A wheel specifically designed for extraterrestrial vehicles, featuring an airless tire and an optimized rim.

Abstract

The present invention relates to a vehicle assembly (10) comprising a rim (100) and an airless tire (1) mounted on said rim (100). The airless tire (1) comprises, radially from the inside out, a load-bearing structure (2) integral with an outer surface (101) of the rim (100), a shear strip (3) integral with the load-bearing structure (2), and a tread (4) integral with the shear strip (3). The outer surface (101) of the rim (100) comprises a plurality of successive patterns (102) distributed circumferentially around the perimeter of the outer surface (101) of the rim (100). Figure for the abbreviation: Fig 2A

Description

Title of the invention: Wheel, in particular for an extraterrestrial vehicle, comprising an airless tire and an optimized rim. Technical field of the invention

[0001] The present invention relates to the field of wheels comprising an airless tire, particularly intended for equipping an extraterrestrial exploration vehicle, specifically designed to travel, 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.

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

[0003] A conventional tire subjected to the internal pressure of an inflation gas, generally air, or a solid or pneumatic tire without conventional air, not subjected to the internal pressure of an inflation gas, are not suitable for such use, because the usual rubber-based materials which constitute them have mechanical properties incompatible with use in an environment which 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, increasing the load capacity of these airless tires requires:

[0024] - either to increase the thickness of the structural elements of the frame, which This implies an increase in stresses within these structural elements. Indeed, increasing the thickness of a structural element designed to work in bending, such as, for example, a load-bearing structural radius, will lead to an increase in bending stresses.

[0025] - either to increase the number of structural elements of the frame, distributed around the rim. However, in the event of a heavy load, contact between the structural elements may occur.

[0026] Thus, when the airless tire is subjected to a strong vertical load, an interpenetration of the spokes of the supporting structure is observed at the junction with the rim, i.e. an overlap of the spokes of the supporting structure in the initial unloaded state, which is not acceptable.

[0027] It is therefore not possible to increase the number of spokes beyond a certain quantity without modifying the rest of the structure and while ensuring suitable mechanical operation.

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

[0029] The inventors aim to design an airless tire capable of supporting loads between 5 daN and 200 daN per wheel, in particular by choosing an appropriate rim.

[0030] 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.

[0031] The present invention relates to a wheel assembly for a vehicle comprising a rim and an airless tire mounted on said rim, the airless tire comprising, radially from the inside out, a load-bearing structure attached to an outer surface of the rim, a shear strip attached to the load-bearing structure and a tread attached to the shear strip, the load-bearing structure comprising a plurality of radii regularly distributed circumferentially.

[0032] The outer surface of the rim comprises a plurality of successive patterns distributed circumferentially around the perimeter of the outer surface of the rim.

[0033] In other words, the outer surface of the rim is corrugated, therefore not cylindrical, unlike the cylindrical outer surface of existing wheel rims.

[0034] Such patterns make it possible to increase the number of spokes of the supporting structure, i.e. to densify it without risk of the spokes overlapping each other in the initial unloaded state, in order 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 casing beyond a threshold value depending on the material.

[0035] By "successive patterns" is meant a succession of patterns along the perimeter of the outer surface of the rim.

[0036] The term "rim" refers to a structure that connects to the vehicle and provides central support for the tire. The rim comprises, in a known manner, a mounting hub intended to be fixed to the vehicle and at least one outer flange defining the outer surface of the rim. The mounting hub is connected to the outer flange by a connecting structure, for example, one or two radial flanges.

[0037] Advantageously, the patterns of a plurality of patterns are identical to each other and are regularly distributed over the perimeter of the outer surface of the rim.

[0038] For example, each motif extends over an angular sector with an angle between 5° and 15°.

[0039] Advantageously, each motif of a plurality of motifs comprises at least one convex shape, at least one concave shape and a substantially planar anchoring section.

[0040] By "concave" is meant a shape curved towards the inside of the tire.

[0041] By "convex", we mean a shape curved outwards from the tire, opposite to concave.

[0042] Advantageously, the anchoring section of a pattern on the outer surface of the rim cooperates with a first inner end of a radius of the supporting structure.

[0043] Without limitation, the spokes herein each comprise an inner end attached to the rim, for example by means of fastening, such as screws (screws / nuts) or rivets, a concave portion and an outer end attached to the shear strip by means of screws or rivets.

[0044] Preferably, the first internal end of each radius of the supporting structure is tangential to the anchoring section of a corresponding pattern of the outer surface of the rim.

[0045] For example, the anchoring section of a pattern on the outer surface of the rim connects tangentially at each of its ends to the straight sections of the adjacent patterns.

[0046] For example, the anchoring section of a pattern on the outer surface of the rim forms with a cylindrical geometry passing through two ends of each pattern, an angle between 5° and 30°, preferably equal to 10°.

[0047] According to a non-limiting variant, each motif of the outer surface of the rim successively circumferentially comprises the convex shape, the concave shape and the anchoring section.

[0048] Alternatively, the convex shape could be located between the anchoring section and the concave shape.

[0049] For example, the number of patterns on the outer surface of the rim is equal to the number of spokes in the supporting structure.

[0050] In other words, the number of motifs corresponds to the number of anchor sections.

[0051] Preferably, the radii of the supporting structure are distributed circumferentially according to a regular pitch and extend radially between the outer surface of the rim and the shear strip.

[0052] For example, the shear band comprises, radially from the inside out, an internal shear membrane, a shear structure consisting of a plurality of circumferentially distributed shear elements and an external shear membrane.

[0053] 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.

[0054] In no way limitingly, each shear element comprises two opposing curvatures.

[0055] For example, and in no way limiting, the internal shear membranes and the external shear membranes of the shear strip are cylindrical.

[0056] Alternatively, it could be provided that the radially inner membrane and / or the radially outer membrane of the shear band comprises a plurality of successive patterns distributed circumferentially over the circumferential perimeter of the corresponding shear membrane.

[0057] Each motif comprising at least one concave shape, at least one convex shape and an anchoring section cooperating with a shearing element.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] The Young's tensile modulus 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 tensile modulus E is a tangent modulus measured at low strain.

[0062] 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 intended operating temperatures.

[0063] 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 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.

[0064] 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.

[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. Brief description of the drawings

[0066] 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:

[0067] [Fig.1] represents an overall perspective view of a wheel comprising an airless tire according to a first embodiment of the invention;

[0068] [Fig.2] illustrates a front view of the wheel of the [Fig.l];

[0069] [Fig.2A] represents a detail of [Fig. 2]; and

[0070] [Fig.2B] represents a detail of [Fig.2A].

[0071] Detailed description of at least one embodiment

[0072] 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.

[0073] 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 refers to a direction perpendicular to the axis of rotation XI-XI of the tire 1.

[0074] 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.

[0075] By "rim" we mean a structure for connection with the vehicle and central support of the tire 1.

[0076] 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.

[0077] 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.

[0078] The supporting structure 2 is made up, here, of a plurality of radii 21 regularly distributed circumferentially.

[0079] The spokes 21 of the supporting structure 2 are fixed to the outer surface 101 of the rim 100.

[0080] 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).

[0081] 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.

[0082] 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.

[0083] 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.

[0084] Without limiting the foregoing, each shear element 32a comprises two opposing curvatures.

[0085] The load-bearing structure 2 is made of a high-performance thermoplastic polymer material.

[0086] The material constituting at least the load-bearing structure 2 has the following mechanical characteristics, measured according to ASTM D638 of 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.

[0087] As illustrated in detail in [Fig.2A], the rim 100 comprises an outer surface 101 comprising a plurality of successive patterns 102 distributed circumferentially around the perimeter of the outer surface 101 of the rim 100.

[0088] In other words, the perimeter of the outer surface 101 of the rim 100 is not circular, unlike the perimeter of the outer surface of the rim of existing wheels.

[0089] Such motifs 102 make it possible to increase the number of rays 21 of the supporting structure 2, that is to say to densify it without risk of overlap of the rays 21 on each other in the initial unloaded state.

[0090] By "successive patterns" is meant a succession of patterns along the perimeter of the outer surface 101 of the rim 100.

[0091] The motifs 102 of a plurality of motifs are here identical to each other and are regularly distributed over the perimeter of the outer surface 101 of the rim 100.

[0092] As illustrated in [Fig.2B], each motif 102 of the outer surface 101 of the rim 100 comprises successively a convex shape 102a, a concave shape 102b and an anchoring section 102c substantially flat.

[0093] As illustrated in [Fig.2B], the anchoring section 102c of the outer surface 101 of the rim 100 cooperates with a first internal end 21a of a radius 21 of the supporting structure 2.

[0094] By "concave" is meant a shape curved towards the inside of the tire.

[0095] By "convex", we mean a shape curved outwards from the tire, opposite to concave.

[0096] The patterns of the outer surface 101 of the corresponding rim 100 are periodic, that is to say they are distributed according to a constant pitch.

[0097] The anchoring section 102c is made so as to connect tangentially at each of its ends to the straight sections of the adjacent motifs.

[0098] The anchoring section 102c of each motif 102 forms with a cylindrical geometry C, passing through the two ends 102d, 102e of each motif 102, an angle a between 5° and 30°, preferably equal to 10°.

[0099] Each motif 102 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 102d, 102e and the center XC1-XC1 of the corresponding cylindrical geometry Cl.

[0100] In the illustrated example, and in no way limitingly, the internal shear membranes 31 and the external shear membranes 33 of the shear band 3 are cylindrical.

[0101] Alternatively, the radially inner membrane 31 and / or the radially outer membrane 33 of the shear strip 3 could be provided to comprise a plurality of successive motifs distributed circumferentially around the circumferential perimeter of the corresponding shear membrane. Each motif comprising at least one concave shape, at least one convex shape, and an anchoring section cooperating with a shear element 32a.

[0102] Such an optimized rim makes it possible to increase the number of spokes in the supporting structure, in order to support a greater vertical load on the airless tire.

Claims

Demands

1. Assembly (10) for a vehicle comprising a rim (100) and an airless tire (1) mounted on said rim (100), the airless tire (1) comprising, radially from the inside out, a load-bearing structure (2) integral with an outer surface (101) of the rim (100), a shear strip (3) integral with the load-bearing structure (2) and a tread (4) integral with the shear strip (3), the load-bearing structure (2) comprising a plurality of radii (21) regularly distributed circumferentially, characterized in that the outer surface (101) of the rim (100) is corrugated and not cylindrical and comprises a plurality of successive patterns (102) distributed circumferentially around the perimeter of the outer surface (101) of the rim (100), each pattern (102) of a plurality of patterns successively circumferentially comprising a convex shape (102a),a concave shape (102b) and a substantially flat anchoring section (102c).

2. Assembled assembly (10) according to claim 1, wherein the patterns (102) of a plurality of patterns are identical to each other and are regularly distributed over the perimeter of the outer surface (101) of the rim (100).

3. Assembled assembly (10) according to claim 1 or 2, wherein each motif (102) extends over an angular sector of angle (|3) between 5° and 15°.

4. Assembly mounted (10) according to any one of the preceding claims, wherein the anchoring section (102c) of a pattern (102) of the outer surface (101) of the rim (100) cooperates with a first internal end (21a) of a radius (21) of the supporting structure (2).

5. Assembled assembly (10) according to claim 4, wherein the first internal end (21a) of each radius (21) of the supporting structure (2) is tangential to the anchoring section (102c) of a corresponding pattern (102) of the outer surface (101) of the rim (100).

6. Assembled assembly (10) according to any one of the preceding claims, wherein the anchoring section (102c) of a motif (102) of the outer surface (101) of the rim (100) connects to tangentially at each of its ends to the straight sections of the adjacent patterns.

7. Assembly mounted (10) according to any one of the preceding claims, wherein the anchoring section (102c) of a motif (102) of the outer surface (101) of the rim (100) forms with a cylindrical geometry (C) passing through two ends (102d, 102e) of each motif (102), an angle (a) between 5° and 30°, preferably equal to 10°.

8. Assembly assembled (10) according to any one of the preceding claims, wherein the number of motifs (102) of the outer surface (101) of the rim (100) is equal to the number of spokes (21) of the supporting structure (2).

9. Assembly (10) according to any one of the preceding claims, wherein the spokes (21) of the supporting structure (2) are distributed circumferentially in a regular pitch and extend radially between the outer surface (101) of the rim (100) and the shear strip (3).

10. Assembly (10) according to any one of the preceding claims, wherein the load-bearing structure (2), the shear strip (3) and the tread (4) are each made of the same material.

11. An assembly (10) according to any one of the preceding claims, wherein the load-bearing 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 at 40 MPa and at most equal to 260 MPa.

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