Bumper module

A bumper module for a vehicle includes a cross beam and two fastening flanges for fastening the cross beam to a longitudinal body beam. A layer included of fiber-reinforced plastic extends continuously from the cross beam until into the fastening flange.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No. 102016002635.9, filed Mar. 3, 2016, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure pertains to a bumper module for a vehicle, in particular a road vehicle, with at least one cross beam encompassing at least one layer included of fiber-reinforced plastic.

SUMMARY

The present disclosure provides a bumper module that exhibits a high load-bearing capacity at a low weight, and can still be efficiently and cost-effectively manufactured.

In one embodiment of the present disclosure, a bumper module for a vehicle includes a cross beam and two fastening flanges for fastening the cross beam to a longitudinal body beam. A layer of fiber-reinforced plastic extends continuously from the cross beam into the fastening flange. Such a layer can include a so-called organic sheet or organo sheet, which can be molded into the three-dimensional shape required for the bumper module by thermoforming. A continuous progression can be realized especially easily for the layer having fiber-reinforced plastic if the cross beam extends between the fastening flanges, adjoining flush with the latter.

In order to achieve the shock-absorbing effect required during a collision in which a foreign object hits the cross beam and divert the impact forces to the longitudinal beam, the cross beam between the fastening flanges should be outwardly bowed or bulged toward the vehicle exterior.

For purposes of a tear-resistant attachment to the longitudinal body beam, it is useful for at least one screw hole of one of the fastening flanges to cross the layer having fiber-reinforced plastic.

However, a fastening flange may be enhanced by injection molding a plastic material. In this way, fiber-reinforced plastic waste can be minimized in a segment of the fastening flange extending out over a longitudinal edge of the cross beam.

The fiber-reinforced plastic layer can be bent along a first longitudinal edge of the cross beam, so as to form at least one outer and one inner wall, and thereby elevate the load-bearing capacity of the cross beam.

Should this be the case, the fiber-reinforced plastic layer cannot extend over this longitudinal edge. In which case, it makes sense to fabricate it via injection molding so that when a flange segment is needed beyond this longitudinal edge.

The first longitudinal edge is preferably an upper edge of the cross beam. The U-profile that resulted from bending the layer is then open at the bottom, and no dirt or deposits can accumulate therein.

In order to further improve the load-bearing capacity of the cross beam, the inner and outer wall can be joined together by ribs injection molded between them.

In an alternative embodiment, the fiber-reinforced plastic layer can be formed into a groove open in the longitudinal direction of the vehicle, or into several such grooves running one next to the other. Here as well, ribs can be injection molded inside of the groove to increase the load-bearing capacity.

The depth of the groove should gradually taper from the middle of the cross beam to the fastening flanges, so as to provide a continuous transition to the fastening flanges free of highly curved or angular regions that are particularly vulnerable to failure in the event of a collision.

In the event of a collision, the upper and lower flanks of the groove tend to be upwardly or downwardly deflected by kinking when exposed to a load. In order to counter this tendency, the cross beam can exhibit a hat-shaped cross section. Having regions corresponding to the brim of the hat adjoin the flanks of the groove from above and below allows them to hamper the outward kinking of the flanks, thereby contributing significantly to the load-bearing capacity.

In order to achieve a sufficient shock-absorbing effect even when a foreign body hits the vehicle right before one of the longitudinal beams, an energy absorber can be secured to the exterior of the fastening flange.

In order to enable an efficient production, the energy absorber can be injection molded onto the fastening flange, just like the aforementioned supplemental segment.

An energy absorber with a honeycomb structure is especially suitable for injection molding.

Having the combs of the honeycomb structure be open in the vertical direction permits the use of simple molding tools with a low number of mold parts that are movable relative to each other.

DETAILED DESCRIPTION

FIG. 1shows a bumper module1for a motor vehicle according to a first embodiment of the present disclosure in a perspective view. A cross beam2of the bumper module1is formed as an elongated, downwardly open groove with an inner wall3facing the interior of the vehicle in a state mounted to the vehicle, an outer wall4sheathed by a bumper skin, and a rounded apex5that joins the inner and outer wall3,4as a single piece. A central portion6of the cross beam2is convexly curved toward the vehicle exterior as viewed from above. Lateral segments8extending along a straight line in the transverse direction of the vehicle adjoin the central portion on either side, over short, outwardly concavely curved intermediate segments7.

FIG. 2shows a cross section through one of the lateral segments8. The cross beam2is obtained by thermoforming a rectangular blank out of organo sheet, and an internal fiber layer9of the organo sheet extends continuously over the inner wall3, apex5and outer wall4. The fiber layer9is embedded into a matrix10included of thermoplastic material; onFIG. 2, the matrix10forms surface layers that surround the fiber layer on both sides; in practice, the fibers in the layer9can reach as far as the surfaces of the cross beam2.

Injection molded over the entire width of the cross beam2inside of the groove are ribs11, which integrally join the inner and outer wall3,4together. The plastic including the ribs11is chemically identical to that of the matrix10; at the temperature at which the ribs11are injection molded onto the cross beam2, the matrix10is thus also soft, and can enter into an integral bond with the molded on material.

At the height of the lateral segment8, the inner wall3forms a respective fastening flange12, which is provided to be fastened at the end of a longitudinal beam13of the vehicle (denoted by dashed lines onFIG. 2) by means of screws, bolts or the like. Initial holes14for these screws are located in a lower edge area15of the fastening flange12, below a lower edge16of the outer wall4. As a result, they are readily accessible from outside while mounting the bumper module1onto the longitudinal beams. The holes14cross the fiber layer9, which here extends until directly the lower edge of the fastening flange12.

Additional holes17are formed on a segment18of the fastening flange12, which lengthens the inner wall3in a flush manner, extending upwardly until beyond the apex5. The segment18is molded onto the cross beam2just like the ribs, and melted with the plastic including the matrix10. In order to create a connection with the cross beam2that can bear a load, the segment18has a wedge-shaped cross section, with a wall thickness that increases toward the cross beam2.

In one variant, a lower edge of the inner wall3runs at the same height as the lower edge16of the outer wall4in the central portion6. The fiber layer9then does not extend until the lower edge area15of the fastening flange12, with this edge area15instead being created via through injection molding, just like the segment18.

FIG. 1shows a block-shaped energy absorber19at the lateral segments8in front of the outer wall4. The energy absorber19is also created via injection molding on the cross beam2. As evident fromFIG. 2, the energy absorber19has a honeycomb structure, with a base plate20that extends horizontally outward from the outer wall, and walls22that protrude upwardly and downwardly from the base plate, bordering combs21that are open at the upper and lower sides of the energy absorber19.

Lines23at which the walls22intersect each other each lie parallel to the outer wall4. This makes it possible, in a single operation, to use only two molding tool parts24,25, which are moved toward each other in the direction of the lines23, to mold the organo sheet blank to the cross beam2, injection mold the segments18, ribs11and energy absorber19and potentially edge areas15to the cross beam with the mold closed, and demold the finished bumper module by pulling apart the molding tool parts24,25along the lines23.

FIG. 3shows variants of energy absorbers19in a top view. The energy absorber19onFIG. 3ahas diamond-shaped combs21on a rectangular base area, which is flush with the fastening flange12in the longitudinal direction of the vehicle.

OnFIG. 3b, diagonally oriented walls22of the energy absorber19extend beyond the fastening flange12until the concavely curved intermediate segment7, and stiffen the latter.

In the variant onFIG. 3c, the energy absorber19fills the entire space between the cross beam2and a bumper skin26, wherein the expansion by the energy absorber19in the longitudinal direction of the vehicle gets increasingly smaller toward the middle of the central portion6, and can reach zero.

Of course, the combs21can also exhibit base areas that are not diamond shaped, e.g., triangular or hexagonal ones.

FIGS. 4 and 5show a second embodiment of the bumper module in a perspective view, as well as in several sections. Here as well, the cross beam2is obtained by thermoforming a rectangular organo sheet blank, but the latter is not formed with two walls. Instead, the blank remains unformed in the fastening flanges12, so as to abut flatly against the ends of the longitudinal beam, and a horizontally running groove27open to the vehicle interior is formed in blank in the intermediate segments7and central portion6. Strips28that protrude over and under the groove27impart a hat-shaped cross section to the cross beam2. The depth d of the groove27increases from the sides to the middle of the cross beam2. Since the organo sheet is not expanded in the thermoforming process, the vertical dimension h of the bumper module is largest at the fastening flanges12, as illustrated onFIG. 5a, and reaches a minimum in the central portion6onFIG. 5c, wherein the depth d is the largest.

Forming the hat profile and stiffening ribs11inside of the groove27requires two molding tool parts, which can move relative to each other in the longitudinal direction of the vehicle.

Two additional molding tool parts are required for molding energy absorbers19with upwardly and downwardly open combs21onto the fastening flange12, as depicted onFIG. 5a.

In order to reduce the number of required molding tool parts, consideration could be given to an energy absorber19with combs21open in the longitudinal direction of the vehicle, as shown onFIG. 6. However, as a result of the long demolding path, the walls22of the energy absorber19reach a high thickness at their end facing the fastening flange12. As a consequence, and also for reasons of weight and an improved compressibility, preference goes to an energy absorber19with a base plate that extends in the longitudinal direction of the vehicle and combs that extend from this base plate in opposite directions, as shown onFIGS. 2 and 5.