Reinforcing fabric comprising a plurality of metal reinforcing elements

Abstract

The present invention relates to a reinforced fabric comprising a plurality of metal reinforcing elements arranged in a transverse direction, substantially parallel to each other and extending in a main direction perpendicular to the transverse direction, embedded in an elastomeric composition based on at least one elastomer, a reinforcing filler and a crosslinking system, each metal reinforcing element having a cross-section inscribed in a rectangle having a length W and a height T in a plane perpendicular to the main direction.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of reinforcing fabrics, in particular for pneumatic tires, and to the field of pneumatic tires. BACKGROUND

[0002] It is known that a pneumatic tire for passenger vehicles or trucks having a radial carcass reinforcement comprises a tread, two non-extensible beads, two flexible sidewalls connecting the beads to the tread and a rigid crown reinforcement or "belt" arranged circumferentially between the carcass reinforcement and the tread.

[0003] The crown reinforcement comprises a plurality of reinforcing fabrics, called plies, and is generally composed of at least two superimposed crossed rubber plies, called "working plies", "triangular plies" or "working reinforcements", generally reinforced with metal cords arranged substantially parallel to each other and inclined with respect to the circumferential mid-plane of the pneumatic tire, and a rubber ply, called "hoop ply" or "hoop reinforcement", generally reinforced with reinforcing filaments called "circumferential", the main role of which is to withstand the centrifugal action of the crown at high speed. These plies can optionally be associated with other rubber plies and / or fabrics. The main role of the working plies is to impart high drift thrust or cornering stiffness to the tire, which is known to be necessary to achieve good handling of motor vehicles.

[0004] Such a belt structure, ultimately composed of a multilayer composite laminate comprising at least one hoop ply, generally of fabric, and two working plies, generally of metal, is well known to those skilled in the art and does not need to be described in greater detail herein. Such a belt structure is shown, for example, in US 4371025 and FR 2504067.

[0005] The availability of increasingly strong and durable steels means that tire manufacturers currently tend as much as possible to use cords having a very simple structure in the belts of their tires, in particular cords having only two filaments, or even a single filament, to simplify manufacturing and reduce costs, and to reduce the thickness of the reinforcing plies, thereby reducing the hysteresis of the tire and ultimately the energy consumption of the vehicle equipped with such a tire.

[0006] However, efforts aimed at reducing the mass of the tyre, in particular by reducing the thickness of its belt and of the rubber layers made of said belt, naturally encounter physical limits that can generate many difficulties. In particular, it sometimes occurs that the bead action provided by the bead reinforcement and the reinforcing action provided by the working reinforcement are insufficiently distinct from one another and can interfere with one another. This is detrimental to the correct operation of the crown of the tyre and to the performance and overall durability of the tyre.

[0007] Thus, patent applications WO 2013 / 117476 and WO 2013 / 117477 propose a multilayer composite laminate having a particular structure, which makes it possible to significantly reduce the weight of the belt of the tyre and thus to reduce its rolling resistance, while overcoming the aforementioned drawbacks, said multilayer composite laminate being made of a fabric bead ply and two working plies comprising metal filaments. WO 2019 / 020888 aims to further reduce the mass of the plies while improving the flexing resistance by linking the diameter of the metal filaments, the density of said filaments and the thickness of the plies.

[0008] Other works, such as that disclosed in JP 2001 / 328407, involve the implementation of metal reinforcing elements whose cross-section is no longer circular but is inscribed in a rectangle, in order in particular to thin the plies, thus making them lighter and leading to a reduction in the rolling resistance of the pneumatic tyre. JP 2017 / 048351 discloses the use of flattened reinforcements associated with a particular elastomer composition, the aspect ratio of said flattened reinforcements being preferably between 0.4 and 0.5 and the intra-cable distance, i.e. the distance between two successive reinforcing elements, being between 0.15 mm and 0.54 mm, thus reducing the rolling resistance, limiting the heat problems and avoiding the ply separation problems.

[0009] However, the increase in the weight and the performance improvement of the vehicle in particular require an increase in the breaking force of the plies. This force can be increased, for example, by increasing the mechanical strength of the metal reinforcements, under the limits inherent to the availability of steel, or by increasing the diameter and / or the density of these reinforcements, which can lead to an increase in the thickness and / or the mass of the plies and thus to an increase in the weight of the pneumatic tyre and / or to a reduction in the space separating two successive metal reinforcing elements within the ply. The rubber bridges located between the reinforcing elements are then difficult to fill, which can be detrimental to the durability of one or more plies and thus to the durability of the pneumatic tyre, in particular due to the risk of splitting, which corresponds to the appearance of a crack propagation between the working plies. The reduction in the intra-cable distance can also make the ply difficult to manufacture, since it requires a large number of metal wires to be placed parallel to one another at a small distance. SUMMARY

[0010] During the course of the continuing research, the Applicant has found a particular construction of a fabric reinforced with metal reinforcing elements, which has very good breaking strength, lower rolling resistance and sufficient cable internal distance to avoid any cracking problems compared to the reinforcing fabrics of the prior art.

[0011] Definitions

[0012] The main direction means the direction in which the metal reinforcing elements extend with their largest dimension, which coincides with the axis of the reinforcing elements.

[0013] The transverse direction means the direction perpendicular to the main direction.

[0014] Substantially means within the limits of mechanical tolerances or of the measurement method.

[0015] The carbon-containing compounds mentioned in the description can be fossil or biobased carbon-containing compounds. In the case of biobased carbon-containing compounds, they can be derived in part or completely from biomass or obtained from renewable raw materials derived from biomass. This in particular relates to polymers, plasticizers, fillers, etc.

[0016] Reinforcing fabric

[0017] The present invention relates to a reinforcing fabric comprising a plurality of substantially parallel metal reinforcing elements extending in a main direction, arranged at a laying pitch p expressed in mm in a transverse direction perpendicular to the main direction, and embedded in an elastomeric composition based on at least one elastomer, a reinforcing filler and a crosslinking system, each metal reinforcing element having a cross-section inscribed in a rectangle having a width W and a height T in a plane perpendicular to the main direction, and having a breaking strength R F expressed in MPa measured according to ISO 6892:1984 equal to R n , the fabric having a breaking force expressed in N / mm equal to R F / R n (a-1 + π / 4).T 2 where a = W / T and the range of 1 / a is 0.35 to 0.75.

[0018] It is evident that these characteristics are able to satisfactorily fill the rubber bridge between two consecutive reinforcing elements, while at the same time lightening the reinforcing fabric, while maintaining particularly advantageous "edge" and "out-of-plane" breaking strength and stiffness properties compared to the reinforcing fabrics of the prior art.

[0019] The laying pitch is defined, as known to the person skilled in the art, as the distance between the geometric centers of two immediately adjacent metal reinforcing elements measured in the transverse direction.

[0020] Preferably, the laying pitch p satisfies p < 1.2.R F / R n (a - 1 + π / 4).T 2 When the pitch becomes too large, the cooperation between the side-by-side metal reinforcing elements deteriorates when the fabric is used as a working ply in pneumatic tires.

[0021] Very preferably, the laying pitch p satisfies 0.9.R F / R n (a - 1 + π / 4).T 2 ≤ p ≤ 1.1.R F / R n (a - 1 + π / 4).T 2 .

[0022] Reinforcing element

[0023] Each reinforcing element is metallic. Preferably, the reinforcing element comprises a steel core covered with a metallic coating made of a metal other than steel, in order to improve, for example, the processability of the reinforcing element, or the service properties of the reinforcing element and / or of the tire (for example, adhesion properties, corrosion resistance or aging resistance). For example, the metal of the metallic coating is chosen from zinc, copper, tin and alloys of these metals. Examples of alloys of these metals include brass and bronze.

[0024] The steel can have a pearlitic, ferritic, austenitic, bainitic or martensitic microstructure, or a microstructure resulting from a mixture of these microstructures.

[0025] According to one preferred embodiment, when a carbon steel is used, its carbon content (in weight % of steel) is in the range 0.2% to 1.2%; according to another preferred embodiment, the carbon content of the steel is in the range 0.6% to 0.8%.

[0026] The application particularly relates to high-strength (HT) steel cords, preferably very high-strength (SHT) or even ultra-high-strength (UHT), in which case the tensile strength (R F ) of the reinforcing element is preferably greater than or equal to 3650 - 2000.D (where D is expressed in mm and is equal to (T + W) / 2), more preferentially greater than or equal to 4000 - 2000.D, most preferentially greater than or equal to 4350 - 2000.D. The total elongation at break (At) of these reinforcements, which is the sum of the elastic elongation and the plastic elongation, is preferentially greater than 2.0%.

[0027] Preferably, the torsional elastic deformation C (expressed in absolute value) of each reinforcing element is less than or equal to 6 turns per 6 m of metal reinforcement, preferably less than or equal to 3 turns per 6 m of metal reinforcement.

[0028] This low elastic deformation makes it possible to obtain a fabric that is sufficiently flat to be easily incorporated into a rubber article, in particular an inflated tire. In a preferred arrangement, the reinforcing elements can be positioned in the fabric so that their elastic deformations alternate, as disclosed in WO2017 / 203119.

[0029] Each metal reinforcing element has a cross-section that is inscribed in a rectangle having a length W and a height T in a plane perpendicular to the main direction.

[0030] Such reinforcing elements are known per se in the prior art and are described, for example, in JP2001 / 328407 and DE102015209343. Such reinforcing elements can be obtained, for example, by drawing using a substantially rectangular die, in which the corners can be rounded, or by passing a metal reinforcing element having a circular cross-section through rollers to crush it.

[0031] The ratio 1 / a of each metal reinforcing element of the fabric according to the application, which represents the ratio of its height or thickness T to its width W, is preferably in the range 0.35 to 0.65, preferably in the range 0.45 to 0.65. Such a preferred ratio makes it possible to significantly increase the “edge” stiffness (i.e. in the axial direction of an inflated tire comprising such a fabric as a working cord layer), without significantly modifying the “out-of-plane” stiffness (i.e. in the radial direction of an inflated tire comprising such a fabric as a working cord layer), the lower out-of-plane stiffness making it possible to improve the flatness of the inflated tire on a horizontal ground.

[0032] Preferably, the height or thickness T of each metal reinforcing element is in the range 0.15 mm to 0.70 mm, preferably 0.15 mm to 0.40 mm, more preferably 0.20 mm to 0.30 mm. Such a thickness, associated with the other characteristics of the metal reinforcing elements, makes it possible to obtain a good compromise between the total thickness of the working cord layer and its breaking force.

[0033] Breaking force R of the reinforcing fabric n Preferably greater than or equal to 220 N / mm, preferably greater than or equal to 300 N / mm, more preferably between 330 N / mm and 470 N / mm. Such a breaking strength is particularly advantageous when the fabric according to the application is implemented in an inflated tire intended to withstand relatively heavy loads, for example a modern passenger vehicle (in particular a sport utility vehicle) or a truck.

[0034] The total thickness of the reinforcing fabric is equal to the thickness of the metal reinforcing elements plus the thickness of the rubber located on both sides of the reinforcing elements (called "back thicknesses") measured in the radial direction of the plane formed perpendicularly to the transverse direction and to the main direction. These two back thicknesses on both sides of the reinforcement can be identical or different and are denoted "edos_1" and "edos_2". Thus, the total thickness of the reinforcing fabric measured in the radial direction is denoted edos_1 + T + edos_2. In the particular arrangement where edos_1 = edos_2, the rubber thickness of the reinforcement back is simply denoted "edos" and the total thickness of the reinforcing fabric measured in the radial direction is equal to T + 2.edos.

[0035] The smaller the thickness of the fabric, the more the hysteresis and the rolling resistance of the pneumatic tire comprising such a fabric decrease. The rubber bridges between the reinforcing elements are able to properly withstand the forces exerted on the or each ply. However, an insufficient thickness of the fabric leads to a significant risk of incomplete formation of the rubber bridges and thus to a significant risk of difficulty for the fabric to withstand forces when the fabric is used as one or more working plies in a pneumatic tire. Moreover, in a pneumatic tire, an insufficient thickness of the fabric leads to a risk of reduction of the distance between the metal reinforcing elements of the fabric located radially outside the bead reinforcement.

[0036] Thus, on both sides of the metal reinforcing elements, the reinforcing fabric according to the application has a rubber thickness on the back of the metal reinforcing elements denoted "edos_1" and "edos_2" respectively, said rubber thickness being measured in the radial direction of the plane formed perpendicularly to the transverse direction and to the main direction, so that edos_1 and edos_2 range independently of each other from 0.10 mm to 0.4 mm, preferably from 0.10 mm to 0.25 mm, more preferably from 0.15 mm to 0.22 mm.

[0037] Elastomeric composition

[0038] The reinforcing elements are embedded in an elastomeric composition, where embedded means "completely coated" (except possibly the cross-section of the fabric).

[0039] By elastomeric composition is meant a composition exhibiting elastomeric behavior. Such a composition is advantageously based on at least one elastomer and one other ingredient.

[0040] Preferably, the elastomer is a diene elastomer, that is to say, as will be recalled, any elastomer (single elastomer or mixture of elastomers) derived at least partially (i.e. homopolymer or copolymer) from diene monomers (i.e. monomers bearing two conjugated or non-conjugated carbon-carbon double bonds).

[0041] The diene elastomer is more preferably chosen from polybutadienes (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers, such copolymers being in particular chosen from styrene-butadiene copolymers (SBR), butadiene-isoprene copolymers (BIR), styrene-isoprene copolymers (SIR) and styrene-butadiene-isoprene copolymers (SBIR).

[0042] One particularly preferred embodiment consists in using an "isoprene" elastomer, i.e. an isoprene homopolymer or copolymer, in other words a diene elastomer chosen from natural rubber (NR), synthetic polyisoprene (IR), different isoprene copolymers and mixtures of these elastomers.

[0043] The elastomer composition can comprise one or more diene elastomers and all or part of the additives generally used in compositions intended for the manufacture of tyres, such as, for example, reinforcing fillers (such as carbon black or silica), coupling agents, anti-aging agents, antioxidants, plasticizers or extender oils, whether of aromatic nature or not (in particular oils of very weakly aromatic or non-aromatic nature, such as naphthenic or paraffinic type oils, with a higher or preferably lower viscosity, MES oils or TDAE oils), plasticizing resins with a high glass transition temperature (higher than 30°C), agents improving the processability of the green state of the composition, tackifying resins, anti-reversion agents, methylene acceptors and donors (such as HMT (hexamethylene tetramine) or H3M (hexamethoxymethyl melamine)), reinforcing resins (such as resorcinol or bismaleimides), adhesion promoter systems of the known metal salt type (such as, in particular, salts of cobalt, nickel or lanthanides) and crosslinking systems or vulcanization systems.

[0044] Preferably, the system for crosslinking the elastomer composition is a system known as a crosslinking system, i.e. a system based on sulfur (or a sulfur donor agent) and a primary vulcanization accelerator. Various known secondary vulcanization accelerators or vulcanization activators can be added to this basic vulcanization system. Sulfur is used in a content preferably between 0.5 and 10 phr, and a primary vulcanization accelerator (such as a secondary sulfenamide) is used in a content preferably between 0.5 and 10 phr. The content of reinforcing filler (such as carbon black and / or silica) is preferably greater than 30 phr, in particular between 30 and 100 phr. The term "phr" means parts by weight per hundred parts of elastomer.

[0045] All carbon blacks conventionally used for tires (in particular of HAF, ISAF or SAF type) ("tire grade" carbon blacks) are suitable. These carbon blacks more particularly include carbon blacks of 300, 600 or 700 (ASTM) grade (for example N326, N330, N347, N375, N683 or N772). The BET surface area of these carbon blacks is less than 450 m 2 / g, preferably 30 m 2 / g to 400 m 2 / g, preferably 30 m F / g to 400 m 4 According to the present description, the person skilled in the art will know how to adjust the formulation of the rubber composition to achieve the desired level of properties (in particular the modulus of elasticity) and will know how to adjust the formulation to adapt to the specific application envisaged. 3 3 Preferably, in the crosslinked state, the tensile secant modulus at 10% elongation of the elastomeric composition is between 4 MPa and 25 MPa, more preferably between 4 MPa and 20 MPa; in particular, values between 5 MPa and 15 MPa prove to be particularly suitable. Unless otherwise stated, the modulus measurements are carried out under tension according to the standard ASTM D412 of 1998 (specimen "C"): the "true" secant modulus (i.e. with respect to the actual cross section of the specimen) is measured at 10% elongation on the second elongation (i.e. after conditioning cycle) and is denoted herein as Ms and expressed in MPa (according to the standard ASTM D1349 of 1999 under standard temperature and relative humidity conditions). 2 Pneumatic tire

[0001] The present application also relates to a pneumatic tire comprising a crown comprising a tread, two sidewalls each connecting one of the beads to the crown, a carcass reinforcement anchored in each of the beads and extending in the sidewalls and in the crown, a crown reinforcement extending in the crown in the circumferential direction and radially between the carcass reinforcement and the tread, the crown reinforcement comprising a working reinforcement comprising at least a first working ply and a second working ply, wherein at least one of the working plies is a reinforcing fabric according to the present application.

[0002] The axial direction means the direction substantially parallel to the axis of rotation of the tire.

[0003] The circumferential direction means the direction substantially perpendicular to the axial direction and to the radius of the tire (in other words, tangent to a circle centered on the axis of rotation of the tire).

[0004] The radial direction means the direction along the radius of the tyre, i.e. any direction that intersects the axis of rotation of the tyre and is substantially perpendicular to this axis.

[0053] The circumferential median plane, denoted M, means the plane that is perpendicular to the axis of rotation of the tyre, is located midway between the two beads and passes through the middle of the crown reinforcement.

[0054] In one preferred embodiment, the reinforcing elements of the first working ply form an angle with the circumferential direction of between 10 and 45 degrees.

[0055] In one preferred embodiment, the reinforcing elements of the second working ply form an angle with the circumferential direction of between 10 and 45 degrees.

[0056] Advantageously, the reinforcing elements of the first working ply and of the second working ply cross each other between the first working ply and the second working ply. Thus, if the angle formed by the reinforcing elements of the first working ply with the circumferential direction is a positive angle, the angle formed by the reinforcing elements of the second working ply with this same circumferential direction is a negative angle. Conversely, if the angle formed by the reinforcing elements of the first working ply with the circumferential direction is a negative angle, the angle formed by the reinforcing elements of the second working ply with this same circumferential direction is a positive angle.

[0057] In one preferred embodiment, the absolute value of the angle formed by the reinforcing elements of the first working ply with the circumferential direction is substantially equal to the angle formed by the reinforcing elements of the second working ply with this same circumferential direction.

[0058] Preferably, each of the two working plies is constituted by a reinforcing fabric according to the application.

[0059] Preferably, the tyre also comprises a bead reinforcement comprising at least one bead ply comprising textile reinforcing elements arranged substantially parallel to each other in the bead ply. Preferably, these textile reinforcing elements are embedded in an elastomeric composition. The bead ply is preferably located between the radially outermost working ply and the tread.

[0060] The textile reinforcing elements can have any known form; they can be monofilaments, but they are generally constituted by multifilament fibres twisted together in the form of a textile cord.

[0061] Preferably, the textile reinforcing elements form an angle with the circumferential direction of at most equal to 10°, preferably of between 5° and 10°.

[0062] Preferably, the textile reinforcing elements are heat-shrinkable. This means that the material forming the textile reinforcing elements shrinks as the temperature increases. The heat shrinkage CT of the textile reinforcing elements, measured after 2 minutes at 185°C under the test conditions listed below, is advantageously less than 7.5%, preferably less than 3.5%, more preferably less than 3%, these values having proved to be optimal for the manufacture and dimensional stability of the tyre, in particular during the course of its curing and cooling phases. Unless otherwise stated, the parameter CT is measured according to ASTM D1204-08, for example on a "TESTRITE" instrument, with a so-called standard pretension of 0.5 cN / tex (thus, the standard pretension is expressed relative to the titre or linear density of the sample being tested). At constant length, the maximum shrinkage force (expressed as FC) is also measured using the above test, this time at a temperature of 180°C and with an elongation of 3%. This shrinkage force FC is preferably greater than 20 N (Newtons). A high shrinkage force has proved to be particularly advantageous for the hoop ability of the heat-shrinkable textile reinforcing elements relative to the crown reinforcement of the tyre when the latter is warmed up at high running speeds.

[0063] The above parameters CT and FC can be measured indifferently on the initially adhesive-coated textile reinforcing elements before incorporation into the ply and the tyre, or on the reinforcing elements extracted from the central zone of the vulcanized tyre and preferably "de-rubberized" (i.e. stripped of the elastomer composition in which they are embedded).

[0064] Any heat-shrinkable textile material meeting the above shrinkage characteristics CT is suitable. Preferably, the heat-shrinkable textile material is chosen from polyamides, polyesters and polyketones. The polyamides include in particular polyamide 4.6, 6, 6.6, 11 or 12. The polyesters include for example PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PPT (polypropylene terephthalate) and PPN (polypropylene naphthalate). Hybrid reinforcements consisting of two (at least two) different materials (for example aramid / nylon, aramid / polyester and aramid / polyketone hybrid cords) can also be used, provided that they meet the recommended characteristics CT.

[0065] In the reinforcing textile according to the application, the different geometric characteristics, such as the thicknesses edos_1 and edos_2, the lay spacing p, the length W and the height T, are measured in the central portion of the textile in the green (i.e. unvulcanized) state, over a total axial width of 4 cm, by calculating the mean of all the reinforcing elements present.

[0066] In the pneumatic tire according to the application, in the central portion of the crown reinforcement of the tire in the vulcanized state on both sides of the median plane M, over a total axial width of 4 cm, the different geometric characteristics, such as the thicknesses edos_1 and edos_2, the laying pitch p, the width W and the height T, are measured by calculating the average of all the reinforcing elements present in the central portion of the working reinforcement in the axial interval extending between -2 cm and +2 cm with respect to the median plane M. BRIEF DESCRIPTION OF DRAWINGS

[0067] Figure 1 Figure 1 is a schematic representation of a portion of a reinforcing fabric according to the application. This figure shows, in a cross-sectional plane perpendicular to the main direction of the metal reinforcing elements, three reinforcing elements having a width W and a height or thickness T, where these elements are juxtaposed with a laying pitch p and embedded in an elastomeric composition, so that the fabric has a rubber thickness on both sides of each reinforcing element in the radial direction, denoted respectively "edos_1" and "edos_2". DETAILED DESCRIPTION

[0068] MEASURING METHODS

[0069] The absolute breaking force of a ply is measured in N by multiplying the number of reinforcing elements present over a length of 10 cm of the ply in the transverse direction by the individual breaking force of each reinforcing element. The measurements of breaking force, breaking strength (expressed as R F (in MPa)) and breaking elongation (expressed as At (total elongation in %)) are carried out under tension according to ISO 6892:1984.

[0070] The breaking force of a ply is obtained by dividing the absolute breaking force of the ply, as determined as indicated above, by 100, and it is expressed in N / mm.

[0071] The torsional elastic deformation is measured over a given length of the metal reinforcing element, for example a length ranging from 5 m to 10 m, and the value found is expressed relative to 6 m, thereby obtaining the value C. To do this, a very long workbench is provided, the length of which is at least equal to the length of the metal reinforcing body for which the torsional elastic deformation is being measured, and one end of the metal reinforcing body is fixed to one end of the workbench. The metal reinforcing body is unwound and the metal reinforcing body is held very carefully so as to prevent it from rotating itself around its main axis. At the other end, the metal reinforcing body is suspended from the edge of the workbench and a rod is fixed to its end, perpendicular to the main axis of the metal reinforcing body. The suspended end of the metal reinforcing body is then free to rotate. The number of turns of the rod is then measured. If the rod turns through an incomplete turn, the angle of the turn is expressed as a non-integer value of the turn. Thus, an angle of 180° will be expressed as 0.5 turn. ​​

[0072] For a reinforcing element having a circular cross-section, the bending stiffness is evaluated by the equation Y.d 4 / 64, where d is the diameter of the reinforcing element having a circular cross-section and T is the Young's modulus of the element. By construction, a reinforcing element having a circular cross-section has the same edge bending stiffness and out-of-plane bending stiffness.

[0073] For a reinforcing element having a length W and a height T, the bending stiffness is evaluated by the equations Y.T.W 3 / 12 (for the edge bending stiffness) and Y.W.T 3 / 12 (for the out-of-plane bending stiffness), where Y is the Young's modulus of the element.

[0074] Examples

[0075] The following tests show the advantages of the reinforcing fabric according to the application.

[0076] Fabrics T1 and T3 are fabrics of the prior art implementing a single metal monofilament as reinforcing element, T1 having a diameter of 0.32 mm and T2 having a diameter of 0.35 mm. Fabric T2 is a fabric having the same thickness as fabric C1 according to the application.

[0077] Fabrics C1 and T1 and C3 and T3 have the same in-cable distance. Fabric T2 has the same thickness as fabric C1. Fabric C2 has the same mass per 1 m 2 of fabric as fabric T2. Fabric C4 comprises the same metal reinforcing elements as fabric C3 and has the same ply strength as fabric T3.

[0078] Concerning the mass, the results are given with base 100 for fabrics C1, T2 and C2 relative to fabric T1 and with base 100 for fabrics C3 and C4 relative to fabric T3. A value greater than 100 means that the mass of the fabric is greater than the mass of the reference fabric and a value less than 100 means that the mass of the fabric is less than the mass of the reference fabric. A greater mass of the fabric leads to a greater rolling resistance of the pneumatic tire comprising this fabric.

[0079] [Table 1]

[0080]

[0081]

Claims

1. A reinforced fabric comprising a plurality of parallel metallic reinforcing elements extending in a main direction, arranged at a laying pitch p in a transverse direction perpendicular to the main direction, expressed in mm, embedded in an elastomeric composition based on at least one elastomer, a reinforcing filler and a crosslinking system, each metallic reinforcing element having a cross-section inscribed in a rectangle having a width W and a height T in a plane perpendicular to the main direction, and a breaking strength R expressed in MPa measured according to ISO 6892:1984 equal to R F , the reinforced fabric having a breaking force expressed in N / mm equal to R n , wherein, W < 0.5 p < 2 T < 0.5 p < 2 The laying pitch of the metal reinforcing elements is p ≥ 0.8 · R F / R n • (a - 1 + π / 4) · T 2 where a = W / T and the range of 1 / a is 0.35 to 0.

75. ​​​​​ 2. Reinforcing fabric according to the preceding claim, wherein, The ratio 1 / a ranges from 0.35 to 0.

65.

3. The reinforcing fabric according to any of the preceding claims, wherein, The height T ranges from 0.15 mm to 0.70 mm.

4. The reinforcing fabric according to any of the preceding claims, wherein, The laying pitch p satisfies p < 1.2R F / R n (a - 1 + π / 4)T 2 .

5. The reinforcing fabric according to any of the preceding claims, wherein, Each metal reinforcing element is at least of high strength grade, i.e. having a breaking strength R F greater than or equal to 3650 - 2000 · D, where D is expressed in mm and is equal to (T + W) / 2.

6. The reinforcing fabric according to any of the preceding claims, wherein, each metallic reinforcing element is at least of an extremely high strength class, i.e. a breaking strength R F greater than or equal to 4000 - 2000 · D, where D is expressed in mm and is equal to (T + W) / 2.

7. The reinforcing fabric according to any of the preceding claims, wherein, each metallic reinforcing element is at least of ultra-high strength class, i.e. having a breaking strength R F greater than or equal to 4350 - 2000 · D, where D is expressed in mm and is equal to (T + W) / 2.

8. The reinforcing fabric according to any one of the preceding claims, having on both sides of the metal reinforcing elements a rubber thickness, denoted respectively "edos_1" and "edos_2" on the back of the metal reinforcing elements, measured in the radial direction of the plane formed perpendicularly to the transverse direction and to the main direction, so that the range of edos_1 and edos_2, independently of each other, is from 0.10 mm to 0.4 mm.

9. The reinforcing fabric according to any of the preceding claims, wherein, Each reinforcing element comprises a steel core covered with a metal coating made of a metal other than steel.

10. The reinforcing fabric according to any of the preceding claims, wherein, Each reinforcing element has a torsional elastic deformation C, the absolute value of which is less than or equal to 6 turns / 6 m of metal reinforcement.

11. The reinforcing fabric according to any of the preceding claims, wherein, R n greater than or equal to 220 N / mm.

12. The reinforcing fabric according to any of the preceding claims, wherein, The elastomer of the elastomeric composition is a diene elastomer.

13. A pneumatic tire comprising a crown, two sidewalls and two beads, the crown comprising a tread, each sidewall connecting each bead to the crown, a carcass reinforcement anchored in each bead and extending in the sidewall and in the crown, a crown reinforcement extending in the crown in a circumferential direction and radially between the carcass reinforcement and the tread, the crown reinforcement comprising a working reinforcement, the working reinforcement comprising at least a first working ply and a second working ply, wherein, At least one working ply is a reinforcing fabric according to any one of the preceding claims.

14. Pneumatic tire according to the preceding claim, wherein, Each of the first and second working plies is composed of a reinforcing fabric according to any one of claims 1 to 12.

15. Pneumatic tire according to claim 13 or 14, comprising a bead reinforcement comprising at least one bead ply comprising fabric reinforcing elements arranged parallel to each other in the bead ply.

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