FR3160376A1 - Reinforced motor vehicle side member and underbody assembly comprising such a side member - Google Patents

Abstract

Reinforced motor vehicle side member and underbody assembly comprising such a side member. The invention relates to a longitudinal side member (7d) of a vehicle underbody assembly, comprising a longitudinal hollow body and a reinforcement device comprising a honeycomb structure (19) comprising a plurality of tubes (21), said honeycomb structure being arranged transversely relative to said longitudinal hollow body. According to the invention, at least two of said tubes (21) each comprise an attachment interface, said attachment interfaces being adapted to cooperate with each other. Figure 9

Description

Reinforced motor vehicle side member and underbody assembly comprising such a side member

The invention relates to the field of motor vehicles, in particular to the field of passive safety of the motor vehicle to provide protection in the event of a side impact and a frontal impact.

The invention relates more particularly to a longitudinal lateral side member of an underbody assembly of a motor vehicle and an underbody assembly comprising such a side member.

A motor vehicle body structure comprises a set of sheet metal structural elements providing stiffness to the motor vehicle, assembled together and forming the frame of the motor vehicle.

The body structure comprises, in particular, among these sheet metal elements, a left side structure and a right side structure. Each side structure comprises a set of upper and lower horizontal elements, extending substantially longitudinally relative to the body, and a set of vertical elements, extending substantially vertically relative to the body.

The lower horizontal elements include lateral longitudinal side members defining part of the perimeter of the underbody.

The left and right side structures are connected to each other in the lower part of the vehicle by a floor, belonging to a vehicle underbody assembly and bordered laterally by the right and left side longitudinal side members.

The underbody assembly defines a vehicle base which is used to receive vehicle design elements, called “silhouettes”, which vary depending on the vehicle’s dimensions.

Among the many tests used for the approval of motor vehicles, a side impact is carried out, in particular in order to reveal performance criteria relating to the protection of occupants.

Among the different types of side impacts, a so-called "pole" impact consists of projecting the motor vehicle at a speed of approximately 30 km/h laterally against a rigid pole, so that the vehicle defines an angle of approximately 75° relative to the pole.

In the event of a side impact, the post becomes embedded in the motor vehicle, at the level of the front door, driver's side or passenger's side.

The impact absorption capabilities of the vehicle's underbody assembly are, in part, provided by the lateral longitudinal side members, which absorb part of the forces occurring when the vehicle is subjected to such a side impact.

Similarly, when the vehicle is subjected to a frontal impact, the impact absorption capacities at the level of the underbody assembly are partly provided by the lateral longitudinal side members.

A recurring problem is therefore to increase the capacity of the longitudinal side members to absorb the forces.

Also, when the vehicle is a battery electric motor vehicle (BEV), the vehicle has a traction battery that powers the electric motor of the motor vehicle. The traction battery has a set of battery modules, mounted in a battery tray. The battery tray is mounted under the floor of the underbody assembly. The battery tray defines one of the silhouettes on board the underbody assembly when the vehicle is an electric vehicle. The sizing of the battery tray differs depending on the dimensions of the vehicle.

When the motor vehicle is subjected to a side impact, the electric battery must be protected in order to avoid damage to the battery and to limit the risk of fire.

Therefore, there is a need to reinforce the side longitudinal members, especially when the vehicle is an electric motor vehicle with battery.

Also, when the motor vehicle is electric, the absorption capacities of the longitudinal side members must be further increased, the mass of an electric vehicle being much greater than that of a thermal vehicle.

A solution known from the prior art consists of using a reinforcing element made of extruded aluminum alloy, which connects the battery to the longitudinal side members.

However, machining such a solid aluminum reinforcement element is complex and generates material loss.

Therefore, a solution aimed at using longitudinal side members made of aluminum and steel is not satisfactory. Indeed, such a solution would add mass to the vehicle, which would go against the general and recurring problem of reducing the mass of a motor vehicle.

Document EP 3 747 736 A1 is also known, which discloses a device for reinforcing the longitudinal lateral side member of a motor vehicle underbody assembly, the reinforcing device comprising a set of honeycomb profiles stacked transversely throughout the volume of the side member.

The presence of honeycomb profiles makes it possible to structurally strengthen the spar, while limiting its mass.

However, the honeycomb profiles are stacked throughout the volume of the spar, i.e. over the entire length and height of the spar.

Thus, the reinforcement device is voluminous and is identical regardless of the silhouette carried by the underbody assembly.

Therefore, the arrangement of the reinforcement device in the longitudinal side member is not optimized according to the silhouette type.

The present invention aims to overcome the aforementioned drawbacks, and to do so relates to a longitudinal lateral side member of a motor vehicle underbody assembly, said side member comprising a longitudinal hollow body and a device for reinforcing said longitudinal hollow body, said reinforcing device comprising a honeycomb structure comprising a plurality of tubes, said honeycomb structure being arranged transversely relative to said longitudinal hollow body, said side member being remarkable in that at least two of said tubes of said honeycomb structure each comprise an attachment interface, said attachment interfaces being adapted to cooperate with each other.

Thus, by providing a longitudinal lateral spar comprising a reinforcing device comprising a honeycomb structure comprising a plurality of tubes among which at least two of said tubes each comprise an attachment interface, said attachment interfaces being adapted to cooperate with each other, the tubes of the honeycomb structure can be attached relative to each other.

In this way, the tubes can be integrated in a modular manner into the longitudinal side member.

The reinforcement of the longitudinal side member is thus managed in a personalized manner, unlike the prior art where the reinforcement of the longitudinal side member is carried out regardless of the silhouette chosen.

This prevents the honeycomb structure from occupying the entire length and height of the longitudinal side member, as is the case in the prior art.

This allows the volume of the side member to be limited, particularly in a transverse direction, which allows battery volume to be saved when the motor vehicle is electric, and therefore optimizes the vehicle's range.

According to optional characteristics of the spar according to the invention:
- each of said tubes comprises a peripheral wall defining a tubular hollow body, and each of said attachment interfaces is arranged outside said peripheral wall of said tubes;
- at least one of said tubes of said honeycomb structure is filled at least in part with an aluminum foam;
- several of said tubes of said honeycomb structure are filled at least in part with aluminum foams of different densities;
- said attachment interfaces cooperate with each other by interlocking;
- the spar comprises an external closing envelope, contained inside said longitudinal hollow body, said external closing envelope enclosing said reinforcement device;
- all of said tubes of said honeycomb structure extend over a length equal to the thickness of said spar;
- at least one of said tubes of said honeycomb structure extends over a length less than the thickness of said spar;
- said plurality of tubes of said honeycomb structure defines a plurality of stages, each of said stages comprising at least one of said tubes.

The invention also relates to an underbody assembly for a motor vehicle, comprising:
- a floor,
- lateral longitudinal side members, laterally bordering said floor,
said underbody assembly being remarkable in that at least one of said lateral longitudinal side members is according to the invention.

Other characteristics, aims and advantages of the invention will appear on reading the detailed description which follows, for the understanding of which reference will be made to the appended drawings in which:

FIG. 1 shows an underbody assembly of a motor vehicle according to the invention, seen in perspective from below.

FIG. 2 is a partial perspective cutaway view of a longitudinal side member of the underbody assembly of the invention.

FIG. 3 shows a front view of the longitudinal side member, the hollow body of said member having been hidden.

FIG. 4 is a perspective view of one of the tubes of the honeycomb structure of the longitudinal side member reinforcement device.

FIG. 5 is a perspective view of an example of the assembly of several tubes together, forming a level of the honeycomb structure.

FIG. 6 shows a first example of the construction of the longitudinal lateral spar seen at the level of zone A of the FIG. 2 , a portion of the outer closing envelope being hidden for better visibility.

FIG. 7 is a view similar to the FIG. 6 , the longitudinal lateral spar being according to a second embodiment.

FIG. 8 is a view similar to the FIG. 6 , the longitudinal side member being according to a third embodiment.

FIG. 9 is a sectional view along line BB of the FIG. 3 , the longitudinal lateral spar being according to a fourth embodiment.

FIG. 10 is a view similar to the FIG. 9 , the longitudinal lateral spar being according to a fifth embodiment.

FIG. 11 shows, in top view and in section, an example of integration of the longitudinal side member into an underbody assembly of a motor vehicle.

In the remainder of the description, elements having an identical structure or similar functions are designated by the same reference.

By convention, we will adopt, without limitation, longitudinal, vertical and transverse orientations indicated by the direct trihedron (L, V, T) designating the longitudinal, vertical and transverse axes of the vehicle.

In the following, the terms "left", "right", "lower" and "upper" refer to the vehicle.

Similarly, the terms "front" and "rear" are understood in relation to the general orientation of the vehicle as taken in its normal direction of travel.

We refer to the FIG. 1 showing an underbody assembly 1 of a motor vehicle 3, seen in perspective from below.

The underbody assembly 1 belongs to a body structure comprising a set of sheet metal structural elements providing stiffness to the motor vehicle 3, assembled together and forming the frame of the motor vehicle.

Among these sheet metal elements, the body structure includes a 5g left side structure and a 5d right side structure.

The body structure has a longitudinal median plane of symmetry. Thus, the description given for the left lateral structure 5g applies by analogy to the right lateral structure of the body structure.

Each lateral structure comprises a set of upper and lower horizontal elements, extending substantially longitudinally relative to the body, and a set of vertical elements, extending substantially vertically relative to the body.

The lower horizontal elements comprise lateral longitudinal side members 7g, 7d extending substantially longitudinally relative to the motor vehicle 3.

At the front, the lateral longitudinal side members 7g, 7d are connected to a front block 9 of the motor vehicle 3. At the rear, the lateral longitudinal side members 7g, 7d are connected to the rear axle 11 of the motor vehicle 3.

The left and right side structures 5g, 5d are connected to each other in the lower part of the motor vehicle 3 by a floor 13.

In the embodiment illustrated in the figures, the motor vehicle 3 is an electric motor vehicle with battery (motor vehicle known as “BEV”, an English acronym for “Battery Electric Vehicle”). For this purpose, the motor vehicle 3 comprises a traction battery (not shown) powering the electric motor (not shown) of the motor vehicle 3.

The traction battery comprises a set of battery modules, mounted in a battery tray mounted under the floor 13.

We refer to the FIG. 2 which is a partial perspective cutaway view of the longitudinal side member 7d.

The longitudinal side member 7d comprises a longitudinal hollow body 15 extending substantially longitudinally relative to the motor vehicle 3 when the longitudinal side member 7d is mounted in the motor vehicle 3.

The longitudinal lateral spar 7d further comprises a reinforcement device 17 for the longitudinal hollow body 15, comprising a honeycomb structure 19 comprising a plurality of tubes 21.

The honeycomb structure 19 is arranged transversely relative to the longitudinal hollow body 15.

In other words, the tubes 21 extend transversely relative to the longitudinal hollow body 15, that is to say they extend transversely relative to the motor vehicle 3 when the longitudinal side member 7d is mounted in the motor vehicle 3.

In the embodiment illustrated in the figures, the longitudinal lateral spar 7d comprises an external closing envelope 23, contained inside the longitudinal hollow body 15 and enclosing the reinforcement device 17, and the function of which is explained in the remainder of the description.

We refer to the FIG. 3 showing a front view of the longitudinal side member 7d, the hollow body 15 having been hidden.

The outer closing envelope 23 comprises an outer closing half-envelope 23a and an outer closing half-envelope 23b which may, for example, be made of aluminum sheet.

The fixing between the outer closing half-envelopes 23a, 23b can, for example, be carried out at the fixing points 22, 24 by means of welding beads and/or by gluing and/or by electric welding points and/or by screws, etc.

In an embodiment not shown in the figures, the longitudinal lateral spar 7d does not have any external closing envelope 23, the reinforcement device 17 then being contained directly in the longitudinal hollow body 15.

We refer to the FIG. 4 showing in perspective one of the tubes 21 of the honeycomb structure 19 of the reinforcement device 17.

The tube 21 constitutes a primary element of the honeycomb structure 19. The tube 21 comprises a peripheral wall 25, defining a tubular hollow body.

The primary element of the honeycomb structure 19 defined by the tube 21 may, for example, be made of a metallic material such as aluminum.

The tube 21 can, for example, be manufactured by extruding aluminum, then by cutting according to the need, in order to allow modularity of the tubes in terms of height.

The characteristics of the tubes 21 are configurable depending on the vehicle in which they are mounted. For example, the thickness of the wall of the tube 21 is adjustable, as is the width of the tube 21.

Also, the shape of each tube 21 is adapted to give stiffness to the entire honeycomb structure 19.

In the embodiment illustrated in the figures, the tubes 21 have a substantially hexagonal geometric shape, in the form of a cell.

According to an alternative embodiment not shown, the tubes 21 have a different geometric shape, for example circular, polygonal, for example rectangular, etc.

Also, not all tubes 21 of the honeycomb structure 19 are necessarily identical. For example, some tubes 21 may be hexagonal in shape with a certain thickness and width while other tubes 21 of the same honeycomb structure 19 may have a different geometric shape, with a thickness and/or width that may be different, etc.

According to the invention, at least two of the tubes 21 of the honeycomb structure 19 each comprise an attachment interface 27.

The attachment interfaces 27 are adapted to cooperate with each other, so as to allow two tubes 21 to be attached to each other.

Thus, by virtue of the present invention, the tubes 21 of the honeycomb structure 19 can be attached relative to each other.

In this way, the tubes 21 can be integrated in a modular manner into the longitudinal side member.

The reinforcement of the longitudinal side member is thus managed in a personalized manner, unlike the prior art where the reinforcement of the longitudinal side member is carried out regardless of the silhouette chosen.

This prevents the honeycomb structure from occupying the entire length and height of the longitudinal side member, as is the case in the prior art.

This allows the volume of the side member to be limited, particularly in a transverse direction, which allows battery volume to be saved when the motor vehicle is electric, and therefore optimizes the vehicle's range.

In the exemplary embodiment illustrated in the figures, each of the attachment interfaces 27 is arranged outside the peripheral wall 25 of the tube 21, which makes it easy to manipulate the attachment interfaces 27.

In the embodiment illustrated in the figures, the attachment interfaces 27 cooperate with each other by interlocking, or by clipping.

However, according to an alternative embodiment not shown in the figures, the attachment interfaces 27 can cooperate with each other by any other type of connection, for example using glue, welding, etc.

When the attachment interfaces 27 cooperate with each other by interlocking, the attachment interfaces 27 may for example comprise a male attachment interface 29 and a female attachment interface 31.

The male attachment interfaces 29 and/or the female attachment interfaces 31 can be obtained during the extrusion of the tube 21.

In the embodiment illustrated in the figures, the tube 21 comprises three male attachment interfaces 29 and three female attachment interfaces 31.

As shown in the FIG. 5 , several tubes 21 are fitted together so that the male attachment interface 29 of one of the tubes 21 cooperates with the female attachment interface 31 of another of the tubes 21. A stage 33 of the honeycomb structure 19 is then obtained.

We refer to the FIG. 6 showing a first example of the construction of the longitudinal lateral spar 7d seen at the level of zone A of the FIG. 2 , the outer closing half-envelope 23b having been hidden for better visibility.

In the example of realization given in the FIG. 6 , some tubes 21 of the honeycomb structure 19 are filled with an aluminum foam 35.

The tubes 21 into which the aluminum foam 35 is introduced are chosen according to the stiffness requirement of the area of the vehicle in question. In this way, the reaction of the longitudinal side member to the impact is controlled as precisely as possible.

Due to the presence of pores, aluminum foam is lighter than aluminum, which makes it possible to give stiffness to the longitudinal side member while limiting the mass of the member, and therefore of the motor vehicle, which makes it possible to optimize the vehicle's autonomy, in particular when the vehicle is electric.

The tubes 21 containing aluminum foam 35 may be completely or only partially filled with the aluminum foam 35.

Also, depending on the stiffness requirement, it is envisaged within the framework of the invention to use aluminum foams 35 of identical or different densities to fill the tubes 21 of the honeycomb structure 19.

The aluminum foam used in the context of the present invention may be recyclable and/or derived from recycling.

The aluminum foam expands when the body structure undergoes a baking phase, following a phase of application of a cataphoresis treatment used to combat corrosion.

In this regard, the cataphoresis stage involves immersing the vehicle's body structure in a bath, used to combat corrosion. This treatment allows for a uniform deposit across the entire vehicle's body structure.

When leaving this bath, the cataphoresis is evacuated by gravity.

The presence of the outer closing envelope 23, contained inside the longitudinal hollow body 15 and enclosing the reinforcing device 17, makes it possible to prevent the cataphoresis from entering the tubes 21 of the honeycomb structure 19. In this way, the cataphoresis is prevented from remaining enclosed in the pores of the aluminum foam 35 when the body structure leaves the cataphoresis bath.

The honeycomb structure 19 can be fixed to the outer closing envelope 23, for example, by gluing or welding.

We refer to the FIG. 7 showing a second example of the longitudinal lateral spar 7d seen at the level of zone A of the FIG. 2 , the outer closing half-envelope 23b being hidden for better visibility.

In the example embodiment illustrated in the FIG. 7 , all the tubes 21 of the honeycomb structure 19 extend over a length L ₁ equal to the thickness E (shown in Figures 2 and 11) of the longitudinal lateral spar 7d. The thickness E of the longitudinal lateral spar 7d is defined by the width of the longitudinal lateral spar 7d in the transverse direction.

We refer to the FIG. 8 showing a third example of the longitudinal lateral spar 7d seen at the level of zone A of the FIG. 2 , the outer closing half-envelope 23b being hidden for better visibility.

According to the embodiment variant illustrated in the FIG. 8 , several of the tubes 21 of the honeycomb structure 19 extend over a length L ₂ less than the thickness E of the longitudinal lateral spar 7d.

Alternatively, only one of the tubes 21 of the honeycomb structure 19 can extend over a length L ₂ less than the thickness E of the longitudinal lateral spar 7d.

We refer to the FIG. 9 which is a sectional view along line BB of the FIG. 3 showing a fourth example of the longitudinal side member 7d.

In the example embodiment illustrated in the FIG. 9 , the tubes 21 of the honeycomb structure 19 define three stages 33, each stage 33 comprising several tubes 21. The number of stages 33 can be adapted at will, in particular depending on the need in terms of stiffness.

To the FIG. 9 , the floors 33 are joined together. However, in an alternative embodiment illustrated in the FIG. 10 which is a sectional view along line BB of the FIG. 3 , the floors can be separated, that is to say that in this case there is no direct connection between the floors 33.

We refer to the FIG. 11 showing an example of integration of the longitudinal side member 7d, in top view and in section, in a base assembly 1 of a motor vehicle comprising a sliding side door (not shown).

The sliding side door moves along a slide 37. The slide 37 is fixed to the longitudinal side member 7d by means of a fixing plate 39 mounted inside the longitudinal side member 7d.

To do this, the tubes 21 of the honeycomb structure 19 extend, at the location intended to receive the fixing plate 39 of the slide 37, over a length L ₃ less than the thickness E of the longitudinal lateral spar 7d.

Thus, thanks to the present invention, it is possible to easily manage areas of the motor vehicle where it is necessary to integrate elements on the longitudinal side member 7d.

As goes without saying, the present invention is not limited to the embodiments of this side member and this underbody assembly, described above solely as illustrative examples, but on the contrary it embraces all variants involving the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

Claims (10)

Longitudinal lateral side member (7d, 7g) of a motor vehicle (3) underbody assembly (1), said side member (7d, 7g) comprising a longitudinal hollow body (15) and a reinforcement device (17) for said longitudinal hollow body (15), said reinforcement device (17) comprising a honeycomb structure (19) comprising a plurality of tubes (21), said honeycomb structure (19) being arranged transversely relative to said longitudinal hollow body (15), said side member (7d, 7g) being characterized in that at least two of said tubes (21) of said honeycomb structure (19) each comprise an attachment interface (27), said attachment interfaces (27) being adapted to cooperate with each other. A spar (7d, 7g) according to claim 1, wherein each of said tubes (21) comprises a peripheral wall (25) defining a tubular hollow body, characterized in that each of said attachment interfaces (27) is arranged outside said peripheral wall (25) of said tubes (21). Longeron (7d, 7g) according to one of claims 1 or 2, characterized in that at least one of said tubes (21) of said honeycomb structure (19) is filled at least in part with an aluminum foam (35). Longeron (7d, 7g) according to claim 3, characterized in that several of said tubes (21) of said honeycomb structure (19) are filled at least in part with aluminum foams (35) of different densities. Longeron (7d, 7g) according to any one of claims 1 to 4, characterized in that said attachment interfaces (27) cooperate with each other by interlocking. Longeron (7d, 7g) according to any one of claims 1 to 5, characterized in that it comprises an external closing envelope (23), contained inside said longitudinal hollow body (15), said external closing envelope (23) enclosing said reinforcement device (17). Longeron (7d, 7g) according to any one of claims 1 to 6, characterized in that all of said tubes (21) of said honeycomb structure (19) extend over a length (L ₁ ) equal to the thickness of said longeron (7d, 7g). Longeron (7d, 7g) according to any one of claims 1 to 6, characterized in that at least one of said tubes (21) of said honeycomb structure (19) extends over a length (L ₂ , L ₃ ) less than the thickness of said longeron (7d, 7g). Longeron (7d, 7g) according to any one of claims 1 to 8, characterized in that said plurality of tubes (21) of said honeycomb structure (19) defines a plurality of stages (33), each of said stages (33) comprising at least one of said tubes (21). Underbody assembly (1) of a motor vehicle (3), comprising:
- a floor (13),
- lateral longitudinal side members (7g, 7d), laterally bordering said floor (13),
said underbody assembly (1) being characterized in that at least one of said lateral longitudinal side members (7d, 7g) is according to any one of claims 1 to 9.