JP2021054327A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire reducing occurrence of defects such as annular groove crack.SOLUTION: An objective tire comprises: a tread part 3 forming a ground plane 33; a buttress part 70 which is an area from the end of the tread part 3 to the maximum width portion Wh in the tire side wall face 7 located at the outside WD1 of the tread part 3 in a tire width direction; and at least two annular grooves 9 which are formed to the buttress part 70, extend in a tire circumferential direction CD to become toric and also extend toward the inside WD2 in a tire width direction. Each of at least two annular grooves 9 has a first annular groove 9a nearest to the ground plane 33 and a second annular groove 9b further separate from that plane 33 compared to the groove 9a. Groove bottoms 91 of the first and second annular grooves 9a and 9b is formed into a circular arc shape in a tire meridian cross section. The curvature radius R1 of the groove bottom 91 in the first annular groove 9a is larger than that radius R2 of the groove bottom 91 in the second annular groove 9b.SELECTED DRAWING: Figure 9

Description

The present disclosure relates to pneumatic tires.

It is known that pneumatic tires used for trucks and buses have a high contact pressure at the shoulder end, which is the end of the contact patch formed by the tread, and the shoulder end is easily worn.

Patent Document 1 discloses a tire in which two annular grooves are formed in a buttress portion of a tire side wall surface in order to reduce the contact pressure at the shoulder end portion.

JP-A-2019-99077

Distortion occurs in the groove bottom of the annular groove formed in the buttress portion, and if the strain is too large, cracks in the groove bottom will occur. When at least two annular grooves are provided, the annular groove near the ground plane is easily deformed, so that strain is likely to be concentrated in the annular groove near the ground plane and cracks are likely to occur.

The present disclosure provides a pneumatic tire in which the occurrence of defects such as cracks in the annular groove is reduced.

The pneumatic tire of the present disclosure is a region from the end portion of the tread portion to the maximum width portion of the tire among the tread portion forming the ground contact surface and the tire side wall surface located outside the tread portion in the tire width direction. A buttless portion and at least two annular grooves formed in the buttless portion and extending in the tire circumferential direction to form an annular shape and extending inward in the tire width direction are provided, and the at least two annular grooves are formed on the ground contact surface. It has a first annular groove closest to the tire and a second annular groove that is farther from the ground contact surface than the first annular groove, and the groove bottoms of the first annular groove and the second annular groove are tires. It is formed in an arc shape in the meridional cross section, and the radius of curvature of the groove bottom of the first annular groove is larger than the radius of curvature of the groove bottom of the second annular groove.

If the bottom of the annular groove has an angular shape, cracks will occur starting from the corner. Further, the closer to the ground plane, the greater the deformation of the annular groove. Therefore, since the groove bottoms of the first annular groove and the second annular groove are formed in an arc shape in the cross section of the tire meridian, it is possible to eliminate the corners and suppress the occurrence of cracks. Nevertheless, since the radius of curvature of the groove bottom of the first annular groove closest to the ground plane is larger than the radius of curvature of the groove bottom of the second annular groove, the strain acting on the groove bottom of the first annular groove is dispersed to disperse the cracks. It is possible to suppress the occurrence.

A tire meridian sectional view showing a main part of an example of a pneumatic tire according to the first embodiment. Side view of the pneumatic tire of the first embodiment A tire meridian sectional view showing a main part of an example of a pneumatic tire according to the first embodiment. Tire meridian cross section showing a modified example Tire meridian cross section showing a modified example Tire meridian cross section showing a modified example Tire meridian cross section showing a modified example Tire meridian cross section showing a modified example Tire meridian cross section showing a modified example Tire meridian cross section showing a modified example

Hereinafter, the pneumatic tire of the first embodiment of the present disclosure will be described with reference to the drawings. In the figure, "CD" means the tire circumferential direction, "WD" means the tire width direction, and "RD" means the tire radial direction. Each figure shows the shape of a new tire.

As shown in FIGS. 1 and 2, the pneumatic tire includes a pair of bead portions 1, a sidewall portion 2 extending from each bead portion 1 to the tire radial outer side RD1, and a tire radial outer side of the sidewall portion 2. It is provided with a tread portion 3 that connects RD1 ends to each other. An annular bead core (not shown) formed by coating a convergent body such as a steel wire with rubber and a bead filler made of hard rubber (not shown) are arranged in the bead portion 1. The bead portion 1 is attached to a bead seat of a rim (not shown), and if the air pressure is a predetermined pressure (for example, the air pressure determined by JATTA), the bead portion 1 is appropriately fitted to the rim flange by the tire internal pressure, and the tire fits into the rim. Will be combined.

Further, this tire includes a toroid-shaped carcass 4 extending from the tread portion 3 to the bead portion 1 via the sidewall portion 2. The carcass 4 is provided between a pair of bead portions 1, and is locked in a state where the end portions thereof are wound up via a bead core. An inner liner rubber 5 for holding the air pressure is arranged on the inner peripheral side of the carcass 4.

On the outer circumference of the carcass 4 in the tread portion 3, a plurality of belt plies 6a, 6b, 6c, 6d for reinforcing the carcass 4 (four in the present embodiment) and a tread rubber 30 are arranged from the inside to the outside. They are provided in order toward each other. On the surface of the tread portion 3, a plurality of main grooves 31 extending along the tire circumferential direction CD and ribs 32 partitioned by the main grooves 31 and continuous with the tire circumferential direction CD are formed. In the present embodiment, since the tire is a rib tire, a block divided in the tire circumferential direction CD is not formed. In the present embodiment, two main grooves 31 are formed on one side of the tire, and there are four main grooves 31 in total, but the present invention is not limited to this. For example, the total number may be three or five or more.

The four belt plies 6a, 6b, 6c, and 6d each include a plurality of steel cords arranged in parallel in a bamboo blind shape, and are formed by coating them with rubber. Of the four belt plies 6a, 6b, 6c, 6d, the cords of the second and third belt plies 6b, 6c from the carcass 4 toward the outer circumference are inclined in opposite directions with respect to the tire axis. Crossing. The second and third belt plies 6b and 6c are so-called main belts and sandwich the tread rubber 30.

As shown in FIG. 1, the tread portion 3 forms a ground plane 33. The outer WD1 of the tread portion 3 in the tire width direction has a tire side wall surface 7 formed of sidewall rubber. The buttress portion 70 is a region of the tire side wall surface 7 from the end portion LE (ground contact end LE) of the tread portion 3 to the tire maximum width portion Wh. The ground contact end LE is the end of the outer WD1 of the ground contact surface 33 in the tire width direction, and the ridge line between the tread portion 3 and the tire side wall surface 7 corresponds to the heavy load tire.

FIG. 3 is an enlarged view of a main part of FIG. As shown in FIGS. 1 to 3, for example, at least two annular grooves 9 are formed in the buttress portion 70. At least two annular grooves 9 extend in the tire circumferential direction CD to form an annular shape and extend toward the inner WD2 in the tire width direction. At least two annular grooves 9 are, as shown in FIGS. 1 and 3, a first annular groove 9a closest to the ground plane 33 and a second annular groove 9b farther from the ground plane than the first annular groove 9a. Has. The second annular groove 9b is located inside the tire radial direction with respect to the first annular groove. The annular groove 9 extends linearly in the tire meridian cross section, and the groove bottom is formed in an arc shape.

By forming the annular groove 9 in the buttress portion 70, it is possible to reduce the ground contact pressure of the shoulder end portion (land portion 32 around the ground contact end LE) and reduce uneven wear. Further, when overcoming a rut or cornering, a large lateral force is generated, but since at least two annular grooves are formed, the stress applied to the groove bottom can be dispersed and the occurrence of cracks can be suppressed.

By the way, the annular groove 9 formed in the buttress portion 70 is deformed during traveling, but if the deformation of the annular groove 9 is large, the wandering (wobble) that occurs when overcoming the rut becomes large, and the steering stability performance deteriorates. There is a risk of doing so.

The first annular groove 9a closest to the ground contact surface 33 is farther from the belt ply (6a to 6d) than the second annular groove 9b, so that rigidity is difficult to be secured, and deformation during traveling tends to be large. Therefore, in order to deal with this problem, it is preferable that the groove depth D1 of the first annular groove 9a is smaller than the groove depth D2 of the second annular groove 9b as in the embodiment shown in FIG. As described above, since the groove depth D1 of the first annular groove 9a is smaller than the groove depth D2 of the second annular groove 9b, the deformation of the first annular groove 9a can be suppressed, and it occurs when the rut is overcome. It is possible to suppress the wandering that is obtained and improve the steering stability performance. Of course, when the purpose is not to solve this problem, the groove depths of the first annular groove 9a and the second annular groove 9b may be the same, or the groove depth of the first annular groove 9a is the second. It may be larger than the groove depth of the annular groove 9b.

As shown in FIG. 3, the maximum depths of the first annular groove 9a and the second annular groove 9b are perpendicular lines L0 passing through a position separated from the ground contact end LE to the inner WD2 in the tire width direction by 3% of the tread width W. It should not exceed. The perpendicular line L0 is along the tire radial direction RD. This is because if the first annular groove 9a and the second annular groove 9b are too deep, the wandering becomes large and the steering stability performance deteriorates.

By the way, when the annular groove 9 formed in the buttress portion 70 extends linearly to the inner WD2 in the tire width direction in the tire meridional cross section, when the annular groove 9 is clogged with stones depending on the extending direction of the annular groove 9 ( During stone biting), cracks may occur and stone drilling may occur that damages internal members such as belt plies 6a, 6b, 6c, and 6d. Therefore, it is preferable to provide a pneumatic tire in which the occurrence of defects such as stone drilling is reduced. In particular, as shown in FIG. 4, when the first annular groove 9a faces the sixth direction S6, the first annular groove 9a becomes close to the belt plies 6b and 6c, and it has been found that stone drilling is likely to occur. .. The sixth direction S6 shown in FIG. 4 is a direction in which the groove bottom is the inner RD2 in the tire radial direction as compared with the case of the first direction S1 shown in FIG. As shown in FIGS. 1 and 5, the first direction S1 is a virtual straight line connecting the intersection P1 of the tire equatorial line CL and the contact patch 33 and the ridgeline LE of the contact patch 33 and the tire side wall surface 7 in the tire meridional cross section. This is the direction in which the groove center axis L2 is parallel to L1.

Therefore, in order to suppress stone drilling, the first annular groove 9a extends linearly in the tire meridian cross section, and the first annular groove 9a is the first direction S1 (see FIG. 5) or the second direction S2. It is preferable to face (see FIG. 3). This is because stone drilling can be suppressed by preventing the groove bottom from getting too close to the belt ply. Of course, if the purpose is not to solve this problem, the direction of the first annular groove 9a may be any direction. As shown in FIG. 3, the second direction S2 is a direction in which the groove bottom is the outer RD1 in the tire radial direction as compared with the case where the tire meridian cross section faces the first direction S1.

On the other hand, if the first annular groove 9a faces the second direction S2 and the groove bottom is too close to the ground contact surface 33, the buttress portion 70 of the tire radial outer RD1 may be torn off from the first annular groove 9a. Therefore, the effect of reducing the contact pressure by the first annular groove 9a is impaired. In order to avoid thea, as shown by the arrow Y1 shown in FIG. 5, the first annular groove 9a is separated from the ground contact end LE by 8 mm or more along the tire side wall surface 7 and faces the first direction S1. Is most preferable, but even in the second direction S2, it is preferable that the angle θ1 formed by the virtual straight line L1 and the groove center axis L2 is 20 degrees or less in order to suppress the tire. In order to suppress both thea and stone drilling, it is preferable that the first annular groove 9a faces the first direction S1.

As shown in FIGS. 3, 6 and 7, the second annular groove 9b has a cross section of the tire meridian in order to prevent the corner portion between the groove wall surface 90 of the second annular groove 9b and the tire side wall surface 7 from being chipped. The second annular groove 9b faces either the third direction S3 (see FIG. 6), the fourth direction S4 (see FIG. 3), or the fifth direction S5 (see FIG. 7). Is preferable. As shown in FIGS. 3, 6 or 7, if the second annular groove 9b faces any of the third direction S3, the fourth direction S4 or the fifth direction S5, the second annular groove 9b It is possible to prevent or suppress the loss of the corner portion between the groove wall surface 90 and the tire side wall surface 7. Of course, if the purpose is not to solve this problem, the second annular groove 9b may face in any of the directions shown in FIGS. 3, 6, 7, and 8. As shown in FIG. 6, the third direction S3 is a direction in which the groove wall surface 90 is parallel to the virtual straight line L1 in the tire meridian cross section. As shown in FIG. 3, the fourth direction S4 is a direction in which the groove wall surface 90 of the second annular groove 9b is perpendicular to the tire side wall surface 7 in the tire meridian cross section. As shown in FIG. 7, the fifth direction S5 is a direction between the third direction S3 and the fourth direction S4. In the second direction S2 shown in FIG. 8, the second annular groove 9b has a groove bottom that is further outer RD1 in the tire radial direction than that of the third direction S3.

By the way, strain is generated in the groove bottom of the annular groove formed in the buttress portion, and if the strain is too large, cracks in the groove bottom will occur. When at least two annular grooves are provided, the annular groove near the ground plane is easily deformed, so that strain is likely to be concentrated on the annular groove and cracks are likely to occur. Therefore, it is preferable to provide a pneumatic tire in which the occurrence of defects such as cracks in the annular groove is reduced.

Therefore, in order to suppress cracks in the first annular groove 9a, as shown in FIG. 9, the groove bottoms 91 of the first annular groove 9a and the second annular groove 9b are formed in an arc shape, and the first annular groove 9a The radius of curvature R1 of the groove bottom 91 is preferably larger than the radius of curvature R2 of the groove bottom 91 of the second annular groove 9b. In the present embodiment, the center of the radius of curvature is the center of the groove width. Of course, when the purpose is not to solve this problem, both radii of curvature R1 and R2 may be the same as shown in FIG. Further, the radius of curvature R1 of the first annular groove 9a may be smaller than the radius of curvature R2 of the second annular groove 9b. Further, the groove bottom 91 of the first annular groove 9a and the second annular groove 9b may not be formed in an arc shape.

If the groove bottom of the annular groove 9 has an angular shape, cracks will occur starting from the corners. Further, the closer to the ground plane, the greater the deformation of the annular groove 9. Since the groove bottom 91 of the first annular groove 9a and the second annular groove 9b is formed in an arc shape in the cross section of the tire meridian, it is possible to eliminate the corners and suppress the occurrence of cracks. Nevertheless, since the radius of curvature R1 of the groove bottom 91 of the first annular groove 9a closest to the ground plane is larger than the radius of curvature R2 of the groove bottom 91 of the second annular groove 9b, it acts on the groove bottom 91 of the first annular groove 9a. It is possible to disperse the strain to be generated and suppress the occurrence of cracks.

In the present embodiment, as shown in FIG. 9, the groove widths W1 and W2 of the straight portion and the radius of curvature R1 and R2 of the arc portion of the groove bottom 91 are the same, but as shown in FIG. The radius of curvature R1 and R2 of the arc portion of the groove bottom 91 may be made larger than the groove widths W1 and W2 of the portion to form a flask shape.

In order to suppress stone biting into the first annular groove 9a, the groove width W1 of the first annular groove 9a is preferably larger than the groove width W2 of the second annular groove 9b. The narrower the groove widths W1 and W2 of the annular groove 9, the more likely it is that stone biting will occur. If the groove widths W1 and W2 of the annular groove 9 are the same, stone biting is more likely to occur as the groove is closer to the ground plane 33. Therefore, by making the groove width W1 of the first annular groove 9a where stone biting is likely to occur larger than the groove width W2 of the second annular groove 9b, it is possible to reduce the stone biting of the first annular groove 9a. Of course, when the purpose is not to solve this problem, the groove width W1 of the first annular groove 9a and the groove width W2 of the second annular groove 9b may be the same, and the groove width W1 of the first annular groove 9a is the first. It may be smaller than the groove width W2 of the two annular grooves 9b. Further, the groove bottom 91 of the first annular groove 9a and the second annular groove 9b may not be formed in an arc shape. As shown in FIGS. 9 and 10, the groove widths W1 and W2 are obtained along the direction orthogonal to the groove central axis L2.

For example, the closer it is to the contact patch 33, the greater the deformation due to the annular groove 9 during traveling, and if the deformation is large, the wandering becomes large when overcoming a rut, and the steering stability performance may deteriorate. Therefore, when improving steering stability performance rather than suppressing stone biting, it is preferable that the groove width W1 of the first annular groove 9a is smaller than the groove width W2 of the second annular groove 9b.

The groove widths W1 and W2 of the first annular groove 9a and the second annular groove 9b are preferably 2 mm or more and 5 mm or less. If the groove widths W1 and W2 of the annular groove 9 are less than 2 mm, the effect of reducing the contact pressure at the shoulder end is difficult to be exhibited. Further, if the groove widths W1 and W2 of the annular groove 9 are larger than 5 mm, the rigidity of the shoulder portion becomes small, the deformation of the tire becomes large, and the steering stability performance is reduced. When the groove widths W1 and W2 of the annular groove 9 are 2 mm or more and 5 mm or less, it is possible to appropriately obtain the effect of reducing the contact pressure at the shoulder end while ensuring the steering stability performance.

When the annular groove 9 is arranged in or near the tire maximum width portion Wh, the tire is greatly deformed, so that the annular groove 9 is likely to be cracked. Therefore, as shown in FIG. 1, the first annular groove 9a and the second annular groove 9b have a tire diameter larger than the intermediate diameter φ3 between the tire outer diameter φ1 and the tire maximum width portion Wh diameter φ2 in the tire meridian cross section. It is preferably arranged on the outer RD1 in the direction. This is because cracks can be suppressed. The above diameter is determined in a no-load state in which a tire is attached to an applicable rim and a predetermined internal pressure is applied. The applicable rim is a rim defined for each tire in a standard system including a standard on which the tire is based, and refers to a rim specified by, for example, JATTA, TRA, ETRTO, or the like. The predetermined internal pressure is the air pressure defined for each tire by each standard in the above standard system.

In order to maintain the effect of the annular groove 9 from the initial stage of tire wear to the final stage of wear, at least two annular grooves 9 are inside the tire radial direction from the top surface of the TWI (Tread Wear Indicator) formed in the main groove 31. It is preferably in RD2.

As described above, in the pneumatic tire of the present embodiment, of the tread portion 3 forming the ground contact surface 33 and the tire side wall surface 7 located on the outer WD1 of the tread portion 3 in the tire width direction, the end portion of the tread portion 3 A buttless portion 70 which is a region from the tire maximum width portion Wh to the tire maximum width portion Wh, and at least two annular grooves 9 formed in the buttless portion 70 and extending in the tire circumferential direction CD to form an annular shape and extending toward the inner WD2 in the tire width direction. , Equipped with. At least two annular grooves 9 have a first annular groove 9a closest to the ground plane 33 and a second annular groove 9b that is farther from the ground surface 33 than the first annular groove 9a. The groove depth D1 of the first annular groove 9a is smaller than the groove depth D2 of the second annular groove 9b.

The first annular groove 9a closest to the ground contact surface 33 is farther from the belt plies 6b and 6c than the second annular groove 9b, so that rigidity is difficult to be secured, and deformation during traveling tends to be large. As described above, since the groove depth D1 of the first annular groove 9a is smaller than the groove depth D2 of the second annular groove 9b, the deformation of the first annular groove 9a can be suppressed, and the wandering that may occur when overcoming a rut can be achieved. It is possible to suppress and improve steering stability performance. Further, when overcoming a rut or cornering, a large lateral force is generated, but since at least two annular grooves 9 are formed, the stress applied to the groove bottom 91 can be dispersed and the occurrence of cracks can be suppressed. Become.

In the pneumatic tire of the present embodiment, of the tread portion 3 forming the ground contact surface 33 and the tire side wall surface 7 located on the outer WD1 of the tread portion 3 in the tire width direction, the maximum width portion of the tire from the end portion of the tread portion 3 It includes a buttless portion 70 which is a region up to Wh, and at least two annular grooves 9 formed in the buttless portion 70 and extending in the tire circumferential direction CD to form an annular shape and extending toward the inner WD2 in the tire width direction. The two annular grooves 9 have a first annular groove 9a closest to the ground contact surface 33 and a second annular groove 9b that is farther from the ground contact surface 33 than the first annular groove 9a, and the first annular groove 9a. Is linearly extended in the tire meridional cross section, the first annular groove 9a faces the first direction S1 or the second direction S2, and the first direction S1 is the tire equatorial CL and the ground contact surface 33 in the tire meridional cross section. The groove central axis L2 is parallel to the virtual straight line L1 connecting the intersection P1 of the tire and the ridge line LE of the ground contact surface 33 and the tire side wall surface 7, and the second direction S2 is the second direction in the tire meridional cross section. It is preferable that the groove bottom 91 is in the direction of the outer RD1 in the tire radial direction as compared with the case of the one direction S1.

If the first annular groove 9a is in the sixth direction S6 in which the groove bottom 91 is the inner RD2 in the tire radial direction as compared with the case where the first annular groove 9a faces the first direction S1, the first annular groove 9a is closer to the belt plies 6b and 6c. Therefore, there is a possibility that cracks may occur at the time of stone biting and stone drilling that damages the belt plies 6b and 6c may occur. When the first annular groove 9a faces the first direction S1 or the second direction S2, stone drilling can be suppressed.

As in the present embodiment, it is preferable that the first annular groove 9a faces the first direction S1.

If the first annular groove 9a faces the second direction S2 and the groove bottom 91 is too close to the ground contact surface 33, the buttress portion 70 located on the tire radial outer side RD1 of the annular groove 9 may be torn off. .. If the first annular groove 9a faces the first direction S1, both thea and stone drilling can be suppressed.

As in the present embodiment, the second annular groove 9b extends linearly in the tire meridional cross section, and the second annular groove 9b is either the third direction S3, the fourth direction S4, or the fifth direction S5. The third direction S3 is a groove wall surface with respect to a virtual straight line L1 connecting the intersection P1 of the tire equatorial line CL and the ground contact surface 33 and the ridge line LE of the ground contact surface 33 and the tire side wall surface 7 in the tire meridional cross section. 90 is a parallel direction, the fourth direction S4 is a direction in which the groove wall surface 90 of the second annular groove 9b is perpendicular to the tire side wall surface 7 in the tire meridional cross section, and the fifth direction S5 is a direction. The direction is preferably between the third direction S3 and the fourth direction S4.

When the second annular groove 9b faces the fourth direction S4, the corner portion between the groove wall surface 90 of the second annular groove 9b and the tire side wall surface 7 becomes vertical and is less likely to be chipped. When the second annular groove 9b faces the second direction S2 in which the groove bottom is the outer RD1 in the tire radial direction than the third direction S3, the groove wall surface 90 of the second annular groove 9b and the tire side wall surface 7 are provided. The corners become too sharp and defects are likely to occur. Therefore, if the second annular groove 9b faces any of the third direction S3, the fourth direction S4, or the fifth direction S5, the angle between the groove wall surface 90 of the second annular groove 9b and the tire side wall surface 7 It is possible to prevent or suppress the loss of the part.

As in the present embodiment, the second annular groove 9b preferably faces the fourth direction S4.

With this configuration, it is possible to prevent the corner portion between the groove wall surface 90 of the second annular groove 9b and the tire side wall surface 7 from being damaged.

In the pneumatic tire of the present embodiment, of the tread portion 3 forming the ground contact surface 33 and the tire side wall surface 7 located on the outer WD1 of the tread portion 3 in the tire width direction, the maximum width portion of the tire from the end portion of the tread portion 3 It is provided with a buttless portion 70 which is a region up to Wh, and at least two annular grooves 9 formed in the buttless portion 70 and extending in the tire circumferential direction CD to form an annular shape and extending toward the inner WD2 in the tire width direction. The two annular grooves 9 have a first annular groove 9a closest to the ground contact surface 33 and a second annular groove 9b that is farther from the ground contact surface 33 than the first annular groove 9a, and the first annular groove 9a. The groove bottom 91 of the second annular groove 9b is formed in an arc shape in the tire meridional cross section, and the radius of curvature R1 of the groove bottom 91 of the first annular groove 9a is the radius of curvature R2 of the groove bottom 91 of the second annular groove 9b. Is preferably larger than.

If the groove bottom 91 of the annular groove 9 has an angular shape, cracks will occur starting from the corners. Further, the closer to the ground plane 33, the greater the deformation of the annular groove 9.
Therefore, if the groove bottom 91 of the first annular groove 9a and the second annular groove 9b is formed in an arc shape in the cross section of the tire meridian as in the present embodiment, the corners are eliminated to suppress the occurrence of cracks. Can be done. Nevertheless, since the radius of curvature R1 of the groove bottom 91 of the first annular groove 9a closest to the ground plane 33 is larger than the radius of curvature R2 of the groove bottom 91 of the second annular groove 9b, the groove bottom 91 of the first annular groove 9a It is possible to disperse the acting strain and suppress the occurrence of cracks.

As in the present embodiment, the groove width W1 of the first annular groove 9a is preferably larger than the groove width W2 of the second annular groove 9b.

The narrower the groove widths W1 and W2 of the annular groove 9, the more likely it is that stone biting will occur. If the groove widths of the annular grooves 9 are the same, stone biting is more likely to occur as the groove width is closer to the ground contact surface 33. As in the present embodiment, the stone biting of the first annular groove 9a can be reduced by making the groove width W1 of the first annular groove 9a, which is likely to cause stone biting, larger than the groove width W2 of the second annular groove 9b. It becomes.

The groove width W1 of the first annular groove 9a is preferably smaller than the groove width W2 of the second annular groove 9b.

For example, the closer the annular groove 9 is to the ground contact surface 33, the greater the deformation caused by the annular groove 9 during traveling, and if the deformation is large, the wandering becomes large when overcoming a rut, and the steering stability performance may deteriorate. Therefore, if the groove width W1 of the first annular groove 9a is smaller than the groove width W2 of the second annular groove 9b, it is possible to improve the steering stability performance.

As in the present embodiment, the groove widths W1 and W2 of the first annular groove 9a and the second annular groove 9b are preferably 2 mm or more and 5 mm or less, respectively.

If the groove widths W1 and W2 of the annular groove 9 are less than 2 mm, the effect of reducing the contact pressure at the shoulder end is difficult to be exhibited. Further, if the groove widths W1 and W2 of the annular groove 9 are larger than 5 mm, the rigidity of the shoulder portion becomes small, the deformation of the tire becomes large, and the steering stability performance is reduced. When the groove widths W1 and W2 of the annular groove 9 are 2 mm or more and 5 mm or less as in the present embodiment, it is possible to appropriately obtain the effect of reducing the contact pressure at the shoulder end while ensuring the steering stability performance. It becomes.

As in the present embodiment, the first annular groove 9a and the second annular groove 9b are RD1 outside the tire radial direction with respect to the intermediate diameter φ3 between the tire outer diameter φ1 and the diameter φ2 of the tire maximum width portion Wh in the tire meridian cross section. It is preferably arranged in.

When the annular groove 9 is arranged in or near the tire maximum width portion Wh, the tire is greatly deformed, so that the annular groove 9 is likely to be cracked. By arranging the annular groove 9 at the above position as in the present embodiment, cracks in the annular groove 9 can be suppressed.

Although the embodiments of the present disclosure have been described above with reference to the drawings, it should be considered that the specific configuration is not limited to these embodiments. The scope of the present disclosure is shown not only by the description of the above-described embodiment but also by the scope of claims, and further includes all modifications within the meaning and scope equivalent to the scope of claims.

It is possible to adopt the structure adopted in each of the above embodiments in any other embodiment. The specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present disclosure.

3 Tread part 33 Ground surface 7 Tire side wall surface 70 Butless part 9 Circular groove 9a 1st annular groove 9b 2nd annular groove 90 Groove wall surface 91 Groove bottom WD1 Tire width direction outside WD2 Tire width direction inside Wh Tire maximum width part CD Tire circumference Direction D1 Groove depth of 1st annular groove D2 Groove depth of 2nd annular groove S1 1st direction S2 2nd direction S3 3rd direction S4 4th direction S5 5th direction L1 Virtual straight line L2 Groove center axis φ1 Tire outer diameter φ2 tire maximum width part diameter φ3 intermediate diameter

Claims (10)

The tread that forms the ground plane and
Of the tire side wall surface located on the outer side of the tread portion in the tire width direction, a buttress portion which is a region from the end portion of the tread portion to the maximum tire width portion and a buttless portion.
It is provided with at least two annular grooves formed in the buttress portion and extending in the tire circumferential direction to form an annular shape and extending inward in the tire width direction.
The at least two annular grooves have a first annular groove closest to the ground plane and a second annular groove that is farther from the ground plane than the first annular groove.
The groove bottoms of the first annular groove and the second annular groove are formed in an arc shape in the tire meridian cross section.
A pneumatic tire in which the radius of curvature of the groove bottom of the first annular groove is larger than the radius of curvature of the groove bottom of the second annular groove. The tire according to claim 1, wherein the groove width of the first annular groove is larger than the groove width of the second annular groove. The tire according to claim 1, wherein the groove width of the first annular groove is smaller than the groove width of the second annular groove. The tire according to any one of claims 1 to 3, wherein the groove widths of the first annular groove and the second annular groove are 2 mm or more and 5 mm or less, respectively. The tire according to any one of claims 1 to 4, wherein the groove depth of the first annular groove is smaller than the groove depth of the second annular groove. The first annular groove extends linearly in the tire meridian cross section.
The first annular groove faces the first direction or the second direction,
The first direction is a direction in which the groove center axis is parallel to the virtual straight line connecting the intersection of the tire equatorial line and the contact patch and the ridge line between the contact patch and the tire side wall surface in the tire meridional cross section. ,
The tire according to any one of claims 1 to 5, wherein the second direction is a direction in which the groove bottom is outside in the tire radial direction as compared with the case of the first direction in the tire meridian cross section. The tire according to claim 6, wherein the first annular groove faces the first direction. The second annular groove extends linearly in the tire meridian cross section.
The second annular groove faces any of the third, fourth, and fifth directions.
The third direction is a direction in which the groove wall surface is parallel to the virtual straight line connecting the intersection of the tire equatorial line and the ground contact surface and the ridge line between the ground contact surface and the tire side wall surface in the tire meridional cross section.
The fourth direction is a direction in which the groove wall surface of the second annular groove is perpendicular to the tire side wall surface in the tire meridian cross section.
The tire according to any one of claims 1 to 7, wherein the fifth direction is a direction between the third direction and the fourth direction. The tire according to claim 8, wherein the second annular groove faces the fourth direction. The first annular groove and the second annular groove are arranged outside the tire radial direction from the intermediate diameter between the tire outer diameter and the diameter of the tire maximum width portion in the tire meridian cross section, claims 1 to 9. Tires listed in any of.

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