TIRE WITH LOW ROLLING RESISTANCE AND METHOD FOR PRODUCING SAME

Abstract

A tire comprises a crown reinforcement comprising: a working reinforcement comprising a single working layer and a hoop reinforcement arranged radially outside the working reinforcement and comprising at least one hooping filamentary reinforcing element (170) wound circumferentially helically so as to extend axially from one axial edge to the other axial edge of the hoop reinforcement. The or each hooping filamentary reinforcing element (170) consists of: two multifilament strands (1701, 1702) of aromatic polyamide or aromatic copolyamide and one multifilament strand (1703) of aliphatic polyamide or of polyester, or three polyester multifilament strands, each multifilament strand (1701, 1702, 1703) being wound in a helix around a main axis (W) common to the three multifilament strands (1701, 1702, 1703). The hoop reinforcement has a tangent modulus at 1.3% elongation ranging from 200 to 650 daN/mm.

Claims

1.-14. (canceled)

15. A tire (10) comprising a crown (12), two sidewalls (22) and two beads (24), each sidewall (22) connecting each bead (24) to the crown (12), the tire (10) comprising a carcass reinforcement (32) anchored in each bead (24) and extending in each sidewall (22) and radially internally at the crown (12), the carcass reinforcement (32) comprising a carcass layer (34), the crown (12) comprising: a tread (20) intended to come into contact with a ground when the tire (10) is rolling; and a crown reinforcement (14) arranged radially between the tread (20) and the carcass reinforcement (32), the crown reinforcement (14) comprising: a working reinforcement (16) comprising a single working layer (18); and a hoop reinforcement (17) arranged radially outside the working reinforcement (16), the hoop reinforcement (17) being axially delimited by two axial edges (17A, 17B) of the hoop reinforcement (17) and comprising at least one hooping filamentary reinforcing element (170) wound circumferentially helically so as to extend axially from one axial edge (17A, 17B) to the other axial edge (17A, 17B) of the hoop reinforcement (17), wherein the or each hooping filamentary reinforcing element (170) consists of: two multifilament strands (1701, 1702) of aromatic polyamide or aromatic copolyamide and one multifilament strand (1703) of aliphatic polyamide or of polyester; or three polyester multifilament strands, each multifilament strand (1701, 1702, 1703) being wound in a helix around a main axis (W) common to the three multifilament strands (1701, 1702, 1703), and wherein the hoop reinforcement (17) has a tangent modulus (M13%) at 1.3% elongation ranging from 200 to 650 daN/mm.

16. The tire (10) according to claim 15, wherein the or each hooping filamentary reinforcing element (170) consists of two multifilament strands (1701, 1702) of aromatic polyamide or aromatic copolyamide and of one multifilament strand (1703) of aliphatic polyamide or of polyester, each multifilament strand (1701, 1702, 1703) being wound in a helix around a main axis (W) common to the three multifilament strands (1701, 1702, 1703).

17. The tire (10) according to claim 15, wherein a ratio of a total count, expressed in tex, of aromatic polyamide or aromatic copolyamide to a total count, expressed in tex, of the or each hooping filamentary reinforcing element (170) ranges from 0.60 to 0.90.

18. The tire (10) according to claim 15, wherein the hoop reinforcement (17) has a tangent modulus (M13%) at 1.3% elongation greater than or equal to 220 daN/mm.

19. The tire according to claim 15, wherein the hoop reinforcement (17) has a tangent modulus (M13%) at 1.3% elongation less than or equal to 600 daN/mm.

20. The tire (10) according to claim 15, wherein the hoop reinforcement (17) develops, under a force equal to 2 daN/mm, a tangent modulus (M2D) ranging from 150 to 400 daN/mm.

21. The tire (10) according to claim 20, wherein the hoop reinforcement (17) develops, under a force equal to 2 daN/mm, a tangent modulus (M2D) greater than or equal to 200 daN/mm.

22. The tire (10) according to claim 20, wherein the hoop reinforcement (17) develops, under a force equal to 2 daN/mm, a tangent modulus (M2D) less than or equal to 350 daN/mm.

23. The tire according to claim 15, wherein a twist coefficient K of the or each hooping filamentary reinforcing element (170) defined by the relation K=R×[(T/(1000.Math.ρ)]½, where R is an assembly twist of the three multifilament strands (1701, 1702, 1703) around the common main axis (W), expressed in turns per meter, T is a total count of the or each hooping filamentary reinforcing element (170) expressed in tex, and ρ is an average density of the material constituting the or each hooping filamentary reinforcing element (170), ranges from 140 to 260.

24. The tire (10) according to claim 15, wherein the or each hooping filamentary reinforcing element (170) extends axially from one axial edge (17A, 17B) to the other axial edge (17A, 17B) of the hoop reinforcement (17) in a main direction (D1) of the or each hooping filamentary reinforcing element (170) forming, with the circumferential direction (Z) of the tire (10), an angle (AF), in absolute value, less than or equal to 10°.

25. The tire (10) according to claim 15, wherein the working layer (18) is delimited axially by two axial edges (18A, 18B) of the working layer (18) and comprises working filamentary reinforcing elements (180) extending axially from one axial edge (18A, 18B) to the other axial edge (18A, 18B) of the working layer (18) substantially parallel to one another in a main direction (D2) of each working filamentary reinforcing element (180), the main direction (D2) of each working filamentary reinforcing element (180) of the working layer (18) forming, with the circumferential direction (Z) of the tire (10), an angle (AT), in absolute value, strictly greater than 10°.

26. The tire (10) according to claim 15, wherein the or each carcass layer (34) is delimited axially by two axial edges (34A, 34B) of the or each carcass layer (34) and comprises carcass filamentary reinforcing elements (340) extending axially from one axial edge (34A, 34B) to the other axial edge (34A, 34B) of the or each carcass layer (34), each carcass filamentary reinforcing element (340) extending in a main direction (D3) of each carcass filamentary reinforcing element (340), the main direction (D3) of each carcass filamentary reinforcing element (340) of the or each carcass layer (34) forming, with the circumferential direction (Z) of the tire (10): an angle (ACS), in absolute value, strictly less than 80° in a portion (34S) of the carcass layer (34) extending axially in radial line with the working layer (18), and an angle (ACF), in absolute value, ranging from 80° to 90° in at least one portion (34F) of the carcass layer (34) extending radially in each sidewall (22).

27. The tire (10) according to claim 26, wherein the main direction (D3) of each carcass filamentary reinforcing element (340) forms, with the circumferential direction (Z) of the tire (10), an angle (ACS), in absolute value, greater than or equal to 10°, in the portion (34S) of the carcass layer (34) extending axially in radial line with the working layer (18).

28. A method for producing a tire (10) according to claim 15 comprising the steps: winding a carcass ply (51) or a plurality of carcass plies (51) around a support (60) having a substantially cylindrical shape around a main axis (A), to form one or more wound carcass assemblies (52), the wound carcass assemblies (52) being intended to form the carcass layer (34); winding a working ply (49) or a plurality of working plies (50), radially outside the wound carcass assembly(ies) (52), to form a wound working assembly (50) intended to form the working layer (18), the wound carcass assemblies (52) and the wound working assembly (50) forming an assembly (58) of substantially cylindrical shape around the main axis (A) of the support (60), the assembly (58) of substantially cylindrical shape around the main axis (A) of the support (60) is deformed so as to obtain an assembly (58) of substantially toric shape around the main axis (A) of the support (60); and after the deformation step, arranging radially around the assembly (58) of substantially toric shape around the main axis (A) of the support (60), a wound hooping assembly (76) intended to form the hoop reinforcement (17), the wound hooping assembly (76) being formed by helical winding of the or each hooping filamentary reinforcing element (170) or of a hooping ply (74) obtained by embedding the or each hooping filamentary reinforcing element (170) in an elastomeric matrix.

Description

DESCRIPTION OF THE EXAMPLES

[0161] The invention as well as its advantages will be easily understood in the light of the detailed description and the nonlimiting exemplary embodiments which follow, as well as from FIGS. 1 to 20 relating to these examples in which:

[0162] FIG. 1 is a view in section in a meridian section plane of a tyre according to the invention;

[0163] FIG. 2 is a schematic cutaway view of the tyre of FIG. 1 illustrating the arrangement of the filamentary reinforcing elements in radial line with and radially overhanging the working layer;

[0164] FIG. 3 is a schematic view of the carcass filamentary reinforcing elements arranged in the sidewall of the tyre of FIG. 1;

[0165] FIG. 4 is a view in a section plane perpendicular to the axial direction of a portion of the crown of the tyre of FIG. 1;

[0166] FIG. 5 is a view in a section plane perpendicular to the main direction in which each hooping filamentary reinforcing element of the tyre of FIG. 1 extends;

[0167] FIG. 6 is a force-elongation curve of a hooping filamentary reinforcing element of the tyre of FIG. 1;

[0168] FIGS. 7 to 16 illustrate the different steps of the method according to the invention making it possible to manufacture the tyre of FIG. 1;

[0169] FIGS. 17 and 18 illustrate, for different models, the coefficient of correlation R2 between the simulated rolling resistance and the tangent modulus of the hoop reinforcement for a tyre according to the invention respectively with imposed force and with imposed elongation, and

[0170] FIGS. 19 and 20 illustrate, for different models, the coefficient of correlation R2 between the simulated rolling resistance and the tangent modulus of the hoop reinforcement for a conventional tyre respectively with imposed force and with imposed elongation.

[0171] In the figures relating to the tyre, there is shown a reference frame X, Y, Z corresponding to the usual axial (X), radial (Y) and circumferential (Z) directions, respectively, of a tyre. In the figures relating to the method, there is shown a reference frame x, y, z corresponding to the usual axial (x), radial (y) and circumferential (z) directions, respectively, of a manufacturing support deformable between a substantially cylindrical shape and a toric shape around the x axis.

[0172] FIG. 1 shows a tyre according to the invention and denoted by the general reference 10. The tyre 10 is substantially of revolution about an axis substantially parallel to the axial direction X. The tyre 10 is here intended for a passenger vehicle and has dimensions 245/45R18.

[0173] The tyre 10 comprises a crown 12 comprising a tread 20 intended to come into contact with the ground during rolling and a crown reinforcement 14 extending in the crown 12 in the circumferential direction Z. The tyre 10 also comprises a sealing layer 15 for sealing against an inflation gas being intended to define an internal cavity closed with a mounting support for the tyre 10 once the tyre 10 has been mounted on the mounting support, for example a rim. The sealing layer 15 comprises an elastomeric composition comprising an elastomeric matrix comprising at least 50 phr of one or more butyl elastomers.

[0174] The crown reinforcement 14 comprises a working reinforcement 16 comprising a working layer 18 and a hoop reinforcement 17 comprising a single hooping layer 19. Here, the working reinforcement 16 comprises a single working layer 18 and, in this case, consists of the single working layer 18. In the following description, mention will be made, for the sake of simplification, of the working layer 18 without restating each time that this layer is single. The hoop reinforcement 17 consists of the hooping layer 19.

[0175] The crown reinforcement 14 is surmounted radially by the tread 20. Here, the hoop reinforcement 17, here the hooping layer 19, is arranged radially outside the working reinforcement 16 and is therefore radially interposed between the working reinforcement 16 and the tread 20. In the embodiment illustrated in FIG. 2, the hoop reinforcement 17 has an axial width smaller than the axial width of the working layer 18. Thus, the hoop reinforcement 17 is axially the narrowest of the working layer 18 and of the hoop reinforcement 17.

[0176] The tyre 10 comprises two sidewalls 22 extending the crown 12 radially inwards. The tyre 10 further comprises two beads 24 radially inside the sidewalls 22. Each sidewall 22 connects each bead 24 to the crown 12.

[0177] Each bead 24 comprises at least one circumferential reinforcing element 26, in this case a bead wire 28 surmounted radially by a mass of filling rubber 30.

[0178] The tyre 10 comprises a carcass reinforcement 32 anchored in each bead 24. The carcass reinforcement 32 extends in each sidewall 22 and radially inwardly at the crown 12. The crown reinforcement 14 is arranged radially between the tread 20 and the carcass reinforcement 32.

[0179] The carcass reinforcement 32 comprises a carcass layer 34. Here, the carcass reinforcement 32 comprises a single carcass layer 34, and in this case consists of the single carcass layer 34. In this embodiment, mention will be made, for the sake of simplification, of the carcass layer 34 without restating each time that this layer is single.

[0180] The carcass layer 34 comprises a portion 34T of the carcass layer 34 wound around each circumferential reinforcing element 26 so as to form in each bead 24 an axially inner portion 38 and an axially outer portion 40. The mass of filling rubber 30 is interposed between the axially inner and outer portions 38, 40. Other methods of anchoring the carcass layer 34 are possible, for example as described in U.S. Pat. No. 5,702,548.

[0181] Each working 18, hooping 19 and carcass 34 layer comprises an elastomeric matrix in which are embedded one or more filamentary reinforcing elements of the corresponding layer. These layers will now be described with reference to FIGS. 1 to 4.

[0182] The hoop reinforcement 17, here the hooping layer 19, is delimited axially by two axial edges 17A, 17B of the hoop reinforcement 17. The hoop reinforcement 17 comprises a plurality of hooping filamentary reinforcing elements 170 wound circumferentially helically so as to extend axially from the axial edge 17A to the other axial edge 17B of the hooping layer 17 in a main direction D1 of each hooping filamentary reinforcing element 170. The main direction D1 forms, with the circumferential direction Z of the tyre 10, an angle AF, in absolute value, less than or equal to 10°, preferably less than or equal to 7° and more preferably less than or equal to 5°. Here, AF=−5°. The hoop reinforcement has an average axial density of 69 threads per decimetre, or 0.69 threads per mm.

[0183] The working layer 18 is delimited axially by two axial edges 18A, 18B of the working layer 18. The working layer 18 comprises working filamentary reinforcing elements 180 extending axially from the axial edge 18A to the other axial edge 18B of the working layer 18 substantially parallel to one another. Each working filamentary reinforcing element 180 extends in a main direction D2 of each working filamentary reinforcing element 180. The direction D2 forms, with the circumferential direction Z of the tyre 10, an angle AT, in absolute value, strictly greater than 10°, preferably ranging from 15° to 50° and more preferably ranging from 18° to 30°. Here, AT=24°.

[0184] The carcass layer 34 is delimited axially by two axial edges 34A, 34B of the carcass layer 34. The carcass layer 34 comprises carcass filamentary reinforcing elements 340 extending axially from the axial edge 34A to the other axial edge 34B of the carcass layer 34.

[0185] Each carcass filamentary reinforcing element 340 extends in a main direction D3 of each carcass filamentary reinforcing element 340 forming, with the circumferential direction Z of the tyre 10, an angle ACS, in absolute value, strictly less than 80° in a portion 34S of the carcass layer 34 extending axially in radial line with the working layer 18. Advantageously, in this portion 34S of the carcass layer 34 extending axially in radial line with the working layer 18, the main direction D3 of each carcass filamentary reinforcing element 340 forms, with the circumferential direction Z of the tyre 10, an angle ACS, in absolute value, greater than or equal to 10°, preferably ranging from 20° to 75° and more preferably ranging from 35° to 70°. Here, ACS=43°.

[0186] The portion 34S of the carcass layer 34 extending axially in line with the working layer 18 has an axial width equal to at least 40%, preferably at least 50%, of the axial width L of the working layer 18 and equal to at most 90%, preferably at most 80%, of the axial width L of the working layer 18 and in this case equal to 60% of the working layer 18. The median plane M of the tyre 10 intersects this portion 34S. More preferably, this portion 34S is axially centred on the median plane M of the tyre 10.

[0187] As illustrated in FIGS. 1 and 3, the main direction D3 of each carcass filamentary reinforcing element 340 forms, with the circumferential direction Z of the tyre 10, an angle ACF, in absolute value, ranging from 80° to 90° in at least one portion 34F of the carcass layer 34 extending radially in each sidewall 22. Here, ACF=90°.

[0188] Each portion 34F of the carcass layer 34 extending radially in each sidewall 22 has a radial height equal to at least 5%, preferably at least 15% and more preferably at least 30%, of the radial height H of the tyre 10 and equal to at most 80%, preferably at most 70% and more preferably at most 60%, of the radial height H of the tyre 10 and in this case equal to 41% of the radial height H of the tyre 10. The equatorial circumferential plane E of the tyre 10 intersects each portion 34F of the carcass layer 34 located in each sidewall 22.

[0189] The main direction D3 of each carcass filamentary reinforcing element 340 forms, with the circumferential direction Z of the tyre 10, an angle ACT, in absolute value, strictly greater than 0°, preferably ranging from 27° to 150° and more preferably ranging from 56° to 123°, in the wound portion 34T of the carcass layer 34.

[0190] As illustrated in FIG. 2, the main direction D1 of each of hooping filamentary reinforcement 170, the main direction D2 of each working filamentary reinforcing element 180 and the main direction D3 of each carcass filamentary reinforcing element 340 form, with the circumferential direction Z of the tyre 10, in a portion PS′ of the tyre 10 lying axially between the axial edges 17A, 17B of the hoop reinforcement 17, paired angles different in absolute value. In addition, the main direction D2 of each working filamentary reinforcing element 180 and the main direction D3 of each carcass filamentary reinforcing element 340 form, with the circumferential direction Z of the tyre 10, in a portion PS of the tyre 10 lying axially between the axial edges 18A, 18B of the working layer 18, angles AT and ACS of opposite orientations. In this case, AT=−24° and ACS=+43°.

[0191] In the embodiment described, each portion PS, PS′ of the tyre 10 has an axial width equal to at least 40%, preferably at least 50%, of the axial width L of the working layer 18 and equal to at most 90%, preferably at most 80%, of the axial width L of the working layer 18 and in this case equal to 60% of the axial width L of the working layer 18. The median plane M of the tyre 10 intersects each portion PS, PS′ of the tyre 10. More preferably, each portion PS, PS′ of the tyre 10 is axially centred on the median plane M of the tyre 10.

[0192] Each working filamentary reinforcing element 180 is an assembly of two steel monofilaments that each have a diameter equal to 0.30 mm, the two steel monofilaments being wound together at a pitch of 14 mm.

[0193] Each carcass filamentary reinforcing element 340 conventionally comprises two multifilament strands, each multifilament strand consisting of a monofilament yarn of polyesters, here of PET, these two multifilament strands being individually over-twisted at 240 turns per metre in one direction and then twisted together at 240 turns per metre in the opposite direction. These two multifilament strands are wound in a helix around one another. Each of these multifilament strands has a count equal to 220 tex.

[0194] As illustrated in FIG. 5, each hooping filamentary reinforcing element 170 consists of three multifilament strands 1701, 1702, 1703, and in this case consists of two multifilament strands 1701, 1702 of aromatic polyamide or aromatic copolyamide and of one multifilament strand 1703 of aliphatic polyamide or of polyester, and here consists of two multifilament strands 1701, 1702 of aromatic polyamide, for example of Kevlar from the company Dupont Maydown, and of one multifilament strand 1703 of aliphatic polyamide, for example of Nylon T728 from the company Kordsa. Each multifilament strand 1701, 1702, 1703 is wound in a helix around a main axis W common to the three multifilament strands.

[0195] The count of each multifilament strand of aromatic polyamide 1701, 1702 ranges from 150 tex to 350 tex and in this case is equal to 330 tex. The count of the multifilament strand of aliphatic polyamide 1703 ranges from 120 tex to 250 tex and in this case is equal to 188 tex. The ratio of the total count, expressed in tex, of aromatic polyamide to the total count, expressed in tex, of each hooping filamentary reinforcing element 170 ranges from 0.60 to 0.90, preferably from 0.65 to 0.80 and is here equal to 0.78.

[0196] Each hooping filamentary reinforcing element 170 is twist-balanced and is obtained by a method comprising a first step of twisting each multifilament strand 1701, 1702, 1703 according to a number of turns per metre N1 in a first direction of twisting. The method comprises a second step of assembling by twisting the three multifilament strands 1701, 1702, 1703 according to a number of turns per metre N2 in a second direction of twisting opposite to the first direction of twisting around the common main axis W, with here N1=N2. The assembly twist N2 of the three multifilament strands 1701, 1702, 1703 around the common main axis W ranges from 150 turns per metre to 400 turns per metre and in this case N2=270 turns per metre.

[0197] The twist coefficient K of each hooping filamentary reinforcing element 170 described above ranges from 140 to 260, preferably from 180 to 220 and even more preferably from 205 to 220 and here is equal to 212 with an average density of the constituent material of each hooping filamentary reinforcing element 170 equal to 1.37 taking an aromatic polyamide density equal to 1.44 and an aliphatic polyamide density equal to 1.14.

[0198] The hoop reinforcement 17 also has a tangent modulus M13% at 1.3% elongation ranging from 200 to 650 daN/mm. The tangent modulus M13% is determined from the tangent modulus M13′% at 1.3% elongation of each hooping filamentary reinforcing element 170, illustrated in FIG. 6, which has been multiplied by the average axial density of hooping filamentary reinforcing elements 170 per mm of hoop reinforcement, and here by the average number of turns of the hooping filamentary reinforcing elements per mm of hoop reinforcement 17. Here M13′%=4.67 daN/% and N=0.69 turns per mm. More precisely, the tangent modulus M13% is greater than or equal to 220 daN/mm and less than or equal to 600 daN/mm, preferably less than or equal to 500 daN/mm and here equal to 322 daN/mm.

[0199] The hoop reinforcement 14 develops, under a force equal to 2 daN/mm, a tangent modulus M2D ranging from 150 to 400 daN/mm. More precisely, the hoop reinforcement 14 develops, under a force equal to 2 daN/mm, a tangent modulus M2D greater than or equal to 200 daN/mm and less than or equal to 350 daN/mm. In the example illustrated, taking into account the average axial density of hooping filamentary reinforcing elements 170 equal to 0.69 elements per mm, the force equal to 2 daN/mm represents a force equivalent to 2.9 daN/hooping filamentary reinforcing element, which, in FIG. 6, gives an equivalent tangent modulus M2′D equal to 4.35 daN/%, that is to say a modulus M2D equal to 300 daN/mm for the hoop reinforcement 14.

[0200] The tyre 10 is obtained by a method according to the invention which will be described with reference to FIGS. 7 to 13.

[0201] First, a wound working assembly 50 and a wound carcass assembly 52 are manufactured by arranging the filamentary reinforcing elements 180 and 340 of each assembly 50 and 52 parallel to one another and by embedding them, for example by calendering, in an uncrosslinked composition comprising at least one elastomer, the composition being intended to form an elastomeric matrix once crosslinked. A ply known as a straight ply is obtained, in which the filamentary reinforcing elements are parallel to one another and are parallel to the main direction of the ply. Then, portions of each straight ply are cut at a cutting angle and these portions are butted against one another so as to obtain a ply known as an angled ply, in which the filamentary reinforcing elements of the ply are parallel to one another and form an angle with the main direction of the ply equal to the cutting angle.

[0202] In the embodiment described, there is obtained, on the one hand, a single working ply 49 and a single carcass ply 51, the axial width of each of which, that is to say the dimension in a direction perpendicular to the longitudinal edges of each ply, is equal to the axial width respectively of each wound working 50 and carcass 52 assembly which will be formed subsequently.

[0203] Referring to FIG. 7, in a first step of assembling a green blank, there is formed, by winding a sealing ply 70 around a support 60 having a substantially cylindrical shape around its main axis A, a wound sealing assembly 72 intended to form the sealing layer 15. The support 60 has a substantially cylindrical laying surface with a radius equal to 235 mm.

[0204] Then, with reference to FIG. 8, radially outside the wound sealing assembly 72, there is formed, by winding the carcass ply 51 around the support 60, the wound carcass assembly 52 intended to form the carcass layer 34. The wound carcass assembly 52 is axially delimited by two axial edges 52A, 52B of the carcass assembly 52 and comprises the carcass filamentary reinforcing elements 340 extending substantially parallel to one another axially from the axial edge 52A to the other axial edge 52B of the wound carcass assembly 52. Each carcass filamentary reinforcing element 340 extends, in the carcass ply 51, in a main direction K3 of each carcass filamentary reinforcing element 340 in the carcass ply 51. The main direction K3 forms, with the circumferential direction z of the support 60, an initial angle A3 of each carcass filamentary reinforcing element 340, in absolute value, strictly greater than 0°, preferably ranging from 27° to 150° and more preferably ranging from 56° to 123°. Here A3=75°.

[0205] Referring to FIGS. 9 and 10, then, the two circumferential reinforcing elements 26 are arranged around the wound carcass assembly 52 and each axial edge 52A, 52B of the wound carcass assembly 52 is turned axially inwards so as to radially cover each circumferential reinforcing element 26 by each axial edge 52A, 52B of the wound carcass assembly 52 and to form a portion 59 of the wound carcass assembly 52 wound around each circumferential reinforcing element 26. The portion 59 of the wound carcass assembly 52 is intended to form the portion 34T of the carcass layer 34 wound around each circumferential reinforcing element 26 in the tyre.

[0206] There is shown in FIG. 11 a diagram illustrating the arrangement of the carcass filamentary reinforcing elements 340 at the end of the step of axially turning the axial edges 52A, 52B of the wound carcass assembly 52 around the circumferential reinforcing elements 26. In this FIG. 11, there is shown the initial angle A3 described above as well as each portion 59.

[0207] Then, with reference to FIG. 12, there is formed, by winding the working ply 49, radially outside the wound carcass assembly 52, the wound working assembly 50 intended to form the working layer 18. The wound working assembly 50 is axially delimited by two axial edges 50A, 50B of the wound working assembly 50 and comprises the working filamentary reinforcing elements 180 extending substantially parallel to one another axially from the axial edge 50A to the other axial edge 50B of the wound working assembly 50. Each working filamentary reinforcing element 180 extends, in the working ply 49, in a main direction K2 of each working filamentary reinforcing element 180 in the working ply 49. With reference to FIG. 13, the main direction K2 forms, with the circumferential direction z of the support 60, an initial angle A2 of each working filamentary reinforcing element 180, in absolute value, strictly greater than 0°, preferably ranging from 4° to 60° and more preferably ranging from 16° to 47°. Here, A2=35°.

[0208] The wound carcass assembly 52 and the wound working assembly 50 then form an assembly 58 of substantially cylindrical shape around the main axis A of the support 60.

[0209] There is shown in FIG. 13 a diagram similar to that of FIG. 11 illustrating the arrangement of the carcass filamentary reinforcing elements 340 and the working filamentary reinforcing elements 180 at the end of the step of forming the wound working assembly 50. In this FIG. 13, the initial angles A2 and A3 have been shown.

[0210] The main direction K2 of each working filamentary reinforcing element 180 and the main direction K3 of each carcass filamentary reinforcing element 340 form, with the circumferential direction z of the support 60, in a portion AC of the assembly 58 lying axially between the axial edges 50A, 50B of the wound working assembly 50, initial angles A2 and A3 of opposite orientations. Here, the axial width of the portion AC is substantially equal to the axial width of the wound working assembly 50. In this case, A2=−35° and A3=+75°.

[0211] Then, the assembly 58 of substantially cylindrical shape around the main axis A of the support 60 is deformed so as to obtain the assembly 58 of substantially toric shape around the main axis A of the support 60. The deformed assembly 58 illustrated in FIG. 14 is obtained. The laying surface of the support 60 then has, at the level of the median plane of the support, a radius equal to 327 mm.

[0212] Referring to FIG. 15, the assembly 58 of substantially cylindrical shape around the main axis A of the support 60 is deformed so as to obtain an assembly 58 of substantially toric shape around the main axis A of the support 60 so that the main direction K3 of each carcass filamentary reinforcing element 340 forms, with the circumferential direction z of the support 60, a final angle B3S of each carcass filamentary reinforcing element 340, in absolute value, strictly less than 80°, in a portion 52S of the wound carcass assembly 52 extending axially in radial line with the wound working assembly 50. Advantageously, the final angle B3S is, in absolute value, greater than or equal to 10°, preferably ranges from 20° to 75° and more preferably ranges from 35 to 70°. Here, B3S=43°. The portion 52S of the wound carcass assembly 52 is intended to form the portion 34S of the carcass layer 34.

[0213] The portion 52S of the wound carcass assembly 52 extending axially in radial line with the wound working assembly 50 has an axial width equal to at least 40%, preferably at least 50%, of the axial width I of the wound working assembly 50 and equal to at most 90%, preferably at most 80%, of the axial width I of the wound working assembly 50 and, in this case, is equal to 60% of the axial width I of the wound working assembly 50. The median plane m of the assembly 58 intersects this portion 52S. More preferably, this portion 52S is axially centred on the median plane m of the assembly 58.

[0214] The assembly 58 of substantially cylindrical shape around the main axis A of the support 60 is deformed so as to obtain the assembly 58 of substantially toric shape around the main axis A of the support 60 also so that the main direction K3 of each carcass filamentary reinforcing element 340 forms, with the circumferential direction z of the support 60, a final angle B3F of each carcass filamentary reinforcing element 340 ranging, in absolute value, from 80° to 90°, in a portion 52F of the wound carcass assembly 52 intended to extend radially in each sidewall 22 of the tyre 10. Each portion 52F of the wound carcass assembly 52 is intended to form each portion 34F of the carcass layer 34.

[0215] Each portion 52F of the wound carcass assembly 52 intended to extend radially in each sidewall 22 has a radial height equal to at least 5%, preferably at least 15% and even more preferably at least 30%, of the radial height H of the manufactured tyre and equal to at most 80%, preferably at most 70% and even more preferably at most 60%, of the radial height H of the manufactured tyre, and in this case is equal to 41% of the radial height H of the manufactured tyre. The equatorial circumferential plane e of the assembly 58 intersects each portion 52F of the wound carcass assembly 52 intended to be located in each sidewall 22.

[0216] During the deformation step, the final angle B3T formed by the main direction K3 of each carcass filamentary reinforcing element 340, with the circumferential direction z of the support 60, in the wound portion 59 of the wound carcass assembly 52, is substantially identical to the initial angle A3 before the deformation step.

[0217] The assembly 58 of substantially cylindrical shape around the main axis A of the support 60 is deformed so as to obtain the assembly 58 of substantially toric shape around the main axis A of the support 60 also so that the main direction K2 of each working filamentary reinforcing element 340 forms, with the circumferential direction z of the support 60, a final angle B2 of each working filamentary reinforcing element 340, in absolute value, strictly greater than 10°. Advantageously, the final angle B2 ranges, in absolute value, from 15° to 50°, preferably from 18° to 30° and here B2=24°.

[0218] The main direction K2 of each working filamentary reinforcing element 180 and the main direction K3 of each carcass filamentary reinforcing element 340 form, with the circumferential direction z of the support 60, in the portion AC of the assembly 58 lying axially between the axial edges 50A, 50B of the wound working assembly 50, final angles B2 and B3S of opposite orientations. In this case, B2=−24° and B3S=+43°.

[0219] During the method, a plurality of hooping filamentary reinforcing elements 170, preferably adhered, are embedded in an elastomeric matrix to form a hooping ply 74.

[0220] Then, as illustrated in FIG. 16, there is arranged, radially around the assembly 58 previously formed on the support 60, a wound hooping assembly 76 intended to form the hoop reinforcement 17. Here, the wound hooping assembly 76 is formed by helical winding of the hooping ply 74 on a toric shape and then the wound hooping assembly 76 is transferred using a transfer ring radially outside the assembly 58 previously formed. As a variant, the hooping ply 74 may be directly wound circumferentially helically around the assembly 58 previously formed so as to form the wound hooping assembly 76.

[0221] The wound hooping assembly 76 develops, under a force equal to 2 daN/mm, a tangent modulus M2D ranging from 155 to 420 daN/mm. More precisely, the hooping assembly 76 develops, under a force equal to 2 daN/mm, a tangent modulus M2Dc greater than or equal to 210 daN/mm and less than or equal to 368 daN/mm. In the example illustrated, the average axial density of hooping filamentary reinforcing elements 170 in the wound hooping assembly 76 is slightly less than that of the hoop reinforcement 17, in this case equal to 0.66 elements per mm, the force equal to 2 daN/mm represents a force equivalent to 3.03 daN/hooping filamentary reinforcing element, which corresponds to an equivalent tangent modulus M2′Dc equal to 4.57 daN/%, i.e. a modulus M2Dc equal to 301 daN/mm for the wound hooping assembly 76.

[0222] In the illustrated embodiment, the wound hooping assembly 76 has an axial width smaller than the axial width of the wound working assembly 50. Thus, the wound hooping assembly 76 is axially the narrowest of the wound working 50 and wound hooping 76 assemblies.

[0223] The angle A1 formed by the main direction K1 of each hooping filamentary reinforcing element 170 with the circumferential direction z of the support 60 is, in absolute value, less than or equal to 10°, preferably less than or equal to 7° and more preferably less than or equal to 5° and here equal to 5°.

[0224] The main direction K1 of each hooping filamentary reinforcing element 170, the main direction K2 of each working filamentary reinforcing element 180 and the main direction D3 of each carcass filamentary reinforcing element 340 form, with the circumferential direction z of the support 60, in a portion AC′ of the assembly 58 and of the wound hooping assembly 76 lying axially between the axial edges 76A, 76B of the wound hooping assembly 76, paired angles different in absolute value.

[0225] The portion AC′ of the assembly 58 and of the wound hooping assembly lying axially between the axial edges 76A, 76B of the wound hooping assembly 76 has an axial width equal to at least 40%, preferably at least 50%, of the axial width L of the wound working assembly 50 and at most 90%, preferably at most 80%, of the axial width L of the wound working assembly 50 and in this case here 60% of the axial width L of the wound working assembly 50. The median plane m of the assembly 58 intersects this portion AC′. More preferably, this portion AC′ is axially centred on the median plane m of the assembly 58.

[0226] Then, a strip of polymeric material intended to form the tread 20 is arranged, radially outside the wound hooping assembly 76, so as to form a green blank of the tyre 10. In one variant, the strip of polymeric material intended to form the tread 20 may be arranged radially outside the hooping assembly 76, then this assembly may be transferred radially outside the assembly 58 previously formed on the support 60. In another variant, it is possible, after having arranged the wound hooping assembly 76 radially around the assembly 58 previously formed on the support 60, to arrange the strip of polymeric material intended to form the tread 20.

[0227] Then, the green blank of the tyre 10 formed from the previously formed assembly 58 and the wound hooping assembly 76 is moulded by radially and circumferentially expanding the green blank so as to press a radially external surface of the green blank against a moulding wall of a crosslinking mould.

[0228] Then, the green blank is crosslinked in the crosslinking mould so as to obtain the tyre 10, for example by vulcanization.

[0229] Comparative Tests

[0230] For the purposes of the invention, the most relevant descriptor for evaluating the rolling resistance of tyres comprising a single working layer was determined first of all. For this, we correlated, using various correlation functions conventionally used by those skilled in the art, for example linear, quadratic or cubic functions (Function 1, Function 2, Function 3, Function 4), the correlation between the tangent modulus of the hoop reinforcement and the rolling resistance simulated on tyres comprising a single working layer similar to the tyre 10 described above and comprising various hooping filamentary reinforcing elements. Thus, rolling resistance simulations were carried out for hooping filamentary reinforcing elements having different tangent modulus values. Then, the various forces for which this tangent modulus can be calculated were scanned. Then, it was sought to pass each correlation function into the simulated rolling resistance point cloud and the correlation coefficient R2 was recorded for each of the correlation functions at each level of force. The results of these simulations are shown in FIG. 17. A similar approach was carried out by scanning various elongations for which the tangent modulus can be calculated. The results of these simulations are shown in FIG. 18. From these FIGS. 17 and 18, we note that the most relevant descriptor is the tangent modulus M13% at an elongation equal to 1.3% correlated using the correlation function 1.

[0231] The same approach was reproduced for a conventional tyre of the prior art comprising a carcass layer comprising carcass filamentary reinforcing elements extending in a main direction forming, with the circumferential direction of the tyre, a substantially constant angle equal to 90° and two working layers comprising working filamentary reinforcing elements. The main direction in which each working filamentary reinforcing element of the radially innermost working layer extends and the main direction in which each working filamentary reinforcing element of the radially outermost working layer extends form, with the circumferential direction of the tyre, angles of opposite orientations and equal, in absolute value, to 26°. The results of these simulations are shown in FIGS. 19 and 20. We note that the most relevant descriptor is the tangent modulus M1% at an elongation equal to 1% correlated using the correlation function 1.

[0232] Table 1 below compiles the tangent moduli M13% at 1.3% of nine hooping filamentary reinforcing elements as well as the corresponding rolling resistance RR13 of a tyre comprising a single working layer similar to those simulated. Table 1 below also compiles the tangent moduli M1% at 1% elongation simulated for hooping assemblies comprising the same nine hooping filamentary reinforcing elements as well as the corresponding rolling resistance R1 of a tyre comprising two working layers similar to those simulated.

[0233] Element 1 is the hooping filamentary reinforcing element 170 described above.

[0234] Element 2 consists of two multifilament strands of aromatic polyamide of 250 tex each and of one multifilament strand of aliphatic polyamide of 140 tex wound individually then together in a helix with a twist equal to 300 turns per metre.

[0235] Element 3 consists of two multifilament strands of aromatic polyamide of 250 tex each and of one multifilament strand of aliphatic polyamide of 210 tex wound individually then together in a helix with a twist equal to 300 turns per metre.

[0236] Element 4 consists of two multifilament strands of aromatic polyamide of 250 tex each and of one multifilament strand of polyethylene terephthalate of 220 tex wound individually then together in a helix with a twist equal to 300 turns per metre.

[0237] Element 5 consists of two multifilament strands of aromatic polyamide of 167 tex each and of one multifilament strand of aliphatic polyamide of 140 tex wound individually then together in a helix with a twist equal to 360 turns per metre.

[0238] Element 6 consists of three multifilament strands of polyethylene terephthalate of 440 tex each wound individually then together in a helix with a twist equal to 160 turns per metre.

[0239] Elements 7 and 8 have a “Core Insertion” type structure as described in WO2019/122621. Element 7 comprises an aliphatic polyamide core strand of 47 tex individually wound at 340 turns per metre and three aromatic polyamide layer strands of 167 tex each individually wound at 315 turns per metre, the core and layer strands being wound together at 315 turns per metre. Element 8 comprises an aliphatic polyamide core strand of 47 tex individually wound at 300 turns per metre and three aromatic polyamide layer strands of 167 tex each individually wound at 270 turns per metre, the core and layer strands being wound together at 270 turns per metre.

[0240] Element 9 has a triple twist structure A110/1/2/3 as described in WO2019/180367.

TABLE-US-00001 TABLE 1 M13% RR13 M1% RR1 (daN/mm) (kg/t) (daN/mm) (kg/t) Element 1 322 5.31 314 5.91 Element 2 349 5.31 332 5.92 Element 3 226 5.34 218 5.89 Element 4 434 5.32 398 5.95 Element 5 222 5.33 218 5.89 Element 6 297 5.32 291 5.91 Element 7 40 5.43 36 5.95 Element 8 112 5.39 101 5.93 Element 9 935 5.39 887 6.10

[0241] It should be noted that, in a conventional tyre comprising two working layers, elements 1 to 6 do not make it possible to obtain significantly improved rolling resistance (by significantly improved is meant here lower by at least 0.05 kg.Math.t) in relation to elements 7 to 9, and particularly in relation to elements 7 and 8. By contrast, and unexpectedly, these elements 1 to 6 make it possible to obtain a significantly improved rolling resistance (lower by at least 0.05 kg.Math.t) in relation to elements 7 to 9 in a tyre comprising a single working layer. Thus, even having tangent moduli at 1% elongation significantly different in relation to elements 7 to 9, it was impossible to suspect that elements 1 to 6 could make it possible to improve the rolling resistance of tyres according to the invention.

[0242] The same approach was also reproduced in order to determine the capacity of the tyre to reach and contain the expected volume under a predetermined inflation pressure. For this, in a similar way to the rolling resistance, we correlated, using various correlation functions (Function 1, Function 2, Function 3, Function 4), the correlation between the tangent modulus of the hoop reinforcement and the radial elongation CF of tyres comprising a single working layer similar to the tyre 10 under a pressure of 2.5 bar and comprising various hooping filamentary reinforcing elements. The same was done with tyres comprising two working layers. The results of this study showed that: [0243] the most relevant descriptor for simulating the capacity of a tyre comprising a single working layer to achieve and contain the expected volume under a predetermined inflation pressure was the tangent modulus M2D at a force of 2 daN/mm, and [0244] the most relevant descriptor for simulating the capacity of a tyre comprising two working layers to achieve and contain the expected volume under a predetermined inflation pressure was the tangent modulus M1D at a force of 1 daN/mm.

[0245] The simulation results of the tyres comprising the hooping filamentary reinforcing elements 1 to 9 are compiled in Table 2.

TABLE-US-00002 TABLE 2 M2D CF2 M1D CF1 (daN/mm) (mm) (daN/mm) (mm) Element 1 300 4.8 264 2.4 Element 2 315 4.8 290 2.3 Element 3 218 4.9 195 3.3 Element 4 312 4.5 248 2.3 Element 5 216 4.9 210 3.2 Element 6 274 4.9 283 1.1 Element 7 110 4.1 50 8.4 Element 8 131 4.5 100 5.4 Element 9 787 2.6 715 0.8

[0246] It should be noted that, for a conventional tyre comprising two working layers, elements 1 to 6 present a risk of not reaching the expected volume, in particular with respect to element 8. By contrast, and unexpectedly, these elements 1 to 6 make it possible to reach the expected volume without the risk of not containing it, unlike element 9 which would not make it possible to obtain the expected volume for a tyre comprising a single working layer. Thus, even having tangent moduli at 1% elongation significantly different in relation to elements 7 to 9, it was impossible to suspect that elements 1 to 6 could make it possible to achieve and contain the expected volume of the tyre under a predetermined inflation pressure.

[0247] The invention is not limited to the embodiments described above.

[0248] Specifically, it is possible in particular to implement the invention by using two carcass layers instead of a single carcass layer.

[0249] In addition, as for element 6 described above, it is also possible to envisage a variant in which the or each hooping filamentary reinforcing element consists of three polyester multifilament strands. Preferably, in this variant, the count of each polyester multifilament strand ranges from 300 tex to 500 tex, for example is equal to 440 tex, and the assembly twist of the three polyester multifilament strands around the common main axis ranges from 100 turns per metre to 250 turns per metre, for example is equal to 160 turns per metre. The twist coefficient K of the or each hooping filamentary reinforcing element of this variant ranges from 120 to 260, preferably from 130 to 200 and even more preferably from 130 to 160, for example is equal to 156.