GB2154520A - Vehicle suspension wishbone - Google Patents

Abstract

A vehicle suspension wishbone is made by a filament winding process. To improve strength and rigidity a mandrel on which the filaments e.g. of glass fibre, are wound preferably remains in the structure. The mandrel, e.g. of polyurethane or polyethylene foam, may be made by a moulding process during which metal inserts, e.g. a 22 bearing flange 10, pivot bushes 20 and attachment studs 22, are incorporated. The filaments 27 are coated or impregnated with resin, e.g. polyester, epoxy or vinyl ester, and wound along geodesic paths. <IMAGE>

Description

SPECIFICATION Vehicle suspension wishbone Vehicle suspension wish bones serve to form a connection between a road wheel and the bodywork of a vehicle. A spring and a shock absorber are conventionally attached between the vehicle body and the wishbone to isolate the bodywork from imperfections on the road surface.

Suspension wish bones are thus highly stressed components. They are conventionally made of steel and are heavy. Since they form part of the unsprung mass of the vehicle, it is very desirable that their weight be reduced.

According to the invention, there is provided a vehicle suspension wishbone made by a filament winding technique.

The filament winding will take place around a mandrel, and the mandrel is preferably left in place in the wound structure.

The shape of the wishbone, as compared with a conventional metal wishbone, may be modified to facilitate winding by making the limb which sup ports the wheel bearing as a closed section with a longitudinal passage through the limb to accommodate the driveshaft.

A wishbone made using these techniques can be at least 50% lighter than its metal equivalent. The shape may also be improved, because the lateral flanges which appear on a metal wishbone and where two pressed steel halves are connected together, will be omitted.

The invention will now be further described, by way of example, with reference to the accompany ing drawings, in which: Figure 1 shows a structural foam mandrel in the form of a motor vehicle suspension wishbone, to be wound with filaments; Figure 2 is a section through a vehicle suspension wishbone, taken on the line Il-Il from Figure 3; Figure 3 shows the wishbone formed by winding on the mandrel of Figure 1; Figure 4 shows the wishbone of Figure 3, with additional components attached; Figures 5 and 6 are respectively elevation and plan views of a simplified representation of part of the wishbone; Figure 7 is an end view of the wishbone flange where the wheel bearing will be fitted; Figure 8 is a section on the line VIII-VIII from Fig ure 7; Figures 9 and 10 are plan and elevation views both partly in section, of the end of a wishbone arm; and Figures 11 and 12 show a method of fixing an insert into a filament wound structure, Figure 11 being a section taken on the line XI-XI of Figure 12.

The mandrel 5 shown in Figure 1 is in a shape suitable for forming a suspension wishbone for a Ford Sierra car, and has a bearing flange 10, a spring well 12 and two wishbone arms 14 and 16.

The limb extending from the spring well to the bearing flange has a passage 18 through it, for a drive shaft. The wishbone arms have pivot bushes 20 at their free ends. The flange 10 and the pivot bushes 20 are steel components anchored to the mandrel.

In use of the finished wishbone, the pivot bushes 20 will be pivoted on a sub frame of the vehicle. A spring 11 will have its lower end received in the spring well 12 (see Figure 2). A road wheel bearing will be attached to the bearing flange 10, and a drive shaft for the road wheel have its lower end attached to the wishbone through a bracket which will be attached to a set of studs 22a on a stud plate 24a.

Studs 22 on other stud plates 24 are provided for receiving other wishbone fittings.

The mandrel is made by a moulding process.

The process used will depend on the mandrel material. For a polyurethane foam mandrel, a reaction injection moulding process can be used. The mould can be made in two halves, with a side mould piece. For experimental purposes, the mould can be made from glass reinforced plastics.

For production purposes, a metal mould would be used. Foam will be injected through a nozzle situated in the upper mould half. This upper mould half also forms the spring well and contains a removable core plug. This core plug forms the passage 18. The plug is supported at one end by the bearing flange and at the other end by the upper mould half.

As well as forming the cavity for the mandrel, the mould will also locate the inserts, i.e. the bearing flange 10, the pivot bushes 20 and the stud plates 24. The stud plates are held temporarily to the inside surface of the mould cavity by a weak adhesive prior to foaming.

After cure, the mould can be disassembled to reveal the mandrel illustrated in Figure 1.

Alternatively, a polyethylene foam mandrel can be produced. In this case, two moulds are used.

Each mould will produce one half of a two part hollow shell mandrel. The two cured halves will then be snap fitted together to form a completed mandrel.

Because of the higher moulding pressures needed for polyethylene as compared with polyurethane, the mould will have to be made from aluminium or steel and firmly clamped in an injection or transfer moulding machine.

A metal dish 25 will be fitted at the bottom of the well 12 to provide a seat for the spring 11 and to prevent abrasion of the fibres by the spring.

Figures 7 and 8 show the bearing flange 10 which has a tapered collar 38 at the rear. Tapered pegs 40 project from this collar and anchor the metal flange 10 in the foam mandrel 5. The filament wound skin 34 which is wound onto the mandrel covers the tapered collar 38 and, together with the pegs 40, holds the flange 10 in place.

Figures 9 and 10 show the pivot bushes 20 and the mandrel 5 in the absence of any filament wound skin. Each bush 20 is formed with an integral peg 42 which is moulded in to the mandrel.

These pegs serve to hold the bushes and the mandrel together before and during winding.

To form the filament wound surface of the com ponent, filaments 27 such as glass fibres are wound around the mandrel 5. The fibres are coated or impregnated with a resin, which may be polyester or epoxy or vinyl ester resin, before application to the mandrel. Once the necessary number of windings have been applied, the structure is allowed to cure whereupon the resin sets and locks the strong filaments in place to produce an extremely strong component. This filament winding technology is well established.

It is necessary to apply the windings in a manner such that they do not slip over the mandrel surface after application. This is of particular importance when applying the process to large scale production of filament wound components, and reproducibility of winding patterns is then extremely important. To avoid any possibility of slippage, the filaments must be applied along geodesic or near geogesic paths on the mandrel surface. A geodesic path is the shortest distance between two points on a surface. For a complex shape, these paths are difficult to determine, but if the complex shape is approximated with regular shapes, the task is simplified. Geodesic paths are relatively easy to determine on a regular shape such as a cylinder or a cone.

In the present case, the wishbone structure can be considered to consist of a cylindrical portion 30 (see Figures 5 and 6) forming the spring well and an oblique truncated conical portion 32 forming the limb supporting the bearing flange 10. The wishbone arms (which are not shown in Figures 5 and 6) can be considered as cylindrical shapes.

These shapes interpenetrate each other as shown.

The geodesic lines on these shapes, which each have a single axis of rotational symmetry, are easy to determine.

Winding of the structure takes place to produce the wishbone shown in Figure 3. A cross section through this wishbone will appear as shown in Figure 2, with the mandrel 5 covered by a wound layer 34.

Winding will be performed along some or all of helical, longitudinal and circumferential geodesic paths. Longitudinal windings give bending stiffness and helical windings give both bending and torsional stiffness. Circumferential windings improve coverage and diametral stiffness.

The oblique cone 32 is wound with helical and longitudinal windings. The cylindrical portion 30 is wound with a combination of helical, longitudinal and circumferential windings, especially longitudi nal windings to resist the force induced by the coil suspension spring 11. The arms 14 and 16 are wound with both circumferential and helical wind ings. Longitudinal windings may also be needed.

The pivot bushes 20 provide a natural turn-around for filament paths.

To permit access for the drive-shaft and coil spring, an unwound portion exists around the spring well 12. This is a naturally wound opening (i.e. the filaments are continuous around the open ing) as opposed to a cut opening which could seri ously weaken the structure.

Once complete coverage is obtained, it is then possible to repeat the coverage or to reinforce the structure locally in highly stressed areas with extra filaments.

A typical stud plate 24 is shown in Figures 11 and 12. The plate has a base 50 with a bevelled perimeter. A stud 22 is upstanding from this base. In the mould, this base and stud are lightly affixed to the mould wall, so that the base 50 projects into the mould cavity. When foaming takes place, the foam flows around the tapered base and thus locks the base into the foam structure. When the mould is opened, the bond between the base and stud and the mould wall is broken and the stud plate remains fixed in the relatively high density material which forms the external skin of the mandrel.

The filament wound skin 34 is then applied to the mandrel, over the base 50 and around the root of the stud 22. If necessary, additional reinforcing patches 52 may be included in the filament wound structure.

Once the filament wound structure 34 has cured, any required fitting 54 can be bolted on using a nut 56 on the projecting threaded stud 22. Examples of fitted brackets 54 are shown in place in Figure 4.

The mandrel 5 remains as part of the wishbone, and contributes to its strength.

Claims (5)

1. A vehicle suspension wishbone made by a filament winding technique.

2. A wishbone as claimed in Claim 1, wherein filaments are wound around a mandrel, and the mandrel is left in place in the wound structure.

3. A wishbone as claimed in Claim 1 or Claim 2, which has a closed section limb which supports the wheel bearing and as a longitudinal passage therethrough to accommodate the driveshaft.

4. A wishbone as claimed in any preceding claim, wherein the mandrel is formed by a moulding process, and metal inserts in the wishbone are moulded in to the mandrel surface.

5. A vehicle suspension wishbone, substantially as herein described, with reference to any one embodiment shown in the accompanying drawings.