Modular rear structure of automotive body featuring a giga-molded rear block

Abstract

The invention relates to a rear body structure (1) for a motor vehicle, comprising: - a rear block (100) made in one piece by giga-molding and comprising two lateral wheel arch frames (110), two lateral side members (120) each projecting longitudinally at the rear of said respective lateral wheel arch frame, as well as at least one rear axle cross member (130) extending transversely between these two lateral wheel arch frames; - a rear bumper reinforcement (200) comprising a beam (210) extending transversely as well as two lateral absorbers (220) each integral with a corresponding lateral end portion of said beam and extending in line with said lateral side members;and- two lateral extensions of stringers (300) each extending longitudinally between the rear end of a respective stringer and the front end of a corresponding absorber to which it is rigidly fixed. Figure to be published with the abbreviation: Fig. 1;

Description

Title of the invention: Modular rear structure for a motor vehicle body with a giga-molded rear block. Technical field

[0001] The invention relates generally to the rear body structure of motor vehicles. It relates in particular to such a rear body structure comprising a rear block obtained in one piece by giga-molding. Previous technique

[0002] The automotive industry is constantly evolving, continually seeking ways to reduce costs, improve efficiency and enhance vehicle safety. One of the most revolutionary recent innovations in this field is giga-molding, commonly referred to by the English term "giga-casting".

[0003] Described in particular in US document 2019 / 0217380 Al, this technology consists of using gigantic pressure casting machines to manufacture important parts of the body structure of a vehicle in one piece and in a single operation.

[0004] Compared to traditional processes for designing such a body structure, which require the assembly of numerous parts by welding, riveting, or bolting, gigamolding significantly reduces the number of constituent parts of this body structure as well as the assembly steps required. This simplification results in, among other things, lower production costs, reduced manufacturing time, improved assembly quality, and enhanced rigidity and structural strength of the vehicle, thus contributing to greater occupant safety.

[0005] The rear body structure of certain models of motor vehicles now includes a rear block made by giga-molding and combining in a single piece several main elements of this structure such as the two lateral frames of the rear wheel arch, the two side rails, as well as at least one rear axle crossmember connecting these two lateral frames of the wheel arch.

[0006] The use of such blocks made by giga-molding presents, however, certain disadvantages, including in particular the significantly higher cost of repairs following an impact.

[0007] Thus, in the event of a rear-end collision at medium or high speed and depending on the angle of contact, the lateral absorbers included in the rear bumper reinforcement may no longer be sufficient to absorb all of the energy of this impact, which can cause the deterioration of at least one of the side rails integrated into the rear block obtained by giga-molding.

[0008] In such a case, the replacement of this rear block then proves indispensable, which leads to additional repair costs compared to vehicles with a more conventional chassis structure for which only the damaged side member(s) would need to be replaced.

[0009] Such an additional cost is not only linked to the price of the rear block to be replaced but also to the significant cost of the labor required for its replacement (obligation to use qualified operators for this type of repair and significant increase in the time spent which is in practice almost twice as important).

[0010] These high repair and replacement costs thus tend to lead to a substantial increase in insurance premiums for vehicles equipped with giga-molded components.

[0011] Moreover, due to their size and the complexity of their manufacture, replacement blocks may not be available quickly, which can lead to prolonged delays for repairs. Description of the invention

[0012] The present invention therefore aims to improve the situation.

[0013] To this end, it proposes a rear body structure for a motor vehicle, comprising: - a rear block made in one piece by giga-molding and comprising two lateral wheel arch frames, two lateral side members each projecting longitudinally at the rear of said respective lateral wheel arch frame, as well as at least one rear axle crossmember extending transversely between said lateral wheel arch frames; - a rear bumper reinforcement comprising a beam extending transversely and two lateral absorbers each attached to a corresponding lateral end portion of said beam and extending in line with said lateral side members; characterized in that it further comprises two lateral extensions of stringers each extending longitudinally between the rear end of a said respective stringer and the front end of a said corresponding absorber to which it is rigidly fixed.

[0014] The interposition of these lateral extensions of the side members between the absorbers of the rear bumper reinforcement and the side members of the rear block obtained by giga-molding thus makes it possible to considerably reduce the risk of deterioration of this rear block in case of moderate or severe rear impact, so as to limit the resulting repair costs.

[0015] Furthermore, the invention also offers the possibility of using a single reference rear block obtained by giga-molding for different vehicle silhouettes based on the same rolling base but with different rear overhangs, so as to ensure a faster amortization of the cost of the giga-molding press enabling the manufacture of this rear block.

[0016] According to preferred characteristics of the rear body structure according to the invention: - the length of said extensions of the longitudinal beam is between 100 and 300 millimeters; - said extensions of the longitudinal member are identical; - said extensions of the longitudinal beam are each made in one piece by molding in a metallic material; - said rear block and said longitudinal frame extensions are made of the same aluminium alloy; - each lateral extension of the longitudinal member comprises a main body of rectangular or square section, as well as two front and rear fixing plates arranged at the two longitudinal ends of this main body and fixed by bolting to fixing plates arranged respectively at the rear end of said longitudinal member and at the front end of said corresponding absorber; - the front and rear fixing plates of each said longitudinal extension have a rectangular or square shape and have, near their corners, holes each through which a screw also passes through a corresponding hole made in the fixing plate of said longitudinal or corresponding absorber and is screwed either into a thread made on one of the two holes passed through, or onto a nut welded around the perimeter of one of these two holes; - the front and rear mounting plates of said side member extensions also include indexing means capable of cooperating with complementary means provided on the mounting plates of said side members and said absorbers, so as to ensure isostatic retention of these side member extensions vis-à-vis said side members and said rear bumper reinforcement; and / or - each said lateral extension of the longitudinal member includes a cylindrical sleeve projecting longitudinally from the front face of the central portion of its front fixing plate and cooperating by form fitting with a complementary cylindrical housing provided in the rear portion of a corresponding longitudinal member.

[0017] The invention also relates, in a second aspect, to a motor vehicle comprising such a rear body structure. Brief description of the drawings

[0018] 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.l] represents an exploded perspective view of a rear body structure for a motor vehicle according to the invention; - [Fig.2] is a perspective view in assembled configuration of the rear body structure of [Fig.1]; - [Fig.3] represents an enlarged three-quarter front perspective view of one of the longitudinal extensions of the rear body structure of [Fig.1]; - [Fig.4] is an enlarged three-quarter rear perspective view of one of the longitudinal extensions of the rear body structure of [Fig.1]; - [Fig. 5] shows an enlarged three-quarter front perspective view of a longitudinal extension according to one embodiment variant; and - [Fig.6] illustrates different configurations of rear body structures according to the invention corresponding to different vehicle silhouettes comprising the same rear block. Description of the implementation methods

[0019] Figures 1 and 2 represent two views respectively in exploded view and in assembled configuration of a rear body structure 1 for a motor vehicle according to the invention.

[0020] A direct orthogonal frame XYZ is defined with respect to this rear body structure 1 for a motor vehicle, 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.

[0021] 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.

[0022] 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.

[0023] The rear body structure 1 comprises a rear block 100 made in one piece by giga-molding in a metallic material such as an aluminum alloy and comprising two side wheel arch frames 110, two side longitudinal members 120 each projecting longitudinally at the rear of a respective side wheel arch frame 110, as well as at least one rear axle cross member 130 extending transversely between these two side wheel arch frames 110.

[0024] This rear body structure 1 also conventionally includes a rear bumper reinforcement 200 comprising a hollow metal beam 210 extending transversely and two metal side absorbers 220 each attached to a corresponding lateral end portion of the beam 210 and extending in line with the side rails 120.

[0025] Conventionally obtained by forming or extrusion, the beam 210 is designed to transmit to the lateral absorbers 220 the forces experienced during a collision with the rear of the vehicle. It may include internal reinforcing metal plates extending transversely and intended to improve its mechanical strength.

[0026] According to the invention and as illustrated by figures 1 and 2, the rear body structure 1 further comprises two lateral extensions of longitudinal members 300 each extending longitudinally between the rear end of a respective longitudinal member 120 and the front end of a corresponding absorber 220 to which it is rigidly fixed.

[0027] Advantageously made of the same metallic material (for example, an aluminum alloy) as that forming the rear block 100, the two lateral extensions of the longitudinal members 300 are also preferably each made in one piece by molding.

[0028] With reference to figures 3 and 4, each lateral extension of the longitudinal member 300 comprises a main body of rectangular or square cross-section 310 and two front mounting plates 320 and rear mounting plates 330 arranged at the two longitudinal ends of this main body 310 and fixed by bolting to mounting plates 121, 221 arranged respectively at the rear end of a longitudinal member 120 and at the front end of a corresponding absorber 220.

[0029] Having a rectangular or square shape, the front mounting plate 320 of each extension 300 has, as can be clearly seen in [Fig.3], four circular holes 321 each through which a screw also passes through a corresponding hole provided in the mounting plate 121 of a longitudinal member 120 and is screwed either into a thread provided on one of the two holes passed through, or onto a nut welded around the perimeter of one of these two holes.

[0030] The orifices 321 also have a diameter slightly larger than that of the screws in order to take into account the manufacturing dimensional tolerances relating to their positioning.

[0031] The front mounting plate 320 of each extension 300 also includes indexing means cooperating with complementary means provided on the mounting plate 121 of a corresponding longitudinal member 120 so as to ensure isostatic retention of this extension 300 vis-à-vis this longitudinal member 120.

[0032] These indexing means comprise in this case a first circular hole 322 provided near a first edge of the front fixing plate 320 of each extension of the longitudinal member 300 and cooperating by form fitting with a first pin (not shown in the figures) projecting longitudinally from the rear face of the fixing plate 121 of a corresponding longitudinal member 120, so as to prevent any relative translational movement between this extension 300 and this longitudinal member 120 in a vertical transverse plane.

[0033] These indexing means also include in this case a second oblong hole 323 provided near a second edge, opposite to said first edge, of the front fixing plate 320 of each extension of the longitudinal member 300 and crossed by a second pin (not visible in the figures) projecting longitudinally from the rear face of the fixing plate 121 of a corresponding longitudinal member 120 and whose diameter corresponds to the width of this second oblong hole 323, so as to prevent any relative rotational movement between this extension 300 and this longitudinal member 120 around a longitudinal axis.

[0034] Having a rectangular or square shape advantageously identical to that of its front plate 320, the rear mounting plate 330 of each extension 300 has, as can be clearly seen in [Fig.4], four circular holes 331 provided near its four corners and each through which is passed a screw also passing through a corresponding hole provided in the mounting plate 221 of an absorber 220 of the rear bumper reinforcement 200 and screwing either into a thread provided on one of the two holes passed through, or onto a nut welded on the periphery of one of these two holes.

[0035] Just like the orifices 321, the orifices 331 also have a diameter slightly larger than that of the screws in order to take into account the manufacturing dimensional tolerances relating to their positioning.

[0036] The rear mounting plates 330 of the extensions 300 also include indexing means cooperating with complementary means provided on the mounting plates 221 of the absorbers 220 so as to ensure isostatic retention of these extensions 300 vis-à-vis the rear bumper reinforcement 200.

[0037] These indexing means include in this case a pin 332 projecting longitudinally from the rear face of the rear fixing plate 330 of each extension of the longitudinal member 300, near one of its edges.

[0038] The pin 332 of the rear plate 330 of one of the extensions 300 cooperates by form fitting with a circular hole (not shown in the figures) provided in the fixing plate 221 of a corresponding absorber 220, so as to prevent any relative translational movement between these extensions 300 and the rear bumper reinforcement 200 in a vertical transverse plane.

[0039] The pin 332 of the rear plate 330 of the other of the extensions 300 passes through an oblong hole (not shown in the figures) provided in the fixing plate 221 of the other corresponding absorber 220 and whose width corresponds to the diameter of this pin 332 so as to prevent any relative rotational movement between these extensions 300 and the rear bumper reinforcement 200 around a longitudinal axis.

[0040] Figure 5 shows an extension of the longitudinal member 301 conforming to an alternative embodiment. In the following text and in Figure 5, the same reference numerals are used for elements identical to an extension 300.

[0041] This extension 301 is similar to an extension 300 except that it includes a cylindrical sleeve 340 projecting longitudinally from the front face of the central portion of its front fixing plate 320 and cooperating by form fitting with a complementary cylindrical housing (not shown in the figures) provided in the rear portion of a corresponding longitudinal member 120 of the rear block 100.

[0042] The addition of such a sleeve 340 makes it possible to reinforce the mechanical rigidity of the connection between an extension 301 and the corresponding spar 120 while also ensuring the function of anti-translation indexing in a vertical transverse plane (which makes it possible to do without the circular holes 322).

[0043] Having a mechanical rigidity lower than that of the beam 210, the side members 120 and the side member extensions 300, the two lateral absorbers (or “crashboxes” according to the English name) 220 are designed, in the event of a rear impact at low speed (typically less than or equal to 16 km / h), to crush and thus absorb the energy of this impact so as to avoid any damage to these lateral cradle extensions.

[0044] In the event of a rear impact at medium or high speed and depending on the angle of contact, these lateral absorbers 220 may no longer be sufficient to absorb all of the energy of this impact, so that part of this energy will be transmitted to the extensions of the side member 300 which may then crack and / or tear locally.

[0045] In such a case, the damaged extension(s) 300 will then have to be replaced by substitute side rail extensions, without it being necessary to change the rear block 100 (unless of course the latter has also been damaged during the impact due to an excessive amount of energy to absorb).

[0046] The invention thus makes it possible to limit the costs of repairing the vehicle in the event of a rear-end collision and to obtain a better classification of the vehicle with insurance companies.

[0047] Advantageously, the two extensions of the side member 300 of the rear body structure 1 are identical, which makes it possible to reduce investment costs (for example, using a single mold for their manufacture), management and storage of spare parts.

[0048] Furthermore, and as illustrated by [Fig.6], the invention also allows the use of a single reference rear block 100 obtained by giga-molding for different vehicle silhouettes sharing the same rolling base but with different rear overhangs (the term "rear overhang" designating the distance between the beam of the rear bumper reinforcement and the axle of the rear wheels).

[0049] The combination of the side extensions of the longitudinal member 300 and the bumper reinforcement 200 with the rear block 100 may, for example, correspond to a sedan or a medium-sized SUV with a first rear overhang.

[0050] For a vehicle silhouette having a second rear overhang shorter than this first overhang and corresponding for example to a compact sedan, this same rear block 100 will be associated with side rail extensions 300' having a length shorter than those of the extensions 300. This vehicle may also be equipped with a rear bumper reinforcement 200' having absorbers 220' shorter than those 220 of the rear bumper reinforcement 200.

[0051] For a vehicle silhouette with a third rear overhang greater than the first overhang, corresponding for example to a large sedan or a large SUV, this same rear block 100 will be associated with lateral side rail extensions 300” having a length greater than those of the extensions 300. This vehicle may also be equipped with a rear bumper reinforcement 200” with absorbers 220” longer than those 220 of the rear bumper reinforcement 200.

[0052] The length of the lateral extensions of the longitudinal member 300 will thus advantageously be between 100 and 300 millimeters depending on the silhouette of the vehicle concerned.

[0053] According to alternative embodiments not shown, these two lateral extensions of longitudinal members 300 could each be formed by an assembly of several stamped parts welded together.

[0054] According to other unrepresented embodiments, the indexing means provided on the fixing plates of the side extensions of the longitudinal member, the side longitudinal members and the absorbers of the rear bumper reinforcement could be of a different type.

[0055] The rear block may also integrate other elements of the vehicle chassis such as two rear side rails extending in front of the side wheel arch frames.

[0056] Many other embodiments 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 the embodiments within the reach of a person skilled in the art.

Claims

Demands

1. Rear body structure (1) for a motor vehicle, comprising: - a rear block (100) made in one piece by giga-molding and comprising two side wheel arch frames (110), two side members (120) each projecting longitudinally from the rear of said respective side wheel arch frame (110), as well as at least one rear axle crossmember (130) extending transversely between said side wheel arch frames (110); - a rear bumper reinforcement (200) comprising a beam (210) extending transversely as well as two side absorbers (220) each integral with a corresponding lateral end portion of said beam (210) and extending in line with said side members (120); characterized in that it also comprises two lateral extensions of longitudinal members (300; 301; 300';300”) each extending longitudinally between the rear end of a respective spar (120) and the front end of a corresponding absorber (220) to which it is rigidly fixed.;

2. Rear body structure (1) according to claim 1, characterized in that the length of said longitudinal extensions (300; 301; 300'; 300") is between 100 and 300 millimeters.

3. Rear body structure (1) according to any one of claims 1 or 2, characterized in that said longitudinal extensions (300; 301; 300'; 300") are identical.

4. Rear body structure (1) according to any one of claims 1 to 3, characterized in that said side member extensions (300; 301; 300'; 300") are each made in one piece by molding in a metallic material.

5. Rear body structure (1) according to any one of claims 1 to 4, characterized in that said rear block (100) and said longitudinal frame extensions (300; 301; 300'; 300") are made of the same aluminum alloy.

6. Rear body structure (1) according to any one of claims 1 to 5, characterized in that each lateral extension of the longitudinal member (300; 301; 300'; 300") comprises a main body with a rectangular or square cross-section (310), as well as two mounting plates front (320) and rear (330) arranged at the two longitudinal ends of this main body (310) and fixed by bolting to fixing plates (121, 221) arranged respectively at the rear end of a said longitudinal member (120) and at the front end of a said absorber (220) corresponding.

7. Rear body structure (1) according to claim 6, characterized in that the front (320) and rear (330) mounting plates of each said longitudinal member extension (300; 301; 300'; 300") have a rectangular or square shape and have, near their corners, holes (321) each through which a screw also passes through a corresponding hole provided in the mounting plate (121, 221) of said longitudinal member (120) or of said corresponding absorber (220) and screwing either into a thread provided on one of the two holes passed through, or onto a nut welded around the perimeter of one of these two holes.

8. Rear body structure (1) according to any one of claims 6 or 7, characterized in that the front (320) and rear (330) mounting plates of said side member extensions (300; 301; 300'; 300") also include indexing means (322, 323, 332) capable of cooperating with complementary means provided on the mounting plates (121, 221) of said side members (120) and said absorbers (220), so as to ensure isostatic retention of these side member extensions (300) vis-à-vis said side members (120) and said rear bumper reinforcement (200).

9. Rear body structure (1) according to any one of claims 6 to 8, characterized in that each said lateral extension of side member (301) comprises a cylindrical sleeve (340) projecting longitudinally from the front face of the central portion of its front fixing plate (320) and cooperating by form fitting with a complementary cylindrical housing provided in the rear portion of a corresponding side member (120).

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

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