Tire for vehicle wheels

Abstract

A tyre for vehicle wheels comprises a carcass structure comprising at least a carcass ply having a plurality of hybrid reinforcing cords (10). Each hybrid reinforcing cord (10) comprises at least two strands (20a, 20b) twisted together with a predetermined twisting pitch (P). Each of the at least two strands (20a, 20b) comprises at least one monofilament textile thread made of polyester fibre and at least one multifilament textile yarn (22a, 22b) comprising a plurality of textile filaments (23a, 23b) made of aramid fibre and / or polyester fibre and / or rayon fibre. In any cross section of the hybrid reinforcing cord (10), the at least one monofilament textile thread is at least partially embedded in the filaments (23a, 23b) of the at least one multifilament textile yarn (22a, 22b).

Description

TECHNICAL FIELD

[0001] The present application relates to a tyre for vehicle wheels.

[0002] The tyre of the present application is preferably a tyre for vehicle wheels of high performance and ultra-high performance sports cars, even electric cars.

[0003] Tyres for high performance and ultra-high performance sports cars, generally defined as "HP" or "UHP" tyres, are in particular those which allow to reach speeds exceeding 190 km / h up to exceeding 300 km / h. Examples of such tyres are tyres according to the E.T.R.T.O. (European Tyre and Rim Technical Organisation) speed code "T", "U", "H", "V", "Z", "W", "Y" and racing tyres, in particular for high- power four-wheeled vehicles. Typically, tyres holding the above speed codes have a cross-sectional width equal to or greater than 185 mm, preferably between 195 mm and 385 mm, more preferably between 195 mm and 355 mm. Such tyres are preferably mounted on rims having a mating diameter equal to or greater than 13 inches, preferably not greater than 24 inches, more preferably between 16 inches and 23 inches.

[0004] The tyre of the present application can be a standard tyre or a self-supporting tyre as defined hereinafter in the present description.

[0005] The tyre of the present application comprises a hybrid reinforcing cord as defined hereinafter in the present description. BACKGROUND

[0006] Tyres with reinforcing cords comprising a core made of a textile material and a winding of one or more textile filaments made of a material different from that of the core around the core are described, for example, in US 7222481 B2, EP 3196343 A1, US 4343343 A1, EP 329590 A1.

[0007] US 2015 / 239301 A1, EP 2233318 A1, EP 3 441 237 B1 describe reinforcing cords comprising a textile filament of a first material twisted together with a textile filament of a second material. SUMMARY

[0008] Throughout the description and the appended claims, when certain values of certain angles are mentioned, unless otherwise specified, they refer to absolute values, i.e. both positive and negative values, with respect to a reference plane or a reference direction.

[0009] Furthermore, when referring to any range of values included between a minimum and a maximum value, unless otherwise stated, the aforementioned minimum and maximum values are intended to be included in the aforementioned range.

[0010] Furthermore, all ranges are inclusive of the maximum and minimum values described, and of any intermediate ranges, even if not explicitly described.

[0011] Any numerical value is deemed to be preceded by the term "about" even if not explicitly stated, to indicate that any such numerical value is slightly different from the value described, for example to account for typical dimensional tolerances in the referenced art.

[0012] In the following, the following definitions apply.

[0013] The term "self-supporting tyre" is used to indicate a tyre which differs from a standard tyre in that it is able to support the load of a vehicle under conditions of considerable or complete loss of pressure, for example due to a puncture, thus allowing the driver to travel a certain distance to reach a repair shop, without having to stop to change the tyre in potentially dangerous conditions.

[0014] The term "equatorial plane" of a tyre is used to indicate a plane which is perpendicular to the rotation axis of the tyre and which divides the tyre into two symmetrically equal parts.

[0015] The terms "radial" and "axial" and the expressions "radially internal / external" and "axially internal / external" are used with reference to a direction substantially parallel and a direction substantially perpendicular to the equatorial plane of the tyre, respectively, i.e. with reference to a direction substantially perpendicular and a direction substantially parallel to the rotation axis of the tyre, respectively.

[0016] The terms "circumferential" and "circumferentially" are used with reference to the direction of the annular extension of the tyre, i.e. the rolling direction of the tyre, which corresponds to the direction lying on a plane coincident or substantially parallel to the equatorial plane of the tyre.

[0017] The term "substantially axial direction" is used to indicate a direction which is inclined with respect to the equatorial plane of the tyre by an angle comprised between 70° and 90°.

[0018] The term "substantially circumferential direction" is used to indicate a direction which is oriented with respect to the equatorial plane of the tyre by an angle comprised between 0° and 10°.

[0019] The term "elastomeric material" or "elastomer" is used to indicate a material comprising vulcanizable natural or synthetic polymers and reinforcing fillers, wherein such material can have, at room temperature and after having been vulcanized, a deformation caused by a force and is able to quickly and positively recover the substantially original shape and size after the removal of the deforming force (according to the definition of Standard ASTM D1566-11 Standard Terminology Relating To Rubber).

[0020] The expression "reinforcing cord" or simply "cord" is used to indicate an element consisting of one or more elongated elements (hereinafter also referred to as "threads" or "yarns"), optionally coated with an elastomeric material or embedded in a matrix of elastomeric material.

[0021] In the following, the expression "thread" will be used to indicate a single elongated element made of metallic material or a single elongated element consisting of a single textile filament (in this case, the expression "monofilament textile thread" will also be used), while the expression "yarn" will be used to indicate an elongated element consisting of an aggregation of a plurality of textile filaments (in this case, the expression "multifilament textile yarn" will also be used).

[0022] Each filament can also be referred to as "fiber".

[0023] The yarn can have one or more "ends", wherein the term "end" is used to indicate a bundle of filaments twisted together. Preferably, only a single end or at least two ends twisted together are provided.

[0024] The term "linear density" or "count" of a cord or thread / yarn / end is used to indicate the weight of the cord or thread / yarn / end per unit length of cord or thread / yarn / end. The linear density can be measured in dtex (grams per 10 km length). According to the test prescribed by BISFA, for the measurement of the linear density, reference is made to flat threads / yarns, without application of twisting in the test step or twisting step. For example, reference is made to:

[0025] For aramid fibers (AR):

[0026] - Test method for aramid fiber yarns, 2002 edition,

[0027] - Determination of linear density - Chapter 6

[0028] - Determination of tensile properties - Chapter 7 - Test procedure - Paragraph 7.5 - Procedure with initial pre-tensioning;

[0029] For lyocell fibers:

[0030] - Determination of linear density - Chapter 6

[0031] - Test method for viscose, cupro, acetate, triacetate and lyocell filament yarns - 2007 edition, Determination of tensile properties - Chapter 7 - Tensile test conditions: oven-dry test - Table 7.1 - Test procedure - paragraph 7.5 - Oven-dry test on relaxed specimens - sub-paragraph 7.5.2.4.

[0032] A textile reinforcing cord can be identified with the symbol representative of the fabric material, the number of the fibre used and the number of warp yarns forming the reinforcing cord. For example, a reinforcing cord with a part made of an aromatic polyamide identified as Ar1672 represents a cord comprising an aromatic polyamide fibre with a number of 1670 dtex, formed of two warp yarns twisted together.

[0033] The term "strands" is used to denote the association of at least two threads or yarns to constitute an elongated element intended to be twisted with at least another elongated element to form a reinforcing cord, the two strands forming the reinforcing cord being identical to each other or different from each other.

[0034] The expression "hybrid reinforcing cord" is used to denote a reinforcing cord comprising at least one monofilament textile thread and at least one multifilament textile yarn, wherein the thread and the yarn are made of the same textile material or of different textile materials.

[0035] The term "diameter" of a reinforcing cord or thread or yarn is used to denote the diameter measured as specified in the method BISFA E10 (The International Bureau For The Standardization Of Man-Made Fibres, Internationally Agreed Methods For Testing Steel Tyre Cords, 1995 edition).

[0036] In the case of a yarn, the term "diameter" of a yarn is used to denote the diameter of an ideal circumference circumscribing all the filaments defining the yarn.

[0037] The terms "left-hand twist" and "right-hand twist" are used to indicate the twist direction of the reinforcing cord or its thread, yarn or end when the reinforcing cord is vertically oriented and one looks at the inclination of the turns and / or of the portions of the turns of the helix defined by the thread, yarn or end. The twist direction is left-hand when the above-mentioned turns and / or portions are inclined in an S shape, while the twist direction is right-hand when the above-mentioned turns and / or portions are inclined in a Z shape. Thus, the left-hand twist direction is also simply indicated with "S", while the right-hand twist direction is indicated with "Z".

[0038] The term "twist number" is used to indicate the number of twists per unit length of thread, yarn or end imparted to the reinforcing cord or its thread, or yarn, or end. The twist number is expressed in TPI (twists per inch) and thus indicates the number of twists in one inch of thread, yarn or end. In case the thread, yarn or end has to be twisted, the twisting is carried out before manufacturing the cord.

[0039] The expressions of type (48x48) and in general (nxn) are used to indicate with the first number the twist imparted to the yarn / end and with the second number the twist imparted to the reinforcing cord obtained by twisting together a plurality of yarns / ends. Such twists are expressed in twists per decimeter (dm). The symbol "Z" and "S" possibly present beside each of the above-mentioned numbers indicates the direction of the imparted twist.

[0040] The terms "breaking load" and "elongation at break" of the reinforcing cord are used to indicate, respectively, the load and the percentage elongation at which the reinforcing cord breaks, evaluated using the method BISFA E6 (The International Bureau For The Standardization Of Man-Made Fibres, Internationally Agreed Methods For Testing Steel Tyre Cords, 1995 edition).

[0041] The term "partial load elongation" of a reinforcing cord is used to denote the difference between the percentage elongation obtained by placing the reinforcing cord under a traction of 50 N and the percentage elongation obtained by placing the reinforcing cord under a traction of 2.5 N. The partial load elongation is evaluated using the method BISFA E7 (The International Bureau For The Standardization Of Man-Made Fibres, Internationally Agreed Methods For Testing Steel Tyre Cords, 1995 edition).

[0042] The term "stiffness" of a reinforcing cord is used to denote the bending moment of resistance at a predetermined angle (typically 15°) using the method BISFA E8 (The International Bureau For The Standardization Of Man-Made Fibres, Internationally Agreed Methods For Testing Steel Tyre Cords, 1995 edition).

[0043] The term "modulus" is used to denote the ratio between the load (or force) and the elongation at any point of the load-elongation curve according to the BISFA standard. This curve is plotted by calculating the first derivative of the load-elongation function defining the above curve and normalizing it to the linear density expressed in Tex. Thus, the modulus is expressed in cN / Tex or Mpa. In the load-elongation graph, the modulus is determined by the slope of the above curve with respect to the X axis.

[0044] In the context of the present application, the term "high modulus" is used to denote a modulus greater than 5 Mpa, while the term "low modulus" is used to denote a modulus lower than 5 Mpa.

[0045] The term "substantial axial direction" is used to denote a direction parallel to the axis of rotation of the tyre and substantially parallel to the direction of travel of the vehicle on which the tyre is mounted.

[0046] The term "cross-belt structure" is used to indicate a belt structure comprising a first belt layer comprising reinforcing cords substantially parallel to each other and inclined at a predetermined angle comprised between 15° and 45° with respect to the equatorial plane of the tyre, and at least one second belt layer arranged in a radially outer position with respect to the first belt layer and comprising reinforcing cords substantially parallel to each other but oriented with an opposite inclination with respect to the equatorial plane of the tyre to one of the reinforcing cords of the first layer.

[0047] The term "zero-degree belt" is used to indicate a reinforcing layer comprising at least one reinforcing cord wound on the belt structure according to a substantially circumferential winding direction.

[0048] The term "number of cords" of a layer is used to indicate the number of reinforcing cords provided per unit of length in an elastomeric material layer, such as for example a carcass ply or a belt layer. The number of cords can be measured in cords / dm (number of cords per decimetre).

[0049] Tires for high performance (HP) and ultra-high performance (UHP) motor vehicles (electric and non-electric) need to have a high adhesion to the ground in order to be able to effectively discharge the high driving torques they are subjected to to the ground and thus obtain high thrust and effective braking forces. Such tires must also provide a sufficient response to the various stresses to which the tire is subjected during straight travel and during cornering.

[0050] The above tires generally comprise a longitudinal carcass structure extending between opposite bead structures, a barrier layer of elastomeric material (also known as "liner") arranged in a radially inner position with respect to the carcass structure, a cross-belt structure arranged in a radially outer position with respect to the carcass structure, a zero-degree reinforcing layer arranged in a radially outer position with respect to the cross-belt structure, a tread band arranged in a radially outer position with respect to the zero-degree reinforcing layer, and a pair of sidewalls arranged on opposite sides with respect to the carcass structure and in axially outer positions with respect to the bead structures, each sidewall comprising a layer of elastomeric material extending radially between the respective bead structure and the respective axially outer portion of the tread band.

[0051] The carcass structure is configured to provide the tire with the required features of integrity and structural strength.

[0052] The belt structure, in addition to contributing to provide the above-mentioned features of integrity and structural strength, is configured to transmit to the carcass structure the lateral and longitudinal stresses to which the tire is subjected during travel in contact with the road surface, in order to provide the tire with the required performance features (i.e. grip, travel stability, controllability, directionality, stability) and comfort.

[0053] The zero-degree reinforcing layer is configured to limit the radial deformation of the belt structure.

[0054] The sidewall is configured to protect the carcass structure from atmospheric agents and lateral impacts, for example against the edge of a sidewalk. In self-supporting tyres, the sidewall is also configured to provide the tyre with sufficient strength to adequately withstand the load of a car when the tyre is used in deflated condition, on the one hand, and good comfort and anti-rolling characteristics when the tyre is in working conditions under normal inflation, on the other hand. To this end, a reinforcing insert made of elastomeric material is arranged in an axially outer position with respect to the liner and in an axially inner position with respect to the sidewall to define a sidewall structure configured to adequately support the tyre in deflated condition, preventing the sidewall itself from yielding or bulging, without compromising the normal driving conditions.

[0055] In view of the overall trend to reduce the emissions of CO2 into the atmosphere, the Applicant has considered the problem of reducing the rolling resistance of its standard tyres and self-supporting tyres, including for high- and ultra-high-performance sports cars, electric and non-electric.

[0056] With particular reference to tyres for electric cars, the Applicant has also observed that a reduction in the rolling resistance would result in a favourable increase in the autonomy of the batteries dedicated to propelling the car.

[0057] The Applicant has observed that, with other conditions being equal, it is possible to reduce the rolling resistance of a tyre by increasing the stiffness of its carcass structure and reducing the hysteresis caused by excessive deformation of the tyre.

[0058] The Applicant has therefore considered using such textile reinforcing cords in the carcass structure of its standard tyres or self-supporting tyres for high-performance (HP) and ultra-high-performance (UHP) sports cars, both electric and non-electric, having a construction suitable for achieving the required integrity and structural strength aspects, as well as the required stiffness and reduced hysteresis.

[0059] The Applicant has observed that, depending solely on the type of elongated element used in the textile reinforcing cord (monofilament textile thread, multifilament textile yarn and / or possible combinations of one or more of the above threads with one or more of the above yarns), it is possible to make a plurality of hybrid reinforcing cords having characteristics that achieve the above-mentioned purposes and others, thus being theoretically suitable for use in the carcass structure of the above-mentioned tyres for sports cars, both electric and non-electric.

[0060] In particular, the Applicant has observed that, with equal material and diameter, monofilament textile threads are more suitable than multifilament textile yarns for withstanding possible compressive stresses and reducing hysteresis, while multifilament textile yarns are more suitable than monofilament textile threads for withstanding bending stresses and adhering to the surrounding elastomeric material, which are normally borne by the reinforcing cords of the carcass structure.

[0061] The Applicant has considered that in the carcass structure of tyres for any type of vehicle it is necessary to ensure good adhesion of the reinforcing cords to the surrounding elastomeric material. This would lead to the use of reinforcing cords comprising multifilament textile yarns.

[0062] However, the Applicant has considered that in order to reduce hysteresis and also to provide the above-mentioned reinforcing cords with the desired resistance to the possible compressive stresses that they can be subjected to, as mentioned above, monofilament textile threads are the most suitable.

[0063] In order to solve this contradiction, the Applicant has found that a hybrid reinforcing cord, made by twisting together at least two strands made of textile material, wherein each of the above-mentioned strands comprises at least one multifilament textile yarn and a monofilament textile thread, arranged in such a way that in all cross sections of the reinforcing cord the monofilament textile thread is at least partially embedded or incorporated in the filaments of the at least one multifilament textile yarn, has both excellent adhesion to the surrounding elastomeric material, excellent fatigue resistance and an excellent compromise in terms of resistance to bending and compression and in terms of hysteresis.

[0064] Moreover, thanks to the above-mentioned embedding, the hybrid reinforcing cord has a substantially uniform behaviour when subjected to compressive stresses, i.e. all components of the reinforcing cord (monofilament textile thread and filaments of the multifilament textile yarn) are stressed in substantially the same way.

[0065] According to the Applicant, with particular reference to adhesion, even just partial embedding of the monofilament textile thread in the filaments of the multifilament textile yarn ensures that in each cross section of the reinforcing cord at least one sufficiently large portion of the outer surface of the reinforcing cord is defined by the filaments of the multifilament textile yarn and is therefore provided with excellent adhesion to the surrounding elastomeric material. The greater the portion of the monofilament textile thread embedded in the multifilament textile yarn in any cross section of the hybrid reinforcing cord, the greater this adhesion will be.

[0066] The Applicant has also considered that the monofilament textile thread and the filaments of the multifilament textile yarn of which the carcass structure should be made should be made of materials that provide the tyre with the required stiffness, structural strength / integrity and reduced hysteresis, and has considered that it is suitable to use polyester fibres for the monofilament textile thread and aramid and / or polyester and / or rayon fibres for the filaments of the multifilament textile yarn.

[0067] The Applicant has indeed observed that polyester fibres are particularly cost-effective, so that making the monofilament textile thread and the multifilament textile yarn with this fibre is particularly advantageous. The Applicant has also observed that, as regards the multifilament textile yarn, it is possible to use aramid fibres, which are particularly suitable for providing the carcass structure with high modulus, and rayon fibres, which are also particularly cost-effective.

[0068] According to the present applicant, for the multifilament textile yarns, it is thus possible to use polyester or rayon fibers, with priority given to cost savings, while using aramid fibers, with priority given to modulus. The use of polyester fibers or rayon fibers instead of aramid fibers can also be advantageous to overcome the periodic difficulties that can exist in obtaining aramid fibers due to their extensive use in military applications.

[0069] The present application thus relates, in a first aspect, to a tire for vehicle wheels, comprising a carcass structure.

[0070] Preferably, the carcass structure comprises at least one carcass ply having a plurality of hybrid reinforcing cords.

[0071] Preferably, each hybrid reinforcing cord comprises at least two strands twisted together with a predetermined twist pitch.

[0072] Preferably, each of the at least two strands comprises at least one monofilament textile thread.

[0073] Preferably, the at least one monofilament textile thread is made of polyester fibers.

[0074] Preferably, each of the at least two strands comprises at least one multifilament textile yarn comprising a plurality of textile filaments.

[0075] Preferably, the textile filaments are made of aramid and / or polyester and / or rayon fibers.

[0076] Preferably, in any cross-section of the hybrid reinforcing cord, the at least one monofilament textile thread is at least partially embedded in the filaments of the at least one multifilament textile yarn.

[0077] The use of such hybrid reinforcing cords allows to adapt the carcass structure to provide the tire with the required stiffness and to reduce hysteresis (and thus to provide the required reduction of rolling resistance) and structural strength / integrity, while ensuring sufficient adhesion of the reinforcing cord to the surrounding elastomeric material (due to the fact that the outer surface of the reinforcing cord is mainly defined by the filaments of the multifilament textile yarn, since the monofilament textile thread is always at least partially embedded or incorporated in the filaments of the multifilament textile yarn), and to achieve the above-mentioned benefits in terms of resistance to the various stresses to which the carcass structure is subjected.

[0078] Moreover, the provision of two strands twisted together of the above-mentioned type allows to improve the fatigue resistance of the reinforcing cord, while maintaining the above-mentioned benefits.

[0079] In its second aspect, the present application relates to a hybrid reinforcing cord.

[0080] Preferably, the hybrid reinforcing cord comprises at least two strands twisted together with a predetermined twist pitch.

[0081] Preferably, each of the at least two strands comprises at least one monofilament textile thread.

[0082] Preferably, the at least one monofilament textile thread is made of polyester fibers.

[0083] Preferably, each of the at least two strands comprises at least one multifilament textile yarn comprising a plurality of textile filaments.

[0084] Preferably, the textile filaments are made of aramid and / or polyester and / or rayon fibers.

[0085] Preferably, in any cross section of the hybrid reinforcing cord, the at least one monofilament textile thread is at least partially embedded in the filaments of the at least one multifilament textile yarn.

[0086] The Applicant believes that the hybrid reinforcing cord as described above can be used in the carcass structure of a tire for motor and / or electric vehicles, thus achieving the benefits described above.

[0087] In at least one of the aforementioned aspects, the present application can have at least one of the following preferred features.

[0088] Preferably, in any cross section of the hybrid reinforcing cord, at least 50% of the outer surface of the monofilament textile thread is arranged between or embedded in the filaments of the at least one multifilament textile yarn. In this way, the portion of the outer surface of the monofilament textile thread that would be directly exposed to the surrounding elastomeric material in each cross section of the hybrid cord will have an extension that will not compromise the excellent adhesion of the hybrid reinforcing cord to the surrounding elastomeric material.

[0089] Preferably, the hybrid reinforcing cord comprises at least one portion at which, in any cross section of the hybrid reinforcing cord, the at least one monofilament textile thread is completely embedded in the filaments of the at least one multifilament textile yarn.

[0090] Preferably, the diameter of the at least one monofilament textile thread is greater than 0.15 mm, more preferably greater than 0.20 mm.

[0091] Preferably, the diameter of the at least one monofilament textile thread is less than 0.50 mm, more preferably less than 0.40 mm.

[0092] In a preferred embodiment, the diameter of the at least one monofilament textile thread is comprised between 0.15 mm and 0.50 mm, preferably between 0.20 mm and 0.40 mm, for example equal to 0.30 mm.

[0093] The Applicant has observed that the use of multifilament textile yarns having the above-mentioned linear density values helps to best meet the requirements of providing the hybrid reinforcing cord used in the carcass structure with the required breaking load and the required partial load elongation.

[0094] Generally, it is preferred that the more the monofilament textile threads contained in each strand of the hybrid reinforcing cord, the smaller the diameter of said monofilament textile threads will be.

[0095] Preferably, the linear density of said at least one multifilament textile yarn is greater than 840 dtex, more preferably greater than 940 dtex.

[0096] Preferably, the linear density of said at least one multifilament textile yarn is lower than 2100 dtex, more preferably lower than 1840 dtex.

[0097] In a preferred embodiment, the linear density of said at least one multifilament textile yarn is comprised between 840 dtex and 2100 dtex, preferably between 940 dtex and 1840 dtex, for example equal to 1100 dtex.

[0098] The Applicant has observed that the use of multifilament textile yarns having the above-mentioned linear density values helps to best meet the requirements of providing the hybrid reinforcing cord used in the carcass structure with the required breaking load and the required partial load elongation.

[0099] Preferably, the number of threads of said at least one carcass ply is greater than 70 cords / dm, more preferably greater than 75 cords / dm.

[0100] Preferably, the number of threads of said at least one carcass ply is lower than or equal to 95 cords / dm, more preferably lower than or equal to 90 cords / dm.

[0101] In a preferred embodiment, the number of threads of said at least one carcass ply is comprised between 70 cords / dm and 95 cords / dm, preferably between 75 cords / dm and 90 cords / dm, for example equal to 85 cords / dm.

[0102] The Applicant has observed that providing the above-mentioned number of threads helps to best meet the requirement of increasing as much as possible the number of hybrid reinforcing cords provided in the carcass ply, and is compatible with the need of still providing a distance between adjacent hybrid reinforcing cords sufficient to ensure the presence of an amount of elastomeric material sufficient to ensure the required mechanical properties of the carcass structure. The Applicant believes that such distance must preferably have an extension not lower than 0.10 mm, more preferably not lower than 0.15 mm, for example equal to 0.20 mm.

[0103] Preferably, the thickness of said at least one carcass ply is greater than 0.7 mm, more preferably greater than 0.9 mm.

[0104] Preferably, said at least one carcass ply has a thickness lower than 1.5 mm, more preferably lower than 1.3 mm.

[0105] In preferred embodiments, said at least one carcass ply has a thickness comprised between 0.7 mm and 1.5 mm, preferably between 0.9 mm and 1.3 mm, for example equal to 1.1 mm.

[0106] The Applicant has observed that providing the above-mentioned thickness values helps to best meet the need of providing, in radially outer and radially inner positions with respect to the hybrid reinforcing cords of the carcass ply, layers of elastomeric material sufficient to ensure the required mechanical properties and the required geometric shape of the carcass structure. The Applicant believes that such layers must preferably have a thickness not lower than 0.10 mm, more preferably not lower than 0.15 mm, for example equal to 0.20 mm.

[0107] In some preferred embodiments, the carcass structure comprises a single carcass ply (single-ply tire). In this way, an advantageous reduction of the weight of the carcass structure (and therefore of the tire) is obtained, and therefore a significant reduction of the rolling resistance of the tire is obtained.

[0108] In other preferred embodiments, the carcass structure comprises at least two carcass plies, preferably only two carcass plies (double-ply tire), placed side by side to each other.

[0109] In this case, the reinforcing cords of the first carcass ply can be substantially parallel to the reinforcing cords of the other carcass plies or inclined at an angle smaller than 40°, preferably smaller than 35°, with respect to the reinforcing cords of the other carcass plies.

[0110] In some preferred embodiments, each hybrid reinforcing cord comprises only two strands.

[0111] Preferably, each of said two strands comprises a single monofilament textile thread.

[0112] Preferably, each of said two strands comprises a single multifilament textile yarn.

[0113] In this case, preferably, in any cross section of the hybrid reinforcing cord, at least 50% of the outer surface of each monofilament textile thread is arranged between or embedded in the filaments of the respective multifilament textile yarn. In this way, the likelihood of a portion of the outer surface of the monofilament textile thread being directly exposed to the elastomeric material is very low.

[0114] Preferably, the hybrid reinforcing cord comprises at least one portion at which, in any cross section of the hybrid reinforcing cord, each monofilament textile thread is completely embedded in the filaments of the respective multifilament textile yarn.

[0115] In other preferred embodiments, each strand comprises more than one monofilament textile thread and more than one multifilament textile yarn.

[0116] Such reinforced cord is particularly suitable for use in the carcass structure of self-supporting tires, since it has sufficient rigidity to allow a deflated tire to travel long distances (up to 100 km).

[0117] Preferably, each of said two strands comprises at least two end tips twisted together, more preferably only two end tips.

[0118] Preferably, each of said at least two end tips comprises at least one monofilament textile thread in any cross section of the hybrid reinforced cord.

[0119] Preferably, in any cross section of the hybrid reinforced cord, said at least one monofilament textile thread is at least partially embedded in the filaments of at least one multifilament textile yarn.

[0120] Preferably, each of said at least two end tips comprises a single monofilament textile thread.

[0121] Preferably, each of said at least two end tips comprises a single multifilament textile yarn.

[0122] In further preferred embodiments, each strand comprises more than one monofilament textile thread (e.g. two monofilament textile threads) and a single multifilament textile yarn.

[0123] In further embodiments, each strand comprises a single monofilament textile thread and more than one multifilament textile yarn (e.g. two multifilament textile yarns).

[0124] In further embodiments, each strand comprises more than one monofilament textile thread (e.g. two monofilament textile threads) and more than one multifilament textile yarn (e.g. two multifilament textile yarns).

[0125] In all embodiments discussed above, the polyester fibers of the monofilament textile thread are selected from polybutylene terephthalate fibers, polyethylene terephthalate fibers, polyethylene isophthalate fibers or mixtures thereof.

[0126] More preferably, the polyester fibers mentioned above are polyethylene terephthalate (PET) fibers.

[0127] In all embodiments discussed above, preferably, the filaments of said at least one multifilament textile yarn are made of aramid fibers or polyester fibers (e.g. polybutylene terephthalate fibers, polyethylene terephthalate fibers, polyethylene isophthalate fibers) or mixtures thereof.

[0128] More preferably, in case the multifilament textile yarns comprise polyester fibers, they are polyethylene terephthalate (PET) fibers.

[0129] In all embodiments, preferably the twisting pitch is greater than 1 mm, more preferably greater than 2 mm.

[0130] Preferably, the twisting pitch is less than 20 mm, more preferably less than 15 mm.

[0131] In preferred embodiments, the twisting pitch is comprised between 1 mm and 20 mm, more preferably between 2 mm and 15 mm.

[0132] Said at least one monofilament textile thread can be twisted by itself at a predetermined first twisting pitch. The Applicant has observed that such a provision helps optimizing the behavior of the reinforcing cord under fatigue.

[0133] Preferably, said first twisting pitch is equal to said predetermined twisting pitch. In this way, the embedding of the monofilament textile thread in the filaments of the corresponding multifilament textile yarn is maximized, to favor the adhesion of the reinforcing cord to the surrounding elastomeric material.

[0134] Said at least one multifilament textile yarn can be twisted by itself at a predetermined second twisting pitch or can not be twisted by itself. In case it is twisted by itself, preferably the second twisting pitch is equal to said twisting pitch. This is done to maximize the embedding of the monofilament textile thread in the filaments of the multifilament textile yarn.

[0135] In some preferred embodiments, said at least one multifilament textile yarn is substantially parallel to said at least one monofilament textile thread.

[0136] In other preferred embodiments, the filaments of said at least one multifilament textile yarn are helically wound onto the monofilament textile thread at a predetermined winding pitch, embedding said monofilament textile thread in said filaments.

[0137] Also to maximize the embedding of the monofilament textile thread in the filaments of the multifilament textile yarn, preferably said winding pitch is equal to said twisting pitch.

[0138] Preferably, the filaments of said at least one multifilament textile yarn are coated with a tacky substance, or are subjected to a chemical or physical tackifying treatment, to further improve the adhesion to the elastomeric material in which they are embedded or with which they are coated.

[0139] Preferably, the tire of the application holds one of the following speed codes according to E.T.R.T.O. standards: "T", "U", "H", "V", "Z", "W", "Y".

[0140] Preferably, the tire of the application is a self-supporting tire. BRIEF DESCRIPTION OF DRAWINGS

[0141] Further features and advantages of the tyre of the present application will become more apparent from the following detailed description of preferred embodiments thereof, with reference to the attached drawings. In such drawings:

[0142] - Figure 1 is a schematic partial half-section view of a portion of a tyre according to an embodiment of the present application;

[0143] - Figure 2 is a schematic side view of a segment of a first embodiment of a hybrid reinforcing cord used in the carcass structure of the tyre of Figure 1 ;

[0144] - Figure 3 is an enlarged schematic view of a cross-section of the hybrid reinforcing cord of Figure 1 , incorporated in a portion of the carcass structure of the tyre of Figure 2 , the cross-section being taken on section S-S drawn in Figure 2 ;

[0145] - Figure 4 is a schematic perspective view of the hybrid reinforcing cord of Figure 2 , wherein a portion of its components has been removed to show components that would otherwise be hidden;

[0146] - Figure 5 is a schematic perspective view of a second embodiment of the hybrid reinforcing cord of Figure 2 , wherein a portion of its components has been removed to show components that would otherwise be hidden;

[0147] - Figure 6 is an enlarged schematic view of a cross-section of another embodiment of a hybrid reinforcing cord usable in the carcass structure of the tyre of Figure 1 . DETAILED DESCRIPTION

[0148] For the sake of simplicity, Figure 1 only a portion of an exemplary embodiment of a tyre 100 according to the present application is shown, the remaining portion not being shown being substantially identical and arranged symmetrically with respect to the equatorial plane M-M of the tyre.

[0149] Figure 1 The tyre 100 shown is in particular an embodiment of a tyre for a four-wheeled vehicle.

[0150] Preferably, the tyre 100 is a HP or UHP tyre for high- or ultra-high- performance motor vehicles, both electric and non-electric.

[0151] In particular, according to the E.T.R.T.O. standard, the tyre 100 holds one of the following speed codes: "T", "U", "H", "V", "Z", "W", "Y".

[0152] In Figure 1 In the following, for simplicity of description, reference will be made to an embodiment of the tyre 100 comprising a single carcass ply 111 (single-ply tyre). However, it is understood that the description made in relation to the carcass ply 111 also applies to each carcass ply of a tyre comprising more than one carcass ply, unless otherwise stated. In fact, there are embodiments of the tyre 100 of the present application in which the carcass structure 101 comprises, for example, two carcass plies 111 (double-ply tyre).

[0153] The tyre 100 comprises a carcass structure 101 of the radial type, which in turn comprises at least one carcass ply 111.

[0154] In the following, for simplicity of description, reference will be made to an embodiment of the tyre 100 comprising a single carcass ply 111 (single-ply tyre). However, it is understood that the description made in relation to the carcass ply 111 also applies to each carcass ply of a tyre comprising more than one carcass ply, unless otherwise stated. In fact, there are embodiments of the tyre 100 of the present application in which the carcass structure 101 comprises, for example, two carcass plies 111 (double-ply tyre).

[0155] The carcass ply 111 comprises a plurality of reinforcing cords 10' coated with a crosslinked elastomeric material or embedded in a layer thereof. In the case where the tyre 100 is of the double-ply type, the reinforcing cords of the first carcass ply can be substantially parallel to the reinforcing cords of the other carcass ply or inclined at an angle of less than 40° with respect to the reinforcing cords of the other carcass ply.

[0156] The number of threads of the carcass ply 111 is preferably greater than 70 threads / dm and lower than or equal to 95 threads / dm, more preferably comprised between 75 threads / dm and 90 threads / dm. For example, in the aforementioned preferred embodiment of the tyre 100 of the present application, the number of threads is equal to 85 threads / dm.

[0157] The thickness of the carcass ply 111 is preferably comprised between 0.7 mm and 1.5 mm, more preferably between 0.9 mm and 1.3 mm. For example, in the aforementioned preferred embodiment of the tyre 100 of the present application, the aforementioned thickness is equal to 1.1 mm.

[0158] The carcass ply 111 has axially opposite end edges which are engaged with respective annular anchoring structures 102, called bead cores, possibly associated with elastomeric fillers 104. The area of the tyre 100 comprising the bead cores 102 and possibly the elastomeric fillers 104 forms an annular reinforcing structure 103, called "bead structure" and intended to allow the anchoring of the tyre 100 on a corresponding mounting rim, not shown.

[0159] Each annular reinforcing structure 103 is associated with the carcass structure 101 by folding (or turning up) opposite end edges of at least one carcass ply 111 around the bead core 102 and possibly the elastomeric filler 104 so as to form so-called turned-up portions 101a of the carcass structure 101.

[0160] In an embodiment, the coupling between the carcass structure 101 and the annular reinforcing structure 103 can be carried out by applying a layer (not shown in the figures) in a radially outer position with respect to the carcass ply 111. Figure 1

[0161] The wear strip 105 is arranged at each annular reinforcing structure 103 so as to surround the annular reinforcing structure 103 along the axially inner, axially outer and radially inner regions of the annular reinforcing structure 103, so as to be located between the annular reinforcing structure and the rim of the wheel when the tyre 100 is mounted on the rim. However, such a wear strip 105 can not be provided.

[0162] The tyre 100 comprises, in a radially outer position with respect to the carcass structure 101, a cross-belt structure 106 comprising at least two belt layers 106a, 106b arranged radially alongside each other with respect to each other.

[0163] The belt layers 106a, 106b comprise respectively a plurality of reinforcing cords 10a, 10b. Such reinforcing cords 10a, 10b have an orientation with an angle between 15° and 45°, preferably between 20° and 40°, with respect to the circumferential direction of the tyre 100 or with respect to the equatorial plane M-M of the tyre 100. For example, such an angle is equal to 30°.

[0164] The tyre 100 can also comprise a further belt layer (not shown) arranged between the carcass structure 101 and the radially innermost belt layer of the above-mentioned belt layers 106a, 106b, and comprising a plurality of reinforcing cords having an orientation with an angle equal to 90° with respect to the circumferential direction of the tyre 100 or with respect to the equatorial plane M-M of the tyre 100.

[0165] The tyre 100 can also comprise a further belt layer (not shown) arranged in a radially outer position with respect to the radially outermost belt layer of the above-mentioned belt layers 106a, 106b, and comprising a plurality of reinforcing cords having an orientation with an angle between 20° and 70° with respect to the circumferential direction of the tyre 100 or with respect to the equatorial plane M-M of the tyre 100.

[0166] The reinforcing cords 10a, 10b of the belt layers 106a, 106b are parallel to each other and have a crossed orientation with respect to the reinforcing cords of the other belt layer 106b, 106a.

[0167] ​In ultra-high performance tires, the belt structure 106 can be a turned-up cross-ply belt structure. Such a belt structure is made by arranging at least one belt layer on a support element and turning up opposite lateral end edges of the at least one belt layer. Preferably, a first belt layer is first placed on the support element, the support element is then radially inflated, a second belt layer is subsequently placed on the first belt layer, and finally opposite axial end edges of the first belt layer are turned up onto the second belt layer to at least partially cover the second belt layer, which is the radially outermost layer. In some cases, a third belt layer can be arranged on the second belt layer. Advantageously, turning up axial opposite end edges of a belt layer on another belt layer arranged in a radially outer position with respect to the first belt layer provides a tire with greater reactivity and responsiveness when cornering.

[0168] The tire 100 comprises, in a radially outer position with respect to the cross-ply belt structure 106, at least one zero-degree reinforcing layer 106c, commonly referred to as "zero-degree belt". The zero-degree reinforcing layer comprises reinforcing cords 10c oriented in a substantially circumferential direction. Such reinforcing cords 10c thus form an angle of a few degrees (typically less than 10°, for example between 0° and 6°) with respect to the equatorial plane M-M of the tire 100.

[0169] The reinforcing cords 10a, 10b, 10c are coated with an elastomeric material or embedded in a matrix of cross-linked elastomeric material.

[0170] A tread band 109 made of elastomeric material is applied in a radially outer position with respect to the zero-degree reinforcing layer 106c.

[0171] Corresponding sidewalls 108 made of elastomeric material are also applied on the lateral surfaces of the carcass structure 101 in axially outer positions with respect to the carcass structure 101 itself. Each sidewall 108 extends from one of the lateral edges of the tread band 109 up to the corresponding annular reinforcing structure 103.

[0172] The wear strip 105, if provided, extends at least up to the corresponding sidewall 108.

[0173] In some particular embodiments, the stiffness and integrity of the annular reinforcing structure 103 and of the sidewalls 108 can be improved, as shown and described here, by providing a reinforcing layer 120 commonly referred to as "bead chafer" or additional strip-like insert.

[0174] The bead chafer 120 is wrapped around the corresponding bead core 102 and elastomeric filler 104 so as to at least partially enclose the annular reinforcing structure 103. In particular, the bead chafer 120 encloses the annular reinforcing structure 103 along the axially inner region, the axially outer region and the radially inner region of the annular reinforcing structure 103.

[0175] The bead flippers 120 are arranged between the turned-up end edges of the carcass plies 111 and the respective annular reinforcing structures 103. Typically, the bead flippers 120 are in contact with the carcass plies 111 and the annular reinforcing structures 103.

[0176] In some specific embodiments, as shown and described here, the annular reinforcing structures 103 can also comprise a further reinforcing layer 121, commonly referred to by the terms "bead filler" or "protection strip", and having the function of increasing the stiffness and integrity of the annular reinforcing structures 103.

[0177] The bead filler 121 is associated with the respective turned-up end edge of the carcass ply 111 in an axially outer position with respect to the respective annular reinforcing structure 103 and extends radially towards the sidewall 108 and the tread band 109.

[0178] The bead flippers 120 and the bead filler 121 comprise reinforcing cords 10d (in the figures, the reinforcing cords of the bead flippers 120 are not visible) coated with an elastomeric material or embedded in a matrix of crosslinked elastomeric material.

[0179] The tread band 109 has, in its radially outer position, a rolling surface 109a intended to come into contact with the ground. Circumferential grooves (not shown in the figures) are formed on the rolling surface 109a, which are connected by transverse notches (not shown in the figures) so as to define, on the rolling surface 109a, a plurality of blocks (not shown in the figures) of various shapes and sizes. Figure 1 Figure 1 Figure 1

[0180] The sub-ply 107 is arranged between the cross-belt structure 106 and the tread band 109.

[0181] In some specific embodiments, as shown and described here, it is possible to provide, in the connection area between the sidewall 108 and the tread band 109, a strip 110 composed of an elastomeric material, commonly referred to as "mini sidewall". The mini sidewall 110 is typically obtained by co-extrusion with the tread band 109 and allows to improve the mechanical interaction between the tread band 109 and the sidewall 108.

[0182] Preferably, the end portion of the sidewall 108 directly covers the lateral edge of the tread band 109.

[0183] In the case of a tubeless tyre, as shown and described here, it is also possible to provide, in a radially inner position with respect to the carcass ply 111, a layer of rubber 112, commonly referred to as "liner", to provide the necessary impermeability to the inflation air of the tyre 100.

[0184] ​​​In the case of a self-supporting tyre, a reinforcing insert (not shown) made of elastomeric material is arranged in an axially outer position with respect to the liner 112 and in an axially inner position with respect to the sidewall 108, said reinforcing insert being configured to prevent the sidewall 108 from yielding or bulging when the tyre is deflated.

[0185] At least some of the reinforcing cords 10’ of the carcass structure 101 (preferably all the reinforcing cords 10’) are Figures 2-6 hybrid reinforcing cords 10 of the type shown in Fig. 1 and described below.

[0186] The reinforcing cords 10a, 10b, 10c and 10d can also be Figures 2-6 hybrid reinforcing cords 10 of the type shown in Fig. 1 or reinforcing cords of a different type.

[0187] With reference to Figures 2-4 , the hybrid reinforcing cord 10 comprises two strands 20a, 20b twisted together with a predetermined twist pitch P.

[0188] Preferably, the two strands 20a, 20b are identical.

[0189] As shown in Figs. 1 and 2, each strand 20a, 20b comprises a single monofilament textile thread 21a, 21b and a single multifilament textile yarn 22a, 22b defined by a plurality of filaments 23a, 23b. However, each strand 20a, 20b can comprise more than one monofilament textile thread and more than one multifilament textile yarn. Figure 3 Figure 4 In any cross-section of the reinforcing cord 10, the monofilament textile thread 21a, 21b is embedded in the filaments 23a, 23b of the multifilament textile yarn 22a, 22b of the respective strand 20a, 20b.

[0190] In the embodiment shown in Figs. 1 and 2, the monofilament textile thread 21a, 21b is completely embedded in the filaments 23a, 23b of the multifilament textile yarn 22a, 22b of the respective strand 20a, 20b in any cross-section of the reinforcing cord 10, and therefore the aforementioned filaments 23a, 23b are arranged around the respective monofilament textile thread 21a, 21b so as to completely surround the monofilament textile thread 21a, 21b.

[0191] In the embodiment shown in Figs. 1 and 2, the monofilament textile thread 21a, 21b is completely embedded in the filaments 23a, 23b of the multifilament textile yarn 22a, 22b of the respective strand 20a, 20b in any cross-section of the reinforcing cord 10, and therefore the aforementioned filaments 23a, 23b are arranged around the respective monofilament textile thread 21a, 21b so as to completely surround the monofilament textile thread 21a, 21b. Figure 3 Figure 4 In the embodiment shown in Figs. 1 and 2, the monofilament textile thread 21a, 21b is completely embedded in the filaments 23a, 23b of the multifilament textile yarn 22a, 22b of the respective strand 20a, 20b in any cross-section of the reinforcing cord 10, and therefore the aforementioned filaments 23a, 23b are arranged around the respective monofilament textile thread 21a, 21b so as to completely surround the monofilament textile thread 21a, 21b.

[0192] Therefore, in Figure 2 , the monofilament textile thread 21a, 21b is not visible, since it is completely covered by the filaments 23a, 23b of the multifilament textile yarn 22a, 22b of the respective strand 20a, 20b.

[0193] Although Figures 2-4 embodiments (as well as the embodiments discussed below)​​Figure 5 Particularly preferred is an embodiment in which the monofilament textile threads 21a, 21b are fully embedded in the filaments 23a, 23b of the multifilament textile yarns 22a, 22b of the respective strand 20a, 20b in any cross section of the reinforcing cord 10, but other embodiments are likewise preferred in which the monofilament textile threads 21a, 21b are only partially embedded in the filaments 23a, 23b of the multifilament textile yarns 22a, 22b of the respective strand 20a, 20b in any cross section of the reinforcing cord 10, and particularly in which at least 50% of the outer surface of the monofilament textile threads 21a, 21b is embedded in the filaments 23a, 23b of the multifilament textile yarns 22a, 22b of the respective strand 20a, 20b.

[0194] The monofilament textile threads 21a, 21b extend along the longitudinal direction A, as shown in Figure 2 .

[0195] The mutual arrangement of the monofilament textile threads 21a, 21b and the filaments 23a, 23b of the multifilament textile yarns 22a, 22b along the longitudinal direction A can be such that the monofilament textile threads 21a, 21b extend substantially parallel to the filaments 23a, 23b of the multifilament textile yarns 22a, 22b of the respective strand 20a, 20b, as shown in Figure 4 , or such that the filaments 23a, 23b of the multifilament textile yarns 22a, 22b are helically wound on the respective monofilament textile thread 21a, 21b with a predetermined winding pitch W, said predetermined winding pitch preferably being equal to the twisting pitch P.

[0196] In the latter case, the twisting direction of the two strands 20a, 20b is preferably the same as the direction of the winding of the filaments 23a, 23b of the multifilament textile yarns 22a, 22b on the monofilament textile threads 21a, 21b, but can also be the opposite direction.

[0197] The twisting pitch P is preferably comprised between 1 mm and 20 mm, more preferably between 2 mm and 15 mm, for example equal to 12.5 mm.

[0198] Figure 5 An embodiment of a hybrid reinforcing cord 10 is shown, which differs from the embodiment shown in Figures 2-4 only in that the monofilament textile threads 21a, 21b are twisted themselves with a predetermined twisting pitch T.

[0199] Preferably, the twisting pitch T is equal to the twisting pitch P.

[0200] The twisting direction of the monofilament textile threads 21a, 21b can be the same or opposite to the twisting direction of the two strands 20a, 20b.

[0201] The monofilament textile threads 21a, 21b are made of polyester fibers, for example polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), or mixtures thereof.

[0202] The filaments 23a, 23b of each multifilament textile thread 22a, 22b are made of aramid fibers, or polyester fibers, for example polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), or rayon fibers, or any mixture of the above-mentioned fibers.

[0203] Regardless of the specific type of textile material used for the filaments 23a, 23b of the multifilament textile threads 22a, 22b, such material is suitably tackified on the surface so as to provide sufficient adhesion to the surrounding elastomeric material. Typically, the tackifying treatment can be carried out by coating with a tacky substance or by chemical or physical treatment.

[0204] For example, the tackifying treatment is carried out by immersing the hybrid reinforcing cord 10 in a solution comprising a tacky substance after the two strands 20a, 20b have been twisted together.

[0205] The diameter of the monofilament textile threads 21a, 21b is preferably comprised between 0.15 mm and 0.50 mm, more preferably between 0.20 mm and 0.40 mm. For example, in the preferred embodiment of the carcass structure 101 of the tire 100, the above-mentioned diameter is equal to 0.30 mm.

[0206] The linear density of the multifilament textile threads 22a, 22b is preferably comprised between 840 dtex and 2100 dtex, preferably between 940 dtex and 1840 dtex. For example, in the preferred embodiment of the carcass structure 101 of the tire 100, the above-mentioned linear density is equal to 1100 dtex.

[0207] In the preferred embodiment of the carcass structure 101 of the tire 100, the multifilament textile threads 22a, 22b are arranged in a plurality of layers, each layer being formed by a plurality of multifilament textile threads 22a, 22b. Figures 2-5In the preferred embodiment of the hybrid reinforcing cord 10 shown and used in the above preferred embodiment of the carcass structure 101 of the tyre 100, the hybrid reinforcing cord 10 has two strands 20a, 20b twisted together. In each strand 20a, 20b, the monofilament textile thread 21a, 21b is made of PET fibre and has a diameter equal to 0.30 mm, while the multifilament textile yarn 22a, 22b is made of aramid and has a linear density equal to 1110 dtex. In this hybrid reinforcing cord 10, for example, 310 twists have been imparted to the multifilament textile yarn 22a, 22b and to the monofilament textile thread 21a, 21b of each of the two strands 20a, 20b in the right-hand direction (Z), while 180 twists have been imparted to each of the two strands 20a, 20b in the left-hand direction (S). This reinforcing cord can therefore be indicated as (PET 0.30 + AR 1100) x 2 310Z / 180S.

[0208] Figures 2-5 Another preferred embodiment of the hybrid reinforcing cord 10 shown differs from the above-described embodiment only in that the multifilament textile yarn 22a, 22b is made of rayon and has a linear density equal to 1840 dtex. In this hybrid reinforcing cord 10, for example, 300 twists or 310 twists have been imparted to the multifilament textile yarn 22a, 22b and to the monofilament textile thread 21a, 21b of each of the two strands 20a, 20b in the right-hand direction (Z), while 180 twists have been imparted to each of the two strands 20a, 20b in the left-hand direction (S). This reinforcing cord can therefore be indicated as (PET 0.30 + RY 1840) x 2 300Z / 180S and (PET 0.30 + RY 1840) x 2 310Z / 180S, respectively.

[0209] Figures 2-5 Another preferred embodiment of the hybrid reinforcing cord 10 shown differs from the above-described embodiment only in that the multifilament textile yarn 22a, 22b made of rayon has a linear density equal to 1220 dtex. In this hybrid reinforcing cord 10, for example, 300 twists have been imparted to the multifilament textile yarn 22a, 22b and to the monofilament textile thread 21a, 21b of each of the two strands 20a, 20b in the right-hand direction (Z), while 150 twists have been imparted to each of the two strands 20a, 20b in the left-hand direction (S). This reinforcing cord can therefore be indicated as (PET 0.30 + RY 1220) x 2 300Z / 150S.

[0210] In Figures 2-5In another preferred embodiment of the hybrid reinforcing cord 10 shown, the two strands 20a, 20b are not identical. For example, while the monofilament textile threads 21a, 21b are made of PET fiber and have a diameter equal to 0.30 mm in both strands 20a, 20b, the multifilament textile yarn 22a of the strand 20a is made of rayon and has a linear density equal to 1220 dtex, and the multifilament textile yarn 22b of the other strand 20b is made of rayon and has a linear density equal to 1840 dtex. In this hybrid reinforcing cord 10, for example, 300 twists have been imparted to the multifilament textile yarn 22a, 22b and to the monofilament textile thread 21a, 21b of each of the two strands 20a and 20b in the right-hand direction (Z), while 150 twists have been imparted to each of the two strands 20a, 20b in the left-hand direction (S). This reinforcing cord can therefore be indicated with (PET 0.30 + RY 1220) + (PET 0.30 + RY 1840) 300Z / 150S.

[0211] The Applicant has also manufactured hybrid reinforcing cords by twisting together three strands according to the present application. For example, in an embodiment of this type of hybrid reinforcing cord, each strand comprises a monofilament textile thread made of PET fiber and having a diameter equal to 0.30 mm and a multifilament textile yarn made of rayon and having a linear density equal to 1220 dtex, for example. In this hybrid reinforcing cord, for example, 300 twists have been imparted to the multifilament textile yarn and to the monofilament textile thread of each of the three strands in the right-hand direction (Z), while 150 twists have been imparted to each of the three strands in the left-hand direction (S). This reinforcing cord can therefore be indicated with (PET 0.30 + RY 1220) x 3 300Z / 150S.

[0212] Figure 6 Another preferred embodiment of a hybrid reinforcing cord 10 is shown, which can be used in the carcass structure 101 of a tire 100 according to the present application, preferably of the self-supporting type.

[0213] Figure 6 The hybrid reinforcing cord 10 of Figures 2-4 differing from the hybrid reinforcing cord shown in Figure 6 The blank space at the center of the hybrid reinforcing cord 10 shown in

[0214] The strand 20a comprises two end tips 20a' twisted together with a twist pitch that can be the same as or different from the twist pitch of the two strands 20a, 20b. Similarly, the strand 20b comprises two end tips 20b' twisted together with a twist pitch that can be the same as or different from the twist pitch of the two end tips 20a'.

[0215] Each of the two end tips 20a' of the strand 20a comprises a monofilament textile thread 21a at least partially embedded in the filaments 23a of the multifilament textile yarn 22a. Similarly, each of the two end tips 20b' of the strand 20b comprises a monofilament textile thread 21b at least partially embedded in the filaments 23b of the multifilament textile yarn 22b.

[0216] In Figure 6 In the preferred embodiment of the hybrid reinforcing cord 10 illustrated, the monofilament textile threads 21a, 21b are made of PET fiber and have a diameter equal to 0.30 mm, while the multifilament textile yarns 22a, 22b are made of aramid and have a linear density equal to 1110 dtex. In such a hybrid reinforcing cord 10, for example, 310 twists have been applied to the end tips 20a', 20b' of each strand 20a and 20b in the right-hand direction (Z), while 280 twists have been applied to each of the two strands 20a, 20b in the left-hand direction (S). The reinforcing cord can therefore be indicated as 2x2 (PET 0.30 + AR 1100) 310Z / 280S.

[0217] Comparative tests

[0218] The Applicant has carried out various comparative tests, which were suitable for comparing the performance of the tires manufactured according to the present application with the performance of reference tires successfully produced and commercialized by the Applicant.

[0219] Self-supporting tires

[0220] In a first series of tests aimed at evaluating the suitability of the tires of the present application for use as self-supporting tires and at meeting the constant need to reduce the emissions of CO2 into the atmosphere (hereinafter referred to as "environmental need"), the Applicant compared a reference self-supporting tire of the type 245 / 45R18 100 Y XL, which is commercialized under the trademark Cinturato P7 TMRUNFLAT and whose carcass structure comprises reinforcing cords made of rayon and, in the sidewall, a reinforcing insert made of elastomeric material with high modulus, whose thickness is equal to 7 mm (hereinafter this tire is indicated as PI), with the following two tires:

[0221] - a tire that differs from the tire PI only in that it has, in the sidewall, a reinforcing insert made of elastomeric material whose thickness is smaller, equal to 6 mm (hereinafter this tire is indicated as P2);

[0222] - a tyre manufactured according to the application, which differs from the tyre P1 only in that it has, in its carcass structure, mixed reinforcing cords as defined above, and in the sidewall has a reinforcing insert made of an elastomeric material having a low modulus, therefore a low hysteresis, with a thickness equal to 8 mm (this tyre is indicated below with INV).

[0223] The reinforcing cords of the carcass structure of the tyres P1 and P2 are of the type RY1840x2 (48Zx48S), i.e. they each comprise two twisted together multifilament textile yarns made of rayon, in which 48 twists have been applied to each multifilament textile yarn in the right-hand direction (Z) and 48 twists have been applied to the reinforcing cord in the left-hand direction (S). This reinforcing cord is arranged in the carcass structure with a number equal to 120 cords / dm.

[0224] The mixed reinforcing cords of the carcass structure of the tyre INV are of the type (PET0.30+AR1680)x2310Z / 180S, i.e. they each comprise two strands, each strand comprising two monofilament textile threads made of PET with a diameter equal to 0.30 mm and a multifilament textile yarn made of aramid with a linear density equal to 1689 dte. The two strands are twisted together by applying 310 twists in the right-hand direction (Z), while each multifilament textile yarn is twisted to the respective monofilament textile thread by applying 180 twists in the left-hand direction (S). This mixed reinforcing cord is arranged in the carcass structure with a number equal to 85 cords / dm.

[0225] The applicant has measured the rolling resistance of the tyres P1, P2 and INV according to the EU regulation no. 1235 / 2011 and obtained the values given in Table 1 below.

[0226] P1 P2 INV 6.3 6.1 6.1

[0227] Table 1

[0228] The applicant has therefore verified that the tyres P2 and INV meet the environmental requirements described above. The good performance of the tyre P2 is expected due to the reduction in the thickness of the reinforcing insert made of elastomeric material, while the good performance of the tyre INV confirms the applicant's intuition that it is possible to reduce the rolling resistance of a tyre by increasing the stiffness of its carcass structure and reducing the hysteresis.

[0229] In order to evaluate the suitability of the tyres P2 and INV for use as self-supporting tyres, the applicant has carried out outdoor track tests by mounting the tyres P1, P2 and INV on the left rear wheel of a BMW series 5 and applying a vertical load of 570 kg on the above-mentioned wheel.

[0230] The Applicant has verified that, while the tyre P2 allows to travel for a few kilometres in the event of tyre deflation, it is much less than the tyre P1 and, for example, does not allow to use the tyre P2 as a self-supporting tyre, but the distance that the tyre INV allows to travel in the event of tyre deflation is absolutely comparable to the distance travelled by the tyre P1.

[0231] Therefore, such tests have verified that the tyre of the application is suitable both for being used as a self-supporting tyre and for meeting the need of reducing the emissions of CO2 into the atmosphere.

[0232] Standard tyre

[0233] In a second series of tests, which were carried out on standard tyres, i.e. non self-supporting tyres, and which were aimed at evaluating the performance of the tyre of the application, the Applicant compared a reference tyre of the type 245 / 45 R17 91 Y XL (hereinafter this tyre is indicated with P1*) commercialized with the trademark Cinturato P7™ and whose carcass structure comprises reinforcing cords made of rayon and a rigid tread band, with a tyre manufactured according to the application (hereinafter this tyre is indicated with INV*). The tyre manufactured according to the application differs from the tyre P1* only in that it has, in its carcass structure, mixed reinforcing cords as defined above and a tread band which is less rigid than the tread band of the tyre P1*.

[0234] The reinforcing cords of the carcass structure of the tyre P1* are the same as those described above with reference to the tyres P1 and P2. Such reinforcing cords are arranged in the carcass structure with a number of threads equal to 120 cords / dm.

[0235] The mixed reinforcing cords of the carcass structure of the tyre INV* are the same as those described above with reference to the tyre INV. Such mixed reinforcing cords are arranged in the carcass structure with a number of threads equal to 85 cords / dm.

[0236] The reference tyre is a tyre appreciated by the customers for its excellent driving and braking performance on dry and wet road surfaces.

[0237] The choice of providing, in the tyre of the application, a tread band which is less rigid than the tread band of the reference tyre is aimed at compensating the greater rigidity of the carcass structure of the tyre of the application with respect to the carcass structure of the reference tyre. The Applicant indeed intended to carry out a comparative test based on the same vertical rigidity.

[0238] The tyres P1* and INV* were mounted on a Mini Cooper S, the front tyres were inflated to 2.6 bar and the rear tyres were inflated to 2.2 bar, and were subjected to a series of test drives of a race track lap.

[0239] The judgement provided by the test driver is given in the following table 2, in which the symbol "=" indicates a good judgement and the symbol "+" indicates an improvement with respect to the reference tyre.

[0240]

[0241] Table 2

[0242] Table 2 shows how the tyre of the application has provided improved results with respect to already excellent results of the reference tyre in all performance classes, without any deterioration in the other classes.

[0243] In the following table 3 some data detected during a lap of the race track using the tyres P1* and INV* and using the reference tyre are given, where also in this case the symbol "=" indicates a quite excellent value obtained using the reference tyre, the symbol "+" indicates an improvement with respect to the reference tyre.

[0244]

[0245] Table 3

[0246] The data of table 3 show the excellent performance of the tyre of the application in braking on dry pavement, braking on wet pavement and time spent to complete a lap on wet pavement. The excellent performance during braking is the result of the possibility of using a tread band less rigid than that of the reference tyre in the tyre of the application. This is due to the greater rigidity of the carcass structure of the tyre of the application with respect to the carcass structure of the reference tyre.

[0247] The application has been described with reference to some preferred embodiments. Different changes can be made to the above-described embodiments, while remaining still within the protection scope of the application, as defined by the following claims.

Claims

1. Tyre (100) for vehicle wheels, comprising a carcass structure (101) comprising at least one carcass ply (111) having a plurality of hybrid reinforcing cords (10), each of said hybrid reinforcing cords (10) comprising at least two strands (20a, 20b) twisted together with a predetermined twisting pitch (P), wherein each of said at least two strands (20a, 20b) comprises: - at least one monofilament textile thread (21a, 21b) made of polyester fibers, wherein said monofilament textile thread (21a, 21b) is a single elongated element consisting of a single textile filament; - at least one multifilament textile yarn (22a, 22b) comprising a plurality of textile filaments (23a, 23b) made of aramid and / or polyester and / or rayon fibers, wherein said multifilament textile yarn (22a, 22b) is an elongated element consisting of an aggregation of a plurality of textile filaments; wherein, in any cross section of said hybrid reinforcing cord (10), said at least one monofilament textile thread (21a, 21b) is at least partially embedded in said filaments (23a, 23b) of said at least one multifilament textile yarn (22a, 22b).

2. Tyre (100) according to claim 1, wherein, in any cross section of at least one segment of said hybrid reinforcing cord (10), said at least one monofilament textile thread (21a, 21b) is completely embedded in said filaments (23a, 23b) of said at least one multifilament textile yarn (22a, 22b).

3. Tyre (100) according to claim 1, wherein said at least one monofilament textile thread (21a, 21b) has a diameter comprised between 0.15 mm and 0.50 mm.

4. Tyre (100) according to claim 1, wherein said at least one multifilament textile yarn (22a, 22b) has a linear density comprised between 840 dtex and 2100 dtex.

5. Tyre (100) according to claim 1, wherein said at least one carcass ply (111) has a number of cords greater than 70 cords / dm and lower than or equal to 95 cords / dm.

6. Tyre (100) according to claim 1, wherein said at least one carcass ply (111) has a thickness comprised between 0.7 mm and 1.5 mm.

7. Tyre (100) according to claim 1, wherein said carcass structure (101) comprises a single carcass ply (111).

8. Tyre (100) according to claim 1, wherein each hybrid reinforcing cord (10) comprises only two strands (20a, 20b).

9. Tyre (100) according to claim 8, wherein each of said two strands (20a, 20b) comprises a single monofilament textile thread (21a, 21b) and a single multifilament textile yarn (22a, 22b).

10. Tyre (100) according to claim 1, wherein each of said two strands (20a, 20b) comprises at least two end tips (20a', 20b') twisted together, wherein each of said at least two end tips (20a', 20b') comprises, in any cross section of said hybrid reinforcing cord (10), at least one monofilament textile thread (21a, 21b) at least partially embedded in said filaments (23a, 23b) of said at least one multifilament textile yarn (22a, 22b).

11. Tyre (100) according to claim 10, wherein each of said at least two end tips (20a', 20b') comprises a single monofilament textile thread (21a, 21b) and a single multifilament textile yarn (22a, 22b).

12. Tyre (100) according to claim 10, wherein each of said two strands (20a, 20b) comprises only two end tips (20a', 20b').

13. Tyre (100) according to claim 1, wherein said tyre (100) holds one of the following speed codes according to E.T.R.T.O. standards: "T", "U", "H", "V", "Z", "W", "Y".

14. Tyre (100) according to claim 1, wherein said tyre (100) is a self-supporting tyre.

15. Hybrid reinforcing cord (10) comprising at least two strands (20a, 20b) twisted together with a predetermined twist pitch (P), wherein each of said at least two strands (20a, 20b) comprises: - at least one monofilament textile thread (21a, 21b) made of polyester fibre, wherein said monofilament textile thread (21a, 21b) is a single elongated element consisting of a single textile filament; - at least one multifilament textile yarn (22a, 22b) comprising a plurality of textile filaments (23a, 23b) made of aramid and / or polyester and / or rayon fibre, wherein said multifilament textile yarn (22a, 22b) is an elongated element consisting of an aggregation of a plurality of textile filaments; wherein, in any cross section of said hybrid reinforcing cord (10), said at least one monofilament textile thread (21a, 21b) is at least partially embedded in said filaments (23a, 23b) of said at least one multifilament textile yarn (22a, 22b).

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