JP5098400B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve the tire tear resistance while maintaining the uneven wear resistance of the tire.

  In heavy-duty pneumatic tires that have rib patterns and are mounted on the steer shaft, in order to suppress uneven wear on the land (particularly uneven wear on the land in the tread shoulder region), multi-sipe is applied to the edge of the land. (Sipes arranged at a fine pitch) are arranged.

  However, in such a configuration, there is a problem that when the tire rides on a curb or the like, a tier is generated starting from this multi-sipe.

  In addition, the technique described in patent document 1 is known for the conventional pneumatic tire which has such a multi sipe.

JP 2001-55013 A

  An object of the present invention is to provide a pneumatic tire capable of improving the tire tear resistance while maintaining the tire's uneven wear resistance.

In order to achieve the above object, a pneumatic tire according to the present invention includes a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of land portions defined by the circumferential main grooves as tread portions. A plurality of main sipes and a plurality of auxiliary sipes are arranged in the tire circumferential direction along an edge portion of the land portion, and at least one auxiliary sipe is disposed between the adjacent main sipes. is arranged, when calling the sipe area an area for cutting the land portion by sipe, the sipe area S of the main sipes and the sipes area s of the auxiliary sipes have a relationship of S> s, sipes of the main sipes When a sipe is divided into a tread surface side region and a tire inner side region with an intermediate position of the depth as a boundary, the sipe area a of the tread side region of the auxiliary sipe and the sipe area b ( s-a) and are have a relation of a> b, and, the main sipes and sipe area A of the tread side regions and sipes area a tread side region of the auxiliary sipe is 0.50 ≦ a / A ≦ The sipe area B in the tire inner side region of the main sipe and the sipe area b in the tire inner side region of the auxiliary sipe have a relationship of 0 ≦ b / B ≦ 0.25. It is characterized by.

In this pneumatic tire, an auxiliary sipe is disposed between adjacent main sipes, so that the sipe density on the tread of the land portion is appropriately ensured. In such a configuration, when the tire is in contact with the tire, the compression amount of the land portion in the tire circumferential direction is appropriately absorbed by the main sipe and the auxiliary sipe. As a result, uneven wear of the land portion is reduced, and there is an advantage that the uneven wear resistance performance of the tire is maintained appropriately. Further, since the sipe area S of the main sipe and the sipe area s of the auxiliary sipe have a relationship of S> s, the rigidity of the land portion is higher than that of the configuration in which the main sipe and the auxiliary sipe have the same sipe area. high. Thereby, since generation | occurrence | production of the tear in a land part is reduced, there exists an advantage which the tear resistance performance of a tire improves. Moreover, since the sipe area a of the tread side area of the auxiliary sipe and the sipe area b (= sa) of the tire inner side area have a relationship of a> b, the sipe density of the land portion is on the tread side of the land portion. It becomes dense (sparse inside the land). In such a configuration, the compression amount of the land portion is properly absorbed by the main sipe and the auxiliary sipe on the tread side of the land portion. As a result, the uneven wear of the land portion is more effectively reduced, so that the uneven wear resistance performance of the tire is maintained appropriately.
In this pneumatic tire, the distribution of the sipe area s of the auxiliary sipe is optimized in the tread side region (sipe area a) and the tire inner side region (sipe area b). The rigidity inside the tire is optimized. As a result, uneven wear of the land portion is reduced, and there is an advantage that the uneven wear resistance performance of the tire is maintained appropriately.

  In the pneumatic tire according to the present invention, the sipe interval Ps in the tire circumferential direction of the sipe group including the main sipe and the auxiliary sipe and the sipe depth D of the main sipe are 0.2 ≦ Ps / D ≦ 0. .5 relationship.

  In this pneumatic tire, the arrangement density of the sipe in the land portion is optimized by optimizing the sipe interval Ps of the sipe group. As a result, uneven wear of the land portion is reduced, and there is an advantage that the uneven wear resistance performance of the tire is maintained appropriately.

  Moreover, in the pneumatic tire according to the present invention, the sipe interval Pb in the tire circumferential direction between the adjacent main sipes is substantially uniform over the entire tire circumference.

  In this pneumatic tire, since the main sipes that have a great influence on the rigidity of the land portion are arranged at the edge portions of the land portion at equal intervals, the main sipes are arranged at uneven intervals and In comparison, the ground contact pressure at the land is made uniform. As a result, uneven wear of the land portion is reduced, and there is an advantage that the uneven wear resistance performance of the tire is improved.

  Moreover, in the pneumatic tire according to the present invention, the sipe interval Ps in the tire circumferential direction between the adjacent main sipe and the auxiliary sipe changes as it goes in the tire circumferential direction.

  In this pneumatic tire, generation of pattern noise during tire rolling is suppressed as compared with a configuration in which sipes are arranged at uniform sipe intervals. Thereby, there exists an advantage which the noise performance of a tire improves.

  Further, in the pneumatic tire according to the present invention, the distribution of the sipe area of the auxiliary sipe is gradually reduced from the tread surface side of the land portion toward the tire inner side.

  In this pneumatic tire, the distribution of the sipe area s of the auxiliary sipe is optimized, and the remaining amount of the auxiliary sipe when the land wear progresses is optimized. Thus, there is an advantage that the function of the auxiliary sipe is ensured from the early wear stage to the late wear stage, and the uneven wear resistance performance of the tire is properly maintained.

  In the pneumatic tire according to the present invention, the sipe depth D of the main sipe and the groove depth GD of the circumferential main groove are 0.5 ≦ D / GD ≦ 1.0.

  In this pneumatic tire, by defining the sipe depth D of the main sipe, the remaining amount of the main sipe when the wear of the land portion progresses is optimized. Thereby, there is an advantage that the function of the main sipe is ensured from the initial wear of the land portion to the late wear, and the uneven wear resistance performance of the tire is properly maintained.

  In the pneumatic tire according to the present invention, the sipe area S, the sipe depth D, and the sipe width W of the main sipe have a relationship of 0.7 ≦ S / (D × W) ≦ 1.0.

  In this pneumatic tire, since the sipe area S of the main sipe is optimized with respect to the installation range of the main sipe, the function of the main sipe is appropriately ensured. Thereby, there exists an advantage by which the uneven wear-proof performance of a tire is maintained appropriately.

  In the pneumatic tire according to the present invention, the sipe width W in the tire width direction of the main sipe and the auxiliary sipe on the tread surface of the land portion and the land width WL in the tire width direction of the land portion are 0. 1 ≦ W / WL ≦ 0.2.

  In this pneumatic tire, the functions of the main sipe and the auxiliary sipe are appropriately ensured by defining the sipe width W of the main sipe and the auxiliary sipe. Thereby, there exists an advantage by which the uneven wear-proof performance of a tire is maintained appropriately.

  In the pneumatic tire according to the present invention, the sipe depth D of the main sipe and the sipe depth d of the auxiliary sipe have a relationship of d / D ≦ 0.5.

  In this pneumatic tire, since the auxiliary sipe has a groove depth d (≦ D / 2) shallower than the groove depth D of the main sipe, the main sipe and the auxiliary sipe have a same sipe depth. Therefore, the sipe density of the land part becomes denser on the tread side of the land part. As a result, the uneven wear of the land portion is more effectively reduced, so that the uneven wear resistance performance of the tire is maintained appropriately.

  In the pneumatic tire according to the present invention, the main sipe and the auxiliary sipe are disposed in the land portion of the tread shoulder region.

  Uneven wear tends to occur at the land portion of the tread shoulder region, particularly at the edge portion of the land portion on the outer side in the tire width direction. Therefore, by arranging the main sipe and the auxiliary sipe in the land portion, uneven wear of the land portion is effectively reduced. Thereby, there is an advantage that the uneven wear resistance performance of the tire can be obtained more remarkably.

  In the pneumatic tire according to the present invention, the land portion having the main sipe and the auxiliary sipe is a rib extending in a tire circumferential direction.

  In the rib-like land portion, uneven wear tends to occur at the edge portion. Therefore, by arranging the main sipe and the auxiliary sipe in the land portion, uneven wear of the land portion is effectively reduced. Thereby, there is an advantage that the uneven wear resistance performance of the tire can be obtained more remarkably.

  The pneumatic tire according to the present invention is applied to a heavy duty radial tire.

  In a heavy-duty radial tire, uneven wear of the tire tends to increase. Therefore, by using such a pneumatic tire as an application target, there is an advantage that the effect of improving the uneven wear resistance performance of the tire can be obtained more remarkably.

  In the pneumatic tire according to the present invention, the auxiliary sipe is disposed between the adjacent main sipes, so that the sipe density on the tread of the land portion is appropriately ensured. In such a configuration, when the tire is in contact with the tire, the compression amount of the land portion in the tire circumferential direction is appropriately absorbed by the main sipe and the auxiliary sipe. As a result, uneven wear of the land portion is reduced, and there is an advantage that the uneven wear resistance performance of the tire is maintained appropriately. Further, since the sipe area S of the main sipe and the sipe area s of the auxiliary sipe have a relationship of S> s, the rigidity of the land portion is higher than that of the configuration in which the main sipe and the auxiliary sipe have the same sipe area. high. Thereby, since generation | occurrence | production of the tear in a land part is reduced, there exists an advantage which the tear resistance performance of a tire improves. Moreover, since the sipe area a of the tread side area of the auxiliary sipe and the sipe area b (= sa) of the tire inner side area have a relationship of a> b, the sipe density of the land portion is on the tread side of the land portion. It becomes dense (sparse inside the land). In such a configuration, the compression amount of the land portion is properly absorbed by the main sipe and the auxiliary sipe on the tread side of the land portion. As a result, the uneven wear of the land portion is more effectively reduced, so that the uneven wear resistance performance of the tire is maintained appropriately.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a plan view showing a tread surface of a pneumatic tire according to an embodiment of the present invention. 2 to 5 are an enlarged plan view (FIG. 2), a cross-sectional view taken along line AA (FIG. 3), a cross-sectional view taken along the view B (FIG. 4) and C showing the shoulder land portion of the pneumatic tire shown in FIG. 1. FIG. 6 is a sectional view (FIG. 5). 6-9 is explanatory drawing which shows the modification of the pneumatic tire described in FIG. FIG. 10 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

[Pneumatic tire]
The pneumatic tire 1 includes a plurality of circumferential main grooves 21 and 22 extending in the tire circumferential direction, and a plurality of land portions 31 to 33 defined by the circumferential main grooves 21 and 22 as tread portions. (See FIG. 1). The plurality of land portions 31 to 33 are divided into the center land portions 31 and 32 on the inner side in the tire width direction and the shoulder land portion 33 on the outer side in the tire width direction, with the circumferential main groove 22 on the outermost side in the tire width direction as a boundary. Partitioned.

  For example, in this embodiment, four circumferential main grooves 21 and 22 are formed, and these circumferential main grooves 21 and 22 form ribs and five land portions (center ribs 31 and 32 and A shoulder rib 33) is defined. A tread pattern based on ribs is formed in the tread portion by these land portions 31 to 33.

[Multi sipe]
In the pneumatic tire 1, a sipe (multi-sipe) group 4 is formed on at least one land portion 33 (see FIGS. 1 to 3). The sipe group 4 includes a plurality of main sipes 41 and a plurality of auxiliary sipes 42 and is disposed at the edge portion of the land portion 33. The plurality of main sipes 41 and the plurality of auxiliary sipes 42 are arranged in the tire circumferential direction along the edge portion of the land portion 33. Further, at least one auxiliary sipe 42 is disposed between the adjacent main sipes 41, 41. A plurality of auxiliary sipes 42 may be disposed between the adjacent main sipes 41, 41 (not shown).

  Here, the area where the land portion is cut by sipe (the area of the cut end) is called the sipe area. At this time, the sipe area S of the main sipe 41 and the sipe area s of the auxiliary sipe 42 have a relationship of S> s (see FIGS. 4 and 5). That is, the sipe area s of the auxiliary sipe 42 is set smaller than the sipe area S of the main sipe 41.

  Further, the sipe is divided into a tread surface side region and a tire inner side region (tire axis side region) with the intermediate position of the sipe depth as a boundary (see FIGS. 4 and 5). At this time, the sipe area a of the tread side region of the auxiliary sipe 42 and the sipe area b (= sa) of the tire inner region have a relationship of a> b. That is, the sipe area a in the tread side region is set larger than the sipe area b in the tire inner region.

  For example, in this embodiment, the sipe group 4 is formed on the shoulder ribs 33 on the left and right sides of the tire among the five rib-shaped land portions 31 to 33 (see FIGS. 1 to 3). Further, the sipe group 4 is disposed at the edge portion on the circumferential main groove 22 side of the shoulder rib 33 and the edge portion on the outer side in the tire width direction, and is arranged in the tire circumferential direction along the edge portion of the shoulder rib 33. Has been. The sipe group 4 is composed of a plurality of main sipes 41 and auxiliary sipes 42. The main sipe 41 and the auxiliary sipe 42 extend in the tire width direction from the edge portion of the shoulder rib 33 in a plan view of the tread portion. The main sipes 41 and the auxiliary sipes 42 are alternately arranged in the tire circumferential direction along the edge portions of the shoulder ribs 33. As a result, one auxiliary sipe 42 is disposed between the adjacent main sipes 41, 41.

  Moreover, the main sipe 41 has a substantially rectangular shape in a cross-sectional view of the land portion by the sipe, and the two sides open to the tread surface and the side surface of the land portion 33 (see FIG. 4). Further, in the main sipe 41, the sipe area A of the tread side region and the sipe area B (= SA) of the tire inner side region are equal (A = B).

  Moreover, the auxiliary sipe 42 has a substantially triangular shape in a cross-sectional view of the land portion by the sipe, and the two sides open to the tread surface and the side surface of the land portion 33 (see FIG. 5). For this reason, the sipe width of the auxiliary sipe 42 is narrowed from the tread side toward the tire inner side. Thus, the sipe area S of the main sipe 41 and the sipe area s of the auxiliary sipe 42 have a relationship of S> s. Further, the sipe area a in the tread side region of the auxiliary sipe 42 and the sipe area b (= sa) in the tire inner region have a relationship of a> b. Specifically, s / S = 0.50, a / A = 0.75, and b / B = 0.25.

[effect]
In this pneumatic tire 1, the auxiliary sipe 42 is disposed between the adjacent main sipes 41, 41, so that the sipe density on the tread surface of the land portion 33 is appropriately ensured (see FIGS. 1 and 2). In such a configuration, the compression amount of the land portion 33 in the tire circumferential direction is properly absorbed by the main sipe 41 and the auxiliary sipe 42 when the tire is in contact with the tire. As a result, uneven wear of the land portion 33 is reduced, and there is an advantage that the uneven wear resistance performance of the tire is maintained appropriately.

  Further, since the sipe area S of the main sipe 41 and the sipe area s of the auxiliary sipe 42 have a relationship of S> s, the land portion 33 is compared with the configuration in which the main sipe and the auxiliary sipe have the same sipe area. High rigidity. Thereby, since generation | occurrence | production of the tear in the land part 33 is reduced, there exists an advantage which the tear resistance performance of a tire improves.

  In addition, since the sipe area a in the tread side region of the auxiliary sipe 42 and the sipe area b (= sa) in the tire inner region have a relationship of a> b, the sipe density of the land portion 33 is It becomes dense on the tread side (sparse within the land portion 33). In such a configuration, the compression amount of the land portion 33 is properly absorbed by the main sipe 41 and the auxiliary sipe 42 on the tread side of the land portion 33. Thereby, since the uneven wear of the land part 33 is reduced more effectively, there is an advantage that the uneven wear resistance performance of the tire is appropriately maintained.

[Additional matter 1]
In the pneumatic tire 1, the sipe interval Ps in the tire circumferential direction of the sipe group 4 including the main sipe 41 and the auxiliary sipe 42 and the sipe depth D of the main sipe 41 are 0.2 ≦ Ps / D ≦ 0. .5 (refer to FIG. 3). In such a configuration, the sipe arrangement density in the land portion 33 is optimized by optimizing the sipe interval Ps of the sipe group 4. As a result, uneven wear of the land portion 33 is reduced, and there is an advantage that the uneven wear resistance performance of the tire is maintained appropriately.

  In the configuration in which a plurality of auxiliary sipes 42 are arranged between adjacent main sipes 41, 41 (not shown), the sipe interval Ps1 between the adjacent main sipes 41 and auxiliary sipes 42 and the adjacent auxiliary sipes 42, 42 are included. Sipe interval Ps2 is set to the above relationship (0.2 ≦ Ps1 / D ≦ 0.5, 0.2 ≦ Ps2 / D ≦ 0.5) with respect to the sipe depth D of the main sipe 41, respectively. The

  Moreover, in this pneumatic tire 1, it is preferable that the sipe interval Pb of the adjacent main sipes 41, 41 in the tire circumferential direction is substantially uniform over the entire tire circumference (see FIG. 2). That is, the main sipe 41 having a wide sipe area S is disposed at the edge portion of the land portion 33 at a substantially constant sipe interval Pb. In such a configuration, the main sipes 41 that have a great influence on the rigidity of the land portion 33 are arranged at the edge portions of the land portion 33 at equal intervals, so that the main sipes are arranged at non-uniform intervals. As compared with the above, the ground pressure of the land portion 33 is made uniform. Thereby, since uneven wear of the land portion 33 is reduced, there is an advantage that the uneven wear resistance performance of the tire is improved.

  Moreover, in this pneumatic tire 1, it is preferable that the sipe interval Ps between the adjacent main sipe 41 and auxiliary sipe 42 changes as it goes in the tire circumferential direction (not shown). That is, it is preferable that a pitch variation structure is adopted for the arrangement of the sipe group 4. In such a configuration, generation of pattern noise at the time of tire rolling is suppressed as compared with a configuration in which sipes are arranged at uniform sipe intervals. Thereby, there exists an advantage which the noise performance of a tire improves.

  In particular, the sipe interval Pb in the tire circumferential direction between the adjacent main sipes 41 and 41 is substantially uniform over the entire tire circumference, and the sipe interval Ps in the tire circumferential direction between the adjacent main sipe 41 and the auxiliary sipe 42 is the tire. In the configuration that changes as it goes in the circumferential direction, pattern noise can be reduced while reducing uneven wear of the land portion 33. As a result, there is an advantage that both the uneven wear resistance performance of the tire and the noise performance of the tire can be achieved.

[Additional matter 2]
In this pneumatic tire 1, the sipe area A of the tread side region of the main sipe 41 and the sipe area a of the tread side region of the auxiliary sipe 42 have a relationship of 0.50 ≦ a / A ≦ 0.75. And it is preferable that the sipe area B of the tire inner side region of the main sipe 41 and the sipe area b of the auxiliary sipe 42 in the tire inner side region have a relationship of 0 ≦ b / B ≦ 0.25 (FIG. 4 and FIG. 4). (See FIG. 5). In this configuration, the distribution of the sipe area s of the auxiliary sipe 42 is optimized in the tread side region (sipe area a) and the tire inner side region (sipe area b). The side rigidity is optimized. As a result, uneven wear of the land portion 33 is reduced, and there is an advantage that the uneven wear resistance performance of the tire is maintained appropriately.

  In the above configuration, the sipe area A of the tread side region of the main sipe 41 and the sipe area a of the tread side region of the auxiliary sipe 42 have a relationship of 0.50 ≦ a / A ≦ 0.65, and More preferably, the sipe area B in the tire inner side region of the main sipe 41 and the sipe area b in the tire inner side region of the auxiliary sipe 42 have a relationship of 0 ≦ b / B ≦ 0.10 (FIG. 4 and FIG. 4). 5). Thereby, the uneven wear of the land portion 33 is more effectively reduced, so that there is an advantage that the uneven wear resistance performance of the tire is maintained more appropriately.

  Moreover, in this pneumatic tire 1, it is preferable that the distribution of the sipe area s of the auxiliary sipe 42 is gradually reduced from the tread surface side of the land portion 33 toward the tire inner side (see FIG. 5). That is, the auxiliary sipe 42 is formed so that the distribution of the sipe area s of the auxiliary sipe 42 increases toward the tread surface side of the land portion 33.

  In this configuration, the distribution of the sipe area s of the auxiliary sipe 42 is optimized, and the remaining amount of the auxiliary sipe 42 when the wear of the land portion 33 progresses is optimized. Thus, there is an advantage that the function of the auxiliary sipe 42 is ensured from the early wear stage to the late wear stage of the land portion 33, and the uneven wear resistance performance of the tire is properly maintained.

[Additional matter 3]
In the pneumatic tire 1, the sipe depth D of the main sipe 41 and the groove depth GD of the circumferential main groove 22 are preferably 0.5 ≦ D / GD ≦ 1.0 (see FIG. 3). ). In such a configuration, the remaining amount of the main sipe 41 when the wear of the land portion 33 progresses is optimized by defining the sipe depth D of the main sipe 41. Thus, there is an advantage that the function of the main sipe 41 is ensured from the early wear stage to the late wear stage of the land portion 33 and the uneven wear resistance performance of the tire is properly maintained.

  In the pneumatic tire 1, the sipe area S, the sipe depth D, and the sipe width W of the main sipe 41 preferably have a relationship of 0.7 ≦ S / (D × W) ≦ 1.0 (FIG. 4). In such a configuration, the sipe area S of the main sipe 41 is optimized with respect to the installation range of the main sipe 41, so that the function of the main sipe 41 is appropriately ensured. Thereby, there exists an advantage by which the uneven wear-proof performance of a tire is maintained appropriately.

  In the pneumatic tire 1, the sipe width W in the tire width direction of the main sipe 41 and the auxiliary sipe 42 on the tread surface of the land portion 33 and the land width WL in the tire width direction of the land portion 33 are 0.1 ≦. It is preferable to have a relationship of W / WL ≦ 0.2 (see FIGS. 1 and 2). In such a configuration, by defining the sipe width W of the main sipe 41 and the auxiliary sipe 42, the functions of the main sipe 41 and the auxiliary sipe 42 are appropriately ensured. Thereby, there exists an advantage by which the uneven wear-proof performance of a tire is maintained appropriately.

[Additional matter 4]
Moreover, in this pneumatic tire 1, it is preferable that the sipe depth D of the main sipe 41 and the sipe depth d of the auxiliary sipe 42 have a relationship of d / D ≦ 0.5 (see FIGS. 6 to 8). . That is, the sipe depth D of the main sipe 41 and the sipe depth d of the auxiliary sipe 42 may be different.

  In such a configuration, since the auxiliary sipe 42 has a groove depth d (≦ D / 2) shallower than the groove depth D of the main sipe 41, the main sipe and the auxiliary sipe have the same sipe depth (FIG. 3). Compared with the reference), the sipe density of the land portion 33 becomes denser on the tread side of the land portion 33. Thereby, since the uneven wear of the land part 33 is reduced more effectively, there is an advantage that the uneven wear resistance performance of the tire is appropriately maintained.

  In the above configuration, the cross-sectional shape of the land portion 33 by the auxiliary sipes 42 may have a substantially triangular shape (see FIG. 7) or a substantially arc shape (see FIG. 8). By changing the cross-sectional shape of the auxiliary sipe 42, the sipe area s of the auxiliary sipe 42, the sipe width at the time of progress of wear, and the like can be adjusted.

  In addition, the sipe depth D of the main sipe 41 and the sipe depth d of the auxiliary sipe 42 may be set to be equal (D = d) (see FIGS. 3 and 9).

[Additional matter 5]
Moreover, in this pneumatic tire 1, it is preferable that the main sipe 41 and the auxiliary sipe 42 are disposed on the land portion 33 in the tread shoulder region (see FIG. 1). Uneven wear tends to occur at the land portion 33 in the shoulder region of the tread portion, particularly at the edge portion of the land portion 33 on the outer side in the tire width direction. Therefore, by arranging the main sipe 41 and the auxiliary sipe 42 in the land portion 33, uneven wear of the land portion 33 is effectively reduced. Thereby, there is an advantage that the uneven wear resistance performance of the tire can be obtained more significantly.

  Moreover, in this pneumatic tire 1, it is preferable that the land part which has the main sipe 41 and the auxiliary sipe 42 is a rib extended in a tire circumferential direction (refer FIG. 1). Uneven wear is likely to occur at the edge portion of the land portion 33 (rib). Therefore, by arranging the main sipe 41 and the auxiliary sipe 42 in the land portion 33, uneven wear of the land portion 33 is effectively reduced. Thereby, there is an advantage that the uneven wear resistance performance of the tire can be obtained more remarkably.

[Applicable to]
The pneumatic tire 1 is preferably a heavy duty radial tire. In such a pneumatic tire, uneven wear of the tire tends to increase. Therefore, by using such a pneumatic tire as an application target, there is an advantage that the effect of improving the uneven wear resistance performance of the tire can be obtained more remarkably.

[performance test]
In this example, performance tests on (1) tear resistance and (2) uneven wear resistance were performed on a plurality of pneumatic tires with different conditions (see FIG. 10). In this performance test, a pneumatic tire having a tire size of 295 / 80R22.5 is assembled to an applicable rim specified by JATMA, and a specified internal pressure and a specified load are applied to the pneumatic tire. The pneumatic tire is attached to the front wheel of a 2-D4 test vehicle.

  (1) In the performance test for uneven wear resistance, the test vehicle travels 60,000 [km] on a predetermined test course at 80 [km / h]. Thereafter, the amount of uneven wear generated on the shoulder rib is measured and evaluated. The evaluation is performed by index evaluation using a conventional pneumatic tire as a reference (100), and the larger the value, the better.

  (2) In the performance test related to tear resistance, the test vehicle enters and exits at a constant angle with respect to the step provided in the test course. Then, after the entry / exit is repeated 10 times, the number of tiers generated in the shoulder rib is observed and evaluated. The evaluation is performed by index evaluation using a conventional pneumatic tire as a reference (100), and the larger the value, the better.

  The conventional pneumatic tire has four circumferential main grooves and five ribs defined by the circumferential main grooves on the tread surface (rib pattern). A plurality of sipes are formed at the edge portions of the ribs in the tread shoulder region. These sipes all have the same sipe width, sipe depth, and sipe area.

  The pneumatic tire of the invention example has four circumferential main grooves 21 to 23 and five ribs (land portions) 31 to 33 defined by the circumferential main grooves 21 to 23 on the tread surface. (See FIG. 1). Further, a plurality of main sipes 41 and a plurality of auxiliary sipes 42 are formed at the edge portions of the ribs 33 in the tread portion shoulder region. Further, at least one auxiliary sipe 42 is disposed between adjacent main sipes 41. The sipe depth D of the main sipe 41 is set to D = 10 [mm] (see FIG. 3). Further, the sipe interval Pb between the adjacent main sipes 41, 41 is set to Pb = 10 [mm], and the sipe interval Ps between the adjacent main sipes 41 and the auxiliary sipes 42 is set to Ps = 5 [mm]. Yes. Further, the sipe width W of the main sipe 41 and the auxiliary sipe 42 is set to 4 [mm]. FIG. 10 shows the relationship between the sipe areas A and B of each region of the main sipe 41 and the sipe areas a and b of each region of the auxiliary sipe 42, and the cross-sectional shape of the land portion 33 by the auxiliary sipe 42. Each is set.

  As shown in the test results, it can be seen that in the pneumatic tires 1 of Invention Examples 1 to 8, the tire anti-wear performance is maintained while the tire anti-wear performance is maintained (see FIG. 10). It can also be seen that the tear resistance performance of the tire is further improved by optimizing the cross-sectional shape of the land portion 33 by the a / A and b / B or the auxiliary sipe 42.

  As described above, the pneumatic tire according to the present invention is useful in that it can improve the tire tear resistance while maintaining the uneven wear resistance of the tire.

It is a top view which shows the tread surface of the pneumatic tire concerning the Example of this invention. It is an enlarged plan view which shows the shoulder land part of the pneumatic tire described in FIG. FIG. 2 is a cross-sectional view taken along line AA showing a shoulder land portion of the pneumatic tire depicted in FIG. 1. FIG. 2 is a B cross-sectional view illustrating a shoulder land portion of the pneumatic tire illustrated in FIG. 1. FIG. 2 is a cross-sectional view taken along the line C showing a shoulder land portion of the pneumatic tire depicted in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is a graph which shows the result of the performance test of the pneumatic tire concerning the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 21, 22 Circumferential main groove 31, 32 Center land part 33 Shoulder land part 4 Sipe group 41 Main sipe 42 Auxiliary sipe

Claims (12)

A pneumatic tire having a plurality of circumferential main grooves extending in a tire circumferential direction and a plurality of land portions defined by the circumferential main grooves in a tread portion,
A plurality of main sipes and a plurality of auxiliary sipes are arranged in the tire circumferential direction along the edge portion of the land portion, and at least one auxiliary sipes are disposed between the adjacent main sipes,
The area of cutting the land portion by sipe when called a sipe area, the sipe area S of the main sipes and the sipes area s of the auxiliary sipes have a relationship of S> s,
When a sipe is partitioned into a tread surface side region and a tire inner side region with a middle position of the sipe depth of the main sipe as a boundary, the sipe area a of the tread side region of the auxiliary sipe and the sipe area of the tire inner side region b (= s-a) and is have a relationship of a> b, and,
The sipe area A of the tread side region of the main sipe and the sipe area a of the tread side region of the auxiliary sipe have a relationship of 0.50 ≦ a / A ≦ 0.75, and the tire inner side region of the main sipe A pneumatic tire characterized in that a sipe area B of the auxiliary sipe and a sipe area b of a region inside the tire of the auxiliary sipe have a relationship of 0 ≦ b / B ≦ 0.25 .   The sipe interval Ps in the tire circumferential direction of the sipe group including the main sipe and the auxiliary sipe and the sipe depth D of the main sipe have a relationship of 0.2 ≦ Ps / D ≦ 0.5. Pneumatic tires.   The pneumatic tire according to claim 1 or 2, wherein sipe intervals Pb in the tire circumferential direction of the adjacent main sipes are substantially uniform over the entire tire circumference.   The pneumatic tire according to any one of claims 1 to 3, wherein a sipe interval Ps in the tire circumferential direction between the adjacent main sipe and the auxiliary sipe changes in the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 4 , wherein the distribution of the sipe area of the auxiliary sipe is gradually reduced from the tread surface side of the land portion toward the inside of the tire. The pneumatic tire according to any one of claims 1 to 5 , wherein a sipe depth D of the main sipe and a groove depth GD of the circumferential main groove are 0.5 ≦ D / GD ≦ 1.0. . The air according to any one of claims 1 to 6 , wherein a sipe area S, a sipe depth D, and a sipe width W of the main sipe have a relationship of 0.7 ≦ S / (D × W) ≦ 1.0. Enter tire. The relationship between the sipe width W in the tire width direction of the main sipe and the auxiliary sipe on the tread of the land portion and the land width WL in the tire width direction of the land portion is 0.1 ≦ W / WL ≦ 0.2. The pneumatic tire according to any one of claims 1 to 7 . The pneumatic tire according to any one of claims 1 to 8 , wherein a sipe depth D of the main sipe and a sipe depth d of the auxiliary sipe have a relationship of d / D ≦ 0.5. The pneumatic tire according to any one of claims 1 to 9 , wherein the main sipe and the auxiliary sipe are arranged in the land portion of a tread portion shoulder region. The pneumatic tire according to any one of claims 1 to 10 , wherein the land portion having the main sipe and the auxiliary sipe is a rib extending in a tire circumferential direction. The pneumatic tire according to any one of claims 1 to 11 applied to a heavy duty radial tire.

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