TIRE COMPRISING REINFORCING ELEMENTS IN THE FORM OF LAMINATED STRIPS

Abstract

The tire comprises a crown reinforcing zone comprising a ply of strips, each forming an angle of less than or equal to 10° with the circumferential direction. Each reinforcing strip is formed by a laminate made up of n inner composite layers comprising low-modulus oriented fibres parallel to each other, the angle of which with the circumferential direction is, in absolute terms, less than or equal to 10°, together with m outer composite layers on either side of the inner composite layers, comprising high-modulus oriented fibres parallel to each other, the angle of which with the circumferential direction is, in absolute terms, strictly greater than 10°. The high- and low-modulus fibres are coated with a polymer matrix.

Claims

1.-15. (canceled)

16. A tire comprising a carcass ply connecting two beads via two sidewalls, the carcass ply being surmounted radially toward an outside of the tire by a crown reinforcing zone which is itself surmounted radially toward the outside of the tire by a tread, the crown reinforcing zone comprising a plurality of reinforcing strips arranged in at least one ply of reinforcing strips, the reinforcing strips of each ply being arranged so that they are juxtaposed axially and each forms an angle of less than or equal to 10° with the circumferential direction, and the circumferential direction corresponding to a periphery of the tire and being defined by a direction of running of the tire, wherein each reinforcing strip is made up of a laminate consisting of n>1 inner composite layer or layers, wherein if n>1, the inner composite layers are juxtaposed radially with each other, each inner composite layer comprising oriented fibers parallel to each other, the angle of which to the circumferential direction is less than or equal to 10° in absolute terms, the oriented fibers of each inner composite layer having a modulus of extension of less than or equal to 30 GPa and being coated with a polymer matrix, and the inner composite layer or layers being framed radially on either side, respectively, by m≥1 outer composite layers, wherein if m>1, the outer composite layers are juxtaposed radially with each other on either side of the inner composite layer or layers, each outer composite layer comprising oriented fibers parallel to each other, the angle of which with the circumferential direction is greater than 10° in absolute terms, and the oriented fibers of each outer composite layer having a modulus of extension greater than or equal to 55 GPa and being embedded in a polymer matrix.

17. The tire according to claim 16 further comprising at least two plies of reinforcing strips, a first ply of reinforcing strips radially on an inside and a second ply of reinforcing strips radially on an outside, the reinforcing strips of each first and second ply being arranged so as to be juxtaposed axially and each forms an angle of less than or equal to 10° with the circumferential direction.

18. The tire according to claim 17, wherein a mean overlap between the reinforcing strips of the first and second plies is greater than or equal to 20%.

19. The tire according to claim 17, wherein a mean overlap between the reinforcing strips of the first and second plies is less than or equal to 80%.

20. The tire according to claim 16, wherein each ply of reinforcing strips is embedded in a matrix of rubber compound which, when cross-linked, has a secant extension modulus at 10% elongation greater than or equal to 10 MPa.

21. The tire according to claim 16, wherein the angle formed by the oriented fibers of each inner composite layer with the circumferential direction is, in absolute terms, less than or equal to 5°.

22. The tire according to claim 16, wherein the angle formed by the oriented fibers of each outer composite layer with the circumferential direction ranges, in absolute terms, from 30° to 60°.

23. The tire according to claim 16, wherein n ranges from 1 to 20.

24. The tire according to claim 16, wherein m ranges from 1 to 8.

25. The tire according to claim 16, wherein a sum of the angles formed with the circumferential direction by the oriented fibers of all the outer composite layers arranged radially on any one side of the inner composite layer or layers of each laminate is equal in absolute terms to a sum of the angles formed with the circumferential direction by the oriented fibers of all the outer composite layers arranged radially on the other side of a mid-plane of the laminate.

26. The tire according to claim 16, wherein a sum of the angles formed with the circumferential direction by the oriented fibers of the outer composite layers of each laminate is equal to 0°.

27. The tire according to claim 16, wherein the angle of the oriented fibers of two outer composite layers positioned symmetrically on each side of the inner composite layer or layers is identical.

28. The tire according to claim 16, wherein the angle of the oriented fibers of two outer composite layers positioned symmetrically on each side of the inner composite layer or layers is identical in absolute terms but of opposite sign.

29. The tire according to claim 16, wherein an absolute value of a ratio of each angle formed by the oriented fibers of an outer composite layer of each laminate to the angle formed by the oriented fibers of each other outer composite layer of the laminate ranges from 0.8 to 1.2.

30. The tire according to claim 16, wherein the polymer matrix of each composite layer of laminate comprises a thermosetting polymer or a thermoplastic polymer.

Description

[0071] The invention will be understood better on reading the following description, which is given purely by way of non-limiting example and with reference to the drawings, in which:

[0072] FIG. 1 is a schematic perspective depiction of a tyre according to the prior art;

[0073] FIG. 2 is a sectional view of a tyre according to the invention;

[0074] FIG. 3A is a schematic representation of a crown reinforcing zone of the tyre according to the invention as shown in FIG. 2;

[0075] FIG. 3B is a schematic representation of a reinforcing zone according to a second embodiment of the invention; and

[0076] FIG. 4 is an exploded view of a strip of the crown reinforcing zone of FIG. 3A.

[0077] A frame of reference X, Y, Z corresponding to the usual respectively axial (along the Y direction), radial (along the Z direction) and circumferential (along the X direction) orientations of a tyre has been represented in the figures.

[0078] A “longitudinal direction” or “circumferential direction” means a direction which corresponds to the periphery of the tyre and which is defined by the direction in which the tyre runs.

[0079] An “axial direction” means a direction parallel to the axis of rolling of the tyre.

[0080] The “tread” of a tyre means a quantity of elastomeric compound delimited by lateral surfaces and by two main surfaces, one of which is intended to come into contact with a road surface when the tyre is rolling.

[0081] The “sidewall” of a tyre means a lateral surface of the tyre, said surface being disposed between the tread of the tyre and a bead of this tyre.

[0082] The “bead” of a tyre means a part of the tyre that is intended to be seated on a wheel rim.

[0083] FIG. 1 illustrates a perspective view of a tyre, partially cut away layer by layer, for a conventional passenger vehicle according to the prior art. A carcass reinforcement 2 connected to the beads 5 around bead wires 7 extends along the sidewalls 3 and the crown 4. The carcass reinforcement 2 is formed of radially oriented reinforcers. The reinforcers are textile cords (for example made of nylon, rayon, polyester). At the crown of the tyre, the carcass is surmounted by two crossed triangulation layers 20, 21 and a belt 22. The two crossed crown triangulation layers 20, 21 comprise reinforcers oriented at an angle of substantially between 20 and 40 degrees on either side of the circumferential direction of the tyre. Metal cords constitute the reinforcers of the crossed layers 20, 21. A layer 8 of elastomeric sealing compound covers the internal cavity of the tyre. A tread 6 surmounts the whole. This architecture involves several semi-finished layers, requiring a manufacturing method with numerous intermediate steps. The numerous layers render the tyre relatively heavy.

[0084] FIG. 2 shows a tyre 1 according to the invention, comprising a carcass ply 2 connecting two beads 5 via two sidewalls 3. The carcass ply 2 is surmounted radially towards the outside of the tyre by a crown 4, which comprises a crown reinforcing zone 10 and is itself surmounted radially towards the outside of the tyre by a tread 6. Thus the crown reinforcing zone 10 is arranged radially between the tread 6 and the carcass ply 2. The carcass ply 2 extends from one bead 5 to the other, passing through the sidewalls 3 and the crown 4.

[0085] The crown 4 is, with the exception of the crown reinforcing zone 10, devoid of any ply reinforced by filamentary reinforcing elements arranged substantially parallel to one another and embedded in a matrix of rubber compound. The filamentary reinforcing elements of such reinforced plies excluded from the crown 4 of the tyre 1 comprise the metal filamentary reinforcing elements and the textile filamentary reinforcing elements. In this instance, the crown 4 is made up of the crown reinforcing zone 10 and the tread 6.

[0086] The tyre 1 is, radially between the carcass ply 2 and the crown 4, devoid of any ply that is reinforced by filamentary reinforcing elements arranged substantially parallel to one another and embedded in a matrix of rubber compound. The filamentary reinforcing elements of such reinforced plies excluded from in between the carcass ply 2 and the crown 4 comprise the metal filamentary reinforcing elements and the textile filamentary reinforcing elements.

[0087] The crown reinforcing zone 10 comprises a plurality of reinforcing strips 14 arranged in at least one ply 12 of strips. The strips 14 of each ply 12 of strips are arranged in an axially juxtaposed manner. In this instance, the crown reinforcing zone 10 comprises at least two plies of strips, a first ply of strips radially on the inside and a second ply of strips radially on the outside. Each strip 14 forms an angle of less than or equal to 10° with the circumferential direction Z, preferably an angle of less than or equal to 5° with the circumferential direction Z, and in this case, very preferably, substantially zero with the circumferential direction.

[0088] Each ply 12 of strips 14 is embedded in a matrix 13 of rubber compound which, in the cross-linked state, has a secant extension modulus at 10% elongation greater than or equal to 10 MPa, and preferably less than or equal to 30 MPa, and more preferably less than or equal to 20 MPa, and in this case equal to 12 MPa.

[0089] In this instance, the matrix 13 of rubber compound used here is a high-stiffness compound, typically of the type for tyre crown plies, based on natural rubber, carbon black (around 75 phr), antioxidant, a vulcanization system with a high sulphur content (around 7 phr), and the customary vulcanization additives. The adhesion between the strips 14 and the matrix 13 of rubber compound is provided by an adhesive of the RFL type which has been deposited, in a known manner, on the strips 14.

[0090] In the embodiment of FIG. 3A, the strips 14 of each ply of strips 14 are arranged with a lateral offset of each of the two plies 12 of strips 14 of around half a width of the strip. Such an arrangement has the effect of covering the bridges of rubber compound of the first ply with the strips that make up the second ply of strips. The bridges of rubber compound between the strips of the first ply of strips are thus positioned substantially at the middle of the respective widths of the strips of the adjacent ply of strips. In this example, the radially outer ply of strips has one less winding in order to compensate for the effect of the lateral offset. In a ply 12 of strips, the quincuncial positioning of the strips 14 is provided, for example, by a first winding-off starting at a given azimuth, and a second winding-off with an identical path starting at 180 degrees. In a variant, the strips 14 are positioned by first winding-off in one given axial direction, followed by second winding-off in the opposite axial direction.

[0091] Each strip 14 has an axial width of 15 mm and the rubber bridge separating two axially adjacent strips of any one ply of strips is equal to 1 mm in this case. The space in the radial (or thickness) direction between two successive plies of strips occupied by the matrix 13 of rubber compound is preferably between 0.05 and 2 mm, more preferably between 0.1 and 1 mm. For example, thicknesses of 0.2 to 0.8 mm have proved to be perfectly suitable for reinforcing a tyre. The thickness of the matrix 13 of rubber compound between the two plies of strips 12 is 0.2 mm in this case, this relatively small thickness allowing excellent coupling between the plies of strips, owing to the moderate value of the secant extension modulus at 10% of elongation MA10 of the matrix 13 of rubber compound.

[0092] The mean overlap between the strips 14 of the first and second plies 12 of strips is greater than or equal to 20%, preferably greater than 40% and less than or equal to 80%, preferably equal to 60%, and in this case equal to 46%.

[0093] The crown reinforcing zone 10 is, with the exception of the plies 12 of strips 14 embedded in the matrix 13 of rubber compound, devoid of any ply that is reinforced by filamentary reinforcing elements arranged substantially parallel to one another and embedded in a matrix of rubber compound. The filamentary reinforcing elements of such reinforced plies excluded from the crown reinforcing zone 10 of the tyre 1 comprise the metal filamentary reinforcing elements and the textile filamentary reinforcing elements. In this instance, the crown reinforcing zone 10 is made up of the plies 12 of strips 14 embedded in the matrix 13 of rubber compound.

[0094] Each reinforcing strip 14 of the plies of strips 14 is composed of a laminate 16 made up of at least 3 composite layers 17. In this instance, the laminate 17 is made up of n≥1 inner composite layer(s) 17a and m≥1 outer composite layers 17b, 17c, the inner composite layer or layers 17a being framed radially on either side, respectively, by one or more outer composite layers 17b and one or more outer composite layers 17c.

[0095] Advantageously, n ranges from 1 to 20, preferably from 1 to 12, and more preferably from 1 to 6, and in this case n=6. Advantageously, m ranges from 1 to 8, or preferably from 1 to 4, and more preferably m=1 or 2, and in this case m=2.

[0096] In this case, the n inner composite layers 17a are radially juxtaposed with each other, and the m outer composite layers 17b, 17c are, on either side of the inner composite layers 17a, radially juxtaposed with each other.

[0097] Each inner composite layer 17a comprises oriented fibres 15 parallel to each other, at an angle to the circumferential direction Z which is, in terms of absolute value, less than or equal to 10°, preferably less than or equal to 5°, and in this case substantially zero.

[0098] Each outer composite layer 17b, 17c comprises oriented fibres 15′, 15″ respectively, parallel to each other, at an angle to the circumferential direction Z which is, in terms of absolute value, strictly greater than 10°, preferably in the range from 30° to 60° and this case equal, in absolute terms, to 45°. In this embodiment, the angles of the oriented fibres 15′, 15″ of two outer composite layers 17b, 17c arranged symmetrically on each side of the inner composite layers 17a are identical. In another embodiment, not illustrated but exhibiting the same mechanical performance in respect of noise and ease of application in the tyre manufacturing process, the angles of the oriented fibres 15′, 15″ of two outer composite layers 17b, 17c arranged symmetrically on each side of the inner composite layers 17a are identical in absolute terms but of opposite sign.

[0099] In this case, the oriented fibres 15′ of the outer composite layer 17b1 radially on the inside are at an angle equal to +45°. The oriented fibres 15′ of the outer composite layer 17b2 radially on the outside and in contact with the inner composite layers 17a are at an angle equal to −45°. The oriented fibres 15″ of the outer composite layer 17c1 radially on the inside and in contact with the inner composite layers 17a are at an angle equal to −45°. The oriented fibres 15″ of the outer composite layer 17c2 radially on the outside are at an angle equal to +45°.

[0100] The absolute value of the ratio of each angle formed by the oriented fibres 15′, 15″ of each outer composite layer 17b, 17c of the laminate 16 to the angle formed by the oriented fibres 15′, 15″ of each other outer composite layer 17b, 17c of the laminate 16 ranges from 0.8 to 1.2, preferably from 0.9 to 1.1, and more preferably is equal to 1.

[0101] Additionally, the sum of the angles formed with the circumferential direction by the oriented fibres 15′, 15″ of the outer composite layers 17b and 17c of the laminate 16 is equal to 0°.

[0102] Furthermore, the sum of the angles formed with the circumferential direction Z by the oriented fibres 15′ of all the outer composite layers 17b arranged radially on any one side of the inner composite layers 17a of the laminate 16, 0 in this case, is equal in value, and also equal in absolute terms in this case, to the sum of the angles formed with the circumferential direction Z by the oriented fibres 15″ of all the outer composite layers 17c arranged radially on the other side of the mid-plane P of the laminate 16, which sum is also 0 in this case.

[0103] The oriented fibres 15 of each inner composite layer 17a are low-modulus and have a modulus of extension less than or equal to 30 GPa, whereas the oriented fibres 15′, 15″ of each outer composite layer 17b, 17c are high-modulus and have a modulus of extension greater than or equal to 55 GPa. The oriented fibres 15, 15′, 15″ are coated with a polymer matrix.

[0104] The composite strips 14 may be made from preimpregnated composite layers NTPT ThinPreg 450™ or NTPT ThinPreg 402™ (which can be obtained notably by applying the method described in document WO 2016/198171).

[0105] The preimpregnated composite layers are laid raw or unpolymerized at the desired lamination angles and form a width the dimension of which is greater than the width of the strips. The laminated sheet is cut into raw or unpolymerized strips of a desired width. The raw strips are wound off onto a drum of large diameter (i.e. 2 metres in diameter). The strips are cured under vacuum (−850 mbar) and under pressure (5 bar) using the usual curing peripherals (such as peel ply, bleeder cloth, microperforated or non-perforated release film, vacuum-bagging film, etc.). According to another embodiment, the laminated width is laid on a large-diameter drum and cured under vacuum (−850 mbar) and under pressure (5 bar) using the usual curing peripherals. After curing, the sheet is cut into strips. As a preference, the strips have a thickness less than or equal to 1 mm, and more preferably less than or equal to 0.7 mm.

[0106] The polymer matrix of each composite layer of the laminate 16 comprises a thermosetting polymer or a thermoplastic polymer, used respectively by itself or as a blend with other polymers. Preferentially, the polymer matrix may be selected from among the thermosetting resins of the polyepoxide, unsaturated polyester, vinyl ester, ester cyanate, bismaleimide, type, polyurethanes, and a blend of such resins, or else from thermoplastic resins such as polyesters (PET, PBT, PEN, PBN), polyamides (nylon, aramid), polyimides, polyethersulfones, polyphenylenesulfones, polyketones (PK, PEEK). Of the aforementioned resins, those that are particularly suitable are thermosetting resins having a glass transition temperature greater than or equal to 160° C., and thermoplastic resins having a melting point greater than or equal to 180° C. Note that reinforcing fillers (silica, carbon black) or thermoplastic fillers (Orgasol by Arkema) or elastomeric fillers (Kane Ace by Kaneka) may be added to the above resins. In this instance, the polymer matrix used is a thermosetting polymer matrix consisting of a polyepoxide resin marketed by the NTPT company under the trade name “ThinPreg 402™”.

[0107] Particularly well-suited to the invention are composite layers that have a surface density of around 200 g/m.sup.2 and a pre-curing thickness of around 0.2 mm.

[0108] As a preference, use is made of finer layers having a surface density less than or equal to 80 g/m.sup.2, more preferably this density ranging from 18 g/m.sup.2 to 80 g/m.sup.2, and a pre-curing thickness less than 0.06 mm.

[0109] The person skilled in the art will know how to adapt the number of composite layers according to the surface density of these composite layers.

[0110] The low-modulus oriented fibres 15 of each inner composite layer 17a are chosen from among polyester fibres, cellulose fibres, aliphatic polyamide fibres, and mixtures of these fibres. The low-modulus oriented fibres 15 of each inner composite layer 17a comprise polyethylene terephthalate fibres, reference 755-220 tex, made by DuraFiberTech, having a modulus of extension equal to 10 GPa. Preferably, the polyethylene terephthalate oriented fibres predominate, that is to say represent more than 50% of the fibres of any one inner composite layer 17a. More preferably still, the oriented fibres 15 of each inner composite layer are made up of polyethylene terephthalate fibres. The polymer matrix/oriented fibres 15 ratio by volume in each inner composite layer 17a ranges from 25/75 to 55/45, and in this case is equal to 50/50.

[0111] The high-modulus oriented fibres 15′, 15″ of each outer composite layer 17b, 17c are chosen from among glass fibres, carbon fibres, aromatic polyamide or copolyamide fibres, basalt fibres, quartz fibres, and mixtures of these fibres. In this case, the high-modulus oriented fibres 15′, 15″ comprise carbon fibres, reference HS40, made by Mitsubishi, having a modulus of extension equal to 455 GPa. Preferably, the carbon fibres are predominant, meaning that they represent more than 50% of the fibres of any one outer composite layer 17b, 17c. More preferably still, in this case, the oriented fibres of each outer composite layer 17b, 17c of the laminate 16 are made up of carbon fibres. The polymer matrix/oriented fibres ratio by volume in each outer composite layer 17b, 17c ranges from 30/70 to 90/10, and in this case is around 50/50.

[0112] In other possible variants, the high-modulus oriented fibres 15′, 15″ comprise glass fibres. Preferably, the glass fibres are predominant, meaning that they represent more than 50% of the fibres of any one outer composite layer 17b, 17c. More preferably still, the oriented fibres of each outer composite layer 17b, 17c of the laminate 16 are made up of glass fibres. In these variants, the polymer matrix/fibre ratio by volume in each composite layer of laminate ranges from 30/70 to 70/30, and is preferably around 45/55.

[0113] In yet another variant, the high-modulus oriented fibres 15′, 15″ comprise aramid fibres, basalt fibres or quartz fibres.

[0114] FIG. 3B illustrates another embodiment of a crown reinforcing zone 10 of a tyre according to the invention. According to this embodiment, the crown reinforcing zone 10 is made up of four plies 12 of strips 14 embedded in a matrix 13 of rubber compound. In this embodiment, the mean overlap between the strips of each ply of strips overlapping the strips of the ply of strips radially on the inside thereof is greater than or equal to 20%, preferably greater than or equal to 40%, and less than or equal to 80%, preferably less than or equal to 60%.

[0115] Comparative Tests

[0116] The tyre 1 according to the invention, described above (also denoted by the reference P1 in the following text), a tyre PT1 according to the prior art WO2017/013575 (FIG. 8) comprising strips BT1, and three control tyres PT2, PT3 and PT4 whose characteristics are described below, comprising strips BT2, BT3, BT4 respectively, were compared.

[0117] The strips of the tyre PT1 according to the prior art WO2017/013575 are made with a PET (polyethylene terephthalate) matrix incorporating filamentary reinforcing elements (aramid, plied yarns made up of 2 strands of 167 Tex twisted together with a twist of 315 tpm) at 0°. They have a thickness of 0.5 mm.

[0118] The tyre PT2 is identical to the tyre P1 except for the fact that the oriented fibres 15 of the inner composite layers 17a are fibres with a high modulus of more than 55 GPa, in this case type H high-modulus glass fibres marketed by the Owens Corning company, having a modulus of extension equal to 80 GPa.

[0119] The tyre PT3 is identical to the tyre P1 except in that the crown reinforcing zone of the tyre PT3 comprises a hooping ply comprising a filamentary hoop reinforcing element (aramid, plied yarn consisting of two 167 tex strands twisted together with a twist of 315 tpm) at 0°, and in that each laminate 16 is made up of 6 composite layers comprising type H high-modulus glass fibres marketed by the Owens Corning company, parallel to each other and forming an angle of −45° or +45° with the circumferential direction, so that the composite layers are such that they are arranged two by two, radially on either side of the mid-plane at an equal distance therefrom, so that the angle formed with the circumferential direction by the fibres of the first of the composite layers of the pair of layers concerned, which is located on one side of the mid-plane, is the opposite of the angle formed with the circumferential direction by the fibres of the second of the composite layers of the pair of layers concerned, which is located on the other side of the mid-plane. Each laminate 16 comprises no low-modulus fibres and no fibres oriented at an angle of less than 10° in absolute terms.

[0120] The tyre PT4 is identical to the tyre P1 except for the fact that the oriented fibres 15 of the inner composite layers 17a are fibres with a high modulus of more than 55 GPa, in this case type H high-modulus glass fibres marketed by the Owens Corning company, and in that the fibres 15′, 15″ of the outer composite layers 17b, 17c are fibres with a low modulus of less than 30 GPa, in this case 220 tex PET fibres, reference 755, made by DuraFiberTech, having a modulus of extension equal to 10 GPa.

[0121] Mass of the Tyre

[0122] The tyre was weighed using scales.

[0123] An index of 100 is attributed arbitrarily to the mass of a control tyre. An index lower than 100 for the tyres compared with the control tyre indicates that the compared tyres have a lower mass than the control tyre, something which is highly favourable for rolling resistance performance.

[0124] Cornering Stiffness

[0125] In order to measure drift thrust, each tyre was mounted on a wheel of appropriate size and inflated to 2.4 bar. The tyre was driven at a speed of 80 km/h on a suitable automatic machine (machine of the “flat-track” type marketed by MTS). The load, denoted “Z”, was varied for a slip angle of 1 degree, and the cornering rigidity or drift thrust denoted “D” (corrected for the thrust at zero drift) was measured in the known way by recording, by means of sensors, the transverse load on the wheel as a function of this load Z; the drift thrust is the gradient of the D(Z) curve at the origin. An index of 100 is attributed arbitrarily to the control tyre. An index higher than 100 for the tyres compared with the control tyre indicates that the compared tyres have a cornering stiffness that is improved by comparison with the control tyre.

[0126] Noise Generated

[0127] The noise known as “coast-by” noise represents the acoustic annoyance suffered by a resident when a vehicle passes by at constant speed on ground having an intermediate particle size, such as a motorway: a vehicle is made to pass by at a given speed, with the gearbox in neutral and the engine switched off, over a standardized measurement area (ISO DIS 10 844 standard); microphones record the noise levels in dB(A).

[0128] Conformability

[0129] Conformability is evaluated by measuring the force required to provide the necessary radial and circumferential deformations for moulding the tyre in its curing mould. The tyre PT1 is denoted ‘=’. The greater the force, the less conformable the tyre is (denoted ‘-’ or ‘ - -’). The smaller the force, the more conformable the tyre is (denoted ‘+’ or ‘++’).

[0130] Hooping

[0131] To estimate the hooping capacity, the extension stiffnesses of the strips in the circumferential direction are calculated. As this extension stiffness increases, and if it is above 100 (the extension stiffness of the strip BT1), the hooping of the tyre will improve. Conversely, as this extension stiffness decreases, and if it is below 100, the hooping of the tyre will be poorer.

[0132] Table 1 below summarizes all the results for a comparison of the mass, the cornering stiffness, the noise generated, and the ease of using the tyre manufacturing method (conformability).

TABLE-US-00001 TABLE 1 BT1 BT2 BT3 BT4 14 Hooping 100 165 6 165 115 PT1 PT2 PT3 PT4 P1 Mass 100 98 96 98 98 Cornering stiffness 100 103 97 100 102 Noise generated 100 100 98 100 96 Conformability − − + − ++

[0133] It can be seen that the tyre P1 according to the invention exhibits improved performance in terms of extension and shear by comparison with the tyres PT1, these improvements being demonstrated by the results for hooping and cornering stiffness.

[0134] Additionally, because of the use of low-modulus reinforcing elements forming an angle of less than or equal to 10° with the circumferential direction, the tyres PT3 and P1 generate little noise by comparison with tyres PT1, PT2 and PT4, in which the reinforcing elements forming an angle of less than or equal to 10° with the circumferential direction have a high modulus. The observed differences of 2 and 4 points in the generated noise performance index are significant.

[0135] Finally, because of the use of reinforcing elements in the form of inner composite layers in which the oriented fibres form an angle of less than or equal to 10° with the circumferential direction, the hooping provided by the strips 14 of the tyre P1 is better than that provided by the strips BT1 of the tyre PT1, and greatly superior to that provided by the strips BT3 of the tyre PT3, which requires the use of a supplementary hooping ply.