Reinforcing product having fixed cord geometry and having dual modulus behavior and adapted stiffness

Abstract

The invention relates to a reinforced product (R) comprising a polymeric matrix (Ma) and at least one cord (50) comprising a single layer of N metallic reinforcing elements which can be: - metal filaments (F) having a diameter Df, wherein the metallic reinforcing elements (54) have a diameter Dh and a diameter D, the diameter Dh being the diameter of the theoretical circle passing through the centres of the filaments (F) of the layer in a plane perpendicular to the main axis of the cord, the diameter D being the outer diameter of the cord (50); or, - strands (T) helically wound around a main axis (A), each strand (T) comprising a single layer (56) of M > 1 metal filaments (FT) helically wound around an axis (B) and having a diameter Df, wherein the metallic reinforcing elements (54) have a diameter Dh and a diameter D, the diameter Dh being the diameter of the theoretical circle passing through the centres of the filaments (FT) of the layer (56) in a plane perpendicular to the main axis of the strand (T), the diameter D being the outer diameter of the strand (T); D, Dh and Df being expressed in millimetres: 0.10 < Jr < 0.20, with Jr = N / (pi x (D-Df)) x (DhxSin(pi / N) - (Df / Cos(alpha x pi / 180))), alpha being the helix angle of each metal filament, expressed in degrees; the polymeric matrix (Ma) having a secant modulus MA10 at 10% deformation in the range 2.5 MPa to 18.0 MPa; the modulus ratio Emax / Emin of the reinforced product (R1) satisfies 1 < Emax / Emin < 4, Emin being the minimum tensile secant modulus and Emax being the maximum tangent modulus of the same load-elongation curve; and - the structural elongation As of the reinforced product (R) satisfies 0 < As < 1%.

Description

Technical Field

[0001] This invention relates to a reinforced product and to a tire comprising such a product.

[0002] Although the invention is not limited to such applications, it will be described more specifically with reference to tires intended for mounting on vehicles that carry heavy loads, such as trucks, tractors, trailers, or road buses. Background Technology

[0003] A tire is understood as an outer tube designed to form a cavity by cooperating with a supporting element (e.g., a rim), which can be pressurized to pressures above atmospheric pressure. The tire according to the invention has a substantially annular structure.

[0004] A tire comprising a crown reinforcement is known from the prior art, the crown reinforcement comprising bimodulus cords as described in application WO2020021006. However, in order to obtain a reinforced product with sufficient stiffness, it is necessary to select cords that have the desired stiffness after being embedded in a polymer matrix.

[0005] Therefore, it is necessary to select cords based on their location within the tire (especially in the tread ply), which requires high stiffness to ensure tire strength and sufficient elongation to support tire manufacturing / curing processes, thus necessitating some degree of bimodal behavior. This step of selecting compliant cords to enhance the product has proven to be both time-consuming and cumbersome.

[0006] Typically, to change the stiffness of a reinforced product, those skilled in the art would primarily alter the structure of the cords, such as changing the helix angle. Therefore, it is necessary to develop various cord geometries to modify the stiffness of the reinforced product, thereby adapting it to its intended use.

[0007] The object of the present invention is a reinforced product whose stiffness and bimodulus behavior can be more easily controlled by changing the polymer matrix without changing the cord. Summary of the Invention

[0008] Therefore, the subject of this invention is a reinforced product comprising a polymer matrix and at least one cord, the cord comprising a single layer consisting of N helically wound metal reinforcing elements, wherein, as the cord extends in a substantially linear direction, each metal reinforcing element of the layer forms a helical path around a principal axis substantially parallel to the substantially linear direction, such that, in a cross-section substantially perpendicular to the principal axis, the distance between the center of each metal reinforcing element of the layer and the principal axis is substantially constant and identical for all metal reinforcing elements of the layer, wherein the metal reinforcing elements are:

[0009] - A metal wire having a diameter Df, wherein the metal reinforcing element has a diameter Dh and a diameter D, the diameter Dh being the diameter of the theoretical circle passing through the center of the layer of wires in a plane perpendicular to the main axis of the cord, and the diameter D being the outer diameter of the cord;

[0010] - Alternatively, strands helically wound around the main axis, each strand comprising a single layer composed of M>1 metal wires helically wound around an axis and having a diameter Df, wherein the metal reinforcing element has a diameter Dh and a diameter D, the diameter Dh being the diameter of the theoretical circle passing through the center of the layer of wires in a plane perpendicular to the axis of the strand, and the diameter D being the outer diameter of the strand;

[0011] where D, Dh, and Df are expressed in millimeters:

[0012] - The relative radial clearance Jr of the cord satisfies 0.10 ≤ Jr ≤ 0.20,

[0013] Jr = N / (π×(D - Df))×(Dh×Sin(π / N) - (Df / Cos(α×π / 180))), where α is the helix angle of each metal wire, expressed in degrees;

[0014] - The secant elastic modulus MA10 of the polymer matrix at 10% deformation, determined according to the standard NF ISO 37 of February 2018, ranges from 2.5 MPa to 18.0 MPa;

[0015] - The modulus ratio of Emax to Emin of the reinforcing product satisfies 1 < Emax / Emin < 4, where Emin is the minimum secant tensile elastic modulus, i.e., the slope of the straight line connecting the origin (0%; 0 MPa) of the stress - elongation curve (obtained under the conditions of the standard ASTM D 2969 - 04 of 2014), and Emax is the maximum tangent modulus of the same force - elongation curve; and

[0016] - The structural elongation As of the reinforcing product, determined by the standard ASTM D2969 - 04 of 2014, satisfies 0 < As < 1%.

[0017] The inventors of the present invention have noted that by fixing the geometry of the cord, especially its relative clearance, it is possible to control the stiffness of the reinforcing product by changing the stiffness of the polymer matrix, and also to change the bi - modulus behavior of the reinforcing product by changing the stiffness of the polymer matrix. Therefore, by changing the stiffness of the polymer matrix, the same cord can be used at different positions in a tire.

[0018] Thus, the reinforcing product according to the present invention can significantly change the stiffness of the reinforcing product without changing the steel grade or the quality of the metal involved.

[0019] An elastomeric matrix is ​​understood as a matrix having elastic behavior resulting from the crosslinking of an elastomeric composition. Therefore, the elastomeric matrix is ​​based on an elastomeric composition. Similar to the elastomeric matrix, the filler material is also based on an elastomeric composition; in this case, the composition of the filler material is the same as the composition of the matrix into which the cord is embedded.

[0020] The values ​​of characteristics Dh, D, Df, Dv, Rf, and α, as well as other characteristics described below, are measured or determined directly on the cord after manufacturing (i.e., prior to any step of embedding into the elastomeric matrix), or on the cord after it has been removed from the elastomeric matrix (e.g., from the tire) and thus undergone a cleaning step (in which any elastomeric matrix, particularly any material present within the cord, is removed from the cord). To ensure its pristine condition, the adhesive interface between each metal reinforcement element and the elastomeric matrix must be eliminated, for example, by electrochemical treatment in a sodium carbonate bath. By removing the ply and cord, the effects of the molding steps in the tire manufacturing method described below are eliminated, particularly the elongation of the cord; during removal, the ply and cord essentially regain their properties prior to the molding steps.

[0021] The cord according to the invention comprises a single layer of helically wound metal reinforcing elements. In other words, the cord according to the invention comprises one layer of helically wound metal reinforcing elements, rather than two or more layers. The layer is composed of metal reinforcing elements (i.e., multiple metal reinforcing elements, not just one). In one embodiment of the cord, for example, at the completion of its manufacturing process, the cord according to the invention comprises a layer of wound metal reinforcing elements; in other words, the cord does not include any other metal reinforcing elements besides the metal reinforcing elements in this layer.

[0022] In one embodiment, the cord according to the invention has a single helix. By definition, a single-helix cord is a cord in which the axis of each metal reinforcing element in a layer forms a single helix, unlike a double-helix cord, in which the axis of each metal reinforcing element forms a first helix around the axis of the cord and a second helix around the axis of the cord. In other words, when the cord extends in a substantially linear direction, the cord comprises a single layer of metal wire elements spirally wound together, each metal reinforcing element of the layer forming a helical path around a main axis that is substantially parallel to a substantially linear direction, such that in a section substantially perpendicular to the main axis, the distance between the center of each metal reinforcing element of the layer and the main axis is substantially constant and the same for all metal reinforcing elements of the layer. In contrast, when a double-helix cord extends in a substantially linear direction, the distance between the center of each metal reinforcing element of the layer and the substantially linear direction is not the same for all metal reinforcing elements of the layer.

[0023] In another embodiment, the cord according to the invention has a double helix.

[0024] The cord according to the invention does not have a central metal core. This is also referred to as a 1xN structure cord or an open cord. In the cord as defined above according to the invention, the inner loops are empty, therefore there is no filler material, and in particular no elastomer composition. This is then referred to as a filler-free cord.

[0025] According to the invention, the cord's circumference is defined by metal reinforcing elements and corresponds to a volume defined by a theoretical circle, which is radially inward of each metal reinforcing element and tangent to each metal reinforcing element on the other hand. The diameter of this theoretical circle is equal to the circumference diameter Dv.

[0026] A filamentary element is understood to be an element extending longitudinally along a principal axis and having a cross-section perpendicular to the principal axis, wherein the maximum dimension G of the cross-section is relatively small compared to the dimension L along the principal axis. The expression "relatively small" means that L / G is greater than or equal to 100, preferably greater than or equal to 1000. This definition includes both filamentary elements with circular cross-sections and those with non-circular cross-sections (e.g., polygonal or oblong cross-sections). Each metal reinforcing element is very preferably to have a circular cross-section.

[0027] By definition, the term metal means a filamentary element that is primarily (i.e., greater than 50% by weight) or entirely (100% by weight) made of metallic material. Each metal reinforcing element is preferably made of steel, more preferably of pearlitic or ferritic-pearlitic carbon steel (commonly referred to as carbon steel by those skilled in the art), or of stainless steel (by definition, steel containing at least 10.5% chromium).

[0028] Structural elongation As is a parameter well known to those skilled in the art, determined, for example, by applying the 2014 standard ASTM D2969-04 to the tested reinforced product to obtain a force-elongation curve. As is derived from the curve obtained by the intersection of the tangent of the elastic portion of the force-elongation curve with the elongation axis, corresponding to the elongation (in percentage). It should be remembered that the force-elongation curve includes structural, elastic, and plastic portions in the direction of increasing elongation. The structural portion corresponds to the structural elongation of the cord caused by the movement of the different metal reinforcing elements constituting the cord together. In some embodiments, the layers of N metal reinforcing elements separate at the end of the structural portion due to the relatively small relative radial gap Jr, resulting in a one-time increase in the cord modulus. The elastic portion corresponds to the elastic elongation produced by the structure of the cord (particularly the angles of the layers and the diameter of the filaments). The plastic portion corresponds to the plastic elongation produced by the plasticity (irreversible deformation beyond the elastic limit) of one or more metal reinforcing elements of the reinforced product.

[0029] The relative radial gap Jr represents the distance separating each pair of adjacent filaments minus the available length of the filaments positioned on the layer. Therefore, the larger Jr is, the greater the space separating two adjacent filaments relative to the maximum number of filaments that the layer can accommodate. Conversely, the smaller Jr is, the smaller the space separating two adjacent filaments relative to the maximum number of filaments that the layer can accommodate. Within the scope of the invention, Jr can maximize the number of filaments on the layer, thereby improving the reinforcement capacity of the cord, without sacrificing the ability to accommodate longitudinal compressive deformation.

[0030] like Figure 7 and Figure 8 As shown, the ratio Emax / Emin is determined based on the force-elongation curves obtained under the conditions of the 2014 standard ASTM D 2969-04.

[0031] Emin is the minimum secant tensile modulus, which is the slope of the straight line connecting the origin (0%; 0 MPa) of the stress-elongation curve (obtained under the conditions of the 2014 standard ASTM D 2969-04), expressed in GPa.

[0032] Emax is the maximum tangent modulus of the same force-elongation curve, expressed in GPa.

[0033] The helix angle α is a parameter known to those skilled in the art and can be determined using the following iterative calculation involving three iterations, where the exponent i represents the number of iterations: 1, 2, or 3. Given the structural elongation As (in %), the helix angle α(i) is: α(i) = Arcos[(100 / (100+As)×Cos[Arctan((π×Df) / (P×Cos(α(i-1))×Sin(π / N))]], where P is the pitch of each metal reinforcement element (in millimeters), N is the number of metal reinforcement elements in the layer, Df is the diameter of each metal reinforcement element (in millimeters), and Arcos, Cos, Arctan, and Sin represent the arccosine, cosine, arctangent, and sine functions, respectively. For the first iteration, i.e., when calculating α(1), α(0) = 0. In the third iteration, when α is expressed in degrees, the obtained α(3) = α has at least one significant digit after the decimal point.

[0034] The helix diameter Dh (in millimeters) is calculated using the formula Dh = P × Tan(α) / π, where P is the winding pitch of each metal reinforcement element (in millimeters), α is the helix angle of each metal reinforcement element as determined above, and Tan is the tangent function. The helix diameter Dh corresponds to the diameter of the theoretical circle passing through the center of the metal reinforcement element in a plane perpendicular to the axis of the cord.

[0035] The diameter of the ring, Dv (in millimeters), is calculated using the formula Dv = Dh - Df, where Df is the diameter of each metal reinforcing element and Dh is the helix diameter, both in millimeters.

[0036] When the metal reinforcing element is a wire, the diameter or visible diameter (denoted as D) of the cord is measured using a thickness gauge. The diameter of the thickness gauge contact is at least 1.5 times the winding pitch P of the wire element (for example, the KAEFER JD50 thickness gauge, with an accuracy of 1 / 100 mm and equipped with a type a contact, has a contact pressure of approximately 0.6 N). The measurement scheme involves repeating a series of three measurements (each series consisting of three measurements) perpendicular to the cord axis and under zero tension. The directions of the second and third measurements are angularly offset by one-third of a turn from the direction of the previous measurement, and the measurement direction rotates around the cord axis.

[0037] When the reinforcing element is a strand, the diameter or visible diameter (denoted as D) of the strand is measured by clamping the cord between two fully upright rods, each 200 mm long, and then measuring the space the cord enters using the gauge described below. For example, the KAEFER JD50 / 25 model, with an accuracy of 1 / 100 mm and equipped with type a contacts, has a contact pressure of approximately 0.6 N. The measurement scheme involves repeating a series of measurements (each series consisting of three measurements) three times (perpendicular to the cord axis and under zero tension).

[0038] It should be remembered that the pitch of each metal reinforcing element is the length covered by that filament element, measured parallel to the axis of the cord in which it is located, and at the end of the pitch, the filament element with that pitch forms a complete loop around the axis of the cord.

[0039] The optional features described below can be combined with each other, provided that such combination is technically compatible.

[0040] In an advantageous implementation, all the metal wires have the same diameter Df.

[0041] The cord of the reinforced product according to the invention is manufactured using a method employing the apparatus described in documents WO2016083265 and WO2016083267. This method employing a segmented step must differ from conventional cord manufacturing methods, which include a single assembly step in which the metal reinforcing elements are spirally wound, followed by a pre-forming step of the metal reinforcing elements prior to the assembly step to significantly increase the value of the structural elongation. These methods and apparatuses are described in documents EP0548539, EP1000194, EP0622489, or EP0143767. In these methods, the metal monofilaments are individually pre-formed to obtain the maximum possible structural elongation. However, this step of individually pre-forming the metal monofilaments requires special equipment, not only making the method relatively less productive than methods without a pre-forming step and unable to achieve a large structural elongation, but also negatively impacting the metal monofilaments pre-formed in this manner due to friction with the pre-forming tool. This negative impact creates fracture initiation points on the surface of the metal monofilament, thus negatively affecting its durability, especially under compression. The presence of these pre-forming marks can be observed under an electron microscope after understanding the manufacturing process, or more simply by examining the methods used to manufacture the cord.

[0042] By definition, MA10 is the secant tensile modulus of elasticity of a vulcanized polymer matrix measured at 10% elongation based on a stress-elongation curve obtained according to the recommendations of standard NF ISO 37 of February 2018. It is the modulus of elasticity of the compound, measured during a uniaxial tensile test at an elongation of 0.1 (i.e., 10% elongation, expressed as a percentage). Uniaxial tension is applied to the specimen at a constant rate, and then the elongation and force are measured. Measurements are performed using an INSTRON type tensile testing machine at a temperature of 23°C and a relative humidity of 50% (standard ISO 23529). The conditions used to measure and utilize the results to determine elongation and stress are described in standard NF ISO 37:2018-02. The stress at 0.1 elongation is determined, and then the modulus of elasticity at 10% is calculated by calculating the ratio of this stress value to the elongation value. Those skilled in the art understand how to select and adjust the specimen size based on the amount of available and usable compound, particularly when the specimen is taken from finished products such as tires.

[0043] Any range of values ​​expressed as “between a and b” refers to a range of values ​​from greater than a to less than b (i.e., excluding endpoints a and b), while any range of values ​​expressed as “from a to b” means a range of values ​​from a to b (i.e., including strict endpoints a and b).

[0044] In this article, “radial cross section” or “radial section” means a cross section or section in a plane that contains the axis of rotation of the tire.

[0045] The term "axial direction" refers to a direction that is substantially parallel to the axis of rotation of the tire.

[0046] The term "circumferential direction" refers to a direction that is substantially perpendicular to both the axial direction and the tire radius (in other words, tangent to a circle centered on the tire's axis of rotation).

[0047] The term "radial direction" refers to the direction along the tire's radius, that is, any direction that intersects the tire's axis of rotation and is substantially perpendicular to that axis.

[0048] The center plane (denoted as M) is a plane perpendicular to the tire's axis of rotation, located in the middle between the two bead sections and passing through the center of the crown reinforcement.

[0049] The equatorial circumferential plane of a tire (denoted as E) is a theoretical plane passing through the tire's equator, perpendicular to the midline plane and the radial direction. The tire's equator is an axis in the circumferential section plane (a plane perpendicular to the circumferential direction and parallel to the radial and axial directions), parallel to the tire's axis of rotation, and equidistant between the outermost radial point of the tread intended to contact the ground and the innermost radial point of the tire intended to contact a support (e.g., the rim), the distance between which is equal to H.

[0050] The orientation of the angle refers to the clockwise or counterclockwise direction of rotation required to reach another line of the defined angle from a reference line (in this case, the circumferential direction of the tire). Advantageously, the metal reinforcing elements define an inner coil (58) of cord with a diameter of Dv, each metal reinforcing element having a diameter of Df, and a helical radius of curvature Rf defined by Rf = P / (π × Sin(2α)), where P is the pitch of each metal reinforcing element in millimeters, α is the helix angle of each metal reinforcing element (54), and Dv = Dh - Df, where Dv, Dh, and Df are in millimeters.

[0051] 1.30≤Dv / Df≤4.50, and preferably, 1.60≤Dv / Df≤3.20.

[0052] The radius of curvature Rf (in millimeters) is calculated using the formula Rf = P / (π × Sin(2α)), where P is the pitch of each metal reinforcement element (in millimeters), α is the helix angle of each metal reinforcement element, and Sin is a sine function.

[0053] Favorably, 9 ≤ Rf / Df ≤ 30.

[0054] Preferably, the total elongation At is >1.5% as determined by the 2014 standard ASTM D2969-04.

[0055] Advantageously, the helical diameter Dh of each metal reinforcing element (54) satisfies 0.70mm≤Dh≤1.60mm, preferably 0.75mm≤Dh≤1.60mm, and more preferably 0.80mm≤Dh≤1.60mm.

[0056] Advantageously, Df satisfies 0.10mm≤Df≤0.50mm, preferably 0.15mm≤Df≤0.50mm, and more preferably 0.15mm≤Df≤0.45mm.

[0057] Advantageously, Dv satisfies Dv≥0.40mm, preferably 0.50mm≤Dv≤1.20mm.

[0058] Each metal reinforcing element is preferably wound with a pitch P, which satisfies 3mm ≤ P ≤ 15mm, preferably 5mm ≤ P ≤ 13mm, and more preferably 7mm ≤ P ≤ 11mm. It can also be noted that, compared to other elastic cords, the reinforcing product according to the invention allows for a wider range of adjustment of the stiffness of the reinforcing product by changing the pitch of the braid.

[0059] Advantageously, the diameter of the cord or strand is D≤2.10mm, preferably 0.90mm≤D≤2.10mm, and more preferably 0.95mm≤D≤2.05mm.

[0060] In a first preferred embodiment, each metal reinforcing element of the cord is a metal wire, wherein N ranges from 3 to 18, preferably from 4 to 15.

[0061] In a second preferred embodiment, each metal reinforcing element of the cord is a strand, wherein N ranges from 3 to 5, and M ranges from 3 to 18, and is preferably 4 to 15.

[0062] In this second preferred embodiment, advantageously, the strands define an inner loop of the cord with a diameter of Dvc, each strand having a diameter of D, and the helical radius of curvature Rt is defined by Rt=Pe / (πxSin(2αe)), where Pe is the pitch of each strand in millimeters, αe is the helix angle of each strand (T), and Dvc, D, and Rt are in millimeters. The cord satisfies the following relationship: 5≤Rt / D≤750 and 0.10≤Dvc / D≤0.50.

[0063] The cords of the reinforced product according to the second embodiment have excellent longitudinal compressibility and, all other things being equal, a relatively small diameter.

[0064] The inventors of this invention hypothesize that because the radius of curvature Rt is sufficiently large relative to the diameter D of each strand, the cord has adequate breathability, thereby reducing the risk of bending. Furthermore, the relatively large spacing between each strand and the longitudinal axis of the cord allows the strands, due to their helical shape, to accommodate relatively high longitudinal compressive deformation. In contrast, because the radius of curvature Rt of each strand in prior art cords is smaller relative to the diameter D, the filamentary elements are closer to the longitudinal axis of the cord and, due to their helical shape, can accommodate much smaller longitudinal compressive deformation.

[0065] Furthermore, if the radius of curvature Rt of each strand is too large, the longitudinal stiffness of the cord according to the present invention is insufficient during compression, and it cannot ensure that it plays a reinforcing role, such as the reinforcing role of a tire.

[0066] Furthermore, if the inner ring diameter Dvc is too large, the diameter of the cord will also be too large relative to the diameter of the strands.

[0067] The values ​​of characteristics Dt, Dvc, and Rt, as well as other characteristics described above, are measured or determined directly on the cord after manufacturing (i.e., prior to any step of embedding into the elastomeric matrix), or on the cord after it has been removed from the elastomeric matrix (e.g., from the tire) and thus undergone a cleaning step (in which any elastomeric matrix, particularly any material present within the cord, is removed from the cord). To ensure its original state, the adhesive interface between each filament element and the elastomeric matrix must be eliminated, for example, by electrochemical treatment in a sodium carbonate bath. By removing the ply and cord, the effects of the molding steps in the tire manufacturing method described below are eliminated, particularly the elongation of the cord; during removal, the ply and cord essentially regain their properties prior to the molding steps.

[0068] According to this second embodiment, the cord circumference of the reinforced product is defined by strands and corresponds to a volume defined by a theoretical circle located radially inward of each strand and tangent to each strand. The diameter of this theoretical circle is equal to the circumference diameter Dvc.

[0069] The helix angle αe of each strand is a parameter known to those skilled in the art and can be determined using the following formula: tanαe=2xπ×Re / Pe, where Pe is the pitch of each strand winding, expressed in millimeters; Re is the helix radius of each strand, expressed in millimeters; tan refers to the tangent function. αe is expressed in degrees.

[0070] The helix diameter De (in millimeters) is calculated using the formula De = Pe × Tan(αe) / π, where Pe is the pitch of each strand (in millimeters), αe is the helix angle of each strand as determined above, and Tan is the tangent function. The helix diameter De corresponds to the diameter of the theoretical circle passing through the center of the strand in a plane perpendicular to the main axis of the cord.

[0071] The diameter of the coil, Dvc (in millimeters), is calculated using the formula Dvc = De - D, where D is the diameter of each strand and De is the diameter of the spiral, both in millimeters.

[0072] The radius of curvature Rt (in millimeters) is calculated using the formula Rt=Pe / (πx Sin(2αe)), where Pe is the pitch of each strand (in millimeters), αe is the helix angle of each strand, and Sin is the sine function.

[0073] It should be remembered that the pitch of each strand is the length covered by the filamentous element, measured parallel to the axis of the cord in which it is located, and after the pitch, each strand with that pitch forms a complete loop around the axis of the cord.

[0074] In this second preferred embodiment, advantageously, the pitch Pe of each strand ranges from 20 mm to 120 mm.

[0075] Tires according to the present invention

[0076] Another subject of the invention is a tire comprising at least one of the reinforcing products as defined above.

[0077] Preferably, the tire includes a crown, two sidewalls, and two beads. The crown includes a tread and a crown reinforcement. Each sidewall connects each bead to the crown. The crown reinforcement extends within the crown in the circumferential direction of the tire. The tire includes a carcass reinforcement anchored in each bead and extending within the sidewalls and crown. The crown reinforcement is radially located between the carcass reinforcement and the tread. The crown reinforcement includes at least one reinforcement product as defined above.

[0078] The tread reinforcement preferably includes a hoop reinforcement, which comprises at least one hoop ply and preferably a single hoop ply. The hoop reinforcement is preferably formed from hoop plies. This embodiment is particularly suitable for tires designed for use in heavy-duty vehicles such as industrial vehicles (i.e., subways, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles), agricultural vehicles, or construction site vehicles, or other transport or handling vehicles.

[0079] The crown reinforcement preferably includes a working reinforcement, which includes at least one working cord layer.

[0080] In heavy-duty vehicle applications for load transport, hoop reinforcements typically include hoop cord layers produced by circumferentially winding hoop wires or continuous hoop strips at an angle of up to 5° to the circumferential direction.

[0081] In one embodiment, the hoop reinforcement is radially positioned between the two working reinforcements.

[0082] Advantageously, the hoop fabric layer includes at least one reinforcing product as defined above.

[0083] The tire is preferably designed for heavy-duty vehicles. Therefore, the tire has a base diameter (in inches) of the rim on which it is intended to be mounted, which is greater than or equal to 20 inches. Attached Figure Description

[0084] The invention can be better understood by reading the following embodiments given only by way of non-limiting examples and with reference to the accompanying drawings, in which:

[0085] - Figure 1 It is a cross-sectional view perpendicular to the circumferential direction of the tire according to the present invention;

[0086] - Figure 2 yes Figure 1 Detailed view of area II in the middle;

[0087] - Figure 3 This is a cross-sectional view of the reinforced product (R) according to the present invention;

[0088] - Figure 4 It is a schematic cross-sectional view of the cord (50) of the reinforcing product (R) according to the first embodiment of the present invention (assuming that the cord axis is straight and stationary);

[0089] - Figure 5 Is with Figure 4 A similar diagram of the cord (50') of the reinforced product (R) according to a second embodiment of the present invention;

[0090] - Figure 6 The stress-elongation curves of a reinforced product (R1; R1'; R1”; R1”') comprising cords (50) according to a first mode of the present invention are shown;

[0091] - Figure 7 A portion of the stress-elongation curve of a reinforced product (R1) comprising cords (50) according to a first mode of the present invention is shown, and the moduli Emin and Emax are schematically displayed; and

[0092] - Figure 8 A portion of the stress-elongation curve of a reinforced product (R2) including cords (50') according to a second mode of the present invention is shown, and the moduli Emin and Emax are schematically shown. Detailed Implementation

[0093] Embodiments of tires according to the present invention

[0094] Figure 1 and Figure 2 Reference frames X, Y, and Z are shown, which correspond to the tire's usual axial direction (X), radial direction (Y), and circumferential direction (Z), respectively.

[0095] The tire's "circumferential midplane" M is a plane perpendicular to the tire's axis of rotation and equidistant from the annular reinforcement structure of each bead.

[0096] Figure 1 and Figure 2 A tire according to the invention, indicated by the overall designation P, is shown.

[0097] Tire 10 is used on heavy-duty vehicles with heavy loads. Therefore, tire 10 has a size of 315 / 70R 22.5.

[0098] Tire 10 has a crown 12 (reinforced by crown reinforcement 14), two sidewalls 16, and two beads 18, each of which is reinforced by an annular structure, in this case by bead lines 20. Crown reinforcement 14 is radially covered by tread 22 and connected to the beads 18 via the sidewalls 16. Carcass reinforcement 24 is anchored in the two beads 18, in this case wrapped around the two bead lines 20, and includes a flange 26 facing outwards from the tire 20, which is shown here as being mounted on a wheel rim 28. Carcass reinforcement 24 is radially covered by crown reinforcement 14.

[0099] The carcass reinforcement 24 includes at least one carcass ply reinforced by radial carcass cords (not shown). The carcass cords are arranged substantially parallel to each other and extend from one bead 18 to the other, thereby forming an angle between 80° and 90° with the circumferential midplane M (a plane perpendicular to the tire's axis of rotation, located between the two bead 18 and passing through the center of the crown reinforcement 14).

[0100] The tire 10 also includes a sealing ply (commonly referred to as a “liner”) made of an elastomer, which defines the radial inner surface of the tire 10 and is designed to protect the carcass ply from the diffusion of air from the interior space of the tire 10.

[0101] The crown reinforcement 14 includes a working reinforcement extending radially from the outer side to the inner side of the tire 10, and the working reinforcement is arranged radially inside the tread 22.

[0102] The working reinforcement includes a first working ply and a second working ply. The first ply is formed of metal cords oriented at an angle equal to 20°. The hoop reinforcement includes a single hoop ply 19, and the hoop ply 19 includes a reinforcing product as described below. The second working ply is formed of metal cords oriented at an angle equal to 44° and crossing the metal cords of the first working ply. The cords of each of the working plies are located on both sides of the circumferential direction.

[0103] The crown reinforcement 14 is covered by the tread 20.

[0104] Embodiment of the reinforcing product according to the invention

[0105] Figure 3 There is shown a reinforcing product according to the invention designated by the overall reference R. The reinforcing product R includes at least one cord 50 embedded in a polymer matrix Ma, and in this case a plurality of cords 50.

[0106] Figure 3 A polymer matrix Ma with cords 50 is shown in a reference system X, Y, Z, where Y is the radial direction and X and Z are the axial and circumferential directions. In Figure 3 , the reinforcing product R includes a plurality of cords 50 which are arranged side by side in the main direction X, extend parallel to each other within the reinforcing product R, and are jointly embedded in the polymer matrix Ma.

[0107] In this case, the polymer matrix Ma is an elastomeric matrix based on an elastomer blend.

[0108] The polymer matrix has a secant modulus of elasticity MA10 at 10% deformation, determined according to the NF ISO 37 standard of February 2018, in the range of 2.5 MPa to 18.0 MPa. In this case, for the reinforcing product R1, it is 2.5 MPa.

[0109] The reinforcing product R is the reinforcing product R1 and the modulus ratio of Emax to Emin satisfies 1 < Emax / Emin < 4, where Emin is the minimum secant tensile modulus of elasticity, that is, the slope of the straight line connecting the origin (0%; 0 MPa) of the stress - elongation curve (obtained under the conditions of the standard ASTM D 2969 - 04 of 2014), and Emax is Figure 7 the maximum tangent modulus of the same force - elongation curve shown.

[0110] In this case, Emin = 46 GPa.

[0111] In this case, Emax = 134 GPa.

[0112] Furthermore, Emax / Emin = 2.9, which is between 1 and 4.

[0113] The structural elongation As of reinforced product R1, as determined according to the 2014 standard ASTM D2969-04, meets the requirement of 0. <As<1%。

[0114] In this case, As = 0.6%.

[0115] The cord of the reinforcing product according to the first embodiment of the present invention

[0116] Figure 4 The cord 50 of the reinforcing product according to a first embodiment of the present invention is shown.

[0117] The cord 50 comprises a single layer of N = 7 spirally wound metal reinforcing elements 54. As the cord 50 extends in a substantially linear direction, each metal reinforcing element 54 of the layer 52 forms a spiral path around a main axis (A) that is substantially parallel to the substantially linear direction, such that in a cross section substantially perpendicular to the main axis (A), the distance between the center of each metal reinforcing element 54 of the layer 52 and the main axis (A) is substantially constant and the same for all metal reinforcing elements 54 of the layer 52. The metal reinforcing elements 54 are metal wires F with a diameter Df (in this case, 7 metal wires). The metal reinforcing elements 54 have diameters Dh and D, where Dh is the diameter of the theoretical circle passing through the center of the wires F in a plane perpendicular to the main axis of the cord, and D is the outer diameter of the cord 50. D, Dh, and Df are expressed in millimeters.

[0118] -0.10≤Jr≤0.20

[0119] Where Jr=N / (πx(D-Df))x(Dh x Sin(π / N)-(Df / Cos(αxπ / 180))), where α is the helix angle of each metal wire F, expressed in degrees.

[0120] In this case, Jr = 0.19.

[0121] The cord of the reinforced product according to the second embodiment of the present invention

[0122] Figure 5 The cord 50' of the reinforced product according to a second embodiment of the present invention is shown.

[0123] The cord 50' comprises a single layer consisting of N = 3 helically wound metal reinforcing elements 54. As the cord 50' extends in a substantially linear direction, each metal reinforcing element 54 of the layer 52 forms a helical path around a main axis (A) that is substantially parallel to the substantially linear direction, such that in a cross section substantially perpendicular to the main axis (A), the distance between the center of each metal reinforcing element 54 of the layer 52 and the main axis (A) is substantially constant and the same for all metal reinforcing elements 54 of the layer 52. The metal reinforcing element 54 is a strand T (in this case, 3 strands) helically wound around the main axis (A). Each strand T comprises a single layer 56 consisting of M > 1 metal wires FT helically wound around an axis (B) and having a diameter Df. The metal reinforcing element 54 has a diameter Dh and a diameter D, where the diameter Dh is the diameter of the theoretical circle passing through the center of the wire FT in the layer 56 in a plane perpendicular to the main axis of the strand T, and the diameter D is the outer diameter of the strand T. D, Dh, and Df are expressed in millimeters.

[0124] -0.10≤Jr≤0.20

[0125] Where Jr=N / (π×(D-Df))x(Dh×Sin(π / N)-(Df / Cos(α×π / 180))), where α is the helix angle of each metal wire F, expressed in degrees.

[0126] In this case, Jr = 0.19.

[0127] Method for manufacturing an enhanced product according to a first embodiment of the present invention

[0128] The cord 50 of the enhanced product R1 according to the first embodiment is produced by the method described in application WO 2020 / 021006 and by using the apparatus described in documents WO2016083265 and WO2016083267.

[0129] The reinforced product R1 is then obtained by embedding the cord 50 into the polymer matrix Ma. In this case, the polymer matrix Ma is an elastomer matrix.

[0130] Method for manufacturing an enhanced product according to a second embodiment of the present invention

[0131] The cord 50' of the enhanced product R2 according to the second embodiment is produced by the method described in application WO2021140287.

[0132] Then, the reinforced product R2 is obtained by embedding the cord 50' into the polymer matrix Ma. In this case, the polymer matrix Ma is an elastomer matrix.

[0133] Comparative Test

[0134] Tables 1 and 2 below summarize the features of the enhanced products of the first and second embodiments of the present invention.

[0135] like Figure 6 As shown, stress-elongation curves for reinforced products R1, R1', R1”, and R1”' with cord 50 according to the first embodiment of the present invention were plotted using the 2014 standard ASTM D 2969-04, and are as follows. Figure 7 The ratio Emax / Emin of R1 and the structural elongation As were determined.

[0136] The results are summarized in Table 1 below.

[0137] [Table 1]

[0138]

[0139]

[0140] By applying the 2014 standard ASTM D 2969-04, the stress-elongation curve of the reinforced product R2 with cord 50' according to the second embodiment of the present invention was plotted, and as shown... Figure 8 The ratio Emax / Emin and the structural elongation As were determined.

[0141] The ratio Emax / Emin and structural elongation As of the reinforced product R2' were also determined.

[0142] Table 2 below summarizes the results for enhanced products R2 and R2'.

[0143] [Table 2]

[0144]

[0145]

[0146] Tables 1 and 2 show that the reinforced products R1, R1', R1”, R1”', R2 and R2' according to the present invention are reinforced products using cords with predetermined geometries. In particular, due to the relative gap Jr of the cords, the stiffness and bimodal behavior of the reinforced products can be controlled by changing the polymer matrix without changing the cords.

[0147] Therefore, the enhanced product according to the present invention can solve the problems mentioned in the preamble.

[0148] The present invention is not limited to the embodiments described above.

Claims

1. An enhanced product (R), characterized in that, The reinforced product (R) comprises a polymer matrix (Ma) and at least one cord (50; 50'), the cord (50; 50') comprising a single layer (52) made up of N helically wound metallic reinforcing elements (54). When the cord (50; 50') extends in a substantially straight direction, each metallic reinforcing element (54) of the single layer (52) forms a helical path around a cord main axis (A) that is substantially parallel to the substantially straight direction, such that in a cross-section substantially perpendicular to the main axis (A), the distance between the centre of each metallic reinforcing element (54) of the single layer (52) and the main axis (A) is substantially constant and the same for all metallic reinforcing elements (54) of the single layer (52). The metallic reinforcing element (54) is: - a metallic wire (F) having a diameter Df, where the metallic reinforcing element (54) has a diameter Dh and a diameter D, the diameter Dh being the diameter of the theoretical circle passing through the centres of the metallic wires (F) of the single layer in a plane perpendicular to the cord main axis, and the diameter D being the outer diameter of the cord (50); - or, a strand (T) helically wound around the main axis (A), each strand (T) comprising a single layer (56) made up of M>1 metallic wires (FT) helically wound around the axis (B) of the strand (T) and having a diameter Df, where the metallic reinforcing element (54) has a diameter Dh and a diameter D, the diameter Dh being the diameter of the theoretical circle passing through the centres of the metallic wires (FT) of the single layer (56) in a plane perpendicular to the axis (B) of the strand (T), and the diameter D being the outer diameter of the strand (T); where D, Dh and Df are expressed in millimetres: - the relative radial clearance Jr of the cord satisfies: 0.10 ≤ Jr ≤ 0.20 where Jr = N / (π×(D - Df))×(Dh×Sin(π / N)-(Df / Cos(α×π / 180))), where α is the helix angle of each metallic wire, expressed in degrees; - the secant tensile elastic modulus MA10 of the polymer matrix (Ma) at 10% deformation, determined according to the standard NF ISO 37 of February 2018, ranges from 2.5 MPa to 18.0 MPa; - the modulus ratio of Emax to Emin of the reinforced product (R) satisfies 1 < Emax / Emin < 4, where Emin is the minimum secant tensile elastic modulus, i.e. the slope of the straight line connecting the origin (0%; 0 MPa) of the stress-strain curve obtained under the conditions of the standard ASTM D 2969-04 of 2014, and Emax is the maximum tangent modulus of the same stress-strain curve; and - the structural elongation As of the reinforced product (R), determined by the standard ASTM D2969-04 of 2014, satisfies 0 < As < 1%.

2. The enhanced product (R) according to the preceding claim, wherein, Metal reinforcing elements (54) define an inner coil (58) of cord with a diameter of Dv, each metal reinforcing element (54) having a diameter of Df, and a helical radius of curvature Rf defined by Rf = P / (π × Sin(2α)), where P is the pitch of each metal reinforcing element in millimeters, α is the helix angle of each metal reinforcing element (54), and Dv = Dh - Df, where Dv, Dh, and Df are in millimeters. 1.30≤Dv / Df≤4.

50.

3. The enhanced product (R) according to the preceding claim, wherein, 9≤Rf / Df≤30.

4. The enhanced product (R) according to any one of the preceding claims, wherein, The total elongation At > 1.5% is determined by the 2014 standard ASTM D2969-04.

5. The enhanced product (R) according to claim 1, wherein, The diameter Dh of each metal reinforcing element (54) satisfies 0.70mm≤Dh≤1.60mm.

6. The enhanced product (R) according to claim 1, wherein, Df satisfies 0.10mm≤Df≤0.50mm.

7. The enhanced product (R) according to claim 2, wherein, Dv satisfies Dv≥0.40mm.

8. The enhanced product (R) according to claim 2, wherein, The pitch P of each metal reinforcing element (54) is 3mm ≤ P ≤ 15mm.

9. The enhanced product (R) according to claim 1, wherein, D≤2.10mm.

10. The enhanced product (R) according to claim 1, wherein, Each metal reinforcing element (54) of the cord (50) is a metal wire (F) with N ranging from 3 to 18.

11. The enhanced product (R) according to claim 1, wherein, Each metal reinforcing element (54) of the cord (50') is a strand (T), with N ranging from 3 to 5 and M ranging from 3 to 18.

12. The enhanced product (R) according to the preceding claim, wherein, The strands (T) define the inner loops (V) of the cord (50') with a diameter of Dvc. The diameter of each strand (T) is D, and the helical radius of curvature Rt is defined by Rt=Pe / (π×Sin(2αe)), where Pe is the pitch of each strand in millimeters, αe is the helix angle of each strand (T), and Dvc, D and Rt are in millimeters. The cord (50') satisfies the following relationship: 5≤Rt / D≤750 and 0.10≤Dvc / D≤0.

50.

13. The enhanced product (R) according to the preceding claim, wherein, The pitch Pe of each strand ranges from 20mm to 120mm.

14. A tire (10), characterized in that, The tire (10) includes at least one reinforced product (R) according to any one of claims 1 to 13.

15. The tire (10) according to the preceding claim, the tire (10) comprising a crown (12), two sidewalls (22) and two bead (24), the crown (12) comprising a tread (20) and a crown reinforcement (14), each sidewall (22) connecting each bead (24) to the crown (12), the crown reinforcement (14) extending within the crown (12) in a circumferential direction (Z) of the tire (10), the tire (10) comprising a carcass reinforcement anchored in each bead (24) and extending within the sidewalls (22) and the crown (12), the crown reinforcement (14) being radially disposed between the carcass reinforcement and the tread (20), the crown reinforcement (14) comprising at least one reinforcement product (R) according to any one of claims 1 to 13.

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