Pneumatic tire

Abstract

To provide a pneumatic tire that can make both traction performance and uneven wear resistance compatible.SOLUTION: In a pneumatic tire according to an embodiment, at least two rows of block rows, in which a plurality of blocks 21 and a plurality of inclined grooves 22 are arranged alternately in a tire circumferential direction, are formed and a main groove (10) is formed between the two block rows. The main groove 10 is formed zigzag, so that convex-shape portions 23 in which the blocks 21 protrude toward the main groove 10 and concave-shape portions 24 in which the blocks 21 dent toward a block-side direction are alternately formed in the tire circumferential direction, at both sides in a tire axial direction of the main groove 10. Expansion regions 25 in which the main groove 10 grows wider toward a direction in which the concave-shape portions 24 are further dented toward the blocks 21 are formed in the concave-shape portions 24 respectively, and the inclined grooves 22 open to the expansion region 25.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] A pneumatic tire is known that has at least two rows of blocks, each row having a plurality of blocks and a plurality of grooves alternately arranged in the circumferential direction of the tire, and a main groove extending in the circumferential direction of the tire between the two rows of blocks (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-151087 Summary of the Invention [Problem to be solved by the invention]

[0004] In the pneumatic tire, if the main grooves extending in the tire circumferential direction are made zigzag, traction performance is improved. To further improve traction performance, it is conceivable to increase the amplitude of the zigzag (i.e., to increase the axial deflection of the zigzag). However, increasing the amplitude of the zigzag makes it more likely that uneven wear will occur in the blocks.

[0005] In light of this, an object of the present invention is to provide a pneumatic tire that combines high traction and high resistance to uneven wear. [Means for solving the problem]

[0006] The present invention includes the embodiments shown below.

[0007] [1] A pneumatic tire having at least two block rows formed therein, each row having a plurality of blocks and a plurality of inclined grooves inclined with respect to the tire circumferential direction, alternately arranged in the tire circumferential direction, and a main groove formed between the two block rows. The main groove has a zigzag shape in which first groove portions and second groove portions inclined in different directions with respect to the tire circumferential direction are alternately arranged, so that on both axial sides of the main groove, convex portions in which the blocks are convex toward the main groove and concave portions in which the blocks are concave toward the block side are alternately formed in the tire circumferential direction, and in each of the concave portions, an expanded region is formed in which the width of a part of the main groove is expanded in a direction that makes the concave portion further concave toward the block side, and the inclined groove is open to the expanded region.

[0008] [2] The pneumatic tire according to [1], wherein the expansion region increases the width of a portion of the first groove portion, and the difference between the width of the first groove portion where the expansion region is present and the width of the first groove portion where the expansion region is not present is 5 mm or less.

[0009] [3] The pneumatic tire according to [1] or [2], wherein the expansion area is trapezoidal, and the walls that form the boundary between the expansion area and the block include a first wall that corresponds to one leg of the trapezoid, a second wall that corresponds to the other leg of the trapezoid, and a third wall that corresponds to the shorter base of the trapezoid, and the longer base of the trapezoid is located within the main groove.

[0010] [4] The pneumatic tire according to [3], wherein the first wall is inclined in the same direction as the inclined groove with respect to the tire circumferential direction.

[0011] [5] The pneumatic tire according to [3] or [4], wherein the second wall is inclined in the opposite direction to the inclined groove with respect to the tire circumferential direction.

[0012] [6] The pneumatic tire according to any one of [3] to [5], wherein the inclined groove opens between the second wall and the third wall, the angle θ1 formed between the second wall and the third wall is smaller than the angle θ2 formed between the first wall and the third wall, and θ1 is 90° or more and 120° or less. [Effects of the Invention]

[0013] The pneumatic tire of the embodiment achieves both high traction and high resistance to uneven wear. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing a tread pattern according to an embodiment, with groove bottom protrusions omitted. [Figure 2] 1 is a diagram showing a tread pattern according to an embodiment, in which groove bottom protrusions are displayed. [Figure 3] FIG. 10 is a diagram showing the center main groove and shoulder main grooves when it is assumed that no expansion regions are formed. [Figure 4] An enlarged view of part C in Figure 3. [Figure 5] An enlarged view of part A in Figure 1. [Figure 6] An enlarged view of the expanded area in the center main groove. [Figure 7] An enlarged view of part B in Figure 1. [Figure 8] An enlarged view of part A in Figure 1. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] Cross-sectional view taken along the CC cutting line in Figure 2. [Figure 12] Cross-sectional view taken along line DD in Figure 2. DETAILED DESCRIPTION OF THE INVENTION

[0015] The pneumatic tire of the embodiment has a typical cross-sectional structure of a pneumatic tire, except for the tread. Specifically, beads (beads are portions consisting of bead cores and bead fillers) are provided on both axial sides of the tire, and a carcass ply is provided from one bead to the other axially. A belt is provided on the outer diameter side of the carcass ply, and a tread is provided on the outer diameter side of the belt. An inner liner is provided inside the carcass ply, and sidewall rubber is provided on both axial sides of the carcass ply. In addition to the above, a pneumatic tire is configured with a plurality of rubber members.

[0016] The rubber tread has a tread pattern as shown in Figures 1 and 2. Figures 1 to 8 are development views of the tread. In Figures 1 to 8, the direction of arrow X is the tire axial direction, and the direction of arrow Y is the tire circumferential direction.

[0017] 1 and 2, the tread pattern includes one center main groove 10 and two shoulder main grooves 11, which are wide grooves extending circumferentially of the tire. The shoulder main grooves 11 are located on both sides of the tire in the axial direction, and the center main groove 10 is located between the two shoulder main grooves 11.

[0018] A center land 20 is formed between the center main groove 10 and the shoulder main groove 11. The center land 20 is a block row in which a plurality of center blocks 21 and a plurality of inclined grooves 22 inclined relative to the tire circumferential direction are alternately arranged in the tire circumferential direction. Two center lands 20 are lined up near the center in the axial direction of the tire.

[0019] A shoulder land 30 is formed between the shoulder main groove 11 and the axial end of the tread. The shoulder land 30 is a block row in which multiple shoulder blocks 31 and multiple slits 32 inclined relative to the tire circumferential direction are alternately arranged in the tire circumferential direction. The slits 32 are a type of groove.

[0020] A block is an area that is surrounded by two main grooves and two grooves (wider than sipes) that connect the two main grooves at two points around the tire, and is independent of its surroundings. A block is also an area that is surrounded by one main groove and two grooves (wider than sipes) that connect the axial end of the tread and the main groove and the axial end of the tread at two points around the tire, and is independent of its surroundings.

[0021] The center main groove 10 and the two shoulder main grooves 11 are each zigzag main grooves. Specifically, each of these main grooves 10, 11 includes first groove portions 10a, 11a that extend at an incline relative to the tire circumferential direction, and second groove portions 10b, 11b that extend at an incline in the opposite direction relative to the first groove portions 10a, 11a. The tire circumferential ends of the first groove portions 10a, 11a are connected to the tire circumferential ends of the second groove portions 10b, 11b. The first groove portions 10a, 11a are longer than the second groove portions 10b, 11b.

[0022] Figure 3 shows the center main groove 110 and shoulder main grooves 111 assuming that the expanded regions 25 and 35 described below are not formed. Grooves other than the main grooves 110 and 111 are omitted in Figure 3. In this figure, the first groove portion 110a of the center main groove 110, the second groove portion 110b of the center main groove 110, the first groove portion 111a of the shoulder main groove 111, and the second groove portion 111b of the shoulder main groove 111 all have a constant width.

[0023] Because the center main groove 110 is zigzag, the sidewalls of the center main groove 110 (shown in solid lines in FIG. 3) also have zigzag shapes with amplitude in the tire axial direction. A line passing through any position within the zigzag range of the sidewalls and extending in the tire circumferential direction is defined as a reference line L1 (shown in dashed lines in FIGS. 3 and 4). In the embodiment shown in FIG. 1 and other figures, the reference line L1 can be considered to pass through the boundary between the expanded region 25 and the narrow region 10c (described later).

[0024] As shown in Figures 3 and 4, the center land 120 has a convex portion 123 that is a triangular convex portion toward the center main groove 110 with respect to the reference line L1, and a concave portion 124 that is a triangular concave portion toward the center land 120 with respect to the reference line L1. The convex portion 123 and the concave portion 124 are arranged alternately in the tire circumferential direction. The convex portion 123 and the concave portion 124 are formed on both sides of the center main groove 110 in the tire axial direction. In Figure 4, one of the convex portion 123 is shown as a hatched area.

[0025] 3, the sidewalls of each shoulder main groove 111 are also zigzag, and a reference line L2 can be drawn along the sidewalls, extending in the tire circumferential direction, similar to the reference line L1. The center land 120 is formed with a convex portion 133 that is triangularly convex toward the shoulder main groove 111 relative to the reference line L2, and a concave portion 134 that is triangularly concave toward the center land 120 relative to the reference line L2. The convex portions 133 and the concave portions 134 are arranged alternately in the tire circumferential direction.

[0026] Such a shape consisting of first groove portions 110a, 111a and second groove portions 110b, 111b, and forming convex portions 123, 133 and concave portions 124, 134, is the basic shape of a zigzag main groove.

[0027] As shown in Fig. 1, the tread of this embodiment is based on a configuration in which convex portions 23, 33 and concave portions 24, 34 are alternately arranged in the tire circumferential direction on both axial sides of each of two center land sections 20 (i.e., two block rows). Here, the convex portions 23, 33 and concave portions 24, 34 in this embodiment are identified by the above-described method using Figs. 3 and 4, assuming that expansion regions 25, 35 are not formed. Each oblique groove 22 opens between the two convex portions 23 on the center main groove 10 side, and also opens between the two convex portions 33 on the shoulder main groove 11 side.

[0028] As shown in Figures 1 and 5, on both sides of the two center lands 20 in the axial direction of the tire, the concave portions 24, 34 are further concave toward the center block 21, thereby forming expanded regions 25, 35 in which the width of a portion of the first groove portions 10a, 11a of the main grooves 10, 11 is increased.

[0029] The difference between the width W1 of the first groove portions 10a, 11a where the expansion regions 25, 35 are present and the width W2 of the first groove portions 10a, 11a where the expansion regions 25, 35 are not present (see FIG. 5 for W1 and W2) is 5 mm or less, preferably 2 mm or more and 5 mm or less. In other words, the recessed distance of the expansion regions 25, 35 toward the center block 21 (the distance in a direction perpendicular to the extension direction of the first groove portions 10a, 11a) relative to the main grooves 10, 11 assuming the expansion regions 25, 35 are not present is 5 mm or less, preferably 2 mm or more and 5 mm or less. The groove width of the main grooves 10, 11, etc., refers to the length perpendicular to the extension direction of the groove when viewed from the radially outer side of the tire.

[0030] In FIG. 5, the extension regions 25, 35 are shown as hatched regions. Each extension region 25, 35 is trapezoidal. There are three walls that form the boundaries between the extension region 25, 35 and the center block 21, corresponding to the three sides of the trapezoid. The three walls are a first wall 26, 36 that corresponds to one leg of the trapezoid, a second wall 27, 37 that corresponds to the other leg of the trapezoid, and a third wall 28, 38 that corresponds to the shorter base of the trapezoid. The longer base of the trapezoid is located within the main grooves 10, 11 at the position of the side wall of the main groove (the edge of the hatched region in FIG. 5) if the extension regions 25, 35 were not present.

[0031] Each of the first walls 26, 36 is inclined in the same direction as the inclined groove 22 of the center land 20 with respect to the tire circumferential direction. The difference between the inclination angle of the first walls 26, 36 with respect to the tire circumferential direction and the inclination angle of the inclined groove 22 with respect to the tire circumferential direction (this difference is the same as the difference between the inclination angle α1 of the first walls 26, 36 with respect to the tire axial direction (see FIG. 6) and the inclination angle α2 of the inclined groove 22 with respect to the tire axial direction (see FIG. 6)) is 20° or less. Furthermore, each of the second walls 27, 37 is inclined in the opposite direction to the inclined groove 22 of the center land 20 with respect to the tire circumferential direction.

[0032] Angle θ1 (see FIG. 6) formed between second walls 27, 37 and third walls 28, 38 is smaller than angle θ2 (see FIG. 6) formed between first walls 26, 36 and third walls 28, 38. Specifically, angle θ1 formed between second walls 27, 37 and third walls 28, 38 is equal to or greater than 90° and equal to or less than 120°. Furthermore, angle θ2 formed between first walls 26, 36 and third walls 28, 38 is equal to or greater than 90° and equal to or less than 130°.

[0033] 1 and 5, each inclined groove 22 formed in the center land 20 opens to both the expanded region 25 of the center main groove 10 and the expanded region 35 of the shoulder main groove 11. The width of the inclined groove 22 is shorter than the circumferential length of the third walls 28, 38 of the expanded regions 25, 35. Each inclined groove 22 opens between the second walls 27, 37 and the third walls 28, 38.

[0034] The expanded regions 25, 35 are arranged at equal intervals in the circumferential direction of the tire on both axial sides of each center land 20. However, the locations of the expanded regions 25, 35 on one axial side of the center land 20 and the other axial side of the tire are shifted in the circumferential direction of the tire.

[0035] Focusing on the center main groove 10, the expanded region 25 on one center land 20 side and the expanded region 25 on the other center land 20 side are offset in the tire circumferential direction. As shown in FIG. 7, a narrow region 10c where the groove width is not increased by the expanded region 25 is formed in the first groove portion 10a of the center main groove 10. The circumferential length m of the narrow region 10c (see FIG. 7) is 6% or more of the length n of the center block 21 in the direction perpendicular to the extension direction of the oblique grooves 22 (see FIG. 7). Such narrow regions 10c are formed at equal intervals in the tire circumferential direction.

[0036] When a large load is applied to the center land 20, the center blocks 21 on both sides of the narrow region 10c are connected to each other, supporting each other. This increases the rigidity of the center blocks 21 and suppresses uneven wear. By making the length m 6% or more of the length n as described above, the effect of suppressing uneven wear is enhanced.

[0037] Focusing on the shape of the center blocks 21, each center block 21 has rotational symmetry around the center of gravity of the center block 21, specifically, two-fold symmetry. All center blocks 21 in the tread have the same shape. The shape of the center blocks 21 will be explained in detail below with reference to Figure 8.

[0038] First, on the center main groove 10 side, there is a notch 40 formed in the first wall 26 and the third wall 28 of the expansion region 25 at one circumferential block end of the tire. Also, on the shoulder main groove 11 side, there is a notch 41 formed in the first wall 36 and the third wall 38 of the expansion region 35 at the other circumferential block end of the tire.

[0039] Additionally, on the center main groove 10 side, a chamfered shape 42 is formed on the second wall 27 of the expansion region 25 at the block end on the other side in the tire circumferential direction (the opposite side from the cutout 40). Additionally, on the shoulder main groove 11 side, a chamfered shape 43 is formed on the second wall 37 of the expansion region 35 at the block end on one side in the tire circumferential direction (the opposite side from the cutout 41).

[0040] The notch 40 on the center main groove 10 side and the chamfered shape 43 on the shoulder main groove 11 side are connected by the sidewall of the inclined groove 22, and the notch 41 on the shoulder main groove 11 side and the chamfered shape 42 on the center main groove 10 side are connected by the sidewall of another inclined groove 22. Furthermore, on the center main groove 10 side, the notch 40 and the chamfered shape 42 are connected by the sidewall of the first groove portion 10a of the center main groove 10, and on the shoulder main groove 11 side, the notch 41 and the chamfered shape 43 are connected by the sidewall of the first groove portion 11a of the shoulder main groove 11.

[0041] 1, the center line L3 of the inclined groove 22 formed in the center land 20 and the center line L4 of the slit 32 formed in the shoulder land 30 are parallel to each other. The distance p between these center lines L3 and L4 in the direction perpendicular to these center lines L3 and L4 is 30% or less of the length n of the center block 21 in the direction perpendicular to the extension direction of the inclined groove 22.

[0042] In this way, by setting the interval p to 30% or less of the length n, excessive movement of the center block 21 is suppressed. Also, the arrangement of the center block 21 and the shoulder block 31 is balanced, which suppresses uneven wear.

[0043] Two parallel sipes 50 are formed in each center block 21. These sipes 50 are wavy and extend in the same direction as the inclined grooves 22. Note that a sipe is a groove with a thickness of less than 1.5 mm.

[0044] The center main groove 10 and the shoulder main grooves 11 have the same depth. The depth of the oblique grooves 22 is 30% to 70% of the depth of the center main groove 10.

[0045] At the bottom of each inclined groove 22, a sipe 51 is formed in an increasing depth direction (see FIGS. 7 to 9). At the center of the extension direction of the sipe 51, a raised bottom 52 is formed, in which the depth of the sipe 51 is shallower than that of the sipes on either side. The raised bottom 52 connects two center blocks 21 lined up in the tire circumferential direction inside the sipe 51. The height H2 of the raised bottom 52 is 50% to 70% of the depth H1 of the sipe 51.

[0046] The presence of the inclined grooves 22 in the center land 20 ensures traction, but the presence of the sipes 51 at the bottom of the inclined grooves 22 further improves traction. The presence of the raised bottoms 52 in the sipes 51 suppresses uneven wear in the vicinity of the sipes 51.

[0047] 1 and 2, one bent sipe 53 is formed in each shoulder block 31. As shown in Fig. 2, each bent sipe 53 is composed of a circumferential sipe portion 53a extending circumferentially from the slit 32 into the shoulder block 31, an inclined sipe portion 53b extending in the shoulder block 31 at an angle relative to the tire axial direction, and a bending point 53c where the circumferential sipe portion 53a and the inclined sipe portion 53b are connected and where the bent sipe 53 is bent. The inclined sipe portion 53b of this bent sipe 53 is inclined in the same direction as the slit 32.

[0048] Since the inclined sipe portions 53b and the slits 32 are inclined in the same direction, excessive movement and uneven wear are unlikely to occur in the shoulder blocks 31. In addition, the inclined sipe portions 53b contribute to traction.

[0049] 10, a shallower bottom portion 54 is formed in the center of the slit 32 in the extension direction. The bottom portion 54 connects two shoulder blocks 31 that are aligned in the tire circumferential direction inside the slit 32. The height H3 of the bottom portion 54 from the bottom of the slit 32 is 50% to 70% of the depth H5 of the shoulder main groove 11.

[0050] A recess 55 is formed on the upper surface of the raised bottom 54. The depth H4 of the recess 55 is 8% to 17% of the depth H5 of the shoulder main groove 11. The depth of the portion of the slit 32 without the raised bottom 54 is the same as the depth of the shoulder main groove 11.

[0051] The slits 32 in the shoulder land 30 ensure traction, and the raised bottoms 54 in the slits 32 suppress uneven wear near the slits 32. The recesses 55 in the raised bottoms 54 improve traction.

[0052] The inclined grooves 22 formed in the two center lands 20, the slits 32 formed in the two shoulder lands 30, the second groove portions 10b, 11b of the center main groove 10 and the shoulder main groove 11, the sipes 50 of the center block 21, and the inclined sipe portions 53b of the shoulder block 31 are all inclined in the same direction. As a result of the grooves, slits, and sipes being inclined in the same direction, excessive movement of the blocks 21, 31 is suppressed, and uneven wear and cracks are suppressed.

[0053] 2, a plurality of groove bottom protrusions 12, 13 are formed on the bottom of each of the center main groove 10 and the two shoulder main grooves 11. Where there are no groove bottom protrusions 12, 13, the groove bottoms of the main grooves 10, 11 are flat as shown in FIG. 11, but where there are groove bottom protrusions 12, 13, protrusions are formed on the groove bottoms of the main grooves 10, 11 as shown in FIG.

[0054] 2, in the center main groove 10, groove bottom protrusions 12 are formed in a location including the expanded region 25. For example, two groove bottom protrusions 12 are formed for one expanded region 25.

[0055] In the shoulder main groove 11, a groove bottom protrusion 13 is formed on a line (a dashed line L5 in FIG. 2) connecting the slit 32 and the inclined groove 22. In the shoulder main groove 11, a groove bottom protrusion 13 is also formed in a location including the expanded region 35. For example, one groove bottom protrusion 13 is formed for one expanded region 35.

[0056] The groove bottom protrusions 12, 13 make it difficult for stones to get caught in the main grooves 10, 11. In addition, the groove bottom protrusions 12, 13 make it easier for stones to be ejected even if they get caught in the main grooves 10, 11.

[0057] A pneumatic tire having the above characteristics is a pneumatic tire that combines high traction and high resistance to uneven wear, as will be explained below.

[0058] In the pneumatic tire of this embodiment, at least two block rows are formed, each row having a plurality of center blocks 21 and a plurality of inclined grooves 22 inclined relative to the tire circumferential direction, arranged alternately in the tire circumferential direction, and a center main groove 10 is formed between the two block rows. Furthermore, because the center main groove 10 is zigzag, convex portions 23 where the center blocks 21 are convex toward the center main groove 10 and concave portions 24 where the center blocks 21 are concave toward the center block 21 are alternately formed in the tire circumferential direction on both axial sides of the center main groove 10. In this way, the presence of the plurality of inclined grooves 22 and the zigzag shape of the center main groove 10 ensure traction.

[0059] Furthermore, in each recessed portion 24, the recessed portion 24 is further recessed toward the center block 21, thereby forming an expanded region 25 in which the width of the center main groove 10 is increased. Such expanded region 25 further improves the traction of the pneumatic tire, but unlike when the zigzag amplitude of the center main groove 10 is increased, it is less likely to reduce uneven wear resistance.

[0060] Furthermore, because the inclined grooves 22 open into the expanded region 25, the shape of the center block 21, which is formed by the center main groove 10 and the inclined grooves 22, has a corner that is cut off by the expanded region 25. Because the center block 21 has a corner that is cut off, the resistance to uneven wear is improved.

[0061] For these reasons, the pneumatic tire of the embodiment achieves both high traction and high resistance to uneven wear.

[0062] Although the expanded region 25 widens a portion of the center main groove 10, the difference between the width of the first groove portion 10a where the expanded region 25 is located and the width of the first groove portion 10a where the expanded region 25 is not located is 5 mm or less, which prevents a decrease in uneven wear resistance due to the expanded region 25 being too large. Furthermore, if this distance is 2 mm or more, traction is likely to be improved.

[0063] The expansion region 25 is trapezoidal, and the boundaries between the expansion region 25 and the center block 21 include a first wall 26 corresponding to one leg of the trapezoid, a second wall 27 corresponding to the other leg of the trapezoid, and a third wall 28 corresponding to the shorter base of the trapezoid. The longer base of the trapezoid is located within the center main groove 10 (more specifically, the position of the sidewall of the zigzag main groove if the expansion region 25 were not present). The expansion region 25 is provided with this shape and orientation, which makes it easier to achieve both traction and uneven wear resistance.

[0064] Furthermore, because the first walls 26 are inclined in the same direction as the inclined grooves 22 with respect to the tire circumferential direction, the first walls 26 and the inclined grooves 22 provide excellent traction. Also, because they are inclined in the same direction, the center blocks 21 are less likely to move excessively, making uneven wear less likely to occur. Here, if the difference between the inclination angle of the first walls 26 with respect to the tire circumferential direction and the inclination angle of the inclined grooves 22 with respect to the tire circumferential direction is 20° or less, the effect of uneven wear resistance is fully exhibited.

[0065] Furthermore, the angle θ1 between the second wall 27 and the third wall 28 is smaller than the angle θ2 between the first wall 26 and the third wall 28. As a result, the second wall 27 extends in a direction close to the tire axial direction, contributing to traction. Furthermore, the angle between the inclined groove 22 and the second wall 27 (the angle marked with the symbol P in FIG. 6) is not too small, and the rubber volume around the corner is not too small, so uneven wear at the corner is less likely to occur. Furthermore, water hitting the second wall 27 is easily guided into the inclined groove 22, improving drainage.

[0066] Here, by setting the angle θ1 to 90° or more, uneven wear is less likely to occur near the second wall 27 (particularly the location marked with symbol Q in FIG. 6). Furthermore, by setting the angle θ1 to 120° or less, the effects of traction and drainage are greater, and uneven wear is less likely to occur at the corner marked with symbol P in FIG. 6.

[0067] Furthermore, when the angle θ2 is 90° or more, uneven wear is less likely to occur near the first wall 26. When the angle θ2 is 130° or less, the traction effect is increased, and the volume and rigidity of the center block 21 are maintained, making uneven wear less likely to occur.

[0068] In addition, the shoulder main groove 11 is also zigzag-shaped, and an expansion area 35 similar to the expansion area 25 described above is also formed in the shoulder main groove 11, thereby further improving the traction of the pneumatic tire while suppressing a decrease in resistance to uneven wear.

[0069] The above embodiment is merely an example, and various modifications can be made to the above embodiment. Any modifications of the above embodiment that do not deviate from the spirit of the present invention are considered to be included in the scope of the present invention. [Explanation of symbols]

[0070] 10...center main groove, 10a...first groove portion, 10b...second groove portion, 10c...narrow width region, 11...shoulder main groove, 11a...first groove portion, 11b...second groove portion, 12...groove bottom protrusion, 13...groove bottom protrusion, 20...center land, 21...center block, 22...inclined groove, 23...convex portion, 24...concave portion, 25...extension region, 26...first wall, 27...second wall, 28...third wall, 30...shoulder land, 31...shoulder block, 32...slit, 33...convex portion, 34...concave portion, 35...extension region, 36...first wall, 37...second wall, 38...third wall, 40...notch, 41...notch, 42...chamfered shape, 43...chamfered shape, 50...sipe, 51...sipe, 52...bottom-up, 53...bent sipe, 53a...circumferential sipe portion, 53b...inclined sipe portion, 53c...bending point, 54...bottom-up, 55...depression, 110...center main groove, 110a...first groove portion, 110b...second groove portion, 111...shoulder main groove, 111a...first groove portion, 111b...second groove portion, 120...center land, 123...convex portion, 124...concave portion, 133...convex portion, 134...concave portion

Claims

1. A pneumatic tire having at least two block rows formed therein, each block row having a plurality of blocks and a plurality of inclined grooves inclined with respect to the tire circumferential direction, alternately arranged in the tire circumferential direction, and a main groove formed between the two block rows, The main groove has a zigzag shape in which first groove portions and second groove portions having different inclination directions with respect to the tire circumferential direction are alternately arranged, so that convex portions in which the blocks are convex toward the main groove side and concave portions in which the blocks are concave toward the block side are alternately formed in the tire circumferential direction on both sides of the main groove in the tire axial direction, In each of the recessed portions, an expanded region is formed in which a width of a part of the main groove is expanded in a direction in which the recessed portion is further recessed toward the block side, A pneumatic tire, characterized in that the inclined grooves are open to the expansion region.

2. the expansion region widens a portion of the first groove portion; 2. The pneumatic tire according to claim 1, wherein a difference between a width of the first groove portion at a location where the expansion region is present and a width of the first groove portion at a location where the expansion region is not present is 5 mm or less.

3. the expansion area is trapezoidal; walls that form boundaries between the extension area and the block include a first wall that corresponds to one leg of the trapezoid, a second wall that corresponds to the other leg of the trapezoid, and a third wall that corresponds to a shorter base of the trapezoid; The pneumatic tire according to claim 1 or 2, wherein a longer base of the trapezoid is located within the main groove.

4. The pneumatic tire according to claim 3 , wherein the first wall is inclined in the same direction as the inclined groove with respect to the tire circumferential direction.

5. The pneumatic tire according to claim 4 , wherein the second wall is inclined in a direction opposite to the inclined groove with respect to the tire circumferential direction.

6. the inclined groove opens between the second wall and the third wall, 6. The pneumatic tire according to claim 5, wherein an angle θ1 formed between the second wall and the third wall is smaller than an angle θ2 formed between the first wall and the third wall, and θ1 is greater than or equal to 90° and less than or equal to 120°.

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