WO1986000266A1

WO1986000266A1 - Suspension for motor vehicle

Info

Publication number: WO1986000266A1
Application number: PCT/GB1985/000277
Authority: WO
Inventors: Anthony Stevens
Original assignee: Gkn Technology Limited
Priority date: 1984-06-27
Filing date: 1985-06-24
Publication date: 1986-01-16
Also published as: GB2187420B; EP0217799A1; GB8629090D0; GB2187420A

Abstract

A suspension for a pair of wheels, preferably non-steerable, of a motor vehicle, comprising a composite, fibre reinforced plastics, leaf spring (13, 130) at each side of the vehicle, connected at one end to the vehicle to extend as a cantilever generally longitudinally of the vehicle and at the other end to a wheel carrier (12, 135). The wheel carriers (12, 135) are interconnected by a member which is of generally U-shape, comprising a torsionally resilient portion (16, 145) extending transversely of the vehicle and end portions (17, 134), and which provides an anti-roll effect and maintains correct alignment between the wheels.

Description

SUSPENSION FOR MOTOR VEHICLE

This invention relates to a suspension for a pair of wheels, preferably the non-steerable wheels, of a motor vehicle.

It is the ^"broad object of the invention to provide a suspension which is simple and cost effective, and enables effective use to be made of the properties of modern materials and techniques, in particular of composite, fibre reinforced plastics, springs-

Motor vehicle suspensions are known wherein springs in the form of elongate leaves are utilised in the cantilever mode, i.e. load from a wheel carrier or axle component is applied to each spring at or adjacent one of its ends, the spring being supported relative ^'to the structure of the vehicle at a position between its ends and at its other end. Such an arrangement can result in space savings compared with the conventional manner of use of leaf springs wherein each spring is connected to the vehicle structure at both its ends and to an axle component between its ends. One example of a suspension utilising leaf springs in the cantilever mode has been disclosed in British Patent Specification 1460956. In that suspension, the springs are disposed to extend generally longitudinally of the vehicle, with their rear¬ most ends connected to a rigid axle beam and their foremost parts mounted in channel members in the vehicle body structure. As well as providing for vertical springing of the wheels relative to the vehicle structure, the springs locate the rear axle longitudinally and transversely, and provide desired roll and compliance steer effects. However, by use of an axle beam between the free ends of the springs whether driven or not, the space occupied thereby is essentially unavailable for the disposition of other components which^' may be required. Further, the roll stiffness of the suspension, i.e. the resistance to roll of the vehiclej e.g. when cornering, is the same as that of a conventional leaf spring suspension. It is an object of the present invention to provide a suspension improved in these respects.

10 According to the invention, we provide a suspension for a pair of wheels of a motor vehicle, comprising two leaf springs, one each side of the vehicle and each connected on the one hand to the vehicle to extend as a cantilever generally longitudinally thereof and on the

15 other hand to a respective wheel carrier member, and a member having a torsionally resilient portion extending generally transversely of the vehicle spaced forwardly or rearwardly of said wheel carrier members and. having end portions connected, preferably rigidly connected, to said

20. wheel carrier members.

In a suspension according to the invention, the use of springs in the cantilever mode can give very effective wheel location in directions transversely of the vehicle, while at the same time being relatively

25 light in weight and mechanically simple compared with some systems using complex linkages as proposed hitherto. The transverse torsionally resilient member and its end portions connected to the wheel carrier members assist maintenance of the correct alignment of the wheels

30 relative to one another and, additionally, acts as an anti-roll bar. It will be appreciated that roll of the vehicle, i.e. different vertical displacements of the wheels relative to the vehicle structure, results in torsion of the transversely extending portion of the member, resisted by the torsional resilience thereof.

The torsionally resilient portion and end portions of said member may together form a generally U-shape in plan view. In one of the embodiments described hereafter, the member is formed of tubular material, and in the other embodiment herein described it is made from sheet metal by pressing, bending and welding.

The end portions of said member may themselves constitute the wheel carrier members, and springs may be connected thereto adjacent said torsionally resilient portion of the member.

The effect of this is a reduction in the number of separate components used in the suspension.

The cantilever connection of each leaf spring to the vehicle may be established by supporting each spring between its ends for pivotal movement about a substantially horizontal axis, the spring bearing against a reaction member at or adjacent its end remote from the wheel carrier member. The reaction member may be disposed within a housing, the spring being supported for pivotal movement by a part of the housing where it emerges therefrom. The housing and spring then forms a unit which may easily be secured to or incorporated in the structure of a motor vehicle.

According to a further feature of the invention, the position of the reaction member may be adjustable within the housing. This renders it possible to adjust the characteristics of the suspension to suit different loading conditions for the vehicle. Conventional practice in vehicle suspensions design is to select springs of dimensions and load-de lection characteristics suitable for the vehicle under average loading conditions. Springs so selected may not, however, be adequate for the condition when the vehicle is fully loaded, when the static position assumed by the vehicle relative to the ^"surface on which it is driven may be too low, with a large proportion of the total available suspension movement taken up by the heavy vehicle load so that further movement to deal with road irregularities is restricted. In a suspension according to the invention, adjustment of the reaction member within the housing in a direction generally perpendicular to the spring may be used, in effect, to preload the spring so that it is better able to cope with heavy vehicle loads.

The reaction member may be movable in a manner to provide for adjustment of its position of engagement with the spring in directions longitudinally of the spring, as well as generally perpendicular thereto in the direction of bending of the spring. Thereby the rate of the spring is altered (by changing the effective length of the spring within the housing), as well as a preload being applied to the spring as above described. These effects may be achieved by providing the reaction member with a curved surface engaging the spring, and mounting the reaction member within the housing for pivotal movement about a transverse axis adjacent the end of the spring within the housing. In the embodiment described hereafter, such movement of the reaction member is effected by an electric motor by way of a suitable transmission arrangement.

Preferably the springs of the suspension are made of composite, fibre reinforced plastics, material. It is well known that the use of composite springs in vehicle suspension effects a saving in weight, but in a suspension according to the invention further advantages are obtained. In particular, the use of composite materials enables the thickness of the spring to be varied along its length to provide required characterics. The part of each spring lying outside its housing may be of increased thickness compared with that within the housing, such that the part of the spring outside the housing is substantially rigid under normal service loads, with all or substantially all the resilient bending of the spring occuring within the housing. Since the part of the spring within the housing is more effectively controlled by its engagement with the reaction member than that outside the housing, this enables effective control of the characteristics of the suspension.

These and other features of the invention will now be described by way of example with reference to the accompanying drawings, of which:-

Figure 1 is a plan of one embodiment of suspension according to the invention;

Figure 2 is a side elevation of the suspension of Figure 1 ;

Figure 3 is a rear elevation of the suspension of Figure 1 ;

Figure 4 is an elevation, partly in section, of a further embodiment of suspension according to the invention; Figure 5 is a plan of part of the suspension of Figure 4-

Referring firstly to Figures 1 to 3 of the drawings, the illustrated suspension is for the rear wheels 10 of a motor vehicle, e.g. a passenger car. The axis of rotation of the wheels is indicated at 11 in Figure 1. The wheels are supported by a hub and bearing arrangement, not shown, on wheel carrier members 12. As illustrated, the wheels are not drivable, but the general suspension arrangement described hereafter would also be suitable for drivable wheels, in which case a differential gear unit would be mounted to the vehicle between the wheels and universally jointed drive shafts extend transversely therefrom.

The main components of the suspension are two leaf springs 13, one on each side of the vehicle. Each is connected on the one hand to the vehicle to extend rearwardly thereof as a cantilever, and on the other hand at its rearmost end to its respective wheel carrier member 12. The leaf springs 13 are made of a composite, fibre reinforced plastics material, and the thickness of the springs varies along their length to give them the desired springing properties. The rearmost end of each spring 13 lies within an elastomeric element 14 which is held to wheel carrier 12 by a rigid element 15 which compresses the elastomeric element and prevents the spring being released therefrom. At the same time, the connection is effected in a vibration absorbing manner.

The two wheel carriers 12 are connected by a member 16 which is U-shaped in plan and extends transversely of the vehicle with its main portion lying forwardly of the wheel carriers. End portions 17 on the member 16 extend rearwardly and are rigidly connected to the wheel carriers 12. The member 16 conveniently is a steel tube, and thus may be welded to the wheel carriers 12. The member 16 acts as an anti-roll bar by virtue of the torsional resilience of its transversely extending portion, and assists transverse location of the wheels relative to one another. The member 16 could be of any convenient shape and could be disposed forwardly or rearwardly of the wheel carriers 12 and still have the same effect.

Conventional telescopic dampers 18 are provided, one connected between each wheel carrier 12 and the structure of the vehicle.

The cantilever connection of the forward ends of springs 13 to the vehicle is shown most clearly in

Figures 1 and 2. Each spring extends forwardly i to a housing 19 which is bolted to the vehicle structure. At the point where the spring enters the housing, it is supported for pivotal movement about a generally horizontal axis, the spring having a portion 20 with part-cylindrical upper and lower surfaces, which lies within an elastomeric element 21 in turn lying within part-cylindrical portions 22 of the housing 19. The pivotal movement of the spring is achieved by flexing of "the elastomeric element 21.

The free end of the spring 13 within the housing 19 fits within a shoe 23 of metal or a rigid plastics material. An elastomeric element 24 is interposed between the spring and shoe. The shoe 25 has a part-spherical formation 25 on its underside , which lies within a correspondingly shaped depression in the upper surface of a reaction member 26. The reaction member 26 has screw threaded engagement with an upstanding support member 27 within the housing 19« Thus it is possible to adjust the vertical position of the reaction member 26 within the housing 19- This enables a desired ride height for the vehicle to be achieved under differing vehicle loads, by an effect analogous to preloading of the spring. The sides of shoe 23 fit closely between walls 28 of housing 19 so that the spring is tightly constrained laterally within the housing.

The housing 19 also contains an electric motor 29. This is arranged to rotate the reaction member 26 and thereby adjust its position within the housing, by way of a toothed belt 30 which engages a toothed outer cylindrical surface 31 on the reaction member 26. By the use of suitable sensors responsive to the attitude of an appropriate suspension part or parts and a control system, a self-levelling suspension system can be provided.

Referring now to Figures 4 and 5 of the drawings, there is shown a suspension comprising at each side of the vehicle, a spring 150 extending into a housing 131 • Where it emerges from the housing, the spring is supported between elastomeric elements 132 so that it is able to undergo limited pivotal movement about a substantially horizontal axis. Outside the housing 131 , the free end portion 133 of the spring is connected to a member 134 which is adapted, at its end 135_> to carry a wheel. The spring end portion 133 is secured to the member 134 by being held captive within a sheet metal element 133a secured to the member 134, with the interposition of a layer of elastomeric material. The member 134, as well as constituting a wheel carrier member) forms an end portion of a member which further has a portion 145 extending transversely of the vehicle, spaced forwardly of the axis of rotation (155a) of the wheel. The portion 145 is torsionally resilient and is analogous in function to the transversely extending portion 16 in the embodiment of Figures 1 to 3- The member 134, 145 is formed from sheet metal by appropriate pressing, bending and welding operations.

Within the housing 131, the other end 136 of each spring 130 is constrained within an elastomeric element 137 in the housing. The element 137 also holds one end of a reaction member 138 which has a curved upper surface engaging the underside of the spring. The reaction member 138 is, in effect, held for pivoting about a transverse axis adjacent the end 136 of the spring.

The spring 130 is of composite, fibre reinforced plastics) material. The part of the spring including the end portion 133, lying outside the housing 131 , is relatively thick compared with the part of the spring within the housing, and relatively short compared with that inside the housing. When the spring is loaded, the part thereof outside the housing 131 ^is substantially rigid, and all or substantially all the bending of the spring under load takes place within the housing. Thus, the characteristics of the spring are more fully controlled by adjustment of the reaction member as hereafter described) as compared with the embodiment of Figures 1 to 3 wherein the part of the spring outside the housing 19 will undergo substantial bending when the spring is loaded and is not affected by movement of the reaction member 26. \ 0

The reaction member 138 is connected, by way of a link 139, to a quadrant member 140 pivotally supported at 141 within the housing 131 • The quadrant member 140 carries gear teeth in the form of a rack 142, engageable with a pinion 143 arranged to be rotated, through the intermediary of suitable reduction gearing, not shown, by an electric motor 1 •

In this embodiment of the invention, pivotal movement of the reaction member about its end held in the elastomeric element 137 effects a change in the position at which it is engaged by the spring 130, in directions both longitudinally of the spring and vertically in the plane of the drawing, Figure 4« Thereby the effective spring rate and static position assumed by the suspension elements under a given load can be adjusted. This adjustment can be effected in small increments between the limits determined by the uppermost and lowermost positions of the quadrant member 140.

In both the embodiments of Figures 1 to 3 and Figures 4 and 5 of the drawings, it will be appreciated that other means could be utilised for moving the reaction member in such suspensions. For example, fluid pressure operated means could be used.

Claims

1. A suspension for a pair of wheels of a motor vehicle, comprising two leaf springs (13, 130), one each side of the vehicle and each connected on the one hand to the vehicle to extend as a cantilever generally longitudinally thereof and on the other hand to a respective wheel carrier member (12, 135), and a member having a torsionally resilient portion (16, 145) extending transversely of the vehicle spaced forwardly or rearwardly of said wheel carrier members (12, 135) and end portions (17) 134) connected to said wheel carrier members (12, 135) •

2. A suspension according to Claim 1 further characterised in that said torsionally resilient portion (16, 145) and end portions (17, 134) of said member together form a generally U-shape in plan view.

3. A suspension according to Claim 2 further characterised in that said end portions of said member (134) constitute said wheel carrier members (135), and said springs (130) are connected thereto adjacent said torsionally resilient portion (1 5) -

4- A suspension according to any one of the preceding claims further characterised in that each of said springs (13, 136) is supported between its ends for pivotal movement about a substantially horizontal axis) and bears against a reaction member (26, 138) at or adjacent its end remote from said wheel carrier member.

5. A suspension according to Claim 4 further characterised by a housing (19, 131) within which said reaction member (26, 138) is disposed, the spring (13, 130) being supported for said pivotal movement by part of said housing (19, 131) where it emerges therefrom.

6. A suspension according to Claim 5 further characterised in that the position of said reaction member (26) 138) is adjustable within said housing (19, 131).

7. A suspension according to Claim 6 further characterised in that said reaction member (138) is movable in a manner to provide for adjustment of its position of engagement with the spring (130) in directions longitudinally of the spring and generally perpendicular thereto in the direction of bending of the spring.

8. A suspension according to Claim 7 further characterised in that said reaction member (138) affords a curved surface engaging said spring (130), and is mounted within said housing (131) for generally pivotal movement about a transverse axis adjacent the end of "che spring (130) within said housing (131).

9- A suspension according to any one of the preceding claims further characterised in that said springs (13, 130) are made of composite, fibre reinforced plastics, material.

10. A suspension according to Claim 9, as appendant to

Claim 5, further characterised in that the part of the spring (130) outside said housing (131) is substantially rigid under normal service loads.