Tire for a Mixed-Use Agricultural Vehicle

Abstract

A tire for an agricultural vehicle, having a tread consisting of blocks in pairs separated by voids and arranged, over the width of the tread, in a median row, two intermediate rows and two lateral rows. To obtain compromise between rolling resistance and service life in terms of wear in road use, two consecutive blocks of the median row) are separated by a transverse void with a width (E1) at most 2.5 mm, the mean circumferential slenderness ratio of every block) of the median row is at least 0.95 and at most 1.15, every block of each intermediate row has a leading face) in the circumferential rolling direction tire which forms a mean angle (D2) equal at least to 30? with a radial direction (ZZ) tire, and the mean circumferential slenderness ratio of every block in each lateral row is at most 0.9.

Claims

1. A tire for an agricultural vehicle, comprising a tread with an axial width (L) and consisting of pairs of blocks separated by voids and arranged, over the width of the tread, in a median row, two intermediate rows and two lateral rows, the voids being either transverse voids which form an angle at least equal to 60? with a circumferential direction (XX) of the tire or circumferential voids which form an angle at most equal to 30? with the circumferential direction (XX), the median row being centred on a median circumferential plane (E) of the tire, the two intermediate rows being positioned axially on either side of the median row and separated therefrom by circumferential voids, and the two lateral rows being positioned respectively axially outside an intermediate row and separated therefrom by a circumferential void, each median row, intermediate row and lateral row comprising a circumferential distribution of pairs of blocks separated by transverse voids and each having a mean radial height (H1, H2, H3), a mean circumferential length (B1, B2, B3) and a mean circumferential slenderness ratio defined as the ratio between the mean radial height and the mean circumferential length of the block, the blocks; of a same lateral row extending axially towards the outside in the extension of the blocks of the adjacent intermediate row, such that any set of two blocks of the lateral row and intermediate row respectively, in the extension of one another, forms a lug, wherein two consecutive blocks in the median row are separated by a transverse void with a width (E1) equal at most to 2.5 mm, the mean circumferential slenderness of any block in the median row; is at least equal to 0.95 and at most equal to 1.15, and every block of each intermediate row comprises a leading face in the circumferential rolling direction of the tire which forms a mean angle (D2) equal at least to 30? with a radial direction (ZZ) of the tire, and wherein the mean circumferential slenderness of any block in each lateral row is at most equal to 0.9.

2. The tire as claimed in claim 1, wherein the median row has an axial width (L1) at least equal to 15% and at most equal to 25% of the axial width (L) of the tread.

3. The tire as claimed in claim 1, wherein the median row has a local volumetric void ratio at most equal to 20%.

4. The tire as claimed in claim 1, wherein every transverse void separating two consecutive blocks of the median row forms an angle at least equal to 70? with the circumferential direction (XX).

5. The tire as claimed in claim 1, wherein every transverse void separating two consecutive blocks of the median row has a depth (P1) at least equal to 50% of the mean radial height (H1) of the block.

6. The tire as claimed in claim 1, wherein every transverse void separating two consecutive blocks of the median row is extended radially inwardly by a cavity.

7. The tire as claimed in claim 1, wherein each intermediate row has an axial width (L2) at least equal to 15% and at most equal to 25% of the axial width (L) of the tread-.

8. The tire as claimed in claim 1, wherein each intermediate row has a local volumetric void ratio at least equal to 40%.

9. The tire as claimed in claim 1, wherein the mean circumferential slenderness ratio of every block of each intermediate row is at least equal to 0.5 and at most equal to 1.0.

10. The tire as claimed in claim 1, wherein every block of an intermediate row comprises a leading face which forms a mean angle (D2) at least equal to 35? with a radial direction (ZZ) of the tire.

11. The tire as claimed in claim 1, wherein each lateral row has an axial width (L3) at least equal to 15% and at most equal to 25% of the axial width (L) of the tread.

12. The tire as claimed in claim 1, wherein each lateral row has a local volumetric void ratio at least equal to 40%, preferably at least equal to 55%.

13. The tire as claimed in claim 1, wherein the mean circumferential slenderness ratio of every block of each lateral row is at most equal to 0.8.

14. The tire as claimed in claim 1, wherein the mean circumferential slenderness ratio of every block of each lateral row is at least equal to 0.6.

15. The tire as claimed in claim 1, wherein every block of a lateral row comprises a leading face which forms a mean angle (D3) at least equal to 10? and at most equal to 30? with a radial direction (ZZ) of the tire.

16. The tire as claimed in claim 1, wherein every block of a lateral row comprises a leading face and a trailing face which form, with a radial direction (ZZ) of the tire, mean angles (D3, D3) which are equal in absolute values.

17. The tire as claimed in claim 1, wherein the circumferential distribution of blocks of each intermediate row and lateral row comprises at least 26 blocks.

18. The tire as claimed in claim 1, wherein the circumferential distribution of blocks of each intermediate row and lateral row comprises at most 32 blocks.

Description

[0072] The present invention will be understood better with the aid of FIGS. 1 to 6 described below:

[0073] FIG. 1: shows a perspective view of a tire according to the invention,

[0074] FIG. 2: shows a front view of a tire according to the invention,

[0075] FIG. 3: shows a meridian section of a tread of a tire according to the invention,

[0076] FIG. 4: shows a circumferential section of a median row portion of a tread of a tire according to the invention,

[0077] FIG. 5: shows a circumferential section of an intermediate row portion of a tread of a tire according to the invention,

[0078] FIG. 6: shows a circumferential section of a lateral row portion of a tread of a tire according to the invention.

[0079] FIG. 1 is a perspective view of a tire according to the invention. The tire 1 for an agricultural vehicle comprises a tread 2 consisting of blocks (31, 32, 33) in pairs separated by voids (41, 42, 43, 51, 52) and arranged, over the width of the tread 2, in a median row 21, two intermediate rows 22 and two lateral rows 23. The voids (41, 42, 43, 51, 52) are either transverse voids (41, 42, 43) or circumferential voids (51, 52).

[0080] FIG. 2 is a front view of a tire according to the invention; The tire 1 for an agricultural vehicle, with a diameter D in a state not mounted on a rim and not inflated, comprises a tread 2 with an axial width L in an axial direction YY and consisting of pairs of blocks (31, 32, 33) separated by voids (41, 42, 43, 51, 52) and arranged, over the width of the tread 2, in a median row 21, two intermediate rows 22 and two lateral rows 23. The voids (41, 42, 43, 51, 52) are either transverse voids (41, 42, 43) which form an angle at least equal to 60? with a circumferential direction XX of the tire 1, or circumferential voids (51, 52) which form an angle at most equal to 30? with the circumferential direction XX. The median row 21 with an axial width L1 is centred on a median circumferential plane E of the tire. The two intermediate rows 22, each with an axial width L2, are axially positioned on either side of the median row 21 and separated therefrom by circumferential voids 51, each with a width E2. The two lateral rows 23, each with an axial width L3, are axially positioned respectively outside an intermediate row 22 and separated therefrom by a circumferential void 52, with a width E3. Each respective median row 21, intermediate row 22 and lateral row 23 consists of a circumferential distribution of blocks (31, 32, 33) in pairs separated by transverse voids (41, 42, 43) and each having a mean circumferential length (B1, B2, B3). The circumferential length B1 of a block 31 of the median row 21 is the circumferential distance measured between the two incision-type transverse voids 41 delimiting it. The circumferential length B2 of a block 32 of the intermediate row 22 is the mean circumferential distance measured between a leading face 321 and a trailing face 322 of said block 32. The circumferential length B3 of a block 33 of the lateral row 23 is the mean circumferential distance measured between a leading face 331 and a trailing face 332 of said block 33. The blocks 33 of a same lateral row 23 extend axially towards the outside in the extension of the blocks 32 of the adjacent intermediate row 22, such that any set of two blocks (33, 32) of the lateral row 23 and intermediate row 22 respectively, in the extension of one another, forms a lug.

[0081] FIG. 3 shows a meridian section of a tread of a tire according to the invention. The tread has an axial width L and is divided into a median row 21 with an axial width L1, two intermediate rows 22 each with an axial width L2, and two lateral rows 23 each with an axial width L3. Each intermediate row 22 is respectively separated from the median row 21 by a circumferential void 51 with a width E2 and a depth P2, and from the closest lateral row 23 by a circumferential void 52 with a width E3 and a depth P3.

[0082] FIG. 4 shows a circumferential section, on a plane XZ, of a portion of a median row 21 of a tread of a tire according to the invention. The median row 21 consists of a circumferential distribution of blocks 31 each having a circumferential length B1 and a height H1. The blocks 31 are separated in pairs by transverse incision-type voids 41 with a width E1. According to the invention, two consecutive blocks 31 of the median row 21 are separated by a transverse void 41 with a width E1 at most equal to 2.5 mm. In the embodiment shown, transverse incisions 41 with depth H1 alternate with ones with a depth of less than H1. This choice facilitates production of the tire by reducing the force necessary for removing the tire from the mold after curing, thanks to the smaller depth of some of the transverse incisions.

[0083] FIG. 5 shows a circumferential section, on a plane XZ, of a portion of an intermediate row 22 of a tread of a tire according to the invention. The intermediate row 22 consists of a circumferential distribution of blocks 32 each with a circumferential length B2mean distance measured between a leading face 321 and a trailing face 322and a height H2. The blocks 32 are separated in pairs by transverse groove-type voids 42. According to the invention, every block 32 of each intermediate row 22 comprises a leading face 321 in the circumferential direction of rolling of the tire, which forms a mean angle D2 at least equal to 30? with a radial direction ZZ of the tire, and a trailing face 322 forming a mean angle D2 with the radial direction ZZ of the tire.

[0084] FIG. 6 shows a circumferential section, on a plane XZ, of a portion of a lateral row 23 of a tread of a tire according to the invention. The lateral row 23 consists of a circumferential distribution of blocks 33 each with a circumferential length B3mean distance measured between a leading face 331 and a trailing face 332and a height H3. The blocks 33 are separated in pairs by transverse groove-type voids 43. According to the invention, the mean circumferential slenderness ratio of every block 33 of each lateral row 23 is at most equal to 0.9. Also, every block 33 of each the lateral row 23 comprises a leading face 331 in the circumferential direction of rolling of the tire, which forms a mean angle D3 at least equal to 10? and at most equal to 30? with a radial direction ZZ of the tire, and a trailing face 332 forming a mean angle D3 with the radial direction ZZ of the tire.

[0085] The invention has been studied more particularly in the case of an agricultural tire of size 600/70 R 30.

[0086] Table 1 below presents the technical features of a preferred exemplary embodiment of the invention, as shown in FIGS. 1 to 6.

TABLE-US-00001 TABLE 1 Geometric features Values Comments Axial width L of the tread 2 606 mm External diameter D of tire 1609 mm Measured on the tire not fitted on the rim and not inflated Axial width L1 of the median row 21 124 mm 124/606 = 20% of L => Between 15% and 25% of L Axial width L2 of each intermediate row 115 mm 115/606 = 19% of L => 22 Between 15% and 25% of L Axial width L3 of each lateral row 23 104 mm 115/606 = 19% of L => Between 15% and 25% of L Total volumetric void ratio of tread 2 53% Local volumetric void ratio of median 11% Less than 20% row 21 Local volumetric void ratio of each 64% More than 55% intermediate row 22 Local volumetric void ratio of each 63% More than 55% lateral row 23 Mean radial height H1 of a block 31 in 48 mm median row 21 Mean circumferential length B1 of a 43 mm block 31 in median row 21 Circumferential slenderness ratio H1/B1 1.12 Between 0.95 and 1.15 of a block 31 in median row 21 Width E1 of a transverse void 41 1.6 mm Less than 2.5 mm => Incision between two consecutive blocks 31 in median row 21 Depth of transverse void 41 between two 48 mm Equal to height H1 of block consecutive blocks 31 in median row 21 Depth of secondary transverse incision 31 Equal to 70% of height H1 of 411 in a block 31 in median row 21 block Mean angle of transverse void 41 75? Greater than 60? between two consecutive blocks 31 in median row, relative to circumferential direction XX4 Mean radial height H2 of a block 32 in 46 mm intermediate row 22 Mean circumferential length B2 of a 71 mm block 32 in intermediate row 22 Circumferential slenderness ratio H2/B2 0.65 Between 0.5 and 1 of a block 32 in intermediate row 22 Mean angle D2 of leading face 321 of Between 34? and 45? Greater than 30? block 32 in intermediate row 22 Mean angle of transverse void 42 67? Greater than 60? between two consecutive blocks 32 in intermediate row 22, relative to circumferential direction Mean radial height H3 of a block 33 in 46 mm lateral row 23 Mean circumferential length B3 of a 64 mm block 33 in lateral row 23 Circumferential slenderness ratio H3/B3 0.72 Less than 0.9, preferably of a block 33 in lateral row 23 between 0.6 and 0.8. Mean angle D3 of leading face 331 of Between 20? and 28? Greater than 10? and less than block 33 in lateral row 23 30? Mean angle of transverse void 43 75? Greater than 60? between two consecutive blocks 33 in lateral row 23 Number of blocks N of an intermediate 28 Between 26 and 32 row 22 or lateral row 23 (over entire circumference of tire) Width E2 of intermediate 131 mm At level of tread surface in circumferential void 51 new condition Depth P2 of intermediate circumferential 46 mm void 51 Width E3 of intermediate 121.5 mm At level of tread surface in circumferential void 52 new condition Depth P3 of intermediate circumferential 46 mm void 52

[0087] The inventors have compared, by digital simulation and/or internal testing, the performance levels according to the invention and those of a reference tire 600/70 R 30 Michelin MACHXBIB. The rolling resistance in road use for a tire subjected to a load Z=3801 Kg, inflated to a pressure P=1.8 bar and travelling at a speed V=15 km/h, was reduced from 14.8 kg/t for the reference tire to 11.6 kg/t for the tire according to the invention, or a reduction of 21%. The service life in terms of wear, defined as the mileage travelled on the road before removal of the fully worn tire, for the tire according to the invention, is 20% greater than that of the reference tire.