GB2341157A

GB2341157A - Six wheel steering system

Info

Publication number: GB2341157A
Application number: GB9819388A
Authority: GB
Inventors: Steven James Randle
Original assignee: TOTAL MOBILITY VEHICLES Ltd
Current assignee: TOTAL MOBILITY VEHICLES Ltd
Priority date: 1998-09-04
Filing date: 1998-09-04
Publication date: 2000-03-08
Anticipated expiration: 2018-09-04
Also published as: GB2341157B; GB9819388D0

Abstract

A vehicle (2) comprising six driven wheels (4) and a steering arrangement (6) comprising at least one drag link (8) for operating the middle pair of the wheels (4), at least one drag link (10) for operating the rear pair of the wheels (4). A pivot (12) which is movable between two different modes of steering. Firstly an on-road position in which the pivot (12) permits operation of the drag link (8) for the middle pair of the wheels (4) but not the rear pair of the wheels (4). Secondly an off-road position in which the pivot (12) permits operation of the drag link (10) for the rear pair of the wheels (4) and not the middle pair of the wheels (4). The system also includes a means for moving the pivot (12) between the on-road and the off-road positions.

Description

1 2341157 AN AZL-TERRAIN VEHICLE This invention relates to an all-terrain

vehicle.

There are various types of known all-terrain vehicles. The all-terrain vehicles may have four or six wheels. The known all-terrain vehicles having six wheels are such that they have steering arrangements which do not give optimum steering capabilities when the vehicle is being driven in on-road conditions and in off-road conditions.

It is an aim of the present invention to obviate or reduce the above mentioned problem.

Accordingly, in one non-limiting embodiment of the present invention there is provided an all-terrain vehicle comprising six driven wheels and a steering arrangement for the wheels: the wheels being positioned on the vehicle such that they form a front pair of the wheels, a middle pair of the wheels and a rear pair of the wheels; and the steering arrangement comprising at least one drag link for operating the middle pair of the wheels, at least one drag link for operating the rear pair of the wheels, pivot means which is pivotable between an on-road position in which the pivot means permits operation of the drag link for the middle pair of the wheels and not the rear pair of the wheels, and an off-road position in 2 which the pivot means permits operation of the drag link for the rear pair of the wheels and not the middle pair of the wheels, and mover means for moving the. pivot means between the on-road and the off-road positions.

The mover means may be an electric mover means, a pneumatic mover means, or a hydraulic mover means. A preferred electric mover means is a linear actuator.

The pivot means may be a sliding pivot means or a swinging link pivot means. The swinging link pivot means may comprise first and second arms which slide with respect to each-other on connecting members which are pivotally connected to the first and the second arms.

Usually, the first and the second arms will be positioned one on top of the other with the first arm being connected to the first and the second drag links.

Usually, the steering arrangement will include power steering means. Any suitable and appropriate known power steering means may be employed.

In a preferred embodiment of the invention, the all-terraIn vehicle has a steering box which sits just forward of a mid-axle centreline. An output shaft of the steering box is vertical. A rocker assembly sits on top of the output shaft. The rocker assembly has a 3 tilting axis which extends substantially longitudinally of the vehicle.

In a rear mode, a ball joint connecting a drag link to the mid axle steering gear is directly above, and aligned with, the steering box output shaft. Hence, steering inputs cause no motion in this drag link, and the mid wheels do not steer. They are however locked from moving around like castors. Hence, there is no need for any additional lock-out mechanisms, which can themselves present a failure mode problem.

When the rocker tilts from the rear steer to a mid steer position, the ball jointed drag link to the rear steering gear ends up directly above the steering box output shaft. Hence, only one actuator is needed, and the failure modes are simple and manageable.

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

Figure I is a schematic top view of an all-terrain vehicle of the invention; Figures 2 and 3 shows schematically the operation of a steering arrangement of the all-terrain vehicle shown in Figure 1, Figure 2 showing the position of pivot means for on-road conditions, and Figure 3 4 showing the position of pivot means for off-road conditions; Figure 4 is a perspective view of part of a first steering arrangement for effecting the movement of the pivot means between the positions shown in Figures 2 and 3; Figure 5 is a perspective view of part of a second spring arrangement for effecting the movement of the pivot means between the positions shown in Figures 2 and 3; Figure 6 is an end view of the part of the steering arrangement shown in Figure 5 corresponding to on-road conditions as shown in Figure 2; Figure 7 is an end view of the part of the steering arrangement shown in Figure 5 but corresponding to off-road conditions as shown in Figure 3; and Figures 8, 9 and 10 illustrate a preferred steering arrangement and the operation thereof.

Referring to Figure 1, there is shown part of an all-terrain vehicle 2 having six wheels 4 and a steering arrangement 6 for the wheels 4. As can be seen, the wheels 4 are so positioned on the vehicle 2 that they form a front pair of the wheels 4, a middle pair of the wheels 4, and a rear pair of the wheels 4.

The steering arrangement 6 comprises a drag link 8 for operating the middle pair of the wheels 4, and a drag link 10 for operating the rear pair of the wheels 4.. The steering arrangement 6 also comprises pivot means 12 which is movable between an,on-road position in which the pivot means 12 permits operation of the drag link for the middle pair of the wheels 4 and not the rear pair of the wheels 4, and an off-road position in which the pivot means 12 permits operation of the drag link 10 for the rear pair of the wheels 4 and not the middle pair of the wheels 4. The steering arrangement 6 still further comprises mover means (not shown in Figure 1) for moving the pivot means 12 between the on-road and the offroad positions.

Referring to Figures 2 and 3, there are shown the drag links 8, 10 and the pivot means 12. Also shown is a drag link 14 which is connected to a f ront axle for the front pair of the wheels 4. The pivot means 12 is movable as mentioned above. Figure 2 shows the position of the pivot means 12 for on-road driving of the vehicle 2. The pivot means 12 as shown in Figure 2 is adjacent the drag link 10. This means that the rear axle for the rear pair of the wheels 4 is fixed. The middle axle for the middle pair of the wheels 4 is able to give 50% of the turning movement that is achievable from the front pair of the wheels 4.

6 In the off-road driving condition for the vehicle 2, the pivot means 12 is moved to be adjacent the drag link 8 as shown in Figure 3. In this position of the pivot means 12, the middle axle for the middle pair of the wheels 4 is f ixed. The rear axle f or the rear pair of the wheels 4 is able to achieve 100% of the turning action of the front pair of the wheels 4. In the off-road driving condition, the rear pair of the wheels 4 will give a counter-steer, that is a steering angle equal to that achieved by the f ront pair of the wheels 4 but in the opposite direction.

Figure 4 shows a first steering arrangement 6 for perTnitting movement of the pivot means 12. As can be seen, the drag links 8, 10, 14 are connected to a bar 16. The pivot means 12 is moved by mover means 18. The mover means 18 comprises a cylindrical body 20 and a piston-device 22 which is movable in and out of the cylindrical body 20. The mover means 18 may be in the form of an electric mover means such as a linear motor. Alternatively, the mover means may be a pneumatic or a hydraulic mover means operating on a piston and cylinder arrangement. The mover means is able to move the pivot means 12 between the position shown in full lines and the position shown in dotted lines. The pivot means 12 is shown as a complete unit 7 which is physically moved between the required on-road position and off- road position.

Figure 5 is a perspective view of an alternative pivot means 12 which comprises first and second arms 24,' 26 which slide with respect to each other on connecting members 28, 30 as shown. The connecting members 28, 30 are pivotally connected to the first and the second arms 24, 26 by pivots 32. The first and the second arms 24, 26 are positioned one on top of each other as shown, with the f irst arm 24 being connected to the drag links 8, 10, 14, and the second arm being connected to a chassis part 34 of the vehicle 2 as shown in Figures 6 and 7. Fig-are 6 shows the position of the pivot means 12 corresponding to on-road driving conditions shown in Figure 2. Figure 7 shows the position of the pivot means 12 corresponding to the off-road driving conditions shown in Figure 3.

The vehicle 2 will usually be such that steering is effected by power steering means (not shown). Any suitable and appropriate known type of power steering means may be employed.

All-terrain vehicles which have six driven wheels need small turning circles in off-road driving conditions. For off-road driving conditions, a turning circle diameter of the order of 25ft is very 8 des--rable, as compared with a turning circle diameter of the order of 40ft when driving in on-road conditions. The steering arrangement used in the present invention enables the achievement of the required smaller turning circle in off-road driving conditions. Advantageously, the rear pair of the wheels 4 counter steers with the middle pair of the wheels being fixed during off-road steering as shown in Figure 3. This gives good control and stability, good climbing out of hollows and ruts, and equally good turning in reverse. It also reduces the steering lock angle for the front pair of the wheels 4 (for a given turning circle diameter), thereby enabling the easier production of required constant velocity joints. Still further, the steering arrangement 6 gives large steering changes for small wheel movements. For on-road driving conditions, the vehicle 2 is able to behave conventionally for stability at high speeds, for example on motorways.

This is permitted because the rear axle is locked straight ahead and the middle axle steers proportionally to its position in the overall wheel base of the vehicle 2. The middle axle will normally be centrally positioned between the front and rear axles but it need not be exactly centrally positioned if desired.

9 The vehicle of the present invention enables the required on-road and off- road steering to be achieved using identical hub units with track rods on all axles. Idler units are employed as shown in Figure 1. The longitudinally extending drag links, 8, 10, 12 interconnect between vehicle axles as shown in Figure 7. The steering wheel and the power steering box always directly control the front axle 38. The pivot means 12 and the mover means 18 enable the switching required for on-road conditions and off-road conditions.

Referring now to Figures 8, 9 and 10, there is shown a preferred steering arrangement and the operation thereof. In Figures 8, 9 and 10, the right hand side only of the all-terrain vehicle has been shown for ease of illustration. The preferred steering arrangement is such that a steering box sits just forward of a mid-axle centreline. An output shaft of the steering box is vertical. A rocker assembly sits on top of the output shaft. The rocker assembly has a tilting axis which extends substantially longitudinally of the vehicle.

In a rear mode, a ball joint connecting a drag link to the mid axle steering gear is directly above, and aligned with, the steering box output shaft. Hence., steering inputs cause no motion in this drag link, and the mid wheels do not steer. They are however locked from moving around like castors. Hence, there is no need for any additional lock-out mechanisms, which can themselves present a failure mode problem.

When the rocker tilts from the rear steer to a mid steer position, the ball jointed drag link to the rear steering gear ends up directly above the steering box output shaft. Hence, ony one actuator is needed, and the failure modes are simple and manageable.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Thus, for example, other types of pivot means 12 and mover means 18 to those shown may be employed.

CLAMS 1. An all-terrain vehicle comprising six driven wheels and a steering arrangement for the wheels: the wheels being so positioned on the vehicle such that they form a front pair of the wheels, a middle pair of the wheels, and a rear pair of the wheels; and the steering arrangement comprising at least one drag link for operating the middle pair of the wheels, at least one drag link for operating the rear pair of the wheels, pivot means which is movable between an onroad position in which the pivot means permits operation of the drag link for the middle pair of the wheels and not the rear pair of the wheels, and an off-road position in which the pivot means permits operation of the drag link for the rear pair of the wheels and not the middle pair of the wheels, and mover means for moving the pivot means between the onroad and the off-road positions.

2. An all-terrain vehicle according to claim 1 in which_ the mover means is an electric mover means, a pneumatic mover means, or a hydraulic mover means.

3. An all-terrain vehicle according to claim 2 in which the mover means is an electric mover means, and 12 in which the electric mover means is a linear actuator.

4. An all-terrain vehicle according to any one of the preceding claims in which the pivot means is a sliding pivot means.

5. An all-terrain vehicle according to any one of claims 1 - 3 in which the pivot means is a swinging link pivot means.

6. An all-terrain vehicle according to claim 5 in which the swinging link pivot means comprises first and second arms which slide with respect to each other on connecting members which are pivotally connected to the first and the second arms.

7. An all-terrain vehicle according to claim 6 in which the first and the second arms are positioned one on top of the other with the first arm being connected to the first and the second drag links.

8. An all-terrain vehicle according to any one of the preceding claims in which the steering arrangement includes power steering means.

13 9. An all-terrain vehicle according to any one of the preceding claims in which a steering box sits just forward of a mid-axle centreline, in which an output shaft of the steering box extends vertically, and in which a rocker assembly sits on top of the output shaft.

10. An all-terrain vehicle according to claim 9 in which the rocker assembly has a tilting axis which extends substantially longitudinally of the vehicle.

11. An all-terrain vehicle substantially as herein described with reference to the accompanying drawings.