Pneumatic tire comprising reinforcing elements in the form of multi-layer tapes

Abstract

A tire includes a carcass ply, two beads, two sidewalls, and a crown reinforcing zone. The carcass ply connects the two beads by way of the two sidewalls. The crown reinforcing zone is positioned radially external to the carcass ply. The crown reinforcing zone includes a plurality of reinforcing strips disposed in at least two layers. The reinforcing strips are coated in an elastomeric composition. A mean overlap between the reinforcing strips of the two layers is greater than 40%. The reinforcing strips are made of a thermoplastic film having a modulus greater than 0.9 GPa, and preferably greater than 2 GPa, in a main direction and in a transverse direction.

Claims

1. A tire comprising: a carcass ply; two beads; two sidewalls; a tread; and a crown reinforcing zone, wherein the carcass ply connects the two beads by way of the two sidewalls, wherein the crown reinforcing zone is positioned radially external to the carcass ply and radially internal to the tread, wherein the crown reinforcing zone includes a plurality of reinforcing strips disposed in at least a first row and a second row such that: the first row is positioned radially internal to the second row, and the reinforcing strips of the first row and second row are disposed in a substantially circumferential direction, with the reinforcing strips of the first row being disposed in a staggered manner relative to the reinforcing strips of the second row, wherein the reinforcing strips of the first and second rows are coated in an elastomeric composition and are separated by bridges of the elastomeric composition, wherein a mean overlap between the reinforcing strips of the first row and second row is greater than 40%, and wherein the reinforcing strips are made of a thermoplastic film having a modulus greater than 0.9 GPa in a main direction and in a transverse direction.

2. The tire according to claim 1, wherein the modulus of the thermoplastic film is greater than 2 GPa.

3. The tire according to claim 1, wherein an aspect ratio of the thermoplastic film is greater than or equal to 5.

4. The tire according to claim 1, wherein the thermoplastic film is made of: a thermally stabilized, biaxially drawn polyester, or a thermally stabilized, monoaxially drawn polyester, or a polyamide.

5. The tire according to claim 1, wherein the reinforcing strips are integrated in a matrix made of an elastomeric matrix mixture.

6. The tire according to claim 5, wherein the elastomeric matrix mixture is a diene elastomeric mixture.

7. The tire according to claim 5, wherein the elastomeric matrix mixture has a modulus at 10% elongation in a range of from 3 MPa to 20 MPa.

8. The tire according to claim 5, wherein the elastomeric matrix mixture has a modulus at 10% elongation of greater than 20 MPa.

9. The tire according to claim 5, wherein the matrix includes circumferential filamentary reinforcing elements integrated therein.

10. The tire according to claim 5, wherein an interface between the reinforcing strips and the elastomeric matrix mixture is adhesive.

11. The tire according to claim 1, wherein circumferential filamentary reinforcing elements are integrated in the thermoplastic film forming the reinforcing strips.

12. The tire according to claim 1, wherein the reinforcing strips are composite strips, wherein each composite strip includes: a strip of thermoplastic film, an alignment of reinforcing threads arranged in a vicinity of the strip of thermoplastic film, and a matrix of an elastomeric mixture into which the strip of thermoplastic film and the alignment of reinforcing threads are integrated.

13. The tire according to claim 12, wherein the elastomeric mixture is a diene elastomeric mixture.

Description

DESCRIPTION OF THE FIGURES

(1) All the embodiment details are given in the description which follows, which is supplemented by FIGS. 1 to 9, which are given solely by way of non-limiting examples and in which:

(2) FIG. 1 is a schematic perspective depiction of a tire according to the prior art;

(3) FIG. 2 is a sectional view of a tire according to the invention;

(4) FIG. 3A is a schematic depiction of an example of a tire crown reinforcing element according to the invention, having alignments of strips;

(5) FIG. 3B is a schematic depiction of another example of a tire crown reinforcing element according to the invention, having alignments of strips;

(6) FIG. 4A is a schematic depiction of another example of a crown reinforcing element having an alignment of textile reinforcing cords and two alignments of thermoplastic strips;

(7) FIG. 4B is a schematic depiction of another example of a crown reinforcing element according to the invention, made up of an alignment of textile reinforcing cords and two alignments of thermoplastic strips;

(8) FIG. 5 is a schematic depiction of an example of a crown reinforcing element having alignments of strips disposed on either side of a row of textile reinforcing cords;

(9) FIG. 6 is a schematic depiction of an example of a crown reinforcing element made up of alignments of textile reinforcing cords and thermoplastic strips, disposed in alternation;

(10) FIG. 7A is a schematic depiction of an example of a composite strip according to the invention, made up of textile reinforcing cords, thermoplastic strips and a diene matrix;

(11) FIG. 7B is a schematic depiction of a variant of a composite strip, in which the arrangement of textile cords and thermoplastic strips is reversed;

(12) FIG. 8 is a schematic depiction of a two-element composite strip in which the textile reinforcing cords are integrated in a thermoplastic strip;

(13) FIG. 9 is a schematic depiction of an example of a tire crown reinforcing element in which composite strips are aligned.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

(14) In the present document, the expression overlap of the strips means an arrangement in which the strips of a radially outer layer overlap the strips of the radially inner layer, that is to say that the projection in the radial direction of one strip onto the strip at a lower level is not zero. The percentage of overlap may vary depending on the embodiment. This overlap forms a linkage between the layers, creating cohesion of the whole of the reinforcing zone of the crown. This linkage allows in particular transmission of shear forces between the layers.

(15) A longitudinal direction or circumferential direction means a direction which corresponds to the periphery of the tire and which is defined by the direction in which the tire rolls.

(16) An axial direction means a direction parallel to the rolling axis of the tire.

(17) The expression Shore A hardness means the hardness of the compositions after curing, which is assessed in accordance with the ASTM D 2240-86 standard.

(18) A tire means all types of resilient tread, whether or not it is subjected to an internal pressure.

(19) The tread of a tire means a quantity of elastomeric mixture delimited by lateral surfaces and by two main surfaces, one of which is intended to come into contact with a road surface when the tire is being driven on.

(20) The sidewall of a tire means a lateral surface of the tire, said surface being disposed between the tread of the tire and a bead of this tire.

(21) The bead of a tire means a part of the tire that is intended to be seated on a wheel rim.

(22) In the present document, a carcass, or carcass ply, means a reinforcing structure for a tire in the form of a layer made up of a matrix of elastomeric material in which filaments or threads, generally textile, are arranged in a substantially parallel and longitudinal alignment. The carcass ply is advantageously manufactured flat, in great lengths, then cut to the appropriate dimensions for the manufacture of a tire to which the carcass ply is suited.

(23) The nominal secant moduli (or apparent stress, in MPa) are measured in second elongation (i.e. after an accommodation cycle at the extension rate provided for the measurement itself) at 10% elongation (denoted MA 10) and at 100% elongation (denoted MA 100) at 23 C.2 C., and under normal hygrometry conditions.

(24) FIG. 1 illustrates a perspective view of a passenger vehicle tire, partially cut away layer by layer, according to the prior art. A carcass reinforcement 2 connected to the beads 5 about bead wires 7 extends along the sidewalls 3 and the crown 4. The carcass reinforcement 2 is formed of radially oriented reinforcing elements. The reinforcing elements are textile cords (for example made of nylon, rayon, polyester). At the crown of the tire, the carcass is surmounted by two crossed triangulation layers 20, 21 and a belt 22. The two crossed crown triangulation layers 20, 21 comprise reinforcing elements oriented at an angle of substantially between 20 and 40 degrees on either side of the circumferential direction of the tire. The reinforcing elements of the crossed layers generally form metal cords. A layer 8 of sealing elastomeric mixture covers the internal cavity of the tire. A tread 6 surmounts the whole. This architecture involves several semi-finished layers, requiring a manufacturing method with numerous intermediate steps. The numerous layers render the tire relatively heavy.

(25) FIG. 2 shows a tire 1 according to the invention, comprising sidewalls 3 surmounted by a crown 4 and a carcass 2 extending from one bead 5 to the other, passing via the sidewalls 3 and the crown 4. At the crown 4, more specifically between the carcass 2 and the tread 6, the tire provides a crown reinforcing zone 10 provided with circumferential strips, that is to say strips oriented substantially at 0 with respect to the circumferential direction. Various embodiments of the strips are described below with regard to FIGS. 3 to 9.

Embodiments of the Strips

(26) FIGS. 3A and 3B illustrate a first embodiment of a crown zone 10 according to the invention. According to this embodiment, the strips 12 made of a thermoplastic film are disposed side by side at an angle substantially in the region of 0 degree, and more broadly at an angle less than substantially 12 degrees to the circumferential direction. The whole is embedded in a matrix 13 made up of an elastomeric mixture, preferably a diene elastomeric mixture. The staggered arrangement of the strips is realized for example by first traverse winding starting at a given azimuth, and second traverse winding starting at 180 degrees. In a variant, the strips are positioned by first traverse winding in a given axial direction, followed by second traverse winding in the opposite axial direction.

(27) In the exemplary embodiment in FIG. 3A, with a symmetrical disposition, two rows of strips are arranged with a lateral offset between the positions of the strips of the two rows of around half a pitch of the strip. The main plane P-P of each row is substantially axial. Such an arrangement has the effect of covering the bridges of elastomeric mixture of the first row with the strips that make up the second row. The bridges of elastomeric mixture between the strips of the first row are thus positioned substantially at the middle of the respective widths of the strips of the adjacent layer. In this example, the radially outer layer has one fewer winding in order to compensate for the effect of the lateral offset. The mean overlap between the strips of the two rows is at least 20% and preferably greater than 40%.

(28) The exemplary embodiment in FIG. 3B has two rows of the same width, one of which is offset with respect to the other, in order to produce a tire having asymmetric characteristics.

(29) In a variant, the starting and end points of the layers may optionally be the same in order to ensure a certain uniformity.

(30) FIGS. 4A and 4B illustrate variant embodiments of FIGS. 3A and 3B that comprise, in addition to the above-described rows of strips, an alignment of reinforcing threads 11 provided in a radially outer position. The threads 11 are preferably textile threads. In addition to providing a certain stiffness, the circumferential threads make it possible to protect the radially inner layers.

(31) FIG. 5 illustrates a variant of the example in FIG. 4A, in which the alignment of threads 11 is provided between the two rows of strips 12.

(32) FIG. 6 illustrates another variant of the example in FIG. 4A, in which the alignment of threads 11 in a radially outer position is supplemented by a second alignment of threads 11 provided between the two rows of strips 12 in order to further stiffen the crown zone.

Composite Strips

(33) A second embodiment of the strips is presented with regard to FIGS. 7A, 7B and 8. FIG. 7A illustrates an exemplary embodiment in which a thermoplastic film 12 as described above is surmounted by a row 11 of reinforcing threads, preferably textile. The whole is embedded in a matrix 15 made up of an elastomeric mixture, preferably a diene elastomeric mixture, and forms a composite strip 14. FIG. 7B presents a variant composite strip 14 with a reverse geometry, the row of threads being arranged radially on the inside with respect to the thermoplastic film.

(34) FIG. 8 illustrates a third example of a composite strip in which a row of reinforcing threads 11 is integrated directly into a thermoplastic film. This variant has the additional advantages of greater lightness of weight and very high compactness.

(35) FIG. 9 illustrates a staggered disposition of the composite strips 14. In this example, two rows of composite strips are provided, the radially outer row being the narrowest.

(36) The composite strips make it possible to simplify the steps of manufacturing the crown zone of the tire. By altering only the type of strip, without changing the other architectural elements of the tire, the composite strips make it possible to vary the characteristics of the crown zone depending on needs, providing greater flexibility in the design of tires.

(37) For each of the abovementioned embodiments, different parameters can be altered, such as the relative width of the constituent elements, different widths in different layers, the thicknesses of the components, the number of alignments of strips, which may be greater than two, in particular for specific tires such as for heavy-duty vehicles, all-terrain vehicles or for aircraft.

Constituent Elements and Materials

(38) The thermoplastic film of the reinforcing strips 12 is advantageously produced with the aid of materials selected from the following: thermally stabilized biaxially or monoaxially drawn polyester, polyamide (for example nylon 6.6). In a variant, these materials can be loaded with isotropic or anisotropic inclusions or inclusions of fibrillar form.

(39) The strips 12 of thermoplastic film have a ratio between the dimensions length/width and width/thickness of greater than or equal to 5. The thermoplastic film has a modulus in the main direction (corresponding to the circumferential direction of the tire) and the transverse direction of greater than 0.9 GPa and preferably greater than 2 GPa.

(40) The matrix 13 or 15 in which the strips 12 or 14 are integrated is made up of an elastomeric mixture, preferably a diene elastomeric mixture, having a modulus at 10% elongation that is conventional (typically between 3 and 20 MPa), or preferably stiff (that is to say greater than 20 MPa). A suitable adhesive system according to the nature of the reinforcing elements and the mixtures can be used in order to obtain the necessary cohesion. This adhesive system is obtained for example by physical or chemical preparation or activation of the surfaces and then by using an adhesive.

(41) The reinforcing cords 11 are made up of materials selected from the following: aramid, polyester (PET, PEN, PTT), nylon, rayon, polyketone, metal thread or cord, or composite thread of cord (glass or carbon with resin), or a hybrid reinforcing element made up of a combination of the above materials.

(42) Table 1 below illustrates an example of results obtained using architectures according to the features of the invention. At size 175/65R14, a reference with a crown having two crown plies and a layer of nylon threads oriented at 0 is compared with a variant within the scope of the invention that is made of two layers of PET strips with a width of 15 mm and a thickness of 0.5 mm, laid in staggered rows. Each strip is separated from its neighbour by 1 mm. A diene mixture with a thickness of 0.3 mm separates the two layers of PET strip, this embodiment also being supplemented by a 0 PET 4403 thread (variant 1) or an aramid thread (variant 2).

(43) TABLE-US-00001 TABLE 1 comparison of masses, cornering stiffness and rolling resistance for tires according to the invention, with reference to a control tire of conventional architecture. D(Z) at 0.8ZETRTO and Mass 2.4 bar RRt Reference 100% Variant 1 270 g/ref 108% 0.55 kg/T/ref Variant 2 450 g/ref 108% 0.35 kg/T/ref

(44) Significant improvements in mass and rolling resistance obtained with the embodiments according to the invention are observed.

REFERENCE NUMERALS EMPLOYED IN THE FIGURES

(45) 1 Tire

(46) 2 Carcass

(47) 3 Sidewall

(48) 4 Crown

(49) 5 Beads

(50) 6 Tread

(51) 7 Bead wires

(52) 8 Sealing layer

(53) 10 Crown reinforcing element

(54) 11 Reinforcing thread or cord

(55) 12 Reinforcing strip made of thermoplastic film

(56) 13 Matrix (elastomer mixture, preferably diene elastomer mixture)

(57) 14 Composite reinforcing strip (thermoplastic film and reinforcing threads)

(58) 15 Matrix (elastomer mixture, preferably diene elastomer mixture)

(59) 20 Crossed triangulation layer

(60) 21 Crossed triangulation layer

(61) 22 Belt