GB2180318A

GB2180318A - Vehicle suspension system

Info

Publication number: GB2180318A
Application number: GB08512978A
Authority: GB
Inventors: Joseph David Aled Hughes; Alan James Wootton
Original assignee: UK Secretary of State for Trade and Industry
Current assignee: UK Secretary of State for Trade and Industry
Priority date: 1985-05-22
Filing date: 1985-05-22
Publication date: 1987-03-25
Also published as: GB8512978D0

Abstract

A vehicle suspension system includes a tension spring connected between a wheel mounting and a vehicle body, the spring having at least one surface (at 20) formed as a surface of revolution and comprising a reinforced outer layer (20) of elastomeric substance and an inner core (23,40) of material which is compliantly resistant to deformation of the outer layer. The inner core can be formed from elastomeric material or can be connected to a reservoir (42) and contain fluid. The spring may include a stiffener (25, Fig. 4) to prevent buckling. <IMAGE>

Description

SPECIFICATION Vehicle suspension systems The present invention relates to vehicle suspension systems.

It is a countinuing aim of vehicle design to reduce the overall weight thereof. It has long been known that vehicle bodies can be made of Fibre Reinforced Plastic (FRP) which can have characteristics similar to those of the metals from which car bodies are more conventionally made, whilst being lighter that the metals. In recent years developments in FRP technology have been such that this type of material is being considered for more extensive use in vehicles: for example in engines and suspension units.

It is also known that when a flexible member of circular cross section is stretched in its total volume decreases. If the member is a tube the tube can be filled with a substance such as an elastomer which resists the change in volume and hence resists any change in shape of the tube. This fact has been used as the basis of a suggestion that elastic tubes filled with elastomeric substances or liquids be used as moorings for wave energy converters.

The present invention makes use of the same physical facts.

According to the present invention a vehicle suspension system includes a tension spring connected between a wheel mounting and a vehicle body and having at least one surface formed as a surface of revolution, the spring having a reinforced outer layer of elastomeric substance and an inner core of material arranged to be compliantly resistant to deformation of the outer layer.

The spring can be of spherical, cylindrical or ovoid form. When the spring is of cylindrical form a stiffener, such as, for example, a telescopic unit having two co-axial overlapping metal tubes one secured to each end of the spring, can be used to prevent buckling of the spring as it contracts following an extension.

The inner tube may be solid. The inner core material can be an elastomeric material. Alternatively the inner core material can be fluid in the form of a liquid or of a gas which is transferrd to and from a reservoir or an accumulator as the spring deforms.

The elastomeric substance can be reinforced by an outer sheath of helically wound material such as a fibre reinforced elastomer.

Suitable elastomeric materials include polyurethanes, silicone elastomers, natural rubber, polyisoprene, styrene butadiene, butadiene, polyacrylics, isobutene isoprene (butyl rubber), chloroprene (neoprene), nitrile butadiene, chlorosulphonated polyethtylene, chlorinated polythylene, ethylene propylene, flourocarbons, epichlorohydrin, flourosilicones, co-polyesters, styrene co-polymers and olefins.

Some embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, of which: Figure 1 is an elevation of a vehicle body using the invention, Figure 2 is another embodiment of the invention similar to that illustrated in Fig. 1, Figure 3 is an elevation of a tubular exten sibn spring for use in embodiments of the invention, Figure 4 is an elevation in section along the centre line of the spring illustrated in Fig. 3, Figure 5 is a section along line IV-IV of Fig.

3, Figure 6 is a elevation, in section, of another type of tubular extension spring for use with the invention, Figure 7 is an elevation, in section, of an accumulator for use with the embodiment of the invention illustrated in Fig. 6 and Figure 8 is an elevation of a spherical tension spring for use with embodiments of the invention.

A vehicle suspension system (Fig. 1) has a wheel 10 mounted on a first arm 11 of a crank 12. The crank 12 is pivotably mounted by pivot 13 on a vehicle body shown generally at 14. A second arm 15 angle relative to the first arm 11 is connected by a tension link 16 to a tension spring 17 rigidly mounted on the body 14.

An alternative arrangement of a suspension system, as illustrated in Fig. 2 in which like parts have like identification numbers, has the pivot 13 situated in a pair of brackets (not shown) securably mounted on the body 14. In this embodiment the tension link 16 and spring 1 7 are contained within the body 14.

A tension spring 17 for use with the invention, as illustrated in Fig. 3, 4 and 5, is of cylindrical form and has an outer layer in the form of a tube 20 of elastomeric material. The tube 20 is enclosed within a sheath formed from helically wound fibre reinforced elastomeric material. In the preferential embodiment illustrated in Fig. 3 there are at least two helical windings, 21 and 22, wound in opposite senses. This arrangement resists twisting of the tube 20. The tension spring 17 has an inner core formed from a plurality of annular cylinders, such as those shown at 23, 24 in Fig. 5 (but not shown in Fig. 4). The annular cylinders 23, 24 are formed from elastomeric material, the compliance of the material in each cylinder differing from the compliance of that in the other cylinders.

To each end of the tension spring 17 is bonded an annular flange 30, 31 formed, for example, from fibre reinforced plastic material, by means of which the spring can be attached to an autombile body 14 or to a tension link 16 which connects the spring to a wheel suspension system.

Within the annular cylinders 23, 24 is a telescopic unit 25 having two co-axial overlap ping tubes the outer of which, 26, is secured to the annular flange 30 and the inner of which, 27, is secured to the annular flange 31. The inner tube 27 is illustrated as being annular, but it may alternatively be solid. The space within the telescopic unit 25 is vented by a vent 28 in the flange 30.

In an alternative form of tension spring 17 (Figure 6) an elastomeric tube 20 has its core 40 filled with fluid which is allowed to pass through a small first orifice 41 in annular Flange 31 and through a non-return valve 43 and a large orifice 44 to a reservoir 42. The fluid can pass back to the core 40 only through the first orifice 41 thus providing a damping effect. A telescopic unit 25 similar to that used in the embodiment described with reference to Figs. 3 to 5 can be installed within the tube 20 to prevent buckling as the tube contracts. For reasons of clarity this unit has not been illustrated in Fig. 6.

As an alternative to the reservoir 42 the interior of the elastomeric tube 20 can be connected to an accumulator 50 (Fig. 7). The accumulator is divided into two chambers 51, 52 separated by a flexible membrane 53. The chamber 52 is filled with gas. Fluid can pass into chamber 51 through an orifice 54 in the annular flange 31. As spring 17 is extended fluid is forced into chamber 51 and the gas in chamber 52 is compressed, so building up a store of energy to quickly return the fluid to the interior of the elastomeric tube 20 as the spring 17 contracts. Alternative forms of accumulator, for example those using pistons, are well known.

In use the tension spring 17 absorbs the shocks of relative motion between the wheel 10 and body 14 as a result of the resistance of the core material to changes in internal volume of the tube 20 due to stretching of the tube. The resilience of the system will be a function of the compliance of the core cylinders 23, 24; of the control orifice 44; or of the characteristics of the accumulator 50. The characteristics of the control orifice 44 may be adapted to be adjustable to allow, for example, for different loadings in the vehicle body 14.

An alternative form of tension spring (Fig. 8) has a substantially spherical body 100 bonded to flange members 130, 131. The body 100 can contain resilient elastomeric material in the manner of the tension spring 17 described with reference to Figs. 3, 4 and 5 or can contain fluid as described with the embodi menus described with reference to Figs. 6 and 7.

It will be apparent to those skilled in the art that the embodiments of the invention herein described with reference to the accompanying drawings are merely examples and that many alternative forms of the suspension system, and of its components, within the scope of the invention, are possible.

Claims

1. A vehicle suspension system including a tension spring connected between a wheel mounting and a vehicle body and having at least one surface formed as a surface of revolution, the spring having a reinforced outer layer of elastomeric substance and an inner core of material arranged to be compliantly resistant to deformation of the outer layer.

2. A vehicle suspension system as claimed in claim 1 wherein the inner core is formed from elastomeric material.

3. A vehicle suspension system as claimed in Claim 2 wherein the elastomeric material is formed from at least two layers having different compliances.

4. A vehicle suspension system as claimed in Claim 1 wherein the inner core contains a fluid which is forced into a reservoir as the spring is extended.

5. A vehicle suspension system as claimed in Claim 1 wherein the inner core contains a fluid which is forced into an accumulator as the spring is extended.

6. A vehicle suspension system as claimed in any one of Claims 1 to 5 wherein the spring is of cylindrical form and includes a stiffener to prevent buckling of the spring.

7. A vehicle suspension system as claimed in Claim 6 wherein the stiffener is a telescopic member in the form of two co-axial overlapping tubes each secured to a different end of the spring.

8. A vehicle suspension system as claimed in Claim 7 wherein the overlapping tubes are formed from metal.

9. A vehicle suspension system as claimed in any one of Claims 1 to 5 wherein the spring is of spherical form when unextended.

10. A vehicle suspension system as claimed in any one of Claims 1 to 5 wherein the spring is of ovoid form.

11. A vehicle suspension system as claimed in any one of Claims 1 to 10 wherein the outer layer of the spring is reinforced by at least one helically wound sheath of fibre reinforced elastomeric material.

12. A vehicle suspension system as claimed in Claim 11 having at least two helical windings of fibre reinforced elastomeric material wound in opposite senses.

13. A vehicle suspension system substantially as herein described.

14. A vehicle suspension system substantially as herein described with reference to Figs. 1 to 8 of the accompanying drawings.