WO2013082261A1

WO2013082261A1 - Vehicle with body-mounted energy absorber apparatus

Info

Publication number: WO2013082261A1
Application number: PCT/US2012/067023
Authority: WO
Inventors: Darin Evans; Dhiraj Uikey
Original assignee: Shape Corp.
Priority date: 2011-12-02
Filing date: 2012-11-29
Publication date: 2013-06-06

Abstract

A vehicle rear end assembly includes a closure panel subassembly forming a rear portion of a vehicle, and a beamless energy absorbing system directly engaging the closure panel subassembly and supporting a fascia on the closure panel subassembly. The energy absorbing system includes an injection-molded polymeric energy absorber with a plurality of spaced-apart hollow crush lobes abuttingly engaging an outer surface of the closure panel subassembly and that also engage/support the vehicle fascia, form pendulum-catching crush lobes, and include wraparound portions with laterally-facing side-impact crush lobes. The plurality of crush lobes are configured to spread and distribute stress from an impact to stiffer regions on the closure panel subassembly while also crushingly collapsing to absorb energy.

Description

VEHICLE WITH BODY-MOUNTED ENERGY ABSORBER APPARATUS

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims benefit under 35 USC § 119(e) of provisional application

Serial No. 61/566,351, filed December 2, 2011, entitled VEHICLE WITH BODY-MOUNTED EN ERGY ABSORBER APPARATUS, the entire contents of which are incorporated herein by reference

BACKGROUN D

[0002] The present invention relates to an energy absorbing apparatus including an

energy absorber mounted directly to a vehicle unibody or body-in-white without a traditional underlying bumper reinforcement beam.

[0003] Many modern passenger vehicle bumper systems are designed to transfer impact forces to a rigid under-vehicle frame by using a rigid cross-car bumper reinforcement beam which transfers impact forces to right and left sides of the vehicle and then into the right and left vehicle frame components/rails. This traditional thinking has resulted in the widespread use of rigid cross-car bumper reinforcement beams in modern vehicles, with an emphasis on high strength-to-weight, high loading, high bending strength, and effective side-distributing stress transfer. However, the cross-car bumper reinforcement beams are necessarily heavy in order to provide the stiffness and bending moments desired. Unfortunately, weight directly and adversely affects vehicle gas mileage. Further, such beams take up space and force vehicles to be larger in order to accommodate the beams. Also, they require additional components, including the beam itself, beam- mounting components, and fasteners. An improved apparatus is desired that effectively and efficiently manages (absorbs and also transmits) impact forces, while distributing the energy into the vehicle at optimal locations and with good dissipative action, yet while reducing total parts and overall vehicle weight. It is also desirable that the energy absorbing system be designed to manage and distribute stress into the vehicle in a manner minimizing vehicle damage (or at least distributing forces to cause damage in optimal locations), and minimizing passenger injury, while optimizing consistent and predictable absorption of energy. SUMMARY OF THE PRESENT INVENTION

[0004] In one aspect of the present invention, a vehicle assembly includes a closure

panel subassembly forming a rear portion of a vehicle and that includes stiffer regions and weaker regions, and a beamless energy absorbing system engaging the closure panel subassembly. The energy absorbing system includes a polymeric energy absorber adapted to support fascia covering the assembly, and includes a plurality of crush lobes abuttingly engaging an outer surface of the closure panel subassembly. The plurality of crush lobes are configured to spread and distribute stress from an impact toward the stiffer regions of the closure panel subassembly while also crushingly collapsing to absorb energy upon impact.

[0005] In another aspect of the present invention, a vehicle apparatus includes a vehicle body including a rear end structure including welded flanges and bends forming areas of increased strength, the body defining a non-planar vertically-extending rear surface extending transversely on the vehicle but characteristically not including a cross-vehicle rigid bumper reinforcement beam. The apparatus further includes a polymeric energy absorber having an interior surface matingly engaging the rear surface of the rear end structure, the energy absorber including ribs and stiffening structure directing impact energy from an exterior surface of the energy absorber toward the areas of increased strength.

[0006] In a narrower aspect, the welded flanges include sheet metal components with overlapping flanges welded together, and/or the areas of increased strength include embossments and/or bends.

[0007] In another aspect of the present invention, an energy-absorbing apparatus

includes a vehicle body including a rear end structure defining a rear-facing surface and defining laterally-facing surfaces generally perpendicular to the rear-facing surface; and a polymeric energy absorber having a center section with an interior surface matingly engaging the rear-facing surface of the rear end structure and having wraparound sections engaging the laterally-facing surfaces.

[0008] In another aspect of the present invention, an energy-absorbing apparatus

includes a vehicle body including a rear end structure defining a non-planar rear-facing surface and side-facing surfaces forming corners on the rear end structure, and a polymeric energy absorber having a center section with an interior surface matingly engaging the rear-facing surface and side-facing surfaces of the rear end structure the energy absorber including marginal material forming a recess generally at each corner adapted to protect a reflector positioned in the recess.

[0009] In a narrower aspect, the energy absorber includes functional features including at least one of a wiring attachment for routing wiring, a light mount for mounting a light thereto, a reflector mount for mounting a reflector thereto, a license plate pocket, and a rear backup sensor mount.

[0010] In another aspect of the present invention, an apparatus includes a vehicle body including a rear end structure defining a non-planar rear-facing surface, and a polymeric energy absorber having a center section with an interior surface matingly engaging the rear-facing surface of the rear end structure, the energy absorber including an upper section of crush lobes with rear surface for absorbing impact forces that defines a first vertical plane, and including a rearwardly-protruding horizontal-ridge-defining pendulum catching feature located vertically from the upper section and extending rearward from the first vertical plane for first impact against a pendulum impactor.

[0011] In a narrower aspect, the rearwardly-protruding ridge is positioned below a

centerline of the energy absorber.

[0012] In another aspect of the present invention, an apparatus includes a vehicle body including a rear end structure including welded flanges and bends forming areas of increased strength, and including frame rails near sides of the vehicle body, the body defining a non-planar vertically-extending rear surface extending transversely on the vehicle but characteristically not including a cross-vehicle rigid bumper reinforcement beam. The apparatus further includes a polymeric energy absorber having an interior surface matingly engaging the rear surface of the rear end structure. The energy absorber includes crush lobes and includes at least one of: stiffening inserts aligned with the frame rails for communicating an increased amount of energy to the frame rails, and a metal cover plate covering an exterior of the energy absorber for distributing impact energy across the energy absorber upon impact at a specific location.

[0013] An objective is to reduce vehicle mass while supporting vehicle designs that meet or exceed the aggressive increases in gas mileage, CAFE standards and C0₂ emission reduction requirements of new and coming government regulations. [0014] An objective is to reduce vehicle weight by eliminated cross-car bumper reinforcement beams on the rear ends of vehicle unibodies, while providing vehicle rear end structure that supports and protects the battery packs, such as those used in electric and electric/hybrid vehicles.

[0015] An objective is to provide optimal energy absorption during a rear end vehicle crash, including minimization of large load spikes and also providing wide distribution of stress from focused impacts.

[0016] These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0017] Fig. 1 is an exploded perspective view showing a rear end assembly of a vehicle unibody and a body-mounted energy management system mounted thereon, including an injection-molded energy absorber shaped to buttingly engage a closure panel of the rear end assembly;

[0018] Fig. 2 is an enlarged view of the energy absorber in Fig. 1;

[0019] Figs. 3-4 are a vertical cross section and a horizontal cross section through Fig. 1 after assembly, with the cross sections showing a size and shape of crush lobes, and Fig. 4A is similar to Fig. 4 but shows the energy absorber with several illustrated shear walls being partially crushed from an impact and with the body undamaged;

[0020] Figs. 5-6 are graphs comparing force/deflection results of an impact against the present body-mounted energy absorber apparatus (line B) (Fig. 5) as compared to an existing rear bumper system with rigid cross-vehicle reinforcement beam (line A) (Fig. 5), and also a rear bumper test according to NHS test standards ("NHS" stands for test standards promulgated by the Insurance Institute for Highway Safety) against the present apparatus (line B) (Fig. 6) as compared to the existing rear bumper system (line A) (Fig. 6);

[0021] Figs. 7, 7A, 8, and 8A are perspective views showing a vehicle unibody rear end assembly, Fig. 7 showing the unibody rear end assembly with an exposed closure panel (also called "closeout panel") of the rear end assembly of the unibody rear end assembly, Fig. 7A showing the closure panel only, Fig. 8 showing the unibody rear end assembly of Fig. 7 with the modified energy absorber installed abuttingly against the closure panel, and Fig. 8 showing the energy absorber;

[0022] Fig. 9 is an end view of several modified energy absorbers from Fig. 8 nested

together for dense shipment;

[0023] Fig. 10 is a graph comparing force versus displacement of two competing body- mounted energy absorbing systems, the first system including a foam-filled energy absorber (line E) on a vehicle rear end assembly (see vehicle rear end in Fig. 1), and the second system including an injection molded energy absorber (line F) embodying the present invention as shown in Fig. 8 and positioned against the closure panel of an identical unibody rear end assembly (see vehicle rear end in Fig. 1), the graph showing a quicker loading and higher early energy absorption by the second system (line F) with injection molded energy absorber (as compared to the foam-based first system, line E);

[0024] Fig. 11 is an exploded perspective view of a beam-type rear bumper system

similar to that in prior art for energy management including a cross-car rigid rear bumper reinforcement beam for transferring stress to the vehicle side frame rails;

[0025] Fig. 12 is a graph comparing load versus deflection for three rear-end energy- absorbing systems, including a (baseline) foam first system (line A), a roll-formed second system (line B) with a "traditional" cross-car steel bumper reinforcement beam system, and a third energy absorbing system with body-mounted injection-molded energy absorber (line C) abutting a rear closure panel for transferring energy into the rear closure panel, and Fig. 13 is a chart showing data taken from Fig. 12;

[0026] Fig. 14 is a schematic top view illustrating a pendulum impact test and resulting stress distribution paths shown as arrows PI during a test impact against a "traditional" cross-car steel bumper reinforcement beam system like that of Fig. 11;

[0027] Fig. 15 is a cross sectional view of the reinforcement beam from Fig. 14;

[0028] Fig. 16 is a schematic top view illustrating an impact test similar to Figs. 14-15, but showing the present energy absorbing system with body mounted energy absorber of Figs. 1 and 8, with much more diverse and more distributed stress distribution path P2, and Fig. 16A is a cross section through a crush lobe in the energy absorber of Fig. 16;

[0029] Fig. 17 is a schematic cross sectional view taken vertically through the rear end assembly and energy absorbing system of Fig. 8, taken at a location laterally offset just outside of the license plate area of the system; [0030] Fig. 18 is an outside-perspective view of another embodiment of the present invention with bumper system, this embodiment having an injection-molded body- mounted polymeric energy absorber with hollow crush lobes and with crush cans (steel, aluminum, other metal or high-strength plastic) insert-molded into the outermost crush lobes in the energy absorber in positions aligned with the rails to further increase the loading rate at this locally stronger area of the body structure;

[0031] Fig. 19 is a rear perspective view of a vehicle rear end with attached energy

absorber, where the energy absorber has wraparound portions that extend

overlappingly onto lateral sides of the vehicle body structure (also called "body-in- white") in recessed locations under the fender fascia and outside of the body-in-white vehicle structure and rearward of the vehicle's rear wheels;

[0032] Fig. 20 is an enlarged view of the wraparound portion of the energy absorber in

Fig. 19;

[0033] Fig. 21 is a rear/bottom perspective view of an energy absorber for mounting abuttingly against a closeout panel of a vehicle body rear end, the energy absorber including crush lobes and a pendulum catching feature under the crush lobes, the energy absorber having ends with marginal material forming a recess for receiving and protecting a reflector;

[0034] Fig. 22 is a side view showing engagement of a pendulum test apparatus against a rear bumper system including a body mounted energy absorber, the energy absorber including the pendulum catching feature illustrated in Fig. 21;

[0035] Figs. 23-26 are rear (exterior), top, bottom, and inner (interior) views of an

assembly including a vehicle rear closure panel and an energy absorber from Fig. 21; and

[0036] Figs. 27-29 are rear (exterior) perspective, front (interior) perspective, and rear

(exterior) perspective views showing a modified energy absorber having a relatively-flat curved sheet metal face plate attached to its outer surface.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0037] The illustrated vehicle 20 (Fig. 1) comprises a body-in-white vehicle structure including a unibody rear end assembly 21 defining a rear opening 22. A lower portion of the rear opening 22 is formed in part by a rear panel subassembly 23 and generally covered by rear fascia 2 (Fig. 4). The present innovative energy absorbing system engages/abuts the unibody rear end assembly 21 (Fig. 3) and is designed to eliminate the need for a separate bumper reinforcement beam and rail extensions/crush boxes. The rear panel subassembly 23 includes rear-positioned horizontal cross-car stamped/welded metal components (illustrated as closure panel 24 forming a rear portion of a spare tire tub and a vehicle trunk). The closure panel 24 (also called a "closeout panel" herein) is generally planar but includes bends and stiffening embossment(s) 25 and/or spot-welded double-thick walls/flange 25' providing selected stiffened areas (also called "stiffer regions" herein) designed to meet aesthetic and functional requirements of the unibody rear end assembly 21.

[0038] The present apparatus focuses on a beamless energy absorbing system where an energy absorber 26 abuttingly engages a rear surface of the rear panel subassembly 23, including the closure panel 24. The molded energy absorber 26 (injection-molded or thermoformed) is made of non-foam energy-absorbing polymeric material, such as an injection molded or thermoformed material. Such polymeric materials are known and commercially available, and are commonly used in bumper systems. For example, NETFLEX° material is one such material that is commercially available from Shape Corp. The energy absorber 26 is positioned abuttingly against the closure panel 24, with a vehicle-adjacent portion of the energy absorber 26 abutting portions of the rear panel subassembly 23. Specifically, the energy absorber 26 includes a base flange 26' abutting the closure panel 24 and/or abutting other parts of the rear end assembly 21. The energy absorber 26 further includes spaced-apart hollow crush lobes 27 extending away from the base flange 26' and configured to crush and crumple to absorb energy.

[0039] The crush lobes 27 are hollow and include shear walls 40-43 extending generally horizontally away from the base flange 26' (in a rearward direction when in a vehicle- mounted position), and further include outer end walls 44 closing a protruding end of the crush lobes 27. The perimeter flange of the absorber is designed to align with the existing stiff architecture of the rear end, such as the weld flanges and shear walls of the spare tire well and the double thickness of steel at various weld flanges. The crush lobes 27 are also constructed to support rear colored/painted fascia aesthetically covering the assembly. Further, the shear walls 40-43 (also called "side walls") and outer end wall 44 abutting engage the fascia 21', supporting its shape and preventing drooping and sagging, and further providing support sufficient to support light vertical loads placed thereon, such as a person stepping on the bumper. During an impact, the walls 40-44 are configured to crumple and crush against the rear panel subassembly 23, and absorb substantial and predictable amounts of energy while distributing impact loads directly into the stronger and stiffer areas of rear end assembly 21, thus eliminating, or at least minimizing, any damage to the vehicle. The impact is not unlike striking a pillow, with stress being widely but locally distributed. The amount of energy and minimization of damage by the present inventive system is considered surprising and unexpected in modern vehicle bumper art, given the historical thinking concerning the use of rigid cross-car reinforcement beams commonly used in traditional systems (see Fig. 14-16A, for example).

[0040] The illustrated closure panel 24 (Figs. 3 and 8) is spot-welded to other

components (such as spare tire tub or rear trunk forming member 24') of the rear end assembly 21 and also stamped and bent to shape. The result is that, at the spot-welds, there are double-thick walls welds/flange 25' and work-hardened bent areas (including corrugated and embossed areas) of increased strength in the panel subassembly 23 and the rear end assembly 21. The base flange 26' of the energy absorber 26 along with corners formed by joinder of the base flange and shear walls 40-43 engage these areas of increased strength. By this mechanism, energy is absorbed during an impact and distributed at strategic locations into the rear end assembly 21 across a width of the vehicle, including into the mid-portion of the rear end panel subassembly 23. This contrasts to traditional bumper systems, where impact loads are directed to right and left sides of the vehicle. Notably, the crush lobes 27 can be sized, shaped, and

constructed to absorb optimal amounts of energy at their specific locations across the vehicle in view of the particular characteristics of the unibody. This includes modifying a thickness of shear walls 40-43 and end wall 44 and also modifying the crush lobes by placing apertures into the walls 40-44 (see Fig. 8A discussed below).

[0041] For example, as shown in Figs. 3-4, the crush lobes 27 extend laterally across the vehicle so that they contact and support the fascia as assembled with minimal (e.g. less than 3 mm or more preferably, less than 1 mm) or zero gap, and while still staying within aesthetic design requirements of a shape of the rear end assembly 21. In each location, the crush lobes 27 include an inboard end (formed by the shear walls 40-43 joining the base flange 26') abutting the rear end assembly 21 at stronger areas of the closure panel 24 as discussed above, and include the outboard end wall 44 abutting and supporting the rear painted/colored fascia. Notably, the crush lobes 27 can be adjusted (at the time of designing the part) in shape, size, wall thickness, and orientation of end walls 44 to match a desired energy absorption profile and to facilitate aesthetic design of the vehicle's rear end, including support for painted/colored fascia attached to the rear end. The illustrated energy absorber 26 may also include apertured tabs and attachment sites at top and bottom and side locations for securing the fascia with fasteners (e.g. screws, snap- attachment fasteners, and the like). The energy absorber 26 also includes protective recesses and/or mounts for other accessories, such as reflectors, backup lights, rear vehicle lights, wiring, sensors, and the like.

[0042] Figs. 3-4 are vertical and horizontal cross sectional views of Fig. 1 of the energy absorber 26 assembled to the unibody rear end assembly 21. As shown in Fig. 3, the energy absorber 26 has vertically-smaller-dimension top crush lobes 27 and vertically- larger-dimension bottom crush lobes 27. As shown in Fig. 4, the crush lobes 27 of the energy absorber 26 vary in width and depth across the vehicle. The varied-height crush lobes 27 provide maximum crush strokes at each location while also meeting functional and aesthetic requirements for supporting rear fascia on the vehicle. Fig. 4A is similar to Fig. 4 but shows a portion of the energy absorber (including several illustrated shear walls 40-43) partially crushed during an impact. The "impact crush" is shown by multiple bends in the shear walls 40-43, which illustrates how the shear walls 40-43 of the energy absorber 26 absorb considerable energy due to the multiple bends and crumpling collapse due to their tubular geometric box-like shape. Further, the shear walls also direct impact energy toward strongest areas of the rear end assembly 21, which strongest areas are generally located at a "foot" (i.e. interior part) of the shear walls where the energy absorber 26 abuts the closure panel 24 of the rear end assembly 21.

[0043] As noted above, the present beamless rear end subassembly apparatus 23/26 includes a rear end closure panel 24 with welded flanges forming double-thick walls and embossments/bends forming areas of increased strength over other areas of the panel, with the body defining a generally non-planar vertically-extending rear surface extending transversely on the vehicle but characteristically not including a cross-vehicle rigid bumper reinforcement beam. Further, the beamless rear end assembly apparatus 23/26 includes a polymeric energy absorber 26 having an interior surface matingly abuttingly engaging the rear surface of the rear end subassembly 23, the energy absorber 26 including crush lobes, ribs and stiffening structure directing impact energy from an exterior surface of the energy absorber toward the areas of increased strength.

[0044] Fig. 5 is a graph comparing force/deflection on a standardized flat barrier impact test, and establishes a baseline comparison to an existing vehicle rear end. The results include a first line labeled as "A" showing results of an impact against an existing prior art rear bumper system (with cross-car stiff reinforcement beam), and a second line labeled as "B" showing results of an impact against the present body-mounted beamless energy absorber system with body-mount injection-molded energy absorber (Fig. 1), both being a rear flat barrier bumper test commonly used to test rear end vehicle bumper systems.

[0045] Fig. 6 is a graph comparing force/deflection on a standardized NHS bumper barrier impact test intended to establish a baseline comparison to an existing vehicle rear end. The results include a first line labeled as "C" showing results of an impact against an existing rear bumper system (with reinforcement beam), and a second line labeled as "D" showing results of an impact against the present body-mounted beamless energy absorber system (Fig. 1), both being conducted according to NHS test standards.

[0046] It is noted that many features can be integrated into the energy absorber 26, since the energy absorber 26 is injection molded and made from a material suitable for both absorbing energy and for mounting accessories thereto. For example, the energy absorber 26 (Fig. 1) includes integrated upper fascia bracket attachment sites 30, low speed energy management (based on crush lobe design and shape and wall thicknesses), step support surfaces 31 (based on upper surfaces of the crush lobes), wire harness mounting and routing detail (such as channels 32 for wire routing and attachment locations), sensor mounting (such as for rear vehicle proximity sensors, vehicle keyless entry sensors, impact sensors), lower fascia attachment 33, vehicle light mounting structure, openings/recess 34 for positioning of lighting devices on the unibody, and license plate mount/recess 35.

[0047] Additional embodiments are shown and described using the same numbers for identical and similar components, features, and characteristics, but adding a letter "A" or "B" or "C". This is done to reduce redundant discussion, but it is intended that descriptions carry over where appropriate, as will be understood by persons skilled in this art. [0048] Figs. 7, 7 A, 8, 8A are perspective views showing a different rear vehicle unibody rear end assembly 21A. Fig. 7 showing the unibody rear end assembly 21A with a modified energy absorber 26A shown as transparent to reveal underlying components, Fig. 7A showing the closure panel 24A with embossment 25A forming a lower portion of the unibody rear end assembly 21A of Fig. 7, and Fig. 8 showing the unibody rear end assembly 21A with bumper system including the modified energy absorber 26A installed and shown with opaque shading abutting the closure panel 27A, Fig. 8A showing the energy absorber 26A alone. Notably, the embossment 25A is ridge-shaped (or channel- shaped), and provides a beam-like structure across a rear of the end panel assembly 21A. The energy absorber 26A includes a mating channel shaped to receive the ridge-shaped embossment 25A, such that the energy absorber 26A closely engages the closure panel 24A along the energy absorber's base flange and rear surface. Thus, the energy absorber 26A directs energy into the beam-like embossment 25A, while simultaneously

distributing energy generally across the closure panel 24A into the end panel assembly 21A and vehicle rear end. This minimizes damage of parts and components, while maximizing energy absorption and rear vehicle impact strength and integrity.

[0049] Fig. 9 is an end view of several of the modified energy absorbers 26A in Fig. 8A nested together for dense shipment. This can be a very significant benefit, since it can substantially reduce shipping costs.

[0050] Fig. 10 is a graph showing force versus displacement of the present energy

absorbing apparatus incorporating the modified energy absorber 26A with injection molded energy absorber having crush lobes of Fig. 8, as compared to a foam-based energy absorbing system. The graph shows the energy absorbing system with injection molded energy absorber 26A has a uniform energy absorption (line F) without undesired load spikes, and shows that the modified energy absorber 26A (line F) has a much faster loading than the foam-based system (line E). Thus, the energy absorbing system with injection molded energy absorber 26A provides higher resistance forces during an initial crush stroke as well as a continued high loading during the continued crush stroke.

[0051] By the above concepts, large weight savings can be accomplished, while reducing total part count, reducing total mass, and reducing total cost in vehicles. For example, in one proposed system for a vehicle, the part count was reduced by 4 major components, over 3 kg was saved (i.e., a 30 percent+ savings), and cost to the manufacturer was reduced by over 50 percent (compare Figs. 11 and 8A). These benefits are believed to be dramatic, surprising and unexpected to persons skilled in this art. For example, compare Fig. 11 (illustrating a typical "traditional" beam based energy absorber) as compared to the present innovative system (of Fig. 8).

[0052] Notably, the illustrated injection molded plastic energy absorber is designed to follow the contour of the fascia in abutting contact (see Figs. 3-4), and therefore it loads up quickly upon a test pendulum impact (or upon a real vehicle impact). The column loading gives rapid rise in load level and subsequent crush helps maintain the load level as shown in the graphs of Figs. 5, 6, and 10.

[0053] Contrastingly, in a traditional system including a roll-formed metal reinforcement beam having a continuous arcuate curvature (also called "sweep") (see the beam system of Fig. 11 and the energy absorption curves of Figs. 13-14), the roll-formed beam cannot be designed to match the fascia contours due to manufacturing limitations. This leaves gaps, often as much as 18 mm, between the first point of contact on a roll-formed steel beam. Therefore, the roll-formed steel beam does not load up until as much as 18 mm of deflection. When finally loaded, the steel loads up more quickly because steel is a stiffer material, however as noted, the loading of the roll-formed steel beam is "delayed." Further a primary mode of energy absorption by a roll-formed steel beam is bending, as illustrated by Figs. 14-15. This contrasts to the primary mode of energy absorption in crush lobes of an injection molded energy absorber, as illustrated in Figs. 16-16A.

[0054] At least one known bumper system incorporates EPP foam designed to follow the contour of a vehicle rear fascia. However, the foam loads (i.e. provides resistance to impact) at a slower rate (see line A in Fig. 13) compared to the injection-molded plastic (see line C in Fig. 13). This is because injection-molded plastic exhibits column loading behavior (see Fig. 16-16A). Restated, injection-molded plastic energy absorbers load more efficiently than EPP foam, because the plastic energy absorber provides higher initial resistance force more quickly, and then maintains that high load for a long crush stroke. In addition, the foam system loads the closure panel in a "non-directed" manner, including the weak and unsupported areas of the back panel and thus results in more damage to the vehicle body.

[0055] Fig. 11 illustrates a typical rear bumper system with reinforcement beam found in prior art. The illustrated system 100 includes side-frame-rail mounts 101, a roll-formed primary reinforcement beam 102 of steel, a secondary top reinforcement beam 103, and an energy absorber 104. Figs. 14-15 also illustrate a typical energy absorption system with rigid beam 102.

[0056] Fig. 12 is a graph and Fig. 13 is a chart comparing load versus deflection, and

system strokes and total loads, for three rear-end energy-absorbing systems, including a (baseline) foam first system, a roll-formed second system with a "traditional" cross-car steel bumper reinforcement beam system, and a third energy absorbing system with body-mounted injection-molded energy absorber abutting a rear closure panel.

[0057] Fig. 14 is a schematic top view illustrating an impact test and resulting stress

distribution paths during a test impact against a "traditional" cross-car steel bumper reinforcement beam system. Fig. 15 is a cross sectional view of the reinforcement beam from Fig. 14. The deflection in the beam is illustrated by the recognized engineering formula, where deflection = PL³/48EI. The steel beam works according to beam bending theory where deflection is dependent upon beam cross section moment of inertia (I), the rail span (L) and modules of elasticity (E) of thickness, resulting in higher mass beam material. To reduce the beam deflection, the moment of inertia has to be increased by increasing the section depth. Stress distribution to the side rails are indicated by paths PI.

[0058] Fig. 16 is a schematic top view illustrating an impact test similar to Fig. 14 and showing different stress distribution paths P2 during the impact against the present body-mounted energy absorbing system 23/26 with injection-molded energy absorber

26, 26A, and 26B like that shown in Figs. 1, 8 and 8A. The plastic body mounted energy absorbers 26, 26A, and 26B work on the column loading principle. The deflection in a column (i.e., against a crush lobe 27) is illustrated by the recognized engineering formula, where deflection = PL³/3EI. Each crush lobe 27 of the energy absorber 26 (and 26A, 26B) acts as a column which has a high sectional moment of inertia due to higher depth

(110mm versus 35mm of the steel beam). The pendulum engages two such columns

(crush lobes 27), resulting in more energy absorption. Therefore, even though the modulus of plastic is lower compared to steel, comparable load levels can be achieved with plastic. Also, in the column loading case, L represents the column height versus the rail span of a traditional bumper system. This typically results in an order of magnitude reduction of L, which is very significant given it is a cubed item in each equation. When cubed, it is three orders of magnitude lower than the beam bending scenario, thus could result in lower intrusions even with lower stiffness material; in this case, plastic versus steel or aluminum for beams. The example shown in FIGS. 12 and 13 demonstrates that we can achieve similar low speed impact protection of a steel bumper, but at one-third the mass. Again, this is "surprising" and demonstrates a very significant weight reduction opportunity which is very important to improving fuel economy.

[0059] Fig. 17 is a schematic cross sectional view taken vertically through the rear end assembly and energy absorbing system of Fig. 8, taken at a location laterally offset to a position just outside of the license plate area of the system. As shown, the closure panel 24A has multiple bends and embossed channels C extending cross-car to increase its stiffness. It is noted that more or fewer embossed channels and/or other bends can be included in the closure panel 24A to achieve a desired strength for vehicle integrity, rear end rigidity, overall stability, and robustness of the vehicle rear end assembly. Also, an inner panel 24A' is attached to an inside of a top of the closure panel 24A, thus providing a semi-tubular structure at a rear of the vehicle's rear trunk that provides even more vehicle integrity, rear end rigidity, stability, and robustness.

[0060] Fig. 18 is an outside-perspective view of another embodiment of the present invention, where the bumper system has an injection-molded body-mounted polymeric energy absorber 26C with metal stiffener crush cans 50C (e.g., steel, aluminum, other metal, plastic, and/or plastic composite) positioned in crush lobes 27D at the rails (i.e. sides of the vehicle). The inserted crush cans 50D further increase the loading rate at the locally stronger side areas of the body structure. It is contemplated that the crush cans can be insert molded or simply mechanically inserted inside (or positioned on an outside of) the crush lobes.

[0061] Specifically, in Fig. 18, a bumper system has a closure panel 24B and an injection- molded body-mounted polymeric energy absorber 26B with stamped metal

components 50B insert molded into the outermost crush lobes 27B and positioned against the closure panel 24B. In the bumper system, the subassembly 23B with closure panel 24C has a rear tail light supporting end component (e.g., bracket 53C) attached to the closure panel 24B (such as by welding) and forming an end of the subassembly 23B. An extender plate 54B can also be attached under the outermost crush lobe 27B to the bracket 53C and to an end of the closure panel 24B for increased corner strength. In addition to functionally mounting and supporting the light socket or reflector, the plate 54B would provide a backstop against which the outer shear wall of the outermost crush lobe 27B engages. This arrangement can allow existing vehicle rear panel subassemblies 23B to receive the present inventive beamless bumper system with injection molded energy absorber 26B, while still complying with industry and federal corner impact test requirements. Furthermore, an optional crush bracket may also be incorporated with the design (e.g., on plate 54B) to provide even faster and higher loading at the rails, which may be desirable for high speed rear impacts and-or global bumper tests, such as the Danner test.

[0062] Specifically, the energy absorber 26B (Fig. 18) is made of polymeric material and has an interior surface matingly engaging the rear surface of the rear end structure, the energy absorber including metal cans aligned with the vehicle's frame rails for communicating an increased amount of energy to the frame rails along sides of the vehicle body-in-white vehicle structure.

[0063] Fig. 19 is a rear perspective view of a vehicle rear end 21C with closure panel assembly 24C with abutting/assembled energy absorber 26C, where the energy absorber 26C has wraparound portions 60C that extend overlappingly onto lateral sides of the vehicle body structure 22C (also called "body-in-white", see the EPDM corrosion treated sheet metal body in Fig. 1). The wraparound portions 60C fit into recesses 61C in the corner of the body-in-white vehicle structure 21C. The wraparound portions 60C are located under the fender/rear-fascia and outside of the body-in-white vehicle rear end structure 21C and rearward of the vehicle's rear wheels. The wraparound portions 60C include a main panel base flange 62C, and include one, or more, hollow crush lobes 63C extending laterally from the base flange 62C. The illustrated crush lobe 62C is elongated in a longitudinal direction defined by the vehicle, and includes four shear walls 64C-66C forming a generally rectangular section and an outer wall 67C closing the crush lobe 62C. The illustrated top and bottom walls 63C and 65C include undulations for increased strength, the undulations reducing a weight of the energy absorber 26C by allowing a thinner wall section while increasing energy absorption during crush.

[0064] Fig. 20 is an enlarged view of the wraparound portion 60C of the energy absorber

26C in Fig. 19. The wraparound sections 60C of the energy absorber 26C include functional features including at least one of a trunk vent 70C, a mount for attaching a reflector, and/or a recess (see Fig. 21) with marginal material around the recess providing an attachment structure and forming a protecting barrier for a reflector 73C mounted within the recess. A significant aspect is that the polymeric energy absorber 26C includes accessory mounting and protecting features, such as a recess with marginal material protecting a reflector positioned in the recess. Also, the energy absorber can include other functional features, such as a wiring attachment and path for routing wiring, a light (reflector) mount for mounting a light thereto, a reflector mount for mounting a reflector thereto, a license plate pocket and/or, and a rear backup sensor mount. This feature provides a level of rear side impact protection not available with traditional beam-type bumper systems (new and novel).

[0065] Fig. 21 in particular is a rear/bottom perspective view of an energy absorber 26E, and Fig. 22 shows the energy absorber 26E mounted abuttingly against a support (i.e. closeout panel 24E of a vehicle body rear end 21E). The energy absorber 26E includes crush lobes 27E and further includes a lower pendulum catching feature 80E under the crush lobes 27E and an upper pendulum catching feature 80E' above the crush lobes 27E. The pendulum catching feature 80E (i.e. long crush lobes with narrow cross sectional size) are substantially a horizontal arrangement (or horizontal ridge) of protruding crush lobes under the primary crush lobes 27E. The pendulum catching feature 80E' is a protruding ridge formed above the crush lobes 27E. It is contemplated that the pendulum catching features can be any desired size, but the illustrated catching features 80E and 80E' define a rearwardly protruding horizontal ridge across the energy absorber 26E that is particularly positioned to be the first vehicle structure to engage an impacting pendulum. This has proven to be beneficial, since passing the specific pendulum impact testing required by government and insurance industries is particularly critical in gaining permission to sell the vehicle commercially. The illustrated features 80E share a common wall (i.e. the lower wall of the crush lobes) with the crush lobes 27E. The pendulum catching features 80E and crush lobes 27E form a channel 81E for receiving a protruding edge/nose 83E of a test impact and pendulum 82E. The upper pendulum catching features 80E' also serve a similar purpose for the upper impact pendulum 82E' (shown in dashed lines).

[0066] Pendulums 82E (and 82E') are used as part of standardized bumper impact testing of vehicles. Passing the pendulum impact tests is important, since they must be "passed" in order for the original equipment manufacturer (OEM) to sell vehicles. Fig 22 shows a bumper impact pendulum 82E (and 82E') immediately before impacting/engaging the pendulum catching feature 80E (and 80E') of the energy absorber in the beamless bumper system of Fig. 22. This illustrates how a shape of the energy absorber, including the protruding nature of the pendulum catching feature and its relation to a shape of the pendulum's front impacting surface, allows the energy absorber to "catch" the pendulum by providing a first contact point and first stress distributing action for optimal impact absorption and minimizing part damage. These features essentially increase the height of bumper coverage significantly greater than standard bumper beams, thus improving the potential engagement area for an opposing bumper, improving the compatibility, and reducing the opportunity of over/under ride of the bumper.

[0067] Specifically, the present apparatus (Fig. 23-26) includes a vehicle body including a rear end structure defining a non-planar rear-facing surface. The apparatus further includes a polymeric energy absorber 26E having a center section with an interior surface matingly engaging the rear-facing surface of the rear end structure 21E, the energy absorber 26E including an upper section (i.e. crush lobes 27E) with rear surface for absorbing primary impact forces that defines a first vertical plane. The energy absorber 26E (Fig. 22) further includes a pendulum catching feature 80E extending below and coplanar to or outwardly from the first vertical plane VI of end walls 44E for catching the pendulum impactor 82E. The pendulum catching feature 80E is formed of multiple narrow crush lobes and is positioned below a centerline of the energy absorber in a position where they form a horizontal ridge that engages the pendulum 82E ahead of a main force of impact against the energy absorber 26E. Further, the pendulum catching feature 80E defines a triangular channel 81E for receiving a protruding nose 83E of the pendulum 82E.

[0068] There is also an upper pendulum catching feature of the energy absorber 26E

(Fig. 22) that includes an upper arrangement of protruding pendulum-catching protrusions forming a outboard-facing horizontal ridge with a horizontal channel under it that extends along the upper edge of the crush lobes 27. The illustrated upper pendulum catching features are integrally formed as part of the face of the multiple "primary" crush lobes. The illustrated upper pendulum-catching features do not (but could) potentially form a tube separate from the crush lobes, and in such event would share a common wall with the crush lobes, such as if functional considerations require extra stability and/or stiffness and/or shape.

[0069] Figs. 23-26 are rear (exterior), top, bottom, and inner (interior) views of an

assembly including details of a vehicle rear closure panel 24E and of the abutting/mating energy absorber 26E from Fig. 21. The Figs. 23-26 show features of both that matingly engage, such as the cross channel and embossments, especially where the base flange of the energy absorber 26E abuts against similar features in the closure panel 24E, such as in direct contact or at least within 3 mm or more preferably within 1 mm or less. The side walls of the crush lobes 7E join to the base flange at strategic locations, such as near double-wall-thick welded portions and such as near work-hardened embossed channel rib areas and bends in the closure panel 24E. The illustrated closure panel 24E includes a plurality of spot welds (shown by dots) where two walls of sheet metal parts are welded together, thus providing an area of increased strength both due to the double thick walls and also due to the weld.

[0070] An end-extended flange 90E on the base flange also includes marginal

material 91E forming a pocket or recess 34E for receiving a reflector (or light), the marginal material 91E forming a protective ridge around the pocket to minimize damage to the reflector 93E during an impact. An inside portion of the pocket 92E is formed into the outer side wall of the outermost crush lobes 27E for increased protection via the outermost crush lobe. Notably, the illustrated energy absorber 26E extends to and slightly below and under the closure panel 24E. An upper edge of the illustrated energy absorber 26E terminates short of the closure panel 24E. As illustrated, a center of the energy absorber 2E extends to about half a height of the closure panel 24E. Notably, an outer front wall of the center crush lobe 27E also defines a recess forming a license plate pocket 95E.

[0071] Figs. 27-29 are rear (exterior) perspective, front (interior) perspective, and rear

(exterior) perspective views showing a modified energy absorber 26F with crush lobes 27F. The rearward (exterior) surface of the crush lobes 27F support a relatively-flat curved sheet metal (steel) face plate 85F, which is attached to the outer surface such as by mechanical fasteners 86F or other means known in the art. The plate 85F helps distribute impact loads across the crush lobes 27F in a manner reducing point impact loading. It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A vehicle assembly comprising:

a closure panel subassembly forming a rear portion of a vehicle and having stiffer regions and weaker regions; and

a beamless energy absorbing system engaging the closure panel subassembly and adapted to support fascia covering the closure panel subassembly, the energy absorbing system including a polymeric energy absorber with a plurality of hollow crush lobes abuttingly engaging an outer surface of the closure panel subassembly, with the plurality of crush lobes being configured to spread and distribute stress from an impact toward the stiffer regions of the closure panel subassembly while also crushingly collapsing to absorb energy upon impact.

2. The assembly defined in claim 1, wherein the crush lobes are spaced apart.

3. The assembly defined in claim 1, wherein the energy absorber includes a base flange and wherein the crush lobes include relatively flat shear walls extending from the base flange, the crush lobes further including an end wall connecting the shear walls.

4. The assembly defined in claim 1, wherein the energy absorber includes a base flange and wherein the crush lobes project different distances from the base flange to thus define different crush stroke distances along a length of the energy absorber.

5. The assembly defined in claim 1, including a fascia covering the rear portion and the energy absorber.

6. A vehicle apparatus comprising:

a vehicle body including a rear end structure including welded flanges and bends forming areas of increased strength, the body defining a non-planar vertically-extending rear surface extending transversely on the vehicle but characteristically not including a cross-vehicle rigid bumper reinforcement beam; and a polymeric energy absorber having an interior surface matingly engaging the rear surface of the rear end structure, the energy absorber including ribs and stiffening structure and shear walls directing impact energy from an exterior surface of the energy absorber toward the areas of increased strength.

7. The apparatus of claim 6, wherein the welded flanges include sheet metal components with overlapping flanges welded together.

8. The apparatus of claim 6, wherein the rear end structure includes sheet metal parts having one of an embossment and stiffening ribs forming one of the areas of increased strength, and the energy absorber is configure to focus impact forces toward the one of the embossment and stiffening ribs.

9. The apparatus of claim 6, wherein the interior surface of the energy absorber defines a surface shape substantially similar to the vertically-extending rear surface of the body and closely engages same with gaps less than about 3 mm so that impact energy is quickly transmitted through the energy absorber to the rear end structure without delay upon impact.

10. The apparatus of claim 6, wherein the rear end structure includes first and second sheet metal components and the energy absorber is configured to focus impact energy towards the first sheet metal component so that, upon impact, the first sheet metal component is damaged prior to damage to the second sheet metal component, thus limiting damage to fewer parts and reducing a cost of replacement parts.

11. The apparatus of claim 6, wherein the energy absorber includes metal inserts near end portions that are located in general alignment with frame rails on the vehicle body.

12. An apparatus comprising:

a vehicle body including a rear end structure defining a rear-facing surface and defining laterally-facing surfaces generally perpendicular to the rear-facing surface; and a polymeric energy absorber having a center section with an interior surface matingly engaging the rear-facing surface of the rear end structure and having wraparound sections engaging the laterally-facing surfaces.

13. The apparatus of claim 12, wherein the wraparound sections of the energy absorber include at least one crush lobe facing laterally and configured to crushingly absorb impact energy from a corner or side impact.

14. The apparatus of claim 12, wherein the wraparound sections fit partially into recesses in the laterally-facing surfaces and are adapted to lie under a fender-forming component.

15. The apparatus of claim 12, wherein the laterally-facing surfaces of the rear end structure define out-facing body structure, and the wraparound sections of the energy absorber are shaped to abuttingly matingly engage the out-facing structure.

16. The apparatus of claim 12, wherein the wraparound sections of the energy absorber include functional features including at least one of a trunk vent, a mount for attaching a reflector, a recess with marginal material around the recess forming a protecting barrier for a reflector mounted within the recess.

17. An apparatus comprising:

a vehicle body including a rear end structure defining a non-planar rear-facing surface and side-facing surfaces forming corners on the rear end structure; and

a polymeric energy absorber having a center section adapted to support fascia and with an interior surface matingly engaging the rear-facing surface and side facing surfaces of the rear end structures, the energy absorber including marginal material forming a recess generally at each corner and adapted to protect a reflector positioned in the recess.

18. The apparatus of claim 17, wherein the energy absorber includes functional features including at least one of a wiring attachment for routing wiring, a light mount for mounting a light thereto, a reflector mount for mounting a reflector thereto, a license plate pocket, a rear backup sensor mount, and other accessory mount.

19. The apparatus of claim 17, wherein the energy absorber has crush boxes facing different directions.

20. An apparatus comprising:

a vehicle body including a rear end structure defining a non-planar rear-facing surface; and

a polymeric energy absorber having a center section with an interior surface matingly engaging the rear-facing surface of the rear end structure, the energy absorber including an upper section with crush lobes having a rear surface for absorbing impact forces that defines a first vertical plane, and including a rearwardly-protruding horizontal-ridge-defining pendulum catching feature located vertically from the upper section and extending rearward from the first vertical plane for first impact against a pendulum impactor.

21. The apparatus of claim 20, wherein the rearwardly-protruding pendulum catching feature is positioned below a centerline of the energy absorber.

22. An apparatus comprising:

a vehicle body including a rear end structure including welded flanges and bends forming areas of increased strength, and including frame rails near sides of the vehicle body, the body defining a non-planar vertically-extending rear surface extending transversely on the vehicle but characteristically not including a cross-vehicle rigid bumper reinforcement beam; and

a polymeric energy absorber having an interior surface matingly engaging the rear surface of the rear end structure, the energy absorber including crush lobes and at least one of: stiffening inserts aligned with the frame rails for communicating an increased amount of energy to the frame rails, and a metal cover plate, section, or tube covering an exterior of the energy absorber for distributing impact energy across the energy absorber upon impact at a specific location.