WO2006135240A1

WO2006135240A1 - Bumper system

Info

Publication number: WO2006135240A1
Application number: PCT/NO2005/000397
Authority: WO
Inventors: Roald Helland Pedersen
Original assignee: Norsk Hydro Asa
Priority date: 2004-10-20
Filing date: 2005-10-20
Publication date: 2006-12-21
Also published as: NO20044489D0

Abstract

The invention refers to a bumper system with a bumper beam attachable to a front or rear end of at least one side member or to a crash box of a vehicle, wherein the bumper beam, at least in a region thereof in front of said side member or crash box, comprises an upper chamber defined by upper outer, top and bottom walls, a lower chamber defined by lower outer, top and bottom walls, and a connecting means, connecting an inner part of said upper bottom wall with an inner part of said lower top wall. According to the invention, said connecting means is coupled to an abutting means, and said upper top wall and/or said lower bottom wall is/are coupled to a first crash energy absorbing means.

Description

BUMPER SYSTEM

The present invention refers to a bumper system with a bumper beam attachable to a front or rear end of at least one side member or to a crash box of a vehicle, wherein the bumper beam, at least in a region thereof in front of said side member or crash box, comprises

an upper chamber defined by upper outer, top and bottom walls, a lower chamber defined by lower outer, top and bottom walls, and a connecting means, connecting an inner part of said upper bottom wall with an inner part of said lower top wall.

In other words, the invention is about a new crash module for cars, particularly passenger cars, with improved performance. Here "crash module" refers to a system typically consisting of a transverse bumper beam being coupled together with energy absorbing elements, being situated at the extreme front or rear of the car. From here on this description refers to front crash modules. It is, however, understood that said rear modules are within this inventive scope as well, as are also side impact- and roll over protection systems. "Improved performance" refers to both the different crash demands as well as other desirable characteristics such as utilization of space (compactness) and improving overall vehicle cost, weight and bulk.

The previously known crash systems typically consist of transverse (bumper) beams being fixed to the car structural side members (siderails, longitudinals) directly or through intermediate energy absorbers such as crash boxes (deformation elements) or reversible dampers. Frequently the transverse beams support a layer of polymeric foam which can dissipate some energy in the case of small crash impacts. Sometimes the energy absorber being supported by the beam is a plastic or composite plastic solution. In other cases the beams themselves are flexible and can absorb some impact energy without getting permanently deformed.

The different objectives of the crash systems may be summarized like this:

Protect the legs of pedestrians from severe injury when being impacted by the vehicle.

- Protect the vehicle against any damage at crash impacts of up to 4 to 8-9 km per hour (2.5 to 5 miles per hour) of impact speed.

- Limit the damage to the car - thus repair costs - at impacts between 4 and 16 km per hour.

- Contribute to the protection of the car at crashes above 16 km per hour, both when negotiating hard and deformable objects, in the lower speed range to reduce the damage of the vehicle, in the higher speed range to protect the occupants of the car as well as any other person involved in the accident, against injury.

To solve these issues, a variety of solutions are proposed, from which a few are mentioned:

- US 6,511 ,109 displays a bumper system comprising a composite facia with a channel of varying height between integral upper and lower valances, said channel being closed by an open section cover beam. - WO 2004/011306 comprises as system with an open section bumper beam with an open section plastic energy absorber mounted to it. The energy absorber is transversely extending the length of the beam, and consists of channels which deform upon an impact with a pedestrian.

- US 5,967,592 shows a system consisting of a bumper outer shell made of a fiber reinforced plastic which is spaced from a stiff inner beam. The outer shell deforms elastically and reversible upon low impact, whereas the inner beam transfers high impact loads. - US 6,179,355 describes a bumper assembly consisting of a beam with multiple recesses extending transversely the length of the beam, featuring energy absorbing caps inside the beam adjacent to the fixation to the side members. The crash deformation takes place in steps of different crash force magnitude.

In addition, there is known a great variety of different metallic and plastic bumpers, comprising different beam cross sections of either an open-channel type or in a closed chamber configuration. The closed chamber configuration may have one, two, three or a multitude of chambers.

The variety of the different objects which a car can hit, crash with or be rammed by, is great. It is for example quite common to hit hard objects such as walls, trees and poles. On the other hand, vehicle to vehicle crashes are common as are unfortunately also impacts with pedestrians. A vehicle which is well laid out to absorb impacts transforms its structure plastically during the impacts to absorb crash energy, and may be defined as "deformable". The deformable crash test barriers represent the vehicle body structure of the "crash partner vehicle".

Unfortunately, due to the different needs of the different crash situations, many crash modules suffer from compromises when it comes to how they perform in crash and otherwise. For example it is quite common for a crash module to be designed to yield a high resistance (force) during an impact. This is very beneficial when negotiating impacts with hard objects, as obviously this force can be established when meeting said objects, and the crash energy is absorbed with as little deformation as possible of the vehicle structure. On the other hand it is then difficult to start the desired deformation in the case of hitting a yielding, deformable object such as another vehicle with distinct deformation zones. What then frequently may happen is that the other object is being cut into in an aggressive manner, something being recognized as undesirable, ultimately exposing both involved vehicles as well as the occupants of these vehicles to large damage and injury.

Conversely, if a crash module is laid out to be deformed at a low force, it may more easily be triggered - starting to be deformed - in a crash with a deformable object, will however display much larger deformation itself before the crash energy is absorbed.

It is clear that, if the crash module displays a large surface area towards the deformable object which is hit, a larger resistance (force) may be accumulated from this object, and a high resistance in own structure may then also here be utilized. Due to the cramped space available for crash modules, especially at the front of vehicles, it is difficult to arrange for a large crash surface: Among other things, air ingress to the engine compartment for cooling must be considered. Then there are main lights above the crash module, frequently air ducts and auxiliary lights under the module, object- and distance sensors, light washing devices and so on which also must be considered.

However, not only the problem of providing a large crash area must be solved, the other critical issue is to provide for the crash forces to reach the side members by means of the crash module. This means that the load carrying capacity as expressed through the ability of the bumper beam to withstand shear forces as well as bending- and torsional moments or a combination of any of said loads must be high when the crash starts, as well as being upheld during most of the crash sequence. Furthermore it is now recognized that in order to stabilize a severe crash deformation of a vehicle structure, it is beneficial to preserve the integrity of the structure during the crash sequence in order to ensure that the crash deformation takes place as foreseen when lying out the structure. Now this means that the structural members being deformed are not torn off or collapse in an unforeseen manner, furthermore it also means that certain critical structural members, such as the bumper beam, are not flattened in the impact, thus preserving their ability to stabilize the rest of the structure through bending and torsional stiffness.

US 6,511 ,109 depicts a bumper cover beam with varying height, however in an open section configuration, with a very limited bending resistance due to having an ineffective cross section against bending, which thus cannot by itself transfer heavy loads such as needed in impacts against deformable objects. As the facia by itself also is an open channel configuration, the same applies to the facia parts such as the valances and the channel in between.

WO 2004/011306 enables a soft initial impact with a pedestrian, however both the bumper beam and the energy absorber are open section channels providing little bending and torsional resistance in the case of impacts with higher impact speeds and -energies. The larger crash surface area created in an impact cannot be utilized in impacts with deformable objects such as cars because the section of the absorption element is not strong enough to transfer crash forces from its vertically extended parts.

US 5,967,592 has a shell which deflects easily at low energy impacts, and which extend its crash surface in some impacts, however again will not be able to transfer major crash forces from its extended edges due to the cross section adjacent to said edges being squeezed flat.

US 6,179,355 will, in the areas ahead of the side members, extend its crash area vertically, in other areas, however, will not do so and tends to be flattened in an impact.

Some closed section bumpers provide high initial bending and torsional resistance together with an ability to increase their cross section height somewhat during an impact. The problem with these, however, as exemplified by flattening a square tube, is that then both bending and torsional resistance is quickly lost. There are examples of closed chamber configured beams expanding their nose section into a mushroom shape during an impact, preserving the rear portion of the beam as a closed chamber. In order to utilize this mechanism, the beam section must both be high and deep (as seen in the longitudinal direction of the vehicle, something being prohibitive in the cramped environments of vehicles today).

To sum up: The crash modules of today are frequently compromised in their performance due to the demands being so different that it is difficult to satisfy them with one common system. One major consequence of this is that vehicles and their occupants are exposed to crash hazards. Another consequence is that vehicles are configured heavy and bulky to compensate for the performance of their crash structure.

In view of the above, it is an object of the present invention to enhance the heretofore known bumper systems. Particularly, it is an object of the invention to provide a bumper system with, in the case of a crash, a stable and predictable deformation of not only the bumper beam thereof, but also the crash structure surrounding the bumper beam, such as the side members or the crash box.

According to the invention, the above object is achieved in that said connection means is coupled to an abutting means, and said upper top wall and/or said lower bottom wall is/are coupled to a first crash energy absorbing means.

Since said connection means is coupled to an abutting means, the abutting means, at least in a certain period of a crash, serves as a hinge around which the upper chamber and/or the lower chamber rotate(s), thereby expanding the crash silhouette, what is advantageous particularly in case of hitting a yielding, defomnable object.

Since, furthermore, said upper top wall and/or said lower bottom wall is/are coupled to a first crash energy absorbing means, due to said rotating around said abutting means, said walls serve for triggering said first crash energy absorbing means, so that an early crash energy absorbance is obtained.

Preferably, said first crash energy absorbing means is a top or bottom wall of said side member or of said crash box. In this case, what can particularly be considered is to connect said upper top wall and said lower bottom wall, respectively, with said top or bottom wall of said side member or of said crash box by welding, by riveting or using bolts in an overlap joint configuration or by any other means found suitable at the time of production.

In order to obtain a high degree of compactness, what is, furthermore, preferred is that said abutting means is a middle wall of said side member or of said crash box. Thereby, said middle wall serves several purposes. Namely, it serves as said hinge means in an early period of a crash, so that said upper and lower chambers can rotate thereabout, whereas it serves as another crash energy absorbing means in a later period.

It can furthermore be shown, that the partition of the crash box into two or more chambers beneficially influences the so called "buckling folding" wavelength as well as force amplitude, still further improving the crash energy absorbing efficiency of the crash box.

Said upper and/or said lower chamber comprise(s) preferably an inner wall. Thereby, said chambers can be designed to have a closed structure, particularly with rectangular form, said closed structure being quite stiff and having high bending and torsional resistance. This is particularly important with view to transferring crash forces acting on the outer wall, via the upper top/lower bottom wall to said first crash energy absorbing means, both initially as well as later in the crash sequence.

According to another preferred embodiment of the invention, said upper and/or said lower inner wall(s) serve(s) for coupling of said upper top wall or said lower bottom wall to said first crash energy absorbing means. In other words, said upper top wall or said lower bottom wall need not be coupled to said first crash energy absorbing means directly, but might be coupled thereto via said inner wall(s).

In order to simplify the overall system, what is preferred is that said connecting means is an extension of said upper and/or lower inner wall(s).

According to a highly preferred embodiment, said upper and/or said lower inner wall(s) is/are inclined so that an upper part of said upper inner wall and/or a lower part of said lower inner wall is/are positioned more outside than a lower or upper part thereof. This V-structure is particularly advantageous with view to said rotation of said upper and lower chambers around said hinge (abutting means) for obtaining said expansion of the crash silhouette and for triggering said first crash energy absorbing means.

Contrary thereto, said upper and/or lower outer wall(s) is/are perpendicular relative to a longitudinal direction of said vehicle. Thereby, the complete vertical widths of said outer walls serve as the crash area, what is advantageous particularly with view to the case of hitting a yielding, deformable object.

Preferably, what is provided for is a kink in said upper bottom wall and/or in said lower top wall in order to weaken the overall structure, so that the bumper beam quite easily deforms in an early phase of a crash. Contrary thereto, thereafter, said upper and lower chambers are preferably of rectangular structure, so that they have high bending and torsional resistance.

According to a particularly preferred embodiment, a second crash energy absorbing means is held in front of a channel between said upper and lower chambers. Said second crash energy absorbing means is compressed in combination to being pressed into said channel in case of a crash, thereby absorbing the energy necessary to deform said second crash energy absorbing means so that it fits into said channel. It is now realized that the distance that said means protrudes outwards from the bumper beam when compressed is less than would otherwise be the case, enabling a more compact system as seen in the longitudinal direction of the vehicle.

The bumper system preferably has a third outer wall bridging the upper outer wall and lower outer wall in certain areas such as in the regions where the attachment to the crash box or side member is provided. The third outer wall will serve as a stiffening means of the beam section in said regions, again controlling the expansion of the beam section. At least a part of the outer wall can be provided with an indentation.

Moreover, the invention provides for a bumper system comprising a bumper beam attachable to a front or rear end of at least one side member or to a crash box of a vehicle, particularly a bumper system as described above, wherein a total width of said bumper beam in the vertical direction is greater in one region thereof in front of said side member as compared to at least one other region. In the case of the bumper beam being fabricated from a pre-fabricated or extruded bar with said bridging outer wall integrated, said variation of width may be through the means of at least partly indenting said bridging outer wall.

As said, the crash silhouette is greater in a region backed by said side member as compared to other regions. Thereby, the bumper system has high compactness particularly in said other regions, so that there is more room for other elements of the vehicle, such as cooling means, auxiliary lights and the like.

Finally, what is preferred is that the at least one other region is a middle region between 2 side members or crash boxes. This is particularly advantageous for most motor vehicles.

In other words: The new crash module is variable by being adapted as well as adapting to the different crash situations. The "silhouette" - which is the surface area of the module towards a crash (the crash area) - is relatively small. The silhouette is made larger where it is useful for the behaviour in the crash, such as near to the attachment to the side members. This silhouette may remain in some parts of the beam in the case of an impact. In some parts of the beam, from where the crash forces may be transferred to the side members, the silhouette may grow in an impact. In parallel, the module may yield initially in certain ways, such as bending somewhat backwards from the impact, in order to achieve an early movement which may give an early signal to crash sensors, thus activating protection equipment such as air-bags and seat belt tensioners.

The bumper beam is thin and high and preferably comprises closed chamber configured sections which have a large bending and torsion resistance initially. Furthermore, the closed chamber configuration is upheld even at large crash forces and deformations. The bumper beam may be so coupled to the crash boxes, eventually directly to the side members, that there may be a useful and direct interaction of the deformation behaviour of the top and bottom walls of said members, again enabling said expansion of the crash silhouette.

In this way, optimum performance in all crash situations is safeguarded, and the crash module needs not display compromised crash performance. In addition, the space needed for the module is small relative to its performance, both as seen in the vertical and longitudinal direction of the vehicle, providing useful space for other objects.

The purpose of the invention is to enable crash modules which need not be compromised in their performance, thus improving the crash performance in many situations, particularly in impacts with deformable objects such as passenger cars. This again particularly will lessen the hazard for both vehicles and the occupants of these vehicles in crashes. Furthermore, the invention is about enabling a stable and predictable deformation of not only said crash module, but also the crash structure surrounding the module, such as the side members.

The present invention was made to enhance vehicle structures as follows: Now that a high crash force can be used in impacts with hard objects, and a higher force than hereto in impacts with deformable objects, the vehicle is not so dependent on having long deformation zones for crash protection. This means, for example, that the so-called overhang at the front and the rear of the vehicle may be shortened, again bringing down the bulk, weight and cost of the vehicle.

The term "overhang" here refers to the distance the car body protrudes out from the wheels of the vehicle, seen in a side view perspective of the vehicle.

In addition, as mentioned, the occupants of a vehicle so equipped, in the case of a car to car crash, will be less exposed to high crash forces. This is due to now achieving an earlier build-up of the crash force in said crash, resulting in a more effective crash energy absorption. This again will lessen the magnitude and duration of the dangerous peak force at the end of the crash sequence.

As a further consequence of the lowered crash force peak, the main structure of the car may be configured somewhat less substantial whilst still giving an improved crash protection, consequently bringing down weight, bulk and cost of the vehicle.

In the following the invention is described with further details. Particularly, preferred embodiments are described, referring to the enclosed drawings, in which:

Fig. 1 schematically shows a first conventional bumper system,

Fig. 2 schematically shows a second conventional bumper system, Fig. 3 shows the same view as Figs. 7 and 8, but of a bumper system according to the invention,

Fig. 4 shows the same view as Fig. 9, but in a later period of a crash.

Fig. 5 schematically shows a first embodiment of the bumper system according to the invention,

Fig. 6 schematically shows a second embodiment,

Fig. 7 schematically shows a third embodiment,

Fig. 8 schematically shows a fourth embodiment,

Fig. 9 schematically shows a fifth embodiment, Fig. 10 schematically shows a sixth embodiment,

Fig. 11 schematically shows a seventh embodiment.

Figs. 1 to 4 show different crash situations between a vehicle and a deformable barrier. As already mentioned, the deformable barriers, which are standardized, represent the structure of other cars, and are used for crash tests. A car, showing a good behaviour when being crashed into a deformable barrier, is recognized as being a safe car in a car to car crash. In the figures, 1 is a bumper beam which is fixed to a crash box 2, said crash box 2 being attached to a vehicle body 3 through side members 4.

It is to be noted that the invention is not limited to embodiments comprising crash boxes as crash energy absorbing means. Rather, alternatively or additionally, side members 4 may as well serve as crash energy absorbing means. In other words, crash box 2 might be dispensed with, so that bumper beam 1 is directly fixed to side members 4.

The deformable barrier 5 is depicted by its deformable honeycomb structure sandwiched between layers of sheet. Ahead of the barrier, crushable blocks 6 are fixed to the first layer of sheet of the barrier. The crushing resistance of said blocks 6 is significantly higher than that of the barrier itself. The barrier 5 is fixed to a non-deformable backing 7 which either is of considerable mass or is fixed so that it will not move in a crash impact.

Figure 1 shows a crash situation where a conventional bumper system, and particularly bumper beam 1 , cuts into the soft barrier 5 by pushing the upper ones of the blocks 6 into the first sheet layer without being triggered to deform more than just bending bumper beam 1. In such a situation, the vehicle will cut through the first sheet layer in an aggressive manner, cut through the barrier 5 with a lowered force, and then ram backing 7 in the barrier creating a high force pulse 8 as shown in the force-displacement diagram of Figure 1. Bearing in mind that the deformable barrier 5 represents another vehicle, it becomes clear that this behaviour in crash can be aggressive both to the vehicle which is hit and the vehicle which is hitting, as well as to occupants of both vehicles.

Figure 2 shows a somewhat improved situation in the case of another conventional bumper system, where, in the partition between the deformation elements of crash box 2 and side members 4, flanges 9 of considerable surface area protrude. When this area is sufficient, said flanges 9 will encounter a large resistance when the bumper system has cut enough into the barrier 5 so that said flanges meet the barrier. Simultaneously, crash forces of other substantial parts of the vehicle, such as the grille, the forward parts of the hood, light surrounds and so on may in parallel be led into the side members 4 through said flanges 9.

The respective "collected" resistance force of the deformable barrier 5 will then be sufficient to start the deformation of one of the side members 4, as indicated by crimpled area 10. This offset-type of crash makes the moving vehicle 3 turn around its centre of gravity 11 and steer into the barrier. At the same time, the non-deformed side of the vehicle structure resists the deformation by restraining bumper beam 1. In effect, the impact on one of side members 4 together with the respective deformation elements of crash box 2, which in this context may be regarded as one continuous column, are subject to a bending moment. Unfortunately, the portion of this column which is crimpled (folded) is not adjacent to the front end of said column, because crash box 2 is not deformed. It can be shown through design stress and strain analysis that an area of a column which is being deformed beyond the yield strength of the material in said area may easily be deformed further with little extra use of force. What this means here is that crimpled area 10 is unstable and may be regarded as a (knee) joint in the continuous column consisting of side member 4 and crash box 2.

It is now realized that the bending moment acting upon said column due to the crash may force the column to swing out with the deformed area as its joint. This is disadvantageous for the crash performance, because side member 4 and crash box 2 will not take up crash energy through folding buckling. The resistance towards the barrier will drop, again leading to poorer crash energy absorption, with negative consequences for the hitting vehicle as well as for the hit vehicle represented by the soft barrier, and for the occupants of both vehicles as well. Reference numeral 12 refers to the respective force- displacement diagram.

Figures 3 and 4 conversely show an improved behaviour of the elements of the bumper system, and particularly of crash box 2 and side members 4. Here, as indicated in Fig. 3, bumper beam 1 initially transfers enough force to crash box 2 to start deforming the same. This rapid rise of the resistance of the crash module means that the crash energy is being absorbed initially more through deformation "work" in the vehicle structure than by cutting aggressively into the barrier 5, as is also indicated by tracking force-displacement diagram 12 of Figure 3.

Figure 4 shows the situation after the crash is nearly finished, crash box 2 is completely folded, and much of side member 4 is folded as well. Now the intrusion into the vehicle represented by deformable barrier 5 is later in the crash sequence, possibly with a smaller intrusion and without a final high force peak, as depicted by force-displacement diagram 12 in Figure 10. If the sequence is with the same intrusion as before, then it has a lower final force peak and a smaller peak duration.

As already detailed above, it is an object of the invention to ensure a crash behaviour and performance as described with reference to Figures 3 and 4 when encountering deformable barriers, thus other cars, at the same time yielding a high performance in the other relevant crash situations, at the same time being effective when it comes to space and weight utilization as well as being cost-effective, both when it comes to the manufacturing costs of the bumper system itself, but also how it influences the costs of other elements of the vehicle as well.

Figure 5 shows a vertical section view through a part of the bumper system according to a first preferred embodiment of the invention. Particularly, Figure 5 shows a sectional view in front of side member 4 or crash box 2. Other parts of the bumper system are designed differently, as detailed hereinunder.

According to Figure 5, a bumper beam 1 comprises an upper chamber 14 and a lower chamber 15. Upper chamber 14 is defined by outer wall 16, top wall 17, inner wall 18 and bottom wall 19. Lower chamber 15 is defined by outer wall

16', top wall 17', inner wall 18" and bottom wall 19'. Bottom wall 19 of upper chamber 14 has a kink 20 whereas the top wall 17' of the lower chamber 15 is mainly straight. A kink defines a bend between two portions of a wall. It is to be noted that the desired effect of the kink 20 can be reached though indenting the wall, the indentation being a curved shape.

Any of said walls may be provided with a kink. 20 If so desired, both said bottom wall 19 of upper chamber 14 and top wall 17' of lower chamber 15 may be provided with a kink 20 or be held mainly straight. Is should also be noted that the angle of the kink can be adjusted to fit any requirement and that any wall of the bumper beam may be provided with a kink if this is found suitable. Bottom wall 19 of upper chamber 14 and top wall 17' of lower chamber 15 are connected at their inner parts by a connecting wall 21. Inner walls 18, 18' are inclined with view to a vertical line in Figure 5, so that they form a V-shape. It should also be noted that the outer walls 16 can be prolonged outside the top wall 17 of upper chamber 14 and bottom wall 19' of lower chamber 15 thereby forming flanges 22, 22' protruding out from the bumper beam. The flanges 22, 22' are indicated on Figure 7.

The side member 4 can also be replaced by a crash box 2 comprising an upper wall 23, a middle wall 24 and a lower wall 25.

In Figure 5, the left-hand side shows the bumper system 1 before a crash, whereas the right-hand side shows the bumper system 1 shortly after the start of the crash. As is to be taken from Figure 5, chambers 14 and 15 are deformed in the initial phase of a crash so that they become predominantly rectangular closed chambers, making the structure rigid with high resistance against bending and torsion. The kink 20 may facilitate said deformation. Furthermore, during said initial phase of the crash, middle wall 24 of crash box 2 serves as an abutment of connecting wall 21 , so that the same is a hinge around which chambers 14 and 15 rotate. Particularly, the inner parts of top wall 17 of upper chamber 14 and bottom wall 19' of lower chamber 15 move around said hinge. Since they are coupled to upper wall 23 and lower wall 25 of crash box 2, said walls 23 and 25 are triggered to deform, so that crash box 2 as crash energy absorbing means can start to absorb energy at a very early stage of the crash.

What is to be noted is that the inclination of inner walls 18, 18' (V-shape) assists the rotation of top wall 17 and bottom wall 19' around hinge 24 resulting in said early triggering of the bending of walls 23 and 25.

Said rotation of top wall 17 and bottom wall 19' furthermore results in an expansion of the crash silhouette as seen from the left-hand side in Figure 5, with certain advantages in the crash performance, such as being less prone to cutting into a deformable object at the same as a high crash force, thus efficient crash energy absorption, is established.

It is realized, that the top wall 17 of the top chamber 14 may extend upwards as shown in figure 5, correspondingly the bottom wall 19" of the bottom chamber 15 may extend downwards, in both cases beneficially adding to the width of the beam. It can furthermore be shown through crash computational simulations, that said angled configuration of said walls is beneficial for said crash deformation behaviour of the beam.

In later stages of the crash, middle wall 24 of crash box 2 might deform as well, thereby contributing to energy absorbance.

The embodiment shown in Figure 6 differs from the embodiment of Figure 5 particularly in that chambers 14 and 15 are of closed rectangular shape already initially, leading to a even greater expansion of the crash silhouette as compared to the case of Figure 5.

What is depicted on the left-hand side of Figure 7 is a schematic vertical section view of another preferred embodiment of the invention. Particularly, the left- hand side of Figure 7 shows upper chamber 14 and lower chamber 15 of bumper beam 1 in front of a side member (not shown). What is shown, in addition, in hatched lines is the silhouette of an outer connecting wall 26 connecting outer walls 16 and 16' in a region of bumper beam 1 not in front of a side member.

The right-hand side of Figure 7 shows the same view as the left-hand side thereof, but of a part of bumper beam 1 between the side members, and particularly in the middle of bumper beam 1. In this middle part, outer connecting wall 26 has an indentation 27 serving two purposes. On the one hand, by indentation 27, chambers 14 and 15 are drawn closer to one another, making the crash silhouette smaller in the middle region as compared to the regions in front of side members 4, what is advantageous with view to the restricted room in the respective region. Moreover, the wall provided with an indentation 27 serves for enhancing rigidity of bumper beam 1 in the middle region by controlling the deformation of the cross section of the beam when hitting objects such as poles in a crash. It is furthermore recognized that the connecting wall 21 may correspondingly be indented somewhat to facilitate a still further change of bumper width.

Hg. 7 shows the option of employing upwards and downwards extending flanges 22, 22' to the top and bottom outer walls 16, 16', enlarging the crash silhouette still, as already mentioned. It is furthermore recognized, that said flanges may be cropped whenever needed in areas such as in the mid-section of the beam.

Figure 8 shows a perspective view of the embodiment according to Figure 7. The left-hand side of Figure 7 corresponds to regions 28 in front of crash boxes 2 or side members 4 (not shown), respectively, while the right hand part of figure 7 corresponds to middle region 29. Regions 28 comprise a cut-out 30 to separate chambers 14 and 15 from one another, so that they can rotate independently from one another as detailed above.

Figure 9 shows a perspective view of a second embodiment of an abutting means (24) according to the invention. The bumper beam 1 is attached to a side member (not shown) or crash box 2 provided with abutting flanges 31 following the length axes of the crash box 2. The abutting flanges will serve as abutting means during a crash situation as the inner walls 18, 18' will rotate around the hinge 24 which will abut against the abutting flanges 31.

Figure 10 shows a front view of the embodiments of figures 5 and 6. Dashed line 32 shows the expanded crash silhouette of the right-hand side of the bumper beam shown in Figures 2 and 3 as result of a crash. It is recognized, that the outer connecting wall 26 bridging the upper and lower chambers 14, 15 in certain areas, may be added on compared to being integral as shown. Said added on outer connecting wall will then be formed as bridge pieces which may then be attached to the upper and lower chambers through welding, riveting, bolting or the like.

The force-displacement graph of Figure 9 shows three phases of a crash. Peak 33 indicates the initial resistance of bumper beam 1 towards being bent during the initial contact in a crash. Peaks 33' and 33" indicate, consecutively, the resistance of the system when starting to deform crash box 2 and side member 4. It is understood that the force to crush the cross section of bumper beam 1 is greater than the force required to crumple crash box 2.

Figure 11 shows an embodiment of the invention with an energy absorbing element 34 held in front of channel 35 between chambers 14 and 15. Said energy absorbing element 34 is made from polymeric foam, for example. The left-hand side of Figure 11 shows a situation before a crash, whereas the right- hand side shows the situation after a crash, for example a crash with a pedestrian. As is to be taken from Figure 6, energy absorbing element 34 must be deformed to be pressed into channel 35. The deforming "work" is absorbed. This enables a protruding length 36 of element 34 to be kept at a minimum, enabling the crash module to be placed further forward, thus configuring said module with a greater length, again enabling a greater energy absorbing in high speed crashes.

Summarizing, the invention provides a bumper system which, on the one hand, yields a high resistance when being hit by, or hitting, hard objects in a crash. This is most beneficial because this increases 'the effectiveness of energy absorption during such crashes. On the other hand, if the crash silhouette is adapted to engaging deformable objects in such a way that a high impact force may be achieved, this enables the deformation of the bumper system, at the same time as being compatible in a crash towards said objects.

Claims

1. Bumper system with a bumper beam (1 ) attachable to a front or rear end of at least one side member (4) or to a crash box (2) of a vehicle, wherein the bumper beam, at least in a region thereof in front of said side member or crash box, comprises

- an upper chamber (14) defined by upper outer, top and bottom walls (16, 17, 19), - a lower chamber (15) defined by lower outer, top and bottom walls

(16¹. 17', 19"), and

- a connecting means (21), connecting an inner part of said upper bottom wall with an inner part of said lower top wall, characterized in that said connecting means is coupled to an abutting means (24), and said upper top wall and/or said lower bottom wall is/are coupled to a first crash energy absorbing means (23, 25).

2. The bumper system of claim 1 , characterized in that said first crash energy absorbing means is a top or bottom wall (23, 25) of said side member (4) or of said crash box (2).

3. The bumper system according to claim 1 or 2, characterized in that said abutting means is at least a part of a middle wall (24) of said side member (4) or of said crash box (2).

4. The bumper system of any preceding claim, characterized in that said upper and/or said lower chamber (14, 15) comprise(s) an inner wall (18, 18').

5. The bumper system of claim 4, characterized in that said upper and/or said lower inner wall(s) (18, 18') serve(s) for coupling of said upper top wall (17) or said lower bottom wall (19¹) to said first crash energy absorbing means (23, 25).

6. The bumper system according to claim 4 or 5, characterized in that said connecting means (21) is an extension of said upper and/or lower inner wall(s) (18, 18¹).

7. The bumper system according to any of claims 4 to 6, characterized in that said upper and/or said lower inner wall(s) (18, 18¹) is/are inclined so that an upper part of said upper inner wall (18) and/or a lower part of said lower inner wall (18¹) is/are positioned more outside than a lower or upper part thereof.

8. The bumper system according to any preceding claims 1-7, characterized in that said upper and/or said lower outer wall(s) (16, 16') is/are perpendicular relative to a longitudinal direction of said vehicle.

9. The bumper system of any preceding claims 1-8, characterized in that said upper top wall (17) is inclined so that an outer part of said top wall (17) is positioned aboved an inner part of said top wall and/or said lower bottom wall (19') is inclined so that an outer part of said bottom wall (19') is positioned below an inner part of said bottom wall.

10. The bumper system of any preceding claims 1-9, characterized by a kink (20) in said upper bottom wall (19) and/or in said lower top wall (17).

11. The bumper system of any preceding claims 1 -10, characterized by a second crash energy absorbing means (33) held in front of a channel (34) between said upper and lower chambers (14,15).

12. The bumper system of any preceding claims 1-11 , characterized by an indentation (27) provided to at least a part of a wall,

13. A bumper system comprising a bumper beam (1) attachable to a front or rear end of at least one side member (4) or to a crash box (2) of a vehicle, particularly according to any preceding claim, characterized in that a total width of said bumper beam in the vertical direction is greater in a region (28) thereof in front of said side member as compared to at least one other region (29).

14. The bumper system of claim 13, characterized in that said at least one other region (29) is a middle region between two side members (4) or crash boxes (2).