FR3161387A1 - Tire with reduced undercut and quiet tread - Google Patents

Abstract

The tire has a mean radial distance E1m between: - the surface (100) passing through the radially innermost point of the deepest cutout (26, 28) and substantially parallel to the tread surface (16), and - the radially outer surface (102) passing through the radially outermost points of the radially outermost reinforcing elements (720) among the reinforcing elements of the radially outermost layer (72) such that E1m ≤ 2.0 mm. The first axially lateral portion comprises a linear density DR1 of first transverse grooves and a linear density DI1 of first transverse incisions satisfying DR1 ≤ 0.43 cm-1 and DR1 + DI1 ≥ 0.45 cm-1. Figure for abstract: Fig 4

Description

Tire featuring a reduced undercut and a quiet tread

The present invention relates to a tire, particularly for passenger vehicles. A tire is defined as a band designed to form a cavity by cooperating with a support element, for example a rim, this cavity being capable of being pressurized to a pressure greater than atmospheric pressure. A tire according to the invention has a substantially toroidal structure of revolution around a principal axis of the tire.

We are familiar with the state of the art for a tire as described in WO2019/102148. Despite its excellent performance, it has been noted that this tire generates external noise and its wet grip performance could be improved. Furthermore, in the ongoing pursuit of reduced vehicle fuel consumption, efforts are being made to reduce tire rolling resistance.

The invention aims to reduce external noise without degrading rolling resistance and to improve grip on wet surfaces.

To this end, the invention relates to a tire comprising a crown including a tread and a crown reinforcement arranged radially inside the tread,
the apex reinforcement comprising a radially outermost layer and including reinforcing elements embedded in a polymer matrix,
the tread comprising principal circumferential cutouts having a depth greater than or equal to 50% of the tread height comprising first and second principal circumferential cutouts axially external arranged axially on either side of the median plane of the tire, the first and second principal circumferential cutouts axially external being the outermost principal circumferential cutouts axially of the tread,
the tread comprising:
- the first and second axially lateral portions of the tread arranged axially outside each of the first and second main axially external circumferential cutouts, respectively
an axially central portion of the tread extending from the first axially lateral portion of the tread to the second axially lateral portion of the tread,
the average radial distance E1m in the axially central portion of the tread between:
- the surface passing through the radially innermost point of the deepest cut made in the axially central portion of the tread and substantially parallel to the tread surface, and
- the radially outer surface passing through the radially outermost points of the radially outermost reinforcing elements among the reinforcing elements of the radially outermost layer arranged vertically above the axially central portion of the tread,
is such that E1m ≤ 2.0 mm,
at least the first axially lateral portion includes initial transverse cutouts formed at least partially within the first axially lateral portion comprising:
- the first transverse grooves,
the first transverse incisions having a width strictly less than the width of the first transverse grooves,
the linear density DR1 of first transverse grooves being defined by the ratio of the total number of first transverse grooves formed at least in part in the first axially lateral portion to the circumference of the tire measured on the median plane and inflated to 2.5 bars,
the linear density DI1 of first transverse incisions being defined by the ratio of the total number of first transverse incisions made at least partially in the first axially lateral portion to the circumference of the tire measured on the median plane and inflated to 2.5 bars,
DR1 and DI1 satisfy DR1 ≤ 0.43 cm-1 and DR1 + DI1 ≥ 0.45 cm-1.

The tire according to the invention makes it possible to reduce external noise without degrading rolling resistance and to improve grip on wet ground compared to that described in WO2019/102148.

To reduce rolling resistance, the inventors designed a tire in which the average radial distance E1m is relatively small. This allows for a reduction in the thickness of material between the two surfaces described above, thereby reducing the shear stress between the tread and the crown reinforcement and thus reducing heat dissipation in the tire crown. However, the inventors discovered that this relatively small average radial distance E1m has the drawback of stiffening the tire crown, which in turn generates more noise. Indeed, under impact conditions such as those occurring when the tread contacts the road surface, a relatively rigid structure generates more noise than a relatively soft structure with a relatively large average radial distance E1m.

To compensate for this increased noise generated by the tire's crown, the inventors of the invention developed a tread pattern that achieves lower noise levels compared to the tire described in WO2019/102148, independently of the reduced rolling resistance resulting from the relatively small average radial distance E1m, and while improving wet grip. Indeed, the inventors understood that wet grip is directly proportional to the number of transverse cuts. However, too many transverse cuts, especially if they are too wide, lead to an increase in external noise generated by the tire. Thus, the invention proposes to provide a large number of transverse cuts and to distribute this large number between, on the one hand, transverse grooves whose relatively large width allows them to contribute mainly to the adhesion on wet ground and, on the other hand, transverse incisions whose smaller width allows them to generate less noise than the transverse grooves while still guaranteeing a significant contribution to the adhesion on wet ground.

The determination of the average radial distance E1m is carried out in the axially central portion of the tread by measuring, between surfaces, several axially distributed radial distances across the axial width of the axially central portion of the tread. For example, a distance is measured every centimeter along the axial direction, starting from the first and second axial edges of the axially central portion of the tread. Obviously, if the outermost radial point of the outermost reinforcing element is radially outside the surface passing through the innermost radial point of the deepest cut or cut and substantially parallel to the tread surface, the measured radial distance is considered negative. Conversely, and in the vast majority of cases, if the outermost radially point of the outermost radially point of the reinforcement element is radially inside the surface passing through the innermost radially point of the deepest cutout or cutout and substantially parallel to the running surface, the measured radial distance is considered positive.

These measurements will be taken in several equally spaced meridian planes around the circumference of the tire, for example, in four meridian planes. The radial distances thus measured will then be averaged to obtain the average radial distance E1m.

Radial distance between two surfaces means the straight distance between a point on one of the surfaces and its projection onto the other surface along the radial direction of the tire.

By the vertical of the axially central portion of the tread, we mean the radially outer surface resulting from the projection in the radial direction of said axially central portion of the tread onto the radially outer surface passing through the outermost radial points of the outermost radially outer reinforcing elements among the reinforcing elements of the outermost radially layer.

Conventionally, the tread surface is axially delimited by first and second axial edges, which coincide respectively with the first and second axial edges of the tread. The first and second axial edges are determined on a tire mounted on a nominal rim and inflated to the nominal pressure as defined in the ETRTO 2023 standard manual. The first and second axial edges are positioned on either side of the tire's median plane and are formed by lines substantially parallel to the tire's circumferential direction. If there is a clear boundary between the tread surface and the rest of the tire, the first and second axial edges are easily determined. If the tread surface is continuous with the outer surfaces of the tire sidewalls, the first and second axial edges are usually determined by loading the tire to 80% of its load capacity according to the ETRTO 2023 standard manual, and the first and second axial edges are identified as the axial limits of the tread in contact with the ground.

A matrix is said to be polymeric because it is based on a polymeric composition, this polymeric composition being able to include one or more polymers, for example chosen from thermoplastic polymers, thermosetting polymers, elastomers, thermoplastic elastomers, but also fillers and other components usually used in the field of tire compositions, in particular compositions for embedding reinforcement elements.

Preferably, the polymer matrix is an elastomeric matrix. An elastomeric matrix is defined as a matrix exhibiting elastomeric behavior in the crosslinked state. Such a matrix is advantageously obtained by crosslinking a composition comprising at least one elastomer and at least one other component. Preferably, the composition comprising at least one elastomer and at least one other component includes an elastomer, a crosslinking system, and a filler. The compositions used for these layers are conventional compositions for calendering reinforcements, typically based on natural rubber or another diene elastomer, a reinforcing filler such as carbon black, a vulcanizing system, and standard additives. The adhesion between the wire reinforcement elements and the matrix in which they are embedded is ensured for example by a standard adhesive composition, for example an RFL type glue or equivalent glue such as for example described in WO2013017421 or WO2017168109.

A reinforcing element is defined as an element that provides mechanical reinforcement to the polymer matrix in which it is embedded. Preferably, each reinforcing element is wire-like, meaning that each element has a length at least 10 times greater than the longest dimension of its cross-section, regardless of the cross-section's shape: circular, elliptical, oblong, polygonal, and in particular rectangular, square, or oval. In the case of a rectangular cross-section, the wire-like reinforcing element is in the form of a strip.

A cutout or a portion of a cutout has two main characteristic dimensions: a width and a curvilinear length such that the curvilinear length is at least twice the width. A cutout or a portion of a cutout is therefore delimited by at least two main lateral faces determining its curvilinear length and connected by a base, the two main lateral faces being separated from each other by a non-zero distance, called the width of the cutout or portion of the cutout.

The principal direction of a cut is the direction along which the curve equidistant from each edge of the cut to the radial dimension of the running surface passes. The curvilinear length is the length measured along this curve equidistant from each edge of the cut to the radial dimension of the running surface, between each end of the cut. The mean direction is the shortest curve joining the two ends of the cut.

The width of a cut or portion of a cut on a new tire is the maximum distance between the two principal sidewalls measured, by default, if the cut or portion of the cut does not include a chamfer, at a radial dimension coinciding with the tread surface, and by default, if the cut or portion of the cut includes a chamfer, at the outermost radial dimension of the cut or portion of the cut and radially inner dimension of the chamfer. The width is measured substantially perpendicular to the principal sidewalls. If a width other than the default width is specified, for example, a width at a particular dimension, the width is equal to the distance between the two principal sidewalls at the particular dimension of the cut or portion of the cut.

The depth of a cut or portion of a cut on a new tire is the maximum radial distance between the bottom of the cut or portion and its projection onto the ground during tire movement. The maximum depth of cuts is called the tread depth. Preferably, the maximum depth of the main circumferential cuts is called the tread depth. Thus, preferably, the deepest cut in the tread is a main circumferential cut.

A cutout or a portion of a cutout can be transverse or circumferential.

A cut or cross-section is such that the cut extends along an average direction forming an angle strictly greater than 30°, preferably greater than or equal to 45°, with the circumferential direction of the tire, i.e., forming an angle less than or equal to 60°, preferably strictly less than 45°, with the axial direction of the tire. A cut or cross-section may be continuous, i.e., not interrupted by a tread block or another cut, such that the two principal lateral faces determining its length are uninterrupted along the length of the cross-section or cross-section. A cut or cross-section may also be discontinuous, i.e., interrupted by one or more tread blocks and/or one or more cuts, such that the two principal lateral faces determining its length are interrupted by one or more tread blocks and/or one or more cuts.

A cut or circumferential portion is such that the cut or portion extends along an average direction forming an angle of 30° or less, preferably 10° or less, with the circumferential direction of the tire, i.e., forming an angle strictly greater than 60°, preferably strictly greater than 80°, with the axial direction of the tire. In the case of a continuous circumferential cut, the two ends coincide and are joined by a curve making a complete rotation of the tire. A cut or circumferential portion can be continuous, i.e., not interrupted by a tread block or another cut, so that the two principal lateral faces determining its length are uninterrupted over the entire circumference of the tire. A circumferential cut can also be discontinuous, that is to say interrupted by one or more blocks of carving and/or one or more cuts so that the two main lateral faces determining its length are interrupted by one or more blocks of carving and/or one or more cuts over the whole of a turn of the tire.

The tire according to the invention has a substantially toroidal shape around an axis of revolution substantially coinciding with the axis of rotation of the tire. This axis of revolution defines three directions classically used by those skilled in the art: an axial direction, a circumferential direction, and a radial direction.

Axial direction refers to the direction substantially parallel to the axis of revolution of the tire, that is, the axis of rotation of the tire.

By circumferential direction, we mean the direction which is substantially perpendicular to both the axial direction and to a radius of the tire (in other words, tangent to a circle whose center is on the axis of rotation of the tire).

By radial direction, we mean the direction along a radius of the tire, that is to say any direction intersecting the axis of rotation of the tire and substantially perpendicular to this axis.

By median plane of the tire (denoted M), we mean the plane perpendicular to the axis of rotation of the tire which is located at mid-axial distance of the two ribs and which passes through the axial midpoint of the crown reinforcement.

The circumferential equatorial plane of a tire, in a meridional cross-section, is defined as the plane passing through the tire's equator, perpendicular to the median plane and the radial direction. The tire's equator, in a meridional cross-section (a plane perpendicular to the circumferential direction and parallel to the radial and axial directions), is the axis parallel to the tire's axis of rotation and located equidistant between the outermost radial point of the tread intended to be in contact with the ground and the innermost radial point of the tire intended to be in contact with a support, such as a rim.

By meridian plane, we mean a plane parallel to the axis of rotation of the tire and containing the axis of rotation of the tire and perpendicular to the circumferential direction.

Radially inside and radially outside refer to the area closest to the tire's axis of rotation and further from it, respectively. Axially inside and axially outside refer to the area closer to the tire's median plane and further from it, respectively.

The bead is the portion of the tire designed to allow the tire to be attached to a mounting surface, such as a wheel with a rim. Each bead is specifically designed to make contact with a hook on the rim, enabling it to be secured.

Any range of values designated by the expression "between a and b" represents the range of values from more than a to less than b (i.e., bounds a and b excluded) while any range of values designated by the expression "from a to b" means the range of values from a to b (i.e., including the strict bounds a and b).

Unless otherwise stated, any angle made between two directions is the smallest of the angles made by those two directions with each other.

In preferred embodiments of the invention, the tires are intended for passenger vehicles as defined in the European Tyre and Rim Technical Organisation (ETRTO) standard, 2023. Such a tire has a cross-section in a meridional plane characterized by a section height H and a nominal section width or bead size S as defined in the European Tyre and Rim Technical Organisation (ETRTO) standard, 2023, such that the H/S ratio, expressed as a percentage, is at most 90 and at least 20, and the nominal section width S is at least 115 mm and at most 385 mm. Furthermore, the hook diameter D, defining the diameter of the tire's mounting rim, is at least 12 inches and at most 30 inches.

In preferred embodiments of the invention, the tires are summer tires. By summer, we mean tires that are neither all-season or four-season tires, nor winter tires.

Winter tires are identified by the M+S marking (M+S stands for "Mud + Snow") and/or the 3PMSF marking (3PMSF stands for "3 Peak Mountain Snow Flake"). All-season tires, due to their performance on snow, also display the M+S and/or 3PMSF markings. Summer tires, however, do not have the M+S or 3PMSF markings.

In advantageous but optional embodiments, the second axially lateral portion includes second transverse cutouts formed at least partially in the second axially lateral portion comprising:
- the second transverse grooves, and
- second transverse incisions with a width strictly less than the width of the second transverse grooves,
the linear density DR2 of second transverse grooves being defined by the ratio of the total number of second transverse grooves formed at least in part in the second axially lateral portion to the circumference of the tire measured on the median plane and inflated to 2.5 bars,
the linear density DI2 of second transverse incisions being defined by the ratio of the total number of second transverse incisions made at least partially in the second axially lateral portion to the circumference of the tire measured on the median plane and inflated to 2.5 bars,
DR2 and DI2 satisfy DR2 ≤ 0.43 cm-1 and DR2 + DI2 ≥ 0.45 cm-1.

Thus, we take advantage of the two axially lateral portions to reduce the noise generated by the tire.

In advantageous but optional embodiments, each first and/or second transverse groove has a width greater than or equal to 1.6 mm, preferably 1.8 mm and more preferably 2.0 mm.

In advantageous but optional embodiments, each first and/or second transverse groove has a width less than or equal to 7.0 mm, preferably 5.0 mm.

In advantageous but optional embodiments, each first and/or second transverse incision has a width less than or equal to 1.5 mm, preferably 1.2 mm, more preferably 1.0 mm and even more preferably 0.7 mm.

In advantageous but optional embodiments, each first and/or second transverse incision has a width greater than or equal to 0.2 mm, preferably 0.4 mm.

In advantageous but optional embodiments, DR1 + DI1 ≥ 0.50 cm-1, preferably DR1 + DI1 ≥ 0.55 cm-1, more preferably DR1 + DI1 ≥ 0.60 cm-1, even more preferably DR1 + DI1 ≥ 0.65 cm-1 and very preferably DR1 + DI1 ≥ 0.70 cm-1.

In advantageous but optional embodiments in which the second axially lateral portion is taken advantage of, DR2 + DI2 ≥ 0.50 cm-1, preferably DR2 + DI2 ≥ 0.55 cm-1, more preferably DR2 + DI2 ≥ 0.60 cm-1, even more preferably DR2 + DI2 ≥ 0.65 cm-1 and very preferably DR2 + DI2 ≥ 0.70 cm-1.

Too few transverse grooves lead to increased interior noise, particularly rattling noise, especially when the tire is worn. Increasing the number of transverse grooves reduces this interior noise.

In advantageous but optional embodiments, DR1 +DI1 ≤ 0.90 cm-1, preferably DR1 +DI1 ≤ 0.80 cm-1.

In advantageous but optional embodiments in which the second axially lateral portion is taken advantage of, DR2 +DI2 ≤ 0.90 cm-1, preferably DR2 +DI2 ≤ 0.80 cm-1.

Too many cross cuts, especially cross grooves, would increase the risk of generating too much noise.

In advantageous but optional embodiments, DR1 ≤ 0.40 cm-1, preferably DR1 ≤ 0.38 cm-1.

In advantageous but optional embodiments in which the second axially lateral portion is taken advantage of, DR2 ≤ 0.40 cm-1, preferably DR2 ≤ 0.38 cm-1.

By reducing the number of transverse grooves, the external noise generated by the tire is reduced accordingly.

In advantageous but optional embodiments, DR1 ≥ 0.30 cm-1, preferably DR1 ≥ 0.35 cm-1.

In advantageous but optional embodiments in which the second axially lateral portion is taken advantage of, DR2 ≥ 0.30 cm-1, preferably DR2 ≥ 0.35 cm-1.

The wet grip performance is higher when the number of transverse cuts, and therefore transverse grooves, is high.

In advantageous but optional embodiments, DI1 ≥ 0.29 cm-1, preferably DI1 ≥ 0.32 cm-1 and more preferably DI1 ≥ 0.34 cm-1.

In advantageous but optional embodiments in which the second axially lateral portion is taken advantage of, DI2 ≥ 0.29 cm-1, preferably DI2 ≥ 0.32 cm-1 and more preferably DI2 ≥ 0.34 cm-1.

The higher the number of transverse incisions, the higher the wet grip performance.

In advantageous but optional embodiments, DI1 ≤ 0.43 cm-1, preferably DI1 ≤ 0.40 cm-1 and more preferably DI1 ≤ 0.38 cm-1.

In advantageous but optional embodiments in which the second axially lateral portion is taken advantage of, DI2 ≤ 0.43 cm-1, preferably DI2 ≤ 0.40 cm-1 and more preferably DI2 ≤ 0.38 cm-1.

By reducing the number of transverse incisions, the rigidity of the corresponding axially lateral portion is increased, which improves both the grip on dry ground and reduces the wear of this axially lateral portion.

In advantageous but optional embodiments, the top reinforcement includes a working reinforcement comprising at least one working layer comprising metallic reinforcing elements extending substantially parallel to each other, each metallic reinforcing element comprising a metallic monofilament.

A metallic reinforcement element comprising a single metallic monofilament exhibits greater rigidity than a metallic reinforcement element comprising an assembly of several metallic monofilaments, which has relatively moderate rigidity due to the helix formed by the metallic monofilaments. Furthermore, the use of metallic reinforcement elements made of metallic monofilaments allows for working layers with relatively reduced thicknesses and therefore less dissipative properties compared to working layers using metallic reinforcement elements comprising assemblies of several metallic monofilaments. Thus, a metallic reinforcement element comprising a single metallic monofilament further reduces the tire's rolling resistance, at the cost of increased noise generated by the tire's crown reinforcement, which, according to the invention, is effectively compensated by the tread.

In some embodiments, the top reinforcement includes a shrink-fit reinforcement, and the outermost radial layer is a shrink-fit layer.

Conventionally, the shrink-fit reinforcement comprises several substantially parallel textile shrink-fit wire reinforcement elements embedded in the polymer matrix. In some embodiments, the shrink-fit reinforcement comprises a strip wound helically in several circumferential turns, the strip comprising several substantially parallel textile shrink-fit wire reinforcement elements embedded in the polymer matrix.

Advantageously, each wire reinforcement element of textile wrapping extends along a main wrapping direction forming, with the circumferential direction of the tire, an angle, in absolute value, less than or equal to 10°, preferably less than or equal to 7° and more preferably less than or equal to 5°.

Conventionally, the top reinforcement comprises a working reinforcement arranged radially inside the shrink-fit reinforcement. The working reinforcement advantageously comprises at least one working layer, each working layer or layers comprising wire reinforcement elements extending substantially parallel to each other within each working layer. The wire reinforcement elements are preferably metallic wire elements. Preferably, in embodiments where the working reinforcement comprises a radially inner working layer and a radially outer working layer arranged radially outside the radially inner working layer, the principal direction in which each wire reinforcement element of the innermost radially working layer extends and the principal direction in which each wire reinforcement element of the outermost radially working layer extends form opposite angles with the circumferential direction of the tire. These opposite angles may have equal or different absolute values.

Advantageously, the wire reinforcement elements of the or each working layer extend substantially parallel to each other in a direction forming an angle strictly greater than 10°, preferably from 15° to 50° and more preferably from 15° to 35° with the circumferential direction of the tire.

We can also consider a shrink-fit armature and a working armature such as those described in particular in US20190152262A1.

In advantageous but optional embodiments, E1m ≤ 1.9 mm, preferably E1m ≤ 1.8 mm. By further reducing the value of E1m, rolling resistance is further reduced, but the noise generated by the apex is increased, which, according to the invention, is effectively compensated by the tread.

In advantageous but optional embodiments, the tire has a volumetric notch ratio greater than or equal to 27.0%, preferably 28.0% and more preferably 29.0% and even more preferably ranging from 29.0% to 31.0%.

By opting for a relatively high volumetric groove ratio, wet grip performance is further enhanced. Moreover, a tire's tread is more flexible the higher its volumetric groove ratio. Indeed, the more grooves a tread has, the more susceptible it is to deformation under stress, particularly at its cutouts, which form areas highly prone to deformation. Thus, the invention, by stiffening the tread crown through the reduction of E1m, is particularly advantageous in the case of a relatively grooved tread.

The volumetric notch ratio of the tread is the ratio of the total volume of tread cuts in the new condition to the total volume of the tread in its new condition without any cuts. The tread is axially bounded by two planes perpendicular to the tire's axis of rotation and passing through the axial edges of the tread surface. One of the methods described in WO2021/089958 may be used to measure this volumetric notch ratio.

In advantageous but optional embodiments, the tire has a tread height greater than or equal to 6.6 mm and preferably within a range of 6.6 to 7.7 mm.

Such a tread depth is relatively high and allows for simultaneous improvement in tire life while also improving wet grip performance.

In advantageous but optional embodiments, the tread comprises a tread layer comprising elastomeric material based on a low glass transition temperature elastomer, having a glass transition temperature strictly less than or equal to -70°C, preferably from -70°C to -110°C, more preferably from -80°C to -110°C and even more preferably from -80°C to -100°C.

Such an elastomeric material significantly improves the tread's resistance to wear, thus extending tire life. These elastomeric materials are described in WO2018115722 and WO2022162292. The glass transition temperature (Tg) of the elastomer is determined using a differential scanning calorimeter according to ASTM E1356-08 (2014).

The expression "part by weight per hundred parts by weight of elastomer" (or pce) is to be understood in the context of the present invention as the part, by mass per hundred parts by mass of elastomer.

In this application, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) by mass.

The expression "based on" means a material comprising the mixture and/or the in situ reaction product of the different constituents used, some of these constituents having reacted with each other, at least partially, during the different phases of manufacturing the elastomeric material.

In advantageous but optional embodiments, the elastomeric matrix comprises at least 30 parts per cubic centimeter, preferably at least 40 parts per cubic centimeter, of the low glass transition temperature elastomer. Optionally, the elastomeric matrix comprises at most 100 parts per cubic centimeter, preferably at most 70 parts per cubic centimeter, and more preferably at most 60 parts per cubic centimeter, of the low glass transition temperature elastomer.

In optional embodiments, the elastomeric matrix comprises only the low glass transition temperature elastomer. In other words, the elastomeric matrix consists of the low glass transition temperature elastomer.

In other advantageous but optional embodiments, the elastomeric matrix whose elastomeric material is based on comprises an elastomer, said to have a high glass transition temperature, having a glass transition temperature strictly greater than -70°C, preferably ranging from -40°C to -70°C.

In embodiments where the elastomeric matrix comprises a high glass transition temperature elastomer, the elastomeric matrix comprises at least 30 parts per million, preferably at least 40 parts per million, of the high glass transition temperature elastomer. Optionally, the elastomeric matrix comprises at most 70 parts per million, preferably at most 60 parts per million, of the high glass transition temperature elastomer.

In advantageous but optional embodiments, the low glass transition temperature and/or high glass transition temperature elastomer comprises a butadiene-styrene copolymer. A "butadiene-styrene copolymer" is defined as any copolymer obtained by copolymerizing one or more styrenic compounds with one or more butadiene(s). Suitable styrene monomers include, in particular, styrene, methylstyrene, para-tert-butylstyrene, methoxystyrene, and chlorostyrene. Suitable butadiene monomers include, in particular, 1,3-butadiene. These elastomers may have any microstructure that depends on the polymerization conditions used, including the presence or absence of a modifying and/or randomizing agent and the quantities of modifying and/or randomizing agents used. Elastomers can be, for example, block, statistical, sequenced, or microsequenced. Such butadiene-styrene-based copolymers can be obtained by a process as described in WO2021005295 or WO2022162292. In advantageous but optional embodiments, the butadiene-styrene-based copolymer is a butadiene-styrene copolymer (SBR). It should be noted that SBR can be prepared as an emulsion (ESBR) or as a solution (SSBR). Whether ESBR or SSBR, SBR can have any microstructure compatible with a glass transition temperature below –70°C. Specifically, the butadiene-styrene copolymer can have a styrene content of between 1% and 15% by weight, and more particularly between 1% and 5%, and a 1,2-linkage content (molar %) of the butadiene portion of between 4% and 25%. Advantageously, the butadiene-styrene copolymer is an SSBR.

Optionally, the elastomeric material is based on at least one reinforcing filler known for its ability to strengthen an elastomeric material suitable for tire manufacturing. The reinforcing filler may include carbon black, an inorganic reinforcing filler, for example silica, or a mixture thereof. Examples of reinforcing fillers usable in the context of the invention are described in particular in WO2022162292.

Advantageously, the reinforcing filler comprises predominantly an inorganic reinforcing filler, preferably silica. For the purposes of this invention, "predominant" means that this compound is the major component among the compounds of the same type in the elastomeric material; that is, it is the one that represents the largest quantity by mass among the compounds of the same type. Thus, a so-called major filler is that representing the largest mass among the fillers in the elastomeric material. Preferably, "major" means present at more than 50%, and more preferably more than 60%, 70%, 80%, or 90%.

In optional but advantageous embodiments, the reinforcing charge ratio in the elastomeric material of the tire tread may be in the range of 60 to 180 pc, preferably 80 to 160 pc, preferably 100 to 140 pc.

In optional but advantageous embodiments, the elastomeric material is based on at least one plasticizer comprising at least one plasticizing resin, the percentage of the plasticizing resin(s) may be in the range of 25 to 100 parts per annum, preferably 50 to 100 parts per annum, more preferably 55 to 90 parts per annum.

The term "resin" is reserved in this application, by definition known to those skilled in the art, for a compound that is solid at room temperature (23°C), as opposed to a liquid plasticizing compound such as an oil. Examples of plasticizing resins are described in more detail in WO2021/005295.

Although not necessary for the implementation of the present invention, the plasticizing system of the elastomeric material of the tire tread may include a liquid plasticizer at 23°C, for example such as those described in WO2021/005295.

Examples of other constituents on which the elastomeric material can be based are described in WO2022162292.

In advantageous but optional embodiments, the elastomeric material has a dynamic shear modulus measured at 23°C at 10% strain and at a frequency of 10 Hz according to ASTM D 5992-96 greater than or equal to 1.70 MPa, preferably 1.85 MPa and more preferably 2.00 MPa.

Such a relatively high dynamic shear modulus improves adhesion on dry ground.

In advantageous but optional embodiments, the elastomeric material has a dynamic shear modulus measured at 23°C at 10% strain and at a frequency of 10 Hz according to ASTM D 5992-96 strictly less than 2.30 MPa, preferably less than or equal to 2.25 MPa and more preferably less than or equal to 2.20 MPa.

Such a relatively moderate dynamic shear modulus further improves tire life. Moreover, the higher the previously described dynamic shear modulus, the more dissipative the elastomeric material becomes, thus degrading rolling resistance performance. Therefore, such a relatively moderate dynamic shear modulus also helps to minimize rolling resistance.

In advantageous but optional embodiments, the elastomeric material has a dynamic shear modulus measured at 60°C and an imposed stress of 0.7 MPa and a frequency of 10 Hz according to ASTM D 5992-96 less than or equal to 1.30 MPa, preferably 1.20 MPa and more preferably 1.10 MPa.

Such a relatively moderate dynamic shear modulus further improves grip on wet surfaces.

Optionally, the elastomeric material has a dynamic shear modulus measured at 60°C and an imposed stress of 0.7 MPa and a frequency of 10 Hz according to ASTM D 5992-96 greater than or equal to 0.80 MPa, preferably 0.90 MPa.

Such a dynamic shear modulus helps to avoid excessive softening of the tread layer and thus improves the longevity of the tire.

In advantageous but optional embodiments, said elastomeric material extends axially from the first axially lateral portion to the second axially lateral portion, preferably extending axially over the entire width of the tread.

The elastomeric material extending axially from the first axially lateral portion to the second axially lateral portion means that at least a portion of the tread layer of each first and second axially lateral portion comprises said elastomeric material. The elastomeric material extending axially across the entire width of the tread means that the entire tread layer of each first and second axially lateral portion comprises said elastomeric material.

In advantageous but optional embodiments suitable for summer tires, the axially central portion of the tread comprises at least one central rib, the central rib or rib being axially delimited by two axially adjacent main circumferential cutouts.

In advantageous but optional embodiments allowing for the reduction of noise generated by the tire, the central rib or ribs comprise transverse cutouts formed in said central rib, the transverse cutouts formed in said central rib extend along an average direction forming an angle greater than or equal to 20°, preferably 25°, more preferably 30°, even more preferably 35° and very preferably 40° with the axial direction of the tire.

Indeed, by significantly angling the average direction of the transverse grooves relative to the circumferential direction, the noise generated by the pumping of air between the transverse groove and the ground is spread out over time when the groove is in the contact patch. Thus, the transverse grooves contribute to reducing external noise, firstly by reducing the rigidity of the axially central portion of the tread, and secondly by spreading out the pumping noise from the angled transverse grooves.

The cross cuts made in said at least one of the central ribs are described in more detail in applications PCT/EP2024/056080 and PCT/EP2024/056087 filed on behalf of the applicant of this application.

In advantageous but optional embodiments, each transverse cut-out formed in said central rib has a variable depth along said transverse cut-out.

One drawback of the steep incline of the transverse grooves is a reduction in drift stiffness. Indeed, the transverse grooves create a discontinuity in the central part of the tread, which softens this central area when lateral forces are applied. This softening is all the more significant when the groove extends in a direction close to perpendicular to the forces. Thus, transverse grooves make the central part less rigid with respect to the lateral forces applied during drift, hence the reduction in drift stiffness. The steeper the incline of the transverse grooves, i.e., the greater the angle, the more the drift stiffness decreases. To compensate for this reduction, instead of eliminating the transverse grooves altogether, the depth of certain portions of them is reduced. This allows the initial drift stiffness to be restored without sacrificing the performance gains in external noise.

The characteristic that each transverse cut in said central rib has a variable depth along said transverse cut means that the depth is not constant across the entire width of said transverse cut. Optionally, in order to advantageously stiffen the central rib, the ratio between the maximum depth and the minimum depth of said transverse cut is greater than or equal to 1.2, preferably 1.5, and more preferably 1.7. Optionally, in order that each transverse cut performs a cutting function, the ratio between the maximum depth and the minimum depth of said transverse cut is less than or equal to 3.0, and preferably 2.0.

Most advantageously, each transverse cut made in said central rib includes at least one portion, said to be of reduced depth, having a depth less than or equal to 70%, preferably 60%, and more preferably 50% of the height of the sculpture continuously along said portion of reduced depth.

The feature whereby the reduced depth portion or portions has a maximum depth that is continuously reduced along said reduced depth portion ensures that the depth is reduced without interruption along the reduced depth portion.

The reduced depth portion(s) may have a constant or variable depth. The reduced depth portion(s) extend between two extremities beyond which the condition(s) characterizing the reduced depth portion are no longer satisfied, including the condition relating to the depth of the reduced depth portion.

In advantageous but optional embodiments allowing for the reduction of noise generated by the tire, it may be envisaged that the transverse cutouts made in said at least one of the central ribs are arranged as described in EP3065955, EP3065956, EP3292002, EP3292003, EP3292004, EP3535139, EP3535140, EP3535141 or even in EP4253090 and EP4253091.

In embodiments in which the main circumferential cutouts are relatively deep, each main circumferential cutout has a depth ranging from 4.0 mm to the carving height, preferably ranging from 5.0 mm to the carving height and more preferably ranging from 5.5 mm to the carving height.

In embodiments in which the main circumferential cutouts are relatively deep, each main circumferential cutout has a depth greater than or equal to 75% of the sculpture height, preferably 90% of the sculpture height.

In embodiments in which the main circumferential cutouts are relatively wide main circumferential grooves, each main circumferential cutout has a minimum width greater than or equal to 3.0 mm, preferably greater than or equal to 5.0 mm and more preferably ranging from 5.0 mm to 20.0 mm.

In advantageous and optional variants, the tread includes a radially inner layer arranged radially inside the wearing course and separate from the wearing course.

In other variants, the tread does not include an inner radial layer. Thus, the tread layer is in direct contact with the crown reinforcement of the tire, for example as described above.

Conventionally, a tire comprises a crown, two sidewalls, and two beads, with each sidewall connecting each bead to the crown. The tire also includes a carcass reinforcement anchored in each bead and extending radially into each sidewall and axially into the crown, radially internal to the crown reinforcement.

In embodiments enabling the achievement of radial tire performance, for example as defined by ETRTO, the carcass reinforcement comprises at least one carcass layer, each layer comprising wire carcass reinforcement elements, each wire carcass reinforcement element extending substantially along a principal direction forming an angle, in absolute value, of 80° to 90° with the circumferential direction of the tire. Alternatively, a variable angle of 80° to 90° may be used in at least a portion of the sidewall and strictly less than 80° in at least a portion of the crown, as described, for example, in US20190152262.

The invention will be better understood upon reading the following description, given solely by way of non-limiting example and made with reference to the drawings in which:
- there FIG. 1 is a view, in a meridian cross-sectional plane, of a tire according to the invention,
- there FIG. 2 is a top view of the tire tread of the FIG. 1 ,
- there FIG. 3 is a detailed view of the tire tread in Figures 1 and 2 illustrating the cross-sections, and
- there FIG. 4 is a detailed view of an axially central part of the top of the tire in figures 1 and 2.

In the figures relating to the tire, we have represented a coordinate system X, Y, Z corresponding to the usual directions respectively axial (Y), radial (Z) and circumferential (X) of a tire.

Figures 1 to 4 show a tire conforming to the invention and designated by the general reference 10. The tire 10 has a substantially toroidal shape around an axis of revolution substantially parallel to the axial direction Y. The tire 10 is intended for a passenger vehicle and has dimensions 225/50 R17. In the various figures, the tire 10 is shown in its new condition, i.e., having not yet been driven on.

The tire 10 includes a crown 12 comprising a tread 14 carrying a tread surface 16 intended to come into contact with a ground during the rolling of the tire 10. The tread surface 16 is axially delimited by first and second axial edges 18, 20. The tread 14 and the tread surface 16 have an axial width LSR measured as the axial distance from the first axial edge 18 to the second axial edge 20.

The tread 14 comprises an axially central portion P0b of the tread 14 and the first and second axially lateral portions P1b, P2b of the tread 14 arranged axially outside the axially central portion P0b on either side axially of the axially central portion P0b of the tread 14.

The tread 14 includes several main circumferential cutouts, here four main circumferential grooves, comprising first, second, third and fourth main circumferential cutouts respectively designated by references 22, 24, 26, 28. The first and second main circumferential cutouts 22, 24 are arranged axially on either side of the median plane M of the tire 10 and are the outermost axially main circumferential cutouts of the tread 14 and below referred to as the outermost axially main circumferential cutouts 22, 24.

The first axially lateral portion P1b and the second axially lateral portion P2b are arranged axially outside the first axially external main circumferential cutout 22 and the second axially external main circumferential cutout 24, respectively. The first axially lateral portion P1b extends axially from the first axial edge 18 of the tread surface 16 to the axially external edge 19 of the first axially external main circumferential cutout 22. The second axially lateral portion P2b extends axially from the second axial edge 20 of the tread surface 16 to the axially external edge 21 of the second axially external main circumferential cutout 24. The axially central portion P0b of the tread 14 extends axially from the first axially lateral portion P1b of the tread 14 to the second axially lateral portion P2b of the tread 14.

As illustrated on the FIG. 2 Each main circumferential cutout 22 to 28 has a depth Hr ranging from 4.0 mm to the carving height Hs, preferably from 5.0 mm to the carving height Hs, and more preferably from 5.5 mm to the carving height Hs. Each depth Hr is greater than or equal to 50%, preferably 75%, and more preferably 90% of the carving height Hs. The carving height Hs is greater than or equal to 6.6 mm, and preferably within a range of 6.6 mm to 7.7 mm. Here, Hs=7.0 mm, Hr=6.5 mm for each first and second main axially external circumferential cutout 22, 24 and Hs=Hr=7.0 mm for each main circumferential cutout 26, 28. Each main circumferential cutout 22 to 28 has respectively a minimum width greater than or equal to 3.0 mm, preferably greater than or equal to 5.0 mm and more preferably ranging from 5.0 mm to 20.0 mm.

The axially central portion P0b comprises central ribs and here the first, second and third central ribs respectively designated by references 32, 34, 36. Each central rib 32, 34, 36 is arranged axially between two of the main axially adjacent circumferential cutouts 22 to 28 and here delimited by two of the main axially adjacent circumferential cutouts 22 to 28. Each central rib 32, 34, 36 comprises transverse cutouts 38, 40, 42 formed in the central ribs 32, 34, 36.

Each transverse cutout 38 opens into the circumferential cutouts 22, 26 in the first and second opening zones Z1, Z2 respectively. The azimuth AZ1 of a point in the first opening zone AZ1 of a transverse cutout 38 is substantially circumferentially aligned with the azimuth AZ2 of a point in the second opening zone AZ2 of another of the transverse cutouts 38. Similarly, each transverse cutout 40 opens into the circumferential cutouts 26, 28 in the first and second opening zones Z1, Z2 respectively. The azimuth AZ1 of a point in the first opening zone AZ1 of a transverse cut 40 is substantially circumferentially aligned with the azimuth AZ2 of a point in the second opening zone AZ2 of another of the transverse cuts 40. Similarly, each transverse cut 42 opens into the circumferential cuts 28, 24 in the first and second opening zones Z1, Z2 respectively. The azimuth AZ1 of a point in the first opening zone AZ1 of a transverse cut 42 is substantially circumferentially aligned with the azimuth AZ2 of a point in the second opening zone AZ2 of another of the transverse cuts 42.

Each transverse cut 38, 40, 42 extends between its first and second ends along an average direction forming an angle greater than or equal to 20°, preferably 25°, more preferably 30°, even more preferably 35° and very preferably 40° with the axial direction Y of the tire 10. Here, each angle respectively noted A38, A40, A42 with the axial direction Y of the tire 10 is such that A38=A40=A42=40°.

With reference to the FIG. 3 Each transverse cut 38, 42 has a variable depth along its length. Each transverse cut 38, 42 comprises two portions 381, 383 and 421, 423, each with a depth of 5.3 mm. Each transverse cut 38, 42 includes a portion 382, 422, referred to as the reduced-depth portion, with a depth less than or equal to 70%, preferably 60%, and more preferably 50%, of the sculpture height Hs, continuously along said reduced-depth portion. Here, each portion 382, 422 has a depth of 2.8 mm. The ratio between the maximum depth, here 5.3 mm, and the minimum depth, here 2.8 mm, of each transverse cut 38, 42 is greater than or equal to 1.2, preferably to 1.5 and more preferably to 1.7 and less than or equal to 3.0 and preferably to 2.0 and here equal to 1.9.

Each transverse cut 40 has a substantially constant depth along each transverse cut 40 and is equal to 5.4 mm.

Each transverse cut 38, 40, 42 has a width less than or equal to 1.5 mm, preferably 1.2 mm, more preferably 1.0 mm and even more preferably 0.7 mm and greater than or equal to 0.2 mm, preferably 0.4 mm and here equal to 0.4 mm.

Each first and second axially lateral portion P1b, P2b comprises respectively a first and second lateral rib respectively designated by reference 44, 46. The tread 14 comprises first and second transverse cutouts 47, 50 formed at least in part in each first and second axially lateral portion P1b, P2b.

Each first and second transverse cut 47, 50 extends between its first and second ends along an average direction forming an angle substantially zero with the axial direction Y of the tire 10.

The first transverse cuts 47 include first transverse grooves 48 and first transverse incisions 49 having a width strictly less than the width of the first transverse grooves 47. The second transverse cuts 50 include second transverse grooves 51 and second transverse incisions 52 having a width strictly less than the width of the second transverse grooves 51.

With reference to the FIG. 3 , each first and second transverse cut 47, 50 has a variable depth along each first and second transverse cut 47, 50. Each first and second transverse cut 47, 50 includes a portion 471, 501 having a depth equal to 5.2 mm and a portion 472, 502 having a depth equal to 2.8 mm.

Each first and second transverse groove 48, 51 has a width greater than or equal to 1.6 mm, preferably 1.8 mm and more preferably 2.0 mm and less than or equal to 7.0 mm, preferably 5.0 mm and here equal to 2.6 mm.

Each first and second transverse incision 49, 52 has a width less than or equal to 1.5 mm, preferably 1.2 mm, more preferably 1.0 mm and even more preferably 0.7 mm and greater than or equal to 0.2 mm, preferably 0.4 mm and here equal to 0.4 mm.

Each first and second linear density DR1, DR2 of transverse grooves is defined as the ratio of the total number of first and second transverse grooves 48, 51 formed respectively in each first and second axially lateral portion P1b, P2b to the circumference C of the tire 10 measured on the median plane M and inflated to 2.5 bar. Each first and second linear density DI1, DI2 of transverse incisions is also defined as the ratio of the total number of first and second transverse incisions 49, 52 formed respectively in each first and second axially lateral portion P1b, P2b to the circumference C of the tire 10 measured on the median plane and inflated to 2.5 bar.

Thus, DR1 ≤ 0.43 cm-1 and DR2 ≤ 0.43 cm-1, preferably DR1 ≤ 0.40 cm-1 and DR2 ≤ 0.40 cm-1, and more preferably DR1 ≤ 0.38 cm-1 and DR2 ≤ 0.38 cm-1. Furthermore, DR1 ≥ 0.30 cm-1 and DR2 ≥ 0.30 cm-1, preferably DR1 ≥ 0.35 cm-1 and DR2 ≥ 0.35 cm-1. Furthermore, DI1 ≥ 0.29 cm-1 and DI2 ≥ 0.29 cm-1, preferably DI1 ≥ 0.32 cm-1 and DI2 ≥ 0.32 cm-1 and more preferably DI1 ≥ 0.34 cm-1 and DI2 ≥ 0.34 cm-1. In addition, DI1 ≤ 0.43 cm-1 and DI2 ≤ 0.43 cm-1, preferably DI1 ≤ 0.40 cm-1 and DI2 ≤ 0.40 cm-1 and more preferably DI1 ≤ 0.38 and DI2 ≤ 0.38.

In addition, DR1 + DI1 ≥ 0.45 cm-1 and DR2 + DI2 ≥ 0.45 cm-1, preferably DR1 + DI1 ≥ 0.50 cm-1 and DR2 + DI2 ≥ 0.50 cm-1, more preferably DR1 + DI1 ≥ 0.55 cm-1 and DR2 + DI2 ≥ 0.55 cm-1, even more preferably DR1 + DI1 ≥ 0.60 cm-1 and DR2 + DI2 ≥ 0.60 cm-1, very preferably DR1 + DI1 ≥ 0.65 cm-1 and DR2 + DI2 ≥ 0.65 cm-1 and extremely preferably DR1 + DI1 ≥ 0.70 cm-1 and DR2 + DI2 ≥ 0.70 cm-1. Furthermore, DR1 +DI1 ≤ 0.90 cm-1 and DR2 +DI2 ≤ 0.90 cm-1 and preferably DR1 +DI1 ≤ 0.80 cm-1 and DR2 +DI2 ≤ 0.80 cm-1.

The tire 10 has a circumference C here equal to 207 cm, 75 first transverse grooves 48, 75 first transverse incisions 49, 75 second transverse grooves 51 and 75 second transverse incisions 52 so that here DR1=DR2=0.36 cm-1, DI1=DI2=0.36 cm-1 and DR1 +DI1= DR2 +DI2=0.72 cm-1.

All the cross cuts described above have chamfers which are not shown.

Due to the presence of the various transverse cuts described above, tread 14 has a volumetric notch ratio TEV greater than or equal to 27.0%, preferably 28.0% and more preferably 29.0% and even more preferably ranging from 29.0% to 31.0% and here equal to 30.0%.

The tread 14 comprises a wearing layer 53 and a radially inner layer 54 arranged radially inside the wearing layer 53 and separate from the wearing layer 53.

The wearing course 53 comprises an elastomeric material M0 having a dynamic shear modulus G*0 measured at 23°C at 10% strain and at a frequency of 10 Hz according to ASTM D 5992 – 96 greater than or equal to 1.70 MPa, preferably 1.85 MPa and more preferably 2.00 MPa and strictly less than 2.30 MPa, preferably less than or equal to 2.25 MPa and more preferably less than or equal to 2.20 MPa and here equal to 2.15 MPa. The elastomeric material M0 has a Shore hardness DS of 61. The wearing course 53 has a dynamic shear modulus G*’0 measured at 60°C and under applied stress (0.7 MPa) greater than or equal to 0.80 MPa, preferably 0.90 MPa, and less than or equal to 1.30 MPa, preferably 1.20 MPa, and more preferably 1.10 MPa, and here equal to 1.05 MPa. The wearing course 53 has a maximum dynamic loss tanDMAX23-0 of 0.37 and a glass transition temperature Tg0 of -13°C. The elastomeric material M0 extends axially from the first axially lateral portion P1b to the second axially lateral portion P2b, and here extends axially over the entire LSR width of the tread 14.

The radially inner layer 54 comprises an MS elastomeric material. In practice, and as is usually done in the pneumatic industry, the radially inner layer 54 comprises the MS elastomeric material as well as a significant proportion of M0 elastomeric material, for example between 40% and 60% by mass of the M0 material.

The complex shear modulus G* is a well-known dynamic property for those skilled in the art and is measured on a Metravib VA4000 or DMA+450 viscoanalyzer using specimens containing a baked composition extracted from tires. The response of the specimen subjected to a sinusoidal alternating simple shear load at a frequency of 10 Hz is recorded under specified temperature conditions (here 23°C) according to ASTM D1349-99. A strain amplitude sweep is performed from 0.1% c-c to 100% c-c (forward cycle), then from 100% c-c to 0.1% c-c (reverse cycle), c-c meaning peak-to-peak. The specimen has a cylindrical cross-section as described in ASTM D 5992-96 (2011 reapproved version, originally approved in 1996) in Figure X2.1 (circular embodiment) and a diameter of 10 mm [0 to +0.04 mm] and a thickness of 2 mm [1.83-2.33]. The complex dynamic shear modulus G* is defined as the square root of the sum of the squares of G' and G'', where G' represents the elastic modulus and G'' represents the viscous modulus. The complex shear modulus G* is measured at 10% c-c strain on the return cycle.

Shore hardness, for example, is measured according to the JIS K6253 standard at 23°C using a type A durometer.

The complex shear modulus G*’ under imposed stress is determined using a Metravib VA4000 or DMA+450 viscoanalyzer with specimens containing a cured composition extracted from tires. The response of the specimens subjected to a sinusoidal alternating simple shear load at a frequency of 10 Hz under a force of 55 N is recorded. A temperature sweep is performed between -80°C and 80°C at a rate of 1.5°C/min after the specimens have been previously conditioned to 100% peak-to-peak strain at a temperature of 40°C or lower, for example, 23°C. The specimen has a cylindrical cross-section as described in ASTM D 5992-96 (2011 re-approved version, originally approved in 1996) in Figure X2.1 (circular embodiment) and has a diameter of 10 mm [0 to +0.04 mm] and a thickness of 2 mm [1.83-2.33]. It should be noted that a force of 55 N, in the case of a specimen with a diameter of 10.00 mm, is equivalent to a peak-to-peak stress of 0.7 MPa. The complex shear modulus G*’ is measured at 60°C.

The dynamic loss tanDMAX23 is another well-known dynamic property for those skilled in the art and is measured on the same Metravib VA4000 or DMA+450 type viscoanalyzer using specimens containing a baked composition extracted from tires. The response of the specimens subjected to a sinusoidal alternating simple shear load at a frequency of 10 Hz is recorded under specified temperature conditions (here 23°C) according to ASTM D1349-99. A strain amplitude sweep is performed from 0.1% c-c to 100% c-c (forward cycle), then from 100% c-c to 0.1% c-c (reverse cycle), c-c meaning peak-to-peak. The specimen has a cylindrical cross-section as described in ASTM D 5992-96 (2011 re-approved version, originally approved in 1996) in Figure X2.1 (circular embodiment) and has a diameter of 10 mm [0 to +0.04 mm] and a thickness of 2 mm [1.83-2.33]. The tangent tanD of the phase angle D between the force exerted on the specimen and its displacement represents a dynamic loss and is equal to the ratio G''/G'. The maximum value tanDMAX of the tangent tanD of the phase angle D observed during the deformation return cycle is recorded.

The glass transition temperature (Tg) is determined using a Metravib VA4000 or DMA+450 viscoanalyzer with test specimens containing a baked composition extracted from tires. The response of the specimens subjected to sinusoidal alternating simple shear loading at a frequency of 10 Hz under a force of 55 N is recorded. A temperature sweep is performed between -80°C and 80°C at a rate of 1.5°C/min. The specimen has a cylindrical cross-section as described in ASTM D 5992-96 (2011 re-approved version, originally approved in 1996) in Figure X2.1 (circular embodiment) and has a diameter of 10 mm [0 to +0.04 mm] and a thickness of 2 mm [1.83-2.33]. It should be noted that a force of 55 N, in the case of a specimen with a diameter of 10.00 mm, is equivalent to a peak-to-peak stress of 0.7 MPa. The glass transition temperature Tg is taken to be the temperature at which the tangent of the phase angle tanD is maximum. The tangent tanD of the phase angle D between the force exerted on the sample and its displacement represents a dynamic loss and is equal to the ratio G''/G'.

Table 1 below shows the composition from which material M0 was manufactured in a conventional manner known to those skilled in the art. The values are given in pieces.

Composition M0 Elastomer 1 (1) 30-100 Elastomer 2 (2) 0-70 Charge(s) (3) 60-180 Silane (4) 5-50 Resin (5) 25-100 Other additives (6) 5-40

(1) - Styrene-Butadiene Elastomer described as polymer E on page 34 of WO2018115722; (2) - Styrene-Butadiene Elastomer described as control polymer A on page 39 of WO2022162292; (3) - Carbon black grade 234 according to ASTM D-1765 and 160MP Silica from Solvay; (4) - Silane selected from "Si69" and "Si75" from Evonik; (5) - "PR-383" Hydrogenated DCPD Resin; (6) – The other additives are classically known to those skilled in the art and include here in particular a protective wax, N-1,3-dimethylbutyl-N-phenylparaphenylenediamine, N-cyclohexyl-benzothiazyl sulphenamide, diphenylguanidine, sulfur, stearic acid, zinc oxide, oleic sunflower oil.

It should be noted in particular that the elastomeric material M0 is based on an elastomeric matrix comprising the elastomer (1), known as a low glass transition temperature elastomer, having a glass transition temperature less than or equal to -70°C, preferably ranging from -70°C to -110°C, more preferably from -80°C to -110°C, and even more preferably from -80°C to -100°C, and here equal to -88°C. The elastomeric matrix of which the elastomeric material M0 may comprise the elastomeric matrix (2), known as a high glass transition temperature elastomer, having a glass transition temperature strictly greater than -70°C, preferably ranging from -40°C to -70°C, and here equal to -65°C.

With reference to Figures 1 and 4, the apex 12 includes an apex reinforcement 60 extending into the apex 12 along the circumferential direction X. The tire 10 also includes a sealing layer 62 for an inflation gas intended to delimit an internal cavity closed with a mounting support for the tire 10 once the tire 10 is mounted on the mounting support, for example, a rim. The apex reinforcement 60 includes a working reinforcement 64 and a shrink-fit reinforcement 66.

The working reinforcement 64 comprises two working layers 68, 70. The radially outer working layer 70 is arranged radially outside the radially inner working layer 68.

The 66 shrink frame comprises at least one shrink layer and here comprises a shrink layer 72.

The top reinforcement 60 is arranged radially inside the tread 14. The shrinkage reinforcement 66, here the shrinkage layer 72, is arranged radially outside the working reinforcement 64 and radially inside the tread 14. The shrinkage reinforcement 66 is therefore radially interposed between the working reinforcement 64 and the tread 14. The shrinkage layer 72 is therefore the outermost radially outermost layer of the top reinforcement 60.

The tire 10 comprises two sidewalls 74 extending radially inwards from the apex 12. The tire 10 further comprises two beads 76 radially inwards from the sidewalls 74. Each sidewall 74 connects each bead 76 to the apex 12.

The tire 10 comprises a carcass reinforcement 78 anchored in each bead 76, in this case wound around two beads 80. The carcass reinforcement 78 extends radially in each sidewall 74 and axially in the crown 12 radially internally to the crown reinforcement 60. The crown reinforcement 60 is arranged radially between the tread 14 and the carcass reinforcement 78. The carcass reinforcement 78 comprises at least one carcass layer and here comprises a single carcass layer 82.

With reference to the FIG. 4 Each working layer 68, 70, shrink-fit layer 72, and carcass layer 82 comprises a polymer matrix, in this case an elastomeric matrix, in which one or more wire reinforcement elements of the corresponding layer are embedded. Thus, each working layer 68, 70 comprises working wire reinforcement elements 680, 700 respectively, the shrink-fit layer 72 comprises shrink-fit wire reinforcement elements 720, and the carcass layer 82 comprises carcass wire reinforcement elements 820.

The wire reinforcement elements of the 720 swaging are textile and are circumferentially helically wound in a main direction forming, with the circumferential direction X of the tire 10, an angle, in absolute value, less than or equal to 10°, preferably less than or equal to 7° and more preferably less than or equal to 5°.

The working wire reinforcement elements 680, 700 are metallic and extend substantially parallel to each other within each working layer 68, 70 along principal directions forming, with the circumferential direction X of the tire 10, angles of opposite orientation between the two working layers 68, 70 and in absolute value, strictly greater than 10°, preferably ranging from 15° to 50° and more preferably from 15° to 30°, and here equal to -26° and +26°. Each working wire reinforcement element 680, 700 comprises a metallic monofilament having a diameter of 0.32 mm.

The wire reinforcement elements of the 820 carcass are textile and extend along a main direction forming with the circumferential direction X of the tire 10, an angle, in absolute value, greater than or equal to 60°, preferably ranging from 80° to 90° and here substantially equal to 90°.

Each wire reinforcement element of the 720 shrink-fit and 820 carcass is, for example, identical to those described in applications WO2021250331, WO2022074341 or WO2022069819.

The interfaces between two adjacent layers are represented by dashed lines. On the FIG. 4 We have represented:
- the surface 100 passing through the innermost radial point of the deepest cut in the axially central portion P0b of the tread 14 and substantially parallel to the tread surface, here passing through the innermost point of the main circumferential cuts 26, 28 and substantially parallel to the tread surface 16,
- the radially outer surface 102 passing through the radially outermost points of the wire reinforcement elements 720 most radially outer among the wire reinforcement elements 720 of the radially outermost layer 72 arranged vertically above the axially central portion P0b of the tread 14.

In the axially central portion P0b of the tread 14, the average radial distance E1m of the distances E1 between the surface 100 and the radially outer surface 102 is such that E1m ≤ 2.0 mm and preferably E1m ≤ 1.9 mm, more preferably E1m ≤ 1.8 mm. Furthermore, E1m ≥ 0.5 mm, preferably E1m ≥ 1.0 mm. In this case, E1 = 1.7 mm.

COMPARATIVE TESTS

We compared tires I0, I1 and I2 according to the invention with reference tires T0, T1 and T2 whose characteristics are indicated in Table 2 below and in which we have gathered the results of tests of rolling resistance (RR), external noise, wet grip and internal noise.

The results of the different tests are given with reference to the reference tire T0.

The rolling resistance test was conducted according to ISO 28580:2018. For a tested tire, the result is the rolling resistance coefficient, which represents the ratio of the tire's resistance force to the vehicle's forward motion (due to hysteresis) divided by the load carried. A reduction in rolling resistance corresponds to an improvement in performance.

External noise was measured by driving the vehicle on a track compliant with ISO 10844 regulations and certified by UTAC. A designated measurement area on the track was equipped with Müller-BBM vibro-acoustic recording equipment. The noise generated by each tire with the engine off was measured at a speed of 80 km/h (conditions similar to those used in regulation R117). The raw noise measurement was then corrected for ground temperature as specified in UN regulation R117. A reduction in external noise corresponds to an improvement in performance.

The wet grip test is conducted by measuring the distance traveled during deceleration from 80 km/h to 20 km/h in a 1 mm water spray. The shorter the braking distance, the better the tire's performance. A result above 100 indicates an improvement compared to the reference tire (T0).

The interior noise test is a subjective test conducted by an experienced driver regarding the vehicle's interior noise. A "-" sign indicates an increase in interior noise, and an "=" sign indicates that the perceived interior noise level remains the same.

T0 T1 T2 I0 I1 I2 DR1 (cm-1) 0.44 0.44 0.55 0.28 0.36 0.36 DI1 (cm-1) 0.00 0.00 0.00 0.28 0.36 0.36 DR2 (cm-1) 0.44 0.44 0.55 0.28 0.36 0.36 DI2 (cm-1) 0.00 0.00 0.00 0.28 0.36 0.36 DR1+DI1 (cm-1) 0.44 0.44 0.55 0.56 0.72 0.72 DR2+DI2 (cm-1) 0.44 0.44 0.55 0.56 0.72 0.72 E1m (mm) 2.0 1.5 2.0 2.0 2.0 1.7 TEV (%) 26.5 26.5 27.5 27.5 30.0 30.0 Hs (mm) 6.5 6.5 7.0 7.0 7.0 7.0 RR (kg/t) Ref -0.15 -0.1 -0.1 -0.1 -0.2 External noise (dB) Ref +0.6 +0.5 -0.2 -0.2 0 Adhesion on wet surfaces 100 98 102 103 105 103 Interior noise Ref - - - - = -

The results of the tests described above show a reduction in external noise without degradation of rolling resistance as well as an improvement in wet grip of I0, I1 and I2 tires compared to T0, T1, T2 tires.

Comparison of T0 and T1 tires shows that reducing E1m leads to a significant reduction in rolling resistance in exchange for a significant increase in external and internal noise generated by the top of the tire.

In particular, tires I0, I1, and I2 each meet the characteristic that DR1 ≤ 0.43 cm⁻¹ and DR1 + DI1 ≥ 0.45 cm⁻¹, which reduces external noise generated by the tread pattern. This reduction in external noise compensates for the increase in external noise due to the reduction in the E1m value, as shown by the comparison of tires T0, T1, I0, I1, and I2.

Comparison of T2 and I0 tires shows that too high a DR1 value in the T2 tire leads to a sharp increase in external noise generated by the tread pattern, while the introduction of incisions and the reduction of DR1 simultaneously reduces external noise generated by the tread pattern and improves grip on wet surfaces.

Finally, comparing tires I0 and I1 shows that increasing DR1 + DI1 reduces interior noise. By reducing the E1m value of tire I1, the rolling resistance of tire I2 is reduced, while accepting an increase in interior noise compared to tires T0 and I1, the same exterior noise level as tire T0, and improving wet grip compared to tires T0, T1, and T2.

It may also be expected that the tread will include noise reduction devices, including Helmholtz resonators as described for example in EP0989000, EP2011671, EP2240335, EP2627524.

It may also be provided that the tire includes a noise reduction device as described in WO2022/069822 or as described in EP1219944, EP1253025, EP1184207, EP1110763, EP1876038.

Claims (15)

Tire (10) comprising a crown (12) comprising a tread (14) and a crown reinforcement (60) arranged radially inside the tread (14),
the apex reinforcement (60) comprising a radially outermost layer (72) and comprising reinforcing elements (720) embedded in a polymer matrix,
the tread (14) comprising main circumferential cutouts (22, 24, 26, 28) having a depth greater than or equal to 50% of the tread height (Hs) comprising first and second main circumferential axially external cutouts (22, 24) arranged axially on either side of the median plane (M) of the tire (10), the first and second main circumferential axially external cutouts (22, 24) being the outermost main circumferential axial cutouts of the tread (14),
the tread (14) comprising:
- the first and second axially lateral portions (P1b, P2b) of the tread (14) arranged axially outside each of the first and second main axially external circumferential cutouts (22, 24),
- an axially central portion (P0b) of the tread (14) extending from the first axially lateral portion (P1b) of the tread (14) to the second axially lateral portion (P2b) of the tread (14),
characterized in that the average radial distance E1m in the axially central portion (P0b) of the tread (14) between:
- the surface (100) passing through the radially innermost point of the deepest cut (26, 28) formed in the axially central portion (P0b) of the tread (14) and substantially parallel to the tread surface (16), and
- the radially outer surface (102) passing through the radially outermost points of the most radially outer reinforcing elements (720) among the reinforcing elements of the radially outermost layer (72) arranged vertically above the axially central portion (P0b) of the tread (14),
is such that E1m ≤ 2.0 mm
and in that at least the first axially lateral portion (P1b) comprises first transverse cutouts (47) formed at least in part in the first axially lateral portion (P1b) comprising:
- the first transverse grooves (48),
- the first transverse incisions (49) having a width strictly less than the width of the first transverse grooves (48),
the linear density DR1 of first transverse grooves (48) being defined by the ratio of the total number of first transverse grooves (48) formed at least in part in the first axially lateral portion (P1b) to the circumference of the tire measured on the median plane (M) and inflated to 2.5 bars,
the linear density DI1 of first transverse incisions (49) being defined by the ratio of the total number of first transverse incisions (49) made at least in part in the first axially lateral portion (P2b) to the circumference of the tire measured on the median plane (M) and inflated to 2.5 bars,
DR1 and DI1 satisfy DR1 ≤ 0.43 cm-1 and DR1 + DI1 ≥ 0.45 cm-1. Pneumatic (10) according to the preceding claim, wherein the second axially lateral portion (P2b) comprises second transverse cutouts (50) formed at least partially in the second axially lateral portion (P2b) comprising:
- the second transverse grooves (51), and
- second transverse incisions (52) having a width strictly less than the width of the second transverse grooves (51),
the linear density DR2 of second transverse grooves (51) being defined by the ratio of the total number of second transverse grooves (51) formed at least in part in the second axially lateral portion (P2b) to the circumference of the tire measured on the median plane (M) and inflated to 2.5 bars,
the linear density DI2 of second transverse incisions (52) being defined by the ratio of the total number of second transverse incisions (52) made at least in part in the second axially lateral portion (P2b) to the circumference of the tire measured on the median plane (M) and inflated to 2.5 bars,
DR2 and DI2 satisfy DR2 ≤ 0.43 cm-1 and DR2 + DI2 ≥ 0.45 cm-1. Pneumatic (10) according to any one of the preceding claims, wherein DR1 + DI1 ≥ 0.50 cm-1, preferably DR1 + DI1 ≥ 0.55 cm-1, more preferably DR1 + DI1 ≥ 0.60 cm-1, even more preferably DR1 + DI1 ≥ 0.65 cm-1 and most preferably DR1 + DI1 ≥ 0.70 cm-1. Pneumatic (10) according to any one of the preceding claims, wherein DR1 ≤ 0.40 cm-1, preferably DR1 ≤ 0.38 cm-1. Pneumatic (10) according to any one of the preceding claims, wherein DR1 ≥ 0.30 cm-1, preferably DR1 ≥ 0.35 cm-1. Pneumatic (10) according to any one of the preceding claims, wherein DI1 ≥ 0.29 cm-1, preferably DI1 ≥ 0.32 cm-1 and more preferably DI1 ≥ 0.34 cm-1. Pneumatic (10) according to any one of the preceding claims, wherein DI1 ≤ 0.43 cm-1, preferably DI1 ≤ 0.40 cm-1 and more preferably DI1 ≤ 0.38 cm-1. Pneumatic (10) according to any one of the preceding claims, wherein the top reinforcement (60) comprises a working reinforcement (64) comprising at least one working layer (68, 70) comprising metallic reinforcing elements (680, 700) extending substantially parallel to each other, each metallic reinforcing element (680, 700) comprising a metallic monofilament. Pneumatic (10) according to any one of the preceding claims, having a volumetric notch ratio greater than or equal to 27.0%, preferably 28.0% and more preferably 29.0% and even more preferably from 29.0% to 31.0%. Pneumatic (10) according to any one of the preceding claims, having a tread height (Hs) greater than or equal to 6.6 mm and preferably within a range of 6.6 to 7.7 mm. Tire (10) according to any one of the preceding claims, wherein the tread (14) comprises a tread layer (53) comprising elastomeric material (M0) based on an elastomer having a glass transition temperature strictly less than or equal to -70°C, preferably from -70°C to -110°C, preferably from -80°C to -110°C and even more preferably from -80° to -100°C. Pneumatic (10) according to any one of the preceding claims, wherein the axially central portion (P0b) of the tread (14) comprises at least one central rib (32, 34, 36), the or each central rib (32, 34, 36) being axially delimited by two axially adjacent main circumferential cutouts (22, 24, 26, 28). Tire (10) according to the preceding claim, wherein the or each central rib (32, 34, 36) comprises transverse cutouts (38, 40, 42) formed in said central rib (32, 34, 36), the transverse cutouts (38, 40, 42) formed in said central rib (32, 34, 36) extend along an average direction forming an angle greater than or equal to 20°, preferably 25°, more preferably 30°, even more preferably 35° and very preferably 40° with the axial direction (Y) of the tire (10). Pneumatic (10) according to the preceding claim, wherein each transverse cutout (38, 42) formed in said central rib (32, 36) has a variable depth along said transverse cutout (38, 42). Pneumatic (10) according to the preceding claim, wherein each transverse cut (38, 42) formed in said central rib (32, 36) comprises at least one portion (382, 422), said to be of reduced depth, having a depth less than or equal to 70%, preferably 60% and more preferably 50% of the tread height (Hs) continuously along said portion of reduced depth (382, 422).