TIRE COMPRISING THREE WORKING LAYERS

Abstract

The tire includes a crown reinforcement which is formed of three working crown layers of reinforcing elements. The reinforcing elements of the two radially outermost working layers are crossed from one layer to the other, making with the circumferential direction angles of between 20 and 45 the circumferential direction, of the reinforcing elements of the radially innermost working layer being between 15 and 20. The reinforcing elements of the two radially innermost working layers are oriented in the same direction with respect to the circumferential direction. The difference between the angles of the reinforcing elements of the radially innermost working layers is greater than 10. The widths of the two radially outermost working layers are greater than the 0.7 times the width of the tread, and the width of the radially innermost working layer is strictly less than 0.7 times the width of the tread.

Claims

1- A tire with a radial carcass reinforcement for a vehicle of the heavy duty type comprising a crown reinforcement comprising three working crown layers of reinforcing elements, itself capped radially by a tread, said tread being connected to two beads by two sidewalls, wherein the reinforcing elements of the two radially outermost working layers are crossed from one layer to the other, making with the circumferential direction angles of between 20 and 45, in that the angles, formed with the circumferential direction, of the reinforcing elements of the radially innermost working layer are between 15 and 20, wherein the reinforcing elements of the two radially innermost working layers are oriented in the same direction with respect to the circumferential direction, wherein the difference between the angles of the reinforcing elements of the radially innermost working layers is greater than 10, wherein the widths of the two radially outermost working layers are greater than 0.7 times the width of the tread, and wherein the width of the radially innermost working layer is strictly less than 0.7 times the width of the tread.

2- The tire according to claim 1, wherein the difference between the absolute values of the angles of the reinforcing elements of the radially outermost working layers is greater than 45.

3- The tire according to claim 1, wherein the reinforcing elements of at least one working layer are cords comprising an internal layer of M internal thread(s) and an external layer of N external threads, and wherein the external layer is wound around the internal layer.

4- The tire according to claim 3, wherein M=1 or 2 and N=5, 6, 7, 8 or 9.

5- The tire according to claim 3, wherein at least one of the internal or external threads of each cord exhibits a mechanical strength at break R expressed in MPa such that R41802130D with D being the diameter of the thread expressed in mm.

6- The tire according to claim 1, wherein the reinforcing elements of the three working layers are cords comprising an internal layer of M internal thread(s) and an external layer of N external threads, the external layer being wound around the internal layer, with M=1 or 2 and N=5, 6, 7 or 8, and wherein at least one of the internal or external threads of each cord exhibits a mechanical strength at break R expressed in MPa such that R41802130D with D being the diameter of the thread expressed in mm.

7- The tire according to claim 1, wherein the stiffness per unit width of each of the working crown layers is between 50 and 80 daN/mm.

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

9- 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 20 and 45 and in the same direction as the angle formed by the reinforcing elements of the working crown layer radially adjacent to it.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0059] In order to make it easier to understand, the FIGURE is not drawn to scale. The FIGURE shows only a half-view of a tire which extends symmetrically about the axis XX which represents the circumferential median plane, or equatorial plane, of a tire.

DETAILED DESCRIPTION OF THE ENABLING EMBODIMENT

[0060] In the FIGURE, the tire 1, of size 315/80 R 22.5 Y, has an aspect ratio H/S equal to 0.80, H being the height of the tire 1 on its mounting rim and S being its maximum axial width. The tire 1 comprises a radial carcass reinforcement 2 anchored in two beads, not shown in the FIGURE. The carcass reinforcement 2 is formed of a single layer of metal cords. They further comprise a tread 5.

[0061] In the FIGURE, the carcass reinforcement 2 is hooped in accordance with the disclosure by a crown reinforcement 4 formed radially, from the inside to the outside: [0062] of a first working layer 41 formed of metal cords oriented at an angle equal to 18, [0063] of a second working layer 42 formed of metal cords oriented at an angle equal to 30, [0064] of a third working layer 43 formed of metal cords oriented at an angle equal to 22, [0065] of a protective layer 44 formed of E18.23 elastic metal cords parallel to the metal threads of the working layer 43.

[0066] The metal cords that make up the reinforcing elements of the three working layers are cords of formula 9.30 of the UHT type having a diameter of 1.23 mm. Threads of SHT type 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 thread, equal to 0.80 mm.

[0067] The axial width L.sub.41 of the first working layer 41 is equal to 85 mm.

[0068] The axial width L.sub.42 of the second working layer 42 is equal to 119 mm.

[0069] The axial width L.sub.43 of the third working layer 43 is equal to 109 mm.

[0070] The axial width L.sub.44 of the protective layer 44 is equal to 88 mm.

[0071] The axial width of the tread, L.sub.5, is equal to 130 mm.

[0072] The combined mass of the three working layers 41, 42, 43 and of the protective layer 44, including the mass of the metal cords and of the skim compounds, thus amounts to 5.8 kg.

[0073] The tire according to the disclosure is compared against a reference tire of the same size which differs from the tire according to the disclosure in terms of its crown reinforcement which is formed radially, from the inside to the outside: [0074] of a triangulation layer 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 65, [0075] of a first working layer formed of non-wrapped inextensible 11.35 metal cords which are continuous across the entire width of the ply, oriented at an angle of 26, [0076] of a second working layer formed of non-wrapped inextensible 11.35 metal cords which are continuous across the entire width of the ply, oriented at an angle of 18 and crossed with the metal cords of the first working layer, [0077] of a protective layer formed of elastic 18.23 metal cords.

[0078] The inextensible 11.35 metal cords of the working layers of the reference tire 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 thread, equal to 1 mm.

[0079] The combined mass of the working layers of the reference tire, of the protective layer and of the triangulation layer, including the mass of the metal cords and of the skim compounds, amounts to 6.6 kg.

[0080] Tests have been conducted with tires produced according to the disclosure as depicted in FIG. 1, and with the reference tire.

[0081] 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 tire (the speed index) under an initial load of 4000 kg progressively increased in order to reduce the duration of the test.

[0082] 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 disclosure under conditions identical to those applied to the reference tires.

[0083] The tests thus carried out showed that the distances covered during each of these tests are substantially identical for the tires according to the disclosure and the reference tires. It is thus apparent that the tires according to the disclosure exhibit performance in terms of endurance which is substantially the equivalent of that of the reference tires when running on bituminous surfaces.

[0084] Three tests aimed at reproducing use of worksite type were also conducted. For each of these tests, the measurements illustrated are referenced to a base 100 for the reference tire.

[0085] A first test involved running over an obstacle to simulate the presence of a rock. The values measured correspond to the height of the obstacle, expressed in mm, that causes a breakage of the crown tread block of the tire.

TABLE-US-00001 Reference 100 Disclosure >140

[0086] The test was stopped for the tire according to the disclosure without having observed the slightest loss of pressure.

[0087] The second test involved pressing cylindrically shaped polars onto the tread of the tire. The values express the energy required to cause the crown tread block to break. The results are expressed with reference to a base 100 which corresponds to the value measured for the reference tire.

TABLE-US-00002 Reference 100 Disclosure 128

[0088] The third test is a test of crown puncturing by running over an obstacle that simulates the presence of a nail. The values express the range of angles of orientation of the nail with respect to the plane of the ground that carry a risk of puncturing. The smaller the range, the lower the probability of puncturing.

TABLE-US-00003 Reference 100 Disclosure 80

[0089] Regarding this third test, the superiority of the tires according to the disclosure as compared with the reference tires can be interpreted as being due to the fact that the distances between the reinforcing elements of one and the same layer are closer together.