CA1293985C

CA1293985C - Vehicle bumper

Info

Publication number: CA1293985C
Application number: CA000585860A
Authority: CA
Inventors: Norman S. Loren
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-12-28
Filing date: 1988-12-14
Publication date: 1992-01-07
Anticipated expiration: 2009-01-07
Also published as: DE3883508D1; JPH01197147A; EP0323038A2; JP2537083B2; EP0323038A3; DE3883508T2; US4941701C1; EP0323038B1; MX168557B; US4941701A; ES2043851T3; AU609544B2; AU2632688A; BR8806909A

Abstract

IMPROVED VEHICLE BUMPER

ABSTRACT

An impact energy managing bumper structure having a configuration and component members that cooperatively provide, as a function of position along its length, predetermined levels of resilient opposition to deformation and displacement. A semirigid resilient fascia is spaced forwardly of the bumper structure, and the volume defined therebetween is filled with an integral skin urethane foam that is resiliently deformable and integrally bonded to both members.

Description

~2~3~

IMPROVED VEHICLE BUMPER

~ECHNICAL nACKGROUND

This invention relates to an impact energy managing bumper structure fox vehicles.

BAC}~GROUND AR~

A number of vehicle bumpers have been designed for the purpose of managing moderate impact forces without incurring damage to the bumper or to the vehicle to which it is attached. One approach has been to use plastic bumper members having a greater thickness at their centers and end~ to provide added rigidity to areas where impact forces would most likely tend to displace them. Another approach has been to use plastic bumper members having ribs and multicellular energy managing material. Yet another approach has been to mount bumpers to vehicles with shock absorbers or with impact-displacing, corrugated or staggered supports. See, for example, U.S. Patent Numbers 2,320,835: 3,866,963; 3,g33,387; ~061,384;
4,070,052; 4,208,069; 4,328,986; 4,385,779; 4,386,799;
4,533,166; ~,586,177; 4,586,739; 4,586,866; and 4,586,984.
The present invention comprises an ef~ective combination o~ elements that at once minimize the weight and cost of the bumper while maximizing its capacity to prevent damage to the bumper or to the vehicle upon receiving impacts.

.

2 710~37-198 DISCLOSURE OF THE ~NVENTION
In accordance with the present invention, a bumper is provided -that is capable oE managing moderate impact Eorces without damage -to the bumper or to the vehicle -to which it is attached, that can be manufactured and assembled economically, and that is relatively light.
According to a broad aspect of the present invention, there is provided a bumper beam for use as the principal energy management member in a vehicle bumper of the type adapted to mount to a vehicle at a pair of mounting points spaced from the longitudinal center line of the vehicle, the bumper beam comprising an integrally molded, one-piece, elonga-ted plastic body having a generally open channel shape defined by upper and lower, substantially horizontal surfaces joined by a substantially ver-tical surface and a pair of mounting surfaces formed as recesses in the vertical surface in alignment with the mounting points.
One preferred embodiment oE the present invention contemplates an impact energy managing bumper structure having a configuration and component members that cooperatively provide, as a function of position along its length, predetermined levels of resilient opposition to deformation and displacement. Other embodiments contemplate the addition o various means Eor increasing specific energy managing properties at predetermined points along the length of the bumper structure.
Yet other embodiments contemplate the use oE urethane foam molded in situ between and bonded to the surfaces of particular members of the bumper structure. When these . .

~2~3~il5 2a 71087-198 embodiments oE the bumper oE the present inventlon receive impact forces, speciEic structure component members and speciic portions o foam are deEormed. Resulting tension and compression Eorces created in the bonded foam inhibit and delay the member deormation and assist in postimpact structural restitution. The cooperative combination oE the elements oE the bumper structure provide for a progressive deformation of the structure members and thereby signiEicantly enhances its impact energy management capabilities.

~.~

1~3~

St~ll anothex embodiment o~ the presenk invention contemplates the use o~ gas assisted injection molding to create channel~ to reduce stresses introduced during molding processes and to increase the reslstance to the deformation and displacement of ~he bump~r structure, thereby contributing to its impact energy management capabilities.

BRIEF DESCRIPTION OF_5rHE DRAWINGS

In the drawings, in which like reference characters indicate corresponding parts in all the views:
FIG. 1 is a fragmentary plan view, partly broken away and partly in section, of a preferred embodiment of the impact energy managing bumper;
FIG. 2 is a fragmentary perspective view from the front of the bumper structure of FIG. 1;
FIG. 3 is a fragmentary perspective view from the rear of the bumper structure of FIG. l;
FIG. 4 is a section view taken along line 4-4 o~ FIG. 2 and illustrating added energy management means;
FIG's. 5 and 6 are vertical section views, partly broken away, taken along the line 5-5 of FIG. 1 and illustrating added energy management means;
FIG. 7 is a vertical section view illustrating added energy means and taken along the line 7-7 of FIG. 1;

FIG. 8 is a vertical section view, partly broken away, taken along the line 5-5 of FIG. 1 and illustrating the disposition of energy management means;

33~3~5 FIG. g is a vertical section view illustrating an additional embodiment of the bumper structure and taken along the line 5-5 of FIG. l; and FIG's. ~o through 12 are vertical section views, similar to that of FIG. 9, illustrating additional embodiments of the invention.

OF P}~EFERRBD E~BODIMEN~5 OF T~E IN'VI~N~ION

With reference to FIG. 1, shown is an impact energy managing bumper structure having a body 10 secured to a vehicle by, for example, a pair o~ column rails 14 disposed parallel to and equally spaced from the longitudinal center line of the vehicle. Also shown i~
a resiliently deformable fascia 60 disposed forward of and substantially enclosing those portions of the body lo that would otherwise be exposed to view when the bumper structure is mounted.
As shown in FIG. 2, the body 10 includes a beam 12, which may be made of injection molded plastic, having a front portion 16, an upper flange 18, and a lower flange 20. The upper flange 7 8 and the lower ~lange 20 coextend along a substantial length of the front portion 16 and form with it a channel 21 having, generally, a U-shaped cross section. Shown disposed along a substantial portion of the rear edge of the upper flange 18 is an integrally molded channel 22 having, generally, a U-shaped cross section integrally formed of an upper flange 24 and a lower flange 26. The channel 22 is an optional member that may be used to provide increased beam sti~fness and to fasten the fascia 60 to th~ beam 12 as shown in FIG. 8.
Integrally molded with and extending vertically across the front portion 16 of the beam 12 are energy managing buckling columns 28, one of which is disposed along a line extending vertically through the center of 3~

the beam 12 and the remainder o~ which are disposed in pairs that are parallel to and equally spaced there~rom.
FIGIs. 2 and 3 show that, integrally molded with and extending along a substantial portion of the length of the rear surface of th~ front portion 16 of the beam 12 are horizontal ribs 30. Integrally molded with the horizontal ribs 30 and with the rear surface of the front portion lfi of the beam 12 are vertical ribs 32, one of which is disposed along a line extending vertically through the center of the beam 12 and the remainder of which are disposed in pairs that are parallel to and equally spaced therefrom; however, the ribs and buckling columns may be arranged in any manner to suit specific requirements.
Equally spaced from the center o~ the beam 12 are formed mounting portions 34 for effectively attaching the beam 12 to khe column rails ~4 shown in FIG. 1. ~t the outer ends of the mounting portions 34 are vertical members 36. A metal plate 35 may be disposed on the forward surface of the mounting portion 34 to distribute resultant impact forces across the mounting portion 34 and may be used as a tapping plate for faskening. The vertical ribs 32 disposed behind the front portion 16 of the beam 12 and between the mounting portions 34 may be coplanar with the like-positioned buckling column 2~
projecting forwardly from the front portion 16 of the beam 12.
As shown in FIG I 8 . 1 through 3, the mounting portions 34 form, with buckling columns 3a and so, channels ~2 having, generally, U-shaped cross sections and extending along the beam 12 from vertical members 36 to 44.
With the bumper structure shown in FIG's. 1 through 3, an impact ~orce would be resiliently opposed by reaction forces created as the body 10 resists displacement and deformation. Increasing amounts of impact force would be opposed by similarly increasing reaction forces created as more and more o~ the body 10 and its component memhers are dlsplaced and deformed.
For exampl~, an impact force applied generally between the mounting portions 3~ would be subjected to initial dissipation due to its opposition by compression and tension forces created primarily as the buckling columns ~8 resist displacement and deformation. Any remaining impact force would be further dissipated due to its opposition forces created primarily as a result of the compression and tension of the front portion 16, of the flanges 18, 20, ~4, and 26, and the ribs 30 and 32 as the body lo is displaced and deformed.
An impact force applied to the body 10 at a point outwardly disposed from one of the column rails 14 would be dissipated due to its opposition by reaction forces created primarily as a result of the compression and tension of the front portion 16, the flanges 18, 20, 24, and 2~, the buckling columns 38 and ~o, the vertical member 36, and the ribs 30 and 32 as the body 10 is displaced and deformed. An impact force applied to the body lo colinearly with one of the column rails 14 would be dissipated due to its opposition by reaction forces primarily as a result of the aompression and tension of the buckling columns 3~ and 40, and the vertical members 36 and 44 a~ the body 10 is deformed.
Since the body 10 is secured to the column rails 14, it is not free to be displaced with respect thereto by an impact force applied to these areas; and the reaction forces acting to dissipate the impact force are created principally by the component members of the body 10 as they resist compressive defo~mation. Since the body 10 is free to be displaced by an impact force applied to other areas along its length, reaction forces created as a result of the compression and tension of the component members o~ the body lo as it is displaced lZ ~ ~3~

P-3~5 - 7 -represent a significant component of the total reaction orce acting to dis~ipatQ the impact force.
To dissipate greater impac-t forces applied colinearly with a column rail 14 (shown in FIG. 1) than can effectively be opposed by reaction forces created by the component members of the body lo, additional energy managing members, or inserts, ~6 illustratad in FIG. 4 may be added forward of the mounting portions 3~. The inserts 46 may be formed o~ re~ilient plastlc buckling columns 48 integrally molded to a backing member 50. The buckling columns 48 may be disposed in a number of arrangements to form, for example, parallel slots or honeycomb-shaped chambers. The slots or chambers formed between the buckling columns 48 may be filled with a plastic foam 52 having different resilient properties than those of the buckling columns 48, and the foam 5~ may be bonded to the buckling columns 48 and to the backing member 50. Inserts 46 may also be formed entirely of foam that may be bonded to a suitable backing member 50 for support and to facilitate mounting. Any combination of plastic inserts, foam inserts or plastic inserts with foam in situ may be mounted to the bumper structure wherever additional energy managing means are required.
With the body lO secured to column rails 14 (shown in FIG. 1) as with mounting bolts 54, an impact force applied to the body 10 colinearly with a column rail would -be opposed by reaction forces created as the insert 46 and the body 10 resist deeormation. In addition to the reaction forces created primarily as a result of the compression and tension of the buckling columns 38 and 40, and the vertical members 36 and 44 of the body 10, other reaction forces are created as a result of the compression and tension o~ the buckling columns 48 and foam 52. If the foam 52 is bonded to the insert buckling columns ~8, as the former is compressed by the impact force, larger portions of it will be placed in tension and 12~3~S

compression, significantly delaying the deformation of the insert buckling columns 48 and thereby providing additional reaction forces to contribute to dissipating the impact foxce. The foam 52 will also assist the s buckling columns ~8 in recovering their pre-impact shapes.
To dissipate greater impact forces applied along the length of the body lo at points between the mounting portions 34 (shown in FIG's. ~ through 4) than can effectively be opposed by reaction forces created by the component members of the body lo, additional energy managing material, such as plastic foam, 56 illustrated in FIG. 5 may be added forward of the front portion ~6 of the beam 12 and between the buckling columns 28 and the vertical members 4~. The foam 56 may be self-skinning and have different resilient properties than those of the buckling columns 28, and it may be bonded to the buckling columns 28 and the vertical members 44 and to the forward surface of the front portion 16 of the beam 12. This foam may also be added within and outboard of the mounting portions 34.
An impact force applied generally between the mounting portions 34 (shown in FIG' 5 . 1 through ~) would be subjected to dissipation, similar to that previously described, due to its opposition by compression and tension forces created as the body 10 and its component members are displaced and deformed. More of the impact force is dissipated by reaction forces created as the foam 56 is stretched and compressed. If the foam g~ is bonded to the buckling columns 28 and the vertical members 44 and to the front portion 16, as the former is deformed by the impact force, substantial portions of the foam 56 will be placed in tension and compression, significantly delaying the deformation of the members and thereby providing additional reaction forces to contribute to dissipating the impact force. The foam 56 will also assist the buckling columns 28 and other energy managing ~93~
P-345 - 9 ~
members in recovering their pre-impact shapes.
~s shown in FIG. 6, plastic Eoam 58 may also be added behind the front portion 16 of the beam 1~ between the horizontal and vertical ribs 30 and 32 respectively.
As be~ore, tha ~oam 5~ may be self-skinning and have different resilient properties than those of the ribs 30 and 32; and it may be bonded to the rear surface of the front portion 16, to the ribs 30 and 32, and to the upper and lower flanges 18 and 20 respectively. The foam may also be extended rearwardly to fill a substantially greater portion of the channel 21.
With such an arrangement, an impact force applied generally between the mounting portions 34 (shown in FIG's. 1 through 4) would be subjected to dissipation similar to that previously described; but substantially greater tension and compression ~orces would be created in the foam 5~ as it significantly delays the deformation of the various component members of the body 10, particularly the upper and lower flanges 18 and 20 respectively and thereby provides additional reaction forces to contribute to dissipating the impact force. The foam 5~ will also assist the flanges 18 and 20 and other energy managing members in recovering their pre-impact shapes.
As shown in FIG. 7, plastic foam 58 may also be added behind the front portion 16, of the beam 12, that is outwardly disposed from one of the mounting portions 34 (shown in FIG's. 1 through 4) and between the horizontal and vertical ribs 30 and 32 (shown in FIG. 3) and the upper and lower flanges la and 20 respectively. The foam 5~ may be bonded to the sur~aces oE these members and may also be extended rearwardly to fill a substantially greater portion of the channel 21.
The dissipation oE an impact force applied to a point on the body 10 outwardly disposed from the mounting members 34 would be substantially as descri~ed 31 ~93~

for a force applied generally therebetween.
As shown in FIG's. 1 and 8, a resiliently deformable fascia member 60 may be added forward of the body 10. As also shown in FIG. 8, plastic foam 56 may be disposed between the fascia 60 and the body lo. The foam 56 may be molded in situ by positioning the fascia ~0 and the body lo, which extends substantially the full length of the fascia 6U, in the desired spaced relationship and introducing the foam 56 into at least a portion of the volume defined therebetween.
Foam surfaces not boundsd by the fascia 60 and the body 10 are bounded by core pieces having shapes selected to provide the desired configuration of the exposed foam. The core pieces may be pretreated with mold release materials; and the volume-defining surfaces of the fascia 60 and the body lo may be prepaxed to enhance bonding by, depending on the materials selected, adhesive application, flame treatment, priming or the likeO
formable plastic, pre~erably a resiliently flexible urethane foam that cures with a resiliently compressible core and an integral skin that tenaciously bonds to the surfaces of the fascia 60 and the body lo, may be introduced into the defined volume and allowed to expand and cure to a semirigid state of desired resilience and compressibility An impact force applied to the fascia 60 would be subjected to dissipation, similar to that previously described, arising from its opposition by compression and tension forces created as the body 10 and its component members are displaced and deformed. In this case, the impact force is additionally dissipated by compression and tension forces created as the fascia 60 is displaced and deformed. More of the impact force is dissipated by the reaction forces created as the foam s6 is stretched and compressed. Since the foam 56 is bonded to the surfaces of the fascia 60 and the body 19, as the former is deformed, substantial portions of the ~oam 56 will be placed in tension and compression, significantly delaying the deformation of the fascia 60 and the body 10 and thereby providing additional reaction forces to contribute to dissipating the impact force. The ~oam 56 will also assist the fascia 60 and the body ~o and other energy managing members in recovering their pre-impact shapes.
FIG. g illustrates how the plastic body 10 and the fascia 60 may be molded with hollow portions 62 to substantially reduce in-molded stresses, which often cause deformation and structural weakness, introduced during their manufacture. After molten plastic has been introduced into a mold and begins to cool, it hardens from its outer surface inwardly. Gas injected at appropriate points into the plastic at this time will expand into the warmer, softer central areas, pressing the plastic outwardly against the mold and creating hollow portions 62 in the plastic. In addition to reducing the stresses introduced during a molding process, the hollow portions 62 also increase the strength o~ the body lo and the fascia ~o and increase their resistance to de~ormation and displacement, thereby contributing to their ability to dissipate impact ~orces.
When a large part is injection molded, multiple gating is usually required to fill the mold; and high injection pressures are usually re~uired to properly form the part. Multiple yating results in knit lines, which are structurally weak, being created as multiple ~lows of resin join. This can adversely affect the resilient performances of the structural members when the latter are sub;ected to progressively increasing impact forces.
These undesirable knit lines can be eliminated by using gas assisted injection molding because only one gate need be used to ~ill a mold and form a part.
The cooperative combination of the fascia 60;
the buckling columns 28, 3~, 40 and 48, the vertical 3~

members, the ribs 30 and 3~; the foam 52, 56 and 5~; and the beam 12 provide for a progres~ive deformation of the bumper structure, managing impact energy effectively as a functio~ of its amplitude and its point and direction of application, and preventing thereby a premature collapse of that portion of the structure ln the immediate area of an impact.
Distributing the ~orces associated with an impact is particularly imporkant when the impact forces are confined to a small area; and the integrally molded ribs and the foam bonded to the structure members contribute significantly to this distribution. For example, if the bumpex structure strikes a relatively narrow ob~ect such as a telephone pole, those structure members directly in line with the impact will begin to deform. As the members deform, resulting tension and compression forces will be communicated to physically associated members by the ribs and foam; and the associaked members will develop reaction forces that will oppose and dissipate the impact forces and reduce, by an amount proportional to the reaction forces developed, the amount of deformation experienced by the members in line with the impact.
FIG. 10 shows a bumper structure including a body 10 and a fascia 60 relatively disposed as previously described. In this emhodiment, the fascia has integrally molded ribs 64 pro;ecting toward tha body to provide additional impact energy management.
FIG. 11 illustrates a representative means for attaching the fascia 60 to the body 10. The channel 22 formed along the upper rear edge of the body 10 is designed to provide increased body stiffness and also to provide a means for seauring the fascia 60 to the body 10.
As shown, the fascia 60 may be secured to the upper flange 24 of the channel 22 by a screw 66 or the like.
The fascia 60 and the body lo may, of course, also be ~3~8~i joined along the upper flange 24 by adhesive means (not shown).
FIG. 12 illustrates another embodiment of the body lO having a front portion 16, an upper flange 18, and a lower flange 20. The upper flangP 18 and the lower flange ~0 coextend along a substantial length of the front portion 16 and form with it a channel 21 having, generally, a U-shaped cross section. The front portion l~
of the body 10 is provided with corrugations 68 to effectively increase the stiffness of the body 10 by predetermined amounts.

Claims

1. A bumper beam for use as the principal energy management member in a vehicle bumper of the type adapted to mount to a vehicle at a pair of mounting points spaced from the longitudinal center line of the vehicle, the bumper beam comprising an integrally molded, one-piece, elongated plastic body having a generally open channel shape defined by upper and lower, substantially horizontal surfaces joined by a substantially vertical surface and a pair of mounting surfaces formed as recesses in the vertical surface in alignment with the mounting points.

2. A bumper beam as defined in claim 1, further comprising force distribution members to laterally distribute impact forces incident at the mounting surfaces.

3. A bumper beam as defined in claim 2, wherein each force distribution member comprises a buckling column.

4. A bumper beam as defined in claim 2, wherein each mounting surface has first and second force distribution members.

5. A bumper beam as defined in claim 1, further comprising integral ribs formed on the body at selected positions to assist in management of impact forces.

6. A bumper beam as defined in claim 1, wherein the body has a substantially arcuate shape in plan view with the center portion projecting outwardmost from the vehicle.