Tyre having a less temperature-sensitive rolling resistance

Abstract

The invention relates to a tyre (10) comprising a tread (12) comprising a tread layer (20) comprising: - a central portion (24) comprising a central elastomeric material (240) having a glass transition temperature Tgc, the central portion (24) extending axially on either side of a median plane (M) of the tyre (10), - at least one first lateral portion (26) comprising a first lateral elastomeric material (260) having a glass transition temperature Tgl1. Tgc ≤ -10°C, Tgl1 ≤ -10°C and 12°C ≤ Tgc-Tgl1 ≤ 23°C.

Description

Tire with rolling resistance less sensitive to temperature

[0001] The present invention relates to a tire. By tire is meant a bandage intended to form a cavity by cooperating with a support element, for example a rim, this cavity being capable of being pressurized to a pressure higher than atmospheric pressure. A tire according to the invention has a structure of substantially toroidal shape of revolution around a main axis of the tire.

[0002] Known from the state of the art is a summer tire for a passenger vehicle comprising a tread intended to come into contact with the ground when the tire is rolling via a rolling surface. The tread comprises a tread layer and a support layer arranged at least partly radially inside the tread layer. Such a tire is described in particular in WO2021 / 111083.

[0003] Users have noticed that passenger vehicles fitted with these tires, particularly electric vehicles, show a significant reduction in range when the temperature is low, and this is even more so when the temperature drop is significant.

[0004] The invention therefore aims to make the autonomy of vehicles less sensitive to a drop in temperature.

[0005] To this end, the subject of the invention is a tire comprising a tread delimited axially by first and second axial edges, the tread comprising a tread layer comprising: - a central portion extending between first and second axial edges of the central portion, the central portion comprising at least one central elastomeric material having a glass transition temperature Tgc, the central portion extending axially on either side of a median plane of the tire, - at least one first lateral portion extending between the first axial edge of the tread and the first axial edge of the central portion, the first lateral portion comprising at least one first lateral elastomeric material having a glass transition temperature Tgl 1 , a tire in which Tgc < -10°C, Tgl1 < -10°C and 12°C < Tgc-Tgl1 < 23°C.

[0006] Indeed, the inventors behind the invention discovered that the drop in temperature led to a significant increase in rolling resistance, an increase that was even greater the lower the temperature. However, rolling resistance has an effect on the vehicle's range. Thus, the invention makes it possible to make the range of vehicles less sensitive to a drop in temperature. The tires according to the invention thus make it possible to drive in a relatively wide temperature range, for example from 25°C to -7°C, with rolling resistance that is less sensitive to temperature.

[0007] Once this effect was discovered, the inventors had to find a way to reduce the influence of temperature on rolling resistance. This is made possible by using a central elastomeric material and at least the first lateral elastomeric material with both relatively low glass transition temperatures, here such as Tgc < -10°C, Tgl1 < -10°C, and at the same time sufficiently different, here such as 12°C < Tgc-Tgl1 < 23°C.

[0008] In addition to reducing the influence of temperature on rolling resistance as shown by the tests described in the present application, the characteristics of the tire materials show an amplification of the reduction in the influence of temperature on rolling resistance with the decrease in temperature. This result is unexpected because it contradicts the observation made that the rolling resistance of the tire of the state of the art increases all the more as the temperature decreases. This unexpected result therefore makes it possible to at least partially compensate for the increase in rolling resistance with the decrease in temperature.

[0009] The characteristic whereby Tgc < -10°C, Tgl1 < -10°C prevents elastomeric materials from dissipating too much energy at very low operating temperatures, for example -5°C or even -7°C. Indeed, the closer the operating temperature is to the glass transition, the more the material dissipates energy and increases the rolling resistance of the tire. This is particularly important for at least the first lateral elastomeric material which contributes mainly to the rolling resistance due to its positioning on the tread. Indeed, by being positioned axially laterally, the first lateral portion requires significant forces to flatten the tire and therefore dissipates more energy.

[0010] Too large a difference between the Tgc and Tgl1 temperatures would, for a given Tgc temperature, lead to a reduction in the tire's wet braking performance. Indeed, a relatively low Tgl1 temperature of the lateral portion would lead to a reduction in the tire's wet braking performance.

[0011] For a given temperature Tgl1, too large a difference between the temperatures Tgc and Tgl1 would lead to a relatively high temperature Tgc and therefore to a reduction in rolling resistance performance for very low operating temperatures as explained previously. Thus, the invention also makes it possible to preserve the tire's wet braking performance and rolling resistance.

[0012] The central portion of the tread layer comprises the median plane of the tire. Preferably, the central portion of the tread layer has an axial width strictly greater than the axial width of the or each lateral portion.

[0013] Conventionally, the tread surface is delimited axially by first and second axial edges merged respectively with the first and second axial edges of the tread. The first and second axial edges are determined on a tire mounted on a nominal rim and inflated to the nominal pressure within the meaning of the ETRTO 2021 standard manual. The first and second axial edges are arranged on either side of the median plane of the tire and formed by lines substantially parallel to the circumferential direction of the tire. In the case of an obvious boundary between the tread surface and the rest of the tire, the first and second axial edges are determined simply.In the case where the tread surface is continuous with the outer surfaces of the tire sidewalls, the first and second axial edges are usually determined by loading the tire to 80% of its load capacity according to the ETRTO 2021 standard manual and the first and second axial edges are identified as the axial limits of the tread in contact with the ground.

[0014] Each glass transition temperature Tgc, Tgl1 is determined using a Metravib VA4000 or DMA+450 type viscoanalyzer using specimens comprising a cured composition extracted from the tire. The response of the specimens subjected to alternating simple sinusoidal shear stress at a frequency of 10 Hz under a force equal to 55 N is recorded. A temperature sweep is carried out between -80°C and 80°C at a speed of 1.5°C / min. The test piece is of cylindrical section as described in ASTM D 5992 - 96 (version reapproved in 2011, 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 [1.83-2.33]. It will be noted that the force of 55 N is equivalent, in the case of a test piece with a diameter equal to 10.00 mm, to a stress of an amplitude equal to 0.7 MPa peak-peak.The glass transition temperature Tg is taken equal to the temperature for which the value of the tangent of the phase angle tanD is maximum. The tangent tanD of the phase angle D between the force exerted on the sample and its displacement reflects a dynamic loss and is equal to the ratio G” / G'.

[0015] An elastomeric material is a material exhibiting elastomeric behavior. Such a material is 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. The crosslinkable compositions used for the tread layer are conventional tire tread compositions, typically based on a diene elastomer, a reinforcing filler such as carbon black or silica, a vulcanization system and the usual additives.

[0016] 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.

[0017] Axial direction means the direction substantially parallel to the axis of revolution of the tire, i.e. the axis of rotation of the tire.

[0018] Circumferential direction means the direction which is, in each meridian plane, 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).

[0019] Radial direction means 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.

[0020] 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 midpoint of the two beads and passes through the axial center of the crown reinforcement.

[0021] By equatorial circumferential plane of the tire (denoted E), we mean, 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, the distance between these two points being equal to H.

[0022] By meridian plane is meant a plane parallel to and containing the axis of rotation of the pneumatic and perpendicular to the circumferential direction.

[0023] 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.

[0024] By 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.

[0025] 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).

[0026] The tires are, in preferred embodiments of the invention, intended for passenger vehicles as defined within the meaning of the European Tire and Rim Technical Organization or "ETRTO" standard, 2021. Such a tire has a section in a meridian section plane characterized by a section height H and a nominal section width or bead thickness S within the meaning of the European Tire and Rim Technical Organization or "ETRTO" standard, 2021 such that the H / S ratio, expressed as a percentage, is at most equal to 90, preferably at most equal to 70 and is at least equal to 30, and the nominal section width S is at least equal to 115 mm, preferably at least equal to 175 mm and at most equal to 385 mm, preferably at most equal to 315 mm. In addition, the diameter at hook D, defining the diameter of the tire mounting rim, is at least 12 inches, preferably at least 16 inches and at most 24 inches.

[0027] In preferred but optional embodiments, Tgc-Tgl1 > 13°C, preferably Tgc-Tgl1 > 14°C.

[0028] The greater the difference between the temperatures Tgc and Tgl1, the less influence the temperature has on the increase in rolling resistance with decreasing temperature.

[0029] In preferred but optional embodiments, Tgc-Tgl1 < 22°C, preferably Tgc-Tgl1 < 20°C and more preferably Tgc-Tgl1 < 18°C. As explained above, the compromise between wet braking performance and rolling resistance is improved.

[0030] In advantageous but optional embodiments, Tgc > -18°C, of preferably Tgc > -15°C and more preferably Tgc > -13°C.

[0031] Too low a glass transition temperature Tgc of the central portion would lead to a reduction in the wet braking performance of the tire, particularly in straight-line braking, a situation in which the performance of the central portion is predominant compared to that of the first lateral portion.

[0032] In advantageous but optional embodiments, Tgl1 < -15°C, preferably Tgl1 < -20°C.

[0033] Too high a glass transition temperature Tgl1 would lead to an undesirable increase in rolling resistance, especially at temperatures closer to the glass transition temperature Tgl1 as explained previously.

[0034] In advantageous but optional embodiments, Tgl1 > -35°C, preferably Tgl 1 > -30°C and more preferably Tgl 1 > -27°C.

[0035] Too low a glass transition temperature Tgl1 would lead to a reduction in the wet braking performance of the tire.

[0036] Advantageously but optionally to limit rolling resistance at normal operating temperatures, the central elastomeric material has a dynamic loss tanDMAX23c measured according to ASTM D-5992-96, at a temperature of 23°C and at a frequency of 10Hz, such that tanDMAX23c < 0.50, preferably tanDMAX23c < 0.35.

[0037] Advantageously but optionally, making it possible to limit the rolling resistance at normal operating temperatures, the first lateral elastomeric material has a dynamic loss tanDMAX23l1 measured according to the ASTM D- 5992-96 standard, at a temperature of 23°C and at a frequency of 10Hz such that tanDMAX23l1 < 0.20, preferably tanDMAX23l1 < 0.15.

[0038] Each dynamic loss tanDMAX23 is yet another dynamic property well known to those skilled in the art and is measured on the same viscoanalyzer of the Metravib VA4000 or DMA+450 type using specimens comprising a cured composition extracted from the tire. 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 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 tangent tanD 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 maximum value tanDMAX of the tangent tanD of the phase angle D observed on the deformation return cycle is recorded.

[0039] Advantageously but optionally allowing good behavior to be obtained due to the majority contribution of the central portion to the rigidity of the wearing course: - the central elastomeric material having a complex dynamic shear modulus G*C measured at 10% deformation according to ASTM D-5992-96, at a temperature of 23°C and at a frequency of 10Hz, - the first lateral elastomeric material exhibiting a complex dynamic shear modulus G*I1 measured at 10% strain according to ASTM D-5992-96, at a temperature of 23°C and at a frequency of 10Hz, G*C>G*I1.

[0040] In addition, the first lateral elastomeric material being softer than the central elastomeric material, it promotes good flattening of the tire which limits the dissipation of the first lateral portion. This reduces the rolling resistance of the tire.

[0041] 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 dynamic complex 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* is measured at 10% cc strain on the return cycle.

[0042] In optional embodiments, G*C > 1.7 MPa, preferably G*C > 2.3 MPa and more preferably G*C > 2.5 MPa.

[0043] In optional embodiments, G*I1 > 1.3 MPa, preferably G*I1 > 1.5 MPa and more preferably G*I1 > 1.7 MPa.

[0044] An advantage of the relatively low value of Tgl1 is that a relatively high value of G*I1 can be achieved without it having any influence on the value of Tgl1. Thus, both the technical effect of the invention can be achieved and other performances of the tire can also be independently improved, in this case its behavior and more specifically its drift stiffness.

[0045] In other embodiments sometimes compatible with the optional embodiments described above and allowing a greater reduction in rolling resistance, G*I1 < 1.9 MPa, preferably G*I1 < 1.6 MPa and more preferably G*I1 < 1.4 MPa.

[0046] In highly advantageous and optional embodiments, the tread layer comprises a second lateral portion extending between the second axial edge of the tread and the second axial edge of the central portion, the second lateral portion comprising at least one second lateral elastomeric material having a glass transition temperature Tgl2 such that Tgl2 < -10°C and 12°C < Tgc-Tgl2 < 23°C.

[0047] More generally, in the present application, whenever a feature is applicable to the first lateral portion, it is optionally more advantageous to apply this feature to each first and second lateral portion. All the advantages described above in relation to the first lateral portion are deduced mutatis mutandis for the second lateral portion.

[0048] Thus, the principle of the invention is applied to the second lateral portion, which also contributes to rolling resistance due to its positioning on the tread in a manner similar to the first lateral portion.

[0049] In other words, the tread layer is such that the first and second lateral portions are arranged axially outside the central portion on either side axially of the central portion relative to the median plane of the tire.

[0050] Optionally and for the same reasons as for the first lateral portion, the second lateral portion is such that Tgc-Tgl2 > 13°C, preferably Tgc-Tgl2 > 14°C.

[0051] Optionally and for the same reasons as for the first lateral portion, the second lateral portion is such that Tgc-Tgl2 < 22°C, preferably Tgc-Tgl2 < 20°C and more preferably T gc-T gl2 < 18°C.

[0052] Optionally and for the same reasons as for the first lateral portion, the second lateral elastomeric material is such that Tgl2 < -15°C, preferably Tgl2 < -20°C.

[0053] Optionally and for the same reasons as for the first lateral portion, the second lateral elastomeric material is such that Tgl2 > -35°C, preferably Tgl2 > -30°C and more preferably Tgl2 > -27°C.

[0054] Optionally and for the same reasons as for the first lateral portion, the second lateral elastomeric material has a dynamic loss tanDMAX23l2 measured according to the ASTM D-5992-96 standard, at a temperature of 23°C and at a frequency of 10Hz such that tanDMAX23l2 < 0.20, preferably tanDMAX23l2 < 0.15.

[0055] Optionally and for the same reasons as for the first side portion: - the central elastomeric material having a complex dynamic shear modulus G*C measured at 10% deformation according to ASTM D-5992-96, at a temperature of 23°C and at a frequency of 10Hz, - the second lateral elastomeric material having a complex dynamic shear modulus G*I2 measured at 10% deformation according to standard ASTM D- 5992-96, at a temperature of 23°C and at a frequency of 10Hz, G*C>G*I2.

[0056] Optionally and for the same reasons as for the first lateral portion, the second lateral elastomeric material is such that G*I2 > 1.3 MPa, preferably G*I2 > 1.5 MPa and more preferably G*I2 > 1.7 MPa.

[0057] In other embodiments sometimes compatible with the optional embodiments described above and allowing a greater reduction in rolling resistance, G*I2 < 1.9 MPa, preferably G*I2 < 1.6 MPa and more preferably G*I2 < 1.4 MPa.

[0058] The values ​​of Tgl2, tanDMAX23l2 and G*I2 are determined as described previously for Tgc, Tgl1, tanDMAX23c, tanDMAX23l2, G*c and G*I1.

[0059] In preferred and advantageous embodiments, the central portion is made of the central elastomeric material and each first and second side portion is made of the first and second side elastomeric material, respectively.

[0060] In optional embodiments, the tread comprises a layer arranged radially within the central portion and at least a portion of each first and second lateral portion.

[0061] In variations of these optional embodiments, the layer arranged radially within the central portion and at least a portion of each first and second side portions is a support layer of the rolling. Such a support layer, also called an underlay, is intended not to come into contact with the ground when the tire is rolling, for example until a regulatory wear threshold is reached.

[0062] In other variants of these optional embodiments, the layer arranged radially inside the central portion and at least a portion of each first and second lateral portion is a radially inner tread layer. Such a radially inner tread layer is intended to come into contact with the ground when the tire is rolling, for example before a regulatory wear threshold is reached.

[0063] In optional embodiments compatible with treads particularly well suited to tires intended to run in a relatively wide temperature range, for example from 25°C to -7°C, the tread comprises main circumferential cutouts having a depth greater than or equal to 50% of the tread height comprising first and second axially outer main circumferential cutouts arranged axially on either side of the median plane of the tire, the first and second axially outer main circumferential cutouts being the axially outermost main circumferential cutouts of the tread, a first interface between the first lateral portion and the central portion is arranged axially outside the first axially outer main circumferential cutout,and / or a second interface between the second lateral portion and the central portion is arranged axially outside the second axially outer main circumferential cutout.,

[0064] A cutout or a portion of a cutout has, on the rolling surface, two main characteristic dimensions: a width and a curvilinear length such that the curvilinear length is at least twice the width. 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.

[0065] The width 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 does not include a chamfer, at a radial dimension coincident with the rolling surface, and by default and in the case where the cutout includes a chamfer, at the radial dimension most radially external of the cutout and radially internal to the chamfer. The width is measured substantially perpendicular to the major side 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 smallest distance between the two major side faces at the particular dimension of the cutout.

[0066] The depth of a cut is, on a new tire, the maximum radial distance between the bottom 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.

[0067] A circumferential cutout is such that the cutout 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. The mean direction is the shortest curve joining the two ends of the cutout and parallel to the rolling surface. 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 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.

[0068] Preferably, each main circumferential cutout has a depth greater than or equal to 75% and more preferably 90% of the sculpture height.

[0069] In embodiments in which the main circumferential cutouts are relatively deep and suitable for passenger vehicle tires, each main circumferential cutout has a depth ranging from 4.0 mm at the tread height, preferably from 5.0 mm at the tread height, and more preferably from 5.5 mm at the tread height.

[0070] In embodiments in which the main circumferential cutouts are relatively wide main circumferential grooves suitable for passenger vehicle tires, each main circumferential cutout has an axial width greater than or equal to 1.0 mm, preferably greater than or equal to 5.0 mm and more preferably ranging from 5.0 mm to 20.0 mm.

[0071] Optionally: - the first lateral portion extends axially from the first interface to at least the first axial edge of the tread, and / or - the second lateral portion extends axially from the second interface to at least the second axial edge of the tread.

[0072] The tire is, in preferred embodiments of the invention, a summer tire. By summer, we mean tires which are not so-called 4-season or all-season tires, nor so-called winter tires.

[0073] Winter tires are identified by an M+S marking (M+S being the acronym for "Mud + Snow") and / or 3PMSF (3PMSF being the acronym for "3 Peak Mountain Snow Flake"). 4-season or all-season tires, due to their performance on snow, also have the M+S and / or 3PMSF markings. Thus, a summer tire does not have an M+S marking or a 3PMSF marking.

[0074] Conventionally, the tire comprises a crown, two sidewalls, two beads, each sidewall connecting each bead to the crown. Also conventionally, the crown comprises the tread and a crown reinforcement arranged radially inside the tread. The tire also comprises a carcass reinforcement anchored in each bead and extending radially in each sidewall and axially in the crown radially inside the crown reinforcement.

[0075] Conventionally, the crown reinforcement comprises at least one crown layer comprising reinforcing elements. These reinforcing elements are preferably textile or metal wire elements.

[0076] In embodiments allowing the performance of so-called radial tires to be obtained, for example as defined by the ETRTO, the carcass reinforcement comprises at least one carcass layer, the or each carcass layer comprising carcass cord reinforcement elements, each carcass cord reinforcement element extending substantially in a main direction forming with the circumferential direction of the tire, an angle, in absolute value, ranging from 80° to 90° at least in a portion of the sidewall.

[0077] Another object of the invention is the use of a tire as defined above for an electric or hybrid vehicle, preferably an electric vehicle. Indeed, the invention is particularly interesting on such vehicles where it is desired that the variation in autonomy with temperature be as low as possible.

[0078] Preferably, electric vehicles are chosen from among the vehicles extended-range electric vehicles (designated by the acronym "E-REV" meaning "Electrical Vehicle with Range Extender"), 100% electric vehicles (designated by the acronym "BEV" meaning "Battery Electric Vehicle") and fuel cell electric vehicles (designated by the acronym "FCEV" meaning "Fuel Cell Electric Vehicle"). Preferably, the hybrid vehicles are chosen from mild hybrid vehicles (designated by the acronym "mHEV" meaning "Mild Hybrid Electric Vehicle"), conventional hybrid vehicles (designated by the acronym "sHEV" meaning "Strong Hybrid Electric Vehicle"), and rechargeable hybrid vehicles (designated by the acronym "PHEV" meaning "Plug-In Hybrid Electric Vehicle").

[0079] The invention will be better understood upon reading the description which follows, given solely as a non-limiting example and with reference to Figure 1 which is a view in a meridian section plane of a tire according to the invention.

[0080] An X, Y, Z reference point is shown corresponding to the usual axial (Y), radial (Z) and circumferential (X) directions of a tire.

[0081] With reference to Figure 1, the tire according to the invention is designated by the general reference 10. The tire 10 has a substantially toric shape around an axis of revolution substantially parallel to the axial direction Y. The tire 10 is intended for a passenger vehicle and has dimensions 235 / 55 R19. The tire 10 is a summer tire which is in particular intended to be used on an electric or hybrid vehicle. The tire 10 is shown in new condition, that is to say not having yet been driven.

[0082] The tire 10 comprises a tread 12 intended to come into contact with a ground when rolling. The tire 10 further comprises a conventional structure, such as for example described in applications WO2021250331, WO2022074341 or WO2022069819 or even WO2021123522.

[0083] The tread 12 comprises a rolling surface 14 via which the tread 12 is intended to come into contact with the ground when the tire 10 rolls on the ground. The tread 12 and the rolling surface 14 are axially delimited by first and second axial edges 16, 18.

[0084] The tread 12 comprises a tread layer 20 and a support layer 22. The tread layer 20 comprises a central portion 24 and first and second lateral portions 26, 28. The central portion 24 extends axially on either side of the median plane M of the tire and comprises the median plane of the tire. The first and second lateral portions 26, 28 are arranged axially outside the central portion 24 on either side axially of the central portion 24 relative to the median plane M of the tire 10. The central portion 24 has an axial width strictly greater than the axial width of each first and second lateral portion 26, 28.

[0085] The support layer 22 is arranged radially inside the central portion 24 and each first and second lateral portion 26, 28.

[0086] The central portion 24 extends axially between first and second axial edges 30, 32 of the central portion 24. The first lateral portion 26 extends between the first axial edge 16 of the tread 12 and the first axial edge 30 of the central portion 24. The second lateral portion 28 extends between the second axial edge 18 of the tread 12 and the second axial edge 32 of the central portion 24. A first interface 27 is present between the first lateral portion 26 and the central portion 24. A second interface 29 is present between the second lateral portion 28 and the central portion 24. The first lateral portion 26 extends axially from the first interface 27 to the first axial edge 16. The second lateral portion 28 extends axially from the second interface 29 to the second axial edge 18.

[0087] The tread 12 comprises N>1 main circumferential cutouts, here N=4 main circumferential grooves designated by the references 34, 36, 38, 40. The axially outer main circumferential cutouts 34, 40, called first and second axially outer main circumferential cutouts 34, 40, are arranged axially on either side of the median plane M of the tire 10 and are the axially outermost main circumferential cutouts of the tread 12.

[0088] The first interface 27 is arranged axially outside the first axially outer main circumferential cutout 34 and the second interface 29 is arranged axially outside the second axially outer main circumferential cutout 40.

[0089] Each main circumferential cutout 34 to 40 has a depth ranging from 4.0 mm to the tread height Hs, preferably ranging from 5.0 mm to the tread height Hs and more preferably ranging from 5.5 mm to the tread height Hs. Each depth is greater than or equal to 50%, preferably 75% and more preferably 90% of the tread height Hs. Here, Hs=6.3 mm. The depth of each first and second axially outer main circumferential cutout 34, 40 is equal to 5.8 mm, the depth of each main circumferential cutout 36, 38 is equal to 6.3 mm.

[0090] Each main circumferential cutout 34 to 40 respectively has an axial width greater than or equal to 1.0 mm, preferably greater than or equal to 5.0 mm. mm and more preferably ranging from 5.0 mm to 20.0 mm. Here, the width of each first and second axially outer main circumferential cutout 34, 40 is equal to 7.0 mm and the width of each main circumferential cutout 36, 38 is equal to 14.0 mm.

[0091] The central portion 24 comprises at least one central elastomeric material, here consisting of a central elastomeric material 240. The central elastomeric material 240 has a dynamic loss tanDMAX23c measured according to the ASTM D-5992-96 standard, at a temperature of 23°C and at a frequency of 10Hz, such that tanDMAX23c < 0.50, preferably tanDMAX23c < 0.35. Here, tanDMAX23c = 0.31. The central elastomeric material 240 has a complex dynamic shear modulus G*C measured at 10% deformation according to the ASTM D-5992-96 standard, at a temperature of 23°C and at a frequency of 10Hz such that G*C > 1.7 MPa, preferably G*C > 2.3 MPa and more preferably G*C > 2.5 MPa. Here, G*C = 2.7 MPa. The central elastomeric material 240 has a glass transition temperature Tgc such that Tgc < -10°C and Tgc > -18°C, preferably Tgc > -15°C and more preferably Tgc > - 13°C. Here Tgc = -11 °C.

[0092] Each first and second lateral portion 26, 28 respectively comprises a, here is made respectively of a first and second lateral elastomeric material 260, 280. Here, the first and second lateral elastomeric materials 260, 280 are identical. Each first and second lateral elastomeric material 260, 280 has a dynamic loss tanDMAX23l1, tanDMAX23l2 measured according to the ASTM D-5992-96 standard, at a temperature of 23°C and at a frequency of 10Hz such that tanDMAX23l1 < 0.20 and tanDMAX23l2 < 0.20, preferably tanDMAX23l1 < 0.15 and tanDMAX23l2 < 0.15. Here tanDMAX23l1 = tanDMAX23l2 = 0.13.Each first and second lateral elastomeric material 260, 280 has a complex dynamic shear modulus G*I1, G*I2 measured at 10% strain according to ASTM D-5992-96, at a temperature of 23°C and at a frequency of 10Hz such that G*I1 > 1.3 MPa and G*I2 > 1.3 MPa, preferably G*I1 > 1.5 MPa and G*I2 > 1.5 MPa and more preferably G*I1 > 1.7 MPa and G*I2 > 1.7 MPa and such that G*I1 < 1.9 MPa and G*I2 < 1.9 MPa. Here G*I1 = G*I2 = 1.7 MPa. Each first and second lateral elastomeric material 260, 280 has a glass transition temperature Tgl1, Tgl2 such that Tgl1 < -10°C, Tgl2 < -10°C, preferably Tgl1 < -15°C and Tgl2 < -15°C, and more preferably Tgl1 < -20°C and Tgl2 < -20°C and such that Tgl 1 > -35°C and Tgl2 > -35°C, preferably Tgl 1 > -30°C and Tgl2 > -30°C and even more preferably Tgl 1 > -27°C and Tgl2 > -27°C. Here, Tgl 1 = Tgl2 = -27°C.

[0093] Note that G*C>G*I1 and G*C>G*I2. Note also that 12°C < Tgc-Tgl1< 23°C and 12°C < Tgc-Tgl2< 23°C. It should also be noted that Tgc-Tgl1 > 13°C and Tgc-Tgl2 > 13°C, preferably Tgc-Tgl1 > 14°C and Tgc-Tgl2 > 14°C. Finally, it should be noted that Tgc-Tgl1 < 22°C and Tgc-Tgl2 < 22°C, preferably Tgc-Tgl1 < 20°C and Tgc-Tgl2 < 20°C and more preferably Tgc-Tgl1 < 18°C ​​and Tgc-Tgl2 < 18°C.

[0094] Comparative tests

[0095] The tire 10 according to the invention previously described was compared with: - a control tire T having a tread comprising a single elastomeric material between the first and second axial edges, and - a tire 10' also in accordance with the invention, distinguished from the tire 10 solely by the use of first and second elastomeric materials different from those of the tire 10.

[0096] The rolling resistance RR of these tires was measured at different temperatures (25°C, 5°C, and -7°C) using tests commonly used in the tire industry. Their straight-line braking performance Pf on wet ground and their drift stiffness performance Dz were also measured, allowing their behavior to be evaluated.

[0097] The results of the various tests have been compiled in Table 1 below. The Pf and Dz performances are given on a base of 100 compared to tire T. A value above 100 indicates an improvement in performance. A value below 100 indicates a deterioration in performance.

[0098] [Table 1]

[0099] Table 2 below lists the compositions A, B, C from which the different elastomeric materials 240, 260, 280 of the T, 10 and 10' tires were manufactured. The values ​​are given in pce.

[0100] Concerning the sensitivity of the rolling resistance to the drop in temperature, it is observed that the tires 10 and 10' according to the invention have a difference between the rolling resistances RR at -7°C and 5°C and the rolling resistance RR at 25°C lower than those of the control tire T. Thus, the rolling resistance RR of the tires 10 and 10' is much less sensitive to the drop in temperature. It is noted that the rolling resistance is all the less sensitive as the differences Tgc-Tgl1 and Tgc-Tgl2 are large.

[0101] It is also observed that the rolling resistance of the tires 10 and 10' according to the invention is, for a given temperature, lower than that of the control tire 10 and that, very surprisingly as explained previously, this reduction in rolling resistance is all the greater the lower the operating temperature.

[0102] Finally, we note a very weak influence of the characteristics of the materials on the Pf performance and an almost zero influence on the Dz performance.

[0103] [Table 2]

[0104] (1) - Styrene-Butadiene Elastomer described as polymer B on page 34 of WO2018115722; (2) - Styrene-Butadiene Elastomer from Arlanxeo having a Mooney viscosity equal to 54 UM according to ASTM D 1646 (1+4 @ 100°C), a vinyl content unit rate equal to 18%, an average styrene rate equal to 27% and a glass transition temperature equal to -48°C; (3) - Styrene-Butadiene Elastomer described as polymer C on page 34 of WO2018115722; (4) - Carbon black grade 234 according to ASTM D-1765; (5) - Silica 160MP from Solvay; (6) - "Si69" from Evonik; (7) - N-tert-butyl-2-benzothiazyl sulfenamide (marketed by Flexsys; (8) - The other additives are conventionally known to those skilled in the art and here include in particular a protective wax, N-1,3-dimethylbutyl-N-phenylparaphenylenediamine, N-cyclohexyl-benzothiazyl sulfenamide, diphenylguanidine, sulfur, stearic acid, zinc oxide, oleic sunflower oil and an AM 070 processing agent.

[0105] The invention is not limited to the embodiment described above.

[0106] Indeed, it could be considered that the first and second lateral portions are not arranged symmetrically with respect to the median plane M.

[0107] It may also be envisaged that one of the lateral portions does not have an elastomeric material whose glass transition temperature Tg is such that Tg < -10°C and 12°C < Tgc-Tg < 23°C. Thus, it may be envisaged that the elastomeric material is such that Tg < -10°C and Tgc-Tg < 12°C or Tgc-Tg > 23°C. It may also be envisaged that the elastomeric material is such that Tg > -10°C and 12°C < Tgc-Tg < 23°C.

[0108] It may also be envisaged that the central portion extends to the second edge of the tread so that the second edge of the central portion coincides with the second edge of the tread. Thus, the tread layer does not include a second lateral portion.

[0109] It may also be envisaged that the tread does not comprise a layer arranged radially inside the central portion and at least part of each first and second lateral portion.

[0110] Finally, it may be possible to envisage one or more other portions being inserted between the central portion and the first and / or second lateral portion.

Claims

CLAIMS 1. A tire (10) comprising a tread (12) axially delimited by first and second axial edges (16, 18), the tread (12) comprising a tread layer (20) comprising: - a central portion (24) extending between first and second axial edges (30, 32) of the central portion (24), the central portion (24) comprising at least one central elastomeric material (240) having a glass transition temperature Tgc, the central portion (24) extending axially on either side of a median plane (M) of the tire (10), - at least one first lateral portion (26) extending between the first axial edge (16) of the tread (12) and the first axial edge (30) of the central portion (24), the first lateral portion (26) comprising at least one first lateral elastomeric material (260) having a glass transition temperature Tgl1, characterized in that Tgc < -10°C, Tgl1 < -10°C and 12°C < Tgc-Tgl1 < 23°C.

2. Tire (10) according to the preceding claim, in which Tgc-Tgl1 > 13°C, preferably Tgc-Tgl1 > 14°C.

3. Tire (10) according to any one of the preceding claims, in which Tgc-Tgl1 < 22°C, preferably Tgc-Tgl1 < 20°C and more preferably Tgc-Tgl1 < 18°C.

4. Tire (10) according to any one of the preceding claims, in which Tgc > -18°C, preferably Tgc > -15°C and more preferably Tgc > -13°C.

5. Tire (10) according to any one of the preceding claims, wherein Tgl1 < -15°C, preferably Tgl1 < -20°C.

6. Tire (10) according to any one of the preceding claims, in which Tgl 1 > -35°C, preferably Tgl 1 > -30°C and more preferably Tgl 1 > -27°C.

7. A tire (10) according to any preceding claim, wherein: - the central elastomeric material (240) having a complex dynamic shear modulus G*C measured at 10% deformation according to standard ASTM D- 5992-96, at a temperature of 23°C and at a frequency of 10Hz, - the first lateral elastomeric material (260) having a complex dynamic shear modulus G*I1 measured at 10% deformation according to standard ASTM D- 5992-96, at a temperature of 23°C and at a frequency of 10Hz, G*C>G*I1.

8. Tire (10) according to the preceding claim, in which G*C > 1.7 MPa, preferably G*C > 2.3 MPa and more preferably G*C > 2.5 MPa.

9. Tire (10) according to claim 7 or 8, in which G*I1 > 1.3 MPa, preferably G*I1 > 1.5 MPa and more preferably G*I1 > 1.7 MPa.

10. A tire (10) according to any one of the preceding claims, wherein the tread layer (20) comprises a second lateral portion (28) extending between the second axial edge (18) of the tread (12) and the second axial edge (32) of the central portion (24), the second lateral portion (28) comprising at least one second lateral elastomeric material (280) having a glass transition temperature Tgl2 such that Tgl2 < -10°C and 12°C < Tgc-Tgl2 < 23°C.

11. Tire (10) according to the preceding claim, in which Tgc-Tgl2 > 13°C, preferably Tgc-Tgl2 > 14°C.

12. Tire (10) according to claim 10 or 11, in which Tgc-Tgl2 < 22°C, preferably Tgc-Tgl2 < 20°C and more preferably Tgc-Tgl2 < 18°C.

13. Tire (10) according to any one of claims 10 to 12, wherein Tgl2 < -15°C, preferably Tgl2 < -20°C.

14. Tire (10) according to any one of claims 10 to 13, in which Tgl2 > -35°C, preferably Tgl2 > -30°C and more preferably Tgl2 > -27°C.

15. Use of a tire (10) according to any one of the preceding claims for an electric or hybrid vehicle, preferably an electric vehicle.

Images