Airless tire for extraterrestrial vehicles featuring a three-dimensional fabric tread

Abstract

The present invention relates to an airless tire for a vehicle capable of operating in an extraterrestrial environment, at very low temperatures, and on various types of terrain. Such an airless tire comprises, radially from the inside out, a load-bearing structure designed to cooperate with a rim, a shear strip, 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 of 20°C, of ​​at least 1 GPa and at most 6 GPa, and, measured at a temperature of -196°C, of ​​at least 1.2 GPa and at most 9 GPa, and a maximum tensile stress Sm, measured at a temperature of 20°C, of ​​at least 25 MPa and at most 150 MPa, and, measured at a temperature of -196°C, of ​​at least 40 MPa and at most 260 MPa, these mechanical characteristics being measured according to ASTM D638 and the tread (4) is made exclusively of a three-dimensional fabric (T). Figure for the abbreviation: 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 for use on extraterrestrial exploration vehicles designed to travel, for example, on the Moon or on Mars, in environments subject to very extreme temperature variations, ranging from extremely low temperatures down to -243°C to extremely high temperatures up to +130°C. Such a thermal gradient is notably measured at the Moon's South Pole. It relates more particularly to the tread of such an airless tire. Prior art

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

[0003] It is known that, as a technical alternative to a conventional tire, there is an airless tire, or more generally a tire without inflation gas, which carries the load thanks to structural components and has performance comparable to that of a conventional tire. An airless tire, mounted on a hub or 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 what follows, 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 in relation to an “outer” element.

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

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

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

[0010] - a tread, intended to transmit the forces to the shear strip rolling resistance, wear and tear, and ensuring tire grip on the ground.

[0011] The load-bearing structure comprises, radially from the inside out, means for connecting with a rim or hub, radial elements or spokes, and means for connecting with the shear strip.

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

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

[0014] - a first inner membrane,

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

[0016] - a second outer membrane.

[0017] In the example described, the first and second membranes have a circumferential tensile modulus of elasticity often significantly greater than the shear modulus of elasticity of the polymer shear layer, such that, under the applied load, the membranes do not elongate or elongate very little when the tire is flattened during rolling. The relative displacement of the membranes with respect to each other occurs by shearing in the shear layer. For example, the inner and outer membranes, respectively, comprise superimposed layers of reinforcements embedded in a polymer material.

[0018] The shear layer made of polymeric material is, for example, made of a polymeric material, such as natural rubber or synthetic rubber, or polyurethane. Typically, the shear layer material has a shear modulus of at least 3 MPa and at most 20 MPa, which allows for easier flattening of the shear strip 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 complete 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 strip (in (English, "shear-band"), a load-bearing structure, consisting of highly resistant polyresin spokes and a hub made of two pieces of reinforced steel.

[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 strip, have levels of rigidity which will generate high contact pressures, implying a risk of the tire sinking into soft ground, especially as on the moon, and generate high rolling resistance, implying high energy consumption, penalizing with regard to the energy autonomy of the extraterrestrial vehicle.

[0023] In addition, common polymeric materials, such as natural rubber or synthetic rubber, which are generally used to make up 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. Description of the invention

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

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

[0027] The present invention relates to an airless tire for a vehicle, comprising, radially from the inside out, a load-bearing structure, intended to cooperate with a rim or a wheel hub, a shear strip and a tread.

[0028] The shear strip comprises, radially from the inside out, a radially inner membrane, a shear structure and a radially outer membrane.

[0029] The load-bearing structure, the shear strip and the tread are each made of at least one material, preferably thermoplastic, having the following mechanical characteristics, measured according to ASTM D638 of the ASTM (American Society for Testing and Materials) International: - a Young's modulus in tension E, measured at a temperature of 20°C, of ​​at least 1 GPa and at most 6 GPa, and, measured at a temperature of -196°C, of ​​at least 1.2 GPa and at most 9 GPa, and -a maximum tensile stress Sm, measured at a temperature of 20°C, of ​​at least 25 MPa and at most 150 MPa, and, measured at a temperature of -196°C, of ​​at least 40 MPa and at most 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 "constituted exclusively", it is meant that the tissue is not embedded in a matrix.

[0033] By "three-dimensional" or "three-dimensional" fabric, we mean a fabric comprising at least two knitted membranes, for example in warp, which have been extended in a third dimension, for example by bonding yarns 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 operate in an extraterrestrial environment that can vary between very low and very high temperatures, typically in the range [-243°C; 130°C], and on soils of various kinds, which can be sandy or stony, the Applicant has selected materials having, essentially, a Young's modulus in tension E and a maximum tensile stress Sm within specific ranges both at ambient temperature, taken as 20°C, and at very low temperature, taken as -196°C.

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

[0037] The Young's modulus in tension E determines the stiffness and load-bearing capacity of the airless tire at the intended operating temperatures. The maximum tensile stress Sm determines the endurance of the airless tire at the temperatures intended uses.

[0038] Consequently, the inventors have chosen materials whose aforementioned mechanical characteristics guarantee a satisfactory compromise between the load capacity and endurance required for the airless tire under the intended operating conditions. 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 typically capable of traveling at a maximum speed of 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 area with the ground, which makes it possible to improve the traction of airless tires without degrading them.

[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 inner knitted membrane and an outer knitted membrane, radially connected to each other by a plurality of bonding yarns. Each knitted membrane comprises an inner surface and an outer surface, the inner surface of the inner knitted membrane being, for example, integral with the shear strip, in particular with the outer radial membrane thereof, and the outer surface of the outer knitted membrane being configured to be in contact with the ground surface.

[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 outer knitted membrane, defined as the ratio between the total surface area of ​​alveoli and the surface area of ​​the outer 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 area of ​​the external surface of the external knitted membrane with the ground and thus to minimize the contact pressure.

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

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

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

[0050] Preferably, the coverage rate of the inner knitted membrane, defined as the ratio between the total surface area of ​​alveoli and the surface area of ​​the inner knitted membrane, is less than the coverage rate of the outer 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 limitingly, the alveoli of the inner knitted membrane and the outer knitted membrane overlap in the radial direction.

[0053] Alternatively, it could be provided that the alveoli of the inner knitted membrane are staggered in relation to the alveoli of the outer knitted membrane.

[0054] For example, the connecting threads, linking 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 polyaryletherketone (PAEK) family. A polyetheretherketone, such as, for example, Victrex CT 100™ and Victrex 450G™ materials, marketed by Victrex®, has the required mechanical characteristics, particularly at cryogenic temperatures.

[0060] A polyimide, such as, for example, the Aurum PL500A™ material, has excellent mechanical properties at cryogenic temperatures, but is more difficult to implement 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 surprisingly demonstrated that such a high-percentage 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 taken at -196°C.

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

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

[0065] According to a preferred embodiment, the load-bearing structure, the shear strip, and the tread are each made of the same material. Using the same material for all the components of an airless tire simplifies manufacturing and facilitates adhesion between the different components.

[0066] For example, the shear structure consists of a plurality of circumferentially distributed shear elements. Such a discrete shear structure has the advantage of being lighter than a continuous shear structure. Furthermore, its stiffness can be more precisely optimized.

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

[0068] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0069] [Fig.1] represents an overall perspective view of a wheel comprising an airless tire according to an embodiment of the invention;

[0070] [Fig.2] illustrates in detail the tread of the tire in [Fig.1] according to an embodiment of the invention;

[0071] [Fig.3] represents 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 with respect 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. 1 is an overall perspective view of an assembled wheel 10 comprising a rim 100 and an airless tire 1 mounted on said rim 100.

[0077] By "rim" we mean 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 out, a load-bearing structure 2, intended to cooperate with the rim 100, a shear strip 3 integral with the load-bearing structure 2 and a tread 4 integral with the shear strip 3.

[0080] The supporting structure 2 is made up, here, of a plurality of radii 21 regularly distributed circumferentially.

[0081] Without limitation, the spokes 21 each here comprise an inner end 21a attached to the rim 100, for example by means of fastening (not shown), such as screws (screws / nuts) or rivets (not shown), a concave portion 21b and an outer end 21c attached to the shear strip 3 by means of screws or rivets (not shown).

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

[0083] The shear strip 3 comprises, radially from the inside out, 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 made up of a plurality of shear elements 32a, here regularly distributed circumferentially between the radially inner membrane 31 and the radially outer membrane 33.

[0085] Without limitation, each shear element 32a comprises two opposing curvatures.

[0086] The load-bearing structure 2 and the shear strip 3 are each made of a high-performance thermoplastic polymeric material.

[0087] The material constituting at least the load-bearing structure 2 and the shear strip 3 have 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 of 20°C, of ​​at least 1 GPa and at most 6 GPa, and, measured at a temperature of -196°C, of ​​at least 1.2 GPa and at most 9 GPa, and -a maximum tensile stress Sm, measured at a temperature of 20°C, of ​​at least 25 MPa and at most 150 MPa, and, measured at a temperature of -196°C, of ​​at least 40 MPa and at most 260 MPa. Tread

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

[0089] By "constituted exclusively", it 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 inner knitted membrane M1 and an outer knitted membrane M2 and a plurality of connecting yarns F radially linking 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 in warp, which have been extended in a third dimension, here by the bonding threads F.

[0092] Each knitted membrane Ml, M2 comprises an internal surface Ml a, M2a and an external 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 external surface M2b of the external knitted membrane M2 is configured to cooperate with the soil surface.

[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 (unreferenced) alveoli or meshes regularly distributed circumferentially.

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

[0098] The outer knitted membrane M2 comprises a plurality of (unreferenced) alveoli or meshes regularly distributed circumferentially.

[0099] The alveoli of the external knitted membrane M2 are here open alveoli 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 ​​the alveoli 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 area 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 inner knitted membrane M1, defined as the ratio between the total surface area of ​​alveoli and the surface area of ​​the inner knitted membrane M1, is less than the coverage rate of the outer knitted membrane M2, defined as the ratio between the total surface area of ​​alveoli and the surface area of ​​the outer 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 no way limitingly, the alveoli of the inner knitted membrane M1 and of the outer knitted membrane M2 overlap in the radial direction.

[0104] Alternatively, the alveoli of the inner knitted membrane M1 could be staggered relative to the alveoli of the outer knitted membrane M2.

[0105] The connecting wires F, linking the inner knitted membrane M1 and the outer 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 fabric T, forming the tread 4, has a total thickness between 3 mm and 20 mm.

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

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

[0111] Alternatively, one could provide that one and / or the other of the internal knitted membranes M1 and external M2 respectively is made up of 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 case 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- ketone, (PEKK).

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

[0115] The three-dimensional fabric T forming the tread 4 has a compression pressure defined according to the DIN EN ISO 3386-1 standard 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 fabric T 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 envisaged, for example, demountable ones.

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

[0120] The Victrex CT100™ PEEK material is considered particularly interesting for the production of an airless tire intended to equip an extraterrestrial exploration vehicle designed to travel, for example, on the moon or on the planet Mars, down to very low temperatures, for example, -243°C. This material has the advantage of having both a high tensile Young's modulus 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 skills test with three test specimens: a smooth test specimen A, a test specimen B with a staggered pattern and a test specimen C formed by the three-dimensional fabric T according to the invention.

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

[0123] Each test tube A, B, C is placed in a container filled with sand or regolith.

[0124] A load Fz is applied along the vertical axis Z to each specimen, then the loaded specimen is moved 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 of 20 °C.

[0126] The curve illustrated in [Fig.4] represents the results for each specimen A, B, C of the coefficient of friction q = Fx / Fz (on the ordinates) with respect to the displacement dx of the specimen, along the longitudinal axis X, in mm (on the abscissas).

[0127] It is observed that the three-dimensional fabric T specimen C allows a coefficient of friction greater than the smooth specimen A and the specimen B for displacements up to 35 mm.

[0128] Moreover, the three-dimensional fabric T has the advantage of not altering the flattening of the tire, unlike the test specimen B.

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

[0130] Such a tread pattern 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

Demands

1. An airless tire (1) for a vehicle, comprising, radially from the inside out, a carrier structure (2) for cooperating with a rim (100) of a wheel (10), a shear strip (3) and a tread (4), the shear strip (3) comprising, radially from the inside out, a radially inner membrane (31), a shear structure (32) and a radially outer membrane (33), characterized in that the carrier structure (2), the shear strip (3) and the tread (4) are each made of at least one material, preferably thermoplastic, having the following mechanical properties, measured according to ASTM D638 of ASTM International (American Society for Testing and Materials): - a Young's modulus in tension E, measured at a temperature of 20°C, of ​​at least 1 GPa and at most equal to 6 GPa,and, measured at a temperature of -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 of 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature of -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. Pneumatic (1) according to claim 1, wherein the three-dimensional fabric (T) forming the tread (4) comprises, at least two knitted membranes (M1, M2), namely an inner knitted membrane (M1) and an outer knitted membrane (M2) connected radially by a plurality of connecting wires (F), each knitted membrane (M1, M2) comprising an inner surface (M1a, M2a) and an outer surface (M1b, M2b), the inner surface (M1a) of the inner knitted membrane (M1) 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. Pneumatic (1) according to claim 2, wherein the inner knitted membrane (M1) and the outer knitted membrane (M2) have different structures.

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

5. Pneumatic (1) according to any one of claims 2 to 4, wherein the coverage rate of the outer knitted membrane (M2), defined as the ratio between the total area of ​​alveoli and the area of ​​the outer knitted membrane (M2), is at least equal to 20% and strictly less than 100%, preferably at least equal to 80%.

6. Pneumatic (1) according to claim 5, wherein the coverage rate of the inner knitted membrane (M1), defined as the ratio between the total alveolar area and the area of ​​the inner knitted membrane (M1), is less than the coverage rate of the outer knitted membrane (M2).

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

8. 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. Tire (1) according to any one of the preceding claims, wherein the three-dimensional fabric (T) 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 1kPa and the contact pressure of the tire increased by 1OkPa.

10. Pneumatic (1) according to any one of the preceding claims, wherein the carrier structure (2), the shear strip (3) and the tread (4) are each made of the same material.

11. Airless pneumatic (1) according to any one of the preceding claims, wherein the shear structure (32) is constituted by a plurality of circumferentially distributed shear elements (32a).

12. Wheel (10) comprising an airless tire (1) according to any one of the preceding claims mounted on a rim (100).

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