Pneumatic tire

Abstract

The invention relates to a pneumatic tire. Provided is a pneumatic tire having both traction properties and uneven wear resistance. According to the pneumatic tire of the embodiment, a plurality of pattern blocks (21) and a plurality of inclined grooves (22) are alternately arranged in the circumferential direction of the tire to form at least two pattern block rows, main grooves (10) are formed between the two pattern block rows, and the pneumatic tire is characterized in that the main grooves (10) are zigzag. As a result, convex portions (23) formed by protruding the pattern blocks (21) toward the main groove (10) and concave portions (24) formed by recessing the pattern blocks (21) toward the pattern blocks (21) are alternately formed in the tire circumferential direction on both sides of the main groove (10) in the tire axial direction. An expansion region (25) in which the width of the main groove (10) expands in the direction in which the concave portion (24) is further recessed toward the block (21) side is formed in each of the concave portions (24), and the inclined groove (22) opens in the expansion region (25).

Description

[0001] This application is based on and claims priority to Japanese Patent Application No. 2024-070602 (Filing date: April 24, 2024). This application includes the entire content of Japanese Patent Application No. 2024-070602. TECHNICAL FIELD

[0002] The present application relates to a pneumatic tire. BACKGROUND

[0003] Known is a pneumatic tire in which a plurality of blocks and a plurality of grooves are alternately arranged in a tire circumferential direction to form a block row, and at least two rows of the block row are formed, and a main groove extending in the tire circumferential direction is formed between the two rows of the block row (for example, refer to Patent Literature 1).

[0004] Patent Literature 1: Japanese Patent Application Publication No. 2015-151087 SUMMARY

[0005] With the above-described pneumatic tire, if the main groove extending in the tire circumferential direction is formed in a zigzag shape, the traction is improved. In order to further improve the traction, it is conceivable to increase the amplitude of the zigzag (i.e., to increase the amplitude of the zigzag in the tire axial direction). However, if the amplitude of the zigzag is increased, it is easy to cause uneven wear in the block.

[0006] In view of this, an object of the present application is to provide a pneumatic tire that balances a high traction and a high uneven wear resistance.

[0007] With the pneumatic tire of the embodiment, a plurality of blocks and a plurality of inclined grooves inclined with respect to the tire circumferential direction are alternately arranged in a tire circumferential direction to form a block row, and at least two rows of the block row are formed, and a main groove is formed between the two rows of the block row, characterized in that the main groove is a zigzag shape in which a first groove portion and a second groove portion that are different in the direction of inclination with respect to the tire circumferential direction are alternately arranged, and as a result, on both sides of the tire axial direction of the main groove, a convex portion in which the block protrudes toward the main groove side and a concave portion in which the block is recessed toward the block side are alternately formed in the tire circumferential direction, an expansion region in which the width of the portion of the main groove formed in each of the concave portions expands in a direction in which the concave portion is further recessed toward the block side is formed, and the inclined groove is opened in the expansion region.

[0008] With the pneumatic tire of the embodiment, a high traction and a high uneven wear resistance are balanced. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a drawing in which the groove bottom protrusion is omitted with respect to the tread pattern of the embodiment.

[0010] Figure 2FIG. 1 is a view showing a tread pattern of an embodiment.

[0011] Figure 3 FIG. 2 is a view showing a center main groove and a shoulder main groove in a case where an extended region is not formed.

[0012] Figure 4 FIG. 3 is a view showing a tread pattern of an embodiment. Figure 3

[0013] Figure 5 FIG. 4 is a view showing a tread pattern of an embodiment. Figure 1

[0014] Figure 6 FIG. 5 is a view showing an extended region of a center main groove.

[0015] Figure 7 FIG. 6 is a view showing a tread pattern of an embodiment. Figure 1

[0016] Figure 8 FIG. 7 is a view showing a tread pattern of an embodiment. Figure 1

[0017] Figure 9 FIG. 8 is a view showing an elongated direction of an inclined groove.

[0018] Figure 10 FIG. 9 is a view showing an elongated direction of a slit.

[0019] Figure 11 FIG. 10 is a view showing a C-C cross-sectional line of FIG. 1. Figure 2

[0020] FIG. 11 is a view showing a D-D cross-sectional line of FIG. 1. Figure 12 Figure 2

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] ​​​​​​10…Center main groove; 10a…First groove portion; 10b…Second groove portion; 10c…Narrow area; 11…Shoulder main groove; 11a…First groove portion; 11b…Second groove portion; 12…Groove bottom protrusion; 13…Groove bottom protrusion; 20…Center land portion; 21…Center tread block; 22…Angled groove; 23…Convex portion; 24…Concave portion; 25…Extension area; 26…First wall; 27…Second wall; 28…Third wall; 30…Shoulder land portion; 31…Shoulder tread block; 32…Slit; 33…Convex portion; 34…Concave portion; 35…Extension area; 36…First wall; 37…Second wall; 38…Third wall ; 40…incision; 41…incision; 42…chamfered shape; 43…chamfered shape; 50…sipe pattern; 51…sipe pattern; 52…bottom protrusion; 53…curved sipe pattern; 53a…circumferential sipe pattern portion; 53b…inclined sipe pattern portion; 53c…bending point; 54…bottom protrusion; 55…recess; 110…central main groove; 110a…first groove portion; 110b…second groove portion; 111…shoulder main groove; 111a…first groove portion; 111b…second groove portion; 120…central land portion; 123…convex portion; 124…concave portion; 133…convex portion; 134…concave portion. DETAILED DESCRIPTION

[0023] In addition to the tread portion, the pneumatic tire of the embodiment has a normal cross-sectional structure as a pneumatic tire. Specifically, bead portions are provided on both axial sides of the tire (the bead refers to the portion consisting of the bead core and the bead outer protective rubber), and a carcass cord is provided from the bead portion on one axial side of the tire to the bead portion on the other axial side. A belt is provided on the outer diameter side of the carcass cord, and a tread portion is provided on the outer diameter side of the belt. In addition, an inner liner is provided on the inner side of the carcass cord, and sidewall rubber is provided on both axial sides of the carcass cord. In addition to the above components, a plurality of rubber components are provided, thereby constituting a pneumatic tire.

[0024] The rubber tread is formed with Figure 1 and Figure 2 The tread pattern shown. In addition, Figures 1-8 This is the expanded view of the tread. Figures 1-8 In the figure, the arrow X direction is the tire axial direction, and the arrow Y direction is the tire circumferential direction.

[0025] about Figure 1 and Figure 2 The tread pattern shown is formed with a central main groove 10 and two shoulder main grooves 11 as wide grooves extending in the tire circumferential direction. The shoulder main grooves 11 are located on both sides of the tire axial direction, and the central main groove 10 is located between the two shoulder main grooves 11.

[0026] A central land portion 20 is formed between the central main groove 10 and the shoulder main groove 11. The central land portion 20 is a block row in which a plurality of central blocks 21 and a plurality of inclined grooves 22 inclined with respect to the tire circumferential direction are alternately arranged in the tire circumferential direction. Two central land portions 20 are arranged near the tire axial center.

[0027] In addition, a shoulder land portion 30 is formed between the shoulder main groove 11 and the tire axial end of the tread portion. The shoulder land portion 30 is a block row in which a plurality of shoulder blocks 31 and a plurality of slits 32 inclined with respect to the tire circumferential direction are alternately arranged in the tire circumferential direction. The slit 32 is one kind of groove.

[0028] Further, a portion surrounded by two main grooves and two grooves (but the width is larger than that of a sipe) connecting the two main grooves at two positions in the tire circumferential direction, respectively, and independent with respect to the surroundings is referred to as a block. In addition, a portion surrounded by one main groove, the tire axial end of the tread portion, and two grooves (but the width is larger than that of a sipe) connecting the main groove and the tire axial end of the tread portion at two positions in the tire circumferential direction, respectively, and independent with respect to the surroundings is referred to as a block.

[0029] The central main groove 10 and the two shoulder main grooves 11 are zigzag-shaped main grooves. That is, the main grooves 10, 11 are structured such that a first groove portion 10a, 11a extending obliquely with respect to the tire circumferential direction and a second groove portion 10b, 11b extending obliquely with respect to the tire circumferential direction in the opposite direction of the first groove portion 10a, 11a are alternately arranged in the tire circumferential direction. Further, the tire circumferential end of the first groove portion 10a, 11a is connected to the tire circumferential end of the second groove portion 10b, 11b. In addition, the first groove portion 10a, 11a is longer than the second groove portion 10b, 11b.

[0030] Here, Figure 3 The central main groove 110 and the shoulder main groove 111 are shown in a case where the extension regions 25, 35 described later are not formed. Figure 3 Grooves other than the main grooves 110, 111 are omitted in the drawing. In the drawing, the width of each of the first groove portion 110a of the central main groove 110, the second groove portion 110b of the central 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 is constant.

[0031] The central main groove 110 is zigzag-shaped, and therefore, the side wall (the side wall is drawn by a solid line in the drawing) of the central main groove 110 is also zigzag-shaped having an amplitude in the tire axial direction. Figure 3 In the drawing, a line passing through an arbitrary position in the range of the zigzag shape of the side wall and extending in the tire circumferential direction is set as a reference line L1. Figure 3 , Figure 4In the figure, it is indicated by a single dot-dashed line. In addition, Figure 1 In the embodiments shown in FIG. 1 and FIG. 2 , it is sufficient to consider that the reference line L1 passes through the boundary between the expanded area 25 and the narrow area 10 c , which will be described later.

[0032] like Figure 3 and Figure 4 As shown, central land portion 120 includes a convex portion 123 that protrudes triangularly toward central main groove 110 relative to reference line L1, and a concave portion 124 that is concave triangularly toward central land portion 120 relative to reference line L1. Concave portions 123 and concave portions 124 are alternately arranged in the tire circumferential direction. Concave portions 123 and concave portions 124 are formed on both sides of central main groove 110 in the tire's axial direction. Figure 4 In FIG. 1 , one convex portion 123 is shown as a hatched area.

[0033] In addition, if Figure 3 As shown, the sidewalls of each shoulder main groove 111 also have a zigzag shape. Similar to the aforementioned reference line L1, a reference line L2 extending in the tire circumferential direction can be drawn relative to the sidewalls. The center land portion 120 is formed with a convex portion 133 that projects triangularly toward the shoulder main groove 111 relative to reference line L2, and a concave portion 134 that is triangularly recessed toward the center land portion 120 relative to reference line L2. The convex portions 133 and concave portions 134 are alternately arranged in the tire circumferential direction.

[0034] This shape composed of the first groove portions 110 a and 111 a and the second groove portions 110 b and 111 b and forming the convex portions 123 and 133 and the concave portions 124 and 134 is the basic shape of the sawtooth main groove.

[0035] Regarding the tread portion of the embodiment, Figure 1 As shown, in each of the two central land portions 20 (i.e., two rows of pattern blocks), the basic structure is a structure in which convex portions 23, 33 and concave portions 24, 34 are alternately arranged in the tire circumferential direction on both sides of the tire axial direction. Here, it is assumed that no expansion areas 25, 35 are formed, and by using Figure 3 、 Figure 4 The convex portions 23, 33 and the concave portions 24, 34 of the embodiment are determined by the above-mentioned method. Each inclined groove 22 opens between the two convex portions 23 on the central main groove 10 side and also opens between the two convex portions 33 on the shoulder main groove 11 side.

[0036] like Figure 1 and Figure 5As shown, each of the first groove portions 10a, 11a of the main grooves 10, 11 formed by the recessed portions 24, 34 further recessed toward the central block 21 side on both sides in the tire axial direction of the respective central land portions 20 has an extension region 25, 35 in which the width of a portion of the first groove portion 10a, 11a of the main groove 10, 11 is expanded.

[0037] The difference between the width Wl of the first groove portion 10a, 11a of the main groove 10, 11 at the location where the extension region 25, 35 is present and the width W2 of the first groove portion 10a, 11a of the main groove 10, 11 at the location where the extension region 25, 35 is not present (see Figure 5 ) is 5 mm or less, and is preferably 2 mm or more and 5 mm or less. In other words, the distance by which the extension region 25, 35 is recessed toward the central block 21 side with respect to the main groove 10, 11 when the extension region 25, 35 is not present is 5 mm or less, and is preferably 2 mm or more and 5 mm or less. Furthermore, the width of the groove of the main groove 10, 11 refers to the length in the direction perpendicular to the extension direction of the groove when viewed from the tire radial direction outer side.

[0038] Figure 5 The extension regions 25, 35 are shown as hatched regions in FIG. 2. Each of the extension regions 25, 35 is a trapezoid. The three walls that constitute the boundary between the extension region 25, 35 and the central block 21 are three walls corresponding to the three sides of the trapezoid. The three walls are: a first wall 26, 36 corresponding to one side of the trapezoid; a second wall 27, 37 corresponding to the other side of the trapezoid; and a third wall 28, 38 corresponding to the shorter base of the trapezoid. In addition, the longer base of the trapezoid is positioned at the position of the side wall of the main groove 10, 11 (the edge of the hatched region of the main groove 10, 11 when the extension region 25, 35 is not present) when the extension region 25, 35 is not present. Figure 5

[0039] Each of the first walls 26, 36 is inclined in the same direction as the inclined groove 22 of the central land portion 20 with respect to the tire circumferential direction. The difference between the inclination angle of the first wall 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 (the difference between the inclination angle of the first wall 26, 36 with respect to the tire axial direction and the inclination angle of the inclined groove 22 with respect to the tire axial direction is the same) is 20° or less. In addition, each of the second walls 27, 37 is inclined in the opposite direction to the inclined groove 22 of the central land portion 20 with respect to the tire circumferential direction. Figure 6 Figure 6 The angle of the angle θl (see ) formed by the second wall 27, 37 and the third wall 28, 38 is smaller than the angle of the angle θ2 (see

[0040] ) formed by the first wall 26, 36 and the third wall 28, 38. Figure 6 Figure 6 ​​). As a specific size of the angle, the angle θ1 of the angle formed by the second wall 27, 37 and the third wall 28, 38 is 90° or more and 120° or less. Further, the angle θ2 of the angle formed by the first wall 26, 36 and the third wall 28, 38 is 90° or more and 130° or less.

[0041] As shown in FIG. 1, the central land portion 20 is formed in the central main groove 10. The central land portion 20 is formed in the central main groove 10 so as to be continuous in the tire axial direction. The central land portion 20 is formed in the central main groove 10 so as to be continuous in the tire circumferential direction. The central land portion 20 is formed in the central main groove 10 so as to be continuous in the tire radial direction. Figure 1 and Figure 5 As shown in FIG. 1, each of the inclined grooves 22 formed in the central land portion 20 is opened at both of the extension region 25 of the central main groove 10 and the extension region 35 of the shoulder main groove 11. The width of the inclined groove 22 is smaller than the length of the third wall 28, 38 in the tire circumferential direction of the extension region 25, 35. Each of the inclined grooves 22 is opened between the second wall 27, 37 and the third wall 28, 38.

[0042] The extension regions 25, 35 are arranged at equal intervals in the tire circumferential direction on both sides of each of the central land portions 20. However, the locations of the extension regions 25, 35 on one side and the other side of the central land portion 20 are offset in the tire circumferential direction.

[0043] Focusing on the central main groove 10, the extension region 25 on one side of the central land portion 20 and the extension region 25 on the other side of the central land portion 20 are offset in the tire circumferential direction. Further, as shown in FIG. 1, the narrow region 10c in which the groove width is not expanded by the extension region 25 is formed in the first groove portion 10a of the central main groove 10. The length m (refer to FIG. 2) of the narrow region 10c in the tire circumferential direction is 6% or more of the length n (refer to FIG. 2) of the central block 21 in the direction perpendicular to the extension direction of the inclined groove 22. Figure 7 Figure 7 The length m (refer to FIG. 2) of the narrow region 10c in the tire circumferential direction is 6% or more of the length n (refer to FIG. 2) of the central block 21 in the direction perpendicular to the extension direction of the inclined groove 22. Such a narrow region 10c is formed at equal intervals in the tire circumferential direction. Figure 7

[0044] If a large load is applied to the central land portion 20, the central blocks 21 on both sides of the narrow region 10c are connected to each other so that the central blocks 21 support each other. Thus, the rigidity of the central blocks 21 is improved, and the eccentric wear is suppressed. As described above, the effect of suppressing the eccentric wear is increased because the length m is 6% or more of the length n.

[0045] Focusing on the shape of the central block 21, each of the central blocks 21 has rotational symmetry with the center of gravity of the central block 21 as the center, specifically, 2-fold symmetry. All of the central blocks 21 in the tread portion are provided in the same shape. Next, the shape of the central block 21 will be described in detail based on Figure 8

[0046] ​​​First, on the central main groove 10 side, the block end on one side in the tire circumferential direction has a cutout 40 formed by the first wall 26 and the third wall 28 of the extended region 25. Also, on the shoulder main groove 11 side, the block end on the other side in the tire circumferential direction has a cutout 41 formed by the first wall 36 and the third wall 38 of the extended region 35.

[0047] Also, on the central main groove 10 side, the block end on the other side in the tire circumferential direction (the opposite direction of the cutout 40) has a chamfered shape 42 formed by the second wall 27 of the extended region 25. Also, on the shoulder main groove 11 side, the block end on one side in the tire circumferential direction (the opposite direction of the cutout 41) has a chamfered shape 43 formed by the second wall 37 of the extended region 35.

[0048] The cutout 40 on the central main groove 10 side and the chamfered shape 43 on the shoulder main groove 11 side are connected by the side wall of the inclined groove 22, and the cutout 41 on the shoulder main groove 11 side and the chamfered shape 42 on the central main groove 10 side are connected by the side wall of the other inclined groove 22. Also, on the central main groove 10 side, the cutout 40 and the chamfered shape 42 are connected by the side wall of the first groove portion 10a of the central main groove 10, and on the shoulder main groove 11 side, the cutout 41 and the chamfered shape 43 are connected by the side wall of the first groove portion 11a of the shoulder main groove 11.

[0049] Again, attention is directed to the grooves, as Figure 1 As shown, the center line L3 of the inclined groove 22 formed in the central land portion 20 is parallel to the center line L4 of the slit 32 formed in the shoulder land portion 30. Also, the interval p of the center lines L3, L4 in the direction perpendicular to the center lines L3, L4 is 30% or less of the length n of the central block 21 in the direction perpendicular to the extension direction of the inclined groove 22.

[0050] Thus, excessive movement of the central block 21 is suppressed because the interval p is 30% or less of the length n. Also, balance in the arrangement of the central block 21 and the shoulder block 31 is achieved. Therefore, eccentric wear is suppressed.

[0051] In each central block 21, 2 sipes 50 are formed in parallel. The sipes 50 are wavy and extend in the same direction as the inclined groove 22. Also, a sipe refers to a groove having a thickness of less than 1.5 mm.

[0052] The central main groove 10 and the shoulder main groove 11 are the same depth. The depth of the inclined groove 22 is 30% or more and 70% or less of the depth of the central main groove 10.

[0053] In the bottom portion of each inclined groove 22, a sipe 51 is formed in a direction of further deepening (refer to FIG. 2). Figures 7-9A bottom protrusion 52 is formed at the center of the sipe 51 in the extended direction. The depth of the sipe 51 is shallower than that of the sipes on either side. The bottom protrusion 52 connects two central blocks 21 arranged in the tire circumferential direction within the sipe 51. The height H2 of the bottom protrusion 52 is not less than 50% and not more than 70% of the depth H1 of the sipe 51.

[0054] The inclined grooves 22 in the center land portion 20 ensure traction, and the sipes 51 at the bottoms of the inclined grooves 22 further improve traction. The bottom protrusions 52 in the sipes 51 suppress uneven wear near the sipes 51.

[0055] In addition, if Figure 1 、 Figure 2 As shown in FIG. 1 , a curved sipe 53 is formed on each shoulder block 31. Figure 2 As shown, each curved sipe 53 includes a circumferential sipe portion 53a extending from the slit 32 into the shoulder block 31 in the tire circumferential direction; an inclined sipe portion 53b extending in the shoulder block 31 in an inclined direction relative to the tire axial direction; and a bending point 53c connecting the circumferential sipe portion 53a and the inclined sipe portion 53b, which is the curved portion of the curved sipe 53. The inclined sipe portion 53b of the curved sipe 53 is inclined in the same direction as the slit 32.

[0056] The inclined sipe portion 53b and the slit 32 have the same inclination direction, so that excessive movement and uneven wear are unlikely to occur in the shoulder block 31. In addition, the inclined sipe portion 53b is advantageous in traction.

[0057] like Figure 10 As shown, a bottom protrusion 54 is formed at the center of the slit 32 in the extension direction, which makes the slit 32 shallower. The bottom protrusion 54 connects two shoulder blocks 31 arranged in the tire circumferential direction within the slit 32. The height H3 of the bottom protrusion 54 relative to the bottom of the slit 32 is not less than 50% and not more than 70% of the depth H5 of the shoulder main groove 11.

[0058] A recess 55 is formed on the upper surface of the bottom protrusion 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 bottom protrusion 54 is the same as the depth of the shoulder main groove 11.

[0059] The slits 32 provided in the shoulder land portion 30 ensure traction, and the bottom protrusions 54 provided in the slits 32 suppress uneven wear near the slits 32. The bottom protrusions 54 provided with the recesses 55 improve traction.

[0060] The inclined grooves 22 formed in the two center land areas 20, the slits 32 formed in the two shoulder land areas 30, the second groove portions 10b and 11b of the center main groove 10 and shoulder main groove 11, the sipes 50 of the center block 21, and the inclined sipe portions 53b of the shoulder blocks 31 are all inclined in the same direction. By having the grooves, slits, and sipes inclined in the same direction, excessive movement of the blocks 21 and 31 is suppressed, thereby preventing uneven wear and breakage.

[0061] In addition, if Figure 2 As shown, a plurality of groove bottom protrusions 12 and 13 are formed at the bottom of the central main groove 10 and the two shoulder main grooves 11. In places where there are no groove bottom protrusions 12 and 13, the groove bottoms of the main grooves 10 and 11 are as shown in FIG. Figure 11 As shown in FIG, the groove bottom is flat, but at the location of the groove bottom protrusions 12 and 13, the groove bottom of the main grooves 10 and 11 is as shown in FIG. Figure 12 As shown, protrusions are formed.

[0062] according to Figure 2 It can be seen that the groove bottom protrusions 12 are formed at locations including the expanded region 25 in the central main groove 10. For example, two groove bottom protrusions 12 are formed for one expanded region 25.

[0063] In addition, in the shoulder main groove 11, the line connecting the slit 32 and the inclined groove 22 ( Figure 2 A groove bottom protrusion 13 is formed on the line L5 (shown by a dotted line in FIG). In addition, a groove bottom protrusion 13 is also formed in the shoulder main groove 11 at a location including the expansion area 35. For example, one groove bottom protrusion 13 is formed for each expansion area 35.

[0064] Because of having groove bottom protrusion 12,13, it is difficult to clamp stones in main groove 10,11. In addition, owing to having groove bottom protrusion 12,13, even if main groove 10,11 clamps stones, also this stone is easily discharged.

[0065] The pneumatic tire having the above characteristics is a pneumatic tire that achieves both high traction and high uneven wear resistance.

[0066] In the pneumatic tire according to the embodiment, the plurality of central blocks 21 and the plurality of inclined grooves 22 inclined with respect to the tire circumferential direction are alternately arranged in the tire circumferential direction, and at least two rows of block rows are formed, and the central main groove 10 is formed between the two rows of block rows. Also, the central main groove 10 is zigzag, and on both sides of the central main groove 10 in the tire axial direction, a convex portion 23 in which the central block 21 is convex toward the central main groove 10 and a concave portion 24 in which the central block 21 is concave toward the central block 21 are alternately formed in the tire circumferential direction. Thus, since the plurality of inclined grooves 22 are provided and the central main groove 10 is zigzag, the traction is ensured.

[0067] Also, in each of the concave portions 24, an extension region 25 in which the central main groove 10 is widened is formed by further concaving the concave portion 24 toward the central block 21. Such an extension region 25 further improves the traction of the pneumatic tire, but unlike the case where the amplitude of the zigzag of the central main groove 10 is increased, the corner wear resistance does not decrease.

[0068] Also, the inclined groove 22 is opened at the extension region 25, and thus the shape of the central block 21 surrounded by the central main groove 10 and the inclined groove 22 is a shape in which the corner is missing due to the extension region 25. Thus, since the central block 21 is a shape in which the corner is missing, the corner wear resistance is good.

[0069] According to the pneumatic tire according to the embodiment, both the high traction and the high corner wear resistance are achieved.

[0070] Also, the width of a portion of the central main groove 10 is widened by the extension region 25, but the difference between the width of the first groove portion 10a at the site where the extension region 25 is present and the width of the first groove portion 10a at the site where the extension region 25 is not present is 5 mm or less, and thus it is difficult for the corner wear resistance to decrease due to excessive increase by the extension region 25. Also, if the distance is 2 mm or more, the traction is easily improved.

[0071] Also, the extension region 25 is a trapezoid, and as a wall that constitutes the boundary between the extension region 25 and the central block 21, there are a first wall 26 that corresponds to one side of the trapezoid, a second wall 27 that corresponds to the other side of the trapezoid, and a third wall 28 that corresponds to the shorter base of the trapezoid. Also, the longer base of the trapezoid is present inside the central main groove 10 (in detail, the position of the side wall of the zigzag main groove in the case where the extension region 25 is not present). Since the extension region 25 is provided in the above-described shape and orientation, it is easy to achieve both the traction and the corner wear resistance.

[0072] Further, the first wall 26 is inclined in the same direction as the inclined groove 22 with respect to the tire circumferential direction, and thus, greater traction is generated due to the first wall 26 and the inclined groove 22. Further, since the first wall 26 is inclined in the same direction as described above, it is difficult to cause the central block 21 to excessively move, and it is difficult to cause uneven wear. Here, if the difference between the inclination angle of the first wall 26 with respect to the tire circumferential direction and the inclination angle of the inclined groove 22 with respect to the tire circumferential direction is 20° or less, the effect of the resistance to uneven wear is sufficiently exerted.

[0073] Further, the angle θ1 of the angle formed by the second wall 27 and the third wall 28 is smaller than the angle θ2 of the angle formed by the first wall 26 and the third wall 28. Thus, the second wall 27 extends in a direction close to the tire axial direction, and the traction is favorably exerted. Further, the angle of the angle (the angle marked with the reference sign P) formed by the inclined groove 22 and the second wall 27 is not excessively reduced, and further, the rubber volume around the angle is not excessively reduced, and thus, it is difficult to cause uneven wear at the angle. Further, it is easy to guide water that contacts the second wall 27 to the inclined groove 22, and the water drainage property is improved. Figure 6

[0074] Here, the angle θ1 is 90° or more, and thus, it is difficult to cause uneven wear near the second wall 27 (particularly, the place marked with the reference sign Q). Further, the angle θ1 is 120° or less, and thus, the effects of the traction and the water drainage property become greater, and further, it is difficult to cause uneven wear at the angle marked with the reference sign P. Figure 6 Figure 6 Here, the angle θ2 is 90° or more, and thus, it is more difficult to cause uneven wear near the first wall 26. Further, the angle θ2 is 130° or less, and thus, the effect of the traction becomes greater, and further, the volume and the rigidity of the central block 21 are maintained, and it is difficult to cause uneven wear.

[0075] Further, the shoulder main groove 11 is also zigzag, and an extension region 35 that is the same as the above-described extension region 25 is formed in the shoulder main groove 11, and thus, the decrease in the resistance to uneven wear is suppressed, and further, the traction of the pneumatic tire is improved.

[0076] Further, the above-described embodiment is merely an example, and various modifications can be made to the above-described embodiment. The range obtained by appropriately modifying the above-described embodiment within the scope of the gist of the present application is included in the scope of the present application.

[0077] Further, the above-described embodiment is merely an example, and various modifications can be made to the above-described embodiment. The range obtained by appropriately modifying the above-described embodiment within the scope of the gist of the present application is included in the scope of the present application.​​

Claims

1. A pneumatic tire, a plurality of blocks and a plurality of inclined grooves inclined with respect to a tire circumferential direction are alternately arranged in a block row in a tire circumferential direction, and at least two rows of the block rows are formed, and a main groove is formed between the two rows of the block rows, characterized in that the main groove is zigzagged by a first groove portion and a second groove portion, which are inclined in different directions with respect to the tire circumferential direction, being alternately arranged, and thereby a convex portion in which the block is convex to the main groove side and a concave portion in which the block is concave to the block side are alternately formed in the tire circumferential direction on both sides of the main groove in a tire axial direction, respectively, an expansion region in which a width of a portion of the main groove is expanded in a direction in which the concave portion is further concave to the block side is formed in each of the concave portions, and the inclined groove is opened in the expansion region.

2. The pneumatic tire according to claim 1, characterized in that a width of a portion of the first groove portion is expanded by the expansion region, and a difference between the width of the first groove portion at a place where the expansion region is present and the width of the first groove portion at a place where the expansion region is not present is 5 mm or less.

3. The pneumatic tire according to claim 1 or 2, characterized in that the expansion region is a trapezoid, as a wall that constitutes a boundary between the expansion region and the block, a first wall that corresponds to one side of the trapezoid, a second wall that corresponds to the other side of the trapezoid, and a third wall that corresponds to a shorter base of the trapezoid are present, and a longer base of the trapezoid is present in the main groove.

4. The pneumatic tire according to claim 3, characterized in that 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, characterized in that the second wall is inclined in the opposite direction of the inclined groove with respect to the tire circumferential direction.

6. The pneumatic tire according to claim 5, characterized in that the inclined groove is opened between the second wall and the third wall, an angle θ1 of an angle formed by the second wall and the third wall is smaller than an angle θ2 of an angle formed by the first wall and the third wall, and θ1 is 90° or more and 120° or less. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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