Suspension assembly

Abstract

A suspension assembly 12 for a vehicle (10, Figure 1) is provided. The assembly 12 comprises: a knuckle 30 comprising a wheel bearing (32, Figure 13), the wheel bearing having a bearing axis (33, Figure 7) defining an axis of rotation for a road wheel 20 of the vehicle; a damper 44 mounted to a first coupling 72 that is fixed relative to the knuckle 30; and a suspension arm 42 pivotally mounted to a second coupling 54 that is fixed relative to the knuckle 30, the suspension arm 42 comprising a spring seat (58, Figure 14). The spring seat and the first coupling 72 are disposed on opposite longitudinal sides of the bearing axis so that, when a spring 48 is seated in the spring seat, a gap is defined between the spring 48 and the damper 44 that is intersected by the bearing axis. A vehicle suspension system and / or a driven axle incorporating such an assembly; and a vehicle comprising such a suspension assembly are also disclosed.

Description

Technical Field The present disclosure relates to a suspension assembly for a vehicle. In particular, but not exclusively, the present disclosure relates to a suspension assembly for a driven wheel of a vehicle. Aspects of the invention relate to a suspension assembly, to a suspension system, to a driven axle assembly and to a vehicle. Background Suspension systems perform several functions within a vehicle. Fundamentally, they should reduce the noise, vibration and harshness (NVH) of the vehicle, to isolate passengers from unwanted road inputs. Suspension systems also impact vehicle dynamics and regulate the stability of the vehicle, by enabling continuous contact between the wheels and the road while maintaining proper wheel geometry. A suspension system can also be tuned to provide a desired balance between vehicle driving characteristics, in particular ride comfort and handling. There are two main categories of suspension systems: dependent and independent. Dependent, or ‘rigid axle’ systems have the two front or back wheels connected on the same axle. This system is mechanically straightforward, and therefore generally robust. However, as the wheels react to road shocks in conjunction, the efficacy and refinement of the system is lower than for independent suspension systems. Independent systems, as the name suggests, are configured so that individual wheels can move independently from one another, reacting separately to road disturbances to control individual wheel geometries, including the steered direction, and the camber, caster and toe angle alignments. The configuration of independent suspension systems can be relatively complex, but such systems allow for enhanced vehicle handling and stability and so tend to be selected for modern vehicles, especially passenger vehicles designed to be primarily driven on the road. The MacPherson strut type suspension is a common front suspension system that uses a damper-spring assembly as an upper steering pivot, thereby eliminating some of the elements of other suspension systems and producing a light and compact arrangement. This can be particularly useful for front suspensions where packaging volumes tend to be tightly constrained. However, these advantages of the MacPherson strut typically come at the cost of diminished camber and toe alignment control. Precise positioning of the damper-spring assembly is also required to achieve a suitable caster angle, which may not always be practical. Another common independent suspension system is the double wishbone system, which comprises upper and lower wishbone (typically A-shape or L-shape) links, or arms, that are generally in parallel when in the usual ride position. The upper and lower links connect a wheel hub to an axle or vehicle structure, and act to control the position of the wheel. For example, it is common to have the upper link shorter than the lower link to generate negative camber, counteracting the positive camber typically induced during cornering. A more advanced approach is the multilink suspension system, which is derived from the double wishbone system but comprises at least three generally horizontal links and one or more upright links, all of which are typically provided with ball joints or bushings at the link joints. Increasing the number of independent links allows the horizontal and vertical forces, and consequently the wheel geometries, to be configured and handled more precisely than in other suspension systems, ultimately improving the handling of the vehicle whilst augmenting passenger comfort. In general terms, then, improved suspension performance is usually accompanied by increased system complexity, in turn leading to higher costs and greater packaging demands. This may present a particular challenge, for example, when designing platforms intended for mass-market vehicles that require a large load and / or passenger space without compromising on ride comfort. It is against this background that the present invention has been devised. Summary of the Invention Aspects and embodiments of the invention provide a suspension assembly, a suspension system, a driven axle assembly and a vehicle as claimed in the appended claims. According to an aspect of the present invention there is provided a suspension assembly for a vehicle. The assembly comprises: a knuckle comprising a wheel bearing, the wheel bearing having a bearing axis defining an axis of rotation for a road wheel of the vehicle; a damper mounted to a first coupling that is fixed relative to the knuckle; and a suspension arm pivotably mounted to a second coupling that is fixed relative to the knuckle, the suspension arm comprising a spring seat. The spring seat and the first coupling are disposed on opposite longitudinal sides of the bearing axis so that, when a spring is seated in the spring seat, a gap is defined between the spring and the damper that is intersected by the bearing axis. By separating the spring seat and the damper and arranging them to either side of the wheel bearing axis, the overall height of the assembly is significantly reduced compared with a traditional MacPherson strut. This is a significant benefit in terms of both packaging and performance, in that the extent to which the assembly intrudes into a vehicle interior is minimal, whilst the reduced height of the arrangement in turn reduces bending moments and so allows for lighter components to be used. The assembly may comprise a toe-link pivotably coupled to a third coupling that is fixed relative to the knuckle. The toe-link optionally comprises a fourth coupling at its distal end arranged for coupling the toe-link to a vehicle structure, in which case the fourth coupling comprises a pivot axis that is angled towards a rear of the vehicle when coupled to the vehicle structure. The inclusion of the toe-link allows for an arrangement that provides the required strength and stiffness whilst being compact, which is a particular benefit in a battery-electric vehicle where packaging spaces are tightly constrained. It further enables the main lower support elements of the assembly to be arranged for longitudinal continuity whilst being relatively short laterally, thereby enhancing the compactness of the arrangement and minimising any incursion into the interior of the vehicle by the suspension components. The toe-link may also be capable of providing a degree of passive steering, in turn reducing a turning circle of the vehicle at low speeds. The suspension arm may comprise multiple longitudinally spaced mounting formations configured to mount pivotably to complementary formations on the vehicle. When the assembly is installed on a vehicle, the spring seat may be disposed forward of the first coupling. The assembly may comprise a spring in engagement with, or seated in, the spring seat. The second coupling may comprise a pivot axis that extends generally longitudinally. The damper may be mounted to the first coupling at a point disposed between opposed ends of the damper. In such embodiments, the damper may be mounted such that a portion of the damper extends below the suspension arm. The damper is optionally a telescopic damper, in which case a piston of the damper may be mounted to the first coupling, and a cylinder of the damper may extend upwardly from the piston. The wheel bearing may be configured to support a driveshaft. The invention also extends to a vehicle suspension system comprising a pair of suspension assemblies according to the above aspect. The vehicle suspension system may comprise a support structure connecting the assemblies, and may be configured as a rear suspension system. Another aspect of the invention provides a driven axle assembly comprising the vehicle suspension system of the above aspect and an electric drive unit (EDU). A further aspect of the invention provides a vehicle comprising a suspension assembly, a vehicle suspension system or a driven axle assembly according to the above aspects. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. Brief Description of the Drawings One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a side, schematic view of a vehicle including a suspension system according to an embodiment of the invention; Figure 2 shows the vehicle of Figure 1 in perspective view from below to reveal a driven axle assembly according to an embodiment of the invention; Figures 3 and 4 show detail views of the driven axle assembly of the vehicle of Figure 1; Figure 5 shows a rear perspective view of the driven axle assembly of the vehicle of Figure 1 in isolation, including one of the vehicle wheels; Figure 6 corresponds to Figure 5 but shows the driven axle assembly from an elevated perspective; Figure 7 corresponds to Figure 5 but shows the driven axle assembly in side view; Figure 8 corresponds to Figure 5 but shows the driven axle assembly in plan view; Figure 9 corresponds to Figure 5 but shows the driven axle assembly from the rear; Figures 10 and 11 show, respectively, side and rear views of the driven axle assembly of the vehicle of Figure 1 attached to a sub-frame of the vehicle; Figures 12 shows a rear perspective view of a left rear suspension assembly of the vehicle of Figure 1; Figure 13 corresponds to Figure 12 but shows the suspension assembly in side view from the right; Figure 14 corresponds to Figure 12 but shows the suspension assembly from below with a road wheel hidden; Figure 15 corresponds to Figure 14 but shows the suspension assembly in plan view; Figure 16 corresponds to Figure 15 but shows the suspension assembly from the front; Figure 17 corresponds to Figure 14 but shows a perspective view of the suspension assembly from the front left; Figure 18 corresponds to Figure 14 but shows a perspective view of the suspension assembly from the left; Figure 19 corresponds to Figure 14 but shows a perspective view of the suspension assembly from the rear right; Figure 20 corresponds to Figure 14 but shows the suspension assembly from the rear; and Figure 21 shows an exploded view of the suspension assembly of Figures 12 to 20. Detailed Description Embodiments of the invention provide suspension assemblies, and corresponding suspension systems and driven axle assemblies, that are configured to provide a sophisticated performance, particularly in terms of ride comfort, whilst keeping to a small packaging space and low weight. Moreover, the suspension assemblies involve relatively few components and linkages and are therefore relatively low cost. Such suspension assemblies may of course be useful on any vehicle, but find particular benefit in platforms for mass-market vehicles for which there is a desire to maximise the interior space without compromising ride comfort. Such vehicles may include forthcoming electrically-powered, semi- or fully autonomously-driven vehicles, which may have different design and performance priorities to more traditional vehicles. Moreover, the different powertrain layout of electrically-powered vehicles creates new packaging challenges, as spaces that might have been available for suspension components in a traditional platform may now be occupied by a battery pack or an electric machine. In general terms, suspension assemblies in accordance with the invention are based on the traditional MacPherson strut, in the sense that the assemblies include dampers that are fixed relative to a knuckle or wheel hub and therefore act to control wheel geometry. Accordingly, suspension assemblies of the invention offer the benefits of compactness and low weight that are inherent to MacPherson strut architectures. However, the suspension assemblies of this disclosure depart with convention in that they are not necessarily used with steered wheels and are instead configured to accommodate a driveshaft and thereby enable use with driven wheels; although they can equally be used with non-driven and / or steered wheels. Moreover, relative to traditional MacPherson struts suspension assemblies of the invention offer improved performance, rendering them suitable for use in vehicle platforms for which ride comfort is a priority. In particular, in embodiments of the invention the damper and the spring of the suspension assembly are not assembled together end-to-end (in a vertical stack) as in conventional strut arrangements, which are generally coaxial, but are instead separated. This allows the spring and the damper to be positioned one to each side of a rotational axis of the supported wheel to accommodate a driveshaft, which also improves the overall balance and performance of the assembly. The balance and stability of the assembly is further enhanced by the inclusion of a toelink in addition to a main lower suspension arm, the toe-link acting between the knuckle and a vehicle structure such as a frame to spread loads over a wider area and thereby restraining bending of the other suspension elements. The toe-link can also maintain plan angle and provide a level of passive steering when used in a rear suspension assembly in some cases. The use of the toe-link also allows the suspension arm to be relatively narrow longitudinally, to account for the presence of the battery and / or EDU. In contrast, traditional MacPherson struts typically employ relatively large longitudinal control members and short lateral members, for which there is often insufficient space in a battery electric vehicle. Referring now to Figure 1, a vehicle 10 including a pair of suspension assemblies 12 according to an embodiment of the invention is shown, the suspension assemblies 12 being implemented as rear suspension assemblies. In this example, the vehicle 10 is a battery electric vehicle, which may be operated in some situations in an autonomous mode. As is evident from Figure 1, the vehicle 10 has the general form of a multi-purpose vehicle (MPV), with a relatively high roof and a short wheelbase having an overall length of under 4.6m, yet featuring an occupant compartment 14 that may accommodate up to three rows of passenger seats. Accordingly, the design constraints for this vehicle 10 include maximising the interior space and providing a relatively relaxed driving profile characterised by premium ride comfort. These objectives are in part achieved through the use of the suspension assemblies 12 of the invention, as shall become clear from the description that follows. In general terms, meeting these objectives will entail ensuring that the suspension assemblies 12 perform well without intruding into the passenger space, or a luggage compartment or cargo bay in other vehicles, or into the areas occupied by the electric drive components. Hence, the compactness of the MacPherson strut based configuration offers a clear benefit in this respect. In turn, that compactness reduces the extent to which the vehicle body must be lifted to clear the movable parts of the suspension system, making the structure more efficient and therefore able to deliver the required strength and stiffness within a smaller and more lightweight package. Figures 2 to 4 show the vehicle 10 in perspective view to reveal its underside, so that a battery pack 16 and a driven rear axle assembly 18 of the vehicle 10 are visible. The driven rear axle assembly 18 is mounted to a rear sub-frame structure of the vehicle 10, and includes a rear road wheel 20 at each end, each rear road wheel 20 being supported by a respective rear suspension assembly 12. Only the left rear suspension assembly 12 is visible in the figures, but it should be appreciated that the right rear suspension assembly is a mirror-image of the left rear suspension assembly 12. The left and right rear suspension assemblies collectively define a rear suspension system. The driven rear axle assembly 18 further includes a centrally-mounted electric drive unit (EDU) 22 comprising an electric machine, a transmission and a differential. The EDU 22 is cradled by a handlebar-shaped support frame 24, which is visible in the partial subassembly views of Figures 5 to 11. The EDU 22 is therefore disposed between and inline with the rear road wheels 20. A driveshaft 26 extends generally laterally from each end of the EDU 22 to couple to a respective rear road wheel 20, enabling the EDU 22 to deliver propulsive power to the road wheels 20 using electrical energy supplied by the battery pack 16. The driven rear axle assembly 18 including the rear suspension system may be embodied as a vehicle sub-assembly, which may include further components associated with the powertrain or suspension system, including air compressors, brakes, a transmission, a differential, etc., but these are omitted for clarity. As best seen in Figures 5 and 10, the support frame 24 of the driven rear axle assembly 18 is suspended between parallel longitudinal members 28 (longitudinals, also referred to as ‘longis’ or ‘longits’ in the art) of the vehicle body structure. Figure 10 shows that a rear portion 28a of each longitudinal (‘rear longitudinal’) of the vehicle frame is slightly elevated relative to a corresponding main, central region 28b of the longitudinal (‘main longitudinal’) extending below the occupant compartment 14 of the vehicle 10. This elevation accommodates the depth of the driven rear axle assembly 18, in particular the depth of the rear suspension assemblies 12 and more particularly the depth of the driveshafts 26. While it is conventional to provide elevated rear longitudinals 28a to accommodate suspension systems, it is noted that the relative elevation shown in Figure 10 is considerably less than would be expected in a conventional vehicle platform. For example, in this example the relative elevation is approximately 150mm or less, whereas 200mm would be typical for a conventional saloon (sedan) platform and anything up to 300mm is known for consumer vehicles. Indeed, the vehicle 10 of this example has relatively large road wheels 20 and a low-slung central section, and so the offset between the rear and main longitudinals 28a, 28b may be smaller still in other examples. This reflects the compactness of the rear suspension assemblies 12. Also, as the lower parts of the suspension assembly 12 are arranged in longitudinal succession and almost in a common plane, the elevation between the rear and main longitudinals 28a, 28b need only accommodate the driveshaft 26, unlike many known systems in which the extent of the elevation is also driven by the need to accommodate suspension components. In turn, the relatively low position of the rear longitudinals 28a increases the space available at the rear of the occupant compartment 14, in this example allowing a third row of seats to be provided. The vehicle 10 further includes a pair of front road wheels 20, each supported by a respective front suspension assembly. In this example, the front suspension assemblies are different to the rear suspension assemblies 12 and do not represent embodiments of the invention. It is noted that in other examples the front suspension assemblies may alternatively be similar to the rear suspension assemblies 12 and therefore fall within the scope of the present invention. As Figure 2 makes clear, the battery pack 16 occupies the majority of the space between front road wheels 20 and the driven rear axle assembly 18. Meanwhile, much of the space between the rear road wheels 20 is taken up by the EDU 22. The packaging space available for the rear suspension assemblies 12 is therefore tightly constrained. Moreover, the rear suspension assemblies 12 cannot extend too far vertically without intruding into the area required for the passenger space. It is also desirable to minimise the heights of the upper attachment points of springs and dampers of the suspension assemblies 12 to the vehicle body for improved stiffness and noise reduction. In view of these constraints, as Figures 1 and 7 in particular make clear, the suspension assemblies 12 are almost entirely contained within the envelope of their respective wheels 20. This is enabled by configuring them as a variant on a MacPherson strut architecture as noted above, as will become clearer from the following description of the left rear suspension assembly 12, with reference generally to Figures 12 to 21. The rear suspension assembly 12 comprises a wheel hub or knuckle 30, which includes a wheel bearing 32 that supports the respective rear road wheel 20, the wheel bearing 32 having a bearing axis 33 that defines an axis of rotation for the rear road wheel 20. The wheel bearing 32 also engages and supports a driveshaft 26 extending from the EDU 22. The driveshaft 26 is provided with a universal joint 34 to accommodate movement of the rear road wheel 20 relative to the vehicle body in use. As best seen in Figures 17 to 19, the knuckle 30 also supports a brake assembly 36 comprising a brake disc 38 and a brake caliper 40. In turn, elements of the rear suspension assembly 12 attach to and support the knuckle 30, in a manner that accommodates relative movement between the knuckle 30 and the vehicle body as the vehicle 10 moves. These elements include a suspension arm 42, a damper 44 and a toe-link 46. The suspension assembly 12 further includes a spring 48 that acts between the suspension arm 42 and the rear longitudinal 28a of the vehicle body. The suspension arm 42 acts as a main lower support for the knuckle 30, extending between the support frame 24 of the driven rear axle assembly 18 and the underside of the knuckle 30. The suspension arm 42 has the general form of a wishbone, being defined by a generally planar triangular plate 50 having first and second laterally-extending branches 52 at an inboard end where the suspension arm 42 mounts to the support frame 24, and tapering into a knuckle mounting point 54 defined by parallel, longitudinally-spaced mounting arms 55 at an outboard end. The first and second branches 52 include circular, longitudinally extending apertures defining respective vehicle mounting points 56, the first mounting point 56a being rearward of the second mounting point 56b with respect to the vehicle 10. The suspension arm 42 is of steel in this example, but it will be appreciated that the suspension arm 42 may be formed from other materials with suitable mechanical properties, such as aluminium alloy, as may be desired. As is clearest in Figure 14, the tapering of the triangular plate 50 is skewed, such that the knuckle mounting point 54 is at a longitudinal position that is much closer to the longitudinal position of the first vehicle mounting point than that of the second vehicle mounting point. The first branch 52 of the suspension arm 42 therefore extends almost parallel to the driveshaft 26. In consequence, the first vehicle mounting point acts to some extent as a control point around which the rest of the suspension assembly 12 flexes in a prescribed manner in a horizontal plane to adjust toe, in use; although some controlled flexing will also occur at the first mounting point 56a. The triangular plate 50 of the suspension arm 42 includes a substantially circular recess close to midway between the knuckle mounting point 54 and the second vehicle mounting point, the recess defining a spring cup or spring seat 58 that supports the spring 48. In this embodiment, the spring 48 is a coil spring that acts between the spring seat 58 and the rear longitudinal 28a of the vehicle body. For example, the rear longitudinal 28a - or another part of the body in white (BiW) fixed relative to the longitudinal 28a - may include a corresponding circular recess mirroring and opposed to that of the suspension arm 42 defining an upper spring seat, such that the upper spring seat has minimal impact on the shape and form of the longitudinal 28a. The spring 48 is positioned longitudinally forward of the driveshaft 26 and is oriented with its central axis generally upright but with a slight inclination towards the vehicle body, as is visible in Figure 16. It is noted that it is an advantage of the suspension assembly 12 that the spring 48 engages a relatively rigid part of the vehicle 10, namely the rear longitudinal 28a, which aids stiffness and reduces noise. The noise reducing effect is further enhanced by the low position of the spring 48 compared with conventional MacPherson strut architectures, in which the spring is mounted coaxially at the upper end of the damper and therefore above the road wheel 20 and hence closer to the ears of any passengers inside the vehicle 10. The vehicle mounting points 56 of the suspension arm 42 each include bushings that facilitate pivoting of the suspension arm 42 around a substantially longitudinally-extending axis, the respective axes of the mounting points being coaxial, to allow vertical movement of the rear road wheel 20. However, as Figure 13 makes clear the pivot axes of the mounting points are slightly inclined relative to the horizontal, such that the road wheel 20 moves rearwardly as well as upwardly when it negotiates a bump in the road surface, thereby improving kinematic regression by extending the time over which the wheel 20 traverses the bump and, in turn, reducing the maximum forces generated in the suspension assembly 12 and reducing the effective impact vector of the wheel 20 tangent to ascend the bump. The bushings are also configured to provide a degree of controlled compliance to allow limited rotation of the suspension arm 42 in all directions, to accommodate some fore and aft movement of the rear road wheel 20 relative to the vehicle body. Accordingly, the suspension arm 42 allows the rear road wheel 20 to move within a predefined area relative to the vehicle body. As seen most clearly in Figure 14, at the knuckle mounting point 54 a mounting formation 60 extends from the underside of the knuckle 30 into a space between the mounting arms 55. A pivot bolt is inserted through aligned apertures in the mounting arms 55 and the mounting formation 60 to hold them together whilst facilitating relative pivoting of the arms and formation about a generally longitudinal axis. The mounting formation 60 includes a bushing to afford a degree of compliance at the joint, in a similar manner to the vehicle mounting points 56. Completing the lower support to the knuckle 30 is the toe-link 46, which is an elongate rod-like element disposed rearward of the suspension arm 42 that couples, via bushed joints, to the knuckle 30 at a proximal end and to a bracket 62 attached to the support frame 24 of the driven rear axle assembly 18 at a distal end. It will be appreciated that the toe-link 46 may be formed of any material with suitable mechanical properties and in the example shown is formed from lightweight aluminium alloy. The toe-link 46 couples to a rearward or trailing side of the knuckle 30 at bushed joint defining a toe-link knuckle mount 64, which is at a level above that of the mounting formation 60 to which the suspension arm 42 connects but below the level of the bearing axis 33. At the inboard end of the toe-link 46, a second bushed joint defines a toe-link vehicle mount 66 by which the toe-link 46 couples to the bracket 62 extending from the support frame 24, the toe-link vehicle mount 66 being at a similar height to the second vehicle mounting point and therefore above the first mounting point 56a, thereby balancing the assembly or giving slight bias in the desired direction for safe, compliant handling. The relative positions of the toe-link knuckle mount 64 and the toe-link vehicle mount 66 are such that the toe-link 46 extends slightly upwardly and rearwardly from the knuckle 30 to the bracket 62, as best seen in Figures 13 and 14. Accordingly, the toe-link 46 provides a third mounting point to the vehicle body to supplement those provided by the suspension arm 42, the three mounting points being spaced in longitudinal series as is clearest in Figures 14 and 15. The toe-link 46 contributes to the overall stiffness and balance of the suspension assembly 12, in particular for improved toe control by controlling the degree to which the assembly flexes at the first and second mounting point bushings when the road wheel 20 encounters a shock-inducing road feature such as a bump in the road. The higher mounting point of the toe-link 46 to the knuckle 30 relative to the suspension arm 42 also resists rotation of the knuckle 30 about the bearing axis 33 and limits camber, thereby enhancing stability. The bushed joints at each end of the toe-link 46 provide for rotation about substantially longitudinal axes in a similar manner to the mounting points of the suspension arm 42. Indeed, as Figure 13 shows the toe-link vehicle mount has a pivot axis that is at substantially the same inclination to the horizontal as the corresponding axes of the vehicle mounting points 56 of the suspension arm 42. However, as Figure 14 shows, the pivot axis of the toe-link vehicle mount 66 is not parallel to the axes of the suspension arm mounting points, but instead is inclined towards the rear of the vehicle 10. So, the toe-link 46 pivots in a slightly different way to the suspension arm 42 at the inboard end, such that the suspension arm 42 and toe-link 46 define different arcuate trajectories between full droop and full bump. Specifically, the toe-link 46 acts to pull the knuckle 30 rearwardly to induce negative toe when the knuckle 30 moves upwardly. Correspondingly, if the knuckle 30 moves downwardly the toe-link 46 acts to push the knuckle 30 forward and therefore increase toe. In this way, the toe-link 46 provides a degree of passive steering during cornering by effectively converting camber into toe, thereby reducing the turning circle of the vehicle 10 at low speeds. The relationship between toe and bump due to the toe-link 46 is defined according to desired roll centres and anti-dive / anti-squat geometry, based on known principles. The damper 44 is a telescopic damper, having a piston 68 received inside a damper housing 70, the damper 44 itself being conventional but being mounted in an unconventional way; specifically, in an inverted orientation and clamped at a point between the ends of the damper 44. In this respect, the damper 44 is fixed to the knuckle 30 by a damper collar 72 or clamp tube, which is substantially level with the bearing axis 33 on the rearward side of the knuckle 30, as best seen in Figures 12 & 13. The damper 44 is oriented in a generally upright position, but slightly inclined when viewed from the side such that an upper end of the damper 44 is longitudinally forward of the lower end. As Figure 16 shows, the damper 44 is also oriented such that it is inclined towards the vehicle body at substantially the same angle as the spring 48. Accordingly, the spring 48 and the damper 44 exhibit gradual upward convergence and therefore assume a generally triangular formation, the shape of which is determined primarily by the position of the damper 44 relative to the pitch centre and a desire to house the elements of the suspension assembly 12 within the wheel envelope. The triangular arrangement also creates a strong and balanced arrangement with greatly improved performance, and greatly reduced packaging volume, relative to a traditional MacPherson strut architecture with a single upright link. The spring 48 and the damper 44 are spaced from one another longitudinally, one to each side of the bearing axis 33, to create a gap between the spring 48 and the damper 44 that is intersected by the bearing axis 33 and is of sufficient size to accommodate the driveshaft 26, allowing also for movement of the knuckle 30 and the resultant change in angle of the portion of the driveshaft 26 that is supported by the wheel bearing 32. By positioning the spring 48 forward of the damper 44 to reduce the overall height of the suspension assembly 12, gradients defined by lateral, longitudinal and vertical offsets between surrounding supporting vehicle body structures, in particular between a sill and the rear longitudinal 28a, can be reduced whilst still preventing the spring 48 from clashing with the other parts of the suspension assembly 12 and the driveshafts 26. This in turn reduces the bending moments that the corresponding vehicle structures are subjected to, allowing more lightweight and less costly components to be used. A further benefit of limiting the bending to which the spring 48 is subjected is that the spring 48 twists less relative to the spring seat 58, yielding a quieter suspension package and reduced spring failure. The damper collar 72 is located at a point close to a midpoint of the damper 44, such that the damper 44 extends downwardly below the knuckle 30, and indeed between and below the suspension arm 42 and the toe-link 46. The damper 44 is subjected to relatively high loads in use, and typically takes a significantly greater load than the spring 48. Mounting the damper 44 at an intermediate position along its length effectively shortens its length, minimising bending moments induced in the damper 44 as a result of the loads that it is subjected to, without any compromise in stroke. Accordingly, the positioning of the damper 44 reduces the demands placed on it, allowing lighter parts to be used for the damper 44. In turn, the loads and noise transferred to the BiW are reduced in a corresponding manner. The damper 44 is mounted by its piston 68, so that the damper housing 70 surmounts the piston 68 and extends upwardly to engage a damper mounting 76 (as shown in Figure 4) located at the top or middle of a wheel arch in the vehicle body that accommodates the suspension assembly 12 and rear road wheel 20. In this respect, as Figure 1 shows the damper 44 extends slightly above the wheel and tyre envelope, but to a far lesser extent than for conventional MacPherson struts by virtue of the midmounting of the damper 44 and the separation of the damper 44 from the spring 48. In the examples shown in the Figures, the height of the damper mounting 76 above the ground is approximately 800mm, is therefore substantially lower than for other suspension architectures. For example, the corresponding dimension for a typical small sports utility vehicle (SUV) may be 1100mm or more. The collective effect of the components of the suspension assembly 12, and their interaction with one another, is to provide: high levels of refinement in terms of kinematic progression and regression characteristics; precise toe and camber control; high levels of wheel travel; low un-sprung mass and hence reduced NVH and good tyre contact; and low intrusion into the vehicle interior. This is achieved with a relatively lightweight and low-cost assembly. It should be appreciated that the suspension system described above is only an example, and in practice the assembly will be configured and tuned to suit the requirements of each application. In particular, the suspension assembly may be used as a front suspension assembly, in which case the toe-link can be replaced by a steering control arm. Also, any suitable type of spring or damper may be used in embodiments of the invention. In general terms, it will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. 5

Claims

1. A suspension assembly for a vehicle, the assembly comprising:a knuckle comprising a wheel bearing, the wheel bearing having a bearing axis defining an axis of rotation for a road wheel of the vehicle;a damper mounted to a first coupling that is fixed relative to the knuckle; anda suspension arm pivotably mounted to a second coupling that is fixed relative to the knuckle, the suspension arm comprising a spring seat;wherein the spring seat and the first coupling are disposed on opposite longitudinal sides of the bearing axis so that, when a spring is seated in the spring seat, a gap is defined between the spring and the damper that is intersected by the bearing axis.

2. The assembly of claim 1, comprising a toe-link pivotably coupled to a third coupling that is fixed relative to the knuckle.

3. The assembly of claim 2, wherein the toe-link comprises a fourth coupling at its distal end arranged for coupling the toe-link to a vehicle structure, wherein the fourth coupling comprises a pivot axis that is angled towards a rear of the vehicle when coupled to the vehicle structure.

4. The assembly of any preceding claim, wherein the suspension arm comprises multiple longitudinally spaced mounting formations configured to mount pivotably to complementary formations on the vehicle.

5. The assembly of any preceding claim, wherein, when the assembly is installed on a vehicle, the spring seat is disposed forward of the first coupling.

6. The assembly of any preceding claim, comprising a spring in engagement with the spring seat.

7. The assembly of any preceding claim, wherein the second coupling comprises apivot axis that extends generally longitudinally.

8. The assembly of any preceding claim, wherein the damper is mounted to the first coupling at a point disposed between opposed ends of the damper.

9. The assembly of claim 8, wherein the damper is mounted such that a portion of the damper extends below the suspension arm.

10. The assembly of any preceding claim, wherein the damper is a telescopic damper, and wherein a piston of the damper is mounted to the first coupling, and a cylinder of the damper extends upwardly from the piston.

11. The assembly of any preceding claim, wherein the wheel bearing is configured to support a driveshaft.

12. A vehicle suspension system comprising a pair of suspension assemblies according to any preceding claim.

13. The vehicle suspension system of claim 12, comprising a support structure connecting the assemblies.

14. The vehicle suspension system of claim 12 or claim 13, configured as a rear suspension system.

15. A driven axle assembly comprising the vehicle suspension system of any of claims 12 to 14 and an electric drive unit.

16. A vehicle comprising a suspension assembly according to any of claims 1 to 11, a vehicle suspension system according to any of claims 12 to 14 or a driven axle assembly according to claim 15.

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