GB2484180A

GB2484180A - Vehicle bonnet

Info

Publication number: GB2484180A
Application number: GB201115562A
Authority: GB
Inventors: Uwe Schmitz; Joachim Scha Fer; Grace Mary Thompson
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2010-09-08
Filing date: 2011-09-08
Publication date: 2012-04-04
Anticipated expiration: 2031-09-08
Also published as: DE102010044668A1; GB201115562D0; GB2484180B

Abstract

AÂ planar vehicle body part for a motor vehicle, in particular a front hood or bonnet, comprises a visible plate 2 and a stiffening structure, which is fastened on an inner side of the visible plate 2 and is formed from planar material. At least one elongated concavity 10, 12 is formed on a surface of the stiffening structure facing away from the visible plate 2. At least one tension band 14 is fastened to the stiffening structure on both sides of the concavity 10, 12 and bridges the concavity 10, 12 spaced apart therefrom.

Description

Vehicle body part for a motor vehicle

Description

The present invention relates to a planar vehicle body part, which is exposed on a motor vehicle body and is capable of coming into contact with a pedestrian and being deformed. In particular, the invention relates to a front hood for a motor vehicle.

In order to meet the legal requirements for pedestrian protection, such vehicle body parts must have a precisely optimized stiffness, in order to yield upon a collision with a pedestrian and thus J 5 be able to soften the impact, on the one hand, but to prevent the pedestrian from crashing * through onto parts of the vehicle which are concealed by the vehicle body part and are not * ** .o * * yielding, such as an engine block, on the other hand. sS**

°°* A planar vehicle body part according to the preamble of Claim 1 is known from DEl 01 09663Al.

** 0 sSO * 0 The engine hood described in this document comprises a visible plate or an upper plate and a stiffening structure located underneath. The stiffening structure comprises a frame connected to the edges of the visible plate as well as multiple bows, which extend within the frame and 00*00* * support the visible plate. The bows each have a hat-shaped cross-section having edge webs pressing against the visible plate, a middle part spaced apart from the visible plate, and side walls, which each connect the middle part to one edge web and are to buckle if the hood is strongly strained, for example, in the event of contact with a pedestrian. In order to achieve different required stiffness values in each of the various areas of the engine hood, it is proposed that the side walls of the bows, which support an area of the hood in which greater flexibility is desired, be provided with slots along the target buckle lines. Therefore, the material expenditure for the manufacturing of the bows is high in relation to their stiffening effect. The material costs for the manufacturing of the hood are therefore substantial, and its high weight increases the fuel consumption of a motor vehicle in which it is installed.

The object of the present invention is to provide a planar vehicle body part for a motor vehicle, which allows a required stiffness to be achieved with little material expenditure and correspondingly low costs and low weight.

The object is achieved in that, in a planar vehicle body part having a visible plate and a stiffening structure, which is fastened on an inner side of the visible plate and is formed from flat material, and which has at least one concavity on its surface facing away from the visible plate, at least one tension-resistant element is fastened to the stiffening structure on both sides of the concavity and bridges the concavity spaced apart therefrom. In that this element is placed under tension upon strain of the vehicle body part, for example, by an impacting pedestrian, it is capable of forcing a multiple fold of the flat material of the stiffening structure on the bridge concavity and in this way dissipating a large quantity of impact energy even in the event of a low wall thickness of the visible plate and the stiffening structure. Since the tension-resistant element locally reinforces the vehicle body part, instead of locally weakening it, thin-walled flat J 5 material can be used for the visible plate and the stiffening structure, and material costs and * weight can be saved.

***.** * * The stiffening structure essentially completely fills up the inner side of the visible plate, in order to be able to better withstand the forces generated in case of strain by the tension belt, which *I*,Ss * ±0 act tangentially to the surface of the vehicle body part.

* The tension-resistant element can overlap a large area of an area of the vehicle body part to be S.....

* stiffened. However, in order to minimize the weight of the vehicle body part, it is preferably implemented as band-shaped.

Such a band-shaped tension-resistant element is expediently oriented in the direction of an expansion occurring in the event of deformation of the vehicle body part, in order to make it more difficult, i.e., in the case of an elongated cavity, whose edges move apart from one another during deformation, the tension-resistant element is to be oriented transversely to the concavity.

According to a first embodiment, at least one rib having two side walls and a middle part connecting the side walls is formed between two areas supporting the visible plate in the stiffening structure, and the tension band is fastened on the two supporting areas and traverses the rib. The above-mentioned elongated concavity is provided twice in this case and formed in each case by one side wall and the supporting area of the stiffening structure adjoining thereto.

According to a second embodiment, at least one rib having two side walls and a middle part connecting the side walls, which supports the visible plate here, however, is formed between two areas spaced apart from the visible plate in the stiffening structure, and the tension band is fastened on the two spaced-apart areas, traversing the rib. I.e., while the rib faces away from the visible plate in the first embodiment, it faces toward it in the second embodiment and presses against it.

The ribs can run parallel to one another over the inner side of the visible plate.

Alternatively, a star-shaped arrangement of the ribs also comes into consideration. Such a star-shaped arrangement is expedient in particular to prevent a central area of the planar vehicle body part, which is far away from the edges of the planar vehicle body part supported on the * other vehicle body parts, from yielding more easily under load than areas close to the edge. * S

In order to additionally improve the stiffness of this central area, a tension band can span a center point of this star-shaped arrangement. * 20

In order to be able to monitor the flexibility of areas of the vehicle body part enclosing this center point, tension bands can be placed in an arc around the center point. * S

In order to simplify the assembly of the vehicle body part, it can be provided that one tension band traverses multiple ribs.

This tension band can be fastened on each traversed rib, or it can be fastened to the stiffening structure on both sides of each traversed rib.

In order to force a strong deformation of the areas of the reinforcement structure bridged by the tension band in the event of an impact, the tension band is preferably inelastic. Such an inelastic tension band preferably comprises metal, for example, it can be cut to size in a' strip shape from sheet metal.

In the interest of simple and cost-effective manufacturing, it is preferable for the tension band to comprise the same material as the visible plate and/or the stiffening structure.

Further features and advantages of the invention result from the following description of exemplary embodiments with reference to the appended figures. In the figures: Figure 1 shows a schematic view from below of a motor vehicle front hood as an example of a planar vehicle body part according to the invention; Figure 2 shows a schematic section through the hood of Figure 1 along the section line of Figure 1 identified by Il-Il; Figure 3 shows a schematic section along line Ill-Ill from Figure 1; *15 Figure 4 shows a view similar to Figure 1 of a motor vehicle front hood according to a * S.. S. * : second embodiment of the invention; ***.** * I Figure 5 shows a section through the hood of Figure 4 along the line identified by V-V; and S..... * 20

Figure 6 shows a section similar to FigureS according to a further embodiment; and S...

*....S * Figure 7 shows a view similar to Figure 1 of a motor vehicle front hood according to a third embodiment of the invention.

A first embodiment of the vehicle body part according to the invention will be described with reference to Figures 1 to 3. Figure 1 shows the vehicle body part, a front hood 1, in a view from below, Figure 2 shows it in longitudinal section along plane Il-Il from Figure 1, and Figure 3 shows it in cross-section along plane Ill-Ill. The front hood I comprises a visible plate 2, which is exposed after the installation of the front hood 1 in a motor vehicle, and which, in the view of Figure 1, is ony not concealed by a reinforcement structure 3 therein, where the latter has openings, e.g., for the attachment of a hood latch, cushions, or the like. Both the visible plate 1 and also the reinforcement structure 3 are formed from steel or aluminum plate. Trenches 4, 5, 6, which are pressed into the reinforcement structure 3, form a frame, which extends along the edges of the front hood 1. The trenches 4, 5, 6 are each flanked on both sides by strips 7, 8, which press against the inner side of the visible plate 2 and are fastened thereon in any arbitrary suitable way. The fastening can be performed, for example, by gluing; in the case of the edge-side strips 7, fastening by flanging the strips 7 with the edge of the visible plate 2 also comes into consideration.

The strips 8 enclose a central area 9 of the reinforcement structure 3, in which multiple ribs 10 running parallel to one another in the vehicle longitudinal direction are formed. Middle parts 11 of the ribs 10 press against the visible plate 2 and are fastened thereto in the same way as the strips 8. Side walls 12 of the ribs 10 flanking the middle parts 11 extend diagonally from the visible plate 2 and are connected to one another and to the strips 8 by the zones 13 of the central area 9 which are spaced apart from the front hood 1. A tension band 14, which is formed from steel or aluminum plate like the reinforcement structure 3, bridges the ribs 10 and is fastened on both sides of each rib 10 to the spaced-apart zones 13, e.g., by spot welds 15 or by clinching. * S

* If pressure acts from above, for example, on a point of the front hood I identified by 16 in Figure 3, the front hood 1 tends to yietd under this pressure. The tension band 14 is thus placed under 1: tension. The tension band 14 thus prevents the side waIls 12 of the rib 10 lying directly below r':2o the point 16 from yielding to the pressure in the lateral direction. Inelastic yielding of the hood 1 under the pressure is therefore only possible if the side waIls 12 of this rib 10 buckle under the pressure. Since these side walls are narrow in comparison to the spaced-apart zones 13 S.. .S.

* adjoining them, a substantially higher force is required for compressing the side walls 12 than if the side waIls 12 only yielded and the spaced-apart zones 13 were bent, As a result, a high bending strength of the hood I can be implemented even with low material thickness of the visible plate 2 and/or the reinforcement structure 3. Furthermore, as a result of the fastening of the tension band 14 on the spaced-apart zones 13, the force acting on the point 16 is distributed in the width direction of the hood 1. In order to allow yielding of the hood 1, therefore, not only must the side walls of the rib 10 directly adjacent to the action point 16 be deformed, but rather also the remote ribs 10. This also contributes to the improved stiffness.

In the illustration of Figure 3, the middle parts 11 are clearly narrower than the spaced-apart zones 13. However, the middle parts 11 can also be just as wide or even wider than the spaced-apart zones 13, so that one spaced-apart zone 13 and the side walls 12 adjoining it can be considered to be one rib, which protrudes from a central area 9 of the reinforcement structure essentially pressing against the visible plate 2.

Figure 4 shows a view similar to Figure 1 of a front hood I according to a second embodiment of the invention. This embodiment takes into consideration the fact that the front hood I is generally supported, via the peripheral frame 4, 5, 6 of the reinforcement structure 3, on other vehicle body parts and, if no suitable countermeasures are taken, yields more easily under an externally acting force the further the action point 16 of this force is from the frame. ln that in this embodiment ribs 10 having middle parts 11 pressing against the visible plate 2 run toward a center point 17 of the hood or cross it, the flexibility of the hood 1 is decreased in the surroundings of the center point 17.

As an additional contribution to the stiffening of the hood 1 in the surroundings of the center point 17, a tension band 18 is provided here, which spans the rib 10 crossing the center point 17 J 5 and is fastened on both sides thereof on zones 13 of the reinforcement structure 3 spaced apart * from the visible plate 2.

I.. *SS * S As a measure for stiffening the hood, additional tension bands 19, 20 can also be provided in the further surroundings of the center point 17, which each traverse one or more of the ribs 10 S.....

* 20 running toward the center point 17 from various directions. Since the tension bands are each most effective when they traverse the ribs 10 perpendicularly, the tension bands 191 which each only traverse one single rib 10, form an arc around the center point 17. * S

In order to accelerate the assembly of the hood 1, the tension bands 19, as shown in the right half of Figure 4, can be replaced by a single arc-shaped tension band 21.

As may be recognized in Figure 5, the attachment of the tension band 18 to the central rib 10 crossing the center point 17 is similar to the case shown in Figure 3; spot welds 15 or clinches or similar features fix the tension band 18 on zones 13 spaced apart from the visible plate 2 on both sides of the rib 10. The middle parts 11 are also significantly narrower than the spaced-apart zones 13 in Figure 5. The middle parts 11 can also be just as wide or even wider than the spaced-apart zones 13.

Figure 6 shows a section similar to Figure 5 according to a third embodiment of the front hood.

The central area 9 of the reinforcement structure 3 predominantly presses directly against the visible plate 2 here and only the ribs 10 -which may be distributed as shown in Figure 1 or Figure 4 -are spaced apart from the visible plate 2. One side wall 12 of the rib 10 and one strip 22 of the central area 9, which adjoins the side wall and touches the visible plate 2, form a concavity in each case here, which is spanned by a tension band 23, which is welded on both sides of the rib 10 to the reinforcement structure 3 and optionally also on the middle part 11 of the rib 10. As in the above-described embodiments, the tension band 23 forces the side wall 12 to buckle under load in a small space under high force expenditure and thus contributes to the stiffness of the front hood 1.

Instead of the tension band 23 shown in Figure 6, which spans a single rib 10, a tension band which is wavy in cross-section, bridges multiple ribs, and is fastened to the reinforcement structure 3 between the ribs can also be used.

S.....

* Figure 7 shows a third embodiment of the front hood I in a view similar to Figure 1 and Figure r°: 4. The plurality of the tension bands of the second embodiment is replaced here by a single plate 24, which covers the same areas of the reinforcement structure as these tension bands °* and additionally also areas lying in between. The large-area coverage by the plate 24 allows *.*..

* 0 multiple pairs of spot welds 15 or clinch connections to be attached over the length of the ribs lOin each case. An imaginary connection line between two spot welds 15 or clinch connections * * of such a pair extends like the above-described tension bands transversely to the rib 10, which * they flank, so that a tension force acting between the two spot welds 15 or clinch connections in the plate 24 does not cause a strain of the rib 10 in its longitudinal direction.

Fundamentally the principle of the tension band can be successfully applied to optimize the deformation behavior of a vehicle hood independently of the rib shape, so that hood weight can be saved with equal or better pedestrian protection performance.

List of reference numerals 1 front hood 2 visible plate 3 stiffening structure 4 trench trench LO 6 trench 7 strip 8 strip 9 central area rib 11 rniddlepart *S ** * 12 sidewall * *.*** * * 13 spaced-apart zone 14 tension band sen spotweld *.*s*.

16 action point 17 centerpoint 5.,, 18 tension band * C 19 tension band tension band 21 tension band 22 strip 23 tension band 24 plate

Claims

Patent Claims 1. A planar vehicle body part (1) having a visible plate (2) and a stiffening structure (3), which is fastened on an inner side of the visible plate (2) and is formed from planar material, and which has at least one concavity (10; 12, 22) on its surface facing away from the visible plate (2), characterized in that at least one tension-resistant element (14; 18; 19; 21; 23) is fastened to the stiffening structure (3) on both sides of the concavity (10; 12, 22) and bridges the concavity (10; 12, 22) spaced apart therefrom.
2. The vehicle body part according to Claim I characterized in that the tension-resistant element (14; 18; 19; 21; 23) is band-shaped.
3. The vehicle body part according to Claim 2, characterized in that the concavity (10; 12, * efl* * 22) is elongated and the band-shaped tension-resistant element (14; 18; 19; 21; 23) * ***** * extends transversely to the concavity (10; 12, 22). S.
4. The vehicle body part according to Claim 1, 2, or 3, characterized in that, in the stiffening ** SSS' * 20 structure (3), at least one rib (10) having two side walls (12) and a middle part (11) connecting the side walls (12) is formed between two areas (22) supporting the visible *0S plate (2), and the tension band (23) is fastened on the two supporting areas (22) and *5S.** * traverses the rib (10).
5. The vehicle body part according to Claim 1, 2, or 3, characterized in that, in the stiffening structure (3), at least one rib (10) having two side walls (12) and a middle part (11), which supports the visible plate (2) and connects the side walls (12), is formed between two areas (13) spaced apart from the visible plate (2), and the tension band (14; 18; 19; 20; 21) is fastened on the two spaced-apart areas (13) and traverses the rib (10).
6. The vehicle body part according to Claim 4 or 5, characterized in that the ribs (10) run parallel adjacent to one another over the inner side of the visible plate (2).
7. The vehicle body part according to Claim 4 or 5, characterized in that the ribs (10) are situated in a star shape.
8. The vehicle body part according to Claim 7, characterized in that tension bands (19, 21) are placed in an arc around a center point (17) of the star-shaped arrangement.
9. The vehicle body part according to Claim 7 or 8, characterized in that a tension band (18) spans a center point (17) of the star-shaped arrangement.
10. The vehicle body part according to one of Claims 6 to 9, characterized in that the at least one tension band (14; 20; 21) traverses multiple ribs (10).
11. The vehicle body part according to Claim 10, characterized in that the tension band (14) is fastened on each traversed rib (12, 13). *15

*
12. The vehicle body part according to Claim 10, characterized in that the tension band (14; 18; 19; 21; 23) is fastened to the reinforcement structure on both sides of each traversed rib (10). *.**

* *20
13. The vehicle body part according to one of the preceding claims, characterized in that the tension band (14; 18; 19; 21; 23) is inelastic. ****

*
14. The vehicle body part according to one of the preceding claims, characterized in that the tension band (14; 18; 19; 21; 23) comprises the same material as the visible plate (2) and/or the stiffening structure (3).
15. The vehicle body part according to one of the preceding claims, characterized in that it is a front hood (1).