Pneumatic tire

Abstract

To provide a pneumatic tire capable of improving braking performance on a snow road.SOLUTION: This pneumatic tire comprises: a plurality of longitudinal grooves 10 extending in a tire circumferential direction on a tread surface; and a plurality of lands 20 divided by the longitudinal grooves 10. The lands 20 include a center land 25 relatively positioned inside in a tire axial direction and a mediation land 24 relatively positioned outside in the tire axial direction. In the center land 25 and the mediation land 24, a wavy siping 5 extending in a direction intersecting the tire circumferential direction and a shallow groove 6 shallower than the wavy siping 5 are respectively formed. An intersection place number Na between the top 5t of the wavy siping 5 and the shallow groove 6 in the center land 25 and an intersection place number Nb between the top 5t of the wavy siping 5 and the shallow groove 6 in the mediation land 24 satisfy a relationship of Na<Nb.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire having wave-shaped sipes and shallow grooves formed in land portions of a tread surface. [Background technology]

[0002] In winter tires and all-season tires, rubber with a high friction coefficient is used on the tread surface in order to improve driving performance on snowy and icy roads, but in order to fully demonstrate this effect, several hundred kilometers of break-in driving is required. Therefore, in order to ensure that performance can be demonstrated even in the initial state (especially when new) without sufficient break-in driving, it is known to form shallow grooves shallower than the sipes in the land portion of the tread surface in addition to the cut-shaped sipes. As such sipes, wave-shaped sipes, which appear on the surface of the land portion and extend in a wave-like or zigzag shape, are generally used (see, for example, Patent Documents 1 and 2).

[0003] On snowy and icy roads, the more uniform the ground pressure of the land portion during braking, the better the ground contact and the better the braking performance. The inventor's research revealed that when a wavy sipe is formed on the land portion, the ground pressure is high near the peak located at the tip side of the wave amplitude direction, which tends to concentrate distortion, and this tendency is particularly pronounced at the intersection between the peak of the wavy sipe and the shallow groove, because the peak is divided by the shallow groove, and as a result, the ground pressure of the land portion tends to become uneven. Therefore, although it is desirable to focus on this point and improve braking performance on snowy and icy roads, a specific structure suitable for this purpose has not been known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-132217 A [Patent Document 2] Patent Publication No. 2022-46330 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a pneumatic tire capable of improving braking performance on icy and snowy road surfaces.

Means for Solving the Problems

[0006] The above object can be achieved by the present invention as follows. That is, the pneumatic tire of the present invention includes a plurality of longitudinal grooves extending along the tire circumferential direction on the tread surface, and a plurality of land portions divided by the plurality of longitudinal grooves. The plurality of land portions include a first land portion located relatively inward in the tire axial direction and a second land portion located relatively outward in the tire axial direction. In the first land portion and the second land portion, a corrugated siped extending in a direction intersecting the tire circumferential direction and a shallow groove shallower than the corrugated siped are respectively formed. The number of intersection points Na between the top of the corrugated siped and the shallow groove in the first land portion and the number of intersection points Nb between the top of the corrugated siped and the shallow groove in the second land portion satisfy the relationship Na < Nb.

Brief Description of the Drawings

[0007] [Figure 1] Plan view of the tread surface of the pneumatic tire according to the present embodiment [Diagram 2] Plan view of the block [Diagram 3] Enlarged view within the broken line frame BF shown in FIG. 2 [Figure 4] Plan view of the block in the modification [Diagram 5] Plan view of the tread surface showing another example of the tread pattern

Embodiments for Carrying Out the Invention

[0008] Embodiments of the present invention will be described with reference to the drawings.

[0009] Fig. 1 is a plan view showing a tread surface of a pneumatic tire of this embodiment. A plurality of longitudinal grooves 10 extending in the tire circumferential direction and a plurality of land portions 20 partitioned thereby are provided on the tread surface Tr of the pneumatic tire T. The tire T is a studless tire for automobiles including a pair of bead portions (not shown), a pair of sidewall portions (not shown) extending radially outward from each of the pair of bead portions, and a tread portion 1 continuing to the radially outer ends of each of the pair of sidewall portions, and the tread surface Tr forms the outer peripheral surface of the tread portion 1. The tire T shown in Fig. 1 is new, and the tread surface Tr is in an unworn state.

[0010] Here, the tire circumferential direction is the direction around the central axis (axis of rotation) of the tire T, and corresponds to the left-right direction in FIG. 1. The tire radial direction is the direction along the diameter of the tire T. The side closer to the central axis of the tire T is the inner side in the tire radial direction, and the side away from the central axis of the tire T is the outer side in the tire radial direction. The tire axial direction is a direction parallel to the central axis of the tire T, and corresponds to the up-down direction in FIG. 1. The side closer to the tire equator TC is the inner side in the tire axial direction, and the side away from the tire equator TC is the outer side in the tire axial direction. The tire equator TC is an imaginary line located in the center of the tire T in the axial direction, and is perpendicular to the central axis of the tire T in a plan view of the tread.

[0011] In the example of Fig. 1, five land portions 20 are partitioned by four longitudinal grooves 10. Each of the five land portions 20 has a lateral groove 30 formed therein, which extends in a direction intersecting the tire circumferential direction. The five land portions 20 include a pair of shoulder land portions 21, 22 including a ground contact end TE, a pair of intermediate land portions 23, 24 adjacent to the shoulder land portions 21, 22 with the longitudinal groove 10 therebetween, and a center land portion 25 adjacent to the intermediate land portions 23, 24 with the longitudinal groove 10 therebetween. The four longitudinal grooves 10 include a pair of shoulder longitudinal grooves 11, 12 located between the shoulder land portions 21, 22 and the intermediate land portions 23, 24, and a pair of center longitudinal grooves 13, 14 located between the intermediate land portions 23, 24 and the center land portion 25.

[0012] The contact edge TE is the outermost position in the axial direction of the tire contact surface when the tire T is mounted on a regular rim, inflated to the regular internal pressure, placed vertically on a flat road surface, and loaded with the regular load. The regular internal pressure is the air pressure determined for each tire by each standard in the standard system including the standard on which the tire is based. For truck and bus tires and light truck tires, it is the maximum air pressure for JATMA, the value corresponding to the Load Index listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. For passenger car tires, it is usually 180kPa, but for tires labeled "Extra Load" or "Reinforced", it is 220kPa.

[0013] The regular rim is a rim that is determined for each tire by each standard in the standard system including the standard on which the tire is based, for example, the standard rim for JATMA, and the "Measuring Rim" for TRA and ETRTO. The regular load is a load that is determined for each tire by each standard in the standard system including the standard on which the tire is based, for example, the "Maximum Load Capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "LOAD CAPACITY" for ETRTO. If the tire is for a passenger car, it is a load equivalent to 88% of the above load.

[0014] The land portion 20 is formed with wavy sipes 5 and shallow grooves 6 shallower than the wavy sipes 5. The wavy sipes 5 extend in a direction intersecting with the tire circumferential direction and have the function of improving braking performance and traction performance on icy and snowy road surfaces. The wavy sipes 5 have a width W5 (see FIG. 2) of preferably 1.5 mm or less, more preferably 1.0 mm or less. The width W5 of the wavy sipes 5 is, for example, 0.3 mm or more. The wavy sipes 5 have a depth of preferably 2.0 mm or more, more preferably 5.0 mm or more. The depth of the wavy sipes 5 is, for example, 6.0 to 9.0 mm. The depth of the wavy sipes 5 is set to be equal to or less than the depth of the longitudinal grooves 10. The longitudinal grooves 10 have a width of, for example, 4.0 mm or more and a depth of 5.0 mm or more.

[0015] The wavy sipe 5 is a sipe whose sipe shape appearing on the surface of the land portion 20 extends in a wavy shape. The wavy shape here is, for example, a sine wave shape or a triangular wave shape (zigzag shape), but is not limited thereto. Both ends of the wavy sipe 5 are open to the longitudinal grooves 10, but are not limited thereto, and one or both ends may be closed within the land portion 20. The wavy sipe 5 is formed by a two-dimensional sipe whose sipe shape appearing on the surface of the land portion 20 is constant along the depth direction, but is not limited thereto, and may be formed by a three-dimensional sipe whose sipe shape appearing on the surface of the land portion 20 changes along the depth direction.

[0016] The shallow grooves 6 have a function of improving the running performance on snowy and icy road surfaces in the initial state before sufficient break-in. The shallow grooves 6 preferably have a depth of 0.1 mm or more, more preferably 0.2 mm or more, in order to exert an edge effect and a water removal effect. The shallow grooves 6 preferably have a depth of 2.0 mm or less, more preferably 1.5 mm or less, in order to suppress a decrease in the rigidity of the surface portion of the land portion 20. The shallow grooves 6 have a width W6 (see FIG. 2) of, for example, 0.5 to 1.5 mm. The shallow grooves 6 are formed in a rectangular cross-sectional shape, but are not limited thereto. In this embodiment, the shallow grooves 6 do not form a mesh shape by themselves, and therefore do not have any intersections that intersect with other shallow grooves 6 in a cross or X-shape.

[0017] The transverse groove 30 formed in the center land portion 25 opens into the longitudinal grooves 10 on both sides (i.e., the center longitudinal groove 13 and the center longitudinal groove 14) that partition the land portion 20. The center land portion 25 is divided into a plurality of blocks 4. In other words, the center land portion 25 is formed by a block row. The same applies to the other land portions 20, and the shoulder land portions 21, 22 and the intermediate land portions 23, 24 are all formed by block rows. However, it is not limited to this, and part or all of the land portion 20 may be formed by ribs extending continuously in the tire circumferential direction.

[0018] This tire T includes a plurality of land portions 20, a first land portion located relatively inward in the tire axial direction and a second land portion located relatively outward in the tire axial direction. In the first land portion and the second land portion, a corrugated sipe 5 extending in a direction intersecting the tire circumferential direction and a shallow groove 6 shallower than the corrugated sipe 5 are respectively formed. The number of intersection points Na between the top of the corrugated sipe 5 and the shallow groove 6 in the first land portion and the number of intersection points Nb between the top of the corrugated sipe 5 and the shallow groove 6 in the second land portion satisfy the relationship Na < Nb. Hereinafter, an example in which the center land portion 25 corresponds to the first land portion and the intermediate land portion 24 corresponds to the second land portion will be specifically described.

[0019] FIG. 2 shows an enlarged view of a part of the tread surface Tr shown in FIG. 1. The center land portion 25 is composed of an array of blocks 45, and the intermediate land portion 24 is composed of an array of blocks 44. The center land portion 25 corresponds to the first land portion located relatively inward in the tire axial direction, and the intermediate land portion 24 corresponds to the second land portion located relatively outward in the tire axial direction. A corrugated sipe 5 and a shallow groove 6 are respectively formed in the center land portion 25 and the intermediate land portion 24. The shallow groove 6 extends in a direction intersecting the corrugated sipe 5. Also, the shallow groove 6 extends in a direction intersecting the tire circumferential direction.

[0020] The waveform pattern 5 has a top portion 5t located on the tip side in the amplitude direction of the waveform. The block 4 includes a tapered portion 4d that tapers toward the top portion 5t. As a result of the research by the present inventor, since the deformation is large at the tip of the tapered portion 4d, the ground pressure tends to be high, and therefore the strain during braking tends to concentrate in the vicinity of the top portion 5t. In particular, at the intersection CP between the top portion 5t and the shallow groove 6, since the top portion 5t is divided by the shallow groove 6 and the surface portion of the tapered portion 4d becomes even narrower, this tendency becomes prominent, and it has been found that the ground pressure of the land portion 20 tends to become non-uniform. Further, during braking on an icy or snowy road surface, the ground pressure in the region on the tire equator TC side is higher than that in the region on the ground contact end TE side of the tread surface Tr, so the latter contributes more to the braking performance.

[0021] Therefore, in this tire T, a configuration is adopted in which the number Na of intersections between the top portion 5t and the shallow groove 6 in the center land portion 25 and the number Nb of intersections between the top portion 5t and the shallow groove 6 in the intermediate land portion 24 satisfy the relationship Na < Nb. According to such a configuration, the number of intersections CP can be relatively reduced in the region that contributes highly to the braking performance on an icy or snowy road surface (the region on the tire equator TC side of the tread surface Tr) to equalize the ground pressure, and thus the braking performance on an icy or snowy road surface can be improved. Since the same effect is expected during driving, the traction performance on an icy or snowy road surface can also be improved. In the present embodiment, 0 < Na, and the relationship 0 < Na < Nb is satisfied.

[0022] In FIG. 3, virtual straight lines L1 to L3 that extend parallel to the amplitude center line AC of the corrugated sipes 5 are shown. Straight line L1 passes through the position where the amplitude is maximum on the sipes wall surface 51 on the outer side of the curvature of the top 5t. Straight line L2 passes through the middle between straight line L1 and straight line L3. Straight line L3 passes through a position shifted by half of the width W5 from the amplitude center line AC toward the top 5t side, and in the corrugated sipes 5 including the straight line portion on the amplitude center line AC, it extends along the sipes wall surface 51 of that straight line portion. At the intersection point CP, a part of the shallow groove 6 overlaps with the corrugated sipes 5 (the hatched area) within the region X sandwiched between straight line L1 and straight line L2. Locations not corresponding to this are not counted as the intersection point CP between the top 5t and the shallow groove 6.

[0023] The relationship of Na < Nb only needs to be satisfied in the comparison between the number of intersection points Na over the entire tire circumference in the first land portion (the center land portion 25 in this embodiment) and the number of intersection points Nb over the entire tire circumference in the second land portion (the mediate land portion 24 in this embodiment). The ratio (Na / Nb) of the number of intersection points Na to the number of intersection points Nb over the entire tire circumference is preferably 0.85 or less. Also, the relationship of Na < Nb may be satisfied in the comparison between the number of intersection points Na within the ground contact surface in the first land portion and the number of intersection points Nb within the ground contact surface in the second land portion, in addition to or instead of the above-described comparison over the entire tire circumference. The ratio (Na / Nb) of the number of intersection points Na to the number of intersection points Nb within the ground contact surface is preferably 0.75 or less. The ground contact surface is defined in the above-described normal state.

[0024] In this embodiment, a plurality of corrugated sipes 5 are arranged for one block 4, and they are arranged side by side at a predetermined pitch interval P5. The inclination angle θ5 of the corrugated sipes 5 on the acute angle side with respect to the tire axial direction is 0 degrees, but it is not limited to this. From the viewpoint of enhancing the braking performance and traction performance on an ice and snow road surface, the inclination angle θ5 is preferably 30 degrees or less, and more preferably 15 degrees or less. The inclination angle θ5 is obtained based on the amplitude center line AC of the corrugated sipes 5.

[0025] In this embodiment, a plurality of shallow grooves 6 are arranged for one block 4, and they are arranged side by side at a predetermined pitch interval P6. The inclination angle θ6 on the acute angle side of the shallow groove 6 with respect to the tire axial direction is 45 degrees or more, but is not limited thereto. The inclination angle θ6 is set, for example, to 10 to 40 degrees. In this example, one shallow groove 6 is formed so as not to intersect a single corrugated cycle 5 at a plurality of locations. Both ends of the shallow groove 6 are each open to the transverse groove 30, but are not limited thereto and may be open to the longitudinal groove 10. Also, one end or both ends of the shallow groove 6 may be blocked within the land portion 20.

[0026] In order to enhance the driving performance on an ice and snow road surface in the initial state, it is preferable that the pitch interval P6 of the shallow groove 6 is smaller than the pitch interval P5 of the corrugated cycle 5. The pitch interval P5 is obtained along the width direction of the corrugated cycle 5, and the pitch interval P6 is obtained along the width direction of the shallow groove 6. From the viewpoint of suppressing a decrease in the rigidity of the surface portion of the land portion 20, the pitch interval P6 is preferably 2.5 mm or more, and more preferably 3 mm or more. Also, from the viewpoint of ensuring the function of enhancing the driving performance on an ice and snow road surface in the initial state, the pitch interval P6 is preferably 4.5 mm or less, and more preferably 4 mm or less.

[0027] Although not adopted in this embodiment, a configuration may be such that the pitch interval Pa of the shallow groove 6 in the first land portion (the center land portion 25 in this embodiment) and the pitch interval Pb of the shallow groove 6 in the second land portion (the mediate land portion 24 in this embodiment) satisfy the relationship Pa > Pb. According to such a configuration, since the formation density of the shallow groove 6 in the first land portion becomes relatively small, it is convenient for realizing a configuration that satisfies the relationship Na < Nb.

[0028] When driving on an icy and snowy road surface, a thin film of water is generated on the surface of the land portion 20 pressed against the road surface. The width W6 of the shallow groove 6 is preferably larger than the width W5 of the wave-shaped sipe 5 intersecting with the shallow groove 6, thereby enhancing the drainage effect of the water generated on the surface of the land portion 20, and thus the driving performance on an icy and snowy road surface can be improved. In addition, since the contribution to drainage is higher in an area closer to the ground contact edge TE, when the shallow groove 6 of the second land portion (the intermediate land portion 24 in this embodiment) is formed wider than the shallow groove 6 of the first land portion (the center land portion 25 in this embodiment), the drainage effect of the shallow groove 6 is enhanced.

[0029] 4 shows a modified example in which the shallow groove 6 has a narrow portion 61 that is relatively narrow and located at the center of the shallow groove 6 in the longitudinal direction, and a wide portion 62 that is relatively wide and located at both ends of the shallow groove 6 in the longitudinal direction. Since ground pressure tends to be relatively high at the center of the block 4 on snowy and icy road surfaces, this configuration can suppress a decrease in rigidity of the surface portion of the land portion 20 in the area where ground pressure is high (the center of the block 4), and can increase the drainage effect of water generated on the surface of the land portion 20 in the surrounding area, thereby satisfactorily improving braking performance and traction performance on snowy and icy road surfaces.

[0030] In the example of Fig. 4, the narrow portion 61 and the wide portion 62 are each formed with a constant width, and are connected via a wavy sipe 5. The block 4 shown in Fig. 4 is a block 45 constituting the first land portion (center land portion 25 in this embodiment), but such shallow grooves 6 can also be applied to the block 44 constituting the second land portion (mediate land portion 24 in this embodiment). The shallow groove 6 having the narrow portion 61 and the wide portion 62 can be applied to at least one of the first land portion and the second land portion, but it is preferable to apply it to at least the second land portion because the contribution to drainage increases as the region is closer to the ground contact edge TE.

[0031] As described above, in the present embodiment, the center land portion 25 corresponds to the first land portion, and the mediate land portion 24 adjacent to the center land portion 25 with the longitudinal groove 10 interposed therebetween corresponds to the second land portion. Therefore, the first land portion is adjacent to the inner side in the tire axial direction of the center longitudinal groove 14 as the first longitudinal groove included in the plurality of longitudinal grooves 10, and the second land portion is adjacent to the outer side in the tire axial direction of the first longitudinal groove. Further, the second land portion is located on the inner side in the tire axial direction than the shoulder longitudinal groove 12 as the second longitudinal groove located on the outermost side in the tire axial direction among the plurality of longitudinal grooves 10. More specifically, the second land portion is adjacent to the inner side in the tire axial direction of the shoulder longitudinal groove 12 as the second longitudinal groove.

[0032] So far, it has been explained that the relationship of Na < Nb is satisfied between the center land portion 25 and the mediate land portion 24. However, in the present embodiment, the relationship of Na < Nb is also satisfied between the center land portion 25 and the mediate land portion 23. That is, between the center land portion 25 and the pair of mediate land portions 23 and 24 located on both sides in the tire axial direction thereof, the relationship of Na < Nb is satisfied respectively. According to such a configuration, the braking performance on the ice and snow road surface can be more effectively improved. The mediate land portion 23 has substantially the same shape as the mediate land portion 24 as shown in FIG. 1, but is not limited thereto.

[0033] Further, in the present embodiment, the relationship of Na < Nb is satisfied between the center land portion 25 and the shoulder land portion 21, and between the center land portion 25 and the shoulder land portion 23, respectively. That is, between the center land portion 25 and the pair of shoulder land portions 21 and 22 located on both sides in the tire axial direction thereof, the relationship of Na < Nb is satisfied respectively. According to such a configuration, the braking performance on the ice and snow road surface can be more effectively improved. The shoulder land portions 21 and 22 have substantially the same shape as the mediate land portion 24 as shown in FIG. 1, but are not limited thereto.

[0034] The tread surface Tr only needs to have at least one combination of a first land portion and a second land portion that satisfies the relationship Na < Nb. Such a combination of the first land portion and the second land portion is not limited to the center land portion and the intermediate land portion, and may be the center land portion and the shoulder land portion, or the intermediate land portion and the shoulder land portion, and it is also possible to use them in combination. However, since the contribution to the braking performance on the ice and snow road surface is higher in the region closer to the tire equator TC, the combination of the first land portion and the second land portion that satisfies the relationship Na < Nb preferably includes the center land portion, and more preferably is the center land portion and the intermediate land portion.

[0035] The tread pattern formed on the tread surface Tr is not particularly limited. In FIG. 1, a pattern in which blocks of the same shape are monotonously repeated along the tire circumferential direction is shown, but it is of course not limited to this. Also, since the number of the longitudinal grooves 10 is not particularly limited, for example, as shown in FIG. 5, a pattern in which four land portions (a pair of shoulder land portions 26, 27 and a pair of center land portions 28, 29) are partitioned by three longitudinal grooves 10 may be used. In the example of FIG. 5, the relationship Na < Nb is satisfied between the center land portion 28 and the shoulder land portion 26, and between the center land portion 29 and the shoulder land portion 27, respectively.

[0036] [1] As described above, the pneumatic tire T of the present embodiment includes a plurality of longitudinal grooves 10 extending along the tire circumferential direction on the tread surface Tr, and a plurality of land portions 20 partitioned by the plurality of longitudinal grooves 10. The plurality of land portions 20 include a first land portion (specifically, the center land portion 25) located relatively inside in the tire axial direction and a second land portion (specifically, the intermediate land portion 24) located relatively outside in the tire axial direction. In the first land portion and the second land portion, a corrugated sipes 5 extending in a direction intersecting the tire circumferential direction and a shallow groove 6 shallower than the corrugated sipes 5 are respectively formed. The number Na of intersection points between the top 5t of the corrugated sipes 5 and the shallow groove 6 in the first land portion and the number Nb of intersection points between the top 5t of the corrugated sipes 5 and the shallow groove 6 in the second land portion satisfy the relationship Na < Nb. According to such a configuration, it is possible to improve the braking performance on the ice and snow road surface.

[0037] [2] In the pneumatic tire T of [1] above, the first land portion is adjacent to the inner side in the tire axial direction of the first longitudinal groove (specifically, the center longitudinal groove 14) included in the plurality of longitudinal grooves 10, and the second land portion may be adjacent to the outer side in the tire axial direction of the first longitudinal groove. In this case, the relationship of Na < Nb is satisfied in the comparison between the land portions adjacent to each other with the first longitudinal groove interposed therebetween.

[0038] [3] In the pneumatic tire T of [1] or [2] above, the second land portion may be located on the inner side in the tire axial direction than the second longitudinal groove (specifically, the shoulder longitudinal groove 12) located on the outermost side in the tire axial direction among the plurality of longitudinal grooves 10. Since the contribution to the braking performance on the ice and snow road surface is higher in the region closer to the tire equator TC, according to such a configuration, the improvement of the braking performance on the ice and snow road surface can be achieved more favorably.

[0039] [4] In the pneumatic tire T of any one of [1] to [3] above, in at least one of the first land portion and the second land portion, it is preferable that the shallow groove 6 has a narrow portion 61 that is located on the central side in the longitudinal direction of the shallow groove 6 and is relatively narrow in width, and a wide portion 62 that is located on both end sides in the longitudinal direction of the shallow groove 6 and is relatively wide in width. According to such a configuration, the braking performance on the ice and snow road surface can be improved more favorably.

[0040] [5] In the pneumatic tire T of any one of [1] to [4] above, it is preferable that the pitch interval Pa of the shallow groove 6 in the first land portion and the pitch interval Pb of the shallow groove 6 in the second land portion satisfy the relationship of Pa > Pb. According to such a configuration, since the formation density of the shallow groove 6 in the first land portion becomes relatively small, it is convenient for realizing the configuration that satisfies the relationship of Na < Nb.

[0041] The pneumatic tire of the present invention is equivalent to a normal pneumatic tire except that it has the above-mentioned configurations regarding the wave-shaped sipes and shallow grooves, and any of the conventionally known materials, shapes, structures, etc. can be adopted in the present invention. The pneumatic tire of the present invention is useful as a winter tire or an all-season tire.

[0042] Although the embodiment of the present invention has been described based on the drawings, the specific configuration should not be considered to be limited to this embodiment. The scope of the present invention is indicated not only by the description of the embodiment but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0043] The tire according to the present invention is not limited to the above-mentioned embodiment, and is not limited to the above-mentioned action and effect. The tire according to the present invention can be improved or modified in various ways without departing from the spirit of the tire. In addition, the configurations employed in the above-mentioned embodiment can be combined in any desired manner. [Explanation of symbols]

[0044] 5 Wave sipes 5t top 6 Shallow Groove 10 Vertical groove 12 Shoulder longitudinal groove (corresponding to the second longitudinal groove) 14 Center longitudinal groove (corresponding to the first longitudinal groove) 20 Land 24 Mediate Land Section (corresponding to the 2nd Land Section) 25 Center Land Section (corresponding to the 1st Land Section) 30 Yokomizo 61 Narrow part 62 Wide section Tr tread surface

Claims

1. The tire has a plurality of longitudinal grooves extending along a circumferential direction of the tire on a tread surface, and a plurality of land portions divided by the plurality of longitudinal grooves, The plurality of land portions include a first land portion located relatively inward in the tire axial direction and a second land portion located relatively outward in the tire axial direction, In each of the first land portion and the second land portion, a wavy sipe extending in a direction intersecting with the tire circumferential direction and a shallow groove shallower than the wavy sipe are formed, A pneumatic tire, wherein a number Na of intersections between the tops of the wavy sipes and the shallow grooves in the first land portion and a number Nb of intersections between the tops of the wavy sipes and the shallow grooves in the second land portion satisfy a relationship of Na<Nb.

2. The first land portion is adjacent to a first longitudinal groove included in the plurality of longitudinal grooves on an inner side in the tire axial direction, The pneumatic tire according to claim 1 , wherein the second land portion is adjacent to an outer side of the first longitudinal groove in the tire axial direction.

3. The pneumatic tire according to claim 1 , wherein the second land portion is located axially more inward than a second longitudinal groove that is located axially outermost among the plurality of longitudinal grooves.

4. 2. The pneumatic tire according to claim 1, wherein in at least one of the first land portion and the second land portion, the shallow groove has a narrow portion that is located at a center side of the shallow groove in the longitudinal direction and has a relatively small width, and a wide portion that is located at both ends of the shallow groove in the longitudinal direction and has a relatively large width.

5. The pneumatic tire according to any one of claims 1 to 4, wherein a pitch interval Pa of the shallow grooves in the first land portion and a pitch interval Pb of the shallow grooves in the second land portion satisfy a relationship of Pa>Pb.

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