Radial tire

Abstract

A radial tire (21) is disclosed, comprising a pair of sidewall portions (27) and a pair of bead portions (23). The tire (21) further comprises: a carcass reinforcing cord layer (29) comprising a cord layer turn-up portion (33), each cord layer turn-up portion comprising a radially outward cord layer end portion (35); and a wheel tread reinforcement layer (37) disposed at each cord layer turn-up portion, having a radially outward wheel tread reinforcement layer end portion (39). The profile of the axially outer surface of the sidewall portion is from the axially outermost point of the axially outer surface (43) to point A at a distance G from the carcass reinforcing cord layer, and connecting the axially outer surface (43) of the bead portion at point B. The axially outer surface of the sidewall portion follows a first curve extending from point A and having a center of curvature located axially outward of the carcass reinforcing cord layer, and a second curve connecting point B and having a center of curvature located axially inward of the axially outer surface of the tire.

Description

Technical Field

[0001] The present disclosure relates to pneumatic radial tires. More particularly, the present invention relates to the structure of radial tires for heavy load vehicles such as trucks and buses. Background Art

[0002] In a heavy-load tire, the rubber of the tire side portion (such as in the portion on the bead portion side) tends to deform due to friction with the rim flange and thrust from the rim flange. In order to limit such deformation, the rubber thickness of the tire side portion, especially the rubber thickness of its portion on the bead portion side, may be increased. However, due to this deformation of the rubber, making the rubber thicker tends to generate more heat, which causes the bead portion to deteriorate faster, thereby reducing the service life of the tire.

[0003] Prior art tire 1 Figure 1 and Figure 2 . The prior art tire 1 includes a pair of bead portions 3 and a corresponding bead core 5 embedded in each bead portion. A corresponding sidewall portion 7 extends radially outward from each bead portion 3 to a tread 9 that contacts the ground. The prior art tire 1 is reinforced by a carcass reinforcement ply 11 that extends annularly from one of the bead portions 3 to another of the bead portions. A belt reinforcement assembly 13 is provided between the carcass reinforcement ply 11 and the tread 9. A main portion 15 of the carcass reinforcement ply extends radially inward toward a tire rim (not shown) and rotates around each bead core 3 to form a ply turnup. The ply turnup extends at a single angle relative to a radial line that is tangential to the axial outermost point of the bead core 3 and parallel to the equatorial plane of the tire 1. Each ply turnup includes a radially outward end 17. A heel reinforcement layer 19 is provided around the radially inward surface of the ply turnup.

[0004] From the perspective of reducing greenhouse gas emissions, it is desirable to improve the rolling resistance of the tires produced. This can be achieved by reducing the overall weight of the tire, which can be achieved by reducing the rubber thickness of the sidewall portion and / or the bead portion and / or by reducing the weight of the tire's internal structure (such as the carcass reinforcement ply and / or reinforcing elements). However, any reduction in tire weight should ideally be achieved in a manner that does not compromise the tire's performance characteristics or service life. More specifically, the stability and / or durability of the tire should be maintained, or at least an acceptable compromise should be found. It should further be noted that care should be taken to avoid heat accumulation to prevent the outer rubber layer from deteriorating through heat generation, which would also reduce fuel economy.

[0005] US 5,526,863 describes a radial pneumatic tire with reduced bead mass and improved rolling resistance. The bead portion has a molded single bead filler extending radially outward from an apex portion, having a substantially constant thickness portion and a tapered portion. When the tire is mounted on a rim, an outer filler sheet extends radially outward from a point radially inward of the designed rim flange near the bead core to a position near the mid-height of the tire. The outer filler sheet may extend radially outward beyond the radial extent of a single bead filler, or a single bead filler may extend radially outward beyond the radial extent of the outer filler sheet. For tires with reduced bead mass, the total bead mass is reduced by up to 15%, and the rolling resistance is reduced by up to 5%.

[0006] EP-A-2873539 describes a tire comprising: a tread portion contacting a road surface; a tire sidewall portion extending from the tread portion; a bead portion extending from the tire side portion; and a carcass portion extending through the tread portion, the tire side portion and the bead portion, wherein the carcass portion comprises a main portion extending from the tread portion through the tire side portion to a bead core of the bead portion, and a folded back portion folded back around the bead core, a circumferentially recessed portion that is recessed inwardly in the tire width direction and extends in the tire circumferential direction is formed on an outer surface of the tire side portion, and ... a circumferentially recessed portion that is recessed inwardly in the tire width direction and extends in the tire circumferential direction. In the tire cross section in the tire radial direction and the tire radial direction, the rim side outer surface formed in the range from the rim separation point in contact with the rim flange to the inner side end of the circumferential recessed portion in the tire radial direction is formed along a given arc curve having a center of a radius of curvature on the inner side in the tire width direction, and in the tire cross section, when a virtual arc curve drawn by extending the given arc curve is defined, the depth of the circumferential recessed portion based on the virtual arc curve is not less than 5 mm and not more than 35 mm in a range of not less than 22% and not more than 28% of the tire height from the bead end. The document does not mention the rolling resistance of the tire described therein.

[0007] EP-A-2808183 describes a pneumatic tire having a recessed portion in the side rubber near the bead portion. The recessed portion is provided in the side rubber region from the rim separation point to the tire maximum width position. This allows for a reduction in the weight of the tire while ensuring sufficient handling stability and durability when the relative positions of the bead core of the bead portion and the ply body are changed.

[0008] EP-A-2213484 describes a pneumatic tire in which a thin-walled recess consisting of one or more circular arcs is formed in the side rubber at the outer surface of at least one of the sidewall portion and the bead portion in the width direction cross section of the tire, the thin-walled recess having a center located outside the carcass in the width direction. The recess is preferably defined by a single circular arc. The document describes an improvement in the rolling resistance of the tire described therein.

[0009] Both WO-A-2020 / 012121 and WO-A-2020 / 012122 describe tires with radial carcass reinforcements formed by a single layer of reinforcing elements anchored in each bead by rolling up around the bead wire and reinforced by a reinforcing member. Between the axially outermost point of the outer surface and the point on the outer surface located radially outside of a circle centered on the end of the turn-up portion of the carcass reinforcement, any point on the profile of the outer surface of the sidewall is at a constant distance from the main part of the tire carcass reinforcement. The profile of the outer surface of the sidewall described in these documents allows the risk of damage to be reduced when the tire contacts the curb.

[0010] There remains a need for a pneumatic radial tire structure, such as a radial tire for a heavy load vehicle, which exhibits improved rolling resistance and at the same time exhibits good durability and / or endurance. Summary of the invention

[0011] The invention relates to a tyre according to claim 1 .

[0012] The dependent claims relate to preferred embodiments of the invention.

[0013] It has been found that a defined profile of the outer surface of the sidewall portion can result in a tire with reduced rolling resistance and reduced heat generation. The reduction in rolling resistance is obtained by the disclosed shaping of the bead portion, which allows the bead mass to be reduced with an acceptable compromise in terms of bead durability.

[0014] According to a first preferred aspect of the present invention, there is provided a radial tire, the tire comprising a tread portion, a pair of sidewall portions, a pair of bead portions, wherein each bead portion comprises a bead core; a carcass reinforcing cord layer, the carcass reinforcing cord layer comprising a cord layer turn-up portion at each bead core, each cord layer turn-up portion comprising a radially outward end forming a cord layer end; and a wheel reinforcement layer, which is arranged at each cord layer turn-up portion and has a radially outward wheel reinforcement layer end portion, the wheel reinforcement layer end portion being radially located below the cord layer end portion; wherein

[0015] - the profile of the outer surface of the sidewall portion, from the axially outermost point of said outer surface up to point A, at a distance G from the carcass reinforcing ply, and joining the outer surface of the bead portion at point B, wherein the outer surface of the sidewall portion preferably follows two consecutive curves, wherein a first curve extending from point A has a centre of curvature situated axially outwards of the carcass reinforcing ply, and a second curve joining point B has a centre of curvature situated axially inwards of the outer surface of the tyre;

[0016] - the profile of the outer surface of the side wall portion in the portion extending from point A to point B is tangent to a circle C1 centered on the ply end and having a radius R1 ranging from 5 mm to 15 mm, and further wherein

[0017] - The profile of the outer surface of the sidewall portion in point B is tangent to a circle C2 centered on the radially outward chipper end.

[0018] According to a second preferred aspect of the present invention, there is provided a radial tire, the tire comprising a tread portion, a pair of sidewall portions, a pair of bead portions, wherein each bead portion comprises a bead core; a carcass reinforcing cord layer, the carcass reinforcing cord layer comprising a cord layer turn-up portion at each bead core, each cord layer turn-up portion comprising a radially outward end portion forming a cord layer end; and a wheel reinforcement layer, which is arranged at each cord layer turn-up portion and has a radially outward wheel reinforcement layer end portion, the wheel reinforcement layer end portion being radially located below the cord layer end portion; wherein

[0019] - the profile of the outer surface of the sidewall portion, from the axially outermost point of said outer surface up to point A, at a distance G from the carcass reinforcing ply, and joining the outer surface of the bead portion at point B, wherein the outer surface of the sidewall portion follows two continuous curves, wherein a first curve extending from point A has a centre of curvature situated axially outwards of the carcass reinforcing ply, and a second curve joining point B has a centre of curvature situated axially inwards of the outer surface of the tyre; wherein

[0020] - In the portion extending from point A to point B, the profile of the outer surface of the side wall portion is tangent to a circle C1 centered on the end of the ply, and further, wherein

[0021] - The distance of point A from the end of the ply ranges from 10 mm to 30 mm.

[0022] According to a third preferred aspect of the present invention, there is provided a radial tire, the tire comprising a tread portion, a pair of sidewall portions, a pair of bead portions, wherein each bead portion comprises a bead core; a carcass reinforcing cord layer, the carcass reinforcing cord layer comprising a cord layer turn-up portion at each bead core, each cord layer turn-up portion comprising a radially outward end forming a cord layer end; and a heel reinforcement layer, which is arranged at each cord layer turn-up portion; wherein

[0023] - the profile of the outer surface of the sidewall portion, from the axially outermost point of said outer surface up to point A at a distance G from the carcass reinforcing ply and joining the outer surface of the bead portion at point B, wherein the outer surface of the sidewall portion follows two continuous curves, wherein a first curve extending from point A has a centre of curvature situated axially outwards of the carcass reinforcing ply and a second curve joining point B has a centre of curvature situated axially inwards of the outer surface of the tyre; wherein

[0024] - the contour of the outer surface of the side wall portion in the portion extending from point A to point B is tangent to a circle C1 centered on the end of the ply, wherein

[0025] - the profile of the outer surface of the sidewall portion in point B is tangent to a circle C2 centered on the radially outward end of the chipper; and further, wherein

[0026] - The distance of point A from the end of the ply ranges from 10 mm to 30 mm.

[0027] Regardless of which of the above-mentioned preferred aspects is considered, one or more of the following characteristics may be used to further define the radial tire according to the invention.

[0028] Preferably, the radially outward chipper end is radially below the carcass end. This means that the radially outward chipper end extends in the sidewall portion less than the height of the carcass end.

[0029] Preferably, the carcass end and the radially outward chipper end are preferably separated by a distance of at least 8 mm; preferably, at least 10 mm; more preferably, at least 12 mm.

[0030] Preferably, the circle C1 centered on the ply end has a radius R1 ranging from 5 mm to 15 mm. The distance between the radially outward chipper end and the outer surface of the sidewall portion (expressed by the radius R1) affects the durability of the tire.

[0031] Preferably, a circle C2 centered at the radially outward chipper end has a radius R2 ranging from 2 mm to 12 mm. The distance between the radially outward chipper end and the outer surface of the bead portion, expressed by radius R2, affects the durability of the tire.

[0032] Preferably, the circle C1 centered on the carcass end has a radius R1 that is equal to or greater than the radius R2 of the circle C2 centered on the radially outward chipper end.

[0033] Preferably, the circle C1 centered on the carcass end has a radius R1 that is greater than the radius of the circle C2 centered on the radially outward chipper end.

[0034] Preferably, point A is at a distance of at least 10 mm or at least 15 mm from the end of the ply.

[0035] Preferably, point A is at a distance of at most 30 mm or at most 25 mm from the end of the ply.

[0036] Preferably, the distance of point A from the end of the ply ranges from 10 mm to 30 mm or from 15 mm to 25 mm.

[0037] Preferably, the distance between the end of the ply on which circle C1 is centered and the radially outward chipper end on which circle C2 is centered is equal to or less than the distance from point A to the end of the ply.

[0038] Preferably, the distance G is equal to or smaller than the radius R1 of a circle C1 centered at the end of the ply.

[0039] Preferably, the height of the outward ply end is at least 35 mm, wherein the height of the outward ply end is determined in radial direction and measured from the bead toe; for example, at least 38 mm; for example, at least 40 mm; for example, at least 42 mm.

[0040] Preferably, the chipper comprises a radially outward chipper end and an opposite chipper end, the radially outward chipper end being axially outward of the opposite chipper end, the height of the opposite chipper end being at least 25 mm; the height of the opposite chipper end being determined in the radial direction and measured from the toe of the tire.

[0041] Preferably, the second curve connecting the points B has a radius of curvature R4 that is greater than the radius R2 of the circle C2.

[0042] Preferably, the radius of curvature R3 is greater than the radius of curvature R4. For example, the radius of curvature R3 is in the range of 1.2 to 5 times the radius of curvature R4; preferably, from 1.5 to 4 times.

[0043] Preferably, the two curves are arranged end to end. Alternatively, the two curves may be separated by a straight portion. When present, the straight portion preferably has a length ranging from 0.5 mm to 2.0 mm; more preferably ranging from 0.8 mm to 1.5 mm.

[0044] Preferably, the second curve extends radially outwards through point B. Preferably, the second curve extends axially outwards through point B.

[0045] Preferably, the tire is a heavy load tire and / or has a nominal bead diameter of at least 22.5 inches.

[0046] Preferably, the tire is a commercial truck tire including a nominal bead diameter of at least 22.5 inches.

[0047] Preferably, the tyre has an aspect ratio of at least 60 or at least 70. For example, the tyre has an aspect ratio ranging from 60-90, or from 70-90 or from 60-80.

[0048] Preferably, and in all herein described embodiments of the invention, circle C1 is located completely within the tire and the bead portion of the tire.

[0049] Preferably, and in all herein described embodiments of the invention, circle C2 is located completely within the tire and the bead portion of the tire.

[0050] definition

[0051] “Apexel” or “bead filler apex” means an elastomeric filler located radially above the bead core and between the main portion of the carcass reinforcing ply and the ply turn-ups.

[0052] The "aspect ratio" of a tire is the ratio of its section height (SH) to its section width (SW) multiplied by 100%, expressed as a percentage.

[0053] "Axial" and "axially" mean lines or directions parallel to the tire's axis of rotation.

[0054] "Axially inward" and "axially inwardly" mean axial directions toward the equatorial plane of the tire.

[0055] "Axially outward" and "axially outwardly" refer to an axial direction away from the equatorial plane of the tire.

[0056] “Bead” means that portion of the tire that includes the annular tensile member wrapped and shaped by the ply cords, with or without other reinforcing elements such as flippers, chippers, apex, toe guards and chafers to fit the designed rim.

[0057] “Chipper” refers to a textile or steel cord belt located in the bead portion, whose function is to reinforce the bead portion and / or stabilize the lower sidewall of the tire.

[0058] "Circumferential" means lines or directions extending along the perimeter of the surface of the annular tread that are perpendicular to the axial direction.

[0059] "Cord" refers to one of the reinforcing strands that make up the plies in a tire.

[0060] “Equatorial Plane (EP)” means the plane perpendicular to the tire’s axis of rotation and passing through the center of its tread.

[0061] "Gauge size" refers generally to a measurement, and particularly to thickness.

[0062] "Ply" means a continuous layer of rubber-coated parallel cords, either textile or metal.

[0063] "Radial" and "radially" mean lines or directions perpendicular to the tire's axis of rotation.

[0064] “Radially inwardly” and “radially inwardly” refer to radial directions toward the center axis of rotation of the tire.

[0065] “Radially outward” and “radially outwardly” refer to radial directions away from the tire's center axis of rotation.

[0066] "Radial tire" or "radial-ply tire" means a belted or circumferentially restrained pneumatic tire in which the ply cords extending from bead to bead are laid at cord angles of 65 to 90 degrees relative to the equatorial plane of the tire.

[0067] “Sidewall” or “sidewall portion” means the portion of the tire between the tread and the bead.

[0068] "Tread" means that portion of the tire that contacts the road when normally inflated and loaded. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 is a schematic cross-sectional view of an exemplary tire of the prior art.

[0070] Figure 2 yes Figure 1 A partial enlarged view of the bead portion of the tire shown in FIG.

[0071] Figure 3 is an enlarged fragmentary view of a bead portion of an exemplary embodiment of a tire of the present disclosure.

[0072] Like numbers refer to like parts as used throughout the drawings. DETAILED DESCRIPTION

[0073] An exemplary embodiment of a radial tire 21 of the present disclosure is shown in Figure 3 The overall construction of the tire is somewhat similar to that of the tire 1 of the prior art, and the main differences will be described in detail below. The radial tire 21 is preferably a pneumatic radial tire.

[0074] The tire 21 includes a pair of bead portions 23 (only one is shown) and a corresponding bead core 25 embedded in each bead portion 23. The bead core 25 may include a wound steel wire coated with rubber, or a wound high modulus organic cord coated with rubber (such as aromatic polyamide). A corresponding sidewall portion 27 extends radially outward from each bead portion 23 to a tread (not shown) that contacts the ground. A carcass reinforcement ply 29 is preferably wound around each bead core 25. The carcass reinforcement ply 29 includes cords, preferably steel cords and / or organic fiber cords. The organic fiber cords may be selected from polyester, rayon, nylon, aromatic polyamide, and any combination thereof. A main portion 31 of the carcass reinforcement ply extends radially inward toward the tire rim (not shown) and rotates around each bead core 25 to form a ply turnup 33. The carcass reinforcement ply is also wrapped around a bead apex (not shown). In this way, the carcass reinforcing ply encapsulates the bead core 25 and at least the lower portion of the bead apex in each bead portion 23 .

[0075] The ply turnup 33 terminates at a radially outward end forming a ply end or radially outermost ply end 35 and may include an end cap (not shown). Thus, the ply end or radially outward ply end 35 is the radially outermost point of the ply turnup 33. The carcass reinforcement ply 29 is preferably formed of a single layer of reinforcing elements.

[0076] Chipper 37 is disposed about the radially inward surface of ply turnup 33. Chipper 37 terminates at a radially outward end 39 and may include an end cap (not shown). Radially outward chipper end 39 is axially outward from ply end 35 and axially outward from opposing chipper end 41. For example, the height of outward ply end 35 is at least 35 mm; for example, at least 38 mm; for example, at least 40 mm; for example, at least 42 mm. The height of the outward ply end is determined in the radial direction and is measured from bead toe 49.

[0077] The respective radially outward chipper end 39 is thus the respective radially outermost point of the respective chipper 37 on the axially outer side of each respective bead portion 23 or bead core 25. The respective opposing chipper end 41 is thus the respective radially outermost point of the respective chipper 37 on the axially inner side of each respective bead portion 23 or bead core 25.

[0078] The respective chipper plies 37 extend radially inwardly of the carcass reinforcing ply 29 under the respective bead cores 25 .

[0079] The radially outward chipper end 39 is preferably radially below the ply end 35. In other words, the ply end 35 extends in the sidewall 27 above the height of the radially outward chipper end 39. The ply end 35 and the radially outward chipper end 39 are preferably separated by a distance of at least 8 mm; preferably at least 10 mm; more preferably, at least 12 mm. The ply end 35 and the radially outward chipper end 39 are preferably separated by a distance of at most 30 mm; preferably, at most 25 mm; more preferably, at most 20 mm.

[0080] For example, the height of the radially outward chipper end 39 is at most 40 mm; for example, at most 35 mm; for example, at most 30 mm; for example, at most 25 mm. The height of the radially outward chipper end 39 is determined in the radial direction and measured from the bead toe 49.

[0081] Preferably, at least one of the ply ends 35 and / or the radially outward chipper end 39 includes an end cap so that the ply end portion and the outward chipper end portion are non-parallel and separated by a rubber strip.

[0082] The opposite end 41 of the chipper 37 is also preferably radially below the ply end 35. The opposite end 41 of the chipper 37 is preferably located in the bead portion 23. The opposite end 41 of the chipper 37 preferably extends above the height in the bead portion 23 of the radially outer surface of the bead core 25. For example, the height of the opposite chipper end 41 is at least 25 mm; for example, at least 30 mm; for example, at least 35 mm; for example, at least 40 mm. For example, the height of the opposite chipper end 41 is at most 60 mm; for example, at most 55 mm; for example, at most 50 mm; for example, at most 45 mm. The height of the opposite chipper end 41 is determined in the radial direction and measured from the bead toe 49.

[0083] The profile of the outer surface 43 of the sidewall portion 27 of the tire 21 is at a distance G from the carcass reinforcing ply 29 from the axially outermost point of the outer surface until point A, and joins the outer surface of the bead portion 23 at point B. Between points A and B, the outer surface 43 follows two continuous curves, a first curve 45 extending from point A and having a center of curvature located axially outward of the carcass reinforcing ply 29; and a second curve 47 joining point B having a center of curvature located axially inward of the outer surface of the tire. The outer surface of the tire includes the outer surface 43 of the sidewall portion and the outer surface of the bead portion. In a preferred embodiment, the distance G is constant. The distance G is preferably in the range of 2 mm to 10 mm, more preferably in the range of from 3 mm to 7 mm. In one embodiment, the distance G is equal to or less than the radius R1 of the circle C1 centered on the ply end 35. The distance G is called constant when it does not vary by more than 0.5 mm. The variation in distance is due to creep phenomena during tire manufacturing and vulcanization.

[0084] In one embodiment, the distance between the carcass end 35 and the radially outward chipper end 39 is equal to or less than the distance of point A from the carcass end 35; that is, the distance between the carcass end 35 and the radially outward chipper end 39 is equal to or less than 30 mm, preferably equal to or less than 28 mm, and more preferably equal to or less than 25 mm.

[0085] According to the present disclosure, the outer surface profile of the tire sidewall in the portion extending from point A to point B is tangent to a circle C1 centered on the cord layer end 35 and tangent to a circle C2 centered on the radially outward tread reinforcement layer end 39. Preferably, the portion extending from point A to point B is a spline curve including two curves 45, 47, which shows a radius of curvature that is reversed and arranged end to end or separated by a straight portion. The spline curve is preferably tangent to the circle C2 in point B and tangent to the circle C1 in a point different from point B. The spline curve is preferably tangent to the circle C1 in a point located between point A and point B. For example, when the spline includes a straight portion, the straight portion has a length ranging from 0.5 mm to 2.0 mm; preferably ranging from 0.8 mm to 1.5 mm. For example, when the spline curve includes a straight portion, the spline curve can be tangent to the circle C1 in a point located in the straight portion arranged between the first curve 45 and the second curve 47.

[0086] The circle C1 centered at the ply end 35 preferably has a radius R1 ranging from 5 mm to 15 mm. For example, the radius R1 of the circle C1 is at least 5 mm, or at least 7 mm, or at least 9 mm. For example, the radius R1 of the circle C1 is at most 15 mm, or at most 13 mm, or at most 11 mm.

[0087] The circle C2 centered at the radially outward chipper end 39 preferably has a radius R2 ranging from 2 mm to 12 mm. For example, the radius R2 of the circle C2 is at least 2 mm, or at least 5 mm, or at least 7 mm. For example, the radius R2 of the circle C2 is at most 12 mm, or at most 10 mm, or at most 9 mm, or at most 8 mm.

[0088] In one embodiment, a circle C1 centered at the carcass end 35 has a radius R1 that is equal to or greater than a radius R2 of a circle C2 centered at the radially outward chipper end 39 .

[0089] like Figure 2 As shown in FIG. 1 , circle C1 is completely within tire 21 and its bead portion 23 , and the same is true for circle C2 .

[0090] It will be appreciated that the portion of the tire sidewall showing the defined constant gauge dimensions is extended in height compared to prior art tires of the same size. As a result, the outer surface of the sidewall appears to present an outer cavity. It was found that this resulted in a tire with reduced rolling resistance with an acceptable compromise in terms of bead durability due to the reasonable distance maintained between the outer surface of the tire (i.e., the outer cavity) and both the ply end 35 and the radially outward chipper end 39. In addition, a reduction in heat build-up was observed.

[0091] The shape of the sidewall outer surface is tangent to both circles C1 and C2 centered on the carcass end 35 and the radially outward chipper end 39, which helps to obtain a smooth surface between the sidewall and the bead portion, avoiding strain concentration in the rubber as shown, and thereby contributing to the durability of the tire.

[0092] The compromise of bead durability according to the present disclosure is obtained in particular by the distance of point A from the end 35 of the ply being at most 30 mm; preferably at most 28 mm, more preferably at most 25 mm. Preferably, the distance of point A from the end of the ply is at least 10 mm; preferably at least 12 mm; more preferably at least 15 mm. The distance of point A from the end 35 of the ply is thus in the range from 10 mm to 30 mm; preferably in the range from 12 mm to 28 mm, more preferably from 15 mm to 25 mm. According to the present disclosure, the distance of point A from the end 35 of the ply is less than the distance of point A from the radially outward chipper end 39.

[0093] The first curve 45 extending from point A has a radius of curvature R3 greater than the radius R1 of circle C1 and / or greater than the radius R2 of circle C2. The second curve 47 connecting point B has a radius of curvature R4 greater than the radius R1 of circle C1 and / or greater than the radius R2 of circle C2. For example, the radius of curvature R3 is greater than the radius of curvature R4. For example, the radius of curvature R3 ranges from 1.2 to 5 times the radius of curvature R4; preferably, from 1.5 to 4 times.

[0094] The apex is at least partially located in the ply turnup portion proximate the bead core 25. The apex not only helps mate the ply turnup 33 with the main portion 31 of the carcass reinforcement ply 29, but also prevents any air bubbles from being trapped in the sidewall 27 of the tire 21 during manufacturing.

[0095] The durability of the tire 21 is achieved by a combination of the internal structure of the tire 21, in which a gap is found between the carcass end 35 and the radially outward chipper end 39, and the shape of the outer surface 43 of the sidewall portion 27 between point A and point B. In addition, the smooth shape of the spline curve forming the outer surface 43 of the sidewall portion 27, which spline curve connects the bead portion at point B, avoids strain concentration in the bead portion 23 and the sidewall portion 27 and facilitates the manufacture of the tire 21.

[0096] Example

[0097] A radial tire having a design according to the present disclosure was produced and tested. The tire was 315 / 70R22.5, where 315 is the nominal cross-section given in mm (metric), 70 is the aspect ratio, R represents radial, and 22.5 is the nominal bead diameter (also called the nominal wheel diameter) given in inches (1 inch = 25.4 mm). The radius R1 of the circle C1 centered at the end of the ply was 9 mm. The radius R2 of the circle C2 centered at the radially outward tread reinforcement layer end was 6 mm. The height of the ply end was 42 mm. The ply end and the radially outward tread reinforcement layer end were separated by a distance of 10 mm. The rolling resistance and durability of the tire were evaluated.

[0098] Rolling resistance testing was performed in accordance with ISO 28580 (tire rolling on a 67-inch diameter drum).

[0099] Durability test: Tires mounted on 9”x22.5” rims, rolled on a 67” diameter drum at 60 km / h with a load of 5000 kg and a pressure of 10 bar.

[0100] The test values ​​are normalized and reported in the following table:

[0101] standard New Design Rolling resistance 100 102 Durability 100 99.5 weight 100 102

[0102] .

[0103] Improvements in rolling resistance (RR) performance (i.e. normalized values ​​over 100) mean lower rolling resistance. Improvements in weight performance (i.e. normalized values ​​over 100) mean lighter tires. Improvements in durability (i.e. normalized values ​​over 100) mean higher durability.

[0104] From the results it can be seen that the performance is that the rolling resistance and weight of the tire are improved (+2), while no significant loss of durability performance is observed (-0.5). Therefore, the design of the present disclosure provides an improved compromise between rolling resistance, durability and weight performance.

[0105] Thermal tests for finite element analysis were performed on tires under the same RR test conditions as ISO 28580. The temperature curves show that the tires Figure 2 Compared to tires with designs of the type described above, a heat reduction of several degrees was achieved with the design of the present disclosure.

[0106] It should be understood that the structure of the tire 21 described above may be changed or rearranged, or components or steps known to those skilled in the art may be omitted or added without affecting the overall concept or operation of the present invention. For example, the teachings herein are applicable to a wide range of tires and can be used in tire production lines, such as, but not limited to, passenger car tires, medium truck radial tires, aircraft tires and off-road tires, run-flat tires, etc. Preferably, the tire 21 is a heavy-duty tire. For example, the tire is a commercial truck tire including a nominal bead diameter of at least 22.5 inches.

[0107] For example, the tire has an aspect ratio of at least 60; preferably at least 70. For example, the tire has an aspect ratio of from 60 to 90, or from 70 to 90 or from 60 to 80.

[0108] Furthermore, the present disclosure is applicable to tires formed with any type of belt structure or tread construction.

Claims

1. A radial tire, the tire (21) comprising a tread portion; a pair of sidewall portions (27); a pair of bead portions (23), each bead portion (23) comprising a bead core (25); a carcass reinforcing cord layer (29), comprising a cord layer turn-up portion (33), each cord layer turn-up portion (33) comprising a radially outward cord layer end portion (35); and a wheel reinforcement layer (37), which is arranged at each cord layer turn-up portion (33) and has a radially outward wheel reinforcement layer end portion (39), wherein the wheel reinforcement layer end portion (39) is located radially below the radially outward cord layer end portion (35); wherein: The profile of the axially outer surface of the sidewall portion (27) extends from the axially outermost point of the axially outer surface (43) to a point A at a distance G from the carcass reinforcing cord layer (29), and connects the axially outer surface (43) of the bead portion (23) at point B, wherein the axially outer surface of the sidewall portion (27) follows two curves, a first curve extending from point A and having a center of curvature located axially outward of the carcass reinforcing cord layer (29), and a second curve connecting point B and having a center of curvature located axially inward of the axially outer surface of the tire (21); and wherein, in the portion extending from point A to point B, the profile of the axially outer surface of the sidewall portion (27) is tangent to a circle C1 centered on a radially outward cord layer end (35), and the radial tire is characterized by (i) said circle C1 has a radius R1 ranging from 5 to 15 mm and said profile of said axially outer surface of said sidewall portion (27) is tangent to a circle C2 centered at said radially outward chipper end (39) at said point B; and (ii) The distance between said point A and said radially outward ply end (35) is in the range of 10 mm to 30 mm.

2. The radial tire according to claim 1, characterized in that: At least one of the following is true: (i) the circle C2 centered at the radially outward chipper end (39) has a radius R2 ranging from 2 mm to 12 mm; (ii) The circle C1 centered at the radially outward ply end (35) has a radius R1 ranging from 8 mm to 12 mm.

3. The radial tire according to claim 1, characterized in that: The radially outward ply end (35) and the radially outward chipper end (39) are separated by a distance of at least 8 mm, and / or wherein the distance of point A from the radially outward ply end (35) is in the range of from 15 mm to 25 mm.

4. The radial tire according to claim 1, characterized in that: The second curved line connecting the points B has a curvature radius R4 that is greater than the radius R2 of the circle C2.

5. The radial tire according to claim 1, characterized in that: The two curved lines are arranged end to end, or the two curved lines are separated by a straight portion.

6. The radial tire according to claim 1, characterized in that: The chipper (37) includes a radially outward chipper end (39) and an opposing chipper end (41), wherein the radially outward chipper end (39) is axially outward of the opposing chipper end (41), and the height of the opposing chipper end (41) is at least 25 mm, and the height of the opposing chipper end (41) is determined in the radial direction and measured from the tire toe (49).

7. The radial tire according to claim 1, characterized in that: The profile of the axially outer surface of the sidewall portion (27) in the point B is tangent to the circle C2 centered at the radially outward chipper end (39), the circle C2 having a radius R2 ranging from 2 mm to 12 mm.

8. The radial tire according to claim 6, characterized in that: The height of the radially outward ply end (35) is at least 35 mm, the height of the radially outward ply end (35) being determined in the radial direction and measured from the bead toe (49).

9. The radial tire according to claim 1, characterized in that: The distance G is equal to or less than the radius R1 of the circle C1 centered at the radially outward carcass end (35).

10. The radial tire according to claim 1, characterized in that: The second curve extends radially outward through the point B.

11. The radial tire according to claim 2, characterized in that: The circle C2 has a radius R2 ranging from 5 mm to 9 mm.

12. The radial tire according to claim 7, characterized in that: The circle C2 has a radius R2 ranging from 5 mm to 9 mm.

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