AU2020213301A1 - Suspension - Google Patents

Abstract

P1571AUAU ABSTRACT A vehicle comprising sprung mass 3, a set of trailing arms 13, 15 and unsprung mass 19 comprising a transverse beam and, at ends of the beam, wheels having rotation axes. The set comprises on each side of the vehicle a top arm 15 and a 5 bottom arm 13 each pivotally connected, in front of the rotation axes, to the sprung mass, each connected to the beam, and rearwardly diverging from each other in plan. The unsprung mass is transversely constrained, relative to the sprung mass, at least predominantly by the set. 3/4 FIGURE 3 0 7 FIGURE 4

Description

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FIGURE 3

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FIGURE 4

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SUSPENSION FIELD

The invention relates to connecting the sprung mass of a vehicle to the unsprung mass of the vehicle.

The invention will be described with reference to a semi-trailer by way of example only. Other variants of the concept may be implemented in the context of other vehicles.

BACKGROUND

Figure 1a illustrates a combination C comprising a prime mover PM and a semi-trailer ST. As the word 'vehicle' is used herein, the combination, prime mover and semi trailer are each examples of a vehicle.

The prime mover and semi-trailer include complementary coupling features in the form of a fifth wheel FW and a kingpin KP. Other means of coupling are possible. Wheels W are rearwardly set along the trailer ST whereby a large proportion of the weight of any cargo carried by the trailer is borne by the prime mover PM. The trailer ST is a flatbed trailer comprising a pair of chassis rails CR running the length of the trailer and supporting a deck D.

The wheels W are connected to the chassis rails CR via suspension S to enable the wheels W (or more accurately, the rotation axes of the wheels W) to move relative to the chassis rails CR and the deck D. In line with the conventional usage of the terminology in this art:

• the wheels and the components fixed relative to the rotation axes are referred to as 'unsprung mass'; and

• components such as the chassis rails CR and deck D supported by the suspension S are referred to as 'sprung mass'.

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It is highly desirable to reduce the weight of the trailer ST. Typically, any reduction in weight leads directly to increased cargo-carrying capacity because maximum gross vehicle weights are enforced by law.

Figure 1b illustrates an existing suspension system SS1 comprising, for each side of the trailer, a trailing arm TA formed of box-section steel. The trailing arm TA is pivotally connected to a hanger H at one end. The other end of the trailing arm TA is connected to an airbag AB. A beam B in the form of a tubular steel axle runs transversely and is rigidly connected to the trailing arm on each side of the vehicle.

The hangers H and the top plates of the airbags B are fixed to the chassis rails and thus constitute part of the sprung mass, whereas the beam B is fixed relative to the rotation axes of the wheels and therefore constitutes part of the unsprung mass.

Large, elaborate rubber bushes RB are fitted at the pivotal connections between the hangers and the trailing arms to provide compliance to enable the pivot axes to move to accommodate asymmetric loadings on the suspension system SS1, e.g. to accommodate loadings associated with the vehicle cornering. In use, the beam B is subjected to bending and torsional loads and functions as a sway bar.

Shock absorbers SA run between the beam B and the sprung mass to dampen oscillations. Semi-trailer suspension systems are subjected to enormous loads and harsh conditions. Typically, the tubular axle (beam B) is formed of 16 mm thick tube steel. Nonetheless, it is not unheard of for axles to fail. The complex rubber bushes RB necessary to tolerate these forces whilst providing the requisite compliance are expensive. At the time of writing, such bushes cost about A$185 and require periodic replacement. Moreover, replacing such bushes is not easy, thus adding to the running costs of the suspension system SS1.

US Patent No. 9,085,212 discloses various alternative suspension systems. Figure 8B of that patent is reproduced herein as Figure 1c. That figure shows a suspension system comprising, for each side of the vehicle, a top trailing arm TTA and a bottom trailing arm BTA, each pivotally connected to a hanger H. The centre lines of the arms TTA, BTA forwardly converge at a virtual centre some distance in front of

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hanger H. The unsprung mass comprises the beam B having a differential DI midway therealong. A Panhard rod PR connects the unsprung mass to the sprung mass to transversely constrain the unsprung mass relative to the sprung mass. Other suspension systems incorporate a Watt's linkage for this purpose.

In effect, the suspension system SS2 comprises ten pivotal connections in place of the two rubber bushes RB.

The present inventors have recognised that neither of the suspension systems SS1, SS2 control the movement of the wheels (relative to the sprung mass) as well as they might. Furthermore, the present inventors have recognised that tyre life may be extended, fuel consumption may be reduced and/or handling may be improved by improving this control. Watt's linkages are known to provide better control than Panhard rods but are typically considered to be more expensive options. Relative to Panhard rods, Watt's linkages have three additional pivotal connections, all of which typically require servicing from time to time.

With the foregoing in mind, variants of the invention aim to provide improvements in and for vehicles, or at least to provide a useful alternative for those concerned with vehicles.

It is not admitted that any of the information in this patent specification is common general knowledge, or that the person skilled in the art could be reasonably expected to ascertain or understand it, regard it as relevant or combine it in any way before the priority date.

SUMMARY

One aspect of the invention provides a vehicle comprising

sprung mass;

a set of trailing arms; and

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unsprung mass comprising a transverse beam and, at ends of the beam, wheels having rotation axes;

the set comprising on each side of the vehicle a top arm and a bottom arm

each pivotally connected, in front of the rotation axes, to the sprung mass;

each connected to the beam; and

rearwardly diverging from each other in plan;

the unsprung mass being transversely constrained, relative to the sprung mass, at least predominantly by the set.

On each side of the vehicle the top arm and the bottom arm might be mounted to pivot, relative to the sprung mass, about a pivot axis. Preferably on each side of the vehicle a member defines the top arm and the bottom arm. Most preferably on each side of the vehicle the top arm and the bottom arm rearwardly diverge from each other in elevation.

Optionally on each side of the vehicle:

the top arm connects to the beam above the rotation axes and/or

the bottom arm connects to the beam below the rotation axes.

Preferably on each side of the vehicle an at-least-compliant top connection connects the top arm to the beam. Optionally on each side of the vehicle an at-least-compliant bottom connection connects the bottom arm to the beam. In some embodiments at least-compliant connections connecting the sprung mass to the top arms and the bottom arms.

The sprung mass may comprise chassis rails comprising a chassis rail on each side of the vehicle, in which case preferably on each side of the vehicle a rear of the top arm is positioned to move alongside the chassis rail.

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Optionally a cross member mutually connects the chassis rails and is an upright plate. Preferably the cross member is on each side of the vehicle pivotally connected to at least one of the trailing arms.

Preferably on each side of the vehicle, the upright plate defines a fork, or at least one side of a fork, for pivotally mounting at least one of the trailing arms. Preferably on each side of the vehicle, the fork is lower than, and most preferably under, the chassis rail.

Optionally on each side of the vehicle, bracing is below and connected to the chassis rail to brace the upright plate against fore-aft load from the at least one of the trailing arms.

Another aspect of the invention provides a vehicle comprising

sprung mass;

unsprung mass; and

suspension connecting the sprung mass to the unsprung mass;

the sprung mass comprising

chassis rails comprising a chassis rail on each side of the vehicle; and

a cross member;

the cross member

mutually connecting the chassis rails,

being an upright plate, and

on each side of the vehicle being connected to the suspension.

The vehicle may be a trailer.

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Another aspect of the invention provides a suspension system for a vehicle;

the vehicle comprising sprung mass;

the system comprising

a set of trailing arms; and

unsprung mass;

the unsprung mass comprising a transverse beam for carrying, at ends of the beam, wheels having rotation axes; and

the set comprising for each side of the vehicle a top arm and a bottom arm

each pivotally connectable, in front of the rotation axes, to the sprung mass;

each connected to the beam; and

rearwardly diverging from each other in plan;

the system being configured such that, when the system is installed, the unsprung mass is transversely constrained, relative to the sprung mass, at least predominantly by the set.

Preferably the beam is a non-driven axle.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1a is a side view of a vehicle combination;

Figure 1b is a rear perspective view of a suspension system;

Figure 1c is a rear perspective view of a suspension system;

Figure 2 is a rear perspective view of a suspension system;

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Figure 3 is a front perspective view of the suspension system of Figure 2;

Figure 4 is a front perspective view from below of the suspension system of Figure 2;

Figure 5 is a plan view of a suspension system;

Figure 6 is a front view of the suspension system of Figure 5; and

Figure 7 is a side view of the suspension system of Figure 5.

DESCRIPTION OF EMBODIMENTS

Figures 2 to 7 illustrate suspension systems 1, 101 fitted to chassis rails 3, 103. Short portions of the chassis rails are illustrated. In the context of a semi-trailer, such as the semi-trailer ST, the chassis rails span at least most of the length of the trailer. The rails 3 are I-beam chassis rails, whereas the rails 103 are C-section rails.

The rails 3 are mutually connected by a cross member 5 in the form of an upright plate. In this example, the plate is 20 mm thick steel plate. The member 5 is preferably cut from plate stock although additive and/or formative techniques are also possible. The plate 5 connects to the top half of each of the beams 3. In this example, the plate is welded to an underside of the top web of each rail and welded to the vertical web of the chassis rail. The plate 5 projects downwardly below, and wraps around the underside of, each rail 3 to define a fork 7 for pivotally mounting the chassis components. In this example, the member 5 is utilised for mounting trailing arms, although this advantageous plate-like construction may find application in entirely different suspension systems, e.g. the plate 5 might be usefully applied to mount a leaf spring.

The plate 5 replaces a conventional cross member and a conventional hanger, thus potentially reducing weight and simplifying construction. As a further weight-saving measure, the plate 5 is penetrated by lightening holes and has concave top and bottom edges to eliminate under-stressed material that would otherwise be more or less dead weight. Of course, the holes need not be circular and the concave portions need not be continuously curved, albeit that curvature to avoid stress concentration

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factors is preferred. Each side of the plate 5 has a side slot 9 to fit over the bottom flange of the chassis rail on that side.

The plate 5 serves to distribute load from the unsprung mass to the chassis rails.

In this case, each fork 7 sits in register with and underneath the corresponding chassis rail 3. Upright longitudinal webbing 11 is welded in fore and aft of the plate connecting the lower reaches of the plate 5 to the underside of the beam 3 to brace the plate 5 against fore and aft loads thereon from the trailing arms mounted thereto. In this example, webbing 11 sits in front and behind the plate 5, although other variants may have bracing in only one of those positions.

In place of the plate 5, the suspension system 101 comprises a pair of hangers 107 on the underside of the rails 103.

The suspension system 1 further comprises, on each side of the vehicle, a bottom arm 13 and a top arm 15. In this example, the arms 13, 15 are defined by a single V member 17.

Each member 17 comprises a front cylinder welded to straight rod portions defining most of the arms 13, 15. The arms 13, 15 rearwardly diverge from the cylinder 17a. The rear end of the bottom arm 13a comprises a cylinder 17b welded to its rod body whilst the rear end of the top arm 15 comprises a cylinder 17c welded to the rear end of its rod body.

The cylinder 17a is concentrically assembled about a pivot pin and separated therefrom by a compliant bush. The pivot pin horizontally spans and is bolted to the fork 7 to complete the front pivotal joint 21a on that side of the suspension system.

A horizontal beam 19 in the form of a tubular axle runs transversely. Flanges are welded to the exterior of the beam 19 to define clevises for receiving the rear end of the arms 13, 15. The bottom joint 21b and top joint 21c are completed with central pins, in this case bolts, and suitable bushings, in this case double-tapered bushings.

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Each of the joints 21a, 21b, 21c is a compliant joint to enable complex movement of the unsprung mass relative to the sprung mass and to minimise the application of bending loads to the arms 13, 15. In principle, other forms of joint such as rose joints could be used to minimise the application of bending loads to the arms. As used herein, the wording 'at-least-compliant connection' embraces such other joints. Preferably the joints 21a, 21b, 21c comprise bushes. One of ordinary skill in the art will appreciate that there are a wide variety of bushes proven in other suspension applications readily available at cost far below one third of the cost of the rubber bushes RB.

The suspension system is configured to load the arms 13, 15 at least mostly in pure tension or pure compression. In this context, relatively light weight slender rod portions can be used. The suspension system 101 incorporates a V-member 117 akin to the member 17. As best seen in Figure 5, trailing arms 113, 115 rearwardly diverge from each other and the top arm 115 on one side of the vehicle rearwardly converges with its counterpart on the other side of the vehicle. The arms 113, 115 thereby serve as diagonal bracing to constrain transverse movement between the sprung and unsprung masses.

Whilst each of the arms 13, 15 is loaded at least mostly axially, the arms together apply complex bending and torsional loads to the beam 3 whereby the beam functions as a sway bar.

The illustrated arms are straight arms whereby a notional straight line, connecting the pivotal connections at the ends of an arm, is substantially coincident with a centerline of the arm. This geometry in conjunction with the at least most axially loading is generally preferred, although in some applications it may be advantageous to adopt arms that are not straight, e.g. to adopt an arm that is shaped to clear some other component. For the avoidance of doubt, the direction of the arm is characterised by the notional line connecting the mounting points at the ends of the arm.

The unsprung mass further comprises mounting arms 23, 123 connected to and projecting rearwardly from the beam 19, 119. Airbags 25, 125 are sandwiched by the mounting points 23, 123 and the chassis rails 3, 103.

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The airbags 25, 125 are examples of resilient elements to store and return energy when the suspension is compressed. Airbags provide negligible transverse support whereby in the suspension systems 1, 101 substantially all of the transverse support is provided by the trailing arms. Airbags are preferred to facilitate easy adjustment to suit any particular cargo. Other forms of springs, such as coil springs, are another option. Typical coil springs mounted in place of the airbags 25, 125 would provide only a small degree of transverse constraint whereby the unsprung mass would be constrained predominantly by the set of trailing arms.

The rearward ends of the top arms 15, 115 sit inboard of their corresponding chassis rail so that they can move up alongside the chassis rail when the suspension is compressed.

Preferably a shock absorber is mounted on each side of the vehicle. The suspension systems 1, 101 comprise shock absorbers diagonally down to the beams 19, 119 to act between the sprung mass and the unsprung mass. Other variants are possible. By way of example, the airbags 25, 125 might be replaced by coil-overs.

Semi-trailer suspension is but one possible application of the suspension systems 1, 101. Variants of these systems may be usefully applied in the context of other trailers, e.g. in the context of a small box trailer or a caravan. Indeed, some variants may be usefully applied in the context of driven vehicles such as a car or a truck.

The invention is not limited to the examples described herein. Rather the invention is defined by the claims.

The term 'comprises' and its grammatical variants has a meaning that is determined by the context in which it appears. Accordingly, the term should not be interpreted exhaustively unless the context dictates so.

Claims (20)

P1571AUAU 11 CLAIMS

1. A vehicle comprising

sprung mass;

a set of trailing arms; and

unsprung mass comprising a transverse beam and, at ends of the beam, wheels having rotation axes;

the set comprising on each side of the vehicle a top arm and a bottom arm

each pivotally connected, in front of the rotation axes, to the sprung mass;

each connected to the beam; and

rearwardly diverging from each other in plan;

the unsprung mass being transversely constrained, relative to the sprung mass, at least predominantly by the set.

2. The vehicle of claim 1 wherein on each side of the vehicle the top arm and the bottom arm are mounted to pivot, relative to the sprung mass, about a pivot axis.

3. The vehicle of claim 1 comprising on each side of the vehicle a member defining the top arm and the bottom arm.

4. The vehicle of claim 1, 2 or 3 wherein on each side of the vehicle the top arm and the bottom arm rearwardly diverge from each other in elevation.

5. The vehicle of any one of claims 1 to 4 wherein on each side of the vehicle the top arm connects to the beam above the rotation axes.

6. The vehicle of any one of claims 1 to 5 wherein on each side of the vehicle the bottom arm connects to the beam below the rotation axes.

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7. The vehicle of any one of claims 1 to 6 comprising on each side of the vehicle an at-least-compliant top connection connecting the top arm to the beam.

8. The vehicle of any one of claims 1 to 7 comprising on each side of the vehicle an at-least-compliant bottom connection connecting the bottom arm to the beam.

9. The vehicle of any one of claims 1 to 8 comprising at-least-compliant connections connecting the sprung mass to the top arms and the bottom arms.

10. The vehicle of any one of claims 1 to 9 wherein

the sprung mass comprises chassis rails comprising a chassis rail on each side of the vehicle; and

on each side of the vehicle a rear of the top arm is positioned to move alongside the chassis rail.

11. The vehicle of claim 10 comprising across member

mutually connecting the chassis rails,

being an upright plate, and

being on each side of the vehicle, pivotally connected to at least one of the trailing arms.

12. The vehicle of any one of claims 1 to 9 wherein the sprung mass comprises

chassis rails comprising a chassis rail on each side of the vehicle; and

a cross member

mutually connecting the chassis rails,

being an upright plate, and

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being on each side of the vehicle, pivotally connected to at least one of the trailing arms.

13. The vehicle of claim 12 wherein, on each side of the vehicle, the upright plate defines at least one side of a fork for pivotally mounting at least one of the trailing arms.

14. The vehicle of claim 13 wherein, on each side of the vehicle, the upright plate defines a fork for pivotally mounting at least one of the trailing arms.

15. The vehicle of claim 13 or 14 wherein, on each side of the vehicle, the fork is lower than the chassis rail.

16. The vehicle of claim 15 wherein, on each side of the vehicle, the fork is under the chassis rail.

17. The vehicle of claim any one of claims 11 to 16 comprising, on each side of the vehicle, bracing below and connected to the chassis rail to brace the upright plate against fore-aft load from the at least one of the trailing arms.

18. A vehicle comprising

sprung mass;

unsprung mass; and

suspension connecting the sprung mass to the unsprung mass;

the sprung mass comprising

chassis rails comprising a chassis rail on each side of the vehicle; and

a cross member;

the cross member

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mutually connecting the chassis rails,

being an upright plate, and

on each side of the vehicle being connected to the suspension.

19. The vehicle of any one of claims 1 to 18 being a trailer.

20. A suspension system for a vehicle;

the vehicle comprising sprung mass;

the system comprising

a set of trailing arms; and

unsprung mass;

the unsprung mass comprising a transverse beam for carrying, at ends of the beam, wheels having rotation axes; and

the set comprising for each side of the vehicle a top arm and a bottom arm

each pivotally connectable, in front of the rotation axes, to the sprung mass;

each connected to the beam; and

rearwardly diverging from each other in plan;

the system being configured such that, when the system is installed, the unsprung mass is transversely constrained, relative to the sprung mass, at least predominantly by the set.