Tire Tread for a Heavy Vehicle with an Improved Resistance to Stresses

Abstract

A tread for a tire for a heavy-duty vehicle for mixed use and aims to improve the endurance of the crown of the tire following retention of stones in the tread. The tread (1) has voids (3) with a first, radially outer void portion (31) of groove type, having a width W11 on the tread surface (2), a width W12 at a groove bottom (311), and a depth H1, and a second, radially inner void portion (32) of sipe type, having a width W2 and a depth H2 and leading into the groove bottom (311) at a distance E with respect to the mean surface (S1) of the groove (31). The distance E is at least equal to the width W12 of the groove bottom (311) divided by 6.

Claims

1. A tread for a tire for a heavy-duty vehicle, which tread is intended to come into contact with the ground via a tread surface and comprises voids that are delimited by elements in relief with respect to a bottom surface and extend over a specific length, at least one void comprising, over at least some of its length, a first, radially outer void portion leading into the tread surface, and a second, radially inner void portion leading into the first void portion, the first void portion being a groove having a width W11, measured on the tread surface perpendicularly to a mean surface (S1) of the groove, and having a depth H1, measured perpendicularly from the tread surface to a groove bottom having a width W12, the second void portion being a sipe having a width W2, measured perpendicularly to a mean surface of the sipe, and having a depth H2, measured perpendicularly from the groove bottom to a sipe bottom, the depth H1 of the groove being at least equal to 0.5 times the depth H2 of the sipe and at most equal to twice the depth H2 of the sipe, the sipe leading into the groove bottom at a distance E, measured between the mean surface (S1) of the groove and the mean surface (S2) of the sipe, wherein the distance E at which the sipe leads into the groove bottom is at least equal to the width W12 of the groove bottom divided by 6.

2. The tread according to claim 1, wherein the distance E is at most equal to half of the width W12 of the groove bottom.

3. The tread according to claim 1, wherein the width W11 of the groove is at least equal to the width W12 of the groove bottom.

4. The tread according to claim 1, wherein the width W11 of the groove is at least equal to 4 mm.

5. The tread according to claim 1, wherein the width W2 of the sipe is at most equal to 2 mm.

6. The tread according to claim 1, wherein the width W2 of the sipe is at least equal to 0.4 mm.

7. The tread according to claim 1, wherein the sipe has a mean surface (S2) forming an angle D at most equal to 15° with respect to a radial direction (ZZ′) perpendicular to the tread surface.

8. The tread according claim 1, wherein the sipe bottom has a rounded contour having a minimum radius R at least equal to 1.5 times the width W2 of the sipe.

9. The tread according to claim 1, wherein the mean surface (S1) of the groove forms an angle at most equal to 45° with the longitudinal direction (XX′).

10. The tread according to claim 9, wherein the void is continuous over the entire length of the tread.

11. The tread according to claim 1, wherein the mean surface (S1) of the groove forms an angle at most equal to 45° with the transverse direction (YY′).

12. The tread according to claim 11, wherein the void is positioned in a median portion of the tread having a width preferably equal to the width of the tread divided by 3.

13. The tread for a heavy-duty vehicle, comprising a tread according to claim 1.

Description

[0040] The features of the invention are illustrated in the following schematic FIGS. 1 to 3, which are not shown to scale:

[0041] FIG. 1: View in radial section of a stepped void according to the invention.

[0042] FIG. 2: Perspective view of an exemplary portion of tread according to the invention.

[0043] FIG. 3: View in radial section of a stepped void from the exemplary portion of tread according to the invention, shown in FIG. 2.

[0044] FIG. 1 is a view in radial section of a stepped void according to the invention. The radial section is made through a plane defined by the radial direction zz′ and a direction yy′, which is perpendicular to a mean direction of the void xx′. The void 3 of the tread 1 for a tire for a heavy-duty vehicle, which tread is intended to come into contact with the ground via a tread surface 2, is delimited by elements 4 in relief with respect to a bottom surface 5 and extends over a specific length. The void 3 comprises, over at least some of its length, a first, radially outer void portion 31 leading into the tread surface 2, and a second, radially inner void portion 32 leading into the first void portion 31. The first void portion 31 is a groove having a width W11, measured on the tread surface 2 perpendicularly to a mean surface S1 of the groove 31, and having a depth H1, measured perpendicularly from the tread surface 2 to a groove bottom 311 having a width W12. The second void portion 32 is a sipe having a width W2, measured perpendicularly to a mean surface S2 of the sipe 32, and having a depth H2, measured perpendicularly from the groove bottom 311 to a sipe bottom 321. The sipe 32 leads into the groove bottom 311 at a distance E, measured between the mean surface S1 of the groove 31 and the mean surface S2 of the sipe 32. According to the invention, the distance E at which the sipe 32 leads into the groove bottom 311 is at least equal to the width W12 of the groove bottom 311 divided by 6. In the embodiment shown in FIG. 1, the sipe 32 has a mean surface S2 forming an angle D at most equal to 15° with respect to a radial direction zz′ perpendicular to the tread surface 2. In addition, the sipe bottom 321 has a rounded contour having a minimum radius R at least equal to 1.5 times the width W2 of the sipe 32.

[0045] FIG. 2 is a perspective view of an exemplary portion of tread 1 according to the invention. The directions shown in the figure are respectively the circumferential direction XX′, the transverse direction YY′, and a radial direction ZZ′ of the tread. FIG. 2 shows a portion of tread 1 for a tire for a heavy-duty vehicle, which tread is intended to come into contact with the ground via a tread surface 2 and comprises voids 3, according to the invention, that are delimited by elements 4 in relief with respect to a bottom surface 5. At least some of the voids 3, in particular the substantially longitudinal voids 3, comprise a first, radially outer void portion 31 leading into the tread surface 2, and a second, radially inner void portion 32 leading into the first void portion 31. The tread 2 also comprises substantially transverse voids 3 that are positioned in a median portion and in two lateral portions, said substantially transverse voids leading into the substantially longitudinal voids. The tread pattern of such a tread is therefore a block tread pattern which is particularly suited for use on a driven axle of a heavy-duty vehicle.

[0046] FIG. 3 is a view in radial section of a stepped void from the exemplary portion of tread according to the invention, as shown in FIG. 2. Said radial section is made through a plane defined by the radial direction zz′ and a direction yy′, which is perpendicular to a mean direction of the void xx′. The directions xx′, yy′ and zz′ define a local frame of reference relative to the void under consideration, the local radial direction zz′ corresponding to the radial direction ZZ′ of the tread, as shown in FIG. 2. The features shown in FIG. 2 are identical to those in FIG. 1. In the particular case that is shown, the sipe 32 leads into the groove bottom 311 at a distance E with respect to the mean surface S1 of the groove 31 that is equal to half of the width W12 of the groove bottom 311, that is to say at the wall base with maximum eccentricity. Moreover, the sipe 32 is perpendicular to the groove bottom 311, this meaning that its mean surface S2 is parallel to the mean surface S1 of the groove 31.

[0047] The exemplary tread shown in FIGS. 2 and 3 is an example which has been studied by the inventors for the tire size 13R22.5, for a mixed-use tire more particularly intended to be fitted to a driven axle. This tire is intended to bear a load equal to 4000 kg, for an inflation pressure equal to 8.6 bar, in accordance with the “Standards Manual 2019” of the ETRTO standard.

[0048] Table 1 below shows the characteristics of the tread which was tested:

TABLE-US-00001 TABLE 1 Characteristics Values Width W11 of the groove 31 10.4 mm Width W12 of the groove 31 4 mm Height H1 of the groove 31 10 mm Width W2 of the sipe 32 0.8 mm Height H2 of the sipe 32 11.2 mm Inclination D of the sipe 32 0° Distance E 2 mm

[0049] The tread according to the invention, which was developed for a conventional tire subject to inflation pressure, may also be used for a non-pneumatic tire, but also for any non-pneumatic rolling assembly with which a vehicle is intended to be equipped.