HK1066196B - Energy absorber system for attachment to a vehicle - Google Patents

Description

Energy absorbing system for attachment to a vehicle

Technical Field

The present invention relates to energy absorbing systems, and more particularly to energy absorbing vehicle bumper systems.

Background

Bumpers typically extend widthwise across the front and rear of the vehicle and are mounted on longitudinally extending bars. The energy absorbing bumper system required minimizes vehicle damage by controlling the impact energy of a collision with a minimum amount of intrusion while not exceeding the load limit of the vehicle's beam. The ideal energy absorber achieves high efficiency by quickly placing the load just below the load limit of the rod and holding the load constant until the impact energy is dissipated.

U.S. patent No.4,762,352 to Kaisha describes an energy absorbing bumper system. According to this patent, a foam type resin of polypropylene, polyurethane or the like is positioned between the support beam and the exterior wall panel to form an assembly.

Another foam-type energy absorbing bumper system is described in U.S. Pat. No.4,941,701 to Loren. According to this patent, a semi-rigid, resilient fascia is spaced forwardly of the bumper structure and the volume defined therebetween is filled with an integral shell polyurethane foam which is resiliently deformable and integrally bonded to the two components.

Disadvantages of foam-type systems include slow loading upon impact, which results in high displacement. Generally, the foam may produce sixty or seventy percent compression. Beyond this point, the foam becomes incompressible such that the impact energy is not fully absorbed. The remaining impact energy is absorbed by deformation of the support beam and/or the vehicle structure. Foams are also temperature sensitive, such that displacement and shock absorption characteristics may vary significantly with temperature. Generally, as the temperature decreases, the foam becomes stiffer, resulting in higher loads. Conversely, as the temperature increases, the foam becomes more compliant, resulting in higher displacements and possible vehicle damage.

U.S. patent No.4,533,166 to Stokes describes a non-foam energy absorbing system that uses a channel section shaped inner beam positioned inside a profiled outer beam having a channel section. The outer beam has transverse ribs that reinforce the vertical portion and longitudinal stiffeners extending between the ribs. The inner beam has a transverse intermediate beam support section molded to the outside of the beam. The center beam support is positioned longitudinally away from the bumper support to secure the outer beam member to the inner beam member in a spaced apart relationship. The double beam bumper design is relatively insensitive to the location of the impact point, as long as the energy absorption and impact forces are directed to the purpose of eliminating the bumper shock absorber. This system requires separately molded outer and inner beam components having a specific shape.

Disclosure of Invention

The present invention relates to an energy absorbing system of the non-foam type designed to achieve rapid loading and efficient energy absorption upon impact. The impact force during a low speed impact is maintained just below a predetermined level by deforming the energy absorber until the kinetic energy of the impact action is absorbed. Once the impact is over, the absorber returns substantially to its original shape and maintains sufficient integrity to withstand subsequent impacts.

In accordance with the present invention, there is provided an elongate unitary energy absorber adapted for attachment to a vehicle, the energy absorber comprising: a flanged frame for attachment to the vehicle and a body extending from the frame, the body comprising a first transverse wall, a second transverse wall spaced from the first transverse wall, and a plurality of adjustable crush zones extending therebetween, the crush zones being spaced apart along a longitudinal axis of the body and having irregularly shaped open areas disposed therebetween, the crush zones having a generally three-dimensional I-shape, the crush zones comprising side walls and a rear wall, the side walls and the rear wall having a nominal wall thickness of about 1.75mm-3.0mm, the energy absorber being a unitary and integrally molded thermoplastic component.

According to the present invention, there is also provided an energy absorbing system for a motor vehicle, comprising: a reinforcing beam; an energy absorber comprising a flanged frame for attachment to the reinforcement beam and a body extending from the frame, the body comprising a first transverse wall, a second transverse wall spaced apart from the first transverse wall, and a plurality of adjustable crush zones extending therebetween, the crush zones being spaced apart along a longitudinal axis of the body and having irregularly shaped open areas disposed therebetween, the crush zones having a generally three-dimensional I-shape, the crush zones comprising side walls and a rear wall, the side walls and the rear wall having a nominal wall thickness of about 1.75mm-3.0mm, the energy absorber being a unitary and integrally molded thermoplastic component; and an outer wall panel connectable to the energy absorber to substantially encase the reinforcement beam and the energy absorber.

The energy absorbing system of the present invention has a structure that promotes superior energy absorption efficiency and rapid loading. This structure allows the present system to be enclosed in a relatively small space compared to conventional foam systems. This provides the vehicle designer with the freedom to design a bumper system with reduced overhang while enhancing the impact performance of the system. The enhanced bumper impact performance results in: the cost of repairing a "fender correction device" at a low speed is reduced, and the safety of passengers during a high-speed collision is increased. Since the primary energy absorbing system can be realized with thermoplastic engineering resins molded in one piece and in one piece, the primary energy absorbing system can be easily recycled. Because no foam is used, more consistent impact performance can be achieved at varying temperatures. Another desirable feature of the present invention is a smooth, predictable loading response, substantially independent of load direction. This is particularly important for front energy absorption applications where consistent bumper system response is important for the crash severity sensor.

According to the present invention, there is also provided a method of making an energy absorber, comprising the steps of: a) defining a set of impact load characteristics; b) selecting a thermoplastic material with reference to the impact load characteristics; and c) forming an energy absorber from the thermoplastic material, the energy absorber having a flanged frame for attachment to the vehicle and a body extending from the frame, the body including a first transverse wall, a second transverse wall spaced from the first transverse wall, and a plurality of adjustable crush zones extending therebetween, the crush zones are spaced apart along a longitudinal axis of the body and have irregularly shaped open areas disposed therebetween, the crush zone having a generally three-dimensional I-shape, the crush zone including side walls and a rear wall, the nominal wall thickness of the side and back walls is about 1.75mm to 3.0mm, the energy absorber is a unitary and integrally molded thermoplastic member with at least one of the walls having a window of preselected geometry to meet the impact load characteristics.

According to the present invention, there is also provided a method of making an energy absorber, comprising:

a first energy absorber is formed by a plurality of outwardly extending crush boxes having outer walls and side walls, the first energy absorber has a flanged frame for attachment to the vehicle and a body extending from the frame, the body including a first transverse wall, a second transverse wall spaced from the first transverse wall, and a plurality of adjustable crush zones extending therebetween, the crush zones are spaced apart along a longitudinal axis of the body and have irregularly shaped open areas disposed therebetween, the crush zone having a generally three-dimensional I-shape, the crush zone including side walls and a rear wall, the nominal wall thickness of the side and back walls is about 1.75mm to 3.0mm, the energy absorber is a unitary and integrally molded thermoplastic member, at least one of the walls having a window of preselected geometry therein to define a first set of impact load characteristics; and forming a second energy absorber having substantially the same structure as the first energy absorber except for a different window geometry to provide the second energy absorber with different impact load characteristics.

Drawings

FIG. 1 is a cross-sectional view of a prior art energy absorber shown in a state prior to an impact;

FIG. 2 is a cross-sectional view of a prior art energy absorber shown in a state after an impact;

FIG. 3 is an exploded perspective view of an energy absorbing system according to the teachings of the present invention;

FIG. 4 is an assembled cross-sectional view of the energy absorbing system of FIG. 3;

FIG. 5 is a rear perspective view of a portion of an energy absorber according to the teachings of the present invention;

FIG. 6 is a front perspective view of a portion of an energy absorber according to the teachings of the present invention;

FIG. 7 is a front perspective view of a portion of the energy absorber of the present invention shown in a condition after an impact;

FIG. 8 is a cross-sectional view of the energy absorber of the present invention shown in a condition after an impact; and

fig. 9 is a perspective view of an energy absorber, and fig. 9A-9E show enlarged partial perspective views of additional window configurations.

Detailed Description

Referring to fig. 1 and 2, a prior art energy absorber 10 is shown in cross-section for use in association with a reinforcement beam 12. As shown, the energy absorber includes upper and lower flanges 14 and 16, respectively, which overlap a portion of the beam when installed. As shown more clearly with reference to fig. 2, prior art energy absorbers tend to twist, as opposed to absorbing and dissipating the impact energy generated by a collision. Of course, this is undesirable and contrary to the energy absorber of the present invention.

As shown in FIG. 3, the present invention is directed to an energy absorbing system 20 including an energy absorber 22, the energy absorber 22 being positioned between a reinforcement beam 24 and an fascia 26, the fascia 26, when assembled, forming a bumper of a vehicle. It will be appreciated by those skilled in the art that the reinforcement beam is attached to a longitudinally extending frame bar (not shown) and is made of a high strength material such as steel, aluminum, synthetic resin or thermoplastic resin.

The exterior wall panels 26 are typically formed of a thermoplastic material that is preferably suitable for finishing using conventional vehicle painting and/or coating techniques. In general, the fascia will envelop the energy absorber 22 and reinforcement beam 24 so that neither component is visible when attached to the vehicle.

As best shown with reference to fig. 4-6, the energy absorber 22 includes a frame 30 having first and second longitudinally extending flanges 32 and 34, respectively, that overlap the reinforcement beam 24. Flanges 32 and 34 may be configured to have a particular shape during the molding process to facilitate connection of the exterior wall panels. For example, in the illustrated embodiment, the first flange 32 includes a generally U-shaped edge 36 that at least partially overlaps an edge 40 of the outer wall panel 26. Similarly, the second flange 34 includes a generally L-shaped edge 38 that partially overlaps a second edge 42 of the outer wall panel 26.

Extending outwardly from the energy absorber frame 30 is a body 44 including a first transverse wall 46 and a second transverse wall 48 having a plurality of adjustable crush lobes 54 extending therebetween. The transverse walls 46, 48 are preferably corrugated, including alternating raised areas 50 and recessed areas 52 that provide the transverse walls with increased stiffness to resist deflection upon impact. It should also be noted that the width and depth dimensions of the corrugations may be modified to achieve different stiffness characteristics as desired.

Also, depending largely on the impact energy requirements of the vehicle, crush boxes 54 extending away from reinforcement beam 24 may have any of a number of different geometries. A presently preferred design as shown in fig. 5 will generally include a plurality of spaced crush lobes 54(a-d) having a generally three-dimensional I-shape. Thus, the I-shaped crush relief portion includes a wing or top portion 56 proximate the first transverse wall 46 and a bottom wing portion 58 proximate the second transverse wall 48 and parallel to the first top portion 56, with a longitudinal cross member portion 60 abutting the top and bottom portions 56-58. The crush boxes 54 as shown in fig. 5 include side walls 62 and a rear wall 64, viewed in three dimensions. An open area 66 is provided between crush boxes 54 that generally extends to the inner frame 30 and terminates at a connecting member 74, which will be described in more detail below.

The crush boxes 54 of the energy absorber 22 are designed for at least two important functions. The first function relates to the stability of the energy absorber during impact. In this regard, the crush impact portion provides an axial crush mode upon impact of the barrier and pendulum impact, in accordance with Federal Motor Vehicle Safety Standard (FMVSS) and Canadian Motor Vehicle Safety Standard (CMVSS). The second function involves stiffness adjustability to meet the desired impact load deflection criteria. That is, the crush boxes 54 may be specifically modified in an effort to meet target criteria for any given application. For example, the crush zone preferably includes a plurality of windows 70 and 71 in the side and rear walls 62 and 64, respectively, as shown in fig. 9A-9E. The windows 70 and 71 may be, but are not limited to, squares (not shown), differently sized rectangles 70(a, c-e) and 71(a, c-e), and teardrops 70b, 71b to achieve the desired stiffness of the crush zone. To form the windows, a typical mold will include an open draft angle of about 5 ° in order to achieve optimum processing conditions, as will be appreciated by those skilled in the thermoplastic molding industry.

The adjustability of crush boxes 54 may also be tailored to the particular application by varying the thickness of the side and rear walls. For example, the nominal wall thickness of the side and back walls 62, 64 may range broadly from about 1.75mm to about 3.0 mm. More specifically, for certain low impact applications, the nominal wall thickness may typically be about 1.75mm to about 2.0mm, while for other applications, particularly those of 5mph FMVSS or CMVSS systems, the nominal wall thickness of the side and rear walls is more likely to be about 2.5mm to 3.0 mm.

Another aspect of properly tuning the energy absorber 22 is the selection of the thermoplastic resin to be used. The resin used may be a low modulus, medium modulus or high modulus material as desired. By carefully considering each of these variables, an energy absorber can be made that meets the desired energy impact objectives.

Another important design feature of the present invention, as best shown in fig. 6, is an integrally molded connecting member 74, which connecting member 74 extends perpendicularly between the first and second transverse walls 46 and 48, respectively. The connecting member 74 may be in the form of a vertically extending post 76a, or may have a cross-shaped structure including a vertically extending post 76a and a horizontally extending post 76 b. Regardless of the design of the connecting member, along the front wall 80 of the vertically extending post 76a, the connecting member preferably has a minimum average width to height ratio of 1: 5, with the height being measured as the distance between the first and second lateral walls 46 and 48, respectively. If the attachment feature 74 includes a window 73, the aspect ratio is more preferably 1: 3. As best shown with reference to fig. 4, the front wall 80 of the attachment member 74 is positioned adjacent the outer face of the reinforcement beam 24 when the energy absorber 22 and the fascia 26 are attached together.

Referring to fig. 7 and 8, the energy absorber 22 is shown in a theoretical post-impact condition. As can be seen, the energy absorber is crushed, but should remain in contact with the reinforcement beam 24, particularly along the first and second longitudinal flanges 32 and 34, respectively.

Preferred characteristics of the material used to form the energy absorber include high toughness/ductility, thermal stability, high energy absorption capacity, good modulus to elongation ratio and recyclability, among others.

Although the energy absorber may be molded in sections, it is preferably a unitary structure made of a tough plastic material. The preferred material for molding the energy absorber is an engineering thermoplastic resin. Typical engineering thermoplastic values include, but are not limited to: acrylonitrile-butadiene-styrene (ABS), polycarbonate/ABS blends, polycarbonate polyester copolymers, acrylic-styrene-acrylonitrile (ASA), acrylonitrile- (ethylene-diamine modified polypropylene) -styrene (AES), polyphenylene ether resins, polyphenylene ether/polyamide blends (NORYL GTX ® from General Electric Company), polycarbonate/PET/PBT blends, polybutylene terephthalate and impact modifiers (XENOY ® resin from General Electric Company), polyamides, polyphenylene sulfide resins, polyvinyl chloride PVC, High Impact Polystyrene (HIPS), low/high density polyethylene (L/HDPE), polypropylene (PP) and Thermoplastic Polyolefin (TPO), among others.

While it is apparent that the disclosed preferred embodiment of the invention is well calculated to fulfill the objects stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the spirit thereof.

Claims (14)

1. An elongated unitary energy absorber adapted for attachment to a vehicle, said energy absorber comprising:

a flanged frame for attachment to the vehicle and a body extending from the frame, the body comprising a first transverse wall, a second transverse wall spaced from the first transverse wall, and a plurality of adjustable crush zones extending therebetween, the crush zones being spaced apart along a longitudinal axis of the body and having irregularly shaped open areas disposed therebetween, the crush zones having a generally three-dimensional I-shape, the crush zones comprising side walls and a rear wall, the side walls and the rear wall having a nominal wall thickness of about 1.75mm-3.0mm, the energy absorber being a unitary and integrally molded thermoplastic component.

2. The energy absorber of claim 1 wherein said first and second transverse walls are corrugated.

3. The energy absorber of claim 1 wherein said side and rear walls include windows of predetermined shape and size.

4. The energy absorber of claim 1 further comprising a plurality of connecting members extending between said first and second transverse walls.

5. The energy absorber of claim 4 wherein said connecting member comprises a vertically extending post having a front wall with a minimum average width to height ratio of about 1: 5.

6. The energy absorber of claim 5 wherein at least some of said connecting members further comprise horizontally extending posts to define connecting members having a cross-shape.

7. An energy absorbing system for a motor vehicle, comprising:

a reinforcing beam;

an energy absorber comprising a flanged frame for attachment to the reinforcement beam and a body extending from the frame, the body comprising a first transverse wall, a second transverse wall spaced apart from the first transverse wall, and a plurality of adjustable crush zones extending therebetween, the crush zones being spaced apart along a longitudinal axis of the body and having irregularly shaped open areas disposed therebetween, the crush zones having a generally three-dimensional I-shape, the crush zones comprising side walls and a rear wall, the side walls and the rear wall having a nominal wall thickness of about 1.75mm-3.0mm, the energy absorber being a unitary and integrally molded thermoplastic component; and

an outer wall panel is attachable to the energy absorber to substantially encase the reinforcement beam and the energy absorber.

8. The energy absorbing system of claim 7, wherein the first and second transverse walls are corrugated.

9. The energy absorbing system of claim 7, wherein the side and rear walls include windows of a predetermined shape and size.

10. The energy absorbing system of claim 7, further comprising a plurality of connecting members extending between the first and second transverse walls.

11. The energy absorbing system of claim 10, wherein the connecting member comprises a vertically extending post having a front wall with a minimum average aspect ratio of about 1: 5.

12. The energy absorbing system of claim 11, wherein at least some of the connecting members further comprise horizontally extending posts to define connecting members having a cross shape.

13. A method of making an energy absorber, comprising the steps of:

a) defining a set of impact load characteristics;

b) selecting a thermoplastic material with reference to the impact load characteristics; and

c) forming an energy absorber from the thermoplastic material, the energy absorber having a flanged frame for attachment to the vehicle and a body extending from the frame, the body including a first transverse wall, a second transverse wall spaced from the first transverse wall, and a plurality of adjustable crush zones extending therebetween, the crush zones are spaced apart along a longitudinal axis of the body and have irregularly shaped open areas disposed therebetween, the crush zone having a generally three-dimensional I-shape, the crush zone including side walls and a rear wall, the nominal wall thickness of the side and back walls is about 1.75mm to 3.0mm, the energy absorber is a unitary and integrally molded thermoplastic member with at least one of the walls having a window of preselected geometry to meet the impact load characteristics.

14. A method of making an energy absorber, comprising:

a first energy absorber is formed by a plurality of outwardly extending crush boxes having outer walls and side walls, the first energy absorber has a flanged frame for attachment to the vehicle and a body extending from the frame, the body including a first transverse wall, a second transverse wall spaced from the first transverse wall, and a plurality of adjustable crush zones extending therebetween, the crush zones are spaced apart along a longitudinal axis of the body and have irregularly shaped open areas disposed therebetween, the crush zone having a generally three-dimensional I-shape, the crush zone including side walls and a rear wall, the nominal wall thickness of the side and back walls is about 1.75mm to 3.0mm, the energy absorber is a unitary and integrally molded thermoplastic member, at least one of the walls having a window of preselected geometry therein to define a first set of impact load characteristics; and

a second energy absorber is formed having substantially the same structure as the first energy absorber except for a different window geometry to provide the second energy absorber with different impact load characteristics.