JP2007314029A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of making traction performance and groove crack resistance performance compatible with each other. <P>SOLUTION: This pneumatic tire 1 has a plurality of circumferential direction grooves 2 extending in the tire circumferential direction and land parts 3 formed by being partitioned by these circumferential direction grooves 21 on a tread part. Additionally, groove walls 21 of the circumferential direction grooves 2 extend zigzag in the tire circumferential direction on their groove opening parts as seen at a flat level of the tread part on this pneumatic tire 1. Furthermore, at least the groove wall 21 on the side of a shoulder part SH out of the groove walls 21 of the circumferential direction grooves 2 extends roughly in a straight line in the tire circumferential direction of a boundary part 23 with a groove bottom 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can achieve both traction performance and groove crack resistance.

  In recent pneumatic tires, in order to improve the traction performance of the tire, a configuration is adopted in which circumferential grooves in the tread shoulder region extend in a zigzag shape toward the tire circumferential direction. For example, a technique described in Patent Document 1 is known as a conventional pneumatic tire adopting such a configuration. A conventional pneumatic tire is a pneumatic tire in which a plurality of zigzag circumferential grooves are provided along the circumferential direction of the tread so that ribs are formed on the tread surface and lug grooves are formed on the shoulder portion of the tread. Thus, with respect to the lateral force applied to the shoulder portion of the tread, the difference in rigidity due to the thickness difference in the width direction of the shoulder portion side rib between the region with the lug groove and the region without the lug groove is the smallest. Thus, the shape of the circumferential groove cross section is changed along the circumferential direction.

  Moreover, in a pneumatic tire, there exists a request | requirement which should suppress generation | occurrence | production of the groove crack in a circumferential groove | channel. This is because such groove cracks cause a decrease in tire life.

JP 2001-187518 A

  An object of the present invention is to provide a pneumatic tire capable of achieving both traction performance and groove crack resistance.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire having a plurality of circumferential grooves extending in a tire circumferential direction and a land portion defined by the circumferential grooves in a tread portion. In the plan view of the tread portion, the groove wall of the circumferential groove extends zigzag in the tire circumferential direction at the groove opening, and at least the shoulder portion side of the groove wall of the circumferential groove. The groove wall extends substantially linearly in the tire circumferential direction at the boundary with the groove bottom.

  In this pneumatic tire, (1) since the groove wall of the circumferential groove has a zigzag shape at the groove opening, compared with a configuration in which the groove wall has a linear shape at the groove opening, Increases shear force in snow. Thereby, there exists an advantage which the snow traction performance of a tire improves. Further, (2) since at least the groove wall on the shoulder portion side of the groove wall of the circumferential groove has a substantially straight shape at the boundary portion with the groove bottom, from this boundary portion to the edge portion on the shoulder portion side of the land portion (Distance of land line diagonal) L is substantially uniform in the tire circumferential direction. Then, when the tire is in contact with the ground, the rotational moment acting on the land portion with the boundary portion as a fulcrum becomes substantially uniform in the tire circumferential direction. Thereby, there is an advantage that stress concentration at the boundary portion is relaxed and the occurrence of groove cracks is suppressed.

  The pneumatic tire according to the present invention is a pneumatic tire having a plurality of circumferential grooves extending in the tire circumferential direction and a land portion defined by the circumferential grooves in the tread portion. In the plan view, the groove wall of the circumferential groove extends in a zigzag shape in the tire circumferential direction at the groove opening, and the shoulder groove side groove of the circumferential groove in a sectional view in the tire meridian direction The diagonal distance L from the boundary part between the wall and the groove bottom to the edge part on the shoulder part side of the land part constituting the groove wall is substantially uniform in the tire circumferential direction.

  In this pneumatic tire, (1) since the groove wall of the circumferential groove has a zigzag shape at the groove opening, compared with a configuration in which the groove wall has a linear shape at the groove opening, Increases shear force in snow. Thereby, there exists an advantage which the snow traction performance of a tire improves. (2) Since the distance L from the boundary between the groove wall and the groove bottom to the edge portion on the shoulder portion side of the land portion (distance of the diagonal line of the land portion) is substantially uniform in the tire circumferential direction, The rotational moment acting on the land portion with the boundary portion as a fulcrum becomes substantially uniform in the tire circumferential direction. Thereby, there is an advantage that stress concentration at the boundary portion is relaxed and the occurrence of groove cracks is suppressed.

  Further, in the pneumatic tire according to the present invention, in the plan view of the tread portion, the groove wall of the circumferential groove has a zigzag shape with the inclination angles α1 and α2 with respect to the tire circumferential direction at the groove opening. In addition, the inclination angles α1 and α2 have a relationship of 5 [deg] <α1 + α2.

  In this pneumatic tire, there is an advantage that the traction performance of the tire is ensured by having a predetermined relationship between the inclination angles α1 and α2 of the groove wall in the groove opening.

  Further, in the pneumatic tire according to the present invention, in the plan view of the tread portion, the groove wall of the circumferential groove has a zigzag shape with the inclination angles α1 and α2 with respect to the tire circumferential direction at the groove opening. In addition, the inclination angles α1 and α2 have a relationship of α1 + α2 <60 [deg].

  In this pneumatic tire, since the sum α1 + α2 of the inclination angles α1 and α2 of the groove wall at the groove opening is defined within a predetermined range, there is an advantage that the uneven wear resistance performance of the tire is ensured.

  In the pneumatic tire according to the present invention, the inclination angles α1 and α2 of the groove walls have a relationship of α1 <40 [deg] and α2 <40 [deg].

  In this pneumatic tire, since the upper limit values of the inclination angles α1 and α2 of the groove wall are optimized, the zigzag shape of the edge portion of the land portion is appropriately ensured. Thereby, there exists an advantage which the uneven wear-proof performance of a tire improves.

  In the pneumatic tire according to the present invention, the groove depth D and the groove width H of the circumferential groove have a relationship of 0.2 <H / D <1.0.

  By applying this pneumatic tire to a tire in which the groove depth D and the groove width H of the circumferential groove have the above relationship, there is an advantage that the effect of suppressing groove cracks can be obtained more remarkably.

  In the pneumatic tire according to the present invention, the groove width H of the circumferential groove and the zigzag amplitudes T1 and T2 of the circumferential groove satisfy T1 / H <1.0 and T2 / H <1.0. Have a relationship.

  In this pneumatic tire, there is an advantage that the uneven wear resistance performance of the tire is improved by having a predetermined relationship between the groove width H of the circumferential groove and the inclination angles α1 and α2 of the groove wall.

  In the pneumatic tire according to the present invention, the land portion is a shoulder land portion, and the land portion is partitioned by the circumferential groove.

  In this pneumatic tire, there is an advantage that the effect of suppressing groove cracks can be obtained more significantly by dividing the shoulder land portion by the circumferential groove.

  Further, in the pneumatic tire according to the present invention, the division position of the tire manufacturing mold in the tread portion deviates from the intersection of the groove wall having one inclination angle α1 and the groove wall having the other inclination angle α2. Placed in position.

  In this pneumatic tire, since the division position of the tire manufacturing mold is arranged at a position different from the position where the groove crack is likely to occur (the zigzag top of the groove wall), the generation of the groove crack is more effective. There is an advantage to be suppressed.

  In the pneumatic tire according to the present invention, the zigzag pitch of the groove wall changes in the tire circumferential direction.

  In this pneumatic tire, since the pitch variation structure is adopted for the zigzag shape of the groove wall, there is an advantage that pattern noise is reduced and the noise performance of the tire is improved.

  In the pneumatic tire according to the present invention, (1) since the groove wall of the circumferential groove has a zigzag shape at the groove opening, compared with the configuration in which the groove wall has a linear shape at the groove opening. Increases the shear force during snow movement. Thereby, there exists an advantage which the snow traction performance of a tire improves. Further, (2) since at least the groove wall on the shoulder portion side of the groove wall of the circumferential groove has a substantially straight shape at the boundary portion with the groove bottom, from this boundary portion to the edge portion on the shoulder portion side of the land portion (Distance of land line diagonal) L is substantially uniform in the tire circumferential direction. Then, when the tire is in contact with the ground, the rotational moment acting on the land portion with the boundary portion as a fulcrum becomes substantially uniform in the tire circumferential direction. Thereby, there is an advantage that stress concentration at the boundary portion is relaxed and the occurrence of groove cracks is suppressed.

  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 perspective view showing a tread portion of a pneumatic tire according to an embodiment of the present invention. 2 to 5 are a perspective view (FIG. 2) showing a main groove of the pneumatic tire shown in FIG. 1, a plan view in the groove length direction (FIGS. 3 and 4), and a sectional view in the groove depth direction (FIG. 2). FIG. 5). FIG. 6 is an explanatory view showing the operation of the pneumatic tire shown in FIG. 7 and 8 are explanatory views showing modifications of the pneumatic tire depicted in FIG. FIG. 9 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. 10-12 is explanatory drawing which shows the generation | occurrence | production principle of a groove crack. FIGS. 13 and 14 are a perspective view (FIG. 13) and an operation explanatory view (FIG. 14) showing a main groove of a conventional pneumatic tire.

[Groove crack generation principle]
The general pneumatic tire 10 is designed so that the bead interval (bead base width) on both sides in the no-load state (before filling with internal pressure) is larger than the rim width in order to maintain the air filling property when assembling the rim. (See FIG. 10). This tendency is particularly remarkable in tubeless tires. In such a configuration, the bead base width is narrowed when the rim is assembled, and the radius radius R of the tire inner peripheral surface is reduced. Then, a tensile stress in the tire width direction is generated on the tread surface due to a difference in diameter between the center crown portion CC and the shoulder portion SH (see FIG. 11). Further, when an internal pressure is applied to the tire, the outer diameter of the tire grows and the tensile stress in the tire width direction increases. In particular, in a pneumatic tire having a high flatness ratio, this tensile stress becomes larger because the internal pressure sharing ratio in the belt layer is high.

  When such tensile stress is generated, the circumferential groove 11 of the tread portion is expanded in the tire width direction (see FIG. 12). At this time, in the circumferential groove 11, the shoulder portion SH side is pulled more in the tire width direction than the center crown portion CC side. For this reason, stress concentration occurs at the boundary portion 113 between the groove wall 111 and the groove bottom 112 on the shoulder portion SH side. When a repeated stress (contact pressure) is applied to the circumferential groove 11 during rolling of the tire, a groove crack is generated at the boundary 113.

  In particular, in the conventional pneumatic tire 10 having the zigzag circumferential groove 11, the zigzag shape in which the boundary portion 113 between the groove wall 111 and the groove bottom 112 in the circumferential groove 11 matches the edge shape of the tread surface of the land portion 12. (See FIG. 13). In such a conventional pneumatic tire, a groove crack is likely to occur at the zigzag top (the circle in FIG. 13) in the boundary portion 113 on the shoulder portion SH side. This is because the distance L ′ of the diagonal line of the land portion 12 from the boundary portion 113 on the shoulder portion SH side to the edge portion of the shoulder portion SH is longer than the periphery at the top of the zigzag shape. This is because a concentrated stress (a rotational moment with the boundary 113 as a fulcrum) is generated (see FIG. 14).

[Pneumatic tire]
The pneumatic tire 1 includes a plurality of circumferential grooves (circumferential main grooves) 2 extending in the tire circumferential direction and a plurality of land portions (ribs) 3 defined by the circumferential grooves 2 as treads. (See FIG. 1). Here, the groove wall 21 of the circumferential groove 2 extends in a zigzag shape in the tire circumferential direction at the groove opening (see FIGS. 1 to 3). In other words, in the plan view of the tread portion, the edge portion of the tread surface of the land portion 3 on the circumferential groove 2 side is formed in a zigzag shape toward the tire circumferential direction. Further, the groove wall 21 of the circumferential groove 2 extends substantially linearly with respect to the tire circumferential direction at the boundary 23 with the groove bottom 22 (see FIG. 4). That is, the boundary 23 between the groove wall 21 and the groove bottom 22 extends substantially linearly in the tire circumferential direction in a plan view of the groove bottom 22.

  The groove wall 21 of the circumferential groove 2 has a three-dimensional twist in the groove depth direction so as to have a zigzag shape at the groove opening and a substantially linear shape at the boundary 23 with the groove bottom 22. It is formed with. In addition, the inclination angle between the groove wall 21 and the tire circumferential direction in plan view of the tread portion is the maximum (α1, α2) at the groove opening, and gradually decreases toward the groove depth direction. It becomes the minimum (β1, β2) at the boundary portion 23 with the groove bottom 22. In addition, the substantially linear shape mentioned here means that the absolute values of the inclination angles β1 and β2 with respect to the tire circumferential direction are less than 3 [deg] (0 [deg] ≦ β1 <3 [deg], 0 [deg]. ] ≦ β2 <3 [deg]). Further, a ridge line appears on the groove wall 21 of the circumferential groove 2 from the groove opening toward the groove bottom 22.

  In such a configuration, (1) since the groove wall 21 of the circumferential groove 2 has a zigzag shape at the groove opening, compared with a configuration (not shown) in which the groove wall has a linear shape at the groove opening. The snow shear force during rolling increases. Thereby, there exists an advantage which the snow traction performance of a tire improves. (2) At least the groove wall 21 on the shoulder portion SH side of the groove wall 21 of the circumferential groove 2 has a substantially linear shape at the boundary portion 23 with the groove bottom 22. The distance to the edge portion on the shoulder portion SH side (distance of the diagonal line of the land portion 3) L is substantially uniform in the tire circumferential direction. Then, when the tire is in contact with the ground, the rotational moment acting on the land portion 3 with the boundary portion 23 as a fulcrum becomes substantially uniform in the tire circumferential direction. Thereby, there is an advantage that the stress concentration at the boundary portion 23 is relaxed and the occurrence of groove cracks is suppressed.

[Additional matter 1]
In the pneumatic tire 1, the groove wall 21 of the circumferential groove 2 extends in a zigzag shape while having inclination angles α1 and α2 with respect to the tire circumferential direction at the groove opening in a plan view of the tread portion. It is preferable that these inclination angles α1 and α2 have a relationship of 5 [deg] <α1 + α2 (see FIG. 3). These inclination angles α1, α2 are angles formed by the groove wall 21 of the circumferential groove 2 with respect to the tire circumferential direction at the groove opening, and are defined by absolute values (α1> 0, α2> 0). Moreover, the zigzag shape of the groove wall 21 in the groove opening is defined by these inclination angles α1 and α2. In such a configuration, the inclination angles α1 and α2 of the groove wall 21 in the groove opening portion have a predetermined relationship (5 [deg] <α1 + α2), so that there is an advantage that the traction performance of the tire is ensured (see FIG. 9). . For example, when α1 + α2 ≦ 5 [deg], the shape of the groove wall 21 in the groove opening (the edge shape of the tread surface of the land portion 3 on the circumferential groove 2 side) is substantially linear. Then, since sufficient shear force in snow cannot be obtained at the time of tire rolling, the traction performance of the tire is not ensured.

  In the above configuration, it is more preferable that the inclination angles α1 and α2 of the groove wall 21 have a relationship of 30 [deg] <α1 + α2. Thereby, there exists an advantage which the traction performance of a tire improves more effectively (refer FIG. 9).

[Additional matter 2]
In the pneumatic tire 1, the inclination angles α1 and α2 of the groove wall 21 preferably have a relationship of α1 + α2 <60 [deg] (see FIG. 3). In such a configuration, since the sum α1 + α2 of the inclination angles α1 and α2 of the groove wall 21 at the groove opening is defined within a predetermined range, there is an advantage that the uneven wear resistance performance of the tire is ensured (see FIG. 9). For example, when 60 [deg] ≦ α1 + α2, since the lateral element of the ridgeline of the groove wall 21 (inclination angle of the groove wall 21 with respect to the groove depth direction) increases, heel and toe wear occurs in the land portion 3. Further, when the land portion 3 is a shoulder rib, the change in the rib width is abrupt, the change in the contact area of the land portion 3 in the tire circumferential direction is increased, and uneven wear is likely to occur in the land portion 3. .

  In the above configuration, the inclination angles α1 and α2 of the groove wall 21 preferably have a relationship of α1 <40 [deg] and α2 <40 [deg] (see FIG. 3). That is, since the upper limit values of the inclination angles α1 and α2 of the groove wall 21 are optimized, the zigzag shape of the edge portion of the land portion 3 is appropriately ensured. This has the advantage of improving the uneven wear resistance performance of the tire (see FIG. 9).

[Additional matter 3]
Moreover, in this pneumatic tire 1, it is preferable that the groove depth D and the groove width H of the circumferential groove 2 have a relationship of 0.2 <H / D <1.0 (see FIG. 5). By applying this pneumatic tire 1 to a tire in which the groove depth D and the groove width H of the circumferential groove 2 have the above relationship, there is an advantage that the effect of suppressing groove cracks can be obtained more remarkably. is there. For example, in many pneumatic tires for trucks and buses, the groove depth D and the groove width H of the circumferential groove 2 have the above-described relationship, and the problem relating to the occurrence of groove cracks is serious.

[Additional matter 4]
In the pneumatic tire 1, the groove width H of the circumferential groove 2 and the zigzag amplitudes T1 and T2 preferably have a relationship of T1 / H <1.0 and T2 / H <1.0. (See FIG. 3). That is, the zigzag amplitudes T1 and T2 of the groove wall 21 in the groove opening are preferably smaller than the groove width H. Thereby, there exists an advantage which the uneven wear-proof performance of a tire improves. For example, if the amplitude of the zigzag shape of the groove wall 21 is too large, the lateral element of the ridge line of the groove wall 21 (inclination angle of the groove wall 21 with respect to the groove depth direction) becomes large, and heel and toe wear occurs in the land portion 3. To do. Further, when the land portion 3 is a shoulder rib, the change in the rib width is abrupt, the change in the contact area of the land portion 3 in the tire circumferential direction is increased, and uneven wear is likely to occur in the land portion 3.

  In such a configuration, it is preferable that the groove width H of the circumferential groove 2 and the zigzag-shaped amplitudes T1 and T2 have a relationship of 0.2 <T1 / H and 0.2 <T2 / H. That is, it is preferable that the zigzag amplitudes T1 and T2 of the groove wall 21 are larger than 1/5 of the groove width H. Thereby, the zigzag shape of the edge part of the land part 3 is ensured appropriately, and there exists an advantage which the uneven wear-proof performance of a tire improves.

[Additional matter 5]
Generally, in the circumferential groove that divides the shoulder land portion (shoulder rib), the moment acting on the shoulder rib at the time of tire contact (rotational moment with the boundary 23 of the circumferential groove 2 as a fulcrum) is larger than that in the center land portion. Therefore, groove cracks are likely to occur. Therefore, in the pneumatic tire 1, the land portion 3 is preferably a shoulder land portion, and the shoulder land portion is preferably partitioned by the circumferential groove 2 (see FIGS. 1 and 6). Thereby, there exists an advantage by which the suppression effect of a groove crack is acquired more notably. The shoulder land portion refers to the land portion 3 within the range of W / 4 from the outer side in the tire width direction with respect to the contact width W of the tread portion.

[Additional matter 6]
Further, at the zigzag top of the groove wall 21, since a moment (rotational moment with the boundary 23 of the circumferential groove 2 as a fulcrum) acting when the tire contacts the ground is large, a groove crack is likely to occur. Further, since stress concentration tends to occur at the division position of the tire manufacturing mold, groove cracks are likely to occur. Therefore, in this pneumatic tire 1, the division position of the tire manufacturing mold in the tread portion deviates from the intersection (the position where the ridgeline appears) between the groove wall 21 having the inclination angle α1 and the groove wall 21 having the inclination angle α2. It is preferable to arrange in a position (not shown). That is, the division position of the tire manufacturing mold is arranged at a position different from the zigzag top of the groove wall 21. For example, the division positions of the tire manufacturing mold are arranged in a zigzag linear portion or a valley portion. Thereby, there exists an advantage by which generation | occurrence | production of a groove crack is suppressed more effectively.

[Additional matter 7]
Moreover, in this pneumatic tire, it is preferable that the zigzag pitches P1 and P2 of the groove wall 21 change with respect to the tire circumferential direction (not shown). That is, it is preferable that a pitch variation structure is adopted for the zigzag shape of the groove wall 21. Thereby, there is an advantage that pattern noise is reduced and the noise performance of the tire is improved.

[Modification]
In the pneumatic tire 1, at least the groove wall 21 on the shoulder portion SH side of the groove wall 21 of the circumferential groove 2 extends substantially linearly in the tire circumferential direction at the boundary portion 23 with the groove bottom 22. (See FIGS. 1, 2 and 4). Thereby, the stress concentration at the boundary portion 23 is relaxed, and the occurrence of groove cracks is suppressed. On the other hand, the shape of the boundary portion between the groove wall on the center crown portion CC side and the groove bottom 22 is not particularly limited. For example, the boundary portion on the center crown portion CC side may be formed in a substantially linear shape like the boundary portion 23 on the shoulder portion SH side (see FIG. 4), or may be formed in a zigzag shape (see FIG. 4). 7 and FIG. 8).

[performance test]
In this example, performance tests on (1) crack occurrence rate, (2) traction performance, and (3) uneven wear resistance performance were performed on a plurality of types of pneumatic tires with different conditions (see FIG. 9). In this performance test, a pneumatic tire having a tire size of 275 / 70R22.5 is mounted on a regular rim defined by JATMA, and an air pressure and a regular load of 80% of the regular internal pressure are applied to the pneumatic tire. A pneumatic tire is mounted on a drive shaft of a test vehicle of 2-D · 4 (2-wheel-drive double-wheel / double-wheel).

  (1) In the performance test of the crack occurrence rate, a test vehicle equipped with a pneumatic tire travels 50000 [km] on a prescribed course, and thereafter the groove crack occurrence rate is evaluated. This incidence is 15% or less and is considered a pass line. (2) In the performance test of traction performance, a test vehicle equipped with pneumatic tires runs on a climbing course in a muddy area, and the climbing performance is indexed. This evaluation is more preferable as the numerical value is higher. (3) In the performance test of uneven wear resistance performance, the degree of occurrence of uneven wear is evaluated as an index for the pneumatic tire used in the performance test of crack generation rate. This evaluation is more preferable as the numerical value is higher.

  In the conventional pneumatic tire, the circumferential groove 11 has a zigzag shape, and the boundary 113 between the groove wall 111 and the groove bottom 112 in the circumferential groove 11 is matched to the edge shape of the tread surface of the land portion 12. It has a zigzag shape (see FIG. 13). In the pneumatic tire 1 of Invention Example 1, the groove wall 21 of the circumferential groove 2 has a zigzag shape at the groove opening, and the groove wall 21 on the shoulder portion SH side of the groove wall 21 of the circumferential groove 2. Only has a substantially linear shape at the boundary 23 with the groove bottom 22 (see FIGS. 7 and 8). In the pneumatic tire 1 of Invention Example 2, the groove wall 21 of the circumferential groove 2 has a zigzag shape at the groove opening, and the groove walls 21 on both sides of the circumferential groove 2 are boundary portions with the groove bottom 22. 23 has a substantially linear shape (see FIGS. 2 to 4). In the pneumatic tires 1 of Invention Examples 3 to 5, the inclination angles α1, α2, β1, and β2 of the groove wall 21 are changed with respect to the pneumatic tire 1 of Invention Example 2. In the display of (numerical value / numerical value) in FIG. 13, the left side shows the evaluation result on the shoulder portion SH side of the circumferential groove 2, and the right side shows the evaluation result on the center crown portion CC side of the circumferential groove 2. Yes. In these pneumatic tires, the groove width H = 11.5 [mm], the groove depth D = 15 [mm], and the amplitude T1 = T2 = 3.5 [mm] are common.

  As shown in the test results, it can be seen that in the pneumatic tires 1 of Invention Examples 1 to 5, the incidence of groove cracks is reduced and the traction performance is improved. Further, comparing Invention Example 1 and Invention Example 2, the configuration in which the groove walls 21 on both sides of the circumferential groove 2 have a substantially linear shape at the boundary portion 23 with the groove bottom 22 (Invention Example 2), The groove wall 21 on both sides of the circumferential groove 2 is preferable in that the generation of groove cracks is suppressed and the uneven wear resistance performance is improved. Further, when Invention Example 2, Invention Example 3 and Invention Example 5 are compared, it can be seen that the traction performance of the tire is improved by optimizing the sum α1 + α2 of the inclination angles α1 and α2 of the groove wall 21. Further, when Invention Example 2 and Invention Example 4 are compared, the upper limit values of the inclination angles α1 and α2 of the groove wall 21 are optimized, so that the occurrence of groove cracks is suppressed and the traction performance and resistance to unevenness of the tire are reduced. It can be seen that the wear performance is improved.

  As described above, the pneumatic tire according to the present invention is useful in that both traction performance and groove crack resistance can be achieved.

It is a perspective view which shows the tread part of the pneumatic tire concerning the Example of this invention. It is a perspective view which shows the main groove | channel of the pneumatic tire described in FIG. It is a top view of the groove length direction which shows the main groove of the pneumatic tire described in FIG. It is a top view which shows the main groove | channel of the pneumatic tire described in FIG. It is sectional drawing of the groove depth direction which shows the main groove of the pneumatic tire described in FIG. It is explanatory drawing which shows the effect | action 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. It is explanatory drawing which shows the generation principle of a groove crack. It is explanatory drawing which shows the generation principle of a groove crack. It is explanatory drawing which shows the generation principle of a groove crack. It is a perspective view which shows the main groove of the conventional pneumatic tire. It is action explanatory drawing which shows the main groove | channel of the conventional pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Circumferential groove 3 Land part 21 Circumferential groove 21 Groove wall 22 Groove bottom 22 Groove bottom 23 Boundary part

Claims (10)

A pneumatic tire having a plurality of circumferential grooves extending in a tire circumferential direction and a land portion defined by the circumferential grooves in a tread portion,
In a plan view of the tread portion, the groove wall of the circumferential groove extends in a zigzag shape in the tire circumferential direction at the groove opening, and at least the groove wall on the shoulder portion side of the groove wall of the circumferential groove. A pneumatic tire characterized by extending substantially linearly in the tire circumferential direction at the boundary with the groove bottom. A pneumatic tire having a plurality of circumferential grooves extending in a tire circumferential direction and a land portion defined by the circumferential grooves in a tread portion,
In plan view of the tread portion, the groove wall of the circumferential groove extends in a zigzag shape in the tire circumferential direction at the groove opening, and in the tire meridian cross-sectional view, the shoulder portion side of the circumferential groove The diagonal distance L from the boundary portion between the groove wall and the groove bottom to the edge portion on the shoulder portion side of the land portion constituting the groove wall is substantially uniform in the tire circumferential direction. tire.   In a plan view of the tread portion, the groove wall of the circumferential groove extends in a zigzag shape while having an inclination angle α1, α2 with respect to the tire circumferential direction at the groove opening, and these inclination angles α1, The pneumatic tire according to claim 1 or 2, wherein α2 has a relationship of 5 [deg] <α1 + α2.   In a plan view of the tread portion, the groove wall of the circumferential groove extends in a zigzag shape while having an inclination angle α1, α2 with respect to the tire circumferential direction at the groove opening, and these inclination angles α1, The pneumatic tire according to claim 1, wherein α2 has a relationship of α1 + α2 <60 [deg].   The pneumatic tire according to claim 4, wherein the inclination angles α1 and α2 of the groove walls have a relationship of α1 <40 [deg] and α2 <40 [deg].   The pneumatic tire according to any one of claims 1 to 5, wherein a groove depth D and a groove width H of the circumferential groove have a relationship of 0.2 <H / D <1.0.   The groove width H of the circumferential groove and the zigzag amplitudes T1 and T2 of the circumferential groove have a relationship of T1 / H <1.0 and T2 / H <1.0. The pneumatic tire according to one.   The pneumatic tire according to any one of claims 1 to 7, wherein the land portion is a shoulder land portion, and the land portion is partitioned by the circumferential groove.   The division position of the tire manufacturing mold in the tread portion is arranged at a position deviated from the intersection of the groove wall having one inclination angle α1 and the groove wall having the other inclination angle α2. The pneumatic tire according to any one of the above.   The pneumatic tire according to any one of claims 1 to 9, wherein the zigzag pitch of the groove wall changes in a tire circumferential direction.

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