Airless tire for extraterrestrial vehicle with three-dimensional fabric tread

Abstract

The present invention relates to an airless tire for a vehicle capable of running in an extraterrestrial environment, at very low temperatures and on various types of ground. Such an airless tire comprises, radially from the inside to the outside, a supporting structure, intended to cooperate with a rim, a shear band and a tread (4). According to the invention, the material constituting the tread (4) has a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 GPa, and, measured at a temperature equal to -196°C, at least equal to 1.2 GPa and at most equal to 9 GPa, and a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature equal to -196°C, at least equal to 40 MPa and at most equal to 260 MPa, these mechanical characteristics being measured according to standard ASTM D638 and the tread (4) is made exclusively of a three-dimensional fabric (T). Figure for the abstract: Fig 2.

Description

Title of the invention: Airless tire for extraterrestrial vehicle comprising a three-dimensional fabric tread Technical field of the invention

[0001] The present invention relates to the field of airless tires, intended to equip an extraterrestrial exploration vehicle, intended to move, for example, on the moon or on the planet Mars, in an environment subject to very strong temperature variations, which can reach very low temperatures down to -243°C and very high temperatures up to +130°C. Such a thermal gradient is notably measured at the South Pole of the moon. It relates more particularly to the tread of such an airless tire. State of the prior art

[0002] A conventional tire, subjected to the internal pressure of an inflation gas, generally air, or a conventional solid tire are not suitable for such use, because the usual rubber-based materials from which they are made have mechanical properties incompatible with use in an environment which can reach very low temperatures, also called cryogenic temperatures.

[0003] It is known to have, as an alternative technical solution to a conventional tire, an airless tire, or more generally a tire without inflation gas, which carries the load thanks to structural components and which has performances comparable to those of a conventional tire. An airless tire, mounted on a hub, or a rim, is sometimes called a "non-pneumatic elastic wheel".

[0004] Such an airless tire has been described, by way of example, in documents WO 2003 / 018332 - Al, FR 2 964 597 - Bl, WO 2012 / 102932 - Al, WO 2018 / 101937 -Al, WO 2018 / 102303 - Al, WO 2018 / 102560 - Al, WO 2018 / 125186 - Al.

[0005] In the following, the circumferential or longitudinal direction designates the direction of rotation of the tire, the axial or transverse direction designates a direction parallel to the axis of rotation of the tire and the radial direction designates a direction perpendicular to the axis of rotation of the tire.

[0006] The term “inner” element means the part closer to the axis of rotation of the tire relative to an “outer” element.

[0007] An airless tire generally comprises, radially from the inside to the outside:

[0008] - a supporting structure, intended to structurally support at least in part the load and to cooperate with a rim or hub;

[0009] - a shear band, intended to transmit by shear the forces of rolling to the supporting structure and to contribute at least in part to carrying the load, and

[0010] - a tread, intended to transmit to the shear band the forces rolling, to be worn and to guarantee the grip of the tire on the ground.

[0011] The supporting structure comprises, radially from the inside to the outside, means of connection with a rim or a hub, radial elements or spokes, and means of connection with the shear band.

[0012] However, the supporting structure does not generally define a sealed internal cavity for containing a pressurized gas, as in a conventional tire. Therefore, an airless tire does not need to have a sealed connection to a rim or hub.

[0013] The shear band comprises, radially from the inside to the outside:

[0014] - a first inner membrane,

[0015] - a shear layer consisting of one or more polymeric materials, And

[0016] - a second outer membrane.

[0017] In the example described, the first and second membranes have a modulus of elasticity in circumferential extension often substantially greater than the modulus of elasticity in shear of the shear layer of polymeric material, such that, under the applied load, the membranes do not elongate or elongate only slightly when the tire is flattened while rolling. The relative displacement of the membranes relative to each other occurs by shear in the shear layer. For example, the membranes, respectively inner and outer, comprise superimposed layers of reinforcements coated in a polymeric material.

[0018] The shear layer of polymeric material is made, for example, of a polymeric material, such as a natural rubber or a synthetic rubber, or of a polyurethane. Typically, the material of the shear layer has a shear modulus of at least 3 MPa and at most 20 MPa, which allows for easier flattening of the shear band under load.

[0019] Finally, the tread, which is the radially outer component of the tire, is most often made of a polymeric material, such as natural rubber or synthetic rubber.

[0020] For several years, Michelin North America has marketed a mounted assembly, consisting of an airless tire, as previously described, and a wheel, under the name MICHELIN® TWEEL®. This technical solution mainly comprises a tread, a shear band (in English, "shear-band"), a supporting structure, consisting of highly resistant polyresin spokes and a hub made of two reinforced steel pieces.

[0021] However, in very low temperature applications, the usual polymeric materials constituting an airless tire are incompatible with the specified temperature range.

[0022] Thus, the usual polymeric materials, used, in particular, for the shear band, have levels of rigidity which will generate high contact pressures, involving a risk of the tire sinking into soft ground, in particular as on the moon, and generate high rolling resistance, involving high energy consumption, which is detrimental to the energy autonomy of the extraterrestrial vehicle.

[0023] Furthermore, common polymeric materials, such as natural rubber or synthetic rubber, generally constituting the tread of an airless tire, are also incompatible with the specified temperature range.

[0024] Thus, there is a need to remedy the aforementioned drawbacks. Statement of the invention

[0025] The inventors aim to design an airless tire that can roll in an extraterrestrial environment, at very low temperatures, typically in the range [-243°C; +130°C], and on soils of various types, which may be sandy or stony.

[0026] The invention aims in particular to improve the traction of the airless tire while protecting it from ground damage, in particular by choosing an appropriate tread.

[0027] The present invention relates to an airless tire for a vehicle, comprising, radially from the inside to the outside, a supporting structure, intended to cooperate with a rim or a hub of a wheel, a shear band and a tread.

[0028] The shear band comprises, radially from the inside to the outside, a radially inner membrane, a shear structure and a radially outer membrane.

[0029] The supporting structure, the shear band and the tread are each made of at least one material, preferably thermoplastic, having the following mechanical characteristics, measured according to the ASTM D638 standard of the ASTM (“American Society for Testing and Materials”) International: - a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 Gpa, and, measured at a temperature equal to -196°C, at least equal to 1.2 Gpa and at most equal to 9 Gpa, and - a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 Mpa and at most equal to 150 Mpa, and, measured at a temperature equal to -196°C, at least equal to 40 Mpa and at most equal to 260 Mpa.

[0030] The tread is made exclusively of a three-dimensional or three-dimensional fabric.

[0031] Such an airless tire is intended to equip an extraterrestrial vehicle and is capable of withstanding strong temperature gradients ranging from -243°C to +130°C.

[0032] By "exclusively constituted" is meant that the tissue is not embedded in a matrix.

[0033] By “three-dimensional” or “three-dimensional” fabric is meant a fabric comprising at least two knitted membranes, for example warp knitted, which have been extended by a third dimension, for example by connecting threads F.

[0034] The three-dimensional fabric is used here in a particular application to ensure very low contact pressure and improve the traction of the tire.

[0035] To enable an airless tire to roll in an extraterrestrial environment that can vary between very low temperatures and very high temperatures, typically in the range [-243°C; 130°C], and on soils of various types, which can be sandy or stony, the Applicant has selected materials having, essentially, a Young's modulus in traction E and a maximum tensile stress Sm included in specific ranges both at room temperature, taken equal to 20°C, and at very low temperature, taken equal to -196°C.

[0036] The Young's modulus in tension E and the maximum tensile stress Sm are measured on a tensile curve "stress - elongation", established from a tensile test carried out on a standardized test piece, in accordance with the ASTM D638 standard ("Standard Test Method for Tensile Properties of Plastics"), developed by ASTM ("American Society for Testing and Materials") International. The standardized test piece has a length equal to 84 mm and a thickness equal to 2 mm, and includes a necking having a length equal to 25 mm and a width equal to 4 mm. The tensile speed applied to the test piece is equal to 500 mm / min. The Young's modulus in tension E is a tangent modulus measured at low deformation.

[0037] The Young's modulus in traction E conditions the rigidities and the load capacity of the airless tire, at the target operating temperatures. The maximum tensile stress Sm conditions the endurance of the airless tire, at the temperatures intended uses.

[0038] Consequently, the inventors have chosen materials whose aforementioned mechanical characteristics make it possible to guarantee a satisfactory compromise between the load capacity and the endurance required for the airless tire under the intended conditions of use. The airless tire must be capable of carrying a load typically between 16 and 200 daN, and is intended to be mounted on a vehicle which can typically travel up to a maximum speed equal to 20 km / h.

[0039] The tread according to the invention makes it possible to minimize the contact pressure with the ground by maximizing the contact surface with the ground, which makes it possible to improve the traction of an airless tire without degrading it.

[0040] Such a tread has a flattening pressure, in contact with the ground, of between 0.05 bar and 0.3 bar, which further improves the crossing capacity, therefore the traction as well as the energy consumption.

[0041] Finally, such a tread also has the advantage of being particularly light compared to known treads.

[0042] Advantageously, the three-dimensional fabric forming the tread comprises at least two knitted membranes, namely an internal knitted membrane and an external knitted membrane connected to each other radially by a plurality of connecting threads. Each knitted membrane comprises an internal surface and an external surface, the internal surface of the internal knitted membrane being, for example, integral with the shear strip, in particular with the radially external membrane thereof, and the external surface of the external knitted membrane being configured to be in contact with the surface of the ground.

[0043] Preferably, the inner knitted membrane and the outer knitted membrane have different structures.

[0044] For example, the outer knitted membrane comprises a plurality of cells or meshes, for example, regularly distributed circumferentially.

[0045] The coverage rate of the external knitted membrane, defined as the ratio between the total surface area of ​​cells and the surface area of ​​the external knitted membrane, is at least equal to 20% and strictly less than 100%, preferably at least equal to 80%.

[0046] This makes it possible to maximize the contact surface of the external surface of the external knitted membrane with the ground and thus to minimize the contact pressure.

[0047] For example, the cells of the external knitted membrane are here open cells connected to each other by material.

[0048] For example, the internal knitted membrane comprises a plurality of cells or meshes, regularly distributed circumferentially.

[0049] The cells of the internal knitted membrane are, for example, open cells connected to each other by material.

[0050] Preferably, the coverage rate of the internal knitted membrane, defined as the ratio between the total surface area of ​​cells and the surface area of ​​the internal knitted membrane, is lower than the coverage rate of the external knitted membrane.

[0051] For example, the coverage rate of the internal knitted membrane is at least equal to 20% and strictly less than 100%.

[0052] For example, and in no way limiting, the cells of the internal knitted membrane and of the external knitted membrane overlap in the radial direction.

[0053] Alternatively, it could be provided that the cells of the internal knitted membrane are offset in a staggered manner relative to the cells of the external knitted membrane.

[0054] For example, the connecting threads, connecting the inner knitted membrane and the outer knitted membrane, each have a diameter between 0.05 mm and 2 mm and a radial distance between 0.05 mm and 2 mm.

[0055] For example, the thickness of the internal knitted membrane is between 0.15 mm and 3 mm.

[0056] For example, the thickness of the outer knitted membrane is between 0.15 mm and 3 mm.

[0057] Preferably, the three-dimensional fabric, forming the tread, has a total thickness of between 3 mm and 20 mm. The total thickness is measured between the inner surface of the inner knitted membrane and the outer surface of the outer knitted membrane.

[0058] Preferably, the three-dimensional fabric forming the tread is made of a thermoplastic polymeric material included in the group comprising polyetheretherketone (PEEK), polyetherimide (PEI), polyimide (PI) and polyetherketoneketone (PEKK).

[0059] A polyetheretherketone (PEEK) is a thermoplastic polymeric material belonging to the family of polyaryletherketones (PAEK). A polyetheretherketone, such as, for example, the materials Victrex CT 100™ and Victrex 450G™, marketed by the company Victrex®, have the required mechanical characteristics, in particular at cryogenic temperatures.

[0060] A polyimide, such as, for example, the Aurum PL500A™ material, has excellent mechanical characteristics at cryogenic temperatures, but is more difficult to process than a polyetheretherketone, such as the Victrex CT 100™ material.

[0061] A polyetherimide such as, for example, the Ultem 1010™ material, has mechanical properties comparable to those of a polyetheretherketone, such as the Victrex CT100™ material, but with a lower elongation at break. It has the advantage of being more economical.

[0062] In the context of the present invention, the inventors have demonstrated, surprisingly, that such a high-performance thermoplastic polymeric material formances also makes it possible to achieve a satisfactory compromise between high structural rigidity, high endurance and low mass of the airless tire, at very low cryogenic temperatures, as shown by measurements carried out at -196°C.

[0063] Preferably, the three-dimensional fabric forming the tread has a compression pressure defined according to standard DIN EN ISO 3386-1 between the contact pressure of the tire increased by 1kPa and the contact pressure of the tire increased by 10kPa.

[0064] This prevents the fabric from collapsing under the contact pressure imposed on the tire.

[0065] According to a preferred embodiment, the supporting structure, the shear band and the tread are each made of the same material. An identical material for all the constituents of an airless tire simplifies manufacturing and allows for easier adhesion between the different constituents.

[0066] For example, the shear structure is constituted by a plurality of shear elements distributed circumferentially. Such a discrete shear structure has the advantage of being lighter than a continuous shear structure. In addition, its rigidities can be more finely optimized.

[0067] According to a second aspect, the invention relates to a wheel comprising an airless tire as described previously mounted on a rim. Brief description of the drawings

[0068] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0069] [Fig.l] represents an overall perspective view of a wheel comprising an airless tire according to one embodiment of the invention;

[0070] [Fig.2] illustrates in detail the tread of the tire of [Fig.l] according to one embodiment of the invention;

[0071] [Fig.3] depicts in detail the three-dimensional fabric forming the tread of the [Fig.2] ; and

[0072] [Fig.4] represents a diagram of the results of an experiment with a test tube containing in particular the three-dimensional fabric according to [Fig.3].

[0073] Detailed description of at least one embodiment

[0074] In the following description, the terms “circumferential”, “axial” and “radial” are defined relative to the axis of rotation XI-XI of the tire 1.

[0075] The “circumferential” direction designates a direction of a plane perpendicular to the axis of rotation XI-XI tangent to the tread of the tire 1, the “axial” direction is the direction of the axis of rotation XI-XI of the tire 1 and a “radial” direction designates a direction perpendicular to the axis of rotation XI-XI of the tire 1.

[0076] [Fig.l] is an overall perspective view of a mounted assembly or wheel 10 comprising a rim 100 and an airless tire 1 mounted on said rim 100.

[0077] By “rim” is meant a structure for connection with the vehicle and central support of the tire 1.

[0078] The airless tire 1 is intended to equip an extraterrestrial vehicle and is capable of withstanding strong temperature gradients ranging from -243°C to +130°C.

[0079] The airless tire 1 comprises, radially from the inside to the outside, a supporting structure 2, intended to cooperate with the rim 100, a shear band 3 integral with the supporting structure 2 and a tread 4 integral with the shear band 3.

[0080] The supporting structure 2 is constituted, here, of a plurality of spokes 21 regularly distributed circumferentially.

[0081] In a non-limiting manner, the spokes 21 each here comprise an internal end 21a secured to the rim 100, for example by fixing means (not shown), such as screw means (screws / nuts) or by rivets (not shown), a concave portion 21b and an external end 21c secured to the shear band 3 by screw means or by rivets (not shown).

[0082] By way of non-limiting example, said fixing means could be configured to fix both a spoke 21 of the tire 1 and the rim 100.

[0083] The shear band 3 comprises, radially from the inside to the outside, a radially inner membrane 31, integral with the supporting structure 2, a shear structure 32 and a radially outer membrane 33.

[0084] As illustrated, the shear structure 32 is constituted by a plurality of shear elements 32a, here regularly distributed circumferentially between the radially inner membrane 31 and the radially outer membrane 33.

[0085] In a non-limiting manner, each shear element 32a comprises two opposite curvatures.

[0086] The supporting structure 2 and the shear strip 3 are each made of a thermoplastic polymer material, said to be high-performance.

[0087] The material constituting at least the supporting structure 2 and the shear band 3 has the following mechanical characteristics, measured according to the ASTM standard ASTM D638 (American Society for Testing and Materials) International: - a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 GPa, and, measured at a temperature equal to -196°C, at least equal to 1.2 GPa and at most equal to 9 GPa, and - a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature equal to -196°C, at least equal to 40 MPa and at most equal to 260 MPa. Tread

[0088] The tread 4 is made exclusively of a three-dimensional T fabric.

[0089] By "exclusively constituted" is meant that the tissue is not embedded in a matrix.

[0090] As illustrated in [Fig.3], the three-dimensional fabric T comprises, here, two knitted membranes, namely an internal knitted membrane M1 and an external knitted membrane M2 and a plurality of connecting threads F radially connecting the two knitted membranes M1, M2.

[0091] By “three-dimensional” or “three-dimensional” fabric, we mean a fabric comprising at least two knitted membranes, for example warp knitted, which have been extended by a third dimension, here by the connecting threads F.

[0092] Each knitted membrane Ml, M2 comprises an inner surface Ml a, M2a and an outer surface Mlb, M2b.

[0093] The internal surface Mla of the internal knitted membrane Ml is integral with the shear band 3, in particular with the radially external membrane 33 of said shear band 3.

[0094] The outer surface M2b of the outer knitted membrane M2 is configured to cooperate with the surface of the ground.

[0095] Thus, the inner knitted membrane M1 and the outer knitted membrane M2 preferably have different structures.

[0096] The internal knitted membrane Ml comprises a plurality of cells (not referenced) or meshes regularly distributed circumferentially.

[0097] The cells of the internal knitted membrane Ml are here open cells connected to each other by material.

[0098] The external knitted membrane M2 comprises a plurality of cells (not referenced) or meshes regularly distributed circumferentially.

[0099] The cells of the external knitted membrane M2 are here open cells connected to each other by material.

[0100] Preferably, the coverage rate of the external knitted membrane M2, defined as the ratio between the total surface area of ​​cells and the surface area of ​​the knitted membrane external M2, is at least equal to 20% and strictly less than 100%, preferably at least equal to 80% in order to maximize the contact surface of the external surface M2b of the external knitted membrane M2 with the ground and thus minimize the contact pressure.

[0101] The coverage rate of the internal knitted membrane M1, defined as the ratio between the total surface area of ​​cells and the surface area of ​​the internal knitted membrane M1, is lower than the coverage rate of the external knitted membrane M2 defined as the ratio between the total surface area of ​​cells and the surface area of ​​the external knitted membrane M2.

[0102] For example, the coverage rate of the internal knitted membrane Ml is at least equal to 20% and strictly less than 100%.

[0103] As illustrated in [Fig.3] and in a non-limiting manner, the cells of the internal knitted membrane M1 and of the external knitted membrane M2 overlap in the radial direction.

[0104] Alternatively, it could be provided that the cells of the knitted internal membrane M1 are offset in a staggered manner relative to the cells of the knitted external membrane M2.

[0105] The connecting threads F, connecting the internal knitted membrane M1 and the external knitted membrane M2, each have a diameter between 0.05 mm and 2 mm and a radial distance between 0.05 mm and 2 mm.

[0106] The thickness of the internal knitted membrane Ml is between 0.15 mm and 3 mm.

[0107] The thickness of the external knitted membrane M2 is between 0.15 mm and 3 mm.

[0108] The three-dimensional T-fabric, forming the tread 4, has a total thickness of between 3 mm and 20 mm.

[0109] Alternatively, more than two knitted membranes could be provided, connected radially to each other by connecting threads, for example at least three knitted membranes, forming a number of superimposed layers of fabric greater than one.

[0110] As illustrated in [Fig.2], each inner M1 and outer M2 knitted membrane is made up of a single strip of fabric.

[0111] Alternatively, it could be provided that one and / or the other of the knitted membranes, respectively internal M1 and external M2, is constituted by a juxtaposition of strips of fabric.

[0112] In this case, the tread 4 is thus made in several parts, which makes it easy to replace an element in the event of damage.

[0113] The three-dimensional fabric T forming the tread 4 is made of a thermoplastic polymeric material included in the group comprising polyetheretherketone (PEEK), polyetherimide (PEI), polyimide (PI) and polyether- ketoneketone, (PEKK).

[0114] The three-dimensional T-fabric forming the tread 4 has the following mechanical characteristics, measured according to the ASTM D638 standard of ASTM (“American Society for Testing and Materials”) International: - a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 GPa, and, measured at a temperature equal to -196°C, at least equal to 1.2 GPa and at most equal to 9 GPa, and - a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature equal to -196°C, at least equal to 40 MPa and at most equal to 260 MPa.

[0115] The three-dimensional T-fabric forming the tread 4 has a compression pressure defined according to DIN EN ISO 3386-1 between the contact pressure of the tire increased by 1 kPa and the contact pressure of the tire increased by 10 kPa.

[0116] This prevents the fabric T from collapsing under the contact pressure imposed on the tire.

[0117] The three-dimensional T-fabric forming the tread 4 is assembled, for example, by gluing onto the shear strip 3. The gluing is preferably carried out with a low-viscosity glue.

[0118] Other assembly solutions could also be provided, for example, removable ones.

[0119] The three-dimensional T fabric is used here in a particular application to guarantee very low contact pressure and improve the traction of the tire 1 and in particular of the wheel 10.

[0120] The Victrex CT100™ material, of the PEEK type, is considered particularly interesting for the production of an airless tire, intended to equip an extraterrestrial exploration vehicle, intended to move, for example, on the moon or on the planet Mars, down to very low temperatures which can reach, for example, -243°C. This material has the advantage of having both a high Young's modulus in tension E (7 GPa), guaranteeing satisfactory rigidity, and a high maximum tensile stress Sm (252 MPa), guaranteeing satisfactory endurance, at very low temperatures (-196°C).

[0121] The Applicant carried out a motor test with three test pieces: a smooth test piece A, a test piece B having a staggered pattern and a test piece C formed by the three-dimensional fabric T according to the invention.

[0122] Each test piece measures 6 mm in thickness.

[0123] Each test piece A, B, C is placed in a container containing sand or regolith.

[0124] A load Fz is applied along the vertical axis Z to each test piece, then the loaded test piece is set in motion along the longitudinal axis X perpendicular to the vertical axis Z. The load Fz is here equal to 15 daN.

[0125] The experiment is carried out in an ambient atmosphere, and at a temperature equal to 20°C.

[0126] The curve illustrated in [Fig.4] represents the results for each test piece A, B, C of the coefficient of friction q = Fx / Fz (on the ordinate) in relation to the displacement dx of the test piece, along the longitudinal axis X, in mm (on the abscissa).

[0127] It is noted that the three-dimensional fabric T specimen C makes it possible to obtain a coefficient of friction higher than the smooth specimen A and the specimen B for displacements of up to 35 mm.

[0128] Furthermore, the three-dimensional T fabric has the advantage of not modifying the flattening of the tire, unlike test piece B.

[0129] Thanks to the particular structure of the tread of the airless tire, formed exclusively in three-dimensional fabric, the contact pressure with the ground is minimized by maximizing the contact surface with the ground, which makes it possible to improve the traction of the airless tire without degrading it.

[0130] Such a tread also promotes the flattening of the tire on the ground.

[0131] Finally, such a tread also has the advantage of being particularly light compared to known treads.

Claims

Claims

1. Airless pneumatic tire (1) for a vehicle, comprising, radially from the inside to the outside, a supporting structure (2), intended to cooperate with a rim (100) of a wheel (10), a shear band (3) and a tread (4), the shear band (3) comprising, radially from the inside to the outside, a radially inner membrane (31), a shear structure (32) and a radially outer membrane (33), characterized in that the supporting structure (2), the shear band (3) and the tread (4) are each made of at least one material, preferably thermoplastic, having the following mechanical characteristics, measured according to ASTM D638 standard of the ASTM (“American Society for Testing and Materials”) International: - a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 GPa,and, measured at a temperature equal to -196°C, at least equal to 1.2 GPa and at most equal to 9 GPa, and -a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature equal to -196°C, at least equal to 40 MPa and at most equal to 260 MPa, and in that the tread (4) is made exclusively of a three-dimensional fabric (T).,

2. A tire (1) according to claim 1, wherein the three-dimensional fabric (T) forming the tread (4) comprises at least two knitted membranes (Ml, M2), namely an inner knitted membrane (Ml) and an outer knitted membrane (M2) connected together radially by a plurality of connecting threads (F), each knitted membrane (Ml, M2) comprising an inner surface (Mla, M2a) and an outer surface (Mlb, M2b), the inner surface (Mla) of the inner knitted membrane (Ml) being integral with the shear strip (3), and the outer surface (M2b) of the outer knitted membrane (M2) being configured to be in contact with the ground surface.

3. A tire (1) according to claim 2, wherein the inner knitted membrane (M1) and the outer knitted membrane (M2) have different structures.

4. A tire (1) according to claim 2 or 3, wherein the outer knitted membrane (M2) comprises a plurality of cells distributed circumferentially.

5. Tire (1) according to any one of claims 2 to 4, in which the coverage rate of the external knitted membrane (M2), defined as the ratio between the total surface area of cells and the surface area of the external knitted membrane (M2), is at least equal to 20% and strictly less than 100%, preferably at least equal to 80%.

6. A tire (1) according to claim 5, wherein the coverage rate of the internal knitted membrane (M1), defined as the ratio between the total surface area of cells and the surface area of the internal knitted membrane (M1), is lower than the coverage rate of the external knitted membrane (M2).

7. Tire (1) according to any one of the preceding claims, in which the three-dimensional fabric (T) forming the tread (4) has a total thickness at least equal to 3 mm and at most equal to 20 mm.

8. A tire (1) according to any one of the preceding claims, wherein the three-dimensional fabric (T) forming the tread (4) is made of a thermoplastic polymeric material included in the group comprising polyetheretherketone (PEEK), polyetherimide (PEI), polyimide (PI) and polyetherketoneketone (PEKK).

9. A tire (1) according to any preceding claim, wherein the three-dimensional fabric (T) forming the tread (4) has a compression pressure defined according to DIN EN ISO 3386-1 between the tire contact pressure increased by 1kPa and the tire contact pressure increased by 10kPa.

10. A tire (1) according to any preceding claim, wherein the supporting structure (2), the shear band (3) and the tread (4) are each made of the same material.

11. An airless tire (1) according to any preceding claim, wherein the shear structure (32) is constituted by a plurality of circumferentially distributed shear elements (32a).

12. A wheel (10) comprising an airless tire (1) according to any preceding claim mounted on a rim (100).

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