Underbody assembly and motor vehicle comprising such an assembly

Abstract

Underbody assembly and motor vehicle comprising such an assembly. The invention relates to an underbody assembly (1) for a motor vehicle (3), comprising:- a floor, comprising two half-floors,- a longitudinal central tunnel (7), extending between said half-floors,- a front crossmember (11) of the front seat, fixed to said floor and comprising a first end and a second end fixed to a longitudinal side member (9g) laterally bordering said floor,- a rear crossmember (13) of the front seat, fixed to said floor and comprising a first end and a second end fixed to said longitudinal side member (9g).According to the invention, the underbody assembly comprises an interface piece (23) fixed only to said central tunnel (7), extending longitudinally relative to said underbody assembly and on which said first ends of said front (11) and rear (13) crossmembers of the front seat are fixed.The invention also relates to a motor vehicle comprising such an underbody assembly. Figure 5.

Description

Title of the invention: Underbody assembly and motor vehicle comprising such an assembly Technical field

[0001] 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.

[0002] The invention relates more particularly to a base assembly and a motor vehicle comprising such an assembly. Prior art

[0003] A motor vehicle body comprises a set of sheet metal structural elements providing stiffness to the motor vehicle, assembled together and forming the frame of the motor vehicle.

[0004] The vehicle body includes, among these sheet metal elements, a left side structure and a right side structure.

[0005] 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.

[0006] The upper horizontal elements comprise, from the front to the rear of the body, bay uprights and roof arches, and the lower horizontal elements comprise lateral side members defining a part of the perimeter of the body underbody.

[0007] The vertical elements comprise, from the front to the rear of the body, front legs, central legs, or middle legs, connecting the side members to both the bay uprights and the roof arches, and rear legs.

[0008] The left and right side structures are connected to each other in the lower part of the vehicle by a floor, belonging to a motor vehicle underbody assembly.

[0009] The floor comprises a right half-floor and a left half-floor, separated from each other by a central tunnel extending longitudinally relative to the motor vehicle and consisting of a hollow body. The floor is bordered laterally by the right and left side rails.

[0010] The underbody assembly further comprises a front seat cross member and a front seat rear cross member, extending transversely relative to the vehicle and connecting the right and left side members to the central tunnel, for example by welding.

[0011] The front and rear cross members of the front seat support slides on which the seats are mounted and extend generally on either side of the front seats of the vehicle.

[0012] Among the plurality of tests used for the approval of motor vehicles, a so-called "pole" impact, also called "side impact" is carried out, in particular in order to reveal performance criteria relating to the protection of occupants.

[0013] This test consists of projecting the motor vehicle at a speed of approximately 32 km / h laterally against a rigid post, so that the vehicle defines an angle of approximately 75° relative to the post.

[0014] In the event of a side impact, the post becomes embedded in the motor vehicle at the driver's side front door. The seat crossmembers, acting as a force path in the event of a side impact, are then put under stress.

[0015] The sleepers are then stressed and transmit the forces to the connection points with the tunnel.

[0016] At the instant of maximum intrusion of the post into the vehicle, the local application of the force causes a rupture of the connection between the tunnel and the floor, which can lead to a tear in the tunnel.

[0017] The rupture of the tunnel results in uncontrolled behavior of the vehicle during impact, a deterioration in the behavior of the seat on the impact side.

[0018] Document FR3082494B1 is known from the prior art, which discloses the addition of an added part acting as a strut between the tunnel and the rear seat crossmember. Indeed, the side impact test provides for centering the impact of the shock at the level of the occupant. It is thus generally at the level of the rear crossmember that the post is embedded in the vehicle.

[0019] The presence of the reinforcing piece makes it possible to better distribute the forces over a larger surface area of ​​the tunnel, making it possible to limit the risk of the tunnel tearing. Thus, the solution provided by this document makes it possible to resolve the problems of tunnel tears when the impact comes from near the front seat rear cross member.

[0020] However, if the point of impact moves away from the rear cross member of the front seat, and this point instead impacts the front cross member of the front seat, the strut no longer plays its role of distributing the forces, and rupture of the tunnel is inevitable.

[0021] Also known is document EP1792808A1, which discloses a coupe-type motor vehicle, not having a central pillar as a vertical reinforcing element. In this type of vehicle, the underbody floor is designed to be structural, unlike vehicles which have a central pillar where the floor is very thin and is not structural. In order to reinforce the body structure of such a vehicle without a central pillar, and in particular to allow the vehicle to absorb lateral impacts in the absence of a central foot, an interface piece is arranged longitudinally and connects the seat crosspieces to the tunnel and is fixed to the floor to the heel board, an intermediate transverse piece present between the front and rear rows of seats. This solution makes it possible to transmit part of the forces to the floor and to the heel board, which makes it possible to reduce the loading of the tunnel.

[0022] The transposition of this solution into a motor vehicle which has a thinner floor of the type used when the vehicle does not have a central pillar would not be possible because the forces transmitted to the floor, which is not structural, could break the weld points ensuring the connection of the interface part on the floor and on the heel board or could even cause tears in the floor. Presentation of the invention

[0023] The present invention aims to overcome the aforementioned drawbacks, and to this end relates to an underbody assembly for a motor vehicle, comprising: - a floor, comprising two half-floors, - a longitudinal central tunnel, extending between said half-floors, - a front seat cross member, fixed to said floor and comprising a first end and a second end fixed to a longitudinal side member laterally bordering said floor, - a front seat rear cross member, fixed to said floor and comprising a first end and a second end fixed to said longitudinal side member, said underbody assembly being remarkable in that it comprises an interface piece fixed only to said longitudinal central tunnel, extending substantially longitudinally relative to said underbody assembly and to which said first ends of said front and rear front seat crossmembers are fixed.

[0024] Thus, by providing for fixing the interface part only on the longitudinal central tunnel, it is possible to avoid transmitting forces to the floor and to the heel board as is the case in the prior art, which makes the underbody assembly according to the invention compatible with integration into a motor vehicle comprising a non-structural floor.

[0025] Also, the fact that the interface part on which the front and rear cross members of the front seat are fixed extends longitudinally relative to the underbody assembly makes it possible to distribute the forces homogeneously at the front and rear of the central tunnel, regardless of the location of the point of impact, which makes it possible to avoid localized stress concentrations on the central tunnel.

[0026] In this way, the risk of breaking the connection between the central tunnel and the floor, which can lead to a tear in the central tunnel, which improves the safety of the motor vehicle.

[0027] According to optional characteristics of the base assembly according to the invention: - said interface part comprises at least one reinforcing rib arranged longitudinally relative to said interface part; - said at least one reinforcing rib has a thickness of between approximately 8 mm and approximately 12 mm; - the thickness of said interface part is greater than or equal to approximately 20 mm; - the distance between a front edge of said front seat crossmember and a front edge of said interface piece is at least equal to the distance between a median plane of said front seat crossmember and said front edge of said front seat crossmember; - the distance between a rear edge of said front seat rear crossmember and a rear edge of said interface piece is at least equal to the distance between a median plane of said front seat rear crossmember and said rear edge of said front seat rear crossmember; - the length of said interface piece is greater than or equal to the sum of the distance between said median plane of said front seat crossmember and said median plane of said front seat rear crossmember, of said distance between said front edge of said front seat crossmember and said front edge of said interface piece, of said distance between said rear edge of said front seat rear crossmember and said rear edge of the interface piece; - the height between said floor and an upper edge of said interface piece is greater than or equal to 1.5 times the height between said floor and an upper edge of said front seat crossmember; - the height between said floor and an upper edge of said interface piece is greater than or equal to 1.5 times the height between said floor and an upper edge of said front seat rear crossmember.

[0028] The invention also relates to a motor vehicle comprising an underbody assembly, remarkable in that said underbody assembly is according to the invention. Brief description of the drawings

[0029] 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:

[0030] [Fig-1] shows an underbody assembly of a motor vehicle according to the invention, seen from above.

[0031] [Fig.2] shows the base assembly according to the invention, centered on zone II of [Fig.l].

[0032] [Fig.3] is an enlargement of zone II of [Fig.l].

[0033] [Fig.4] shows zone II of [Fig.l] seen along a transverse axis of the base assembly according to the invention.

[0034] [Fig.5] shows a top view of the kinematics undergone by the underbody assembly during a side impact. Description of the embodiments

[0035] In the remainder of the description, elements having an identical structure or similar functions are designated by the same reference.

[0036] 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.

[0037] In the following, the terms “left”, “right”, “lower” and “upper” are understood in relation to the vehicle.

[0038] 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.

[0039] Reference is made to [Fig.l] showing an underbody assembly 1 of a motor vehicle 3 according to the invention, seen from above.

[0040] The underbody assembly 1 comprises a floor 5, in the lower part of the motor vehicle 3.

[0041] The floor 5 comprises a right half-floor 5d and a left half-floor 5g, separated from each other by a longitudinal central tunnel 7, extending substantially longitudinally relative to the motor vehicle 3 and consisting of a hollow body.

[0042] Laterally, the floor 5 is bordered by a right longitudinal side member 9d and by a left longitudinal side member 9g defining part of the perimeter of the body underbody.

[0043] The underbody assembly 1 further comprises a set of front cross members 11 for the front seat and a set of rear cross members 13 for the front seat.

[0044] The front 11 and rear 13 cross members are fixed to the floor 5, for example by welding.

[0045] The front cross members 11 comprise a right front cross member 11d and a left front cross member 11g.

[0046] Similarly, the rear cross members 13 comprise a right rear cross member 13d and a left rear cross member 13g.

[0047] The front crosspieces 11 each have a first end 15 and a second end 17.

[0048] Similarly, the rear crosspieces 13 each have a first end 19 and a second end 21.

[0049] The front 11 and rear 13 cross members are transverse, that is to say that they both extend substantially transversely relative to the underbody assembly 1 and are adapted to support slides (not shown) on which the front seats are mounted.

[0050] We refer to [Fig.2] showing the base assembly 1 in perspective, centered on zone II of [Fig.l].

[0051] The second end 17 of the front cross member 11 is fixed to the side member, here to the left side member 9g, for example by welding. In the same way, the second end 21 of the rear cross member 13 is fixed to the side member, here to the left side member 9g, for example by welding.

[0052] The base assembly 1 further comprises at least one interface piece 23 extending substantially longitudinally relative to the base assembly 1.

[0053] The interface part 23 is fixed only to the longitudinal central tunnel 7, for example by welding.

[0054] On the interface piece 23 are fixed the first end 15 of the front cross member 11 and the first end 19 of the rear cross member 13.

[0055] Thus, by providing for fixing the interface part 23 only on the longitudinal central tunnel 7 and by providing for fixing the front 11 and rear 13 cross members on the interface part 23, the forces undergone by the front 11 and rear 13 cross members during a lateral impact of the motor vehicle 3 are transmitted to the interface part 23.

[0056] The fact that the interface part 23 is fixed only to the central tunnel 7 makes it possible to avoid the transmission of forces to the floor 5 and to the heel board (not shown), as is the case in the prior art.

[0057] Also, the fact that the interface part 23 extends substantially longitudinally relative to the base assembly 1 allows the interface part 23 to distribute the forces homogeneously at the front and at the rear of the central tunnel 7, regardless of the location of the point of impact, which makes it possible to avoid localized stress concentrations on the central tunnel 7.

[0058] In the embodiment illustrated in the figures, the interface part 23 comprises two reinforcing ribs 25, 27 arranged longitudinally relative to the interface part 23.

[0059] Thus, a compression stiffness is obtained which is adapted to the forces transmitted by the front 11 and rear 13 cross members of the front seat in the event of an impact, without impacting the thickness of interface part 23.

[0060] In an exemplary embodiment, the reinforcing ribs 25, 27 each have a thickness of between approximately 8 mm and approximately 12 mm, which makes it possible to obtain sufficient compression stiffness. For example, the thickness of the interface part 23 is approximately 10 mm.

[0061] According to an alternative embodiment not shown in the figures, the interface part 23 comprises a single reinforcing rib.

[0062] According to another variant embodiment not shown in the figures, the interface part 23 does not include any reinforcing rib. In this case, the thickness of the interface part 23 is increased compared to the variant embodiment where the interface part 23 includes one or more reinforcing ribs.

[0063] Reference is made to [Fig.3] which is an enlargement of zone II of [Fig.l].

[0064] In the embodiment illustrated in the figures, the thickness E of the part interface 23 is greater than or equal to approximately 20 mm, which allows it to have sufficient compression stiffness to transmit the forces to the central tunnel 7 during a side impact.

[0065] In one embodiment, the distance d2 between a front edge 29 of the front crossmember 11 of the front seat and a front edge 31 of the interface part 23 is at least equal to the distance dl between a median plane PI of the front crossmember 11 of the front seat and the front edge 29 of the front crossmember 11 of the front seat.

[0066] At the level of the rear cross member 13 of the front seat, in one embodiment, the distance d4 between a rear edge 33 of the rear cross member 13 of the front seat and a rear edge 35 of the interface piece 23 is at least equal to the distance d3 between a median plane P2 of the rear cross member 13 of the front seat and the rear edge 33 of the rear cross member 13 of the front seat.

[0067] In one embodiment, the length L of the interface part is greater than or equal to the sum of the distance d2, the distance d4 and the distance d5 between the median plane PI of the front cross member 11 of the front seat and the median plane P2 of the rear cross member 13 of the front seat.

[0068] We refer to [Fig.4] showing zone II of [Fig.l] seen along a transverse axis of the base assembly 1.

[0069] In one embodiment, the height H3 of the interface part 23, between the floor 5 and an upper edge 37 of the interface part 23, is greater than or equal to 1.5 times the height H2 between the floor 5 and an upper edge 39 of the front cross member 11 of the front seat.

[0070] According to another arrangement, in one embodiment, the height H3 of the interface part 23 is greater than or equal to 1.5 times the height H1 between the floor 5 and an upper edge 41 of the rear cross member 13 of the front seat.

[0071] We refer to [Fig.5] showing, in top view, the kinematics undergone by the underbody assembly 1 during a lateral impact.

[0072] When the motor vehicle 3 undergoes a lateral impact, materialized here by the impact of a post 43 against the motor vehicle 3 between the front 11 and rear 13 cross members, the longitudinal side member, here the left longitudinal side member 9g, is pushed towards the inside of the underbody assembly 1.

[0073] The forces pass through the front 11 and rear 13 cross members of the front seat, as represented by the arrows 45, 47, from the longitudinal side member to the interface piece 23.

[0074] The interface part 23, on which the front 11 and rear 13 cross members of the front seat are fixed, and whose shape extends longitudinally relative to the underbody assembly 1, distributes the forces homogeneously at the front and at the rear of the central tunnel 7, as represented by the arrows 49, which makes it possible to avoid localized stress concentrations on the central tunnel 7.

[0075] By avoiding such a concentration of localized stresses on the central tunnel 7, the risk of rupture of the connection between the central tunnel 7 and the floor 5 is limited, which could lead to a tear in the central tunnel 7, which makes it possible to improve the safety of the motor vehicle 3 comprising such an underbody assembly 1.

[0076] In the embodiment illustrated in the figures, the base assembly 1 comprises two interface pieces 23 distributed symmetrically relative to the central tunnel 7, as visible in [Fig.l].

[0077] As goes without saying, the present invention is not limited to the sole embodiments of this underbody assembly and of this motor vehicle comprising such an assembly, described above solely as illustrative examples, but on the contrary it embraces all the variants involving the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

Claims

Claims

1. Underbody assembly (1) for a motor vehicle (3), comprising: - a floor (5), comprising two half-floors (5d, 5g), - a longitudinal central tunnel (7), extending between said half-floors (5d, 5g), - a front seat crossmember (11), fixed to said floor (5) and comprising a first end (15) and a second end (17) fixed to a longitudinal side member (9g, 9d) laterally bordering said floor (5), - a front seat crossmember (13), fixed to said floor (5) and comprising a first end (19) and a second end (21) fixed to said longitudinal side member (9g, 9d), said underbody assembly (1) being characterized in that it comprises an interface piece (23) fixed only to said longitudinal central tunnel (7), extending substantially longitudinally relative to said underbody assembly (1) and on which said first ends (15,19) of said front cross member (11) and of said rear cross member (13) of the front seat.,

2. Base assembly (1) according to claim 1, characterized in that said interface piece (23) comprises at least one reinforcing rib (25, 27) arranged longitudinally relative to said interface piece (23).

3. Base assembly (1) according to claim 2, characterized in that said at least one reinforcing rib (25, 27) has a thickness of between 8mm and 12mm.

4. Base assembly (1) according to any one of claims 1 to 3, characterized in that the thickness of said interface part (23) is greater than or equal to 20 mm.

5. Underbody assembly (1) according to any one of claims 1 to 4, characterized in that the distance (d2) between a front edge (29) of said front cross member (11) of the front seat and a front edge (31) of said interface piece (23) is at least equal to the distance (dl) between a median plane (PI) of said front cross member (11) of the front seat and said front edge (29) of said front cross member (11) of the front seat.

6. Base assembly (1) according to any one of the claims- indications 1 to 5, characterized in that the distance (d4) between a rear edge (33) of said rear cross member (13) of the front seat and a rear edge (35) of said interface piece (23) is at least equal to the distance (d3) between a median plane (P2) of said rear cross member (13) of the front seat and said rear edge (33) of said rear cross member (13) of the front seat.

7. Underbody assembly (1) according to claims 5 and 6, characterized in that the length (L) of said interface piece (23) is greater than or equal to the sum: - of the distance (d5) between said median plane (PI) of said front cross member (11) of the front seat and said median plane (P2) of said rear cross member (13) of the front seat, - of said distance (d2) between said front edge (29) of said front cross member (11) of the front seat and said front edge (31) of said interface piece (23), - of said distance (d4) between said rear edge (33) of said rear cross member (13) of the front seat and said rear edge (35) of the interface piece (23).

8. Underbody assembly (1) according to any one of claims 1 to 7, characterized in that the height (H3) between said floor (5) and an upper edge (37) of said interface piece (23) is greater than or equal to 1.5 times the height (H2) between said floor (5) and an upper edge (39) of said front seat front cross member (11).

9. Underbody assembly (1) according to any one of claims 1 to 8, characterized in that the height (H3) between said floor (5) and an upper edge (37) of said interface piece (23) is greater than or equal to 1.5 times the height (H1) between said floor (5) and an upper edge (41) of said front seat rear cross member (13).

10. Motor vehicle (3) comprising an underbody assembly (1), characterized in that said underbody assembly (1) is according to any one of claims 1 to 9.

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