Tire Comprising Working Layers Formed By Individual Wires

Abstract

Tire comprising a crown reinforcement formed of four working crown layers of reinforcing elements. In a meridian plane, the thickness of the four working crown layers, measured in the equatorial plane, is less than 5 mm, the reinforcing elements of the four working crown layers being individual metal wires of diameter less than 0.50 mm, the distance between the reinforcing elements, measured along the normal to the direction of the mean line of the wire, being strictly less than 1 mm, and the axial width of each of the four working crown layers being greater than 60% of the axial width of the tread.

Claims

1. A fire with radial carcass reinforcement for a vehicle of the heavy-duty type comprising a crown reinforcement comprising four working crown layers of reinforcing elements, crossed from one layer to the other, making with the circumferential direction angles of between 10 and 45, which is itself capped radially by a tread, the said tread being connected to two beads by two sidewalls, wherein, in a meridian plane, the thickness of the four working crown layers, measured in the equatorial plane, is less than 5 mm, wherein the reinforcing elements of the four working crown layers are individual metal wires of diameter less than 0.50 mm, wherein the distance between the reinforcing elements, measured along the normal to the direction of the mean line of the wire, is strictly less than 1 mm, and wherein the axial width of each of the four working crown layers is greater than 60% of the axial width of the tread.

2. The tire according to claim 1, wherein the diameter of the individual metal wires of the four working crown layers is greater than or equal to 0.25 mm.

3. The tire according to claim 1, a working crown layer of reinforcing elements comprising two skim layers between which the reinforcing elements are positioned, wherein the skim thickness measured in a radial direction on each side of a reinforcing element is less than 0.30 mm.

4. The tire according to claim 1, wherein the stiffness per unit width of each of the working crown layers is between 35 and 70 daN/mm.

5. The tire according to claim 1, wherein a layer of rubber compound is arranged between at least the ends of two working crown layers.

6. The tire according to claim 1, wherein the crown reinforcement is supplemented by a layer of circumferential reinforcing elements.

7. The tire according to claim 6, wherein the layer of circumferential reinforcing elements is radially positioned between two working crown layers.

8. The tire according to claim 6, wherein the axial widths of the working crown layers radially adjacent to a layer of circumferential reinforcing elements are greater than the axial width of said layer of circumferential reinforcing elements.

9. The tire according to claim 6, 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 in the range from 10 to 120 GPa and a maximum tangent modulus of less than 150 GPa.

10. 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 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 reinforcing elements of the working crown layer radially adjacent to it.

Description

[0069] Other advantageous details and features of the invention will become evident hereinbelow from the description of the embodiments of the invention, with reference to FIGS. 1 and 2, which represent:

[0070] FIG. 1: a meridian view of a diagram of a tire according to an embodiment of the invention,

[0071] FIG. 2: a schematic meridian view of a tire according to the prior art.

[0072] In order to make them easier to understand, the figures have not been drawn to scale. The figures represent only a half-view of a tire, which extends symmetrically with respect to the axis XX, which represents the circumferential median plane, or equatorial plane, of a tire.

[0073] In FIGS. 1 and 2, the tires 1, 21, of size 385/55 R 22.5, have an aspect ratio H/S equal to 0.55, H being the height of the tire 1 on its mounting rim and S its maximum axial width. The said tires 1, 21 comprise a radial carcass reinforcement 2, 22 anchored in two beads, not depicted in the figures. The carcass reinforcement 2, 22 is formed of a single layer of metal cords. They further comprise a tread 5, 25.

[0074] In FIG. 1, the carcass reinforcement 2 is hooped according to the invention by a crown reinforcement 4 formed radially, from the inside to the outside: [0075] of a first working layer 41 formed of metal wires oriented at an angle equal to 18, [0076] of a second working layer 42 formed of metal wires oriented at an angle equal to 18, [0077] of a third working layer 43 formed of metal wires oriented at an angle equal to 18, [0078] of a fourth working layer 44 formed of metal wires oriented at an angle equal to 18, [0079] of a protective layer 45 formed of 6.35 elastic metal cords parallel to the metal wires of the working layer 44.

[0080] The metal wires that make up the reinforcing elements of the four working layers are wires of the UHT type having a diameter of 0.35 mm Wires of SHT type or of higher grades may also be used. They are distributed within each of the working layers with a distance between the reinforcing elements, measured along the normal to the direction of the mean line of the wire, equal to 0.35 mm.

[0081] The axial width L.sub.41 of the first working layer 41 is equal to 300 mm.

[0082] The axial width L.sub.42 of the second working layer 42 is equal to 320 mm.

[0083] The axial width L.sub.43 of the third working layer 43 is equal to 300 mm.

[0084] The axial width L.sub.44 of the fourth working layer 44 is equal to 280 mm.

[0085] The axial width L.sub.45 of the protective layer 45 is equal to 220 mm.

[0086] The axial width of the tread, L5, is equal to 312 mm.

[0087] The thickness of the four working crown layers, measured in the equatorial plane, is equal to 3.3 mm and therefore less than 5 mm.

[0088] In FIG. 2, the carcass reinforcement 22 is hooped by a crown reinforcement 24 formed radially, from the inside to the outside: [0089] of a first triangulation layer 240 formed of non-wrapped 9.35 metal cords oriented at an angle equal to 50, [0090] of a first working layer 241 formed of non-wrapped 9.35 metal cords, which are continuous across the entire width of the ply, and oriented at an angle equal to 18, [0091] of a second working layer 242 formed of non-wrapped 9.35 metal cords which are continuous over the entire width of the ply, which are oriented with an angle equal to 18 and which are crossed with the metal cords of the layer 241, [0092] of a protective layer 243 formed of elastic 6.35 metal cords.

[0093] The inextensible 9.35 metal cords of the working layers 241 and 242 are distributed within each of the working layers with a distance between the reinforcing elements, measured along the normal to the direction of the mean line of the wire, equal to 1 mm.

[0094] The axial width L.sub.240 of the triangulation layer 240 is equal to 302 mm.

[0095] The axial width L.sub.241 of the first working layer 241 is equal to 318 mm.

[0096] The axial width L.sub.242 of the second working layer 242 is equal to 296 mm.

[0097] The axial width L.sub.243 of the protective layer 243 is equal to 220 mm.

[0098] The axial width of the tread, L5, is equal to 312 mm.

[0099] The thickness of the three crown layers 240, 241, 242, measured in the equatorial plane, is equal to 6.5 mm.

[0100] The combined mass of the four working layers 41, 42, 43 and 44, including the mass of the metal wires and of the skim compounds, thus amounts to 6.3 kg. The mass of the tire according to the invention, produced as depicted in FIG. 1, is equal to 61 kg.

[0101] The combined mass of the crown layers 240, 241, 242, including the mass of the metal cords and of the skim compounds, amounts to 12.6 kg. The mass of the tire produced as depicted in FIG. 2, is equal to 67 kg.

[0102] Tests were conducted on each of these tires, the tire produced in accordance with FIG. 2 being the reference tire.

[0103] First endurance tests were conducted on a test machine, each tire being made to roll in a straight line at a speed equal to the maximum speed rating (or speed index) specified for said tire under an initial load of 4000 kg which was progressively increased to reduce the duration of the test.

[0104] Other endurance tests were conducted on a test machine, a transverse force and a dynamic overload being applied to the tires in a cyclic manner. The tests were carried out for the tires according to the invention with conditions identical to those applied to the reference tires.

[0105] The tests thus carried out showed that the distances covered during each of these tests are substantially identical for the tires according to the invention and the reference tires. It is thus apparent that the tires according to the invention exhibit a performance in terms of endurance which is substantially the equivalent of that of the reference tires.

[0106] Other tests were carried out to evaluate the wear performance of the tires under actual conditions on vehicles. The rolling conditions, in particular the circuit followed, are determined so as to be representative of a particular type of use, in the circumstances use of the motorway type that is more disadvantageous as regards uneven wear. At the end of the running, the wear on the tires according to the invention was found to be more even, indicating potential for increased life.