Underbody assembly for motor vehicles

Abstract: An underbody assembly (10) for a motor vehicle (12) includes a floorpan (20) extending longitudinally and transversely. The underbody assembly (10) also includes a side sill (22) operatively connected to the floorpan to provide more than one underbody load floor height of the floorpan (20) relative to body side assemblies (14) of the motor vehicle (12).

Description: The present invention relates generally to bodies for motor vehicles and, more particularly, to an underbody assembly for a motor vehicle. It is known to provide an underbody for a motor vehicle. A motor vehicle may include a rear-wheel drive having the underbody at a load floor height to clear a differential carried by a rear axle of the rear-wheel drive. Also, a motor vehicle may include a front-wheel drive having the underbody at a load floor height which is lower to the ground because the rear axle does not carry the differential. As a result, motor vehicle manufacturers typically develop two different body structures for both front-wheel and rear-wheel drive motor vehicles to serve both light and heavy duty ends of the market. One attempt to overcome this disadvantage is to use a common body structure and raise a ride height of the motor vehicle for the rear-wheel drive. However, this creates other disadvantages such as reduced interior roof height (and accompanying reduction in interior and volume) of the motor vehicle if an exterior roof height which will fit into standard parking garages is maintained. As a result, there is a need in the art to provide a modular platform design that allows the sharing of nearly all structural sheet metal parts and assembly tooling to achieve two underbody load floor heights for the same motor vehicle, in an automated assembly manufacturing operation. Further attempts to combat this problem exist in the form of FR 2335389 disclosing an underbody assembly according the preamble of claim 1, and US 3873120 which provide for a floor movable between different heights using the same vehicle platform. The construction of such vehicles is labour intensive and therefore disadvantageously costly. According to the present invention, there is provided an underbody assembly for a motor vehicle having two body side assemblies, comprising a floorpan extending in use longitudinally and transversely between the body side assemblies; wherein side sills are connectable to the body side assemblies, which sills are each formed with a top surface and a ledge that are spaced vertically from one another, and characterised by the floorpan being selectively connectable to the top surface and the ledge of the sills so as to permit the floorpan to be positioned at different underbody load floor heights relative to the body side assemblies. The invention enables the same modules to be interconnected in different ways to provide two different underbody load floor heights. This allows optimisation of load space within a given exterior vehicle dimension for both front-wheel drive and rear-wheel drive configurations for a motor vehicle. Furthermore, both variants of the underbody assembly can be constructed on the same body assembly line to minimise up-front investment and increase assembly plant flexibility. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: FIG. 1 is an exploded view of an underbody assembly, according to the present invention, having a high underbody load floor height for a motor vehicle; FIG. 2 is a view similar to FIG. 1 having a low underbody load floor height for the motor vehicle; FIG. 3 is an elevational view of the motor vehicle of FIG. 1; and FIG. 4 is an elevational view of the motor vehicle of FIG. 2. Referring to the drawings and in particular FIG. 1, one embodiment of an underbody assembly 10, according to the present invention, is shown for a motor vehicle, generally indicated at 12. The motor vehicle 12 includes a pair of body side assemblies 14 operatively connected to sides of the underbody assembly 10. It should be appreciated that only one body side assembly 14 is illustrated. The motor vehicle 12 includes a front end assembly 16 operatively connected to a forward or front end of the underbody assembly 10. The motor vehicle 12 also includes a pair of rear cargo doors 18 operatively adjoined to a rear or back end of the underbody assembly 10. It should be appreciated that the motor vehicle 12 includes a roof (not shown) and other closures (not shown) which are also common for the two load floor heights. It should also be appreciated that, except for the underbody assembly 10, the motor vehicle 12 is conventional and known in the art. The underbody assembly 10 includes an underbody load floor or floorpan 20 extending longitudinally and transversely. The underbody assembly 10 also includes a side sill 22 extending longitudinally along each side of the floor pan 20. The side sill 22 has a top surface 24 and a bottom surface 26 and a ledge 28 extending longitudinally and disposed between the top surface 24 and the bottom surface 26. For a high underbody load height for a rear-wheel drive configuration of the motor vehicle 12 illustrated in FIGS. 1 and 3, the floorpan 20 is operatively connected to the top surface 24 of the side sills 22 by suitable means such as welding. It should be appreciated that the side sills 22 are used along the load floor to body side interface along the edges of the floorpan 20 to take up the different position of the floorpan 20 relative to the body side assemblies 14. The underbody assembly 10 includes a transition structure, generally indicated at 30, operatively connected between the floorpan 20 and the front body assembly 16. The transition structure 30 includes a pair of side members 32 extending longitudinally and transversely spaced. The side members 32 are operatively connected to front rails (not shown) of the front end assembly 16 by suitable means such as welding. The transition structure 30 also includes a floorpan extension 34 extending transversely and disposed on an upper surface of the side members 32. The floorpan extension 34 is generally planar and operatively connected to the side members 32 by suitable means such as welding. It should be appreciated that the floorpan extension 34 is used to make a transition between the floorpan 20 and a front floor 35 of the front end assembly 16 (which is fixed at the same position for both the high and low underbody load floors forward of a B-pillar (not shown) to maintain the position of a driver of the motor vehicle 12). It should also be appreciated that the transition structure 30 is used to achieve the different underbody load floor heights for the high and low underbody load floors to accommodate the different heights of the rear relative to the front of the motor vehicle 12. The underbody assembly 10 may include a pair of extensions 36 positioned on the bottom of the rear side members 37 connected to the floorpan 20 and a rear sill (not shown) for the high underbody load floor of FIGS. 1 and 3 to maintain the size of a rear door opening, allowing the use of the common rear doors 18. The extensions 36 extend longitudinally and are operatively connected to the rear side members by suitable means such as welding. The extensions 36 allow the rear side members 37 to make a transition to the rear door opening. Referring to FIG. 2, an underbody assembly 110, according to the present invention, is shown for a low underbody load height for the motor vehicle 12. Like parts of the underbody assembly 10 have like reference numerals increased by one hundred (100). The underbody assembly 110 has the floorpan 120 operatively connected to the ledge 128 of the side sill 122 by suitable means such as welding. The underbody assembly 110 also includes the transition structure 130. The transition structure 130 includes the side members 132 extending longitudinally. The side members 132 having an upper portion 140, a lower portion 142 and a transition portion 144 to accommodate a difference in height between the upper portion 140 and lower portion 142. The transition structure 130 also includes the floor extension 134 extending transversely and disposed on an upper surface of the lower portion 142 of the side members 132 and operatively connected thereto by suitable means such as welding. It should be appreciated that the floorpan extension 134 is used to make a transition between the floorpan 120 and the front floor 35. Referring to FIG. 3, the underbody assembly 10 is illustrated for a high underbody load floor height for a rear-wheel drive motor vehicle 12. The motor vehicle 12 has an external height "A" measured from a ground 150 to a roof line 152 of the motor vehicle 12. The underbody assembly 10 is at an underbody load floor height "B" measured from the ground 150 to the floorpan 20 such that the underbody assembly 10 clears a differential (not shown) on a rear axle of the motor vehicle 12. It should be appreciated that the dimension "B" is less than the dimension "A". It should also be appreciated that a higher load floor is required to package the driveline for rear wheel drive applications. Referring to FIG. 4, the underbody assembly 110 is illustrated for a low underbody load floor height for a front-wheel drive motor vehicle 12. The motor vehicle 12 again has the same external height "A", but the underbody assembly 110 is at an underbody load floor height "C" measured from the ground 150 to the floorpan 120. The dimension "C" is less than the dimension "B". It should be appreciated that the low underbody load floor height is used on front wheel drive applications to achieve a lower load floor to ease loading and unloading and to achieve additional load volume within the external height "A" of the motor vehicle 12. Accordingly, the underbody assembly 10,110 achieves multiple underbody heights with a common set of body side assemblies 14. The underbody assembly 10 may be stretched lengthwise and located up and down relative to the body side assemblies 14. The underbody assembly 10 permits the location of the common underbody structure at different positions within a common set of body side assemblies 14 to maximise load space efficiency for both front-wheel and rear-wheel drive applications, eliminating the need for two unique platforms.

Claims: An underbody assembly (10) for a motor vehicle (12) having two body side assemblies (14), comprising a floorpan (20) extending in use longitudinally and transversely between the body side assemblies (14); wherein side sills (22) are connectable to the body side assemblies (14), which sills (22) are each formed with a top surface (24) and a ledge (28) that are spaced vertically from one another, and characterized by the floorpan (20) being selectively connectable to the top surface (24) and the ledge (28) of the sills (22) so as to permit the floorpan (20) to be positioned at different underbody load floor heights (B,C) relative to the body side assemblies (14). An underbody assembly as claimed in claim 1, further comprising a transition structure (30) to transition between said floorpan (20) and a front body assembly (16) of the motor vehicle. An underbody assembly as claimed in claim 2, wherein said transition structure )30) comprises a pair of side members (32) extending longitudinally and operatively connected to said floorpan (20) and the front body assembly (16). An underbody assembly as claimed in claim 2 or 3, wherein said transition structure (30) includes a floorpan extension (34) operatively connected to said side members (32) to transition between said floorpan (20) and a front floor (35) of the front body assembly (16). An underbody assembly as claimed in claim 2, 3 or 4, wherein each of said side members (32) comprises an upper portion, a lower portion and a transition portion to accommodate a difference in height between said upper portion and said lower portion. An underbody assembly as claimed in any preceding claim, further comprising a pair of rear side members (37) connected to the floorpan (20) and a pair of extensions (36) disposed between rear side members and a pair of rear doors (18) of the motor vehicle. An underbody assembly as claimed in claim 6, wherein each of said extensions (36) is operatively connected to said rear side members (37) and extends longitudinally. A motor vehicle including an underbody assembly as claimed in any preceding claim.

Inventors: BRUFORD STEPHEN LEWIS, HARAJLI YEHIA, JEWELL NORMAN H, MIANZO KAREN BURNS, WILKINSON ALAN L, BRUFORD, STEPHEN LEWIS, HARAJLI, YEHIA, JEWELL, NORMAN H., MIANZO, KAREN BURNS, WILKINSON, ALAN L.
Applicants: FORD GLOBAL TECH LLC, FORD GLOBAL TECHNOLOGIES, LLC
Application year: 1999
Main classification: B62D25
IPC codes: B62D25, B62D33