GB2462244A

GB2462244A - Vehicle chassis with a crash structure

Info

Publication number: GB2462244A
Application number: GB0809786A
Authority: GB
Inventors: David John Marler; Richard Alan Rackham
Original assignee: Lotus Cars Ltd
Current assignee: Lotus Cars Ltd
Priority date: 2008-05-29
Filing date: 2008-05-29
Publication date: 2010-02-03
Anticipated expiration: 2028-05-29
Also published as: GB0809786D0; GB2462244B

Abstract

The chassis comprises an occupant compartment (10); a crash structure (11) for deforming in a crash; and a joint assembly (15) connecting the crash structure (11) to the occupant compartment (10). The joint assembly comprises a joining plate (11) spanning the occupant compartment (10) and the crash structure (11), having a first section of a first thickness overlying an outboard face of the occupant compartment (10) and a second section of a second lesser thickness overlying an outboard face of the crash structure (11). The joining plate (11) is secured to the occupant compartment (10) and the crash structure (11) by a plurality of mechanical fasteners (18), the mechanical fasteners (18) permitting unfastening of the joining plate and thereby 20 replacement of the crash structure (11).

Description

A VEHICLE CHASSIS AND A METHOD OF CONSTRUCTION OF A VEHICLE

CHASSIS

The present inventions relates to a vehicle chassis and to a method of constructions of a vehicle chassis.

It is known to construct a vehicle chassis with a front sub-frame structure extending forwardly of a central vehicle chassis tub providing an occupant compartment. There is a technical challenge to ensure that damage occasioned by a front-end collision is contained in the front sub-frame and not passed on to the chassis tub.

The present invention provides a vehicle chassis comprising an occupant arrangement, a crash structure and a joint assembly connecting the crash structure to the passenger compartment. The joint assembly comprises a joining plate spanning the occupant compartment and the crash structure, having a first section of a first thickness overlying an outboard face of the occupant compartment and a second section of a second lesser thickness overlying an outboard face of the crash structure. The joining plate is secured to the occupant compartment and the crash structure by a plurality of mechanical fasteners, the mechanical fasteners permitting unfastening of the joining plate and thereby replacement of the crash structure.

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first joint between a chassis tub and a front sub-frame according to the present inventions; Figure 2 is a plan view of the joint of Figure 1; Figure 3 is a perspective view of a second joint between a chassis tub and a rear sub-frame according to the present invention; Figure 4 is a plan view of the joint of Figure 3; Figure 5 is a plan view of a variant of the joint of Figures 1 and 2; and Figure 6 is an isometric view of an abutment part used in the joint of Figure 4.

Turning to Figure 1, there can be seen a chassis tub 10 of a road vehicle. The chassis tub shown forms an occupant compartment of a car and is formed from extruded aluminium components, bonded and screwed or riveted together.

Extending forwardly of the chassis tub 10 is an aluminium sub-frame 11. The sub-frame 11 comprises a pair of parallel struts 12,13 which extend forwardly from the chassis tub 10 in parallel spaced apart relationship and are interconnected by a transverse cross-member 14. Each of the struts 12,13 extends roughly parallel to a longitudinal axis of the vehicle, running fore-and-aft of the vehicle. Each strut 12,13 has a root portion at which the strut is joined to the chassis tub 10 by a joining plate, e.g. the plate 15 shown in the Figure 1. The root portions are mirror-images of each other, as are their respective joining plates and so ,-1+-1R 11 b LL)L) L-LJL'LL IJL J L1-.L j-'JL -L.

in detail.

Figure 2 shows in detail the root portion of the strut 12. The strut 12 is provided with an L-shaped abutment part 16 integrally formed therewith or secured thereto. The chassis tub 10 is provided with a corresponding abutment part 17 again integrally formed therewith or secured thereto. The joining plate 15 extends over outboard faces of each of the abutment parts 16,17. Bolts 18 extend through the joining plate 15, through an outboard section of abutment part 17 to the chassis tub 10 or via an outboard section of abutment part 16 to the strut 12, the bolts 18 securing the joining plate 15 to both the chassis tub 10 and the strut 12 and also attaching the abutment parts 16,17 respectively to the strut 12 and the chassis tub 10 in the event that the parts 16,17 are not integrally formed respectively with the strut 12 and chassis tub 10. A separate bolt 19 extends through both the inboard sections of both abutment parts 16,17 to join them to the chassis tub 10. The terms "inboard" and "outboard" should be considered to indicate that "inboard" sections are nearer to a centre line of the vehicle than the "outboard" sections.

The abutment part 17 is provided with slots 20 and 21 which run generally vertically when the vehicle is on a flat horizontal surface. The joining plate 15 has matching ribs 22,23 which engage with the slots 20,21.

The arrangement described above is designed to ensure that damage incurred in a crash is not passed from the 1') 1 r, fm 1hc r'hcc fi,h ifl Th Ci1flflCT r11 i is of a thickness of material less than the thickness of material of the abutment parts 16,17. Also the thickness of the material varies along the length of the joining plate 15; the section of the joining plate 15 overlying the strut 12 is of a constant thickness narrower than the constant thickness of the section of the joining plate 15 overlying the chassis tub 10, with a region of tapering thickness connecting these two sections. The previously described features provide for initiation of crash failure by elongation in shear of the holes in the joining plate 15, starting in the section which overlies the strut 12. A plastic hinge can also form in the joining plate, e.g. in the region of tapering thickness between the two constant thickness sections of joining plate 15. The section of the joining plate 15 overlaying the chassis tub 10 is kept in place relative to the chassis tub 10 by the interaction of the ribs 22,23 in the slots 20,21. Relative motion between the strut 12 and the joining plate 15 may be occasioned during crash failure.

The design described above is intended to limit crash damage to the front end structure, to parts which can be detached simply by unfastening the bolts 18 and 19.

Replacement components can then be bolted in place.

A second embodiment of the invention is shown in Figures 3 and 4. A rear sub-frame 110 is secured by a joining plate 115 to a vehicle occupant compartment provided by a chassis tub 100. As with the first embodiment two abutment parts 116 and 117 are provided, in this case as independent components. The abutment part 116 is associated 1-h I-i,h 1C1l r,-1 hr11rl 1-r 1-h zc 1-nh 100 by two bolts 118. The abutment part 116 is associated with the rear sub-frame assembly 110 and is bolted to the sub-frame assembly by a bolt 119. Spanning the abutment parts 116 and 117 is the joining plate 115. A first section of the joining plate 115 of a first constant thickness and overlies the abutment part 116. A second section of the joining plate 115 is of a second greater constant thickness and overlies the abutment part 117. The two constant thickness sections of the joining plate 115 are connected by a section of tapering thickness.

The joining plate 115 is secured to the chassis tub 100 by the bolts 118 which extend through the abutment part 116.

The joining plate 115 is secured to the sub-frame assembly by bolt 119 extending through the abutment part 116.

The abutment part 117 has two slots 120,121 in its face and the joining plate 115 has two ribs 122,123 which extend into the slots 120,121 and engage with the slots 120,121 to secure the joining plate 115 in position relative to the chassis tub 100.

As with the first embodiment, the assembly shown in Figures 3 and 4 is designed to protect the chassis tub 100 from damage during an impact by limiting damage to the sub-frame 110. During a crash the sub-frame 110 will deform and there may be relative motion between the sub-frame and the joining plate 115. The bolt hole in the joining plate 115 will elongate in shear. A plastic hinge can form in the joining plate 115 outside of the section of plate 115 which overlies the chassis tub 100, most likely in the connecting section of tapering cross-section. The engagement of ribs 122,123 in the slots 120,121 prcvcnts movement of the plate 115 relative to the chassis tub 100.

To repair the vehicle, the bolts 118,119 are undone and the joining plate 115 and abutment parts 116,117 removed. A new rear sub-frame 110 is then mounted on the chassis tub by fresh bolts 118 and 119 and replacement set of joining plate 15 and abutment parts 116 and 117.

Figure 5 shows a variant of the embodiment of Figures 1 and 2, which is identical in all regards except that the abutment parts 16,17 of Figure 1 and 2 have been replaced by abutment parts 216,217. The abutment parts 216,217 are largely identical to the abutment parts 16 and 17 in that they have outboard faces which are overlain by the joining plate 15 and inboard faces which abut one another; also the outboard face of abutment part 16 has slots for receiving ribs of the joining plate 15. However, the abutment part 217 has an inboard limb 200 parallel to and spaced apart from outboard section 204 of the part 217. Similarly, the abutment part 216 has an inboard limb 201 parallel to and spaced apart from outboard section 205 of the part 216. The limb 200 allows the abutment part 217 to be bonded to an inboard wall 203 of the chassis tub. The limb 201 allows the abutment part 216 to be bonded to an inboard wall 204 of the strut 12. Figure 6 shows the abutment part 216 with the limb 201 formed of three separate sections 201A, 201B and 2OlC; the sections 201B and 2OlC have apertures for allowing the use of mechanical fasteners in addition to bonding. The abutment parts 216 and 217 are preferably machined extrusions.

All of the abutment parts 16, 116 and 216 can be bonded to the chassis tub 10 and can have fine surface ribbing to set a bond depth. All of the abutment parts 17, 117 and 217 can be bonded to a strut or sub-frame and can have fine surface ribbing to set a bond depth.

The use of joining plates 15 and 115 in the embodiments described above allows for adjustment of relative position during assembly and hence aids assembly.

Whilst the use of bolts l8,19;1l8,119 has been described above, other mechanical fasteners could be used.

Typically, all of the components (i.e. the bolts 18,19;118,119, the chassis tub 10;100, the crash structure 11,12,13;llO, the abutment parts 16, 17;116, 117 and the joining plates 15;115) will be formed of aluminium or alloy of aluminium. However, it is also possible that different material could be used; where components of different materials about a coating will be provided to inhibit corrosion.

The use of joints as described above allows the front or the rear sub frame to be loaded with components before attachment to the chassis tub. The positioning of the mechanical fastenings allows them to be accessed even when the sub frame is fully loaded. As well as being useful for repair, in manufacture of the vehicle this features allows loading of e.g. the front sub frame with the steering system, suspension, air conditioning and heating system and engine cooling system, prior to attachment to the chassis tub. This methodology ilows sub assembly away from the chassis tub where better access is possible.

Claims

CLA I MS1. A vehicle chassis comprising: an occupant arrangement; a crash structure; a joint assembly connecting the crash structure to the passenger compartment; wherein: the joint assembly comprises a joining plate spanning the occupants compartment and the crash structure, having a first section of a first thickness overlying an outboard face of the occupant compartment and a second section of a second lesser thickness overlying an outboard face of the crash structure, the joining plate being secured to the occupant compartment and the crash structure by a plurality of mechanical fasteners, the mechanical fasteners permitting unfastening of the joint plate and thereby replacement of the crash structure.
2. A vehicle chassis as claimed in claim 1 wherein the joining place has a tapering thickness section joining the first and second sections.
3. A vehicle chassis as claimed in claim 1 or claim 2 wherein the first section of the joining plate is provided with a plurality of ribs which locate in slots formed in the outboard face of the occupant compartment.
4. A vehicle chassis as claimed in claim 3 wherein the vehicle chassis has an occupant compartment abutment part formed integrally therewith or mounted thereon, the occupant compartment abutment part providing the outboard face of the occupant compartment overlain and abutted by the joining plate and also the slots for receiving the ribs of the joining plate.
5. A vehicle chassis as claimed in claim 4 wherein the crash structure has a crash structure abutment part formed integrally therewith or mounted thereon, the crash structure abutment part providing the outboard face of the crash structure overlain and abutted by the joining plate, the crash structure abutment part also having an inboard surface which abuts an inboard surface of the passenger compartment abutment part.
6. A vehicle chassis as claimed in claim 5 wherein the mechanical fasteners additionally fasten the occupant compartment abutment part to the occupant compartment and the crash structure abutment part to the crash structure.
7. A vehicle chassis as claimed in claim 5 or claim 6 wherein the crash structure abutment part is mounted on the crash structure and has an outboard section providing the outboard face of the crash structure which can be bonded to a first surface of the crash structure and an inboard arm spaced apart from the outboard section which can be bonded to second surface of the crash structure.
8. A vehicle chassis as claimed in any one of claims 4 to 7 wherein the occupant component abutment part is mounted on the occupant compartment and has an outboard section providing the outboard face of the occupant compartment which can be bonded to a first surface of the occupant compartment and an inboard arm spaced apart fromI-10 -the outboard section which can be bonded to a second surface of the occupant compartment.
9. A vehicle chassis as claimed in any one of the preceding claims wherein the mechanical fasteners are bolts and a greater number of bolts are used to fasten the joining plate to the occupant compartment than to fasten the joining plate to the crash structure.
10. A vehicle chassis as claimed in any one of the preceding claims wherein the crash structure comprises at least one strut extending forwardly of the passenger compartment and the crash structure face overlain by the joining plate is an outboard face of a root section of the strut.
11. A method of repair of the vehicle chassis claimed in any one of the preceding claims comprising: unfastening the mechanical fasteners to separate the joining plate and the crash structure from the passenger compartment; and joining a replacement crash structure to the passenger compartment using a new joining plate and new mechanical fasteners.
12. A vehicle chassis substantially as hereiribefore described with reference to and as shown in the accompanying drawings.Amendments to the claims have been filed as followsCLAI MS1. A vehicle chassis comprising: an occupant compartment; a crash structure which can deform during a crash of the vehicle; a joint assembly connecting the crash structure to the occupant compartment; wherein: the joint assembly comprises a joining plate spanning the occupants compartment and the crash structure, having a first section of a first thickness overlying an outboard face of the occupant compartment and a second section of a second lesser thickness overlying an outboard face of the crash structure, the joining plate being secured to the occupant compartment and the crash structure by a plurality of mechanical fasteners, the mechanical fasteners permitting unfastening of the joining plate and thereby replacement of the crash structure.2. A vehicle chassis as claimed in claim 1 wherein the joining plate has a tapering thickness section joining the first and second sections.3. A vehicle chassis as claimed in claim 1 or claim 2 wherein the first section of the joining plate is provided .. with a plurality of ribs which locate in slots formed in the *..S ..... outboard face of the occupant compartment. * **4. A vehicle chassis as claimed in claim 3 wherein *** * the occupant compartment has an occupant compartment *: abutment part formed either as an integral part thereof or S. *S as a separate part mounted on a remainder of the occupant compartment, the occupant compartment abutment part providing the outboard face of the occupant compartment overlain and abutted by the joining plate and also the slots for receiving the ribs of the joining plate.5. A vehicle chassis as claimed in claim 4 wherein the crash structure has a crash structure abutment part formed either as an integral part thereof or as a separate part mounted on a remainder of the crash structure, the crash structure abutment part providing the outboard face of the crash structure overlain and abutted by the joining plate, the crash structure abutment part also having an inboard surface which abuts an inboard surface of the passenger compartment abutment part.6. A vehicle chassis as claimed in claim 5 wherein the mechanical fasteners additionally fasten the occupant compartment abutment part to the occupant compartment and the crash structure abutment part to the crash structure.7. A vehicle chassis as claimed in claim 5 or claim 6 wherein the crash structure abutment part is a separate part mounted on the remainder of the crash structure and has an outboard section providing the outboard face of the crash structure, which outboard section is bonded to a first . : surface of the remainder of the crash structure, and an inboard arm spaced apart from the outboard section, which * * inboard arm is bonded to second surface of the remainder of the crash structure. S.. * I* S. SIS SSIIS8. A vehicle chassis as claimed in any one of claims 4 to 7 wherein the occupant component abutment part is a separate part mounted on the remainder of the occupant compartment and has an outboard section providing the outboard face of the occupant compartment, which outboard section is bonded to a first surface of the remainder of the occupant compartment, and an inboard arm spaced apart from the outboard section, which inboard arm is bonded to a second surface of the remainder of the occupant compartment.9. A vehicle chassis as claimed in any one of the preceding claims wherein the mechanical fasteners are bolts and a greater number of bolts are used to fasten the joining plate to the occupant compartment than to fasten the joining plate to the crash structure.10. A vehicle chassis as claimed in any one of the preceding claims wherein the crash structure comprises at least one strut extending forwardly of the passenger compartment and the crash structure face overlain by the joining plate is an outboard face of a root section of the strut.11. A method of repair of the vehicle chassis claimed in any one of the preceding claims comprising: unfastening the mechanical fasteners to separate the joining plate and the crash structure from the passenger I...**** compartment; and joining a replacement crash structure to the passenger compartment using a new joining plate and new e.mechanical fasteners.I. **. * I I I. S S. SS SSS SI12. A vehicle chassis substantially as hereinbefore described with reference to and as shown in the accompanying drawings. *. I e. * * * * I * I II. * * a. * a. * * S S * **