Tire for a Heavy Duty Vehicle with Improved Grip

Abstract

A tire (1) for a trailer of a heavy-duty vehicle having a tread (2), which has at least one complex circumferential cut (7) in a median portion (4) having a first family of transverse cuts, referred to as transverse through-sipes (81), having a thickness (E1) at most equal to 0.8 mm, a depth (P1) at least equal to 20% of the maximum depth-of-cut (H), and being at a distance (D1), from the nearest external cavity (71), at least equal to 7 mm, and/or a second family of transverse cuts, referred to as blind transverse cuts (82), that stop near an external cavity (71), that have a thickness (E2) at least equal to 1 mm, a depth (P2) at most equal to 20% of the maximum depth-of-cut (H), and being at a distance (D2), from said external cavity (71), at least equal to 3 mm.

Claims

1. A tire for a heavy-duty vehicle comprising a tread, intended to come into contact with the ground via a tread surface, comprising a median portion and two lateral portions, the median portion being separated from each lateral portion by a circumferential cut forming, with a circumferential direction (XX) of the tire, a mean angle less than 45, the median portion comprising at least one complex circumferential cut, forming, with the circumferential direction (XX) of the tire, a mean angle less than 45, the at least one complex circumferential cut comprising, when the tire is new, an alternation of external cavities, opening onto the tread surface, and of internal cavities, that are hidden inside the tread and connected to the tread surface by a circumferential sipe, two consecutive cavities, respectively an external cavity and an internal cavity being connected to one another, the median portion comprising a plurality of transverse cuts, having at least one transverse portion forming, with the circumferential direction (XX) of the tire, a mean angle (T, B1) at least equal to 45, the tread having a maximum depth-of-cut (H), wherein the plurality of transverse cuts comprises a first family of transverse cuts, referred to as transverse through-sipes, that intersect at least one complex circumferential cut between two consecutive external cavities and that each have a thickness (E1) at most equal to 0.8 mm and a depth (P1) at least equal to 20% of the maximum depth-of-cut (H), each transverse through-sipe being at a distance (D1), from the nearest external cavity of said complex circumferential cut, at least equal to 7 mm, and/or wherein the plurality of transverse cuts comprises a second family of transverse cuts, referred to as blind transverse cuts, that stop near an external cavity of a complex circumferential cut, and that each have a thickness at least equal to 1 mm and a depth (P2) at most equal to 20% of the maximum depth-of-cut (H), each blind transverse cut being at a distance (D2), from said external cavity, at least equal to 3 mm.

2. The tire according to claim 1, wherein the plurality of transverse cuts comprises a first family of transverse through-sipes, and wherein each transverse through-sipe has a thickness (E1) at least equal to 0.4 mm.

3. The tire according to claim 1, wherein the plurality of transverse cuts comprise a first family of transverse through-sipes, and wherein each transverse through-sipe has a depth (P1) at most equal to the maximum depth-of-cut (H).

4. The tire according to claim 1, wherein the plurality of transverse cuts comprises a first family of transverse through-sipes, wherein the distance (D1) between each transverse through-sipe and the nearest external cavity is at least equal to 10 mm.

5. The tire according to claim 1, wherein the plurality of transverse cuts comprises a second family of blind transverse cuts, wherein each blind transverse cut has a thickness (E2) at least equal to 2 mm.

6. The tire according to claim 1, wherein the plurality of transverse cuts comprises a second family of blind transverse cuts, and wherein each blind transverse cut has a thickness (E2) at most equal to 5 mm.

7. The tire according to claim 1, wherein the plurality of transverse cuts comprises a second family of blind transverse cuts, and wherein each blind transverse cut has a depth (P2) at least equal to 10% of the maximum depth-of-cut (H).

8. The tire according to any claim 1, wherein the plurality of transverse cuts comprises a second family of blind transverse cuts (82), and wherein at least one blind transverse cut comprises a first transverse portion, forming, with the circumferential direction (XX) of the tire, a mean angle (B1) at least equal to 45, and a blind end portion (822) forming, with the circumferential direction (XX) of the tire, a mean angle (B2) less than 45.

9. The tire according to claim 1, wherein the circumferential pitch spacing (Pc) between two consecutive transverse cuts of the plurality of transverse cuts is at least equal to 10 mm, preferably at least equal to 20 mm.

10. The tire according to claim 1, wherein the circumferential pitch spacing (Pc) between two consecutive transverse cuts of the plurality of transverse cuts is at most equal to 50 mm.

Description

[0039] The features of the invention are illustrated by the schematic FIGS. 1 and 2, which are not drawn to scale:

[0040] FIG. 1: View from above of a portion of a tread of a tire according to the invention,

[0041] FIG. 2: Circumferential median cross section of a portion of the tread of a tire according to the invention.

[0042] FIG. 1 is a view, from above, of a portion of a tread 2 of a tire 1 according to the invention, more specifically a tire of size 245/70R17.5. The tire 1 intended to be fitted to a heavy-duty vehicle, and more particularly to a trailer of a heavy-duty vehicle, comprises a tread 2, intended to come into contact with the ground via a tread surface 3, comprising a median portion 4 and two lateral portions 5. The median portion 4 is separated from each lateral portion 5 by a circumferential cut 6 forming, with a circumferential direction XX of the tire, a mean angle equal, in the embodiment depicted, to 0. The median portion 4 comprises a single complex circumferential cut 7, forming, with the circumferential direction XX of the tire, a mean angle equal to 0. The complex circumferential cut 7 comprises, when the tire is new, an alternation of external cavities 71, opening onto the tread surface 3, and of internal cavities 72, that are hidden inside the tread 2 (and not visible in FIG. 1) and connected to the tread surface 3 by a circumferential sipe 721, two consecutive cavities, respectively an external cavity 71 and an internal cavity 72 being connected to one another. The median portion 4 comprises a plurality of transverse cuts (81, 82) having at least one portion forming, with the circumferential direction XX of the tire, a mean angle equal to 60. The tread 2 has a maximum depth-of-cut H (not visible in FIG. 1) equal to 13 mm. According to the invention, the plurality of transverse cuts (81, 82) comprises a first family of transverse cuts, referred to as transverse through-sipes 81, intersecting the complex circumferential cut 7 between two consecutive external cavities 71 and each having a thickness E1 equal to 0.6 mm and a depth P1 equal to 4 mm, representing 31% of the maximum depth-of-cut H. Each transverse through-sipe 81 is at a distance D1, from the nearest external cavity 71 of said complex circumferential cut 7, equal to 10 mm. The plurality of transverse cuts (81, 82) also comprises a second family of transverse cuts, referred to as blind transverse cuts 82, stopping near an external cavity 71 of the complex circumferential cut 7 and each having a thickness E2 equal to 2 mm and a depth P2 equal to 2 mm, representing 16% of the maximum depth-of-cut H. Each blind transverse cut 82 is at a distance D2, from said external cavity 71, equal to 3 mm. Each blind transverse cut 82 comprises a first transverse portion 821, forming, with the circumferential direction XX of the tire, a mean angle B1 equal to 60, and a blind end portion 822 forming, with the circumferential direction XX of the tire, a mean angle B2 equal to 25. The circumferential pitch spacing Pc between two consecutive transverse cuts of the plurality of transverse cuts (81, 82), respectively between a transverse through-sipe 81 and a blind transverse cut 82, is equal to 35 mm.

[0043] FIG. 2 is a circumferential median cross section of a portion of the tread 2 of a tire 1 according to the invention. This circumferential median cross section is taken on the plane of section A-A of FIG. 1, corresponding to the median circumferential plane XZ passing through the middle of the tread, and cuts through the complex circumferential cut 7 along the mean line thereof. The complex circumferential cut 7, situated in the median portion 4 of the tread 2, comprises, when the tire is new, an alternation of external cavities 71, opening onto the tread surface 3, and of internal cavities 72, that are hidden inside the tread 2 and connected to the tread surface 3 by a circumferential sipe 721, two consecutive cavities, respectively an external cavity 71 and an internal cavity 72 being connected to one another. In the embodiment depicted, the complex circumferential cut 7 extends radially from the tread surface 3 over a depth H corresponding to the maximum depth-of-cut. In FIG. 2 two blind transverse cuts 82 of depth P2 are depicted in dotted line (because they do not open onto the plane XZ). Transverse through-sipes 81, of thickness E1 and depth P1 are also depicted, in cross section.

[0044] The inventors have more specifically studied this invention for a tire I of size 245/70R17.5 intended to be fitted to the axles of a trailer of a heavy-duty vehicle with a maximum load capacity equal to 2725 kg for an inflation pressure equal to 9 bar.

[0045] Table 1 below summarizes the characteristics of the tire I according to the invention, studied by the inventors:

TABLE-US-00001 TABLE 1 Comments on the characteristics Characteristics Min I Max of I Maximum depth-of-cut H 13 mm Maximum tread height Mean angle T (/XX) of 45 60 90 Greater than 45 a transverse through- sipe 81 Thickness E1 of a 0.4 mm 0.6 mm 0.8 mm Comprised transverse through- between 0.4 mm sipe 81 and 0.8 mm Depth P1 of a transverse 20% H 4 mm H P1/H = 4/13 = through-sipe 81 31% => greater than 20% H Distance D1 from a 7 mm, 10 mm Greater than transverse through-sipe preferably 7 mm 81 to the nearest 10 mm external cavity 71 Mean angle B1 (/XX) 60 Greater than of the first transverse 45 portion 821 of a blind transverse cut 82 Mean angle B2 (/XX) 25 Less than 45 of the second blind end and even less portion 822 of a blind than 30 transverse cut 82 Thickness E2 of a blind 1 mm, 2 mm 5 mm, Comprised transverse cut 82 preferably preferably between 2 mm 2 mm 4 mm and 4 mm Depth P2 of a blind 10% H 2 mm 20% H P2/H = 2/13 = transverse cut 82 16% => less than 20% H Distance D2 from the 3 mm 3 mm 10 mm Comprised blind transverse cut 82 between 3 mm to the nearest external and 10 mm cavity 71 Circumferential pitch 10 mm, 35 mm 50 mm, Comprised spacing Pc of the preferably preferably between 20 mm transverse sipes 20 mm 35 mm and 35 mm

[0046] The results of the performance tests, carried out on the aforementioned size 245/70 R 17.5 being studied, showed compliance with the expected results. In particular, the grip on snowy ground, tested in accordance with the method described in Annex 7 of Regulation UN 117 of the United Nations Economic Commission for Europe, is markedly improved compared to the reference Michelin tire 245/70 R 17.5 X MULTI T2, with a 35% improvement in traction. In addition, the wet grip performance, measured in accordance with the method described in Annex 5 of Regulation UN 117, and the performance in terms of road noise, measured in accordance with the method described in Annex 3 of Regulation UN 117, are on a par with the reference tire. Finally, the performance in terms of resistance to chunking is in the process of being confirmed on customer running tests.