Optimized structure of a tire for civil engineering

Abstract

A radial carcass tyre for civil engineering vehicles comprises two tyre bead cores (2) having a radial height Ht and a carcass reinforcement consisting of two plies. A first radially innermost ply (1) having a radial height Hdc is anchored in each bead to form a main portion (11) and a bead flange (12). A second carcass ply (3) is radially outer than said first ply (1). The free end (A) of the bead flange (12) is located at a certain radial distance from the radially outermost point (21) of the tyre bead core, which is at least equal to 1 times Ht and at most equal to 2 times Ht. From the end A of the bead flange (12) to a point B at 85% of the radial height Hdc, the distance between the carcass plies is at least equal to 2 times the diameter of the metal reinforcement of the first carcass ply (1) and at most equal to 11 times said diameter.

Description

Technical Field

[0001] The subject of this invention is a radial tire intended for mounting on heavy-duty vehicles of the civil engineering type, and more specifically, the invention relates to a carcass reinforcement of said tire. Background Technology

[0002] The European Tire & Rim Technology Organization (ETRTO) standards specify radial tires designed for mounting on heavy-duty civil engineering vehicles.

[0003] For example, within the meaning of the European Tire & Rim Technology Organization (ETRTO) standard, radial tires for heavy-duty civil engineering vehicles are intended to be mounted on rims with a diameter of at least 25 inches. While not limited to this type of application, the present invention describes radial tires intended to be mounted on dump trucks, particularly on vehicles used for transporting materials extracted from quarries or open-pit mines, using rims with a diameter of at least 35 inches (potentially up to 57 inches, or even 63 inches).

[0004] Because tire geometry exhibits rotational symmetry about its axis of rotation, it is typically described in the meridional plane that contains the tire's axis of rotation. For a given meridional plane, the radial, axial, and circumferential directions represent the directions perpendicular to, parallel to, and perpendicular to the meridional plane, respectively. The circumferential direction is tangent to the tire's circumference.

[0005] In the following text, "radially inner / radially located inside" and "radially outer / radially located outside" refer to being "closer" to the tire's axis of rotation and "farther" from the tire's axis of rotation, respectively. "Axially inner / axially located inside" and "axially outer / axially located outside" refer to being "closer" to the tire's equatorial plane and "farther" from the tire's equatorial plane, which is a plane that passes through the middle of the tread surface and is perpendicular to the axis of rotation, respectively.

[0006] Typically, a tire includes a tread that is designed to contact the ground through its surface, and two axial ends of the tread are connected to two beads via two sidewalls, which provide a mechanical connection between the tire and a rim designed to mount the tire.

[0007] The radial tire further includes a reinforcement consisting of a crown reinforcement located radially inside the tread and a carcass reinforcement located radially inside the crown reinforcement.

[0008] The carcass reinforcement of radial tires used in heavy-duty civil engineering vehicles typically comprises a carcass layer, which usually includes a metal reinforcement (or reinforcing element) coated with an elastomeric or elastic polymer material obtained through blending and referred to as a coated compound. The carcass layer includes the main portion that connects two beads together and typically forms a beaded edge within each bead by wrapping a circumferential metal reinforcing element, commonly referred to as a bead line, from the inside to the outside of the tire. The metal reinforcements of the carcass layer are substantially parallel to each other and form an angle between 80° and 90° with the circumferential direction.

[0009] The crown reinforcement of radial tires for civil engineering vehicles comprises stacked crown layers extending circumferentially outward along the radial direction outside the carcass reinforcement. Each crown layer is typically composed of metal reinforcements parallel to each other and coated with an elastomeric or compound-type polymer material.

[0010] Both from the perspective of maximum load and pressure, the tire carcass reinforcement is a limiting factor restricting the use of civil engineering tires. There is a relationship between tire internal pressure and its maximum load. Higher pressure results in a greater maximum load. Furthermore, higher pressure makes the tire stiffer because it has a weaker ability to absorb impact deformation. Higher pressure requires a larger diameter of the carcass ply cords, causing the outermost strands to move further away from the central axis, which is extremely detrimental to its fatigue strength. Lower pressure results in greater sidewall skew under load and greater bending of the carcass ply. Moreover, increasing pressure and increasing cord diameter necessitates the use of cords made from individual strands with diameters larger than those optimal for fatigue strength, as it is difficult to manufacture cords containing a large number of individual metal strands.

[0011] The inventors set a goal for themselves: for radial tires used in civil engineering vehicles, when the inflation pressure is equal to the nominal pressure, the load-bearing capacity is increased by 25% compared to the nominal load, or, under the same load, for a load equal to the nominal load, the inflation pressure can be reduced to improve the tire crown's resistance to impact loads. Summary of the Invention

[0012] According to the present invention, this objective has been achieved by a radial carcass-reinforced tire for civil engineering vehicles, the tire comprising:

[0013] • A crown reinforcement, located radially inside the tread, the tread being connected to two bead via two sidewalls.

[0014] • A carcass reinforcement extending between two beads and comprising two carcass layers, each carcass layer including a metal reinforcement forming an angle between -10° and 10° with respect to the radial direction.

[0015] • The first carcass layer is the radially innermost carcass layer and is anchored in each bead by wrapping around a bead line having a geometric center and a radial height Ht, thereby forming the main portion and the crimp. The main portion extends from one bead line to the other, and the crimp is axially located outside the main portion in each bead and has a free end.

[0016] The first carcass layer has a radial height Hdc measured from its innermost radial point to its outermost radial point.

[0017] • A second carcass layer extends from one bead to another and is located radially outside the first carcass layer in the crown region of the tire. The distance from the second carcass layer to the main portion of the first carcass layer is measured between the central axis of the second carcass layer and the central axis of the main portion of the first carcass layer.

[0018] • Each free end of each rolled edge of the first carcass layer in each bead is located at a certain radial distance from the outermost point of the bead line, the radial distance being at least equal to 1 times and at most equal to 2 times the radial height Ht of the bead line.

[0019] • In each bead, the end of the second carcass layer is located radially inside the geometric center of the bead line.

[0020] • In each bead, the point from the free end of the crimp of the first carcass layer to the radial distance from the innermost radial point of the first carcass layer to a distance equal to 85% of the radial height of the first carcass layer, wherein the distance between the main portion of the first carcass layer and the second carcass layer is at least equal to twice the diameter of the metal reinforcement of the first carcass layer and at most equal to 11 times the diameter.

[0021] • The metal reinforcement of the two carcass layers is a cord composed of individual filaments, of which at least 50% of the individual filaments have a diameter of at least 0.17 mm and at most 0.23 mm, and all of the individual filaments have a diameter of at least 0.17 mm and at most 0.26 mm.

[0022] This invention relates to a radial civil engineering tire comprising two metal carcass layers. This solution is complex to implement due to the need for metal cords to withstand the stresses in this type of use, and the complexity of managing the fatigue strength of the carcass reinforcements (especially in the flexural areas of the sidewall and bead). Specifically, the two-carcass layer solution allows the sidewall to behave like a beam, but the disadvantage is that the two layers are located on opposite sides of the sidewall's central axis. The type of stress between the two carcass layers varies depending on their location on the sidewall and their flexural pattern. For example, directly above the rim flange, the radially innermost first carcass layer is relatively under tension, while the second carcass layer is relatively under compression. At the outermost axial point of the tire and at the shoulder where the sidewall meets the tire crown, the radially innermost first carcass layer is relatively under compression, while the second carcass layer is relatively under tension. The stress can be relatively balanced between these different areas with certain operating patterns.

[0023] Currently, maintaining good performance of metal carcass layers under compressive loads is extremely complex. Therefore, solutions including two carcass layers, each located on either side of the centerline, are considered impractical for heavy-duty tires or civil engineering tires with rim sizes greater than 19 inches. Specifically, due to their technical applications, such tires do not use reinforcements other than metal in the carcass layers. However, surprisingly, this invention can be implemented in civil engineering tires, thereby improving tire durability, allowing for increased load at the same operating pressure, or allowing for reduced pressure at the same maximum load. This is achieved due to the cord dimensions of individual carcass layers in tires according to existing technology. These reinforcements have large diameters and low flexibility, which is detrimental to their flexural strength.

[0024] According to the invention, the reinforcements of the two carcass layers have a small diameter and are composed of individual metal wires with a diameter between 0.17 mm and 0.23 mm, which exhibit optimal flexural behavior for this type of tire. Having two carcass layers allows the diameter of the reinforcements used to be reduced by 30% to 50%, depending on the spacing applied to the carcass layers. Specifically, the smaller diameter reinforcements are naturally more flexible due to the reduced inertia of the cross-section, but can also be laid at smaller spacing. The increased flexibility of the reinforcements according to the invention largely compensates for the formation of a central axis between the two carcass layers, provided that the distance between the carcass layers in the sidewall is appropriate and the ends of the carcass layers are positioned in a manner that controls their risk of cracking.

[0025] The first rule is that the free end of the crimp of the first carcass ply must be located in the uncompressible region of the tire and radially outside the outermost point of the bead line to prevent the first carcass ply from loosening in case of bead overheating. The radial height Ht of the bead line is measured on a meridional section from one or more of its innermost radial points to one or more of its outermost radial points. The free end of the crimp of the first carcass ply must be located at a certain radial distance from the outermost point of the bead line, which is at least equal to 1 and at most equal to 2 times the radial height Ht of the bead line.

[0026] The end of the second carcass layer needs to be located in a region where deformation is minimal or even non-deformable. This condition is satisfied if the end of the second carcass layer is radially located inside the geometric center of the bead line. The geometric center of the bead line is considered to be the intersection of the diagonals of the smallest rectangle containing the bead line. Preferably, the end of the second carcass layer is radially located inside the innermost point of the bead line. Preferably, to prevent cracking of the rubber compound below the bead line, the end of the second carcass layer is axially located inside the geometric center of the bead line. Preferably, if the innermost point of the bead line constitutes a segment or base, it is advantageous that the end of the second carcass layer is not perpendicular to this base. Specifically, although the movement in this region is small, the compressive load perpendicular to the base is at its maximum, especially in the middle of the base. This compressive load can damage the end of the reinforcement of the second carcass layer. This presents a high risk of a single filament penetrating the rubber compound and reaching the outside of the tire, thus forming a water ingress channel, which can lead to oxidation of the bead line or the second carcass layer, potentially resulting in a decrease in tire durability. Therefore, the end of the second carcass layer is preferably located axially outside the outermost point of the bead line base, or axially inside the innermost point of the bead line base, more particularly axially outside the midpoint of the bead line base or axially inside the midpoint. The advantage of this configuration, where the end of the second carcass layer is located axially inside the innermost point of the bead line base, is that the bead can maximally resist loosening of the carcass layer when it is pressed against the bead line base.

[0027] For this invention to function, the distance between the two carcass layers must be controlled between the free end of the first carcass layer's rolled edge and the shoulder where it meets the sidewall and crown. In the case of civil engineering tires, this shoulder is located at a point where the radial distance from the innermost radial point of the carcass layer is equal to 85% of the radial height Hdc of the first carcass layer, measured on a meridional section aligned with the tire's outer section mounted on the nominal rim. To minimize the problems of bending and relative positioning of the carcass layers with respect to the centerline, one solution could be to bring the two carcass layers as close together as possible, but surprisingly, this solution does not provide any significant improvement. In contrast, setting the distance between the two carcass layers along the tire sidewall in a specific manner provides a solution to the problem, provided that smaller diameter cords are used, thus offering greater flexibility than cords used in solutions comprising only one carcass layer. This condition is met by individual filaments, of which at least 50% have a diameter between 0.17 mm and 0.23 mm, and all of these individual filaments have a diameter of at least 0.17 mm and at most 0.26 mm. Preferably, the metal reinforcement of the two carcass layers (1, 3) is a cord composed of individual filaments, of which at least 60% have a diameter of at least 0.17 mm and at most 0.2 mm.

[0028] For a tire with a nominal pressure P, the diameter of the cords in the carcass layers can be correlated with the tire size. For a carcass reinforcement consisting of two carcass layers, the tire according to the invention has:

[0029] Nominal pressure P (in bar),

[0030] • The diameter d (in mm) of the metal reinforcement in the carcass layer

[0031] • The radial distance R13 (in mm) from the innermost point of the first carcass layer to the tire's axis of rotation.

[0032] • The radial distance R14 (in mm) from the outermost point of the first tire carcass layer to the tire's axis of rotation.

[0033] Therefore, when the product Q equals (R14-R13)*(3R14+R13) / 8 (in mm) 2If the quotient 1000*d*R13 / (P*Q) is at least equal to 0.25 and at most equal to 0.6, then the lower limit allows the carcass reinforcement to withstand sufficient internal pressure while also possessing adequate fatigue strength. The upper limit enables the production of tires with metal reinforcements in the carcass layers, the diameter of which is significantly smaller than the diameter of the cords in a single carcass layer of a tire according to the prior art, between 30% and 50%. This allows for adjustment of durability performance by varying the spacing of the metal reinforcements. Limiting the cord diameter allows for control over tire weight and raw material consumption. Using smaller diameter cords improves industrial efficiency. Specifically, these smaller diameter cords are easier to manufacture, cut, process, and lay.

[0034] Tests show that the performance trade-off is acceptable if the distance between the first and second carcass layers is at least twice the diameter of the metal reinforcement of the first carcass layer and at most 11 times the diameter, preferably at least three times the diameter of the metal reinforcement of the first carcass layer and at most eight times the diameter, between the free end of the rolled edge of the first carcass layer and the point in the first carcass layer where the radial distance from the innermost radial point of the first carcass layer is equal to 85% of the radial height Hdc of the first carcass layer.

[0035] The distance between the two carcass layers can be constant, extending from the free end of the rolled edge of the first carcass layer to the shoulder where the sidewall meets the crown. However, for a constant distance within this region, some points experience greater stress than others, making this solution less than optimal.

[0036] The improvement of the present invention is achieved when the distance DA between the main portion of the first carcass layer and the second carcass layer is greater than the distance DB between the first and second carcass layers, wherein the distance DA is measured at the free end of the rolled edge of the first carcass layer, and the distance DB is measured at a point on the first carcass layer that is a radial distance equal to 85% of the radial height Hdc of the first carcass layer from its innermost radial point. Specifically, due to the presence of the rim flange that provides support during bending, a larger distance at the rim flange compared to the tire shoulder where the sidewall meets the tire crown promotes crown flattening while maintaining sufficient flexural stiffness of the sidewall. Therefore, the risk of fatigue failure in this area is lower. Thus, increasing the distance separating the two carcass layers at the free end of the rolled edge of the first carcass layer compared to the tire shoulder where the sidewall meets the tire crown is more beneficial to the shear strength of the rubber.

[0037] For similar reasons, another improvement of the invention is achieved when the distance DA between the main portion of the first carcass layer and the second carcass layer is greater than the distance DE between the first and second carcass layers, wherein the distance DA is measured at the free end of the rolled edge of the first carcass layer, and the distance DE is measured at the outermost axial point of the first carcass layer. The outermost axial point of the first carcass layer is the location of the greatest bending, and therefore it is necessary to minimize the force generated by the separation of the carcass layer from the central axis at this location.

[0038] Furthermore, to better distribute flexural forces across the tire sidewall height, the distance between carcass layers at the outermost axial point of the first carcass layer is similar to the distance between carcass layers at the shoulder where the sidewall and crown meet. This condition is satisfied if the distance DE between the first and second carcass layers is at least 0.9 times the distance DB between the first and second carcass layers, wherein the distance DE is measured at the outermost axial point of the first carcass layer, and the distance DB is measured at a point on the first carcass layer at a radial distance equal to 85% of the radial height Hdc of the first carcass layer from its radial innermost point. Preferably, from the outermost axial point E of the first carcass layer to point B, a radial distance equal to 85% of the radial height Hdc of the first carcass layer from its radial innermost point, the distance between the main portion of the first carcass layer and the second carcass layer is at most 1.1 times the distance DE between the first and second carcass layers, wherein the distance DE is measured at the outermost axial point of the first carcass layer.

[0039] There is a weak point where the sign of bending stress changes between the free end of the crimp of the first carcass ply (bent around the center of curvature located on the outer side of the tire) and the outermost axial point of the first carcass ply (bent around the center of curvature located on the inner side of the tire). To reduce the impact of this phenomenon occurring near point I of the first carcass ply on durability, it is suitable to reduce the distance DI between the two carcass ply at this point relative to the distance between the carcass ply at the free end of the crimp of the first carcass ply and at the outermost axial point of the first carcass ply, where point I is located at a distance from the free end of the crimp of the first carcass ply, this distance being equal to 0.65 times the distance between the free end of the crimp of the first carcass ply and the outermost axial point of the first carcass ply. It is known that, preferably, the distance between the two carcass layers at the free end of the rolled edge of the first carcass layer is greater than the same distance at the outermost axial point of the first carcass layer. Therefore, it is advantageous that the distance DI between the first carcass layer and the second carcass layer is less than the distance DE between the first carcass layer and the second carcass layer, wherein the distance DI is measured at point I of the first carcass layer and the distance DE is measured at the outermost axial point of the first carcass layer.

[0040] For optimal design, it is suitable that the distance between the two carcass layers varies between 1.5 and 4 times the cord diameter of the first carcass layer, between the free end of the first carcass layer's cuff and the shoulder where it meets the sidewall and crown. This limitation on the variation prevents one area of ​​the sidewall from becoming particularly rigid due to beam-like behavior, while another area becomes particularly flexible. Specifically, a particularly flexible area absorbs most of the bending when the crown flattens, thus becoming a weak point in durability. Therefore, it is advantageous that the distance DA between the main portion of the first carcass layer and the second carcass layer, measured at the free end of the first carcass layer's cuff, minus the minimum distance between the two carcass layers, is at least 1.5 times and at most 4 times the diameter of the metal reinforcement of the first carcass layer, measured between the free end of the first carcass layer's cuff and the point where the radial distance from the innermost radial point of the first carcass layer is equal to 85% of the radial height Hdc of the first carcass layer.

[0041] Although it is advantageous for two carcass layers to have identical metal reinforcements in both composition and structure for obvious standardization reasons, the carcass layers can also have different metal reinforcements. Attached Figure Description

[0042] The tire is a reference size of 24.00R35, shown schematically and not to scale. Figure 1 The features of the present invention are described. Detailed Implementation

[0043] Figure 1The diagram shows a meridional half-section of a tire for a heavy-duty vehicle used in civil engineering applications. The tire includes a carcass reinforcement having a first carcass layer 1 and a second carcass layer 3. The first carcass layer 1 is the radially innermost carcass layer and is anchored in each bead by wrapping around a bead line 2. The first carcass layer 1 has a main portion 11 and a rolled edge 12 extending from bead line 2 to another bead line in another bead. The rolled edge 12 has a free end A referred to as the radially outermost end A. Between the radially innermost point 13 of the first carcass layer (located below bead line 2) and the radially outermost point 14 of the first carcass layer (typically located in the crown at the tire's equatorial plane), the first carcass layer has a radial height Hdc, measured on a meridional section positioned when mounted on a nominal rim. Point B, where the tread meets the sidewall, is located at a certain radial distance from the innermost radial point 13 of the first carcass layer 1, which is equal to 85% of Hdc. Point E refers to the outermost axial point of the meridional section of the first carcass layer when it is mounted on the nominal rim. Hae is the radial distance between points A and E. Point I represents a point on the first carcass layer located at a radial distance from point A equal to 0.65 times Hae. Points A, B, E, and I are considered along the centerline of the first carcass layer. Associated with each of these points is a distance D, which are distances DA, DB, DE, and DI from the centerline of the main portion 11 of the first carcass layer 1 to the centerline of the second carcass layer 3, respectively. The bead line 2 has a radial height Ht measured between its innermost radial point and its outermost radial point 21. Point 22 is the geometric center of the bead line, corresponding to the center of the smallest rectangle in the meridional section that includes the bead line. The innermost radial end 31 of the second carcass layer 3 is located radially inside the geometric center of the bead line. The free end A of the rolled edge of the first carcass layer is located at a certain radial distance from the outermost radial point 21 of the bead line 2, which is between one and two times the radial height Ht. For all points of the first carcass layer between points A and B, the distance from the first carcass layer to the second carcass layer is between two and eleven times the diameter of the metal reinforcement of the first carcass layer. Furthermore, DA is greater than DE and DB, DE is at least equal to 0.9 times DB, and DI is less than DE. Between points A and B, the distance between the two carcass layers varies between 1.5 and 4 times the diameter of the metal reinforcement of the first carcass layer.

[0044] The invention was tested on a tire with a size of 24.00R35. In each test, the tire according to the invention was compared with a reference tire of the same size.

[0045] The reference tire has a single carcass layer whose metal reinforcement is a cord with 7 strands of 2.24 mm diameter laid below the bead line at a spacing of 2.6 mm, the strands comprising 7 0.23 mm steel wires.

[0046] The tire according to the invention comprises two carcass layers, the metal reinforcement of which is a cord having 27 0.18 mm steel wires laid at a spacing of 1.8 mm, the cord having a diameter of 1.38 mm. Both the cords of the reference tire and the cords of the tire according to the invention are wrapped cords.

[0047] The distance DA (the maximum distance between the two carcass layers between A and B) is 8 mm. The distance DB is 4.4 mm, which is the minimum distance between the two carcass layers between points A and B. The distance DI (the minimum distance between the two carcass layers between points A and E) is 5.9 mm, and the distance DE is 6.4 mm. Between A and B, the distance between the two carcass layers is indeed between 2 and 11 times the diameter of the metal reinforcement of the first carcass layer. DA-DB is indeed between 1.5 and 4 times the diameter of the metal reinforcement of the first carcass layer.

[0048] The other components of the comparison tire are the same as those of the tire according to the present invention (tire structure, rubber compound, etc.).

[0049] The tires were tested on a machine. First, the tires were planed downwards to the bottom of the tread pattern to concentrate stress loads in the sidewalls and bead. The tread profile of the planed tire corresponds to that of a brand new tire. Under a pressure of 6.2 bar (i.e., 1.05 bar lower than the nominal pressure), two tires were compressed against each other by a force of 25,000 daN, corresponding to the nominal load plus a 25% overload. The tires were driven against each other at a speed of 15 km / h. The tire according to the invention can operate continuously for more than 1000 hours without damage, while the tire according to the prior art stops after 800 hours due to rubber compound cracking in the sidewall.

[0050] Therefore, when used under overload and underinflation conditions, the present invention can indeed improve the durability of the sidewall and bead by at least 20%.

Claims

1. Radial reinforced tires for civil engineering vehicles, comprising: • A crown reinforcement, located radially inside the tread, the tread being connected to two bead via two sidewalls. • A carcass reinforcement extending between two bead layers and comprising two carcass layers (1, 3), the two carcass layers (1, 3) including a metal reinforcement forming an angle between -10° and 10° with respect to the radial direction. • A first carcass layer (1), which is the radially innermost carcass layer, is anchored in each bead by wrapping around a bead line (2) having a geometric center (22) and a radial height Ht, thereby forming a main part (11) and a serration (12), the main part (11) extending from one bead line to another, and the serration (12) being located axially outside the main part (11) in each bead and having a free end (A). • The first carcass layer (1) has a radial height Hdc measured from its innermost radial point (13) to its outermost radial point (14). • The second carcass layer (3) extends from one bead to another and is located radially outside the first carcass layer (1) in the crown region of the tire. The distance from the second carcass layer (3) to the main portion (11) of the first carcass layer (1) is measured between the central axis of the second carcass layer (3) and the central axis of the main portion (11) of the first carcass layer (1). • Characterized by, The first carcass layer (1) has each free end (A) of each crimp (12) in each bead located at a certain radial distance from the outermost point (21) of the bead line, the radial distance being at least equal to 1 times and at most twice the radial height (Ht) of the bead line. • In each bead, the end (31) of the second carcass layer (3) is located radially inside the geometric center (22) of the bead line (2). • In each bead, between the free end (A) of the rolled edge (12) of the first carcass layer (1) and the point (B) of the first carcass layer (1) at a radial distance equal to 85% of the radial height (Hdc) of the first carcass layer (1) from the innermost radial point (13) of the first carcass layer (1), the distance between the main portion (11) of the first carcass layer (1) and the second carcass layer (3) is at least twice the diameter of the metal reinforcement of the first carcass layer (1) and at most eleven times the diameter. • The metal reinforcement of the two carcass layers (1, 3) is a cord composed of individual filaments, at least 50% of which have a diameter of at least 0.17 mm and at most 0.23 mm, and all of which have a diameter of at least 0.17 mm and at most 0.26 mm.

2. The tire according to claim 1, wherein, The distance DA between the main part (11) of the first carcass layer (1) and the second carcass layer (3) is greater than the distance DB between the first carcass layer (1) and the second carcass layer (3). The distance DA is measured at the free end (A) of the rolled edge of the first carcass layer (1), and the distance DB is measured at a point (B) of the first carcass layer (1) that is 85% of the radial height (Hdc) of the first carcass layer (1) from the radial innermost point (13) of the first carcass layer (1).

3. The tire according to claim 1 or 2, wherein, The distance DA between the main part (11) of the first carcass layer (1) and the second carcass layer (3) is greater than the distance DE between the first carcass layer (1) and the second carcass layer (3). The distance DA is measured at the free end (A) of the rolled edge (12) of the first carcass layer (1), and the distance DE is measured at the outermost point (E) of the first carcass layer (1) in the axial direction.

4. The tire according to claim 1, wherein, The distance (DE) between the first carcass layer (1) and the second carcass layer (3), measured at the outermost axial point (E) of the first carcass layer (1), is at least equal to 0.9 times the distance (DB) between the first carcass layer (1) and the second carcass layer (3), measured at a point (B) on the first carcass layer (1) that is a radial distance equal to 85% of the radial height (Hdc) of the first carcass layer (1) from the innermost radial point (13) of the first carcass layer (1).

5. The tire according to claim 1, wherein point I of the first carcass layer (1) is located at a certain radial distance from the free end (A) of the rolled edge (12) of the first carcass layer (1), the radial distance being equal to 0.65 times the distance (Hae) between the free end (A) of the rolled edge (12) of the first carcass layer (1) and the outermost point (E) of the first carcass layer (1) along its axial direction, wherein, The distance (DI) between the first carcass layer (1) and the second carcass layer (3) measured at point I of the first carcass layer is less than the distance (DE) between the first carcass layer (1) and the second carcass layer (3) measured at the outermost point (E) of the first carcass layer (1) in the axial direction.

6. The tire according to claim 1, wherein, The distance (DA) between the main part (11) of the first carcass layer (1) and the second carcass layer (3), measured at the free end (A) of the rolled edge (12) of the first carcass layer (1), minus the minimum distance between the two carcass layers (1, 3) is at least 1.5 times and at most 4 times the diameter of the metal reinforcement of the first carcass layer (1), the minimum distance being measured between the free end (A) of the rolled edge (12) of the first carcass layer (1) and the point (B) where the radial distance from the radial innermost point (13) of the first carcass layer (1) is equal to 85% of the radial height (Hdc) of the first carcass layer (1).

7. The tire according to claim 1, wherein, In each bead, from the free end (A) of the rolled edge (12) of the first carcass layer (1) to the point (B) of the first carcass layer (1) at a radial distance equal to 85% of the radial height (Hdc) of the first carcass layer (1) from the innermost radial point (13) of the first carcass layer (1), the distance from the first carcass layer (1) to the second carcass layer (3) is at least 3 times the diameter of the metal reinforcement of the first carcass layer (1) and at most 8 times the diameter.

8. The tire according to claim 1, wherein, The end (31) of the second carcass layer is located on the inner side of the innermost point of the bead line (2) in the radial direction.

9. The tire according to claim 1, wherein the tire has a nominal pressure P in bar, a diameter d in mm of the metal reinforcement of the carcass ply, a radial distance R13 in mm from the innermost radial point (13) of the first carcass ply to the tire rotation axis, and a radial distance R14 in mm from the outermost radial point (14) of the first carcass ply to the tire rotation axis, wherein, When in mm 2 The product Q is equal to (R14-R13)*(3R14+R13) / 8, so the quotient 1000*d*R13 / (P*Q) is at least equal to 0.25 and at most equal to 0.

6.

10. The tire according to claim 1, wherein, The metal reinforcement of the two carcass layers (1, 3) is a cord composed of individual filaments, of which at least 60% of the individual filaments have a diameter of at least 0.17 mm and at most 0.2 mm.

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