TYRE WITH A LIGHTENED BEAD AREA

Abstract

The invention relates to a tire with a radial carcass reinforcement, consisting of a single layer of reinforcing elements anchored in each of the beads by turning up around a bead wire. According to the invention, the turning up of the carcass reinforcement layer and the main part of the carcass reinforcement layer are coupled, the turning up of the carcass reinforcement layer and the main part of the carcass reinforcement layer are the only layers of reinforcing elements whose elongation at break is less than 6% present in the sidewall and the arrangement and choice of polymeric mixtures of the bead zone of the tire promote endurance performance whatever the driving conditions, in particular when driving in extreme conditions in terms of loads transported or inflation pressure. Figure for abstract: Fig 1

Description

Title of the invention: TYRE WITH A LIGHTENED BEAD AREA

[0001] The present invention relates to a tire, with a radial carcass reinforcement and more particularly a tire intended to equip vehicles carrying heavy loads and traveling at high speed, such as, for example, trucks, tractors, trailers or road buses.

[0002] Generally speaking, in heavy-duty tires, the carcass reinforcement is anchored on either side in the bead area and is radially surmounted by a crown reinforcement consisting of at least two layers, superimposed and formed of parallel wires or cables in each layer and crossed from one layer to the next, making angles of between 10° and 45° with the circumferential direction. Said working layers, forming the working reinforcement, may also be covered with at least one so-called protective layer and formed of advantageously metallic and extensible reinforcement elements, called elastic.It may also comprise a layer of low-extensibility metal wires or cables forming an angle of between 45° and 90° with the circumferential direction, this ply, called the triangulation ply, being radially located between the carcass reinforcement and the first crown ply, called the working ply, formed of parallel wires or cables having angles at most equal to 45° in absolute value. The triangulation ply forms with at least said working ply a triangulated reinforcement, which, under the various stresses to which it is subjected, exhibits little deformation, the triangulation ply having the essential role of absorbing the transverse compression forces to which all the reinforcing elements in the area of ​​the crown of the tire are subjected.

[0003] Cables are said to be inextensible when said cables exhibit, under a tensile force equal to 10% of the breaking force, a relative elongation at most equal to 0.2%.

[0004] Cables are said to be elastic when said cables exhibit, under a tensile force equal to the breaking load, a relative elongation at least equal to 3% with a maximum tangent modulus less than 150 GPa.

[0005] Circumferential reinforcing elements are reinforcing elements which make angles with the circumferential direction in the range +2.5°, -2.5° around 0°.

[0006] The circumferential direction of the tire, or longitudinal direction, is the direction corresponding to the periphery of the tire and defined by the rolling direction of the tire.

[0007] The transverse or axial direction of the tire is parallel to the axis of rotation of the tire.

[0008] The radial direction is a direction intersecting the axis of rotation of the tire and perpendicular to it.

[0009] The axis of rotation of the tire is the axis around which it rotates in normal use.

[0010] A radial or meridian plane is a plane that contains the axis of rotation of the tire.

[0011] The circumferential median plane, or equatorial plane, is a plane perpendicular to the axis of rotation of the tire and which divides the tire into two halves.

[0012] With regard to metal wires or cables, the measurements of breaking force (maximum load in N), breaking strength (in MPa), elongation at break (total elongation in %) and modulus (in GPa) are carried out in tension according to standard ASTM D 2969-04 of 2014.

[0013] With regard to rubber compositions, the secant modulus of elasticity at 10% elongation is the elastic modulus of the mixture measured during a uniaxial tensile experiment, at an elongation value of 0.1 (i.e. 10% elongation, expressed as a percentage) and the secant modulus of elasticity at 100% elongation is the elastic modulus of the mixture measured at an elongation value of 1 (i.e. 100% elongation, expressed as a percentage). A constant uniaxial tensile speed is imposed on the test piece, and its elongation and the force are measured. The measurement is carried out using an INSTRON type tensile machine, at a temperature of 23°C, and a relative humidity of 50% (ISO 23529 standard). The conditions for measuring and using the results to determine the elongation and stress are as described in standard NF ISO 37: 2012-03. The stress is determined for an elongation of 0.1 and the secant modulus of elasticity at 10% elongation is calculated by dividing this stress value by the elongation value. In the same way, the stress is determined for an elongation of 1 and the secant modulus of elasticity at 100% elongation is calculated by dividing this stress value by the elongation value. A person skilled in the art will be able to choose and adapt the dimensions of the test piece according to the quantity of mixture accessible and available, particularly in the case of taking samples from a finished product such as a tire. When the quantity of mixture is however not sufficient, for example in the case of calendering layers of a layer of reinforcing elements whose thickness is too thin, it is intended to carry out the measurement on a sample of the layer of reinforcing elements.To do this, a sample of the layer of reinforcing elements is extracted from the tire in the form of a rectangle of 3 cm in the direction of the reinforcing elements and at least 8 cm in the perpendicular direction. determines the diameter "d" of the overall dimension of a reinforcing element. The sample is positioned between the jaws of an INSTRON type tensile testing machine so that an extension perpendicular to the reinforcing elements can be exerted. The distance "D" between the jaws is measured and the number "N" of reinforcing elements located between the jaws is counted, this number "N" having to be greater than or equal to 10. The elongation of the calendering layer corresponds to the elongation of the test piece multiplied by the ratio D / (DN*d). The value of the secant modulus of elasticity at 100% is the stress measured for the elongation of (DN*d) / D.

[0014] Such tires still usually include at the level of the beads one or more layers of reinforcing elements called stiffeners. These layers are most often made up of reinforcing elements oriented relative to the circumferential direction by an angle of less than 45°, and most often less than 25°. These layers of reinforcing elements have the particular function of limiting the longitudinal displacements of the materials constituting the bead relative to the rim of the wheel to limit premature wear of said bead. They also make it possible to limit the permanent deformation of the bead on the rim hook, due to the phenomenon of dynamic fining of the elastomeric materials. This deformation of the bead can prevent the retreading of the tires when it is excessive.They also contribute to the protection of the lower areas of the tire against the attacks suffered during the mounting and removal of tires on the rims.

[0015] Furthermore, in the case of anchoring the carcass reinforcement around a bead wire, which consists of winding at least part of the carcass reinforcement around a bead wire in each of the beads, forming a turn-up extending more or less high in the sidewall, the layers of reinforcing or stiffening elements also make it possible to avoid or delay the unwinding of the carcass reinforcement during accidental and excessive heating of the rim.

[0016] These layers of reinforcing elements or stiffeners are most often arranged axially outside the turn-up of the carcass reinforcement and extend over a height in the sidewall greater than that of the turn-up, in particular to cover the free ends of the reinforcing elements of said turn-up.

[0017] Such tire designs are for example described in documents FR 2779387 or US 2006 / 0000199.

[0018] The presence of these layers of reinforcing or stiffening elements complicates the design of these areas of the tire beads. The presence of an additional layer on the one hand and its arrangement in relation in particular to the turn-up of the carcass reinforcement and to the bead wire on the other hand lead to a design requiring rubber compounds to separate the ends of the layers and ensure the desired positioning of the different ends.

[0019] In its application WO2018 / 011510, the applicant has already proposed tires for "Heavy Goods Vehicles" vehicles, the endurance performance of which, in particular the endurance of the bead areas, is retained and the design of which is simplified and advantageously the overall mass of the tire is reduced.

[0020] The tires according to this design comprise in particular a carcass reinforcement layer whose turn-up has a length greater than the more usual designs, this being coupled with the main part of the carcass reinforcement layer and is characterized in particular by the absence of a stiffener.

[0021] In applications WO2020 / 065176 and WO2020 / 094952, the applicant has further proposed developments of such tire designs having improved endurance performance of the bead areas in certain driving configurations.

[0022] If these tires are satisfactory under given conditions of use and driving, the inventors have shown that risks of lower performance in terms of endurance remain in the case of driving under extreme conditions, particularly in terms of loads transported or inflation pressure.

[0023] The inventors have thus set themselves the task of producing tires whose design is simplified and advantageously whose overall mass of the tire is reduced while ensuring performance in terms of endurance whatever the driving conditions, including when used in extreme conditions, particularly in terms of loads transported or inflation pressure.

[0024] This object has been achieved according to the invention by a tire intended to be mounted on a hollow rim of the 15° drop center type, comprising a radial carcass reinforcement, consisting of a single layer of carcass reinforcement formed of reinforcing elements inserted between two layers of polymeric mixture calendering, said tire comprising a crown reinforcement, itself radially capped with a tread, said tread being joined to two beads by means of two sidewalls, the layer of reinforcing elements of the carcass reinforcement being anchored in each of the beads by turning up around a bead wire to form a main part of the carcass reinforcement layer extending from one bead wire to the other and a turning up of the carcass reinforcement layer in each of the beads,said turn-up of the carcass reinforcement layer being separated from the main part of the carcass reinforcement layer by a first layer of polymeric mixture extending radially from the bead wire axially between the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer and said turn-up of the carcass reinforcement layer being axially outwards in contact with a second layer of mixture po , lymeric, itself at least in contact with a third layer of polymeric mixture forming the outer surface of the tire in the bead area, said third layer of polymeric mixture being intended in particular to come into contact with the rim, said third layer of polymeric mixture being radially outwards in contact with a fourth layer of polymeric mixture forming the outer surface of a sidewall, in a meridian section of said tire, - the distance dR between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire being between 45 and 90% of the distance dE between the axially outermost point of the main part of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire, - radially outwards, from a point C of the turn-up of the carcass reinforcement layer located at a distance dc from the radially innermost point of the circle circumscribed to the bead wire of between 30 and 55% of the distance dR between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire, the turn-up of the carcass reinforcement layer and the main part of the carcass reinforcement layer being coupled, - the upturn of the carcass reinforcement layer and the main part of the carcass reinforcement layer being the only layers of reinforcing elements whose elongation at break is less than 6% present in an area of ​​the sidewall constituting at least 90% of the surface of the sidewall lying radially between the end of the upturn of the carcass reinforcement layer and the radially outermost point of the bead wire, - the radially outermost point of the first layer of polymeric mixture in contact with the turn-up of the carcass reinforcement layer being radially inner to the end of the turn-up of the carcass reinforcement layer and at a distance from the end of the turn-up of the carcass reinforcement layer of between 5 and 15 mm, - a fifth layer of polymeric mixture being radially external and in contact with the first layer of polymeric mixture and, in part, axially between the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer, - the radially outermost end of said fifth layer of polymeric mixture being radially outer to the end of the turn-up of the carcass reinforcement layer, - the modulus of elasticity under tension at 100% elongation of the fifth layer of polymer mixture being at least 25% lower than the modulus of elasticity under tension at 100% elongation of the first layer of polymer mixture, - at least one layer of radially oriented textile reinforcing elements being axially positioned between the main part of the carcass reinforcement layer and the fourth layer of polymer mixture and / or between the main part of the carcass reinforcement layer and the second layer of polymer mixture, - the density of textile reinforcing elements in said at least one layer of textile reinforcing elements being greater than the density of reinforcing elements in the carcass reinforcement layer, the modulus of elasticity under tension at 100% elongation of the calendering layers of said at least one layer of textile reinforcing elements being less than or equal to the modulus of elasticity under tension at 100% elongation of the fifth layer of polymeric mixture.

[0025] For the purposes of the invention, a hollow rim of the 15° drop center type or wedged seat rim is a one-piece rim, as defined in the ETRTO, the seats of which intended to receive the beads of the tire have a truncated cone shape, the angle formed with the axial direction being substantially equivalent to 15°. These seats are also extended by rim hooks of reduced height compared to rim hooks with flat bases whose rim seats have substantially cylindrical shapes.

[0026] For the purposes of the invention, radially oriented reinforcing elements means that the reinforcing elements are in a plane forming an angle with a radial plane less than or equal to 10°, the two planes being intersecting along an axis perpendicular to the axis of rotation.

[0027] The position of the axially outermost point of the main part of the carcass reinforcement is determined on a tire mounted and inflated according to the nominal conditions. This determination can be carried out for example using a tomography technique.

[0028] The positions of the radially innermost and radially outermost points of the circle circumscribed to the bead wire can also be determined using a tomography technique or are determined on a section of a tire, the bead spacing of which is the same as when the tire is mounted on the mounting rim recommended by the ETRTO, the latter therefore being neither mounted nor inflated.

[0029] The distance between the axially outermost point of the main part of the carcass reinforcement layer and the radially innermost point of the circle circumscribed around the bead wire is measured on a tire mounted and inflated according to the nominal conditions. This measurement can be carried out for example using a tomography technique.

[0030] Other distances, in particular measured from the radially most inside the circle circumscribed to the bead, can also be measured using a tomography technique or are measured on a section of a tire, the bead spacing of which is the same as when the tire is mounted on the mounting rim recommended by ETRTO, the latter therefore being neither mounted nor inflated.

[0031] For the purposes of the invention, the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer are said to be coupled if the respective reinforcing elements of the main part of the carcass reinforcement layer and of the turn-up of the carcass reinforcement layer are separated by a substantially constant thickness of rubber compound of at most 5 mm over a length greater than 15% of the distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire. The thickness of rubber compound separating the respective reinforcing elements of the main part of the carcass reinforcement layer and of the turn-up of the carcass reinforcement layer is measured in the direction normal to the reinforcing elements of the main part of the carcass reinforcement layer.Advantageously according to the invention, the respective reinforcing elements of the main part of the carcass reinforcement layer and of the turn-up of the carcass reinforcement layer are separated by a substantially constant thickness of rubber mixture of at most 3.5 mm and preferably they are separated by a substantially constant thickness of rubber mixture of at least 0.8 mm and more preferably by a substantially constant thickness of rubber mixture of at least 2.5 mm.

[0032] For the purposes of the invention, a substantially constant thickness of rubber mixture separating the respective reinforcing elements of the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer is a thickness which does not vary by more than 0.5 mm. The variations in thickness are then only due to the phenomena of finishing during the manufacture and curing of the tire.

[0033] Advantageously according to the invention, the crown reinforcement comprising at least one layer of reinforcing elements, the ratio of the radial distance between the axially outermost point of the main part of the carcass reinforcement layer and the radially outermost point of the nominal rim, i.e. the radially outermost point of the rim hook, to the radial distance between the axially outer end of the axially widest layer of reinforcing elements of the crown reinforcement and the radially outermost point of the nominal rim is less than or equal to 55%.

[0034] The radial distance between the axially outermost point of the main part of the carcass reinforcement layer and the radially outermost point of the rim nominal is measured on a tire mounted and inflated according to the nominal conditions. This measurement can be carried out, for example, using a tomography technique.

[0035] The radial distance between the axially outer end of the axially widest layer of reinforcing elements of the crown reinforcement and the radially outermost point of the nominal rim can also be measured using a tomography technique, with the tire mounted and inflated to nominal conditions.

[0036] Advantageously still according to the invention, the ratio of the radial distance between the axially outermost point of the main part of the carcass reinforcement layer and the radially outermost point of the nominal rim to the radial distance between the axially outer end of the axially widest layer of reinforcing elements of the crown reinforcement and the radially outermost point of the nominal rim is less than 53%.

[0037] Also preferably according to the invention, the modulus of elasticity under tension at 100% elongation of the fifth layer of polymeric mixture is at least 30% lower than the modulus of elasticity under tension at 100% elongation of the first layer of polymeric mixture, and more preferably at least 35% lower than the modulus of elasticity under tension at 100% elongation of the first layer of polymeric mixture.

[0038] Advantageously also according to the invention, the density of textile reinforcing elements in said at least one layer of textile reinforcing elements is greater than 1.25 times the density of reinforcing elements of the carcass reinforcement layer, and preferably greater than 1.5 times the density of reinforcing elements of the carcass reinforcement layer.

[0039] More preferably, the modulus of elasticity under tension at 100% elongation of the calendering layers of said at least one layer of textile reinforcing elements is less than 95% of the modulus of elasticity under tension at 100% elongation of the fifth layer of polymeric mixture.

[0040] The tests have shown that the tires thus produced according to the invention combine a reduced mass, in particular in comparison with tires of more usual design, comprising for example layers of additional reinforcement elements of the stiffener type, and performances in terms of endurance, and in particular in terms of endurance of the bead zones, at least as good as those of tires such as those described in applications WO2018 / 011510, WO2020 / 065176 and WO2020 / 094952, or even superior, whatever the conditions of use, in particular when driving in particularly severe conditions in terms of loads transported or inflation pressure.

[0041] The inventors believe they have demonstrated that said at least one layer of radially oriented textile reinforcing elements, its positioning and its dimensioning, as well as the stiffness properties of the calendering layers of said at least one layer of textile reinforcing elements, combined with the positioning of the fifth layer of polymeric mixture, with regard to the turning over of the carcass reinforcement layer, and the stiffness properties of said fifth layer of polymeric mixture are favorable to a reduction in the initiation and propagation of cracks.

[0042] The inventors first believe that they have demonstrated that the positioning of the fifth layer of polymeric mixture, with regard to the turning of the carcass reinforcement layer, and the stiffness properties of said fifth layer of polymeric mixture associated with the stiffness properties of the calendering layers of the layer of textile reinforcing elements allow a reduction in the available energy density which is favorable to the propagation of a crack. The impact of the energy density on the propagation of cracks is described in GJ Lake (1995) Fatigue and Fracture of Elastomers. Rubber Chemistry and Technology: July 1995, Vol. 68, No. 3, pp. 435-460. The energy density is evaluated using a finite element simulation.

[0043] In addition, said at least one layer of textile reinforcing elements appears to make it possible to limit the opening of cracks which initiate in the polymeric mixtures at the end of the turn-up of the carcass reinforcement layer.

[0044] The inventors have thus been able to demonstrate that the tires produced in accordance with the invention and which have in particular a turn-up of the carcass reinforcement layer with a length greater than certain more usual designs, a coupling of the turn-up of the carcass reinforcement layer with the main part of the carcass reinforcement layer, associated with the relative dimensions and positioning of the different constituent elements of the bead zone of the tire, make it possible to lighten the tire and, against all expectations, to maintain satisfactory properties in terms of endurance, or even to improve them, whatever the conditions of use and in particular when driving in extreme conditions in terms of loads transported or inflation pressure.

[0045] According to one embodiment of the invention, said at least one layer of radially oriented textile reinforcing elements is axially positioned at least partially between the turn-up of the carcass reinforcement layer and the main part of the carcass reinforcement layer.

[0046] Advantageously, according to any one of the embodiments of the invention, said at least one layer of radially oriented textile reinforcing elements is axially in contact with the end of the turn-up of the carcass reinforcement layer.

[0047] According to a first variant embodiment of the invention, in its part axially in contact with the turn-up of the carcass reinforcement layer, said at least one layer of textile reinforcing elements is axially inside the turn-up of the carcass reinforcement layer.

[0048] According to a second variant embodiment of the invention, in its part axially in contact with the turn-up of the carcass reinforcement layer, said at least one layer of textile reinforcing elements is axially external to the turn-up of the carcass reinforcement layer.

[0049] According to this second variant embodiment of the invention, said at least one layer of textile reinforcing elements separates the end of the turn-up of the carcass reinforcement layer from the fourth layer of polymer mixture and / or from the second layer of polymer mixture.

[0050] According to a third variant embodiment of the invention, the tire comprises two layers of textile reinforcing elements, a first layer of textile reinforcing elements axially outside the turn-up of the carcass reinforcement layer in its part axially in contact with the turn-up of the carcass reinforcement layer and a second layer of textile reinforcing elements axially inside the turn-up of the carcass reinforcement layer in its part axially in contact with the turn-up of the carcass reinforcement layer.

[0051] Advantageously according to the invention, the diameter of the textile reinforcing elements of said at least one layer of textile reinforcing elements is less than 0.65 mm and preferably less than 0.50 mm.

[0052] Such a choice of diameter of the textile reinforcing elements makes it possible to avoid the risk of recreating ends likely to be the source of the initiation of cracks in the surrounding polymeric mixtures.

[0053] Preferably according to the invention, said at least one layer of textile reinforcing elements extends radially internally at the end of the turn-up of the carcass reinforcement layer over at least 8 mm.

[0054] Also preferably according to the invention, said at least one layer of textile reinforcing elements extends radially outwardly beyond the end of the turn-up of the carcass reinforcement layer by at least 8 mm.

[0055] More preferably according to the invention, the distance between the end of the turn-up of the carcass reinforcement layer and each of the ends of said at least one layer of textile reinforcing elements is greater than 17 mm.

[0056] According to one embodiment of the invention, the radially outermost end of the fifth layer of polymeric mixture is radially outer to the end of the turn-over of the layer of textile reinforcing elements.

[0057] According to a preferred embodiment of the invention, in a meridian section of said tire, the radially outermost point of the first layer of polymeric mixture in contact with the main part of the carcass reinforcement layer is located in a zone, around the orthogonal projection of the end of the turn-up of the carcass reinforcement layer on the main part of the carcass reinforcement layer delimited, radially outwards by a point located at a distance from said projection equal to 10 mm and radially inwards by a point located at a distance from said projection equal to 15 mm.

[0058] According to a preferred embodiment of the invention, the modulus of elasticity under tension at 10% elongation of the second layer of polymeric mixture is greater than or equal to the modulus of elasticity under tension at 10% elongation of the calendering of the carcass reinforcement layer and strictly less than 25 MPa.

[0059] Such an embodiment of the invention further contributes to performance in terms of endurance whereas, according to more usual tire configurations, the second layer of polymeric mixture positioned axially on the outside and in contact with the turn-up of the carcass reinforcement layer has a modulus of elasticity under tension at 10% elongation lower than that of the calendering layers of the carcass reinforcement, in particular to limit temperature increases in the bead area of ​​the tire.

[0060] Advantageously according to the invention, the end of the turn-up of the carcass reinforcement layer is radially external to the radially external end of the second layer of polymeric mixture,

[0061] Advantageously still according to the invention, the radially outer end of the second layer of polymeric mixture is radially outer to the radially outer end of the third layer of polymeric mixture.

[0062] Advantageously also according to the invention, the radially inner end of the second layer of polymeric mixture is radially between the radially outermost point of the circle circumscribed to the bead wire and the radially innermost point of the circle circumscribed to the bead wire. This positioning is determined on a section of a tire, the bead spacing of which is the same as when the tire is mounted on the mounting rim recommended by the ETRTO, the latter therefore being neither mounted nor inflated.

[0063] According to a preferred embodiment of the invention, the modulus of elasticity under tension at 100% elongation of the calendering layers of the carcass reinforcement layer is between 2 and 7 MPa and preferably between 2.5 and 5 MPa. These values ​​make it possible in particular to define the desired compromise between the endurance performance of the tire and its performance in terms of rolling resistance.

[0064] Preferably according to the invention, the modulus of elasticity under tension at 100% elongation of the first layer of polymeric mixture is less than or equal to the modulus of elasticity under tension at 100% elongation of the calendering of the carcass reinforcement layer. This choice makes it possible in particular to concentrate the shear forces within the first layer of polymeric mixture.

[0065] More preferably according to the invention, the modulus of elasticity under tension at 100% elongation of the first layer of polymeric mixture is greater than 50% of the modulus of elasticity under tension at 100% elongation of the calendering of the carcass reinforcement layer and preferably is greater than 70% of the modulus of elasticity under tension at 100% elongation of the calendering of the carcass reinforcement layer. This choice makes it possible to maintain the shear forces within the first layer of polymeric mixture while ensuring sufficient transfer of forces between the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer for good endurance performance.

[0066] Advantageously according to the invention, the modulus of elasticity under tension at 10% elongation of the second layer of polymeric mixture is less than 150% of the modulus of elasticity under tension at 10% elongation of the calendering of the carcass reinforcement layer. According to this advantageous embodiment of the invention, the second layer of polymeric mixture provides sufficient rigidity to ensure good endurance performance of the tire when pressed on the rim hooks while ensuring satisfactory performance in terms of rolling resistance.

[0067] According to a preferred embodiment of the invention, to promote the compromise between endurance and rolling resistance performance, the modulus of elasticity under tension at 10% elongation of the first layer of polymeric mixture is greater than or equal to the modulus of elasticity under tension at 10% elongation of the third layer of polymeric mixture which is itself greater than or equal to the modulus of elasticity under tension at 10% elongation of the fourth layer of polymeric mixture.

[0068] An advantageous variant of the invention provides that radially outwardly from said point C of the turn-up of the carcass reinforcement layer, the turn-up of the carcass reinforcement layer and the main part of the carcass reinforcement layer are coupled over a length of between 15 and 65% of the distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire, to then be decoupled by the first layer of polymeric mixture and / or the fifth layer of polymeric mixture up to the end of the turn-up of the carcass reinforcement layer.

[0069] For the purposes of the invention, the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer are said to be decoupled if, radially outside the coupling zone, the thickness of rubber mix separating the respective reinforcing elements of the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer is greater than that of the coupling zone. The respective reinforcing elements of the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer are then advantageously separated by a thickness of rubber mix of between 3 and 8 mm, said thickness of rubber mix being measured in the direction normal to the reinforcing elements of the main part of the carcass reinforcement layer between the respective reinforcing elements of the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer.Preferably according to the invention, in the decoupling zone, the respective reinforcing elements of the main part of the carcass reinforcement layer and of the turn-up of the carcass reinforcement layer are separated by at most 6 mm and preferably they are separated by at least 4 mm.

[0070] According to an advantageous embodiment of the invention, the decoupling zone may consist of a first part, called a transition part, extending the coupling zone in which the thickness of the rubber mixture separating the respective reinforcing elements of the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer increases and a second, radially outermost part in which the thickness of the rubber mixture separating the respective reinforcing elements of the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer is substantially constant.

[0071] According to this variant embodiment of the invention, the increase in the thickness of the first layer of polymer mixture and / or of the fifth layer of polymer mixture makes it possible to compensate for the reduction in tension in the reinforcing elements of the carcass reinforcement when approaching the end of its turn-up in order to absorb the shear stresses between the main part of the carcass reinforcement layer and its turn-up.

[0072] Advantageously again, the decoupling length is between 5 and 40% of the distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire and preferably between 15 and 35% of the distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire.

[0073] Preferably according to the invention, the turning of the carcass reinforcement layer and the main part of the carcass reinforcement layer are coupled over a length of between 25 and 40% of the distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed around the bead wire.

[0074] According to a preferred embodiment of the invention, in any meridian plane, over a length of the turn-up of the carcass reinforcement layer delimited radially between the end of said turn-up of the carcass reinforcement layer and a point situated at a distance from the radially innermost point of the circle circumscribed to the bead wire equal to 65% of the distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire, any point of the turn-up of the carcass reinforcement layer is at a distance from the outer surface of the tire of less than 10 mm.More preferably, any point of the turn-up of the carcass reinforcement layer is at a distance from the outer surface of the tire of less than 10 mm over a length of the turn-up of the carcass reinforcement layer delimited radially between the end of said turn-up and a point located at a distance from the radially innermost point of the circle circumscribed to the bead wire equal to 50% of the distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire.

[0075] Advantageously still according to the invention, in any meridian plane, over a radial distance greater than 4 mm, and preferably greater than 10 mm, starting radially outside the end of the turn-up of the carcass reinforcement layer and at a radial distance from the end of the turn-up of the carcass reinforcement layer equal to 2.5 times the diameter of a reinforcing element of the carcass reinforcement and extending radially outwards, the thickness, measured in the direction normal to the reinforcing elements of the turn-up of the carcass reinforcement layer at the end of the turn-up of the carcass reinforcement layer, of the fourth layer of polymeric mixture forming the outer surface of a sidewall is substantially constant.

[0076] Advantageously still according to the invention, in any meridian plane, over a radial distance greater than 4 mm, and preferably greater than 10 mm, starting radially inside the end of the turn-up of the carcass reinforcement layer and at a radial distance from the end of the turn-up of the carcass reinforcement layer equal to 2.5 times the diameter of a reinforcing element of the carcass reinforcement and extending radially inwards, the thickness, measured in the direction normal to the reinforcing elements of the turn-up of the carcass reinforcement layer at the end of the turn-up of the carcass reinforcement layer, of the fourth layer of polymeric mixture forming the outer surface of a flank is substantially constant.

[0077] For the purposes of the invention, the expression a substantially constant thickness means that it does not vary by more than 0.5 mm. These variations in thickness are only due to creep phenomena during the manufacture and curing of the tire.

[0078] The fourth layer of polymeric mixture thus produced according to the invention appears to contribute to the better positioning of the first layer of polymeric mixture and to its installation to ensure the coupling and possibly the decoupling of the main part of the carcass reinforcement layer and the turning of the carcass reinforcement layer.

[0079] According to an advantageous embodiment of the invention, in any meridian plane, in each bead, the tire comprises a containment reinforcement surrounding the bead wire and a volume of rubber mixture directly in contact with the bead wire.

[0080] Such a containment reinforcement makes it possible, during use of the tire, to limit changes in the shape of the bead wire and thus to maintain satisfactory performance, particularly in terms of endurance. Indeed, the tire according to the invention, the structure of which leads to its lightening, could, in certain cases of use or types of rolling, lead to a geometric evolution in the bead zone potentially detrimental to the tire's performance in terms of endurance. The presence of a containment reinforcement such as proposed makes it possible to delay or even prevent such a geometric evolution. Advantageously still according to the invention, the containment reinforcement is made up of a layer of textile reinforcing elements of the aliphatic polyamide type.

[0081] Advantageously according to the invention, the rods are packet rods, that is to say rods formed from an assembly of gummed wires wound around a shape, preferably hexagonal in shape.

[0082] Advantageously still according to the invention, the metallic reinforcing elements of the layer of the carcass reinforcement are cables with at least two layers.

[0083] Advantageously still according to the invention, at least one internal layer of the metal cables is sheathed with a layer consisting of a non-crosslinkable, crosslinkable or crosslinked rubber composition, preferably based on at least one diene elastomer.

[0084] According to an alternative embodiment of the invention, the crown reinforcement of the tire is formed from at least two working crown layers of inextensible reinforcing elements, crossed from one layer to the other making angles of between 10° and 45° with the circumferential direction.

[0085] According to other variant embodiments of the invention, the crown reinforcement also comprises at least one layer of circumferential reinforcing elements.

[0086] A preferred embodiment of the invention further provides that the crown reinforcement is completed radially on the outside by at least one additional layer, called a protective layer, of so-called elastic reinforcing elements, oriented relative to the circumferential direction with an angle between 10° and 45° and in the same direction as the angle formed by the inextensible elements of the working layer which is radially adjacent to it.

[0087] The protective layer may have an axial width less than the axial width of the narrowest working layer. Said protective layer may also have an axial width greater than the axial width of the narrowest working layer, such that it covers the edges of the narrowest working layer and, in the case of the radially upper layer being the narrowest, such that it is coupled, in the axial extension of the additional reinforcement, with the widest working crown layer over an axial width, to then be, axially on the outside, decoupled from said widest working layer by profiles of thickness at least equal to 2 mm.The protective layer formed of elastic reinforcing elements may, in the case cited above, be on the one hand possibly decoupled from the edges of said narrower working layer by profiles of thickness substantially less than the thickness of the profiles separating the edges of the two working layers, and on the other hand have an axial width less than or greater than the axial width of the widest top layer.

[0088] According to any of the embodiments of the invention mentioned above, the crown reinforcement can also be completed, radially on the inside between the carcass reinforcement and the radially inner working layer closest to said carcass reinforcement, by a triangulation layer of inextensible metallic reinforcing elements made of steel making, with the circumferential direction, an angle greater than 60° and in the same direction as that of the angle formed by the reinforcing elements of the layer radially closest to the carcass reinforcement.

[0089] Other details and advantageous characteristics of the invention will emerge below from the description of the exemplary embodiments of the invention, in particular with reference to Figures 1 and 2 which represent: - [Fig.l], a meridian view of a diagram of a tire according to an embodiment of the invention, - [Fig.2], an enlarged schematic representation of the bead area of ​​the tire of [Fig.l].

[0090] The figures are not shown to scale to simplify understanding.

[0091] [Fig.l] represents only a half-view of a tire which extends symmetrically with respect to the circumferential median plane, or equatorial plane, of a tire.

[0092] In [Fig.l], the tire 1 is of dimension 12 R 22.5. Said tire 1 comprises a radial carcass reinforcement 2 anchored in two beads 3. The carcass reinforcement 2 is hooped to the top of the tire by a crown reinforcement 5, itself topped with a tread 6.

[0093] The carcass reinforcement 2, formed from a single layer of metal cables, is wound in each of the beads 3 around a bead wire 4 and forms in each of the beads 3 a turn-up of the carcass reinforcement layer 7 having an end 8.

[0094] The carcass reinforcement 2 is made up of reinforcing elements between two calendering layers whose modulus of elasticity under tension at 100% elongation is equal to 4.5 MPa and whose modulus of elasticity under tension at 10% elongation is equal to 9.8 MPa.

[0095] The reinforcing elements of the carcass reinforcement 2 are cables 19.18 whose elongation at break is equal to 2.5%.

[0096] [Fig.l] further illustrates a layer of textile reinforcing elements 18 axially external to the turn-up of the carcass reinforcement layer, in its part axially in contact with the turn-up of the carcass reinforcement layer.

[0097] [Fig.l] illustrates the tire mounted on its nominal rim J; the axially outermost point E of the main part of the carcass reinforcement layer 2 is thus determined with the tire inflated to its nominal pressure, for example by tomography.

[0098] [Fig.2] illustrates in an enlarged form a schematic cross-sectional representation of a bead 3 of the tire in which we find a part of the carcass reinforcement layer 2 wound around a bead wire 4 to form a turn-up 7 with an end 8.

[0099] In this [Fig.2], the circle T circumscribed to the bead 4 is materialized and the radially innermost point A of said circle T appears. This point A is defined on a radial section of the tire, the bead spacing of which is the same as when the tire is mounted on the mounting rim recommended by the ETRTO, the latter not being mounted on a rim.

[0100] We also determine the radially outermost point B of the circle T.

[0101] The distance dE between point E and point A is equal to 128 mm.

[0102] The distance between point 8 and point A is equal to 90 mm.

[0103] The ratio of the distance dR to the distance dE is equal to 70% and therefore between 45 and 90%.

[0104] The radial distance dCj between the axially outermost point of the main part of the carcass reinforcement layer and the radially outermost point of the nominal rim is equal to 108.2 mm.

[0105] The radial distance dSJ between the axially outer end of the layer of reinforcement elements of the axially widest crown reinforcement and the radially outermost point of the nominal rim is equal to 206.7 mm.

[0106] The ratio of the distance dCJ to the distance dSJ is equal to 52.3% and therefore less than 53%.

[0107] The turn-up 7 of the carcass reinforcement layer is coupled to the main part of the carcass reinforcement layer 2 from point C, such that the distance dc between point C and point A is equal to 37 mm.

[0108] The ratio of the distance dc to the distance dR is equal to 41% and therefore between 30 and 55%.

[0109] The turn-up 7 of the carcass reinforcement layer is then decoupled from the main part of the carcass reinforcement layer 2 from point D, such that the distance dD between point D and point A is equal to 66 mm and such that the coupling length between point C and point D is equal to 29 mm and therefore between 25 and 40% of the distance dR. The coupling length is measured along the straight line passing through points C and D.

[0110] The coupling thickness between the main part of the carcass reinforcement layer 2 and the turn-up 7 of the carcass reinforcement layer, measured in the direction normal to the reinforcing elements of the main part of the carcass reinforcement layer 2 between the respective reinforcing elements of the main part of the carcass reinforcement layer and the turn-up of the carcass reinforcement layer 2, is substantially constant and equal to 2.9 mm.

[0111] The decoupling length between point D and point 8 is equal to 21 mm and therefore between 15 and 35% of the distance dR. The decoupling length is measured along the straight line passing through points D and 8.

[0112] The turn-up 7 of the carcass reinforcement layer 2 is separated from the main part of the carcass reinforcement layer 2 by a first layer of polymeric mixture 9a, having a radially outer end 10a in contact with the turn-up 7 of the carcass reinforcement layer 2, radially inner to the end 8 of said turn-up 7 at a distance diOa from the point 8 equal to 7 mm. The first layer of polymeric mixture 9a, also has a radially outer end 10b in contact with the main part of the carcass reinforcement layer 2, at a distance diOb from the orthogonal projection 8p of the point 8 on the main part of the carcass reinforcement layer equal to 5 mm. The first layer of polymeric mixture 9a has a modulus of elasticity under tension at 10% elongation lower than the modulus of elasticity under tension at 10% elongation of the calendering layers of the carcass reinforcement 2.

[0113] The first layer of polymeric mixture 9a is profiled to come to bear on the rod 4 and ensure the coupling and decoupling between the turn-up 7 of the layer carcass reinforcement and the main part of the carcass reinforcement layer 2.

[0114] Radially to the outside of the first layer of polymeric mixture 9a, a fifth layer of polymeric mixture 9b radially extends said first layer of polymeric mixture 9a and has a radially outermost end 10c radially outside the end 8 of the turn-up 7 of the carcass reinforcement layer 2. The radially outermost end 10c of the fifth layer of polymeric mixture 9b is at a distance diOc from the point A, equal to 117 mm.

[0115] The fifth polymer blend layer 9b has a modulus of elasticity under tension at 100% elongation lower than the modulus of elasticity under tension at 100% elongation of the first polymer blend layer 9a.

[0116] Axially in contact with the turn-up 7 of the carcass reinforcement layer 2, there is arranged a layer of textile reinforcing elements 18 which extends radially between its radially innermost end 20 to its radially outermost end 19. The distance d^ between the end 8 of the turn-up 7 of the carcass reinforcement layer 2 and the end 19 of said layer 18 is equal to 10 mm. The distance d2o between the end 8 of the turn-up 7 of the carcass reinforcement layer 2 and the end 20 of said layer 18 is equal to 17 mm.

[0117] The layer of textile reinforcing elements 18 is made up of reinforcing elements made of PET (Polyethylene terephthalate) of formula 144 / 2 290 / 290 distributed at a pitch equal to 0.96 mm. The diameter of the cables is equal to 0.62 mm. The layer of textile reinforcing elements 18 thus has a density of reinforcing elements equal to 104 cables per decimeter. The density of reinforcing elements of the carcass reinforcement layer 2 is equal to 72 cables per decimeter. The calendering layers of the layer 18 are made up of a polymeric mixture conventionally used with textile reinforcements which does not include an agent for adhering to the metal. The modulus of elasticity under tension at 100% elongation of the calendering layers of the layer of textile reinforcing elements 18 is lower than that of the fifth layer of polymeric mixture.

[0118] According to this representation of the invention, the tire comprises a layer of textile reinforcing elements 18 axially arranged between the turn-up 7 of the carcass reinforcement layer 2 and the second and fourth layers of polymeric mixture. It could, according to another embodiment, be arranged between the main part of the carcass reinforcement layer 2 and its turn-up 7. The tire could also comprise two layers of textile reinforcing elements axially on either side of the turn-up 7 of the carcass reinforcement layer 2.

[0119] Axially outside the turn-up 7 of the carcass reinforcement layer is represented the second layer of polymeric mixture 11 whose radially outer end 12 is radially inside the end 8 of the turn-up 7 of the carcass reinforcement layer. The radially inner end 13 of the second layer of polymeric mixture 11 is radially between the points A and B, respectively radially the innermost and radially the outermost of the circle circumscribed to the bead wire.

[0120] The second layer of polymeric mixture 11 has a modulus of elasticity under tension at 10% elongation equal to 9.8 MPa and therefore identical to the modulus of elasticity under tension at 10% elongation of the calendering layers of the carcass reinforcement 2.

[0121] In contact with the second layer of polymeric mixture 11 and radially under the bead wire, there is the third layer of polymeric mixture 14, the axially outermost end 15 of which is radially inside the end 12 of the second layer of polymeric mixture 11.

[0122] The third layer of polymeric mixture 14 has a modulus of elasticity under tension at 10% elongation equal to 7.1 MPa.

[0123] Axially in contact with the fifth layer of polymeric mixture 9b, the second layer of polymeric mixture 11, and the third layer of polymeric mixture 14, is the fourth layer of polymeric mixture 16. The radially inner end 17 of the fourth layer of polymeric mixture 16 is radially inner to the end 15 of the third layer of polymeric mixture 14.

[0124] The fourth layer of polymeric mixture 16 has a modulus of elasticity under tension at 10% elongation equal to 3.1 MPa.

[0125] In areas located on either side of the end 8 of the turn-up 7 of the carcass reinforcement layer, the profile of the fourth layer of polymeric mixture 16 is such that said fourth layer of polymeric mixture 16 has a thickness, measured in the direction normal to the reinforcing elements of the carcass reinforcement 2 at the end 8 of the turn-up 7, substantially constant and equal to 3.3 mm, over two radial lengths of approximately 5 mm from each of the two points located on either side of the end 8 at distances from said end 8 equal to 2.5 mm corresponding to more than 2.5 times the diameter of the carcass reinforcement cables, the latter being equal to 0.9 mm.

[0126] Tests were carried out with tires II produced according to the invention in accordance with the representation of figures 1 and 2, tires 12 and with tires RI, R2, R3, R4, R5, R6 and R7 called reference tires.

[0127] The tires 12 differ from the tires II by the nature of the mixtures constituting the calendering of the carcass reinforcement ply and the first layer of polymer blend.

[0128] The reference tires RI differ from the tires according to the invention by the presence of stiffeners and a more usual bead zone with in particular a distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire equal to 37% of the distance between the axially outermost point of the main part of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire and layers of polymeric mixtures between the main part of the carcass reinforcement layer and its turn-up as well as on each side of the stiffener.

[0129] The mass of the RI tire is equal to 63.9 kg while the tires according to the invention as well as the other reference tires have a mass of 61.1 kg.

[0130] The reference tires R2 differ from the tire II according to the invention by the absence of the layer of textile reinforcing elements 18 and by the absence of the fifth layer 9b, the layer 9a then having an end radially outside the end 8 of the turn-up 7 of the carcass reinforcement layer.

[0131] The reference tires R3 differ from the tires II according to the invention by the absence of the fifth layer 9b, the layer 9a then having an end radially outside the end 8 of the turn-up 7 of the carcass reinforcement layer.

[0132] The reference tires R4 differ from the tires II according to the invention by the absence of the layer of textile reinforcement elements 18.

[0133] The R5 reference tires differ from the II tires according to the invention by a density of textile reinforcement elements of layer 18 equal to 60 cables per decimeter.

[0134] The reference tires R6 differ from the tires II according to the invention by a higher value of the modulus of elasticity under tension at 100% calendering elongation of the layer 18, higher than the modulus of elasticity under tension at 100% elongation of the fifth layer.

[0135] The R7 reference tires differ from the R3 tires by a higher value of the modulus of elasticity under tension at 100% calendering elongation of layer 18, identical to that of the R6 reference tires.

[0136] Endurance tests were carried out with particularly oxidizing inflation conditions. The tires are mounted on suitable rims and are inflated with an overpressure of 20% compared to the nominal pressure with air saturated with humidity and whose oxygen content has been increased to 30% to accelerate the aging of the mixtures. These tires are then rolled on a steering wheel, under a high load (20% overload compared to the nominal load) and at a speed of 40 km / h. The test is stopped when a crack appears in the area of ​​the tip of the rollover on the outer surface of the tire with or without loss of pressure. The tire performance is the number of kilometers traveled. The results are shown in the following table. They are expressed in relative distance, a value of 100 being assigned to the R2 tire. The maximum energy density at point 8 is also given in relative value, a value of 100 being assigned to the R2 tire.

[0137] The reference tire RI is not tested during this test because its different design leads to another type of damage. [Tables 1] R3 PA Ri as D7 II PîHHæsatkpe 12 Passage Carc 4.5 4.5 4.5 4.5 45 4.5 4.5 2.55 Carcass 9.8 9.8 9.8 9.8 9.8 9.8 9.8 5.75 MA,.” {MPal - 1.6 - 1.6 •4.5 4.5 1.6 1.6 cslisazass crads i S - 3.3 - 3.3 9.8 9.8 3.3 3.3 first ocîsühe 4.5 4.5 4.5 4.5 4.5 4.5 4.5 2.55 first GGiiche 9.8 9.8 9.8 9.8 9.8 9.8 9.8 5.75 storage space - - 1.73 1.73 145 110 220' 200

[0138] The results obtained with the tires according to the invention demonstrate that their design makes it possible to reduce the initiation and propagation of cracks, particularly around the end of the turn-up of the carcass reinforcement layer, and allows for better performance in terms of endurance of these tires when driving in extreme conditions.

Claims

1. Claims A tire (1) intended to be mounted on a hollow rim (J) of the 15° drop center type, comprising a radial carcass reinforcement (2) consisting of a single layer of carcass reinforcement formed of reinforcing elements inserted between two layers of polymeric mixture calendering, said tire comprising a crown reinforcement (5) itself radially capped with a tread (6), said tread being joined to two beads (3) by means of two sidewalls, the layer of reinforcing elements of the carcass reinforcement (2) being anchored in each of the beads by turning up around a bead wire (4) to form a main part of the carcass reinforcement layer (2) extending from one bead wire to the other and a turn-up (7) of the carcass reinforcement layer in each of the beads (3),said turn-up (7) of the carcass reinforcement layer being separated from the main part of the carcass reinforcement layer (2) by a first layer of polymeric mixture (9a) extending radially from the bead wire (4) axially between the main part of the carcass reinforcement layer (2) and the turn-up (7) of the carcass reinforcement layer and said turn-up (7) of the carcass reinforcement layer being axially outwardly in contact with a second layer of polymeric mixture (11), itself at least in contact with a third layer of polymeric mixture (14) forming the outer surface of the tire in the area of ​​the bead (3), said third layer of polymeric mixture (14) being intended in particular to come into contact with the rim (J), said third layer of polymeric mixture (14) being radially outwardly in contact with a fourth layer of polymeric mixture (16) forming the outer surface of a sidewall,in a meridian section of said tire, - the distance dR between the end (8) of the turn-up (7) of the carcass reinforcement layer and the radially innermost point (A) of the circle (T) circumscribed to the bead wire (4) is between 45 and 90% of the distance dE between the axially outermost point (E) of the main part of the carcass reinforcement layer (2) and the radially innermost point (A) of the circle (T) circumscribed to the bead wire (4), - radially outwards, from a point (C) of the turn-up (7) of the carcass reinforcement layer located at a distance dc from the point (A) radially the innermost part of the circle (T) circumscribed to the bead wire (4) between 30 and 55% of the distance dR between the end (8) of the turn-up (7) of the carcass reinforcement layer and the point (A) radially the innermost part of the circle (T) circumscribed to the bead wire (4), the turn-up (7) of the carcass reinforcement layer and the main part of the carcass reinforcement layer (2) are coupled, - the turn-up (7) of the carcass reinforcement layer and the main part of the carcass reinforcement layer (2) are the only layers of reinforcing elements whose elongation at break is less than 6% present in a zone of the sidewall constituting at least 90% of the surface of the sidewall comprised radially between the end (8) of the turn-up (7) of the carcass reinforcement layer and the point (B) radially the outermost part of the bead wire (4), - the radially outermost point (10a) of the first layer of polymeric mixture (9a) in contact with the turn-up (7) of the carcass reinforcement layer is radially inner to the end (8) of the turn-up (7) of the carcass reinforcement layer and at a distance diOa from the end (8) of the turn-up (7) of the carcass reinforcement layer of between 5 and 15 mm, - a fifth layer of polymeric mixture (9b) is radially external and in contact with the first layer of polymeric mixture (9a) and, in part, axially between the main part of the carcass reinforcement layer (2) and the turn-up (7) of the carcass reinforcement layer, - the radially outermost end (10c) of said fifth layer of polymeric mixture (9b) is radially outer to the end (8) of the turn-up (7) of the carcass reinforcement layer, - the modulus of elasticity under tension at 100% elongation of the fifth layer of polymeric mixture (9b) is at least 25% lower than the modulus of elasticity under tension at 100% elongation of the first layer of polymeric mixture (9a), characterized in that, - at least one layer of radially oriented textile reinforcing elements is axially positioned between the main part of the carcass reinforcement layer and the fourth layer of polymer mixture (16) and / or between the main part of the carcass reinforcement layer and the second layer of polymer mixture, - the density of textile reinforcing elements in said at least one layer of textile reinforcing elements is greater than the density of reinforcing elements of the carcass reinforcement layer, - the modulus of elasticity under tension at 100% elongation of the calendering layers of said at least one layer of textile reinforcing elements is less than or equal to the modulus of elasticity under tension at 100% elongation of the fifth layer of polymeric mixture (9b).

2. A tire according to claim 1, characterized in that the density of textile reinforcing elements in said at least one layer of textile reinforcing elements is greater than 1.25 times the density of reinforcing elements in the carcass reinforcement layer, and preferably greater than 1.5 times the density of reinforcing elements in the carcass reinforcement layer.

3. A tire according to claim 1 or 2, characterized in that the modulus of elasticity under tension at 100% elongation of the calendering layers of said at least one layer of textile reinforcing elements is less than 95% of the modulus of elasticity under tension at 100% elongation of the fifth layer of polymeric mixture (9b).

4. A tire according to one of claims 1 to 3, characterized in that said at least one layer of radially oriented textile reinforcing elements is axially positioned at least partially between the turn-up of the carcass reinforcement layer and the main part of the carcass reinforcement layer.

5. A tire according to one of claims 1 to 4, characterized in that said at least one layer of radially oriented textile reinforcing elements is axially in contact with the end of the turn-up of the carcass reinforcement layer.

6. A tire according to one of the preceding claims, characterized in that said at least one layer of textile reinforcing elements extends radially internally at the end of the turn-up of the carcass reinforcement layer over at least 8 mm.

7. A tire according to one of the preceding claims, characterized in that said at least one layer of textile reinforcing elements extends radially outwardly beyond the end of the turn-up of the carcass reinforcement layer by at least 8 mm.

8. A tire according to one of the preceding claims, characterized in that the distance between the end of the turn-up of the carcass reinforcement layer and each of the ends of said at least one layer of textile reinforcing elements is greater than 17 mm.

9. Tire according to one of the preceding claims, characterized in that the diameter of the textile reinforcing elements is less than 0.65 mm.

10. A tire (1) according to one of the preceding claims, characterized in that the radially outermost point (10b) of the first layer of polymeric mixture (9a) in contact with the main part of the carcass reinforcement layer (2) is located in a zone, around the orthogonal projection (8P) of the end (8) of the turn-up (7) of the carcass reinforcement layer on the main part of the carcass reinforcement layer (2) delimited, radially outwards by a point located at a distance diOb from said projection (8P) equal to 10 mm and radially inwards by a point located at a distance from said projection equal to 15 mm.

11. A tire according to one of the preceding claims, characterized in that the modulus of elasticity under tension at 100% elongation of the calendering layers of the carcass reinforcement layer is between 2 and 7 MPa and preferably between 2.5 and 5 MPa.

12. A tire according to one of the preceding claims, characterized in that the modulus of elasticity under tension at 100% elongation of the first layer of polymeric mixture is less than or equal to the modulus of elasticity under tension at 100% elongation of the calendering of the carcass reinforcement layer.

13. A tire according to one of the preceding claims, characterized in that the modulus of elasticity under tension at 100% elongation of the first layer of polymeric mixture is greater than 50% of the modulus of elasticity under tension at 100% elongation of the calendering of the carcass reinforcement layer and preferably is greater than 70% of the modulus of elasticity under tension at 100% elongation of the calendering of the carcass reinforcement layer.

14. A tire according to any preceding claim, characterized in that radially outwardly from said point C of the turn-up of the carcass reinforcement layer, the turn-up of the carcass reinforcement layer and the main part of the carcass reinforcement layer are coupled over a length of between 15 and 65% of the distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire, to then be decoupled by the first polymer mixture layer up to the end of the carcass reinforcement layer turn-over.

15. A tire according to claim 14, characterized in that the decoupling length is between 5 and 40% of the distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire and preferably between 15 and 35% of the distance between the end of the turn-up of the carcass reinforcement layer and the radially innermost point of the circle circumscribed to the bead wire.

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