tyre

Abstract

The invention relates to a tyre (100) comprising a sidewall-foot-crown layer (162A) integrally forming a crown portion (162A1), which is arranged in the crown (110) of the tyre against a carcass layer (151) and is radially interposed between the carcass layer and a lateral portion (114AA) of a radially inner working layer (114), and a sidewall portion (162A.2), which is arranged in the sidewall (120A) of the tyre against the carcass layer and extends radially from the crown to the bead of the tyre. The crown portion has an axially innermost end (162A.1E) spaced apart from the axial end edge (114A) of the radially inner working layer by a distance D1 ranging from 4.0 to 12.0 mm. The sidewall-foot-crown layer is made of an elastomeric composition comprising one or more natural rubbers having a content of at least 35 phr and one or more butadiene rubbers having a content of at least 50 phr.

Description

[0001] Pneumatic

[0002] The present invention relates to a pneumatic tire.

[0003] The invention relates in particular, but not exclusively, to tires for light vehicles, especially passenger cars, particularly four-wheeled vehicles. The term "tire" refers to a tire designed to form a cavity by cooperating with a mounting support, commonly referred to as a "rim," this cavity being capable of being pressurized to a pressure greater than atmospheric pressure. The tire has a substantially toroidal shape of revolution around an axis of revolution of the tire, which coincides with an axis of rotation around which the tire can be driven to roll on the ground. This axis of revolution defines three directions, namely an axial direction, a circumferential direction, and a radial direction, conventionally used by those skilled in the art to describe the tire according to the following conventions:

[0004] - by axial direction, we mean the direction substantially parallel to the axis of revolution of the tire, that is to say the axis of rotation of the tire;

[0005] - by radial direction, we mean the direction along a radius of the tire, that is to say any direction intersecting the axis of rotation of the tire and substantially perpendicular to this axis;

[0006] - by circumferential direction, we mean the direction which is substantially perpendicular to both the axial direction and to a radius of the tire; in other words, the circumferential direction is tangent to a circle whose center is on the axis of rotation of the tire; the circumferential direction is thus tangent to a tread surface of the tire, intended to be in contact with the ground when the tire is rolling;

[0007] - by median plane of the tire, we mean the plane perpendicular to the axis of rotation of the tire, which passes through the axial midpoint of the tire's rolling surface;

[0008] - by meridian plane of the tire, we mean a plane containing the axis of rotation of the tire, the meridian plane thus being perpendicular to the circumferential direction;

[0009] - by radially inside, respectively radially outside, we mean closer to the axis of rotation of the tire, respectively further from the axis of rotation of the tire; - by axially inside, respectively axially outside, we mean closer to the median plane of the tire, respectively further from the median plane of the tire.

[0010] Typically, a tire consists of a crown, which radially forms the tread on the outside, the part that contacts the ground when the tire is in motion. This crown extends radially inward on either side of the tire's median plane, consisting of first and second sidewalls, and then first and second bead sections designed to contact the wheel rim. The crown, first and second sidewalls, and first and second bead sections define a toroidal inflation cavity for the tire. A bead section is the radial portion of the tire designed to allow the tire to be attached to the rim or, more generally, a similar mounting surface. Each bead section is specifically designed to make contact with a rim hook, enabling it to be attached.The bead is thus delimited radially internally by the innermost radial end of the tire and radially externally by an axial line passing through the outermost radial point in contact with a standard nominal rim as defined by the European Tyre and Rim Technical Organisation (ETRTO) standard, 2023. The sidewall is defined as the radial portion of the tire connecting the bead associated with the sidewall at its apex. The sidewall is delimited radially externally by an edge of the tread. The two axial edges of the tread are determined on a tire mounted on a nominal rim and inflated to the nominal pressure as defined in the ETRTO, 2023 standard manual: these two axial edges are arranged on either side of the median plane of the tire and are formed respectively by lines substantially parallel to the circumferential direction of the tire.In the case of a clear boundary between the tread and the sidewall of the tire, the edges are easily determined. Where the tread is continuous with the sidewalls, the edges are usually determined by loading the tire to 80% of its load capacity according to the ETRTO 2023 standard manual. The edges are identified as the axial limits of the tread in contact with the ground. The sidewall is delimited radially on the inside by an axial line passing through the outermost radial point in contact with a standard nominal rim as defined by the European Tyre and Rim Technical Organisation (ETRTO) standard, 2023.

[0011] For reinforcement purposes, the crown comprises a crown reinforcement, arranged radially within the tread, typically radially between the tread and a carcass reinforcement anchored in each of the first and second beads and extending from the first and second beads, respectively, in the first and second sidewalls to the crown. In each sidewall, the carcass reinforcement is covered by one or more layers of elastomeric sidewall, which are interposed between the carcass reinforcement and an external sidewall surface in contact with atmospheric air when the tire is mounted on the rim. These layers serve, among other things, to protect the carcass reinforcement from external aggressions such as impacts, abrasion, atmospheric ozone, UV radiation, etc.It should be noted that, in this document, "elastomeric" means a composition or material consisting mainly by weight of one or more elastomers, this composition may also include fillers and other components commonly used in the field of tire compositions, such as at least one reinforcing filler of the carbon black and / or silica type, a crosslinking system most often based on sulfur, and protective agents.

[0012] The crown reinforcement comprises a working reinforcement and, often, a reinforcing reinforcement which is arranged radially between the working reinforcement and the tread. The working reinforcement usually comprises two radially superimposed working layers, each comprising wire reinforcements which are embedded in an elastomeric matrix and which, in each working layer, extend parallel to each other from one to the other of two axial end edges of the working layer, forming angles with the circumferential direction of the tire having opposite orientations from one working layer to the other.

[0013] The radially inner working layer includes a central portion, which extends axially on either side of the median plane of the tire and is applied radially against a carcass layer of the carcass reinforcement, and two lateral portions, which extend axially from the central portion respectively to the axial end edges of the radially inner working layer and which radially overhang the carcass layer, with interposition, between the latter and each of these lateral portions, of an elastomeric layer, usually called the "foot-to-top layer".The two tread-crown layers of the tire are designed, in their respective crown areas, to ensure a gradual transition in stiffness between the carcass layer and the tread reinforcement, to strengthen the tire structure by protecting the interface between the carcass layer and the tread reinforcement against mechanical stresses, and to improve tire durability by limiting the risks of delamination and cracking. To this end, each tread-crown layer is, firstly, made of an elastomeric composition, the majority or even exclusive elastomer of which is natural rubber and which contains reinforcing fillers, such as carbon black, and, secondly, embedded radially beneath the inner tread layer over a large axial extent of the latter from its corresponding axial end edge, typically at least fifteen millimeters.

[0014] Due to its specific composition, each crown-side layer is often distinct from the aforementioned sidewall layer(s). However, a known alternative approach involves using a single elastomeric component, commonly referred to as the "crown-sidewall layer," to form both the sidewall layer(s) and the crown-side layer, located on the same axial side of the tire's median plane. Using this crown-sidewall layer reduces the number of separate parts required for assembly during tire manufacturing, thereby improving tire assembly productivity.However, this sidewall-to-crown layer proves both difficult to formulate chemically, due to its different mechanical functions in the sidewall and the crown, and challenging to manufacture, particularly to extrude, prior to assembly with the rest of the tire, because of its large size along a direction corresponding to the axial direction of the tire once the sidewall-to-crown layer is assembled to it. The industrial cost and / or the performance of the tire may be negatively impacted as a result.

[0015] The aim of the present invention is to propose a tire having a sidewall-foot-crown layer that is improved with regard to, among other things, its manufacture and its contribution to tire performance.

[0016] To this end, the invention relates to a tire comprising a crown, two sidewalls, each extending radially inwards from the crown and which are arranged axially on either side of a median plane of the tire, and two bead ribs, which extend radially inwards respectively from the two sidewalls and which are adapted to mount the tire on a rim.The apex comprises an apex reinforcement including a working reinforcement which comprises two radially superimposed working layers, namely an inner radial working layer and an outer radial working layer, each of these two working layers (i) including a central portion, which extends axially on either side of the median plane, and two lateral portions, which are arranged axially on either side of the median plane and which extend axially from the central portion to respectively two axial end edges of the working layer, and (ii) comprising wire reinforcements, which are embedded in an elastomeric matrix of the working layer and which extend substantially parallel to each other from one to the other of the two axial end edges of the working layer.The tire comprises a carcass reinforcement, which extends from either of the beads respectively in the sidewalls to the crown, being anchored in either of the beads and being, in the crown, arranged radially inside the working reinforcement, and which comprises a carcass layer, which (i) in the crown, is applied radially against the central portion of the radially inner working layer, and (ii) comprises wire reinforcements, which are embedded in an elastomeric matrix of the carcass layer and which extend from either of two axial end edges of the carcass layer respectively in the sidewalls to the crown.The tire comprises a so-called sidewall-to-crown layer, which is made of an elastomeric composition and is arranged on one axial side of the median plane so as to form, in a single piece, (i) a crown portion, which is arranged in the crown by being applied against the carcass layer and which is radially interposed between the carcass layer and the corresponding lateral portion of the radially inner working layer, and (ii) a sidewall portion, which is arranged in the corresponding sidewall by continuously extending the crown portion monolithically and being applied against the carcass layer, and which extends radially from the crown to substantially the corresponding bead. The crown portion of the sidewall-to-crown layer has its innermost axial end offset from the corresponding axial end edge of the radially inner working layer by a distance D1 ranging from 4.0 to 12.0 mm.The elastomeric composition of the side-foot-top layer comprises both one or more natural rubbers, having a content of at least 35 parts per million, and one or more butadiene rubbers, having a content of at least 50 parts per million.

[0017] One of the ideas underlying the invention is to optimize the dimensions of the sidewall-to-crown layer along the axial direction of the tire, by limiting the axial extent of its engagement under the radially inner working layer, while formulating this sidewall-to-crown layer to achieve a performance compromise beneficial to the tire. The invention thus provides that the gap distance D1 from the innermost axial end of the crown portion of the sidewall-to-crown layer to the axial end edge of the radially inner working layer is at most 12 mm, preferably less as detailed later. This corresponds to an engagement of the sidewall-to-crown layer under the radially inner working layer that can be described as short and which goes against standard tire sizing practices in the field.This results in increased productivity in the manufacturing process, particularly by extrusion, of the sidewall-to-crown layer before its assembly with the rest of the tire. For the crown portion of the sidewall-to-crown layer to perform its mechanical functions at the interface between the carcass layer and the radially inner working layer, the gap distance D1 is at least 4 mm, or preferably greater, as detailed later.Furthermore, the elastomeric composition of the side-to-top layer is, according to the invention, provided to comprise at least 35 parts per cent of one or more natural rubbers, which provides, among other things, heat dissipation and resistance to mechanical fatigue, in particular to crack propagation, which are particularly used in the top portion of the side-to-top layer, and at least 50 parts per cent of one or more butadiene rubbers, which provides, among other things, mechanical resilience and resistance to aging and crack initiation, which are particularly used in the side portion of the side-to-top layer.The inventors have established, in particular by calculations and tests, that, despite the short engagement of the sidewall-foot-crown layer under the radially inner working layer, the performance of the tire according to the invention, in particular in endurance, is similar to that of a prior art tire, having, on each side of its median plane, a foot-crown layer that is both distinct from its sidewall layer(s) and engaged over a large axial extent under the radially inner working layer.

[0018] It should be noted that, in this document, "natural rubber" refers to a material obtained by processing the latex secreted by certain plants, such as the rubber tree (Hevea brasiliensis). Natural rubber(s), which are usually designated by the abbreviation NR, are as defined in ASTM D1418.

[0019] Similarly, "butadiene rubber" refers to a well-known rubber, usually designated "BR," which is a polybutadiene manufactured by polymerizing the 1,3-butadiene monomer (typically a homopolymerization) in a solution polymerization process using appropriate catalysts known to those skilled in the art. Due to the two double bonds present in the butadiene monomer, the resulting polybutadiene can exist in three different forms: cis-1,4, trans-1,4, and vinyl-1,2. The cis-1,4 and trans-1,4 elastomers are formed by monomers connecting end-to-end, while the vinyl-1,2 elastomer is formed by monomers connecting between the ends of the monomer. The choice of catalyst and the process temperature are known to be the variables generally used to control the cis-1,4 bonding content of the polybutadiene.Such polybutadienes can be produced using a neodymium catalyst in a manner well known to those skilled in the art, for example according to a process described in document JP 60 / 23406 A and WO 03 / 097708 A1. Such polybutadienes are also commercially available, for example, Buna® CB 22 marketed by Lanxess.

[0020] In practice, all the elastomers in the elastomeric composition of the sidewall-toe-top layer, which constitute at least 50% by weight, are divided between natural rubber(s) and butadiene rubber(s), meaning that the sum of the respective contents of natural rubber(s) and butadiene rubber(s) in this elastomeric composition is equal to 100 parts per cent (ppm). For example, the contents of natural rubber(s) and butadiene rubber(s) in this elastomeric composition could be 35 ppm and 65 ppm respectively, or 40 ppm and 60 ppm, or 50 ppm and 50 ppm.In all cases, as mentioned above in connection with the term "elastomeric", the elastomeric composition of the sidewall-foot-crown layer advantageously contains, in addition to natural rubber(s) and butadiene rubber(s), fillers and other components commonly used in the field of tire compositions, such as at least one reinforcing filler of the carbon black and / or silica type, a crosslinking system most often based on sulfur, and protective agents.

[0021] In a preferred embodiment of the tire according to the invention, the tire further comprises a rim layer, which is made of an elastomeric composition and which is arranged in the top of the same axial side of the median plane as the sidewall-foot-top layer, bordering the corresponding lateral portion of the radially inner working layer so as to form in one piece:

[0022] - a radially inner portion, which is radially interposed between the corresponding lateral portion of the radially inner working layer and the apex portion of the flank-toe-top layer, and which is applied against the corresponding lateral portion of the radially inner working layer,

[0023] - a radially outer portion which is radially interposed between the radially inner working layer and the corresponding lateral portion of the radially outer working layer, being applied against at least the corresponding lateral portion of the radially inner working layer, and

[0024] - an axially external portion which continuously connects the radially internal and external portions of the border layer, by being applied against the corresponding axial end edge of the radially internal working layer.

[0025] Due to its arrangement and elastomeric composition, this edge layer ensures mechanical decoupling between the lateral portion of the radially inner working layer, against which the edge layer is applied, and the rest of the top. In particular, the sidewall-toe-top layer is separated from the corresponding lateral portion of the radially inner working layer by the edge layer, more precisely by the radially inner portion of the latter. By thus combining the sidewall-toe-top layer and the edge layer, the edge layer is advantageously designed to, at the interface between the carcass layer and the lateral portion of the radially inner working layer, compensate for some of the effects of the sidewall-toe-top layer.In particular, as detailed later, the edge layer is advantageously more efficient than the flank-foot-top layer with regard to resistance to crack propagation, which is particularly interesting given that the edge layer is applied against the working layer radially inward, bordering at least the lateral portion on both its axial end edge and its radially inward and outward faces.

[0026] According to additional advantageous characteristics of the tire according to the invention, which enhance the benefit of the edge layer in association with the sidewall-foot-crown layer:

[0027] - the top portion of the flank-toe-top layer and the radially inner portion of the edge layer are dimensioned so that, along a normal to the carcass layer passing through the corresponding axial end edge of the radially inner working layer, the wire reinforcements of the carcass layer are separated from the wire reinforcements of the radially inner working layer by a distance D2 which goes from 1.6 mm to 2.2 mm;

[0028] - the top portion of the flank-toe-top layer and the radially inner portion of the edge layer have, along a normal to the carcass layer passing through the corresponding axial end edge of the radially inner working layer, respective thicknesses W1 and W2 such that W1 / W2 goes from 2 / 3 to 1;

[0029] - the radially outer portion of the edge layer is dimensioned so that, following a radial direction of the tire, the corresponding axial end edge of the radially outer working layer is separated from the radially inner working layer by a distance D3 which goes from 0.8 to 1.1 mm;

[0030] - the elastomeric composition of the flank-foot-top layer has a nominal secant modulus at 10% elongation, which ranges from 0.5 to 1.5 times that of the elastomeric composition of the border layer, and which, preferably, is worth 3 to 9 MPa;

[0031] - the elastomeric composition of the edge layer exhibits a crack propagation velocity of 900 J / m 2 energy release rate, which is less than 10 nanometers per cycle.

[0032] Furthermore, according to other advantageous optional characteristics of the tire according to the invention, taken individually or in all technically possible combinations:

[0033] - the distance D1 goes from 4.0 to 9.0 mm, preferably from 5.0 to 9.0 mm, even more preferably from 6.0 to 8.0 mm;

[0034] - the elastomeric composition of the flank-foot-top layer has a delta tangent at 23°C and 10% deformation, which goes from 0.10 to 0.15;

[0035] - a ratio, expressed as a percentage, between the section height and the nominal section width of the tire as defined in the ETRTO 2023 standard is at most equal to 90 and is at least equal to 20, and in which the nominal section width is at least equal to 115 mm and at most equal to 385 mm.

[0036] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the drawings in which:

[0037] - [Fig 1] Figure 1 is a schematic section of a tire according to the invention, this section being in a cutting plane corresponding to a meridian plane of the tire;

[0038] - [Fig 2] Figure 2 is a larger-scale schematic view of the detail boxed II in Figure 1; and

[0039] - [Fig 3] Figure 3 is a view similar to Figure 1, showing only a part of the section of a variant of the tire according to the invention.

[0040] Figures 1 and 2 show a tire 100 and a geometric coordinate system whose X, Y, and Z directions correspond respectively to the radial, axial, and circumferential directions of the tire 100, as defined in the introductory section of this document. The tire 100 has a substantially toroidal shape around an axis of revolution, which is substantially parallel to the axial direction Y and coincides with an axis of rotation of the tire 100 around which the latter can be driven to rotate and roll on the ground.

[0041] In Figure 1, the tire 100 is associated with a nominal rim 10, as defined by the European Tyre and Rim Technical Organisation (ETRTO) standard, 2023, on which the tire 100 can be mounted, as schematically illustrated by the dotted lines. The rim 10 thus forms a mounting surface for the tire 100.

[0042] The 100 tire is preferably intended for passenger vehicles as defined by ETRTO 2023. Such a tire has a cross-section in a meridian plane, such as that schematically illustrated in Figure 1, which is characterized by a section height H and a nominal section width S, as defined by ETRTO 2023. The section height H and the nominal section width S are as shown in Figure 1, their respective definitions being detailed later. In practice, the values ​​of S and H are generally indicated on the tire sidewall marking. Preferably, the 100 tire is such that the H / S ratio, expressed as a percentage, is at most 90 and at least 20, and the nominal section width S is at least 115 mm and at most 385 mm.Also preferentially, the diameter at the hook of the tire 100, defining the diameter of the nominal rim 10 on which the tire is mountable, is at least equal to 12 inches and at most equal to 30 inches.

[0043] As schematically represented in Figure 1, the tire 100 comprises a vertex 110 with a tread 111, intended to come into contact with the ground during the rolling of the tire 100. Along the circumferential direction Z, the tread 111 extends around the entire circumference of the tire 100, and along the axial direction Y, the tread 111 extends on either side of a median plane M of the tire 100, this median plane M being as defined in the introductory section of this document. The tread 111 is axially delimited by axial edges 111A and 111B, which are arranged axially on either side of the median plane M.

[0044] In practice, the structural and dimensional specifications of the tread 111 are not limiting. In particular, in the figures, the tread 111 is represented in monolithic form, but this representation is only schematic, in the sense that the tread can be produced by joining several sections during the manufacture of the tire 100.

[0045] For the purpose of its reinforcement, the summit 110 includes a summit reinforcement 112 which extends in the summit 110 in the circumferential direction Z over the entire circumference of the tire 100, being radially surmounted by the tread 111.

[0046] The top reinforcement 112 includes a working reinforcement 113, which comprises, or is made up of, at least one working layer and which, in this case, consists of two radially superimposed working layers, namely an inner radially working layer 114 and an outer radially working layer 115. In practice, each of the working layers 114 and 115:

[0047] - is axially delimited by two axial end edges of the working layer, which are arranged axially on either side of the median plane M and which are respectively referenced 114A and 114B for the radially inner working layer 114 and 115A and 115B for the radially outer working layer 115,

[0048] - includes a central portion, which extends axially on either side of the median plane M and which is referenced 114C for the radially inner working layer 114 and 115C for the radially outer working layer 115, and

[0049] - also includes two lateral portions, which are arranged axially on either side of the median plane M and which extend axially from the central portion to respectively the two axial end edges of the working layer, the lateral portions of the radially inner working layer 114 being respectively referenced 114AA and 114BB while the lateral portions of the radially outer working layer 115 are respectively referenced 115AA and 115BB.

[0050] The central portion 114C of the radially inner working layer 114 and the central portion 115C of the radially outer working layer 115 are applied radially against each other, forming a contact interface between the radially outer face of the radially inner working layer 114 and the radially inner face of the radially outer working layer 115. As detailed later, each of the lateral portions 114AA and 114BB of the radially inner working layer 114 is radially distant from the radially outer working layer 115, and each of the lateral portions 115AA and 115BB of the radially outer working layer 115 is radially distant from the radially inner working layer 114.Moreover, here the axial end edges 114A and 114B extend axially outwards respectively from the axial end edges 115A and 115B, and the axial end edges 115A and 115B are arranged radially perpendicular to the lateral portions 114AA and 114BB respectively of the radially inner working layer 114; in an unshown variant, it is otherwise.

[0051] Each of the working layers 114 and 115 includes wire reinforcements embedded in an elastomeric matrix of the working layer, extending lengthwise from one axial end edge of the working layer to the other in a substantially parallel fashion. These wire reinforcements are not detailed in the figures, except for a very partial depiction in Figure 2 of only one of the wire reinforcements in the radially inner working layer 114, labeled 114R. In practice, the wire reinforcements of each of the working layers 114 and 115 extend lengthwise along a principal direction forming, with the circumferential direction Z of the tire 100, an angle ranging, in absolute value, from 10° to 50°, it being noted that the angle associated with the radially inner working layer 114 and that associated with the radially outer working layer 115 have respective orientations which are opposite to each other.

[0052] The structural and dimensional specifications of the wire reinforcements in each of the working layers 114 and 115 are not limiting. Thus, each of these wire reinforcements can be made of metal and / or textile.

[0053] In the embodiment considered here, the top reinforcement 112 also includes a shrink-fit reinforcement 116, which includes, or even consists of, at least one shrink-fit layer and which, here, consists of a single shrink-fit layer 117. The shrink-fit reinforcement 116, here the shrink-fit layer 117, is arranged radially outside the working reinforcement 113 and is therefore radially intercalated between the tread 111 and the working reinforcement 113, here the radially outer working layer 115 of the latter.

[0054] The shrink-fit reinforcement 116, here the shrink-fit layer 117, is axially delimited by two axial end edges 116A and 116B of the shrink-fit reinforcement 116, arranged axially on either side of the median plane M. Here, the axial end edges 116A and 116B extend axially outwards respectively from the axial end edges 114A and 114B of the radially inner working layer 114; in an unrepresented variant, it is otherwise.

[0055] The shrink-fit reinforcement 116, here the shrink-fit layer 117, comprises one or more wire reinforcements, not detailed in the figures, which are embedded in an elastomeric matrix of the shrink-fit reinforcement 116, and which are circumferentially wound in a helix from one to the other of the axial end edges 116A and 116B of the shrink-fit reinforcement 116 extending lengthwise along a principal direction forming, with the circumferential direction Z of the tire 100, an angle which, in absolute value, is less than or equal to 10°, preferably less than or equal to 5°.

[0056] The structural and dimensional specifications of the wire reinforcement(s) of the shrink-fit reinforcement 116, here of the shrink-fit layer 117, are not limiting. Thus, each of these wire reinforcements can be made of metal and / or textile.

[0057] The tire 100 further comprises two sidewalls 120A and 120B, which each extend radially inwards from the top 110, extending respectively from the axial edges 111A and 111B of the tread 111, and which are arranged axially on either side of the median plane M.

[0058] The 100 tire also features two ribs 130A and 130B, which radially extend inwards the sidewalls 120A and 120B respectively. Thus, the sidewall 120A connects the bead 130A to the apex 110 while the sidewall 120B connects the bead 130B to the apex 110, the two bead 130A and 130B being opposite each other with respect to the median plane M. Each of the bead 130A and 130B is provided with a bead, respectively 131A and 131B, which extends in the corresponding bead along the circumferential direction Z and whose specific features are not limiting since these bead 131A and 131B allow the tire 100 to be mounted on the nominal rim 10, in particular on the respective hooks of the latter, as schematically illustrated in figure 1.

[0059] The top 110, the sidewalls 120A and 120B and the bead 130A and 130B together define a toroidal cavity 140 of the tire 100, delimited by an internal surface 141 of the tire 100. This toroidal cavity 140 allows the tire 100 to be inflated when the latter is mounted on the nominal rim 10. In the mounted state of the tire 100 on this rim, the toroidal cavity 140 is jointly closed by the tire 100 and the rim so as to be able to be pressurized by an inflation gas, which is introduced into the toroidal cavity 140 and with which the internal surface 141 is then in contact. In practice, all or part of the internal surface 141 is advantageously supported by a sealing layer 142 of the tire 100, which is substantially impermeable to the inflation gas and whose composition includes, for example, one or more butyl rubbers, such as that described in W02016 / 001226.

[0060] The apex 110, the sidewalls 120A and 120B and the bead 130A and 130B jointly delimit an external surface 143 of the tire 100, which is in contact with atmospheric air when the tire 100 is mounted on the nominal rim 10. The section height H in the sense of the ETRO 2023 standard, as mentioned above, corresponds to the radial distance separating, in meridional section, the outermost radial point of the tire 100, which is carried by the tread 111 and which is here located at the intersection between the median plane M and the external surface 143, and the innermost radial point of the tire 100, which is carried by one of the two bead 130A and 130B and which is here located on the innermost axial circumferential line of this bead.The nominal section width S in the sense of the ETRO 2023 standard, as mentioned above, corresponds to the axial distance separating, in meridian section, the two outermost axial points of the tire 100 arranged on either side of the median plane M, which belong to the external surface 143 and which are respectively carried here by the sidewalls 120A and 120B.

[0061] As shown in Figure 1, the tire 100 also includes a carcass reinforcement 150 extending from one of the two beads 130A and 130B in the sidewalls 120A and 120B respectively to the crown 110. Here, the carcass reinforcement 150 thus extends continuously from one bead 130A to the other. In the crown 110, the carcass reinforcement 150 is arranged radially inside the crown reinforcement 112, more precisely within the working reinforcement 113 of the latter. Here, the carcass reinforcement 150 is arranged radially outside the sealing layer 142.

[0062] The carcass reinforcement 150 comprises, or is made up of, at least one carcass layer and, here, is made up of a single carcass layer 151, which, in the top 110, is applied radially against the central portion 114C of the radially inner working layer 114. In the top 110, the carcass layer 151 is thus radially in contact with the central portion 114C of the radially inner working layer 114, forming a contact interface between the radially outer face of the carcass layer 151 and the radially inner face of the central portion 114C of the radially inner working layer 114, while the carcass layer 151 is radially distant from each of the lateral portions 114AA and 114BB of the radially inner working layer 114, as detailed later.

[0063] In the embodiment considered here, the carcass layer 151 is anchored in each bead 130A, 130B by being folded around the bead 131A, 131B of the corresponding bead. In other words, for the purpose of its anchoring, the carcass layer 151 wraps around each of the two bead 131A and 131B, from the inside to the outside of the tire 100.The inverted carcass layer 151 thus forms a main part 152 and two inverts 153A and 153B: as shown in Figure 1, the main part 152 extends from either of the rods 131A and 131B respectively in the flanks 120A and 120B to the top 110, running here continuously from one to the other of the rods 131A and 131B and being, in the top 110, applied against the central portion 114C of the radially inner working layer 114, while the inverts 153A and 153B are arranged axially outside the main part 152 and extend from this main part 152 to respectively two edges 151A and 151B of the inverted carcass layer 151, which are axially opposed to each other, being arranged axially on either side of the median plane M. The edge 151A belongs to the inversion 153A and the edge 151B belongs to the inversion 153B.

[0064] Edge 151A is arranged within bead 130A and / or flank 120A, being embedded in the mass of materials constituting this bead 130A and / or flank 120A, while edge 151B is arranged within bead 130B and / or flank 120B, being embedded in the mass of materials constituting this bead 130B and / or flank 120B. Here, according to advantageous arrangements which are illustrated in Figure 1:

[0065] - a packing mass 160A, respectively 160B, which is made of an elastomeric composition, extends radially outwards from the rod 131A, respectively 131B, and is applied both against the main part 152 and the reversible part 153A, respectively 153B, so as to axially separate the reversible part 153A, respectively 153B, from the main part 152; and

[0066] - a protective mass 161A, respectively 161B, which is made of an elastomeric composition, forms a portion of the bead 130A, respectively 130B, by which the latter is brought into contact with the nominal rim 10 when the tire 100 is mounted on this rim, and extends radially outwards, here into the sidewall 120A, respectively 120B, being applied against the inversion 153A, respectively 153B, and, as here, against the main part 152, so as to axially separate the inversion 153A, respectively 153B, and, here, the main part 152 from the external surface 143 of the tire 100.

[0067] In practice, although not detailed in the figures, each of the 160A and 160B packing masses and the 161A and 161B protective masses consists of one or more complexed elastomeric layers.

[0068] In all cases, the carcass layer 151 includes wire reinforcements which are embedded in an elastomeric matrix of the carcass layer 151 and which extend lengthwise from one edge 151 A and 151 B respectively in the flanks 120A and 120B up to the top 110. These wire reinforcements thus extend from one edge 151 A and 151 B to the other in a principal direction which, at least in the principal part 152, forms with the circumferential direction Z an angle which, in absolute value, is greater than or equal to 60°, preferably from 80° to 90°, and this at least in all or part of the flanks 120A and 120B.In embodiments enabling the achievement of radial tire performance as defined by ETRTO, each wire reinforcement of the carcass layer 151 extends lengthwise, at least in the main portion 152, along a principal direction forming an angle with the circumferential direction Z of 80° to 90° in absolute value. Alternatively, this angle is variable, ranging from 80° to 90° in at least a portion of each of the two sidewalls 120A and 120B and being strictly less than 80° in at least a portion of the crown 110. In the figures, these wire reinforcements of the carcass layer 151 are not detailed, except very partially in Figure 2 where one of these reinforcements is referenced as 141 R.

[0069] The structural and dimensional specifications of the wire reinforcements in the 151 carcass layer are not limiting. Thus, each of these wire reinforcements can be made of metal and / or textile.

[0070] In all cases, as clearly seen in Figure 1, the tire 100 also comprises two layers called sidewall-foot-top, each of which is made of an elastomeric composition and which are arranged on either side of the median plane M, the sidewall-foot-top layer located on the same axial side of the median plane M as the sidewall 120A being referenced 162A while the sidewall-foot-top layer located on the same axial side of the median plane M as the sidewall 120B is referenced 162B. Subsequently, we will describe in more detail the flank-foot-top layer 162A, it being understood that the elastomeric composition and arrangements of the flank-foot-top layer 162B are similar to those of the flank-foot-top layer 162A, these arrangements being notably symmetrical to those of the flank-foot-top layer 162A with respect to the median plane M.

[0071] As clearly visible in Figures 1 and 2, the flank-foot-top layer 162A includes both a portion of the top 162A.1, arranged in the top 110, and a portion of the flank 162A.2, arranged in the flank 120A, which came from the material together, thus jointly forming a single piece made of the elastomeric composition of the flank-foot-top layer 162A. Each of the portions of top 162A.1 and flank 162A.2 thus continuously extends the other of these portions of top and flank, in a monolithic manner.

[0072] The top portion 162A.1 and the side portion 162A.2 are both applied against the carcass layer 151, here against the main part 152 of the latter. Thus, in the vertex 110, the vertex portion 162A.1 is in contact with the carcass layer 151, forming a summit contact interface between the radially inner face of the vertex portion 162A.1 and the radially outer face of the carcass layer 151, while, in the flank 120A, the flank portion 162A.2 is in contact with the carcass layer 151, forming a lateral contact interface between the axially inner face of the flank portion 162A.2 and the axially outer face of the carcass layer 151. The aforementioned summit contact interface extends continuously from a most axially inner end 162A.1E of the vertex portion 162A.1 up to the aforementioned lateral contact interface, which itself extends continuously radially inwards from the summit contact interface, here to the outermost radial end 161AE of the protective mass 161 A. Radially inwards from the outermost radial end 161AE of the protective mass 161A, the flank portion 162A.2 is here applied against the protective mass 161 A.

[0073] In all cases, as clearly visible in Figure 1, the side portion 162A.2 extends radially from the apex 110 to substantially the ridge 130A. In other words, the side portion 162A.2 extends radially from the apex 110 over substantially the entire radial extent of the side 120A, typically over at least 90%, preferably at least 95%, or even 100% of the radial extent of the side 120A. In this way, the side portion 162A.2 helps, among other things, to protect the carcass layer 151, particularly against external impacts.

[0074] Furthermore, the sidewall portion 162A.2 extends axially from the carcass layer 151, here from the main part 152 of the latter, towards the external surface 143 of the tire 100, here up to this external surface 143. Thus, in the embodiment considered here, the portion of the external surface 143, located in the sidewall 120A, is supported by the sidewall portion 162A.2.

[0075] The crown portion 162A.1 extends axially from its innermost axial end 162A.1E to the axial edge 111A of the tread 111 and extends radially outwards from the carcass layer 151, here the main part 152 thereof. The crown portion 162A.1 thus has a wedge shape, which tapers axially inwards progressively and whose apex is formed by the innermost axial end 162A.1E. The crown portion 162A.1 is radially interposed between the carcass layer 151, here the main part 152 thereof, and the lateral portion 114AA of the radially inner working layer 114. Thus, the crown portion 162A.1 is engaged radially along the lateral portion 114AA of the radially inner working layer 114, which, among other things, ensures a gradual transition in stiffness between the carcass layer 151 and the working reinforcement 113 and limits the risk of mechanical damage to the interface between them. As shown in Figure 2, this engagement is dimensionally characterized by a distance D1 separating the innermost axial end 162A.1E of the apex portion 162A.1 from the axial end edge 114A of the radially inner working layer 114. This distance D1 ranges from 4.0 to 12.0 mm. In an advantageous configuration, the distance D1 ranges from 4.0 to 9.0 mm, preferably from 5.0 to 9.0 mm, and even more preferably from 6.0 to 8.0 mm.

[0076] To enable the sidewall-toe-top layer 162A to perform the functions indicated above, respectively dedicated to its top portion 162A.1 and its sidewall portion 162A.2, the elastomeric composition of the sidewall-toe-top layer 162A comprises both one or more natural rubbers, having a content of at least 35 parts per million (ppm), and one or more butadiene rubbers, having a content of at least 50 parts per million (ppm). In practice, this natural rubber(s) and this butadiene rubber(s) constitute all the elastomers in the elastomeric composition of the sidewall-toe-top layer 162A. For example, the proportions of natural rubber(s) and butadiene rubber(s) in this elastomeric composition are 35 parts per million and 65 parts per million, or 40 parts per million and 60 parts per million, or 50 parts per million and 50 parts per million, respectively. In all cases, this elastomeric composition advantageously includes a reinforcing filler, such as carbon black.

[0077] Preferably, the elastomeric composition of the flank-foot-top layer 162A has a delta tangent at 23°C and 10% strain, which goes from 0.10 to 0.15. The hysteresis of this elastomeric composition is thus low, which, among other things, contributes to reducing the rolling resistance of the 100 tire. The tangent delta at 23°C and 10% strain, sometimes called "dynamic loss at 23°C and 10% strain", is a dynamic property well known to those skilled in the art and is measured by subjecting a specimen of the aforementioned elastomeric composition, extracted from the 100 tire, to a viscoelastic analyzer, such as the Metravib VA4000 or DMA+450. The specimen has a cylindrical cross-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 and a thickness of 2 mm.The response of a specimen subjected to both a temperature of 23°C and an alternating sinusoidal shear load at a frequency of 10 Hz, according to ASTM D1349-99, is recorded. A strain amplitude sweep is performed from 0.1% cc to 100% cc on one forward cycle, then from 100% cc to 0.1% cc on a reverse cycle, where cc means peak-to-peak. The tangent of the phase angle between the force applied to the specimen and its displacement represents a dynamic loss. The value of the tangent of the phase angle observed on the reverse strain cycle at 10% strain corresponds to the tangent delta at 23°C and 10% strain.

[0078] Whatever the specifics of the flank-foot-top layer 162A, the latter is advantageously associated with a border layer 163A, which is made of an elastomeric composition and which, as illustrated in figures 1 and 2, is arranged in the top 110 on the same axial side of the median plane M as the flank-foot-top layer 162A, bordering the lateral portion 114AA of the radially inner working layer 114A. Here, the tire 100 includes, in addition to the edge layer 163A associated with the sidewall-foot-top layer 162A, an edge layer 163B associated with the sidewall-foot-top layer 162B, which is made of an elastomeric composition and is arranged in the top 110 on the same axial side of the median plane M as the sidewall-foot-top layer 162B, bordering the lateral portion 114BB of the radially inner working layer 114A.Subsequently, we will describe in more detail the border layer 163A, it being understood that the elastomeric composition and the arrangements of the border layer 163B are similar to those of the border layer 163A, these arrangements being in particular symmetrical to those of the border layer 163A with respect to the median plane M.

[0079] As clearly visible in Figure 2, the border layer 163A comprises, in one piece:

[0080] - a radially inner portion 163A.1 and a radially outer portion 163A.2, which are arranged radially on either side of the lateral portion 114AA of the radially inner working layer 114 and which are applied radially against this lateral portion 114AA, advantageously over substantially the entire axial extent of the latter, and

[0081] - an axially external portion 163A.3, which continuously connects the radially internal 163A.1 and external 163A.2 portions monolithically, and which is applied against the axial end edge 114A of the radially internal working layer 114.

[0082] The radially inner portion 163A.1 is radially interposed between the lateral portion 114AA of the radially inner working layer 114 and the top portion 162A.1 of the flank-foot-top layer 162A. In the embodiment considered here, the radially inner portion 163A.1 and the top portion 162A.1 are applied against each other, thus forming a contact interface between them which extends axially outwards from the most axially inner end 162A.1E of the top portion 162A.1. Axially inwards from the innermost axial end 162A.1E, the radially inner portion 163A.1 is here applied against the carcass layer 151, becoming radially interposed between the carcass layer 151, here the main part 152 of the latter, and the lateral portion 114AA of the radially inner working layer 114.

[0083] In all cases, it is understood that the radially inner portion 163A.1 and the top portion 162A.1 overlap radially between the lateral portion 114AA of the radially inner working layer 114 and the carcass layer 151, which allows, among other things, for the reinforcement of the mechanical decoupling between this lateral portion 114AA of the radially inner working layer 114 and the carcass layer 151.

[0084] In particular, to ensure that the aforementioned mechanical decoupling is especially effective, the radially inner portion 163A.1 and the apex portion 162A.1 are advantageously dimensioned so that, along a normal N to the carcass layer 151, passing through the axial end edge 114A of the radially inner working layer 114, :

[0085] - the wire reinforcements 151 R of the carcass layer are separated from the wire reinforcements 114R of the inner radial working layer 114 by a distance D2 ranging from 1.6 to 2.2 mm, and / or

[0086] - a thickness W1 of the vertex portion 162A.1 and a thickness W2 of the radially interior portion 163A.1 are such that the ratio W1 / W2 goes from 2 / 3 to 1.

[0087] The radially outer portion 163A.2 is radially interposed between the lateral portion 115AA of the radially outer working layer 115 and the radially inner working layer 114, thereby mechanically decoupling this lateral portion 115AA from the latter. More precisely, here, the radially outer portion 163A.2 is radially interposed on one side between the lateral portion 115AA of the radially outer working layer 115 and the lateral portion 114AA of the radially inner working layer 114, and on the other side between the lateral portion 115AA of the radially outer working layer 115 and the central portion 114C of the radially inner working layer 114. For this decoupling to be effective, the radially outer portion 163A.2 is advantageously dimensioned so that, along the radial direction X, the axial end edge 115A of the radially outer working layer 115 is separated from the radially inner working layer 114 by a distance D3 which goes from 0.8 to 1.1 mm.

[0088] In the embodiment considered here, the radially outer portion 163A.2, in addition to being applied against the radially inner working layer 114, in particular against at least the lateral portion 114AA of the latter, is advantageously applied against the lateral portion 115AA of the radially outer working layer 115, in particular over substantially the entire axial extent of this lateral portion 115AA. Therefore, the distance D3 corresponds to the radial dimension of the radially outer portion 163A.2, measured radially above the axial end edge 115A of the radially outer working layer 115. In practice, the aforementioned radial dimension is advantageously substantially constant over most of the axial extent of the radially outer portion 163A.2.

[0089] The axially external portion 163A.3 is, for its part, radially interposed between the top portion 162A.1, being applied here against the latter, and the shrink-fit reinforcement 116, being applied here against the shrink-fit layer 117. The axially external portion 163A.3 thus fills the region separating the axial end edge 114A of the radially internal working layer 114 and the axial end edge 116A of the shrink-fit reinforcement 116. In the embodiment considered here, the axial end edge 116A of the shrink-fit reinforcement 116 is applied locally against the top portion 162A.1 of the side-to-toe-top layer 162A, it being noted that this may be otherwise in an alternative. In all cases, axially outwards from the axially outward portion 163A.3 and, where applicable, from the axial end edge 116A of the shrink-fit armature 116, the top portion 162A.1 is applied against the tread 111, here up to the axial edge 111 A of the latter.

[0090] Regardless of the specific characteristics of the 163A edge layer, the elastomeric composition of the 162A side-to-top layer advantageously exhibits a nominal secant modulus at 10% elongation that ranges from 0.5 to 1.5 times that of the elastomeric composition of the 163A edge layer. This ensures that the respective stiffnesses of the 162A side-to-top layer and the 163A edge layer are compatible. In practice, the nominal secant modulus at 10% elongation of the 162A side-to-top layer is preferably between 3 and 9 MPa. The nominal secant modulus at 10% elongation is the modulus of the elastomeric composition measured during a uniaxial tensile test, at a strain value of 10%, applied to either a standardized dumbbell-shaped specimen made of the elastomeric composition, or a specimen extracted from tire 100.To perform this test, a constant uniaxial tensile speed of 500 mm / min is applied to the specimen, and its elongation and stress are measured. The measurement is carried out using an INSTRON tensile testing machine at a temperature of 23°C and a relative humidity of 50%, in accordance with ISO 23529. The measurement and data processing conditions for determining elongation and stress are as described in NF ISO 37:2012-03. Before proceeding with the measurement, the specimen is pre-accommodated with a displacement level of 9 mm.The nominal stress F / SO is determined, with F being the force measured for a deformation of 10% and S0 the initial section of the specimen, and the secant modulus of elasticity at 10% elongation is calculated, in MPa, by taking the ratio of this stress value to the deformation value deltaL / LO, with L0 the initial length of the specimen and deltaL the length of the specimen at 10% deformation.

[0091] Furthermore, the elastomeric composition of the edge layer 163A is advantageously designed to resist cracking, particularly more so than the elastomeric composition of the side-to-toe-top layer 162A. In this way, the edge layer 163A acts, in a sense, as a barrier to cracking from the radially inner working layer 114 to the side-to-toe-top layer 162A. For this purpose, the elastomeric composition of the edge layer 163A advantageously exhibits a crack propagation rate of 900 J / m 2The energy release rate is less than 10 nanometers per cycle. The cracking rate is measured on a specimen made of the elastomeric composition of the 163A edge layer, using an MTS 381 type cyclic fatigue testing machine. This involves measuring crack resistance by applying repeated tensile forces to the initially prepared specimen, which has undergone a first tensile cycle and is then notched. The specimen has a parallelepiped shape, for example, with a thickness between 0.5 and 1.5 mm, a length between 60 and 100 mm, and a width between 4 and 8 mm. Both lateral edges are covered lengthwise with a cylindrical rubber bead, for example, with a diameter of 5 mm, allowing it to be anchored in the machine's jaws.The prepared specimen is tested after baking and accelerated aging in an oven at 77°C for 14 days and for 21 days in a ventilated chamber. The tensile test is conducted in air at a temperature of 60°C. After accommodation, four very fine notches, for example, 5 to 7 mm in length, are made with a razor blade at mid-width and aligned lengthwise along the specimen, one at each end and two on either side of the center, before the test begins. At each tensile cycle, the strain rate of the specimen is automatically adjusted to maintain the energy release rate, i.e., the amount of energy released during crack propagation, at a constant value of approximately 900 J / m. 2 The crack propagation speed is measured in nanometers per cycle.

[0092] As a non-limiting example, the elastomeric composition of the 163A edge layer contains one or more natural rubbers, at a content of 100 parts per cent.

[0093] Figure 3 shows a variant of tire 100, designated 200. Tire 200 is similar, if not identical, to tire 100, except that it also includes a sidewall layer 264A, as detailed below. Apart from this sidewall layer 264A, the components of tire 200 have the same part numbers as the corresponding components of tire 100, plus one hundred.

[0094] The sidewall layer 264A carries, in the sidewall 220A, the majority of the external surface 243 of the tire 200. The sidewall-foot-crown layer 262A is found, in the sidewall 200A, interposed axially between the sidewall layer 264A, against which the sidewall-foot-crown layer 262A is applied here, and the carcass layer 251. In practice, the sidewall layer 264A consists of an elastomeric composition which is advantageously formulated to provide at least one additional function to the sidewall 200A, for example a function of protection against UV or ozone from the atmospheric air and / or a decorative function.

[0095] Of course, what has just been described for the 220A sidewall is applicable to the other sidewall of the 200 tire, not visible in figure 3.

[0096] The 200 tire variant more generally illustrates the fact that the 262A sidewall-foot-crown layer is compatible with external 220A sidewall arrangements, such as the 264A sidewall layer.

[0097] According to another variant of the tire 100, which is not illustrated in the figures and which is applicable to the tire 200, the carcass reinforcement 150 comprises several carcass layers which, in the crown 110, are radially superimposed. In this case, the sidewall-foot-crown layers 162A and 162B are applied against the carcass layer which is the outermost radially in the crown.

[0098] According to yet another variant of the 100 tire, which is not illustrated in the figures and which is applicable to the 200 tire, the 100 tire has only one sidewall-foot-top layer out of the two sidewall-foot-top layers 162A and 162B.

[0099] According to yet another variant of the pneumatic 100, which is not illustrated in the figures and which is applicable to the pneumatic 200, the top reinforcement 112 is devoid of a shrink-fit reinforcement, such as the shrink-fit reinforcement 116.

[0100] The invention is not limited to the embodiments described above. In particular, new embodiments can be derived by combining all or part of each of the embodiments described so far with all or part of the other embodiments.

Claims

25 Demands 1. Tire (100; 200), comprising a crown (110), two sidewalls (120A, 120B; 220A), each extending radially inwards from the crown and arranged axially on either side of a median plane (M) of the tire, and two beads (130A, 130B), which extend radially inwards from the two sidewalls respectively and are adapted for mounting the tire on a rim (10), in which the crown (110) has a crown reinforcement (112) comprising a working reinforcement (113) which comprises two radially superimposed working layers, namely an inner radial working layer (114) and an outer radial working layer (115), each of these two working layers: - including a central portion (114C, 115C), which extends axially on either side of the median plane (M), and two lateral portions (114AA, 114BB, 115AA, 115BB), which are arranged axially on either side of the median plane and which extend axially from the central portion to respectively two axial end edges (114A, 114B, 115A, 115B) of the working layer, and - comprising wire reinforcements (114R), which are embedded in an elastomeric matrix of the working layer and which extend substantially parallel to each other from one to the other of the two axial end edges of the working layer, wherein the tire comprises a carcass reinforcement (150), which extends from one and the other of the beads (130A, 130B) respectively in the sidewalls (120A, 120B; 220A) to the crown (110), being anchored in one and the other of the beads and being, in the crown, arranged radially inside the working reinforcement (113), and which comprises a carcass layer (151), which: - at the top, is applied radially against the central portion (114C) of the radially inner working layer (114), and - includes wire reinforcements (151 R), which are embedded in an elastomeric matrix of the carcass layer (151) and which extend from either of two axial end edges (151 A, 151 B) of the carcass layer respectively in the flanks (120A, 120B; 220A) to the top (110), in which the tire comprises a so-called sidewall-foot-crown layer (162A, 162B; 262A), which is made of an elastomeric composition and which is arranged on an axial side of the median plane (M) so as to form in one piece: - a crown portion (162A.1), which is arranged in the crown (110) by being applied against the carcass layer (151), and which is radially interposed between the carcass layer and the corresponding lateral portion (114AA) of the radially inner working layer (114), and - a flank portion (162A.2), which is arranged in the corresponding flank (120A), by continuously extending the top portion (162A.1) monolithically and being applied against the carcass layer (151), and which extends radially from the top (110) to substantially the corresponding ridge (130A), in which the top portion (162A.1) of the flank-foot-top layer (162A, 162B; 262A) has a most axially inner end (162A.1E) which is separated from the corresponding axial end edge (114A) of the radially inner working layer (114), by a distance D1 which goes from 4.0 to 12.0 mm, and wherein the elastomeric composition of the side-foot-top layer (162A, 162B; 262A) comprises both one or more natural rubbers, having a content of at least 35 parts per million, and one or more butadiene rubbers, having a content of at least 50 parts per million.

2. Tire according to claim 1, wherein the tire (100; 200) further comprises a rim layer (163A, 163B), which is made of an elastomeric composition and which is arranged in the top (110) on the same axial side of the median plane (M) as the sidewall-foot-top layer (162A, 162B; 262A), bordering the corresponding lateral portion (114AA) of the radially inner working layer (114) so ​​as to form in one piece: - a radially inner portion (163A.1), which is radially interposed between the corresponding lateral portion (114AA) of the radially inner working layer (114) and the top portion (162A.1) of the flank-toe-top layer (162A, 162B; 262A), and which is applied against the corresponding lateral portion of the radially inner working layer, - a radially outer portion (163A.2) which is radially interposed between the radially inner working layer (114) and the corresponding lateral portion (115AA) of the radially outer working layer (115), by being applied against at least the corresponding lateral portion (114AA) of the radially inner working layer (114), and - an axially external portion (163A.3) which continuously connects the radially internal (163A.1) and external (163A.2) portions of the border layer (163A, 163B) to each other, by being applied against the corresponding axial end edge (114A) of the radially internal working layer (114).

3. Tire according to claim 2, wherein the top portion (162A.1) of the sidewall-foot-top layer (162A, 162B; 262A) and the radially inner portion (163A.1) of the rim layer (163A, 163B) are dimensioned such that, along a normal (N) to the carcass layer (151) passing through the corresponding axial end edge (114A) of the radially inner working layer (114), the wire reinforcements (151R) of the carcass layer are separated from the wire reinforcements (114R) of the radially inner working layer (114) by a distance D2 which goes from 1.6 mm to 2.2 mm.

4. Tire according to any one of claims 2 or 3, wherein the apex portion (162A.1) of the sidewall-foot-apex layer (162A, 162B; 262A) and the radially inner portion (163A.1) of the rim layer (163A, 163B) have, along a normal (N) to the carcass layer (151) passing through the corresponding axial end edge (114A) of the radially inner working layer (114), respective thicknesses W1 and W2 such that W1 / W2 goes from 2 / 3 to 1.

5. A tire according to any one of claims 2 to 4, wherein the radially outer portion (163A.2) of the edge layer (163A, 163B) is dimensioned so that, along a radial direction (X) of the tire (100; 200), the corresponding axial end edge (115A) of the radially outer working layer (115) is separated from the radially inner working layer (114) by a distance D3 ranging from 0.8 to 1.1 mm.

6. Tire according to any one of claims 2 to 5, wherein the elastomeric composition of the sidewall-foot-top layer (162A, 162B; 262A) has a nominal secant modulus at 10% elongation, which is from 0.5 to 1.5 times that of the elastomeric composition of the rim layer (163A, 163B), and which preferably is from 3 to 9 MPa.

7. Pneumatic according to any one of claims 2 to 6, wherein the elastomeric composition of the edge layer (163A, 163B) has a velocity28 crack propagation at 900 J / m 2 energy release rate, which is less than 10 nanometers per cycle.

8. Pneumatic according to any one of the preceding claims, wherein the distance D1 is from 4.0 to 9.0 mm, preferably from 5.0 to 9.0 mm, even more preferably from 6.0 to 8.0 mm.

9. Tire according to any one of the preceding claims, wherein the elastomeric composition of the sidewall-foot-top layer (162A, 162B; 262A) has a delta tangent at 23°C and 10% strain, which goes from 0.10 to 0.

15.

10. Tire according to any one of the preceding claims, wherein a ratio, expressed as a percentage, between the section height (H) and the nominal section width (S) of the tire (100; 200) as defined in ETRTO 2023 is at most equal to 90 and is at least equal to 20, and wherein the nominal section width (S) is at least equal to 115 mm and at most equal to 385 mm.

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