Reinforced fabric with multiple metal reinforcing elements

Abstract

The present invention relates to a reinforced woven fabric comprising a plurality of metal reinforcing elements arranged in a transverse direction, substantially parallel to one another and extending in a main direction perpendicular to the transverse direction, the metal reinforcing elements being 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 that fits inside a rectangle of length W and height T in a plane perpendicular to the main direction.

Description

[Technical Field]

[0001] This invention relates to reinforcing fabrics, particularly reinforcing fabrics used in pneumatic tires, and to the field of pneumatic tires. [Background technology]

[0002] A pneumatic tire having radial carcass reinforcements for a passenger car or van, as is well known, comprises a tread, two non-stretchable beads, two flexible sidewalls connecting the beads to the tread, and a rigid crown reinforcement or "belt" circumferentially positioned between the carcass reinforcements and the tread.

[0003] The crown reinforcement generally consists of at least two overlapping cross rubber plies known as “actuated plies,” “triangular plies,” or “actuated reinforcements,” which comprise a plurality of reinforcing fabrics known as plies and are reinforced with metal cables, usually positioned substantially parallel to each other and inclined with respect to the circumferential midplane of the pneumatic tire; and a rubber ply located above (on the tread side of) the actuated plies, known as “hoop plies” or “hoop reinforcements,” which are reinforced with reinforcing threads, generally known as “circumferential,” and whose primary function is to withstand the centrifugal action of the crown at high speeds. These plies can optionally be associated with other rubber plies and / or fabrics. The primary function of the actuated plies is to provide the tire with the high drift thrust or cornering stiffness necessary to achieve good handling for the vehicle, as is well known.

[0004] Such belt structures, ultimately composed of a multilayer composite laminate comprising at least one hoop ply, which is usually fabric, and two actuation ply, which are usually metal, are known to those skilled in the art and do not need to be described in further detail here. Such belt structures are exemplified, for example, in U.S. Patent No. 4,371,025 and French Patent No. 2,504,067.

[0005] The increasing availability of stronger and more durable steel means that today's tire manufacturers tend to use tire belts made of cables with a very simple structure of just two threads or even individual filaments, in order to simplify manufacturing and reduce costs as much as possible, and to reduce the thickness of the reinforcing plies, i.e., the hysteresis of the tire, and ultimately reduce the energy consumption of the vehicle fitted with such tires.

[0006] However, efforts aimed at reducing tire mass, particularly by reducing the thickness of their belts and the rubber layers from which they are made, naturally encounter physical limitations that can lead to several difficulties. In particular, the hooping function provided by the hoop reinforcement and the hardening function provided by the actuation reinforcement sometimes become indistinguishable from each other and may interfere with one another. This is detrimental to the proper operation of the tire crown and to the tire's performance and overall durability.

[0007] International Patent Publication Nos. 2013 / 117476 and 2013 / 117477 propose a multilayer composite laminate having a specific structure consisting of a fabric hooping ply and two working plies with metal monofilaments, which allows for a significant reduction in the weight of the tire belt while overcoming the aforementioned drawbacks, and thus reducing their rolling resistance. International Patent Publication No. 2019 / 020888 aims to further reduce the mass of the ply while improving resistance to buckling by linking the diameter of the metal monofilament, the density of the monofilament, and the thickness of the ply.

[0008] Other achievements, such as those disclosed in Japanese Patent Publication No. 2001 / 328407, relate in particular to the implementation of metal reinforcing elements whose cross-section is no longer circular but rather inscribed in a rectangle, in order to make the plies thinner, i.e., lighter, and result in a reduction in the rolling resistance of pneumatic tires. Japanese Patent Publication No. 2017 / 048351 discloses the use of a flat reinforcing element associated with a particular elastomer composition, in which the cable distance between 0.15 and 0.54 mm, i.e., the distance between two continuous reinforcing elements, is preferably between 0.4 and 0.5, in order to reduce rolling resistance, limit heating problems, and avoid ply separation problems.

[0009] However, increasing the weight and performance of the vehicle requires, in particular, 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, although there are inherent limitations to the availability of steel, or by increasing the diameter and / or density of these reinforcements, which may result in an increase in the thickness and / or mass of the plies and thus the weight of the pneumatic tire and / or a decrease in the space separating two consecutive metal reinforcement elements within the plies. Filling the rubber bridges located between the reinforcement elements then becomes difficult, which can be detrimental to the durability of one or more plies and thus the pneumatic tire, in particular due to the risk of tearing corresponding to the appearance of cracks propagating between the working plies. Shortening the distance between cables can also make it difficult to manufacture the plies, as it requires placing a large number of metal threads parallel to each other at small distances. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] U.S. Patent No. 4371025 [Patent Document 2] French Patent No. 2504067 [Patent Document 3] International Patent Application Publication No. 2013 / 117476 [Patent Document 4] International Application Publication No. 2013 / 117477 [Patent Document 5] International Application Publication No. 2019 / 020888 [Patent Document 6] Japanese Patent Application Laid-Open No. 2001 / 328407 [Patent Document 7] Japanese Patent Application Laid-Open No. 2017 / 048351 [Patent Document 8] International Application Publication No. 2017 / 203119 [Patent Document 9] German Patent Application Publication No. 102015209343 [Summary of the Invention] [Problems to be Solved by the Invention]

[0011] Continuing the research, the applicant has discovered a specific configuration of a fabric reinforced with metal reinforcing elements having very good breaking strength, lower rolling resistance, and a cable distance sufficient to avoid any tearing problems compared to the prior art reinforcing fabrics. [Means for Solving the Problems]

[0012] definition The main direction is given such that it means the direction in which the maximum dimension of the metal reinforcing element, which coincides with the axis of the reinforcing element, extends.

[0013] The transverse direction is given such that it means the direction perpendicular to the main direction.

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

[0015] The compounds comprising carbon referred to in this specification can be of fossil origin or of bio-origin. In the latter case, they can be derived partially or completely from biomass or obtained from renewable raw materials derived from biomass. This relates in particular to polymers, plasticizers, fillers, etc.

[0016] Reinforced fabric The present invention relates to a reinforcing fabric comprising a plurality of substantially parallel metal reinforcing elements extending in a main direction, arranged in a transverse direction perpendicular to the main direction at a laying pitch p expressed in mm and embedded in an elastomeric composition based on at least one elastomer, a reinforcing filler, and a crosslinking system. Each metal reinforcing element has a cross-section inscribed in a rectangle of length W and height T in a plane perpendicular to the main direction, and a breaking strength R measured according to ISO 6892:1984 and expressed in MPa. F The fabric has a breaking force expressed in N / mm equal to R n and the laying pitch of the metal reinforcing elements is such that p ≧ 0.8.R F / R n .(a - 1 + π / 4).T 2 where a = W / T and 1 / a ranges from 0.35 to 0.75.

[0017] Such features have been shown to make it possible to satisfactorily fill the rubber bridges between two consecutive reinforcing elements while reducing the weight of the reinforcing fabric compared to prior art reinforcing fabrics, while maintaining particularly advantageous 'edgewise' and 'out-of-plane' breaking strength and stiffness characteristics.

[0018] As is known to those skilled in the art, the laying pitch is defined as the distance between the geometric centers of two immediately adjacent metal reinforcing elements measured in the transverse direction.

[0019] Preferably, the laying pitch p is such that p ≦ 1.2.R F / R n .(a - 1 + π / 4).T 2 When the pitch is excessively large, the cooperation between juxtaposed metal reinforcing elements deteriorates when the fabric is used as an operating ply in a pneumatic tire.

[0020] Very preferably, the laying pitch p is such that 0.9.R F / R n .(a - 1 + π / 4).T 2 ≦ p ≦ 1.1.R F / Rn .(a-1+π / 4).T 2 It is something like that.

[0021] Reinforcement elements Each reinforcing element is made of metal. Preferably, the reinforcing element comprises a steel core covered with a metal coating layer made of a metal other than steel, for example, to improve the workability of the reinforcing element or to improve the usage characteristics of the reinforcing element and / or the tire, such as adhesiveness, corrosion resistance, or aging resistance. For example, the metal of the metal coating layer is selected from zinc, copper, tin, and alloys of these metals. Examples of alloys of these metals include brass and bronze.

[0022] Steel may have a microstructure derived from pearlite, ferritic, austenitic, bainite, or martensitic microstructures, or mixtures thereof.

[0023] In one preferred embodiment, when carbon steel is used, its carbon content (weight %) is in the range of 0.2% to 1.2%, and in another preferred embodiment, the carbon content of the steel is in the range of 0.6% to 0.8%.

[0024] This invention relates particularly to high-tensile (HT) steel cords, preferably super-high-tensile (SHT), or even more specifically, ultra-high-tensile (UHT), in which case the reinforcing element has a tensile strength (R) of preferably greater than or equal to 3,650-2,000.D, more preferably greater than or equal to 4,000-2,000.D, and most preferably greater than or equal to 4,350-2,000.D, when D, expressed in mm, is equal to (T+W) / 2. F The total elongation at fracture (At) of these reinforcements, which is the sum of elastic elongation and plastic elongation, is preferably greater than 2.0%.

[0025] Preferably, each reinforcing element has a torsional elastic deformation C expressed in absolute value as fewer than or equal to 6 turns per 6m of the metal reinforcing body, preferably fewer than or equal to 3 turns per 6m of the metal reinforcing body.

[0026] This low elastic deformation makes it possible to obtain a fabric that is flat enough to be easily incorporated into rubber articles, particularly pneumatic tires. In a preferred arrangement, reinforcing elements can be positioned in the fabric to alternate their elastic deformation, as disclosed in WO2017 / 203119.

[0027] Each metal reinforcing element has a cross-section that is inscribed in a rectangle of length W and height T in a plane perpendicular to the principal direction.

[0028] Such reinforcing elements are known in the prior art and are described, for example, in Japanese Patent Application Publication No. 2001 / 328407 and German Patent Application Publication No. 102015209343. These reinforcing elements can be obtained, for example, by drawing using a substantially rectangular die capable of rounding the corners, or by crushing a metal reinforcing element having a circular cross-section by passing it through rollers.

[0029] Preferably, each metal reinforcing element of the fabric according to the present invention has a ratio 1 / a representing the ratio of its height or thickness T to its width W in the range of 0.35 to 0.65, preferably in the range of 0.45 to 0.65. Such preferred ratios allow for a significant increase in "edgewise" stiffness, i.e., the axial stiffness of a pneumatic tire having such fabric as an actuating ply, without substantially modifying the "out-of-plane" stiffness, i.e., the radial stiffness of a pneumatic tire having such fabric as an actuating ply, and lower out-of-plane stiffness allows for improved flattening of the pneumatic tire on a horizontal ground surface.

[0030] Preferably, each metal reinforcing element has a height or thickness T in the range of 0.15 to 0.70 mm, preferably 0.15 to 0.40 mm, and more preferably 0.20 to 0.30 mm. Such thickness, associated with other features of the metal reinforcing element, allows for a good compromise between the total thickness of the working ply and its breaking force.

[0031] The reinforcing fabric preferably has a breaking force R greater than or equal to 220 N / mm, preferably greater than or equal to 300 N / mm, and more preferably between 330 and 470 N / mm. n Such a breaking force is particularly advantageous when the fabric according to the present invention is implemented in pneumatic tires intended to withstand relatively heavy loads, such as those of modern passenger cars, especially sports utility vehicles or vans.

[0032] The total thickness of the reinforcing fabric is equal to the thickness of the metal reinforcing element, plus the thickness of the rubber located on both sides of the reinforcing element, known as the "back thickness," measured radially perpendicular to the plane formed by the transverse and principal directions. These two back thicknesses on both sides of the reinforcing body can be the same or different and are denoted as "edos_1" and "edos_2." The total thickness of the reinforcing fabric measured radially is expressed as edos_1 + T + edos_2. In a particular configuration where edos_1 = edos_2, the rubber thickness on the back of the reinforcing body is simply indicated as "edos," and the total thickness of the reinforcing fabric measured radially is equal to T + 2.edos.

[0033] The thinner the fabric, the greater the hysteresis, and therefore the lower the rolling resistance of a pneumatic tire with such a fabric. Rubber bridges between reinforcing elements allow the forces acting on it or each ply to be properly absorbed. However, insufficient fabric thickness results in incomplete rubber bridge formation, thus posing a significant risk that the fabric will not reliably absorb forces when used as one or more working plies in a pneumatic tire. In addition, in pneumatic tires, insufficient fabric thickness also poses a risk that the metal reinforcing elements of the fabric located radially outward from the hoop reinforcement will be closer to each other.

[0034] The reinforcing fabric according to the present invention is, preferably, indicated by "edos_1" and "edos_2" respectively, measured in the radial direction perpendicular to the plane formed by the transverse and principal directions on both sides of the metal reinforcing element, and has a rubber thickness on the back of the metal reinforcing element such that edos_1 and edos_2 are independently 0.10 to 0.40 mm, preferably 0.10 to 0.25 mm, and more preferably 0.15 to 0.22 mm.

[0035] Elastomer composition The reinforcing elements are embedded in the elastomer composition, where embedded is given to mean "completely covered" with the possible exception of the cross-sectional plane of the fabric.

[0036] The term "elastomer composition" is given to mean a composition that exhibits elastomeric behavior. Such a composition is favorably based on at least one elastomer and one other component.

[0037] Preferably, the elastomer is a diene elastomer, i.e., as can be thought of, an elastomer (a single elastomer or a mixture of elastomers) that is at least partially derived from a diene monomer, i.e., a monomer supporting two conjugated or unconjugated carbon-carbon double bonds (i.e., a homopolymer or copolymer).

[0038] The diene elastomer is more preferably selected from the group consisting of polybutadiene (BR), natural rubber (NR), synthetic polyisoprene (IR), butadiene copolymer, isoprene copolymer, and mixtures thereof, and such copolymers are particularly selected from the group consisting of styrene-butadiene copolymer (SBR), butadiene-isoprene copolymer (BIR), styrene-isoprene copolymer (SIR), and styrene-butadiene-isoprene copolymer (SBIR).

[0039] One particularly preferred embodiment consists of using an "isoprene" elastomer, i.e., an isoprene homopolymer or copolymer, in other words, a diene elastomer selected from the group consisting of natural rubber (NR), synthetic polyisoprene (IR), different isoprene copolymers, and mixtures thereof.

[0040] The elastomer composition may comprise one or more diene elastomers and all or some of the additives commonly used in compositions intended for the manufacture of tires, such as reinforcing fillers such as carbon black or silica, coupling agents, anti-aging agents, antioxidants, plasticizers, or extension oils, regardless of whether the latter are essentially aromatic or non-aromatic (especially oils that are very slightly aromatic or non-aromatic, such as naphthenic or paraffinic types and of high viscosity or preferably low viscosity MES or TDAE oils), plasticizing resins having a high glass transition temperature (higher than 30°C), agents that improve the processability of the composition in its green state, tackifying resins, anti-reversal agents, methylene acceptors and donors, such as HMT (hexamethylenetetramine) or HMMM (hexamethoxymethylmelamine), reinforcing resins (such as resorcinol or bismaleimide), known adhesion promoter systems of the metal salt type, such as salts of cobalt, nickel, or lanthanides, and crosslinking or vulcanizing systems.

[0041] Preferably, the system for crosslinking the elastomer composition is a system called a vulcanization system, i.e., a system based on sulfur (or a sulfur donor) 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 preferred content between 0.5 and 10 phr, and a primary vulcanization accelerator, such as sulfenamide, is used in a preferred content between 0.5 and 10 phr. The content of reinforcing fillers, such as carbon black and / or silica, is preferably higher than 30 phr, and particularly between 30 and 100 phr. The term "phr" is given to mean parts by weight per 100 parts of elastomer.

[0042] In particular, all HAF, ISAF, or SAF type carbon blacks ("tire grade" carbon blacks) conventionally used in tires are suitable. More specifically, these include 300, 600, or 700 (ASTM) grade carbon blacks (e.g., N326, N330, N347, N375, N683, or N772). 450m 2 Less than / g, preferably 30 to 400m 2 Precipitated or fumed silica having a BET surface area of ​​1 / g is particularly suitable as silica.

[0043] Those skilled in the art will know, in light of this specification, how to adjust the formulation of a rubber composition to achieve a desired level of properties (particularly modulus of elasticity), and how to adapt the formulation to suit a particular intended application.

[0044] Preferably, the elastomer composition, in its crosslinked state, has a secondary modulus of elongation between 4 and 25 MPa at 10% elongation, more preferably between 4 and 20 MPa, with values ​​between 5 and 15 MPa being particularly suitable. Modulus measurements are performed under tension according to ASTM D412-98 (test specimen "C") unless otherwise specified, and the "true" secant modulus (i.e., with respect to the actual cross-section of the test specimen) is measured at a second elongation at 10% elongation (i.e., after the acceptance cycle), indicated here by Ms, and expressed in MPa (under standard temperature and relative humidity conditions according to ASTM D1349-99).

[0045] Pneumatic tires The present invention also relates to a pneumatic tire comprising a crown having a tread, two sidewalls, and two beads, each sidewall connecting each bead to the crown, a carcass reinforcement fixed within each of the beads and extending within the sidewalls and within the crown, a crown reinforcement extending circumferentially within the crown and radially positioned between the carcass reinforcement and the tread, the crown reinforcement comprising an actuation reinforcement comprising at least a first and a second actuation ply, and at least one actuation ply being a reinforcing fabric according to the present invention.

[0046] The axial direction is given to mean a direction substantially parallel to the tire's axis of rotation.

[0047] The circumferential direction is given to mean a direction substantially perpendicular to both the axial direction and the tire radius (in other words, a tangent to a circle centered on the tire's axis of rotation).

[0048] The radial direction is given to mean any direction along the radius of the tire, i.e., any direction that intersects the tire's axis of rotation and is substantially perpendicular to that axis.

[0049] The circumferential intermediate plane (denoted as M) is given to mean a plane located midway between the two beads and passing through the midpoint of the crown reinforcement, perpendicular to the rotational axis of the tire.

[0050] In one preferred embodiment, the reinforcing element of the first working ply forms an angle with the circumferential direction in the range of 10 to 45 degrees.

[0051] In one preferred embodiment, the reinforcing element of the second working ply forms an angle with the circumferential direction in the range of 10 to 45 degrees.

[0052] Advantageously, the reinforcing elements of the first and second actuation plies intersect each other between the first and second actuation plies. That is, if the angle formed by the reinforcing element of the first actuation ply with the circumferential direction is positive, the angle formed by the reinforcing element of the second actuation ply with the same circumferential direction is negative. Conversely, if the angle formed by the reinforcing element of the first actuation ply with the circumferential direction is negative, the angle formed by the reinforcing element of the second actuation ply with the same circumferential direction is positive.

[0053] In one preferred embodiment, the angle formed by the reinforcing element of the first actuation ply with respect to the circumferential direction is substantially equal in absolute terms to the angle formed by the reinforcing element of the second actuation ply with respect to this same circumferential direction.

[0054] Preferably, each of the two working plies is made of the reinforcing fabric according to the present invention.

[0055] Preferably, the tire further comprises a hoop reinforcement having at least one hooping ply having fabric reinforcement elements arranged substantially parallel to each other within the hooping ply. Preferably, these fabric reinforcement elements are embedded in an elastomer composition. The hooping ply is preferably located between the radially outermost working ply and the tread.

[0056] Fabric reinforcement elements can take any known form; they can be monofilaments, but they are usually composed of multifilament fibers twisted together in the form of fabric cords.

[0057] Preferably, the fabric reinforcing element forms an angle equal to a maximum of 10° with respect to the circumferential direction, preferably an angle in the range of 5° to 10°.

[0058] Preferably, the fabric reinforcement element is heat-shrinkable. This means that the material forming the fabric reinforcement element shrinks as the temperature rises. The heat shrinkage rate CT of the fabric reinforcement element, measured after 2 minutes at 185°C, is favorably less than 7.5%, preferably less than 3.5%, and more preferably less than 3%, under the test conditions listed below, and these values ​​have proven to be optimal for tire manufacturing and dimensional stability, particularly during the curing and cooling phases. The parameter CT is measured, unless otherwise specified, according to ASTM D1204-08, for example on a "TESTRITE" apparatus at a so-called standard pre-tension of 0.5 cN / tex (thus expressed in terms of titration concentration or linear density of the tested sample). At a given length, the maximum shrinkage force (denoted as FC) is also measured using the above test, this time at a temperature of 180°C with 3% elongation. This shrinkage force FC is preferably greater than 20 N (Newtons). High shrinkage force has proven particularly beneficial for the hooping function of heat-shrinkable fabric reinforcement elements against the crown reinforcement of tires when heated at high driving speeds.

[0059] The parameters CT and FC described above can be measured indiscriminately for the initial adhesive-coated fabric reinforcing elements before they are incorporated into the ply and tire, or for the reinforcing elements after they have been extracted from the central zone of the vulcanized tire and preferably "de-rubbed" (i.e., after the elastomer composition in which they are embedded has been stripped away).

[0060] Any heat-shrinkable fabric material that satisfies the above-described shrinkage characteristics CT is suitable. Preferably, this heat-shrinkable fabric material is selected from the group consisting of polyamide, polyester, and polyketone. Polyamide includes polyamide 4, 6, 6, 6, 6.11, or 12 in particular. Polyester includes, for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PPT (polypropylene terephthalate), and PPN (polypropylene naphthalate). Hybrid reinforcements composed of two (at least two) different materials, such as aramid / nylon, aramid / polyester, and aramid / polyketone hybrid cords, can also be used, provided that they satisfy the recommended characteristics CT.

[0061] In the reinforced fabric according to the present invention, different geometric properties such as thickness edos_1 and edos_2, laying pitch p, length W, and height T are measured over a full axial width of 4 cm in the green, i.e., the central portion of the fabric in its unvulcanized state, by calculating the average of all the reinforcing elements present.

[0062] In the pneumatic tire according to the present invention, different geometric properties such as thickness edos_1, edos_2, laying pitch p, length W, and height T are measured in the central portion of the crown reinforcement of the tire in a vulcanized state on both sides of the midplane M over a total axial width of 4 cm by calculating the average of all reinforcing elements present in the central portion of the working reinforcement with axial spacing extending between -2 cm and +2 cm with respect to the midplane M. [Brief explanation of the drawing]

[0063] [Figure 1]This is a schematic diagram of a portion of a reinforcing fabric according to the present invention, showing three reinforcing elements with width W and height or thickness T in a cross-sectional plane perpendicular to the main direction of the metal reinforcing elements, and showing that these elements are laid side by side at a laying pitch p and embedded in an elastomer composition such that the fabric has rubber thicknesses indicated as "edos_1" and "edos_2" on both sides of each reinforcing element in the radial direction. [Modes for carrying out the invention]

[0064] Measurement method The absolute breaking force of a ply, expressed in N, is measured by multiplying the number of reinforcing elements present over a 10 cm length of the transverse ply by the individual breaking force of each reinforcing element. The breaking force, breaking strength (in MPa) indicated by RF, and elongation at break (total elongation as a percentage) indicated by At are measured under tension in accordance with ISO 6892:1984. The breaking force of the ply is obtained by dividing the absolute breaking force of the ply determined as described above by 100, and is expressed in N / mm.

[0065] The torsional elastic deformation is measured over a given length of the metal reinforcing element, for example, in the range of 5 to 10 cm, and the value found is expressed relative to 6 m to obtain a value C. For this purpose, a very long table is provided, the length of which is at least equal to the length of the metal reinforcing element whose torsional elastic deformation is being measured, and one end of the metal reinforcing element is fastened to one end of the table. The metal reinforcing element is unwound, taking great care to hold it so that it does not rotate on itself around its main axis. At the other end, the metal reinforcing element is suspended over the edge of the table, and a rod is fastened to its end perpendicular to the main axis of the metal reinforcing element. The suspended end of the metal reinforcing element is then made free to rotate. The number of turns the rod makes is then measured. If the rod makes an incomplete turn, the angle advanced on that turn is expressed as a non-integer value of the turns; that is, an angle of 180° will be expressed as 0.5 turns.

[0066] The bending stiffness for a reinforcing element with a circular cross-section is given by the equation Yd 4 It is estimated by / 64, where d is the diameter of the reinforcing element having a circular cross-section and Y is the Young's modulus of the element. By configuration, reinforcing elements having a circular cross-section have the same edgewise and out-of-plane bending stiffness.

[0067] The bending stiffness for a reinforcing element of length W and height T is given by the equation YTW for edgewise bending stiffness. 3 YWT for / 12 and out-of-plane bending stiffness 3 It is estimated by / 12, where Y is the Young's modulus of the element.

[0068] Examples The following tests demonstrate the advantages of the reinforcing fabric according to the present invention.

[0069] Fabrics T1 and T3 are conventional fabrics in which individual metal monofilaments are implemented as reinforcing elements having a diameter of 0.32 mm for T1 and 0.35 mm for T2. Fabric T2 is a fabric having the same thickness as fabric C1 according to the present invention.

[0070] Fabrics C1 and T1, and C3 and T3 have the same cable-to-cable distance. Fabric T2 has the same thickness as fabric C1. Fabric C2 is the same fabric as fabric T2, 1m 2 It has a mass per unit area. Fabric C4 has the same metal reinforcing elements as fabric C3 and has the same ply strength as fabric T3.

[0071] With respect to mass, the results are given with respect to fabric T1 for fabrics C1, T2, and C2, and with respect to fabric T3 for fabrics C3 and C4, using a base of 100. A value greater than 100 means that the fabric has a greater mass than the base fabric, and a value less than 100 means that the fabric has a smaller mass than the base fabric. A larger amount of fabric material results in greater rolling resistance for pneumatic tires equipped with such fabric.

[0072] (Table 1) JPEG0007851315000001.jpg64169 [Explanation of symbols]

[0073] edos_1, edos_2 Rubber thickness p Laying pitch T Reinforcement element height or thickness Width of the W reinforcement element

Claims

1. It is a reinforcing fabric, A plurality of substantially parallel metal reinforcing elements are embedded in an elastomer composition based on at least one elastomer, a reinforcing filler, and a crosslinking system, arranged in a transverse direction perpendicular to the principal direction with a laying pitch p expressed in mm. Equipped with, Each metal reinforcing element has a cross-section inscribed within a rectangle of length W and height T in a plane perpendicular to the principal direction, and has a fracture strength R measured in MPa according to ISO 6892:1984. F It has, and the fabric is R n It has a breaking force expressed in N / mm that is equal to, 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 1 / a is in the range of 0.35 to 0.

75. A reinforcing fabric characterized by the following features.

2. The reinforcing fabric according to claim 1, characterized in that the ratio 1 / a is in the range of 0.35 to 0.

65.

3. The reinforcing fabric according to any one of claims 1 to 2, characterized in that the height T is in the range of 0.15 mm to 0.70 mm.

4. The reinforcing fabric according to any one of claims 1 to 3, characterized in that the laying pitch p is such that p ≤ 1.2・R F / R n ・(a-1 + π / 4)・T 2.

5. Each metal reinforcing element has at least a high tensile strength grade, i.e., a fracture strength R higher than or equal to 3,650-2,000·D. F The reinforcing fabric according to any one of claims 1 to 4, wherein D, in this case expressed in mm, is equal to (T + W) / 2.

6. Each metal reinforcing element has at least an ultra-high tensile strength grade, i.e., a fracture strength R higher than or equal to 4,000-2,000·D. F The reinforcing fabric according to any one of claims 1 to 5, wherein D, in this case expressed in mm, is equal to (T + W) / 2.

7. Each metal reinforcing element has at least an ultra-high tensile strength grade, i.e., a fracture strength R higher than or equal to 4,350-2,000·D. F The reinforcing fabric according to any one of claims 1 to 6, wherein D, in this case expressed in mm, is equal to (T + W) / 2.

8. The reinforcing fabric according to any one of claims 1 to 7, characterized in that on both sides of the metal reinforcing element, the rubber thickness on the back surface of the metal reinforcing element, indicated by "edos_1" and "edos_2", measured in the radial direction perpendicular to the plane formed by the transverse direction and the principal direction, is such that edos_1 and edos_2 are in the range of 0.10 to 0.40 mm, independently of each other.

9. The reinforcing fabric according to any one of claims 1 to 8, characterized in that each reinforcing element comprises a steel core covered with a metal coating layer made of a metal other than steel.

10. It is a pneumatic tire, A crown comprising a tread, two side walls, and two beads, wherein each side wall connects each bead to the crown, Equipped with, The carcass reinforcement is fastened to each of the beads and extends within the side wall and the crown, The crown reinforcement extends circumferentially within the crown and is radially positioned between the carcass reinforcement and the tread, and the crown reinforcement comprises an actuation reinforcement having at least a first and a second actuation ply, At least one working ply is a reinforcing fabric according to any one of claims 1 to 9. A pneumatic tire characterized by its features.

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