GB2056382A

GB2056382A - A rigid-axle suspension system for motor vehicles

Info

Publication number: GB2056382A
Application number: GB8023882A
Authority: GB
Original assignee: Fiat Auto SpA
Current assignee: Fiat Auto SpA
Priority date: 1979-07-26
Filing date: 1980-07-22
Publication date: 1981-03-18
Also published as: DE3028124A1; IT7953449V0; FR2462283B1; FR2462283A1

Abstract

In order to improve the performance of a rigid axle 1 the axle extends forwardly to a pivotal connection with a vehicle cross member 6. The arrangement thereby reduces the no-suspended mass of the axle while preserving the advantages of rigid-axle suspensions over independent-wheel suspensions. <IMAGE>

Description

SPECIFICATION A rigid-axle suspension system for motor vehicles The invention relates to a rigid-axle suspension system for motor vehicles, comprising a rigid axle having ends bearing two vehicle wheels around a common axis, a pair of longitudinal arms having their rear ends pivotably connected to the ends of the rigid axle and their front ends pivotably connected to the vehicle bearing structure around a common transverse axis perpendicular to the longitudinal plane of symmetry of the vehicle and disposed at the front of the wheel axis, and a pair of substantially vertical helical springs disposed between the ends of the rigid axle and the bearing structure of the vehicle.

Rigid-axle suspension systems of the aforementioned kind have an advantage over independent-wheel suspensions in that they always hold the wheels so that their axis of rotation extends parallel to the ground, thus ensuring a good grip on the road and reduced wear on the tyres.

On the other hand rigid-axle suspension systems have a disadvantage compared with independent-wheel suspensions in that there is a considerable amount of non-suspended mass, i.e.

mass moving integrally with the wheels relative to the vehicle bearing structure when the suspension jolts. This reduces the comfort of the occupants when the vehicle is in motion.

The object of the invention is to construct a rigid-axle suspension system for motor vehicles which preserves the advantages of rigid-axle suspensions over independent-wheel suspensions without having the aforementioned disadvantages.

To this end, the invention relates to a rigid-axle suspension means of the aforementioned kind, characterised in that the rigid axle is curved towards the front of the vehicle and has a central portion pivotably connected to the vehicle bearing structure around the aforementioned common transverse axis.

Owing to the aforementioned feature the suspension system according to the invention, besides preserving the advantages of rigid-axle suspensions, also ensures that the comfort during travelling is comparable with that obtainable with an independent-wheel suspension system.

Most of the mass of the rigid axle is moved along the common pivoting axis of the longitudinal arms of the suspension, thus appreciably reducing the moment of inertia of the axle relative to the aforementioned axis, which is fixed relative to the vehicle bearing structure. In other words, the amount of non-suspended mass in the suspension system according to the invention is relatively reduced, thus ensuring that the occupants of the vehicle are sufficiently comfortable during motion, more particularly over rough ground. This is due in practice to the fact that when there is a reduction in the non-suspended mass, there is an increase in the natural frequency of oscillation of the suspension system, thus further improving the grip on the road, particularly on rough ground.

Another advantage of the suspension system according to the invention is that it has a small number of parts and is relatively simple in structure. More particularly, the connection between the central part of the rigid axle and the vehicle bearing structure is such as to avoid the use of means (e.g. a rigid "Panhard" bar) for transversely securing the suspension, such means being used in prior art rigid-axle suspension systems.

The suspension system according to the invention can be used either for the front wheels or the back wheels of a vehicle. If the suspension is used for the back wheels of a rear-wheel drive vehicle, the differentiai axle is secured to the bearing structure and connected to the wheels by universal joints, thus further reducing the nonsuspended mass.

Other characteristics and advantages of the invention will be clear from the following description with reference to the accompanying drawings, which are given by way of nonlimitative example only and in which: Figure 1 is a perspective view of a rigid-axle suspension system according to the invention, and Figure 2 is a view in section through a detail of Figure 1.

The suspension system illustrated in the drawing is of use for the back wheels of a frontwheel drive motor vehicle.

The suspension system comprises a rigid axle 1 having two holders 2 secured to its end. A stub holding a vehicle wheel 3 is adapted to be secured to each holder 2. Wheels 3 are therefore borne by the ends of the rigid axle 1 around a common axis, indicated by reference number 5.

The suspension system also comprises a pair of longitudinal arms 4 having back ends 4a (one of which is visible in Figure 1) pivoted to the respective holders 2 around transverss axes parallel to axis 5.

The front ends (reference 4b) of longitudinal arms 4 are pivotably connected to a crossmember 6 forming part of the vehicle bearing structure, around a common transverse axis 7 perpendicular to the longitudinal plane of symmetry of the vehicle.

In Figure 1, arrow A indicates the direction of motion of the vehicle.

The suspension system also comprises a pair of substantially vertical helical springs 8 and a pair of shock-absorbers 9 disposed between the vehicle bearing structure and the holders 2 secured to the ends of rigid axle 1.

The bottom ends of shock-absorbers 9 are pivoted at 10 to the respective holders 2, whereas the bottom ends of helical springs 8 rest on cupshaped bearing elements 11, one of which is visible in Figure 1, forming part of holders 2.

The main feature of the aforementioned rigidaxle suspension system is that the rigid axle 1 is curved toward the front and has a central portion la pivotably connected to cross-member 6 around the common pivoting axis 7 of the longitudinal arms 4.

Consequently, most of the mass of axle 1 is moved near the axis 7, thus reducing the moment of inertia of axle 1 relative to axis 7. This avoids the disadvantages of rigid-axle suspension systems due to the considerable amount of nonsuspended mass in the aforementioned kind of suspension systems.

In addition, the rigid axle 1 is connected to the vehicle bearing structure, thus obviating.the need of a rigid "Panhard" bar for transversely securing the suspension system, as conventionally used in rigid-axle suspension systems.

Accordingly the suspension system according to the invention, besides obviating the disadvantages of rigid-axle suspension systems, has a relatively simple structure and is made up of a reduced number of parts.

As illustrated in Figure 2, the central portion 1a of cross-member 6 forming part of the vehicle bearing structure can be pivotably connected by a bush of elastomeric material 12 secured by a bolt 3 between a pair of flanges 14 secured to axle 1 and a holder 15 secured to cross-member 6.

Of course, without departing from the principle of the invention, details of the construction and embodiment can be widely varied from those described and illustrated by way of example only, without thereby departing from the scope of the invention.

More particularly, the aforementioned suspension system could be used to suspend the back wheels of a rear-wheel drive vehicle instead of a front-wheel drive vehicle. In such cases, the rear differential axle of the vehicle will be secured to the bearing structure, in order further to limit the non-suspended mass, and will be connected to wheels 3 by universal joints.

The aforementioned suspension system could be used also for suspending the front wheels of a vehicle, since the rigid axle 1 is curved towards the front, thus providing the necessary space for the vehicle engine.

Finally, the helical springs 8 of the aforementioned suspension are disposed at the front of the- wheel axis 5, thus giving a stabilizing anti-roll torque when the suspension jolts.

Claims

1. A rigid-axle suspension system for motor vehicles, comprising a rigid axle having ends bearing two vehicle wheels around a common axis, a pair of longitudinal arms having their rear ends pivotably connected to the ends of the rigid axle and their front ends pivotably connected to the vehicle bearing structure around a common transverse axis perpendicular to the longitudinal plane of symmetry of the vehicle and disposed at the front of the wheel axis and a pair of substantially vertical helical springs disposed between the ends of the rigid axle and the bearing structure of the vehicle, characterised in that the rigid axle (1) extends towards the front of the vehicle and has an intermediate portion (1a) pivotably connected to the vehicle bearing structure (6) around the aforementioned common transverse axis.

2. A rigid-axle suspension system according to Claim 1, characterised in that a holder (2) for the respective wheel (3) is secured to each end of the rigid axle (1) and has attachments for securing the rear end (4a) of the respective longitudinal arm (4) and the bottom end of the respective helical spring (8).

3. A rigid-axle suspension system according to Claim 1, characterised in that the helical springs (8) are disposed in front of the wheel axis (5).

4. A rigid-axle suspension system substantially as herein described with reference to, and as shown in, the accompanying drawings.