This invention relates to a front portion for vehicles of the kind indicated in the preamble to patent claim 1.

State of the art

To prevent sheetmetal damage to vehicles due to collisions during parking, in queues, in cramped garages etc., vehicles are equipped with bumpers which cope with a collision up to a certain speed without the vehicle itself sustaining damage. A modern bumper for vehicles incorporates a strong steel rail which stretches across the vehicle and is fastened to structural elements of the vehicle. An elongated flexible housing is fastened to and conceals the steel rail and an energy absorbing device arranged between the rail and the housing.

Modern bumpers have satisfactory impact energy absorption behaviour in collisions at vehicle speeds of up to approximately 8 km/h. In collisions at greater speeds the steel rail acts as an undeformable spacer, with the result that the structure behind the steel rail, i.e. structural elements of the vehicle, is deformed during the course of a collision and gives rise to damage which is relatively expensive to repair. As most low speed collisions occur at speeds between 10 and 15 km/h, it is obvious that there are a large number of vehicles which require costly repairs. This is of course a problem for both vehicle owners and insurance companies that have to pay the cost of repairs.

Certain vehicle manufacturers have realised the problem and

have tried to solve it by complicated and expensive solutions which incorporate shock absorbers and the like. As those solutions are so complicated, they have not been put into production to any major extent.

Object of the invention

The object of this invention is to eliminate the disadvantages mentioned and to achieve a front portion with a bumper system which has good impact energy absorption behaviour at speeds of up to at least 15 km/h. To this end, the invention is distinguished by the features indicated in the characterising part of patent claim 1.

The solution according to the invention absorbs deformations in the most commonly occurring low speed collisions without causing damage to structural elements of the vehicle. This obviously reduces repair costs both for insurance companies and for vehicle owners. The invention is also relatively simple and affords significant advantages from the production point of view in that it is inexpensive and involves a small number of parts which are easy to assemble.

Other features characterising the invention are indicated in the attached patent claims and in the description below of an embodiment exemplifying the invention. The description is given with reference to the attached figures.

Brief description of the figures

Figure 1 shows a vehicle provided with an arrangement according to the invention.

Figure 2 shows a simplified diagram of the front structure of the vehicle depicted in Figure 1. Figure 3 shows a cross-section of the vehicle's bumper and the forward section of the latter's front structure. Figure 4 shows a cross-section of an arrangement according to the invention after a collision.

Description of the embodiment

Figure 1 shows a vehicle, in this case a passenger car, with a bumper 1 which forms part of the vehicle front structure 60 (Fig.2) and stretches horizontally across the vehicle in order to protect the latter from impacts and collisions. The bumper 1 is at the same time arranged to become deformed during energy absorption when it is subjected to a collision force which exceeds a predetermined force.

Figure 2 shows the front structure 60. As the structure 60 is symmetrical about a plane of symmetry longitudinal to the vehicle, the invention is only described on one side of the plane of symmetry but it is implicit that substantially the same conditions prevail on the other side.

The front structure 60 incorporates a side beam 61 longitudinal to the vehicle, a longitudinal central beam 62 and a first brace 63 which connects the side beam 61 to the central beam 62. The front structure also incorporates a supporting device 80 mainly comprising a transverse bumper beam 2, a subframe 64 and a second brace 66 which connects the central beam 62 to the subframe 64.

Both the first and the second braces 63, 66 slant rearwards in

the longitudinal direction of the vehicle, i.e. their ends fastened to the central beam 62 are situated closer to the supporting device 80 than their ends fastened respectively to the side beam 61 and the subframe 64. At the same time, the braces 63, 66 demarcate a forward beam section 67, which is intended to form a deformation zone, from a rear beam section 68.

The central beam 62 is substantially straight and stretches in a horizontal plane forwards in the longitudinal direction of the vehicle. Its forward end 70 is connected to the supporting device 80, while its rear end 71 is connected to an undepicted floor beam which forms part of the vehicle's structural elements. The side beam 61 and the subframe 64 are also connected to the vehicle's structural elements, which means that in a collision the load to which the central beam 62 is subjected via the supporting device 80 is transmitted to the vehicle's structural elements via the central beam 62 itself, the braces 63, 66, the side beam 61 and the subframe 64.

According to this embodiment, the supporting device 80 incorporates not only the bumper beam 2 but also an end-piece 73 which advantageously has a U-shaped cross-section with arms 74, 75 which stretch out from the vehicle and embrace the bumper beam 2. The main purpose of the end-piece 73 is to facilitate the fitting of the bumper beam 2, which involves the end-piece 73 being first secured to the end section 70, e.g. by welding, after which the bumper beam 2 is applied and secured to the end-piece 73.

Figure 3 shows how the bumper 1 incorporates not only the supporting device 80 but also a covering device 3 which is

fastened to the bumper beam 2 and which covers the whole or part of the bumper beam 2 and an energy absorbing device 4 which is arranged between the covering device 3 and the bumper beam 2 and is designed to become deformed when subjected to a predetermined force.

The bumper beam 2 consists of at least one light metal rail, a pressure-shaped plate or the like, the vertical extent of which exceeds the vertical extent of the adjoining central beam 62. The result is the formation of a rearwardly free overhung section B (hereinafter called the overhang) of the supporting device 80, which is used as an energy absorbing structure, the function of which is described later. As shown in Figure 3 there is an overhang both above and below the central beam 62, and it is advantageous that these two overhangs B be substantially equal in size as in this embodiment. In alternative embodiments it need not necessarily be the case that they are of equal size.

The bumper beam 2 stretches across the vehicle and has a mainly U-shaped cross-section with arms 5, 6 stretching out from the vehicle and having the energy absorbing device 4 and part of the covering device 3 situated between them. Each arm 5, 6 is designed with an indentation or embossing (8 and 9 respectively) which forms a bearing shoulder for the energy absorbing device 4 and also delineates a cavity 10, 11 which stretches along the whole bumper beam 2. The respective arms 6, 7 are also provided with a flange 12, 13 directed outwards, with respective outer end 14, 15 bent back towards the vehicle as seen in its longitudinal direction and with a lip or projection 16, 17 directed inwards and arranged to accommodate by snap-in lock the locking devices described below.

The covering device 3 stretches along the whole bumper 1, takes the form of a flexible protective housing with rubber-like hardness and incorporates a substantially vertical forward wall 20 which is continued by upper and lower walls 21, 22 which are directed rearwards and stretch towards the vehicle body so as to seal a gap between the bumper 1 and the vehicle body and thereby conceal both the energy absorbing device 4 and the bumper beam 2.

Between the upper and lower walls 21, 22 there is a wall 23 which constitutes the rear boundary of an elongated hollow space 24 in which the energy absorbing device 4 extends. The wall 23 may be unbroken or, as in this embodiment, be provided with a longitudinal aperture 25 which divides the wall into upper and lower wall sections 26, 27. Each wall section 26, 27 is provided in this embodiment with two (although there may be more than two) portions 28, 29 and 30, 31 respectively which stretch towards the interior of the vehicle and which are advantageously, but not necessarily, parallel with one another.

The one portion 28, 30 is hereinafter called the locking device 28, 30 because it is used for locking the covering device 3 to the bumper beam 2. Each of the locking devices 28, 30 forms an integral part of the covering device 3 and incorporates an elongated arm 35, 36, the end portion of which is provided with a hooklike projection 37, 38 intended to lockingly grip the edge 16, 17 of the bumper beam 2.

The other portion 29, 31, which is hereinafter called the flange 29, 31, fits into the recess 10, 11 of the bumper 2. The respective flange 29, 31 is provided with an outer first bearing surface 50, 51 which bears against the bumper beam 2,

and an inner second bearing surface 52, 53 which bears against the energy absorbing device 4 so as to fix the latter's position relative both to the covering device 3 and to the bumper beam 2.

The energy absorbing device 4 is made of some elastic material such as foam plastics, cellular plastics or rubber and is provided with an inner narrower section 45 and an outer broader section 46 manufactured as a single piece. The inner narrower section 45 stretches in between the flanges 5, 6 of the bumper beam 2 and bear against a substantially vertical middle section 18 of the bumper beam 2, against the indentations 8, 9 and against the radially inner surface 52, 53 of the respective flange 29, 31, while the outer broader section 46 stretches into the covering device 3, where it bears against the forward section 20 of the covering device 3 and delineates upper and lower spaces 54, 55.

In a transition zone between the inner narrower section 45 and the outer broader section 46 there is a stop face 56 which either bears against or, as in this case, is intended to be brought to bear against the covering device 3. The stop face 56 stretches substantially in a vertical plane and substantially parallel with the respective upper and lower wall portion 26, 27 and with the respective flange 12, 13 and is arranged at a distance A of not more than 3 cm from the covering device 3.

As mentioned previously, not only the central beam 62 but also the side beam 61 and the subframe 64 are connected to the vehicle's structural elements. The forces resulting from any collision are therefore transmitted from the bumper 1 to the

vehicle's structural elements via the central beam 62, the braces 63, 66, the subframe 64 and the side beam 61.

At the time of a collision, the bumper 1 will first absorb the collision energy. If the collision speed is below approximately 8 km/h, the stop face 56 will be pressed against the supporting device, resulting in deformation of the energy absorbing device 4 but not the supporting device 80 and the forward section 67 of the central beam 62. As there is a gap A between the stop face 56 and the bumper beam 2, the result is a certain delay before the energy absorbing device 4 comes into contact with the bumper beam 2. This delay is advantageous from the energy absorption point of view.

If the collision speed exceeds approximately 8 km/h but is less than approximately 15 km/h, the energy absorbing device 4 will in the manner indicated above absorb part of the collision energy, while the remainder of the collision energy, as illustrated in Figure 4, is transmitted to the supporting device 80. This results in the overhang B of the latter becoming deformed as it absorbs collision energy, while the arms 74, 75 of the end-piece 73 also become deformed, without any damage to the central beam 62 and elements to the rear of it. If a greater degree of energy absorption is required, i.e. at collision speeds over approximately 15 km/h, the energy absorption is continued by deformation of the forward sections 67 of the central beam 62 and also, depending on the collision speed, by the braces 63, 66, the side beams 61 and the subframe 64.

As the supporting device 80 designed according to the invention with overhangs B relative to the central beam 62 results in

controlled energy absorption, collisions at speeds below approximately 15 km/h do not damage the central beam 62 and elements to the rear of it but only the bumper 1 itself. As it is significantly cheaper and easier to change the bumper 1 than to straighten or replace damaged central beams 62, braces 63, 66, side beams 61 or subframe 64 by new ones, the result is significant gains both for vehicle owners and for insurance companies.

According to the invention, the deformation characteristics of the end-piece 73 are chosen such that the overhang B can be subjected to controlled deformation substantially to a level in the longitudinal direction of the vehicle which corresponds to the level for the forward end 70 of the central beam 62 without initiating any substantial deformation of the central beam 62. The dimensions of the overhang B in the vertical direction exceed at least twice the plate thickness of the supporting device 80, i.e. the bumper beam 2 and the end-piece 73 combined. The height of the overhang B is a maximum of 50mm and preferably a maximum of 20mm.

The embodiment described above does not set any limits upon the invention, which may be employed in alternative embodiments without departing from the concept of the invention. For example, the end-piece 73 may be eliminated, in which case the bumper beam 2 is fitted directly to the central beam 62. Moreover, both the bumper beam 2 and the front structure 60 may also be designed in a different manner.