GB2332406A

GB2332406A - Automobile chassis and steering mechanism

Info

Publication number: GB2332406A
Application number: GB9823144A
Authority: GB
Inventors: Raymond Henry Greenly
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-10-23
Filing date: 1998-10-23
Publication date: 1999-06-23
Anticipated expiration: 2018-10-23
Also published as: GB9823144D0; GB2332406A9; GB2332406B

Abstract

An automobile has a chassis with wheels in an elongated kite shaped layout. The automobile is provided with a steering mechanism suitable for either right or left hand drive which transmits motion to the fore and aft steered wheels so that the vehicle can not only turn in a smaller circle but also have lower ground clearances and centre of gravity, improved stability, better roadholding, cabin capacity and passenger protection.

Description

1 2332406 AUTOMOBILE CHASSIS AND STEERING MECHANISM

I, RAYMOND HENRY GREENLY, a British subject of 46 High Street, Corsham, Wiltshire, SN13 OHF, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it may be performed, to be particularly described in and by the following statement:-

This invention relates to a wheeled automobile with the wheels in a cruciform or kite shaped configuration, with a mechanism for steering the front and the rear wheels, whereby the operation of the steering wheel, which may be either on the right or the left hand side of the vellicle, results in the front wheel turning in one direction, and the rear wheel in the other direction, but by a precisely and automatically determined smaller amount, resulting in a much enhanced manoeuvrability, as well as better road-holding in general.

In this invention one wheel is placed at the front and one wheel at the rear of the chassis, both on the centre line running from front to back. Both these wheels are steerable. The other wheels are on the right and the left of the chassis on a line at right angles to that of the above centre line, equidistant to the right and to the left. These wheels are not steerable and are the driven wheels. There may be more than one wheel mounted at each end of this axle. The line of these middle wheels is closer to the front of the vehicle than to the rear, thus forming a cruciform or kite shaped layout. The distance from the cgntre of the kite shape to the rear wheel compared to that of the front wheel is termed the kite ratio. This ratio is considerably greater than one and may be typically about two.

In this invention the steering mechanism differs from a conventional Ackermann type mechanism. A longitudinal rod is mounted on the chassis which ultimately connects at the forward end with the front wheel and at the rearward end with the rear wheel. This rod can be rotated because it is provided with bearings at each end and if required one or more universal joints. Rotation is provided by a steering wheel which slopes down to a gearbox near the forward - end---of th - e---longitudinal-rodWhdn the-steering wheel is turne6-'the gearbox causes the longitudinal rod to rotate in the opposite sense. Fixed to each end of the longitudinal rod are arms at right angles pointing upwards. When the steering wheel is rotated these arms move in their respective planes parallel to the line of the middle wheels. These arms are of identical dimensions. Each arm is connected by suitable joints to a track rod which connects at the other ends respectively to the front and rear wheels via king pins and stub axles. Each of these track rods is of equal length. In the vehicle straight ahead position they are horizontal. At the front end of the vehicle the joint connecting the front track rod to the king pin is at a distance from the king pin's centre of rotation, which can amount to say D mm. At the rear end the joint connecting the rear end track rod to the king pin's centre of rotation is at a distance of D mro. multiplied by the kite ratio.

When the steering wheel is turned the front wheel will move by an angle and the rear wheel by a much smaller angle. The trigonometric tangent of the angle made by the front wheel 2- divided by the trigonometric tangent of the angle made by the rear wheel will always be equal to the kite ratio.

The king pins may not be absolutely vertical and need to take into account caster and king pin inclinations. On absolutely strict geometry the kite ratio may not be exactly invariable. As the lock increases each end of the track rods moves in circular motions. However these variations from any given exact ratio are entirely negligible and of no more practical importance than the similar inexactitudes arising from the Ackerman steering mechanism. In real life the forces arising when turning at speed, which for example results in the vehicle moving with slip angles on all wheels, are far more important.

In this invention all wheels may be independently sprung, provided with disc brakes, ABS.and electronic control systems, while steering mechanisms may be power assisted.

This invention greatly increases the manoeuvrability of vehicles in negotiating crowded towns and cities. It represents not just a marginal improvement but rather a quantum leap. To describe the comparisons which follow the term full lock is assumed to be when in Ackermann the inner front wheel makes an angle of say 35 degrees. For the kite layout described in this invention 35 degrees is the angle the front wheel makes when at full lock. These angles are assumed to be similar to avoid introducing misleading bias to the comparison. In each case the turning circle diameter is that made by the wheels of the vehicle when driven at full lock round a complete turn.

For example a large car with Ackermann layout might have a minimum turning circle of around 10 meters. With this invention a car of similar size could have a minimum turning circle of no more than 4 meters. A small conventional vehicle with a wheelbase of 1800 mm and track of 900 mm could have a minimum turning circle of about 7 meters. With this invention with the long wheelbase of 180Omm divided into 600 mm fore and 1200 mm aft (in this example a kite ratio of 2) the minimum turning circle could be no more than 3 meters. As a rule of thumb turning circles in this invention are less than 40% of those provided in conventional designs.

This great reduction in minimum turning circles across the entire spectrum of vehicle sizes greatly- improves the ability to manoeuvre. In the case of an articulated goods vehicle it is a major advantage especially when backing into a constricted space. This is also true when the articulation is of a trailer or caravan.

Even when articulation is not a factor, there is an additional advantage especially in urban situations where parking may be a problem. To drive into a tight space with a conventional vehicle may leave the rear of the vehicle protuding so that it may then be necessary to go back and forwards to "tuck one's tail in". Because of this drivers often back in first.

With this invention parkability would be greatly improved. It may be possible to drive into a space in one attempt. The wheels would then be in the exit position and it may be possible to exit without further ado. In any event the amount of manoeuvring needed to enter or to leave a parking space is greatly reduced.

With this invention the natural position of the motor propelling the vehicle is amidships, that is driving the nonsteered wheels. In conventional layouts, there are three major 1 categories of design, none of which is entirely satisfactory. Many vehicles have the motor in the front and drive the rear wheels via a cardan shaft running longitudinally to the differential at the rear. In many vehicles the motor and it's drive train is at the rear. In others the motor is at the front driving the steered wheels. All of these systems have in practice important disadvantages too numerous and diverse to cite in any detail the subject of interminable debates. They concern such matters as understeer or oversteer, roll angles, centres of gravity under varying loading and so on.

In this invention the motor being amidships avoids or at least mitigates many of these dilemmas. The motor and associated driving trains actuating the middle wheels are closer to the vehicle's centre of gravity. ' This improves the vehicle's stability, roadholding and drivability characteristics.

Further, the wheelbase being divided into fore and aft sections means that the driving train, the heaviest part of the chassis, can be closer to the ground than with conventional designs. This reduction in ground clearance with the resulting lowering of the centre of gravity provides important dynamic benefits. To cite just one example - the recent problem with the "elk test" which sent the Mercedes designers back to the drawing board. The kite format is inherently more stable due to the ability to incorporate a much lower centre of gravity.

Considering road surface irregularities, the effect of a transverse ridge or gully would hit the front wheel first, then the mid wheels, and finally the rear wheel. Spreading the shocks over three events rather than two would result in a smoother ride. If the road bump or pothole were a singleton, wherever it occurred in relation to the wheels, the chances of a disturbance are at worst no greater than with a conventional layout and at best could be lesser. As well as road surface irregularities it is important to consider the effects of wind. A side wind would be less likely to cause a disturbance to a vehicle with an engine amidship than with conventional designs.

Another benefit arising from this invention is the ability to provide more volumetric capacity to the cabin of the vehicle. This is because the ratio of the wheel-track to the wheel-base can be increased. Coupled with the ability toreduce the groundclearance, the ability to make the cabin even slightly more closely spherical is important. For example, a mere 2% advantage in each of the 3 dimensions amounts to 6% in total.

Considering now crash resistances, the conventional layout exposes all wheels to view. In this invention, only middle wheels in the strong midships of the vehicle are exposed, thus improving the ability to increase the wrap around passenger protection.

q_ Figure 1 shows configuration. Figure 2 shows schematically in plan the wheels at full lock on a left turn. Figure 3 shows a schematic isometric perspective of the steering mechanism at full lock on a left turn, with the steering wheel on the right side of the vehicle. Figure 4 shows a schematic isometric perspective of the steering mechanism at full lock on a left turn, with the steering wheel on the left side of the vehicle. Figure 5 shows turning circles with this mechanism compared with conventional mechanisms.

schematically a plan of the kite shaped

Claims

1. An automobile vehicle with wheels arranged in cruciform or kite formatiion with one steerable wheel disposed at the front of the vehicle and one steerable wheel disposed at the rear of the vehicle, both on the longitudinal centre line thereof, the wheels at the sides of the vehicle being driven. The steerable wheel at the front of the vehicle is much closer to the point where the line of the side wheels intersects the longitudinal centre line than that of the steerable wheel at the rear of the vehicle. The ratio of the rear distance to the front distance may be typically about double. When the steering wheel is rotated the front wheel on its stub axle is rotated around its king pin in the appropriate direction while that carrying the rear wheel is rotated in the opposite direction. The mechanism is constructed so that the ratio of the trigonometrical tangent of the angle turned by the front wheel to the trigonometrical tangent of the angle turned by the rear wheel is always equal to the ratio of the distance of the centre of the rear wheel from the point of intersection of the kite layout to the distance of the centre of the front wheel to the point of intersection of the kite layout. The steerable wheels may be actuated by mechanisms suitable for either right hand or left hand drive.

2. An automobile vehicle substantially as described herein with reference to figures 1-5 of the accompanying drawings.

2. An automobile vehicle as described in claim one which provides for smaller turning circles and ease of parking than are feasible with conventional designs.

3. An automobile vehicle substantially as described herein with reference to figures 1-5 of the accompanying drawings.

6 Amendments to the claims have been filed as follows 1. An automobile vehicle suitable for driving either on the right or on the left hand side of the road with wheels arranged in cruciform or kite formation with one steerable wheel disposed at the front of the vehicle and one steerable wheel disposed at the rear of the vehicle, both on the longitudinal centre line thereof, the wheels at the sides of the vehicle being driven, the steerable wheel at the front of the vehicle being at a distance from the point of intersection of the line of the driven wheels with the above mentioned longitudinal centre line proportionately smaller than the corresponding distance of the steerable wheel at the rear of the vehicle from the above mentioned point of intersection, so that when a steering wheel of the vehicle is turned the front wheel turns in the desired direction and the rear wheel is turned in the opposite direction, the ratio of the trigonometrical tangent of the angle turned by the front wheel to the trigonometrical tangent of the angle turned by the rear wheel being always equal to the ratio of the distance of the centre of the rear wheel from the point of intersection of the kite layout to the distance of the centre of the front wheel to the point of intersection of the kite layout.