HK1234707A1 - Vehicle suspension - Google Patents

Description

Vehicle suspension

Technical Field

The present invention relates to a suspension for a vehicle.

Background

Vehicles require a suspension system in order to keep the wheels in contact with the surface on which the vehicle is driving and to isolate the body of the vehicle from at least some of the undulations in this surface. The former requirement is necessary in order to ensure safe and efficient handling of the vehicle, and the latter is necessary in order to provide the necessary level of ride comfort. In general, these two needs act in opposite directions, and the suspension system is therefore a compromise between the two. A series of suspension systems are known.

The MacPherson strut suspension, which is commonly used for front suspensions, comprises a wishbone or substantially compressed link stabilized by a second link, which provides a bottom mounting point for the hub or axle. This lower arm system provides lateral and longitudinal position of the wheel. The upper portion of the hub is rigidly secured to the inner portion of the sprung and cushioned strut, which extends directly up to a mount in the body shell of the vehicle.

The dual wishbone suspension positions the wheel through the use of two (upper and lower) arms, each in the shape of an "a" or wishbone. Each arm has two mounting points on the chassis and one joint at the knuckle. A shock absorber and a coil spring are mounted to the wishbone to control vertical movement. The double wishbone design allows an engineer to carefully control the motion of the wheel throughout the suspension travel, thereby controlling parameters such as camber, caster, toe mode, roll center height, king pin offset, wear and more.

Multi-link suspensions use three or more lateral arms along with one or more trailing arms to define and constrain the motion of the hub. The arms need not be the same length and may be angled away from their "apparent" direction. Typically each arm has a ball joint (ball joint) or rubber bushing at each end and therefore reacts loads along its own length in tension or compression but not in bending. Some multi-links also use trailing arms or wishbones that have two bushings at one end.

All solutions have relative advantages and disadvantages, generally reflecting the variations in the level of ride comfort or handling achievable with respect to the cost and complexity of the system.

Summary of the invention

The present invention seeks to provide a suspension system for a vehicle which provides a level of ride comfort and/or handling which meets or exceeds the requirements standards set now, but by using a significantly smaller number of parts.

This reduction in the number of parts provides a great advantage in use. Of course, a direct advantage is the cost of the system, since the cost of the resulting assembly is directly reduced if fewer parts need to be manufactured and assembled. However, other advantages also arise from the reduced part count, as the level of parts inventory required by assemblers and dealers is reduced, material usage is reduced, the weight of the system and vehicle is reduced, and so forth. It also reduces the construction costs of the vehicle, these factors directly contributing to a reduction in the running costs of the vehicle in terms of its fuel consumption, service costs and environmental impact.

The present invention therefore provides a vehicle suspension comprising: an assembly of a hub carrier and a support arm attached to the hub carrier at two points spaced from each other in a direction of travel and extending inwardly therefrom to a support arm attachment point for securing to the chassis, a tow link extending from the assembly in a direction transverse to the support arm toward a tow link attachment point for securing to the chassis, and a toe control link attached to the hub carrier at a position spaced vertically from the two points and extending inwardly therefrom to an attachment point for securing to the chassis.

The trailing link preferably extends from the assembly in a forward direction, thereby placing it under tension, reducing the likelihood of it buckling, and thus allowing for a more slender article having less weight and using less material in its production. It is preferably directly connected to the hub carrier.

A strut may be provided extending upwardly towards the attachment point for fixing to the chassis to provide (preferably) the necessary vertical positioning of the suspension in conjunction with the usual spring and damper.

The toe control link is desirably attached to the hub bracket at a point that is outside of the two points where the support arm is attached to the hub bracket. Similarly, we prefer that the single attachment point at which the toe control link is attachable to the chassis is inboard of the support arm attachment point at which the support arm is attachable to the chassis.

The support arm may comprise a pair of arms extending divergently from the attachment point to each of the two points. Of these two arms, one is preferably shorter than the toe control link. I.e. in fact, forms a wishbone but is mounted in an orientation opposite to the usual orientation. The fixation of the support arm attachment point is preferably one that allows movement of the support arm relative to the chassis in all directions, such as one in which the support arm is mounted to the chassis via a cylindrical section (mounted on a post via a rubber bushing).

The hub carrier may include a pivot pin extending in a fore/aft alignment through the two pivot points on the support arm to thereby define the two points. The appropriate end of the pivot pin then provides a convenient location for attaching the trailing link to the hub bracket. This configuration is shown in our earlier patent application WO 2010/100412. Alternatively, a ball joint may be used to connect each of the two arms of the support arm to the hub carrier.

The hub carrier preferably carries an axle which may be driven via a drive shaft extending from an engine or from a suitable differential or other gearbox. The wheel may be fitted to the axle.

The toe control link provides additional dynamic geometry control, especially under high load conditions, such as is typically required in a sport or high performance automobile.

The invention also relates to a vehicle comprising a chassis and at least two wheels, one on each side of the vehicle, each wheel being attached to the chassis via a suspension as defined above.

Such a design has particular advantages for vehicles with narrow track widths, as it allows the suspension to be encapsulated within very narrow confines. This also makes the suspension particularly suitable for vehicles with rear or mid-engine powertrain installations (both lateral and inline), as the more limited space required for the suspension allows for larger space for the engine and powertrain. Most designers struggle to package the suspension, drive shaft and powertrain within the available space and have to use complex pressurized metal suspensions.

In this application, reference to a direction or orientation is intended to be interpreted relative to a vehicle to which the suspension is mounted or intended to be mounted. Thus, a "forward" or "front" direction means a direction toward the front of the vehicle, and a "rearward" or "rear" direction will be similarly explained. Similarly, a direction such as "inward" means a direction toward the centerline of the vehicle and "outward" means the opposite. It is not intended to represent a strict geometric alignment (unless otherwise indicated); thus, the "forward" direction is not necessarily limited to being precisely aligned with the direction of vehicle travel, but rather indicates a forward direction as opposed to a rearward or inward direction.

Brief description of the drawings

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows a perspective view of a suspension system;

FIG. 2 shows a view of the suspension system from above;

FIG. 3 shows a view of the suspension system from the rear; and is

Figure 4 shows a view of the rear of a vehicle fitted with the suspension system of the present invention.

Detailed description of the embodiments

Modern lightweight and efficient ultra-compact urban automobiles require independent lightweight rear suspensions with excellent camber and toe control. For packaging reasons we also require that the suspension allows the rear laterally mounted engine and transmission units to be mounted in close proximity. Normal practice is to use trailing arm, semi-trailing arm, De-Dion or semi De-Dion type suspensions. However, these are very heavy, expensive and provide very poor caster and toe control at the tire contact patch. In many cases, they do not provide independence from side to side. We sought to design a system that provided all of the advantages of the conventional macpherson strut system, with the added advantage of more effectively decoupling the lateral compliance from the longitudinal compliance.

Figure 1 shows an embodiment of the invention in the form shown in which the wheels and associated suspension are separated from the vehicle chassis to which they are to be attached in use.

Thus, the wheel 10, including the tire 12 fitted onto the rim 14, is bolted to the hub 16. Which is attached to the wheel axle and the assembly is rotatably supported on the hub carrier 20. From the differential, a drive shaft 21 leads to the wheel shaft 18 in order to transmit drive torque to the wheels 10 and propel the vehicle.

The hub carrier 20 includes mounts for the axle 18 and the hub 16, the mounts including suitable bearings (not visible) to allow rotation thereof, and a set of stiffening flanges extending inwardly therefrom to provide rigidity to the hub carrier 20 and mounting points for the suspension elements. An upper flange 22 extends from the upper edge of the hub carrier 20, together with two side flanges (in the form of a forward flange 24 and a rearward flange 26) and a lower flange 27. The primary suspension member is connected to these flanges as follows.

First, the inverted wishbone 28 provides lateral compliance to the system. This is reversed because, contrary to common practice, there is a single attachment point 30 at the chassis, from which two wishbone arms 32, 34 extend (respectively) to a forward attachment point 36 and a rearward attachment point 38 on the lower flange 27, near the junction of the lower flange with the respective side flanges 24, 26 of the hub carrier 20. Each attachment point 30 allows for proper articulation of the connection via a ball joint.

An alternative form for the anterior and posterior attachment points is a rod that passes through holes in side flanges 24, 26 and through respective cylindrical sections at the ends of wishbone arms 32, 34. Thus, the wishbone arms 32, 34 are anchored to the rod 40, allowing the necessary relative rotation as the wheel is raised and lowered. This configuration is shown in our earlier application WO 2010/100412.

A similar ball joint is included in the chassis attachment point 30, oriented vertically to allow for some fore/aft adjustability. Which is mounted via rubber bushings 44 to suitable posts 42 (not shown in fig. 1) or the like on the chassis to allow limited movement of the wishbone arm 28 in all directions.

A trailing link 46 is also provided to provide forward and aft compliance. It is connected to the chassis by a horizontally aligned cylindrical connector 48 mounted on a similar post via a rubber bushing 52. This allows the trailing link 46 to easily rotate in a vertical plane as the wheel 10 is raised and lowered, and also allows some movement in other directions to accommodate suspension geometry.

At its other end, the drag link 46 is attached to the front end of the lower flange 27 via another ball joint. Alternatively, the trailing arms may be connected as shown in our application WO 2010/100412.

The third primary suspension element is a strut 60. This is a conventional spring and damper unit attached to the chassis via a top mount 62 and to the hub bracket 20 via a bracket 64, the bracket 64 being clamped to the lower end of the strut 60 and bolted to the front flange 24 in two locations. The struts thus maintain the hub carrier in a generally upright alignment and provide a downward force on the wheel 10 to maintain it in contact with the ground, as well as a cushion to upward and downward movement of the wheel 10.

Finally, a toe control link 66 is provided. Which is a rigid rod extending from the hub carrier 20 to a hard point on the chassis (not shown) generally parallel to but spaced upwardly from the posterior wishbone arm 34. The connection is made separately at both ends via ball joints or conventional bushings 70, allowing some articulation of the connection. This linkage 66 enhances dynamic geometry control under high load conditions by further limiting the movement of the hub carrier 26 to the manner dictated by the wishbone 28 and the strut 60. While this does not affect the geometry under low load conditions, it prevents transient distortion under high loads by providing additional support and rigidity, thus ensuring that the geometry remains correct.

Figure 3 shows the system from one side. The wheel 10 is shown schematically mounted on a hub 16. An inverted wishbone 28 is shown attached to a rod 40, which can be seen angled upwardly toward the front of the vehicle. Similarly, the trailing arm 46 is angled downwardly from its chassis mount 50 to a U-section bracket 54 on the bar 40. The struts are angled slightly forward with the top mount 62 somewhat forward of the bracket 64. These angles and orientations may be adjusted in the design of the suspension system to provide desired handling performance.

Figure 2 shows the system from above, showing a slight forward angle of the post 60, with the top mount 62 somewhat forward of the bracket 64. The posterior wishbone arm 34 is shorter than the forearm 32, meaning that the attachment point 30 to the chassis is rearward of the wheel centerline. This allows space for the drive shaft 21 to pass in front of the attachment point 30 and over the front wishbone arm 32 to the hub 16.

Fig. 3 shows the system from the rear, with the drive shaft 21 passing over the inverted wishbone 28. It can be seen that the attachment point 38 for the posterior wishbone arm 34 is slightly lower than the attachment point 36 for the forearm 32. These and other angles and orientations can of course be adjusted in the design of the suspension system to provide the desired handling performance.

As can be seen in fig. 2 and 3, the toe control link 66 is longer than each of the front wishbone arm 32 and the rear wishbone arm 34. The chassis hard point attached via bushing 70 is located inboard of the chassis attachment point for wishbone 28; similarly, the attachment point to the hub 16 is outboard of the attachment point for each of the anterior wishbone arm 32 and the posterior wishbone arm 34. These lengths and mounting points affect the motion of the suspension under load and help provide the benefits outlined above.

Fig. 4 shows a schematic view from the rear of a compact town car fitted with the suspension system described above. The chassis 72 provides the necessary mounting points and houses the engine and gearbox 74. A pair of drive shafts 21 project outwardly from the gear box 74 in both directions and toward the hub 16 on either side of the vehicle. One wheel 10 is mounted on each hub 16, and each wheel is supported by the suspension system as described above, including the inverted wishbone 28, strut 60 and trailing arm (not visible in fig. 4).

As is apparent from fig. 4, the illustrated system is designed to meet the needs of rear wheels in a rear engine, rear wheel drive configuration. However, it may be applied in other configurations, such as driven or non-driven wheels of a front wheel drive (or other) arrangement.

This "inverted wishbone" system not only provides the ride and handling advantages of an independent suspension system, but is also designed with a two-part linkage (inverted wishbone 28 plus drag link 46) to allow separation of the front and rear compliance for ride and comfort and the lateral compliance for vehicle handling control (camber and toe). Together with the strut 60 and toe control arm 66, the overall system is extremely lightweight and has low production costs, as it includes only three links per vehicle side and only four flexible elements per vehicle side.

The described system also requires only a small number of attachment points to the chassis and allows them to be spaced appropriately from the drive shaft. This makes the system particularly suitable for small and efficient town automobiles, where component space is limited and the wheels can be mounted close to the engine, gearbox, etc.

It will of course be appreciated that many variations may be made to the above-described embodiments without departing from the scope of the present invention.

Claims (19)

1. A vehicle suspension comprising: an assembly of a hub carrier and a support arm attached to the hub carrier at two points spaced from each other in a direction of travel and extending inwardly therefrom to a support arm attachment point for securing to a chassis, a tow link extending from the assembly in a direction transverse to the support arm toward a tow link attachment point for securing to the chassis, and a toe control link attached to the hub carrier at a single location spaced vertically from the two points and extending inwardly therefrom to a single attachment point for securing to the chassis.

2. The vehicle suspension of claim 1, wherein the trailing link extends from the assembly in a forward direction.

3. A vehicle suspension according to claim 1 or claim 2 further comprising a strut extending upwardly towards an attachment point for fixing to a chassis.

4. The vehicle suspension of claim 3, wherein the strut carries a spring.

5. A vehicle suspension according to claim 3 or claim 4 in which the strut carries a shock absorber.

6. The vehicle suspension of any one of the preceding claims wherein the single location where the toe control link is attached to the hub bracket is outboard of the two points where the support arm is attached to the hub bracket.

7. The vehicle suspension of any one of the preceding claims wherein the single point of attachment at which the toe control link is attachable to the chassis is inboard of the support arm point of attachment at which the support arm is attachable to the chassis.

8. A vehicle suspension according to any one of the preceding claims in which the support arm comprises a pair of arms extending divergently from the attachment point to each of the two points.

9. The vehicle suspension of claim 8, wherein the toe control link is longer than at least one of the pair of arms.

10. The vehicle suspension of any one of the preceding claims wherein the hub bracket includes a pivot pin extending in fore/aft alignment and the pivot pin passes through two pivot points on the support arm to thereby define the two points.

11. A vehicle suspension according to any one of the preceding claims in which the attachment of the support arm attachment point is an attachment that allows movement of the support arm relative to the chassis in all directions.

12. A vehicle suspension according to any one of the preceding claims in which the support arm is mounted to the chassis via a cylindrical section mounted on a post via a rubber bush.

13. A vehicle suspension according to any one of the preceding claims in which the trailing link is connected to a hub carrier.

14. The vehicle suspension of claim 7, wherein the trailing link is connected to an end of the pivot pin.

15. A vehicle suspension according to any one of the preceding claims further comprising an axle carried by the hub carrier.

16. A vehicle suspension according to claim 10 in which the axle is a driven axle.

17. A vehicle suspension according to claim 11, further comprising a wheel fitted to the axle.

18. A vehicle comprising a chassis and at least two wheels, one on each side of the vehicle, each wheel being attached to the chassis via a suspension according to claim 10 or claim 11.

19. A vehicle suspension substantially as herein described with reference to and/or as illustrated in the accompanying drawings.