TIRES FOR VEHICLES WITH A STIFFENING STRUCTURE

Description

[0001] The invention relates to a radial tire intended to equip a vehicle.

[0002] The tire category studied in particular is that of passenger car tires whose meridional cross-section is characterized by a section width S and a section height H, as defined by the European Tyre and Rim Technical Organisation (ETRTO) standard, such that the H / S ratio, expressed as a percentage, is at most 65, and the section width S is at least 195 mm. Furthermore, the seat diameter D, defining the diameter of the tire's mounting rim, is at least 15 inches, and generally at most 21 inches. The example studied in particular, within the scope of the invention, is a tire with size 255 / 35R19.

[0003] However, a tire according to the invention can also be used on any other type of vehicle such as a two-wheeled vehicle, a heavy goods vehicle, an agricultural vehicle, a civil engineering vehicle or an aircraft and, more generally, on any rolling device.

[0004] In what follows, and by convention, the circumferential direction XX', axial direction YY', and radial direction ZZ' respectively denote a direction tangent to the tire's tread surface in the direction of tire rotation, a direction parallel to the tire's axis of rotation, and a direction perpendicular to the tire's axis of rotation. "Radially inside" and "radially outside" respectively mean "closer to the tire's axis of rotation" and "farthest from the tire's axis of rotation." "Axially inside" and "axially outside" respectively mean "closer to the tire's equatorial plane" and "farthest from the tire's equatorial plane," the tire's equatorial plane XZ being the plane passing through the center of the tire's tread surface and perpendicular to the tire's axis of rotation.

[0005] Generally, a tire comprises a crown with two axial ends, each extended radially inward by a sidewall and then by a bead designed to contact a rim, the whole assembly defining an internal toroidal cavity. More precisely, the crown includes, radially from the outside in, a tread, designed to contact the ground via a tread surface, and a crown reinforcement designed to strengthen the crown of the tire. A carcass reinforcement connects the two sidewalls and is anchored, in each bead, to a circumferential reinforcing element, most often a bead.

[0006] Tire standards, such as those of the ETRTO, define nominal operating conditions for a tire of a given size, characterized by a section width S, a section height H, and a seat diameter D. Thus, a tire of a given size is intended to be mounted on a nominal rim, inflated to a nominal pressure P, and subjected to a nominal load Z. The load applied to the tire is thus absorbed by the tire, thanks to its pneumatic stiffness, resulting from the inflation pressure, and thanks to its intrinsic structural rigidity.

[0007] A tire must meet a range of performance requirements, including, but not limited to, handling, rolling resistance, grip, wear, and noise, which often leads to conflicting design choices. It is therefore common for design choices aimed at improving one performance aspect to result in a degradation of another. This is the case, for example, when seeking a satisfactory compromise between handling and rolling resistance.

[0008] It is well known that the behavior of a tire, which characterizes its ability to withstand the various mechanical stresses to which it is subjected during driving, such as sideslip and / or lateral stresses, depends primarily on its respective mechanical stiffnesses: sideslip (DZ) and lateral (Kyy). The higher these mechanical stiffnesses, the better the tire's performance.

[0009] In the prior art, to improve tire performance, those skilled in the art have designed, for example, tire bead designs with high rigidity and significant volume, resulting from a high axial thickness and / or radial height, and composed of elastomeric materials with high modulus of elasticity and hysteresis—that is, materials that are both rigid and dissipative. Such a design has, conversely, increased rolling resistance, thus degrading rolling resistance performance and, consequently, increasing fuel consumption.

[0010] In document WO2017005713, an alternative to conventional pneumatics was proposed through a pneumatic-type device comprising two radially external and radially internal structures of revolution, a load-bearing structure made up of identical load-bearing elements, in extension outside the contact area with the ground and in compression within the contact area, and two flanges. The load-bearing elements are wire-like and are connected respectively to the radially internal face of the radially external structure of revolution by a radially external fabric and to the radially external face of the radially internal structure of revolution by a radially internal fabric.Furthermore, the average surface density D of the load-bearing elements per unit area of ​​the radially external structure of revolution, expressed in 1 / m², is at least equal to (S / SE)*Z / (A*Fr), where S is the surface area, in m², of the radially internal face of the radially external structure of revolution, SE is the bonding surface area, in m², of the radially external fabric with the radially internal face of the radially external structure of revolution, Z is the nominal radial load, in N, A is the ground contact area, in m², and Fr is the breaking strength, in N, of a load-bearing element. This solution eliminates the dissipative bulges of a conventional tire, thus drastically reducing rolling resistance, while ensuring good performance thanks to the absorption of drift and transverse mechanical stresses by the wire elements of the load-bearing structure.However, this pneumatic system has the particular disadvantage of requiring the use of a non-standard rim.

[0011] Another tire is known from FR 2 638 398 A1 on which the preamble of the attached claim 1 is based.

[0012] Other tires are also known from JP 2015 077922 A, US 2005 / 279438 A1 and GB 2 299 554 A.

[0013] Document WO 2019 / 115917 A1 is a prior art document according to Article 54(3) EPC.

[0014] The inventors set themselves the objective of designing a tire, suitable for mounting on a standard rim, with improved performance compared to a standard tire of the state of the art, and with a rolling resistance no more than equal to that of this reference tire.

[0015] This objective has been achieved for a vehicle tire according to claim 1.

[0016] The principle of the invention is to incorporate, within a conventional tire, a stiffening structure designed to increase the overall rigidity of the tire. This stiffness has a structural component, called structural rigidity, provided by the tire's reinforcement structure, and a pneumatic component, called pneumatic rigidity, provided by the inflation gas pressure. The stiffening structure contributes to the tire's overall rigidity.

[0017] More specifically, the stiffening structure according to the invention simultaneously increases the radial stiffness K ZZ, the transverse or axial stiffness Kyy, and the drift stiffness DZ of the tire, compared to the reference tire. The radial stiffness K ZZ, expressed in daN / mm, is the radial force FZ generated by the tire when a radial displacement of 1 mm is applied. The transverse or axial stiffness Kyy, expressed in daN / mm, is the axial force Fy generated by the tire when an axial displacement of 1 mm is applied. Finally, the drift stiffness DZ, expressed in daN / °, is the axial force FY generated by the tire when rolling at an angle of 1° around a radial axis ZZ'.

[0018] By increasing the radial stiffness K ZZ, the stiffening structure limits radial deformations of the tread during rolling, and in particular, camber, i.e., the radial deformation opposite the contact patch of the tire's tread with the ground. Thus, during tire rotation, with each wheel revolution, the stiffening structure limits the amplitude of cyclic deformations of the tire, and especially of its tread, and therefore limits the resulting energy dissipation, which contributes to a reduction in rolling resistance. Furthermore, under radial load, the contact patch with the ground remains unchanged, i.e., it retains essentially the same surface area, thus maintaining the same grip performance as the reference tire.

[0019] By increasing the transverse or axial stiffness (Kyy) and the drift stiffness (DZ), the stiffening structure will contribute to improved behavior under transverse loading, for example, during a drift roll. Furthermore, under transverse loading, the contact area with the ground ensures a more homogeneous distribution of contact pressures, which increases transverse grip performance.

[0020] Furthermore, the stiffening structure contributes at least partially to the load-bearing capacity of the tire, such that this applied load is jointly supported by the tire, thanks to its pneumatic and intrinsic structural rigidity, and by the stiffening structure. Regarding load-bearing capacity, when the tire is subjected to a nominal radial load Z, the portion of the stiffening structure connected to the portion of the tire in contact with the ground is subjected to compressive buckling, and the portion of the stiffening structure connected to the portion of the tire not in contact with the ground is at least partially in tension.

[0021] Therefore, the presence of a stiffening structure reduces the contribution of the tire's reinforcement to load-bearing capacity and thus allows, where necessary, a reduction in its intrinsic structural rigidity, for example by reducing the volume of the bead. Since the bead of a conventional tire dissipates a significant amount of energy due to its volume and the hysteretic nature of its constituent elastomeric compound, reducing its volume would significantly reduce rolling resistance.

[0022] Structurally, according to the invention, the stiffening structure comprises two stiffening elements extending continuously within the inner toroidal cavity, from a crown interface, connected to a radially inner face of the crown, to a bead interface, connected to an axially inner face of the bead. In other words, the stiffening structure comprises two stiffening elements connecting the crown of the tire to a bead, thus creating a triangulation between the crown of the tire and each bead. The respective connections of the stiffening element to the crown and the bead can be either direct or indirect, for example, via a fastening means.

[0023] Furthermore, the stiffening structure is distributed circumferentially around the entire circumference of the tire. More precisely, the stiffening structure either extends circumferentially and continuously around the entire circumference of the tire, or is distributed circumferentially and periodically around the entire circumference of the tire. Consequently, the triangulation between the crown and the tire beads is effective around the entire circumference of the tire.

[0024] According to the invention, the apex interface of the stiffening element is positioned, relative to the equatorial plane, at an axial distance A not exceeding 0.45 times the axial width S. Beyond this value, the stiffening element's direction forms too small an angle with the radial direction ZZ', resulting in an insufficient contribution to the transverse stiffness Kyy and the lateral stiffness DZ, respectively. However, even at an angle close to 0°, the inventors observed an increase in the radial stiffness KZZ, the transverse stiffness Kyy, and the lateral stiffness DZ, respectively.

[0025] According to the invention, the bead interface of the stiffening element is positioned, relative to the innermost radial point of the inner axial face of the bead, at a radial distance B of at least 0.10 times the radial height H and at most 0.5 times the radial height H. Beyond 0.5 times the radial height H, any stiffening element has a direction forming too large an angle with respect to the radial direction ZZ', which makes an insufficient contribution to the radial stiffness KZZ. Below 0.10 times the radial height H, the bead interface is positioned in a rigid area of ​​the bead, near the rim bead, which promotes the transmission of noise between the top of the tire in contact with the ground and the bead in contact with the rim.The choice of the radial distance B thus results from a compromise between achieving sufficient radial, transverse, and drift stiffness, respectively, through an appropriate inclination of the stiffening element relative to the equatorial plane, and achieving an acceptable noise level by avoiding positioning the bead interface within the rigid zone of the bead. Furthermore, a sufficiently large radial positioning of the bead interface allows for greater tolerance to variations in the length of the stiffening element, thanks to the positioning of this interface in a less rigid area of ​​the tire than that of the bead.

[0026] Preferably, the two stiffening elements are positioned symmetrically on either side of the equatorial plane. This design allows for a balanced distribution of the forces acting on the stiffening structure between the two halves of the tire, thus resulting in symmetrical tire behavior during rolling. Furthermore, manufacturing a symmetrical stiffening structure is simpler.

[0027] Advantageously the vertex interface is positioned, relative to the equatorial plane, at an axial distance A of at least 0.05 times and at most 0.15 times the axial width S. The inventors have in fact shown that an axial distance A substantially equal to 0.10 times the axial width S was an advantageous embodiment.

[0028] Preferably the bead interface is positioned, relative to the most radially interior point of the axially interior bead face, at a radial distance B not more than 0.35 times the radial height H. According to the inventors, a range of values ​​for the radial distance B between 0.1 times and 0.35 times the radial height H is optimal with respect to the compromise between the performance of behavior and noise respectively.

[0029] The vertex interface is advantageously distributed over a width A1 at least equal to 0.1 times the axial width S. Below this value, the local stresses at the vertex interface become too high, hence a risk of tearing of the vertex interface.

[0030] According to an alternative embodiment of the invention, which can be combined with the alternative described below, the vertex interface comprises an elastomeric compound cushion, positioned at least partially between the stiffening element and the radially inner face of the vertex. The presence of an elastomeric cushion at the vertex interface allows for better distribution of local interface stresses.

[0031] Since the apex interface is distributed over a width A1, the flange interface is advantageously distributed over a width B1 at least equal to the width A1. This is because the flange interface must transmit the same tensile forces as the apex interface, as these two interfaces are the two ends of a stiffening element operating in tension, but with a greater inclination of the stiffening element relative to the attachment surface, resulting in a greater normal pull-out force at the flange. It is therefore necessary to distribute this normal force sufficiently.

[0032] According to an alternative embodiment of the invention, which can be combined with the alternative described above, the bead interface comprises an elastomeric compound cushion in contact, at least partially, with the stiffening element and the axially inner face of the bead. The presence of an elastomeric cushion at the bead interface allows for better distribution of local interface stresses.

[0033] According to a variant of the preferred embodiment of the bead interface, the elastomeric compound cushion of the bead interface is at least partially in contact with a reinforcing layer, such that the cushion is bounded by the stiffening element, the axially inner face of the bead, and the reinforcing layer. The presence of a reinforcing layer, radially outwardly bounding the cushion, allows for a more symmetrical anchoring of the stiffening element, comprising two reinforcing layer elements on either side of the mid-plane of the stiffening element. This reinforcing layer also helps to limit deformations of the elastomeric cushion, and therefore energy dissipation within the cushion, which contributes to reducing rolling resistance.

[0034] Regarding the materials used in the stiffening structure, each stiffening element advantageously comprises a polymeric material, such as an aliphatic polyamide, an aromatic polyamide, or a polyester, or a metallic material, such as steel, or a glass or carbon-type material, or any combination thereof. Polymeric materials, particularly elastomeric materials, and metallic materials, such as steel, are commonly used in the tire industry. Glass and carbon are alternative materials that can be considered for use in tires. In a first material variant, each stiffening element advantageously comprises polyethylene terephthalate (PET). PET is commonly used in the tire industry due to a good compromise between its mechanical properties, such as its tensile strength, and its cost.In a second material variant, any stiffening element also advantageously includes an aliphatic polyamide, such as nylon. Nylon is also commonly used in the tire industry for the same reasons as PET.

[0035] In an advantageous embodiment, the stiffening element is not airtight. Thus, the stiffening element allows the inflation gas to pass through on both sides. Consequently, the stiffening element does not define a secondary pressurized cavity within the tire. By "not airtight," it is understood that the stiffening element is not sealed against the tire's inflation gas and is therefore permeable to this gas, ensuring that the pressure remains homogeneous within the inner toroidal cavity at all times.

[0036] According to a preferred embodiment of the stiffening element, each stiffening element comprises wire reinforcement elements embedded, at least in the vicinity of the respective apex and flange interfaces, in an elastomeric compound, such that the stiffening element is not watertight. Wire or one-dimensional reinforcement elements exhibit wire-like mechanical behavior, meaning they can only be subjected to tensile or compressive forces along their neutral axes. Most often, wire reinforcement elements are textile reinforcements, consisting of an assembly of textile yarns made of a polymeric material, such as an aliphatic polyamide, an aromatic polyamide, or a polyester, or metal cables, consisting of an assembly of metal wires, generally steel.Furthermore, the wire reinforcement elements are at least partially uncoated, except near the apex and flange interfaces, or are coated with an elastomeric compound containing holes, so as to allow the inflation gas to pass through on either side of the stiffening element, as described above. In other words, the wire reinforcement elements are not entirely coated with an elastomeric compound, as in the reinforcement fabrics commonly used in the tire industry. Consequently, as described above, the stiffening element does not define a secondary cavity under pressure within the tire.

[0037] According to a first variant of the preferred embodiment of the stiffening element, each stiffening element consists of a family of parallel wire reinforcement elements, forming, with a circumferential direction, an angle C1 of at least 85° and at most 95°. In this first variant, the stiffening element therefore comprises a single layer of wire reinforcement elements positioned in substantially meridional planes, a meridian plane being defined by the axial direction and a radial direction.

[0038] According to a second variant of the preferred embodiment of the stiffening element, each stiffening element consists of a first set of parallel wire reinforcement elements, forming an angle C1 of at least 45° and at most 75° with a circumferential direction, intersecting a second set of parallel wire reinforcement elements, forming an angle C2 of at least 45° and at most 75° with a circumferential direction. In this second variant, the stiffening element thus comprises two layers of intersecting wire reinforcement elements, each layer being significantly inclined with respect to the circumferential direction, but not necessarily inclined at the same angle.This significant inclination of the wire reinforcement elements contributes to an increase in the circumferential stiffness K XX, corresponding to the circumferential force FX generated by the tire during a circumferential displacement of 1 mm. It therefore helps to limit deformations of the tire's contact surface with the ground during longitudinal braking or acceleration stresses.

[0039] Regarding this second variant, angles C1 and C2 are still preferably equal in absolute value and opposite. In this particular case, the wire reinforcement elements are inclined symmetrically with respect to the circumferential direction, resulting in identical circumferential stiffening in both directions of tire rotation.

[0040] The invention is illustrated by the figures referenced below, not shown to scale and described below: Figure 1: Meridional cross-section of a tire according to the invention. Figure 2 : Meridional section of a tire according to a preferred embodiment of the invention, with elastomeric cushions at the apex and bead interfaces. Figure 3 : Perspective view of a preferred embodiment of the invention, with stiffening elements comprising wire reinforcement elements. Figure 4 : Stiffening element comprising wire reinforcement elements coated, in the vicinity of the top and bottom edge interfaces, in an elastomeric mixture. Figure 5 : Stiffening element comprising wire reinforcement elements embedded in a perforated elastomeric mixture. Figure 6 : Stiffening element comprising a family of substantially radial wire reinforcement elements. Figure 7: Stiffening element comprising two families of wire reinforcement elements inclined with respect to the circumferential direction and crossed from one family to the other. Figure 8 : Radial stiffnesses K ZZ compared between a tire according to the invention and a reference tire from the prior art. Figure 9 : Transverse or axial stiffness K YY compared between a tire according to the invention and a reference tire from the prior art.

[0041] There figure 1Figure 1 represents a meridional cross-section of a tire according to the invention. The tire 1 is intended to be mounted on a nominal rim 5 and inflated to a nominal pressure P, and has an axial width S and a radial height H in the mounted and inflated state. The tire 1 comprises a crown 2 having a radially external tread surface 21, intended to come into contact with the ground, and two axial ends 22, each extended radially inward by a sidewall 3 and then by a bead 4 intended to come into contact with the rim 5. The crown 2, the sidewalls 3, and the bead 4 define an internal toroidal cavity 6. The tire 1 has an equatorial plane XZ passing through the midpoint of its tread surface 21 and perpendicular to an axis of rotation YY'.According to the invention, the tire 1 comprises a stiffening structure 7, including two stiffening elements 8 extending continuously within the inner toroidal cavity 6, from a vertex interface 81, connected to a radially inner face of the vertex 23, to a bead interface 82, connected to an axially inner face of the bead 41. The stiffening structure 7 is distributed circumferentially around the entire circumference of the tire. The two stiffening elements 8, constituting the stiffening structure 7, are not connected to each other within the inner toroidal cavity 6, extend continuously within the inner toroidal cavity 6 without intersecting the equatorial plane XZ, and are symmetrical with respect to the equatorial plane XZ. The vertex interface 81 of the stiffening element 8 is positioned, relative to the equatorial plane XZ, at an axial distance A at most equal to 0.45 times the axial width S.The bead interface 82 of stiffening element 8 is positioned, with respect to a point I most radially inside of the axially inside face of bead 41, at a radial distance B at least equal to 0.10 times the radial height H and at most equal to 0.5 times the radial height H.

[0042] There figure 2 represents a meridional cross-section of a tire according to a preferred embodiment of the invention, with elastomeric cushions at the apex and bead interfaces. The additional elements compared to the figure 1are described below. The vertex interface 81 is distributed over a width A1 at least equal to 0.1 times the axial width S and includes an elastomeric compound cushion 811, positioned at least partially between the stiffening element 8 and the radially inner face of the vertex 23. The bead interface 82 is distributed over a width B1 at least equal to the width A1 and includes an elastomeric compound cushion 821, in contact at least partially with the stiffening element 8 and the axially inner face of the bead 41. Finally, the elastomeric compound cushion 821 of the bead interface 82 is at least partially in contact with a reinforcing layer 822, such that the cushion 821 is delimited by the stiffening element 8, the axially inner face of the bead 41, and the reinforcing layer 822.

[0043] There figure 3This represents a perspective view of a preferred embodiment of the invention, with stiffening elements comprising wire reinforcement elements. The stiffening structure 7 consists of two stiffening elements 8 comprising wire reinforcement elements 83, extending continuously within the inner toroidal cavity, from a vertex interface 81, connected to a radially inner face of the vertex 23, to a flange interface 82, connected to an axially inner face of the flange 41. The stiffening element 8 is not sealed. In this case, the wire reinforcement elements 83 are embedded, at least in the vicinity of the respective vertex 81 and flange 82 interfaces, in an elastomeric mixture 84, such that the stiffening element 8 is not sealed.

[0044] There figure 4represents a stiffening element comprising wire reinforcement elements embedded in an elastomeric compound near the apex and flange interfaces. The stiffening element 8 comprises wire reinforcement elements 83, embedded in an elastomeric compound 84 near the apex 81 and flange 82 interfaces, respectively, such that the stiffening element 8 is not airtight. Consequently, the inflation gas pressure is identical on both sides of the stiffening element 8, which therefore does not define a secondary cavity with a pressure different from that of the main cavity.

[0045] There figure 5represents a stiffening element comprising wire reinforcement elements embedded in a perforated elastomeric compound. The stiffening element 8 comprises wire reinforcement elements 83, embedded along their entire length between the respective apex interface 81 and flange interface 82, in a perforated elastomeric compound 84, such that the stiffening element 8 is not watertight. This is another embodiment of a non-watertight stiffening element.

[0046] There figure 6represents a stiffening element comprising a family of substantially radial wire reinforcement elements. The stiffening element 8 consists of a family of parallel wire reinforcement elements 83, forming, with a circumferential direction XX', an angle C1 of at least 85° and at most 95°. The wire reinforcement elements 83 are all embedded, in the vicinity of the respective vertex interface 81 and flange interface 82, in an elastomeric mixture 84, such that the stiffening element 8 is not watertight.

[0047] There figure 7represents a stiffening element comprising two families of wire reinforcement elements inclined with respect to the circumferential direction and crossed from one family to the other. The stiffening element 8 consists of a first family of wire reinforcement elements 83, parallel to each other, and forming, with a circumferential direction XX', an angle C1 of at least 45° and at most 75°, crossed with respect to a second family of wire reinforcement elements 83, parallel to each other, and forming, with a circumferential direction XX', an angle C2 of at least 45° and at most 75°. In the case shown, angles C1 and C2 are equal in absolute value and opposite, that is to say, symmetrical with respect to the circumferential direction XX'.The wire reinforcement elements 83 are all coated, in the vicinity of the respective apex interfaces 81 and bead interface 82, in an elastomeric mixture 84, so that the stiffening element 8 is not sealed.

[0048] There figure 8 This is a graph comparing the radial stiffnesses K ZZ between a tire according to the invention and a prior art reference tire. For a given inflation pressure P and radial deflection f, the radial force Z generated by the tire according to the invention is higher than that generated by the reference tire. The slope of the radial force Z curve as a function of the radial deflection f of the tire, i.e., the radial displacement of the tire's crown, represents the radial stiffness K ZZ of the tire. Consequently, the radial stiffness K ZZ of the tire according to the invention is higher than that of the reference tire.

[0049] There figure 9This is a graph showing the comparative transverse or axial stiffnesses KYY between a tire according to the invention and a prior art reference tire. For a given inflation pressure P, radial deflection f, and transverse offset d, the transverse force Y generated by the tire according to the invention is higher than that generated by the reference tire. The slope of the substantially linear portion of the transverse force curve Y as a function of the tire's transverse offset d, i.e., its transverse displacement, represents the transverse stiffness Kyy of the tire. The substantially linear portion of the transverse force curve Y corresponds, in the case shown, to a transverse offset of at most approximately 20 mm. Consequently, the transverse stiffness KYY of the tire according to the invention is higher than that of the reference tire.Beyond a lateral offset of 20 mm, the lateral force Y reaches a plateau due to the slippage of the tire's contact patch on the ground. In the case of the invention, this stabilization of the lateral force Y occurs at a higher level, beyond 25 mm, due to a higher lateral stiffness KYY, which allows for a more homogeneous pressure distribution in the contact area under the lateral force Y.

[0050] The invention was studied more specifically for a passenger car tire of size 255 / 35R19. A reference tire R was thus compared to a first example of a tire I1 according to the invention, with crown and bead interfaces conforming to the figure 2, and comprising two stiffening elements consisting of a family of parallel, cable-type wire reinforcement elements, forming an angle C1 approximately equal to 90° with the circumferential direction in accordance with the figure 4 It was also compared to a second example of an I2 tire according to the invention, with apex and bead interfaces conforming to the figure 2 , and comprising two stiffening elements consisting of a first family of parallel cable-type wire reinforcement elements, forming, with a circumferential direction, an angle C1 equal to 60°, intersected with a second family of parallel cable-type wire reinforcement elements, forming, with the circumferential direction, an angle C2 equal to angle C1 in absolute value but opposite in accordance with the figure 7 .

[0051] The reference tires R, according to invention I1 and according to invention I2, are mounted on a nominal rim 9J19 and inflated to a nominal pressure P of 2.5 bar. Their respective axial widths S and radial heights H, when mounted and inflated, are 255 mm and 89 mm respectively.

[0052] The first example, I1, is characterized by a stiffening structure, as represented on the figure 2with two stiffening elements symmetrical with respect to the equatorial plane of the tire. Each stiffening element is composed of a juxtaposition of parallel, cable-type wire reinforcement elements with a cross-section of 0.8 mm², spaced at 1.25 mm intervals. The material of the stiffening elements is a fabric made of polyester (or PET) textile reinforcements coated near the crown and bead interfaces with an elastomeric compound. The textile reinforcements are positioned in approximately meridional planes of the tire. The crown and bead interfaces are distributed over axial widths A1, ranging from 0.1 to 0.15 times the axial width S of the tire, and B1, ranging from 0.25 to 0.3 times the radial height H of the tire.Furthermore, they respectively include elastomeric cushions, positioned between the stiffening element and the attachment wall. In addition, the apex and flange interfaces are formed by hot vulcanization.

[0053] The second example I2 differs from the first example I1 by the constitution of the two stiffening elements, each consisting of two families of wire reinforcement elements of cable type, crossed with respect to each other, forming, with the circumferential direction, two angles C1 and C2 equal in absolute value at 60° and opposite.

[0054] Table 1 below summarizes the performance differences obtained respectively between the first tire example I1 and the reference tire R, and the second tire example I2 and the reference tire: Table 1 Performance characteristics Performance differences between tire I1 and tire R Performance differences between the I2 tire and the R tire Radial stiffness K ZZ No gap +20% Transverse stiffness K YY +70% +85% Rolling resistance (calculated) -0.8kg / t Not determined Vehicle interior noise No gap Not determined

[0055] The results in Table 1 show an improved performance compromise between rolling resistance and behavior for the invention. It should be noted that this compromise is adjustable. Indeed, the preload applied to the stiffening elements during tire inflation can be modulated, thus modulating the stiffnesses, and in particular the transverse stiffness Kyy, as a function of the preload level.

Claims

1. - Vehicle tyre (1), which is intended to be mounted on a nominal rim (5) and inflated to a nominal pressure P, has an axial width S and a radial height H in the mounted and inflated state, and comprises: - a crown (2) having a radially outer tread surface (21), intended to come into contact with the ground, and two axial ends (22), each extended radially towards the inside by a sidewall (3) and then by a bead (4) intended to come into contact with the rim (5), - the crown (2), the sidewalls (3) and the beads (4) delimiting a toroidal interior cavity (6), - the tyre (1) having an equatorial plane (XZ) passing through the middle of its tread surface (21) and perpendicular to an axis of rotation (YY'), characterized in that the tyre (1) comprises a stiffening structure (7) comprising two stiffening elements (8), each extending continuously in the toroidal interior cavity (6) from a crown interface (81) connected to a radially inner face of the crown (23) to a bead interface (82) connected to an axially inner face of the bead (41), in that the stiffening structure (7) is distributed circumferentially around the entire circumference of the tyre, in that the crown interface (81) is positioned, with respect to the equatorial plane (XZ), at an axial distance A at most equal to 0.45 times the axial width S, in that the bead interface (82) is positioned, with respect to a radially innermost point (I) of the axially inner face of the bead (41), at a radial distance B at least equal to 0.10 times the radial height H and at most equal to 0.5 times the radial height H, and in that the crown interface (81) comprises a cushion (811) made of elastomer compound positioned at least partially between the stiffening element (8) and the radially inner face of the crown (23), and / or the bead interface (82) comprises a cushion (821) made of elastomer compound at least partially in contact with the stiffening element (8) and the axially inner face of the bead (41).

2. - Tyre according to the preceding claim, wherein the two stiffening elements (8) are positioned symmetrically on either side of the equatorial plane (XZ).

3. - Tyre according to any one of the preceding claims, wherein the crown interface (81) is positioned, with respect to the equatorial plane (XZ), at an axial distance A at least equal to 0.05 times and at most equal to 0.15 times the axial width S.

4. - Tyre according to any one of the preceding claims, wherein the bead interface (82) is positioned, with respect to a radially innermost point (I) of the axially inner face of the bead (41), at a radial distance B at most equal to 0.35 times the radial height H.

5. - Tyre according to any one of the preceding claims, wherein the crown interface (81) is distributed across a width A1 at least equal to 0.1 times the axial width.

6. - Tyre according to any one of the preceding claims, wherein the two stiffening elements (8) are not connected to one another inside the toroidal interior cavity (6).

7. - Tyre according to any one of the preceding claims, the crown interface (81) being distributed across a width A1, wherein the bead interface (82) is distributed across a width B1 at least equal to the width A1.

8. - Tyre according to any one of the preceding claims, wherein the cushion (821) made of elastomer compound of the bead interface (82) is at least partially in contact with a reinforcing layer (822), such that the cushion (821) is delimited by the stiffening element (8), the axially inner face of the bead (41) and the reinforcing layer (822).

9. - Tyre according to any one of the preceding claims, wherein any stiffening element (8) comprises a polymeric material, such as an aliphatic polyamide, an aromatic polyamide or a polyester, or a metal material, such as steel, or a glass- or carbon-type material or any combination of the above materials.

10. - Tyre according to any one of the preceding claims, wherein the stiffening element (8) is not sealed.

11. - Tyre according to any one of the preceding claims, wherein each stiffening element (8) comprises filamentary reinforcing elements (83) that are coated, at least in the vicinity of the crown interface (81) and bead interface (82), respectively, with an elastomer compound (84), such that the stiffening element (8) is not sealed.

12. - Tyre according to Claim 11, wherein each stiffening element (8) is made up of a family of filamentary reinforcing elements (83) that are mutually parallel and form, with a circumferential direction (XX'), an angle C1 at least equal to 85° and at most equal to 95°.

13. - Tyre according to Claim 11, wherein each stiffening element (8) is made up of a first family of filamentary reinforcing elements (83) that are mutually parallel and form, with a circumferential direction (XX'), an angle C1 at least equal to 45° and at most equal to 75°, said first family being crossed with respect to a second family of filamentary reinforcing elements (83) that are mutually parallel and form, with a circumferential direction (XX'), an angle C2 at least equal to 45° and at most equal to 75°.

14. - Tyre according to the preceding claim, wherein the angles C1 and C2 are equal in terms of absolute value and opposite.