Tire having improved dynamic properties

Abstract

Tire comprising a crown reinforcement formed of at least two working crown layers of reinforcing elements, crossed from one layer to the other making with the circumferential direction angles comprised between 10 and 45. A first layer S of polymer compound is in contact with at least one working crown layer and in contact with the carcass reinforcement, the first layer S of polymer compound extending axially as far as at least the axial end of the tread, the first layer S of compound polymer compound is made up of a filled elastomer blend having a macro dispersion coefficient Z greater than or equal to 65 and a maximum tan() value, denoted tan()max, less than 0.100 and its complex dynamic shear modulus G*, measured at 10% and 60 C. on the return cycle is greater than 1.35 MPa.

Claims

1. Tire with a radial carcass reinforcement comprising a crown reinforcement formed of at least two working crown layers of reinforcing elements, crossed from one layer to the other making with the circumferential direction angles comprised between 10 and 45, a first layer of polymer compound being in contact with at least one working crown layer and in contact with the carcass reinforcement, said first layer of polymer compound extending axially as far as at least the axial end of the tread, said tread radially capping the crown reinforcement and being connected to two beads by two sidewalls, wherein said first layer of polymer compound is made up of a filled elastomeric compound having a macro dispersion coefficient greater than or equal to 65 and a maximum tan () value, denoted tan()max, less than 0.100 and wherein the complex dynamic shear modulus, measured at 10% and 60 C. on the return cycle, of said first layer of polymer compound is greater than 1.35 MPa and less than 2 Ma.

2. The tire according to claim 1, wherein the crown reinforcement comprises at least one layer of circumferential reinforcing elements.

3. The tire according to claim 2, wherein the layer of circumferential reinforcing elements is placed radially between two working crown layers.

4. The tire according to claim 3, wherein the axial widths of the working crown layers radially adjacent to the layer of circumferential reinforcing elements are greater than the axial width of said layer of circumferential reinforcing elements.

5. The tire according to claim 4, wherein the working crown layers adjacent to the layer of circumferential reinforcing elements are, on each side of the equatorial plane and in the immediate axial continuation of the layer of circumferential reinforcing elements, coupled over an axial width and then decoupled by profiled elements made of rubber compound at least over the remainder of the width that said two working layers have in common.

6. The tire according to claim 2, wherein the reinforcing elements of at least one layer of circumferential reinforcing elements are metallic reinforcing elements having a secant modulus at 0.7% elongation comprised between 10 and 120 GPa and a maximum tangent modulus less than 150 GPa.

7. The tire according to claim 1, wherein the elastomer compound of the first layer of polymer compound comprises, by way of reinforcing filler, at least carbon black used at a content comprised between 10 and 50 phr, and wherein the carbon black has a BET specific surface area greater than 90 m.sup.2/g.

8. The tire according to claim 1, wherein the elastomer compound of the first layer of polymer compound comprises a blend of carbon black, of BET specific surface area greater than 90 m.sup.2/g, and of a white filler, wherein the reinforcing filler is used at a content comprised between 10 and 60 phr, and wherein the ratio of carbon black to white filler is greater than 2.7.

9. The tire according to claim 1, the tire comprising a second layer of polymer compound axially in contact with the first layer S of polymer compound radially between the carcass reinforcement and the radially innermost layer of reinforcing elements of the crown reinforcement, wherein said second layer of polymer compound is made up of a filled elastomer compound having a macro dispersion coefficient greater than or equal to 65 and a maximum tan () value, denoted tan()max, less than 0.100 and wherein the complex dynamic shear modulus, measured at 10% and 60 C. on the return cycle, of said second layer of polymer compound is greater than 1.35 MPa.

10. The tire according to claim 9, wherein the complex shear modulus, measured at 10% and 60 C. on the return cycle, of the second layer of polymer compound is less than 2 MPa.

11. The tire according to claim 9, wherein the elastomer compound of the second layer of polymer compound comprises, by way of reinforcing filler, at least carbon black used at a content comprised between 10 and 50 phr, and wherein the carbon black has a BET specific surface area greater than 90 m.sup.2/g.

12. The tire according to claim 9, wherein the elastomer compound of the second layer of polymer compound comprises a blend of carbon black, of BET specific surface area greater than 90 m.sup.2/g, and of a white filler, wherein the reinforcing filler is used at a content comprised between 10 and 60 phr, and wherein the ratio of carbon black to white filler is greater than 2.7.

13. The tire according to claim 9, wherein the elastomer compound of the second layer of polymer compound comprises, by way of reinforcing filler, at least carbon black used at a content comprised between 10 and 50 phr, and wherein the carbon black has a BET specific surface area greater than or equal to 120 m.sup.2/g.

14. The tire according to claim 9, wherein the elastomer compound of the second layer of polymer compound comprises a blend of carbon black, of BET specific surface area greater than or equal to 120 m.sup.2/g, and of a white filler, wherein the reinforcing filler is used at a content comprised between 10 and 60 phr, and wherein the ratio of carbon black to white filler is greater than 2.7.

15. The tire according to claim 1, wherein the reinforcing elements of the working crown layers are inextensible.

16. The tire according to claim 1, wherein the crown reinforcement is supplemented radially on the outside by at least one additional ply, referred to as a protective ply, of reinforcing elements referred to as elastic elements, which are oriented with respect to the circumferential direction at an angle of between 10 and 45 in the same direction as the angle formed by the inextensible elements of the working ply radially adjacent to it.

17. The tire according to claim 1, wherein the crown reinforcement further comprises a triangulation layer formed of metallic reinforcing elements making angles greater than 60 with the circumferential direction.

18. The tire according to claim 1, wherein the elastomer compound of the first layer of polymer compound comprises, by way of reinforcing filler, at least carbon black used at a content comprised between 10 and 50 phr, and wherein the carbon black has a BET specific surface area greater than or equal to 120 m.sup.2/g.

19. The tire according to claim 1, wherein the elastomer compound of the first layer of polymer compound comprises a blend of carbon black, of BET specific surface area greater than or equal to 120 m.sup.2/g, and of a white filler, wherein the reinforcing filler is used at a content comprised between 10 and 60 phr, and wherein the ratio of carbon black to white filler is greater than 2.7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further details and advantageous features of the invention will become apparent hereinafter from the description of exemplary embodiments of the invention, with reference to FIGS. 1 and 2 which depict:

(2) FIG. 1: a schematic meridian view of a tire according to a first embodiment of the invention,

(3) FIG. 2: a schematic meridian view of a tire according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) In order to make them easier to understand, the Figures are not shown to scale. The figures depict only half a view of a tire which extends symmetrically with respect to the axis XX that represents the circumferential meridian plane, or equatorial plane, of a tire.

(5) In FIG. 1, the tire 1, of size 315/70 R 22.5, has an aspect ratio H/S equal to 0.70, H being the height of the tire 1 on its mounting rim and S being its maximum axial width. The said tire 1 comprises a radial carcass reinforcement 2 fixed in two beads, not shown in the FIG. The carcass reinforcement is formed of a single layer of metal cords. This carcass reinforcement 2 is hooped by a crown reinforcement 4 formed radially, from the inside to the outside: of a first working layer 41 formed of non-wrapped inextensible 9.28 metal cords, which are continuous across the entire width of the ply, and oriented at an angle equal to 24, of a layer of circumferential reinforcing elements 42, formed of 2123 steel metal cords, of the bimodulus type, of a second working layer 43 formed of non-wrapped inextensible 9.28 metal cords, which are continuous across the entire width of the ply, oriented at an angle equal to 24, and crossed with the metal cords of the layer 41, of a protective layer 44 formed of elastic 6.35 metal cords.

(6) The crown reinforcement is itself capped by a tread 6.

(7) The maximum axial width W of the tire is equal to 317 mm.

(8) The axial width L.sub.41 of the first working layer 41 is equal to 252 mm.

(9) The axial width L.sub.43 of the second working layer 43 is equal to 232 mm. The difference between the widths L.sub.41 and L.sub.43 is equal to 15 mm.

(10) As for the axial width L.sub.42 of the layer of circumferential reinforcing elements 42, this is equal to 194 mm.

(11) The last crown ply 44, referred to as the protective ply, has a width L.sub.44 equal to 124 mm.

(12) According to the invention, a first layer S of rubber compound is placed between the carcass reinforcement 2 and the first working layer 41.

(13) In FIG. 2, the tire 1 differs from the one depicted in FIG. 1 in that a second layer G axially extends the first layer S, radially between the carcass reinforcement 2 and the first working layer 41.

(14) Tests have been conducted with various tires S1 and S2 produced according to the invention. The tire S2 is produced in accordance with the depiction of FIG. 1, and the tire S1 has no layer of circumferential reinforcing elements. These tires according to the invention S1 and S2 are compared against a reference tire T1 having no layer of circumferential reinforcing elements and of which the complex dynamic shear modulus G*, measured at 10% and 60 C. on the return cycle, of the said first layer S of polymer compound is less than 1.35 MPa.

(15) The various compounds used for the first layer S are listed below.

(16) TABLE-US-00001 Compound R1 Compound 1 NR 100 100 Black N330 35 Black N234 35 Silica 165G 5 Antioxidant 0.7 1.7 (6PPD) Stearic acid 1.4 0.5 Zinc oxide 2.1 5 Sulphur 2.15 3.13 Accelerator CBS 1 1.10 Retarder CTP 0.08 PVI) MA.sub.10 (MPa) 3.4 3.5 tan ().sub.max 0.074 0.080 P60 (%) 11.3 12 G* 10% at 60 C. 1.25 1.43 (return cycle) Z coefficient 60 65 Bound rubber 27.5 48.1

(17) The values for the constituent ingredients are expressed in phr (parts by weight per hundred parts of elastomer).

(18) Reference tire T1 has a first layer S made of the compound R1.

(19) The tires according to the invention S1 and S2 have a first layer S made of the compound 1.

(20) The first endurance tests were run on a test machine that forced each of the tires to run in a straight line at a speed equal to the maximum speed rating prescribed for the said tire (the speed index) under an initial load of 4000 kg progressively increased in order to reduce the duration of the test.

(21) It was found that all the tires tested exhibited substantially comparable results.

(22) Other endurance tests were conducted on a test machine that cyclically imposed a transverse loading and a dynamic overload on the tires. The tests were carried out for the tires according to the invention under conditions identical to those applied to the reference tires.

(23) The distances covered varied from one type of tire to another, failures occurring as a result of degradation of the rubber compounds at the ends of the working layers. The results are set out in the table which follows with reference to a base 100 fixed for the reference tire T1.

(24) TABLE-US-00002 Tire T1 Tire S1 Tire S2 100 125 135

(25) These results show that the first layer S according to the invention, of which the complex dynamic shear modulus G*, measured at 10% and 60 C. on the return cycle, is greater than 1.35 MPa, allows a very significant improvement in the endurance performance and, more particularly, the cornering stiffness properties of the tire, even when a layer of circumferential reinforcing elements is present.

(26) The scope of protection of the invention is not limited to the examples given hereinabove. The invention is embodied in each novel characteristic and each combination of characteristics, which includes every combination of any features which are stated in the claims, even if this feature or combination of features is not explicitly stated in the examples.