GB2211913A

GB2211913A - Leaf springs of composite material

Info

Publication number: GB2211913A
Application number: GB8825161A
Authority: GB
Inventors: Andrew Pollard
Original assignee: GKN Technology Ltd
Current assignee: GKN Technology Ltd
Priority date: 1987-10-30
Filing date: 1988-10-27
Publication date: 1989-07-12
Also published as: GB8725501D0; GB8825161D0

Abstract

A leaf spring (in plan view in Fig. 1) of fibre reinforced plastics material, for a vehicle suspension, has a central portion (10) and end portions (11, 12) inclined thereto, with reinforcing fibres increasing the cross-sectional area of the spring at least in transition regions (section B-B) between the central and end portions. <IMAGE>

Description

LEAF SPRING OF COMPOSITE MATERIAL This invention relates to a leaf spring made of composite (fibre reinforced plastics) material for use in a vehicle suspension, the spring comprising a central portion and end portions which are inclined to the central portion. Such a spring will hereafter be referred to as a spring of the kind specified.

A spring of the kind specified is intended for use in a suspension wherein the spring extends transversely of the vehicle and is supported to the vehicle structure, for pivotal movement about axes extending generally longitudinally of the vehicle, at two spaced positions between the ends of the spring. The end portions of the spring engage respective wheel supporting members, e.g.

wishbone members, and because the end portions of the spring are inclined to the central portion thereof a substantially clear space is left directly between the wheel supporting members. This facilitates accommodation of, e.g. the vehicle's engine between the wheel supporting members, if the suspension is for the front wheels of the vehicle. The positions at which the spring is supported relative to the vehicle structure would usually be at transition regions between the end portions and central portion of the spring, and the end portions of the spring may be, in the embodiments described hereafter, of straight or curved configuration.

Examples of springs of the kind specified, and suspensions incorporating such springs, are disclosed in our International patent application publication number W087/06539, which was not published at the priority date of the present application.

When such a spring is in use, the forces and stresses which arise therein are very complex with torsional stresses superimposed upon bending stresses.

It is the object of the present invention to provide a spring construction which is better able to withstand such stresses.

According to the present invention, we provide a spring of the kind specified wherein at least regions of transition between the central portion and the end portions thereof are reinforced by additional fibres providing such regions of the spring with an increased cross sectional area.

Various ways in which a spring may be reinforced according to the invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a plan view of one embodiment of a spring according to the invention, including as insets the cross sections thereof at different positions along the spring; Figure 2 is a view as Figure 1, of a further embodiment of a spring.

Referring firstly to Figure 1 of the drawings, there is shown a leaf spring comprising a central portion 10 and two end portions 11, 12 which are inclined to the central portion. The two ends of the spring are mirror image identical to one another about the centre of the central portion 10 where the cross section C-C shown on Figure 1 is taken. The spring is intended for use in a vehicle suspension, in which application it would be supported relative to the vehicle structure at two positions at the ends of the central portion, for angular movement about axes extending generally lengthwise of the vehicle and transversely to the central portion 10 of the spring. One such support position, and also one such axis, would be where indicated by the cross section line B-B in the drawing.The free ends of the end portions 11, 12 of the spring would bear on wheel supporting members, e.g. pivoted suspension wishbone members or arms.

The spring is made of composite, fibre reinforced plastics, material. The centre portion 10 of the spring is primarily made of fibres which extend lengthwise of such portion, as indicated at 13. The end portions of the spring are made mainly of fibres extending substantially lengthwise of the respective end portions, as indicated at 14 for the end portion 11. At the regions of transition between the central portion and each end portion, the respective lengthwise extending fibres overlap as indicated at 15, to produce an increased spring cross section at the section B-B compared with the cross-sections A-A and C-C at the end portions and centre portion of the spring.Thereby the strength of the transition regions between the central portion and end portions of the spring is increased, and the spring is better able to withstand the bending and torsional loads imposed thereon in such region in service. The thickness of the spring is increased particularly at the inside corner of the transition region.

Referring now to Figure 2 of the drawings, there is shown a further embodiment of a spring with a central portion 20 and end portions 21, 22. The end portions are of somewhat S-shaped curved configuration and, considered in their entirety, are inclined to the central portion 20 although they actually merge into the central spring portion 20 and there can be considered to be fairly extensive transition regions between the central portion and end portion. In use, the spring would be mounted to a vehicle structure at the positions indicated by lines 23, 24.

The spring is made from fibres which, throughout the entire spring, extend lengthwise of the central portion of the spring, such fibres being indicated at 25, 26, 27. In the end portions of the spring, additional fibres extending lengthwise of the end portion, as indicated at 28, 29, and as indicated at 29 such additional fibres extend up to the mounting positions of the spring. Such additional fibres have the result that the end portions of the spring have an increased thickness and hence cross sectional area over most of their length as shown at the line A-A, as compared with the cross section of the central portion of the spring as shown at the line B-B.

The additional fibres in the end portions of the spring may be applied in layers overlying the fibres 26, 27 parallel to the central portion of the spring, and preferably such additional fibres are applied on both sides of each end portion of the spring. Thus the end portions of the spring throughout their length comprise fibres extending in mutually intersecting directions, so that the end portions are well able to withstand the complex bending and torsional loads experienced in use.

Springs of the general shape shown in Figure 2 inters it with one another so that a succession of springs in side-by-side relationship can be cut from sheet material, with suitable removal of such material at the free ends thereof. Such springs can be manufactured by cutting from material in which the fibres extend parallel to the central portions of the springs, after which the additional fibres can be applied to the end portions.

Thereafter the springs can be subjected to whatever process, e.g. a moulding process at elevated temperature, is required to cure the resin content and bring the springs to their finished state.

Claims

1. A spring of the kind specified wherein at least regions of transition between the central portion and the end portions thereof are reinforced by additional fibres providing such regions of the spring with an increased cross sectional area.

2. A spring according to Claim 1 wherein the central portion of the spring comprises fibres extending lengthwise of the central portion and the end portions of the spring comprise fibres extending lengthwise of the respective end portions, which fibres overlap in the transition regions to provide the increased cross section.

3. A spring according to Claim 1 wherein both the central portion and end portions of the spring comprise fibres extending in a direction lengthwise of the central portion, and the end portions are provided additionally with fibres extending lengthwise of the respective end portions.

4. A spring according to any one of the preceding claims wherein said transition regions have an increased thickness at the inside corner or curve thereof.

5. A spring substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawing.