GB2513837A

GB2513837A - Cross-Vehicle Linkage

Info

Publication number: GB2513837A
Application number: GB1304821.0A
Authority: GB
Inventors: Steven James Randle
Original assignee: McLaren Automotive Ltd
Current assignee: McLaren Automotive Ltd
Priority date: 2013-03-15
Filing date: 2013-03-15
Publication date: 2014-11-12
Anticipated expiration: 2033-03-15
Also published as: GB2513837B; GB201304821D0

Abstract

A vehicle has a body and two wheels 117, each attached to the body by a suspension mechanism 101, 102 allowing wheel 117 to move relative to the body in steer and camber. A steering mechanism is mounted on the body and is attached to each suspension mechanism 101, 102 by a track rod 111 and a camber link 122. When the attachment points of a track rod 111 and a camber link 122 of one wheel 117 on the steering mechanism move together, wheels 117 move in camber; when the attachment points move relative to each other, wheels 117 move in steer. The steering mechanism may comprise a rack (13, Figure 1) and pinion (14, Figure 1) or a Pitman arm connected to a steering box (12, Figure 1), and may comprise a part translating transversely across the vehicle. A camber axis 135 may be below a running surface of wheels 117. Camber motion of one wheel 117 may simultaneously cause camber motion of the other wheel 117.

Description

I

CROS&VEHICLE UNKAGE This invention relates to linkages across vehicles, It is conventional for a whe&ed vehicle such as an automobile to have a pair of steerable whe&s, normally at the front of the vehicle. In adthtion to having the abllfty to rotate about a generally horizontal axis as the vehicle moves along, the steerable whe&s can rotate about a generally vertical steer axis to allow the driver to control the direction of trayS of the vehicle. The steer axis is normally offset from vertical by a few degrees! and fixed relative to the body of the vehicle.

Figure 1 illustrates a pair of steerable wheSs in one example of a vehicle suspension arrangement. The wheels 1, 2 are mounted on hub carriers 3, 4. Each wheel can rotate relative its respective hub carrier about a generally hodzontal axis. Each hub carrier is mounted to the body 5 of the vehicle by a suspension mechanism indicated generally at 6, 7. The suspension mechanisms are mounted to the hub carriers in such a way that each hub carrier can rotate about a respective steer axis 8, 9. The steedng attitude of the wheels 1. 2 is controlled by track rods 10, 11.

The vehicle!s steering is controlled by a rack mechanism. The rack mechanism comprises a rack body 12, a steering rack 13 and a pinion 14, The rack body 12 is fast with the body 5 of the vehicle. The steering rack 13 is a toothed bar which is held captive in the rack body 12 in such a way that the rack is only free to translate relative to the rack body transversSy across the vehicle. The pinion 14 is mounted within the rack body in such a way that it engages with the steering rack, A steering shaft 15 connects the pinion to a steering wheel 16 so that when a driver turns the steering wheel the pinion rotates and causes the rack to translate relative to the body of the vehicle. The track rods 10, 11 run between the steering rack 13 and the hub carriers 3, 4. Each track rod is mounted to its respective hub carrier at a point offset from the hub carriers steer axis. In this way when the driver turns the steering wheel the wheels 1 2 rotate about their steer axes.

The camber angle of a vehicle's whe& is the inclination of the wheers plane of rotation from vertical when the vehide is on a horizontal surface. In the suspension mechanism of figure 1, the camber axis is fixed. However, it has been suggested that it would be desirable for the wheels of a vehide to be movable in camber as the vehicle corners, independently of bump traveL with a view to maintaining a more even load across the wheers periphery and thereby improving grip. This would require the wheels on the outer side of the corner to reduce in camber (i.e. towards increasing negative camber) and the wheels on the inner side of the corner to increase in camber (i.e. towards increasing positive camber) as the vehicle enters the corner. Several ways of achieving this have been proposed. In US 3,497,233 lower suspension control arms are mounted on pivoted drop inks, and roll of the vehicle body is transmitted to those drop inks to cause the camber of the wheels to alter. In the "LoachSensltive Camber Control Mechanism for a Vehicle Suspension 1992" described at: http://www.malicky.com/davidm/projectslprojects. html a wheel is arranged on a linkage such that the wheel has freedom to move in camber about a virtual pivot point. Because that point is below the road surface the lateral cornering force on the contact patch of the wheel causes the wheel to move in negative camber when on the outer side of a corner and vice versa. In US 6,776,426 a wheel carrier is mounted on a trapezoidal element that can rotate relative to the body of the vehicle about a substantiaUy vertical axis. The configuration of the trapezoid provides the wheel with a virtual pivot point for camber that can be below the ground.

It is apparent that in any suspension mechanism that permits camber freedom adverse handling consequences would result if a pair of front or rear wheels were to camber at significantly different angles. If the wheels of the pair were totally independent then they might adopt different angles due to gyroscopic effects, or if they were subject to different levels of grip. In a vehicle with camber freedom it is therefore advisable to link the wheels of a pair together so that they camber with a common motion. Various mechanisms have been proposed for coordinating camber motion, For example in US 7246,8O6 camber motion is transmitted between opposite whe&s by means of a translating rod, and in US 64O6O36 camber motion is transmitted by means of a rocker.

There is a need for an improved mechanism for coordinating camber motion across a vehide.

According to the present invention there is provided a vehide having: a body; a pair of wheels, each wheel being attached to the body of the vehicle by a respective suspension mechanism that provides its wheel with freedom to move relative to the body of the vehicle in both steer and camber; and a steering mechanism movably mounted to the body of the vehicle, and attached to the suspension mechanism of one of the whe&s by a first track rod and a first camber Unk and to the suspension mechanism of the other of the wheels by a second track rod and a second camber link, the steering mechanism being configured so that when the points of attachment of the first track rod and the first camber link to the steering mechanism move together r&ative to the body of the vehicle the wheels move in camber, and when the points of attachment of the first track rod and the first camber link to the steering mechanism move relative to each other the wheels move in steer.

The steering mechanism may be configured so that when the points of attachment of the second track rod and the second camber link to the steering mechanism move together relative to the body of the vehicle the wheels move in camber and when the points of attachment of the second track rod and the second camber ink to the steering mechanism move relative to each other the wheels move in steer.

The steering mechanism may comprise a steering body movable relative to the vehicle and a steering actuator carried by the steering body and movabe relative to the steering body in response to steering inputs, the first and second track rods being attached to the steering actuator and the first and second camber links being attached to the steering body.

According to a second aspect of the present invention there is provided a vehicle having: a body; a pair of wheels, each wheel being attached to the body of the vehicle by a respective suspension mechanism that provides its wheel with freedom to move relative to the body of the vehicle in both steer and camber; a steering controller; and a steering mechanism movably mounted to the body of the vehicle, and attached to the suspension mechanism of one of the wheels by a first track rod and a first camber link and to the suspension mechanism of the other of the wheels by a second track rod and a second camber link, the steering mechanism having a first mode of operation in which movement of the steering mechanism relative to the body of the vehicle couples the wheels to move together in camber without movement of the steering cordroHer and a second mode of operation in which the points of attachment of the first track rod and the first camber Unk to the steering mechanism move relative to each other in response to movement of the steering controller to confer steer motion on the said one of the wheels, In the second mode of operation the points of attachment of the second track rod and the second camber link to the steering mechanism move relative to each other in response to movement of the steering controUer to confer steer motion on the said other of the wheels.

The steering actuator may be a rack bar and the steering body may be a rack housing. The steering body may have freedom to translate across the vehicle. The steering actuator may have freedom to translate relative to the steering body in a direction across the vehicle.

The steering actuator is a Pitman arm and the steering body may be a steering box.

The steering body may have freedom to rotate relative to the vehicle about a first axis transverse to the vehicle. The steering actuator may have freedom to rotate relative to the vehicle about an axis transverse to the first axis.

The vehicle may comprise a driveroperable steering controller, e.g. a steering wheel or a hydraulic actuator and the steering actuator is configured to move relative to the steering body in response to operation of the steering controiler.

The wheels of the vehicle may be configured to support the vehicle on a running surface. The axes of the wheels' camber motions may be located below the running surface.

The points of attachment of the first track rod and the first camber link to the suspension mechanism of the first wheel may be substantially equidistant from the camber axis of the first wheel. The points of attachment of the second track rod and the second camber link to the suspension mechanism of the second wheel may be substantially equidistant from the camber axis of the second wheel.

The point of attachment of the first camber link to the suspension mechanism of the first wheel may be substantially on the steer axis of the first wheel. The point of attachment of the second camber link to the suspension mechanism of the second wheel may be substantially on the steer axis of the second wheel.

The first and second camber links may be constituted by drive shafts for their respective wheels.

Camber motion of one of the wheels may cause camber motion of the other wheel by virtue of motion of the steering mechanism relative to the body of the vehicle.

The present invention will now bedsoibedby ikithliàftSiiSt6 thè accompanying drawings.

In the drawings: FIgure 1 shows part of a vehicle having a prior art suspension and steering mechanism.

Figures 2 and 3 show an example of a suspension mechanism that permits camber freedom. In figure 3 a wheel, brake rotor, vehicle body and suspension damper are omitted for clarity.

FIgure 418 a partial plan view of a vehicle having a steering mechanism that provides camber and steer linkage between a paIr of wheels.

Figure 5 is a plan view of an alternative steering mechanism.

In the arrangements to be described below, a pair of steerable wheels are linked by a steering device which can operate to urge the wheels to rotate about a steer axis.

Rather than being fixed to the body of the vehicle, the entire steering device is capable of sliding laterally across the vehicle. The steering device Is coupled to the wheels so that camber motion of the wheels is coordinated by virtue of the steering device.

Figures 2 and 3 show an example of a suspension mechardsm that provides a wheel with camber freedom.

The suspension system shown in figures 2 and 3 comprises a pair of suspension arms or wlshbones 101, 102. Each wishbone is mounted to the body 118 of the vehicle by a respective revolute joint 107 at Its inboard end. Those axes are preferably substantially parallel with the longitudinal (X) axis of the vehicle but they could deviate significantly from It. Other mechanisms than coupled suspension arms could to provide bUmjfravél: ft iiáthIithükhlkilóártkii struts; and if the vehicle were not to have any bump travel then suspension arms could be omitted and the wings 103, 104 could be attached to appropriate mounting points directly on the body of the vehicle that provide sufficient freedom (e.g. some vertical translation freedom at at least one of the mounts) that the desired camber motion is not Inhibited.

The motion of the suspension arms relative to the body of the vehicle can be moderated by means such as springs and/or dampers in the normal way. For example, a damper 108 (figure 2) with a coil spring over It could extend between one of the suspension arms and the body of the vehicle. Conveniently the damper extends to the lower arm since that can provide more room for it to be accommodated in a whe&arch of the vehicle.

The upper wing 104 is a rigid body which is shaped to provide mountings to other parts, as wUl be described below, and to fit among the other components of the suspension without fouling them as the suspension moves through its range of motion, -A first mounting of the upper wing is joint 109 between it and the upper suspension arm 101. The joint 109 is conveniently a spherical joint. The joint 109 may be located at the outboard end of the upper suspension arm, The joint 109 may be located at the uppermost end of the upper wing. Conveniently the joint 109 can be constituted by an extension of the upper wing being located in a spherical socket of the upper suspension arm.

-, A second mounting of the upper wing is joint 121 between it and a camber control rod 122. The joint 121 is conveniently a spherical joint. The joint 121 may be located at the outermost end of the camber control rod 121. Camber control rod 122 is coupled at its inboard end to a camber control mechanism 122a which wiN be described in more detail below. This mechanism may constrain the inboard end of the camber control rod so that it moves substantiauy linearly in a lateral direction with respect to the vehicle. The camber control rod can conveniently be connected to the camber control mechanism by a sphericS joint such as a baN joint at its inboard end.

Alternatively, the camber confrol rod could be flexible.

A third mounting of the upper wing is joint 113 between it and the wheel upright 100. The joint 113 permits relative rotation of the upper wing and the wheel upright.

It may be a revolute joint or a cylindrical joint. The way in which the joint 113 is presented can depend on packaging considerations, but in one convenient embodiment it can be constituted by two separate spaced-apart revolute or cylindrical attachment points, as shown in the figures, one on either side of the lower wing. Afternatively, it could be constituted by a single attachment point.

A fourth mounting of the upper wing is joint 114 between it and the lower wing. The nature of this joint wiN be discussed in more detail below.

The lower wing 103 is a rigid body which is shaped to provide mountings to other parts, as will be described below, and to fit among the other components of the suspension without fouling them as the suspension moves through its range of motion.

-. A first mounting of the lower wing is joint 120 between it and the lower suspension arm. The joint 120 is conveniently a spherical Joint. The joint 120 may be located at the outboard end of the lower suspension arm, The joint 120 may be located at the lowermost end of the lower wing. Conveniently the joint 120 can be constituted by an extension of the lower wing being located in a spherical socket of the lower suspension arm, A second mounting of the lower wing is joint 110 between it and a steering track rod 111 The joint 110 is conveniently a spherical joint. The joint 110 may be located at the foremost or reamiost end of the lower wing, or elsewhere. The joint may be located at the outermost end of the track rod 111. Track rod 111 is coupled at its inboard end to a steering rack 112 (figure 2) or similar device for moving the inboard end of the track rod laterally across the vehicle in response to steering inputs from a driver, Otherwise, the inner end of the track rod is constrained. The track rod can conveniently be connected to the steering rack via a spherical joint such as a ball joint at its inboard end, A third mounting of the lower wing is joint 122 between it and the wheel upright 100. The joint 122 permits relative rotation of the lower wing and the wheel upright.

It may be a revolute joint or a cylindrical joint, The way in which the joint 122 is presented can depend on packaging considerations, It could be constituted by two separate spacedapart revolute or cylindrical attachment points or by a single attachment point.

A fourth mounting of the lower wing is Joint 114 between it and the upper wing, which will be discussed in more detail below.

Conveniently joint 121 is offset in the vehicl&s longitudinal direction from joint 110, so that track rod 111 and camber control rod 122 can extend generally laterally with respect to the vehicle without clashing.

In a first embodiment the joints 113 and 122 between the wheel upright and the upper and lower wings are cylindrical joints (thus they permit relative rotation about an axis and translational motion along that axis but resist other forms of motion), and the joint 114 between the upper and lower wings is a spherical joint (thus the parts it interconnects are free to rotate about any axis but cannot translate relative to each other at the joint). The manner in which the camber mechanism provides camber freedom in this first embodiment will now be described.

Suppose that the vehicle's bump travel and steering input are constant, Since the vehicle's bump travel is constant the positions of the mounts 109 and 120 at the outer ends of the suspension arms are constant (although some limited relative movement of them may take place to accommodate camber motion). Since the vehicle's steering input is constant the position of the inboard end of track rod 111 is constant and hence the position of its outer end, at joint 110, is substantially fixed. In this condition, lower suspension mount 120 and steering joint 110 define an axis (lower wing axis") 133 about which the lower wing is substantially constrained to rotate. The lower wing is configured so that the lower wing axis 133 is coplanar with and not paraflel with the rotation axis 134 of the joint 122 between the lower wing and the wheel upright 100. As a result, axes 133 and 134 will intersect at a point 135. The camber axis 136 passes through point 135. A further axis 130 is constructed such that it joins upper suspension mount 109 and another point 132 that lies on the camber axis 136. Joint 113 is configured such that its rotation axis 131, between the upper wing 104 and the wheel upright 1001 will intersect the camber axis at point 132.

It is convenient for axes 131 and 134, between the wheel upright and the upper and lower wings respectively, to be significantly offset from each other. For example, they could make an angle of between 700 and 110°, more preferably 80° to 100 to each other when resolved into a plane containing one or both of those axes.

Conveniently axes 131 and 134 lie in or substantially in a common plane, although they need not do so.

In this embodiment, if joints 113 and 122 were revolute joints then the system would be fully constrained and no camber motion would be provided, However, since joints 113 and 122 permit relative translation of the wheel upright 100 and the upper and lower wings 104, 103 &ong axes 131 and 134 respectiv&y, the upper and lower wings are able to move in a coordinated way by rotating about axes 130 and 133 respectiv&y. This imposes a motion on whe& upright 100, which motion is essentially a rotation about axis 136 camber axis") joining points 132 and 135. By suitable arrangement of the design to fix axes 130, 131, 133 and 134, points 132 and can be fixed so that the camber axis is in a desired location. The running surface for the vehicle is tangential to opposite wheels of the vehicle at their lowest points. For the reasons discussed above, one useful location of the camber axis is b&ow the running surface of the wheel, and generally parallel with both the running surface and the plane of rotation of the wheel. However, other design criteria could dictate a different location for the camber axis, and that could be accommodated by suitable design of the suspension components.

The joint 114 between the wings is configured, e.g. in location and range of motion, such that relative motion of the first and second wings imposes a velocity ratio between the motions (a) of the upper wing relative to the upper suspension arm at joint 109 and (b) of the lower wing relative to the lower suspension arm at joint 120.

Since one of the suspension arm joints is above the other, that velocity ratio results in cambering of the wheel when the wings move relative to each other. The relationship of the axis of that camber motion to the rotation axis of the wheel can be fixed by the design of the hub carrier 100: specifically by it rigidly connecting the wheel hub and the hub carriers interconnections to joints 113 and 122 in an appropriate way.

In one example mechanism, when the vehicle undergoes bump travel mounting points 109 and 120 will move substantialty vertically by rotation about joints 107.

This can be achieved by the suspension arms 101, 102 being of equal or substantially equal length. Since only one of those parts (101, 102) that link points 109 and 120 to the body is damped by damper 108 relative to the body of the vehicle, the relative positions of the mounts 109 and 120 wUl be substantiafly unchanged by bump motion and such motion wW not significantly affect the relative configuration of the wings 103, 104. Thus the wheel can move in bump at substantiaHy constant camber, In another example mechanism, one of the suspension arms can be significantly anger than the other. For instance, the lower suspension arm can be significantly longer than the upper suspension arm. This will cause bump travel to result in some camber variation of the wheeL The camber motion due to the camber mechanism provided by free relative motion of wings 103, 104 can be superimposed on that bumpdependent camber motion. The range of camber motion that can result from the camber mechanism is preferably greater than that that can result from bump traveL For example, the range of camber motion that can result from the camber mechanism can be greater than that that can result from bump travel by a factor of two, three or even four. As an illustration, the range of camber variation due to bump travel could be around 30, whereas the range of camber variation due to the camber mechanism could be greater than 10°, for

example around 14°,

When the vehicle undergoes steer inputs the inner end of track rod 111 will move lateraHy and its outer end at joint 110 wifi move accordingly. This will cause both wings 103, 104 to rotate about a steer or kingpin axis 180 running through the upper and lower suspension mounts 109, 120, without significantly affecting the relative configuration of the wings 103, 104. Thus the wheel can move in steer at substantiafly constant camber.

A suspension mechanism that is a mirror image of the one shown in figures 2 and 3 can be provided for the opposite wheel of the vehicle.

This suspension mechanism is described further in the applicants copending patent application entitled Suspen&on System'.

One way of constraining the motion of the vehicle's suspension mechanism is to attach the inboard end of track rod 111 to a steering rack whose rack body is fast with the vehicl&s body, and to have camber control rod 122 extend across the vehicle from joint 121 to the analogous joint on the suspension mechanism of the opposite wheel in such a way that it is free to translate lateraUy across the vehicle.

With this arrangement, motion of the steering rack wiU cause the wheels to move together in steer; and when the wheels move in camber theft motions will be inked by means of the camber control rod 122.

Figure 4 illustrates an alternative arrangement. In figure 4 opposite wheels 200, 201 are attached to the body 202 of a vehicle by suspension mechanisms of the type shown in figures 2 and 3. The suspension mechanisms are not shown in detail in figure 4 but are indicated generaHy at 203, 204. For wheel 200 the suspension mechanism 203 defines a generaUy vertical steer axis 205 and a generaHy horizontal camber axis 206 which is below the road surface. For wheel 201 the suspension mechanism 204 defines a generafly vertical steer axis 207 and a camber axis 208.

Preferably camber axis 208 is below the road surface, at least in the vicinity of the wheel. The outboard end of track rod 209 for wheel 200 is attached to the suspension mechanism 203 at joint 210 (analogous to joint 120 in figure 2), which is offset from the steer axis 205 of that wheel. The outboard end of camber control rod 211 for wheel 200 is attached to the suspension mechanism 203 at joint 212 (analogous to joint 121 in figure 2). Joint 212 is preferably on or near the steer axis 205. The outboard end of track rod 213 for wheel 201 is attached to the suspension mechanism 204 at joint 214 (analogous to joint 120 in figure 2), which is offset from the steer axis 207 of that wheel. The outboard end of camber control rod 215 for wheel 201 is attached to the suspension mechanism 204 at joint 216 (an&ogous to joint 120 in figure 2). Joint 216 is preferably on or near the steer axis 207.

A steering rack mechanism shown generally at 220 is mounted on the body of the vehicle. Most conveniently the rack mechanism is mounted to the body at a location between the wheels, but it could be located elsewhere: for example on the midline of the vehicle above or behind the wheels. The steering rack mechanism comprises a traverse rail 221, a rack body 222, a steering rack 223 and a pinion 224. The traverse rail is fast with the body of the vehicle and runs laterally across the vehicle: preferably parall& or generally parall& with the Y axis of the vehicle, The rack body mounted to the traverse rafi so that it free to slide llnearly along the traverse rail.

Thus the rack body is free to translate with a component transverse to the vehicle, and most conveniently to translate substanUally parallel to the Y axis of the vehicle: that is in a dftection directly across the vehide, Otherwise, the rack body is rotationally and translationafly fixed, by means of the traverse raU, relative to the body of the vehicle. The steering rack 223 is mounted on the rack body in such a way that it can sllde relative to the rack body in a direction translate with a component transverse to the vehicle, and most conveniently to translate substantially parafiS to the Y axis of the vehicle. The pinion 224 is mounted to the rack body in such a way that it can rotate about an axis transverse to the translational axis of the steering rack's motion relative to the rack body, and so that teeth on the pinion engage teeth on the steering rack. In that way rotation of the pinion causes the steering rack to translate relative to the rack body.

The pinion is attached to a steering wheel 225 by a steering shaft 226. The steering wheel is located in the cabin of the vehicle in the conventional way, so that the driver can rotate it to control the vehicle's direction of travel. To permit the steering shaft to maintain attachment to both the pinion and the steering wheel when the rack body 222 moves on the traverse rail 221 the steering shaft has an upper section 227 and a lower section 228. The upper section is attached to the steering wheel. The upper and lower sections are connected to each other by a universal joint 229. The lower section 228 is connected to the pinion 224 by a universal joint 230. The lower section is capable of transmitting rotation from one end to the other and also of being varied in length. To this end, the lower section could comprise a shaft attached to universal joint 229 and a sleeve extending around the shaft and being attached to universal joint 230, the shaft and the sleeve being rotationally fast by virtue of a sphned interface between the two, In this way, the length of the lower section 228 of the steering shaft can vary freely as the rack body moves on the traverse rail, whilst still communicating rotation between the steering wheel and the pinion.

The inboard ends of the track rods 209, 213 are attached to the steering rack bar 223, for example by spherical joints or elastomeric bushes. The inboard ends of the camber control rods 211, 215 are attached to the rack body, for example by spherical joints or elastomeric bushes. The result of this is twofold.

Fftst, the motions of the wheels 200, 201 about their camber axes 206, 208 are linked together by virtue of the rigid track rods 209, 213, the rigid camber links 211, 215 and the rigid rack body 222. When one wheel moves in camber, that camber motion causes the track rod and the camber link of that wheel to move generaUy transversSy to the vehicle, That motion causes the rack body 222 to sUde transvers&y on the traverse raU 221, which in turn transmits generafly transverse motion to the other track rod and camber Unk, causing the other wheel also to move in camber, During pure camber motion, when the steering wheel remains fixed, the track rod and the camber Unk of each whe& move in unison.

Second, when the driver turns the steering wheel that urges the rigid steering rack to move relative to the rack body. This causes a differential motion of the track rods (which are attached to the steering rack) and the camber Unks (which are attached to the rack body). This differential motion causes the wheels to move together in steer.

In summary, when the track rods and the camber links move in unison, or in phase, the wheels undergo camber motion; and when the track rods and the camber links move differentially, or out of phase, the wheels undergo steer motion. It wiU be appreciated that compound motions of simUltaneous steer and camber change are also possible.

For each wheel, the effective steering arm of the suspension lies between the points of attachment of the track rod to the steerable part of the suspension mechanism (210, 214) and of the camber link to the steerable part of the suspension mechanism (212, 216). The length of that arm dictates the sensitivity of the steering to relative motion of the steering rack and the rack body. Various relationships of those points of attachment to the steer and camber axes are possible.

It is preferred that those points are substantially equidistant from the wheel's camber axis, to prevent camber motion from causing parasitic steer to an extent that is noticeable to a driver. However, for some types of vehicle a greater degree of parasitic steer might be tolerable or indeed desirable.

It is preferred that the camber fink fies substantiafly on the steer axis, to prevent steer motion from causing parasitic camber to an extent that is noticeable to a driver, and for the track rod to be located at a suitably remote distance from the steer axis to provide the desired degree of steering sensitivity. However, for sonic types of vehicle a greater degree of parasitic camber might be tolerable, Furthermore, it is possible for the fink from the steering rack to the suspension mechanism (La the part hitherto described as the track rod) to be attached to the suspension mechanism substantiafly on the steer axis, and for the link from the rack body to the suspension mechanism (i.e. the part hitherto described as the camber fink) to be attached to the suspension mechanism remotely from the steer axis, This would have the effect of inverting the steer motion, The suspensbn mechanism need not be as shown in figure 2. It could be of any design that permits steer and camber freedom, preferably about a centre below the road surface. The camber link for each wheel is attached to a part of the suspension mechanism that can move in camber and that is preferably substantially insensitive to steer. The track rod for each wheel is attached to a part of the suspen&on mechanism that can move in both camber and steer, The steering mechanism could take other forms than a rack and pinion. It could, for example, be a hydraulic or eIectrahydrauiic system, or could employ a rocker or a recirculating bafi race. In each case, there is preferably a body for the steering mechanism, which is free to traverse across the vehicle with a lateral component and which is attached to the camber links; and an actuator which can be moved relative to the body in response to steering inputs and which is attached to the track rods.

The actuator is conveniently borne by the body but it could simply be linked or associated with the body mechanically or otherwise in such a way that the two exhibit the desired relative motions, The steering mechanism could permit the camber links to move freely, or it could comprise means to control that motion, for example a spring and/or a damper. The motion could be biased to a central camber position by means of a spring connected between the body of the vehicle and the rack body.

Instead of translating across the vehicle when the wheels camber, the body could pivot about an axis that is nonparallel with the vehide's Y axis, and preferably that is in a plane substantiafly perpendicular to the vehicle's Y axis. This arrangement can still permit transverse motion of the outboard end of one camber link to be transmitted to the outboard end of the other. Figure 5 shows an example of such an arrangement. Figure 5 shows a crossvehicle linkage for linking two wheels that can move in steer and camber. The linkage comprises track rods 250, 251 and camber links 252. 253. These would extend to the suspension mechanisms of the vehicle's wheels, as described above. A steering box 254 is mounted on the vehicle's body in such a way that it can Pivot, as illustrated at 25$, about axis 255 which is parallel with the vehicle's X axis, The steering box is linked to a steering wheel (not shown) which can cause an actuator or Pitman arm 257 carried by the steering box to pivot relative to the steering box about an axis 258. Axis 258 is perpendicular to axis 255 and swings as the steering box pivots. An intermediate steer strut 259 attaches the inboard ends of the track rods to each other. An intermediate camber strut 260 attaches the inboard ends of the camber inks to each other. The actuator arm is attached flexibly to the camber strut at a point where the camber strut intersects axis 258. The distal end of the actuator arm is attached flexibly to the steer strut, A follower mechanism 261 supports the camber and steer struts, permitting them to move with the actuator arm. This mechanism allows the track rods to move transversely across the vehicle in unison with the camber links when the actuator arm remains fixed relative to the steering box, and differentially when the actuator arm is moved relative to the steering box, Preferably, the cross-link of the follower mechanism 261 rotates about a fixed axis parallel to axis 255 in camber, and about a second axis parallel to axis 258 in steer, The vehicle's steering could be controlled automatically rather than by a driver, One of the track rod and the camber Hnk goftig to a whe& could be consfituted by a driveshaft for that wheel. Preferably, this is the camber link since it can be attached to the suspension mechanism on the steering axis and can therefore be subject to less motion during steer.

The wheels Unked by the cross-vehide mechanism are preferably directly opposite wheels of the vehicle: for example both front wheels of an automobile, or alternatively both rear wheels of an automobile. R would also be possible to link diagonally opposite wheels using the mechanism described above.

The mechanism may be such that the wheel is able to move in camber substantially independently of bump and steer during normal motion of the vehicle.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the Ught of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims, The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

CLAiMS 1. A vehicle having: a body; a pair of whe&s, each whe& being attached to the body of the vehicle by a respective suspension mechanism that provides its wheel with freedom to move relative to the body of the vehicle in both steer and camber; and a steering mechanism movably mounted to the body of the vehicle, and attached to the suspension mechanism of one of the whe&s by a first track rod and a first camber flnk and to the suspension mechanism of the other of the wheels by a second track rod and a second camber fink, the steering mechanism being configured so that when the points of attachment of the first track rod and the first camber ink to the steering mechanism move together relative to the body of the vehicle the wheels move in camber, and when the points of attachment of the first track rod and the first camber ink to the steering mechanism move relative to each other the wheels move in steer.
2. A vehide as claimed in claim I, wherein the steering mechanism is configured so that when the points of attachment of the second track rod and the second camber fink to the steering mechanism move together relative to the body of the vehicle the wheels move in camber and when the points of attachment of the second track rod and the second camber link to the steering mechanism move relative to each other the wheels move in steer.
3. A vehicle as claimed in claim 1 or 2, wherein the steering mechanism comprises a steering body movable relative to the vehicle and a steering actuator carried by the steering body and movable relative to the steering body in response to steering inputs, the first and second track rods being attached to the steering actuator and the first and second camber finks being attached to the steering body.
4. A vehicle as claimed in claim 3, wherein the steering actuator is a rack bar and the steering body is a rack housing.
5. A vehicle as claimed in daim 3, wherein the steering actuator is a Pitman arm and the steering body is a steering box.
6. A vehicle as claimed in claim 3 or 4, wherein the steering body has freedom to translate across the vehicle.
7. A vehicle as claimed in any of claims 3, 4 or 6, wherein the steering actuator has freedom to translate relative to the steering body in a direction across the vehicle.
8. A vehicle as claimed in any preceding claim, wherein the vehicle comprises a driveroperable steering controller and the steering actuator is configured to move relative to the steering body in response to operation of the steering controller.
9. A vehicle as claimed in any preceding claim, wherein the wheels of the vehicle are configured to support the vehicle on a running surface and the axes of the whe&s' camber motions are located below the running surface.
10. A vehicle as claimed in claim 9. wherein the points of attachment of the first track rod and the first camber link to the suspension mechanism of the first wheel are substantially equidistant from the camber axis of the first wheel, and the points of attachment of the second track rod and the second camber link to the suspension mechanisn, of the second wheel are substantially equidistant from the camber axis of the second wheeL
11. A vehicle as claimed in any preceding claim, wherein the point of attachment of the first camber link to the suspension mechanism of the first wheel is substantially on the steer axis of the first wheel, and the point of attachment of the second camber link to the suspension mechanism of the second wheel is substantially on the steer axis of the second wheel,
12. A vehicle as claimed in any preceding claim, wherein the first and second camber nks are constituted by drive shafts for their respective wheels.
13. A vehicle as claimed in any preceding claim, wherein camber motion of one of the wheels can cause camber motion of the other wheel by virtue of motion of the steering mechanism relative to the body of the vehicle,
14. A vehicle having: a body; a pair of whe&s, each wheel being attached to the body of the vehicle by a respective suspension mechanism that provides its wheel with freedom to move relative to the body of the vehicle in both steer and camber; a steering controller; and a steering mechanism movably mounted to the body of the vehicle, and attached to the suspension mechanism of one of the wheels by a first track rod and a first camber link and to the suspension mechanism of the other of the wheels by a second track rod and a second camber ink, the steering mechanism having a first mode of operation in which movement of the steering mechanism relative to the body of the vehicle couples the wheels to move together in camber without movement of the steering controller and a second mode of operation in which the points of attachment of the first track rod and the first camber link to the steering mechanism move relative to each other in response to movement of the steering controller to confer steer motion on the said one of the wheels.
15. A vehicle as claimed in claim 14, wherein in the second mode of operation the points of attachment of the second track rod and the second camber link to the steering mechanism move relative to each other in response to movement of the steering controller to confer steer motion on the said other of the wheels.
16. A vehicle as claimed in claim 14 or 15. wherein the steering mechanism comprises a steering body movable r&ative to the vehicle and a steering actuator carried by the steering body and movable relative to the steering body in response to steering inputs from the steering controfler, the first and second track rods being attached to the steering actuator and the first and second camber links being attached to the steering body
17. A vehicle as claimed in claim 16, wherein the steering actuator is a rack bar and the steering body is a rack housing.
18. A vehicle as claimed in claim 1$, wherein the steering actuator is a Pitman arm and the steering body is a steering box.
19. A vehicle as claimed in claim 16 or 17, wherein the steering body has freedom to translate across the vehicle,
20. A vehicle as daimed in any of claims 18, 17 or 19, wherein the steering actuator has freedom to translate relative to the steering body in a direction across the vehicle.
21. A vehicle as claimed in any of claims 14 to 20, wherein the wheels of the vehicle are configured to support the vehicle on a running surface and the axes of the wheels' camber motions are located below the running surface.
22. A vehicle as claimed in claim 21, wherein the points of attachment of the first track rod and the first camber link to the suspension mechanism of the first wheel are substantiaUy equidistant from the camber axis of the first wheel, and the points of attachment of the second track rod and the second camber Unk to the suspension mechanism of the second wheel are substantially equidistant from the camber axis of the second wheel.
23. A vehicle as claimed in any of claims 14 to 22, wherein the point of attachment of the first camber link to the suspension mechanism of the first wheel is substantially on the steer axis of the first wheel, and the point of attachment of the second camber ink to the suspension mechanism of the second whe& is substantiaHy on the steer axis of the second wheeL
24. A vehicle as claimed in any of claims 14 to 23, wherein the first and second camber flnks are constituted by drive shafts for their respective wheels.
25. A vehicle substantiaHy as herein described with reference to figures 2 to 5 of the accompanying drawings.