Optimized carcass of an airless tire produced 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, said structural elements 25 being produced by continuous deposition of the printing material 21 and reinforcement by said long fibers, thereby improving the load-bearing capacity and mechanical strength of said carcass 24. Figure for the abbreviation: Figure 5

Description

Title of the invention: Optimized 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 US document 6,722,872.

[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 connecting structure, 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 bonding structure, -a junction structure, -a radially outer membrane, intended to receive the tread and connected to the radially intermediate membrane by the junction structure.

[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 carcass therefore comprises a plurality of elements called structural elements which may include, for example, a radially inner membrane, a connecting structure, a radially intermediate membrane, a junction structure and a radially outer membrane.

[0014] Carcasses for airless tires produced by additive manufacturing are known to those skilled in the art and are obtained by depositing the printing material in successive layers.

[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 connecting structure having a fourth width, -a radially intermediate membrane connected to the radially inner membrane by the bonding structure, said radially intermediate membrane having a second width, -a junction structure having a fifth width, -a radially outer membrane, intended to receive a tread and connected to the radially intermediate membrane by the joining structure, 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 resistance compared to the same casing produced by additive manufacturing of a thermoplastic material without reinforcing fibers. In certain embodiments of the invention, it may be desirable to maintain the same load-bearing capacity or resistance. mechanical resistance for the carcass reinforced with long fibers, which allows the manufacture of structural elements with smaller sections, consequently generating gains in material, weight and manufacturing time, making said manufacture 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 the structural elements are made of the same printing material comprising the percentage P of long fibers embedded in the thermoplastic matrix, the reinforcement of all the 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 connecting structure, the junction structure, the radially inner membrane, the radially intermediate membrane, or even the radially outer 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 fracture initiation when the frame is subjected to stress. 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 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, bonding structure and junction structure, 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, bonding structure and junction structure, allowing the rigidity or flexibility to be specified for each of the structural elements.

[0027] In one embodiment, the connecting structure links the radially inner membrane to the radially intermediate membrane via a plurality of connecting portions, said connecting structure having a plurality of first interpenetrating zones with the radially inner membrane, each of said first interpenetrating zones having a first arc length and, along a radial direction, a first maximum thickness, said connecting structure having a plurality of second interpenetrating zones with the radially intermediate membrane, each of said second interpenetrating zones having a second arc length and, along a radial direction, a second maximum thickness, and still in this same embodiment, the junction structure links the radially intermediate membrane to the radially outer membrane via a plurality of junction portions,said junction structure having a plurality of third zones interpenetrating with the radially intermediate membrane, each of said interpenetrating third zones having a third arc length and, along a radial direction, a third maximum thickness, said junction structure having a plurality of fourth zones interpenetrating with the radially external membrane, each of said interpenetrating fourth zones having a fourth arc length and, along a radial direction, a fourth thickness, maximum.

[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 plurality of connecting portions comprises at least two connecting portions of different patterns, each of the connecting portions of different pattern being distributed circumferentially according to a constant pitch.

[0030] Preferably, the plurality of junction portions includes at least two junction portions of different patterns, each of the junction portions of different pattern being distributed circumferentially according to a constant pitch.

[0031] The distribution according to a constant pitch of the at least two connecting portions of different pattern and of the at least two junction portions of different pattern 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 defined above, said method employing an additive manufacturing machine comprising a manufacturing 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 process being characterized by the following steps: (a) manufacturing a first layer of said frame, 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 internal membrane, -a radially intermediate membrane, -a radially external membrane, -a linking structure, -a junction structure, (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 casing of the invention makes it possible to obtain a casing for an airless tire by putting in employs a unique process without having to assemble several parts together to constitute the said carcass. Each structural element of the carcass is thus constituted by 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 manufacture of the carcass of the airless tire, while improving the mechanical resistance of the carcass.

[0035] Other objects, features and advantages of the invention will become apparent in more detail from the following description, as well as from the accompanying drawings, which are provided purely for illustrative purposes and are not intended to be limiting: - [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 linking structure 28 intended to connect the radially inner membrane 7 and the shear strip 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 bonding structure, -a junction structure 29, -an outer radial membrane 5, intended to receive the tread 2 and connected to the intermediate radial membrane 10 by the junction structure 29.

[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 carcass 24 is thus made up of structural elements 25 comprising the radially inner membrane 7, the connecting structure 28, the radially intermediate membrane 10, the junction structure 29 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. This adjustment is achieved by varying the feed rate of the reinforcing fiber yarn 17 relative to the feed rate of the thermoplastic cord 18. This makes it possible to obtain a printing material 21 with a variable percentage of long fibers 15.

[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 connecting structure 28 having a fourth width R4, -a radially intermediate membrane 10 connected to the radially inner membrane 7 by the linking structure 28, said radially intermediate membrane 10 having a second width R2, -a junction structure 29 having a fifth width R5, -a radially external membrane 5, intended to receive a tread and connected to the radially intermediate membrane 10 by the junction structure 29, 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] As can be seen in particular by looking at figures 2 and 3, the link structure 28 and the junction structure 29 are structural elements 25 which are made by depositing continuous beads 13 of the printing material 21. The continuity of the beads 13 of the link structure 28 and the junction structure 29 makes it possible to minimize the stop and start phases during additive manufacturing, thus generating a saving of time and a better manufacturing quality of the carcass of the airless tire.

[0053] In a particular embodiment, all the 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.

[0054] 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%.

[0055] 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 connecting structure 28 or the joining structure 29, 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.

[0056] 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 connecting structure 28, the junction structure 29, the radially inner membrane 7, the radially intermediate membrane 10 or even the radially outer membrane 5.

[0057] 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.

[0058] 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).

[0059] 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.

[0060] Therefore, depending on the choice of the material of the thermoplastic matrix 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.

[0061] 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.

[0062] 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, bonding structure 28 and junction structure 29. 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.

[0063] 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, bonding structure 28 and junction structure 29. 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.

[0064] As illustrated in [Fig. 5] and [Fig. 6], the linking structure 28 connects the radially inner membrane 7 to the radially intermediate membrane 10 via a plurality of linking portions 26, said linking structure 28 having a plurality of first interpenetrating zones ZI with the ra- membrane internally 7, each of the said first interpenetrating zones ZI having a first arc length L1 and, following a radial direction, a first maximum thickness El.

[0065] As shown in [Fig.5] and [Fig.7], the bonding structure 28 has a plurality of second interpenetrating zones Z2 with the radially intermediate membrane 10, each of said second interpenetrating zones Z2 having a second arc length L2 and, along a radial direction, a second maximum thickness E2.

[0066] As can be seen in [Fig.5] and [Fig.8], the junction structure 29 connects the radially intermediate membrane 10 to the radially outer membrane 5 via a plurality of junction portions 27, said junction structure 29 having a plurality of third interpenetrating zones Z3 with the radially intermediate membrane 10, each of said third interpenetrating zones Z3 having a third arc length L3 and, along a radial direction, a third maximum thickness E3.

[0067] As can be seen in [Fig.5] and [Fig.8], the junction structure 27 has a plurality of fourth interpenetrating zones Z4 with the radially outer membrane 5, each of said fourth interpenetrating zones Z4 having a fourth arc length L4 and, along a radial direction, a fourth maximum thickness E4.

[0068] As can be seen in Figures 2 to 4, the casing 24, produced by additive manufacturing, is obtained by depositing several layers of the printing material 21, said casing 24 thus being a single piece and of height H along the axial direction Z. The height H of the casing 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.

[0069] 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.

[0070] The creation of interpenetration zones Z1, Z2, Z3 and Z4 during the deposition of the printing material 21 allows, on the one hand, the bonding structure 28 to adhere perfectly to the radially inner membrane 7 and to the radially intermediate membrane 10, and on the other hand, the junction structure 29 to adhere also perfectly to the radially intermediate membrane 10 and to the radially outer membrane 5.

[0071] This perfect adhesion between the structural elements 25 of the frame 24 makes it possible to obtain very high mechanical resistance and / or very good fatigue resistance of said frame 24 during stresses in operation.

[0072] Preferably, during the manufacturing of a layer of the carcass 24, the nozzle 12 begins the deposition of a layer of the inner radial membrane 7 at a starting point which 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.

[0073] 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.

[0074] 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.

[0075] In a particular embodiment, and as illustrated in [Fig.5], the first width RI, the second width R2, the third width R3, the fourth width R4 and the fifth width R5 are equal to each other, thus reducing the time required to prepare the model of the carcass and saving manufacturing time.

[0076] Advantageously, the first width RI, the second width R2, the third width R3, the fourth width R4 and the fifth width R5 are respectively at least equal to 0.15 mm and at most equal to 4 mm, 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.

[0077] 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.

[0078] 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.

[0079] 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.

[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, of preference 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, fourth thicknesses El, E2, E3, E4 respectively allow the interpenetration of successive layers to be maximized without introducing excess material which would accumulate and cause manufacturing defects, or even the stopping and degradation of the machine.

[0085] Advantageously, the first arc length L1 is at least equal to 3 times and at most equal to 150 times the smallest of the first and fourth widths RI, R4, preferably at least equal to 10 times and at most equal to 60 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 150 times the smallest of the second and fourth widths R2, R4, preferably at least equal to 10 times and at most equal to 60 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 150 times the smallest of the second and fifth widths R2, R5, preferably at least equal to 10 times and at most equal to 60 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 150 times the smallest of the third and fifth widths R3, R5, preferably at least equal to 10 times and at most equal to 60 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, the weld bead of a structural element 25 of the frame 24 is tangent to the weld bead of 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 make a layer of each of said structural elements 25.

[0093] Preferably, the plurality of connecting portions 26 comprises at least two connecting portions 26 of different patterns, each of the connecting portions 26 of different pattern being distributed circumferentially according to a constant pitch.

[0094] Preferably, the plurality of junction portions 27 comprises at least two junction portions 27 of different patterns, each of the junction portions 27 of different pattern being distributed circumferentially according to a constant pitch.

[0095] Advantageously, the thermoplastic matrix 16 has a melting temperature of at least 180°C and at most 450°C.

[0096] 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 connecting structures 28, -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 joining structures 29.

[0097] 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 the production of a 300 / 90R16 tire without long fiber reinforcement. Carcass for the production of 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 bond structure: 0-40%. Percentage of long fiber in the junction structure: 0-40%. Number of layers: 100. Number of bond segments: 36. Number of junction segments: 36. First arc length L1: 12mm. Second arc length L2: 12mm. Third arc length L3: 12mm. Fourth arc length L4: 12mm. First maximum thickness El 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

[0098] 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.

[0099] The invention also relates to an airless tire 1 comprising the carcass 24 of the invention as described above.

[0100] 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 linking structure 28, -a junction structure 29, (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 connecting structure (28) having a fourth width (R4), - a radially intermediate membrane (10) connected to the radially inner membrane (7) by the connecting structure (28), said radially intermediate membrane (10) having a second width (R2), - a joining structure (29) having a fifth width (R5), - a radially outer membrane (5),intended to receive a tread and connected to the radially intermediate membrane (10) by the joining structure (29), 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), bonding structure (28) and junction structure (29).

3. Carcass (24) for airless tire (1) produced by additive manufacturing according to any one of claims 1 or 2 wherein 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), of link structure (28) and of junction structure (29).

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 the connecting structure (28) connects the radially inner membrane (7) to the radially intermediate membrane (10) via a plurality of connecting portions (26), said connecting structure (28) having a plurality of first interpenetrating zones (Z1) with the radially inner membrane (7), each of said first inter- penetrated (Zl) having a first arc length (Ll) and, along a radial direction, a first maximum thickness (E1), said connecting structure (28) having a plurality of second interpenetrating zones (Z2) with the radially intermediate membrane (10), each of said second interpenetrating zones (Z2) having a second arc length (L2) and, along a radial direction, a second maximum thickness (E2) and in which the junction structure (29) connects the radially intermediate membrane (10) to the radially outer membrane (5) via a plurality of junction portions (27), said junction structure (29) having a plurality of third interpenetrating zones (Z3) with the radially intermediate membrane (10), each of said third interpenetrating zones (Z3) having a third arc length (L3) and, along a radial direction, a third maximum thickness (E3),said junction structure (27) having a plurality of fourth interpenetrating zones (Z4) with the radially outer membrane (5), each of said fourth interpenetrating zones (Z4) having a fourth arc length (L4) and, along a radial direction, a fourth maximum thickness (E4).

10. Carcass (24) for airless tire (1) produced by additive manufacturing according to any one of claims 1 to 9 in which the plurality of connecting portions (26) comprises at least two connecting portions (26) of different patterns, each of the connecting portions (26) of different pattern being distributed circumferentially according to a constant pitch.

11. Carcass (24) for airless tire (1) produced by additive manufacturing according to any one of claims 1 to 10 in which the plurality of joining portions (27) comprises at least two joining portions (27) of different patterns, each of the joining portions (27) of different pattern being distributed circumferentially according to a constant pitch.

12. Airless tire (1) comprising a casing (24) according to any one of claims 1 to 11.

13. A 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 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 circum- XY ferrule perpendicular to the axial direction Z, said additive manufacturing process 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 outer membrane (5), -a bonding structure (28), -a junction structure (29), (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.

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