Carcass of an airless tire made by additive manufacturing using a material reinforced with long fibers

Abstract

Carcass 24 for an airless tire 1 produced by additive manufacturing, said carcass 24 comprising various structural elements 25 produced by depositing a printing material 21 using a nozzle 12, said printing material 21 comprising a percentage P of long fibers 15 embedded in a thermoplastic matrix 16, the reinforcement by said long fibers improving the load-bearing capacity and mechanical strength of said carcass 24. Figure for the abbreviation: Figure 5

Description

Title of the invention: Carcass of an airless tire produced by additive manufacturing using a material reinforced with long fibers

[0001] The present invention relates to the field of manufacturing airless tires intended to equip a vehicle.

[0002] The present invention relates more particularly to the carcass of an airless tire manufactured by an additive manufacturing process using three-dimensional printing machines having a co-extrusion nozzle that allows the co-extrusion of layers comprising simultaneously a malleable material and a reinforcing fiber. The use of a co-extrusion nozzle makes it possible to incorporate the reinforcing fiber within said malleable material and to produce said carcass by successively depositing a predetermined number of layers.

[0003] A three-dimensional printing machine that co-extrudes a malleable material and a reinforcing fiber generally comprises a chamber forming an enclosure delimited by a wall, inside which is a platform for supporting a part being printed, as well as the nozzle for co-extruding both the malleable material and the reinforcing fiber. The material resulting from the co-extrusion, comprising the malleable material and the reinforcing fiber, is called the printing material. To generate the shape of the part, drive systems are provided, including a lift for vertically moving either the platform or the nozzle, and cross-translation tables for horizontally driving either the platform or the nozzle responsible for delivering the printing material constituting the part.

[0004] Such printing machines are described in particular by document US11673322B2.

[0005] An airless tire, or more generally a tire without inflation gas, is a tire that carries the load thanks to structural elements, constituting a carcass, and which has performance comparable to that of a conventional tire subjected to the internal pressure of a gas, generally air. An airless tire, mounted on a hub or rim, is sometimes called a "non-pneumatic elastic wheel".

[0006] In what follows, the circumferential or longitudinal direction designates the direction of rotation of the tire, the axial or transverse direction designates the 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.

[0007] An airless tire generally comprises, radially from the inside out: -a carcass, made up of structural elements, designed to cooperate with a rim or hub, -a tread, intended to cooperate with the carcass and to transmit rolling forces to said carcass, to be worn and to guarantee the grip of the tire on a ground.

[0008] The frame comprises, radially from the inside out: -a load-bearing structure, designed to structurally support at least part of the load, -a shear strip, intended to transmit rolling forces to the supporting structure by shear and to contribute at least in part to the load-bearing capacity.

[0009] The load-bearing structure generally comprises, radially from the inside out: -a radially internal membrane intended to be fixed by means of connection to a rim or hub, -a plurality of radial elements or rays, intended to be fixed by means of connection to the radially inner membrane and to the shear strip.

[0010] 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.

[0011] The shear strip comprises, in a known embodiment, radially from the inside to the outside: -a radially intermediate membrane, interfacing with the load-bearing structure, -a plurality of shearing elements, -a radially outer membrane, intended to receive the tread and connected to the radially intermediate membrane by the plurality of shear elements.

[0012] Generally, the tread is fixed to the outer radial membrane of the shear strip by fastening means which may be, for example, gluing or shrink-fitting means.

[0013] The frame therefore comprises a plurality of elements called structural elements which may include, for example, a radially inner membrane, a plurality of radii, a radially intermediate membrane, a plurality of shear elements and a radially outer membrane.

[0014] Airless tire casings produced by additive manufacturing are known to those skilled in the art and are obtained by depositing successive layers of printing material.

[0015] Such casings are described in document US20220402301. These casings obtained by additive manufacturing have the disadvantage of having limited mechanical characteristics. When the casing is then used to produce an airless tire, the load capacities of said tire are limited and do not allow for tires with performance equivalent to those of traditional tires.

[0016] The invention therefore aims to remedy the aforementioned drawbacks and to provide a carcass for airless tires made by additive manufacturing and having increased load capacities, said carcass being obtainable at low cost from a wide range of malleable materials and reinforcing fibers, while ensuring excellent manufacturing reproducibility and perfect adhesion between the different structural elements of the carcass of the airless tire.

[0017] The invention essentially relates to a carcass for an airless tire, produced by additive manufacturing by depositing a printing material using a nozzle, said carcass comprising structural elements, said structural elements comprising radially from the inside out: -a radially inner membrane intended to be fixed by means of connection to a rim or hub, said radially inner membrane having a first width, -a plurality of radii having a fourth width, -a radially intermediate membrane connected to the radially inner membrane by a plurality of radii, said radially intermediate membrane having a second width, -a plurality of shear elements having a fifth width, -a radially outer membrane, intended to receive a tread and connected to the radially intermediate membrane by the plurality of shear elements, said radially outer membrane having a third width, said carcass for airless tire being characterized in that at least one structural element is made up of a printing material comprising a volume percentage P of long fibers embedded in a thermoplastic matrix, said long fibers having a fiber diameter d and a fiber length L greater than at least 1500 times the diameter d.

[0018] Essentially, the airless tire casing, obtained by additive manufacturing and having at least one structural element comprising a matrix with long fibers, exhibits higher load-bearing capacities and mechanical strength compared to the same casing produced by additive manufacturing of a thermoplastic material without reinforcing fibers. In certain embodiments of The invention allows for the maintenance of the same load-bearing capacity or mechanical resistance for the carcass reinforced with long fibers, making it possible to manufacture structural elements with smaller sections, consequently generating gains in material, weight and manufacturing time, making said manufacturing therefore easier and more economical.

[0019] In addition, the smaller sections make it possible to reduce the deformations and hysteresis of the materials, thus reducing the rolling resistance of the airless tire using said airless tire casing.

[0020] In a particular embodiment, all structural elements are made up of the printing material comprising the percentage P of long fibers embedded in the thermoplastic matrix, the reinforcement of all structural elements making it possible to obtain a very high load capacity for the carcass of the airless tire.

[0021] Advantageously, the volume percentage P of long fibers embedded in the thermoplastic matrix, in any structural element, is between 0 and 60% and preferably between 25 and 50%, allowing the rigidity or mechanical strength of said structural element to be adapted according to its role in the functioning of the airless tire carcass, consequently improving the properties of the airless tire carcass and in particular its load capacity or ride comfort. Thus, the volume percentage P of long fibers can vary depending on the structural element of the carcass.Furthermore, depending on the type of airless tire (for example, airless tire for passenger cars or vans), it is possible to adapt the rigidity or mechanical resistance of the spokes, shear elements, inner radial membrane, intermediate radial membrane, or outer radial membrane.

[0022] Advantageously, the long fibers of the structural elements comprising said long fibers have a length L corresponding to the length of the mean line of said structural element. This characteristic thus facilitates the additive manufacturing of each structural element while avoiding the appearance of areas without long fibers or the appearance of junction areas between two long fibers that could potentially be areas of breakage during stress on the frame. Furthermore, the continuity of the long fibers in the structural elements avoids coupling areas in which long fibers must overlap to prevent any break in the continuity of the long fiber reinforcement.

[0023] Preferably, the thermoplastic matrix is ​​a polyester (PES), a vinyl ester (VE), a urethane, a polypropylene (PP), a polyethylene terephthalate (PET), an aliphatic polyamide (PA), a polyphenylene sulfide (PPS), a polyetherimide (PEI), a polyimide (PI), a polyaryletherketone (PAEK), a polycarbonate (PC).

[0024] The long fiber material has a melting point higher than the melting point of the thermoplastic matrix material and is selected from glass, carbon, basalt, polyethylene terephthalate (PET), polyhexamethylene adipamide (nylon), aramid, ramie, silk, or flax, and preferably from glass or basalt. The preferential use of glass fiber or basalt fiber allows for high load-bearing capacity and significant endurance during operation.

[0025] Preferably, the material of the thermoplastic matrix is ​​different between at least two structural elements among the structural elements respectively of radially inner membrane, radially intermediate membrane, radially outer membrane, radii and shear elements, thus allowing the rigidity or flexibility to be specified for each of the structural elements.

[0026] Preferably, the material of the long fibers is different between at least two types of structural elements among the structural elements respectively of radially inner membrane, radially intermediate membrane, radially outer membrane, rays and shear elements, allowing the rigidity or flexibility to be specified for each of the structural elements.

[0027] In one embodiment, each of the rays comprises at least a first zone interpenetrating with the radially inner membrane, said first interpenetrating zone having a first arc length and, along a radial direction, a first maximum thickness, each of said rays also comprising at least a second zone interpenetrating with the radially intermediate membrane, said second interpenetrating zone having a second arc length and, along a radial direction, a second maximum thickness, and still in this same embodiment, each of the shear elements comprises at least a third zone interpenetrating with the radially intermediate membrane, said third interpenetrating zone having a third arc length and, along a radial direction, a third maximum thickness, each of said shear elements comprises at least a fourth zone interpenetrating with the radially outer membrane,said fourth interpenetrating zone having a fourth arc length and, along a radial direction, a fourth maximum thickness.

[0028] The interpenetration of the different structural elements improves the adhesion of the different structural elements, thus contributing to obtaining better mechanical resistance and / or fatigue limit properties of the frame.

[0029] Preferably, the rays are distributed circumferentially according to a constant pitch.

[0030] Preferably, the shear elements are distributed circumferentially according to a constant pitch.

[0031] The distribution of radii and shear elements according to a constant pitch makes it possible to obtain a carcass whose mechanical operation, in particular under an imposed radial force, is identical over the entire circumference of the airless tire.

[0032] The invention also relates to an airless tire comprising the carcass of the invention as described above.

[0033] The invention also relates to a method for manufacturing the carcass of an airless tire as defined above, said method employing an additive manufacturing machine comprising a build platform, perpendicular to the axis of revolution of the carcass, said axis of revolution having an axial direction Z, and a nozzle, capable of moving along the axial direction Z and in any circumferential plane XY perpendicular to the axial direction Z, said additive manufacturing method being characterized by the following steps: (a) manufacturing a first layer of said carcass, extending along the axial direction Z, by depositing, on the build platform, a printing material, comprising long fibers embedded in a thermoplastic matrix, in the form of cords, by said nozzle, to form, in any order, -a radially inner membrane, -a radially intermediate membrane,-a radially external membrane, -a plurality of radii, , -a plurality of shear cords, (b) production of at least one additional layer following step (a), the welds of the at least one additional layer being superimposed, along an axial direction Z, on the welds of the previous axially adjacent layer with remelting of the interface between the previous layer and the at least one additional layer.

[0034] The use of an additive manufacturing process to produce the carcass of the invention makes it possible to obtain a carcass for an airless tire by implementing a single process without having to assemble several parts together to constitute said carcass. Each structural element of the carcass is thus made up of an axial superposition of layers, each layer being made up of a single cord or "mono-cord" of a thermoplastic matrix reinforced with long fibers, the use of a mono-cord making it possible to save time and improve the quality of the manufacturing of the airless tire carcass, while also improving the mechanical strength of the carcass.

[0035] Other objects, features and advantages of the invention will become apparent in more detail later Details can be obtained by reading the description below, as well as with the help of the attached drawings, provided for illustrative purposes only and not as a limitation: - [Fig.l]: Overview and perspective view of an airless tire comprising a carcass according to the invention. - [Fig.2]: Overview of an additive manufacturing machine used to produce the frame of the invention. - [Fig.3]: Overview and top view of the frame of the invention being manufactured on the platform of the additive manufacturing machine. - [Fig.4]: Axial and partial cross-sectional view of an airless tire including the carcass of the invention. - [Fig.5]: Circumferential and partial cross-sectional view of an airless tire casing according to the invention. - [Fig.6]: Circumferential cross-sectional view of the first interpenetration zone. - [Fig.7]: Circumferential cross-sectional view of the second interpenetration zone. - [Fig.8]: Circumferential cross-sectional view of the third and fourth interpenetration zones.

[0036] In what follows, for the sake of clarity, the horizontal direction and the vertical direction correspond to the natural orientation of figures 1 to 8. Similarly, the terms "top", "bottom", "lower", "upper" and their variants should be understood with reference to the vertical direction of the figures.

[0037] As can be seen in [Fig. 1], an airless tire 1 comprises, radially from the inside out: -a carcass 24 intended to cooperate with a rim or hub 4, -a tread 2, intended to cooperate with the carcass 24.

[0038] The frame 24 comprises, radially from the inside out: -a load-bearing structure 9, designed to cooperate with the rim or hub 4, -a shear strip 3, intended to cooperate with the tread 2.

[0039] The load-bearing structure 9 comprises, radially from the inside out: -a radially internal membrane 7 intended to be fixed by means of connection to the rim or hub 4, -a plurality of radii 8 intended to connect the radially inner membrane 7 and the shear band 3.

[0040] The means for connecting the radially inner membrane 7 to the rim or hub 4 may be, by way of example, means of bonding, riveting, bolting or shrink-fitting.

[0041] The shear strip 3 comprises, in a known embodiment, radially from the inside to the outside: -a radially intermediate membrane 10, interfacing with the load-bearing structure 9, -a plurality of shear elements 11, -a radially outer membrane 5, intended to receive the tread 2 and connected to the radially intermediate membrane 10 by the plurality of shear elements 11.

[0042] The tread 2 can be fixed to the radially outer membrane 5 of the shear strip 3 by fastening means which may be, by way of example, gluing or shrink-fitting means.

[0043] The frame 24 is thus made up of structural elements 25 comprising the radially inner membrane 7, the rays 8, the radially intermediate membrane 10, the shear elements 11 and the radially outer membrane 5.

[0044] Figure 2 is an overview of an example of an additive manufacturing machine 20 implemented to produce the frame 24 of the invention. The additive manufacturing machine 20 comprises a nozzle 12 capable of receiving, on the one hand, a reinforcing fiber 17 in the form of a continuous strand and, on the other hand, a thermoplastic cord 18 in the form of a continuous cord. The additive manufacturing machine also comprises a build platform 14, a horizontal movement system 22 in any circumferential plane XY, a vertical movement system 23 along an axial direction Z, perpendicular to any circumferential plane XY, and a cutting system 19, enabling the reinforcing fiber 17 to be cut to the desired length.

[0045] The cutting system 19 allows the reinforcing fiber yarn 17 to be cut to form long fibers 15 having a predefined length L, said long fibers being conveyed to an inlet orifice of the nozzle 12.

[0046] As known to those skilled in the art, the nozzle 12 allows for the simultaneous reception of: - the long fiber 15 through a first inlet orifice, and the thermoplastic cord 18 through a second inlet orifice, -heating said thermoplastic cord 18 until it is sufficiently molten and malleable to flow through an orifice, -the conveyance of the molten thermoplastic material from the thermoplastic cord 18 to the long fiber 15 present inside said nozzle 12, -the sheathing of the long fiber 15 by a thermoplastic matrix 16 molten from the thermoplastic cord 18, to form a printing material 21 which may comprise the long fiber 15 surrounded by the thermoplastic matrix 16 molten from the thermoplastic cord 18, - the extrusion, through an outlet orifice, of the printing material 21.

[0047] As known to those skilled in the art, it is possible to adjust the percentage of the long fiber volume relative to the thermoplastic matrix volume. The percentage adjustment is achieved by varying the filament feed speed. fiber reinforcement 17 relative to the feed speed of the thermoplastic cord 18. It is thus possible to obtain a printing material 21 whose percentage of long fibers 15 varies.

[0048] The horizontal movement system 22 and the vertical movement system 23 allow for the relative movement of the nozzle 12 with respect to the build platform 14 so that said nozzle 12 can deposit the molten printing material 21 in the form of preferably continuous beads 13. Each bead 13 may comprise a long fiber 15 and a thermoplastic matrix 16.

[0049] As can be seen in [Fig.5], the long fibers 15 are oriented, during the deposition of the cord 13 by the nozzle 12, in the direction of the movement of said nozzle 12 in any circumferential plane XY, thus allowing to specify directly, during the deposition, the direction in which the fiber will subsequently be stressed.

[0050] Any other type of additive manufacturing machine by depositing a bead 13 of a printing material 21 is suitable, such as, for example, machines in which the relative movement of the nozzle 12 with respect to the build platform 14 is achieved by the movement of said build platform 14.

[0051] As illustrated by Figures 1 to 3, the object of the invention is a casing 24 for an airless tire 1, produced by additive manufacturing by depositing a printing material 21 using a nozzle 12, said casing 24 comprising structural elements 25, said structural elements 25 comprising radially from the inside to the outside: -a radially internal membrane 7 intended to be fixed by means of connection to a rim or hub 4, said radially internal membrane 7 having a first width RI, -a plurality of radii 8 having a fourth width R4, -a radially intermediate membrane 10, connected to the radially inner membrane 7 by the plurality of radius 8, said radially intermediate membrane 10 having a second width R2, -a plurality of shear elements 11 having a fifth width R5, -a radially outer membrane 5, intended to receive a tread 2 and connected to the radially intermediate membrane 10 by the plurality of shear elements 11, said radially outer membrane 5 having a third width R3, said carcass 24 for airless tire 1 being characterized in that at least one structural element 25 is made up of a printing material 21 comprising a volume percentage P of long fibers 15 embedded in a thermoplastic matrix 16, said long fibers 15 having a fiber diameter d and a fiber length L greater than at least 1500 times the diameter d.

[0052] In a particular embodiment, all the structural elements 25 are made of the same printing material 21 comprising the percentage P of long fibers coated 15 in the thermoplastic matrix 16.

[0053] In a particular embodiment, the volume percentage P of long fibers 15 embedded in the thermoplastic matrix 16, in any structural element 25, is between 0 and 60% and preferably between 25 and 50%.

[0054] In certain particular embodiments, it is thus possible to produce a frame 24 in which only certain structural elements 25, such as, for example, the radii 8 or the shear elements 11, are made with the printing material 21 comprising a percentage P of long fibers 15 greater than zero. The remaining structural elements 25 are made with a printing material 21 not comprising long fibers 15, that is to say, with a percentage P equal to zero.

[0055] The possibility of varying the percentage P according to the structural element 25 makes it possible to adapt the rigidity or the mechanical resistance of said structural element 25 according to its role in the operation of the airless tire 1 comprising the carcass 24. Depending on the type of airless tire 1 (for example airless tire 1 for passenger car or for van) it is possible to adapt the rigidity or the mechanical resistance of the spokes 8, the shear elements 11, the radially inner membrane 7, the radially intermediate membrane 10 or even the radially outer membrane 5.

[0056] In certain embodiments, the long fibers 15 of the structural elements 25 comprising said long fibers 15 have a length L corresponding to the length of the mean line of said structural element 25.

[0057] Preferably, the thermoplastic matrix 16 is a polyester (PES), a vinyl ester (VE), a urethane, a polypropylene (PP), a polyethylene terephthalate (PET), an aliphatic polyamide (PA), a polyphenylene sulfide (PPS), a polyetherimide (PEI), a polyimide (PI), a polyaryletherketone (PAEK), a polycarbonate (PC).

[0058] As is known to those skilled in the art, the use of an additive manufacturing machine 20, carrying out the sheathing of the long fiber 15 by a thermoplastic matrix 16, requires choosing the material of said long fibers 15 from among materials having a melting temperature higher than the melting temperature of the material of said thermoplastic matrix 16 in order to avoid any degradation of the mechanical properties of said long fibers 15.

[0059] Therefore, depending on the choice of the thermoplastic matrix material 16, the long fibers 15 are in a material that can meet the temperature condition explained above and, said long fibers 15 are preferably in a material chosen from glass, carbon, basalt, polyethylene terephthalate (PET), polyhexamethylene adipamide (nylon), aramid, ramie, silk or flax and preferably from glass or basalt.

[0060] By way of example, if the material of the thermoplastic matrix 16 is a PAEK whose melting temperature is about 340°C, then the long fibers 15 used may be made of glass fibers whose melting temperature is about 800°C.

[0061] Advantageously, the material of the thermoplastic matrix 16 is different between at least two structural elements 25 among the structural elements respectively of radially inner membrane 7, radially intermediate membrane 10, radially outer membrane 5, radii 8 and shear elements 11. Thus, each of the structural elements 25 having a different functional requirement, for example in rigidity or flexibility, it is possible to choose the material of the thermoplastic matrix 16 having the most suitable technical characteristics for the realization of each of the structural elements 25.

[0062] Advantageously, the material of the long fibers 15 is different between at least two types of structural elements 25 among the structural elements respectively of radially inner membrane 7, radially intermediate membrane 10, radially outer membrane 5, radii 8 and shear elements 11. As before, it is possible, for each of the structural elements 25, to choose a long fiber 15 having technical characteristics adapted to the functional need of said structural elements 25.

[0063] As illustrated in [Fig.5] and [Fig.6], each of the rays 8 comprises at least a first interpenetrating zone ZI with the radially inner membrane 7, said first interpenetrating zone ZI having a first arc length L1 and, along a radial direction, a first maximum thickness El.

[0064] As shown in [Fig.5] and [Fig.7], each of the rays 8 also includes at least one second interpenetrating zone Z2 with the radially intermediate membrane 10, said second interpenetrating zone Z2 having a second arc length L2 and, along a radial direction, a second maximum thickness E2.

[0065] As can be seen in [Fig.5] and [Fig.8], each of the shear elements 11 comprises at least one third interpenetrating zone Z3 with the radially intermediate membrane 10, said third interpenetrating zone Z3 having a third arc length L3 and, along a radial direction, a third maximum thickness E3.

[0066] As can be seen in [Fig.5] and [Fig.8], each of the shear elements 11 also includes at least one fourth interpenetrating zone Z4 with the radially outer membrane 5, said fourth interpenetrating zone Z4 having a fourth arc length L4 and, along a radial direction, a fourth maximum thickness E4.

[0067] As can be seen in Figures 2 to 4, the frame 24, produced by manufacturing Additive, is obtained by depositing several layers of the printing material 21, the carcass 24 thus being monobloc and of height H along the axial direction Z. The height H of the carcass 24 is obviously adapted to the type of airless tire 1 to be produced and in particular, said height H is adjusted to the width of the tread 2 of the airless tire 1.

[0068] Remelting the interface between two adjacent layers allows for a very strong bond between each layer, thus enabling the manufacture of monobloc 24 frames with high mechanical strengths.

[0069] The creation of interpenetration zones Z1, Z2, Z3 and Z4 during the deposition of the printing material 21 allows, on the one hand, the rays 8 to adhere perfectly to the radially inner membrane 7 and to the radially intermediate membrane 10, and on the other hand, the shear elements 11 to adhere also perfectly to the radially intermediate membrane 10 and to the radially outer membrane 5.

[0070] This perfect adhesion between the structural elements 25 of the frame 24 makes it possible to obtain very high mechanical strength and very good fatigue resistance of said frame 24 during stresses in operation.

[0071] Preferably, when manufacturing a layer of the carcass 24, the nozzle 12 starts depositing a layer of the radially inner membrane 7 at a starting point that is different from the starting point of the previous layer, in order to obtain junction zones located at different horizontal azimuths between two adjacent layers.

[0072] Similarly, the deposition of a layer of the intermediate membrane 10 and outer membrane 5 is preferably done with different starting and ending points of the nozzle 12 than the previous layer, also allowing to obtain junction zones, between the beginnings and ends of the beads 13, located along different horizontal azimuths.

[0073] Obtaining, for each of the membranes respectively inner 7, intermediate 10 and outer 5, junction zones located along different horizontal azimuths makes it possible to strengthen the mechanical resistance of the carcass 24 by preventing the propagation of possible cracks in said junction zones.

[0074] In a particular embodiment, and as illustrated in [Fig.5], the first width RI, the second width R2, the third width R3, the plurality of fourth widths R4 and the plurality of fifth widths R5 are equal to each other, thus reducing the time required to prepare the model of the frame and saving production time.

[0075] Advantageously, the first width RI, the second width R2, the third width R3, the plurality of fourth widths R4 and the plurality of fifth widths R5 are respectively at least equal to 0.15 mm and at most equal to 4 mm, of preferably at least equal to 0.4 mm and at most equal to 2 mm, such dimensional ranges allowing the object to be manufactured with standard nozzle diameters and existing additive manufacturing machine parameter settings.

[0076] In another embodiment, it is possible to optimize the resistance of each of the structural elements 25 by adapting the widths RI, R2, R3, R4 and R5 of said structural elements 25. Indeed, each of the structural elements 25 of the frame 24 having a different shape and stress, it is possible to determine as precisely as possible each of the widths RI, R2, R3, R4 and R5.

[0077] These differences in thickness also make it possible to reduce the weight of the carcass 24, and to save on the amount of material deposited and on manufacturing time.

[0078] Preferably, and as can be seen in figures 6 to 8, the first maximum thickness El, the second maximum thickness E2, the third maximum thickness E3 and the fourth maximum thickness E4 are equal to each other, thus reducing the preparation time of the model of the frame 24 and saving production time.

[0079] Preferably, the first arc length L1, the second arc length L2, the third arc length L3 and the fourth arc length L4 are equal to each other, thus reducing the preparation time of the model of the frame 24 and saving production time.

[0080] Advantageously, the first maximum thickness El is at least equal to 2% and at most equal to 20% of the smallest of the first and fourth widths RI, R4, preferably at least equal to 5% and at most equal to 10% of the smallest of the first and fourth widths RI, R4.

[0081] Advantageously, the second maximum thickness E2 is at least equal to 2% and at most equal to 20% of the smallest of the second and fourth widths R2, R4, preferably at least equal to 5% and at most equal to 10% of the smallest of the second and fourth widths R2, R4.

[0082] Even more advantageously, the third maximum thickness E3 is at least equal to 2% and at most equal to 20% of the smallest of the second and fifth widths R2, R5, preferably at least equal to 5% and at most equal to 10% of the smallest of the second and fifth widths R2, R5.

[0083] Advantageously, the fourth maximum thickness E4 is at least equal to 2% and at most equal to 20% of the smallest of the third and fifth widths R3, R5, preferably at least equal to 5% and at most equal to 10% of the smallest of the third and fifth widths R3, R5.

[0084] The intervals defined previously for the first, second, third, and fourth thicknesses E1, E2, E3, and E4 respectively allow for maximizing the interpenetration of the successive layers without introducing excess material which would accumulate and lead to manufacturing defects, or even the shutdown and degradation of the machine.

[0085] Advantageously, the first arc length L1 is at least equal to 3 times and at most equal to 100 times the smallest of the first and fourth widths RI, R4, preferably at least equal to 10 times and at most equal to 50 times the smallest of the first and fourth widths RI, R4.

[0086] Even more advantageously, the second arc length L2 is at least equal to 3 times and at most equal to 100 times the smallest of the second and fourth widths R2, R4, preferably at least equal to 10 times and at most equal to 50 times the smallest of the second and fourth widths R2, R4.

[0087] Advantageously, the third arc length L3 is at least equal to 3 times and at most equal to 100 times the smallest of the second and fifth widths R2, R5, preferably at least equal to 10 times and at most equal to 50 times the smallest of the second and fifth widths R2, R5.

[0088] Even more advantageously, the fourth arc length L4 is at least equal to 3 times and at most equal to 100 times the smallest of the third and fifth widths R3, R5, preferably at least equal to 10 times and at most equal to 50 times the smallest of the third and fifth widths R3, R5.

[0089] The intervals defined previously for the first, second, third and fourth arc lengths make it possible to obtain sufficient adhesion between the structural elements without increasing the rigidity and mass of the frame.

[0090] As can be seen in [Fig. 5], in the interpenetrating zones Z1, Z2, Z3, Z4, each structural element 25 of the frame 24 is tangent to the adjacent structural element 25. This tangency allows the structural elements 25 to have geometries adapted to the types of stresses experienced by the frame 24, thus improving the mechanical strength and fatigue resistance of said structural elements 25.

[0091] As is well known to those skilled in the art, the width and height of the bead 13 depend on the geometric dimensions of the nozzle outlet section 12 and the setting parameters of the additive manufacturing machine 20.

[0092] Advantageously, the nozzle 12 of the additive manufacturing machine 20 can be changed during the manufacturing of a layer of the frame 24 in order to make the width of the bead 13 deposited coincide with the widths RI, R2, R3, R4 and R5 of each of the structural elements 25, allowing a single pass with the nozzle 12 to produce a layer of each of said structural elements 25.

[0093] Preferably, the radii 8 and the shear elements 11 are distributed circumferentially according to a constant pitch.

[0094] Advantageously, the thermoplastic matrix 16 has a melting temperature at less than or equal to 180°C and at most equal to 450°C.

[0095] The invention can be generalized to the case of a carcass 24 of the airless tire 1 comprising, radially from the inside to the outside: -at least two load-bearing structures 9, the first radially inner membrane 7 of the first load-bearing structure 9 being intended to be fixed to the rim or hub 4, each of the other radially inner membranes 7 serving as an interface between each of the pluralities of radial elements or spokes 8, -and / or at least two shear bands 3, the last radially outer membrane 5 being intended to receive the tread 2, each of the other radially outer membranes 5 serving as an interface between each of the plurality of shear elements 11.

[0096] Table 1 below compares the characteristics of one embodiment of a frame 24 made with a thermoplastic matrix 16 of polyamide 6 (PA6) without long fiber reinforcement 15 and another embodiment of the same frame 24 made with a thermoplastic matrix 16 of polyamide 6 (PA6) reinforced with long glass fibers 15. The ratio of long fibers 15 in the thermoplastic matrix 16 is 40% for all structural elements 25 of the frame 24. [Tables 1] Carcass for manufacturing a 300 / 90R16 tire without long fiber reinforcement. Carcass for manufacturing a 300 / 90R16 tire with long fiber reinforcement. Thermoplastic matrix material: PA6. Long fiber material: Fiberglass. Percentage of long fiber in the inner radial membrane: 0-40%. Percentage of long fiber in the intermediate radial membrane: 0-40%. Percentage of long fiber in the outer radial membrane: 0-40%. Percentage of long fiber in the spokes: 0-40%. Percentage of long fiber in the shear elements: 0-40%. Number of layers: 100. Number of spokes: 36. Number of shear elements: 36. First arc length L1: 12mm. Second arc length L2: 12mm. Third arc length L3: 12mm. Fourth arc length L4: 12mm. First thickness. Maximum thickness E1 0.1mm 0.1mm Second maximum thickness E2 0.1mm 0.1mm Third maximum thickness E3 0.1mm 0.1mm Fourth maximum thickness E4 0.1mm 0.1mm Width RI 2mm 2mm Width R2 1.5mm 1.5mm , Width R3 1.5mm 1.5mm Width R4 1.36mm 1.36mm Width R5 1.36mm 1.36mm Height H 300mm 300mm Maximum permissible load 100 600

[0097] Following the additive manufacturing of the carcasses 24 with and without long fiber reinforcement 15, maximum permissible static load tests were carried out. As shown in Table 1, the maximum permissible load is 6 times greater for the carcasses 24 with long fiber reinforcement 15 compared to the carcasses 24 without long fiber reinforcement 15.

[0098] The invention also relates to an airless tire 1 comprising the carcass 24 of the invention as described above.

[0099] The invention also relates to a method for manufacturing the carcass 24 of an airless tire 1 defined above, said method employing an additive manufacturing machine 20 comprising a build platform 14, perpendicular to the axis of revolution of the carcass 24, said axis of revolution having an axial direction Z, and a nozzle 12, capable of moving along the axial direction Z and in any circumferential plane XY perpendicular to the axial direction Z, said additive manufacturing method being characterized by the following steps: (a) manufacturing a first layer of said carcass 24, extending along the axial direction Z, by depositing, onto the build platform 14, a printing material 21, comprising long fibers 15 embedded in a thermoplastic matrix 16, in the form of cords 13, by said nozzle 12, to form, in any order, -a radially internal membrane 7, -a radially intermediate membrane 10, -a radially external membrane 5, -a plurality of radii 8, -a plurality of shear elements 11, (b) production of at least one additional layer following step (a), the cords 13 of the at least one additional layer being superimposed, along an axial direction Z, on the cords 13 of the previous axially adjacent layer with remelting of the interface between the previous layer and the at least one additional layer.

Claims

Demands

1. Carcass (24) for an airless tire (1), produced by additive manufacturing by depositing a printing material (21) using a nozzle (12), said carcass (24) comprising structural elements (25), said structural elements (25) comprising radially from the inside out: - a radially inner membrane (7) intended to be fixed by connection means to a rim or hub (4), said radially inner membrane (7) having a first width (RI), - a plurality of spokes (8) having a fourth width (R4), - a radially intermediate membrane (10) connected to the radially inner membrane (7) by the plurality of spokes (8), said radially intermediate membrane (10) having a second width (R2), - a plurality of shear elements (11) having a fifth width (R5), - a radially outer membrane (5),intended to receive a tread (2) and connected to the radially intermediate membrane (10) by the plurality of shear elements (11), said radially outer membrane (5) having a third width (R3), said carcass (24) for airless tire (1) being characterized in that at least one structural element (25) is made of a printing material (21) comprising a volume percentage P of long fibers (15) embedded in a thermoplastic matrix (16), said long fibers (15) having a fiber diameter d and a fiber length L greater than at least 1500 times the diameter d.,

2. Carcass (24) for airless tire (1) produced by additive manufacturing according to claim 1 wherein the material of the thermoplastic matrix (16) is different between at least two structural elements (25) among the structural elements respectively of radially inner membrane (7), radially intermediate membrane (10), radially outer membrane (5), radii (8) and shear elements (11).

3. Carcass (24) for an airless tire (1) produced by additive manufacturing according to claim 1 or 2, wherein the material of the long fibers (15) differs between at least two types of structural elements (25) among the structural elements respectively of a radially inner membrane (7), of a radially inner membrane, and of a radially inner membrane. intermediate dialement (10), radially outer membrane (5), rays (8) and shear elements (11).

4. Carcass (24) for airless tire (1) produced by additive manufacturing according to claim 1 in which all structural elements (25) are made of the same printing material (21) comprising the percentage P of long fibers (15) embedded in the thermoplastic matrix (16).

5. Carcass (24) for airless tire (1) produced by additive manufacturing according to any one of claims 1 to 4 in which the volume percentage P of long fibers (15) embedded in the thermoplastic matrix (16), in any structural element (25), is between 0 and 60% and preferably between 25 and 50%.

6. Carcass (24) for airless tire (1) produced by additive manufacturing according to any one of claims 1 to 5 wherein the long fibers (15) of the structural elements (25) comprising said long fibers (15) have a length L corresponding to the length of the mean line of said structural element (25).

7. Carcass (24) for airless tire (1) made by additive manufacturing according to any one of claims 1 to 6 wherein the thermoplastic matrix (16) is a polyester (PES), a vinylester (VE), a urethane, a polypropylene (PP), a polyethylene terephthalate (PET), an aliphatic polyamide (PA), a polyphenylene sulfide (PPS), a polyetherimide (PEI), a polyimide (PI), a polyaryletherketone (PAEK), a polycarbonate (PC).

8. Carcass (24) for airless tire (1) produced by additive manufacturing according to any one of claims 1 to 7 wherein the long fibre material (15) has a melting temperature higher than the melting temperature of the thermoplastic matrix material (16) and is selected from glass, carbon, basalt, polyethylene terephthalate (PET), polyhexamethylene adipamide (nylon), taramide, ramie, silk or flax and preferably from glass or basalt.

9. Carcass (24) for an airless tire (1) produced by additive manufacturing according to any one of claims 1 to 8, wherein each of the radii (8) comprises at least one first interpenetrating zone (Zl) with the radially inner membrane (7), said first interpenetrating zone (Zl) having a first arc length (Ll) and, along a radial direction, a first maximum thickness

10.

11.

12.

13. (E1), each of said rays (8) also comprising at least a second interpenetrating zone (Z2) with the radially intermediate membrane (10), said second interpenetrating zone (Z2) having a second arc length (L2) and, along a radial direction, a second maximum thickness (E2) and in which each of the shear elements (11) comprises at least a third interpenetrating zone (Z3) with the radially intermediate membrane (10), said third interpenetrating zone (Z3) having a third arc length (L3) and, along a radial direction, a third maximum thickness (E3), each of said shear elements (11) comprises at least a fourth interpenetrating zone (Z4) with the radially external membrane (5), said fourth interpenetrating zone (Z4) having a fourth arc length (L4) and, along a radial direction, a fourth maximum thickness (E4). A casing (24) for an airless tire (1) produced by additive manufacturing according to any one of claims 1 to 9, wherein the radii (8) are distributed circumferentially with a constant pitch. A casing (24) for an airless tire (1) produced by additive manufacturing according to any one of claims 1 to 10, wherein the shear elements (11) are distributed circumferentially with a constant pitch. Airless tire (1) comprising a casing (24) according to any one of claims 1 to 11. Method for manufacturing the carcass (24) of an airless tire (1) defined according to claims 1 to 11, said method employing an additive manufacturing machine (20) comprising a manufacturing platform (14), perpendicular to the axis of revolution of the carcass (24), said axis of revolution having an axial direction Z, and a nozzle (12), capable of moving along the axial direction Z and in any circumferential plane XY perpendicular to the axial direction Z, said additive manufacturing method being characterized by the following steps: (a) manufacturing a first layer of said frame (24), extending along the axial direction Z, by depositing, on the manufacturing platform (14), a printing material (21), comprising long fibers (15) embedded in a thermoplastic matrix (16), in the form of cords (13), by said nozzle (12), to form, in any order, -a radially inner membrane (7), -a radially intermediate membrane (10), -a radially external membrane (5), -a plurality of radii (8), -a plurality of shear elements (11), (b) production of at least one additional layer following step (a), the cords (13) of the at least one additional layer being superimposed, along an axial direction Z, on the cords (13) of the previous axially adjacent layer with remelting of the interface between the previous layer and the at least one additional layer.