GB2557964A

GB2557964A - Motor vehicle and crash box therefore

Info

Publication number: GB2557964A
Application number: GB1621734.1A
Authority: GB
Inventors: V Mazur Dmitriy; Boettcher Curd-Sigmund; Holderried Stefan
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2016-12-20
Filing date: 2016-12-20
Publication date: 2018-07-04
Also published as: GB201621734D0

Abstract

A crash box 2 for a motor vehicle has a first end 7 for connecting to a side member 1, a second end 15 for connecting to a bumper beam 3 and inboard and outboard sidewalls 8, 9 which diverge from said first end towards said second end. Longitudinally extending hollow webs 33, 34, 35 may be formed within the crash box, wherein two of the hollow webs 34, 35 may have an interruption 36 formed between them. Preferably, the crash box has top and bottom walls 23, 28, in which the hollow webs are formed. A reinforcing member 18 may be present, connected to the sidewalls. The crash box could be assembled from at least two pieces 26, 27 of sheet material of different gauge and/or composition. The outboard sidewall may extends at an acute angle (α) with respect to the vehicle longitudinal direction.

Description

(54) Title of the Invention: Motor vehicle and crash box therefore Abstract Title: Vehicle crash box (57) A crash box 2 for a motor vehicle has a first end 7 for connecting to a side member 1, a second end 15 for connecting to a bumper beam 3 and inboard and outboard sidewalls 8, 9 which diverge from said first end towards said second end. Longitudinally extending hollow webs 33, 34, 35 may be formed within the crash box, wherein two of the hollow webs 34, 35 may have an interruption 36 formed between them. Preferably, the crash box has top and bottom walls 23, 28, in which the hollow webs are formed. A reinforcing member 18 may be present, connected to the sidewalls. The crash box could be assembled from at least two pieces 26, 27 of sheet material of different gauge and/or composition. The outboard sidewall may extends at an acute angle (a) with respect to the vehicle longitudinal direction.

212

-1MOTOR VEHICLE AND CRASH BOX THEREFORE

Description

The present invention relates to a crash box for connecting a bumper beam to a side member in a motor vehicle, and to a motor vehicle comprising such a crash box.

In order to ensure a maximum level of occupant safety, a motor vehicle should be designed such that in case of a front crash, the vehicle front portion can yield and absorb impact energy, while deformation of the occupant compartment is kept at a minimum. This requirement is particularly hard to fulfil in a shallow offset crash, i.e. a crash in which only a lateral region of the vehicle front portion comes in contact with an obstacle. Since in such a case, impact energy can only be absorbed by a small part ofthe vehicle front portion, low impact speeds can be sufficient to cause serious deformations which affect the occupant compartment.

Since side members of a vehicle body have to pass between the wheel arches of the front wheels, the distance between their front ends is considerably smaller than the overall width ofthe vehicle body. In order to provide protection also in case of a shallow offset collision, a front bumper beam has to span as much as possible of the width of the vehicle body, i.e. it is considerably wider than the distance between the forward ends of two side members supporting it and has end portions which project in an outboard direction beyond the side members. Such end portions tend to bend easily when subject to pressure from an obstacle in case of a shallow offset collision, so that the obstacle easily penetrates into the vehicle body and affects a wheel arch behind the bent end portion. The rims ofthe vehicle wheels have to be rigid, so that they hardly absorb energy due to lack of deformation. The tyres, on the other hand, may yield, but hardly absorb energy in the process of doing so. Therefore, once the wheel arch is affected, the occupant compartment behind it is likely to be deformed, too.

It is therefore an object of the present invention to improve occupant safety in case of a shallow overlap collision.

This object is achieved according to an embodiment of the present invention by a crash box for a motor vehicle having a first end for connecting to a side member and a second end for connecting to a bumper beam, in which inboard and outboard sidewalls diverge from said first end towards said second end.

By being wider at its second end than at its first end, the crash box can provide support to a region of a bumper beam which is laterally offset in the outboard direction with respect to the side member and extends in front of a wheel arch. Such improved support facilitates a lateral displacement of the vehicle in the course of the collision, which will increase the offset between the vehicle and the obstacle and, ideally, causes the vehicle to bypass the obstacle.

Top and bottom edges of said sidewalls should be connected by top and bottom walls of the crash box. Typically, the top wall and adjacent portions of the sidewalls (and/or the bottom wall and adjacent portions of the sidewalls) can be manufactured unitarily from a same piece of sheet material.

In order to control the resistance of at least one of said top and bottom walls and said sidewalls against bending in case of a collision, at least one longitudinally extending hollow web may be formed in said wall.

Such a web may increase the resistance against bending if it extends without interruption over the entire length of the wall; if an interruption is formed in the web, it may yield more easily to a collision force than an uninterrupted web or even a web-free wall, so that by judiciously placing such interruptions, a designer can control the way in which the crash box is crushed in case of a collision.

In a preferred embodiment, the inboard sidewall has at least one web in which an interruption is formed, and the outboard sidewall hasn’t. The outboard sidewall may have no web at all, or if it has, the web is uninterrupted, thus accounting for the fact that when the crash box is installed in a vehicle, the outboard sidewall will be more inclined with respect to the vehicle longitudinal direction than the inboard sidewall and is therefore more easily deformed by a longitudinally oriented collision force than the inboard sidewall.

As a further measure to balance the respective strengths of the inboard and outboard sides of the crash box, in at least one of said top and bottom walls at least two longitudinally extending hollow webs may be formed, a first one of which one is located adjacent to the outboard sidewall, and a second one of which is located adjacent to the inboard sidewall and has more interruptions than the first web.

A longitudinally extending reinforcing member is connected to said sidewalls between top and bottom edges thereof, thus dividing an inner cavity of the crash box into upper and lower portions.

Preferably, the reinforcing member extends between said first end and an intermediate portion of the crash box, thus protecting the side member and the first end from deformation, while a region near the second end of the crash box, where the reinforcing member does not extend, yields to a collision rather easily. If the collision speed is low enough to keep deformation confined to the vicinity of the second end, replacement of the crash box is facilitated because the reinforcing member helps to avoid a deformation of the first end.

In order to control its deformation behaviour, the crash box may be assembled from at least two pieces of sheet material of different gauge and/or composition. It should be noted in this respect that composition differences can refer not only to chemical composition but also to crystalline structure, e.g. the at least two pieces might be made from a same steel alloy but might differ in hardness due to different heat treatments.

Nuts by which the crash box and the side member can be screwed together can be mounted at the first end of the crash box, preferably in the sidewalls, so as to receive screws extending in the vehicle transverse direction.

According to another embodiment of the present invention the object is achieved by a motor vehicle comprising a crash box as described above.

In such a vehicle, the outboard sidewall ofthe crash box should extend at an acute angle with respect to the vehicle longitudinal direction.

The inboard sidewall should deviate less from the vehicle longitudinal direction than the outboard sidewall; it may extend substantially in the longitudinal direction.

In the vehicle, a side member is connected to the crash box first end and a bumper beam is connected to the crash box second end. In order for the crash box to strengthen the bumper beam substantially up to its outboard end, the distance, measured in the vehicle transverse direction, between a junction where the outboard sidewall meets the bumper beam and an outboard end of said bumper beam should be less than the distance between said junction and an outboard side of said side member.

Joining the side member and the crash box is easy if both form a plug-in connection.

Preferably, in this connection, the crash box first end engages within the side member.

Further features and advantages ofthe invention will become apparent from the subsequent description of embodiments thereof, referring to the appended drawings:

Fig

Fig is a top view of a crash box installed between a side member and a bumper bar of a motor vehicle;

is a cross section ofthe crash box along plane ll-ll of Fig. 1;

is a longitudinal section of the crash box along plane

Ill-Ill of Fig. 1;

is a top view of a crash box according to a second embodiment of the invention;

Fig. 5 is a cross section of the crash box along plane V-V of

Fig. 4; and

Fig. 6 is a longitudinal section of the crash box along plane

VI-VI of Fig. 4;

Figs. 1 to 3 illustrate a crash box and a motor vehicle body according to an elementary embodiment ofthe invention. The vehicle body comprises two side members 1 and a bumper bar 3 connected to the side members 1 by crash boxes 2. Since the vehicle body has specular symmetry, only half ofthe bumper bar 3, one crash box 2 and a forward portion of one side member 1 are shown in Fig. 1. The side member 1 is a tubular body. In a region extending between an engine compartment 4 and a front wheel arch 5, the side member 1 is slightly arcuate, a concave side of it facing the wheel arch 5. At its foremost end, walls 6 of the side member 1 extend in the vehicle longitudinal direction, forming a receptacle into which is plugged a narrow first end 7 of crash box 2.

The crash box 2 has an inboard sidewall 8 and an outboard sidewall 9, rear portions 10, 11 of which engage inside the side member 1. These rear portions 10,11 extend in the vehicle longitudinal direction, so that they can be drawn into intimate frictional contact with the inner sides of walls of the side member 1 by means of screws 12. The screws 12 extend through overlapping holes in the side member 1 and the rear portions 10, 11 of the sidewalls 8, 9 and engage in nuts 13 welded to an inner side of said rear portions 10, 11.

A main portion 14 of inboard sidewall 8 extends in the vehicle longitudinal direction to the bumper beam 3. A forward second end 15 of the crash box 2 comprises a junction 17 where the sidewall 8 is welded to a rear wall 16 of said bumper beam 3.

A main portion 19 of outboard sidewall 9 extends at an acute angle a with respect to the vehicle longitudinal direction and meets the rear wall 16 of bumper beam 3 at a junction 20 close to an outboard end 21 ofthe bumper beam 3. Measured in the vehicle lateral direction, the distance d1 between the junction 20 and an outboard side 22 of side member 1 is far larger, at least two times larger, than the distance d2 between the junction 20 and the outboard end 21, so that an outboard portion of the bumper beam 3 extending in front ofthe wheel arch 5 is supported against a collision force by outboard sidewall 9.

A top wall 23 extends between the upper edges ofthe sidewalls 8, 9, increasing in width from rear end 7 to forward end 15 ofthe crash box 2. At the forward end 15, the top wall 23 extends beyond the rear wall 18, extends along horizontal or slightly inclined wall portion 24 and is welded to a front wall 25 of the bumper beam 3.

As can be seen in the sections of Fig. 2 and 3, the crash box 2 is assembled from two pieces 26, 27 of sheet metal, one of which, 26, forms the top wall 23 and upper portions of the sidewalls 8, 9, whereas the other, 27, forms a bottom wall 28 and lower portions ofthe sidewalls 8, 9. In the section of Fig. 2, the two pieces 26, 27 appear to be butt welded along seams 29 extending in the middle between upper and lower edges of the main portions 14,19 of the sidewalls 8, 9, so that one half of each sidewall main portion 10, 11 is formed by the upper sheet metal piece 26 and the other by the lower sheet metal piece 27. Alternatively, the two pieces 26, 27 might overlap along the seams, or welding flanges protruding from the sidewalls might be formed along the edges of the two pieces 26, 27.

The lower sheet metal piece 27 may have thicker walls or be formed of a more rigid material than the upper sheet metal piece 26, so that in case of a collision the top wall 23 tends to yield first, causing the crash boxes 2 to bend in the upward direction so that if the obstacle causing the collision is low enough, the vehicle body may slide over the obstacle, thus minimizing deformation ofthe vehicle body.

At the first end 7 of the crash box 2, the seams 29 extend not in the middle of sidewall rear portions 10, 11 but in corners between the top wall 23 and sidewall rear portions 10,11. In this way, no projecting welding residues are formed at the outer sides of the rear portions 10, 11, so that the first end fits neatly into the opening of side member 1.

Since due to the flared shape of the crash box 2 the portion of the bumper bar 3 which protrudes beyond the junction 20 in the outboard direction is extremely short, and there is practically no possibility of this portion yielding to an impact by bending while the crash box remains unaffected. The outboard sidewall 9 cannot yield to the impact by flexing in the outboard direction, since this would require the top and bottom walls 23, 28 to stretch in the vehicle transverse direction. This makes the crash box highly resistant in case of a shallow offset collision, and facilitates a lateral displacement of the vehicle by which the offset between the vehicle and the obstacle is further increased or, eventually, the vehicle may bypass the obstacle.

In a rear portion of the crash box 2, rigidity may be increased further by a reinforcing member 18 shown in Fig. 2 and 3. The reinforcing member 18 is fixed to rear portions 10, 11 of both sidewalls 8, 9 at an intermediate level between top and bottom walls 23, 28 and extends in the forward direction along part of the sidewall 8, 9 main portions 14, 19. In each sidewall 8, 9, one of the nuts 13 is located above the reinforcing member 18 and another, below.

The reinforcing member 18 is a piece of sheet metal comprising a horizontal central portion 30 and flanges 31, 32 bent at right angles and extending along front and lateral edges of the main portion. In the main portions 14, 19 of the sidewalls 8, 9, the lateral flanges 32 of the reinforcing member 18 extend along the seams 29 and, by being welded to both sheet metal pieces 26, 27, help to prevent these from being torn apart in a crash.

A second effect of the reinforcing member 18 is that at a moderate collision speed deformation of the crash box 2 can be confident to a non-reinforced portion between the second end 15 and the flange 31. When the rear end 7 keeps its shape after a collision, the assembly made up of bumper bar 3 and crash boxes 2 can be replaced easily by just removing the screws 12 and pulling the assembly out of the side members 1.

Figs 4-6 illustrate a more sophisticated embodiment of the present invention. The side member 1 and the bumper bar 3 are the same as in the embodiment of Fig. 13, and the overall shape of the crash box is unchanged, too. A difference between the two embodiments is in that here, hollow webs 33, 34, 35 are formed in some of the walls 8, 9, 23, 28 of the crash box 2.

Fig 4. shows two such webs 33, 34 in the top wall 23. The web 33, adjacent to the outboard side wall 9, extends continuously between first and second ends 7, 15 of the crash box 2, thus increasing rigidity of the top wall 23. The other web 34, adjacent to inboard sidewall 8, has an interruption 36 in which its height is reduced; here the interruption 36 is flush with the top wall 23 at both sides of the web 34.

Webs 33, 34 in bottom wall 28 are specular images of those in top wall 23.

Webs 35 formed in the inboard sidewall 8 also have interruptions 36. In the vehicle longitudinal direction, these interruptions 36 are aligned with the interruptions of the webs 34, so that if an impact hits a central region of bumper bar 3 between the crash boxes 2, the inboard sidewalls 8 of these will start yielding, and outboard sidewalls 9 will eventually follow soon after. The outboard sidewall 9 has no webs.

At the outboard sides of the crash box 2, rigidity is maintained or even increased over that of the first embodiment, so that the benefits described above in case of a shallow offset collision prevail.

The webs 33, 34, 35 do not extend into the first end 7 of the crash box, engaged inside the side member 1. Rather, rear ends 37 of the webs 33, 34, 35 may serve as abutments which, by abutting against the forward edge of side member 1, define a position in which screw holes in side member 1 overlap with the nuts 13 of crash box 2, thus facilitating installation of the crash box 2.

In an alternative embodiment, two interruptions might be formed in webs 34, 35 of the inboard sidewall and at an inboard side of top and bottom walls of the crash box 2, whereas just one is formed in a web of top and bottom walls adjacent to the outboard sidewall. Here, in a frontal collision, the doubly interrupted webs at the inboard side of the crash box will be the first to yield, followed by the webs at the outboard side of top and bottom walls, and, finally, the outboard sidewall.

It should be understood that the above detailed description and the drawings disclose specific embodiments of the invention, but that they are intended only for illustration purposes and must not be construed as limiting the scope of the invention. Various modifications of the described embodiments can be made within the scope of the appended claims and their range of equivalents. In particular, from the description and the drawings, features may become apparent which are not mentioned in the claims. Such features may appear in other combinations besides those specifically disclosed here. The fact that several such features may be mentioned in the same sentence or in some other kind of contextual relation must not lead to the conclusion that they can only appear in the combination specifically disclosed; rather, it should be assumed that among such a plurality of features, one or more features can be left away or modified, as far as this does not jeopardize the correct operation of the invention.

List of reference numerals side member crash box bumper bar engine compartment wheel arch wall first end inboard sidewall outboard sidewall rear portion rear portion screw nut main portion second end rear wall junction reinforcing member main portion junction outboard end outboard side top wall wall portion front wall sheet metal piece sheet metal piece bottom wall seam reinforcing member flange flange web web web interruption rear end

Claims

Patent Claims

1. A crash box (2) for a motor vehicle having a first end (7) for connecting to a side member (1), a second end (15) for connecting to a bumper beam (3) and inboard and outboard sidewalls (8, 9) which diverge from said first end (7) towards said second end (15).
2. The crash box of claim 1, wherein top and bottom edges of said sidewalls (8, 9) are connected by top and bottom walls (23, 28).
3. The crash box of claim 2, wherein in at least one of said top and bottom walls (23, 28) and said sidewalls (8, 9) at least one longitudinally extending hollow web (33, 34, 35) is formed.
4. The crash box of claim 3, wherein an interruption (36) is formed in the web (34, 35).
5. The crash box of claim 2, wherein the inboard sidewall (8) has at least one web (35) in which an interruption (36) is formed, and the outboard sidewall (9) hasn’t.
6. The crash box of claim 2 or 5, wherein in at least one of said top and bottom walls (23, 28) at least two longitudinally extending hollow webs (33, 34) are formed, a first one (33) of which one is located adjacent to the outboard sidewall (9), and a second one (34) of which is located adjacent to the inboard sidewall (8) and has more interruptions (36) than the first web.
7. The crash box of any of the preceding claims, wherein a longitudinally extending reinforcing member (18) is connected to said sidewalls (8, 9) between top and bottom edges thereof.
8. The crash box of claim 7, wherein the reinforcing member (18) extends between said first end (7) and an intermediate portion of the crash box (2).
9. The crash box of any of the preceding claims, assembled from at least two pieces (26, 27) of sheet material of different gauge and/or composition.
10. The crash box of any of the preceding claims, wherein nuts (13) for connecting to the side member (1) are mounted at the first end (7).
11. A motor vehicle comprising the crash box (2) of any of the preceding claims,

5 wherein the outboard sidewall (9) extends at an acute angle (a) with respect to the vehicle longitudinal direction.
12. The motor vehicle of claim 10, wherein the inboard sidewall (8) deviates less from the vehicle longitudinal direction than the outboard sidewall (9). io
13. The motor vehicle of claim 10 or 11, wherein a side member (1) is connected to the crash box (2) first end (7) and a bumper beam (3) is connected to the crash box (2) second end (15), and the distance, measured in the vehicle lateral direction, between a junction (20) where the outboard sidewall (9)

15 meets the bumper beam (3) and an outboard end (21) of said bumper beam (3) is less than between said junction (20) and an outboard side (22) of said side member (1).
14. The motor vehicle of claim 10, 11 or 12, wherein the side member (1) and

20 the crash box (2) form a plug-in connection.
15. The motor vehicle of claim 13, wherein the crash box first end (7) engages within the side member (1).

Intellectual

Property

Office