AU2002358415B2

AU2002358415B2 - Front structure of a motor vehicle

Info

Publication number: AU2002358415B2
Application number: AU2002358415A
Authority: AU
Inventors: Curd-Sigmund Bottcher
Original assignee: Adam Opel GmbH
Current assignee: Adam Opel GmbH
Priority date: 2001-11-03
Filing date: 2002-11-02
Publication date: 2008-04-03
Anticipated expiration: 2022-11-02
Also published as: DE10154113A1; ES2243785T3; DE50203595D1; EP1451041B1; JP2005510395A; WO2003039915A1; CN1330516C; CN1694824A; ATE299102T1; EP1451041A1

Abstract

According to the invention, the requirements for the protection of pedestrians in a collision and the requirements for easy repair of collided vehicles can be combined, whereby the front structure comprises two bumpers (4, 5), supported on each of both sides on a longitudinal support (2, 3), by means of a crash box (10, 10', 11, 11'). A foam layer (25) is provided on a transverse support (6) for the upper bumper (5), which takes the impact of a collision with a pedestrian, and the crash boxes (10, 10') for the lower bumper (4) run forwards over the foam layer (25) such that the forces of a light collision with another vehicle or a fixed obstacle are absorbed by deformation directly after the first contact. As the foam layer (25) is set back relative to the lower crash box (10, 10'), a protection for pedestrians can be achieved without leading to a significant increase in vehicle length.

Description

Front structure of a motor vehicle The invention concerns the front structure of a motor vehicle with a bottom E bumper bar and a top bumper bar arranged above it.

A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was, in "Australia, known or that the information it contains was part of the common (0 Cc general knowledge as at the priority date of any of the claims.

Such a front structure is described in FR 2 445 783. Both bumper bars are fastened on a front transverse wall of the chassis via lamellae-like mountings.

EP 1 138 557 is also known to the applicant. According to it both bumper bars are provided with a foam material cushion.

A front structure is known to the applicant also from EP 1 000 840 A2. The front structure presented there has two superposed transverse supports, forming the bumper bar, the transverse supports fastened independently from one another on a pair of longitudinal supports. With such an arrangement several load paths are to be produced to absorb the energy of the impact and distribute it to the front structure in conjunction with a large-area impact shield.

In addition, a better protection of the passenger against impact is to be achieved. This is particularly valid for the bottom transverse support that can be tuned to suit a collision with a pedestrian.

However, the bottom transverse support is not decisive as far as the severity of injury is concerned for a pedestrian that is hit frontally by a vehicle. The typical progress of movement is rather that both bumper bars will hit the lower leg of the pedestrian, due to which the pedestrian experiences a rotation relative to the vehicle and impacts with the upper body on the bonnet. This is described as the wrapping of the body around the contour of the vehicle. On this occasion in the initial phase of the movement the leg tilts about the top bumper bar and is simultaneously disengaged from the bottom bumper bar, so that as T:MDDM O2358415retped pages(12.3 08) doc la oo o far as the severity of the injury is concerned the decisive factor is the force acting upon the top transverse support.

A system of two superposed transverse supports for bumper bars is known to the applicant also from DE 198 02 841 Al. These are displaceably arranged relative to the oo iO T:DDMff2002358415-reped pages(12.3.08) doc longitudinal axis of the chassis. In the basic position the top transverse support is situated in the front of the bottom transverse support, so that the initial contact of the pedestrian takes place with the top transverse support. To ensure that the body of the pedestrian will actually hit the bonnet and is not thrown forward, the bottom transverse support, affected by the collision, should be extended and the pedestrian lifted, as it were, onto the bonnet.

However, for the most common pedestrian accidents such a construction is not necessary, because the top transverse support engages the body of the pedestrian already so far below the centre of gravity of the body, that the pedestrian will hit the bonnet even without the arrangement described in DE 198 02 841 Al.

It is decisive, generally and in both of the above suggestions, that the forces, introduced into the top transverse support, lie below a certain limit value, so that the legs will not break, at lea'st below a certain collision speed. The limit values are determined by law or by decrees. It has been established that this can be achieved only when the top transverse support is padded, i.e. is provided with a relatively soft layer of foam material, that is approx. 8 cm thick.

When the vehicle is driven against another vehicle or a firm obstacle, the foam material layer cannot offer any effective resistance due to its softness. Therefore the collision energy occurring on this occasion has to be absorbed by parts of the chassis that are situated behind the bumper bars. Thus the layer of foam results, corresponding to its thickness, in an extension of the length of the vehicle, that is not always desirable.

One could think of correspondingly shorten the longitudinal supports of the vehicle, which absorb the energy in the case of a high-energy impact, i.e. in the case of an impact with another vehicle or a firm obstacle. This, however, cannot be accepted at all, since in that case neither the regulations regarding an impact at 50 or 60 km/h, for example, against a firm obstacle nor the Danner requirements (see below) could be adhered to.

AMENDED PAGE 3 00 oo Thus the invention is based on the problem to produce a front structure, that is Scompatible with pedestrians, i.e. is so constructed that in the case of a collision Swith a pedestrian only such forces are introduced into the legs of the pedestrian which are below a certain limit value, as well as it is capable to absorb energy in the case of a high-energy impact, therefore in the case of an impact with another vehicle or a firm obstacle. This should, however, be achieved under the condition that an extension of the length of the vehicle is, 00 as far as possible, prevented. In addition, in the case of light collisions of this 00 Ckind the front structure should be able to be easily repaired.

SAccording to a broad aspect of the present invention, there is provided a frontal structure of a motor vehicle including a lower bumper and an upper bumper arranged thereabove, wherein the front face of the upper bumper includes a layer of foamed material having a front surface for limiting the forces acting on the pedestrian's legs in the event of a collision with a pedestrian and wherein the lower bumper likewise includes a front face which, as viewed in the longitudinal direction of the motor vehicle, is located in approximately the same vertical plane as or in front of the front surface of the upper bumper, wherein the lateral ends of the bumpers are fixed to longitudinal members of the motor vehicle, in that upper crash boxes are arranged between the ends of the longitudinal members and the rear face of a cross beam forming the upper bumper and lower crash boxes are arranged between the ends of the longitudinal members and the rear face of the cross beam forming the lower bumper, wherein the longitudinal rigidity of said crash boxes is smaller than that of the longitudinal members, and wherein the lower crash boxes extend forwardly to a greater extent than the upper crash boxes.

Accordingly, the bottom transverse support is not provided with a foam material layer, so that in the case of a high-energy collision it can provide high resistance forces immediately, leading to a defined deceleration of the entire vehicle.

T:AOCM 2002358415-reped pages(12.308).doc 3a 0 In the case of a collision with a pedestrian an undamped impact on the leg of Nc the pedestrian occurs due to the contact with the non-cushioned front surface of the bottom bumper bar. This has, however, a relatively short duration, Sbecause a tilting takes place immediately about the top transverse support with the foam material layer, so that due to the briefness of the contact with the bottom bumper bar one does not need to expect too serious injuries. The main support of the leg is carried out rather on the cushioned front surface of 00 the top transverse support. The forces are limited here due to the foam material layer

CIA

r--l T:M)DMM235U1l5-MpWd pages(12.3 08).doc Therefore the idea of the invention is that there are two load-absorbing planes at the front, namely one rigid bottom plane and a top plane, that is soft in the initial phase.

The bumper bars have preferably transverse supports, that extend from one longitudinal support to the other, and which for the purpose of achieving an adequate stiffening of the vehicle's frame, formed by the longitudinal and transverse supports, have a rearward open U-shape.

To keep the additional length, resulting from the foam material layer, as small as possible, the foam material layer is inserted into recesses in the top bumper bar, the depth of which corresponds to the length of the block of the foam material.

This means that the foam material layer protrudes forward past the transverse AMENDED PAGE support only as far as it can be actually deformed. This reduces the effective lengthening of the vehicle to 6 cm when, for example, a foam material layer with a thickness of 8 cm is used.

A particularly good stiffening is achieved when the two transverse supports are executed integrally, i.e. constitute sections of a component, that has a rearward facing indentation between the sections forming the transverse support.

It is conceivable to join the two transverse supports or the sub-assembly directly with the longitudinal supports of the vehicle. However, the disadvantage of this arrangement is that even small deforming forces can be conveyed far into the longitudinal supports, so that the vehicle will be damaged within the engine compartment.

Therefore requirements exist for a long time, known in the technical world as the Danner-requirements (named after Prof. Danner, who developed these), according to which a vehicle, damaged by a collision with a firm obstacle at low speeds, should be able to be repaired without great expenses. This means, that damages of such a collision have to be limited to a small region of the chassis and this is to be so constructed, that the damaged parts van be easily replaced.

The adherence to the Danner-requirements is significant for the classification of vehicles with regard to insurance.

Therefore in the region of the front structure there are so called crashboxes present. In this case one deals principally with lengthenings of the longitudinal supports which, however, are constructed markedly softer than the longitudinal supports, while a rigid separating plate between the crashbox and the actual longitudinal support prevents the transfer of deformations. At low collision speeds these crashboxes absorb exclusively the deformations. The repair is easily carried out, since only the damaged crashboxes have to be separated from the support plate and replaced by new ones.

This requirement is satisfied by arranging the top crashbox behind the top transverse support and the bottom crashbox below the bottom transverse support. Since the bottom crashbox extends further forward, during a collision with a firm obstacle it solely absorbs the energy until the foam material layer is compressed and the top crashbox will also participate in the collision.

By virtue of the forward protruding bottom crashbox the deformation energy is absorbed immediately after the first contact with a heavy obstacle and thus it will be achieved, that in the case of collisions at low speeds the Danner requirements are satisfied. Because the foam material layer is arranged, relative to the longitudinal direction of the vehicle, at the same level as the bottom crashbox, no excessive lengthening of the vehicle will occur.

A further aspect to be considered is that in collisions at low speeds units in the engine compartment should, if possible, not be effected, since their replacement is associated with great expenses. Especially the radiator is a critical item here, that is provided relatively far forward in the engine compartment of the motor vehicle.

Therefore the invention provides a mounting system, whereby in the case of a collision the radiator is moved out from the collision zone. For this purpose a support, that can be easily crumpled in the longitudinal direction of the vehicle, is provided behind the bumper bars, the radiator is fastened on this support, while the support is joined with its rear end to a transverse support joining the longitudinal supports and with its front end to one of the bumper bars, preferably to the bottom bumper bar.

When during a collision first the bottom crashbox is crumpled, the support of the radiator will also be crumpled, with the result that the radiator fastened on it is moved rearward away from the crash zone, so that in many cases one can expect that the radiator would not be damaged.

In the case of the support one can deal in principle with two struts. However, a plate is also conceivable, that has the additional advantage of enclosing the bottom.

For a further reinforcing of the chassis the invention provides a transverse support for the engine compartment, that extends above the radiator and joins the two support plates with one another. Thus the transverse support for the engine compartment forms a kind of cover for the radiator and with the forward incline forms a dumping surface for the body of the pedestrian rolling onto it. Because the radiator is situated below the transverse support, one needs not worry about parts protruding from it into the path of the body rolling on and cause additional injuries to the pedestrian.

The invention is explained in detail in the following based on an embodiment.

They show in: Fig. 1 a perspective illustration of the frontstructure of a motor vehicle with bumper bars, viewed from the front, Fig.2 the same front structure, viewed from the rear, Figs.3 and 4 a cross-section each through the arrangement of the bumper bars in the vehicle structure.

First reference is made to Fig.1. It shows the front structure 1 of a motor vehicle in the front region. Longitudinal supports 2, 3, of which in Fig.1 only the left longitudinal support 2 can be seen, extend to both sides of the vehicle. These longitudinal supports 2, 3 form the basic framework for the chassis of the motor vehicle and their various executions are well known to the person skilled in the art.

In front of the ends of the longitudinal supports 2, 3, transversely to the longitudinal direction of the vehicle, there extends a bumper bar arrangement, comprising a bottom bumper bar 4 and a top bumper bar 5. Both bumper bars 4, have a transverse support 6, 7, the cross-section of which is U-shaped open to the rear.

Both transverse supports 6, 7 are executed as a single component, having an indentation 8. Therein are air-intake openings 9.

The sub-assembly, comprising the two transverse supports 6, 7, is joined with the respective longitudinal support 2, 3 via crashboxes 10, 10', 11, 11'. In the case of the crashboxes one deals with sheet metal tubes having square or rectangular cross-section, the lateral sides of which have corrugations, so that to facilitate a crumpling in the longitudinal direction. The joining with the respective longitudinal support 2, 3 is carried out via a support plate 12, 12', that is fastened vertically aligned on the front end of the respective longitudinal support 2, 3. To achieve a secure support for the support plate 12, 12' over its entire height, there is a shoe 13 below the longitudinal supports 2 and 3; The crashboxes 10, 11, 10', 11' are welded or bolted to the front of the support plates 12, 12'.

The front ends of the top crashboxes 11, 11' protrude into the U-shaped section of the top transverse support 6. The front:ends of the bottom crashboxes 10, have a stepped design, so that a smaller portion protrudes into the U-shaped section of the bottom transverse support 7, while a reset portion abuts against the indentation 8. Consequently the sub-assembly of the two bumper bars 4, 5 and of the indentation 8 are supported on the entire area on both sides along their entire height.

The top bumper bar 6 is provided with a layer of foam material, the thickness of which is such, that its front surface is in the same plane as the front surface 14 of the bottom transverse support 7. For the sake of clarity the foam material layer is not shown in Fig.l, but it is shown in Figs.3 and 4.

As this can be seen in Fig.l, there is a radiator 20 behind the two transverse supports 6, 7. Its fastening is illustrated in detail in Fig.2. This figure shows the construction according to Fig.1 viewed from the rear. The same parts have the same reference numerals. One can again recognise particularly clearly, that the top crashboxes 11, 11' protrude into the U-shaped section of the top transverse support 6, while the bottom crashboxes 10, 10' support both the bottom transverse support 7 and the indentation 8.

To fasten the radiator 20 mentioned, there is in the region between the crashboxes 10, 10', 11, 11' a carrier plate 21, the front end of which is joined with the rear side of the bottom transverse support 7, that by virtue of this enclosed section obtains an increased rigidity. The rear end is welded to an engine transverse support 22, that is fastened on the longitudinal supports below the shoes 13, already mentioned. The main purpose of this engine transverse support 22 is the mounting of the engine of the vehicle.

On the carrier plate 21 two fastening points 23, of which one can be seen, are provided. The radiator 20 is fastened on them. The carrier plate 21 is so oriented, that during a crumpling of the crashboxes 10, 10', 11, 11' it will also be crumpled and pushed rearward. At the same time it carries the radiator 20 with it rearward, due to which the distance of the radiator to the front bumper bars 4, 5 remains and consequently in the case of small depths of deformations it will not get damaged.

Fig.3 shows a cross-section through the arrangement in the region of the radiator Fig.4 shows a cross-section through the arrangement in the region of the crashboxes 10, 10', 11, 11'. Identical parts have the same reference numerals in this case too. In addition, the foam material layer 25 is also shown here schematically. It is situated on the top transverse support 6, that for this purpose has an impression in which the foam material layer 25 lies over part of its length, this length corresponding to the length of its block. The foam material layer protrudes forward only to the extent that corresponds to its maximum possible deformation.

It can be well seen in both Figs.3 and 4, that the front surface 26 of the foam material layer 25 of the top transverse support 6 and the front surface 14 of the bottom transverse support 7 are in the same plane or that the front surface 14 of the bottom transverse support 7 is situated in front of the front surface 26 of the foam material layer As it can be seen from Fig.4, this will make it possible to have the bottom crashbox 10, 10' markedly longer than the top crashbox 11, 11'. In the case of a frontal collision with a firm obstacle the bottom crashbox 10, 10' is immediately involved and can absorb high level of energy. As soon as the deformation has reached approx. 6 cm, the top cashbox 11, 11' will also be involved in the deformation. In this manner the energy of the impact with another vehicle or a firm obstacle can be dissipated in a short distance without involving the longitudinal supports 2, 3 behind the crashboxes 10, 10', 11, 11' in the deformation.

Thus the foam material layer 25 is situated above the bottom crashbox 10, that is possibly somewhat longer, so that to ensure that only it is effective in the initial phase of the collision. By virtue of the illustrated combination of the arrangement of the crashboxes and the foam material layer no marked lengthening of the vehicle will result.

By virtue of having a bottom and a top bumper bar an improvement of the sidecrash behaviour will also be achieved, especially when the vehicle according to the invention hits another vehicle, since the bottom bumper bar according to the invention impacts a firm vehicle structure, in particular the door pillar. Due to this the energy of the impact is diverted to the bottom bumper bar, so that in the subsequent impacting of the side door by the top bumper bar the B-column of the other vehicle will be subjected to a smaller load.

In the case of a collision with a pedestrian the lower region of the leg is hit immediately by the non-cushioned bottom bumper bar 4, what can produce very high initial forces. However, because of the elevated centre of gravity of the body a tilting about the foam material layer 25 is triggered immediately, the leg is disengaged from the bottom bumper bar 4 already after a short period, so that the affect of the force is small. A further support is carried out by the foam material layer 25, that is compressed in a defined manner and due to its softness allows only a level of the force at which no heavy injuries of the lower extremities of the pedestrian hit are expected.

List of reference numerals 1 Front structure 2 Left longitudinal support 3 Right longitudinal support 4 Bottom bumper bar Top bumper bar 6 Transverse support 7 Transverse support 8 Indentation 9 Air intake opening Crashbox Crashbox 11 Crashbox 11' Crashbox 12 Support plate 12' Support plate 13 Shoe 14 Front surface Radiator 21 Carrier plate 22 Engine transverse support 23 Fastening point Foam material layer 26 Front surface 27 Transverse support for the engine compartment

Claims

1. A frontal structure of a motor vehicle including a lower bumper and an Supper bumper arranged thereabove, wherein the front face of the upper bumper includes a layer of foamed material having a front surface for limiting the forces acting on the pedestrian's legs in the event of a collision with a pedestrian and wherein the lower bumper likewise includes a front face which, 00 as viewed in the longitudinal direction of the motor vehicle, is located in 0o V approximately the same vertical plane as or in front of the front surface of the upper bumper, wherein the lateral ends of the bumpers are fixed to longitudinal Smembers of the motor vehicle, in that upper crash boxes are arranged between the ends of the longitudinal members and the rear face of a cross beam forming the upper bumper and lower crash boxes are arranged between the ends of the longitudinal members and the rear face of the cross beam forming the lower bumper, wherein the longitudinal rigidity of said crash boxes is smaller than that of the longitudinal members, and wherein the lower crash boxes extend forwardly to a greater extent than the upper crash boxes.

2. A frontal structure in accordance with Claim 1, wherein the layer of foamed material is applied to the front face of an upper cross beam which extends from one of the longitudinal members to the other.

3. A frontal structure in accordance with Claim 2, wherein the cross beam includes a rearwardly open U-shaped profile.

4. A frontal structure in accordance with any of Claims 1 to 3, wherein the block length of the layer of foamed material lies in a depression in the cross beam.

5. A frontal structure in accordance with Claim 1, wherein the front face of the lower bumper is formed by a lower cross beam which likewise extends from one of the longitudinal members to the other. T:DWU002358415-fetpd pages(12.3.08).doc 12 00 0

6. A frontal structure in accordance with any of the Claims 1 to 5, wherein Sthe cross beams form a component which includes a rearwardly set back recess between the sections thereof forming the cross beams.

7. A frontal structure in accordance with Claim 1, wherein a respective approximately vertically extending support plate is attached to the front ends of the longitudinal members, and a crash box for the upper cross beam and a 00crash box for the lower cross beam is attached to the front face of said support 00 Cc plate.

8. A frontal structure in accordance with Claim 7, wherein the lower crash box is longer than the upper crash box.

9. A frontal structure in accordance with Claim 7 or 8, wherein the height of the lower crash box is such that it supports both the lower cross beam and the recess.

A frontal structure in accordance with any of the preceding claims, wherein an easily compressible supporting member, to which the radiator is fixed, runs behind the bumpers and between the crash boxes, wherein the rear end of the supporting member is fixed to an engine cross beam which connects the longitudinal members together and the front end thereof is fixed to one of the bumpers.

11. A frontal structure in accordance with Claim 10, wherein the supporting member is in the form of a mounting plate which is fixed to the lower cross beam.

12. A frontal structure in accordance with Claim 7 or 10, wherein the support plates are connected to an engine compartment cross beam which runs above the radiator and includes a front chamfering.

13. A frontal structure substantially as herein described and illustrated. T:DDl 2023584t5-retPed pages(i2.3.08) doc