The object of the invention is a suspension arrangement for the wheels of a vehicle as defined in the preamble of claim 1.

The solution according to the invention is particularly suited to vehicles intended to move in off-road terrain. In these types of vehicles, such as in e.g. various power tools and forest machinery, the properties of the wheels and tyres and the suspension solutions of the wheels are important, because they essentially affect how the vehicle travels in possible rough terrain. The grip between the tyres and the underlying surface must be good so that the tyres do not slip in bad terrain. In. addition, the wheels and tyres must also be suited to moving on an uneven underlying surface and to passing over various obstructions, in which case the suspension of the wheels is of critical importance. The biggest problem in off-road driving is known to be slipping of the wheels and passing over various obstructions, which considerably hampers moving in off-road terrain. Another problem is the tyre structures according to prior art, in which tyres a stiff frame must be used for achieving sufficient counter- force to the force produced by carrying a load and by an ob- struction. This counterforce is produced almost entirely from a rise in the air pressure of the tyre and the air pressure is directed at the whole area of the inner part of the tyre. In order for the deformation of the surface of the tyre to remain within reasonable bounds, a stiff structure and high air pressure must be used, which properties in turn stiffen the adaptability of the contact surface. A tyre thus comprises only two load-bearing structures, i.e. the sides of the tyre. The aim of this invention is to eliminate the aforementioned drawbacks and to achieve a suspension arrangement for the wheels of a vehicle, by the aid of which, inter alia, the locomotion of various off-road vehicles in rough terrain is fa- cilitated. The suspension arrangement according to the invention is characterized by what is presented in the characterization part of claim 1. Other embodiments of the invention are characterized by what is disclosed in the other claims. One advantage of the solution according to the invention is that it improves the grip of tyres and the ability to pass over obstructions in, inter alia, vehicles being driven in rough terrain, such as in various power tools and forest machinery. From this follows the advantage that locomotion with off-road vehicles in difficult terrain becomes easier and it is possible to access more difficult locations with them. Another advantage is that very lightweight and low-profile tyres with very high lateral stiffness can be used. In this case, the force produced by one contact patch does not really raise the internal pressure. At the same time the ability of the contact patch to flex is retained, i.e. it . is able to grip better.

In the following, the invention will be described in more de- tail by the aid of some examples of its embodiment with reference to the attached drawings, wherein

Fig. 1 presents an oblique view from the side and top of one suspension arrangement according to the inven- tion for a wheel of a vehicle, in which suspension arrangement the second wheel is removed for the sake of graphical clarity,

Fig. 2 presents an oblique view from the side and top of one suspension arrangement according to the inven- tion for a wheel of a vehicle, in which suspension arrangement both wheels of one axle system are in their positions,

presents a rear view of one suspension arrangement according to the invention for a wheel of a vehicle, in which suspension arrangement both wheels of one axle system are presented when cross-sectioned, presents a top view of one suspension arrangement according to the invention for a wheel of a vehicle, in which suspension arrangement one wheel of one axle system is presented when sectioned,

presents an oblique view from the side and top of one suspension arrangement according to the invention for a wheel of a vehicle, in which suspension arrangement one wheel of one axle system and a part of the axle system are presented when sectioned, presents a top view of one suspension arrangement according to the invention for a wheel of a vehicle, in which suspension arrangement one wheel of the axle system is, e.g. owing to an obstruction, turned outwards in its direction of travel,

presents a front view of one suspension arrangement according to the invention for a wheel of a vehicle, in which suspension arrangement both wheels of one axle system are presented when cross-sectioned, and wherein the wheels are inclined to the side according to the shapes of the terrain,

presents a diagrammatic and simplified side view of the principle of a suspension arrangement according to the invention for a wheel of a vehicle,

presents a diagrammatic, simplified and oblique rear view of the principle of a suspension arrangement according to the invention for a wheel of a vehicle in different operating, situations,

presents a simplified, diagrammatic and oblique view from the top and side of one sectioned tyre to be used in an arrangement according to the invention, and

Fig. 11 presents a simplified and diagrammatic view of a part of a cross-section of the tyre according to Fig. 10.

Fig. 1 presents one suspension arrangement according to the invention for wheels of a vehicle at the point of one axle system, seen obliquely from the side and from above. The sus- pension arms 2 of the wheels 1 are pivoted at their first ends to a coupling part 3 of the suspension by the aid of a joint 12. The suspension arms 2 are comprised of two parts. In its initial position, when the vehicle is e.g. on a flat underlying surface, the first parts, i.e. the frame parts 2a, of the suspension arms 2, which parts are fixed at their first ends in a pivoted manner to the coupling part 3 of the axle system, point from the coupling part 3 straight to the side and sloping slightly downwards from the horizontal plane, after which there is an angle in the frame parts 2a and the direction of the frame parts 2a changes to sloping slightly upwards.

A second part of the suspension arm 2 is fixed at its first end to the second end of the frame part 2a of both suspension arms 2, i.e. said second part being a suspension rod part 2b of essentially a roughly semicircular shape or of a corresponding angularly shaped structure, which suspension rod part points at first with its first part orthogonally with respect to the frame part 2a e.g. forwards in the direction of travel of the vehicle and turns to point with its second part obliquely downwards and at the same time obliquely towards the wheel 1 almost immediately beside its fixing point. After this the suspension rod part 2b of the suspension arm 2 travels with its third part some distance essentially straight downwards and at the same time slightly more obliquely towards the wheel 1, after which the suspension rod part 2b turns to point with its fourth, i.e. last, part back, e.g. towards the rear, and at the same time again slightly more obliquely towards the wheel 1, which fourth part forms a curved end part of an essentially semicircular curve. The fourth part of the suspension rod part 2b forms the second end of the suspension rod part 2b of the suspension arm 2 and extends at its free end essentially to the same point in the direction of travel of the vehicle as the start end of the first end of the suspension rod part 2b. As an entity, the suspension rod part 2b is a curved part of essentially semicircular shape, which is disposed, as viewed from the front of the vehicle, in an oblique position in such a way that the higher first end of the suspension rod part 2b is closer to the longitudinal center line of the vehicle than the lower second end of the suspension rod part 2b, which second end is also always inside the rim 13 of the wheel rim functioning as the wheel disc of the wheel 1 and to which second end of the suspension rod part 2b the wheel 1 is arranged to be fixed.

The bottom part of the suspension rod part 2b of the suspension arm 2 comprises fixing lugs 4 and 5 for hinging the suspension of the wheel 1. The first fixing lug 4 is right at the second end of the suspension rod part 2b and extends from the second end of the suspension rod part 2b towards the wheel 1. The second fixing lug 5 is essentially the distance of the radius of the curve of the suspension rod part 2b away from the first fixing lug 4 forwards in the direction of travel of the vehicle and is fixed e.g. to the bottom end of the third part of the suspension rod part 2b to point in essentially the same direction as the first fixing lug 4. Both fixing lugs 4 and 5 are arranged to extend from their free end to inside the rim 13 of the wheel rim of the wheel 1. The free ends of the fixing lugs 4, 5 have coupling means for the ball joints 7 and 8 to be referred to hereinafter. To the fixing lugs 4 and 5 of the second end of the suspension rod part 2b of the suspension arm 2 is connected at its bottom part, e.g. by the aid of the ball joint 7 as well as by the aid of the ball joints 8 and 9 and the plate-shaped coupling part 10, a suspension element 6 of the wheel 1. The coupling part 10 is connected to the fixing lug 4 by the aid of the ball joint 8 and to the suspension element 6 by the aid of the ball joint 9. A motor 11, which is e.g. a hydrau- lie motor, functioning as a hub motor is also fixed to the suspension element 6. The suspension element 6 and the motor 11 together form the bearings of the wheel 1. To each wheel 1 is connected its own motor 11, fixed to the center part 13a of the wheel rim.

The suspension element 6 of the wheel 1 and at the same time also the wheel 1 are arranged to turn and to incline within the limits permitted by the movement of the ball joints 7, 8 and 9 and of the coupling part 10. Thanks to suitable shaping of the suspension arm 2 and suitable pivoting of the suspension element 6, i.e. to suitable adjustment settings, the wheel 1 can turn and incline into different positions at rather large angles without the suspension arm 2 or suspension element 6 hitting the inside surface of the rim 13 of the wheel rim of the wheel 1. The suspension arm 2 is arranged to turn at its first end around the joint 12 in relation to the coupling part 3, in which case the wheel 1 can also move up and down in the vertical direction. Thanks to this type of suspension arrangement the wheels 1 follow dif- ferent difficult shapes of the terrain and obstructions very well, when driving with the vehicle in off-road terrain.

The center axes of the first ball joint 7 and of the second ball joint 8 are always on the same straight line as each other, which line is called the caster line CL, but the posi- tion of the third ball joint 9 with respect to the aforementioned straight line and to the second ball joint 8 changes according to the turning and inclining of the wheel. Thus the ball joint 9 rotates in a conical pendulum manner around the straight line formed by the ball joints 7 and 8, i.e. around the caster line CL . For ensuring flexible and effective operation, the joint 7 is disposed close to the inside edge of the rim 13 of the wheel rim, in which case the parts of the axle system that are inside the rim 13 of the wheel rim need a lot of space inside the rim 13 of the wheel rim. Thanks to the shape, placement and dimensioning of the support structure of the axle system, i.e. to the adjustment settings, the fixing of the wheel 1 turns and inclines into different positions with the ball joint 7 as the center point, i.e., in re- lation to the ball joint 7. The ball joints 7 and 8 are arranged to distribute the load acting on the wheel 1 according to their leverage ratio, which load on a flat underlying surface in an idle state is essentially one-half on both joints 7 and 8, in which case the ball joints 7 and 8 distribute the load roughly half and half. As viewed from the side of the wheel 1, the ball joints 8 and 9 are on a first side of the vertical center line of the wheel passing via the hub of the wheel 1, i.e. on the rear side of the aforementioned center line in the direction of travel of the vehicle, and the ball joint 7 is on the second side of the vertical center line of the wheel passing via the hub of the wheel 1, i.e. on the front side of the aforementioned center line in the direction of travel of the vehicle. The shock absorbers 14 and 15 also function as inclination dampers and both stabilize and damp inclining movements and turning movements of the wheel. The axle system with wheels 1 is connected to the vehicle with a coupling part 3. There can be e.g. two, three or four essentially similar axle systems consecutively in a vehicle. Fig. 2 presents an oblique view from the side and top of one suspension arrangement according to the invention for a wheel of a vehicle, in which suspension arrangement both wheels 1 of one axle system are in their positions, and Fig. 3 presents the same axle system as viewed from the rear in the direction of travel of the vehicle in such a way that both wheels 1 of the axle system are presented cross-sectioned. In both figures, the axle system and wheels 1 are in their ini- tial position in an idle state and on an essentially flat un- - derlying surface. Fig. 3 in particular shows the inclined position of the suspension rod parts 2b of the suspension arms 2 well, in which position the suspension rod part 2b is in a sloping position in such a way that the bottom end of the suspension rod part 2b is inside the rim 13 of the wheel rim of the wheel 1 below the axis of rotation of the wheel 1 and below both the motor 11 and suspension element 6. At the same time the bottom end of the suspension rod part 2b is farther from the center line in the direction of travel of the vehi- cle on which center line is e.g. the pivoting 12 of the suspension arms 2 in the coupling part 3.

In addition, Fig. 3 clearly shows that the tyre profile is very low, which enables good tyre grip and good traveling properties in off-road terrain. Inside the rim 13 of the wheel rim is a large enough space, in which most of the parts belonging to the axle system and its support structures are disposed, e.g. inter alia the suspension rod parts 2b of the suspension arms 2 completely except for the very top part, and the suspension element 6 and also the ball joints 7, 8 and 9, and the motor 11, which is fixed to the hub of the wheel 1 and functions as a hub motor, and also the second end . of the spring cylinder functioning as a shock absorber 14. Fig. 4 presents a top view of one suspension arrangement according to the invention for a wheel 1 of a vehicle, in which suspension arrangement one wheel 1 of one axle system is presented when sectioned. Correspondingly, Fig. 5 presents an oblique view from the side and top of one suspension arrangement according to the invention for a wheel 1 of a vehicle, in which suspension arrangement one wheel 1 of one axle system and a part of the axle system is presented when sectioned. Fig. 4 shows, inter alia, that the ball joint 7 and the ball joint 8 on the same straight line CL with it are disposed essentially on the center line of the wheel 1 in the width direction of the wheel 1, although the ball joint 8 is not presented in the figure. Fig. 6 presents a top view of one suspension arrangement according to the invention for a wheel 1 of a vehicle, in which suspension arrangement the wheel .1 of the right-hand side of the axle system is, e.g. owing to an obstruction, turned outwards in its direction of travel. When the wheel 1 encounters an obstruction, the ball joint 7, thanks to the dimensioning and structure of the support structure as well as thanks to the adjustment settings, bears essentially all the load being exerted on the structure via the wheel 1. When the wheel _. 1 encounters an obstruction, the second wheel 1 of the axle system can, thanks to the structure of the supporting axle system and thanks to the placement of the ball joints 7-9, turn independently of the other wheel e.g. outwards or inwards with respect to its direction of travel. When the wheel 1 has turned outwards with respect to its direction of travel, the ball joints 8 and 9 are on the same plane, i.e. the ball joint 9 has swiveled towards the center of the vehicle, by the aid of the movement of the coupling part 10, either to close to the height of the ball joint 8, to the height of the ball joint 8, or even to below the ball joint 8, in which case therefore the ball joint 8 is above the ball joint 9. When the wheel 1 encounters an obstruction, the coupling part 10 swivels to one side or the other, either inwards or outwards, depending on the shape of the obstruction and then upwards, as a consequence of which the ball joint 9 rotates around the ball joint 8 at a constant distance from it. This property enables effective operation when the wheel 1 seeks a path of travel according to the least resistance. In addition, it releases the surface of the tyre from transverse forces since the wheel 1 is able to turn when it en- counters lateral obstructions.

Thanks to the structure of the suspension arrangement according to the invention, the wheel is able to make rocking motions in a vertical plane according to the direction of travel. When, for example, some elevation arises in front of the wheel 1 on the right-hand side of the axle system, the coupling part 10 with the ball joint 9 swivels first to the side and turns finally, if necessary, completely upside-down with respect to its initial position in such a way that the ball joint 8, which in an unobstructed driving situation is below the ball joint 9, is now in fact above the ball joint 9. In this case the wheel 1 that encountered the elevation remains after the second wheel 1 traveling without obstruction of the same axle system without the whole axle system turning. In this situation also the suspension arm 2 of the wheel 1 that encountered the elevation rises upwards, turning around the joint 12. As a result of the driving moment of the wheel 1, the load acting on the wheel of the wheel 1 that encountered the elevation has shifted entirely onto the ball joint 7. The ball joints 8 and 9 are correspondingly unloaded when the coupling part 10, with the ball joint 9, has swiv- eled into sloping upwards. This property of the structure enables even double the moment, because the moment of the hydraulic motor 11 exerts via the wheel support a second mo- ment, in addition to the rim moment of the wheel 1, that is just as large, which moment tries to shift the loading point of the wheel 1 to the front of the obstruction. Thus passing over an obstruction is facilitated. Fig. 7 presents a front view of one suspension arrangement according to the invention for a wheel 1 of a vehicle, in which suspension arrangement both wheels 1 of one axle system are presented when cross-sectioned, and wherein the wheels 1 are inclined to the side according to the shapes of the ter- rain. For the sake of clarity the special structure of the tyres is not presented in this figure either. Fig. 7 graphically presents the inclining movements of the wheels 1 and of the suspension arms 2. As a result of the structure of the axle system, the dimensioning and the location positions of the ball joints, i.e. the adjustment settings, and of the special structure of the tyres, the wheels 1 are able both to adapt to large unevennesses in the terrain and they are able to settle in the lateral direction always according to the ground surface seeking the most extensive possible contact patch. One advantage, among others, following from this is that the wheels 1 find small unevennesses of the terrain for ensuring a good grip even on a . slippery underlying surface. The force exerted on the wheel 1 is distributed evenly on the whole tyre and the wheel 1 harms nature less than conven- tional wheel solutions and tyre solutions.

Figs. 8 and 9 present in a diagrammatic and simplified manner the principle of a suspension arrangement according to the invention for a wheel of a vehicle. The first ball joint 7 is crucial to the suspension arrangement according to the invention. Through the center point of this ball joint 7 run all the axle lines, in relation to which the various functions occur when the vehicle moves. The wheel 1 rotates, by the aid of the motor 11 functioning as. a hub motor, around its own center axis, i.e. around its axis of rotation, but functions in a new way around exactly the ball joint 7. The ball joints 7-9 comprise a spherical inner part, and casings functioning as coupling means around it. Thus the ball joints 7-9 can function between two different structural elements.

The suspension arrangement according to the invention has essentially three basic settings, namely; the location, the caster line setting, and the steering angle. There is one basic setting between the ball joints 7 and 8, which is called the caster line CL . Correspondingly, the steering line SL is configured between the ball joints 7 and 9. In addition, a third line is the steering axis line SA, around which line the lateral steering of the wheel 1 occurs. In the idle state on a flat underlying surface the weight acts on the ball joints 7-9 according to the leverage ratios resulting from the position of the joints, which leverage ratios are diagrammatically presented in Fig. 8. The joints 7 and 8 of the caster line CL are fixed to the suspension rod part 2b of the suspension arm 2 and the weight of the vehicle acts on these ball joints. The weight from the ball joint 8 is transmitted to the ball joint 9 via the coupling part 10.

The position of the wheel 1 in relation to the position of the vehicle follows the positions of the caster line CL and of the steering line SL in the different phases of movement of the vehicle. The lines CL and SL can also change position in relation either to the inclination or to the steering of the wheel 1. Only the caster line CL is fixed and continu- ously follows the trajectory of the suspension arm 2 and of the suspension rod part 2b and the change in position resulting from it. The ball parts of the ball joints 7 and 9 are fixed to the suspension element 6 and the whole structure is suspended on the hub of the wheel 1. The ball part of the ball joint 8 is attached to the fixing lug 4 of the suspen- sion rod part 2b of the suspension arm 2. Correspondingly, the casing parts functioning as the coupling means of the ball joints 8 and 9 are attached to the coupling part 10. The forces from the suspension arm 2 are exerted on the wheel 1 via the ball joints 7 and 8, and the ball joint 9 functions according to the situation. Correspondingly, the forces from the wheel 1 are exerted on the suspension arm 2 via the ball joints 7 and 9, in which case the ball joint 9 also functions as a reacting part, which the ball joint 8 steers. The momen- tary change in the amount of the forces can be very large. Likewise the flexes and trajectories produced can be very considerable .

The main factors of the suspension arrangement of a wheel are the inclination, steering, shifting of the center of mass and utilization of countermoment of the wheel 1. The center of mass shifts forwards and backwards in the area between the arrow A presented in Fig. 8. The center of mass shifts forwards either from the collision movement caused by the ob- struction 0 or as a result of the increased resistance. The value of the countermoment then exceeds the effect of the weight acting on the ball joints 8 and 9. Since the operation of the suspension arrangement changes as a result of a change in where the weight acts and a change in leverage ratios, the operation of the suspension arrangement, its rigidity, reaction speed and the steerability of the wheel 1 can be adjusted by changing the position of the ball joints 7-9 in relation to each other and to the hub of the wheel 1. In this case the directing of the weight onto the ball joints 7-9 changes, and the position of the lines CL and SL with respect to the contact patch between the wheel 1 and the underlying surface also changes.

One adjustment item is the caster line CL . In normal use the position of the ball joints 7-9 and the caster line CL are e.g. in, or near, the locations presented by Figs. 8 and 9. The basic setting of the caster line CL is an angle towards the drive direction. This angle is e.g. rising towards the front compared to the horizontal plane, in which case a posi- tive angle of incidence is in question.

One adjustment item is the steering line SL and its angle of incidence. With the angle of incidence of the steering line SL, the amount of steering of the wheel 1 is adjusted. The wheel 1 operates completely according to the forces produced by the angles of incidence and the underlying drive surface. It reacts only to the forces produced by the underlying drive surface according to the leverage ratios. Fig. 9 presents the principle of operation of the steering line SL. The speed of steering and amount of movement of the wheel 1 depend on the setting of the steering angle. When passing over an obstruction, the steering also changes many times during the passing. The wheel 1 does not try to repel an obstruction, but instead steers towards it, even if the obstruction were on either side of the wheel 1. By inclining, the wheel 1 obtains a larger and better grip from the obstruction. The wheel 1 can pass over smaller obstructions just by inclining, without it affecting the height position of the ball joint 7. Thanks to the structure of the suspension arrangement, the wheel 1 always follows the trajectory of the ball joint 7, also when locked in inclining, in which case it also steers itself. With very large steering angles the ball joint 7 rises up to even the height of the front edge of the wheel 1 and the center of mass rises along with it. This results in an ability to pass over large obstructions, which is impossible for a rigid wheel. Combined in inclination and steering, the wheel damps all the forces and also restrains longitudinal forces. It is exactly the change in relative speed caused by the path of movement that evens out longitudinal forces. Correspond- ingly, the inclination and steering of the wheel, as well as the special structure of the tyre, restrain lateral forces. Thus the wheel harms nature very little and leaves only minor traces, if any, on its underlying surface. As stated earlier, the ball joints 7 and 8 are, as viewed from the top, preferably on the center line of the wheel 1 in the width direction of the wheel 1. In this case also the caster line CL is on the center line of the wheel 1 in the width direction of the wheel 1. In the idle state the lines CL and SL are parallel with each other when viewed exactly from above. The contact patch of the wheel 1 with its underlying surface is midway between the ball joints 7 and 8 in the direction of travel of the vehicle. If the wheel 1 encounters an obstruction, for instance on the right-hand side of the aforementioned center line, it produces torsion, which shifts the ball joint 9 to the left-hand side of the center line. The wheel 1 then steers to the right. Simultaneously the wheel 1 is able to incline and steer towards the obstruction. When the ball joint 9 is on the top of the circle pre- sented in Fig. 9 with a dot-and-dash line, the steering of the wheel 1 is fast. On the sides of the circle, e.g. in position 9a, on the other hand, the flex rearwards is fast.

A problem in suspension structures and tyre structures ac- cording to prior art is that the center of mass acting from the vehicle is disposed always in the center point of the wheel, in both the lateral direction and in the height direction. The center of mass does not change in any situation at all. In the structure according to the invention, the center of mass instead always changes to forwards from the center line of the wheel 1 in the drive direction e.g. in the following situations: a) when starting, in which case the counterforce is the own weight of the vehicle and wheel. In this case the own weight of the wheel 1 helps even on mirror ice in shifting the center of mass, b) always when tractive resistance increases, e.g. owing to an obstruction, to over the leverage ratio, c) as a displacement by a mechanical impact, e.g. when the wheel encounters an obstruction. In the structure according to the invention the center of mass in the height direction is on the caster line CL between the ball joints 7 and 8. For this reason a tyre with as low a profile as possible is needed. At the same time the center of mass being exerted from the vehicle shifts from the hub of the wheel 1 to near the surface of the underlying drive surface. It is exactly this property that is a complete paradigm shift compared to solutions according to prior art. When passing over an obstruction the weight acting on the wheel must be levered over the obstruction. The higher the obstruc- tion, the more additional force is needed. This is exactly the greatest drawback of structures according to prior art. The center of mass does not shift and the contact patch moves away from the center line. The ability to grip is always lost if the speed is not sufficient to pass over the obstruction. Additional force in this case only increases the slip of the wheel .

The structure according to the invention comprises motors 11 functioning as hub motors, which are disposed on the hub of the wheels 1. A short driving shaft rotating the wheel 1 and the casings of the motor 11 are in connection with the structure. In this case the countermoment of the force transmission is exerted on the casings and the torque both produced by the motor 11 and caused by the countermoment are utilized in a sector with a double steering angle. For example, 2X15=30 degrees. This force cannot be utilized in this way otherwise than with the suspension structure according to the invention . In the preceding the operation of the suspension arrangement of a vehicle according to the invention has been explained simplifying the operation in such a way that it is presented as the extreme positions of individual movements. In prac- tice, all the rolling and inclining movements are involved at the same time in the operation of a wheel 1. In this case the axle system automatically seeks the positions according the easiest way of traveling and the surface of the tyre always seeks its way optimally for the direction of underlying travel surface, in which , case the loading force is always in the normal direction of its support surface. In this case the best possible advantage is obtained from the low-profile tyre structure according to the invention and from its adaptability.

Figs. 10 and 11 present a simplified and diagrammatic view of one tyre to be used in the solution according to the invention. The tyre is extremely low profile and its flexible part is constructed on the outer surface of the rim 13 of a thin e.g. metal wheel rim disc, such as a wheel rim, in such a way that the tyre comprises at least e.g. a metal wheel rim part and an air-filled flexible part comprising a flexible material, e.g. rubber, on its outer rim. On the second edge, preferably the outer edge, or near it, of the inner surface of the rim 13 of the wheel rim is a shallow reinforcing ring 13b, with fixing lugs 16, extending towards the center axis of the rim of the wheel rim 13, to which fixing lugs the center part 13a of the wheel rim, with the hub of the wheel, is fixed by the aid of fixing holes 17 and suitable fastening means, such as fixing bolts.

The flexible part of the tyre comprises a surface layer 22, in which is a suitable tread pattern and an air space 20, in which are air ducts 24 and a wall 25 between them of essen- tially flexible material separating the air ducts 24 from each other. The air space is composed e.g. of air hoses 27 that are side-by-side under the surface layer 22, which air hoses are fitted e.g. by vulcanizing onto the outer surface of the rim 13 of the wheel rim. In this case the wall 25 of flexible material comprises two walls of air hoses 27 that are side-by-side and against each other, though some other suitable filler material can additionally be between the hoses. Closest to the outer surface of the rim 13 of the wheel rim is a thin layer 18 of adhesion-improving agent, which can also be e.g. of raw rubber, which is brushed onto the outer surface of the rim 13 of the wheel rim. The outer edge of the rim 13 of the wheel rim is also preferably turned slightly upwards, which fold supports, either directly or via a filler, the edgemost turns of the layer formed from the air hoses 27 or from corresponding air-duct structures.

On the outer surface of the layer 18 of adhesion-improving agent is a thin binder layer 19 of fabric netting or corresponding material, which is configured to bind the air-duct structures, such as air hoses 27, of the air space 20 to each other and to support the air hoses 27. The adhesion between the air hoses 27 and the adhesion of the air hoses 27 to the outer surface of the rim 13 of the wheel rim is configured to support evenly the rim 13 of the wheel rim .essentially for the whole width of the rim 13 of the wheel rim. Preferably a reinforcement layer 21, e.g. a cross-wound textile fiber layer, the whole width of the tyre is further on top of the air hoses 27 or other air-duct structure. Further, the topmost layer is the surface layer 22, which can be e.g. of treaded rubber on its outer surface. The surface layer 22 binds all .the surface structures of the tyre together and also, if necessary, closes off the surplus gaps in the air space 20, e.g. the gaps between air hoses 27. The profile ratio of the tyre can be freely selected determined by the diameter and shape of the air ducts 24, or also by the number of air duct layers one on top of another. The diameter of an air hose 27 functioning as an air duct 24 is preferably smaller than 50 mm. The shape of the cross-section of an air duct 24 can be e.g. round, rectangular or elliptical. The air ducts 24 of the air space 20 are preferably composed of e.g. a structure comprising one air hose 27, which is wound into a spiral on the outer surface of the rim 13 of the wheel rim in such a way that each adjacent layer is either right next to each other or material is suitably disposed between adjacent layers. Thus there can be wedge-shaped rubber filling, such as pins both above and below, between air-hose coils or air ducts 24, or flat gripping rubbers can be between them. The harder points between the air ducts 24 remain raised when the points filled with air flex. In this way the grip of the tyre can be improved.

At the end of the edgemost air-duct coil on the outer edge of the tyre, i.e. at the end of e.g. the air-hose coil, is an air valve 23 for filling the air ducts 24. A preferred structure also comprises additional reinforcements of the edgemost, i.e. outermost, hose coil, for which additional reinforcement fabric of ribbon type or of twisted cord type can be used. Additional reinforcements are advantageous in case e.g. the wheel 1 grazes a sharp stone or other obstruction when it is moving in the terrain.

The so-called neutral contact enabled by the suspension solu- tion according to the invention and by the new tyre structure results from the self-steerability of the wheel 1. The ball joints 7 and 8 are attached to the suspension arm 2 and the ball joint 9 is attached to the suspension element 6 of a motor 11 functioning as a hub motor. The aforementioned neutral contact always keeps the contact as close to static friction as is generally possible. Inclination of the wheel 1, on the other hand, distributes the surface pressure in the contact patch and always takes a larger contact surface than old structures. The wheel does this fully on the terms of the un- derlying drive surface, whereas the suspension structure of a wheel according to prior art operates only on the terms of the suspension of the wheel. The tyre according to the invention is able to adapt to small unevennesses in the underlying drive surface because it does not have a solid and stiff bearing structure. The carrying capacity is based on many tubular parts, which together form the load-bearing capability.

It is obvious to the person skilled in the art that the invention is not limited solely to the example described above, but that it may be varied within the scope of the claims presented below. Thus, for example, the pivoting of the wheels does not necessarily need to be based on a ball joint, but instead some other type of pivoting, e.g. pin-sliding bushing pivoting, can be used.

It is also obvious to the person skilled in the art that the locations of the joints can differ to what is presented above .