Tire Having An Optimized Architecture

Abstract

Tire (1) for a vehicle, comprising a radially outermost working layer (41) which comprises at least one undulation (412) in line with a rib (26). The undulation (412) is such that it is radially on the outside of the points of the working layer (41) that are in line with the centre of the bottom face (243) of the circumferential groove (25) closest to the undulation (412) and that the minimum radial distance (do), between the radially outer surface of the radially outermost working layer (41) and the tread surface (21) is at least 1 mm less than the radial distance (dc) between the radially outer surface (ROS) of the radially outermost working layer (41) and the tread surface (21), which is the distance in line with the circumferential groove (25) closest to the undulation (412) concerned.

Claims

1. Tire for a vehicle, comprising: a tread which is adapted to come into contact with the ground via a tread surface; the tread surface comprising grooves, the grooves forming a space opening onto the tread surface and being delimited by at least two main lateral faces connected by a bottom face; at least one said groove being substantially circumferential, being referred to as a circumferential groove, having a width W, defined by the distance between the two lateral faces, at least equal to 5 mm, and a depth D, defined by the maximum radial distance between the tread surface and the bottom face, at least equal to 4 mm, at least one rib; the tire further comprising a crown reinforcement radially on the inside of the tread, and comprising a working reinforcement; the working reinforcement comprising at least one working layer; the at least one working layer extending radially from a radially inner surface to a radially outer surface; and the at least one working layer comprising reinforcing elements which are continuous from one axially outer edge of the working layer to the opposite axially outer edge, at least partially made of metal coated in an elastomer material, mutually parallel and which with the circumferential direction (XX) of the tire form an oriented angle the absolute value of which is at least equal to 15 and at most equal to 50, wherein the radially outermost working layer comprises at least one undulation in line with a rib, wherein the at least one said undulation in the radially outermost working layer is such that the working layer portion of the undulation is radially on the outside of the points of the working layer that are in line with the centre of the bottom face of the circumferential groove closest to said undulation, wherein the at least one said undulation in the radially outermost working layer is such that, in line with the rib on the tread surface comprising an undulation, the minimum radial distance, between the radially outer surface of the radially outermost working layer and the tread surface, is at least 1 mm less than the radial distance (dc) between the radially outer surface of the radially outermost working layer and the tread surface, which is the distance in line with the circumferential groove closest to undulation concerned, and wherein the minimum radial distance between the radially outer surface of the radially outermost layer of the crown reinforcement and the tread surface is at most equal to the depth D of the closest circumferential groove, increased by 2 mm.

2. The ire according to claim 1, wherein, in line with at least one said rib on the tread surface comprising an undulation, the minimum radial distance between the radially outer surface of the radially outermost working layer and the tread surface is at least 1.5 mm, less than the radial distance (dc) between the radially outer surface of the radially outermost working layer and the tread surface, which is the distance in line with the circumferential groove closest to the undulation concerned.

3. The tire according to claim 1, wherein, in line with at least one said rib on the tread surface comprising an undulation, the radial distance between the radially outer surface of the radially outermost working layer and the tread surface is at most 5 mm less than the radial distance between the points on the radially outer surface of the radially outermost working layer and the tread surface, which is the distance in line with the circumferential groove closest to the undulation concerned.

4. The tire according to claim 1, wherein the radial distance between the radially outer surface of the radially outermost working layer and the bottom face of the circumferential grooves is at least equal to 1 mm and at most equal to 5 mm.

5. The tire according to claim 1, wherein a said undulation of the radially outermost working layer is present in line with all the ribs on the tread surface.

6. The tire according to claim 1, wherein a said undulation of the radially outermost working layer is present only in line with the ribs on the tread surface that are axially closest to the median circumferential plane, on each side of this plane.

7. The tire having wear indicators according to claim 1, wherein the radial distance between the radially outer surface of the radially outermost layer of the crown reinforcement and the tread surface is at least equal to the radial distance between the tread surface and the radially outermost point of the wear indicators.

8. The tire according to claim 1, wherein the minimum radial distance between the radially outer surface of the radially outermost layer of the crown reinforcement and the tread surface is at least equal to the depth D of the closest circumferential groove, decreased by 2 mm.

9. The tire according to claim 1, wherein the depth D of the at least one circumferential groove is at least equal to 6 mm and at most equal to 20 mm.

10. The tire according to claim 1, wherein the radially outermost layer of the working reinforcement is comprised of reinforcing elements comprised of textile of a type involving a combination of aliphatic polyamide and aromatic polyamide, of polyethylene terephthalate or of rayon type, which are mutually parallel and form, with the circumferential direction of the tire, an angle B at most equal to 10, in terms of absolute value.

11. The tire according to claim 1, wherein at least one element of padding rubber, having a radial thickness at least equal to 0.3 mm, is in line with any said undulation of the radially outermost working layer.

12. The tire according to claim 11, the tread being comprised of a rubber compound, wherein the element of padding rubber is a rubber compound that has a dynamic loss tan 1, measured at a temperature of 10 C. and under a stress of 0.7 MPa at 10 Hz, at most equal to the dynamic loss tan 2 of the rubber material of which the tread is made, measured at a temperature of 10 C. and under a stress of 0.7 MPa at 10 Hz.

13. The tire according to claim 1, wherein the crown reinforcement consists of 2 working plies of opposite angles and one hooping ply.

14. The tire according to claim 1, wherein the elements of padding rubber are radially on the inside of all the working layers of the working reinforcement.

15. The tire according to claim 1, wherein, in line with at least one said rib on the tread surface comprising an undulation, the minimum radial distance between the radially outer surface of the radially outermost working layer and the tread surface is at least 2 mm less than the radial distance between the radially outer surface of the radially outermost working layer and the tread surface, which is the distance in line with the circumferential groove closest to the undulation concerned.

16. The tire according to claim 1, wherein, in line with at least one said rib on the tread surface comprising an undulation, the radial distance between the radially outer surface of the radially outermost working layer and the tread surface is at most 3 mm less than the radial distance between the points on the radially outer surface of the radially outermost working layer and the tread surface, which is the distance in line with the circumferential groove closest to the undulation concerned.

17. The tire according to claim 1, wherein the radial distance between the radially outer surface of the radially outermost working layer and the bottom face of the circumferential grooves is at least equal to 2 mm and at most equal to 4 mm.

18. The tire according to claim 1, wherein the radially outermost layer of the working reinforcement is comprised of reinforcing elements comprised of textile, of the aliphatic polyamide, aromatic polyamide type, of a type involving a combination of aliphatic polyamide and aromatic polyamide, of polyethylene terephthalate or of rayon type, which are mutually parallel and form, with the circumferential direction of the tire, an angle B at most equal to 10, in terms of absolute value.

19. The tire according to claim 11, the tread being comprised of a rubber compound, wherein the element of padding rubber is a rubber compound that has a dynamic loss tan 1, measured at a temperature of 10 C. and under a stress of 0.7 MPa at 10 Hz, at most 30% less than the dynamic loss tan 2 of the rubber material of which the tread is made, measured at a temperature of 10 C. and under a stress of 0.7 MPa at 10 Hz.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The features and other advantages of the invention will be understood better with the aid of FIGS. 1 to 5, the said figures being drawn not to scale but in a simplified manner so as to make it easier to understand the invention:

[0065] FIG. 1 is part of a tire, particularly the architecture, the tread and a circumferential groove (25) and a rib (26) thereof.

[0066] FIG. 2 depicts a meridian section through the crown of a tire according to the invention, with an undulation under a rib (26), and illustrates the various radial distances do, d1, D, du, dc and an element of padding rubber (6) capable of creating an undulation (412) in the radially outermost working layer.

[0067] FIG. 3 depicts a meridian section through the crown of a tire according to the invention, with an undulation under each rib (26), it being possible for each rib to have a different radial thickness and axial width, as well as radial distance df.

[0068] FIG. 4 depicts a meridian section through the crown of a tire according to the invention, with an undulation under each of the ribs (26) axially closest to the median circumferential plane.

[0069] FIG. 5 depicts a meridian section through the crown of a tire according to the invention with an undulation under certain ribs (26), the elements of padding rubber all being radially on the inside of the working layers and radially on the outside of the carcass layer (8) constituting the carcass reinforcement.

[0070] Numerous combinations of arrangements and dimensions of the undulations under the ribs are possible. The figures and the description do not attempt to describe all of these explicitly.

DETAILED DESCRIPTION OF THE DRAWINGS

[0071] FIG. 1 depicts a perspective view of a part of the crown of a tire. A cartesian frame of reference (XX, YY, ZZ) is associated with each meridian plane. The tire comprises a tread 2 which is intended to come into contact with the ground via a tread surface 21. Arranged in the tread are grooves and circumferential grooves 25 of width W possibly differing from one circumferential groove to another, each having main profiles 241 and 242 and a bottom face 243. The tire further comprises a crown reinforcement 3 comprising a working reinforcement 4 and here, by way of example, a hoop reinforcement 5. The working reinforcement comprises at least one working layer and here, for example, two working layers 41 and 42 each comprising mutually parallel reinforcing elements. The radially outer surface ROS of the radially outermost working layer 41 is also depicted.

[0072] FIG. 2 depicts a schematic meridian section through the crown of the tire according to the invention. It illustrates in particular an undulation of the radially outermost working layer 41 and an element of padding rubber 6 positioned in line therewith. FIG. 2 also illustrates the following radial distances: [0073] D: the depth of a groove, which is the maximum radial distance between the tread surface 21 and the bottom face 243 of the circumferential groove 25, [0074] dc: the radial distance between the radially outer surface ROS of the radially outermost working layer 41 and the tread surface 21, which is the distance in line with the centre of the bottom face 243 of the circumferential groove 25 closest to the said undulation 412. [0075] df: the radial distance between the tread surface (21) and the radially outermost point of the wear indicator (7). [0076] do: the radial distance between the radially outer surface ROS of the radially outermost working layer 41 and the tread surface at the undulation 412. [0077] du: the minimum radial distance between the radially outer surface (ROS) of the radially outermost layer of the crown reinforcement 3 and the tread surface 21. [0078] d1: the radial distance between the radially outer surface ROS of the radially outermost working layer 41 and the bottom face 243 of the circumferential grooves 25.

[0079] FIG. 3 depicts a schematic meridian section through the crown of the tire according to the invention. It illustrates in particular, df: the radial distance between the tread surface 21 and the radially outermost point of the wear indicator 7.

[0080] A meridian section through the tire is obtained by cutting the tire on two meridian planes. This section is used to determine the various radial distances, the centre of the bottom faces of the grooves and of the circumferential grooves.

[0081] The invention was carried out on a tire A of size 305/30 ZR20 intended to be fitted to a passenger vehicle. The depths D of the grooves of the tread pattern are comprised between 4 and 7 mm and equal to 7 mm in the case of the circumferential grooves, for widths W which are variable in the case of the grooves and equal to 15 mm in the case of the circumferential grooves. The crown reinforcement is made up of two working layers the reinforcing elements of which make an angle of + or 38 with the circumferential direction and of a hooping layer the reinforcing elements of which make an angle of + or 3 with the circumferential direction. The reinforcing elements of the working layer are continuous metallic cords.

[0082] The radially outermost working layer is undulated under the 5 ribs of the tread. The radial distance (do) between the radially outer surface (ROS) of the radially outermost working layer (41) and the tread surface is 2 mm less than the radial distance (dc) between the radially outer surface (ROS) of the radially outermost working layer (41) and the tread surface, which is the distance in line with the centre of the bottom face (243) of the circumferential groove (25) closest to the undulation in the case of the 3 axially inner ribs, and 1 mm in the case of the 2 axially innermost ribs. Likewise, the axial width of the undulations is equal to 21 mm for the 3 axially inner ribs and equal to 7 mm for the 2 axially outermost ribs. The radial distance (d1) between the radially outer surface (ROS) of the radially outermost working layer (41) and the bottom face (243) of the circumferential grooves (25) is comprised between 2 mm and 3.5 mm.

[0083] The undulations are created using elements of padding rubber laid in line with the 5 ribs of the tread. These elements of padding rubber are radially on the outside of the carcass layer and radially on the inside of the two working layers thereby ensuring a flat geometry under the crown, optimal carcass layer geometry and optimal coupling between the said working layers.

[0084] Tires A were compared with tires B of the same size, having the same characteristics except that the working layers were not undulated.

[0085] The padding compound used to create the undulations has a dynamic loss tan 1, measured at a temperature of 10 C. and under a stress of 0.7 MPa at 10 Hz, 60% less than that of the rubber material of which the tread is made.

[0086] The improvement in terms of rolling resistance was evaluated on a standard machine for measurements standardized in accordance with ISO 2850:2009. The tests reveal a more than 10% improvement by comparison with the reference tire B.

[0087] Furthermore, a measurement of the characteristic Dz of the Pacejka tire behaviour model well known to those skilled in the art reveals a 13% improvement in this characteristic for a pressure of 2.6 b, hot. The improvement in dry grip varies between 1 and 5% depending on the stress loading conditions.

[0088] The tires were also fitted to a sports-type vehicle and tested on a winding circuit capable of generating significant transverse loadings. A professional driver, trained in assessing tires, compares tires A according to the invention with tires B according to the prior art and according to a rigourous testing process, under the same temperature conditions and ground running conditions, without knowing the features of the tires being tested, repeating the measurement. The driver assigns scores to the tires. In all the tests performed, tires A according to the invention outclass tires B in terms of vehicle behaviour, roadholding, on dry ground and in terms of grip. Furthermore, the behavioural performance is more constant during a behaviour test on a vehicle fitted with a tire according to the invention than with a tire according to the prior art.