Beltless tires for automobiles

Abstract

A beltless tire (1) for an automobile includes a carcass structure (2) having two carcass plies (3, 4), each of which includes a plurality of parallel cords (13, 14). The parallel cords (13, 14) of the two carcass plies (3, 4) cross each other at a crossing angle (Δ) between 20° and 60° and define angles (α, β) between 60° and 80° relative to a circumferential direction (C) of the tire (1). A reinforcing cord (9) is wound in a plurality of circumferential windings located radially outward relative to the carcass structure (2). The reinforcing cord (9) has a predetermined elongation (Sp) and a "tensile load-elongation" curve including a first section (T1) located upstream of the predetermined elongation (Sp) and having a first gradient, and a second section (T2) located downstream of the predetermined elongation (Sp) and having a second gradient. The ratio of the second slope to the first slope is greater than one.

Description

[Technical Field]

[0001] The present invention relates to a beltless tire for a motor vehicle. Preferably, but not exclusively, the invention relates to a road tire intended to equip hybrid or electric motor vehicles.

[0002] definition "Curvature ratio", with respect to a tire, means the ratio, measured in the radial plane of the tire, of the distance from a line passing through the lateral ends of the tread itself to the radially outermost point of the tread band to the distance measured along the tire cord between said ends.

[0003] By "automobile tire" is meant a tire exhibiting a curvature ratio of less than 0.15, preferably between 0.03 and 0.1, and more preferably close to 0.05.

[0004] The terms "radial," "axial," and "circumferential" refer to the axis of rotation of the tire.

[0005] "Radial plane" means the plane that contains the axis of rotation of the tire.

[0006] "Beltless" tire means a tire without a belt structure (comprising cross-reinforcing cords disposed between a carcass structure and a tread band).

[0007] The "tensile load-elongation" curve of a reinforcing cord means a curve drawn on a graph with the elongation of the reinforcing cord (e.g., elongation percentage) on the horizontal axis and the tensile force (e.g., expressed in N) acting on the reinforcing cord on the vertical axis.

[0008] The "tensile load-elongation" curves for metal cords are obtained according to the BISFA standard - Internationally agreed methods for testing steel tyre cords 1995, chapter E6.

[0009] The "tensile load-elongation" curve of the textile cord is obtained according to the BISFA standard - Testing method for polyamide filament yarns 2004, chapter 7.

[0010] "Density" means the number of cords present per unit width, for example per dm (EPDM).

[0011] "Textile cord" means a cord made of one or several threads of the same textile material.

[0012] "Hybrid cord" means a cord made from yarns of at least two different textile materials.

[0013] "Metal cord" means a cord made of one or more metal threads. [Background technology]

[0014] Automobile tires generally include a carcass structure with a belt structure.

[0015] The carcass structure comprises one or more carcass plies, each having opposing end flaps engaged with a respective annular fixing structure called a bead core with a filler insert. The tire area comprising the bead core and the filler insert forms a bead structure intended to fix the tire to a corresponding mounting rim. The belt structure comprises several belt layers radially overlapping each other and the carcass structure, with metallic, textile or hybrid reinforcing cords cross-oriented with respect to the circumferential development of the tire. A tread band is positioned radially outward from the belt structure.

[0016] Document US20190202241 shows a tire with a belt structure comprising two or more layers, these layers comprising steel or organic fiber cords oriented obliquely relative to the circumferential direction of the tire and making an angle of less than or equal to 10° with such direction.

[0017] Document DE 19545954 A1 shows a beltless tire with a double cross-ply carcass. Each of the two plies contains parallel polyamide reinforcing cords embedded in an elastomer layer. The cords of the two plies cross each other and form an angle of 20° to 40° with the circumferential direction of the tire. Radially outward from the carcass plies and beneath the tread, a band is arranged with parallel reinforcing elements extending in the circumferential direction and oriented at an angle of approximately 0° with respect to the circumferential direction. The reinforcing elements of the band are polyamide monofilaments with a flattened oval or elliptical cross section.

[0018] Document GB 769,325 describes a tire with a carcass having thread-like reinforcing elements and a reinforcing ring made of rubber-coated metal threads or textile cords. In one embodiment, the carcass has one or more carcass layers, and these thread-like reinforcing elements form an angle of 10° or less with respect to a plane containing the tire's rotation axis. The reinforcing ring has one or more layers with rubber-coated metal threads or textile cords arranged at an angle of less than 20° with respect to the circumferential center plane. In another embodiment, the carcass has two or more carcass layers, and these thread-like reinforcing elements form an angle of 20° or less with each other. The reinforcing ring has multiple layers, and the rubber-coated metal threads or textile cords of one layer form an angle of 40° or less with those of adjacent layers.

[0019] Tires with radial carcasses or oblique cords are shown, for example, in documents US20130206309, US9156315, US4967817, US2939502A, and EP0093451A2. Reinforcing cords for tires are shown, for example, in documents GB2034363A, EP1213159A2, EP0461646B1, EP0335588A2, US2004 / 0118499A1, WO2015 / 019214A1, WO2009 / 052844A1, WO2021 / 124133A1, WO2021 / 124138, WO2021 / 124154, and WO2022 / 064436. Summary of the Invention [Problem to be solved by the invention]

[0020] The use of layered belt structures with crossed reinforcing cords in tires has been necessary to meet the demands of adapting tires to the ever-increasing performance of automobiles and to improve their driving characteristics, for example with regard to stiffness, driving stability and driving readiness.

[0021] Tires with belt structures having belt layers with cross-oriented cords can, in fact, typically provide greater drift force for the same drift angle than beltless tires. Tires with such belt structures can also typically provide greater self-aligning torque at low drift angles than beltless tires.

[0022] For several years, the Applicant has been paying attention to the environmental impact exerted, both direct and indirect, by tires during use. In particular, in order to curb motor vehicle consumption, which has an impact on energy consumption and therefore on the emission of carbon dioxide into the atmosphere, the Applicant manufactures tires with low rolling resistance, i.e. tires with a fuel economy class corresponding to "A" (according to European Regulation EU 2020 / 740).

[0023] Against this background, the Applicant has set itself the objective of further reducing the rolling resistance of tires intended to equip new hybrid and fully electric vehicles, in particular, but not exclusively, in order to reduce their environmental impact.

[0024] The applicant has set himself the further objective of reducing fuel consumption or increasing the autonomy of motor vehicles.

[0025] The Applicant has set itself a further objective of reducing the heating of the tire during running.

[0026] In particular, the applicant has set himself the goal of achieving the above objectives without compromising the performance and riding characteristics of modern tires, especially tires with cross-belt construction. [Means for solving the problem]

[0027] However, the applicant has unexpectedly discovered that the above object can be achieved by employing a specific beltless structure.

[0028] More precisely, the applicant has discovered that the above-mentioned objectives can be achieved by a beltless tire that combines a carcass structure having reinforcing cords that are crossed with each other at a predetermined appropriate angle, with a reinforcing structure (generally defined as a zero-degree layer) that has reinforcing cords that have a specific "tensile load-elongation" curve.

[0029] According to a first aspect, the invention relates to a beltless tire for a motor vehicle.

[0030] Preferably, the tire comprises a carcass structure comprising two carcass plies, each of the two carcass plies comprising a plurality of parallel cords and having an end flap engaged with a respective annular fastening structure.

[0031] Preferably, the parallel cords of the two carcass plies cross each other and form a crossing angle of 20° to 60° with respect to each other.

[0032] Preferably, the parallel cords of each of the two carcass plies form an angle of 60° to 80° with respect to the circumferential direction of the tire.

[0033] Preferably, the tire comprises at least one reinforcing cord wound in a plurality of circumferential wraps disposed at a radially outer position relative to the carcass structure.

[0034] Preferably, the tire comprises a tread band attached at a radially outer position relative to the reinforcing cords.

[0035] Preferably, the at least one reinforcing cord has a predetermined elongation.

[0036] Preferably, the at least one reinforcing cord has a "tensile load-elongation" curve having a first section located upstream (on the side with a smaller value) of the predetermined elongation rate, a second section located downstream (on the side with a larger value) of the predetermined elongation rate, and a third connecting section located between the first section and the second section.

[0037] Preferably, the second slope of the second section is greater than the first slope of the first section.

[0038] The applicant has verified that the present invention can reduce the rolling resistance of a tire to a value lower than that of a tire having a belt structure.

[0039] Applicant has also verified that the present invention allows for performance and driving characteristics suitable for modern automotive equipment.

[0040] In particular, applicant has verified that tires made in accordance with the present invention are capable of providing drifting forces comparable to those provided by tires having a belted construction.

[0041] Applicant has also verified that tires made in accordance with the present invention provide a more progressive self-aligning torque curve compared to the self-aligning torque curve provided by tires having a belted construction, and therefore provide torque decay at the steering wheel that is more manageable by the driver.

[0042] The present invention, in at least one of its above aspects, can exhibit one or more of the following preferred features.

[0043] Preferably, the first section is delimited between zero elongation and a first point on the "tensile load-elongation" curve, the second section extends downstream of the second point on the "tensile load-elongation" curve, and the third connecting section is delimited between the first point and the second point.

[0044] Preferably, the first point corresponds to the point where the first depression in the "tensile load-elongation" curve encountered when starting from zero elongation turns upward.

[0045] Preferably, if the depression in the "tensile load-elongation" curve downstream of the first point remains upward until failure, the second point on the "tensile load-elongation" curve is the point of maximum depression.

[0046] Alternatively, a second point on the "tensile load-elongation" curve is an inflection point if, downstream of the first point, the upward-pointing depression in the "tensile load-elongation" curve becomes downward-pointing at an inflection point.

[0047] Preferably, the predetermined elongation corresponds to the intersection of a first tangent to the "tensile load-elongation" curve at a first point and a second tangent to the "tensile load-elongation" curve at a second point.

[0048] Preferably, the ratio of the second slope of the second section to the first slope of the first section is greater than five.

[0049] Preferably, the circumferential wrap of said at least one reinforcing cord is embedded in a layer of elastomeric material.

[0050] Preferably, the circumferential wrap of the at least one reinforcing cord and the layer of elastomeric material define a reinforcing layer.

[0051] Preferably, the reinforcing structure is positioned directly against the carcass structure.

[0052] Preferably, the tread band is arranged to abut the reinforcing structure.

[0053] Preferably, the ratio of the second slope of the second section to the first slope of the first section is less than 50.

[0054] Preferably, the ratio of the second slope of the second section to the first slope of the first section is 5 to 40, more preferably, the ratio of the second slope of the second section to the first slope of the first section is 10 to 35, for example, equal to 27.

[0055] Preferably, the first gradient of the first section is 1 to 20 N / elongation rate.

[0056] Preferably, the second gradient of the second section is 35 to 500 N / elongation rate.

[0057] Preferably, the third connecting section forms a kind of elbow or knee with the recess facing upwards.

[0058] Preferably, the first point coincides with the point of zero elongation, in which case the first section is shortened to the first point.

[0059] Preferably, the first section has a downwardly facing recess.

[0060] Preferably, the second section has an upwardly facing recess or a downwardly facing recess.

[0061] Preferably, the winding density of the reinforcing cord in the circumferential direction is 40 turns / dm to 130 turns / dm, and more preferably 75 turns / dm to 115 turns / dm.

[0062] Preferably, the predetermined elongation rate is 1% to 5%, more preferably, 1.5% to 4.5%, and even more preferably, the predetermined elongation rate is 3%.

[0063] Preferably, in the "tensile load-elongation" curve, the force corresponding to a predetermined elongation rate is 5N to 200N, and more preferably 15N to 90N.

[0064] Preferably, said at least one reinforcing cord is metallic or hybrid.

[0065] Preferably, the at least one metal reinforcing cord comprises a plurality of steel threads, preferably of the same diameter, which are individually twisted and wound together in such a manner that each thread does not contact its immediate neighbors in multiple cross-sections of the cord.

[0066] Preferably, the at least one metal reinforcing cord comprises at least two strands, each strand comprising a plurality of steel threads, preferably of the same diameter, wound together in each strand according to a predetermined winding pitch, and the at least two strands are wound together in the same manner as the threads of the strand and at a winding pitch equal to or different from the predetermined winding pitch.

[0067] Preferably, the at least one metal reinforcing cord comprises a single metal yarn or at least two twisted metal yarns.

[0068] Preferably, the at least one metallic reinforcing cord comprises at least one spiral metallic thread.

[0069] Preferably, the at least one hybrid reinforcing cord comprises one or more textile filaments having a high modulus twisted in one direction and one or more textile filaments having a low modulus twisted in the same direction, the textile filaments having a high modulus and the textile filaments having a low modulus being twisted together.

[0070] Preferably, each yarn of the hybrid reinforcement cord has its filaments twisted together according to a respective predetermined number of twists per unit length of the yarn, and the different yarns are twisted together according to a predetermined number of twists per unit length of the reinforcement cord.

[0071] Preferably, said at least one hybrid reinforcing cord comprises two aromatic polyamide fiber yarns and one polyamide-aliphatic and / or polyester fiber yarn.

[0072] Preferably, the at least one hybrid reinforcement cord comprises at least one hybrid yarn comprising a plurality of filaments obtained from a first yarn having a plurality of filaments with a first initial tangent modulus and at least one second yarn having a plurality of filaments with a second initial tangent modulus, wherein the first initial tangent modulus and the second initial tangent modulus are different from each other, and wherein each of the first yarn and the second yarn comprises a plurality of individual filaments, and the individual filaments of each of the first yarn and the second yarn are at least partially intermixed in the hybrid yarn.

[0073] Preferably, the circumferential winding of the reinforcing cord defines an angle between 0° and 5° relative to the circumferential direction.

[0074] Preferably, said at least one reinforcing cord wound in a plurality of circumferential wraps is embedded in a layer of elastomeric material.

[0075] Preferably, said at least one reinforcing cord wound in a plurality of circumferential wraps forms a reinforcing layer.

[0076] Preferably, the reinforcing layer is produced by winding a continuous elongated element into adjacently arranged windings, the continuous elongated element including the at least one reinforcing cord, whereby the at least one reinforcing cord is wound into a plurality of circumferential windings.

[0077] Preferably, the continuous elongate element comprises an elastomeric material and said at least one reinforcing cord is embedded in said elastomeric material.

[0078] Preferably, the continuous elongate element comprises a plurality of reinforcing cords.

[0079] Preferably, the continuous elongate element comprises between 1 and 500 reinforcing cords.

[0080] Preferably, the continuous elongate element has a flat cross section.

[0081] Preferably, the reinforcing cords are arranged side by side in a continuous elongated element.

[0082] Preferably, the density of the reinforcing cords within the continuous elongate element is between 40 cords / dm and 130 cords / dm, more preferably between 75 cords / dm and 115 cords / dm.

[0083] Preferably, the number of carcass plies present in the carcass structure is two.

[0084] Preferably, the parallel cords of each of the two carcass plies subtend an angle between 65° and 75°, optionally equal to 70°, with respect to the circumferential direction of the tire.

[0085] Preferably, the parallel cords of the two carcass plies are arranged in opposite directions and at equal angles to the circumferential direction of the tire, and are therefore arranged symmetrically with respect to the circumferential direction of the tire.

[0086] Alternatively, the parallel cords of the two carcass plies are arranged in opposite directions and at different angles relative to the circumferential direction of the tire, so that the parallel cords of the two carcass plies are asymmetrically arranged with respect to the circumferential direction of the tire.

[0087] Preferably, the intersection angle is between 30° and 50°, optionally equal to 40°.

[0088] Preferably, the two carcass plies include a first carcass ply, preferably radially inner, and a second carcass ply, preferably radially outer.

[0089] Preferably, the cords of the first carcass ply are inclined at a first angle α relative to the circumferential direction of the tire, measured counterclockwise.

[0090] Preferably, the cords of the second carcass ply are inclined at a second angle β measured clockwise relative to the aforementioned circumferential direction.

[0091] Preferably, the cords of the first carcass ply define a crossing angle Δ=180°−β−α with the cords of the second carcass ply.

[0092] Preferably, at least one auxiliary element is arranged at each of two opposite axial ends of the plurality of circumferential turns.

[0093] Preferably, the auxiliary element is arranged between the plurality of circumferential turns and the tread band and / or between the plurality of circumferential turns and the carcass structure.

[0094] Preferably, at least one auxiliary element can be arranged at each of two opposite axial ends of the circumferential winding.

[0095] Preferably, said at least one auxiliary element is arranged astride each axial end.

[0096] Preferably, the auxiliary element can be arranged before winding the successive elongated elements into side-by-side windings, so that said at least one auxiliary element is between the circumferential winding and the carcass structure, and / or the auxiliary element can be arranged after winding the successive elongated elements into close-to-one windings, so that said at least one auxiliary element is between the circumferential winding and the tread band.

[0097] Preferably, the auxiliary element comprises an elastomer and / or aramid and / or metallic material.

[0098] Preferably, the auxiliary element has an axial extension of 15% to 25% of the axial width of the plurality of circumferential turns.

[0099] Preferably, the auxiliary element can be arranged before winding the successive elongated elements into adjacently arranged windings, and the successive elongated elements can be wound into adjacently arranged windings, leaving the axially outer portions of the auxiliary element free, and the axially outer axial portions being folded at the axial ends of each of the adjacently arranged windings, so that the auxiliary element is arranged across the respective axial ends.

[0100] Further features and advantages will become more apparent from the detailed description of the preferred, but non-limiting, embodiments of a beltless tire for an automobile.

[0101] Such description will now be made with reference to the accompanying drawings, which are provided by way of example only and therefore not by way of limitation. [Brief explanation of the drawings]

[0102] [Figure 1] 1 is a cross-sectional view along a radial plane of a beltless tire for a motor vehicle according to the invention; [Figure 2] FIG. 2 is an enlarged view of a portion of FIG. [Figure 3A] FIG. 2 is a schematic top view of the tire elements referenced in the previous figures. [Figure 3B] FIG. 2 is a schematic top view of the tire elements referenced in the previous figures. [Figure 4] FIG. 2 is a diagram of a continuous elongated element used to make the tire referenced in the previous figure. [Figure 5A] 1 is a graph of the "tensile load-elongation" curve of the reinforcing cord of the tire referenced in the previous figure. [Figure 5B] 1 is a graph of the "tensile load-elongation" curves of different reinforcing cords. [Figure 5C] 5C is a graph of a detail of the "tensile load-elongation" curve of FIG. 5A and FIG. 5B. [Figure 6] FIG. 1 is a diagram comparing the rolling resistance of a tire with that of a reference tire. [Figure 7A]4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 7B] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 7C] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 7D] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 8A] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 8B] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 8C] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 8D] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 9A] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 9B] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 9C] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 9D] 4 is a graph of the drift force of a tire according to the invention and a reference tire. [Figure 10] 1 is a graph of the self-aligning torque of a pair of tires according to the present invention and a reference tire. [Figure 11] 1 is an enlarged view of a portion of a modified tire according to the present invention; [Figure 12] 1 is an enlarged view of a portion of a modified tire according to the present invention; [Figure 13] 1 is an enlarged view of a portion of a modified tire according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0103] FIG. 1 shows a cross section along a radial plane of a beltless tire 1 for motor vehicles according to the invention.

[0104] The tire 1 comprises a carcass structure 2 having a first radially inner carcass ply 3 and a second radially outer carcass ply 4. Each of the first carcass ply 3 and the second carcass ply 4 has opposed end flaps engaged with respective annular anchoring structures 5 called bead cores with filler inserts 6.

[0105] The tire area 1 comprising the bead core 5 and the filling insert 6 forms a bead structure 7 intended to secure the tire 1 to a corresponding mounting rim, not shown.

[0106] The carcass structure 2 includes a reinforcing structure 8 (zero degree layer) having at least one reinforcing cord 9 wound in a plurality of circumferential turns arranged in a radially outer position relative to the carcass structure 2 (FIG. 2). The circumferential turns are preferably arranged to form an angle of 0° to 5° with the circumferential direction C of the tire 1.

[0107] The reinforcing structure 8 shown in Figures 1 and 2 comprises a layer of elastomeric material in which are embedded circumferential turns of reinforcing cords 9. The reinforcing structure 8 is preferably arranged to abut against the carcass structure 2, in particular the second carcass ply 4.

[0108] The tire 1 according to the present invention is beltless, and a tread band 10 made of an elastomer compound similar to the other semi-finished products that make up the tire 1 is attached to a position radially outside the reinforcing structure 8. The tread band 10 is arranged so as to abut against the reinforcing structure 8.

[0109] Furthermore, respective sidewalls 11 of elastomeric compound are attached at axially outer positions on the lateral surfaces of the carcass structure 2 and extend from one of the lateral edges of the tread band 10 of each bead structure 7 .

[0110] A waterproof rubber layer 12, commonly known as a "liner," which provides the necessary impermeability to the inflation air of the tire 1, is disposed at a radially inner position relative to the first carcass ply 3. The waterproof rubber layer 12 is preferably attached so as to abut against the first carcass ply 3.

[0111] Each of the two carcass plies 3, 4 comprises a plurality of cords 13, 14 that are parallel to one another and covered by or embedded in an elastomeric material. Such parallel cords 13, 14 of the two carcass plies 3, 4 may be textile and / or hybrid.

[0112] 3A and 3B, the cords 13 of the first carcass ply 3 are inclined at a first angle α measured counterclockwise relative to the circumferential direction C of the tire 1, and the cords 14 of the second carcass ply 4 are inclined at a second angle β measured clockwise relative to said circumferential direction C. From another perspective, the cords 14 of the second carcass ply 4 are inclined at a third angle Ω measured counterclockwise relative to said circumferential direction C, where Ω=180°-β.

[0113] Therefore, the cords 13 of the first carcass ply 3 cross the cords 14 of the second carcass ply 4. The cords 13 of the first carcass ply 3 define a crossing angle Δ=180°-β-α=Ω-α with the cords 14 of the second carcass ply 4.

[0114] Examples of such angles are shown in Table 1 below. In cases B, C, and D, as shown in the example of Figure 3A, the two carcass plies 3, 4 are inclined at equal angles in opposite directions relative to the circumferential direction C of the tire 1 (the parallel cords 13, 14 of the two carcass plies 3, 4 are arranged symmetrically with respect to the circumferential direction C of the tire 1). In cases F and G, as shown in the example of Figure 3B, the two carcass plies 3, 4 are inclined at different angles in opposite directions relative to the circumferential direction C of the tire 1 (the parallel cords 13, 14 of the two carcass plies 3, 4 are arranged asymmetrically with respect to the circumferential direction C of the tire 1).

[0115] [Table 1]

[0116] The reinforcing cords 9 wound in a circumferential winding and part of the reinforcing structure 8 have a predetermined elongation Sp between 1% and 5%, preferably between 1.5% and 4.5%, for example equal to 3%.

[0117] Such a reinforcing cord 9 also has a "tensile load-elongation" curve including a first section T1 located upstream of the predetermined elongation rate Sp and having a first slope measured at a first point P1, and a second section T2 located downstream of the predetermined elongation rate Sp and having a second slope measured at a second point P2, the second slope being greater than the first slope. In other words, the reinforcing cord 9 increases in stiffness when stretched beyond the predetermined elongation rate Sp. When the reinforcing cord 9 has such a predetermined elongation rate Sp in a completed tire 1, this means that as the tire 1 rolls on a road, the tire 1 deforms and the reinforcing cord 9, or a portion thereof, is subjected to tension, causing the reinforcing cord 9 to behave as if it had a high stiffness corresponding to the slope of the second section T2.

[0118] Examples of such "tensile load-elongation" curves are shown in the graphs of Figures 5A and 5B, which show the elongation (%) of some possible reinforcing cords 9 according to the present invention on the horizontal axis and the tensile force (expressed in Newtons) on the vertical axis.

[0119] The first section T1 is defined between zero elongation and the first point P1 of the "tensile load-elongation" curve, the second section T2 extends downstream of the second point P2 of the "tensile load-elongation" curve, and the third connecting section K is defined between the first point P1 and the second point P2. The first and second sections T1 and T2 of the "tensile load-elongation" curve are connected with an increasing slope at the third connecting section K. The third connecting section K forms a kind of elbow or knee with the concave pointing upward.

[0120] The "tensile load-elongation" curve in Figure 5A refers to a 3x4x0.20 HEHT steel metal cord.

[0121] As can be seen, the "tensile load-elongation" curve in Figure 5A has a first section T1 (visible in the enlarged view of Figure 5C) where the indentation faces downward, followed by a third connecting section K where the indentation faces upward, and then a second section T2 where the indentation first faces upward and then downward.

[0122] Therefore, the curve in FIG. 5A has an inflection point between the first section T1 and the third connecting section K, and an inflection point at the beginning of the second section T2. ​​The first point P1 corresponds to the point where the first depression in the "tensile load-elongation" curve, starting from zero elongation, turns upward. In the graph in FIG. 5A, the first point P1 is located immediately after the inflection point in the first section T1. The second point P2 is an inflection point at the beginning of the second section T2.

[0123] The "tensile load-elongation" curve in Figure 5B refers to a hybrid cord of ARx2 / NY 1670 / 940 (20 / 20x20) type.

[0124] As can be seen, the "tensile load-elongation" curve in Figure 5B has a first section T1 where the concavity faces downwards (as shown in Figure 5C), followed by a third connection section K where the concavity faces upwards, and then a second section T2 where the concavity always faces upwards (up to the breaking load), unlike the curve in Figure 5A.

[0125] As in Figure 5A, the first point P1 corresponds to the point where the first concave portion of the "tensile load-elongation" curve, starting from zero elongation, begins to point upward. Unlike Figure 5A, the second point P2 of the "tensile load-elongation" curve in Figure 5B is the point of maximum concavity.

[0126] In both Figures 5A and 5B, the predetermined elongation Sp corresponds to the elongation located at the intersection of a first tangent to the "tensile load-elongation" curve at a first point P1 and a second tangent to the "tensile load-elongation" curve at a second point P2.

[0127] In the graph of Figure 5A, the predetermined elongation Sp is equal to about 1.7%, and the force F corresponding to such predetermined elongation Sp is equal to about 60 N. In the graph of Figure 5B, the predetermined elongation Sp is equal to about 3.4%, and the force F corresponding to such predetermined elongation Sp is equal to about 85 N.

[0128] In the reinforcing cord 9 according to the present invention, the force corresponding to the predetermined elongation percentage Sp is preferably 5N to 200N, and more preferably 15N to 90N.

[0129] The ratio between the second slope and the first slope of the "tensile load-elongation" curve of the reinforcing cord 9 according to the present invention is preferably greater than 5, more preferably between 5 and 40, and even more preferably between 10 and 35; for example, such a ratio is equal to 27. For example, the first slope of the first section T1 is preferably between 1 and 20 N / elongation, and the second slope of the second section T2 is preferably between 35 and 500 N / elongation. In the example of the graph of FIG. 5A, the first slope of the first section T1 is approximately 20 N / elongation, and the second slope of the second section T2 is approximately 470 N / elongation, so the aforementioned ratio is approximately 24. In the example of the graph of FIG. 5B, the first slope of the first section T1 is approximately 12 N / elongation, and the second slope of the second section T2 is approximately 120 N / elongation, so the aforementioned ratio is approximately 10.

[0130] To obtain this double gradient behavior, the reinforcing cord 9, also called "high elongation", comprises two or more twisted metal threads or at least one spiral metal thread, as shown, for example, in documents WO2021 / 124133, WO2021 / 124138, WO2021 / 124154A1 and WO2022 / 064436A1 of the same applicant.

[0131] In a different example, the reinforcing cord 9 may comprise a single strand of n steel yarns of a given diameter, the yarns being individually twisted and spirally wound together, but not so tightly that each yarn comes into contact with its neighbors, as described, for example, in the same applicant's document GB2034363A. As a specific example, the reinforcing cord 9 may be of the 1x5x0.25 or 5x0.25 type. These types of cords are accurately described in the art as "open" due to the fact that the constituent yarns are not in contact with their neighbors at multiple cross sections of the cord. This gap is particularly useful because it allows the elastomeric material to flow during vulcanization, filling any gaps and uniformly rubberizing the resulting cord, thus avoiding harmful moisture infiltration during use.

[0132] Another example of an open-type reinforcing cord 9 provides 2 to 7 single-ply yarns with elastomeric material penetrating between the yarns over the entire length of the cord, as shown, for example, in document EP 1 213 159 A2.

[0133] In a further example, the reinforcing cord 9 comprises a given number, for example, 2 to 5 strands, each of which is made of a specific number, for example, 2 to 10, of metal threads, preferably having a diameter of 0.12 mm to 0.25 mm. The threads of a strand and the strands of the cord are spirally wound together in the same direction, with the winding pitch of the threads and strands being equal or different. As a specific example, the reinforcing cord 9 may be a 3x7x0.12 HE type cord, as described in document EP 0 461 646 B1 of the same applicant, or a 3x4x0.20 HEHT type cord as described above.

[0134] The reinforcing cord 9 may also be of a hybrid type, formed for example by twisting one or more filaments having a high modulus (for example of aromatic polyamide fibres) in one direction, one or more filaments having a low modulus (for example of aliphatic polyamide fibres) in the same direction and finally, preferably in opposite directions, the aforesaid high and low modulus filaments, as described for example in document EP 0 335 588 A2.

[0135] In another example, each yarn of the reinforcing cord 9 may have its filaments twisted a given number of times per unit length of the yarn, or more preferably, several yarns twisted a given number of times per unit length of the cord, as shown, for example, in document US 2004 / 0118499 A1. Furthermore, the twist direction of the cord or yarn is different compared to the direction of the cord or yarn itself, which is held perpendicular. The filaments are of high modulus (e.g., aromatic polyamide) and low modulus (e.g., aliphatic polyamide).

[0136] The reinforcing cord 9 may also consist of two aromatic polyamide fiber yarns and one aliphatic polyamide and / or polyester fiber yarn having suitable linear density and initial modulus characteristics combined by a twisting process, as shown, for example, in document WO 2015 / 019214 A1 of the same applicant.

[0137] A further embodiment of the reinforcing cord 9 comprises at least one hybrid yarn, preferably twisted, comprising a plurality of filaments obtained from a first yarn having a plurality of filaments with a first initial tangent modulus of elasticity and at least one second yarn having a plurality of filaments with a second initial tangent modulus of elasticity, wherein the first and second initial tangent moduli are different from each other, and wherein each of the first and second yarns having a plurality of filaments comprises a plurality of individual filaments, and wherein the individual filaments of each of the first and second yarns are at least partially intermixed, as shown, for example, in document WO 2009 / 052844 A1 of the same applicant.

[0138] Since the reinforcing structure 8 includes a plurality of circumferential windings formed by the reinforcing cords 9, the reinforcing structure 8 also has a respective stiffness that depends on the density of the circumferential windings and the characteristics of the reinforcing cords 9. For example, the circumferential winding density is preferably 40 turns / dm to 130 turns / dm, and more preferably 75 turns / dm to 115 turns / dm.

[0139] The tire 1 can be manufactured through the following process.

[0140] For example, the carcass structure 2 as described above can be made by placing various structural components on a building drum. The carcass structure 2 made preferably includes a waterproof rubber layer (or liner) 12, a first carcass ply 3, a second carcass ply 4, a bead structure 7, and a sidewall 11.

[0141] A continuous elongated element 15 (partially shown in FIG. 4 ) including one or more reinforcing cords 9 embedded in or covered with an elastomeric material 16 is then wound around the carcass structure 2 in adjacent or partially overlapping windings. The continuous elongated element 15 preferably includes 1 to 500 reinforcing cords 9. In the exemplary embodiment of FIG. 4 , the continuous elongated element 15 has a flat cross-section and includes the reinforcing cords 9 arranged side by side. The density of the reinforcing cords 9 within the continuous elongated element 15 is preferably between 40 cords / dm and 130 cords / dm, for example, equal to 75 cords / dm. By winding the continuous elongated element 15, the reinforcing cords 9 are also arranged according to the aforementioned multiple circumferential windings.

[0142] When placed, the continuous elongated element 15 is tensioned to impart a first elongated rate to the continuous elongated element 15 and each reinforcing cord 9, and this first elongated rate is substantially maintained when the continuous elongated element 15 is wrapped around and attached to the carcass structure 2.

[0143] The arrangement of successive elongated elements 15 forms a reinforcing structure 8 which extends axially until it overlaps at the axial end opposite the end flap of the sidewall 11, as shown in FIG.

[0144] Finally, a tread band 10 is placed around the reinforcing structure 8. The tread band 10 is attached to the reinforcing structure 8 and to the ends of each of the two sidewalls 11 (Figures 1 and 2).

[0145] The uncured tire 1 thus produced is inserted into a vulcanization mold, where it is shaped and vulcanized in order to determine the structural stability of the tire 1 by crosslinking the elastomeric material, as well as to give the tread band 10 the desired tread pattern and any distinctive markings on the sidewalls 11.

[0146] During molding and vulcanization, the uncured tire 1 is heated and radially expanded by introducing pressurized gas into its interior or into a membrane therein so as to radially press its radially outer surface against the mold.

[0147] During molding and vulcanization, the reinforcing cords 9 of the reinforcing structure 8 are subjected to a second elongation rate under the action of the pressurized gas.

[0148] All circumferential turns, after curing and molding, will exhibit an elongation that may vary based on axial position and corresponds to a certain approximation of the given elongation Sp shown above, depending on the placement process (on a cylindrical or toroidal surface).

[0149] 11, 12 and 13 show respective variants of the tire 1 according to the invention, which also comprise at least one auxiliary element 17, 17A, 17B arranged on each of the two opposite axial ends of the plurality of circumferential windings or reinforcing structure 8. This auxiliary element 17, 17A, 17B is, for example, a tape comprising an elastomer and / or aramid and / or metal material, wound on each of said two opposite axial ends of the reinforcing structure 8.

[0150] In the variant of Figure 11, the auxiliary element 17 is placed before placing the reinforcing structure 8. The continuous elongate element 15 is then wound, leaving the axially outer part of the auxiliary element 17 free. Said axially outer part of the auxiliary element 17 is then turned over onto the reinforcing structure 8, so that the auxiliary element 17 is placed astride the edges of each axial end of the reinforcing structure 8. Finally, the tread band 10 is applied.

[0151] The variant of Figure 12 comprises a first auxiliary element 17A arranged above the reinforcing structure 8, i.e. in a radially outer position relative to the reinforcing structure 8, and a second auxiliary element 17B arranged below the reinforcing structure 8, i.e. in a radially inner position relative to the reinforcing structure 8. In this variant, each of the two opposite axial ends of the reinforcing structure 8 is accompanied by two separate auxiliary elements.

[0152] 13 comprises a single auxiliary element 17 at each of the two opposite axial ends of the reinforcing structure 8. Such auxiliary element 17 is located below the reinforcing structure 8, i.e. radially inward relative to the reinforcing structure 8.

[0153] In all three illustrated variants, the auxiliary elements 17, 17A, 17B are in a radially outward position relative to the end flaps of the respective side surfaces 11. Furthermore, the single auxiliary element 17 or the first and second auxiliary elements 17A, 17B comprise a plurality of circumferential turns, i.e., an axial extension "W" (shown in Figures 11, 12, and 13) of 15% to 25% of the axial width "L" (shown in Figure 1) of the reinforcing structure 8. test

[0154] Eight types of tires B, C, D, E, F, G, H, and I were compared with Reference Tire A using finite element simulation (FEA). All tires correspond to the P7 Cinturato model, size 245 / 45 R18 100Y. Reference Tire A includes a radial monoply carcass structure, a two-ply belt structure with crossed cords, and a hybrid 0-degree ply consisting of hybrid cords. Eight tires B, C, D, E, F, G, H, and I include a carcass structure with two crossed plies and a metallic 0-degree layer (i.e., formed by metallic cords) with a double gradient as described above. Eight tires B, C, D, E, F, G, H, and I do not include a belt structure, i.e., a belt layer with crossed cords. The eight tires B, C, D, E, F, G, H, and I differ from each other in the angles α, β, Ω, and Δ of the cords 13 and 14 of carcass plies 3 and 4, as shown in Tables 2A and 2B below. Tires B, C, D, F, and G are the same as in Table 1. Materials used for the simulation Carcass ply cord: RY 1840 / 2 (48x48) EPDM 120 Zero degree metal (steel): 2x0.15 HE EPDM 79 Zero Degree Hybrid: AR / NY 1100 / 1400 (28 / 7x28) EPDM 79

[0155] [Table 2]

[0156] [Table 3]

[0157] First of all, it can be seen that tires B, C, D, E, F, G, H, and I are lighter than the reference tire A. In fact, if the weight of reference A is equal to 100, then all eight tires B, C, D, E, F, G, H, and I are 7.4% lighter in weight.

[0158] Figure 6 shows the rolling resistance coefficient RR of tires A, B, C, D, E, F, G, H, and I. The rolling coefficients were normalized with the value of reference tire A set to 100. As can be seen, tires B, C, D, F, G, H, and I have a rolling resistance coefficient RR (RR A RR (RR = 100) B =87.7, RR C =83.3, RR D =86.0, RR F =83.3, RR G =83.5, RR1 H =89.6, RR I Tire E, characterized by smaller angles α and β than the other tires, instead has a RR (RR E = 103.0) has deteriorated. In addition to the RR values ​​shown in Figure 6, Table 3 below also shows the reduction rate of the rolling resistance coefficient RR of tires B, C, D, F, G, H, and I relative to standard A.

[0159] [Table 4]

[0160] The advantage in terms of reduced rolling resistance RR exhibited by tires B, C, D, F, G, H and I is clear and significant.

[0161] Figures 7A to 7D show the drift force Fs (Newtons) as a function of the drift angle SA for tires A, B, C, D, F, G, H, and I at a vertical load of 2866 N (low vertical load), which corresponds to the operating condition of the wheel on the inside of the curve.

[0162] At the low vertical loads of Figures 7A, 7B, and 7C, the drift forces Fs of tires B, C, D, F, and G pass through zero at a lower drift angle in absolute value than the drift forces Fs of tire reference A, thereby improving straight-line centring performance. Furthermore, tires B, C, F, and G produce drift force levels Fs that are substantially consistent with reference A.

[0163] Referring to FIG. 7B, tire F, which has a slightly asymmetric carcass structure, produces a drift force level Fs that nearly overlaps with the drift force level of tire C's symmetric cross-carcass structure.

[0164] Referring to FIG. 7C, tire G, which has a significantly asymmetric carcass structure, produces a drift force level Fs that is higher than that of tire D's symmetric cross-carcass structure.

[0165] FIG. 7D shows instead that tires H and I, which also have a carcass structure with a significantly asymmetric crossover (but different from tire G), produce significantly lower absolute levels of drift force Fs in the negative drift section (left curve) and slightly higher absolute levels of drift force Fs in the positive drift section (right curve) than tire C's symmetric crossover carcass structure. Overall, the average drift force that can be generated by tires H and I at the same drift angle is lower than that of tire C's symmetric carcass structure. Furthermore, tires H and I exhibit force zero crossovers with opposite signs to criterion A and at higher absolute drift angles, which worsens straight-line centering performance.

[0166] 8A to 8D show the drift force Fs as a function of the drift angle SA for tires A, B, C, D, F, G, H, and I at a vertical load of 4337 N (average vertical load, when entering a curve with both wheels on an axle or when starting a lane change).

[0167] At the average vertical loads in Figures 8A, 8B, and 8C, tires B, C, D, F, and G continue to have zero-crossing forces at drift angles lower in absolute value than the drift force Fs of reference tire A. Furthermore, tires B, C, F, and G produce slightly lower drift force levels Fs than reference A (difference <10%).

[0168] Referring to Figure 8B, tire F, which has a slightly asymmetric carcass structure, produces a drift force level Fs that substantially overlaps with that of the symmetric cross-carcass structure of tire C. Referring to Figure 8C, tire G, which has a significantly asymmetric carcass structure, still produces a higher level of drift force Fs than the symmetric cross-carcass structure of tire D. Figure 8D shows that the behavior of the drift forces produced by tires H and I (also with significantly asymmetric cross-carcass structures) at moderate vertical loads is similar to that shown in Figure 7D at low vertical loads.

[0169] 9A-9D show the drift force F (N) as a function of the drift angle SA for tires A, B, C, D, F, G, H, and I at a vertical load of 5808 N (high vertical load, applied to the outside wheel when cornering).

[0170] At high vertical loads in Figures 9A, 9B and 9C, tires B, C, D, F and G continue to have zero crossings of the drift force Fs at lower drift angles in absolute value.

[0171] Under these conditions, tire B (α=60°, β=60°) continues to have a limited drift force deficiency Fs (<10%) compared to the baseline, while tire C (α=70°, β=70°) has a drift force deficiency Fs of 15% to 20%.

[0172] Referring to FIG. 9B, tire F, with its slightly asymmetric carcass structure, continues to produce drift force levels Fs that substantially overlap with the drift force levels of tire C's symmetric cross-carcass structure.

[0173] Referring to FIG. 9C, tire G, with its significantly asymmetric carcass structure, still produces a drift force level Fs that is higher than that of tire D's symmetric cross-carcass structure.

[0174] However, the deficiency in the drift force Fs of tires B, C, F, and G is limited and does not cause a significant disadvantage in terms of potential driving performance when cornering.

[0175] Figure 9D shows that the behavior of the drift forces generated by tires H and I (also with a highly asymmetric cross-carcass structure) at high vertical loads is similar to that shown in Figure 7D at low vertical loads and in Figure 8D at medium vertical loads.

[0176] Figure 10 shows the self-aligning torque T (N*m) as a function of the drift angle SA for tires A and C. There are two curves because they represent two different tires for each of the two types of carcass structures.

[0177] It can be seen that the curve of the self-aligning torque T (to which the steering torque is proportional at the front axle) has a more progressive shape (changing towards a lower peak in absolute value and a higher absolute drift angle). A more progressive shape of the curve for tire C is generally preferable because it reduces the unpleasant drop in self-aligning torque and steering torque at angles of greater absolute value than the peak angle. In other words, the more progressive the trend of the self-aligning torque at the front axle, the more limited the torque drop at the steering wheel and therefore the more manageable it will be.

[0178] Tires B, C, D, F, and G within the scope of the present invention all provide a significant reduction in rolling resistance. In addition to a significant reduction in rolling resistance, tires B, C, F, and G also provide excellent cornering performance, while the cornering performance of tire D remains good.

Claims

1. A beltless tire for an automobile, a carcass structure (2) comprising two carcass plies (3, 4), each of the two carcass plies (3, 4) comprising a plurality of parallel cords (13, 14) and having an end flap engaged with a respective fixed annular structure (5), the parallel cords (13, 14) of the two carcass plies (3, 4) crossing each other and forming with each other a crossing angle (Δ) comprised between 20° and 60°, and the parallel cords (13, 14) of each of the two carcass plies (3, 4) defining respective angles (α, β) comprised between 60° and 80° with respect to a circumferential direction (C) of the tire (1); at least one reinforcing cord (9) wound in a plurality of circumferential turns disposed at a radially outer position relative to the carcass structure (2); a tread band (10) attached to a radially outer position relative to the reinforcing cord (9); Equipped with the at least one reinforcing cord (9) has a predetermined elongation (Sp), the at least one reinforcing cord (9) has a "tensile load-elongation" curve including a first section (T1) located upstream of the predetermined elongation (Sp), a second section (T2) located downstream of the predetermined elongation (Sp), and a third connecting section (K) located between the first section (T1) and the second section (T2), A tire wherein the second gradient of the second section (T2) is greater than the first gradient of the first section (T1).

2. 2. Tire according to claim 1, wherein the ratio of said second gradient of said second section (T2) to said first gradient of said first section (T1) is greater than 5.

3. 2. Tire according to claim 1, wherein the ratio of said second gradient of said second section (T2) to said first gradient of said first section (T1) is less than 50.

4. Tyre according to claim 1, 2 or 3, wherein the ratio between the second gradient of the second section (T2) and the first gradient of the first section (T1) is comprised between 5 and 40.

5. Tyre according to claim 4, wherein the ratio between said second gradient of said second section (T2) and said first gradient of said first section (T1) is comprised between 10 and 35.

6. 6. Tire according to any one of claims 1 to 5, wherein the first gradient of the first section (T1) is comprised between 1 and 20 N / elongation and the second gradient of the second section (T2) is comprised between 35 and 500 N / elongation.

7. Tire according to any one of the preceding claims, wherein the circumferential winding density of the reinforcing cord (9) is comprised between 40 turns / dm and 130 turns / dm.

8. Tyre according to claim 7, wherein said density of said circumferential turns of said reinforcing cord (9) is comprised between 75 turns / dm and 115 turns / dm.

9. Tire according to any one of the preceding claims, wherein said predetermined elongation (Sp) is comprised between 1% and 5%.

10. 10. Tire according to claim 9, wherein said predetermined elongation (Sp) is comprised between 1.5% and 4.5%.

11. Tire according to any one of claims 1 to 10, wherein the force corresponding to the predetermined elongation percentage (Sp) in the "tensile load-elongation" curve is comprised between 5N and 200N.

12. Tire according to claim 11, wherein the force corresponding to the predetermined elongation percentage (Sp) in the "tensile load-elongation" curve is comprised between 15N and 90N.

13. Tyre according to any one of the preceding claims, wherein said at least one reinforcing cord (9) is metallic or hybrid.

14. 14. A tire according to claim 13, wherein said at least one reinforcing cord (9) is metallic and comprises a plurality of steel threads, said threads being individually twisted and wound together in such a way that each thread does not contact its immediate neighbours in a plurality of cross sections of said cord.

15. 14. Tire according to claim 13, wherein said at least one reinforcing cord (9) is metallic and comprises at least two strands, each strand comprising a respective plurality of steel threads, said plurality of steel threads being wound together in each strand according to a predetermined winding pitch, said at least two strands being wound together in the same manner as the threads of said strand and at a winding pitch equal to or different from said predetermined winding pitch.

16. 14. Tyre according to claim 13, wherein said at least one reinforcing cord (9) is metallic and comprises only one metallic thread, or two or more metallic threads twisted together, or at least one spiral metallic thread.

17. 14. Tire according to claim 13, wherein said at least one reinforcing cord (9) is hybrid and comprises one or more textile filaments having a high modulus twisted in one direction and one or more textile filaments having a low modulus twisted in the same direction, said textile filaments having a high modulus and said textile filaments having a low modulus being twisted together.

18. 14. Tire according to claim 13, wherein the filaments of each yarn of said hybrid reinforcing cord (9) are twisted together according to a respective predetermined number of twists per unit length of said yarn, said different yarns being twisted together according to a predetermined number of twists per unit length of said reinforcing cord (9).

19. 14. Tire according to claim 13, wherein said at least one reinforcing cord (9) is hybrid and comprises two aromatic polyamide fibre yarns and one polyamide-aliphatic and / or polyester fibre yarn.

20. 14. Tire according to claim 13, wherein said at least one reinforcing cord (9) is hybrid and comprises at least one hybrid yarn comprising a plurality of filaments obtained from a first yarn having a plurality of filaments with a first initial tangent modulus and at least one second yarn having a plurality of filaments with a second initial tangent modulus, said first initial tangent modulus and said second initial tangent modulus being different from one another, said first yarn and said second yarn each comprising a plurality of individual filaments, said individual filaments of each of said first yarn and said second yarn being at least partially intermixed in said hybrid yarn.

21. Tyre according to any one of the preceding claims, wherein the circumferential turns of the reinforcing cord (9) subtend an angle with the circumferential direction comprised between 0° and 5°.

22. Tyre according to any one of the preceding claims, wherein the parallel cords (13, 14) of each of the two carcass plies (3, 4) subtend an angle (α, β) with respect to the circumferential direction (C) of the tyre (1) comprised between 65° and 75°.

23. Tire according to one of the preceding claims, wherein the parallel cords (13, 14) of the two carcass plies (3, 4) are at equal angles in opposite directions relative to the circumferential direction (C) of the tire (1).

24. Tyre according to one of the preceding claims, wherein the parallel cords (13, 14) of the two carcass plies (3, 4) are at different angles in opposite directions relative to the circumferential direction (C) of the tyre (1).

25. Tire according to any one of the preceding claims, wherein said crossing angle (Δ) is comprised between 30° and 50°.

26. 26. A tire according to any one of the preceding claims, comprising at least one auxiliary element (17, 17A, 17B) arranged at each of the two opposite axial ends of said plurality of circumferential turns, said auxiliary element (17, 17A, 17B) being arranged between said plurality of circumferential turns and said tread band (10) and / or between said plurality of circumferential turns and said carcass structure (2).

27. 27. Tyre according to claim 26, wherein said at least one auxiliary element (17, 17A, 17B) is arranged astride said respective axial ends.

28. 28. Tyre according to claim 26 or 27, wherein said auxiliary element (17, 17A, 17B) comprises an elastomeric material and / or aramid and / or metal.

29. Tyre according to any one of claims 26 to 28, wherein said auxiliary element (17, 17A, 17B) has an axial extension (W) comprised between 15% and 25% of the axial width (L) of said plurality of circumferential turns.

30. Tyre according to any one of the preceding claims, wherein said at least one reinforcing cord (9) wound in said plurality of circumferential wraps is embedded in a layer of elastomeric material.

31. A tire according to any one of the preceding claims, wherein the number of said carcass plies (3, 4) present in said carcass structure (2) is two.

Images