Tire Comprising a Tread

Abstract

A tire with a tread (10) having at least one series (12) of rubber blocks (13.sub.i−1, 13.sub.i, 13.sub.i+1, 13.sub.i+2) delimited pairwise by a series of sipes (14.sub.i−1,14.sub.i, 14.sub.i+1,14.sub.i+2,14.sub.i+3), with the blocks (13.sub.i−1, 13.sub.i, 13.sub.i+1, 13.sub.i+2) extending one after another in a circumferential direction (X), each block (13.sub.1−1, 13.sub.i, 13.sub.i+1, 13.sub.i+2) of the series (12) of rubber blocks having a circumferential length (L.sub.i−1, L.sub.i, L.sub.i+1, L.sub.i+2)), each sipe (14.sub.i−1,14.sub.i, 14.sub.i+1, 14.sub.i+2,14.sub.1+3) having a circumferential width (E.sub.i−1, E.sub.i,E.sub.i+1, E.sub.i+2, E.sub.i+3). The series (12) of rubber blocks have blocks belonging to at least two different classes of blocks ((13.sub.i−113.sub.i); (13.sub.i+1, 13.sub.i+2)), the blocks of the one same class having a substantially identical circumferential length, the blocks of two different classes of blocks having distinct circumferential lengths.

Claims

1. A tire comprising a tread, said tread comprising at least one series of rubber blocks delimited pairwise by a series of sipes, said blocks extending one after another in a circumferential direction (X), each block of the series of rubber blocks having a circumferential length, each sipe having a circumferential width wherein the series of rubber blocks comprises blocks belonging to at least two different classes of blocks, the blocks of the one same class having a substantially identical circumferential length, the blocks of two different classes of blocks having distinct circumferential lengths, and wherein the series of sipes comprises sipes belonging to at least two different classes of sipes, the sipes of the one same class of sipes having a substantially identical circumferential width, the sipes of two different classes of sipes having distinct circumferential widths, and wherein the blocks belonging to the class of blocks of smallest circumferential length Cb.sub.min are delimited, at least in part, by sipes belonging to the class of sipes of smallest circumferential width Cs.sub.min and wherein the blocks belonging to the class of blocks of greatest circumferential length Cb.sub.max are delimited, at least in part, by sipes belonging to the class of sipes of greatest circumferential width Cs.sub.max. 2. The tire according to Claim 1, wherein blocks belonging to the class of blocks of smallest circumferential length Cb.sub.min are delimited by two sipes belonging to the class of sipes of smallest circumferential width CS.sub.min and/or blocks belonging to the class of blocks of greatest circumferential length Cb.sub.max are delimited by two sipes belonging to the class of sipes of greatest circumferential width CS.sub.max. 3. The tire according to Claim 1, wherein the number of classes of blocks is less than or equal to 5. 4. The tire according to Claim 1, wherein the number of classes of sipes is less than or equal to 5.

5. The tire according to Claim 1, wherein a first ratio R1 corresponding to the ratio between the circumferential width of a sipe belonging to the class of sipes of smallest circumferential width Cs.sub.min to the circumferential length of a block belonging to the class of blocks of smallest circumferential length Cb.sub.min and a second ratio R2 corresponding to the ratio between the circumferential width of a sipe belonging to the class of sipes of greatest circumferential width Cs.sub.max to the circumferential length of a block belonging to the class of blocks of greatest circumferential length Cb.sub.max, wherein the first ratio R1 and the second ratio R2 are determined in such a way that the ratio of said first ratio R1 to said second ratio R2 is at least equal to 0.9 and at most equal to 1.1.

6. The tire according to Claim 1, wherein the ratio between the circumferential length of a block belonging to the class of blocks of greatest circumferential length Cb.sub.max to the circumferential length of a block belonging to the class of blocks of smallest circumferential length Cb.sub.min is at least equal to 1.2 and at most equal to 2.

7. The tire according to Claim 1, wherein the tread comprises a tread surface, wherein the sipes form lines on said tread surface, said lines being linear and inclined with respect to an axial direction (Y) by an angle of inclination α, said angle of inclination a being at least equal to 5 degrees and at most equal to 60 degrees or the sipes form lines on said tread surface, said lines being curved.

8. The tire according to Claim 1, wherein the tread is delimited by two edges, and wherein the series of rubber blocks is positioned near to one of said edges of the tread.

9. The tire according to Claim 2, wherein the number of classes of blocks is less than or equal to 5.

10. The tire according to claim 3, wherein the number of classes of sipes is less than or equal to 5.

11. The tire according to claim 1, wherein the number of classes of blocks is less than or equal to 3.

12. The tire according to claim 1, wherein the number of classes of sipes is less than or equal to 3.

Description

[0031] FIG. 1 is a schematic view showing part of a tread of a tire according to a first embodiment of the invention;

[0032] FIG. 2 is a view in section on A-A of FIG. 1;

[0033] FIG. 3 is a schematic view showing part of a tread of a tire according to a second embodiment of the invention.

[0034] In the various figures, identical or similar elements bear the same references.

[0035] FIG. 1 is a schematic view showing part of a tread 10 of a tire according to a first embodiment of the invention. FIG. 2 is a view in section on A-A of FIG. 1. The tread 10 is delimited axially by two edges 11A and 11 B. These two edges 11A, 11B determine the width W of the tread 10. Beyond these two edges 11A, 11B extend the two sidewalls of the tire.

[0036] The tread 10 is delimited radially by a surface of the tread. This tread surface groups together all the points of the tire that will come into contact with the ground under normal running conditions. More specifically, the tread 10 comprises n rubber blocks of which only some of these blocks 13.sub.i−1, 13.sub.i, 13.sub.i+1, 13.sub.i+2 are referenced in FIG. 1. These rubber blocks are organized as a series 12 of rubber blocks which extend one after another in a circumferential direction. This series 12 of blocks therefore forms a rubber rib. This rubber rib here extends along the entire circumference of the tire. In the embodiment of FIG. 1, the series 12 of rubber blocks 13.sub.i−1, 13.sub.i, 13.sub.i+1, 13.sub.i+2 extends in the central part of the tread 12. As a variant, the series 12 of rubber blocks 13.sub.i−1, 13.sub.i, 13.sub.i+1, 13.sub.i+2 is offset with respect to this central part. For example, the series 12 of rubber blocks is positioned near one of said edges 11A, 11B of the tread 10.

[0037] The rubber blocks 13.sub.i−1, 13.sub.i, 13.sub.i+1, 13.sub.i+2 are delimited pairwise by a series of sipes 14.sub.i−1,14.sub.i, 14.sub.i+1, 14.sub.i+2. These sipes determine a circumferential length L.sub.i−1, L.sub.i,L.sub.i+1, L.sub.i+2 for each block 13.sub.i−1, 13.sub.i, 13i.sub.i+1, 13.sub.i+2. Certain circumferential block-lengths are substantially identical. It is therefore possible to classify the blocks 13.sub.i−1, 13.sub.i, 13.sub.i+1, 13.sub.i+2 into at least two different classes of blocks. The blocks of the one same class have a substantially identical circumferential length, and the blocks of two different classes of blocks have distinct circumferential lengths. Thus, in the embodiment of FIGS. 1 and 2, the blocks 13.sub.i−1, 13.sub.i can be associated within the one same first class of blocks as the length of the block 13.sub.i−1 is substantially identical to the length L.sub.i of the block 13.sub.i. Likewise, the blocks 13.sub.i+1, 13.sub.i+2 can be associated within the one same second class of blocks as the length L.sub.i+1 of the block 13.sub.i+1 is substantially identical to the length L.sub.i+2 of the block 13.sub.i+2. The blocks belonging to the first class of blocks here have a greater circumferential length than the blocks belonging to the second class of blocks. The first class of blocks will be referred to hereinafter as Cbmax and the second class of blocks will also be referred to hereinafter as Cb.sub.min.

[0038] As has already been specified, the rubber blocks 13.sub.i−1, 13.sub.i, 13.sub.i+1,13.sub.i+2 are delimited by a series of sipes 14.sub.i−1,14.sub.i, 14.sub.i+2,14.sub.i+3. Each sipe 14.sub.i−1,14.sub.i, 14.sub.i+1, 14.sub.i+2,14.sub.i+3 has a circumferential width E.sub.i−1, E.sub.i,E.sub.i+1, E.sub.i+2, E.sub.i+3. Certain circumferential sipe-widths are substantially identical. It is therefore possible to classify the sipes 14.sub.i−1, 14.sub.i, 14.sub.i+1, 14.sub.1+2, 14.sub.i+3 into at least two different classes of sipes. The sipes of the one same class have a substantially identical circumferential width, and the sipes of two different classes have distinct circumferential widths. Thus, in the embodiment of FIGS. 1 and 2, the sipes 14.sub.i−1, 14.sub.i, can be associated within the one same first class of sipes as the circumferential width E.sub.i−1 of the sipe is substantially identical to the circumferential width E.sub.i of the sipe 14.sub.i. Likewise, the sipes 14.sub.i+2, 14.sub.i+3 can be associated within the one same second class of sipes as the circumferential width E.sub.i+2 of the sipe 14.sub.i+2 is substantially identical to the circumferential width E.sub.i+3 of the sipe 14.sub.i+3. A third class of sipes here comprises the sipe 14.sub.i+1 of circumferential width E.sub.i+1. The sipes 14.sub.i−1, 14.sub.i belonging to the first class of sipes here have a greater circumferential width than the sipes 14.sub.i+2, 14.sub.+3 belonging to the second class of sipes and than the sipe 14.sub.i+1 belonging to the third class of sipes. The sipe belonging to the third class of sipes has a greater circumferential width than the sipes belonging to the second class of sipes. The first class of sipes will be referred to hereinafter as Cs.sub.max and the second class of sipes will also be referred to hereinafter as Cs.sub.min. The blocks 13.sub.i−1, 13.sub.i, 13.sub.i+1, 13.sub.i+2 and the sipes 14.sub.i−1,14.sub.i, 14.sub.i+2,14.sub.i+3 are organized in such a way that the blocks 13.sub.i+1, 13.sub.i+2 belonging to the class of blocks of smallest circumferential length Cb.sub.min are delimited, at least in part, by sipes 14.sub.i+2, 14.sub.i+3 belonging to the class of sipes of smallest circumferential width Cs.sub.min and the blocks 13.sub.i−1, 13.sub.i belonging to the class of blocks of greatest circumferential length Cb.sub.max are delimited, at least in part, by sipes 14.sub.i−1,14.sub.i belonging to the class of sipes of greatest circumferential width Cs.sub.max. More specifically, in the embodiment of FIGS. 1 and 2, the block 13.sub.i+2 belonging to the class of blocks of smallest circumferential length Cb.sub.min is delimited by two sipes 14.sub.i+2, 14.sub.i+3 belonging to the class of sipes of smallest circumferential width Cs.sub.min and the block 13.sub.i-1 belonging to the class of blocks of greatest circumferential length Cb.sub.max is delimited by two sipes 14.sub.i−1,14.sub.i belonging to the class of sipes of greatest circumferential width Cs.sub.max.

[0039] Within the one same class of sipes, the circumferential width of the sipes may differ significantly. However, this difference is minimal. Thus it is considered that, at most, the difference in circumferential width between the sipe of greatest circumferential width of the class of sipes and the sipe of smallest circumferential width of said class of sipes is at most equal to 0.1 mm. Likewise, blocks are considered to belong to the one same class of blocks even if their circumferential length differs significantly. However, this difference should be minimal. Thus it is considered that, at most, the difference in circumferential length between the block of greatest circumferential length of the class of blocks and the block of smallest circumferential length of said class of blocks is at most equal to 0.1 mm.

[0040] Furthermore, it is possible to determine a first ratio R1 corresponding to the ratio between the circumferential width E.sub.i+2, E.sub.i+3 of a sipe 14.sub.i+2, 14.sub.i+3 belonging to the class of sipes of smallest circumferential width Cs.sub.min to the circumferential length L.sub.i+1, L.sub.i+2 of a block 13.sub.i+i, 13.sub.i+2 belonging to the class of blocks of smallest circumferential length Cb.sub.min. It is also possible to determine a second ratio R2 corresponding to the ratio between the circumferential width E.sub.i−1, E.sub.i of a sipe 14.sub.i−1, 14.sub.i belonging to the class of sipes of greatest circumferential width Cs.sub.max to the circumferential length L.sub.i−1, L.sub.i of a block 13.sub.i−1, 13.sub.i belonging to the class of blocks of greatest circumferential length Cb.sub.max. The first ratio R1 and the second ratio R2 are determined in such a way that the ratio of said first ratio R1 to said second ratio R2 is greater than or equal to 0.9 and less than or equal to 1.1.

[0041] In addition, the ratio between the circumferential length , L.sub.i−1, L.sub.i of a block belonging to the class of blocks of greatest circumferential length Cb.sub.max to the circumferential length L.sub.i+1, L.sub.i+2 of a block 13.sub.i+1,13.sub.i+2 belonging to the class of blocks of smallest circumferential length Cb.sub.min is at least equal to 1.2 and at most equal to 2. As a preference, this ratio is comprised between 1.4 and 1.75.

[0042] Finally, in the embodiment of FIGS. 1 and 2, the sipes 14.sub.i−1,14.sub.i, 14.sub.i+1, 14.sub.i+2,14.sub.i+3 form linear lines on the tread surface of the tread 10. These lines here are oriented in an axial direction Y.

[0043] In the embodiment of FIG. 3, the sipes 14.sub.i−1,14.sub.i, 14.sub.i+1, 14.sub.i+2, 14i.sub.i+3 form linear lines which are inclined with respect to the axial direction Y. It will now be noted that the foregoing description of the blocks 13.sub.i−1, 13.sub.i, 13.sub.i+1, 13.sub.i+2 and of the sipes 14.sub.i−1,14.sub.i, 14.sub.i+1, 14.sub.i+2, 14.sub.i+3 and their arrangement in the tread applies mutatis mutandis to the embodiment of FIG. 3. The lines here are inclined by an angle of inclination α. This angle of inclination α is at least equal to 5 degrees and at most equal to 60 degrees. As a preference, this angle of inclination is at least equal to 30 degrees and at most equal to 50 degrees.

[0044] In an embodiment which has not been depicted, the sipes form curved lines on the tread surface of the tread 10.

[0045] In the embodiments of FIG. 1 and of FIG. 3, the number of classes of sipes is equal to 3. As a variant, this number of classes of sipes is less than or equal to 5. For example, the number of classes of sipes is equal to 4. In such a case, the sipes of the classes of sipes may have the following circumferential-width values: 0.8 mm, 1 mm, 1.2 mm, 1.5 mm. As has already been specified, within the one same class of sipes the circumferential-width values may differ significantly. Thus, the 0.8-mm class of sipes may group together sipes with circumferential-width values comprised between 0.75 mm and 0.85 mm. Likewise, the 1-mm class of sipes may group together sipes with circumferential-width values comprised between 0.95 mm and 1.05 mm. The 1.2-mm class of sipes may group together sipes with circumferential-width values comprised between 1.15 mm and 1.25 mm, and finally, the 1.5-mm class of sipes may group together sipes with circumferential-width values comprised between 1.45 mm and 1.55 mm.

[0046] In the embodiments of FIG. 1 and of FIG. 3, the number of classes of blocks is equal to 2. As a variant, the number of classes of blocks is less than or equal to 5. As a preference, this number of classes of blocks is equal to 3. In such a case, the blocks may have the following circumferential-length values: 17.9 mm, 21.2 mm, 25.8 mm. As has already been specified, within the one same class of blocks the circumferential-length values may differ significantly. Thus, the 17.9-mm class of blocks may group together blocks with circumferential-length values comprised between 17.4 mm and 18.4 mm. Likewise, the 21.2-mm class of blocks may group together blocks with circumferential-length values comprised between 20.7 mm and 21.7 mm, and finally, the 25.8-mm class of blocks may group together blocks with circumferential-length values comprised between 25.3 mm and 26.3 mm.