Tire Tread For A Farm Vehicle

Abstract

Tire for a vehicle for agricultural use comprises tread (2), comprising lugs (3) separated by grooves (4), each lug (3) extending radially outwards, over a radial height H, from a bottom surface (5) as far as a contact face (6). A first lug portion (31), made of a first elastomeric compound, extends radially inwards, from the contact face (6) as far as a first interface (7), over a radial distance D.sub.1 between 0.5 H (the radial height) and H. A second lug portion (32), made of a second elastomeric compound, extends radially inwards, from the first interface (7) as far as the bottom surface (5), over a radial distance D.sub.2. The second elastomeric compound extends radially into the lugs (3) and grooves (4), from the bottom surface (5), as far as a second interface (8), over a radial distance D.sub.3 between 3 mm and 15 mm.

Claims

1. A tire for a vehicle for agricultural use, comprising: a tread, adapted to come into contact with the ground, comprising lugs 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; the grooves being defined at least partially by portions of the bottom surface separating the lugs; wherein, in each said lug, a first lug portion, made of a first elastomeric compound, extends radially inwards, from the contact face as far as a first interface, over a radial distance D.sub.1 at least equal 0.5 times and at most equal to 1 times the radial height H of the lug, wherein, in each said lug, a second lug portion, made of a second elastomeric compound, extends radially inwards, from the first interface as far as the bottom surface, over a radial distance D.sub.2, wherein the second elastomeric compound extends radially into the lugs and the grooves, from the bottom surface as far as a second interface, over a radial distance D.sub.3, and wherein the radial distance D.sub.3 between the bottom surface and the second interface is at least equal to 3 mm and at most equal to 15 mm.

2. The tire according to claim 1, the first elastomeric compound having a complex dynamic shear modulus G.sub.1* at 50% deformation and at 60 C., wherein the complex dynamic shear modulus G.sub.1* of the first elastomeric compound is at least equal to 1.2 MPa.

3. The tire according to claim 1, the first elastomeric compound having a loss factor tan (.sub.1) at 60 C., wherein the loss factor tan (.sub.1) of the first elastomeric compound is at least equal to 0.18 and at most equal to 0.32.

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

5. The tire according to claim 1, the second elastomeric compound having a loss factor tan (.sub.2) at 60 C., wherein the loss factor tan (.sub.2) of the second elastomeric compound is at least equal to 0.15 and at most equal to 0.28.

6. The tire according to claim 2, wherein the complex dynamic shear modulus G1* of the first elastomeric compound is at most equal to 2 MPa.

7. The tire according to claim 4, wherein the complex dynamic shear modulus G.sub.2* of the second elastomeric compound is at most equal to 1.7 MPa.

Description

[0044] 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:

[0045] FIG. 1: a perspective view of a tire for a vehicle for agricultural use,

[0046] FIG. 2: a view in a radial direction (Z) of the tread of a tire for a vehicle for agricultural use,

[0047] FIG. 3: a view in section on a meridian plane (XY) of a portion of tread of a tire according to the invention.

[0048] FIGS. 1 and 2 respectively depict a perspective view of a tire 1 for a vehicle for agricultural use, 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. This lug 3 extends radially outwards, from the 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.

[0049] FIG. 3 shows a view in cross section, on a meridian plane (XY), of a portion of tread 2 of a tire according to the invention. In each lug 3, a first lug portion 31, made of a first elastomeric compound, 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 0.5 times and at most equal to 1 times the radial height H of the lug. Also in each lug 3, a second lug portion 32, made of a second elastomeric compound, extends radially inwards, from the first interface 7 as far as the bottom surface 5, over a radial distance D.sub.2. In addition, the second elastomeric compound extends radially into the lugs 3 and the grooves 4 from the bottom surface 5 as far as a second interface 8 over a radial distance D.sub.3. The portion of tire comprised between the bottom surface 5 and the second interface 8 constitutes the void rubber.

[0050] 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 (.sub.1) equal to 0.29, and the second elastomeric compound has a complex dynamic shear modulus G.sub.2* equal to 1.31 MPa and a loss factor tan (.sub.2) equal to 0.22.

[0051] The first and second elastomeric compounds may have chemical compositions that differ from those described hereinabove, depending on the desired performance sought.

[0052] The invention can be extended to a tread comprising lugs made of a first and of a second elastomeric compound, the second elastomeric compound being bounded by the bottom surface. The tire portion radially on the inside of the bottom surface may be made of at least a third elastomeric compound with a chemical composition different from those of the first and second elastomeric compounds.

[0053] The invention can be applied 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 tire.