GB2059365A - Vehicle suspensions - Google Patents

Abstract

A vehicle independent road wheel suspension arrangement provides that the major part of spring induced loads are reacted at a final drive unit mount 17, at the forward end of the axle casing to enable a light-duty mount 24 to be employed at the aft end of the casing. <IMAGE>

Description

SPECIFICATION Vehicle suspensions This invention relates to vehicle suspensions and in particular to suspensions wheren a final drive casing is mounted on the vehicle frame, that is the chassis or, in the case of a vehicle of unitary construction having no separate chassis, the body structure.

The invention provides a vehicle having a road wheel suspension, including a final drive casing, a hub carrier for a road wheel connected to said final drive casing by a suspension link pivotally mounted on the final drive casing, a mount for said final drive located out of a vertical plane transverse to the vehicle and passing through the hub centre, and a spring unit which is so located that it produces a minimal torsional loading by said final drive casing on said mount.

Preferably, the spring unit is so located that a vertical plane through the centre of the wheel's contact patch with the ground and through the point of attachment of the spring unit to the suspension members, intersects a vertical plane including the pivotal axis of said suspension link and said final drive casing on a line which is located at, adjacent or on the side remote from the contact patch of, a vertical plane transverse to the vehicle which passes through said mount.

Preferably, the mount is located at the forward end of the final drive casing. With such an arrangement the major suspension loads can be transmitted to the vehicle ahead of the rear axle line enabling the rear of the vehicle to be more lightly constructed.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 shows a rear view of one side of a vehicle rear suspension in accordance with the invention; Figure2 shows a plan view of the suspension of Figure 1.

The drawings show the left hand side ofthe rear suspension of a vehicle having a central longitudinal plane CP. The suspension is symmetric about CP.

A road wheel 11 is rotatably carried by a hub carrier 12 connected to a final drive casing 13 by a suspension link 14. Suspension link 14 is connected to the hub carrier and the final drive casing 13 for pivotal movement about substantially horizontal, parallel axes, such that any torque induced in the link 14 is transmitted to the casing 13.

Drive is transmitted to the road wheel 11 from the final drive through a drive shaft 15 which includes a universal coupling 16 at each end.

Final drive casing 13 is mounted on the vehicle frame at its forward end by a sub-frame comprising an upper diagonal member 17 and a lower horizontal member 18, which members are joined at their outboard ends 19, 20, where the sub-frame is mounted on the vehicle frame 21. The inboard ends 22 and 23 of the members are connected to the top and bottom respectively of the forward end of the final drive casing. A much lighter duty mount 24 connects the rear of the final drive casing to the vehicle frame 21.

The suspension is sprung by a spring damper unit 25 acting between the vehicle frame 21 and a mounting 26 on the suspension link 14 intermediate its ends. A coil spring 27 acts between spring pans on two relatively slideable parts of a telescopic damper 28. The spring force acts on the forward side of the suspension link, ahead of the line joining the rear wheel centres, and exerts a downward reaction on the final drive casing behind the mounts at which the casing sub-frame is mounted on the vehicle frame, in addition to a torque in a sense which tends to cause the forward end of the final drive to dip and the rearward end to rise.

Drive from an engine and change-speed gearbox unit is transmitted to the final drive by a propeller shaft 29 which drives a pinion inside the casing. The pinion is meshed with a crown wheel and drive is thereafter transmitted via differential gears to the drive shaft 15. When drive is transmitted from the propeller shaft to the road wheels a wind-up torque is produced acting on casing 13 in known manner about an axis transverse to CP passing through the inboard ends of the drive shafts. When the vehicle is driven forwards, the wind-up torque is such that it causes the forward end of the final drive casing to rise and the rear to dip. The reverse situation obtains under braking and when the vehicle is driven backwards.

Spring unit 25 is so located that its net effect is to produce only a downward load on the forward mount at 19,20, with no torsional loading on the mount, and thus no change in the loading on mount 24. The requirement for this condition is shown to be satisfied in Figure 2, since a vertical plane X-X through the centre of the wheel's contact patch at C and through the point at which the spring unit acts on mounting 26, intersects a vertical plane Y-Y including the pivotal axis of link 14 along a line which is in a vertical plane Z-Z transverse to the vehicle and including the mount at 19, 20.If X-X and Y-Y intersected along a line forward of the plane Z-Z a torque would be exerted on casing 13 such as to cause the forward end to dip and the rear to rise; such an arrangement could be desirable to relieve mount 24 in the static condition of any load due to the weight of the final drive, and produce an actual condition of zero moment about the forward final drive mount. It will be appreciated that either condition is within the scope of the invention; moreover, if X-X and Y-Y intersect adjacent Z-Z the major benefit of reduced moment about the forward mount and hence low loading at 24 will be achieved, and such an arrangement would be within the scope of the invention.By producing a predominantly vertical loading on the forward mount, representing the majority ofthe spring loading, the vehicle frame can be constructed relatively lightly aft of the rear axle line with consequent weight savings.

Moreover, as shown the effects of acceleration and deceleration on the forward mount due on the one hand to vehicle weight transfer and on the other to wind-up torque, will be to some extent selfcancelling. Thus under acceleration, for example, weight transfer to the rear of the vehicle will cause increased spring force and hence increased down ward spring load on the forward mount. This will be part-cancelled however by the wind up torque which causes the acceleration, and tends to apply an upward force to the forward end of the casing.

Therefore the forward mount can be relatively lightly constructed, whilst the rear mount 24 is a light duty component required to cope largely with dynamic loads only and not to any great extent spring induced loads.

It will be appreciated that numerous variations of the invention are possible. For example, different spring means could be used, and these could act on the hub carrier rather than the suspension link, provided the requirements for minimising the torsional loading on the forward mounts were satisfied.

Again, a different arrangement of suspension links or a different mounting arrangement for the final drive could be provided. Essentially, however, the suspension is arranged so that there is minimal torsional loading, at least under static conditions, about a transverse axis through the principal final drive mount.

Claims (9)

1. A road wheel suspension, including a final drive casing, a hub carrier for a road wheel con nected to said final driving casing by a suspension link pivotally mounted on the final drive casing, a mount for said final drive located out of a vertical plane transverse to the vehicle and passing through the hub centre, and a spring unit which is so located that it produces a minimal torsional loading by said final drive casing on said mount.

2. A suspension as claimed in claim 1, wherein the spring unit is so located that a vertical plane through the centre of the wheel's contact patch with the ground and through the point of attachment of the spring unit to the suspension members, in tersects a vertical plane including the pivotal axis of said suspension link and said final drive casing on a line which is located at, adjacent or on the side remote from the contact patch of, a vertical plane transverse to the vehicle which passes through said mount.

3. A suspension as claimed in claim 1 or 2, wherein said mount is located at the forward end of the final drive casing.

4. A suspension as claimed in claim 1, 2 or 3, wherein said spring unit produces a substantially vertical downward loading on said mount.

5. A suspension as claimed in any one of claims 1 to 4, wherein said spring unit acts such that in a static condition of the vehicle the spring loading counteracts the torque produced at said mount by the weight of the final drive unit.

6. A suspension as claimed in any preceding claim, wherein said suspension link is pivotable on said final drive casing about an exis extending substantially longitudinally of the vehicle, and is pivotable on said hub carrier about a substantially parallel axis, said spring unit acting between the vehicle frame and a point on said link located forward of a transverse vertical plane including the hub axis.

7. A suspension as claimed in any preceding claim wherein a drive shaft extending between the final drive and the hub, serves to locate the hub centre transversely of the vehicle.

8. A suspension as claimed in any preceding claim, wherein the change in loading on said mount caused by weight transfer during vehicle acceleration is counter to the change in loading caused be final drive wind-up torque reaction.

9. A road wheel suspension substantially as hereinbefore described with reference to the accompanying drawings.