A wheel, notably for an extraterrestrial vehicle, comprising an airless tire and a plurality of spoke connections from the supporting structure to the rim

Abstract

The present invention relates to a vehicle assembly (10) comprising a rim (100) having a cylindrical outer surface (101) 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 load-bearing structure (2) comprises a plurality of spokes (21) regularly distributed circumferentially and a plurality of connecting portions (22) configured to connect each spoke (21) to the outer surface (101) of the rim (100). Figure for the abbreviation: Fig 2

Description

Title of the invention: Wheel, particularly for an extraterrestrial vehicle, comprising an airless tire and a plurality of spoke connections from the supporting structure to the 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 connection between the spokes of a supporting structure and a 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 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 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.

[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 that is 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 an assembled tire, 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, particularly 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 the appropriate connection between the spokes of a supporting structure and a 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 having a cylindrical outer surface and an airless tire mounted on said rim, the airless tire comprising, radially from the inside to the outside, a carrier structure attached to an outer surface of the rim, a shear strip attached to the carrier structure and a tread attached to the shear strip.

[0032] The supporting structure comprises a plurality of spokes regularly distributed circumferentially and a plurality of connecting portions or wedges configured to connect each a spoke to the outer surface of the rim.

[0033] In other words, the spokes of the supporting structure are attached to the outer surface of the rim, via at least one connecting portion.

[0034] Such an optimized connection between the spokes of the supporting structure and the rim makes it possible to increase the number of spokes of the supporting structure, in order to support a greater vertical load on the airless tire.

[0035] Indeed, such connecting portions make it possible to increase the number of spokes of the supporting structure, that is to say to densify it without risk of overlap of the spokes on 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, that is to say of the carcass beyond a threshold value depending on the material.

[0036] It follows that the inner end of each spoke of the supporting structure is not tangent to the cylindrical outer surface of the rim and forms an angle with a tangent to the outer surface of the rim strictly greater than 0°, preferably between 1° and 35°, so that it is possible to add spokes to the perimeter of the rim without risking overlap of the spokes with each other in the initial unloaded state.

[0037] 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.

[0038] Advantageously, the radii of the supporting structure each comprise an internal end integral with at least one connecting portion, at least one intermediate portion, for example concave or convex, and an external end integral with the shear strip, for example, by means of screws or rivets.

[0039] Preferably, the inner end of each radius of the supporting structure forms an angle with a tangent to the outer surface of the rim strictly greater than 0°, preferably between 1° and 35°.

[0040] In other words, the inner end of each spoke of the supporting structure is not tangent to the cylindrical outer surface of the rim, so that it is possible to add spokes to the perimeter of the rim without risking overlap of the spokes with each other in the initial unloaded state.

[0041] Advantageously, each connecting portion comprises a fixing surface in conformity of form with the cylindrical outer surface of the rim and integral with said outer surface, an anchoring surface in conformity of form with the inner end of an associated radius and integral with said inner end and a substantially radial connecting surface linking the fixing surface to the anchoring surface.

[0042] By "substantially radial" is meant a direction parallel to the radial direction or a direction inclined at an angle between 0° and 25° with respect to the radial direction.

[0043] According to one embodiment, the connecting portions are solid.

[0044] According to another embodiment, the connecting portions are hollow.

[0045] For example, the fixing surface of each connecting portion extends over an angular sector between 50% and 100% of the perimeter of the outer surface of the rim.

[0046] For example, the anchoring surface of each link portion extends over less than 25%, preferably less than 10%, of the curvilinear length of the associated radius. The smaller the anchoring surface, the more the radius is subjected to bending.

[0047] For example, the connecting portion associated with a radius of the supporting structure extends transversely over at least 50% of the width of the outer surface of the rim, preferably over said entire width.

[0048] By "width" we mean the dimension along an axis parallel to the axis of rotation of the wheel.

[0049] In the case where the supporting structure includes a plurality of connecting portions associated with a radius, the set of said connecting portions extends transversely over at least 50% of the width of the outer surface of the rim.

[0050] According to one embodiment, the inner end of the spokes of the supporting structure is joined to the associated connecting portion by first fastening means, such as, for example, screwing means (screws / nuts) or rivets, and each connecting portion is joined to the rim by said first fastening means.

[0051] In other words, said first fastening means are configured to fix both a tire radius, a connecting portion and the rim.

[0052] According to another embodiment, the inner end of the radii of the supporting structure is fixed to the associated connecting portion by means of first fastening, such as, for example, screws (screws / nuts) or rivets, and in which each portion of the connection is attached to the rim by second means of attachment, distinct from the first means of attachment.

[0053] Preferably, but in no way limitingly, the connecting portion forms a single piece, i.e. monobloc, made of material, with the associated radius of the supporting structure.

[0054] Alternatively, the connecting portion could be a separate part from the associated radius and attached to the associated radius by any means of fastening, gluing, welding, screws, rivets, etc...

[0055] 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.

[0056] 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.

[0057] Without limitation, each shear element comprises at least two opposing curvatures.

[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];

[0070] [Fig.3], [Fig.4] and [Fig.5] are partial cross-sectional views illustrating variants of the arrangement of the portion or portions of connection over the width of a radius of the load-bearing structure.

[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 designates 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] The term "rim" means a structure for connecting to the vehicle and providing central support for the tire 1. 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.

[0076] The rim 100 here comprises an outer cylindrical surface 101.

[0077] 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.

[0078] 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.

[0079] As illustrated in the figures, the supporting structure 2 comprises a plurality of spokes 21 regularly distributed circumferentially and a plurality of connecting portions or wedges 22 configured to connect a spoke 21 to the outer surface 101 of the rim 100.

[0080] In other words, the spokes 21 of the supporting structure 2 are fixed to the outer surface 101 of the rim 100, by means of a single portion of link 22 as illustrated in figures 3 and 4 or of several portions of link 22 as illustrated in [Fig.5].

[0081] As illustrated, the bonding portions 22 are solid, that is to say filled with matter.

[0082] Alternatively, the connecting portions could be provided for to be hollow.

[0083] Without limitation, the radii 21 each here comprise an internal end 21a attached to the connecting portion 22, a concave portion 21b and an external end 21c attached to the shear strip 3 by means of serial screws or rivets (not shown).

[0084] According to an example, illustrated in detail A of [Fig.2], the inner end 21a of the spokes 21 is attached to the connecting portion 22 by first fastening means 25, such as screws (screws / nuts) or rivets, and each connecting portion 22 is attached to the rim by said first fastening means 25.

[0085] In other words, said first fastening means 25 are configured to fix both a radius 21 of the tire 1, a connecting portion 22 and the rim 100.

[0086] According to another example, illustrated in detail B of [Fig.2], the inner end 21a of the spokes 21 is joined to the connecting portion 22 by first fastening means 26, such as screwing means (screws / nuts) or rivets, and the connecting portion 22 is joined to the rim by second fastening means 27, distinct from the first fastening means.

[0087] Alternatively, it could also be provided that the connecting portion 22 forms a single piece, i.e. monobloc, made of material, with the associated radius 21 of the supporting structure 22.

[0088] The inner end 21a of each spoke 21 of the supporting structure 2 is not tangent to the cylindrical outer surface 101 of the rim 100 and forms an angle α with a tangent T to the outer surface 101 of the rim 100 strictly greater than 0°, preferably between 1° and 35°, so that it is possible to add spokes to the perimeter of the rim without risking overlap of the spokes with each other in the initial unloaded state.

[0089] Each connecting portion 22 comprises a fixing surface 22a in conformity of form with the cylindrical outer surface 101 of the rim 100 and integral with said outer surface 101, an anchoring surface 22b in conformity of form with the inner end 21a of an associated radius 21 and integral with said inner end 21a and a substantially radial connecting surface 22c linking the fixing surface 22a to the anchoring surface 22b.

[0090] By "substantially radial" is meant a direction parallel to the radial direction or a direction inclined at an angle between 0° and 25° with respect to the radial direction.

[0091] For example, the fixing surface 22a of each connecting portion 22 extends over an angular sector between 50% and 100% of the perimeter of the outer surface 101 of the rim 100.

[0092] For example, the anchorage surface 22b of each link portion 22 extends over less than 25%, preferably less than 10%, of the curvilinear length of the associated radius 21. The smaller the anchorage surface 22b, the more the radius 21 is subjected to bending.

[0093] As illustrated in [Fig.3], the connecting portion 22 associated with a radius 21 extends transversely over the entire width of the outer surface 101 of the rim 100. Alternatively, as illustrated in [Fig.4], the connecting portion 22 associated with a radius 21 extends transversely over a part of the width of the outer surface 101 of the rim 100.

[0094] In the example illustrated in [Fig. 5], the spokes 21 of the supporting structure 2 are fixed to the outer surface 101 of the rim 100, by means of two connecting portions 22. The two connecting portions 22 extend transversely over at least 50% of the width of the outer surface 101 of the rim 100,

[0095] In general, the supporting structure 2 includes at least one connecting portion 22 associated with a radius 21 and extending transversely over at least 50% of the width of the outer surface 101 of the rim 100.

[0096] The shear strip 3 comprises, radially from the inside out, a radially inner membrane 31, integral with the supporting structure 2, in particular with the outer end 21c of the radii 21, a shear structure 32 and a radially outer membrane 33.

[0097] 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.

[0098] Without limitation, each shear element 32a comprises two opposing curvatures.

[0099] The load-bearing structure 2 is made of a high-performance thermoplastic polymer material.

[0100] 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.

[0101] Such an optimized connection between the spokes of the supporting structure and the rim makes it possible to increase the number of spokes of 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) having a cylindrical outer surface (101) and an airless tire (1) mounted on said rim (100) having an outer surface (101), the airless tire (1) comprising, radially from the inside out, a carrier structure (2) integral with the outer surface (101) of the rim (100), a shear strip (3) integral with the carrier structure (2) and a tread (4) integral with the shear strip (3), the carrier structure (2) comprising a plurality of spokes (21) regularly distributed circumferentially and a plurality of connecting portions (22) configured to connect each of a spoke (21) to the outer surface (101) of the rim (100), the spokes (21) of the carrier structure (2) each comprising an inner end (21a) integral with at least one connecting portion (22),at least one intermediate portion (21b) convex or concave and an external end (21c) integral with the shear strip (3), characterized in that the internal end (21a) of each radius (21) of the supporting structure (2) forms an angle (a) with a tangent to the external surface (101) of the rim (100) of between 1° and 35° and in that each connecting portion (22) comprises a fixing surface (22a) in conformity of form with the cylindrical external surface (101) of the rim (100) and integral with said external surface (101), an anchoring surface (22b) in conformity of form with the internal end (21a) of an associated radius (21) and integral with said internal end (21a) and a substantially radial connecting surface (22c) linking the fixing surface (22a) to the anchoring surface (22b).

2. Assembly mounted (10) according to claim 1, wherein the set of fixing surfaces (22a) of each connecting portion (22) extends over an angular sector between 50% and 100% of the perimeter of the outer surface (101) of the rim (100).

3. Assembled assembly (10) according to claim 1 or 2, wherein the anchoring surface (22b) of each connecting portion (22) extends over at least 25% of the curvilinear length of the associated radius (21).

4. Assembled assembly (10) according to any one of the preceding claims, wherein the connecting portion (22) associated with a radius (21) of the supporting structure (2) extends transversely over at least 50% of the width of the outer surface (101) of the rim (100), preferably over the entire said width.

5. Assembly (10) according to any one of the preceding claims, wherein the inner end (21a) of the spokes (21) of the supporting structure (2) is integral with the connecting portion (22) associated by first fastening means (25), and wherein each connecting portion (22) is integral with the rim (100) by said first fastening means (25).

6. Assembly (10) according to any one of claims 1 to 4, wherein the inner end (21a) of the spokes (21) of the supporting structure (2) is integral with the connecting portion (22) associated by first fastening means (26), and wherein each connecting portion (22) is integral with the rim (100) by second fastening means (27), distinct from the first fastening means (X).

7. Assembly (10) according to any one of the preceding claims, wherein the connecting portion (22) forms a single piece with the associated radius (21) of the supporting structure (22).

8. 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.

9. 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, at least equal to 40 MPa and at most equal to 260 MPa.

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