Tire with carcass reinforcers, hooping reinforcers, and working reinforcers constituting a triangulation

Abstract

A passenger vehicle tire having hooping layer (71) that has a force at break FR per mm of axial width of the hooping layer at least equal to 35 daN/mm and has a secant extension modulus MA at least equal to 250 daN/mm, for an applied force F equal to 15% of FR. Working reinforcement (6) comprises a single working layer (61) the working reinforcers of which form, with the circumferential direction (YY′), an angle A.sub.T at least equal to 30° and at most equal to 50°. The carcass reinforcers of the at least one carcass layer (81) form, with the circumferential direction (YY′) and in the equatorial plane (XZ), an angle A.sub.C2 at least equal to 55° and at most equal to 80° and having an orientation opposite of that of angle A.sub.T of the working reinforcers so that the carcass reinforcers and the working reinforcers constitute a triangulation.

Claims

1. A tire for a passenger vehicle, comprising: a tread intended to come into contact with the ground and connected, at its axial ends, radially towards the inside, via two sidewalls, to two beads adapted to come into contact with a rim; a single working reinforcement, radially on the inside of the tread, and comprising at least one working layer comprising metal working reinforcers coated in an elastomeric material, wherein in each working layer, said working reinforcers of a respective working layer forming, with a circumferential direction of the tire, the same angle A.sub.T at least equal to 10°; a hoop reinforcement, radially on the inside of the tread, and radially adjacent to the working reinforcement, and comprising a single hooping layer comprising hoop reinforcers coated in an elastomeric material, said hoop reinforcers forming, with the circumferential direction, the same angle A.sub.F at most equal to 5°; a carcass reinforcement, joining the two beads together, radially on the inside of the working reinforcement and of the hoop reinforcement, and comprising at least one carcass layer comprising textile carcass reinforcers coated in an elastomeric material, wherein in each carcass layer, said carcass reinforcers of a respective carcass layer forming, with the circumferential direction, in the sidewalls throughout a portion extending radially between axial straight lines positioned respectively at radial distances of 3H/8 and of H/8 away from the radially outermost point of the tread, the same angle A.sub.C1 at least equal to 85°; wherein the tire comprises a crown reinforcement constituted by the working reinforcement and by the hoop reinforcement; and wherein the hooping layer has a force at break per mm of axial width of the hooping layer FR at least equal to 35 daN/mm, wherein the hooping layer has a secant extension modulus MA at least equal to 250 daN/mm, for an applied force F equal to 15% of the force at break FR of said hooping layer, wherein the working reinforcement comprises a single working layer the working reinforcers of which form, with the circumferential direction, the same angle A.sub.T at least equal to 30° and at most equal to 50°, and wherein in each carcass layer of the carcass reinforcement, the carcass reinforcers of a respective carcass layer form, with the circumferential direction and in the equatorial plane, the same angle A.sub.C2 at least equal to 55° and at most equal to 80° and having an orientation the opposite of that of the angle A.sub.T of the working reinforcers so that the carcass reinforcers, the hooping reinforcers, and the working reinforcers constitute a triangulation.

2. The tire according to claim 1, wherein the hooping layer has a force at break per mm of axial width of the hopping layer FR at least equal to 45 daN/mm.

3. The tire according to claim 1, wherein the hooping layer has a secant extension modulus MA at least equal to 300 daN/mm, for an applied force F equal to 15% of the force at break FR of said hooping layer.

4. The tire according to claim 1, wherein the hooping layer has a secant extension modulus MA at most equal to 1800 daN/mm, for an applied force F equal to 15% of the force at break FR of said hooping layer.

5. The tire according to claim 1, wherein the hooping layer has a secant extension modulus MA at most equal to 1600 daN/mm, for an applied force F equal to 15% of the force at break FR of said hooping layer.

6. The tire according to claim 1, wherein the hoop reinforcers have a diameter D and are spaced one from the next by an inter-reinforcer distance L, wherein the ratio D/L between the diameter D of each hoop reinforcer and the distance L separating two consecutive hoop reinforcers is at least equal to 1 and at most equal to 8.

7. The tire according to claim 1, wherein the hoop reinforcers have a diameter D and are spaced one from the next by an inter-reinforcer distance L, wherein the ratio D/L between the diameter D of each hoop reinforcer and the distance L separating two consecutive hoop reinforcers is at least equal to 2 and at most equal to 5.

8. The tire according to claim 1, wherein the hoop reinforcers are textile material hoop reinforcers and the textile material is aromatic polyamide, aliphatic polyamide, polyester, polyketone or cellulose.

9. The tire according to claim 1, wherein the hoop reinforcers are hybrid hoop reinforcers which comprise a combination of at least two distinct textile materials.

10. The tire according to claim 1, wherein the hoop reinforcers are metallic material hoop reinforcers.

11. The tire according to claim 1, wherein the working reinforcers of the working layer form, with the circumferential direction, an angle A.sub.T within a range of 35° to 45°.

12. The tire according to claim 1, wherein the carcass reinforcers of the at least one carcass layer form, with the circumferential direction and in the equatorial plane, an angle A.sub.C2 within a range of 60° to 70°.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In what follows, embodiments of the invention are described with the aid of the attached FIGS. 1 to 5 and of the examples described in Tables 1 to 5, all given by way of illustration.

DETAILED DESCRIPTION OF THE DRAWINGS

(2) FIG. 1 schematically shows the cross section of half a tire according to the invention, in a radial plane. As FIG. 1 shows, the tire 1 according to the invention comprises a tread 2, intended to come into contact with the ground and connected, at its axial ends 21, radially towards the inside, via two sidewalls 3, to two beads 4 intended to come into contact with a rim 5. The working reinforcement 6, radially on the inside of the tread 2, comprises a working layer 61 comprising metal working reinforcers (not depicted) coated in an elastomeric material, the said working reinforcers forming, with the circumferential direction YY′ of the tire, an angle A.sub.T at least equal to 10°. The hoop reinforcement 7, radially on the inside of the tread 2, and radially on the outside of the working reinforcement 6, comprises a single hooping layer 71 comprising hoop reinforcers coated in an elastomeric material, the said hoop reinforcers forming, with the circumferential direction YY′, an angle A.sub.F at most equal to 5°. The carcass reinforcement 8, joining the two beads 4 together, radially on the inside of the working reinforcement 6 and of the hoop reinforcement 7, comprises at least one carcass layer 81 comprising textile carcass reinforcers (not depicted) coated in an elastomeric material, the said carcass reinforcers forming, with the circumferential direction YY′, at least partially in the sidewalls 3, an angle A.sub.C2 at least equal to 85°.

(3) FIG. 2 shows a curve of the typical behaviour of a hooping layer, representing the tensile force F applied to the hooping layer, expressed in daN/mm, namely in daN per mm of axial width of the hooping layer, as a function of its deformation in extension DX/X. FIG. 2 in particular indicates the breaking force FR of the hooping layer and the secant extension modulus MA, measured at a force F equal to 0.15 times the breaking force FR and in a standardized manner characterizing the tensile stiffness of the hooping layer.

(4) FIG. 3 shows various curves of the tensile behaviour of a hooping layer, showing the variation in the tensile force per mm of axial width of the hooping layer F, expressed in daN/mm, as a function of its deformation in extension DX/X, for various types of hoop reinforcers.

(5) The curves in FIG. 3 were established for a hooping layer of a passenger vehicle tire of size 205/55 R 16, intended to be mounted on a 6.5J16 rim and to be inflated to a nominal pressure of 2.5 bar under “normal load” and 2.9 bar under “extra load”, in accordance with the ETRTO (European Tire and Rim Technical Organisation) standard. Curve A is the tensile curve for a hooping layer the hoop reinforcers of which are made up of 2, 144-tex strands (144/2) of PET with a twist of 290 turns per metre (290 tpm), the pitch P of the reinforcers being equal to 0.8 mm Curve B is the tensile curve for a hooping layer the hybrid hoop reinforcers of which are made up of a combination of a 334 tex thread count PET and a 330 tex thread count aramid, twisted together with a balanced twist of 210 turns per metre. Curve C is the tensile curve for a hooping layer the hoop reinforcers of which are made up of 2, 167-tex strands (167/2) of aramid, with a twist of 315 turns per metre (315 tpm), the pitch P of the reinforcers being equal to 0.8 mm Curve D is the tensile curve for a hooping layer the hoop reinforcers of which are made of metal cords made of steel made up of an assembly of 3, 0.26 mm metal threads, the pitch P of the reinforcers being equal to 0.85 mm. The straight line S is the threshold-line corresponding to a force per mm of axial width of hooping layer equal to 35 daN/mm, beyond which the forces at break per mm of axial width of hooping layer FR of the various hooping layers depicted lie.

(6) FIG. 4 shows the portion extending radially between axial straight lines positioned respectively at radial distances of 3H/8 and H/8 away from the radially outermost point of the tire tread.

(7) FIG. 5 shows a ratio of the hoop reinforcer diameter D to the hoop reinforcer inter-reinforcer distance L separating two consecutive hoop reinforcers.

(8) The invention was studied more particularly for a passenger vehicle tire of size 205/55 R 16, intended to be mounted on a 6.5J16 rim and to be inflated to a nominal pressure of 2.5 bar under “normal load” and 2.9 bar under “extra load”, in accordance with the ETRTO (European Tire and Rim Technical Organisation) standard. A reference tire of the prior art R, a comparative example E that does not fall within the scope of the invention and three alternative forms of embodiment of the invention, V1, V2 and V3, were compared.

(9) Table 1 below shows the characteristics of the hooping layers of comparative example E that does not fall within the scope of the invention and of the three alternative forms of embodiment of the invention V1, V2, V3 for a tire of size 205/55R16:

(10) TABLE-US-00001 TABLE 1 Characteristics of the hooping layers in 205/55R16 Force at break per mm of axial Secant Reinforcer Reinforcer Reinforcer width of the Deformation modulus MA Hoop Force at break diameter D pitch P Ratio hooping layer FR 15% of FR at 15% of FR at 15% of FR reinforcer (N) (mm) (mm) D/L (daN/mm) (daN/mm) (%) (daN/mm) Comparative PET 144/2 185 0.63 0.8 3.4 23 3.4 1.92 178 example E 290 tpm Alternative Aramid 167/2 550 0.67 0.8 5.2 69 10.3 0.98 1052 form V1 315 tpm Alternative PET 440/3 820 1.24 1.5 4.8 55 8.2 1.74 471 form V2 210 tpm Alternative Metal 475 0.58 0.85 2.1 66 8.4 0.54 1552 form V3 cord 3.26

(11) The hoop reinforcers of comparative example E consist of 2 strands of 144 tex PET (144/2) with a twist of 290 turns per metre (290 tpm). The hoop reinforcers of alternative form V1 consist of 2 strands of 167 tex aramid (167/2) with a twist of 315 turns per metre (315 tpm). The hoop reinforcers of alternative form V2 consist of 3 strands of 440 tex PET (440/3) with a twist of 210 turns per metre (210 tpm). The hoop reinforcers of alternative form V3 are metal cords consisting of 3 steel threads of diameter 0.26 mm assembled in a helix with a pitch of 14 mm.

(12) The inter-reinforcer distance L in the formula D/L is equal to the difference between the pitch P spacing between the reinforcers, measured between the axes of two consecutive reinforcers, and the diameter D of a reinforcer.

(13) It should be noted that, for the four types of hooping layers studied, the secant extension modulus values at 15% of the force at break of the hooping layer FR are equal to 178 daN/mm, for comparative example E, outside the scope of the invention, and respectively to 1052 daN/mm, 471 daN/mm and 1552 daN/mm for alternative forms of embodiment V1, V2 and V3, as compared with the threshold value of 250 daN/mm. The forces at break per mm of axial width of hooping layer FR of the hooping layers of comparative example E and of the alternative forms V1, V2 and V3 are respectively equal to 23 daN/mm, 69 daN/mm, 55 daN/mm, 66 daN/mm, as compared with the threshold value of 35 daN/mm Finally, the ratios D/L between the diameter D of a reinforcer and the inter-reinforcers distance L are respectively equal to 3.4, 5.2, 4.8 and 2.1.

(14) Table 2 below shows the types of reinforcers and the angles, formed by the said reinforcers, for the carcass, working and hoop reinforcements, for a passenger vehicle tire of size 205/55R16, in the case of a reference design of the prior art R, of the comparative example E not falling within the scope of the invention and of the three alternative forms of embodiment of the invention V1, V2, V3:

(15) TABLE-US-00002 TABLE 2 Types and angles of the reinforcers of carcass, working and hoop reinforcements in 205/55R16 Angle A.sub.C2 in Angle A.sub.T in Angle A.sub.F in the equatorial Type of the equatorial the equatorial Type of carcass plane working plane Type of hoop plane reinforcer (°) reinforcer (°) reinforcer (°) Reference of PET 144/2 90 Steel 2.30 +/−25 Nylon N140/2 0 the prior art R 290 tpm P = 1.2 mm 98 f/dm Comparative PET 144/2 67 Steel 2.30 −40 PET 144/2 0 example E 290 tpm P = 0.9 mm 290 tpm Alternative PET 144/2 67 Steel 2.30 −40 Aramid 167/2 0 form V1 290 tpm P = 0.9 mm 315 tpm Alternative PET 144/2 67 Steel 2.30 −40 PET 440/3 0 form V2 290 tpm P = 0.9 mm 210 tpm Alternative PET 144/2 67 Steel 2.30 −40 Metal 0 form V3 290 tpm P = 0.9 mm cord 3.26

(16) According to Table 2, the carcass reinforcement, in all configurations, is made up of a single carcass layer the carcass reinforcers of which are made up of 2, 144-tex strands (144/2) of PET with a twist of 290 turns per metre (290 tpm). For the reference of the prior art, the carcass reinforcers of the carcass layer form, with the circumferential direction and in the equatorial plane, an angle A.sub.C2 equal to 90°. For all the other configurations, the carcass reinforcers of the carcass layer form, with the circumferential direction and in the equatorial plane, an angle A.sub.C2 equal to 67°.

(17) The working reinforcement, for the reference of the prior art, is made up of two working layers the working reinforcers of which are metal cords made of steel containing 0.7% carbon, made up of 2 threads having a diameter equal to 0.30 mm, and laid at a pitch P equal to 1.2 mm, the said working reinforcers forming, with the circumferential direction, an angle equal to 25° and crossed from one working layer to the next. The working reinforcement, for all the other configurations studied, is made up of a single working layer the working reinforcers of which are metal cords made of steel containing 0.7% carbon, made up of 2 threads having a diameter equal to 0.30 mm, and laid at a pitch P equal to 0.9 mm, the said working reinforcers forming, with the circumferential direction, an angle equal to −40°.

(18) Table 3 hereinbelow presents theoretical results relating to the radial Rxx and shear Gxy stiffnesses, derived from analytical calculations, and theoretical burst pressures for a tire of size 205/55R16:

(19) TABLE-US-00003 TABLE 3 Stiffnesses and burst pressures calculated on 205/55R16 Radial stiffness Rxx as a Shear stiffness Gxy Burst relative value as a relative value pressure as a (%) (%) relative value (%) Reference of 100 100 100 the prior art R Comparative 32 11 36 example E Alternative 113 15 110 form V1 Alternative 80 14 82 form V2 Alternative — — — form V3

(20) The radial stiffness Rxx, expressed in daN/mm, is the radial force that needs to be applied to the tire in order to obtain a 1 mm radial displacement of its crown. The shear stiffness Gxy, expressed in daN/mm, is the axial force that needs to be applied to the tire in order to obtain a 1 mm axial displacement of its crown. The theoretical burst pressure of the tire, expressed in bar, is a characteristic of the ability of the tire to withstand pressure. The radial stiffness Rxx and shear stiffness Gxy characteristics, and the burst pressure, are expressed in the form of a relative value with respect to the corresponding characteristics of the prior-art reference R, considered as the base 100.

(21) According to Table 3, the alternative forms V1 and V2 exhibit values of radial stiffness Rxx and of burst pressure which are close to the values obtained for the prior-art reference R. By contrast, the shear stiffnesses Gxy are very much lower than the reference R.

(22) Table 4 hereinbelow shows the results of measurements and tests relating to the various tire designs studied, for a tire of size 205/55 R16:

(23) TABLE-US-00004 TABLE 4 Cornering stiffnesses, breaking energy and burst pressures measured on 205/55R16 Breaking Burst Cornering energy (J) for pressure stiffness an inflation of the tire as a relative pressure inflated with value (%) of 2.2 bar water (bar) Reference of the prior art R 100 >588 J >16 bar Comparative example E — <588 J <15 bar Alternative form V1 110 >588 J >16 bar Alternative form V2  98 >588 J >16 bar Alternative form V3 107 >588 J >16 bar

(24) The cornering stiffness Dz of a tire is the axial force applied to the tire in order to generate a 1° rotation of the tire about a radial direction. In Table 4, the cornering stiffness is expressed in the form of a relative value, namely as a percentage of the prior-art reference considered as base 100, for a tire of size 205/55R16, subjected to a load equal to 0.8 times its nominal load, within the meaning of the ETRTO standard, the said nominal load being equal to 4826 N.

(25) The perforation energy or breaking energy is measured by indentation by a cylindrical or polar obstacle having a diameter of 19 mm, the tire being inflated to a pressure equal to 2.2 bar (extraload condition). During the course of this test, the energy is measured at the moment that the polar perforates the crown and is compared against a minimum threshold value. For a tire of this size, the minimum threshold value that is to be respected to meet the so-called “Extraload” requirement of the standard cover is equal to 588 J.

(26) The burst-pressure test on the tire is carried out on a tire inflated with water. The minimum threshold value adapted to guarantee the tire's ability to withstand the pressure with a satisfactory margin of safety is taken as 16 bar.

(27) According to Table 4, in comparison with the results obtained for the reference R, the alternative forms of the invention V1, V2 and V3 exhibit a cornering stiffness Dz at the same level as the reference (between 98% and 110%), a breaking energy value likewise higher than the minimum threshold value of 588 J and a burst pressure higher than the minimum threshold value of 16 bar. These results are obtained for lightened tire structures comprising just one working layer rather than two working layers that are crossed with respect to one another in the case of the reference R. Comparative example E with one hooping layer, but which does not fall within the description of the patent, meets none of the breaking energy and burst pressure criteria. It should be noted that, despite the fact that the alternative forms V1, V2, V3 exhibit a range of calculated stiffnesses that is markedly offset in relation to the reference, the cornering stiffnesses actually measured are close to that of the reference R.

(28) Table 5 hereinbelow presents results of simulations for various tire sizes and various reinforcement designs: cornering stiffness Rxx, shear stiffness Gxy and theoretical burst pressure in terms of relative value in relation to the reference of the prior art in 205/55R16.

(29) TABLE-US-00005 TABLE 5 calculated stiffnesses and burst pressures for various sizes of passenger vehicle tire, in terms of relative value in relation to the reference 205/55R16 Angle A.sub.C2 in Angle A.sub.T in Radial Shear the equatorial Type of the equatorial Type of stiffness stiffness Burst Type of carcass plane working plane hoop Rxx Gxy pressure Dimension reinforcer (°) reinforcer (°) reinforcer (%) (%) (%) R 205/55R16 PET 144/2 90 Steel 2.30NF +/−25 Nylon N140/2 100 100 100 (reference) 290 tpm P = 1.2 mm 98 f/dm V1 205/55R16 PET 144/2 67 Steel 2.30NF −40 Aramid 167/2 113 15 110 290 tpm P = 0.9 mm 315 tpm V11 165/80R13 PET 144/2 60 Steel 2.30 −40 Aramid 167/2 113 14 124 290 tpm P = 0.9 mm 315 tpm V12 245/45R18 PET 144/2 69 Steel 2.30 −40 Aramid 167/2 113 15 100 290 tpm P = 0.9 mm 315 tpm V2 205/55R16 PET 144/2 67 Steel 2.30 −40 PET 440/3 80 14 82 290 tpm P = 0.9 mm 210 tpm V21 165/80R13 PET 144/2 60 Steel 2.30 −40 PET 440/3 80 14 92 290 tpm P = 0.9 mm 210 tpm V22 245/45R18 PET 144/2 69 Steel 2.30 −40 PET 440/3 80 14 74 290 tpm P = 0.9 mm 210 tpm

(30) Table 5 demonstrates that, with respect to the tire of size 205/55R16 described in the preceding paragraphs, the analytical calculations performed on tires of different sizes, such as, for example, on 165/80R13 (alternative forms V11 and V21) and on 245/45R18 (alternative forms V12 and V22), and which have the features of the invention, demonstrate that these offer compromises between radial stiffness Rxx and shear stiffness Gxy which are very similar to those obtained for alternative forms V1 and V2, the measurement results for which are defined in Table 4, these compromises moreover being entirely satisfactory with regard to the reference of the prior art R. It should be noted that the optimal choice of essential characteristics for tires of different sizes, falling within the context of the invention, may vary from one size to another. For example, while for 205/55R16, the optimum angles A.sub.C2, for the carcass reinforcers in the equatorial plane, and A.sub.T, for the working reinforcers, are respectively equal to 67° and −40°, for alternative form V21 in 165/80R13, the optimum angles A.sub.C2 and A.sub.T are 60° and −40°, and for alternative form V22 in 245/45R18, the optimum angles A.sub.C2 and A.sub.T are 69° and −40°.

(31) In the field of passenger vehicle tires, the invention is not restricted to the carcass reinforcers and to the working reinforcers described hereinabove. The carcass reinforcers may be made of any type of textile material such as, for example and non-exhaustively, PET, aramid, nylon or any combination of these materials. Working reinforcers are metal cords which may be of various assemblies such as, for example and non-exhaustively, cords of formula 3.26 (assembly of 3 threads, 0.26 mm in diameter), 3.18 (assembly of 3 threads, 0.18 mm in diameter), 2.30 (assembly of 2 threads, 0.30 mm in diameter, with a helix pitch of 14 mm) or mono-filaments 0.40 mm in diameter.

(32) The invention is not restricted to a tire for a passenger vehicle but may be extended, non-exhaustively, to tires intended to be fitted to 2-wheeled vehicles such as motorbikes, vehicles of the heavy duty or construction plant type.