JP5980548B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  In a tread pattern having a plurality of main grooves extending in the circumferential direction in the tire tread portion, in order to improve hydroplaning performance, the drainage performance is improved by increasing the groove width and depth of the main groove. It is effective. On the other hand, in order to improve the steering stability performance on a dry road surface, it is effective to widen the rib width and shallow the groove depth in order to increase the rigidity of the ribs and blocks. In this way, hydroplaning performance and steering stability performance on dry road surfaces are in a trade-off relationship. To improve hydroplaning performance, if the groove width is set wide and the groove depth is set deep, the rigidity of the ribs and blocks is increased. As a result, the steering stability performance is impaired.

  Conventionally, in a tread pattern of a pneumatic tire, various proposals have been made in order to improve various tire performances. For example, in the following Patent Document 1, by forming the cross-sectional groove wall shape of the groove that divides the block into a concave curved surface, even after the block surface wears, a sharp edge is left on the ground contact surface on a wet road surface. Maintaining braking / driving performance is disclosed. Japanese Patent Application Laid-Open No. H11-228688 discloses that a concave portion is formed on the groove wall surface of the main groove, thereby suppressing the groove wall surface from bulging during loading and suppressing uneven wear of the land portion edge. Patent Document 3 below discloses that the stone wall surface of the main groove is provided with a plurality of concave wall surfaces adjacent to each other in the groove depth direction, thereby improving the stone biting prevention performance without impairing the wet grip performance. Yes.

  On the other hand, Patent Document 4 below discloses that a sipes extending along the main groove is added in the vicinity of the main groove forming the block, thereby reducing the vibration of the groove bottom and reducing the noise level. Yes. Further, in Patent Document 5 below, in the block of the shoulder region of the tread portion, by providing a sipe extending along the tire circumferential direction in the vicinity of the main groove, it is possible to suppress the shoulder drop wear and step down wear of the block. It is disclosed.

  However, conventionally, it is known to improve hydroplaning performance by providing a shallow circumferential sipe in the vicinity of the main groove in the shoulder land portion while providing a recess in the wall surface of the main groove forming the shoulder land portion. There wasn't.

JP 2005-035370 A JP 2010-1116064 A JP 2011-093392 A Japanese Patent Laid-Open No. 7-040713 JP 2011-116319 A

  In general, in a pneumatic tire, the main groove in the vicinity of the shoulder portion has a large movement before and after the load is applied, and when the load is applied, the main groove in the vicinity of the shoulder portion tends to be crushed and the groove volume tends to decrease. This is considered to be one of the factors that deteriorate the hydroplaning performance. Of these, the region where the groove volume decreases is the center in the depth direction of the groove wall surface on the outer side in the tire width direction of the main groove. That is, as shown in FIG. 8, in the main groove 102 that defines the shoulder land portion 100, the groove wall surface 104 on the outer side in the tire width direction has a central portion in the depth direction inside the main groove 102 when a load is applied. The volume of the main groove 102 is thereby reduced. Therefore, securing the groove volume at this portion is effective for improving the hydroplaning performance.

  This invention is made | formed in view of the above point, and it aims at providing the pneumatic tire excellent in hydroplaning performance.

The pneumatic tire according to the present invention is a pneumatic tire including a tread portion including a main groove extending in the tire circumferential direction and a shoulder land portion defined by the main groove. The shoulder land portion includes the shoulder land portion. On the groove wall surface on the outer side in the tire width direction of the main groove forming the land portion, there is a recess extending in the tire circumferential direction so that the center part of the groove wall surface in the depth direction of the main groove is recessed in the tire width direction outer side. The shoulder land portion extends along the main groove in the vicinity of the main groove, and has a depth equal to or shallower than the bottom position of the depression in the depth direction of the main groove. Is provided with a circumferential sipe.

As a preferred aspect of the present invention, the shoulder land portion may be a land portion continuous in the tire circumferential direction. As another aspect, in the cross-sectional shape in the tire width direction, a cross-sectional area of the circumferential sipe is V _1, and is a line that defines the groove wall surface on the outer side in the tire width direction, and a straight line connecting the upper end and the lower end of the recess a reference line, the cross-sectional area of said a rubber portion of the tread surface side of the recess, before and Kimoto directrix, the recess rubber portion bottom point surrounded by the straight line parallel to the street and the reference line Where V ₂ is V ₁ / V ₂ = 0.5 to 2.0. As yet another aspect, in the cross-sectional shape in the tire width direction, the upper end and the lower end of the recess in the depth direction of the main groove have a distance from the bottom point to the lower end of the recess, from the bottom point to the upper end. It may be set larger than the distance. As yet another aspect, the shoulder land portion is provided with lateral grooves extending in a direction intersecting the tire circumferential direction at intervals in the tire circumferential direction, so that the lateral grooves do not open to the main groove. The circumferential sipe may be provided between the terminal end of the lateral groove and the main groove. In this case, the circumferential sipe may be set such that the depth at the circumferential position where the lateral groove is provided is shallower than the depth at the circumferential position of the block portion where the lateral groove is not provided. Each of these aspects can be combined as appropriate.

  According to the present invention, the groove wall surface on the outer side in the tire width direction of the main groove forming the shoulder land portion is provided with a recess having a recessed shape in the center in the depth direction, and in the vicinity of the main groove in the shoulder land portion. By providing the circumferential sipe having a shallow depth below the bottom position of the depression, the hydroplaning performance can be improved while suppressing the deterioration of the steering stability performance on the dry road surface.

It is an expanded view which shows the tread pattern of the pneumatic tire which concerns on 1st Embodiment. It is an expanded sectional view of the shoulder land part periphery of the tread part concerning the embodiment. FIG. 3 is an enlarged cross-sectional view of a main part of a tread portion in which a part of FIG. It is a principal part expanded sectional view of the tread part at the time of load loading. It is a partially expanded development view showing a tread pattern according to the second embodiment. FIG. 3 is an enlarged cross-sectional view of a main part when a tire of Comparative Example 1 is loaded. FIG. 6 is an enlarged cross-sectional view of a main part when a tire of Comparative Example 2 is loaded. It is a principal part expanded sectional view at the time of the load load of the conventional tire.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
The pneumatic tire according to the embodiment is not illustrated, but the pair of left and right bead portions and sidewall portions and the radially outer ends of the left and right sidewall portions are connected to each other between the sidewall portions. The tread portion 10 is provided, and includes a carcass extending between the pair of bead portions. The carcass is composed of at least one carcass ply having both ends locked by an annular bead core embedded in the bead portion through the sidewall portion from the tread portion 10 and reinforces each of the above portions. A belt composed of two or more rubber-coated steel cord layers is provided on the outer peripheral side of the carcass in the tread portion 10, and the tread portion 10 is reinforced at the outer periphery of the carcass.

  As shown in FIG. 1, a plurality of main grooves 12 extending straight in the tire circumferential direction A are provided on the surface of the tread portion 10. In this example, two inner center main grooves 12A and 12A arranged on both sides of the tire equator C, and two shoulder mains arranged on the outer side in the tire width direction B of the center main groove 12A, respectively. Four main grooves 12 with grooves 12B and 12B are provided.

  As a result, the tread portion 10 has a straight rib-shaped central land portion 14 between the two center main grooves 12A and 12A, and a straight rib-shaped intermediate land portion between the center main groove 12A and the shoulder main groove 12B. 16 and 16, shoulder land portions 18 and 18 are respectively formed on the outer side in the tire width direction B of the shoulder main groove 12B.

  The shoulder land portion 18 that is partitioned from the inner region in the tire width direction B by the shoulder main groove 12B is not divided in the tire circumferential direction A, and is a land portion that continues in the tire circumferential direction A. Specifically, in this example, the shoulder land portion 18 is provided with a plurality of lateral grooves 20 extending in a direction intersecting with the tire circumferential direction A at predetermined intervals in the tire circumferential direction A. The lateral groove 20 is a groove extending from the inner side of the tire width direction B to the outer side of the tire width direction B from the inner side of the tread grounding end E to the outer side of the tire width direction B. Is terminated in the shoulder land portion 18 so as not to open. As a result, the shoulder land portion 18 is formed in the rib portion 22 that is continuous in the tire circumferential direction A with the inner end portion in the tire width direction B being relatively narrow, and the outer region thereof is in the tire circumferential direction A. The block portion 24 is formed in the partitioned block portion 24, and the block portion 24 is connected via the rib portion 22.

  As shown in FIG. 2, the shoulder land portion 18 has a tire circumferential direction on the groove wall surface 25 outside the tire width direction B of the shoulder main groove 12 </ b> B (that is, the side surface inside the tire width direction B of the shoulder land portion 18). A recess 26 extending to A is formed. The recess 26 is a recess having a shape in which the central portion in the depth direction of the groove wall surface 25 is recessed outward in the tire width direction B. In this example, the concave curve is recessed toward the tread grounding end E side in the central portion in the depth direction. It is formed in a planar shape. The recess 26 is formed over the entire circumference in the tire circumferential direction A. Therefore, the shoulder main groove 12B is formed in a cross-sectional shape in the tire width direction B shown in FIG. 2 over the entire circumference of the tire.

  As shown in FIG. 3, the bottom point 28 of the recess 26 (a position where the recess amount with respect to the groove wall surface 25 is maximized) 28 is set at a substantially center in the depth direction of the groove wall surface 25 of the shoulder main groove 12B. . A position corresponding to the bottom point 28 of the recess 26 in the depth direction of the shoulder main groove 12B is indicated by a line F in FIG. That is, the line F is a line passing through the bottom point 28 of the recess 26 and parallel to the tread surface (profile line) 30 in the tire width direction B cross-sectional shape shown in FIG. 3, and the depth direction of the shoulder main groove 12B. The bottom point position of the depression 26 in FIG.

  In the recess 26, the upper end 26A and the lower end 26B are set as follows in the cross-sectional shape in the tire width direction B. That is, the upper end 26A and the lower end 26B of the recess 26 in the depth direction of the groove wall surface 25 are set such that the distance from the bottom point 28 to the lower end 26B of the recess 26 is larger than the distance from the bottom point 28 to the upper end 26A. Yes.

  Accordingly, the length of the slope 34 extending from the bottom point 28 to the lower side, that is, the bottom side of the shoulder main groove 12B, is longer than the length of the slope 32 extending from the bottom point 28 to the upper side, that is, the tread surface 30 side. It is getting bigger. That is, in the recess 26, the slope 32 extending upward from the bottom point 28 intersects the groove wall surface 25 at a position closer to the bottom point position F in the depth direction of the shoulder main groove 12B than the slope 34 extending downward. Accordingly, the slope 34 on the lower side of the recess 26 is set to have an inclination closer to the reference line J that defines the groove wall surface 25 than the slope 32 on the upper side.

Also, with this setting, when the cross-sectional area of the recess 26 (the area surrounded by the reference line J and the upper and lower slopes 32, 34) is divided by the line F corresponding to the bottom point position, the upper side, that is, the tread surface 30 sectional area _{V 3} side is set smaller than the lower, i.e. the shoulder main groove 12B the cross-sectional area _{V 4} on the bottom side of the _(V 3 _<V 4). Here, the reference line J is a straight line connecting the upper and lower ends 26 </ b> A and 26 </ b> B of the recess 26.

Incidentally, (maximum depression amount with respect to the reference line J of the groove wall surface 25) _{H 1} depth of the recess 26 is not particularly limited, is preferably about 0.5 to 2.0 mm.

  As shown in FIG. 3, a chamfered portion 36 is provided on the groove wall surface 25 on the outer side in the tire width direction B of the shoulder main groove 12 </ b> B at the open end, that is, the upper end corner that intersects the tread surface 30. In this example, the chamfered portion 36 is formed in a curved surface convex upward, but may be formed in a planar shape. The groove wall surface 38 on the inner side in the tire width direction B of the shoulder main groove 12B is not provided with the above-mentioned depression, and is formed in a flat shape except for the chamfered upper and lower ends.

As shown in FIG. 2, the shoulder land portion 18 is provided with a circumferential sipe 40 extending in the tire circumferential direction A along the main groove 12B in the vicinity of the shoulder main groove 12B. The circumferential sipe 40 is a narrow groove or notch that is narrow enough to allow the opposing wall surfaces to contact each other when a load is applied, and is not particularly limited, but the groove width d ₁ (see FIG. 3) is 0. It is preferable that it is 5-1.5 mm, More preferably, it is 0.5-1.0 mm.

The circumferential sipe 40 is for securing the groove volume on the upper side of the shoulder main groove 12B by the rubber part on the tread surface 30 side of the recess 26 falling to the outer side in the tire width direction B when a load is applied. Therefore, it is provided in the vicinity of the shoulder main groove 12 </ b> B in the shoulder land portion 18. Distance of _{H 2} from the groove wall surface 25 until the circumferential sipe 40 (see FIG. 3) is not particularly limited, is preferably 3 to 10 mm, more preferably from 5 to 10 mm. When the distance H ₂ becomes too large, ensuring groove volume by collapse of the difficult.

  In this example, as shown in FIGS. 1 and 2, the circumferential sipe 40 is provided in the narrow rib portion 22 between the terminal end 20A of the lateral groove 20 provided in the shoulder land portion 18 and the shoulder main groove 12B. The rib portion 22 is formed over the entire circumference in the tire circumferential direction A at the outer end portion in the tire width direction B. The circumferential sipe 40 may be provided so as to be connected to the end 20A of the lateral groove 20, or the circumferential sipe 40 may be formed to be divided in the tire circumferential direction A by the lateral groove 20.

As shown in FIG. 3, the circumferential sipe 40 is formed so as to have a depth that is the same as or shallower than the bottom point position F of the recess 26 in the depth direction of the shoulder main groove 12B. . Thus, by providing the relatively shallow circumferential sipe 40 having a depth equal to or less than the bottom point 28 of the depression 26, the tire in the rubber portion above the depression 26 while maintaining a certain degree of rigidity. It is possible to fall to the outside in the width direction B, and to secure a groove volume on the upper side of the shoulder main groove 12B. The depth h ₁ of the circumferential sipe 40 is not particularly limited, but is preferably 1.5 mm or more, and more preferably 2.0 mm or more. Further, it is preferable that the depth is shallower than the bottom position F of the depression 26.

Further, in the cross-sectional shape in the tire width direction B shown in FIG. 3, the cross-sectional area of the circumferential sipe 40 is V _1, and is a rubber portion closer to the tread surface 30 than the recess 26, and the reference line J defining the groove wall surface 25 V ₁ / V ₂ = 0.5 to 2.0, where V ₂ is the cross-sectional area of the rubber portion 42 that passes through the bottom point 28 of the depression 26 and is surrounded by the straight line K parallel to the reference line J. It is set to satisfy the relationship. Thereby, the rubber part 42 above the depression 26 can be allowed to fall down more efficiently than the outer side in the tire width direction B. V ₁ / _{V 2} is more preferably 1.0 to 2.0.

  In the pneumatic tire according to the present embodiment as described above, the recess 26 is provided in the groove wall surface 25 of the shoulder main groove 12B, and the shallow circumferential sipe 40 is provided in the vicinity of the shoulder main groove 12B in the shoulder land portion 18. By these combinations, the hydroplaning performance can be improved while suppressing the deterioration of the steering stability performance on the dry road surface. The reason why this effect is achieved will be described in detail.

  As shown in FIG. 4, in the configuration of the present embodiment, the depression 26 is provided in the groove wall surface 25 of the shoulder main groove 12B, thereby suppressing expansion of the central portion in the depth direction of the groove wall surface 25 when a load is applied. It is done. Further, since the circumferential sipe 40 is provided in proximity to the outer side of the recess 26 in the tire width direction B, the rubber portion 42 above the recess 26 can fall down toward the outer side of the tire width direction B. Expansion of the rubber portion 42 toward the inside in the tire width direction B can be suppressed. Therefore, the shape after load application indicated by the solid line L in FIG. 4 is close to the shape before load application indicated by the dotted line L ′, and the volume of the shoulder main groove 12B can be maintained. That is, the upper side of the shoulder main groove 12B is a circumferential sipe 40, and the central portion is a depression 26, so that the expansion of rubber toward the inner side in the tire width direction B can be suppressed. Can be maintained. Further, since the depression 26 is provided, the rigidity of the groove wall surface 25 is reduced, and the upper rubber portion 42 can be easily collapsed to the outside in the tire width direction B. It is easy to secure. From these facts, the hydroplaning performance can be improved while maintaining the groove area ratio on the tread surface.

  On the other hand, since the circumferential sipe 40 is set to have a shallow depth, the rigidity can be maintained, and the circumferential sipe 40 is completely closed when the rubber portion 42 falls down when a load is applied. From this point, the rigidity of this portion can be maintained. In addition, when the load is applied, the rubber portion 42 falls to the outer side in the tire width direction B, so that the groove wall surface 25 on the outer side in the tire width direction B of the shoulder main groove 12B has a relatively flat shape as shown in FIG. Since the hollow shape is not emphasized as in Comparative Example 1 according to FIG. 6 to be described later, it is possible to suppress the decrease in the longitudinal rigidity of the groove wall surface 25. From these things, the deterioration of the steering stability performance on a dry road surface can be suppressed.

  On the other hand, in the structure of the comparative example 1 shown in FIG. 6, although the hollow 26 is provided in the groove wall surface 25 of the shoulder main groove 12B, the circumferential sipe 40 is not provided. In this case, when the load is applied from the state before the load application indicated by the dotted line M ′, the shape indicated by the solid line M is obtained. By providing the recess 26, expansion in the central portion in the depth direction of the groove wall surface 25 is suppressed. However, since there is no circumferential sipe 40, the rubber portion 42 above the recess 26 is outside the tire width direction B. I can't fall down. Therefore, since the groove volume of the shoulder main groove 12B is reduced, the effect of improving the hydroplaning performance as in the present embodiment cannot be obtained. Further, the rubber portion 42 on the upper side of the recess 26 expands inward in the tire width direction B, so that the recess shape in the groove wall surface 25 is emphasized, so that the longitudinal rigidity of the groove wall surface 25 is reduced, and therefore, the steering on the dry road surface is performed. Stability performance will deteriorate.

  In the configuration of Comparative Example 2 shown in FIG. 7, the circumferential sipe 40 is provided, but the recess 26 is not provided in the groove wall surface 25 of the shoulder main groove 12B. In this case, when the load is applied from the state before the load application indicated by the dotted line N ′, the shape indicated by the solid line N is obtained. Since the recess 26 is not provided, expansion at the center in the depth direction of the groove wall surface 25 is large, and the groove volume is reduced. By providing the circumferential sipe 40, the groove wall surface 25 may fall to the outside in the tire width direction B to some extent, but the rigidity of the groove wall surface 25 is high, so the fall is small. Therefore, the improvement effect of hydroplaning performance cannot be obtained.

  As described above, even if only one of the recess 26 in the groove wall surface 25 and the shallow circumferential sipe 40 in the vicinity of the shoulder main groove 12B are incorporated, as a result, the groove volume of the shoulder main groove 12B is secured. However, by combining the two, the groove volume of the shoulder main groove 12B can be ensured while maintaining rigidity to some extent, and the steering stability performance on the dry road surface and the hydroplaning performance can both be achieved.

Further, according to the present embodiment, since the distance from the bottom point 28 to the lower end 26B is set longer than the distance from the bottom point 28 to the upper end 26A of the recess 26 (V ₃ <V ₄ ), it is above the recess 26. The volume of the rubber part 42 can be increased to increase the amount of collapse to the outside in the tire width direction B when a load is applied. Further, since the slope 34 below the depression 26 has an inclination close to the original groove wall surface 25, the longitudinal rigidity of the groove wall surface 25 can be maintained, which is advantageous for the steering stability performance on the dry road surface. is there.

(Second Embodiment)
The pneumatic tire according to the second embodiment shown in FIG. 5 differs from the first embodiment in that the depth of the circumferential sipe 40 is not constant in the tire circumferential direction A but is changed. .

  Specifically, the circumferential sipe 40 is formed at the circumferential position of the first sipe portion 40A having the first depth at the circumferential position where the lateral groove 20 is provided and the block portion 24 where the lateral groove 20 is not provided. And a second sipe portion 40B having a second depth, and the first depth is set to be shallower than the second depth. A gradual change section 40C in which the depth gradually changes is provided between the first sipe portion 40A and the second sipe portion 40B.

  In the shoulder land portion 18 provided with the lateral groove 20 as described above, the rubber volume is small at the circumferential position where the lateral groove 20 is provided. The rubber volume is large and the load fluctuation is large at the circumferential position of the block portion 24 that is not present. Therefore, the second sipe portion 40B corresponding to the block portion 24 has a deep sipe depth and exhibits the above-described effect of improving the hydroplaning performance, while the first sipe corresponding to the circumferential position where the lateral groove 20 is provided. By setting the sipe depth shallow in the portion 40A, the rigidity of the tread pattern can be secured without impairing the hydroplaning performance, and the steering stability performance on the dry road surface can be improved.

  Thereby, the hydroplaning performance and the steering stability performance on the dry road surface can be further balanced. About 2nd Embodiment, the other structure and effect are the same as that of 1st Embodiment, and description is abbreviate | omitted.

(Other embodiments)
In the above embodiment, the shoulder land portions 18 on both sides in the tire width direction B of the tread portion 10 are provided in combination with the configuration of the recess 26 and the circumferential sipe 40. However, at least one of the shoulder land portions 18 has these configurations. Provided embodiments are also included.

  Moreover, in the said embodiment, although the chamfer 36 was provided in the opening edge part of the shoulder main groove 12B, the same effect is show | played also in what does not provide the chamfer 36.

  Moreover, in the said embodiment, although the horizontal groove 20 was provided in the shoulder land part 18, the horizontal groove 20 in the shoulder land part 18 is not essential. Although not enumerated one by one, various modifications can be made without departing from the spirit of the present invention.

  Pneumatic radial tires (205 / 55R16) for passenger cars of Examples 1 to 3, Comparative Examples 1 to 3, and a conventional example were made as trial products. Each of these prototype tires is manufactured by changing the specifications shown in Table 1 with the same basic tread pattern and tire internal structure. Examples 1 and 2 correspond to the first embodiment, and thus are examples in which the configurations of the recess 26 and the circumferential sipe 40 are combined. Example 3 corresponds to the second embodiment, and is an example in which the depth of the circumferential sipe 40 is changed in the tire circumferential direction A. Comparative Example 1 has the structure shown in FIG. 6, and thus is an example in which the recess 26 is provided but the circumferential sipe 40 is not provided. Comparative Example 2 has the structure shown in FIG. 7, and thus is an example in which the circumferential sipe 40 is provided but the recess 26 is not provided. Comparative Example 3 is an example in which the depth of the circumferential sipe 40 is formed deeper than the bottom point position of the recess 26 with respect to Example 1. The conventional example is an example in which neither the recess 26 nor the circumferential sipe 40 is provided in the first embodiment. In Examples 1 to 3 and Comparative Examples 1 and 3, the bottom point position F of the recess 26 was 4 mm from the tread surface. The depth of the shoulder main groove 12B was 8 mm.

  Each pneumatic radial tire was mounted on a rim (size: 16 × 6.5), the air pressure was 210 kPa, four wheels were mounted on a 2000 cc FF vehicle, and hydroplaning performance and steering stability performance on a dry road surface were evaluated. The evaluation method is as follows.

Hydroplaning performance: The speed at which hydroplaning occurs in straight running on a wet road surface with a water depth of 8 mm was examined, and the index was evaluated with an index based on the conventional example of 100. The larger the index, the higher the speed at which hydroplaning occurs. Therefore, the hydroplaning phenomenon hardly occurs and the hydroplaning performance is excellent.

-Steering stability performance on dry road surface: Steering stability performance when driving on a dry road surface was evaluated in seven stages, with the conventional example set to 4 by sensory evaluation of a test driver. The larger the value, the better the steering stability performance.

  The results are as shown in Table 1, and in Comparative Example 1 in which only the depressions 26 are provided with respect to the conventional example, the effect of improving the hydroplaning performance is small, and the steering stability performance on the dry road surface is impaired. . Moreover, in the comparative example 2 which provided only the circumferential sipe 40 with respect to the conventional example, the improvement effect of hydroplaning performance was not acquired.

  On the other hand, in Examples 1 to 3 in which both the recess 26 and the circumferential sipe 40 are provided, the hydroplaning performance is improved without impairing the steering stability performance on the dry road surface. In Comparative Example 3, since the depth of the circumferential sipe 40 is set deeper than the bottom position of the recess 26 with respect to Example 1, the rigidity of the land portion between the circumferential sipe 40 and the shoulder main groove 12B is lowered. The hydroplaning performance was rather deteriorated because the land portion collapsed toward the shoulder main groove 12B, and the steering stability on the dry road surface was also impaired.

DESCRIPTION OF SYMBOLS 10 ... Tread part 12B ... Shoulder main groove 18 ... Shoulder land part 20 ... Lateral groove 20A ... End of transverse groove 24 ... Block part 25 ... Groove wall surface on the outer side in the tire width direction 26 ... Indentation 26A ... Indentation upper end 26B ... Indentation lower end 28 ... Dimple bottom point 30 ... Tread surface 32, 34 ... Dimple slope 40 ... Circumferential sipe A ... Tire circumferential direction B ... Tire width direction F ... Dimple bottom point position J ... Base line defining groove wall surface K ... Bottom point Straight line parallel to the reference line

Claims (6)

In a pneumatic tire provided with a main groove extending in the tire circumferential direction in the tread portion and a shoulder land portion defined by the main groove,
The shoulder land portion has a shape in which the central portion of the groove wall surface in the depth direction of the main groove is recessed outward in the tire width direction on the groove wall surface on the outer side in the tire width direction of the main groove forming the shoulder land portion. A depression extending in the tire circumferential direction is provided, and the shoulder land portion extends along the main groove in the vicinity of the main groove, and the bottom position of the depression in the depth direction of the main groove A pneumatic tire characterized in that a circumferential sipe having the same or shallower depth is provided.   The pneumatic tire according to claim 1, wherein the shoulder land portion is a land portion continuous in a tire circumferential direction. In the cross-sectional shape in the tire width direction, the cross-sectional area of the circumferential sipe is V ₁ , a line that defines the groove wall surface on the outer side in the tire width direction, and a straight line connecting the upper end and the lower end of the recess is used as a reference line. even rubber portion of the tread surface side, front Kimoto and the directrix, the cross-sectional area of the rubber portion of the valley surrounded by the straight line parallel to the street and the reference line of the recess as V _2, V ₁ The pneumatic tire according to claim 1, wherein a relationship of / V ₂ = 0.5 to 2.0 is satisfied. In the cross-sectional shape in the tire width direction, the upper end and the lower end of the recess in the depth direction of the main groove are set such that the distance from the bottom point to the lower end of the recess is larger than the distance from the bottom point to the upper end. The pneumatic tire according to any one of claims 1 to 3, wherein:   The shoulder land portion is provided with a transverse groove extending in a direction intersecting the tire circumferential direction at an interval in the tire circumferential direction, and the transverse groove is terminated in the shoulder land portion so as not to open to the main groove. The pneumatic tire according to claim 1, wherein the circumferential sipe is provided between a terminal end of the lateral groove and the main groove.   The circumferential sipe is characterized in that a depth at a circumferential position where the lateral groove is provided is set to be shallower than a depth at a circumferential position of a block portion where the lateral groove is not provided. 5. The pneumatic tire according to 5.

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