Tire for motor vehicle

Abstract

A tire for a motor vehicle includes a carcass ply (3), a belt structure (11), and a reinforcing structure (16) having zero-degree reinforcing cords (17). The belt structure (11) is formed by a first belt strip (12) and a second belt strip (13) that are axially adjacent or partially overlapped with each other at or near the centerline plane (M) of the tire (1). The first belt strip (12) and the second belt strip (13) have belt cords (14, 15) that define angles (α, β) between 25° and 40° with respect to the circumferential direction (C) of the tire (1) and angles (γ) between 50° and 80° between the belt cords. Each reinforcing cord (17) has a "tensile load-elongation" curve that includes a first segment (T1) upstream of a predefined percentage elongation (Sp) and a second segment (T2) downstream of a predefined percentage elongation (Sp). The second slope of the second segment (T2) is greater than the first slope of the first segment (T1).

Description

Technical Field

[0001] This invention relates to a tire for motor vehicles. Specifically, it relates to a low rolling resistance tire designed to equip (e.g., but not limited to) new hybrid and all-electric motor vehicles to reduce environmental impact.

[0002] definition

[0003] The "curvature ratio" of a tire refers to the ratio between the distance from the outermost radial point of the tread band, measured on the radial plane of the tire, to the line passing through the lateral opposite ends of the tread itself, and the distance measured along the tire cords between those ends.

[0004] "Motor vehicle tire" means a tire with a curvature ratio that is approximately less than 0.15, preferably between 0.03 and 0.1, and more preferably close to 0.05.

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

[0006] "Radial plane" refers to the plane on which the axis of rotation of the tire is located.

[0007] The "tire centerline plane" refers to the plane that is equidistant from the tire bead and orthogonal to the tire's axis of rotation.

[0008] The “axial width” mentioned above is measured along the corresponding direction parallel to the axis of rotation of the tire.

[0009] "Axial width of belt structure" refers to the width of the semi-finished product that constitutes the belt structure in the finished tire.

[0010] "Reinforcing cords oriented in the circumferential direction" means that all reinforcing cords are oriented at 0°+ / -10° relative to the circumferential direction of the tire.

[0011] "Carcass cords oriented along the axial direction" means that each of the existing carcass cords lies in a plane that forms an angle of 90° + / - 10° with the centerline plane of the tire.

[0012] "Overlapping portion" refers to the overlapping area between the first belt strip and the second belt strip.

[0013] "Axial width of the overlapping portion" refers to the width of the overlapping portion present in the finished tire.

[0014] The "tensile load-elongation" curve of a reinforcing cord refers to a curve plotted on a graph that shows the elongation (e.g., percentage elongation) of the reinforcing cord on the horizontal axis and the tensile force (e.g., in N) applied to the reinforcing cord on the vertical axis.

[0015] The tensile load-elongation curve of the metal cord was obtained according to the internationally recognized method for testing steel wire tire cords, as per BISFA Standard – Chapter E6, 1995.

[0016] The tensile load-elongation curve of the fabric cord was obtained according to the BISFA standard – Chapter 7, 2004, Test Methods for Polyamide Filament Yarns.

[0017] "Density" refers to the number of cords present per unit width (e.g., 1 dm).

[0018] "Fabric cord" refers to a cord made of one or more threads of fabric material.

[0019] "Mixed cord" refers to cord made of threads from at least two different fabric materials.

[0020] "Metal cord" refers to a cord made of one or more metal wires.

[0021] "The diameter of the cord" refers to the diameter of the circumference of the cross-section of the cord. Background Technology

[0022] Tires used in motor vehicles typically include a carcass structure connected to a belt structure.

[0023] The carcass structure includes one or more carcass plies having corresponding opposing end wraps that engage with a corresponding annular anchoring structure (referred to as a bead core), which is associated with a filler insert. The tire region including the bead core and filler insert forms a bead structure designed to anchor the tire to a corresponding mounting rim. The belt structure includes a plurality of belt strips arranged radially overlapping each other and relative to the carcass structure, having metal reinforcing cords oriented in a cross-direction relative to the tire's circumferential development direction. The tread belt is arranged radially outward relative to the belt structure.

[0024] The use of a strip belt structure with reinforcing cords that intersect each other in a tire is to meet the requirements of adapting the tire to the ever-increasing performance of motor vehicles and improving driving characteristics such as stiffness, driving stability and driving responsiveness.

[0025] Compared to beltless tires, tires with a belted structure, including belted strips with cross-oriented cords, are generally able to provide greater lateral force at the same slip angle. Tires with this belted structure are also generally able to provide greater self-aligning torque at low slip angles compared to beltless tires.

[0026] For many years, the applicant has been concerned about the direct and indirect environmental impacts of tires during their use. Specifically, in order to control the consumption of motor vehicles (which affects energy consumption and also carbon dioxide emissions into the atmosphere), the applicant produces tires with low rolling resistance, i.e., tires with a fuel efficiency rating of “A” (in accordance with EU Regulation EU2020 / 740).

[0027] A tire configured to reduce rolling resistance is illustrated in document JPH05286309A. This tire comprises a radial carcass with polyester cords, and a single belt layer formed by right and left portions of the belt layer, which are adjacent to or partially stacked and provided with steel cords. The steel cords in the two portions are arranged symmetrically and form a 22-degree angle relative to the circumferential direction of the tire. A reinforcing layer composed of rubber-coated nylon cord strips is spirally wound around the belt layer. Furthermore, JPH05286309A includes an additional reinforcing layer placed across two adjacent belt portions and configured to provide a wraparound effect. Summary of the Invention

[0028] In this context, the applicant has set a target for further reducing the rolling resistance of tires (for example, but not limited to) designed to equip new hybrid electric vehicles and all-electric electric vehicles (particularly autonomous driving) in order to reduce environmental impact.

[0029] Specifically, the applicant has set its own objective of achieving the above goals without compromising the performance and driving characteristics of modern tires (especially those with cross-belt structures).

[0030] The applicant has discovered that the above objectives can be achieved by employing a specific tire structure that combines at least one carcass ply with two belt strips placed side-by-side or partially stacked, the two belt strips being covered by a reinforcing structure having reinforcing cords with an elongation-tensile load curve including two segments with different slopes.

[0031] According to a first aspect, the present invention relates to a tire for a motor vehicle, the tire having: a carcass structure, a tread belt, a belt structure located between the carcass structure and the tread belt, and a reinforcing structure located between the belt structure and the tread belt.

[0032] Preferably, the carcass structure has a carcass ply, which has axially opposite end edgings that engage with a corresponding anchoring ring structure.

[0033] Preferably, the belt structure includes a first belt strip and a second belt strip.

[0034] Preferably, the first belt strip and the second belt strip are adjacent to each other and axially adjacent or partially overlapped at or near the centerline plane of the tire.

[0035] Preferably, the first belt strip has a first belt cord, the first belt cord defining a first angle between 25° and 40° with respect to the circumferential direction of the tire.

[0036] Preferably, the second belt strip has a second belt cord, the second belt cord defining a second angle between -25° and -40° with respect to the circumferential direction of the tire.

[0037] Preferably, the first belt cord and the second belt cord define a third angle between 50° and 80°.

[0038] Preferably, the reinforcing structure includes reinforcing cords oriented along the circumferential direction of the tire.

[0039] Preferably, each reinforcing cord has a predefined percentage elongation.

[0040] Preferably, each reinforcing cord has a "tensile load-elongation" curve, which includes a first segment upstream of a predefined percentage elongation, a second segment downstream of a predefined percentage elongation, and a third connecting segment between the first and second segments.

[0041] Preferably, the second slope of the second segment is greater than the first slope of the first segment.

[0042] According to another aspect, the present invention relates to a tire having a structure in which a carcass ply is combined with a first belt strip and a second belt strip; the carcass ply defines a carcass structure; and the first belt strip and the second belt strip define a belt structure.

[0043] Preferably, the belt structure is sandwiched between the tire carcass structure and the tread belt.

[0044] Preferably, the reinforcing structure is located between the belt structure and the tread belt.

[0045] Preferably, the carcass ply has axially opposite end edgings that engage with the corresponding anchoring ring structure.

[0046] Preferably, the first belt strip and the second belt strip are adjacent to each other and axially adjacent or partially overlapped at or near the centerline plane of the tire.

[0047] Preferably, the first belt strip has a first belt cord, the first belt cord defining a first angle between 25° and 40° with respect to the circumferential direction of the tire.

[0048] Preferably, the second belt strip has a second belt cord, the second belt cord defining a second angle between -25° and -40° with respect to the circumferential direction of the tire.

[0049] Preferably, the first belt cord and the second belt cord define a third angle between 50° and 80°.

[0050] Preferably, the reinforcing structure includes reinforcing cords oriented along the circumferential direction of the tire.

[0051] Preferably, each reinforcing cord has a predefined percentage elongation.

[0052] Preferably, each reinforcing cord has a "tensile load-elongation" curve, which includes a first segment upstream of a predefined percentage elongation, a second segment downstream of a predefined percentage elongation, and a third connecting segment between the first and second segments.

[0053] Preferably, the second slope of the second segment is greater than the first slope of the first segment.

[0054] The applicant believes that the present invention allows for a significant reduction in the rolling resistance of tires.

[0055] The applicant has also verified that the invention allows for providing performance and driving characteristics suitable for equipping modern motor vehicles.

[0056] Specifically, the applicant has verified that the tires manufactured according to the present invention can provide lateral force suitable for everyday road use.

[0057] The present invention may exhibit one or more of the following preferred features in at least one of the foregoing aspects.

[0058] Preferably, the tire is of the low rolling resistance type.

[0059] Preferably, there is only one tire carcass ply layer.

[0060] Preferably, the belt structure consists only of a first belt strip and a second belt strip.

[0061] Preferably, the first angle is between 26° and 30°.

[0062] Preferably, the first angle is equal to 26°, 27°, 28°, 29° or 30°.

[0063] Preferably, the second angle is between -26° and -30°.

[0064] Preferably, the second angle is equal to -26°, -27°, -28°, -29° or -30°.

[0065] Preferably, the first angle is equal to the second angle in absolute value. Alternatively, the first angle may be different from the second angle.

[0066] Preferably, the third angle is between 52° and 60°.

[0067] Preferably, the first belt cord and the second belt cord form a V shape, and when the tire is mounted on a motor vehicle, the apex of the V faces one of the rolling directions of the tire or the opposite direction.

[0068] Preferably, the vertex of V is located on the centerline plane of the tire.

[0069] Preferably, if the first belt strip and the second belt strip abut against each other and axially, the axial inner peripheral edge of the first belt strip abuts against the axial inner peripheral edge of the second belt strip.

[0070] Preferably, if the first belt strip and the second belt strip abut each other and axially, the axial inner peripheral edges of the first belt strip and the second belt strip are located on or spaced apart from the centerline plane of the tire.

[0071] Preferably, the overlapping portion between the partially stacked first belt layer and the second belt layer is symmetrical or asymmetrical with respect to the centerline plane of the tire.

[0072] Preferably, the ratio between the axial width of the overlapping portion and the axial width of the belt structure is less than 0.3.

[0073] Preferably, the ratio between the axial width of the overlapping portion and the axial width of the belt structure is less than 0.2.

[0074] Preferably, the axial width of the overlapping portion is less than 50 mm.

[0075] Preferably, the axial width of the overlapping portion is less than 30 mm.

[0076] Preferably, the first segment is defined between zero percentage elongation and the first point of the "tensile load-elongation" curve, the second segment develops 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.

[0077] Preferably, the first point corresponds to the first point on the "tensile load-elongation" curve starting from the zero percentage elongation, at which the concavity of the "tensile load-elongation" curve is zero or the surface is upward.

[0078] Preferably, if the concavity of the "tensile load-elongation" curve remains upward until fracture downstream of the first point, then the second point of the "tensile load-elongation" curve is the point with the maximum concavity.

[0079] Alternatively, if the concavity of the upward-facing "tensile load-elongation" curve changes to downward-facing downstream of the first point, then the second point of the "tensile load-elongation" curve is the inflection point.

[0080] Preferably, the predefined percentage elongation corresponds to the intersection of the first tangent line of the "tensile load-elongation" curve at the first point and the second tangent line of the "tensile load-elongation" curve at the second point.

[0081] Preferably, the ratio of the second slope of the second segment to the first slope of the first segment is greater than 2.5.

[0082] Preferably, the ratio of the second slope of the second segment to the first slope of the first segment is greater than 10.

[0083] Preferably, the ratio of the second slope of the second segment to the first slope of the first segment is less than 50.

[0084] Preferably, the ratio of the second slope of the second segment to the first slope of the first segment is less than 35.

[0085] Preferably, the first slope of the first segment is between 1 N / % elongation and 25 N / % elongation.

[0086] Preferably, the second slope of the second section is between 35 N / % elongation and 500 N / % elongation.

[0087] Preferably, the default percentage elongation is between 1% and 5%.

[0088] Preferably, the default percentage elongation is between 1.5% and 4.5%.

[0089] Preferably, in the "tensile load-elongation" curve, the force corresponding to the predefined percentage elongation is between 5N and 200N.

[0090] Preferably, the force corresponding to the predefined percentage elongation is between 15N and 90N.

[0091] Preferably, the density of the reinforcing cords in the reinforcing structure is between 30 cords / dm and 120 cords / dm, more preferably between 40 cords / dm and 110 cords / dm.

[0092] Preferably, the reinforcing cord is metallic. Alternatively, the reinforcing cord is composite.

[0093] Preferably, each of the metal-reinforced cords comprises at least two strands, each strand comprising a corresponding plurality of steel wires wound together in each strand according to a predetermined winding pitch.

[0094] Preferably, the at least two strands are wound together in the same direction as the filaments in the strands and at a winding pitch equal to or different from the predetermined winding pitch.

[0095] Preferably, each of the metal reinforcing cords comprises a single metal wire or at least two metal wires twisted together.

[0096] Preferably, each of the metal reinforcing cords comprises at least one spiral metal wire.

[0097] Preferably, each of the metal reinforcing cords has a diameter between 0.15 mm and 0.30 mm.

[0098] Preferably, the density of the metal reinforcing cords in the reinforcing structure is between 40 cords / dm and 50 cords / dm.

[0099] Preferably, each of the mixed reinforcing cords comprises one or more high-modulus fabric filaments twisted in one direction and one or more low-modulus fabric filaments twisted in the same direction.

[0100] Preferably, the high-modulus fabric filament and the low-modulus fabric filament are twisted together.

[0101] Preferably, the high-modulus fabric filament is made of aramid fiber.

[0102] Preferably, the low-modulus fabric filaments are made of nylon.

[0103] Preferably, the high-modulus fabric filament has a linear density between 1100 dTex and 1200 dTex.

[0104] Preferably, the low-modulus fabric filament has a linear density between 1300 dTex and 1600 dTex.

[0105] Preferably, the density of the mixed reinforcing cords in the reinforcing structure is between 70 cords / dm and 90 cords / dm.

[0106] Preferably, the first belt cord and / or the second belt cord are made of metal.

[0107] Preferably, each of the first metal belt cord and / or the second metal belt cord comprises at least two strands, each strand comprising a corresponding plurality of steel wires wound together in each strand according to a predetermined winding pitch.

[0108] Preferably, the density of the first belt cord and / or the second belt cord is between 60 cords / dm and 180 cords / dm, more preferably between 80 cords / dm and 135 cords / dm.

[0109] Preferably, the carcass ply has carcass cords.

[0110] Preferably, at the tire crown, which includes the belt structure and the tread belt, the carcass cords are oriented along the axial direction of the tire.

[0111] Preferably, the tire carcass cords are located in corresponding planes, and each plane forms an angle of 90°+ / -10° with the centerline plane of the tire.

[0112] Preferably, the tire cords are made of fabric or a blend.

[0113] Preferably, the density of the carcass cords is between 60 cords / dm and 140 cords / dm, more preferably between 85 cords / dm and 130 cords / dm.

[0114] Preferably, the first belt strip and the second belt strip are positioned to contact the tire carcass structure.

[0115] Preferably, the reinforcing structure is positioned to contact the first and second belt strands.

[0116] Preferably, the tread strip is positioned to contact the reinforcing structure.

[0117] Further features and advantages will become clearer from the detailed description of preferred, but not exclusive, embodiments of the tires for motor vehicles according to the invention. Attached Figure Description

[0118] This description is given below with reference to the accompanying drawings, which are provided for illustrative and therefore non-limiting purposes only, wherein:

[0119] - Figure 1 A half-section along the radial plane is illustrated in an embodiment of a tire for a motor vehicle according to the present invention;

[0120] - Figure 1A yes Figure 1 A magnified portion;

[0121] - Figure 2 A half-section along the radial plane is illustrated for different embodiments of a tire for a motor vehicle according to the present invention;

[0122] - Figure 2A yes Figure 2 A magnified portion;

[0123] - Figure 3 yes Figure 1 A schematic top view of the components of a tire;

[0124] - Figure 4 yes Figure 2 A schematic top view of the components of a tire;

[0125] - Figure 5 yes Figure 1 or Figure 2 A further amplification portion;

[0126] - Figure 6 An example is shown of a continuous elongated element used to manufacture the tire shown in the previous figure;

[0127] - Figure 7 The tensile load-elongation curve of the tire reinforcement cord mentioned in the previous figure is illustrated.

[0128] - Figure 7A yes Figure 7 An enlarged portion of the curve;

[0129] - Figure 8 Examples of "tensile load-elongation" curves for different reinforcing cords are shown;

[0130] - Figure 9 An example is given of the rolling resistance of a tire according to the invention, normalized relative to a reference tire;

[0131] - Figure 10 Examples Figure 9 The lateral stiffness of the tire is a function of the vertical load;

[0132] - Figure 11 Examples of the same Figure 9 and Figure 10 The points corresponding to the standardized rolling resistance and standardized lateral stiffness of the tire in the diagram;

[0133] - Figure 12 Examples Figure 9 , Figure 10 and Figure 11 The rolling resistance of one tire and two variants shown;

[0134] - Figure 13 Examples Figure 12 The lateral force of the tire is a function of the slip angle. Detailed Implementation

[0135] Figure 1 A half-section along the radial plane of a tire 1 for a motor vehicle according to the present invention is illustrated. Figure 1 The tire 1 shown for a motor vehicle has a curvature ratio of approximately 0.05.

[0136] Tire 1 includes a carcass structure 2 formed by carcass plies 3. The carcass plies 3 have a first end sheath 3A that engages with a first annular anchoring structure 4A (referred to as an annular rim) associated with a first infill insert 5A, and a second end sheath 3B that engages with a second annular anchoring structure 4B associated with a second infill insert 5B. Two regions of tire 1, each including annular anchoring structures 4A, 4B and infill inserts 5A, 5B, form a first bead structure 6 and a second bead structure 7 intended for anchoring tire 1 to corresponding mounting rims (not illustrated).

[0137] The carcass ply 3 includes multiple carcass cords 8 parallel to each other and immersed in or covered by an elastomeric material. Figure 3 (Illustratively illustrated). The carcass cords 8 are substantially located in the respective radial planes, i.e., in the plane containing the axis of rotation of the tire 1. At the crown of the tire 1, the carcass cords 8 are oriented according to the substantially axial direction of the tire 1. In a variant embodiment not shown, the carcass cords are located in respective planes, each plane forming an angle of 90° + / - 10° with the centerline plane "M" of the tire 1. Therefore, the carcass ply 3 is radial. The carcass cords 8 can be woven or blended. For example, the carcass cords 8 are made of rayon. The density of the carcass cords 8 in the carcass ply 3 is, for example, between 60 cords / dm and 140 cords / dm, or more preferably between 85 cords / dm and 130 cords / dm.

[0138] One or more layers of elastomeric material (commonly referred to as the impermeable “liner” 9 and the “lower liner” 10 necessary to provide the inflation air for the tire 1) are arranged in a radially inward position relative to the carcass ply 3. The liner 9 and the lower liner 10 are applied against the carcass structure 2.

[0139] Associated with the carcass structure 2 is a belt structure 11 formed by a first belt strip 12 and a second belt strip 13. Each of the first belt strip 12 and the second belt strip 13 extends circumferentially around the radially outer portion of the carcass structure 2 and contacts the carcass structure. Figure 1 , Figure 1A and Figure 3In one embodiment, the first belt strip 12 and the second belt strip 13 are adjacent to each other and axially adjacent at the centerline plane "M" of the tire 1. Therefore, the first belt strip 12 and the second belt strip 13 form a single belt layer. The first belt strip 12 has an axially outer peripheral edge 12A and an opposing axially inner peripheral edge 12B. The second belt strip 13 has an axially outer peripheral edge 13A and an opposing axially inner peripheral edge 13B. The axially inner peripheral edge 12B of the first belt strip 12 abuts against the axially inner peripheral edge 13B of the second belt strip 13, and these circumferential edges lie on the centerline plane "M" of the tire 1. In an embodiment not illustrated in the figures, the axially inner peripheral edges 12B of the first belt strip 12 and the axially inner peripheral edges 13B of the second belt strip 13 are staggered relative to the centerline plane "M" of the tire 1.

[0140] The first belt strip 12 includes a plurality of first belt cords 14 that are parallel to each other and are immersed in or covered by an elastomer material. Figure 3 The second belt strip 13 includes multiple second belt cords 15 parallel to each other and immersed in or covered by an elastomeric material. The first belt cord 14 defines a first angle "α" between 25° and 40° with respect to the circumferential direction "C" of the tire 1; the second belt cords 15 define a second angle "β" between -25° and -40° with respect to the circumferential direction "C"; and furthermore, the first belt cord 14 and the second belt cord 15 define a third angle "γ" between 50° and 80° between them. The third angle "γ" is the sum of the first angle "α" and the second angle "β".

[0141] exist Figure 3 In this embodiment, the absolute values ​​of the first angle "α" and the second angle "β" are less than approximately 40°. In embodiments not illustrated, the absolute values ​​of the first angle "α" and the second angle "β" are between 26° and 30°, for example, equal to 26°, 27°, 28°, 29°, or 30°, and therefore the third angle "γ" is between 52° and 60°.

[0142] Therefore, the first belt cord 14 and the second belt cord 15 form a V-shape, i.e., a herringbone pattern. When the tire 1 is mounted on a motor vehicle, the apex of the V can face one of the rolling directions of the tire 1 or the opposite direction. Figure 1 , Figure 1A and Figure 3 In one embodiment, the vertex of V lies on the centerline plane "M" of tire 1, and furthermore, since the first angle "α" is equal to the second angle "β", V is symmetrical with respect to the centerline plane "M". In a variant embodiment not illustrated in the figures, the first angle "α" is different from the second angle "β", and therefore V is asymmetrical with respect to the centerline plane "M".

[0143] The first belt cord 14 and the second belt cord 15 are metallic. For example, each of these first belt cords 14 and second belt cords 15 comprises two or more strands, each strand comprising a corresponding plurality of steel wires wound together in each strand according to a predetermined winding pitch. The density of the first belt cord 14 and / or the second belt cord 15 in the corresponding first belt strip 12 and second belt strip 13 is between 60 cords / dm and 180 cords / dm, more preferably between 80 cords / dm and 135 cords / dm.

[0144] Associated with the belt structure 11 is a reinforcing structure 16 (zero-degree layer), which includes reinforcing cords 17 oriented according to the circumferential direction "C" of the tire 1. The reinforcing cords 17 are wound in multiple circumferential turns and arranged in a radially outer position within the belt structure 11. The circumferential turns are arranged to form an angle between 0° and 10° with the circumferential direction "C" of the tire 1. The reinforcing structure 16 (in...) Figure 1A , Figure 1 B and Figure 5 (As better illustrated) includes an elastomeric material layer in which reinforcing cord 17 is immersed. The reinforcing cord 17 can be, for example, wound with a continuous elongated element 18 (in... Figure 6 (Example shown in the middle section) The continuous elongated elements comprise one or more reinforcing cords 17 immersed in or covered by an elastomeric material 19, which are then placed side-by-side or partially stacked. The density of the reinforcing cords 17 in the reinforcing structure 16 is, for example, between 30 cords / dm and 120 cords / dm, more preferably between 40 cords / dm and 110 cords / dm.

[0145] The reinforcing structure 16 is positioned to directly abut against the first belt strip 12 and against the second belt strip 13, and in Figure 1 In one embodiment, the reinforcing structure protrudes axially beyond the axial outer peripheral edge 12A of the first belt strip 12 and the axial outer peripheral edge 13A of the second belt strip 13. The ratio of the axial width "L1" of the belt structure 11 to the axial width "L2" of the reinforcing structure 16 is, for example, 0.9. Therefore, as Figure 5 As illustrated, the opposite axial edge of the reinforcing structure 16 rests against the carcass ply 3 or against the belt under insert 16A.

[0146] The reinforcing cord 17 can be a metal cord or a composite cord. Furthermore, each reinforcing cord 17 has a tensile load-elongation curve with sections having different slopes.

[0147] For example, each of the metal reinforcing cords 17 comprises two or more strands, each strand comprising a corresponding plurality of steel wires wound together in each strand according to a predetermined winding pitch. The two or more strands may be wound together in the same direction as the wires in the strand and at a winding pitch equal to or different from the predetermined winding pitch. For example, each of the metal reinforcing cords 17 comprises a single metal wire or two or more metal wires twisted together. For example, each of the metal reinforcing cords 17 comprises one or more helical metal wires. Each of the metal reinforcing cords 17 preferably has a diameter between 0.15 mm and 0.30 mm. The density of the metal reinforcing cords 17 in the reinforcing structure 16 is, for example, between 40 cords / dm and 50 cords / dm.

[0148] For example, Figure 7 and Figure 7A The tensile load-elongation curve for metal-reinforced cord 17 is illustrated. This type of tensile load-elongation curve is obtained according to the internationally recognized method for testing steel-wire tire cords, as per BISFA Standard – Chapter E6, 1995. Metal-reinforced cord 17 is a 3 x 4 x 0.20 HEHT type steel-wire cord.

[0149] Figure 7 and Figure 7A The horizontal axis shows the percentage elongation (%) and the vertical axis shows the tensile force (in Newtons).

[0150] As can be seen, Figure 7 and Figure 7A The tensile load-elongation curve has a first segment T1 with the concave surface facing downwards (in Figure 7A (As can be seen in the magnification), followed by the third connecting segment K with the concave surface facing upwards, and then the second segment T2 with the concave surface first facing upwards and then downwards. Therefore, Figure 7 The curve in the curve has an inflection point between the first segment T1 and the third connecting segment K, and also has an inflection point at the beginning of the second segment T2.

[0151] Let “first point P1” be defined as the first point encountered by the “tensile load-elongation” curve starting from zero elongation. At this first point, the concavity of the “tensile load-elongation” curve faces upward (in...). Figure 7A In the curve diagram, the first point P1 is placed exactly after the inflection point of the first segment T1, and the "second point P2" is defined as the inflection point at the beginning of the second segment T2. The "predefined percentage elongation Sp" is defined as the elongation at the intersection of the first tangent line of the "tensile load-elongation" curve at the first point P1 and the second tangent line of the "tensile load-elongation" curve at the second point P2.

[0152] The first segment T1 is defined between zero elongation and the first point P1 of the "tensile load-elongation" curve. The second segment T2 develops 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, which has an increasing slope. The third connecting segment K forms a bend or angle with the concave surface facing upwards.

[0153] exist Figure 7 In the curve, the default percentage elongation Sp is approximately 1.7%, and the force F corresponding to such a default percentage elongation Sp is approximately 35 N.

[0154] A first segment T1, located upstream of a predefined percentage elongation Sp, is provided with a first slope measured at a first point P1, and a second segment T2, located downstream of the predefined percentage elongation Sp, is provided with a second slope measured at a second point P2. The second slope is greater than the first slope.

[0155] For example, each of the composite reinforcing cords 17 comprises one or more high-modulus fabric filaments twisted in one direction and one or more low-modulus fabric filaments twisted in the same direction. The high-modulus and low-modulus fabric filaments are twisted together. For example, the high-modulus fabric filaments are made of aramid and have a linear density between 1100 dTex and 1200 dTex. For example, the low-modulus fabric filaments are made of nylon and have a linear density between 1300 dTex and 1600 dTex.

[0156] The density of the mixed reinforcing cord 17 in the reinforcing structure 16 is, for example, between 70 cords / dm and 90 cords / dm.

[0157] For example, Figure 8 The tensile load-elongation curve for hybrid reinforced cord 17 is illustrated. The tensile load-elongation curve for the fabric or hybrid cord is obtained according to the BISFA standard – Chapter 7, 2004, Test Methods for Polyamide Filament Yarns. Hybrid reinforced cord 17 is an Ar / Ny 1100 / 1400 type cord.

[0158] As can be seen, Figure 8 The tensile load-elongation curve in the figure has a first segment T1 with the concave surface facing downwards (e.g., Figure 7A (As shown), followed by the third connecting section K with the concave surface facing upwards, and then the second section T2 with the concave surface always facing upwards (until the fracture load) (which is consistent with...). Figure 7 (The curves in the text are different).

[0159] For example, regarding Figure 7 The first point P1 corresponds to the first point encountered by the "tensile load-elongation" curve starting from zero elongation. At this first point, the concavity of the "tensile load-elongation" curve faces upwards. Figure 7 The difference is, Figure 8 The second point P2 on the "tensile load-elongation" curve is the point with the maximum concavity.

[0160] exist Figure 8 In the curve, the default percentage elongation Sp is approximately 2.9%, and the force F corresponding to such a default percentage elongation Sp is approximately 23.6 N.

[0161] Regardless of the specific example illustrated, the predefined percentage elongation Sp of the reinforcing cord 17 used in this invention is between 1% and 5%, preferably between 1.5% and 4.5%. The force corresponding to the predefined percentage elongation is preferably between 5N and 200N, more preferably between 15N and 90N. Preferably, the first slope of the first segment is between 1N / % elongation and 25N / % elongation, and the second slope of the second segment is between 35N / % elongation and 500N / % elongation. The ratio of the second slope of the second segment T2 to the first slope of the first segment T1 is preferably between 2.5 and 50, preferably between 10 and 35.

[0162] exist Figure 7 In the example of the curve, the first slope of the first segment T1 is approximately 22 N / % elongation, and the second slope of the second segment T2 is approximately 470 N / % elongation, therefore the above ratio is approximately 21.4. Figure 8 In the example of the curve in the graph, the first slope of the first segment T1 is about 7 N / % elongation, and the second slope of the second segment T2 is about 18 N / % elongation, so the above ratio is about 2.6.

[0163] In other words, when the reinforcing cord 17 is stretched beyond a predefined percentage elongation Sp, the reinforcing cord increases its stiffness. Given that the reinforcing cord 17 has such a predefined percentage elongation Sp in the finished tire 1, this means that when the tire 1 deforms during rolling on a road to subject the reinforcing cord 17 or portions thereof to tension, the reinforcing cord 17 behaves as if it had high stiffness corresponding to the slope of the second segment T2.

[0164] A tread band 20 is applied in a radially outer position to the reinforcing structure 16. This tread band, like other semi-finished products constituting the tire 1, is made of an elastomeric compound. The tread band 20 is positioned directly against the reinforcing structure 16. Furthermore, corresponding sidewalls 21 of the elastomeric compound are applied in an axially outer position on the side surface of the carcass structure 2, each sidewall extending from one of the lateral edges of the tread band 20 at a corresponding bead structure 6, 7.

[0165] Figure 2 and Figure 4 Tires and Figure 1 and Figure 3 The difference in the tires is that the first belt strip 12 and the second belt strip 13 partially overlap at the centerline plane "M" of the tire 1, rather than being placed side by side. In the illustrated embodiment, the overlap 22 between the first belt strip 12 and the second belt strip 13 is symmetrical with respect to the centerline plane "M", and the ratio of the axial width "L3" of such overlap 22 to the axial width "L1" of the belt structure 11 is approximately 0.25. Such a ratio is preferably less than 0.3. In variant embodiments, such a ratio is less than 0.2. For example, the axial width "L3" of the overlap 22 is less than 50 mm, preferably less than 30 mm.

[0166] test

[0167] Four tires B, C, D, and E according to the invention were compared with reference tire A through road testing. All tires are designated as PZERO models and are sized 235 / 50 R20 XL 104Y. Reference tire A includes a radial single-ply carcass structure, a double-layer belt structure with cross-cords, and a hybrid zero-degree ply (i.e., composed of mixed cords). The four tires B, C, D, and E include a radial single-ply carcass structure, two adjacent or partially overlapping belt strips with belt cords symmetrically inclined with respect to the circumferential direction, and a zero-degree metallic or hybrid ply with double-slope cords, as illustrated above.

[0168] Cord material:

[0169] - Carcass ply: RY 1840 / 2 (48x48) EPDM 120;

[0170] - Belt straps (steel wire): 2 + 2 x 0.25;

[0171] -Metal reinforcement structure (steel wire): 3x4x0.2 HE EPDM 45 ( Figure 7 (The "tensile load-elongation" curve in the figure).

[0172] - Hybrid reinforced structure: AR / NY 1100 / 1400 (28 / 7x28) EPDM 79 ( Figure 8 The "tensile load-elongation" curve in the figure.

[0173] The test shall be performed in accordance with the following: UNECE 117R02 / 15 (2023), Annex 6 (torque method) - ISO 28580:2018 (paragraph 4b (torque method)) - Notification No. 2022-165 (Ministry of Trade, Industry and Energy of Korea).

[0174] Wheel rim: 20x7.5”

[0175] Pressure: 2.5 bar

[0176] Vertical load: 720kg

[0177] The characteristics of tires A, B, C, D, and E are shown in Table 1 below.

[0178] Table 1

[0179] Figure 9 The rolling resistance coefficient RR% for tires A, B, C, D, and E is shown. The rolling resistance coefficient RR has been normalized by assigning a value of 100 to reference tire A. As can be seen, tires B, C, D, and E have a rolling resistance coefficient RR% greater than that of reference tire A. A = 100) Low RR (RR%) B = 91.8, RR% C = 87.7, RR% D = 86.9, RR% E = 86.9).

[0180] In Table 2 below, except Figure 9 In addition to the normalized RR values ​​shown, the experimental RR values ​​(in N / kN) for tires B, C, D, and E compared to reference A, as well as the percentage reduction in the rolling resistance coefficient RR, are also reported.

[0181] Table 2

[0182] The advantages of tires B, C, D, and E in reducing rolling resistance (RR) are obvious and significant.

[0183] In addition, tests were performed to detect lateral stiffness.

[0184] Rim: 20x8”

[0185] Pressure: 2.5 bar

[0186] Figure 10 The lateral stiffness (CS) of tires A, B, C, D, and E is illustrated as a function of vertical load (VL) in Newtons, normalized by assigning a value of 100 to the maximum lateral stiffness of reference A corresponding to a vertical load of approximately 8000 N. The lateral stiffness curves of tires B, C, and D closely approximate the lateral stiffness curve of reference tire A. Tire B exhibits approximately a 5% decrease in lateral stiffness under low vertical loads below 8000 N, while showing an increase of up to approximately 10% under higher vertical loads above 8000 N. Tires C and D show a decrease in lateral stiffness of less than 10% along the entire curve. Tire E's curve is lower, but still at a level that will not have a significant adverse effect on non-sporty road driving.

[0187] This result was achieved by employing the belt structure described and claimed herein, without the need for additional reinforcing elements, such as the reinforcing layer placed across two adjacent belt portions as described in the prior art document JPH05286309A cited above.

[0188] Figure 11 The graph illustrates the points corresponding to tires A, B, C, D, and E. The graph has a normalized lateral stiffness on the horizontal axis under a vertical load of 6750 N and a normalized rolling resistance coefficient on the vertical axis. As can be seen, all points for tires B, C, D, and E are grouped to the bottom right, i.e., at a low rolling resistance coefficient and sufficiently high lateral stiffness.

[0189] The rolling resistance coefficient and lateral force F (in Newtons) were evaluated using finite element analysis (FEA) as a function of the asymmetry of the belt cords relative to the tire's centerline plane "M" (i.e., the first angle "α" and the second angle "β"). The simulated tires were characterized by those features of tire C in Table 1, where the third angle "γ" between the first and second belt cords remained constant and equal to 52°, while the first angle "α" and the second angle "β" were varied according to Table 3 below.

[0190] Table 3

[0191] Figure 12 The rolling resistance coefficients RR for tires C, C', and C'" are illustrated. The rolling resistance coefficients have been normalized by assigning a value of 100 to the reference C. As can be seen, the variation in the rolling resistance coefficient due to asymmetry is less than 0.5% and is therefore negligible.

[0192] Figure 13The variation of the lateral force F of tires C, C', and C” as a function of the slip angle SA is illustrated. As can be seen, the curves are parallel to each other and are translated according to the asymmetry of the belt strips. The lateral force F of the symmetrical tire C crosses zero at a slip angle that is essentially zero, while the lateral force F of the asymmetrical tires C' and C” crosses zero at slip angles other than zero, and this allows for modifications, for example, to straight-line self-centering performance.

Claims

1. A tire for a motor vehicle, the tire having: a carcass structure (2), a tread belt (20), a belt structure (11) located between the carcass structure (2) and the tread belt (20), and a reinforcing structure (16) located between the belt structure (11) and the tread belt (20). The carcass structure (2) has a carcass ply (3) having axially opposite end edgings (3A, 3B) that engage with the corresponding anchoring ring structures (4A, 4B). The belt structure (11) includes a first belt layer (12) and a second belt layer (13); wherein the first belt layer (12) and the second belt layer (13) are axially adjacent to each other or partially overlapped at or near the centerline plane (M) of the tire (1); wherein the first belt layer (12) has a first belt cord (14) that defines a first angle (α) between 25° and 40° with respect to the circumferential direction (C) of the tire (1); wherein the second belt layer (13) has a second belt cord (15) that defines a second angle (β) between -25° and -40° with respect to the circumferential direction (C) of the tire (1); wherein the first belt cord (14) and the second belt cord (15) define a third angle (γ) between 50° and 80° between them. The reinforcing structure (16) includes reinforcing cords (17) oriented according to the circumferential direction (C) of the tire (1); each reinforcing cord (17) has a predefined percentage elongation (Sp); each reinforcing cord (17) has an elongation-tensile load curve, the curve including a first segment (T1) upstream of the predefined percentage elongation (Sp), a second segment (T2) downstream of the predefined percentage elongation (Sp), and a third connecting segment (K) between the first segment (T1) and the second segment (T2); wherein the second slope of the second segment (T2) is greater than the first slope of the first segment (T1).

2. The tire according to claim 1, wherein the first angle (α) is between 26° and 30°, and the second angle (β) is between -26° and -30°.

3. The tire according to claim 1 or 2, wherein the first angle (α) is equal in absolute value to the second angle (β).

4. The tire according to any one of claims 1 to 3, wherein the overlapping portion (22) between the partially stacked first belt layer (12) and the second belt layer (13) is symmetrical or asymmetrical with respect to the centerline plane (M) of the tire (1).

5. The tire according to claim 4, wherein the ratio between the axial width (L3) of the overlapping portion (22) and the axial width (L1) of the belt structure (11) is less than 0.

3.

6. The tire according to claim 5, wherein the ratio between the axial width (L3) of the overlapping portion (22) and the axial width (L1) of the belt structure (11) is less than 0.

2.

7. The tire according to any one of the preceding claims, wherein the ratio between the second slope of the second segment (T2) and the first slope of the first segment (T1) is greater than 2.5 and less than 50.

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

9. The tire according to any one of the preceding claims, wherein the first slope of the first segment (T1) is between 1 N / elongation % and 25 N / elongation % and wherein the second slope of the second segment (T2) is between 35 N / elongation % and 500 N / elongation % 10. The tire according to any one of the preceding claims, wherein the predefined percentage elongation (Sp) is between 1% and 5%.

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

12. The tire according to any one of the preceding claims, wherein the reinforcing cord (17) is metallic or a composite.

13. The tire of claim 12, wherein the reinforcing cord (17) is metallic and each reinforcing cord comprises at least two strands, each strand comprising a corresponding plurality of steel wires wound together in each strand according to a predetermined winding pitch, wherein the at least two strands are wound together along the same winding direction as the wires in the strand and at a winding pitch equal to or different from the predetermined winding pitch.

14. The tire of claim 12, wherein the reinforcing cord (17) is a hybrid cord, and each reinforcing cord comprises one or more fabric filaments having a high modulus of elasticity twisted in one direction and one or more fabric filaments having a low modulus of elasticity twisted in the same direction, wherein the aforementioned fabric filaments having a high modulus of elasticity and the aforementioned fabric filaments having a low modulus of elasticity are twisted together.

15. The tire according to any one of the preceding claims, wherein the first belt cord (14) and the second belt cord (15) are metallic.

16. The tire according to any one of the preceding claims, wherein the carcass ply (3) has carcass cords (8); wherein, At the crown of the tire (1), which includes the belt structure (11) and the tread belt (20), the carcass cords (8) are oriented according to the axial direction of the tire (1).

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