Tyre with optimized rolling resistance

Abstract

The invention relates to a tyre (1) for a motor vehicle, comprising a crown (4) having a crown reinforcement (20) and a tread (6) comprising an elastomeric compound M1 having a dynamic loss Tan (δ1). In each groove (62), the volume defined by the groove bottom surface (620) and by the radially inward extension of the walls (621, 622) as far as a radially outer contour of the crown reinforcement (20) comprises an elastomeric compound (M2) having a viscoelastic loss Tan (δ2). Tan (δ2) < 0.75xTan (δ1).

Description

Tire optimized for rolling resistance Field of invention [OOOlJThe present invention relates to a tire whose crown is optimized to achieve an advantageous performance compromise in road behavior and rolling resistance compared to conventional designs. Although not limited to this type of application, the invention is more particularly described with reference to a radial tire intended to be mounted on a passenger vehicle or van. Definitions

[0002] The tire according to the invention has a substantially toric shape around an axis of revolution substantially coincident with the axis of rotation of the tire. This axis of revolution defines three directions conventionally used by those skilled in the art: an axial direction, a circumferential direction and a radial direction.

[0003] Axial direction means the direction substantially parallel to the axis of revolution of the tire, i.e. the axis of rotation of the tire.

[0004] Circumferential direction means the direction which is substantially perpendicular to both the axial direction and a radius of the tire (in other words, tangent to a circle whose center is on the axis of rotation of the tire).

[0005] By radial direction is meant 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.

[0006] By median plane of the tire (noted M), we mean the plane perpendicular to the axis of rotation of the tire which is located at the axial mid-distance of the two beads and which passes through the axial center of the crown reinforcement.

[0007] The equatorial circumferential plane of the tire means, in a meridian section plane, the plane passing through the equator of the tire, perpendicular to the median plane and to the radial direction. The equator of the tire is, in a meridian section plane (plane perpendicular to the circumferential direction and parallel to the radial and axial directions) the axis parallel to the axis of rotation of the tire and located equidistant between the radially outermost point of the tread intended to be in contact with the ground and the radially innermost point of the tire intended to be in contact with a support, for example a rim.

[0008] Meridian plane means 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.

[0009] By radially inner, respectively radially outer, is meant closer to the tire's axis of rotation, respectively further from the tire's axis of rotation. By axially inner, respectively axially outer, is meant closer to the tire's median plane, respectively further from the tire's median plane. [OOlOJBy bead is meant the portion of the tire intended to allow the tire to be attached to a mounting support, for example a wheel comprising a rim. Thus, each bead is in particular intended to be in contact with a hook on the rim allowing it to be attached. [OOllJThe constitution of the tire is usually described by a representation of its constituents in a meridian plane. Such a choice is motivated by, as a first approximation, the axisymmetry of the geometry of the tire around its axis of rotation.

[0012] Any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​from more than a to less than b (i.e., excluding the limits a and b), while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from a to b (i.e., including the strict limits a and b).

[0013] Unless otherwise stated, any angle made between two directions is the smallest of the angles made by those two directions with each other.

[0014] In this description, the term "groove" corresponds to the definition of the terms "circumferential cut" or "circumferential cut portion", as mentioned below.

[0015] 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 distant from each other by a non-zero distance, called the width of the cutout or of the portion of the cutout.

[0016] The principal direction of a cut is the direction in which the curve equidistant from each of the edges of the cut passes to the radial dimension of the rolling surface. The curvilinear length is the length measured along this curve equidistant from each of the edges of the cutout to the radial dimension of the rolling surface, and this between each end of the cutout. The mean direction is the shortest curve joining the two ends of the cutout.

[0017] The width of a cutout or portion of a cutout is, on a new tire, the maximum distance between the two main lateral faces measured, by default and in the case where the cutout or portion of a cutout does not include a chamfer, at a radial dimension coincident with the rolling surface, and by default and in the case where the cutout or portion of a cutout includes a chamfer, at the radial dimension that is the most radially outermost of the cutout or portion of a cutout and radially innermost of the chamfer. The width is measured substantially perpendicular to the main lateral faces. 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 main lateral faces at the particular dimension of the cutout or portion of the cutout.

[0018] The depth of a cut or a portion of a cut is, on a new tire, the maximum radial distance between the bottom of the cut or portion of the cut and its projection onto the ground when the tire is rolling. The maximum value of the depths of the cuts is called the tread height. Preferably, the maximum value of the depths of the main circumferential cuts is called the tread height. Thus, preferably, the deepest cut in the tread is a main circumferential cut.

[0019] A cutout or portion of a cutout may be transverse or circumferential.

[0020] A transverse cutout or a portion of a transverse cutout is such that the cutout extends in a mean 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 transverse cutout or portion may be continuous, i.e. not interrupted by a tread block or another cutout so that the two main lateral faces determining its length are uninterrupted over the length of the transverse cutout or portion. A transverse cutout or portion may also be discontinuous, i.e. interrupted by one or more tread blocks and / or one or more cutouts so that the two main lateral faces determining its length are interrupted by one or more sculpture blocks and / or one or more cutouts.

[0021] A circumferential cutout or a portion of a circumferential cutout is such that the cutout or the portion extends in a mean direction forming an angle less than or equal to 30°, preferably less than or equal to 10° 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 cutout, the two ends coincide with each other and are joined by a curve making a complete turn of the tire. A circumferential cutout or portion may be continuous, i.e. not be interrupted by a tread block or another cutout so that the two main lateral faces determining its length are uninterrupted over the entire turn of the tire.A circumferential cutout may also be discontinuous, i.e. interrupted by one or more tread blocks and / or one or more cutouts so that the two main lateral faces determining its length are interrupted by one or more tread blocks and / or one or more cutouts over the entire circumference of the tire.

[0022] A tire comprises a crown, intended to come into contact with a ground by means of a tread, the two axial ends of which are connected by means of two sidewalls with two beads ensuring the mechanical connection between the tire and the rim on which it is intended to be mounted. The rolling surface of the tire is the surface of the tread by which the tire mounted on a rim is brought into contact with the ground when it rolls on this ground at a nominal load and pressure.

[0023] A radial tire further comprises a reinforcing reinforcement, consisting of a crown reinforcement, radially inside the tread, and a carcass reinforcement, radially inside the crown reinforcement.

[0024] The crown reinforcement of a radial tire comprises a superposition of crown layers extending circumferentially, radially outside the carcass reinforcement. Each crown layer is made up of reinforcements parallel to each other and coated with a polymeric material of the elastomer type or elastomeric mixture. The assembly consisting of the crown reinforcement and the tread is called the crown.

[0025] The radially outer contour of the crown reinforcement corresponds to the cylinder having as its axis the axis of rotation of the tire and having as its radius the greatest distance, measured in a radial direction, between the axis of rotation of the tire and a radially outer point of the crown reinforcement composed of reinforcements coated in an elastomeric compound. In other words, the radially outer contour of the crown reinforcement corresponds to the cylinder having as its axis the axis of rotation of the tire and in which the radially outermost crown reinforcement is inscribed, the crown reinforcement being composed of reinforcements coated in an elastomeric compound. In this definition, the term “cylinder” means the surface generated by the revolution, around a fixed axis, of a straight line parallel to this axis. [0026JThe carcass reinforcement of a radial tire concerned by the invention usually comprises at least one carcass layer consisting of metallic or textile reinforcing elements each coated in an elastomeric coating mixture. Said at least one carcass layer comprises a main part, connecting the two beads together and is wound, in each bead, around an annular reinforcing structure, which is most often a bead wire.

[0027] An elastomeric blend is an elastomeric material obtained by mixing its various constituents. An elastomeric blend typically comprises an elastomeric matrix with at least one diene elastomer of natural or synthetic rubber type, at least one reinforcing filler of carbon black type and / or silica type, a crosslinking system most often based on sulfur, and protective agents. For certain applications, the elastomers considered may also include thermoplastics (TPE).

[0028] The expression "based on" composition means a composition comprising the mixture and / or the reaction product of the different constituents used, some of these basic constituents being capable of, or intended to, react with each other, at least in part, during the different phases of manufacture of the composition, in particular during its crosslinking or vulcanization.

[0029] The expression "part by weight per hundred parts by weight of elastomer" (or pce) means the part, by mass per hundred parts of elastomer present in the rubber composition considered.

[0030] An elastomeric mixture can be characterized mechanically, in particular after curing, by its dynamic properties, such as a complex shear modulus G*= (G'2+G”2)l / 2, where G' is the elastic modulus and G' ' the viscous modulus, and a dynamic loss Tan(ô)=G'7G'. The complex shear modulus G* is also known as the "dynamic shear modulus", the dynamic loss Tan(ô) being otherwise known as the "viscoelastic loss".

[0031] The complex shear modulus G* is a dynamic property well known to those skilled in the art and is measured on a Metravib VA4000 or DMA+450 type viscoanalyzer using specimens comprising a cured composition extracted from the tire. The response of the specimen subjected to alternating simple sinusoidal shear stress is recorded at a frequency of 10 Hz under determined temperature conditions (here 23°C) according to the ASTM D1349-99 standard. A strain amplitude sweep is carried out from 0.1% cc to 100% cc (forward cycle), then from 100% cc to 0.1% cc (return cycle), cc meaning peak-peak. The test piece is of cylindrical section as described in ASTM D 5992 - 96 (version reapproved in 2011, 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 complex dynamic shear modulus G* is defined as the square root of the sum of the square of G' and the square of G” in which G' represents the elastic modulus and G” represents the viscous modulus. The complex shear modulus G* therefore corresponds to the measurement of the complex shear modulus G* at 10% cc of deformation on the return cycle at 23°C.

[0032] The dynamic loss Tan(ô) is yet another dynamic property well known to those skilled in the art and is measured on the same viscoanalyzer of the Metravib VA4000 type using specimens extracted from the tire. The specimen has a cylindrical section as described in the ASTM D 5992 - 96 standard (version published in September 2006, initially 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 [1.85-2.20]. The response of the specimen subjected to a sinusoidal stress in alternating simple shear is recorded, at a frequency of 10 Hz under determined temperature conditions (here 23 °C) according to the ASTM D1349-99 standard. A strain amplitude sweep is performed from 0.1% cc to 100% cc (forward cycle), then from 100% cc to 0.1% cc (return cycle), cc meaning peak-peak.The tangent of the phase angle D between the force exerted on the sample and its displacement reflects a dynamic loss and is equal to the ratio G” / G'. The dynamic loss Tan(ô) corresponds to the maximum value Tan(ô) of the tangent of the phase angle D observed on the deformation return cycle. Prior art

[0033] The skilled person, a tire designer, knows that the expected functions of a tire are at least three in number. Firstly, it is a question of carrying the load, resulting from the mass of the vehicle and all the overloads linked to the dynamic movements of the vehicle as well as any aerodynamic overloads at high speed. Secondly, it is necessary to be able to guide the vehicle on the trajectories decided by the driver, and finally, it is necessary to transmit to the ground the acceleration or braking forces decided by the driver. [0034JThe crown reinforcement is an essential element that contributes decisively to the three functions of carrying, guiding, and transmitting. In usual design, said crown reinforcement with at least two crossed metal layers surrounds the carcass reinforcement to provide the tire with the necessary strength to fulfill its carrying function.

[0035] The Steering function is also known as "road handling." It refers to the responses of a vehicle / tire assembly to multiple driver inputs (steering, acceleration, braking, etc.). Handling is essential both in terms of safety for the vehicle's stability and for driving pleasure.

[0036] The tire plays a key role in road behavior because it ensures, at the end of the chain, the transmission of forces between the vehicle and the ground in order to maintain the trajectory defined by the driver.

[0037] When cornering, to keep the vehicle on a trajectory, it is necessary to generate a force equivalent to (but in the opposite direction) the centrifugal force that tends to eject the vehicle from the trajectory. This lateral force must be generated by the vehicle's 4 tires to overcome the centrifugal force.

[0038] The deformation of the rubber blocks in contact with the ground generates a lateral force. The mechanism that allows the tire to deform the rubber blocks when cornering is drift. Drift is the angle between the direction of the wheel and the trajectory followed by the vehicle. When cornering, this angle is not zero in order to allow the tire to deform the rubber blocks of the tread and thus generate the necessary lateral forces.

[0039] Transverse drift stiffness refers to the variation in transverse forces generated in the contact patch of the moving tire crushed by the load carried, as a function of the drift angle applied to the tire. Transverse drift stiffness is expressed in Newtons per degree (N / °) and is often referred to as Dz.

[0040] For small drift angles, i.e. angles less than 4°, the transverse force, in a direction parallel to the tire's axis of rotation, is proportional to the drift angle. The transverse drift stiffness is equal to this coefficient of proportionality.

[0041] Transverse drift stiffness is an essential mechanical quantity which connects the tire to the vehicle and which determines the quality of the vehicle's behavior on the road.

[0042] Rolling resistance is another performance addressed in the invention. Rolling resistance is one of the forces that oppose the vehicle's forward movement. The rolling resistance coefficient of a tire (RRC) is the rolling resistance force related to the load carried by the tire. The coefficient is expressed in kg / t.

[0043] Rolling resistance is primarily related to tire deformation. For example, the beads associated with the sidewalls represent 20% to 30% of the tire's rolling resistance, while the tread contributes 60% to 80%.

[0044] Reducing greenhouse gas emissions from transportation is one of the major challenges facing vehicle manufacturers today. Tires represent a significant source of progress, through lower rolling resistance, as this has a direct impact on the vehicle's fuel consumption. For example, a 20% reduction in the rolling resistance of a passenger car tire saves approximately 3% of fuel per 100 km in a combined cycle.

[0045] The choice of tread plays a key role in establishing a compromise between road behavior and rolling resistance. Among the tire design parameters, those skilled in the art are familiar with treads consisting of a stack of sub-layers with material and geometric properties appropriate to each sub-layer. An example of a sub-layer, i.e. a rubber layer inserted between the crown reinforcement and the tread material, is described in document FR 2 954 333.

[0046] Another example where this time the material constituting the underlayer is flush with the bottom of the grooves of the tread is given by the document EP 2 865 543. In general, underlayer materials are used under the tread in order to improve the rolling resistance of the tire with a low hysteretic material, or to stiffen the tread in shear, but with modest rigidities so as not to too much to oppose the flattening of the tire tread in the contact area with the ground.

[0047] Furthermore, to converge more quickly towards the desired performance compromise, the number of different elastomeric compounds constituting the tread can be increased so as to be able to adapt the properties of the tire according to the area in which these compounds are located. It is possible to encounter a tread with no less than seven distinct elastomeric compounds.

[0048] The manufacture of such a tread increasingly calls for the use of complex products obtained in the form of complex profiles in order to reduce the number of successive product installations in assembly and thus reduce the cost.

[0049] A complexed profile is obtained by coextrusion, blends of different compositions are converged towards an output die, which means that a raw bonding is carried out, under pressure and temperature of the blends, without contact in the open air and before profiling. This makes it possible to obtain good resistance of the coextruded product at the interfaces between the blends. However, due to the fact that the rheological properties differ from one blend to another, it is difficult to perfectly control the geometry of the assembly, in particular the difficulty of positioning a product of a certain blend in relation to another and its maintenance over time. This difficulty leads to material scraps during the extrusion and assembly phases, which under very specific conditions will be used to form recycled materials, reused in the rest of the manufacturing process.

[0050] The inventors set themselves the objective of identifying levers linked to the architecture and the properties of the materials of the crown of a tire, to further improve the rolling resistance performance of state-of-the-art tires and preferably improve the compromise between rolling resistance performance and drift stiffness. Statement of the invention

[0051] This aim has been achieved for a tire comprising a crown, the crown comprising a crown reinforcement and a tread, the tread comprising an elastomeric compound Ml having a dynamic loss Tan(ôl); the tread having a tread surface and comprising at least one groove, each groove being delimited axially by two walls extending from the tread surface to a groove bottom surface; the crown having for each groove a thickness ESC measured radially from the groove bottom surface to a radially outer contour of the crown reinforcement. The tire according to the invention is characterized in that the crown comprises for the or each groove a sub-groove volume extending radially, from the groove bottom surface to a bottom of the sub-groove volume and extending axially between each of the extensions of the walls of the or each groove, the or each sub-groove volume comprising an elastomeric mixture M2 having a dynamic loss Tan(52) such that Tan(52) < 0.75xTan(ôl); Tan(ôl), and Tan(52) being measured at 23°C under an alternating shear stress at a frequency of 10 Hz and at 10% deformation.

[0052] The tires are, in preferred embodiments of the invention, intended for passenger vehicles as defined within the meaning of the European Tyre and Rim Technical Organisation or “ETRTO” standard, 2023. Such a tire has a section in a meridian section plane characterized by a section height H and a nominal section width or flange thickness S within the meaning of the European Tyre and Rim Technical Organisation or “ETRTO” standard, 2023 such that the H / S ratio, expressed as a percentage, is at most equal to 90 and is at least equal to 20, and the nominal section width S is at least equal to 115 mm and at most equal to 385 mm. In addition, the hook diameter D, defining the diameter of the rim on which the tire is mounted, is at least equal to 12 inches and at most equal to 30 inches.

[0053] The crown of the tire is an area that includes the tread, any sub-layer and the crown reinforcement comprising the composite layers that surround the carcass reinforcement. This description is made in the direction from the outside to the inside of the tire.

[0054] By groove is meant a circumferential cutout or a portion of a circumferential cutout, preferably having a distance between the walls of material which delimit it greater than or equal to 2 mm and preferably having a depth greater than or equal to 1 mm.

[0055] In a meridian section, each groove is delimited axially by two side walls, for example in the shape of a “V”, said side walls being able to form an angle with the radial direction for example in the range of 0° to 30°, and extending towards the inside of the tire. The bottom of the groove is delimited by a surface which connects the two side walls. Said groove bottom surface is in contact with the ambient environment, in particular the ambient air. The radial depth of the groove is the distance measured from the rolling surface to the groove bottom surface at its center.

[0056] In the or each groove, the under-groove volume is considered to be defined, radially externally, by the groove bottom surface and radially internally by the first interface encountered radially when moving radially inwards from the groove bottom surface, for example with the tread, or with an under-layer to the tread, or with the crown reinforcement. The under-groove volume is defined axially by the radially internal extension of the walls axially delimiting the or each groove.

[0057] Thus, in embodiments, the elastomeric mixture M2 is entirely included in the under-groove volume. In a variant of these embodiments, the under-groove volume comprises exclusively the elastomeric mixture M2. In another variant of these embodiments, the under-groove volume comprises the elastomeric mixture M2 and another layer of another elastomeric mixture. In other embodiments, the elastomeric mixture M2 is present in the under-groove volume and outside the under-groove volume, for example axially outside the extensions of the walls axially delimiting the groove.

[0058] The choice of the M2 mixture plays a key role in establishing a compromise between road handling and rolling resistance. The inventors observed that an under-groove mixture has disproportionate viscoelastic dissipation, otherwise known as hysteresis, compared to its small volume, as illustrated in the examples below.

[0059] This disproportionate dissipation of the mixture under the grooves is explained by the fact that the groove bottoms are the site of significant flexions (hinges) and therefore of energy dissipation which is not favorable to rolling resistance performance. Since the groove bottoms are never in contact with the road (position below the wear indicator), high wear and grip performance is not necessary at this position, which leaves a possibility of designing mixtures with fewer constraints.

[0060] The tire according to the invention presents a compromise of performance in road behavior and rolling resistance in particular thanks to the dynamic properties of the M2 groove base mixture.

[0061] The inventors have identified a way of controlling the viscoelastic dissipation in a tire according to the invention by choosing the value of the dynamic loss of the elastomeric mixture M2 to a value such that Tan (52) < 0.75xTan (51).

[0062] In other words, taking into account the impact of the elastomeric compound M2 on rolling resistance, this compound must be chosen so that its dynamic loss is strictly less than 75% of the dynamic loss of the elastomeric compound Ml of the tread.

[0063] It is thus possible to design a tire comprising an elastomeric compound M2 with low hysteresis, i.e. low dynamic loss, while freeing itself from the constraints of a composition with high performance in terms of grip and / or wear and / or rigidity. Therefore, it is possible, for example and without this being limiting of the invention, to envisage an elastomeric compound M2 with low hysteresis which dissipates less than a tread elastomeric compound while having a complex shear modulus close to that of said tread, the advantage of such a solution being to provide a gain in terms of road behavior. It is also possible, for example and without this being limiting of the invention, to envisage an elastomeric compound M2 with low hysteresis having a high capacity to resist attack by ozone from the ambient environment, or an elastomeric compound M2 with good resistance to the risk of oxidation and attack by stones.It is also possible, for example and without this being limiting of the invention, to envisage an elastomeric mixture M2 already existing among the elastomeric mixtures used for the manufacture of the tire, for example in the sidewalls so that in addition to the reduction in the rolling resistance of the tire, the industrial performance is improved by reinforcing the standardization of the elastomeric mixtures used.

[0064] Other characteristics, linked to different embodiments of the invention, contribute to further improving the performance compromise of the tire. Most often, these are geometric characteristics, but above all the mechanical and viscoelastic properties of the elastomeric mixtures used in the different parts of the crown.

[0065] In optional and advantageous embodiments, the tread comprising several grooves, the elastomeric mixture(s) M2 of said grooves form axially separated sections. For example, the tread comprises a number NB S of grooves, NB S being equal to 3 or 4 depending on the axial width of the tread.

[0066] In optional and advantageous embodiments, the top having for each groove a thickness ESC measured radially from the groove bottom surface to a radially outer contour of the top reinforcement, the volume under the groove has an ESCM2 thickness measured radially from the groove bottom surface to the bottom of the under-groove volume and having an ESCM2 / ESC ratio, reduced to a percentage, within a range from 20% to 100%, preferably within a range from 20% inclusive to 100% exclusive. [0067JThe thickness ESCM2 may be equal to the thickness ESC and in this case, the thickness ESC is measured radially between the groove bottom surface and the radially outer contour of the crown reinforcement. More preferably, the thickness ESCM2 may be in the range from 20% to 100% exclusive, very preferably in the range from 20% to 80%, and even more preferably in the range from 20% to 50%, of the thickness ESC measured radially, for example when the tire has a continuous tread in the axial direction of the tire and / or when the tire has a continuous sub-layer in the axial direction of the tire.

[0068] The term "radially outer contour of the crown reinforcement" means the profile, in a meridian section plane, passing through the radially outer ends of each of the reinforcements of the most radially outer layer of the crown reinforcement.

[0069] In certain optional and advantageous embodiments, the elastomeric mixture M2 may be in contact with the elastomeric mixture M1, for example at least on the part of the sides of the volume under the groove, the sides being composed of the extension of the walls of the groove.

[0070] Preferably, the ESCM2 thickness of the volume under the groove is within a range from 1.0 mm to 3.5 mm.

[0071] The inventors have provided a preferred range of ESCM2 thickness values. It should preferably be greater than or equal to 1.0 mm. Below 1.0 mm, ESCM2, which also has a protective function, induces a risk of not being able to combat the oxidation of the metal reinforcements. The ESCM2 thickness should preferably be less than or equal to 3.5 mm. Indeed, beyond 3.5 mm, this thickness can lead to a deterioration in rolling resistance.

[0072] In optional and advantageous embodiments making it possible to improve road behavior, the elastomeric mixture M1 having a complex shear modulus Gl*, the elastomeric mixture M2 having a complex shear modulus G2*, G2* is less than or equal to Gl*, preferably G2* is strictly less than Gl*, Gl* and G2* being measured at 23°C under alternating shear stress at a frequency of 10 Hz and 10% strain.

[0073] In optional and advantageous embodiments, Gl* is less than or equal to 4.0 MPa and preferably less than or equal to 2.5 MPa.

[0074] -In optional and advantageous embodiments, G2* is less than or equal to 2.0 MPa and preferably less than or equal to 1.0 MPa.

[0075] In optional and advantageous embodiments, the elastomeric mixture M2 is a pure material; a pure material being a material containing no more than 3% recycled elastomeric mixture; a recycled material being derived from a composition of elastomeric mixtures containing at least one elastomeric mixture rejected from a previous extrusion or assembly step during the manufacture of said tire, and said recycled material being post-treated by a homogenization device.

[0076] This configuration requires the use of a pure material for the volume of elastomeric mixture M2. The technical effect of choosing a pure material is to guarantee the stability of the mechanical properties of the material, and therefore the durability of the tire's performance.

[0077] It is known that during the manufacture of a tire, in the extrusion and assembly phases, offcuts of mixtures are added to obtain a recycled material which in turn is used in the manufacturing. The inventors have observed, in a particular embodiment, that the invention works fully and sustainably when the elastomeric material M2 is pure.

[0078] A recycled material is derived from a composition of elastomeric mixtures containing at least one elastomeric mixture rejected from an extrusion or assembly step during the manufacture of said tire, and said recycled material being post-treated by a homogenization device so that the proportion of rejected elastomeric mixture represents a rate in the range from 20% to 100% of the mass of the recycled material. The term rejected material means that the material has been shaped a first time for use in one of the stages of manufacturing a tire, without having actually been used and that it is remixed with another portion of material in order to be shaped a second time for use in one of the stages of manufacturing the tire.

[0079] The inventors have designed specific compositions for recycled materials involving the incorporation of scrap mixtures into a pure material. Under certain conditions, the proportion of scrap materials can be up to 100% of the total mass of the recycled material, but most often the recycled material includes pure mixtures in the range of 20% to 70%. Of course, the choice of pure material depends on the elastomeric mixtures rejected. Material expertise is therefore necessary to properly identify the components to be incorporated.

[0080] Based on the composition of the recycled material, a homogenization step is implemented. Homogenization consists of vigorously mixing the mixtures of the composition to incorporate and disperse, in a determined order and under well-defined shear and temperature conditions, the elements of the composition previously established according to the specifications.

[0081] In optional and advantageous embodiments, Tan (52) < 0.5xTan (51). With an elastomeric mixture M2 having such a level of dynamic loss, the operation of the invention in this particular embodiment is optimal with a significant gain in rolling resistance.

[0082] In optional and advantageous embodiments, Tan (51) is greater than or equal to 0.20, preferably 0.25.

[0083] In optional and advantageous embodiments, Tan (52) is less than or equal to 0.15, preferably 0.10.

[0084] According to an optional and advantageous embodiment, the crown comprises an underlayer positioned radially inside the tread, and radially outside the crown reinforcement.

[0085] The invention works, in particular embodiments, with several types of summit, such as the one where an underlay is introduced. This particular embodiment has the advantage of adding complementary levers with the geometry and / or the dynamic properties of the underlay to more easily find an advantageous compromise of performance between rolling resistance and road behavior.

[0086] In optional and advantageous embodiments, the underlayer comprises at least one recycled material; a recycled material being derived from a composition of elastomeric mixtures containing at least one elastomeric mixture rejected from an extrusion or assembly step during the manufacture of said tire, and said recycled material being post-treated by a homogenization device.

[0087] This case is a variant of the previous embodiment, where the introduced underlayer makes it possible to recycle offcuts of mixtures from the extrusion and / or assembly phases. Preferably, in this variant, neither the tread nor the undergroove mixture contain recycled materials.

[0088] In optional and advantageous embodiments, the elastomeric mixture Ml having a complex shear modulus Gl* and the sub-layer comprising an elastomeric mixture M3 having a complex shear modulus G3* measured at 23°C and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, G3* is strictly less than Gl*.

[0089] In optional and advantageous embodiments, the elastomeric mixture M2 having a complex shear modulus G2* and the underlayer comprising an elastomeric mixture M3 having a complex shear modulus G3* measured at 23°C and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, G3* is strictly less than G2*.

[0090] In optional and advantageous embodiments, the underlayer comprising an elastomeric mixture M3 having a complex shear modulus G3* measured at 23°C, and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, G3* is less than or equal to 2.0 MPa, preferably less than or equal to 1.5 MPa, and very preferably less than or equal to 0.6 MPa.

[0091] In optional and advantageous embodiments, the underlayer comprising an elastomeric mixture M3 having a dynamic loss Tan(53) measured at 23°C and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, Tan(53) is strictly less than Tan(ôl).

[0092] In optional and advantageous embodiments, the underlayer comprising an elastomeric mixture M3 having a dynamic loss Tan(53) measured at 23°C and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, Tan(53) is strictly greater than Tan(52).

[0093] In optional and advantageous embodiments, the underlayer comprising an elastomeric mixture M3 having a dynamic loss Tan(53) measured at 23°C at 10 Hz and under an alternating shear strain of 10% strain, Tan(53) is less than or equal to 0.20, preferably 0.15.

[0094] In a first configuration, the underlay is in contact with the tread.

[0095] In embodiments of this first configuration, the underlay is in contact with the crown reinforcement.

[0096] In other embodiments of this first configuration, the underlayer is in contact with a bonding layer arranged radially between the crown reinforcement and the underlayer. Such a bonding layer is notably used to improve the tack between the underlayer and the crown reinforcement during the tire manufacturing process.

[0097] In embodiments of this first configuration, the underlayer is in contact with the undergroove volume comprising the elastomeric material M2.

[0098] In a second configuration, the crown comprises a covering layer positioned radially outwardly of the underlayment, and radially inwardly of the tread.

[0099] In optional and advantageous embodiments, the covering layer comprising an elastomeric mixture M4 having a complex shear modulus G4* measured at 23°C and under alternating shear stress at a frequency of 10 Hz and at 10% strain, G4* is greater than G3* and / or G4* is greater than G2* and / or G4* is greater than Gl*. In optional and advantageous embodiments, G4* is greater than 1.25 x G3*. [OOlOOJThese characteristics not only allow a reduction in rolling resistance, but also an improvement in road handling. [OOlOlJIn optional and advantageous embodiments, G4* is greater than or equal to 5 MPa, preferably greater than or equal to 7 MPa, and more preferably greater than or equal to 12 MPa.

[0102] In optional and advantageous embodiments, the covering layer comprising an elastomeric mixture M4 having a dynamic loss Tan (54) measured at 23°C, and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, Tan (54) is strictly less than Tan (ôl) and / or Tan (54) is strictly greater than Tan (52) and / or Tan (54) is strictly greater than Tan (53).

[0103] In optional and advantageous embodiments, Tan (54) is greater than or equal to 0.25.

[0104] Regardless of the configuration, in optional and advantageous embodiments, the tread is axially continuous between two shoulders of the tire. Alternatively, the tread comprises several axially separated sections, preferably the tread is interrupted under the grooves and more preferably interrupted under the grooves by the under-groove volume comprising the elastomeric mixture M2.

[0105] Regardless of the configuration, in optional and advantageous embodiments, the underlayer is axially continuous between two shoulders of the tire. Alternatively, the underlayer comprises several axially separated sections, preferably the underlayer is interrupted under the grooves and more preferably interrupted under the grooves by the under-groove volume comprising the elastomeric mixture M2.

[0106] In optional and advantageous embodiments of the second configuration, the covering layer is axially continuous between two shoulders of the tire. Alternatively, the covering layer comprises several axially separated sections, preferably the underlayer is interrupted under the grooves and more preferably interrupted under the grooves by the under-groove volume comprising the elastomeric mixture M2.

[0107] Advantageously, the groove bottom volume is made of an M2 elastomeric mixture from another part of the tire. In this configuration, we are moving towards standardizing materials by limiting their number to manufacture the tire.

[0108] For example, the tire has two sidewalls each comprising at least one sidewall layer, and the elastomeric compound M2 is the same material as that constituting the at least one sidewall layer. This embodiment is justified by the fact that the sidewalls as well as the sub-groove compound are in contact with the ambient environment. The use of a compound designed for the sidewalls at this position improves the endurance of the tire, in particular its ability to resist external aggressions when the tire is rolling.

[0109] According to an optional and advantageous embodiment, the elastomeric mixture M2 is based on the same composition as the composition based on the elastomeric mixture M3.

[0110] Advantageously, the tread comprises at least one recycled material. A recycled material is derived from a composition of elastomeric mixtures containing at least one elastomeric mixture rejected from a previous extrusion or assembly step during the manufacturing of said tire. A recycled material is processed by a homogenization device. [OOlllJPreferably, the elastomeric mixture M2 of the or each volume under the groove has a rubber composition based on at least one blend of polyisoprene, natural rubber and polybutadiene, a crosslinking system, and a reinforcing filler at an overall rate of at most 45 pce, and comprising carbon black, at a rate of at most 5 pce, and predominantly silica at a rate of at least 20 pce and at most 40 pce.

[0112] Alternatively, the elastomeric mixture M2 of the or each volume under the groove has a rubber composition based on at least one blend of polyisoprene, natural rubber and polybutadiene, a crosslinking system, and a reinforcing filler at an overall rate of at most 45 pce, and comprising carbon black at a rate of at least 20 pce and at most 40 pce.

[0113] According to an optional and advantageous embodiment, the tread comprises at least one tread portion, hereinafter referred to as a tread wing, at at least one of the axial ends of the tread, said tread wing having an axially outer contour delimited by a first point, located at the intersection of the axially and radially outer contour of the sidewall and the axially and radially outer contour of the tread, and a second point located at a curvilinear distance of between 5% and 25% of the nominal bead width of the tire dimension, said tread wing being radially inwardly in contact with the covering layer. Such tires are known from documents WO2012 / 175444, WO2021 / 111083.

[0114] Preferably, the presence of a tread wing makes it possible to further improve the rolling resistance by replacing at least one extreme part of the tread with a material of lower hysteresis than the material of the central portion of the tread. Thus, the complex shear modulus of the tread wing is at most equal to 80% of the complex shear modulus of the central portion of the tread, the complex shear moduli being measured at 23°C and under alternating shear stress at a frequency of 10 Hz and at 10% deformation.

[0115] Preferably, the dynamic loss of at least one tread wing is at most equal to 80% of the dynamic loss of the central portion of the tread, the dynamic loss of at least one wing and the dynamic loss of the central portion being measured at 23°C and under alternating shear stress at a frequency of 10 Hz and at 10% deformation. Brief description of the drawings

[0116] The present invention will be better understood upon reading the detailed description of embodiments taken as examples, in no way limiting and illustrated by the appended drawings in which: • Figure 1 shows a schematic meridian section of a tire according to a first embodiment of the invention, with a continuous tread; • Figure 2 shows a schematic meridian section of a tire according to a variant of the first embodiment of the invention, with a discontinuous tread; • Figure 3 shows a schematic meridian section of a tire according to a second embodiment of the invention, with a continuous underlayer; • Figure 4 shows a schematic meridian section of a tire according to a variant of the second embodiment of the invention, with a discontinuous underlayer; • Figure 5 shows a schematic meridian section of a tire according to a third embodiment of the invention with a tread and a continuous underlay; • Figure 6 shows a schematic meridian section of a tire according to a fourth embodiment of the invention; and • Figure 7 shows a schematic meridian section of a tire according to a fifth embodiment of the invention. Detailed description of the invention

[0117] The invention has been more particularly studied for a tire for a motor vehicle, here for a passenger vehicle of standardized designation, according to the specification standard of the ETRTO (European Technical Organization for Rims and Tires), 245 / 45R18 100 W.

[0118] In the various figures, identical or similar elements bear the same references. Given the symmetry of the tread, for the readability of the figures, the elements are referenced only once on one side of a meridian plane.

[0119] In the embodiment shown in Figure 1, the tread 6 is laid radially outwardly at the crown 4, without an underlay.

[0120] Figure 1 shows a tire 1, an equatorial plane CP, two beads 50 and two sidewalls 3 each connected to a bead 50. The tire has a crown 4, which has a crown reinforcement 20 and a tread 6. The tread comprises an elastomeric compound M1 having a complex shear modulus G1 * and a dynamic loss Tan (51) measured at 23°C under alternating shear stress at a frequency of 10 Hz and at 10% deformation. The tread 6 extends axially from one shoulder 60 to the other shoulder 60 and is axially continuous between the two shoulders 60. The tread 6 comprises a rolling surface 61 intended to come into contact with the roadway during rolling of the tire. The tread 6 comprises sculpture blocks 63 and grooves 62 oriented essentially circumferentially separating the sculpture blocks 63.Each groove 62 forms a groove, which extends longitudinally, in the tread 6. Each groove 62 is delimited axially by two walls 621, 622 extending from the tread surface 61 to a groove bottom surface 620. Under the groove bottom surface 620, the tire 1 comprises a sub-groove volume V delimited by the groove bottom surface 620, by the radially internal extension of the walls 621 and 622 and by a bottom 623 of the sub-groove volume V. The sub-groove volume V comprises an elastomeric material called M2.

[0121] The bead 50 comprises at least one carcass layer, shown in FIG. 1 in broken lines. The carcass layer is formed of reinforcements coated with an elastomeric mixture. The carcass layer comprises a main part 53, connecting the two beads 50 together and is wound in each bead 50, from the inside to the outside of the tire around a circumferential reinforcement element, most often metallic, called a bead wire 51, to form a turn-up 52. The reinforcements of a carcass layer are substantially parallel to each other and form, with the circumferential direction, an angle of between 85° and 95°.

[0122] As known per se, the crown reinforcement 20 comprises layers of cables or monofilament reinforcements generally coated with a thin layer of rubber. The reinforcement of crown 20 comprises two crossed layers 22, 23 consisting of reinforcements coated in an elastomeric mixture. The reinforcements of the crossed layers 22, 23 make an angle of between 10° and 45° with the circumferential direction. A third reinforcement layer 21 binds the two previous layers. Said layer 21 also comprises reinforcements coated in an elastomeric mixture, which make an angle of approximately ±2.5° with the circumferential direction.

[0123] The crown 4 comprises, for each groove 62, a sub-groove volume V extending radially from the groove bottom surface 620 to the bottom 623 of the sub-groove volume V. The sub-groove volume V extends axially between each of the extensions of the walls 621, 622 of each groove 62. The bottom 623 is here formed by the interface between the elastomeric mixture M1 of the tread 6 and the elastomeric mixture M2 included in the sub-groove volume V.

[0124] The elastomeric mixture M2 has a complex shear modulus G2* and a dynamic loss Tan (52) measured at 23°C under alternating shear stress at a frequency of 10 Hz and at 10% strain. We have Tan (52) < 0.75xTan (51), preferably Tan (52) < 0.5xTan (51).

[0125] We also have Tan (51) greater than or equal to 0.20, preferably 0.25 and Tan (52) less than or equal to 0.15, preferably 0.10.

[0126] We also have G2* less than or equal to Gl*, preferably G2* strictly less than G1*. G1* is less than or equal to 4.0 MPa and preferably less than or equal to 2.5 MPa. G2* is less than or equal to 2.0 MPa and preferably less than or equal to 1.0 MPa.

[0127] The crown 4 has for each groove 62, a thickness ESC measured radially from the groove bottom surface 620 to a radially outer contour of the crown reinforcement 20. For each groove 62, the thickness ESCM2 is measured radially from the groove bottom surface 620 to the bottom 623. For each groove 62, the thickness ESCM1 is measured radially from the bottom 623 to the radially outer contour of the crown reinforcement 20. In the embodiment of FIG. 1, the ratio ESCM2 / ESC, reduced to a percentage, is within an interval ranging from 20% to 100%, preferably ranging from 20% inclusive to 100% exclusive, more preferably ranging from 20% exclusive to 100% exclusive, very preferably ranging from 20% to 80% and even more preferably ranging from 20% at 50%. Preferably, the ESCM2 thickness is in the range from 1.0 mm to 3.5 mm.

[0128] With reference to figure 1, the elastomeric mixture M2 of the under-groove volume V is in contact with the elastomeric mixture M1 of the tread 6, at least on the part of the sides of the volume V composed by the extension of the walls 621, 622 of the groove 62 extending over the thickness ESCM2.

[0129] We will now describe a tire according to a variant of the first embodiment with reference to figure 2. In this figure, the elements similar to those of the first embodiment are designated by identical references.

[0130] The variant illustrated in Figure 2 differs from the tire according to the first embodiment illustrated in Figure 1 in that the tread 6 comprises several axially separated sections. The tread 6 is interrupted under the grooves by the under-groove volume V comprising the elastomeric mixture M2. Indeed, the under-groove volume V extends from the groove bottom surface 620 to the radially outer contour of the crown reinforcement 20. In other words, the thickness ESCM2 is equal to the thickness ESC which are both measured radially from the groove bottom surface 620 and to the bottom 623, here the radially outer contour of the crown reinforcement 20.

[0131] We will now describe a tire according to a second embodiment with reference to figure 3. In this figure, the elements similar to those of the first embodiment and its variant are designated by identical references.

[0132] The second embodiment illustrated in Figure 3 differs from the first embodiment illustrated in Figure 1 in that the crown 4 comprises an underlayer 71 positioned radially inside the tread 6 and radially outside the crown reinforcement 20. The underlayer 71 is in contact with the tread 6 and in contact with the crown reinforcement 20. In addition, the underlayer 71 is positioned radially inside the under-groove volume V comprising the elastomeric material M2. The underlayer 71 is axially continuous between the two shoulders 60.

[0133] The underlayer 71 comprises an elastomeric mixture M3 having a complex shear modulus G3* and a dynamic loss Tan(53) measured at 23°C and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation. [00134JG3* is strictly less than Gl* and G2*. G3* is less than or equal to 2.0 MPa, preferably less than or equal to 1.5 MPa, and very preferably less than or equal to 0.6 MPa. Tan(53) is strictly less than Tan(ôl) and Tan(53) is strictly greater than Tan(52). Tan(53) is less than or equal to 0.20, preferably 0.15.

[0135] We will now describe a tire according to a variant of the second embodiment with reference to Figure 4. In this figure, elements similar to those of the embodiments and variants previously described are designated by identical references. The variant illustrated in Figure 4 differs from the tire according to the second embodiment illustrated in Figure 3 in that the sub-layer 71 comprises several axially separated sections. The sub-layer 71 is interrupted under the grooves 62 by the sub-groove volume V comprising the elastomeric mixture M2.

[0136] We will now describe a tire according to a third embodiment with reference to Figure 5. In this figure, the elements similar to those of the embodiments and variants previously described are designated by identical references. Unlike the tire according to the second embodiment, the tire according to the third embodiment illustrated in Figure 5 is such that the bottom 623 of the under-groove volume V is formed by an interface between the elastomeric mixture M2 included in the under-groove volume V and the elastomeric mixture M1 of the tread 6.

[0137] We will now describe a tire according to a fourth embodiment with reference to Figure 6. In this figure, elements similar to those of the embodiments and variants previously described are designated by identical references. Unlike the tires according to the second embodiment, the tire according to the fourth embodiment illustrated in Figure 6 is such that the elastomeric mixture M2 is based on the same composition as the composition based on the elastomeric mixture M3. In addition, ESC=ESCM2.

[0138] A tire according to a fifth embodiment will now be described with reference to Figure 7. In this figure, elements similar to those of the embodiments and variants previously described are designated by identical references. Unlike the tires according to the third embodiment, the tire according to the fifth embodiment illustrated in Figure 7 comprises a covering layer 72 positioned radially outside the sub-layer 71 and radially inside the tread 6. The covering layer 72 is axially continuous between the two shoulders 60. The covering layer 72 comprises an elastomeric mixture M4 having a complex shear modulus G4* and a dynamic loss Tan (54) measured at 23°C and under alternating shear stress at a frequency of 10 Hz and at 10% deformation. G4* is greater than G3*, G2* and Gl*. Preferably, G4* is greater than 1.25 x G3*.G4* is greater than or equal to 5 MPa, preferably greater than or equal to 7 MPa, and more. preferably greater than or equal to 12 MPa. Tan(54) is strictly less than Tan(ôl). Tan(54) is strictly greater than Tan(52) and Tan(53). Tan (54) is greater than or equal to 0.25.

[0139] In the embodiments and variants described above, the elastomeric mixtures Ml of the tread which can be used are for example those based on the composition described in the table below. The formulations are given by mass (pce meaning percentage of the mass of elastomer).

[0140] (a) SBR with 27% styrene, butadiene -1,2:5%, cis-1,4:15%, trans-1,4:80% Tg - 48°C; (b) Silica “Zeosill 165MP” from Solvay with BET surface area 160m2 / g; (c) Silane TESPT “SI69” from the company Evonik; (d) “Flexon 630” TDAE oil from Shell; (e) “Escorez 2173” resin from Exxon; (f) “Santoflex 6PPD” antioxidant from Solutia; (g) “Santocure CBS” accelerator from Solutia.

[0141] In the embodiments and variants described above, the elastomeric mixtures M2 of the under-groove volume which can be used are for example those based on the composition described in the table below. The formulations are given by mass (pce meaning percentage of the mass of elastomer).

[0142] In the applicable embodiments and variants described above, the elastomeric mixtures M3 of the underlayer which can be used are for example those based on the composition described in the table below. The formulations are given by mass (pce meaning percentage of the mass of elastomer).

[0143] In the applicable embodiments and variants described above, the elastomeric mixtures M4 of the covering layer which can be used are for example those based on the composition described in the table below. The formulations are given by mass (pce meaning percentage of the mass of elastomer). Comparative tests

[0144] A PI tire, according to the invention, of size 245 / 45R18 100 W, according to the ETRTO (European Technical Organization for Rims and Tires) specification standard, intended to equip a passenger vehicle was evaluated to highlight the performance provided by the invention. The results of the evaluation tests are compared with those obtained for control tires T and Tl of the same size, 245 / 45R18 100 W.

[0145] The control tire T includes a tread and does not include an underlay. The elastomeric compound Ml of the tread has a complex shear modulus Gl* equal to 2.3 MPa and a dynamic loss Tan(ôl) equal to 0.37.

[0146] The control tire T1 consists of a tread and a sub-layer. The elastomeric compound M1 of the tread is identical to that of the control tire T. The elastomeric compound M3 of the sub-layer has a complex shear modulus G3* equal to 1.75 MPa and a dynamic loss Tan(53) equal to 0.14.

[0147] The tire PI according to the invention is in accordance with the second embodiment and comprises a tread 6 and a sub-layer 71. The under-groove volume V comprises an elastomeric mixture M2 having a low hysteresis characterized by a dynamic loss value Tan(52) equal to 0.08 and having a complex shear modulus G2* equal to 0.85 MPa. The elastomeric mixture is based on a chemical composition suitable for exposure to the ambient environment, in particular air. Furthermore, the elastomeric mixture M1 of the tread 6 is chosen in particular to satisfy stiffness and crack resistance properties of the tire with a dynamic loss value Tan(ôl) equal to 0.37 and having a complex shear modulus G1 * of 2.3 MPa.

[0148] Table 1 below summarizes the characteristics of the T, Tl and PI tire mixtures.

[0149] Table 1

[0150] The rolling resistance RRT and the drift stiffness Dz were simulated by the finite element method for the tire PI of the invention and the control tires T and Tl. A result higher (respectively lower) than 100% means an improvement (respectively a deterioration) of the considered performance. The results are shown in Tables 2 and 3 below. Table 2 Table 3

[0151] These examples confirm that the claimed relationship between the dynamic properties of the elastomeric compounds M1 and M2 leads to good operation of the tire with an improvement in rolling resistance and while maintaining, or only very slightly degrading, the drift stiffness. Thus, the comparative examples show that the present invention makes it possible to improve the rolling resistance performance and, moreover, the compromise between rolling resistance and drift stiffness.

[0152] The invention not being limited to the embodiments previously described, it may be envisaged, in order to improve rolling resistance and drift rigidity, to use wedge-shaped elements in the wearing part of the tread.The tread thus comprises sculpture blocks separated by grooves oriented essentially circumferentially, the covering layer is, axially opposite certain sculpture blocks, extended radially outwards by at least one reinforcing element extending radially from the radially outer surface of the covering layer towards the outside of the tread up to a radial height greater than 50% of the radial thickness of the tread, said reinforcing element being of variable axial width, from a maximum value less than 50% of the axial width of said sculpture block, said axial width decreasing when moving radially upwards. Tires comprising such sculpture blocks are known, for example such as those described in WO20 19 / 016440, WO2022 / 090652.

Claims

Claims

1. A tire (1) for a motor vehicle comprising a crown (4), the crown (4) comprising a crown reinforcement (20) and a tread (6), the tread (6) comprising an elastomeric mixture Ml having a dynamic loss Tan (51);the tread (6) having a running surface (61) and comprising at least one groove (62), each groove (62) being delimited axially by two walls (621, 622) extending from the running surface (61) to a groove bottom surface (620), characterized in that the crown (4) comprises, for the or each groove (62), a sub-groove volume (V) extending radially from the groove bottom surface (620) to a bottom (623) of the sub-groove volume (V) and extending axially between each of the extensions of the walls (621, 622) of the or each groove (62), the or each sub-groove volume (V) comprising an elastomeric mixture M2 having a dynamic loss Tan (52) such that Tan (52) < 0.75xTan (51) ; Tan (51), and Tan (52) being measured at 23°C under alternating shear stress at a frequency of 10 Hz and at 10% strain.;

2. Tire (1) according to the preceding claim, in which the tread (6) comprises several grooves (62), the elastomeric mixture(s) M2 of said grooves (62) form axially separated sections.

3. Tire (1) according to any one of the preceding claims, in which, the crown (4) having for each groove (62) a thickness ESC measured radially from the groove bottom surface (620) to a radially outer contour of the crown reinforcement (20), the under-groove volume (V) has a thickness ESCM2 measured radially from the groove bottom surface (620) to the bottom (623) of the under-groove volume (V) and having a ratio ESCM2 / ESC, reduced to a percentage, comprised in an interval going from 20% to 100%, preferably in an interval going from 20% inclusive to 100% exclusive.

4. Tire (1) according to the preceding claim, in which the thickness ESCM2 of the under-groove volume (V) is within a range from 1.0 mm to 3.5 mm.

5. Tire (1) according to any one of the preceding claims, in which, the elastomeric mixture M1 having a complex shear modulus Gl*, the elastomeric mixture M2 having a complex shear modulus G2*, G2* is less than or equal to Gl*, preferably G2* is strictly less than Gl*, Gl* and G2* being measured at 23°C under alternating shear stress at a frequency of 10 Hz and 10% strain.

6. A tire (1) according to any preceding claim, wherein Tan (52) < 0.5xTan (51).

7. Tire (1) according to any one of the preceding claims, in which the crown (4) comprises an underlayer (71) positioned radially inside the tread (6) and radially outside the crown reinforcement (20).

8. Tire (1) according to the preceding claim, wherein the elastomeric mixture M1 having a complex shear modulus Gl* and the sub-layer comprising an elastomeric mixture M3 having a complex shear modulus G3* measured at 23°C and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, G3* is less than Gl*.

9. A tire (1) according to claim 7 or 8, wherein the elastomeric mixture M2 having a complex shear modulus G2* and the sub-layer comprising an elastomeric mixture M3 having a complex shear modulus G3* measured at 23°C and under alternating shear stress at a frequency of 10 Hz and at 10% strain, G3* is less than G2*.

10. Tire (1) according to any one of claims 7 to 9, wherein the underlayer (71) comprises an elastomeric mixture M3 having a complex shear modulus G3* measured at 23°C and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, G3* is less than or equal to 2.0 MPa, preferably less than or equal to 1.5 MPa, and very preferably less than or equal to 0.6 MPa.

11. Tire (1) according to any one of claims 7 to 10, in which the underlayer (71) comprising an elastomeric mixture M3 having a dynamic loss Tan(53) measured at 23°C and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, Tan(53) is strictly less than Tan(ôl).

12. Tire (1) according to any one of claims 7 to 11, in which the underlayer (71) comprising an elastomeric mixture M3 having a dynamic loss Tan(53) measured at 23°C and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, Tan(53) is strictly greater than Tan(52).

13. Tire (1) according to any one of claims 7 to 12, wherein the sub-layer (71) comprising an elastomeric mixture M3 having a dynamic loss Tan(53) measured at 23°C and under an alternating shear stress at a frequency of 10 Hz and at 10% deformation, Tan(53) is less than or equal to 0.

15.

14. Tire (1) according to any one of claims 7 to 13, wherein the sub-layer (71) is in contact with the tread (6).

15. Tire (1) according to any one of claims 7 to 14, wherein the underlayer (71) is in contact with the crown reinforcement (20) or in contact with a connecting layer arranged radially between the crown reinforcement (20) and the underlayer (71).

Images