Tire with optimized rolling resistance performance
The tire architecture with a reduced inter-cable distance and shrink-fit reinforcement addresses the challenge of controlling temperatures and rolling resistance, achieving efficient fuel consumption by limiting mechanical stress and shear forces.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- MICHELIN & CO (CIE GEN DES ESTAB MICHELIN)
- Filing Date
- 2024-12-12
- Publication Date
- 2026-06-19
AI Technical Summary
Existing tire designs face challenges in controlling operating temperatures and optimizing rolling resistance due to the use of thick packing compounds that increase mechanical stress and shear forces, leading to increased fuel consumption.
A tire architecture with a reduced inter-cable distance (DI) between textile reinforcement elements in the decoupling portion, combined with a shrink-fit reinforcement, limits mechanical deformation and shear stresses, thereby reducing the need for excessive packing thickness and optimizing rolling resistance.
The solution effectively controls operating temperatures and reduces rolling resistance, minimizing fuel consumption by preventing radial movement of textile elements during curing and optimizing tire dimensions.
Smart Images
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Abstract
Description
Title of the invention: Tire exhibiting optimized rolling resistance performance
[0001] The invention relates to tires, and more particularly to passenger car tires. Technological background
[0002] A tire is an object with a revolution geometry, substantially toric, about an axis of revolution, the axis of revolution coinciding with the axis of rotation of the tire. A tire comprises two beads intended to be mounted on a rim, two sidewalls connected to the beads, and a crown. The crown comprises a crown reinforcement and a tread intended to come into contact with the ground, the tread being arranged radially externally to the crown reinforcement. The tread is intended to contact the ground during the use of the tire on a vehicle via a tread surface. A first axial side of the crown is connected to the radially external end of one of the two sidewalls, and the second side of the crown is connected to the radially external end of the other sidewall.An equatorial or median plane, perpendicular to the axis of rotation of the tire and passing through the center of the tread surface, separates the tire into two halves that are substantially symmetrical with respect to the median plane.
[0003] Document FR2799411A1 describes a passenger car tire having a crown reinforcement. The crown reinforcement comprises a first working layer, a second working layer, and a reinforcing layer. It is now common practice, particularly for passenger car tires intended for high-speed driving, to use an additional reinforcing layer, known as a reinforcing layer, to strengthen the crown. This layer comprises circumferentially oriented reinforcing elements. Each of the first and second working layers comprises metallic reinforcements embedded in at least one elastomeric compound. The reinforcing layer comprises textile reinforcing elements. The carcass reinforcement, then the crown reinforcement, and finally the tread reinforcement are arranged successively from the innermost to the outermost radially.The first working layer is arranged radially internally to the second working layer, and the second working layer is arranged radially internally to the shrink-fit reinforcement. On either side of the median plane, the first working layer has a first point El at its axial end, and the second working layer has a second point E2 at its axial end, the first point El being axially external to the . second point E2. The top includes a packing volume between the ends of the working layers, the packing volume serving to control the operating temperature by limiting the maximum levels of mechanical stress at said ends of the first and second working layers.
[0004] Mechanical stresses related to the flattening of the tread during tire use generate stresses at the crown reinforcement, and more specifically, shear stresses between the crown layers. These cyclic mechanical stresses lead to an increase in operating temperature, particularly at the axial ends of the first and second tread layers. It is known to insert a packing material between the ends of the first and second tread layers to create mechanical decoupling between these ends and limit shear stresses. Such a decoupling material exhibits very good cohesion with the first and second tread layers.Furthermore, introducing such a large filling volume, particularly between the ends, also impacts the tire's rolling resistance performance. Excessive thickness in the filling volume design leads to increased rolling resistance and therefore increased fuel consumption for the passenger vehicle. However, until now, excessive thickness has always been used in the design because tire designers, bound by the tire manufacturing process, must account for the thinning of the filling compound. The filling compound of the uncured tire, once cross-linked, corresponds to the filling volume of the cured tire. This thinning is particularly noticeable between the reinforcements of the shrink-wrap structure during the curing stage of the uncured tire. The thinning is linked to the pressure and temperature applied to the uncured tire in its curing mold.Consequently, the textile reinforcement elements of the tire reinforcement will move radially closer together internally as they penetrate the decoupling portion of the packing compound. Therefore, the tire designer must plan for a packing compound thickness that is significant to compensate for this compression. Such a thick packing compound in the raw tire inevitably increases the average thickness of the tire's packing mass and thus degrades the tire's rolling resistance.
[0005] The object of the present invention makes it possible to obtain a tire architecture offering both control of operating temperatures in the apex and optimization of rolling resistance performance. Description of the invention
[0006] According to the invention, the tire comprises a crown and a carcass reinforcement, the crown comprising a tread and a crown reinforcement, being arranged radially externally to the carcass reinforcement, the crown reinforcement comprising: - a first working layer and a second working layer, each of the first and second working layers comprising metallic reinforcements embedded in at least one elastomer coating, the first working layer being arranged radially internally to the second working layer, the first working layer having a point El at each axial end of the first working layer, the second working layer having a point E2 at each axial end of the second working layer, the point El being axially external to the point E2, - a reinforcing cage, comprising textile reinforcement elements, embedded in at least one coating elastomer and arranged radially externally to the top reinforcement and radially internally to the tread, - a padding volume arranged between the first working layer and the shrinkage reinforcement, the padding volume comprising a decoupling portion extending axially from point El to point E2, the shrinkage reinforcement having a support portion in line with the decoupling portion, the intercable DI between the textile reinforcement elements of the support portion of the shrinkage reinforcement is strictly less than 0.05 mm, preferably less than or equal to 0.04 mm, more preferably less than or equal to 0.03 mm.
[0007] The packing volume, and in particular the decoupling portion of the packing volume, is subjected to shear stresses imposed by the first and second working layers when the tire flattens. Flattening is linked to the phenomenon of the tire being crushed against the ground in use. This cyclical shear causes a substantial increase in operating temperature between and around the ends E1, E2 of the first and second working layers.
[0008] The use of the shrink-fitting reinforcement allows for good support of the tire at high speed, the shrink-fitting reinforcement here having a support portion in line with the decoupling portion, other shear forces are thus generated in the decoupling portion of the packing volume by the presence of the shrink-fitting reinforcement, the shrink-fitting reinforcement being moreover integral with the decoupling portion of the packing volume.
[0009] The packing volume, and in particular the decoupling portion of the packing volume, thus allows mechanical decoupling not only between the first and second working layers, but also with the shrink-fit reinforcement, the levels Mechanical deformation will thus be limited by improving cohesion and mechanical strength.
[0010] Furthermore, although necessary to control the operating temperature at the ends of the first and second working layers, the introduction of such a volume of packing negatively impacts the rolling resistance performance of the tire, negatively impacting the energy consumption of the vehicle.
[0011] Without the invention presented here, the tire designer must provide a significant thickness in the dimensioning of the decoupling portion, particularly to account for the thinning phenomenon, which induces inhomogeneous geometric variations during the curing of a raw tire. Indeed, during the pressure and temperature application in the curing mold, displacements are observed in the textile reinforcement elements of the shrink-fit reinforcement along a radially inward direction, reducing the effective decoupling thickness after curing the raw tire.
[0012] In order to optimize the average thickness of the decoupling portion of the filling volume, while avoiding excessive thickness in the design, the inter-cable DI is chosen according to the invention to be particularly small, namely strictly less than 0.05 mm. Thus, the clumping of the filling mixture during the raw tire manufacturing process is contained by the bottleneck formed by the inter-cable Dl. The clumping phenomenon is therefore significantly reduced, or even completely eliminated. In other words, the textile reinforcement elements no longer move radially internally, as the filling mixture cannot flow through the inter-cable during pressure and temperature control in the curing mold.Therefore, excessive thickness in the dimensioning is no longer necessary; the thickness in the decoupling portion of the packing volume can be reduced by the tire designer to limit rolling resistance.
[0013] The term "inter-cable" refers to the minimum average distance separating, in a meridian plane of the tire, two axially consecutive reinforcements. This minimum average distance is calculated over an axial measurement portion between 50% and 80% of the axial width of the decoupling portion of the padding volume, said axial measurement portion being axially centered between the ends E1 and E2. A textile reinforcement element has a contour that is not necessarily cylindrical; thus, an inter-cable distance is determined by the minimum distance between two contours of two axially consecutive textile reinforcement elements.
[0014] The term "raw pneumatic" refers to a set of elements of crosslinkable composition in their uncrosslinked state and arranged on a manufacturing support presenting a shape essentially toroidal around the axis of revolution, the principal axis of revolution being collinear with the axial direction, well known to those skilled in the art. The tire blank is an assembly suitable for being positioned in a curing mold, the curing process comprising a step of pressurizing and heating said blank, followed by a curing step proper to obtain the tire.
[0015] Points El and E2 are determined by taking, in a meridian cutting plane, the center of the section of the most axially external reinforcement of the considered working layer on either side of the median plane.
[0016] A textile reinforcing element is defined as at least one textile monofilament. Such monofilaments are obtained, for example, by melt spinning, solution spinning, or gel spinning. Textile monofilaments are usually classified into two main categories: natural monofilaments and chemical monofilaments. Natural monofilaments include monofilaments of plant origin (including cotton), animal origin, and mineral origin. Chemical monofilaments include artificial monofilaments and synthetic monofilaments. Artificial monofilaments are manufactured from natural raw materials and include, in particular, viscose made from wood cellulose. Synthetic monofilaments include organic polymeric monofilaments (e.g., polyesters and polyamides) as well as inorganic polymeric monofilaments (e.g., glass and carbon).For reasons of protection against corrosive agents, the textile monofilament(s) used here are preferably chosen from among chemical monofilaments, preferably from synthetic monofilaments, and most preferably from organic polymeric monofilaments. Examples include aliphatic polyamides, particularly polyamide 6-6, polyesters, particularly polyethylene terephthalate, and aromatic polyamides, particularly aramid.
[0017] By axial direction, we mean the direction parallel to the axis of revolution of the tire, that is to say the axis of rotation of the tire.
[0018] By circumferential direction, we mean the direction which is perpendicular to the axial direction and to a radius of the tire.
[0019] By radial direction, we mean the direction along a radius of the tire, that is to say a direction intersecting the axis of rotation and perpendicular to this axis.
[0020] By meridian plane, we mean a plane containing the axis of rotation of the tire.
[0021] By median plane of the tire (denoted M), we mean the plane perpendicular to the axis of rotation of the tire and which passes through the middle of the tread.
[0022] By radially inside, and radially outside respectively, we mean closer to the axis of rotation of the tire, and further from the axis of rotation of the tire respectively. By axially inside, and axially outside respectively, we mean closer to the median plane of the tire, and further from the median plane of the tire respectively.
[0023] Advantageously, the linear mass or count of the textile reinforcement elements ranges from 10 to 100 tex, preferably from 30 to 70 tex, very preferably from 40 to 60 tex.
[0024] In a first optional embodiment, the shrink-fit armature outside the bearing portion has a cable spacing DI strictly less than 0.05 mm.
[0025] In a second optional embodiment, the shrink-fit armature outside the bearing portion has a cable spacing DI greater than or equal to 0.05 mm.
[0026] The fineness (or linear mass) is determined according to ASTM D1423. The fineness is given in tex (mass in grams of 1000 m of product - reminder: 0.111 tex equals 1 denier).
[0027] Any interval of values designated by the expression "between a and b" represents the domain of values going from more than a to less than b (i.e., bounds a and b excluded) while any interval of values designated by the expression "from a to b" means the domain of values going from a to b (i.e., including the strict bounds a and b).
[0028] In a particular embodiment, in a meridian cutting plane, the textile reinforcement elements of the shrink-wrapping frame in the decoupling portion are not in direct contact.
[0029] By preventing direct contact through the use of adhesive and / or the elastomeric matrix, friction between two consecutive textile reinforcement elements is avoided, as such friction could be detrimental to the proper functioning of the tire. For example, such friction could cause localized wear during tire use.
[0030] In a first optional embodiment, the average diameter of each of the textile reinforcement elements of the bearing portion of the shrink-fit reinforcement is less than or equal to 0.54 mm and preferably less than 0.40 mm.
[0031] The term "average diameter" of textile reinforcement elements, in a meridian cutting plane, means the smallest possible diameter of the circle containing the textile reinforcement element in question and which is not secant with said element.
[0032] In a variant of the first optional embodiment, the shrink-fit reinforcement comprises an elastomer layer, referred to as the coating, arranged radially internally to the textile reinforcement elements and in contact with the textile reinforcement elements, the minimum distance D2 between the textile reinforcement elements of the portion support and the portion of packing rubber is less than or equal to 0.20 mm, preferably 0.15 mm, very preferably 0.12 mm.
[0033] This thickness D2 is an average value calculated on an axial measurement portion between 50% and 80% of the axial width of the decoupling portion of the packing volume, the axial measurement portion being centered between the ends El and E2.
[0034] By combining the inter-cable Dl with a diameter of the textile reinforcement elements less than or equal to 0.54 mm, the overall dimensions of the compression frame are optimized, resulting in a weight reduction. Furthermore, the diameters of the textile reinforcement elements also allow for a significant reduction in the thickness of the elastomer layer arranged radially inside the textile reinforcement elements. This variant of the first embodiment is therefore particularly advantageous for reducing rolling resistance and tire weight.
[0035] According to this variant of the first embodiment, the wire reinforcement elements are embedded in a polymer matrix, preferably an elastomeric matrix. The compositions used for these matrices are conventional compositions for calendering reinforcements, typically based on natural rubber or other diene elastomer, a reinforcing filler such as carbon black, a vulcanizing system, and standard additives. Adhesion between the wire reinforcement element(s) and the matrix in which they are embedded is ensured, for example, by a standard adhesive composition, such as an RFL (Resorcinol-Formaldehyde-Latex) type adhesive or an equivalent adhesive, for example, as described in WO2013017421 or WO2017168109.
[0036] By a first means of verification, the decoupling portion of the packing volume has an average thickness A between the most radially inner points of the shrink-fit reinforcement and the most radially outer points of the first working layer, the average thickness A ranging from 0.5 to 1.5 mm.
[0037] By a second means of verification, the set of points of intersection between the straight segment [El, E2] and the textile reinforcement elements of the support portion of the shrink-fit reinforcement is the empty set.
[0038] By a third means of verification, the decoupling portion of the packing volume having, in a meridian cutting plane, a first radial height H1 from E1 to the coating layer of the shrinkage reinforcement and a second radial height H2 passing through E2 and from the radially outer surface of the coating layer of the first working layer to the radially inner surface of the coating layer of the textile reinforcement elements of the shrinkage reinforcement, the ratio, in percentage, of H1 on H2 is greater than 80%.
[0039] Each of the first, second, and third means allows verification of the optimization of rolling resistance while controlling the operating temperature of the tire at the tips of the first and second tread layers. Each of the first, second, and third verification means can be combined with the others. The combination of the three means presents an optimum in terms of the performance trade-off.
[0040] The first verification method consists of limiting the average thickness A, A being chosen by the tire designer taking into account the largely limited or even absent sagging phenomenon due to the particularly reduced inter-cable DI. The average thickness A is determined over an axial portion between 90% and 100% of the axial width of the decoupling section of the packing volume, the axial portion being centered between the ends E1 and E2. The average thickness A is the average of the distances measured experimentally in the radial direction, in a meridional cross-sectional plane of the tire. It is recommended to take at least 10 measurements evenly distributed over said axial portion where the measurement points extend.
[0041] The second means of verification consists of tracing the straight segment [E1,E2] on a meridian cutting plane, said straight segment [E1,E2] does not have any point having an intersection with any of the textile reinforcement elements of the support portion of the shrink-fitting reinforcement.
[0042] The third verification method consists of drawing the first height H1 in the radial direction and the second height H2 also in the radial direction. El' is the point located at the intersection between the interface of the first working layer and the packing volume, and the radial axis passing through EL. E2' is the point located at the intersection between the interface of the second working layer and the shrink-fit reinforcement, and the radial axis passing through E2.
[0043] In a particular embodiment, the tire is a passenger car tire.
[0044] The tires of the invention, in particular, can be intended for motor vehicles of the passenger car type, 4x4, "SUV" (Sport Utility Vehicles), but also for vehicles for professional use such as road transport vehicles (vans, trucks, tractors, trailers), off-road vehicles, agricultural or civil engineering vehicles.
[0045] Preferably, the tires can be intended for motor vehicles of the passenger car, 4x4, "SUV" (Sport Utility Vehicles) type.
[0046] In preferred embodiments of the invention, the tires are intended for passenger vehicles as defined in the European Tyre and Rim Technical Organisation or "ETRTO" standard, 2023. Preferably and optionally, such a tire has a cross-section, in a cutting plane meridian, characterized by a section height H and a nominal section width or bead size S as defined by the European Tyre and Rim Technical Organisation (ETRTO) standard, 2023, such that the H / S ratio, expressed as a percentage, is at most 90 and at least 20, and the nominal section width S is at least 115 mm and at most 385 mm. Furthermore, the hook diameter D, defining the diameter of the tire mounting rim, is at least 12 inches and at most 30 inches. Description of the figures
[0047] The invention and its advantages will be readily understood in the light of the detailed, non-limiting description that follows and with reference to [Fig. 1] and [Fig. 2] and [Fig. 3]. - [Fig. 1] is a cross-sectional view, in a meridian cutting plane, of a preferred embodiment of the pneumatic 1. - Figure [Fig. 2] is a detailed view of area I of Figure [Fig. 1] illustrating an area around the ends E1 and E2 of tire 1 - Fig. 3 is a detailed view of zone II of Fig. 2 illustrating one embodiment of the shrink-fitting frame 19 of the tire 1.
[0048] In the three figures relating to tire 1, a coordinate system X, Y, Z is shown, corresponding to the usual circumferential (X), axial (Y), and radial (Z) directions of a tire 1. Tire 1 is substantially of revolution about an axis parallel to the axial direction Y. Tire 1 is intended for a passenger vehicle. Tire 1 is intended to be mounted on a mounting support, for example, a rim not shown in the figures.
[0049] With reference to [Fig. 1], the tire 1 comprises a crown 7, two sidewalls 3, two bead 5, each sidewall 3 connecting each bead 5 to the crown 7. The crown 7 of the tire 1 comprises a tread 13 and also a crown reinforcement 8 arranged radially internally to the tread 13 and a carcass reinforcement 9 arranged radially internally to the crown reinforcement 8 and anchored in each of the two bead 5, the carcass reinforcement 9 being wound around a bead 2. The tread 13 has a tread surface 13 intended to come into contact with the ground. The apex reinforcement 8 and the tread 13 are arranged in contact with each other and extend into the apex 7 in the circumferential direction X. Here the carcass reinforcement includes a carcass layer 11.
[0050] With further reference to [Fig. 1], the top reinforcement 8 comprises a shrink-fit reinforcement 19, a first working layer 15 and a second working layer 17, each of the first and second working layers 15 and 17 comprising metal reinforcements not shown in the figures. The shrink-fit reinforcement 19 The system includes textile reinforcement elements 31, which are helically wound in the circumferential direction X and extend axially along the direction Y. The carcass reinforcement 9, the apex reinforcement 8, and the tread 13 are arranged respectively and successively from the innermost to the outermost radially. The first working layer 15 is arranged radially inward to the second working layer 17, the first working layer 15 having a point El at each of the axial ends of the first working layer 15.The second working layer 17 has a point E2 at each of its axial ends, with point El being axially outside point E2. The apex 7 comprises a packing volume 21 arranged between the first working layer 15 and the shrinkage reinforcement 19. The packing volume 21 includes a decoupling portion 22 extending axially from point El to point E2. A bearing portion 18 of the shrinkage reinforcement 19 is defined with respect to the decoupling portion 22. In a meridional cutting plane, the center of the section of the most axially external reinforcement of the considered working layer determines point El and point E2.
[0051] In one embodiment, the shrink-fit reinforcement 19 can be formed from a continuous strip wound in several circumferential turns. The strip comprises, for example, eight to ten wire shrink-fit reinforcement elements embedded in an elastomeric matrix 33 to form a strip with a width ranging from 5.0 mm to 15.0 mm and a thickness ranging from 0.4 mm to 0.8 mm, the strip not being shown in the figures.
[0052] By way of deviation from [Fig. 1] and with reference to the detail views of [Fig. 2] and [Fig. 3], the figures illustrate the textile reinforcement elements 31 of the shrink frame 19 embedded in an elastomeric matrix 33 forming an elastomer layer 35 of the shrink frame 19. The elastomer layer 35 of the shrink frame 19 is arranged radially internally to the textile reinforcement elements 31. The elastomer layer 35 of the shrink frame 19 is in contact with the textile reinforcement elements 31 by means of an adhesive system, here an RFL (Resorcinol-Formaldehyde-Latex) type adhesive. The elastomer layer 35 here has a minimum thickness D2 between the interface between the elastomer layer 35 and the padding volume 21 and the textile reinforcement elements 31. The elastomeric matrix 33 here has a complementary layer 37 of elastomer allowing a radially external covering of the textile reinforcement elements 31 by said matrix.The complementary layer 37 and the elastomer layer 35 may have an interface passing substantially through the curve S. The curve S passes through the center of each of the reinforcements of the shrink-fit structure in a meridional plane. The complementary layer 37 and the elastomer layer 35 are here made of the same material.
[0053] The detailed view of [Fig.2] shows a first means of verifying an optimized tire architecture according to the invention, i.e. a decoupling portion 22 of the packing volume 21 having an average thickness A between the most radially internal points of the shrink-fit reinforcement 19 and the most radially external points of the first working layer 15.
[0054] The detailed view of [Fig.2] shows a second means of verifying an optimized tire architecture according to the invention, i.e. a straight segment [El, E2] not intersecting with the textile reinforcement elements 31 of the support portion 18 of the shrink-fitting frame 19.
[0055] The detailed view of [Fig.2] shows a third means of verifying an optimized tire architecture according to the invention, i.e. in a first height H1 starting from El', H1 extending radially to the textile reinforcement elements 31 of the shrink frame 19, and a second height H2 passing axially through E2' and extending radially from the radially outer surface of the first working layer 15 to the textile reinforcement elements 31 of the shrink frame 19, the ratio, in percentage, of H1 to H2 is here greater than 80%. Test plan
[0056] In order to highlight the benefit of the invention, a test plan, including the manufacture and testing of tires, is carried out. The test plan compares a control tire T1 with a first tire PI and a second tire P2.
[0057] In this respect, the test tire 1 Tl is a Michelin ePrimacy 245 / 45R18. The test tire Tl has a shrink-fit reinforcement 19 with an average thickness E of 0.77 mm. While embedded in an elastomeric matrix 33, the textile reinforcement elements 31 of the shrink-fit reinforcement 19, here made of nylon, have an average diameter D of 0.54 mm, a fiber content of 94 tex, and a cord spacing of 0.30 mm. The tire 1 includes a packing volume 21 arranged between the first working layer 15 and the shrink-fit reinforcement 19, the packing volume 21 being sized to take into account the thinning phenomenon. Thinning is related to the cord spacing value at the time the uncured tire is pressurized and heated in its curing mold.The elastomer layer 35 of the reinforcement cage 19 of the test tire Tl, arranged radially internally within the textile reinforcement elements 31, has a maximum thickness D2 of 0.13 mm with respect to each of the textile reinforcement elements 31 of the bearing portion 18. The minimum distance D2 is measured between the textile reinforcement elements 31 of the bearing portion 18 and the portion 22 of the filling rubber 21. The following table summarizes the main properties of the test tire TL. Specifications: Test wire, Type of strands / thickness (tex) / number, Nylon / 94 / 2, Twist (turns / m) 320 / 320, Density (threads / dm) 120, D (mm) 0.54, E (mm) 0.77, Inter-strand (mm) 0.30, D2 (mm) 0.13
[0058] The tire PI of the test plan, starting from the first control tire Tl, has a reinforcing cage 19 with an average thickness E of 0.50 mm. While embedded in the same elastomeric matrix 33 as the control Tl, the textile reinforcement elements 31 of the reinforcing cage 19 of P2 have an average diameter of 0.37 mm, a fiber content of 55 tex, and an inter-strand of 0.03 mm, the inter-strand being chosen according to the invention. The elastomer layer 35 of the reinforcing cage 19 of the control Tl, arranged radially internally to the textile reinforcement elements 31, has a maximum thickness D2 of 0.10 mm with respect to each of the textile reinforcement elements 31 of the support portion 18.
[0059] Each element of the textile reinforcement elements 31 comprises a yarn element assembly. Each yarn element here comprises an assembly consisting of two multifilament polyester strands, the two strands being helically wound around each other and the reinforcement element being torsionally balanced. The fiber count of each polyester strand is 10 to 100 tex, preferably 30 to 70 tex, more preferably 40 to 60 tex. Here the fiber count is 55 tex.
[0060] The density of textile reinforcement elements, here of 250 threads / dm, is the number of reinforcement elements taken on one decimeter of the shrink-fitting reinforcement 19 along the direction perpendicular to the direction along which the reinforcement elements extend parallel to each other, here the axial direction in a meridian cutting plane.
[0061] The average diameter D of the textile reinforcement elements of the 31 is less than or equal to 0.54 mm and preferably less than 0.40 mm, here 0.37 mm.
[0062] The following table summarizes the main properties of the TL tire Pneumatic Tl Nature strands / title (tex) / number PET / 55 / 2 Torque (revolutions / m) 500 / 500 D (mm) 0.37 Density (threads / dm) 250 E (mm) 0.55 Inter-cable (mm) 0.03 D2 (mm) 0.10
[0063] The P2 tire in the test plan has the same characteristics as the PI tire; however, the volume of the packing chamber 21 is optimized, meaning that the average thickness A ranges from 0.5 to 1.5 mm, being 1 mm in this case. The P2 tire thus benefits greatly from the 0.03 mm inter-cable width, which limits the thinning during the pressurization and heating of the tire blank in its curing mold. An optimized packing chamber 21 means that its thickness is not excessive in its dimensions.
[0064] The rolling resistance of the tire considered (PI or P2) is expressed in kg / T, by difference from the control tire Tl, a negative value signifying a decrease in rolling resistance and therefore an improvement in performance itself.
[0065] Following the tests, the results are summarized in the table below and show the benefit of PI and P2 compared to the control T1, P2 combining both the effect related to the characteristics of the shrink-fit armature 19 and the effect related to the relative volume occupied by the reduced packing volume 21. Rolling resistance gain (kg / t) Tire Tl Reference Tire PI -0.11 Tire P2 -0.12
Claims
Demands
1. A tire (1) comprising a crown (7) and a carcass reinforcement (9), the crown (7) comprising a tread (13) and a crown reinforcement (8), being arranged radially externally to the carcass reinforcement (9), the crown reinforcement (8) comprising: - a first working layer (15) and a second working layer (17), each of the first and second working layers (15)(17) comprising metallic reinforcements embedded in at least one coating elastomer, the first working layer (15) being arranged radially internally to the second working layer (17), the first working layer (15) having a point E1 at each axial end of the first working layer (15), the second working layer (17) having a point E2 at each axial end of the second working layer (17), the point E1 being axially external to the point E2, - a reinforcing reinforcement (19),comprising textile reinforcement elements (31), coated in at least one coating elastomer (33) and arranged radially externally to the top reinforcement (8) and radially internally to the tread (13), - a packing volume (21) arranged between the first working layer (15) and the reinforcing reinforcement (19), the packing volume (21) comprising a decoupling portion (22) extending axially from point E1 to point E2, characterized in that the reinforcing reinforcement (19) has a bearing portion (18) vertically aligned with the decoupling portion (22), the inter-cable DI between the textile reinforcement elements (31) of the bearing portion (18) of the reinforcing reinforcement (19) is strictly less than 0.05 mm.
2. Pneumatic (1) according to claim 1, wherein the intercable DI is less than or equal to 0.04 mm, preferably less than or equal to 0.03 mm.
3. Pneumatic (1) according to any one of the preceding claims, wherein the average diameter of each of the textile reinforcement elements (31) of the bearing portion (18) of the shrink-fitting reinforcement (19) is less than or equal to 0.54 mm and preferably less than 0.40 mm.
4. Pneumatic (1) according to any one of the preceding claims, wherein the shrink-fitting reinforcement (19) comprising an elastomer layer (35), referred to as the coating, arranged radially internally to the textile reinforcement elements (31) and in contact with the textile reinforcement elements (31), the minimum distance D2 between the textile reinforcement elements (31) of the bearing portion (18) and the portion (22) of the packing rubber (21) is less than or equal to 0.20 mm, preferably 0.15 mm, most preferably 0.12 mm.
5. Pneumatic (1) according to any one of claims 1 to 4, wherein the decoupling portion (22) of the packing volume (21) has an average thickness A between the innermost radial points of the shrink-fit reinforcement (19) and the outermost radial points of the first working layer (15), the average thickness A ranging from 0.5 to 1.5 mm.
6. Pneumatic (1) according to any one of claims 1 to 4, wherein the set of intersection points between the straight segment [El, E2] and the textile reinforcement elements (31) of the bearing portion (18) of the shrink-fitting reinforcement (19) is the empty set.
7. Pneumatic (1) according to any one of claims 1 to 4, wherein the decoupling portion (22) of the packing volume (21) having, in a meridian cutting plane, a first radial height H1 from E1 to the coating layer of the shrinkage reinforcement (19) and a second radial height H2 passing through E2 and from the radially outer surface of the coating layer of the first working layer (15) to the radially inner surface of the coating layer of the textile reinforcement elements (31) of the shrinkage reinforcement (19), the ratio, in percentage, of H1 to H2 is greater than 80%.
8. Tire (1) according to any one of the preceding claims, wherein the tire (1) is a passenger car tire.