Wheel, in particular for an extraterrestrial vehicle, comprising an airless tire and a plurality of portions for connecting the spokes of the supporting structure to the rim

Abstract

The present invention relates to a mounted assembly (10) for a vehicle comprising a rim (100) comprising a cylindrical outer surface (101) and an airless tire (1) mounted on said rim (100), the airless tire (1) comprising, radially from the inside to the outside, a supporting structure (2) secured to an outer surface (101) of the rim (100), a shear band (3) secured to the supporting structure (2) and a tread (4) secured to the shear band (3). The supporting structure (2) comprises a plurality of spokes (21) regularly distributed circumferentially and a plurality of connecting portions (22) configured to each connect a spoke (21) to the outer surface (101) of the rim (100). Figure for abstract: Fig 2

Description

Title of the invention: Wheel, in particular for an extraterrestrial vehicle, comprising an airless tire and a plurality of portions for connecting the spokes of 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, in particular intended to equip an extraterrestrial exploration vehicle, in particular intended to move, for example, on the moon or on the planet Mars, in an environment subject to very strong temperature variations, which can reach very low temperatures down to -243°C and very high temperatures up to +130°C. Such a thermal gradient is notably measured at the South Pole of the moon.

[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. State of the 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 from which they are made have mechanical properties incompatible with use in an environment which can reach very low temperatures, also called cryogenic temperatures.

[0004] It is known to have, as an alternative technical solution to a conventional tire, an airless tire, or more generally a tire without inflation gas, which carries the load thanks to structural components and which has performances comparable to those of a conventional tire. An airless tire, mounted on a hub, or a rim, is sometimes called a "non-pneumatic elastic wheel".

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

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

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

[0008] - a carcass made up of structural elements and intended to cooperate with a rim or hub; and

[0009] - a tread secured to the carcass and intended to transmit to said carcass, rolling forces, to be worn and to guarantee the grip of the tire with the ground.

[0010] The carcass comprises, radially from the inside to the outside:

[0011] - a supporting structure, intended to structurally support at least in part the load applied to the tire and secured to the rim or hub; and

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

[0013] The supporting structure comprises, radially from the inside to the outside, means of connection with a rim or a hub, radial elements or spokes, and means of connection with the shear band.

[0014] However, the supporting structure does not generally define a sealed internal cavity intended to contain a pressurized gas, as in a conventional tire. Therefore, an airless tire does not need to have a sealed connection with respect to a rim or a hub.

[0015] The shear band comprises, radially from the inside to the outside:

[0016] - a first radially inner membrane,

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

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

[0019] Generally, the first and second membranes have a modulus of elasticity in circumferential extension often substantially greater than the modulus of elasticity in shear of the shear layer of polymeric material, such that, under the applied load, the membranes do not elongate or elongate only slightly when the tire is flattened while rolling. The relative displacement of the membranes relative to each other occurs by shear in the shear layer. For example, the membranes, respectively inner and outer, comprise a layer or a superposition of layers of reinforcements coated in a polymeric material.

[0020] The shear layer of polymeric material is made, for example, of a polymeric material, such as a natural rubber or a synthetic rubber, or of a polyurethane. Typically, the material of the shear layer has a shear modulus of at least 3 MPa and at most 20 MPa, which allows for easier flattening of the shear band under load.

[0021] Finally, the tread, which is the radially outer component of the tire, is most often made of a polymeric material, such as a ca- natural or synthetic rubber.

[0022] For several years, Michelin North America has marketed a mounted assembly, consisting of an airless tire, as previously described, and a wheel, under the name MICHELIN® TWEEL®. This technical solution mainly comprises a tread, a shear-band, a load-bearing structure, consisting of highly resistant polyresin spokes and a hub consisting of two reinforced steel parts.

[0023] However, increasing the load capacity of these airless tires requires:

[0024] - either to increase the thickness of the structural elements of the carcass, which involves an increase in stresses in these structural elements. Indeed, an increase in the thickness of a structural element, intended to work in bending, such as, for example, a beam of a load-bearing structure, will lead to an increase in bending stresses.

[0025] - either to increase the number of structural elements of the carcass, distributed around of the rim. However, in the event of 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, that is to say an overlap of the spokes of the supporting structure, in particular 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 guaranteeing suitable mechanical operation.

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

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

[0030] Another objective is to design an airless tire capable of rolling in an extraterrestrial environment, at very low temperatures, typically in the range [-243°C; +130°C]. The tire according to the invention can also be adapted for rolling in a terrestrial environment and on soils of various types, which may be sandy or stony.

[0031] The present invention relates to a mounted assembly or wheel for a vehicle comprising a rim comprising a cylindrical outer surface and a airless tire mounted on said rim, the airless tire comprising, radially from the inside to the outside, a supporting structure secured to an outer surface of the rim, a shear band secured to the supporting structure and a tread secured to the shear band.

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

[0033] In other words, the spokes of the supporting structure are integral with the outer surface of the rim, by means of 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, i.e. to densify it without risk of the spokes overlapping each other in the initial unloaded state, with the aim of supporting 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.

[0036] As a result, the internal 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 the spokes overlapping each other in the initial unloaded state.

[0037] By "rim" is meant a structure for connection with the vehicle and central support of the tire. The rim comprises, in a known manner, a fixing hub intended to be fixed to the vehicle and at least one outer ferrule delimiting the outer surface of the rim. The fixing hub is connected to the outer ferrule by a connection structure, for example one or two radial flanges.

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

[0039] Preferably, the internal end of each spoke of the supporting structure forms an angle with a tangent to the external 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 the spokes overlapping each other in the initial unloaded state.

[0041] Advantageously, each connecting portion comprises a fixing surface matching in shape with the cylindrical outer surface of the rim and secured to said outer surface, an anchoring surface matching in shape with the inner end of an associated spoke and secured to said inner end and a substantially radial connecting surface connecting 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 of between 0° and 25° relative 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 connecting portion extends over less than 25%, preferably less than 10%, of the curvilinear length of the associated spoke. The smaller the anchoring surface, the more the spoke works in bending.

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

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

[0049] In the case where the supporting structure comprises a plurality of connecting portions associated with a spoke, all of said connecting portions extend transversely over at least 50% of the width of the outer surface of the rim.

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

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

[0052] According to another embodiment, the internal end of the spokes of the supporting structure is secured to the associated connecting portion by first fixing means, such as for example screw means (screws / nuts) or rivets, and in which each connecting portion is secured to the rim by second fixing means, distinct from the first fixing means.

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

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

[0055] For example, the shear band comprises, radially from the inside to the outside, an inner shear membrane, a shear structure constituted by a plurality of circumferentially distributed shear elements and an outer shear membrane.

[0056] Advantageously, the shear elements of the shear structure are distributed circumferentially at a regular pitch and extend radially between the internal shear membrane and the external shear membrane.

[0057] In a non-limiting manner, each shear element comprises at least two opposing curvatures.

[0058] Preferably, the supporting structure, the shear band and the tread are each made of at least one material, preferably thermoplastic, having the following mechanical characteristics, measured according to the ASTM D638 standard of the ASTM (“American Society for Testing and Materials”) International: - a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 GPa, and, measured at a temperature equal to -196°C, at least equal to 1.2 GPa and at most equal to 9 GPa, and - a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature equal to -196°C, at least equal to 40 MPa and at most equal to 260 MPa.

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

[0061] The Young's modulus in tension E and the maximum tensile stress Sm are measured on a "stress - elongation" tensile curve, established from a tensile test carried out on a standardized test piece, in accordance with the standard ASTM D638 ("Standard Test Method for Tensile Properties of Plastics"), developed by ASTM ("American Society for Testing and Materials") International. The standard test piece has a length of 84 mm and a thickness of 2 mm, and includes a necking having a length of 25 mm and a width of 4 mm. The tensile speed applied to the test piece is 500 mm / min. The tensile Young's modulus E is a tangent modulus measured at low strain.

[0062] The Young's modulus in traction E conditions the rigidities and the load capacity of the airless tire, at the target operating temperatures. The maximum tensile stress Sm conditions the endurance of the airless tire, at the target operating temperatures.

[0063] Consequently, the inventors have chosen materials whose aforementioned mechanical characteristics make it possible to guarantee a satisfactory compromise between the load capacity and the endurance required for the airless tire under the intended conditions of use. The airless tire must be capable of carrying a load typically between 5 daN and 200 daN, and is intended to be mounted on a vehicle which can typically travel up to a maximum speed of 20 km / h.

[0064] In the context of the present invention, the inventors have demonstrated, surprisingly, 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 carried out at -196°C.

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

[0066] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0067] [Fig.l] 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 [Fig.l];

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

[0070] [Fig.3], [Fig.4] and [Fig.5] are partial sectional views illustrating alternative arrangements of the connecting portion or portions across the width of a radius of the supporting structure.

[0071] Detailed description of at least one embodiment

[0072] In the following description, the terms “circumferential”, “axial” and “radial” are defined relative 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.l] is an overall perspective view of a mounted assembly or wheel 10 comprising a rim 100 and an airless tire 1 mounted on said rim 100.

[0075] By "rim" is meant a structure for connection with the vehicle and central support of the tire 1. The rim comprises, in a known manner, a fixing hub intended to be fixed to the vehicle and at least one outer ferrule delimiting the outer surface of the rim. The fixing hub is connected to the outer ferrule by a connection structure, for example one or two radial flanges.

[0076] The rim 100 here comprises a cylindrical outer 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 to the outside, a supporting structure 2, intended to cooperate with the rim 100, a shear band 3 secured to the supporting structure 2 and a tread 4 secured to the shear band 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 shims 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 integral with the outer surface 101 of the rim 100, by means of a single connecting portion 22 as illustrated in FIGS. 3 and 4 or of several connecting portions 22 as illustrated in [Fig.5].

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

[0082] Alternatively, it could be provided that the connecting portions are hollow.

[0083] In a non-limiting manner, the spokes 21 each comprise here an internal end 21a secured to the connecting portion 22, a concave portion 21b and an external end 21c secured 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 internal end 21a of the spokes 21 is secured to the associated connecting portion 22 by first fixing means 25, such as screw means (screws / nuts) or by rivets, and each connecting portion 22 is secured to the rim by said first fixing means 25.

[0085] In other words, said first fixing means 25 are configured to fix both a spoke 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 internal end 21a of the spokes 21 is secured to the connecting portion 22 by first fixing means 26, such as screw means (screws / nuts) or by rivets, and the connecting portion 22 is secured to the rim by second fixing means 27, distinct from the first fixing means.

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

[0088] The internal 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 a 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 the spokes overlapping each other in the initial unloaded state.

[0089] Each connecting portion 22 comprises a fixing surface 22a matching in shape with the cylindrical outer surface 101 of the rim 100 and secured to said outer surface 101, an anchoring surface 22b matching in shape with the inner end 21a of an associated spoke 21 and secured to said inner end 21a and a substantially radial connecting surface 22c connecting 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 of between 0° and 25° relative 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 anchoring surface 22b of each connecting portion 22 extends over less than 25%, preferably less than 10%, of the curvilinear length of the associated spoke 21. The smaller the anchoring surface 22b, the more the spoke 21 works in bending.

[0093] As illustrated in [Fig.3], the connecting portion 22 associated with a spoke 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 spoke 21 extends transversely over a portion 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 integral with 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] Generally, the supporting structure 2 comprises at least one connecting portion 22 associated with a spoke 21 and extending transversely over at least 50% of the width of the outer surface 101 of the rim 100.

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

[0097] As illustrated, the shear structure 32 is constituted by a plurality of shear elements 32a, here distributed circumferentially according to 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] In a non-limiting manner, each shear element 32a comprises two opposite curvatures.

[0099] The supporting structure 2 is made of a thermoplastic polymer material, said to be high-performance.

[0100] The material constituting at least the supporting structure 2 has the following mechanical characteristics, measured according to the ASTM D638 standard of ASTM (“American Society for Testing and Materials”) International: - a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 GPa, and, measured at a temperature equal to -196°C, at least equal to 1.2 GPa and at most equal to 9 GPa, and - a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature equal to -196°C, at least equal to 40 MPa and at most equal to 260 MPa.

[0101] Such an optimized connection between the spokes of the supporting structure and the rim allows to increase the number of spokes of the supporting structure, in order to support a greater vertical load on the airless tire.

Claims

Claims

1. Mounted assembly (10) for a vehicle comprising a rim (100) comprising a cylindrical outer surface (101) and an airless tire (1) mounted on said rim (100), the airless tire (1) comprising, radially from the inside to the outside, a supporting structure (2) secured to an outer surface (101) of the rim (100), a shear band (3) secured to the supporting structure (2) and a tread (4) secured to the shear band (3), characterized in that the supporting structure (2) comprises a plurality of spokes (21) regularly distributed circumferentially and a plurality of connecting portions (22) configured to each connect a spoke (21) to the outer surface (101) of the rim (100).

2. Mounted assembly (10) according to claim 1, in which the spokes (21) of the supporting structure (2) each comprise an internal end (21a) secured to at least one connecting portion (22), at least one intermediate portion (21b) and an external end (21c) secured to the shear strip (3).

3. Mounted assembly (10) according to claim 2, in which the inner end (21a) of each spoke (21) of the supporting structure (2) forms an angle (a) with a tangent to the outer surface (101) of the rim (100) strictly greater than 0°, preferably between 1° and 35°.

4. Mounted assembly (10) according to claim 2 or 3, in which each connecting portion (22) comprises a fixing surface (22a) in shape matching the cylindrical outer surface (101) of the rim (100) and integral with said outer surface (101), an anchoring surface (22b) in shape matching the inner end (21a) of an associated spoke (21) and integral with said inner end (21a) and a substantially radial connecting surface (22c) connecting the fixing surface (22a) to the anchoring surface (22b).

5. Mounted assembly (10) according to claim 4, in which 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).

6. Mounted assembly (10) according to claim 4 or 5, in which the anchoring surface (22b) of each connecting portion (22) extends over at least 25% of the curvilinear length of the associated radius (21).

7. A mounted assembly (10) according to any one of the preceding claims- preceding, in which the connecting portion (22) associated with a spoke (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.

8. Mounted assembly (10) according to claim 4 taken in combination with any one of the preceding claims, in which the internal end (21a) of the spokes (21) of the supporting structure (2) is integral with the associated connecting portion (22) by first fixing means (25), and in which each connecting portion (22) is integral with the rim (100) by said first fixing means (25).

9. Mounted assembly (10) according to claim 4 taken in combination with any one of claims 1 to 7, in which the internal end (21a) of the spokes (21) of the supporting structure (2) is integral with the associated connecting portion (22) by first fixing means (26), and in which each connecting portion (22) is integral with the rim (100) by second fixing means (27), distinct from the first fixing means (X).

10. A mounted assembly (10) according to any preceding claim, wherein the connecting portion (22) forms a single piece with the associated spoke (21) of the supporting structure (22).

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

12. Mounted assembly (10) according to any one of the preceding claims, in which the supporting structure (2), the shear band (3) and the tread (4) are each made of at least one material, preferably thermoplastic, having the following mechanical characteristics, measured according to ASTM D638 standard of ASTM (American Society for Testing and Materials) International: - a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 GPa, and, measured at a temperature equal to -196°C, at least equal to 1.2 GPa and at most equal to 9 GPa, and - a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature equal to -196°C, at least equal to 40 MPa and at most equal to 260 MPa.

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