Belless tyre for a motor vehicle

Abstract

A beltless tyre (1) for a motor vehicle comprises a carcass structure (2) having two carcass plies (3, 4), each carcass ply being equipped with a plurality of parallel cords (13, 14), the parallel cords (13, 14) of the two carcass plies (3, 4) crossing together at an intersection angle (A) of between 20 DEG and 60 DEG and delimiting an angle (alpha, 3) of between 60 DEG and 80 DEG with the circumferential direction (C) of the tyre (1). The reinforcing cord (9) is wound in a plurality of circumferential turns arranged in a radially outer position with respect to the carcass structure (2). The reinforcing cord (9) has a predetermined percentage elongation (Sp) and a "tensile load-elongation" curve comprising a first section (T1) located upstream of the predetermined percentage elongation (Sp) and having a first slope and a second section (T2) located downstream of the predetermined percentage elongation (Sp) and having a second slope. A ratio of the second slope to the first slope is greater than 1.

Description

TECHNICAL FIELD

[0001] The present invention relates to a beltless tire for a motor vehicle. The present invention preferably but not exclusively relates to a road tire intended to be fitted to a hybrid or electric vehicle.

[0002] DEFINITIONS

[0003] The "curvature ratio" of a tire refers to the ratio between the distance between the radially outermost point of the tread band measured in the radial plane of the tire and the line passing through the laterally opposite ends of the tread itself and the distance measured along the tire cords between said ends.

[0004] A "motor vehicle tire" is a tire having a curvature ratio schematically less than 0.15, preferably between 0.03 and 0.1, more preferably close to 0.05.

[0005] The terms "radial", "axial" and "circumferential" refer to the axis of rotation of the tire.

[0006] The "radial plane" is the plane in which the axis of rotation of the tire lies.

[0007] A "beltless" tire is a tire without a belt structure arranged between the carcass structure and the tread band and comprising layers provided with reinforcing cords that cross each other.

[0008] The "tensile load - elongation" curve of a reinforcing cord is the curve plotted on a graph having the elongation of the reinforcing cord (e.g., percentage elongation) on the abscissa and the tensile force applied to the reinforcing cord (e.g., expressed in N) on the ordinate.

[0009] The "tensile load - elongation" curve of a metal cord is obtained according to the BISFA standard - Chapter E6 of the internationally recognized test methods for steel cords for tires, 1995 edition.

[0010] The "tensile load - elongation" curve of a textile cord is obtained according to the BISFA standard - Chapter 7 of the test methods for polyamide filament yarns, 2004 edition.

[0011] "Density" refers to the number of cords (EPDM) present per unit width (e.g., 1 dm).

[0012] A "textile cord" is a cord made of one or more threads of the same textile material.

[0013] A "hybrid cord" is a cord made of threads of at least two different textile materials.

[0014] A "metal cord" is a cord made of one or more metal wires. BACKGROUND OF THE INVENTION

[0015] A tire for a motor vehicle generally includes a carcass structure associated with a belt structure.

[0016] The carcass structure includes one or more carcass plies having opposite end flaps respectively joined to corresponding annular anchoring structures (referred to as bead cores), the annular anchoring structures being associated with filling inserts. The tire area including the bead core and the filling insert forms a bead structure intended to anchor the tire to a corresponding mounting rim. The belt structure includes a plurality of belt plies radially superposed relative to one another and relative to the carcass structure and having metal or fabric or hybrid reinforcing cords cross-oriented relative to the circumferential extension direction of the tire. The tread band is arranged in a radially outer position relative to the belt structure.

[0017] Document US20190202241 shows a tire having a belt structure including two or more plies. The plies are provided with steel cords or organic fiber cords diagonally inclined relative to the circumferential direction of the tire and forming an angle not exceeding 10° with this circumferential direction.

[0018] Document DE 195 45 954A1 shows a beltless tire provided with a carcass of double-crossed plies. Each of the two plies includes polyamide reinforcing cords parallel to one another and incorporated into an elastomeric layer. The cords of the two plies cross one another and form an angle between 20° and 40° with the circumferential direction of the tire. In a radially outer position relative to the carcass ply and under the tread, a circumferentially extending band is arranged, the band being provided with parallel reinforcing elements oriented at an angle of approximately 0° relative to the circumferential direction. The reinforcing elements of the band are polyamide monofilaments having a flat cross-section, an oval cross-section or an elliptical cross-section.

[0019] Document GB 769,325 shows a tire including a carcass provided with linear reinforcing elements and a reinforcing ring made of rubberized metal wires or fabric cords. In one embodiment, the carcass includes one or more carcass plies and the linear reinforcing elements form an angle not exceeding 10° relative to a plane containing the axis of rotation of the tire. The reinforcing ring includes one or more plies with rubberized metal wires or fabric cords arranged at an angle of less than 20° relative to an intermediate circumferential plane. In another embodiment, the carcass includes two or more carcass plies and the linear reinforcing elements form an angle not exceeding 20° relative to one another. The reinforcing ring includes a plurality of plies and the rubberized metal wires or fabric cords of one ply form an angle not exceeding 40° with the rubberized metal wires or fabric cords of an adjacent ply.

[0020] For example, tires with a radial carcass or tires with angled cords are shown in documents US20130206309, US9156315, US4967817, US2939502A and EP0093451A2. For example, reinforcing cords for tires are shown 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

[0021] To meet the requirements of adapting tires to the increasingly improved performance of motor vehicles and improving driving performance in terms of, for example, stiffness, driving stability and driving agility, tires need to adopt a layered belt structure provided with mutually intersecting reinforcing cords.

[0022] Compared with non-belted tires, tires having a belt structure (which has belt layers with cross-oriented cords) can actually generally provide greater drift force at the same drift angle. Tires having such a belt structure can also generally provide greater self-aligning torque at low drift angles than non-belted tires.

[0023] For many years, the applicant has been concerned about the environmental impacts directly and indirectly imposed by tires during their use. In particular, in order to control the consumption of motor vehicles that affect energy consumption and carbon dioxide emissions into the atmosphere, the applicant has produced tires with low rolling resistance, that is, tires with a fuel efficiency class equal to "A" (according to European regulation EU 2020 / 740).

[0024] In this context, the applicant has set itself the goal of further reducing the rolling resistance of tires, especially but not only those intended to equip new hybrid motor vehicles and all-electric motor vehicles, in order to reduce the environmental impact.

[0025] The applicant has set itself a further goal of reducing vehicle consumption or increasing the autonomy of the vehicle.

[0026] The applicant has set itself a further goal of reducing tire heating during driving.

[0027] In particular, the applicant has set itself the goal of achieving the above objectives without sacrificing the performance and driving characteristics of modern tires, especially those provided with a cross-belt structure.

[0028] However, the applicant has unexpectedly found that the above object can be achieved by adopting a specific beltless structure.

[0029] More precisely, the applicant has found that the above object can be achieved by a beltless tire which combines a carcass structure with reinforcing cords crossing at a suitable preset angle and a reinforcing structure (commonly defined as the zero-degree layer) including reinforcing cords having a specific "tensile load - elongation" curve.

[0030] According to its first aspect, the present invention relates to a beltless tire for a motor vehicle.

[0031] Preferably, the tire includes a carcass structure including two carcass ply layers, each of the two carcass ply layers including a plurality of parallel cords and having end flaps joined to corresponding annular anchoring structures.

[0032] Preferably, the parallel cords of the two carcass ply layers cross each other and form an included angle between 20° and 60° with respect to each other.

[0033] Preferably, the parallel cords of each of the two carcass ply layers define a corresponding angle between 60° and 80° with the circumferential direction of the tire.

[0034] Preferably, the tire includes at least one reinforcing cord wound in a plurality of circumferential turns arranged in a radially outer position with respect to the carcass structure.

[0035] Preferably, the tire includes a tread band applied in a radially outer position with respect to the reinforcing cord.

[0036] Preferably, the at least one reinforcing cord has a predetermined percentage elongation.

[0037] Preferably, the at least one reinforcing cord has a "tensile load - elongation" curve including a first segment upstream of the predetermined percentage elongation, a second segment downstream of the predetermined percentage elongation, and a third connecting segment between the first segment and the second segment.

[0038] Preferably, the second slope of the second segment is greater than the first slope of the first segment.

[0039] The applicant has confirmed that the present invention allows the rolling resistance of the tire to be reduced to a value lower than that of a tire provided with a belt structure.

[0040] The applicant has also confirmed that the present invention allows the performance and driving characteristics suitable for equipping modern motor vehicles.

[0041] In particular, the Applicant has confirmed that the tires manufactured according to the present invention are capable of providing a drift force comparable to that provided by tires provided with a belt structure.

[0042] The Applicant has also confirmed that the tires manufactured according to the present invention provide a more progressive self-aligning torque curve compared to the curve provided by tires provided with a belt structure, and thus the driver can more easily control the torque decay at the steering wheel.

[0043] The present invention may exhibit one or more of the following preferred features in at least one of its above aspects.

[0044] Preferably, the first segment is defined between zero percent elongation and the first point of the "tensile load - elongation" curve, the second segment extends downstream of the second point of the "tensile load - elongation" curve, and the third connecting segment is defined between the first point and the second point.

[0045] Preferably, the first point corresponds to the first point of the "tensile load - elongation" curve starting from the zero percent elongation, wherein the concave surface of the "tensile load - elongation" curve faces upward.

[0046] Preferably, if the concavity of the "tensile load - elongation" curve downstream of the first point remains upward until failure, the second point of the "tensile load - elongation" curve is the point with the maximum concavity.

[0047] Alternatively, if the concavity of the upward-facing "tensile load - elongation" curve downstream of the first point becomes downward at an inflection point, the second point of the "tensile load - elongation" curve is the inflection point.

[0048] Preferably, the predetermined percent elongation corresponds to the intersection point between the first tangent of the "tensile load - elongation" curve at the first point and the second tangent of the "tensile load - elongation" curve at the second point.

[0049] Preferably, the ratio of the second slope of the second segment to the first slope of the first segment is greater than 5.

[0050] Preferably, the circumferential turns of the at least one reinforcing cord are embedded in the elastomeric material layer.

[0051] Preferably, the circumferential turns of the at least one reinforcing cord and the elastomeric material layer define a reinforcing layer.

[0052] Preferably, the reinforcing structure is positioned directly against the carcass structure.

[0053] Preferably, the tread band is positioned directly against the reinforcing structure.

[0054] Preferably, the ratio of the second slope of the second segment to the first slope of the first segment is less than 50.

[0055] Preferably, the ratio of the second slope of the second segment to the first slope of the first segment is between 5 and 40, and more preferably between 10 and 35, for example, equal to 27.

[0056] Preferably, the first slope of the first segment is between 1 N / % elongation and 20 N / % elongation.

[0057] Preferably, the second slope of the second segment is between 35 N / % elongation and 500 N / % elongation.

[0058] Preferably, the third connecting segment forms an elbow or knee shape with an upward concavity.

[0059] Preferably, the first point coincides with the zero elongation point, and in this case, the first segment is shortened to the first point.

[0060] Preferably, the first segment has a downward concavity.

[0061] Preferably, the second segment has an upward concavity or a downward concavity.

[0062] Preferably, the density of the circumferential turns of the reinforcing cord is between 40 turns / dm and 130 turns / dm, and more preferably between 75 turns / dm and 115 turns / dm.

[0063] Preferably, the predetermined percentage elongation is between 1% and 5%, and more preferably between 1.5% and 4.5%. Even more preferably, the predetermined percentage elongation is 3%.

[0064] Preferably, in the "tensile load - elongation" curve, the force corresponding to the predetermined percentage elongation is between 5 N and 200 N, and more preferably between 15 N and 90 N.

[0065] Preferably, the at least one reinforcing cord is a metal cord or a hybrid cord.

[0066] Preferably, the at least one metal reinforcing cord includes a plurality of steel wires preferably having the same diameter, and the steel wires are independently twisted and wound together such that in multiple cross-sections of the cord, each steel wire does not contact the adjacent steel wire.

[0067] Preferably, the at least one metal reinforcing cord includes at least two strands, each strand including a respective plurality of steel wires, preferably the steel wires having the same diameter, and in each strand, the plurality of steel wires are wound together with a predetermined winding pitch, wherein the at least two strands are wound together along a direction the same as the direction of the steel wires in the strand and with a winding pitch equal to or different from the predetermined winding pitch.

[0068] Preferably, the at least one metal reinforcing cord includes a single metal wire or at least two metal wires twisted together.

[0069] Preferably, the at least one metal reinforcing cord includes at least one helical metal wire.

[0070] Preferably, the at least one hybrid reinforcing cord includes one or more fabric filaments with a high elastic modulus twisted in one direction and one or more fabric filaments with a low elastic modulus twisted in the same direction, wherein the aforementioned fabric filaments with a high elastic modulus and the aforementioned fabric filaments with a low elastic modulus are twisted together.

[0071] Preferably, the filaments of each yarn of the hybrid reinforcing cord are 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 reinforcing cord.

[0072] Preferably, the at least one hybrid reinforcing cord includes two aromatic polyamide fiber yarns and one aliphatic polyamide fiber yarn and / or polyester fiber yarn.

[0073] Preferably, the at least one hybrid reinforcing cord includes at least one hybrid yarn, the hybrid yarn including a plurality of filaments obtained from a first yarn with a plurality of filaments having a first initial tangential modulus and at least one second yarn with a plurality of filaments having a second initial tangential modulus, the first initial tangential modulus and the second initial tangential modulus being different from each other, wherein each of the first yarn and the second yarn includes a plurality of independent filaments, and the independent filaments of each of the first yarn and the second yarn are at least partially mixed together in the hybrid yarn.

[0074] Preferably, the circumferential turns of the reinforcing cord define an angle between 0° and 5° with the circumferential direction.

[0075] Preferably, the at least one reinforcing cord wound with a plurality of circumferential turns is embedded in an elastomeric material layer.

[0076] Preferably, the at least one reinforcing cord wound with a plurality of circumferential turns forms a reinforcing layer.

[0077] Preferably, the reinforcement layer is produced by winding continuous elongate elements in closely placed turns, the continuous elongate elements comprising the at least one reinforcing cord, wherein the at least one reinforcing cord is wound in a plurality of circumferential turns.

[0078] Preferably, the continuous elongate elements comprise an elastomeric material and the at least one reinforcing cord is embedded in the elastomeric material.

[0079] Preferably, the continuous elongate elements comprise a plurality of reinforcing cords.

[0080] Preferably, the continuous elongate elements comprise from 1 to 500 reinforcing cords.

[0081] Preferably, the continuous elongate elements have a flat cross-section.

[0082] Preferably, the reinforcing cords are arranged side by side in the continuous elongate elements.

[0083] Preferably, the density of the reinforcing cords in the continuous elongate elements is between 40 cords / dm and 130 cords / dm, more preferably between 75 cords / dm and 115 cords / dm.

[0084] Preferably, the number of carcass plies present in the carcass structure is two.

[0085] Preferably, the parallel cords of each of the two carcass plies define an angle between 65° and 75°, optionally an angle of 70°, with the circumferential direction of the tyre.

[0086] Preferably, the parallel cords of the two carcass plies form angles of equal magnitude and opposite direction with respect to the circumferential direction of the tyre. Thus, the parallel cords of the two carcass plies are symmetrically arranged with respect to the circumferential direction of the tyre.

[0087] Alternatively, the parallel cords of the two carcass plies form angles of different magnitude and opposite direction with respect to the circumferential direction of the tyre. Thus, the parallel cords of the two carcass plies are asymmetrically arranged with respect to the circumferential direction of the tyre.

[0088] Preferably, the crossing angle is between 30° and 50°, optionally equal to 40°.

[0089] Preferably, the two carcass plies comprise a first carcass ply (preferably located radially internally) and a second carcass ply (preferably located radially externally).

[0090] Preferably, the cords of the first carcass ply are inclined at a first angle α measured in the counterclockwise direction with respect to the circumferential direction of the tyre.

[0091] Preferably, the cords of the second carcass ply are inclined at a second angle β measured in the clockwise direction with respect to the aforementioned circumferential direction.

[0092] Preferably, the included angle Δ defined by the cords of the first carcass ply and the cords of the second carcass ply is Δ = 180° - β - α.

[0093] Preferably, at least one auxiliary element is positioned at each of the two opposite axial ends of the plurality of circumferential turns.

[0094] Preferably, the auxiliary element is placed between the plurality of circumferential turns and the tread band and / or between the plurality of circumferential turns and the carcass structure.

[0095] Preferably, it is provided that at least one auxiliary element is laid at each of the two opposite axial ends of the circumferential turns.

[0096] Preferably, the at least one auxiliary element is positioned straddling the respective axial end.

[0097] Preferably, it is provided that the auxiliary element is laid before winding the continuous elongate element with turns placed side by side, such that the at least one auxiliary element is located between the circumferential turns and the carcass structure, and / or it is provided that the auxiliary element is laid after winding the continuous elongate element with turns placed closely together, such that the at least one auxiliary element is located between the circumferential turns and the tread band.

[0098] Preferably, the auxiliary element comprises an elastomeric material and / or aramid and / or a metallic material.

[0099] Preferably, the circumferential extension length of the auxiliary element is between 15% and 25% of the axial width of the plurality of circumferential turns.

[0100] Preferably, it is provided that the auxiliary element is laid before winding the continuous elongate element with turns placed closely together; the continuous elongate element is wound with turns placed adjacent to each other, leaving the axial outer part of the auxiliary element free; the axial outer part is folded onto the respective axial ends of the adjacent turns, such that the auxiliary element is positioned straddling the respective axial end.

[0101] Further features and advantages will become more clearly apparent from a detailed description of a preferred but non - exclusive embodiment of a beltless tire for a motor vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] This description will be made hereinafter with reference to the drawings, which are provided for illustrative purposes only and thus are not intended for limiting purposes, wherein:

[0103] - Figure 1 shows a cross - section taken along a radial plane of a beltless tire for a motor vehicle according to the present invention;

[0104] - Figure 2 is Figure 1 an enlarged portion of;

[0105] - Figure 3A and 3B is a schematic view seen from above the elements of the tire mentioned in the foregoing figures;

[0106] - Figure 4 shows a continuous elongate element for manufacturing the tire mentioned in the foregoing figures;

[0107] - Figure 5A shows the "tensile load - elongation" curve of the reinforcing cords of the tire mentioned in the foregoing figures;

[0108] - Figure 5B shows the "tensile load - elongation" curves of different reinforcing cords;

[0109] - Figure 5C shows Figure 5A and 5B the details of the "tensile load - elongation" curve of;

[0110] - Figure 6 shows the rolling resistance comparison between the tire and a reference tire;

[0111] - Figures 7A - 7D 8A - 8D and 9A - 9D show the drift forces of the tire according to the present invention and a reference tire;

[0112] - Figure 10 shows the self - aligning torque of a pair of tires according to the present invention and a reference tire;

[0113] - Figure 11 、 12 and 13 are enlarged portions of variants of the tire according to the present invention. Detailed Description

[0114] Figure 1 shows a cross - section taken along a radial plane of a beltless tire 1 for a motor vehicle according to the present invention.

[0115] The tire 1 includes a carcass structure 2, which includes 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 opposite end flaps, which are joined to corresponding annular anchoring structures 5 (called bead cores), and the annular anchoring structures are associated with filling inserts 6.

[0116] The tire area 1 including the bead core 5 and the filling insert 6 forms a bead structure 7, which is intended to anchor the tire 1 to a corresponding mounting rim (not shown).

[0117] The carcass structure 2 is associated with a reinforcement structure 8 (zero-degree layer) comprising at least one reinforcing cord 9 wound in a plurality of circumferential turns arranged in a radially external position relative to the carcass structure 2 ( Figure 2 ). The circumferential turns are arranged so as to form an angle preferably comprised between 0° and 5° with the circumferential direction C of the tyre 1 .

[0118] Figure 1 and Figure 2 The reinforcement structure 8 shown comprises a layer of elastomeric material in which are embedded circumferential turns of reinforcing cords 9. The reinforcement structure 8 is preferably positioned directly against the carcass structure 2, in particular against the second carcass ply 4.

[0119] The tyre 1 according to the invention is beltless and has a tread band 10 applied in a radially external position to the reinforcing structure 8, said tread band being made of an elastomeric compound like the other semifinished products constituting the tyre 1. The tread band 10 is positioned directly against the reinforcing structure 8.

[0120] Furthermore, respective sidewalls 11 made of elastomeric compound are applied on the lateral surfaces of the carcass structure 2 in an axially outer position, each extending from one of the lateral edges of the tread band 10 at the respective bead structure 7 .

[0121] A waterproof rubber layer 12 (commonly called “liner”) is arranged in a radially inner position relative to the first carcass ply 3 , said waterproof rubber layer providing the necessary impermeability for inflation of the tyre 1 . The waterproof rubber layer 12 is preferably applied directly against the first carcass ply 3 .

[0122] Each of the two carcass plies 3, 4 comprises a plurality of cords 13, 14 which are parallel to one another and which are covered with or embedded in an elastomeric material. The parallel cords 13, 14 of the two carcass plies 3, 4 may be textile cords and / or hybrid cords.

[0123] like Figure 3A and 3B As shown, the cords 13 of the first carcass ply 3 are inclined at a first angle α measured in the counterclockwise direction relative to the circumferential direction C of the tire 1, while the cords 14 of the second carcass ply 4 are inclined at a second angle β measured in the clockwise direction relative to the aforementioned circumferential direction C. Viewed from a different angle, the cords 14 of the second carcass ply 4 are inclined at a third angle Ω measured in the counterclockwise direction relative to the aforementioned circumferential direction C, where Ω = 180° - β.

[0124] Thus, 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 and the cords 14 of the second carcass ply 4 define an intersection angle Δ = 180° - β - α = Ω - α.

[0125] Examples of these angles are shown in Table 1 below. In Examples B, C, and D, the two carcass plies 3, 4 are inclined at equal and opposite angles with respect to the circumferential direction C of the tire 1, as Figure 3A shown in the example (the parallel cords 13, 14 of the two carcass plies 3, 4 are symmetrically arranged with respect to the circumferential direction C of the tire 1). In Examples F and G, the two carcass plies 3, 4 are inclined at different and opposite angles with respect to the circumferential direction C of the tire 1, as Figure 3B shown in the example (the parallel cords 13, 14 of the two carcass plies 3, 4 are asymmetrically arranged with respect to the circumferential direction C of the tire 1).

[0126] Table 1

[0127]

[0128]

[0129] The reinforcing cord 9 that is wound in a circumferential turn and forms part of the reinforcing structure 8 has a predetermined percentage elongation Sp that is between 1% and 5%, preferably between 1.5% and 4.5%, and for example equal to 3%.

[0130] The reinforcing cord 9 also has a "tensile load - elongation" curve that includes a first segment T1 and a second segment T2. The first segment is upstream of the predetermined percentage elongation Sp and is provided with a first slope measured at a first point P1. The second segment is downstream of the predetermined percentage elongation Sp and is provided with a second slope measured at a second point P2, where the second slope is greater than the first slope. In other words, when the reinforcing cord 9 is stretched beyond the predetermined percentage elongation Sp, its stiffness increases. Assuming that the reinforcing cord 9 has such a predetermined percentage elongation Sp in the finished tire 1, this means that during the rolling of the tire 1 on the road, when the tire 1 deforms such that the reinforcing cord 9 or a portion thereof is subjected to tension, the reinforcing cord 9 behaves as if it has a high stiffness corresponding to the slope of the second segment T2.

[0131] Figure 5A and 5B An example of this "tensile load - elongation" curve is shown in the graph of

[0132] The first segment T1 is defined between zero elongation and the first point P1 of the "tensile load - elongation" curve. The second segment T2 extends downstream of the second point P2 of the "tensile load - elongation" curve. The third connecting segment K is defined between the first point P1 and the second point P2. The first segment T1 and the second segment T2 of the "tensile load - elongation" curve are connected by the third connecting segment K with an increasingly larger slope. The third connecting segment K forms an elbow - shaped or knee - shaped surface with the concavity facing upward.

[0133] Figure 5A The "tensile load - elongation" curve in refers to 3×4×0.20 HEHT steel cord.

[0134] It can be seen that Figure 5A the "tensile load - elongation" curve in has a first segment T1 with a downward - facing concavity (visible in the enlarged view of Figure 5C ), followed by a third connecting segment K with an upward - facing concavity, and then a second segment T2 with a concavity that first faces upward and then downward.

[0135] Therefore, Figure 5A the curve in has an inflection point between the first segment T1 and the third connecting segment K and an inflection point at the start of the second segment T2. The first point P1 corresponds to the first point of the "tensile load - elongation" curve encountered starting from zero elongation, where the "tensile load - elongation" curve has an upward - facing concavity. In the graph of Figure 5A , the first point P1 is located directly behind the inflection point of the first segment T1. The second point P2 is the inflection point at the start of the second segment T2.

[0136] Figure 5B The "tensile load - elongation" curve in refers to a hybrid cord of the AR×2 / NY 1670 / 940 (20 / 20×20) type.

[0137] It can be seen that Figure 5B the "tensile load - elongation" curve in has a first segment T1 with a downward - facing concavity (as shown in Figure 5C ), followed by a third connecting segment K with an upward - facing concavity, and then a second segment T2. Different from the curve in Figure 5A , the concavity of this second segment always faces upward (until the breaking load).

[0138] For Figure 5A , the first point P1 corresponds to the first point of the "tensile load - elongation" curve encountered starting from zero elongation, where the "tensile load - elongation" curve has an upward - facing concavity. Different from Figure 5A , Figure 5BThe second point P2 of the "tensile load - elongation" curve in

[0139] In Figure 5A and 5B the predetermined percentage elongation Sp corresponds to the elongation at the intersection between the first tangent to the "tensile load - elongation" curve at the first point P1 and the second tangent to the "tensile load - elongation" curve at the second point P2.

[0140] In Figure 5A the graph, the predetermined percentage elongation Sp is equal to approximately 1.7%, and the force F corresponding to this predetermined percentage elongation Sp is equal to approximately 60 N. In Figure 5B the graph, the predetermined percentage elongation Sp is equal to approximately 3.4%, and the force F corresponding to this predetermined percentage elongation Sp is equal to approximately 85 N.

[0141] The reinforcing cord 9 according to the invention has a force corresponding to the predetermined percentage elongation Sp, which force is preferably between 5 N and 200 N, more preferably between 15 N and 90 N.

[0142] The ratio between the second slope and the first slope of the "tensile load - elongation" curve of the reinforcing cord 9 according to the invention is preferably greater than 5, more preferably between 5 and 40, even more preferably between 10 and 35. For example, this ratio is equal to 27. For example, the first slope of the first section T1 is preferably between 1 N / % elongation and 20 N / % elongation, and the second slope of the second section T2 is preferably between 35 N / % elongation and 500 N / % elongation. In Figure 5A the example of the graph, 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 above - mentioned ratio is approximately 24. In Figure 5B the graph example, 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.

[0143] To obtain this double - slope behavior, the reinforcing cord 9 (also called "high elongation" because of its behavior) includes, for example, two or more twisted metal wires or at least one helical metal wire, as shown in the documents WO 2021 / 124133, WO 2021 / 124138, WO 2021 / 124154A1 and WO 2022 / 064436A1 under the same applicant.

[0144] In different examples, the reinforcing cord 9 comprises a single strand of n steel wires having a given diameter, the steel wires being independently twisted and helically wound together, but not wound so tightly that each wire is in contact with the adjacent wire, as described in the document GB 2034363A of the same applicant. As a specific example, the reinforcing cord 9 can be of the 1×5×0.25 or 5×0.25 type. These types of cords are specifically described in the art as "open" cords precisely because in multiple cross-sections of the cord, each component wire is not in contact with the adjacent wire. This space is particularly useful because it allows the elastomeric material to flow during vulcanization, thereby filling every space and uniformly rubberizing the formed cord: thus, during use, ingress of moisture, which is harmful to the cord itself, can be avoided.

[0145] Another example of an open reinforcing cord 9 provides 2 to 7 single-twisted wires, wherein, along the entire length of the cord, there are penetration portions for the elastomeric material between the wires with respect to each other, as shown, for example, in the document EP1213159A2.

[0146] In a further example, the reinforcing cord 9 comprises a given number of strands, for example 2 to 5 strands, each strand being composed of a certain number of metal wires, for example 2 to 10 metal wires, the diameter of the metal wires preferably being between 0.12 mm and 0.25 mm. The wires in the strand and the strands in the cord are helically wound together in the same direction, wherein the winding pitches of the wires and the strands are the same or different. As a specific example, a cord of the 3×7×0.12HE type can be used as the reinforcing cord 9, as described, for example, in the document EP0461646B1 of the same applicant, or a cord of the 3×4×0.20HEHT type as described above.

[0147] The reinforcing cord 9 can also be of a hybrid type, for example, formed by: twisting one or more filaments having a high elastic modulus (for example, aromatic polyamide fibers) in one direction and twisting one or more filaments having a low elastic modulus (for example, aliphatic polyamide fibers) in the same direction, and finally twisting the above-mentioned high-elasticity-modulus filaments and low-elasticity-modulus filaments together, preferably in the opposite direction, as described, for example, in the document EP0335588A2.

[0148] In another example, the filaments of each yarn of the reinforcing cord 9 can be twisted together a given number of times per unit length of the yarn, and more preferably, multiple yarns are twisted together a given number of times per unit length of the cord, for example, as shown in document US2004 / 0118499A1. In addition, the twist direction of the cord or yarn is different from the direction of the cord or yarn held vertically. The filaments have a high elastic modulus (e.g., aromatic polyamide) and a low elastic modulus (e.g., aliphatic polyamide).

[0149] The reinforcing cord 9 can also be composed of two aromatic polyamide fiber yarns and one aliphatic polyamide fiber yarn and / or polyester fiber yarn, and the aromatic polyamide fiber yarn and the aliphatic polyamide fiber yarn and / or polyester fiber yarn are assembled by a twisting process, wherein the aromatic polyamide fiber yarn has suitable linear density and initial elastic modulus characteristics, for example, as shown in document WO2015 / 019214A1 under the same applicant.

[0150] Another example of the reinforcing cord 9 includes at least one hybrid yarn, preferably twisted, the hybrid yarn including multiple filaments obtained from a first yarn and at least one second yarn, the first yarn including multiple filaments having a first initial tangential modulus, the second yarn including multiple filaments having a second initial tangential modulus, the first initial tangential modulus and the second initial tangential modulus being different from each other, wherein each of the first yarn having multiple filaments and the second yarn having multiple filaments includes multiple independent filaments, and the independent filaments of each of the first yarn and the second yarn are at least partially mixed together, for example, as shown in document WO2009 / 052844A1 under the same applicant.

[0151] Since the reinforcing structure 8 includes a plurality of circumferential turns formed by the reinforcing cord 9, the reinforcing structure 8 also has a corresponding stiffness, which depends on the density of the circumferential turns and the characteristics of the reinforcing cord 9. For example, the density of the circumferential turns is preferably between 40 turns / dm and 130 turns / dm, and more preferably between 75 turns / dm and 115 turns / dm.

[0152] The above-mentioned tire 1 can be manufactured by the following steps.

[0153] For example, it is specified that the carcass structure 2 as described above is manufactured by laying the respective structural components on a building drum. The constructed carcass structure 2 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.

[0154] Then, the continuous elongate element 15 (at Figure 4(partially shown in) are wound around the carcass structure 2 in turns that are placed close to each other or partially overlapping, the continuous elongate element comprising one or more reinforcing cords 9 embedded in or covered by an elastomeric material 16. The continuous elongate element 15 preferably comprises between 1 and 500 reinforcing cords 9. In Figure 4 an exemplary embodiment of, the continuous elongate element 15 has a flat cross-section and comprises reinforcing cords 9 arranged side by side. The density of the reinforcing cords 9 in the continuous elongate element 15 is preferably between 40 cords / dm and 130 cords / dm, for example equal to 75 cords / dm. The winding of the continuous elongate element 15 also arranges the reinforcing cords 9 according to the aforementioned plurality of circumferential turns.

[0155] During laying, the continuous elongate element 15 is placed under tension in order to provide a first percentage elongation for the continuous elongate element 15 and the corresponding reinforcing cords 9, which is substantially maintained once the continuous elongate element 15 is wound and applied around the carcass structure 2.

[0156] The laying of the continuous elongate element 15 forms a reinforcing structure 8 that axially extends until it overlaps at its axial end opposite the end flap of the sidewall 11, as Figure 1 shown.

[0157] Finally, the tread band 10 is placed around the reinforcing structure 8. The tread band 10 is applied against the reinforcing structure 8 and against the end portions of each of the two sidewalls 11 ( Figure 1 and Figure 2 ).

[0158] The green tire 1 thus constructed is inserted into a vulcanization mold in which a molding and vulcanization process is carried out, aimed at determining the structural stability of the tire 1 through crosslinking of the elastomeric material and at imparting a desired tread pattern on the tread band 10 and any distinctive graphic symbols at the sidewalls 11.

[0159] During molding and vulcanization, in addition to heating the green tire 1, it is radially expanded by introducing a pressurized gas into the interior of the green tire or into a membrane located inside the green tire, in order to radially press the radially outer surface against the mold.

[0160] During molding and vulcanization, the reinforcing cords 9 of the reinforcing structure 8 undergo a second percentage elongation under the action of the pressurized gas.

[0161] All the circumferential turns exhibit a certain elongation after vulcanization and molding, depending on the laying process (on a cylindrical or annular surface), which can vary based on the axial positioning and to a certain extent approximately corresponds to the aforementioned predetermined percentage elongation Sp.

[0162] Figure 11 , 12 Figures 12 and 13 illustrate respective variants of the tire 1 according to the present invention. These variants also include at least one auxiliary element 17, 17A, 17B, which is positioned at each of the two opposite axial ends of the plurality of circumferential turns or the reinforcement structure 8. The auxiliary element 17, 17A, 17B is, for example, a strip including an elastomeric material and / or aramid and / or metallic material, which is wound around each of the above two opposite axial ends of the reinforcement structure 8.

[0163] For Figure 11 the variant, the auxiliary element 17 is placed before placing the reinforcement structure 8. Then the continuous elongate element 15 is wound, leaving the axial outer portion of the auxiliary element 17 free. Subsequently, the said axial outer portion of the auxiliary element 17 is flipped over the reinforcement structure 8 such that the auxiliary element 17 is positioned straddling the edge of the corresponding axial end of the reinforcement structure 8. Finally, the tread band 10 is applied.

[0164] Figure 12 The variant of

[0165] Figure 13 includes a first auxiliary element 17A placed above the reinforcement structure 8 (i.e., in a radially outer position relative to the reinforcement structure 8) and a second auxiliary element 17B placed below the reinforcement structure 8 (i.e., in a radially inner position relative to the reinforcement structure 8). In this variant, each of the two opposite axial ends of the reinforcement structure 8 is associated with two different auxiliary elements.

[0166] In all three illustrated variants, the auxiliary elements 17, 17A, 17B are in a radially outer position relative to the end flaps of the respective sidewall 11. Further, the axial extension length "W" of the single auxiliary element 17 or the first and second auxiliary elements 17A, 17B (indicated in Figure 11 , 12 and 13) is between 15% and 25% of the axial width "L" of the plurality of circumferential turns (indicated in Figure 1 ), i.e., between 15% and 25% of the axial width "L" of the reinforcement structure 8.

[0167] Test

[0168] Eight tires B, C, D, E, F, G, H, I were compared to a reference tire A via finite element analysis (FEA). All tires were of the P7 Cinturato model with a size of 245 / 45R18 100Y. The reference tire A included a radial single-ply carcass structure, a two-ply belt structure with cross cords, and a hybrid zero-degree ply (i.e., composed of hybrid cords). The eight tires B, C, D, E, F, G, H, I included a carcass structure with two cross plies and a metallic zero-degree layer with the double slope as described above (i.e., formed by metallic cords). The eight tires B, C, D, E, F, G, H, I did not have a belt structure, i.e., they did not include a belt layer with cross cords. The eight tires B, C, D, E, F, G, H, I differed from each other in terms of the angles α, β, Ω, and Δ of the cords 13, 14 in the carcass plies 3, 4, as shown in Tables 2A and 2B below. Tires B, C, D, F, G are the same as in Table 1.

[0169] Materials for simulation:

[0170] Carcass ply cords: RY 1840 / 2 (48×48) EPDM 120;

[0171] Zero-degree metal (steel): 2×0.15HE EPDM 79;

[0172] Zero-degree hybrid: AR / NY 1100 / 1400 (28 / 7×28) EPDM 79.

[0173] Table 2A

[0174]

[0175] Table 2B

[0176]

[0177]

[0178] First, it should be noted that tires B, C, D, E, F, G, H, I are lighter than the reference tire A. In fact, if the weight of the reference tire A is considered as 100, then the weights of all eight tires B, C, D, E, F, G, H, I are reduced by 7.4%.

[0179] Figure 6 The rolling resistance coefficients RR of tires A, B, C, D, E, F, G, H, I are shown. The rolling coefficients have been normalized by assigning the value 100 to the reference tire A. It can be seen that the RR of tires B, C, D, F, G, H, I (RR 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 = 91.6) is less than the rolling resistance coefficient RR of the reference tire A (RR A = 100). Tire E is characterized in that the angles α and β are smaller than those of other tires, but compared with the reference tire A, the RR of this tire is worse (RR E = 103.0). In addition to showing Figure 6 the RR values shown, Table 3 below also shows the percentage reduction in the rolling resistance coefficient RR of tires B, C, D, F, G, H, I compared to the reference tire A.

[0180] Table 3

[0181] A Reference B C D F G H I RR% 100 87.7 83.3 86.0 83.3 83.5 89.6 91.6 Reduction % - -12.3 -16.7 -14.0 -16.7 -16.5 -10.4 -8.4

[0182] The advantages of tires B, C, D, F, G, H, I in reducing the rolling resistance RR are obvious and significant.

[0183] Figures 7A - 7D Shows the variation of the drift force Fs (in Newtons) of tires A, B, C, D, F, G, H, I with the drift angle SA under a vertical load (low vertical load) of 2866 N corresponding to the operating conditions of the inner wheel of the bend.

[0184] At Figure 7A , 7B and the low vertical load of 7C, compared with the drift force Fs of the reference tire A, the drift force Fs of tires B, C, D, F, G crosses zero at a lower absolute value of the drift angle, which improves the straight-line centring performance. In addition, the drift force level Fs generated by tires B, C, F, G is basically the same as that of the reference tire A.

[0185] Refer to Figure 7B , the drift force level Fs generated by tire F with a slightly asymmetric carcass structure almost overlaps with the drift force level of the symmetric cross carcass structure of tire C.

[0186] Refer to Figure 7C , the drift force level Fs generated by tire G with a highly asymmetric carcass structure is higher than the drift force level of the symmetric cross carcass structure of tire D.

[0187] On the contrary, Figure 7DIt is shown that tires H and I, which also have a carcass structure with highly asymmetric crossovers (but different from tire G), produce a significantly lower absolute value of the drift force level Fs in the negative drift branch (left curve) than the drift force level of tire C with a symmetric crossover carcass structure, and are slightly higher in the positive drift branch (right curve). Overall, the average drift force that tires H and I may produce at the same drift angle is lower than that produced in the case of the symmetric carcass structure of tire C. In addition, tires H and I show a zero crossing of the force when the drift angle sign is opposite to that of the reference tire A and the absolute value is higher, which deteriorates the straight-ahead return performance.

[0188] Figures 8A - 8D Shows the variation of the drift force Fs of tires A, B, C, D, F, G, H, I with the drift angle SA under a vertical load of 4337 N (average vertical load - the situation when a coaxial double-wheel enters a curve or starts to change lanes).

[0189] At Figure 8A 、 8B and the average vertical load of 8C, tires B, C, D, F, G continue to have a zero crossing of the force under drift angle conditions where the absolute value of the drift force Fs is lower than that of the reference tire A. In addition, the drift force level Fs generated by tires B, C, F, G is slightly lower than that of the reference tire A (the difference < 10%).

[0190] Reference Figure 8B , the drift force level Fs generated by tire F with a slightly asymmetric carcass structure basically overlaps with the drift force level generated by the symmetric crossover carcass structure of tire C. Refer to Figure 8C , tire G with a highly asymmetric carcass structure still produces a higher drift force level Fs than the symmetric crossover carcass structure of tire D. Figure 8D Shows that the behavior of the drift force generated by tires H and I (which also have a highly asymmetric crossover carcass structure) under medium vertical load is similar to the behavior shown in Figure 7D under low vertical load.

[0191] Figures 9A - 9D Shows the variation of the drift force F (N) of tires A, B, C, D, F, G, H, I with the drift angle SA under a vertical load of 5808 N (high vertical load - the outer wheel is at rest during turning).

[0192] At Figure 9A 、 9B and the high vertical load of 9C, tires B, C, D, F, G continue to have a zero crossing of the drift force Fs under drift angle conditions with a lower absolute value.

[0193] Under these conditions, compared to the reference tire, tire B (α = 60°, β = 60°) continues to have a limited understeer force Fs (< 10%). The understeer force Fs of tire C (α = 70°, β = 70°) is between 15% and 20%.

[0194] reference Figure 9B , tire F with a slightly asymmetrical carcass structure continues to produce a level of understeer force Fs that substantially overlaps with the level of understeer force of the symmetrical cross - carcass structure of tire C.

[0195] reference Figure 9C , tire G with a highly asymmetrical carcass structure produces a level of understeer force Fs that is still higher than the level of understeer force of the symmetrical cross - carcass structure of tire D.

[0196] However, the understeer of the understeer force Fs of tires B, C, F, G is limited such that it does not cause a significant loss in driving performance potential during cornering.

[0197] Figure 9D Shows the behavior of the understeer force produced by tires H and I (also having a highly asymmetrical cross - carcass structure) at high vertical loads is similar to Figure 7D at low vertical loads and Figure 8D at medium vertical loads as shown.

[0198] Figure 10 Shows the variation of the self - aligning torque T (N*m) of tires A and C with the slip angle SA. There are two curves because for each of the two carcass structure types, they correspond to two different tires.

[0199] It can be seen that the curve of the self - aligning torque T (the steering torque at the front axle is proportional to its value) is more progressive (the peak with a lower absolute value moves towards the direction of the slip angle with a higher absolute value). The more progressive the shape of the curve of tire C, the more preferable it is generally, because it reduces the adverse loss of the self - aligning torque and the steering torque for angles with an absolute value greater than the peak. In other words, the more progressive form of the self - aligning torque trend at the front axle determines a more limited decrease in the torque at the steering wheel, and thus it is also easier to control.

[0200] Tires B, C, D, F, G all fall within the scope of the present invention, and they all provide a significant reduction in rolling resistance. In addition to a substantial reduction in rolling resistance, tires B, C, F, G also provide excellent cornering performance, while the cornering performance of tire D remains good.

Claims

1. A beltless tire for a motor vehicle, comprising: a carcass structure (2), said carcass structure including two carcass plies (3, 4), each of said two carcass plies (3, 4) including a plurality of parallel cords (13, 14) and having a terminal flap joined to a corresponding anchoring annular structure (5), the parallel cords (13, 14) of said two carcass plies (3, 4) crossing each other and forming an intersection angle (Δ) between 20° and 60° with respect to each other; the parallel cords (13, 14) of each of said two carcass plies (3, 4) defining a corresponding angle (α, β) between 60° and 80° with the circumferential direction (C) of the beltless tire (1); at least one reinforcing cord (9) wound in a plurality of circumferential turns, said plurality of circumferential turns being arranged in a radially outer position with respect to the carcass structure (2); a tread band (10), said tread band being arranged in a radially outer position with respect to the reinforcing cord (9); said at least one reinforcing cord (9) having a predetermined percentage elongation (Sp); said at least one reinforcing cord (9) having a "tensile load - elongation" curve, said "tensile load - elongation" curve including a first segment (T1) upstream of said predetermined percentage elongation (Sp), a second segment (T2) downstream of said predetermined percentage elongation (Sp), and a third connecting segment (K) between said first segment (T1) and said second segment (T2); wherein the second slope of said second segment (T2) is greater than the first slope of said first segment (T1).

2. The beltless tire according to claim 1, wherein, The ratio between the second slope of said second segment (T2) and the first slope of said first segment (T1) is greater than 5.

3. The beltless tire according to claim 1, wherein, The ratio between the second slope of said second segment (T2) and the first slope of said first segment (T1) is less than 50.

4. The beltless tire according to claim 1, 2 or 3, wherein, The ratio between the second slope of said second segment (T2) and the first slope of said first segment (T1) is between 5 and 40.

5. The beltless tire according to claim 4, wherein, The ratio between the second slope of said second segment (T2) and the first slope of said first segment (T1) is between 10 and 35.

6. The beltless tire according to any one of the preceding claims, wherein, The first slope of said first segment (T1) is between 1 N / elongation % and 20 N / elongation %, and wherein the second slope of said second segment (T2) is between 35 N / elongation % and 500 N / elongation %.

7. The beltless tire according to any one of the preceding claims, wherein, The density of the circumferential turns of said reinforcing cord (9) is between 40 turns / dm and 130 turns / dm.

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

9. The beltless tire according to any one of the preceding claims, wherein, Said predetermined percentage elongation (Sp) is between 1% and 5%.

10. The beltless tire according to claim 9, wherein, Said predetermined percentage elongation (Sp) is between 1.5% and 4.5%.

11. The beltless tire according to any one of the preceding claims, wherein, In said "tensile load - elongation" curve, the force corresponding to said predetermined percentage elongation (Sp) is between 5 N and 200 N.

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

13. The beltless tire according to any one of the preceding claims, wherein, The at least one reinforcing cord (9) is a metal reinforcing cord or a hybrid reinforcing cord.

14. The beltless tire according to claim 13, wherein, The at least one reinforcing cord (9) is a metal reinforcing cord and includes a plurality of steel wires, the steel wires being independently twisted and wound together such that in a plurality of transverse cross-sections of the reinforcing cord, each steel wire does not contact an adjacent steel wire.

15. The beltless tire according to claim 13, wherein, The at least one reinforcing cord (9) is a metal reinforcing cord and includes at least two strands, each strand including a respective plurality of steel wires, wherein in each strand, the plurality of steel wires are wound together with a predetermined winding pitch, and wherein the at least two strands are wound together along the same direction as the steel wires in the strand and with a winding pitch equal to or different from the predetermined winding pitch.

16. The beltless tire according to claim 13, wherein, The at least one reinforcing cord (9) is a metal reinforcing cord and includes only one metal wire, or includes two or more metal wires twisted with each other, or includes at least one helical metal wire.

17. The beltless tire according to claim 13, wherein, The at least one reinforcing cord (9) is a hybrid reinforcing cord and includes one or more high modulus of elasticity fabric filaments twisted in one direction and one or more low modulus of elasticity fabric filaments twisted in the same direction, wherein the high modulus of elasticity fabric filaments and the low modulus of elasticity fabric filaments are twisted together.

18. The beltless tire according to claim 13, wherein, The filaments of each yarn of the hybrid reinforcing cord (9) are twisted together with a respective predetermined number of yarn twists per unit length, and different yarns are twisted together with a predetermined number of reinforcing cord (9) twists per unit length.

19. The beltless tire according to claim 13, wherein, The at least one reinforcing cord (9) is a hybrid reinforcing cord and includes two aramid fiber yarns and one aliphatic polyamide fiber yarn and / or polyester fiber yarn.

20. The beltless tire according to claim 13, wherein, The at least one reinforcing cord (9) is a hybrid reinforcing cord and includes at least one hybrid yarn, the hybrid yarn including a plurality of filaments obtained from a first yarn and at least one second yarn, the first yarn carrying a plurality of filaments having a first initial tangential modulus, the second yarn carrying a plurality of filaments having a second initial tangential modulus, the first initial tangential modulus and the second initial tangential modulus being different from each other, wherein each of the first yarn and the second yarn includes a plurality of independent filaments, and the independent filaments of each of the first yarn and the second yarn are at least partially mixed together in the hybrid yarn.

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

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

23. The beltless tire according to any one of claims 1 to 22, wherein, The parallel cords (13, 14) of the two carcass plies (3, 4) form angles equal in magnitude and opposite in direction with respect to the circumferential direction (C) of the beltless tire (1).

24. The beltless tire according to any one of claims 1 to 22, wherein, The parallel cords (13, 14) of the two carcass plies (3, 4) form angles of unequal magnitudes and opposite directions with respect to the circumferential direction (C) of the beltless tire (1).

25. The beltless tire according to any one of the preceding claims, wherein, The intersection angle (Δ) is between 30° and 50°.

26. The beltless tire according to any one of the preceding claims, wherein, The beltless tire includes at least one auxiliary element (17; 17A, 17B) positioned at each of two opposite axial ends of the plurality of circumferential turns, wherein the auxiliary element (17; 17A, 17B) is located between the plurality of circumferential turns and the tread band (10) and / or between the plurality of circumferential turns and the carcass structure (2).

27. The beltless tire according to claim 26, wherein, The at least one auxiliary element (17; 17A, 17B) straddles the respective axial end.

28. The beltless tire according to claim 26 or 27, wherein, The at least one auxiliary element (17; 17A, 17B) comprises an elastomeric material and / or aramid and / or metal.

29. The beltless tire according to any one of claims 26 to 28, wherein, The axial extension length (W) of the at least one auxiliary element (17; 17A, 17B) is between 15% and 25% of the axial width (L) of the plurality of circumferential turns.

30. The beltless tire according to any one of the preceding claims, wherein, The at least one reinforcing cord (9) wound in a plurality of circumferential turns is embedded in an elastomeric material layer.

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

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