VEHICLE BUMPERS WITH DIFFERENTIATED SHOCK ABSORPTION DEPENDING ON THE TYPE OF IMPACT

Abstract

The invention relates to a vehicle bumper comprising at least two interconnected beams (2, 12), characterized in that it comprises a first beam (2) connected by at least two energy-absorbing elements (7) to a second beam (12), the stiffness of the first beam being greater than that of the second beam. The invention also relates to a vehicle equipped with at least one such bumper. Figure to be published with the abstract: Fig. 1

Description

Title of the invention: VEHICLE BUMPER WITH DIFFERENTIATED SHOCK ABSORPTION ACCORDING TO THE SHOCK

[0001] The invention relates to a vehicle bumper with shock absorption differentiated according to the impact.

[0002] Here the term vehicle designates a car, a van, a truck, a public transport vehicle, a public works or agricultural machine, regardless of the type of engine, thermal, electric or hybrid.

[0003] The regulations relating to the passive safety of a vehicle vary depending on the country concerned. Thus, in the USA, all vehicles sold are subject to the standards issued by the Federal Motor Vehicle Safety Standards (FMVSS). In particular, according to the FMVSS 301 standard, vehicles must ensure their integrity and the safety of passengers during a standardized impact on a bumper of the vehicle, the impact occurring on one side of the bumper and at approximately 81 km / h. Due to the speed at the time of impact and the location of the impact, the bumper must be able to absorb the energy of the impact by transmitting a maximum of forces to the opposite side of the bumper. On the other hand, in Europe, the tests are carried out at lower impact speeds, around 16 km / h, the impact occurring on the entire bumper, therefore frontally.In this case, during a test in Europe, the energy to be absorbed is less than during the test according to the FMVSS 301 standard and therefore the repairability of the bumper is prioritized. In other words, in Europe, the rigidity of the bumper will be less, it will deform more easily. Because of this difference in passive safety requirements, there are two solutions when you want to market the same vehicle in Europe and the USA. Either you prioritize one or the other of the tests, so you either have a bumper that is resistant to high-speed impacts but cannot be repaired, which is a safe but expensive solution, or you make a compromise by reinforcing a bumper that originally had a high repairability. Such solutions are not fully satisfactory in terms of passive safety and offer limited repairability.US-B-6 764 119 thus describes a bumper consisting of two beams, one of which has a U-shaped cross-section defining, between the branches of the U, a housing for receiving a second beam. The beams are connected to each other only by their ends. Such a beam does not allow it to respond optimally to the various impact resistance tests. There is therefore a need for a bumper that is resistant to side impacts at high speed while being easily repairable when the impact occurs frontally and at low speed.

[0004] The object of the invention is to improve the passive safety of vehicles in the event of impacts. on a bumper, regardless of the speed at impact and the position of the latter on the bumper.

[0005] To this end, the invention relates to a vehicle bumper comprising at least two beams connected to each other, characterized in that it comprises a first beam connected by at least two energy absorption members to a second beam, the stiffness of the first beam being greater than that of the second beam.

[0006] Thus, thanks to the invention, a bumper of simple construction is provided which makes it possible to respond to different types of tests, and therefore to have optimal efficiency for one type of impact, without altering the effectiveness of the bumper for another type of impact. In addition, due to its simple construction, such a bumper allows a saving in mass.

[0007] According to advantageous but not mandatory aspects of the invention, such a bumper may comprise one or more of the following characteristics:

[0008] The first beam is made of steel and the second beam is made of aluminum.

[0009] The first and second beams extend the entire length of the bumper.

[0010] The first beam is adapted to be fixed directly to a part of the chassis of a vehicle by means of a fixing plate.

[0011] The at least two energy absorption members are placed near the ends of the beams.

[0012] The energy absorption members are made of steel or aluminum.

[0013] The second beam is removably mounted on the energy absorption members.

[0014] Each beam complies with a given impact test.

[0015] the invention also relates to a vehicle equipped with at least one bumper conforming to at least one of the preceding characteristics.

[0016] The invention will be better understood and other advantages thereof will appear more clearly on reading the description which follows, given solely by way of non-limiting example and with reference to the appended drawings in which:

[0017] [Fig-1] is a partial perspective view of the beams of a bumper conforming to an embodiment of the invention in place on a part of the chassis of a vehicle.

[0018] [Fig.l] partially illustrates a part of a vehicle, more particularly a lower part of the chassis 1. This is the area of ​​the chassis receiving a bumper, this part 1 being by definition the most exposed to impacts, due to its position and / or its configuration, generally projecting relative to the rest of the vehicle. Here, it is the rear part 1 of the vehicle. For greater readability, the exterior trim of the bumper is not illustrated, as are any elements mounted on the bumper such as lights, indicators or others. Only the beams constituting the bumper intended to react in the event of impacts are illustrated here. The first beam 2 is made of steel or a high-strength, high-rigidity steel alloy. Alternatively, it is made of a composite material or it is made of several materials. As a reminder, the rigidity of a material is its ability to resist deformation when an external stress is applied, for example in the event of an impact. Conversely, the elasticity of a material concerns its ability to return to its initial shape when the stress is no longer exerted. Rigidity is measured in Nm. Furthermore, the stiffness of a beam depends not only on the rigidity of the material constituting the beam but also on its geometry, in particular the ratio between its cross-section and its length as well as its configuration: hollow or not, honeycomb or other. It is therefore recalled here that, by definition, rigidity concerns materials and stiffness concerns structures and elements, therefore here the beams.

[0019] The first beam 2, in the example illustrated, is the beam fixed directly to the chassis 1. Here, the fixing is carried out at each end 3 of the beam 2 using two identical plates 4, welded or screwed onto the chassis 1. These plates 4 are metallic. Alternatively, they are made of a material, composite or polymers.

[0020] The beam 2 is here configured in rectangular cross-section. Alternatively, it has another cross-section, for example square. Alternatively, it is configured in honeycomb. In all cases, the first beam 2 is advantageously hollow, which optimizes its mechanical strength while lightening it. The beam 2 comprises, substantially in the middle position along its length, a longitudinal groove 5 extending over more than 80% of the thickness of the first beam 2. The first beam 2 is advantageously permanently fixed by welding to the fixing plate 4. The outer face 6 of the first beam 2 comprises at least one energy absorption member 7.

[0021] This energy absorption member 7 is positioned, in the illustrated embodiment, in the vicinity of each end 3 of the first beam 2. Alternatively, there are more than two energy absorption members 7, the latter being, for example, regularly distributed over the length of the first beam 2. The energy absorption members 7 are made of aluminum or steel. Alternatively, they are made of composite materials. In all cases, the members 7 are made of an energy-absorbing material, for example a polymer-based composite material or a metallic material having, in this case, a particular configuration facilitating its deformation in the event of an impact. Here, the energy absorption members 7 are rectangular parallelepipeds. Alternatively, they are square parallelepipeds. The members 7 are hollow here or, alternatively, solid.

[0022] The members 7 are fixed to the end 3 of the first beam 2 by their face 8 of smaller area, namely here that corresponding to the cross-section of the end 9 of the member 7. The end 10 opposite the end 9 receives an end 11 of the second beam 12. The beam 12 is of a configuration similar to that of the first beam 2, namely hollow with a rectangular cross-section, with a longitudinal groove 13 in the middle position. Here the width of the groove 13 is much greater, which de facto contributes to the deformation of this second beam 12 in the event of an impact since this reduces the stiffness of the beam 12. Alternatively, it is of a different configuration than that of the first beam 2. This second beam 12 is in all cases made of a material whose rigidity is less than that of the material used for the first beam 2, regardless of the configuration of the beam 12. Thus the second beam 12 is advantageously made of aluminum or an aluminum-based alloy.

[0023] This second beam 12 is preferably held in a removable manner by screwing or bolting onto the end 10 of the energy absorbing member 7 by a fixing part 14 which covers the end 11 of the second beam 12 at least over a portion of its thickness in the manner of a stirrup. Thus, in the event of an impact at low speed generally along the longitudinal axis of the vehicle on which the bumper is mounted, the second beam 12 absorbs the impact and deforms due to its structure and configuration as well as by the presence of the energy absorbing members 7, whereas the first beam 2 will be little or not at all affected by the impact. All, or at least the majority, of the energy is absorbed and dissipated by the second beam 12 and by the energy absorbing members 7 placed at the ends 11.If the impact is sufficiently violent to permanently deform the second beam 12, it will be easy to change the latter by separating it from the energy absorption members 7 by dismantling the fixing members 14. If necessary, the energy absorption members 7 can also be changed. In all cases, the second beam 12 and the energy absorption members 7 are configured to be easily repairable in the event of a low-speed impact.

[0024] When the impact occurs at high speed, typically around 80 km / h, and it is not made frontally, the elastic deformations of the second beam 12 and the absorption members 7 reach their limits of elasticity and are not sufficient to completely absorb the impact. Such an impact can cause a rupture of the second beam 12. In this case the impact is sufficiently violent to indirectly impact the first beam 2 via the second beam 12 and the energy absorption members 7. The latter has sufficient stiffness to absorb the energy that has not been absorbed by the second beam 12 and therefore preserve the structural integrity of the vehicle and ensure optimal safety of the passengers. It is understood that in the event of such an impact it will be necessary to replace both beams 2 and 12.

[0025] The invention can be used on the front and rear bumpers of the vehicle as well as on the bumpers fitted to a trailer towed by a vehicle such as a truck. In all cases, thanks to high elastic resistance steels used for the first beam 2 and a second beam 12 made of aluminum, the invention allows a weight saving while reinforcing part 1 of the bumper. The invention makes it possible to respond to the technical problems posed in the event of a different impact without weighing down the chassis of the vehicle and without involving significant structural modifications, therefore with a controlled cost.

Claims

Claims

1. Vehicle bumper comprising at least two beams (2, 12) connected to each other, characterized in that it comprises a first beam (2) connected by at least two energy absorption members (7) to a second beam (12), the stiffness of the first beam being greater than that of the second beam.

2. Bumper according to claim 1, characterized in that the first beam (2) is made of steel and the second beam (12) is made of aluminum.

3. Bumper according to claim 1, characterized in that the first and second beams (2, 12) extend over the entire length of the bumper.

4. Bumper according to claim 1, characterized in that the first beam (2) is adapted to be fixed directly to a part (1) of the chassis of a vehicle by means of a fixing plate (4).

5. Bumper according to claim 1, characterized in that the at least two energy absorbing members (7) are placed in the vicinity of the ends (3, 11) of the beams (2, 12).

6. Bumper according to claim 1, characterized in that the energy absorbing members (7) are made of aluminum or steel.

7. Bumper according to claim 1, characterized in that the second beam (12) is removably mounted on the energy absorbing members (7).

8. Bumper according to claim 1, characterized in that the stiffness of each beam (2, 12) complies respectively with the requirements of a standardized test during a side impact on the bumper at 81 km / h and a test during a frontal impact on the bumper at 16 km / h.

9. Vehicle equipped with at least one bumper according to any one of the preceding claims.

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