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    • 专利摘要:
    The invention relates to a tire having a H / L aspect ratio of 0.75 or less, comprising a crown reinforcement consisting of two working crown layers of reinforcing elements. According to the invention, the two working crown layers are alone present to constitute the crown reinforcement over at least 40% of the width of the tread, the absolute value of the difference between the absolute values of the angles α2 and α1 being greater than 15 °, α2 being greater than α1 in absolute value, the average angle α satisfying the relation 14 + 131 * exp (-L / 100) <α <20 + 164 * exp (-L / 100) and the utilization ratio of the fracture potential F2 / FR2 of the radially outermost working layer being less than 1/6.
    公开号:FR3048382A1
    申请号:FR1651770
    申请日:2016-03-02
    公开日:2017-09-08
    发明作者:Orel Fournier；Luc Bestgen
    申请人:Michelin Recherche et Technique SA Switzerland ；Compagnie Generale des Etablissements Michelin SCA；Michelin Recherche et Technique SA France；
    IPC主号:
    专利说明:

    avec
    P2 : le pas de pose des éléments de renforcement de la couche de sommet de travail radialement la plus extérieure, mesuré perpendiculairement aux éléments de renforcement au niveau du plan médian circonférentiel,
    Rs = Re - Es,
    Re : rayon extérieur du pneumatique mesuré au point radialement le plus extérieur sur la surface de la bande de roulement du pneumatique, ladite surface étant extrapolée pour combler les éventuels creux,
    Es : distance radiale entre le point radialement le plus à l’extérieur du pneumatique et sa projection orthogonale sur la face radialement extérieure d’un élément de renforcement de la couche de sommet de travail radialement la plus intérieure,
    Rl : moyenne des rayons des points axialement les plus à l’extérieur de chaque côté du pneumatique,
    Rt : le rayon du cercle passant par trois points situés sur la surface extérieure de la bande de roulement en dehors des creux, définis à partir d’une extrémité d’épaulement à des distances axiales respectives égales à '/4, '/2 et y4 de la largeur axiale de la bande de roulement.
    [0022] Le rapport d’aspect H/L est le rapport de la hauteur H du pneumatique sur jante sur la largeur axiale maximale L du pneumatique, lorsque ce dernier est monté sur sa jante de service et gonflé à sa pression nominale. La hauteur H, est définie comme la différence entre le rayon maximal de la bande de roulement Re et le rayon minimal du bourrelet.
    [0023] La largeur L et les différents rayons sont mesurés sur un pneumatique monté sur sa jante nominale et gonflé à sa pression nominale, et sont exprimés en millimètres [0024] L’épaisseur Es et le pas p2 sont mesurés sur une coupe du pneumatique et sont exprimés en millimètres.
    [0025] Les angles al et a2, exprimés en degré, sont également mesurés sur une coupe du pneumatique. Les mesures d’angles sont selon l’invention réalisées au niveau du plan médian circonférentiel.
    [0026] De préférence selon l’invention, les éléments de renforcement desdites deux couches de sommet de travail sont métalliques.
    [0027] Les résultats obtenus avec des pneumatiques conformes à l’invention ont effectivement mis en évidence que les performances en termes d’endurance peuvent être améliorées notamment lors de roulage sur sol caillouteux, l’armature sommet du pneumatique étant allégée. L’allègement de l’armature sommet du pneumatique s’accompagne d’une simplification de fabrication et d’une diminution des coûts de fabrication.
    [0028] Contre toute attente, les résultats ont effectivement mis en évidence que les pneumatiques selon l’invention peuvent être allégés en diminuant le nombre de couches constitutives de l’armature sommet tout en conservant voire améliorant les propriétés d’endurance du sommet du pneumatique notamment à l’égard de chocs apparaissant sur la bande de roulement par exemple lors de roulage sur sol caillouteux. Il est en effet connu de l’homme du métier que pour améliorer les performances d’endurance de l’armature sommet d’un pneumatique à l’égard de ce type de chocs, il est usuel d’augmenter le nombre de couches d’éléments de renforcement.
    [0029] Les inventeurs pensent interpréter ces résultats du fait de l’angle formé avec la direction circonférentielle par les éléments de renforcement de la couche de sommet de travail radialement la plus intérieure qui est plus petit en valeur absolue que celui formé par les éléments de renforcement de la couche de sommet de travail radialement la plus extérieure. Ils ont constaté que cet angle plus petit semble entraîner un retard dans la prise de tension par les éléments de renforcement lors d’un tel choc. Usuellement, lors de chocs comparables à ceux observés lors d’un roulage sur sol caillouteux la rupture d’éléments de renforcement si elle intervient s’observe sur la couche radialement la plus intérieure. Ces constats semblent indiquer que face à ce type d’agressions, la différence d’angles des éléments de renforcement entre les deux couches de sommet de travail permet d’améliorer les performances d’endurance du pneumatique tout en diminuant le nombre de couches de l’armature de sommet.
    [0030] Les inventeurs ont encore fait le constat que le choix de la valeur absolue la différence entre les valeurs absolues des angles précités al et a2 associé à l’angle moyen a et au ratio d’utilisation du potentiel de rupture F2/FR2 tels que définis selon l’invention peuvent permettre d’éliminer la couche de protection usuellement mise en place radialement à l’extérieur des autres couches de l’armature de sommet. Une telle couche est habituellement présente pour être sacrifiée en cas d’agressions du pneumatique de type coupures pouvant venir altérer l’intégrité d’éléments de renforcement métalliques par des phénomènes de corrosion associés à la fatigue desdits éléments de renforcement. Les inventeurs font effectivement le constat que les éléments de renforcement de la couche de sommet de travail radialement la plus extérieure, d’un pneumatique selon l’invention, sont moins sollicités lors du gonflage du pneumatique ou bien lors de son utilisation en roulage normal que les éléments de renforcement d’une couche de sommet de travail radialement la plus extérieure d’un pneumatique plus usuel ; un tel pneumatique plus usuel présente des différences d’angles en valeur absolue entre les éléments de renforcement des différentes couches de travail plus petites, un angle des éléments de renforcement de la couche de travail radialement la plus intérieure supérieur ou égal en valeur absolue à celui des éléments de renforcement de la couche de travail radialement la plus extérieure et un ratio d’utilisation du potentiel de rupture F2/FR2 plus important. Les éléments de renforcement de la couche de sommet de travail radialement la plus extérieure d’un pneumatique selon l’invention présentent ainsi des propriétés d’endurance bien supérieures à ceux d’un pneumatique plus usuel ; les inventeurs font ainsi le constat que la suppression de la couche de protection est rendue possible et permet de contribuer à l’allègement du pneumatique.
    [0031] Selon un mode de réalisation préféré de l’invention, la valeur absolue de la différence entre les valeurs absolues des angles a2 et al est supérieure à 18°. Selon ce mode de réalisation, et conformément aux interprétations données ci-dessus, il va être possible d’améliorer encore les performances d’endurance des éléments de renforcement de la couche de travail radialement la plus extérieure et/ou améliorer encore les performances du pneumatique à l’égard de chocs tels que ceux subis lors de roulage sur des sols caillouteux.
    [0032] Avantageusement encore selon l’invention, le ratio d’utilisation du potentiel de rupture F2/FR2 de la couche de travail radialement la plus extérieure est inférieur à 1/8. Un tel ratio d’utilisation du potentiel de rupture F2/FR2 contribue encore à améliorer les performances d’endurance des éléments de renforcement de la couche de travail radialement la plus extérieure lors de l’utilisation du pneumatique.
    [0033] De préférence selon l’invention, le ratio d’utilisation du potentiel de rupture Fl/FRl de la couche de travail radialement la plus intérieure est inférieur à 1/3, dans lequel :
    avec
    Pi : le pas de pose des éléments de renforcement de la couche de sommet de travail radialement la plus intérieure, mesuré perpendiculairement aux éléments de renforcement au niveau du plan médian circonférentiel.
    [0034] De préférence encore, le ratio d’utilisation du potentiel de rupture Fl/FRl de la couche de travail radialement la plus intérieure est au moins 30 % supérieur au ratio d’utilisation du potentiel de rupture F2/FR2 de la couche de travail radialement la plus extérieure.
    [0035] Selon un mode de réalisation de l’invention, les éléments de renforcement des couches de sommet de travail sont des câbles métalliques inextensibles.
    [0036] Selon un mode de réalisation avantageux de l’invention, les deux couches de sommet de travail sont seules présentes pour constituer l’armature de sommet sur au moins 60% de la largeur axiale de l’armature sommet et avantageusement encore sur au moins 80% de la largeur axiale de l’armature sommet. Ces modes de réalisations avantageux de l’invention vont dans le sens d’un allègement encore plus important du pneumatique.
    [0037] Selon un mode de réalisation préféré de l’invention, optimisant l’allègement du pneumatique, les deux couches de sommet de travail sont seules présentes pour constituer l’armature de sommet sur la totalité de la largeur axiale de l’armature sommet.
    [0038] Selon d’autres variantes de réalisation de l’invention décalant le compromis de performance du pneumatique de façon moins favorable pour ce qui concerne l’allégement, l’armature de sommet comporte une couche supplémentaire, dite de protection, radialement extérieure aux couches de sommet de travail, de préférence centrée sur le plan médian circonférentiel. Les éléments de renforcements d’un telle couche de protection sont de préférence des éléments de renforcement dits élastiques, orientés par rapport à la direction circonférentielle avec un angle compris entre 8° et 45° et de même sens que l'angle formé par les éléments de renforcement de la couche de travail qui lui est radialement adjacente. De préférence encore, les éléments de renforcements d’une telle couche de protection sont parallèles aux éléments de renforcement de la couche de travail qui lui est radialement adjacente.
    [0039] D’autres variantes peuvent encore prévoir que l’armature de sommet peut être complétée 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 45° 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. Avantageusement, ladite couche de triangulation est constituée de deux demi-couches positionnées axialement de part et d’autre du plan médian circonférentiel.
    [0040] Le pneumatique selon l’invention peut encore comporter une ou plusieurs couches d’éléments de renforcement circonférentiels, avantageusement constituée de deux demi-couches positionnées axial ement de part et d’autre du plan médian circonférentiel.
    [0041] D’autres détails et caractéristiques avantageux de l’invention ressortiront ci-après de la description d’un exemple 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.
    [0042] La figure n’est pas représentée à l’échelle pour en simplifier la compréhension. La figure ne représentent qu’une demi-vue d’un pneumatique qui se prolonge de manière symétrique par rapport à l’axe XX’ qui représente le plan médian circonférentiel, ou plan équatorial, d’un pneumatique.
    [0043] Sur la figure, le pneumatique 1, de dimension 385/65 R 22.5, a un rapport de forme H/L égal à 0,65, H étant la hauteur du pneumatique 1 sur sa jante de montage et L sa largeur axiale maximale. Ledit pneumatique 1 comprend une armature de carcasse radiale 2 ancrée dans deux bourrelets, non représentés sur la figure. L’armature de carcasse 2 est formée d'une seule couche de câbles métalliques. Ils comportent encore une bande de roulement 5.
    [0044] Sur la figure, l’armature de carcasse 2 est frettée conformément à l’invention par une armature de sommet 4, formée radialement de l'intérieur à l'extérieur : d'une première couche de travail 41 formée de câbles métalliques orientés d'un angle égal â 12°, d'une deuxième couche de travail 42 formée de câbles métalliques orientés d'un angle égal â 40° et croisés avec les câbles métalliques de la première couche de travail 41, les câbles de chacune des couches de travail 41, 42 étant orientés de part et d’autre de la direction circonférentielle.
    [0045] Les câbles métalliques constituant les éléments de renforcement des deux couches de travail sont des câbles de formule 9.35. Ils sont répartis dans chacune des couches de travail avec une distance entre les éléments de renforcement, mesurée selon la normale à la direction de la ligne moyenne du câble égale à 2 mm.
    [0046] Le pneumatique est gonflé à une pression de 9 bars.
    [0047] La largeur axiale L^^ de la première couche de travail 41 est égale à 280 mm.
    [0048] La largeur axiale L^^ de la deuxième couche de travail 42 est égale à 260 mm.
    [0049] La largeur axiale de la bande de roulement L5 est égale à 303 mm.
    [0050] La largeur axiale L est égale à 377 mm.
    [0051] La masse cumulée des deux couches de travail 41, 42, comprenant la masse des câbles métalliques et des mélanges de calandrage, se monte ainsi à 9.1 Kg.
    [0052] La différence entre les angles formés par les câbles de la première couche de sommet de travail avec la direction circonférentielle et ceux des câbles de la deuxième couche de sommet de travail est égale à 28°.
    [0053] L’angle moyen est égal à 22.9° et est bien compris entre 17° et 23.8°.
    [0054] La valeur mesurée de Re est égale à 536.9 mm.
    [0055] La valeur mesurée de Es est égale à 24.9 mm.
    [0056] La valeur moyenne RL des rayons mesurés est égale â 409 mm [0057] La valeur Rt déterminée sur le pneumatique est égale â 1400 mm [0058] La valeur calculée de Te est égale à 395.9 N/mm.
    [0059] La valeur calculée de C est égale à -0.01.
    [0060] La valeur de Fl est égale à 655.3 N.
    [0061] La valeur de F2 est égale à 267.7 N.
    [0062] Les forces ruptures des éléments de renforcement des couches de sommet de travail FRI et FR2 sont égales à 2600 N.
    [0063] Le ratio d’utilisation du potentiel de rupture F2/FR2 est égal à 10.3 %.
    [0064] Le ratio d’utilisation du potentiel de rupture Fl/FRl est égal à 25.2 %.
    [0065] Le ratio d’utilisation du potentiel de rupture Fl/FRl est 145 % supérieur au ratio d’utilisation du potentiel de rupture F2/FR2.
    [0066] Le pneumatique selon l’invention est comparé à un pneumatique de référence de même dimension qui diffère du pneumatique selon l’invention par son armature de sommet formée radialement de l'intérieur à l'extérieur : - d’une couche de triangulation formée de câbles métalliques orientés d'un angle égal à 50°, d'une première couche de travail formée de câbles métalliques orientés d'un angle égal à 18°, du même côté que les câbles de la couche de triangulation par rapport â la direction circonférentielle, d’une seconde couche de travail formée de câbles métalliques orientés d'un angle égal à 18° et croisés avec les câbles métalliques de la première couche de travail, les câbles de chacune des couches de travail étant orientés de part et d’autre de la direction circonférentielle, - d’une couche de protection formées de câbles métalliques élastiques 6.35, dont la distance entre les éléments de renforcement, mesurée selon la normale â la direction de la ligne moyenne du câble est égal â 2.5 mm, orientés d’un angle égal à 18°, du même côté que les câbles de la seconde couche de travail.
    [0067] Les câbles métalliques des deux couches de travail et de la couche de triangulation sont des câbles de formule 9.35. Ils sont répartis dans chacune des couches de travail avec une distance entre les éléments de renforcement, mesurée selon la normale à la direction de la ligne moyenne du câble égale à 2.5 mm.
    [0068] Le pneumatique de référence est gonflé à une pression de 9 bars.
    [0069] La largeur axiale de la couche triangulation est égale à 260 mm.
    [0070] La largeur axiale de la première couche de travail est égale à 280 mm.
    [0071] La largeur axiale de la deuxième couche de travail est égale à 260 mm.
    [0072] La largeur axiale de la couche de protection est égale à 200 mm.
    [0073] La masse cumulée des couches de travail, de la couche de protection et de la couche de triangulation du pneumatique de référence, comprenant la masse des câbles métalliques et des mélanges de calandrage, se monte â 14.1 Kg.
    [0074] La valeur absolue de la différence entre les valeurs absolues des angles formés par les câbles de la première couche de sommet de travail avec la direction circonférentielle et ceux des câbles de la deuxième couche de sommet de travail est nulle, les angles étant identiques, contrairement à l’invention.
    [0075] L’angle moyen est égal à 18°.
    [0076] La valeur de Fl est égale à 600 N.
    [0077] La valeur de F2 est égale à 523 N.
    [0078] Les valeurs Fl et F2 sont obtenues par une simulation éléments finis, le nombre élevés de nappes de renforcement dans le sommet ne permettant pas l’utilisation d’un modèle analytique simple.
    [0079] Les forces ruptures des éléments de renforcement des couches de sommet de travail FRI et FR2 sont égales à 2600 N.
    [0080] Le ratio d’utilisation du potentiel de rupture F2/FR2 est égal à 20.1 %.
    [0081] Le ratio d’utilisation du potentiel de rupture Fl/FRl est égal à 23.1 %.
    [0082] Le ratio d’utilisation du potentiel de rupture Fl/FRl est 15 % supérieur au ratio d’utilisation du potentiel de rupture F2/FR2.
    [0083] Des essais ont été réalisés avec des pneumatiques réalisés selon l’invention conformément à la figure 1 et avec le pneumatique de référence.
    [0084] Des premiers essais d’endurance ont été réalisés sur une machine de test imposant à chacun des pneumatiques un roulage ligne droite à une vitesse égale à l’indice de vitesse maximum prescrit pour ledit pneumatique (speed index) sous une charge initiale de 4500 Kg progressivement augmentée pour réduire la durée du test.
    [0085] D’ autres essais d’endurance ont été réalisés sur une machine de tests imposant de façon cyclique un effort transversal et une surcharge dynamique aux pneumatiques. Les essais ont été réalisés pour les pneumatiques selon l’invention avec des conditions identiques à celles appliquées aux pneumatiques de référence.
    [0086] Les essais ainsi réalisés ont montré que les distances parcourues lors de chacun de ces tests sont sensiblement identiques pour les pneumatiques selon l’invention et les pneumatiques de référence. Il apparaît donc que les pneumatiques selon l’invention présentent des performances sensiblement équivalentes en termes d’endurance à celles des pneumatiques de référence lors de roulage sur des sols bitumineux.
    [0087] Des tests visant à caractériser la résistance à la rupture d’une armature de sommet de pneumatique soumise à des chocs ont également été réalisés. Ces tests consistent à faire rouler un pneumatique, gonflé à une pression recommandée et soumis à une charge recommandée, sur un obstacle ou indenteur cylindrique de diamètre égal à 1.5 pouce, soit 38.1 mm, et d’une hauteur déterminée. La résistance à la rupture est caractérisée par la hauteur critique de l’indenteur, c’est-à-dire la hauteur maximale de l’indenteur entraînant une rupture totale de l’armature de sommet, c’est-à-dire de la rupture de toutes les couches de sommet. Les valeurs expriment l’énergie nécessaire pour obtenir la rupture du bloc sommet. Les valeurs sont exprimées à partir d’une base 100 correspondant à la valeur mesurée pour le pneumatique de référence.
    Ces résultats montrent que malgré un allégement du pneumatique par une diminution de la masse de son armature sommet, l’énergie à rupture lors d’un choc sur la surface de la bande de roulement est significativement supérieure.
    PNEUMATIC SUMMIT ARMATURE CONSISTING OF TWO TRAVATT TOP SLEEPERS.
    The present invention relates to a tire, radial carcass reinforcement and more particularly a tire for fitting vehicles carrying heavy loads, 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 metal wires or 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 crown ply of work, 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 at most equal to 0.2%.
    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] 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, 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 rotation axis of the tire.
    The radial direction is a direction intersecting the axis of rotation of the tire and perpendicular thereto.
    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, or equatorial plane, is a plane perpendicular to the axis of rotation of the tire and which divides the tire into two halves.
    As regards the metal wires or cables, the measurements of force at break (maximum load in N), tensile strength (in MPa), elongation at break (total elongation in%) and of module (in GPa) are made in traction according to the ISO 6892 standard of 1984.
    Some current tires, called "road", are intended to run at high average speeds and on longer and longer journeys, because of the improvement of the road network and the growth of the motorway network in the world. . The set of conditions under which such a tire is called to roll, undoubtedly allows an increase in the number of kilometers traveled, the wear of the tire being less. This increase in the life expectancy in terms of kilometers, combined with the fact that such conditions of use are likely to result, under heavy load, in relatively high peak temperatures, require an at least proportional increase in the endurance potential of the crown of the tires.
    There are indeed constraints at the crown reinforcement and more particularly shear stresses between the crown layers which, in the case of too high a rise in the operating temperature at the ends of the crown. the axially shorter crown layer, result in the appearance and propagation of cracks in the rubber at said ends. The same problem exists in the case of edges of two layers of reinforcement elements, said other layer not necessarily being radially adjacent to the first.
    In order to improve the endurance of the tire crown reinforcement, the French application FR 2 728 510 proposes to have, on the one hand, between the carcass reinforcement and the reinforcing steel working ply. radially closest to the axis of rotation, an axially continuous sheet formed of non-extensible metal cables forming an angle of at least 60 ° with the circumferential direction, and whose axial width is at least equal to the axial width of the shortest working crown ply, and secondly between the two working crown plies an additional ply formed of metal elements, oriented substantially parallel to the circumferential direction.
    In addition, the French application WO 99/24269 proposes, on either side of the equatorial plane and in the immediate axial extension of the additional layer of reinforcement elements substantially parallel to the circumferential direction, to couple, over a certain axial distance, the two working crown plies formed of reinforcing elements crossed from one ply to the next ply and then decoupling them by rubber mixing profiles at least over the remainder of the width common to the two tablecloths.
    Furthermore, the use of tires on vehicles for trucks "type site" leads the tires to suffer shocks when driving on stony ground. These shocks are of course detrimental to performance in terms of endurance.
    It is still known to those skilled in the art to increase the number of webs constituting the crown reinforcement to improve the endurance of the tire with respect to such shocks.
    Whatever one of these solutions as presented above, the presence of one or more layers of additional reinforcing elements leads to a larger mass of the tire and higher tire manufacturing costs.
    An object of the invention is to provide tires for "heavy-weight" vehicles, for example of the "site approach" type, whose endurance performance is preserved or even improved, particularly with regard to the shocks suffered on the belt. and whose overall mass is reduced.
    This object is achieved according to the invention by a tire for a heavy vehicle type vehicle, whose aspect ratio H / L is less than or equal to 0.75 and whose inflation pressure P is greater than or equal to 6.5 bar, radial carcass reinforcement, comprising a crown reinforcement comprising two working crown layers of reinforcing elements crossed from one ply to the other, making with the circumferential direction angles (a1, a2) between 8 ° and 45 °, said angles α1 and α2 being oriented on either side of the circumferential direction, the crown reinforcement being capped radially with a tread, said tread being joined to two beads by intermediate two sides, the two working crown layers being only present to constitute the crown reinforcement on at least 40% of the axial width of the crown reinforcement, the reinforcing elements of the working layer radially the an outer angle forming an angle α2 with the circumferential direction greater than the absolute angle α formed by the reinforcement elements of the radially innermost working layer with the circumferential direction, the absolute value of the difference between the absolute values of the angles a2 and a1 being greater than 15 °, the average angle a satisfying the relationship: 14 + 13l * exp (-L / 100) <a <20 + 164 * exp (-L / 100), a being defined by the Arctan relation ((tan (| al |) * tan (| a2 |)) '^^), where L is the maximum width of the tire measured in the axial direction and expressed in mm, the utilization ratio of the rupture potential F2 / FR2 of the radially outermost working layer being less than 1/6, wherein: FR2 is the breaking force in uniaxial extension of the cables of the radially outermost working layer,
    with
    P2: the laying pitch of the reinforcing elements of the radially outermost working crown layer, measured perpendicularly to the reinforcing elements at the circumferential mid-plane,
    Rs = Re - Es,
    Re: outer radius of the tire measured at the radially outermost point on the surface of the tread of the tire, said surface being extrapolated to fill any cavities,
    Es: radial distance between the radially outermost point of the tire and its orthogonal projection on the radially outer face of a reinforcing element of the radially innermost working crown layer,
    R1: average of the radii of the axially outermost points on each side of the tire,
    Rt: the radius of the circle passing through three points on the outer surface of the tread outside the recesses, defined from a shoulder end at respective axial distances equal to / 4, / 2 and y4 the axial width of the tread.
    The aspect ratio H / L is the ratio of the height H of the tire on rim to the maximum axial width L of the tire, when the latter is mounted on its service rim and inflated to its nominal pressure. The height H is defined as the difference between the maximum radius of the tread Re and the minimum radius of the bead.
    The width L and the different radii are measured on a tire mounted on its nominal rim and inflated to its nominal pressure, and are expressed in millimeters [0024] The thickness Es and the pitch p2 are measured on a section of the tire. and are expressed in millimeters.
    The angles α1 and α2, expressed in degrees, are also measured on a section of the tire. The angle measurements are according to the invention made at the circumferential mid-plane.
    Preferably according to the invention, the reinforcing elements of said two working crown layers are metallic.
    The results obtained with tires according to the invention have indeed demonstrated that the performance in terms of endurance can be improved especially when driving on stony ground, the crown reinforcement of the tire being lightened. The lightening of the crown reinforcement of the tire is accompanied by a simplification of manufacture and a reduction in manufacturing costs.
    Against all expectations, the results have indeed shown that the tires according to the invention can be reduced by reducing the number of constituent layers of the crown reinforcement while maintaining or even improving the endurance properties of the tire crown. in particular against shocks appearing on the tread for example when driving on stony ground. It is known to those skilled in the art that in order to improve the endurance performance of the crown reinforcement of a tire with respect to this type of impact, it is customary to increase the number of layers of reinforcing elements.
    The inventors think to interpret these results because of the angle formed with the circumferential direction by the reinforcing elements of the radially innermost working crown layer which is smaller in absolute value than that formed by the elements of reinforcing the radially outermost working crown layer. They found that this smaller angle seems to cause a delay in the tensioning by the reinforcing elements during such an impact. Usually, during shocks comparable to those observed during a taxiing on stony ground the breaking of reinforcing elements if it occurs is observed on the radially innermost layer. These findings seem to indicate that in the face of this type of attack, the difference in angles of the reinforcing elements between the two working crown layers makes it possible to improve the endurance performance of the tire while reducing the number of layers of the tire. crown frame.
    The inventors have also made the observation that the choice of the absolute value the difference between the absolute values of the aforementioned angles al and a2 associated with the average angle a and the utilization ratio of the rupture potential F2 / FR2 such that defined according to the invention may allow to eliminate the protective layer usually placed radially outside the other layers of the crown reinforcement. Such a layer is usually present to be sacrificed in the event of an attack of the tire-type cuts that can alter the integrity of metal reinforcing elements by corrosion phenomena associated with the fatigue of said reinforcing elements. The inventors actually observe that the reinforcement elements of the radially outermost working crown layer, of a tire according to the invention, are less stressed during inflation of the tire or during its use in normal running than the reinforcing elements of a radially outermost working crown layer of a more usual tire; such a more usual tire has differences in angles in absolute value between the reinforcing elements of the different smaller working layers, an angle of the reinforcing elements of the radially innermost working layer greater than or equal in absolute value to that reinforcing elements of the radially outermost working layer and a higher utilization ratio of the F2 / FR2 fracture potential. The reinforcing elements of the radially outermost working crown layer of a tire according to the invention thus have endurance properties which are much greater than those of a more usual tire; the inventors thus realize that the removal of the protective layer is made possible and contributes to the lightening of the tire.
    According to a preferred embodiment of the invention, the absolute value of the difference between the absolute values of the angles a2 and al is greater than 18 °. According to this embodiment, and in accordance with the interpretations given above, it will be possible to further improve the endurance performance of the reinforcing elements of the radially outermost working layer and / or to further improve the performance of the tire. with regard to shocks such as those suffered while taxiing on stony ground.
    Advantageously also according to the invention, the utilization ratio of the fracture potential F2 / FR2 of the radially outermost working layer is less than 1/8. Such a ratio of utilization of the breaking potential F2 / FR2 further contributes to improving the endurance performance of the reinforcing elements of the radially outermost working layer during the use of the tire.
    Preferably according to the invention, the utilization ratio of the fracture potential F1 / FR1 of the radially innermost working layer is less than 1/3, in which:
    with
    Pi: the laying pitch of the reinforcing elements of the radially innermost working crown layer, measured perpendicularly to the reinforcing elements at the circumferential mid-plane.
    More preferably, the utilization ratio of the fracture potential F1 / FR1 of the radially innermost working layer is at least 30% greater than the utilization ratio of the fracture potential F 2 / FR 2 of the radially the most external work.
    According to one embodiment of the invention, the reinforcing elements of the working crown layers are inextensible metal cables.
    According to an advantageous embodiment of the invention, the two working crown layers are only present to form the crown reinforcement over at least 60% of the axial width of the crown reinforcement and advantageously still at minus 80% of the axial width of the crown reinforcement. These advantageous embodiments of the invention are in the direction of an even greater relief of the tire.
    According to a preferred embodiment of the invention, optimizing the lightening of the tire, the two working crown layers are only present to form the crown reinforcement over the entire axial width of the crown reinforcement. .
    According to other embodiments of the invention offsetting the compromise of performance of the tire in a less favorable manner with regard to lightening, the crown reinforcement comprises an additional layer, called protective, radially external to the working crown layers, preferably centered on the circumferential mid-plane. The reinforcing elements of such a protective layer are preferably so-called elastic reinforcing elements, oriented with respect to the circumferential direction with an angle of between 8 ° and 45 ° and in the same direction as the angle formed by the elements. reinforcing the working layer which is radially adjacent thereto. More preferably, the reinforcing elements of such a protective layer are parallel to the reinforcing elements of the working layer which is radially adjacent thereto.
    Other variants may also provide that the crown reinforcement can be completed between the carcass reinforcement and the radially inner working layer closest to said carcass reinforcement, by a triangulation layer of elements of the carcass reinforcement. inextensible steel metal reinforcing making, with the circumferential direction, an angle greater than 45 ° and in the same direction as that of the angle formed by the reinforcing elements of the radially closest layer of the carcass reinforcement. Advantageously, said triangulation layer consists of two half-layers positioned axially on either side of the circumferential mid-plane.
    The tire according to the invention may also comprise one or more layers of circumferential reinforcing elements, advantageously consisting of two half-layers positioned axially on either side of the circumferential mid-plane.
    Other details and advantageous features of the invention will emerge below from the description of an exemplary embodiment of the invention with reference to the figure which shows a meridian view of a diagram of a tire according to an embodiment of the invention.
    The figure is not shown in scale to simplify understanding. The figure represents only a half-view of a tire which extends symmetrically with respect to the axis XX 'which represents the circumferential median plane, or equatorial plane, of a tire.
    In the figure, the tire 1, of size 385/65 R 22.5, has a shape ratio H / L equal to 0.65, H being the height of the tire 1 on its mounting rim and L its axial width. Max. Said tire 1 comprises a radial carcass reinforcement 2 anchored in two beads, not shown in the figure. The carcass reinforcement 2 is formed of a single layer of metal cables. They still include a tread 5.
    In the figure, the carcass reinforcement 2 is shrunk in accordance with the invention by a crown reinforcement 4, formed radially from the inside to the outside of a first working layer 41 formed of metal cables. oriented at an angle equal to 12 °, a second working layer 42 formed of metal cables oriented at an angle equal to 40 ° and crossed with the metal cables of the first working layer 41, the cables of each of working layers 41, 42 being oriented on either side of the circumferential direction.
    The metal cables constituting the reinforcing elements of the two working layers are cables of formula 9.35. They are distributed in each of the working layers with a distance between the reinforcing elements, measured according to the normal to the direction of the average line of the cable equal to 2 mm.
    The tire is inflated to a pressure of 9 bar.
    The axial width L ^^ of the first working layer 41 is equal to 280 mm.
    The axial width L ^^ of the second working layer 42 is equal to 260 mm.
    The axial width of the tread L5 is equal to 303 mm.
    The axial width L is equal to 377 mm.
    The cumulative mass of the two working layers 41, 42, comprising the mass of the metal cables and calendering mixtures, is thus 9.1 Kg.
    The difference between the angles formed by the cables of the first working crown layer with the circumferential direction and those of the cables of the second working crown layer is equal to 28 °.
    The average angle is equal to 22.9 ° and is well between 17 ° and 23.8 °.
    The measured value of Re is equal to 536.9 mm.
    The measured value of Es is equal to 24.9 mm.
    The average value RL of the measured rays is equal to 409 mm. The value Rt determined on the tire is equal to 1400 mm. The calculated value of Te is equal to 395.9 N / mm.
    The calculated value of C is equal to -0.01.
    The value of Fl is equal to 655.3 N.
    The value of F2 is equal to 267.7 N.
    The breaking forces of the reinforcing elements of the working crown layers FRI and FR2 are equal to 2600 N.
    The utilization ratio of the rupture potential F2 / FR2 is equal to 10.3%.
    The utilization ratio of the rupture potential F1 / FR1 is equal to 25.2%.
    The utilization ratio of the rupture potential F1 / FR1 is 145% greater than the utilization ratio of the rupture potential F2 / FR2.
    The tire according to the invention is compared with a reference tire of the same size which differs from the tire according to the invention by its crown reinforcement formed radially from the inside to the outside: of a triangulation layer formed of metal cables oriented at an angle equal to 50 °, a first working layer formed of metal cables oriented at an angle equal to 18 °, on the same side as the cables of the triangulation layer relative to the circumferential direction, a second working layer formed of metal cables oriented at an angle of 18 ° and crossed with the metal ropes of the first working layer, the cables of each of the working layers being oriented on both sides and other of the circumferential direction; - a protective layer made of elastic metal cables 6.35, the distance between the reinforcing elements, measured according to normal the direction of the mean line of the cable is equal to 2.5 mm, oriented at an angle of 18 °, the same side as the cables of the second working layer.
    The metal cables of the two working layers and the triangulation layer are cables of formula 9.35. They are distributed in each of the working layers with a distance between the reinforcing elements, measured according to the normal to the direction of the average line of the cable equal to 2.5 mm.
    The reference tire is inflated to a pressure of 9 bar.
    The axial width of the triangulation layer is equal to 260 mm.
    The axial width of the first working layer is equal to 280 mm.
    The axial width of the second working layer is equal to 260 mm.
    The axial width of the protective layer is equal to 200 mm.
    The cumulative mass of the working layers, the protective layer and the triangulation layer of the reference tire, comprising the mass of the metal cables and calendering mixtures, amounts to 14.1 Kg.
    The absolute value of the difference between the absolute values of the angles formed by the cables of the first working crown layer with the circumferential direction and those of the cables of the second working crown layer is zero, the angles being identical. , contrary to the invention.
    The average angle is equal to 18 °.
    The value of Fl is equal to 600 N.
    The value of F2 is equal to 523 N.
    The values Fl and F2 are obtained by a finite element simulation, the high number of reinforcement plies in the top not allowing the use of a simple analytical model.
    The breaking forces of the reinforcing elements of the working crown layers FRI and FR2 are equal to 2600 N.
    The utilization ratio of the rupture potential F2 / FR2 is equal to 20.1%.
    The utilization ratio of the rupture potential F1 / FR1 is equal to 23.1%.
    The utilization ratio of the rupture potential F1 / FR1 is 15% higher than the utilization ratio of the rupture potential F2 / FR2.
    Tests were carried out with tires made according to the invention in accordance with Figure 1 and with the reference tire.
    First endurance tests were performed on a test machine imposing on each tire a straight line running at a speed equal to the maximum speed index prescribed for said tire (speed index) under an initial load of 4500 Kg gradually increased to reduce the duration of the test.
    Other endurance tests were carried out on a test machine imposing cyclically a transverse force and a dynamic overload to the tires. The tests were carried out for the tires according to the invention with conditions identical to those applied to the reference tires.
    The tests thus carried out showed that the distances traveled during each of these tests are substantially identical for the tires according to the invention and the reference tires. It therefore appears that the tires according to the invention have substantially equivalent performances in terms of endurance to those of the reference tires when driving on bituminous floors.
    Tests to characterize the breaking strength of a tire crown reinforcement subjected to shocks were also carried out. These tests consist in rolling a tire, inflated to a recommended pressure and subjected to a recommended load, on an obstacle or cylindrical indenter of diameter equal to 1.5 inches, that is to say 38.1 mm, and of a determined height. The breaking strength is characterized by the critical height of the indenter, that is to say the maximum height of the indenter resulting in a total rupture of the crown reinforcement, that is to say of the breaking of all vertex layers. The values express the energy necessary to obtain the break of the vertex block. The values are expressed from a base 100 corresponding to the value measured for the reference tire.
    These results show that, despite lightening of the tire by a reduction in the mass of its crown reinforcement, the energy at rupture during a shock on the surface of the tread is significantly greater.
    权利要求:
    Claims (9)
    [1" id="c-fr-0001]
    1 - Pneumatic tire for a truck-type vehicle, whose H / L aspect ratio is less than or equal to 0.75 and whose inflation pressure P is greater than or equal to 6.5 bar, with a radial carcass reinforcement comprising crown reinforcement comprising two working crown layers of reinforcing elements crossed from one ply to the other by making with the circumferential direction angles (a1, a2) of between 8 ° and 45 °, said angles al and a2 being oriented on either side of the circumferential direction, the crown reinforcement being capped radially with a tread, said tread being joined to two beads by means of two flanks, characterized in that the said two working crown layers alone are present to constitute the crown reinforcement over at least 40% of the axial width of the crown reinforcement, in that the reinforcing elements of the radial working layer the outermost direction form an angle α2 with the circumferential direction greater than the absolute angle α the angle formed by the reinforcing elements of the radially innermost working layer with the circumferential direction, in that the absolute value of the difference between the absolute values of the angles a2 and al is greater than 15 °, in that the average angle satisfies the relation:

    a being defined by the Arctan relation ((tan (| al |) * tan (| a2 |)) ^^^), where L is the maximum width of the tire measured along the axial direction and expressed in mm, in that the ratio for using the fracture potential F2 / FR2 of the radially outermost working layer is less than 1/6, in which: FR2 is the breaking force in uniaxial extension of the cables of the radially outermost working layer,

    with Te = 0.092 * P * Rs * (1- (Rs2-RL2) / (2 * Rt * Rs)), C = 0.00035 * (min ((L-80) / sin (| al |), (L- 80) / sin (| a2 |), 480) -480), P2: the laying pitch of the reinforcing elements of the radially outermost working crown layer, measured perpendicularly to the reinforcing elements at the circumferential median, Rs = Re - Es, Re: outer radius of the tire measured at the radially outermost point on the surface of the tread of the tire, said surface being extrapolated to fill any cavities. Es: radial distance between the radially outermost point of the tire and its orthogonal projection on the radially outer face of a reinforcing element of the radially innermost working crown layer, RL: average of radii of the axially outermost points on each side of the tire, Rt: the radius of the circle passing through three points on the outer surface of the tread outside the troughs, defined from one end of the tread; shoulder at respective axial distances equal to 1/4, 1/2 and the width of the tread.
    [2" id="c-fr-0002]
    2 - A tire according to claim 1, characterized in that the reinforcing elements of said two working crown layers are metallic.
    [3" id="c-fr-0003]
    3 - A tire according to claim 1 or 2, characterized in that the absolute value of the difference between the absolute values of angles a2 and al is greater than 18 °.
    [4" id="c-fr-0004]
    4 - tire according to one of claims 1 to 3, characterized in that the utilization ratio of the fracture potential F2 / FR2 of the radially outermost working layer is less than 1/8.
    [5" id="c-fr-0005]
    5 - tire according to one of claims 1 to 4, characterized in that the utilization ratio of the fracture potential Fl / FRl of the radially innermost working layer is less than 1/3, wherein:

    with Pi: the laying pitch of the reinforcing elements of the radially innermost working crown layer, measured perpendicularly to the reinforcing elements at the circumferential mid-plane.
    [6" id="c-fr-0006]
    6 - A tire according to claim 5, characterized in that the utilization ratio of the fracture potential F1 / FR1 of the radially innermost working layer is at least 30% greater than the utilization ratio of the fracture potential F 2 / FR2 of the radially outermost working layer.
    [7" id="c-fr-0007]
    7 - A tire according to one of the preceding claims, characterized in that at most said two working crown layers are only present to form the crown reinforcement on at least 60% of the axial width of the crown reinforcement, and preferably at least 80% of the axial width of the crown reinforcement.
    [8" id="c-fr-0008]
    8 - A tire according to one of the preceding claims, characterized in that the two working crown layers are only present to form the crown reinforcement over the entire axial width of the crown reinforcement
    [9" id="c-fr-0009]
    9 - tire according to one of the preceding claims, characterized in that the reinforcing elements of the working crown layers are inextensible metal cables.
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    同族专利:
    公开号 | 公开日
    FR3048382B1|2018-03-09|
    WO2017149222A1|2017-09-08|
    EP3423292A1|2019-01-09|
    EP3423292B1|2019-12-25|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US3175598A|1959-11-10|1965-03-30|Pirelli|Pneumatic tires|
    US4034791A|1975-06-30|1977-07-12|Uniroyal, S.A.|Pneumatic tire with reinforcing belt|
    FR2887808A1|2005-06-30|2007-01-05|Michelin Soc Tech|PNEUMATIC FOR HEAVY VEHICLES|
    DE102013107475A1|2013-07-15|2015-01-15|Continental Reifen Deutschland Gmbh|Vehicle tires|
    FR3094278B1|2019-03-29|2021-02-19|Michelin & Cie|Tire crown reinforcement made up of two working crown layers|
    FR3096931B1|2019-06-06|2021-05-21|Michelin & Cie|PNEUMATIC FEATURING OPTIMIZED SIDES AND A TOP REINFORCEMENT CONSISTING OF TWO WORKING TOP LAYERS AND ONE LAYER OF CIRCUMFERENTIAL REINFORCEMENT ELEMENTS|
    FR3096933B1|2019-06-06|2021-05-14|Michelin & Cie|PNEUMATIC FEATURING OPTIMIZED SIDES AND A TOP REINFORCEMENT CONSISTING OF TWO WORKING TOP LAYERS AND ONE LAYER OF CIRCUMFERENTIAL REINFORCEMENT ELEMENTS|
    FR3096932B1|2019-06-06|2021-05-14|Michelin & Cie|PNEUMATIC FEATURING A TOP REINFORCEMENT CONSISTING OF TWO WORKING TOP LAYERS AND OPTIMIZED SIDES|
    FR3096930B1|2019-06-06|2021-05-14|Michelin & Cie|PNEUMATIC FEATURING A TOP REINFORCEMENT CONSISTING OF TWO WORKING TOP LAYERS AND OPTIMIZED SIDES|
    FR3103740B1|2019-11-28|2021-10-29|Michelin & Cie|PNEUMATIC CONTAINING A TREAD CONSTRUCTION OF SEVERAL ELASTOMERIC MIXTURES|
    法律状态:
    2017-03-22| PLFP| Fee payment|Year of fee payment: 2 |
    2017-09-08| PLSC| Publication of the preliminary search report|Effective date: 20170908 |
    2018-03-23| PLFP| Fee payment|Year of fee payment: 3 |
    2019-11-29| ST| Notification of lapse|Effective date: 20191106 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1651770|2016-03-02|
    FR1651770A|FR3048382B1|2016-03-02|2016-03-02|PNEUMATIC SUMMIT REINFORCEMENT CONSISTING OF TWO WORKING SUMMIT LAYERS|FR1651770A| FR3048382B1|2016-03-02|2016-03-02|PNEUMATIC SUMMIT REINFORCEMENT CONSISTING OF TWO WORKING SUMMIT LAYERS|
    PCT/FR2017/050396| WO2017149222A1|2016-03-02|2017-02-23|Tyre crown reinforcement formed by two working crown layers|
    EP17710347.0A| EP3423292B1|2016-03-02|2017-02-23|Tyre crown reinforcement formed by two working crown layers|
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