TIRE COMPRISING A TREAD WITH REINFORCING ELEMENTS

Abstract

A tire having a tread comprising at least one circumferential reinforcing element 8 of which at least part of the meridional cross section has the shape of a triangle, the vertex of which is oriented radially towards the outside, the circumferential reinforcing element 8 comprising a skin 81 and a core 82, the skin material being at least twice as stiff as the core material.

Claims

1.-10. (canceled)

11. A tire comprising a crown reinforcement and a tread radially on the outside of the crown reinforcement, the tread having a contact face intended to come into contact with the roadway when the tire is running, and the tread comprising at least one circumferential reinforcing element of which at least part of the meridional cross-section has a shape of a triangle, the vertex of which is oriented radially toward the outside, wherein the circumferential reinforcing element comprises a skin and a core, the skin being at least twice as stiff as the core.

12. The tire according to claim 11, wherein the skin and the core are each made of a rubber compound, a dynamic shear modulus G*, measured at 60° C. at 10 Hz and under an alternating shear stress of 0.7 MPa, of the rubber compound of the skin being at least twice as high as a dynamic shear modulus G*, measured at 60° C. at 10 Hz and under an alternating shear stress of 0.7 MPa, of the rubber compound of the core.

13. The tire according to claim 12, wherein a remainder of the tread, other than the at least one circumferential reinforcing element, is made from a rubber compound, a dynamic shear modulus G* of the rubber compound of the skin being at least twice as high as a dynamic shear modulus G* of the rubber compound of the remainder of the tread.

14. The tire according to claim 12, wherein the rubber compound of the skin has a dynamic shear modulus G* greater than 5 MPa.

15. The tire according to claim 11, wherein the tread comprises a plurality of tread pattern blocks, two tread pattern blocks being axially separated by a groove, each of the grooves extending at least partially circumferentially, each of the grooves being axially delimited by two lateral faces and delimited radially toward the inside by a groove bottom, and wherein at least some of the tread pattern blocks comprise at least one circumferential reinforcing element.

16. The tire according to claim 15, wherein the at least one circumferential reinforcing element forms one of the lateral faces of a circumferential groove.

17. The tire according to claim 11, wherein a remainder of the tread, other than the at least one circumferential reinforcing element, has a dynamic shear modulus G*, measured at 60° C. at 10 Hz and under an alternating shear stress of 0.7 MPa, of less than or equal to 1.3 MPa.

18. The tire according to claim 11, wherein the core is empty of any material.

19. The tire according to claim 18, further comprising an additional reinforcing element made of a single material.

20. The tire according to claim 11, wherein the at least one circumferential reinforcing element appears at the contact face of the tread that is intended to come into contact with the roadway while the tire is running.

Description

DESCRIPTION OF THE FIGURES

[0018] The objects of the invention will now be described with the aid of the appended drawing, in which:

[0019] FIG. 1 depicts, highly schematically (without being true to a specific scale), a meridional section through a tyre in accordance with one embodiment of the invention;

[0020] FIG. 1b depicts, highly schematically (without being true to a specific scale), a meridional section through a tyre comprising a sublayer in accordance with one embodiment of the invention;

[0021] FIGS. 2a to 2e, 3a to 3d, 4a and 4b depict, in meridional section, variations in the shape of an element of the invention;

[0022] FIG. 5 highly schematically depicts an alternative form of embodiment of the invention;

[0023] the drawings that make up FIG. 6 highly schematically depict alternative forms of embodiment of the invention when 2 reinforcing elements are positioned either side of a longitudinal groove.

DETAILED DESCRIPTION OF THE INVENTION

[0024] FIG. 1 shows a tyre 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 exterior end of each of the two sidewalls. The crown 2 comprises a tread 5. FIG. 1 shows an equatorial plane EP, which plane is perpendicular to the axis of rotation of the tyre, situated mid-way between the two beads 4 (mounted on rim) and passing through the middle of the belt reinforcement; 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.

[0025] Each bead has 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, made up of cords; in this implementation, textile cords; these cords are arranged substantially parallel to one another and extending from one bead to the other in such a way that they form an angle of between 80° and 90° with the equatorial plane EP.

[0026] The tread 5 comprises a plurality of tread pattern blocks 51. Two tread pattern blocks are axially separated by a groove 7, each of the said grooves 7 extending at least partially circumferentially, each circumferential groove 7 being axially delimited by two lateral faces 72 and delimited radially towards the inside by a groove bottom 71. At least some of the said tread pattern blocks 51 comprise at least one circumferential reinforcing element. In FIG. 1, there is just one circumferential reinforcing element 8 in just one tread pattern block 51.

[0027] The crown 2 comprises a crown reinforcement 6 comprising two belt plies 61, 62; the carcass ply 41 is also present in the crown. In a very conventional way, the belt plies 61, 62 are formed of metal cords arranged parallel to one another. In a way that is well known, the reinforcing elements that the cords of the carcass ply 41 and the cords of the belt plies 61, 62 form are oriented in at least three different directions so as to form a triangulation.

[0028] The crown reinforcement 6 could also comprise a hooping ply made up of hoop reinforcers formed of organic or aromatic polyamide fibres forming, with the circumferential direction, an angle at most equal to 5°. The crown reinforcement 6 could also comprise other reinforcers, oriented at an angle closer to 90°; the makeup of the crown reinforcement does not form part of the invention and, in this document, when reference is made to the radially exterior surface of the belt reinforcement, that means the radially outermost level of the radially outermost layer of reinforcing threads or of cords, including the fine layer of skim compound skim-coating the reinforcing threads or cords if such a layer exists.

[0029] One of the tread pattern blocks 51 also comprises a circumferential reinforcing element 8. This circumferential reinforcing element 8 comprises a skin 81 and a core 82. The reader may refer to Table 1 (paragraph 77) of the aforementioned patent application WO2016/174100 in order to learn of a rubber composition cited for the “mono-material” reinforcing element, which is a rubber compound suitable for the skin. The mixture of rubbers that makes up the rubber compound of the skin 81 thus produced has a dynamic shear modulus G* (measured at 60° C. at 10 Hz and under an alternating shear stress of 0.7 MPa) of 30.3 MPa. The reader may refer to Table 2 (paragraph 88) of the aforementioned patent application WO2016/174100 in order to learn of a rubber composition cited for the predominant material used for the tread, which is a rubber compound suitable for the core and, of course, also suitable for the tread. The mixture of rubbers that makes up the rubber compound thus produced has a dynamic shear modulus G* of 0.9 MPa.

[0030] Advantageously, all of the blocks 51 are provided with a circumferential reinforcing element 8. The shape of the circumferential reinforcing elements depicted is triangular, but this shape may vary and the lateral walls may be concave, convex or in the form of a staircase, notably without departing from the scope of this invention. In FIG. 1, as in FIG. 1b, the circumferential reinforcing element 8 has an external contour in the shape of a triangle and a core 82 likewise in the shape of a triangle, the axially exterior lateral face of the triangle corresponding to one of the lateral faces of a groove 7. FIG. 1b shows a solution in which the circumferential reinforcing element 8 is laid on a sublayer 10 of a thickness from 1 mm to 2 mm.

[0031] The circumferential reinforcing element 8 appears at the contact face of the tread that is intended to come into contact with the roadway while the tyre is being driven on. The circumferential reinforcing element 8 forms one of the lateral faces 72 of a circumferential groove 7; as an alternative, being delimited, the circumferential reinforcing element 8 is able to not be at the edge of a tread pattern block 51, the distance from the circumferential reinforcing element 8 to one of the lateral surfaces 72 then preferably being less than 2 mm.

[0032] FIGS. 2b to 2c show variations in shape along these lines. FIGS. 2a and 2b show a reinforcing element in the shape of a triangle which is inclined axially, whereas the reinforcing element in FIG. 2c forms an isosceles triangle, i.e. is axially symmetric. In FIG. 2b, the core 82-2b is empty of any material, this being a highly specific form of embodiment of a material that is less stiff than the skin material. In FIGS. 2d and 2e, the core 82-2d, 82-2e is in the shape of a bell, empty of any material in the case of FIG. 2e.

[0033] In FIGS. 3a to 3d, the skin material is extended to form a sole 810 at the base of the triangle. In FIGS. 3a and 3c, the meridional cross section of the core 82-3a, 82-3c has an oval shape, the core 82-3c being empty of any material in the alternative form of FIG. 3c. In FIG. 3b, the core has a meridional cross section of triangular shape and is empty of any material; of course, it could be filled with a core material as in the case of FIG. 3a. The core 82-3d is also empty of any material in the case of FIG. 3d, in which the core is approximately circular in shape and is surmounted radially by a slit 85 leading to the vertex of the triangle. On account of its closed structure, the solution of FIG. 3a makes the reinforcing element easier to produce by coextrusion. Again on account of their closed structures, the solutions set out in FIGS. 3b and 3c also make production by extrusion easier, by comparison with the solutions 2b and 2e. Solution 3d has the advantage that it can be moulded using a sipe blade which at its base has a cylindrical form creating a “teardrop”.

[0034] In FIG. 4a, the reinforcing element 8-4 comprises a main part, in the shape of a triangle identical to the example of FIG. 1, the sole 81-4 of the said part being extended axially by a tongue 86 of the same material as the skin compound. The example of FIG. 4b is comparable with that of FIG. 4a, except that it comprises a tongue extending the sole of the said main part axially on the other side. The solutions depicted in FIGS. 4a and 4b offer the advantage of improving the anchorage of the reinforcing element to the crown reinforcement.

[0035] Note too that it is possible to use a reinforcing element according to the present invention with other types of reinforcing elements such as, for example, a reinforcing element according to any one of the teachings of the aforementioned documents. FIG. 5 illustrates the combined use of a reinforcing element 8 comprising a skin 81 and a core 82 according to the present invention, and a reinforcing element 9 made of one single material, as is found in document WO2016/174100. This application allows for a better distribution of stress through the block 51, making the reinforcement more effective, particularly in the case of high transverse stress loadings.

[0036] In instances where reinforcing elements on each side of a longitudinal groove are planned, precise forms of embodiment are exemplified in FIG. 6.

[0037] These variations in the shape of the meridional cross section can be used for any position of the reinforcing element within the tread. The illustrated variations in the shape of the reinforcing element are nonlimiting.