Crash box for a motor vehicle

Abstract

Crash box (10) for a motor vehicle (2) with a filler body (14) with an auxetic structure, wherein the filler body (14) made of an auxetic structure is arranged in the crash box (10), wherein the filler body (14) is connected to the crash box (10) by a positive fit, wherein at least one engagement element (26) is assigned to the filler body (14) made of an auxetic structure, wherein the engagement element (26) extends into a recess in the crash box (10), and wherein the positive fit is designed as a dovetail connection.

Description

[0001] The invention relates to a crash box for a motor vehicle.

[0002] In automotive engineering, a crash box (also called a crash can) is a shock absorber system.

[0003] In the event of a rear-end collision, kinetic energy is dissipated by deformation of the crash box, thereby reducing the deceleration force exerted on the vehicle occupants and the entire body of the vehicle. This is intended to prevent unacceptable deformation of the body (which can sometimes result in total loss) and injuries to the vehicle occupants. Crash boxes are designed for collisions up to a certain impact speed, e.g., 15 km / h. They can be replaced after an accident with relatively little effort. Such crash boxes are known, for example, from US 7 160 621 B2, US 7 350 851 B2, CN 1 07 139 874 A, US 2017 / 0 151 921 A1 or DE 10 2006 058 604 A1. Furthermore, CN 1 07 145 626 A discloses a shock absorber system with a negative Poisson's ratio.

[0004] From DE 60 2005 004 701 T2 a crash box for a motor vehicle with a filler body having an auxetic structure is known, wherein the filler body made of an auxetic structure is arranged in the crash box, wherein the filler body is connected to the crash box by form-fitting, wherein connecting elements are assigned to the crash box which extend into the filler body.

[0005] From US 2019 / 0 168 480 A1 an auxetic structure is known, among other things, for a crash box of a motor vehicle.

[0006] A fuel arrangement with an inflatable tank is known from DE 10 2016 114 302 A1.

[0007] A battery cell with auxetic components is known from DE 10 2013 224 751 A1.

[0008] From DE 10 2014 225 069 A1 a component for force absorption and / or force distribution in a battery cell module is known.

[0009] From DE 10 2012 024 510 A1 an energy absorption element for a motor vehicle is known with a hollow body and a stiffening element inserted into the hollow body, which are connected to each other by means of a snap-in connection.

[0010] From DE 10 2018 106 007 A1, a crash box for a motor vehicle with a filler body having an auxetic structure is known, wherein the filler body made of an auxetic structure is arranged in the crash box, wherein the filler body is integrally connected to the crash box by adhesive bonding.

[0011] At the same time, crash boxes are also designed for accidents with higher impact speeds, such as 56 km / h. In this accident scenario, the crash boxes must be sufficiently rigid to contribute to impact energy absorption. This increases the design effort, and the design for the lower impact speed limits the crash box's contribution to impact energy absorption. Furthermore, this type of design requires a certain minimum length for the crash boxes, which results in an overhang at both the front and rear of the vehicle.

[0012] There is therefore a need to identify ways in which such crash boxes can be improved.

[0013] The object of the invention is achieved by a crash box for a motor vehicle with a filler body having an auxetic structure, wherein the filler body made of an auxetic structure is arranged in the crash box, wherein the filler body is connected to the crash box by positive locking, wherein at least one engagement element is assigned to the filler body made of an auxetic structure, wherein the engagement element extends into a recess of the crash box, and wherein the positive locking is designed as a dovetail connection.

[0014] The filler body is thus connected to the crash box by a form-fit connection, either stationary and / or transmitting force. Form-fit connections are created by the interlocking of at least two connecting partners. This prevents the connecting partners from coming apart, even without or with interrupted force transmission. In other words, in a form-fit connection, one connecting partner is in the way of the other. Because at least one engagement element extends into a recess in the crash box, no additional parts, such as fastening parts, are required. Instead, the recess can be created using a material-removing process, such as milling or drilling.

[0015] Thus, the previously unused cavity inside the crash box is used to accommodate a body with the auxetic structure. No additional installation space is required. An auxetic structure (from ancient Greek αúξητóς auxetos, German "stretchable") is defined as a structure that expands when stretched transversely to the stretching direction. It is therefore characterized by a negative Poisson's ratio. The crash box with the filler body with the auxetic structure can be integrated into various passive safety systems of the vehicle, such as a bumper, a battery side impact bar, a passenger side impact bar, or an occupant head protection system.

[0016] By designing the recess as a guide groove and the engagement element as a slotted nut of a dovetail joint, displacement along a first axis, i.e., along the extension direction of the guide groove, is possible, but not in the direction of other axes. This allows, for example, simple assembly by inserting the filler body into the crash box by displacing the filler body along the extension direction of the guide groove.

[0017] According to one embodiment, the filler with the auxetic structure is a 3D-printed component. Alternatively, the filler with the auxetic structure can also be a folded part or a deep-drawn part. 3D printing (also known as additive manufacturing, additive manufacturing (AM), generative manufacturing, or rapid technologies) is a comprehensive term for all manufacturing processes in which material is applied layer by layer to create three-dimensional objects. The layer-by-layer construction is computer-controlled from one or more liquid or solid materials according to specified dimensions and shapes. During construction, physical or chemical curing or melting processes take place. Typical materials for 3D printing are plastics, synthetic resins, ceramics, and metals.The most important techniques are laser beam melting and electron beam melting for metals and laser sintering for polymers, ceramics, and metals; stereolithography and digital light processing for liquid synthetic resins; and polyjet modeling and fused layer modeling for plastics and some synthetic resins. Compared to injection molding, 3D printing has the advantage of eliminating the time-consuming process of mold production and mold changes. Compared to all material-removing processes such as cutting, turning, and drilling, 3D printing has the advantage of eliminating the additional processing step after primary forming. A further advantage is that it can also produce bodies with complex geometries. The folded part can consist of several strip-shaped material cuts, and the deep-drawn part can consist of several deep-drawn sub-elements.

[0018] According to a further embodiment, the filler body with the auxetic structure is a wire frame component. Thus, the filler body has a particularly low weight.

[0019] According to a further embodiment, the filler body with the auxetic structure is designed such that the filler body with the auxetic structure is flexible when deformed below a predetermined limit and rigid when deformed above the predetermined limit. Thus, the filler body with the auxetic structure can behave in a yielding manner in the event of an impact at a low speed, e.g. 15 km / h, and rigidly in the event of an impact at a higher speed, e.g. 56 km / h. In other words, when deformed below the predetermined limit, the filler body with the auxetic structure is more flexible than when deformed above the predetermined limit. For example, the body with the auxetic structure can behave auxetically up to a predetermined limit, but non-auxeticly once the limit is exceeded, i.e. like a normal material.This means the crash box can be flexibly adapted to different requirements.

[0020] According to a further embodiment, the crash box, together with the filler body with the auxetic structure, is designed to absorb forces. In other words, the filler body with the auxetic structure has an additional mechanism that makes an additional contribution to the energy absorption of the crash box. Thus, the crash box can be designed to be shorter in the axial direction, i.e., in the direction of impact, than without the filler body with the auxetic structure. This allows the overhang of the motor vehicle to be shortened at both its front and rear.

[0021] According to a further embodiment, the filler body is connected to the crash box in a fixed and / or force-transmitting manner. The filler body can be connected to the crash box in a fixed and / or force-transmitting manner by force-lock (frictional engagement) and / or form-lock and / or material bond. Force-locked connections require a normal force acting on the surfaces to be joined. Their mutual displacement is prevented as long as the counterforce caused by static friction is not exceeded. Examples include clamped connections. Material-locked connections are all connections in which the connecting partners are held together by atomic or molecular forces. Examples include connections formed by soldering, welding, gluing, or vulcanization.

[0022] The invention further includes a crash box designed as a position holder, a crash box providing a force-locking connection, a filler body with the auxetic structure for such a crash box, a safety system with such a crash box, and a motor vehicle with such a safety system. The safety system can be, for example, a bumper, a battery side impact protection system, or a passenger head protection system of the motor vehicle.

[0023] The invention will now be explained with reference to a drawing. It shows: Fig. 1 in schematic exploded view components of a bumper of a motor vehicle. Fig. 2 shows a schematic representation of some of the Fig. 1 shown components in assembled state. Fig. 3 shows a schematic section through a Fig. 2 crash box shown. Fig. 4 shows a schematic section through the Fig. 3 shows a crash box with an inserted filler body with an auxetic structure. Fig. 5A - 5D show schematic representations of various auxetic structures. Fig. 6 shows a schematic representation of a comparison of the deformation of a crash box with and without a filler with an auxetic structure. Fig. 7A - 7E show schematic representations of different views of another auxetic structure. Fig. 8A - 8B in schematic representations of further views of the Fig. 7A - 7E shown auxetic structure. Fig. 9A- 9C show schematic representations of a one-piece design of the Fig. 7A - 7E and 8A - 8B shown auxetic structure. Fig. 10A - 10C show schematic representations of a packing based on a Miura fold with an auxetic structure. Fig. 11A - 11B show schematic representations of further views of the Fig. 10A - 10C shown filler with the auxetic structure. Fig. 12A - 12D in schematic representations of a filler body with an auxetic structure based on a cube structure as a basic element. Fig. 13A - 13B show schematic representations of another structure serving as a base element for the filler body with an auxetic structure. Fig. 14A - 14B show schematic representations of another structure serving as a base element for the filler body with an auxetic structure. Fig. 15A - 15C show schematic representations of various views of a battery side impact protection device. Fig. 16A - 16C show schematic representations of various views of a passenger side impact protection device. Fig. 17A - 17C show schematic representations of various views of an occupant head protection device.

[0024] First, the Fig. 1 and Fig. 2 is referred to.

[0025] Shown is a passive safety system 4 of a motor vehicle 2, such as a passenger car, which in the present embodiment is designed as a bumper.

[0026] In the present embodiment, the passive safety system or bumper is designed as an energy-absorbing bumper. It comprises a cover 6, e.g., made of plastic, another component 8, a bumper support 12, e.g., made of steel, two crash boxes 10 attached to the bumper support 12, and a base plate 16 connected to each of the crash boxes 10.

[0027] The two crash boxes 10 are designed to dissipate kinetic energy in the event of a rear-end collision by deforming the crash box in order to expose the vehicle occupants and the entire body to a lower deceleration force.

[0028] It will now also Fig. 3 referred to.

[0029] In the present embodiment, the two crash boxes 10 have a substantially cylindrical basic shape with an interior space 18.

[0030] It will now also focus on the Fig. 4 and 5A - 5D.

[0031] In Fig. 4 shows the crash box 10 with a filling body 14 with an auxetic structure inserted into the interior 18.

[0032] The auxetic structure expands perpendicular to the stretching direction when stretched. It is therefore characterized by a negative Poisson's ratio.

[0033] In the present embodiment, the auxetic structure as a wire frame component has a honeycomb-like structure with many spaces arranged in such a way that it expands in width instead of length when the auxetic structure reacts mechanically.

[0034] Such three-dimensional auxetic structures expand in all directions perpendicular to the tensile direction. These are usually structures that impart the auxetic properties to the material, not the material used to create them. However, there are also materials that naturally exhibit such structures, and materials that are artificially transformed into an auxetic structure, such as the diamond-fold structure (RFS), which is created from a surface independent of the material.

[0035] In the present embodiment, the filler body 14 with the auxetic structure is a 3D-printed component. This means that to produce the filler body 14, material was applied layer by layer, thus creating the filler body 14 with the auxetic structure. This makes it particularly easy to Fig. 5A - 5D shown as examples.

[0036] In the present exemplary embodiment, the filler body 14 with the auxetic structure is formed in two parts and / or of a non-uniform material, at least together with the crash box. The crash box 10 has recesses designed as internal guide grooves 30 for positioning the filler body 14 with the auxetic structure. The respective sliding blocks 32 engage in these recesses. These sliding blocks are assigned to the filler body 14 with the auxetic structure and are, for example, integrally formed thereon. Thus, the filler body 14 with the auxetic structure can be formed in one piece with the sliding blocks 32 and made of the same material in order to connect them to one another by a positive fit.

[0037] Furthermore, in addition to the filler body 14 with the auxetic structure and the crash box 10, other components can be formed in one piece and from the same material, such as the base plate 16.

[0038] The filler body 14 with the auxetic structure is designed such that it is flexible when deformed below a predetermined limit and rigid when deformed above the predetermined limit. Thus, the filler body 14 with the auxetic structure can behave in a yielding manner in the event of an impact at a low speed, e.g., 15 km / h, and rigid when deformed at a higher speed, e.g., 56 km / h. In other words, the filler body 14 with the auxetic structure is more flexible when deformed below the predetermined limit than when deformed above the predetermined limit.

[0039] Because the crash box 10, together with the filler body 14 with the auxetic structure, is designed to absorb forces, the crash box 10 is provided with an additional mechanism that makes an additional contribution to energy absorption. Thus, the crash box 10 can be designed to be shorter in the axial direction R, ie, in the direction of impact, than without the filler body 14 made of the auxetic structure. This shows Fig. 6, which shows the deformation s in [mm] resulting from a force F in [kN], with curve I of a crash box 10 without a filler body 14 with an auxetic structure being compared with curve II of a crash box 10 with a filler body 14 with the auxetic structure. Thus, an overhang of the motor vehicle 2 can be shortened both at its front and at its rear. Additionally, a crash box wall thickness and / or a thickness of the base plate 16 and / or a side rail thickness can be reduced.

[0040] It will now also focus on the Fig. 7A - 7E and 8A - 8B.

[0041] Shown is a filling body 14 of auxetic structure, which is constructed from a plurality of inverted tetrapods, wherein the Fig. 7D and Fig. 7E show how inverted tetrapods deform to provide the negative Poisson number.

[0042] Groups of inverted tetrapods can be combined to form layered elements 20, which - after being 3D printed - are inserted one after the other into the crash box 10, or several layered elements are formed as one component 22, which is then inserted into the crash box 10.

[0043] The multiple layer elements 20 or the component 22 are welded at welding points 24 after insertion into the crash box 10.

[0044] It will now also focus on the Fig. 9A - 9C are referred to.

[0045] Shown is a one-piece design of the Fig. 7A-7E and 8A-8B, with an auxetic internal structure as the filler body 14. Thus, the crash box 10 is integrally formed with the filler body 14 having an auxetic structure. Therefore, no weld points 24 are provided.

[0046] It will now also focus on the Fig. 10A - 10C are referred to.

[0047] Shown is a filler 14 made of auxetic material based on a Miura fold. The fold pattern consists of a tessellation of parallelograms whose edges form straight lines in one direction and a zigzag pattern in the other direction. Each parallelogram is axially symmetrical with respect to the straight line to the adjacent parallelogram. Each intersection point of folds borders three valley folds and one mountain fold, or three mountain folds and one valley fold.

[0048] It will now also focus on the Fig. 11A - 11B.

[0049] It is shown that in a two-part design of the crash box 10 with the filler body 14 having an auxetic structure, these welding points 24 connect, whereas in a one-part design of the crash box 10 with the filler body 14 having an auxetic structure, these welding points 24 are omitted.

[0050] It will now also focus on the Fig. 12A - 12D.

[0051] Shown is a filler body 14 with an auxetic structure, which is based on a cube structure as the basic element.

[0052] Furthermore, it is shown that in the illustrated two-part design of the crash box 10 with the filler body 14 having the auxetic structure, the filler body 14 has engagement elements formed as molded-on locking lugs 26 that engage in corresponding recesses of the crash box 10, which are formed as holes 28, in order to connect them to one another by a positive fit. Thus, the filler body 14 with the auxetic structure can be formed in one piece and from the same material with the locking lugs 28.

[0053] It will now also focus on the Fig. 13A - 13B.

[0054] Shown is a filler body 14 with an auxetic structure based on another cube structure as a base element.

[0055] It will now also focus on the Fig. 14A - 14B.

[0056] Shown is a filler body 14 with an auxetic structure based on strip elements as the base element.

[0057] In the present exemplary embodiment, the crash box 10 with the filler body 14 having the auxetic structure was integrated into a bumper of a motor vehicle 2. Deviating from the present exemplary embodiment, the crash box 10 with a filler body 14 having an auxetic structure can also be integrated into a battery side impact protection device (see Fig. 15A - 15C), into a passenger side impact protection system (see Fig. 16A - 16C) or occupant head protection (see Fig. 17A - 17C) are integrated.

[0058] Thus, such crash boxes 10 can be improved so that they can be adapted for different applications. List of reference symbols 2 motor vehicles 4 Security system 6 aperture 8 Component 10 Crashbox 12 bumper supports 14 filler with an auxetic structure 16 Base plate 18 Interior 20 layer elements 22 Component 24 welding points 26 locking lug 28 holes 30 guide groove 32 T-slot nut I History II Course R axial direction

Claims

[1] Crash box (10) for a motor vehicle (2) with a filler body (14) with an auxetic structure, wherein the filler body (14) made of an auxetic structure is arranged in the crash box (10), wherein the filler body (14) is connected to the crash box (10) by positive locking, wherein at least one engagement element (26) is assigned to the filler body (14) made of an auxetic structure, wherein the engagement element (26) extends into a recess in the crash box (10), and wherein the positive locking is designed as a dovetail connection. [2] Crashbox (10) according to claim 1, wherein the filler body (14) with the auxetic structure is a 3D printed component or folded part or deep-drawn part or cast injection-molded part or a composite material part. [3] Crashbox (10) according to claim 2, wherein the filler body (14) with the auxetic structure is a wire frame component. [4] Crash box (10) according to one of claims 1 to 3, wherein the filler body (14) with the auxetic structure is designed such that the filler body (10) with the auxetic structure is flexible when deformed below a predetermined limit value and rigid when deformed above the predetermined limit value. [5] Crashbox (10) according to one of claims 1 to 4, wherein the crashbox (10) together with the filler body (14) with the auxetic structure is designed to absorb forces. [6] Crashbox (10) according to one of claims 1 to 5, wherein the filling body (14) is connected to the crashbox (10) in a stationary and / or force-transmitting manner. [7] Crashbox (10) according to one of claims 1 to 6, wherein the crashbox (10) is designed as a position holder. [8] Crashbox (10) according to one of claims 1 to 7, wherein the crashbox (10) is designed to provide a force-locking connection. [9] Filler body (14) with an auxetic structure for a crash box (10) according to one of claims 1 to 8. [10] Safety system (4) with a crash box (10) according to one of claims 1 to 8. [11] Safety system (4) according to claim 10, wherein the safety system (4) is a bumper, a battery side impact protection or an occupant head protection. [12] Motor vehicle (2) with a safety system (4) according to claim 11.

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