Bumper for a motor vehicle

A bumper for a motor vehicle includes, but is not limited to a bumper shell having an outer surface and a cut-out opening. A cut edge of the opening meets the outer surface at a sharp edge. A frame inserted into the opening covers the cut edge and an exposed outer surface of the frame has a convex curvature with a curvature radius of at least approximately 2 mm.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No. 102009048336.5, filed Oct. 6, 2009, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a bumper, more preferably a rear bumper for a motor vehicle.

BACKGROUND

The bumpers of modern motor vehicles mostly comprise a large-area bumper shell that forms a part of the visible outer skin of the vehicle. On the one hand it is designed in order to absorb and yield backwards subject to minor energy absorption, on the other hand it covers parts of the bumper such as a cross member which are able to deform subject to the absorption of large amounts of energy.

It is desirable that the bumper does not have any unnecessarily sharp exposed edges. A motor vehicle in Europe can therefore only be approved for road traffic if it does not have any edges with a curvature radius of less than 2.5 mm which could come in contact with a test body of 100 mm diameter impacting the body. In order to satisfy this requirement, openings of the bumper shell which for instance are required for the installation of headlamps are usually not simply punched out of the bumper shell but comprise a short socket extending all around the opening and engaging into the vehicle interior which socket via a continuous curvature merges with the outer surface of the bumper shell. During the molding of the bumper shell, this curvature can be easily created with the necessary radius but requires adapted tooling in each case.

An opening, which is only present in a part of the bumpers of a series, increases the cost of production substantially since separate sets of molding tools for the production of bumper shells with and without opening are required. In order to avoid these costs the applicant has developed a bumper wherein an opening of the bumper shell through which a load carrier, more preferably a bicycle carrier, can be pulled out of the body, is subsequently cut into a finished molded bumper shell. Although through the subsequent cutting of the opening a sharp edge, at which a cut edge of the opening meets the outer surface of the bumper, is created, this does not however create any licensing problems since the opening is formed in a depression of the bumper that also accommodates the license plate so that the sharp edge is not accessible to the above-mentioned test body. If however the opening can only be formed in a depression of the bumper shell this results in substantial restrictions in the design freedom of the body.

Therefore, there is at least a need for a bumper for a motor vehicle which despite an opening cut out with a sharp edge can be licensable without the opening on the bumper shell having to be arranged in a depressed manner. In addition, other needs, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.

SUMMARY

A bumper for a motor vehicle is provided with a bumper shell having an outer surface and a cut-out opening, wherein a cut edge of the opening meets a sharp edge on the outer surface, a frame inserted in the opening covers the cut edge and a freely exposed outer surface of the frame comprises a convex curvature with a curvature radius of at least 2 mm. Here it is thus not the recessed arrangement of the opening that prevents the contact of the test body with the sharp edge but the frame inserted in the opening.

According to one embodiment, the freely exposed outer surface of the frame joins the outer surface of the bumper shell in a flush manner (SeeFIG. 2); alternatively it is also possible that the frame protrudes over the outer surface of the bumper shell. Any sharp curvature in the common outer surface of the bumper shell and the frame at the transition between the two possibly resulting from this protrusion does not impair the licensability of a vehicle equipped with the bumper according to the invention, since this curvature is concave and it cannot be entered by a test body.

While the bumper shell can be cost-effectively deep drawn in the usual manner known per se the frame is preferentially injection molded. Since the dimensions of the frame in general are significantly smaller than those of the bumper shell, the costs involved in the provision of molding tools for the frame as a rule are substantially lower than the costs of a second set of molding tools for a complete bumper shell, even if the first are injection molding tools and the latter deep drawing tools.

In order to anchor the frame on the bumper over a large area that can be subjected to load the frame is preferentially provided with a leg bearing against an inner surface of the bumper shell. This leg is preferentially welded to the inner surface of the bumper shell, more preferably ultrasound-welded or glued.

In order to exactly determine the position of the frame on the bumper shell despite possible manufacturing tolerances and more preferably to guarantee a small gap width between the cut edge and the part of the frame covering it, openings can be provided on the leg that are penetrated by protrusions of the bumper shell. Such protrusions can be joined to the bumper shell but these can also be lugs of the bumper shell obtained when cutting the opening of the bumper shell and angled-off into the interior of the body.

The bumper shell at least on its outer surface is usually provided with a coat of paint in order to lend it a uniform appearance with adjoining body panels. The cut edge is preferentially free of the paint layer. Such a bumper shell can be practically obtained in that the opening is cut after the painting. This has advantages in terms of manufacturing logistics since for the production of different vehicle types painted bumper shells with and without opening need not be stocked separately.

The frame, too, preferentially has a paint layer at least on its outer surface so that on the finish assembled vehicle it is not conspicuous as an element separate from the bumper shell. By painting bumper shells and frames with paint of a same batch, deviations in shades of color between both can be easily avoided.

In that the bumper shells and frames are painted separately, separate paint layers are obtained on both and there is no risk of tearing open of a continuous paint layer at a joint between bumper shell and frame.

Preferentially, a movable lid is arranged in the opening in order to conceal an equipment part extendable through the opening when not in use. A stop defining a position of the lid that is flush with the outer surface of the bumper shell can be formed on the frame. The equipment part preferentially is a load carrier, more preferably for bicycles.

For the case that a license plate is mounted to the bumper or another part of the motor vehicle body above the opening so that it can be obscured by a load placed on the load carrier, an additional license plate is practically extendable with the load carrier from the opening.

DETAILED DESCRIPTION

FIG. 1shows a bumper shell1for the tail area of a motor vehicle in a schematic perspective view. The bumper shell1is unitarily deep drawn from plastic. It comprises a horizontal center piece2which extends over the entire width of the vehicle body and two arms4extending upwards from the ends of the center piece on both sides of a tail gate clearance3covering vertical edges of the tail of the body.

In a transition region between the center piece2and the arms4, openings5for rear fog lamps are provided. These openings5are obtained through pressing-in a depression in the flat material of the bumper shell1during the deep drawing and punching-out of a bottom of the depression and are thus each surrounded by a short socket reaching into the interior of the body, whose inner surface via an evenly curved edge region merges with the outer surface of the bumper shell1. The curvature of this edge region is predetermined through the shape of the molding tools used for deep drawing and can typically amount to about 5 to 6 mm.

A large-area opening6in a central region of the centerpiece2is provided in order to extend through it a bicycle carrier lowered into the body when not in use, as still described in more detail by means ofFIG. 2. Since such a bicycle carrier is not available as standard with all vehicles of a same type but is ordered by the customer if required, the opening6is only required with a part of the bumper shells of a given vehicle type. In order to be able to deep draw the bumper shells with and without the opening6with a same set of tools it is therefore practical to subsequently produce the opening6in the deep drawn bumper shell1, more preferably through punching out. As is evident in the section ofFIG. 2, cut edges8substantially orientated at a right angle to the outer surface7of the bumper shell1are created which, where these meet with the outer surface7, form a sharp edge9.

Since the edge9is not located in a depression of the bumper shell1- a depression accommodating a license plate can for example be provided on the tailgate of the vehicle which is not shown - contact of the edge9with a test body striking it is not excluded if no suitable countermeasures are taken. These countermeasures consist of a square frame10unitarily injection molded and inserted into the opening6whose four sides each comprise a leg11bearing against an inner surface of the bumper shell1and fastened to this inner surface through gluing or welding, more preferably ultrasonic welding and a second leg12crossing this first leg11substantially at a right angle, wherein a section of the leg12protruding over the leg11which conceals the cut edges8comprises an outer surface13which at the edge9joins the outer surface7of the bumper shell1in a flush manner. An evenly curved section of this outer surface13has a curvature radius of 2.5 mm or more. Thus, contact of the test body with surface regions having a smaller curvature radius than about 2.5 mm is excluded.

A bicycle carrier14extendable through the opening6is shown in the sunk position inFIG. 2in which a lid15of the bicycle carrier14closes the opening6substantially flush with the outer surface7. The lid15is held by two longitudinal members16movable in vehicle longitudinal direction which are arranged on both sides of the cutting plane ofFIG. 2. Buffers24fastened to the frame10form a stop for the lid15in the sunken position. A holder17with a license plate18fastened thereto is pivotably fastened to an outer end of the two members16so that when the bicycle carrier14is extended from the opening6it can be folded into an upright position in which the license plate18as substitute for the license plate of the tailgate possibly obscured by the bicycles mounted on the bicycle carrier14is visible.

On the longitudinal members16several pairs of cross members19are displaceably mounted in vehicle transverse direction. Each cross member19carries a clamp20on a longitudinal end each for gripping a front or rear wheel of a bicycle. The cross members19are adjustable in vehicle transverse direction between a pushed-together position in which they fit through the opening6and a pulled-apart position in which they laterally extend in front of the centerpiece2beyond the opening6. Between two pairs of cross members19pillars21are accommodated which in the extended position of the vehicle carrier14can be pivoted into an upright position about axes oriented in vehicle longitudinal direction, in which position the frame of a bicycle held in the clamps20of the cross members19can be fixed in each case.

The bumper shell1and the frame10are each painted in the same shade of color separately from each other, so that in the finished joined state it is not conspicuous that these are two separate parts. On the bumper shell1the paint layer is only applied to the outer surface7before the punching out of the opening6; on the frame10at least the surface of the leg11facing the bumper shell1is cleared from the paint layer so as not to hinder the welding of the frame10to the bumper shell1.

Manufacturing tolerances during deep drawing of the bumper shell1or during punching out of its opening6or during the injection molding of the frame10can result in that between the cut edges8and the leg12of the frame10a gap remains open. In order to prevent this or in order to guarantee a uniform width of this gap over its entire length, it is proposed according to a second configuration of the invention to punch out the opening6in the form shown inFIG. 3with straps23protruding into the interior, wherein the straps23in a further processing step following the punching or preferentially through the punching tool itself are bent off at a right angle into the interior of the bumper shell1. Matching the straps23, slits24are formed in the leg11of the frame10directly adjoining the protruding leg12, as is shown in the front view ofFIG. 4. By inserting the straps23into the slits24during the installation of the frame a uniform small gap width all around the opening6can be ensured.FIG. 5shows a section through the bumper shell1and the frame10along the plane designated V-V inFIGS. 3 and 4each, in which the engagement of the straps23in the slits24is shown.

FIG. 6shows a modification of the principle described with reference toFIG. 3toFIG. 5according to which on the bumper shell1during the punching-out of the opening6instead of the straps23non-visible reference marks25are formed on the outer surface7. These reference marks formed with minimum tolerance relative to the cut edges8define the locations on the inner surface of the bumper shell1in which in a subsequent production step molded bodies26are fastened each of which molded bodies comprises a foot27bearing against the inner surface of the bumper shell1in a flat manner and at least one strap28standing away. The frame10in turn is provided with slits24which are so placed on the leg11that when these accommodate the straps27the cut edges8immediately bear against the legs12of the frame10. Thus, the gap width between the legs12and the cut edges8can be reduced to a minimum.