Patent Publication Number: US-9403498-B2

Title: Energy absorbing assembly for vehicle

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Ser. No. 61/803,746 filed on Mar. 20, 2013, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to energy absorbing components for a vehicle and, more particularly, to energy absorbing components coupled between a vehicle bumper and a vehicle frame. 
     BACKGROUND 
     Various types of energy absorbing components, such as crush rails, tips, boxes, etc., have been used and are designed to absorb energy during a vehicle collision. More specifically, energy absorbing components have been attached to the front and rear vehicle bumpers so that during a collision, some of the associated energy or force is absorbed by the component instead of being transmitted to the vehicle cabin. 
     The total amount of energy absorbed during a collision is one consideration for the design of such a component, while minimizing the energy profile peaks and valleys and thereby smoothing the energy profile associated with the collision may be another. 
     SUMMARY 
     According to one aspect, there is provided an energy absorbing assembly for use with a vehicle. The energy absorbing assembly comprising: a first axial end for coupling to a vehicle bumper; a second axial end for coupling to a vehicle frame; and a plurality of segments extending between the first and second axial ends of the assembly and being welded together, the plurality of segments includes a first segment that extends from the first axial end, a second segment that extends from the first segment, and a welded junction that is located at the interface of the first and second segments and includes a non-linear portion. The non-linear portion is configured to influence the transmission of energy from the first segment to the second segment across the welded junction during a collision event. 
     According to another aspect, there is provided an energy absorbing assembly for use with a vehicle. The energy absorbing assembly, comprising: a first axial end for coupling to a vehicle bumper; a second axial end for coupling to a vehicle frame; a plurality of segments extending between the first and second axial ends of the assembly and being welded together, the plurality of segments includes a first segment, a second segment, and a welded junction that is located at the interface of the first and second segments and includes at least one junction feature; and at least one secondary feature being formed in one of the first or second segments and being axially spaced from the at least one junction feature. Wherein the at least one junction feature and the at least one secondary feature are aligned along the assembly in order to cooperate with one another and influence the transmission of energy through the assembly during a collision event. 
     According to another aspect there is provided a method of absorbing energy at a front or rear bumper of a vehicle. The method may comprise the steps of: receiving an external collision force at a first axial end of an energy absorbing assembly via the front or rear bumper, the energy absorbing assembly having first and second segments joined to one another by a welded junction, the welded junction includes a non-linear portion with one or more junction features; absorbing a portion of the energy of the external collision force in the first segment nearest the bumper; lessening energy profile peaks and energy profile valleys as the energy of the external collision propagates across the weld joint from the first segment to the second segment, wherein the lessening of the energy profile peaks and valleys is at least partially caused by the non-linear portion; and absorbing a portion of the energy of the external collision force in the second segment. 
    
    
     
       DRAWINGS 
       Preferred exemplary embodiments will hereinafter be described in conjunction with the appended drawings, wherein like designations denote like elements, and wherein: 
         FIG. 1  is a perspective view of a portion of a vehicle front end, where a pair of exemplary energy absorbing assemblies are coupled or mounted between a vehicle front bumper and a vehicle frame; 
         FIGS. 2-6  are perspective views of different exemplary embodiments of energy absorbing assemblies; 
         FIG. 7  is a perspective view of a conventional or baseline energy absorbing assembly; and 
         FIGS. 8 and 9  are graphs that illustrate test data for collision-related performance profiles of several different energy absorbing assemblies, including ones from  FIGS. 2-6 . 
     
    
    
     DETAILED DESCRIPTION 
     There is disclosed an energy absorbing assembly or member  10  (also referred to as a crush tip assembly) that may be attached or mounted to a body-on-frame vehicle, either behind a front or rear bumper, so that the assembly absorbs energy in during a collision. With reference to  FIG. 1 , there is shown a vehicle front end  12  that carries a pair of energy absorbing assemblies  10  that are installed between a front bumper  14  and a portion of the vehicle frame. It should be recognized, however, that the energy absorbing assemblies  10  may be employed in any number of different settings or applications, including vehicle front and/or rear bumpers, and are not limited to the examples described herein. 
     The energy absorbing assembly  10  may be designed to collapse or deform along its longitudinal axis in an effort to absorb energy during a collision event and minimize injuries to the vehicle occupants. The energy absorbing assembly  10  is a multi-piece assembly that may be designed to influence or manipulate the absorption and/or transmission of energy in the assembly during impact and generally includes a body  18  having a first segment  20 , a second segment  22 , and a third segment  24 . According to this particular embodiment, the energy absorbing assembly  10  has a generally uniform cross-sectional shape and size (e.g., a rectangular shape) along its longitudinal axis from a first axial end  30  to a second axial end  32 . The different segments of the energy absorbing assembly  10  may have different axial lengths, they may be made of different gauge metal, and/or they may be made with different types of metals having different strengths and other properties, to cite a few possibilities. This multi-piece arrangement allows for a customized or tailored assembly, where the characteristics of each segment can be separately selected. Any reference in the following description to “axial” or “axially” is intended to refer to the longitudinal or central axis of the energy absorbing assembly  10 . 
     According to the exemplary arrangement shown in  FIG. 2 , first segment  20  is located closest to a vehicle bumper and, thus, is the first of the several segments of the multi-piece assembly  10  to experience the associated force or energy of a collision. In one example, the first segment  20  extends from a proximate end  20   a  to a distal end  20   b  and is made from a relatively thin metal (e.g., some type of high-strength or ultra high-strength steel of about 1.75 mm-2.0 mm in thickness) and is designed to buckle first and, thus, absorb some of the initial force or impact of a collision event. The first segment  20  may include or may be connected to a mounting flange  40 , which is located at the first axial end  30  of the assembly  10  and is designed for secure attachment to the vehicle bumper  14 . 
     The second segment  22  is connected to and extends from the first segment  20  and includes a proximate end  22   a  and a distal end  22   b . The proximate end  22   a  is connected to the distal end  20   b  at a first welded junction  42 , which laterally or radially extends across the width of the assembly and may be a laser or other type of weld seam joining the two segments  20 ,  22  together. In this particular embodiment, second segment  22  can be made from a somewhat thicker metal than that of the first segment  20  (e.g., a high-strength or ultra high-strength steel of about 2.0 mm-2.25 mm in thickness), and the second segment is somewhat longer in axial length than the first segment. During a collision event, it is generally desirable for the energy to be absorbed in each segment of the assembly  10  and for it smoothly transfer or propagate across welded junctions located therebetween. For instance, as energy from a collision event is being absorbed and transmitted along the axial length of the first segment  20 , it is preferable that the energy have as smooth a transition as possible across the first junction  42  and into the second segment  22 . This may help reduce force- or impact-related spikes and transients that can be seen in an energy profile, as will be described in greater detail below. The phrase “collision event” may include any event that applies enough force to the vehicle to at least partially collapse one or more segments of the assembly  10 .  FIG. 1  shows an example where the second segment  22  may be designed to receive a bracket  44 , which can then be attached to some other member or device as shown. This is an optional feature. 
     The third segment  24  is connected to and extends from the second segment  22  and includes a proximate end  24   a . The proximate end  24   a  is likewise connected to the distal end  22   b  of the second segment  22  at a second welded junction  46  and can also be a laser or other type of weld seam. According to one example, the third segment  24  is comprised of a somewhat thicker metal material than that of the first and second segments  20 ,  22  (e.g., a high-strength or ultra high-strength steel of about 2.25 mm-2.75 mm in thickness) and can be somewhat longer in length than the preceding segments  20 ,  22  as well. In addition, the metals or other materials of the first, second, and third segments  20 ,  22 ,  24  may be individually selected and can differ from one another in order to exhibit a certain energy absorbing performance. According to one possibility, first segment  20  is made from a thinner or weaker metal and/or is shorter in axial length than second segment  22 , and the second segment  22  is made from a thinner or weaker metal and/or is shorter in axial length than third segment  24 . This arrangement is not necessary, but it may be beneficial for energy absorbing assembly  10  to buckle or deform like an accordion during a collision event where the first segment  20  buckles first, followed by the second and third segments  22 ,  24 . 
     It should be appreciated that the energy absorbing assembly  10  is not limited to the exemplary three-piece embodiment shown in the drawings, as assemblies with more or less segments could be used instead. Moreover, it is not necessary that the different segments have different axial lengths, material compositions, thicknesses, strengths, etc., as the segments could be uniform or equal in one or more of these areas. Any combination of steels (e.g., traditional steels, high-strength steels, ultra-high strength steels, etc.), as well as other materials like those based on aluminum may be used to make one or more of the different segments. 
       FIGS. 2-5  show exemplary embodiments of energy absorbing assemblies  10  having a variety of different first and second welded junctions  42 ,  46 . Each of the welded junctions  42 ,  46  is located at an interface of adjacent segments and includes at least one non-linear portion that is configured to influence the transmission of force or energy from one segment to another across that junction. In each of these embodiments, the adjacent segments have the same cross-sectional shape and size at the interface so that the welded junction  42 ,  46  includes a non-overlapping butt joint, as opposed to an overlapping lap joint or the like. This is not mandatory, however, as the non-linear portions described herein could be used with other types of joints and are not limited to butt joints. 
     According to one embodiment, the energy absorbing assembly  10  includes first, second, and third segments  20 ,  22 ,  24  connected by first and second welded junctions  42 ,  46  having a non-linear portion  50  with one or more junction features—i.e., the non-linear portion  50  has one or more junction features  52 , such as a peak, a valley, an angled straight section, a curved section, etc. The illustrated embodiments have straight features, curved features, or a combination of both. For example, the junction features  52  in  FIG. 2  resemble a large single-peak. In  FIG. 3 , the junction features resemble a large single-valley or a reverse single-peak (reverse with respect the orientation of  FIG. 2 ). The junction features  52  of  FIG. 4  resemble a double-peak (e.g., having an alternating peak and valley) and are somewhat smaller or less pronounced than in the preceding embodiments. And in  FIG. 5  some of the junction features resemble a double-valley or a reverse double-peak. These are, of course, merely examples and other non-linear portions  50  and junction features  52  are possible. The size, shape, location, orientation, etc. of the junction features may be selected for certain properties and may differ from those examples shown in the drawings. Groupings or arrangements of multiple junction features may be made to form a generally sinusoidal waveform that extends mostly or entirely along the width of the energy absorbing assembly  10 . It should be appreciated that non-linear portions  50  and/or junction features  52  may or may not be the same on different sides or faces  60  of the assembly  10 . In at least one embodiment, the non-linear portions  50  and/or junction features  52  on one side  60  mirror those on the opposing side. 
     Each of the inter-segment junctions  42 ,  46  are designed to manipulate or influence the transfer of collision energy across the boundary from one segment to another. By specifically locating the junction features  52 —for example, by locating two or more peaks and valleys on the wider sides or faces  60  of the assembly  10 —collision energy transmission across the welded junctions  42 ,  46  may be controlled in a manner that mitigates the spikes mentioned above. 
     In some instances (e.g.,  FIGS. 2-5 ), the non-linear portions  50  and junction features  52  may be on the narrower top and/or bottom sides or faces  62 ,  64  as well. It should be appreciated that any combination of junction features  52 , including peaks, valleys, straight sections, radiuses, curves, etc. may be used, and that different size junction features may be included along a single junction in order to vary the energy transmission properties of that junction. Embodiments also exist having entirely straight junctions (i.e., no non-linear portion  50 ) on the top side  62 , the bottom side  64 , either or both of the wider sides  60 , or any combination thereof. Furthermore, even though junction features  52  shown in  FIGS. 2-5  are the same at the first junction  42  and the second junction  46 , this is not required; the first junction  42  may have different non-linear portions  50  and features  52  than the second junction  46 . 
     Turning now to  FIG. 6 , there is shown another embodiment of an energy absorbing assembly  10 ′ which is also a multi-piece assembly, however, this assembly is generally tapered from a first axial end  30 ′ to a second axial end  32 ′. The illustrated embodiment includes first, second and third segments  20 ′,  22 ′,  24 ′ separated by welded junctions  42 ′,  46 ′ with at least one non-linear portion  50 ′ or junction feature  52 ′. Here, each segment of the energy absorbing assembly  10 ′ is varied by some combination of segment length, metal material thickness, material grade or type and/or cross-sectional size in an effort to obtain a collision energy profile that is most desirable. 
     The illustrated embodiments of  FIGS. 2-6  have secondary features that comprise strategically located holes or openings  66  and/or strengthening ribs or features  68 ; these features are collectively referred to as “secondary features.” For example, a series of openings  66  are located along the longitudinal length of the energy absorbing assembly  10 ,  10 ′, and these openings  66  can be sized, shaped and/or located in a certain manner that interacts or cooperates with the various junction features  52 ,  52 ′, etc., if such features are included, to further control the collision energy profile. For instance, the openings can be axially aligned with a peak or valley or other junction feature  52 ,  52 ′ (e.g., a straight section) on at least one of the top, bottom, or wider sides  62 ,  64 ,  60  in order to manipulate the energy absorption and/or transmission in that area. Other embodiments and arrangements, such as those including combinations of holes and slots, are certainly possible. 
     The ribs  68  may be provided to strengthen or otherwise influence the structural integrity of the assembly  10 ,  10 ′ (e.g., see  FIG. 5 ). The rib(s)  68  may include any longitudinally extending feature that protrudes or extends radially inwardly or radially outwardly (e.g., a ridge feature  68  or channel feature  68 ′). Possible arrangements include: a single rib, multiple ribs, sequentially aligned ribs, parallel aligned ribs, short or long ribs, ribs of different lengths, widths or thicknesses, radial depths or heights, as well as others. In some embodiments, the rib extends across one or more of the welded junctions; and in other embodiments they do not. Like the holes above, the ribs may be axially aligned or misaligned with (or offset from) one or more of the non-linear portions  50  or junction features  52  discussed above (e.g., a peak or valley). In addition, some of the secondary features may be aligned or purposefully misaligned with one another. For example, holes may be aligned (or misaligned) with other holes and/or ribs. 
     Impact or collision performance data for some of the energy absorbing assemblies described above is shown in the graphs of  FIGS. 8 and 9 . The graph in  FIG. 8  compares four different energy absorbing assemblies: energy profile A is for a baseline or conventional assembly (e.g., assembly  10 ″ in  FIG. 7  which has no junctions); energy profile B is for an assembly that has a solitary flat or straight circumferential junction (not shown); energy profile C is for an assembly with a single peak, such as that shown in  FIG. 2 ; and energy profile D is for an assembly with a double peak like that shown in  FIG. 4 . The graph plots instantaneous force (kN) on the y-axis and time (mS) on the x-axis, and extends from the beginning of impact to the moment when the respective assembly is fully crushed or compressed. 
     The energy profiles of  FIG. 8  may be used to evaluate the smoothing or segment-to-segment energy transfer characteristics of the different assemblies; e.g., skilled artisans may compare or contrast the energy profiles having junctions (B, C, and D) with the baseline profile A to determine whether the addition of junctions minimizes spikes and transients during a collision event. Or the energy profiles C or D having non-linear portions  50  may be compared or contrasted with profile B that has a flat junction; e.g., to determine which arrangement better minimize spikes and transients. 
       FIG. 9  illustrates an integration of each of the forces plotted in  FIG. 8 —thus, profiles for the same assemblies A, B, C, and D are shown. More specifically,  FIG. 9  shows the cumulative or total absorbed energy (kJ) as a function of time (ms).  FIG. 9  shows that the baseline assembly (A) is fully crushed or compressed at the point  70 , which results in a shorter amount of energy absorbing duration than the other assemblies (B, C, D) which continue to crush and absorb energy until point  72 . This affects the total amount of energy absorbed. In this particular testing sample, it was determined that assembly associated with profile D (having the double-peak junction) experienced roughly a 7% energy absorption improvement compared with the baseline profile A. This performance should be considered in light of the fact that assemblies C and D exhibited smaller spikes at some of the inter-segment junctions and weighed as much as 38% less than the assembly of baseline profile A. 
     In summary, skilled artisans will appreciate that a number of factors may be considered when determining the better profile—e.g., including the total energy absorbed by the assembly, the smoothing characteristics associated with the junctions  42 ,  46  in the assembly  10 , the weight of the assembly  10 , etc., just to name a few examples. 
     According to an exemplary process, any of the energy absorbing assemblies described above can be manufactured by the following sequence of steps: creating a flat, laser-welded blank that includes the first, second, and third segments  20 ,  22 ,  24  all laser welded together (e.g., a tailor-welded blank); next, press-break forming, U-forming, U-O-forming and/or otherwise forming the laser welded blank from the preceding step into the desired cross-section (which could be octagonal, hexagonal, pentagonal, rectangular, square, circular, oval, etc.); next, a longitudinal laser or other weld could be used to close the profile of the assembly  10  and could be provided with or without additional material, like filler material. The resulting energy absorbing assembly  10  can be lighter in weight, less expensive to build, have improved performance, and may be shorter in length, to cite several possibilities. 
     It is to be understood that the foregoing description is not a definition of the invention, but is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims. 
     As used in this specification and claims, the terms “for example,” “e.g.,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.