LIGHTWEIGHT SHOCK ABSORPTION DEVICE for MOTOR VEHICLES

Abstract

The invention relates to a crash box type shock absorbing device comprising a hollow profile (1) having a first end section (1a) intended to be connected to a bumper cross member (2) and a second end section (1b) intended to be connected to the vehicle body, said profile being delimited by an upper wall (11), a lower wall (12) and two side walls (13, 14), said walls being provided with a series of recesses (10a, 10b, 10c) intended to increase the deformation capacity of the profile, characterized in that said recesses (10) are of variable dimensions between the first end section (1a) and the second end section (1b). Abstract figure (Fig. 2)

Description

Title of the invention: LIGHTWEIGHT SHOCK ABSORPTION DEVICE for MOTOR VEHICLES

[0001] The invention relates, in general, to the field of motor vehicle safety and is more particularly concerned with systems intended for absorbing impacts occurring at the front or rear and in the lower part of vehicles.

[0002] Motor vehicles are generally equipped with devices integrated into bumpers and intended to ensure the absorption of kinetic energy resulting from collisions with an obstacle, another vehicle or a physical person. These devices (called "crash boxes") are produced in the form of an assembly of profiled and stamped shells.

[0003] The weight of these devices is significant and they therefore contribute to the weight gain of the vehicle while the current trend is towards weight reduction.

[0004] Furthermore, the deformation capacity of these devices and, in particular, their compressibility, in the event of contact with the legs of a pedestrian, is relatively low.

[0005] Patent DE102011051442B4 describes the integration of crash boxes into a sleeper metal provided with a pedestrian protection element. This protection element is made of a material having a lower hardness than the material of the crossbar, the crossbar being convertible between a pedestrian guard position and a collision position.

[0006] Patent application EP1477371A3 describes a crash box arranged between a side member and a cross member of a vehicle bumper. This crash box comprises a profile in the form of at least one longitudinal hollow body provided with lateral tabs which compensate, by deformation, the forces generated by an impact.

[0007] However, the deformations of these existing crash boxes are not satisfactorily controlled during the impact phase, which is problematic in the event of a collision with pedestrians.

[0008] In this context, the invention sought an improved technical solution to overcome the shortcomings of the prior art and, in particular, which is better suited to the protection of pedestrians. Thus, in principle, the invention aims to propose a lightweight shock-absorbing device whose deformation capacity evolves variably during the impact phase.

[0009] This object is achieved, according to a first aspect of the invention, by means of a crash box type shock absorption device comprising a hollow profile having a first end section intended to be connected to a bumper cross member and a second end section intended to be connected to the body of the vehicle, said profile being delimited by an upper wall, a lower wall and two side walls, said walls being provided with a series of recesses intended to increase the deformation capacity of the profile, characterized in that said recesses are of variable dimensions between the first end section and the second end section.

[0010] According to an advantageous characteristic of the invention, the dimensions of the recesses of the upper and lower walls decrease from the first end section to the second end section in order to increase the compressibility of the profile at the start of the impact against the crosspiece.

[0011] According to another characteristic, the recesses provided on the side walls are narrower than the recesses provided on the upper and lower walls of the first end section in order to avoid spillage during impact.

[0012] According to a first variant embodiment of the device of the invention, the recesses of the upper and lower walls are made symmetrically on the profile.

[0013] According to a second variant embodiment of the device of the invention, the recesses of the side walls are identical and made symmetrically on either side of the profile.

[0014] According to yet another variant embodiment of the device of the invention, the profile has an intermediate section between the first section and the second end section and the upper, lower and lateral walls of which are devoid of recesses in order to locally reduce the compressibility of the profile.

[0015] Preferably, the contours of the recesses are at least partially rounded.

[0016] Another object of the invention is a motor vehicle bumper provided with a crash box type shock absorption device as defined above.

[0017] Yet another object of the invention is a motor vehicle equipped with at least one crash box type shock absorption device having the characteristics defined above.

[0018] Thus, in its most general principle, the invention proposes a high-performance device for absorbing kinetic energy resulting from impacts, the deformation capacity of which is controlled in order to best protect pedestrians during a collision with a motor vehicle.

[0019] The device of the invention can be used both at the front and at the rear of a vehicle. Thanks to the presence of the series of recesses whose dimensions and positions are determined according to safety standards, the device of the invention is lighter than traditional crash boxes.

[0020] Furthermore, the effectiveness of the device of the invention is improved because the compressibility of the section of the crash box hitting the lower limbs of pedestrians is significantly increased, which helps reduce the risk of severe trauma.

[0021] Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures, for which:

[0022] [Fig-1] is an overall perspective view of a preferred embodiment of a bumper according to the invention.

[0023] [Fig.2] is a perspective view from above of the energy absorption device kinetic (crash box) integrated into the bumper of [Fig.l].

[0024] [Fig.3] is a top view of the kinetic energy absorption device (crash box) of [Fig.2].

[0025] For clarity, identical or similar elements are identified by identical reference signs throughout the figures.

[0026] Naturally, the embodiments of the kinetic energy absorption device according to the invention illustrated schematically by the figures presented above and described below, are given only as non-limiting examples. It is explicitly provided within the scope of the invention that different modes can be proposed and combined with each other to propose others.

[0027] It is specified that all the characteristics, as they emerge for a person skilled in the art on reading the present description, the figures and the associated claims, even if concretely they have only been described in relation to other determined characteristics, both individually and in any combinations, can be combined with other characteristics or groups of characteristics disclosed here, provided that this has not been expressly excluded or that the technical context makes such combinations impossible or meaningless.

[0028] The invention relates to the general field of passive safety of motor vehicles and is more particularly concerned with devices for absorbing kinetic energy (also called crash boxes) resulting from impacts at the front or rear of vehicles.

[0029] More specifically, the invention sought to develop a technical solution integrating an absorption device which, while being lightened, has a controlled deformation capacity in order to improve the safety of pedestrians in the event of an accidental collision with a vehicle.

[0030] In a known manner and as illustrated by [Fig.l], the crash box type shock absorption devices comprise a hollow profile 1 having a first end section 1a intended to be connected to a bumper cross member 2 and a second end section 1b intended to be connected to the body of the vehicle (not shown) by means of a plate 3.

[0031] This profile 1 is delimited, respectively, by an upper wall 11, a lower wall 12 and two side walls 13, 14, as illustrated in detail by [Fig.2]. The walls 12 to 14 are provided with a series of recesses 10a, 10b, 10c intended to increase the deformation capacity of the profile 1 by reducing as much as possible the flat and solid surfaces on these walls.

[0032] The invention aims to optimize the characteristics of the series of recesses on the profile 1 to selectively and locally improve its deformation capacity and, in particular, its compressibility with respect to impacts. This objective is achieved mainly by producing recesses of variable dimensions between the first end section 1a and the second end section 1b.

[0033] More precisely, the invention provides that the dimensions (i.e. the surfaces or areas) of the recesses 10a, 10b of the upper 11 and lower 12 walls decrease going from the first end section 1a (connected here to the front bumper of the vehicle) to the second end section 1b (connected here to the body).

[0034] In the embodiment shown in the figures, two recesses 10a are made above and below the first section 1a and two other recesses 10b are made above and below the second section 1b. However, it is possible, without departing from the scope of the invention, to adjust the number, position and dimensional characteristics of the different recesses according to the type of vehicle and the desired safety levels.

[0035] This specific configuration of the invention makes it possible to increase the compressibility of the profile 1 at the start of an impact occurring against the cross member 2 of the bumper (as in the direction of the arrow in [Fig.3]). The surface area of ​​the recesses 10a of the upper 11 and lower 12 faces of the first section 1a is therefore larger than that of the recesses 10b located above and below the second section 1b.

[0036] Indeed, the reduction of material in the parts of the profile 1 where the recesses are located is accompanied by a local weakening. Now, this weakening is essential in the area of ​​the crash box most exposed to impacts, that is to say, in the end section 1a connected to the cross member 2 of the bumper, in order to minimize its resistance at the start of the impact. Thus, the front section 1a of the profile 1 will crush more quickly and more easily at the start of the impact, which makes it possible to better protect the lower limbs of pedestrians.

[0037] Furthermore, the recesses naturally correspond to areas where the material is absent and these areas will therefore not be deformed during the kinematics of movement of the crash box towards the body of the vehicle, beyond section 1b. Thus, thanks to the invention, the compression level is increased at the start of the impact and controlled in terms of forces over time. At the same time, the compression level is reduced at the end of the impact after reaching a peak force.

[0038] Still in pursuit of this objective and in a complementary manner, the recesses 10c provided on the side walls 13, 14 are narrower (or of smaller surface area) than the recesses 10a provided on the upper 11 and lower 12 walls of the first end section 1a. In addition, these recesses 10c (here three in number on each side of the profile) are positioned and dimensioned in order to avoid a tilting towards the right or towards the left during the impact. In the embodiment shown in [Fig.2], the recesses 10c are offset longitudinally relative to the recesses 10a, 10b.

[0039] It is possible, without departing from the scope of the invention, to provide that the dimensional characteristics of the recesses 10c of the side walls 13, 14 are possibly identical to those of the recesses 10b made on the upper 11 and lower 12 walls of the second end section 1b of the profile 1.

[0040] In the embodiment shown in the figures, the recesses of the upper 11 and lower 12 walls are made symmetrically. Similarly, the recesses of the side walls 13, 14 are here identical and made symmetrically on either side of the profile 1.

[0041] The profile 1 here has an intermediate section 1c between the first end section 1a and the second end section 1b. On this intermediate section 1c, the upper 11, lower 12 and side walls 13, 14 are all without recesses. This section 1c thus delimits a zone where the rigidity is greater in order to increase the peak force during impact and to locally reduce the compressibility of the profile 1.

Claims

Claims

1. Crash box type shock absorbing device comprising a hollow profile (1) having a first end section (1a) intended to be connected to a bumper cross member (2) and a second end section (1b) intended to be connected to the vehicle body, said profile being delimited by an upper wall (11), a lower wall (12) and two side walls (13, 14), said walls being provided with a series of recesses (10a, 10b, 10c) intended to increase the deformation capacity of the profile, said recesses (10) being of variable dimensions between the first end section (1a) and the second end section (1b), characterized in that the dimensions of said recesses (10a, 10b) of the upper (11) and lower (12) walls decrease from the first end section (1a) to the second end section (1b) in order to increase the compressibility of the profile (1) at the start of the impact against the crosspiece (2).

2. Device according to the preceding claim, characterized in that the recesses (10c) provided on the side walls (13, 14) are narrower than the recesses (10a provided on the upper (11) and lower (12) walls of the first end section (la) in order to avoid spillage during impact.

3. Device according to one of the preceding claims, characterized in that the recesses (10a, 10b) of the upper (11) and lower (12) walls are made symmetrically on the profile (1).

4. Device according to one of the preceding claims, characterized in that the recesses of the side walls (13, 14) are identical and made symmetrically on either side of the profile (1).

5. Device according to one of the preceding claims, characterized in that the profile has an intermediate section (le) between the first end section (la) and the second end section (1b) and the upper (11), lower (12) and lateral (13, 14) walls of which are devoid of recesses in order to locally reduce the compressibility of the profile (1).

6. Device according to one of the preceding claims, characterized in that the contours of said recesses (10a, 10b, 10c) are at least partially rounded.

7. Motor vehicle bumper provided with a crash box type shock absorbing device according to one of the preceding claims

8. Motor vehicle equipped with at least one crash box type shock absorption device according to one of claims 1 to 6.

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