VEHICLE SUSPENSION SYSTEM

Abstract: A vehicle has mounted inside the upper end of a suspension tower of its wheel suspension system, a support assembly for holding the upper end of a macpherson strut. The assembly has an inner bearing (32) supported in a resilient rubber bush (18). The axis of the bearing is arranged eccentrically to the centre of one, or preferably two pairs of overlapping rings (21,22 and 33,100). Each pair of rings can be clamped against rotation, or freed to allow one of the rings to be rotated with respect to the other. Rotation of the unclamped ring produces a repositioning of the upper end of the strut so that its misalignment in camber and cator can be corrected. The two rings can then be re-clamped together.

Description: Field of the invention This invention relates to a wheel suspension system for a vehicle and is more specifically concerned with supporting the upper end of an upright strut, usually a MacPherson strut, through which part of the weight of the vehicle is transmitted to one of its front wheels. State of the art Normally the upper end of a MacPherson strut is supported by a thrust-bearing support assembly. This comprises a bearing engaged by the top of the strut and supported in an annular, resiliently deformable bush made of rubber. The outside of the bush is bonded to a mounting plate which is bolted to the underside of a suspension tower built into the upper part of a wheel arch of the vehicle. The bearing allows the strut to turn about its vertical axis when the front wheel is turned, and the rubber bush accommodates axial vibration and tilting of the strut which occurs when the vehicle is travelling over rough ground. It is important that the strut should remain substantially vertical so that it is subjected to minimum bending moment. However, wear of mechanical parts of the wheel-suspension system can cause the position of the lower end of the strut to change with respect to its upper end. The strut is then no longer vertical. If the wheel is displaced by wear outwardly, it is known as camber change, and if the wheel is displaced forwardly it is known as caster change. In both cases there is a change in the pressure pattern of the wheel's tread with the surface of the road. The resultant increased wear on one side of the tyre with respect to the other is often the first indication the average driver has that there may be a suspension misalignment problem. If such a problem is left unattended, the road-handling characteristics of the vehicle will deteriorate and, in an extreme case the vehicle can be pronounced unfit to drive. In order to correct misalignment caused by inclination of the MacPherson strut, it is known, for example from US-A-4 213 631, US-A-4 581 802 and EP-A-0 092 066, to re-locate its upper end. In older cars this is done by bodily moving the thrust-bearing support assembly to bring the strut into vertical alignment. In US-A-4 213 631 it has been proposed to make provision in the thrust-bearing support assembly for accommodating some variation in the position of the upper end of the MacPherson strut. This is achieved by providing a mounting ring of the assembly with a number of bolt holes spaced equi-angularly from one another around a circle. The thrust-bearing is arranged eccentrically with respect to the centre of the circle. It is possible with this arrangement to re-position the upper end of the MacPherson strut by unbolting the mounting plate, turning it through a sector, and then re-bolting it in position. This allows a limited amount of correction to be applied to the upper end of the strut. If more correction is necessary, that can be achieved by filing the bolt holes into slots elongated in the direction in which it is required to move the bearing, as suggested by US-A-4,581,802. However, this has the disadvantage that the contact areas between the heads of the bolts securing the thrust-support assembly in position, and the mounting ring, are reduced to a value beneath the designed value. Also, the physical strength of the mounting plate itself is weakened by the filing out of the bolt holes. Object of the invention The invention seeks to provide a thrust-support assembly which enables a wide range of repositioning of the upper end of a strut without physical weakening of the support. Summary of the invention According to the present invention, there is provided a thrust-support assembly for mounting the upper end of a strut in a vehicle wheel-suspension system, comprising a thrust bearing for fitting to the upper end of the strut; an inner rigid annular member supporting the thrust-bearing; an outer rigid annular member spaced radially outwardly of the inner member, a resiliently-deformable annular bush having shock-absorbing properties located between the inner and outer rigid members; and means for adjustably mounting the assembly in a suspension tower of the vehicle; characterised in that the assembly incorporates at least one annular element extending outwardly from the thrust-bearing, or from the outer rigid member, and having an outer circular rim disposed eccentrically with respect to the axis of the thrust bearing, a cylindrical surface is provided on the inner rigid member, or on the suspension tower, respectively, for engaging the outer rim of the annular element, and releasable clamping means are provided for clamping the annular element in any desired angular position, relative to the said cylindrical surface, the annular element being rotatable when the clamping means are released to enable adjustment of the position of the axis of the thrust bearing relative to the suspension tower. The assembly of the invention has the advantage that it allows repositioning of the upper end of a MacPherson strut over a wider range of positions than has hitherto been possible, without having to unbolt and then reposition the assembly, and without having to weaken it structurally. Such re-positioning is achieved simply by loosening the clamping means, turning the annular member to re-locate the thrust-bearing and then re-tightening the clamping means. Conveniently one annular element is provided outside the bush and the other inside the bush. The practical advantage of such an arrangement is that access to the individual annular elements is easier than when both are arranged outside the bush which is a theoretically possible alternative configuration. It is not essential to provide the thrust-bearing support assembly with two annular elements. In one arrangement a single annular element is used, one of the cylindrical surfaces being formed on the assembly mounting plate and the other on a metal flange extending circumferentially around the bush. In an alternative arrangement the thrust bearing is arranged eccentrically in the bush. A circular flange eccentrically surrounding the bush, has one cylindrical surface formed by its outer marginal edge. The complementary cylindrical surface is formed by a stepped inside rim of the mounting plate which conveniently provides a clamping ring. Suitably the clamping means are provided by bolts used to anchor the clamping ring in position. Loosening of these bolts allows the two cylindrical surfaces to be relatively rotated. Suitably the cylindrical surface may be formed by a flange on a bush-holder which projects slightly above the clamping ring. When the bolts are tightened, the clamping ring locks the outer marginal edge of the flange between itself and the underside of the suspension tower so that rotational movement between the inter-engaging circular surfaces is prevented. Brief description of the drawings The invention will now be described further, by way of example, with reference to the accompanying drawings, in which : FIGURE 1 is a diagrammatic vertical section through a front wheel arch of a motor vehicle, FIGURE 2 is a vertical section through a thrust bearing support assembly mounted in the underside of the upper end of a suspension tower in the wheel arch, FIGURE 3 is a plan view of Figure 2, FIGURE 4 is an enlarged scrap view of part of figure 2, FIGURE 5 is a plan view of a second embodiment of a support assembly, FIGURE 6 is a plan view of a third embodiment of a support assembly, FIGURE 7 is a vertical section through Figure 6 taken on the angled line and in the direction indicated by the arrows VII-VII in that figure, FIGURE 8 is a plan view of a fourth embodiment of a support assembly, and FIGURE 9 is a vertical section through the assembly of Figure 8 taken on the line and in the direction indicated by the arrows IX-IX in that figure. Figure 1 shows a motor vehicle wheel arch 10 having a suspension tower 1 at its upper end. A road wheel 2 is located in the wheel arch and has a stub shaft 3 extending to a joint 4. A radius link 5 defines the permissible horizontal path of movement of the joint 4. The vertical movement of the joint 4 is controlled by an upright MacPherson strut 6 having its lower end mounted on the joint 4 and its upper end located in a thrust-bearing support assembly 7 mounted in the underside of the suspension tower 1. This method of mounting a front wheel of a motor car is, of course, well known in the art. Description of the first embodiment Referring now to Figure 2, the suspension tower 1 has its upper portion turned inwardly at 12 and is provided adjacent its inner marginal edge with three equi-angularly spaced holes which receive respective bolts 13. These hold the assembly in place against the underside of the tower 1. A clamping ring 14 on the outside of the assembly has a stepped inner rim 20, shown clearly in figure 4, which provides a cylindrical inner locating surface, referenced 21 in Figure 4. A second cylindrical surface, referenced 22, is provided by the circular outer rim of an outwardly-turned, flange or disc 24 formed at the upper end of an inverted frusto-conical rigid bush-holder 17. The thickness of the flange 24 is greater than the height of the step formed in the inside rim of the clamping ring 14 so that, when the bolts 13 are tightened, the flange 24 is tightly gripped between the ring 14 and the underside of the tower 1. When the bolts 13 are loosened, as shown in Figure 4, the flange 24 can be rotated in the stepped portion of the rim 20. As shown in Figures 2 and 3, the frusto-conical bush-holder 17 is eccentrically mounted with respect to the circular outer rim of the flange 25. A rubber bush 18 which is resiliently deformable and has shock-absorbing properties, has its outside surface bonded to the inside face of the holder 17. The inside surface of the bush 18 is cylindrical and bonded to the outside of a rigid sleeve 19 having its lower marginal edge turned inwardly at 100 to provide a base. An annular, rigid, eccentric 33 having an inwardly turned annular lip 31 rests on the base 100 and is welded to the underside of an outer race 38 of a thrust bearing 32. The angular position of the eccentric 33 in the sleeve 19 is controlled by a superimposed guard ring 34 connected by steel dowel pins 39 to the eccentric 33 beneath. The upper inner marginal portion of the guard ring 34 is formed with angularly spaced holes 38 arranged opposite one another and which enable a tool to be inserted into the sleeve 19 to engage spaced pins on the tool (not shown) with corresponding holes 35 in the guard ring 34. The upper inside surface of the sleeve 19 is threaded to co-operate with external threads provided on a locking ring 45 which is screwed down the sleeve 19 to engage the upper surface of the guard ring 34. A set of circumferentially-spaced bores 41 in the locking ring 45 enable it to be tightened or loosened with respect to the guard ring 34. When the locking ring 4S is loose, the tool for altering the angular position of the eccentric 33 can be applied to change the position of the thrust bearing 32 along a circular path. Figure 2 shows the upper end 47 of a MacPherson strut having a threaded spindle 48 which passes through the centre of the thrust bearing 32 and is held in position by a locking nut 49. Operation of the first embodiment When manufactured, the MacPherson strut 47 of the vehicle has its longitudinal axis upright. Through wear or damage, the upright axis can become inclined and the strut 47 is then subjected to a bending moment. The thrust-bearing support assembly is adjustable to reposition the upper end of the MacPherson strut 47 as follows. The bolts 13 are first slackened and the flange 25 manually rotated to correct the misalignment as far as possible. As the correction is effected by movement of the bush 18 along a circular path, the correction of an error in camber may introduce an error in caster subsequently corrected as explained below. The bolts 13 are then tightened to lock the circular support surfaces 21 and 22 together. The locking ring 45 is next loosened and the tool is applied to rotate the eccentric 33 in a direction which corrects any caster error present. The locking ring 45 is then tightened when the strut 47 is once again vertically above the joint 4. Description of second embodiment In the first embodiment the rotatable eccentric elements which enable adjustment to be carried out (namely, the eccentric element 33 and the eccentric flange 22) are respectively located inside and outside the rubber bush 18. However, in some circumstances two eccentric elements may be located outside the bush which then has the thrust-support bearing 12 mounted coaxially in its centre as is shown in Figure 5. In Figure 5 the support assembly locates the upper end of a MacPherson strut having an axial extension in the form of a threaded spindle onto which is screwed a nut 71. The spindle passes through a thrust-bearing 72 located concentrically inside a steel sleeve 73. The outside of the sleeve 73 is bonded to the inside surface of all annular rubber bush 74 made of a resiliently deformable material having shock-absorbing properties. The outside surface of the bush 74 is bonded to the inside wall of a steel bush-holder 75 of circular cross-section and having a flange 76 projecting radially from its upper end. The rim of the flange is circular and is eccentric with respect to the axis of the thrust-bearing, as shown. The marginal portion of the rim of the flange 76 is in overlapping relationship, as indicated by the shaded circle 77, with the inner rim of an eccentric flat ring 78 which, at its outer marginal edge, rests on a stepped inside rim of a clamping ring 79 similar to that described with reference to earlier figures. The shaded circle 80 shows where the rings 78 and 79 overlap one another. Bolts 81 hold the assembly in position and, when released, permit the ring 78 to be rotated with respect to the ring 79. Clamping pieces (not shown but also operated by bolts) overlap the shaded circle 77 and are releasable to permit the flange 76 to be rotated with respect to the ring 78. Tightening the bolts of the clamping pieces locks the flange 76 and ring 78 together so that relative rotation cannot occur between them. As the thrust bearing 72 is mounted eccentrically with respect to the axes of the two shaded circles 77 and 80, and the pairs of circular interengaging surfaces of each pair are separately operable, the two pairs enable correction to be applied to the position of the strut for an error in caster as well as an error in camber, as has already been explained with respect to the first embodiment. The clamping pieces referred to above and not shown, can be of any type. For example, they may comprise radial fingers held by releasable bolts to the ring 78 and extending radially inwardly to overlap the upper surface of the flange 76 located in the shaded circle 77. A ring of radially-extending teeth can be provided on the flange 76 beneath the position of the fingers and these can be provided with complementary teeth. When the bolts are tightened the teeth on the finger pieces engage the teeth on the flange 76 and prevent its rotation with respect to the ring 78. A disadvantage of such an arrangement is that the clamping pieces are necessarily close to the clamping ring 79 and the limitations on the available space make it hard to produce a cheap and easily adjustable design of thrust-bearing support assembly with such a configuration. Description of third embodiment Figures 6 and 7 show a thrust-bearing support assembly having a single eccentric. . Referring jointly to Figures 6 and 7, a suspension tower 91 of a vehicle wheel arch has its upper end turned in at 82 to provide a support surface for the bearing assembly shown at 83. The assembly 83 is held in position by a clamping ring 84 secured by bolts 85 to the underside of the support surface 82. The inner rim of the clamping ring 84 is stepped at 95 to provide an annular bearing surface 96 and 97. This surface is engaged by a second annular bearing surface 97 on the outer rim of an eccentric steel radial flange 98 formed at the upper end of an inverted frusto-conical bush-holder 99. The inside surface of the holder 99 is bonded to the outside surface of an annular rubber bush 200 which is resiliently deformable and has shock-absorbing properties. The bush 200 is lined with a steel sleeve 101 bonded to its inside surface and having an enlarged lower end 102. A MacPherson strut 103 surrounded by a coil-compression spring 104, has its upper end 105 of reduced diameter. A thrust bearing 106 is seated on the end 105 and is held in position by a top nut 107 screwed onto the top of the portion 105. A cap 108 encloses the upper end of the spring 104 and transfers its upward thrust to the underside of the bearing 106 thereby holding it firmly in the enlarged portion 102 of the sleeve 101. The frusto-conical holder 99 is coaxial with the bush 109 and the thrust bearing 106 (which may comprise a simple journal sleeve) but is eccentric with respect to the axis of the circular rim of the flange 98. Thus, once the bolts 35 are slackened, the holder 99 can be turned to move the axis of the upper end of the strut 103 around a circular path to bring its upper end more closely into vertical alignment with its lower end. The bolts 35 can then be tightened. Rotation of the holder 99 is conveniently effected by providing the upper end rim of the sleeve 101 with vertical slots 149. A tool having a pair of diametrically spaced blades (not shown) can be fitted from above to the sleeve 101 so that the blades enter the slots 149. Turning the tool will then turn the assembly 83 within the stepped clamping ring 84. Description of the fourth embodiment Figures 8 and 9 show in simplified form an embodiment of the invention in which a thrust bearing support assembly 250 is held in place in the underside of a suspension tower (not shown) by an external clamping ring 251 having the same stepped configuration as the clamping rings referred to in connection with earlier described embodiments. The tightness of the clamping ring 251 is again varied by bolts 252 as with earlier figures. A set of annular bearing surfaces 254 and 255 are respectively formed on the stepped portion of the inside rim of the clamping rim 251, and on the underside of a steel flange 255 arranged symmetrically around the upper end of a cylindrical bush holder 256. The inside of the holder is bonded to the outside of an eccentric rubber bush 257 which is resiliently deformable and shock-absorbing. The bush has an eccentrically arranged opening lined with a cylindrical steel sleeve 258 having an outwardly turned upper end 259, and an inwardly turned lower end 260. The sleeve 258 holds in place a thrust bearing 261 encircling the upper end of a strut 262, which may be a MacPherson strut. A nut 263 screwed onto an axial, externally-threaded spindle 264 of the strut retains its upper end in the bearing 261. The thrust-support bearing assembly of Figures 8 and 9 is adjusted in the same way as the assembly of Figures 7 and 9. However it is the eccentricity of the bush 257, rather than the flange 255, which produces the circular movement of the upper end of the strut 262 to locate it in a better position. It will be observed that in all of the above embodiments, the position of the upper end of the MacPherson or other suspension strut is varied without having to reposition or remove the bearing assembly from the suspension tower, and without having to weaken parts of the assembly physically. Although the first and second embodiments of the invention give a finer degree of control over the position of the upper end of the strut than the embodiments of figures 6 to 9, this degree of control is not essential and for many vehicles that provided by the third and fourth embodiments of the invention is quite sufficient.

Claims: A thrust-support assembly for mounting the upper end of a strut in a vehicle wheel-suspension system, comprising a thrust bearing (32; 72; 106; 261) for fitting to the upper end of the strut (47; 103; 262); an inner rigid annular member (19; 73; 101; 258) supporting the thrust-bearing; an outer rigid annular member (17; 75; 99; 256) spaced radially outwardly of the inner member, a resiliently-deformable annular bush (18; 74; 200; 257) having shock-absorbing properties located between the inner and outer rigid members; and means for adjustably mounting the assembly in a suspension tower of the vehicle (1; 91); characterised in that the assembly incorporates at least one annular element (33, 22; 76, 78; 98; 256), said annular element(s) extending outwardly from the thrust-bearing, and/or from the outer rigid member, each annular element having an outer circular rim disposed eccentrically with respect to the axis of the thrust bearing, a cylindrical surface/cylindrical surfaces is/are provided on the inner rigid member, and/or connected to the suspension tower, respectively, for engaging the outer rim of the annular element, and releasable clamping means (45, 14; 81; 95; 251) are provided for clamping the annular element in any desired angular position, relative to the said cylindrical surface, the annular element being rotatable when the clamping means are released to enable adjustment of the position of the axis of the thrust bearing relative to the suspension tower. An assembly as claimed in claim 1, including two annular elements (33, 22; 76, 78) having outer circular rims disposed eccentrically with respect to the axis of the thrust bearing, and two independently operable clamping means for enabling each annular element to be locked in any desired angular position relative to the thrust bearing, independently of the angular position of the other annular element. An assembly as claimed in claim 2, in which the annular elements (33, 22) are arranged one (33) radially inside and the other (22) radially outside the rubber bush (18). An assembly as claimed in claim 3, in which each clamping means includes two radially overlapping flat annular surfaces (21 ,22), one on the outer rim of the annular element to be clamped and the other on the inner marginal portion of an associated stepped clamping ring. An assembly as claimed in claim 1, having a single annular element (98; 256) extending outwardly from the thrust-bearing or the outer rigid member, and having an outer circular rim disposed eccentrically with respect to the axis of the thrust bearing. An assembly as claimed in claim 5, wherein the annular element is constituted by a flange on the outer rigid member, the latter constituting a bush-holder (99). An assembly as claimed in claim 6, wherein the flange (98) is of non-uniform radial extent. An assembly as claimed in claim 6, wherein the rubber bush (257) is of non-uniform radial extent.

Inventors: DALE, CRAIG, FERMAN, MICHAEL
Applicants: ARINDOL PTY. LIMITED
Application year: 1987
Main classification: B62D17
IPC codes: B60G17, B60G3, B60G11, F16C23, B60G15, B60G13, B62D17