GB2388346A - Vehicle suspension - Google Patents

Abstract

A suspension assembly (400) to support a road wheel of a vehicle has an upper linkage (401) and a lower linkage (402) which support a wheel carrier (403) and a spring/damper assembly (408) is connected to both the upper and the lower linkages and is worked by both the suspension linkages (401, 402).

Description

IMPROVEMENTS RELATING TO VEHICLES

This invention relates to improvements in vehicles, more particularly land vehicles. It especially relates to a suspension assembly for a land vehicle.

For many years vehicles have been produced which comprise a separate chassis onto which a passenger compartment is located. The role of the chassis is to support the major components or subassemblies that make up the complete vehicle, such as the engine, gearbox, suspension, bodywork 10 etc. The passenger compartment is typically attached to the chassis through resilient rubber bushes. These help prevent shock being transmitted from the suspension through the chassis to the passenger compartment as well as isolating engine vibration from the passenger compartment. Recent trends in vehicle design have moved away from providing a separate chassis. In an alternative arrangement, land vehicles have been produced which use a chassisless monocoque construction. In these vehicles there is no separate chassis. However, it is common to provide a 20 sub frame which is attached to the monocoque and which supports the suspension and even a subframe to support the engine. These subframes help to isolate road shocks from the passengers.

To meet present safety legislation, particularly for crash protection of 25 passengers, the chassis or monocoque needs to be designed in such a way as to absorb the energy of impact. Typically this is achieved by providing areas of the chassis or monocoque which are intended to collapse in a controlled manner in the event of a crash. As the areas collapse energy is absorbed in deforming the material.

( A problem with both conventional chassis and monocoque vehicles is that such collapse due to an accident often results in the vehicle being written off. To repair the vehicle a whole new monocoque or complete chassis may be needed. In most cases such a repair is uneconomical. At best, a 5 section of the chassis must be cut away and a new section welded in place It is an object of the invention to provide a suspension assembly for a road vehicle.

10 In accordance with a first aspect of the invention we provide a suspension assembly for a land vehicle comprising a wheel carrier which is adapted to support a road wheel, upper and lower suspension linkage which are adapted to support the wheel carrier relative to the body of the vehicle so as to permit movement of the wheel carrier relative to the vehicle, and a IS spring/damper assembly which is adapted to control movement of the wheel carrier, and is connected to both the upper and lower linkages so that the spring/damper assembly is worked by both suspension linkages.

In the prior art, it is known to provide a suspension assembly in which

20 one end of the spring/damper assembly is worked by either the upper linkage (or arm) or lower Linkage (or arm) whilst the other end is fixed to the vehicle body or a sub frame. In the present invention, it is preferred that the spring/damper assembly is connected to the suspension arms so that on movement of the road wheel carrier in one direction (i.e. upwards) 25 both the lower linkage and the upper linkage act to compress the spring/damper assembly. Thus, compared to a prior art arrangement in

which only one linkage works the spring/damper assembly more compression can be achieved for a given wheel travel. This provides superior wheel control.

( The upper linkage may comprise a wishbone or substantially v-shaped or u-shaped arm. The lower linkage may also comprise a wishbone or substantially v-shaped or u-shaped arm. The two arms may be spaced apart one above the other to form a dual - wishbone suspension. The 5 linkages may comprise welded tubular portions or may be forged or machined or pressed to form a single rigid component.

Each linkage may define a base portion at one end and a pair of spaced apart arms at the other defining three take off points. The take off point 10 at the base may be pivotally connected to the wheel carrier. The take off points on the arms may connect to the vehicle body or a sub frame to allow the arm to rotate about an axis which passes through the take-off points of the two arms. This axis is preferably substantially horizontal and longitudinal substantially of the vehicle.

IS The arms may connect directly to the vehicle body or to a sub frame which is in turn attached to the vehicle body. This may be through rubber bushes or roller bearings or rose joints.

20 The lower linkage may be longer than the upper linkage. The axis about which the lower linkage rotates may therefore be spaced further from the wheel carrier than the axis of rotation of the upper linkage.

The spring/damper assembly may connect to the upper linkage and lower 25 linkage at a point along the linkage spaced from the pivot axis of rotation of the linkages. Movement of the wheel carrier relative to the vehicle body therefore causes the linkage to act as a lever to work the spring/damper assembly.

( ( The spring/damper assembly may be connected at a first end to a portion of the lower suspension linkage that is spaced between the axis of rotation of the linkage and the wheel carrier whilst the other end connects to a portion of the upper linkage which is spaced on the opposite side of the 5 axis of rotation of the upper linkage away from the wheel carrier. The upper linkage may therefore have an extended portion that extends from the axis of rotation away from the wheel carrier to support the spring/damper assembly.

10 In both cases, the distance from spring/damper to the pivot axis relative to the distance from wheel carrier to the axis should be chosen to ensure the ratio of movement of the wheel carrier to movement of the spring/damper assembly is optimised for a particular vehicle.

15 The spring/damper assembly may comprise a spring which is located concentrically around a damper unit Other arrangements are, of course, envisaged. Indeed, the spring and the damper may connect to the suspension arms at different locations if desired. Also, either the spring or the damper may be omitted if required.

The suspension assembly may be provided at the front or the rear of a vehicle for front or rear wheels.

In accordance with a second aspect of the invention, we provide a land 25 vehicle which includes a suspension assembly according to the first aspect of the invention.

The land vehicle may include a rear axle driving two rear wheels. On each side of the vehicle, a suspension assembly according to the third 30 aspect of the invention may be associated with each rear wheel.

The two suspension assemblies may be independent from each other in their operation.

There will now be described by way of example only, an embodiment of 5 the present invention of which: Figure l is an isometric view of an embodiment of a suspension assembly for a road vehicle in accordance with a further aspect of the present invention; Figure 2 is a front view (looking back along the vehicle) of the suspension assembly of Figure 1; Figure 3 is a plan view of the suspension assembly of Figure 1; 15 and Figure 4 is an end view of the suspension assembly of Figure 1.

An embodiment of a suspension assembly 400 in accordance with the 20 invention is illustrated in the accompanying drawings.

Figure 1 is a perspective illustration of one half of a rear axle suspension set-up. Only the suspension assembly associated with a drivers side rear wheel is therefore illustrated. It will, of course, be readily understood that 25 the assembly for the far-side rear wheel is simply a mirror image of that shown. Also, the suspension is shown without the presence of a roadwheel or the vehicle body to aid clarity. Other Views of the assembly are provided in Figures 2 to 4 of the accompanying drawings.

The suspension assembly 400 as shown comprises of an upper suspension linkage or arm 401 and a lower suspension linkage or arm 402, Each arm is a substantially U-shape with the base of the U connecting to a wheel carrier 403 through a pivot 404, 405. The two ends of each of the arms 5 respectively define two take-off points for connection to a vehicle subframe (or directly to the body). An axis X-X' and Y-Y' connecting the two take-off points defines the axis about which each of the suspension arms may rotate, The arms are made from welded tubular bar although they could in fact be forged or pressed from sheet material if required.

The lower arm is longer than the upper arm (or wishbone) and so the axis Y-Y' about which it rotates is both lower than and also inboard of the vehicle compared to the rotation axis X-X' of the upper arm. The connection from the arms 401, 402 to the wheel carrier 403 is such that at 15 rest the wheel carrier 403 is held vertically to support the road wheel (not shown) vertically. The difference in length of the arms 401, 402 help eliminate tilt of the wheel carrier 403 under deflection and helps keep the caster angle constant.

20 For increased rigidity, each arm includes a respective tubular cross beam which connects the two take off points of each arm, and the arms connect to the subframe through spherical joints (not shown). The axis of rotation I therefore passes through each cross beam 406, 407.

25 A springidamper assembly 408 is provided which connects at one end 409 to the upper arm 401 and at the other end 410 to the lower arm 402. The assembly 408 compares a spring 411 which is located concentrically around a damping strut 412. Movement of the ends 409, 410 of the assembly 408 together is resisted by the spring and movement of the ends

( is damped by fluid in a chamber of the damping strut 412. This provides for control of the suspension.

The lower end of the spring/damper assembly 408 connects to the lower 5 arm at a point spaced between the axis Y-Y' connecting the vehicle body (or subframe) take off points and the wheel carrier. It is actually closer to the rotation axis than the wheel carrier. The lower arm therefore acts as a lever so that when the wheel carrier moves up to absorb a bump in a surface the end of the spring/damper unit 408 also moves up but by a 10 smaller distance.

The other end of the spring damper unit 408 connects to the upper arm at a point spaced from the axis X-X' connecting the vehicle body (or subframe) take off points opposed to the wheel carrier 403. In practice, 15 this is achieved by extending a portion of the upper arm beyond the axis and correcting the spring/damper to this extended portion. This can be clearly seen in Figure 10 of the accompanying drawings.

The upper arm 401 also acts as a lever so that in the case when the wheel 20 carrier 403 moves upwards the top of the spring/damper assembly 408 actually moves in the opposite direction, i.e. downwards.

It can therefore be seen that both ends of the spring/damper assembly 408 are worked by the suspension arms. More compression can therefore be 25 achieved for a given travel of the wheel carrier 403 when compared to prior art arrangements in which one end of the spring/damper assembly

connects to the vehicle body.

The characteristics of the suspension assembly can be altered by varying 30 the ratio of the distance between the pivot axis of the arms, the point of

connection of the wheel carrier and the point of connection of the spring/damper assembly.

The anns 401, 302 connect to the vehicle body through a subframe (not 5 shown) that is connected to the rear of the chassis. Resilient rubber or elastomer mountings can be used to isolate vibration caused by the movement of the subframe from the chassis and hence passengers.

However, since the spring damper assembly connects to the arms rather than the vehicle body an extremely comfortable ride has been found to be 10 possible even at high wheel load rates.

Claims (8)

1. A suspension assembly for a land vehicle comprising a wheel carrier which is adapted to support a road wheel, upper and lower 5 suspension linkages which are adapted to support the wheel carrier relative to the body of the vehicle so as to permit movement of the wheel carrier relative to the vehicle, and a spring/damper assembly which is adapted to control movement of the wheel carrier, and is connected to both the upper and lower linkages so that the spring/damper assembly is 10 worked by both suspension linkages.

2. A suspension assembly according to claim 1 in which the spring/damper assembly is connected to the suspension arms so that on movement of the road wheel carrier in one direction both the lower 15 linkage and the upper linkage act to compress the spring/damper assembly.

3. A suspension assembly according to claim 1 or claim 2 in which the upper linkage comprises a wishbone or substantially v-shaped or 20 u-shaped arm and the lower linkage comprises a wishbone or substantially v-shaped or u-shaped arm.

4. A suspension assembly according to claim 3 in which each linkage comprises a base portion at one end and a pair of spaced apart arms at the 25 other defining three take off points, the take off point at the base being pivotally connected to the wheel carrier and the take off points on the arms being connected to the vehicle body or a sub-frame to allow the arm to rotate about an axis which passes through the take-off points of the two arms.

5. A suspension assembly according to claim 4 in which the lower linkage is longer than the upper linkage and the axis about which the lower linkage rotates is spaced further from the wheel carrier than the axis of rotation of the upper linkage, and further in which the 5 spring/damper assembly is connected to the upper linkage and lower linkage at a point along the linkage spaced from the pivot axis of rotation of the linkages.

6. A suspension assembly according to any preceding claim in which 10 the spring/damper assembly is connected at a first end to a portion of the lower suspension linkage that is spaced between the axis of rotation of the linkage and the wheel carrier whilst the other end of the spring/damper assembly connects to a portion of the upper linkage which is spaced in the opposite side of the axis of rotation of the upper linkage to away from the 15 wheel carrier.

7. A suspension assembly substantially as described herein with reference to and as illustrated the accompanying drawings.

20

8. A land vehicle including a suspension assembly according to any preceding claim.