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Title:
PNEUMATIC TYRE WITH MULTIPLE CHAMBERS
Document Type and Number:
WIPO Patent Application WO/2014/057282
Kind Code:
A1
Abstract:
A tyre for a wheel having an axis of rotation (A) comprises a crown having first and second regions (31, 33) mutually spaced in a direction parallel to the axis of rotation of the wheel; the first region at least partially defining a first chamber (63) configured to accommodate gas at a first pressure, and the second region at least partially defining a second chamber (61) configured to accommodate gas at a second pressure, different to the first pressure.

Inventors:
HALL, Gregory (Fusion Innovations Ltd, Oak CottageShelfield, Alcester Warwickshire B49 6JW, GB)
Application Number:
GB2013/052653
Publication Date:
April 17, 2014
Filing Date:
October 11, 2013
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
FUSION INNOVATIONS LTD (Oak Cottage, Shelfield, Alcester Warwickshire B49 6JW, GB)
International Classes:
B60C5/22; B60C11/00
Domestic Patent References:
WO2012001360A1
Foreign References:
US2217122A
DE19710434A1
US5479976A
EP1987966A1
GB1507082A
Attorney, Agent or Firm:
HARTWELL, Ian (Ollila Law Limited, First Floor Unit 5 The Courtyard,Wixford Park, Bidford on Avon Warwickshire B50 4JS, GB)
Download PDF:
Claims:
Tyre for a wheel having an axis of rotation, the tyre comprising:

a crown having first and second regions mutually spaced in a direction parallel to the axis of rotation of the wheel;

the first region at least partially defining a first chamber configured to accommodate gas at a first pressure, and the second region at least partially defining a second chamber configured to accommodate gas at a second pressure, different to the first pressure.

Tyre according to claim 1, wherein the crown has a third region spaced from the first and second regions in a direction parallel to the axis of rotation of the wheel, the third region at least partially defining a third chamber configured to accommodate a gas at a third pressure, different to the first and/or the second pressure.

Tyre according to claim 1 or claim 2 and comprising first and second sidewalls attached at their outer peripheries to respective sides of the crown, the tyre further comprising at least one wall that extends from the crown to the sidewall and that separates the first chamber from the second chamber.

Tyre according to claim 3 and comprising a first wall attached along one edge to the crown and along another, opposite edge to the first sidewall and a second wall attached along one edge to the crown and along another, opposite edge to the second sidewall.

5. Tyre according to claim 4, wherein the first and second walls are attached to the crown at respective first and second locations that are mutually spaced in a direction parallel to the axis of rotation of the wheel;

6. Tyre according to any one of claims 3 to 5 and comprising a third wall that extends between the first and second sidewalls and that partially, together with the second region of the crown, defines the second chamber

7. Tyre according to claim 6, wherein the first and second sidewalls each comprise a bead portion along their radially innermost edges for engagement with a wheel rim, the third wall engaging the first and second sidewalls at locations radially outwards of the bead portions.

8. Tyre according to claim 7, wherein the third wall is configured to define a fourth chamber radially inward of the second chamber.

9. Tyre according to any preceding claim, wherein the second chamber comprises multiple sub-chambers.

10. Tyre according to claim 8 or claim 9, wherein the fourth chamber comprises multiple sub-chambers.

11. Tyre according to any preceding claim, wherein the second region of the tread extends over the centre line of the tyre in a direction parallel to the axis of rotation of the wheel and the first region lies to one side of the centre line of the tyre in a direction parallel to the axis of rotation of the wheel, and wherein the first region of the tread is configured to lie out of the plane of the second region when the pressure of gas in the first chamber is less than the pressure of gas in the second chamber.

12. Tyre assembly for a wheel having an axis of rotation and comprising a tyre according to any preceding claim and at least one valve configured to vary the gas pressure in one or more of the first, second, third or fourth chambers while the wheel is rotating.

13. Tyre comprising a crown having a tread, the crown comprising an actuator configured to displace the tread in the radial direction of the tyre.

14. Tyre according to claim 13, wherein the actuator is an expandable chamber embedded within the crown of the tyre profile itself.

15. Tyre according to claim 14, wherein the tyre comprises sidewalls which, together with the crown, define an internal cavity configured to accommodate gas at a first pressure, the expandable chamber being configured to accommodate fluid at a pressure different to the first pressure.

Description:
PNEUMATIC TYRE WITH MULTIPLE CHAMBERS

TECHNICAL FIELD

The present invention relates to vehicle wheels and tyres and in particular, but not exclusively, to a passenger car wheels and tyres.

BACKGROUND ART

The vast majority of road vehicles, and particularly passenger vehicles, use a form of pneumatic tyre as the interface between the vehicle and the road surface. The characteristics of the tyre vary dependent on the road surface, the type of vehicle and the type of use of the vehicle. For example, a tyre for a heavy goods vehicle (HGV) will have a deep side wall relative to the tyre width in order to accommodate the weight of the vehicle and load. In contrast, a tyre for a performance car will have a shallow side wall in relation to the tyre width in order to minimise the wheel displacement relative to the road surface. A family saloon might have a tyre of intermediate side wall depth in order to provide improved comfort for the passengers of the vehicle, whilst still providing acceptable levels of vehicle handling performance.

However, a common feature of all tyres is a trade-off between the grip generated between the tyre and the road surface (a function of the tyre coefficient of friction), and the rolling resistance of the tyre. Whilst increased grip is clearly beneficial with respect to vehicle safety, the increase in grip inevitably leads to an increased rolling resistance of the tyre, which can make the vehicle less efficient when driving in a straight line. Developments have been made to tyre compounds in order to optimize the trade-off between tyre friction and rolling resistance. However this design point remains an issue for tyre designers attempting to improve the fuel consumption of the associated vehicle whilst maintaining tyre grip for cornering ability and vehicle safety.

Prior art devices teach the use of an actuator in order to additionally extend the central portion in a radial direction. However this solution is complex and presents problems in terms of operating the device upon sudden braking at high speed in that the actuator is unlikely to be able to retreat from the inner portion of the tyre sufficiently quickly to allow the outer portions to contact the road to provide for rapid braking.

Additionally, known systems require an external pressure source in order to operate. This adds substantial complexity to the system. Furthermore the use of an actuator to extend the central portion adversely affects the ride quality of the tyre since tyre compliancy is greatly reduced by the application of a high pressure over a low surface area of the tyre.

WO2012/001360 discloses a tyre assembly having a tyre, a moveable structure and an expandable chamber positioned within the tyre, the expandable chamber being arranged to displace the movable structure in use between the retracted position and a deployed position, wherein the movable structure contacts an inner surface of the tyre when in its deployed position so as to alter an outer profile of the tyre.

DISCLOSURE OF INVENTION

According to a first aspect, there is provided a tyre for a wheel having an axis of rotation, the tyre comprising: a crown having first and second regions mutually spaced in a direction parallel to the axis of rotation of the wheel; the first region at least partially defining a first chamber configured to accommodate gas at a first pressure, and the second region at least partially defining a second chamber configured to accommodate gas at a second pressure, different to the first pressure. Such a tyre can be naturally stressed in a low carbon mode to run on a partial low carbon central tread, distorting to a wider contact area by increasing the pressure and thus stiffness at the tyre side wall. By controlling different local pressures and stiffnesses within the tyre at each side wall - and optionally at a central chamber - the tyre can have a varying contact patch, returning naturally to its narrower and longer contact patch when pressures are reduced at the side wall chambers and optionally increased at the central tread chamber. Such distortion of the tyre under an uneven pressure distribution enables a full contact patch that is greater at the sides so as to flatten out the profile. Varying pressures within the multiple internal chambers changes the contact area of the tread pattern and also the physical characteristics of the tyre properties.

The crown may have a third region spaced from the first and second regions in a direction parallel to the axis of rotation of the wheel, the third region at least partially defining a third chamber configured to accommodate a gas at a third pressure, different to the first and/or the second pressure.

The tyre may comprise first and second sidewalls attached at their outer peripheries to respective sides of the crown, the tyre further comprising at least one wall that extends from the crown to the sidewall and that separates the first chamber from the second chamber. The tyre may comprise first and second walls attached to the crown and to the first and second sidewalls respectively and that separate the first chamber from the second chamber and the second chamber from the third chamber respectively.

The first and second walls may be attached to the crown at respective first and second locations that are mutually spaced in a direction parallel to the axis of rotation of the wheel.

The tyre may comprise a third wall that extends between the first and second sidewalls and that partially, together with the second region of the crown, defines the second chamber

The first and second sidewalls may each comprise a bead portion along their radially innermost edges for engagement with a wheel rim, the third wall engaging the first and second sidewalls at locations radially outwards of the bead portions.

The third wall may be configured to define a fourth chamber radially inward of the second chamber.

The second chamber may comprise multiple sub-chambers.

The fourth chamber may comprise multiple sub-chambers.

The second region of the tread may extend over the centre line of the tyre in a direction parallel to the axis of rotation of the wheel and the first region lies to one side of the centre line of the tyre in a direction parallel to the axis of rotation of the wheel, and wherein the first region of the tread is configured to lie out of the plane of the second region when the pressure of gas in the first chamber is less than the pressure of gas in the second chamber.

The invention further provides a tyre assembly for a wheel having an axis of rotation and comprising a tyre as set out above and at least one valve configured to vary the gas pressure in one or more of the first, second, third or fourth chambers while the wheel is rotating.

According to a second aspect of the present invention there is provided a tyre comprising a crown having a tread, the crown comprising an actuator configured to displace the tread in the radial direction of the tyre.

An actuator in the crown of the tyre can be engineered into the design on a local scale rather than be dependent upon that available through the tyre as a whole on a global scale. The actuator thus becomes lighter in weight, quicker in response and lower in manufacturing cost. In particular, the actuator operates outside of the main tyre structure, avoiding the need to create distortion of the tyre's central construction, enabling a simpler tyre construction overall. In contrast, some prior art designs rely upon the circumferential distortion of the tyre to create the radial growth of the profile, such distortion having the undesirable effect of decreasing the durability of a normal tyre and requiring additional strengthening of the tyre construction to cater for the characteristic. The present invention does not distort the main construction carcass of the tyre and in fact supports it.

The actuator may be an expandable chamber embedded within the crown of the tyre profile itself. The chamber may be expandable under fluid pressure, in particular gas pressure. It will be appreciated that any associated pumping mechanism has now to control a far smaller volume than in prior art devices and as such can be simpler in construction. Several mechanisms can be utilised to perform this function, inter alia an electro-mechanical micro pump or a capillary style pump that is pumped by the vehicle's weight rolling the air along the direction of rotation from the ambient entry point into the high pressure area. Such arrangements are amenable to lightweight construction using materials such as those used in the high pressure cycle tyre industry. The valve and pumping mechanism are also significantly lighter than those of the prior art. The tyre may further comprise sidewalls which, together with the crown, define an internal cavity configured to accommodate gas at a first pressure. The expandable chamber may be configured to accommodate fluid at a pressure different to the first pressure. The fluid may be gas.

The internal cavity may be configured to accommodate gas at a first pressure in a first region adjacent the crown and gas at a second pressure in a second region adjacent a sidewall. The first pressure may be greater than the second pressure. Such an arrangement can prevent the main tyre profile from distorting inwards towards the wheel under the non-uniform load, the high pressure supporting chamber acting to support the tyre crown to prevent distortion when the radial growth occurs and the central tread becomes loaded and the outer tread unloaded. The tyre may comprise a wall that separates the first and second regions.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a sectional view of a tyre according to a first embodiment of the invention;

Figure 2A illustrates the force distribution of a conventional tyre, while figures 2B and C illustrate the force distribution of a tyre according to an embodiment of the invention in full economy and full braking mode respectively;

Figure 3 is a perspective sectional view of a second embodiment of the invention;

Figure 4 is a sectional view of a third embodiment of the invention; Figure 5 is a perspective sectional view of a fourth embodiment of the invention; Figure 6 is a perspective sectional view of a fifth embodiment of the invention;

Figure 7 is a perspective sectional view of a sixth embodiment of the invention.

Figures 8A-C are schematic sectional views of an eighth embodiment of the invention in low rolling resistance mode, braking mode and cornering mode respectively.

MODE(S) FOR CARRYING OUT THE INVENTION

Referring to figure 1, a tyre 10 has a crown region 20 with a tread 30. The tyre has multiple chambers: firstly, a main internal annular tyre chamber 40 defined by the crown and sidewalls 70 as known from conventional tyre technology and containing air at a conventional tyre pressure. Radially outwards of the main tyre chamber and embedded within the crown of the tyre profile is arranged a second, actuation chamber 50, expandable under air pressure. A third annular chamber 60 is located radially inwards of the second chamber and contains gas at a pressure that will prevent the main tyre profile from distorting when the expandable chamber 60 contains a pressure sufficient enough to provide the radial growth of the tread. The first and third chambers 40,60 are separated by a wall 80, which delimits chamber 60 at its radially outward periphery, the chamber 60 being delimited at its radially inward perimeter by the rim 90 of the wheel, against which both sidewalls 70 and chamber walls 80 are sealed. Tyre and chamber walls are made from resilient, viscoelastic material. The expandable chamber 50 is able to alternate between the high pressure from the supporting chamber to the normal pressure of the main tyre chamber. This is performed by a series of valves, an associated controller and pump, as discussed in more detail below. The ability to alternate between the two pressures allows the mechanism to rapidly change profile when under the required operating condition.

The construction of the inner chamber behaves in a similar manner to a high pressure bicycle tyre (although construction can be organised in such a way to prevent expansion of the chamber and distortion of the tyre). Such a construction is easy to manipulate, easy to construct in the moulding of the chamber, light weight yet strong and low cost. The inner chamber does not experience the same environmental conditions as the tyre and therefore does not require the same robust construction methods. Specifically, the inner chamber will not wear or have a friction force applied to it on its contact area as both surfaces can distort in the same axis of motion.

Moreover, the supporting chamber 60 can provide a more even force distribution, allowing for improved tyre interaction under braking and accelerating than a conventional tyre. Figure 2A shows the statically uneven force distribution of a conventional tyre (whilst it is acknowledged that as the centripetal acceleration increases that this forces becomes more evenly distributed however under average driving conditions between 30 to 60 mph, this effect is not significant). A tight corner at 30 mph has a significant load distribution towards the outer edges of the tyre from the tyre walls. As shown in figures 2B and 2C, the supporting chamber can provide a more even distribution.

The valve mechanisms themselves can be simple pneumatic valves and can be controlled either electrically or pneumatically to create an inbuilt operational system that does not require external complex regulation. The ability to control the life cycle from within the wheel assembly has major advantages over the prior art in cost, weight and manufacturability. The control valving can be fitted either close to or within the tyre profile itself, as shown in figure 3 which shows a mechanism 100 with built in valves and capillary pump. This has a substantial advantage in terms of both the manufacturability and assembly of the unit, allowing the inner mechanism to have a similar fitting behaviour to that of the main tyre itself that does not restrict the fitting of the main tyre or enable it to be damaged in any way by the fitting.

Valves may include an outer two way valve able to allow inflation from an external source, ambient airflow into the pumping mechanism and air exhausting. Alternatively, an outer one way valve may be provided if using the lower chamber as a high pressure reservoir to cope with the fluctuation in load and changes its pressure accordingly. An external valve requires fixing attachment to the valve on the inside of the wheel.

The function of the valve is no longer to just allow a pressured air feed to inflate the tyre. It is a valve that must also allow an air flow out of the tyre when the mechanism exhausts and a flow into the device when the mechanism pumps. The function of the air to and from the device has a primary requirement to avoid water and dirt ingress into the device. Simple structural design is necessary to avoid direct ingress, whilst the mechanism is capable of clearing the air flow or even detecting blockages by monitoring the inlet pressure and sending a pressurised exhaust or in the case of standing water it would not take air in until the obstruction cleared. The valve will have a dual connection, a first, conventional, one way connection being to the tyre chambers and the second connection being to the device.

A controller (not shown) may process sensor input information (which may include G-force, slip angle, distortion, angle of steer, braking requirement, traction requirement, temperature, vehicle load, rain, snow, ice) and produce an output that will control a series of valves controlling the air flow within the mechanism, distributing the air pressures within the tyre and creating the distortions necessary to adapt the contact patch and tyre stiffness to the correct attributes for environment. Since 90% plus of the load is supported by the air pressure, small changes in the effective stiffness of the sidewalls through increasing the pressure in the outer air chambers can make a significant difference. In particular, this can eliminate or control over steer and under steer, increase performance of the tyre over a normal tyre and thus also improve safety, lower rolling resistance and improve dynamic ride handling and control.

The control system can use data from sensors within the tyre assembly to control the pressure to stimulus such as stress between the road surface and tyre contact area or centrifugal forces generated by a manoeuvre. The control system can also use data from within the vehicle to control the pressure to stimulus such as steering wheel orientation, braking or powertrain traction generated by inputs from the driver. Alternatively / in addition, the control system can operate to optimise the tyre distortion such as to react to stimulus from other tyres within a vehicle.

As regards rolling resistance and the associated energy loss, the invention can save energy in driving, braking and cornering. In the straight line running condition the higher pressure in the central segment of the tyre can also contribute to reducing energy losses.

Moreover, the tyre is the major comfort creating component of a vehicle. If the tyre comfort capability can be controlled relative to substrate conditions the suspension and mounts of the vehicle may be simplified and energy losses with these components reduced. Sensors (which may be incorporated into a so-called 'intelligent' tyre) can detect road mega and macro texture roughness and reduce tyre segment pressures accordingly. Greater ride and comfort will result but tyre rolling resistance will suffer. As regards vehicle handling and stability, optimising the tyre segment pressures in order to create the optimum tyre contact patch geometry can greatly help vehicle handling and stability and other vehicle related handling problems. This could in turn allow smaller tyre sizes of lower weight.

Wet road handling and straight line braking can also be enhanced by the optimisation of the tyre to road contact patch geometry initially for bulk water clearance and then for tyre tread rubber to road surface friction generation.

Loss of vehicle control associated with tyre puncture can also be reduced given that a tyre according to the present invention is likely to suffer a puncture in only one section of the air components.

Moreover, the strengthened tyre side walls associated with the present invention can also enable a 'run flat' capability.

In particular, the tyre can maintain a temporary safe operating pressure when a loss of air is experienced by one or more chambers within the tyre, either by maintaining integrity within undamaged chambers or by redistributing air to the damaged chamber in order minimise a sudden pressure decrease. Such air could be redistributed from the inner lower high pressure chamber or multiple chambers to improve control of the vehicle.

A divided air chamber with segments at different pressures in accordance with the invention can also alter the tyre resonances and can result in a tyre of lower straight line driving tyre to road noise. A tyre according to the invention can also adapt to road conditions, including off road conditions that may be considered as ultra rough, soft and unbound. This may be particularly appropriate for 4x4 vehicles, farm and light construction vehicles.

Power to activate the electronics and the valves may be provided by an energy scavenging device (although it is also desirable that the control unit allow the tyre unit to inflate properly from an external feed even when the unit is not powered). Pressurised air may be provided by a pump such as Goodyear' s peristaltic pump system.

Alternatively, the control unit to modify the pressures using the tyre's own rolling motion to power the air distribution around the chambers using a series of valves, as known from the aforementioned WO2012/001360. Such an assembly can use the loading characteristics of a rolling tyre on a chassis with mass to distribute pressures within the tyre. (Through valve actuation or buckling mechanism), using a control system through valve actuation to redistribute pressures within the tyre and using a pumping mechanism powered by the vehicle's rolling mass to return pressure to a standard operating state.

Where a pumping system is built into a (so-called 'intelligent') tyre, this can act as a pneumatic sensor as well.

It will be appreciated that the controller can be connected to a central digital cluster either wirelessly or wired where it can integrate with the vehicle's on board dynamics systems such as traction control and ABS. Such a digital cluster can also centrally calculate, in a 'holistic' approach, that make the tyres contact patch areas and properties be adapted to optimise the dynamics of the vehicle as a whole rather than an individual tyre. Similarly, the controller can work alongside the powertrain to best optimise the power delivery of the power train to the road. As shown in figure 4, supporting chamber 60 can be divided by means of a dividing wall 65, which may be integral with wall 80 and/or may be resilient, into a radially- outward ('upper' in figure 5) supporting chamber 61 and a radially-inward ('lower' in figure 5) supporting chamber 62.

The outer chamber 61 is delimited by walls 80 and 63 and contains a pressure that acts against the inner surface 11 of the tyre 10. Inner chamber 62 is delimited by wall 63 and the (rigid) rim 90 of the wheel and contains a pressure that acts against chamber 61.

Chamber 61 is preferably a radially pocketed chamber, embodiments of which are set out below, each pocket being connected to an air in tube and each to an air out tube. Each pocket has a simple one way valve preferably a reed type valve that connects it to the air in and air out. The control unit controls the air in and air out as discussed above. An air pump and power supply (not shown) may also be necessary.

Walls 80,80' extend from respective edges 63 ',64' attached to either side of the crown to respective edges 63 ",64" attached to the two sidewalls 70,70', thereby defining chamber 63 between sidewall 70 and wall 80 and chamber 64 between sidewall 70' and wall 80', the air in and air out being connected to these chambers via a control unit. It will be evident chambers 63,61,64 are defined by respective regions 33,31,34 of the tread (spaced in a direction parallel to the axis A of rotation of the wheel), the regions being supported by the gas pressure in the respective chambers. The tyre is structured so that its natural profile is more rounded than a conventional tyre, being more akin to a motorcycle tyre, and under uniform pressure distribution the tyre will retain this shape in which it is more curved instead of flat (i.e. the first region of the tread lies out of the plane of the second region), the air being distributed within the main cavity in such a way as to create a differential pressure in the different chambers and thus provide a variable ability to distort the profile. An example of this is that the tyre profile can be rounded with a longer thinner contact area under normal driving conditions of low stress where rolling resistance needs to be low. The inner mechanism can receive inputs from intelligent devices within the tyre that will enable the contact patch to deform and adapt to the optimum contact patch area for the particular driving condition. A left hand corner for example will stiffen up the side wall on the right hand side by increasing the pressure in chamber 64 in figure 4. This will have the effect of stiffening and straightening the side wall on the right. In order to provide the optimum contact patch area for the high stress left hand corner the left side wall will also be stiffened and straightened by increasing the pressure in chamber 63 in figure 4. For a right hand side corner the opposite is true. The inner device also reduces the pressure in chamber 61 in figure 4, which enables the profile to adapt more easily. The pressure increases in chambers 63 and 64 come from the decrease in chamber 61.

The rotating load on the vehicle under operation is able to exhaust air from chamber 61 by the control unit opening the air out valve. The pocketing of this chamber means that the local pressure of the pocket under the load is increased by the weight of the vehicle instead of uniformly being distributed around the radial chamber. The chamber beneath it as shown in figure 4 (chamber 62) is of a higher pressure than chamber 61 so that when the pockets are locked for air in and out the load of the vehicle will squeeze the pocket to the pressure of the chamber below it. This increase in pressure allows the air to be forced out and into the lower pressured cavities of chambers 63 and 64 which are radially distributed. It is preferable to have chamber 62 at a much higher pressure than chambers 61, 63 and 64 as it will allow faster response and also the off-road re-inflation ability as well as providing extra stiffness to the bead area of the main tyre. The control unit is able to control how much air is exhausted individually in chambers 63 and 64 according to sensor data and the resulting contact patch requirement. The control unit is able to equalise the pocketed chambers by connecting the outer and inner connects together. Alternatively the control unit could also connect to chamber 62 to vary its pressure as well by using it to increase or decrease the pressures in the chambers 61, 62 and 63.

The tyre is forcibly distorted by the higher pressure in chambers 63 and 64, to return the tyre to its equilibrium state the control unit is able to re-inflate the pockets by opening the air-in to the chambers and because the unloaded part of the tyre in the rotation is going to try to force itself back into its natural equilibrium profile and squeeze the air back into the unloaded pockets. The loaded pockets will no longer be able to exhaust to the air out and the original profile is returned. By using this mechanism the control unit is able to vary the pressures of the chamber and thus alter the contact patch of the tyre.

Moreover, upon inflation of the tyre chambers, the control unit can be open at static and inflate uniformly but maintain a condition where a differential valve between chamber 62 and chambers 61, 63 and 64 is set to stay at 1 bar greater, then the control unit can function to pump air into or let air out of this chamber dependent upon the load or mode required. In doing this the only air that needs to be pumped is a low maintenance quantity from external, or a load change as stated above.

The design of the supporting chamber 60 can allow for additional control mechanisms to be incorporated into it to provide additional functionality. In one embodiment, shown in figure 5, a controlled inner collapsing chamber 150 can be operated remotely by either wired or wireless systems and powered internally by a power generator or pneumatic actuation. The purpose of the chamber is to sit radially outwardly of the supporting chamber and, when collapsed, to prevent the supporting chamber from operating. Such a use could be used for an off-road type application where the tyre's main cavity is required to run at a far reduced tyre pressure over rough terrain. The collapsing chamber can then be reactivated when the low pressure is no longer required, supporting the main tyre until the correct pressure is achieved again by the unit's internal pumping system.

Alternatively, the mechanism can function to support the tyre whilst the out chamber returns to normal pressure. In yet another embodiment, the high pressure is used to inflate the normal pressure chamber, the pump returning the high pressure chamber to its operational pressure before the mechanism begins its normal operational cycle.

Such an internal collapsing chamber can be either pneumatic or mechanical in nature. A mechanical system is suitable for a segmented design where, upon reactivation, it can activate under the unloaded sections of the wheel as it rotates. Figure 6 shows an embodiment incorporating an internal collapsing slip chamber 160.

A pneumatic version may have a secondary chamber within the high pressure chamber but that, at the top, can discharge into the main cavity. The remaining high pressure chamber should be sized so that there is sufficient pressure to return the whole unit to a normal pressure once an off-road activation had finished. Such a pneumatic embodiment may be simpler and lighter and also increase the damping abilities mentioned above.

Figure 7 is a perspective sectional view of a further embodiment of the invention in which the supporting chamber 60 has multiple sub-chambers 170, the pressures therein being proportionate to enable better damping characteristics whilst still providing the necessary supporting structure. As shown, the 'pocketed' structure of multiple sub-chambers 170 is located in the radially-outward chamber, where the radially-inward chamber being at a much higher pressure allows the pocket to itself increase in pressure when under load and thus compression to vary the pressures in the other chambers.

Figure 8A is a schematic radial cross-sectional view of another embodiment of the invention having multiple higher-pressure 'pocketed' sub-chambers 200 in the radially inward chamber 62 (and which potentially provide a 'run flat' capability as well as baffling noise). Sub-chambers 200 also act as an air reservoir for radially- outward chamber 61 is also formed with first sub-chamber 210 and second sub- chambers 211,212.

Figure 8A depicts the tyre in the condition of normal straight-ahead driving (typically experience in excess of 90% of the time) in which it is configured for low rolling resistance, the pressure in chambers 200 being greater than that in chamber 210 which is in turn greater than that in chambers 211,212. As shown, section 215 of the tyre profile contacts the road R (the profile of the tyre has been exaggerated to facilitate understanding).

Figure 8B depicts the tyre in a braking condition and in which pressures are redistributed from the first sub-chamber 210 to the second sub-chambers 211,212 so as to allow the tyre surface to flatten, increasing the contact area of the sections 220 of the tyre. These sections may have different wear and/or grip properties, and may comprise different compound(s), to section 215.

Figure 8C depicts the tyre in a cornering condition in which a pressure differential between chambers 211 and 212 across the width of the tyre is implemented (the pressure in chamber 211 being higher than that in chamber 212) in a controlled manner so as to define the location of the contact patch and provide effective differential sidewall stiffness. This in turn provides improved cornering grip and controllability (oversteer/understeer) capability.

In an alternative embodiment, not shown, the distribution of pressures could also be effected mechanically through designs meant to utilise the stressed condition to buckle and thus change the volumes of the chambers or even the use of actuators to change the volumes and pressures.

The manufacturing method of a tyre more akin in function to that of a motorcycle tire allowing the elimination of the fatigue issue and failure caused by belt separation. In motorcycle tyres there is no real belt edge that is subjected to the same usage as that of a normal automobile tyre. The belt edge on a car tyre is a very common area of failure that does not occur in the same magnitude on a motorcycle tyre. On a motorcycle tyre this can be eliminated. Motorcycle tyres can also be of a bias ply or radial ply. The design restriction of the conventional automobile tyre prevents this type of tyre design. Run flat tyres in particular generate a large amount of heat at the tire edge where the belt edges occur.

The present invention proposes a design of tyre that is naturally stressed and constructed in manufacture similar to that of a motorcycle tyre. The construction in conjunction with the assembly allows the tyre to function correctly as an automobile tyre needs to but without the complications of manufacturing methods of belt construction of automobile tyres caused by the belt edges.

The fitment of the assembly utilises a simple rubber to rubber seal of the inner mechanism to the main outer tyre at the lower bead extremities of the main manufactured items and the rim of the wheel. The high pressure and bead of the inner mechanism enable an air proof seal between the two structures and the wheel rim. The inner mechanism does not experience wear in the same circumstances of an external tyre therefore enabling a simple high pressure carcass to be employed. No tread is required and so a simple lightweight radial plie is a minimum that is required with the correct impermeable compounds to allow for structural integrity and pressure integrity. The lower high pressure chamber requires a design that uses one or more inner strengthening structures or chambers to maintain the shape integrity of the upper chamber when it is under pressure.

The design is intended to be powered by either an energy harvesting internal device or an external inductance or similar type device powered from the vehicle itself.

The design is intended to be manufactured as a modular device that can be separated into the tyre, the inner mechanism and the control module. The assembly of the parts would be by partial fitment of the tyre then the inner mechanism and control module then the full fitment of the tyre.