Device for energy absorption in the event of a load impact in the area of ​​the A-pillar of a vehicle cabin

Abstract

Device for absorbing impact energy on a motor vehicle, wherein an A-pillar of a vehicle cabin has a deformable element for absorbing a load impact by energy absorption, wherein - the A-pillar (42) is designed as a hollow profile in which a longitudinal string element (1) is present, the ends of which are attached to adjacent structures of the vehicle cabin (4), on the one hand a floor assembly (41) and on the other hand a structurally reinforced roof pillar (44), - the strand element (1) is a low-density strand material made of at least one plastic fiber (12) with a high elongation at break > 5% or tensile strength greater than 6 MPa, arranged within the A-pillar, - = the strand element (1) is guided tightly in the hollow profile of the A-pillar (42) in the initial state, without prestressing the hollow profile, and in the event of a load impact, the impact energy (E) is dissipated by initially elastic and subsequently plastic longitudinal elongation. A) absorbed, whereby - the strand element (1) has a minimum length for an effective cross-sectional area of ​​the strand element (1) determined by the installation space of the hollow profiles, which depends on a given maximum impact energy E A , which can accommodate the strand element (1) according to its thickness, is to be chosen such that the approximation formula EA = 0.5 × breaking force × length change of the strand element is fulfilled and the minimum length of the string element (1) is adapted by means of deflection pulleys (3) and the placement of attachment points (21; 22) in the floor assembly (41) and / or the roof rail (44) of the vehicle cabin (4).

Description

[0001] The invention relates to a device for absorbing impact energy on a motor vehicle, in which an A-pillar of a vehicle cabin has a deformable element for absorbing a load impact by energy absorption, in particular for A-pillars of a driver's cab of a truck or a mobile crane.

[0002] In order to maintain the survival space of a vehicle driver, reliable and effective energy absorption by the so-called A-pillars is required, particularly in the front area of ​​the driver's cab, where there are frontal and lateral viewing windows that cannot absorb elastic or plastic deformation energy in the event of a load impact.

[0003] Therefore, a front pillar impact protection system is required for a driver's cab according to ECE R29-03, which requires a defined energy absorption of 29.4 kJ through the A-pillars.

[0004] In the current state of automotive technology, impact energy is traditionally absorbed by the deformation of body struts aligned in the direction of travel in front of the A-pillar. Only with the increasing abundance of components in the engine compartment and the elimination of chassis, as well as increasingly thinner outer longitudinal struts and radiator grilles offering little resistance, have cross struts arranged transversely between the longitudinal struts gained importance. These cross struts undergo bending deformation during a frontal impact and convert the resulting length reduction into compression by clamping devices located outside the longitudinal struts.

[0005] For example, EP 1 355 078 A1 discloses an impact energy absorption device which comprises a high-strength material with a longitudinal direction transverse to the direction of impact, wherein a structural system of longitudinal struts aligned in the direction of travel with a defined distance from one another contains front plates for fastening the ends of the high-strength material which is compressed or deflected in the event of an impact and thereby absorbs the impact energy.

[0006] US 2015 / 0210315 A1 discloses a solution that includes a traction cable for each of the vehicle's front wheels, with at least one deflection element, one end of which is attached to a body part and the other end to a front wheel. When deactivated, the cable system executes a steering movement, and when activated, the front wheel is turned toward the obstacle in the event of a collision. Between the attachment points, each cable system has a cable loop and a locking unit designed to lock the cable.

[0007] Furthermore, in order to implement side impact protection on a passenger car, DE 10 2012 019 073 A1 describes a side structure on a side pillar (B-pillar), which is fastened on the one hand to the roof construction and on the other hand to the floor assembly and has an energy absorber essentially transverse to the direction of travel.

[0008] A motor vehicle body whose passenger compartment has a supporting structure consisting of hollow sills and cross members is known from DE 42 08 408 C2. Here, a self-contained first tension element is mounted inside the sills and cross members to redirect absorbed energy to non-involved components and involve them in absorbing the energy.

[0009] A device for stiffening hollow profiles is known from DE 10 2006 011 808 A1, wherein a pre-stressed cable is arranged in an arc shape at least in sections and is fastened to an adjacent component at at least two spaced-apart locations of the hollow profile, so that the pre-stress generated by the pre-stressed cable counteracts an expected force.

[0010] US 6 206 458 B1 discloses such tensioning cables made of plastic, and the documents DE 100 59 261 A1 and DE 196 44 384 A1 disclose associated tensioning devices.

[0011] The invention is based on the object of finding a new possibility for energy absorption in the event of a load impact in the area of ​​the A-pillars of a vehicle cabin, in which a prescribed survival space is guaranteed inside the vehicle cabin for a defined load impact without the installation of additional bumpers in front.

[0012] The object is achieved in a device for absorbing impact energy on a motor vehicle, in which an A-pillar of a vehicle cabin has a deformable element for absorbing a load impact by energy absorption, wherein the A-pillar is designed as a hollow profile in which a strand element is provided longitudinally, the ends of which are fastened in adjacent structures of the vehicle cabin, on the one hand a floor assembly and on the other hand a structurally reinforced roof spar, in that one strand element each, which is a strand material of low density made of at least one plastic bevel with a high elongation at break > 5% or tensile strength greater than 6 MPa / mm 2is arranged within the A-pillar, so that the strand element is initially guided taut in the hollow profile of the A-pillar, without pre-stressing the hollow profile and absorbs the impact energy in the event of a load impact through initially elastic and subsequently plastic elongation. The strand element has a minimum length for an effective cross-sectional area of ​​the strand element predetermined by the installation space of the hollow profiles, which is to be selected as a function of a predetermined maximum impact energy EA that the strand element can absorb depending on its thickness, so that the approximate formula EA = 0.5 x breaking force x change in length of the strand element is satisfied. In addition, the minimum length of the strand element is adapted by means of deflection pulleys and the relocation of fastening points to the floor assembly and / or the roof pillar of the vehicle cabin.

[0013] The strand material is advantageously a plastic or a fiber-reinforced plastic with a density < 2.6 g / cm 3 The strand material is preferably a polyamide or elastomer.

[0014] It proves to be advantageous that the elongation at break of the extruded element is at least a factor of 2 higher than the elongation at break of the A-pillar material.

[0015] Furthermore, it is expedient to arrange at least one deflection roller between the ends of the strand element in order to keep kinks or bends of the A-pillar free from contact with the strand element.

[0016] In a further advantageous embodiment, the minimum length of the strand element can be increased with a meandering strand guide via additional deflection rollers within the floor group.

[0017] The minimum length of the strand element can be conveniently increased by guiding the strand element in a meandering, horizontal or diagonal manner via additional deflection rollers in a front area of ​​the cabin between the A-pillars.

[0018] Furthermore, it is advantageous to provide at least one deflection roller arranged between the ends of the strand element with a tensioning device (5) in order to keep the strand element taut.

[0019] The strand element preferably consists of a strand of at least one plastic fiber or plastic composite. However, it can also be composed of a round, cylindrical bundle of several plastic fibers or a flat bundle of several layers of adjacent plastic fibers. In this case, it is also advantageous to use the possibility of the strand element consisting of braided bundles of plastic fibers.

[0020] The strand element is advantageously covered by a protective sheath to protect it from notch cracks and thus premature breakage.

[0021] In a preferred embodiment, the strand element is pre-tensioned. The pre-tensioning of the strand element is advantageously achieved by means of a tensioning device that has a displacement device either on a fastening eyelet or on a deflection pulley.

[0022] The invention is based on the basic idea that, due to a prescribed survival space inside a vehicle driver's cab, the large viewing windows of a crane cab should not be restricted by additional bumpers or other forward crumple zones and therefore the prescribed energy absorption of the cab in the area of ​​the A-pillars can only be increased by integrating additional energy absorbers into the A-pillars.The problem that the necessary energy absorption cannot be achieved by additional solid metal bracing of the A-pillars due to weight reasons is solved according to the invention by incorporating strand elements made of plastic fibers or fiber-reinforced plastics (flexibly embedded plastic fibers whose matrix has an elongation comparable to that of the absorber strand) into the existing hollow profiles of the A-pillars. The energy absorption of these strand elements due to elastic and / or plastic longitudinal elongation is used to better absorb a load impact on one or both A-pillars. In addition to a high elongation at break (> 5) and high energy absorption, the material of the strand elements also has the lowest possible density (< 2.6 g / cm³). -3 ). These specifications are preferably achieved using thermoplastic fibers, such as polyamide fibers or elastomers.

[0023] Furthermore, the strand length is also crucial for high energy absorption, because the longer the clamped strand element, the greater the potential elongation before failure. At the same time, with the same impact load and a longer strand length, either the required diameter or the material-dependent elongation at break of the strand element and the necessary load absorption by the connection points of the strand elements can be reduced. The required elongation at break of the strand material should be at least 2 to 3 times greater than that of the A-pillar material.

[0024] To install the pre-tensioned strand elements in the A-pillar, an upper and a lower connection point are required for each A-pillar. However, these do not have to be identical to the beginning and end of the A-pillar for the selection of the strand length. To increase the strand length, additional deflection elements can be provided for the strand element. These allow a change in the direction of the strand path at the beginning and end of the A-pillar to lead to further rearward parts of the vehicle cabin, thus extending the strand. Additional deflection pulleys may be necessary to accommodate any bending points in the A-pillar.

[0025] At least one of the aforementioned deflection points, which are preferably designed as pulleys to ensure uniform strand elongation in a load impact situation, can also be used to set a defined strand preload. This advantageously ensures that the strand elongation begins as soon as possible after the load impact and the buckling of the A-pillar, is stretched almost constantly by the impact load, and the elastic elongation range does not account for an excessive portion. Preloading of the strand elements can also be achieved using other additional tensioning elements, e.g., turnbuckles, etc.

[0026] The invention demonstrates a novel way of achieving the necessary increase in energy absorption in the area of ​​the A-pillars of a vehicle cabin during a frontal load impact, ensuring a prescribed survival space inside the vehicle cabin for a defined load impact without the need to install additional forward bumpers or make the A-pillars more solid. In addition to increasing the absorbable impact energy, the invention achieves a negligible increase in weight.

[0027] The invention is explained in more detail below using exemplary embodiments and illustrations. In the following: Fig. 1: a schematic diagram of a vehicle driver's cab with an integrated device according to the invention (energy absorber); Fig. 2a: a schematic representation of a first embodiment of the invention with the implementation of a deflection roller at a bending point of the A-pillar and a strand tensioning device on this deflection roller; Fig. 2b: a schematic representation of a second embodiment of the invention with implementation without a deflection pulley and a strand tensioning device on one of the fastening eyes; Fig. 2c: a schematic representation of a third embodiment of the invention with realization of a strand extension via two deflection rollers and a strand tensioning device on one of the fastening eyes; Fig. 2d: a schematic representation of a fourth embodiment of the invention with realization of a strand extension via four deflection rollers and a strand tensioning device on one of these deflection rollers; Fig. 3a: a sectional view of a first embodiment of the strand element in the form of a round plastic rope with a surrounding protective sheath; Fig. 3b: a sectional view of a second embodiment of the strand element in the form of a cylindrical bundle of several plastic fibers in an enveloping protective sheath; Fig. 3c: a sectional view of a third embodiment of the strand element in the form of a flat plastic band with a surrounding protective sheath; Fig. 3d: a sectional view of a fourth embodiment of the strand element in the form of a flat bundle combined in several layers of plastic fibers in an enveloping protective sheath.

[0028] The structure of the device according to the invention, which - functionally - shall be referred to as an energy absorber, is according to Fig. 1 is integrated in a driver's cabin (hereinafter referred to as cabin 4) of a crane and has a strand element 1 which is arranged within the A-pillars 42 of the cabin 4 and is attached to two fastening eyes 2 between a lower fastening point 21 and an upper fastening point 22 (not in Fig. 1). If the A-pillar has a kink or a bend, the device according to the invention includes a deflection roller 3 at least at this point, which forms one of the so-called deflection points 31, 32, ... of the strand element 1.

[0029] The lower attachment points 21 engage the floor assembly 41 of the cabin 4, while the upper attachment points 22 are preferably attached to one of the roof members 44, which support the roof 45 and establish the upper connection to the A-pillars 42. The roof members 44 are integrated into the B-pillars 43 in the rear area of ​​the cabin 4, which in turn are rigidly connected to the floor assembly 41 in a manner similar to the A-pillars 42.

[0030] The energy absorber of the strand element 1 is an expandable plastic strand with high tensile and creep strength, preferably made of polyamide 6, polyamide 6.6, polyetheretherketone, polyetherimide, polyethersulfone, polyethylene terephthalate, or polyoxymethylene copolymer. This strand is attached to a fixed upper attachment point 22 of the roof spar 44, while a deflection point 31 can be realized by a slightly movable deflection pulley 3. The attachment eyelet 2 must be positioned so that it is not damaged by the energy introduced by the load impact. In some cases, reinforcements in the rear area of ​​the roof spar 44 may also be necessary for this purpose.

[0031] To prevent the strand element 1 from prematurely tearing due to excessive stress on sharp edges during load impact, the strand element 1 is preferably covered with a flexible, stretchable protective sheath 13 (made of an elastomer, thermoplastic, or duromer, such as aramid, PVC, silicone, polyurethane, etc.) similar to the absorber. This sheath can be applied in a closed form or in the form of a braided sheath.

[0032] The strand element 1 should be slightly prestressed to prevent sagging in the assembled state and to absorb energy from the very beginning upon load impact through material expansion (initially elastic and subsequently plastic). Thus, in the event of a frontal load impact on the A-pillar(s) 42, the longitudinal expansion of the strand material reduces the impact energy to such an extent that the driver's survival space is maintained. Strictly speaking, with regard to energy absorption, this device separates the functions of the hollow profile of the A-pillar 42, which represents the bending deformation of a static structure (up to a kink failure), and the strand element 1, which represents the extension deformation of a flexible structure (strand element 1).The increased energy dissipation due to the functional separation between A-pillar 43 (static structure) and strand element 1 (flexible strand element) may require additional reinforcement of the structural elements supporting A-pillar 42. To prevent excessive buckling of the roof 45 during load impact, the roof 45 must be reinforced, made more solid, or designed with structural profiles (longitudinal profile of roof 45), as already mentioned above.

[0033] The energy absorption / density ratio is crucial for the energy absorption of the string element 1 – with regard to the lightweight construction of the cabin 4. The higher this ratio is, the larger the survival space for the driver can be, even with a lightweight design of the cabin 4.

[0034] In Fig. 2a to Fig. 2d shows different embodiments of the energy absorber according to the invention within a cabin 4 in sectional views through a plane of the A and B pillars 42 and 43, respectively.

[0035] Fig. 2a shows a first variant in which the strand element 1 is firmly anchored with its lower attachment point 21 in the floor assembly 41 of the cabin 4, while the upper attachment point 22 is selected at the front end of the roof spar 44 to rigidly connect the upper end of the strand element 1 to the structural reinforcement 46 of the roof spar 44. The strand element 1 can be fastened, for example, by means of a high-strength eyebolt in the lower attachment point 21 to an angle screwed to the floor (not shown) or can be realized in the upper attachment point 22 in the same way directly to the roof spar 44 or to its structural reinforcement 46.The exact position of the lower fastening point 21 is to be selected according to the same criteria as that of the upper fastening point 22 on the roof pillar 44, so that a robust anchoring in solid components of the cabin 4 (floor assembly 41, structural reinforcement 46) is carried out at a position that ensures contact-free guidance of the strand element 1 through the hollow profile of the A-pillar 42.

[0036] At a symbolically indicated bending point of the A-pillar 42, a deflection point 31 is selected, at which a slightly movable deflection roller 3 deflects the strand element 1, so that a notch crack damage of the strand element 1 at the bending point due to a local overload of the strand material cannot lead to a reduction in the breaking strength of the strand element 1. A further measure to prevent notch cracks is - as below in Fig. 3a to Fig. 3d shown in detail - achieved by enclosing the strand core 11 of the strand element 1 with a protective sheath 13, which preferably consists of an elastomer.

[0037] Furthermore, pre-tensioning of the strand element 1 is desirable, as the strand element 1 should not sag in the assembled state, but rather absorb energy from the outset in the event of a load impact. In this case, the pre-tensioning is adjustable by a movable deflection pulley 3, with a tensioning device 5 driving the deflection pulley 3 to the left, thereby further expanding the arc of the strand element 1 outward and ensuring the pre-tensioning.

[0038] In a minimal version of the energy absorber according to the invention, which is Fig. As shown in Figure 2b, the strand element 1 is guided directly in a straight line from the lower to the upper attachment point 21 or 22 along a straight line through the A-pillar 42, whereby no deflection roller 3 is required. A deflection roller 3 is not absolutely necessary, but may be necessary for design requirements, e.g., due to kinked or curved profiles of the A-pillars or the need to increase the strand length in order to manage with a smaller diameter of the strand element 1.

[0039] The minimum length of the string element 1 is determined by the available installation space of the specific A-pillar 42. To comply with the corresponding maximum permissible degree of elongation, the thickness of the string element 1 must be adjusted accordingly so that the effective cross-sectional area can absorb the energy of the load impact. The maximum permissible impact energy is calculated as a first, very rough approximation: EA=0.5×breaking force×change in length (path) of the strand.

[0040] The longer the strand element 1 is, the lower the breaking elongation of the strand element 1 can be selected while maintaining the same load energy absorption. Assuming the strand has a breaking elongation of 10%, a 1 m rope (measured in absolute terms) will then only experience half the change in length at break as a 2 m strand element 1. One such example is Fig. 2c. Here, the strand element 1 is deflected by two deflection rollers 3 at the attachment points 31 and 32. The deflection takes place in the lower part of the A-pillar 42 (at a lower deflection point 32) at its bend and at an upper deflection point 32 at the front end of the roof pillar 44. The upper attachment point 22 in this example is set back to a rear part of the cabin 4, which in this case is attached to the upper structural reinforcement 46 within the roof pillar 44. The strand length thus obtained corresponds to a first approximation to one and a half times the length of the original Fig. 2a and Fig. 2b shown strand element 1.

[0041] To adjust the pre-tension of the strand element 1, in the example of Fig. 2c, at its lower fastening 21, a tensioning device 5 is provided, which can be adjusted within the base group 14 so that the strand element 1 is tensioned over a straight line.

[0042] A further variant with an extended string element 1 with the same window area is shown in Fig. 2d. In this variant, the extended strand guide is not only provided on the upper roof beam 44, but also within the floor assembly 41. Furthermore, with a meandering strand guide over two additional deflection rollers 3 within the floor assembly 41, the strand length is almost tripled compared to the examples of Fig. 2a and Fig. 2b. The lower attachment point 21 is located - as in the three previous examples - in the front area of ​​the cabin 4. From there, the strand element 1 is deflected by 180° at the deflection point 33 via a deflection pulley 3 located in the rear part of the floor assembly 41 and deflected via the deflection pulley 34 into the A-pillar 42. In this case, the tensioning device 5 is integrated into the deflection pulley 3 at the deflection point 33.

[0043] Similarly large extensions of the string element 1 can be achieved by guiding the string element 1 in a meandering manner in the front area of ​​the cabin 4 and tensioning it horizontally or diagonally in the area between the two A-pillars 42.

[0044] The strand element 1 has in a first embodiment, as in Fig. 3a, a substantially circular strand core 11 made of individual fibers of the selected strand material, surrounded by a protective sheath 13. The parallel-arranged individual fibers made of a plastic, preferably polyamide, are combined into a bundle dimensioned according to the load to be absorbed. The protective sheath 13 is an elastic material from the group of aramid, PVC, silicone, and polyurethane. The protective sheath 13 holds the bundle of individual fibers together and protects the strand core from mechanical damage, such as friction or notch impact on the structure of the cabin 4.

[0045] A further embodiment of the strand element 1 is shown in Fig. 3b. The strand core 11, surrounded by the protective sheath 13, is composed of a cylindrical bundle of plastic fibers 12 with a smaller diameter. The circular plastic fibers 12 together form the essentially circular cross-section of the strand core 11.

[0046] In another embodiment of the strand element 1, as shown in Fig. As shown in Figure 3c, the strand core 11 has a flat-band-shaped cross-section. The strand core 11 thus designed is surrounded by the protective sheath 13.

[0047] Fig. Figure 3d shows a strand element 1 with a flat-band-shaped strand core 11, wherein the strand core 11 is composed of a number of stacked plastic fibers 12. The plastic fibers 12 in turn form the flat band of the strand core 11 and, as in the previous Fig. 3a-3c, surrounded by a protective sheath 13.

[0048] Regardless of the specific cross-sectional shape of the strand element 1, it is different from the Fig. 3b and Fig. 3d, it is also possible to arrange the individual plastic fibers 12 as partial bundles of the strand core 11 not parallel to one another, but in a braided manner.

[0049] The device according to the invention for energy absorption in the event of a frontal load impact in the area of ​​the A-pillars 42 of a cab 4 is reinforced by the strand element 1 integrated into the A-pillar 42. This reinforcement meets legal standards and regulations and is adaptable to virtually any vehicle cab. Further applications are directed at the vehicle cabs of passenger cars, small vans, and trucks with large window areas and a small engine compartment in front of the vehicle cab. List of reference symbols 1 strand element 11 strand core 12 plastic fiber 13 Protective cover 2 mounting eyelets 21 lower attachment point 22 upper attachment point 3 pulley 31, 32 Deflection point 33, 34 Deflection point 4 cabins 41 floor group 42 A-pillar 43 B-pillar 44 roof beam 45 roof 46 Structural reinforcement 5 clamping device

Claims

[1] Device for absorbing impact energy on a motor vehicle, in which an A-pillar of a vehicle cabin has a deformable element for absorbing a load impact by energy absorption, wherein - the A-pillar (42) is designed as a hollow profile in which a strand element (1) is provided longitudinally, the ends of which are fastened in adjacent structures of the vehicle cabin (4), on the one hand a floor assembly (41) and on the other hand a structurally reinforced roof spar (44), - the strand element (1) is a low-density strand material made of at least one plastic fiber (12) with a high elongation at break > 5% or tensile strength greater than 6 MPa arranged within the A-pillar, - = the strand element (1) in the hollow profile of the A-pillar (42) is guided taut in the initial state, without pre-tensioning the hollow profile, and in the event of a load impact, the impact energy (E A) absorbed, whereby - the extruded element (1) has a minimum length, with an effective cross-sectional area of ​​the extruded element (1) predetermined by the installation space of the hollow profiles, which is dependent on a predetermined maximum impact energy E A , which the strand element (1) can accommodate according to its thickness, must be selected so that the approximate formula EA=0.5×breaking force×change in length of the strand element is fulfilled and the minimum length of the strand element (1) is adapted by means of deflection rollers (3) and laying of fastening points (21; 22) in the floor assembly (41) and / or the roof spar (44) of the vehicle cabin (4). [2] Device according to claim 1, characterized by that the strand material is a plastic or a fiber-reinforced plastic with a density < 2.6 g / cm 3 is. [3] Device according to claim 2, characterized by that the strand material is a polyamide. [4] Device according to claim 1, characterized by that the elongation at break of the strand element (1) is at least a factor of 2 higher than the elongation at break of the material of the A-pillar. [5] Device according to claim 1, characterized by that at least one deflection roller (3) is arranged between the ends of the strand element (1) in order to keep kinks or bends in the A-pillar (42) free from contact with the strand element (1). [6] Device according to claim 1, characterized by that the minimum length of the strand element (1) can be increased by means of a meandering strand guide via additional deflection rollers (3) within the base group (41). [7] Device according to claim 1, characterized by that the minimum length of the strand element (1) can be increased by guiding the strand element (1) in a meandering, horizontal or diagonal manner via additional deflection rollers (3) in a front area of ​​the cabin (4) between the A-pillars (42). [8] Device according to claim 1, characterized by that at least one deflection roller (3) arranged between the ends of the strand element (1) is provided with a tensioning device (5). [9] Device according to claim 1, characterized by that the strand element (1) consists of a strand of a plastic composite. [10] Device according to claim 1, characterized by that the strand element (1) is composed of a round cylindrical bundle of several plastic fibers (12). [11] Device according to claim 1, characterized by that the strand element (1) is composed of a flat bundle of several layers of adjacent plastic fibers (12). [12] Device according to claim 10 or 11, characterized by that the strand element (1) is composed of braided bundles of several plastic fibers (12). [13] Device according to claim 1, characterized bythat the strand element (1) is enclosed by a protective sheath (13). [14] Device according to claim 1, characterized by that the tightening of the strand element (1) takes place by means of a tensioning device (5) which has a displacement device either on a fastening eyelet (2) or on one of the deflection rollers (3).

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