GB2344800A

GB2344800A - Vehicle steering

Info

Publication number: GB2344800A
Application number: GB9827949A
Authority: GB
Inventors: William Richard Hutchins
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1998-12-19
Filing date: 1998-12-19
Publication date: 2000-06-21
Anticipated expiration: 2018-12-19
Also published as: GB9827949D0; GB2344800B

Abstract

A suspension for a pair of front steerable vehicle wheels 10, 12, includes a beam axle 12 located laterally be means of a Watts linkage 20. The steering linkage is also in the form of a Watts linkage 36 of which the central link 38 is pivotably connected to a steering input member 40 movable laterally of the vehicle to steer the wheels. As the wheels move vertically, the two Watts linkages operate parallel to one another and the steering angle of the wheels is therefore substantially unaffected.

Description

Vehicle Steering The present invention relates to vehicle steering and is particularly useful in vehicles with beam axles.

It can be a problem with vehicle steering systems, particularly with front beam axles, that vertical movement of the steered wheels produces undesirable steering effects. This is because, as the wheels move vertically relative to the vehicle body, they also move relative to the steering box or rack. If the steering rods are of a fixed length, which is conventionally the case, the change in distance from the steering box or rack to the wheels produces a steering effect.

The present invention provides a steering and suspension system for a pair of steerable wheels of a vehicle comprising two steering knuckles on which the wheels can be mounted, support means on which the steering knuckles are pivotably mounted for rotation about respective steering axes, a locating Watts linkage having its central link pivotably connected to the vehicle body and its ends connected to the support means to provide lateral location thereof relative to the body, and a steering mechanism comprising steering Watts linkage having its outer links connected to the steering knuckles at points offset from the steering axes, and its central link connected to a steering input means and movable laterally of the vehicle to steer the wheels.

Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawing which is a schematic perspective view of a system according to the invention.

Two steerable front wheels 10,12 of a vehicle are mounted on respective steering knuckles 14,16, which in turn are rotatably mounted on opposite ends of a beam axle 18 such that they can be rotated relative to the beam axle about respective steering axes X-X, Y-Y. A lateral location Watts linkage 20 has the outer ends of its two outer links 22,24 pivotably connected to the ends of the beam axle 18, and the centre of its central link 26 mounted on the vehicle body by means of a bracket (not shown) such that it is rotatable about a horizontal axis Z-Z which runs longitudinally of the vehicle on its centre line. This linkage 20 provides lateral location of the beam axle, and therefore of the wheels 10,12 relative to the body.

A steering arm 28,30 extends forwards from each of the steering knuckles 14, 16, and has its front end pivotably connected to the end of a respective outer link 32,34 of a second Watts linkage 36 which is a steering linkage. The central link 38 of this steering linkage is pivotably connected to a steering input member 40 which is movable laterally of the vehicle in the direction of the arrow A. This member 40 can be connected to any form of steering input such as a steering box or a steering rack.

A track control rod 42 has each of its ends pivotably connected to a track control arm 44,46 extending from the rear of a respective one of the steering knuckles 14,16. This controls the relationship between the steering angles of the two wheels 10,12, keeping them essentially parallel to each other as they are steered from side to side.

The two Watts linkages 20,36 are arranged to be symmetrical, their central links 38,26 being of the same length and their outer links 22,24,32,34 being the same length. Also when the wheels 10,12 are in the straight ahead position the pivot axis of the central link 38 of the steering linkage is aligned with that Z-Z of the central link 26 of the lateral location linkage. This means that as the beam axle 18 moves vertically relative to the body the two Watts linkages will operate parallel to one another, and the outer ends of their outer links 22,32, connected to the right steering knuckle will remain in the same fixed relationship relative to each other, as will the outer ends of the two outer links 24,34 connected to the left steering knuckle. The steering angle of the wheels 10,12 is therefore substantially unaffected by vertical wheels travel.

It will be appreciated that the beam axle can be connected to the vehicle body in a variety of known ways which will generally include load bearing springs and some form of longitudinal location relative to the body. It will also be appreciated that, although no means of driving the wheels 10,12 is shown, this type of steering and suspension arrangement has particular application in off-road vehicles which generally have four wheels drive. To this end drive can be provided in any known manner, such as via a differential mounted on the beam axle.

Claims

CLAIMS 1. A steering and suspension system for connecting a pair of steerable wheels to a vehicle body, the system comprising two steering knuckles on which the wheels can be mounted, support means on which the steering knuckles are pivotably mounted for rotation about respective steering axes, a locating Watts linkage having its central link pivotably connectable to the body and its ends connected to the support means to provide lateral location thereof relative to the body, and a steering mechanism comprising steering Watts linkage having its outer links connected to the steering knuckles at points offset from the steering axes, and its central link connected to a steering input means and movable laterally of the body to steer the wheels.
2. A system according to claim 1 wherein the support means comprises a rigid beam having the steering knuckles supported on its ends.
3. A system according to claim 1 or claim 2 further comprising a track control link connected between the steering knuckles to control the relationship between the steering angles of the two wheels.
4. A system according to any foregoing claim wherein the wheels are driven wheels and the system further comprises drive means for transmitting drive torque to the wheels.
5. A system according to any foregoing claim wherein the central links of the two Watts linkages are of substantially the same length.
6. A system according to any foregoing claim wherein the outer links of the two Watts linkages are of substantially the same length.
7. A system according to any foregoing claim wherein the central links of the two Watts linkages mounted such that, when the wheels are in the straight-ahead position, the pivot axes of the central links of the two Watts linkages are aligned with one another.
8. A steering and suspension system for a vehicle substantially as hereinbefore described with reference to the accompanying drawings.