1   b  is therefore used to protect a person impacting against the engine hood M during a first impact directly after the inflation of the airbag  10  against coming into contact with rigid vehicle parts placed below the engine hood M, by raising the engine hood M. Upon a later, second impact there is furthermore (additionally) still a controlled dissipation of impact energy with the engine hood M moving counter to the deflecting direction a. 
     Since, in the case of an accident-induced impact of a person against the engine hood of a motor vehicle, generally first the upper body and then the head impacts against the engine hood, the greatest possible protection is provided for the impacting head and, in particular, a reduction in the deformation distance s even before the impact of the head is prevented. 
     In a development of the arrangement illustrated in  FIGS. 1   a  and  1   b,  the size of the vent openings serving for discharging gas from the airbag  10  can be time-controlled, so that a certain, specified time window can be made available in a specific manner, in which a dissipation of impact energy is possible by the engine hood M moving counter to the deflecting direction a. In this case, provision may also be made, for example, for the force acting during a first impact against the engine hood M and the deflecting device  1  to change the size of the vent openings in such a manner that a certain specifiable pressure level is made available for the second impact of the person (with his head) that is to be anticipated within a certain period of time. 
     As modification of the exemplary embodiment illustrated in  FIG. 1   a,    FIG. 2   a  illustrates an arrangement for raising the engine hood M, the deflecting device  2  comprising, instead of an airbag, a piston  21  which is guided in a cylinder  20 , can be raised by a gas produced by means of a gas generator  22  and then, according to  FIG. 2   b,  acts via a force transmission element  25  on the engine hood M in such a manner that the latter is raised by a defined distance s along a deflection direction a. 
     In this case too, the pressure with which the deflecting device  2  acts on the engine hood M in the region of its rear end H can be varied by gas being discharged from the piston/cylinder arrangement  20 ,  21 . It is thereby possible, in the same manner as in the exemplary embodiment illustrated in  FIGS. 1   a  and  1   b,  for a movement of the engine hood M counter to the deflecting direction a to initially still not be possible directly after the engine hood M has been deflected by means of the piston  21  whereas, at a later instant, after gas has been discharged from the deflecting device  2 , the engine hood M can be moved counter to the deflecting direction a, with the piston  21  again being displaced a certain amount into the cylinder  20 . 
       FIG. 3   a  illustrates a modification of the arrangement from  FIG. 2   a,  according to which the deflecting device  2 , comprising a cylinder  20  with piston  21  (compare  FIG. 3   b ), is connected to the engine hood M in the region of its rear end H on the passenger-cell side via a force transmission element in the form of a deformation element  26 . This deformation element  26  can be of such elastically deformable design that it yields when a person impacts against the engine hood M in the environment of the deformation element  26 , and thus permits a movement of the engine hood M counter to the direction a along which it had been raised previously, according to  FIG. 3   b,  by the piston  21  of the deflecting device  2  being raised. 
     The deformation element  26  can be provided as an addition or alternative to the time control of the deflecting device  2  that is described with reference to  FIGS. 2   a  and  2   b.  That is to say, the deformation element  26  permits the engine hood M to move counter to the deflecting device a even if the piston  21  cannot be pushed back into the cylinder  20  upon an impact of a body part against the engine hood M. However, it is important for the impact in the environment of the deformation element  26  to take place in the region of the rear end H of the engine hood M, i.e. in the region in which, during an accident, a person&#39;s head frequently strikes and then acts with a corresponding force F h  on the engine hood M. 
     The design of the force transmission element ( 26 ) as a deformation element is in particular of importance if the deflecting device ( 2 ) is not of reversible design, i.e. the piston ( 21 ) cannot be pushed back again into the associated cylinder  20  under the action of the force (F h ) occurring during the impact of the head. 
     By contrast, forces F b  which arise from an impact in the region of the front end V of the engine hood M and arise, for example, from the impact of a person&#39;s legs do not result in a deformation of the deformation element  26  and therefore in the engine hood M moving counter to its deflecting direction a. This is, inter alia, a consequence of the curved design of the engine hood M. 
     With the exemplary embodiment illustrated in  FIGS. 3   a  and  3   b,  a spatial control of the deflecting device  2  (if appropriate in addition to the time control described with reference to  FIGS. 1   a  to  2   b ) can therefore be achieved in such a manner that, after the engine hood M is raised, a movement counter to the deflecting direction a and the reduction in the deformation distance made available during the deflection only take place if the impact in the environment of the deflecting device  2  takes place at the rear end H of the engine hood M. Since the head of a pedestrian or cyclist involved in the accident frequently impacts in this region, this serves in turn for a special protection of the head of the corresponding person. 
     Furthermore, provision may be made for the force/distance characteristic of the deformation element  26  to be anisotropic, for example by a particularly severe deformation of the deformation element  26  being possible if the corresponding force F h  acts essentially perpendicularly to the engine hood M, as is frequently the case upon an impact of a head. 
     In the exemplary embodiment, shown in  FIG. 4   a,  of an arrangement for raising the engine hood M in the region of its rear end H facing the windshield W, the deflecting device  3  comprises a traction means  31  which engages at one end on a force transmission element  35  provided on the engine hood M and is arranged at the other end in a tensioning device  32 . The flexible traction means  31  can be formed, for example, by a cable and is deflected at least once between its two ends by means of a deflecting element  30 . 
     In the event of a crash the tensioning device  32  is activated and then, for example by means of a pyrotechnic charge or by means of an electric drive, exerts a tensile force on the traction means  31 , so that the latter is tightened, with the engine hood M being raised, according to  FIG. 4   b,  in the region of its rear end H. When the engine hood M is raised in the region of its rear end H, it pivots about a pivot, which is formed at its front end V, in the hood lock. The distance by which the engine hood M is raised in the region of its rear end H compared to its starting position (illustrated by dashed lines in  FIG. 4   b ) depends here on the position of the deflecting element  30 . The force with which the engine hood M is held in its raised position depends in turn on the tensioning of the traction means  31  that is produced by the traction device  32 . 
     Upon an impact of a person&#39;s head against the engine hood M in the region of its rear end H as a consequence of an accident, the engine hood M can be moved counter to the deflecting direction a because of the impact force F h  effective here counter to the action of the tensioning of the traction means, thus enabling impact energy to be dissipated in a controlled manner. In this case, the extent of the movement depends on the location of the impact in the region of the rear end H of the engine hood M and on the direction of the associated force F h . 
     By contrast, impact forces F b  which occur because of the impact of a body part, e.g. the legs, in the region of the front end V of the engine hood M, do not cause the engine hood M to move counter to the deflecting direction a. In this case too, the curvature of the engine hood M is again of importance. 
     If appropriate, the tensioning at which the traction means  31  is kept may also be varied in time, for example may be reduced with increasing duration of time after the deflecting device  3  has been activated. 
       FIG. 5   a  illustrates a development of the exemplary embodiment from  FIG. 4   a,  in which, to raise the engine hood M, there is additionally provided a sloping plane  37  which is connected to the engine hood M via a deformation element  36  and which interacts with a rotationally symmetrical element  38  arranged in a positionally fixed manner on a load-bearing part of the motor vehicle. The design of the sloping plane  37 , e.g. the length and inclination thereof, defines the distance by which the engine hood M is raised by tightening of the traction means  31  when the traction device  32  is activated, compare  FIG. 5   b.  Since the sloping plane  37  is connected to the engine hood M via a deformation element  36 , the possibility, described with reference to  FIGS. 4   a  and  4   b,  of the engine hood M moving counter to the deflecting direction a under the action of appropriate impact forces is not obstructed. 
     In the arrangement, illustrated in  FIG. 6   a,  for raising the engine hood M in the region of its rear end H in the event of a crash, the deflecting device  4  has a lever  41  which is mounted pivotably about a pivot  40  and is coupled at one end  41   b  (compare  FIG. 6   b ) to a spring element  42 . This spring element  42 , which is designed as a tension spring, is fixed at the other end on a load-bearing body part T and exerts on the pivot lever  41  a force which has the tendency to pivot the latter about the pivot  40 , in which case the engine hood M would be raised in the region of its rear end H. However, this pivoting movement is prevented by a hook  43  which acts on the pivot lever  41  and which prevents the pivoting movement which can be produced by the spring element  42 . 
     If, as a consequence of an accident, a person impacts with a body part against the engine hood M in the region of the front end V, the impact forces F b  arising in this case cause the hook  43  to be unlocked and to thereby release the pivot lever  41 . The latter then pivots about its axis of rotation  40  under the action of the spring element  42  and, in the process, acts with its end  41   a  facing away from the spring element  42  against a force transmission element  45  arranged on the engine hood M in the region of its rear end H on the passenger-cell side, so that the engine hood M is raised there. 
     Even in its end position, illustrated in  FIG. 6   b,  after the engine hood M is raised, the pivot lever  41  is still inclined in such a manner that it is pivoted by an impact force F h , which acts in the region of the rear end H of the engine hood M and may arise, for example, by the impact of a person&#39;s head, counter to the action of the spring element  42  in such a manner that the engine hood M can be lowered counter to its deflecting direction a. In this case, the spring constant of the spring element  42  determines the impact force required for moving the engine hood M. By contrast, the inclination of the pivot lever  41  in the deflected state of the deflecting device  4  defines the directions of the force F h  which may trigger a pivoting-back of the lever  41 . The less the pivot lever  41  is inclined with respect to the vertical, the smaller is the directional region within which the direction of the force F h  has to lie in order to trigger a pivoting-back of the lever  41 . 
     All in all, the selectable parameters which are important in this deflecting device  4  comprise the spring constant of the spring element  42 , the lengths of the two lever arms of the pivot lever  41 , the mass of the engine hood M and the period of time required for raising the engine hood M. 
     In the arrangement illustrated in  FIGS. 6   a  and  6   b,  a first impact of a body part of a person against the engine hood M therefore firstly releases the deflecting device  4  which then causes the engine hood M to be raised and thereby makes available a deformation distance for a subsequent, second impact, in particular of the head of the corresponding person. 
     In the exemplary embodiment illustrated in  FIG. 7 , the deflecting device  5  for raising the engine hood M in the event of a crash comprises a lever arrangement  51 ,  52  with a pivot lever  51 , which is mounted pivotably about a pivot  50 , and a push rod  52 , which is coupled to a bumper S of the vehicle. The push rod  52  is connected in an articulated manner to the lower end  51   b  of the pivot lever  51 . The upper end  51   a  of the pivot lever  51  is guided in a longitudinal guide  57  which is fixed in turn on the engine hood M via a deformation element  55 . In this case, the deformation element  55  and the longitudinal guide  57  are arranged in the region of the rear end H of the engine hood M directly in front of the windshield W of the motor vehicle. If, in the event of a crash, a force F b  triggered by the impact of a person acts on the bumper S, then the latter triggers a movement of the push rod  52  rearward in the longitudinal direction of the vehicle (counter to the forward direction of travel) which, in turn, produces a pivoting movement of the pivot lever  51  about the axis of rotation  50 . This raises the engine hood M in the region of its rear end H, the upper end  51   a  of the pivot lever  51  sliding in the longitudinal guide  57 . As a result, a deformation distance is made available for a subsequent, second impact against the engine hood M of the person affected by the accident, in particular for the impact of the person&#39;s head against the engine hood M. Depending on the location and direction of the impact in the region of the rear end H of the engine hood M, the deformation element  55  and, if appropriate, a pivoting-back of the pivot lever  51  make it possible for the engine hood M to move counter to the deflecting direction A. 
     In the arrangement, illustrated in  FIG. 7 , for raising the engine hood  7 , instead of a lever mechanism a traction means or a sloping plane may also be provided as the deflecting means, in which case the latter would have to be coupled in each case to the bumper S. Furthermore, the bumper S can interact with the push rod  52  via a step-up ratio in order to increase the displacement distance of the push rod  52 . 
       FIG. 8   a  illustrates an arrangement for raising the engine hood M, the deflecting device  6  of which is formed, as in the exemplary embodiment illustrated in  FIG. 3   a,  by a piston  61  which is guided in a cylinder  60  (compare  FIG. 8   b ) and can be deflected by a gas-producing device  62  in order to raise the engine hood M in the region of its rear end H. The coupling of the piston  61  to the engine hood M also takes place here via a force transmission element  65 . In contrast to the exemplary embodiment according to  FIG. 3   a,  in the present case the cylinder  60  is mounted pivotably about a pivot D on a load-bearing motor vehicle part T. 
     After the deflecting device  6  has been activated by means of a suitable sensor, the piston  61  and therefore also the engine hood M according to  FIG. 8   b  are raised, the cylinder  60  simultaneously being pivoted slightly about the axis of rotation D. The compressive force F f  existing in the cylinder  60  keeps the engine hood M in its deflected position. Upon an impact of a body part, in particular the head, of a person against the engine hood M in the region of its rear end, said engine hood can be moved counter to its deflecting direction a for the controlled dissipation of the impact energy if the force F h  associated with the impact opposes the force F f  produced by the gas in the cylinder  60 . 
     If, by contrast, an impact force F b  acts in the region of the front end V of the engine hood M, which force is caused by a body part impacting there, then this does not result in the engine hood M moving counter to the deflecting direction a, since the corresponding force F b  does not have a component or a sufficiently large component opposing the force F f  exerted by the piston  61 . 
     Furthermore, provision may be made for the piston  61  (e.g. in the region of its piston rod) to interact with clamping elements which oppose a displacement of the piston  61  counter to the deflecting direction a, the arrangement being designed in such a manner that the clamping forces in a typical impact of the upper body of a person are significantly greater than in the impact of the head, specifically in such a manner that a displacement of the piston  61  counter to the deflecting direction a is possible only in the case of an impact of a head. 
       FIG. 9   a  shows a modification of the exemplary embodiment from  FIG. 1   a,  in which the deflecting device  1 , which has an inflatable airbag  10 , is arranged between a support structure Mt and the external paneling (outer side Ma) of the engine hood. That is to say, in the present case the engine hood M is of two-part design with a comparatively stable support structure Mt and an outer side Ma determining the external design of the engine hood M. According to  FIG. 9   a,  the airbag  10  is arranged in the folded state between these components of the engine hood M, the support structure Mt of the engine hood M having a corresponding depression R for accommodating the airbag  10  and a gas generator  12 , which protrudes into the airbag  10 , for inflating the airbag. The airbag  10  and the gas generator  12  are jointly fastened to the support structure Mt of the engine hood M by means of suitable fastening elements  13  (e.g. in the form of screws or rivets). 
     If a directly imminent accident or an accident which has already occurred is detected by a sensor, the airbag  10  is inflated by means of the gas generator  12  and, as a result, as can be seen with reference to  FIG. 9   b,  the outer side Ma of the engine hood M is lifted off the support structure Mt. By this means, a deformation distance for a pedestrian or cyclist impacting against the outer side Ma of the engine hood M is again made available. The airbag  10  can be controlled in the same manner as described above with reference to  FIGS. 1   a  and  1   b.  That is to say, by a specific discharge of gas out of the airbag  10  after the outer side Ma of the engine hood M has been raised, the pressure level within the airbag  10  and therefore also the force with which the airbag  10  acts on the outer side Ma of the engine hood M can be varied in time. This takes place in particular with regard to setting a pressure level at the instant of a probable impact of the head of a person who is involved in the accident and is situated outside the motor vehicle, the pressure level permitting the outer side Ma of the engine hood M to move counter to its deflecting direction. 
     Due to the comparatively low rigidity of the outer side Ma of the engine hood M compared with a complete engine hood comprising the support structure Mt and outer side Ma, the airbag  10  has to have a comparatively large volume in order to support the outer side Ma of the engine hood M over an extensive area. This also permits the airbag  10  to be subdivided into a plurality of chambers, of which the chambers to be assigned to an impacting upper body are filled first and with a comparatively high internal pressure while the chambers assigned to an impacting head (situated in the region of the rear end of the engine hood M) are filled following this and with a comparatively low internal pressure. This may be ensured, for example, by means of overflow openings through which gas flows out of the chambers assigned to the upper body into the chambers assigned to the head. As an alternative, a plurality of airbags which are filled in a manner offset in terms of time and with different internal pressures may be provided for the different impact regions. 
     In the exemplary embodiment illustrated in  FIG. 10 , an airbag  10  again serves as the deflecting device  1  for raising the outer side Ma of an engine hood M with respect to the support structure Mt thereof in order to protect a person situated outside the motor vehicle in the event of an accident. In this case, the airbag, in the inflated state, is supported at one end on the support structure Mt and acts at the same time on the outer side Ma of the engine hood M in such a manner that the latter is deflected. 
     The airbag  10  here is designed in such a manner that it protrudes with a rear section  100  behind the rear end H of the engine hood M and protrudes with a further section  101  laterally next to the engine hood M. A corresponding, laterally protruding section of the airbag  10  may also be provided on the other, opposite side of the engine hood M. These sections  100 ,  101  of the airbag  10  that protrude next to the engine hood can be used to cover additional regions of the vehicle body, such as, for example, fenders, the A-pillars and the frame of a window. This further reduces the risk of injury for a person situated outside the motor vehicle. 
     At the same time, this design of the airbag  10 , which supports the outer side Ma of the engine hood M in the inflated state both in the region of its rear end H and in the region of its longitudinal sides S, provides a particularly homogeneous impact surface for an impacting person, so that a comparatively soft interception of the head, the upper body or other body parts of an impacting person is possible uniformly over the entire engine hood M. 
     The arrangement according to  FIG. 10  can also be used in the same manner for the situation in which not only is the outer side Ma of the engine hood M, but also the entire engine hood M raised by a deflecting device  1  in the form of an airbag  10 . 
     In the exemplary embodiment according to  FIG. 11 , the engine hood M is raised in its entirety, in the event of an accident, by a deflecting device  1  in the form of an essentially U-shaped airbag  10 ′ which extends with its base section  100 ′ along the rear end H of the engine hood M and with its two limbs  101 ′,  102 ′, which are angled away from the base region  100 ′, below the engine hood M along the longitudinal sides S thereof. The engine hood M is therefore supported in the raised state on three sides by means of the airbag  10 ′. 
     In the case of this arrangement too, homogeneous conditions are made available over the entire surface of the engine hood M in the raised state of the engine hood M in order to intercept a person impacting against the engine hood M, irrespective of the location of the impact against the engine hood M, as softly as possible by the engine hood M being moved counter to its deflecting direction. 
     In the exemplary embodiments, illustrated with reference to  FIGS. 1   a  to  11 , of an arrangement for raising an engine hood in order to protect a person situated outside the motor vehicle, the engine hood M is pivoted in each case about its front end V (e.g. about a front lock subassembly) and, in the process, is raised in particular in the region of its rear end H. On the other hand, it is necessary, in order to swing up the engine hood in the event of a repair, to change the oil or for other reasons, to be able to pivot the engine hood H about its rear end too. That is to say, the engine hood M has to be coupled in each case, on the one hand, in the region of its rear end H pivotably to the vehicle body in order to be able to swing said engine hood up for repair purposes, and, on the other hand, it has to be able to be raised in the region of its rear end H in order to enable the protective function according to the invention in an accident involving a person situated outside the motor vehicle. 
     A hinge with which these stipulations can be fulfilled is illustrated in  FIG. 12   a.  The hinge  9  has a base part  90  which is fixed on the vehicle body, and an upper part  95  which can be pivoted with respect to the base part  90  and can be connected to an engine hood. The upper part  95  is connected to the base part  90  via two adjusting levers  91 ,  92  which are connected in an articulated manner in the region of their lower ends, in each case via hinge points  91   a,    92   a,  to a retaining element  900 , which is connected to the base part  90 , and in the region of their upper ends, in each case via further hinge points  91   b,    92   b,  to the upper part  95  of the hood hinge  9 . This enables the upper part  9  to be pivoted with respect to the base part  90  by means of the adjusting levers  91 ,  92 , the engine hood being pivoted about its rear end, so that the front end of the engine hood swings upward and that region of the vehicle which is concealed by the engine hood becomes accessible. 
     The retaining element  900 , to which the two adjusting levers  91 ,  92  are pivotably coupled by their lower ends, is connected to the base part  90  by means of two fastening elements  90   a,    90   b,  e.g. in the form of rivets. The fastening elements  90   a,    90   b  of the elongated retaining element  900  are provided here on the two ends of the retaining element on the longitudinal side. The front fastening element  90   b  in the direction of travel—in the case of the hood hinge  9  being arranged in a motor vehicle in the region of the rear end of an engine hood—is designed in such a manner or has such a region of weakening that the front connection between the base part  9  and the retaining element  900  can be released in order to raise the rear end of the engine hood. This is because, after the front fastening element  90   b  is released, the rear fastening element  90   a  acts as a joint, with the result that the retaining element  900  can be pivoted about this rear joint  90   a  with respect to the base part  9 . This is illustrated in  FIG. 12   b.  The retaining element  900  then forms with the two adjusting levers  91 ,  92  a lever arrangement which permits an essentially vertical raising of the rear end of the corresponding engine hood, as is required in the case of the arrangements illustrated in  FIGS. 1   a  to  11 . 
     The design, illustrated in  FIGS. 12   a  and  12   b,  of a hood joint or hood hinge  9  is therefore based on the principle of the hood hinge being modified by the action of certain specifiable forces in such a manner that a raising of the rear end of an engine hood (which is coupled to the vehicle body via the hood hinge) is made possible. According to one alternative, the forces required for this can be applied by the deflecting device  1  (cf.  FIGS. 1   a  to  11 ) itself, used for deflecting the engine hood M. According to another embodiment, a separate device may be provided acting specifically on a certain section of the hood hinge  9  in order to modify the latter in such a manner that the raising of the rear hood end of the engine hood is made possible. 
     Of course, it is also conceivable to completely decouple the engine hood in the region of its rear end from the vehicle body by destruction of the hood hinge  9 . To this end, the adjusting levers  91 ,  92 , for example, could be uncoupled either from the base part  90  or from the upper part  95 . The embodiment, illustrated in  FIGS. 12   a  and  12   b,  of a hood hinge which, for raising the rear end of an engine hood, is merely modified, but not destroyed, has the advantage of enabling the hood hinge  9  to be used at the same time to limit the raising of the engine hood M by means of the deflecting device (in the manner of an intercepting strap), so that excessive raising is avoided. This is because this could in turn result in an impacting person striking against the rear edge of the engine hood, which could increase the risk of injury. 
     Given the disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims.