WO1999059862A1

WO1999059862A1 - Vehicle chassis

Info

Publication number: WO1999059862A1
Application number: PCT/GB1999/001459
Authority: WO
Inventors: Anthony Francis Spillane
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1998-05-20
Filing date: 1999-05-10
Publication date: 1999-11-25
Anticipated expiration: 2000-11-20
Also published as: GB9810796D0; GB2353982A; EP1080004A1; GB0027977D0; GB2353982B; AU3939299A

Abstract

A chassis for a motor vehicle has front and rear chassis portions (4, 5) each having two wheels mounted on opposite sides thereof. The two chassis portions are connected together by at least one pivot having a pivot axis parallel to the vehicle's longitudinal centre line (10) so that the chassis portions (4, 5) are rotatable relative to each other around the pivot axis. On each side of the chassis, a control bar (21, 22) is provided having each end pivotably connected to a respective one of the chassis portions (4, 5) and having a connecting means (27, 28) for the vehicle body member at its centre. This allows significant cross articulation between the front and rear pairs of wheels, whilst maintaining the body in a level position.

Description

Vehicle Chassis

This invention relates to a motor vehicle, and more particularly, to a

vehicle for use both on-road and off-road.

It is known from ZA 8901756 and AT 389281 to provide vehicles which

have a chassis frame built of two parts comprising a front frame portion and

a rear frame portion. The two sub-chassis overlap each other longitudinally

and are connected to each other near the two extremities of the overlap. The

connections and the two sub-chassis are adapted to allow limited pivoting

about a substantially longitudinal axis with respect to each other.

According to the invention there is provided a motor vehicle having a

chassis comprising front and rear chassis portions each having two wheels

mounted on opposite sides thereof by means of a suspension system,

wherein the two chassis portions are connected together by at least one

pivot having a pivot axis substantially parallel to the vehicle's longitudinal

centre line so that the chassis portions are rotatable relative to each other

around the pivot axis, and the body member is mounted on the chassis such

that it can rotate about a longitudinal axis relative to each of the chassis

portions, and control means is provided for controlling rotation of the body

member such that during rotation of one of the chassis portions relative to

the other the body member the body will rotate relative to said other of the chassis portions in the same direction as said one chassis portion but by a

smaller amount.

In this arrangement, the vehicle wheels can be attached to the chassis,

generally two to the front chassis portion and two to the rear chassis

portion, by means of a conventional suspension system. This may, for

example, be of the independent type, or may include one or two beam axles.

The articulation provided between the two chassis portions will therefore be

largely in addition to that provided by the suspension system connecting the

wheels to the chassis.

Preferably the control means comprises, on at least one side of the

chassis, a control bar having each end pivotably connected to a respective

one of the chassis portions and having connecting means for connecting to

the body member thereon.

The connecting means is preferably between the two points of

connection between the control bar and the respective chassis portions, and

may be substantially equidistant from those two points.

The control bar may be extendible to accommodate changes in distance

between the points of connection between the control bar and the respective

chassis portions. Alternatively these changes may be accommodated by flexibility in the connections between the control bar and the two chassis

portions.

Preferably the vehicle comprises two such control bars, one on each side

of the vehicle.

Alternatively the control means may be fluid operated, and may

comprise a pair of fluid operated units, each controUing movement of one of

the chassis portions relative to the body member. Conveniently the units are

interconnected so as to control the relative movements of the two chassis

portions and the body member.

Preferably at least one further mounting means for the vehicle body

member is provided on the chassis on the longitudinal centre line towards

one end of the chassis.

Preferably the vehicle has a propeller shaft extending longitudinally of

the vehicle between the two chassis portions substantially along the axis of

the pivot.

Indeed the present invention further provides a motor vehicle having a

chassis comprising front and rear chassis portions each having two wheels

mounted on opposite sides thereof by means of a suspension system, wherein the two chassis portions are connected together by at least one

pivot having a pivot axis substantially parallel to the vehicle's longitudinal

centre line so that the chassis portions are rotatable relative to each other

around the pivot axis, the vehicle further comprising a propeller shaft

extending longitudinally of the vehicle between the two chassis portions

substantially along the axis of the pivot.

Preferably each of the chassis portions comprises a rigid tubular

member, the tubular members being rotatably joined together to form the

pivot, and the propeller shaft extends through the tubular members.

The invention will now be described by the way of example only with

reference to the accompanying drawings, in which :

Figure 1 is a perspective view showing schematically the main chassis

members and wheel sets of a vehicle in accordance with an embodiment of

the invention,

Figure 2 is a plan view of the main chassis members as shown in figure

1,

Figure 3 is a schematic rear or front elevation of the embodiment of

Figure 1 in which the front and rear axle are pivoted relative to each other, Figure 4 is a schematic view of a second embodiment of the invention,

and

Figure 5 shows a part of a third embodiment of the invention.

As shown in Figures 1 and 2, in a first embodiment of the invention a

vehicle chassis 1 carries a front pair of wheels 2 and a rear pair of wheels 3.

This chassis 1 is divided into front and rear sub-frames or chassis portions 4

and 5 each of which carries one of the pairs of wheels. The inner ends 6 and

7 of these chassis portions 4 and 5 are connected together by a pivot 8, the

axis 9 of which is arranged parallel to the vehicle's horizontal longitudinal

centre line 10, so that the chassis portions 4 and 5 are rotatable relative to

each other around the pivot axis 9. The pivot 8 allows cross-articulation

between the front pair of wheels 2 and the rear pair of wheels 3. The pivot 8,

which is only shown schematically, needs to provide beaming stiffness in the

vertical and horizontal planes. This can be achieved, for example, by

forming the pivot 8 as a long rod extending along the whole length of the

chassis and being rigidly connected to one of the chassis portions 4, 5, and

rotatably connected to the other both near the centre of the chassis and near

the end. Each chassis portion 4 and 5 has a closed frame structure and

comprises two longitudinal beams 13, 14 and 15, 16 connected at least at the

inner ends 6, 7 by a cross beam 17 and 18.

On each side 19 and 20 of the chassis 1 a control bar 21, 22 for the

vehicle body is provided. As can best be seen in Figure 2, each control bar 21

and 22 is fastened at each of its ends 21a, 21b and 22a, 22b by a pivot 23a,

23b and 24a , 24b to a respective one of the front and rear chassis portions

4, 5. The pivots 23a, 23b and 24a , 24b are connected to the opposing

longitudinal beams of the frame portions 4 and 5 and are spaced from the

inner ends 6, 7 of the chassis portions 4, 5 by a distance equal to about half

of the width of the chassis 1. The pivots 23 and 24 comprise voided resilient

bushes (not shown) which can accommodate the change in distance between

the two pivots 23a, 23b, 24a, 24b on each side as the two chassis portions

rotate relative to each other. It will be understood that the lengths of the

control bars 21, 22 and the amount of movement of allowed by the bushes

will need to be adjusted so that the assembly can accommodate the

maximum amount of cross articulation desired between the two chassis

portions 4, 5 which might be of the order of 30 degrees to each side of a

normal aligned position.

At the centre of each of the control bars 21 and 23 is provided

connecting means 27 ,28 for a vehicle body 29, schematically shown in / -

Figure 3. Additionally at the front end 30 of the front chassis portion 4, and

the rear end 31 of the rear chassis portion 5 are provided mounting means

32 and 33 for fastening the vehicle body 29. These are arranged on the

longitudinal centre line 10 of the vehicle chassis 1.

As shown in Figure 1, the wheels 2, 3 are connected to the chassis 1 by

conventional suspension means 34 which allow vertical movement of the

wheels relative to the chassis under the control of spring 34 and damper

mechanisms. The suspension system can take any form, for example being

fully independent or of a rigid axle type, although this embodiment includes

coil springs 34 and a trailing arm rear suspension.

In use, the chassis 1 will behave as a normal chassis under many

conditions. For example in roll, pitch and bounce all movement of the

wheels 2, 3 relative to the body 29 will be accommodated by the suspension

system 34. However, in cross articulation the front and rear chassis portions

4, 5 can rotate relative to each other to allow for significant extra wheel

travel, beyond that which coil springs 34 can accommodate. During such

cross articulation, the mounting means 27, 28 and 32, 33 allow movement of

the body 29 relative to each of the two chassis portions 4, 5, and give a

means of controUing the vehicle body' s movements relative to the chassis 1

in such a way that the vehicle body 29 moves at the average rotation of the

two chassis portions 4, 5. This construction reduces the rotation of the vehicle's body 29 compared to what it would be if the body were rigidly

connected to either the front or the rear chassis portion 4, 5.

It will be appreciated that, whilst in this embodiment the connections

27, 28 for the vehicle body are in the centre of the control links 21, 22, they

could be positioned in a variety of locations along the control Hnks. For

example if they were closer to the front end of the control links, the body

would rotate less relative to the front chassis portion 4 than relative to the

rear chassis portion 5 during relative rotation of the two chassis portions 4,

As mentioned above, the bushes joining the control bars 21, 22 to the

chassis portions 4, 5 wiU limit the amount of movement possible between

the two chassis portions 4, 5, and they will also provide a certain amount of

resUience opposing such movement. If they take the form of hydraulic

bushes, they can also provide damping for this movement. However, it may

be preferable to provide further limit stops to limit the rotational movement

and further resilience and damping. For example a separate piston and

cylinder arrangement could be provided to perform one or more of these

functions.

Furthermore, since the increased cross articulation provided by this

system would only generaUy be required in off-road situations, and the cross articulation aUowed between the two chassis portions might reduce the

overall rigidity of the vehicle, it might be desirable to provide a locking

mechanism whereby the two chassis portions 4, 5 could be locked together

in rotation for on-road driving, and released to allow cross articulation for

off-road driving. This could be achieved, for example, by a simple shut-off

valve in the hydraulic damping system referred to above. Alternatively a

mechanical locking device could be provided between the two chassis

portions. Another way of addressing the problem would be to provide

appropriately tuned dampers interconnecting the two chassis portions

which would discriminate between on-road and off-road dynamics, for

example by being highly resistant to high frequency osciUations such as

would generaUy be encountered on-road, but less resistant to lower

frequency osciUations such as would normaUy produce high levels of cross

articulation off road.

Referring to Figure 4, in a second embodiment of the invention the

chassis is made up of two chassis portions 104, 105, each of which comprises

a rigid tubular longitudinal portion 113, 115 and a transversely extending

end portion 117, 118. The tubular portions 113, 115 are joined together at

the centre of the vehicle such that they can rotate relative to each other

about their common longitudinal axis, and control bars 121, 122 are

connected between them in the same way as the chassis portions of the first

embodiment, having body mountings 127 128 on them. Two wheels, which are not shown for the sake of clarity, are mounted on opposite sides of each

of the transverse chassis end portions 117, 118.

The vehicle's engine and gearbox 130 are mounted on the rear chassis

end portion 118 and drive both front and both rear wheels. The driving

connection to the rear wheels is not shown, but that to the front wheels

includes a propeller shaft 132 which extends along the common axis of the

two tubular chassis portions 113, 115 and is connected by means of a

differential 134, mounted on the front transverse chassis portion 117, to

drive shafts 136, 137 for the two front wheels. As with the first embodiment

the body is mounted by pivots on at least one of the chassis portions 104,

105 and directly or by means of links to the mountings 127, 128 on the

control bars 121, 122. The wheels are also connected to the chassis end

portions 117, 118 by means of a suspension system which is also not shown.

This embodiment has two advantages over that shown in Figures 1 and

2. Firstly, because the propeUer shaft 132 lies substantiaUy on the

longitudinal pivot axis between the two chassis halves, it can be made in

one rigid piece and does not have to change shape or orientation to

accommodate cross articulation between the chassis portions 104, 105.

Indeed this feature could be used in any vehicle with a two part chassis and

a propeller shaft extending longitudinaUy between the two chassis parts.

Secondly the tubular structure of the chassis portions reduces the volume they sweep out as they rotate. This makes it much easier to ensure that the

body remains clear of the chassis portions as they rotate relative to it.

As with the first embodiment, the postion of the mountings 127 127 on

the control bars 121 122 could be varied so as to vary the degree to whcih

the body follows the two chassis portions 104, 105 during relative rotation

between them.

Referring to Figure 5, in a third embodiment of the invention the

control bars of the first embodiment are replaced by a hydrauHc control

mechanism for controlling the rotation of the body 229 relative to the two

chassis portions 204, 205. The system comprises two hydrauHc piston and

cylinder units 240, 241 on each side of the vehicle, only those on one side

being shown. Each unit 240, 241 acts between a respective one of the

chassis portions 204, 205 and the body and each comprises a cyhnder 242

connected to the body and a piston 243 connected to the chassis portion 204,

205 and dividing the cyhnder into an upper chamber 244 and a lower

chamber 245. The two upper chambers 244 are hydrauHcaUy inter¬

connected with each other and the two lower chambers 254 are

hydrauHcaUy inter-connected with each other. It wiU be appreciated that

with this arrangement, if one side of either of the chassis portions 204, 205

moves vertically whUe the other stays still, the corresponding side of the

body 229 will move vertically in the same direction but by half the amount. The combined effect of the systems on both sides of the vehicle is therefore

to produce roll of the body 229 about the central longitudinal axis of the

vehicle which is the average of that of the two chassis portions 204, 205, in

an equivalent manner to the control bars of the first embodiment of the

invention.

Claims

1. A motor vehicle having a chassis comprising front and rear chassis

portions each having two wheels mounted on opposite sides thereof by

means of a suspension system, wherein the two chassis portions are

connected together by at least one pivot having a pivot axis

substantially paraUel to the vehicle's longitudinal centre line so that

the chassis portions are rotatable relative to each other around the

pivot axis, characterized in that the body member is mounted on the

chassis such that it can rotate about a longitudinal axis relative to each

of the chassis portions, and control means is provided for controUing

rotation of the body member such that during rotation of one of the

chassis portions relative to the other the body member the body will

rotate relative to said other of the chassis portions in the same direction

as said one chassis portion but by a smaUer amount.

2. A vehicle according to claim 1 wherein the control means comprises , on

at least one side of the chassis, a control bar having each end pivotably

connected to a respective one of the chassis portions and having

connecting means for connecting to the body member thereon.

3. A vehicle according to claim 2 wherein the connecting means is

substantially equidistant from the two points of connection between the

control bar and the respective chassis portions.

4. A vehicle according to claim 2 or claim 3 wherein the control bar

extends substantially longitudinally of the vehicle.

5. A vehicle according to any one of claims 2 to 4 wherein the control bar is

extendible to accommodate changes in distance between the points of

connection between the control bar and the respective chassis portions.

6. A vehicle according to any one of claims 2 to 5 comprising two such

control bars, one on each side of the vehicle.

7. A vehicle according to claim 1 wherein the control means is fluid

operated.

8. A vehicle according to claim 7 wherein the control means comprises a

pair of fluid operated units, each controUing movement of one of the

chassis portions relative to the body member.

9. A vehicle according to claim 8 wherein the units are interconnected so

as to control the relative movements of the two chassis portions and the

body member.

10. A vehicle as claimed in any foregoing claim wherein each chassis

portion comprises a frame.

11. A chassis as claimed in any one of the preceding claims, wherein at

least one further mounting means for the vehicle body member is

provided on the chassis on the longitudinal centre line towards one end

of the chassis.

12. A chassis according to claim 11 wherein a mounting means for the body

member is provided on each of the chassis portions on the vehicle

longitudinal centre Hne.

13. A vehicle according to any foregoing claim having a propeUer shaft

extending longitudinaUy of the vehicle between the two chassis portions

substantiaUy along the axis of the pivot.

14. A motor vehicle having a chassis comprising front and rear chassis

portions each having two wheels mounted on opposite sides thereof by

means of a suspension system, wherein the two chassis portions are

connected together by at least one pivot having a pivot axis

substantially parallel to the vehicle's longitudinal centre Hne so that

the chassis portions are rotatable relative to each other around the

pivot axis, the vehicle further comprising a propeUer shaft extending

longitudinally of the vehicle between the two chassis portions

substantiaUy along the axis of the pivot.

15. A vehicle according to claim 13 or claim 14 wherein each of the chassis

portions comprises a rigid tubular member, the tubular members being

rotatably joined together to form the pivot, and the propeUer shaft

extends through the tubular members.

16. A chassis as claimed in any foregoing claim wherein the two chassis

portions can rotate relative to each other through an angle of about +/-

30 degree.

17. A chassis for a vehicle substantiaUy as hereinbefore described with

reference to the accompanying drawings.