Tire having improved grip on wet ground at the end of life

Abstract

The present invention relates to a tire (10) for a passenger vehicle, comprising a tread including at least one defined wear indicator (46) defining a defined wear threshold, a tread layer (52) and a support layer (54) for the tread layer (52), the tread layer (52) comprising an elastomeric tread material having a complex dynamic shear modulus G*_1 and a dynamic loss tanD0_1, and the support layer (54) comprising an elastomeric support material having a complex dynamic shear modulus G*_2 and a dynamic loss tanD0_2, satisfying tanD0_2≥0.37x tanD0_1 and G*_2≥0.90x G*_1.

Description

Technical Field

[0001] This invention relates to a tire for passenger vehicles. Background Technology

[0002] A tire sold under the trade name MICHELIN Primacy 4 is known from the prior art, having a generally toroidal shape about an axis of rotation substantially coincident with the tire's axis of rotation. The tire includes a crown, two sidewalls, and two beads, each sidewall connecting each bead to the crown. The tire also includes a carcass reinforcement anchored in each bead and extending radially inward in each sidewall and in the crown. The crown includes a tread and a crown reinforcement arranged radially inward of the tread.

[0003] The tread includes cuts that separate the tread blocks from each other. These cuts specifically include grooves and sipes. Grooves include circumferential grooves, and wear indicators are arranged at the bottom of these circumferential grooves. Such wear indicators are specified, for example, by UN regulations R30 and R54, US standard FMVSS139, or Chinese standard GB97743, and aim to enable tire users to identify a specified tire wear threshold beyond which driving is dangerous, especially on wet surfaces. Therefore, these wear indicators are called specified wear indicators. Each specified wear indicator is formed by a protrusion that extends radially from the bottom of the circumferential groove, particularly the bottom of the deepest circumferential groove, and extends radially outward by a radial height substantially equal to 1.6 mm. This radial height allows the tire's wear potential (5.4 mm in this case) to be defined as the radial height between the outermost radial point of the specified wear indicator when the tire is new and the projection of that outermost radial point onto the ground when the tire is in motion. In other words, wear potential is equal to the difference between the tread depth of a brand new tire (7.0 mm in this case) and the radial height of the specified wear indicator (1.6 mm in this case).

[0004] The tire tread comprises a tread layer and a backing layer for the tread layer. The tread layer is designed to contact the ground via its surface during tire travel. The backing layer is arranged radially inside the tread layer. The tread layer contains an elastomeric tread material, and the backing layer contains an elastomeric backing material different from the elastomeric tread material. Therefore, the tread layer and the backing layer are continuous in the meridional plane of the tire via an interface that displays an interface trajectory.

[0005] The backing layer is designed to prevent contact with the ground while the tire is in motion, at least until a specified wear threshold is reached. In other words, by defining a specified wear path in the meridional plane that is parallel to the tread surface of a new tire and passes through the outermost radial point of the specified wear indicator, an interface path located radially below the tread blocks is arranged radially inside the specified wear path in the meridional plane.

[0006] The aforementioned MICHELIN Primacy 4 tire is particularly characterized by very low rolling resistance. This is because both the elastomer tread and the backing material have relatively small dynamic losses of 0.38 and 0.15, respectively, expressed as tanDMAX23_1 and tanDMAX23_2, and measured according to standard ASTM D-5992-96 at a temperature of 23°C and a frequency of 10Hz.

[0007] The result of seeking relatively small dynamic loss values ​​tanDMAX23_1 and tanDMAX23_2 in order to obtain very low rolling resistance is that braking performance on wet surfaces is compromised compared to brand new tires after more than half of the wear potential has been achieved. Summary of the Invention

[0008] The subject of this invention is a tire that, after more than half of its wear potential has been achieved, exhibits improved braking performance on wet surfaces compared to prior art tires.

[0009] Therefore, the subject of this invention is a tire for passenger vehicles, comprising a tread with slits and tread blocks, the slits separating the tread blocks from each other, the tread being designed to contact the ground via its surface during tire travel, the tread including at least one defined wear indicator defining a defined wear threshold, and...

[0010] In the axially central portion of the tread having an axial width equal to at least 70% of the width of the tread surface, the tread includes:

[0011] - A tread layer with a tread surface, the tread layer comprising an elastomeric tread material having:

[0012] -The complex dynamic shear modulus G*_1, measured at 10% strain at a temperature of 23°C and a frequency of 10Hz according to standard ASTM D-5992-96, and

[0013] - The dynamic loss tanD0_1 was measured at 0°C and 10Hz according to standard ASTM D-5992-96.

[0014] - A backing layer for the tread layer, the backing layer being radially disposed inside the tread layer and comprising an elastomeric backing material having:

[0015] -The complex dynamic shear modulus G*_2, measured at 10% strain at a temperature of 23°C and a frequency of 10Hz, according to standard ASTM D-5992-96.

[0016] - The dynamic loss tanD0_2 was measured at 0°C and 10Hz according to standard ASTM D-5992-96.

[0017] The elastomeric tread material differs from the elastomeric backing material such that the tread layer and the backing layer are continuous in a meridional cross-sectional plane including a specified wear indicator via an interface that displays an interface trajectory.

[0018] Its characteristic is that tanD0_2≥0.37x tanD0_1 and G*_2≥0.90x G*_1,

[0019] In the axial central portion of the tread, a specified wear track is defined in the meridional section plane, parallel to the tread surface of a new tire and passing through the outermost radial point of the specified wear indicator. At least 75% of the length of the interface track located radially below the tread block is arranged radially inside the specified wear track in the meridional section plane.

[0020] In the axial central portion of the tread, at least 75% of the length of the interface track located radially below the tread pattern block is arranged in the meridional section plane at an average radial distance of less than or equal to 2.0 mm from the specified wear track.

[0021] After more than half of its wear potential has been achieved, the tire according to the invention exhibits significantly improved braking performance on wet surfaces compared to prior art tires, as shown in the comparative tests described below.

[0022] Of particular note of this invention is that, although the majority of the backing layer is not intended to be in contact with the ground while the tire is in motion, the backing layer enables improved braking performance of the tire on wet surfaces after more than half of its wear potential has been achieved.

[0023] On the one hand, the dynamic loss tanD0 measured at 0°C allows for characterization of grip potential on wet surfaces. This is because when a tire travels on a wet surface with irregularities, the tread deforms to conform to the top of the indentation formed by the irregularity. Once the tire has exceeded half of its wear potential, the backing layer will be more effective at mitigating this indentation mechanism if the dynamic loss tanD0 of the backing layer measured at 0°C is relatively higher than that of the tread layer measured at 0°C. Therefore, by satisfying the characteristic tanD0_2 ≥ 0.37 x tanD0_1, the tire's grip potential on wet surfaces after exceeding half of its wear potential is improved.

[0024] On the other hand, the complex dynamic shear modulus G*, measured at 10% strain at 23°C, characterizes the stiffness of the ply and thus its ability to prevent the tread from deforming under water pressure when the tire is driven on a wet surface. This tread deformation mechanism, known as blistering, can cause a portion of the contact patch to lose contact with the ground, thereby reducing tire grip. Once the tire has exceeded half of its wear potential, the backing layer will be more effective against this blistering mechanism if its complex dynamic shear modulus G*, measured at 10% strain at 23°C, is relatively higher than that of the tread layer. Therefore, by satisfying the characteristic G*_2≥0.90x G*_1, the stiffness of the backing layer, and thus the stiffness of the tread, is improved after exceeding half of the wear potential.

[0025] It should be noted that, according to the present invention, it is necessary to control the tread's grip potential and stiffness. This is because improving grip potential on wet surfaces is only beneficial when the tread is properly positioned on the ground, and vice versa.

[0026] The complex shear modulus G* is a kinetic property well known to those skilled in the art and was measured using a tire-derived specimen on a Metravib VA4000 viscometer. The response of the specimen was recorded after it was subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz under standard temperature conditions (23°C in this case) according to standard ASTM D1349-99. Strain amplitude scans were performed from 0.1% to 100% (outward cycle) and then from 100% to 0.1% (backward cycle). The specimen had a cylindrical cross-section as described in Figure X2.1 (circular style) in standard ASTM D 5992-96 (the version published in September 2006, which was originally approved in 1996), and had a diameter of 10 mm [0 to +0.04 mm] and a thickness of 2 mm [1.85 to 2.20]. 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* at 10% strain is then measured in a return loop.

[0027] The kinetic loss tanD0 is another kinetic property well known to those skilled in the art, and was measured using the same specimens taken from the tire on the same Metravib VA4000 viscometer. To determine this property, a temperature scan was performed, increasing at a temperature gradient of 1.5 °C per minute from a temperature Tmin below the material's glass transition temperature Tg to a temperature Tmax corresponding to the rubber stability level of the elastomer material. Before starting the scan, the sample was stabilized at temperature Tmin for 20 minutes to allow for uniform temperature throughout the specimen. For each temperature value, the specimen's response was recorded, having been subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz until the stress representing the operating point of the elastomer material in the tire (0.7 MPa in this case). The value of the kinetic loss tanD0 is a measurement obtained for a temperature equal to 0 °C.

[0028] The kinetic loss tanDMAX23 is another kinetic property well known to those skilled in the art, and was measured using the same specimens taken from tires on the same Metravib VA4000 viscometer. The response of the specimens, subjected to simple alternating sinusoidal shear stress at a frequency of 10 Hz under defined temperature conditions (23°C in this case) according to standard ASTM D1349-99, was recorded. Strain amplitude scans were performed from 0.1% to 100% (outward cycle) and then from 100% to 0.1% (backward cycle). The tangent of the phase angle D between the force applied to the sample and its displacement is represented as the kinetic loss, which is equal to the ratio G” / G’. The maximum value of the tangent of the phase angle D, tanDMAX, observed on the strain return cycle was recorded.

[0029] At least 75% of the length of the interface track located radially below the tread blocks is arranged radially inside the prescribed wear track in the meridional section plane. This feature manifests in the fact that the majority of the backing layer is designed not to contact the ground during tire operation, at least as long as a prescribed wear threshold has not been reached. Compared to prior art tires, in the tire according to the invention, the backing layer can partially contact the ground, i.e., at most 25% of the length of the interface track located radially below the tread blocks. This is because, due to the relatively high value of the dynamic loss tanD0_2 of the backing layer, the grip potential provided by the backing layer in contact with the ground will be greater than that provided by the backing layer of a prior art tire in contact with the ground. In other words, if the backing layer of the tire according to the invention contacts the ground, the grip potential is not significantly impaired.

[0030] This feature is particularly advantageous because it allows for the avoidance of scrapping a non-negligible portion of the backing layer that rises radially above the prescribed wear track. This radial rise is particularly observed near the cut, the molding of which causes an outward axial flow of the elastomeric tread and backing material located radially below the cut, thus causing an outward radial flow of the elastomeric tread and backing material located radially near the cut.

[0031] Furthermore, according to the invention, a specific arrangement of the tread layers and backing layers, as well as the properties of the tread and backing materials, are observed on the axially central portion of the tread. This feature reflects the fact that the invention requires the arrangement and properties of materials on a large axial portion of the tread intended to contact the ground (in this case, at least 70% of the width of the tread surface). The axially central portion includes the tire's midplane.

[0032] In a first preferred variant, according to the invention, the axial width of the axial central portion of the tread is equal to the axial width of the tread. In other words, the axial width of the axial central portion of the tread is equal to 100% of the width of the tread surface.

[0033] In a second variant of the invention, the axial width of the axially central portion of the tread is strictly smaller than the axial width of the tread surface, such that the tread includes axially oriented side portions arranged axially outside the axially central portion, each axially oriented side portion having an axial width at most 15% of the axial width of the tread. In a first configuration of this second variant, the axially oriented side portions have a specific arrangement different from that of the axially central portion. In a second configuration of this second variant, the axially oriented side portions have material properties different from those of the axially central portion.

[0034] Conventionally, the tread surface is defined on a tire mounted on a nominal rim and inflated to the nominal pressure. If there is a clear boundary between the tread surface and the rest of the tire, the axial width of the tread surface can be simply measured. If the tread surface is continuous with the outer surface of the tire sidewall, the axial boundary of the tread surface passes through the point where the angle between the tangent to the tread surface and a straight line parallel to the axial direction passing through that point is equal to 30°. When there are multiple points in the meridional section plane where the absolute value of the angle is equal to 30°, the outermost radial point is used.

[0035] The radial interface track located below the tread blocks is defined by two straight lines along the axial direction. These two straight lines are perpendicular to the tread surface and, when the tire is brand new, pass through the axial ends of each tread block that is part of the tread surface.

[0036] According to the invention, the backing layer needs to be not too far from the tread surface in the radial direction after the tire has exceeded half of its wear potential, so that the backing layer has a significant effect on the aforementioned indentation and blistering mechanisms. Therefore, a large portion (at least 75% in this case) of the length of the interface track located radially below the tread blocks is arranged in the meridional section plane at a relatively small distance from the prescribed wear track, in this case less than or equal to 2.0 mm. To determine the average radial distance between the interface track and the prescribed wear track, the average of several radial distances between the interface track and the prescribed wear track will be used, these radial distances being measured regularly (e.g., every millimeter) along the interface track located radially below the tread blocks.

[0037] The fact that the tread and backing layers are continuous is particularly evident in the fact that the tread material and the backing material are in direct contact with each other along the interface, with no other material inserted radially between the tread and backing layers.

[0038] To determine the length of the interface track located radially below the tread blocks, the curve length of the interface track arranged radially below the tread surface is measured in the meridional section plane. This implicitly excludes the length of the interface track arranged radially below the individual cuts (which themselves do not have a surface intended to contact the ground).

[0039] To determine whether the length of the radially located interface track beneath the tread blocks lies radially inside or outside the specified wear track, for each point on the interface track, its radial projection onto the specified wear track is determined to be radially inside or outside that point. Similarly, to determine the distance between the radially located interface track beneath the tread blocks and the specified wear track, for each point on the interface track, the distance between that point on the interface track and its radial projection onto the specified wear track is determined.

[0040] The geometric features described in this application can be easily determined in the meridional section of the tire.

[0041] Elastomer materials are materials that exhibit elastomeric properties. Such materials are advantageously obtained by crosslinking a crosslinkable composition comprising at least one elastomer and at least one other component. Preferably, the crosslinkable composition comprising at least one elastomer and at least one other component comprises an elastomer, a crosslinking system, and a filler. Crosslinkable compositions for tread and backing layers are conventional compositions for tire treads, typically based on diene elastomers, reinforcing fillers (e.g., carbon black and / or silica), vulcanization systems, and conventional additives.

[0042] To facilitate water drainage and ensure good grip on wet surfaces, the tire tread according to the invention includes slits. Slits represent notches, grooves, or sipes, and form spaces leading to the tread surface.

[0043] On the tread surface, sipes or grooves have two characteristic primary dimensions: width W and length Lo, where length Lo is at least twice the width W. A sipe or groove is thus defined by at least two principal side surfaces, which determine its length Lo and are connected by a bottom surface. The two principal side surfaces are separated from each other by a non-zero distance, referred to as the width W of the sipe. On a brand-new tire, the width W of the sipe is the maximum distance between the two principal side surfaces, measured on the radial side coinciding with the tread surface when the sipe is not chamfered, and on the outermost radial side of the sipe and the innermost radial side of the chamfer when the sipe is chamfered. On a brand-new tire, the depth of the sipe is the maximum radial distance between the bottom of the sipe and its projection onto the ground when the tire is in motion. The maximum value of the sipe depth is called the tread depth.

[0044] The sipes satisfy the following condition: the distance between the main side surfaces is suitable for allowing at least partial contact between the main side surfaces defining the sipes in the contact patch, especially when the tire is brand new and under normal driving conditions (particularly those conditions including the fact that the tire is under nominal load and nominal pressure). Typically, the width of the sipes is less than or equal to 2 mm.

[0045] The grooves satisfy the following condition: the distance between the main side surfaces ensures that these main side surfaces do not come into contact with each other under normal driving conditions (especially conditions that include the fact that the tire is under nominal load and nominal pressure). Typically, the width of the grooves is strictly greater than 2 mm, preferably greater than or equal to 5 mm, and more preferably greater than or equal to 8 mm.

[0046] The grooves are particularly circumferential grooves, that is, grooves extending in a principal direction forming an angle of less than or equal to 30°, preferably less than or equal to 10°, with respect to the circumferential direction of the tire. Circumferential grooves can be continuous, that is, uninterrupted by tread blocks or other cuts, so that the two principal side surfaces determining their length are uninterrupted over the entire circumference of the tire. Circumferential grooves can also be discontinuous, that is, interrupted by one or more tread blocks and / or one or more other cuts, so that the two principal side surfaces determining their length are interrupted by one or more tread blocks and / or one or more other cuts. Typically, the depth of the circumferential grooves in a brand-new tire is greater than or equal to 85% of the tread depth, preferably 90%. Very conventionally, the depth of the circumferential grooves in a brand-new tire is greater than or equal to 4.0 mm, preferably greater than or equal to 5.0 mm, more preferably greater than or equal to 5.5 mm. The cuts separating the tread blocks of the tire according to the invention are very preferably circumferential grooves.

[0047] The tire according to the invention has a generally toroidal shape about an axis of rotation substantially coincident with the axis of rotation of the tire. This axis of rotation defines three directions commonly used by those skilled in the art: axial direction, circumferential direction, and radial direction.

[0048] The term "axial direction" refers to the direction that is substantially parallel to the axis of rotation of the tire (i.e., the axis of rotation of the tire).

[0049] The term "circumferential direction" refers to a direction that is substantially perpendicular to both the axial direction and the tire radius (in other words, tangent to a circle centered on the tire's axis of rotation).

[0050] The term "radial direction" refers to the direction along the tire's radius, that is, any direction that intersects the tire's axis of rotation and is substantially perpendicular to that axis.

[0051] The tire's midplane (denoted by M) is understood as a plane perpendicular to the tire's axis of rotation, located at the mid-axis distance between the two bead sections and passing through the axial center of the crown reinforcement.

[0052] The equatorial circumferential plane of a tire (denoted by E) is understood as the meridional section plane, which passes through the tire's equator and is perpendicular to the midplane and radial direction. The tire's equator is the axis in the meridional section plane (a plane perpendicular to the circumferential direction and parallel to the radial and axial directions), which is parallel to the tire's axis of rotation and is equidistant between the outermost radial point of the tread intended to contact the ground and the innermost radial point of the tire intended to contact a support (e.g., the rim), the distance between which is equal to H.

[0053] The meridional plane is understood as a plane that is parallel to the axis of rotation of the tire, contains the axis of rotation, and is perpendicular to the circumferential direction.

[0054] "Radially located inside" and "radially located outside" mean "closer to the tire's axis of rotation" and "farther from the tire's axis of rotation," respectively. "Axially located inside" and "axially located outside" mean "closer to the tire's midplane" and "farther from the tire's midplane," respectively.

[0055] A tire bead is understood as the portion of a tire designed to allow it to be attached to a mounting support (such as a wheel including a rim). Therefore, each tire bead is specifically designed to contact the flange of the rim for attachment.

[0056] Any numerical interval expressed as "between a and b" represents a range of values ​​from greater than a to less than b (i.e., excluding the extreme values ​​a and b), while any numerical interval expressed as "from a to b" means a range of values ​​from a to b (i.e., including the strict extreme values ​​a and b).

[0057] The tire of the present invention is intended for use in passenger vehicles as defined by the European Tire and Rim Technology Organization (ETRTO) standard of 2019. According to the ETRTO standard of 2019, such a tire has a cross-section characterized in the meridional plane by a section height H and a nominal section width S.

[0058] The tire of the present invention is preferably intended for use in passenger vehicles. This tire has a cross-section in the meridional plane characterized by a ratio, expressed as a percentage, of at least 90 for the nominal section width S and at least 80 for the section height H, according to the European Tire and Rim Technology Organization (ETRTO) standard in Standards Manual 2019, preferably at least 70 and at least 30, preferably at least 40; and a nominal section width S of at least 115 mm, preferably at least 155 mm, more preferably at least 175 mm and at most 385 mm, preferably at most 315 mm, more preferably at most 285 mm, and even more preferably at most 255 mm. Furthermore, the diameter D of the rim flange defines the diameter of the mounting rim for the tire, which is at least 12 inches, preferably at least 16 inches and at most 24 inches, preferably at most 20 inches.

[0059] As described above, even when the backing layer is in contact with the ground, the backing layer will not significantly impair its grip potential, and it is preferable to minimize the proportion of the backing layer that is in contact with the ground. Therefore, advantageously, at least 80%, preferably at least 90%, of the length of the interface track located radially below the tread blocks is arranged radially inside the prescribed wear track in the meridional section plane.

[0060] To maximize the effect of the backing layer on the denting and blistering mechanisms, it will be understood that it is preferable that the largest possible proportion of the backing layer is located relatively close to the prescribed wear track in the radial direction. Thus, advantageously, at least 80%, preferably at least 90%, of the length of the interface track located radially below the tread blocks is arranged at a radial distance of less than or equal to 2.0 mm in the meridional section plane.

[0061] To maximize the effect of the backing layer on the denting and blistering mechanisms, it will be understood that it is preferable for the backing layer to be located radially closest to the prescribed wear track, regardless of the proportion of the backing layer. Therefore, at least 75%, preferably at least 80%, more preferably at least 90% of the length of the interface track located radially below the tread blocks is arranged in the meridional section plane at a radial distance advantageously less than or equal to 1.2 mm, more preferably less than or equal to 1.0 mm from the prescribed wear track.

[0062] To improve the effect of the backing layer on the indentation mechanism, in an advantageous embodiment, tanD0_2 ≥ 0.5 x tanD0_1, preferably tanD0_2 ≥ 0.75 x tanD0_1, more preferably tanD0_2 ≥ tanD0_1, even more preferably tanD0_2 > tanD0_1, and very preferably tanD0_2 ≥ 1.10 x tanD0_1. Specifically, the greater the increase in the value of tanD0_2, the greater the improvement in the tire's grip potential on wet surfaces after more than half of its wear potential has been achieved. In the more preferred and very preferred cases where tanD0_2 > tanD0_1 and tanD0_2 ≥ 1.10 x tanD0_1, if the backing layer of the tire according to the invention comes into contact with the ground, the grip potential is not only not significantly impaired, but on the contrary, is actually improved.

[0063] To improve the effect of the backing layer on the blistering mechanism, in an advantageous embodiment, G*_2 ≥ 0.92 x G*_1, preferably G*_2 ≥ G*_1, and more preferably G*_2 > G*_1. Specifically, the greater the increase in the value of G*_2, the greater the increase in the stiffness of the backing layer, and therefore the greater the increase in the stiffness of the tread after it has exceeded half of its wear potential.

[0064] In a specific embodiment that maximizes the effect of the backing layer on the denting and blistering mechanisms, at least 75% of the length of the interface track located radially below the tread blocks in the axial central portion of the tread is arranged radially outside the track in the meridional section plane, the track being parallel to the tread surface of a new tire and passing through the deepest cut or the radially innermost point of each deepest cut. In other words, in the deepest axial continuation of the specified wear indicator, the interface track is located on the radial side. Specifically, the specified wear indicator is very preferably arranged at the bottom of the deepest cut or one of the deepest cuts.

[0065] If multiple cuts of the same depth are the deepest cuts, then the above features are confirmed for each deepest cut including the specified wear indicator.

[0066] To maximize the effect of the backing layer on the denting and blistering mechanisms, it will be understood that it is preferable that the largest possible proportion of the backing layer is located in the axial continuation of the deepest part of the wear indicator in the radial direction. Therefore, advantageously, at least 80%, preferably at least 90%, of the length of the interface track located radially below the tread blocks is arranged radially outside the track in the meridional section plane, said track being parallel to the tread surface of a new tire and passing through the innermost radial point of the deepest cut or each deepest cut (if multiple cuts of the same depth exist (all cuts are the deepest cuts on the tread)).

[0067] To avoid the frequent occurrence of the backing layer rising through the tread layer and thus having to scrap defective tires (because an excessive proportion of their backing layer is in contact with the ground), at least 75% of the length of the interface track located radially below the tread blocks in the central axial portion of the tread is arranged in the meridional section plane at an average radial distance of less than or equal to 0.4 mm, preferably greater than or equal to 0.6 mm, from the specified wear track. Furthermore, for a given tread thickness, the volume of the elastomeric backing material used is reduced by increasing the radial distance between the interface track and the specified wear track.

[0068] To further enhance the reduction of wear and minimize the volume of the elastomer backing material used, it is advantageous that at least 80%, preferably at least 90%, of the length of the interface track located radially below the tread block is arranged in the meridional section plane at a radial distance greater than or equal to 0.4 mm, preferably greater than or equal to 0.6 mm from the specified wear track.

[0069] In a particularly advantageous embodiment that allows for localized rise of the backing layer and avoids systematic tire wear (where a small portion of the interface track lies radially outside the defined wear track), in the central axial portion of the tread, at least a non-zero length of the interface track radially located below the tread blocks is arranged radially outside the defined wear track in the meridional section plane. According to the invention, this length is at most equal to 25% of the length of the interface track radially located below the tread blocks.

[0070] In embodiments that optimize the effect of the tread layer on the dent-causing mechanism, tanD0_1 ranges from 0.50 to 1.00, more preferably from 0.50 to 0.85.

[0071] In embodiments that optimize the effect of the backing layer on the indentation mechanism, tanD0_2 ranges from 0.60 to 1.10, more preferably from 0.60 to 1.00.

[0072] In an embodiment that optimizes the effect of the tread layer on the blistering mechanism, G*_1 ranges from 1.30 MPa to 4.10 MPa, preferably from 1.30 MPa to 3.00 MPa.

[0073] In embodiments that optimize the effect of the backing layer on the foaming mechanism, G*_2 is greater than or equal to 2.00 MPa, preferably ranging from 2.00 MPa to 4.10 MPa, and more preferably ranging from 2.15 MPa to 3.50 MPa.

[0074] Conventionally, a tire includes a crown, two sidewalls, and two beads, with each sidewall connecting each bead to the crown. Again, in a conventional manner, the crown includes a tread and a crown reinforcement arranged radially inside the tread. The tire also includes a carcass reinforcement anchored in each bead and extending radially inside each sidewall and the crown.

[0075] Conventionally, the tread reinforcement comprises at least one tread layer containing reinforcing elements. These reinforcing elements are preferably fabric filament elements or metal filament elements.

[0076] In an implementation that achieves the performance of a tire referred to as a radial tire as defined by ETRTO, the carcass reinforcement includes at least one carcass layer, said carcass layer or each carcass layer including a carcass filamentary reinforcement element, each carcass filamentary reinforcement element extending substantially in a principal direction forming an absolute value range of 80° to 90° with respect to the circumferential direction of the tire.

[0077] Advantageously, the tire includes a crown comprising crown reinforcements arranged radially inside the tread. In the axial central portion of the tread, the average distance between the layer comprising the outermost radially reinforcing element of the crown reinforcement and the deepest cut or the radially innermost point of each deepest cut is less than or equal to 2.50 mm, preferably less than or equal to 2.25 mm. As described above, when the tire is molded, it can be observed that the elastomeric tread and backing materials located radially below the cut undergo outward axial flow, and therefore the elastomeric tread and backing materials located radially near the cut undergo outward radial flow. These flows are more significant when the thickness of the elastomeric material located radially outside the crown reinforcement and radially inside each cut (more particularly radially inside the deepest cut) is small. Since the present invention allows the backing layer to partially rise through the tread layer, the thickness of the elastomeric material located radially outside the crown reinforcement and radially inside each cut (more particularly radially inside the deepest cut) can be reduced. This reduction allows for a decrease in tire mass and rolling resistance.

[0078] If multiple cuts of the same depth are the deepest cuts, then the above features are confirmed for each deepest cut. Preferably, since the deepest cut is a circumferential groove, the average distance between the layer of the outermost radial reinforcing element of the crown reinforcement and the innermost radial point of each circumferential groove in the axial central portion of the tread is less than or equal to 2.50 mm, preferably less than or equal to 2.25 mm.

[0079] However, in order to protect the crown reinforcement from external attacks, the tire includes a crown, which includes crown reinforcements arranged radially inside the tread, wherein in the axial central portion of the tread, the average distance between the layer of the outermost radial reinforcing element including the crown reinforcement and the deepest cut or the radial innermost point of each deepest cut is greater than or equal to 1.0 mm.

[0080] If multiple cuts of the same depth are the deepest cuts, the above features are confirmed for each deepest cut. Preferably, since the deepest cut is a circumferential groove, the average distance between the layer of the outermost radial reinforcing element of the crown reinforcement and the innermost radial point of each circumferential groove in the axial central portion of the tread is greater than or equal to 1.0 mm.

[0081] To determine the average distance between the layer of the outermost radial reinforcing element of the crown reinforcement and the innermost radial point of the deepest cut or each deepest cut or each circumferential groove, the average value of the straight-line distance (e.g., every millimeter) between the layer of the outermost radial reinforcing element of the crown reinforcement and the innermost radial point of the deepest cut or each deepest cut or each circumferential groove will be used.

[0082] In the meridional section plane, the straight-line distance between the innermost point of the deepest cut or each deepest cut or each circumferential groove and its radial projection on the trajectory of the outermost point of the reinforcing element passing through the outermost radial crown layer is measured between the layer comprising the crown reinforcement and the innermost point of the deepest cut or each deepest cut or each circumferential groove.

[0083] In embodiments readily industrially implementable (e.g., using extrusion equipment), the axial portion of the tread located radially below the deepest cut or each deepest cut comprises a tread layer with a non-zero radial thickness and a backing layer with a non-zero radial thickness. Preferably, to reduce the problem of uneven flow of elastomeric material below the cut during extrusion, the ratio of the radial thickness of the tread layer to the radial thickness of the backing layer ranges from 0.40 to 0.60.

[0084] In embodiments where the backing layer is located only in positions that improve grip on wet surfaces and thus minimize the amount of elastomer backing material used, the axial portion of the tread radially below the deepest cut or each deepest cut is comprised of a tread layer. Preferably, the axial portion of the tread radially below each circumferential groove is comprised of a tread layer. In other words, no elastomer backing material in the tread is radially located below the deepest cut or each deepest cut, or radially located below each circumferential groove.

[0085] In the above embodiment, the axial portion of the tread located radially below the deepest cut or each deepest cut or each circumferential groove is defined axially by two straight lines perpendicular to the tread surface and, when the tire is brand new, passing through the axial ends of each tread block that defines the cut or each groove and is part of the tread surface.

[0086] To obtain tires with the lowest possible rolling resistance, the elastomeric tread material has a dynamic loss tanDMAX23_1 ranging from 0.13 to 0.70, preferably from 0.13 to 0.47, measured according to standard ASTM D-5992-96 at a temperature of 23°C and a frequency of 10Hz. This is because the dynamic loss tanDMAX23, measured at 23°C and 10Hz, characterizes the hysteresis of the elastomeric material and thus its rolling resistance.

[0087] Similarly, in order to minimize the effect of the backing layer on the rolling resistance of the tire, the elastomeric backing material has a dynamic loss tanDMAX23_2 in the range of 0.13 to 0.53, preferably 0.13 to 0.46, as measured according to standard ASTM D-5992-96 at a temperature of 23°C and a frequency of 10Hz.

[0088] As described above, the wear indicator is preferably located at the bottom of the deepest cut. The wear indicator is also preferably located at the bottom of the circumferential groove.

[0089] In a particularly simple implementation, the wear indicator is formed by a protrusion that extends radially from the bottom of the cut and extends radially outward by a range of 1.45 mm to 1.75 mm, preferably substantially equal to a radial height of 1.6 mm.

[0090] Advantageously, in order to give the tire a relatively large wear potential and thus increase its life, the tread height of a new tire ranges from 5.0 to 9.0 mm, preferably from 6.0 to 7.5 mm. The maximum depth of the tread is the tread height.

[0091] To enable effective drainage when driving on wet surfaces, the surface area porosity of a tire with a tread height of 2.0 mm after wear ranges from 20% to 35%, preferably from 22% to 30%. The use of a backing layer according to the invention is more advantageous when the tire has such a surface area porosity after wear, because the backing layer allows for compensation of the decrease in drainage capacity that occurs with wear, a decrease that is greater when the surface area porosity is low.

[0092] The surface area void ratio of a tire is the ratio of the following two:

[0093] - The difference between the total surface area AT of the tire tread (inflated to nominal pressure and under nominal load) at the contact patch (where the tire contacts a flat surface (e.g., a glass plate)) and the surface area AC of the tread elements (which contact the ground where the tire travels), and

[0094] - The total surface area AT of the tire tread (which is inflated to the nominal pressure and under the nominal load) where the tire contacts the flat ground.

[0095] To determine the surface area porosity, the nominal load is equal to 80% of the load rating given by the European Tire and Rim Technology Organization (ETRTO) standard of 2019, and the nominal pressure is equal to 2.5 bar.

[0096] To minimize the amount of elastomer backing material used, the volume of the elastomer tread material in the axial central portion of the tread is greater than or equal to 60% of the volume of the axial central portion of the tread, preferably greater than or equal to 65% of the volume of the axial central portion of the tread, and the volume of the elastomer backing material in the axial central portion of the tread is less than or equal to 40% of the volume of the axial central portion of the tread, preferably less than or equal to 35% of the volume of the axial central portion of the tread.

[0097] In a particularly advantageous embodiment from the perspective of industrial complexity and tread manufacturing process, at least 90% of the volume of the axially central portion of the tread is made of tread material and backing material. In the possible remaining volume of the axially central portion of the tread (which may be at most 10% of the volume of the axially central portion of the tread), the tread may include a layer with a small axial thickness of less than 0.4 mm, disposed between the radially outermost layer of the crown reinforcement and the backing layer to provide a connection between the two layers. Furthermore, the tread may also include strips with a small axial width made of conductive material, thereby forming a conductive path between the ground on which the tire travels and the crown reinforcement, enabling the tire to meet conductivity standards.

[0098] In an embodiment where the backing layer protrudes axially to the axial side portion (which is axially arranged outside the axial central portion of the tread) and thus allows the aforementioned denting and bubbling mechanisms to act on the outside of the axial central portion, the axial width of the backing layer is greater than or equal to 90% of the axial width of the tread surface, preferably greater than or equal to 100% of the axial width of the tread surface.

[0099] In another embodiment, where the backing layer is axially confined in the central portion to minimize the amount of elastomeric backing material used, the axial width of the backing layer is less than or equal to 90% of the width of the tread. Attached Figure Description

[0100] Based on the following detailed description and non-limiting exemplary embodiments, and in connection with these embodiments... Figures 1 to 8 The invention and its advantages will be readily understood, wherein:

[0101] - Figure 1 This is a meridional cross-sectional plan view of a tire according to a first embodiment of the present invention.

[0102] - Figure 2 for Figure 1 A cross-sectional view of the tire, showing the arrangement of filamentous reinforcing elements in and below the tread.

[0103] - Figures 3 to 6 for Figure 1 Detailed image of the tire crown of the medium tire.

[0104] - Figure 7 and Figure 8 The tires according to the second and third embodiments respectively Figure 3 Similar diagrams. Detailed Implementation

[0105] The diagram relating to the tire shows reference frames X, Y, and Z, which correspond to the tire's usual axial direction (Y), radial direction (Z), and circumferential direction (X), respectively.

[0106] Figure 1 A tire according to the invention, designated by the overall designation 10, is shown. The tire 10 has a generally torus shape about an axis of rotation substantially parallel to the axial direction Y. The tire 10 is intended for use in passenger vehicles and has a size of 225 / 45R17. In the various figures, the tire 10 is depicted as brand new, i.e., before it has been driven.

[0107] Tire 10 includes a crown 12, which includes a tread 14 intended to contact the ground during driving and a crown reinforcement 16 extending in the circumferential direction X within the crown 12. Tire 10 also includes an airtight layer 18 for inflation gas, which is intended to define a closed internal cavity with the mounting support for tire 10 when tire 10 is mounted on a mounting support (e.g., a rim).

[0108] The crown reinforcement 16 includes a working reinforcement 20 and a ring reinforcement 22. The working reinforcement 16 includes at least one working layer, in this case including two working layers 24, 26. In this particular case, the working reinforcement 16 is composed of two working layers 24, 26. The radially inner working reinforcement 24 is arranged radially inside the radially outer working layer 26.

[0109] The hoop reinforcement 22 includes at least one hoop layer, in this case including a hoop layer 28. The hoop reinforcement 22 is constituted by the hoop layer 28 in this case.

[0110] The crown reinforcement 16 is radially covered by the tread 14. In this case, the hoop reinforcement 22 (in this case, the hoop layer 28) is arranged radially outside the working reinforcement 20, and thus radially inserted between the working reinforcement 20 and the tread 14. Preferably, it is conceivable that the hoop reinforcement 22 has an axial width at least as large as the axial width of the working reinforcement 20, in this particular case, in Figure 1 In the embodiment shown, the hoop reinforcement 22 has an axial width that is larger than the axial width of the working reinforcement 20.

[0111] The tire 10 includes two sidewalls 30 extending radially inward from the crown 12. The tire 10 also has two beads 32 located radially inside the sidewalls 30. Each sidewall 30 connects each bead 32 to the crown 12.

[0112] Tire 10 includes a carcass reinforcement 34 anchored in each bead 32 and, in this particular case, rolled up around a bead line 33. The carcass reinforcement 34 is in each sidewall 30 and extends radially inward of the crown 12. A crown reinforcement 16 is radially disposed between the tread 14 and the carcass reinforcement 34. The carcass reinforcement 34 includes at least one carcass ply, in this case, a single carcass ply 36. In this particular case, the carcass reinforcement 34 is composed of a single carcass ply 36.

[0113] Each working layer 24, 26, hoop layer 28, and carcass layer 34 comprises an elastomeric matrix with one or more filamentary reinforcing elements embedded in the respective layer. Reference will now be made to... Figure 2 Describe these layers.

[0114] The hoop reinforcement 22 (in this case, the hoop layer 28) is defined axially by two axial edges 28A and 28B. The hoop reinforcement 22 includes one or more hoop filament reinforcement elements 280, which are circumferentially helically wound to extend axially from the axial edge 28A to the other axial edge 28B along the principal direction D0 of each hoop filament reinforcement element 280. The principal direction D0 forms an angle AF with the circumferential direction X of the tire 10 with an absolute value less than or equal to 10°, preferably less than or equal to 7°, and more preferably less than or equal to 5°. In this case, AF = -5°. The hoop layer 28 has a density of 98 hoop filament reinforcement elements per decimeter of the hoop layer, which is measured perpendicular to the direction D0.

[0115] The radially inner working layer 24 is defined axially by two axial edges 24A and 24B. The radially inner working layer 24 includes working filamentary reinforcing elements 240 that extend axially from axial edge 24A to the other axial edge 24B in a manner substantially parallel to each other along a principal direction D1. Similarly, the radially outer working layer 26 is defined axially by two axial edges 26A and 26B. The radially outer working layer 26 includes working filamentary reinforcing elements 260 that extend axially from axial edge 26A to the other axial edge 26B in a manner substantially parallel to each other along a principal direction D2. The principal direction D1 of each working filamentary reinforcing element 240 of the radially inner working layer 24 and the principal direction D2 of each working filamentary reinforcing element 260 of the additional radially outer working layer 26 form angles AT1 and AT2, respectively, with opposite orientations to the circumferential direction X of the tire 10. Each principal direction D1, D2 forms an angle AT1, AT2 with the circumferential direction X of the tire 10, with an absolute value strictly greater than 10°, preferably ranging from 15° to 50°, and more preferably ranging from 15° to 30°. In this case, AT1 = -26° and AT2 = +26°.

[0116] Carcass layer 36 is defined axially by two axial edges 36A and 36B. Carcass layer 36 includes carcass filamentary reinforcement elements 360 that extend axially from axial edge 36A to another axial edge 36B along a principal direction D3, wherein the principal direction D3 forms an angle AC with the circumferential direction X of tire 10 with an absolute value greater than or equal to 60°, preferably in the range of 80° to 90°, and in this case AC = +90°.

[0117] Each hoop-shaped filamentary reinforcing element 280 typically comprises two multifilament cord layers, each composed of yarns of aliphatic polyamide (nylon in this case) monofilaments with a yarn count of 140 tex. These two multifilament cord layers are each helically twisted in one direction at 250 turns / meter, and then helically twisted together in the opposite direction at 250 turns / meter. The two multifilament cord layers are spirally wound around each other. Alternatively, the hoop-shaped filamentary reinforcing element 280 may be used comprising one multifilament cord layer composed of yarns of aliphatic polyamide (nylon in this case) monofilaments with a yarn count of 140 tex and another multifilament cord layer composed of yarns of aramid (aramid in this case) monofilaments with a yarn count of 167 tex. These two multifilament cord layers are each helically twisted in one direction at 290 turns / meter, and then helically twisted together in the opposite direction at 290 turns / meter. The two multifilament cord layers are spirally wound around each other.

[0118] Each working filamentary reinforcing element 180 is an assembly having two steel monofilaments spirally wound at a pitch of 1.2 or 1.05 mm, each steel monofilament having a diameter of 0.30 mm. In another embodiment, each working filamentary reinforcing element 180 is composed of a steel monofilament with a diameter of 0.30 mm. More typically, the diameter of the steel monofilament ranges from 0.25 mm to 0.32 mm.

[0119] Each carcass filamentary reinforcing element 340 typically comprises two multifilament cord layers, each composed of yarns of polyester (PET in this case) monofilaments. These two multifilament cord layers are each helically twisted in one direction at 240 turns / meter, and then helically twisted together in the opposite direction at 240 turns / meter. Each of these multifilament cord layers has a yarn count of 220 tex. In other variant forms, yarn counts of 144 tex or 334 tex may be used.

[0120] refer to Figure 1 The tread 14 includes a tread surface 38, through which the tread 14 contacts the ground. The tread 14 also includes cutouts 40 and tread blocks 42, the cutouts 40 separating the tread blocks 42 from each other. Figure 1In the meridional section plane, the cut 40 includes a plurality of circumferential grooves 44, wherein at least one circumferential groove 44 forms the deepest cut of the tire 10. When the tire is brand new, the depth of the deepest circumferential groove 44 defines the tread height HS of the tire, which ranges from 5.0 to 9.0 mm, preferably from 6.0 to 7.5 mm, in which case HS = 7.0 mm, as in Figure 6 As shown in the image.

[0121] The tread surface 38 is designed to contact the ground when the tire 10 travels along the ground, and is axially defined by two axial boundaries 39 passing through each point N on both sides of the midplane M, wherein for each point N, the angle between the tangent T on the tread surface 38 and the straight line R parallel to the axial direction Y and passing through the point is equal to 30°.

[0122] In this case, the tread 14 includes an axially central portion P1, which includes the midplane of the tire 10 and is centered on the midplane M of the tire 10 along the axial direction. The axial width L1 of the axially central portion P1 is at least 70% of the axial width L of the tread surface 38, in which case L1 = L.

[0123] The tread 14 also includes a plurality of specified wear indicators 46 that define a specified wear threshold, below which the tire does not meet the corresponding wear requirements. Figure 1 and Figures 3 to 6 The wear indicator 46 shown is disposed at the bottom 48 of the deepest cut, in this case at the bottom 48 of a circumferential groove 44. In this particular case, the wear indicator 46 is defined as being formed by a protrusion 50 extending radially from the bottom 48 of the circumferential groove 44 and extending radially outward for a radial height HT ranging from 1.45 mm to 1.75 mm (in this case substantially equal to 1.6 mm). The wear indicator 46 is defined as having a radially outermost point, which in this case is formed by the radially outer surface 51 of the wear indicator 46.

[0124] After wear occurs to the point where the tread height equals 2.0 mm, the surface area porosity of the tire ranges from 20% to 35%, preferably from 22% to 30%, and in this case equals 25%.

[0125] refer to Figure 1 and Figure 3The tread 14 includes a tread layer 52 with a tread surface 38 and a backing layer 54 for the tread layer 52, the backing layer 54 being arranged radially inside the tread layer 52. This backing layer 54 is commonly referred to as the underlayer. The axial width J of the backing layer 54 is greater than or equal to 90% of the axial width L of the tread surface 38, in which case the axial width J of the backing layer 54 is greater than or equal to 100% of the axial width L of the tread surface 38, and in which case it is equal to 105% of the axial width L of the tread surface 38.

[0126] Including the specified wear indicator 46 Figure 3 In the meridional cross-sectional plane, the tread layer 52 and the backing layer 54 are continuous via the interface 56, which displays the interface trajectory 58.

[0127] Still in Figure 3 In the meridional section plane, a defined wear trajectory 60 is defined, which is parallel to the tread surface 38 of the tire 10 and passes through the radial outer surface 51 of the defined wear indicator 46. Figure 3 In the middle, the specified wear trajectory 60 is shown by a dashed line.

[0128] refer to Figure 3 In the axial central portion P1 of the tread 14, the interface track 58 has a length I radially located below the tread pattern block 42. Length I is equal to the sum of lengths I1, I2, and I3 radially located below the tread pattern block 42. The remaining length of the interface track 58 is equal to the sum of lengths U1 and U2 radially located below the cutout 40 (in this case, below the circumferential groove 44). In this specific case, in half of the axial central portion P1 of the tread 14, the length of the interface track is equal to the sum of lengths I1, I2, I3, U1, and U2 and equal to 8.13 cm, where I1 = 2.90 cm, I2 = 2.28 cm, I3 = I2 / 2 = 1.14 cm, U1 = 0.65 cm, and U2 = 1.16 cm.

[0129] In half of the axial central portion P1 of the tread 14, at least 75%, preferably at least 80%, and even more preferably 90% of the length I of the interface track 58 located radially below the tread block 42 (in this case, at least 75%, preferably at least 80%, and even more preferably 90% of the length I) is present. Figure 3 The radially arranged sides of the meridional cross-section plane are positioned inside the specified wear track 60. In this specific case, the lengths I1, I2, and I3 located radially below the tread blocks 42 are all radially located inside the specified wear track 60, thus ensuring that 100% of the length I of the interface track 58 located radially below the tread blocks 42 is within the specified wear track 60. Figure 3 They are arranged radially inside the specified wear trajectory 60 in the meridional section plane.

[0130] In addition, in half of the axial central portion P1 of the tread 14, at least 75%, preferably at least 80%, even more preferably 90% (in this case, at least 75%, preferably at least 80%, even more preferably 90% of the length I) of the length of the interface locus 58 located radially below the tread block 42 is Figure 4 arranged in the meridian cross-sectional plane of Figure 4 at an average radial distance d1 from the specified wear locus 60 that is less than or equal to 2.0 mm, preferably less than or equal to 1.2 mm, more preferably less than or equal to 1.0 mm. In this particular case, the lengths K1 < I1, K2 < I2, K3 < I3 correspond to the length of the interface locus 58 located at an average radial distance d1 from the specified wear locus 60 that is less than or equal to 1.0 mm. In this case, K1 = 2.85 cm, K2 = 2.18 cm, K3 = 1.09 cm, so that 97% of the length I is

[0131] arranged in the meridian cross-sectional plane of Figure 4 at an average radial distance d1 from the specified wear locus 60 that is less than or equal to 1.0 mm. Figure 4 In addition, in half of the axial central portion P1 of the tread 14, at least 75%, preferably at least 80%, even more preferably 90% (in this case, at least 75%, preferably at least 80%, even more preferably 90% of the length I) of the length of the interface locus 58 located radially below the tread block 42 is

[0132] arranged in the meridian cross-sectional plane of Figure 4 at an average radial distance d1 from the specified wear locus 60 that is greater than or equal to 0.4 mm, preferably greater than or equal to 0.6 mm. In this particular case, the lengths I1, I2, I3 located radially below the tread block 42 are all arranged at an average radial distance d1 from the specified wear locus 60 that is greater than or equal to 0.6 mm, so that 100% of the length I is

[0133] Figure 4 arranged in the meridian cross-sectional plane of at an average radial distance d1 from the specified wear locus 60 that is greater than or equal to 0.6 mm.

[0132] In this way, the radial distance between the specified wear locus 60 and the entire length I of the interface locus 58 located radially below the tread block 42 varies between 0.8 mm and 2.65 mm. If defined as the lengths K1, K2, K3 located radially below the tread block 42, 97% of the length I of the interface locus 58 located radially below the tread block 42 is arranged at a radial distance between 0.6 mm and 1.0 mm from the specified wear locus 60, and the radial distance corresponds to Figure 4 an average radial distance d1 equal to 0.85 mm in the meridian cross-sectional plane of

[0133] Furthermore, in half of the axial central portion P1 of the tread 14, at least 75%, preferably at least 80%, and even more preferably 90% of the length of the interface track 58 located radially below the tread block 42 (in this case, at least 75%, preferably at least 80%, and even more preferably 90% of the length I) is present. Figure 5 The interface track 58 is radially arranged outside the track 62 in the meridional section plane. The track 62 is parallel to the tread surface 38 of the new tire 10 and passes through the radial innermost point of the deepest cut, in this case, through the bottom 48 of each circumferential groove 44. In this particular case, lengths F1, F2, and F3 (which satisfy K1 < F1 < I1, K2 < F2 < I2, K3 < F3 < I3) correspond to the length of the interface track 58 radially arranged outside the track 62. In this case, F1 = 2.86 cm, F2 = 2.20 cm, and F3 = 1.10 cm, such that 97% of the length I of the interface track 58 radially located below the tread block 42 in half of the axial central portion P1 of the tread 14 is within the... Figure 5 They are arranged radially outside trajectory 62 in the meridional section plane.

[0134] refer to Figure 6 In the axial central portion P1 of the tread 14, the axial portion of the tread 14 located radially below the deepest cut (in this case, radially below each circumferential groove 44) includes a tread layer 52 of non-zero radial thickness E1 and a backing layer 54 of non-zero radial thickness E2. The ratio E1 / E2 varies between 0.40 and 0.60, and in this case is substantially equal to 0.50.

[0135] Still referencing Figure 6 In half of the axial central portion P1 of the tread 14, the average distance d2 between the layer comprising the outermost radial reinforcing element of the crown reinforcement 16 (in this case, the ring layer 28) and the innermost radial point of the deepest cut (in this case, the bottom 48 of each circumferential groove 44) is less than or equal to 2.50 mm, preferably less than or equal to 2.25 mm and greater than or equal to 1.0 mm. In this particular case, d2 = 2.10 mm.

[0136] It should be noted that, because the tire is symmetrical with respect to the midplane M, Figure 1 and Figures 3 to 6 The calculations shown, representing half of the meridional section and half of the axial central portion P1 of the tire 10, are also applicable to the entire meridional section and the entire axial central portion P1 of the tire 10.

[0137] Tread layer 52 comprises an elastomeric tread material M1, and backing layer 54 comprises an elastomeric backing material M2, which is different from the elastomeric tread material. In this particular case, the elastomeric tread material is based on composition CD1 as described in WO2018115722, while the elastomeric backing material is based on composition CC1 as described in WO2018115722. However, without departing from the scope of the invention, other compositions can certainly be used by varying the content of the various components to obtain performance suitable for a particular application.

[0138] The volume of the elastomeric tread material M1 in the central portion P1 is greater than or equal to 60% of the volume of the central portion P1, preferably greater than or equal to 65% of the volume of the central portion P1, and in this case, equal to 70% of the volume of the central portion P1. The volume of the elastomeric backing material M2 in the central portion P1 is less than or equal to 40% of the volume of the central portion P1, preferably less than or equal to 35% of the volume of the central portion P1, and in this case, equal to 30% of the volume of the central portion P1.

[0139] The complex dynamic shear modulus G*_1 of the elastomeric tread material M1, measured at 10% strain at a temperature of 23°C and a frequency of 10Hz according to standard ASTM D-5992-96, ranges from 1.30 MPa to 4.10 MPa, with a preferred range of 1.30 MPa to 3.00 MPa. In this case, G*_1 = 2.13 MPa.

[0140] The complex dynamic shear modulus G*_2 of the elastomer backing material M2, measured at 10% strain at a temperature of 23°C and a frequency of 10Hz according to standard ASTM D-5992-96, is greater than or equal to 2MPa, preferably in the range of 2.00MPa to 4.10MPa, more preferably in the range of 2.15MPa to 3.50MPa, and in this case, G*_2 = 2.14MPa.

[0141] It should be noted that G*_2≥0.90x G*_1, or even G*_2≥0.92x G*_1, or even G*_2≥G*_1, and in this case G*_2>G*_1.

[0142] The dynamic loss tanD0_1 of the elastomeric tread material M1, measured according to standard ASTM D-5992-96 at a temperature of 0°C and a frequency of 10Hz, ranges from 0.50 to 1.00, more preferably from 0.50 to 0.85, and in this case tanD0_1 = 0.67.

[0143] The dynamic loss tanD0_2 of the elastomer backing material M2, measured according to standard ASTM D-5992-96 at a temperature of 0°C and a frequency of 10 Hz, ranges from 0.60 to 1.10, more preferably from 0.60 to 1.00, and in this case tanD0_2 = 0.65.

[0144] It should be noted that tanD0_2 ≥ 0.37 x tanD0_1, or even tanD0_2 ≥ 0.5 tanD0_1, preferably tanD0_2 ≥ 0.75 x tanD0_1. It should also be noted that in other highly advantageous embodiments where the elastomer backing material M2 is modified to increase tanD0_2, tanD0_2 ≥ tanD0_1 is preferred, tanD0_2 > tanD0_1 is highly advantageous, and even tanD0_2 ≥ 1.10 x tanD0_1. To increase the value of tanD0_2, as is known to those skilled in the art, the glass transition temperature of the elastomer backing material and / or its silica content can be increased.

[0145] Among the other properties of elastomer materials M1 and M2, it should be noted that the dynamic loss tanDMAX23_1 of elastomer tread material M1, measured according to standard ASTM D-5992-96 at a temperature of 23°C and a frequency of 10Hz, ranges from 0.13 to 0.70, preferably from 0.13 to 0.47, and in this case is equal to 0.25. It should also be noted that the dynamic loss tanDMAX23_1 of elastomer backing material M2, measured according to standard ASTM D-5992-96 at a temperature of 23°C and a frequency of 10Hz, ranges from 0.13 to 0.53, preferably from 0.13 to 0.46, and in this case is equal to 0.31.

[0146] exist Figure 7 The image shows a tire according to the second embodiment. Elements similar to those shown in the previous figures are indicated by the same reference numerals.

[0147] Compared with the tire according to the first embodiment, according to Figure 7 The second embodiment of the tire has a backing layer 54 rising vertically below each tread block 42 near the cutout 40 (in this case, the circumferential groove 44) in the axial central portion P1 of the tread 14. Therefore, in the axial central portion P1 of the tread 14, the interface track 58 located radially below the tread block 42 has at least a non-zero length l'. Figure 7The radially arranged outer side of the specified wear track 60 in the meridional section plane. In this case, I = I1 + I2 + I3 + I4 + I5 + I6 + I7 + I', I' = I1' + I2' + I3' + I4', where I1 = 2.44cm, I2 = 1.64cm, I3 = I2 / 2 = 0.82cm, I4 = I5 = I6 = I7 = 0.25cm, I1' = I2' = I3' = I4' = 0.35cm. At most 25% of the total length I of the interface track 58 located radially below the tread block 42 is within Figure 7 In the meridional section plane, it is arranged radially outside the specified wear trajectory 60. In this case, I' / I = 1.40 / 5.9 = 23%.

[0148] exist Figure 8 The figure shows a tire according to the third embodiment. Elements similar to those shown in the previous figure are indicated by the same reference numerals.

[0149] Compared to the aforementioned embodiment, the axial length L1 of the axial central portion P1 of the tread 14 is strictly less than the axial width L of the tread surface 38, thereby causing the tread 14 to include axial side portions P2 arranged axially outside the axial central portion P1. The axial width L2 of each axial side portion P2 is at most equal to 15% of the axial width L of the tread, in which case L2 / (L1+L2) = 4%. Figure 8 In one embodiment, the tread layer 52 of each axial side portion P2 contains an elastomeric material different from the elastomeric material of the axial central portion P1. For example, an elastomeric material with relatively low rolling resistance, such as that described in WO2014 / 090845, would be selected.

[0150] Comparative Test

[0151] In a test of grip on wet surfaces after the tire had exceeded half of its wear potential, the tire 10 according to the first embodiment was compared with a prior art MICHELIN Primacy 4 tire of the same size. For comparative purposes, the elastomer tread material of the prior art MICHELIN Primacy 4 tire is the same as the elastomer material M1 of the tire 10 according to the first embodiment. The elastomer backing material of the prior art MICHELIN Primacy 4 tire has:

[0152] -The complex dynamic shear modulus G*_2T, equal to 1.90 MPa, was measured at 23°C with 10% strain according to standard ASTM D-5992-96.

[0153] - The dynamic loss tanD0_2T is equal to 0.23, measured at 0°C and 10Hz according to standard ASTM D-5992-96.

[0154] First, each tire is planed downwards until a tread depth of 2 mm is achieved, simulating a level of use where more than half of its wear potential (93% in this case) has been utilized. Tread depth is defined as the radial height between the deepest cut or the innermost radial point of each deepest cut and its projection onto the ground when the tire is in motion. This tread depth satisfies the condition of not reaching a specified wear track, which corresponds to a tread depth of 1.6 mm and represents a late-stage wear condition of the tire, in this particular case, more than half of its wear potential (93% of the wear potential has been utilized). The downward planing is performed on a roller press equipped with a planing head in a manner known to those skilled in the art, with the tire in contact with the planing head driven under driving conditions representing normal driving conditions.

[0155] At the end of the planing step, under the same conditions and on the same vehicle, four planed MICHELIN Primacy 4 tires and four planed tires 10 according to the invention were tested to determine the average deceleration of the vehicle equipped with these tires between 80 km / h and 20 km / h. The test was conducted using the recommendations of standard ISO 23671-2006 in such a manner that the braking force coefficient (BFCT) of the prior art MICHELIN Primacy 4 tire and the braking force coefficient (BFCA) of the tire 10 according to the invention could be determined. A higher braking force coefficient indicates better performance of the tested tire. The test results satisfied BFCA / BFCT = 106, thus confirming that the tire according to the invention has improved braking performance on wet surfaces compared to the prior art tires.

[0156] The present invention is not limited to the embodiments described above.

Claims

1. A tire (10) for a passenger vehicle, comprising a tread (14) having slits (40) and tread blocks (42), the slits (40) separating the tread blocks (42) from each other, the tread (14) being designed to contact the ground via a tread surface (38) when the tire (10) is in motion, the tread (14) including at least one defined wear indicator (46) defining a defined wear threshold, and In the axial central portion (P1) of the tread (14) having an axial width (L1) equal to at least 70% of the width (L) of the tread surface (38), the tread (14) comprises: - A tread layer (52) having a tread surface (38), the tread layer (52) comprising an elastomeric tread material having: -The complex dynamic shear modulus G*_1, measured at 10% strain at a temperature of 23°C and a frequency of 10Hz according to standard ASTM D-5992-96, and - The dynamic loss tanD0_1 was measured at 0°C and 10Hz according to standard ASTM D-5992-96. - A backing layer (54) for the tread layer (52), the backing layer (54) being arranged radially inside the tread layer (52) and comprising an elastomeric backing material having: -The complex dynamic shear modulus G*_2, measured at 10% strain at a temperature of 23°C and a frequency of 10Hz, according to standard ASTM D-5992-96. - The dynamic loss tanD0_2 was measured at 0°C and 10Hz according to standard ASTM D-5992-96. The elastomeric tread material is different from the elastomeric backing material, such that the tread layer (52) and the backing layer (54) are continuous in a meridional cross-sectional plane including a specified wear indicator (46) via an interface (56) showing an interface trajectory (58). Its characteristic is that tanD0_2≥0.37x tanD0_1 and G*_2≥0.90x G*_1, In the axial central portion (P1) of the tread (14), by defining a specified wear track (60) in the meridional section plane that is parallel to the tread surface (38) of the new tire (10) and passes through the radially outermost point (51) of the specified wear indicator (46), at least 75% of the length (I) of the interface track (58) located radially below the tread block (42) is arranged radially inside the specified wear track (60) in the meridional section plane, and In the axial central portion (P1) of the tread (14), at least 75% of the length (I) of the interface track (58) located radially below the tread block (42) is arranged in the meridional section plane at an average radial distance (d1) less than or equal to 2.0 mm from the specified wear track (60).

2. The tire (10) according to claim 1, wherein, tanD0_2≥0.5x tanD0_1.

3. The tire (10) according to claim 1, wherein, tanD0_2≥tanD0_1.

4. The tire (10) according to claim 1, wherein, G*_2≥G*_1.

5. The tire (10) according to claim 1, wherein, In the axial central portion (P1) of the tread (14), at least 75% of the length (I) of the interface track (58) located radially below the tread block (42) is arranged radially outside the track (62) in the meridional section plane, the track (62) being parallel to the tread surface (38) of the new tire (10) and passing through the deepest cut (44) or the radial innermost point (48) of each deepest cut (44).

6. The tire (10) according to claim 1, wherein, In the axial central portion (P1) of the tread (14), at least 75% of the length (I) of the interface track (58) located radially below the tread block (42) is arranged in the meridional section plane at an average radial distance (d1) greater than or equal to 0.4 mm from the specified wear track (60).

7. The tire (10) according to claim 1, wherein, The range of tanD0_1 is 0.50 to 1.

00.

8. The tire (10) according to claim 1, wherein, The range of tanD0_2 is from 0.60 to 1.

10.

9. The tire (10) according to claim 1, wherein, The range of G*_1 is from 1.30 MPa to 4.10 MPa.

10. The tire (10) according to claim 1, wherein, G*_2 is greater than or equal to 2.00 MPa.

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