WO2018002487A1 - Tyre with a tread comprising reinforcing elements - Google Patents

Abstract

A tyre (1) comprising two beads (4), two sidewalls (3) joined to the beads, a crown (2) joined to the ends of the two sidewalls, a radially external tread (5), the tread comprising a plurality of tread bars (51), two tread bars being separated by a groove (7), at least one of said tread bars (51) comprising a circumferential reinforcing element (52) consisting of a rubber mixture with a dynamic shear modulus G* at least twice as high as the dynamic shear modulus G* of the rubber mixture of the rest of the bars of the tread, the circumferential reinforcing element (52) extending radially from the radially external surface of said crown reinforcement (6) towards the surface of said tread with an axial width that gradually decreases, moving radially outwards, said axial width having a maximum value (520) that is less than 50% of the axial width (510) of said bar, said circumferential reinforcing element (52) extending radially at least over a height "h" corresponding to 50% of the thickness "p" of the tread, the median plane n of the circumferential reinforcing element (52) being positioned approximately 20% from the centre of said axial width (510) of said bar.

Description

 PNEUMATIC WITH A TREAD TAPE COMPRISING

STRENGTHENING ELEMENTS

Field of the Invention [0001] The present invention relates to tires, and more particularly to a tire whose adhesion performance is improved.

In general, a tire is an object having a geometry of revolution with respect to an axis of rotation. A tire comprises two beads intended to be mounted on a rim; it also comprises two flanks connected to the beads, a top having a tread intended to come into contact with the ground, the top having a first side connected to the radially outer end of one of the two sidewalls and having a second side connected to the radially outer end of the other of the two sides.

The constitution of the tire is usually described by a representation of its constituents in a meridian plane, that is to say a plane containing the axis of rotation of the tire. The radial, axial and circumferential directions respectively designate the directions perpendicular to the axis of rotation of the tire, parallel to the axis of rotation of the tire and perpendicular to any meridian plane. In what follows, the expressions "radially", "axially" and "circumferentially" respectively mean "in a radial direction", "in the axial direction" and "in a circumferential direction" of the tire. The terms "radially inner or radially outer" mean "closer or farther away from the axis of rotation of the tire in a radial direction". The equatorial plane is a plane perpendicular to the axis of revolution of the tire, positioned axially so as to cut the surface of the tread substantially halfway between the beads. The terms "axially inner, respectively axially outer" mean "closer or more distant respectively, the equatorial plane of the tire, in the axial direction."

2015PAT00409WO State of the art

In known manner, the tread of a tire is provided with a sculpture comprising in particular sculpture blocks delimited by various main grooves, longitudinal or circumferential, axial or oblique, the elementary blocks may further comprise various incisions or slices finer. The grooves are channels for evacuating water when running on wet ground; the walls of these grooves also define the edges of the sculpture blocks; depending on the orientation of the forces to which a rolling tire is subjected, it is called the leading edge of a block of sculpture when the force is oriented towards the center of the block, the trailing edge of a block of sculpture being the opposite edge.

To improve the adhesion of a tire, and more particularly for adhesion on dry ground and wet ground, it is well known to reduce the stiffness or hardness of the rubber compound constituting the tread. This decrease in rigidity of the tread allows it to better marry the rough surface of the running ground and thus the actual surface of contact with the driving floor is increased and the adhesion performance improved compared to a band of rolling whose rubbery mixture is more rigid.

However, the use of a less rigid rubber tread mixture promotes the shearing of the carving blocks when the tire must oppose an axially oriented force, which causes the tilting of the carving blocks; this generates strong overpressures on the leading edges of the sculpture blocks; these strong overpressures, in turn, generate very significant warm-ups.

These overpressures and these overheating can contribute to a very rapid damage to the tread of the tire and to a non-optimal exploitation of the adhesion potential of the tread mixture.

EP0869016 A2 discloses a tire with a tread comprising two superimposed rubber mixtures, wherein the inner and outer mixtures have different characteristics, to maintain good adhesion of the tire after partial wear of the tread and the appearance on the surface of this interior mixture. However, there is an increase

2015PAT00409WO significant of the rolling resistance of such a tire compared to a tire using in the tread only the mixture of low rigidity, all other things being equal.

To improve the adhesion performance of tires by stabilizing the carving blocks, the document EP 2 708 382 A1 proposes a tire whose tread comprises a circumferential reinforcement consisting of a rubber compound of rigidity greater than the stiffness mixing the rest of the tread.

This tire is such that the circumferential reinforcement comprises a reinforcing element placed under each circumferential groove and extending radially from the radially inner surface of the tread to form the entire bottom of the groove.

The reinforcement of the circumferential grooves thus produced makes it possible to increase the drifting thrust of the tire, but the presence of a rigid mixture at the bottom of the groove causes difficulty in molding the wear indicators. There is also a significant increase in the rolling resistance related in particular to the limitation of flattening of the tread in the axial direction and in the longitudinal direction.

Documents JP2014 / 11392A, EP1967390A1, WO2014005926A1 and US2015 / 107735 also show tires with treads comprising two distinct knotty mixtures.

None of these teachings makes it possible to use, for the tread of a tire for a vehicle with four or more wheels (passenger vehicle, in particular sports type), rubber mixtures with high adhesion without resulting in rapid wear when the tire is under heavy stress.

Brief description of the invention

The invention relates to a tire for a vehicle with three or more wheels, comprising a crown reinforcement and a radially outer tread, the tread having a contact face intended to come into contact with the roadway.

2015PAT00409WO during the rolling of the tire, said tread comprising a plurality of tread blocks oriented at least partially circumferentially and a plurality of grooves extending at least partially circumferentially, a tread block being axially limited on one side by one of the grooves and being axially limited on the other side by another of the grooves, characterized in that at least one of said truing blocks comprises a circumferential reinforcement element consisting of a rubbery mixture of dynamic shear modulus G * at less than twice the dynamic shear modulus G * of the rubber mixture of the remainder of the tread blocks, in that the circumferential reinforcing element extends radially from the radially outer surface of said crown reinforcement to the surface of said tread with an axial width which decreases progressively as it moves rad outwardly, said axial width having a maximum value less than 50% of the axial width of said block, said circumferential reinforcing element extending radially at least over a height "h" corresponding to 50% of the thickness " p "of the tread, and in that the median plane π of the circumferential reinforcing element is positioned at plus or minus 20%> of the center of said axial width of said block.

The circumferential reinforcing element (s) thus disposed (s) substantially axially at the center of the sculpture blocks (forming circumferential ribs if these blocks are continuous circumferentially, or forming circumferential alignments of patterns if the blocks comprise oriented grooves substantially axially) thus opposes by its or their high stiffness in shear, shear and tilting of these blocks of sculpture, without causing axially oriented spurious thrust as can be seen with axially non-symmetrical designs. This makes it possible to maintain a contact surface with the heavy rolling ground, to limit the overpressures on the leading edge of the rib or of the carving blocks and thus to limit the overheating as well as the rapid wear of the leading edge. of the rib. The presence of a reinforcing element thus disposed in the sculpture block (s) makes it possible to rigidify in axial shear the sculpture blocks symmetrically, so with a very good

2015PAT00409WO effectiveness in practice. This improved axial shear reinforcement efficiency makes it possible to use a smaller volume of rigid reinforcement material, with the benefit of a lesser disturbance in the contact of the tire on the road surface, and thus to the benefit of a lower local penalty. adhesion and wear. This strengthening in axial shear allows an improvement in the drift rigidity of the tire and therefore the handling of the vehicle. The presence of a reinforcing element for a single carving rib already makes it possible to obtain a significant improvement in the handling and axial grip performance of the tires of a vehicle.

The circumferential reinforcing element also has the important characteristic of directly leaning on the armature of the crown of the tire. This makes it possible to have a good point of support to stiffen the top and the tread.

It should also be noted that the invention provides excellent stiffening by using a volume of gum of relatively low stiffness, of the order of 5% to 10% of the total volume of rubber in the tread, which which causes a significant advantage in adhesion, wear, rolling resistance of the tire relative to the tires disclosed by EP 2 708 382 Al cited.

Preferably, the circumferential reinforcement comprises two reinforcing elements placed respectively in the adjacent sculpture blocks, and preferably in all the blocks. This enhances the favorable effect in terms of axial adhesion and the drift thrust of the tire without generating parasitic thrust due to crushing.

According to an advantageous embodiment, the circumferential reinforcing elements are arranged symmetrically relative to the equatorial plane EP of the tire.

According to a particular embodiment, the tread having a circumferential groove traversed by the equatorial plane, two circumferential reinforcing elements are arranged axially close to and on either side of the circumferential groove traversed by the equatorial plane. EP.

2015PAT00409WO The shape of the circumferential reinforcing element is of tapered section radially outwardly. This enhances its effectiveness as a fulcrum. The walls of this circumferential reinforcing element may be concave, convex or stepped. Preferably, the angle α that form the section the two side walls of the circumferential reinforcing element or elements in the meridian plane (that is to say in a plane comprising the axis of rotation of the tire) is between 35 and 45 degrees. Below 35 degrees, the effectiveness of the fulcrum is reduced and beyond 45 degrees, the volume of the circumferential reinforcement element becomes too great. Advantageously, the constituent rubber mixture of the circumferential reinforcement has a dynamic shear modulus G * measured at 60 ° C at 10 Hz and under an alternating shear stress of 0.7 MPa greater than 20 MPa and preferably greater than 30 MPa .

Very advantageously, the tread rubber mixture has a dynamic shear modulus G * measured at 60 ° C at 10 Hz and under an alternating shear stress of 0.7 MPa less than or equal to 1.3 MPa and preferably less than 1.1 MPa. The presence of the circumferential reinforcement makes it possible to make full use of the adhesion capacities of such a tread mixture of very low rigidity. This is particularly useful in the case of a passenger car tire. According to another advantageous embodiment, the tread comprises two separate mixtures arranged axially one above the other. The mixture arranged radially internally is usually called "underlayer". This underlayer may have more favorable hysteretic properties than the mixture in contact with the pavement, which improves the overall rolling resistance of the tire. Alternatively, the underlayer may also be more rigid than the rubbery mixture of the tread to stiffen it. The reinforcing element can then rest on the external surface of this underlayer, while keeping the advantage, in terms of the operation of the tire, of leaning directly or almost directly on the armature of the crown of the tire. .

2015PAT00409WO The invention relates more particularly to tires for equipping tourism-type motor vehicles, SUV ("Sports Utility Vehicles"), aircraft, such as industrial vehicles chosen from pickup trucks, "heavy vehicles" (it is ie metro, bus, road transport equipment (trucks, tractors, trailers), off-the-road vehicles such as agricultural or civil engineering equipment), other transport or handling vehicles. It is pointed out that the invention is aimed at a tire for a vehicle with three or more wheels, which means that it is a tire designed to operate while maintaining its axis of rotation substantially parallel to the ground, unlike the "two wheels" the tires of which work, in a turn, in an attitude where the axis of rotation can be very inclined relative to the ground; The result is a general appearance, seen in meridian section, typical, in which the summit is very rounded.

Description of the Figures

The objects of the invention are now described with the aid of the accompanying drawing in which:

- Figure 1 shows very schematically (without respecting a specific scale), a meridian section of a tire according to one embodiment of the invention;

 - Figures 2 to 7 show in meridian section tires according to different embodiments of the invention;

 - Figure 8 shows, in meridian section, alternative embodiments of a circumferential reinforcing element according to the invention.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a tire 1 comprising a crown 2, two sidewalls 3 each connected to a bead 4. The crown 2 is connected on each side to the radially outer end of each two flanks. The top 2 comprises a tread 5. FIG. 1 shows an equatorial plane EP, plane perpendicular to the axis of rotation of the tire, situated at a distance from the two beads 4 (mounted on the rim) and

2015PAT00409WO passing through the middle of the belt frame; FIG. 1 also indicates, by arrows placed just above the tread 5, on the equatorial plane EP, the axial X, circumferential C and radial Z directions.

Each bead comprises a bead wire 40. A carcass ply 41 is wrapped around each bead wire 40. The carcass ply 41 is radial and is, in a manner known per se, constituted by cables; in this case of implementation, it is about textile cables; these cables are arranged substantially parallel to each other and extending from one bead to the other so that they form an angle between 80 ° and 90 ° with the equatorial plane EP. The tread 5 comprises a plurality of tread blocks 51. Two axially adjacent tread blocks 51 are separated by a groove 7 extending at least partly circumferentially; each groove 7 is delimited radially inwards by a groove bottom and groove side walls.

The top 2 comprises a crown reinforcement 6 comprising two belt plies 62, 63; the top 2 also comprises said carcass ply 41. In a very conventional manner, the belt plies 62, 63 are formed by metal cables arranged parallel to each other. As is well known, the reinforcing elements formed by the cables of the carcass ply 41 and the cables of the waist plies 62, 63 are oriented in at least three different directions so as to form a triangulation. The crown reinforcement 6 could also comprise a hooping sheet consisting of reinforcing reinforcements formed by organic fibers or aromatic polyamide, forming, with the circumferential direction an angle at most equal to 5 °. The crown reinforcement 6 could also include other reinforcements, oriented at an angle closer to 90 °; the constitution of the crown reinforcement is not part of the invention and in the present specification, when reference is made to the radially outer surface of the waist reinforcement, the aim is the radially outermost level of the layer of radially outermost reinforcing wires or cables, including the thin layer of calendering mixture of reinforcing wires or cables if there is such a layer.

2015PAT00409WO One of the sculpture blocks 51 also comprises a circumferential reinforcing element 52. This circumferential reinforcing element 52 consists of a rubbery mixture of rigidity much greater than the stiffness of the rubbery mixture of the rest of the blocks of the strip. rolling; the reader will refer to the specific paragraphs below for complete information on rubber mix compositions.

The circumferential reinforcing element 52 extends radially from the radially outer surface of said crown reinforcement 6 towards the surface of said tread with an axial width which decreases progressively as it moves radially outwards and less on a height "h" corresponding to 50% of the thickness "P" of the tread. The thickness "P" of the tread is measured radially between the radially outer end of the crown reinforcement 6 and the contact surface with the ground of the tread 5. In particular, FIG. showing the height h of a circumferential reinforcing element 52.4. The circumferential reinforcing element 52 is of axial width having a maximum value 520, at the junction with the crown reinforcement 6, less than 50%, and preferably less than 30%> of the axial width. 510 of said block, measured where the groove side walls meet the groove bottom. In particular, FIG. 1 will be consulted. [0036] According to the invention, the circumferential reinforcing element 52 is substantially axially centered; this means that, considering the median plane π of the circumferential reinforcing element 52, the circumferential reinforcing element 52 is positioned within plus or minus 5 mm from the center of said axial width 510 of said block. Note that the circumferential reinforcing element 52 is not necessarily symmetrical with respect to the median plane π. It has been found that, for the same triangular shape of the circumferential reinforcing element 52 seen in meridian section, and for the same angle value at the apex (about 40 °), with a dynamic shear modulus reinforcement mixture G * Valleys 30MPa, it is much more advantageous to position the circumferential reinforcing element 52 in the middle of a block 51 than on one of its axial edges.

2015PAT00409WO The circumferential reinforcing element 52 opposes tilting and shearing of the rib formed by the block 51 provided with such a circumferential reinforcing element 52. Preferably, the set of blocks 51 is provided with circumferential reinforcement 52 as shown in Figures 3 to 7. [0038] Figures 2 to 7 illustrate examples of implementation of the invention in which the tread 2 comprises an underlayer 8. This sub-layer 8 is interposed between the crown reinforcement 6 and said blocks 51, without being interposed between the crown reinforcement 6 and the circumferential reinforcing element 52 in the examples illustrated by FIGS. 2 to 4 and, for part of the axial width of the underlayer, also in Figure 6, while the underlayer 85 is interposed between the crown reinforcement 6 and said blocks 51 and also between the crown reinforcement 6 and each circumferential reinforcing element 52.5 of the said blocks 51 in the example illutré in Figure 5. In the case of a low hysteresis sub-layer, obviously it uses less reinforcing material, the latter being more hysteretic. In the case of a rigid underlayer, as long as the underlayer thickness is not too great, the reinforcement is just as effective.

In FIGS. 6 to 7, exemplary embodiments of the invention are shown in which the tread 2 comprises an underlayer 86, respectively 87, disposed radially over the extended bases 526.6 (respectively 526.7) circumferential reinforcing members 52.6 (respectively 52.7). These geometries have the advantage of increasing the transverse rigidity of the block and also to prevent the tilting of the block under transverse force.

As regards the radial height of the circumferential reinforcing element 52, in FIG. 4, it can be seen that it is limited to approximately 50% of the thickness "p" of the tread, said axial width having a zero value at the highest radial position, forming a kind of tip buried in the thickness of the circumferential reinforcement 52. This already allows to obtain a significant reinforcing effect, while leaving in contact with the floor only the rubbery mixture of the lowest stiffness up to mid-wear of the tire. However, preferably, as in FIGS. 1 to 3 and 5 to 7, the radial height of the circumferential reinforcing element 52 corresponds to 100% of

2015PAT00409WO the thickness "P" of the tread, said axial width having a zero value at the radial position corresponding to the ground contact surface when the tire is new; Of course, those skilled in the art can easily adjust the performance of the tire by adopting for the radial height all intermediate values between the values indicated above.

The shape of the circumferential reinforcing elements presented is triangular, but this shape can vary and the side walls can be concave, convex or stairs especially without departing from the scope of this invention. The reader will refer to FIG. 8 in which, for reference, a circumferential reinforcing element 528a seen in meridian section has a triangular shape as used in all the preceding illustrations, the side walls seen in meridian section thus being straight lines. . In the variant formed by the circumferential reinforcing element 528b, the meridian section thereof is a trapezium, the lateral walls seen in meridian section being also straight lines; the radially outer limit of this circumferential reinforcing element 528b is also a line and, for example, it is flush with the surface of the tread. In the variant formed by the circumferential reinforcing element 528c, the side walls seen in meridian section are straight line segments, the angle angle that each of these segments forms with the radial direction varying from one segment to the next ( decreasing going radially outwards in the figure). In the variant formed by the circumferential reinforcing element 528d, the lateral walls seen in meridian section are curved, convex; they could be concave. In the variant formed by the circumferential reinforcing element 528e, the side walls seen in meridian section form stairs. These variations in shape of the meridian section may be used with all the variants previously described. According to the objective of the designer of the tire, the mixture of this underlayer may be low hysteresis and thus improve the rolling resistance of the tire or be more rigid than the other constituent mixture of the tread, in this case the underlayer has a stiffening action of the crown of the tire. All the reinforcing features mentioned above are compatible with the use of this underlayer. This underlayer is located above the base of the elements of

2015PAT00409WO reinforcement when the base exists so that the reinforcement builds directly and in priority on the crown reinforcement. That is to say on the calendering of the web of the topmost radially arranged crown architecture.

The circumferential reinforcing elements must serve as a fulcrum to oppose the shearing and tilting of the sculpture blocks that contain them. For this the mixture constituting these circumferential reinforcing elements is preferably very significantly more rigid than that of the tread. Preferably, the dynamic shear modulus G * measured at 60 ° C, at 10 Hz and under an alternating shear stress of 0.7 MPa is greater than 20 MPa, and very preferably greater than 30 MPa.

Such mixtures are described in particular in the application WO 2011/045342 Al of the Applicants.

Table 1 below gives an example of such a formulation.

Table 1

 (1) Natural rubber;

 (2) Carbon black N326 (designation according to ASTM D-1765);

 (3) novolac formophenolic resin ("Peracit 4536K" from Perstorp);

 (4) Zinc oxide (industrial grade - Umicore company);

 (5) Stearin ("Pristerene 4931" from Uniqema);

 (6) N-1,3-Dimethylbutyl-N-phenylparaphenylenediamine

 (Santoflex 6-PPD from Flexsys);

 (7) Hexamethylenetetramine (from Degussa);

 (8) N-cyclohexybenzothiazyl sulphenamide (Santocure CBS from Flexsys).

2015PAT00409WO This formulation makes it possible to obtain mixtures of high rigidity. The dynamic shear modulus G * measured under an alternating shear stress of 0.7 MPa at 10 Hz and 60 degrees Celsius is 30.3 MPa.

This very rigid material for circumferential reinforcement is preferably used in treads of low rigidity with dynamic shear modules G * less than 1.3 MPa and preferably less than or equal to 1.1 MPa, and even more preferably, less than or equal to 0.9 MPa.

The following Table 2 gives an example of a suitable formulation:

Table 2

The formulations are given in mass.

 (a) SBR with 27% styrene, butadiene -1, 2: 5%, cis-1, 4: 15%, trans -1, 4: 80% Tg -48 ° C

(b) "Zeosill l 65MP" silica of the company Solvay BET surface area 160m ² / g

 (c) Silane TESPT "SI69" from Evonik

 (d) Shell Flexon 630 TDAE Oil

 (e) Escorez 2173 Resin from Exxon Company

 (f) Antioxidant "Santoflex 6PPD" from the company Solutia

 (g) "Santocure CBS" accelerator from Solutia

p: part by weight per 100 parts of elastomer.

2015PAT00409WO The dynamic shear modulus G * after vulcanization is 0.9 MPa.

The skilled person, tire designer can adapt the number and position of the circumferential reinforcing elements to obtain optimum resistance to tilting and shear ribs and carving blocks and that for asymmetric tires or not.

tests

The rubber mixtures are characterized as indicated below.

The dynamic mechanical properties are well known to those skilled in the art. These properties are measured on a viscoanalyzer (Metravib VA4000) with specimens taken from a tire. The test pieces used are described in ASTM D 5992-96 (using the version published in September 2006 but initially approved in 1996) in Figure X2.1 (Circular Specimens). The diameter "d" of the specimens is 10 mm (the circular section is thus 78.5 mm ² ), the thickness "L" of each mixing portion is 2 mm, giving a ratio "d / L" of 5 ( as opposed to the ISO 2856 standard, mentioned in paragraph X2.4 of the ASTM standard, which recommends a d / L value of 2).

The response of a sample of vulcanized composition subjected to a sinusoidal stress in alternating simple shear at the frequency of 10 Hz is recorded. The maximum imposed shear stress is 0.7 MPa. The measurements are made with a temperature variation of 1.5 ° C per minute, a minimum temperature below the glass transition temperature (Tg) of the mixture or rubber to a maximum temperature greater than 100 ° C. vs. Before the beginning of the test, the test piece is conditioned at the minimum temperature for 20 minutes to ensure a good temperature homogeneity in the test piece. The result used is in particular the value of the dynamic shear modulus G * at the temperature of 60 ° C.

2015PAT00409WO The performance of the tires according to the objects of the invention were measured during the following tests:

Longitudinal braking distance: measure the distance needed to go from 80 to 20 km / h on wet ground.

 Drift rigidity: the axial force of lateral thrust of the tire for a given drift angle is measured on an MTS machine during rolling.

testing

The tread 110 of the tires according to the invention was made in the following manner. A profile containing the two mixtures constituting the tread 113 and the underlayer 115 was obtained by coextrusion. This profile had four grooves. Profiles of the same length corresponding to the four circumferential reinforcing elements were also made by extrusion. Then four volumes of mixture each corresponding to the volume and shape of a circumferential reinforcing member were removed from the coextruded profile of the two tread mixtures with a heating gouge and the four reinforcing elements were manually placed in place. circumferential in the four volumes thus prepared. The thus assembled treads were then set up in a manner well known to a person skilled in the art at the top of a tire to complete it. The complete tires were then vulcanized as usually in a baking press. The "R" reference tires are of the Michelin brand, Pilot Sport 3 types, of 225/45 RI 7 size, pressure 2.3 bars.

These reference tires "R" have a tread with a mixture whose dynamic shear modulus G * at 60 ° C is 1.4 MPa. The tread of these tires is identical to that of FIG. 1 with the exception of the circumferential reinforcing element and the underlayer which are absent. These tires have a tread formed solely by the four circumferential grooves indicated. The tread mixture of the reference tires "R" has a value of G * at 60 ° C of 0.9 MPa.

2015PAT00409WO The tires according to the invention "T" have a tread mixture whose value of G * is 0.9 MPa and the circumferential reinforcement elements are made with a mixture whose value of G * is 30 MPa. These "T" tires have a circumferential reinforcement corresponding to that of FIG. 3 but no underlayer. By way of example, the circumferential reinforcing element 52 illustrated has a triangular meridian section, has a height "h" identical to the thickness "p" of the tread, the tip of the radially outer triangle is flush with the the surface of the rolling band in the new state, it forms at said tip an angle of 40 °; the maximum value 520 of the axial width reaches 7.3 mm, for blocks 51 (considering only the blocks which are not axially the outermost) of axial width 510 equal to 25 mm.

Table 3

The use of a tread of lower stiffness very normally decreases the rigidity of drift of the tire and improves the braking performance on wet ground. The presence of circumferential reinforcements in the tread thus makes it possible to make full use of the bonding potential of tread mixtures of lower rigidity.

By the combination of the choice of the mixture of the tread, the choice of the mixture of the underlayer and circumferential reinforcements it is then possible for the tire designer to shift the compromises between the adhesion and the behavior respectively. rolling resistance, which is not achievable by the choice of a single material of the tread.

2015PAT00409WO

Claims

1. A tire (1) for a vehicle with three or more wheels, comprising a crown reinforcement (6) and a radially outer tread (5), the tread having a contact face intended to come into contact with the roadway during the rolling of the tire, said tread (5) comprising a plurality of carving blocks (51) oriented at least partly circumferentially and a plurality of grooves (7) extending at least partly circumferentially, a block (51) ) of sculpture being axially limited on one side by one of the grooves (7) and being axially limited on the other side by another of the grooves (7), characterized in that at least one of said sculpting blocks (51) comprises a circumferential reinforcing element (52) consisting of a rubbery mixture of dynamic shear modulus G * at least twice greater than the dynamic shear modulus G * of the mixture of the remainder of the blocks of the tread, in that the circumferential reinforcing element (52) extends radially from the radially outer surface of said crown reinforcement (6) towards the surface of said tread with a axial width which decreases progressively as it moves radially outwards, said axial width having a maximum value (520) less than 50% of the axial width (510) of said block, said circumferential reinforcing element (52) extends radially at least on a height "h" corresponding to 50% of the thickness "p" of the tread, and in that the median plane π of the circumferential reinforcing element (52) is positioned at plus or minus 20%> of the center of said axial width (510) of said block. The tire (1) according to claim 1, wherein each of said carving blocks (51) has a circumferential reinforcing member (52). A tire according to one of claims 1 or 2, wherein said height "h" corresponding to 100% of the thickness "p" of the tread, said axial width having a zero value at the radial position corresponding to the area of contact with the ground when the tire is new. 2015PAT00409WO 4. A tire according to any one of the preceding claims, wherein said axial width has a maximum value (520) less than 30% of the axial width (510) of said block. 5. A tire according to any one of the preceding claims, comprising an underlayer (8) interposed between the crown reinforcement (6) and said blocks (51). 6. A tire according to any one of claims 1 to 4, comprising an underlayer (85) interposed interposed between the crown reinforcement (6) and said blocks (51) and between the crown reinforcement (6). ) and each circumferential reinforcing element (52.5) of said blocks (51). A tire according to any one of claims 1 to 3, wherein the circumferential reinforcing members (52) comprise extended bases 526.6, 526.7. 8. A tire according to any one of the preceding claims, wherein the angle formed by the section of the two side walls of the reinforcing element or elements in the meridian plane is between 35 and 45 degrees. Tire according to any one of the preceding claims, wherein the rubber mixture constituting the circumferential reinforcement has a dynamic shear modulus G * measured at 60 ° C at 10 Hz and under an alternating shear stress of 0.7 MPa higher. at 20 MPa and preferably above 30 MPa. A tire according to any one of the preceding claims, wherein the tread rubber compound has a dynamic shear modulus G * measured at 60 ° C at 10 Hz and at an alternate shear stress of 0.7 MPa lower. or equal to 1.3 MPa and preferably less than 1.1 MPa. 2015PAT00409WO