Airless tire, specifically designed for extraterrestrial vehicles, featuring an optimized shear strip

Abstract

The present invention relates to an airless tire (1) for a vehicle, comprising, radially from the inside out, a carrier structure (2), intended to cooperate with a rim (100) of a wheel (10), a shear strip (3) integral with the carrier structure (2) and a tread (4) integral with the shear strip (3), the shear strip (3) comprising, radially from the inside out, an internal shear membrane (31), a shear structure (32) constituted by a plurality of circumferentially distributed shear elements (32a) and an external shear membrane (33). The internal shear membrane (31) and the external shear membrane (33) of the shear strip (3) comprise a plurality of successive motifs (34, 35) distributed circumferentially around the circumferential perimeter of the corresponding shear membrane (33, 34). Figure for the abstract: Fig 2

Description

Title of the invention: Airless tire, particularly for extraterrestrial vehicles, comprising an optimized shear strip. Technical field of the invention

[0001] The present invention relates to the field of airless tires, particularly those intended for use on extraterrestrial exploration vehicles, specifically designed to travel, for example, on the Moon or on Mars, in environments subject to very high temperature variations, ranging from very low temperatures down to -243°C to very high temperatures up to +130°C. Such a thermal gradient is notably measured at the Moon's South Pole.

[0002] The present invention relates more particularly to the shear strip of such an airless tire. Prior art

[0003] A conventional tire subjected to the internal pressure of an inflation gas, generally air, or a conventional airless or solid tire, not subjected to the internal pressure of an inflation gas, 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.

[0004] 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 which has performance comparable to that of a conventional tire. An airless tire, mounted on a hub, or a rim, is sometimes called a "non-pneumatic elastic wheel".

[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 frame made up of structural elements and intended to cooperate with a rim or a hub; and

[0009] - a tread integral with the carcass and intended to transmit to said carcass, rolling stresses, to be worn and to guarantee the tire's grip with the ground.

[0010] The frame comprises, radially from the inside out:

[0011] - a load-bearing structure, intended to structurally support at least part of the load applied to the tire and attached to the rim or hub; and

[0012] - a shear strip, intended to transmit by shear the forces of rolling to the load-bearing structure and to contribute at least in part to carrying the load.

[0013] The load-bearing structure includes, 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.

[0014] 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.

[0015] The shear strip comprises, radially from the inside out:

[0016] - a first radially inner membrane,

[0017] - a shear layer consisting of one or more shear elements, And

[0018] - a second radially external membrane intended to receive the strip of bearing and connected to the inner radial membrane by the shear layer.

[0019] Generally, 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 a layer or a superposition of layers of reinforcements embedded in a polymer material.

[0020] 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.

[0021] 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.

[0022] 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 band, a load-bearing structure made of highly resistant polyresin spokes, and a hub made of two pieces of reinforced steel.

[0023] However, the shear strips of a state-of-the-art airless tire have two main disadvantages, which are a generally high mass and a generation of ground contact pressures within a relatively narrow range of values.

[0024] Thus, high contact pressures can only be generated by a shear strip having a very high mass, which is neither mechanically viable nor economically acceptable.

[0025] Furthermore, the high levels of rigidity of the shear band will generate high contact pressures, implying a risk of the tire sinking into soft ground, particularly as on the moon, and generate high rolling resistance, generating high energy consumption, penalizing with regard to the energy autonomy of the extraterrestrial vehicle.

[0026] Thus, in applications with severe environmental constraints, particularly in very low temperature applications, the shear levels of the shear band, necessary to generate low contact pressures, are difficult to achieve with a shear layer made of conventional polymeric materials.

[0027] Finally, by increasing the load applied to the tire, for example between 50 daN and 100 daN per wheel, it was found that the constituent elements of the tire overlap, and in particular the shear elements, which is not acceptable.

[0028] Consequently, there is a need to remedy the aforementioned drawbacks. Description of the invention

[0029] The inventors aim to design an airless tire with an improved flatness in order to improve the traction of the airless tire while being able to support loads between 5 daN and 200 daN per wheel, in particular by choosing an appropriate shear strip.

[0030] The invention aims in particular to increase the length of the contact area at iso load and at iso maximum stress in the overall structure.

[0031] Another objective is to design an airless tire capable of operating in an extraterrestrial environment at very low temperatures, typically within the range of -243°C to +130°C. The tire according to the invention can also be adapted for use in a terrestrial environment and on various types of soil, including sandy and stony ground.

[0032] The present invention relates to an airless tire for a vehicle, comprising, radially from the inside out, a carrier structure intended to cooperate with a rim or a wheel hub, a shear strip integral with the carrier structure and a tread integral with the shear strip.

[0033] The shear strip comprises, radially from the inside out, a radially inner or internal shear membrane, a shear structure made up of a plurality of circumferentially distributed shear elements and a radially outer or external shear membrane.

[0034] The internal shear membrane and / or the external shear membrane of the shear strip comprises a plurality of successive motifs distributed circumferentially on the circumferential perimeter of the corresponding shear membrane.

[0035] In other words, the respective perimeters of the internal shear membrane and the external shear membrane of the shear band are not circular, unlike the respective perimeters of the internal and external shear membranes of the shear band of existing airless tires.

[0036] Such patterns make it possible to increase the length of the corresponding shear membrane compared to a shear membrane with a circular circumferential perimeter.

[0037] Indeed, we observe a length of the corresponding shear membrane increased by 0.01% to 5% compared to a shear membrane with a circular circumferential perimeter.

[0038] Thus, when the wheel goes flat, the patterns will allow the internal and external corrugated shear membranes respectively to lengthen in the circumferential direction and thus increase the circumferential length of the contact with the ground, and thus decrease the average contact pressure of the tire on the ground.

[0039] By "successive patterns" is meant a succession of patterns along the perimeter of the corresponding shear membrane.

[0040] Thanks to the particular structure of the shear band, the average 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 while being able to support high loads, between 5 daN and 200 daN per wheel, and without increasing the maximum stress in the overall structure, i.e. of the carcass beyond a threshold value depending on the material.

[0041] Such a shear strip also promotes the flattening of the tire on the ground.

[0042] Such a discrete shear structure has the advantage of being lighter than a continuous shear structure. Furthermore, its stiffness can be more precisely optimized.

[0043] The shear strip according to the invention makes it possible to minimize the average contact pressure with the ground, between 0.10 bar and 0.15 bar, preferably 0.12 bar, for a wheel width of 300mm, an average diameter between 800 mm and 900 mm, and a load of 100 daN, by maximizing the contact area with the ground, which makes it possible to improve tire traction.

[0044] Finally, such a shear band also has the advantage of being particularly light compared to known shear bands.

[0045] Furthermore, the corrugated shape of one or both of the shear strip membranes in combination with the modulus of elasticity of the material(s) constituting the corresponding membrane makes it possible to optimize the mechanical stiffness characteristics of the shear strip, in order to obtain the distribution and value of the contact pressures with the ground, adapted to the use of the vehicle concerned.

[0046] Advantageously, the patterns of a plurality of patterns are identical to each other and are regularly distributed over the circumferential perimeter of the corresponding shear membrane.

[0047] For example, each motif extends over an angular sector with an angle between 5° and 15°, preferably between 8° and 10°.

[0048] Preferably, each motif of a plurality of motifs includes a substantially flat anchoring section, at least one concave shape and at least one convex shape.

[0049] By "concave" is meant a shape curved towards the inside of the tire.

[0050] By "convex", we mean a shape curved outwards from the tire, opposite to concave.

[0051] Advantageously, the anchoring section of the internal shear membrane cooperates, preferably tangentially, with a first internal end of a shear element of the shear structure and the supporting structure.

[0052] Advantageously, the anchoring section of the external shear membrane cooperates, preferably tangentially, with a second external end of a shear element of the shear structure and the tread.

[0053] For example, the anchoring section of a pattern connects tangentially at each of its ends to straight sections of adjacent patterns.

[0054] For example, the anchoring section forms with a cylindrical geometry passing through two ends of each motif, an angle between 5° and 30°.

[0055] According to one embodiment, each motif of the internal shear membrane successively circumferentially comprises the substantially flat anchoring section, the concave shape and the convex shape.

[0056] According to one embodiment, each motif of the external shear membrane successively comprises circumferentially the substantially flat anchoring section, the concave shape and the convex shape.

[0057] Alternatively, the convex shape could be located between the anchoring section and the concave shape.

[0058] In the case where the internal shear membrane and the external shear membrane of the shear strip each comprise a plurality of motifs, the plurality of motifs of the internal shear membrane is parallel to the plurality of motifs of the external shear membrane.

[0059] For example, the concave shape of each motif of the internal shear membrane is radially opposite the concave shape of each motif of the external shear membrane and the convex shape of each motif of the internal shear membrane is radially opposite the convex shape of each motif of the external shear membrane.

[0060] Alternatively, one could provide for an angular offset of the patterns of the internal shear membrane relative to the patterns of the external shear membrane.

[0061] It could also be envisaged that the patterns of the internal shear membrane would be different from the patterns of the external shear membrane

[0062] Alternatively, it could also be provided that the plurality of motifs of the internal shear membrane forms a mirror image, with respect to the average surface of the shear structure, of the plurality of motifs of the external shear membrane.

[0063] For example, the concave shape of each motif of the internal shear membrane is radially opposite the convex shape of each motif of the external shear membrane and the convex shape of each motif of the internal shear membrane is radially opposite the concave shape of each motif of the external shear membrane.

[0064] For example, the number of motifs is equal to the number of shear elements of the shear structure.

[0065] Each motif comprises at least one convex part, at least one concave part and a single anchoring section.

[0066] In other words, the number of motifs corresponds to the number of anchor sections.

[0067] Advantageously, the shear elements of the shear structure are distributed circumferentially in a regular pitch and extend radially between the internal shear membrane and the external shear membrane.

[0068] Without limitation, each shear element comprises two opposing curvatures.

[0069] Preferably, 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.

[0070] 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.

[0071] 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.

[0072] The Young's modulus in tension E and the maximum tensile stress Sm are measured on a stress-stretch 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 ("American Society for Testing and Materials"). (Materials) International. 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.

[0073] The Young's tensile modulus 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 intended operating temperatures.

[0074] Consequently, the inventors have chosen materials whose aforementioned mechanical characteristics ensure a satisfactory compromise between the load capacity and durability required for the airless tire under the intended operating conditions. The airless tire must be capable of carrying a load typically between 5 daN and 200 daN, and is intended to be mounted on a vehicle typically capable of traveling at a maximum speed of 20 km / h.

[0075] In the context of the present invention, the inventors have surprisingly demonstrated that such a high-performance thermoplastic polymeric material 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.

[0076] 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.

[0077] For example, the supporting structure consists of a plurality of radii regularly distributed circumferentially. Without limitation, each spoke herein comprises an inner end fixed to the rim, for example by fastening means such as screws (nuts / bolts) or rivets, a concave portion, and an outer end fixed to the shear strip by means of screws or rivets. By way of further, and without limitation, said fastening means could be configured to secure both a spoke of the tire and the rim.

[0078] 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

[0079] 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:

[0080] [Fig.1] represents an overall perspective view of a wheel comprising an airless tire according to an embodiment of the invention;

[0081] [Fig.2] illustrates a front view of the wheel of [Fig.1], illustrating the flattening of the tire;

[0082] [Fig.2A] represents a detail of [Fig.2];

[0083] [Fig.2B] represents a detail of [Fig.2A];

[0084] [Fig.2C] represents a detail of [Fig.2A];

[0085] [Fig.3] represents a graph comparing the contact area of ​​the tire with the ground of the tire according to the invention with respect to a known airless tire whose inner and outer shear band membrane perimeter is circular;

[0086] [Fig.4] represents a graph comparing the stresses in the external and internal corrugated shear membranes respectively, as well as in the shear elements of the tire according to the invention; and

[0087] [Fig.5] represents a table summarizing, for a wheel width of 300mm, under a load of 100 daN, the measured wheel area length, the average contact pressure, the deflection corresponding to the radial crushing of the tire and various maximum stresses.

[0088] Detailed description of at least one embodiment

[0089] 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.

[0090] 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.

[0091] The [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.

[0092] By "rim" we mean a structure for connection with the vehicle and central support of the tire 1.

[0093] 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.

[0094] The airless tire 1 comprises, radially from the inside out, a load-bearing structure 2, intended to cooperate with the rim 100 or a hub, a shear strip 3 integral with the load-bearing structure 2 and a tread 4 integral with the shear strip 3.

[0095] The supporting structure 2 is made up, here, of a plurality of radii 21 regularly distributed circumferentially.

[0096] 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).

[0097] 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.

[0098] 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.

[0099] As illustrated, the shear structure 32 consists of a plurality of shear elements 32a, here distributed circumferentially in a regular pitch and extending radially between the radially inner membrane or internal shear membrane 31 and the radially outer membrane or external shear membrane 33.

[0100] Without limitation, each shear element 32a comprises two opposing curvatures.

[0101] The load-bearing structure 2 is made of a high-performance thermoplastic polymer material.

[0102] The material constituting at least the load-bearing structure 2 has the following mechanical characteristics, measured according to 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.

[0103] As illustrated in detail in Figures 2A, 2B and 2C, the radially inner membrane 31 and the radially outer membrane 33 of the shear strip 3 comprise a plurality of successive patterns 34, 35, visible respectively in Figures 2B and 2C, distributed circumferentially over the circumferential perimeter of the corresponding shear membrane.

[0104] In other words, the respective perimeters of the radially inner membrane 31 and the radially outer membrane 33 of the shear band 3 are not circular, unlike the respective perimeters of the radially inner and radially outer membranes of the shear band of existing tires.

[0105] Such motifs 34, 35 make it possible to increase the length of the corresponding shear membrane compared to a shear membrane with a circular circumferential perimeter. Indeed, the length of the corresponding shear membrane is increased by 0.01% to 5% compared to a shear membrane with a circular circumferential perimeter.

[0106] Thus, when the wheel 10 goes flat, the patterns 34, 35 will allow the internal and external corrugated shear membranes respectively to lengthen in the circumferential direction and thus increase the circumferential length of contact with the ground, and thus decrease the average contact pressure of the tire on the ground.

[0107] Generally, the radially inner membrane 31 and / or the radially outer membrane 33 of the shear band 3 comprises a plurality of successive motifs 34, 35 distributed circumferentially over the circumferential perimeter of the corresponding shear membrane.

[0108] By "successive patterns" is meant a succession of patterns along the perimeter of the corresponding shear membrane.

[0109] Motifs 34, 35 of a plurality of motifs are here identical to each other and are regularly distributed over the circumferential perimeter of the corresponding shear membrane.

[0110] As illustrated in [Fig.2B], each internal motif 34 of the internal shear membrane 31 comprises successively an anchoring section 34a substantially planar, a concave shape 34b and a convex shape 34c.

[0111] As illustrated in [Fig.2C], each external motif 35 of the external shear membrane 33 comprises successively an anchoring section 35a substantially planar, a concave shape 35b and a convex shape 35c.

[0112] In general, each motif 34, 35 of a plurality of motifs comprises an anchoring section 34a, 35a substantially planar, at least one concave shape 34b, 35b and at least one convex shape 34c, 35c.

[0113] As illustrated in [Fig.2B], the anchoring section 34a of the internal shear membrane 34 cooperates with a first internal end 32b of a shear element 32a of the shear structure 32 and the supporting structure 2.

[0114] As illustrated in [Fig.2C], the anchoring section 35a of the external shear membrane 33 cooperates with a second external end 32c of a shear element 32a of the shear structure 32 and the tread 4.

[0115] By "concave" is meant a shape curved towards the inside of the tire.

[0116] By "convex", we mean a shape curved outwards from the tire, opposite to concave.

[0117] The patterns of the corresponding shear membrane are periodic, that is to say they have a constant pitch.

[0118] The anchoring section 34a, 35a is made so as to connect tangentially at each of its ends to the straight sections of the adjacent motifs.

[0119] The anchoring section 34a of each internal motif 34 forms with a cylindrical geometry Cl, passing through the two ends 34d, 34e of each internal motif 34, an angle a between 5° and 30°.

[0120] The anchoring section 35a of each external motif 35 forms with a cylindrical geometry C2, passing through the two ends 35d, 35e of each external motif 35, an angle a between 5° and 20°.

[0121] Each motif 34, 35 extends over an angular sector of angle [3] between 5° and 15°, preferably between 8° and 10°. The angle [3] is formed between two straight lines each passing through an endpoint 34d, 34e; 35d, 35e and the center XC1-XC1; XC2-XC2 of the corresponding cylindrical geometry Cl; C2.

[0122] As illustrated, the inner membrane 31 and the outer membrane 33 of the shear strip 3 each comprise a plurality of motifs 34, 35.

[0123] In the illustrated example, and in no way limiting, the concave shape 34b of the pattern 34 of the inner membrane 31 is radially opposite the concave shape 35b of the pattern 35 of the outer membrane 33 and the convex shape 34c of the pattern 34 of the inner membrane 31 is radially opposite the convex shape 35c of the pattern 35 of the outer membrane 33.

[0124] In other words, the plurality of patterns 35 of the outer membrane 33 is parallel to the plurality of patterns 34 of the inner membrane 31.

[0125] Alternatively, an angular offset could be provided between the motifs 34 of the inner membrane 31 and the motifs 35 of the outer membrane 33.

[0126] It could also be foreseen that the plurality of patterns 34 of the inner shear membrane 31 forms a mirror image, with respect to an average surface of the shear structure 32, of the plurality of patterns 35 of the outer shear membrane 33.

[0127] Figures 3 and 4 illustrate two graphs showing the gains obtained for an airless tire whose shear band includes corrugated external and internal shear membranes respectively, with reference to [Fig.2A], compared to a known airless tire whose internal and external shear band membranes respectively have a circular perimeter.

[0128] It can be seen that, according to the invention, the circumferential length of the contact area of ​​the tire with the ground is increased by 80% compared to the circumferential length of the contact area of ​​a known tire. In this example, the circumferential length of the contact area of ​​tire 1 according to the invention is equal to 90 mm and the circumferential length of the contact area of ​​a known tire is 50 mm.

[0129] It is also observed that the stresses in the corrugated external and internal shear membranes respectively, as well as in the shear elements 32 of the shear structure 32 of the tire 1 according to the invention, are less than or equal to the stresses in the shear membranes of the known airless tire.

[0130] For reading the graph on stress levels, it should be noted that 1 daN / mm2 is equal to 1 bar which is equal to 0.1 MPa.

[0131] Fig. 5 represents a table summarizing, for a wheel width of 300 mm, an average diameter of the external shear membrane 33 of 840 mm, and an average diameter of the internal shear membrane 31 of 720 mm, under a load of 100 daN, the circumferential length of the measured contact area, the average contact pressure, the deflection corresponding to the radial crushing of the tire and various maximum stresses relative to a control, i.e. to a tire comprising shear membranes of circular perimeter.

[0132] In the tire according to the invention, a greater deflection than the witness is observed with a greater circumferential length of contact area, which makes it possible to reduce the pressure on the ground.

[0133] Such an optimized shear band makes it possible to reduce the rigidity of the shear band without increasing the maximum stress generated in the shear band and thus to obtain the lowest possible average contact pressure of the tire with the ground.

[0134] Such a shear strip also promotes the flattening of the tire on the ground.

[0135] Furthermore, not increasing the maximum stress prevents degradation of endurance compared to known tires.

Claims

Demands

1. An airless tire (1) for a vehicle, comprising, radially from the inside out, a carrier structure (2) designed to cooperate with a rim (100) of a wheel (10), a shear strip (3) integral with the carrier structure (2), and a tread (4) integral with the shear strip (3), the shear strip (3) comprising, radially from the inside out, an internal shear membrane (31), a shear structure (32) consisting of a plurality of circumferentially distributed shear elements (32a), and an external shear membrane (33), characterized in that the internal shear membrane (31) and / or the external shear membrane (33) of the shear strip (3) comprises a plurality of successive motifs (34, 35) circumferentially distributed on the circumferential perimeter of the corresponding shear membrane (33, 34),the respective perimeters of the internal shear membrane (31) and / or the external shear membrane (33) of the shear strip (3) not being circular, each motif (34, 35) of a plurality of motifs comprising an anchoring section (34a, 35a) substantially planar, at least one concave shape (34b, 35b) and at least one convex shape (34c, 35c).

2. Pneumatic (1) according to claim 1, wherein the patterns (34, 35) of a plurality of patterns are identical to each other and are regularly distributed over the circumferential perimeter of the corresponding shear membrane (31, 33).

3. Pneumatic (1) according to claim 1 or 2, wherein each motif (34, 35) extends over an angular sector of angle (|3) between 5° and 15°.

4. Pneumatic (1) according to any one of the preceding claims, wherein the anchoring section (34a) of the internal shear membrane (34) cooperates with a first internal end (32b) of a shear element (32a) of the shear structure (32) and the supporting structure (2).

5. Pneumatic (1) according to any one of the preceding claims, wherein the anchoring section (35a) of the external shear membrane (33) cooperates with a second end (32c) external of a shear element (32a) of the shear structure (32) and the tread (4).

6. Pneumatic (1) according to any one of the preceding claims, wherein the anchoring section (34a, 35a) of a motif (34, 35) connects tangentially at each of its ends to the straight sections of the adjacent motifs.

7. Pneumatic (1) according to any one of the preceding claims, wherein the anchoring section (34a, 35a) forms with a cylindrical geometry (C) passing through two ends (34d, 34e; 35d, 35e) of each motif (34, 35), an angle (a) between 5° and 20°.

8. Pneumatic (1) according to any one of the preceding claims, wherein each motif (34) of the internal shear membrane (31) successively circumferentially comprises the substantially planar anchoring section (34a), the concave shape (34b) and the convex shape (34c).

9. Pneumatic (1) according to any one of the preceding claims, wherein each motif (35) of the external shear membrane (33) successively circumferentially comprises the substantially planar anchoring section (35a), the concave shape (35b) and the convex shape (35c).

10. Pneumatic (1) according to any one of claims 4 to 9, wherein the concave shape (34b) of each motif (34) of the internal shear membrane (31) is radially opposite the concave shape (35b) of each motif (35) of the external shear membrane (33) and the convex shape (34c) of each motif (34) of the internal shear membrane (31) is radially opposite the convex shape (35c) of each motif (35) of the external shear membrane (33).

11. Pneumatic (1) according to any one of the preceding claims, wherein the number of motifs (34, 35) is equal to the number of shear elements (32a) of the shear structure (32).

12. Pneumatic (1) according to any one of the preceding claims, wherein the shear elements (32a) of the shear structure (32) are distributed circumferentially in a regular pitch and extend radially between the internal shear membrane (31) and the external shear membrane.

13. 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.

14. A tire (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 at least one material, preferably thermoplastic, having the following mechanical properties, measured according to ASTM International Standard D638: - a tensile Young's modulus 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 equal to 260 MPa.

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