Rear section of a motor vehicle body underbody equipped with a force-transmitting spare wheel carrier

Abstract

The invention relates to a rear subframe (1) of a motor vehicle, comprising a rear floor (2), two side members (3, 4) extending longitudinally under said rear floor (2), a cross member (7) extending transversely under said rear floor (2) between said side members (3, 4) to which it is rigidly fixed by its two lateral ends, and a spare wheel support (100) (8) mounted to pivot on said cross member (7); characterized in that said spare wheel support (100) (8) comprises a metal frame (110) including two main bars (111, 112) extending obliquely rearward and toward each other from their respective front ends, which are pivotally mounted on said cross member (7). Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: Rear section of a motor vehicle body underbody equipped with a force-transmitting spare wheel support. Technical field

[0001] The invention relates to the field of passive vehicle safety equipment. In particular, the invention relates to the field of vehicle protection against rear-end collisions. Previous technique

[0002] Current regulations require motor vehicle manufacturers to comply with certain safety requirements and to conduct tests in order to obtain the necessary approvals for marketing. Thus, regulations in Europe, Japan, and most countries worldwide require that the vehicle be designed for a rear-end collision in which it is struck by a rigid barrier at a speed of 50 km / h. In the United States, the rear-end collision protocol is more stringent. In this protocol, the vehicle is struck from behind by a 1368 kg NHTSA-type barrier (National Highway Traffic Safety Administration) at high speed (80 km / h) and over a partial lateral overlap area corresponding to 70% of the vehicle's width as measured at the right rear axle. These are therefore high-energy impacts, with a large, very rigid barrier that is highly aggressive to the vehicle.

[0003] The rear part of the body underbody of a motor vehicle classically comprises a rear floor on which are mounted two lateral longitudinal members connected transversely by a rear axle crossmember.

[0004] Such a rear body underbody also traditionally includes a shock absorption system, also commonly referred to by its acronym SAC, and comprising a rear crossbeam and two lateral absorbers each attached to a corresponding lateral end portion of this beam and fixed to the rear ends of the two side members.

[0005] These side absorbers (commonly referred to by their English name "crashboxes") are designed, in the event of a high-speed rear-end collision, to deform by forming folds like an accordion in order to dissipate some of the impact energy and limit the stresses on the side members. This type of deformation is also commonly referred to as "baling" because these absorbers take on a ringed shape after deformation that resembles tied hay bales.

[0006] The transverse beam also allows, when the impact is partially lateral, the transmission of part of the forces to the lateral side of the body underbody opposite to this impact.

[0007] Due to their design, the rear part of the body underbody of certain types of vehicles cannot be equipped with such a shock absorption system SAC.

[0008] This is particularly the case for certain vehicles with a rear loading platform bordered by vertical walls that delimit a loading volume extending approximately halfway up the vehicle's height above the load floor. Commonly referred to by the English term "pick-up," these vehicles are generally equipped, in order to facilitate user access to their loading platform, with a step integrated into their rear bumper, thus preventing the installation of such a shock absorption system.

[0009] Such an absence of a rear SAC results, in the event of a partial lateral impact, in a greater stress on the side member located on the side of the impact, which must then absorb approximately 80% of the forces. Consequently, and in order to prevent their buckling, these side members must be oversized accordingly, which leads to a significant increase in the vehicle's mass.

[0010] The rear part of the body underbody of certain motor vehicles may also include a support for a spare wheel, mounted pivotally articulated at its front end and via a pair of hinges on a cross member, so as to allow the removal of the spare wheel.

[0011] Conventionally formed from wires or small section metal rods welded together, these spare wheel supports have low mechanical strength in the event of a rear impact so that they participate very little in absorbing the energy of this impact despite their significant deformation.

[0012] Document KR1020010035655A discloses a spare wheel support comprising a first fixed retaining element rigidly fixed under the load floor, and a second movable retaining element mounted to slide longitudinally under this rear floor and to the rear of this first fixed element via adjustment means comprising a threaded rod passing through a reinforcement plate integral with the rear bumper stop shield.

[0013] These two retaining elements are thus able to ensure that the spare wheel is held together under the load floor.

[0014] In the event of a rear impact, the threaded rod and the reinforcement plate push the second movable retaining element against the spare wheel tire, which deforms by absorbing part of the energy of this impact.

[0015] However, the proportion of the impact energy absorbed by this type of spare wheel support proves to be relatively small and insufficient to significantly reduce the over-stress on the side member located on the side of this impact. Description of the invention

[0016] The present invention aims to limit more effectively, in the event of a rear impact with partial lateral overlap, the over-stressing of the lateral side member located on the side of this impact.

[0017] It proposes for this purpose a rear part of the underbody of a motor vehicle, comprising a rear floor, two lateral longitudinal members extending longitudinally under said rear floor, a cross member extending transversely under said rear floor between said lateral longitudinal members to which it is rigidly fixed by its two lateral ends, and a support for a spare wheel mounted tilting on said cross member; characterized in that said spare wheel support comprises a metal frame including two main bars extending diagonally backwards and towards each other from their respective front ends mounted pivotally articulated on said cross member.

[0018] Such a configuration of the metal chassis of the spare wheel support thus makes it possible, in the event of a high-speed rear impact with partial lateral overlap over at least half the width of the vehicle, to generate an auxiliary force path allowing the transmission, via the crossmember, of a larger part of the forces towards the lateral side member located on the side opposite to this impact.

[0019] This better distribution of the stresses experienced by the two lateral longitudinal members thus makes it possible to considerably limit, or even avoid, their oversizing compared to those present on the rear part of a body underbody equipped with a SAC shock absorption system.

[0020] According to preferred characteristics of said rear part of the body subframe according to the invention: - each said main bar forms, with the median vertical longitudinal plane of said vehicle, a respective angle of inclination between 15 and 30°; - the angle of inclination between each of said main bars and the median vertical longitudinal plane of said vehicle is between 20 and 25°; - that the front ends of said main bars are arranged opposite the rear face of said crossbar; - said main bars are arranged symmetrically with respect to the median vertical longitudinal plane of said vehicle; - said frame also includes at least one connecting bar extending transversely between the two said main bars and whose two ends are rigidly fixed to the latter; - said main bars meet at their respective rear ends fixed to each other so as to form a V whose point is oriented towards the rear of said vehicle; - said main bars are formed by rectangular steel tubes with a thickness between 2 and 3 millimeters; and / or - said support also includes a receiving basket fixed on top of said chassis and forming a hollow housing for said spare wheel.

[0021] The invention also relates, in a second aspect, to a motor vehicle comprising such a rear part of the body underbody. Brief description of the drawings

[0022] 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 bottom view of a rear section of the body underbody according to the invention of a motor vehicle; and - [Fig.2] is a cross-sectional view of the rear part of the body base of [Fig.1], taken along the vertical longitudinal plane II of this figure. Description of the implementation methods

[0023] Figures 1 and 2 represent views respectively from below and in vertical longitudinal section of a rear part of the underbody of a motor vehicle, without a rear shock absorption system.

[0024] In the following description, and by convention, an orthogonal frame XYZ comprising three axes perpendicular in pairs is defined with respect to this rear part of the body subframe 1, namely: - an X axis, defining a longitudinal direction, parallel to the longitudinal axis of the vehicle; - a Y-axis, defining a horizontal, transverse direction, which, together with the X-axis, defines a horizontal XY plane; and - a Z-axis, defining a vertical direction, perpendicular to the horizontal XY plane.

[0025] In the remainder of the description and with reference to the frame of reference 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.

[0026] 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 rearward-facing position of a vehicle in the same horizontal direction.

[0027] Furthermore, the term "substantially" will be used to indicate that a slight deviation is permitted from a predetermined nominal position or orientation, while remaining within the scope of the invention. For example, "substantially vertical" indicates that a deviation of approximately 10° from a strictly vertical orientation is permitted within the scope of the invention.

[0028] With reference to figures 1 and 2, the rear part of the body underbody 1 conventionally comprises a rear floor 2 made of sheet metal, located at the level of the rear loading platform of the vehicle, and extending along a substantially horizontal average plane.

[0029] This rear part of the body underbody 1 also includes two rear structural side profiles 3, 4 commonly referred to as longitudinal members and extending longitudinally under the rear floor 2 along each one of the respective rear wheel arches 5, 6.

[0030] Generally formed by hot stamping from a sheet blank of very high yield strength (VHS) or ultra high yield strength (UHLS) steel, these two side rails 3, 4 are connected by means of a rear axle cross member 7, the two ends of which are respectively fixed to one and the other of these side rails 3, 4.

[0031] As illustrated in the figures, the rear part of the body underbody 1 is further equipped with a spare wheel support 100 8, arranged under the rear floor 2 at the rear of the rear axle crossmember 7 on which it is mounted pivoting around an axis transverse to the vehicle between a high securing position illustrated by figures 1 to 4 and a low position giving access to this spare wheel 8 so as to allow, in the event of a puncture, its removal and replacement by the punctured wheel.

[0032] The support 100 comprises a metal frame 110 including two main bars 111, 112 extending obliquely rearward and towards each other from their respective front ends mounted pivotally on the rear axle crossmember 7. Each main bar 111, 112 thus forms a respective angle of inclination 0b 02 with the median vertical longitudinal plane PM of the vehicle.

[0033] Such a configuration of the metal chassis 110 of the spare wheel carrier 100 thus allows, in the event of a high-speed (80 km / h) rear-end collision and overlapping partial lateral impact over at least half the width of the vehicle, to generate an auxiliary load path allowing the transmission, via the rear axle crossmember 7, of a larger part of the loads to the side member 3 or 4 located on the opposite side to this impact (namely, the left side member 3 for a rear impact with partial lateral overlap over at least the right half of the vehicle, and the right side member 4 for a rear impact with partial lateral overlap over at least the left half of the vehicle).

[0034] This better distribution of the stresses experienced by the two lateral longitudinal members 3, 4 thus makes it possible to considerably limit, or even avoid, their oversizing compared to those present on the rear part of a body underbody equipped with a shock absorption system SAC.

[0035] In order to ensure a sufficient part of the forces are transmitted to the side member 3 or 4 located on the side opposite the impact while limiting the risk of bending of the main bars 111, 112 due to the shear stresses suffered, the angle of inclination 02 of each main bar 111, 112 with the median vertical longitudinal plane of the vehicle PM will preferably be between 15 and 30° and even more preferably between 20 and 25°.

[0036] In order to ensure identical transmission of forces on both sides of the vehicle, the main bars 111, 112 are advantageously arranged symmetrically with respect to this same median vertical longitudinal plane PM.

[0037] The chassis 110 also preferably includes at least one connecting bar 113 extending transversely between the two main bars 111, 112 and whose two lateral ends are rigidly fixed to these main bars 111, 112 advantageously by welding.

[0038] As can be seen in [Fig.2], the central part of the rear axle crossmember 7 is vertically distant from the rear floor 2 by a distance e allowing the insertion of a portion of the spare wheel 8 between this rear floor 2 and this crossmember 7.

[0039] Still with reference to this [Fig.2], the front ends of the main bars 111, 112 of the chassis 110 are preferably arranged opposite the rear face of the rear axle crossmember 7. Such an arrangement thus prevents, in the event of a high-speed rear impact, these main bars 111, 112 from being able to "slide" under this crossmember 7 so as to prevent the transmission of forces between these structural elements.

[0040] The spare wheel support 100 can be held in its high lashing position by a retaining device 9 arranged below the rear floor 2 to which it is attached by means of a lashing rod 10 passing through this rear floor 2 and bearing axially against its upper face.

[0041] As illustrated in [Fig. 2], this retaining device 9 is provided with a hook adapted to engage with a latch 114 formed at the free rear end of the frame 110, so as to secure the support 100 in its raised position. This latch 114 is, for example, formed by a curved steel wire welded to the top of this frame 110.

[0042] According to alternative embodiments not shown, the spare wheel support 100 can be provided with a receiving basket fixed on top of the chassis 110 and forming a hollow housing for receiving the spare wheel 8.

[0043] This welcome basket can, for example, be made from an assembly of steel wires bent and welded together. It can also be molded from a single piece of thermoplastic material.

[0044] According to other unrepresented embodiments, the chassis 110 of the spare wheel support 100 can be shaped differently and include, for example, a rear transverse bar rigidly connected by its two lateral ends to the rear ends of the two main bars 111, 112.

[0045] According to other unrepresented embodiments, the respective front ends of the two main bars 111, 112 of the chassis 110 can be mounted pivotally articulated on another cross member of the rear subframe 1, also extending transversely under the rear floor 2 between the side rails 3, 4 to which it is rigidly fixed by its two lateral ends.

[0046] Numerous other variants are conceivable, and it should be noted in this regard that the present invention is not limited to the embodiments described and illustrated, but also encompasses all variants of execution within the grasp of a person skilled in the art.

Claims

Demands

1. Rear underbody part of motor vehicle body (1), comprising a rear floor (2), two side rails (3, 4) extending longitudinally under said rear floor (2), a cross member (7) extending transversely under said rear floor (2) between said side rails (3, 4) to which it is rigidly fixed by its two lateral ends, and a support (100) for spare wheel (8) mounted pivoting on said cross member (7); characterized in that said support (100) for spare wheel (8) comprises a metal frame (110) comprising two main bars (111, 112) extending obliquely rearward and toward each other from their respective front ends mounted pivotally articulated on said cross member (7).

2. Rear body underbody part (1) according to claim 1, characterized in that each said main bar (111, 112) forms, with the median vertical longitudinal plane (PM) of said vehicle, a respective angle of inclination (0b 02) between 15 and 30°.

3. Rear body underbody part (1) according to claim 2, characterized in that the angle of inclination (0b 02) between each said main bar (111, 112) and the median vertical longitudinal plane (PM) of said vehicle is between 20 and 25°.

4. Rear part of body base (1) according to any one of claims 1 to 3, characterized in that the front ends of said main bars (111, 1112) are arranged opposite the rear face of said cross member (7).

5. Rear body underbody part (1) according to any one of claims 1 to 4, characterized in that said main bars (111, 112) are arranged symmetrically with respect to the median vertical longitudinal plane (PM) of said vehicle.

6. Rear body subframe part (1) according to any one of claims 1 to 5, characterized in that said chassis (110) also comprises at least one connecting bar (113) extending transversely between said two main bars (111, 112) and whose two ends are rigidly fixed to the latter.

7. Rear part of a body subframe (1) according to any one of claims 1 to 6, characterized in that said main bars (111, 112) meet at their ends respective rear ends fixed to each other so as to form a V whose point is oriented towards the rear of said vehicle.

8. Rear part of body base (1) according to any one of claims 1 to 7, characterized in that said main bars (111, 112) are formed by steel tubes with rectangular cross-section and a thickness between 2 and 3 millimeters.

9. Rear part of body underbody (1) according to any one of claims 1 to 8, characterized in that said support (100) also includes a receiving basket fixed on top of said chassis (110) and forming a hollow receiving housing for said spare wheel (8).

10. Motor vehicle comprising a rear body underbody part (1) conforming to any one of claims 1 to 9.

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