Land vehicles – Wheeled – Running gear
Patent
1991-03-11
1992-08-11
Rice, Kenneth R.
Land vehicles
Wheeled
Running gear
180140, B62D 602
Patent
active
051372916
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a rear wheel steering arrangement for a motor vehicle, and in particular to a steering arrangement where all four wheels of the car are steered.
Various designs of four wheel steering systems are known. In such systems, the front wheels are always the fundamental steering components, and turning of the front wheels is the major controlling factor on the steering of the vehicle. The rear wheels are steered to a lesser degree; at low speeds to assist in parking and manoeuvring and at high speeds to improve handling and stability of the vehicle. At low speeds it is conventional to turn the rear wheels in the same direction as the front wheels whilst at high speeds it is conventional to turn the rear wheels in the opposite sense to the front wheels.
These different requirements are accomplished in various different ways by known four wheel steering systems, but it is normally the case that the rear wheel suspension/drive/steering arrangement requires considerable modification as compared with a conventional vehicle with non-steered rear wheels. This leads to added complexity and cost, and may compromise the suspension layout.
SUMMARY OF THE INVENTION
According to the invention there is provided a rear wheel steering arrangement for a motor vehicle, the arrangement including a pair of rear wheels which are each connected to the vehicle by a forward and by a rearward transverse suspension arm, and a steering mechanism which has an input and an output, characterised in that the output of the steering mechanism is connected to a common actuator mounted on the vehicle so that movement of the steering mechanism output produces movement of the actuator on either side of :he vehicle centreline, the inboard ends of two of the suspension arms, one on each side of the vehicle, being connected to the actuator so that they are moved transversely in common by the common actuator to produce a steering action on the rear wheels.
This arrangement allows the inboard ends of the suspension/steering arms to be kept close to the centre line of the vehicle and this has significant advantages for the suspension geometry of the steered wheels. Because one set of arms is able to act both as suspension and as steering links and no dedicated steering links are required, considerable complexity reductions can be made.
In one form of the invention, the inboard ends of the suspension arms may be connected to the common actuator which is pivoted at a fixed point on the centreline of the vehicle.
The fact that the actuator is pivoted on a fixed part of the vehicle (or on a chassis sub-frame) has the result that the pivot bearing supports a substantial part of the load which would otherwise be carried directly by the steering mechanism output.
The steering mechanism may be a conventional end take-off steering gear with the take-off shaft being mounted to one or other side of the vehicle centreline and connected to the common actuator through a transfer linkage.
The common actuator may be pivotally mounted on the steering mechanism housing, the housing itself being rigidly mounted to the vehicle body.
The transfer linkage preferably takes the form of a hinged link which is hinged at one end to an arm mounted on the steering mechanism take-off shaft and-at the other end to the common actuator.
The steering arms may be connected to the actuator through flexible joints which preferably incorporate rubber bushes.
In another form of the invention, the common actuator is in the form of a slide member which is slidably mounted on a transversely extending body member of the vehicle between the rear wheels, the steering mechanism is arranged to drive the slide member to and fro along the transverse member, and the suspension/steering arms are connected to the slide member so that a steering action is produced as the slide member moves along the transverse member.
The steering mechanism can be a motor (electrical or hydraulic) which is controlled by a control unit which determines the desired ste
REFERENCES:
patent: 4505491 (1985-03-01), Sano et al.
patent: 4787645 (1988-01-01), Ohbayashi et al.
Brunning Alan D.
Woods Peter R.
Coppiellie Raymond L.
Ford Motor Company
May Roger L.
Rice Kenneth R.
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