GB2059887A - Wheels for vehicles - Google Patents

Abstract

A wheel for a vehicle comprises a hub 10, a wheel rim 12, and radially deformable means, e.g. telescopic spokes 13, which connect the hub and rim and whose deformation is controlled, e.g. by springs 14. The wheel rim 12 may be flexible so that the part thereof in contact with the ground conforms to the contour of the ground, or may be rigid. The wheel serves to provide or contribute to the spring suspension of a vehicle to which it is fitted, and the adhesion between the wheel and the ground is also improved. Electrical, mechanical, pneumatic or hydraulic means may be provided to successively extend and contract the spokes 13, in such manner as to impart rotation to the wheel. In an alternative construction the spokes are replaced by leaf springs interconnecting the hub and rim. <IMAGE>

Description

SPECIFICATION Improvements in or relating to ground-engaging wheels for vehicles The invention relates to ground-engaging wheels for vehicles and sets out to provide a wheel which is particularly suitable for use on uneven ground and on vehicles requiring high manoeuvrability with improved adhesion between the wheel and the ground. A wheel according to the invention may also require low levels of energy consumption.

In conventional powered vehicles considerable energy losses occur in the transmission between the power source and the wheels, particularly in view of the necessity of providing a spring suspension between the wheels and the vehicle body. This necessity also imposes limitations on the design of steering mechanisms and this, in turn, tends to limit the manoeuvrability of conventional vehicles.

Attempts have been made to overcome these problems by providing individual power units mounted on each wheel, the power units usually being in the form of hydraulic or electric motors. Although this can reduce transmission losses and increase manoeuvrability, the use of conventional power units in the wheels leads to an increase in the unsprung weight of the vehicle, and the problem of co-ordinating the drive to the wheels under varying operating conditions.

The invention sets out to provide a groundengaging wheel which may improve the adhesion between the wheel and the ground, which may provide or contribute to the spring suspension of the vehicle, and which may also, in some embodiments, incorporate its own power unit in a manner to reduce transmission losses.

According to the invention a ground-engaging wheel for a vehicle comprises a hub, a wheel rim encircling the hub and spaced therefrom, radially deformable means connected between the hub and the wheel rim, and means for controlling the radial deformation of said means.

Preferably the wheel rim is flexible so that the part thereof in contact with the ground conforms to the contour of the ground. This may improve adhesion due to the increased area of contact between the wheel and the ground.

In use of the wheel on a vehicle, the hub is rotatably mounted on an axle which is fixed or, in the case of a steerable wheel, is mounted for steering movement. Under the weight of the vehicle, the lower part of the flexible wheel rim conforms to the contour of the ground and thus deforms towards the hub, causing corresponding deformation of the deformable means connecting the hub to the wheel rim. This controlled deformation of the deformable means contributes to, or constitutes, the spring suspension of the vehicle, and the conventional spring suspension between the mounting for the wheel and the body of the vehicle may not be necessary.

Said radially deformable means may comprise a plurality of springs connected between the hub and the wheel rim, the radial deformation of said springs being controlled, at least in part, by the resilience thereof. For example, the springs may be leaf springs capable of bending resiliently in the general plane of the wheel. Each leaf spring may be pivotally connected to the hub and wheel rim respectively for pivoting relative thereto about axes parallel to the axis of rotation of the wheel.

There may be provided two sets of springs so disposed that the circumferential forces applied to the wheel rim by the two sets of springs respectively act in opposite directions and hence cancel each other out.

In an alternative embodiment said radially deformable means comprise a plurality of eleongate spoke elements connected between the hub and the wheel rim, each spoke element being longitudinally extensible and contractable, and means being provided to control the extension and contraction thereof.

The means for controlling extension and contraction of each spoke element may comprise means biasing the spoke element towards the extended condition and opposing contraction of the spoke element.

Means may be provided for extending the spoke elements of the wheel successively and selectively as the wheel rotates. The means for extending the spoke elements may comprise hydraulic, pneumatic, electrical, mechanical or electro-mechanical means.

For example, the means for extending the spoke elements successively and selectively may also comprise a cam follower on each spoke which cooperates with a fixed cam track.

The means for extending the spoke elements may be double acting so as also to contract the spoke elements successively and selectively during rotation of the wheel.

Although the wheels may be used merely to provide spring suspension, one or more of the wheels on the vehicle is preferably self-powered so as also to provide or contribute to the motive power for the vehidle. In this case said means are arranged to extend the spoke elements successively and selectively in a manner to impart rotation to the wheel when the wheel rim is in engagement with the ground.

Preferably the wheel rim is inextensible in the peripheral direction and means are provided for accommodating the change in geometry required upon longitudinal contraction and extension of the spoke elements. For example, each spoke element may be connected to the hub for pivotal movement relatively thereto about an axis substantially paral lel to the axis of rotation of the wheel.

In this case, if means are provided biasing the spoke elements towards the extended condition, the wheel will be in unstable equilibrium and the biasing means will tend to rotate the hub relatively to the wheel rim until a position of stable equilibrium is reached. Preferably, therefore, means, for example resilient means, are provided for limiting the pivotal movement of each spol < e element relatively to the hub.

Alternatively the spoke elements may be connected between the hub and the flexible wheel rim in pairs so that the biasing force applied to one spoke element of the pair is opposed by the biasing force applied to the other spoke element of the pair.

In the accompanying drawings: Figure 1 shows diagrammatically a ground engaging wheel in accordance with the invention, Figure 2 shows an alternative form of wheel, Figures 3 and 4 show diagrammatically alternative methods for overcoming the inherent instability of the wheel of Fig. 2, and Figure 5 shows a typical configuration adopted by the wheel of Fig. 2 when mounted on a vehicle and in engagement with the ground.

Referring to Fig. 1, the wheel comprises a central hub 10 capable of revolving freely about a fixed axle 11 on the vehicle which supports it but does not provide any rotational restraint. The flexible outer rim 1 2 of the wheel is substantially non-elastic in the peripheral direction and may therefore be considered of constant length. The wheel rim may, for example, be formed from spring steel having laminated thereto an outer peripheral surface of rubber or similar material.

Twelve spokes 9 connect the wheel rim 1 2 to the hub 10, although any other suitable number may be provided. Each spoke 9 comprises a leaf spring attached to the hub at one end and to the wheel rim 1 2 at the other end, and capable of bending in the plane of the wheel. Each spring is preferably attached to the hub and rim respectively by pivotal connections so as to pivot relatively thereto about axes parallel to the axis of rotation of the wheel. Each leaf spring has sufficient axial depth to resist axial forces on the wheel. Any unacceptable tendency of the rim to rotate around the hub under the action of the forces applied by the leaf springs may be counteracted by suitable spring design.Alternatively there may be provided two sets of springs so disposed that the circumferential forces applied to the wheel rim by the two sets of springs respectively act in opposite directions and cancel each other out.

In the alternative embodiment shown in Fig. 2, twelve extensible and contractable spokes 1 3 connect the wheel rim 1 2 to the hub 10, although any other suitable number may be provided. Each spoke, which may comprise two or more telescoping parts 14, 15, is biased towards the extended condition by a spring 1 6. The radially inner end of each spoke is connected at 1 7 to the hub for pivotal movement relatively thereto about an axis substantially parallel to the axis of rotation of the wheel, and the radially outer end of the spoke is similarly pivotally connected at 18 to the wheel rim.

Instead of the wheel rim 1 2 being resilient, the rim may be formed of material having zero bending stiffness in which case the rim will adopt the position indicated in dotted lines at 12a in Figs. 2 and 5.

In the arrangement shown diagrammatically in Fig. 3, the spokes 1 3 are arranged in pairs oppositely inclined between the wheel rim 1 2 and hub 10 so that the biasing force on one spoke of the pair is balanced by the biasing force on the other spoke of the pair. In the alternative arrangement shown diagrammatically in Fig. 4, springs 19 are arranged between each spoke 1 3 and lugs 20 or bosses secured to the hub. It will be appreciated that such means may not be necessary if the spokes are so mounted on the hub that the force applied to the hub by each spoke, when under load, passes through the central axis of rotation of the hub.

The pivotal connections 17, 1 8 between the spokes and the hub and wheel rim are necessary owing to the change in geometry which occurs when the wheel rests on the ground under the weight of the vehicle as shown in Fig. 5, and under the effect of the propulsive forces. Since the wheel rim 1 2 is effectively of constant peripheral length it is necessary for the angle between adjacent spokes to increase as the spokes contract. The radially inner ends of the spokes could be rigidly connected to the hub 10 but in this case the connections between the radially outer ends of the spokes and the wheel rim must be such as to permit the contraction of the spokes without corresponding increase in the angle between them.

Where the spring biasing force is the sole force acting on the spokes, the wheel will remain in equilibrium when it is resting on the ground under the weight of the vehicle and is deformed as shown in Fig. 5. In this case the outwardly-biased spokes serve merely to provide or supplement the necessary spring suspension for the vehicle.

The unsprung mass of the wheel is quite small and consists in the main of that part of the rim in contact with the ground and those portions of the spokes which are directly connected to this part of the rim. The portions of the spokes connected directly to the hub do not move radially and are free to move only a small amount angularly and hence their mass is not a direct part of the unsprung mass. For this reason, and because the wheel can accommodate ground irregularities of large amplitude (say, up to half the radius of the wheel) it is feasible to connect the wheel axle to the vehicle without the use of an intermediate spring of large amplitude.

The biasing force on the spokes may be provided by means other than the spring indicated, for example by pneumatic, hydraulic, mechanical or electro-mechanical means.

When the wheel is loaded, as shown in Fig.

5, the exact wheel shape will be determined by the stiffness of the springs 1 6 on the spokes 1 3 and by the moment of resistance of the resilient rim 1 2. The area of contact between the rim and the ground may be varied to a certain extent by changing these stiffness parameters.

However, if it is wished to enlarge the contact area more than is possible by such means, means may be provided to adjust the spoke lengths beyond the lengths naturally adopted to support the weight of the vehicle.

For example, each spoke may carry a cam follower which co-operates with a fixed cam track on the body of the vehicle. The cam follower is attached to a guide sleeve which is free to slide on the portion 1 4 of each spoke, the spring 1 6 being formed in two parts on opposite sides of the sleeve so as to oppose sliding movement thereof. Hence the cam followers are forced to follow the cam track profile under the action of the springs, and the ground contact area of the wheel can be varied by use of a suitable cam track profile.

A wheel according to the invention may simply provide or supplement the vehicle suspension as described above, in which case it may be free-running or driven through its hub in conventional fashion. However, the wheel may also provide a part or all of the power drive for the vehicle, and in the embodiment of Fig. 2 the drive may be supplied by the successive and selective extension of the spokes of the wheel. To this end there is provided, in addition to the biasing means described above, or instead of the biasing means, power means for extending the spokes successively and selectively in a manner to impart rotation to the wheel. Referring to Fig.

5, it will be seen that application of an extension force to spokes connected to a part of the wheel rim in engagement with the ground to the left of the wheel axis will impart clockwise rotation to the wheel. The extension force on the spokes may be applied pneumatically, hydraulically, mechanically or electromechanically. The arrangement may be double-acting so that as the wheel rotates clockwise the spokes connected to the part of the wheel rim in contact with the ground to the righthand side of the wheel axis are contracted as the wheel rotates.

Various means may be provided for controlling the extension, or extension and contraction, of the spokes. For example each spoke may carry at some fixed distance along its length a reversible switch determining the application of the extension or contraction force along the spoke to which the switch is connected. The switches on only those spokes connected to part of the wheel rim in contact with the ground engage with a cam whose working surface consists of a straight edge parallel to the wheel surface and capable of being inclined at a variable angle to the ground by the vehicle driver. Such a mechanism enables the driver to control the magnitude and direction of the tractive force.

Since the driver thus controls the polarity of the force applied to the spokes, a braking force rather than a driving force can be applied to the vehicle if required by applying to the spokes on the forward-running side of the wheel a force which opposes the contraction of those spokes as the wheel rotates.

In the arrangements described the extension forces applied to the spokes are applied in the plane of the wheel. However in an alternative arrangement the spokes may be so arranged that they may deform the wheel rim laterally outside the general plane of the wheel and this may be used to effect or assist in steering of the vehicle.

It will be appreciated that it is not essential for the wheel rim to be flexible so as partly to conform to the contour of the ground. The invention is also applicable to an arrangement having a conventional rigid wheel rim connected to the hub by extensible and contractable spokes. Such spokes may provide suspension and propulsive force to the wheel in this case also.

As previously mentioned, the invention includes within its scope any arrangement where the hub and rim of the wheel are connected by a structure which is radially deformable in a controlled manner. For example, the effect of a plurality of resilient or extensible spokes and the means for stabilising their action may be provided by any form of continuous elastic disc between the hub and the rim. The disc would incorporate means for distorting the shape of the disc and rim.

Claims (18)

1. A ground-engaging wheel for a vehicle comprising a hub, a wheel rim encircling the hub and spaced therefrom, radially deformable means connected between the hub and the wheel rim, and means for controlling the radial deformation of said means.

2. A wheel according to claim 1, wherein the wheel rim is flexible so that the part thereof in contact with the ground conforms to the contour of the ground.

3. A wheel according to claim 1 or claim 2, wherein said radially deformable means comprise a plurality of springs connected be tween the hub and the wheel rim, the radial deformation of said springs being controlled, at least in part, by the resilience thereof.

4. A wheel according to claim 3, wherein said springs are leaf springs capable of bending resiliently in the general plane of the wheel.

5 A wheel according to claim 4, wherein each leaf spring is pivotally connected to the hub and wheel rim respectively for pivoting relative thereto about axes parallel to the axis of rotation of the wheel.

6. A wheel according to any of claims 3 to 5, wherein there are provided two sets of springs so disposed that the circumferential forces applied to the wheel rim by the two sets of springs respectively act in opposite directions and hence cancel each other out.

7. A wheel according to claim 1, wherein said radially deformable means comprise a plurality of elongate spoke elements connected between the hub and the wheel rim, each spoke element being longitudingally extensible and contractable, and means being provided to control the extension and contraction of the spoke elements.

8. A wheel according to claim 7, wherein the means for controlling extension and contraction of each spoke element comprise means biasing the spoke element towards the extended condition and opposing contraction of the spoke element.

9. A wheel according to claim 7 or claim 8, wherein means are provided for extending the spoke elements of the wheel successively and selectively as the wheel rotates.

10. A wheel according to claim 9, wherein the means for extending the spoke elements comprise hydraulic, pneumatic, electrical, mechanical or electro-mechanical means.

11. A wheel according to claim 9 or claim 10, wherein said means are arranged to extend the spoke elements successively and selectively in a manner to impart rotation to the wheel when the wheel rim is engagement with the ground.

1 2. A wheel according to claim 9, wherein said means for extending the spoke elements successively and selectively comprise a cam follower on each spoke which cooperates with a fixed cam track.

1 3. A wheel according to any of claims 9 to 12, wherein said means for extending the spoke elements are double acting so as also to contract the spoke elements successively and selectively during rotation of the wheel.

14. A wheel according to any of claims 7 to 13, wherein the wheel rim is inextensible in the peripheral direction and means are provided for accommodating the change in geometry required upon longitudinal contraction and extension of the spoke elements.

1 5. A wheel according to claim 14, wherein each spoke element is connected to the hub for pivotal movement relatively thereto about an axis substantially parallel to the axis of rotation of the wheel.

1 6. A wheel according to claim 15, wherein resilient means are provided for limiting the pivotal movement of each spoke element relatively to the hub.

1 7. A wheel according to claim 15, wherein the spoke elements are connected between the hub and the wheel rim in pairs so that the biasing force applied to the one spoke element of the pair is opposed by the biasing force applied to the other spoke element of the pair.

18. A ground-engaging wheel for a vehicle, substantially as hereinbefore described with reference to Fig. 1, Figs. 2 and 5, Fig. 3, or Fig. 4 of the accompanying drawings.

1 9. A vehicle having one or more groundengaging wheels according to any of the preceding claims.