FR2776254A1 - Arrangements, in vehicle, for absorbing kinetic energy of shock loads e.g. due to a collision - Google Patents

Abstract

The kinetic energy absorption device (13) is located between an element of the drive train (10) and protective assembly (2), defining the front of the vehicle. This absorption device is carried by the protective assembly and has maximal absorption capacity.

Description

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  ARRANGEMENT IN A MOTOR VEHICLE OF A

  DEVICE FOR ABSORPTION OF KINETIC ENERGY DUE A

  A COLLISION, DUDIT VEHICLE, AGAINST AN OBSTACLE

  The invention relates to an arrangement, in a motor vehicle, of a device for absorbing kinetic energy, of a collision of said motor vehicle against an obstacle, and more particularly of a device complementary to the absorption means constituted over there

  structure and shield of said vehicle.

  Motor vehicles are generally provided with kinetic energy absorption devices, created during a collision of said vehicle against an obstacle. These devices are intended to limit the physical constraints of the vehicle passengers during the impact. The amount of kinetic energy is linked in particular to the general mass of the vehicle and to

its speed at the moment of impact.

  The absorption devices are defined according to dissipated energy ranges, and are, in general, provided according to a standardized speed of the vehicle. In order to provide good kinetic energy dissipation, while preserving the possibility of vehicle repair, the kinetic energy dissipation devices can be classified in two ways - the energy dissipating devices without producing irreversible deformation of the kinetic energy. the structure of the vehicle, this corresponds to

low speed collisions.

  - the elements of the vehicle structure intended for the dissipation of kinetic energy, in the event of an impact at a higher speed, no

  absorbed by the aforementioned elements.

  US-A-5139297 discloses a structure of a motor vehicle shield for absorbing the kinetic energy of shock produced at low speed. Since such protection is designed to absorb a low level of energy, the increase in the collision speed then causes a transmission of the kinetic energy, which is not dissipated, on the structural elements of the motor vehicle. If the structure of the vehicle is too rigid, the kinetic energy will be transmitted to the passengers of the vehicle, creating on them, lesions usually fatal. The publication WO 92/11165 describes a motor vehicle front structure which allows the absorption of a large part of the non-dissipated kinetic energy by the other means similar to the publication US-A-5139297 mentioned above. This structure consists mainly of passenger compartment limiting elements extended longitudinally towards the front of the vehicle by deformable spars.

  carrying at their ends a transom equipped with a shield.

  The assembly of such kinetic energy absorption devices limits the deformations of the passenger compartment cell as well as the effects on the

passengers.

  The structure of the front block of the vehicle is generally intended to receive the powertrain consisting in particular of the engine and the gearbox. The powertrain is a rigid element with a large mass. Due to its rigidity, the powertrain can not absorb a portion of the energy of the shock but instead performs a direct transmission of said energy to the elements in contact with said powertrain. This transmission is amplified by the fact that the powertrain is suspended on flexible fasteners

  allowing the filtration of vibrations.

  In addition, during the impact, the transition with a rigid element, such as the powertrain, with an element of the vehicle structure, such as, for example, the limiting elements of the passenger compartment, generates an acceleration peak. on passengers during the phase of absorption of kinetic energy. This peak of acceleration can create, for example, 3 - irreversible brain lesions proportional to the extension of said peak

in time.

  The abrupt variations of the acceleration during the absorption phase of the kinetic energy does not allow to obtain a good coupling between the means of retaining the passengers and the latter. During a violent impact the first absorption devices, made through the shield and its cross, are crushed. The obstacle then constrains the structure of the vehicle to meet the obstacle with the powertrain. The obstacle being in direct contact with the o10 powertrain, the kinetic energy produced by the latter and the rest of the vehicle is retransmitted to the structure of said vehicle and more particularly to the limiting elements of the passenger compartment. The phenomenon is accentuated when the shock is not distributed over the whole front face of the vehicle, the absorption of the energy to be dissipated then being concentrated in

much on a single spar.

  In order to overcome these drawbacks, the object of the invention is an arrangement of a device for absorbing kinetic energy, which makes it possible, during a violent impact, to improve the coupling of the passengers with their retaining means. The invention also relates to an arrangement of a kinetic energy absorption device which improves the dissipation of said energy during an impact distributed over a portion of the front face of the vehicle. The invention also relates to an arrangement of an absorption device which makes it possible to shorten the crush length of the

  vehicle during the energy absorption phase.

  According to one characteristic of the invention, the device for absorbing kinetic energy is located between a powertrain member.

  and a shield assembly defining the front portion of the vehicle.

  According to another characteristic of the invention, the absorption device is

worn by the shield set.

  According to another characteristic of the invention, the absorption device is carried by a spar. According to another characteristic of the invention, the absorption device is

  powered by the powertrain.

  According to another characteristic of the invention, the absorption device is

carried by the gearbox.

  According to another characteristic of the invention, the absorption device has a maximum kinetic energy absorption capacity for a direction of the stress oriented at an angle of plus or minus 20 with respect to

the longitudinal axis of the vehicle.

  According to another characteristic of the invention, the absorption device is sized to absorb at least the kinetic energy of the powertrain. Other features and advantages of the invention will become apparent

  reading the description of exemplary embodiments of an arrangement of a

  device for absorbing the kinetic energy of a collision of a motor vehicle against an obstacle with reference to the appended drawing in which: FIG. 1 represents the schematic structure of a front block of

  motor vehicle having a power train.

  FIG. 2 represents two schematic curves of the dissipation of the specific energy of a motor vehicle during a collision against an obstacle, one corresponding to a behavior according to the state of the art, the other corresponding to a behavior of a vehicle equipped

of the device according to the invention.

  FIG. 3 represents the schematic structure of a front block of a motor vehicle in a first phase of absorption of the kinetic energy. FIG. 4 represents the schematic structure of a front block of a motor vehicle in a second phase of absorption of the kinetic energy. - Figure 5 shows the schematic structure of a front block of a motor vehicle in a third phase of absorption of kinetic energy.

  In the following description, and particularly in Figure 2, it is made

  refers to the specific energy defined by: Es () = og (e) of = _ [vo-v ()] g (e) = -d> of = vdt dt I being the strain length Vl being the velocity after a deformation I V0 being the initial speed At the end of shock = 2vo As shown in Figure 1, the vehicle comprises a front block 1 delimited transversely at its rear portion by limiting elements of the passenger compartment 6, such as a crossbar and an apron, and at its front by a shield assembly 2 and laterally by longitudinal members 3a and 3b. The shield assembly 2 consists, in general, of a plastic covering portion carried by a cross-member sheet -6- or profile, other types of design exist. The front block 1 receives a powertrain 10 which comprises, for example, a heat engine 11 coupled to a gearbox 12. The powertrain can be constituted by all types of engine, electric, turbine, .. or by a battery pack. In our exemplary embodiment, a cooling device 4, of the motor 11, is arranged

  between the shield assembly 2 and the power train 10.

  The dissipation of the specific energy of a motor vehicle, according to the state of the art, during a collision, is shown in Figure 2 by o the schematic curve S1. The abscissa corresponds to the depression of the vehicle, the ordinate to the acceleration. The area delimited by the SI curve corresponds to the amount of kinetic energy dissipated. The bearing, between the zones A, and Cl, corresponds to the meeting of the power train 10 with the obstacle 20 and the limiting elements of the passenger compartment 6. The transfer of the kinetic energy, specific to the power unit 10, is

  directly to the structure of the motor vehicle.

  The shield assembly 2 is considered to be mounted on means 5 for absorbing kinetic energy relative to collisions against a low-speed obstacle. The spars 3a and 3b are sized to achieve an absorption of the kinetic energy not absorbed by the

  devices of the shield set 2.

  A complementary absorption element 13 of the kinetic energy is located between the power unit 10 and the cooling device 4 or the shield assembly 2, if said set of

  cooling 4 is disposed of elsewhere or nonexistent.

  The complementary absorption element 13 can be fixed on the power unit 10, and more particularly on the gearbox 12 in our example, or laterally on one of the longitudinal members 3a and / or 3b, or on the cross member of the assembly Shield 2. The additional absorption element 13 is made to obtain maximum absorption in a crushing direction within an angular variation of +20 relative to the longitudinal axis of the motor vehicle. The sizing of the complementary absorption element 13 is designed to initially absorb the kinetic energy induced by the power unit 10 alone and secondly to absorb a portion of the kinetic energy induced by the vehicle. other part of said kinetic energy being absorbed by the elements of the structure of the motor vehicle provided for this purpose, such as the longitudinal members 3a and 3b, or o10 other elements if the shock occurs at too high a speed. In order to obtain the best absorption in a restricted space, the complementary absorption element 13 must have the lowest possible incompressible residue. The incompressible residue corresponds to the remaining portion of the absorption element 13 whose level of stress to absorb the kinetic energy is greater than the level of stress necessary for the structure of the vehicle to absorb the kinetic energy. As a result, the structure of the vehicle is deformed but the element

absorption 13.

  FIG. 2 represents a schematic curve S2 of the dissipation of the specific energy during the collision against an obstacle of a motor vehicle equipped with the complementary absorption device 13 according to the invention. The abscissa corresponds to the depression of the vehicle, the ordinate to the acceleration. The area delimited by curve S2, and represented by zones A2, B and C2, corresponds to the quantity of energy

  specific dissipated during the collision.

  Figure 3 shows the front block 1 of the motor vehicle in contact with an obstacle 20 in a collision against the latter. The shield assembly 2 is crushed as well as the cross member, the assembly comes into contact with the cooling device 4. This first phase of -8the crushing of the vehicle corresponds to the zones A, and A2 of the curves SI and

S2 shown in Figure 2.

  The crushing of the vehicle continues, and moves the shield assembly 2 and the cooling device 4 to the contact of the latter with the complementary absorption element 13. At this level of displacement, the kinetic energy has begun. to be partly absorbed by the spar 3a, our shock example not being distributed over the entire face

before the vehicle.

  The powertrain 10 bears directly on the obstacle 20

  1o through the complementary absorption element 13.

  The kinetic energy produced by the power unit 10 is then absorbed by a portion of the complementary absorption element 13 during the further crushing of the front of the vehicle. This second phase of the crushing of the vehicle corresponds to the zone B of the second curve S2 shown in FIG. 2. In the case of a vehicle according to the state of the art, there would be a direct transition between the zone AI and the CI area, shown in Figure 2, with the risk of getting a bad

  coupling between the passengers and their means of restraint.

  The power of the powertrain 10 being largely absorbed, the complementary element 13 acts in parallel with the structure of the vehicle,

  and more particularly the spar 3a.

  If the kinetic energy of the vehicle is very important, the complementary absorption element 13 will be constrained to obtain an incompressible residue. The rest of the kinetic energy will then be dissipated in

the structure of the vehicle.

  Since the complementary absorption element 13 is no longer effective, the meeting of the powertrain with the passenger compartment limiting elements 6 occurs in order to continue the dissipation of the kinetic energy 9 in the vehicle structure. This third phase of the crushing of the vehicle, represented in FIG. 5, corresponds to the zone C1

  and C2 of the first and second curves S1 and S2 shown in Figure 2.

  By comparing the curves S1 and S2 of FIG. 2, it can be noticed that the zone B of the curve S2 makes it possible to accentuate the progressiveness between the zones A2 and C2 and thus to improve the coupling between the passengers and their means of detention. In addition, the zone B makes it possible to reduce the area C2 by a value C 'corresponding to the area of the surface B' (represented by hatching) of said zone B. This reduction in the area C2 thus makes it possible to limit the length crushing of the vehicle during the complete absorption of the specific energy of the motor vehicle and more particularly to reduce the time of exposure of passengers to a high acceleration level. In addition, the gain over the crush length of the vehicle reduces the risk of intrusion of the power train 10

in the cockpit.

  In general, the additional absorption device 13 can be carried by elements having a large mass, and more particularly if it is suspended, and capable of generating a large amount of kinetic energy during a collision of the motor vehicle against an obstacle. In order to optimize the dissipation of the specific energy it can be used several absorption devices

complementary 13.

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Claims (6)

  1) Arrangement, in a motor vehicle, of a device for absorbing kinetic energy due to a collision against an obstacle, characterized in that the absorption device (13) of the kinetic energy is located between a powertrain element (10) and a shield set   (2) delimiting the front part of the vehicle.   2) Arrangement according to claim 1, characterized in that the device   absorption (13) is carried by the shield assembly (2).   3) Arrangement according to claim 1, characterized in that the device   absorption (13) is carried by a spar (3a) and / or (3b).   4) Arrangement according to claim 1, characterized in that the device   absorption (13) is carried by the power unit (10).   Arrangement according to claim 4, characterized in that the device   absorption (13) is carried by the gearbox (12).   6) Arrangement according to any one of the preceding claims,   characterized in that the absorption device (13) has a maximum kinetic energy absorption capacity for a direction of stress oriented at an angle of plus or minus 20 to the axis longitudinal axis of the vehicle.   7) Arrangement according to any one of the preceding claims,   characterized in that the absorption device (13) is sized to   absorbing at least the kinetic energy of the power unit (10).