Airless tire for extraterrestrial vehicle capable of traveling at very low temperatures

Abstract

The invention relates to an airless tire (1) for a vehicle capable of traveling in an extraterrestrial environment at very low temperatures and on a variety of different surfaces. Such an airless tire (1) comprises, in the radial direction from inside to outside, a support structure (2) intended to cooperate with a rim or hub (3), a shear band (4) and a tread (6). According to the invention, at least one constituent material of the support structure (2), the shear band (4) and the tread (6) has a Young's modulus E, measured at a temperature of 20 DEG C, of at least 1 GPa and at most 6 GPa, a Young's modulus E, measured at a temperature of-196 DEG C, of at least 1.2 GPa and at most 9 GPa, a maximum tensile stress Sm, measured at a temperature of 20 DEG C, of at least 25 MPa and at most 150 MPa, and a maximum tensile stress Sm measured at a temperature of-196 DEG C is at least equal to 40 MPa and at most equal to 260 MPa, said mechanical properties being measured according to standard ASTM D638.

Description

Technical Field

[0001] The subject of the present invention is a non-pneumatic tire intended to be mounted on an extraterrestrial exploration vehicle intended to move around in an environment where extremely low temperatures can be reached (generally in the range of [-243 °C; +53 °C], as measured at the South Pole of the Moon), such as on the Moon or Mars. Background Art

[0002] Conventional pneumatic tires or conventional solid tires subjected to the internal pressure of an inflation gas (usually air) are not suitable for this use because the common rubber-based materials from which they are made have mechanical properties that are incompatible with use in an environment where extremely low temperatures (also known as cryogenic temperatures) can be reached.

[0003] Metal wheels for extraterrestrial vehicles have been produced. However, the disadvantage of such metal wheels is that they have non-linear vertical stiffness (i.e., constant within a limited operating range and changing rapidly when the maximum load is reached until the stiffness collapses), have a relatively large mass and have limited durability, which is not conducive to long-term use.

[0004] Furthermore, as an alternative technology to conventional tires, a non-pneumatic tire, or more generally a tire without an inflation gas, is known, which bears the load through structural components and has performance aspects comparable to those of conventional tires. A non-pneumatic tire mounted on a hub or rim is sometimes referred to as a "non-inflatable elastic wheel". Such non-pneumatic tires are described, for example, in documents WO 2003018332A1, FR2964597, WO 2012102932A1, WO 2018101937A1, WO 2018102303A1, WO 2018102560A1 and WO2018125186A1.

[0005] Hereinafter, the circumferential direction or longitudinal direction represents the rotational direction of the tire, the axial direction or transverse direction represents the direction parallel to the rotational axis of the tire, and the radial direction represents the direction perpendicular to the rotational axis of the tire.

[0006] A non-pneumatic tire generally includes, from the inside to the outside in the radial direction:

[0007] - a support structure intended to structurally bear at least part of the load and cooperate with a rim or hub,

[0008] - a shear band intended to transmit the driving force to the support structure by shear and contribute at least in part to bearing the load,

[0009] - and a tread intended to transmit the driving force to the shear band, intended to wear and intended to ensure the grip of the tire on the ground.

[0010] The support structure includes, radially from the inside outwards, means for connection to the rim or the hub, radial elements or spokes, and means for connection to the shear band. However, the support structure generally does not define a sealed internal cavity intended to contain pressurized gas as in a conventional tire. Thus, a non-pneumatic tire does not need to have a sealed connection to the rim or the hub.

[0011] In known embodiments, the shear band includes, radially from the inside outwards:

[0012] - a first inner membrane,

[0013] - a shear layer made of one or more polymeric materials,

[0014] - a second outer membrane.

[0015] In the above embodiments, the first and second membranes have a circumferential tensile elastic modulus that is generally significantly greater than the shear elastic modulus of the shear layer made of polymeric material, such that under an applied load, when the tire flattens during travel, the membranes hardly elongate. The relative movement of the membranes with respect to each other is achieved by shear in the shear layer. In a preferred embodiment, the inner and outer membranes each include a stack of reinforcing bodies coated with polymeric material.

[0016] The shear layer made of polymeric material is made of, for example, a polymeric material such as natural rubber or synthetic rubber or polyurethane. Generally, the material of the shear layer has a shear modulus of at least equal to 3 MPa and at most equal to 20 MPa, such that the shear band flattens more easily under load.

[0017] For several years, Michelin North America has been selling a mounting assembly consisting of the above non-pneumatic tire and wheel under the name This technical solution mainly includes a tread, a shear band, a support structure (consisting of very strong spokes made of synthetic resin), and a hub (consisting of two pieces of reinforced steel).

[0018] However, in applications at very low temperatures, the common polymeric materials used to manufacture non-pneumatic tires are not compatible with the specified temperature range. In addition, the stiffness level of the common polymeric materials used (especially those for the shear band) will generate high contact pressures (which means there is a risk that the tire will sink into soft ground, such as on the moon), and will generate high rolling resistance (which means high energy consumption), which is not conducive to the energy autonomy of extraterrestrial vehicles. Summary of the Invention

[0019] The objective set by the inventor is to design a non-pneumatic tire as described above, which can travel in an extraterrestrial environment at extremely low temperatures (usually in the range of [-243°C; +53°C]) and on various types of ground (which can be sandy or rocky).

[0020] This objective has been achieved by a non-pneumatic tire for a vehicle, which radially from the inside to the outside includes a support structure, a shear band, and a tread, intended to cooperate with a rim or a hub.

[0021] - The shear band radially from the inside to the outside includes a radial inner membrane, a shear structure, and a radial outer membrane.

[0022] - The support structure, the shear band, and the tread are each made of at least one material.

[0023] - At least one material for manufacturing the support structure, the shear band, and the tread has the following mechanical properties measured according to the ASTM (American Society for Testing and Materials) international standard ASTM D638:

[0024] - The tensile Young's modulus E measured at a temperature equal to 20°C is at least equal to 1 GPa and at most equal to 6 GPa, and the tensile Young's modulus E measured at a temperature equal to -196°C is at least equal to 1.2 GPa and at most equal to 9 GPa.

[0025] - The maximum tensile stress Sm measured at a temperature equal to 20°C is at least equal to 25 MPa and at most equal to 150 MPa, and the maximum tensile stress Sm measured at a temperature equal to -196°C is at least equal to 40 MPa and at most equal to 260 MPa.

[0026] In order for the non-pneumatic tire to travel in an extraterrestrial environment where extremely low temperatures (usually in the range of [-243°C; +53°C]) may be reached and on various types of ground (which can be sandy or rocky), the materials selected by the inventor have a tensile Young's modulus E and a maximum tensile stress Sm that are substantially within specific ranges at ambient temperature (equal to 20°C) and extremely low temperature (equal to -196°C).

[0027] The tensile Young's modulus E and the maximum tensile stress Sm are measured on a "stress-strain" tensile curve, which is established based on a tensile test performed on a standard specimen according to the standard ASTM D638 (Standard Test Method for Tensile Properties of Plastics) developed by the ASTM (American Society for Testing and Materials) international organization. The length of the standard specimen is equal to 84 mm, the thickness is equal to 2 mm, and it includes a narrow part with a length equal to 25 mm and a width equal to 4 mm. The tensile speed applied to the specimen is equal to 500 mm / min. The tensile Young's modulus E is the tangent modulus measured at low deformation.

[0028] The tensile Young's modulus E determines the stiffness and load-bearing capacity of the airless tire at the expected operating temperature. The maximum tensile stress Sm determines the durability of the airless tire at the expected operating temperature.

[0029] Therefore, the inventors have chosen materials in which the above mechanical properties can ensure a satisfactory compromise between the load-bearing capacity and durability required for the airless tire under the expected operating conditions. The airless tire should be able to withstand loads typically between 16 daN and 160 daN and is intended to be mounted on vehicles that can move at a maximum speed typically equal to 20 km / h.

[0030] Preferably, at least one of the materials for manufacturing the support structure, the shear band, and the tread is a high-performance thermoplastic polymer material. It is known that this type of material, which has excellent properties at ambient temperature, can still maintain good mechanical properties in terms of mechanical strength and stiffness at high temperatures (usually at least equal to 150 °C). In the case of the present invention, the inventors have unexpectedly demonstrated that this high-performance thermoplastic polymer material can also achieve a satisfactory compromise between high structural stiffness, high durability, and low mass of the airless tire at extremely low cryogenic temperatures, as demonstrated by measurements carried out at -196 °C.

[0031] According to a first advantageous embodiment, at least one of the materials for manufacturing the support structure, the shear band, and the tread is polyaryletherketone (PAEK). The general term "polyaryletherketone" (PAEK) refers to a family of technical polymers with high thermomechanical properties, especially at high temperatures. As shown in Table 1 of the present application, polyaryletherketone (e.g., the material Victrex AM200 sold by TM ) is particularly easy to use and has good mechanical properties at very low temperatures.

[0032] According to a second advantageous embodiment, at least one of the materials for manufacturing the support structure, the shear band, and the tread is polyetheretherketone (PEEK). Polyetheretherketone is a thermoplastic polymeric material belonging to the polyaryletherketone family. Polyetheretherketone (e.g., the materials Victrex CT100 sold by TM and Victrex 450G TM ) has the required mechanical properties, especially at cryogenic temperatures.

[0033] According to a third advantageous embodiment, at least one of the materials for manufacturing the support structure, the shear band, and the tread is polyimide (PI). Polyimide (e.g., the material Aurum PL500A TM ) has excellent mechanical properties at cryogenic temperatures but is more difficult to use than polyetheretherketone (e.g., the material Victrex CT100 TM ).

[0034] According to a fourth advantageous embodiment, at least one of the materials for manufacturing the support structure, the shear band, and the tread is polyetherimide (PEI). The mechanical properties of polyetherimide (such as the material Ultem 1010 TM ) are comparable to those of polyetheretherketone (such as the material Victrex CT100 TM ), but the elongation at break is lower. Its advantage is that it is more economical.

[0035] Preferably, the support structure, the shear band, and the tread are all made of the same material. Using the same material for all components of the airless tire simplifies manufacturing and makes it easier to bond between different parts.

[0036] Also preferably, the shear structure consists of a plurality of shear elements distributed circumferentially. This discrete shear structure has the advantage of being lighter than a continuous shear structure. In addition, its stiffness can be more finely optimized.

[0037] The second subject of the present invention is a wheel including the airless tire as described above mounted on a rim.

[0038] Another subject of the present invention is a method for manufacturing the airless tire as described above, the airless tire including, from the inside to the outside in the radial direction, a support structure, a shear band, and a tread made of at least one high-performance thermoplastic polymer material.

[0039] The first method for manufacturing an airless tire uses injection molding technology. This injection molding manufacturing method includes injecting the material for manufacturing the airless tire into a mold.

[0040] The second method for manufacturing an airless tire uses additive manufacturing technology. The additive manufacturing method uses a 3D printer that deposits a ductile printing material in successive layers through a nozzle. Such a 3D printer generally includes a chamber forming a field delimited by walls, and a platform for supporting the part being printed is present in the chamber, as well as a nozzle for supplying the material for manufacturing the part. To be able to form the shape of the part, a drive system is provided, the drive system including a lift for vertically moving the platform or the nozzle and mutually intersecting translational displacement tables for horizontally steering the platform or the nozzle intended to convey the material for manufacturing the part.

[0041] The first variant form of the manufacturing method using injection molding technology or additive manufacturing technology includes a single step of manufacturing a tire made of a single component.

[0042] The second variant form of the manufacturing method using injection molding technology or additive manufacturing technology successively includes a step of manufacturing the basic components constituting the airless tire and a step of joining the basic components together.

[0043] Preferably, a manufacturing method including the step of manufacturing basic components includes the step of joining the basic components together by rivets.

[0044] According to a first variant form of the step of joining the basic components together by rivets, the manufacturing method includes the step of joining the basic components together by metal rivets (preferably made of stainless steel or aluminum).

[0045] According to a second variant form of the step of joining the basic components together by rivets, the manufacturing method includes the step of joining the basic components together by rivets made of a thermoplastic polymer material.

[0046] According to a first embodiment of the step of joining the basic components together by rivets made of a thermoplastic polymer material, the manufacturing method includes the step of joining the basic components together by a single rivet made of a thermoplastic polymer material heated and compressed by using heat conduction or electrical conduction or ultrasonic heating.

[0047] According to a second embodiment of the step of joining the basic components together by rivets made of a thermoplastic polymer material, the manufacturing method includes the step of joining the basic components together by rivets made of a thermoplastic polymer material assembled in a plate-like manner by using heat conduction or electrical conduction or ultrasonic heating for heating and compression.

[0048] Advantageously, a manufacturing method including the step of manufacturing basic components includes the step of joining the basic components together by bonding.

[0049] According to a first variant form of the step of joining the basic components together by bonding, the manufacturing method includes the step of joining the basic components together by bonding using a thermoplastic adhesive of the same type as a high-performance thermoplastic material of one of the two basic components intended to be joined together.

[0050] According to a second variant form of the step of joining the basic components together by bonding, the manufacturing method includes the step of joining the basic components together by bonding using a polymer adhesive (preferably an epoxy adhesive). Description of the Drawings

[0051] Figure 1 An example of a tubeless tire according to the present invention is shown. Detailed Description

[0052] Figure 1Is an overall perspective view of the non-pneumatic tire 1 for a vehicle. The non-pneumatic tire 1 includes, from the inside to the outside in the radial direction, a support structure 2, a shear band 4, and a tread 6 that are intended to cooperate with a rim or a hub 3. The shear band 4 includes, from the inside to the outside in the radial direction, a radial inner membrane 41, a shear structure 40, and a radial outer membrane 42. In the illustrated embodiment, the shear structure 40 is composed of a plurality of circumferentially distributed shear elements 5. The support structure 2, the shear band 4, and the tread 6 are all made of a single high-performance thermoplastic polymer material, which is the same as the material of each of the above components. In this case, the non-pneumatic tire 1 is obtained by a manufacturing method using additive manufacturing technology.

[0053] The inventors studied several high-performance thermoplastic polymer materials, and their mechanical properties (meeting the standards of the present invention) are listed in Table 1 below:

[0054] [Table 1]

[0055]

[0056] The material Victrex CT100 of the PEEK type TM Is considered particularly advantageous for the production of non-pneumatic tires intended to be installed on extraterrestrial exploration vehicles, which are intended to move around, for example, on the Moon or Mars where extremely low temperatures, such as those that can reach -243 °C, may be encountered. The advantage of this material is that it has a high tensile Young's modulus (7 GPa), ensuring satisfactory stiffness and a high maximum tensile stress Sm (252 MPa), ensuring satisfactory durability at extremely low temperatures (-196 °C).

Claims

1. Non-pneumatic tire (1) for a vehicle, said non-pneumatic tire (1) comprising, from the inside to the outside in the radial direction, a support structure (2) intended to cooperate with a rim or a hub (3), a shear band (4) and a tread (6), - said shear band (4) comprising, from the inside to the outside in the radial direction, a radial inner membrane (41), a shear structure (40) and a radial outer membrane (42), - said support structure (2), shear band (4) and tread (6) being made of at least one material respectively, It is characterized in that At least one material for manufacturing the support structure (2), shear band (4) and tread (6) has the following mechanical properties measured according to ASTM (American Society for Testing and Materials) international standard ASTM D638: - The tensile Young's modulus E measured at a temperature equal to 20 °C is at least equal to 1 GPa and at most equal to 6 GPa, and the tensile Young's modulus E measured at a temperature equal to -196 °C is at least equal to 1.2 GPa and at most equal to 9 GPa, - The maximum tensile stress Sm measured at a temperature equal to 20 °C is at least equal to 25 MPa and at most equal to 150 MPa, and the maximum tensile stress Sm measured at a temperature equal to -196 °C is at least equal to 40 MPa and at most equal to 260 MPa.

2. The airless tire (1) according to claim 1, wherein, At least one material for manufacturing the support structure (2), shear band (4) and tread (6) is a high-performance thermoplastic polymer material.

3. The non-pneumatic tire (1) according to claim 2, wherein, At least one material for manufacturing the support structure (2), shear band (4) and tread (6) is polyaryletherketone (PAEK).

4. The airless tire (1) according to claim 3, wherein, At least one material for manufacturing the support structure (2), shear band (4) and tread (6) is polyetheretherketone (PEEK).

5. The airless tire (1) according to claim 2, wherein, At least one material for manufacturing the support structure (2), shear band (4) and tread (6) is polyimide (PI).

6. The airless tire (1) according to claim 2, wherein, At least one material for manufacturing the support structure (2), shear band (4) and tread (6) is polyetherimide (PEI).

7. The airless tire (1) according to any one of claims 1 to 6, wherein, The support structure (2), shear band (4) and tread (6) are all made of the same material.

8. The airless tire (1) according to any one of claims 1 to 7, wherein, The shear structure (40) is composed of a plurality of shear elements (5) distributed circumferentially.

9. A wheel, said wheel comprising the non-pneumatic tire according to any one of claims 1 to 8 mounted on a rim.

10. A method for manufacturing the non-pneumatic tire (1) according to any one of claims 2 to 8, said method using an additive manufacturing technique.

11. The manufacturing method according to claim 10, said manufacturing method comprising a single step of manufacturing a tire made of a single component.

12. The manufacturing method according to claim 10, said manufacturing method sequentially comprising a step of manufacturing basic components constituting the non-pneumatic tire and a step of joining said basic components together.

13. The manufacturing method according to claim 12, said manufacturing method comprising a step of joining the basic components together by rivets.

14. The manufacturing method according to claim 13, said manufacturing method comprising a step of joining the basic components together by rivets made of a thermoplastic polymer material.

15. The manufacturing method according to claim 14, wherein the manufacturing method includes a step of joining basic components together by a single rivet made of a thermoplastic polymer material heated and compressed by using heat conduction, or electric conduction, or ultrasonic heating.

16. The manufacturing method according to claim 14, wherein the manufacturing method includes a step of joining basic components together by a rivet made of thermoplastic polymer materials assembled in a plate shape and heated and compressed by using heat conduction, or electric conduction, or ultrasonic heating.

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