AU2002321001B2 - Front structure of a motor vehicle comprising a front bonnet that deforms during a head impact - Google Patents

Abstract

The aim of the invention is to increase the protection of pedestrians during a collision with a vehicle. To achieve this, the front structure and the front bonnet in particular are configured in such a way that for typical accident situations, which are reconstructed in defined simulations, the HIC value for a head impact does not exceed 1,000. It has been proven that this can be achieved if the deceleration curve has an initially high deceleration peak. According to the invention, a front structure that guarantees this has deformation elements (6) consisting of several sub-sections (10a - 10d), which are interconnected by breaking points (11a - 11c). When subjected to dynamic stress, such as occurs during a head impact, the breaking points fracture in such a way that the individual sub-sections (10a - 10d) are pushed against one another with zero force.

Description

00 0 Front structure of a motor vehicle comprising a front bonnet that N deforms during a head impact The invention concerns a front structure of a motor vehicle with a bonnet that yields when struck by a head and with deforming elements, that provide resistance to a static load, so that in the case of such a load an irreversible indentation of the bonnet is prevented and they yield in the case of a determined load when an impact-like force acts.

A reference herein to a patent document or other matter which is given as prior N 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 general knowledge as at the priority date of any of the claims.

Such a front structure is described in DE 199 02 311 Al. This publication shows, in particular, a two-skin bonnet with a cover skin and a carrier skin provided below it, that laterally rests on two struts of the front structure.

Between the skins an energy-absorbing intermediate layer is formed. An execution of the intermediate layer comprises a plurality of honeycombs with round or elliptical cross-section. They are so designed, that in the case of a determined force, acting from above on the bonnet, they break and consequently provide flexibility over a deformation path.

Since this intermediate layer is described as an energy-absorbing one, it is assumed that the honeycombs are so constructed that they produce an opposing force over the entire deformation path. Accordingly, the document points out that the bonnet should be so designed, that a rectangular deformation characteristic will occur during the deformation of the intermediate layer.

Experiments have, however, shown that a continuous deceleration acting over a longer period is not necessarily the optimum with regard to the severity of the injuries of an impacting head. To evaluate the severity of the injury the so called HIC value is used, that represents a relationship between the T ODseis20310-eye pages (14.4.08) dSc 17. APR. 2008 14:36... PHILLIPS ORMONDE FITZPATRICK NO. 5926-P. 3/6-- 00 2 0 deceleration and the time period within which the deceleration acts. The HLC Svalue is sufficiently precisely described and defined in the technical literature.

0^ So that to prevent severe injuries, its value has to be below 1000. Its definition takes into consideration that higher decelerations are bearable when they act for a short period only.

Therefore reference has already been made to that a deceleration progress, o whereby at the commencement of the head impacting a relatively high l deceleration acts for a short time period and afterwards the deceleration is C 10 brought to a lower level, is more favourable as far as the reaching of the HIC 0 threshold value of 1000 is concerned than a constant deceleration over a longer time period.

The honeycombs described in the above mentioned document are supposed to have the attribute to build up, when compressed, a relatively constant counter-force over the deformation path that, with regard to the just mentioned considerations, is extremely disadvantageous as far as the severity of the injuries is concerned.

Thus the invention is based on the problem to produce a front structure with a bonnet, the deforming elements of which are so constructed that they break with a jolt above a certain load and enable a deformation path essentially without any constraint.

According to the present invention, there is provided a front structure of a motor vehicle including a front bonnet, which behaves in a yielding manner in the event of a head impact, and including deformation elements, which resist a static loading so that in the event of such loading an irreversible denting of the front bonnet is prevented and which give way in the event of a specific loading during an impact-like force, wherein the deformation elements include at least two portions, which are connected to one another in each case by a failure point, which above a specific loading abruptly breaks and' hence allows a deformation path, wherein the portions are held or guided in such a way that, after the failure point gives way, because of the impact-like action of the force T\B0ttM&eiee2oo32iOO1.raywd DGONt(.I.06)AO COMS ID No: ARCS-187223 Received by IP Australia: Time 14:38 Date 2008-04-17 the portions travel the deformation path in a force-free manner and take up a defined new position.

The term failure position (or failure point) is to express that the structure of the deforming elements, which allow to withstand the static load, essentially depends on the existence of the failure positions. When these yield, i.e. break, bend or lose their function in any other manner, the structure also loses its ability to build up a counter-force and collapses essentially without any constraint. To make this possible, the individual part-elements of the deforming elements have to be so arranged that after yielding the failure positions travel through a deformation path without any constraint and assume a new defined position. Since the position of the individual part-elements is clearly defined after the yielding of the failure T:DOMkspaCies\2D02321001.etyped paqes (14408).doc position, a new unintentional structure, that would present a further unintentional resistance to the impact of the head, cannot occur by the free part-elements hooking into one another.

As it has been already stated in the above mentioned document, the deforming elements can be positioned between an external cover skin and a carrier skin of the bonnet provided below it. The advantage of this arrangement is that he bonnet is pre-assembled in toto and can be integrated as such into the front structure. In this manner particularly all critical areas of the bonnet, first of all those areas under which the sub-assemblies of the vehicle are situated, can be reinforced according to the invention. A further possibility to position the deforming elements is to arrange them between the bonnet and a longitudinal beam of the front structure of the motor vehicle. Thus they will become a part of the vehicle body and are constructed together with it.

A particularly critical region is the transition to the mudguards. In the case of an inserted bonnet it overlaps a flange at the edge of the mudguard, the flange rigidly joined in the edge region with a longitudinal beam extending below it. To achieve in this case the desired deceleration progress in the case of an impacting head, it is suggested to carry out the joint between this flange and the longitudinal beam by one of the deforming elements described in the following.

A particularly clearly defined deceleration progress with a very distinct initial deceleration peak is obtained when the failure positions are constructed as predetermined breaking positions, while a deforming element comprises at least two part-elements offset relative one another and are joined by a bridge containing the predetermined breaking position, and the part-elements essentially retain their orientation relative to the direction of load even after the breaking of the failure position. At the same time the predetermined breaking position is so designed, that it breaks under a precisely defined force. By aligning the partelements offset to the direction of the load, after the failure of the predetermined breaking positions they slide past one another and will be arranged adjacent to one another, so that a considerable deformation path becomes available. This path is travelled through essentially without any resistance because the structure fails after the breakage of the predetermined breaking positions. No hooking into one another or anything similar can occur by the new positions occupied in the structure by the individual part-elements. The more part-elements are joined with one another by predetermined breaking positions, the greater the deformation path will be. The individual part-elements are preferably offset from one plane to another in one direction, so that a part-element in the middle is guided by the two others. The predetermined breaking positions between the individual planes can be so executed, that they will break essentially simultaneously or consecutively, by virtue of which the initial deceleration peak will be increased and reduced stepby-step.

Another possibility to arrange the part-elements of the deforming element is to let them converge at an angle and join them at the tip of the angle via a kink position forming the failure position.

When the deforming element is made up, for example, from two part-elements, they fold up and lie flat against one another, resulting in a relatively long deformation path relative to the height of the deforming element. The failure position can be constructed in this case also as a predetermined breaking position, resulting in a clearly defined load value at which the deforming element yields.

A number of part-elements may be joined with one another via a kink position each according to this solution also, so that a sort of accordion will result and, depending on the predetermined breaking force for which the individual kink position is designed, break simultaneously or consecutively under a load.

As a rule, several deforming elements may be arranged next to one another, so that independently from the actual position of the impact of the head one deforming element will be immediately effective. Particularly in the case of the execution whereby the individual part-elements are at angle to one another, the arrangement can be such that the kink positions push against one another and form an intersection forming the failure position. A honeycomb-shaped construction will altogether result, wherein the joints of the individual honeycombs form the failure positions.

In the case of the individual part-elements one preferably deals with lamellae, joined with one another linearly at one edge, while the joining line forms the failure position. In this manner a deforming element can bridge over a relatively wide position. At the same time the length of the joining position can also determine the force at which the failure position should break or yield. In addition, such deforming elements can be relatively easily produced by extrusion.

So that to prevent an indeterminate breakage of the lamellae by themselves, it is proposed to thin the lamellae towards the failure position.

Particularly in the case of the execution wherein the lamellae slide along one another, a deforming element may have an enclosed, annular shape, so that the part-elements can slide into one another telescope like.

The shape of the predetermined breaking position can be realised in many ways.

They can be formed, for example, by a thin lip, that tears under a load. The tearing force can be relatively precisely set by the thickness and/or length of the lip, so that a clearly defined deceleration progress will result.

A further possibility is to form the predetermined breaking position by a cutting edge that is formed on a part-element and is superimposed on a shearable fin on the other part-element and possibly has a thin joint with it. In the case of a load the cutting edge cuts off the fins. Defined forces are necessary for this also, so that the predetermined breaking position can be well set by the construction.

Instead of the lamella shape the part-elements may be arcs at right angles to the direction of load, the arcs lying against one another alternately with their concave and convex sides, so that approximately circular honeycombs will result.

The ends of the arcs, that blend into a short counter arc, abut against one another by frictional locking and are only lightly joined with one another. When a load occurs in the direction of the load the ends are pressed against one another and held together by an adhesive frictional lock. Only when that is overcome will the joint disengage, while a sliding frictional force remains defining the level of deceleration over the deformation path.

A further possibility to realise a deforming element is that it has a destructible casing filled with gas, that is arranged in a reducible chamber formed by a top and bottom shell. Provided the casing is enclosed, the shells can get only slightly closer and the deforming element remains rigid. As soon as the casing is destructed, the deforming element loses its resisting force, so that the shells can draw closer without any resistance. For this purpose a pin is provided on one of the shells that, when the shells are moved towards one another against the resistance of the gas enclosed in the casing, penetrates the casing and destructs it. At that moment the counter-pressure of the enclosed gas is suddenly terminated, so that both shells can be moved towards one another practically without any resistance.

So that the gas could escape and the pin would not set tightly in the opening scored by it, it is provided with a gas channel between its tip and its base, so that the air can escape via this channel. Because this channel simultaneously forms a throttle, the discharge velocity can be controlled within certain extent, by virtue of which the descending flank of the initial deceleration can be set for an impacting head.

The invention is explained in detail in the following based on a plurality of embodiments, illustrated in several figures. They show in: Fig.1 deforming elements with lamella-like part-elements, manifoldly offset stepby-step, Fig.2 deforming elements in the form of a stepped pyramid, Fig.3 deforming elements with offset lamella-like part-elements, simply offset step-by-step, Fig.4 deforming elements from two arc-shaped part-elements combined into a circle and deforming elements with lamella-like part-elements enclosing an angle, Fig.5 deforming elements with a destructible gas casing in a reducible chamber, Fig.6 an arrangement of deforming elements between a longitudinal beam of a vehicle body and the edge of a mudguard, above which the bonnet is situated, Fig.7 a principal illustration of the execution according to Fig.3, Figs.7a to 7c various executions of bridges between the part-elements of a deforming element according to Fig.7, Fig.8 a principal illustration of the execution according to Fig.1, Figs.8a to 8c various executions of bridges between the part-elements of a deforming element according to Fig.8, Fig.9 a box-shaped combination of deforming elements, a wall-like combination of deforming elements, Fig.11 a combination of arc-shaped deforming elements with a honeycomb shape, Fig.1 la a first execution of the joint between two adjacent honeycomb cells according to Fig. 11, Fig. 1 b a second execution of the joint between two adjacent honeycomb cells according to Fig.11, Fig.12 a further type of combination of arc-shaped deforming elements with a honeycomb shape, Fig.13 a perspective illustration of the execution according to Fig.12.

Figs.1 to 5 show a bonnet 1 each with a cover skin 2 in the region of a front transverse beam 4. A support skin 3 is provided at least in sections below the cover skin 2. The cover skin 2 as well as the support skin 3 form a hollow space the section of which is approximately lens-shaped. Inside the hollow space there is a plurality of deforming elements 6, that are fastened on a top and bottom carrier plate 7, 8 or are integrally produced with them. The carrier plates 7, 8 abut flat against the cover skin 2 and the support skin 3, respectively, and are bonded with them, indicated by the hatched adhesive layer 9. Each deforming element 6 comprises a plurality of lamella-like part-elements 10a to 10d, joined with one another by bridges I la to I1 lc. The individual part-elements 10a to 10d are offset relative one another step-by-step, by virtue of which, when the bridges 1 la to 11 c break, they can slide past one another without any resistance, what is shown in principle, inter alia, in Fig.7.

The numeral 12 designates a ball, illustrating an impacting head or an impacting simulated body. The direction of impact is indicated by arrow 13. One can recognise that the individual part-elements are offset relative one another at right angles to the direction of impact.

When an impact occurs, the cover skin 2 will draw closer to the support skin 3 on the one hand, on the other the entire bonnet 1 is pushed downward until the support skin 3 abuts against the transverse beam 4. As soon as the path of the bonnet is completely used up, the impacting head 12 presses the deforming elements 6, so that the bridges I la to I lc will be under load. Depending on their resistance forces, a high initial head deceleration will occur until the bridges I la to 11 c break or tear or shear off. At this moment the deforming element 6 becomes ineffective, so that the decelerations still acting will be generated only by the deflection of the cover skin 2 and after a complete compression of the hollow space 5 by the support skin 3. On this occasion, however, considerably smaller decelerations take place, so that a deceleration progress takes place that is characterised by a high, but short initial deceleration value.

Fig.2 essentially corresponds to the execution according to Fig. 1 However, in this case the deforming elements 6 form stepped pyramids 15, so that the individual planes of the part-elements 10 a to 10 Od slide into one another telescope like when an external load occurs. The individual stepped pyramids 15 can be inserted with their heads into corresponding mountings 16 on the bottom carrier plate 8.

Fig.3 shows a further embodiment, wherein the individual deforming elements 6 comprise two lamella-like part-elements 10a, 10Ob stepped in the same direction, whereas in the case of Fig.1 the individual deforming elements 6 are stepped alternately in opposite directions. Thus in the embodiment illustrated in Fig.3 the action is with a somewhat more dense layout of the hollow space 5 with the deforming elements 6. In addition, in the case of this embodiment each deforming element 6 is formed merely from two part-elements 10a, 10Ob, joined with one another by a bridge each. Therefore the maximum deformation is only half of the height of the deforming elements 6 in the intact state. Both carrier plates 7, 8 can draw close only to an overall dimension that is determined by the height of one of the part-elements 10a, 10b. In many cases, however, this is adequate.

Fig.4 shows two further embodiments of the deforming elements 6. According to the execution on the left, a deforming element 6 comprises two arcs 20, 21 that are combined into a circle, while the respective zenith of the arc is joined to the cover skin 2 or the support skin 3. The arcs 20, 21 are joined at their ends with one another by failure positions, while the joints have both on the outside and the inside indentations 22 with semi-circular cross-sections.

A further version is illustrated on the right of the drawing. Both part-elements 10b are arranged obliquely to one another and converge in a kink position 25 at an angle slightly more than 90 This kink position 25 is constructed as a failure position, i.e. it is very thin and has an indentation 26. In the case of an impact-like load the kink position 25 first acts as a hinge, so that both part-elements 10a, will draw closer to one another and the included angle will become smaller. By doing so the kink position 25 is stressed until it breaks. Afterwards the deceleration is essentially determined by the strength of the joint of the base of the part-elements 10a, 10Ob with the respective carrier plate 7, 8.

Fig.5 shows an execution of the deforming element 6 that works, as it were, by pneumatic means. Each carrier plate 7, 8 has walls 30 which can be partly inserted into one another, so that enclosed chambers 31 will result. Into each of these chambers 31 air or gas cushions 33 are placed in a casing 32.

The top carrier plate 7 has recesses 34, in which a pin 35 is situated. The casing 32 is fully filled with air or gas, so that it can be compressed only by a considerable force against the pressure acting in the casing 32.

When an impact-like force acts on the cover skin 2 and consequently on the top carrier plate 7, the chambers 31 are reduced, due to which the casing 32 with the gas is pressed into the recess 34. From a certain force on the pin 35 presses the casing 32, so that it bursts and no longer can offer any resistance. Both carrier plates 7, 8 and the cover skin 2 and the support skin 3 can be moved towards one another without any, force.

Fig.6 shows a somewhat different arrangement for a deforming element 6. For this purpose the figure shows a cross-section of a mudguard 40 of a motor vehicle with an adjacent bonnet 1. Below the mudguard 40 a longitudinal beam 41 of the vehicle's body is situated. The mudguard 40 has a downward turned flange 42, over which the edge of the bonnet 1 extends. One or several deforming elements 6 are situated between the downward turned flange 42 and the longitudinal beam 41.

When a head, symbolically illustrated by the ball 12, strikes in the transition region between the bonnet 1 and the mudguard 40, first the edge of the hood 1 hooks into the upward turned edge of the flange 42. As already explained above, the deforming elements 6 offer a first resistance to the impact, so that the deceleration of the head increases strongly. When a certain impact force is reached, the deforming elements 6 break and the bonnet 1 draw closer to the longitudinal beam 41. The force exerted after the deforming elements 6 have yielded is the result essentially of the hooked-in structure of the mudguard 40 and bonnet 1. Should a second, indirect impact of the head occur on the longitudinal beam 41, the speed of the head is reduced by then to a great extent, so that no high decelerations, and consequently severe injuries, are anticipated.

The following figures show once again on some examples the principal construction of the deforming elements 6 and their combination into a deforming structure.

Fig.7 shows a plurality of deforming elements 6, that are made up from a plurality of part-elements 10 a-10f, each of them offset relative one another. In the case of a head striking the top carrier plate 7 the bridges I la to 1 If break between the part-elements 1 a to 10 Of and they will slide next to one another, so that a situation, illustrated in dotted lines in the central portion of the figure, will occur.

The resulting overall height is determined by the height of the individual parts. In accordance with the number of the part-elements 1 Oa-1 Of the resulting deformation path is calculated from the height of a deforming element 6 minus the height of a part.

Figs.7a, 7b and 7c illustrate some predetermined breaking positions. As Fig.7a shows, such a predetermined breaking position comprises a bridge 1 la, that joins the ends facing one another of two part-elements 10a, 1Gb arranged superposed.

As this is shown in Fig.7a, such a bridge 1 a can be relatively short. As Figs.7b and 7c show, in addition one or both ends of the part-elements 10 a, 10b may be chamfered, so that a smooth transition to the bridge I la will result.

Fig.8 illustrates the principle of a solution according to Figs.1 and 2. The individual part-elements 10a-1Of are offset relative one another, so that they can be inserted into one another and after the breaking of the bridges 11 a-1 le joining them they assume the position illustrated in dotted lines for a connecting element 6. The overall height is in this case too according to the height of a part-element 10a-1Of. Figs.8a, 8b, 8c illustrate some possible predetermined breaking positions. Fig.8a corresponds to the solution according to Fig.7a with a somewhat wider bridge 1 la. Fig.8b shows a bridge 1 la in the form of a lip, that joins two tapered part-elements 10a, 10Ob. Figs.8c and 8d show a cutting edge 45 on a part-element 10a, that abuts against a fin 46 of the next part-element 10Ob. The cutting edge 45 may have either a tip (as illustrated in Fig.8c) or an edge (as illustrated in Fig.8d). When an impact force acts on the top part-element 10a, the fin 46 is severed from the part-element 1Ob by the cutting edge 45 as soon as the force is great enough.

Fig.9 shows a box-like combination of the various deforming elements 6, joined with one another by connecting webs 50 extending horizontally to the deforming elements. Thus each vertical wall of a box 51 forms a deforming element 6 that has a kink position 25 according to Fig.4, on the right. Accordingly, each wall of a box 51 is divided by a notch into two part-elements 10a, 10Ob, while, as illustrated, both part-elements 10a, 1Ob may be at an angle of 1800 to one another.

Fig. 10 shows an arrangement wherein the individual deforming elements 6 are combined into a honeycomb, while each part-element 10a-1 Of of a deforming element 6 is joined at both sides by a continuous connecting web 50 with the part-element lying on the same height of an adjacent deforming element so that a kind of brickwork will result, as this is illustrated. The break and consequently the failure of the structure takes place at the transitions of the partelements to the respective connecting web 50. For this purpose the part-elements Oa-1 Of are pointed and rest on the connecting web 50 which have notches below the part-elements 10Oa-10 Of, as this is illustrated on an enlarged scale in Fig. 11 shows an execution, wherein the part-elements 10a-1Of have an arc shape, in fact so that a convex side of a part-element is situated opposite a concave side of the following part-element. The ends of the part-elements 10 a- 1 Of transits into a counter arch 55a-55f, that blends into the corresponding counter arc of an adjacent part-element situated at the same height. Thus nodes 56 are formed with four approaches. These nodes 56 are constructed as failure positions. For this purpose they are either weakened by an opening 57 (see Fig. la) or held together by an adhesive frictional contact (see Fig.1 while additionally the ends of the individual part-elements 10a-1 Of are lightly bonded.

Due to the arc-like structure the individual nodes 56 are stressed in the case of a head impacting. At a certain magnitude of the load the nodes 56 break up, so that the structure fails. In the case of a frictional joint, a sliding frictional contact remains in the nodes 56 after the breakdown, determining the deceleration of the head after the initial deceleration peak.

The execution according to Fig.12 differs from that according to Fig.11, that in this case the failure positions are present in the form of predetermined breaking positions 60 at the zenith of the arcs formed by the part-elements 10 a, 10a' and Ob, 1 Ob', respectively. The joints of the arcs can buckle, so that the partelements 10a, 10Ob and 10a', 10Ob' fold against one another when the predetermined breaking point breaks. Furthermore, the arcs of a circle are arranged offset relative one another what is illustrated perspectively in Fig.13.

When the deforming element 6 fails, the part-elements 10a, 10a' and 10Ob, 1Ob' forming the arcs will lie not on top of one another but adjacent to one another, resulting in a very low overall height, so that the available deformation path is particularly long.

List of reference numerals 1 2 3 4 6 7 8 9 10f 11a 11e 12 13 14 16 21 22 26 31 32 33 34 41 42 46 51 56 57 61 Bonnet Cover skin Support skin Transverse beam Hollow space Deforming element Carrier plate Carrier plate Adhesive layer Part-elements Bridges Ball Arrow Mounting Stepped pyramid Mounting Arc Arc Indentation Kink position Indentation Wall Chamber Casing Air/gas cushion Recess Pin Mudguard Longitudinal beam Flange Cutting edge Fin Connecting web Box Counter arc Node Opening Predetermined breaking point Kink position

Claims (9)

1. 2. A front structure according to claim 1, including an outer top shell and a supporting shell disposed under the top shell, and between the outer top shell and supporting shell, the deformation elements for reinforcing the front bonnet are disposed.
2. 3. A front structure according to claim 1, wherein the deformation elements are disposed between the front bonnet and a longitudinal member of the front structure of the motor vehicle.
3. 4. A front structure according to claim 3, including two inwardly curved wings, between which the front bonnet extends, wherein the inner edges of the wings facing the front bonnet each have a downwardly offset flange, on which the associated edge of the front bonnet rests, and at least one of the deformation elements is disposed between the downwardly offset flange and the longitudinal member. A front structure according to any one of the preceding claims, wherein the failure points are configured as predetermined breaking points and that at least one of the deformation elements includes at least two mutually offset portions, which are connected to one another by a bridge including the TA)~pce\03 I O reye pages (14.4,08).doc I 00 0 predetermined breaking point, wherein the portions even after fracture of the failure point substantially retain their alignment in relation to the loading Sdirection.
4. 6. A front structure according to claim 5, wherein at least one of the deformation elements includes more than three mutually offset portions, which are connected to one another in each case by a bridge including a predetermined breaking point, wherein the portions are disposed in such a way relative to one another that, after the predetermined breaking points break, a middle portion is guided by the other portions.
5. 7. A front structure according to any one of the preceding claims, wherein the portions are lamellae and the failure points extend along a line parallel to the lateral extent of the lamella.
6. 8. A front structure according to claim 7, wherein the lamellae become thinner in the direction of the failure point.
7. 9. A front structure according to claim 5 or 6, wherein the deformation elements have a closed, annular shape so that the portions are slidable telescopically one into the other. A front structure according to claim 5, wherein the predetermined breaking point is formed by a thin lip that tears in the event of loading.
8. 11. A front structure according to claim 5, wherein the predetermined breaking point is formed by a cutting edge on one of the portions and a shear- off flap on another of the other portions.
9. 12. A front structure of a motor vehicle according to any one of the embodiments substantially as herein described and illustrated in Figs. 1 to 4 and 6 to 13. T:kDDMhspeies\20232100l-retyped pages (14.OB),doC