Patent Publication Number: US-2013227818-A1

Title: Hinge mechanism

Description:
TECHNICAL FIELD 
     The invention relates to a hinge mechanism for a bonnet of a vehicle. 
     BACKGROUND OF THE INVENTION 
     If a motor vehicle, such as a car, is involved in an accident in which the front part of the vehicle hits a pedestrian, it is not uncommon that the head of the pedestrian impacts on the bonnet of the vehicle and the pedestrian may in that case be severely injured. The severity of the injury results from the fact that the front or bonnet, which is usually formed from thin metal sheet, would tend to bend, and then deforms on hard engine parts which are beneath the bonnet, such as the engine block. In order to reduce the severity of these accidents, it is well-known to use a deployable bonnet. By raising the rear part of the deployable bonnet to a raised position an “impact position” is reached, such that the distance between the bonnet and the hard engine parts is increased. 
     In addition to the deployable bonnet, a motor vehicle may also have a safety arrangement in the form of a pedestrian airbag, which, in a deployed state, at least partly covers the windscreen and/or the A-pillars. Such a pedestrian airbag may be inflated through the opening created between the deployable bonnet and the windscreen when the deployable bonnet is raised. 
     With such a deployable bonnet according to the prior art, the risk is reduced, or preferably avoided, that the pedestrian, and especially his/her head, may hit the hard engine parts. However, a conventional hinge mechanism is, by its construction rigid, in itself, also when retaining the bonnet in the raised position. Therefore, although the raised position is preferred over the normal position of the bonnet during a pedestrian collision, the pedestrian, and especially his/her head, would meet a certain rigidity upon impact with the bonnet due to the rigid hinge mechanism. 
     A known drawback with hinge mechanisms of many prior art solutions is that they involve many individual components. This makes the hinge mechanism heavy and requires large packaging volume, as well as making it expensive and difficult to assemble in the vehicle at the production facility. 
     As may be realized from the above, there is a desire for an improved hinge mechanism, which is able to raise the bonnet to a raised position creating a distance to the hard engine parts, which hinge mechanism is not rigid in itself. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to overcome or at least ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. 
     It is desirable to provide a hinge mechanism, which is able to raise the bonnet to a raised position, thereby creating a distance to the hard engine parts and which hinge mechanism is not rigid in itself. 
     It also desirable to provide a hinge mechanism comprising few components. 
     The object above may be achieved by the invention according to claim  1 . 
     In a first aspect of the present invention there is provided a hinge mechanism for a bonnet of a vehicle. The hinge mechanism is adapted to provide a hinged connection between the bonnet and a body structure of the vehicle. The hinge mechanism comprises
         a first hinge member connectable to the bonnet,   a second hinge member having a first end and a second end, and   a third hinge member connectable to the body structure.       

     The first end of the second hinge member is pivotally connected to the first hinge member, and the second end of the second hinge member is pivotally connected to the third hinge member. 
     The hinge mechanism is displaceable between
         a first state, corresponding to an open or closed bonnet, wherein the first and second hinge members are releasably engaged to each other, and   a second state, corresponding to the bonnet being in a raised position, the second state being different from the first state.       

     The hinge mechanism is displaceable from the first state to the second state by a pivotal displacement of the first hinge member with respect to the second hinge member. The hinge mechanism further comprises an abutment member attached to one of the first or second hinge members, such that when the hinge mechanism is in the second state, the other of the first and second hinge members abuts in a predetermined position relative to the abutment member, while the first and second hinge members are displaceable relative to each other via the abutment member. 
     The hinge mechanism may be sold as a separate part. Alternatively it is intended to be mounted in a vehicle and sold as a part of the vehicle. 
     A bonnet can be provided with two hinge mechanisms. They may be located adjacent to each lateral side of the bonnet. 
     The pivotal connections between the second and third hinge members makes it possible to displace the bonnet between a closed position, covering the engine compartment and being the normal position of the bonnet during driving and parking, and an open position allowing access to the engine compartment. The hinge mechanism is for both the closed position and the open position, and during the displacement between the two positions, in its first state, in which the first and second hinge members are releasably engaged to each other. The first and second hinge members are thus not pivoted in relation to each other during the displacement between the closed and the open positions. Instead they are releasably engaged to each other, e.g. by an engaging means such as a shear screw. The engaging means is further adapted to release the first hinge member from the second hinge member in order to allow a displacement of the bonnet to the raised position. 
     During displacement of the bonnet to the raised position, a displacement which is normally started from the closed position of the bonnet, the hinge mechanism is displaced from the first to the second state by a pivotal displacement between the first and second hinge members. This pivotal displacement is made about the connection between the first hinge member and the first end of the second hinge member. 
     The hinge mechanism further comprises an abutment member. The predetermined position is a result of the shape of the abutment member. 
     In an embodiment the abutment member is attached to the second hinge member. When the hinge mechanism is in its second state, corresponding to the raised position of the bonnet, the first hinge member in that case abuts against the abutment member in a predetermined position relative to the abutment member. The first hinge member may for example abut against a top surface of the abutment member, a groove or an indentation in the abutment member. Thereby the first hinge member is prevented from sinking in relation to the abutment member. Further, when the hinge mechanism is in its second state, the first and second hinge members are displaceable in relation to each other via the abutment member. The abutment member may move and/or there may be movement within the abutment member. The abutment member may for example act as a spring, such that the movement is elastic, in that case preferably damped elastic. The movement may also, or instead, plastically deform the abutment member. The practical effect of the displaceability between the first and second hinge members is that, when a body part of the pedestrian, e.g. his/her head, hits the bonnet, the bonnet will not be completely rigid, but will instead be able to move slightly downwards in a movement determined by the properties of the abutment member, such that the risk of an injury to the pedestrian is less than would have been the case for a rigid engagement between the first hinge member and the second hinge member. 
     In an alternative embodiment, the abutment member is instead attached to the first hinge member. When the hinge mechanism is in its second state, the second hinge member in that case abuts against the abutment member in a predetermined position relative to the abutment member. The second hinge member may for example abut against a bottom surface of the abutment member, a groove or an indentation in the abutment member. Except for the geometrical differences from the above embodiment, such an abutment member functions in an equivalent way as already described. 
     In the first state of the hinge mechanism, the first and second hinge members may be substantially oriented with parallel longitudinal axes. This is suitable for a closed or open bonnet. 
     In the second state of the hinge mechanism, the first and second hinge members may be substantially oriented with an angle α between their longitudinal axes. The angle α may be between 5 and 75 degrees, preferably between 10 and 45 degrees and most preferably between 15 and 35 degrees. This is suitable when the bonnet has been raised to the raised position. 
     In case the abutment member is attached to the second hinge member, the abutment member may be arranged to press in a lateral direction against the first hinge member. Herein the term “lateral direction” relates to how the hinge mechanism is intended to be mounted in the vehicle; the lateral direction of the hinge mechanism being the same as the lateral direction of the vehicle. 
     In an embodiment, the first hinge member comprises a protrusion, the protrusion facing the second hinge member. The abutment member may then be arranged to press in a lateral direction against the protrusion on the first hinge member in the first state of the hinge mechanism. Further, in the second state of hinge mechanism, the protrusion may form an abutment for the abutment member, the protrusion thereby defining the predetermined position. During the displacement between the first and the second state of the hinge mechanism, the abutment member is first laterally pressed against the protrusion of the first hinge member. However, as the protrusion has moved so far that it has passed the abutment member, the abutment member will instead press against the surface of the first hinge member below the protrusion. The protrusion then acts as a stop for the abutment member providing the predetermined position of the first hinge member relative to the abutment member, in particular preventing the first hinge member from sinking in relation to the abutment member. 
     In an alternative embodiment, the protrusion is instead located on the abutment member. Such a protrusion may be arranged such that it fits in a corresponding hole, indentation or groove in the other of the first and second hinge members, i.e. the hinge member to which the abutment member is not attached, when the hinge mechanism is in the second state, thereby providing the predetermined position. 
     The displaceability between the first and second hinge members relative to each other via the abutment member in the second state of the hinge mechanism may be substantially in a vertical direction, vertical direction being related to how the hinge mechanism is intended to be mounted in the vehicle. 
     The displaceability between the first and second hinge members relative to each other via the abutment member in the second state of the hinge mechanism may be substantially elastic movability by means of the abutment member. 
     The abutment member may act as a damped harmonic oscillator. 
     In real oscillators, friction, or damping, slows the motion of the system. In many vibrating systems the frictional force F f  can be modeled as being proportional to the velocity v of the object: F f =−cv, where c is called the viscous damping coefficient. 
     The damped harmonic oscillator consists of a mass m, which experiences a single force, F, which pulls the mass in the direction of the point x=0 and depends on the mass&#39;s position x and a constant k. Newton&#39;s second law for damped harmonic oscillators is then: 
     
       
         
           
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     is called the “damping ratio”. 
     The abutment member according to the invention may act as damped harmonic oscillator as regards the displaceability between the first and second hinge members relative to each other via the abutment member in the second state of the hinge mechanism. An overdamped system, having ζ&gt;1, returns to equilibrium without oscillating along an exponential curve. The larger the values are for the damping ratio ζ, the slower is the return to equilibrium. A critically damped system, with ζ=1, returns to equilibrium as quickly as possible without oscillating. Preferably, the damping ratio ζ≧1, most preferably ζ=1. The system may also be underdamped, having ζ&lt;1, but in that case the system would oscillate with the amplitude gradually approaching zero. 
     The possible maximal displacement between the first and second hinge members may be in the range of 0-50 mm, preferably 10-40 mm, most preferably 20-30 mm. If the impacting force is low, the displacement will not be maximal. If the abutment acts as a damped harmonic oscillator the maximal displacement corresponds to the maximal amplitude of the oscillator. 
     The abutment member may comprise a leaf spring, preferably being substantially L-shaped, C-shaped or U-shaped. Such a spring could acts a damped harmonic oscillator. 
     If the leaf spring is L-shaped, it may be attached to an underside of the second hinge member with the attachment being located at the side of the underside of the second hinge member facing away from the first hinge member. Thereby the spring may be given the desired elastic properties. 
     The hinge mechanism may be displaceable from the second state to the first state by pressing the abutment member towards the one of the first and second hinge members it is attached to, thereby releasing the abutment of the other of the first and second hinge members. Optionally, an extra tool is needed for this operation. Thereby, it is possible to move the bonnet back from the raised position to the closed position. This may be done after the collision situation in order to make it easier for the vehicle to be driven away from the collision area. It could also be useful, if the bonnet has been raised due to an erroneous triggering. 
     In a second aspect of the present invention, there is provided a vehicle comprising a hinge mechanism as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be further explained by means of non-limiting examples with reference to the appended figures wherein: 
         FIG. 1  is a schematic side view of a front portion of a vehicle with a hinge mechanism according to the invention and illustrating the bonnet in a closed position and in an open position, 
         FIG. 2  is the front portion of  FIG. 1  illustrating the bonnet in the closed position and in a raised position, 
         FIG. 3  is a perspective top view of a hinge mechanism according to the invention assuming the bonnet is in its closed position with the hinge mechanism being in a first state, 
         FIG. 4  is a perspective side view of the hinge mechanism of  FIG. 3 , 
         FIG. 5  is a perspective side view of the hinge mechanism of  FIG. 3 , assuming the bonnet is in its open position with the hinge mechanism being in the first state, 
         FIG. 6  is a perspective side view of the hinge mechanism of  FIG. 3 , assuming the bonnet is in its raised position with the hinge mechanism being in a second state, 
         FIGS. 7   a,b  is a detailed view of an abutment member being in the first state and in the second state respectively, and 
         FIGS. 8   a,b  is a detailed view of an alternative abutment member being in the first state and in the second state respectively. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The invention will, in the following, be exemplified by non-limiting embodiments. It should however be realized that the embodiments are included in order to explain principles of the invention and not to limit the scope of the invention, defined by the appended claims. Details from two or more of the embodiments may be combined with each other. The words front and rear used below relate to the vehicle, where front is the part coming first in the normal forward driving direction. The words longitudinal, lateral and vertical also relate to the vehicle. Longitudinal is in the longitudinal direction of the vehicle. Lateral is perpendicular to the longitudinal direction but being the same horizontal plane, i.e. sideways in the vehicle. Vertical is perpendicular to that plane. All directions relate to a vehicle being on a flat ground; if the ground is sloped the directions change accordingly. 
       FIG. 1  is a schematic side view of a front end of a vehicle  10 , here a car. The vehicle is provided with a bonnet  12 , which covers an engine compartment  14  and allows access to the engine compartment  14  for maintenance and repair. The bonnet  12  is connected to the vehicle  10  by a hinge mechanism  16 , normally one hinge mechanism  16  adjacent to each lateral side of the bonnet  12 . A rear end  18  of the bonnet  12  is directed towards a windscreen  20  of the vehicle  10 . Normally the bonnet  12  is in a closed position A covering the engine compartment  14 . The bonnet  12  can be lifted to an open position B allowing normal access to the engine compartment  14 . The vehicle  10  is then normally stationary. 
       FIG. 2  is a schematic side view of the front end of the vehicle  10  showing the bonnet  12  in a raised position C. The closed position A is also shown as a reference. The bonnet  12  is connected to an actuator  22 , only schematically illustrated, which is positioned somewhere in the vehicle, generally beneath the bonnet  12 . The actuator  22  is arranged to raise the bonnet  12  at its rear end  18  to the raised position C after sensor input that the vehicle  10  is about to hit a pedestrian and/or has hit a pedestrian. When the actuator  22  raises the bonnet  12 , a distance is formed between the bonnet  12  and hard engine parts, allowing deflection of the bonnet  12  without the risk of the head of the pedestrian hitting any hard engine parts. The bonnet  12  may be raised at both ends, but normally the rear end  18  is raised to a higher position. The distance formed between the bonnet  12  and the hard engine parts is typically between 50 and 130 millimetres. Further, a pedestrian airbag (not illustrated) may be deployed along at least part of the windscreen  20  and/or the A-pillars. It should be realized that the actuator  22  may also be activated by, for example, an animal running out in front of the vehicle  10  or a cyclist. Normally, one or more sensors (not shown) are used to detect a collision with the pedestrian. In case of a collision, the actuator  22  is activated. The actuator  22  may be an inflatable member, such as a pedestrian airbag, a pyrotechnical device, a mechanical spring, a compressed-air piston, an electrical lifter, a rack or a lifting arm. 
     To be able to raise the bonnet  12  to the raised position C, the hinge mechanism  16  needs to move in a different way in relation to how it moves when the bonnet  12  is displaced to the normal opening positioning B. Therefore, the hinge mechanism  16  is adapted for these two different ways of movement, as described below. It should be noted that the hinge mechanism  16  shown in  FIGS. 1 and 2  is not drawn to scale. The details of the hinge mechanism  16  will be described in more detail with reference to  FIGS. 3-8 . 
     In  FIG. 3  a perspective top view of the hinge mechanism  16  in accordance with the invention is shown, assuming the bonnet  12 , to which the hinge mechanism  16  is arranged, is in the closed position A.  FIG. 4  shows the corresponding side view. The hinge mechanism  16  comprises a first hinge member  24 , a second hinge member  26  and a third hinge member  28 . The first hinge member  24  is a piece of material that is fixedly attachable to the bonnet  12  by any suitable fastening means, for example by screwing, bolt and nut connection or by welding. The second hinge member  26  is an elongated hinge arm extending substantially in the longitudinal direction of the vehicle. Its first end  30  is connected to the first hinge member  24 . The opposite end of the second hinge member  26 , i.e. the second end  32 , is pivotally connected to the third hinge member  28  by means of e.g. a pivot pin  34 . The hinge mechanism  16  is in a first state, wherein the first hinge member  24  and the second hinge member  26  are releasably engaged to each other. 
     The third hinge member  28  comprises a first portion  36 , a second portion  38  and a base portion  40 . The first portion  36  is adapted to take up forces in the longitudinal direction of the vehicle imparted on it by the second hinge member  26 , for example forces arising in a frontal collision. The base portion  40  is adapted to be fixedly attached to the body structure of the vehicle  10  by any suitable fastening means, for example by screwing, bolt and nut connection or by welding. The first  36  and the second  38  portions may be separate from each other, as in the illustrated embodiment, or they may be different regions of the same part. Normally, the first portion  36  is located longitudinally in front of the second portion  38 . 
     In  FIGS. 3-4  the second hinge member  26  is arranged to engage with the first portion  36  of the third hinge member  28 , when the second hinge member  26  is subjected to a force or a force component acting in the longitudinal direction of the vehicle. When the bonnet  12  is subjected to such a force, the force will be transferred via the first hinge member  24  to the second hinge member  26 . As a result thereof, the second hinge member  26  will be pushed rearwards until it engages with the first portion  36 . Thereafter further rearward motion is hindered, and the bonnet  12  is prevented from intruding into the windscreen  20 . 
     In the shown embodiment, the engagement is secured by a front crash hook  44  adapted to be located at least partly around the first portion  36  of the third hinge member  28  at engagement, but the invention would also work with another arrangement, such as two opposing flat surfaces. However, the hook shape is advantageous, since it also prevents lateral movement, except for a few millimeters within the front crash hook  44 . As an alternative, the first portion  36  may comprise a hook shape, which can grip around the second hinge member  26 . 
     Even if the embodiment of  FIGS. 3-6  illustrates the front crash hook  44  adapted to be located at least partly around the first portion  36  of the third hinge member  28  at engagement, the front crash hook  44  does not influence the function disclosed by the invention for providing a non-rigid raised position of the bonnet  12 . Therefore, the front crash hook  44  could be omitted. 
     Further, the first hinge member  24  and the second hinge member  26  are releasably engaged to each other by engaging means  46 . The engaging means  46  is adapted to keep the first  24  and second  26  hinge member together, when the bonnet  12  is in the closed position A or the open position B, or during displacement therebetween. The engaging means  46  is further adapted to release the first hinge member  24  from the second hinge member  26  upon activation from the actuator  22 . Accordingly, when the bonnet  12  is displaced upwards during deployment in order to reach the raised position C, the engaging means  46  is released and the first hinge member  24  can move pivotally relative to the second hinge member  26 , for example around a pivot pin  48 . The engaging means may be a shear screw  46 , as in the illustrated embodiment. The shear screw  46  has a weakened portion, which will initiate the break of the shear screw  46  when the actuator  22  is activated, thereby allowing the bonnet  12  to be raised. 
       FIG. 3  further illustrates an abutment member  54  in between the first hinge member  24  and the second hinge member  26  adjacent to its first end  30 . The abutment member  54  has the shape of an L-shaped leaf spring. It is attached to an underside of the second hinge member  26  by attachment means  56 , e.g. a screw, a bolt and nut connection or by welding. The attachment means  56  is located such that a distance x is created to the side of the second hinge member  26  facing the first hinge member  24 , which is illustrated below in  FIG. 7   a . The abutment member  54  presses against the first hinge member  24  in a lateral direction of the vehicle. The first hinge member  24  comprises a protrusion  58  on the side facing the second hinge member  26 . The abutment member  54  thus presses against the protrusion  58 . The abutment member  54  and its function is described in more detail in conjunction with  FIGS. 7   a  and  7   b.    
       FIG. 3  also illustrates that the first hinge member  24  comprises a hook  50  which abuts against a protrusion  52 , e.g. a bolt. Thereby the first hinge member  24  is prevented from downward movement with respect to the second hinge member  26 . The hook  50  will further help to stabilize the hinge mechanism  16 . The protrusion  52  may have a head having a wider diameter than the rest of the protrusion. Such a head may prevent lateral movement. The hook  50  and protrusion  52  are optional features, which may be omitted. 
       FIG. 5  shows the position of the hinge mechanism  16  when the bonnet  12  is in its open position B. In order to reach this position, the second hinge member  26  pivots in relation to the third hinge member  28  about the pivot pin  34 . The hinge mechanism  16  is in its first state, wherein the first hinge member  24  is releasably engaged with the second hinge member  26  by means of the engaging means  46 . The abutment member  54  therefore is in the same position relative to the first hinge member  24  as in  FIGS. 3 and 4 . 
     During the normal opening or closing operation of the bonnet  12 , the hinge mechanism  16  remains in the first state. Further, in the illustrated embodiment comprising the crash hook  44 , the first portion  36  does not restrict the movement of the second hinge member  26 . In particular, the front crash hook  44  moves freely without engaging the first portion  36 . 
     In  FIG. 6 , a perspective view of the hinge mechanism  16  in accordance with the invention is shown, when the bonnet  12  has been displaced to the raised position C and the hinge mechanism  16  has been displaced to the second state. 
     In the event that a pedestrian collision is detected and the actuator  22  is activated, at least the rear end  18  of the bonnet  12  will be raised. When the bonnet  12  is being raised, the engaging means  46  is released and the first hinge member  24  and the second hinge member  26  are released from each other and become pivotally displaceable relative to each other about a pivot point, here defined by the pivot pin  48 . The second hinge member  26  also pivots at its opposite end, the second end  32 , around the pivot pin  34  during raising of the bonnet  12 . Thereby the hinge mechanism  16  reaches its second state, in which the longitudinal axes of the first and second hinge members forms an angle α between each other. The angle α is between 5 and 75 degrees, preferably between 10 and 45 degrees and most preferably between 15 and 35 degrees. 
       FIG. 6  also illustrates that the protrusion  58  has been displaced relative to the abutment member  54 , such that the protrusion  58  in the raised position C abuts against the abutment member  54 , thereby giving the first hinge member  24  a predetermined position in relation to the abutment member  54 . During the displacement between the first and the second state of the hinge mechanism  16 , the abutment member  54  is first laterally pressed against the protrusion  58  of the first hinge member  24  as described above for  FIG. 3 . However, as the protrusion  58  has moved so far that it has passed the abutment member  54 , the abutment member  54  will instead press against the surface of the first hinge member  24  below the protrusion  58 . The protrusion  58  then acts as a stop for the abutment member  54  providing a predetermined position of the first hinge member  24  relative to the abutment member  54 , in particular preventing the first hinge member  24  from sinking in relation to the abutment member  54 . See also  FIG. 7   b . Optionally, but not illustrated, the upper surface of the abutment member  54  may have a groove corresponding to the shape of the protrusion  58 , thereby securing the position of the protrusion  58  in relation to the abutment member  54 . 
     It is further seen in  FIG. 6  that the front crash hook  44  can grip around the first portion  36  of the third hinge member  28  during raising of the bonnet  12  and in the raised position C. Thereby, a force or a force component acting in the longitudinal direction of the vehicle may be transferred to the first portion  36  also during the raising movement and not only at the end positions of the hinge mechanism  16  corresponding to the closed bonnet A or the raised bonnet C. 
       FIG. 6  also illustrates the hook  50  and protrusion  52 , which were explained above in conjunction with  FIG. 3 . 
       FIG. 7   a  is a cross-section of an upper part of the hinge mechanism  16  being in the first state. The abutment member  54  is attached adjacent to the first end  30  of the second hinge member  26  by attachment means  56 . There is a distance x between the attachment means  56  and the side of the second hinge member  26  facing the first hinge member  24 . The abutment member  54  presses laterally against the protrusion  58 , which is located on the surface of the first hinge member  24 . 
       FIG. 7   b  is a cross-section of a part of the hinge mechanism  16  being in the second state. The protrusion  58  forms an abutment for the abutment member  54 . Therefore, if/when the pedestrian hits the bonnet  12  of the vehicle with the bonnet being in the raised position C, the first hinge member  24  will be supported by the protrusion  58  abutting against abutment member  54 . The first hinge member  24  can thus not be displaced downwards in relation to the abutment member  54 . However, the curvature  60  of the abutment member  54  will act as a leaf spring, such that the first hinge member  24  can move downwards in relation to the second hinge member  26  via the abutment member  54 . The first hinge member  24  will thus be locked to the second hinge member  26  in a flexible way. The practical effect of this is that, when a part of the pedestrian, e.g. his/her head, hits the bonnet  12 , the bonnet  12  will not be completely rigid, but can instead move slightly downwards in a movement determined by the properties of the abutment member  54 , such that the impact to the pedestrian is less than would have been the case for a rigid locking between the first hinge member  24  and the second hinge member  26 . The movement is preferably due to an elastic deformation of the abutment member  54 , however if the impact force is high, there may be a plastic deformation as well, or instead. The stroke length of the movement is adapted such that there is still enough distance to the hard engine parts, e.g. in the range of 0-50 mm, preferably 10-40 mm, most preferably 20-30 mm. The properties of the abutment member  54  may be influenced by choice of material, geometric dimensions and location of the attachment means  56 . Purely as an example, the further away the attachment means  56  is located from the first hinge member  24 , the more elastic will the abutment member  54  be, assuming material and geometric dimensions are the same. 
       FIGS. 8   a  and  b  illustrate an alternative abutment member  54 ′, wherein the abutment member  54 ′ has a U-shaped form. The abutment member  54 ′ is attached to the side of the second hinge member  26  facing the first hinge member  24 . The function is otherwise similar as to what has been described with reference to  FIGS. 7   a  and  b.    
     The illustrated embodiment shows a bonnet which is opened at its front end, but there are also vehicles having a bonnet which is opened at its rear end, i.e. at the end adjacent to the windscreen. In that case, there will be one or more bonnet latches located at the rear end of the bonnet used for holding the bonnet in the closed position. In such a case, the functions of the hinge mechanism described above could be incorporated into the bonnet latch. In order to open the bonnet in a normal way to access the engine compartment, there are also hinges arranged at the front end of such a bonnet. In the case that a rear-opened bonnet is deployable to a raised position, a hinge mechanism providing deployment may be arranged at the rear end of the bonnet, possibly incorporated into the bonnet latch. Such a hinge mechanism may be according to an embodiment of the invention. 
     Further modifications of the invention within the scope of the appended claims are feasible. As such, the present invention should not be considered as limited by the embodiments and figures described herein. Rather, the full scope of the invention should be determined by the appended claims, with reference to the description and drawings.