Tire Tread for an Agricultural Vehicle

Abstract

Tread of a tire for an agricultural vehicle. The tread (2) comprises a first, median portion (21) having an axial width L.sub.1, at least equal to 0.25 times and at most equal to 0.75 times the axial width L, and second and third, lateral portions (22, 23) that respectively extend axially outwards from the first, median portion (21) as far as an axial end (E, E′) and have respective axial widths (L.sub.2, L.sub.3). Each lug portion (311) that is axially contained in the first, median portion (21) and extends radially inwards, from the contact face (6) as far as a first interface (7), over a radial distance D.sub.1 at least equal to 0.5 times and at most equal to 1 time the radial lug height H, includes a first elastomeric compound. Each lug portion (321) that is axially contained in one of the second or third, lateral portions (22, 23) and extends radially inwards, from the contact face (6) as far as a second interface (8), over a radial distance D.sub.2 at least equal to 0.5 times and at most equal to 1 time the radial lug height H, includes a second elastomeric compound.

Claims

1. A fire for an agricultural vehicle, comprising: a tread that is intended to come into contact with the ground and has an axial width L measured between two axial ends; the tread comprising lugs that are separated from one another by grooves; each lug extending radially outwards, over a radial height H, from a bottom surface as far as a contact face; wherein the grooves include the portions of the bottom surface separating the lugs; wherein the tread comprises a first, median portion having an axial width L.sub.1 at least equal to 0.25 times and at most equal to 0.75 times the axial width L, and second and third, lateral portions that respectively extend axially outwards from the first, median portion as far as said axial ends and have respective axial widths, wherein each lug portion that is axially contained in the first, median portion and extends radially inwards, from the contact face as far as a first interface, over a radial distance D.sub.1 at least equal to 0.5 times and at most equal to 1 time the radial lug height H, comprises a first elastomeric compound, and wherein each lug portion that is axially contained in one of the second or third, lateral portions and extends radially inwards, from the contact face as far as a second interface, over a radial distance D.sub.2 at least equal to 0.5 times and at most equal to 1 time the radial lug height H, consists of comprises a second elastomeric compound.

2. The tire according to claim 1, wherein each said lug portion that is axially contained in the first, median portion and extends radially inwards, from the first interface as far as a third interface positioned radially inside the bottom surface at a radial distance D.sub.3 at least equal to 3 mm, comprises the first elastomeric compound.

3. The tire according to claim 1, wherein each lug portion that is axially contained in one of the second or third, lateral portions and extends radially inwards, from the second interface as far as a third interface positioned radially inside the bottom surface at a radial distance D.sub.3 at least equal to 3 mm, comprises the second elastomeric compound.

4. The tire according to claim 2, wherein the radial distance D.sub.3 between the bottom surface and the third interface is at most equal to 15 mm.

5. The tire according to claim 1, wherein the radial distance D.sub.1 between the contact face and the first interface, and the radial distance D.sub.2 between the contact face and the second interface are the same.

6. The tire according to claim 1, the first elastomeric compound having a complex dynamic shear modulus G.sub.1* at 50% deformation and 60° C., wherein the complex dynamic shear modulus G.sub.1* of the first elastomeric compound is at least equal to 1.4 MPa and at most equal to 2 MPa.

7. The tire according to claim 1, the first elastomeric compound having a loss factor tan (δ.sub.1) at 60° C., wherein the loss factor tan (δ.sub.1) of the first elastomeric compound is at least equal to 0.22 and at most equal to 0.30.

8. The tire according to claim 1, the second elastomeric compound having a complex dynamic shear modulus G.sub.2* at 50% deformation and 60° C., wherein the complex dynamic shear modulus G.sub.2* of the second elastomeric compound is at least equal to 1.3 MPa and at most equal to 1.9 MPa.

9. The tire according to claim 1, the second elastomeric compound having a loss factor tan (δ.sub.2) at 60° C., wherein the loss factor tan (δ.sub.2) of the second elastomeric compound is at least equal to 0.24 and at most equal to 0.32.

Description

[0057] The present invention will be better understood with the aid of the appended FIGS. 1 to 3 which are schematic and not drawn to scale:

[0058] FIG. 1: a perspective view of a tire for an agricultural vehicle,

[0059] FIG. 2: a view in a radial direction (Z) of the tread of a tire for an agricultural vehicle,

[0060] FIG. 3: a view in section on a meridian plane (YZ) of a portion of tread of a tire according to the invention.

[0061] FIGS. 1 and 2 respectively show a perspective view of a tire 1 for an agricultural vehicle, and a view, in a radial direction Z, of the tread of such a tire. The tread 2, intended to come into contact with the ground via a tread surface, comprises lugs 3 separated from one another by grooves 4. Each lug 3 extends radially outwards, from a bottom surface 5 as far as a contact face 6 positioned in the tread surface. The grooves 4 consist of the portions of the bottom surface 5 that separate the lugs 3.

[0062] In FIG. 2, the tread 2 has an axial width L measured between two axial ends (E, E′). It comprises a first, median portion 21 (hatched) having an axial width L.sub.1, at least equal to 0.25 times and at most equal to 0.75 times the axial width L, and second and third, lateral portions (22, 23) that respectively extend axially outwards from the first, median portion 21 as far as an axial end (E, E′) and have respective axial widths (L.sub.2, L.sub.3). In the case shown, the axial width L.sub.1 of the median portion 21 of the tread 2 is equal to 0.5 times the axial width L of the tread, and the respective axial widths (L.sub.2, L.sub.3) of the second and third, lateral portions are the same as one another and respectively equal to 0.25 times the axial width L of the tread 2. In accordance with the invention, the lug portions 3 that are axially positioned in the first, median portion 21 consist, over at least a part of their radial height H, of a first elastomeric compound, while the lug portions 3 that are axially positioned in one of the second or third, lateral portions (22, 23) consist, over at least a part of their radial height H, of a second elastomeric compound.

[0063] FIG. 3 shows a view in section on a meridian plane (YZ) of the tread 2 of a tire according to a particular embodiment of the invention. The tread 2, having an axial width L measured between two axial ends (E, E′), comprises a first, median portion 21 having an axial width L.sub.1 equal, in the case shown, to 0.5 times the axial width L, and second and third, lateral portions (22, 23) that respectively extend axially outwards from the first median portion 21 as far as an axial end (E, E′) and have respective axial widths (L.sub.2, L.sub.3) that are the same as one another and are respectively equal to 0.25 times the axial width L. In the first, median portion 21, a lug portion 311 consisting of a first elastomeric compound (hatched) that is resistant to wear when used on the road extends radially inwards from the contact face 6 as far as a first interface 7, over a radial distance D.sub.1 at least equal to 0.5 times and at most equal to 1 time the radial lug height H. In the third, lateral portion 23, a lug portion 321 consisting of a second elastomeric compound (dotted) that is resistant to attack when used in the fields extends radially inwards from the contact face 6 as far as a second interface 8, over a radial distance D.sub.2 at least equal to 0.5 times and at most equal to 1 time the radial lug height H. The tire portion contained between the bottom surface 5 and a third interface 9, radially inside the bottom surface 5 at a radial distance D.sub.3, forms the void rubber. In the case shown, a third elastomeric compound, different from the first and second elastomeric compounds, extends radially inwards from the first and second interfaces (7, 8) as far as the third interface 9.

[0064] The invention has been studied in more particular detail for an agricultural tire in which the first elastomeric compound has a complex dynamic shear modulus G.sub.1* equal to 1.72 MPa and a loss factor tan (δ.sub.1) equal to 0.30, and the second elastomeric compound has a complex dynamic shear modulus G.sub.2* equal to 1.47 MPa and a loss factor tan (32) equal to 0.32.

[0065] The first and second elastomeric compounds may have chemical compositions that differ from those described above, depending on the performance sought for the tire.

[0066] The invention is applicable, more generally, to any tire the tread of which comprises raised elements and which is likely to run over ground comprising aggressive indenting features, such as a construction plant vehicle tire.