Lightweight rear body structure of an automobile

Abstract

The invention relates to a rear body structure (1) of a motor vehicle comprising a load floor (400) extending transversely between two side members (110), and longitudinally between a rear axle crossmember (130) and a rear trunk panel (200), said load floor (400) comprising a main panel (410) made of a plastic or composite material; characterized in that said load floor (400) also comprises several reinforcing blades (420) of composite material projecting in relief from the underside of said main panel (410) and extending longitudinally along the latter. Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: Lightweight rear body structure for a motor vehicle technical field

[0001] The present invention relates generally to the rear body structure of a motor vehicle comprising a load floor fixed between two sheet metal side members and a rear panel extending transversely between the two respective rear ends of the two side members. It relates in particular to such a lightweight rear body structure. Previous technique

[0002] The rear structure at the level of the trunk of a motor vehicle generally includes a load floor extending transversely between two rear side members and longitudinally between a rear axle crossmember and a rear trunk panel.

[0003] This load floor is conventionally made of a sheet of steel spot-welded to the rear side members, the rear axle crossmember and the rear trunk panel, using a welding clamp which is moved by a robot to the body-in-place station where all the sheet metal parts of the vehicle are assembled.

[0004] The disadvantage of such a steel sheet load floor is that it has a high mass.

[0005] In order to reduce the mass of the vehicle so as to reduce in particular its energy consumption, this load floor can also be made of a panel made of a lower density material such as a plastic or composite material.

[0006] However, the mechanical resistance of such a plastic or composite load floor in the event of a rear impact often proves insufficient, so that its replacement is often necessary.

[0007] In order to improve this mechanical resistance, it is known from document FR 3 001 943 Al, to add under the plastic or composite panel, a metal reinforcement stringer made of sheet steel having a U-shaped cross-section and whose ends of the two lateral wings each include a folded edge which is rigidly fixed to this panel.

[0008] The rear part of this side member is further reinforced by a U-shaped cross-section metal insert, engaged and fixed inside or outside the U formed by said side member.

[0009] Its rear end also includes two bent tabs welded to the rear panel of the trunk.

[0010] Although it makes it possible to significantly improve the mechanical resistance of the load floor in the event of a rear impact, the addition of such a reinforcing metal longitudinal member nevertheless considerably limits the mass gain compared to a conventional sheet metal load floor. Description of the invention

[0011] The present invention therefore aims to improve the situation.

[0012] For this purpose, it proposes a rear structure of a motor vehicle body comprising a load floor extending transversely between two side rails, and longitudinally between a rear axle crossmember and a rear trunk panel, said load floor comprising a main panel made of a plastic or composite material; characterized in that said load floor also includes several reinforcing blades of composite material projecting in relief from the underside of said main panel and extending longitudinally along the latter.

[0013] The addition of these reinforcing blades thus makes it possible to significantly improve the mechanical strength of the load floor according to the invention in the event of a rear impact without significantly increasing the mass and cost of this floor.

[0014] Moreover, the relative elastic flexibility of these reinforcement blades makes it possible to avoid their deterioration in the event of a rear impact at moderate speed, so as to limit repair costs.

[0015] According to preferred characteristics of said rear body structure according to the invention: - said reinforcing blades were molded from a thermoplastic polymer resin loaded with natural and / or synthetic fibers; - said reinforcing blades were molded in one piece with said main panel; - said reinforcing blades have a honeycomb structure composed of an outer envelope with a rectangular cross-section and a network of internal partitions dividing the internal volume of this envelope; - said reinforcing blades are spaced transversely at regular intervals across the width of said main panel; - the front ends of said reinforcing blades protrude in front of said main panel and fit together by matching shape into respective housings provided in said rear axle crossmember; - the peripheral perimeter of said main panel rests fixedly on horizontally projecting rebates extending respectively from the internal faces of said panel side rails, the rear face of said rear axle crossmember and the front face of said rear trunk panel; - the fixing of said load-bearing floor to said attachment grooves is ensured by bolting via a plurality of screws passing successively through the first holes made in the peripheral perimeter of said main panel and then through the second holes made in these grooves and screwing into nuts welded to the lower perimeter of these second holes; and / or - said rear side members and said rear axle cross member are made in one piece by giga-molding.

[0016] The invention finally aims, in a second aspect, at a motor vehicle comprising such a rear body structure. Brief description of the drawings

[0017] The description of the invention will now be continued by a detailed description of an example embodiment, given below by way of illustration but not limitation, with reference to the accompanying drawings, on which: - [Fig.1] represents a perspective view of a rear body structure for a motor vehicle according to the invention; - [Fig.2] is a simplified cross-sectional view of the rear body structure of [Fig.1], taken along a vertical transverse plane passing through the load floor; and - [Fig.3] represents a simplified cross-sectional view of the rear body structure of [Fig.1], taken along its median vertical longitudinal plane. Description of the implementation methods

[0018] Fig. 1 represents a three-quarter rear perspective view of a rear body structure 1 of a motor vehicle according to the invention.

[0019] A direct orthogonal frame XYZ is defined with respect to this rear body structure 1, comprising three axes perpendicular in pairs, namely: - a horizontal longitudinal axis X, parallel to the ground and oriented according to the general direction of movement of the vehicle; - a horizontal transverse axis Y, also parallel to the ground and perpendicular to the X axis; and - a vertical axis Z, perpendicular to the ground as well as to the horizontal XY plane.

[0020] In the remainder of the description and with reference to the reference frame defined above, the terms "Longitudinal" or "longitudinally" will refer to a direction parallel to the X axis, the terms "transverse" or "transversely" will refer to a direction parallel to the Y axis, and the terms "vertical" or "vertically" will refer to a direction parallel to the Z axis.

[0021] Furthermore, and by convention, the terms "lower," "upper," "front," and "rear" shall be understood in relation to the overall orientation of the vehicle. The terms "lower" and "low" shall indicate a closer proximity to the ground in the vertical direction than the terms "upper" or "high." The term "front" shall indicate a forward-facing position of a vehicle in the horizontal direction, and the term "rear" shall indicate a rear-facing position of a vehicle in the same horizontal direction.

[0022] The rear body structure 1 comprises a rear block 100 made in one piece by giga-molding (or “giga-casting” in English) in a metallic material such as an aluminum alloy and comprising in this case two side rails 110, two side wheel arch frames 120, as well as a rear axle crossmember 130 extending transversely between two front ends of these side rails 110.

[0023] This rear body structure 1 also includes a rear metal trunk panel 200 extending transversely between the two respective rear ends of the two longitudinal members 110, as well as a rear bumper reinforcement 300 fixedly bolted to the rear trunk panel 200 and to the rear ends of the two longitudinal members 110.

[0024] This rear bumper reinforcement 300 comprises a metal beam 310 extending transversely and two metal side absorbers 320 each attached to a corresponding lateral end portion of the beam 310 and extending in line with the side rails 110.

[0025] The rear body structure 1 further comprises a load floor 400 extending transversely between the two side rails 110, and longitudinally between the rear axle crossmember 130 and the rear trunk panel 200.

[0026] Delimiting the lower part of the vehicle's trunk area, this load floor 400 includes a main panel 410 made of a plastic or composite material.

[0027] In order to improve its mechanical rigidity so as to avoid in particular its sagging when it supports heavy loads, the load floor 400 also includes several reinforcing blades of composite material 420 projecting in relief from the underside of the main panel 410 and extending longitudinally along the latter.

[0028] Advantageously, these 420 reinforcement blades are molded from a thermoplastic polymer resin (such as, for example, polypropylene) filled (preferably at a rate of 10 to 35% by mass) with natural and / or synthetic fibers (for example, lamellar mineral fillers such as talc or mineral micro-fibrils and nano-fibrils such as glass fibers, etc.).

[0029] The thermoplastic polymer used will preferably be chosen from Polypropylene (PP), PolyButylene Terephthalate / Acrylonitrile Styrene Acrylate (PBT-ASA), or Acrylonitrile Butadiene Styrene (ABS).

[0030] In this case, three in number, these reinforcing blades 420 are advantageously spaced transversely in a regular manner over the width of the main panel 410, as illustrated by [Fig.2].

[0031] Having in this case a cross-section of substantially rectangular or square shape, the reinforcing blades 420 advantageously present a honeycomb structure composed of an outer envelope 421 of rectangular section and a network of inner partitions 422 gridding the inner volume of this envelope 421.

[0032] Such a honeycomb structure of the reinforcing blades 420 makes it possible to provide a high rigidity to the load floor 400 for a small amount of material used, which makes it possible to considerably limit the increase in the overall mass of this floor 400 caused by the addition of these reinforcing blades 420.

[0033] For reasons of ease of manufacture and cost, the reinforcing blades 420 are advantageously made from a single piece of molding with the main panel 410.

[0034] As illustrated by figures 2 and 3, the peripheral perimeter of the main panel 410 of the load floor 400 rests fixedly on attachment grooves 111, 131, 201 projecting horizontally respectively from the inner faces of the side rails 110, the rear face of the rear axle crossmember 130 and the front face of the rear trunk panel 200.

[0035] The fixing of this load floor 400 to the attachment grooves 111, 131, 201 of the side rails 110, the rear axle cross member 130 and the rear trunk panel 200 is advantageously ensured by bolting via a plurality of screws V (some of them being shown in [Fig.2]) passing successively through first holes made in the peripheral perimeter of the main panel 410 and then through second holes made in these grooves 111, 131, 201 and screwing into nuts E welded on the lower perimeter of these second holes (some of these nuts E being shown in [Fig.2]).

[0036] In order to preserve moisture and dust tightness at the functional areas between the load floor 400 and the elements 110, 130, 200, a sealing cord C is advantageously applied along the assembly surfaces between the peripheral perimeter of the main panel 410 and the attachment rebates 111, 131, 201 of these elements.

[0037] Furthermore, and in order to guarantee this sealing at the screw fixing points, a washer made of elastomer material (not shown) is also included. preferably sleeved onto the threaded rod of each fixing screw V, prior to screwing operations.

[0038] As illustrated by [Fig.3] and in order to ensure better transmission of forces between the load floor 400 and the rear axle crossmember 130 in the event of a severe rear impact, the front ends 420A of the reinforcement blades 420 advantageously protrude in front of the main panel 410 and fit together by matching shape in respective housings 132 provided in this rear axle crossmember 130.

[0039] According to alternative embodiments not shown, the number of reinforcement blades in the load floor may be different from three and for example equal to two, four or five.

[0040] According to other embodiments not shown, the reinforcement blades can be made independently of the main panel against the underside of which they are advantageously fixed by gluing so as to avoid sealing problems.

[0041] According to yet other unrepresented embodiments, the main panel of the load floor can be made in one piece with the rear trunk panel in a plastic or composite material.

[0042] Furthermore, the rear side members, the wheel arch frames and said rear axle cross member can be made independently of each other, for example from stamped sheet metal welded together.

[0043] Many other variants are conceivable and it is recalled in this regard that the present invention is not limited to the embodiments described and represented, but also encompasses all variants of execution within the reach of a person skilled in the art.

Claims

Demands

1. Rear body structure (1) of a motor vehicle comprising a load floor (400) extending transversely between two side members (110), and longitudinally between a rear axle crossmember (130) and a rear trunk panel (200), said load floor (400) comprising a main panel (410) made of a plastic or composite material; characterized in that said load floor (400) also comprises several reinforcing blades (420) made of composite material projecting in relief from the underside of said main panel (410) and extending longitudinally along the latter.

2. Rear body structure (1) according to claim 1, characterized in that said reinforcement blades (420) are molded from a thermoplastic polymer resin loaded with natural and / or synthetic fibers.

3. Rear body structure (1) according to any one of claims 1 or 2, characterized in that said reinforcement blades (420) are molded in one piece with said main panel (410).

4. Rear body structure (1) according to any one of claims 1 to 3, characterized in that said reinforcement blades (420) have a honeycomb structure composed of an outer envelope (421) of rectangular section and a network of inner partitions (422) gridding the inner volume of this envelope (421).

5. Rear body structure (1) according to any one of claims 1 to 4, characterized in that said reinforcing blades (420) are spaced transversely in a regular manner over the width of said main panel (410).

6. Rear body structure (1) according to any one of claims 1 to 5, characterized in that the front ends (420A) of said reinforcement blades (420) protrude in front of said main panel (410) and fit together by matching shape into respective housings (132) provided in said rear axle crossmember (130).

7. Rear body structure (1) according to any one of claims 1 to 6, characterized in that the peripheral perimeter of said main panel (410) rests fixedly on attachment grooves (111, 131, 201) projecting horizontally respectively from the inner faces of said side members (110), the rear face of said rear axle crossmember (130) and the front face of said rear trunk panel (200).

8. Rear body structure (1) according to claim 7, characterized in that the attachment of said load floor (400) to said attachment grooves (111, 131, 201) is ensured by bolting through a plurality of screws (V) passing successively through first holes made in the peripheral perimeter of said main panel (410) and then through second holes made in these grooves (111, 131, 201) and screwing into nuts (E) welded on the lower perimeter of these second holes.

9. Rear body structure (1) according to any one of claims 7 or 8, characterized in that said rear side members (110) and said rear axle cross member (130) are made in one piece by giga-molding.

10. Motor vehicle comprising a rear body structure (1) according to any one of claims 1 to 9.

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