Tire Including A Casing Layer That Includes Sheathed Casing Reinforcement Elements

Abstract

The tire (10) comprises a crown (12) surmounted by a tread (22), two sidewalls (24), two beads (26), each sidewall (24) connecting each bead (26) to the crown (12), a carcass reinforcement (34) anchored in each of the beads (26) and extending in the sidewalls (24) as far as the crown (12). The carcass reinforcement (34) comprises one carcass ply (44) comprising carcass reinforcing elements (46) having a mean laying pitch (P) strictly greater than 1.5 mm. The carcass ply (44) comprises an elastomer matrix (54) in which the carcass reinforcing elements (46) are embedded, each carcass reinforcing element (46) comprising: one filamentary element (56), and one sheath (58) coating the filamentary element (56) and comprising at least one layer (60) of a thermoplastic polymer composition.

Claims

1. A tire comprising a crown surmounted by a tread, two sidewalls, two beads, each sidewall connecting each bead to the crown, a carcass reinforcement anchored in each of the beads and extending in the sidewalls as far as the crown, the carcass reinforcement comprising at least one carcass ply comprising carcass reinforcing elements arranged side by side parallel to one another in a main direction substantially perpendicular to the overall direction in which the carcass reinforcing elements extend at a mean laying pitch strictly greater than 1.5 mm, the carcass ply comprising an elastomer matrix in which the carcass reinforcing elements are embedded, wherein each carcass reinforcing element comprises: at least one filamentary element, and at least one sheath coating the filamentary element and comprising at least one layer of a thermoplastic polymer composition.

2. The tire according to claim 1, wherein the mean laying pitch of the carcass reinforcing elements in the main direction is greater than or equal to 1.7 mm.

3. The tire according to claim 1, wherein the mean thickness of the sheath on the back of each filamentary element ranges from 1 m to 2 mm.

4. The tire according to claim 1, wherein each filamentary element comprises an assembly of individual metal threads.

5. The tire according to claim 1, wherein each individual metal thread has a diameter ranging from 0.10 mm to 0.35 mm.

6. The tire according to claim 1, wherein the thermoplastic polymer composition comprises a thermoplastic polymer, a functionalized diene elastomer, a poly(p-phenylene ether) or a mixture of these materials.

7. The tire according to claim 1, wherein the carcass reinforcing elements make an angle ranging from 80 to 90 with the circumferential direction of the tire.

8. The tire according to claim 1, comprising a crown reinforcement radially interposed between the carcass reinforcement and the tread.

9. The tire according to claim 8, wherein the crown reinforcement comprises a working reinforcement comprising at least two working plies, each said working ply comprising several reinforcing elements referred to as working reinforcing elements arranged side by side parallel to one another, the working reinforcing elements making an angle ranging from 10 to 45 with the circumferential direction of the tire.

10. The tire according to claim 9, wherein the working reinforcing elements are crossed from one working ply with respect to the other.

11. The tire according to claim 8, wherein the crown reinforcement comprises a hoop reinforcement comprising at least one hooping ply comprising reinforcing elements referred to as hoop reinforcing elements arranged side by side parallel to one another, the hoop reinforcing elements making an angle at most equal to 10 with the circumferential direction of the tire.

12. The tire according to claim 8, wherein the crown reinforcement comprises a protective reinforcement comprising at least one protective ply comprising reinforcing elements referred to as protective reinforcing elements arranged side by side parallel to one another, the protective reinforcing elements making an angle at least equal to 10 with the circumferential direction of the tire.

13. The tire according to claim 8, wherein the crown reinforcement comprises a triangulation reinforcement comprising at least one triangulation ply comprising reinforcing elements referred to as triangulation reinforcing elements arranged side by side parallel to one another, the triangulation reinforcing elements making an angle ranging from 30 to 65 with the circumferential direction of the tire.

14. The tire according to claim 1, for industrial vehicles, preferably for road haulage vehicles.

15. The tire according to claim 1, wherein the mean laying pitch of the carcass reinforcing elements in the main direction is greater than or equal to 1.8 mm.

16. The tire according to claim 1, wherein the mean thickness of the sheath on the back of each filamentary element ranges from 10 m to 1 mm.

17. The tire according to claim 1, wherein each individual metal thread has a diameter ranging from 0.12 mm to 0.26 mm.

18. The tire according to claim 8, wherein the crown reinforcement comprises a protective reinforcement comprising at least one protective ply comprising reinforcing elements referred to as protective reinforcing elements arranged side by side parallel to one another, the protective reinforcing elements making an angle ranging from 10 to 35 with the circumferential direction of the tire.

Description

[0051] The invention will be better understood from reading the description which will follow, given solely by way of nonlimiting example and made with reference to the drawings in which:

[0052] FIG. 1 is a view in section of a tire according to a first embodiment of the invention;

[0053] FIG. 2 is a view in section of a carcass ply of the tire of FIG. 1;

[0054] FIG. 3 is a view in section of a carcass reinforcing element of the carcass ply of FIG. 2; and

[0055] FIG. 4 is a view similar to that of FIG. 2 of a carcass ply of a tire of the prior art.

[0056] In the description which follows, when using the term radial it is appropriate to make a distinction between the various different uses made of this word by those skilled in the art. Firstly, the expression refers to a radius of the tire. It is in this sense that a point, a ply or a reinforcement P1 is said to be radially inside a point, a ply or a reinforcement P2 (or radially on the inside of the point P2) if it is closer to the axis of rotation of the tire than is the point, the ply or the reinforcement P2. Conversely, a point, a ply or a reinforcement P3 is said to be radially outside a point, a ply or a reinforcement P4 (or radially on the outside of the point, a ply or a reinforcement P4) if it is further away from the axis of rotation of the tire than is the point, the ply or the reinforcement P4. Progress will be said to be radially inwards (or outwards) when it is in the direction towards smaller (or larger) radii. It is this sense of the term that applies also when matters of radial distances are being discussed.

[0057] By contrast, a reinforcing element or a reinforcement is said to be radial when the reinforcing element or the reinforcing elements of the reinforcement make an angle greater than or equal to 80 and less than or equal to 90 with the circumferential direction.

[0058] An axial direction is a direction parallel to the axis of rotation of the tire. A point, a ply or a reinforcement P5 is said to be axially inside a point, a ply or a reinforcement P6 (or axially on the inside of the point, the ply or the reinforcement P6) if it is closer to the median plane M of the tire than is the point, the ply or the reinforcement P6. Conversely, a point, a ply or a reinforcement P7 is said to be axially outside a point P8 (or axially on the outside of the point, the ply or the reinforcement P8) if it is further away from the median plane M of the tire than is the point, the ply or the reinforcement P8. The median plane M of the tire is the plane which is normal to the axis of rotation of the tire and lies equal distances from the annular reinforcing structures of each bead.

[0059] A circumferential direction is a direction which is perpendicular both to a radius of the tire and to the axial direction.

[0060] Furthermore, any range of values denoted by the expression from a to b means the range of values extending from the end-point a to the end-point b, namely including the strict end-points a and b.

[0061] Example of a Tire According to the Invention

[0062] A frame of reference X, Y, Z corresponding to the usual axial (X), radial (Y) and circumferential (Z) directions of a tire respectively has been indicated in the figures.

[0063] FIG. 1 depicts a tire according to a first embodiment of the invention and denoted by the overall reference 10. The tire 10 is substantially axisymmetric about an axis substantially parallel to the axial direction X. The tire 10 here is intended for an industrial vehicle, for example a road haulage vehicle and in this instance a lorry. The tire 10 has the dimensions 315/70R22.5.

[0064] The tire 10 comprises a crown 12 comprising a crown reinforcement 14 comprising a working reinforcement 16, a hoop reinforcement 18 and a protective reinforcement 20.

[0065] The crown reinforcement 14 is surmounted by a tread 22. Two sidewalls 24 extend the crown 12 radially towards the inside of the tire 10. The tire 10 furthermore comprises two beads 26 radially on the inside of the sidewalls 24 and each comprising an annular reinforcing structure 28, in this instance a bead wire 30, surmounted by a mass of filling rubber 32.

[0066] The tire 10 also comprises a radial carcass reinforcement 34. The crown reinforcement 14 is radially interposed between the carcass reinforcement 34 and the tread 22. Each sidewall 24 connects each bead 26 to the crown 12.

[0067] The working reinforcement 16 comprises first and second working plies 36, 38 of working reinforcing elements (which have not been depicted). The first working ply 36 is arranged radially on the inside of the second working ply 38. The working reinforcing elements are arranged side by side parallel to one another and make an angle ranging from 10 to 45 with the circumferential direction Z of the tire 10, here an angle equal to 18. The working reinforcing elements are crossed from one working ply with respect to the other. The working reinforcing elements are metallic assemblies of 11.35 type.

[0068] The hoop reinforcement 18 comprises a hooping ply 40. The hoop reinforcement 18 is radially interposed between the first and second working ply 36, 38. The hooping ply 40 comprises hoop reinforcing elements (which have not been depicted) arranged side by side parallel to one another and making an angle at most equal to 10 with the circumferential direction Z of the tire 10, here an angle equal to 0. The hoop reinforcing elements are metallic assemblies of 21.23 type.

[0069] The protective reinforcement 20 comprises a protective ply 42 comprising protective reinforcing elements arranged side by side parallel to one another (which have not been depicted). The protective reinforcement 20, in this case the protective ply 42, is radially on the outside of the other reinforcements and radially on the inside of the tread 22. The protective reinforcing elements make an angle at least equal to 10, preferably ranging from 10 to 35 and more preferably from 15 to 30 with the circumferential direction Z of the tire 10, here equal to 18. The protective reinforcing elements are metallic assemblies of 6.35 type.

[0070] The carcass reinforcement 34 preferably comprises a single carcass ply 44 of radial carcass reinforcing elements 46 visible in greater detail in FIGS. 2 and 3.

[0071] The carcass reinforcement 34 is anchored in each of the beads 26 by a turnup around the bead wire 30 so as to form, in each bead 26, a main strand 48 extending from the beads 26 through the sidewalls 24 as far as the crown 12, and a turnup 50, the radially outer end 52 of the turnup 50 being radially on the outside of the annular reinforcing structure 28. The carcass reinforcement 32 thus extends from the beads 24 through the sidewalls 22 into the crown 12. In this embodiment, the carcass reinforcement 34 also extends axially through the crown 12.

[0072] Each working ply 36, 38, hooping ply 40, protective ply 42 and carcass ply 44 comprises an elastomer matrix 54 in which the reinforcing elements of the corresponding ply are embedded. The rubber compositions for the elastomer matrices 54 are compositions which are conventional for skimming reinforcing elements conventionally containing a diene elastomer, for example natural rubber, a reinforcing filler, for example carbon black and/or silica, a cross-linking system, for example a vulcanization system, preferably containing sulphur, stearic acid and zinc oxide, and possibly a vulcanization retarder and/or an accelerator and/or various additives.

[0073] FIGS. 2 and 3 respectively depict cross sections of the carcass ply 44 and of a carcass reinforcing element 46 on a plane of section perpendicular to the axial direction X. The carcass reinforcing elements 46 are arranged side by side parallel to one another in a main direction Z1. The carcass reinforcing elements 46 extend in an overall direction X1 and make an angle greater than or equal to 80 and less than or equal to 90 with the circumferential direction Z of the tire 10. Here, the overall direction X1 in which the carcass reinforcing elements 46 extend is substantially parallel to the axial direction X and the angle that these carcass reinforcing elements make with the circumferential direction Z of the tire 10 is therefore here equal to 90.

[0074] Each carcass reinforcing element 46 comprises at least one filamentary element 56 and at least one sheath 58 coating the filamentary element 56 and comprising at least one layer 60 of a thermoplastic polymer composition.

[0075] Each carcass reinforcing element 46 comprises a single filamentary element 56. Each filamentary element 56 comprises an assembly 62 of individual metal threads 64.

[0076] Here, the assembly comprises an internal layer of one or M>1 individual metal threads 64, an intermediate layer of N>1 individual metal threads 64 wound in a helix around the internal layer and an external layer of P>1 individual metal threads 64 wound in a helix around the intermediate layer.

[0077] In this instance, each individual metal thread 64 is here made of steel coated with a protective coating for example containing brass or zinc. Each individual metal thread 64 has a diameter ranging from 0.10 mm to 0.35 mm, preferably from 0.12 mm to 0.26 mm and more preferably from 0.14 mm to 0.23 mm and here equal to 0.18 mm. Here, the assembly 62 is of the 1+6+12 type and has no wrapping wire. According to the nomenclature in usage, the assembly 62 is referred to as 19.18NF.

[0078] The sheath 58 has a mean thickness G on the back of each filamentary element 56 in the direction Y1 perpendicular to the main direction Z1 ranging from 1 m to 2 mm, preferably from 10 m and 1 mm and more preferably from 35 m to 200 m. Here, G=150 m.

[0079] The sheath 58 comprises a single layer 60 of the thermoplastic polymer composition comprises a thermoplastic polymer, a functionalized diene elastomer, a poly (p-phenylene ether) or a mixture of these materials. Here, the thermoplastic polymer composition comprises a thermoplastic polymer, for example polyamide 66. Optionally, the thermoplastic polymer composition may comprise a functionalized diene elastomer, for example a thermoplastic stirene comprising an epoxide, carbonyl, anhydride or ester functional group and/or a poly-p-phenylene ether.

[0080] The sheath 58 is coated with a layer of tackifying adhesive (not depicted) promoting adhesion between the sheath 58 and the elastomer matrix 54.

[0081] The mean laying pitch P of the carcass reinforcing elements 46 in the main direction Z1 is strictly greater than 1.5 mm, advantageously greater than or equal to 1.7 mm, preferably greater than or equal to 1.8 mm and more particularly greater than or equal to 1.9 mm. Here, P=2.0 mm.

[0082] Comparative Tests

[0083] The tire 10 according to the invention described hereinabove was compared against a control tire T of the prior art. The control tire T is identical to the tire 10 according to the invention except for its carcass ply depicted in FIG. 4. The carcass ply of the control tire T comprises carcass reinforcing elements comprising assemblies of individual metal threads of type 19.18 directly embedded in an elastomer matrix and therefore having no sheath. Furthermore, the mean laying pitch of the carcass reinforcing elements of the control tire T is equal to 1.5 mm.

[0084] The tires T and 10 were subjected to a low-pressure running test. During this test, the tires T and 10 were run until the tire burst. The greater the distance covered, the better the endurance of the tire to the low-pressure running test.

[0085] The mass of metal in the carcass ply of each tire T and 10 was also weighed, which means to say the mass of metal carcass reinforcing elements. The masses of metal were then referenced to base 100 with respect to the carcass ply of the control tire T. The greater the extent to which the value obtained is above 100, the lighter in weight the carcass ply is.

[0086] The results are collated in table 1 below.

TABLE-US-00001 TABLE 1 Tire performances T 10 Mass of metal in the carcass ply (base 100) 100 125 Distance covered during the low-pressure 100 99 running test (km)

[0087] Thus, it is found that for a lower mass of tire T the invention makes it possible to obtain a low-pressure running endurance that is almost identical to that of the tire T.

[0088] The invention is not restricted to the embodiments described hereinabove.

[0089] Specifically, it is also possible to conceive of a tire according to the invention in which the crown reinforcement also comprises a triangulation reinforcement. Such a triangulation reinforcement comprises at least one triangulation ply comprising reinforcing elements referred to as triangulation reinforcing elements arranged side by side parallel to one another. The triangulation reinforcing elements make an angle ranging from 30 to 65 with the circumferential direction of the tire.

[0090] It is also possible to conceive of a tire comprising several carcass plies at least one of which is as described hereinabove.