WO2019197769A1 - Tire, the carcass reinforcement of which is reinforced with a ply of reinforcing elements in the bead region - Google Patents

Tire, the carcass reinforcement of which is reinforced with a ply of reinforcing elements in the bead region Download PDF

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Publication number
WO2019197769A1
WO2019197769A1 PCT/FR2019/050821 FR2019050821W WO2019197769A1 WO 2019197769 A1 WO2019197769 A1 WO 2019197769A1 FR 2019050821 W FR2019050821 W FR 2019050821W WO 2019197769 A1 WO2019197769 A1 WO 2019197769A1
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WO
WIPO (PCT)
Prior art keywords
reinforcing elements
layer
tire
stiffener
equal
Prior art date
Application number
PCT/FR2019/050821
Other languages
French (fr)
Inventor
Nathalie Salgues
Christophe Gayton
Katia BARAN
Arnaud Gommez
Original Assignee
Compagnie Generale Des Etablissements Michelin
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from FR1853079A external-priority patent/FR3079838B1/en
Priority claimed from FR1903284A external-priority patent/FR3094273A1/en
Application filed by Compagnie Generale Des Etablissements Michelin filed Critical Compagnie Generale Des Etablissements Michelin
Publication of WO2019197769A1 publication Critical patent/WO2019197769A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/04—Carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
    • B60C2001/005—Compositions of the bead portions, e.g. clinch or chafer rubber or cushion rubber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C15/00—Tyre beads, e.g. ply turn-up or overlap
    • B60C15/06—Flipper strips, fillers, or chafing strips and reinforcing layers for the construction of the bead
    • B60C15/0628—Flipper strips, fillers, or chafing strips and reinforcing layers for the construction of the bead comprising a bead reinforcing layer
    • B60C2015/065—Flipper strips, fillers, or chafing strips and reinforcing layers for the construction of the bead comprising a bead reinforcing layer at the axially outer side of the carcass turn-up portion not wrapped around the bead core
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C15/00—Tyre beads, e.g. ply turn-up or overlap
    • B60C15/06—Flipper strips, fillers, or chafing strips and reinforcing layers for the construction of the bead
    • B60C15/0628—Flipper strips, fillers, or chafing strips and reinforcing layers for the construction of the bead comprising a bead reinforcing layer
    • B60C2015/0685—Physical properties or dimensions of the cords, e.g. modulus of the cords
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C15/00—Tyre beads, e.g. ply turn-up or overlap
    • B60C15/06—Flipper strips, fillers, or chafing strips and reinforcing layers for the construction of the bead
    • B60C15/0628—Flipper strips, fillers, or chafing strips and reinforcing layers for the construction of the bead comprising a bead reinforcing layer
    • B60C2015/0685—Physical properties or dimensions of the cords, e.g. modulus of the cords
    • B60C2015/0689—Cord density in width direction
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K2201/00—Specific properties of additives
    • C08K2201/002—Physical properties
    • C08K2201/006—Additives being defined by their surface area

Definitions

  • the present invention relates to a tire, radial carcass reinforcement and more particularly to a tire intended to equip vehicles carrying heavy loads and rolling at a high speed, such as, for example, trucks, tractors, trailers or road buses.
  • the carcass reinforcement is anchored on both sides in the bead zone and is radially surmounted by a crown reinforcement consisting of at least two layers, superimposed and formed of son or parallel cables in each layer and crossed from one layer to the next in making with the circumferential direction angles between 10 ° and 45 °.
  • Said working layers, forming the working armature can still be covered with at least one so-called protective layer and formed of advantageously metallic and extensible reinforcing elements, called elastic elements.
  • It may also comprise a layer of low extensibility wires or metal cables forming with the circumferential direction an angle of between 45 ° and 90 °, this so-called triangulation ply being radially located between the carcass reinforcement and the first ply of plywood.
  • so-called working top formed of parallel wires or cables having angles at most equal to 45 ° in absolute value.
  • the triangulation ply forms with at least said working ply a triangulated reinforcement, which presents, under the different stresses it undergoes, few deformations, the triangulation ply having the essential role of taking up the transverse compression forces of which the object all the reinforcing elements in the area of the crown of the tire.
  • Cables are said to be inextensible when said cables have under a tensile force equal to 10% of the breaking force a relative elongation of at most equal to Cables are said elastic when said cables have under tensile force equal to the breaking load a relative elongation of at least 3% with a maximum tangent modulus of less than 150 GPa.
  • Circumferential reinforcing elements are reinforcing elements which make angles with the circumferential direction in the range + 2.5 °, -2.5 ° around 0 °.
  • the circumferential direction of the tire is the direction corresponding to the periphery of the tire and defined by the rolling direction of the tire.
  • the transverse or axial direction of the tire is parallel to the axis of rotation of the tire.
  • the radial direction is a direction intersecting the axis of rotation of the tire and perpendicular to it.
  • the axis of rotation of the tire is the axis around which it rotates in normal use.
  • a radial or meridian plane is a plane which contains the axis of rotation of the tire.
  • the circumferential mid-plane is a plane perpendicular to the axis of rotation of the tire and which divides the tire into two halves.
  • modulus of elasticity of a rubber mix, a secant modulus of extension at 10% deformation and at room temperature.
  • the modulus measurements are made in tension according to the AFNOR-NFT-46002 standard of September 1988: the secant modulus is measured in second elongation (ie, after an accommodation cycle). nominal (or apparent stress, in MPa) at 10% elongation (normal conditions of temperature and hygrometry according to AFNOR-NFT-40101 of December 1979).
  • Such tires still usually comprise at the beads one or more layers of reinforcing elements called stiffeners or tongues. These layers are usually made of reinforcing elements oriented relative to the circumferential direction of an angle less than 45 °, and usually less than 25 °.
  • These reinforcing element layers have the particular function of limiting the longitudinal displacements of the constituent materials of the bead relative to the rim of the wheel to limit premature wear of said bead. They also make it possible to limit the permanent deformation of the bead on the rim hook, due to the phenomenon of dynamic creep of the elastomeric materials; this deformation of the bead can prevent the retreading of the tires when it is excessive. They further contribute to the protection of the low areas of the tire against the aggressions suffered during the assembly and disassembly of the tires on the rims.
  • layers of reinforcing elements or stiffener can further prevent or delay the unwinding of the carcass reinforcement during accidental and excessive heating of the rim.
  • An object of the invention is to provide lightweight tires whose properties including endurance are preserved regardless of the use.
  • a radial carcass reinforcement tire comprising a crown reinforcement, the latter being capped radially with a tread, said tread being joined to two beads via of two flanks, at least one layer of reinforcing elements of the carcass reinforcement being anchored in each of the beads by turning around a bead wire, said carcass reinforcement overturning being reinforced by at least one layer of elements reinforcement or stiffener, the reinforcement elements of said at least one stiffener being cables whose diameter is less than 1.1 mm, the distribution pitch of said cables in said at least one stiffener being less than 2.1 mm, the rigidity of said cables at said at least one stiffener being greater than 190 GPa and the calendering layers of said at least one stiffener being made of an elastomeric mixture based on e natural rubber or synthetic polyisoprene predominantly chained cis-l, 4 and optionally at least one other diene elastomer, the natural rubber or synthetic polyisoprene in case of
  • BET specific surface measurement is carried out according to the method of BRUNAUER, EMMET and TELLER described in "The Journal of the American Chemical Society", vol. 60, page 309, February 1938, corresponding to standard NFT 45007 of November 1987.
  • the structure index of black COAN (Compressed Oil Absorption Number) is measured according to the ASTM D3493 standard.
  • a white filler is a filler of silica and / or alumina type having SiOH and / or AlOH surface functions chosen from the group formed by precipitated or pyrogenic silicas, aluminas or aluminosilicates. .
  • reinforcing fillers having the morphology and SiOH and / or AlOH surface functions of the silica and / or alumina materials and which can be used according to the invention as partial or total replacement thereof
  • the crosslinking density measurements are made from the equilibrium swelling method.
  • the mixtures, prepared in the form of samples are swollen in cyclohexane for 72 hours.
  • the weight of the samples is measured immediately after removing the excess solvent with blotting paper.
  • the swelling of the samples and the absorption of solvent is inversely proportional to the presence and therefore to the density of crosslinking bridges.
  • the samples are then dried under vacuum until a constant weight is reached. From the difference between the two measured weight values, a swelling rate is deduced. Blackness swelling restriction is dispensed with by applying Flory Rhener's theory described in "Journal of Applied Polymer Science, 2016, 133, 43932". It is thus possible to determine the pontic density in 10 5 mol / cm 3 .
  • the carbon black content whose BET specific surface area is at most equal to 30 m 2 / g is between 20 and 80 phr, preferably between 40 and 65 phr. and more preferably between 45 and 60 phr.
  • said carbon black whose BET surface area is at most equal to 30 m 2 / g has a COAN index of at least 65 ml / 100 g, and preferably at least 70 ml / 100 g.
  • said carbon black whose BET specific surface area is at most equal to 30 m 2 / g has a COAN index of at most 90 mElOO g.
  • the BET specific surface area of said carbon black at most equal to 30 m 2 / g is at most equal to 25 m 2 / g, and preferably greater than 15 m 2 / g.
  • a coupling agent and / or covering selected from agents known to those skilled in the art.
  • preferential coupling agents are sulphurised alkoxysilanes of the bis (3-trialkoxysilylpropyl) polysulfide type, and of these, in particular, bis (3-triethoxysilylpropyl) tetrasulfide marketed by DEGUSSA under the Si69 denominations for pure liquid product and X50S for solid product (50/50 by weight blend with N330 black).
  • coating agents examples include a fatty alcohol, an alkylalkoxysilane such as hexadecyltrimethoxy or triethoxysilane respectively marketed by DEGUSSA under the names Sil 16 and Si 16, diphenylguanidine, a polyethylene glycol, a silicone oil which may be modified with OH or alkoxy functions.
  • the covering agent and / or coupling agent is used in a weight ratio relative to the filler> at 1/100 and ⁇ at 20/100, and preferably between 2/100 and 15/100 when the clear filler represents the all of the reinforcing filler and between 1/100 and 20/100 when the reinforcing filler is constituted by a carbon black and clear charge cutting.
  • diene elastomers which can be used in a blend with natural rubber or a synthetic polyisoprene with a majority of cis-1,4 linkages
  • BR polybutadiene
  • SBR styrene-butadiene copolymer
  • BIR butadiene-isoprene copolymer
  • SBIR styrene-butadiene-isoprene terpolymer
  • elastomers may be modified elastomers during polymerization or after polymerization by means of branching agents such as divinylbenzene or starch agents such as carbonates, halogenotins, halosilicons or else by means of functionalization leading to grafting on the chain or at the end of the chain of oxygen functions carbonyl, carboxyl or an amine function such as for example by the action of dimethyl or diethylamino benzophenone.
  • branching agents such as divinylbenzene or starch agents
  • carbonates, halogenotins, halosilicons or else by means of functionalization leading to grafting on the chain or at the end of the chain of oxygen functions carbonyl, carboxyl or an amine function such as for example by the action of dimethyl or diethylamino benzophenone.
  • the natural rubber or the synthetic polyisoprene is preferably used at a majority rate. and more preferably at a rate greater than 70 phr.
  • the cables of said stiffener in the tire according to the invention having diameters smaller than in the more usual designs contribute to lighten the tire, although the distribution pitch of said cables are smaller than those of said more usual designs. Furthermore, these smaller cables associated with smaller steps lead to a lightening of the rubbery mass due to a reduced mass of calender layers, the size of the intervals between cables being reduced in two directions.
  • elastomeric mixtures comprising a black carbon type filler having a BET specific surface area at most equal to 30 m 2 / g and an oil absorption index of Compressed samples (COAN) at least equal to 60 ml / 100 g makes it possible to confer on the layers of calenders properties including elongation at break enabling the endurance properties of the tire to be retained despite the use of cables of small diameters. It is indeed known to those skilled in the art that such cables associated with pitch between cables smaller than the usual designs lead to performance in terms of reduced endurance during heavy demands. Common mixtures that present a lower breaking elongation does not effectively reduce the distance between the cables at the risk of promoting the propagation of cracks that initiate cable ends.
  • the elongation at break of the calendering layers of said at least one stiffener is greater than 120%.
  • the elongation at break (in%) is measured in accordance with the AFNOR-NF-T-46-002 standard of September 1988.
  • the tensile measurements to determine the breaking properties are carried out at a temperature of 100 ° C. C ⁇ 2 ° C, and under normal humidity conditions (50 ⁇ 5% relative humidity), according to the French standard NF T 40-101 (December 1979).
  • a measurement is made on samples taken directly from a new tire and another measurement is carried out on samples taken from a new tire and which are first aged for 10 days at 77 ° C. in air. This aging simulates an extreme use of the tire throughout its lifetime.
  • the modulus of elasticity under tension at 10% elongation of the calendering layers of said at least one stiffener is less than 8.5 MPa.
  • tensile modulus of elasticity at 10% elongation of the calenders of the stiffeners are greater than 8.5 MPa and most often greater than 9 MPa.
  • the maximum value of tan ( ⁇ ), denoted tan ( ⁇ ) max , of the calendering layers of said at least one stiffener is less than 0.055.
  • the loss factor tan ( ⁇ ) is a dynamic property of the layer of rubber mix. It is measured on a viscoanalyzer (Metravib VA4000), according to ASTM D 5992-96. The response of a sample of vulcanized composition is recorded (Cylindrical specimen 2 mm thick and 78 mm 2 in section) subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, at a temperature of 100 ° C. A strain amplitude sweep of 0.1 to 50% (forward cycle) and then 50% to 1% (return cycle) are performed. For the return cycle, the maximum value of tan ( ⁇ ) observed, denoted tan ( ⁇ ) max, is indicated .
  • the rolling resistance is the resistance that appears when the tire rolls. It is represented by the hysteretic losses related to the deformation of the tire during a revolution.
  • the frequency values related to the revolution of the tire correspond to values of tan ( ⁇ ) measured between 30 ° C. and 100 ° C.
  • the value of tan ( ⁇ ) at 100 ° C thus corresponds to an indicator of the rolling resistance of the rolling tire.
  • said reinforcing elements of said at least one stiffener are saturated layer cables, at least one inner layer being sheathed with a layer consisting of a polymeric composition such that a non-crosslinkable, crosslinkable or crosslinked rubber composition, preferably based on at least one diene elastomer.
  • So-called “layered cords” or “multilayer” cables are cables consisting of a central core and one or more layers of strands or substantially concentric son disposed around this central core.
  • a saturated layer of a layered cable is a layer consisting of wires in which there is not enough room to add at least one additional wire.
  • the inventors have demonstrated that the presence of the cables as just described as strengthening elements of the working crown layers can contribute to better performance in terms of endurance. Indeed, it appears as explained above that the rubber mixtures calendering said at least one stiffener can reduce the rolling resistance of the tire. This results in lower temperatures of these rubber mixes, when using the tire, which can cause less protection of the reinforcing elements vis-à-vis the oxidation phenomena in some cases of use of the tire.
  • the properties of the rubber compounds relating to the oxygen blocking decrease with temperature and the presence of oxygen can lead to a gradual degeneration of the mechanical properties of the cables, for the most severe driving conditions, and can alter the lifetime of these cables.
  • composition based on at least one diene elastomer is understood to mean, in a known manner, that the composition comprises predominantly (i.e. in a mass fraction greater than 50%) this or these diene elastomers.
  • sheath according to the invention extends continuously around the layer it covers (that is to say that this sheath is continuous in the "orthoradial" direction of the cable which is perpendicular to its radius), so as to form a continuous sleeve of cross section which is preferably substantially circular.
  • the rubber composition of this sheath may be crosslinkable or crosslinked, that is to say that it comprises by definition a crosslinking system adapted to allow the crosslinking of the composition during its baking ( ie, its hardening and not its fusion); thus, this rubber composition can be described as infusible, since it can not be melted by heating at any temperature.
  • elastomer or "diene” rubber is meant in known manner an elastomer derived at least in part (ie a homopolymer or a copolymer) from monomers dienes (monomers bearing two carbon-carbon double bonds, conjugated or otherwise).
  • the system for crosslinking the rubber sheath is a so-called vulcanization system, that is to say based on sulfur (or a sulfur donor agent) and a primary accelerator of vulcanization.
  • vulcanization system based on sulfur (or a sulfur donor agent) and a primary accelerator of vulcanization.
  • sulfur or a sulfur donor agent
  • a primary accelerator of vulcanization To this basic vulcanization system may be added various known secondary accelerators or vulcanization activators.
  • the rubber composition of the sheath according to the invention may comprise, in addition to said crosslinking system, all the usual ingredients that can be used in tire rubber compositions, such as reinforcing fillers based on carbon black and / or a reinforcing inorganic filler such as silica, anti-aging agents, for example antioxidants, extension oils, plasticizers or agents facilitating the use of the compositions in the raw state, acceptors and donors of methylene, resins, bismaleimides, known adhesion promoter systems of the "RFS" type (resorcinol-formaldehyde-silica) or metal salts, especially cobalt salts.
  • anti-aging agents for example antioxidants, extension oils, plasticizers or agents facilitating the use of the compositions in the raw state
  • acceptors and donors of methylene, resins, bismaleimides known adhesion promoter systems of
  • the composition of this sheath is chosen identical to the composition used for the calender layer of said at least one stiffener that the cables are intended to reinforce.
  • the composition of this sheath is chosen identical to the composition used for the calender layer of said at least one stiffener that the cables are intended to reinforce.
  • said cables of said at least one stiffener are cables with building layers [L + M], having a first layer C1 to L son of diameter di wound together in a helix according to a step pi with L ranging from 1 to 4, surrounded by at least one intermediate layer C2 to M son of diameter d 2 wound together in a helix in a pitch p 2 with M ranging from 3 to 12, a sheath made of a rubber composition non-crosslinkable, crosslinkable or crosslinked based on at least one diene elastomer, covering, in the construction, said first layer C 1.
  • the diameter of the wires of the first layer of the inner layer (Cl) is between 0.10 and 0.5 mm and the diameter of the wires of the outer layer (C2) is between 0.10 and 0.5 mm and more preferably the diameter of the son of the layers (C1) and (C2) is greater than 0.2 mm.
  • the pitch of the winding helix of said son of the outer layer (C2) is between 8 and 25 mm.
  • the pitch of the helix represents the length, measured parallel to the axis of the cable, at the end of which a wire having this pitch performs a complete revolution around the axis of the cable; thus, if the axis is divided by two planes perpendicular to said axis and separated by a length equal to the pitch of a wire of a constituent layer of the cable, the axis of this wire has in these two planes the same position on the two circles corresponding to the layer of the wire considered.
  • Said cables according to the invention may be obtained according to various techniques known to those skilled in the art, for example in two steps, first by sheathing via an extrusion head of the core or layers Cl, step followed in a second step of a final operation of wiring or twisting the remaining M son (layer C2) around the layer Cl and sheathed.
  • the problem of stickiness in the green state posed by the rubber sheath, during any intermediate operations of winding and uncoiling can be solved in a manner known to those skilled in the art, for example by the use of a spacer film. plastic material.
  • Such cables of at least one stiffener are for example selected from the cables described in patent applications WO 2006/013077 and WO 2009/083212.
  • the crown reinforcement is formed of at least two working crown layers of reinforcement elements, crossed from one layer to the other by making with the direction circumferential angles between 10 ° and 45 °.
  • the reinforcing elements of said at least two working crown layers are inextensible.
  • the crown reinforcement comprises a layer of circumferential reinforcing elements.
  • the layer of circumferential reinforcing elements is radially arranged between two working crown layers.
  • the reinforcing elements of at least one layer of circumferential reinforcing elements are metal reinforcing elements having a secant modulus at 0.7% elongation between 10 and 120 GPa and a maximum tangent modulus less than 150 GPa.
  • a preferred embodiment of the invention further provides that the crown reinforcement is completed radially on the outside by at least one additional layer, called protective layer, of so-called elastic reinforcing elements, oriented with respect to the direction. circumferential with an angle between 10 ° and 45 ° and in the same direction as the angle formed by the inextensible elements of the working layer which is radially adjacent thereto.
  • the crown reinforcement can be further completed, radially inwardly between the carcass reinforcement and the nearest radially inner working layer. of said carcass reinforcement, by a triangulation layer of steel non-extensible reinforcing elements making, with the circumferential direction, an angle greater than 60 ° and in the same direction as that of the angle formed by the reinforcing elements of the layer radially closest to the carcass reinforcement.
  • the tire according to the invention as just described therefore has a reduced mass in comparison with more usual tires while maintaining performance in terms of endurance comparable.
  • the tire 1, of dimension 315/70 R 22.5 comprises a radial carcass reinforcement 2 anchored in two beads 3, around rods 4.
  • the carcass reinforcement 2 is formed of a single layer wire ropes.
  • the carcass reinforcement 2 is fretted by a crown reinforcement 5, itself capped with a tread 6.
  • the crown reinforcement 5 is formed radially from the inside to the outside: of a layer of triangulation 51 formed of non-waisted metal cables 2 + 7x0.28, continuous over the entire width of the web, oriented by an angle equal to 65 °, of a first working layer 52 formed of non-stretched inextensible metal cables 0.12 + 3 + 8x0.35, continuous over the entire width of the web, oriented at an angle equal to 18 °, of a second working layer 53 formed of inextensible non-woven wire cables 0.12 + 3 + 8x0.35, continuous over the entire width of the web, oriented at an angle of 18 ° and crossed with the metal cables of the first working layer, - a protective layer 54 formed of elastic metal cables 3x2x0.35.
  • the carcass reinforcement layer 2 is wound around a bead wire 4 to form an upturn 7.
  • the upturn 7 is further reinforced by a layer of reinforcing elements or stiffener 8 which comes capping the end 9 of the upturn 7.
  • the cables of the stiffeners 8 are two-layer assemblies consisting of 9 son of 0.26 mm.
  • the cables thus formed have a diameter d of 1 mm and therefore less than 1.1 mm.
  • the steel wires forming the cables have a SHT grade.
  • the distribution pitch of said cables in the stiffeners 8 is equal to 2 mm and therefore less than 2.1 mm.
  • the stiffness of the stiffener cables 8 is equal to 196 GPa and is greater than 190 GPa.
  • the calendering layers of the stiffeners 8 are made from the following mixture I:
  • the values of the constituents are expressed in phr (parts by weight per hundred parts of elastomers).
  • the mass of the stiffener comprising the mass of the metal cables and calendering mixtures, is equal to 0.44 Kg.
  • the mass of the tire I is equal to 59.56 Kg.
  • the crosslinking density measured according to the equilibrium swelling method on the calendering layers of the stiffeners 8 is 19.10 5 mol / crrf and therefore between 13.10 5 mol / crrf and 21.10. 5 mol / cm
  • the modulus of elasticity under tension at 10% elongation of the calendering layers of the stiffeners 8 is equal to 5.7 MPa and therefore less than 8.5 MPa.
  • tan ( ⁇ ) max of the calender layers of the stiffeners 8 is equal to 0.050 and therefore less than 0.055. Tests have been made with different tires made according to the invention in accordance with the representation of the figure and compared with a reference tire T1 also according to the representation of the figure.
  • the tire T1 differs from the tire according to the invention on the one hand, by the nature of the constituent mixtures the calendering layers of the stiffeners 8 and on the other hand, by the cables of the stiffeners 8 which are 9.35 cables whose diameter is equal to 1.35 mm, the steel wires forming said cables having a grade SHT.
  • the distribution pitch of said cables in the stiffeners 8 of the tire T1 is equal to 2.5 mm.
  • the stiffness of the stiffener cables 8 of the tire T1 is equal to 185 GPa.
  • the calendering layers of the stiffeners 8 of the reference tire T1 are made from the following mixture R1:
  • the cumulative mass of the stiffeners 8 of the tire R1 comprising the mass of the metal cables and calendering mixtures, is equal to 0.58 Kg.
  • the mass of the tire Tl is equal to 59.7 Kg.
  • the crosslinking density measured according to the equilibrium swelling method on the calendering layers of the stiffeners 8 of the tire T1 is equal to 25.10 5 mol / cm 3 .
  • the tensile modulus of elasticity at 10% elongation of the stiffening calender layers 8 of the tire T1 is equal to 6.12 MPa.
  • tan ( ⁇ ) max of the stiffening layer layers 8 of the tire T1 is equal to 0.056.
  • the elongation at break of the mixtures I and Rl is measured on samples taken on a new tire.
  • a first measurement is performed on the sample taken. Another measurement is performed on a sample taken and then aged for 10 days at 77 ° C in air.
  • the elongation at break (in%) is measured in accordance with the AFNOR-NF-T-46-002 standard of September 1988.
  • the tensile measurements to determine the breaking properties are carried out at a temperature of 100 ° C. C ⁇ 2 ° C, and under normal humidity conditions (50 ⁇ 5% relative humidity), according to the French standard NF T 40-101 (December 1979).
  • Tire rolling tests corresponding to severe conditions of use of the tires were made. These tests are carried out with the tires according to the invention and the reference tires. Before carrying out the tests, the tires undergo an accelerated aging in an oven under conditions of oxygen content of the inflation gas and temperature, adapted to produce a state of thermooxidation of materials representative of average use for a lifetime in clientele. The tires are rolled on a steering wheel under load conditions 20% higher than the rated load and inflation 20% higher than the nominal pressure.
  • the tests are stopped during the appearance of a degradation of the bead area of the tire.
  • the tires are then peeled to allow analysis of the calendering layers of the stiffeners. While the reference tires R1 have highly propagated cracks that could potentially lead to tire failure, the tires according to the invention only have crack initiators at the ends of the stiffeners, which have only been very slightly propagated. .

Abstract

The invention relates to a tire comprising a ply of reinforcement elements reinforcing the carcass reinforcement which is anchored in each of the beads by being wrapped around a bead core, said wrapped-around portion of the carcass reinforcement being reinforced by a stiffener. According to the invention, the stiffener reinforcing elements are in the form of cords which have a diameter of less than 1.1 mm and which are disposed at intervals of less than 2.1 mm, the stiffness of the cords being greater than 190 GPa, and the skim coats being composed of an elastomer blend that contains, as a reinforcing filler, predominantly at least one carbon black having a maximum specific surface area BET of 30 m2/g and a COAN index of at least 60 ml/100 g, the crosslinking density, measured according to the equilibrium swelling method, ranging from 13.10-5 mol/cm3 to 21.10-5 mol/cm3 in the skim coats.

Description

PNEUMATIQUE DONT E’ARMATURE DE CARCASSE EST RENFORCEE PAR UNE COUCHE D’EEEMENTS DE RENFORCEMENT DANS EA ZONE  PNEUMATIC WHOSE EARMATURE OF CARCASS IS REINFORCED BY A REINFORCING ELEMENT LAYER IN THE AREA
DU BOURREEET  BOURREEET
[0001] La présente invention concerne un pneumatique, à armature de carcasse radiale et plus particulièrement un pneumatique destiné à équiper des véhicules portant de lourdes charges et roulant à vitesse soutenue, tels que, par exemple les camions, tracteurs, remorques ou bus routiers. [0002] D'une manière générale dans les pneumatiques de type poids-lourds, l'armature de carcasse est ancrée de part et d'autre dans la zone du bourrelet et est surmontée radialement par une armature de sommet constituée d'au moins deux couches, superposées et formées de fils ou câbles parallèles dans chaque couche et croisés d’une couche à la suivante en faisant avec la direction circonférentielle des angles compris entre 10° et 45°. Lesdites couches de travail, formant l’armature de travail, peuvent encore être recouvertes d’au moins une couche dite de protection et formée d’éléments de renforcement avantageusement métalliques et extensibles, dits élastiques. Elle peut également comprendre une couche de fils ou câbles métalliques à faible extensibilité faisant avec la direction circonférentielle un angle compris entre 45° et 90°, cette nappe, dite de triangulation, étant radialement située entre l’armature de carcasse et la première nappe de sommet dite de travail, formées de fils ou câbles parallèles présentant des angles au plus égaux à 45° en valeur absolue. La nappe de triangulation forme avec au moins ladite nappe de travail une armature triangulée, qui présente, sous les différentes contraintes qu'elle subit, peu de déformations, la nappe de triangulation ayant pour rôle essentiel de reprendre les efforts de compression transversale dont est l’objet l’ensemble des éléments de renforcement dans la zone du sommet du pneumatique. The present invention relates to a tire, radial carcass reinforcement and more particularly to a tire intended to equip vehicles carrying heavy loads and rolling at a high speed, such as, for example, trucks, tractors, trailers or road buses. [0002] In general, in heavy-vehicle tires, the carcass reinforcement is anchored on both sides in the bead zone and is radially surmounted by a crown reinforcement consisting of at least two layers, superimposed and formed of son or parallel cables in each layer and crossed from one layer to the next in making with the circumferential direction angles between 10 ° and 45 °. Said working layers, forming the working armature, can still be covered with at least one so-called protective layer and formed of advantageously metallic and extensible reinforcing elements, called elastic elements. It may also comprise a layer of low extensibility wires or metal cables forming with the circumferential direction an angle of between 45 ° and 90 °, this so-called triangulation ply being radially located between the carcass reinforcement and the first ply of plywood. so-called working top, formed of parallel wires or cables having angles at most equal to 45 ° in absolute value. The triangulation ply forms with at least said working ply a triangulated reinforcement, which presents, under the different stresses it undergoes, few deformations, the triangulation ply having the essential role of taking up the transverse compression forces of which the object all the reinforcing elements in the area of the crown of the tire.
[0003] Des câbles sont dits inextensibles lorsque lesdits câbles présentent sous une force de traction égale à 10% de la force de rupture un allongement relatif au plus égal à [0004] Des câbles sont dits élastiques lorsque lesdits câbles présentent sous une force de traction égale à la charge de rupture un allongement relatif au moins égal à 3% avec un module tangent maximum inférieur à 150 GPa. Cables are said to be inextensible when said cables have under a tensile force equal to 10% of the breaking force a relative elongation of at most equal to Cables are said elastic when said cables have under tensile force equal to the breaking load a relative elongation of at least 3% with a maximum tangent modulus of less than 150 GPa.
[0005] Des éléments de renforcement circonférentiels sont des éléments de renforcement qui font avec la direction circonférentielle des angles compris dans l'intervalle + 2,5°, - 2,5° autour de 0°. [0005] Circumferential reinforcing elements are reinforcing elements which make angles with the circumferential direction in the range + 2.5 °, -2.5 ° around 0 °.
[0006] La direction circonférentielle du pneumatique, ou direction longitudinale, est la direction correspondant à la périphérie du pneumatique et définie par la direction de roulement du pneumatique. [0007] La direction transversale ou axiale du pneumatique est parallèle à l’axe de rotation du pneumatique. The circumferential direction of the tire, or longitudinal direction, is the direction corresponding to the periphery of the tire and defined by the rolling direction of the tire. [0007] The transverse or axial direction of the tire is parallel to the axis of rotation of the tire.
[000S] La direction radiale est une direction coupant l’axe de rotation du pneumatique et perpendiculaire à celui-ci. [0008] The radial direction is a direction intersecting the axis of rotation of the tire and perpendicular to it.
[0009] L’axe de rotation du pneumatique est l’axe autour duquel il tourne en utilisation normale. The axis of rotation of the tire is the axis around which it rotates in normal use.
[0010] Un plan radial ou méridien est un plan qui contient l’axe de rotation du pneumatique. A radial or meridian plane is a plane which contains the axis of rotation of the tire.
[0011] Le plan médian circonférentiel, ou plan équatorial, est un plan perpendiculaire à l’axe de rotation du pneu et qui divise le pneumatique en deux moitiés. [0012] On entend par « module d’élasticité » d’un mélange caoutchouteux, un module sécant d’extension à 10 % de déformation et à température ambiante. The circumferential mid-plane, or equatorial plane, is a plane perpendicular to the axis of rotation of the tire and which divides the tire into two halves. The term "modulus of elasticity" of a rubber mix, a secant modulus of extension at 10% deformation and at room temperature.
[0013] En ce qui concerne les compositions de caoutchouc, les mesures de module sont effectuées en traction selon la norme AFNOR-NFT-46002 de septembre 1988 : on mesure en seconde élongation (i.e., après un cycle d’accommodation) le module sécant nominal (ou contrainte apparente, en MPa) à 10% d'allongement (conditions normales de température et d'hygrométrie selon la norme AFNOR-NFT-40101 de décembre 1979). [0014] De tels pneumatiques comportent encore usuellement au niveau des bourrelets une ou plusieurs couches d’éléments de renforcement appelés raidisseurs ou languettes. Ces couches sont le plus souvent constituées d’éléments de renforcement orientés par rapport à la direction circonférentielle d’un angle inférieur à 45°, et le plus souvent inférieur à 25°. Ces couches d’éléments de renforcements ont notamment pour fonction de limiter les déplacements longitudinaux des matériaux constitutifs du bourrelet par rapport à la jante de la roue pour limiter une usure prématurée dudit bourrelet. Elles permettent également de limiter la déformation permanente du bourrelet sur le crochet de jante, due au phénomène de fluage dynamique des matériaux élastomériques ; cette déformation du bourrelet peut empêcher le rechapage des pneumatiques lorsqu’elle est excessive. Elles contribuent encore à la protection des zones basses du pneumatique contre les agressions subies lors du montage et du démontage des pneumatiques sur les jantes. As regards the rubber compositions, the modulus measurements are made in tension according to the AFNOR-NFT-46002 standard of September 1988: the secant modulus is measured in second elongation (ie, after an accommodation cycle). nominal (or apparent stress, in MPa) at 10% elongation (normal conditions of temperature and hygrometry according to AFNOR-NFT-40101 of December 1979). Such tires still usually comprise at the beads one or more layers of reinforcing elements called stiffeners or tongues. These layers are usually made of reinforcing elements oriented relative to the circumferential direction of an angle less than 45 °, and usually less than 25 °. These reinforcing element layers have the particular function of limiting the longitudinal displacements of the constituent materials of the bead relative to the rim of the wheel to limit premature wear of said bead. They also make it possible to limit the permanent deformation of the bead on the rim hook, due to the phenomenon of dynamic creep of the elastomeric materials; this deformation of the bead can prevent the retreading of the tires when it is excessive. They further contribute to the protection of the low areas of the tire against the aggressions suffered during the assembly and disassembly of the tires on the rims.
[0015] Par ailleurs, dans le cas d’ancrage de l’armature de carcasse réalisé autour d’une tringle, qui consiste à enrouler au moins en partie l’armature de carcasse autour d’une tringle dans chacun des bourrelets en formant un retournement s’étendant plus ou moins haut dans le flanc, les couches d’éléments de renforcement ou raidisseur permettent encore d’éviter ou de retarder le déroulement de l’armature de carcasse lors d’échauffements accidentels et excessifs de la jante. Furthermore, in the case of anchoring the carcass reinforcement made around a rod, which consists in winding at least part of the carcass reinforcement around a rod in each of the beads forming a reversal extending more or less in the sidewall, layers of reinforcing elements or stiffener can further prevent or delay the unwinding of the carcass reinforcement during accidental and excessive heating of the rim.
[0016] Ces couches d’éléments de renforcement ou raidisseurs sont le plus souvent disposées axialement à l’extérieur du retournement de l’armature de carcasse et s’étendent sur une hauteur dans le flanc radialement extérieure à celle du retournement de l’armature de carcasse notamment pour couvrir les extrémités libres des éléments de renforcement dudit retournement. These layers of reinforcing elements or stiffeners are most often arranged axially outside the overturning of the carcass reinforcement and extend over a height in the flank radially external to that of the upturn of the reinforcement. carcass including to cover the free ends of the reinforcing elements of said reversal.
[0017] Bien que les pneumatiques ne soient pas prévus pour ces cas, il est connu que dans certains pays les pneumatiques sont utilisés en dehors des conditions normales notamment en termes de charges portées et de pression de gonflage. La présence de couches d’éléments de renforcement ou raidisseurs permet encore d’améliorer la résistance des pneumatiques à de telles sollicitations. En effet, il semble que le raidisseur va protéger l’armature de carcasse dans la zone du bourrelet du pneumatique contre ces sollicitations correspondant à des usages excessifs. [0018] Un but de l’invention est de fournir des pneumatiques allégés dont les propriétés notamment d’endurance sont conservées quel que soit l’usage. Although the tires are not provided for these cases, it is known that in some countries the tires are used outside normal conditions, particularly in terms of loads and inflation pressure. The presence of layers of reinforcing elements or stiffeners makes it possible to improve the resistance of the tires to such stresses. Indeed, it seems that the stiffener will protect the carcass reinforcement in the area of the bead of the tire against these stresses corresponding to excessive use. An object of the invention is to provide lightweight tires whose properties including endurance are preserved regardless of the use.
[0019] Ce but est atteint selon l’invention par un pneumatique armature de carcasse radiale comprenant une armature de sommet, celle-ci étant coiffée radialement d’une bande de roulement, ladite bande de roulement étant réunie à deux bourrelets par l’intermédiaire de deux flancs, au moins une couche d’éléments de renforcement de l’armature de carcasse étant ancrée dans chacun des bourrelets par retournement autour d’une tringle, ledit retournement d’armature de carcasse étant renforcé par au moins une couche d’éléments de renforcement ou raidisseur, les éléments de renforcement dudit au moins un raidisseur étant des câbles dont le diamètre est inférieur à 1.1 mm, le pas de répartition desdits câbles dans ledit au moins un raidisseur étant inférieur à 2.1 mm, la rigidité desdits câbles dudit au moins un raidisseur étant supérieure à 190 GPa et les couches de calandrage dudit au moins un raidisseur étant constituées d’un mélange élastomérique à base de caoutchouc naturel ou de polyisoprène synthétique à majorité d'enchaînements cis-l,4 et éventuellement d'au moins un autre élastomère diénique, le caoutchouc naturel ou le polyisoprène synthétique en cas de coupage étant présent à un taux majoritaire par rapport au taux de l'autre ou des autres élastomères diéniques utilisés et d'une charge renforçante comprenant majoritairement au moins un noir de carbone, présentant une surface spécifique BET au plus égale à 30 m2/g et un indice d’absorption d’huile d’échantillons comprimés (COAN) au moins égal à 60 ml/ 100 g, ledit mélange élastomérique ne comprenant pas, ou comprenant au plus 20 pce, et de préférence au plus 10 pce de noir de carbone dont la surface spécifique BET est supérieure à 30 m2/g et l’indice COAN est supérieur à 40 ml/ 100 g, ledit mélange élastomérique ne comprenant pas, ou comprenant au plus 20 pce, et de préférence au plus 10 pce de charge blanche et la densité de réticulation mesurée selon la méthode de gonflement à l’équilibre étant comprise entre 13.10 5 mol/crrf et 21.10 5 mol/crrf dans ledit mélange élastomérique constituant les couches de calandrage dudit au moins un raidisseur. This object is achieved according to the invention by a radial carcass reinforcement tire comprising a crown reinforcement, the latter being capped radially with a tread, said tread being joined to two beads via of two flanks, at least one layer of reinforcing elements of the carcass reinforcement being anchored in each of the beads by turning around a bead wire, said carcass reinforcement overturning being reinforced by at least one layer of elements reinforcement or stiffener, the reinforcement elements of said at least one stiffener being cables whose diameter is less than 1.1 mm, the distribution pitch of said cables in said at least one stiffener being less than 2.1 mm, the rigidity of said cables at said at least one stiffener being greater than 190 GPa and the calendering layers of said at least one stiffener being made of an elastomeric mixture based on e natural rubber or synthetic polyisoprene predominantly chained cis-l, 4 and optionally at least one other diene elastomer, the natural rubber or synthetic polyisoprene in case of cutting being present at a majority rate compared to the rate of the other or the other diene elastomers used and a reinforcing filler comprising predominantly at least one carbon black, having a BET specific surface area at most equal to 30 m 2 / g and an oil absorption index of samples tablets (COAN) at least equal to 60 ml / 100 g, said elastomeric mixture not comprising, or comprising at most 20 phr, and preferably at most 10 phr of carbon black whose BET surface area is greater than 30 m 2 and g / the COAN index is greater than 40 ml / 100 g, said elastomeric mixture not comprising, or comprising at most 20 phr, and preferably at most 10 phr of white filler and the crosslink density. the measure measured according to the equilibrium swelling method being between 13.10 5 mol / crrf and 21.10 5 mol / crrf in said elastomeric mixture constituting the calendering layers of said at least one stiffener.
[0020] La mesure de surface spécifique BET est effectuée selon la méthode de BRUNAUER, EMMET et TELLER décrite dans "The Journal of the American Chemical Society", vol. 60, page 309, février 1938, correspondant à la norme NFT 45007 de novembre 1987. [0021] L’indice de structure du noir COAN (Compressed Oil Absorption Number) est mesuré selon la norme ASTM D3493. BET specific surface measurement is carried out according to the method of BRUNAUER, EMMET and TELLER described in "The Journal of the American Chemical Society", vol. 60, page 309, February 1938, corresponding to standard NFT 45007 of November 1987. The structure index of black COAN (Compressed Oil Absorption Number) is measured according to the ASTM D3493 standard.
[0022] Au sens de l’invention, une charge blanche est une charge de type silice et/ou alumine comportant des fonctions de surface SiOH et/ou AlOH choisie dans le groupe formé par les silices précipitées ou pyrogénées, les alumines ou les aluminosilicates. Within the meaning of the invention, a white filler is a filler of silica and / or alumina type having SiOH and / or AlOH surface functions chosen from the group formed by precipitated or pyrogenic silicas, aluminas or aluminosilicates. .
[0023] Comme autres exemples de charges renforçantes ayant la morphologie et les fonctions de surface SiOH et/ou AlOH des matières de type silice et/ou alumine et pouvant être utilisées selon l'invention en remplacement partiel ou total de celles-ci, on peut citer les noirs de carbone modifiés soit au cours de la synthèse par addition à l'huile d'alimentation du four d’un composé du silicium et/ou d’aluminium soit après la synthèse en ajoutant, à une suspension aqueuse de noir de carbone dans une solution de silicate et/ou d’aluminate de sodium, un acide de façon à recouvrir au moins partiellement la surface du noir de carbone de fonctions SiOH et/ou AlOH. Comme exemples non limitatifs de ce type de charges carbonées avec en surface des fonctions SiOH et/ou AlOH, on peut citer les charges type CSDP décrites dans la Conférence N° 24 du Meeting ACS, Rubber Division, Anaheim, Californie, 6-9 mai 1997 ainsi que celles de la demande de brevet EP-A-0 799 854. As other examples of reinforcing fillers having the morphology and SiOH and / or AlOH surface functions of the silica and / or alumina materials and which can be used according to the invention as partial or total replacement thereof, mention may be made of the modified carbon blacks either during the synthesis by addition to the feed oil of the oven of a silicon and / or aluminum compound or after the synthesis by adding to an aqueous suspension of carbon black. carbon in a solution of silicate and / or sodium aluminate, an acid so as to at least partially cover the surface of the carbon black of SiOH and / or AlOH functions. As non-limiting examples of this type of carbonaceous feedstock with SiOH and / or AlOH functions at the surface, mention may be made of the CSDP type feeds described in Conference No. 24 of the ACS Meeting, Rubber Division, Anaheim, California, May 6-9. 1997 as well as those of the patent application EP-A-0 799 854.
[0024] Selon l’invention, les mesures de densités de réticulation sont effectuées à partir de la méthode de gonflement à l'équilibre. Pour mesurer la densité de réticulation on réalise un gonflement des mélanges, préparés sous forme d’échantillons, dans du cyclohexane pendant 72 heures. On mesure le poids des échantillons immédiatement après avoir évacué l'excès de solvant au moyen d'un papier buvard. Le gonflement des échantillons et l'absorption de solvant est inversement proportionnel à la présence et donc à la densité de ponts de réticulation. According to the invention, the crosslinking density measurements are made from the equilibrium swelling method. In order to measure the crosslinking density, the mixtures, prepared in the form of samples, are swollen in cyclohexane for 72 hours. The weight of the samples is measured immediately after removing the excess solvent with blotting paper. The swelling of the samples and the absorption of solvent is inversely proportional to the presence and therefore to the density of crosslinking bridges.
[0025] Les échantillons sont ensuite séchés sous vide jusqu'à atteindre un poids constant. De la différence entre les deux valeurs de poids mesurées, on en déduit un taux de gonflement. On s’affranchit de la restriction au gonflement liée à la présence de noir en appliquant la théorie de Flory Rhener décrit dans «Journal of applied polymer science, 2016, 133, 43932 ». Il est ainsi possible de déterminer la densité pontale en 10 5 mol/cm3. [0026] Selon un mode de réalisation préféré de l’invention, le taux de noir de carbone dont la surface spécifique BET est au plus égale à 30 m2/g est compris entre 20 et 80 pce, de préférence entre 40 et 65 pce et de préférence encore entre 45 et 60 pce. The samples are then dried under vacuum until a constant weight is reached. From the difference between the two measured weight values, a swelling rate is deduced. Blackness swelling restriction is dispensed with by applying Flory Rhener's theory described in "Journal of Applied Polymer Science, 2016, 133, 43932". It is thus possible to determine the pontic density in 10 5 mol / cm 3 . According to a preferred embodiment of the invention, the carbon black content whose BET specific surface area is at most equal to 30 m 2 / g is between 20 and 80 phr, preferably between 40 and 65 phr. and more preferably between 45 and 60 phr.
[0027] Avantageusement selon l’invention, ledit noir de carbone dont la surface spécifique BET est au plus égale à 30 m2/g présente un indice COAN au moins égal à 65 ml/ 100 g, et de préférence au moins égal à 70 ml/ 100 g. Advantageously according to the invention, said carbon black whose BET surface area is at most equal to 30 m 2 / g has a COAN index of at least 65 ml / 100 g, and preferably at least 70 ml / 100 g.
[0028] Avantageusement encore selon l’invention, ledit noir de carbone dont la surface spécifique BET est au plus égale à 30 m2/g présente un indice COAN au plus égal à 90 mElOO g. [0029] Et de préférence selon l’invention, la surface spécifique BET dudit noir de carbone au plus égale à 30 m2/g est au plus égale à 25 m2/g, et de préférence supérieure à 15 m2/g. Advantageously also according to the invention, said carbon black whose BET specific surface area is at most equal to 30 m 2 / g has a COAN index of at most 90 mElOO g. And preferably according to the invention, the BET specific surface area of said carbon black at most equal to 30 m 2 / g is at most equal to 25 m 2 / g, and preferably greater than 15 m 2 / g.
[0030] Dans le cas d'utilisation de charge claire ou charge blanche, il est nécessaire d’utiliser un agent de couplage et/ou de recouvrement choisi parmi les agents connus de l'homme de l'art. Comme exemples d'agents de couplage préférentiel, on peut citer les alcoxysilanes sulfurés du type polysulfure de bis-(3-trialcoxysilylpropyle), et parmi ceux-ci notamment le tétrasulfure de bis-(3-triéthoxysilylpropyle) commercialisé par la Société DEGUSSA sous les dénominations Si69 pour le produit liquide pur et X50S pour le produit solide (coupage 50/50 en poids avec du noir N330). Comme exemples d’agents de recouvrement on peut citer un alcool gras, un alkylalcoxysilane tel qu'un hexadécyltriméthoxy ou triéthoxysilane respectivement commercialisés par la Société DEGUSSA sous les dénominations Sil 16 et SÎ216, la diphénylguanidine, un polyéthylène glycol, une huile silicone éventuellement modifié au moyen des fonctions OH ou alcoxy. L’agent de recouvrement et/ou de couplage est utilisé dans un rapport pondéral par rapport à la charge > à 1/100 et < à 20/100, et préférentiellement compris entre 2/100 et 15/100 lorsque la charge claire représente la totalité de la charge renforçante et compris entre 1/100 et 20/100 lorsque la charge renforçante est constituée par un coupage de noir de carbone et de charge claire. [0031] Parmi les élastomères diéniques pouvant être utilisés en coupage avec le caoutchouc naturel ou un polyisoprène synthétique à majorité d'enchaînements cis-l,4, on peut citer un polybutadiène (BR) de préférence à majorité d'enchaînements cis-l,4, un copolymère styrène-butadiène (SBR) solution ou émulsion, un copolymère butadiène- isoprène (BIR) ou bien encore un terpolymère styrène-butadiène-isoprène (SBIR). Ces élastomères peuvent être des élastomères modifiés en cours de polymérisation ou après polymérisation au moyen d’agents de ramification comme un divinylbenzène ou d’agents d'étoilage tels que des carbonates, des halogénoétains, des halogénosiliciums ou bien encore au moyen d’agents de fonctionnalisation conduisant à un greffage sur la chaîne ou en bout de chaîne de fonctions oxygénées carbonyle, carboxyle ou bien d’une fonction amine comme par exemple par action de la diméthyl ou de la diéthylamino benzophénone. Dans le cas de coupages de caoutchouc naturel ou de polyisoprène synthétique à majorité d'enchaînements cis-l,4 avec un ou plusieurs des élastomères diéniques, mentionnés ci-dessus, le caoutchouc naturel ou le polyisoprène synthétique est utilisé de préférence à un taux majoritaire et plus préférentiellement à un taux supérieur à 70 pce. In the case of using clear charge or white charge, it is necessary to use a coupling agent and / or covering selected from agents known to those skilled in the art. Examples of preferential coupling agents that may be mentioned are sulphurised alkoxysilanes of the bis (3-trialkoxysilylpropyl) polysulfide type, and of these, in particular, bis (3-triethoxysilylpropyl) tetrasulfide marketed by DEGUSSA under the Si69 denominations for pure liquid product and X50S for solid product (50/50 by weight blend with N330 black). Examples of coating agents that may be mentioned include a fatty alcohol, an alkylalkoxysilane such as hexadecyltrimethoxy or triethoxysilane respectively marketed by DEGUSSA under the names Sil 16 and Si 16, diphenylguanidine, a polyethylene glycol, a silicone oil which may be modified with OH or alkoxy functions. The covering agent and / or coupling agent is used in a weight ratio relative to the filler> at 1/100 and <at 20/100, and preferably between 2/100 and 15/100 when the clear filler represents the all of the reinforcing filler and between 1/100 and 20/100 when the reinforcing filler is constituted by a carbon black and clear charge cutting. Among the diene elastomers which can be used in a blend with natural rubber or a synthetic polyisoprene with a majority of cis-1,4 linkages, mention may be made of a polybutadiene (BR), preferably with a majority of cis-1 linkages, 4, a styrene-butadiene copolymer (SBR) solution or emulsion, a butadiene-isoprene copolymer (BIR) or even a styrene-butadiene-isoprene terpolymer (SBIR). These elastomers may be modified elastomers during polymerization or after polymerization by means of branching agents such as divinylbenzene or starch agents such as carbonates, halogenotins, halosilicons or else by means of functionalization leading to grafting on the chain or at the end of the chain of oxygen functions carbonyl, carboxyl or an amine function such as for example by the action of dimethyl or diethylamino benzophenone. In the case of blends of natural rubber or synthetic polyisoprene with a majority of cis-1,4 with one or more of the diene elastomers mentioned above, the natural rubber or the synthetic polyisoprene is preferably used at a majority rate. and more preferably at a rate greater than 70 phr.
[0032] Les câbles dudit raidisseur dans le pneumatique selon l’invention, présentant des diamètres plus petits que dans les conceptions plus usuelles contribuent à alléger le pneumatique, bien que les pas de répartition desdits câbles soient plus petits que ceux desdites conceptions plus usuelles. Par ailleurs, ces câbles plus petits associés à des pas plus petits conduisent à un allègement de la masse caoutchouteuse du fait d’une masse des couches de calandrage réduites, la dimension des intervalles entre câbles étant réduite selon deux directions. The cables of said stiffener in the tire according to the invention, having diameters smaller than in the more usual designs contribute to lighten the tire, although the distribution pitch of said cables are smaller than those of said more usual designs. Furthermore, these smaller cables associated with smaller steps lead to a lightening of the rubbery mass due to a reduced mass of calender layers, the size of the intervals between cables being reduced in two directions.
[0033] Les inventeurs ont encore su mettre en évidence que le choix des mélanges élastomériques comprenant une charge de type noir de carbone présentant une surface spécifique BET au plus égale à 30 m2/g et un indice d’absorption d’huile d’échantillons comprimés (COAN) au moins égal à 60 ml/ 100 g permet de conférer aux couches de calandrages des propriétés notamment d’allongement à rupture permettant de conserver des propriétés d’endurance du pneumatique malgré l’utilisation de câbles de petits diamètres. Il est en effet connu de l’homme du métier que de tels câbles associés à des pas entre câbles plus petits que selon les conceptions usuelles conduisent à des performances en termes d’endurance réduite lors de sollicitations importantes. Les mélanges usuels qui présentent un allongement à rupture plus faible ne permettent effectivement pas de réduire la distance entre les câbles aux risques de favoriser la propagation des fissures qui s’initient en extrémités de câbles. The inventors have further demonstrated that the choice of elastomeric mixtures comprising a black carbon type filler having a BET specific surface area at most equal to 30 m 2 / g and an oil absorption index of Compressed samples (COAN) at least equal to 60 ml / 100 g makes it possible to confer on the layers of calenders properties including elongation at break enabling the endurance properties of the tire to be retained despite the use of cables of small diameters. It is indeed known to those skilled in the art that such cables associated with pitch between cables smaller than the usual designs lead to performance in terms of reduced endurance during heavy demands. Common mixtures that present a lower breaking elongation does not effectively reduce the distance between the cables at the risk of promoting the propagation of cracks that initiate cable ends.
[0034] Selon une variante avantageuse de réalisation de l’invention, l’allongement à rupture des couches de calandrage dudit au moins un raidisseur est supérieur à 120 %. According to an advantageous embodiment of the invention, the elongation at break of the calendering layers of said at least one stiffener is greater than 120%.
[0035] L’allongement à la rupture (en %) est mesuré conformément à la norme AFNOR- NF-T-46-002 de septembre 1988. Les mesures de traction pour déterminer les propriétés de rupture sont effectuées à la température de l00°C ± 2°C, et dans les conditions normales d'hygrométrie (50 ± 5% d'humidité relative), selon la norme française NF T 40-101 (décembre 1979). Une mesure est réalisée sur des échantillons directement prélevés sur pneumatique neuf et une autre mesure est réalisée sur des échantillons prélevés sur pneumatique neuf et qui subissent au préalable un vieillissement de 10 jours à 77°C sous air. Ce vieillissement simule un usage extrême du pneumatique pendant toute sa durée de vie. [0036] Selon un mode préféré de réalisation de l’invention, le module d’élasticité sous tension à 10 % d’allongement des couches de calandrage dudit au moins un raidisseur est inférieur à 8,5 MPa. The elongation at break (in%) is measured in accordance with the AFNOR-NF-T-46-002 standard of September 1988. The tensile measurements to determine the breaking properties are carried out at a temperature of 100 ° C. C ± 2 ° C, and under normal humidity conditions (50 ± 5% relative humidity), according to the French standard NF T 40-101 (December 1979). A measurement is made on samples taken directly from a new tire and another measurement is carried out on samples taken from a new tire and which are first aged for 10 days at 77 ° C. in air. This aging simulates an extreme use of the tire throughout its lifetime. According to a preferred embodiment of the invention, the modulus of elasticity under tension at 10% elongation of the calendering layers of said at least one stiffener is less than 8.5 MPa.
[0037] L’utilisation de tels mélanges dont les modules d’élasticité sont inférieurs à 8.5 MPa va permettre d’améliorer encore les propriétés du pneumatique en matière d’endurance satisfaisante. The use of such mixtures whose elastic modulus are less than 8.5 MPa will further improve the properties of the tire in terms of satisfactory endurance.
[0038] Habituellement, les modules d’élasticité sous tension à 10 % d’allongement des calandrages des raidisseurs sont supérieurs à 8.5 MPa et le plus souvent supérieurs à 9 MPa. Usually, tensile modulus of elasticity at 10% elongation of the calenders of the stiffeners are greater than 8.5 MPa and most often greater than 9 MPa.
[0039] De préférence encore selon l’invention, la valeur maximale de tan(ô), noté tan(ô)max, des couches de calandrage dudit au moins un raidisseur est inférieure à 0.055. More preferably according to the invention, the maximum value of tan (δ), denoted tan (δ) max , of the calendering layers of said at least one stiffener is less than 0.055.
[0040] Le facteur de perte tan(ô) est une propriété dynamique de la couche de mélange caoutchouteux. Il est mesuré sur un viscoanalyseur (Metravib VA4000), selon la norme ASTM D 5992-96. On enregistre la réponse d’un échantillon de composition vulcanisée (éprouvette cylindrique de 2 mm d’épaisseur et de 78 mm2 de section), soumis à une sollicitation sinusoïdale en cisaillement simple alterné, à la fréquence de lOHz, à une température de l00°C. On effectue un balayage en amplitude de déformation de 0,1 à 50% (cycle aller), puis de 50% à 1% (cycle retour). Pour le cycle retour, on indique la valeur maximale de tan(ô) observée, noté tan(ô)max. The loss factor tan (δ) is a dynamic property of the layer of rubber mix. It is measured on a viscoanalyzer (Metravib VA4000), according to ASTM D 5992-96. The response of a sample of vulcanized composition is recorded (Cylindrical specimen 2 mm thick and 78 mm 2 in section) subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, at a temperature of 100 ° C. A strain amplitude sweep of 0.1 to 50% (forward cycle) and then 50% to 1% (return cycle) are performed. For the return cycle, the maximum value of tan (δ) observed, denoted tan (δ) max, is indicated .
[0041] La résistance au roulement est la résistance qui apparaît lorsque le pneumatique roule. Elle est représentée par les pertes hystérétiques liées à la déformation du pneumatique durant une révolution. Les valeurs de fréquence liées à la révolution du pneumatique correspondent à des valeurs de tan(ô) mesurée entre 30°C et l00°C. La valeur de tan(ô) à 100 °C correspond ainsi à un indicateur de la résistance au roulement du pneumatique en roulage. The rolling resistance is the resistance that appears when the tire rolls. It is represented by the hysteretic losses related to the deformation of the tire during a revolution. The frequency values related to the revolution of the tire correspond to values of tan (δ) measured between 30 ° C. and 100 ° C. The value of tan (δ) at 100 ° C thus corresponds to an indicator of the rolling resistance of the rolling tire.
[0042] L’utilisation de tels mélanges dont la valeur tan(ô)max est inférieure à 0.055 va permettre d’améliorer les propriétés du pneumatique en matière de résistance au roulement. The use of such mixtures whose tan (δ) max is less than 0.055 will improve the properties of the tire in terms of rolling resistance.
[0043] Selon un mode de réalisation avantageux de l’invention, lesdits éléments de renforcement dudit au moins un raidisseur sont des câbles à couches saturées, au moins une couche interne étant gainée d’une couche constituée d’une composition polymérique telle qu'une composition de caoutchouc non réticulable, réticulable ou réticulée, de préférence à base d’au moins un élastomère diénique. According to an advantageous embodiment of the invention, said reinforcing elements of said at least one stiffener are saturated layer cables, at least one inner layer being sheathed with a layer consisting of a polymeric composition such that a non-crosslinkable, crosslinkable or crosslinked rubber composition, preferably based on at least one diene elastomer.
[0044] Des câbles dits "à couches" (" layered cords") ou "multicouches" sont des câbles constitués d'un noyau central et d'une ou plusieurs couches de brins ou fils pratiquement concentriques disposées autour de ce noyau central. So-called "layered cords" or "multilayer" cables are cables consisting of a central core and one or more layers of strands or substantially concentric son disposed around this central core.
[0045] Au sens de l’invention, une couche saturée d’un câble à couches est une couche constituée de fils dans laquelle il n'existe pas suffisamment de place pour y ajouter au moins un fil supplémentaire. [0046] Les inventeurs ont su mettre en évidence que la présence des câbles tels qu’ils viennent d’être décrits comme éléments de renforcement des couches de sommet de travail permettent de contribuer à de meilleures performances en termes d’endurance. [0047] En effet, il apparaît comme expliqué ci-dessus que les mélanges caoutchouteux des calandrages dudit au moins un raidisseur permettent de diminuer la résistance au roulement du pneumatique. Cela se traduit par une baisse des températures de ces mélanges caoutchouteux, lors de l’utilisation du pneumatique, qui peut entraîner une moindre protection des éléments de renforcement vis-à-vis des phénomènes d’oxydation dans certains cas d’utilisation du pneumatique. En effet, les propriétés des mélanges caoutchouteux relatives au blocage de l’oxygène diminuent avec la température et la présence d’oxygène peut conduire à une dégénérescence progressive des propriétés mécaniques des câbles, pour les conditions de roulage les plus sévères, et peut altérer la durée de vie de ces câbles. For the purposes of the invention, a saturated layer of a layered cable is a layer consisting of wires in which there is not enough room to add at least one additional wire. The inventors have demonstrated that the presence of the cables as just described as strengthening elements of the working crown layers can contribute to better performance in terms of endurance. Indeed, it appears as explained above that the rubber mixtures calendering said at least one stiffener can reduce the rolling resistance of the tire. This results in lower temperatures of these rubber mixes, when using the tire, which can cause less protection of the reinforcing elements vis-à-vis the oxidation phenomena in some cases of use of the tire. In fact, the properties of the rubber compounds relating to the oxygen blocking decrease with temperature and the presence of oxygen can lead to a gradual degeneration of the mechanical properties of the cables, for the most severe driving conditions, and can alter the lifetime of these cables.
[0048] La présence de la gaine de caoutchouc au sein des câbles décrits ci-dessus vient compenser cet éventuel risque d’oxydation des éléments de renforcement, la gaine contribuant au blocage de l’oxygène. The presence of the rubber sheath within the cables described above compensates for this potential risk of oxidation of the reinforcing elements, the sheath contributing to the blockage of oxygen.
[0049] Par l’expression "composition à base d’au moins un élastomère diénique", on entend de manière connue que la composition comprend à titre majoritaire (i.e. selon une fraction massique supérieure à 50%) ce ou ces élastomères diéniques. The expression "composition based on at least one diene elastomer" is understood to mean, in a known manner, that the composition comprises predominantly (i.e. in a mass fraction greater than 50%) this or these diene elastomers.
[0050] On notera que la gaine selon l’invention s’étend d’une manière continue autour de la couche qu’elle recouvre (c’est-à-dire que cette gaine est continue dans la direction "orthoradiale" du câble qui est perpendiculaire à son rayon), de manière à former un manchon continu de section transversale qui est avantageusement pratiquement circulaire. Note that the sheath according to the invention extends continuously around the layer it covers (that is to say that this sheath is continuous in the "orthoradial" direction of the cable which is perpendicular to its radius), so as to form a continuous sleeve of cross section which is preferably substantially circular.
[0051] On notera également que la composition de caoutchouc de cette gaine peut être réticulable ou réticulée, c’est-à-dire qu'elle comprend par définition un système de réticulation adapté pour permettre la réticulation de la composition lors de sa cuisson (i.e., son durcissement et non sa fusion) ; ainsi, cette composition de caoutchouc peut être qualifiée d’infusible, du fait qu’elle ne peut pas être fondue par chauffage à quelque température que ce soit. It will also be noted that the rubber composition of this sheath may be crosslinkable or crosslinked, that is to say that it comprises by definition a crosslinking system adapted to allow the crosslinking of the composition during its baking ( ie, its hardening and not its fusion); thus, this rubber composition can be described as infusible, since it can not be melted by heating at any temperature.
[0052] Par élastomère ou caoutchouc "diénique", on entend de manière connue un élastomère issu au moins en partie (i.e. un homopolymère ou un copolymère) de monomères diènes (monomères porteurs de deux doubles liaisons carbone-carbone, conjuguées ou non). By elastomer or "diene" rubber is meant in known manner an elastomer derived at least in part (ie a homopolymer or a copolymer) from monomers dienes (monomers bearing two carbon-carbon double bonds, conjugated or otherwise).
[0053] De préférence, le système de réticulation de la gaine de caoutchouc est un système dit de vulcanisation, c’est-à-dire à base de soufre (ou d'un agent donneur de soufre) et d’un accélérateur primaire de vulcanisation. A ce système de vulcanisation de base peuvent s'ajouter divers accélérateurs secondaires ou activateurs de vulcanisation connus. Preferably, the system for crosslinking the rubber sheath is a so-called vulcanization system, that is to say based on sulfur (or a sulfur donor agent) and a primary accelerator of vulcanization. To this basic vulcanization system may be added various known secondary accelerators or vulcanization activators.
[0054] La composition de caoutchouc de la gaine selon l’invention peut comprendre, outre ledit système de réticulation, tous les ingrédients habituels utilisables dans les compositions de caoutchouc pour pneumatiques, tels que des charges renforçantes à base de noir de carbone et/ou d'une charge inorganique renforçante telle que silice, des agents anti-vieillissement, par exemple des antioxydants, des huiles d'extension, des plastifiants ou des agents facilitant la mise en œuvre des compositions à l'état cru, des accepteurs et donneurs de méthylène, des résines, des bismaléimides, des systèmes promoteurs d’adhésion connus du type "RFS" (résorcinol- formaldéhyde-silice) ou sels métalliques, notamment des sels de cobalt. The rubber composition of the sheath according to the invention may comprise, in addition to said crosslinking system, all the usual ingredients that can be used in tire rubber compositions, such as reinforcing fillers based on carbon black and / or a reinforcing inorganic filler such as silica, anti-aging agents, for example antioxidants, extension oils, plasticizers or agents facilitating the use of the compositions in the raw state, acceptors and donors of methylene, resins, bismaleimides, known adhesion promoter systems of the "RFS" type (resorcinol-formaldehyde-silica) or metal salts, especially cobalt salts.
[0055] A titre préférentiel, la composition de cette gaine est choisie identique à la composition utilisée pour la couche de calandrage dudit au moins un raidisseur que les câbles sont destinés à renforcer. Ainsi, il n’y a aucun problème d’incompatibilité éventuelle entre les matériaux respectifs de la gaine et de la matrice de caoutchouc. [0056] Selon une variante de l’invention, lesdits câbles dudit au moins un raidisseur sont des câbles à couches de construction [L+M], comportant une première couche Cl à L fils de diamètre di enroulés ensemble en hélice selon un pas pi avec L allant de 1 à 4, entourée d’au moins une couche intermédiaire C2 à M fils de diamètre d2 enroulés ensemble en hélice selon un pas p2 avec M allant de 3 à 12, une gaine constituée d'une composition de caoutchouc non réticulable, réticulable ou réticulée à base d’au moins un élastomère diénique, recouvrant, dans la construction ladite première couche C 1. Preferably, the composition of this sheath is chosen identical to the composition used for the calender layer of said at least one stiffener that the cables are intended to reinforce. Thus, there is no problem of possible incompatibility between the respective materials of the sheath and the rubber matrix. According to a variant of the invention, said cables of said at least one stiffener are cables with building layers [L + M], having a first layer C1 to L son of diameter di wound together in a helix according to a step pi with L ranging from 1 to 4, surrounded by at least one intermediate layer C2 to M son of diameter d 2 wound together in a helix in a pitch p 2 with M ranging from 3 to 12, a sheath made of a rubber composition non-crosslinkable, crosslinkable or crosslinked based on at least one diene elastomer, covering, in the construction, said first layer C 1.
[0057] De préférence, le diamètre des fils de la première couche de la couche interne (Cl) est compris entre 0.10 et 0.5 mm et le diamètre des fils de la couche externe (C2) est compris entre 0.10 et 0.5 mm et de préférence encore le diamètre des fils des couches (Cl) et (C2) est supérieur à 0.2 mm. Preferably, the diameter of the wires of the first layer of the inner layer (Cl) is between 0.10 and 0.5 mm and the diameter of the wires of the outer layer (C2) is between 0.10 and 0.5 mm and more preferably the diameter of the son of the layers (C1) and (C2) is greater than 0.2 mm.
[0058] De préférence encore, le pas d’hélice d’enroulement desdits fils de la couche externe (C2) est compris entre 8 et 25 mm. [0059] Au sens de l’invention, le pas d’hélice représente la longueur, mesurée parallèlement à l'axe du câble, au bout de laquelle un fil ayant ce pas effectue un tour complet autour de l’axe du câble ; ainsi, si l’on sectionne l’axe par deux plans perpendiculaires audit axe et séparés par une longueur égale au pas d’un fil d’une couche constitutive du câble, l’axe de ce fil a dans ces deux plans la même position sur les deux cercles correspondant à la couche du fil considéré. More preferably, the pitch of the winding helix of said son of the outer layer (C2) is between 8 and 25 mm. For the purposes of the invention, the pitch of the helix represents the length, measured parallel to the axis of the cable, at the end of which a wire having this pitch performs a complete revolution around the axis of the cable; thus, if the axis is divided by two planes perpendicular to said axis and separated by a length equal to the pitch of a wire of a constituent layer of the cable, the axis of this wire has in these two planes the same position on the two circles corresponding to the layer of the wire considered.
[0060] Lesdits câbles selon l’invention pourront être obtenus selon différentes techniques connues de l'homme du métier, par exemple en deux étapes, tout d’abord par gainage via une tête d'extrusion de l'âme ou couches Cl, étape suivie dans un deuxième temps d'une opération finale de câblage ou retordage des M fils restants (couche C2) autour de la couche Cl ainsi gainée. Le problème de collant à l’état cru posé par la gaine de caoutchouc, lors des opérations intermédiaires éventuelles de bobinage et débobinage pourra être résolu de manière connue par l’homme du métier, par exemple par l’emploi d’un film intercalaire en matière plastique. Said cables according to the invention may be obtained according to various techniques known to those skilled in the art, for example in two steps, first by sheathing via an extrusion head of the core or layers Cl, step followed in a second step of a final operation of wiring or twisting the remaining M son (layer C2) around the layer Cl and sheathed. The problem of stickiness in the green state posed by the rubber sheath, during any intermediate operations of winding and uncoiling can be solved in a manner known to those skilled in the art, for example by the use of a spacer film. plastic material.
[0061] De tels câbles d’au moins un raidisseur sont par exemple choisis parmi les câbles décrits dans les demandes de brevet WO 2006/013077 et WO 2009/083212. Such cables of at least one stiffener are for example selected from the cables described in patent applications WO 2006/013077 and WO 2009/083212.
[0062] Selon un mode de réalisation préféré de l’invention, l’armature sommet est formée d'au moins deux couches de sommet de travail d'éléments de renforcement, croisés d’une couche à l’autre en faisant avec la direction circonférentielle des angles compris entre 10° et 45°. [0063] De préférence encore, les éléments de renforcement desdites au moins deux couches de sommet de travail sont inextensibles. According to a preferred embodiment of the invention, the crown reinforcement is formed of at least two working crown layers of reinforcement elements, crossed from one layer to the other by making with the direction circumferential angles between 10 ° and 45 °. [0063] More preferably, the reinforcing elements of said at least two working crown layers are inextensible.
[0064] De préférence encore selon l’invention, l’armature sommet comporte une couche d’éléments de renforcement circonférentiels. [0065] Selon un mode de réalisation préférée de l’invention, la couche d’éléments de renforcement circonférentiels est radialement disposée entre deux couches de sommet de travail. [0064] More preferably according to the invention, the crown reinforcement comprises a layer of circumferential reinforcing elements. According to a preferred embodiment of the invention, the layer of circumferential reinforcing elements is radially arranged between two working crown layers.
[0066] Avantageusement selon ce mode de réalisation de l’invention, les éléments de renforcement d’au moins une couche d’éléments de renforcement circonférentiels sont des éléments de renforcement métalliques présentant un module sécant à 0,7 % d’allongement compris entre 10 et 120 GPa et un module tangent maximum inférieur à 150 GPa. Advantageously according to this embodiment of the invention, the reinforcing elements of at least one layer of circumferential reinforcing elements are metal reinforcing elements having a secant modulus at 0.7% elongation between 10 and 120 GPa and a maximum tangent modulus less than 150 GPa.
[0067] Une réalisation préférée de l’invention prévoit encore que l'armature de sommet est complétée radialement à l'extérieur par au moins une couche supplémentaire, dite de protection, d’éléments de renforcement dits élastiques, orientés par rapport à la direction circonférentielle avec un angle compris entre 10° et 45° et de même sens que l'angle formé par les éléments inextensibles de la couche de travail qui lui est radialement adjacente. A preferred embodiment of the invention further provides that the crown reinforcement is completed radially on the outside by at least one additional layer, called protective layer, of so-called elastic reinforcing elements, oriented with respect to the direction. circumferential with an angle between 10 ° and 45 ° and in the same direction as the angle formed by the inextensible elements of the working layer which is radially adjacent thereto.
[0068] Selon l’un quelconque des modes de réalisation de l’invention évoqué précédemment, l'armature de sommet peut encore être complétée, radialement à l'intérieur entre l'armature de carcasse et la couche de travail radialement intérieure la plus proche de ladite armature de carcasse, par une couche de triangulation d'éléments de renforcement inextensibles métalliques en acier faisant, avec la direction circonférentielle, un angle supérieur à 60° et de même sens que celui de l’angle formé par les éléments de renforcement de la couche radialement la plus proche de l'armature de carcasse. According to any one of the embodiments of the invention mentioned above, the crown reinforcement can be further completed, radially inwardly between the carcass reinforcement and the nearest radially inner working layer. of said carcass reinforcement, by a triangulation layer of steel non-extensible reinforcing elements making, with the circumferential direction, an angle greater than 60 ° and in the same direction as that of the angle formed by the reinforcing elements of the layer radially closest to the carcass reinforcement.
[0069] Le pneumatique selon l’invention tel qu’il vient d’être décrit présente donc une masse réduite en comparaison de pneumatiques plus usuels tout en conservant des performances en termes d’endurance comparables. The tire according to the invention as just described therefore has a reduced mass in comparison with more usual tires while maintaining performance in terms of endurance comparable.
[0070] D’autres détails et caractéristiques avantageux de l’invention ressortiront ci- après de la description des exemples de réalisation de l’invention en référence à la figure qui représente une vue méridienne d’un schéma d’un pneumatique selon un mode de réalisation de l’invention. Other details and advantageous features of the invention will emerge below from the description of the exemplary embodiments of the invention with reference to the figure which shows a meridian view of a diagram of a tire according to a mode. embodiment of the invention.
[0071] La figure n’est pas représentée à l’échelle pour en simplifier la compréhension. [0072] Sur la figure, le pneumatique 1, de dimension 315/70 R 22.5, comprend une armature de carcasse radiale 2 ancrée dans deux bourrelets 3, autour de tringles 4. L’armature de carcasse 2 est formée d'une seule couche de câbles métalliques. L’armature de carcasse 2 est frettée par une armature de sommet 5, elle-même coiffée d’une bande de roulement 6. L’armature de sommet 5 est formée radialement de l'intérieur à l'extérieur : d’une couche de triangulation 51 formée de câbles métalliques inextensibles non frettés 2+7x0.28, continus sur toute la largeur de la nappe, orientés d’un angle égal à 65°, d'une première couche de travail 52 formée de câbles métalliques inextensibles non frettés 0.12+3+8x0.35, continus sur toute la largeur de la nappe, orientés d’un angle égal à 18°, d’une seconde couche de travail 53 formée de câbles métalliques inextensibles non frettés 0.12+3+8x0.35, continus sur toute la largeur de la nappe, orientés d’un angle égal à 18° et croisés avec les câbles métalliques de la première couche de travail, - d’une couche de protection 54 formées de câbles métalliques élastiques 3x2x0.35. The figure is not shown in scale to simplify understanding. In the figure, the tire 1, of dimension 315/70 R 22.5, comprises a radial carcass reinforcement 2 anchored in two beads 3, around rods 4. The carcass reinforcement 2 is formed of a single layer wire ropes. The carcass reinforcement 2 is fretted by a crown reinforcement 5, itself capped with a tread 6. The crown reinforcement 5 is formed radially from the inside to the outside: of a layer of triangulation 51 formed of non-waisted metal cables 2 + 7x0.28, continuous over the entire width of the web, oriented by an angle equal to 65 °, of a first working layer 52 formed of non-stretched inextensible metal cables 0.12 + 3 + 8x0.35, continuous over the entire width of the web, oriented at an angle equal to 18 °, of a second working layer 53 formed of inextensible non-woven wire cables 0.12 + 3 + 8x0.35, continuous over the entire width of the web, oriented at an angle of 18 ° and crossed with the metal cables of the first working layer, - a protective layer 54 formed of elastic metal cables 3x2x0.35.
[0073] Dans chacun des bourrelets 3, la couche d’armature de carcasse 2 est enroulée autour d’une tringle 4 pour former un retournement 7. Le retournement 7 est encore renforcé par une couche d’éléments de renforcement ou raidisseur 8 qui vient coiffer l’extrémité 9 du retournement 7. [0074] Conformément à l’invention, les câbles des raidisseurs 8 sont des assemblages à deux couches constitués de 9 fils de 0.26 mm. Les câbles ainsi constitués présentent un diamètre d de 1 mm et donc inférieur à 1.1 mm. Les fils d’acier formant les câbles présentent un grade SHT. In each of the beads 3, the carcass reinforcement layer 2 is wound around a bead wire 4 to form an upturn 7. The upturn 7 is further reinforced by a layer of reinforcing elements or stiffener 8 which comes capping the end 9 of the upturn 7. [0074] According to the invention, the cables of the stiffeners 8 are two-layer assemblies consisting of 9 son of 0.26 mm. The cables thus formed have a diameter d of 1 mm and therefore less than 1.1 mm. The steel wires forming the cables have a SHT grade.
[0075] Le pas de répartition desdits câbles dans les raidisseurs 8 est égal à 2 mm et donc inférieur à 2.1 mm. The distribution pitch of said cables in the stiffeners 8 is equal to 2 mm and therefore less than 2.1 mm.
[0076] La rigidité des câbles des raidisseurs 8 est égale à 196 GPa et est supérieure à 190 GPa. [0077] Les couches de calandrage des raidisseurs 8 sont réalisées à partir du mélange I suivant : The stiffness of the stiffener cables 8 is equal to 196 GPa and is greater than 190 GPa. The calendering layers of the stiffeners 8 are made from the following mixture I:
Figure imgf000017_0001
Figure imgf000017_0001
(1) Caoutchouc naturel  (1) Natural rubber
(2) Noir de carbone « S204 » de la société Orion Engineered Carbon  (2) Carbon black "S204" from Orion Engineered Carbon
(3) N-l,3-diméthylbutyl-N-phénylparaphénylènediamine « Santoflex 6-PPD » de la société(3) N-1,3-dimethylbutyl-N-phenylparaphenylenediamine "Santoflex 6-PPD" from Society
Flexsys Flexsys
(4) Stéarine (« Pristerene 4931 » de la société Uniqema)  (4) Stearin ("Pristerene 4931" from Uniqema)
(5) Oxyde de zinc, grade industriel, société Umicore  (5) Zinc oxide, industrial grade, Umicore company
(6) Naphténate de cobalt - N° de produit 60830 de la société Fluka  (6) Cobalt Naphthalate - Product No 60830 from the company Fluka
(7) N,N-dicyclohexylbenzothiazole-2-sulfénamide de la société Flexsys (7) N, N-dicyclohexylbenzothiazole-2-sulfenamide from Flexsys
(8) N-cyclohexylthiophtalimide commercialisé sous dénomination « Vulkalent G » par la société Fanxess  (8) N-cyclohexylthiophthalimide sold under the name "Vulkalent G" by the company Fanxess
[0078] Fes valeurs des constituants sont exprimées en pce (parties en poids pour cent parties d’élastomères). [0079] Fa masse du raidisseur comprenant la masse des câbles métalliques et des mélanges de calandrage, est égale à 0.44 Kg. The values of the constituents are expressed in phr (parts by weight per hundred parts of elastomers). The mass of the stiffener comprising the mass of the metal cables and calendering mixtures, is equal to 0.44 Kg.
[0080] Fa masse du pneumatique I est égale à 59.56 Kg. The mass of the tire I is equal to 59.56 Kg.
[0081] Conformément à l’invention, la densité de réticulation mesurée selon la méthode de gonflement à l’équilibre sur les couches de calandrage des raidisseurs 8 est égale à 19.10 5 mol/crrf et donc comprise entre 13.10 5 mol/crrf et 21.10 5 mol/cm\ [0082] Le module d’élasticité sous tension à 10 % d'allongement des couches de calandrage des raidisseurs 8 est égal à 5.7 MPa et donc inférieur à 8.5 MPa. According to the invention, the crosslinking density measured according to the equilibrium swelling method on the calendering layers of the stiffeners 8 is 19.10 5 mol / crrf and therefore between 13.10 5 mol / crrf and 21.10. 5 mol / cm The modulus of elasticity under tension at 10% elongation of the calendering layers of the stiffeners 8 is equal to 5.7 MPa and therefore less than 8.5 MPa.
[0083] La valeur de tan(ô)max des couches de calandrages des raidisseurs 8 est égale à 0.050 et donc inférieure à 0.055. [0084] Des essais ont été réalisés avec différents pneumatiques réalisés selon l’invention conformément à la représentation de la figure et comparés avec un pneumatique de référence Tl également conforme à la représentation de la figure. The value of tan (δ) max of the calender layers of the stiffeners 8 is equal to 0.050 and therefore less than 0.055. Tests have been made with different tires made according to the invention in accordance with the representation of the figure and compared with a reference tire T1 also according to the representation of the figure.
[0085] Le pneumatique Tl diffère du pneumatique selon l’invention d’une part, par la nature des mélanges constituants les couches de calandrage des raidisseurs 8 et d’autre part, par les câbles des raidisseurs 8 qui sont des câbles 9.35 dont le diamètre est égal à 1.35 mm, les fils d’acier formant les dits câbles présentant un grade SHT. The tire T1 differs from the tire according to the invention on the one hand, by the nature of the constituent mixtures the calendering layers of the stiffeners 8 and on the other hand, by the cables of the stiffeners 8 which are 9.35 cables whose diameter is equal to 1.35 mm, the steel wires forming said cables having a grade SHT.
[0086] Le pas de répartition desdits câbles dans les raidisseurs 8 du pneumatique Tl est égal à 2.5 mm. The distribution pitch of said cables in the stiffeners 8 of the tire T1 is equal to 2.5 mm.
[0087] La rigidité des câbles des raidisseurs 8 du pneumatique Tl est égale à 185 GPa. [0088] Les couches de calandrage des raidisseurs 8 du pneumatique de référence Tl sont réalisées à partir du mélange Rl suivant : The stiffness of the stiffener cables 8 of the tire T1 is equal to 185 GPa. The calendering layers of the stiffeners 8 of the reference tire T1 are made from the following mixture R1:
Figure imgf000018_0001
(1) Caoutchouc naturel
Figure imgf000018_0001
(1) Natural rubber
(2) Noir de carbone « N683 » de la société Cabot.  (2) "N683" carbon black from Cabot.
(3) N-l,3-diméthylbutyl-N-phénylparaphénylènediamine « Santoflex 6-PPD » de la société Flexsys (3) N-1,3-dimethylbutyl-N-phenylparaphenylenediamine "Santoflex 6-PPD" from the company Flexsys
(4) Stéarine (« Pristerene 4931 » de la société Uniqema) (4) Stearin ("Pristerene 4931" from Uniqema)
(5) Oxyde de zinc, grade industriel, société Umicore  (5) Zinc oxide, industrial grade, Umicore company
(6) Naphténate de cobalt - N° de produit 60830 de la société Fluka  (6) Cobalt Naphthalate - Product No 60830 from the company Fluka
(7) N,N-dicyclohexylbenzothiazole-2-sulfénamide de la société Flexsys  (7) N, N-dicyclohexylbenzothiazole-2-sulfenamide from Flexsys
(8) N-cyclohexylthiophtalimide commercialisé sous dénomination « Vulkalent G » par la société Lanxess  (8) N-cyclohexylthiophthalimide sold under the name "Vulkalent G" by the company Lanxess
[0089] Les valeurs des constituants sont exprimées en pce (parties en poids pour cent parties d’élastomères). The values of the constituents are expressed in phr (parts by weight per hundred parts of elastomers).
[0090] La masse cumulée des raidisseurs 8 du pneumatique Rl comprenant la masse des câbles métalliques et des mélanges de calandrage, est égale à 0.58 Kg. The cumulative mass of the stiffeners 8 of the tire R1 comprising the mass of the metal cables and calendering mixtures, is equal to 0.58 Kg.
[0091] La masse du pneumatique Tl est égale à 59.7 Kg. The mass of the tire Tl is equal to 59.7 Kg.
[0092] La densité de réticulation mesurée selon la méthode de gonflement à l’équilibre sur les couches de calandrage des raidisseurs 8 du pneumatique Tl est égale à 25.10 5 mol/cm3. The crosslinking density measured according to the equilibrium swelling method on the calendering layers of the stiffeners 8 of the tire T1 is equal to 25.10 5 mol / cm 3 .
[0093] Le module d’élasticité sous tension à 10 % d'allongement des couches de calandrage raidisseurs 8 du pneumatique Tl est égal à 6.12 MPa. The tensile modulus of elasticity at 10% elongation of the stiffening calender layers 8 of the tire T1 is equal to 6.12 MPa.
[0094] La valeur de tan(ô)max des couches de calandrages raidisseurs 8 du pneumatique Tl est égale à 0.056. The value of tan (δ) max of the stiffening layer layers 8 of the tire T1 is equal to 0.056.
[0095] L’allongement à rupture des mélanges I et Rl est mesurée sur des prélèvements faits sur pneumatique neuf. The elongation at break of the mixtures I and Rl is measured on samples taken on a new tire.
[0096] Une première mesure est réalisée sur l’échantillon prélevé. Une autre mesure est réalisée sur un échantillon prélevé puis vieillit 10 jours à 77°C sous air. A first measurement is performed on the sample taken. Another measurement is performed on a sample taken and then aged for 10 days at 77 ° C in air.
[0097] L’allongement à la rupture (en %) est mesuré conformément à la norme AFNOR- NF-T-46-002 de septembre 1988. Les mesures de traction pour déterminer les propriétés de rupture sont effectuées à la température de l00°C ± 2°C, et dans les conditions normales d’hygrométrie (50 ± 5% d’humidité relative), selon la norme française NF T 40-101 (décembre 1979). The elongation at break (in%) is measured in accordance with the AFNOR-NF-T-46-002 standard of September 1988. The tensile measurements to determine the breaking properties are carried out at a temperature of 100 ° C. C ± 2 ° C, and under normal humidity conditions (50 ± 5% relative humidity), according to the French standard NF T 40-101 (December 1979).
[0098] Les mesures sont présentées dans le tableau suivant :
Figure imgf000020_0001
The measurements are presented in the following table:
Figure imgf000020_0001
[0099] Des essais de roulage des pneumatiques correspondant à des conditions sévères d’utilisation des pneumatiques ont été réalisés. Ces essais sont réalisés avec les pneumatiques selon l’invention et les pneumatiques de référence. Avant d’effectuer les essais, les pneumatiques subissent un vieillissement accéléré en étuve dans des conditions de teneur en oxygène du gaz de gonflage et de température, adaptées pour produire un état de thermo -oxydation des matériaux représentatif d’un usage moyen durant une vie en clientèle. Les pneumatiques sont roulés sur un volant dans des conditions de charge 20% supérieures à la charge nominale et de gonflage 20% supérieures à la pression nominale.  Tire rolling tests corresponding to severe conditions of use of the tires were made. These tests are carried out with the tires according to the invention and the reference tires. Before carrying out the tests, the tires undergo an accelerated aging in an oven under conditions of oxygen content of the inflation gas and temperature, adapted to produce a state of thermooxidation of materials representative of average use for a lifetime in clientele. The tires are rolled on a steering wheel under load conditions 20% higher than the rated load and inflation 20% higher than the nominal pressure.
[00100] Les tests sont arrêtés lors de l’apparition d’une dégradation de la zone du bourrelet du pneumatique. Les pneumatiques sont ensuite décortiqués pour permettre l’analyse des couches de calandrage des raidisseurs. Alors que les pneumatiques de référence Rl présentent des fissures fortement propagées pouvant potentiellement conduire à une défaillance du pneumatique, les pneumatiques selon l’invention ne présentent que des amorces de fissures en extrémités des raidisseurs, celles-ci ne s’étant que très faiblement propagées. The tests are stopped during the appearance of a degradation of the bead area of the tire. The tires are then peeled to allow analysis of the calendering layers of the stiffeners. While the reference tires R1 have highly propagated cracks that could potentially lead to tire failure, the tires according to the invention only have crack initiators at the ends of the stiffeners, which have only been very slightly propagated. .

Claims

RE VENDIC ATION S  RE VENDIC ATION S
1 - Pneumatique à armature de carcasse radiale comprenant une armature de sommet, celle-ci étant coiffée radialement d’une bande de roulement, ladite bande de roulement étant réunie à deux bourrelets par l’intermédiaire de deux flancs, au moins une couche d’éléments de renforcement de l’armature de carcasse étant ancrée dans chacun des bourrelets par retournement autour d’une tringle, ledit retournement d’armature de carcasse étant renforcé par au moins une couche d’éléments de renforcement ou raidisseur, caractérisé en ce que les éléments de renforcement dudit au moins un raidisseur sont des câbles dont le diamètre est inférieur à 1.1 mm, en ce que le pas de répartition desdits câbles dans ledit au moins un raidisseur est inférieur à 2.1 mm, en ce que la rigidité desdits câbles dudit au moins un raidisseur est supérieure à 190 GPa et en ce que les couches de calandrage dudit au moins un raidisseur sont constituées d’un mélange élastomérique à base de caoutchouc naturel ou de polyisoprène synthétique à majorité d'enchaînements cis-l,4 et éventuellement d'au moins un autre élastomère diénique, le caoutchouc naturel ou le polyisoprène synthétique en cas de coupage étant présent à un taux majoritaire par rapport au taux de l'autre ou des autres élastomères diéniques utilisés et d'une charge renforçante comprenant majoritairement au moins un noir de carbone, présentant une surface spécifique BET au plus égale à 30 m2/g et un indice d’absorption d’huile d’échantillons comprimés (COAN) au moins égal à 60 ml/ 100 g, en ce que ledit mélange élastomérique ne comprend pas, ou comprend au plus 20 pce de noir de carbone dont la surface spécifique BET est supérieure à 30 m2/g et l’indice COAN est supérieur à 40 ml/ 100 g, en ce que ledit mélange élastomérique ne comprend pas, ou comprend au plus 20 pce de charge blanche et en ce que la densité de réticulation mesurée selon la méthode de gonflement à l’équilibre est comprise entre 13.10 5 mol/crrf et 21.10 5 mol/crrf dans ledit mélange élastomérique constituant les couches de calandrage dudit au moins un raidisseur. 1 - Radial carcass reinforcement tire comprising a crown reinforcement, the latter being capped radially with a tread, said tread being joined to two beads by means of two sidewalls, at least one layer of reinforcement elements of the carcass reinforcement being anchored in each of the beads by turning around a bead wire, said carcass reinforcement overturning being reinforced by at least one layer of reinforcement elements or stiffener, characterized in that the reinforcing elements of said at least one stiffener are cables whose diameter is less than 1.1 mm, in that the distribution pitch of said cables in said at least one stiffener is less than 2.1 mm, in that the rigidity of said cables of said at least one less than a stiffener is greater than 190 GPa and in that the calendering layers of said at least one stiffener consist of an elastomeric mixture based on e natural rubber or synthetic polyisoprene predominantly chained cis-l, 4 and optionally at least one other diene elastomer, the natural rubber or synthetic polyisoprene in case of cutting being present at a majority rate compared to the rate of the other or the other diene elastomers used and a reinforcing filler comprising predominantly at least one carbon black, having a BET specific surface area at most equal to 30 m 2 / g and an oil absorption index of samples tablets (COAN) at least equal to 60 ml / 100 g, in that said elastomeric mixture does not comprise, or comprises at most 20 phr of carbon black, the BET surface area of which is greater than 30 m 2 / g and COAN number is greater than 40 ml / 100 g, in that said elastomeric mixture does not comprise, or comprises at most 20 phr of white filler and in that the crosslinking density measured according to the swelling method equilibrium is between 13.10 5 mol / crrf and 21.10 5 mol / crrf in said elastomeric mixture constituting the calendering layers of said at least one stiffener.
2 - Pneumatique selon la revendication 1, caractérisé en ce que le taux de noir de carbone dont la surface spécifique BET est au plus égale à 30 m2/g est compris entre 20 et 80 pce, et de préférence entre 40 et 65 pce. 3 - Pneumatique selon la revendication 1 ou 2, caractérisé en ce que ledit noir de carbone dont la surface spécifique BET est au plus égale à 30 m2/g présente un indice COAN au moins égal à 65 ml/ 100 g, et de préférence au moins égal à 70 ml/ 100 g. 2 - A tire according to claim 1, characterized in that the carbon black content whose BET surface area is at most equal to 30 m 2 / g is between 20 and 80 phr, and preferably between 40 and 65 phr. 3 - A tire according to claim 1 or 2, characterized in that said carbon black whose BET surface area is at most equal to 30 m 2 / g has a COAN index of at least 65 ml / 100 g, and preferably at least 70 ml / 100 g.
4 - Pneumatique selon l’une des revendications précédentes, caractérisé en ce que ledit noir de carbone dont la surface spécifique BET est au plus égale à 30 m2/g présente un indice4 - tire according to one of the preceding claims, characterized in that said carbon black whose BET surface area is at most equal to 30 m 2 / g has a subscript
COAN au plus égal à 90 mElOO g. COAN at most equal to 90 mElOO g.
5 - Pneumatique selon l’une des revendications précédentes, caractérisé en ce que la surface spécifique BET dudit noir de carbone au plus égale à 30 m2/g est au plus égale à 25 m2/g, et de préférence supérieure à 15 m2/g. 6 - Pneumatique selon l'une des revendications précédentes, caractérisé en ce que lesdits éléments de renforcement dudit au moins un raidisseur sont des câbles à couches saturées, au moins une couche interne étant gainée d’une couche constituée d’une composition polymérique telle qu'une composition de caoutchouc non réticulable, réticulable ou réticulée, de préférence à base d’au moins un élastomère diénique. 7 - Pneumatique selon l'une des revendications précédentes, caractérisé en ce que l’armature sommet comporte une couche d’éléments de renforcement circonférentiels et en ce que la couche d’éléments de renforcement circonférentiels est radialement disposée entre deux couches de sommet de travail. 5 - A tire according to one of the preceding claims, characterized in that the BET specific surface area of said carbon black at most equal to 30 m 2 / g is at most equal to 25 m 2 / g, and preferably greater than 15 m 2 / g. 6 - tire according to one of the preceding claims, characterized in that said reinforcing elements of said at least one stiffener are saturated layer cables, at least one inner layer being sheathed with a layer consisting of a polymeric composition such that a non-crosslinkable, crosslinkable or crosslinked rubber composition, preferably based on at least one diene elastomer. 7 - A tire according to one of the preceding claims, characterized in that the crown reinforcement comprises a layer of circumferential reinforcing elements and in that the layer of circumferential reinforcing elements is radially arranged between two layers of working crown .
8 - Pneumatique selon l'une des revendications précédentes, caractérisé en ce que les éléments de renforcement d’au moins une couche d’éléments de renforcement circonférentiels sont des éléments de renforcement métalliques présentant un module sécant à 0,7 % d’allongement compris entre 10 et 120 GPa et un module tangent maximum inférieur à 150 GPa. 8 - tire according to one of the preceding claims, characterized in that the reinforcing elements of at least one layer of circumferential reinforcing elements are metal reinforcing elements having a secant modulus at 0.7% elongation included between 10 and 120 GPa and a maximum tangent modulus less than 150 GPa.
9 - Pneumatique selon l'une des revendications précédentes, caractérisé en ce que les éléments de renforcement des couches de sommet de travail sont inextensibles. 10 - Pneumatique selon l'une des revendications précédentes, caractérisé en ce que l'angle formé avec la direction circonférentielle par les éléments de renforcement des couches de sommet de travail est inférieur à 30° et de préférence inférieur à 25°. 9 - A tire according to one of the preceding claims, characterized in that the reinforcing elements of the working crown layers are inextensible. 10 - tire according to one of the preceding claims, characterized in that the angle formed with the circumferential direction by the reinforcing elements of the working crown layers is less than 30 ° and preferably less than 25 °.
PCT/FR2019/050821 2018-04-09 2019-04-08 Tire, the carcass reinforcement of which is reinforced with a ply of reinforcing elements in the bead region WO2019197769A1 (en)

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FR1853079A FR3079838B1 (en) 2018-04-09 2018-04-09 RUBBER COMPOSITION INCLUDING A REINFORCING LOAD WITH A LOW SPECIFIC SURFACE
FR1903284 2019-03-28
FR1903284A FR3094273A1 (en) 2019-03-28 2019-03-28 A tire whose carcass reinforcement is reinforced by a layer of reinforcing elements in the bead area

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FR3129324A1 (en) * 2021-11-25 2023-05-26 Compagnie Generale Des Etablissements Michelin Tire with improved rolling resistance performance
FR3129321A1 (en) * 2021-11-25 2023-05-26 Compagnie Generale Des Etablissements Michelin Tire with improved rolling resistance performance
FR3129323A1 (en) * 2021-11-25 2023-05-26 Compagnie Generale Des Etablissements Michelin Tire with improved rolling resistance performance
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WO2023094541A1 (en) * 2021-11-25 2023-06-01 Compagnie Generale Des Etablissements Michelin Tyre with improved rolling resistance performance
WO2023094540A1 (en) * 2021-11-25 2023-06-01 Compagnie Generale Des Etablissements Michelin Tyre having improved performance in terms of rolling resistance

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