Airless tyre carcass produced by additive manufacturing using a material reinforced with long fibres

Abstract

The invention relates to a carcass (24) for an airless tyre (1) produced by additive manufacturing, wherein the carcass (24) comprises various structural elements (25) formed by depositing a printing material (21) using a nozzle (12), wherein the printing material (21) comprises a percentage P of long fibres (15) coated in a thermoplastic matrix (16), and wherein the reinforcement by the long fibres improves the load capacity and the mechanical strength of the carcass (24).

Description

Carcass of an airless tire made 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 coextrusion nozzle for coextruding layers simultaneously comprising a malleable material and a reinforcing fiber. The use of a coextrusion nozzle makes it possible to incorporate the reinforcing fiber inside said malleable material and to produce said carcass by successively depositing a predefined number of layers.

[0003] A three-dimensional printing machine coextruding a malleable material and a reinforcing fiber generally comprises a chamber which forms an enclosure delimited by a wall, and inside which is a plate intended to support a part being printed, as well as the nozzle for coextruding both the malleable material and the reinforcing fiber. The material resulting from the coextrusion and comprising the malleable material and the reinforcing fiber is called printing material. To be able to generate the shape of the part, drive systems are provided comprising an elevator for vertically moving either the plate or the nozzle, and translation tables crossed relative to each other for horizontally controlling either the plate 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 performances comparable to those of a conventional tire subjected to the internal pressure of a gas, generally air. An airless tire, mounted on a hub or a rim, is sometimes called a "non-pneumatic elastic wheel".

[0006] In the following, the circumferential or longitudinal direction means the direction of rotation of the tire, the axial or transverse direction means the direction parallel to the axis of rotation of the tire and the radial direction means a direction perpendicular to the axis of rotation of the tire.

[0007] An airless tire generally comprises, radially from the inside to the outside: - a carcass, made up of structural elements, intended to cooperate with a rim or a 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 the ground.

[0008] The carcass comprises, radially from the inside to the outside: - a supporting structure, intended to structurally carry at least part of the load, - a shear strip, intended to transmit by shear the rolling forces to the supporting structure and to contribute at least in part to carrying the load.

[0009] The supporting structure generally comprises, radially from the inside to the outside: - a radially inner membrane intended to be fixed by connection means to a rim or a hub, - a plurality of radial elements or spokes, intended to be fixed by connection means to the radially inner membrane and to the shear band.

[0010] However, the load-bearing structure does not generally delimit a sealed internal cavity intended to contain a pressurized gas, as in a conventional tire. Therefore, an airless tire does not need to have a sealed connection to a rim or hub.

[0011] The shear band comprises, in a known embodiment, radially from the inside to the outside: - a radially intermediate membrane, interfacing with the supporting structure, - a plurality of shear 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 radially outer membrane of the shear band by fixing means which may be, for example, gluing or hooping means.

[0013] The carcass therefore comprises a plurality of elements called structural elements which may comprise, for example, a radially inner membrane, a plurality of spokes, a radially intermediate membrane, a plurality of shear elements 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 carcasses are described in document US20220402301. These carcasses obtained by additive manufacturing have the disadvantage of having limited mechanical characteristics. When the carcass is then used to produce an airless tire, the load capacities of said tire are limited and do not allow tires with performances equivalent to those of traditional tires to be obtained.

[0016] The invention therefore aims to overcome the aforementioned drawbacks and to propose a carcass for an airless tire produced 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 guaranteeing 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 to the outside: -a radially inner membrane intended to be fixed by connection means to a rim or a hub, said radially inner membrane having a first width, -a plurality of spokes having a fourth width, -a radially intermediate membrane connected to the radially inner membrane by the plurality of spokes, 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 an airless tire being characterized in that at least one structural element is constituted by a printing material comprising a volume percentage P of long fibers coated 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 carcass for an airless tire, obtained by additive manufacturing and having at least one structural element comprising a matrix with long fibers, has higher load capacities and mechanical strength compared to the same carcass made by additive manufacturing of a thermoplastic material without reinforcing fibers. In certain embodiments of the invention, it may be desired to maintain the same load capacity or mechanical strength for the carcass reinforced with long fibers, which makes it possible to manufacture structural elements with smaller sections, consequently generating savings in material, weight and manufacturing time, said manufacturing being consequently easier and more economical.

[0019] In addition, the smaller sections allow for reduced deformations and hysteresis of the materials, thus reducing the rolling resistance of the airless tire using said airless tire carcass.

[0020] In a particular embodiment, all the structural elements are constituted by the printing material comprising the percentage P of long fibers coated in the thermoplastic matrix, the reinforcement of all the elements of structure allowing to obtain a very high load capacity for the carcass of the airless tire.

[0021] Advantageously, the volume percentage P of long fibers coated in the thermoplastic matrix, in any structural element, is between 0 and 60% and preferably between 25 and 50%, making it possible to adapt the rigidity or mechanical strength of said structural element according to its role in the operation of the carcass of the airless tire, consequently improving the properties of the carcass of the airless tire and in particular its load capacity or its rolling comfort. Thus, the volume percentage P of long fibers can be variable depending on the structural element of the carcass. In addition, depending on the type of airless tire (for example, an airless tire for a passenger vehicle or for a van), it is possible to adapt the rigidity or mechanical strength of the spokes, the shear elements, the radially inner membrane, the radially intermediate membrane or even the radially outer membrane.

[0022] Still 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 makes it possible to facilitate the additive manufacturing of each structural element while avoiding the appearance of zones without the presence of long fibers or even the appearance of junction zones between two long fibers which could potentially be zones of initiation of rupture during the stressing of the carcass. In addition, the continuity of the long fibers in the structural elements makes it possible to avoid coupling zones in which long fibers must overlap to avoid any break in the continuity of the reinforcement by long fibers.

[0023] Preferably, the thermoplastic matrix 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).

[0024] The long fiber material has a melting temperature higher than the melting temperature of the thermoplastic matrix material and is selected from glass, carbon, basalt, polyethylene terephthalate (PET), polyhexamethylene adipamide (nylon), aramid, ramie, silk or linen and preferably from glass or basalt. The preferential use of fiberglass or basalt fiber allows for high load bearing 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, spokes and shear elements, thus making it possible to specify the rigidity or flexibility for each of the structural elements.

[0026] Still 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, spokes and shear elements, making it possible to specify the rigidity or flexibility for each of the structural elements.

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

[0028] The interpenetration of the different structural elements makes it possible to improve the adhesion of the different structural elements, thus contributing to obtaining better mechanical resistance and / or fatigue limit properties of the carcass.

[0029] Preferably, the spokes are distributed circumferentially at a constant pitch.

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

[0031] The distribution of the spokes and shear elements at 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 producing the carcass of an airless tire defined above, said method implementing an additive manufacturing machine comprising a manufacturing plate, perpendicular to the axis of revolution of the carcass, said axis of revolution having an axial direction Z, and a nozzle, capable of moving in 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 in the axial direction Z, by depositing, on the manufacturing plate, a printing material, comprising long fibers coated 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 outer membrane, -a plurality of rays, -a plurality of shear cords, (b) production of at least one additional layer following step (a), the beads of the at least one additional layer being superimposed, in an axial direction Z, on the beads of the axially adjacent preceding layer with reflow of the interface between the preceding 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 of 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 constituted by an axial superposition of layers, each layer being constituted by 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 manufacturing of the carcass of the airless tire, while improving the mechanical resistance of the carcass.

[0035] Other objects, characteristics and advantages of the invention will appear in more detail on reading the description which follows, as well as with the aid of the appended drawings, provided for purely illustrative and non-limiting purposes: - Figure 1: Overall and perspective view of an airless tire comprising a carcass according to the invention. - Figure 2: Overview of an additive manufacturing machine used to produce the carcass of the invention. - Figure 3: Overall and top view of the carcass of the invention being produced on the plate of the additive manufacturing machine. - Figure 4: Axial and partial sectional view of an airless tire comprising the carcass of the invention. - Figure 5: Circumferential and partial sectional view of an airless tire carcass according to the invention. - Figure 6: Circumferential sectional view of the first interpenetration zone. - Figure 7: Circumferential sectional view of the second interpenetration zone. - Figure 8: Circumferential sectional view of the third and fourth interpenetration zones.

[0036] In the following, 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 seen in Figure 1, an airless tire 1 comprises, radially from the inside to the outside: - a carcass 24 intended to cooperate with a rim or a hub 4, - a tread 2, intended to cooperate with the carcass 24.

[0038] The carcass 24 comprises, radially from the inside to the outside: - a supporting structure 9, intended to cooperate with the rim or the hub 4, - a shear strip 3, intended to cooperate with the tread 2.

[0039] The supporting structure 9 comprises radially from the inside to the outside: - a radially inner membrane 7 intended to be fixed by connection means to the rim or hub 4, - a plurality of spokes 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, for example, means of gluing, riveting, bolting or hooping.

[0041] The shear band 3 comprises, in a known embodiment, radially from the inside to the outside: - a radially intermediate membrane 10, interfacing with the supporting 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 band 3 by fixing means which can be, by way of example, gluing or hooping means.

[0043] The carcass 24 is thus made up of structural elements 25 comprising the radially inner membrane 7, the spokes 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 used to produce the carcass 24 of the invention. The machine 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 wire and, on the other hand, a thermoplastic cord 18 in the form of a continuous cord. The additive manufacturing machine also comprises a manufacturing plate 14, a horizontal movement system 22 in any circumferential plane XY, a vertical movement system 23 in an axial direction Z, perpendicular to any circumferential plane XY and a cutting system 19, making it possible to cut the reinforcing fiber 17 to the desired length.

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

[0046] As known to those skilled in the art, the nozzle 12 makes it possible to simultaneously carry out: -receiving, through a first inlet orifice, the long fiber 15, and through a second inlet orifice, the thermoplastic cord 18, - 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 towards the long fiber 15 present inside said nozzle 12, - sheathing the long fiber 15 with a melted thermoplastic matrix 16 from the thermoplastic cord 18, to form a printing material 21 which may comprise the long fiber 15 surrounded by the melted thermoplastic matrix 16 from the thermoplastic cord 18, - 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 volume of long fibers relative to the volume of the thermoplastic matrix. The adjustment of the percentage is carried out by varying the feed speed of the reinforcing fiber yarn 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 make it possible to control a relative movement of the nozzle 12 with respect to the plate of manufacturing 14 so that said nozzle 12 can deposit the printing material 21 in melt form and in the form of preferably continuous cords 13. Each cord 13 may comprise a long fiber 15 and a thermoplastic matrix 16.

[0049] As seen in Figure 5, the long fibers 15 are oriented, when the bead 13 is deposited by the nozzle 12, in the direction of movement of said nozzle 12 in any circumferential plane XY, thus making it possible to directly specify, during deposit, 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 manufacturing plate 14 is achieved by the movement of said manufacturing plate 14.

[0051] As illustrated by Figures 1 to 3, the subject of the invention is a 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 to the outside: - a radially inner membrane 7 intended to be fixed by connection means to a rim or a 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 constituted by a printing material 21 comprising a volume percentage P of long fibers 15 coated 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 15 coated in the thermoplastic matrix 16.

[0053] In a particular embodiment, the volume percentage P of long fibers 15 coated 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 carcass 24 in which only certain structural elements 25, such as, for example, the spokes 8 or the shear elements 11, are produced with the printing material 21 comprising a percentage P of long fibers 15 greater than zero. The rest of the structural elements 25 are produced 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 vehicle or for van) it is possible to adapt the rigidity or the mechanical resistance of the spokes 8, of the shear elements 11, of the radially inner membrane 7, of the radially intermediate membrane 10 or even of the radially outer membrane 5.

[0056] In some 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 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).

[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 with a thermoplastic matrix 16, requires choosing the material of said long fibers 15 from materials having a melting temperature higher than the melting temperature of the material of said thermoplastic matrix 16 to avoid any degradation of the mechanical properties of said long fibers 15.

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

[0060] For example, if the material of the thermoplastic matrix 16 is a PAEK whose melting temperature is approximately 340°C, then the long fibers 15 used may be made of glass fibers whose melting temperature is approximately 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, spokes 8 and shear elements 11. Thus, each of the structural elements 25 having a different functional need, 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 production of each of the structural elements 25.

[0062] Still 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, spokes 8 and shear elements 11. As previously, 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 Figure 5 and Figure 6, each of the spokes 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, in a radial direction, a first maximum thickness E1.

[0064] As shown in Figure 5 and Figure 7, each of the spokes 8 also comprises 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, in a radial direction, a second maximum thickness E2.

[0065] As can be seen in Figure 5 and Figure 8, 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, in a radial direction, a third maximum thickness E3.

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

[0067] As can be seen in Figures 2 to 4, the carcass 24, produced by additive manufacturing, is obtained by depositing several layers of the printing material 21, said carcass 24 thus being in one piece and of height H in 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 to be obtained between each layer, thus making it possible to manufacture 24-piece monobloc carcasses with high mechanical resistance.

[0069] The creation of interpenetration zones Z 1, Z2, Z3 and Z4 during the deposition of the printing material 21 allows, on the one hand, the spokes 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 also adhere 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 carcass 24 makes it possible to obtain very high mechanical resistance and very good fatigue resistance of said carcass 24 during operating stresses.

[0071] Preferably, when manufacturing a layer of the carcass 24, the nozzle 12 begins the deposition of a layer of the radially inner 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.

[0072] In the same way, the deposition of a layer of the respectively intermediate 10 and external 5 membranes is preferably done with starting and arrival points of the nozzle 12 different from the previous layer, also making it possible to obtain junction zones, between the beginnings and the ends of beads 13, located according to different horizontal azimuths.

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

[0074] In a particular embodiment, and as illustrated in FIG. 5, the first width R1, 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 making it possible to reduce the preparation time of the carcass model and to save 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, preferably at least equal to 0.4 mm and at most equal to 2 mm, such dimensional ranges making it possible to manufacture the object with standard nozzle diameters and existing settings of the additive manufacturing machine parameters.

[0076] In another embodiment, it is possible to optimize the strength 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 carcass 24 having a different shape and stress, it is possible to determine each of the widths RI, R2, R3, R4 and R5 as accurately as possible.

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

[0078] Preferably, and as can be seen in Figures 6 to 8, the first maximum thickness E1, the second maximum thickness E2, the third maximum thickness E3 and the fourth maximum thickness E4 are equal to each other, thus making it possible to reduce the preparation time of the model of the carcass 24 and to save production time.

[0079] Still 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 making it possible to reduce the preparation time of the model of the carcass 24 and to save production time.

[0080] Advantageously, the first maximum thickness E1 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] Still 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] Still 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] Still 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 E1, E2, E3, E4 respectively make it possible to maximize the interpenetration of the successive layers without causing 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] Still 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] Still 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] Still 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 previously defined intervals for the first, second, third and fourth arc lengths allow sufficient adhesion to be obtained between the structural elements without increasing the rigidity and mass of the carcass.

[0090] As can be seen in Figure 5, in the interpenetrated zones Z1, Z2, Z3, Z4, each structural element 25 of the carcass 24 is tangent to the adjacent structural element 25. This tangency makes it possible to give the structural elements 25 geometries adapted to the types of stresses undergone by the carcass 24, thus improving the mechanical resistance 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 outlet section of the nozzle 12 and the adjustment parameters of the additive manufacturing machine 20.

[0092] Advantageously, the nozzle 12 of the additive manufacturing machine 20 may be changed during the manufacturing of a layer of the carcass 24 in order to make the width of the bead 13 deposited coincide with the widths R1, R2, R3, R4 and R5 of each of the structural elements 25, making it possible to make a single pass with the nozzle 12 to produce a layer of each of said structural elements 25.

[0093] Preferably, the spokes 8 and the shear elements 11 are distributed circumferentially at a constant pitch.

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

[0095] It is possible to generalize the invention to the case of a carcass 24 of the airless tire 1 comprising, radially from the inside to the outside: -at least two supporting structures 9, the first radially inner membrane 7 of the first supporting structure 9 being intended to be fixed to the rim or to the 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 pluralities of shear elements 11.

[0096] Table 1 below compares the characteristics of one embodiment of a carcass 24 made with a thermoplastic matrix 16 of polyamide 6 (PA6) without long fiber reinforcement 15 and another embodiment of the same carcass 24 made with a thermoplastic matrix 16 of polyamide 6 (PA6) reinforced with long fibers 15 of glass. The ratio of long fibers 15 in the thermoplastic matrix 16 is 40% for all the structural elements 25 of the carcass 24. [Table 1]

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

[0099] The invention also relates to a method for producing the carcass 24 of an airless tire 1 defined previously, said method implementing an additive manufacturing machine 20 comprising a manufacturing plate 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 in 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 in the axial direction Z, by depositing, on the manufacturing plate 14, a printing material 21, comprising long fibers 15 coated 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 plurality of spokes 8, -a plurality of shear elements 11, (b) production of at least one additional layer following step (a), the beads 13 of the at least one additional layer being superimposed, in an axial direction Z, on the beads 13 of the axially adjacent preceding layer with reflow of the interface between the preceding layer and the at least one additional layer.

Claims

Claims 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 to the outside: - a radially inner membrane (7) intended to be fixed by connection means to a rim or a 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 an airless tire (1) being characterized in that at least one structural element (25) is constituted by a printing material (21) comprising a volume percentage P of long fibers (15) coated 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 an airless tire (1) produced by additive manufacturing according to claim 1 in which the material of the thermoplastic matrix (16) is different between at least two structural elements (25) among the structural elements respectively of the radially inner membrane (7), of the membrane radially intermediate membrane (10), radially outer membrane (5), spokes (8) and shear elements (11).

3. Carcass (24) for an airless tire (1) produced by additive manufacturing according to one of claims 1 or 2 in which 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), spokes (8) and shear elements (11).

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

5. Carcass (24) for an 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) coated 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 an airless tire (1) produced by additive manufacturing according to any one of claims 1 to 5 in which 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 an airless tire (1) produced by additive manufacturing according to any one of claims 1 to 6 in which 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 an airless tire (1) produced by additive manufacturing according to any one of claims 1 to 7 in which the material of the fibers long (15) has a melting temperature higher than the melting temperature of the thermoplastic matrix material (16) and is chosen from glass, carbon, basalt, polyethylene terephthalate (PET), Polyhexamethylene adipamide (nylon), Taramide, ramie, silk or linen 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 spokes (8) comprises at least a first interpenetrating zone (Z1) with the radially inner membrane (7), said first interpenetrating zone (Z1) having a first arc length (L1) and, in a radial direction, a first maximum thickness (E1), each of said spokes (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, in a radial direction, a second maximum thickness (E2) and wherein 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, in 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 outer membrane (5), said fourth interpenetrating zone (Z4) having a fourth arc length (L4) and, in a radial direction, a fourth maximum thickness (E4)., 10. Carcass (24) for an airless tire (1) produced by additive manufacturing according to any one of claims 1 to 9 in which the spokes (8) are distributed circumferentially at a constant pitch.

11. Carcass (24) for an airless tire (1) produced by additive manufacturing according to any one of claims 1 to 10 in which the shear elements (11) are distributed circumferentially at a constant pitch.

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

13. Method for producing the carcass (24) of an airless tire (1) defined according to claims 1 to 11, said method implementing an additive manufacturing machine (20) comprising a manufacturing plate (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 in 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 in the axial direction Z, by depositing, on the manufacturing plate (14), a printing material (21), comprising long fibers (15) coated 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 plurality of spokes (8), -a plurality of shear elements (11), (b) production of at least one additional layer following step (a), the beads (13) of the at least one additional layer being superimposed, in an axial direction Z, on the beads (13) of the axially adjacent preceding layer with reflow of the interface between the preceding layer and the at least one additional layer.

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