GB2469013A - Bumper assembly and bumper system for motorized vehicles - Google Patents

Abstract

The present invention provides a bumper assembly and a bumper system for motorized vehicles, comprising a beam member 12 having an elongated middle section 14 and at least one impact absorbing member 16, which is adapted and designed to be subject of mechanical deformation in response to an external load acting on the beam member 12, wherein the beam member 12 is mounted and/or mechanically coupled to a vehicle frame by means of the at least one impact absorbing member 16, and wherein at least the impact absorbing member 16 is made of a polymeric material. A mounting member (54, figure 4) is disposed at the vehicle frame, the mounting member having a through opening (52) configured to receive an energy absorbing member. The middle section 14 may also be made of a polymeric material wherein the middle section and impact absorbing member/s integrally form the beam member. There may be two impact absorbing members disposed at opposite ends of the middle section.

Description

Bumper assembly and bumper system for motorized vehicles

Description

The present invention relates to a bumper assembly as well as to a bumper system for motorized vehicles comprising a bumper beam of elongated structure and at least one impact absorbing member, being adapted and designed to be subject of mechanical deformation in response of an external load acting on the bumper beam.

Background and prior art

Bumper assemblies and bumper systems for motorized vehicles typically comprise impact or bumper beams that are designed to absorb a maximum of impact energy over a given stroke. At the same time, they are designed to minimize load spikes and to distribute impact energy in a manner promoting uniform and predictable collapse upon undergoing loading from impact. The bumper assembly therefore has to fulfil certain requirements regarding rigidity and elasticity.

Most known bumper systems include a rather rigid, structural metal beam attached either directly to and between vehicle frame rails or in combination with intermediate rail extension brackets to position and adapt the bumper system appropriately for various packaging conditions.

Further, a polymeric energy absorber may be placed on one face of the metal beam to fill the space between the beam and the outer face and to provide additional energy management capacity. In such embodiments, the rigid structural metal beam is intended to provide a primary energy absorbing structure, while a polymeric energy absorber is configured to crush and to absorb energy during an impact of less severity.

Moreover, a bumper assembly has to comply with different requirement profiles. For so-called low-speed-tests with a maximum impact velocity of 16 km/h, the bumper assembly and system should almost entirely absorb the impact energy, such that the body of the car remains substantially undamaged. Under impact conditions at higher impact velocities however, the bumper assembly, in particular the bumper beam should provide predetermined breaking points in order to exhibit a required and predefined deformed and eventually cracked structure.

The document WO 2007/076096 A2 discloses for instance a bumper system for a vehicle comprising a metal component and a second component comprising a polymeric material. The metal component has a length and opposing ends are adapted for attachment to frame rails of a vehicle frame. The second, polymeric component engages a face of the metal component and is rigidly attached to the metal component continuously along a common interface or at least at several locations along this interface to form a structural beam with the metal component.

Such bumper systems having a structural beam of metal attached to frame rails of a vehicle frame have a relatively large mass and are rather costly in production and assembly. Also, it is rather difficult to achieve a homogeneous energy absorption behaviour in response to an impact load.

Object of the invention The present invention therefore aims to provide a bumper assembly and a bumper system having reduced mass and which can be manufactured cost-efficiently. Further, the invention aims to provide a bumper assembly and a bumper system providing an improved and more homogeneous energy absorption behaviour upon impact load.

Summary of the invention

The underlying problem of the invention is solved by means of a bumper assembly according to claim 1 as well as by means of a bumper system according to claim 14. Preferable embodiments of the invention are set forth in the dependent claims.

The bumper assembly for motorized vehicles according to the invention comprises a beam member, that has an elongated middle section and at least one impact absorbing member. The impact absorbing member is particularly adapted and designed to be subject of mechanical deformation in response to an external load acting on the beam member. The beam member itself is typically designed as a bumper beam. It is mounted and/or mechanically coupled to a vehicle frame, in particular to at least one frame rail, by means of the at least one impact absorbing member. Hence, the impact absorbing member not only provides a predefined crush and energy absorption behaviour but also serves as a mechanical coupling and mounting member for mounting the beam member and its middle section to a vehicle's frame.

Further, the at least one impact absorbing member is made of a polymeric material, being adapted to provide a homogeneous energy absorption behaviour, especially under peak impact loads.

In particular for low-speed-test conditions, a major component of the applied load transfers to a well-defined mechanical deformation of the at least one impact absorbing member, while the residual beam member, in particular, its elongated middle section remains substantially intact and becomes at most only slightly damaged and distorted.

Since the impact absorbing member substantially consists of a polymeric material, its internal structure and geometry can be almost arbitrarily designed by means of an appropriate injection molding process.

According to a preferred embodiment of the invention, also the middle section of the beam member is made of polymeric material. Further, the impact absorbing member and said middle section integrally form the beam member. Hence, the entire beam member is made of and may consist of polymeric material. This way, the entire beam member, or bumper beam can be produced by means of one or several single-or multi-component injection molding processes. The middle section and impact absorbing member can therefore be considered as sections of a unitary beam member, entirely made of polymeric material.

By making use of polymeric material, either by means of a single or multi-component injection molding process for manufacturing the beam member, the overall mass of the bumper assembly and its bumper beam can be remarkably reduced compared to a beam member comprising metal or metal components. At the same time, material expenses and production costs can be lowered.

According to a further preferred embodiment of the invention, the beam member comprises two impact absorbing members, that are disposed at opposite end sections of the elongated middle section. Consequently, the beam member comprises a U-, I-, or H-profile-like shape with the two impact absorbing members as side branches, for example. By means of the two impact or energy absorbing members, the beam member and the bumper assembly can be mounted to the vehicle frame to at least two mounting points, typically located at the vehicle's frame rails.

In this way, an impact load, acting for instance on the middle section of the beam member, can be substantially symmetrically conducted and discharged into the vehicle frame by means of the two symmetrically arranged impact absorbing members.

In a further preferred embodiment, the impact absorbing members extend in a direction substantially perpendicular to the elongation of the middle section.

The extension of the impact absorbing member in this direction further determines a displacement or deformation path and a respective crush zone.

Furthermore, in another embodiment, the impact absorbing member comprises at least one peripheral wall section, which is adapted to receive at least one fastening element for fastening the impact absorbing member and hence the beam member to the vehicle frame.

The impact absorbing member at its peripheral wall section may for instance comprise a receptacle or a through hole for receiving a fastening element, such like a strut or bolt. Generally, the impact absorbing member may comprise any kind of applicable geometry, in particular a cubic-or box-like shape.

In a further embodiment, the impact absorbing member comprises a H-shaped cross section, formed by two oppositely arranged peripheral wall sections, that are interconnected by means of a strut section. In this embodiment, receptacles or through holes of the impact absorbing members peripheral wall sections are disposed outside of the interconnection strut section.

In another preferred embodiment, the fastening element and the impact absorbing member are adapted to allow for a displacement of the beam member relative to the vehicle frame in response to a force effect being above a predefined threshold. The fastening elements and in particular the peripheral wall sections being in engagement with the fastening elements comprise a pre-and well-defined rigidity,elasticity and br load-path, which allow for a predetermined displacement of the impact absorbing member and hence the entire beam member relative to the vehicle frame.

During such an impact induced displacement, the impact absorbing member may remain its overall geometric structure. Alternatively, typically under higher impact load, also the impact absorbing member itself may become subject to deformation, in particular compression.

In a further preferred embodiment, the impact absorbing member is adapted to be slotted or ripped by means of the fastening element during the impact absorbing member displacement relative to the vehicle frame. A receptacle or through hole of the impact absorbing member's peripheral wall, is intended to widen and to become slit-or channel-like in response to an impact-induced force effect acting on the beam member.

In other words, the fastening element will engrave in the peripheral wall section of the impact absorbing member, if a respective force effect is applied to the impact absorbing member or to the integrally connected middle section.

This ripping or engraving functionality can be particularly provided by means of a polymeric material, providing a substantially constant displacement under constant applied load. Since the polymeric material inherently provides a required deformation behaviour, a well-defined slot may exhibit due to an impact load.

However, the overall structure of the impact absorbing member may remain almost unaltered and may still provide sufficient mechanical stability to retain the bumper assembly attached to the vehicle frame and to prevent an unintended release of the entire bumper assembly.

In another preferred embodiment, the bumper assembly further comprises at least a first reinforcement element extending along a peripheral wall section of the beam member's middle section, wherein the first reinforcement element is fixed, in particular rigidly attached to the beam member, for sustaining and for improving the general bending resistivity and rigidity of the beam member, in particular in the region of its elongated middle section.

By making use of such a reinforcement element, discharging or conducting of applied impact load towards the impact absorbing members can be improved. Further, under impact conditions as they arise at higher impact velocity, the reinforcement element may prevent or inhibit an uncontrolled and unintentional disassembling of the beam member, in particular across its elongated middle section. In this way, by means of the at least first reinforcement element, overall stability and rigidity of the bumper assembly can be advantageously improved.

According to a further preferred embodiment, the middle section of the beam member is at least partially sandwiched between the first and an additional, second reinforcement element. By making use of two reinforcement elements disposed and rigidly attached at opposite peripheral wall sections of the beam member's elongated middle section, the overall bending and cracking resistivity of the beam member and its middle section can be enhanced further.

In another preferred embodiment of the invention, the reinforcement element comprises sheet metal, in particular high-grade steel or stainless steel.

It is further of advantage when the reinforcement element entirely engages and abuts against a face of a peripheral -9-.

wall of the beam member and/or its elongated middle section. Further, it is suggested, that the reinforcing sheet metal continuously extends along the entire beam member's middle section, preferably at its oppositely located, outer and inner peripheral faces.

The reinforcement element may further comprise a substantially flat and even geometry, allowing for a particularly low cost production and assembly.

The reinforcement element made of sheet metal or high-grade steel sheet metal may be pre-configured as a pre-formed blank and may comprise an outer geometry and structure that corresponds to the peripheral structure of the beam member.

According to another preferred embodiment of the invention, the reinforcement element and the middle section are positively bonded by means of an adhesive, such like an epoxy resin. Alternatively or additionally, the reinforcement element might be overmolded or sheathed with polymeric material. Also, the rigid attachment of the reinforcing metal sheet to the beam member may be achieved by means of insert molding, where at least a part of the beam member is injection moulded around the reinforcing metal insert.

In a further embodiment, the at least one, preferably, both reinforcement elements comprise a central section and two side sections disposed at opposite ends of the central section. In a final assembly position, the central section butts against a peripheral wall of the beam member's middle section and the side sections of the reinforcement element butt against a -10 -peripheral wall section of the energy absorption member.

Typically, the side sections of the reinforcement element are bended and extend at a certain angle with respect to the elongation of the reinforcement element's central section. In this way, the reinforcement element is adapted to at least partially clasp around the beam member for providing enhanced stability and rigidity also in an intersecting or merging region of middle section and impact absorbing member of the beam member.

Additionally, the beam member may comprise protruding corner sections at its longitudinal end sections and its front face. Correspondingly, the respective reinforcement element to be attached at beam member's front face may comprise respective receptacles.

In this way, also a kind of positive locking of the reinforcement element and the beam member can be achieved, which may facilitate the process of bonding beam member and reinforcement element.

In another independent aspect, the invention provides a bumper system for motorized vehicles, which comprises the above described bumper assembly and further comprises at least one mounting member being disposed and attached to the vehicle frame, in particular at the vehicle's frame rails. The mounting member has as through opening, which is adapted to receive the at least one energy absorbing member of the bumper assembly.

Hence, the mounting member with its through opening generally allows for a relative displacement of beam member and vehicle frame. In an initial assembly position, the energy absorbing member may at least partially be disposed in said through opening.

-11 -Alternatively, the energy absorbing member may be aligned with the mounting member's through opening, such that in case of an impact load, the energy absorbing member may become subject to a displacement or movement into the through opening.

According to another embodiment of the invention, two flange-like mounting brackets are disposed at opposite side edges of the mounting member's through opening. The mounting brackets are further adapted to receive at least one fastening element, in particular a fastening bolt or strut, wherein in an assembly position of the bumper assembly at the vehicle frame, the at least one fastening bolt or strut extends through the at least one peripheral wall section of the impact absorbing member.

The fastening bolts or struts, as well as said mounting brackets and the mounting are preferably made of metal in order to provide a sufficient stability and/or rigidity for mounting and mechanically coupling the bumper assembly to the vehicle frame.

The entire beam member, with its elongated middle section and the two oppositely disposed impact absorbing members may comprise a composite polymeric material. Further, the beam member may comprise fibre reinforced polymeric material, such as fibre reinforced plastics, in particular even nano-reinforced plastics.

For the manufacture of such beam members, a manifold of different injection or compression molding processes, either of single-component or multi-component type may be applicable. In particular, various molding processes, such like sheet molding, bulk molding, long fibre -12 -thermoplastic molding and glass mat thermoplastic molding as well as thermoforming molding processes are generally applicable with the present invention.

The inventive design of a beam member with integrated crush boxes entirely made of polymeric material in combination with reinforcing sheet metal plates, provides a low-cost hybrid bumper beam concept, which combines the contrarian properties of high stability and rigidity on the one hand side and low mass on the other hand side.

It is further to be understood, that both, the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview of framework for understanding the nature and character of the invention as it is claimed.

Brief description of the drawings

In the following, preferred embodiments of the invention will be described in detail by making reference to the drawings, in which: Fig. 1 schematically illustrates a bumper assembly in an exploded perspective view, Fig. 2 in a perspective illustration depicts the beam member made of polymeric material, Fig. 3 illustrates another perspective view of the beam member according to Fig. 2, -13 -Fig. 4 schematically illustrates a mounting of the.

beam member to the vehicle frame in an initial state, Fig. 5 provides a schematic illustration of the bumper system according to Fig. 4 after an applied impact load and Fig. 6 depicts a diagram illustrating applied load versus displacement of impact absorbing members relative to the vehicles body.

The bumper system 10 as illustrated in Fig. 1 comprises three major components, a beam member 12 and two reinforcement members 22, 24, which are intended to be rigidly attached to front and rear faces of the beam member 12. In particular, the reinforcement members 22, 24 are adapted to be entirely engaged and bonded with the middle section 14 of the beam member 12.

The beam member 12, as illustrated in Figs. 2 and 3 comprises a rather elongated and only slightly bended middle section 14. Further the beam member 12 comprises two energy absorbing members 16, 18, being integrally formed with the middle section 14 at its opposite free end sections. The entire beam member 12 is made of polymeric material, such as fibre reinforced plastics, thermosetting plastics and/or thermoplastic elastomers.

The polymer material may comprise a fibre-reinforced polymer and the entire beam member 12, comprising middle section 14 and energy absorbing members -14 - 16, 18 may be manufactured by a single injection molding process, in particular by means of a compression molding by making use of a so-called long fibre thermoplastic-molding process (LFT-process). Additionally or alternatively, the beam member 12 could also be manufactured by means of a glass mat thermoplastic (GMT) molding process.

The middle section 14 of the beam member 12 comprises a variety of stiffening ribs 20, extending at an angle with respect to the elongation of the peripheral side walls or front and rear faces of the middle section 14. In this way, front and rear faces of the middle section and the interstitial stiffening ribs 20 form triangular shaped boxes, in order to enhance the general rigidity of the middle section 14.

The energy absorbing members 16, 18, serving as crush boxes extend substantially perpendicular to the elongation of the middle section 14. In this way, the entire beam member 20 comprises a U-or I-shaped structure -In cross section, the energy absorbing members 16, 18 comprise a H-shaped profile with two oppositely arranged and parallel extending peripheral wall sections 66, 68, that are interconnected by means of a horizontally extending strut section 70. The peripheral sections 66, 68, as illustrated in Fig. 2 in connection with energy absorbing member 18 serve as receptacle for bolt-or strut-like fastening elements 60, 62, as they are depicted in Figs. 4 and 5.

-15 -Each one of this bolts 60, 62 intersects both peripheral walls 66, 68 of the energy absorbing member 18. Further, the illustrated mounting member 54, which is rigidly attached to a not explicitly illustrated vehicle frame 50, further comprises a through opening 52, which is adapted to receive the energy absorbing member 18 in case of an applied impact load, which is illustrated in Fig. 5.

io Since the energy absorbing members 16, 18 are made of polymeric material, having a well-defined elasticity, in response to an impact load, the bolts 62, may engrave or rip the peripheral walls 66, 68 of the energy absorbing member 18, leading to an elongated channel, notch or groove 64 in the respective peripheral walls 66, 68.

This local deformation and engraving of the fastening elements 62, 60 along the peripheral walls 66, 68 allows for a well-defined and homogeneous energy absorption under impact conditions, as for instance illustrated in the diagram of Fig. 6. There, applied load in kN is displayed versus displacement of an energy absorbing element in mm as measured in two different experiments as illustrated by the dashed and continuous lines.

The illustrated displacement can be regarded in two different zones. At the beginning, during a built up of a load, the system behaves almost linear, which means that a rising load leads to an increasing displacement.

But as soon as a particular load limit has been reached, the displacement of the energy absorption member continues. At this given load, the slope of the graph -16 -tends to zero and the graph continues as a rather straight line. In this situation, energy is continuously dissipated and absorbed by the persisting movement and/or deformation of the energy absorption member.

As can be seen from the graph in Figure 6, an applied load above a given threshold results in a continuous and homogeneous displacement of the energy absorbing member 16, 18.

As further illustrated in Fig. 5, the mounting member 54 comprises two oppositely arranged mounting brackets 56, 58 disposed at opposing edges of the through opening 52. These flange-like mounting brackets 56, 58 serve as a mounting means for rigidly attaching energy absorption members 16, 18 to the mounting member 54.

Hence, the mounting bracket 56, 58, as well as the peripheral side walls 66, 68 of the energy absorption member 18 are penetrated by the bolt or strut 60, 62.

As can be seen further from Fig. 1 and 2, the beam member 12 at its front peripheral wall facing towards the front reinforcement member 22 comprises protruding edges 26, 28 at either end of the middle section 14. The corresponding reinforcement member 22 comprises respective receptacles 36, 38, that are adapted to clasp around or to receive these protruding edges 26, 28 of the beam member 12. The reinforcement members 22, 24 are made of stainless steel and may be provided as pre-formed blanks having a contour and geometry adapted to the respective peripheral contour of the beam member 12.

-17 -The corresponding edge portions 26, 28 and the receptacles 36, 38 can provide a kind of positive locking function in the process of rigidly attaching or bonding the beam member 12 and the associated reinforcement members 22, 24. Bonding of reinforcement members 22, 24 and beam member 12 can be provided by means of an appropriate adhesive, for instance by means of an epoxy resin, which after a fixation of the parts 12, 22, 24 is subject to a thermal curing.

As illustrated in Fig. 1, the rear reinforcement member 24 comprises a central section 40 and two oppositely disposed, slightly bended end sections 42, 44, which are adapted to be disposed in the corner formed by the energy absorbing members 16, 18 and the middle section 14 of the beam member 12.

Accordingly, also the front reinforcement member 24 comprises a central section 30 and two bended end sections 32, 34, which are adapted to abut against an outer peripheral wall 68 of the energy absorbing members 16, 18. Further, the reinforcement members 22, 24 are intended to be continuously and rigidly attached and bonded along the entire common interface between reinforcement members 22, 24 and the peripheral faces of the beam member 12.

-18 -List of reference numerals 10 bumper system 12 beam member 14 middle section 16 energy absorbing member 18 energy absorbing member 20 stiffening rip 22 reinforcement member 24 reinforcement member 26 edge 28 edge 30 central section 32 end section 34 end section 36 receptacle 38 receptacle 40 central section 42 end section 44 end section vehicle frame 52 through opening 54 mounting member 56 mounting bracket 58 mounting bracket fastening element 62 fastening element 64 groove 66 peripheral wall 68 peripheral wall interconnecting strut section