AU680913B2 - Self adjusting axle assemblies - Google Patents

Description

VI'OUIU1 I 2B(S/I Regulatlon 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: SELF ADJUSTING AXLE ASSEMBLIES a The following statement is a full description of this invention, including the best methcri of performing it known to me SELF ADJUSTING AXLE ASSEMBLIES The present invention relates to axle assemblies for multiple axle vehicles and in particular to improvements in steerability of such axle assemblies in use.

With large multi-axle vehicles it is desirable from the point of view of minimising tyre wear and maintaining vehicle stability that the axis of rotation of each wheel maintains as far as possible a perpendicular orientation to the line of travel of the vehicle. With fixed axle vehicles this is achieved when cornering only by wheel skid which significantly increases tyre wear and decreases vehicle stability. Axle assemblies which automatically maintain or try to maintain I: 10 wheel orientation as close as possible to the ideal when cornering are known in the art. Such assemblies commonly include outboard slub axles to which the wheels are mounted hinged to a central main axle part permitting the wheel orientation to vary relative to the main axle part. Such assemblies also commonly include a linkage mechanism to maintain the opposed wheel pairs generally in alignment. Generally speaking the known arrangements of this kind are relatively complicated and expensive and moreover do not easily allow same to be retrofitted to a vehicle that originally had fixed axle assemblies installed when initially built. The objective therefore of the present invention is to provide a self adjusting axle assembly of the aforementioned type which is relatively simple in configuration and which is capable of use to modify existing fixed axle assembly vehicles in a cost effective manner.

Accordingly, the present invention provides a mechanism adapt o be fitted to a rigid axle assembly of a multiple-axle vehicle, s mechanism comprising a support member adapted to be mountet a chassis of said vehicle, first connection means enabling connecI of said support member to said rigid axle assembly at or adjacent a point thereof, said first connection means permitting movement of sI rigid axle relative to said support member about a generally upright s whereby opposed lateral ends of said rigid axle assembly can mo orwardly or rearwardly relative to the chassis of said vehicle, an sntrol means to control movement of said lateral ends of said rigid axle sembly within predetermined limits in a forward or rearward direction.

I I Accordingly, the present invention provides a mechanism adapted to be fitted to a rigid axle assembly mounted from a single vehicle chassis having multiple axle assemblies mounted therefrom, said mechanism comprising a support member adapted to be mounted to the chassis, first connection means enabling connection of said support member to a rigid axle of said rigid axle assembly at or adjacent a mid point of said rigid axle, said first connection means permitting movement of said rigid axle relative to said support member about a generally upright axis whereby opposed lateral ends of said rigid axle can move forwardly or rearwardly relative to the chassis of said vehicle, second connection means enabling pivotal connection of said support member to the chassis of said vehicle whereby said support member pivots relative to said chassis about one or more generally horizontal axes, and control means to control movement of said lateral ends of said rigid axle within predetermined limits in a forward or rearward direction wherein said control means includes an arrangement adapted to be mounted between each said lateral end of said rigid axle and spring means of said vehicle operable between the chassis and said rigid axle.

go* *O*o *ooo a"% Conveniently the support member comprises an A or V shaped frame with an apex zone thereof being connected to said first connection means and free ends of legs of said frame being adapted for pivotal connection to said chassis of the vehicle for pivotal movement about at least generally horizontal axis.

Preferably the upright axis is located forwardly of a mid point axis of said rigid axle assembly. Conveniently, the upright axis is located forwardly of said rigid axis assembly. It is believed such arrangements provide a self steer on self adjustment capability of the axle assembly by pivotal movement about the upright axis. As a result of the foregoing structure, an existing rigid (or fixed) axle assembly of a vehicle can be readily modified to provide adjustment (in use) of the orientation of the wheels mounted to the external ends of the axle assembly without substantial modification of the axle assembly itself. As a result, a simple and inexpensive conversion capability is achieved. Of course the system might also be used as original equipment if desired.

Preferably the support member includes second connection means enabling connection thereof to the base chassis frame of the vehicle in a manner permitting movement of the first connection means in an up or down direction.

Conveniently, if needed, the first connection means might also be such as to permit pivoting movement about a generally horizontal axis as well as the aforesaid upright axis.

Conveniently, the control means includes an arrangement adapted to be mounted between each said lateral end of said rigid axle assembly and spring means of said vehicle operable between the chassis and said rigid axle assembly. Preferably each said arrangement comprises a first part adapted to be secured to the spring means, a second part adapted to be secured to the rigid axle assembly with said first and second parts being capable of relative movement over a defined accurate path centred on said upright axis. The first part may include bearing means movable within a guide path defined by the second part. The second part may include stop means at either end of said guide path to limit movement of the lateral ends of said rigid axle assembly.

3 In a particularly preferred embodiment, the control means may include means for preventing movement of the lateral ends of said rigid axle assembly when said vehicle is moved in a reverse direction while said lateral ends of the rigid axle assembly are free to move when said vehicle is moved in a forward direction.

The present invention also anticipates the provision of a vehicle wherein a mechanism as aforesaid is installed between at least one axle assembly and the vehicle chassis.

Preferred embodiments of the present invention will hereinafter be 10 described with reference to the accompanying drawings, in which Figure 1 is a schematic plan view of an adjustment mechanism according to the present invention; Figure 2 is a side elevation view of the control means of the mechanism shown in Figure 1; Figure 3 is a schematic end elevation view of the arrangement shown in Figures 1 and 2; Figure 4 is a plan view illustrating the movement of the rigid axle assembly; Figure 5 is a side elevation view of the control means of a second preferred embodiment; and Figure 6 is a sectional plan view of the embodiment of Figure 7 taken along line VIII-VIII.

Referring to Figure 1 there is shown a conventional rigid axle assembly with outboard wheels 11 rotationally supported thereon. Commonly such rigid axle assemblies might be secured to the mid point of leaf springs 23, air bag suspensions or any other form of suitable suspension. A support member 12 in the form of a V-shaped frame is provided to connection means 13 secured to a mid point of the axle assembly 10. The connection means 13 includes an upright pivot axis 14 so that the member 12 pivots about same relative to the axle 10. The location of the pivot axis 14 may be varied either forwardly, rearwardly or coincident with the central axis 40 of the axle 10. The vertical positioning of the connection 13 may also be varied as desired. It is also possible to make the connection 13, 14 a universal joint having movement at least about a vertical axis 14 and a longitudinal (fore/aft) horizontal axis.

Opposed ends 15 of the member 12 include second connection means 16 with general;y horizontal pivot joints 17 and a bracket 18 adapted to be mounted to the original vehicle chassis not shown.

The mechanism of the present invention also includes control means 19 cooperating with opposed laterally outer ends 20, 21 of the rigid axle assembly Certain details of the control means 19 may also be seen in Figures 2 and 3.

The control means 19 includes a first part 22 secured to an underneath mid zone 10 surface of a said leaf spring assembly 23 or other suitable suspension means.

The first part 22 is conveniently secured in place by bolts 24 passing through the spring leaves and a top mounting plate 30. A bearing structure 31 is secured by fastener means 32 to the first part 22 and by fastener means 33 and mounting formations 34 welded or otherwise rigidly secured to the axle 10. As shown in Figures 1 and 2, the bearing structure 31 and outer member 35 define two inwardly facing arcuate ball races, an inner member 36 defining two outwardly facing ball races and a series of ball bearing members 37 located in each arcuate race between the outer and inner members 35, 36. The outer member 35 is secured by fasteners 33 to the mounting formations 34 and the inner member 36 is secured by fasteners 32 to the first part 22. Each of the arcuate races have their centres of curvature centred on the pivot axis 14.

As can be seen in Figure 4, as the axle 10 pivotally moves about axis 14, the lateral ends 20, 21 move inwardly or outwardly relative to the vehicle chassis by a small distance. The control mechanism 19 needs to be able to adjust for this movement as well as permitting forward and aft movement as discussed above.

Figures 5 and 6 illustrate a still further preferred embodiment wherein the support member 12 (V-shaped frame) is connected via connection means 13 to the rigid axle assembly 10. The connection means 13 forms a vertical pivot axis 14 which is located forwardly of the transverse centre line 40 of the axle assembly. This is desired to assist self steering of the wheels and axle

I.,I

assembly. This arrangement in this embodiment is therefor similar to that which is shown in Figure 1.

At the outer ends of the axle assemblies pairs of bearing guides 50 are provided, one such guide being located on either side of the vehicle spring assembly 23. The bottom of face 51 of each bearing guide 50 is bolted via bolts 52 to flanges 53 welded to the axle assembly 10. As is best seen in Figure 8, each bearing guide 50 is curved in plan view to allow the axle assembly 10 to move about the pivot 14 while still providing suitable support. The radius of curvature of each bearing guide 50 is centered on the pivot axis 14. The bearing 10 guides 50, each house a suitable bearing 54, the outer surface of which rolls between the bearing guide surfaces 55,56. A shaft 57 is supported internally of each bearing 54, which shaft 57 is rigidly carried by a lower plate 58 bolted to the spring assembly 23. This is achieved by bolts 59 passing through a top plate and either around or through the spring assembly 23 to the lower plate 58.

Stabiliser arms 38 are provided pivoted to the vehicle frame at 62 and to the lower plate 58 at 61. Conveniently, each stabiliser arm 38 is hollow housing a pist'_,, 64 and connecting rod 65 which passes rearwardly to a link arm 66 which via universal type joints 67,68 joins the connecting rod 65 to the axle assembly or some part such as flange 53 rigidly secured to the axle assembly 10. The internal zone of each arm 38 forward of the pistons 64 are connected via a S:-i conduit 69 and is filled with a hydraulic fluid. A valve 70 in conduit 69 when open allows fluid to flow between the arms 68 and when closed fixes the fluid and thereby the pistons 64 in their position at the moment of closing. In forward operation, the valve 70 would be left open, however, when it is desired to move rearwardly, the valve 70 would be closed manually (or by suitable automatic means). In addition to the foregoing, a further stabiliser member 71 is provided pivoted at one end 72 about a vertical axis generally coincident with the pivot axis 14. A flange structure 73 welded to a midpoint of the axle assembly is connected to the one end 72.

The thus described arrangements permit existing fixed axle assembly arrangements to be relatively easily modified without major changes to the axle assemblies themselves.

I -Mi

Claims (9)

1. A mechanism adapted to be fitted to a rigid axle assembly mounted from a single vehicle chassis having multiple axle assemblies mounted therefrom, said mechanism comprising a support member adapted to be mounted to the chassis, first connection means erabling connection of said support member to a rigid axle of said rigid axle assembly at or adjacent a mid point of said rigid axle, said first connection means permitting movement of said rigid axle relative to said support member about a generally upright axis whereby opposed lateral ends of said rigid axle can move forwardly or rearwardly relative to the chassis of said vehicle, second connection means enabling pivotal connection of said support member to the chassis of said vehicle whereby said support member pivots relative to said chassis about one or more generally horizontal axes, and control means to control movement of said lateral ends of said rigid axle within predetermined limits in a forward or rearward direction wherein said control means includes an arrangement adapted to be mounted between each said :i lateral end of said rigid axle and spring means of said vehicle operable between the chassis and said rigid axle. 0 o o

2. A mechanism according to claim 1, wherein said support member comprises an A frame with an apex zone of said A frame being connected to said first connection means ard free ends of legs of said A frame being adapted for pivotal connection via said second connection means to said chassis of the 0 0 vehicle.

3. A mechanism according to claim 1 or claim 2, wherein said upright axis is located forwardly of a mid point axis of said rigid axle.

4. A mechanism according to claim 1 or claim 2, wherein said upright axis is located forwardly of said rigid axle.

A mechanism according to claim 1, wherein each said arrangement comprises a first part adapted to be secured to the spring means, a second part adapted to be secured to the rigid axle with said first and second parts being capable of relative movement over a defined arcuate path centred on said upright axis.

6. A mechanism according to claim 5, wherein said first part includes bearing means movable within a guide path defined by said second part.

7. A mechanism according to claim 6, wherein said second part includes stop means at either end of said guide path to limit movement of the lateral ends of said rigid axle.

8. A mechanism according to any one of claims 1 to 7, wherein said control means includes means for preventing movement of the lateral ends of said rigid axle when said vehicle is moved in a reverse direction while said lateral ends of the rigid axle are free to move when said vehicle is moved in a forward direction.

9. A vehicle chassis including at least one mechanism as defined in any one of claims 1 to 8. DATED this 22nd day of May, 1997. BRIAN McKEE WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA SKP:JL DOC 037 AU6860694.WPC il~- ABSTRACT 'The present invention provides a mechanism enabling a self steering capability for the wheels of a vehicle, the mechanism comprising a support member (12) pivotally connected to a chassis of the vehicle so that an end of the member (12) is capable of moving up and down, the said end of the member (12) being pivoted to a mid point in front of an axle assembly (10) so that the axle assembly (10) can pivot about an upright axis relative to the support member, the mechanism further including control means arranged to control movement of *.ees lateral ends of the axle assembly (10) within certain predetermined limits. a 0* 0. S I s